Self-monitoring fiber reinforced polymer strengthening system for civil engineering infrastructures

NASA Astrophysics Data System (ADS)

Jiang, Guoliang; Dawood, Mina; Peters, Kara; Rizkalla, Sami

2008-03-01

Fiber reinforced polymer (FRP) materials are currently used for strengthening civil engineering infrastructures. The strengthening system is dependant on the bond characteristics of the FRP to the external surface of the structure to be effective in resisting the applied loads. This paper presents an innovative self-monitoring FRP strengthening system. The system consists of two components which can be embedded in FRP materials to monitor the global and local behavior of the strengthened structure respectively. The first component of the system is designed to evaluate the applied load acting on a structure based on elongation of the FRP layer along the entire span of the structure. Success of the global system has been demonstrated using a full-scale prestressed concrete bridge girder which was loaded up to failure. The test results indicate that this type of sensor can be used to accurately determine the load prior to failure within 15 percent of the measured value. The second sensor component consists of fiber Bragg grating sensors. The sensors were used to monitor the behavior of steel double-lap shear splices tested under tensile loading up to failure. The measurements were used to identify abnormal structural behavior such as epoxy cracking and FRP debonding. Test results were also compared to numerical values obtained from a three dimensional shear-lag model which was developed to predict the sensor response.

Exploring load, velocity, and surface disorder dependence of friction with one-dimensional and two-dimensional models.

PubMed

Dagdeviren, Omur E

2018-08-03

The effect of surface disorder, load, and velocity on friction between a single asperity contact and a model surface is explored with one-dimensional and two-dimensional Prandtl-Tomlinson (PT) models. We show that there are fundamental physical differences between the predictions of one-dimensional and two-dimensional models. The one-dimensional model estimates a monotonic increase in friction and energy dissipation with load, velocity, and surface disorder. However, a two-dimensional PT model, which is expected to approximate a tip-sample system more realistically, reveals a non-monotonic trend, i.e. friction is inert to surface disorder and roughness in wearless friction regime. The two-dimensional model discloses that the surface disorder starts to dominate the friction and energy dissipation when the tip and the sample interact predominantly deep into the repulsive regime. Our numerical calculations address that tracking the minimum energy path and the slip-stick motion are two competing effects that determine the load, velocity, and surface disorder dependence of friction. In the two-dimensional model, the single asperity can follow the minimum energy path in wearless regime; however, with increasing load and sliding velocity, the slip-stick movement dominates the dynamic motion and results in an increase in friction by impeding tracing the minimum energy path. Contrary to the two-dimensional model, when the one-dimensional PT model is employed, the single asperity cannot escape to the minimum energy minimum due to constraint motion and reveals only a trivial dependence of friction on load, velocity, and surface disorder. Our computational analyses clarify the physical differences between the predictions of the one-dimensional and two-dimensional models and open new avenues for disordered surfaces for low energy dissipation applications in wearless friction regime.

Transient Two-Dimensional Analysis of Side Load in Liquid Rocket Engine Nozzles

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2004-01-01

Two-dimensional planar and axisymmetric numerical investigations on the nozzle start-up side load physics were performed. The objective of this study is to develop a computational methodology to identify nozzle side load physics using simplified two-dimensional geometries, in order to come up with a computational strategy to eventually predict the three-dimensional side loads. The computational methodology is based on a multidimensional, finite-volume, viscous, chemically reacting, unstructured-grid, and pressure-based computational fluid dynamics formulation, and a transient inlet condition based on an engine system modeling. The side load physics captured in the low aspect-ratio, two-dimensional planar nozzle include the Coanda effect, afterburning wave, and the associated lip free-shock oscillation. Results of parametric studies indicate that equivalence ratio, combustion and ramp rate affect the side load physics. The side load physics inferred in the high aspect-ratio, axisymmetric nozzle study include the afterburning wave; transition from free-shock to restricted-shock separation, reverting back to free-shock separation, and transforming to restricted-shock separation again; and lip restricted-shock oscillation. The Mach disk loci and wall pressure history studies reconfirm that combustion and the associated thermodynamic properties affect the formation and duration of the asymmetric flow.

Finite micro-tab system for load control on a wind turbine

NASA Astrophysics Data System (ADS)

Bach, A. B.; Lennie, M.; Pechlivanoglou, G.; Nayeri, C. N.; Paschereit, C. O.

2014-06-01

Finite micro-tabs have been investigated experimentally to evaluate the potential for load control on wind turbines. Two dimensional full span, as well as multiple finite tabs of various aspect ratios have been studied on an AH93W174 airfoil at different chord wise positions. A force balance was used to measure the aerodynamic loads. Furthermore, the wake vortex system consisting of the Karman vortex street as well as the tab tip vortices was analyzed with a 12-hole probe and hot wire anemometry. Finally, conventional oil paint as well as a quantitative digital flow analysis technique called SMARTviz were used to visualize the flow around the finite tab configurations. Results have shown that the devices are an effective solution to alleviate the airfoils overall load. The influence of the tab height, tab position as well as the finite tab aspect ratio on the lift and lift to drag ratio have been evaluated. It could be shown, that the lift difference can either be varied by changing the tab height as well as by altering the aspect ratio of the finite tabs. The drag of a two-dimensional flap is directly associated with the vortex street, while in the case of the finite tab, the solidity ratio of the tabs has the strongest effect on the drag. Therefore, the application of a finite tab system showed to improve the lift to drag ratio.

Non-dimensional physics of pulsatile cardiovascular networks and energy efficiency.

PubMed

Yigit, Berk; Pekkan, Kerem

2016-01-01

In Nature, there exist a variety of cardiovascular circulation networks in which the energetic ventricular load has both steady and pulsatile components. Steady load is related to the mean cardiac output (CO) and the haemodynamic resistance of the peripheral vascular system. On the other hand, the pulsatile load is determined by the simultaneous pressure and flow waveforms at the ventricular outlet, which in turn are governed through arterial wave dynamics (transmission) and pulse decay characteristics (windkessel effect). Both the steady and pulsatile contributions of the haemodynamic power load are critical for characterizing/comparing disease states and for predicting the performance of cardiovascular devices. However, haemodynamic performance parameters vary significantly from subject to subject because of body size, heart rate and subject-specific CO. Therefore, a 'normalized' energy dissipation index, as a function of the 'non-dimensional' physical parameters that govern the circulation networks, is needed for comparative/integrative biological studies and clinical decision-making. In this paper, a complete network-independent non-dimensional formulation that incorporates pulsatile flow regimes is developed. Mechanical design variables of cardiovascular flow systems are identified and the Buckingham Pi theorem is formally applied to obtain the corresponding non-dimensional scaling parameter sets. Two scaling approaches are considered to address both the lumped parameter networks and the distributed circulation components. The validity of these non-dimensional number sets is tested extensively through the existing empirical allometric scaling laws of circulation systems. Additional validation studies are performed using a parametric numerical arterial model that represents the transmission and windkessel characteristics, which are adjusted to represent different body sizes and non-dimensional haemodynamic states. Simulations demonstrate that the proposed non-dimensional indices are independent of body size for healthy conditions, but are sensitive to deviations caused by off-design disease states that alter the energetic load. Sensitivity simulations are used to identify the relationship between pulsatile power loss and non-dimensional characteristics, and optimal operational states are computed. © 2016 The Author(s).

Three-dimensional friction measurement during hip simulation

PubMed Central

Braun, Steffen; Al-Salehi, Loay; Reinders, Joern; Mueller, Ulrike; Kretzer, J. Philippe

2017-01-01

Objectives Wear of total hip replacements has been the focus of many studies. However, frictional effects, such as high loading on intramodular connections or the interface to the bone, as well as friction associated squeaking have recently increased interest about the amount of friction that is generated during daily activities. The aim of this study was thus to establish and validate a three-dimensional friction setup under standardized conditions. Materials and methods A standard hip simulator was modified to allow for high precision measurements of small frictional effects in the hip during three-dimensional hip articulation. The setup was verified by an ideal hydrostatic bearing and validated with a static-load physical pendulum and an extension-flexion rotation with a dynamic load profile. Additionally, a pendulum model was proposed for screening measurement of frictional effects based on the damping behavior of the angular oscillation without the need for any force/moment transducer. Finally, three-dimensional friction measurements have been realized for ceramic-on-polyethylene bearings of three different sizes (28, 36 and 40 mm). Results A precision of less than 0.2 Nm during three-dimensional friction measurements was reported, while increased frictional torque (resultant as well as taper torque) was measured for larger head diameters. These effects have been confirmed by simple pendulum tests and the theoretical model. A comparison with current literature about friction measurements is presented. Conclusions This investigation of friction is able to provide more information about a field that has been dominated by the reduction of wear. It should be considered in future pre-clinical testing protocols given by international organizations of standardization. PMID:28886102

Three-dimensional friction measurement during hip simulation.

PubMed

Sonntag, Robert; Braun, Steffen; Al-Salehi, Loay; Reinders, Joern; Mueller, Ulrike; Kretzer, J Philippe

2017-01-01

Wear of total hip replacements has been the focus of many studies. However, frictional effects, such as high loading on intramodular connections or the interface to the bone, as well as friction associated squeaking have recently increased interest about the amount of friction that is generated during daily activities. The aim of this study was thus to establish and validate a three-dimensional friction setup under standardized conditions. A standard hip simulator was modified to allow for high precision measurements of small frictional effects in the hip during three-dimensional hip articulation. The setup was verified by an ideal hydrostatic bearing and validated with a static-load physical pendulum and an extension-flexion rotation with a dynamic load profile. Additionally, a pendulum model was proposed for screening measurement of frictional effects based on the damping behavior of the angular oscillation without the need for any force/moment transducer. Finally, three-dimensional friction measurements have been realized for ceramic-on-polyethylene bearings of three different sizes (28, 36 and 40 mm). A precision of less than 0.2 Nm during three-dimensional friction measurements was reported, while increased frictional torque (resultant as well as taper torque) was measured for larger head diameters. These effects have been confirmed by simple pendulum tests and the theoretical model. A comparison with current literature about friction measurements is presented. This investigation of friction is able to provide more information about a field that has been dominated by the reduction of wear. It should be considered in future pre-clinical testing protocols given by international organizations of standardization.

A new approach to assess movements and isometric postures of spine and trunk at the workplace.

PubMed

Wunderlich, Max; Rüther, Thomas; Essfeld, Dieter; Erren, Thomas C; Piekarski, Claus; Leyk, Dieter

2011-08-01

Low back pain is regarded as the primary cause of occupational disability in many countries worldwide. However, there is a lack of valid assessment of kinematic spine and trunk parameters to provide further insight into occupational spine loads. A new 3-dimensional mobile measurement system (3D-SpineMoveGuard) was developed and evaluated by means of repeated dynamic and isometric trunk positions by 10 male and 10 female volunteers. The interclass correlation coefficient indicates high test-retest reliability (r = 0.975-0.999) of the 3D-SpineMoveGuard. Moreover, analysis of validity revealed almost identical results for the new measurement system. The evaluation study indicates a good scientific quality for the use in occupational task analyses. The objective assessment of indirectly measured spine and trunk kinematics will give further insight to predict and prevent job-related spine loads.

Three-dimensional dynamics of scientific balloon systems in response to sudden gust loadings. [including a computer program user manual

NASA Technical Reports Server (NTRS)

Dorsey, D. R., Jr.

1975-01-01

A mathematical model was developed of the three-dimensional dynamics of a high-altitude scientific research balloon system perturbed from its equilibrium configuration by an arbitrary gust loading. The platform is modelled as a system of four coupled pendula, and the equations of motion were developed in the Lagrangian formalism assuming a small-angle approximation. Three-dimensional pendulation, torsion, and precessional motion due to Coriolis forces are considered. Aerodynamic and viscous damping effects on the pendulatory and torsional motions are included. A general model of the gust field incident upon the balloon system was developed. The digital computer simulation program is described, and a guide to its use is given.

Single Vector Calibration System for Multi-Axis Load Cells and Method for Calibrating a Multi-Axis Load Cell

NASA Technical Reports Server (NTRS)

Parker, Peter A. (Inventor)

2003-01-01

A single vector calibration system is provided which facilitates the calibration of multi-axis load cells, including wind tunnel force balances. The single vector system provides the capability to calibrate a multi-axis load cell using a single directional load, for example loading solely in the gravitational direction. The system manipulates the load cell in three-dimensional space, while keeping the uni-directional calibration load aligned. The use of a single vector calibration load reduces the set-up time for the multi-axis load combinations needed to generate a complete calibration mathematical model. The system also reduces load application inaccuracies caused by the conventional requirement to generate multiple force vectors. The simplicity of the system reduces calibration time and cost, while simultaneously increasing calibration accuracy.

Two Dimensional Heat Transfer around Penetrations in Multilayer Insulation

NASA Technical Reports Server (NTRS)

Johnson, Wesley L.; Kelly, Andrew O.; Jumper, Kevin M.

2012-01-01

The objective of this task was to quantify thermal losses involving integrating MLI into real life situations. Testing specifically focused on the effects of penetrations (including structural attachments, electrical conduit/feedthroughs, and fluid lines) through MLI. While there have been attempts at quantifying these losses both analytically and experimentally, none have included a thorough investigation of the methods and materials that could be used in such applications. To attempt to quantify the excess heat load coming into the system due to the integration losses, a calorimeter was designed to study two dimensional heat transfer through penetrated MLI. The test matrix was designed to take as many variables into account as was possible with the limited test duration and system size. The parameters varied were the attachment mechanism, the buffer material (for buffer attachment mechanisms only), the thickness of the buffer, and the penetration material. The work done under this task is an attempt to measure the parasitic heat loads and affected insulation areas produced by system integration, to model the parasitic loads, and from the model produce engineering equations to allow for the determination of parasitic heat loads in future applications. The methods of integration investigated were no integration, using a buffer to thermally isolate the strut from the MLI, and temperature matching the MLI on the strut. Several materials were investigated as a buffer material including aerogel blankets, aerogel bead packages, cryolite, and even an evacuated vacuum space (in essence a no buffer condition).

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

Ferreira, C; Ahmad, S; Firestone, B

Purpose: To compare dosimetrically three plan calculation systems (Plato, Varian Brachytherapy, and in-house-made Excel) available for I-125 COMS eye plaque treatment with measurement. Methods: All systems assume homogeneous media and calculations are based on a three-dimensional Cartesian coordinates, Plato and Brachytherapy Planning are based on AAPM TG-43 and the in-house Excel program only on inverse square corrections. Doses at specific depths were measured with EBT3 Gafchromic film from a fully loaded and a partially loaded 16 mm plaque (13 and 8 seeds respectively, I-125, model 6711 GE, Oncura). Measurements took place in a water tank, utilizing solid water blocks andmore » a 3D-printed plaque holder. Taking advantage that gafchromic film has low energy dependence, a dose step wedge was delivered with 6 MV photon beam from a Varian 2100 EX linac for calibration. The gray-scale to dose in cGy was obtained with an Epson Expression 10000 XL scanner in the green channel. Treatment plans were generated for doses of 2200 cGy to a depth of 7 mm, and measurements were taken on a sagittal plane. Results: The calculated dose at the prescription point was 2242, 2344, and 2211 cGy with Excel, Brachyvision and Plato respectively for a fully loaded plaque, for the partially loaded plaque the doses were 2266, 2477, and 2193 cGy respectively. At 5 mm depth the doses for Brachyvision and Plato were comparable (3399 and 3267 cGy respectively), however, the measured dose in film was 3180 cGy which was lower by as much as 6.4% in the fully loaded plaque and 7.6% in the partially loaded plaque. Conclusion: Careful methodology and calibration are essential when measuring doses at specific depth due to the sensitivity and rapid dose fall off of I-125.« less

Three-Dimensional Dynamic Analyses of Track-Embankment-Ground System Subjected to High Speed Train Loads

PubMed Central

2014-01-01

A three-dimensional finite element model was developed to investigate dynamic response of track-embankment-ground system subjected to moving loads caused by high speed trains. The track-embankment-ground systems such as the sleepers, the ballast, the embankment, and the ground are represented by 8-noded solid elements. The infinite elements are used to represent the infinite boundary condition to absorb vibration waves induced by the passing of train load at the boundary. The loads were applied on the rails directly to simulate the real moving loads of trains. The effects of train speed on dynamic response of the system are considered. The effect of material parameters, especially the modulus changes of ballast and embankment, is taken into account to demonstrate the effectiveness of strengthening the ballast, embankment, and ground for mitigating system vibration in detail. The numerical results show that the model is reliable for predicting the amplitude of vibrations produced in the track-embankment-ground system by high-speed trains. Stiffening of fill under the embankment can reduce the vibration level, on the other hand, it can be realized by installing a concrete slab under the embankment. The influence of axle load on the vibration of the system is obviously lower than that of train speed. PMID:24723838

Three-dimensional dynamic analyses of track-embankment-ground system subjected to high speed train loads.

PubMed

Fu, Qiang; Zheng, Changjie

2014-01-01

A three-dimensional finite element model was developed to investigate dynamic response of track-embankment-ground system subjected to moving loads caused by high speed trains. The track-embankment-ground systems such as the sleepers, the ballast, the embankment, and the ground are represented by 8-noded solid elements. The infinite elements are used to represent the infinite boundary condition to absorb vibration waves induced by the passing of train load at the boundary. The loads were applied on the rails directly to simulate the real moving loads of trains. The effects of train speed on dynamic response of the system are considered. The effect of material parameters, especially the modulus changes of ballast and embankment, is taken into account to demonstrate the effectiveness of strengthening the ballast, embankment, and ground for mitigating system vibration in detail. The numerical results show that the model is reliable for predicting the amplitude of vibrations produced in the track-embankment-ground system by high-speed trains. Stiffening of fill under the embankment can reduce the vibration level, on the other hand, it can be realized by installing a concrete slab under the embankment. The influence of axle load on the vibration of the system is obviously lower than that of train speed.

Three-dimensional quantification of pretorqued nickel-titanium wires in edgewise and prescription brackets.

