Simulation-Based Joint Estimation of Body Deformation and Elasticity Parameters for Medical Image Analysis

PubMed Central

Foskey, Mark; Niethammer, Marc; Krajcevski, Pavel; Lin, Ming C.

2014-01-01

Estimation of tissue stiffness is an important means of noninvasive cancer detection. Existing elasticity reconstruction methods usually depend on a dense displacement field (inferred from ultrasound or MR images) and known external forces. Many imaging modalities, however, cannot provide details within an organ and therefore cannot provide such a displacement field. Furthermore, force exertion and measurement can be difficult for some internal organs, making boundary forces another missing parameter. We propose a general method for estimating elasticity and boundary forces automatically using an iterative optimization framework, given the desired (target) output surface. During the optimization, the input model is deformed by the simulator, and an objective function based on the distance between the deformed surface and the target surface is minimized numerically. The optimization framework does not depend on a particular simulation method and is therefore suitable for different physical models. We show a positive correlation between clinical prostate cancer stage (a clinical measure of severity) and the recovered elasticity of the organ. Since the surface correspondence is established, our method also provides a non-rigid image registration, where the quality of the deformation fields is guaranteed, as they are computed using a physics-based simulation. PMID:22893381

Soft tissue deformation modelling through neural dynamics-based reaction-diffusion mechanics.

PubMed

Zhang, Jinao; Zhong, Yongmin; Gu, Chengfan

2018-05-30

Soft tissue deformation modelling forms the basis of development of surgical simulation, surgical planning and robotic-assisted minimally invasive surgery. This paper presents a new methodology for modelling of soft tissue deformation based on reaction-diffusion mechanics via neural dynamics. The potential energy stored in soft tissues due to a mechanical load to deform tissues away from their rest state is treated as the equivalent transmembrane potential energy, and it is distributed in the tissue masses in the manner of reaction-diffusion propagation of nonlinear electrical waves. The reaction-diffusion propagation of mechanical potential energy and nonrigid mechanics of motion are combined to model soft tissue deformation and its dynamics, both of which are further formulated as the dynamics of cellular neural networks to achieve real-time computational performance. The proposed methodology is implemented with a haptic device for interactive soft tissue deformation with force feedback. Experimental results demonstrate that the proposed methodology exhibits nonlinear force-displacement relationship for nonlinear soft tissue deformation. Homogeneous, anisotropic and heterogeneous soft tissue material properties can be modelled through the inherent physical properties of mass points. Graphical abstract Soft tissue deformation modelling with haptic feedback via neural dynamics-based reaction-diffusion mechanics.

A Multi-Scale Simulation Approach to Deformation Mechanism Prediction in Superalloys

NASA Astrophysics Data System (ADS)

Lv, Duchao

High-temperature alloys in general and superalloys in particular are crucial for manufacturing gas turbines for aircraft and power generators. Among the superalloy family, the Ni-based superalloys are the most frequently used due to their excellent strength-to-weight ratio. Their strength results from their ordered intermetallic phases (precipitates), which are relatively stable at elevated temperatures. The major deformation processes of Ni-based and Co-based superalloys are precipitate shearing and Orowan looping. The key to developing physics-based models of creep and yield strength of aircraft engine components is to understand the two deformation mechanisms mentioned above. Recent discoveries of novel dislocation structures and stacking-fault configurations in deformed superalloys implied that the traditional anti-phase boundary (APB)-type, yield-strength model is unable to explain the shearing mechanisms of the gamma" phase in 718-type (Ni-based) superalloys. While the onset of plastic deformation is still related to the formation of highly-energetic stacking faults, the physics-based yield strength prediction requires that the novel dislocation structure and the correct intermediate stacking-fault be considered in the mathematical expressions. In order to obtain the dependence of deformation mechanisms on a materials chemical composition, the relationship between the generalized-stacking-fault (GSF) surface and its chemical composition must be understood. For some deformation scenarios in which one precipitate phase and one mechanism are dominant (e.g., Orowan looping), their use in industry requires a fast-acting model that can capture the features of the deformation (e.g., the volume fraction of the sheared matrix) and reduces lost time by not repeating fine-scale simulations. The objective of this thesis was to develop a multi-scale, physics-based simulation approach that can be used to optimize existing superalloys and to accelerate the design of new alloys. In particular, density functional theory (DFT) was used to calculate the GSF surface of the gamma" phase in the 718-type superalloy. In addition, the deformation pathways inside the gamma" particles were identified, and the dislocation emissions were predicted. Many novel dislocation sources inside the gamma" particles were simulated by using the phase-field method, which predicts and explains the dislocation configurations that appear during the deformation process or that are left as debris. Moreover, based on the stacking-fault energies in the available literature, we calculated the dependence of the chemical composition of the GSF surface of the gamma' phase in Co-based, CoNi-based, and Ni-based superalloys. The phase-field simulation, which used the GSF surfaces as inputs, explained the relationship between the shearing mechanism and chemical composition. Thus, two fast-acting models were developed by using the modified analytic expressions of particle shearing and Orowan looping. These expressions were calibrated by using the GSF surface and the simulation of the phase-field, and they were used to predict the yield strength of 718-type superalloy and the localized creep features of the gamma/gamma' microstructure. The fast-acting yield models were trained by the available experimental results. Since the chemical re-ordering and the segregation effects are not considered in this work, the fast-acting models are designed to the predict mechanical behaviors at the room temperature and the intermediate temperature.

Physics-based interactive volume manipulation for sharing surgical process.

PubMed

Nakao, Megumi; Minato, Kotaro

2010-05-01

This paper presents a new set of techniques by which surgeons can interactively manipulate patient-specific volumetric models for sharing surgical process. To handle physical interaction between the surgical tools and organs, we propose a simple surface-constraint-based manipulation algorithm to consistently simulate common surgical manipulations such as grasping, holding and retraction. Our computation model is capable of simulating soft-tissue deformation and incision in real time. We also present visualization techniques in order to rapidly visualize time-varying, volumetric information on the deformed image. This paper demonstrates the success of the proposed methods in enabling the simulation of surgical processes, and the ways in which this simulation facilitates preoperative planning and rehearsal.

Deformation and Fabric in Compacted Clay Soils

NASA Astrophysics Data System (ADS)

Wensrich, C. M.; Pineda, J.; Luzin, V.; Suwal, L.; Kisi, E. H.; Allameh-Haery, H.

2018-05-01

Hydromechanical anisotropy of clay soils in response to deformation or deposition history is related to the micromechanics of platelike clay particles and their orientations. In this article, we examine the relationship between microstructure, deformation, and moisture content in kaolin clay using a technique based on neutron scattering. This technique allows for the direct characterization of microstructure within representative samples using traditional measures such as orientation density and soil fabric tensor. From this information, evidence for a simple relationship between components of the deviatoric strain tensor and the deviatoric fabric tensor emerge. This relationship may provide a physical basis for future anisotropic constitutive models based on the micromechanics of these materials.

Theory for plasticity of face-centered cubic metals.

PubMed

Jo, Minho; Koo, Yang Mo; Lee, Byeong-Joo; Johansson, Börje; Vitos, Levente; Kwon, Se Kyun

2014-05-06

The activation of plastic deformation mechanisms determines the mechanical behavior of crystalline materials. However, the complexity of plastic deformation and the lack of a unified theory of plasticity have seriously limited the exploration of the full capacity of metals. Current efforts to design high-strength structural materials in terms of stacking fault energy have not significantly reduced the laborious trial and error works on basic deformation properties. To remedy this situation, here we put forward a comprehensive and transparent theory for plastic deformation of face-centered cubic metals. This is based on a microscopic analysis that, without ambiguity, reveals the various deformation phenomena and elucidates the physical fundaments of the currently used phenomenological correlations. We identify an easily accessible single parameter derived from the intrinsic energy barriers, which fully specifies the potential diversity of metals. Based entirely on this parameter, a simple deformation mode diagram is shown to delineate a series of convenient design criteria, which clarifies a wide area of material functionality by texture control.

Theory for plasticity of face-centered cubic metals

PubMed Central

Jo, Minho; Koo, Yang Mo; Lee, Byeong-Joo; Johansson, Börje; Vitos, Levente; Kwon, Se Kyun

2014-01-01

The activation of plastic deformation mechanisms determines the mechanical behavior of crystalline materials. However, the complexity of plastic deformation and the lack of a unified theory of plasticity have seriously limited the exploration of the full capacity of metals. Current efforts to design high-strength structural materials in terms of stacking fault energy have not significantly reduced the laborious trial and error works on basic deformation properties. To remedy this situation, here we put forward a comprehensive and transparent theory for plastic deformation of face-centered cubic metals. This is based on a microscopic analysis that, without ambiguity, reveals the various deformation phenomena and elucidates the physical fundaments of the currently used phenomenological correlations. We identify an easily accessible single parameter derived from the intrinsic energy barriers, which fully specifies the potential diversity of metals. Based entirely on this parameter, a simple deformation mode diagram is shown to delineate a series of convenient design criteria, which clarifies a wide area of material functionality by texture control. PMID:24753563

Prevalence of rickets-like bone deformities in rural Gambian children

PubMed Central

Jones, Helen L.; Jammeh, Lamin; Owens, Stephen; Fulford, Anthony J.; Moore, Sophie E.; Pettifor, John M.; Prentice, Ann

2015-01-01

The aim of this study was to estimate the burden of childhood rickets-like bone deformity in a rural region of West Africa where rickets has been reported in association with a low calcium intake. A population-based survey of children aged 0.5–17.9 years living in the province of West Kiang, The Gambia was conducted in 2007. 6221 children, 92% of those recorded in a recent census, were screened for physical signs of rickets by a trained survey team with clinical referral of suspected cases. Several objective measures were tested as potential screening tools. The prevalence of bone deformity in children < 18.0 years was 3.3%. The prevalence was greater in males (M = 4.3%, F = 2.3%, p < 0.001) and in children < 5.0 years (5.7%, M = 8.3%, F = 2.9%). Knock-knee was more common (58%) than bow-leg (31%) or windswept deformity (9%). Of the 196 examined clinically, 36 were confirmed to have a deformity outside normal variation (47% knock-knee, 53% bow-leg), resulting in more conservative prevalence estimates of bone deformity: 0.6% for children < 18.0 years (M = 0.9%, F = 0.2%), 1.5% for children < 5.0 years (M = 2.3%, F = 0.6%). Three of these children (9% of those with clinically-confirmed deformity, 0.05% of those screened) had active rickets on X-ray at the time of medical examination. This emphasises the difficulties in comparing prevalence estimates of rickets-like bone deformities from population surveys and clinic-based studies. Interpopliteal distance showed promise as an objective screening measure for bow-leg deformity. In conclusion, this population survey in a rural region of West Africa with a low calcium diet has demonstrated a significant burden of rickets-like bone deformity, whether based on physical signs under survey conditions or after clinical examination, especially in boys < 5.0 years. PMID:25871880

The Shapes of Splash-Form Tektites: Their Geometrical Analysis, Classification and Mechanics of Formation

NASA Astrophysics Data System (ADS)

Stauffer, Mel R.; Butler, Samuel L.

2010-12-01

Splash-form tektites are found with a wide range of sizes and in an intriguing array of shapes ranging from spheres to flat discs to dumbbells. Despite the considerable interest that exists in tektites, there has been relatively little effort to develop rational shape descriptors and to understand the origin of their shapes based on basic physics. Tektites represent a natural laboratory experiment that can be analyzed to better understand the physics of rotating fluid drops. In this paper, we propose a classification scheme based on the axial ratios of ellipsoids, and we analyze the frequency of tektite shapes using a database of over 1,000 measured tektites. We show that the shape distribution for tektites from Thailand and Vietnam are very similar and that the most common tektites are moderately deformed discs but there exist also a significant number of moderately deformed dumbbells, and we argue that this distribution comes about because fluid drops first deform as oblate forms and then undergo a non-axisymmetric instability to become prolate. We also find that the largest tektites are most likely to be weakly deformed oblate objects while the most strongly deformed and most highly prolate forms are considerably smaller. A numerical model for the evolution of an axisymmetric fluid drop, such as a tektite in its molten early stage, is presented which demonstrates that drops that deform relatively slowly over a longer period of time are likely to develop central thinning while those that deform more rapidly are more likely to retain the shape of an ellipsoid. For the numerical parameters used the characteristic time scale for deformation was less than 1 s.

Modeling and simulation of tumor-influenced high resolution real-time physics-based breast models for model-guided robotic interventions

NASA Astrophysics Data System (ADS)

Neylon, John; Hasse, Katelyn; Sheng, Ke; Santhanam, Anand P.

2016-03-01

Breast radiation therapy is typically delivered to the patient in either supine or prone position. Each of these positioning systems has its limitations in terms of tumor localization, dose to the surrounding normal structures, and patient comfort. We envision developing a pneumatically controlled breast immobilization device that will enable the benefits of both supine and prone positioning. In this paper, we present a physics-based breast deformable model that aids in both the design of the breast immobilization device as well as a control module for the device during every day positioning. The model geometry is generated from a subject's CT scan acquired during the treatment planning stage. A GPU based deformable model is then generated for the breast. A mass-spring-damper approach is then employed for the deformable model, with the spring modeled to represent a hyperelastic tissue behavior. Each voxel of the CT scan is then associated with a mass element, which gives the model its high resolution nature. The subject specific elasticity is then estimated from a CT scan in prone position. Our results show that the model can deform at >60 deformations per second, which satisfies the real-time requirement for robotic positioning. The model interacts with a computer designed immobilization device to position the breast and tumor anatomy in a reproducible location. The design of the immobilization device was also systematically varied based on the breast geometry, tumor location, elasticity distribution and the reproducibility of the desired tumor location.

Correlated full-field and pointwise temporally resolved measurements of thermomechanical stress inside an operating power transistor

NASA Astrophysics Data System (ADS)

Borza, Dan N.; Gautrelet, Christophe

2015-01-01

The paper describes a measurement system based on time-resolved speckle interferometry, able to record long series of thermally induced full-field deformation maps of die and wire bonds inside an operating power transistor. The origin of the deformation is the transistor heating during its normal operation. The full-field results consist in completely unwrapped deformation maps for out-of-plane displacements greater than 14 μm, with nanometer resolution, in presence of discontinuities due to structural and material inhomogeneity. These measurements are synchronized with the measurement of heatsink temperature and of base-emitter junction temperature, so as to provide data related to several interacting physical parameters. The temporal histories of the displacement are also accessible for any point. They are correlated with the thermal and electrical time series. Mechanical full-field curvatures may also be estimated, making these measurements useful for inspecting physical origins of thermomechanical stresses and for interacting with numerical models used in reliability-related studies.

The evolving energy budget of accretionary wedges

NASA Astrophysics Data System (ADS)

McBeck, Jessica; Cooke, Michele; Maillot, Bertrand; Souloumiac, Pauline

2017-04-01

The energy budget of evolving accretionary systems reveals how deformational processes partition energy as faults slip, topography uplifts, and layer-parallel shortening produces distributed off-fault deformation. The energy budget provides a quantitative framework for evaluating the energetic contribution or consumption of diverse deformation mechanisms. We investigate energy partitioning in evolving accretionary prisms by synthesizing data from physical sand accretion experiments and numerical accretion simulations. We incorporate incremental strain fields and cumulative force measurements from two suites of experiments to design numerical simulations that represent accretionary wedges with stronger and weaker detachment faults. One suite of the physical experiments includes a basal glass bead layer and the other does not. Two physical experiments within each suite implement different boundary conditions (stable base versus moving base configuration). Synthesizing observations from the differing base configurations reduces the influence of sidewall friction because the force vector produced by sidewall friction points in opposite directions depending on whether the base is fixed or moving. With the numerical simulations, we calculate the energy budget at two stages of accretion: at the maximum force preceding the development of the first thrust pair, and at the minimum force following the development of the pair. To identify the appropriate combination of material and fault properties to apply in the simulations, we systematically vary the Young's modulus and the fault static and dynamic friction coefficients in numerical accretion simulations, and identify the set of parameters that minimizes the misfit between the normal force measured on the physical backwall and the numerically simulated force. Following this derivation of the appropriate material and fault properties, we calculate the components of the work budget in the numerical simulations and in the simulated increments of the physical experiments. The work budget components of the physical experiments are determined from backwall force measurements and incremental velocity fields calculated via digital image correlation. Comparison of the energy budget preceding and following the development of the first thrust pair quantifies the tradeoff of work done in distributed deformation and work expended in frictional slip due to the development of the first backthrust and forethrust. In both the numerical and physical experiments, after the pair develops internal work decreases at the expense of frictional work, which increases. Despite the increase in frictional work, the total external work of the system decreases, revealing that accretion faulting leads to gains in efficiency. Comparison of the energy budget of the accretion experiments and simulations with the strong and weak detachments indicate that when the detachment is strong, the total energy consumed in frictional sliding and internal deformation is larger than when the detachment is relatively weak.

A simulation model for analysing brain structure deformations.

PubMed

Di Bona, Sergio; Lutzemberger, Ludovico; Salvetti, Ovidio

2003-12-21

Recent developments of medical software applications--from the simulation to the planning of surgical operations--have revealed the need for modelling human tissues and organs, not only from a geometric point of view but also from a physical one, i.e. soft tissues, rigid body, viscoelasticity, etc. This has given rise to the term 'deformable objects', which refers to objects with a morphology, a physical and a mechanical behaviour of their own and that reflects their natural properties. In this paper, we propose a model, based upon physical laws, suitable for the realistic manipulation of geometric reconstructions of volumetric data taken from MR and CT scans. In particular, a physically based model of the brain is presented that is able to simulate the evolution of different nature pathological intra-cranial phenomena such as haemorrhages, neoplasm, haematoma, etc and to describe the consequences that are caused by their volume expansions and the influences they have on the anatomical and neuro-functional structures of the brain.

Using patient-specific phantoms to evaluate deformable image registration algorithms for adaptive radiation therapy

PubMed Central

Stanley, Nick; Glide-Hurst, Carri; Kim, Jinkoo; Adams, Jeffrey; Li, Shunshan; Wen, Ning; Chetty, Indrin J.; Zhong, Hualiang

2014-01-01

The quality of adaptive treatment planning depends on the accuracy of its underlying deformable image registration (DIR). The purpose of this study is to evaluate the performance of two DIR algorithms, B-spline–based deformable multipass (DMP) and deformable demons (Demons), implemented in a commercial software package. Evaluations were conducted using both computational and physical deformable phantoms. Based on a finite element method (FEM), a total of 11 computational models were developed from a set of CT images acquired from four lung and one prostate cancer patients. FEM generated displacement vector fields (DVF) were used to construct the lung and prostate image phantoms. Based on a fast-Fourier transform technique, image noise power spectrum was incorporated into the prostate image phantoms to create simulated CBCT images. The FEM-DVF served as a gold standard for verification of the two registration algorithms performed on these phantoms. The registration algorithms were also evaluated at the homologous points quantified in the CT images of a physical lung phantom. The results indicated that the mean errors of the DMP algorithm were in the range of 1.0 ~ 3.1 mm for the computational phantoms and 1.9 mm for the physical lung phantom. For the computational prostate phantoms, the corresponding mean error was 1.0–1.9 mm in the prostate, 1.9–2.4 mm in the rectum, and 1.8–2.1 mm over the entire patient body. Sinusoidal errors induced by B-spline interpolations were observed in all the displacement profiles of the DMP registrations. Regions of large displacements were observed to have more registration errors. Patient-specific FEM models have been developed to evaluate the DIR algorithms implemented in the commercial software package. It has been found that the accuracy of these algorithms is patient-dependent and related to various factors including tissue deformation magnitudes and image intensity gradients across the regions of interest. This may suggest that DIR algorithms need to be verified for each registration instance when implementing adaptive radiation therapy. PMID:24257278

Using patient‐specific phantoms to evaluate deformable image registration algorithms for adaptive radiation therapy

PubMed Central

Stanley, Nick; Glide‐Hurst, Carri; Kim, Jinkoo; Adams, Jeffrey; Li, Shunshan; Wen, Ning; Chetty, Indrin J

2013-01-01

The quality of adaptive treatment planning depends on the accuracy of its underlying deformable image registration (DIR). The purpose of this study is to evaluate the performance of two DIR algorithms, B‐spline‐based deformable multipass (DMP) and deformable demons (Demons), implemented in a commercial software package. Evaluations were conducted using both computational and physical deformable phantoms. Based on a finite element method (FEM), a total of 11 computational models were developed from a set of CT images acquired from four lung and one prostate cancer patients. FEM generated displacement vector fields (DVF) were used to construct the lung and prostate image phantoms. Based on a fast‐Fourier transform technique, image noise power spectrum was incorporated into the prostate image phantoms to create simulated CBCT images. The FEM‐DVF served as a gold standard for verification of the two registration algorithms performed on these phantoms. The registration algorithms were also evaluated at the homologous points quantified in the CT images of a physical lung phantom. The results indicated that the mean errors of the DMP algorithm were in the range of 1.0~3.1mm for the computational phantoms and 1.9 mm for the physical lung phantom. For the computational prostate phantoms, the corresponding mean error was 1.0–1.9 mm in the prostate, 1.9–2.4 mm in the rectum, and 1.8–2.1 mm over the entire patient body. Sinusoidal errors induced by B‐spline interpolations were observed in all the displacement profiles of the DMP registrations. Regions of large displacements were observed to have more registration errors. Patient‐specific FEM models have been developed to evaluate the DIR algorithms implemented in the commercial software package. It has been found that the accuracy of these algorithms is patient‐dependent and related to various factors including tissue deformation magnitudes and image intensity gradients across the regions of interest. This may suggest that DIR algorithms need to be verified for each registration instance when implementing adaptive radiation therapy. PACS numbers: 87.10.Kn, 87.55.km, 87.55.Qr, 87.57.nj

Geometric constraints on the space of N = 2 SCFTs. Part I: physical constraints on relevant deformations

NASA Astrophysics Data System (ADS)

Argyres, Philip; Lotito, Matteo; Lü, Yongchao; Martone, Mario

2018-02-01

We initiate a systematic study of four dimensional N = 2 superconformal field theories (SCFTs) based on the analysis of their Coulomb branch geometries. Because these SCFTs are not uniquely characterized by their scale-invariant Coulomb branch geometries we also need information on their deformations. We construct all inequivalent such deformations preserving N = 2 supersymmetry and additional physical consistency conditions in the rank 1 case. These not only include all the ones previously predicted by S-duality, but also 16 additional deformations satisfying all the known N = 2 low energy consistency conditions. All but two of these additonal deformations have recently been identified with new rank 1 SCFTs; these identifications are briefly reviewed. Some novel ingredients which are important for this study include: a discussion of RG-flows in the presence of a moduli space of vacua; a classification of local N = 2 supersymmetry-preserving deformations of unitary N = 2 SCFTs; and an analysis of charge normalizations and the Dirac quantization condition on Coulomb branches. This paper is the first in a series of three. The second paper [1] gives the details of the explicit construction of the Coulomb branch geometries discussed here, while the third [2] discusses the computation of central charges of the associated SCFTs.

Deformation-mechanism map for nanocrystalline metals by molecular-dynamics simulation.

PubMed

Yamakov, V; Wolf, D; Phillpot, S R; Mukherjee, A K; Gleiter, H

2004-01-01

Molecular-dynamics simulations have recently been used to elucidate the transition with decreasing grain size from a dislocation-based to a grain-boundary-based deformation mechanism in nanocrystalline f.c.c. metals. This transition in the deformation mechanism results in a maximum yield strength at a grain size (the 'strongest size') that depends strongly on the stacking-fault energy, the elastic properties of the metal, and the magnitude of the applied stress. Here, by exploring the role of the stacking-fault energy in this crossover, we elucidate how the size of the extended dislocations nucleated from the grain boundaries affects the mechanical behaviour. Building on the fundamental physics of deformation as exposed by these simulations, we propose a two-dimensional stress-grain size deformation-mechanism map for the mechanical behaviour of nanocrystalline f.c.c. metals at low temperature. The map captures this transition in both the deformation mechanism and the related mechanical behaviour with decreasing grain size, as well as its dependence on the stacking-fault energy, the elastic properties of the material, and the applied stress level.

Real-time deformation of human soft tissues: A radial basis meshless 3D model based on Marquardt's algorithm.

PubMed

Zhou, Jianyong; Luo, Zu; Li, Chunquan; Deng, Mi

2018-01-01

When the meshless method is used to establish the mathematical-mechanical model of human soft tissues, it is necessary to define the space occupied by human tissues as the problem domain and the boundary of the domain as the surface of those tissues. Nodes should be distributed in both the problem domain and on the boundaries. Under external force, the displacement of the node is computed by the meshless method to represent the deformation of biological soft tissues. However, computation by the meshless method consumes too much time, which will affect the simulation of real-time deformation of human tissues in virtual surgery. In this article, the Marquardt's Algorithm is proposed to fit the nodal displacement at the problem domain's boundary and obtain the relationship between surface deformation and force. When different external forces are applied, the deformation of soft tissues can be quickly obtained based on this relationship. The analysis and discussion show that the improved model equations with Marquardt's Algorithm not only can simulate the deformation in real-time but also preserve the authenticity of the deformation model's physical properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Occurrence of cohesion of metals during combined plastic deformation

NASA Technical Reports Server (NTRS)

Aynbinder, S. G.; Klokova, E. F.

1980-01-01

Experiments were conducted to study the cohesion of metals with surface films of varying thickness and hardness. It was established that the deformation necessary for the occurrence of cohesion is determined by the correlation of mechanical properties of the films and the base metal. The greater the relative hardness of the film the lower the deformation necessary for the occurrence of cohesion. The films are as plastic as the base metal prevent cohesion, since in this case it is impossible for sections of metal to appear that are free of contaminants. The physical perculiarities of metals that determine their capability for coalescence under conditions of dry friction are the relative hardness and plasticity of the oxide films formed on their surface under atmospheric conditions.

Real-time simulation for intra-operative navigation in robotic surgery. Using a mass spring system for a basic study of organ deformation.

PubMed

Kawamura, Kazuya; Kobayashi, Yo; Fujie, Masakatsu G

2007-01-01

Medical technology has advanced with the introduction of robot technology, making previous medical treatments that were very difficult far more possible. However, operation of a surgical robot demands substantial training and continual practice on the part of the surgeon because it requires difficult techniques that are different from those of traditional surgical procedures. We focused on a simulation technology based on the physical characteristics of organs. In this research, we proposed the development of surgical simulation, based on a physical model, for intra-operative navigation by a surgeon. In this paper, we describe the design of our system, in particular our organ deformation calculator. The proposed simulation system consists of an organ deformation calculator and virtual slave manipulators. We obtained adequate experimental results of a target node at a nearby point of interaction, because this point ensures better accuracy for our simulation model. The next research step would be to focus on a surgical environment in which internal organ models would be integrated into a slave simulation system.

Deformation Theory and Physics Model Building

NASA Astrophysics Data System (ADS)

Sternheimer, Daniel

2006-08-01

The mathematical theory of deformations has proved to be a powerful tool in modeling physical reality. We start with a short historical and philosophical review of the context and concentrate this rapid presentation on a few interrelated directions where deformation theory is essential in bringing a new framework - which has then to be developed using adapted tools, some of which come from the deformation aspect. Minkowskian space-time can be deformed into Anti de Sitter, where massless particles become composite (also dynamically): this opens new perspectives in particle physics, at least at the electroweak level, including prediction of new mesons. Nonlinear group representations and covariant field equations, coming from interactions, can be viewed as some deformation of their linear (free) part: recognizing this fact can provide a good framework for treating problems in this area, in particular global solutions. Last but not least, (algebras associated with) classical mechanics (and field theory) on a Poisson phase space can be deformed to (algebras associated with) quantum mechanics (and quantum field theory). That is now a frontier domain in mathematics and theoretical physics called deformation quantization, with multiple ramifications, avatars and connections in both mathematics and physics. These include representation theory, quantum groups (when considering Hopf algebras instead of associative or Lie algebras), noncommutative geometry and manifolds, algebraic geometry, number theory, and of course what is regrouped under the name of M-theory. We shall here look at these from the unifying point of view of deformation theory and refer to a limited number of papers as a starting point for further study.

Deformable Self-Propelled Micro-Object Comprising Underwater Oil Droplets

NASA Astrophysics Data System (ADS)

Banno, Taisuke; Asami, Arisa; Ueno, Naoko; Kitahata, Hiroyuki; Koyano, Yuki; Asakura, Kouichi; Toyota, Taro

2016-08-01

The self-propelled motion with deformation of micrometer-sized soft matter in water has potential application not only for underwater carriers or probes in very narrow spaces but also for understanding cell locomotion in terms of non-equilibrium physics. As far as we know, there have been no reports about micrometer-sized self-propelled soft matter mimicking amoeboid motion underwater. Here, we report an artificial molecular system of underwater oil droplets exhibiting self-propelled motion with deformation as an initial experimental model. We describe the heterogeneity in a deformable self-propelled oil droplet system in aqueous and oil phases and at their interface based on the behavior and interaction of surfactant and oil molecules. The current results have great importance for scientific frontiers such as developing deformable micro-swimmers and exploring the emergence of self-locomotion of oil droplet-type protocells.

Deformable Self-Propelled Micro-Object Comprising Underwater Oil Droplets.

PubMed

Banno, Taisuke; Asami, Arisa; Ueno, Naoko; Kitahata, Hiroyuki; Koyano, Yuki; Asakura, Kouichi; Toyota, Taro

2016-08-09

The self-propelled motion with deformation of micrometer-sized soft matter in water has potential application not only for underwater carriers or probes in very narrow spaces but also for understanding cell locomotion in terms of non-equilibrium physics. As far as we know, there have been no reports about micrometer-sized self-propelled soft matter mimicking amoeboid motion underwater. Here, we report an artificial molecular system of underwater oil droplets exhibiting self-propelled motion with deformation as an initial experimental model. We describe the heterogeneity in a deformable self-propelled oil droplet system in aqueous and oil phases and at their interface based on the behavior and interaction of surfactant and oil molecules. The current results have great importance for scientific frontiers such as developing deformable micro-swimmers and exploring the emergence of self-locomotion of oil droplet-type protocells.

State variable theories based on Hart's formulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Korhonen, M.A.; Hannula, S.P.; Li, C.Y.

In this paper a review of the development of a state variable theory for nonelastic deformation is given. The physical and phenomenological basis of the theory and the constitutive equations describing macroplastic, microplastic, anelastic and grain boundary sliding enhanced deformation are presented. The experimental and analytical evaluation of different parameters in the constitutive equations are described in detail followed by a review of the extensive experimental work on different materials. The technological aspects of the state variable approach are highlighted by examples of the simulative and predictive capabilities of the theory. Finally, a discussion of general capabilities, limitations and futuremore » developments of the theory and particularly the possible extensions to cover an even wider range of deformation or deformation-related phenomena is presented.« less

Transient deformation from daily GPS displacement time series: postseismic deformation, ETS and evolving strain rates

NASA Astrophysics Data System (ADS)

Bock, Y.; Fang, P.; Moore, A. W.; Kedar, S.; Liu, Z.; Owen, S. E.; Glasscoe, M. T.

2016-12-01

Detection of time-dependent crustal deformation relies on the availability of accurate surface displacements, proper time series analysis to correct for secular motion, coseismic and non-tectonic instrument offsets, periodic signatures at different frequencies, and a realistic estimate of uncertainties for the parameters of interest. As part of the NASA Solid Earth Science ESDR System (SESES) project, daily displacement time series are estimated for about 2500 stations, focused on tectonic plate boundaries and having a global distribution for accessing the terrestrial reference frame. The "combined" time series are optimally estimated from independent JPL GIPSY and SIO GAMIT solutions, using a consistent set of input epoch-date coordinates and metadata. The longest time series began in 1992; more than 30% of the stations have experienced one or more of 35 major earthquakes with significant postseismic deformation. Here we present three examples of time-dependent deformation that have been detected in the SESES displacement time series. (1) Postseismic deformation is a fundamental time-dependent signal that indicates a viscoelastic response of the crust/mantle lithosphere, afterslip, or poroelastic effects at different spatial and temporal scales. It is critical to identify and estimate the extent of postseismic deformation in both space and time not only for insight into the crustal deformation and earthquake cycles and their underlying physical processes, but also to reveal other time-dependent signals. We report on our database of characterized postseismic motions using a principal component analysis to isolate different postseismic processes. (2) Starting with the SESES combined time series and applying a time-dependent Kalman filter, we examine episodic tremor and slow slip (ETS) in the Cascadia subduction zone. We report on subtle slip details, allowing investigation of the spatiotemporal relationship between slow slip transients and tremor and their underlying physical mechanisms. (3) We present evolving strain dilatation and shear rates based on the SESES velocities for regional subnetworks as a metric for assigning earthquake probabilities and detection of possible time-dependent deformation related to underlying physical processes.

Fundamental Studies of Strength Physics--Methodology of Longevity Prediction of Materials under Arbitrary Thermally and Forced Effects

ERIC Educational Resources Information Center

Petrov, Mark G.

2016-01-01

Thermally activated analysis of experimental data allows considering about the structure features of each material. By modelling the structural heterogeneity of materials by means of rheological models, general and local plastic flows in metals and alloys can be described over. Based on physical fundamentals of failure and deformation of materials…

Deformable Self-Propelled Micro-Object Comprising Underwater Oil Droplets

PubMed Central

Banno, Taisuke; Asami, Arisa; Ueno, Naoko; Kitahata, Hiroyuki; Koyano, Yuki; Asakura, Kouichi; Toyota, Taro

2016-01-01

The self-propelled motion with deformation of micrometer-sized soft matter in water has potential application not only for underwater carriers or probes in very narrow spaces but also for understanding cell locomotion in terms of non-equilibrium physics. As far as we know, there have been no reports about micrometer-sized self-propelled soft matter mimicking amoeboid motion underwater. Here, we report an artificial molecular system of underwater oil droplets exhibiting self-propelled motion with deformation as an initial experimental model. We describe the heterogeneity in a deformable self-propelled oil droplet system in aqueous and oil phases and at their interface based on the behavior and interaction of surfactant and oil molecules. The current results have great importance for scientific frontiers such as developing deformable micro-swimmers and exploring the emergence of self-locomotion of oil droplet-type protocells. PMID:27503336

Exact solutions for postbuckling of a graded porous beam

NASA Astrophysics Data System (ADS)

Ma, L. S.; Ou, Z. Y.

2018-06-01

An exact, closed-form solution for the postbuckling responses of graded porous beams subjected to axially loading is obtained. It was assumed that the properties of the graded porous materials vary continuously through thickness of the beams, the equations governing the axial and transverse deformations are derived based on the classical beam theory and the physical neutral surface concept. The two equations are reduced to a single nonlinear fourth-order integral-differential equation governing the transverse deformations. The nonlinear equation is directly solved without any use of approximation and a closed-form solution for postbuckled deformation is obtained as a function of the applied load. The exact solutions explicitly describe the nonlinear equilibrium paths of the buckled beam and thus are able to provide insight into deformation problems. Based on the exact solutions obtained herein, the effects of various factors such as porosity distribution pattern, porosity coefficient and boundary conditions on postbuckling behavior of graded porous beams have been investigated.

A statistical motion model based on biomechanical simulations for data fusion during image-guided prostate interventions.

PubMed

Hu, Yipeng; Morgan, Dominic; Ahmed, Hashim Uddin; Pendsé, Doug; Sahu, Mahua; Allen, Clare; Emberton, Mark; Hawkes, David; Barratt, Dean

2008-01-01

A method is described for generating a patient-specific, statistical motion model (SMM) of the prostate gland. Finite element analysis (FEA) is used to simulate the motion of the gland using an ultrasound-based 3D FE model over a range of plausible boundary conditions and soft-tissue properties. By applying principal component analysis to the displacements of the FE mesh node points inside the gland, the simulated deformations are then used as training data to construct the SMM. The SMM is used to both predict the displacement field over the whole gland and constrain a deformable surface registration algorithm, given only a small number of target points on the surface of the deformed gland. Using 3D transrectal ultrasound images of the prostates of five patients, acquired before and after imposing a physical deformation, to evaluate the accuracy of predicted landmark displacements, the mean target registration error was found to be less than 1.9 mm.

Red blood cell dynamics: from cell deformation to ATP release.

PubMed

Wan, Jiandi; Forsyth, Alison M; Stone, Howard A

2011-10-01

The mechanisms of red blood cell (RBC) deformation under both static and dynamic, i.e., flow, conditions have been studied extensively since the mid 1960s. Deformation-induced biochemical reactions and possible signaling in RBCs, however, were proposed only fifteen years ago. Therefore, the fundamental relationship between RBC deformation and cellular signaling dynamics i.e., mechanotransduction, remains incompletely understood. Quantitative understanding of the mechanotransductive pathways in RBCs requires integrative studies of physical models of RBC deformation and cellular biochemical reactions. In this article we review the physical models of RBC deformation, spanning from continuum membrane mechanics to cellular skeleton dynamics under both static and flow conditions, and elaborate the mechanistic links involved in deformation-induced ATP release. This journal is © The Royal Society of Chemistry 2011

A note on stress-driven anisotropic diffusion and its role in active deformable media.

PubMed

Cherubini, Christian; Filippi, Simonetta; Gizzi, Alessio; Ruiz-Baier, Ricardo

2017-10-07

We introduce a new model to describe diffusion processes within active deformable media. Our general theoretical framework is based on physical and mathematical considerations, and it suggests to employ diffusion tensors directly influenced by the coupling with mechanical stress. The proposed generalised reaction-diffusion-mechanics model reveals that initially isotropic and homogeneous diffusion tensors turn into inhomogeneous and anisotropic quantities due to the intrinsic structure of the nonlinear coupling. We study the physical properties leading to these effects, and investigate mathematical conditions for its occurrence. Together, the mathematical model and the numerical results obtained using a mixed-primal finite element method, clearly support relevant consequences of stress-driven diffusion into anisotropy patterns, drifting, and conduction velocity of the resulting excitation waves. Our findings also indicate the applicability of this novel approach in the description of mechano-electric feedback in actively deforming bio-materials such as the cardiac tissue. Copyright © 2017. Published by Elsevier Ltd.

The impact of patient self assessment of deformity on HRQL in adults with scoliosis

PubMed Central

Tones, Megan J; Moss, Nathan D

2007-01-01

Background Body image and HRQL are significant issues for patients with scoliosis due to cosmetic deformity, physical and psychological symptoms, and treatment factors. A selective review of scoliosis literature revealed that self report measures of body image and HRQL share unreliable correlations with radiographic measures and clinician recommendations for surgery. However, current body image and HRQL measures do not indicate which aspects of scoliosis deformity are the most distressing for patients. The WRVAS is an instrument designed to evaluate patient self assessment of deformity, and may show some promise in identifying aspects of deformity most troubling to patients. Previous research on adolescents with scoliosis supports the use of the WRVAS as a clinical tool, as the instrument shares strong correlations with radiographic measures and quality of life instruments. There has been limited use of this instrument on adult populations. Methods The WRVAS and the SF-36v2, a HRQL measure, were administered to 71 adults with scoliosis, along with a form to report age and gender. Preliminary validation analyses were performed on the WRVAS (floor and ceiling effects, internal consistency and collinearity, correlations with the SF-36v2, and multiple regression with the WRVAS total score as the predictor, and SF-36v2 scores as outcomes). Results The psychometric properties of the WRVAS were acceptable. Older participants perceived their deformities as more severe than younger participants. More severe deformities were associated with lower scores on the Physical Component Summary Score of the SF-36v2. Total WRVAS score also predicted Physical Component Summary scores. Conclusion The results of the current study indicate that the WRVAS is a reliable tool to use with adult patients, and that patient self assessment of deformity shared a relationship with physical rather than psychological aspects of HRQL. The current and previous studies concur that revision of the WRVAS is necessary to more accurately represent the diversity of scoliosis deformities. Ability to identify disturbing aspects of deformity could potentially be improved by evaluating each WRVAS items against indicators of pain, physical/psychosocial function, and self image from previous measures such as the SRS, SF-36 or BSSQ-deformity. PMID:17935634

SU-E-J-92: Validating Dose Uncertainty Estimates Produced by AUTODIRECT, An Automated Program to Evaluate Deformable Image Registration Accuracy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, H; Chen, J; Pouliot, J

2015-06-15

Purpose: Deformable image registration (DIR) is a powerful tool with the potential to deformably map dose from one computed-tomography (CT) image to another. Errors in the DIR, however, will produce errors in the transferred dose distribution. We have proposed a software tool, called AUTODIRECT (automated DIR evaluation of confidence tool), which predicts voxel-specific dose mapping errors on a patient-by-patient basis. This work validates the effectiveness of AUTODIRECT to predict dose mapping errors with virtual and physical phantom datasets. Methods: AUTODIRECT requires 4 inputs: moving and fixed CT images and two noise scans of a water phantom (for noise characterization). Then,more » AUTODIRECT uses algorithms to generate test deformations and applies them to the moving and fixed images (along with processing) to digitally create sets of test images, with known ground-truth deformations that are similar to the actual one. The clinical DIR algorithm is then applied to these test image sets (currently 4) . From these tests, AUTODIRECT generates spatial and dose uncertainty estimates for each image voxel based on a Student’s t distribution. This work compares these uncertainty estimates to the actual errors made by the Velocity Deformable Multi Pass algorithm on 11 virtual and 1 physical phantom datasets. Results: For 11 of the 12 tests, the predicted dose error distributions from AUTODIRECT are well matched to the actual error distributions within 1–6% for 10 virtual phantoms, and 9% for the physical phantom. For one of the cases though, the predictions underestimated the errors in the tail of the distribution. Conclusion: Overall, the AUTODIRECT algorithm performed well on the 12 phantom cases for Velocity and was shown to generate accurate estimates of dose warping uncertainty. AUTODIRECT is able to automatically generate patient-, organ- , and voxel-specific DIR uncertainty estimates. This ability would be useful for patient-specific DIR quality assurance.« less

Phenomenological model for transient deformation based on state variables

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jackson, M S; Cho, C W; Alexopoulos, P

The state variable theory of Hart, while providing a unified description of plasticity-dominated deformation, exhibits deficiencies when it is applied to transient deformation phenomena at stresses below yield. It appears that the description of stored anelastic strain is oversimplified. Consideration of a simple physical picture based on continuum dislocation pileups suggests that the neglect of weak barriers to dislocation motion is the source of these inadequacies. An appropriately modified description incorporating such barriers then allows the construction of a macroscopic model including transient effects. Although the flow relations for the microplastic element required in the new theory are not known,more » tentative assignments may be made for such functions. The model then exhibits qualitatively correct behavior when tensile, loading-unloading, reverse loading, and load relaxation tests are simulated. Experimental procedures are described for determining the unknown parameters and functions in the new model.« less

Human motion analysis with detection of subpart deformations

NASA Astrophysics Data System (ADS)

Wang, Juhui; Lorette, Guy; Bouthemy, Patrick

1992-06-01

One essential constraint used in 3-D motion estimation from optical projections is the rigidity assumption. Because of muscle deformations in human motion, this rigidity requirement is often violated for some regions on the human body. Global methods usually fail to bring stable solutions. This paper presents a model-based approach to combating the effect of muscle deformations in human motion analysis. The approach developed is based on two main stages. In the first stage, the human body is partitioned into different areas, where each area is consistent with a general motion model (not necessarily corresponding to a physical existing motion pattern). In the second stage, the regions are eliminated under the hypothesis that they are not induced by a specific human motion pattern. Each hypothesis is generated by making use of specific knowledge about human motion. A global method is used to estimate the 3-D motion parameters in basis of valid segments. Experiments based on a cycling motion sequence are presented.

Steady state and a general scale law of deformation

NASA Astrophysics Data System (ADS)

Huang, Yan

2017-07-01

Steady state deformation has been characterized based on the experimental results for dilute single-phase aluminium alloys. It was found that although characteristic properties such as flow stress and grain size remained constant with time, a continuous loss of grain boundaries occurred as an essential feature at steady state. A physical model, which takes into account the activity of grain boundary dislocations, was developed to describe the kinetics of steady state deformation. According to this model, the steady state as a function of strain rate and temperature defines the limit of the conventional grain size and strength relationship, i.e., the Hall-Petch relation holds when the grain size is larger than that at the steady state, and an inverse Hall-Petch relation takes over if grain size is smaller than the steady state value. The transition between the two relationships relating grain size and strength is a phenomenon that depends on deformation conditions, rather than an intrinsic property as generally perceived. A general scale law of deformation is established accordingly.

Evaluation of a transient, simultaneous, arbitrary Lagrange-Euler based multi-physics method for simulating the mitral heart valve.

PubMed

Espino, Daniel M; Shepherd, Duncan E T; Hukins, David W L

2014-01-01

A transient multi-physics model of the mitral heart valve has been developed, which allows simultaneous calculation of fluid flow and structural deformation. A recently developed contact method has been applied to enable simulation of systole (the stage when blood pressure is elevated within the heart to pump blood to the body). The geometry was simplified to represent the mitral valve within the heart walls in two dimensions. Only the mitral valve undergoes deformation. A moving arbitrary Lagrange-Euler mesh is used to allow true fluid-structure interaction (FSI). The FSI model requires blood flow to induce valve closure by inducing strains in the region of 10-20%. Model predictions were found to be consistent with existing literature and will undergo further development.

On the mechanism of influence of explosive compounds: Destruction process on sensitivity of these compounds to mechanic impacts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Filin, V.P.; Loboyko, B.G.; Averin, A.N.

1996-05-01

The results of investigations into sensitivity of the HMX-based explosive compound samples to mechanic stimuli are shown in the presented report. As a result of experimental studies it was illustrated, that explosives deformation and destruction processes under mechanical stimuli are accompanied by occurrence of different electric phenomena. The hypothesis on possible influence of electric phenomena occurring under deformation and destruction on the mechanism of formation of zones with high density of energy is discussed in the report. {copyright} {ital 1996 American Institute of Physics.}

Droplet Deformation in an Extensional Flow: The Role of Surfactant Physical Chemistry

NASA Technical Reports Server (NTRS)

Stebe, Kathleen J.

1996-01-01

Surfactant-induced Marangoni effects strongly alter the stresses exerted along fluid particle interfaces. In low gravity processes, these stresses can dictate the system behavior. The dependence of Marangoni effects on surfactant physical chemistry is not understood, severely impacting our ability to predict and control fluid particle flows. A droplet in an extensional flow allows the controlled study of stretching and deforming interfaces. The deformations of the drop allow both Marangoni stresses, which resist tangential shear, and Marangoni elasticities, which resist surface dilatation, to develop. This flow presents an ideal model system for studying these effects. Prior surfactant-related work in this flow considered a linear dependence of the surface tension on the surface concentration, valid only at dilute surface concentrations, or a non-linear framework at concentrations sufficiently dilute that the linear approximation was valid. The linear framework becomes inadequate for several reasons. The finite dimensions of surfactant molecules must be taken into account with a model that includes surfaces saturation. Nonideal interactions between adsorbed surfactant molecules alter the partitioning of surfactant between the bulk and the interface, the dynamics of surfactant adsorptive/desorptive exchange, and the sensitivity of the surface tension to adsorbed surfactant. For example, cohesion between hydrocarbon chains favors strong adsorption. Cohesion also slows the rate of desorption from interfaces, and decreases the sensitivity of the surface tension to adsorbed surfactant. Strong cohesive interactions result in first order surface phase changes with a plateau in the surface tension vs surface concentration. Within this surface concentration range, the surface tension is decoupled from surface concentration gradients. We are engaged in the study of the role of surfactant physical chemistry in determining the Marangoni stresses on a drop in an extensional flow in a numerical and experimental program. Using surfactants whose dynamics and equilibrium behavior have been characterized in our laboratory, drop deformation will be studied in ground-based experiment. In an accompanying numerical study, predictive drop deformations will be determined based on the isotherm and equation of state determined in our laboratory. This work will improve our abilities to predict and control all fluid particle flows.

Modeling and control of a dielectric elastomer actuator

NASA Astrophysics Data System (ADS)

Gupta, Ujjaval; Gu, Guo-Ying; Zhu, Jian

2016-04-01

The emerging field of soft robotics offers the prospect of applying soft actuators as artificial muscles in the robots, replacing traditional actuators based on hard materials, such as electric motors, piezoceramic actuators, etc. Dielectric elastomers are one class of soft actuators, which can deform in response to voltage and can resemble biological muscles in the aspects of large deformation, high energy density and fast response. Recent research into dielectric elastomers has mainly focused on issues regarding mechanics, physics, material designs and mechanical designs, whereas less importance is given to the control of these soft actuators. Strong nonlinearities due to large deformation and electromechanical coupling make control of the dielectric elastomer actuators challenging. This paper investigates feed-forward control of a dielectric elastomer actuator by using a nonlinear dynamic model. The material and physical parameters in the model are identified by quasi-static and dynamic experiments. A feed-forward controller is developed based on this nonlinear dynamic model. Experimental evidence shows that this controller can control the soft actuator to track the desired trajectories effectively. The present study confirms that dielectric elastomer actuators are capable of being precisely controlled with the nonlinear dynamic model despite the presence of material nonlinearity and electromechanical coupling. It is expected that the reported results can promote the applications of dielectric elastomer actuators to soft robots or biomimetic robots.

On the free-precession candidate PSR B1828-11: Evidence for increasing deformation

NASA Astrophysics Data System (ADS)

Ashton, G.; Jones, D. I.; Prix, R.

2017-05-01

We observe that the periodic variations in spin-down rate and beamwidth of the radio pulsar PSR B1828-11 are getting faster. In the context of a free precession model, this corresponds to a decrease in the precession period Pfp. We investigate how a precession model can account for such a decrease in Pfp, in terms of an increase over time in the absolute biaxial deformation (|ɛp| ˜ 10-8) of this pulsar. We perform a Bayesian model comparison against the 'base' precession model (with constant ɛp) developed in Ashton et al., and we obtain decisive odds in favour of a time-varying deformation. We study two types of time variation: (I) a linear drift with a posterior estimate of \\dot{ɛ }_p{˜ }10^{-18} s^{-1} and odds of 1075 compared to the base model, and (II) N discrete positive jumps in ɛp with very similar odds to the linear ɛp drift model. The physical mechanism explaining this behaviour is unclear, but the observation could provide a crucial probe of the interior physics of neutron stars. We also place an upper bound on the rate at which the precessional motion is damped, and translate this into a bound on a dissipative mutual friction-type coupling between the star's crust and core.

Using the PhysX engine for physics-based virtual surgery with force feedback.

PubMed

Maciel, Anderson; Halic, Tansel; Lu, Zhonghua; Nedel, Luciana P; De, Suvranu

2009-09-01

The development of modern surgical simulators is highly challenging, as they must support complex simulation environments. The demand for higher realism in such simulators has driven researchers to adopt physics-based models, which are computationally very demanding. This poses a major problem, since real-time interactions must permit graphical updates of 30 Hz and a much higher rate of 1 kHz for force feedback (haptics). Recently several physics engines have been developed which offer multi-physics simulation capabilities, including rigid and deformable bodies, cloth and fluids. While such physics engines provide unique opportunities for the development of surgical simulators, their higher latencies, compared to what is necessary for real-time graphics and haptics, offer significant barriers to their use in interactive simulation environments. In this work, we propose solutions to this problem and demonstrate how a multimodal surgical simulation environment may be developed based on NVIDIA's PhysX physics library. Hence, models that are undergoing relatively low-frequency updates in PhysX can exist in an environment that demands much higher frequency updates for haptics. We use a collision handling layer to interface between the physical response provided by PhysX and the haptic rendering device to provide both real-time tissue response and force feedback. Our simulator integrates a bimanual haptic interface for force feedback and per-pixel shaders for graphics realism in real time. To demonstrate the effectiveness of our approach, we present the simulation of the laparoscopic adjustable gastric banding (LAGB) procedure as a case study. To develop complex and realistic surgical trainers with realistic organ geometries and tissue properties demands stable physics-based deformation methods, which are not always compatible with the interaction level required for such trainers. We have shown that combining different modelling strategies for behaviour, collision and graphics is possible and desirable. Such multimodal environments enable suitable rates to simulate the major steps of the LAGB procedure.

Models of determining deformations

NASA Astrophysics Data System (ADS)

Gladilin, V. N.

2016-12-01

In recent years, a lot of functions designed to determine deformation values that occur mostly as a result of settlement of structures and industrial equipment. Some authors suggest such advanced mathematical functions approximating deformations as general methods for the determination of deformations. The article describes models of deformations as physical processes. When comparing static, cinematic and dynamic models, it was found that the dynamic model reflects the deformation of structures and industrial equipment most reliably.

Brittle to ductile transition in a model of sheared granular materials

NASA Astrophysics Data System (ADS)

Elbanna, Ahmed; Ma, Xiao

Understanding the fundamental mechanisms of deformation and failure in sheared fault gouge is critical for the development of physics-based earthquake rupture simulations that are becoming an essential ingredient in next generation hazard and risk models. To that end, we use the shear transformation zone (STZ) theory, a non-equilibrium statistical thermodynamics framework to describe viscoplastic deformation and localization in gouge materials as a first step towards developing multiscale models for earthquake source processes that are informed by high-resolution fault zone physics. We will describe an implementation of this theory in a 2D/3D finite element framework, accounting for finite deformation, under both axial and shear loading and for dry and saturated conditions. We examine conditions under which a localized shear band may form and show that the initial value of disorder plays an important role. In particular, our simulations suggest that if the material is more compact initially, the behavior is more brittle and the plastic deformation localizes with large strength drop. On the other hand, an initially loose material will show a more ductile response and the plastic deformations will be distributed more broadly. We will further show that incorporation of pore fluids alters the localization pattern and changes the stress slip response due to coupling between gouge volume changes (compaction and dilation) and pore pressure build up. Finally, we discuss the implications of our model for gouge friction and dynamic weakening.

Towards a physics-based multiscale modelling of the electro-mechanical coupling in electro-active polymers.

PubMed

Cohen, Noy; Menzel, Andreas; deBotton, Gal

2016-02-01

Owing to the increasing number of industrial applications of electro-active polymers (EAPs), there is a growing need for electromechanical models which accurately capture their behaviour. To this end, we compare the predicted behaviour of EAPs undergoing homogeneous deformations according to three electromechanical models. The first model is a phenomenological continuum-based model composed of the mechanical Gent model and a linear relationship between the electric field and the polarization. The electrical and the mechanical responses according to the second model are based on the physical structure of the polymer chain network. The third model incorporates a neo-Hookean mechanical response and a physically motivated microstructurally based long-chains model for the electrical behaviour. In the microstructural-motivated models, the integration from the microscopic to the macroscopic levels is accomplished by the micro-sphere technique. Four types of homogeneous boundary conditions are considered and the behaviours determined according to the three models are compared. For the microstructurally motivated models, these analyses are performed and compared with the widely used phenomenological model for the first time. Some of the aspects revealed in this investigation, such as the dependence of the intensity of the polarization field on the deformation, highlight the need for an in-depth investigation of the relationships between the structure and the behaviours of the EAPs at the microscopic level and their overall macroscopic response.

Structure for identifying, locating and quantifying physical phenomena

DOEpatents

Richardson, John G.

2006-10-24

A method and system for detecting, locating and quantifying a physical phenomena such as strain or a deformation in a structure. A minimum resolvable distance along the structure is selected and a quantity of laterally adjacent conductors is determined. Each conductor includes a plurality of segments coupled in series which define the minimum resolvable distance along the structure. When a deformation occurs, changes in the defined energy transmission characteristics along each conductor are compared to determine which segment contains the deformation.

Method and apparatus for identifying, locating and quantifying physical phenomena and structure including same

DOEpatents

Richardson, John G.

2006-01-24

A method and system for detecting, locating and quantifying a physical phenomena such as strain or a deformation in a structure. A minimum resolvable distance along the structure is selected and a quantity of laterally adjacent conductors is determined. Each conductor includes a plurality of segments coupled in series which define the minimum resolvable distance along the structure. When a deformation occurs, changes in the defined energy transmission characteristics along each conductor are compared to determine which segment contains the deformation.

Rock Physical Interpretation of the Relationship between Dynamic and Static Young's Moduli of Sedimentary Rocks

NASA Astrophysics Data System (ADS)

Takahashi, T.

2017-12-01

The static Young's modulus (deformability) of a rock is indispensable for designing and constructing tunnels, dams and underground caverns in civil engineering. Static Young's modulus which is an elastic modulus at large strain level is usually obtained with the laboratory tests of rock cores sampled in boreholes drilled in a rock mass. A deformability model of the entire rock mass is then built by extrapolating the measurements based on a rock mass classification obtained in geological site characterization. However, model-building using data obtained from a limited number of boreholes in the rock mass, especially a complex rock mass, may cause problems in the accuracy and reliability of the model. On the other hand, dynamic Young's modulus which is the modulus at small strain level can be obtained from seismic velocity. If dynamic Young's modulus can be rationally converted to static one, a seismic velocity model by the seismic method can be effectively used to build a deformability model of the rock mass. In this study, we have, therefore, developed a rock physics model (Mavko et al., 2009) to estimate static Young's modulus from dynamic one for sedimentary rocks. The rock physics model has been generally applied to seismic properties at small strain level. In the proposed model, however, the sandy shale model, one of rock physics models, is extended for modeling the static Young's modulus at large strain level by incorporating the mixture of frictional and frictionless grain contacts into the Hertz-Mindlin model. The proposed model is verified through its application to the dynamic Young's moduli derived from well log velocities and static Young's moduli measured in the tri-axial compression tests of rock cores sampled in the same borehole as the logs were acquired. This application proves that the proposed rock physics model can be possibly used to estimate static Young's modulus (deformability) which is required in many types of civil engineering applications from seismically derived dynamic Young's modulus. References:Mavko, G., Mukerji, T. and Dvorkin, J., 2009, The Rock Physics Handbook, 2nd Edition, Cambridge University Press, Cambridge.

Using Airborne Radar Stratigraphy to Model Surface Accumulation Anomaly and Basal Control over Deformed Basal Ice in Greenland

NASA Astrophysics Data System (ADS)

Das, I.; Bell, R. E.; Creyts, T. T.; Wolovick, M.

2013-12-01

Large deformed ice structures have been imaged at the base of northern Greenland ice sheet by IceBridge airborne radar. Numerous deformed structures lie along the base of both Petermann Glacier and Northeast Ice stream catchments covering 10-13% of the catchment area. These structures may be combinations of basal freeze-on and folded ice that overturns and inverts stratigraphy. In the interior, where the ice velocity is low, the radar imaged height of the deformed structures are frequently a significant fraction of the ice thickness. They are related to basal freeze on and stick-slip at the base of the ice sheet and may be triggered by subglacial water, sediments or local geological conditions. The larger ones (at times up to 700 m thick and 140 km long) perturb the ice stratigraphy and create prominent undulations on the ice surface and modify the local surface mass balance. Here, we investigate the relationship between the deformed structures and surface processes using shallow and deep ice radar stratigraphy. The surface undulations caused by the deformed structures modulate the pattern of local surface snow accumulation. Using normalized differences of several near-surface stratigraphic layers, we have calculated the accumulation anomaly over these deformed structures. The accumulation anomalies can be as high as 20% of the local surface accumulation over some of the larger surface depressions caused by these deformed structures. We observe distinct differences in the phases of the near-surface internal layers on the Petermann and Northeast catchments. These differences indicate that the deformed bodies over Petermann are controlled by conditions at the bed different from the Northeast Ice stream. The distinctly different near-surface stratigraphy over the deformed structures in the Petermann and Northeast catchments have opened up a number of questions including their formation and how they influence the ice dynamics, ice stratigraphy and surface mass balance. In this study we will model the different physical conditions at the bed and ice rheology from their distinct signatures in the near-surface strata. The results will identify the distinct mechanisms that form these bodies and their control over the surface morphology and snow accumulation.

Incorporation of a laser range scanner into image-guided liver surgery: surface acquisition, registration, and tracking.

PubMed

Cash, David M; Sinha, Tuhin K; Chapman, William C; Terawaki, Hiromi; Dawant, Benoit M; Galloway, Robert L; Miga, Michael I

2003-07-01

As image guided surgical procedures become increasingly diverse, there will be more scenarios where point-based fiducials cannot be accurately localized for registration and rigid body assumptions no longer hold. As a result, procedures will rely more frequently on anatomical surfaces for the basis of image alignment and will require intraoperative geometric data to measure and compensate for tissue deformation in the organ. In this paper we outline methods for which a laser range scanner may be used to accomplish these tasks intraoperatively. A laser range scanner based on the optical principle of triangulation acquires a dense set of three-dimensional point data in a very rapid, noncontact fashion. Phantom studies were performed to test the ability to link range scan data with traditional modes of image-guided surgery data through localization, registration, and tracking in physical space. The experiments demonstrate that the scanner is capable of localizing point-based fiducials to within 0.2 mm and capable of achieving point and surface based registrations with target registration error of less than 2.0 mm. Tracking points in physical space with the range scanning system yields an error of 1.4 +/- 0.8 mm. Surface deformation studies were performed with the range scanner in order to determine if this device was capable of acquiring enough information for compensation algorithms. In the surface deformation studies, the range scanner was able to detect changes in surface shape due to deformation comparable to those detected by tomographic image studies. Use of the range scanner has been approved for clinical trials, and an initial intraoperative range scan experiment is presented. In all of these studies, the primary source of error in range scan data is deterministically related to the position and orientation of the surface within the scanner's field of view. However, this systematic error can be corrected, allowing the range scanner to provide a rapid, robust method of acquiring anatomical surfaces intraoperatively.

Changes in the physical and mechanical properties of Al-Mg alloy processed by severe plastic deformation

NASA Astrophysics Data System (ADS)

Krasnoveikin, V. A.; Kozulin, A. A.; Skripnyak, V. A.; Moskvichev, E. N.; Borodulin, D. A.

2017-12-01

This paper presents the results of studies into the effect of severe plastic deformation on the microstructure, physical and mechanical properties of coarse-grained Al-Mg alloy 1560 in the as-received state with an average grain size of 50 µm. Severe plastic deformation is performed by four-pass equal channel angular pressing (ECAP), which results in the formation of an ultrafine-grained structure with an average grain size of 3 µm in the alloy. Analysis of experimental data revealed that the physical and mechanical properties change significantly after severe plastic deformation. The microhardness of the ECAPed alloy increases by 50%, tensile yield strength by 80%, and ultimate strength by 44% in comparison with these parameters in the as-received state. The constants of approximating functions have been determined for the experimental stress-strain curves of the alloy specimens in the as-received and ECAPed states.

Optimizing Cubature for Efficient Integration of Subspace Deformations

PubMed Central

An, Steven S.; Kim, Theodore; James, Doug L.

2009-01-01

We propose an efficient scheme for evaluating nonlinear subspace forces (and Jacobians) associated with subspace deformations. The core problem we address is efficient integration of the subspace force density over the 3D spatial domain. Similar to Gaussian quadrature schemes that efficiently integrate functions that lie in particular polynomial subspaces, we propose cubature schemes (multi-dimensional quadrature) optimized for efficient integration of force densities associated with particular subspace deformations, particular materials, and particular geometric domains. We support generic subspace deformation kinematics, and nonlinear hyperelastic materials. For an r-dimensional deformation subspace with O(r) cubature points, our method is able to evaluate subspace forces at O(r2) cost. We also describe composite cubature rules for runtime error estimation. Results are provided for various subspace deformation models, several hyperelastic materials (St.Venant-Kirchhoff, Mooney-Rivlin, Arruda-Boyce), and multimodal (graphics, haptics, sound) applications. We show dramatically better efficiency than traditional Monte Carlo integration. CR Categories: I.6.8 [Simulation and Modeling]: Types of Simulation—Animation, I.3.5 [Computer Graphics]: Computational Geometry and Object Modeling—Physically based modeling G.1.4 [Mathematics of Computing]: Numerical Analysis—Quadrature and Numerical Differentiation PMID:19956777

Validation of model-based deformation correction in image-guided liver surgery via tracked intraoperative ultrasound: preliminary method and results

NASA Astrophysics Data System (ADS)

Clements, Logan W.; Collins, Jarrod A.; Wu, Yifei; Simpson, Amber L.; Jarnagin, William R.; Miga, Michael I.

2015-03-01

Soft tissue deformation represents a significant error source in current surgical navigation systems used for open hepatic procedures. While numerous algorithms have been proposed to rectify the tissue deformation that is encountered during open liver surgery, clinical validation of the proposed methods has been limited to surface based metrics and sub-surface validation has largely been performed via phantom experiments. Tracked intraoperative ultrasound (iUS) provides a means to digitize sub-surface anatomical landmarks during clinical procedures. The proposed method involves the validation of a deformation correction algorithm for open hepatic image-guided surgery systems via sub-surface targets digitized with tracked iUS. Intraoperative surface digitizations were acquired via a laser range scanner and an optically tracked stylus for the purposes of computing the physical-to-image space registration within the guidance system and for use in retrospective deformation correction. Upon completion of surface digitization, the organ was interrogated with a tracked iUS transducer where the iUS images and corresponding tracked locations were recorded. After the procedure, the clinician reviewed the iUS images to delineate contours of anatomical target features for use in the validation procedure. Mean closest point distances between the feature contours delineated in the iUS images and corresponding 3-D anatomical model generated from the preoperative tomograms were computed to quantify the extent to which the deformation correction algorithm improved registration accuracy. The preliminary results for two patients indicate that the deformation correction method resulted in a reduction in target error of approximately 50%.

Physics-Based Crystal Plasticity Modeling of Single Crystal Niobium

NASA Astrophysics Data System (ADS)

Maiti, Tias

Crystal plasticity models based on thermally activated dislocation kinetics has been successful in predicting the deformation behavior of crystalline materials, particularly in face-centered cubic (fcc) metals. In body-centered cubic (bcc) metals success has been limited owing to ill-defined slip planes. The flow stress of a bcc metal is strongly dependent on temperature and orientation due to the non-planar splitting of a/2 screw dislocations. As a consequence of this, bcc metals show two unique deformation characteristics: (a) thermally-activated glide of screw dislocations--the motion of screw components with their non-planar core structure at the atomistic level occurs even at low stress through the nucleation (assisted by thermal activation) and lateral propagation of dislocation kink pairs; (b) break-down of the Schmid Law, where dislocation slip is driven only by the resolved shear stress. Since the split dislocation core has to constrict for a kink pair formation (and propagation), the non-planarity of bcc screw dislocation cores entails an influence of (shear) stress components acting on planes other than the primary glide plane on their mobility. Another consequence of the asymmetric core splitting on the glide plane is a direction-sensitive slip resistance, which is termed twinning/atwinning sense of shear and should be taken into account when developing constitutive models. Modeling thermally-activated flow including the above-mentioned non-Schmid effects in bcc metals has been the subject of much work, starting in the 1980s and gaining increased interest in recent times. The majority of these works focus on single crystal deformation of commonly used metals such as Iron (Fe), Molybdenum (Mo), and Tungsten (W), while very few published studies address deformation behavior in Niobium (Nb). Most of the work on Nb revolves around fitting parameters of phenomenological descriptions, which do not capture adequately the macroscopic multi-stage hardening behavior and evolution of crystallographic texture from a physical point of view. Therefore, we aim to develop a physics-based crystal plasticity model that can capture these effects as a function of grain orientations, microstructure parameters, and temperature. To achieve this goal, first, a new dilatational constitutive model is developed for simulating the deformation of non-compact geometries (foams or geometries with free surfaces) using the spectral method. The model has been used to mimic the void-growth behavior of a biaxially loaded plate with a circular inclusion. The results show that the proposed formulation provides a much better description of void-like behavior compared to the pure elastic behavior of voids. Using the developed dilatational framework, periodic boundary conditions arising from the spectral solver has been relaxed to study the tensile deformation behavior of dogbone-shaped Nb single crystals. Second, a dislocation density-based constitutive model with storage and recovery laws derived from Discrete Dislocation Dynamics (DDD) is implemented to model multi-stage strain hardening. The influence of pre-deformed dislocation content, dislocation interaction strengths and mean free path on stage II hardening is then simulated and compared with in-situ tensile experiments.

The properties of Q-deformed hyperbolic and trigonometric functions in quantum deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deta, U. A., E-mail: utamaalan@yahoo.co.id, E-mail: utamadeta@unesa.ac.id; Suparmi

2015-09-30

Quantum deformation has been studied due to its relation with applications in nuclear physics, conformal field theory, and statistical-quantum theory. The q-deformation of hyperbolic function was introduced by Arai. The application of q-deformed functions has been widely used in quantum mechanics. The properties of this two kinds of system explained in this paper including their derivative. The graph of q-deformed functions presented using Matlab. The special case is given for modified Poschl-Teller plus q-deformed Scarf II trigonometry potentials.

Geophysical study of the structure and processes of the continental convergence zones: Alpine-Himalayan Belt

NASA Technical Reports Server (NTRS)

Toksoz, M. Nafi; Molnar, Peter

1988-01-01

Intracontinental deformation occurrence and the processes and physical parameters that control the rates and styles of deformation were examined. Studies addressing specific mechanical aspects of deformation were reviewed and the studies of deformation and of the structure of specific areas were studied considering the strength of the material and the gravitational effect.

Facial animation on an anatomy-based hierarchical face model

NASA Astrophysics Data System (ADS)

Zhang, Yu; Prakash, Edmond C.; Sung, Eric

2003-04-01

In this paper we propose a new hierarchical 3D facial model based on anatomical knowledge that provides high fidelity for realistic facial expression animation. Like real human face, the facial model has a hierarchical biomechanical structure, incorporating a physically-based approximation to facial skin tissue, a set of anatomically-motivated facial muscle actuators and underlying skull structure. The deformable skin model has multi-layer structure to approximate different types of soft tissue. It takes into account the nonlinear stress-strain relationship of the skin and the fact that soft tissue is almost incompressible. Different types of muscle models have been developed to simulate distribution of the muscle force on the skin due to muscle contraction. By the presence of the skull model, our facial model takes advantage of both more accurate facial deformation and the consideration of facial anatomy during the interactive definition of facial muscles. Under the muscular force, the deformation of the facial skin is evaluated using numerical integration of the governing dynamic equations. The dynamic facial animation algorithm runs at interactive rate with flexible and realistic facial expressions to be generated.

Quantification of focal adhesion dynamics of cell movement based on cell-induced collagen matrix deformation using second-harmonic generation microscopy.

PubMed

Kang, Yong Guk; Jang, Hwanseok; Yang, Taeseok Daniel; Notbohm, Jacob; Choi, Youngwoon; Park, Yongdoo; Kim, Beop-Min

2018-06-01

Mechanical interactions of living cells with the surrounding environment via focal adhesion (FA) in three dimensions (3-D) play a key role in dynamic biological events, such as tissue regeneration, wound healing, and cancer invasion. Recently, several methods for observing 3-D cell-extracellular matrix (ECM) interactions have been reported, lacking solid and quantitative analysis on the dynamics of the physical interaction between the cell and the ECM. We measured the submicron displacements of ECM deformation in 3-D due to protrusion-retraction dynamics during cell migration, using second-harmonic generation without labeling the matrix structures. We then quantitatively analyzed the mechanical deformation between the ECM and the cells based on spatiotemporal volumetric correlations. The greatest deformations within the collagen matrix were found to occur at sites of colocalization of the FA site-related proteins vinculin and actin, which confirms that FA sites play a critical role in living cells within the ECM as a point for adhesion, traction, and migration. We believe that this modality can be used in studies of cell-ECM interaction during angiogenesis, wound healing, and metastasis. (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE).

A proposal of monitoring and forecasting system for crustal activity in and around Japan using a large-scale high-fidelity finite element simulation codes

NASA Astrophysics Data System (ADS)

Hori, Takane; Ichimura, Tsuyoshi; Takahashi, Narumi

2017-04-01

Here we propose a system for monitoring and forecasting of crustal activity, such as spatio-temporal variation in slip velocity on the plate interface including earthquakes, seismic wave propagation, and crustal deformation. Although, we can obtain continuous dense surface deformation data on land and partly on the sea floor, the obtained data are not fully utilized for monitoring and forecasting. It is necessary to develop a physics-based data analysis system including (1) a structural model with the 3D geometry of the plate interface and the material property such as elasticity and viscosity, (2) calculation code for crustal deformation and seismic wave propagation using (1), (3) inverse analysis or data assimilation code both for structure and fault slip using (1) & (2). To accomplish this, it is at least necessary to develop highly reliable large-scale simulation code to calculate crustal deformation and seismic wave propagation for 3D heterogeneous structure. Actually, Ichimura et al. (2015, SC15) has developed unstructured FE non-linear seismic wave simulation code, which achieved physics-based urban earthquake simulation enhanced by 1.08 T DOF x 6.6 K time-step. Ichimura et al. (2013, GJI) has developed high fidelity FEM simulation code with mesh generator to calculate crustal deformation in and around Japan with complicated surface topography and subducting plate geometry for 1km mesh. Fujita et al. (2016, SC16) has improved the code for crustal deformation and achieved 2.05 T-DOF with 45m resolution on the plate interface. This high-resolution analysis enables computation of change of stress acting on the plate interface. Further, for inverse analyses, Errol et al. (2012, BSSA) has developed waveform inversion code for modeling 3D crustal structure, and Agata et al. (2015, AGU Fall Meeting) has improved the high-fidelity FEM code to apply an adjoint method for estimating fault slip and asthenosphere viscosity. Hence, we have large-scale simulation and analysis tools for monitoring. Furthermore, we are developing the methods for forecasting the slip velocity variation on the plate interface. Basic concept is given in Hori et al. (2014, Oceanography) introducing ensemble based sequential data assimilation procedure. Although the prototype described there is for elastic half space model, we are applying it for 3D heterogeneous structure with the high-fidelity FE model.

A Correction to the Stress-Strain Curve During Multistage Hot Deformation of 7150 Aluminum Alloy Using Instantaneous Friction Factors

NASA Astrophysics Data System (ADS)

Jiang, Fulin; Tang, Jie; Fu, Dinfa; Huang, Jianping; Zhang, Hui

2018-04-01

Multistage stress-strain curve correction based on an instantaneous friction factor was studied for axisymmetric uniaxial hot compression of 7150 aluminum alloy. Experimental friction factors were calculated based on continuous isothermal axisymmetric uniaxial compression tests at various deformation parameters. Then, an instantaneous friction factor equation was fitted by mathematic analysis. After verification by comparing single-pass flow stress correction with traditional average friction factor correction, the instantaneous friction factor equation was applied to correct multistage stress-strain curves. The corrected results were reasonable and validated by multistage relative softening calculations. This research provides a broad potential for implementing axisymmetric uniaxial compression in multistage physical simulations and friction optimization in finite element analysis.

Knowledge representation of rock plastic deformation

NASA Astrophysics Data System (ADS)

Davarpanah, Armita; Babaie, Hassan

2017-04-01

The first iteration of the Rock Plastic Deformation (RPD) ontology models the semantics of the dynamic physical and chemical processes and mechanisms that occur during the deformation of the generally inhomogeneous polycrystalline rocks. The ontology represents the knowledge about the production, reconfiguration, displacement, and consumption of the structural components that participate in these processes. It also formalizes the properties that are known by the structural geology and metamorphic petrology communities to hold between the instances of the spatial components and the dynamic processes, the state and system variables, the empirical flow laws that relate the variables, and the laboratory testing conditions and procedures. The modeling of some of the complex physio-chemical, mathematical, and informational concepts and relations of the RPD ontology is based on the class and property structure of some well-established top-level ontologies. The flexible and extensible design of the initial version of the RPD ontology allows it to develop into a model that more fully represents the knowledge of plastic deformation of rocks under different spatial and temporal scales in the laboratory and in solid Earth. The ontology will be used to annotate the datasets related to the microstructures and physical-chemical processes that involve them. This will help the autonomous and globally distributed communities of experimental structural geologists and metamorphic petrologists to coherently and uniformly distribute, discover, access, share, and use their data through automated reasoning and enhanced data integration and software interoperability.

Highly viscous liquid crystalline mixtures: the alternative to liquid crystalline elastomers

NASA Astrophysics Data System (ADS)

Shibaev, Petr; Schlesier, Cristina; Newman, Leah; McDonald, Scott

2012-02-01

Novel highly viscous liquid crystalline materials based on mixtures of glass forming oligomers and low molar mass liquid crystals were recently designed [1, 2] and studied. In this communication the novel data are presented, the analysis and discussion are extended. It is shown that viscoelastic properties of the materials are due to the physical entanglements between cyclic oligomers and low molar mass mesogens, not due to the chemical crosslinks between molecular moities. However, the mechanical properties of these viscoelastic materials resemble those of chemically crosslinked elastomers (elasticity and reversibility of deformations). The properties of chiral and non-chiral materials loaded with ferromagnetic nanoparticles are discussed in detail. Cholesteric materials undergo gigantic color changes in the wide spectral range under the deformation that allows distant detection of deformation and determination the anisotropy of deformation and its type. The materials doped with laser dyes become mechanically tunable lasers themselves and emit coherent light while pumped by external laser. A simple model is suggested to account for the observed effects; physical properties of the novel materials and liquid crystalline elastomers are compared and discussed. [4pt] [1] P.V. Shibaev, C. Schlesier, R. Uhrlass, S. Woodward, E. Hanelt, Liquid Crystals, 37:12, 1601-1604 [0pt] [2] P.V. Shibaev, P. Riverra, D. Teter, S. Marsico, M. Sanzari, V. Ramakrishnan, E. Hanelt, Optics Express, 16, 2965 (2008)

Efficient inversion of volcano deformation based on finite element models : An application to Kilauea volcano, Hawaii

NASA Astrophysics Data System (ADS)

Charco, María; González, Pablo J.; Galán del Sastre, Pedro

2017-04-01

The Kilauea volcano (Hawaii, USA) is one of the most active volcanoes world-wide and therefore one of the better monitored volcanoes around the world. Its complex system provides a unique opportunity to investigate the dynamics of magma transport and supply. Geodetic techniques, as Interferometric Synthetic Aperture Radar (InSAR) are being extensively used to monitor ground deformation at volcanic areas. The quantitative interpretation of such surface ground deformation measurements using geodetic data requires both, physical modelling to simulate the observed signals and inversion approaches to estimate the magmatic source parameters. Here, we use synthetic aperture radar data from Sentinel-1 radar interferometry satellite mission to image volcano deformation sources during the inflation along Kilauea's Southwest Rift Zone in April-May 2015. We propose a Finite Element Model (FEM) for the calculation of Green functions in a mechanically heterogeneous domain. The key aspect of the methodology lies in applying the reciprocity relationship of the Green functions between the station and the source for efficient numerical inversions. The search for the best-fitting magmatic (point) source(s) is generally conducted for an array of 3-D locations extending below a predefined volume region. However, our approach allows to reduce the total number of Green functions to the number of the observation points by using the, above mentioned, reciprocity relationship. This new methodology is able to accurately represent magmatic processes using physical models capable of simulating volcano deformation in non-uniform material properties distribution domains, which eventually will lead to better description of the status of the volcano.

A new physical model with multilayer architecture for facial expression animation using dynamic adaptive mesh.

PubMed

Zhang, Yu; Prakash, Edmond C; Sung, Eric

2004-01-01

This paper presents a new physically-based 3D facial model based on anatomical knowledge which provides high fidelity for facial expression animation while optimizing the computation. Our facial model has a multilayer biomechanical structure, incorporating a physically-based approximation to facial skin tissue, a set of anatomically-motivated facial muscle actuators, and underlying skull structure. In contrast to existing mass-spring-damper (MSD) facial models, our dynamic skin model uses the nonlinear springs to directly simulate the nonlinear visco-elastic behavior of soft tissue and a new kind of edge repulsion spring is developed to prevent collapse of the skin model. Different types of muscle models have been developed to simulate distribution of the muscle force applied on the skin due to muscle contraction. The presence of the skull advantageously constrain the skin movements, resulting in more accurate facial deformation and also guides the interactive placement of facial muscles. The governing dynamics are computed using a local semi-implicit ODE solver. In the dynamic simulation, an adaptive refinement automatically adapts the local resolution at which potential inaccuracies are detected depending on local deformation. The method, in effect, ensures the required speedup by concentrating computational time only where needed while ensuring realistic behavior within a predefined error threshold. This mechanism allows more pleasing animation results to be produced at a reduced computational cost.

[Preliminary application of an improved Demons deformable registration algorithm in tumor radiotherapy].

PubMed

Zhou, Lu; Zhen, Xin; Lu, Wenting; Dou, Jianhong; Zhou, Linghong

2012-01-01

To validate the efficiency of an improved Demons deformable registration algorithm and evaluate its application in registration of the treatment image and the planning image in image-guided radiotherapy (IGRT). Based on Brox's gradient constancy assumption and Malis's efficient second-order minimization algorithm, a grey value gradient similarity term was added into the original energy function, and a formula was derived to calculate the update of transformation field. The limited Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm was used to optimize the energy function for automatic determination of the iteration number. The proposed algorithm was validated using mathematically deformed images, physically deformed phantom images and clinical tumor images. Compared with the original Additive Demons algorithm, the improved Demons algorithm achieved a higher precision and a faster convergence speed. Due to the influence of different scanning conditions in fractionated radiation, the density range of the treatment image and the planning image may be different. The improved Demons algorithm can achieve faster and more accurate radiotherapy.

Strain buildup and release, earthquake prediction and selection of VLB sites for the margins of the North Pacific

NASA Technical Reports Server (NTRS)

Scholz, C. H.; Johnson, T.

1976-01-01

Microearthquake studies of the southern section of the San Andreas fault system were conducted in order to elucidate the role of known but little studied complications in the fault system which could affect the SAFE measurement. Data reduction from microearthquake studies in Baja California, Mexico, was completed. In addition, styles of deformation on the Alpine fault in New Zealand and on the San Andreas fault were compared. Sections of these faults with comparable physical characteristics seem to deform in a similar manner, indicating that deformation style is controlled by certain fundamental relations and will continue in the future. The geology of eastern New Guinea is also discussed. Deformation in the area is proposed to be related to collision of a series of island arcs with central New Guinea, which is part of the Australian continent. Among other unusual properties, eastern New Guinea contains the highest anomaly of the gravimetrically determined geoid based on GEM 6 and surface gravity data.

Augmented reality visualization of deformable tubular structures for surgical simulation.

PubMed

Ferrari, Vincenzo; Viglialoro, Rosanna Maria; Nicoli, Paola; Cutolo, Fabrizio; Condino, Sara; Carbone, Marina; Siesto, Mentore; Ferrari, Mauro

2016-06-01

Surgical simulation based on augmented reality (AR), mixing the benefits of physical and virtual simulation, represents a step forward in surgical training. However, available systems are unable to update the virtual anatomy following deformations impressed on actual anatomy. A proof-of-concept solution is described providing AR visualization of hidden deformable tubular structures using nitinol tubes sensorized with electromagnetic sensors. This system was tested in vitro on a setup comprised of sensorized cystic, left and right hepatic, and proper hepatic arteries. In the trial session, the surgeon deformed the tubular structures with surgical forceps in 10 positions. The mean, standard deviation, and maximum misalignment between virtual and real arteries were 0.35, 0.22, and 0.99 mm, respectively. The alignment accuracy obtained demonstrates the feasibility of the approach, which can be adopted in advanced AR simulations, in particular as an aid to the identification and isolation of tubular structures. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

Strain-based diffusion solver for realistic representation of diffusion front in physical reactions

PubMed Central

2017-01-01

When simulating fluids, such as water or fire, interacting with solids, it is a challenging problem to represent details of diffusion front in physical reaction. Previous approaches commonly use isotropic or anisotropic diffusion to model the transport of a quantity through a medium or long interface. We have identified unrealistic monotonous patterns with previous approaches and therefore, propose to extend these approaches by integrating the deformation of the material with the diffusion process. Specifically, stretching deformation represented by strain is incorporated in a divergence-constrained diffusion model. A novel diffusion model is introduced to increase the global rate at which the solid acquires relevant quantities, such as heat or saturation. This ensures that the equations describing fluid flow are linked to the change of solid geometry, and also satisfy the divergence-free condition. Experiments show that our method produces convincing results. PMID:28448591

Innovative Design and Processing of Multi-Functional Adaptive Structural Materials

DTIC Science & Technology

2014-01-09

instability, Journal of the Mechanics and Physics of Solids, (02 2013): 611. doi: 10.1016/j.jmps.2012.09.006 C. Keplinger, J.-Y. Sun , C. C. Foo, P... mechanics meets chemistry.” invited session on De-formation and Fracture of Soft Materials, 2012 March Meeting of the American Physical So-ciety, March... mechanics meets chemistry.” invited session on Deformation and Fracture of Soft Materials, 2012 March Meeting of the American Physi-cal Society

Perceived functional impact of abnormal facial appearance.

PubMed

Rankin, Marlene; Borah, Gregory L

2003-06-01

Functional facial deformities are usually described as those that impair respiration, eating, hearing, or speech. Yet facial scars and cutaneous deformities have a significant negative effect on social functionality that has been poorly documented in the scientific literature. Insurance companies are declining payments for reconstructive surgical procedures for facial deformities caused by congenital disabilities and after cancer or trauma operations that do not affect mechanical facial activity. The purpose of this study was to establish a large, sample-based evaluation of the perceived social functioning, interpersonal characteristics, and employability indices for a range of facial appearances (normal and abnormal). Adult volunteer evaluators (n = 210) provided their subjective perceptions based on facial physical appearance, and an analysis of the consequences of facial deformity on parameters of preferential treatment was performed. A two-group comparative research design rated the differences among 10 examples of digitally altered facial photographs of actual patients among various age and ethnic groups with "normal" and "abnormal" congenital deformities or posttrauma scars. Photographs of adult patients with observable congenital and posttraumatic deformities (abnormal) were digitally retouched to eliminate the stigmatic defects (normal). The normal and abnormal photographs of identical patients were evaluated by the large sample study group on nine parameters of social functioning, such as honesty, employability, attractiveness, and effectiveness, using a visual analogue rating scale. Patients with abnormal facial characteristics were rated as significantly less honest (p = 0.007), less employable (p = 0.001), less trustworthy (p = 0.01), less optimistic (p = 0.001), less effective (p = 0.02), less capable (p = 0.002), less intelligent (p = 0.03), less popular (p = 0.001), and less attractive (p = 0.001) than were the same patients with normal facial appearances. Facial deformity caused by trauma, congenital disabilities, and postsurgical sequelae present with significant adverse functional consequences. Facial deformities have a significant negative effect on perceptions of social functionality, including employability, honesty, and trustworthiness. Adverse perceptions of patients with facial deformities occur regardless of sex, educational level, and age of evaluator.

The shear instability energy: a new parameter for materials design?

NASA Astrophysics Data System (ADS)

Kanani, M.; Hartmaier, A.; Janisch, R.

2017-10-01

Reliable and predictive relationships between fundamental microstructural material properties and observable macroscopic mechanical behaviour are needed for the successful design of new materials. In this study we establish a link between physical properties that are defined on the atomic level and the deformation mechanisms of slip planes and interfaces that govern the mechanical behaviour of a metallic material. To accomplish this, the shear instability energy Γ is introduced, which can be determined via quantum mechanical ab initio calculations or other atomistic methods. The concept is based on a multilayer generalised stacking fault energy calculation and can be applied to distinguish the different shear deformation mechanisms occurring at TiAl interfaces during finite-temperature molecular dynamics simulations. We use the new parameter Γ to construct a deformation mechanism map for different interfaces occurring in this intermetallic. Furthermore, Γ can be used to convert the results of ab initio density functional theory calculations into those obtained with an embedded atom method type potential for TiAl. We propose to include this new physical parameter into material databases to apply it for the design of materials and microstructures, which so far mainly relies on single-crystal values for the unstable and stable stacking fault energy.

2D/3D fetal cardiac dataset segmentation using a deformable model.

PubMed

Dindoyal, Irving; Lambrou, Tryphon; Deng, Jing; Todd-Pokropek, Andrew

2011-07-01

To segment the fetal heart in order to facilitate the 3D assessment of the cardiac function and structure. Ultrasound acquisition typically results in drop-out artifacts of the chamber walls. The authors outline a level set deformable model to automatically delineate the small fetal cardiac chambers. The level set is penalized from growing into an adjacent cardiac compartment using a novel collision detection term. The region based model allows simultaneous segmentation of all four cardiac chambers from a user defined seed point placed in each chamber. The segmented boundaries are automatically penalized from intersecting at walls with signal dropout. Root mean square errors of the perpendicular distances between the algorithm's delineation and manual tracings are within 2 mm which is less than 10% of the length of a typical fetal heart. The ejection fractions were determined from the 3D datasets. We validate the algorithm using a physical phantom and obtain volumes that are comparable to those from physically determined means. The algorithm segments volumes with an error of within 13% as determined using a physical phantom. Our original work in fetal cardiac segmentation compares automatic and manual tracings to a physical phantom and also measures inter observer variation.

Optical properties of relativistic plasma mirrors

PubMed Central

Vincenti, H.; Monchocé, S.; Kahaly, S.; Bonnaud, G.; Martin, Ph.; Quéré, F.

2014-01-01

The advent of ultrahigh-power femtosecond lasers creates a need for an entirely new class of optical components based on plasmas. The most promising of these are known as plasma mirrors, formed when an intense femtosecond laser ionizes a solid surface. These mirrors specularly reflect the main part of a laser pulse and can be used as active optical elements to manipulate its temporal and spatial properties. Unfortunately, the considerable pressures exerted by the laser can deform the mirror surface, unfavourably affecting the reflected beam and complicating, or even preventing, the use of plasma mirrors at ultrahigh intensities. Here we derive a simple analytical model of the basic physics involved in laser-induced deformation of a plasma mirror. We validate this model numerically and experimentally, and use it to show how such deformation might be mitigated by appropriate control of the laser phase. PMID:24614748

Using compression calorimetry to characterize powder compaction behavior of pharmaceutical materials.

PubMed

Buckner, Ira S; Friedman, Ross A; Wurster, Dale Eric

2010-02-01

The process by which pharmaceutical powders are compressed into cohesive compacts or tablets has been studied using a compression calorimeter. Relating the various thermodynamic results to relevant physical processes has been emphasized. Work, heat, and internal energy change values have been determined with the compression calorimeter for common pharmaceutical materials. A framework of equations has been proposed relating the physical processes of friction, reversible deformation, irreversible deformation, and inter-particle bonding to the compression calorimetry values. The results indicate that irreversible deformation dominated many of the thermodynamic values, especially the net internal energy change following the compression-decompression cycle. The relationships between the net work and the net heat from the complete cycle were very clear indicators of predominating deformation mechanisms. Likewise, the ratio of energy stored as internal energy to the initial work input distinguished the materials according to their brittle or plastic deformation tendencies. (c) 2009 Wiley-Liss, Inc. and the American Pharmacists Association.

Initial Comparison of Direct and Legacy Modeling Approaches for Radial Core Expansion Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shemon, Emily R.

2016-10-10

Radial core expansion in sodium-cooled fast reactors provides an important reactivity feedback effect. As the reactor power increases due to normal start up conditions or accident scenarios, the core and surrounding materials heat up, causing both grid plate expansion and bowing of the assembly ducts. When the core restraint system is designed correctly, the resulting structural deformations introduce negative reactivity which decreases the reactor power. Historically, an indirect procedure has been used to estimate the reactivity feedback due to structural deformation which relies upon perturbation theory and coupling legacy physics codes with limited geometry capabilities. With advancements in modeling andmore » simulation, radial core expansion phenomena can now be modeled directly, providing an assessment of the accuracy of the reactivity feedback coefficients generated by indirect legacy methods. Recently a new capability was added to the PROTEUS-SN unstructured geometry neutron transport solver to analyze deformed meshes quickly and directly. By supplying the deformed mesh in addition to the base configuration input files, PROTEUS-SN automatically processes material adjustments including calculation of region densities to conserve mass, calculation of isotopic densities according to material models (for example, sodium density as a function of temperature), and subsequent re-homogenization of materials. To verify the new capability of directly simulating deformed meshes, PROTEUS-SN was used to compute reactivity feedback for a series of contrived yet representative deformed configurations for the Advanced Burner Test Reactor design. The indirect legacy procedure was also performed to generate reactivity feedback coefficients for the same deformed configurations. Interestingly, the legacy procedure consistently overestimated reactivity feedbacks by 35% compared to direct simulations by PROTEUS-SN. This overestimation indicates that the legacy procedures are in fact not conservative and could be overestimating reactivity feedback effects that are closely tied to reactor safety. We conclude that there is indeed value in performing direct simulation of deformed meshes despite the increased computational expense. PROTEUS-SN is already part of the SHARP multi-physics toolkit where both thermal hydraulics and structural mechanical feedback modeling can be applied but this is the first comparison of direct simulation to legacy techniques for radial core expansion.« less

Statistical physics when the minimum temperature is not absolute zero

NASA Astrophysics Data System (ADS)

Chung, Won Sang; Hassanabadi, Hassan

2018-04-01

In this paper, the nonzero minimum temperature is considered based on the third law of thermodynamics and existence of the minimal momentum. From the assumption of nonzero positive minimum temperature in nature, we deform the definitions of some thermodynamical quantities and investigate nonzero minimum temperature correction to the well-known thermodynamical problems.

Modeling the Flow Behavior, Recrystallization, and Crystallographic Texture in Hot-Deformed Fe-30 Wt Pct Ni Austenite

NASA Astrophysics Data System (ADS)

Abbod, M. F.; Sellars, C. M.; Cizek, P.; Linkens, D. A.; Mahfouf, M.

2007-10-01

The present work describes a hybrid modeling approach developed for predicting the flow behavior, recrystallization characteristics, and crystallographic texture evolution in a Fe-30 wt pct Ni austenitic model alloy subjected to hot plane strain compression. A series of compression tests were performed at temperatures between 850 °C and 1050 °C and strain rates between 0.1 and 10 s-1. The evolution of grain structure, crystallographic texture, and dislocation substructure was characterized in detail for a deformation temperature of 950 °C and strain rates of 0.1 and 10 s-1, using electron backscatter diffraction and transmission electron microscopy. The hybrid modeling method utilizes a combination of empirical, physically-based, and neuro-fuzzy models. The flow stress is described as a function of the applied variables of strain rate and temperature using an empirical model. The recrystallization behavior is predicted from the measured microstructural state variables of internal dislocation density, subgrain size, and misorientation between subgrains using a physically-based model. The texture evolution is modeled using artificial neural networks.

Brittle and ductile friction and the physics of tectonic tremor

USGS Publications Warehouse

Daub, Eric G.; Shelly, David R.; Guyer, Robert A.; Johnson, P.A.

2011-01-01

Observations of nonvolcanic tremor provide a unique window into the mechanisms of deformation and failure in the lower crust. At increasing depths, rock deformation gradually transitions from brittle, where earthquakes occur, to ductile, with tremor occurring in the transitional region. The physics of deformation in the transition region remain poorly constrained, limiting our basic understanding of tremor and its relation to earthquakes. We combine field and laboratory observations with a physical friction model comprised of brittle and ductile components, and use the model to provide constraints on the friction and stress state in the lower crust. A phase diagram is constructed that characterizes under what conditions all faulting behaviors occur, including earthquakes, tremor, silent transient slip, and steady sliding. Our results show that tremor occurs over a range of ductile and brittle frictional strengths, and advances our understanding of the physical conditions at which tremor and earthquakes take place.

Adiabatically describing rare earths using microscopic deformations

NASA Astrophysics Data System (ADS)

Nobre, Gustavo; Dupuis, Marc; Herman, Michal; Brown, David

2017-09-01

Recent works showed that reactions on well-deformed nuclei in the rare-earth region are very well described by an adiabatic method. This assumes a spherical optical potential (OP) accounting for non-rotational degrees of freedom while the deformed configuration is described by couplings to states of the g.s. rotational band. This method has, apart from the global OP, only the deformation parameters as inputs, with no additional fit- ted variables. For this reason, it has only been applied to nuclei with well-measured deformations. With the new computational capabilities, microscopic large-scale calculations of deformation parameters within the HFB method based on the D1S Gogny force are available in the literature. We propose to use such microscopic deformations in our adi- abatic method, allowing us to reproduce the cross sections agreements observed in stable nuclei, and to reliably extend this description to nuclei far from stability, describing the whole rare-earth region. Since all cross sections, such as capture and charge exchange, strongly depend on the correct calculation of absorption from the incident channel (from direct reaction mechanisms), this approach significantly improves the accuracy of cross sections and transitions relevant to astrophysical studies. The work at BNL was sponsored by the Office of Nuclear Physics, Office of Science of the US Department of Energy, under Contract No. DE-AC02-98CH10886 with Brookhaven Science Associates, LLC.

Sensitivity Analysis of Mechanical Parameters of Different Rock Layers to the Stability of Coal Roadway in Soft Rock Strata

PubMed Central

Zhao, Zeng-hui; Wang, Wei-ming; Gao, Xin; Yan, Ji-xing

2013-01-01

According to the geological characteristics of Xinjiang Ili mine in western area of China, a physical model of interstratified strata composed of soft rock and hard coal seam was established. Selecting the tunnel position, deformation modulus, and strength parameters of each layer as influencing factors, the sensitivity coefficient of roadway deformation to each parameter was firstly analyzed based on a Mohr-Columb strain softening model and nonlinear elastic-plastic finite element analysis. Then the effect laws of influencing factors which showed high sensitivity were further discussed. Finally, a regression model for the relationship between roadway displacements and multifactors was obtained by equivalent linear regression under multiple factors. The results show that the roadway deformation is highly sensitive to the depth of coal seam under the floor which should be considered in the layout of coal roadway; deformation modulus and strength of coal seam and floor have a great influence on the global stability of tunnel; on the contrary, roadway deformation is not sensitive to the mechanical parameters of soft roof; roadway deformation under random combinations of multi-factors can be deduced by the regression model. These conclusions provide theoretical significance to the arrangement and stability maintenance of coal roadway. PMID:24459447

On the thermomechanical coupling in dissipative materials: A variational approach for generalized standard materials

NASA Astrophysics Data System (ADS)

Bartels, A.; Bartel, T.; Canadija, M.; Mosler, J.

2015-09-01

This paper deals with the thermomechanical coupling in dissipative materials. The focus lies on finite strain plasticity theory and the temperature increase resulting from plastic deformation. For this type of problem, two fundamentally different modeling approaches can be found in the literature: (a) models based on thermodynamical considerations and (b) models based on the so-called Taylor-Quinney factor. While a naive straightforward implementation of thermodynamically consistent approaches usually leads to an over-prediction of the temperature increase due to plastic deformation, models relying on the Taylor-Quinney factor often violate fundamental physical principles such as the first and the second law of thermodynamics. In this paper, a thermodynamically consistent framework is elaborated which indeed allows the realistic prediction of the temperature evolution. In contrast to previously proposed frameworks, it is based on a fully three-dimensional, finite strain setting and it naturally covers coupled isotropic and kinematic hardening - also based on non-associative evolution equations. Considering a variationally consistent description based on incremental energy minimization, it is shown that the aforementioned problem (thermodynamical consistency and a realistic temperature prediction) is essentially equivalent to correctly defining the decomposition of the total energy into stored and dissipative parts. Interestingly, this decomposition shows strong analogies to the Taylor-Quinney factor. In this respect, the Taylor-Quinney factor can be well motivated from a physical point of view. Furthermore, certain intervals for this factor can be derived in order to guarantee that fundamental physically principles are fulfilled a priori. Representative examples demonstrate the predictive capabilities of the final constitutive modeling framework.

Design, construction and mechanical testing of digital 3D anatomical data-based PCL-HA bone tissue engineering scaffold.

PubMed

Yao, Qingqiang; Wei, Bo; Guo, Yang; Jin, Chengzhe; Du, Xiaotao; Yan, Chao; Yan, Junwei; Hu, Wenhao; Xu, Yan; Zhou, Zhi; Wang, Yijin; Wang, Liming

2015-01-01

The study aims to investigate the techniques of design and construction of CT 3D reconstructional data-based polycaprolactone (PCL)-hydroxyapatite (HA) scaffold. Femoral and lumbar spinal specimens of eight male New Zealand white rabbits were performed CT and laser scanning data-based 3D printing scaffold processing using PCL-HA powder. Each group was performed eight scaffolds. The CAD-based 3D printed porous cylindrical stents were 16 piece × 3 groups, including the orthogonal scaffold, the Pozi-hole scaffold and the triangular hole scaffold. The gross forms, fiber scaffold diameters and porosities of the scaffolds were measured, and the mechanical testing was performed towards eight pieces of the three kinds of cylindrical scaffolds, respectively. The loading force, deformation, maximum-affordable pressure and deformation value were recorded. The pore-connection rate of each scaffold was 100 % within each group, there was no significant difference in the gross parameters and micro-structural parameters of each scaffold when compared with the design values (P > 0.05). There was no significant difference in the loading force, deformation and deformation value under the maximum-affordable pressure of the three different cylinder scaffolds when the load was above 320 N. The combination of CT and CAD reverse technology could accomplish the design and manufacturing of complex bone tissue engineering scaffolds, with no significant difference in the impacts of the microstructures towards the physical properties of different porous scaffolds under large load.

A Reformulation of Nonlinear Anisotropic Elasticity for Impact Physics

DTIC Science & Technology

2014-02-01

aluminum, copper, and magnesium . 15. SUBJECT TERMS impact physics, shock compression, elasticity, plasticity 16. SECURITY CLASSIFICATION OF: 17... deformation wave propagation code accounting for dissipative inelastic mechanisms. • Accuracy of the new nonlinear elastic- plastic model(s) will be...gradient and its transpose. A new general thermomechanical theory accounting for both elastic and plastic deformations has been briefly outlined in

A theory of viscoplasticity accounting for internal damage

NASA Technical Reports Server (NTRS)

Freed, A. D.; Robinson, D. N.

1988-01-01

A constitutive theory for use in structural and durability analyses of high temperature isotropic alloys is presented. Constitutive equations based upon a potential function are determined from conditions of stability and physical considerations. The theory is self-consistent; terms are not added in an ad hoc manner. It extends a proven viscoplastic model by introducing the Kachanov-Rabotnov concept of net stress. Material degradation and inelastic deformation are unified; they evolve simultaneously and interactively. Both isotropic hardening and material degradation evolve with dissipated work which is the sum of inelastic work and internal work. Internal work is a continuum measure of the stored free energy resulting from inelastic deformation.

A natural example of fluid-mediated brittle-ductile cyclicity in quartz veins from Olkiluoto Island, SW Finland

NASA Astrophysics Data System (ADS)

Marchesini, Barbara; Garofalo, Paolo S.; Viola, Giulio; Mattila, Jussi; Menegon, Luca

2017-04-01

Brittle faults are well known as preferential conduits for localised fluid flow in crystalline rocks. Their study can thus reveal fundamental details of the physical-chemical properties of the flowing fluid phase and of the mutual feedbacks between mechanical properties of faults and fluids. Crustal deformation at the brittle-ductile transition may occur by a combination of competing brittle fracturing and viscous flow processes, with short-lived variations in fluid pressure as a viable mechanism to produce this cyclicity switch. Therefore, a detailed study of the fluid phases potentially present in faults can help to better constrain the dynamic evolution of crustal strength within the seismogenic zone, as a function of varying fluid phase characteristics. With the aim to 1) better understand the complexity of brittle-ductile cyclicity under upper to mid-crustal conditions and 2) define the physical and chemical features of the involved fluid phase, we present the preliminary results of a recently launched (micro)structural and geochemical project. We study deformed quartz veins associated with brittle-ductile deformation zones on Olkiluoto Island, chosen as the site for the Finnish deep repository for spent nuclear fuel excavated in the Paleoproterozoic crust of southwestern Finland. The presented results stem from the study of brittle fault zone BFZ300, which is a mixed brittle and ductile deformation zone characterized by complex kinematics and associated with multiple generations of quartz veins, and which serves as a pertinent example of the mechanisms of fluid flow-deformation feedbacks during brittle-ductile cyclicity in nature. A kinematic and dynamic mesostructural study is being integrated with the detailed analysis of petrographic thin sections from the fault core and its immediate surroundings with the aim to reconstruct the mechanical deformation history along the entire deformation zone. Based on the observed microstructures, it was possible to recognize three distinct episodes of ductile deformation alternating with at least three brittle episodes. Preliminary fluid inclusion data show that, during crystallization and brittle-viscous deformation, quartz crystals hosted homogeneous and heterogeneous (boiling) aqueous fluids with a large salinity (11.7-0 wt% NaCleq) and Thtot (410-200 °C) range. Boiling occurred at 200-260 °C. Variations of fluid temperature and density (hence, viscosity) may thus have induced localized cyclic switches between brittle and ductile deformation in quartz, with implications on the bulk regional crustal strength. Preliminary EBSD analysis also supports the hypothesis of cyclic switches between brittle and viscous deformation.

Analytic Intermodel Consistent Modeling of Volumetric Human Lung Dynamics.

PubMed

Ilegbusi, Olusegun; Seyfi, Behnaz; Neylon, John; Santhanam, Anand P

2015-10-01

Human lung undergoes breathing-induced deformation in the form of inhalation and exhalation. Modeling the dynamics is numerically complicated by the lack of information on lung elastic behavior and fluid-structure interactions between air and the tissue. A mathematical method is developed to integrate deformation results from a deformable image registration (DIR) and physics-based modeling approaches in order to represent consistent volumetric lung dynamics. The computational fluid dynamics (CFD) simulation assumes the lung is a poro-elastic medium with spatially distributed elastic property. Simulation is performed on a 3D lung geometry reconstructed from four-dimensional computed tomography (4DCT) dataset of a human subject. The heterogeneous Young's modulus (YM) is estimated from a linear elastic deformation model with the same lung geometry and 4D lung DIR. The deformation obtained from the CFD is then coupled with the displacement obtained from the 4D lung DIR by means of the Tikhonov regularization (TR) algorithm. The numerical results include 4DCT registration, CFD, and optimal displacement data which collectively provide consistent estimate of the volumetric lung dynamics. The fusion method is validated by comparing the optimal displacement with the results obtained from the 4DCT registration.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Girelli, Florian; Livine, Etera R.; Laboratoire de Physique, ENS Lyon, CNRS UMR 5672, 46 Allee d'Italie, 69007 Lyon

Deformed special relativity (DSR) is obtained by imposing a maximal energy to special relativity and deforming the Lorentz symmetry (more exactly, the Poincare symmetry) to accommodate this requirement. One can apply the same procedure in the context of Galilean relativity by imposing a maximal speed (the speed of light). Effectively, one deforms the Galilean group and this leads to a noncommutative space structure, together with the deformations of composition of speed and conservation of energy momentum. In doing so, one runs into most of the ambiguities that one stumbles onto in the DSR context. However, this time, special relativity ismore » there to tell us what is the underlying physics, in such a way we can understand and interpret these ambiguities. We use these insights to comment on the physics of DSR.« less

Ontology for Structural Geology

NASA Astrophysics Data System (ADS)

Zhong, J.; McGuinness, D. L.; Antonellini, M.; Aydin, A.

2005-12-01

We present our comprehensive process-based ontology for Structural Geology. This ontology covers major domain concepts, especially those related to geological structure type, properties of these structures, their deformation mechanisms, and the factors that control which deformation mechanisms may operate under certain conditions. The structure class in our ontology extends the planetary structure class of the SWEET ontology by providing additional information required for use in the structural geology domain. The classification followed the architectures of structures, such as structure element, set, zone, and pattern. Our deformation mechanism class does not have a corresponding class in SWEET. In our ontology, it has two subclasses, Macro- and Micro- mechanisms. The property class and the factor class are both subclasses of the physical property class of SWEET. Relationships among those concepts are also included in our ontology. For example, the class structure element has properties associated with the deformation mechanisms, descriptive properties such as geometry and morphology, and physical properties of rocks such as strength, compressibility, seismic velocity, porosity, and permeability. The subject matter expertise was provided by domain experts. Additionally, we surveyed text books and journal articles with the goal of evaluating the completeness and correctness of the domain terms and we used logical reasoners and validators to eliminate logical problems. We propose that our ontology provides a reusable extension to the SWEET ontology that may be of value to scientists and lay people interested in structural geology issues. We have also implemented prototype services that utilize this ontology for search.

Nondestructive optical testing of the materials surface structure based on liquid crystals

NASA Astrophysics Data System (ADS)

Tomilin, M. G.; Stafeev, S. K.

2011-08-01

Thin layers of nematic liquid crystals (NLCs) may be used as recording media for visualizing structural and microrelief defects, distribution of low power physical fields and modifications of the surface. NLCs are more sensitive in comparison with cholesteric and smectic LCs having super molecular structures. The detecting properties of NLCs are based on local layers deformation, induced by surface fields and observed in polarizing microscope. The structural surface defects or physical field's distribution are dramatically change the distribution of surface tension. Surface defects recording becomes possible if NLC deformed structure is illuminated in transparent or reflective modes and observed in optical polarizing microscope and appearing image is compared with background structure. In this case one observes not the real defect but the local deformation in NLCs. The theory was developed to find out the real size of defects. The resolution of NLC layer is more than 2000 lines/mm. The fields of NLC application are solid crystals symmetry, minerals, metals, semiconductors, polymers and glasses structure inhomogeneities and optical coatings defects detecting. The efficiency of NLC method in biophotonics is illustrated by objective detecting cancer tissues character and visualizing the interaction traces of grippe viruses with antibodies. NLCs may detect solvent components structure in tea, wine and perfume giving unique information of their structure. It presents diagnostic information alternative to dyes and fluorescence methods. For the first time the structures of some juices and beverages are visualized to illustrate the unique possibilities of NLCs.

Optical Correction Of Space-Based Telescopes Using A Deformable Mirror System

DTIC Science & Technology

2016-12-01

FPA). A fast 5 steering mirror is used to move the FOV within the FOR so that the spacecraft does not need to physically move to a new target as...technology review and development roadmap,” Astro2010: The Astronomy and Astrophysics Decadal Survey, 2009, vol. 2010, p. 23. [8] D. Baiocchi, “Design and

Brittle to ductile transition in a model of sheared granular materials

NASA Astrophysics Data System (ADS)

Ma, X.; Elbanna, A. E.

2016-12-01

Understanding the fundamental mechanisms of deformation and failure in sheared fault gouge is critical for the development of physics-based earthquake rupture simulations that are becoming an essential ingredient in next generation hazard and risk models. To that end, we use the shear transformation zone (STZ) theory, a non-equilibrium statistical thermodynamics framework to describe viscoplastic deformation and localization in gouge materials as a first step towards developing multiscale models for earthquake source processes that are informed by high-resolution fault zone physics. The primary ingredient of the STZ theory is that inelastic deformation occurs at rare and local non-interacting soft zones known as the shear transformation zones. The larger the number of these STZs the more disordered (the more loose) the layer is. We will describe an implementation of this theory in a 2D/3D finite element framework, accounting for finite deformation, under both axial and shear loading and for dry and saturated conditions. We examine conditions under which a localized shear band may form and show that the initial value of disorder (or the initial porosity) plays an important role. In particular, our simulations suggest that if the material is more compact initially, the behavior is more brittle and the plastic deformation localizes with generating large strength drop. On the other hand, an initially loose material will show a more ductile response and the plastic deformations will be distributed more broadly. We will further show that incorporation of pore fluids alters the localization pattern and changes the stress slip response due to coupling between gouge volume changes (compaction and dilation) and pore pressure build up. We validate the model predictions by comparing them to available experimental observations on strain localization and fault gouge strength evolution. Finally, we discuss the implications of our model for gouge friction and dynamic weakening.

Experimental and Numerical Investigations on Strength and Deformation Behavior of Cataclastic Sandstone

NASA Astrophysics Data System (ADS)

Zhang, Y.; Shao, J. F.; Xu, W. Y.; Zhao, H. B.; Wang, W.

2015-05-01

This work is devoted to characterization of the deformation and strength properties of cataclastic sandstones. Before conducting mechanical tests, the physical properties were first examined. These sandstones are characterized by a loose damaged microstructure and poorly cemented contacts. Then, a series of mechanical tests including hydrostatic, uniaxial, and triaxial compression tests were performed to study the mechanical strength and deformation of the sandstones. The results obtained show nonlinear stress-strain responses. The initial microcracks are closed at hydrostatic stress of 2.6 MPa, and the uniaxial compressive strength is about 0.98 MPa. Under triaxial compression, there is a clear transition from volumetric compressibility to dilatancy and a strong dependency on confining pressure. Based on the experimental evidence, an elastoplastic model is proposed using a linear yield function and a nonassociated plastic potential. There is good agreement between numerical results and experimental data.

Non-Newtonian fluid structure interaction in flexible biomimetic microchannels

NASA Astrophysics Data System (ADS)

Kiran, M.; Dasgupta, Sunando; Chakraborty, Suman

2017-11-01

To investigate the complex fluid structure interactions in a physiologically relevant microchannel with deformable wall and non-Newtonian fluid that flows within it, we fabricated cylindrical microchannels of various softness out of PDMS. Experiments to measure the transient pressure drop across the channel were carried out with high sampling frequencies to capture the intricate flow physics. In particular, we showed that the waveforms varies greatly for each of the non-Newtonian and Newtonian cases for both non-deformable and deformable microchannels in terms of the peak amplitude, r.m.s amplitude and the crest factor. In addition, we carried out frequency sweep experiments to evaluate the frequency response of the system. We believe that these results will aid in the design of polymer based microfluidic phantoms for arterial FSI studies, and in particular for studying blood analog fluids in cylindrical microchannels as well as developing frequency specific Lab-on-chip systems for medical diagnostics.

Disclination mediated dynamic recrystallization in metals at low temperature.

PubMed

Aramfard, Mohammad; Deng, Chuang

2015-09-16

Recrystallization is one of the most important physical phenomena in condensed matter that has been utilized for materials processing for thousands of years in human history. It is generally believed that recrystallization is thermally activated and a minimum temperature must be achieved for the necessary atomic mechanisms to occur. Here, using atomistic simulations, we report a new mechanism of dynamic recrystallization that can operate at temperature as low as T = 10 K in metals during deformation. In contrast to previously proposed dislocation-based models, this mechanism relies on the generation of disclination quadrupoles, which are special defects that form during deformation when the grain boundary migration is restricted by structural defects such as triple junctions, cracks or obstacles. This mechanism offers an alternative explanation for the grain refinement in metals during severe plastic deformation at cryogenic temperature and may suggest a new method to tailor the microstructure in general crystalline materials.

Disclination mediated dynamic recrystallization in metals at low temperature

PubMed Central

Aramfard, Mohammad; Deng, Chuang

2015-01-01

Recrystallization is one of the most important physical phenomena in condensed matter that has been utilized for materials processing for thousands of years in human history. It is generally believed that recrystallization is thermally activated and a minimum temperature must be achieved for the necessary atomic mechanisms to occur. Here, using atomistic simulations, we report a new mechanism of dynamic recrystallization that can operate at temperature as low as T = 10 K in metals during deformation. In contrast to previously proposed dislocation-based models, this mechanism relies on the generation of disclination quadrupoles, which are special defects that form during deformation when the grain boundary migration is restricted by structural defects such as triple junctions, cracks or obstacles. This mechanism offers an alternative explanation for the grain refinement in metals during severe plastic deformation at cryogenic temperature and may suggest a new method to tailor the microstructure in general crystalline materials. PMID:26374603

Thermocapillary motion of deformable drops

NASA Technical Reports Server (NTRS)

Haj-Hariri, Hossein; Shi, Qingping; Borhan, Ali

1994-01-01

The thermocapillary motion of initially spherical drops/bubbles driven by a constant temperature gradient in an unbounded liquid medium is simulated numerically. Effects of convection of momentum and energy, as well as shape deformations, are addressed. The method used is based on interface tracking on a base cartesian grid, and uses a smeared color or indicator function for the determination of the surface topology. Quad-tree adaptive refinement of the cartesian grid is implemented to enhance the fidelity of the surface tracking. It is shown that convection of energy results in a slowing of the drop, as the isotherms get wrapped around the front of the drop. Shape deformation resulting from inertial effects affect the migration velocity. The physical results obtained are in agreement with the existing literature. Furthermore, remarks are made on the sensitivity of the calculated solutions to the smearing of the fluid properties. Analysis and simulations show that the migration velocity depends very strongly on the smearing of the interfacial force whereas it is rather insensitive to the smearing of other properties, hence the adaptive grid.

Elasticity of entangled polymer loops: Olympic gels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vilgis, T.A.; Otto, M.

1997-08-01

In this Rapid Communication we present a scaling theory for the elasticity of olympic gels, i.e., gels where the elasticity is a consequence of topology only. It is shown that two deformation regimes exist. The first is the nonaffine deformation regime where the free energy scales linear with the deformation. In the large (affine) deformation regime the free energy is shown to scale as F{proportional_to}{lambda}{sup 5/2} where {lambda} is the deformation ratio. Thus a highly non-Hookian stress-strain relation is predicted. {copyright} {ital 1997} {ital The American Physical Society}

Symptoms in Pectus Deformities: A Scoring System for Subjective Physical Complaints.

PubMed

Ewert, Franziska; Syed, Julia; Kern, Sonja; Besendörfer, Manuel; Carbon, Roman T; Schulz-Drost, Stefan

2017-01-01

Background  The literature is silent on the relationship between symptoms and the Haller index. Nor is there a classification of the severity of the physical complaints. Materials and Methods  Retrospectively, data from 128 patients (102 funnel, 25 pigeon chest patients, and 1 mixed type) were evaluated. To objectify the symptoms, we developed a score to describe the level of physical ailments. This score includes 10 different symptoms as well as the situation or frequency in which they occur and an impact factor. This depends on how much they affect everyday life. Results  Pectus excavatum patients express physical complaints more frequently than pectus carinatum patients who actually suffer more from psychological stress. We could not find a correlation between the Haller index and symptoms or levels of ailment. Conclusion  Pectus deformities are likely to cause physical and psychological complaints. Since the subjective symptoms did not show any correlation to the chest severity index, they are supposed to be independent from the deformity's extent. Georg Thieme Verlag KG Stuttgart · New York.

A physics based method for combining multiple anatomy models with application to medical simulation.

PubMed

Zhu, Yanong; Magee, Derek; Ratnalingam, Rishya; Kessel, David

2009-01-01

We present a physics based approach to the construction of anatomy models by combining components from different sources; different image modalities, protocols, and patients. Given an initial anatomy, a mass-spring model is generated which mimics the physical properties of the solid anatomy components. This helps maintain valid spatial relationships between the components, as well as the validity of their shapes. Combination can be either replacing/modifying an existing component, or inserting a new component. The external forces that deform the model components to fit the new shape are estimated from Gradient Vector Flow and Distance Transform maps. We demonstrate the applicability and validity of the described approach in the area of medical simulation, by showing the processes of non-rigid surface alignment, component replacement, and component insertion.

Physical limits of cell migration: control by ECM space and nuclear deformation and tuning by proteolysis and traction force.

PubMed

Wolf, Katarina; Te Lindert, Mariska; Krause, Marina; Alexander, Stephanie; Te Riet, Joost; Willis, Amanda L; Hoffman, Robert M; Figdor, Carl G; Weiss, Stephen J; Friedl, Peter

2013-06-24

Cell migration through 3D tissue depends on a physicochemical balance between cell deformability and physical tissue constraints. Migration rates are further governed by the capacity to degrade ECM by proteolytic enzymes, particularly matrix metalloproteinases (MMPs), and integrin- and actomyosin-mediated mechanocoupling. Yet, how these parameters cooperate when space is confined remains unclear. Using MMP-degradable collagen lattices or nondegradable substrates of varying porosity, we quantitatively identify the limits of cell migration by physical arrest. MMP-independent migration declined as linear function of pore size and with deformation of the nucleus, with arrest reached at 10% of the nuclear cross section (tumor cells, 7 µm²; T cells, 4 µm²; neutrophils, 2 µm²). Residual migration under space restriction strongly depended upon MMP-dependent ECM cleavage by enlarging matrix pore diameters, and integrin- and actomyosin-dependent force generation, which jointly propelled the nucleus. The limits of interstitial cell migration thus depend upon scaffold porosity and deformation of the nucleus, with pericellular collagenolysis and mechanocoupling as modulators.

Modeling plasticity by non-continuous deformation

NASA Astrophysics Data System (ADS)

Ben-Shmuel, Yaron; Altus, Eli

2017-10-01

Plasticity and failure theories are still subjects of intense research. Engineering constitutive models on the macroscale which are based on micro characteristics are very much in need. This study is motivated by the observation that continuum assumptions in plasticity in which neighbour material elements are inseparable at all-time are physically impossible, since local detachments, slips and neighbour switching must operate, i.e. non-continuous deformation. Material microstructure is modelled herein by a set of point elements (particles) interacting with their neighbours. Each particle can detach from and/or attach with its neighbours during deformation. Simulations on two- dimensional configurations subjected to uniaxial compression cycle are conducted. Stochastic heterogeneity is controlled by a single "disorder" parameter. It was found that (a) macro response resembles typical elasto-plastic behaviour; (b) plastic energy is proportional to the number of detachments; (c) residual plastic strain is proportional to the number of attachments, and (d) volume is preserved, which is consistent with macro plastic deformation. Rigid body displacements of local groups of elements are also observed. Higher disorder decreases the macro elastic moduli and increases plastic energy. Evolution of anisotropic effects is obtained with no additional parameters.

Congenital deformity of the paw in a captive tiger: case report

PubMed Central

2012-01-01

Background The aim of this report was to describe the clinical signs, diagnostic approach, treatment and outcome in the case of a tiger with a deformity of the paw. Case presentation A 1.5-year-old tiger (Panthera tigris) was presented with lameness of the left thoracic limb. A deformity involving the first and second metacarpal bones, and a soft tissue separation between the second and third metacarpal bones of the left front paw were observed. The second digit constantly struck the ground during locomotion. Based on the physical and radiographic evaluations, a diagnosis of ectrodactyly was made. A soft tissue reconstruction of the cleft with excision of both the second digit and distal portion of the second metacarpal bone was performed. Marked improvement of the locomotion was observed after surgical treatment, although the tiger showed a low degree of lameness probably associated with the discrepancy in length between the thoracic limbs. Conclusion This report shows a rare deformity in an exotic feline that it is compatible to ectrodactyly. Reconstructive surgery of the cleft resulted in significant improvement of limb function. PMID:22747639

Novel characteristics of energy spectrum for 3D Dirac oscillator analyzed via Lorentz covariant deformed algebra

PubMed Central

Betrouche, Malika; Maamache, Mustapha; Choi, Jeong Ryeol

2013-01-01

We investigate the Lorentz-covariant deformed algebra for Dirac oscillator problem, which is a generalization of Kempf deformed algebra in 3 + 1 dimension of space-time, where Lorentz symmetry are preserved. The energy spectrum of the system is analyzed by taking advantage of the corresponding wave functions with explicit spin state. We obtained entirely new results from our development based on Kempf algebra in comparison to the studies carried out with the non-Lorentz-covariant deformed one. A novel result of this research is that the quantized relativistic energy of the system in the presence of minimal length cannot grow indefinitely as quantum number n increases, but converges to a finite value, where c is the speed of light and β is a parameter that determines the scale of noncommutativity in space. If we consider the fact that the energy levels of ordinary oscillator is equally spaced, which leads to monotonic growth of quantized energy with the increment of n, this result is very interesting. The physical meaning of this consequence is discussed in detail. PMID:24225900

Novel characteristics of energy spectrum for 3D Dirac oscillator analyzed via Lorentz covariant deformed algebra.

PubMed

Betrouche, Malika; Maamache, Mustapha; Choi, Jeong Ryeol

2013-11-14

We investigate the Lorentz-covariant deformed algebra for Dirac oscillator problem, which is a generalization of Kempf deformed algebra in 3 + 1 dimension of space-time, where Lorentz symmetry are preserved. The energy spectrum of the system is analyzed by taking advantage of the corresponding wave functions with explicit spin state. We obtained entirely new results from our development based on Kempf algebra in comparison to the studies carried out with the non-Lorentz-covariant deformed one. A novel result of this research is that the quantized relativistic energy of the system in the presence of minimal length cannot grow indefinitely as quantum number n increases, but converges to a finite value, where c is the speed of light and β is a parameter that determines the scale of noncommutativity in space. If we consider the fact that the energy levels of ordinary oscillator is equally spaced, which leads to monotonic growth of quantized energy with the increment of n, this result is very interesting. The physical meaning of this consequence is discussed in detail.

Microsurgery Simulator of Cerebral Aneurysm Clipping with Interactive Cerebral Deformation Featuring a Virtual Arachnoid.

PubMed

Shono, Naoyuki; Kin, Taichi; Nomura, Seiji; Miyawaki, Satoru; Saito, Toki; Imai, Hideaki; Nakatomi, Hirofumi; Oyama, Hiroshi; Saito, Nobuhito

2018-05-01

A virtual reality simulator for aneurysmal clipping surgery is an attractive research target for neurosurgeons. Brain deformation is one of the most important functionalities necessary for an accurate clipping simulator and is vastly affected by the status of the supporting tissue, such as the arachnoid membrane. However, no virtual reality simulator implementing the supporting tissue of the brain has yet been developed. To develop a virtual reality clipping simulator possessing interactive brain deforming capability closely dependent on arachnoid dissection and apply it to clinical cases. Three-dimensional computer graphics models of cerebral tissue and surrounding structures were extracted from medical images. We developed a new method for modifiable cerebral tissue complex deformation by incorporating a nonmedical image-derived virtual arachnoid/trabecula in a process called multitissue integrated interactive deformation (MTIID). MTIID made it possible for cerebral tissue complexes to selectively deform at the site of dissection. Simulations for 8 cases of actual clipping surgery were performed before surgery and evaluated for their usefulness in surgical approach planning. Preoperatively, each operative field was precisely reproduced and visualized with the virtual brain retraction defined by users. The clear visualization of the optimal approach to treating the aneurysm via an appropriate arachnoid incision was possible with MTIID. A virtual clipping simulator mainly focusing on supporting tissues and less on physical properties seemed to be useful in the surgical simulation of cerebral aneurysm clipping. To our knowledge, this article is the first to report brain deformation based on supporting tissues.

A Proposal of Monitoring and Forecasting Method for Crustal Activity in and around Japan with 3-dimensional Heterogeneous Medium Using a Large-scale High-fidelity Finite Element Simulation

NASA Astrophysics Data System (ADS)

Hori, T.; Agata, R.; Ichimura, T.; Fujita, K.; Yamaguchi, T.; Takahashi, N.

2017-12-01

Recently, we can obtain continuous dense surface deformation data on land and partly on the sea floor, the obtained data are not fully utilized for monitoring and forecasting of crustal activity, such as spatio-temporal variation in slip velocity on the plate interface including earthquakes, seismic wave propagation, and crustal deformation. For construct a system for monitoring and forecasting, it is necessary to develop a physics-based data analysis system including (1) a structural model with the 3D geometry of the plate inter-face and the material property such as elasticity and viscosity, (2) calculation code for crustal deformation and seismic wave propagation using (1), (3) inverse analysis or data assimilation code both for structure and fault slip using (1) & (2). To accomplish this, it is at least necessary to develop highly reliable large-scale simulation code to calculate crustal deformation and seismic wave propagation for 3D heterogeneous structure. Unstructured FE non-linear seismic wave simulation code has been developed. This achieved physics-based urban earthquake simulation enhanced by 1.08 T DOF x 6.6 K time-step. A high fidelity FEM simulation code with mesh generator has also been developed to calculate crustal deformation in and around Japan with complicated surface topography and subducting plate geometry for 1km mesh. This code has been improved the code for crustal deformation and achieved 2.05 T-DOF with 45m resolution on the plate interface. This high-resolution analysis enables computation of change of stress acting on the plate interface. Further, for inverse analyses, waveform inversion code for modeling 3D crustal structure has been developed, and the high-fidelity FEM code has been improved to apply an adjoint method for estimating fault slip and asthenosphere viscosity. Hence, we have large-scale simulation and analysis tools for monitoring. We are developing the methods for forecasting the slip velocity variation on the plate interface. Although the prototype is for elastic half space model, we are applying it for 3D heterogeneous structure with the high-fidelity FE model. Furthermore, large-scale simulation codes for monitoring are being implemented on the GPU clusters and analysis tools are developing to include other functions such as examination in model errors.

Dependence of laser radiation intensity on the elastic deformation of a revolving optical disk with a reflective coating

NASA Astrophysics Data System (ADS)

Gladyshev, V. O.; Portnov, D. I.

2016-12-01

The physical mechanism of alteration of intensity of linearly polarized monochromatic electromagnetic radiation with λ = 630 nm in a revolving dielectric disk with a mirror coating is examined. The effect is induced by elastic deformation due to the revolution and by thermoelastic deformation of the optically transparent disk. These deformations result in birefringence, the polarization plane rotation, and a 30-40% change in the intensity of reflected radiation.

Logjam Deformation: Experimental analogs with variable flow

NASA Astrophysics Data System (ADS)

Deshpande, N.; Crosby, B. T.

2017-12-01

Observed deformation of a massive, channel-spanning logjam in Big Creek, Idaho inspired a suite of physical experiments exploring logjam kinematics in a simplified but controlled setting. Using chopsticks as surrogates for logs, we conducted experiments in a 6 m long and 1.22 m wide channel with a semi-circular, textured bed. Nails driven into the bed restrain the chopsticks and initialize logjam formation. We conducted 24 hour experiments hours under two discharge conditions: (A) constant base discharge and (B) alternating discharge between the base flow and a doubled flow. After initial stabilization, we use high-resolution down-looking photographs at one-minute intervals to construct time-lapse videos and for Particle Image Velocimetry. Despite identical experimental protocols during stabilization, the starting configuration of chopsticks is markedly different for each run. In Experiment A, the orientations and packing of chopsticks is visibly less ordered than Experiment B. However, deformation in both experiments is accomplished by the same three mechanisms: rigid blocks that propagate downstream as v-shaped fronts bounded by shear planes, logjam-wide adjustments in response to the change in position of a key member, and independent logs whose trajectories either travel underneath the logjam or adjust unbounded in the backwater. Total compression is 46% and 80% for experiment A and B, respectively. Time-series of incremental displacements for both experiments decrease noisily over time, but zero displacement is never reached. Despite very different hydrologic forcings, cumulative rates of deformation for both experiments are similar, suggesting that the progressive deformation of disordered, elongate particles (chopsticks and logs) within a larger ensemble leads to denser packing, and that this mechanism best describes logjam deformation.

Elastic strain and twist analysis of protein structural data and allostery of the transmembrane channel KcsA

NASA Astrophysics Data System (ADS)

Mitchell, Michael R.; Leibler, Stanislas

2018-05-01

The abundance of available static protein structural data makes the more effective analysis and interpretation of this data a valuable tool to supplement the experimental study of protein mechanics. Structural displacements can be difficult to analyze and interpret. Previously, we showed that strains provide a more natural and interpretable representation of protein deformations, revealing mechanical coupling between spatially distinct sites of allosteric proteins. Here, we demonstrate that other transformations of displacements yield additional insights. We calculate the divergence and curl of deformations of the transmembrane channel KcsA. Additionally, we introduce quantities analogous to bend, splay, and twist deformation energies of nematic liquid crystals. These transformations enable the decomposition of displacements into different modes of deformation, helping to characterize the type of deformation a protein undergoes. We apply these calculations to study the filter and gating regions of KcsA. We observe a continuous path of rotational deformations physically coupling these two regions, and, we propose, underlying the allosteric interaction between these regions. Bend, splay, and twist distinguish KcsA gate opening, filter opening, and filter-gate coupling, respectively. In general, physically meaningful representations of deformations (like strain, curl, bend, splay, and twist) can make testable predictions and yield insights into protein mechanics, augmenting experimental methods and more fully exploiting available structural data.

Fiber-reinforced dielectric elastomer laminates with integrated function of actuating and sensing

NASA Astrophysics Data System (ADS)

Li, Tiefeng; Xie, Yuhan; Li, Chi; Yang, Xuxu; Jin, Yongbin; Liu, Junjie; Huang, Xiaoqiang

2015-04-01

The natural limbs of animals and insects integrate muscles, skins and neurons, providing both the actuating and sensing functions simultaneously. Inspired by the natural structure, we present a novel structure with integrated function of actuating and sensing with dielectric elastomer (DE) laminates. The structure can deform when subjected to high voltage loading and generate corresponding output signal in return. We investigate the basic physical phenomenon of dielectric elastomer experimentally. It is noted that when applying high voltage, the actuating dielectric elastomer membrane deforms and the sensing dielectric elastomer membrane changes the capacitance in return. Based on the concept, finite element method (FEM) simulation has been conducted to further investigate the electromechanical behavior of the structure.

A Gradient-Based Multistart Algorithm for Multimodal Aerodynamic Shape Optimization Problems Based on Free-Form Deformation

NASA Astrophysics Data System (ADS)

Streuber, Gregg Mitchell

Environmental and economic factors motivate the pursuit of more fuel-efficient aircraft designs. Aerodynamic shape optimization is a powerful tool in this effort, but is hampered by the presence of multimodality in many design spaces. Gradient-based multistart optimization uses a sampling algorithm and multiple parallel optimizations to reliably apply fast gradient-based optimization to moderately multimodal problems. Ensuring that the sampled geometries remain physically realizable requires manually developing specialized linear constraints for each class of problem. Utilizing free-form deformation geometry control allows these linear constraints to be written in a geometry-independent fashion, greatly easing the process of applying the algorithm to new problems. This algorithm was used to assess the presence of multimodality when optimizing a wing in subsonic and transonic flows, under inviscid and viscous conditions, and a blended wing-body under transonic, viscous conditions. Multimodality was present in every wing case, while the blended wing-body was found to be generally unimodal.

2-3D nonlocal transport model in magnetized laser plasmas.

NASA Astrophysics Data System (ADS)

Nicolaï, Philippe; Feugeas, Jean-Luc; Schurtz, Guy

2004-11-01

We present a model of nonlocal transport for multidimensional radiation magneto-hydrodynamics codes. This model, based on simplified Fokker-Planck equations, aims at extending the formulae of G Schurtz,Ph.Nicolaï and M. Busquet [Phys. Plasmas,7,4238 (2000)] to magnetized plasmas.The improvements concern various points as the electric field effects on nonlocal transport or conversely the kinetic effects on E field. However the main purpose of this work is to generalize the previous model by including magnetic field effects. A complete system of nonlocal equations is derived from kinetic equations with self-consistent E and B fields. These equations are analyzed and simplified in order to be implemented into large laser fusion codes and coupled to other relevent physics. Finally, our model allows to obtain the deformation of the electron distribution function due to nonlocal effects. This deformation leads to a non-maxwellian function which could be used to compute the influence on other physical processes.

Generating patient specific pseudo-CT of the head from MR using atlas-based regression

NASA Astrophysics Data System (ADS)

Sjölund, J.; Forsberg, D.; Andersson, M.; Knutsson, H.

2015-01-01

Radiotherapy planning and attenuation correction of PET images require simulation of radiation transport. The necessary physical properties are typically derived from computed tomography (CT) images, but in some cases, including stereotactic neurosurgery and combined PET/MR imaging, only magnetic resonance (MR) images are available. With these applications in mind, we describe how a realistic, patient-specific, pseudo-CT of the head can be derived from anatomical MR images. We refer to the method as atlas-based regression, because of its similarity to atlas-based segmentation. Given a target MR and an atlas database comprising MR and CT pairs, atlas-based regression works by registering each atlas MR to the target MR, applying the resulting displacement fields to the corresponding atlas CTs and, finally, fusing the deformed atlas CTs into a single pseudo-CT. We use a deformable registration algorithm known as the Morphon and augment it with a certainty mask that allows a tailoring of the influence certain regions are allowed to have on the registration. Moreover, we propose a novel method of fusion, wherein the collection of deformed CTs is iteratively registered to their joint mean and find that the resulting mean CT becomes more similar to the target CT. However, the voxelwise median provided even better results; at least as good as earlier work that required special MR imaging techniques. This makes atlas-based regression a good candidate for clinical use.

Palpation Simulator of Beating Aorta for Cardiovascular Surgery Training

NASA Astrophysics Data System (ADS)

Yamamoto, Yasuhiro; Nakao, Megumi; Kuroda, Tomohiro; Oyama, Hiroshi; Komori, Masaru; Matsuda, Tetsuya; Sakaguchi, Genichi; Komeda, Masashi; Takahashi, Takashi

In field of cardiovascular surgeries, palpation of aorta plays important roles in decision of surgical site.This paper develops palpation simulator of aorta based on a finite element based physical model.The proposed model calculates soft tissue deformation according to the affection of inner pressure and the operation of a surgeon.The proposed method is implemented on a prototype with dual PHANToM device.Experimental results confirmed our model achieves real time simulation of the surgical palpation.

Fluctuations of a q-deformed fermion gas

NASA Astrophysics Data System (ADS)

Zeng, Qijun; Ge, Jing; Luo, Yongsong

2018-05-01

The theory of q-deformed fermions is one of the theories of q-deformed oscillators. Within the framework of this theory and the traditional fluctuation theory, we investigate fluctuations of q-deformed fermion gas and obtain the expressions of fluctuations of the internal energy U, the particle number N and the correlation of fluctuations of the two physical quantities above. Further numerical calculation reveals that fluctuations of such a system have some interesting and particular features. We consider that this work may provide much insight into the theory of q fermions, and may also be helpful for the theory of q-deformed oscillators.

A social discounting model based on Tsallis’ statistics

NASA Astrophysics Data System (ADS)

Takahashi, Taiki

2010-09-01

Social decision making (e.g. social discounting and social preferences) has been attracting attention in economics, econophysics, social physics, behavioral psychology, and neuroeconomics. This paper proposes a novel social discounting model based on the deformed algebra developed in the Tsallis’ non-extensive thermostatistics. Furthermore, it is suggested that this model can be utilized to quantify the degree of consistency in social discounting in humans and analyze the relationships between behavioral tendencies in social discounting and other-regarding economic decision making under game-theoretic conditions. Future directions in the application of the model to studies in econophysics, neuroeconomics, and social physics, as well as real-world problems such as the supply of live organ donations, are discussed.

A nonaffine network model for elastomers undergoing finite deformations

NASA Astrophysics Data System (ADS)

Davidson, Jacob D.; Goulbourne, N. C.

2013-08-01

In this work, we construct a new physics-based model of rubber elasticity to capture the strain softening, strain hardening, and deformation-state dependent response of rubber materials undergoing finite deformations. This model is unique in its ability to capture large-stretch mechanical behavior with parameters that are connected to the polymer chemistry and can also be easily identified with the important characteristics of the macroscopic stress-stretch response. The microscopic picture consists of two components: a crosslinked network of Langevin chains and an entangled network with chains confined to a nonaffine tube. These represent, respectively, changes in entropy due to thermally averaged chain conformations and changes in entropy due to the magnitude of these conformational fluctuations. A simple analytical form for the strain energy density is obtained using Rubinstein and Panyukov's single-chain description of network behavior. The model only depends on three parameters that together define the initial modulus, extent of strain softening, and the onset of strain hardening. Fits to large stretch data for natural rubber, silicone rubber, VHB 4905 (polyacrylate rubber), and b186 rubber (a carbon black-filled rubber) are presented, and a comparison is made with other similar constitutive models of large-stretch rubber elasticity. We demonstrate that the proposed model provides a complete description of elastomers undergoing large deformations for different applied loading configurations. Moreover, since the strain energy is obtained using a clear set of physical assumptions, this model may be tested and used to interpret the results of computer simulation and experiments on polymers of known microscopic structure.

A physics based approach to the pulse wave velocity prediction in compliant arterial segments.

PubMed

Liberson, Alexander S; Lillie, Jeffrey S; Day, Steven W; Borkholder, David A

2016-10-03

Pulse wave velocity (PWV) quantification commonly serves as a highly robust prognostic parameter being used in a preventative cardiovascular therapy. Being dependent on arterial elastance, it can serve as a marker of cardiovascular risk. Since it is influenced by a blood pressure (BP), the pertaining theory can lay the foundation in developing a technique for noninvasive blood pressure measurement. Previous studies have reported application of PWV, measured noninvasively, for both the estimation of arterial compliance and blood pressure, based on simplified physical or statistical models. A new theoretical model for pulse wave propagation in a compliant arterial segment is presented within the framework of pseudo-elastic deformation of biological tissue undergoing finite deformation. An essential ingredient is the dependence of results on nonlinear aspects of the model: convective fluid phenomena, hyperelastic constitutive relation, large deformation and a longitudinal pre-stress load. An exact analytical solution for PWV is presented as a function of pressure, flow and pseudo-elastic orthotropic parameters. Results from our model are compared with published in-vivo PWV measurements under diverse physiological conditions. Contributions of each of the nonlinearities are analyzed. It was found that the totally nonlinear model achieves the best match with the experimental data. To retrieve individual vascular information of a patient, the inverse problem of hemodynamics is presented, calculating local orthotropic hyperelastic properties of the arterial wall. The proposed technique can be used for non-invasive assessment of arterial elastance, and blood pressure using direct measurement of PWV, with account of hyperelastic orthotropic properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

Physics Notes

ERIC Educational Resources Information Center

School Science Review, 1972

1972-01-01

Seventeen experiments in physics are described to demonstrate various physical phenomena. These include the areas of velocity of sound, damped oscillations, plastic deformation of wires, materials, testing, air resistance, spectrum optical filtering, and some new improvised apparatus. (PS)

Spherical solid model system: Exact evaluation of the van der Waals interaction between a microscopic or submacroscopic spherical solid and a deformable fluid interface

NASA Astrophysics Data System (ADS)

Wang, Y. Z.; Wang, B.; Xiong, X. M.; Zhang, J. X.

2011-03-01

In many previous research work associated with studying the deformation of the fluid interface interacting with a solid, the theoretical calculation of the surface energy density on the deformed fluid interface (or its interaction surface pressure) is often approximately obtained by using the expression for the interaction energy per unit area (or pressure) between two parallel macroscopic plates, e.g. σ(D) = - A / 12 πD2or π(D) = - A / 6 πD3for the van der Waals (vdW) interaction, through invoking the Derjaguin approximation (DA). This approximation however would result in over- or even inaccurate-prediction of the interaction force and the corresponding deformation of the fluid interface due to the invalidation of Derjaguin approximation in cases of microscopic or submacroscopic solids. To circumvent the above limitations existing in the previous DA-based theoretical work, a more accurate and quantitative theoretical model, available for exactly calculating the vdW-induced deformation of a planar fluid interface interacting with a sphere, and the interaction forces taking into account its change, is presented in this paper. The validity and advantage of the new mathematical and physical technique is rigorously verified by comparison with the numerical results on basis of the previous Paraboloid solid (PS) model and the Hamaker's sphere-flat expression (viz. F = - 2 Aa3 / (3 D2( D + 2 a) 2)), as well as its well-known DA-based general form of F / a = - A / 6z p02.

General Multimechanism Reversible-Irreversible Time-Dependent Constitutive Deformation Model Being Developed

NASA Technical Reports Server (NTRS)

Saleeb, A. F.; Arnold, Steven M.

2001-01-01

Since most advanced material systems (for example metallic-, polymer-, and ceramic-based systems) being currently researched and evaluated are for high-temperature airframe and propulsion system applications, the required constitutive models must account for both reversible and irreversible time-dependent deformations. Furthermore, since an integral part of continuum-based computational methodologies (be they microscale- or macroscale-based) is an accurate and computationally efficient constitutive model to describe the deformation behavior of the materials of interest, extensive research efforts have been made over the years on the phenomenological representations of constitutive material behavior in the inelastic analysis of structures. From a more recent and comprehensive perspective, the NASA Glenn Research Center in conjunction with the University of Akron has emphasized concurrently addressing three important and related areas: that is, 1) Mathematical formulation; 2) Algorithmic developments for updating (integrating) the external (e.g., stress) and internal state variables; 3) Parameter estimation for characterizing the model. This concurrent perspective to constitutive modeling has enabled the overcoming of the two major obstacles to fully utilizing these sophisticated time-dependent (hereditary) constitutive models in practical engineering analysis. These obstacles are: 1) Lack of efficient and robust integration algorithms; 2) Difficulties associated with characterizing the large number of required material parameters, particularly when many of these parameters lack obvious or direct physical interpretations.

Deformation mechanisms, defects, heat treatment, and thermal conductivity in large grain niobium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bieler, Thomas R., E-mail: bieler@egr.msu.edu; Kang, Di, E-mail: kangdi@msu.edu; Baars, Derek C., E-mail: baarsder@gmail.com

2015-12-04

The physical and mechanical metallurgy underlying fabrication of large grain cavities for superconducting radio frequency accelerators is summarized, based on research of 1) grain orientations in ingots, 2) a metallurgical assessment of processing a large grain single cell cavity and a tube, 3) assessment of slip behavior of single crystal tensile samples extracted from a high purity ingot slice before and after annealing at 800 °C / 2 h, 4) development of crystal plasticity models based upon the single crystal experiments, and 5) assessment of how thermal conductivity is affected by strain, heat treatment, and exposure to hydrogen. Because of themore » large grains, the plastic anisotropy of deformation is exaggerated, and heterogeneous strains and localized defects are present to a much greater degree than expected in polycrystalline material, making it highly desirable to computationally anticipate potential forming problems before manufacturing cavities.« less

Advantages of formulating an evolution equation directly for elastic distortional deformation in finite deformation plasticity

NASA Astrophysics Data System (ADS)

Rubin, M. B.; Cardiff, P.

2017-11-01

Simo (Comput Methods Appl Mech Eng 66:199-219, 1988) proposed an evolution equation for elastic deformation together with a constitutive equation for inelastic deformation rate in plasticity. The numerical algorithm (Simo in Comput Methods Appl Mech Eng 68:1-31, 1988) for determining elastic distortional deformation was simple. However, the proposed inelastic deformation rate caused plastic compaction. The corrected formulation (Simo in Comput Methods Appl Mech Eng 99:61-112, 1992) preserves isochoric plasticity but the numerical integration algorithm is complicated and needs special methods for calculation of the exponential map of a tensor. Alternatively, an evolution equation for elastic distortional deformation can be proposed directly with a simplified constitutive equation for inelastic distortional deformation rate. This has the advantage that the physics of inelastic distortional deformation is separated from that of dilatation. The example of finite deformation J2 plasticity with linear isotropic hardening is used to demonstrate the simplicity of the numerical algorithm.

RHEUMATOID ARTHRITIS. PHYSICAL MEASURES IN TREATMENT OF CHILDREN.

PubMed

EISING, L M; SOULES, B

1964-05-01

Prognosis in rheumatic arthritis in children is good, provided total care is given, deformity prevented and function maintained. Bed rest is desirable until active inflammation of the joints has subsided. During convalescence a balance between rest and exercise must be maintained to avoid recurrence of inflammation of the joints. When there is progressive deformity or disabling pain in the wrist, a molded leather wrist-cuff splint can control the deformity, decrease or abolish pain and lessen swelling. If there is valgus deformity of the knee or external rotation of the tibia, with no more than ten degrees of knee flexion deformity, correction can be obtained by simple manipulations.

EM Bias-Correction for Ice Thickness and Surface Roughness Retrievals over Rough Deformed Sea Ice

NASA Astrophysics Data System (ADS)

Li, L.; Gaiser, P. W.; Allard, R.; Posey, P. G.; Hebert, D. A.; Richter-Menge, J.; Polashenski, C. M.

2016-12-01

The very rough ridge sea ice accounts for significant percentage of total ice areas and even larger percentage of total volume. The commonly used Radar altimeter surface detection techniques are empirical in nature and work well only over level/smooth sea ice. Rough sea ice surfaces can modify the return waveforms, resulting in significant Electromagnetic (EM) bias in the estimated surface elevations, and thus large errors in the ice thickness retrievals. To understand and quantify such sea ice surface roughness effects, a combined EM rough surface and volume scattering model was developed to simulate radar returns from the rough sea ice `layer cake' structure. A waveform matching technique was also developed to fit observed waveforms to a physically-based waveform model and subsequently correct the roughness induced EM bias in the estimated freeboard. This new EM Bias Corrected (EMBC) algorithm was able to better retrieve surface elevations and estimate the surface roughness parameter simultaneously. In situ data from multi-instrument airborne and ground campaigns were used to validate the ice thickness and surface roughness retrievals. For the surface roughness retrievals, we applied this EMBC algorithm to co-incident LiDAR/Radar measurements collected during a Cryosat-2 under-flight by the NASA IceBridge missions. Results show that not only does the waveform model fit very well to the measured radar waveform, but also the roughness parameters derived independently from the LiDAR and radar data agree very well for both level and deformed sea ice. For sea ice thickness retrievals, validation based on in-situ data from the coordinated CRREL/NRL field campaign demonstrates that the physically-based EMBC algorithm performs fundamentally better than the empirical algorithm over very rough deformed sea ice, suggesting that sea ice surface roughness effects can be modeled and corrected based solely on the radar return waveforms.

Ultrathin epidermal strain sensor based on an elastomer nanosheet with an inkjet-printed conductive polymer

NASA Astrophysics Data System (ADS)

Tetsu, Yuma; Yamagishi, Kento; Kato, Akira; Matsumoto, Yuya; Tsukune, Mariko; Kobayashi, Yo; Fujie, Masakatsu G.; Takeoka, Shinji; Fujie, Toshinori

2017-08-01

To minimize the interference that skin-contact strain sensors cause natural skin deformation, physical conformability to the epidermal structure is critical. Here, we developed an ultrathin strain sensor made from poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) inkjet-printed on a polystyrene-polybutadiene-polystyrene (SBS) nanosheet. The sensor, whose total thickness and gauge factor were ˜1 µm and 0.73 ± 0.10, respectively, deeply conformed to the epidermal structure and successfully detected the small skin strain (˜2%) while interfering minimally with the natural deformation of the skin. Such an epidermal strain sensor will open a new avenue for precisely detecting the motion of human skin and artificial soft-robotic skin.

Non extensive statistical physics applied in fracture-induced electric signals during triaxial deformation of Carrara marble

NASA Astrophysics Data System (ADS)

Cartwright-Taylor, Alexis; Vallianatos, Filippos; Sammonds, Peter

2014-05-01

We have conducted room-temperature, triaxial compression experiments on samples of Carrara marble, recording concurrently acoustic and electric current signals emitted during the deformation process as well as mechanical loading information and ultrasonic wave velocities. Our results reveal that in a dry non-piezoelectric rock under simulated crustal pressure conditions, a measurable electric current (nA) is generated within the stressed sample. The current is detected only in the region beyond (quasi-)linear elastic deformation; i.e. in the region of permanent deformation beyond the yield point of the material and in the presence of microcracking. Our results extend to shallow crustal conditions previous observations of electric current signals in quartz-free rocks undergoing uniaxial deformation and support the idea of a universal electrification mechanism related to deformation. Confining pressure conditions of our slow strain rate (10-6 s-1) experiments range from the purely brittle regime (10 MPa) to the semi-brittle transition (30-100MPa) where cataclastic flow is the dominant deformation mechanism. Electric current is generated under all confining pressures,implying the existence of a current-producing mechanism during both microfracture and frictional sliding. Some differences are seen in the current evolution between these two regimes, possibly related to crack localisation. In all cases, the measured electric current exhibits episodes of strong fluctuations over short timescales; calm periods punctuated by bursts of strong activity. For the analysis, we adopt an entropy-based statistical physics approach (Tsallis, 1988), particularly suited to the study of fracture related phenomena. We find that the probability distribution of normalised electric current fluctuations over short time intervals (0.5 s) can be well described by a q-Gaussian distribution of a form similar to that which describes turbulent flows. This approach yields different entropic indices (q-values) for electric current fluctuations in the brittle and semi-brittle regimes (c. 1.5 and 1.8 respectively), implying an increase in interactions between microcracks in the semi-brittle regime. We interpret this non-Gaussian behaviour as a 'superstatistical' superposition of local Gaussian fluctuations that combine to produce a higher-order overall distribution; i.e. the measured electric current is driven to varying, temporary, local equilibria during deformation. This behaviour is analogous to the self-organising avalanche-like behaviour of fracture events, suggesting that the observed behaviour of measured electric current is a direct response to the microcracking events themselves and supporting the idea of a fracture-generated electrification mechanism in the crust. Our results have implications for the earthquake preparation process and the application of Tsallis statistical physics to the analysis of electric earthquake precursors. This research has been funded by the European Union (European Social Fund) and Greek national resources under the framework of the "THALES Program: SEISMO FEAR HELLARC" project of the "Education & Lifelong Learning" Operational Programme.

Numerical Simulation of Multiphase Magnetohydrodynamic Flow and Deformation of Electrolyte-Metal Interface in Aluminum Electrolysis Cells

NASA Astrophysics Data System (ADS)

Hua, Jinsong; Rudshaug, Magne; Droste, Christian; Jorgensen, Robert; Giskeodegard, Nils-Haavard

2018-06-01

A computational fluid dynamics based multiphase magnetohydrodynamic (MHD) flow model for simulating the melt flow and bath-metal interface deformation in realistic aluminum reduction cells is presented. The model accounts for the complex physics of the MHD problem in aluminum reduction cells by coupling two immiscible fluids, electromagnetic field, Lorentz force, flow turbulence, and complex cell geometry with large length scale. Especially, the deformation of bath-metal interface is tracked directly in the simulation, and the condition of constant anode-cathode distance (ACD) is maintained by moving anode bottom dynamically with the deforming bath-metal interface. The metal pad deformation and melt flow predicted by the current model are compared to the predictions using a simplified model where the bath-metal interface is assumed flat. The effects of the induced electric current due to fluid flow and the magnetic field due to the interior cell current on the metal pad deformation and melt flow are investigated. The presented model extends the conventional simplified box model by including detailed cell geometry such as the ledge profile and all channels (side, central, and cross-channels). The simulations show the model sensitivity to different side ledge profiles and the cross-channel width by comparing the predicted melt flow and metal pad heaving. In addition, the model dependencies upon the reduction cell operation conditions such as ACD, current distribution on cathode surface and open/closed channel top, are discussed.

Anthropometric measurements and vertebral deformities. European Vertebral Osteoporosis Study (EVOS) Group.

PubMed

Johnell, O; O'Neill, T; Felsenberg, D; Kanis, J; Cooper, C; Silman, A J

1997-08-15

To investigate the association between anthropometric indices and morphometrically determined vertebral deformity, the authors carried out a cross-sectional study using data from the European Vertebral Osteoporosis Study (EVOS), a population-based study of vertebral osteoporosis in 36 European centers from 19 countries. A total of 16,047 EVOS subjects were included in this analysis, of whom 1,973 subjects (915 males, 1,058 females) (12.3%) aged 50 years or over had one or more vertebral deformities ("cases"). The cases were compared with the 14,074 subjects (6,539 males, 7,535 females) with morphometrically normal spines ("controls"). Data were collected on self-reported height at age 25 years and minimum weight after age 25 years, as well as on current measured height and weight. Body mass index (BMI) and height and weight change were calculated from these data. The relations between these variables and vertebral deformity were examined separately by sex with logistic regression adjusting for age, smoking, and physical activity. In females, there was a significant trend of decreasing risk with increasing quintile of current weight, current BMI, and weight gain since age 25 years. In males, subjects in the lightest quintile for these measures were at increased risk but there was no evidence of a trend. An ecologic analysis by country revealed a negative correlation between mean BMI and the prevalence of deformity in females but not in males. The authors conclude that low body weight is associated with presence of vertebral deformity.