PubMed

Mittal, Nitika; Xia, Zeyang; Chen, Jie; Stewart, Kelton T; Liu, Sean Shih-Yao

2013-05-01

To quantify the three-dimensional moments and forces produced by pretorqued nickel-titanium (NiTi) rectangular archwires fully engaged in 0.018- and 0.022-inch slots of central incisor and molar edgewise and prescription brackets. Ten identical acrylic dental models with retroclined maxillary incisors were fabricated for bonding with various bracket-wire combinations. Edgewise, Roth, and MBT brackets with 0.018- and 0.022-inch slots were bonded in a simulated 2 × 4 clinical scenario. The left central incisor and molar were sectioned and attached to load cells. Correspondingly sized straight and pretorqued NiTi archwires were ligated to the brackets using 0.010-inch ligatures. Each load cell simultaneously measured three force (Fx, Fy, Fz) and three moment (Mx, My, Mz) components. The faciolingual, mesiodistal, and inciso-occluso/apical axes of the teeth corresponded to the x, y, and z axes of the load cells, respectively. Each wire was removed and retested seven times. Three-way analysis of variance (ANOVA) examined the effects of wire type, wire size, and bracket type on the measured orthodontic load systems. Interactions among the three effects were examined and pair-wise comparisons between significant combinations were performed. The force and moment components on each tooth were quantified according to their local coordinate axes. The three-way ANOVA interaction terms were significant for all force and moment measurements (P < .05), except for Fy (P > .05). The pretorqued wire generates a significantly larger incisor facial crown torquing moment in the MBT prescription compared to Roth, edgewise, and the straight NiTi wire.

Analysis of No-load Iron Losses of Turbine Generators by 3D Magnetic Field Analysis

NASA Astrophysics Data System (ADS)

Nakahara, Akihito; Mogi, Hisashi; Takahashi, Kazuhiko; Ide, Kazumasa; Kaneda, Junya; Hattori, Ken'Ichi; Watanabe, Takashi; Kaido, Chikara; Minematsu, Eisuke; Hanzawa, Kazufumi

This paper focuses on no-load iron losses of turbine generators. To calculate iron losses of turbine generators a program was developed. In the program, core loss curves of materials used for stator core were reproduced precisely by using tables of loss coefficients. Accuracy of calculation by this method was confirmed by comparing calculated values with measured in a model stator core. The iron loss of a turbine generator estimated with considering three-dimensional distribution of magnetic fluxes. And additional losses included in measured iron loss was evaluated with three-dimensional magnetic field analysis.

Investigation of maximum local specific absorption rate in 7 T magnetic resonance with respect to load size by use of electromagnetic simulations.

PubMed

Tiberi, Gianluigi; Fontana, Nunzia; Costagli, Mauro; Stara, Riccardo; Biagi, Laura; Symms, Mark Roger; Monorchio, Agostino; Retico, Alessandra; Cosottini, Mirco; Tosetti, Michela

2015-07-01

Local specific absorption rate (SAR) evaluation in ultra high field (UHF) magnetic resonance (MR) systems is a major concern. In fact, at UHF, radiofrequency (RF) field inhomogeneity generates hot-spots that could cause localized tissue heating. Unfortunately, local SAR measurements are not available in present MR systems; thus, electromagnetic simulations must be performed for RF fields and SAR analysis. In this study, we used three-dimensional full-wave numerical electromagnetic simulations to investigate the dependence of local SAR at 7.0 T with respect to subject size in two different scenarios: surface coil loaded by adult and child calves and quadrature volume coil loaded by adult and child heads. In the surface coil scenario, maximum local SAR decreased with decreasing load size, provided that the RF magnetic fields for the different load sizes were scaled to achieve the same slice average value. On the contrary, in the volume coil scenario, maximum local SAR was up to 15% higher in children than in adults. © 2015 Wiley Periodicals, Inc.

A new method for assessing relative dynamic motion of vertebral bodies during cyclic loading in vitro.

PubMed

Dean, J C; Wilcox, C H; Daniels, A U; Goodwin, R R; Van Wagoner, E; Dunn, H K

1991-01-01

A new experimental technique for measuring generalized three-dimensional motion of vertebral bodies during cyclic loading in vitro is presented. The system consists of an orthogonal array of three lasers mounted rigidly to one vertebra, and a set of three mutually orthogonal charge-coupled devices mounted rigidly to an adjacent vertebra. Each laser strikes a corresponding charge-coupled device screen. The mathematical model of the system is reduced to a linear set of equations with consequent matrix algebra allowing fast real-time data reduction during cyclic movements of the spine. The range and accuracy of the system is well suited for studying thoracolumbar motion segments. Distinct advantages of the system include miniaturization of the components, the elimination of the need for mechanical linkages between the bodies, and a high degree of accuracy which is not dependent on viewing volume as found in photogrammetric systems. More generally, the spectrum of potential applications of systems of this type to the real-time measurement of the relative motion of two bodies is extremely broad.

Model Deformation Measurements at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Burner, A. W.

1998-01-01

Only recently have large amounts of model deformation data been acquired in NASA wind tunnels. This acquisition of model deformation data was made possible by the development of an automated video photogrammetric system to measure the changes in wing twist and bending under aerodynamic load. The measurement technique is based upon a single view photogrammetric determination of two dimensional coordinates of wing targets with a fixed third dimensional coordinate, namely the spanwise location. A major consideration in the development of the measurement system was that use of the technique must not appreciably reduce wind tunnel productivity. The measurement technique has been used successfully for a number of tests at four large production wind tunnels at NASA and a dedicated system is nearing completion for a fifth facility. These facilities are the National Transonic Facility, the Transonic Dynamics Tunnel, and the Unitary Plan Wind Tunnel at NASA Langley, and the 12-FT Pressure Tunnel at NASA Ames. A dedicated system for the Langley 16-Foot Transonic Tunnel is scheduled to be used for the first time for a test in September. The advantages, limitations, and strategy of the technique as currently used in NASA wind tunnels are presented. Model deformation data are presented which illustrate the value of these measurements. Plans for further enhancements to the technique are presented.

Effect of fluid loading on left ventricular volume and stroke volume variability in patients with end-stage renal disease: a pilot study

PubMed Central

Kanda, Hirotsugu; Hirasaki, Yuji; Iida, Takafumi; Kanao-Kanda, Megumi; Toyama, Yuki; Kunisawa, Takayuki; Iwasaki, Hiroshi

2015-01-01

Purpose The aim of this study was to investigate fluid loading-induced changes in left ventricular end-diastolic volume (LVEDV) and stroke volume variability (SVV) in patients with end-stage renal disease (ESRD) using real-time three-dimensional transesophageal echocardiography and the Vigileo-FloTrac system. Patients and methods After obtaining ethics committee approval and informed consent, 28 patients undergoing peripheral vascular procedures were studied. Fourteen patients with ESRD on hemodialysis (HD) were assigned to the HD group and 14 patients without ESRD were assigned to the control group. Institutional standardized general anesthesia was provided in both groups. SVV was measured using the Vigileo-FloTrac system. Simultaneously, a full-volume three-dimensional transesophageal echocardiography dataset was acquired to measure LVEDV, left ventricular end-systolic volume, and left ventricular ejection fraction. Measurements were obtained before and after loading 500 mL hydroxyethyl starch over 30 minutes in both groups. Results In the control group, intravenous colloid infusion was associated with a significant decrease in SVV (13.8%±2.6% to 6.5%±2.6%, P<0.001) and a significant increase in LVEDV (83.6±23.4 mL to 96.1±28.8 mL, P<0.001). While SVV significantly decreased after infusion in the HD group (16.2%±6.0% to 6.2%±2.8%, P<0.001), there was no significant change in LVEDV. Conclusion Our preliminary data suggest that fluid responsiveness can be assessed not by LVEDV but also by SVV due to underlying cardiovascular pathophysiology in patients with ESRD. PMID:26527879

Transient Three-Dimensional Analysis of Side Load in Liquid Rocket Engine Nozzles

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2004-01-01

Three-dimensional numerical investigations on the nozzle start-up side load physics were performed. The objective of this study is to identify the three-dimensional side load physics and to compute the associated aerodynamic side load using an anchored computational methodology. The computational methodology is based on an unstructured-grid, and pressure-based computational fluid dynamics formulation, and a simulated inlet condition based on a system calculation. Finite-rate chemistry was used throughout the study so that combustion effect is always included, and the effect of wall cooling on side load physics is studied. The side load physics captured include the afterburning wave, transition from free- shock to restricted-shock separation, and lip Lambda shock oscillation. With the adiabatic nozzle, free-shock separation reappears after the transition from free-shock separation to restricted-shock separation, and the subsequent flow pattern of the simultaneous free-shock and restricted-shock separations creates a very asymmetric Mach disk flow. With the cooled nozzle, the more symmetric restricted-shock separation persisted throughout the start-up transient after the transition, leading to an overall lower side load than that of the adiabatic nozzle. The tepee structures corresponding to the maximum side load were addressed.

An on-line monitoring system for oil-film, pressure and temperature distributions in large-scale hydro-generator bearings

NASA Astrophysics Data System (ADS)

Höbel, M.; Haffner, K.

1999-05-01

Instrumentation that allows the behaviour of a hydro-generator thrust bearing to be monitored during operation is described. The measurement system was developed at the Asea Brown Boveri corporate research centre in Switzerland and was tested under realistic operating conditions at the Harbin Electric Machinery Company bearing-testing facility in the People's Republic of China. Newly developed fibre-optical proximity probes were used for the on-line monitoring of the thin oil film between the static and rotating parts of the bearing. These sensors are based on a back-reflection technique and can be used for various target materials such as Babbitt and Teflon. The monitoring system comprises about 120 temperature sensors, four pressure sensors and five optical oil-film thickness sensors. Temperature sensors are installed at specific static locations, whereas pressure and oil-film sensors are positioned in the runner and generate data during rotation. A special feature of the monitoring equipment is its on-line processing capability. Digital signal processors operating in parallel handle pressure and oil-film thickness data. Important measurement parameters such as the maximum pressure, maximum temperature and minimum oil-film thickness are displayed on-line. Detailed three-dimensional temperature information on one of the load segments can be obtained from subsequent off-line data analysis. The system also calculates two-dimensional plots of the oil-film thickness and pressure for most of the 12 load segments.

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces.

PubMed

Song, Sukho; Drotlef, Dirk-Michael; Majidi, Carmel; Sitti, Metin

2017-05-30

For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ∼26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad.

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

NASA Astrophysics Data System (ADS)

Song, Sukho; Drotlef, Dirk-Michael; Majidi, Carmel; Sitti, Metin

2017-05-01

For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ˜26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad.

Controllable load sharing for soft adhesive interfaces on three-dimensional surfaces

PubMed Central

Song, Sukho; Drotlef, Dirk-Michael; Majidi, Carmel; Sitti, Metin

2017-01-01

For adhering to three-dimensional (3D) surfaces or objects, current adhesion systems are limited by a fundamental trade-off between 3D surface conformability and high adhesion strength. This limitation arises from the need for a soft, mechanically compliant interface, which enables conformability to nonflat and irregularly shaped surfaces but significantly reduces the interfacial fracture strength. In this work, we overcome this trade-off with an adhesion-based soft-gripping system that exhibits enhanced fracture strength without sacrificing conformability to nonplanar 3D surfaces. Composed of a gecko-inspired elastomeric microfibrillar adhesive membrane supported by a pressure-controlled deformable gripper body, the proposed soft-gripping system controls the bonding strength by changing its internal pressure and exploiting the mechanics of interfacial equal load sharing. The soft adhesion system can use up to ∼26% of the maximum adhesion of the fibrillar membrane, which is 14× higher than the adhering membrane without load sharing. Our proposed load-sharing method suggests a paradigm for soft adhesion-based gripping and transfer-printing systems that achieves area scaling similar to that of a natural gecko footpad. PMID:28507143

A large motion zero-gravity suspension system for experimental simulation of orbital construction and deployment. M.S. Thesis

NASA Technical Reports Server (NTRS)

Straube, Timothy Milton

1993-01-01

The design and implementation of a vertical degree of freedom suspension system is described which provides a constant force off-load condition to counter gravity over large displacements. By accommodating motions up to one meter for structures weighing up to 100 pounds, the system is useful for experiments which simulate orbital construction events such as docking, multiple component assembly, or structural deployment. A unique aspect of this device is the combination of a large stroke passive off-load device augmented by electromotive torque actuated force feedback. The active force feedback has the effect of reducing break-away friction by a factor of twenty over the passive system alone. The thesis describes the development of the suspension hardware and the control algorithm. Experiments were performed to verify the suspensions system's effectiveness in providing a gravity off-load and simulating the motion of a structure in orbit. Additionally, a three dimensional system concept is presented as an extension of the one dimensional suspension system which was implemented.

The use of 3d scanner for testing changes in shape of human limbs under the influence of external mechanical load

NASA Astrophysics Data System (ADS)

Kasperska, Kamila; Wieczorowski, Michał; Krolczyk, Jolanta B.

2017-10-01

Three-dimensional scanning is used in many fields: medicine, architecture, industry, reverse engineering. The aim of the article was to analyze the changes in the shape of the limbs under the influence of a mechanical external load using the method of three-dimensional scanner uses white light technology. The paper presents a system of human movement, passive part - skeleton and active part - the muscles, and principles of their interaction, which results in a change of the position of the body. Furthermore, by using the 3D scan, the differences in appearance of the arm and leg depending on the size of the external load in different positions have been presented. The paper shows that with increasing load, which muscles must prevent, increases the volume of certain parts of the legs, while another parts of them will be reduced. Results of the research using three-dimensional scanner allow determining what impact on changing the legs shape has an external mechanical load.

Heat as a tracer to estimate dissolved organic carbon flux from a restored wetland

USGS Publications Warehouse

Burow, K.R.; Constantz, J.; Fujii, R.

2005-01-01

Heat was used as a natural tracer to characterize shallow ground water flow beneath a complex wetland system. Hydrogeologic data were combined with measured vertical temperature profiles to constrain a series of two-dimensional, transient simulations of ground water flow and heat transport using the model code SUTRA (Voss 1990). The measured seasonal temperature signal reached depths of 2.7 m beneath the pond. Hydraulic conductivity was varied in each of the layers in the model in a systematic manual calibration of the two-dimensional model to obtain the best fit to the measured temperature and hydraulic head. Results of a series of representative best-fit simulations represent a range in hydraulic conductivity values that had the best agreement between simulated and observed temperatures and that resulted in simulated pond seepage values within 1 order of magnitude of pond seepage estimated from the water budget. Resulting estimates of ground water discharge to an adjacent agricultural drainage ditch were used to estimate potential dissolved organic carbon (DOC) loads resulting from the restored wetland. Estimated DOC loads ranged from 45 to 1340 g C/(m2 year), which is higher than estimated DOC loads from surface water. In spite of the complexity in characterizing ground water flow in peat soils, using heat as a tracer provided a constrained estimate of subsurface flow from the pond to the agricultural drainage ditch. Copyright ?? 2005 National Ground Water Association.

Three-Dimensional, Inelastic Response of Single-Edge Notch Bend Specimens Subjected to Impact Loading

DTIC Science & Technology

1993-08-01

measure the inherent fracture toughness of a material. A thor- ough understanding of the test specimen behavior is a prerequisite to the application of...measured material properties in structural applications . Three- dimensional dynamic analyses are performed for three different specimen configurations...derstanding of the test specimen behavior is a prerequisite to the application of measured ma- terial properties in structural applications . Three

The influence of patellofemoral joint contact geometry on the modeling of three dimensional patellofemoral joint forces.

PubMed

Powers, Christopher M; Chen, Yu-Jen; Scher, Irving; Lee, Thay Q

2006-01-01

The purpose of this study was to determine the influence of patellofemoral joint contact geometry on the modeling of three-dimensional patellofemoral joint forces. To achieve this goal, patellofemoral joint reaction forces (PFJRFs) that were measured from an in-vitro cadaveric set-up were compared to PFJRFs estimated from a computer model that did not consider patellofemoral joint contact geometry. Ten cadaver knees were used in this study. Each was mounted on a custom jig that was fixed to an Instron frame. Quadriceps muscle loads were accomplished using a pulley system and weights. The force in the patellar ligament was obtained using a buckle transducer. To quantify the magnitude and direction of the PFJRF, a six-axis load cell was incorporated into the femoral fixation system so that a rigid body assumption could be made. PFJRF data were obtained at 0 degrees , 20 degrees , 40 degrees and 60 degrees of knee flexion. Following in vitro testing, SIMM modeling software was used to develop computational models based on the three-dimensional coordinates (Microscribe digitizer) of individual muscle and patellar ligament force vectors obtained from the cadaver knees. The overall magnitude of the PFJRF estimated from the computer generated models closely matched the direct measurements from the in vitro set-up (Pearson's correlation coefficient, R(2)=0.91, p<0.001). Although the computational model accurately estimated the posteriorly directed forces acting on the joint, some discrepancies were noted in the forces acting in the superior and lateral directions. These differences however, were relatively small when expressed as a total of the overall PFJRF magnitude.

In situ measurements of thunderstorm electrical properties

NASA Technical Reports Server (NTRS)

Marshall, T. C.

1982-01-01

An airplane sensor to measure the charge, size and two dimensional shape of precipitation particles and large cloud particles was developed. The basic design of the instrument includes: the transducers and analog electronics, the analog to digital conversion electronics and a microprocessor based system to run the electronics and load the digital data onto magnetic tape. Prototype instrumentation for the proposed lightning mapper satellite was tested by flying it in a U-2 aircraft over severe storms in Oklahoma. Flight data are compared to data from ground based instruments.

A Relationship Between Constraint and the Critical Crack Tip Opening Angle

NASA Technical Reports Server (NTRS)

Johnston, William M.; James, Mark A.