Analytical model for instantaneous lift and shape deformation of an insect-scale flapping wing in hover

PubMed Central

Kang, Chang-kwon; Shyy, Wei

2014-01-01

In the analysis of flexible flapping wings of insects, the aerodynamic outcome depends on the combined structural dynamics and unsteady fluid physics. Because the wing shape and hence the resulting effective angle of attack are a priori unknown, predicting aerodynamic performance is challenging. Here, we show that a coupled aerodynamics/structural dynamics model can be established for hovering, based on a linear beam equation with the Morison equation to account for both added mass and aerodynamic damping effects. Lift strongly depends on the instantaneous angle of attack, resulting from passive pitch associated with wing deformation. We show that both instantaneous wing deformation and lift can be predicted in a much simplified framework. Moreover, our analysis suggests that resulting wing kinematics can be explained by the interplay between acceleration-related and aerodynamic damping forces. Interestingly, while both forces combine to create a high angle of attack resulting in high lift around the midstroke, they offset each other for phase control at the end of the stroke. PMID:25297319

Vibration of a spatial elastica constrained inside a straight tube

NASA Astrophysics Data System (ADS)

Chen, Jen-San; Fang, Joyce

2014-04-01

In this paper we study the dynamic behavior of a clamped-clamped spatial elastica under edge thrust constrained inside a straight cylindrical tube. Attention is focused on the calculation of the natural frequencies and mode shapes of the planar and spatial one-point-contact deformations. The main issue in determining the natural frequencies of a constrained rod is the movement of the contact point during vibration. In order to capture the physical essence of the contact-point movement, an Eulerian description of the equations of motion based on director theory is formulated. After proper linearization of the equations of motion, boundary conditions, and contact conditions, the natural frequencies and mode shapes of the elastica can be obtained by solving a system of eighteen first-order differential equations with shooting method. It is concluded that the planar one-point-contact deformation becomes unstable and evolves to a spatial deformation at a bifurcation point in both displacement and force control procedures.

Effect of the mechanical deformation on the electrical properties of the polymer/CNT fiber

NASA Astrophysics Data System (ADS)

Cho, Hyun Woo; Sung, Bong June; Nano-Bio Computational Chemistry Laboratory Team

2014-03-01

We elucidate the effect of the mechanical deformation on the electrical properties of the polymer/CNT fiber. The conductive polymer fiber has drawn a great attention for its potential application to a stretchable electronics such as wearable devices and artificial muscles, etc. However, the electrical conductivity of the polymer-based stretchable electronics decreases significantly during the deformation, which may limit the applicability of the polymer/CNT fiber for the stretchable electronics. Moreover, its physical origin for the decrease in electrical conductivity has not been explained clearly. In this work, we employ a coarse-grained model for the polymer/CNT fiber, and we calculate the electric conductivity using global tunneling network (GTN) model. We show that the electric conductivity decreases during the elongation of the polymer/CNT fiber. We also find using critical path approximation (CPA) that the structure of the electrical network of the CNTs changes collectively during the elongation of the fiber, which is strongly responsible for the reduction of the electrical conductivity of the polymer/CNT fiber.

Validation of an improved 'diffeomorphic demons' algorithm for deformable image registration in image-guided radiation therapy.

PubMed

Zhou, Lu; Zhou, Linghong; Zhang, Shuxu; Zhen, Xin; Yu, Hui; Zhang, Guoqian; Wang, Ruihao

2014-01-01

Deformable image registration (DIR) was widely used in radiation therapy, such as in automatic contour generation, dose accumulation, tumor growth or regression analysis. To achieve higher registration accuracy and faster convergence, an improved 'diffeomorphic demons' registration algorithm was proposed and validated. Based on Brox et al.'s gradient constancy assumption and Malis's efficient second-order minimization (ESM) algorithm, a grey value gradient similarity term and a transformation error term were added into the demons energy function, and a formula was derived to calculate the update of transformation field. The limited Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm was used to optimize the energy function so that the iteration number could be determined automatically. The proposed algorithm was validated using mathematically deformed images and physically deformed phantom images. Compared with the original 'diffeomorphic demons' algorithm, the registration method proposed achieve a higher precision and a faster convergence speed. Due to the influence of different scanning conditions in fractionated radiation, the density range of the treatment image and the planning image may be different. In such a case, the improved demons algorithm can achieve faster and more accurate radiotherapy.

Material parameter computation for multi-layered vocal fold models.

PubMed

Schmidt, Bastian; Stingl, Michael; Leugering, Günter; Berry, David A; Döllinger, Michael

2011-04-01

Today, the prevention and treatment of voice disorders is an ever-increasing health concern. Since many occupations rely on verbal communication, vocal health is necessary just to maintain one's livelihood. Commonly applied models to study vocal fold vibrations and air flow distributions are self sustained physical models of the larynx composed of artificial silicone vocal folds. Choosing appropriate mechanical parameters for these vocal fold models while considering simplifications due to manufacturing restrictions is difficult but crucial for achieving realistic behavior. In the present work, a combination of experimental and numerical approaches to compute material parameters for synthetic vocal fold models is presented. The material parameters are derived from deformation behaviors of excised human larynges. The resulting deformations are used as reference displacements for a tracking functional to be optimized. Material optimization was applied to three-dimensional vocal fold models based on isotropic and transverse-isotropic material laws, considering both a layered model with homogeneous material properties on each layer and an inhomogeneous model. The best results exhibited a transversal-isotropic inhomogeneous (i.e., not producible) model. For the homogeneous model (three layers), the transversal-isotropic material parameters were also computed for each layer yielding deformations similar to the measured human vocal fold deformations.

Modelling of deformation of underground tunnel lining, interacting with water-saturated soil

NASA Astrophysics Data System (ADS)

Berezhnoi, D. V.; Balafendieva, I. S.; Sachenkov, A. A.; Sekaeva, L. R.

2016-11-01

Built finite element method of calculating the deformation of underground tunnel lining, interacting with dry and water-saturated soils. To simulate the interaction between the lining and soils environments, including physical and non-linear, a special "contact" finite element, which allows to consider all cases of interaction between the contacting surfaces. It solved a number of problems of deformation with the ground subway tunnel lining rings.

Hydrothermal fluid flow models of Campi Flegrei caldera, Italy constrained by InSAR surface deformation time series observations

NASA Astrophysics Data System (ADS)

Lundgren, P.; Lanari, R.; Manzo, M.; Sansosti, E.; Tizzani, P.; Hutnak, M.; Hurwitz, S.

2008-12-01

Campi Flegrei caldera, Italy, located along the Bay of Naples, has a long history of significant vertical deformation, with the most recent large uplift (>1.5m) occurring in 1983-1984. Each episode of uplift has been followed by a period of subsidence that decreases in rate with time and may be punctuated by brief episodes of lesser uplift. The large amplitude of the major uplifts that occur without volcanic activity, and the subsequent subsidence has been argued as evidence for hydrothermal amplification of any magmatic source. The later subsidence and its temporal decay have been argued as due to diffusion of the pressurized caldera fill material into the less porous surrounding country rock. We present satellite synthetic aperture radar (SAR) interferometry (InSAR) time series analysis of ERS and Envisat data from the European Space Agency, based on exploiting the Small Baseline Subset (SBAS) approach [Berardino et al., 2002]; this allows us to generate maps of relative surface deformation though time, beginning in 1992 through 2007, that are relevant to both ascending and descending satellite orbits. The general temporal behavior is one of subsidence punctuated by several lesser uplift episodes. The spatial pattern of deformation can be modeled through simple inflation/deflation sources in an elastic halfspace. Given the evidence to suggest that fluids may play a significant role in the temporal deformation of Campi Flegrei, rather than a purely magmatic or magma chamber-based interpretation, we model the temporal and spatial evolution of surface deformation as a hydrothermal fluid flow process. We use the TOUGH2-BIOT2 set of numerical codes [Preuss et al., 1999; Hsieh, 1996], which couple multi-phase (liquid-gas) and multi-component (H2O-CO2) fluid flow in a porous or fractured media with plane strain deformation and fluid flow in a linearly elastic porous medium. We explore parameters related to the depth and temporal history of fluid injection, fluid composition, circulation geometries, and the physical properties of the media, to explain the InSAR time series. References: Berardino, P., R. Lanari, E. Sansosti (2002), A new Algorithm for surface deformation monitoring based on small baseline differential SAR interferograms, IEEE Transactions on Geoscience and Remote Sensing, 40, 11, 2375-2383. Pruess, L., C. Oldenburg, and G. Moridis (1999), TOUGH2 user's guide, version 2.0, Paper LBNL-43134, Lawrence Berkeley Natl. Lab., Berkeley, Calif. Hsieh, P. A. (1996), Deformation-induced changes in hydraulic head during ground-water withdrawal, Ground Water, 34, 1082-1089.

Mathematical model of rolling an elastic wheel over deformable support base

NASA Astrophysics Data System (ADS)

Volskaia, V. N.; Zhileykin, M. M.; Zakharov, A. Y.

2018-02-01

One of the main direction of economic growth in Russia remains to be a speedy development of north and northeast regions that are the constituents of the 60 percent of the country territory. The further development of these territories requires new methods and technologies for solving transport and technological problems when off-road transportation of cargoes and people is conducting. One of the fundamental methods of patency prediction is imitation modeling of wheeled vehicles movement in different operating conditions. Both deformable properties of tires and physical and mechanical properties of the ground: normal tire deflection and gauge depth; variation of contact patch area depending on the load and pressure of air in the tire; existence of hysteresis losses in the tire material which are influencing on the rolling resistance due to friction processes between tire and ground in the contact patch; existence of the tangential reaction from the ground by entire contact area influence on the tractive patency. Nowadays there are two main trends in theoretical research of interaction wheeled propulsion device with ground: analytical method involving mathematical description of explored process and finite element method based on computational modeling. Mathematical models of interaction tire with the ground are used both in processes of interaction individual wheeled propulsion device with ground and researches of mobile vehicle dynamical models operated in specific road and climate conditions. One of the most significant imperfection of these models is the description of interaction wheel with flat deformable support base whereas profile of real support base surface has essential height of unevenness which is commensurate with radius of the wheel. The description of processes taking place in the ground under influence of the wheeled propulsion device using the finite element method is relatively new but most applicable lately. The application of this method allows to provide the most accurate description of the interaction process of a wheeled propulsion devices and the ground, also this method allows to define tension in the ground, deformation of the ground and the tire and ground’s compression. However, the high laboriousness of computations is essential shortcoming of that method therefore it’s hard to use these models as part of the general motion model of multi-axis wheeled vehicles. The purpose of this research is the elaboration of mathematical model of elastic wheel rolling over deformable rough support base taking into account the contact patch deformation. The mathematical model of rectilinear rolling an elastic wheel over rough deformable support base, taking into account variation of contact patch area and variation in the direction of the radial and tangential reactions also load bearing capacity of the ground, is developed. The efficiency of developed mathematical model of rectilinear rolling an elastic wheel over rough deformable support base is proved by the simulation methods.

Predicting the Performance of Chain Saw Machines Based on Shore Scleroscope Hardness

NASA Astrophysics Data System (ADS)

Tumac, Deniz

2014-03-01

Shore hardness has been used to estimate several physical and mechanical properties of rocks over the last few decades. However, the number of researches correlating Shore hardness with rock cutting performance is quite limited. Also, rather limited researches have been carried out on predicting the performance of chain saw machines. This study differs from the previous investigations in the way that Shore hardness values (SH1, SH2, and deformation coefficient) are used to determine the field performance of chain saw machines. The measured Shore hardness values are correlated with the physical and mechanical properties of natural stone samples, cutting parameters (normal force, cutting force, and specific energy) obtained from linear cutting tests in unrelieved cutting mode, and areal net cutting rate of chain saw machines. Two empirical models developed previously are improved for the prediction of the areal net cutting rate of chain saw machines. The first model is based on a revised chain saw penetration index, which uses SH1, machine weight, and useful arm cutting depth as predictors. The second model is based on the power consumed for only cutting the stone, arm thickness, and specific energy as a function of the deformation coefficient. While cutting force has a strong relationship with Shore hardness values, the normal force has a weak or moderate correlation. Uniaxial compressive strength, Cerchar abrasivity index, and density can also be predicted by Shore hardness values.

An Analysis on the Constitutive Models for Forging of Ti6Al4V Alloy Considering the Softening Behavior

NASA Astrophysics Data System (ADS)

Souza, Paul M.; Beladi, Hossein; Singh, Rajkumar P.; Hodgson, Peter D.; Rolfe, Bernard

2018-05-01

This paper developed high-temperature deformation constitutive models for a Ti6Al4V alloy using an empirical-based Arrhenius equation and an enhanced version of the authors' physical-based EM + Avrami equations. The initial microstructure was a partially equiaxed α + β grain structure. A wide range of experimental data was obtained from hot compression of the Ti6Al4 V alloy at deformation temperatures ranging from 720 to 970 °C, and at strain rates varying from 0.01 to 10 s-1. The friction- and adiabatic-corrected flow curves were used to identify the parameter values of the constitutive models. Both models provided good overall accuracy of the flow stress. The generalized modified Arrhenius model was better at predicting the flow stress at lower strain rates. However, the model was inaccurate in predicting the peak strain. In contrast, the enhanced physical-based EM + Avrami model revealed very good accuracy at intermediate and high strain rates, but it was also better at predicting the peak strain. Blind sample tests revealed that the EM + Avrami maintained good predictions on new (unseen) data. Thus, the enhanced EM + Avrami model may be preferred over the Arrhenius model to predict the flow behavior of Ti6Al4V alloy during industrial forgings, when the initial microstructure is partially equiaxed.

Mapping soil deformation around plant roots using in vivo 4D X-ray Computed Tomography and Digital Volume Correlation.

PubMed

Keyes, S D; Gillard, F; Soper, N; Mavrogordato, M N; Sinclair, I; Roose, T

2016-06-14

The mechanical impedance of soils inhibits the growth of plant roots, often being the most significant physical limitation to root system development. Non-invasive imaging techniques have recently been used to investigate the development of root system architecture over time, but the relationship with soil deformation is usually neglected. Correlative mapping approaches parameterised using 2D and 3D image data have recently gained prominence for quantifying physical deformation in composite materials including fibre-reinforced polymers and trabecular bone. Digital Image Correlation (DIC) and Digital Volume Correlation (DVC) are computational techniques which use the inherent material texture of surfaces and volumes, captured using imaging techniques, to map full-field deformation components in samples during physical loading. Here we develop an experimental assay and methodology for four-dimensional, in vivo X-ray Computed Tomography (XCT) and apply a Digital Volume Correlation (DVC) approach to the data to quantify deformation. The method is validated for a field-derived soil under conditions of uniaxial compression, and a calibration study is used to quantify thresholds of displacement and strain measurement. The validated and calibrated approach is then demonstrated for an in vivo test case in which an extending maize root in field-derived soil was imaged hourly using XCT over a growth period of 19h. This allowed full-field soil deformation data and 3D root tip dynamics to be quantified in parallel for the first time. This fusion of methods paves the way for comparative studies of contrasting soils and plant genotypes, improving our understanding of the fundamental mechanical processes which influence root system development. Copyright © 2016 Elsevier Ltd. All rights reserved.

Using Remote Sensing Data to Constrain Models of Fault Interactions and Plate Boundary Deformation

NASA Astrophysics Data System (ADS)

Glasscoe, M. T.; Donnellan, A.; Lyzenga, G. A.; Parker, J. W.; Milliner, C. W. D.

2016-12-01

Determining the distribution of slip and behavior of fault interactions at plate boundaries is a complex problem. Field and remotely sensed data often lack the necessary coverage to fully resolve fault behavior. However, realistic physical models may be used to more accurately characterize the complex behavior of faults constrained with observed data, such as GPS, InSAR, and SfM. These results will improve the utility of using combined models and data to estimate earthquake potential and characterize plate boundary behavior. Plate boundary faults exhibit complex behavior, with partitioned slip and distributed deformation. To investigate what fraction of slip becomes distributed deformation off major faults, we examine a model fault embedded within a damage zone of reduced elastic rigidity that narrows with depth and forward model the slip and resulting surface deformation. The fault segments and slip distributions are modeled using the JPL GeoFEST software. GeoFEST (Geophysical Finite Element Simulation Tool) is a two- and three-dimensional finite element software package for modeling solid stress and strain in geophysical and other continuum domain applications [Lyzenga, et al., 2000; Glasscoe, et al., 2004; Parker, et al., 2008, 2010]. New methods to advance geohazards research using computer simulations and remotely sensed observations for model validation are required to understand fault slip, the complex nature of fault interaction and plate boundary deformation. These models help enhance our understanding of the underlying processes, such as transient deformation and fault creep, and can aid in developing observation strategies for sUAV, airborne, and upcoming satellite missions seeking to determine how faults behave and interact and assess their associated hazard. Models will also help to characterize this behavior, which will enable improvements in hazard estimation. Validating the model results against remotely sensed observations will allow us to better constrain fault zone rheology and physical properties, having implications for the overall understanding of earthquake physics, fault interactions, plate boundary deformation and earthquake hazard, preparedness and risk reduction.

Measuring High Speed Deformation for Space Applications

NASA Technical Reports Server (NTRS)

Wentzel, Daniel

2014-01-01

PDV (Photonic Doppler Velocimetry) has proven to be a reliable and versatile technique to observe rapid deformation of frangible joints. It will be a valuable technique in order to understand the physics of two-stage light gas guns and the material response to hypervelocity impact.

Droplet Breakup Mechanisms in Air-blast Atomizers

NASA Astrophysics Data System (ADS)

Aliabadi, Amir Abbas; Taghavi, Seyed Mohammad; Lim, Kelly

2011-11-01

Atomization processes are encountered in many natural and man-made phenomena. Examples are pollen release by plants, human cough or sneeze, engine fuel injectors, spray paint and many more. The physics governing the atomization of liquids is important in understanding and utilizing atomization processes in both natural and industrial processes. We have observed the governing physics of droplet breakup in an air-blast water atomizer using a high magnification, high speed, and high resolution LASER imaging technique. The droplet breakup mechanisms are investigated in three major categories. First, the liquid drops are flattened to form an oblate ellipsoid (lenticular deformation). Subsequent deformation depends on the magnitude of the internal forces relative to external forces. The ellipsoid is converted into a torus that becomes stretched and disintegrates into smaller drops. Second, the drops become elongated to form a long cylindrical thread or ligament that break up into smaller drops (Cigar-shaped deformation). Third, local deformation on the drop surface creates bulges and protuberances that eventually detach themselves from the parent drop to form smaller drops.

Rheological behavior of the crust and mantle in subduction zones in the time-scale range from earthquake (minute) to mln years inferred from thermomechanical model and geodetic observations

NASA Astrophysics Data System (ADS)

Sobolev, Stephan; Muldashev, Iskander

2016-04-01

The key achievement of the geodynamic modelling community greatly contributed by the work of Evgenii Burov and his students is application of "realistic" mineral-physics based non-linear rheological models to simulate deformation processes in crust and mantle. Subduction being a type example of such process is an essentially multi-scale phenomenon with the time-scales spanning from geological to earthquake scale with the seismic cycle in-between. In this study we test the possibility to simulate the entire subduction process from rupture (1 min) to geological time (Mln yr) with the single cross-scale thermomechanical model that employs elasticity, mineral-physics constrained non-linear transient viscous rheology and rate-and-state friction plasticity. First we generate a thermo-mechanical model of subduction zone at geological time-scale including a narrow subduction channel with "wet-quartz" visco-elasto-plastic rheology and low static friction. We next introduce in the same model classic rate-and state friction law in subduction channel, leading to stick-slip instability. This model generates spontaneous earthquake sequence. In order to follow in details deformation process during the entire seismic cycle and multiple seismic cycles we use adaptive time-step algorithm changing step from 40 sec during the earthquake to minute-5 year during postseismic and interseismic processes. We observe many interesting deformation patterns and demonstrate that contrary to the conventional ideas, this model predicts that postseismic deformation is controlled by visco-elastic relaxation in the mantle wedge already since hour to day after the great (M>9) earthquakes. We demonstrate that our results are consistent with the postseismic surface displacement after the Great Tohoku Earthquake for the day-to-4year time range.

Effect of Length, Diameter, Chirality, Deformation, and Strain on Contact Thermal Conductance between Single Wall Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Varshney, Vikas; Lee, Jonghoon; Brown, Joshua S.; Farmer, Barry L.; Voevodin, Andrey A.; Roy, Ajit K.

2018-04-01

Thermal energy transfer across physically interacting single-wall carbon nanotube (SWCNT) interconnects has been investigated using non-equilibrium molecular dynamics simulations. The role of various geometrical and structural (length, diameter, chirality) as well as external (deformation and strain) carbon nanotube (CNT) parameters has been explored to estimate total as well as area-normalized thermal conductance across cross-contact interconnects. It is shown that the CNT aspect ratio and degree of lateral as well as tensile deformation play a significant role in determining the extent of thermal energy exchange across CNT contacts, while CNT chirality has a negligible influence on thermal transport. Depending on the CNT diameter, aspect ratio, and degree of deformation at the contact interface, the thermal conductance values can vary significantly –by more than an order of magnitude for total conductance and a factor of 3 to 4 for area-normalized conductance. The observed trends are discussed from the perspective of modulation in number of low frequency out-of-plane (transverse, flexural, and radial) phonons that transmit thermal energy across the contact and govern the conductance across the interface. The established general dependencies for phonon governed thermal transport at CNT contacts are anticipated to help design and performance prediction of CNT-based flexible nanoelectronic devices, where CNT-CNT contact deformation and strain are routinely encountered during device operations.

Deformation strain is the main physical driver for skeletal precursors to undergo osteogenesis in earlier stages of osteogenic cell maturation.

PubMed

Ramani-Mohan, Ram-Kumar; Schwedhelm, Ivo; Finne-Wistrand, Anna; Krug, Melanie; Schwarz, Thomas; Jakob, Franz; Walles, Heike; Hansmann, Jan

2018-03-01

Mesenchymal stem cells play a major role during bone remodelling and are thus of high interest for tissue engineering and regenerative medicine applications. Mechanical stimuli, that is, deformation strain and interstitial fluid-flow-induced shear stress, promote osteogenic lineage commitment. However, the predominant physical stimulus that drives early osteogenic cell maturation is not clearly identified. The evaluation of each stimulus is challenging, as deformation and fluid-flow-induced shear stress interdepend. In this study, we developed a bioreactor that was used to culture mesenchymal stem cells harbouring a strain-responsive AP-1 luciferase reporter construct, on porous scaffolds. In addition to the reporter, mineralization and vitality of the cells was investigated by alizarin red staining and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide. Quantification of the expression of genes associated to bone regeneration and bone remodelling was used to confirm alizarin red measurements. Controlled perfusion and deformation of the 3-dimensional scaffold facilitated the alteration of the expression of osteogenic markers, luciferase activity, and calcification. To isolate the specific impact of scaffold deformation, a computational model was developed to derive a perfusion flow profile that results in dynamic shear stress conditions present in periodically loaded scaffolds. In comparison to actually deformed scaffolds, a lower expression of all measured readout parameters indicated that deformation strain is the predominant stimulus for skeletal precursors to undergo osteogenesis in earlier stages of osteogenic cell maturation. Copyright © 2017 John Wiley & Sons, Ltd.

Deformation and Metasomatic Evolution at the Subduction Plate Interface As Viewed from Study of HP/UHP Metamorphic Rocks

NASA Astrophysics Data System (ADS)

Bebout, G. E.; Penniston-Dorland, S.

2014-12-01

We provide a view of lithologic makeup, deformation, and fluid-rock interaction along the deep forearc to subarc plate interface, based on insights gained from study of HP/UHP metamorphic rocks. Exposures of plate-boundary shear zones on which we base our perspective represent 30-80 km depths and are on Catalina Island and at Monviso, Syros, and New Caledonia. Each contains highly deformed zones with schistose matrix, commonly with a large ultramafic component, containing bodies of less deformed mafic, sedimentary, and ultramafic rocks. These "blocks" have varying geometries, are up to km-scale, and can preserve disparate P-T histories reflecting dynamics of incorporation and entrainment. Sheared matrices contain high-variance, hydrous mineral assemblages in some cases resembling metasomatic zones ("rinds") at block-matrix contacts, and rinds and matrices have homogenized isotopic compositions reflecting extensive fluid-rock interaction. Shearing and related physical juxtaposition of disparate metasomatic rocks can result in mixed or 'hybrid' chemical compositions. The chlorite-, talc-, and amphibole-rich schists developed by these processes can stabilize H2O to great depth and influence its cycling. Fluids (hydrous fluids, silicate melts) released within slabs necessarily interact with highly deformed, lithologically hybridized zones at the plate interface as they ascend to potentially enter mantle wedges. Fluids bearing chemical/isotopic signatures of hybrid rocks appear capable of producing arc magma compositions interpreted as reflecting multiple, chemically distinct fluids sources. Geophysical signatures of these rheologically weak zones are equivocal but many recognize the presence of zones of low seismic velocity at/near the top of slabs and attribute them to hydrated rocks. Whether rocks from this interface buoyantly ascend into mantle wedges, indicated in some theoretical models, remains largely untested by field and geophysical observations.

Monitoring and Modeling: The Future of Volcanic Eruption Forecasting

NASA Astrophysics Data System (ADS)

Poland, M. P.; Pritchard, M. E.; Anderson, K. R.; Furtney, M.; Carn, S. A.

2016-12-01

Eruption forecasting typically uses monitoring data from geology, gas geochemistry, geodesy, and seismology, to assess the likelihood of future eruptive activity. Occasionally, months to years of warning are possible from specific indicators (e.g., deep LP earthquakes, elevated CO2 emissions, and aseismic deformation) or a buildup in one or more monitoring parameters. More often, observable changes in unrest occur immediately before eruption, as magma is rising toward the surface. In some cases, little or no detectable unrest precedes eruptive activity. Eruption forecasts are usually based on the experience of volcanologists studying the activity, but two developing fields offer a potential leap beyond this practice. First, remote sensing data, which can track thermal, gas, and ash emissions, as well as surface deformation, are increasingly available, allowing statistically significant research into the characteristics of unrest. For example, analysis of hundreds of volcanoes indicates that deformation is a more common pre-eruptive phenomenon than thermal anomalies, and that most episodes of satellite-detected unrest are not immediately followed by eruption. Such robust datasets inform the second development—probabilistic models of eruption potential, especially those that are based on physical-chemical models of the dynamics of magma accumulation and ascent. Both developments are essential for refining forecasts and reducing false positives. For example, many caldera systems have not erupted but are characterized by unrest that, in another context, would elicit strong concern from volcanologists. More observations of this behavior and better understanding of the underlying physics of unrest will improve forecasts of such activity. While still many years from implementation as a forecasting tool, probabilistic physio-chemical models incorporating satellite data offer a complement to expert assessments that, together, can form a powerful forecasting approach.

A viscoelastic model for dielectric elastomers based on a continuum mechanical formulation and its finite element implementation

NASA Astrophysics Data System (ADS)

Bueschel, A.; Klinkel, S.; Wagner, W.

2011-04-01

Smart materials are active and multifunctional materials, which play an important part for sensor and actuator applications. These materials have the potential to transform passive structures into adaptive systems. However, a prerequisite for the design and the optimization of these materials is, that reliable models exist, which incorporate the interaction between the different combinations of thermal, electrical, magnetic, optical and mechanical effects. Polymeric electroelastic materials, so-called electroactive polymer (EAP), own the characteristic to deform if an electric field is applied. EAP's possesses the benefit that they share the characteristic of polymers, these are lightweight, inexpensive, fracture tolerant, elastic, and the chemical and physical structure is well understood. However, the description "electroactive polymer" is a generic term for many kinds of different microscopic mechanisms and polymeric materials. Based on the laws of electromagnetism and elasticity, a visco-electroelastic model is developed and implemented into the finite element method (FEM). The presented three-dimensional solid element has eight nodes and trilinear interpolation functions for the displacement and the electric potential. The continuum mechanics model contains finite deformations, the time dependency and the nearly incompressible behavior of the material. To describe the possible, large time dependent deformations, a finite viscoelastic model with a split of the deformation gradient is used. Thereby the time dependent characteristic of polymeric materials is incorporated through the free energy function. The electromechanical interactions are considered by the electrostatic forces and inside the energy function.

Dual-phase steel sheets under cyclic tension-compression to large strains: Experiments and crystal plasticity modeling

NASA Astrophysics Data System (ADS)

Zecevic, Milovan; Korkolis, Yannis P.; Kuwabara, Toshihiko; Knezevic, Marko

2016-11-01

In this work, we develop a physically-based crystal plasticity model for the prediction of cyclic tension-compression deformation of multi-phase materials, specifically dual-phase (DP) steels. The model is elasto-plastic in nature and integrates a hardening law based on statistically stored dislocation density, localized hardening due to geometrically necessary dislocations (GNDs), slip-system-level kinematic backstresses, and annihilation of dislocations. The model further features a two level homogenization scheme where the first level is the overall response of a two-phase polycrystalline aggregate and the second level is the homogenized response of the martensite polycrystalline regions. The model is applied to simulate a cyclic tension-compression-tension deformation behavior of DP590 steel sheets. From experiments, we observe that the material exhibits a typical decreasing hardening rate during forward loading, followed by a linear and then a non-linear unloading upon the load reversal, the Bauschinger effect, and changes in hardening rate during strain reversals. To predict these effects, we identify the model parameters using a portion of the measured data and validate and verify them using the remaining data. The developed model is capable of predicting all the particular features of the cyclic deformation of DP590 steel, with great accuracy. From the predictions, we infer and discuss the effects of GNDs, the backstresses, dislocation annihilation, and the two-level homogenization scheme on capturing the cyclic deformation behavior of the material.

Pectus carinatum.

PubMed

Coelho, Marlos de Souza; Guimarães, Paulo de Souza Fonseca

2007-01-01

Among the deformities of the thoracic wall,pectus carinatum has not received the same attention as has pectus excavatum. Few pulmonologists, pediatricians, and thoracic surgeons are aware of the approaches to treating this condition. As a consequence, patients with pectus carinatum are not referred for treatment. This deformity, with an incidence of 1:1000 teenagers, is oligosymptomatic. However, for aesthetic and emotional reasons, it accounts for a large number of medical appointments. Such patients are introverted and do not engage in physical activities, since they are unwilling to expose their chest, which also discourages them from going to the beach or to swimming pools. The diagnosis is clinical and visual, and details are obtained through chest X-rays and computed tomography. The treatment is based on a well-known organogram that summarizes orthopedic and surgical procedures. Dynamic compression, combined with physical exercises, is indicated for teenagers with flexible thorax in inferior and lateral pectus carinatum, with limited indication for those with superior pectus carinatum. For individuals of any age with rigid thorax, surgery is indicated for aesthetic reasons. Among the techniques described, the modified sternum chondroplasty stands out due to the excellent aesthetic results achieved.

Numerical simulation of bubble deformation in magnetic fluids by finite volume method

NASA Astrophysics Data System (ADS)

Yamasaki, Haruhiko; Yamaguchi, Hiroshi

2017-06-01

Bubble deformation in magnetic fluids under magnetic field is investigated numerically by an interface capturing method. The numerical method consists of a coupled level-set and VOF (Volume of Fluid) method, combined with conservation CIP (Constrained Interpolation Profile) method with the self-correcting procedure. In the present study considering actual physical properties of magnetic fluid, bubble deformation under given uniform magnetic field is analyzed for internal magnetic field passing through a magnetic gaseous and liquid phase interface. The numerical results explain the mechanism of bubble deformation under presence of given magnetic field.

Formation of the structure and properties of an Mg-Al-Zn-Mn alloy during plastic deformation by rolling

NASA Astrophysics Data System (ADS)

Bozhko, S. A.; Betsofen, S. Ya.; Kolobov, Yu. R.; Vershinina, T. N.

2015-03-01

The laws of formation of an ultrafine structure in an Mg-Al-Zn-Mn alloy (MA5 alloy) under severe plastic deformation have been studied during lengthwise section rolling at a strain e = 1.59. The deformation behavior and the physical factors of anisotropy of yield strength during compression tests in various directions with respect to axis of rolling are analyzed. The role of crystallographic texture and twinning processes in the generation of strength processes and the development of plastic deformation of the alloy is analyzed.

Effect of Surgical Curve Correction on Exercise Tolerance and Physical Capacities in Patients of Severe Spinal Deformity.

PubMed

Patil, Prateek C; Rathod, Ashok K; Borde, Mandar; Singh, Vishwajeet; Singh, Hemant U

2016-12-01

Traditionally, surgical intervention for patients with a spinal deformity has been considered for cosmetic benefits, but surgical intervention can alter the lung physiology or volumes and in turn leads to increase in physical capacity and exercise tolerance. Therefore, we conducted this to determine whether a surgical correction would restore the lung physiology, physical capacity and exercise tolerance in patients with kyphoscoliosis. To evaluate the usage of six-minute walk test scores and modified Borg scores as tools/measures for exercise tolerance in patients with spinal deformity and to study the effects of surgical correction of spinal deformity on exercise tolerance with above parameters as the measures. Thirty patients with spinal deformity, who had undergone surgery for deformity correction, were evaluated. All patients were investigated pre-operatively with x-rays of the spine (anteroposterior and lateral views). Clinical tests like breath holding time (after full inspiration) in number of seconds, modified Borg scores, six-minute walk test scores (heart rate, respiratory rate, maximum distance walked); were recorded as measures of exercise tolerance. The patients were followed up on the first, third, sixth and twelfth month post-operatively and tested clinically for breath holding time, modified Borg scores, six-minute walk test scores (heart rate, respiratory rate, maximum distance walked) and x-rays of the spine (anteroposterior and lateral views). In our study, breath holding time (p-value = 0.001) and modified Borg scores (p-value = 0.012) showed a significant improvement at 12 months post-operatively. We noted similar findings with heart rate, respiratory rate and maximum distance walked after a six-minute walk test. Improvements were noted in all the parameters, especially in the group of patients with greater than 60 degrees of cobb angle. However, the differences between the two groups (pre-operative cobb angle less than 60 degrees and pre-operative cobb angle more than 60 degrees) were not significant. The results were analysed and tested for significance using Student's t-test (paired and unpaired as appropriate) and Wilcoxon signed rank test. Surgical correction in cases of spinal deformity improves the cosmetic appearance and balance in the patients. Favourable results of surgical intervention were found in exercise tolerance with improvements in modified Borg scores, six-minute walk test results and breath holding time. The above parameters appear to be good tools for the assessment of physical capacity and exercise tolerance in patients with spinal deformity.

Quasi-static earthquake cycle simulation based on nonlinear viscoelastic finite element analyses

NASA Astrophysics Data System (ADS)

Agata, R.; Ichimura, T.; Hyodo, M.; Barbot, S.; Hori, T.

2017-12-01

To explain earthquake generation processes, simulation methods of earthquake cycles have been studied. For such simulations, the combination of the rate- and state-dependent friction law at the fault plane and the boundary integral method based on Green's function in an elastic half space is widely used (e.g. Hori 2009; Barbot et al. 2012). In this approach, stress change around the fault plane due to crustal deformation can be computed analytically, while the effects of complex physics such as mantle rheology and gravity are generally not taken into account. To consider such effects, we seek to develop an earthquake cycle simulation combining crustal deformation computation based on the finite element (FE) method with the rate- and state-dependent friction law. Since the drawback of this approach is the computational cost associated with obtaining numerical solutions, we adopt a recently developed fast and scalable FE solver (Ichimura et al. 2016), which assumes use of supercomputers, to solve the problem in a realistic time. As in the previous approach, we solve the governing equations consisting of the rate- and state-dependent friction law. In solving the equations, we compute stress changes along the fault plane due to crustal deformation using FE simulation, instead of computing them by superimposing slip response function as in the previous approach. In stress change computation, we take into account nonlinear viscoelastic deformation in the asthenosphere. In the presentation, we will show simulation results in a normative three-dimensional problem, where a circular-shaped velocity-weakening area is set in a square-shaped fault plane. The results with and without nonlinear viscosity in the asthenosphere will be compared. We also plan to apply the developed code to simulate the post-earthquake deformation of a megathrust earthquake, such as the 2011 Tohoku earthquake. Acknowledgment: The results were obtained using the K computer at the RIKEN (Proposal number hp160221).

Integrated monitoring system for ground deformation hazard assessment in Telese Terme (Benevento province, Italy)

NASA Astrophysics Data System (ADS)

Tessitore, S.; Castiello, G.; Fedi, M.; Florio, G.; Fuschini, V.; Ramondini, M.; Calcaterra, D.

2012-04-01

TeleseTerme plain is characterized by a very articulated stratigraphy (levels of travertine, fluvial-marshy and pyroclastic deposits), that allows the occurrence of underground water circulation with overlapping aquifers. These aquifers are locally in pressure and, because of chemical characteristics and physical properties of the water, they may activate processes of accelerated travertine's corrosion; the consequence is the formation of cavity along the ground water's preferential flow paths, and the activation of subsidence and sinkholes phenomena. In particular test area includes two zones, where in 2002 and 2006 occurred two sinkholes events, classified as "piping sinkholes". The hazard evaluation was carried out trhought an integrated monitoring system, based on "traditional" techniques conduced "in situ", as geological-geomorphological and geophysical (microgravity) surveys, integrated by the most innovative techniques of Remote sensing interferometry(Advanced DInSAR Interferometry Techniques). The last allow to evaluate the ground deformation, characterized by a predominantvertical component (typical deformation of sinkholes and subsidence phenomena), and are well suited to operate a continuous and long monitoring ofvery extended areas. Through an initial analysis of the Permanent Scatterers available in the Telese municipality, we found the envelopes of the areal that contain PS with negative and positive mean velocities; these velocities showed the presence of a possible phenomenon of subsidence detected by ERS and ENVISAT satellites. Through interferometric processing of ENVISAT images, the soil deformations of 2002-2010 year sare evaluated and compared with the data obtainedby survey took "in situ" during the same period. The knowledge of the deformation's evolution of the area made it possible to organize a more focused future monitoring through traditional techniques of relief (with the help of geophysical methodologies). Since the zone affected by sinkhole phenomena is located in urbanized area, microgravity method was preferred to other geophysical methodologies. In fact, seismic, magnetic and electromagnetic techniques are strongly influenced by urban noise and this produces a low value of signal to noise ratio. The gravity exploration, based on the identification of anomalies in the Earth's gravity field by measuring the gravity acceleration, allows to define any inhomogeneities generated by sources at different densities in the subsurface structure, such as underground voids. Based on geological informations, geophysical models of the known cavities are made. Establishing the physical and geometrical characteristics of the voids it was possible compute the amplitudes and wavelengths of the expected geophysical signal, in order to establish the procedures of the executive acquisition phase. If the magnitude of the evolution of the sinkhole phenomenon will be detected by gravity observations, the time-lapse gravity monitoring will be an excellent tool at the base of risk mitigation.

Study of the statistical physics bases on superstatistics from the β-fluctuated to the T-fluctuated form

NASA Astrophysics Data System (ADS)

Sargolzaeipor, S.; Hassanabadi, H.; Chung, W. S.

2018-04-01

In this paper, we study the T -fluctuated form of superstatistics. In this form, some thermodynamic quantities such as the Helmholtz energy, the entropy and the internal energy, are expressed in terms of the T -fluctuated form for a canonical ensemble. In addition, the partition functions in the formalism for 2-level and 3-level distributions are derived. Then we make use of the T -fluctuated superstatistics for a quantum harmonic oscillator problem and the thermal properties of the system for three statistics of the Bose-Einstein, Maxwell-Boltzmann and Fermi-Dirac statistics are calculated. The effect of the deformation parameter on these properties is examined. All the results recover the well-known results by removing the deformation parameter.

Well-posed continuum equations for granular flow with compressibility and μ(I)-rheology

NASA Astrophysics Data System (ADS)

Barker, T.; Schaeffer, D. G.; Shearer, M.; Gray, J. M. N. T.

2017-05-01

Continuum modelling of granular flow has been plagued with the issue of ill-posed dynamic equations for a long time. Equations for incompressible, two-dimensional flow based on the Coulomb friction law are ill-posed regardless of the deformation, whereas the rate-dependent μ(I)-rheology is ill-posed when the non-dimensional inertial number I is too high or too low. Here, incorporating ideas from critical-state soil mechanics, we derive conditions for well-posedness of partial differential equations that combine compressibility with I-dependent rheology. When the I-dependence comes from a specific friction coefficient μ(I), our results show that, with compressibility, the equations are well-posed for all deformation rates provided that μ(I) satisfies certain minimal, physically natural, inequalities.

Well-posed continuum equations for granular flow with compressibility and μ(I)-rheology

PubMed Central

Schaeffer, D. G.; Shearer, M.; Gray, J. M. N. T.

2017-01-01

Continuum modelling of granular flow has been plagued with the issue of ill-posed dynamic equations for a long time. Equations for incompressible, two-dimensional flow based on the Coulomb friction law are ill-posed regardless of the deformation, whereas the rate-dependent μ(I)-rheology is ill-posed when the non-dimensional inertial number I is too high or too low. Here, incorporating ideas from critical-state soil mechanics, we derive conditions for well-posedness of partial differential equations that combine compressibility with I-dependent rheology. When the I-dependence comes from a specific friction coefficient μ(I), our results show that, with compressibility, the equations are well-posed for all deformation rates provided that μ(I) satisfies certain minimal, physically natural, inequalities. PMID:28588402

Well-posed continuum equations for granular flow with compressibility and μ(I)-rheology.

PubMed

Barker, T; Schaeffer, D G; Shearer, M; Gray, J M N T

2017-05-01

Continuum modelling of granular flow has been plagued with the issue of ill-posed dynamic equations for a long time. Equations for incompressible, two-dimensional flow based on the Coulomb friction law are ill-posed regardless of the deformation, whereas the rate-dependent μ ( I )-rheology is ill-posed when the non-dimensional inertial number I is too high or too low. Here, incorporating ideas from critical-state soil mechanics, we derive conditions for well-posedness of partial differential equations that combine compressibility with I -dependent rheology. When the I -dependence comes from a specific friction coefficient μ ( I ), our results show that, with compressibility, the equations are well-posed for all deformation rates provided that μ ( I ) satisfies certain minimal, physically natural, inequalities.

Ear Deformations Give Bats a Physical Mechanism for Fast Adaptation of Ultrasonic Beam Patterns

NASA Astrophysics Data System (ADS)

Gao, Li; Balakrishnan, Sreenath; He, Weikai; Yan, Zhen; Müller, Rolf

2011-11-01

A large number of mammals, including humans, have intricate outer ear shapes that diffract incoming sound in a direction- and frequency-specific manner. Through this physical process, the outer ear shapes encode sound-source information into the sensory signals from each ear. Our results show that horseshoe bats could dynamically control these diffraction processes through fast nonrigid ear deformations. The bats’ ear shapes can alter between extreme configurations in about 100 ms and thereby change their acoustic properties in ways that would suit different acoustic sensing tasks.

Production of ultrafine grained aluminum by cyclic severe plastic deformation at ambient temperature

NASA Astrophysics Data System (ADS)

Bereczki, P.; Szombathelyi, V.; Krallics, G.

2014-08-01

In the present study the possibilities of grain refinement was investigated by applying large-scale of cyclic plastic deformation to aluminum at ambient temperature. The specimens are processed by multiaxial forging, which is one of the severe plastic deformation techniques. The aim of the experiments with the aluminum alloy 6082M was the determination of the equivalent stress and strain by multiaxial forging and the investigation of evolution of mechanical properties in relation with the accumulated deformation in the specimen. The mechanical properties of raw material was determined by plane strain compression test as well as by hardness measurements. The forming experiments were carried out on Gleeble 3800 physical simulator with MaxStrain System. The mechanical properties of the forged specimens were investigated by micro hardness measurements and tensile tests. A mechanical model, based on the principle of virtual velocities was developed to calculate the flow curves using the measured dimensional changes of the specimen and the measured force. With respect to the evolution of these curves, the cyclic growth of the flow stress can be observed at every characteristic points of the calculated flow curves. In accordance with this tendency, the evolution of the hardness along the middle cross section of the deformed volume has also a nonmonotonous characteristic and the magnitudes of these values are much smaller than by the specimen after plane strain compression test. This difference between the flow stresses respect to the monotonic and non-monotonic deformation can be also observed. The formed microstructure, after a 10-passes multiaxial forging process, consists of mainly equiaxial grains in the submicron grain scale.

Quantifying Post- Laser Ablation Prostate Therapy Changes on MRI via a Domain-Specific Biomechanical Model: Preliminary Findings

PubMed Central

Toth, Robert; Sperling, Dan; Madabhushi, Anant

2016-01-01

Focal laser ablation destroys cancerous cells via thermal destruction of tissue by a laser. Heat is absorbed, causing thermal necrosis of the target region. It combines the aggressive benefits of radiation treatment (destroying cancer cells) without the harmful side effects (due to its precise localization). MRI is typically used pre-treatment to determine the targeted area, and post-treatment to determine efficacy by detecting necrotic tissue, or tumor recurrence. However, no system exists to quantitatively evaluate the post-treatment effects on the morphology and structure via MRI. To quantify these changes, the pre- and post-treatment MR images must first be spatially aligned. The goal is to quantify (a) laser-induced shape-based changes, and (b) changes in MRI parameters post-treatment. The shape-based changes may be correlated with treatment efficacy, and the quantitative effects of laser treatment over time is currently poorly understood. This work attempts to model changes in gland morphology following laser treatment due to (1) patient alignment, (2) changes due to surrounding organs such as the bladder and rectum, and (3) changes due to the treatment itself. To isolate the treatment-induced shape-based changes, the changes from (1) and (2) are first modeled and removed using a finite element model (FEM). A FEM models the physical properties of tissue. The use of a physical biomechanical model is important since a stated goal of this work is to determine the physical shape-based changes to the prostate from the treatment, and therefore only physical real deformations are to be allowed. A second FEM is then used to isolate the physical, shape-based, treatment-induced changes. We applied and evaluated our model in capturing the laser induced changes to the prostate morphology on eight patients with 3.0 Tesla, T2-weighted MRI, acquired approximately six months following treatment. Our results suggest the laser treatment causes a decrease in prostate volume, which appears to manifest predominantly at the site of ablation. After spatially aligning the images, changes to MRI intensity values are clearly visible at the site of ablation. Our results suggest that our new methodology is able to capture and quantify the degree of laser-induced changes to the prostate. The quantitative measurements reflecting of the deformation changes can be used to track treatment response over time. PMID:27088600

NSR&D FY17 Report: CartaBlanca Capability Enhancements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Long, Christopher Curtis; Dhakal, Tilak Raj; Zhang, Duan Zhong

Over the last several years, particle technology in the CartaBlanca code has been matured and has been successfully applied to a wide variety of physical problems. It has been shown that the particle methods, especially Los Alamos's dual domain material point method, is capable of computing many problems involves complex physics, chemistries accompanied by large material deformations, where the traditional finite element or Eulerian method encounter significant difficulties. In FY17, the CartaBlanca code has been enhanced with physical models and numerical algorithms. We started out to compute penetration and HE safety problems. Most of the year we focused on themore » TEPLA model improvement testing against the sweeping wave experiment by Gray et al., because it was found that pore growth and material failure are essentially important for our tasks and needed to be understood for modeling the penetration and the can experiments efficiently. We extended the TEPLA mode from the point view of ensemble phase average to include the effects of nite deformation. It is shown that the assumed pore growth model in TEPLA is actually an exact result from the theory. Alone this line, we then generalized the model to include finite deformations to consider nonlinear dynamics of large deformation. The interaction between the HE product gas and the solid metal is based on the multi-velocity formation. Our preliminary numerical results suggest good agreement between the experiment and the numerical results, pending further verification. To improve the parallel processing capabilities of the CartaBlanca code, we are actively working with the Next Generation Code (NGC) project to rewrite selected packages using C++. This work is expected to continue in the following years. This effort also makes the particle technology developed with CartaBlanca project available to other part of the laboratory. Working with the NGC project and rewriting some parts of the code also given us an opportunity to improve our numerical implementations of the method and to take advantage of recently advances in the numerical methods, such as multiscale algorithms.« less

Carbon-Nanotube-Based Epoxy Matrix Thermal Interface Materials for Thermal Management in Load Bearing Aerospace Structures

DTIC Science & Technology

2012-01-12

fabrication of the composite indicate physical deformities and defects, including entanglement of carbon nanotubes and fused contacts, that are understood...working distance, and spot size, 2.5) of MWCNT array batch of which the composite was made and tested: (a) Entanglements of Individual Nanotubes...electron, photon and phonon) in these materials is critical to their reliable and robust performance, thus accommodating denser circuits 2 and higher

Impact of polymer film thickness and cavity size on polymer flow during embossing : towards process design rules for nanoimprint lithography.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schunk, Peter Randall; King, William P.; Sun, Amy Cha-Tien

2006-08-01

This paper presents continuum simulations of polymer flow during nanoimprint lithography (NIL). The simulations capture the underlying physics of polymer flow from the nanometer to millimeter length scale and examine geometry and thermophysical process quantities affecting cavity filling. Variations in embossing tool geometry and polymer film thickness during viscous flow distinguish different flow driving mechanisms. Three parameters can predict polymer deformation mode: cavity width to polymer thickness ratio, polymer supply ratio, and Capillary number. The ratio of cavity width to initial polymer film thickness determines vertically or laterally dominant deformation. The ratio of indenter width to residual film thickness measuresmore » polymer supply beneath the indenter which determines Stokes or squeeze flow. The local geometry ratios can predict a fill time based on laminar flow between plates, Stokes flow, or squeeze flow. Characteristic NIL capillary number based on geometry-dependent fill time distinguishes between capillary or viscous driven flows. The three parameters predict filling modes observed in published studies of NIL deformation over nanometer to millimeter length scales. The work seeks to establish process design rules for NIL and to provide tools for the rational design of NIL master templates, resist polymers, and process parameters.« less

Two-step FEM-based Liver-CT registration: improving internal and external accuracy

NASA Astrophysics Data System (ADS)

Oyarzun Laura, Cristina; Drechsler, Klaus; Wesarg, Stefan

2014-03-01

To know the exact location of the internal structures of the organs, especially the vasculature, is of great importance for the clinicians. This information allows them to know which structures/vessels will be affected by certain therapy and therefore to better treat the patients. However the use of internal structures for registration is often disregarded especially in physical based registration methods. In this paper we propose an algorithm that uses finite element methods to carry out a registration of liver volumes that will not only have accuracy in the boundaries of the organ but also in the interior. Therefore a graph matching algorithm is used to find correspondences between the vessel trees of the two livers to be registered. In addition to this an adaptive volumetric mesh is generated that contains nodes in the locations in which correspondences were found. The displacements derived from those correspondences are the input for the initial deformation of the model. The first deformation brings the internal structures to their final deformed positions and the surfaces close to it. Finally, thin plate splines are used to refine the solution at the boundaries of the organ achieving an improvement in the accuracy of 71%. The algorithm has been evaluated in CT clinical images of the abdomen.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, J. P.; Wang, Y. D.; Hao, Y. L.

Two main explanations exist for the deformation mechanisms in Ti-Nb-based gum metals, i.e. the formation of reversible nanodisturbance and reversible stress-induced martensitic transformation. In this work, we used the in situ synchrotron-based high-energy X-ray diffuse-scattering technique to reveal the existence of a specific deformation mechanism, i.e. deformation-induced spatially confined martensitic transformations, in Ti-24Nb-4Zr-8Sn-0.10O single crystals with cubic 13 parent phase, which explains well some anomalous mechanical properties of the alloy such as low elastic modulus and nonlinear superelasticity. Two kinds of nanosized martensites with different crystal structures were found during uniaxial tensile loading along the [11 0](beta) axis at roommore » temperature and 190 K, respectively. The detailed changes in the martensitic phase transformation characteristics and the transformation kinetics were experimentally observed at different temperatures. The domain switch from non-modulated martensite to a modulated one occurred at 190 K, with its physical origin attributed to the heterogeneity of local phonon softening depending on temperature and inhomogeneous composition in the parent phase. An in-depth understanding of the formation of stress-induced spatially confined nanosized martensites with a large gradient in chemical composition may benefit designs of high-strength and high-ductility alloys. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

DEM code-based modeling of energy accumulation and release in structurally heterogeneous rock masses

NASA Astrophysics Data System (ADS)

Lavrikov, S. V.; Revuzhenko, A. F.

2015-10-01

Based on discrete element method, the authors model loading of a physical specimen to describe its capacity to accumulate and release elastic energy. The specimen is modeled as a packing of particles with viscoelastic coupling and friction. The external elastic boundary of the packing is represented by particles connected by elastic springs. The latter means introduction of an additional special potential of interaction between the boundary particles, that exercises effect even when there is no direct contact between the particles. On the whole, the model specimen represents an element of a medium capable of accumulation of deformation energy in the form of internal stresses. The data of the numerical modeling of the physical specimen compression and the laboratory testing results show good qualitative consistency.

A fluidics-based impact sensor

PubMed Central

Takahashi, Daigo; Hara, Keisuke; Okano, Taiji

2018-01-01

Microelectromechanical systems (MEMS)-based high-performance accelerometers are ubiquitously used in various electronic devices. However, there is an existing need to detect physical impacts using low-cost devices with no electronic circuits or a battery. We designed and fabricated an impact sensor prototype using a commercial stereolithography apparatus that only consists of a plastic housing and working fluids. The sensor device responds to the instantaneous acceleration (impact) by deformation and pinch off of a water droplet that is suspended in oil in a sensor cavity. We tested the various geometrical and physical parameters of the impact sensor to identify their relations to threshold acceleration values. We show that the state diagram that is plotted against the dimensionless Archimedes and Bond numbers adequately describes the response of the proposed sensor. PMID:29634750

Geomechanical Modeling of Deformation Banding in the Navajo Sandstone, San Rafael Monocline, Utah

NASA Astrophysics Data System (ADS)

Gutierrez, M.; Sundal, A.; Petrie, E. S.

2017-12-01

Deformation bands are ubiquitous geological features in many types of rocks. Depending on their micro-structure, they can act either as conduits or barriers to fluid flow. Given the significant roles deformation bands play in fluid flow and chemical transport in rocks, it is important to develop fundamental understanding of their origin, and their characteristics as they relate with the host rock properties and their depositional and structural-geological history. We present a forward-modeling technique based on the geomechanical Bifurcation Theory (BT) to predict the formation of deformation bands in sandstone. According to BT, the formation of deformation bands is a result of strain location, which in turn stems from instability in the stress-strain response of materials during loading. Due to bifurcation, a material which undergoes homogeneous deformation can reach a point at which the material experiences instability and deformation starts to become non-homogenous. We implemented BT in the commercially-available geomechanical code FLAC (Fast Langragian Analysis of Continua) and applied it in the field-scale modeling of deformation banding in the Navajo Sandstone in the San Rafael Monocline in Utah induced by fault propagation folding. The results show that geomechanical modeling using BT has a powerful potential to simulate the physical processes in the formation of deformation banding in rocks. Predicted deformation bands, specifically the pervasive bedding-parallel bands in the Navajo sandstone formation, normal faulting in the upper limb and reverse faulting in the lower limb, are generally in agreement with field observations. Predictions indicate that the pervasive bedding-parallel bands in the Navajo Sandstone are transitional compaction-shear bands with alternating zones of volumetric compaction and dilation. These predictions are consistent with petrographic analysis of thin sections of rock samples from the Navajo Sandstone. The most important parameter in the geomechanical modeling is the dilation angle in relation to the friction angle of the host rock. These parameters, as well the elastic properties, should evolve during the geologic history of a site, thus, the main challenge in the modeling is how to calibrate these parameters to yield consistent results.

Design of a Modular Monolithic Implicit Solver for Multi-Physics Applications

NASA Technical Reports Server (NTRS)

Carton De Wiart, Corentin; Diosady, Laslo T.; Garai, Anirban; Burgess, Nicholas; Blonigan, Patrick; Ekelschot, Dirk; Murman, Scott M.

2018-01-01

The design of a modular multi-physics high-order space-time finite-element framework is presented together with its extension to allow monolithic coupling of different physics. One of the main objectives of the framework is to perform efficient high- fidelity simulations of capsule/parachute systems. This problem requires simulating multiple physics including, but not limited to, the compressible Navier-Stokes equations, the dynamics of a moving body with mesh deformations and adaptation, the linear shell equations, non-re effective boundary conditions and wall modeling. The solver is based on high-order space-time - finite element methods. Continuous, discontinuous and C1-discontinuous Galerkin methods are implemented, allowing one to discretize various physical models. Tangent and adjoint sensitivity analysis are also targeted in order to conduct gradient-based optimization, error estimation, mesh adaptation, and flow control, adding another layer of complexity to the framework. The decisions made to tackle these challenges are presented. The discussion focuses first on the "single-physics" solver and later on its extension to the monolithic coupling of different physics. The implementation of different physics modules, relevant to the capsule/parachute system, are also presented. Finally, examples of coupled computations are presented, paving the way to the simulation of the full capsule/parachute system.

Dynamic Deformation of Theatrical Flats

NASA Astrophysics Data System (ADS)

Walton, Jamiahus; Martell, Eric; Martell, Verda

2013-03-01

In theatre, flats are used as walls and background scenery. During construction, flats are often built on the ground and then ``walked up,'' where a group of stagehands manually lift one end while another anchors the other end in place. When flats are very large, they can deform during this process. Stiffeners are used to decrease the amount of deformation in the flat. The purpose of this research is to determine the strain along the flat during the process of raising it up with and without stiffeners. We will also explore the effect of the person anchoring the pivot edge of the flat and discuss the safety concerns this presents. This research is part of the Physics of Theatre Project, an interdisciplinary collaboration designed to improve safety, reduce costs, and increase knowledge of physics principles within the technical theatre community.

Quality of life of patients who have undergone the minimally invasive repair of pectus carinatum.

PubMed

Bostanci, Korkut; Ozalper, Mehmet Hakan; Eldem, Barkin; Ozyurtkan, Mehmet Oguzhan; Issaka, Adamu; Ermerak, Nezih Onur; Yuksel, Mustafa

2013-01-01

Several studies previously demonstrated an improvement in the quality of life (QoL) of the patients undergoing a minimally invasive repair of pectus excavatum, but there are no data about such improvement following the minimally invasive repair of pectus carinatum (PC) deformity. The purpose of this study was to investigate the effects of the minimally invasive repair of PC deformity on the psychosocial and physical functioning of the patients. Among 40 patients who underwent minimally invasive repair for PC deformity from July 2008 to March 2011, 35 patients accepted to answer the QoL questionnaires, and 30 of them who had completed the postoperative 6th month were evaluated in this study. The modified two-step Nuss questionnaire was used for the QoL assessment. All patients and their parents completed the appropriate questionnaires regarding the patients' preoperative psychosocial and physical functioning, and they were asked to answer the same questions on the postoperative 6th month. The results from these questionnaires were analysed using Wilcoxon signed rank test to investigate the effects of the minimally invasive repair of PC deformity on psychosocial and physical functioning of the patients. The questionnaires used in the study confirmed the positive impact of the surgical correction on psychosocial and physical well-being in the patients and their parents. Spearman's ρ correlation coefficient determined how well the answers to the same question at two different times correlated with each other, and Cronbach's alpha demonstrated the internal consistency of these answers. These two parameters showed that the statistical results of the study were reliable enough. Statistical analysis of the scoring of the individual questions and the total scoring of individual patients revealed a statistically significant improvement (P < 0.05) following surgery. Similar significant improvements were observed in the total scoring of individual parents and in most scoring of the individual questions (10 of 13, 77%) in the parental questionnaire (P < 0.05). The results of this study confirm for the first time that minimally invasive repair of PC deformity has a positive impact on both psychosocial and physical functioning of the patient, which is supported by parental assessment.

Techniques for virtual lung nodule insertion: volumetric and morphometric comparison of projection-based and image-based methods for quantitative CT

NASA Astrophysics Data System (ADS)

Robins, Marthony; Solomon, Justin; Sahbaee, Pooyan; Sedlmair, Martin; Choudhury, Kingshuk Roy; Pezeshk, Aria; Sahiner, Berkman; Samei, Ehsan

2017-09-01

Virtual nodule insertion paves the way towards the development of standardized databases of hybrid CT images with known lesions. The purpose of this study was to assess three methods (an established and two newly developed techniques) for inserting virtual lung nodules into CT images. Assessment was done by comparing virtual nodule volume and shape to the CT-derived volume and shape of synthetic nodules. 24 synthetic nodules (three sizes, four morphologies, two repeats) were physically inserted into the lung cavity of an anthropomorphic chest phantom (KYOTO KAGAKU). The phantom was imaged with and without nodules on a commercial CT scanner (SOMATOM Definition Flash, Siemens) using a standard thoracic CT protocol at two dose levels (1.4 and 22 mGy CTDIvol). Raw projection data were saved and reconstructed with filtered back-projection and sinogram affirmed iterative reconstruction (SAFIRE, strength 5) at 0.6 mm slice thickness. Corresponding 3D idealized, virtual nodule models were co-registered with the CT images to determine each nodule’s location and orientation. Virtual nodules were voxelized, partial volume corrected, and inserted into nodule-free CT data (accounting for system imaging physics) using two methods: projection-based Technique A, and image-based Technique B. Also a third Technique C based on cropping a region of interest from the acquired image of the real nodule and blending it into the nodule-free image was tested. Nodule volumes were measured using a commercial segmentation tool (iNtuition, TeraRecon, Inc.) and deformation was assessed using the Hausdorff distance. Nodule volumes and deformations were compared between the idealized, CT-derived and virtual nodules using a linear mixed effects regression model which utilized the mean, standard deviation, and coefficient of variation (Mea{{n}RHD} , ST{{D}RHD} and C{{V}RHD}{) }~ of the regional Hausdorff distance. Overall, there was a close concordance between the volumes of the CT-derived and virtual nodules. Percent differences between them were less than 3% for all insertion techniques and were not statistically significant in most cases. Correlation coefficient values were greater than 0.97. The deformation according to the Hausdorff distance was also similar between the CT-derived and virtual nodules with minimal statistical significance in the (C{{V}RHD} ) for Techniques A, B, and C. This study shows that both projection-based and image-based nodule insertion techniques yield realistic nodule renderings with statistical similarity to the synthetic nodules with respect to nodule volume and deformation. These techniques could be used to create a database of hybrid CT images containing nodules of known size, location and morphology.

Techniques for virtual lung nodule insertion: volumetric and morphometric comparison of projection-based and image-based methods for quantitative CT

PubMed Central

Robins, Marthony; Solomon, Justin; Sahbaee, Pooyan; Sedlmair, Martin; Choudhury, Kingshuk Roy; Pezeshk, Aria; Sahiner, Berkman; Samei, Ehsan

2017-01-01

Virtual nodule insertion paves the way towards the development of standardized databases of hybrid CT images with known lesions. The purpose of this study was to assess three methods (an established and two newly developed techniques) for inserting virtual lung nodules into CT images. Assessment was done by comparing virtual nodule volume and shape to the CT-derived volume and shape of synthetic nodules. 24 synthetic nodules (three sizes, four morphologies, two repeats) were physically inserted into the lung cavity of an anthropomorphic chest phantom (KYOTO KAGAKU). The phantom was imaged with and without nodules on a commercial CT scanner (SOMATOM Definition Flash, Siemens) using a standard thoracic CT protocol at two dose levels (1.4 and 22 mGy CTDIvol). Raw projection data were saved and reconstructed with filtered back-projection and sinogram affirmed iterative reconstruction (SAFIRE, strength 5) at 0.6 mm slice thickness. Corresponding 3D idealized, virtual nodule models were co-registered with the CT images to determine each nodule’s location and orientation. Virtual nodules were voxelized, partial volume corrected, and inserted into nodule-free CT data (accounting for system imaging physics) using two methods: projection-based Technique A, and image-based Technique B. Also a third Technique C based on cropping a region of interest from the acquired image of the real nodule and blending it into the nodule-free image was tested. Nodule volumes were measured using a commercial segmentation tool (iNtuition, TeraRecon, Inc.) and deformation was assessed using the Hausdorff distance. Nodule volumes and deformations were compared between the idealized, CT-derived and virtual nodules using a linear mixed effects regression model which utilized the mean, standard deviation, and coefficient of variation (MeanRHD, and STDRHD CVRHD) of the regional Hausdorff distance. Overall, there was a close concordance between the volumes of the CT-derived and virtual nodules. Percent differences between them were less than 3% for all insertion techniques and were not statistically significant in most cases. Correlation coefficient values were greater than 0.97. The deformation according to the Hausdorff distance was also similar between the CT-derived and virtual nodules with minimal statistical significance in the (CVRHD) for Techniques A, B, and C. This study shows that both projection-based and image-based nodule insertion techniques yield realistic nodule renderings with statistical similarity to the synthetic nodules with respect to nodule volume and deformation. These techniques could be used to create a database of hybrid CT images containing nodules of known size, location and morphology. PMID:28786399

Deformation-induced release of ATP from erythrocytes in a poly(dimethylsiloxane)-based microchip with channels that mimic resistance vessels.

PubMed

Price, Alexander K; Fischer, David J; Martin, R Scott; Spence, Dana M

2004-08-15

The ability of nitric oxide to relax smooth muscle cells surrounding resistance vessels in vivo is well documented. Here, we describe a series of studies designed to quantify amounts of adenosine triphosphate (ATP), a known stimulus of NO production in endothelial cells, released from erythrocytes that are mechanically deformed as these cells traverse microbore channels in lithographically patterned microchips. Results indicate that micromolar amounts of ATP are released from erythrocytes flowing through channels having cross sectional dimensions of 60 x 38 micron (2.22 +/- 0.50 microM ATP). Microscopic images indicate that erythrocytes, when being pumped through the microchip channels, migrate toward the center of the channels, leaving a cell-free or skimming layer at the walls of the channel, a profile known to exist in circulatory vessels in vivo. A comparison of the amounts of ATP released from RBCs mechanically deformed in microbore tubing (2.54 +/- 0.15 microM) vs a microchip (2.59 +/- 0.32 microM) suggests that channels in microchips may serve as functional biomimics of the microvasculature. Control studies involving diamide, a membrane-stiffening agent, suggest that the RBC-derived ATP is not due to cell lysis but rather physical deformation.

Synthetically chemical-electrical mechanism for controlling large scale reversible deformation of liquid metal objects

PubMed Central

Zhang, Jie; Sheng, Lei; Liu, Jing

2014-01-01

Reversible deformation of a machine holds enormous promise across many scientific areas ranging from mechanical engineering to applied physics. So far, such capabilities are still hard to achieve through conventional rigid materials or depending mainly on elastomeric materials, which however own rather limited performances and require complicated manipulations. Here, we show a basic strategy which is fundamentally different from the existing ones to realize large scale reversible deformation through controlling the working materials via the synthetically chemical-electrical mechanism (SCHEME). Such activity incorporates an object of liquid metal gallium whose surface area could spread up to five times of its original size and vice versa under low energy consumption. Particularly, the alterable surface tension based on combination of chemical dissolution and electrochemical oxidation is ascribed to the reversible shape transformation, which works much more flexible than many former deformation principles through converting electrical energy into mechanical movement. A series of very unusual phenomena regarding the reversible configurational shifts are disclosed with dominant factors clarified. This study opens a generalized way to combine the liquid metal serving as shape-variable element with the SCHEME to compose functional soft machines, which implies huge potential for developing future smart robots to fulfill various complicated tasks. PMID:25408295

Synthetically chemical-electrical mechanism for controlling large scale reversible deformation of liquid metal objects.

PubMed

Zhang, Jie; Sheng, Lei; Liu, Jing

2014-11-19

Reversible deformation of a machine holds enormous promise across many scientific areas ranging from mechanical engineering to applied physics. So far, such capabilities are still hard to achieve through conventional rigid materials or depending mainly on elastomeric materials, which however own rather limited performances and require complicated manipulations. Here, we show a basic strategy which is fundamentally different from the existing ones to realize large scale reversible deformation through controlling the working materials via the synthetically chemical-electrical mechanism (SCHEME). Such activity incorporates an object of liquid metal gallium whose surface area could spread up to five times of its original size and vice versa under low energy consumption. Particularly, the alterable surface tension based on combination of chemical dissolution and electrochemical oxidation is ascribed to the reversible shape transformation, which works much more flexible than many former deformation principles through converting electrical energy into mechanical movement. A series of very unusual phenomena regarding the reversible configurational shifts are disclosed with dominant factors clarified. This study opens a generalized way to combine the liquid metal serving as shape-variable element with the SCHEME to compose functional soft machines, which implies huge potential for developing future smart robots to fulfill various complicated tasks.

Analytical modeling of the thermomechanical behavior of ASTM F-1586 high nitrogen austenitic stainless steel used as a biomaterial under multipass deformation.

PubMed

Bernardes, Fabiano R; Rodrigues, Samuel F; Silva, Eden S; Reis, Gedeon S; Silva, Mariana B R; Junior, Alberto M J; Balancin, Oscar

2015-06-01

Precipitation-recrystallization interactions in ASTM F-1586 austenitic stainless steel were studied by means of hot torsion tests with multipass deformation under continuous cooling, simulating an industrial laminating process. Samples were deformed at 0.2 and 0.3 at a strain rate of 1.0s(-1), in a temperature range of 900 to 1200°C and interpass times varying from 5 to 80s. The tests indicate that the stress level depends on deformation temperature and the slope of the equivalent mean stress (EMS) vs. 1/T presents two distinct behaviors, with a transition at around 1100°C, the non-recrystallization temperature (Tnr). Below the Tnr, strain-induced precipitation of Z-phase (NbCrN) occurs in short interpass times (tpass<30s), inhibiting recrystallization and promoting stepwise stress build-up with strong recovery, which is responsible for increasing the Tnr. At interpass times longer than 30s, the coalescence and dissolution of precipitates promote a decrease in the Tnr and favor the formation of recrystallized grains. Based on this evidence, the physical simulation of controlled processing allows for a domain refined grain with better mechanical properties. Copyright © 2015 Elsevier B.V. All rights reserved.

Investigation of shear damage considering the evolution of anisotropy

NASA Astrophysics Data System (ADS)

Kweon, S.

2013-12-01

The damage that occurs in shear deformations in view of anisotropy evolution is investigated. It is widely believed in the mechanics research community that damage (or porosity) does not evolve (increase) in shear deformations since the hydrostatic stress in shear is zero. This paper proves that the above statement can be false in large deformations of simple shear. The simulation using the proposed anisotropic ductile fracture model (macro-scale) in this study indicates that hydrostatic stress becomes nonzero and (thus) porosity evolves (increases or decreases) in the simple shear deformation of anisotropic (orthotropic) materials. The simple shear simulation using a crystal plasticity based damage model (meso-scale) shows the same physics as manifested in the above macro-scale model that porosity evolves due to the grain-to-grain interaction, i.e., due to the evolution of anisotropy. Through a series of simple shear simulations, this study investigates the effect of the evolution of anisotropy, i.e., the rotation of the orthotropic axes onto the damage (porosity) evolution. The effect of the evolutions of void orientation and void shape onto the damage (porosity) evolution is investigated as well. It is found out that the interaction among porosity, the matrix anisotropy and void orientation/shape plays a crucial role in the ductile damage of porous materials.

Synthetically chemical-electrical mechanism for controlling large scale reversible deformation of liquid metal objects

NASA Astrophysics Data System (ADS)

Zhang, Jie; Sheng, Lei; Liu, Jing

2014-11-01

Reversible deformation of a machine holds enormous promise across many scientific areas ranging from mechanical engineering to applied physics. So far, such capabilities are still hard to achieve through conventional rigid materials or depending mainly on elastomeric materials, which however own rather limited performances and require complicated manipulations. Here, we show a basic strategy which is fundamentally different from the existing ones to realize large scale reversible deformation through controlling the working materials via the synthetically chemical-electrical mechanism (SCHEME). Such activity incorporates an object of liquid metal gallium whose surface area could spread up to five times of its original size and vice versa under low energy consumption. Particularly, the alterable surface tension based on combination of chemical dissolution and electrochemical oxidation is ascribed to the reversible shape transformation, which works much more flexible than many former deformation principles through converting electrical energy into mechanical movement. A series of very unusual phenomena regarding the reversible configurational shifts are disclosed with dominant factors clarified. This study opens a generalized way to combine the liquid metal serving as shape-variable element with the SCHEME to compose functional soft machines, which implies huge potential for developing future smart robots to fulfill various complicated tasks.

Spiderweb deformation induced by electrostatically charged insects

PubMed Central

Ortega-Jimenez, Victor Manuel; Dudley, Robert

2013-01-01

Capture success of spider webs has been associated with their microstructure, ornamentation, and wind-induced vibrations. Indirect evidence suggests that statically charged objects can attract silk thread, but web deformations induced by charged insects have not yet been described. Here, we show under laboratory conditions that electrostatically charged honeybees, green bottle flies, fruit flies, aphids, and also water drops falling near webs of cross-spiders (Araneus diadematus) induce rapid thread deformation that enhances the likelihood of physical contact, and thus of prey capture. PMID:23828093

Pocket formula for nuclear deformations of actinides

NASA Astrophysics Data System (ADS)

Manjunatha, H. C.; Sridhar, K. N.

2018-06-01

We have formulated a pocket formula for quadrupole (β2), octupole (β3), hexadecapole (β4) and hexacontatetrapole (β6) deformation of the nuclear ground state of all isotopes of actinide nuclei (89 < Z < 103). This formula is first of its kind and produces a nuclear deformation of all isotopes actinide nuclei 89 < Z < 103 with simple inputs of Z and A. Hence, this formula is useful in the fields of nuclear physics to study the structure and interaction of nuclei.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chung, Won Sang, E-mail: mimip4444@hanmail.net; Hounkonnou, Mahouton Norbert, E-mail: norbert.hounkonnou@cipma.uac.bj; Arjika, Sama, E-mail: rjksama2008@gmail.com

In this paper, we propose a full characterization of a generalized q-deformed Tamm-Dancoff oscillator algebra and investigate its main mathematical and physical properties. Specifically, we study its various representations and find the condition satisfied by the deformed q-number to define the algebra structure function. Particular Fock spaces involving finite and infinite dimensions are examined. A deformed calculus is performed as well as a coordinate realization for this algebra. A relevant example is exhibited. Associated coherent states are constructed. Finally, some thermodynamics aspects are computed and discussed.

My Corporis Fabrica Embryo: An ontology-based 3D spatio-temporal modeling of human embryo development.

PubMed

Rabattu, Pierre-Yves; Massé, Benoit; Ulliana, Federico; Rousset, Marie-Christine; Rohmer, Damien; Léon, Jean-Claude; Palombi, Olivier

2015-01-01

Embryology is a complex morphologic discipline involving a set of entangled mechanisms, sometime difficult to understand and to visualize. Recent computer based techniques ranging from geometrical to physically based modeling are used to assist the visualization and the simulation of virtual humans for numerous domains such as surgical simulation and learning. On the other side, the ontology-based approach applied to knowledge representation is more and more successfully adopted in the life-science domains to formalize biological entities and phenomena, thanks to a declarative approach for expressing and reasoning over symbolic information. 3D models and ontologies are two complementary ways to describe biological entities that remain largely separated. Indeed, while many ontologies providing a unified formalization of anatomy and embryology exist, they remain only descriptive and make the access to anatomical content of complex 3D embryology models and simulations difficult. In this work, we present a novel ontology describing the development of the human embryology deforming 3D models. Beyond describing how organs and structures are composed, our ontology integrates a procedural description of their 3D representations, temporal deformation and relations with respect to their developments. We also created inferences rules to express complex connections between entities. It results in a unified description of both the knowledge of the organs deformation and their 3D representations enabling to visualize dynamically the embryo deformation during the Carnegie stages. Through a simplified ontology, containing representative entities which are linked to spatial position and temporal process information, we illustrate the added-value of such a declarative approach for interactive simulation and visualization of 3D embryos. Combining ontologies and 3D models enables a declarative description of different embryological models that capture the complexity of human developmental anatomy. Visualizing embryos with 3D geometric models and their animated deformations perhaps paves the way towards some kind of hypothesis-driven application. These can also be used to assist the learning process of this complex knowledge. http://www.mycorporisfabrica.org/.

Applications of Synthetic Microchannel and Nanopore Systems

NASA Astrophysics Data System (ADS)

Hinkle, Thomas Preston

This thesis describes research conducted on the physics and applications of micro- and nanoscale ion-conducting channels. Making use of the nanoscale physics that takes place in the vicinity of charged surfaces, there is the possibility that nanopores, holes on the order of 1 nm in size, could be used to make complex integrated ionic circuits. For inspiration on what such circuits could achieve we only need to look to biology systems, immensely complex machines that at their most basic level require precise control of ions and intercellular electric potentials to function. In order to contribute to the ever expanding field of nanopore research, we engineered novel hybrid insulator-conductor nanopores that behave analagously to ionic diodes, which allow passage of current flow in one direction but severely limit the current in the opposite direction. The experiments revealed that surface polarization of the conducting material can induce the formation of an electrical double layer in the same way static surface charges can. Furthermore, we showed that the hybrid device behaved similar to an ionic diode, and could see potential use as a standard rectifying element in ionic circuits. Another application based on ion conducting channels is resistive pulse sensing, a single particle detection and characterization method. We present three main experiments that expand the capacity of resistive pulse sensing for particle characterization. First, we demonstrate how resistive pulse sensing in pores with longitudinal irregularities can be used to measure the lengths of individual nanoparticles. Then, we describe an entirely new hybrid approach to resistive pulse sensing, whereby the electrical measurements are combined with simultaneous optical imaging. The hybrid method allows for validation of the resistive pulse signals and will greatly contribute to their interpretability. We present experiments that explore some of the possibilities of the hybrid method. Then, building off the hybrid method we present experiments performed to measure single particle deformability with resistive pulse sensing. Using a novel microfluidic channel design, we were able to reproducibily induce bidirectional deformation of cells. We describe how these deformations could be detected with the resistive pulse signal alone, paving the way for resistive pulse sensing based cell deformability cytometers.

Sparsity-promoting inversion for modeling of irregular volcanic deformation source

NASA Astrophysics Data System (ADS)

Zhai, G.; Shirzaei, M.

2016-12-01

Kīlauea volcano, Hawaíi Island, has a complex magmatic system. Nonetheless, kinematic models of the summit reservoir have so far been limited to first-order analytical solutions with pre-determined geometry. To investigate the complex geometry and kinematics of the summit reservoir, we apply a multitrack multitemporal wavelet-based InSAR (Interferometric Synthetic Aperture Radar) algorithm and a geometry-free time-dependent modeling scheme considering a superposition of point centers of dilatation (PCDs). Applying Principal Component Analysis (PCA) to the time-dependent source model, six spatially independent deformation zones (i.e., reservoirs) are identified, whose locations are consistent with previous studies. Time-dependence of the model allows also identifying periods of correlated or anti-correlated behaviors between reservoirs. Hence, we suggest that likely the reservoir are connected and form a complex magmatic reservoir [Zhai and Shirzaei, 2016]. To obtain a physically-meaningful representation of the complex reservoir, we devise a new sparsity-promoting modeling scheme assuming active magma bodies are well-localized melt accumulations (i.e., outliers in background crust). The major steps include inverting surface deformation data using a hybrid L-1 and L-2 norm regularization approach to solve for sparse volume change distribution and then implementing a BEM based method to solve for opening distribution on a triangular mesh representing the complex reservoir. Using this approach, we are able to constrain the internal excess pressure of magma body with irregular geometry, satisfying uniformly pressurized boundary condition on the surface of magma chamber. The inversion method with sparsity constraint is tested using five synthetic source geometries, including torus, prolate ellipsoid, and sphere as well as horizontal and vertical L-shape bodies. The results show that source dimension, depth and shape are well recovered. Afterward, we apply this modeling scheme to deformation observed at Kilauea summit to constrain the magmatic source geometry, and revise the kinematics of Kilauea's shallow plumbing system. Such a model is valuable for understanding the physical processes in a magmatic reservoir and the method can readily be applied to other volcanic settings.

A texture-component Avrami model for predicting recrystallization textures, kinetics and grain size

NASA Astrophysics Data System (ADS)

Raabe, Dierk

2007-03-01

The study presents an analytical model for predicting crystallographic textures and the final grain size during primary static recrystallization of metals using texture components. The kinetics is formulated as a matrix variant of the Johnson-Mehl-Avrami-Kolmogorov equation. The matrix form is required since the kinetic and crystallographic evolution of the microstructure is described in terms of a limited set of growing (recrystallizing) and swept (deformed) texture components. The number of components required (5-10) defines the order of the matrix since the kinetic coupling occurs between all recrystallizing and all deformed components. Each such couple is characterized by corresponding values for the nucleation energy and grain boundary mobility. The values of these parameters can be obtained by analytical or numerical coarse graining according to a renormalization scheme which replaces many individual grains which grow via recrystallization in a deformed texture component by a single equivalent recrystallization texture component or by fitting to experimental data. Each deformed component is further characterized by an average stored deformation energy. Each element of the kinetic matrix, reflecting one of the possible couplings between a deformed and a recrystallizing texture component, is then derived in each time step by a set of two differential equations. The first equation describes the thermally activated nucleation and growth processes for the expanded (free) volume for a particular couple of a deformed and a recrystallizing texture component and the second equation is used for calculating the constrained (real) volume for that couple which corrects the free volume for those portions of the deformation component which were already swept. The new method is particularly developed for the fast and physically based process simulation of recrystallization textures with respect to processing. The present paper introduces the method and applies it to the primary recrystallization of low carbon steels.

Interfacial Bubble Deformations

NASA Astrophysics Data System (ADS)

Seymour, Brian; Shabane, Parvis; Cypull, Olivia; Cheng, Shengfeng; Feitosa, Klebert

Soap bubbles floating at an air-water experience deformations as a result of surface tension and hydrostatic forces. In this experiment, we investigate the nature of such deformations by taking cross-sectional images of bubbles of different volumes. The results show that as their volume increases, bubbles transition from spherical to hemispherical shape. The deformation of the interface also changes with bubble volume with the capillary rise converging to the capillary length as volume increases. The profile of the top and bottom of the bubble and the capillary rise are completely determined by the volume and pressure differences. James Madison University Department of Physics and Astronomy, 4VA Consortium, Research Corporation for Advancement of Science.

A proposal of monitoring and forecasting system for crustal activity in and around Japan using a large-scale high-fidelity finite element simulation codes

NASA Astrophysics Data System (ADS)

Hori, T.; Ichimura, T.

2015-12-01

Here we propose a system for monitoring and forecasting of crustal activity, especially great interplate earthquake generation and its preparation processes in subduction zone. Basically, we model great earthquake generation as frictional instability on the subjecting plate boundary. So, spatio-temporal variation in slip velocity on the plate interface should be monitored and forecasted. Although, we can obtain continuous dense surface deformation data on land and partly at the sea bottom, the data obtained are not fully utilized for monitoring and forecasting. It is necessary to develop a physics-based data analysis system including (1) a structural model with the 3D geometry of the plate interface and the material property such as elasticity and viscosity, (2) calculation code for crustal deformation and seismic wave propagation using (1), (3) inverse analysis or data assimilation code both for structure and fault slip using (1)&(2). To accomplish this, it is at least necessary to develop highly reliable large-scale simulation code to calculate crustal deformation and seismic wave propagation for 3D heterogeneous structure. Actually, Ichimura et al. (2014, SC14) has developed unstructured FE non-linear seismic wave simulation code, which achieved physics-based urban earthquake simulation enhanced by 10.7 BlnDOF x 30 K time-step. Ichimura et al. (2013, GJI) has developed high fidelity FEM simulation code with mesh generator to calculate crustal deformation in and around Japan with complicated surface topography and subducting plate geometry for 1km mesh. Further, for inverse analyses, Errol et al. (2012, BSSA) has developed waveform inversion code for modeling 3D crustal structure, and Agata et al. (2015, this meeting) has improved the high fidelity FEM code to apply an adjoint method for estimating fault slip and asthenosphere viscosity. Hence, we have large-scale simulation and analysis tools for monitoring. Furthermore, we are developing the methods for forecasting the slip velocity variation on the plate interface. Basic concept is given in Hori et al. (2014, Oceanography) introducing ensemble based sequential data assimilation procedure. Although the prototype described there is for elastic half space model, we will apply it for 3D heterogeneous structure with the high fidelity FE model.

A three dimensional immersed smoothed finite element method (3D IS-FEM) for fluid-structure interaction problems

NASA Astrophysics Data System (ADS)

Zhang, Zhi-Qian; Liu, G. R.; Khoo, Boo Cheong

2013-02-01

A three-dimensional immersed smoothed finite element method (3D IS-FEM) using four-node tetrahedral element is proposed to solve 3D fluid-structure interaction (FSI) problems. The 3D IS-FEM is able to determine accurately the physical deformation of the nonlinear solids placed within the incompressible viscous fluid governed by Navier-Stokes equations. The method employs the semi-implicit characteristic-based split scheme to solve the fluid flows and smoothed finite element methods to calculate the transient dynamics responses of the nonlinear solids based on explicit time integration. To impose the FSI conditions, a novel, effective and sufficiently general technique via simple linear interpolation is presented based on Lagrangian fictitious fluid meshes coinciding with the moving and deforming solid meshes. In the comparisons to the referenced works including experiments, it is clear that the proposed 3D IS-FEM ensures stability of the scheme with the second order spatial convergence property; and the IS-FEM is fairly independent of a wide range of mesh size ratio.

Analytical model for instantaneous lift and shape deformation of an insect-scale flapping wing in hover.

PubMed

Kang, Chang-kwon; Shyy, Wei

2014-12-06

In the analysis of flexible flapping wings of insects, the aerodynamic outcome depends on the combined structural dynamics and unsteady fluid physics. Because the wing shape and hence the resulting effective angle of attack are a priori unknown, predicting aerodynamic performance is challenging. Here, we show that a coupled aerodynamics/structural dynamics model can be established for hovering, based on a linear beam equation with the Morison equation to account for both added mass and aerodynamic damping effects. Lift strongly depends on the instantaneous angle of attack, resulting from passive pitch associated with wing deformation. We show that both instantaneous wing deformation and lift can be predicted in a much simplified framework. Moreover, our analysis suggests that resulting wing kinematics can be explained by the interplay between acceleration-related and aerodynamic damping forces. Interestingly, while both forces combine to create a high angle of attack resulting in high lift around the midstroke, they offset each other for phase control at the end of the stroke. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Strong coupling in F-theory and geometrically non-Higgsable seven-branes

NASA Astrophysics Data System (ADS)

Halverson, James

2017-06-01

Geometrically non-Higgsable seven-branes carry gauge sectors that cannot be broken by complex structure deformation, and there is growing evidence that such configurations are typical in F-theory. We study strongly coupled physics associated with these branes. Axiodilaton profiles are computed using Ramanujan's theories of elliptic functions to alternative bases, showing explicitly that the string coupling is O (1) in the vicinity of the brane; that it sources nilpotent SL (2 , Z) monodromy and therefore the associated brane charges are modular; and that essentially all F-theory compactifications have regions with order one string coupling. It is shown that non-perturbative SU (3) and SU (2) seven-branes are related to weakly coupled counterparts with D7-branes via deformation-induced Hanany-Witten moves on (p , q) string junctions that turn them into fundamental open strings; only the former may exist for generic complex structure. D3-brane near these and the Kodaira type II seven-branes probe Argyres-Douglas theories. The BPS states of slightly deformed theories are shown to be dyonic string junctions.

Effective temperature dynamics of shear bands in metallic glasses

NASA Astrophysics Data System (ADS)

Daub, Eric G.; Klaumünzer, David; Löffler, Jörg F.

2014-12-01

We study the plastic deformation of bulk metallic glasses with shear transformation zone (STZ) theory, a physical model for plasticity in amorphous systems, and compare it with experimental data. In STZ theory, plastic deformation occurs when localized regions rearrange due to applied stress and the density of these regions is determined by a dynamically evolving effective disorder temperature. We compare the predictions of STZ theory to experiments that explore the low-temperature deformation of Zr-based bulk metallic glasses via shear bands at various thermal temperatures and strain rates. By following the evolution of effective temperature with time, strain rate, and temperature through a series of approximate and numerical solutions to the STZ equations, we successfully model a suite of experimentally observed phenomena, including shear-band aging as apparent from slide-hold-slide tests, a temperature-dependent steady-state flow stress, and a strain-rate- and temperature-dependent transition from stick-slip (serrated flow) to steady-sliding (nonserrated flow). We find that STZ theory quantitatively matches the observed experimental data and provides a framework for relating the experimentally measured energy scales to different types of atomic rearrangements.

Enhancement of conductance of GaAs sub-microwires under external stimuli

NASA Astrophysics Data System (ADS)

Qu, Xianlin; Deng, Qingsong; Zheng, Kun

2018-03-01

Semiconductors with one dimension on the micro-nanometer scale have many unique physical properties that are remarkably different from those of their bulk counterparts. Moreover, changes in the external field will further modulate the properties of the semiconductor micro-nanomaterials. In this study, we used focused ion beam technology to prepare freestanding ⟨111⟩-oriented GaAs sub-microwires from a GaAs substrate. The effects of laser irradiation and bending or buckling deformation induced by compression on the electrical transport properties of an individual GaAs sub-microwire were studied. The experimental results indicate that both laser irradiation and bending deformation can enhance their electrical transport properties, the laser irradiation resulted in a conductance enhancement of ˜30% compared to the result with no irradiation, and in addition, bending deformation changed the conductance by as much as ˜180% when the average strain was approximately 1%. The corresponding mechanisms are also discussed. This study provides beneficial insight into the fabrication of electronic and optoelectronic devices based on GaAs micro/nano-wires.

Quantitative stress measurement of elastic deformation using mechanoluminescent sensor: An intensity ratio model

NASA Astrophysics Data System (ADS)

Cai, Tao; Guo, Songtao; Li, Yongzeng; Peng, Di; Zhao, Xiaofeng; Liu, Yingzheng

2018-04-01

The mechanoluminescent (ML) sensor is a newly developed non-invasive technique for stress/strain measurement. However, its application has been mostly restricted to qualitative measurement due to the lack of a well-defined relationship between ML intensity and stress. To achieve accurate stress measurement, an intensity ratio model was proposed in this study to establish a quantitative relationship between the stress condition and its ML intensity in elastic deformation. To verify the proposed model, experiments were carried out on a ML measurement system using resin samples mixed with the sensor material SrAl2O4:Eu2+, Dy3+. The ML intensity ratio was found to be dependent on the applied stress and strain rate, and the relationship acquired from the experimental results agreed well with the proposed model. The current study provided a physical explanation for the relationship between ML intensity and its stress condition. The proposed model was applicable in various SrAl2O4:Eu2+, Dy3+-based ML measurement in elastic deformation, and could provide a useful reference for quantitative stress measurement using the ML sensor in general.

Convexities move because they contain matter.

PubMed

Barenholtz, Elan

2010-09-22

Figure-ground assignment to a contour is a fundamental stage in visual processing. The current paper introduces a novel, highly general dynamic cue to figure-ground assignment: "Convex Motion." Across six experiments, subjects showed a strong preference to assign figure and ground to a dynamically deforming contour such that the moving contour segment was convex rather than concave. Experiments 1 and 2 established the preference across two different kinds of deformational motion. Additional experiments determined that this preference was not due to fixation (Experiment 3) or attentional mechanisms (Experiment 4). Experiment 5 found a similar, but reduced bias for rigid-as opposed to deformational-motion, and Experiment 6 demonstrated that the phenomenon depends on the global motion of the effected contour. An explanation of this phenomenon is presented on the basis of typical natural deformational motion, which tends to involve convex contour projections that contain regions consisting of physical "matter," as opposed to concave contour indentations that contain empty space. These results highlight the fundamental relationship between figure and ground, perceived shape, and the inferred physical properties of an object.

Evaluation of deformable image registration and a motion model in CT images with limited features.

PubMed

Liu, F; Hu, Y; Zhang, Q; Kincaid, R; Goodman, K A; Mageras, G S

2012-05-07

Deformable image registration (DIR) is increasingly used in radiotherapy applications and provides the basis for a previously described model of patient-specific respiratory motion. We examine the accuracy of a DIR algorithm and a motion model with respiration-correlated CT (RCCT) images of software phantom with known displacement fields, physical deformable abdominal phantom with implanted fiducials in the liver and small liver structures in patient images. The motion model is derived from a principal component analysis that relates volumetric deformations with the motion of the diaphragm or fiducials in the RCCT. Patient data analysis compares DIR with rigid registration as ground truth: the mean ± standard deviation 3D discrepancy of liver structure centroid positions is 2.0 ± 2.2 mm. DIR discrepancy in the software phantom is 3.8 ± 2.0 mm in lung and 3.7 ± 1.8 mm in abdomen; discrepancies near the chest wall are larger than indicated by image feature matching. Marker's 3D discrepancy in the physical phantom is 3.6 ± 2.8 mm. The results indicate that visible features in the images are important for guiding the DIR algorithm. Motion model accuracy is comparable to DIR, indicating that two principal components are sufficient to describe DIR-derived deformation in these datasets.

Clinical Evidence for the Relationship between Nail Configuration and Mechanical Forces

PubMed Central

Ogawa, Rei

2014-01-01

Summary: Mechanobiology is an emerging field of science that focuses on the way physical forces and changes in cell or tissue mechanics contribute to development, physiology, and disease. As nails are always exposed to physical stimulation, mechanical forces may have a particularly pronounced effect on nail configuration and could be involved in the development of nail deformities. However, the role of mechanobiology in nail configuration and deformities has rarely been assessed. This review describes what is currently understood regarding the effect of mechanical force on nail configuration and deformities. On the basis of these observations, we hypothesize that nails have an automatic curvature function that allows them to adapt to the daily upward mechanical forces. Under normal conditions, the upward daily mechanical force and the automatic curvature force are well balanced. However, an imbalance between these 2 forces may cause nail deformation. For example, pincer nails may be caused by the absence of upward mechanical forces or a genetic propensity increase in the automatic curvature force, whereas koilonychias may occur when the upward mechanical force exceeds the automatic curvature force, thereby causing the nail to curve outward. This hypothesis is a new concept that could aid the development of innovative methods to prevent and treat nail deformities. PMID:25289309

Laminated helmet materials characterization by terahertz kinetics spectroscopy

NASA Astrophysics Data System (ADS)

Rahman, Anis; Rahman, Aunik K.

2015-05-01

High speed acquisition of reflected terahertz energy constitutes a kinetics spectrum that is an effective tool for layered materials' deformation characterization under ballistic impact. Here we describe utilizing the kinetics spectrum for quantifying a deformation event due to impact in material used for Soldier's helmet. The same technique may be utilized for real-time assessment of trauma by measuring the helmet wore by athletes. The deformation of a laminated material (e.g., a helmet) is dependent on the nature of impact and projectile; thus can uniquely characterize the impact condition leading to a diagnostic procedure based on the energy received by an athlete during an impact. We outline the calibration process for a given material under ballistic impact and then utilize the calibration for extracting physical parameters from the measured kinetics spectrum. Measured kinetics spectra are used to outline the method and rationale for extending the concept to a diagnosis tool. In particular, captured kinetics spectra from multilayered plates subjected to ballistic hit under experimental conditions by high speed digital acquisition system. An algorithm was devised to extract deformation and deformation velocity from which the energy received on the skull was estimated via laws of nonrelativistic motion. This energy is assumed to be related to actual injury conditions, thus forming a basis for determining whether the hit would cause concussion, trauma, or stigma. Such quantification may be used for diagnosing a Soldier's trauma condition in the field or that of an athlete's.

The mechanism study between 3D Space-time deformation and injection or extraction of gas pressure change, the Hutubi Underground gas storage

NASA Astrophysics Data System (ADS)

Xiaoqiang, W.; Li, J.; Daiqing, L.; Li, C.

2017-12-01

The surface deformation of underground gas reservoir with the change of injection pressure is an excellent opportunity to study the load response under the action of tectonic movement and controlled load. This paper mainly focuses on the elastic deformation of underground structure caused by the change of the pressure state of reservoir rock under the condition of the irregular change of pressure in the underground gas storage of Hutubi, the largest underground gas storage in Xinjiang, at the same time, it makes a fine study on the fault activities of reservoir and induced earthquakes along with the equilibrium instability caused by the reservoir. Based on the 34 deformation integrated observation points and 3 GPS continuous observation stations constructed in the underground gas storage area of Hutubi, using modern measurement techniques such as GPS observation, precise leveling survey, flow gravity observation and so on, combined with remote sensing technology such as InSAR, the 3d space-time sequence images of the surface of reservoir area under pressure change were obtained. Combined with gas well pressure, physical parameters and regional seismic geology and geophysical data, the numerical simulation and analysis of internal changes of reservoir were carried out by using elastic and viscoelastic model, the deformation mechanical relationship of reservoir was determined and the storage layer under controlled load was basically determined. This research is financially supported by National Natural Science Foundation of China (Grant No.41474016, 41474051, 41474097)

Relationship between the cranial base and the mandible in artificially deformed skulls.

PubMed

Ferros, I; Mora, M J; Obeso, I F; Jimenez, P; Martinez-Insua, A

2016-11-01

There is controversy regarding the relationship between mandibular position and alterations of the cranial base that provoke a more anterior location of the glenoid fossa. Artificially deformed skulls display marked alterations of the cranial base. This study evaluates mandibular changes as function of the morphology of the cranial base in these skulls. A geometric morphometric study was performed on lateral cephalometric X-rays of three groups of skulls: 32 with anteroposterior deformity, 17 with circumferential deformity and 39 with no apparent deformity. In artificially deformed skulls, the cranial base was deformed causing the mandibular condyle to be in a more anterior position. There was a complete remodelling of the mandible involving narrowing and elongation of the mandibular ramus, rotation of the corpus of the mandible and increased vertical height of the symphysis. Forward displacement did not occur. Integration between mandible and cranial base is not altered by deformation of the skull. Deformity of the cranial vault exerts an influence on the mandible, supporting the theory of modular units in complete integration. This also supports the theory that mandibular prognathism is a multifactorial result and not a direct effect of displacement of the cranial base. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Steel Alloy Hot Roll Simulations and Through-Thickness Variation Using Dislocation Density-Based Modeling

NASA Astrophysics Data System (ADS)

Jansen Van Rensburg, G. J.; Kok, S.; Wilke, D. N.

2017-10-01

Different roll pass reduction schedules have different effects on the through-thickness properties of hot-rolled metal slabs. In order to assess or improve a reduction schedule using the finite element method, a material model is required that captures the relevant deformation mechanisms and physics. The model should also report relevant field quantities to assess variations in material state through the thickness of a simulated rolled metal slab. In this paper, a dislocation density-based material model with recrystallization is presented and calibrated on the material response of a high-strength low-alloy steel. The model has the ability to replicate and predict material response to a fair degree thanks to the physically motivated mechanisms it is built on. An example study is also presented to illustrate the possible effect different reduction schedules could have on the through-thickness material state and the ability to assess these effects based on finite element simulations.

Rendering-based video-CT registration with physical constraints for image-guided endoscopic sinus surgery

NASA Astrophysics Data System (ADS)

Otake, Y.; Leonard, S.; Reiter, A.; Rajan, P.; Siewerdsen, J. H.; Ishii, M.; Taylor, R. H.; Hager, G. D.

2015-03-01

We present a system for registering the coordinate frame of an endoscope to pre- or intra- operatively acquired CT data based on optimizing the similarity metric between an endoscopic image and an image predicted via rendering of CT. Our method is robust and semi-automatic because it takes account of physical constraints, specifically, collisions between the endoscope and the anatomy, to initialize and constrain the search. The proposed optimization method is based on a stochastic optimization algorithm that evaluates a large number of similarity metric functions in parallel on a graphics processing unit. Images from a cadaver and a patient were used for evaluation. The registration error was 0.83 mm and 1.97 mm for cadaver and patient images respectively. The average registration time for 60 trials was 4.4 seconds. The patient study demonstrated robustness of the proposed algorithm against a moderate anatomical deformation.

40Ar* loss in experimentally deformed muscovite and biotite with implications for 40Ar/39Ar geochronology of naturally deformed rocks

USGS Publications Warehouse

Cosca, Michael; Stunitz, Holger; Bourgiex, Anne-Lise; Lee, John P.

2011-01-01

The effects of deformation on radiogenic argon (40Ar*) retentivity in mica are described from high pressure experiments performed on rock samples of peraluminous granite containing euhedral muscovite and biotite. Cylindrical cores, ~15 mm in length and 6.25 mm in diameter, were drilled from granite collected from the South Armorican Massif in northwestern France, loaded into gold capsules, and weld-sealed in the presence of excess water. The samples were deformed at a pressure of 10 kb and a temperature of 600 degrees C over a period 29 of hours within a solid medium assembly in a Griggs-type triaxial hydraulic deformation apparatus. Overall shortening in the experiments was approximately 10%. Transmitted light and secondary and backscattered electron imaging of the deformed granite samples reveals evidence of induced defects and for significant physical grain size reduction by kinking, cracking, and grain segmentation of the micas.

Red blood cell-deformability measurement: review of techniques.

PubMed

Musielak, M

2009-01-01

Cell-deformability characterization involves general measurement of highly complex relationships between cell biology and physical forces to which the cell is subjected. The review takes account of the modern technical solutions simulating the action of the force applied to the red blood cell in macro- and microcirculation. Diffraction ektacytometers and rheoscopes measure the mean deformability value for the total red blood cell population investigated and the deformation distribution index of individual cells, respectively. Deformation assays of a whole single cell are possible by means of optical tweezers. The single cell-measuring setups for micropipette aspiration and atomic force microscopy allow conducting a selective investigation of deformation parameters (e.g., cytoplasm viscosity, viscoelastic membrane properties). The distinction between instrument sensitivity to various RBC-rheological features as well as the influence of temperature on measurement are discussed. The reports quoted confront fascinating possibilities of the techniques with their medical applications since the RBC-deformability has the key position in the etiology of a wide range of conditions.

Physically Based Modeling and Simulation with Dynamic Spherical Volumetric Simplex Splines

PubMed Central

Tan, Yunhao; Hua, Jing; Qin, Hong

2009-01-01

In this paper, we present a novel computational modeling and simulation framework based on dynamic spherical volumetric simplex splines. The framework can handle the modeling and simulation of genus-zero objects with real physical properties. In this framework, we first develop an accurate and efficient algorithm to reconstruct the high-fidelity digital model of a real-world object with spherical volumetric simplex splines which can represent with accuracy geometric, material, and other properties of the object simultaneously. With the tight coupling of Lagrangian mechanics, the dynamic volumetric simplex splines representing the object can accurately simulate its physical behavior because it can unify the geometric and material properties in the simulation. The visualization can be directly computed from the object’s geometric or physical representation based on the dynamic spherical volumetric simplex splines during simulation without interpolation or resampling. We have applied the framework for biomechanic simulation of brain deformations, such as brain shifting during the surgery and brain injury under blunt impact. We have compared our simulation results with the ground truth obtained through intra-operative magnetic resonance imaging and the real biomechanic experiments. The evaluations demonstrate the excellent performance of our new technique. PMID:20161636

Variable-intercept panel model for deformation zoning of a super-high arch dam.

PubMed

Shi, Zhongwen; Gu, Chongshi; Qin, Dong

2016-01-01

This study determines dam deformation similarity indexes based on an analysis of deformation zoning features and panel data clustering theory, with comprehensive consideration to the actual deformation law of super-high arch dams and the spatial-temporal features of dam deformation. Measurement methods of these indexes are studied. Based on the established deformation similarity criteria, the principle used to determine the number of dam deformation zones is constructed through entropy weight method. This study proposes the deformation zoning method for super-high arch dams and the implementation steps, analyzes the effect of special influencing factors of different dam zones on the deformation, introduces dummy variables that represent the special effect of dam deformation, and establishes a variable-intercept panel model for deformation zoning of super-high arch dams. Based on different patterns of the special effect in the variable-intercept panel model, two panel analysis models were established to monitor fixed and random effects of dam deformation. Hausman test method of model selection and model effectiveness assessment method are discussed. Finally, the effectiveness of established models is verified through a case study.

Dynamic soft tissue deformation estimation based on energy analysis

NASA Astrophysics Data System (ADS)

Gao, Dedong; Lei, Yong; Yao, Bin

2016-10-01

The needle placement accuracy of millimeters is required in many needle-based surgeries. The tissue deformation, especially that occurring on the surface of organ tissue, affects the needle-targeting accuracy of both manual and robotic needle insertions. It is necessary to understand the mechanism of tissue deformation during needle insertion into soft tissue. In this paper, soft tissue surface deformation is investigated on the basis of continuum mechanics, where a geometry model is presented to quantitatively approximate the volume of tissue deformation. The energy-based method is presented to the dynamic process of needle insertion into soft tissue based on continuum mechanics, and the volume of the cone is exploited to quantitatively approximate the deformation on the surface of soft tissue. The external work is converted into potential, kinetic, dissipated, and strain energies during the dynamic rigid needle-tissue interactive process. The needle insertion experimental setup, consisting of a linear actuator, force sensor, needle, tissue container, and a light, is constructed while an image-based method for measuring the depth and radius of the soft tissue surface deformations is introduced to obtain the experimental data. The relationship between the changed volume of tissue deformation and the insertion parameters is created based on the law of conservation of energy, with the volume of tissue deformation having been obtained using image-based measurements. The experiments are performed on phantom specimens, and an energy-based analytical fitted model is presented to estimate the volume of tissue deformation. The experimental results show that the energy-based analytical fitted model can predict the volume of soft tissue deformation, and the root mean squared errors of the fitting model and experimental data are 0.61 and 0.25 at the velocities 2.50 mm/s and 5.00 mm/s. The estimating parameters of the soft tissue surface deformations are proven to be useful for compensating the needle-targeting error in the rigid needle insertion procedure, especially for percutaneous needle insertion into organs.

In-situ monitoring of deformation of clayey and volcanic sequences in the lacustrine plain of Iztapalapa, Mexico City

NASA Astrophysics Data System (ADS)

Carreon-Freyre, D.; Cerca, M.; Barrientos, B.; Gutierrez, R.; Blancas, D.

2012-12-01

Major cities of Central Mexico with lowering of land elevation problems are located in inter-volcanic and fault bounded basins within the central Trans-Mexican Volcanic Belt (TMVB). The most representative and studied case of ground deformation is Mexico City, where the Iztapalapa Municipality presents the highest population density. This area is located over the geological contact between the "Sierra de Santa Catarina" volcanic range and a lacustrine plain. Filling of lacustrine basins includes silty and clayey sediments as well as pyroclastic deposits (coarse and fine grained) and volcanic rocks layers. We used Ground Penetrating Radar (GPR) and MASW prospection to evaluate contrasts in the physical properties of fine grained soils and identify geometry of the deformational features and implemented a mechanical system for in situ monitoring in fractured sites. Deformational features in this basin reflect an interplay between the geological history (depositional conditions), load history, seismic activity, and faulting. Plastic mechanical behaviour predominates in these clayey sediments and differential deformation locally triggers brittle fracturing and/or subsidence of the surface. In this work we present the results of monitoring and characterization of ground deformation and fracturing in different sequences, our results show a dynamic interplay between the mechanisms of ground fracturing and the stress history of sedimentary sequences. Relating the mechanical behaviour of the studied sequences with variations of physical and geological properties should be taken into account to estimate land level lowering and risk of fracturing for urban development planning.

Microstructure-based modelling of arbitrary deformation histories of filler-reinforced elastomers

NASA Astrophysics Data System (ADS)

Lorenz, H.; Klüppel, M.

2012-11-01

A physically motivated theory of rubber reinforcement based on filler cluster mechanics is presented considering the mechanical behaviour of quasi-statically loaded elastomeric materials subjected to arbitrary deformation histories. This represents an extension of a previously introduced model describing filler induced stress softening and hysteresis of highly strained elastomers. These effects are referred to the hydrodynamic reinforcement of rubber elasticity due to strain amplification by stiff filler clusters and cyclic breakdown and re-aggregation (healing) of softer, already damaged filler clusters. The theory is first developed for the special case of outer stress-strain cycles with successively increasing maximum strain. In this more simple case, all soft clusters are broken at the turning points of the cycle and the mechanical energy stored in the strained clusters is completely dissipated, i.e. only irreversible stress contributions result. Nevertheless, the description of outer cycles involves already all material parameters of the theory and hence they can be used for a fitting procedure. In the general case of an arbitrary deformation history, the cluster mechanics of the material is complicated due to the fact that not all soft clusters are broken at the turning points of a cycle. For that reason additional reversible stress contributions considering the relaxation of clusters upon retraction have to be taken into account for the description of inner cycles. A special recursive algorithm is developed constituting a frame of the mechanical response of encapsulated inner cycles. Simulation and measurement are found to be in fair agreement for CB and silica filled SBR/BR and EPDM samples, loaded in compression and tension along various deformation histories.

Computational modelling of large deformations in layered-silicate/PET nanocomposites near the glass transition

NASA Astrophysics Data System (ADS)

Figiel, Łukasz; Dunne, Fionn P. E.; Buckley, C. Paul

2010-01-01

Layered-silicate nanoparticles offer a cost-effective reinforcement for thermoplastics. Computational modelling has been employed to study large deformations in layered-silicate/poly(ethylene terephthalate) (PET) nanocomposites near the glass transition, as would be experienced during industrial forming processes such as thermoforming or injection stretch blow moulding. Non-linear numerical modelling was applied, to predict the macroscopic large deformation behaviour, with morphology evolution and deformation occurring at the microscopic level, using the representative volume element (RVE) approach. A physically based elasto-viscoplastic constitutive model, describing the behaviour of the PET matrix within the RVE, was numerically implemented into a finite element solver (ABAQUS) using an UMAT subroutine. The implementation was designed to be robust, for accommodating large rotations and stretches of the matrix local to, and between, the nanoparticles. The nanocomposite morphology was reconstructed at the RVE level using a Monte-Carlo-based algorithm that placed straight, high-aspect ratio particles according to the specified orientation and volume fraction, with the assumption of periodicity. Computational experiments using this methodology enabled prediction of the strain-stiffening behaviour of the nanocomposite, observed experimentally, as functions of strain, strain rate, temperature and particle volume fraction. These results revealed the probable origins of the enhanced strain stiffening observed: (a) evolution of the morphology (through particle re-orientation) and (b) early onset of stress-induced pre-crystallization (and hence lock-up of viscous flow), triggered by the presence of particles. The computational model enabled prediction of the effects of process parameters (strain rate, temperature) on evolution of the morphology, and hence on the end-use properties.

3D surface flow kinematics derived from airborne UAVSAR interferometric synthetic aperture radar to constrain the physical mechanisms controlling landslide motion

NASA Astrophysics Data System (ADS)

Delbridge, B. G.; Burgmann, R.; Fielding, E. J.; Hensley, S.; Schulz, W. H.

2013-12-01

This project focuses on improving our understanding of the physical mechanisms controlling landslide motion by studying the landslide-wide kinematics of the Slumgullion landslide in southwestern Colorado using interferometric synthetic aperture radar (InSAR) and GPS. The NASA/JPL UAVSAR airborne repeat-pass SAR interferometry system imaged the Slumgullion landslide from 4 look directions on eight flights in 2011 and 2012. Combining the four look directions allows us to extract the full 3-D velocity field of the surface. Observing the full 3-dimensional flow field allows us to extract the full strain tensor (assuming free surface boundary conditions and incompressible flow) since we have both the spatial resolution to take spatial derivates and full deformation information. COSMO-SkyMed(CSK) high-resolution Spotlight data was also acquired during time intervals overlapping with the UAVSAR one-week pairs, with intervals as short as one day. These observations allow for the quantitative testing of the deformation magnitude and estimated formal errors in the UAVSAR derived deformation field. We also test the agreement of the deformation at 20 GPS monitoring sites concurrently acquired by the USGS. We also utilize the temporal resolution of real-time GPS acquired by the UC Berkeley Active Tectonics Group during a temporary deployment from July 22nd - August 2nd. By combining this data with the kinematic data we hope to elucidate the response of the landslide to environmental changes such as rainfall, snowmelt, and atmospheric pressure, and consequently the mechanisms controlling the dynamics of the landslide system. To constrain the longer temporal dynamics, interferograms made from pairs of CSK images acquired in 2010, 2011, 2012 and 2013 reveal the slide deformation on a longer timescale by allowing us to measure meters of motion and see the average rates over year long intervals using pixel offset tracking of the high-resolution SAR amplitude images. The results of this study will also allow us to test the agreement and commensurability of UAVSAR- derived deformation with real-time GPS observations and traditional satellite-based SAR interferometry from the COSMOSkyMed system. We will not only help mitigate the hazards associated with large landslides, but also provide information on the limitations of current geodetic imaging techniques. This unique opportunity to compare several concurrent geodetic observations of the same deformation will provide constraints and recommendations for the design and implementation of future geodetic systems for the monitoring of Earth surface processes.

Diffuse-interface approach to rotating Hele-Shaw flows.

PubMed

Chen, Ching-Yao; Huang, Yu-Sheng; Miranda, José A

2011-10-01

When two fluids of different densities move in a rotating Hele-Shaw cell, the interface between them becomes centrifugally unstable and deforms. Depending on the viscosity contrast of the system, distinct types of complex patterns arise at the fluid-fluid boundary. Deformations can also induce the emergence of interfacial singularities and topological changes such as droplet pinch-off and self-intersection. We present numerical simulations based on a diffuse-interface model for this particular two-phase displacement that capture a variety of pattern-forming behaviors. This is implemented by employing a Boussinesq Hele-Shaw-Cahn-Hilliard approach, considering the whole range of possible values for the viscosity contrast, and by including inertial effects due to the Coriolis force. The role played by these two physical contributions on the development of interface singularities is illustrated and discussed.

Separable Bilayer Microfiltration Device for Label-Free Enrichment of Viable Circulating Tumor Cells.

PubMed

Hao, Sijie; Nisic, Merisa; He, Hongzhang; Tai, Yu-Chong; Zheng, Si-Yang

2017-01-01

Analysis of rare circulating tumor cells enriched from metastatic cancer patients yields critical information on disease progression, therapy response, and the mechanism of cancer metastasis. Here we describe in detail a label-free enrichment process of circulating tumor cells based on its unique physical properties (size and deformability). Viable circulating tumor cells can be successfully enriched and analyzed, or easily released for further characterization due to the novel separable two-layer design.

Laminated Composite Shell Element Using Absolute Nodal Coordinate Formulation and Its Application to ANCF Tire Model

DTIC Science & Technology

2015-04-24

Paramsothy Jayakumar US Army TARDEC 6501 E. 11 Mile Road Warren, MI 48397-5000 Hiroyuki Sugiyama Department of Mechanical and Industrial...Part 2: Development of a Physical Tyre Model", Vehicle System Dynamics, vol. 50, pp. 339-356. [4] Sugiyama, H., Yamashita, H. and Jayakumar , P., 2014... Jayakumar , P. and Sugiyama, H., "Continuum Mechanics Based Bi-Linear Shear Deformable Shell Element using Absolute Nodal Coordinate Formulation", ASME

Modulation of the thermo-rheological properties of the crust beneath Ischia Island (Southern Italy) on the ground deformation pattern

NASA Astrophysics Data System (ADS)

Castaldo, Raffaele; Gola, Gianluca; Santilano, Alessandro; De Novellis, Vincenzo; Pepe, Susi; Manzo, Mariarosaria; Manzella, Adele; Tizzani, Pietro

2017-04-01

We present a model able to simulate the physical process responsible for the long-term ground deformation of Ischia Island Volcano (Southern Italy) by considering the role of the thermo-rheological properties of the crust. To this aim, we develop and implement in a Finite Element (FE) environment an innovative approach that integrates and homogenizes a large amount of data derived from several and different observation techniques (i.e, geological, geophysical and remote sensing). In detail, the main steps of the proposed approach are: (i) the generation of a 3D geological model of the crust beneath the Island by merging the available geological and geophysical information; (ii) the optimization of a 3D thermal model by exploiting the thermal measurements available in literature; (iii) the definition of the 3D B/D (Brittle/Ductile) transition by using the temperature distribution of the crust and the physical information of the rocks; (iv) the optimization of the ground deformation velocity model (that takes into account the rheological stratification) by considering the spatial and temporal information detected via satellite multi-orbit C-Band SAR (Synthetic Aperture Radar) measurements acquired during the 1992-2010 time period. The achieved results allow investigating the physical process responsible for the observed ground deformation pattern. In particular, they reveal how the rheology modulates the spatial and temporal evolution of long-term subsidence phenomenon, highlighting a coupling effect of the viscosities of the rocks and the gravitational loading of the volcano edifice. Moreover, the achieved results provide a very detailed and realistic image of the subsurface crust of the Ischia Island Volcano in order to study the ongoing deformation phenomena.

Numerical investigation of the efficiency of emission reduction and heat extraction in a sedimentary geothermal reservoir: a case study of the Daming geothermal field in China.

PubMed

Guo, Xuyang; Song, Hongqing; Killough, John; Du, Li; Sun, Pengguang

2018-02-01

The utilization of geothermal energy is clean and has great potential worldwide, and it is important to utilize geothermal energy in a sustainable manner. Mathematical modeling studies of geothermal reservoirs are important as they evaluate and quantify the complex multi-physical effects in geothermal reservoirs. However, previous modeling efforts lack the study focusing on the emission reduction efficiency and the deformation at geothermal wellbores caused by geothermal water extraction/circulation. Emission efficiency is rather relevant in geothermal projects introduced in areas characterized by elevated air pollution where the utilization of geothermal energy is as an alternative to burning fossil fuels. Deformation at geothermal wellbores is also relevant as significant deformation caused by water extraction can lead to geothermal wellbore instability and can consequently decrease the effectiveness of the heat extraction process in geothermal wells. In this study, the efficiency of emission reduction and heat extraction in a sedimentary geothermal reservoir in Daming County, China, are numerically investigated based on a coupled multi-physical model. Relationships between the efficiency of emission reduction and heat extraction, deformation at geothermal well locations, and geothermal field parameters including well spacing, heat production rate, re-injection temperature, rock stiffness, and geothermal well placement patterns are analyzed. Results show that, although large heat production rates and low re-injection temperatures can lead to decreased heat production in the last 8 years of heat extraction, they still improve the overall heat production capacity and emission reduction capacity. Also, the emission reduction capacity is positively correlated with the heat production capacity. Deformation at geothermal wellbore locations is alleviated by smaller well spacing, lower heat production rates, and smaller numbers of injectors in the well pattern, and by placing wells at locations with higher rock stiffness. Compared with the reference case with coal burning for heating purposes, the yearly emission reduction capacity can reach 1 × 10 7  kg by switching to the direct utilization of geothermal energy in Daming field.

Characterizing the deformation of reservoirs using interferometry, gravity, and seismic analyses

NASA Astrophysics Data System (ADS)

Schiek, Cara Gina

In this dissertation, I characterize how reservoirs deform using surface and subsurface techniques. The surface technique I employ is radar interferometry, also known as InSAR (Interferometric Synthetic Aperture Radar). The subsurface analyses I explore include gravity modeling and seismic techniques consisting of determining earthquake locations from a small-temporary seismic network of six seismometers. These techniques were used in two different projects to determine how reservoirs deform in the subsurface and how this deformation relates to its remotely sensed surface deformation. The first project uses InSAR to determine land subsidence in the Mimbres basin near Deming, NM. The land subsidence measurements are visually compared to gravity models in order to determine the influence of near surface faults on the subsidence and the physical properties of the aquifers in these basins. Elastic storage coefficients were calculated for the Mimbres basin to aid in determining the stress regime of the aquifers. In the Mimbres basin, I determine that it is experiencing elastic deformation at differing compaction rates. The west side of the Mimbres basin is deforming faster, 17 mm/yr, while the east side of the basin is compacting at a rate of 11 mm/yr. The second project focuses on San Miguel volcano, El Salvador. Here, I integrate InSAR with earthquake locations using surface deformation forward modeling to investigate the explosive volcanism in this region. This investigation determined the areas around the volcano that are undergoing deformation, and that could lead to volcanic hazards such as slope failure from a fractured volcano interior. I use the earthquake epicenters with field data to define the subsurface geometry of the deformation source, which I forward model to produce synthetic interferograms. Residuals between the synthetic and observed interferograms demonstrate that the observed deformation is a direct result of the seismic activity along the San Miguel Fracture Zone. Based on the large number of earthquakes concentrated in this region and the fracturing suggested by the earthquake location results, I conclude that the southwestern slope of San Miguel is the most susceptible to volcanic hazards such as landsliding and flank lava flows. Together these projects explore the dynamics of reservoir systems, both hydrologic and magmatic. They show the utility of geodetic remote sensing to constrain the relative importance of various, complex, subsurface processes, including faulting, fluid migration, and compaction.

Electrostatic Deformation of Liquid Surfaces by a Charged Rod and a Van De Graaff Generator

ERIC Educational Resources Information Center

Slisko, Josip; García-Molina, Rafael; Abril, Isabel

2014-01-01

Authors of physics textbooks frequently use the deflection of a thin, vertically falling water jet by a charged balloon, comb, or rod as a visually appealing and conceptually relevant example of electrostatic attraction. Nevertheless, no attempts are made to explore whether these charged bodies could cause visible deformation of a horizontal water…

Quantum mechanics on the h-deformed quantum plane

NASA Astrophysics Data System (ADS)

Cho, Sunggoo

1999-03-01

We find the covariant deformed Heisenberg algebra and the Laplace-Beltrami operator on the extended h-deformed quantum plane and solve the Schrödinger equations explicitly for some physical systems on the quantum plane. In the commutative limit the behaviour of a quantum particle on the quantum plane becomes that of the quantum particle on the Poincaré half-plane, a surface of constant negative Gaussian curvature. We show that the bound state energy spectra for particles under specific potentials depend explicitly on the deformation parameter h. Moreover, it is shown that bound states can survive on the quantum plane in a limiting case where bound states on the Poincaré half-plane disappear.

Physical and Constructive (Limiting) Criterions of Gear Wheels Wear

NASA Astrophysics Data System (ADS)

Fedorov, S. V.

2018-01-01

We suggest using a generalized model of friction - the model of elastic-plastic deformation of the body element, which is located on the surface of the friction pairs. This model is based on our new engineering approach to the problem of friction-triboergodynamics. Friction is examined as transformative and dissipative process. Structural-energetic interpretation of friction as a process of elasto-plastic deformation and fracture contact volumes is proposed. The model of Hertzian (heavy-loaded) friction contact evolution is considered. The least wear particle principle is formulated. It is mechanical (nano) quantum. Mechanical quantum represents the least structural form of solid material body in conditions of friction. It is dynamic oscillator of dissipative friction structure and it can be examined as the elementary nanostructure of metal’s solid body. At friction in state of most complete evolution of elementary tribosystem (tribocontact) all mechanical quanta (subtribosystems) with the exception of one, elasticity and reversibly transform energy of outer impact (mechanic movement). In these terms only one mechanical quantum is the lost - standard of wear. From this position we can consider the physical criterion of wear and the constructive (limiting) criterion of gear teeth and other practical examples of tribosystems efficiency with new tribology notion - mechanical (nano) quantum.

Monolithic multigrid method for the coupled Stokes flow and deformable porous medium system

NASA Astrophysics Data System (ADS)

Luo, P.; Rodrigo, C.; Gaspar, F. J.; Oosterlee, C. W.

2018-01-01

The interaction between fluid flow and a deformable porous medium is a complicated multi-physics problem, which can be described by a coupled model based on the Stokes and poroelastic equations. A monolithic multigrid method together with either a coupled Vanka smoother or a decoupled Uzawa smoother is employed as an efficient numerical technique for the linear discrete system obtained by finite volumes on staggered grids. A specialty in our modeling approach is that at the interface of the fluid and poroelastic medium, two unknowns from the different subsystems are defined at the same grid point. We propose a special discretization at and near the points on the interface, which combines the approximation of the governing equations and the considered interface conditions. In the decoupled Uzawa smoother, Local Fourier Analysis (LFA) helps us to select optimal values of the relaxation parameter appearing. To implement the monolithic multigrid method, grid partitioning is used to deal with the interface updates when communication is required between two subdomains. Numerical experiments show that the proposed numerical method has an excellent convergence rate. The efficiency and robustness of the method are confirmed in numerical experiments with typically small realistic values of the physical coefficients.

A New CT Reconstruction Technique Using Adaptive Deformation Recovery and Intensity Correction (ADRIC)

PubMed Central

Zhang, You; Ma, Jianhua; Iyengar, Puneeth; Zhong, Yuncheng; Wang, Jing

2017-01-01

Purpose Sequential same-patient CT images may involve deformation-induced and non-deformation-induced voxel intensity changes. An adaptive deformation recovery and intensity correction (ADRIC) technique was developed to improve the CT reconstruction accuracy, and to separate deformation from non-deformation-induced voxel intensity changes between sequential CT images. Materials and Methods ADRIC views the new CT volume as a deformation of a prior high-quality CT volume, but with additional non-deformation-induced voxel intensity changes. ADRIC first applies the 2D-3D deformation technique to recover the deformation field between the prior CT volume and the new, to-be-reconstructed CT volume. Using the deformation-recovered new CT volume, ADRIC further corrects the non-deformation-induced voxel intensity changes with an updated algebraic reconstruction technique (‘ART-dTV’). The resulting intensity-corrected new CT volume is subsequently fed back into the 2D-3D deformation process to further correct the residual deformation errors, which forms an iterative loop. By ADRIC, the deformation field and the non-deformation voxel intensity corrections are optimized separately and alternately to reconstruct the final CT. CT myocardial perfusion imaging scenarios were employed to evaluate the efficacy of ADRIC, using both simulated data of the extended-cardiac-torso (XCAT) digital phantom and experimentally acquired porcine data. The reconstruction accuracy of the ADRIC technique was compared to the technique using ART-dTV alone, and to the technique using 2D-3D deformation alone. The relative error metric and the universal quality index metric are calculated between the images for quantitative analysis. The relative error is defined as the square root of the sum of squared voxel intensity differences between the reconstructed volume and the ‘ground-truth’ volume, normalized by the square root of the sum of squared ‘ground-truth’ voxel intensities. In addition to the XCAT and porcine studies, a physical lung phantom measurement study was also conducted. Water-filled balloons with various shapes/volumes and concentrations of iodinated contrasts were put inside the phantom to simulate both deformations and non-deformation-induced intensity changes for ADRIC reconstruction. The ADRIC-solved deformations and intensity changes from limited-view projections were compared to those of the ‘gold-standard’ volumes reconstructed from fully-sampled projections. Results For the XCAT simulation study, the relative errors of the reconstructed CT volume by the 2D-3D deformation technique, the ART-dTV technique and the ADRIC technique were 14.64%, 19.21% and 11.90% respectively, by using 20 projections for reconstruction. Using 60 projections for reconstruction reduced the relative errors to 12.33%, 11.04% and 7.92% for the three techniques, respectively. For the porcine study, the corresponding results were 13.61%, 8.78%, 6.80% by using 20 projections; and 12.14%, 6.91% and 5.29% by using 60 projections. The ADRIC technique also demonstrated robustness to varying projection exposure levels. For the physical phantom study, the average DICE coefficient between the initial prior balloon volume and the new ‘gold-standard’ balloon volumes was 0.460. ADRIC reconstruction by 21 projections increased the average DICE coefficient to 0.954. Conclusion The ADRIC technique outperformed both the 2D-3D deformation technique and the ART-dTV technique in reconstruction accuracy. The alternately solved deformation field and non-deformation voxel intensity corrections can benefit multiple clinical applications, including tumor tracking, radiotherapy dose accumulation and treatment outcome analysis. PMID:28380247

Physical conditions at the base of a fast moving antarctic ice stream.

PubMed

Engelhardt, H; Humphrey, N; Kamb, B; Fahnestock, M

1990-04-06

Boreholes drilled to the bottom of ice stream B in the West Antarctic Ice Sheet reveal that the base of the ice stream is at the melting point and the basal water pressure is within about 1.6 bars of the ice overburden pressure. These conditions allow the rapid ice streaming motion to occur by basal sliding or by shear deformation of unconsolidated sediments that underlie the ice in a layer at least 2 meters thick. The mechanics of ice streaming plays a role in the response of the ice sheet to climatic change.

Analysis of recent surface deformation at Ischia Island Volcano (South Italy) via multi-platform monitoring systems

NASA Astrophysics Data System (ADS)

Manzo, Mariarosaria; De Martino, Prospero; Castaldo, Raffaele; De Luca, Claudio; Dolce, Mario; Scarpato, Giovanni; Tizzani, Pietro; Zinno, Ivana; Lanari, Riccardo

2017-04-01

Ischia Island is a densely populated volcanic area located in the North-Western sector of the Gulf of Napoli (South Italy), whose activity is characterized by eruptions (the last one occurred in 1302 A.D.), earthquakes (the most disastrous ones occurred in 1881 and in 1883), fumarolic-hydrothermal manifestations and ground deformation. In this work we carry out the surface deformation time-series analysis occurring at the Island by jointly exploiting data collected via two different monitoring systems. In particular, we take advantage from the large amount of periodic and continuous geodetic measurements collected by the GPS (campaign and permanent) stations deployed on the Island and belonging to the INGV-OV monitoring network. Moreover, we benefit from the large, free and open archive of C-band SAR data acquired over the Island by the Sentinel-1 constellation of the Copernicus Program, and processed via the advanced Differential SAR Interferometry (DInSAR) technique referred to as Small BAseline Subset (SBAS) algorithm [Berardino et al., 2002]. We focus on the 2014-2017 time period to analyze the recent surface deformation phenomena occurring on the Island, thus extending a previous study, aimed at investigating the temporal evolution of the ground displacements affecting the Island and limited to the 1992-2003 time interval [Manzo et al., 2006]. The performed integrated analysis provides relevant spatial and temporal information on the Island surface deformation pattern. In particular, it reveals a rather complex deformative scenario, where localized phenomena overlap/interact with a spatially extended deformation pattern that involves many Island sectors, with no evidence of significant uplift phenomena. Moreover, it shows a good agreement and consistency between the different kinds of data, thus providing a clear picture of the recent dynamics at Ischia Island that can be profitably exploited to deeply investigate the physical processes behind the observed deformation phenomena. Acknowledgments This work is partially supported by the IREA-CNR/Italian Department of Civil Protection agreement and the I-AMICA project (Infrastructure of High Technology for Environmental and Climate Monitoring-PONa3_00363). References Berardino, P., G. Fornaro, R. Lanari, and E. Sansosti (2002), A new algorithm for surface deformation monitoring based on small baseline differential SAR interferograms, IEEE Trans. Geosci. Remote Sens., 40, 2375-2383, doi:10.1109/TGRS.2002.803792. Manzo, M., G. P. Ricciardi, F. Casu, G. Ventura, G. Zeni, S. Borgström, P. Berardino, C. Del Gaudio, and R. Lanari (2006), Surface deformation analysis in the Ischia Island (Italy) based on spaceborne radar interferometry, Journal of Volcanology and Geothermal Research, 151, 399-416, doi:10.1016/j.jvolgeores.2005.09.010.

Predicting Deformation Limits of Dual-Phase Steels Under Complex Loading Paths

DOE PAGES

Cheng, G.; Choi, K. S.; Hu, X.; ...

2017-04-05

Here in this study, the deformation limits of various DP980 steels are examined with the deformation instability theory. Under uniaxial tension, overall stress–strain curves of the material are estimated based on a simple rule of mixture (ROM) with both iso-strain and iso-stress assumptions. Under complex loading paths, an actual microstructure-based finite element (FE) method is used to resolve the deformation compatibilities explicitly between the soft ferrite and hard martensite phases. The results show that, for uniaxial tension, the deformation instability theory with iso-strain-based ROM can be used to provide the lower bound estimate of the uniform elongation (UE) for themore » various DP980 considered. Under complex loading paths, the deformation instability theory with microstructure-based FE method can be used in examining the effects of various microstructural features on the deformation limits of DP980 steels.« less

Predicting Deformation Limits of Dual-Phase Steels Under Complex Loading Paths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, G.; Choi, K. S.; Hu, X.

The deformation limits of various DP980 steels are examined in this study with deformation instability theory. Under uniaxial tension, overall stress-strain curves of the material are estimated based on simple rule of mixture (ROM) with both iso-strain and iso-stress assumptions. Under complex loading paths, actual microstructure-based finite element (FE) method is used to explicitly resolve the deformation incompatibilities between the soft ferrite and hard martensite phases. The results show that, for uniaxial tension, the deformation instability theory with iso-strain-based ROM can be used to provide the lower bound estimate of the uniform elongation (UE) for the various DP980 considered. Undermore » complex loading paths, the deformation instability theory with microstructure-based FE method can be used in examining the effects of various microstructural features on the deformation limits of DP980 steels.« less

Predicting Deformation Limits of Dual-Phase Steels Under Complex Loading Paths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, G.; Choi, K. S.; Hu, X.

Here in this study, the deformation limits of various DP980 steels are examined with the deformation instability theory. Under uniaxial tension, overall stress–strain curves of the material are estimated based on a simple rule of mixture (ROM) with both iso-strain and iso-stress assumptions. Under complex loading paths, an actual microstructure-based finite element (FE) method is used to resolve the deformation compatibilities explicitly between the soft ferrite and hard martensite phases. The results show that, for uniaxial tension, the deformation instability theory with iso-strain-based ROM can be used to provide the lower bound estimate of the uniform elongation (UE) for themore » various DP980 considered. Under complex loading paths, the deformation instability theory with microstructure-based FE method can be used in examining the effects of various microstructural features on the deformation limits of DP980 steels.« less

The interplay between rheology and pre-existing structures in the lithosphere and its influence on intraplate tectonics: Insights from scaled physical analogue models.

NASA Astrophysics Data System (ADS)

Santimano, T. N.; Adiban, P.; Pysklywec, R.

2017-12-01

The primary controls of deformation in the lithosphere are related to its rheological properties. In addition, recent work reveals that inherited zones of weakness in the deep lithosphere are prevalent and can also define tectonic activity. To understand how deformation is genetically related to rheology and/or pre-existing structures, we compare a set of physical analogue models with the presence and absence of a fault in the deep lithosphere. The layered lithosphere scaled models of a brittle upper crust, viscous lower crust and viscous mantle lithosphere are deformed in a convergent setting. Deformation of the model is recorded using high spatial and temporal stereoscopic cameras. We use Particle Image Velocimetry (PIV) to acquire a time-series dataset and study the velocity field and subsequently strain in the model. The finished model is also cut into cross-section revealing the finite internal structures that are then compared to the topography of the model. Preliminary results show that deformation in models with an inherited fault in the mantle lithosphere is accommodated by displacement along the fault plane that propagates into the overlying viscous lower crust and brittle upper crust. Here, the majority of the deformation is localized along the fault in a brittle manner. This is in contrast to the model absent of a fault that also displays significant amounts of deformation. In this setting, ductile deformation is accommodated by folding and thickening of the viscous layers and flexural shearing of the brittle upper crust. In these preliminary experiments, the difference in the strength profile between the mantle lithosphere and the lower crust is within the same order of magnitude. Future experiments will include models where the strength difference is an order of magnitude. This systematic study aids in understanding the role of rheology and deep structures particularly in transferring stress over time to the surface and is therefore fundamental in understanding intraplate tectonics and orogenesis.

Acoustic impact on the laminated plates placed between barriers

NASA Astrophysics Data System (ADS)

Paimushin, V. N.; Gazizullin, R. K.; Fedotenkov, G. V.

2016-11-01

On the basis of previously derived equations, analytical solutions are established on the forced vibrations of two-layer and three-layers rectangular plates hinged in an opening of absolutely rigid walls during the transmission of monoharmonic sound waves. It is assumed that the partition wall is situated between two absolutely rigid barriers, one of them by harmonic oscillation with a given displacements amplitude on the plate forms the incident sound wave, and the other is stationary and has a coating of deformable energy absorbing material with high damping properties. The behavior of acoustic environments in the spaces between the deformable plate and the barriers described by classical wave equation based on the ideal compressible fluid model. To describe the process of dynamic deformation of the energy absorbing coating of fixed barrier, two-dimensional equations of motion based on the use of models transversely soft layer are derived with a linear approximation of the displacement field in the thickness direction of the coating and taking into account the damping properties of the material and the hysteresis model for it. The influence of the physical and mechanical properties of the concerned mechanical system and the frequency of the incident sound wave on the parameters of its insulation properties of the plate, as well as on the parameters of the stress-strain state of the plate has been analyzed.

Bringing Perfect Vision to the Daniel K. Inouye Solar Telescope

NASA Astrophysics Data System (ADS)

Matijevich, Russ; Johansson, Erik; Johnson, Luke; Cavaco, Jeff; National Solar Observatory

2016-01-01

The world's largest ground-based solar telescope is one step closer to operation with the acceptance of the deformable mirror engineered by AOA Xinetics, a Northrop Grumman Corporation company. The Daniel K. Inouye Solar Telescope (DKIST), currently under construction in Haleakala, Hawaii, will offer unprecedented high-resolution images of the sun using the latest adaptive optics technology to provide its distortion-free imaging.Led by the National Solar Observatory (NSO) and the Association of Universities for Research in Astronomy (AURA), the Inouye Solar Telescope will help scientists better understand how magnetic fields affect the physical properties of the Sun, what roles they play in our solar system and how they affect Earth.Ground-based telescopes, whether observing the sun or the night sky must contend with atmospheric turbulence that acts as a flexible lens, constantly reshaping observed images. This turbulence makes research on solar activity difficult and drives the need for the latest adaptive optics technology.To provide DKIST with the distortion-free imaging it requires, AOA Xinetics designed a deformable mirror with 1,600 actuators, four times the normal actuator density. This deformable mirror (DM) is instrumental in removing all of the atmospheric blurriness that would otherwise limit the telescope's performance. The mirror also has an internal thermal management system to handle the intense solar energy coming from DKIST's telescope. This poster provides the history behind this incredible success story.

The structural fabric and deformation history of a mountain logjam: cameras, creep, and catastrophe

NASA Astrophysics Data System (ADS)

Deshpande, N.; Crosby, B. T.

2016-12-01

Wood and sediment are integral agents in the river transport processes that facilitate the chemical and physical evolution of landscapes. As such, the two pose an almost poetic contrast to each other: wood is buoyant, organic and elongate while sediment is dead, dense, and round. Despite wide recognition of the value of wood to river corridors, our mechanistic understanding of logjam kinematics and mobility is limited. This is in part due to historic logging practices that alter forests and `natural' river-wood feedbacks as well as contemporary attitudes that regard logjams as a nuisance. Both severely limit our ability to observe logjams in the field. Existing physically-based rules for wood transport are insufficient for this task at hand; a simple force balance approach quickly breaks down in the face of the complexity of the underlying kinematic fabric. Here, we present the results of a yearlong survey of an actively deforming logjam in the Salmon River Mountains, central Idaho. We use interval photography, pressure transducer/water level loggers and total station measurements of 150 logs within the jam (about 10% of the total population), to document where and when logjams move. The mean cumulative magnitude of displacement during the high-flow period is 2.06 m +/- 1.51 m, much of which occurred during a single event. Smaller magnitude creeping movement also occurs as the jam experiences cyclic quasi-diel fluctuations in stage due to snowmelt-generated discharge. Our results highlight the interplay between horizontal drag forces and vertical buoyant forces in governing the network of frictional connections and subsequent deformation within the logjam.

Microstructural analysis of the thermal annealing of ice-Ih using EBSD

NASA Astrophysics Data System (ADS)

Hidas, Károly; Tommasi, Andréa; Mainprice, David; Chauve, Thomas; Barou, Fabrice; Montagnat, Maurine

2017-04-01

Rocks deformed in the middle crust and deeper in the Earth typically remain at high temperature for extended time spans after the cessation of deformation. This results in annealing of the deformation microstructure by a series of thermally activated, diffusion-based processes, namely: recovery and static recrystallization, which may also modify the crystal preferred orientation (CPO) or texture. Understanding the effects of annealing on the microstructure and CPO is therefore of utmost importance for the interpretation of the microstructures and for the estimation of the anisotropy of physical properties of lower crustal and mantle rocks. Ice-Ih -the typical form of water ice on the Earth's surface, with hexagonal crystal symmetry- deforms essentially by glide of dislocations on the basal plane [1], thus it has high viscoplastic anisotropy, which induces strong heterogeneity of stresses and strains at both the intra- and intergranular scales [2-3]. This behavior makes ice-Ih an excellent analog material for silicate minerals that compose the Earth. In situ observations of the evolution of the microstructures and CPO during annealing enable the study of the interplay between the various physical processes involved in annealing (recovery, nucleation, grain growth). They also allow the analysis of the impact of the preexisting deformation microstructures on the microstructural and CPO evolution during annealing. Here we studied the evolution of the microstructure of ice-Ih during static recrystallization by stepwise annealing experiments. We alternated thermal annealing and electron backscatter diffraction (EBSD) analyses on polycrystalline columnar ice-Ih pre-deformed in uniaxial compression at temperature of -7 °C to strains of 3.0-5.2. Annealing experiments were carried out at -5 °C and -2 °C up to a maximum of 3.25 days, typically in 5-6 steps. EBSD crystal orientation maps obtained after each annealing step permit the description of microstructural changes. Decrease in average intragranular misorientation at the sample scale and modification of the misorientation across subgrain boundaries provide evidence for recovery from the earliest stages of annealing. This evolution is similar for all studied samples irrespective of their initial strain or annealing temperature. After an incubation period up to 2 hours, recovery is accompanied by recrystallization (nucleation and grain boundary migration). Grain growth proceeds at the expense of domains with high intra-granular misorientations and its kinetics fits the parabolic growth law. Deformation-induced microstructures (tilt boundaries and kink bands) are stable features during early stages of static recrystallization and locally slow down grain boundary migration, pinning grain growth. REFERENCES 1. Duval, P., Ashby, M.F., Anderman, I., 1983. Rate-controlling processes in the creep of polycrystalline ice. Journal of Physical Chemistry 87, 4066-4074. 2. Grennerat, F., Montagnat, M., Castelnau, O., Vacher, P., Moulinec, H., Suquet, P., Duval, P., 2012. Experimental characterization of the intragranular strain field in columnar ice during transient creep. Acta Materialia 60, 3655-3666. 3. Chauve, T., Montagnat, M., Vacher, P., 2015. Strain field evolution during dynamic recrystallization nucleation: A case study on ice. Acta Materialia 101, 116-124. Funding: Research leading to these results was funded by the EU-FP7 Marie Curie postdoctoral grant PIEF-GA-2012-327226 to K.H.

Projection Moire Interferometry for Rotorcraft Applications: Deformation Measurements of Active Twist Rotor Blades

NASA Technical Reports Server (NTRS)

Fleming, Gary A.; Soto, Hector L.; South, Bruce W.

2002-01-01

Projection Moire Interferometry (PMI) has been used during wind tunnel tests to obtain azimuthally dependent blade bending and twist measurements for a 4-bladed Active Twist Rotor (ATR) system in simulated forward flight. The ATR concept offers a means to reduce rotor vibratory loads and noise by using piezoelectric active fiber composite actuators embedded in the blade structure to twist each blade as they rotate throughout the rotor azimuth. The twist imparted on the blades for blade control causes significant changes in blade loading, resulting in complex blade deformation consisting of coupled bending and twist. Measurement of this blade deformation is critical in understanding the overall behavior of the ATR system and the physical mechanisms causing the reduction in rotor loads and noise. PMI is a non-contacting, video-based optical measurement technique capable of obtaining spatially continuous structural deformation measurements over the entire object surface within the PMI system field-of-view. When applied to rotorcraft testing, PMI can be used to measure the azimuth-dependent blade bending and twist along the full span of the rotor blade. This paper presents the PMI technique as applied to rotorcraft testing, and provides results obtained during the ATR tests demonstrating the PMI system performance. PMI measurements acquired at select blade actuation conditions generating minimum and maximum rotor loads are provided to explore the interrelationship between rotor loads, blade bending, and twist.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Le, K. C.; Tran, T. M.; Langer, J. S.

The statistical-thermodynamic dislocation theory developed in previous papers is used here in an analysis of high-temperature deformation of aluminum and steel. Using physics-based parameters that we expect theoretically to be independent of strain rate and temperature, we are able to fit experimental stress-strain curves for three different strain rates and three different temperatures for each of these two materials. Here, our theoretical curves include yielding transitions at zero strain in agreement with experiment. We find that thermal softening effects are important even at the lowest temperatures and smallest strain rates.

International Conference on Internal Friction and Ultrasonic Attenuation in Solids (ICIFUAS) (10th) held in Roma, Italy on September 6 - 9, 1993

DTIC Science & Technology

1993-09-09

decomposition in Fe-Cr system on non-elastic properties were investigated. Taking mechanism of appearing of microplastic deformation as the base, the...found out the general principles of LPT- induced microplasticity and examined several particular cases. The basic idea is the great change of the line...Physics, Russian Acad. of Sci., 142432 Chernogolovka, Moscow distr., Russia on heefect o sea stes V103 If S The investigations were c rried o4 on

Topology optimization applied to the design of cooling channels for plastic injection

NASA Astrophysics Data System (ADS)

Muñoz, D. A.; Arango, J. P.; González, C.; Puerto, E.; Garzón, M.

2018-04-01

In this paper, topology optimization is applied to design cooling channels in a mold of structural steel. The problem was implemented in COMSOL multiphysics, where two physics were coupled, heat transfer and solid mechanics. The optimization objective is to maximize the conduction heat flux in the mold and minimize the deformations when the plastic is injected. In order to find an optimal geometry for this objective, a density-based method was implemented into the nonlinear program (NLP) for which feasible results were found.

Scoliosis and school screening for spinal deformity.

PubMed

Kane, W J; Brown, J C; Hensinger, R N; Keller, R B

1978-05-01

The onset of "idiopathic" scoliosis is gradual. It goes unnoticed by parent and child alike. The problem is often not detected until the curvature has progressed. Severe scoliosis has serious long-term systemic, cosmetic and psychologic effects. School-based screening programs are very effective in reducing the number of operations required. These programs can be carried out by school nurses, physical education teachers and volunteers who are trained by a knowledgeable physician. Brace treatment is successful when scoliosis is detected only.

Polymer brush coatings for DNA: fundamental polymer physics and nanofabrication applications

NASA Astrophysics Data System (ADS)

de Vries, Renko

Recombinant DNA technology allows for the production of precisely defined self-assembling protein-based polymers. So far, the major applications for such protein-based polymers have been self-assembling hydrogels and micellar structures with biomedical application. Inspired by minimal models for the self-ssembly of rod-shaped viruses such as the tobacco mosaic virus, I have developed protein-polymers that co-assemble with DNA into rod-shaped virus-like particles, and protein-polymers that provide brush coatings around single DNA molecules. In this presentation I will focus on the latter, showing that on the one hand brush coated DNA is a rich model system for exploring the physics of bottle-brush polymers, while on the other hand brush coatings of DNA can also play an important practical role in nanofabrication. A key problem in the physics of bottle-brush polymers that I will address is the scale-dependence of bottle-brush elasticity. For long-wavelength thermal deformations probed by AFM imaging I will demonstrate that there is significant stiffening due to the brush coating, while for short wavelength thermal deformations probed by force spectroscopy, we find that stiffening due to the brush coating disappears completely. DNA brush coatings can also play an important practical role in nanofabrication by acting as a compatibilizer between chemically different building blocks. I will explore the example of DNA origami in combination with gold nanoparticles: while Mg2+ ions and high concentrations of monovalent salts are crucial for the stability of DNA origami, such solution conditions are typically incompatible with the colloidal stability of gold nanoparticles.I will show how DNA brush coatings can dramatically enhance the yield of formation of isolated DNA-gold nanoparticle composite nanostructures.

Deforming black hole and cosmological solutions by quasiperiodic and/or pattern forming structures in modified and Einstein gravity

NASA Astrophysics Data System (ADS)

Bubuianu, Laurenţiu; Vacaru, Sergiu I.

2018-05-01

We elaborate on the anholonomic frame deformation method, AFDM, for constructing exact solutions with quasiperiodic structure in modified gravity theories, MGTs, and general relativity, GR. Such solutions are described by generic off-diagonal metrics, nonlinear and linear connections and (effective) matter sources with coefficients depending on all spacetime coordinates via corresponding classes of generation and integration functions and (effective) matter sources. There are studied effective free energy functionals and nonlinear evolution equations for generating off-diagonal quasiperiodic deformations of black hole and/or homogeneous cosmological metrics. The physical data for such functionals are stated by different values of constants and prescribed symmetries for defining quasiperiodic structures at cosmological scales, or astrophysical objects in nontrivial gravitational backgrounds some similar forms as in condensed matter physics. It is shown how quasiperiodic structures determined by general nonlinear, or additive, functionals for generating functions and (effective) sources may transform black hole like configurations into cosmological metrics and inversely. We speculate on possible implications of quasiperiodic solutions in dark energy and dark matter physics. Finally, it is concluded that geometric methods for constructing exact solutions consist an important alternative tool to numerical relativity for investigating nonlinear effects in astrophysics and cosmology.

Modeling Vehicle Collision Angle in Traffic Crashes Based on Three-Dimensional Laser Scanning Data

PubMed Central

Lyu, Nengchao; Huang, Gang; Wu, Chaozhong; Duan, Zhicheng; Li, Pingfan

2017-01-01

In road traffic accidents, the analysis of a vehicle’s collision angle plays a key role in identifying a traffic accident’s form and cause. However, because accurate estimation of vehicle collision angle involves many factors, it is difficult to accurately determine it in cases in which less physical evidence is available and there is a lack of monitoring. This paper establishes the mathematical relation model between collision angle, deformation, and normal vector in the collision region according to the equations of particle deformation and force in Hooke’s law of classical mechanics. At the same time, the surface reconstruction method suitable for a normal vector solution is studied. Finally, the estimation model of vehicle collision angle is presented. In order to verify the correctness of the model, verification of multi-angle collision experiments and sensitivity analysis of laser scanning precision for the angle have been carried out using three-dimensional (3D) data obtained by a 3D laser scanner in the collision deformation zone. Under the conditions with which the model has been defined, validation results show that the collision angle is a result of the weighted synthesis of the normal vector of the collision point and the weight value is the deformation of the collision point corresponding to normal vectors. These conclusions prove the applicability of the model. The collision angle model proposed in this paper can be used as the theoretical basis for traffic accident identification and cause analysis. It can also be used as a theoretical reference for the study of the impact deformation of elastic materials. PMID:28264517

Modeling Vehicle Collision Angle in Traffic Crashes Based on Three-Dimensional Laser Scanning Data.

PubMed

Lyu, Nengchao; Huang, Gang; Wu, Chaozhong; Duan, Zhicheng; Li, Pingfan

2017-02-28

In road traffic accidents, the analysis of a vehicle's collision angle plays a key role in identifying a traffic accident's form and cause. However, because accurate estimation of vehicle collision angle involves many factors, it is difficult to accurately determine it in cases in which less physical evidence is available and there is a lack of monitoring. This paper establishes the mathematical relation model between collision angle, deformation, and normal vector in the collision region according to the equations of particle deformation and force in Hooke's law of classical mechanics. At the same time, the surface reconstruction method suitable for a normal vector solution is studied. Finally, the estimation model of vehicle collision angle is presented. In order to verify the correctness of the model, verification of multi-angle collision experiments and sensitivity analysis of laser scanning precision for the angle have been carried out using three-dimensional (3D) data obtained by a 3D laser scanner in the collision deformation zone. Under the conditions with which the model has been defined, validation results show that the collision angle is a result of the weighted synthesis of the normal vector of the collision point and the weight value is the deformation of the collision point corresponding to normal vectors. These conclusions prove the applicability of the model. The collision angle model proposed in this paper can be used as the theoretical basis for traffic accident identification and cause analysis. It can also be used as a theoretical reference for the study of the impact deformation of elastic materials.

Deformation of the lithosphere and what microstructures can tell us about it (Stephan Mueller Medal Lecture)

NASA Astrophysics Data System (ADS)

Heilbronner, Renée

2016-04-01

The lithosphere is a roughly stratified and heterogeneous rock body that constitutes the outer layer of our planet. It is subdivided into irregularly shaped stiff plates that move with respect to one another deforming each other along their margins. At the large scale the lithosphere is usually modeled as a flat-lying multi-layer, its rheological profile being based on flow laws determined experimentally for key minerals of the crust and upper mantle. At the somewhat smaller scale of field observations, geometrical and physical complexities become apparent: rocks are folded, sheared and fractured, and - in general - quite heterogeneously deformed. And finally, at the even smaller scale of mechanical testing and microscopic investigations, rocks are seen as polycrystalline aggregates or granular composites whose bulk properties depends both on the composition and shape of the individual grains and the spatial arrangement of the crystals with respect to one another. In other words, the physical properties of the lithosphere and the inferred style or type of deformation depend very much on the scale of observation. Microstructures and textures (crystallographic preferred orientations) of deformed rocks provide a wealth of information: when used as archives of the deformation history, they allow us to unravel the tectonic evolution of the lithosphere at plate boundaries. At the same time, they enable us to assess past and/or present geophysical properties. By comparing the microstructures of experimentally and naturally deformed rocks it is possible to infer the active deformation mechanisms and thus to extrapolate flow laws to geological time scales. With the advent of digital image processing, microstructure and texture analysis have taken a great leap forward. By amalgamating methods from neighbouring disciplines such as mathematical morphometry, stereology, geostatistics, material sciences, etc., microstructure and texture analysis have come a long way since the early days of strain analysis and X-ray texture goniometry. During my lecture, I will try to retrace this development: we will start by taking a dive down to the nano-scale, deep into the ductile regime, and inspect the shape, alignments and preferred orientations of sub-grain boundaries during simple shear deformation. What can the microstructure tell us about the deformation mechanism and the amount of strain that the rock material has undergone, and is it really 'strain' we are looking at? We will also look at orientation images and track the development in space and time of crystallographic orientations with temperature, strain rate and strain: do we reach a 'steady state'? We will then come up in scale and look at various definitions of grain size and test the validity of piezometers: how precise is the flow stress that we determine, does it really only depend on grain size, and what do we mean by 'grains size'? Back at the surface, we will look at brittle microstructures and consider distributions: fractal distributions of grain size and spatial distributions of grains: how can we get a handle on the microstructures of cataclastic deformation or granular flow? - At each step, I hope that it becomes apparent that there is more to microstructure and texture than the aspect ratio of an ellipse, the diameter of a grain, or the maximum of a c-axis pole figure...

Deformed Palmprint Matching Based on Stable Regions.

PubMed

Wu, Xiangqian; Zhao, Qiushi

2015-12-01

Palmprint recognition (PR) is an effective technology for personal recognition. A main problem, which deteriorates the performance of PR, is the deformations of palmprint images. This problem becomes more severe on contactless occasions, in which images are acquired without any guiding mechanisms, and hence critically limits the applications of PR. To solve the deformation problems, in this paper, a model for non-linearly deformed palmprint matching is derived by approximating non-linear deformed palmprint images with piecewise-linear deformed stable regions. Based on this model, a novel approach for deformed palmprint matching, named key point-based block growing (KPBG), is proposed. In KPBG, an iterative M-estimator sample consensus algorithm based on scale invariant feature transform features is devised to compute piecewise-linear transformations to approximate the non-linear deformations of palmprints, and then, the stable regions complying with the linear transformations are decided using a block growing algorithm. Palmprint feature extraction and matching are performed over these stable regions to compute matching scores for decision. Experiments on several public palmprint databases show that the proposed models and the KPBG approach can effectively solve the deformation problem in palmprint verification and outperform the state-of-the-art methods.

Multiscale deformation of a liquid surface in interaction with a nanoprobe

NASA Astrophysics Data System (ADS)

Ledesma-Alonso, R.; Tordjeman, P.; Legendre, D.

2012-06-01

The interaction between a nanoprobe and a liquid surface is studied. The surface deformation depends on physical and geometric parameters, which are depicted by employing three dimensionless parameters: Bond number Bo, modified Hamaker number Ha, and dimensionless separation distance D*. The evolution of the deformation is described by a strongly nonlinear partial differential equation, which is solved by means of numerical methods. The dynamic analysis of the liquid profile points out the existence of a critical distance Dmin*, below which the irreversible wetting process of the nanoprobe happens. For D*≥Dmin*, the numerical results show the existence of two deformation profiles, one stable and another unstable from the energetic point of view. Different deformation length-scales, characterizing the stable liquid equilibrium interface, define the near- and the far-field deformation zones, where self-similar profiles are found. Finally, our results allow us to provide simple relationships between the parameters, which leads to determine the optimal conditions when performing atomic force microscope measurements over liquids.

Numerical models of caldera deformation: Effects of multiphase and multicomponent hydrothermal fluid flow

USGS Publications Warehouse

Hutnak, M.; Hurwitz, S.; Ingebritsen, S.E.; Hsieh, P.A.