2009-01-01

Of the various approaches used to model and predict fracture, the Crack Tip Opening Angle (CTOA) fracture criterion has been successfully used for a wide range of two-dimensional thin-sheet and thin plate applications. As thicker structure is considered, modeling the full three-dimensional fracture process will become essential. This paper investigates relationships between the local CTOA evaluated along a three-dimensional crack front and the corresponding local constraint. Previously reported tunneling crack front shapes were measured during fracture by pausing each test and fatigue cycling the specimens to mark the crack surface. Finite element analyses were run to model the tunneling shape during fracture, with the analysis loading conditions duplicating those tests. The results show an inverse relationship between the critical fracture value and constraint which is valid both before maximum load and after maximum load.

Load partitioning in Ai{sub 2}0{sub 3-}Al composites with three- dimensional periodic architecture.

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

Young, M. L.; Rao, R.; Almer, J. D.

2009-05-01

Interpenetrating composites are created by infiltration of liquid aluminum into three-dimensional (3-D) periodic Al{sub 2}O{sub 3} preforms with simple tetragonal symmetry produced by direct-write assembly. Volume-averaged lattice strains in the Al{sub 2}O{sub 3} phase of the composite are measured by synchrotron X-ray diffraction for various uniaxial compression stresses up to -350MPa. Load transfer, found by diffraction to occur from the metal phase to the ceramic phase, is in general agreement with simple rule-of-mixture models and in better agreement with more complex, 3-D finite-element models that account for metal plasticity and details of the geometry of both phases. Spatially resolved diffractionmore » measurements show variations in load transfer at two different positions within the composite.« less

Loading ultracold gases in topological Floquet bands: the fate of current and center-of-mass responses

NASA Astrophysics Data System (ADS)

Dauphin, Alexandre; Tran, Duc-Thanh; Lewenstein, Maciej; Goldman, Nathan

2017-06-01

Topological band structures can be designed by subjecting lattice systems to time-periodic modulations, as was proposed for irradiated graphene, and recently demonstrated in two-dimensional (2D) ultracold gases and photonic crystals. However, changing the topological nature of Floquet Bloch bands from trivial to non-trivial, by progressively launching the time-modulation, is necessarily accompanied with gap-closing processes: this has important consequences for the loading of particles into a target Floquet band with non-trivial topology, and hence, on the subsequent measurements. In this work, we analyse how such loading sequences can be optimized in view of probing the topology of 2D Floquet bands through transport measurements. In particular, we demonstrate the robustness of center-of-mass responses, as compared to current responses, which present important irregularities due to an interplay between the micro-motion of the drive and inter-band interference effects. The results presented in this work illustrate how probing the center-of-mass displacement of atomic clouds offers a reliable method to detect the topology of Floquet bands, after realistic loading sequences.

A versatile electrostatic trap with open optical access

NASA Astrophysics Data System (ADS)

Li, Sheng-Qiang; Yin, Jian-Ping

2018-04-01

A versatile electrostatic trap with open optical access for cold polar molecules in weak-field-seeking state is proposed in this paper. The trap is composed of a pair of disk electrodes and a hexapole. With the help of a finite element software, the spatial distribution of the electrostatic field is calculated. The results indicate that a three-dimensional closed electrostatic trap is formed. Taking ND3 molecules as an example, the dynamic process of loading and trapping is simulated. The results show that when the velocity of the molecular beam is 10 m/s and the loading time is 0.9964 ms, the maximum loading efficiency reaches 94.25% and the temperature of the trapped molecules reaches about 30.3 mK. A single well can be split into two wells, which is of significant importance to the precision measurement and interference of matter waves. This scheme, in addition, can be further miniaturized to construct one-dimensional, two-dimensional, and three-dimensional spatial electrostatic lattices.

Multi-Hazard Assessment of Scour Damaged Bridges with UAS-Based Measurements

NASA Astrophysics Data System (ADS)

Özcan, O.; Ozcan, O.

2017-12-01

Flood and stream induced scour occurring in bridge piers constructed on rivers is one of the mostly observed failure reasons in bridges. Scour induced failure risk in bridges and determination of the alterations in bridge safety under seismic effects has the ultimate importance. Thus, for the determination of bridge safety under the scour effects, the scour amount under bridge piers should be designated realistically and should be tracked and updated continuously. Hereby, the scour induced failures in bridge foundation systems will be prevented and bridge substructure design will be conducted safely. In this study, in order to measure the amount of scour in bridge load bearing system (pile foundations and pile abutments) and to attain very high definition 3 dimensional models of river flood plain for the flood analysis, unmanned aircraft system (UAS) based measurement methods were implemented. UAS based measurement systems provide new and practical approach and bring high precision and reliable solutions considering recent measurement systems. For this purpose, the reinforced concrete (RC) bridge that is located on Antalya Boğaçayı River, Turkey and that failed in 2003 due to flood-induced scour was selected as the case study. The amount of scour occurred in bridge piers and piles was determined realistically and the behavior of bridge piers under scour effects was investigated. Future flood effects and the resultant amount of scour was determined with HEC-RAS software by using digital surface models that were obtained at regular intervals using UAS for the riverbed. In the light of the attained scour measurements and expected scour after a probable flood event, the behavior of scour damaged RC bridge was investigated by pushover and time history analyses under lateral and vertical seismic loadings. In the analyses, the load and displacement capacity of bridge was observed to diminish significantly under expected scour. Thus, the deterioration in multi hazard performance of the bridge was monitored significantly in the light of updated bridge load bearing system capacity. Regarding the case study, UAS based and continuously updated bridge multi hazard risk detection system was established that can be used for bridges located on riverbed.

Microscopic full-field three-dimensional strain measurement during the mechanical testing of additively manufactured porous biomaterials.

PubMed

Genovese, Katia; Leeflang, Sander; Zadpoor, Amir A

2017-05-01

A custom-designed micro-digital image correlation system was used to track the evolution of the full-surface three-dimensional strain field of Ti6Al4V additively manufactured lattice samples under mechanical loading. The high-magnification capabilities of the method allowed to resolve the strain distribution down to the strut level and disclosed a highly heterogeneous mechanical response of the lattice structure with local strain concentrations well above the nominal global strain level. In particular, we quantified that strain heterogeneity appears at a very early stage of the deformation process and increases with load, showing a strain accumulation pattern with a clear correlation to the later onset of the fracture. The obtained results suggest that the unique opportunities offered by the proposed experimental method, in conjunction with analytical and computational models, could serve to provide novel important information for the rational design of additively manufactured porous biomaterials. Copyright © 2017 Elsevier Ltd. All rights reserved.

On the dimension of complex responses in nonlinear structural vibrations

NASA Astrophysics Data System (ADS)

Wiebe, R.; Spottswood, S. M.

2016-07-01

The ability to accurately model engineering systems under extreme dynamic loads would prove a major breakthrough in many aspects of aerospace, mechanical, and civil engineering. Extreme loads frequently induce both nonlinearities and coupling which increase the complexity of the response and the computational cost of finite element models. Dimension reduction has recently gained traction and promises the ability to distill dynamic responses down to a minimal dimension without sacrificing accuracy. In this context, the dimensionality of a response is related to the number of modes needed in a reduced order model to accurately simulate the response. Thus, an important step is characterizing the dimensionality of complex nonlinear responses of structures. In this work, the dimensionality of the nonlinear response of a post-buckled beam is investigated. Significant detail is dedicated to carefully introducing the experiment, the verification of a finite element model, and the dimensionality estimation algorithm as it is hoped that this system may help serve as a benchmark test case. It is shown that with minor modifications, the method of false nearest neighbors can quantitatively distinguish between the response dimension of various snap-through, non-snap-through, random, and deterministic loads. The state-space dimension of the nonlinear system in question increased from 2-to-10 as the system response moved from simple, low-level harmonic to chaotic snap-through. Beyond the problem studied herein, the techniques developed will serve as a prescriptive guide in developing fast and accurate dimensionally reduced models of nonlinear systems, and eventually as a tool for adaptive dimension-reduction in numerical modeling. The results are especially relevant in the aerospace industry for the design of thin structures such as beams, panels, and shells, which are all capable of spatio-temporally complex dynamic responses that are difficult and computationally expensive to model.

Non-Dimensional Formulation of Ventricular Work-Load Severity Under Concomitant Heart Valve Disease

NASA Astrophysics Data System (ADS)

Dong, Melody; Simon-Walker, Rachael; Dasi, Lakshmi

2012-11-01

Current guidelines on assessing the severity of heart valve disease rely on dimensional disease specific measures and are thus unable to capture severity under a concomitant heart valve disease scenario. Experiments were conducted to measure ventricular work-load in an in-house in-vitro left heart simulator. In-house tri-leaflet heart valves were built and parameterized to model concomitant heart valve disease. Measured ventricular power varied non-linearly with cardiac output and mean aortic pressure. Significant data collapse could be achieved by the non-dimensionalization of ventricular power with cardiac output, fluid density, and a length scale. The dimensionless power, Circulation Energy Dissipation Index (CEDI), indicates that concomitant conditions require a significant increase in the amount of work needed to sustain cardiac function. It predicts severity without the need to quantify individual disease severities. This indicates the need for new fluid-dynamics similitude based clinical guidelines to assist patients with multiple heart valve diseases. Funded by the American Heart Association.

The Quantum Socket: Wiring for Superconducting Qubits - Part 1

NASA Astrophysics Data System (ADS)

McConkey, T. G.; Bejanin, J. H.; Rinehart, J. R.; Bateman, J. D.; Earnest, C. T.; McRae, C. H.; Rohanizadegan, Y.; Shiri, D.; Mariantoni, M.; Penava, B.; Breul, P.; Royak, S.; Zapatka, M.; Fowler, A. G.

Quantum systems with ten superconducting quantum bits (qubits) have been realized, making it possible to show basic quantum error correction (QEC) algorithms. However, a truly scalable architecture has not been developed yet. QEC requires a two-dimensional array of qubits, restricting any interconnection to external classical systems to the third axis. In this talk, we introduce an interconnect solution for solid-state qubits: The quantum socket. The quantum socket employs three-dimensional wires and makes it possible to connect classical electronics with quantum circuits more densely and accurately than methods based on wire bonding. The three-dimensional wires are based on spring-loaded pins engineered to insure compatibility with quantum computing applications. Extensive design work and machining was required, with focus on material quality to prevent magnetic impurities. Microwave simulations were undertaken to optimize the design, focusing on the interface between the micro-connector and an on-chip coplanar waveguide pad. Simulations revealed good performance from DC to 10 GHz and were later confirmed against experimental measurements.

Evaluation of thermal load during laser corneal refractive surgery using infrared thermography

NASA Astrophysics Data System (ADS)

Brunsmann, U.; Sauer, U.; Arba-Mosquera, S.; Magnago, T.; Triefenbach, N.

2010-09-01

Infrared thermography is used for evaluation of the mean temperature as a measure of thermal load during corneal refractive surgery. An experimental method to determine emissivity and to calibrate the thermografic system is presented. In a case study on the porcine eye two dimensional temperature distributions with lateral resolution of 170 μm and line scans with temporal resolution of 13 μs are discussed with respect to the meaning of mean temperature. Using the newest generation of surgery equipment it is shown, that the mean temperature rise can be kept below 5 °C during myopic laser in situ keratomileusis (LASIK) treatments corresponding to an aberration-free correction of -2.75 diopter.

Load measurement system with load cell lock-out mechanism

NASA Technical Reports Server (NTRS)

Le, Thang; Carroll, Monty; Liu, Jonathan

1995-01-01

In the frame work of the project Shuttle Plume Impingement Flight Experiment (SPIFEX), a Load Measurement System was developed and fabricated to measure the impingement force of Shuttle Reaction Control System (RCS) jets. The Load Measurement System is a force sensing system that measures any combination of normal and shear forces up to 40 N (9 lbf) in the normal direction and 22 N (5 lbf) in the shear direction with an accuracy of +/- 0.04 N (+/- 0.01 lbf) Since high resolution is required for the force measurement, the Load Measurement System is built with highly sensitive load cells. To protect these fragile load cells in the non-operational mode from being damaged due to flight loads such as launch and landing loads of the Shuttle vehicle, a motor driven device known as the Load Cell Lock-Out Mechanism was built. This Lock-Out Mechanism isolates the load cells from flight loads and re-engages the load cells for the force measurement experiment once in space. With this highly effective protection system, the SPIFEX load measurement experiment was successfully conducted on STS-44 in September 1994 with all load cells operating properly and reading impingement forces as expected.

A spatial model of wind shear and turbulence for flight simulation. Ph.D. Thesis - Colorado State Univ.

NASA Technical Reports Server (NTRS)

Campbell, C. W.

1984-01-01

A three dimensional model which combines measurements of wind shear in the real atmosphere with three dimensional Monte Carlo simulated turbulence was developed. The wind field over the body of an aircraft can be simulated and all aerodynamic loads and moments calculated.

Transient Three-Dimensional Side Load Analysis of a Film Cooled Nozzle

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Guidos, Mike

2008-01-01

Transient three-dimensional numerical investigations on the side load physics for an engine encompassing a film cooled nozzle extension and a regeneratively cooled thrust chamber, were performed. The objectives of this study are to identify the three-dimensional side load physics and to compute the associated aerodynamic side load using an anchored computational methodology. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Ultimately, the computational results will be provided to the nozzle designers for estimating of effect of the peak side load on the nozzle structure. Computations simulating engine startup at ambient pressures corresponding to sea level and three high altitudes were performed. In addition, computations for both engine startup and shutdown transients were also performed for a stub nozzle, operating at sea level. For engine with the full nozzle extension, computational result shows starting up at sea level, the peak side load occurs when the lambda shock steps into the turbine exhaust flow, while the side load caused by the transition from free-shock separation to restricted-shock separation comes at second; and the side loads decreasing rapidly and progressively as the ambient pressure decreases. For the stub nozzle operating at sea level, the computed side loads during both startup and shutdown becomes very small due to the much reduced flow area.

Methodology for dynamic biaxial tension testing of pregnant uterine tissue.

PubMed

Manoogian, Sarah; Mcnally, Craig; Calloway, Britt; Duma, Stefan

2007-01-01

Placental abruption accounts for 50% to 70% of fetal losses in motor vehicle crashes. Since automobile crashes are the leading cause of traumatic fetal injury mortality in the United States, research of this injury mechanism is important. Before research can adequately evaluate current and future restraint designs, a detailed model of the pregnant uterine tissues is necessary. The purpose of this study is to develop a methodology for testing the pregnant uterus in biaxial tension at a rate normally seen in a motor vehicle crash. Since the majority of previous biaxial work has established methods for quasi-static testing, this paper combines previous research and new methods to develop a custom designed system to strain the tissue at a dynamic rate. Load cells and optical markers are used for calculating stress strain curves of the perpendicular loading axes. Results for this methodology show images of a tissue specimen loaded and a finite verification of the optical strain measurement. The biaxial test system dynamically pulls the tissue to failure with synchronous motion of four tissue grips that are rigidly coupled to the tissue specimen. The test device models in situ loading conditions of the pregnant uterus and overcomes previous limitations of biaxial testing. A non-contact method of measuring strains combined with data reduction to resolve the stresses in two directions provides the information necessary to develop a three dimensional constitutive model of the material. Moreover, future research can apply this method to other soft tissues with similar in situ loading conditions.

PIV measurements in a compact return diffuser under multi-conditions

NASA Astrophysics Data System (ADS)

Zhou, L.; Lu, W. G.; Shi, W. D.

2013-12-01

Due to the complex three-dimensional geometries of impellers and diffusers, their design is a delicate and difficult task. Slight change could lead to significant changes in hydraulic performance and internal flow structure. Conversely, the grasp of the pump's internal flow pattern could benefit from pump design improvement. The internal flow fields in a compact return diffuser have been investigated experimentally under multi-conditions. A special Particle Image Velocimetry (PIV) test rig is designed, and the two-dimensional PIV measurements are successfully conducted in the diffuser mid-plane to capture the complex flow patterns. The analysis of the obtained results has been focused on the flow structure in diffuser, especially under part-load conditions. The vortex and recirculation flow patterns in diffuser are captured and analysed accordingly. Strong flow separation and back flow appeared at the part-load flow rates. Under the design and over-load conditions, the flow fields in diffuser are uniform, and the flow separation and back flow appear at the part-load flow rates, strong back flow is captured at one diffuser passage under 0.2Qdes.

Three-dimensional finite element analysis of a newly designed onplant miniplate anchorage system.

PubMed

Liu, Lin; Qu, Yin-Ying; Jiang, Li-Jun; Zhou, Qian; Tang, Tian-Qi

2016-06-01

The purpose of this research was to evaluate the structural stress and deformation of a newly designed onplant miniplate anchorage system compared to a standard anchorage system. A bone block integrated with a novel miniplate and fixation screw system was simulated in a three-dimensional model and subjected to force at different directions. The stress distribution and deformation of the miniplate system and cortical bone were evaluated using the three-dimensional finite element method. The results showed that the stress on the plate system and bone was linearly proportional to the force magnitude and was higher when the force was in a vertical direction (Y-axis). Stress and deformation values of the two screws (screw 1 and 2) were asymmetric when the force was added along Y-axis and was greater in screw 1. The highest deformation value of the screws was 7.5148 μm, much smaller than the limit value. The load was decreased for each single miniscrew, and the ability of the new anchorage system to bear the load was also enhanced to some degree. It was suggested that the newly designed onplant miniplate anchorage system is effective, easily implanted and minimally invasive.

Overview of aerothermodynamic loads definition study

NASA Technical Reports Server (NTRS)

Gaugler, Raymond E.

1991-01-01

The objective of the Aerothermodynamic Loads Definition Study is to develop methods of accurately predicting the operating environment in advanced Earth-to-Orbit (ETO) propulsion systems, such as the Space Shuttle Main Engine (SSME) powerhead. Development of time averaged and time dependent three dimensional viscous computer codes as well as experimental verification and engine diagnostic testing are considered to be essential in achieving that objective. Time-averaged, nonsteady, and transient operating loads must all be well defined in order to accurately predict powerhead life. Described here is work in unsteady heat flow analysis, improved modeling of preburner flow, turbulence modeling for turbomachinery, computation of three dimensional flow with heat transfer, and unsteady viscous multi-blade row turbine analysis.