2009-01-01

Ground surface displacement (GSD) in large calderas is often interpreted as resulting from magma intrusion at depth. Recent advances in geodetic measurements of GSD, notably interferometric synthetic aperture radar, reveal complex and multifaceted deformation patterns that often require complex source models to explain the observed GSD. Although hydrothermal fluids have been discussed as a possible deformation agent, very few quantitative studies addressing the effects of multiphase flow on crustal mechanics have been attempted. Recent increases in the power and availability of computing resources allow robust quantitative assessment of the complex time-variant thermal interplay between aqueous fluid flow and crustal deformation. We carry out numerical simulations of multiphase (liquid-gas), multicomponent (H 2O-CO2) hydrothermal fluid flow and poroelastic deformation using a range of realistic physical parameters and processes. Hydrothermal fluid injection, circulation, and gas formation can generate complex, temporally and spatially varying patterns of GSD, with deformation rates, magnitudes, and geometries (including subsidence) similar to those observed in several large calderas. The potential for both rapid and gradual deformation resulting from magma-derived fluids suggests that hydrothermal fluid circulation may help explain deformation episodes at calderas that have not culminated in magmatic eruption.

A Biomechanical Modeling Guided CBCT Estimation Technique

PubMed Central

Zhang, You; Tehrani, Joubin Nasehi; Wang, Jing

2017-01-01

Two-dimensional-to-three-dimensional (2D-3D) deformation has emerged as a new technique to estimate cone-beam computed tomography (CBCT) images. The technique is based on deforming a prior high-quality 3D CT/CBCT image to form a new CBCT image, guided by limited-view 2D projections. The accuracy of this intensity-based technique, however, is often limited in low-contrast image regions with subtle intensity differences. The solved deformation vector fields (DVFs) can also be biomechanically unrealistic. To address these problems, we have developed a biomechanical modeling guided CBCT estimation technique (Bio-CBCT-est) by combining 2D-3D deformation with finite element analysis (FEA)-based biomechanical modeling of anatomical structures. Specifically, Bio-CBCT-est first extracts the 2D-3D deformation-generated displacement vectors at the high-contrast anatomical structure boundaries. The extracted surface deformation fields are subsequently used as the boundary conditions to drive structure-based FEA to correct and fine-tune the overall deformation fields, especially those at low-contrast regions within the structure. The resulting FEA-corrected deformation fields are then fed back into 2D-3D deformation to form an iterative loop, combining the benefits of intensity-based deformation and biomechanical modeling for CBCT estimation. Using eleven lung cancer patient cases, the accuracy of the Bio-CBCT-est technique has been compared to that of the 2D-3D deformation technique and the traditional CBCT reconstruction techniques. The accuracy was evaluated in the image domain, and also in the DVF domain through clinician-tracked lung landmarks. PMID:27831866

Mammogram registration using the Cauchy-Navier spline

NASA Astrophysics Data System (ADS)

Wirth, Michael A.; Choi, Christopher

2001-07-01

The process of comparative analysis involves inspecting mammograms for characteristic signs of potential cancer by comparing various analogous mammograms. Factors such as the deformable behavior of the breast, changes in breast positioning, and the amount/geometry of compression may contribute to spatial differences between corresponding structures in corresponding mammograms, thereby significantly complicating comparative analysis. Mammogram registration is a process whereby spatial differences between mammograms can be reduced. Presented in this paper is a nonrigid approach to matching corresponding mammograms based on a physical registration model. Many of the earliest approaches to mammogram registration used spatial transformations which were innately rigid or affine in nature. More recently algorithms have incorporated radial basis functions such as the Thin-Plate Spline to match mammograms. The approach presented here focuses on the use of the Cauchy-Navier Spline, a deformable registration model which offers approximate nonrigid registration. The utility of the Cauchy-Navier Spline is illustrated by matching both temporal and bilateral mammograms.

[Adolescent idiopathic scoliosis].

PubMed

2016-12-01

Adolescent idiopathic scoliosis is a 3D spinal deformity in frontal, sagittal and axial planes, with high relevance in the pediatric population especially in adolescents and females between 10 years of age and the end of growth spurt and skeletal maturity. The radiographic manifestation is a curve greater than 10° measured by Cobb method associated with vertebral rotation. "Idiopathic" diagnosis has to be done after neuroanatomical anomalies of the posterior cerebral fosa and spinal canal have been ruled out. The physical finding of a thoracic or lumbar hump is the clinical manifestation of vertebral rotation seen in a forward bending test (Adam's Test). It is recommended that all curves with a magnitude greater than 20° have to be controlled and treated by a spinal surgeon being observation, bracing and surgery the different treatment options based on the extent, progression of deformity and basically the clinical condition of the patient. Sociedad Argentina de Pediatría.

Investigating the Mobility of Light Autonomous Tracked Vehicles using a High Performance Computing Simulation Capability

NASA Technical Reports Server (NTRS)

Negrut, Dan; Mazhar, Hammad; Melanz, Daniel; Lamb, David; Jayakumar, Paramsothy; Letherwood, Michael; Jain, Abhinandan; Quadrelli, Marco

2012-01-01

This paper is concerned with the physics-based simulation of light tracked vehicles operating on rough deformable terrain. The focus is on small autonomous vehicles, which weigh less than 100 lb and move on deformable and rough terrain that is feature rich and no longer representable using a continuum approach. A scenario of interest is, for instance, the simulation of a reconnaissance mission for a high mobility lightweight robot where objects such as a boulder or a ditch that could otherwise be considered small for a truck or tank, become major obstacles that can impede the mobility of the light autonomous vehicle and negatively impact the success of its mission. Analyzing and gauging the mobility and performance of these light vehicles is accomplished through a modeling and simulation capability called Chrono::Engine. Chrono::Engine relies on parallel execution on Graphics Processing Unit (GPU) cards.

Horava-Lifshitz cosmology, entropic interpretation and quark-hadron phase transition

NASA Astrophysics Data System (ADS)

Kheyri, F.; Khodadi, M.; Sepangi, Hamid Reza

2013-05-01

Based on the assumptions of the standard model of cosmology, a phase transition associated with chiral symmetry breaking after the electroweak transition has occurred at approximately 10 μs after the Big Bang to convert a plasma of free quarks and gluons into hadrons. We consider such a phase transition in the context of a deformed Horava-Lifshitz cosmology. The Friedmann equation for the deformed Horava-Lifshitz universe is obtained using the entropic interpretation of gravity, proposed by Verlinde. We investigate the effects of the parameter ω appearing in the theory on the evolution of the physical quantities relevant to a description of the early universe, namely, the energy density and temperature before, during and after the phase transition. Finally, we study the cross-over phase transition in both high and low temperature regions in view of the recent lattice QCD simulations data.

Constitutive flow behaviour of austenitic stainless steels under hot deformation: artificial neural network modelling to understand, evaluate and predict

NASA Astrophysics Data System (ADS)

Mandal, Sumantra; Sivaprasad, P. V.; Venugopal, S.; Murthy, K. P. N.

2006-09-01

An artificial neural network (ANN) model is developed to predict the constitutive flow behaviour of austenitic stainless steels during hot deformation. The input parameters are alloy composition and process variables whereas flow stress is the output. The model is based on a three-layer feed-forward ANN with a back-propagation learning algorithm. The neural network is trained with an in-house database obtained from hot compression tests on various grades of austenitic stainless steels. The performance of the model is evaluated using a wide variety of statistical indices. Good agreement between experimental and predicted data is obtained. The correlation between individual alloying elements and high temperature flow behaviour is investigated by employing the ANN model. The results are found to be consistent with the physical phenomena. The model can be used as a guideline for new alloy development.

Multiscale Sediment-Laden Flow Theory and Its Application in Flood Risk Management

NASA Astrophysics Data System (ADS)

Cao, Z. X.; Pender, G.; Hu, P.

2011-09-01

Sediment-laden flows over erodible bed normally feature multiple time scales. The time scales of sediment transport and bed deformation relative to the flow essentially measure how fast sediment transport adapts to capacity regime in line with local flow scenario and the bed deforms as compared to the flow, which literally dictate if a capacity based and/or decoupled model is justified. This paper synthesizes the recently developed multiscale theory for sediment-laden flows over erodible bed, with bed load and suspended load transport respectively. It is unravelled that bed load transport can adapt to capacity sufficiently rapidly even under highly unsteady flows and thus a capacity model is mostly applicable, whereas a non-capacity model is critical for suspended sediment because of the lower rate of adaptation to capacity. Physically coupled modeling is critical for cases characterized by rapid bed variation. Applications are outlined on flash floods and landslide dam break floods.

SU-E-J-108: Solving the Chinese Postman Problem for Effective Contour Deformation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, J; Zhang, L; Balter, P

2015-06-15

Purpose: To develop a practical approach for accurate contour deformation when deformable image registration (DIR) is used for atlas-based segmentation or contour propagation in image-guided radiotherapy. Methods: A contour deformation approach was developed on the basis of 3D mesh operations. The 2D contours represented by a series of points in each slice were first converted to a 3D triangular mesh, which was deformed by the deformation vectors resulting from DIR. A set of parallel 2D planes then cut through the deformed 3D mesh, generating unordered points and line segments, which should be reorganized into a set of 2D contour points.more » It was realized that the reorganization problem was equivalent to solving the Chinese Postman Problem (CPP) by traversing a graph built from the unordered points with the least cost. Alternatively, deformation could be applied to a binary mask converted from the original contours. The deformed binary mask was then converted back into contours at the CT slice locations. We performed a qualitative comparison to validate the mesh-based approach against the image-based approach. Results: The DIR could considerably change the 3D mesh, making complicated 2D contour representations after deformation. CPP was able to effectively reorganize the points in 2D planes no matter how complicated the 2D contours were. The mesh-based approach did not require a post-processing of the contour, thus accurately showing the actual deformation in DIR. The mesh-based approach could keep some fine details and resulted in smoother contours than the image-based approach did, especially for the lung structure. Image-based approach appeared to over-process contours and suffered from image resolution limits. The mesh-based approach was integrated into in-house DIR software for use in routine clinic and research. Conclusion: We developed a practical approach for accurate contour deformation. The efficiency of this approach was demonstrated in both clinic and research applications. This work was partially supported by Cancer Prevention & Research Institute of Texas (CPRIT) RP110562.« less

Return to sports after surgery to correct adolescent idiopathic scoliosis: a survey of the Spinal Deformity Study Group.

PubMed

Lehman, Ronald A; Kang, Daniel G; Lenke, Lawrence G; Sucato, Daniel J; Bevevino, Adam J

2015-05-01

There are no guidelines for when surgeons should allow patients to return to sports and athletic activities after spinal fusion for adolescent idiopathic scoliosis (AIS). Current recommendations are based on anecdotal reports and a survey performed more than a decade ago in the era of first/second-generation posterior implants. To identify current recommendations for return to sports and athletic activities after surgery for AIS. Questionnaire-based survey. Adolescent idiopathic scoliosis after corrective surgery. Type and time to return to sports. A survey was administered to members of the Spinal Deformity Study Group. The survey consisted of surgeon demographic information, six clinical case scenarios, three different construct types (hooks, pedicle screws, hybrid), and questions regarding the influence of lowest instrumented vertebra (LIV) and postoperative physical therapy. Twenty-three surgeons completed the survey, and respondents were all experienced expert deformity surgeons. Pedicle screw instrumentation allows earlier return to noncontact and contact sports, with most patients allowed to return to running by 3 months, both noncontact and contact sports by 6 months, and collision sports by 12 months postoperatively. For all construct types, approximately 20% never allow return to collision sports, whereas all surgeons allow eventual return to contact and noncontact sports regardless of construct type. In addition to construct type, we found progressively distal LIV resulted in more surgeons never allowing return to collision sports, with 12% for selective thoracic fusion to T12/L1 versus 33% for posterior spinal fusion to L4. Most respondents also did not recommend formal postoperative physical therapy (78%). Of all surgeons surveyed, there was only one reported instrumentation failure/pullout without neurologic deficit after a patient went snowboarding 2 weeks postoperatively. Modern posterior instrumentation allows surgeons to recommend earlier return to sports after fusion for AIS, with the majority allowing running by 3 months, noncontact and contact sports by 6 months, and collision sports by 12 months. Published by Elsevier Inc.

The course of skull deformation from birth to 5 years of age: a prospective cohort study.

PubMed

van Vlimmeren, Leo A; Engelbert, Raoul Hh; Pelsma, Maaike; Groenewoud, Hans Mm; Boere-Boonekamp, Magda M; der Sanden, Maria Wg Nijhuis-van

2017-01-01

In a continuation of a prospective longitudinal cohort study in a healthy population on the course of skull shape from birth to 24 months, at 5 years of age, 248 children participated in a follow-up assessment using plagiocephalometry (ODDI-oblique diameter difference index, CPI-cranio proportional index). Data from the original study sampled at birth, 7 weeks, 6, 12, and 24 months were used in two linear mixed models. (1) if deformational plagiocephaly (ODDI <104%) and/or positional preference at 7 weeks of age are absent, normal skull shape can be predicted at 5 years of age; (2) if positional preference occurs, ODDI is the highest at 7 weeks and decreases to a stable lowest value at 2 and 5 years of age; and (3) regarding brachycephaly, all children showed the highest CPI at 6 months of age with a gradual decrease over time. The course of skull deformation is favourable in most of the children in The Netherlands; at 5 years of age, brachycephaly is within the normal range for all children, whereas the severity of plagiocephaly is within the normal range in 80%, within the mild range in 19%, and within the moderate/severe range in 1%. Medical consumption may be reduced by providing early tailored counselling. What is Known: • Skull deformation prevalence increased after recommendations against Sudden Infant Death Syndrome, little is known about the longitudinal course. • Paediatric physical therapy intervention between 2 and 6 months of age reduces deformational plagiocephaly at 6 and 12 months of age. What is New: • The course of skull deformation is favourable in most of the children in The Netherlands; at 5 years of age, deformational brachycephaly is within the normal range for all children, whereas the severity of deformational plagiocephaly is within the normal range in 80%, within the mild range in 19%, and within the moderate to severe range in only 1%. • Paediatric physical therapy intervention does not influence the long-term outcome; it only influences the earlier decrease of the severity of deformational plagiocephaly.

Investigate the complex process in particle-fluid based surface generation technology using reactive molecular dynamics method

NASA Astrophysics Data System (ADS)

Han, Xuesong; Li, Haiyan; Zhao, Fu

2017-07-01

Particle-fluid based surface generation process has already become one of the most important materials processing technology for many advanced materials such as optical crystal, ceramics and so on. Most of the particle-fluid based surface generation technology involves two key process: chemical reaction which is responsible for surface softening; physical behavior which is responsible for materials removal/deformation. Presently, researchers cannot give a reasonable explanation about the complex process in the particle-fluid based surface generation technology because of the small temporal-spatial scale and the concurrent influence of physical-chemical process. Molecular dynamics (MD) method has already been proved to be a promising approach for constructing effective model of atomic scale phenomenon and can serve as a predicting simulation tool in analyzing the complex surface generation mechanism and is employed in this research to study the essence of surface generation. The deformation and piles of water molecule is induced with the feeding of abrasive particle which justifies the property mutation of water at nanometer scale. There are little silica molecule aggregation or materials removal because the water-layer greatly reduce the strength of mechanical interaction between particle and materials surface and minimize the stress concentration. Furthermore, chemical effect is also observed at the interface: stable chemical bond is generated between water and silica which lead to the formation of silconl and the reaction rate changes with the amount of water molecules in the local environment. Novel ring structure is observed in the silica surface and it is justified to be favored of chemical reaction with water molecule. The siloxane bond formation process quickly strengthened across the interface with the feeding of abrasive particle because of the compressive stress resulted by the impacting behavior.

Geometry of the Valgus Knee: Contradicting the Dogma of a Femoral-Based Deformity.

PubMed

Eberbach, Helge; Mehl, Julian; Feucht, Matthias J; Bode, Gerrit; Südkamp, Norbert P; Niemeyer, Philipp

2017-03-01

Realignment osteotomies of valgus knee deformities are usually performed at the distal femur, as valgus alignment is considered to be a femoral-based deformity. This dogma, however, has not been proven in a large patient population. Valgus malalignment may also be caused by a tibial deformity or a combined tibial and femoral deformity. The purposes of this study were (1) to analyze the coronal geometry of patients with valgus malalignment and identify the location of the underlying deformity and (2) to investigate the proportion of cases that require realignment osteotomy at the tibia, the femur, or both locations to avoid an oblique joint line. Cross-sectional study; Level of evidence, 3. The analysis included 420 standing full-leg radiographs of patients with valgus malalignment (mechanical femorotibial angle [mFTA], ≥4°). A systematic analysis of the coronal leg geometry was performed including the mFTA, mechanical lateral distal femoral angle (mLDFA), mechanical medial proximal tibial angle (mMPTA), and joint-line convergence angle (JLCA). The localization of the deformity was determined according to the malalignment test described by Paley, and patients were assigned to 1 of 4 groups: femoral-based valgus deformity, tibial-based valgus deformity, femoral- and tibial-based valgus deformity, or intra-articular/ligamentary-based valgus deformity. Subsequently, the ideal osteotomy site was identified with the goal of a postoperative change of the joint line of two different maximum values, ±2° and ±4°, from its physiological varus position of 3°. Measurements of the coronal alignment revealed a mean (±SD) mFTA of 7.4° ± 4.3° (range, 4°-28.2°). The mean mLDFA and mean mMPTA were 84.8° ± 2.4° and 90.9° ± 2.6°, respectively. The mean JLCA was 1.2° ± 3.1°. The majority (41.0%) of valgus deformities were tibial based, 23.6% were femoral based, 26.9% were femoral and tibial based, and 8.6% were intra-articular/ligamentary based. To achieve a straight-leg axis and an anatomic postoperative joint line with a tolerance of ±4°, the ideal site of a corrective osteotomy was tibial in 55.2% of cases and femoral in 19.5% of cases. A double-level osteotomy would be necessary in 25.2% of cases. With a tolerance of ±2°, the ideal osteotomy site was the proximal tibia in 41.0% of cases and the distal femur in 13.6% of cases; a double-level osteotomy would be necessary in 45.5% of cases. In contrast to the widespread belief that valgus malalignment is usually caused by a femoral deformity, this study found that valgus malalignment was attributable to tibial deformity in the majority of patients. In addition, a combined femoral- and tibial-based deformity was more common than an isolated femoral-based deformity. As a clinical consequence, varus osteotomies to treat lateral compartment osteoarthritis must be performed at the tibial site or as a double-level osteotomy in a relevant number of patients to avoid an oblique joint line.

PREFACE: International Symposium on Dynamic Deformation and Fracture of Advanced Materials (D2FAM 2013)

NASA Astrophysics Data System (ADS)

Silberschmidt, Vadim V.

2013-07-01

Intensification of manufacturing processes and expansion of usability envelopes of modern components and structures in many cases result in dynamic loading regimes that cannot be resented adequately employing quasi-static formulations of respective problems of solid mechanics. Specific features of dynamic deformation, damage and fracture processes are linked to various factors, most important among them being: a transient character of load application; complex scenarios of propagation, attenuation and reflection of stress waves in real materials, components and structures; strain-rate sensitivity of materials properties; various thermo-mechanical regimes. All these factors make both experimental characterisation and theoretical (analytical and numerical) analysis of dynamic deformation and fracture rather challenging; for instance, besides dealing with a spatial realisation of these processes, their evolution with time should be also accounted for. To meet these challenges, an International Symposium on Dynamic Deformation and Fracture of Advanced Materials D2FAM 2013 was held on 9-11 September 2013 in Loughborough, UK. Its aim was to bring together specialists in mechanics of materials, applied mathematics, physics, continuum mechanics, materials science as well as various areas of engineering to discuss advances in experimental and theoretical analysis, and numerical simulations of dynamic mechanical phenomena. Some 50 papers presented at the Symposium by researchers from 12 countries covered various topics including: high-strain-rate loading and deformation; dynamic fracture; impact and blast loading; high-speed penetration; impact fatigue; damping properties of advanced materials; thermomechanics of dynamic loading; stress waves in micro-structured materials; simulation of failure mechanisms and damage accumulation; processes in materials under dynamic loading; a response of components and structures to harsh environment. The materials discussed at D2FAM 2013 ranged from traditional ones such as metals, alloys, polymers and composites to advanced and emerging materials, such as foams, cellular materials and metallic glasses, as well as bio-materials. Within the framework of the Symposium, a Special Session 'Parametric Resonance, Vibro-impact and Related Phenomena' was organised by partners of the FP7 IAPP project PARM-2: 'Vibro-impact machines based on parametric resonance: Concepts, mathematical modelling, experimental verification and implementation.' The Session focused on the topics, directly related to the project: excitation, stabilization, control and applications of parametric resonance (PR); multiple degrees of freedom of PR-excited systems; basic principles of PR-based macro and micro tools; design and technological aspects of PR-based machines; vibro-assisted machining; fatigue under high-amplitude vibro-impact conditions and corresponding optimal design; localisation near defects in dynamic response of elastic lattices and structures; dispersive waves and dynamic fracture in non-uniform lattice systems; thermally induced surface-breaking cracks, etc. This issue presents a selection of research papers presented at the International Symposium on Dynamic Deformation and Fracture of Advanced Materials D2FAM 2013. The Symposium Organisers would like to acknowledge its sponsors: Institute of Physics, International Centre of Vibro-Impact Systems and Marie Curie Action: Industry-Academia Partnerships and Pathways of the Seventh Framework Programme (FP7) of the European Commission (PARM-2 consortium). The PARM-2 consortium sponsored twenty scholarships for early-stage researchers to participate in this Symposium.

Liquid Between Macromolecules in Protein Crystals: Static Versus Dynamics

NASA Technical Reports Server (NTRS)

Chernov, A. A.

2005-01-01

Protein crystals are so fragile that they often can not be handled by tweezers. Indeed, measurements of the Young modulus, E, of lysozyme crystals resulted in E approx. equals 0.1 - 1 GPa, the lower figures, 0.1 - 0.5 GPa, being obtained from triple point bending of as-grown and not cross-linked crystals sitting in solution. The bending strength was found to be approx.10(exp -2) E. On the other hand, ultrasound speed and Mandelstam-Raman-Brilloin light scattering experiments led to much higher figures, E approx. equals 2.7 GPa. The lower figures for E were found from static or low frequency crystal deformations measurements, while the higher moduli are based on high frequency lattice vibrations, 10(exp 7) - 10(exp 10) 1/s. The physical reason for the about an order of magnitude discrepancy is in different behavior of water filling space between protein molecules. At slow lattice deformation, the not-bound intermolecular water has enough time to flow from the compressed to expanded regions of the deformed crystal. At high deformation frequencies in the ultra- and hypersound waves, the water is confined in the intermolecular space and, on that scale, behaves like a solid, thus contributing to the elastic crystal moduli. In this case, the reciprocal crystal modulus is expected to be an average of the water protein and water compressibilities (reciprocal compressibilities): the bulk modulus for lysozyme is 26 GPa, for water it is 7 GPa. Anisotropy of the crystal moduli comes from intermolecular contacts within the lattice while the high frequency hardness comes from the bulk of protein molecules and water bulk moduli. These conclusions are based on the analysis of liquid flow in porous medium to be presented.

ICME for Crashworthiness of TWIP Steels: From Ab Initio to the Crash Performance

NASA Astrophysics Data System (ADS)

Güvenç, O.; Roters, F.; Hickel, T.; Bambach, M.

2015-01-01

During the last decade, integrated computational materials engineering (ICME) emerged as a field which aims to promote synergetic usage of formerly isolated simulation models, data and knowledge in materials science and engineering, in order to solve complex engineering problems. In our work, we applied the ICME approach to a crash box, a common automobile component crucial to passenger safety. A newly developed high manganese steel was selected as the material of the component and its crashworthiness was assessed by simulated and real drop tower tests. The crashworthiness of twinning-induced plasticity (TWIP) steel is intrinsically related to the strain hardening behavior caused by the combination of dislocation glide and deformation twinning. The relative contributions of those to the overall hardening behavior depend on the stacking fault energy (SFE) of the selected material. Both the deformation twinning mechanism and the stacking fault energy are individually well-researched topics, but especially for high-manganese steels, the determination of the stacking-fault energy and the occurrence of deformation twinning as a function of the SFE are crucial to understand the strain hardening behavior. We applied ab initio methods to calculate the stacking fault energy of the selected steel composition as an input to a recently developed strain hardening model which models deformation twinning based on the SFE-dependent dislocation mechanisms. This physically based material model is then applied to simulate a drop tower test in order to calculate the energy absorption capacity of the designed component. The results are in good agreement with experiments. The model chain links the crash performance to the SFE and hence to the chemical composition, which paves the way for computational materials design for crashworthiness.

Coupling landscapes to solid-Earth deformation over the ice-age

NASA Astrophysics Data System (ADS)

Pico, T.; Mitrovica, J. X.; Ferrier, K.; Braun, J.

2016-12-01

We present initial results of a coupled ice-age sea level - landscape evolution code. Deformation of the solid Earth in response to the growth and ablation of continental ice sheets produces spatially-variable patterns of sea-level change. Recent modeling has considered the impact of sedimentation and erosion on sea level predictions across the last glacial cycle, but these studies have imposed, a-priori, a record of sediment flux and erosion, rather than computing them from a physics-based model of landscape evolution in the presence of sea-level (topography) changes. These topography changes range from 1-10 m/kyr in the near and intermediate field of the Late Pleistocene ice cover, and are thus comparable to (or exceed) tectonic rates in such regions. Our simulations aim to address the following question: how does solid-Earth deformation influence the evolution of landscapes over glacial periods? To address this issue, we couple a highly-efficient landscape evolution code, Fastscape (Braun & Willett, 2013), to a global, gravitationally-self consistent sea-level theory. Fastscape adopts standard geomorphic laws governing incision and marine deposition, and the sea-level model is based on the canonical work of Farrell & Clark (1976), with extensions to include the effects of rotation and time varying shoreline geometries (Kendall et al., 2005), and sediment erosion and deposition (Dalca et al, 2013). We will present global results and focus on a few regional case studies where deposition rates from a dataset of sedimentary cores can be used as a check on the simulations. These predictions quantify the influence of sea-level change (including that associated with sedimentation and erosion) on geomorphic drivers of landscape evolution, and in turn, the solid Earth deformation caused by these surface processes over an ice age.

Deformation data modeling through numerical models: an efficient method for tracking magma transport

NASA Astrophysics Data System (ADS)

Charco, M.; Gonzalez, P. J.; Galán del Sastre, P.

2017-12-01

Nowadays, multivariate collected data and robust physical models at volcano observatories are becoming crucial for providing effective volcano monitoring. Nevertheless, the forecast of volcanic eruption is notoriously difficult. Wthin this frame one of the most promising methods to evaluate the volcano hazard is the use of surface ground deformation and in the last decades many developments in the field of deformation modeling has been achieved. In particular, numerical modeling allows realistic media features such as topography and crustal heterogeneities to be included, although it is still very time cosuming to solve the inverse problem for near-real time interpretations. Here, we present a method that can be efficiently used to estimate the location and evolution of magmatic sources base on real-time surface deformation data and Finite Element (FE) models. Generally, the search for the best-fitting magmatic (point) source(s) is conducted for an array of 3-D locations extending below a predefined volume region and the Green functions for all the array components have to be precomputed. We propose a FE model for the pre-computation of Green functions in a mechanically heterogeneous domain which eventually will lead to a better description of the status of the volcanic area. The number of Green functions is reduced here to the number of observational points by using their reciprocity relationship. We present and test this methodology with an optimization method base on a Genetic Algorithm. Following synthetic and sensitivity test to estimate the uncertainty of the model parameters, we apply the tool for magma tracking during 2007 Kilauea volcano intrusion and eruption. We show how data inversion with numerical models can speed up the source parameters estimations for a given volcano showing signs of unrest.

Migrating tremors illuminate complex deformation beneath the seismogenic San Andreas fault

USGS Publications Warehouse

Shelly, David R.

2010-01-01

The San Andreas fault is one of the most extensively studied faults in the world, yet its physical character and deformation mode beneath the relatively shallow earthquake-generating portion remain largely unconstrained. Tectonic ‘non-volcanic’ tremor, a recently discovered seismic signal probably generated by shear slip on the deep extension of some major faults, can provide new insight into the deep fate of such faults, including that of the San Andreas fault near Parkfield, California. Here I examine continuous seismic data from mid-2001 to 2008, identifying tremor and decomposing the signal into different families of activity based on the shape and timing of the waveforms at multiple stations. This approach allows differentiation between activities from nearby patches of the deep fault and begins to unveil rich and complex patterns of tremor occurrence. I find that tremor exhibits nearly continuous migration, with the most extensive episodes propagating more than 20 kilometres along fault strike at rates of 15–80 kilometres per hour. This suggests that the San Andreas fault remains a localized through-going structure, at least to the base of the crust, in this area. Tremor rates and recurrence behaviour changed markedly in the wake of the 2004 magnitude-6.0 Parkfield earthquake, but these changes were far from uniform within the tremor zone, probably reflecting heterogeneous fault properties and static and dynamic stresses decaying away from the rupture. The systematic recurrence of tremor demonstrated here suggests the potential to monitor detailed time-varying deformation on this portion of the deep San Andreas fault, deformation which unsteadily loads the shallower zone that last ruptured in the 1857 magnitude-7.9 Fort Tejon earthquake.

A new approach to characterize the effect of fabric deformation on thermal protective performance

NASA Astrophysics Data System (ADS)

Li, Jun; Li, Xiaohui; Lu, Yehu; Wang, Yunyi

2012-04-01

It is very important to evaluate thermal protective performance (TPP) in laboratory-simulated fire scenes as accurately as possible. For this paper, to thoroughly understand the effect of fabric deformation on basic physical properties and TPP of flame-retardant fabrics exposed to flash fire, a new modified TPP testing apparatus was developed. Different extensions were employed to simulate the various extensions displayed during different body motions. The tests were also carried out with different air gaps. The results showed a significant decrease in air permeability after deformation. However, the change of thickness was slight. The fabric deformation had a complicated effect on thermal protection with different air gaps. The change of TPP depended on the balance between the surface contact area and the thermal insulation. The newly developed testing apparatus could be well employed to evaluate the effect of deformation on TPP of flame-resistant fabrics.

Equilibrium stability of a cylindrical body subject to the internal structure of the material and inelastic behaviour of the completely compressed matrix

NASA Astrophysics Data System (ADS)

Gotsev, D. V.; Perunov, N. S.; Sviridova, E. N.

2018-03-01

The mathematical model describing the stress-strain state of a cylindrical body under the uniform radial compression effect is constructed. The model of the material is the porous medium model. The compressed skeleton of the porous medium possesses hardening elastic-plastic properties. Deforming of the porous medium under the specified compressive loads is divided into two stages: elastic deforming of the porous medium and further elastic-plastic deforming of the material with completely compressed matrix. The analytical relations that define the fields of stress and displacement at each stage of the deforming are obtained. The influence of the porosity and other physical, mechanical and geometric parameters of the construction on the size of the plastic zone is evaluated. The question of the ground state equilibrium instability is investigated within the framework of the three-dimensional linearized relationships of the stability theory of deformed bodies.

Atomistic Origin of Deformation Twinning in Biomineral Aragonite.

PubMed

Liu, Jialin; Huang, Zaiwang; Pan, Zhiliang; Wei, Qiuming; Li, Xiaodong; Qi, Yue

2017-03-10

Deformation twinning rarely occurs in mineral materials which typically show brittle fracture. Surprisingly, it has recently been observed in the biomineral aragonite phase in nacre under high rate impact loading. In this Letter, the twinning tendency and the competition between fracture and deformation twinning were revealed by first principles calculations. The ratio of the unstable stacking fault energy and the stacking fault energy in orthorhombic aragonite is hitherto the highest in a broad range of metallic and oxide materials. The underlining physics for this high ratio is the multineighbor shared ionic bonds and the unique relaxation process during sliding in the aragonite structure. Overall, the unique deformation twining along with other highly coordinated deformation mechanisms synergistically work in the hierarchical structure of nacre, leading to the remarkable strengthening and toughening of nacre upon dynamic loading, and thus protecting the mother-of-pearl from predatory attacks.

Deformation twinning of a silver nanocrystal under high pressure. Supplementary materials

DOE PAGES

Huang, X. J.; Yang, W. G.; Harder, R.; ...

2015-10-20

Within a high-pressure environment, crystal deformation is controlled by complex processes such as dislocation motion, twinning, and phase transitions, which change materials’ microscopic morphology and alter their properties. Likewise, understanding a crystal’s response to external stress provides a unique opportunity for rational tailoring of its functionalities. It is very challenging to track the strain evolution and physical deformation from a single nanoscale crystal under high-pressure stress. Here, we report an in situ three-dimensional mapping of morphology and strain evolutions in a single-crystal silver nanocube within a high-pressure environment using the Bragg Coherent Diffractive Imaging (CDI) method. We also observed amore » continuous lattice distortion, followed by a deformation twining process at a constant pressure. The ability to visualize stress-introduced deformation of nanocrystals with high spatial resolution and prominent strain sensitivity provides an important route for interpreting and engineering novel properties of nanomaterials.« less

Deformation measurement for a rotating deformable lap based on inverse fringe projection

NASA Astrophysics Data System (ADS)

Liao, Min; Zhang, Qican

2015-03-01

The active deformable lap (also namely stressed lap) is an efficient polishing tool in optical manufacturing. To measure the dynamic deformation caused by outside force on a deformable lap is important and helpful to the opticians to ensure the performance of a deformable lap as expected. In this paper, a manual deformable lap was designed to simulate the dynamic deformation of an active stressed lap, and a measurement system was developed based on inverse projected fringe technique to restore the 3D shape. A redesigned inverse fringe has been projected onto the surface of the measured lap, and the deformations of the tested lap become much obvious and can be easily and quickly evaluated by Fourier fringe analysis. Compared with the conventional projection, this technique is more obvious, and it should be a promising one in the deformation measurement of the active stressed lap in optical manufacturing.

Rapid, topology-based particle tracking for high-resolution measurements of large complex 3D motion fields.

PubMed

Patel, Mohak; Leggett, Susan E; Landauer, Alexander K; Wong, Ian Y; Franck, Christian

2018-04-03

Spatiotemporal tracking of tracer particles or objects of interest can reveal localized behaviors in biological and physical systems. However, existing tracking algorithms are most effective for relatively low numbers of particles that undergo displacements smaller than their typical interparticle separation distance. Here, we demonstrate a single particle tracking algorithm to reconstruct large complex motion fields with large particle numbers, orders of magnitude larger than previously tractably resolvable, thus opening the door for attaining very high Nyquist spatial frequency motion recovery in the images. Our key innovations are feature vectors that encode nearest neighbor positions, a rigorous outlier removal scheme, and an iterative deformation warping scheme. We test this technique for its accuracy and computational efficacy using synthetically and experimentally generated 3D particle images, including non-affine deformation fields in soft materials, complex fluid flows, and cell-generated deformations. We augment this algorithm with additional particle information (e.g., color, size, or shape) to further enhance tracking accuracy for high gradient and large displacement fields. These applications demonstrate that this versatile technique can rapidly track unprecedented numbers of particles to resolve large and complex motion fields in 2D and 3D images, particularly when spatial correlations exist.

Quantifying the Mechanical Properties of Materials and the Process of Elastic-Plastic Deformation under External Stress on Material

PubMed Central

Valíček, Jan; Harničárová, Marta; Öchsner, Andreas; Hutyrová, Zuzana; Kušnerová, Milena; Tozan, Hakan; Michenka, Vít; Šepelák, Vladimír; Mitaľ, Dušan; Zajac, Jozef

2015-01-01

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by abrasive waterjet technology (AWJ), especially from the point of view of generated surface topography. AWJ is a flexible tool accurately responding to the mechanical resistance of the material according to the accurately determined shape and roughness of machined surfaces. From the surface topography, it is possible to resolve the transition from ideally elastic to quasi-elastic and plastic stress-strain states. For detecting the surface structure, an optical profilometer was used. Based on the analysis of experimental measurements and the results of analytical studies, a mathematical-physical model was created and an exact method of acquiring the equivalents of mechanical parameters from the topography of surfaces generated by abrasive waterjet cutting and external stress in general was determined. The results of the new approach to the construction of stress-strain diagrams are presented. The calculated values agreed very well with those obtained by a certified laboratory VÚHŽ. PMID:28793645

Quantifying the Mechanical Properties of Materials and the Process of Elastic-Plastic Deformation under External Stress on Material.

PubMed

Valíček, Jan; Harničárová, Marta; Öchsner, Andreas; Hutyrová, Zuzana; Kušnerová, Milena; Tozan, Hakan; Michenka, Vít; Šepelák, Vladimír; Mitaľ, Dušan; Zajac, Jozef

2015-11-03

The paper solves the problem of the nonexistence of a new method for calculation of dynamics of stress-deformation states of deformation tool-material systems including the construction of stress-strain diagrams. The presented solution focuses on explaining the mechanical behavior of materials after cutting by abrasive waterjet technology (AWJ), especially from the point of view of generated surface topography. AWJ is a flexible tool accurately responding to the mechanical resistance of the material according to the accurately determined shape and roughness of machined surfaces. From the surface topography, it is possible to resolve the transition from ideally elastic to quasi-elastic and plastic stress-strain states. For detecting the surface structure, an optical profilometer was used. Based on the analysis of experimental measurements and the results of analytical studies, a mathematical-physical model was created and an exact method of acquiring the equivalents of mechanical parameters from the topography of surfaces generated by abrasive waterjet cutting and external stress in general was determined. The results of the new approach to the construction of stress-strain diagrams are presented. The calculated values agreed very well with those obtained by a certified laboratory VÚHŽ.

Detection of plasticity mechanisms in an energetic molecular crystal through shock-like 3D unidirectional compressions: A Molecular Dynamics study

NASA Astrophysics Data System (ADS)

Lafourcade, Paul; Denoual, Christophe; Maillet, Jean-Bernard

2017-06-01

TATB crystal structure consists in graphitic-like sheets arranged in the a-b plane where a, b and c define the edge vectors of the unit cell. This type of stacking provides the TATB monocrystal very anisotropic physical, chemical and mechanical properties. In order to explore which mechanisms are involved in TATB plasticity, we use a Molecular Dynamics code in which the overall deformation is prescribed as a function of time, for any deformation path. Furthermore, a computation of the Green-Lagrange strain tensor is proposed, which helps reveal various defects and plasticity mechanisms. Through prescribed large strain of shock-like deformations, a three-dimensional characterization of TATB monocrystal yield stress has been obtained, confirming the very anisotropic behavior of this energetic material. Various plasticity mechanisms are triggered during these simulations, including counter intuitive defects onset such as gliding along transveral planes containing perfect dislocations and twinning. Gliding in the a-b plane occurs systematically and does not lead to significant plastic behavior, in accordance with a previous study on dislocation core structures for this plane, based on a coupling between the Peierls-Nabarro-Galerkin method and Molecular Dynamics simulations.

Mechanics of Old Faithful Geyser, Calistoga, CA

USGS Publications Warehouse

Rudolph, M.L.; Manga, M.; Hurwitz, Shaul; Johnston, Malcolm J.; Karlstrom, L.; Wang, Chun-Yong

2012-01-01

In order to probe the subsurface dynamics associated with geyser eruptions, we measured ground deformation at Old Faithful Geyser of Calistoga, CA. We present a physical model in which recharge during the period preceding an eruption is driven by pressure differences relative to the aquifer supplying the geyser. The model predicts that pressure and ground deformation are characterized by an exponential function of time, consistent with our observations. The geyser's conduit is connected to a reservoir at a depth of at least 42 m, and pressure changes in the reservoir can produce the observed ground deformations through either a poroelastic or elastic mechanical model.

Mechanics of Old Faithful Geyser, Calistoga, California

NASA Astrophysics Data System (ADS)

Rudolph, M. L.; Manga, M.; Hurwitz, S.; Johnston, M.; Karlstrom, L.; Wang, C.-Y.

2012-12-01

In order to probe the subsurface dynamics associated with geyser eruptions, we measured ground deformation at Old Faithful Geyser of Calistoga, CA. We present a physical model in which recharge during the period preceding an eruption is driven by pressure differences relative to the aquifer supplying the geyser. The model predicts that pressure and ground deformation are characterized by an exponential function of time, consistent with our observations. The geyser's conduit is connected to a reservoir at a depth of at least 42 m, and pressure changes in the reservoir can produce the observed ground deformations through either a poroelastic or elastic mechanical model.

Detection of structural changes and mechanical properties of light alloys after severe plastic deformation

NASA Astrophysics Data System (ADS)

Krasnoveikin, V. A.; Kozulin, A. A.; Skripnyak, V. A.

2017-11-01

Severe plastic deformation by equal channel angular pressing has been performed to produce light aluminum and magnesium alloy billets with ultrafine-grained structure. The physical and mechanical properties of the processed alloys are examined by studying their microstructure, measuring microhardness, yield strength, and uniaxial tensile strength. A nondestructive testing technique using three-dimensional X-ray tomography is proposed for detecting internal structural defects and monitoring damage formation in the structure of alloys subjected to severe plastic deformation. The investigation results prove the efficiency of the chosen method and selected mode of producing ultrafine-grained light alloys.

Numerical modelling of collapsing volcanic edifices

NASA Astrophysics Data System (ADS)

Costa, Ana; Marques, Fernando; Kaus, Boris

2017-04-01

The flanks of Oceanic Volcanic Edifice's (OVEs) can occasionally become unstable. If that occurs, they can deform in two different modes: either slowly along localization failure zones (slumps) or catastrophically as debris avalanches. Yet the physics of this process is incompletely understood, and the role of factors such as the OVE's strength (viscosity, cohesion, friction angle), dimensions, geometry, and existence of weak layers remain to be addressed. Here we perform numerical simulations to study the interplay between viscous and plastic deformation on the gravitational collapse of an OVE (diffuse deformation vs. localization of failure along discrete structures). We focus on the contribution of the edifice's strength parameters for the mode of deformation, as well as on the type of basement. Tests were performed for a large OVE (7.5 km high, 200 km long) and either purely viscous (overall volcano edifice viscosities between 1019-1023 Pa.s), or viscoplastic rheology (within a range of cohesion and friction angle values). Results show that (a) for a strong basement (no slip basal boundary condition), the deformation pattern suggests wide/diffuse "listric" deformation within the volcanic edifice, without the development of discrete plastic failure zones; (b) for a weak basement (free slip basal boundary condition), rapid collapse of the edifice through the propagation of plastic failure structures within the edifice occurs. Tests for a smaller OVE (4.5 km by 30 km) show that failure localization along large-scale listric structures occurs more readily for different combinations of cohesion and friction angles. In these tests, high cohesion values combined with small friction angles lead to focusing of deformation along a narrower band. Tests with a weak layer underlying part of the volcanic edifice base show deformation focused along discrete structures mainly dipping towards the distal sector of the volcano. These tests for a small OVE constitute a promising basis for the study of a currently active slump in the SE flank of Pico Island (Azores, Portugal). We will also address the effect of lithospheric flexure, and discuss initial 3D modelling results.

An anthropomorphic abdominal phantom for deformable image registration accuracy validation in adaptive radiation therapy.

PubMed

Liao, Yuliang; Wang, Linjing; Xu, Xiangdong; Chen, Haibin; Chen, Jiawei; Zhang, Guoqian; Lei, Huaiyu; Wang, Ruihao; Zhang, Shuxu; Gu, Xuejun; Zhen, Xin; Zhou, Linghong

2017-06-01

To design and construct a three-dimensional (3D) anthropomorphic abdominal phantom for geometric accuracy and dose summation accuracy evaluations of deformable image registration (DIR) algorithms for adaptive radiation therapy (ART). Organ molds, including liver, kidney, spleen, stomach, vertebra, and two metastasis tumors, were 3D printed using contours from an ovarian cancer patient. The organ molds were molded with deformable gels made of different mixtures of polyvinyl chloride (PVC) and the softener dioctyl terephthalate. Gels with different densities were obtained by a polynomial fitting curve that described the relation between the Hounsfield unit (HU) and PVC-softener blending ratio. The rigid vertebras were constructed by molding of white cement and cellulose pulp. The final abdominal phantom was assembled by arranging all the fabricated organs inside a hollow dummy according to their anatomies, and sealed by deformable gel with averaged HU of muscle and fat. Fiducial landmarks were embedded inside the phantom for spatial accuracy and dose accumulation accuracy studies. Two channels were excavated to facilitate ionization chamber insertion for dosimetric measurements. Phantom properties such as deformable gel elasticity and HU stability were studied. The dosimetric measurement accuracy in the phantom was performed, and the DIR accuracies of three DIR algorithms available in the open source DIR toolkit-DIRART were also validated. The constructed deformable gel showed elastic behavior and was stable in HU values over times, proving to be a practical material for the deformable phantom. The constructed abdominal phantom consisted of realistic anatomies in terms of both anatomical shapes and densities when compared with its reference patient. The dosimetric measurements showed a good agreement with the calculated doses from the treatment planning system. Fiducial-based accuracy analysis conducted on the constructed phantom demonstrated the feasibility of applying the phantom for organ-wise DIR accuracy assessment. We have designed and constructed an anthropomorphic abdominal deformable phantom with satisfactory elastic property, realistic organ density, and anatomy. This physical phantom can be used for routine validations of DIR geometric accuracy and dose accumulation accuracy in ART. © 2017 American Association of Physicists in Medicine.

Through-process modelling of texture and anisotropy in AA5182

NASA Astrophysics Data System (ADS)

Crumbach, M.; Neumann, L.; Goerdeler, M.; Aretz, H.; Gottstein, G.; Kopp, R.

2006-07-01

A through-process texture and anisotropy prediction for AA5182 sheet production from hot rolling through cold rolling and annealing is reported. Thermo-mechanical process data predicted by the finite element method (FEM) package T-Pack based on the software LARSTRAN were fed into a combination of physics based microstructure models for deformation texture (GIA), work hardening (3IVM), nucleation texture (ReNuc), and recrystallization texture (StaRT). The final simulated sheet texture was fed into a FEM simulation of cup drawing employing a new concept of interactively updated texture based yield locus predictions. The modelling results of texture development and anisotropy were compared to experimental data. The applicability to other alloys and processes is discussed.

Bounds on an energy-dependent and observer-independent speed of light from violations of locality.

PubMed

Hossenfelder, Sabine

2010-04-09

We show that models with deformations of special relativity that have an energy-dependent speed of light have nonlocal effects. The requirement that the arising nonlocality is not in conflict with known particle physics allows us to derive strong bounds on deformations of special relativity and rule out a modification to first order in energy over the Planck mass.

Energy and the Confused Student V: The Energy/Momentum Approach to Problems Involving Rotating and Deformable Systems

ERIC Educational Resources Information Center

Jewett, John W., Jr.

2008-01-01

Energy is a critical concept in physics problem-solving, but is often a major source of confusion for students if the presentation is not carefully crafted by the instructor or the textbook. A common approach to problems involving deformable or rotating systems that has been discussed in the literature is to employ the work-kinetic energy theorem…

Microstructure characterization based on the type of deformed grains in cold-rolled, Cu-added, bake-hardenable steel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, J.S.; Kim, S.I.; Choi, S.-H., E-mail: shihoon@sunchon.ac.kr

2014-06-01

The electron backscatter diffraction technique has been used to characterize the microstructure of deformed grains in cold-rolled, Cu-added, bake-hardenable steel. A new scheme based on the kind and number of average orientations, as determined from a unique grain map of the deformed grains, was developed in order to classify deformed grains by type. The α-fiber components, γ-fiber components and random orientations, those which could not be assigned to either γ-fiber or α-fiber components, were used to define the average orientation of unique grains within individual deformed grains. The microstructures of deformed grains in as-rolled specimens were analyzed based on themore » Taylor factor, stored energy, and misorientation. The relative levels and distributions of the Taylor factor, the stored energy and the misorientation were examined in terms of the types of deformed grains. - Highlights: • We characterized the microstructure of Cu-added BH steel using EBSD. • A new scheme was developed in order to classify deformed grains by type. • Stored energy and misorientation are strongly dependent on the type of deformed grains. • Microstructure was examined in terms of the types of deformed grains.« less

Physical-Mechanical Properties of a Fiber-Reinforced Composite Based on an ELUR-P Carbon Tape and XT-118 Binder

NASA Astrophysics Data System (ADS)

Paimushin, V. N.; Kholmogorov, S. A.

2018-03-01

A series of tests to identify the physical-mechanical properties of a unidirectional carbon-fiber-reinforced composite based on an ELUR-P carbon fibers and an XT-118 epoxy binder were performed. The form of the stress-strain diagrams of specimens loaded in tension in the longitudinal, transverse, and ±45° directions and in compression in the longitudinal and ±45° directions were examined. Tensile diagrams were also determined for the XT-118 binder alone. The relation between the tangential shear modulus and shear strains of the composite was highly nonlinear from the very beginning of loading and depended on the loading type. Such a nonlinear response of the carbon-fiber-reinforced composite in shear cannot be the result of plastic deformation of binder, but can be explained only by structural changes caused by the inner buckling instability of the composite at micro- and mesolevels..

A Hands-on Physical Analog Demonstration of Real-Time Volcano Deformation Monitoring with GNSS/GPS

NASA Astrophysics Data System (ADS)

Jones, J. R.; Schobelock, J.; Nguyen, T. T.; Rajaonarison, T. A.; Malloy, S.; Njinju, E. A.; Guerra, L.; Stamps, D. S.; Glesener, G. B.

2017-12-01

Teaching about volcano deformation and how scientists study these processes using GNSS/GPS may present some challenge since the volcanoes and/or GNSS/GPS equipment are not quite accessible to most teachers. Educators and curriculum materials specialists have developed and shared a number of activities and demonstrations to help students visualize volcanic processes and ways scientist use GNSS/GPS in their research. From resources provided by MEDL (the Modeling and Educational Demonstrations Laboratory) in the Department of Geosciences at Virginia Tech, we combined multiple materials and techniques from these previous works to produce a hands-on physical analog model from which students can learn about GNSS/GPS studies of volcano deformation. The model functions as both a qualitative and quantitative learning tool with good analogical affordances. In our presentation, we will describe multiple ways of teaching with the model, what kinds of materials can be used to build it, and ways we think the model could be enhanced with the addition of Vernier sensors for data collection.

A versatile lab-on-chip test platform to characterize elementary deformation mechanisms and electromechanical couplings in nanoscopic objects

NASA Astrophysics Data System (ADS)

Pardoen, Thomas; Colla, Marie-Sthéphane; Idrissi, Hosni; Amin-Ahmadi, Behnam; Wang, Binjie; Schryvers, Dominique; Bhaskar, Umesh K.; Raskin, Jean-Pierre

2016-03-01

A nanomechanical on-chip test platform has recently been developed to deform under a variety of loading conditions freestanding thin films, ribbons and nanowires involving submicron dimensions. The lab-on-chip involves thousands of elementary test structures from which the elastic modulus, strength, strain hardening, fracture, creep properties can be extracted. The technique is amenable to in situ transmission electron microscopy (TEM) investigations to unravel the fundamental underlying deformation and fracture mechanisms that often lead to size-dependent effects in small-scale samples. The method allows addressing electrical and magnetic couplings as well in order to evaluate the impact of large mechanical stress levels on different solid-state physics phenomena. We had the chance to present this technique in details to Jacques Friedel in 2012 who, unsurprisingly, made a series of critical and very relevant suggestions. In the spirit of his legacy, the paper will address both mechanics of materials related phenomena and couplings with solids state physics issues.

Effects of surface roughening on the mass transport and mechanical properties of ionic polymer-metal composite

NASA Astrophysics Data System (ADS)

Chang, Longfei; Asaka, Kinji; Zhu, Zicai; Wang, Yanjie; Chen, Hualing; Li, Dichen

2014-06-01

Ionic Polymer-Metal Composite (IPMC) has been well-documented of being a promising functional material in extensive applications. In its most popular and traditional manufacturing technique, roughening is a key process to ensure a satisfying performance. In this paper, based on a lately established multi-physical model, the effect of roughening process on the inner mass transportation and the electro-active output of IPMC were investigated. In the model, the electro-chemical field was monitored by Poisson equation and a properly simplified Nernst-Planck equation set, while the mechanical field was evaluated on the basis of volume strain effect. Furthermore, with Ramo-Shockley theorem, the out-circuit current and accumulated charge on the electrode were bridged with the inner cation distribution. Besides, nominal current and charge density as well as the curvature of the deformation were evaluated to characterize the performance of IPMC. The simulation was implemented by Finite Element Method with Comsol Multi-physics, based on two groups of geometrical models, those with various rough interface and those with different thickness. The results of how the roughening impact influences on the performance of IPMC were discussed progressively in three aspects, steady-state distribution of local potential and mass concentration, current response and charge accumulation, as well as the curvature of deformation. Detailed explanations for the performance improvement resulted from surface roughening were provided from the micro-distribution point of view, which can be further explored for the process optimization of IPMC.

Reasons for mini-implants failure: choosing installation site should be valued!

PubMed Central

Consolaro, Alberto; Romano, Fábio Lourenço

2014-01-01

Mini-implant loss is often associated with physical and mechanical aspects that result from choosing an inappropriate placement site. It is worth highlighting that: a) Interdental alveolar bone crests are flexible and deformable. For this reason, they may not offer the ideal absolute anchorage. The more cervical the structures, the more delicate they are, thus offering less physical support for mini-implant placement; b) Alveolar bone crests of triangular shape are more deformable, whereas those of rectangular shape are more flexible; c) The bases of the alveolar processes of the maxilla and the mandible are not flexible, for this reason, they are more likely to receive mini-implants; d) The more cervical a mini-implant is placed, the higher the risk of loss; the more apical a mini-implant is placed, the better its prognosis will be; e) 3D evaluations play a major role in planning the use of mini-implants. Based on the aforementioned considerations, the hypotheses about mini-implant loss are as follows: 1) Deflection of maxillary and mandibular alveolar processes when mini-implants are more cervically placed; 2) Mini-implants placed too near the periodontal ligament, with normal intra-alveolar tooth movement; 3) Low bone density, low thickness and low alveolar bone volume; 4) Low alveolar cortical bone thickness; 5) Excessive pressure inducing trabecular bone microfracture; 6) Sites of higher anatomical weakness in the mandible and the maxilla; 7) Thicker gingival tissue not considered when choosing the mini-implant. PMID:24945511

Evaluating links between deformation, topography and surface temperature at volcanic domes: Results from a multi-sensor study at Volcán de Colima, Mexico

NASA Astrophysics Data System (ADS)

Salzer, Jacqueline T.; Milillo, Pietro; Varley, Nick; Perissin, Daniele; Pantaleo, Michele; Walter, Thomas R.

2017-12-01

Dome building activity is common at many volcanoes and due to the gravitational instability, a dome represents one of the most hazardous volcanic phenomena. Shallow volcanic processes as well as rheological and structural changes of the dome affecting the fluid transport have been linked to transitions in eruptive activity. Also, hydrothermal alteration may affect the structural integrity of the dome, increasing the potential for collapse. However, mapping the deformation and details of fluid escape at the summit of steep sloped volcanoes and integrating these with other types of data is challenging due to difficult access and poor coverage. Here we present for the first time the near-vertical and near-horizontal surface deformation field of a quiescent summit dome and the relationships with degassing and topographic patterns. Our results are derived from high resolution satellite radar interferometry (InSAR) time series based on a year of TerraSAR-X SpotLight acquisitions and Structure from Motion (SfM) processing of overflight infrared data at Volcán de Colima, Mexico. The identified deformation is dominated by localized heterogeneous subsidence of the summit dome exceeding rates of 15 cm/yr, and strongly decreasing over the year 2012, up to the renewal of explosive and extrusive activity in early 2013. We tentatively attribute the deformation to the degassing, cooling and contraction of the dome and shallow conduit material. We also find that the results strongly differ depending on the chosen InSAR time series method, which potentially overprints the true physical complexities of small scale, shallow deformation processes. The combined interpretation of the deformation and infrared data reveals a complex spatial relationship between the degassing pathways and the deformation. While we observe no deformation across the crater rim fumaroles, discontinuities in the deformation field are more commonly observed around the dome rim fumaroles and occasionally on the dome upper surface. We propose that the deformation pattern is also linked to processes controlling the fumarole formation and distribution (topography, permeability and volcanic activity), and the lack of direct relationships may be explained by how the influence of these processes varies across the volcanic summit. The presented work provides a new approach for safely monitoring the activity and stability of internal dome structures, as well as for constraining and validating models of dome degassing pathways and densification processes.

Fundamentals of Structural Geology

NASA Astrophysics Data System (ADS)

Pollard, David D.; Fletcher, Raymond C.

2005-09-01

Fundamentals of Structural Geology provides a new framework for the investigation of geological structures by integrating field mapping and mechanical analysis. Assuming a basic knowledge of physical geology, introductory calculus and physics, it emphasizes the observational data, modern mapping technology, principles of continuum mechanics, and the mathematical and computational skills, necessary to quantitatively map, describe, model, and explain deformation in Earth's lithosphere. By starting from the fundamental conservation laws of mass and momentum, the constitutive laws of material behavior, and the kinematic relationships for strain and rate of deformation, the authors demonstrate the relevance of solid and fluid mechanics to structural geology. This book offers a modern quantitative approach to structural geology for advanced students and researchers in structural geology and tectonics. It is supported by a website hosting images from the book, additional colour images, student exercises and MATLAB scripts. Solutions to the exercises are available to instructors. The book integrates field mapping using modern technology with the analysis of structures based on a complete mechanics MATLAB is used to visualize physical fields and analytical results and MATLAB scripts can be downloaded from the website to recreate textbook graphics and enable students to explore their choice of parameters and boundary conditions The supplementary website hosts color images of outcrop photographs used in the text, supplementary color images, and images of textbook figures for classroom presentations The textbook website also includes student exercises designed to instill the fundamental relationships, and to encourage the visualization of the evolution of geological structures; solutions are available to instructors

A Case Study on the Strata Movement Mechanism and Surface Deformation Regulation in Chengchao Underground Iron Mine

NASA Astrophysics Data System (ADS)

Cheng, Guanwen; Chen, Congxin; Ma, Tianhui; Liu, Hongyuan; Tang, Chunan

2017-04-01

The regular pattern of surface deformation and the mechanism of underground strata movement, especially in iron mines constructed with the block caving method, have a great influence on infrastructure on the surface, so they are an important topic for research. Based on the engineering geology conditions and the surface deformation and fracture features in Chengchao Iron Mine, the mechanism of strata movement and the regular pattern of surface deformation in the footwall were studied by the geomechanical method, and the following conclusions can be drawn: I. The surface deformation process is divided into two stages over time, i.e., the chimney caving development stage and the post-chimney deformation stage. Currently, the surface deformation in Chengchao Iron Mine is at the post-chimney deformation stage. II. At the post-chimney deformation stage, the surface deformation and geological hazards in Chengchao Iron Mine are primarily controlled by the NWW-trending joints, with the phenomenon of toppling deformation and failure on the surface. Based on the surface deformation characteristics in Chengchao Iron Mine, the surface deformation area can be divided into the following four zones: the fracture extension zone, the fracture closure zone, the fracture formation zone and the deformation accumulation zone. The zones on the surface can be determined by the surface deformation characteristics. III. The cantilever beams near the chimney caving area, caused by the NWW-trending joints, have been subjected to toppling failure. This causes the different deformation and failure mechanisms in different locations of the deep rock mass. The deep rock can be divided into four zones, i.e., the fracture zone, fracture transition zone, deformation zone and undisturbed zone, according to the different deformation and failure mechanisms. The zones in the deep rock are the reason for the zones on the surface, so they can be determined by the zones on the surface. Through these findings, the degree of damage to the infrastructure in different locations can be determined based on the surface deformation zones. As the mining continues deeper, the development regulation of the zones on the surface and in deep rock mass can be further studied based on the zones in the deep rock.

Scientific drilling into the San Andreas Fault Zone - an overview of SAFOD's first five years

USGS Publications Warehouse

Zoback, Mark; Hickman, Stephen; Ellsworth, William; ,

2011-01-01

The San Andreas Fault Observatory at Depth (SAFOD) was drilled to study the physical and chemical processes controlling faulting and earthquake generation along an active, plate-bounding fault at depth. SAFOD is located near Parkfield, California and penetrates a section of the fault that is moving due to a combination of repeating microearthquakes and fault creep. Geophysical logs define the San Andreas Fault Zone to be relatively broad (~200 m), containing several discrete zones only 2–3 m wide that exhibit very low P- and S-wave velocities and low resistivity. Two of these zones have progressively deformed the cemented casing at measured depths of 3192 m and 3302 m. Cores from both deforming zones contain a pervasively sheared, cohesionless, foliated fault gouge that coincides with casing deformation and explains the observed extremely low seismic velocities and resistivity. These cores are being now extensively tested in laboratories around the world, and their composition, deformation mechanisms, physical properties, and rheological behavior are studied. Downhole measurements show that within 200 m (maximum) of the active fault trace, the direction of maximum horizontal stress remains at a high angle to the San Andreas Fault, consistent with other measurements. The results from the SAFOD Main Hole, together with the stress state determined in the Pilot Hole, are consistent with a strong crust/weak fault model of the San Andreas. Seismic instrumentation has been deployed to study physics of faulting—earthquake nucleation, propagation, and arrest—in order to test how laboratory-derived concepts scale up to earthquakes occurring in nature.

Elasticity and dislocation anelasticity of crystals

NASA Astrophysics Data System (ADS)

Nikanorov, S. P.; Kardashev, B. K.

The book is concerned with the application of the results of physical acoustic studies of elasticity and dislocation anelasticity to the investigation of interatomic interactions and interactions between lattice defects. The analysis of the potential functions determining the energy of interatomic interactions is based on a study of the elastic properties of crystals over a wide temperature range; data on the dislocation structure and on the interaction between dislocations and point defects are based mainly on a study of inelastic effects. Particular attention is given to the relationship between microplastic effects and the initial stage of plastic deformation under conditions of elastic oscillations, when the multiplication of dislocations is negligible.

USSR and Eastern Europe Scientific Abstracts Physics and Mathematics No. 35

DTIC Science & Technology

1977-06-15

depends on the film thickness, on the conditions of demagnetization , and on the constant of uniaxial magnetic anisotropy. The distribution of...Acoustics 2 Crystals and Semiconductors.. .*. 16 Electricity and Magnetism 51 Fluid Dynamics 64 Lasers and Masers 88 Magnetohydrodynamics 110...Molecular Physics 132 Nuclear Physics 133 Optics and Spectroscopy 158 Stress, Strain and Deformation 165 Superconductivity 170 Theoretical

Neogene rotations and quasicontinuous deformation of the Pacific Northwest continental margin

USGS Publications Warehouse

England, Philip; Wells, Ray E.

1991-01-01

Paleomagnetically determined rotations about vertical axes of 15 to 12 Ma flows of the Miocene Columbia River Basalt Group of Oregon and Washington decrease smoothly with distance from the plate margin, consistent with a simple physical model for continental deformation that assumes the lithosphere behaves as a thin layer of fluid. The average rate of northward translation of the continental margin since 15 Ma calculated from the rotations, using this model, is about 15 mm/yr, which suggests that much of the tangential motion between the Juan de Fuca and North American plates since middle Miocene time has been taken up by deformation of North America. The fluid-like character of the large-scale deformation implies that the brittle upper crust follows the motions of the deeper parts of the lithosphere.

[Micropore filters for measuring red blood cell deformability and their pore diameters].

PubMed

Niu, X; Yan, Z

2001-09-01

Micropore filters are the most important components in micropore filtration testes for assessing red blood cell (RBC) deformability. With regard to their appearance and filtration behaviors, comparisons are made for different kinds of filters currently in use. Nickel filters with regular geometric characteristics are found to be more sensitive to the effects of physical, chemical, especially pathological factors on the RBC deformability. We have critically reviewed the following viewpoint that filters with 3 microns pore diameter are more sensitive to cell volume than to internal viscosity while filters with 5 microns pore diameter are just the opposite. After analyzing the experiment results with 3 microns and 5 microns filters, we point out that filters with smaller pore diameters are more suitable for assessing the RBC deformability.

The classical limit of minimal length uncertainty relation: revisit with the Hamilton-Jacobi method

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Xiaobo; Wang, Peng; Yang, Haitang, E-mail: guoxiaobo@swust.edu.cn, E-mail: pengw@scu.edu.cn, E-mail: hyanga@scu.edu.cn

2016-05-01

The existence of a minimum measurable length could deform not only the standard quantum mechanics but also classical physics. The effects of the minimal length on classical orbits of particles in a gravitation field have been investigated before, using the deformed Poisson bracket or Schwarzschild metric. In this paper, we first use the Hamilton-Jacobi method to derive the deformed equations of motion in the context of Newtonian mechanics and general relativity. We then employ them to study the precession of planetary orbits, deflection of light, and time delay in radar propagation. We also set limits on the deformation parameter bymore » comparing our results with the observational measurements. Finally, comparison with results from previous papers is given at the end of this paper.« less

Deformation of supersymmetric and conformal quantum mechanics through affine transformations

NASA Technical Reports Server (NTRS)

Spiridonov, Vyacheslav

1993-01-01

Affine transformations (dilatations and translations) are used to define a deformation of one-dimensional N = 2 supersymmetric quantum mechanics. Resulting physical systems do not have conserved charges and degeneracies in the spectra. Instead, superpartner Hamiltonians are q-isospectral, i.e. the spectrum of one can be obtained from another (with possible exception of the lowest level) by q(sup 2)-factor scaling. This construction allows easily to rederive a special self-similar potential found by Shabat and to show that for the latter a q-deformed harmonic oscillator algebra of Biedenharn and Macfarlane serves as the spectrum generating algebra. A general class of potentials related to the quantum conformal algebra su(sub q)(1,1) is described. Further possibilities for q-deformation of known solvable potentials are outlined.

Comprehensive rehabilitation of the child with osteogenesis imperfecta.

PubMed

Binder, H; Conway, A; Hason, S; Gerber, L H; Marini, J; Berry, R; Weintrob, J

1993-01-15

Children with osteogenesis imperfecta (OI) that results in considerable deformity are often viewed as poor candidates for aggressive physical therapy and rehabilitation. To determine if this view is realistic, we have entered almost 50 children with OI type III and OI type IV into a comprehensive graduated rehabilitation program, based at the National Institutes of Health, but designed to be implemented by continuing involvement of community resources. Children are begun in the program early with emphasis on gain of head and trunk control and progression to sitting and walking, if possible, with the aid of a variety of physical supports, including internal and external bracing. Although not conducted in a randomized fashion, the program's success in bringing children into graded exercise regimes and fostering their increased involvement in school and social situations suggest that aggressive physical therapy and rehabilitation have a major place in the overall care of the infants and children with OI.

Study protocol and overview of the literature on long-term health and quality of life outcomes in patients treated in adolescence for scoliosis with therapeutic exercises.

PubMed

Plaszewski, Maciej; Kotwicki, Tomasz; Chwala, Wieslaw; Terech, Jacek; Cieśliński, Igor

2015-01-01

Scoliosis, the most prevalent orthopaedic condition affecting children and adolescents, may have lasting physical, psychological and social consequences. With limited evidence-base, scoliosis-specific exercise therapies are an option. An overview of the subject and description of a long-term follow-up study including adults who in adolescence were treated with a scoliosis-specific exercise programme investigating the association of the exercise regime with present physical activity, physical functioning and subjective wellbeing. To the authors' best knowledge, this is the first long-term outcome study on scoliosis-specific exercises, in opposition to a number of studies in adults who were braced or treated surgically in adolescence. Observational, registry-based case-control study. Adult subjects who in adolescence were treated with an exercise programme or were under observation are invited. Spine and trunk deformity, respiratory function, physical capacity and trunk muscles' function are measured. Health-related quality of life with generic and condition-specific instruments, general mental health, depression and anxiety symptoms, disability due to low back problems and physical activity are assessed. The report is believed to provide the readers with an overview of this controversial aspect of rehabilitation, and that the proposed protocol will assist researchers designing their studies.

Tectono-sedimentary evolution of salt controlled minibasin in a fold-an-thrust belt setting Example from the Sivas Basin Turkey and physical model.

NASA Astrophysics Data System (ADS)

Kergaravat, Charlie; Ribes, Charlotte; Darnault, Romain; Callot, Jean-Paul; Ringenbach, Jean-Claude

2017-04-01

The aim of this study is to present the influence of regional shortening on the evolution of a minibasin province and the associated foldbelt geometry based on a natural example, the Sivas Basin, then compared to a physical experiment. The Sivas Basin in the Central Anatolian Plateau (Turkey) is a foreland fold-and-thrust belt, displaying in the central part a typical wall and basin province characterized by spectacularly exposed minibasins, separated by continuous steep-flanked walls and diapirs over a large area (45x25 km). The advance of the orogenic wedge is expressed within the second generation of minibasins by a shortening-induced squeezing of diapirs. Network of walls and diapirs evolve form polygonal to linear pattern probably induced by the squeezing of pre-existing evaporite walls and diapirs, separating linear primary minibasins. From base to top of secondary minibasins, halokinetic structures seem to evolve from small-scale objects along diapir flanks, showing hook and wedges halokinetic sequences, to large stratigraphic wedging, megaflap and salt sheets. Minibasins show progressively more linear shape at right angle to the regional shortening and present angular unconformities along salt structures related to the rejuvenation of pre-existing salt diapirs and walls probably encouraged by the shortening tectonic regime. The advance of the fold-and-thrust belts during the minibasins emplacement is mainly expressed during the late stage of minibasins development by a complex polygonal network of small- and intermediate-scale tectonic objects: (1) squeezed evaporite walls and diapirs, sometimes thrusted forming oblique or vertical welds, (2) allochthonous evaporite sheets, (3) thrusts and strike-slip faults recording translation and rotation of minibasins about vertical axis. Some minibasins are also tilted, with up to vertical position, associated with both the salt expulsion during minibasins sinking, recorded by large stratigraphic wedge, and the late thrust faults developments. The influence of the regional shortening deformation seems to be effective when the majority of the evaporite is remobilized toward the foreland. Results of scaled physical experiments, where continuous shortening is applied during minibasins emplacement, closely match with the deformation patterns observed in the Sivas minibasins. Shortening induce deformations such as translation of minibasins basinward, strike-slip fault zones along minibasin margin, rejuvenation of silicon walls and diapirs, emergence of silicon glaciers and rotation of minibasins along vertical and horizontal axis.

Haptics-based dynamic implicit solid modeling.

PubMed

Hua, Jing; Qin, Hong

2004-01-01

This paper systematically presents a novel, interactive solid modeling framework, Haptics-based Dynamic Implicit Solid Modeling, which is founded upon volumetric implicit functions and powerful physics-based modeling. In particular, we augment our modeling framework with a haptic mechanism in order to take advantage of additional realism associated with a 3D haptic interface. Our dynamic implicit solids are semi-algebraic sets of volumetric implicit functions and are governed by the principles of dynamics, hence responding to sculpting forces in a natural and predictable manner. In order to directly manipulate existing volumetric data sets as well as point clouds, we develop a hierarchical fitting algorithm to reconstruct and represent discrete data sets using our continuous implicit functions, which permit users to further design and edit those existing 3D models in real-time using a large variety of haptic and geometric toolkits, and visualize their interactive deformation at arbitrary resolution. The additional geometric and physical constraints afford more sophisticated control of the dynamic implicit solids. The versatility of our dynamic implicit modeling enables the user to easily modify both the geometry and the topology of modeled objects, while the inherent physical properties can offer an intuitive haptic interface for direct manipulation with force feedback.

Exploring of PST-TBPM in Monitoring Dynamic Deformation of Steel Structure in Vibration

NASA Astrophysics Data System (ADS)

Chen, Mingzhi; Zhao, Yongqian; Hai, Hua; Yu, Chengxin; Zhang, Guojian

2018-01-01

In order to monitor the dynamic deformation of steel structure in the real-time, digital photography is used in this paper. Firstly, the grid method is used correct the distortion of digital camera. Then the digital cameras are used to capture the initial and experimental images of steel structure to obtain its relative deformation. PST-TBPM (photographing scale transformation-time baseline parallax method) is used to eliminate the parallax error and convert the pixel change value of deformation points into the actual displacement value. In order to visualize the deformation trend of steel structure, the deformation curves are drawn based on the deformation value of deformation points. Results show that the average absolute accuracy and relative accuracy of PST-TBPM are 0.28mm and 1.1‰, respectively. Digital photography used in this study can meet accuracy requirements of steel structure deformation monitoring. It also can warn the safety of steel structure and provide data support for managers’ safety decisions based on the deformation curves on site.

Improved texture measurement during deformation of polycrystalline olivine at high pressure

NASA Astrophysics Data System (ADS)

Dixon, N. A.; Durham, W. B.; Kohlstedt, D. L.; Hunt, S. A.

2014-12-01

Unresolved issues in geodynamics demand a better understanding of the bulk mechanical properties of mantle minerals, and also careful analysis of the complex lattice-scale physics behind these properties. Instead of probing the mechanical properties of a material by testing the relationship between "bulk" stress and strain rate in a sample at a variety of conditions (varying P, T, water content, and other environmental variables), synchrotron x-ray diffraction now allows us to observe, in situ, the active deformation physics in much greater detail. This includes in situ monitoring of plastic anisotropy and local stress heterogeneity, grain size, the development of lattice-preferred orientation (LPO), and even the partitioning of stress between multiple phases in the same polycrystalline sample. Here, we present results obtained with the use of the MTEX toolbox for Matlab and energy-dispersive x-ray diffraction, showing the in situ development of LPO in deforming dry San Carlos olivine samples, at pressures from 2-7 GPa. These measurements hint at the active dislocation mechanisms for these conditions. The ability generate a broad range of mantle conditions in the D-DIA, while precisely measuring the structure and conditions within our sample at the grain and lattice scale, demonstrates the promising future of deformation experiments as a means to understanding the evolution of the deep Earth.

Investigation on Insar Time Series Deformation Model Considering Rheological Parameters for Soft Clay Subgrade Monitoring

NASA Astrophysics Data System (ADS)

Xing, X.; Yuan, Z.; Chen, L. F.; Yu, X. Y.; Xiao, L.

2018-04-01

The stability control is one of the major technical difficulties in the field of highway subgrade construction engineering. Building deformation model is a crucial step for InSAR time series deformation monitoring. Most of the InSAR deformation models for deformation monitoring are pure empirical mathematical models, without considering the physical mechanism of the monitored object. In this study, we take rheology into consideration, inducing rheological parameters into traditional InSAR deformation models. To assess the feasibility and accuracy for our new model, both simulation and real deformation data over Lungui highway (a typical highway built on soft clay subgrade in Guangdong province, China) are investigated with TerraSAR-X satellite imagery. In order to solve the unknows of the non-linear rheological model, three algorithms: Gauss-Newton (GN), Levenberg-Marquarat (LM), and Genetic Algorithm (GA), are utilized and compared to estimate the unknown parameters. Considering both the calculation efficiency and accuracy, GA is chosen as the final choice for the new model in our case study. Preliminary real data experiment is conducted with use of 17 TerraSAR-X Stripmap images (with a 3-m resolution). With the new deformation model and GA aforementioned, the unknown rheological parameters over all the high coherence points are obtained and the LOS deformation (the low-pass component) sequences are generated.

Impact of Type of Sport, Gender and Age on Red Blood Cell Deformability of Elite Athletes.

PubMed

Tomschi, Fabian; Bloch, Wilhelm; Grau, Marijke

2018-01-01

Our objective was to detect possible differences in red blood cell (RBC) deformability of elite athletes performing different types of sports and being of different age and gender.182 athletes were included in this cross-sectional study. RBC deformability was measured using the laser-assisted optical rotational cell-analyzer. Maximal elongation index (EI  max ) and shear stress at half-maximum deformation (SS  1/2 ) were calculated. The ratio SS  1/2  /EI  max  (EI  Ratio ) was calculated with low values representing high RBC deformation. Hematocrit (Hct) and mean cellular volume (MCV) were determined in venous blood. Overall RBC deformability did not differ between male and female athletes but, when separated by age of the subjects, RBC deformability increased with age in male but not in female athletes. RBC deformability was lower in Combat sports compared other sport groups. Hct was higher in male compared to female athletes while no difference was observed for MCV. MCV and Hct increased with increasing age. A negative correlation was found between the EI  Ratio  and MCV and between EI  Ratio  and Hct. RBC deformability is influenced by age and endurance rate of the sport which suggests that the RBC system may adapt to changing conditions such as adolescence with the onset effects of sex hormones or physical exercise. © Georg Thieme Verlag KG Stuttgart · New York.

Physical therapy intervention for an adolescent with a knee flexion contracture and diagnosis of multiple pterygium syndrome.

PubMed

Bellamy, Sandra Gail; Gibbs, Karen; Lazaro, Rolando

2007-01-01

The purpose of this case report is to describe a course of physical therapy for a client with a rare genetic condition, multiple pterygium syndrome (MPS). MPS is a rare genetic disorder characterized by connective tissue webbing across multiple joints, dysmorphic facies, and various visceral and skeletal deformities. Before the patient commenced physical therapy, surgical amputation was recommended for the client's knee flexion contracture. The client's treatment plan included stretching, manual therapy, and resisted exercise. Long-term outcomes were decreased back and knee pain and improved range of motion, strength, and ambulation. Therapists using techniques to improve joint range of motion in clients with MPS should be aware that pterygia may include contractile tissue, nerves, and blood vessels and there may be underlying skeletal deformity or weakness in these areas. Children with MPS are at high risk of developing scoliosis and should be appropriately assessed in early childhood.

Diagnostic utility of patient history and physical examination data to detect spondylolysis and spondylolisthesis in athletes with low back pain: A systematic review.