Binaural Simulation Experiments in the NASA Langley Structural Acoustics Loads and Transmission Facility

NASA Technical Reports Server (NTRS)

Grosveld, Ferdinand W.; Silcox, Richard (Technical Monitor)

2001-01-01

A location and positioning system was developed and implemented in the anechoic chamber of the Structural Acoustics Loads and Transmission (SALT) facility to accurately determine the coordinates of points in three-dimensional space. Transfer functions were measured between a shaker source at two different panel locations and the vibrational response distributed over the panel surface using a scanning laser vibrometer. The binaural simulation test matrix included test runs for several locations of the measuring microphones, various attitudes of the mannequin, two locations of the shaker excitation and three different shaker inputs including pulse, broadband random, and pseudo-random. Transfer functions, auto spectra, and coherence functions were acquired for the pseudo-random excitation. Time histories were acquired for the pulse and broadband random input to the shaker. The tests were repeated with a reflective surface installed. Binary data files were converted to universal format and archived on compact disk.

Design of Unstructured Adaptive (UA) NAS Parallel Benchmark Featuring Irregular, Dynamic Memory Accesses

NASA Technical Reports Server (NTRS)

Feng, Hui-Yu; VanderWijngaart, Rob; Biswas, Rupak; Biegel, Bryan (Technical Monitor)

2001-01-01

We describe the design of a new method for the measurement of the performance of modern computer systems when solving scientific problems featuring irregular, dynamic memory accesses. The method involves the solution of a stylized heat transfer problem on an unstructured, adaptive grid. A Spectral Element Method (SEM) with an adaptive, nonconforming mesh is selected to discretize the transport equation. The relatively high order of the SEM lowers the fraction of wall clock time spent on inter-processor communication, which eases the load balancing task and allows us to concentrate on the memory accesses. The benchmark is designed to be three-dimensional. Parallelization and load balance issues of a reference implementation will be described in detail in future reports.

Local Dynamic Stability Associated with Load Carrying

PubMed Central

Lockhart, Thurmon E

2013-01-01

Objectives Load carrying tasks are recognized as one of the primary occupational factors leading to slip and fall injuries. Nevertheless, the mechanisms associated with load carrying and walking stability remain illusive. The objective of the current study was to apply local dynamic stability measure in walking while carrying a load, and to investigate the possible adaptive gait stability changes. Methods Current study involved 25 young adults in a biomechanics research laboratory. One tri-axial accelerometer was used to measure three-dimensional low back acceleration during continuous treadmill walking. Local dynamic stability was quantified by the maximum Lyapunov exponent (maxLE) from a nonlinear dynamics approach. Results Long term maxLE was found to be significant higher under load condition than no-load condition in all three reference axes, indicating the declined local dynamic stability associated with load carrying. Conclusion Current study confirmed the sensitivity of local dynamic stability measure in load carrying situation. It was concluded that load carrying tasks were associated with declined local dynamic stability, which may result in increased risk of fall accident. This finding has implications in preventing fall accidents associated with occupational load carrying. PMID:23515183

The Effect of Load Carriage on Trunk Coordination during Treadmill Walking at Increasing Walking Speed

DTIC Science & Technology

2001-05-01

Kinematic and Kinetic Data Collection Systems. Three-dimensional kinematic data were collected at 100 Hz through an Optotrak 3020 System (Northern...regardless of load. The Optotrak system unit provides an external trigger that was used to trigger the start of the force plate data collection, thereby...synchronizing the kinematic and kinetic data. Optotrak required the use of infrared light emitting diodes (IREDS), which were placed bilaterally on the

Three-dimensional canopy fuel loading predicted using upward and downward sensing LiDAR systems

Treesearch

Nicholas S. Skowronski; Kenneth L. Clark; Matthew Duveneck; John. Hom

2011-01-01

We calibrated upward sensing profiling and downward sensing scanning LiDAR systems to estimates of canopy fuel loading developed from field plots and allometric equations, and then used the LiDAR datasets to predict canopy bulk density (CBD) and crown fuel weight (CFW) in wildfire prone stands in the New Jersey Pinelands. LiDAR-derived height profiles were also...

Load Balancing Strategies for Multiphase Flows on Structured Grids

NASA Astrophysics Data System (ADS)

Olshefski, Kristopher; Owkes, Mark

2017-11-01

The computation time required to perform large simulations of complex systems is currently one of the leading bottlenecks of computational research. Parallelization allows multiple processing cores to perform calculations simultaneously and reduces computational times. However, load imbalances between processors waste computing resources as processors wait for others to complete imbalanced tasks. In multiphase flows, these imbalances arise due to the additional computational effort required at the gas-liquid interface. However, many current load balancing schemes are only designed for unstructured grid applications. The purpose of this research is to develop a load balancing strategy while maintaining the simplicity of a structured grid. Several approaches are investigated including brute force oversubscription, node oversubscription through Message Passing Interface (MPI) commands, and shared memory load balancing using OpenMP. Each of these strategies are tested with a simple one-dimensional model prior to implementation into the three-dimensional NGA code. Current results show load balancing will reduce computational time by at least 30%.

Correlation between Mechanical Behavior and Actuator-type Performance of Ni-Ti-Pd High-temperature Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Bigelow, Glen S.; Padula, Santo A., II; Garg, Anita; Noebe, Ronald D.

2007-01-01

High-temperature shape memory alloys in the NiTiPd system are being investigated as lower cost alternatives to NiTiPt alloys for use in compact solid-state actuators for the aerospace, automotive, and power generation industries. A range of ternary NiTiPd alloys containing 15 to 46 at.% Pd has been processed and actuator mimicking tests (thermal cycling under load) were used to measure transformation temperatures, work behavior, and dimensional stability. With increasing Pd content, the work output of the material decreased, while the amount of permanent strain resulting from each load-biased thermal cycle increased. Monotonic isothermal tension testing of the high-temperature austenite and low temperature martensite phases was used to partially explain these behaviors, where a mismatch in yield strength between the austenite and martensite phases was observed at high Pd levels. Moreover, to further understand the source of the permanent strain at lower Pd levels, strain recovery tests were conducted to determine the onset of plastic deformation in the martensite phase. Consequently, the work behavior and dimensional stability during thermal cycling under load of the various NiTiPd alloys is discussed in relation to the deformation behavior of the materials as revealed by the strain recovery and monotonic tension tests.

Correlation between mechanical behavior and actuator-type performance of Ni-Ti-Pd high-temperature shape memory alloys

NASA Astrophysics Data System (ADS)

Bigelow, Glen S.; Padula, Santo A., II; Garg, Anita; Noebe, Ronald D.

2007-04-01

High-temperature shape memory alloys in the NiTiPd system are being investigated as lower cost alternatives to NiTiPt alloys for use in compact solid-state actuators for the aerospace, automotive, and power generation industries. A range of ternary NiTiPd alloys containing 15 to 46 at.% Pd has been processed and actuator mimicking tests (thermal cycling under load) were used to measure transformation temperatures, work behavior, and dimensional stability. With increasing Pd content, the work output of the material decreased, while the amount of permanent strain resulting from each load-biased thermal cycle increased. Monotonic isothermal tension testing of the high-temperature austenite and low temperature martensite phases was used to partially explain these behaviors, where a mismatch in yield strength between the austenite and martensite phases was observed at high Pd levels. Moreover, to further understand the source of the permanent strain at lower Pd levels, strain recovery tests were conducted to determine the onset of plastic deformation in the martensite phase. Consequently, the work behavior and dimensional stability during thermal cycling under load of the various NiTiPd alloys is discussed in relation to the deformation behavior of the materials as revealed by the strain recovery and monotonic tension tests.

Transient Three-Dimensional Startup Side Load Analysis of a Regeneratively Cooled Nozzle

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2008-01-01

The objective of this effort is to develop a computational methodology to capture the startup side load physics and to anchor the computed aerodynamic side loads with the available data from a regeneratively cooled, high-aspect-ratio nozzle, hot-fired at sea level. The computational methodology is based on an unstructured-grid, pressure-based, reacting flow computational fluid dynamics and heat transfer formulation, a transient 5 s inlet history based on an engine system simulation, and a wall temperature distribution to reflect the effect of regenerative cooling. To understand the effect of regenerative wall cooling, two transient computations were performed using the boundary conditions of adiabatic and cooled walls, respectively. The results show that three types of shock evolution are responsible for side loads: generation of combustion wave; transitions among free-shock separation, restricted-shock separation, and simultaneous free-shock and restricted shock separations; along with the pulsation of shocks across the lip, although the combustion wave is commonly eliminated with the sparklers during actual test. The test measured two side load events: a secondary and lower side load, followed by a primary and peak side load. Results from both wall boundary conditions captured the free-shock separation to restricted-shock separation transition with computed side loads matching the measured secondary side load. For the primary side load, the cooled wall transient produced restricted-shock pulsation across the nozzle lip with peak side load matching that of the test, while the adiabatic wall transient captured shock transitions and free-shock pulsation across the lip with computed peak side load 50% lower than that of the measurement. The computed dominant pulsation frequency of the cooled wall nozzle agrees with that of a separate test, while that of the adiabatic wall nozzle is more than 50% lower than that of the measurement. The computed teepee-like formation and the tangential motion of the shocks during lip pulsation also qualitatively agree with those of test observations. Moreover, a third transient computation was performed with a proportionately shortened 1 s sequence, and lower side loads were obtained with the higher ramp rate.

Earthquake Clustering in Noisy Viscoelastic Systems

NASA Astrophysics Data System (ADS)

Dicaprio, C. J.; Simons, M.; Williams, C. A.; Kenner, S. J.

2006-12-01

Geologic studies show evidence for temporal clustering of earthquakes on certain fault systems. Since post- seismic deformation may result in a variable loading rate on a fault throughout the inter-seismic period, it is reasonable to expect that the rheology of the non-seismogenic lower crust and mantle lithosphere may play a role in controlling earthquake recurrence times. Previously, the role of rheology of the lithosphere on the seismic cycle had been studied with a one-dimensional spring-dashpot-slider model (Kenner and Simons [2005]). In this study we use the finite element code PyLith to construct a two-dimensional continuum model a strike-slip fault in an elastic medium overlying one or more linear Maxwell viscoelastic layers loaded in the far field by a constant velocity boundary condition. Taking advantage of the linear properties of the model, we use the finite element solution to one earthquake as a spatio-temporal Green's function. Multiple Green's function solutions, scaled by the size of each earthquake, are then summed to form an earthquake sequence. When the shear stress on the fault reaches a predefined yield stress it is allowed to slip, relieving all accumulated shear stress. Random variation in the fault yield stress from one earthquake to the next results in a temporally clustered earthquake sequence. The amount of clustering depends on a non-dimensional number, W, called the Wallace number. For models with one viscoelastic layer, W is equal to the standard deviation of the earthquake stress drop divided by the viscosity times the tectonic loading rate. This definition of W is modified from the original one used in Kenner and Simons [2005] by using the standard deviation of the stress drop instead of the mean stress drop. We also use a new, more appropriate, metric to measure the amount of temporal clustering of the system. W is the ratio of the viscoelastic relaxation rate of the system to the tectonic loading rate of the system. For values of W greater than the critical value of about 10, the clustered earthquake behavior is due to the rapid reloading of the fault due to viscoelastic recycling of stress. A model with multiple viscoelastic layers has more complex clustering behavior than a system with only one viscosity. In this case, multiple clustering modes exist; the size and mean period of which are influenced by the viscosities and relative thicknesses of the viscoelastic layers. Kenner, S.J. and Simons, M., (2005), Temporal cluster of major earthquakes along individual faults due to post-seismic reloading, Geophysical Journal International, 160, 179-194.

The effects of loading on the preload and dimensions of the abutment screw for a 3-unit cantilever-fixed prosthesis design.

PubMed

Setia, Gaurav; Yousef, Hoda; Ehrenberg, David; Luke, Allyn; Weiner, Saul

2013-08-01

The purpose of this study was to use an in vitro model system to compare the effects on the screw torque and screw dimensions within 2 commercially available implant systems from occlusal loading on a cantilevered-fixed partial denture. Cantilevered implant-supported 3-unit prostheses with 2 premolar abutments and 1 premolar pontic (7.3 mm in length) were made on resin casts containing 2 implant analogs for 2 implant systems: BioLok Silhouette Tapered Implant System (Birmingham, AL) and Zimmer Tapered Screw-Vent Implant System (Carlsbad, CA) with 10 samples in each group. Each sample was loaded with either of 2 protocols: (1) a load of 50 N on the cantilevered pontic unit and (2) a loading of 150 N on all 3 units. The outcome measures were (1) changes in residual torque of the abutment screws and (2) changes in screw dimension. The BioLok Silhouette Tapered Implant group demonstrated slight but statistically significant torque loss 18.8% to 28.5% in both abutment screws for both protocols, P ≤ 0.05, without any changes in screw dimension. In the Zimmer Tapered Screw-Vent Implant group, there was a significant elongation of the abutment screws and a markedly significant 44.4%, (P ≤ 0.01) loss in torque in the mesial screw and a 28.5%, (P ≤ 0.05) loss in torque in the distal screw when the cantilever alone was loaded. Differences in screw design influence the maintenance of preload and distortion of the shank. The influence of the interface design, namely an internal hex of 1 mm versus an external hex did not influence the preload. Cantilevered prostheses can cause loss of torque and dimensional changes in abutment screws.

Transient Three-Dimensional Analysis of Nozzle Side Load in Regeneratively Cooled Engines

NASA Technical Reports Server (NTRS)

Wang, Ten-See

2005-01-01

Three-dimensional numerical investigations on the start-up side load physics for a regeneratively cooled, high-aspect-ratio nozzle were performed. The objectives of this study are to identify the three-dimensional side load physics and to compute the associated aerodynamic side load using an anchored computational methodology. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet condition based on an engine system simulation. Computations were performed for both the adiabatic and cooled walls in order to understand the effect of boundary conditions. Finite-rate chemistry was used throughout the study so that combustion effect is always included. The results show that three types of shock evolution are responsible for side loads: generation of combustion wave; transitions among free-shock separation, restricted-shock separation, and simultaneous free-shock and restricted shock separations; along with oscillation of shocks across the lip. Wall boundary conditions drastically affect the computed side load physics: the adiabatic nozzle prefers free-shock separation while the cooled nozzle favors restricted-shock separation, resulting in higher peak side load for the cooled nozzle than that of the adiabatic nozzle. By comparing the computed physics with those of test observations, it is concluded that cooled wall is a more realistic boundary condition, and the oscillation of the restricted-shock separation flow pattern across the lip along with its associated tangential shock motion are the dominant side load physics for a regeneratively cooled, high aspect-ratio rocket engine.

Determination of three-dimensional joint loading within the lower extremities in snowboarding.

PubMed

Krüger, Andreas; McAlpine, Paul; Borrani, Fabio; Edelmann-Nusser, Jürgen

2012-02-01

In the biomechanical literature only a few studies are available focusing on the determination of joint loading within the lower extremities in snowboarding. These studies are limited to analysis in a restricted capture volume due to the use of optical video-based systems. To overcome this restriction the aim of the present study was to develop a method to determine net joint moments within the lower extremities in snowboarding for complete measurement runs. An experienced snowboarder performed several runs equipped with two custom-made force plates as well as a full-body inertial measurement system. A rigid, multi-segment model was developed to describe the motion and loads within the lower extremities. This model is based on an existing lower-body model and designed to be run by the OpenSim software package. Measured kinetic and kinematic data were imported into the OpenSim program and inverse dynamic calculations were performed. The results illustrate the potential of the developed method for the determination of joint loadings within the lower extremities for complete measurement runs in a real snowboarding environment. The calculated net joint moments of force are reasonable in comparison to the data presented in the literature. A good reliability of the method seems to be indicated by the low data variation between different turns. Due to the unknown accuracy of this method the application for inter-individual studies as well as studies of injury mechanisms may be limited. For intra-individual studies comparing different snowboarding techniques as well as different snowboard equipment the method seems to be beneficial. The validity of the method needs to be studied further.

Transient Three-Dimensional Analysis of Nozzle Side Load in Regeneratively Cooled Engines

NASA Technical Reports Server (NTRS)

ng, Ten-See

2005-01-01

Nozzle side loads are potentially detrimental to the integrity and life of almost all launch vehicles. the lack of a detailed prediction capability results in reducing life and increased weight for reusable nozzle systems. A clear understanding of the mechanism that contribute to side loads during engine startup, shutdown, and steady-state operations must be established. A CFD based predictive tool must be developed to aid the understanding of side load physics and development of future reusable engine.

Ice sheet load cycling and fluid underpressures in the Eastern Michigan Basin, Ontario, Canada

USGS Publications Warehouse

Neuzil, Christopher E.; Provost, Alden M.

2014-01-01

Strong fluid underpressures have been detected in Paleozoic strata in the eastern Michigan Basin, with hydraulic heads reaching ~400 m below land surface (~4 MPa underpressure) and ~200 m below sea level in strata where unusually low permeabilities (~10−20–10−23 m2) were measured in situ. Multiple glaciations, including three with as much as 3 km of ice cover at the site in the last 120 ka, suggest a causal link with the underpressures. We examined this possibility using a one-dimensional groundwater flow model incorporating mechanical loading from both ice weight and lithospheric flexure. Because hydrologic and mechanical changes during glaciation are not well characterized and subsurface properties are imperfectly known, the model was used inversely to estimate flexural loads and loosely constrained permeabilities by matching observed pressures. Acceptable matches were obtained for a surprisingly wide range of scenarios with permeabilities close to measured values and plausible flexural loads. Matches were not obtained when too many parameters were preselected, or when permeabilities were constrained to be significantly larger than measured values. In successful model runs groundwater expulsion under glacial-mechanical loads caused the underpressuring, and flexural loads were important if aquifer and sub-glacial pressures were significantly elevated during glaciation. Simulated fluid pressures in the low-permeability strata fluctuated by 30–40 MPa during glacial cycles but resulted in advective transport of only tens of meters or less. Although other mechanisms cannot be ruled out, we conclude that glacial-mechanical forcing of a water-saturated system can explain the observed underpressures.

Three-dimensional finite element analysis of occipitocervical fixation using an anterior occiput-to-axis locking plate system: a pilot study.

PubMed

Cai, Xianhua; Yu, Yang; Liu, Zhichao; Zhang, Meichao; Huang, Weibing

2014-08-01

Although there are many techniques for occipitocervical fixation, there have been no reports regarding occipitocervical fixation via the use of an anterior anatomical locking plate system. The biomechanics of this new system were analyzed by a three-dimensional finite element to provide a theoretical basis for clinical application. This was a modeling study. We studied a 27-year-old healthy male volunteer in whom cervical disease was excluded via X-ray examination. The states of stress and strain of these two internal fixation devices were analyzed. A three-dimensional finite element model of normal occiput-C2 was established based on the anatomical data from a Chinese population. An unstable model of occipital-cervical region was established by subtracting several unit structures from the normal model. An anterior occiput-to-axis locking titanium plate system was then applied and an anterior occiput-to-axis screw fixation was performed on the unstable model. Limitation of motion was performed on the surface of the fixed model, and physiological loads were imposed on the surface of the skull base. Under various loads from different directions, the peak values of displacement of the anterior occiput-to-axis locking titanium plate system decreased 15.5%, 12.5%, 14.4%, and 23.7%, respectively, under the loads of flexion, extension, lateral bending, and axial rotation. Compared with the anterior occiput-to-axis screw fixation, the peak values of stress of the anterior occiput-to-axis locking titanium plate system also decreased 3.9%, 2.9%, 9.7%, and 7.2%, respectively, under the loads of flexion, extension, lateral bending, and axial rotation. The anterior occiput-to-axis locking titanium plate system proved superior to the anterior occiput-to-axis screw system both in the stress distribution and fixation stability based on finite element analysis. It provides a new clinical option for anterior occipitocervical fixation. Copyright © 2014 Elsevier Inc. All rights reserved.

Real-time three-dimensional digital image correlation for biomedical applications

NASA Astrophysics Data System (ADS)

Wu, Rong; Wu, Hua; Arola, Dwayne; Zhang, Dongsheng

2016-10-01

Digital image correlation (DIC) has been successfully applied for evaluating the mechanical behavior of biological tissues. A three-dimensional (3-D) DIC system has been developed and applied to examining the motion of bones in the human foot. To achieve accurate, real-time displacement measurements, an algorithm including matching between sequential images and image pairs has been developed. The system was used to monitor the movement of markers which were attached to a precisely motorized stage. The accuracy of the proposed technique for in-plane and out-of-plane measurements was found to be -0.25% and 1.17%, respectively. Two biomedical applications were presented. In the experiment involving the foot arch, a human cadaver lower leg and foot specimen were subjected to vertical compressive loads up to 700 N at a rate of 10 N/s and the 3-D motions of bones in the foot were monitored in real time. In the experiment involving distal tibio fibular syndesmosis, a human cadaver lower leg and foot specimen were subjected to a monotonic rotational torque up to 5 Nm at a speed of 5 deg per min and the relative displacements of the tibia and fibula were monitored in real time. Results showed that the system could reach a frequency of up to 16 Hz with 6 points measured simultaneously. This technique sheds new lights on measuring 3-D motion of bones in biomechanical studies.

A nanoparticulate drug-delivery system for rivastigmine: physico-chemical and in vitro biological characterization.

PubMed

Craparo, Emanuela Fabiola; Pitarresi, Giovanna; Bondì, Maria Luisa; Casaletto, Maria Pia; Licciardi, Mariano; Giammona, Gaetano

2008-03-10

The preparation and characterization of surface-PEGylated polymeric nanoparticles are described. These systems were obtained by UV irradiation of PHM and PHM-PEG(2000) as an inverse microemulsion, using an aqueous solution of the PHM/PHM-PEG(2000) copolymer mixture as the internal phase and triacetin saturated with water as the external phase, and characterized by dimensional analysis, zeta-potential measurements and XPS. in vitro biological tests demonstrated their cell compatibility and their ability to escape from phagocytosis. Rivastigmine was encapsulated into the nanoparticle structure and drug-release profiles from loaded samples were investigated in PBS at pH = 7.4 and human plasma.

Thermal expansion of composites: Methods and results. [large space structures

NASA Technical Reports Server (NTRS)

Bowles, D. E.; Tenney, D. R.

1981-01-01

The factors controlling the dimensional stability of various components of large space structures were investigated. Cyclic, thermal and mechanical loading were identified as the primary controlling factors of the dimensional stability of cables. For organic matrix composites, such as graphite-epoxy, it was found that these factors include moisture desorption in the space environment, thermal expansion as the structure moves from the sunlight to shadow in its orbit, mechanical loading, and microyielding of the material caused by microcracking of the matrix material. The major focus was placed on the thermal expansion of composites and in particular the development and testing of a method for its measurement.

Analysis on the multi-dimensional spectrum of the thrust force for the linear motor feed drive system in machine tools

NASA Astrophysics Data System (ADS)

Yang, Xiaojun; Lu, Dun; Ma, Chengfang; Zhang, Jun; Zhao, Wanhua

2017-01-01

The motor thrust force has lots of harmonic components due to the nonlinearity of drive circuit and motor itself in the linear motor feed drive system. What is more, in the motion process, these thrust force harmonics may vary with the position, velocity, acceleration and load, which affects the displacement fluctuation of the feed drive system. Therefore, in this paper, on the basis of the thrust force spectrum obtained by the Maxwell equation and the electromagnetic energy method, the multi-dimensional variation of each thrust harmonic is analyzed under different motion parameters. Then the model of the servo system is established oriented to the dynamic precision. The influence of the variation of the thrust force spectrum on the displacement fluctuation is discussed. At last the experiments are carried out to verify the theoretical analysis above. It can be found that the thrust harmonics show multi-dimensional spectrum characteristics under different motion parameters and loads, which should be considered to choose the motion parameters and optimize the servo control parameters in the high-speed and high-precision machine tools equipped with the linear motor feed drive system.

Four dimensional variational assimilation of in-situ and remote-sensing aerosol data

NASA Astrophysics Data System (ADS)

Nieradzik, L. P.; Elbern, H.

2012-04-01

Aerosols play an increasingly important role in atmospheric modelling. They have a strong influence on the radiative transfer balance and a significant impact on human health. Their origin is various and so are its effects. Most of the measurement sites in Europe account for an integrated aerosol load PMx (Particulate Matter of less than x μm in diameter) which does not give any qualitative information on the composition of the aerosol. Since very different constituents contribute to PMx, like e.g. mineral dust derived from desert storms or sea salt, it is necessary to make aerosol forecasts not only of load, but also type resolved. The method of four dimensional variational data assimilation (4Dvar) is a widely known technique to enhance forecast skills of CTMs (Chemistry-Transport-Models) by ingesting in-situ and, especially, remote-sensing measurements. The EURAD-IM (EURopean Air pollution Dispersion - Inverse Model), containing a full adjoint gas-phase model, has been expanded with an adjoint of the MADE (Modal Aerosol Dynamics model for Europe) to optimise initial and boundary values for aerosols using 4Dvar. A forward and an adjoint radiative transfer model is driven by the EURAD-IM as mapping between BLAOT (Boundary Layer Aerosol Optical Thickness) and internal aerosol species. Furthermore, its condensation scheme has been bypassed by an HDMR (High-Dimensional-Model-Representation) to ensure differentiability. In this study both in-situ measured PMx as well as satellite retrieved aerosol optical thicknesses have been assimilated and the effect on forecast performance has been investigated. The source of BLAOT is the aerosol retrieval system SYNAER (SYNergetic AErosol Retrieval) from DLR-DFD that retrieves AOT by making use of both AATSR/SCIAMACHY and AVHRR/GOME-2 data respectively. Its strengths are a large spatial coverage, near real-time availability, and the classification of five intrinsic aerosol species, namely water-solubles, water-insolubles, soot, sea salt, and mineral dust which are furthermore size resolved in terms of modes. The skill of the aerosol 4Dvar system was tested in two episodes: 1) July through August 2003, a dry period with strong wildfire activity in Europe, and 2) October through November 2008, the period of the ZEPTER-2 (Second ZEPpelin based Tropospheric photochemical chemistry expERiment) measurement campaign in the area of Lake Constance. In the latter case one-way nesting has been applied from a horizontal grid resolution of 45 km down to 5 km. Overall, the results showed a significant increase in forecast quality of tropospheric aerosol loads.

Active transmission isolation/rotor loads measurement system

NASA Technical Reports Server (NTRS)

Kenigsberg, I. J.; Defelice, J. J.

1973-01-01

Modifications were incorporated into a helicopter active transmission isolation system to provide the capability of utilizing the system as a rotor force measuring device. These included; (1) isolator redesign to improve operation and minimize friction, (2) installation of pressure transducers in each isolator, and (3) load cells in series with each torque restraint link. Full scale vibration tests performed during this study on a CH-53A helicopter airframe verified that these modifications do not degrade the systems wide band isolation characteristics. Bench tests performed on each isolator unit indicated that steady and transient loads can be measured to within 1 percent of applied load. Individual isolator vibratory load measurement accuracy was determined to be 4 percent. Load measurement accuracy was found to be independent of variations in all basic isolator operating characteristics. Full scale system load calibration tests on the CH-53A airframe established the feasibility of simultaneously providing wide band vibration isolation and accurate measurement of rotor loads. Principal rotor loads (lift, propulsive force, and torque) were measured to within 2 percent of applied load.

Experimental measurement of lattice strain pole figures using synchrotron x rays

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

Miller, M.P.; Bernier, J.V.; Park, J.-S.

This article describes a system for mechanically loading test specimens in situ for the determination of lattice strain pole figures and their evolution in multiphase alloys via powder diffraction. The data from these experiments provide insight into the three-dimensional mechanical response of a polycrystalline aggregate and represent an extremely powerful material model validation tool. Relatively thin (0.5 mm) iron/copper specimens were axially strained using a mechanical loading frame beyond the macroscopic yield strength of the material. The loading was halted at multiple points during the deformation to conduct a diffraction experiment using a 0.5x0.5 mm{sup 2} monochromatic (50 keV) xmore » ray beam. Entire Debye rings of data were collected for multiple lattice planes ({l_brace}hkl{r_brace}'s) in both copper and iron using an online image plate detector. Strain pole figures were constructed by rotating the loading frame about the specimen transverse direction. Ideal powder patterns were superimposed on each image for the purpose of geometric correction. The chosen reference material was cerium (IV) oxide powder, which was spread in a thin layer on the downstream face of the specimen using petroleum jelly to prevent any mechanical coupling. Implementation of the system at the A2 experimental station at the Cornell High Energy Synchrotron Source (CHESS) is described. The diffraction moduli measured at CHESS were shown to compare favorably to in situ data from neutron-diffraction experiments conducted on the same alloys.« less

Achievable flatness in a large microwave power transmitting antenna

NASA Technical Reports Server (NTRS)

Ried, R. C.

1980-01-01

A dual reference SPS system with pseudoisotropic graphite composite as a representative dimensionally stable composite was studied. The loads, accelerations, thermal environments, temperatures and distortions were calculated for a variety of operational SPS conditions along with statistical considerations of material properties, manufacturing tolerances, measurement accuracy and the resulting loss of sight (LOS) and local slope distributions. A LOS error and a subarray rms slope error of two arc minutes can be achieved with a passive system. Results show that existing materials measurement, manufacturing, assembly and alignment techniques can be used to build the microwave power transmission system antenna structure. Manufacturing tolerance can be critical to rms slope error. The slope error budget can be met with a passive system. Structural joints without free play are essential in the assembly of the large truss structure. Variations in material properties, particularly for coefficient of thermal expansion from part to part, is more significant than actual value.

[Finite element analysis of the stress distribution of two-piece post crown with different adhesives ].

PubMed

He, Lihui; Liu, Lijie; Gao, Bei; Gao, Shang; Chen, Yifu; Zhihui, Liu

2013-08-01

To establish three-dimensional finite element model of two-piece post crown to the mandibular first molar residual roots, and analyze the stress distribution characteristic to the residual roots with different adhesives, so as to get the best combination under different conditions. The complete mandibular first molar in vitro was selected, the crown was removed along the cemento-enamel junction, then the residual roots were scanned by CT. CT images were imported into a reverse engineering software, and the three-dimensional finite element model of the mandibular first molar residual roots was reconstructed. Titanium two-piece post crown of the mandibular first molar residual roots was produced, then was scanned by CT. The model was reconstructed and assembled by MIMICS. The stress distribution of the root canal and root section under the vertical load and lateral load with different bonding systems were analyzed. Three-dimensional finite element model of two-piece post crown to the mandibular first molar residual roots was established. With the increasing of elastic modulus of the adhesives, the maximum stress within the root canal was also increasing. Elastic modulus of zinc phosphate was the biggest, so the stress within the root canal was the biggest; elastic modulus of Superbond C&B was the smallest, so the stress within the root canal was the smallest. Lateral loading stress was much larger than the vertical load. Under vertical load, the load on the root section was even with different bonding systems. Under lateral load, the maximum stress was much larger than the vertical load. The stress on the root section was minimum using zinc phosphate binder, and the stress on the root section was maximum using Superbond C&B. In two-piece post crown restorations, there is significant difference between different adhesives on tooth protection. When the tooth structure of the root canal orifices is weak, in order to avoid the occurrence of splitting, the larger elastic modulus bonding system is the first choice, such as zinc phosphate binder. When the resistance form of the root canal orifices is good enough but the root is too weak, it is suggested that the smaller elastic modulus bonding system is the first choice, such as Superbond C&B.

Assessment of finger forces and wrist torques for functional grasp using new multichannel textile neuroprostheses.

PubMed

Lawrence, Marc; Gross, Gion-Pitschen; Lang, Martin; Kuhn, Andreas; Keller, Thierry; Morari, Manfred

2008-08-01

New multichannel textile neuroprotheses were developed, which comprise multiple sets of transcutaneous electrode arrays and connecting wires embroidered into a fabric layer. The electrode arrays were placed on the forearm above the extrinsic finger flexors and extensors. Activation regions for selective finger flexion and wrist extension were configured by switching a subset of the array elements between cathode, anode, and off states. We present a new isometric measurement system for the assessment of finger forces and wrist torques generated using the new neuroprostheses. Finger forces (from the middle phalanxes) were recorded using five load cells mounted on a "grasp handle" that can be arbitrarily positioned in space. The hand and the grasp handle were rigidly mounted to a 6-degree of freedom load cell, and the forces and torques about the wrist were recorded. A vacuum cushion was used to comfortably fixate the forearm. The position and orientation of the forearm, wrist, fingers, and handle were recorded using a new three-dimensional position measurement system (accuracy <+/-1 mm). The measurement system was integrated into the real-time multichannel transcutaneous electrode environment, which is able to control the spatiotemporal position of multiple activation regions. Using the combined system and textile neuroprosthesis, we were able to optimize the activation regions to produce selective finger and wrist articulation, enabling improved functional grasp.

The load separation technique in the elastic-plastic fracture analysis of two- and three-dimensional geometries

NASA Technical Reports Server (NTRS)

Sharobeam, Monir H.

1994-01-01

Load separation is the representation of the load in the test records of geometries containing cracks as a multiplication of two separate functions: a crack geometry function and a material deformation function. Load separation is demonstrated in the test records of several two-dimensional geometries such as compact tension geometry, single edge notched bend geometry, and center cracked tension geometry and three-dimensional geometries such as semi-elliptical surface crack. The role of load separation in the evaluation of the fracture parameter J-integral and the associated factor eta for two-dimensional geometries is discussed. The paper also discusses the theoretical basis and the procedure for using load separation as a simplified yet accurate approach for plastic J evaluation in semi-elliptical surface crack which is a three-dimensional geometry. The experimental evaluation of J, and particularly J(sub pl), for three-dimensional geometries is very challenging. A few approaches have been developed in this regard and they are either complex or very approximate. The paper also presents the load separation as a mean to identify the blunting and crack growth regions in the experimental test records of precracked specimens. Finally, load separation as a methodology in elastic-plastic fracture mechanics is presented.

Biomechanical evaluation of two types of short-stemmed hip prostheses compared to the trust plate prosthesis by three-dimensional measurement of micromotions.

PubMed

Fottner, Andreas; Schmid, Markus; Birkenmaier, Christof; Mazoochian, Farhad; Plitz, Wolfgang; Volkmar, Jansson

2009-06-01

Stemless and short-stemmed hip prostheses have been developed to preserve femoral bone stock. While all these prostheses claim a more or less physiological load transfer, clinical long-term results are only available for the stemless thrust plate prosthesis. In this study, the in vitro primary stability of the thrust plate prosthesis was compared to two types of short-stemmed prostheses. In addition to the well-established Mayo prosthesis, the modular Metha prosthesis was tested using cone adapters with 130 degrees and 140 degrees neck-shaft-angles. The prostheses were implanted in composite femurs and loaded dynamically (300-1700 N). Three-dimensional micromotions at the bone-prosthesis interface were measured. In addition, the three-dimensional deformations at the surface of the composite femur were measured to gain data on the strain distribution. For all tested prostheses, the micromotions did not exceed 150 microm, the critical value for osteointegration. The thrust plate prosthesis revealed similar motions as the short-stemmed prostheses. The short-stemmed prosthesis with the 130 degrees cone tended to have the highest micromotions of all tested short-stemmed prostheses. The thrust plate prosthesis revealed the lowest alteration of bone surface deformation after implantation. The comparably low micromotions of the thrust plate prosthesis and the short-stemmed prostheses should be conducive to osseous integration. The higher alteration of load transmission after implantation reveals a higher risk of stress shielding for the short-stemmed prostheses.