PubMed

Grødahl, Linn Helen J; Fawcett, Louise; Nazareth, Madeleine; Smith, Richard; Spencer, Simon; Heneghan, Nicola; Rushton, Alison

2016-08-01

In adolescent athletes, low back pain has a 1-year prevalence of 57% and causes include spondylolysis and spondylolisthesis. An accurate diagnosis enables healing, prevention of progression and return to sport. To evaluate the diagnostic utility of patient history and physical examination data to identify spondylolysis and/or spondylolisthesis in athletes. Systematic review was undertaken according to published guidelines, and reported in line with PRISMA. Key databases were searched up to 13/11/15. athletic population with LBP, patient history and/or physical examination accuracy data for spondylolysis and/or spondylolisthesis, any study design including raw data. Two reviewers independently assessed risk of bias (ROB) using QUADAS-2. A data extraction sheet was pre-designed. Pooling of data and investigation for heterogeneity enabled a qualitative synthesis of data across studies. Of the eight included studies, two were assessed as low ROB, one of which also had no concerns regarding applicability. Age (<20 years) demonstrated 81% sensitivity and 44% specificity and gender (male) 73% sensitivity and 57% specificity for spondylolysis. Difficulty falling asleep, waking up because of pain, pain worse with sitting and walking all have sensitivity >75% for spondylolisthesis. Step-deformity palpation demonstrated 60-88% sensitivity and 87-100% specificity for spondylolisthesis. The one-legged hyperextension test was not supported for spondylolysis (sensitivity 50-73%, specificity 0-87%). No recommendations can be made utilising patient history data. Based on one low ROB study, step deformity palpation may be useful in diagnosing spondylolisthesis. No physical tests demonstrated diagnostic utility for spondylolysis. Further research is required. Copyright © 2016 Elsevier Ltd. All rights reserved.

High-contrast imaging with an arbitrary aperture: active correction of aperture discontinuities

NASA Astrophysics Data System (ADS)

Pueyo, Laurent; Norman, Colin; Soummer, Rémi; Perrin, Marshall; N'Diaye, Mamadou; Choquet, Elodie

2013-09-01

We present a new method to achieve high-contrast images using segmented and/or on-axis telescopes. Our approach relies on using two sequential Deformable Mirrors to compensate for the large amplitude excursions in the telescope aperture due to secondary support structures and/or segment gaps. In this configuration the parameter landscape of Deformable Mirror Surfaces that yield high contrast Point Spread Functions is not linear, and non-linear methods are needed to find the true minimum in the optimization topology. We solve the highly non-linear Monge-Ampere equation that is the fundamental equation describing the physics of phase induced amplitude modulation. We determine the optimum configuration for our two sequential Deformable Mirror system and show that high-throughput and high contrast solutions can be achieved using realistic surface deformations that are accessible using existing technologies. We name this process Active Compensation of Aperture Discontinuities (ACAD). We show that for geometries similar to JWST, ACAD can attain at least 10-7 in contrast and an order of magnitude higher for future Extremely Large Telescopes, even when the pupil features a missing segment" . We show that the converging non-linear mappings resulting from our Deformable Mirror shapes actually damp near-field diffraction artifacts in the vicinity of the discontinuities. Thus ACAD actually lowers the chromatic ringing due to diffraction by segment gaps and strut's while not amplifying the diffraction at the aperture edges beyond the Fresnel regime and illustrate the broadband properties of ACAD in the case of the pupil configuration corresponding to the Astrophysics Focused Telescope Assets. Since details about these telescopes are not yet available to the broader astronomical community, our test case is based on a geometry mimicking the actual one, to the best of our knowledge.

A physical model for strain accumulation in the San Francisco Bay Region

USGS Publications Warehouse

Pollitz, F.F.; Nyst, M.

2005-01-01

Strain accumulation in tectonically active regions is generally a superposition of the effects of background tectonic loading, steady-state dislocation processes, such as creep, and transient deformation. In the San Francisco Bay region (SFBR), the most uncertain of these processes is transient deformation, which arises primarily in association with large earthquakes. As such, it depends upon the history of faulting and the rheology of the crust and mantle, which together determine the pattern of longer term (decade-scale) post-seismic response to earthquakes. We utilize a set of 102 GPS velocity vectors in the SFBR in order to characterize the strain rate field and construct a physical model of its present deformation. We first perform an inversion for the continuous velocity gradient field from the discrete GPS velocity field, from which both tensor strain rate and rotation rate may be extracted. The present strain rate pattern is well described as a nearly uniform shear strain rate oriented approximately N34??W (140 nanostrain yr-1) plus a N56??E uniaxial compression rate averaging 20 nanostrain yr-1 across the shear zone. We fit the velocity and strain rate fields to a model of time-dependent deformation within a 135-kin-wide, arcuate shear zone bounded by strong Pacific Plate and Sierra Nevada block lithosphere to the SW and NE, respectively. Driving forces are purely lateral, consisting of shear zone deformation imposed by the relative motions between the thick Pacific Plate and Sierra Nevada block lithospheres. Assuming a depth-dependent viscoelastic structure within the shear zone, we account for the effects of steady creep on faults and viscoelastic relaxation following the 1906 San Francisco and 1989 Loma Prieta earthquakes, subject to constant velocity boundary conditions on the edges of the shear zone. Fault creep is realized by evaluating dislocations on the creeping portions of faults in the fluid limit of the viscoelastic model. A priori plate-boundary(PB)-parallel motion is set to 38 mm yr -1. A grid search based on fitting the observed strain rate pattern yields a mantle viscosity of 1.2 ?? 1019 Pa s and a PB-perpendicular convergence rate of ???3 mm yr-1. Most of this convergence appears to be uniformly distributed in the Pacific-Sierra Nevada plate boundary zone. ?? 2005 RAS.

Strain Rate Dependant Material Model for Orthotropic Metals

NASA Astrophysics Data System (ADS)

Vignjevic, Rade

2016-08-01

In manufacturing processes anisotropic metals are often exposed to the loading with high strain rates in the range from 102 s-1 to 106 s-1 (e.g. stamping, cold spraying and explosive forming). These types of loading often involve generation and propagation of shock waves within the material. The material behaviour under such a complex loading needs to be accurately modelled, in order to optimise the manufacturing process and achieve appropriate properties of the manufactured component. The presented research is related to development and validation of a thermodynamically consistent physically based constitutive model for metals under high rate loading. The model is capable of modelling damage, failure and formation and propagation of shock waves in anisotropic metals. The model has two main parts: the strength part which defines the material response to shear deformation and an equation of state (EOS) which defines the material response to isotropic volumetric deformation [1]. The constitutive model was implemented into the transient nonlinear finite element code DYNA3D [2] and our in house SPH code. Limited model validation was performed by simulating a number of high velocity material characterisation and validation impact tests. The new damage model was developed in the framework of configurational continuum mechanics and irreversible thermodynamics with internal state variables. The use of the multiplicative decomposition of deformation gradient makes the model applicable to arbitrary plastic and damage deformations. To account for the physical mechanisms of failure, the concept of thermally activated damage initially proposed by Tuller and Bucher [3], Klepaczko [4] was adopted as the basis for the new damage evolution model. This makes the proposed damage/failure model compatible with the Mechanical Threshold Strength (MTS) model Follansbee and Kocks [5], 1988; Chen and Gray [6] which was used to control evolution of flow stress during plastic deformation. In addition the constitutive model is coupled with a vector shock equation of state which allows for modelling of shock wave propagation in orthotropic the material. Parameters for the new constitutive model are typically derived on the basis of the tensile tests (performed over a range of temperatures and strain rates), plate impact tests and Taylor anvil tests. The model was applied to simulate explosively driven fragmentation, blast loading and cold spraying impacts.

High-performance coupled poro-hydro-mechanical models to resolve fluid escape pipes

NASA Astrophysics Data System (ADS)

Räss, Ludovic; Makhnenko, Roman; Podladchikov, Yury

2017-04-01

Field observations and laboratory experiments exhibit inelastic deformation features arising in many coupled settings relevant to geo-applications. These irreversible deformations and their specific patterns suggest a rather ductile or brittle mechanism, such as viscous creep or micro cracks, taking place on both geological (long) and human (short) timescales. In order to understand the underlying mechanisms responsible for these deformation features, there is a current need to accurately resolve the non-linearities inherent to strongly coupled physical processes. Among the large variety of modelling tools and softwares available nowadays in the community, very few are capable to efficiently solve coupled systems with high accuracy in both space and time and run efficiently on modern hardware. Here, we propose a robust framework to solve coupled multi-physics hydro-mechanical processes on very high spatial and temporal resolution in both two and three dimensions. Our software relies on the Finite-Difference Method and a pseudo-transient scheme is used to converge to the implicit solution of the system of poro-visco-elasto-plastic equations at each physical time step. The rheology including viscosity estimates for major reservoir rock types is inferred from novel lab experiments and confirms the ease of flow of sedimentary rocks. Our results propose a physical mechanism responsible for the generation of high permeability pathways in fluid saturated porous media and predict their propagation in rates observable on operational timescales. Finally, our software scales linearly on more than 5000 GPUs.

A multi-dimensional high-order DG-ALE method based on gas-kinetic theory with application to oscillating bodies

NASA Astrophysics Data System (ADS)

Ren, Xiaodong; Xu, Kun; Shyy, Wei

2016-07-01

This paper presents a multi-dimensional high-order discontinuous Galerkin (DG) method in an arbitrary Lagrangian-Eulerian (ALE) formulation to simulate flows over variable domains with moving and deforming meshes. It is an extension of the gas-kinetic DG method proposed by the authors for static domains (X. Ren et al., 2015 [22]). A moving mesh gas kinetic DG method is proposed for both inviscid and viscous flow computations. A flux integration method across a translating and deforming cell interface has been constructed. Differently from the previous ALE-type gas kinetic method with piecewise constant mesh velocity at each cell interface within each time step, the mesh velocity variation inside a cell and the mesh moving and rotating at a cell interface have been accounted for in the finite element framework. As a result, the current scheme is applicable for any kind of mesh movement, such as translation, rotation, and deformation. The accuracy and robustness of the scheme have been improved significantly in the oscillating airfoil calculations. All computations are conducted in a physical domain rather than in a reference domain, and the basis functions move with the grid movement. Therefore, the numerical scheme can preserve the uniform flow automatically, and satisfy the geometric conservation law (GCL). The numerical accuracy can be maintained even for a largely moving and deforming mesh. Several test cases are presented to demonstrate the performance of the gas-kinetic DG-ALE method.

An experimental approach to non - extensive statistical physics and Epidemic Type Aftershock Sequence (ETAS) modeling. The case of triaxially deformed sandstones using acoustic emissions.

NASA Astrophysics Data System (ADS)

Stavrianaki, K.; Vallianatos, F.; Sammonds, P. R.; Ross, G. J.

2014-12-01

Fracturing is the most prevalent deformation mechanism in rocks deformed in the laboratory under simulated upper crustal conditions. Fracturing produces acoustic emissions (AE) at the laboratory scale and earthquakes on a crustal scale. The AE technique provides a means to analyse microcracking activity inside the rock volume and since experiments can be performed under confining pressure to simulate depth of burial, AE can be used as a proxy for natural processes such as earthquakes. Experimental rock deformation provides us with several ways to investigate time-dependent brittle deformation. Two main types of experiments can be distinguished: (1) "constant strain rate" experiments in which stress varies as a result of deformation, and (2) "creep" experiments in which deformation and deformation rate vary over time as a result of an imposed constant stress. We conducted constant strain rate experiments on air-dried Darley Dale sandstone samples in a variety of confining pressures (30MPa, 50MPa, 80MPa) and in water saturated samples with 20 MPa initial pore fluid pressure. The results from these experiments used to determine the initial loading in the creep experiments. Non-extensive statistical physics approach was applied to the AE data in order to investigate the spatio-temporal pattern of cracks close to failure. A more detailed study was performed for the data from the creep experiments. When axial stress is plotted against time we obtain the trimodal creep curve. Calculation of Tsallis entropic index q is performed to each stage of the curve and the results are compared with the ones from the constant strain rate experiments. The Epidemic Type Aftershock Sequence model (ETAS) is also applied to each stage of the creep curve and the ETAS parameters are calculated. We investigate whether these parameters are constant across all stages of the curve, or whether there are interesting patterns of variation. This research has been co-funded by the European Union (European Social Fund) and Greek national resources under the framework of the "THALES Program: SEISMO FEAR HELLARC" project of the "Education & Lifelong Learning" Operational Programme.

Materials science. Modeling strain hardening the hard way.

PubMed

Gumbsch, Peter

2003-09-26

The plastic deformation of metals results in strain hardening, that is, an increase in the stress with increasing strain. Materials engineers can provide a simple approximate description of such deformation and hardening behavior. In his perspective, Gumbsch discusses work by Madec et al. who have undertaken the formidable task of computing the physical basis for the development of strain hardening by individually following the fate of all the dislocations involved. Their simulations show that the collinear dislocation interaction makes a substantial contribution to strain hardening. It is likely that such simulations will play an important role in guiding the development of future engineering descriptions of deformation and hardening.

Large-Deformation Displacement Transfer Functions for Shape Predictions of Highly Flexible Slender Aerospace Structures

NASA Technical Reports Server (NTRS)

Ko, William L.; Fleischer, Van Tran

2013-01-01

Large deformation displacement transfer functions were formulated for deformed shape predictions of highly flexible slender structures like aircraft wings. In the formulation, the embedded beam (depth wise cross section of structure along the surface strain sensing line) was first evenly discretized into multiple small domains, with surface strain sensing stations located at the domain junctures. Thus, the surface strain (bending strains) variation within each domain could be expressed with linear of nonlinear function. Such piecewise approach enabled piecewise integrations of the embedded beam curvature equations [classical (Eulerian), physical (Lagrangian), and shifted curvature equations] to yield closed form slope and deflection equations in recursive forms.

Infiltration of MHD liquid into a deformable porous material

NASA Astrophysics Data System (ADS)

Naseem, Anum; Mahmood, Asif; Siddique, J. I.; Zhao, Lifeng

2018-03-01

We analyze the capillary rise dynamics for magnetohydrodynamics (MHD) fluid flow through deformable porous material in the presence of gravity effects. The modeling is performed using mixture theory approach and mathematical manipulation yields a nonlinear free boundary problem. Due to the capillary rise action, the pressure gradient in the liquid generates a stress gradient that results in the deformation of porous substrate. The capillary rise process for MHD fluid slows down as compared to Newtonian fluid case. Numerical solutions are obtained using a method of lines approach. The graphical results are presented for important physical parameters, and comparison is presented with Newtonian fluid case.

Late-Paleozoic-Mesozoic deformational and deformation related metamorphic structures of Kuznetsk-Altai region

NASA Astrophysics Data System (ADS)

Zinoviev, Sergei

2014-05-01

Kuznetsk-Altai region is a part of the Central Asian Orogenic Belt. The nature and formation mechanisms of the observed structure of Kuznetsk-Altai region are interpreted by the author as the consequence of convergence of Tuva-Mongolian and Junggar lithospheric block structures and energy of collision interaction between the blocks of crust in Late-Paleozoic-Mesozoic period. Tectonic zoning of Kuznetsk-Altai region is based on the principle of adequate description of geological medium (without methods of 'primary' state recovery). The initial indication of this convergence is the crust thickening in the zone of collision. On the surface the mechanisms of lateral compression form a regional elevation; with this elevation growth the 'mountain roots' start growing. With an approach of blocks an interblock elevation is divided into various fragments, and these fragments interact in the manner of collision. The physical expression of collision mechanisms are periodic pulses of seismic activity. The main tectonic consequence of the block convergence and collision of interblock units is formation of an ensemble of regional structures of the deformation type on the basis of previous 'pre-collision' geological substratum [Chikov et al., 2012]. This ensemble includes: 1) allochthonous and autochthonous blocks of weakly deformed substratum; 2) folded (folded-thrust) systems; 3) dynamic metamorphism zones of regional shears and main faults. Characteristic of the main structures includes: the position of sedimentary, magmatic and PT-metamorphic rocks, the degree of rock dynamometamorphism and variety rock body deformation, as well as the styles and concentrations of mechanic deformations. 1) block terranes have weakly elongated or isometric shape in plane, and they are the systems of block structures of pre-collision substratum separated by the younger zones of interblock deformations. They stand out among the main deformation systems, and the smallest are included into the deformation systems. 2) folded (folded-thrust) deformation systems combine deformation zones with relic lenses of Paleozoid substratum, and predominantly conform systems of the main faults. Despite a high degree of regional deformation the sedimentary-stratified and intrusive-contact relations of geological bodies are stored within the deformation systems, and this differs in the main the collision systems from zones of dynamic metamorphism. 3) regional zones of dynamic metamorphism of Kuznetsk-Altai region are the concentration belts of multiple mechanic deformations and contrast dynamometamorphism of complexes. The formational basis of dynamic metamorphism zones is tectonites of the collision stage. Zones of dynamic metamorphism attract special attention in the structural model of Kuznetsk-Altai region. They not only form the typical tectonic framework of collision sutures, but also contain the main part of ore deposits of this region. Pulse mode of structure formation of Kuznetsk-Altai region is detected. Major collision events in Kuznetsk-Altai region were in the late-Carboniferous-Triassic time (307-310, 295-285, 260-250 and 240-220 Ma). This study was supported by a grant of the Russian Foundation for Basic Research (project nos. 14-05-00117).

Quantification of substrate and cellular strains in stretchable 3D cell cultures: an experimental and computational framework.

PubMed

González-Avalos, P; Mürnseer, M; Deeg, J; Bachmann, A; Spatz, J; Dooley, S; Eils, R; Gladilin, E

2017-05-01

The mechanical cell environment is a key regulator of biological processes . In living tissues, cells are embedded into the 3D extracellular matrix and permanently exposed to mechanical forces. Quantification of the cellular strain state in a 3D matrix is therefore the first step towards understanding how physical cues determine single cell and multicellular behaviour. The majority of cell assays are, however, based on 2D cell cultures that lack many essential features of the in vivo cellular environment. Furthermore, nondestructive measurement of substrate and cellular mechanics requires appropriate computational tools for microscopic image analysis and interpretation. Here, we present an experimental and computational framework for generation and quantification of the cellular strain state in 3D cell cultures using a combination of 3D substrate stretcher, multichannel microscopic imaging and computational image analysis. The 3D substrate stretcher enables deformation of living cells embedded in bead-labelled 3D collagen hydrogels. Local substrate and cell deformations are determined by tracking displacement of fluorescent beads with subsequent finite element interpolation of cell strains over a tetrahedral tessellation. In this feasibility study, we debate diverse aspects of deformable 3D culture construction, quantification and evaluation, and present an example of its application for quantitative analysis of a cellular model system based on primary mouse hepatocytes undergoing transforming growth factor (TGF-β) induced epithelial-to-mesenchymal transition. © 2017 The Authors. Journal of Microscopy published by JohnWiley & Sons Ltd on behalf of Royal Microscopical Society.

Stretchable conductors by kirigami patterning of aramid-silver nanocomposites with zero conductance gradient

NASA Astrophysics Data System (ADS)

Lyu, Jing; Hammig, Mark D.; Liu, Lehao; Xu, Lizhi; Chi, Hang; Uher, Ctirad; Li, Tiehu; Kotov, Nicholas A.

2017-10-01

Materials that are both stretchable and electrically conductive enable a broad spectrum of applications in sensing, actuating, electronics, optics and energy storage. The materials engineering concept of stretchable conductors is primarily based on combining nanowires, nanoribbons, nanoparticles, or nanocarbons with rubbery polymers to obtain composites with different abilities to transport charge and alter their nanoscale organization under strain. Although some of these composites reveal remarkably interesting multiscale reconfigurability and self-assembly phenomena, decreasing conductance with increased strain has restricted their widespread implementation. In a broader physical sense, the dependence of conductance on stress is undesirable because it requires a correlated change of electrical inputs. In this paper, we describe highly conductive and deformable sheets with a conductivity as high as 230 000 S cm-1, composed of silver nanoparticles, infiltrated within a porous aramid nanofiber (ANF) matrix. By forming a kirigami pattern, consisting of a regularized network of notches cut within the films, their ultimate tensile strain is improved from ˜2% to beyond 100%. The use of ANFs derived from well-known ultrastrong Kevlar™ fibers imparts high mechanical performance to the base composite. Importantly, the conductance of the films remains constant, even under large deformation resulting in a material with a zero conductance gradient. Unlike other nanocomposites for which strain and conductance are strongly coupled, the kirigami nanocomposite provides a pathway to demanding applications for flexible and stretchable electronics with power/voltage being unaffected by the deformation mode and temperature.

Morphology Evolution of Polymer Blends under Intense Shear During High Speed Thin-Wall Injection Molding.

PubMed

Zhou, Yi; Yu, Feilong; Deng, Hua; Huang, Yajiang; Li, Guangxian; Fu, Qiang

2017-06-29

The morphology evolution under shear during different processing is indeed an important issue regarding the phase morphology control as well as final physical properties of immiscible polymer blends. High-speed thin wall injection molding (HSTWIM) has recently been demonstrated as an effective method to prepare alternating multilayered structure. To understand the formation mechanism better and explore possible phase morphology for different blends under HSTWIM, the relationship between the morphology evolution of polymer blends based on polypropylene (PP) under HSTWIM and some intrinsic properties of polymer blends, including viscosity ratio, interfacial tension, and melt elasticity, is systematically investigated in this study. Blends based on PP containing polyethylene (PE), ethylene vinyl alcohol copolymer (EVOH), and polylactic acid (PLA) are used as examples. Compatibilizer has also been added into respective blends to alter their interfacial interaction. It is demonstrated that dispersed phase can be deformed into a layered-like structure if interfacial tension, viscosity ratio, and melt elasticity are relatively small. While some of these values are relatively large, these dispersed droplets are not easily deformed under HSTWIM, forming ellipsoidal or fiber-like structure. The addition of a moderate amount of compatibilizer into these blends is shown to be able to reduce interfacial tension and the size of dispersed phase, thus, allowing more deformation on the dispersed phase. Such a study could provide some guidelines on phase morphology control of immiscible polymer blends under shear during various processing methods.

Physical examination in adolescent idiopathic scoliosis.

PubMed

Diab, Mohammad

2007-04-01

The following distinguish the physical examination in scoliosis: it is extensive, it is revealing, and it influences treatment. Throughout this discussion, reference frequently is made to evaluation for underlying neural disease. Idiopathic scoliosis is a diagnosis of exclusion, and a neural etiology of spinal deformity must be ruled out in every case.

Unspecific chronic low back pain – a simple functional classification tested in a case series of patients with spinal deformities

PubMed Central

Weiss, Hans-Rudolf; Werkmann, Mario

2009-01-01

Background Up to now, chronic low back pain without radicular symptoms is not classified and attributed in international literature as being "unspecific". For specific bracing of this patient group we use simple physical tests to predict the brace type the patient is most likely to benefit from. Based on these physical tests we have developed a simple functional classification of "unspecific" low back pain in patients with spinal deformities. Methods Between January 2006 and July 2007 we have tested 130 patients (116 females and 14 males) with spinal deformities (average age 45 years, ranging from 14 years to 69) and chronic unspecific low back pain (pain for > 24 months) along with the indication for brace treatment for chronic unspecific low back pain. Some of the patients had symptoms of spinal claudication (n = 16). The "sagittal realignment test" (SRT) was applied, a lumbar hyperextension test, and the "sagittal delordosation test" (SDT). Additionally 3 female patients with spondylolisthesis were tested, including one female with symptoms of spinal claudication and 2 of these patients were 14 years of age and the other 43yrs old at the time of testing. Results 117 Patients reported significant pain release in the SRT and 13 in the SDT (>/= 2 steps in the Roland & Morris VRS). 3 Patients had no significant pain release in both of the tests (< 2 steps in the Roland & Morris VRS). Pain intensity was high (3,29) before performing the physical tests (VRS-scale 0–5) and low (1,37) while performing the physical test for the whole sample of patients. The differences where highly significant in the Wilcoxon test (z = -3,79; p < 0,0001). In the 16 patients who did not respond to the SRT in the manual investigation we found hypermobility at L5/S1 or a spondylolisthesis at level L5/S1. In the other patients who responded well to the SRT loss of lumbar lordosis was the main issue, a finding which, according to scientific literature, correlates well with low back pain. The 3 patients who did not respond to either test had a fair pain reduction in a generally delordosing brace with an isolated small foam pad inserted at the level of L 2/3, leading to a lordosation at this region. Discussion With the exception of 3 patients (2.3%) a clear distribution to one of the two classes has been possible. 117 patients were supplied successfully with a sagittal realignment test-brace (physio-logic® brace) and 13 with a sagittal delordosing brace (spondylogic® brace). There were patients with scoliosies and hyperkyphosiesbrace). Therefore a clear distribution of the patients from this sample to either chronic postural or chronic instability back pain was possible. In 2.3% a combined chronic low back pain from the findings obtained seems reasonable. Conclusion Chronic unspecific low back pain is possible to clearly be classified physically. This functional classification is necessary to decide on which specific conservative approach (physical therapy, braces) should be used. Other factors than spinal deformities contribute to chronic low back pain. PMID:19222845

Unspecific chronic low back pain - a simple functional classification tested in a case series of patients with spinal deformities.

PubMed

Weiss, Hans-Rudolf; Werkmann, Mario

2009-02-17

Up to now, chronic low back pain without radicular symptoms is not classified and attributed in international literature as being "unspecific". For specific bracing of this patient group we use simple physical tests to predict the brace type the patient is most likely to benefit from. Based on these physical tests we have developed a simple functional classification of "unspecific" low back pain in patients with spinal deformities. Between January 2006 and July 2007 we have tested 130 patients (116 females and 14 males) with spinal deformities (average age 45 years, ranging from 14 years to 69) and chronic unspecific low back pain (pain for > 24 months) along with the indication for brace treatment for chronic unspecific low back pain. Some of the patients had symptoms of spinal claudication (n = 16). The "sagittal realignment test" (SRT) was applied, a lumbar hyperextension test, and the "sagittal delordosation test" (SDT). Additionally 3 female patients with spondylolisthesis were tested, including one female with symptoms of spinal claudication and 2 of these patients were 14 years of age and the other 43yrs old at the time of testing. 117 Patients reported significant pain release in the SRT and 13 in the SDT (> or = 2 steps in the Roland & Morris VRS). 3 Patients had no significant pain release in both of the tests (< 2 steps in the Roland & Morris VRS).Pain intensity was high (3,29) before performing the physical tests (VRS-scale 0-5) and low (1,37) while performing the physical test for the whole sample of patients. The differences where highly significant in the Wilcoxon test (z = -3,79; p < 0,0001).In the 16 patients who did not respond to the SRT in the manual investigation we found hypermobility at L5/S1 or a spondylolisthesis at level L5/S1. In the other patients who responded well to the SRT loss of lumbar lordosis was the main issue, a finding which, according to scientific literature, correlates well with low back pain. The 3 patients who did not respond to either test had a fair pain reduction in a generally delordosing brace with an isolated small foam pad inserted at the level of L 2/3, leading to a lordosation at this region. With the exception of 3 patients (2.3%) a clear distribution to one of the two classes has been possible. 117 patients were supplied successfully with a sagittal realignment test-brace (physio-logic brace) and 13 with a sagittal delordosing brace (spondylogic brace). There were patients with scoliosies and hyperkyphosiesbrace). Therefore a clear distribution of the patients from this sample to either chronic postural or chronic instability back pain was possible. In 2.3% a combined chronic low back pain from the findings obtained seems reasonable. Chronic unspecific low back pain is possible to clearly be classified physically. This functional classification is necessary to decide on which specific conservative approach (physical therapy, braces) should be used.Other factors than spinal deformities contribute to chronic low back pain.

Applications of Real Space Crystallography in Characterization of Dislocations in Geological Materials in a Scanning Electron Microscope (SEM)

NASA Astrophysics Data System (ADS)

Kaboli, S.; Burnley, P. C.

2017-12-01

Imaging and characterization of defects in crystalline materials is of significant importance in various disciplines including geoscience, materials science, and applied physics. Linear defects such as dislocations and planar defects such as twins and stacking faults, strongly influence many of the properties of crystalline materials and also reflect the conditions and degree of deformation. Dislocations have been conventionally imaged in thin foils in a transmission electron microscope (TEM). Since the development of field emission scanning electron microscopes (FE-SEM) with high gun brightness and small spot size, extensive efforts have been dedicated to the imaging and characterization of dislocations in semi-conductors using electron channeling contrast imaging (ECCI) in the SEM. The obvious advantages of using SEM over TEM include easier and non-destructive sample preparation and a large field of view enabling statistical examination of the density and distribution of dislocations and other defects. In this contribution, we extend this technique to geological materials and introduce the Real Space Crystallography methodology for imaging and complete characterization of dislocations based on bend contour contrast obtained by ECCI in FE-SEM. Bend contours map out the distortion in the crystal lattice across a deformed grain. The contrast of dislocations is maximum in the vicinity of bend contours where crystal planes diffract at small and positive deviations from the Bragg positions (as defined by Bragg's law of electron diffraction). Imaging is performed in a commercial FE-SEM equipped with a standard silicon photodiode backscattered (BSE) detector and an electron backscatter diffraction (EBSD) system for crystal orientation measurements. We demonstrate the practice of this technique in characterization of a number of geological materials in particular quartz, forsterite olivine and corundum, experimentally deformed at high pressure-temperature conditions. This new approach in microstructure characterization of deformed geologic materials in FE-SEM, without the use of etching or decoration techniques, has valuable applications to both experimentally deformed and naturally deformed specimens.

Network patterns in exponentially growing two-dimensional biofilms

NASA Astrophysics Data System (ADS)

Zachreson, Cameron; Yap, Xinhui; Gloag, Erin S.; Shimoni, Raz; Whitchurch, Cynthia B.; Toth, Milos

2017-10-01

Anisotropic collective patterns occur frequently in the morphogenesis of two-dimensional biofilms. These patterns are often attributed to growth regulation mechanisms and differentiation based on gradients of diffusing nutrients and signaling molecules. Here, we employ a model of bacterial growth dynamics to show that even in the absence of growth regulation or differentiation, confinement by an enclosing medium such as agar can itself lead to stable pattern formation over time scales that are employed in experiments. The underlying mechanism relies on path formation through physical deformation of the enclosing environment.

Extracting material response from simple mechanical tests on hardening-softening-hardening viscoplastic solids

NASA Astrophysics Data System (ADS)

Mohan, Nisha

Compliant foams are usually characterized by a wide range of desirable mechanical properties. These properties include viscoelasticity at different temperatures, energy absorption, recoverability under cyclic loading, impact resistance, and thermal, electrical, acoustic and radiation-resistance. Some foams contain nano-sized features and are used in small-scale devices. This implies that the characteristic dimensions of foams span multiple length scales, rendering modeling their mechanical properties difficult. Continuum mechanics-based models capture some salient experimental features like the linear elastic regime, followed by non-linear plateau stress regime. However, they lack mesostructural physical details. This makes them incapable of accurately predicting local peaks in stress and strain distributions, which significantly affect the deformation paths. Atomistic methods are capable of capturing the physical origins of deformation at smaller scales, but suffer from impractical computational intensity. Capturing deformation at the so-called meso-scale, which is capable of describing the phenomenon at a continuum level, but with some physical insights, requires developing new theoretical approaches. A fundamental question that motivates the modeling of foams is `how to extract the intrinsic material response from simple mechanical test data, such as stress vs. strain response?' A 3D model was developed to simulate the mechanical response of foam-type materials. The novelty of this model includes unique features such as the hardening-softening-hardening material response, strain rate-dependence, and plastically compressible solids with plastic non-normality. Suggestive links from atomistic simulations of foams were borrowed to formulate a physically informed hardening material input function. Motivated by a model that qualitatively captured the response of foam-type vertically aligned carbon nanotube (VACNT) pillars under uniaxial compression [2011,"Analysis of Uniaxial Compression of Vertically Aligned Carbon Nanotubes," J. Mech.Phys. Solids, 59, pp. 2227--2237, Erratum 60, 1753-1756 (2012)], the property space exploration was advanced to three types of simple mechanical tests: 1) uniaxial compression, 2) uniaxial tension, and 3) nanoindentation with a conical and a flat-punch tip. The simulations attempt to explain some of the salient features in experimental data, like 1) The initial linear elastic response. 2) One or more nonlinear instabilities, yielding, and hardening. The model-inherent relationships between the material properties and the overall stress-strain behavior were validated against the available experimental data. The material properties include the gradient in stiffness along the height, plastic and elastic compressibility, and hardening. Each of these tests was evaluated in terms of their efficiency in extracting material properties. The uniaxial simulation results proved to be a combination of structural and material influences. Out of all deformation paths, flat-punch indentation proved to be superior since it is the most sensitive in capturing the material properties.

I in generalized supergravity

NASA Astrophysics Data System (ADS)

Araujo, T.; Ó Colgáin, E.; Sakamoto, J.; Sheikh-Jabbari, M. M.; Yoshida, K.

2017-11-01

We showed in previous work that for homogeneous Yang-Baxter (YB) deformations of AdS_5× S^5 the open string metric and coupling and as a result the closed string density e^{-2 Φ } √{g} remain undeformed. In this work, in addition to extending these results to the deformation associated with the modified CYBE or η -deformation, we identify the Page forms as the open string counterpart for RR fields and demonstrate case by case that the non-zero Page forms remain invariant under YB deformations. We give a physical meaning to the Killing vector I of generalized supergravity and show for all YB deformations: (1) I appears as a current for the center of mass motion on the worldvolume of a D-brane probing the background, (2) I is equal to the divergence of the noncommutativity parameter, (3) I exhibits "holographic" behavior where the radial component of I vanishes at the AdS boundary and (4) in pure spinor formalism I is related to a certain state in the BRST cohomology.

Wrinkling of a spherical lipid interface induced by actomyosin cortex

NASA Astrophysics Data System (ADS)

Ito, Hiroaki; Nishigami, Yukinori; Sonobe, Seiji; Ichikawa, Masatoshi

2015-12-01

Actomyosin actively generates contractile forces that provide the plasma membrane with the deformation stresses essential to carry out biological processes. Although the contractile property of purified actomyosin has been extensively studied, to understand the physical contribution of the actomyosin contractile force on a deformable membrane is still a challenging problem and of great interest in the field of biophysics. Here, we reconstitute a model system with a cell-sized deformable interface that exhibits anomalous curvature-dependent wrinkling caused by the actomyosin cortex underneath the spherical closed interface. Through a shape analysis of the wrinkling deformation, we find that the dominant contributor to the wrinkled shape changes from bending elasticity to stretching elasticity of the reconstituted cortex upon increasing the droplet curvature radius of the order of the cell size, i.e., tens of micrometers. The observed curvature dependence is explained by the theoretical description of the cortex elasticity and contractility. Our present results provide a fundamental insight into the deformation of a curved membrane induced by the actomyosin cortex.

Large strain deformation behavior of polymeric gels in shear- and cavitation rheology

NASA Astrophysics Data System (ADS)

Hashemnejad, Seyed Meysam; Kundu, Santanu

Polymeric gels are used in many applications including in biomedical and in food industries. Investigation of mechanical responses of swollen polymer gels and linking that to the polymer chain dynamics are of significant interest. Here, large strain deformation behavior of two different gel systems and with different network architecture will be presented. We consider biologically relevant polysaccharide hydrogels, formed through ionic and covalent crosslinking, and physically associating triblock copolymer gels in a midblock selective solvent. Gels with similar low-strain shear modulus display distinctly different non-linear rheological behavior in large strain shear deformation. Both these gels display strain-stiffening behavior in shear-deformation prior to macroscopic fracture of the network, however, only the alginate gels display negative normal stress. The cavitation rheology data show that the critical pressure for cavitation is higher for alginate gels than that observed for triblock gels. These distinctly different large-strain deformation behavior has been related to the gel network structure, as alginate chains are much stiffer than the triblock polymer chains.

Modeling drop impacts on inclined flowing soap films

NASA Astrophysics Data System (ADS)

Basu, Saikat; Yawar, Ali; Concha, Andres; Bandi, Mahesh

2015-11-01

Small drops impinging on soap films flowing at an angle primarily exhibit three fundamental regimes of post-impact dynamics: (a) the drop bounces off the film surface, (b) it coalesces with the downstream flow, and (c) it pierces through the film. During impact, the drop deforms along with a simultaneous, almost elastic deformation of the film transverse to the stream direction. Hence, the governing dynamics for this interaction present the rare opportunity to explore the in-tandem effects of elasticity and hydrodynamics alike. In this talk, we outline the analytical framework to study the drop impact dynamics. The model assumes a deformable drop and a deformable three-dimensional soap film and invokes a parametric study to qualify the three mentioned impact types. The physical parameters include the impact angle, drop impact speed, and the diameters of the drop prior to and during impact when it deforms and spreads out. Our model system offers a path towards optimization of interactions between a spray and a flowing liquid.

Microfluidics separation reveals the stem-cell-like deformability of tumor-initiating cells.

PubMed

Zhang, Weijia; Kai, Kazuharu; Choi, Dong Soon; Iwamoto, Takayuki; Nguyen, Yen H; Wong, Helen; Landis, Melissa D; Ueno, Naoto T; Chang, Jenny; Qin, Lidong

2012-11-13

Here we report a microfluidics method to enrich physically deformable cells by mechanical manipulation through artificial microbarriers. Driven by hydrodynamic forces, flexible cells or cells with high metastatic propensity change shape to pass through the microbarriers and exit the separation device, whereas stiff cells remain trapped. We demonstrate the separation of (i) a mixture of two breast cancer cell types (MDA-MB-436 and MCF-7) with distinct deformabilities and metastatic potentials, and (ii) a heterogeneous breast cancer cell line (SUM149), into enriched flexible and stiff subpopulations. We show that the flexible phenotype is associated with overexpression of multiple genes involved in cancer cell motility and metastasis, and greater mammosphere formation efficiency. Our observations support the relationship between tumor-initiating capacity and cell deformability, and demonstrate that tumor-initiating cells are less differentiated in terms of cell biomechanics.

Modelling heat and mass transfer in bread baking with mechanical deformation

NASA Astrophysics Data System (ADS)

Nicolas, V.; Salagnac, P.; Glouannec, P.; Ploteau, J.-P.; Jury, V.; Boillereaux, L.

2012-11-01

In this paper, the thermo-hydric behaviour of bread during baking is studied. A numerical model has been developed with Comsol Multiphysics© software. The model takes into account the heat and mass transfers in the bread and the phenomenon of swelling. This model predicts the evolution of temperature, moisture, gas pressure and deformation in French "baguette" during baking. Local deformation is included in equations using solid phase conservation and, global deformation is calculated using a viscous mechanic model. Boundary conditions are specified with the sole temperature model and vapour pressure estimation of the oven during baking. The model results are compared with experimental data for a classic baking. Then, the model is analysed according to physical properties of bread and solicitations for a better understanding of the interactions between different mechanisms within the porous matrix.

Deformable medical image registration of pleural cavity for photodynamic therapy by using finite-element based method

NASA Astrophysics Data System (ADS)

Penjweini, Rozhin; Kim, Michele M.; Dimofte, Andrea; Finlay, Jarod C.; Zhu, Timothy C.

2016-03-01

When the pleural cavity is opened during the surgery portion of pleural photodynamic therapy (PDT) of malignant mesothelioma, the pleural volume will deform. This impacts the delivered dose when using highly conformal treatment techniques. To track the anatomical changes and contour the lung and chest cavity, an infrared camera-based navigation system (NDI) is used during PDT. In the same patient, a series of computed tomography (CT) scans of the lungs are also acquired before the surgery. The reconstructed three-dimensional contours from both NDI and CTs are imported into COMSOL Multiphysics software, where a finite element-based (FEM) deformable image registration is obtained. The CT contour is registered to the corresponding NDI contour by overlapping the center of masses and aligning their orientations. The NDI contour is considered as the reference contour, and the CT contour is used as the target one, which will be deformed. Deformed Geometry model is applied in COMSOL to obtain a deformed target contour. The distortion of the volume at X, Y and Z is mapped to illustrate the transformation of the target contour. The initial assessment shows that FEM-based image deformable registration can fuse images acquired by different modalities. It provides insights into the deformation of anatomical structures along X, Y and Z-axes. The deformed contour has good matches to the reference contour after the dynamic matching process. The resulting three-dimensional deformation map can be used to obtain the locations of other critical anatomic structures, e.g., heart, during surgery.

Geodetic Imaging of the Earthquake Cycle

NASA Astrophysics Data System (ADS)

Tong, Xiaopeng

In this dissertation I used Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) to recover crustal deformation caused by earthquake cycle processes. The studied areas span three different types of tectonic boundaries: a continental thrust earthquake (M7.9 Wenchuan, China) at the eastern margin of the Tibet plateau, a mega-thrust earthquake (M8.8 Maule, Chile) at the Chile subduction zone, and the interseismic deformation of the San Andreas Fault System (SAFS). A new L-band radar onboard a Japanese satellite ALOS allows us to image high-resolution surface deformation in vegetated areas, which is not possible with older C-band radar systems. In particular, both the Wenchuan and Maule InSAR analyses involved L-band ScanSAR interferometry which had not been attempted before. I integrated a large InSAR dataset with dense GPS networks over the entire SAFS. The integration approach features combining the long-wavelength deformation from GPS with the short-wavelength deformation from InSAR through a physical model. The recovered fine-scale surface deformation leads us to better understand the underlying earthquake cycle processes. The geodetic slip inversion reveals that the fault slip of the Wenchuan earthquake is maximum near the surface and decreases with depth. The coseismic slip model of the Maule earthquake constrains the down-dip extent of the fault slip to be at 45 km depth, similar to the Moho depth. I inverted for the slip rate on 51 major faults of the SAFS using Green's functions for a 3-dimensional earthquake cycle model that includes kinematically prescribed slip events for the past earthquakes since the year 1000. A 60 km thick plate model with effective viscosity of 10 19 Pa · s is preferred based on the geodetic and geological observations. The slip rates recovered from the plate models are compared to the half-space model. The InSAR observation reveals that the creeping section of the SAFS is partially locked. This high-resolution deformation model will refine the moment accumulation rates and shear strain rates, which are not well resolved by previous models.

Deformation Measurement In The Hayward Fault Zone Using Partially Correlated Persistent Scatterers

NASA Astrophysics Data System (ADS)

Lien, J.; Zebker, H. A.

2013-12-01

Interferometric synthetic aperture radar (InSAR) is an effective tool for measuring temporal changes in the Earth's surface. By combining SAR phase data collected at varying times and orbit geometries, with InSAR we can produce high accuracy, wide coverage images of crustal deformation fields. Changes in the radar imaging geometry, scatterer positions, or scattering behavior between radar passes causes the measured radar return to differ, leading to a decorrelation phase term that obscures the deformation signal and prevents the use of large baseline data. Here we present a new physically-based method of modeling decorrelation from the subset of pixels with the highest intrinsic signal-to-noise ratio, the so-called persistent scatters (PS). This more complete formulation, which includes both phase and amplitude scintillations, better describes the scattering behavior of partially correlated PS pixels and leads to a more reliable selection algorithm. The new method identifies PS pixels using maximum likelihood signal-to-clutter ratio (SCR) estimation based on the joint interferometric stack phase-amplitude distribution. Our PS selection method is unique in that it considers both phase and amplitude; accounts for correlation between all possible pairs of interferometric observations; and models the effect of spatial and temporal baselines on the stack. We use the resulting maximum likelihood SCR estimate as a criterion for PS selection. We implement the partially correlated persistent scatterer technique to analyze a stack of C-band European Remote Sensing (ERS-1/2) interferometric radar data imaging the Hayward Fault Zone from 1995 to 2000. We show that our technique achieves a better trade-off between PS pixel selection accuracy and network density compared to other PS identification methods, particularly in areas of natural terrain. We then present deformation measurements obtained by the selected PS network. Our results demonstrate that the partially correlated persistent scatterer technique can attain accurate deformation measurements even in areas that suffer decorrelation due to natural terrain. The accuracy of phase unwrapping and subsequent deformation estimation on the spatially sparse PS network depends on both pixel selection accuracy and the density of the network. We find that many additional pixels can be added to the PS list if we are able to correctly identify and add those in which the scattering mechanism exhibits partial, rather than complete, correlation across all radar scenes.

Foldover-free shape deformation for biomedicine.

PubMed

Yu, Hongchuan; Zhang, Jian J; Lee, Tong-Yee

2014-04-01

Shape deformation as a fundamental geometric operation underpins a wide range of applications, from geometric modelling, medical imaging to biomechanics. In medical imaging, for example, to quantify the difference between two corresponding images, 2D or 3D, one needs to find the deformation between both images. However, such deformations, particularly deforming complex volume datasets, are prone to the problem of foldover, i.e. during deformation, the required property of one-to-one mapping no longer holds for some points. Despite numerous research efforts, the construction of a mathematically robust foldover-free solution subject to positional constraints remains open. In this paper, we address this challenge by developing a radial basis function-based deformation method. In particular we formulate an effective iterative mechanism which ensures the foldover-free property is satisfied all the time. The experimental results suggest that the resulting deformations meet the internal positional constraints. In addition to radial basis functions, this iterative mechanism can also be incorporated into other deformation approaches, e.g. B-spline based FFDs, to develop different deformable approaches for various applications. Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.

Predicting Welding Distortion in a Panel Structure with Longitudinal Stiffeners Using Inherent Deformations Obtained by Inverse Analysis Method

PubMed Central

Liang, Wei; Murakawa, Hidekazu

2014-01-01

Welding-induced deformation not only negatively affects dimension accuracy but also degrades the performance of product. If welding deformation can be accurately predicted beforehand, the predictions will be helpful for finding effective methods to improve manufacturing accuracy. Till now, there are two kinds of finite element method (FEM) which can be used to simulate welding deformation. One is the thermal elastic plastic FEM and the other is elastic FEM based on inherent strain theory. The former only can be used to calculate welding deformation for small or medium scale welded structures due to the limitation of computing speed. On the other hand, the latter is an effective method to estimate the total welding distortion for large and complex welded structures even though it neglects the detailed welding process. When the elastic FEM is used to calculate the welding-induced deformation for a large structure, the inherent deformations in each typical joint should be obtained beforehand. In this paper, a new method based on inverse analysis was proposed to obtain the inherent deformations for weld joints. Through introducing the inherent deformations obtained by the proposed method into the elastic FEM based on inherent strain theory, we predicted the welding deformation of a panel structure with two longitudinal stiffeners. In addition, experiments were carried out to verify the simulation results. PMID:25276856

Predicting welding distortion in a panel structure with longitudinal stiffeners using inherent deformations obtained by inverse analysis method.

PubMed

Liang, Wei; Murakawa, Hidekazu

2014-01-01

Welding-induced deformation not only negatively affects dimension accuracy but also degrades the performance of product. If welding deformation can be accurately predicted beforehand, the predictions will be helpful for finding effective methods to improve manufacturing accuracy. Till now, there are two kinds of finite element method (FEM) which can be used to simulate welding deformation. One is the thermal elastic plastic FEM and the other is elastic FEM based on inherent strain theory. The former only can be used to calculate welding deformation for small or medium scale welded structures due to the limitation of computing speed. On the other hand, the latter is an effective method to estimate the total welding distortion for large and complex welded structures even though it neglects the detailed welding process. When the elastic FEM is used to calculate the welding-induced deformation for a large structure, the inherent deformations in each typical joint should be obtained beforehand. In this paper, a new method based on inverse analysis was proposed to obtain the inherent deformations for weld joints. Through introducing the inherent deformations obtained by the proposed method into the elastic FEM based on inherent strain theory, we predicted the welding deformation of a panel structure with two longitudinal stiffeners. In addition, experiments were carried out to verify the simulation results.

The role of thermo-rheological properties of the crust beneath Ischia Island (Southern Italy) in the modulation of the ground deformation pattern

NASA Astrophysics Data System (ADS)

Castaldo, R.; Gola, G.; Santilano, A.; De Novellis, V.; Pepe, S.; Manzo, M.; Manzella, A.; Tizzani, P.

2017-09-01

In this paper we develop a model of the ground deformation behaviour occurred at Ischia Island (Southern Italy) in the 1992-2010 time period. The model is employed to investigate the forces and physical parameters of the crust controlling the subsidence of the Island. To this aim, we integrate and homogenize in a Finite Element (FE) environment a large amount of data derived from several and different observation techniques (i.e., geological, geophysical and remote sensing). In detail, the main steps of the multiphysics model are: (i) the generation of a 3D geological model of the crust beneath the Island by merging the available geological and geophysical information; (ii) the optimization of a 3D thermal model by exploiting the thermal measurements available in literature; (iii) the definition of the 3D Brittle/Ductile transition by using the temperature distribution of the crust and the physical information of the rocks; (iv) the optimization of the ground deformation velocity model (that takes into account the rheological stratification) by considering the spatial and temporal information detected via satellite multi-orbit C-Band SAR (Synthetic Aperture Radar) measurements acquired during the 1992-2010 time period. The achieved results allow investigating the physical process responsible for the observed ground deformation pattern. In particular, they reveal how the rheology modulates the spatial and temporal evolution of the long-term subsidence phenomenon, highlighting a coupling effect of the viscosities of the rocks and the gravitational loading of the volcano edifice. Moreover, the achieved results provide a very detailed and realistic velocity field image of the subsurface crust of the Ischia Island Volcano.

X-ray beam-shaping via deformable mirrors: surface profile and point spread function computation for Gaussian beams using physical optics.

PubMed

Spiga, D

2018-01-01

X-ray mirrors with high focusing performances are commonly used in different sectors of science, such as X-ray astronomy, medical imaging and synchrotron/free-electron laser beamlines. While deformations of the mirror profile may cause degradation of the focus sharpness, a deliberate deformation of the mirror can be made to endow the focus with a desired size and distribution, via piezo actuators. The resulting profile can be characterized with suitable metrology tools and correlated with the expected optical quality via a wavefront propagation code or, sometimes, predicted using geometric optics. In the latter case and for the special class of profile deformations with monotonically increasing derivative, i.e. concave upwards, the point spread function (PSF) can even be predicted analytically. Moreover, under these assumptions, the relation can also be reversed: from the desired PSF the required profile deformation can be computed analytically, avoiding the use of trial-and-error search codes. However, the computation has been so far limited to geometric optics, which entailed some limitations: for example, mirror diffraction effects and the size of the coherent X-ray source were not considered. In this paper, the beam-shaping formalism in the framework of physical optics is reviewed, in the limit of small light wavelengths and in the case of Gaussian intensity wavefronts. Some examples of shaped profiles are also shown, aiming at turning a Gaussian intensity distribution into a top-hat one, and checks of the shaping performances computing the at-wavelength PSF by means of the WISE code are made.

Mechanisms of plastic deformation in highly cross-linked UHMWPE for total hip components--the molecular physics viewpoint.

PubMed

Takahashi, Yasuhito; Shishido, Takaaki; Yamamoto, Kengo; Masaoka, Toshinori; Kubo, Kosuke; Tateiwa, Toshiyuki; Pezzotti, Giuseppe

2015-02-01

Plastic deformation is an unavoidable event in biomedical polymeric implants for load-bearing application during long-term in-vivo service life, which involves a mass transfer process, irreversible chain motion, and molecular reorganization. Deformation-induced microstructural alterations greatly affect mechanical properties and durability of implant devices. The present research focused on evaluating, from a molecular physics viewpoint, the impact of externally applied strain (or stress) in ultra-high molecular weight polyethylene (UHMWPE) prostheses, subjected to radiation cross-linking and subsequent remelting for application in total hip arthroplasty (THA). Two different types of commercial acetabular liners, which belong to the first-generation highly cross-linked UHMWPE (HXLPE), were investigated by means of confocal/polarized Raman microprobe spectroscopy. The amount of crystalline region and the spatial distribution of molecular chain orientation were quantitatively analyzed according to a combined theory including Raman selection rules for the polyethylene orthorhombic structure and the orientation distribution function (ODF) statistical approach. The structurally important finding was that pronounced recrystallization and molecular reorientation increasingly appeared in the near-surface regions of HXLPE liners with increasing the amount of plastic (compressive) deformation stored in the microstructure. Such molecular rearrangements, occurred in response to external strains, locally increase surface cross-shear (CS) stresses, which in turn trigger microscopic wear processes in HXLPE acetabular liners. Thus, on the basis of the results obtained at the molecular scale, we emphasize here the importance of minimizing the development of irrecoverable deformation strain in order to retain the pristine and intrinsically high wear performance of HXLPE components. Copyright © 2014 Elsevier Ltd. All rights reserved.

Generalized Ehrenfest Relations, Deformation Quantization, and the Geometry of Inter-model Reduction

NASA Astrophysics Data System (ADS)

Rosaler, Joshua

2018-03-01

This study attempts to spell out more explicitly than has been done previously the connection between two types of formal correspondence that arise in the study of quantum-classical relations: one the one hand, deformation quantization and the associated continuity between quantum and classical algebras of observables in the limit \\hbar → 0, and, on the other, a certain generalization of Ehrenfest's Theorem and the result that expectation values of position and momentum evolve approximately classically for narrow wave packet states. While deformation quantization establishes a direct continuity between the abstract algebras of quantum and classical observables, the latter result makes in-eliminable reference to the quantum and classical state spaces on which these structures act—specifically, via restriction to narrow wave packet states. Here, we describe a certain geometrical re-formulation and extension of the result that expectation values evolve approximately classically for narrow wave packet states, which relies essentially on the postulates of deformation quantization, but describes a relationship between the actions of quantum and classical algebras and groups over their respective state spaces that is non-trivially distinct from deformation quantization. The goals of the discussion are partly pedagogical in that it aims to provide a clear, explicit synthesis of known results; however, the particular synthesis offered aspires to some novelty in its emphasis on a certain general type of mathematical and physical relationship between the state spaces of different models that represent the same physical system, and in the explicitness with which it details the above-mentioned connection between quantum and classical models.

Segmentation, modeling and classification of the compact objects in a pile

NASA Technical Reports Server (NTRS)

Gupta, Alok; Funka-Lea, Gareth; Wohn, Kwangyoen

1990-01-01

The problem of interpreting dense range images obtained from the scene of a heap of man-made objects is discussed. A range image interpretation system consisting of segmentation, modeling, verification, and classification procedures is described. First, the range image is segmented into regions and reasoning is done about the physical support of these regions. Second, for each region several possible three-dimensional interpretations are made based on various scenarios of the objects physical support. Finally each interpretation is tested against the data for its consistency. The superquadric model is selected as the three-dimensional shape descriptor, plus tapering deformations along the major axis. Experimental results obtained from some complex range images of mail pieces are reported to demonstrate the soundness and the robustness of our approach.

Microstructure-based approach for predicting crack initiation and early growth in metals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cox, James V.; Emery, John M.; Brewer, Luke N.

2009-09-01

Fatigue cracking in metals has been and is an area of great importance to the science and technology of structural materials for quite some time. The earliest stages of fatigue crack nucleation and growth are dominated by the microstructure and yet few models are able to predict the fatigue behavior during these stages because of a lack of microstructural physics in the models. This program has developed several new simulation tools to increase the microstructural physics available for fatigue prediction. In addition, this program has extended and developed microscale experimental methods to allow the validation of new microstructural models formore » deformation in metals. We have applied these developments to fatigue experiments in metals where the microstructure has been intentionally varied.« less

Quantum Stress: Density Functional Theory Formulation and Physical Manifestation

NASA Astrophysics Data System (ADS)

Hu, Hao; Liu, Feng

2012-02-01

The concept of ``quantum stress (QS)'' is introduced and formulated within density functional theory (DFT), to underlie extrinsic electronic effects on the stress state of solids and thin films in the absence of lattice strain. An explicit expression of QS (σ^Q) is derived in relation to the deformation potential of electronic states (ξ) and the variation of electron density (δn), σ^Q=ξ(δn), as a quantum analog of classical Hook's law. Two distinct QS manifestations are demonstrated quantitatively by DFT calculations: (1) in the form of bulk stress induced by charge carriers; and (2) in the form of surface stress induced by quantum confinement. QS has broad implications in physical phenomena and technological applications that are based on coupling of electronic structure with lattice strain.

Towards the determination of deformation rates - pinch-and-swell structures as a natural and simulated paleo-strain rate gage

NASA Astrophysics Data System (ADS)

Peters, Max; Poulet, Thomas; Karrech, Ali; Regenauer-Lieb, Klaus; Herwegh, Marco

2014-05-01

Layered rocks deformed under viscous deformation conditions frequently show boudinage, a phenomenon that results from differences in effective viscosity between the involved layers. In the case of continuous necking of a mechanically stiffer layer embedded in a weaker matrix, symmetric boudins are interpreted as the result of dominant visco-plastic deformation (Goscombe et al., 2004). However, information on the physical conditions, material properties and deformation processes are yet unknown. Natural samples deformed under low-grade (T<350°C) metamorphic conditions were studied in detail in the Dent de Morcles and Doldenhorn nappes of the Helvetic Alps in order to accurately simulate their deformation styles by numerical models. In these samples, monomineralic calcite (Cc) veins were repeatedly boudinaged on cm- to µm-scale. Remnants of incompletely recrystallized original vein Cc grains in the swells indicate a sequence of deformation twinning, followed by progressive dynamic recrystallization along former twin planes up to complete recrystallization in the pinches (Schmalholz and Maeder, 2012). This sequence suggests dislocation creep to be active as important deformation mechanism. In contrast to the pinch-and-swell structures, the grain size of the Cc in the surrounding matrix is much finer-grained due to pinning by secondary particles, forcing the matrix to deform under viscous granular creep, i.e. by diffusion accommodated grain boundary sliding. The deformation processes observed in the natural samples were incorporated into a numerical model in order to evaluate the rheology of both layer and matrix, using an extension to a user material subroutine (Karrech et al., 2011a) for the finite element solver ABAQUS. We implemented thermo-mechanical coupling allowing elastic, viscous and plastic deformation of Cc (Herwegh et al., in press). We simulate a pure-shear box using finite elements, each representing a grain size distribution, which undergo layer-parallel extension. The box is built up by 3 layers, consisting of a central layer of coarse-grained populations, surrounded by finer-grained populations on bottom and top. The rheology evolves from transient stages (elasticity and strain hardening) to composite viscous flow (GSI & GSS) with increasing shear strain. The small grain sizes in top and bottom layers are strain-invariant and limited in their growth (comparable to Zener pinning) forcing the matrix to deform by exclusively by GSS creep. In contrast, the initially coarse grain sizes of the central layer are allowed to adapt to the physical deformation conditions by either grain growth or grain size reduction following the Paleowattmeter of Austin and Evans (2007) combined with the thermodynamic approach of Regenauer-Lieb and Yuen (2004). Depending on the dissipated energy, grain sizes in these domains vary substantially in space and time. While low strain rates (low stresses) in the swells favor grain growth and GSI dominated deformation, high strain rates in the pinches provoke dramatic grain size reduction with an increasing contribution of GSS as a function of decreasing grain size. The development of symmetric necks observed in nature thus seems to coincide with the transition from dislocation to diffusion creep dominated flow with continuous grain size reduction and growth from swell to neck at relatively high extensional strains. REFERENCES Austin, N. and Evans, B. (2007). Paleowattmeters: A scaling relation for dynamically recrystallized grain size. Geology, 35. Goscombe, B.D., Passchier, C.W. and Hand, M. (2004). Boudinage classification: End-member boudin types and modified boudin structures, Journal of Structural Geology, 26. Herwegh, M., Poulet, T., Karrech, A. and Regenauer-Lieb, K. (in press). From transient to steady state deformation and grain size: A thermodynamic approach using elasto-visco-plastic numerical modeling. Journal of Geophysical Research. Karrech, A., Regenauer-Lieb, K. and Poulet, T. (2011a). A Damaged visco-plasticity model for pressure and temperature sensitive geomaterials. Journal of Engineering Science 49. Regenauer-Lieb, K. and Yuen, D. (2004). Positive feedback of interacting ductile faults from coupling of equation of state, rheology and thermal-mechanics. Physics of the Earth and Planetary Interiors, 142. Schmalholz, S.M. and Maeder, X. (2012). Pinch-and-swell structure and shear zones in viscoplastic layers. Journal of Structural Geology, 34.

Plastic deformation behaviors of Ni- and Zr-based bulk metallic glasses subjected to nanoindentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weizhong, Liang, E-mail: wzliang1966@126.com; Zhiliang, Ning; Zhenqian, Dang

2013-12-15

Plastic deformation behaviors of Ni{sub 42}Ti{sub 20}Zr{sub 21.5}Al{sub 8}Cu{sub 5}Si{sub 3.5} and Zr{sub 51}Ti{sub 5}Ni{sub 10}Cu{sub 25}Al{sub 9} bulk metallic glasses at room temperature were studied by nanoindentation testing and atomic force microscopy under equivalent indentation experimental conditions. The different chemical composition of these two bulk metallic glasses produced variant tendencies for displacement serrated flow to occur during the loading process. The nanoindentation strain rate was calculated as a function of indentation displacement in order to verify the occurrence of displacement serrated flow at different loading rates. Atomic force microscopy revealed decreasing numbers of discrete shear bands around the indentationmore » sites as loading rates increased from 0.025 to 2.5 mNs{sup −1}. Variations in plastic deformation behaviors between Ni and Zr-based glasses materials can be explained by the different metastable microstructures and thermal stabilities of the two materials. The mechanism governing plastic deformation of these metallic glasses was analyzed in terms of an established model of the shear transformation zone. - Highlights: • Plastic deformation of Ni- and Zr-based BMG is studied under identical conditions • Zr-based BMG undergoes a greater extent of plastic deformation than Ni-based BMG • Nanoindentation strain rate is studied to clarify variation in plastic deformation • Metastable microstructure, thermal stability affect BMG plastic deformation.« less

FEM modeling of postseismic deformation of poroelastic material

NASA Astrophysics Data System (ADS)

Kawamoto, S.; Ito, T.; Hirahara, K.

2004-12-01

Following a large earthquake, postseismic deformation in the focal region has been observed by GPS, leveling measurements and the other geodetic measurements. To explain the postseismic deformation, researchers have proposed and well investigated two physical mechanisms of afterslip and viscoelastic relaxation. In some cases, however, there have been observed postseismic deformation which can not be explained by these mechanisms. Therefore, another mechanism has been proposed, where the crust is treated as "poroelastic material". This concept is called "poroelasticity". In this concept, postseismic deformation is caused by pore fluid flow due to the coseismic stress redistribution. We explored, therefore, the postseismic deformation due to pore fluid flow in a poroelastic material using finite element method (FEM), which can easily handle lateral variations of hydraulic diffusivity and elastic or plastic property. We used the FEM program 'CAMBIOT3D' originally developed by Geotech. Lab. Gunma University, Japan (2003). Because this program was developed for soil mechanics, we must have modified so as to calculate deformation due to earthquake faulting. We implemented the 'split node technique' (Melosh and Refsky, 1981) to calculate the coseismic deformation. In addition to this, we modified the program to calculate the deformation taking into account the Skempton's B. This coefficient B determines what fraction of the coseismic stress due to an earthquake is allotted to pore pressure. Without Skempton's B, coseismic pore pressure becomes too large and hence postseismic deformation is calculated too large. We evaluated the postseismic deformation in a poroelastic material to show that the poroelastic deformation is quite different from that of afterslip and viscoelastic relaxation models. In this presentation, we show the postseismic deformation due to pore fluids flow in a poroelastic material and the effect of Skempton's B. Especially, we discuss what different pattern of postseismic deformation is produced depending on the lateral variation of hydraulic diffusivity structures in and around the fault zone, which structures have been differently inferred from fault zone core sampling researches and so on.

Coseismic flow of frictional melts: insights from mini-AMS measurements on pseudotachylyte

NASA Astrophysics Data System (ADS)

Geissman, J. W.; Leibovitz, N.; Meado, A.; Campbell, L.; Ferre, E. C.

2017-12-01

Fault pseudotachylytes, widely regarded as earthquake fossils, are fascinating rocks that may hold important clues on the physics of seismic rupture and the lubrication of fault planes. Forceful injection of rapidly produced melts along a friction zone typically forms a complex network of veins along the slip zone and at a high angle to the generation plane. The flow patterns of these pseudotachylyte melts remain, however, poorly constrained except in rare cases when billow-like folds or other flow structures are preserved. Recent modifications to the anisotropy of magnetic susceptibility (AMS) method allow new directions of investigations of melt kinematics in pseudotachylyte veins, regardless of whether they are generation or injection veins. Here we present new mini-AMS results based on series of 3.5 mm cubes (≈200 times smaller than classic sample size) of pseudotachylyte veins from the Val Gilba (Italian Alps), the Cima di Gratera (Corsica) and Santa Rosa (California) classic localities. These preliminary analyses demonstrate the potential of this new mini-AMS method in tracking the complex coseismic movement of a low viscosity magma through dynamically deformed conduits. The lack of plastic deformation in pseudotachylyte clasts and along the pseudotachylyte margins supports the hypothesis that the coseismic melt flow pattern is frozen in situ without significant subsolidus deformation.

Fluctuation relation based continuum model for thermoviscoplasticity in metals

NASA Astrophysics Data System (ADS)

Roy Chowdhury, Shubhankar; Roy, Debasish; Reddy, J. N.; Srinivasa, Arun

2016-11-01

A continuum plasticity model for metals is presented from considerations of non-equilibrium thermodynamics. Of specific interest is the application of a fluctuation relation that subsumes the second law of thermodynamics en route to deriving the evolution equations for the internal state variables. The modelling itself is accomplished in a two-temperature framework that appears naturally by considering the thermodynamic system to be composed of two weakly interacting subsystems, viz. a kinetic vibrational subsystem corresponding to the atomic lattice vibrations and a configurational subsystem of the slower degrees of freedom describing the motion of defects in a plastically deforming metal. An apparently physical nature of the present model derives upon considering the dislocation density, which characterizes the configurational subsystem, as a state variable. Unlike the usual constitutive modelling aided by the second law of thermodynamics that merely provides a guideline to select the admissible (though possibly non-unique) processes, the present formalism strictly determines the process or the evolution equations for the thermodynamic states while including the effect of fluctuations. The continuum model accommodates finite deformation and describes plastic deformation in a yield-free setup. The theory here is essentially limited to face-centered cubic metals modelled with a single dislocation density as the internal variable. Limited numerical simulations are presented with validation against relevant experimental data.

Modeling of composite coupling technology for oil-gas pipeline section resource-saving repair

NASA Astrophysics Data System (ADS)

Donkova, Irina; Yakubovskiy, Yuriy; Kruglov, Mikhail

2017-10-01

The article presents a variant of modeling and calculation of a main pipeline repair section with a composite coupling installation. This section is presented in a shape of a composite cylindrical shell. The aim of this work is mathematical modeling and study of main pipeline reconstruction section stress-strain state (SSS). There has been given a description of a structure deformation mathematical model. Based on physical relations of elasticity, integral characteristics of rigidity for each layer of a two-layer pipe section have been obtained. With the help of the systems of forces and moments which affect the layers differential equations for the first and second layer (pipeline and coupling) have been obtained. The study of the SSS has been conducted using the statements and hypotheses of the composite structures deformation theory with consideration of interlayer joint stresses. The relations to describe the work of the joint have been stated. Boundary conditions for each layer have been formulated. To describe the deformation of the composite coupling with consideration of the composite cylindrical shells theory a mathematical model in the form of a system of differential equations in displacements and boundary conditions has been obtained. Calculation of a two-layer cylindrical shell under the action of an axisymmetric load has been accomplished.

An introductory review on gravitational-deformation induced structures, fabrics and modeling

NASA Astrophysics Data System (ADS)

Jaboyedoff, Michel; Penna, Ivanna; Pedrazzini, Andrea; Baroň, Ivo; Crosta, Giovanni B.

2013-10-01

Recent studies have pointed out a similarity between tectonics and slope tectonic-induced structures. Numerous studies have demonstrated that structures and fabrics previously interpreted as of purely geodynamical origin are instead the result of large slope deformation, and this led in the past to erroneous interpretations. Nevertheless, their limit seems not clearly defined, but it is somehow transitional. Some studies point out continuity between failures developing at surface with upper crust movements. In this contribution, the main studies which examine the link between rock structures and slope movements are reviewed. The aspects regarding model and scale of observation are discussed together with the role of pre-existing weaknesses in the rock mass. As slope failures can develop through progressive failure, structures and their changes in time and space can be recognized. Furthermore, recognition of the origin of these structures can help in avoiding misinterpretations of regional geology. This also suggests the importance of integrating different slope movement classifications based on distribution and pattern of deformation and the application of structural geology techniques. A structural geology approach in the landslide community is a tool that can greatly support the hazard quantification and related risks, because most of the physical parameters, which are used for landslide modeling, are derived from geotechnical tests or the emerging geophysical approaches.

The generalized Hill model: A kinematic approach towards active muscle contraction

NASA Astrophysics Data System (ADS)

Göktepe, Serdar; Menzel, Andreas; Kuhl, Ellen

2014-12-01

Excitation-contraction coupling is the physiological process of converting an electrical stimulus into a mechanical response. In muscle, the electrical stimulus is an action potential and the mechanical response is active contraction. The classical Hill model characterizes muscle contraction though one contractile element, activated by electrical excitation, and two non-linear springs, one in series and one in parallel. This rheology translates into an additive decomposition of the total stress into a passive and an active part. Here we supplement this additive decomposition of the stress by a multiplicative decomposition of the deformation gradient into a passive and an active part. We generalize the one-dimensional Hill model to the three-dimensional setting and constitutively define the passive stress as a function of the total deformation gradient and the active stress as a function of both the total deformation gradient and its active part. We show that this novel approach combines the features of both the classical stress-based Hill model and the recent active-strain models. While the notion of active stress is rather phenomenological in nature, active strain is micro-structurally motivated, physically measurable, and straightforward to calibrate. We demonstrate that our model is capable of simulating excitation-contraction coupling in cardiac muscle with its characteristic features of wall thickening, apical lift, and ventricular torsion.

Texture development in naturally compacted and experimentally deformed silty clay sediments from the Nankai Trench and Forearc, Japan

NASA Astrophysics Data System (ADS)

Schumann, Kai; Stipp, Michael; Leiss, Bernd; Behrmann, Jan H.

2014-12-01

The petrophysical properties of fine-grained marine sediments to a large extent depend on the microstructure and crystallographic preferred orientations (CPOs). In this contribution we show that Rietveld-based synchrotron texture analysis is a new and valuable tool to quantify textures of water-saturated fine-grained phyllosilicate-rich sediments, and assess the effects of compaction and tectonic deformation. We studied the CPO of compositionally almost homogeneous silty clay drillcore samples from the Nankai Accretionary Prism slope and the incoming Philippine Sea plate, offshore SW Japan. Basal planes of phyllosilicates show bedding-parallel alignment increasing with drillhole depth, thus reflecting progressive burial and compaction. In some samples calcite and albite display a CPO due to crystallographically controlled non-isometric grain shapes, or nannofossil tests. Consolidated-undrained experimental deformation of a suite of thirteen samples from the prism slope shows that the CPOs of phyllosilicate and calcite basal planes develop normal to the experimental shortening axis. There is at least a qualitative relation between CPO intensity and strain magnitude. Scanning electron micrographs show concurrent evolution of preferred orientations of micropores and detrital illite flakes normal to axial shortening. This indicates that the microfabrics are sensitive strain gauges, and contribute to anisotropic physical properties along with the CPO.

The quest for novel modes of excitation in exotic nuclei

NASA Astrophysics Data System (ADS)

Paar, N.

2010-06-01

This paper provides an insight into several open problems in the quest for novel modes of excitation in nuclei with isospin asymmetry, deformation and finite-temperature characteristics in stellar environments. Major unsolved problems include the nature of pygmy dipole resonances, the quest for various multipole and spin-isospin excitations both in neutron-rich and proton drip-line nuclei mainly driven by loosely bound nucleons, excitations in unstable deformed nuclei and evolution of their properties with the shape phase transition. Exotic modes of excitation in nuclei at finite temperatures characteristic of supernova evolution present open problems with a possible impact in modeling astrophysically relevant weak interaction rates. All these issues challenge self-consistent many-body theory frameworks at the frontiers of on-going research, including nuclear energy density functionals, both phenomenological and constrained by the strong interaction physics of QCD, models based on low-momentum two-nucleon interaction Vlow-k and correlated realistic nucleon-nucleon interaction VUCOM, supplemented by three-body force, as well as two-nucleon and three-nucleon interactions derived from the chiral effective field theory. Joined theoretical and experimental efforts, including research with radioactive isotope beams, are needed to provide insight into dynamical properties of nuclei away from the valley of stability, involving the interplay of isospin asymmetry, deformation and finite temperature.

Comparative experimental investigation on the actuation mechanisms of ionic polymer–metal composites with different backbones and water contents

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhu, Zicai; Chang, Longfei; Wang, Yanjie

2014-03-28

Water-based ionic polymer–metal composites (IPMCs) exhibit complex deformation properties, especially when the water content changes. To explore the general actuation mechanisms, both Nafion and Flemion membranes are used as the polymer backbones. IPMC deformation includes three stages: fast anode deformation, relaxation deformation, and slow anode deformation, which is mainly dependent on the water content and the backbone. When the water content decreases from 21 to 14 wt. %, Nafion–IPMC exhibits a large negative relaxation deformation, zero deformation, a positive relaxation deformation, and a positive steady deformation without relaxation in sequence. Despite the slow anode deformation, Flemion–IPMC also shows a slight relaxation deformation,more » which disappears when the water content is less than 13 wt. %. The different water states are investigated at different water contents using nuclear magnetic resonance spectroscopy. The free water, which decreases rapidly at the beginning through evaporation, is proven to be critical for relaxation deformation. For the backbone, indirect evidence from the steady current response is correlated with the slow anode deformation of Flemion-IPMC. The latter is explained by the secondary dissociation of the weak acid group –COOH. Finally, we thoroughly explain not only the three deformations by swelling but also their evolvement with decreasing water content. A fitting model is also presented based on a multi-diffusion equation to reveal the deformation processes more clearly, the results from which are in good agreement with the experimental results.« less

Grain rotation and lattice deformation during photoinduced chemical reactions revealed by in situ X-ray nanodiffraction.

PubMed

Huang, Zhifeng; Bartels, Matthias; Xu, Rui; Osterhoff, Markus; Kalbfleisch, Sebastian; Sprung, Michael; Suzuki, Akihiro; Takahashi, Yukio; Blanton, Thomas N; Salditt, Tim; Miao, Jianwei

2015-07-01

In situ X-ray diffraction (XRD) and transmission electron microscopy (TEM) have been used to investigate many physical science phenomena, ranging from phase transitions, chemical reactions and crystal growth to grain boundary dynamics. A major limitation of in situ XRD and TEM is a compromise that has to be made between spatial and temporal resolution. Here, we report the development of in situ X-ray nanodiffraction to measure high-resolution diffraction patterns from single grains with up to 5 ms temporal resolution. We observed, for the first time, grain rotation and lattice deformation in chemical reactions induced by X-ray photons: Br(-) + hv → Br + e(-) and e(-) + Ag(+) → Ag(0). The grain rotation and lattice deformation associated with the chemical reactions were quantified to be as fast as 3.25 rad s(-1) and as large as 0.5 Å, respectively. The ability to measure high-resolution diffraction patterns from individual grains with a temporal resolution of several milliseconds is expected to find broad applications in materials science, physics, chemistry and nanoscience.

The physics of the unconventional motility strategy of euglenids

NASA Astrophysics Data System (ADS)

Arroyo, Marino; Noselli, Giovanni; Desimone, Antonio

Euglenids are a family of unicellular protists, which use flagella to move in a fluid. However, they are also capable of performing elegantly concerted large amplitude deformations of the cell shape, in what is known as metaboly. To perform metaboly, euglenids use an elaborate cortical complex capable of actively imposing spatially modulated shear deformations on the cell surface. This mode of cell deformation has been linked to motility, but biophysical studies have demonstrated that it leads to very small swimming velocities as compared to flagellar locomotion. Furthermore, why would these cells possess two elaborate apparatus for the same function remains unclear. In this work, we combine experimental observations of euglena gracilis cells with theoretical models to shed light into the function of metaboly. The theoretical models account for the force generation and shape evolution at the cell envelop, together with the mechanical interaction of the cell with its environment. We characterize the efficiency of the two modes of locomotion of this cells in terms of the physical nature of their environment. ERC AdG 340685 MicroMotility.

Correlation of phonatory behavior with vocal fold structure, observed in a physical model

NASA Astrophysics Data System (ADS)

Krane, Michael; Walters, Gage; McPhail, Michael

2017-11-01

The effect of vocal fold shape and internal structure on phonation was studied experimentally using a physical model of the human airway. Model folds used a ``M5'' or a swept ellipse coronal cross-section shape. Models were molded in either 2 or three layers. Two-layer models included a more stiff ``body'' layer and a much softer ``cover'' layer, while the 3-layer models also incorporated an additional, thin, ``ligament/conus'' layer stiffer than the body layer. The elliptical section models were all molded in 3 such layers. Measurements of transglottal pressure, volume flow, mouth sound pressure, and high-speed imaging of vocal fold vibration were performed. These show that models with the ``ligament'' layer experienced much attenuated vertical deformation, that glottal closure was more likely, and that phonation was much easier to initiate. These findings suggest that the combination of the vocal ligament and the conus elasticus stabilize the vocal fold for efficient phonation by limiting vertical deformation, while allowing transverse deformations to occur. Acknowledge support from NIH DC R01005642-11.

High quality transmission Kikuchi diffraction analysis of deformed alloys - Case study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tokarski, Tomasz, E-mail: tokarski@agh.edu.pl

Modern scanning electron microscopes (SEM) equipped with thermally assisted field emission guns (Schottky FEG) are capable of imaging with a resolution in the range of several nanometers or better. Simultaneously, the high electron beam current can be used, which enables fast chemical and crystallographic analysis with a higher resolution than is normally offered by SEM with a tungsten cathode. The current resolution that limits the EDS and EBSD analysis is related to materials' physics, particularly to the electron-specimen interaction volume. The application of thin, electron-transparent specimens, instead of bulk samples, improves the resolution and allows for the detailed analysis ofmore » very fine microstructural features. Beside the typical imaging mode, it is possible to use a standard EBSD camera in such a configuration that only transmitted and scattered electrons are detected. This modern approach was successfully applied to various materials giving rise to significant resolution improvement, especially for the light element magnesium based alloys. This paper presents an insight into the application of the transmission Kikuchi diffraction (TKD) technique applied to the most troublesome, heavily-deformed materials. In particular, the values of the highest possible acquisition rates for high resolution and high quality mapping were estimated within typical imaging conditions of stainless steel and magnesium-yttrium alloy. - Highlights: •Monte Carlo simulations were used to simulate EBSD camera intensity for various measuring conditions. •Transmission Kikuchi diffraction parameters were evaluated for highly deformed, light and heavy elements based alloys. •High quality maps with 20 nm spatial resolution were acquired for Mg and Fe based alloys. •High speed TKD measurements were performed at acquisition rates comparable to the reflection EBSD.« less

Micromechanics Analysis Code With Generalized Method of Cells (MAC/GMC): User Guide. Version 3

NASA Technical Reports Server (NTRS)

Arnold, S. M.; Bednarcyk, B. A.; Wilt, T. E.; Trowbridge, D.

1999-01-01

The ability to accurately predict the thermomechanical deformation response of advanced composite materials continues to play an important role in the development of these strategic materials. Analytical models that predict the effective behavior of composites are used not only by engineers performing structural analysis of large-scale composite components but also by material scientists in developing new material systems. For an analytical model to fulfill these two distinct functions it must be based on a micromechanics approach which utilizes physically based deformation and life constitutive models and allows one to generate the average (macro) response of a composite material given the properties of the individual constituents and their geometric arrangement. Here the user guide for the recently developed, computationally efficient and comprehensive micromechanics analysis code, MAC, who's predictive capability rests entirely upon the fully analytical generalized method of cells, GMC, micromechanics model is described. MAC/ GMC is a versatile form of research software that "drives" the double or triply periodic micromechanics constitutive models based upon GMC. MAC/GMC enhances the basic capabilities of GMC by providing a modular framework wherein 1) various thermal, mechanical (stress or strain control) and thermomechanical load histories can be imposed, 2) different integration algorithms may be selected, 3) a variety of material constitutive models (both deformation and life) may be utilized and/or implemented, and 4) a variety of fiber architectures (both unidirectional, laminate and woven) may be easily accessed through their corresponding representative volume elements contained within the supplied library of RVEs or input directly by the user, and 5) graphical post processing of the macro and/or micro field quantities is made available.

Assessment of mild steel damage characteristics by physical methods

NASA Astrophysics Data System (ADS)

Botvina, L. R.; Soldatenkov, A. P.; Levin, V. P.; Tyutin, M. R.; Demina, Yu. A.; Petersen, T. B.; Dubov, A. A.; Semashko, N. A.

2016-01-01

The deformation and fracture localization characteristics are estimated by the methods of replicas, acoustic emission, metal magnetic memory, ultrasonic attenuation, microhardness, and electrical resistance. The relation between the estimated physical parameters on the one hand and the plastic zone size and the microcrack concentration in this zone, on the other, is considered.

Fluctuating Nonlinear Spring Model of Mechanical Deformation of Biological Particles

PubMed Central

Kononova, Olga; Snijder, Joost; Kholodov, Yaroslav; Marx, Kenneth A.; Wuite, Gijs J. L.; Roos, Wouter H.; Barsegov, Valeri

2016-01-01

The mechanical properties of virus capsids correlate with local conformational dynamics in the capsid structure. They also reflect the required stability needed to withstand high internal pressures generated upon genome loading and contribute to the success of important events in viral infectivity, such as capsid maturation, genome uncoating and receptor binding. The mechanical properties of biological nanoparticles are often determined from monitoring their dynamic deformations in Atomic Force Microscopy nanoindentation experiments; but a comprehensive theory describing the full range of observed deformation behaviors has not previously been described. We present a new theory for modeling dynamic deformations of biological nanoparticles, which considers the non-linear Hertzian deformation, resulting from an indenter-particle physical contact, and the bending of curved elements (beams) modeling the particle structure. The beams’ deformation beyond the critical point triggers a dynamic transition of the particle to the collapsed state. This extreme event is accompanied by a catastrophic force drop as observed in the experimental or simulated force (F)-deformation (X) spectra. The theory interprets fine features of the spectra, including the nonlinear components of the FX-curves, in terms of the Young’s moduli for Hertzian and bending deformations, and the structural damage dependent beams’ survival probability, in terms of the maximum strength and the cooperativity parameter. The theory is exemplified by successfully describing the deformation dynamics of natural nanoparticles through comparing theoretical curves with experimental force-deformation spectra for several virus particles. This approach provides a comprehensive description of the dynamic structural transitions in biological and artificial nanoparticles, which is essential for their optimal use in nanotechnology and nanomedicine applications. PMID:26821264

Microfluidic Separation of Circulating Tumor Cells Based on Size and Deformability.

PubMed

Park, Emily S; Duffy, Simon P; Ma, Hongshen

2017-01-01

Circulating tumor cells (CTCs) have been implicated as the seeds of cancer metastasis and therefore have the potential to provide significant prognostic and diagnostic values. Here, we describe a procedure for separating CTCs from whole blood based on size and deformability using the microfluidic ratchet device. This device leverages the ratcheting motion of single cells created as they are deformed through funnel-shaped constrictions using oscillatory flow in order to divert cells based on differences in size and deformability. Subsequent methods for CTC identification and enumeration using immunofluorescence after separation are also described.

The effect of leprosy-induced deformity on the nutritional status of index cases and their household members in rural South India: a socio-economic perspective.

PubMed

Diffey, B; Vaz, M; Soares, M J; Jacob, A J; Piers, L S

2000-08-01

To determine whether the socioeconomic and nutritional status of cured leprosy patients with residual deformity, and their household members, was lower than that of cured leprosy patients without deformity. Cross-sectional study. One hundred and fifty-five index cases with deformity, 100 without deformity. Also 616 household members comprising 48% of the total members enumerated. Nutritional status was evaluated using anthropometry. Disease characteristics, socio-economic parameters and household information were recorded using a questionnaire. Index cases with deformity had lower community acceptance (P<0.001), and employment (P<0.001) than those cases without deformity. Households of index cases with deformity had a lower income (P<0.01) and a lower expenditure on food (P<0.05). The presence of deformity (odds ratio (OR): 2.1-3.2, P<0.01), unemployment (OR: 2.3-4.3, P<0.01) and female gender (OR: 2.4, P<0. 01) significantly increased the risk of index cases being undernourished, as judged by body mass index (BMI) alone, or BMI and mid-upper arm circumference. A low BMI (<18.5) in the index case significantly increased the odds of other adults (OR 2.2), adolescents (OR 2.9-3.8) and children (OR 2.2) in the household being undernourished. Cured leprosy index cases with physical deformity are more undernourished than index cases without deformity. This is associated with a reduced expenditure on food, possibly brought on by increased unemployment, and a loss of income. Undernutrition in the index case increases the risk of undernutrition in other members of the family. European Journal of Clinical Nutrition (2000) 54, 643-649.

Probabilistic short-term forecasting of eruption rate at Kīlauea Volcano using a physics-based model

NASA Astrophysics Data System (ADS)

Anderson, K. R.

2016-12-01

Deterministic models of volcanic eruptions yield predictions of future activity conditioned on uncertainty in the current state of the system. Physics-based eruption models are well-suited for deterministic forecasting as they can relate magma physics with a wide range of observations. Yet, physics-based eruption forecasting is strongly limited by an inadequate understanding of volcanic systems, and the need for eruption models to be computationally tractable. At Kīlauea Volcano, Hawaii, episodic depressurization-pressurization cycles of the magma system generate correlated, quasi-exponential variations in ground deformation and surface height of the active summit lava lake. Deflations are associated with reductions in eruption rate, or even brief eruptive pauses, and thus partly control lava flow advance rates and associated hazard. Because of the relatively well-understood nature of Kīlauea's shallow magma plumbing system, and because more than 600 of these events have been recorded to date, they offer a unique opportunity to refine a physics-based effusive eruption forecasting approach and apply it to lava eruption rates over short (hours to days) time periods. A simple physical model of the volcano ascribes observed data to temporary reductions in magma supply to an elastic reservoir filled with compressible magma. This model can be used to predict the evolution of an ongoing event, but because the mechanism that triggers events is unknown, event durations are modeled stochastically from previous observations. A Bayesian approach incorporates diverse data sets and prior information to simultaneously estimate uncertain model parameters and future states of the system. Forecasts take the form of probability distributions for eruption rate or cumulative erupted volume at some future time. Results demonstrate the significant uncertainties that still remain even for short-term eruption forecasting at a well-monitored volcano - but also the value of a physics-based, mixed deterministic-probabilistic eruption forecasting approach in reducing and quantifying these uncertainties.

Atomic model of anti-phase boundaries in a face-centred icosahedral Zn Mg Dy quasicrystal

NASA Astrophysics Data System (ADS)

Wang, Jianbo; Yang, Wenge; Wang, Renhui

2003-03-01

An atomic model in the physical space for an anti-phase boundary (APB) in the ordered face-centred icosahedral Zn-Mg-Dy quasicrystal phase is presented, based on a six-dimensional model suggested by Ishimasa and Shimizu (2000 Mater. Sci. Eng. A 294-296 232, Ishimasa 2001 private communication). The physical space atomic positions of the defected structure were used for the calculation of the corresponding exit-plane wavefunction and high-resolution transmission electron microscopy images. The analysis of the defect by inverse Fourier transformation reveals that when superstructure reflection spots are used for back-transformation, then at the APB, bright lattice fringes are found to turn into dark ones, and vice versa. When fundamental reflections are used, the APB is not visible. This phenomenon is the same as the corresponding experimental study recently published by Heggen et al(2001a Phys. Rev. B 64 014202). Based on this atomic model it is found that the APB perpendicular to a fivefold axis A5 (APB-A5) is a non-conservative boundary, while the APB perpendicular to a pseudo-twofold axis A2P (APB-A2P) is a conservative one. This fact is consistent with the experimental observation (Heggen et al2002 J. Alloys Compounds 342 330) that the frequency of occurrence of APB-A5 is 90% in the heat-treated samples compared with that in the deformed samples (45%), while the frequency of occurrence of APB-A2P is 34% in the deformed samples compared with that in the heat-treated samples.

Modelling of photodegradation effect on elastic-viscoplastic behaviour of amorphous polylactic acid films

NASA Astrophysics Data System (ADS)

Belbachir, S.; Zaïri, F.; Ayoub, G.; Maschke, U.; Naït-Abdelaziz, M.; Gloaguen, J. M.; Benguediab, M.; Lefebvre, J. M.

2010-02-01

Polylactic acid (PLA) films were subjected to accelerated ultra-violet (UV) ageing. The UV irradiation leads to the alteration of the chemical structure which influences directly the mechanical response of the polymer. The chemical modification of the polymer was followed by gel permeation chromatography. Uniaxial tension tests were conducted at 50 °C and for different strain rates in order to characterize the large deformation response of PLA. The influence of UV irradiation on the alteration of the large deformation response of PLA was examined. A physically based elastic-viscoplastic model was used to describe the mechanical response of virgin PLA. The photodegradation effect was incorporated into the constitutive model to capture the stress-strain behaviour up to failure of aged PLA. To that end, the measured molecular weight was used as a direct input into the model. The model is shown to be in good agreement with experimental results over a wide range of UV irradiation doses.

Tough Al-alginate/poly(N-isopropylacrylamide) hydrogel with tunable LCST for soft robotics.

PubMed

Zheng, Wen Jiang; An, Ning; Yang, Jian Hai; Zhou, Jinxiong; Chen, Yong Mei

2015-01-28

Tough Al-alginate/poly(N-isopropylacrylamide) (PNIPAM) hydrogel has been synthesized by introducing an interpenetrating network with hybrid physically cross-linked alginate and chemically cross-linked PNIPAM. Varying the concentration of AlCl3 regulates the mechanical properties of the tough hydrogel and tunes its lower critical solution temperature (LCST) as well. The tough Al-alginate/PNIPAM exhibits 6.3 ± 0.3 MPa of compressive stress and 9.95 of uniaxial stretch. Tunability of LCST is also achieved in a wide range within 22.5-32 °C. A bending beam actuator and a four-arm gripper made of bilayer (Na-alginate/PNIPAM)/(Al-alginate/PNIPAM) hydrogel as prototype of all-hydrogel soft robotics are demonstrated. A finite element (FE) simulation model is developed to simulate the deformation of the soft robotics. The FE simulation not only reproduces the deformation process of performed experiments but also predicts more complicated devices that can be explored in the future. This work broadens the application of temperature-responsive PNIPAM-based hydrogels.

Towards mechanism-based simulation of impact damage using exascale computing

NASA Astrophysics Data System (ADS)

Shterenlikht, Anton; Margetts, Lee; McDonald, Samuel; Bourne, Neil K.

2017-01-01

Over the past 60 years, the finite element method has been very successful in modelling deformation in engineering structures. However the method requires the definition of constitutive models that represent the response of the material to applied loads. There are two issues. Firstly, the models are often difficult to define. Secondly, there is often no physical connection between the models and the mechanisms that accommodate deformation. In this paper, we present a potentially disruptive two-level strategy which couples the finite element method at the macroscale with cellular automata at the mesoscale. The cellular automata are used to simulate mechanisms, such as crack propagation. The stress-strain relationship emerges as a continuum mechanics scale interpretation of changes at the micro- and meso-scales. Iterative two-way updating between the cellular automata and finite elements drives the simulation forward as the material undergoes progressive damage at high strain rates. The strategy is particularly attractive on large-scale computing platforms as both methods scale well on tens of thousands of CPUs.

Deformation and Breakup of a Stretching Liquid Bridge

NASA Astrophysics Data System (ADS)

Franses, Elias I.; Liao, Ying-Chih; Basaran, Osman

2004-11-01

Surfactants are routinely used to control the breakup of drops and jets in applications as diverse as ink jet printing, crop spraying, and microarraying. While highly accurate algorithms for studying the breakup of surfactant-free drops and jets are well documented and a great deal of information is now available in such situations, little is known about the closely related problem of interface rupture when surfactant effects cannot be neglected. Here we analyze the deformation and breakup of a stretching liquid bridge whose surface is covered with an insoluble surfactant monolayer by means of a two-dimensional (2-d) finite element algorithm using elliptic mesh generation. That the predictions made with the 2-d algorithm are faithful to the physics is confirmed by demonstrating that the computed results accord well with our new high-speed visualization experiments and existing scaling theories. Comparisons are also made to computations made with a one-dimensional (1-d) algorithm based on the slender-jet equations.

Interferometric imaging of the 2011-2013 Campi Flegrei unrest

NASA Astrophysics Data System (ADS)

De Siena, Luca; Nakahara, Hisashi; Zaccarelli, Lucia; Sammarco, Carmelo; La Rocca, Mario; Bianco, Francesca

2017-04-01

After its 1983-84 seismic and deformation crisis, seismologists have recorded very low and clustered seismicity at Campi Flegrei caldera (Italy). Hence, noise interferometry imaging has become the only option to image the present volcano logical state of the volcano. Three-component noise data recorded before, during, and after Campi Flegrei last deformation and geochemical unrest (2011-2013) have thus been processed with up-to-date interferometric imaging workflow based on MSNoise. Noise anisotropy, which strongly affects measurements throughout the caldera at all frequencies, has been accounted for by self-correlation measurements and smoothed by phase weighted stacking and phase-match filtering. The final group-velocity maps show strong low-velocity anomalies at the location of the last Campi Flegrei eruption (1538 A.D.). The main low-velocity anomalies contour Solfatara volcano and follow geomorphological cross-faulting. The comparison with geophysical imaging results obtained during the last seismic unrest at the caldera suggest strong changes in the physical properties of the volcano, particularly in the area of major hydrogeological hazard.

A regional test of global models for flow, rheology, and seismic anisotropy at the base of the mantle

NASA Astrophysics Data System (ADS)

Ford, Heather A.; Long, Maureen D.

2015-08-01

The study of flow patterns and seismic anisotropy in the lowermost mantle is fraught with uncertainties, given the limitations in our understanding of the physical properties of the lowermost mantle and the relationships between deformation and anisotropy. Here we use a set of SKS, SKKS, and ScS splitting measurements that sample the eastern edge of the African Large Low Shear Velocity Province to test predictions of seismic anisotropy derived from previously published 3D global mantle flow models and anisotropy modeling (Walker et al., 2011). The observations can be fit by a model that invokes flow directed to the southwest with a component of downwelling in our study region, and slip that occurs along the (0 1 0) plane of post-perovskite. Most importantly, we demonstrate the ability of a regional shear wave splitting data set to test the robustness of models for flow and deformation in the lowermost mantle.

Analytic regularization of uniform cubic B-spline deformation fields.

PubMed

Shackleford, James A; Yang, Qi; Lourenço, Ana M; Shusharina, Nadya; Kandasamy, Nagarajan; Sharp, Gregory C

2012-01-01

Image registration is inherently ill-posed, and lacks a unique solution. In the context of medical applications, it is desirable to avoid solutions that describe physically unsound deformations within the patient anatomy. Among the accepted methods of regularizing non-rigid image registration to provide solutions applicable to medical practice is the penalty of thin-plate bending energy. In this paper, we develop an exact, analytic method for computing the bending energy of a three-dimensional B-spline deformation field as a quadratic matrix operation on the spline coefficient values. Results presented on ten thoracic case studies indicate the analytic solution is between 61-1371x faster than a numerical central differencing solution.

Crustal deformation in Great California Earthquake cycles

NASA Technical Reports Server (NTRS)

Li, Victor C.; Rice, James R.

1987-01-01

A model in which coupling is described approximately through a generalized Elsasser model is proposed for computation of the periodic crustal deformation associated with repeated strike-slip earthquakes. The model is found to provide a more realistic physical description of tectonic loading than do simpler kinematic models. Parameters are chosen to model the 1857 and 1906 San Andreas ruptures, and predictions are found to be consistent with data on variations of contemporary surface strain and displacement rates as a function of distance from the 1857 and 1906 rupture traces. Results indicate that the asthenosphere appropriate to describe crustal deformation on the earthquake cycle time scale lies in the lower crust and perhaps the crust-mantle transition zone.

Superstatistics with different kinds of distributions in the deformed formalism

NASA Astrophysics Data System (ADS)

Sargolzaeipor, S.; Hassanabadi, H.; Chung, W. S.

2018-03-01

In this article, after first introducing superstatistics, the effective Boltzmann factor in a deformed formalism for modified Dirac delta, uniform, two-level and Gamma distributions is derived. Then we make use of the superstatistics for four important problems in physics and the thermodynamic properties of the system are calculated. All results in the limit case are reduced to ordinary statistical mechanics. Furthermore, effects of all parameters in the problems are calculated and shown graphically.

Quantum corrections to newtonian potential and generalized uncertainty principle

NASA Astrophysics Data System (ADS)

Scardigli, Fabio; Lambiase, Gaetano; Vagenas, Elias

2017-08-01

We use the leading quantum corrections to the newtonian potential to compute the deformation parameter of the generalized uncertainty principle. By assuming just only General Relativity as theory of Gravitation, and the thermal nature of the GUP corrections to the Hawking spectrum, our calculation gives, to first order, a specific numerical result. We briefly discuss the physical meaning of this value, and compare it with the previously obtained bounds on the generalized uncertainty principle deformation parameter.

A method to map errors in the deformable registration of 4DCT images1

PubMed Central

Vaman, Constantin; Staub, David; Williamson, Jeffrey; Murphy, Martin J.

2010-01-01

Purpose: To present a new approach to the problem of estimating errors in deformable image registration (DIR) applied to sequential phases of a 4DCT data set. Methods: A set of displacement vector fields (DVFs) are made by registering a sequence of 4DCT phases. The DVFs are assumed to display anatomical movement, with the addition of errors due to the imaging and registration processes. The positions of physical landmarks in each CT phase are measured as ground truth for the physical movement in the DVF. Principal component analysis of the DVFs and the landmarks is used to identify and separate the eigenmodes of physical movement from the error eigenmodes. By subtracting the physical modes from the principal components of the DVFs, the registration errors are exposed and reconstructed as DIR error maps. The method is demonstrated via a simple numerical model of 4DCT DVFs that combines breathing movement with simulated maps of spatially correlated DIR errors. Results: The principal components of the simulated DVFs were observed to share the basic properties of principal components for actual 4DCT data. The simulated error maps were accurately recovered by the estimation method. Conclusions: Deformable image registration errors can have complex spatial distributions. Consequently, point-by-point landmark validation can give unrepresentative results that do not accurately reflect the registration uncertainties away from the landmarks. The authors are developing a method for mapping the complete spatial distribution of DIR errors using only a small number of ground truth validation landmarks. PMID:21158288

Predicting translational deformity following opening-wedge osteotomy for lower limb realignment.

PubMed

Barksfield, Richard C; Monsell, Fergal P

2015-11-01

An opening-wedge osteotomy is well recognised for the management of limb deformity and requires an understanding of the principles of geometry. Translation at the osteotomy is needed when the osteotomy is performed away from the centre of rotation of angulation (CORA), but the amount of translation varies with the distance from the CORA. This translation enables proximal and distal axes on either side of the proposed osteotomy to realign. We have developed two experimental models to establish whether the amount of translation required (based on the translation deformity created) can be predicted based upon simple trigonometry. A predictive algorithm was derived where translational deformity was predicted as 2(tan α × d), where α represents 50 % of the desired angular correction, and d is the distance of the desired osteotomy site from the CORA. A simulated model was developed using TraumaCad online digital software suite (Brainlab AG, Germany). Osteotomies were simulated in the distal femur, proximal tibia and distal tibia for nine sets of lower limb scanograms at incremental distances from the CORA and the resulting translational deformity recorded. There was strong correlation between the distance of the osteotomy from the CORA and simulated translation deformity for distal femoral deformities (correlation coefficient 0.99, p < 0.0001), proximal tibial deformities (correlation coefficient 0.93-0.99, p < 0.0001) and distal tibial deformities (correlation coefficient 0.99, p < 0.0001). There was excellent agreement between the predictive algorithm and simulated translational deformity for all nine simulations (correlation coefficient 0.93-0.99, p < 0.0001). Translational deformity following corrective osteotomy for lower limb deformity can be anticipated and predicted based upon the angular correction and the distance between the planned osteotomy site and the CORA.

A three-dimensional numerical simulation of cell behavior in a flow chamber based on fluid-solid interaction.

PubMed

Bai, Long; Cui, Yuhong; Zhang, Yixia; Zhao, Na

2014-01-01

The mechanical behavior of blood cells in the vessels has a close relationship with the physical characteristics of the blood and the cells. In this paper, a numerical simulation method was proposed to understand a single-blood cell's behavior in the vessels based on fluid-solid interaction method, which was conducted under adaptive time step and fixed time step, respectively. The main programme was C++ codes, which called FLUENT and ANSYS software, and UDF and APDL acted as a messenger to connect FLUENT and ANSYS for exchanging data. The computing results show: (1) the blood cell moved towards the bottom of the flow chamber in the beginning due to the influence of gravity, then it began to jump up when reached a certain height rather than touching the bottom. It could move downwards again after jump up, the blood cell could keep this way of moving like dancing continuously in the vessels; (2) the blood cell was rolling and deforming all the time; the rotation had oscillatory changes and the deformation became conspicuously when the blood cell was dancing. This new simulation method and results can be widely used in the researches of cytology, blood, cells, etc.

Using an Android application to assess registration strategies in open hepatic procedures: a planning and simulation tool

NASA Astrophysics Data System (ADS)

Doss, Derek J.; Heiselman, Jon S.; Collins, Jarrod A.; Weis, Jared A.; Clements, Logan W.; Geevarghese, Sunil K.; Miga, Michael I.

2017-03-01

Sparse surface digitization with an optically tracked stylus for use in an organ surface-based image-to-physical registration is an established approach for image-guided open liver surgery procedures. However, variability in sparse data collections during open hepatic procedures can produce disparity in registration alignments. In part, this variability arises from inconsistencies with the patterns and fidelity of collected intraoperative data. The liver lacks distinct landmarks and experiences considerable soft tissue deformation. Furthermore, data coverage of the organ is often incomplete or unevenly distributed. While more robust feature-based registration methodologies have been developed for image-guided liver surgery, it is still unclear how variation in sparse intraoperative data affects registration. In this work, we have developed an application to allow surgeons to study the performance of surface digitization patterns on registration. Given the intrinsic nature of soft-tissue, we incorporate realistic organ deformation when assessing fidelity of a rigid registration methodology. We report the construction of our application and preliminary registration results using four participants. Our preliminary results indicate that registration quality improves as users acquire more experience selecting patterns of sparse intraoperative surface data.

A comparative analysis of numerical approaches to the mechanics of elastic sheets

NASA Astrophysics Data System (ADS)

Taylor, Michael; Davidovitch, Benny; Qiu, Zhanlong; Bertoldi, Katia

2015-06-01

Numerically simulating deformations in thin elastic sheets is a challenging problem in computational mechanics due to destabilizing compressive stresses that result in wrinkling. Determining the location, structure, and evolution of wrinkles in these problems has important implications in design and is an area of increasing interest in the fields of physics and engineering. In this work, several numerical approaches previously proposed to model equilibrium deformations in thin elastic sheets are compared. These include standard finite element-based static post-buckling approaches as well as a recently proposed method based on dynamic relaxation, which are applied to the problem of an annular sheet with opposed tractions where wrinkling is a key feature. Numerical solutions are compared to analytic predictions of the ground state, enabling a quantitative evaluation of the predictive power of the various methods. Results indicate that static finite element approaches produce local minima that are highly sensitive to initial imperfections, relying on a priori knowledge of the equilibrium wrinkling pattern to generate optimal results. In contrast, dynamic relaxation is much less sensitive to initial imperfections and can generate low-energy solutions for a wide variety of loading conditions without requiring knowledge of the equilibrium solution beforehand.

Modeling of Propagation of Interacting Cracks Under Hydraulic Pressure Gradient

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Hai; Mattson, Earl Douglas; Podgorney, Robert Karl

A robust and reliable numerical model for fracture initiation and propagation, which includes the interactions among propagating fractures and the coupling between deformation, fracturing and fluid flow in fracture apertures and in the permeable rock matrix, would be an important tool for developing a better understanding of fracturing behaviors of crystalline brittle rocks driven by thermal and (or) hydraulic pressure gradients. In this paper, we present a physics-based hydraulic fracturing simulator based on coupling a quasi-static discrete element model (DEM) for deformation and fracturing with conjugate lattice network flow model for fluid flow in both fractures and porous matrix. Fracturingmore » is represented explicitly by removing broken bonds from the network to represent microcracks. Initiation of new microfractures and growth and coalescence of the microcracks leads to the formation of macroscopic fractures when external and/or internal loads are applied. The coupled DEM-network flow model reproduces realistic growth pattern of hydraulic fractures. In particular, simulation results of perforated horizontal wellbore clearly demonstrate that elastic interactions among multiple propagating fractures, fluid viscosity, strong coupling between fluid pressure fluctuations within fractures and fracturing, and lower length scale heterogeneities, collectively lead to complicated fracturing patterns.« less

Deformable Image Registration based on Similarity-Steered CNN Regression.

PubMed

Cao, Xiaohuan; Yang, Jianhua; Zhang, Jun; Nie, Dong; Kim, Min-Jeong; Wang, Qian; Shen, Dinggang

2017-09-01

Existing deformable registration methods require exhaustively iterative optimization, along with careful parameter tuning, to estimate the deformation field between images. Although some learning-based methods have been proposed for initiating deformation estimation, they are often template-specific and not flexible in practical use. In this paper, we propose a convolutional neural network (CNN) based regression model to directly learn the complex mapping from the input image pair (i.e., a pair of template and subject) to their corresponding deformation field. Specifically, our CNN architecture is designed in a patch-based manner to learn the complex mapping from the input patch pairs to their respective deformation field. First, the equalized active-points guided sampling strategy is introduced to facilitate accurate CNN model learning upon a limited image dataset. Then, the similarity-steered CNN architecture is designed, where we propose to add the auxiliary contextual cue, i.e., the similarity between input patches, to more directly guide the learning process. Experiments on different brain image datasets demonstrate promising registration performance based on our CNN model. Furthermore, it is found that the trained CNN model from one dataset can be successfully transferred to another dataset, although brain appearances across datasets are quite variable.

[Scoliotic spinal deformity in pilot personnel from aviation physical examination's point of view].

PubMed

Churilov, Iu K; Moiseev, Iu B; Imenovskiĭ, I É; Radchenko, S N

2013-11-01

According to results of performed examinations scoliotic spinal deformity in flight personnel has a low impact on professional health. This is proved by: oligosymptomatic course of disease - lack of complaints of pain, moderate pain, which is revealed only in case of loading tests and palpation; preservation of supporting and movement spinal function; lack of worsening of deformity during the flight service. At the same time in flight personnel suffering from scoliosis was registered a low tolerance to ergometri; robe, which point to insufficient muscle reserve of lower extremities, abdominals and dorsum. This insufficient may have an adverse effect on G-tolerance of pilots serving in maneuvering aviation. According to this fact authors came to conclusion that first-degree scoliotic deformity is of importance for expert examination of pilots of high-performance aircraft. Scoliotic deformity in pilots of other branches of aviation is of importance only in case of clinical implications (pain syndrome, restraint of movement). From there, it is not necessary to make a record in regulatory documents of flight medical board about functional-compensatory spinal deformity (first- and second degree scoliosis) in flight personnel, except flight personnel of high-performance aircraft.

Image-Guided Intraoperative Cortical Deformation Recovery Using Game Theory: Application to Neocortical Epilepsy Surgery

PubMed Central

DeLorenzo, Christine; Papademetris, Xenophon; Staib, Lawrence H.; Vives, Kenneth P.; Spencer, Dennis D.; Duncan, James S.

2010-01-01

During neurosurgery, nonrigid brain deformation prevents preoperatively-acquired images from accurately depicting the intraoperative brain. Stereo vision systems can be used to track intraoperative cortical surface deformation and update preoperative brain images in conjunction with a biomechanical model. However, these stereo systems are often plagued with calibration error, which can corrupt the deformation estimation. In order to decouple the effects of camera calibration from the surface deformation estimation, a framework that can solve for disparate and often competing variables is needed. Game theory, which was developed to handle decision making in this type of competitive environment, has been applied to various fields from economics to biology. In this paper, game theory is applied to cortical surface tracking during neocortical epilepsy surgery and used to infer information about the physical processes of brain surface deformation and image acquisition. The method is successfully applied to eight in vivo cases, resulting in an 81% decrease in mean surface displacement error. This includes a case in which some of the initial camera calibration parameters had errors of 70%. Additionally, the advantages of using a game theoretic approach in neocortical epilepsy surgery are clearly demonstrated in its robustness to initial conditions. PMID:20129844

Experimental Evaluation of a Deformable Registration Algorithm for Motion Correction in PET-CT Guided Biopsy.

PubMed

Khare, Rahul; Sala, Guillaume; Kinahan, Paul; Esposito, Giuseppe; Banovac, Filip; Cleary, Kevin; Enquobahrie, Andinet

2013-01-01

Positron emission tomography computed tomography (PET-CT) images are increasingly being used for guidance during percutaneous biopsy. However, due to the physics of image acquisition, PET-CT images are susceptible to problems due to respiratory and cardiac motion, leading to inaccurate tumor localization, shape distortion, and attenuation correction. To address these problems, we present a method for motion correction that relies on respiratory gated CT images aligned using a deformable registration algorithm. In this work, we use two deformable registration algorithms and two optimization approaches for registering the CT images obtained over the respiratory cycle. The two algorithms are the BSpline and the symmetric forces Demons registration. In the first optmization approach, CT images at each time point are registered to a single reference time point. In the second approach, deformation maps are obtained to align each CT time point with its adjacent time point. These deformations are then composed to find the deformation with respect to a reference time point. We evaluate these two algorithms and optimization approaches using respiratory gated CT images obtained from 7 patients. Our results show that overall the BSpline registration algorithm with the reference optimization approach gives the best results.

Orbital shape in intentional skull deformations and adult sagittal craniosynostoses.

PubMed

Sandy, Ronak; Hennocq, Quentin; Nysjö, Johan; Giran, Guillaume; Friess, Martin; Khonsari, Roman Hossein

2018-06-21

Intentional cranial deformations are the result of external mechanical forces exerted on the skull vault that modify the morphology of various craniofacial structures such as the skull base, the orbits and the zygoma. In this controlled study, we investigated the 3D shape of the orbital inner mould and the orbital volume in various types of intentional deformations and in adult non-operated scaphocephaly - the most common type of craniosynostosis - using dedicated morphometric methods. CT scans were performed on 32 adult skulls with intentional deformations, 21 adult skull with scaphocephaly and 17 non-deformed adult skulls from the collections of the Muséum national d'Histoire naturelle in Paris, France. The intentional deformations group included six skulls with Toulouse deformations, eight skulls with circumferential deformations and 18 skulls with antero-posterior deformations. Mean shape models were generated based on a semi-automatic segmentation technique. Orbits were then aligned and compared qualitatively and quantitatively using colour-coded distance maps and by computing the mean absolute distance, the Hausdorff distance, and the Dice similarity coefficient. Orbital symmetry was assessed after mirroring, superimposition and Dice similarity coefficient computation. We showed that orbital shapes were significantly and symmetrically modified in intentional deformations and scaphocephaly compared with non-deformed control skulls. Antero-posterior and circumferential deformations demonstrated a similar and severe orbital deformation pattern resulting in significant smaller orbital volumes. Scaphocephaly and Toulouse deformations had similar deformation patterns but had no effect on orbital volumes. This study showed that intentional deformations and scaphocephaly significantly interact with orbital growth. Our approach was nevertheless not sufficient to identify specific modifications caused by the different types of skull deformations or by scaphocephaly. © 2018 Anatomical Society.

Tilt and strain deformation induced by hydrologically active natural fractures: application to the tiltmeters installed in Sainte-Croix-aux-Mines observatory (France)

NASA Astrophysics Data System (ADS)

Longuevergne, Laurent; Florsch, Nicolas; Boudin, Frédéric; Oudin, Ludovic; Camerlynck, Christian

2009-08-01

We investigate the deformation induced by water pressure variations in hydrologically active natural fractures, and recorded by tiltmeters and strainmeters. The deformation associated with a single fracture is derived using finite-element modelling (FEM). A range in fracture geometries is explored, first to highlight the sensitivity of each geometrical parameter to the deformation, and secondly to allow transfer to observation sites. Water level variations in the fracture are then derived from a hydrological model, driven by observed rainfall, and calibrated on fracture water flow measurements. The modelling results are explicitly applied to constrain the local hydrological contribution to observations with the 100-m-long hydrostatic tiltmeter installed at Sainte-Croix-aux-Mines (France). Our study shows that well-founded physical modelling of local hydrological effect allows a substantial correction of records in observatories.

Cryodeformation of metals under isotropic compression (Review)

NASA Astrophysics Data System (ADS)

Khaimovich, P. A.

2018-05-01

When low-temperature quasihydroextrusion of metals was originated in the 1970s, it was not initially recognized that this is not simply an addition to the list of processes for deformation of metals at cryogenic temperatures (rolling, drawing, extrusion). The resulting structures and properties, as well as the distinctive implementation of this type of deformation, indicated that this was a new domain of plastic deformation which differed from the existing method in requiring two simultaneous conditions: cryogenic temperatures and isotropic compression. Each of these conditions makes its own "contribution" to forming the structure under this deformation and, therefore, to resulting properties. Until recently, the barocryodeformation process (as it is now called) was carried out only where it was invented, at the Kharkov Institute of Physics and Technology, but these products have been studied in many laboratories in Ukraine and abroad. This review of those studies is intended to draw attention to a new and promising area of materials science.

Modeling crustal deformation near active faults and volcanic centers: a catalog of deformation models and modeling approaches

USGS Publications Warehouse

Battaglia, Maurizio; ,; Peter, F.; Murray, Jessica R.

2013-01-01

This manual provides the physical and mathematical concepts for selected models used to interpret deformation measurements near active faults and volcanic centers. The emphasis is on analytical models of deformation that can be compared with data from the Global Positioning System (GPS) receivers, Interferometric synthetic aperture radar (InSAR), leveling surveys, tiltmeters and strainmeters. Source models include pressurized spherical, ellipsoidal, and horizontal penny-shaped geometries in an elastic, homogeneous, flat half-space. Vertical dikes and faults are described following the mathematical notation for rectangular dislocations in an elastic, homogeneous, flat half-space. All the analytical expressions were verified against numerical models developed by use of COMSOL Multyphics, a Finite Element Analysis software (http://www.comsol.com). In this way, typographical errors present were identified and corrected. Matlab scripts are also provided to facilitate the application of these models.

Deformed photon-added entangled squeezed vacuum and one-photon states: Entanglement, polarization, and nonclassical properties

NASA Astrophysics Data System (ADS)

A, Karimi; M, K. Tavassoly

2016-04-01

In this paper, after a brief review on the entangled squeezed states, we produce a new class of the continuous-variable-type entangled states, namely, deformed photon-added entangled squeezed states. These states are obtained via the iterated action of the f-deformed creation operator A = f (n)a † on the entangled squeezed states. In the continuation, by studying the criteria such as the degree of entanglement, quantum polarization as well as sub-Poissonian photon statistics, the two-mode correlation function, one-mode and two-mode squeezing, we investigate the nonclassical behaviors of the introduced states in detail by choosing a particular f-deformation function. It is revealed that the above-mentioned physical properties can be affected and so may be tuned by justifying the excitation number, after choosing a nonlinearity function. Finally, to generate the introduced states, we propose a theoretical scheme using the nonlinear Jaynes-Cummings model.

Determination of accuracy of winding deformation method using kNN based classifier used for 3 MVA transformer

NASA Astrophysics Data System (ADS)

Ahmed, Mustafa Wasir; Baishya, Manash Jyoti; Sharma, Sasanka Sekhor; Hazarika, Manash

2018-04-01

This paper presents a detecting system on power transformer in transformer winding, core and on load tap changer (OLTC). Accuracy of winding deformation is determined using kNN based classifier. Winding deformation in power transformer can be measured using sweep frequency response analysis (SFRA), which can enhance the diagnosis accuracy to a large degree. It is suggested that in the results minor deformation faults can be detected at frequency range of 1 mHz to 2 MHz. The values of RCL parameters are changed when faults occur and hence frequency response of the winding will change accordingly. The SFRA data of tested transformer is compared with reference trace. The difference between two graphs indicate faults in the transformer. The deformation between 1 mHz to 1kHz gives winding deformation, 1 kHz to 100 kHz gives core deformation and 100 kHz to 2 MHz gives OLTC deformation.

Rolling friction—models and experiment. An undergraduate student project

NASA Astrophysics Data System (ADS)

Vozdecký, L.; Bartoš, J.; Musilová, J.

2014-09-01

In this paper the rolling friction (rolling resistance) model is studied theoretically and experimentally in undergraduate level fundamental general physics courses. Rolling motions of a cylinder along horizontal or inclined planes are studied by simple experiments, measuring deformations of the underlay or of the rolling body. The rolling of a hard cylinder on a soft underlay as well as of a soft cylinder on a hard underlay is studied. The experimental data are treated by the open source software Tracker, appropriate for use at the undergraduate level of physics. Interpretation of results is based on elementary considerations comprehensible to university students—beginners. It appears that the commonly accepted model of rolling resistance based on the idea of a warp (little bulge) on the underlay in front of the rolling body does not correspond with experimental results even for the soft underlay and hard rolling body. The alternative model of the rolling resistance is suggested in agreement with experiment and the corresponding concept of the rolling resistance coefficient is presented. In addition to the obtained results we can conclude that the project can be used as a task for students in practical exercises of fundamental general physics undergraduate courses. Projects of similar type effectively contribute to the development of the physical thinking of students.

Magma supply and primary melt volatile content at Kilauea Volcano from multiphysical modeling of deformation and gas emissions data (Invited)

NASA Astrophysics Data System (ADS)

Anderson, K. R.; Poland, M. P.

2013-12-01

Kilauea Volcano has been intensively studied for more than a century, yet many properties of the volcanic system remain poorly constrained, including short-term rates of magma supply, storage, and eruption, and the volatile content of the primary melt. These properties have traditionally been estimated separately using techniques that do not always produce physically-consistent results, and which require that many unknowns be fixed to assumed values. For instance, gas emissions data can provide constraint on rates of magma supply and eruption, but these inferences require assumptions about the primary melt composition. Physics-based models of volcanic systems can be used to relate a wide range of observations and physical properties to one another in a coherent system. In this work we develop a simple, holistic model of magma ascent, storage, and eruption at Kilauea Volcano. The model is capable of predicting CO2 and SO2 emissions and ground deformation and it allows us to use diverse data sets to simultaneously constrain magma fluxes and properties of the melt. Inversions are performed using a Bayesian approach, which yields probability distributions for all estimated parameters. We use observations from the ongoing Pu`u `O`o eruption of Kilauea Volcano and look for changes associated with an inferred surge in magma supply during 2003-2007. Preliminary results suggest that Kilauea's magma supply rate approximately doubled by 2006 compared to 2001 (in agreement with results by Poland et al. [2012]), that only a relatively small percentage of the magma supply was stored in the summit reservoir system, and that the CO2 content of the primary melt may be high (perhaps >1 wt%) compared with previous estimates [e.g., Gerlach et al., 2002]. This work represents a first step towards the development of more realistic physics-based models of the magma plumbing system. Such models will allow us to better utilize and interpret the remarkable diversity and quantity of geological, geochemical, and geophysical observations available at Kilauea Volcano.

TU-H-CAMPUS-JeP1-05: Dose Deformation Error Associated with Deformable Image Registration Pathways

DOE Office of Scientific and Technical Information (OSTI.GOV)

Surucu, M; Woerner, A; Roeske, J

Purpose: To evaluate errors associated with using different deformable image registration (DIR) pathways to deform dose from planning CT (pCT) to cone-beam CT (CBCT). Methods: Deforming dose is controversial because of the lack of quality assurance tools. We previously proposed a novel metric to evaluate dose deformation error (DDE) by warping dose information using two methods, via dose and contour deformation. First, isodose lines of the pCT were converted into structures and then deformed to the CBCT using an image based deformation map (dose/structure/deform). Alternatively, the dose matrix from the pCT was deformed to CBCT using the same deformation map,more » and then the same isodose lines of the deformed dose were converted into structures (dose/deform/structure). The doses corresponding to each structure were queried from the deformed dose and full-width-half-maximums were used to evaluate the dose dispersion. The difference between the FWHM of each isodose level structure is defined as the DDE. Three head-and-neck cancer patients were identified. For each patient, two DIRs were performed between the pCT and CBCT, either deforming pCT-to-CBCT or CBCT-to-pCT. We evaluated the errors associated by using either of these pathways to deform dose. A commercially available, Demons based DIR was used for this study, and 10 isodose levels (20% to 105%) were used to evaluate the errors in various dose levels. Results: The prescription dose for all patients was 70 Gy. The mean DDE for CT-to-CBCT deformation was 1.0 Gy (range: 0.3–2.0 Gy) and this was increased to 4.3 Gy (range: 1.5–6.4 Gy) for CBCT-to-CT deformation. The mean increase in DDE between the two deformations was 3.3 Gy (range: 1.0–5.4 Gy). Conclusion: The proposed DDF was used to quantitatively estimate dose deformation errors caused by different pathways to perform DIR. Deforming dose using CBCT-to-CT deformation produced greater error than CT-to-CBCT deformation.« less

Flow control by means of a traveling curvature wave in fishlike escape responses

NASA Astrophysics Data System (ADS)

Liu, Geng; Yu, Yong-Liang; Tong, Bing-Gang

2011-11-01

Fish usually bend their bodies into a ‘‘C’’ shape and then beat their tails one or more times to escape from predators (in nature) or stimuli (in experiments). The maneuvering behavior, i.e., the C-shape bending and the return flapping, is called C-start. In this paper, the escaping performance of fishlike C-start motions has been numerically investigated for a flow physics study by the use of a two-dimensional deformable foil bending and stretching quickly. The C-start motions, performed in the quiescent water and based on prescribed deforming modes, are predicted by a numerical method coupling the two-dimensional incompressible Navier-Stokes equations and the deforming body dynamic equations. It has been found earlier that a typical C-start motion consists of (1) a main C-shape bending and (2) a rearward travelling curvature wave which was seldom mentioned in previous studies. In order to reveal the flow control mechanism of the traveling curvature wave in a fish's C-start motion, two kinds of C-start flows with different deforming modes, namely the integrated mode (IM, a C-shape bending plus a travelling curvature wave) and the basic mode (BM, a C-shape bending only) are analyzed and compared in detail. According to the numerical results, it shows that if proper values of the travelling curvature wave parameters are chosen, the foil's escaping maneuverability presented in the IM is much better than that in the BM, i.e. the turn angle and the speed of the center of mass at the end of a C-start in the IM is almost twice as large as those in the BM. Further study shows that the travelling curvature wave not only can enhance the thrust and the centripetal force but also increase the propulsive efficiency. These results suggest that an efficient travelling curvature wave is of great significance in the flow control of a C-start motion. Finally, a parametric study finds that the phase difference between the C-shape bending and the travelling curvature wave (i.e., the initial phase angle in the travelling curvature wave of the deforming model) is a key parameter in the flow control. To achieve the desirable turn angle, escaping speed, and propulsive efficiency in the C-start motions, the initial phase angles must be ranged within specific magnitudes. It is found that for optimum values of the initial phase angle, the foil's flexible deforming process is qualitatively consistent with that of a fish body in nature. The results obtained in this study provide a new physical insight into the understanding of swimming mechanisms of fish's C-start maneuvers.

Flow control by means of a traveling curvature wave in fishlike escape responses.

PubMed

Liu, Geng; Yu, Yong-Liang; Tong, Bing-Gang

2011-11-01

Fish usually bend their bodies into a ''C'' shape and then beat their tails one or more times to escape from predators (in nature) or stimuli (in experiments). The maneuvering behavior, i.e., the C-shape bending and the return flapping, is called C-start. In this paper, the escaping performance of fishlike C-start motions has been numerically investigated for a flow physics study by the use of a two-dimensional deformable foil bending and stretching quickly. The C-start motions, performed in the quiescent water and based on prescribed deforming modes, are predicted by a numerical method coupling the two-dimensional incompressible Navier-Stokes equations and the deforming body dynamic equations. It has been found earlier that a typical C-start motion consists of (1) a main C-shape bending and (2) a rearward travelling curvature wave which was seldom mentioned in previous studies. In order to reveal the flow control mechanism of the traveling curvature wave in a fish's C-start motion, two kinds of C-start flows with different deforming modes, namely the integrated mode (IM, a C-shape bending plus a travelling curvature wave) and the basic mode (BM, a C-shape bending only) are analyzed and compared in detail. According to the numerical results, it shows that if proper values of the travelling curvature wave parameters are chosen, the foil's escaping maneuverability presented in the IM is much better than that in the BM, i.e. the turn angle and the speed of the center of mass at the end of a C-start in the IM is almost twice as large as those in the BM. Further study shows that the travelling curvature wave not only can enhance the thrust and the centripetal force but also increase the propulsive efficiency. These results suggest that an efficient travelling curvature wave is of great significance in the flow control of a C-start motion. Finally, a parametric study finds that the phase difference between the C-shape bending and the travelling curvature wave (i.e., the initial phase angle in the travelling curvature wave of the deforming model) is a key parameter in the flow control. To achieve the desirable turn angle, escaping speed, and propulsive efficiency in the C-start motions, the initial phase angles must be ranged within specific magnitudes. It is found that for optimum values of the initial phase angle, the foil's flexible deforming process is qualitatively consistent with that of a fish body in nature. The results obtained in this study provide a new physical insight into the understanding of swimming mechanisms of fish's C-start maneuvers.

Detecting Slow Deformation Signals Preceding Dynamic Failure: A New Strategy For The Mitigation Of Natural Hazards (SAFER)

NASA Astrophysics Data System (ADS)

Vinciguerra, Sergio; Colombero, Chiara; Comina, Cesare; Ferrero, Anna Maria; Mandrone, Giuseppe; Umili, Gessica; Fiaschi, Andrea; Saccorotti, Gilberto

2014-05-01

Rock slope monitoring is a major aim in territorial risk assessment and mitigation. The high velocity that usually characterizes the failure phase of rock instabilities makes the traditional instruments based on slope deformation measurements not applicable for early warning systems. On the other hand the use of acoustic emission records has been often a good tool in underground mining for slope monitoring. Here we aim to identify the characteristic signs of impending failure, by deploying a "site specific" microseismic monitoring system on an unstable patch of the Madonna del Sasso landslide on the Italian Western Alps designed to monitor subtle changes of the mechanical properties of the medium and installed as close as possible to the source region. The initial characterization based on geomechanical and geophysical tests allowed to understand the instability mechanism and to design the monitoring systems to be placed. Stability analysis showed that the stability of the slope is due to rock bridges. Their failure progress can results in a global slope failure. Consequently the rock bridges potentially generating dynamic ruptures need to be monitored. A first array consisting of instruments provided by University of Turin, has been deployed on October 2013, consisting of 4 triaxial 4.5 Hz seismometers connected to a 12 channel data logger arranged in a 'large aperture' configuration which encompasses the entire unstable rock mass. Preliminary data indicate the occurrence of microseismic swarms with different spectral contents. Two additional geophones and 4 triaxial piezoelectric accelerometers able to operate at frequencies up to 23 KHz will be installed during summer 2014. This will allow us to develop a network capable of recording events with Mw < 0.5 and frequencies between 700 Hz and 20 kHz. Rock physical and mechanical characterization along with rock deformation laboratory experiments during which the evolution of related physical parameters under simulated conditions of stress and fluid content will be also studied and theoretical modelling will allow to come up with a full hazard assessment and test new methodologies for a much wider scale of applications within EU.

Physically-based strength model of tantalum incorporating effects of temperature, strain rate and pressure

DOE PAGES

Lim, Hojun; Battaile, Corbett C.; Brown, Justin L.; ...

2016-06-14

In this work, we develop a tantalum strength model that incorporates e ects of temperature, strain rate and pressure. Dislocation kink-pair theory is used to incorporate temperature and strain rate e ects while the pressure dependent yield is obtained through the pressure dependent shear modulus. Material constants used in the model are parameterized from tantalum single crystal tests and polycrystalline ramp compression experiments. It is shown that the proposed strength model agrees well with the temperature and strain rate dependent yield obtained from polycrystalline tantalum experiments. Furthermore, the model accurately reproduces the pressure dependent yield stresses up to 250 GPa.more » The proposed strength model is then used to conduct simulations of a Taylor cylinder impact test and validated with experiments. This approach provides a physically-based multi-scale strength model that is able to predict the plastic deformation of polycrystalline tantalum through a wide range of temperature, strain and pressure regimes.« less

Aeroelastic Modeling of a Nozzle Startup Transient

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Zhao, Xiang; Zhang, Sijun; Chen, Yen-Sen

2014-01-01

Lateral nozzle forces are known to cause severe structural damage to any new rocket engine in development during test. While three-dimensional, transient, turbulent, chemically reacting computational fluid dynamics methodology has been demonstrated to capture major side load physics with rigid nozzles, hot-fire tests often show nozzle structure deformation during major side load events, leading to structural damages if structural strengthening measures were not taken. The modeling picture is incomplete without the capability to address the two-way responses between the structure and fluid. The objective of this study is to develop a tightly coupled aeroelastic modeling algorithm by implementing the necessary structural dynamics component into an anchored computational fluid dynamics methodology. The computational fluid dynamics component is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, while the computational structural dynamics component is developed under the framework of modal analysis. Transient aeroelastic nozzle startup analyses at sea level were performed, and the computed transient nozzle fluid-structure interaction physics presented,

Studying physical properties of deformed intact and fractured rocks by micro-scale hydro-mechanical-seismicity model

NASA Astrophysics Data System (ADS)

Raziperchikolaee, Samin

The pore pressure variation in an underground formation during hydraulic stimulation of low permeability formations or CO2 sequestration into saline aquifers can induce microseismicity due to fracture generation or pre-existing fracture activation. While the analysis of microseismic data mainly focuses on mapping the location of fractures, the seismic waves generated by the microseismic events also contain information for understanding of fracture mechanisms based on microseismic source analysis. We developed a micro-scale geomechanics, fluid-flow and seismic model that can predict transport and seismic source behavior during rock failure. This model features the incorporation of microseismic source analysis in fractured and intact rock transport properties during possible rock damage and failure. The modeling method considers comprehensive grains and cements interaction through a bonded-particle-model. As a result of grain deformation and microcrack development in the rock sample, forces and displacements in the grains involved in the bond breakage are measured to determine seismic moment tensor. In addition, geometric description of the complex pore structure is regenerated to predict fluid flow behavior of fractured samples. Numerical experiments are conducted for different intact and fractured digital rock samples, representing various mechanical behaviors of rocks and fracture surface properties, to consider their roles on seismic and transport properties of rocks during deformation. Studying rock deformation in detail provides an opportunity to understand the relationship between source mechanism of microseismic events and transport properties of damaged rocks to have a better characterizing of fluid flow behavior in subsurface formations.

Heterogeneity and anisotropy in the lithospheric mantle

NASA Astrophysics Data System (ADS)

Tommasi, Andréa; Vauchez, Alain

2015-10-01

The lithospheric mantle is intrinsically heterogeneous and anisotropic. These two properties govern the repartition of deformation, controlling intraplate strain localization and development of new plate boundaries. Geophysical and geological observations provide clues on the types, ranges, and characteristic length scales of heterogeneity and anisotropy in the lithospheric mantle. Seismic tomography points to variations in geothermal gradient and hence in rheological behavior at scales of hundreds of km. Seismic anisotropy data substantiate anisotropic physical properties consistent at scales of tens to hundreds of km. Receiver functions imply lateral and vertical heterogeneity at scales < 10 km, which might record gradients in composition or anisotropy. Observations on naturally deformed peridotites establish that compositional heterogeneity and Crystal Preferred Orientations (CPOs) are ubiquitous from the mm to the km scales. These data allow discussing the processes that produce/destroy heterogeneity and anisotropy and constraining the time scales over which they are active. This analysis highlights: (i) the role of deformation and reactive percolation of melts and fluids in producing compositional and structural heterogeneity and the feedbacks between these processes, (ii) the weak mechanical effect of mineralogical variations, and (iii) the low volumes of fine-grained microstructures and difficulty to preserve them. In contrast, olivine CPO and the resulting anisotropy of mechanical and thermal properties are only modified by deformation. Based on this analysis, we propose that strain localization at the plate scale is, at first order, controlled by large-scale variations in thermal structure and in CPO-induced anisotropy. In cold parts of the lithospheric mantle, grain size reduction may contribute to strain localization, but the low volume of fine-grained domains limits this effect.

Co- and post-seismic shallow fault physics from near-field geodesy, seismic tomography, and mechanical modeling

NASA Astrophysics Data System (ADS)

Nevitt, J.; Brooks, B. A.; Catchings, R.; Goldman, M.; Criley, C.; Chan, J. H.; Glennie, C. L.; Ericksen, T. L.; Madugo, C. M.

2017-12-01

The physics governing near-surface fault slip and deformation are largely unknown, introducing significant uncertainty into seismic hazard models. Here we combine near-field measurements of surface deformation from the 2014 M6.0 South Napa earthquake with high-resolution seismic imaging and finite element models to investigate the effects of rupture speed, elastic heterogeneities, and plasticity on shallow faulting. We focus on two sites that experienced either predominantly co-seismic or post-seismic slip. We measured surface deformation with mobile laser scanning of deformed vine rows within 300 m of the fault at 1 week and 1 month after the event. Shear strain profiles for the co- and post-seismic sites are similar, with maxima of 0.012 and 0.013 and values exceeding 0.002 occurring within 26 m- and 18 m-wide zones, respectively. That the rupture remained buried at the two sites and produced similar deformation fields suggests that permanent deformation due to dynamic stresses did not differ significantly from the quasi-static case, which might be expected if the rupture decelerated as it approached the surface. Active-source seismic surveys, 120 m in length with 1 m geophone/shot spacing, reveal shallow compliant zones of reduced shear modulus. For the co- and post-seismic sites, the tomographic anomaly (Vp/Vs > 5) at 20 m depth has a width of 80 m and 50 m, respectively, much wider than the observed surface displacement fields. We investigate this discrepancy with a suite of finite element models in which a planar fault is buried 5 m below the surface. The model continuum is defined by either homogeneous or heterogeneous elastic properties, with or without Drucker-Prager plastic yielding, with properties derived from lab testing of similar near-surface materials. We find that plastic yielding can greatly narrow the surface displacement zone, but that the width of this zone is largely insensitive to changes in the elastic structure (i.e., the presence of a compliant zone).

Comparison of MRI-defined back muscles volume between patients with ankylosing spondylitis and control patients with chronic back pain: age and spinopelvic alignment matched study.

PubMed

Bok, Doo Hee; Kim, Jihye; Kim, Tae-Hwan

2017-02-01

To compare MRI-defined back muscle volume between AS patients and age, and spinopelvic alignment matched control patients with chronic back pain. 51 male patients with AS were enrolled. Age and spinopelvic alignment matched controls (male) were found among non-AS patients with chronic back pain. After matching procedure, fully matched controls were found in 31 of 51 AS patients (60.8%), who represent AS patients without deformity. However, matched controls were not found in 20 of 51 AS patients (39.2%), who represent AS patients with deformity. MRI parameters of back muscle (paraspinal muscle and psoas muscle) at L4/5 disc level including cross-sectional area (CSA) and fat-free cross-sectional area (FCSA) were compared between AS patients and matched controls. Covariates, including BMI, self-reported physical activity, and the presence of chronic disease, which can influence back muscle volume, were also investigated. There were no statistical differences in age, body mass index, score of back pain (NRS), and spinopelvic alignment, and physical activity between matched AS patients and control patients except for duration of back pain. All MRI parameters for paraspinal muscle volume in matched AS patients (without deformity) were significantly less than those of control patients, and significantly larger than those of non-matched AS patients (with deformity). Body size adjusted MRI parameters (relative CSA and relative FCSA) of paraspinal muscle showed strong correlations with lumbar lordosis and sacral slope. Such relationship between paraspinal muscle and spinopelvic parameters remained significant even after multivariate adjustment. AS patients without deformity already have decreased paraspinal muscle volume compared with age and spinopelvic alignment matched non-AS patients with chronic back pain. Such decrease in paraspinal muscle volume was significantly associated with kyphotic deformity of AS patients even after multivariate adjustment. Although the result of our study supports the causal relationship between muscle degeneration and kyphotic deformity in AS patients, further study is required to prove the causality.

Synchrotron Radial X-ray Diffraction Studies of Deformation of Polycrystalline MgO

NASA Astrophysics Data System (ADS)

Girard, J.; Tsujino, N.; Mohiuddin, A.; Karato, S. I.

2016-12-01

X-ray diffraction analyses have been used for decades to study mechanical properties of polycrystalline samples during in-situ high-pressure deformation. When polycrystalline materials are deformed, stresses develop in grains and lead to lattice distortion. Using X-ray diffraction we can estimate the lattice strain for each (hkl) diffraction plans and calculate the applied stress for each (hkl), using [Singh, 1993] relation. However, this method doesn't take into account plastic anisotropy. As a results of plastic anisotropy present in the material, stress estimated from this method can be largely differ depending on (hkl) diffraction planes [Karato, 2009]. Studying the stress estimate for each (hkl) plane, might help us distinguish dominant deformation mechanisms activated during deformation such as diffusion (we will observe small stress variation as a function of (hkl) diffraction planes) or dislocation creep (we will observe a stress variation as a function of (hkl) diffraction planes that could also give us clues on potential slip system activity). In this study we observed stress evolution in MgO polycrystalline samples deformed under mantle pressure and temperature for (200) and (220) diffraction planes. Using a range MgO grain sizes we were able to control the active deformation mechanism (for e.g. diffusion creep or dislocation creep). For coarse-grained specimens, we observed strong (hkl) dependence of radial strain indicating the operation of dislocation creep. The observed (hkl) dependence changes with pressure suggesting a change in the slip system: at pressures higher than 27 GPa, (200) shows larger stress estimate than (220). In contrast, at lower pressures, (220) shows larger stress estimate than (200). This might indicate a slip system transition in MgO occurring under lower mantle conditions. From {110} plane to {100} plane. This is in good agreement with theoretical predictions and numerical calculation [Amodeo et al., 2012] and has an important implication for the interpretation of seismic anisotropy in the D" layer [Karato, 1998]. Amodeo, J., Carrey P., and P. Cordier (2012), Philosophical Magazine, 92(12). Karato, S-I. (1998), Earth and planets Space, 50, 1019-1028 Karato, S.-I. (2009), Physical Review. B, 79(21). Singh, A. K., (1993), Journal of Applied Physic, 73, 4278.

Deformed supersymmetric quantum mechanics with spin variables

NASA Astrophysics Data System (ADS)

Fedoruk, Sergey; Ivanov, Evgeny; Sidorov, Stepan

2018-01-01

We quantize the one-particle model of the SU(2|1) supersymmetric multiparticle mechanics with the additional semi-dynamical spin degrees of freedom. We find the relevant energy spectrum and the full set of physical states as functions of the mass-dimension deformation parameter m and SU(2) spin q\\in (Z_{>0,}1/2+Z_{≥0}) . It is found that the states at the fixed energy level form irreducible multiplets of the supergroup SU(2|1). Also, the hidden superconformal symmetry OSp(4|2) of the model is revealed in the classical and quantum cases. We calculate the OSp(4|2) Casimir operators and demonstrate that the full set of the physical states belonging to different energy levels at fixed q are unified into an irreducible OSp(4|2) multiplet.

An electromechanical based deformable model for soft tissue simulation.

PubMed

Zhong, Yongmin; Shirinzadeh, Bijan; Smith, Julian; Gu, Chengfan

2009-11-01

Soft tissue deformation is of great importance to surgery simulation. Although a significant amount of research efforts have been dedicated to simulating the behaviours of soft tissues, modelling of soft tissue deformation is still a challenging problem. This paper presents a new deformable model for simulation of soft tissue deformation from the electromechanical viewpoint of soft tissues. Soft tissue deformation is formulated as a reaction-diffusion process coupled with a mechanical load. The mechanical load applied to a soft tissue to cause a deformation is incorporated into the reaction-diffusion system, and consequently distributed among mass points of the soft tissue. Reaction-diffusion of mechanical load and non-rigid mechanics of motion are combined to govern the simulation dynamics of soft tissue deformation. An improved reaction-diffusion model is developed to describe the distribution of the mechanical load in soft tissues. A three-layer artificial cellular neural network is constructed to solve the reaction-diffusion model for real-time simulation of soft tissue deformation. A gradient based method is established to derive internal forces from the distribution of the mechanical load. Integration with a haptic device has also been achieved to simulate soft tissue deformation with haptic feedback. The proposed methodology does not only predict the typical behaviours of living tissues, but it also accepts both local and large-range deformations. It also accommodates isotropic, anisotropic and inhomogeneous deformations by simple modification of diffusion coefficients.

Anisotropic deformations of spatially open cosmology in massive gravity theory

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazuet, Charles; Volkov, Mikhail S.; Mukohyama, Shinji, E-mail: charles.mazuet@lmpt.univ-tours.fr, E-mail: shinji.mukohyama@yukawa.kyoto-u.ac.jp, E-mail: volkov@lmpt.univ-tours.fr

We combine analytical and numerical methods to study anisotropic deformations of the spatially open homogeneous and isotropic cosmology in the ghost free massive gravity theory with flat reference metric. We find that if the initial perturbations are not too strong then the physical metric relaxes back to the isotropic de Sitter state. However, the dumping of the anisotropies is achieved at the expense of exciting the Stueckelberg fields in such a way that the reference metric changes and does not share anymore with the physical metric the same rotational and translational symmetries. As a result, the universe evolves towards amore » fixed point which does not coincide with the original solution, but for which the physical metric is still de Sitter. If the initial perturbation is strong, then its evolution generically leads to a singular anisotropic state or, for some parameter values, to a decay into flat spacetime. We also present an infinite dimensional family of new homogeneous and isotropic cosmologies in the theory.« less

Multi-instrument observations of pre-earthquake transient signatures associated with 2015 M8.3 Chile earthquake

NASA Astrophysics Data System (ADS)

Ouzounov, D.; Pulinets, S. A.; Hernandez-Pajares, M.; Garcia-Rigo, A.; De Santis, A.; Pavón, J.; Liu, J. Y. G.; Chen, C. H.; Cheng, K. C.; Hattori, K.; Stepanova, M. V.; Romanova, N.; Hatzopoulos, N.; Kafatos, M.

2016-12-01

We are conducting multi parameter validation study on lithosphere/atmosphere /ionosphere transient phenomena preceding major earthquakes particularly for the case of M8.3 of Sept 16th, 2015 in Chile. Our approach is based on monitoring simultaneously a series of different physical parameters from space: 1/Outgoing long-wavelength radiation (OLR obtained from NOAA/AVHRR); 2/ electron and electron density variations in the ionosphere via GPS Total Electron Content (GPS/TEC), and 3/geomagnetic field and plasma density variation (Swarm); and from ground: 3/ GPS crustal deformation and 4/ground-based magnetometers. The time and location of main shock was prospectively alerted in advance using the Multi Sensor Networking Approach (MSNA-LAIC) approach. We analyzed retrospectively several physical observations characterizing the state of the lithosphere, atmosphere and ionosphere several days before, during and after the M8.3 earthquakes in Illapel. Our continuous satellite monitoring of long-wave (LW) data over Chile, shows a rapid increase of emitted radiation during the end of August 2015 and an anomaly in the atmosphere was detected at 19 LT on Sept 1st, 2015, over the water near to the epicenter. On Sept 2nd Swarm magnetic measurements show an anomalous signature over the epicentral region. GPS/TEC analysis revealed an anomaly on Sept 14th and on the same day the degradation of Equatorial Ionospheric Anomaly (EIA) and disappearance of the crests of EIA as is characteristic for pre-dawn and early morning hours (11 LT) was observed. On Sept 16th co-seismic ionospheric signatures consistent with defined circular acoustic-gravity wave and different shock-acoustic waves were also observed. GPS TEC and deformation studies were computed from 48 GPS stations (2013-2015) of National Seismological Center of Chile (CSN) GPS network. A transient signal of deformation has been observed a week in advance correlated with ground-based magnetometers ULF signal fluctuation from closest to the epicenter station from the SAMBA-AMBER network. The characteristics of the observed pre-, and co - seismic transient signals associated with the M8.3 of Illapel, Chile 2015 earthquake suggested that they follow general temporal-spatial evolution pattern, which has been seen in other large earthquakes worldwide.

A fundamental discussion of what triggers localized deformation in geological materials

NASA Astrophysics Data System (ADS)

Peters, Max; Paesold, Martin; Poulet, Thomas; Herwegh, Marco; Regenauer-Lieb, Klaus; Veveakis, Manolis

2015-04-01

Discontinuous or localized structures are often marked by the transition from a homogeneously deforming into a highly localized mode. This transition has extensively been described in ductile shear zones, folding and pinch-and-swell boudinage, in natural examples, rock deformation experiments and numerical simulations, at various scales. It is conventionally assumed that ductile instabilities, which act as triggers for localized deformation, exclusively arise from structural heterogeneities, i.e. geometric interactions or material imperfections. However, Hansen et al. (2012) concluded from recent laboratory experiments that localized deformation might arise out of steady-state conditions, where the size of initial perturbations was either insufficiently large to trigger localization, or these heterogeneities were simply negligible at the scale of observation. We therefore propose the existence of a principal localization phenomenon, which is based on the material-specific rate-dependency of deformation at elevated temperatures. The concept of strain localization out of a mechanical steady state in a homogeneous material at a critical material parameter and/or deformation rate has previously been discussed for engineering materials (Gruntfest, 1963) and frictional faults (Veveakis et al., 2010). We expand this theory to visco-plastic carbonate rocks, considering deformation conditions and mechanisms encountered in naturally deformed rocks. In the numerical simulation, we implement a grain-size evolution based on the Paleowattmeter scaling relationship of Austin & Evans (2007), which takes both grain size sensitive (diffusion) and insensitive (dislocation) creep combined with grain growth into account (Herwegh et al., 2014). Based on constant strain rate simulations carried out under isothermal boundary conditions, we explore the parameter space in order to obtain the criteria for localization. We determine the criteria for the onset of localization, i.e. the critical amount of dissipative work translated into heat over the diffusive capacity of the system by an instability study designed for such materials (Gruntfest, 1963). With respect to our numerical experiments, this critical parameter determines the timing when the entire amount of deformation energy translated into heat cannot be diffusively transported out of the system anymore. The resulting local temperature rise then induces strain localization. In contrast to classical shear heating scenarios with (catastrophic) thermal runaways, temperature variations of less than 1 K are sufficient for this localization mode to occur due to the balance between heat producing (e.g. dislocation creep) and consuming (grain growth) processes in the present setup. We demonstrate that this rise in latent heat is sufficient to provoke grain growth, operating as an endothermic reaction, stabilizing the simulated localized structure in turn. Various localized ductile structures, such as folded or boudinaged layers, can therefore be placed at the same material failure mode due to fundamental energy bifurcations triggered by dissipative work out of homogeneous state. Finally, we will discuss situations, in which structural heterogeneities are considered negligible and where the energy theory described here plays an underlying role by means of a comparison between numerical experiments and natural examples. REFERENCES Austin, N. and Evans, B. (2007). Paleowattmeters: A scaling relation for dynamically recrystallized grain size. Geology, 35. Gruntfest, I.J. (1963). Thermal feedback in liquid flow, plane shear at constant stress. Transactions of the Society of Rheology, 7. Hansen, L.N. and Zimmermann, M.E. and Dillman, A.M. and Kohlstedt, D.L (2012). Strain localization in olivine aggregates at high temperature: a laboratory comparison of constant-strain-rate and constant-stress boundary conditions. Earth and Planetary Science Letters, 333-334. Herwegh, M., Poulet, T., Karrech, A. and Regenauer-Lieb, K. (2014). From transient to steady state deformation and grain size: A thermodynamic approach using elasto-visco-plastic numerical modeling. Journal of Geophysical Research, 119. Veveakis, E., Alevizos, S. and Vardoulakis, I. (2010). Chemical reaction capping of thermal instability during shear of frictional faults. Journal of Mechanics and Physics of Solids, 58.

Static and Monoharmonic Acoustic Impact on a Laminated Plate

NASA Astrophysics Data System (ADS)

Paimushin, V. N.; Gazizullin, R. K.

2017-07-01

A discrete layered damping model of a multilayer plate at small displacements and deformations, with account of the internal damping of layers according to the Thompson-Kelvin-Voight model, is presented. Based on the equations derived, an analytical solution to the static deformation problem for single-layer rectangular plate hinge-supported along its contour and subjected of a uniformly distributed pressure applied to one of its boundary planes is obtained. Its convergence to the three-dimensional solution is analyzed in relation to the dimension of mesh in the thickness direction of the plate. It is found that, for thin plates, the dimension of the problem formulated can be reduced on the basis of simplified hypotheses applied to each layer. An analytical solutions is also constructed for the forced vibrations of two- and three-layer rectangular plates hinged in the opening of an absolutely stiff dividing wall upon transmission of a monoharmonic sound wave through them. It was assumed that the dividing wall is situated between two absolutely stiff barriers; one of them, owing to the harmonic vibration with a given displacement amplitude of the plate, forms an incident sound wave, and the other is stationary and is coated by a energy-absorbing material with high damping properties. Behavior of the acoustic media in spaces between the deformable plate and the barriers is described by the classical wave equations based on the model of an ideal compressible fluid. To describe the process of dynamic deformation of the energy-absorbing coating of the fixed barrier, two-dimensional equations of motion are derived based on the model of a transversely soft layer, a linear approximation of displacement fields in the thickness direction of the coating, and the account of damping properties of its material by using the hysteresis model. The effect of physical and mechanical parameters of the mechanical system considered and of frequency of the incident sound wave on the parameter of its sound insulation, and the characteristics of stress-strain state of the plate is investigated

Dynamic characterization of human breast cancer cells using a piezoresistive microcantilever.

PubMed

Shim, Sangjo; Kim, Man Geun; Jo, Kyoungwoo; Kang, Yong Seok; Lee, Boreum; Yang, Sung; Shin, Sang-Mo; Lee, Jong-Hyun

2010-10-01

In this paper, frequency response (dynamic compression and recovery) is suggested as a new physical marker to differentiate between breast cancer cells (MCF7) and normal cells (MCF10A). A single cell is placed on the laminated piezoelectric actuator and a piezoresistive microcantilever is placed on the upper surface of the cell at a specified preload displacement (or an equivalent force). The piezoelectric actuator excites the single cell in a sinusoidal fashion and its dynamic deformation is then evaluated from the displacement converted by measuring the voltage output through a piezoresistor in the microcantilever. The microcantilever has a flat contact surface with no sharp tip, making it possible to measure the overall properties of the cell rather than the local properties. These results indicate that the MCF7 cells are more deformable in quasi-static conditions compared with MCF10A cells, consistent with known characteristics. Under conditions of high frequency of over 50 Hz at a 1 μm preload displacement, 1 Hz at a 2 μm preload displacement, and all frequency ranges tested at a 3 μm preload displacement, MCF7 cells showed smaller deformation than MCF10A cells. MCF7 cells have higher absorption than MCF10A cells such that MCF7 cells appear to have higher deformability according to increasing frequency. Moreover, larger preload and higher frequencies are shown to enhance the differences in cell deformability between the MCF7 cells and MCF10A cells, which can be used as a physical marker for differentiating between MCF10A cells and MCF7 cells, even for high-speed screening devices.

Integrated studies into characteristics of physical fields using discontinuous geomedium models under external loading

NASA Astrophysics Data System (ADS)

Usoltseva Vostrikov, OM, VI; Tsoy, PA; Semenov, VN

2018-03-01

The article presents the laboratory study of deformation in artificial layered geomaterial samples down to failure with the simultaneous measurement of stresses, strains, micro-strains and signals of microseismic emission. The analysis of the synchronized experimental data made it possible to determine features of change in the microseismicity parameters and micro-strain fields in the samples depending on the deformation stage, and also to reveal the dynamics of evolution of microfailures and the main fracture zone.

Translations on USSR Science and Technology. Physical Sciences and Technology, Number 4

DTIC Science & Technology

1976-11-23

collaboration with the Krivorozhkiy Ore-enrichment Combine and the "Artemugol’" Union, with the L’vov "Kineskop" and with the Black Sea Maritime Steamship... sea and oceans, the development of methods for preventing water pollution by petroleum and petroleum products, maximal use of the maritime fleet and... Microplastic deformation of threadlike crystals of silicon in the elastic phase of deformation in the temperature range of 20-500°C 187 Agalakova, T

The effects of strain heating in lithospheric stretching models

NASA Technical Reports Server (NTRS)

Stanton, M.; Hodge, D.; Cozzarelli, F.

1985-01-01

The deformation by stretching of a continental type lithosphere has been formulated so that the problem can be solved by a continuum mechanical approach. The deformation, stress state, and temperature distribution are constrained to satisfy the physical laws of conservation of mass, energy, momentum, and an experimentally defined rheological response. The conservation of energy equation including a term of strain energy dissipation is given. The continental lithosphere is assumed to have the rheology of an isotropic, incompressible, nonlinear viscous, two layered solid.

GUP parameter from quantum corrections to the Newtonian potential

NASA Astrophysics Data System (ADS)

Scardigli, Fabio; Lambiase, Gaetano; Vagenas, Elias C.

2017-04-01

We propose a technique to compute the deformation parameter of the generalized uncertainty principle by using the leading quantum corrections to the Newtonian potential. We just assume General Relativity as theory of Gravitation, and the thermal nature of the GUP corrections to the Hawking spectrum. With these minimal assumptions our calculation gives, to first order, a specific numerical result. The physical meaning of this value is discussed, and compared with the previously obtained bounds on the generalized uncertainty principle deformation parameter.

Risk factors associated with deforming oral habits in children aged 5 to 11: a case-control study.

PubMed

Reyes Romagosa, Daniel Enrique; Paneque Gamboa, María Rosa; Almeida Muñiz, Yamilka; Quesada Oliva, Leticia María; Escalona Oliva, Damiana; Torres Naranjo, Sonia

2014-03-31

Dental and maxillofacial anomalies have multiple and complex causes. Most frequent among these are poor oral habits. A large number of children present with oral malocclusions, most of which are caused by deforming oral habits. It is important to learn about risk factors for this condition in order to institute preventive measures, early detection and treatment, and identification of low- and high-risk groups. To identify risk factors associated with deforming oral habits, which, if maintained over time, are responsible for occlusion defects, speech disorders, and can affect physical and emotional child development. A case-control study of children presenting with deforming oral habits in the municipality of Manzanillo in Granma province was conducted between January and August 2013. 540 children aged 5 to 11 were included of which 180 had deforming oral habits and were asked to fill out a survey to identify specific type of habits leading to malocclusion. The case group was composed of children with deforming habits, and the remaining 360 children without poor oral habits were the control group. Each case was randomly matched to two control cases. The children mothers were also surveyed to gather supplemental information. Children with deforming oral habits were mostly female. At age 10, onychophagia was the predominant oral deforming habit. Risk factors detected for these habits were sociobiological maternal and child variables such as low and high birth weight, maternal breastfeeding inexperience, and discord in the family. The study identified likely risk factors associated with deforming oral habits. These are discord in the family, birth weight, and lack of breastfeeding experience.

Optimal approximation of harmonic growth clusters by orthogonal polynomials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teodorescu, Razvan

2008-01-01

Interface dynamics in two-dimensional systems with a maximal number of conservation laws gives an accurate theoreticaI model for many physical processes, from the hydrodynamics of immiscible, viscous flows (zero surface-tension limit of Hele-Shaw flows), to the granular dynamics of hard spheres, and even diffusion-limited aggregation. Although a complete solution for the continuum case exists, efficient approximations of the boundary evolution are very useful due to their practical applications. In this article, the approximation scheme based on orthogonal polynomials with a deformed Gaussian kernel is discussed, as well as relations to potential theory.