Laser SRS tracker for reverse prototyping tasks

NASA Astrophysics Data System (ADS)

Kolmakov, Egor; Redka, Dmitriy; Grishkanich, Aleksandr; Tsvetkov, Konstantin

2017-10-01

According to the current great interest concerning Large-Scale Metrology applications in many different fields of manufacturing industry, technologies and techniques for dimensional measurement have recently shown a substantial improvement. Ease-of-use, logistic and economic issues, as well as metrological performance, are assuming a more and more important role among system requirements. The project is planned to conduct experimental studies aimed at identifying the impact of the application of the basic laws of chip and microlasers as radiators on the linear-angular characteristics of existing measurement systems. The project is planned to conduct experimental studies aimed at identifying the impact of the application of the basic laws of microlasers as radiators on the linear-angular characteristics of existing measurement systems. The system consists of a distributed network-based layout, whose modularity allows to fit differently sized and shaped working volumes by adequately increasing the number of sensing units. Differently from existing spatially distributed metrological instruments, the remote sensor devices are intended to provide embedded data elaboration capabilities, in order to share the overall computational load.

In situ three-dimensional reciprocal-space mapping during mechanical deformation.

PubMed

Cornelius, T W; Davydok, A; Jacques, V L R; Grifone, R; Schülli, T; Richard, M I; Beutier, G; Verdier, M; Metzger, T H; Pietsch, U; Thomas, O

2012-09-01

Mechanical deformation of a SiGe island epitaxically grown on Si(001) was studied by a specially adapted atomic force microscope and nanofocused X-ray diffraction. The deformation was monitored during in situ mechanical loading by recording three-dimensional reciprocal-space maps around a selected Bragg peak. Scanning the energy of the incident beam instead of rocking the sample allowed the safe and reliable measurement of the reciprocal-space maps without removal of the mechanical load. The crystal truncation rods originating from the island side facets rotate to steeper angles with increasing mechanical load. Simulations of the displacement field and the intensity distribution, based on the finite-element method, reveal that the change in orientation of the side facets of about 25° corresponds to an applied pressure of 2-3 GPa on the island top plane.

Reponse dynamique des structures sous charges de vent

NASA Astrophysics Data System (ADS)

Gani, Ferawati

The main purpose of this research is to assemble numerical tools that allows realistic dynamic study of structures under wind loading. The availability of such numerical tools is becoming more important for the industry, following previous experiences in structural damages after extreme wind events. The methodology of the present study involves two main steps: (i) preparing the wind loading according to its spatial and temporal correlations by using digitally generated wind or real measured wind; (ii) preparing the numerical model that captures the characteristics of the real structures and respects all the necessary numerical requirements to pursue transient dynamic analyses. The thesis is presented as an ensemble of four articles written for refereed journals and conferences that showcase the contributions of the present study to the advancement of transient dynamic study of structures under wind loading, on the wind model itself (the first article) and on the application of the wind study on complex structures (the next three articles). The articles presented are as follows: (a) the evaluation of three-dimensional correlations of wind, an important issue for more precise prediction of wind loading for flexible and line-like structures, the results presented in this first article helps design engineers to choose a more suitable models to define three-dimensional wind loading; (b) the refinement of design for solar photovoltaic concentrator-tracker structure developed for utility scale, this study addressed concerns related strict operational criteria and fatigue under wind load for a large parabolic truss structure; (c) the study of guyed towers for TLs, the applicability of the static-equivalent method from the current industry documents for the design of this type of flexible TL support was questioned, a simplified method to improve the wind design was proposed; (d) the fundamental issue of nonlinear behaviour under extreme wind loading for single-degree-of-freedom systems is evaluated here, the use of real measured hurricane and winter storm have highlighted the possible interest of taking into account the ductility in the extreme wind loading design. The present research project has shown the versatility of the use of the developed wind study methodology to solve concerns related to different type of complex structures. In addition, this study proposes simplified methods that are useful for practical engineers when there is the need to solve similar problems. Key words: nonlinear, dynamic, wind, guyed tower, parabolic structure, ductility.

Coordinate measuring system based on microchip lasers for reverse prototyping

NASA Astrophysics Data System (ADS)

Iakovlev, Alexey; Grishkanich, Alexsandr S.; Redka, Dmitriy; Tsvetkov, Konstantin

2017-02-01

According to the current great interest concerning Large-Scale Metrology applications in many different fields of manufacturing industry, technologies and techniques for dimensional measurement have recently shown a substantial improvement. Ease-of-use, logistic and economic issues, as well as metrological performance, are assuming a more and more important role among system requirements. The project is planned to conduct experimental studies aimed at identifying the impact of the application of the basic laws of chip and microlasers as radiators on the linear-angular characteristics of existing measurement systems. The project is planned to conduct experimental studies aimed at identifying the impact of the application of the basic laws of microlasers as radiators on the linear-angular characteristics of existing measurement systems. The system consists of a distributed network-based layout, whose modularity allows to fit differently sized and shaped working volumes by adequately increasing the number of sensing units. Differently from existing spatially distributed metrological instruments, the remote sensor devices are intended to provide embedded data elaboration capabilities, in order to share the overall computational load.

Numerical study on wave loads and motions of two ships advancing in waves by using three-dimensional translating-pulsating source

NASA Astrophysics Data System (ADS)

Xu, Yong; Dong, Wen-Cai

2013-08-01

A frequency domain analysis method based on the three-dimensional translating-pulsating (3DTP) source Green function is developed to investigate wave loads and free motions of two ships advancing on parallel course in waves. Two experiments are carried out respectively to measure the wave loads and the freemotions for a pair of side-byside arranged ship models advancing with an identical speed in head regular waves. For comparison, each model is also tested alone. Predictions obtained by the present solution are found in favorable agreement with the model tests and are more accurate than the traditional method based on the three dimensional pulsating (3DP) source Green function. Numerical resonances and peak shift can be found in the 3DP predictions, which result from the wave energy trapped in the gap between two ships and the extremely inhomogeneous wave load distribution on each hull. However, they can be eliminated by 3DTP, in which the speed affects the free surface and most of the wave energy can be escaped from the gap. Both the experiment and the present prediction show that hydrodynamic interaction effects on wave loads and free motions are significant. The present solver may serve as a validated tool to predict wave loads and motions of two vessels under replenishment at sea, and may help to evaluate the hydrodynamic interaction effects on the ships safety in replenishment operation.

Autostereoscopic three-dimensional display by combining a single spatial light modulator and a zero-order nulled grating

NASA Astrophysics Data System (ADS)

Su, Yanfeng; Cai, Zhijian; Liu, Quan; Lu, Yifan; Guo, Peiliang; Shi, Lingyan; Wu, Jianhong

2018-04-01

In this paper, an autostereoscopic three-dimensional (3D) display system based on synthetic hologram reconstruction is proposed and implemented. The system uses a single phase-only spatial light modulator to load the synthetic hologram of the left and right stereo images, and the parallax angle between two reconstructed stereo images is enlarged by a grating to meet the split angle requirement of normal stereoscopic vision. To realize the crosstalk-free autostereoscopic 3D display with high light utilization efficiency, the groove parameters of the grating are specifically designed by the rigorous coupled-wave theory for suppressing the zero-order diffraction, and then the zero-order nulled grating is fabricated by the holographic lithography and the ion beam etching. Furthermore, the diffraction efficiency of the fabricated grating is measured under the illumination of a laser beam with a wavelength of 532 nm. Finally, the experimental verification system for the proposed autostereoscopic 3D display is presented. The experimental results prove that the proposed system is able to generate stereoscopic 3D images with good performances.

Three Dimensional Constraint Effects on the Estimated (Delta)CTOD during the Numerical Simulation of Different Fatigue Threshold Testing Techniques

NASA Technical Reports Server (NTRS)

Seshadri, Banavara R.; Smith, Stephen W.

2007-01-01

Variation in constraint through the thickness of a specimen effects the cyclic crack-tip-opening displacement (DELTA CTOD). DELTA CTOD is a valuable measure of crack growth behavior, indicating closure development, constraint variations and load history effects. Fatigue loading with a continual load reduction was used to simulate the load history associated with fatigue crack growth threshold measurements. The constraint effect on the estimated DELTA CTOD is studied by carrying out three-dimensional elastic-plastic finite element simulations. The analysis involves numerical simulation of different standard fatigue threshold test schemes to determine how each test scheme affects DELTA CTOD. The American Society for Testing and Materials (ASTM) prescribes standard load reduction procedures for threshold testing using either the constant stress ratio (R) or constant maximum stress intensity (K(sub max)) methods. Different specimen types defined in the standard, namely the compact tension, C(T), and middle cracked tension, M(T), specimens were used in this simulation. The threshold simulations were conducted with different initial K(sub max) values to study its effect on estimated DELTA CTOD. During each simulation, the DELTA CTOD was estimated at every load increment during the load reduction procedure. Previous numerical simulation results indicate that the constant R load reduction method generates a plastic wake resulting in remote crack closure during unloading. Upon reloading, this remote contact location was observed to remain in contact well after the crack tip was fully open. The final region to open is located at the point at which the load reduction was initiated and at the free surface of the specimen. However, simulations carried out using the constant Kmax load reduction procedure did not indicate remote crack closure. Previous analysis results using various starting K(sub max) values and different load reduction rates have indicated DELTA CTOD is independent of specimen size. A study of the effect of specimen thickness and geometry on the measured DELTA CTOD for various load reduction procedures and its implication in the estimation of fatigue crack growth threshold values is discussed.

An Elaborate Data Set Characterizing the Mechanical Response of the Foot

PubMed Central

Erdemir, Ahmet; Sirimamilla, Pavana A.; Halloran, Jason P.; van den Bogert, Antonie J.

2010-01-01

Background Mechanical properties of the foot are responsible for its normal function and play a role in various clinical problems. Specifically, we are interested in quantification of foot mechanical properties to assist the development of computational models for movement analysis and detailed simulations of tissue deformation. Current available data are specific to a foot region and the loading scenarios are limited to a single direction. A data set that incorporates regional response, to quantify individual function of foot components, as well as overall response, to illustrate their combined operation, does not exist. Furthermore, combined three-dimensional loading scenarios while measuring the complete three-dimensional deformation response are lacking. When combined with an anatomical image data set, development of anatomically realistic and mechanically validated models becomes possible. Therefore, the goal of this study was to record and disseminate the mechanical response of a foot specimen, supported by imaging data. Method of Approach Robotic testing was conducted at the rear foot, forefoot, metatarsal heads, and the foot as a whole. Complex foot deformations were induced by single mode loading, e.g. compression, and combined loading, e.g. compression and shear. Small and large indenters were used for heel and metatarsal head loading; an elevated platform was utilized to isolate the rear foot and forefoot; and a full platform compressed the whole foot. Three-dimensional tool movements and reaction loads were recorded simultaneously. Computed tomography scans of the same specimen were collected for anatomical reconstruction a-priori. Results Three-dimensional mechanical response of the specimen was nonlinear and viscoelastic. A low stiffness region was observed starting with contact between the tool and foot regions, increasing with loading. Loading and unloading response portrayed hysteresis. Loading range ensured capturing the toe and linear regions of the load deformation curves for the dominant loading direction, with the rates approximating those of walking. Conclusion A large data set was successfully obtained to characterize the overall as well as regional mechanical response of an intact foot specimen under single and combined loads. Medical imaging complemented the mechanical testing data to establish the potential relationship between the anatomical architecture and mechanical response, and for further development of foot models that are mechanically realistic and anatomically consistent. This combined data set has been documented and disseminated in the public domain to promote future development in foot biomechanics. PMID:19725699

Active Response Gravity Offload and Method

NASA Technical Reports Server (NTRS)

Dungan, Larry K. (Inventor); Lieberman, Asher P. (Inventor); Shy, Cecil (Inventor); Bankieris, Derek R. (Inventor); Valle, Paul S. (Inventor); Redden, Lee (Inventor)

2015-01-01

A variable gravity field simulator can be utilized to provide three dimensional simulations for simulated gravity fields selectively ranging from Moon, Mars, and micro-gravity environments and/or other selectable gravity fields. The gravity field simulator utilizes a horizontally moveable carriage with a cable extending from a hoist. The cable can be attached to a load which experiences the effects of the simulated gravity environment. The load can be a human being or robot that makes movements that induce swinging of the cable whereby a horizontal control system reduces swinging energy. A vertical control system uses a non-linear feedback filter to remove noise from a load sensor that is in the same frequency range as signals from the load sensor.

I-125 ROPES eye plaque dosimetry: Validation of a commercial 3D ophthalmic brachytherapy treatment planning system and independent dose calculation software with GafChromic{sup ®} EBT3 films

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

Poder, Joel; Corde, Stéphanie

Purpose: The purpose of this study was to measure the dose distributions for different Radiation Oncology Physics and Engineering Services, Australia (ROPES) type eye plaques loaded with I-125 (model 6711) seeds using GafChromic{sup ®} EBT3 films, in order to verify the dose distributions in the Plaque Simulator™ (PS) ophthalmic 3D treatment planning system. The brachytherapy module of RADCALC{sup ®} was used to independently check the dose distributions calculated by PS. Correction factors were derived from the measured data to be used in PS to account for the effect of the stainless steel ROPES plaque backing on the 3D dose distribution.Methods:more » Using GafChromic{sup ®} EBT3 films inserted in a specially designed Solid Water™ eye ball phantom, dose distributions were measured three-dimensionally both along and perpendicular to I-125 (model 6711) loaded ROPES eye plaque's central axis (CAX) with 2 mm depth increments. Each measurement was performed in full scatter conditions both with and without the stainless steel plaque backing attached to the eye plaque, to assess its effect on the dose distributions. Results were compared to the dose distributions calculated by Plaque Simulator™ and checked independently with RADCALC{sup ®}.Results: The EBT3 film measurements without the stainless steel backing were found to agree with PS and RADCALC{sup ®} to within 2% and 4%, respectively, on the plaque CAX. Also, RADCALC{sup ®} was found to agree with PS to within 2%. The CAX depth doses measured using EBT3 film with the stainless steel backing were observed to result in a 4% decrease relative to when the backing was not present. Within experimental uncertainty, the 4% decrease was found to be constant with depth and independent of plaque size. Using a constant dose correction factor of T= 0.96 in PS, where the calculated dose for the full water scattering medium is reduced by 4% in every voxel in the dose grid, the effect of the plaque backing was accurately modeled in the planning system. Off-axis profiles were also modeled in PS by taking into account the three-dimensional model of the plaque backing.Conclusions: The doses calculated by PS and RADCALC{sup ®} for uniformly loaded ROPES plaques in full and uniform scattering conditions were validated by the EBT3 film measurements. The stainless steel plaque backing was observed to decrease the measured dose by 4%. Through the introduction of a scalar correction factor (0.96) in PS, the dose homogeneity effect of the stainless steel plaque backing was found to agree with the measured EBT3 film measurements.« less

I-125 ROPES eye plaque dosimetry: validation of a commercial 3D ophthalmic brachytherapy treatment planning system and independent dose calculation software with GafChromic® EBT3 films.

PubMed

Poder, Joel; Corde, Stéphanie

2013-12-01

The purpose of this study was to measure the dose distributions for different Radiation Oncology Physics and Engineering Services, Australia (ROPES) type eye plaques loaded with I-125 (model 6711) seeds using GafChromic(®) EBT3 films, in order to verify the dose distributions in the Plaque Simulator™ (PS) ophthalmic 3D treatment planning system. The brachytherapy module of RADCALC(®) was used to independently check the dose distributions calculated by PS. Correction factors were derived from the measured data to be used in PS to account for the effect of the stainless steel ROPES plaque backing on the 3D dose distribution. Using GafChromic(®) EBT3 films inserted in a specially designed Solid Water™ eye ball phantom, dose distributions were measured three-dimensionally both along and perpendicular to I-125 (model 6711) loaded ROPES eye plaque's central axis (CAX) with 2 mm depth increments. Each measurement was performed in full scatter conditions both with and without the stainless steel plaque backing attached to the eye plaque, to assess its effect on the dose distributions. Results were compared to the dose distributions calculated by Plaque Simulator™ and checked independently with RADCALC(®). The EBT3 film measurements without the stainless steel backing were found to agree with PS and RADCALC(®) to within 2% and 4%, respectively, on the plaque CAX. Also, RADCALC(®) was found to agree with PS to within 2%. The CAX depth doses measured using EBT3 film with the stainless steel backing were observed to result in a 4% decrease relative to when the backing was not present. Within experimental uncertainty, the 4% decrease was found to be constant with depth and independent of plaque size. Using a constant dose correction factor of T = 0.96 in PS, where the calculated dose for the full water scattering medium is reduced by 4% in every voxel in the dose grid, the effect of the plaque backing was accurately modeled in the planning system. Off-axis profiles were also modeled in PS by taking into account the three-dimensional model of the plaque backing. The doses calculated by PS and RADCALC(®) for uniformly loaded ROPES plaques in full and uniform scattering conditions were validated by the EBT3 film measurements. The stainless steel plaque backing was observed to decrease the measured dose by 4%. Through the introduction of a scalar correction factor (0.96) in PS, the dose homogeneity effect of the stainless steel plaque backing was found to agree with the measured EBT3 film measurements.

Effect of same-sided and cross-body load carriage on 3D back shape in young adults.

PubMed

O'Shea, C; Bettany-Saltikov, J A; Warren, J G

2006-01-01

Regular carriage of heavy loads such as backpacks, satchels and mailbags results in a variety of acute medical problems and increased potential for back injury. There is a paucity of information about the specific changes in back posture that occur in response to asymmetrical loading. The purpose of this study was to examine the changes in back shape that occurred in response to asymmetrical load carriage, either on one shoulder (same-side) or across the body (cross-body), in healthy young adults. A convenience sample of 21 physiotherapy students randomly performed three trials (unloaded, same-side loaded, cross-body loaded) in standing with a 15% body load. The Microscribe 3DX digitiser (Immersion Group Ltd) recorded the three dimensional coordinates of 15 Key anatomical landmarks on the back in the three conditions. A one-way ANOVA with repeated measures and post-hoc tests was implemented to highlight statistical differences in the data collected (p<0.05). Significant differences were found in the x, y and z coordinates of the anatomical landmarks in the upper back between unloaded and loaded conditions. Results demonstrated significantly less impact on spinal posture from cross-body loading as compared to same-sided loading. This study confirms that there are significant three-dimensional changes in back shape in response to asymmetrical loading. Further work is needed to evaluate the optimal carriage type and maximal body load that results in the least spinal impact and injury potential in young adults.

Multitasking the three-dimensional transport code TORT on CRAY platforms

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

Azmy, Y.Y.; Barnett, D.A.; Burre, C.A.

1996-04-01

The multitasking options in the three-dimensional neutral particle transport code TORT originally implemented for Cray`s CTSS operating system are revived and extended to run on Cray Y/MP and C90 computers using the UNICOS operating system. These include two coarse-grained domain decompositions; across octants, and across directions within an octant, termed Octant Parallel (OP), and Direction Parallel (DP), respectively. Parallel performance of the DP is significantly enhanced by increasing the task grain size and reducing load imbalance via dynamic scheduling of the discrete angles among the participating tasks. Substantial Wall Clock speedup factors, approaching 4.5 using 8 tasks, have been measuredmore » in a time-sharing environment, and generally depend on the test problem specifications, number of tasks, and machine loading during execution.« less

Force dependent internalization of magnetic nanoparticles results in highly loaded endothelial cells for use as potential therapy delivery vectors.

PubMed

MacDonald, Cristin; Barbee, Kenneth; Polyak, Boris

2012-05-01

To investigate the kinetics, mechanism and extent of MNP loading into endothelial cells and the effect of this loading on cell function. MNP uptake was examined under field on/off conditions, utilizing varying magnetite concentration MNPs. MNP-loaded cell viability and functional integrity was assessed using metabolic respiration, cell proliferation and migration assays. MNP uptake in endothelial cells significantly increased under the influence of a magnetic field versus non-magnetic conditions. Larger magnetite density of the MNPs led to a higher MNP internalization by cells under application of a magnetic field without compromising cellular respiration activity. Two-dimensional migration assays at no field showed that higher magnetite loading resulted in greater cell migration rates. In a three-dimensional migration assay under magnetic field, the migration rate of MNP-loaded cells was more than twice that of unloaded cells and was comparable to migration stimulated by a serum gradient. Our results suggest that endothelial cell uptake of MNPs is a force dependent process. The in vitro assays determined that cell health is not adversely affected by high MNP loadings, allowing these highly magnetically responsive cells to be potentially beneficial therapy (gene, drug or cell) delivery systems.

Hydrodynamic compression of young and adult rat osteoblast-like cells on titanium fiber mesh.

PubMed

Walboomers, X F; Elder, S E; Bumgardner, J D; Jansen, J A

2006-01-01

Living bone cells are responsive to mechanical loading. Consequently, numerous in vitro models have been developed to examine the application of loading to cells. However, not all systems are suitable for the fibrous and porous three-dimensional materials, which are preferable for tissue repair purposes, or for the production of tissue engineering scaffolds. For three-dimensional applications, mechanical loading of cells with either fluid flow systems or hydrodynamic pressure systems has to be considered. Here, we aimed to evaluate the response of osteoblast-like cells to hydrodynamic compression, while growing in a three-dimensional titanium fiber mesh scaffolding material. For this purpose, a custom hydrodynamic compression chamber was built. Bone marrow cells were obtained from the femora of young (12-day-old) or old (1-year-old) rats, and precultured in the presence of dexamethasone and beta-glycerophosphate to achieve an osteoblast-like phenotype. Subsequently, cells were seeded onto the titanium mesh scaffolds, and subjected to hydrodynamic pressure, alternating between 0.3 to 5.0 MPa at 1 Hz, at 15-min intervals for a total of 60 min per day for up to 3 days. After pressurization, cell viability was checked. Afterward, DNA levels, alkaline phosphatase (ALP) activity, and extracellular calcium content were measured. Finally, all specimens were observed with scanning electron microscopy. Cell viability studies showed that the applied pressure was not harmful to the cells. Furthermore, we found that cells were able to detect the compression forces, because we did see evident effects on the cell numbers of the cells derived from old animals. However, there were no other changes in the cells under pressure. Finally, it was also noticeable that cells from old animals did not express ALP activity, but did show similar calcified extracellular matrix formation to the cells from young animals. In conclusion, the difference in DNA levels as reaction toward pressure, and the difference in ALP levels, suggest that the osteogenic properties of bone marrow-derived osteoblast-like cells are different with respect to the age of the donor. (c) 2005 Wiley Periodicals, Inc

Lightweight ZERODUR: Validation of Mirror Performance and Mirror Modeling Predictions

NASA Technical Reports Server (NTRS)

Hull, Tony; Stahl, H. Philip; Westerhoff, Thomas; Valente, Martin; Brooks, Thomas; Eng, Ron

2017-01-01

Upcoming spaceborne missions, both moderate and large in scale, require extreme dimensional stability while relying both upon established lightweight mirror materials, and also upon accurate modeling methods to predict performance under varying boundary conditions. We describe tests, recently performed at NASA's XRCF chambers and laboratories in Huntsville Alabama, during which a 1.2 m diameter, f/1.2988% lightweighted SCHOTT lightweighted ZERODUR(TradeMark) mirror was tested for thermal stability under static loads in steps down to 230K. Test results are compared to model predictions, based upon recently published data on ZERODUR(TradeMark). In addition to monitoring the mirror surface for thermal perturbations in XRCF Thermal Vacuum tests, static load gravity deformations have been measured and compared to model predictions. Also the Modal Response(dynamic disturbance) was measured and compared to model. We will discuss the fabrication approach and optomechanical design of the ZERODUR(TradeMark) mirror substrate by SCHOTT, its optical preparation for test by Arizona Optical Systems (AOS). Summarize the outcome of NASA's XRCF tests and model validations

Lightweight ZERODUR®: Validation of mirror performance and mirror modeling predictions

NASA Astrophysics Data System (ADS)

Hull, Anthony B.; Stahl, H. Philip; Westerhoff, Thomas; Valente, Martin; Brooks, Thomas; Eng, Ron

2017-01-01

Upcoming spaceborne missions, both moderate and large in scale, require extreme dimensional stability while relying both upon established lightweight mirror materials, and also upon accurate modeling methods to predict performance under varying boundary conditions. We describe tests, recently performed at NASA’s XRCF chambers and laboratories in Huntsville Alabama, during which a 1.2m diameter, f/1.29 88% lightweighted SCHOTT lightweighted ZERODUR® mirror was tested for thermal stability under static loads in steps down to 230K. Test results are compared to model predictions, based upon recently published data on ZERODUR®. In addition to monitoring the mirror surface for thermal perturbations in XRCF Thermal Vacuum tests, static load gravity deformations have been measured and compared to model predictions. Also the Modal Response (dynamic disturbance) was measured and compared to model. We will discuss the fabrication approach and optomechanical design of the ZERODUR® mirror substrate by SCHOTT, its optical preparation for test by Arizona Optical Systems (AOS), and summarize the outcome of NASA’s XRCF tests and model validations.

Bayesian Exploratory Factor Analysis

PubMed Central

Conti, Gabriella; Frühwirth-Schnatter, Sylvia; Heckman, James J.; Piatek, Rémi

2014-01-01

This paper develops and applies a Bayesian approach to Exploratory Factor Analysis that improves on ad hoc classical approaches. Our framework relies on dedicated factor models and simultaneously determines the number of factors, the allocation of each measurement to a unique factor, and the corresponding factor loadings. Classical identification criteria are applied and integrated into our Bayesian procedure to generate models that are stable and clearly interpretable. A Monte Carlo study confirms the validity of the approach. The method is used to produce interpretable low dimensional aggregates from a high dimensional set of psychological measurements. PMID:25431517

Regression models for predicting peak and continuous three-dimensional spinal loads during symmetric and asymmetric lifting tasks.

PubMed

Fathallah, F A; Marras, W S; Parnianpour, M

1999-09-01

Most biomechanical assessments of spinal loading during industrial work have focused on estimating peak spinal compressive forces under static and sagittally symmetric conditions. The main objective of this study was to explore the potential of feasibly predicting three-dimensional (3D) spinal loading in industry from various combinations of trunk kinematics, kinetics, and subject-load characteristics. The study used spinal loading, predicted by a validated electromyography-assisted model, from 11 male participants who performed a series of symmetric and asymmetric lifts. Three classes of models were developed: (a) models using workplace, subject, and trunk motion parameters as independent variables (kinematic models); (b) models using workplace, subject, and measured moments variables (kinetic models); and (c) models incorporating workplace, subject, trunk motion, and measured moments variables (combined models). The results showed that peak 3D spinal loading during symmetric and asymmetric lifting were predicted equally well using all three types of regression models. Continuous 3D loading was predicted best using the combined models. When the use of such models is infeasible, the kinematic models can provide adequate predictions. Finally, lateral shear forces (peak and continuous) were consistently underestimated using all three types of models. The study demonstrated the feasibility of predicting 3D loads on the spine under specific symmetric and asymmetric lifting tasks without the need for collecting EMG information. However, further validation and development of the models should be conducted to assess and extend their applicability to lifting conditions other than those presented in this study. Actual or potential applications of this research include exposure assessment in epidemiological studies, ergonomic intervention, and laboratory task assessment.

Effects of Palladium Content, Quaternary Alloying, and Thermomechanical Processing on the Behavior of Ni-Ti-Pd Shape Memory Alloys for Actuator Applications

NASA Technical Reports Server (NTRS)

Bigelow, Glen

2008-01-01

The need for compact, solid-state actuation systems for use in the aerospace, automotive, and other transportation industries is currently driving research in high-temperature shape memory alloys (HTSMA) having transformation temperatures above 100 C. One of the basic high temperature systems under investigation to fill this need is NiTiPd. Prior work on this alloy system has focused on phase transformations and respective temperatures, no-load shape memory behavior (strain recovery), and tensile behavior for selected alloys. In addition, a few tests have been done to determine the effect of boron additions and thermomechanical treatment on the aforementioned properties. The main properties that affect the performance of a solid state actuator, namely work output, transformation strain, and permanent deformation during thermal cycling under load have mainly been neglected. There is also no consistent data representing the mechanical behavior of this alloy system over a broad range of compositions. For this thesis, ternary NiTiPd alloys containing 15 to 46 at.% palladium were processed and the transformation temperatures, basic tensile properties, and work characteristics determined. However, testing reveals that at higher levels of alloying addition, the benefit of increased transformation temperature begins to be offset by lowered work output and permanent deformation or "walking" of the alloy during thermal cycling under load. In response to this dilemma, NiTiPd alloys have been further alloyed with gold, platinum, and hafnium additions to solid solution strengthen the martensite and parent austenite phases in order to improve the thermomechanical behavior of these materials. The tensile properties, work behavior, and dimensional stability during repeated thermal cycling under load for the ternary and quaternary alloys were compared and discussed. In addition, the benefits of more advanced thermomechanical processing or training on the dimensional stability of these alloys during repeated actuation were investigated. Finally, the effect of quaternary alloying on the thermal stability of NiTiPdX alloys is determined via thermal cycling of the materials to increasing temperatures under load. It was found that solid solution additions of platinum and gold resulted in about a 30 C increase in upper use temperature compared to the baseline NiTiPd alloy, providing an added measure of over-temperature protection.

Exploratory tests of two strut fuel injectors for supersonic combustion

NASA Technical Reports Server (NTRS)

Anderson, G. Y.; Gooderum, P. B.

1974-01-01

Results of supersonic mixing and combustion tests performed with two simple strut injector configurations, one with parallel injectors and one with perpendicular injectors, are presented and analyzed. Good agreement is obtained between static pressure measured on the duct wall downstream of the strut injectors and distributions obtained from one-dimensional calculations. Measured duct heat load agrees with results of the one-dimensional calculations for moderate amounts of reaction, but is underestimated when large separated regions occur near the injection location. For the parallel injection strut, good agreement is obtained between the shape of the injected fuel distribution inferred from gas sample measurements at the duct exit and the distribution calculated with a multiple-jet mixing theory. The overall fraction of injected fuel reacted in the multiple-jet calculation closely matches the amount of fuel reaction necessary to match static pressure with the one-dimensional calculation. Gas sample measurements with the perpendicular injection strut also give results consistent with the amount of fuel reaction in the one-dimensional calculation.

Fault detection in reciprocating compressor valves under varying load conditions

NASA Astrophysics Data System (ADS)

Pichler, Kurt; Lughofer, Edwin; Pichler, Markus; Buchegger, Thomas; Klement, Erich Peter; Huschenbett, Matthias

2016-03-01

This paper presents a novel approach for detecting cracked or broken reciprocating compressor valves under varying load conditions. The main idea is that the time frequency representation of vibration measurement data will show typical patterns depending on the fault state. The problem is to detect these patterns reliably. For the detection task, we make a detour via the two dimensional autocorrelation. The autocorrelation emphasizes the patterns and reduces noise effects. This makes it easier to define appropriate features. After feature extraction, classification is done using logistic regression and support vector machines. The method's performance is validated by analyzing real world measurement data. The results will show a very high detection accuracy while keeping the false alarm rates at a very low level for different compressor loads, thus achieving a load-independent method. The proposed approach is, to our best knowledge, the first automated method for reciprocating compressor valve fault detection that can handle varying load conditions.

Model tests and numerical analyses on horizontal impedance functions of inclined single piles embedded in cohesionless soil

NASA Astrophysics Data System (ADS)

Goit, Chandra Shekhar; Saitoh, Masato

2013-03-01

Horizontal impedance functions of inclined single piles are measured experimentally for model soil-pile systems with both the effects of local soil nonlinearity and resonant characteristics. Two practical pile inclinations of 5° and 10° in addition to a vertical pile embedded in cohesionless soil and subjected to lateral harmonic pile head loadings for a wide range of frequencies are considered. Results obtained with low-to-high amplitude of lateral loadings on model soil-pile systems encased in a laminar shear box show that the local nonlinearities have a profound impact on the horizontal impedance functions of piles. Horizontal impedance functions of inclined piles are found to be smaller than the vertical pile and the values decrease as the angle of pile inclination increases. Distinct values of horizontal impedance functions are obtained for the `positive' and `negative' cycles of harmonic loadings, leading to asymmetric force-displacement relationships for the inclined piles. Validation of these experimental results is carried out through three-dimensional nonlinear finite element analyses, and the results from the numerical models are in good agreement with the experimental data. Sensitivity analyses conducted on the numerical models suggest that the consideration of local nonlinearity at the vicinity of the soil-pile interface influence the response of the soil-pile systems.

Validation of an in vitro 3D bone culture model with perfused and mechanically stressed ceramic scaffold.

PubMed

Bouet, G; Cruel, M; Laurent, C; Vico, L; Malaval, L; Marchat, D

2015-05-15

An engineered three dimensional (3D) in vitro cell culture system was designed with the goal of inducing and controlling in vitro osteogenesis in a reproducible manner under conditions more similar to the in vivo bone microenvironment than traditional two-dimensional (2D) models. This bioreactor allows efficient mechanical loading and perfusion of an original cubic calcium phosphate bioceramic of highly controlled composition and structure. This bioceramic comprises an internal portion containing homogeneously interconnected macropores surrounded by a dense layer, which minimises fluid flow bypass around the scaffold. This dense and flat layer permits the application of a homogeneous loading on the bioceramic while also enhancing its mechanical strength. Numerical modelling of constraints shows that the system provides direct mechanical stimulation of cells within the scaffold. Experimental results establish that under perfusion at a steady flow of 2 µL/min, corresponding to 3 ≤ Medium velocity ≤ 23 µm/s, mouse calvarial cells grow and differentiate as osteoblasts in a reproducible manner, and lay down a mineralised matrix. Moreover, cells respond to mechanical loading by increasing C-fos expression, which demonstrates the effective mechanical stimulation of the culture within the scaffold. In summary, we provide a "proof-of-concept" for osteoblastic cell culture in a controlled 3D culture system under perfusion and mechanical loading. This model will be a tool to analyse bone cell functions in vivo, and will provide a bench testing system for the clinical assessment of bioactive bone-targeting molecules under load.

Snapshot advantage: a review of the light collection improvement for parallel high-dimensional measurement systems

PubMed Central

Hagen, Nathan; Kester, Robert T.; Gao, Liang; Tkaczyk, Tomasz S.

2012-01-01

The snapshot advantage is a large increase in light collection efficiency available to high-dimensional measurement systems that avoid filtering and scanning. After discussing this advantage in the context of imaging spectrometry, where the greatest effort towards developing snapshot systems has been made, we describe the types of measurements where it is applicable. We then generalize it to the larger context of high-dimensional measurements, where the advantage increases geometrically with measurement dimensionality. PMID:22791926

Speed scanning system based on solid-state microchip laser for architectural planning

NASA Astrophysics Data System (ADS)

Redka, Dmitriy; Grishkanich, Alexsandr S.; Kolmakov, Egor; Tsvetkov, Konstantin

2017-10-01

According to the current great interest concerning Large-Scale Metrology applications in many different fields of manufacturing industry, technologies and techniques for dimensional measurement have recently shown a substantial improvement. Ease-of-use, logistic and economic issues, as well as metrological performance, are assuming a more and more important role among system requirements. The project is planned to conduct experimental studies aimed at identifying the impact of the application of the basic laws of microlasers as radiators on the linear-angular characteristics of existing measurement systems. The project is planned to conduct experimental studies aimed at identifying the impact of the application of the basic laws of microlasers as radiators on the linear-angular characteristics of existing measurement systems. The system consists of a distributed network-based layout, whose modularity allows to fit differently sized and shaped working volumes by adequately increasing the number of sensing units. Differently from existing spatially distributed metrological instruments, the remote sensor devices are intended to provide embedded data elaboration capabilities, in order to share the overall computational load.