Shape Memory Alloys and Their Applications in Power Generation and Refrigeration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Jun

The shape memory effect is closely related to the reversible martensitic phase transformation, which is diffusionless and involves shear deformation. The recoverable transformation between the two phases with different crystalline symmetry results in reversible changes in physical properties such as electrical conductivity, magnetization, and elasticity. Accompanying the transformation is a change of entropy. Fascinating applications are developed based on these changes. In this paper, the history, fundamentals and technical challenges of both thermoelastic and ferromagnetic shape memory alloys are briefly reviewed; applications related to energy conversion such as power generation and refrigeration as well as recent developments will be discussed.

Shape Memory Alloys and their Applications in Power Generation and Refrigeration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Jun

The shape memory effect is closely related to the reversible martensitic phase transformation, which is diffusionless and involves shear deformation. The recoverable transformation between the two phases with different crystalline symmetry results in reversible changes in physical properties such as electrical conductivity, magnetization, and elasticity. Accompanying the transformation is a change of entropy. Fascinating applications are developed based on these changes. In this paper, the history, fundamentals and technical challenges of both thermoelastic and ferromagnetic shape memory alloys are briefly reviewed; applications related to energy conversion such as power generation and refrigeration as well as recent developments will be discussed.

A model for finite-deformation nonlinear thermomechanical response of single crystal copper under shock conditions

NASA Astrophysics Data System (ADS)

Luscher, Darby J.; Bronkhorst, Curt A.; Alleman, Coleman N.; Addessio, Francis L.

2013-09-01

A physically consistent framework for combining pressure-volume-temperature equations of state with crystal plasticity models is developed for the application of modeling the response of single and polycrystals under shock conditions. The particular model is developed for copper, thus the approach focuses on crystals of cubic symmetry although many of the concepts in the approach are applicable to crystals of lower symmetry. We employ a multiplicative decomposition of the deformation gradient into isochoric elastic, thermoelastic dilation, and plastic parts leading to a definition of isochoric elastic Green-Lagrange strain. This finite deformation kinematic decomposition enables a decomposition of Helmholtz free-energy into terms reflecting dilatational thermoelasticity, strain energy due to long-range isochoric elastic deformation of the lattice and a term reflecting energy stored in short range elastic lattice deformation due to evolving defect structures. A model for the single crystal response of copper is implemented consistent with the framework into a three-dimensional Lagrangian finite element code. Simulations exhibit favorable agreement with single and bicrystal experimental data for shock pressures ranging from 3 to 110 GPa.

Process Modelling of Curing Process-Induced Internal Stress and Deformation of Composite Laminate Structure with Elastic and Viscoelastic Models

NASA Astrophysics Data System (ADS)

Li, Dongna; Li, Xudong; Dai, Jianfeng

2018-06-01

In this paper, two kinds of transient models, the viscoelastic model and the linear elastic model, are established to analyze the curing deformation of the thermosetting resin composites, and are calculated by COMSOL Multiphysics software. The two models consider the complicated coupling between physical and chemical changes during curing process of the composites and the time-variant characteristic of material performance parameters. Subsequently, the two proposed models are implemented respectively in a three-dimensional composite laminate structure, and a simple and convenient method of local coordinate system is used to calculate the development of residual stresses, curing shrinkage and curing deformation for the composite laminate. Researches show that the temperature, degree of curing (DOC) and residual stresses during curing process are consistent with the study in literature, so the curing shrinkage and curing deformation obtained on these basis have a certain referential value. Compared the differences between the two numerical results, it indicates that the residual stress and deformation calculated by the viscoelastic model are more close to the reference value than the linear elastic model.

Simulation of Deformation, Momentum and Energy Coupling Particles Deformed by Intense Shocks

NASA Astrophysics Data System (ADS)

Lieberthal, B.; Stewart, D. S.; Bdzil, J. B.; Najjar, F. M.; Balachandar, S.; Ling, Y.

2011-11-01

Modern energetic materials have embedded solids and inerts in an explosive matrix. A detonation in condensed phase materials, generates intense shocks that deform particles as the incident shock diffracts around them. The post-shock flow generates a wake behind the particle that is influenced by the shape changes of the particle. The gasdynamic flow in the explosive products and its interaction with the deformation of the particle must be treated simultaneously. Direct numerical simulations are carried out that vary the particle-to-surrounding density and impedance ratios to consider heavier and lighter particle. The vorticity deposited on the interface due to shock interaction with the particle, the resulting particle deformation and the net momentum and energy transferred to the particle, on the acoustic and longer viscous time scale are considered. The LLNL multi-physics hydrodynamic code ALE3D is used to carry out the simulations. BL, DSS and JBB supported by AFRL/RW AF FA8651-10-1-0004 & DTRA, HDTRA1-10-1-0020 Off Campus. FMN's work supported by the U.S. DOE/ LLNL, Contract DE-AC52-07NA27344. LLNL-ABS-491794.

Anisotropic toughness and strength in graphene and its atomistic origin

NASA Astrophysics Data System (ADS)

Hossain, M. Zubaer; Ahmed, Tousif; Silverman, Benjamin; Khawaja, M. Shehroz; Calderon, Justice; Rutten, Andrew; Tse, Stanley

2018-01-01

This paper presents the implication of crystallographic orientation on toughness and ideal strength in graphene under lattice symmetry-preserving and symmetry-breaking deformations. In symmetry-preserving deformation, both toughness and strength are isotropic, regardless of the chirality of the lattice; whereas, in symmetry-breaking deformation they are strongly anisotropic, even in the presence of vacancy defects. The maximum and minimum of toughness or strength occur for loading along the zigzag direction and the armchair direction, respectively. The anisotropic behavior is governed by a complex interplay among bond-stretching deformation, bond-bending deformation, and the chirality of the lattice. Nevertheless, the condition for crack-nucleation is dictated by the maximum bond-force required for bond rupture, and it is independent of the chiral angle of the lattice or loading direction. At the onset of crack-nucleation a localized nucleation zone is formed, wherein the bonds rupture locally satisfying the maximum bond-force criterion. The nucleation zone acts as the physical origin in triggering the fracture nucleation process, but its presence is undetectable from the macroscopic stress-strain data.

Perceptual transparency from image deformation.

PubMed

Kawabe, Takahiro; Maruya, Kazushi; Nishida, Shin'ya

2015-08-18

Human vision has a remarkable ability to perceive two layers at the same retinal locations, a transparent layer in front of a background surface. Critical image cues to perceptual transparency, studied extensively in the past, are changes in luminance or color that could be caused by light absorptions and reflections by the front layer, but such image changes may not be clearly visible when the front layer consists of a pure transparent material such as water. Our daily experiences with transparent materials of this kind suggest that an alternative potential cue of visual transparency is image deformations of a background pattern caused by light refraction. Although previous studies have indicated that these image deformations, at least static ones, play little role in perceptual transparency, here we show that dynamic image deformations of the background pattern, which could be produced by light refraction on a moving liquid's surface, can produce a vivid impression of a transparent liquid layer without the aid of any other visual cues as to the presence of a transparent layer. Furthermore, a transparent liquid layer perceptually emerges even from a randomly generated dynamic image deformation as long as it is similar to real liquid deformations in its spatiotemporal frequency profile. Our findings indicate that the brain can perceptually infer the presence of "invisible" transparent liquids by analyzing the spatiotemporal structure of dynamic image deformation, for which it uses a relatively simple computation that does not require high-level knowledge about the detailed physics of liquid deformation.

High-temperature behavior of a deformed Fermi gas obeying interpolating statistics.

PubMed

Algin, Abdullah; Senay, Mustafa

2012-04-01

An outstanding idea originally introduced by Greenberg is to investigate whether there is equivalence between intermediate statistics, which may be different from anyonic statistics, and q-deformed particle algebra. Also, a model to be studied for addressing such an idea could possibly provide us some new consequences about the interactions of particles as well as their internal structures. Motivated mainly by this idea, in this work, we consider a q-deformed Fermi gas model whose statistical properties enable us to effectively study interpolating statistics. Starting with a generalized Fermi-Dirac distribution function, we derive several thermostatistical functions of a gas of these deformed fermions in the thermodynamical limit. We study the high-temperature behavior of the system by analyzing the effects of q deformation on the most important thermostatistical characteristics of the system such as the entropy, specific heat, and equation of state. It is shown that such a deformed fermion model in two and three spatial dimensions exhibits the interpolating statistics in a specific interval of the model deformation parameter 0 < q < 1. In particular, for two and three spatial dimensions, it is found from the behavior of the third virial coefficient of the model that the deformation parameter q interpolates completely between attractive and repulsive systems, including the free boson and fermion cases. From the results obtained in this work, we conclude that such a model could provide much physical insight into some interacting theories of fermions, and could be useful to further study the particle systems with intermediate statistics.

TH-CD-206-09: Learning-Based MRI-CT Prostate Registration Using Spare Patch-Deformation Dictionary

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, X; Jani, A; Rossi, P

Purpose: To enable MRI-guided prostate radiotherapy, MRI-CT deformable registration is required to map the MRI-defined tumor and key organ contours onto the CT images. Due to the intrinsic differences in grey-level intensity characteristics between MRI and CT images, the integration of MRI into CT-based radiotherapy is very challenging. We are developing a learning-based registration approach to address this technical challenge. Methods: We propose to estimate the deformation between MRI and CT images in a patch-wise fashion by using the sparse representation technique. Specifically, we assume that two image patches should follow the same deformation if their patch-wise appearance patterns aremore » similar. We first extract a set of key points in the new CT image. Then, for each key point, we adaptively construct a coupled dictionary from the training MRI-CT images, where each coupled element includes both appearance and deformation of the same image patch. After calculating the sparse coefficients in representing the patch appearance of each key point based on the constructed dictionary, we can predict the deformation for this point by applying the same sparse coefficients to the respective deformations in the dictionary. Results: This registration technique was validated with 10 prostate-cancer patients’ data and its performance was compared with the commonly used free-form-deformation-based registration. Several landmarks in both images were identified to evaluate the accuracy of our approach. Overall, the averaged target registration error of the intensity-based registration and the proposed method was 3.8±0.4 mm and 1.9±0.3 mm, respectively. Conclusion: We have developed a novel prostate MR-CT registration approach based on patch-deformation dictionary, demonstrated its clinical feasibility, and validated its accuracy. This technique will either reduce or compensate for the effect of patient-specific treatment variation measured during the course of radiotherapy, is therefore well-suited for a number of MRI-guided adaptive radiotherapy, and potentially enhance prostate radiotherapy treatment outcome.« less

Generalized uncertainty principle and quantum gravity phenomenology

NASA Astrophysics Data System (ADS)

Bosso, Pasquale

The fundamental physical description of Nature is based on two mutually incompatible theories: Quantum Mechanics and General Relativity. Their unification in a theory of Quantum Gravity (QG) remains one of the main challenges of theoretical physics. Quantum Gravity Phenomenology (QGP) studies QG effects in low-energy systems. The basis of one such phenomenological model is the Generalized Uncertainty Principle (GUP), which is a modified Heisenberg uncertainty relation and predicts a deformed canonical commutator. In this thesis, we compute Planck-scale corrections to angular momentum eigenvalues, the hydrogen atom spectrum, the Stern-Gerlach experiment, and the Clebsch-Gordan coefficients. We then rigorously analyze the GUP-perturbed harmonic oscillator and study new coherent and squeezed states. Furthermore, we introduce a scheme for increasing the sensitivity of optomechanical experiments for testing QG effects. Finally, we suggest future projects that may potentially test QG effects in the laboratory.

Spastic diplegia in children with HIV encephalopathy: first description of gait and physical status.

PubMed

Langerak, Nelleke G; du Toit, Jacques; Burger, Marlette; Cotton, Mark F; Springer, Priscilla E; Laughton, Barbara

2014-07-01

The aim of this study was to explore the physical status and gait patterns of children with spastic diplegia secondary to human immunodeficiency virus encephalopathy (HIVE). A cross-sectional study was conducted on children diagnosed with HIVE and spastic diplegia. Sociodemographic and clinical background information was obtained, followed by three-dimensional gait analysis (3DGA) and a physical examination including assessments of muscle tone, strength, motor control, contractures, and bony deformities of the lower extremities. Fourteen children (eight males, six females; mean age 5 y 8 mo [SD 9 mo], range 4 y 4 mo-6 y 10 mo) were studied. The cohort was divided into two groups based on distinctive gait patterns. Nine participants in group I showed only limited abnormalities. Group II displayed a more pathological gait pattern including stiff knee and equinus ankle abnormalities. Results of 3DGA, as with the physical examination outcomes, showed increased impairments from proximal to distal (except for hip extension). This study provides a first description of distinctive gait patterns and related physical characteristics of children with HIVE and spastic diplegia. Further research is necessary. © 2013 Mac Keith Press.

Design method of redundancy of brace-anchor sharing supporting based on cooperative deformation

NASA Astrophysics Data System (ADS)

Liu, Jun-yan; Li, Bing; Liu, Yan; Cai, Shan-bing

2017-11-01

Because of the complicated environment requirement, the support form of foundation pit is diversified, and the brace-anchor sharing support is widely used. However, the research on the force deformation characteristics and the related aspects of the cooperative response of the brace-anchor sharing support is insufficient. The application of redundancy theory in structural engineering has been more mature, but there is little theoretical research on redundancy theory in underground engineering. Based on the idea of collaborative deformation, the paper calculates the ratio of the redundancy degree of the cooperative deformation by using the local reinforcement design method and the structural component redundancy parameter calculation formula based on Frangopol. Combined with the engineering case, through the calculation of the ratio of cooperative deformation redundancy in the joint of brace-anchor sharing support. This paper explores the optimal anchor distribution form under the condition of cooperative deformation, and through the analysis and research of displacement field and stress field, the results of the collaborative deformation are validated by comparing the field monitoring data. It provides theoretical basis for the design of this kind of foundation pit in the future.

Sequence-dependent DNA deformability studied using molecular dynamics simulations.

PubMed

Fujii, Satoshi; Kono, Hidetoshi; Takenaka, Shigeori; Go, Nobuhiro; Sarai, Akinori

2007-01-01

Proteins recognize specific DNA sequences not only through direct contact between amino acids and bases, but also indirectly based on the sequence-dependent conformation and deformability of the DNA (indirect readout). We used molecular dynamics simulations to analyze the sequence-dependent DNA conformations of all 136 possible tetrameric sequences sandwiched between CGCG sequences. The deformability of dimeric steps obtained by the simulations is consistent with that by the crystal structures. The simulation results further showed that the conformation and deformability of the tetramers can highly depend on the flanking base pairs. The conformations of xATx tetramers show the most rigidity and are not affected by the flanking base pairs and the xYRx show by contrast the greatest flexibility and change their conformations depending on the base pairs at both ends, suggesting tetramers with the same central dimer can show different deformabilities. These results suggest that analysis of dimeric steps alone may overlook some conformational features of DNA and provide insight into the mechanism of indirect readout during protein-DNA recognition. Moreover, the sequence dependence of DNA conformation and deformability may be used to estimate the contribution of indirect readout to the specificity of protein-DNA recognition as well as nucleosome positioning and large-scale behavior of nucleic acids.

Strength and deformability of light-toned layered deposits observed by MER Opportunity: Eagle to Erebus craters, Mars

NASA Astrophysics Data System (ADS)

Okubo, Chris H.

2007-10-01

Quantifying host rock deformation is vital to understanding the geologic evolution and productivity of subsurface fluid reservoirs. In support of on-going characterization of fracture controlled fluid flow through the light-toned layered deposits on Mars, key parameters of strength and deformability are derived from Microscopic Imager and Rock Abrasion Tool data collected by the Mars Exploration Rover Opportunity in Meridiani Planum. Analysis of 21 targets of light-toned layered deposits yields a median apparent porosity of 0.25. Additional physical parameters for each target are derived from these porosity measurements. The median value of unconfined compressive strength is 11.23 MPa, Young's modulus is 1.86 GPa, and the brittle-ductile transition pressure is 8.77 MPa.

Mechanistic Insights into Human Brain Impact Dynamics through Modal Analysis

NASA Astrophysics Data System (ADS)

Laksari, Kaveh; Kurt, Mehmet; Babaee, Hessam; Kleiven, Svein; Camarillo, David

2018-03-01

Although concussion is one of the greatest health challenges today, our physical understanding of the cause of injury is limited. In this Letter, we simulated football head impacts in a finite element model and extracted the most dominant modal behavior of the brain's deformation. We showed that the brain's deformation is most sensitive in low frequency regimes close to 30 Hz, and discovered that for most subconcussive head impacts, the dynamics of brain deformation is dominated by a single global mode. In this Letter, we show the existence of localized modes and multimodal behavior in the brain as a hyperviscoelastic medium. This dynamical phenomenon leads to strain concentration patterns, particularly in deep brain regions, which is consistent with reported concussion pathology.

Measurements of Interaction Cross Sections for 19-27F Isotopes

NASA Astrophysics Data System (ADS)

Homma, Akira; Takechi, Maya; Ohtsubo, Takashi; Nishimura, Daiki; Fukuda, Mitsunori; Suzuki, Takeshi; Yamaguchi, Takayuki; Kuboki, Takamasa; Ozawa, Akira; Suzuki, Sinji; Ooishi, Hiroto; Moriguchi, Tetsuaki; Sumikawa, Takashi; Geissel, H.; Aoi, Nori; Chen, Rui-jiu; Fang, De-Qing; Fukuda, Naoki; Fukuoka, Shota; Furuki, Hisahiro; Inaba, Naruki; Ishibashi, Nobuyuki; Ito, Takeshi; Izumikawa, Takuji; Kameda, Daisuke; Kubo, Toshiyuki; Lantz, M.; Lee, C. S.; Ma, Yu-Gang; Mihara, Mototsugu; Momota, Satao; Nagae, Daisuke; Nishikiori, Ryo; Niwa, Takahiro; Ohnishi, Tetsuya; Okumura, Kimitake; Ogura, Toshiyuki; Nagashima, Masayuki; Sakurai, Hiroyoshi; Sato, Kanae; Shimbara, Yoshiriro; Suzuki, Hiroshi; Takeda, Hiroyuki; Takeuchi, Satoshi; Tanaka, Kenji; Uenishi, Hideaki; Winkler, M.; Yanagisawa, Yoshiyuki

Interaction cross sections (σI) and reaction cross sections (σR) are physical quantities which are strongly related to the nuclear size. In our previous study of σI for Ne isotopes, the deformation features of neutron-rich Ne isotopes in the so-called "island of inversion" region have been successfully observed, and also the formation of the deformed halo structure in 31Ne has been indicated. In this study, σI for 19-27F, up to the vicinity of the island of inversion have been measured at around 240A MeV using BigRIPS at RIBF, RIKEN. Our preliminary results are slightly larger than A1/3 systematics and some of the data could be explained by nuclear deformation.

Modelling coastal processes by means of innovative integration of remote sensing and modelling analysis

NASA Astrophysics Data System (ADS)

Taramelli, A.; Zanuttigh, B.; Zucca, F.; Dejana, M.; Valentini, E.

2011-12-01

Coastal marine and inland landforms are dynamic systems undergoing adjustments in form at different time and space scales in response to varying conditions external to the system. Coastal emerged and shallow submerged nearshore areas, affected by short-term perturbations, return to their pre-disturbance morphology and generally reach a dynamic equilibrium. Worldwide in the last century we have experienced in increased coastal inundation, erosion and ecosystem losses. However, erosion can result from a number of other factors, such as altered wind and current patterns, high-energy waves, and reduced fluvial sediment inputs. Direct impacts of human activities, including reclamation of coastal wetlands, deforestation, damming, channelization, diversions of coastal waterways, construction of seawalls and other structures, alter circulation patterns. Also indirect human impacts such as land-uses changes through time (eg. from agricultural to industrial use) have affected coastal ecosystems. The objective of this research is to propose innovative remote sensing applications to monitor specific coastal processes in order to use them within a physical modelling to quantify and model their time evolution. The research was applied in two dynamic and densely populated deltas and coastal areas (the Po and the Plymouth delta) by combining multi-sensor spaceborne remote sensing (SAR and OPTICAL) to physical modelling. The main results are: a) deformation and spatiotemporal variations maps in coastal morphology with a special focus to point out the temporal subsidence evolution, b) inter and intra-annual change detection maps that are both used a to feed a coastal physical modelling (MIKE 21). The basic strategy was to highlight the different components of the coastal system environment through: 1) deformation and spatio-temporal variations maps of coastal morphology, by the use of time-stack from 1992 up today of ESA SAR data (ERS-1/2 and ENVISAT-ASAR sensors) were used to produce deformation maps and to point out the temporal evolution and 2) multitemporal hyperspectral endmembers fractions map of coastal morphology, 3) numerical model well-established through remote sensed based procedures and results in order to produce spatio-temporal scenario in coastal areas. The objective was to locate and characterize important coastal indicators for different regions using multitemporal data from the multi-hyperspectral sensors, as well as topographic elevation, SAR and derived products (eg. coherence) data. The identification of different indicators was based on land spectral properties, topography/landforms (low topography), disturbed areas (agricultural, construction), and vegetation distribution. Moreover, the indicators were assessed at seasonal and interannual time scales over two temporal decades horizons starting from 1990 and 2000.

Impact of hydrothermal alteration on time-dependent tunnel deformation in Neogene volcanic rock sequence in Japan: Petrology, Geochemistry and Geophysical investigation

NASA Astrophysics Data System (ADS)

Yamazaki, S.; Okazaki, K.; Niwa, H.; Arai, T.; Murayama, H.; Kurahashi, T.; Ito, Y.

2017-12-01

Time-dependent tunnel deformation is one of remaining geological problems for mountain tunneling. As a case study of time-dependent tunnel deformation, we investigated petrographical, mineral and chemical compositions of boring core samples and seismic exploration along a tunnel that constructed into Neogene volcanic rock sequence of andesite to dacite pyroclastic rocks and massive lavas with mafic enclaves. The tunnel has two zones of floor heaving that deformed time-dependently about 2 month after the tunnel excavation. The core samples around the deformed zones are characterized secondary mineral assemblages of smectite, cristobalite, tridymite, sulfides (pyrite and marcasite) and partially or completely reacted carbonates (calcite and siderite), which were formed by hydrothermal alteration under neutral to acidic condition below about 100 °C. The core samples also showed localized deterioration, such as crack formation and expansion, which occurred from few days to months after the drilling. The deterioration could be explained as a result of the cyclic physical and chemical weathering process with the oxidation of sulfide minerals, dissolution of carbonate mineral cementation and volumetric expantion of smectite. This weathering process is considered as a key factor for time-dependent tunnel deformation in the hydrothermally altered volcanic rocks. The zones of time-dependent deformation along a tunnel route can be predicted by the variations of whole-rock chemical compositions such as Na, Ca, Sr, Ba and S.

Organochlorine insecticides, polychlorinated biphenyls, and metals in water, sediment, and green frogs from southwestern Michigan.

PubMed

Gillilland, C D; Summer, C L; Gillilland, M G; Kannan, K; Villeneuve, D L; Coady, K K; Muzzall, P; Mehne, C; Giesy, J P

2001-07-01

In an attempt to explain the etiology of frog deformities and population declines, many possible causative factors have been examined, including the input of synthetic chemicals into aquatic systems, where frogs spend much of their lives, including their entire developmental stages. Deformities in populations of green frogs in wetlands of southwestern Michigan that are influenced by agricultural, urban, or industrial inputs were assessed in this study. Of the 1445 green frogs (Rana clamitans) examined, only four (0.3%) exhibited morphological deformities. This deformity rate is less than the recognized background level of deformities for this species, which is approximately 1%. Concentrations of organochlorine insecticides, polychlorinated biphenyls (PCBs), and metals were determined in water, sediment, frog eggs, tadpoles, and adult green frog tissues. Concentrations of all individual organochlorine insecticides in tissue were less than 6 ng/g, wet wt. Concentrations of sigmaPCBs in tissue did not exceed 100 ng/g, wet wt. Concentrations of toxic metals were less than the limits of detection. Because no significant numbers of green frog deformities were observed in this region, it can be assumed that at these low concentrations, physical malformations in green frogs should not be observed. Significance of study. This study provides information on the incidence of deformities in green frog populations in southwestern Michigan and offers background data on chemical residues in green frogs and their environment.

Analysis of Solid State Bonding in the Extrusion Process of Magnesium Alloys --Numerical Prediction and Experimental Verification

NASA Astrophysics Data System (ADS)

Alharthi, Nabeel H.

The automotive industry developments focused on increasing fuel efficiency are accomplished by weight reduction of vehicles, which consequently results in less negative environmental impact. Usage of low density materials such as Magnesium alloys is an approach to replace heavier structural components. One of the challenges in deformation processing of Magnesium is its low formability attributed to the hexagonal close packed (hcp) crystal structure. The extrusion process is one of the most promising forming processes for Magnesium because it applies a hydrostatic compression state of stress during deformation resulting in improved workability. Many researchers have attempted to fully understand solid state bonding during deformation in different structural materials such as Aluminum, Copper and other metals and alloys. There is a lack of sufficient understanding of the extrusion welding in these materials as well as very limited knowledge on this subject for hollow profiles made from Magnesium alloys. The weld integrity and the characteristic of the welding microstructure are generally unknown. In this dissertation three related research projects are investigated by using different tools such as microstructure characterization, mechanical testing, thermo-mechanical physical simulation and finite element numerical modeling. Project 1: Microstructure characterization supported by mechanical testing of the extrusion welding regions in Magnesium alloy AM30 extrudate. The microstructure characterization was conducted using Light Optical Microscopy (LOM), in addition to LOM the electron backscattered diffraction (EBSD) technique was implemented to characterize in depth the deformed and welded microstructure. Project 2: Finite element numerical simulation of AM30 extrudate to model different process parameters and their influence on localized state variables such as strain, strain rate, temperature and normal pressure within the weld zone. Project 3: Physical simulation of the extrusion welding by using Gleeble 3500 thermo-mechanical simulator to create deformation welds in Magnesium alloy AM30 samples in compression test under various temperatures and strain rates conditions. Based on the obtained results from the performed research projects and literature review, a new qualitative criterion of extrusion welding has been introduced as contribution to the field. The criterion and its analysis have provided better understanding of material response to processing parameters and assisted in selecting the processing windows for good practices in the extrusion process. In addition, the new approach contributed to better understanding and evaluating the quality of the solid state bonding of Mg alloy. Accordingly, the criteria help to avoiding formation of potential mechanical and metallurgical imperfections.

Measuring skewness of red blood cell deformability distribution by laser ektacytometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nikitin, S Yu; Priezzhev, A V; Lugovtsov, A E

An algorithm is proposed for measuring the parameters of red blood cell deformability distribution based on laser diffractometry of red blood cells in shear flow (ektacytometry). The algorithm is tested on specially prepared samples of rat blood. In these experiments we succeeded in measuring the mean deformability, deformability variance and skewness of red blood cell deformability distribution with errors of 10%, 15% and 35%, respectively. (laser biophotonics)

Medial-based deformable models in nonconvex shape-spaces for medical image segmentation.

PubMed

McIntosh, Chris; Hamarneh, Ghassan

2012-01-01

We explore the application of genetic algorithms (GA) to deformable models through the proposition of a novel method for medical image segmentation that combines GA with nonconvex, localized, medial-based shape statistics. We replace the more typical gradient descent optimizer used in deformable models with GA, and the convex, implicit, global shape statistics with nonconvex, explicit, localized ones. Specifically, we propose GA to reduce typical deformable model weaknesses pertaining to model initialization, pose estimation and local minima, through the simultaneous evolution of a large number of models. Furthermore, we constrain the evolution, and thus reduce the size of the search-space, by using statistically-based deformable models whose deformations are intuitive (stretch, bulge, bend) and are driven in terms of localized principal modes of variation, instead of modes of variation across the entire shape that often fail to capture localized shape changes. Although GA are not guaranteed to achieve the global optima, our method compares favorably to the prevalent optimization techniques, convex/nonconvex gradient-based optimizers and to globally optimal graph-theoretic combinatorial optimization techniques, when applied to the task of corpus callosum segmentation in 50 mid-sagittal brain magnetic resonance images.

Application of Quaternions for Mesh Deformation

NASA Technical Reports Server (NTRS)

Samareh, Jamshid A.

2002-01-01

A new three-dimensional mesh deformation algorithm, based on quaternion algebra, is introduced. A brief overview of quaternion algebra is provided, along with some preliminary results for two-dimensional structured and unstructured viscous mesh deformation.

Formulation and in vitro evaluation of theophylline matrix tablets prepared by direct compression: Effect of polymer blends

PubMed Central

El-Bagory, Ibrahim; Barakat, Nahla; Ibrahim, Mohamed A.; El-Enazi, Fouza

2011-01-01

The deformation mechanism of pharmaceutical powders, used in formulating directly compressed matrix tablets, affects the characteristics of the formed tablets. Three polymers of different deformation mechanisms were tested for their impact on theophylline directly compressed tablets namely Kollidon SR (KL SR, plastic deformation), Ethylcellulose (EC, elastic deformation) and Carnauba wax (CW, brittle deformation) at different compression forces. However, tablets based mainly on KL SR, the plastically deformed polymer (TN1) exhibited the highest hardness values compared to the other formulae which are based on either blends of KL SR with CW, the very brittle deformed polymer. The upper detected force for TN formulae and the lower punch force were found to dependent mainly on the powder deformation. This difference is attributed to the work done during the compression phase as well as the work lost during the decompression phase. Furthermore, the release profiles of TN from formulae TN2 and TN4 that are based on the composition (2KL SR:1EC) and (1KL SR:2EC), respectively, were consistent with different deformation mechanisms of KL SR and EC and on the physicochemical properties like the water absorptive capacity of EC. Upon increasing the weight ratio of KL SR (TN2), the release rate was greatly retarded (39.4%, 37.1%, 35.0% and 33.6% released after 8 h at 5, 10, 15 and 20 kN. PMID:24115902

Patterns of Alloy Deformation by Pulsed Pressure

NASA Astrophysics Data System (ADS)

Chebotnyagin, L. M.; Potapov, V. V.; Lopatin, V. V.

2015-06-01

Patterns of alloy deformation for optimization of a welding regime are studied by the method of modeling and deformation profiles providing high deformation quality are determined. A model of stepwise kinetics of the alloy deformation by pulsed pressure from the expanding plasma channel inside of a deformable cylinder is suggested. The model is based on the analogy between the acoustic and electromagnetic wave processes in long lines. The shock wave pattern of alloy deformation in the presence of multiple reflections of pulsed pressure waves in the gap plasma channel - cylinder wall and the influence of unloading waves from free surfaces are confirmed.

An efficient and scalable deformable model for virtual reality-based medical applications.

PubMed

Choi, Kup-Sze; Sun, Hanqiu; Heng, Pheng-Ann

2004-09-01

Modeling of tissue deformation is of great importance to virtual reality (VR)-based medical simulations. Considerable effort has been dedicated to the development of interactively deformable virtual tissues. In this paper, an efficient and scalable deformable model is presented for virtual-reality-based medical applications. It considers deformation as a localized force transmittal process which is governed by algorithms based on breadth-first search (BFS). The computational speed is scalable to facilitate real-time interaction by adjusting the penetration depth. Simulated annealing (SA) algorithms are developed to optimize the model parameters by using the reference data generated with the linear static finite element method (FEM). The mechanical behavior and timing performance of the model have been evaluated. The model has been applied to simulate the typical behavior of living tissues and anisotropic materials. Integration with a haptic device has also been achieved on a generic personal computer (PC) platform. The proposed technique provides a feasible solution for VR-based medical simulations and has the potential for multi-user collaborative work in virtual environment.

SU-E-J-111: Finite Element-Based Deformable Image Registration of Pleural Cavity for Photodynamic Therapy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Penjweini, R; Zhu, T

Purpose: The pleural volumes will deform during surgery portion of the pleural photodynamic therapy (PDT) of lung cancer when the pleural cavity is opened. This impact the delivered dose when using highly conformal treatment techniques. In this study, a finite element-based (FEM) deformable image registration is used to quantify the anatomical variation between the contours for the pleural cavities obtained in the operating room and those determined from pre-surgery computed tomography (CT) scans. Methods: An infrared camera-based navigation system (NDI) is used during PDT to track the anatomical changes and contour the lung and chest cavity. A series of CTsmore » of the lungs, in the same patient, are also acquired before the surgery. The structure contour of lung and the CTs are processed and contoured in Matlab and MeshLab. Then, the contours are imported into COMSOL Multiphysics 5.0, where the FEM-based deformable image registration is obtained using the deformed mesh - moving mesh (ALE) model. The NDI acquired lung contour is considered as the reference contour, and the CT contour is used as the target one, which will be deformed. Results: The reconstructed three-dimensional contours from both NDI and CT can be converted to COMSOL so that a three-dimensional ALE model can be developed. The contours can be registered using COMSOL ALE moving mesh model, which takes into account the deformation along x, y and z-axes. The deformed contour has good matches to the reference contour after the dynamic matching process. The resulting 3D deformation map can be used to obtain the locations of other critical anatomic structures, e.g., heart, during surgery. Conclusion: Deformable image registration can fuse images acquired by different modalities. It provides insights into the development of phenomenon and variation in normal anatomical structures over time. The initial assessments of three-dimensional registration show good agreement.« less

Deformable complex network for refining low-resolution X-ray structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Chong; Wang, Qinghua; Ma, Jianpeng, E-mail: jpma@bcm.edu

2015-10-27

A new refinement algorithm called the deformable complex network that combines a novel angular network-based restraint with a deformable elastic network model in the target function has been developed to aid in structural refinement in macromolecular X-ray crystallography. In macromolecular X-ray crystallography, building more accurate atomic models based on lower resolution experimental diffraction data remains a great challenge. Previous studies have used a deformable elastic network (DEN) model to aid in low-resolution structural refinement. In this study, the development of a new refinement algorithm called the deformable complex network (DCN) is reported that combines a novel angular network-based restraint withmore » the DEN model in the target function. Testing of DCN on a wide range of low-resolution structures demonstrated that it constantly leads to significantly improved structural models as judged by multiple refinement criteria, thus representing a new effective refinement tool for low-resolution structural determination.« less

Research of Adhesion Bonds Between Gas-Thermal Coating and Pre-Modified Base

NASA Astrophysics Data System (ADS)

Kovalevskaya, Z.; Zaitsev, K.; Klimenov, V.

2016-08-01

Nature of adhesive bonds between gas-thermal nickel alloy coating and carbon steel base was examined using laser profilometry, optical metallography, transmission and scanning electron microscopy. The steel surface was plastically pre-deformed by an ultrasonic tool. Proved that ultrasound pre-treatment modifies the steel surface. Increase of dislocation density and formation of sub micro-structure are base elements of surface modification. While using high-speed gas-flame, plasma and detonation modes of coatings, surface activation occurs and durable adhesion is formed. Ultrasonic pre-treatment of base material is effective when sprayed particles and base material interact through physical-chemical bond formation. Before applying high-speed gas flame and plasma sprayed coatings, authors recommend ultrasonic pretreatment, which creates periodic wavy topography with a stroke of 250 microns on the steel surface. Before applying detonation sprayed coatings, authors recommend ultrasound pretreatment that create modified surface with a uniform micro-topography.

Varied dose exposures to ultrafine particles in the motorcycle smoke cause kidney cell damages in male mice.

PubMed

Wardoyo, Arinto Y P; Juswono, Unggul P; Noor, Johan A E

2018-01-01

Ultrafine particles (UFPs) are one of motorcycle exhaust emissions which can penetrate the lung alveoli and deposit in the kidney. This study was aimed to investigate mice kidney cell physical damage (deformation) due to motorcycle exhaust emission exposures. The motorcycle exhaust emissions were sucked from the muffler with the rate of 33 cm 3 /s and passed through an ultrafine particle filter system before introduced into the mice exposure chamber. The dose concentration of the exhaust emissions was varied by setting the injected time of the 20s, 40s, 60s, 80s, and 100s. The mice were exposed to the smoke in the chamber for 100 s twice a day. The impact of the ultrafine particles on the kidney was observed by identifying the histological image of the kidney cell deformation using a microscope. The exposure was conducted for 10 days. The kidney observations were carried out on day 11. The results showed that there was a significant linear correlation between the total concentration of ultrafine particles deposited in the kidneys and the physical damage percentages. The increased concentrations of ultrafine particles caused larger cell deformation to the kidneys.

Biomechanical aspects of lower limb torsional deformation correction with the Ilizarov external fixator.

PubMed

Morasiewicz, Piotr; Filipiak, Jarosław; Krysztoforski, Krzysztof; Dragan, Szymon

2014-03-01

The correction of torsional deformities with the Ilizarov apparatus is accompanied by rotational and translational displacement, which affects the biomechanics of the bone fragments. Understanding the biomechanical factors will assist in designing the optimal treatment strategy and mechanical properties of the fixator, thus shortening the duration of treatment and improving the outcomes. In order to determine the impact of different types of derotators on the kinematics of bone fragments in Ilizarov apparatus, physical models were studied. Translational and derotational displacement was measured using non-contact method (Optotrak Certus Motion Capture System). The results of the studies conducted on physical models have shown that regardless of the type of the derotator, the divergence between the applied angle of derotation and the obtained angle of rotation relative to fragments needs to be taken into account. Transverse displacement of fragments occur by 3.5 mm to approximately 9 mm, depending on the angle of derotation. For correction of rotational deformities up to 30°, it is advisable to use the type Z derotators because of its higher accuracy of derotation. Different types of derotators can affect the biomechanical conditions in the regenerating bone tissue through different kinematics characteristics.

Glass Microbeads in Analog Models of Thrust Wedges.

PubMed

D'Angelo, Taynara; Gomes, Caroline J S

2017-01-01

Glass microbeads are frequently used in analog physical modeling to simulate weak detachment zones but have been neglected in models of thrust wedges. Microbeads differ from quartz sand in grain shape and in low angle of internal friction. In this study, we compared the structural characteristics of microbeads and sand wedges. To obtain a better picture of their mechanical behavior, we determined the physical and frictional properties of microbeads using polarizing and scanning electron microscopy and ring-shear tests, respectively. We built shortening experiments with different basal frictions and measured the thickness, slope and length of the wedges and also the fault spacings. All the microbeads experiments revealed wedge geometries that were consistent with previous studies that have been performed with sand. However, the deformation features in the microbeads shortened over low to intermediate basal frictions were slightly different. Microbeads produced different fault geometries than sand as well as a different grain flow. In addition, they produced slip on minor faults, which was associated with distributed deformation and gave the microbeads wedges the appearance of disharmonic folds. We concluded that the glass microbeads may be used to simulate relatively competent rocks, like carbonates, which may be characterized by small-scale deformation features.

Influences of thermal deformation of cavity mirrors induced by high energy DF laser to beam quality under the simulated real physical circumstances

NASA Astrophysics Data System (ADS)

Deng, Shaoyong; Zhang, Shiqiang; He, Minbo; Zhang, Zheng; Guan, Xiaowei

2017-05-01

The positive-branch confocal unstable resonator with inhomogeneous gain medium was studied for the normal used high energy DF laser system. The fast changing process of the resonator's eigenmodes was coupled with the slow changing process of the thermal deformation of cavity mirrors. Influences of the thermal deformation of cavity mirrors to the outcoupled beam quality and transmission loss of high frequency components of high energy laser were computed. The simulations are done through programs compiled by MATLAB and GLAD software and the method of combination of finite elements and Fox-li iteration algorithm was used. Effects of thermal distortion, misaligned of cavity mirrors and inhomogeneous distribution of gain medium were introduced to simulate the real physical circumstances of laser cavity. The wavefront distribution and beam quality (including RMS of wavefront, power in the bucket, Strehl ratio, diffraction limit β, position of the beam spot center, spot size and intensity distribution in far-field ) of the distorted outcoupled beam were studied. The conclusions of the simulation agree with the experimental results. This work would supply references of wavefront correction range to the adaptive optics system of interior alleyway.

A finite element method to correct deformable image registration errors in low-contrast regions

NASA Astrophysics Data System (ADS)

Zhong, Hualiang; Kim, Jinkoo; Li, Haisen; Nurushev, Teamour; Movsas, Benjamin; Chetty, Indrin J.

2012-06-01

Image-guided adaptive radiotherapy requires deformable image registration to map radiation dose back and forth between images. The purpose of this study is to develop a novel method to improve the accuracy of an intensity-based image registration algorithm in low-contrast regions. A computational framework has been developed in this study to improve the quality of the ‘demons’ registration. For each voxel in the registration's target image, the standard deviation of image intensity in a neighborhood of this voxel was calculated. A mask for high-contrast regions was generated based on their standard deviations. In the masked regions, a tetrahedral mesh was refined recursively so that a sufficient number of tetrahedral nodes in these regions can be selected as driving nodes. An elastic system driven by the displacements of the selected nodes was formulated using a finite element method (FEM) and implemented on the refined mesh. The displacements of these driving nodes were generated with the ‘demons’ algorithm. The solution of the system was derived using a conjugated gradient method, and interpolated to generate a displacement vector field for the registered images. The FEM correction method was compared with the ‘demons’ algorithm on the computed tomography (CT) images of lung and prostate patients. The performance of the FEM correction relating to the ‘demons’ registration was analyzed based on the physical property of their deformation maps, and quantitatively evaluated through a benchmark model developed specifically for this study. Compared to the benchmark model, the ‘demons’ registration has the maximum error of 1.2 cm, which can be corrected by the FEM to 0.4 cm, and the average error of the ‘demons’ registration is reduced from 0.17 to 0.11 cm. For the CT images of lung and prostate patients, the deformation maps generated by the ‘demons’ algorithm were found unrealistic at several places. In these places, the displacement differences between the ‘demons’ registrations and their FEM corrections were found in the range of 0.4 and 1.1 cm. The mesh refinement and FEM simulation were implemented in a single thread application which requires about 45 min of computation time on a 2.6 GHz computer. This study has demonstrated that the FEM can be integrated with intensity-based image registration algorithms to improve their registration accuracy, especially in low-contrast regions.

Avalanches, loading and finite size effects in 2D amorphous plasticity: results from a finite element model

NASA Astrophysics Data System (ADS)

Sandfeld, Stefan; Budrikis, Zoe; Zapperi, Stefano; Fernandez Castellanos, David

2015-02-01

Crystalline plasticity is strongly interlinked with dislocation mechanics and nowadays is relatively well understood. Concepts and physical models of plastic deformation in amorphous materials on the other hand—where the concept of linear lattice defects is not applicable—still are lagging behind. We introduce an eigenstrain-based finite element lattice model for simulations of shear band formation and strain avalanches. Our model allows us to study the influence of surfaces and finite size effects on the statistics of avalanches. We find that even with relatively complex loading conditions and open boundary conditions, critical exponents describing avalanche statistics are unchanged, which validates the use of simpler scalar lattice-based models to study these phenomena.

Physical and mechanical metallurgy of NiAl

NASA Technical Reports Server (NTRS)

Noebe, Ronald D.; Bowman, Randy R.; Nathal, Michael V.

1994-01-01

Considerable research has been performed on NiAl over the last decade, with an exponential increase in effort occurring over the last few years. This is due to interest in this material for electronic, catalytic, coating and especially high-temperature structural applications. This report uses this wealth of new information to develop a complete description of the properties and processing of NiAl and NiAl-based materials. Emphasis is placed on the controlling fracture and deformation mechanisms of single and polycrystalline NiAl and its alloys over the entire range of temperatures for which data are available. Creep, fatigue, and environmental resistance of this material are discussed. In addition, issues surrounding alloy design, development of NiAl-based composites, and materials processing are addressed.

Fracture and healing of elastomers: A phase-transition theory and numerical implementation

NASA Astrophysics Data System (ADS)

Kumar, Aditya; Francfort, Gilles A.; Lopez-Pamies, Oscar

2018-03-01

A macroscopic theory is proposed to describe, explain, and predict the nucleation and propagation of fracture and healing in elastomers undergoing arbitrarily large quasistatic deformations. The theory, which can be viewed as a natural generalization of the phase-field approximation of the variational theory of brittle fracture of Francfort and Marigo (1998) to account for physical attributes innate to elastomers that have been recently unveiled by experiments at high spatio-temporal resolution, rests on two central ideas. The first one is to view elastomers as solids capable to undergo finite elastic deformations and capable also to phase transition to another solid of vanishingly small stiffness: the forward phase transition serves to model the nucleation and propagation of fracture while the reverse phase transition models the possible healing. The second central idea is to take the phase transition to be driven by the competition between a combination of strain energy and hydrostatic stress concentration in the bulk and surface energy on the created/healed new surfaces in the elastomer. From an applications point of view, the proposed theory amounts to solving a system of two coupled and nonlinear PDEs for the deformation field and an order parameter, or phase field. A numerical scheme is presented to generate solutions for these PDEs in N = 2 and 3 space dimensions. This is based on an efficient non-conforming finite-element discretization, which remains stable for large deformations and elastomers of any compressibility, together with an implicit gradient flow solver, which is able to deal with the large changes in the deformation field that can ensue locally in space and time from the nucleation of fracture. The last part of this paper is devoted to presenting sample simulations of the so-called Gent-Park experiment. Those are confronted with recent experimental results for various types of silicone elastomers.

Structural characteristics of the décollement zone and underthrust sediments in the Nankai accretionary prism: Geologic architectures in the Site C0023, IODP Expedition 370

NASA Astrophysics Data System (ADS)

Yamamoto, Y.; Okutsu, N.; Yamada, Y.; Bowden, S.; Tonai, S.; Yang, K.; Tsang, M. Y.; Hirose, T.; Kamiya, N.

2017-12-01

Expedition 370 penetrated the accretionary prism, plate boundary décollement zone, and underthrust sediment and touched the basement basalt on the Philippine Sea Plate. The drilling site (C0023) is located 4 km NE from the legacy sites, Sites 808 and 1174. Compared to the legacy sites, the décollement zone is characterized by weak and intermittent negative reflectors in the seismic profile. Onboard physical properties, e.g. porosity and P-wave velocity data, indeed show the smaller gaps at the top of the décollement zone. The nature of the deformation along the décollement zone represented 40 m thick phacoidal deformation zone composed of fragmented mudstone with slickenlines on the surfaces in the Sites 808 and 1174. Compare with this, décollement zone in Site C0023 represented the weaker and non-localized deformation zone comprised of alternating zone of 1 m thick phacoidal deformation zones and a few 10 m of intact intervals in the Site C0023. Many normal faults striking parallel to the trench were identified just below the décollement zone, which is indicative of non-localized deformations along the décollement zone. Many of these faults were accompanied with calcite and sulphate mineral veins (anhydrite and barite), indicative of high-temperature fluid migration just above the ridge-spreading center. Based on the paleomagnetic restoration of structure to the geologic coordinate, attitudes of the bedding and fault planes in the Site C0023 are controlled by two factors: 1) subduction/accretion producing the trench-parallel bedding strikes and trench-perpendicular principal stress and 2) ridge spreading that produces ridge-parallel bedding and vein strikes. The former developed in the accretionary prism and the upper part of the underthrust sediment (<900 mbsf), whereas the latter occurs in the lower part (>900 mbsf). These tectonic variations might affect fluid migration pathways.

High-strain-rate deformation of granular silicon carbide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shih, C.J.; Meyers, M.A.; Nesterenko, V.F.

1998-07-01

Silicon carbide powders with three particle size distributions (average sizes of 0.4, 3 and 50 {micro}m) were subjected to strain-controlled, high-strain-rate deformation ({dot {var_epsilon}} {approx} 3 {times} 10{sup 4}/s) in a cylindrical geometry which imposed simultaneous compressive stresses. The experiments involved two explosive stages to (a) densify the powder and to (b) subject the densified granules to large deformation. The powder, with initial density of 33--59% of theoretical density, was densified to densities between 73 and 94% of theoretical density in the first stage. The densified powders were subjected to a global effective strain of {approx}{minus}0.27 in the second stage.more » Their response to be imposed constraints occurred through both homogeneous deformation (82--100%) and shear localization (0--18%), depending on the particle size. In the coarse powder (50 {micro}m), the shear localization process was primarily due to particle break-up (comminution) and rearrangement of the comminuted particles, through a similar mechanism to the bulk and prefractured SiC (Shih, C.J., Nesterenko, V.F. and Meyers, M.A., Journal of Applied Physics, 1998, 83, 4660). Comminution was observed in the medium powder (3 {micro}m), but was never seen in the fine powder (0.4 {micro}m). In medium and fine granular SiC, the shear localization at sufficiently high displacement (>150 {micro}m) leads to the formation of a thin layer (5--20 {micro}m) of well-bonded material. Calculated temperatures in the centers of the bands are up to 2300 C (using an assumed shear strength of 2 GPa and linear thermal softening), which explain the bonding. An analytical model is developed that correctly predicts break-up of large particles and plastic deformation of the smaller ones. It is based on the Griffith fracture criterion and Weibull distribution of strength, which quantitatively express the fact that the fracture is generated by flaws the size of which is limited by the particle size.« less

The physical volcanology of Mars

NASA Technical Reports Server (NTRS)

Mouginis-Mark, Peter J.; Wilson, Lionel; Zuber, Maria T.

1992-01-01

The physical volcanology of Mars is reviewed, with particular attention given to the diversity of volcanic landforms, the implied styles of eruption associated with the construction of these landforms, the inferred internal structure of the volcanoes, and the influence that the eruptions have had on the Martian environment (both local and global in scale). Volcanism in the central highlands appears to have been explosive in character, while most of the constructional activity in the northern plains was effusive. Highlands volcanism appears to be relatively old compared to that in the northern hemisphere. There is evidence for the existence of large magma chambers and very high effusion rate eruptions on Mars. Tectonic deformation associated with volcanic constructs is primarily a consequence of loading and magma transport, while deformation in the volcanic plains reflects stresses associated with Tharsis and major impact basins.

Frictional contact behaviour of the tyre: the effect of tread slip on the in-plane structural deformation and stress field development

NASA Astrophysics Data System (ADS)

Tsotras, Achillefs; Mavros, George

2010-08-01

The analysis of the in-plane deformation of the tyre in relation to the frictional contact between the road and the tread is a crucial first step in the understanding of its contribution to the longitudinal dynamics of a vehicle. In this work, the physical mechanism of the generation of the two-dimensional contact pressure distribution for a non-rolling tyre is studied. Towards this aim, a physical tyre model is constructed, consisting of an analytical ring under pretension, a non-linear sidewall foundation, and a discretised foundation of viscoelastic elements representing the tread. Tread behaviour is examined first, with focus on the development of shear micro-slip. The tread simulation is enhanced with the combination of radial and tangential tread elements and the benefits of such an approach are identified. Subsequently, the contact of the complete model is examined by implementing an algorithm for transient simulations in the time domain. The effects of the imposed vertical load and sidewall non-linearity on the contact stress and strain fields are identified. The modelling approach is validated by comparison with published experimental results. The physical mechanism that couples the torsional and horizontal/vertical deformations of the carcass with the frictional forces at the tread is identified and discussed in detail. The proposed modelling approach is found appropriate for the description of the development of the two-dimensional contact pressure field as a function of the frictional potential of the contact.

3D High Resolution Mesh Deformation Based on Multi Library Wavelet Neural Network Architecture

NASA Astrophysics Data System (ADS)

Dhibi, Naziha; Elkefi, Akram; Bellil, Wajdi; Amar, Chokri Ben

2016-12-01

This paper deals with the features of a novel technique for large Laplacian boundary deformations using estimated rotations. The proposed method is based on a Multi Library Wavelet Neural Network structure founded on several mother wavelet families (MLWNN). The objective is to align features of mesh and minimize distortion with a fixed feature that minimizes the sum of the distances between all corresponding vertices. New mesh deformation method worked in the domain of Region of Interest (ROI). Our approach computes deformed ROI, updates and optimizes it to align features of mesh based on MLWNN and spherical parameterization configuration. This structure has the advantage of constructing the network by several mother wavelets to solve high dimensions problem using the best wavelet mother that models the signal better. The simulation test achieved the robustness and speed considerations when developing deformation methodologies. The Mean-Square Error and the ratio of deformation are low compared to other works from the state of the art. Our approach minimizes distortions with fixed features to have a well reconstructed object.

Effects of fluids on rock deformation and fault slip: From nature to societal impact (Louis Néel Medal Lecture)

NASA Astrophysics Data System (ADS)

Spiers, Christopher J.

2017-04-01

Understanding the effects of fluid-rock interaction on rock and fault mechanical behaviour is central not only to understanding natural tectonic and seismogenic processes, and phenomena such as resource trapping, but also to evaluating the impact of industrial operations in the Earth's crust. These include activities ranging from extraction of geo-energy to geological storage of fuels, CO2 and wastes. For the assessment of both natural and induced geohazards, a physics-based approach to quantifying rock mechanical behaviour is unmissable. Microstructural studies of rocks deformed naturally in the mid and upper crust, or at seismogenic depths in subduction zones, show widespread evidence for brittle deformation (cataclasis), dissolution-precipitation transfer, fluid-related reactions producing weak minerals, and dilatation/cementation of fractures, cracks and pores. In addition, experimental work on rocks and simulated fault gouges has shown that the presence of water strongly influences their mechanical and transport properties. This implies the operation of fluid-assisted deformation mechanisms, such as stress corrosion cracking and diffusive mass transfer (pressure solution). More recently, other fluid-coupled deformation processes have been recognised, in rocks from peridotites and granites to sandstones, limestones and shales. In this lecture, I will give an overview of progress in this area. I will address the physics of pressure solution and stress corrosion cracking and how they contribute to the deformation and compaction of sandstone, carbonate and evaporite rocks in the mid and upper crust, under natural conditions and in the context of deformation caused by geo-resources production and geo-storage. New results on how these processes are affected by pore fluid salinity, gas content and CO2 activity will also be considered, as will data on the effects of mineral-fluid reactions and associated volume changes on rock deformation, fracturing and transport. The effects of gas and CO2 sorption on the stress-strain behaviour and permeability of clay and shale caprocks, recently reported in relation to seal integrity, will be addressed too, and compared with similar phenomena familiar in seen in coal seams. Lastly, I will address the effects of fluid-rock interaction on the frictional behaviour of faults. Recent low velocity friction experiments (<100 μm/s) performed on simulated carbonate, evaporite and quartz gouges, with varying phyllosilicate content, indicate that pressure solution is key to determining whether frictional slip is velocity-strengthening (stable) or velocity weakening (potentially seismogenic). An important trend seen is a transition from velocity strengthening at low temperatures, to velocity weakening at intermediate temperatures, and back to velocity strengthening at high temperatures. This behaviour and the restrengthening observed when shearing is stopped are strongly influenced by water content. It is inferred that mechanistic models for the frictional behaviour of gouge-filled faults, under crustal conditions, must account for diffusion and stress corrosion cracking, and for slip on grain boundaries. First attempts to do this, assuming diffusive mass transfer as the fluid-assisted mechanism, successfully predict the steady state and transient behaviour seen in experiments and offer new perspectives for providing friction laws as for modelling earthquake rupture nucleation and evaluating seismic hazard, in the context of both natural and induced seismicity.

Melorheostosis: A Retrospective Clinical Analysis of 24 Patients at the Mayo Clinic.

PubMed

Smith, Gabriel C; Pingree, Matthew J; Freeman, Laura A; Matsumoto, Jane M; Howe, Benjamin M; Kannas, Stephanie N; Pyfferoen, Mary D; Struss, Leah T; Wenger, Doris E; Amrami, Kimberly K; Matsumoto, Martha; Jurisson, Mary L

2017-03-01

Current understanding of the clinical features of persons with melorheostosis is restricted primarily to individual case reports and small case series. To assess the clinical features of patients with melorheostosis treated at our institution from 1972 through 2010. Chart review. Tertiary academic medical center. Twenty-three patients with "definite" and one patient with "probable" melorheostosis based on radiographic criteria. The eligible study cohort was identified through the Rochester Medical Index database. Further diagnostic confirmation of patients with melorheostosis was performed by radiographic review. We evaluated age at first visit to our institution, gender, affected body area, number of bones affected, presenting symptoms, surgical evaluation, and therapies provided. The average age at first evaluation at our clinic was 36.5 years (median 41.5 years, range 3-68 years). The female to male ratio was 4:1. The lower extremity was most commonly affected (66.6%), followed by upper extremity (33.3%), spine (16.6%), and head (8.3%). One-third of patients had involvement of a single bone; two-thirds had multiple bone involvement. Pain was the most common presenting concern (83.3%), followed by deformity (54.1%), limitation of movement (45.8%), numbness (37.5%), and weakness (25.0%). Most patients had a physician evaluation (87.5%); patients also underwent orthopedic surgery (45.8%), physical therapy (33.3%), and occupational therapy (12.5%). Melorheostosis is a rare sclerotic bone disease resulting in pain, deformity, and dysfunction. An interdisciplinary approach to care should include nonoperative and operative evaluation, as well as appropriate therapies. A prospective approach to evaluation, including imaging and physical examinations, would provide valuable longitudinal data. IV. Copyright © 2017 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Development of an object-oriented finite element program: application to metal-forming and impact simulations

NASA Astrophysics Data System (ADS)

Pantale, O.; Caperaa, S.; Rakotomalala, R.

2004-07-01

During the last 50 years, the development of better numerical methods and more powerful computers has been a major enterprise for the scientific community. In the same time, the finite element method has become a widely used tool for researchers and engineers. Recent advances in computational software have made possible to solve more physical and complex problems such as coupled problems, nonlinearities, high strain and high-strain rate problems. In this field, an accurate analysis of large deformation inelastic problems occurring in metal-forming or impact simulations is extremely important as a consequence of high amount of plastic flow. In this presentation, the object-oriented implementation, using the C++ language, of an explicit finite element code called DynELA is presented. The object-oriented programming (OOP) leads to better-structured codes for the finite element method and facilitates the development, the maintainability and the expandability of such codes. The most significant advantage of OOP is in the modeling of complex physical systems such as deformation processing where the overall complex problem is partitioned in individual sub-problems based on physical, mathematical or geometric reasoning. We first focus on the advantages of OOP for the development of scientific programs. Specific aspects of OOP, such as the inheritance mechanism, the operators overload procedure or the use of template classes are detailed. Then we present the approach used for the development of our finite element code through the presentation of the kinematics, conservative and constitutive laws and their respective implementation in C++. Finally, the efficiency and accuracy of our finite element program are investigated using a number of benchmark tests relative to metal forming and impact simulations.

Random lattice structures. Modelling, manufacture and FEA of their mechanical response

NASA Astrophysics Data System (ADS)

Maliaris, G.; Sarafis, I. T.; Lazaridis, T.; Varoutoglou, A.; Tsakataras, G.

2016-11-01

The implementation of lightweight structures in various applications, especially in Aerospace/ Automotive industries and Orthopaedics, has become a necessity due to their exceptional mechanical properties with respect to reduced weight. In this work we present a Voronoi tessellation based algorithm, which has been developed for modelling stochastic lattice structures. With the proposed algorithm, is possible to generate CAD geometry with controllable structural parameters, such as porosity, cell number and strut thickness. The digital structures were transformed into physical objects through the combination of 3D printing technics and investment casting. This process was applied to check the mechanical behaviour of generated digital models. Until now, the only way to materialize such structures into physical objects, was feasible through 3D printing methods such as Selective Laser Sintering/ Melting (SLS/ SLM). Investment casting possesses numerous advantages against SLS or SLA, with the major one being the material variety. On the other hand, several trials are required in order to calibrate the process parameters to have successful castings, which is the major drawback of investment casting. The manufactured specimens were subjected to compression tests, where their mechanical response was registered in the form of compressive load - displacement curves. Also, a finite element model was developed, using the specimens’ CAD data and compression test parameters. The FE assisted calculation of specimen plastic deformation is identical with the one of the physical object, which validates the conclusions drawn from the simulation results. As it was observed, strut contact is initiated when specimen deformation is approximately 5mm. Although FE calculated compressive force follows the same trend for the first 3mm of compression, then diverges because of the elasto-plastic FE model type definition and the occurred remeshing steps.

Haptic simulation framework for determining virtual dental occlusion.

PubMed

Wu, Wen; Chen, Hui; Cen, Yuhai; Hong, Yang; Khambay, Balvinder; Heng, Pheng Ann

2017-04-01

The surgical treatment of many dentofacial deformities is often complex due to its three-dimensional nature. To determine the dental occlusion in the most stable position is essential for the success of the treatment. Computer-aided virtual planning on individualized patient-specific 3D model can help formulate the surgical plan and predict the surgical change. However, in current computer-aided planning systems, it is not possible to determine the dental occlusion of the digital models in the intuitive way during virtual surgical planning because of absence of haptic feedback. In this paper, a physically based haptic simulation framework is proposed, which can provide surgeons with the intuitive haptic feedback to determine the dental occlusion of the digital models in their most stable position. To provide the physically realistic force feedback when the dental models contact each other during the searching process, the contact model is proposed to describe the dynamic and collision properties of the dental models during the alignment. The simulated impulse/contact-based forces are integrated into the unified simulation framework. A validation study has been conducted on fifteen sets of virtual dental models chosen at random and covering a wide range of the dental relationships found clinically. The dental occlusions obtained by an expert were employed as a benchmark to compare the virtual occlusion results. The mean translational and angular deviations of the virtual occlusion results from the benchmark were small. The experimental results show the validity of our method. The simulated forces can provide valuable insights to determine the virtual dental occlusion. The findings of this work and the validation of proposed concept lead the way for full virtual surgical planning on patient-specific virtual models allowing fully customized treatment plans for the surgical correction of dentofacial deformities.

Effectiveness of Ear Splint Therapy for Ear Deformities

PubMed Central

2017-01-01

Objective To present our experience with ear splint therapy for babies with ear deformities, and thereby demonstrate that this therapy is an effective and safe intervention without significant complications. Methods This was a retrospective study of 54 babies (35 boys and 19 girls; 80 ears; age ≤3 months) with ear deformities who had received ear splint therapy at the Center for Torticollis, Department of Physical Medicine and Rehabilitation, Ajou University Hospital between December 2014 and February 2016. Before the initiation of ear splint therapy, ear deformities were classified with reference to the standard terminology. We compared the severity of ear deformity before and after ear splint therapy by using the physician's ratings. We also compared the physician's ratings and the caregiver's ratings on completion of ear splint therapy. Results Among these 54 babies, 41 children (58 ears, 72.5%) completed the ear splint therapy. The mean age at initiation of therapy was 52.91±18.26 days and the treatment duration was 44.27±32.06 days. Satyr ear, forward-facing ear lobe, Darwinian notch, overfolded ear, and cupped ear were the five most common ear deformities. At the completion of therapy, the final physician's ratings of ear deformities were significantly improved compared to the initial ratings (8.28±1.44 vs. 2.51±0.92; p<0.001). There was no significant difference between the physician's ratings and the caregiver's ratings at the completion of ear splint therapy (8.28±1.44 vs. 8.0±1.61; p=0.297). Conclusion We demonstrated that ear splint therapy significantly improved ear deformities in babies, as measured by quantitative rating scales. Ear splint therapy is an effective and safe intervention for babies with ear deformities. PMID:28289646

Patterns of postural deformity in non-ambulant people with cerebral palsy: what is the relationship between the direction of scoliosis, direction of pelvic obliquity, direction of windswept hip deformity and side of hip dislocation?

PubMed

Porter, David; Michael, Shona; Kirkwood, Craig

2007-12-01

To investigate: (a) associations between the direction of scoliosis, direction of pelvic obliquity, direction of windswept deformity and side of hip subluxation/ dislocation in non-ambulant people with cerebral palsy; and (b) the lateral distribution of these postural asymmetries. Cross-sectional observational study. Posture management services in three centres in the UK. Non-ambulant people at level five on the gross motor function classification system for cerebral palsy. Direction of pelvic obliquity and lateral spinal curvature determined from physical examination, direction of windswept hip deformity derived from range of hip abduction/adduction, and presence/side of unilateral hip subluxation defined by hip migration percentage. A total of 747 participants were included in the study, aged 6-80 years (median 18 years 10 months). Associations between the direction of scoliosis and direction of pelvic obliquity, and between the direction of windswept hip deformity and side hip subluxation/dislocation were confirmed. A significant association was also seen between the direction of scoliosis and the direction of the windswept hip deformity (P<0.001) such that the convexity of the lateral spinal curve was more likely to be opposite to the direction of windsweeping. Furthermore, significantly more windswept deformities to the right (P=0.007), hips subluxed on the left (P=0.002) and lateral lumbar/lower thoracic spinal curves convex to the left (P=0.03) were observed. The individual asymmetrical postural deformities are not unrelated in terms of direction and not equally distributed to the left/right. A pattern of postural deformity was observed.

Patterns of postural deformity in non-ambulant people with cerebral palsy: what is the relationship between the direction of scoliosis, direction of pelvic obliquity, direction of windswept hip deformity and side of hip dislocation?

PubMed Central

Michael, Shona; Kirkwood, Craig

2008-01-01

Objective: To investigate: (a) associations between the direction of scoliosis, direction of pelvic obliquity, direction of windswept deformity and side of hip subluxation/dislocation in non-ambulant people with cerebral palsy; and (b) the lateral distribution of these postural asymmetries. Design: Cross-sectional observational study. Setting: Posture management services in three centres in the UK. Subjects: Non-ambulant people at level five on the gross motor function classification system for cerebral palsy. Main measures: Direction of pelvic obliquity and lateral spinal curvature determined from physical examination, direction of windswept hip deformity derived from range of hip abduction/adduction, and presence/side of unilateral hip subluxation defined by hip migration percentage. Results: A total of 747 participants were included in the study, aged 6–80 years (median 18 years 10 months). Associations between the direction of scoliosis and direction of pelvic obliquity, and between the direction of windswept hip deformity and side hip subluxation/dislocation were confirmed. A significant association was also seen between the direction of scoliosis and the direction of the windswept hip deformity (P < 0.001) such that the convexity of the lateral spinal curve was more likely to be opposite to the direction of windsweeping. Furthermore, significantly more windswept deformities to the right (P = 0.007), hips subluxed on the left (P = 0.002) and lateral lumbar/lower thoracic spinal curves convex to the left (P = 0.03) were observed. Conclusions: The individual asymmetrical postural deformities are not unrelated in terms of direction and not equally distributed to the left/right. A pattern of postural deformity was observed. PMID:18042604

Micromechanics Analysis Code (MAC) User Guide: Version 1.0

NASA Technical Reports Server (NTRS)

Wilt, T. E.; Arnold, S. M.

1994-01-01

The ability to accurately predict the thermomechanical deformation response of advanced composite materials continues to play an important role in the development of these strategic materials. Analytical models that predict the effective behavior of composites are used not only by engineers performing structural analysis of large-scale composite components but also by material scientists in developing new material systems. For an analytical model to fulfill these two distinct functions it must be based on a micromechanics approach which utilizes physically based deformation and life constitutive models and allows one to generate the average (macro) response of a composite material given the properties of the individual constituents and their geometric arrangement. Here the user guide for the recently developed, computationally efficient and comprehensive micromechanics analysis code, MAC, who's predictive capability rests entirely upon the fully analytical generalized method of cells, GMC, micromechanics model is described. MAC is a versatile form of research software that 'drives' the double or triple ply periodic micromechanics constitutive models based upon GMC. MAC enhances the basic capabilities of GMC by providing a modular framework wherein (1) various thermal, mechanical (stress or strain control), and thermomechanical load histories can be imposed; (2) different integration algorithms may be selected; (3) a variety of constituent constitutive models may be utilized and/or implemented; and (4) a variety of fiber architectures may be easily accessed through their corresponding representative volume elements.

Micromechanics Analysis Code (MAC). User Guide: Version 2.0

NASA Technical Reports Server (NTRS)

Wilt, T. E.; Arnold, S. M.

1996-01-01

The ability to accurately predict the thermomechanical deformation response of advanced composite materials continues to play an important role in the development of these strategic materials. Analytical models that predict the effective behavior of composites are used not only by engineers performing structural analysis of large-scale composite components but also by material scientists in developing new material systems. For an analytical model to fulfill these two distinct functions it must be based on a micromechanics approach which utilizes physically based deformation and life constitutive models and allows one to generate the average (macro) response of a composite material given the properties of the individual constituents and their geometric arrangement. Here the user guide for the recently developed, computationally efficient and comprehensive micromechanics analysis code's (MAC) who's predictive capability rests entirely upon the fully analytical generalized method of cells (GMC), micromechanics model is described. MAC is a versatile form of research software that 'drives' the double or triply periodic micromechanics constitutive models based upon GMC. MAC enhances the basic capabilities of GMC by providing a modular framework wherein (1) various thermal, mechanical (stress or strain control) and thermomechanical load histories can be imposed, (2) different integration algorithms may be selected, (3) a variety of constituent constitutive models may be utilized and/or implemented, and (4) a variety of fiber and laminate architectures may be easily accessed through their corresponding representative volume elements.

Thoracolumbar spinal deformity: Part I. A historical passage to 1990: historical vignette.

PubMed

Kanter, Adam S; Bradford, David S; Okonkwo, David O; Rengachary, Setti S; Mummaneni, Praveen V

2009-12-01

Seven millennia of anthropological artifacts and historical tales reference human spinal deformity, its diagnosis, and treatment-many of the latter of which turned out to be worse than the deformity itself. From Hippocrates to Harrington to the 21st century, the literature base has expanded in exponential fashion to yield an imperfect but constantly improving body of evidence, experience, and understanding of this challenging disease phenomenon. This review details the pre-1990 innovations, whose failures and successes have equally contributed to the advancement and dissemination of the increasingly evidence-based field of spinal deformity.

Effect of mechanical properties on erosion resistance of ductile materials

NASA Astrophysics Data System (ADS)

Levin, Boris Feliksovih

Solid particle erosion (SPE) resistance of ductile Fe, Ni, and Co-based alloys as well as commercially pure Ni and Cu was studied. A model for SPE behavior of ductile materials is presented. The model incorporates the mechanical properties of the materials at the deformation conditions associated with SPE process, as well as the evolution of these properties during the erosion induced deformation. An erosion parameter was formulated based on consideration of the energy loss during erosion, and incorporates the material's hardness and toughness at high strain rates. The erosion model predicts that materials combining high hardness and toughness can exhibit good erosion resistance. To measure mechanical properties of materials, high strain rate compression tests using Hopkinson bar technique were conducted at strain rates similar to those during erosion. From these tests, failure strength and strain during erosion were estimated and used to calculate toughness of the materials. The proposed erosion parameter shows good correlation with experimentally measured erosion rates for all tested materials. To analyze subsurface deformation during erosion, microhardness and nanoindentation tests were performed on the cross-sections of the eroded materials and the size of the plastically deformed zone and the increase in materials hardness due to erosion were determined. A nanoindentation method was developed to estimate the restitution coefficient within plastically deformed regions of the eroded samples which provides a measure of the rebounding ability of a material during particle impact. An increase in hardness near the eroded surface led to an increase in restitution coefficient. Also, the stress rates imposed below the eroded surface were comparable to those measured during high strain-rate compression tests (10sp3-10sp4 ssp{-1}). A new parameter, "area under the microhardness curve" was developed that represents the ability of a material to absorb impact energy. By incorporating this parameter into a new erosion model, good correlation was observed with experimentally measured erosion rates. An increase in area under the microhardness curve led to an increase in erosion resistance. It was shown that an increase in hardness below the eroded surface occurs mainly due to the strain-rate hardening effect. Strain-rate sensitivities of tested materials were estimated from the nanoindentation tests and showed a decrease with an increase in materials hardness. Also, materials combining high hardness and strain-rate sensitivity may offer good erosion resistance. A methodology is presented to determine the proper mechanical properties to incorporate into the erosion parameter based on the physical model of the erosion mechanism in ductile materials.

Using tensor-based morphometry to detect structural brain abnormalities in rats with adolescent intermittent alcohol exposure

NASA Astrophysics Data System (ADS)

Paniagua, Beatriz; Ehlers, Cindy; Crews, Fulton; Budin, Francois; Larson, Garrett; Styner, Martin; Oguz, Ipek

2011-03-01

Understanding the effects of adolescent binge drinking that persist into adulthood is a crucial public health issue. Adolescent intermittent ethanol exposure (AIE) is an animal model that can be used to investigate these effects in rodents. In this work, we investigate the application of a particular image analysis technique, tensor-based morphometry, for detecting anatomical differences between AIE and control rats using Diffusion Tensor Imaging (DTI). Deformation field analysis is a popular method for detecting volumetric changes analyzing Jacobian determinants calculated on deformation fields. Recent studies showed that computing deformation field metrics on the full deformation tensor, often referred to as tensor-based morphometry (TBM), increases the sensitivity to anatomical differences. In this paper we conduct a comprehensive TBM study for precisely locating differences between control and AIE rats. Using a DTI RARE sequence designed for minimal geometric distortion, 12-directional images were acquired postmortem for control and AIE rats (n=9). After preprocessing, average images for the two groups were constructed using an unbiased atlas building approach. We non-rigidly register the two atlases using Large Deformation Diffeomorphic Metric Mapping, and analyze the resulting deformation field using TBM. In particular, we evaluate the tensor determinant, geodesic anisotropy, and deformation direction vector (DDV) on the deformation field to detect structural differences. This yields data on the local amount of growth, shrinkage and the directionality of deformation between the groups. We show that TBM can thus be used to measure group morphological differences between rat populations, demonstrating the potential of the proposed framework.

Effect of accelerated ageing and surface sealing on the permanent deformation of auto-polymerising soft linings.

PubMed

da Silva, Joaquim; Takahashi, Jessica; Nuňez, Juliana; Consani, Rafael; Mesquita, Marcelo

2012-09-01

To compare the effects of different ageing methods on the permanent deformation of two permanent soft liners. The materials selected were auto-polymerising acrylic resin and silicone-based reliners. Sealer coating was also evaluated. Sixty specimens of each reliner were manufactured (12.7 mm diameter and 19 mm length). Specimens were randomly distributed into 12 groups (n = 10) and submitted to one of the accelerated ageing processes. Permanent deformation tests were conducted with a mechanical device described within the American Dental Association specification number 18 with a compressive load of 750 gf applied for 30 s. All data were submitted for statistical analysis. Mann-Whitney test compared the effect of the surface sealer on each material and the permanent deformation of the materials in the same ageing group (p = 0.05). Kruskal-Wallis and Dunn tests compared all ageing groups of each material (p = 0.05). The silicone-based reliner presented a lower permanent deformation than the acrylic resin-based reliner, regardless of the ageing procedure. The surface sealer coating was effective only for the thermocycled silicone group and the accelerated ageing processes affected only the permanent deformation of the acrylic resin-based material. The silicone-based reliner presented superior elastic properties and the thermocycling was more effective in ageing the materials. © 2010 The Gerodontology Society and John Wiley & Sons A/S.

Creep deformation mechanism mapping in nickel base disk superalloys

DOE PAGES

Smith, Timothy M.; Unocic, Raymond R.; Deutchman, Hallee; ...

2016-05-10

We investigated the creep deformation mechanisms at intermediate temperature in ME3, a modern Ni-based disk superalloy, using diffraction contrast imaging. Both conventional transmission electron microscopy (TEM) and scanning TEM were utilised. Distinctly different deformation mechanisms become operative during creep at temperatures between 677-815 °C and at stresses ranging from 274 to 724 MPa. Both polycrystalline and single-crystal creep tests were conducted. The single-crystal tests provide new insight into grain orientation effects on creep response and deformation mechanisms. Creep at lower temperatures (≤760 °C) resulted in the thermally activated shearing modes such as microtwinning, stacking fault ribbons and isolated superlattice extrinsicmore » stacking faults. In contrast, these faulting modes occurred much less frequently during creep at 815 °C under lower applied stresses. Instead, the principal deformation mode was dislocation climb bypass. In addition to the difference in creep behaviour and creep deformation mechanisms as a function of stress and temperature, it was also observed that microstructural evolution occurs during creep at 760 °C and above, where the secondary coarsened and the tertiary precipitates dissolved. Based on this work, a creep deformation mechanism map is proposed, emphasising the influence of stress and temperature on the underlying creep mechanisms.« less

SOURCES OF INFORMATION ON ROCK PHYSICS. CURRENT LITERATURE, FEBRUARY 28, 1962

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burgin, L.

1962-02-28

A literature review on the field of rock physics, rock mechanics, wave propagation and other related subjects is presented. The 206 references, wtth abstracts, are included under the following categories: physical properties, rock deformation, loading, engineering applications, seismology, wave propagation, and instruments and methods. In each section the articles are arranged alphabetically according to author. The titles are from material which was made available at the Colorado School of Mines, Arthur Lakes Library during February 1962. (M.C.G.)

Hidden Symmetries in String Theory

NASA Astrophysics Data System (ADS)

Chervonyi, Iurii

In this thesis we study hidden symmetries within the framework of string theory. Symmetries play a very important role in physics: they lead to drastic simplifications, which allow one to compute various physical quantities without relying on perturbative techniques. There are two kinds of hidden symmetries investigated in this work: the first type is associated with dynamics of quantum fields and the second type is related to integrability of strings on various backgrounds. Integrability is a remarkable property of some theories that allows one to determine all dynamical properties of the system using purely analytical methods. The goals of this thesis are twofold: extension of hidden symmetries known in General Relativity to stringy backgrounds in higher dimensions and construction of new integrable string theories. In the context of the first goal we study hidden symmetries of stringy backgrounds, with and without supersymmetry. For supersymmetric geometries produced by D-branes we identify the backgrounds with solvable equations for geodesics, which can potentially give rise to integrable string theories. Relaxing the requirement of supersymmetry, we also study charged black holes in higher dimensions and identify their hidden symmetries encoded in so-called Killing(-Yano) tensors. We construct the explicit form of the Killing(-Yano) tensors for the charged rotating black hole in arbitrary number of dimensions, study behavior of such tensors under string dualities, and use the analysis of hidden symmetries to explain why exact solutions for black rings (black holes with non-spherical event horizons) in more than five dimensions remain elusive. As a byproduct we identify the standard parameterization of AdSp x Sq backgrounds with elliptic coordinates on a flat base. The second goal of this work is construction of new integrable string theories by applying continuous deformations of known examples. We use the recent developments called (generalized) lambda-deformation to construct new integrable backgrounds depending on several continuous parameters and study analytical properties of the such deformations.