Self-Sensing of Position-Related Loads in Continuous Carbon Fibers-Embedded 3D-Printed Polymer Structures Using Electrical Resistance Measurement

PubMed Central

Luan, Congcong; Shen, Hongyao; Fu, Jianzhong

2018-01-01

Condition monitoring in polymer composites and structures based on continuous carbon fibers show overwhelming advantages over other potentially competitive sensing technologies in long-gauge measurements due to their great electromechanical behavior and excellent reinforcement property. Although carbon fibers have been developed as strain- or stress-sensing agents in composite structures through electrical resistance measurements, the electromechanical behavior under flexural loads in terms of different loading positions still lacks adequate research, which is the most common situation in practical applications. This study establishes the relationship between the fractional change in electrical resistance of carbon fibers and the external loads at different loading positions along the fibers’ longitudinal direction. An approach for real-time monitoring of flexural loads at different loading positions was presented simultaneously based on this relationship. The effectiveness and feasibility of the approach were verified by experiments on carbon fiber-embedded three-dimensional (3D) printed thermoplastic polymer beam. The error in using the provided approach to monitor the external loads at different loading positions was less than 1.28%. The study fully taps the potential of continuous carbon fibers as long-gauge sensory agents and reinforcement in the 3D-printed polymer structures. PMID:29584665

Use of an instrument sandwiched between the hoof and shoe to measure vertical ground reaction forces and three-dimensional acceleration at the walk, trot, and canter in horses.

PubMed

Kai, M; Aoki, O; Hiraga, A; Oki, H; Tokuriki, M

2000-08-01

To develop an instrument that could be sandwiched between the hoof and shoe of horses and that would reliably measure vertical ground reaction forces and three-dimensional acceleration at the walk, trot, and canter. 5 clinically sound Thoroughbreds. The recording instrument (weight, 350 g) consisted of 2 metal plates, 2 bolts, 4 load cells, and 3 accelerometers. It was mounted to the hoof with a glue-on shoe and devised to support as much load exerted by a limb as possible. The load cells and accelerometers were wired to a 16-channel transmitter, and transmitted signals were received and amplified with a telemetry receiver. The recording instrument could measure in real time the 4 components of the ground reaction force or their resultant force along with acceleration in 3 dimensions as horses walked, trotted, or cantered on a treadmill. Patterns of force-time curves recorded for consecutive strides were similar to each other and to those previously reported, using a force plate. The recording instrument developed for use in the present study allowed us to record vertical ground reaction force and acceleration in 3 dimensions in horses at the walk, trot, and canter.

A Dimensionally Aligned Signal Projection for Classification of Unintended Radiated Emissions

DOE PAGES

Vann, Jason Michael; Karnowski, Thomas P.; Kerekes, Ryan; ...

2017-04-24

Characterization of unintended radiated emissions (URE) from electronic devices plays an important role in many research areas from electromagnetic interference to nonintrusive load monitoring to information system security. URE can provide insights for applications ranging from load disaggregation and energy efficiency to condition-based maintenance of equipment-based upon detected fault conditions. URE characterization often requires subject matter expertise to tailor transforms and feature extractors for the specific electrical devices of interest. We present a novel approach, named dimensionally aligned signal projection (DASP), for projecting aligned signal characteristics that are inherent to the physical implementation of many commercial electronic devices. These projectionsmore » minimize the need for an intimate understanding of the underlying physical circuitry and significantly reduce the number of features required for signal classification. We present three possible DASP algorithms that leverage frequency harmonics, modulation alignments, and frequency peak spacings, along with a two-dimensional image manipulation method for statistical feature extraction. To demonstrate the ability of DASP to generate relevant features from URE, we measured the conducted URE from 14 residential electronic devices using a 2 MS/s collection system. Furthermore, a linear discriminant analysis classifier was trained using DASP generated features and was blind tested resulting in a greater than 90% classification accuracy for each of the DASP algorithms and an accuracy of 99.1% when DASP features are used in combination. Furthermore, we show that a rank reduced feature set of the combined DASP algorithms provides a 98.9% classification accuracy with only three features and outperforms a set of spectral features in terms of general classification as well as applicability across a broad number of devices.« less

A Dimensionally Aligned Signal Projection for Classification of Unintended Radiated Emissions

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

Vann, Jason Michael; Karnowski, Thomas P.; Kerekes, Ryan

Characterization of unintended radiated emissions (URE) from electronic devices plays an important role in many research areas from electromagnetic interference to nonintrusive load monitoring to information system security. URE can provide insights for applications ranging from load disaggregation and energy efficiency to condition-based maintenance of equipment-based upon detected fault conditions. URE characterization often requires subject matter expertise to tailor transforms and feature extractors for the specific electrical devices of interest. We present a novel approach, named dimensionally aligned signal projection (DASP), for projecting aligned signal characteristics that are inherent to the physical implementation of many commercial electronic devices. These projectionsmore » minimize the need for an intimate understanding of the underlying physical circuitry and significantly reduce the number of features required for signal classification. We present three possible DASP algorithms that leverage frequency harmonics, modulation alignments, and frequency peak spacings, along with a two-dimensional image manipulation method for statistical feature extraction. To demonstrate the ability of DASP to generate relevant features from URE, we measured the conducted URE from 14 residential electronic devices using a 2 MS/s collection system. Furthermore, a linear discriminant analysis classifier was trained using DASP generated features and was blind tested resulting in a greater than 90% classification accuracy for each of the DASP algorithms and an accuracy of 99.1% when DASP features are used in combination. Furthermore, we show that a rank reduced feature set of the combined DASP algorithms provides a 98.9% classification accuracy with only three features and outperforms a set of spectral features in terms of general classification as well as applicability across a broad number of devices.« less

A novel mechatronic system for measuring end-point stiffness: mechanical design and preliminary tests.

PubMed

Masia, L; Sandini, G; Morasso, P G

2011-01-01

Measuring arm stiffness is of great interest for many disciplines from biomechanics to medicine especially because modulation of impedance represents one of the main mechanism underlying control of movement and interaction with external environment. Previous works have proposed different methods to identify multijoint hand stiffness by using planar or even tridimensional haptic devices, but the associated computational burden makes them not easy to implement. We present a novel mechanism conceived for measuring multijoint planar stiffness by a single measurement and in a reduced execution time. A novel mechanical rotary device applies cyclic radial perturbation to human arm of a known displacement and the force is acquired by means of a 6-axes commercial load cell. The outcomes suggest that the system is not only reliable but allows obtaining a bi-dimensional estimation of arm stiffness in reduced amount of time and the results are comparable with those reported in previous researches. © 2011 IEEE

Development Of Metallic Thermal Protection System For The Expert Re-Entry Vehicle: Design Verification

NASA Astrophysics Data System (ADS)

Fatemi, Javad

2011-05-01

The thermal protection system of the EXPERT re-entry vehicle is subjected to accelerations, vibrations, acoustic and shock loads during launch and aero-heating loads and aerodynamic forces during re-entry. To fully understand the structural and thermomechanical performances of the TPS, heat transfer analysis, thermal stress analysis, and thermal buckling analysis must be performed. This requires complex three-dimensional thermal and structural models of the entire TPS including the insulation and sensors. Finite element (FE) methods are employed to assess the thermal and structural response of the TPS to the mechanical and aerothermal loads. The FE analyses results are used for the design verification and design improvement of the EXPERT thermal protection system.

Vertical dynamic deflection measurement in concrete beams with the Microsoft Kinect.

PubMed

Qi, Xiaojuan; Lichti, Derek; El-Badry, Mamdouh; Chow, Jacky; Ang, Kathleen

2014-02-19

The Microsoft Kinect is arguably the most popular RGB-D camera currently on the market, partially due to its low cost. It offers many advantages for the measurement of dynamic phenomena since it can directly measure three-dimensional coordinates of objects at video frame rate using a single sensor. This paper presents the results of an investigation into the development of a Microsoft Kinect-based system for measuring the deflection of reinforced concrete beams subjected to cyclic loads. New segmentation methods for object extraction from the Kinect's depth imagery and vertical displacement reconstruction algorithms have been developed and implemented to reconstruct the time-dependent displacement of concrete beams tested in laboratory conditions. The results demonstrate that the amplitude and frequency of the vertical displacements can be reconstructed with submillimetre and milliHz-level precision and accuracy, respectively.

Vertical Dynamic Deflection Measurement in Concrete Beams with the Microsoft Kinect

PubMed Central

Qi, Xiaojuan; Lichti, Derek; El-Badry, Mamdouh; Chow, Jacky; Ang, Kathleen

2014-01-01

The Microsoft Kinect is arguably the most popular RGB-D camera currently on the market, partially due to its low cost. It offers many advantages for the measurement of dynamic phenomena since it can directly measure three-dimensional coordinates of objects at video frame rate using a single sensor. This paper presents the results of an investigation into the development of a Microsoft Kinect-based system for measuring the deflection of reinforced concrete beams subjected to cyclic loads. New segmentation methods for object extraction from the Kinect's depth imagery and vertical displacement reconstruction algorithms have been developed and implemented to reconstruct the time-dependent displacement of concrete beams tested in laboratory conditions. The results demonstrate that the amplitude and frequency of the vertical displacements can be reconstructed with submillimetre and milliHz-level precision and accuracy, respectively. PMID:24556668

Influence of two-dimensional hygrothermal gradients on interlaminar stresses near free edges

NASA Technical Reports Server (NTRS)

Farley, G. L.; Herakovich, C. T.

1977-01-01

Interlaminar stresses are determined for mechanical loading, uniform hygrothermal loading, and gradient moisture loading through implementation of a finite element computer code. Nonuniform two-dimensional hygroscopic gradients are obtained from a finite difference solution of the diffusion equation. It is shown that hygroscopic induced stresses can be larger than those resulting from mechanical and thermal loading, and that the distribution of the interlaminar normal stress may be changed significantly in the presence of a two-dimensional moisture gradient in the boundary layer of a composite laminate.

A Special Investigation to Develop a General Method for Three-dimensional Photoelastic Stress Analysis

NASA Technical Reports Server (NTRS)

Frocht, M M; Guernsey, R , Jr

1953-01-01

The method of strain measurement after annealing is reviewed and found to be satisfactory for the materials available in this country. A new general method is described for the photoelastic determination of the principal stresses at any point of a general body subjected to arbitrary load. The method has been applied to a sphere subjected to diametrical compressive loads. The results show possibilities of high accuracy.

Force Dependent Internalization of Magnetic Nanoparticles Results in Highly Loaded Endothelial Cells for Use as Potential Therapy Delivery Vectors

PubMed Central

MacDonald, Cristin; Barbee, Kenneth

2015-01-01

Purpose To investigate the kinetics, mechanism and extent of MNP loading into endothelial cells and the effect of this loading on cell function. Methods MNP uptake was examined under field on/off conditions, utilizing varying magnetite concentration MNPs. MNP-loaded cell viability and functional integrity was assessed using metabolic respiration, cell proliferation and migration assays. Results MNP uptake in endothelial cells significantly increased under the influence of a magnetic field versus non-magnetic conditions. Larger magnetite density of the MNPs led to a higher MNP internalization by cells under application of a magnetic field without compromising cellular respiration activity. Two-dimensional migration assays at no field showed that higher magnetite loading resulted in greater cell migration rates. In a three-dimensional migration assay under magnetic field, the migration rate of MNP-loaded cells was more than twice that of unloaded cells and was comparable to migration stimulated by a serum gradient. Conclusions Our results suggest that endothelial cell uptake of MNPs is a force dependent process. The in vitro assays determined that cell health is not adversely affected by high MNP loadings, allowing these highly magnetically responsive cells to be potentially beneficial therapy (gene, drug or cell) delivery systems. PMID:22234617

The dimensionality of DSM5 alcohol use disorder in Puerto Rico.

PubMed

Caetano, Raul; Vaeth, Patrice A C; Santiago, Katyana; Canino, Glorisa

2016-11-01

Test the dimensionality and measurement properties of lifetime DSM-5 AUD criteria in a sample of adults from the metropolitan area of San Juan, Puerto Rico. Cross-sectional study with survey data collected in 2013-2014. General population. Random household sample of the adult population 18 to 64years of age in San Juan, Puerto Rico (N=1510; lifetime drinker N=1107). DSM-5 alcohol use disorder (2 or more criteria present in 12months). Lifetime reports of AUD criteria were consistent with a one-dimensional model. Scalar measurement invariance was observed across gender, but measurement parameters for tolerance varied across age, with younger ages showing a lower threshold and steeper loading. Results provide support for a unidimensional DSM-5 AUD construct in a sample from a Latin American country. Copyright © 2016 Elsevier Ltd. All rights reserved.

An automated two-dimensional optical force clamp for single molecule studies.

PubMed Central

Lang, Matthew J; Asbury, Charles L; Shaevitz, Joshua W; Block, Steven M

2002-01-01

We constructed a next-generation optical trapping instrument to study the motility of single motor proteins, such as kinesin moving along a microtubule. The instrument can be operated as a two-dimensional force clamp, applying loads of fixed magnitude and direction to motor-coated microscopic beads moving in vitro. Flexibility and automation in experimental design are achieved by computer control of both the trap position, via acousto-optic deflectors, and the sample position, using a three-dimensional piezo stage. Each measurement is preceded by an initialization sequence, which includes adjustment of bead height relative to the coverslip using a variant of optical force microscopy (to +/-4 nm), a two-dimensional raster scan to calibrate position detector response, and adjustment of bead lateral position relative to the microtubule substrate (to +/-3 nm). During motor-driven movement, both the trap and stage are moved dynamically to apply constant force while keeping the trapped bead within the calibrated range of the detector. We present details of force clamp operation and preliminary data showing kinesin motor movement subject to diagonal and forward loads. PMID:12080136

Toward an MRI-based method to measure non-uniform cartilage deformation: an MRI-cyclic loading apparatus system and steady-state cyclic displacement of articular cartilage under compressive loading.

PubMed

Neu, C P; Hull, M L

2003-04-01

Recent magnetic resonance imaging (MRI) techniques have shown potential for measuring non-uniform deformations throughout the volume (i.e. three-dimensional (3D) deformations) in small orthopedic tissues such as articular cartilage. However, to analyze cartilage deformation using MRI techniques, a system is required which can construct images from multiple acquisitions of MRI signals from the cartilage in both the underformed and deformed states. The objectives of the work reported in this article were to 1) design an apparatus that could apply highly repeatable cyclic compressive loads of 400 N and operate in the bore of an MRI scanner, 2) demonstrate that the apparatus and MRI scanner can be successfully integrated to observe 3D deformations in a phantom material, 3) use the apparatus to determine the load cycle necessary to achieve a steady-state deformation response in normal bovine articular cartilage samples using a flat-surfaced and nonporous indentor in unconfined compression. Composed of electronic and pneumatic components, the apparatus regulated pressure to a double-acting pneumatic cylinder so that (1) load-controlled compression cycles were applied to cartilage samples immersed in a saline bath, (2) loading and recovery periods within a cycle varied in time duration, and (3) load magnitude varied so that the stress applied to cartilage samples was within typical physiological ranges. In addition the apparatus allowed gating for MR image acquisition, and operation within the bore of an MRI scanner without creating image artifacts. The apparatus demonstrated high repeatability in load application with a standard deviation of 1.8% of the mean 400 N load applied. When the apparatus was integrated with an MRI scanner programmed with appropriate pulse sequences, images of a phantom material in both the underformed and deformed states were constructed by assembling data acquired through multiple signal acquisitions. Additionally, the number of cycles to reach a steady-state response in normal bovine articular cartilage was 49 for a total cycle duration of 5 seconds, but decreased to 33 and 27 for increasing total cycle durations of 10 and 15 seconds, respectively. Once the steady-state response was achieved, 95% of all displacements were within +/- 7.42 microns of the mean displacement, indicating that the displacement response to the cyclic loads was highly repeatable. With this performance, the MRI-loading apparatus system meets the requirements to create images of articular cartilage from which 3D deformation can be determined.

Theory and application of a three-dimensional model of the human spine.

PubMed

Belytschko, T; Schwer, L; Privitzer, E

1978-01-01

A three-dimensional, discrete model of the human spine, torso, and head was developed for the purpose of evaluating mechanical response in pilot ejection. However, it was developed in sufficient generality to be applicable to other body response problems, such as occupant response in aircraft crash and arbitrary loads on the head-spine system. The anatomy is modelled by a collection of rigid bodies, which represent skeletal segments such as the vertebrae, pelvis, head, and ribs, interconnected by deformable elements, which represent ligaments, cargilagenous joints, viscera and connective tissues. Results are presented for several conditions: different rates of onset, ejection at angles, preejection alignment, and eccentric head loadings. It is shown that slow rates of onset and angling the seat reduce both the peak axial loads and bending moments. In the presence of eccentric head masses, such as helmet-mounted devices, the reflected flexural wave is shown to be the key injury mechanism.

Analysis of load monitoring system in hydraulic mobile cranes

NASA Astrophysics Data System (ADS)

Kalairassan, G.; Boopathi, M.; Mohan, Rijo Mathew

2017-11-01

Load moment limiters or safe load control systems or are very important in crane safety. The system detects the moment of lifting load and compares this actual moment with the rated moment. The system uses multiple sensors such as boom angle sensor, boom length sensor for telescopic booms, pressure transducers for measuring the load, anti-two block switch and roller switches. The system works both on rubber and on outriggers. The sensors measure the boom extension, boom angle and load to give as inputs to the central processing, which calculate the safe working load range for that particular configuration of the crane and compare it with the predetermined safe load. If the load exceeds the safe load, actions will be taken which will reduce the load moment, which is boom telescopic retraction and boom lifting. Anti-two block switch is used to prevent the two blocking condition. The system is calibrated and load tested for at most precision.

Three-dimensional finite element analysis of the shear bond test.

PubMed

DeHoff, P H; Anusavice, K J; Wang, Z

1995-03-01

The purpose of this study was to use finite element analyses to model the planar shear bond test and to evaluate the effects of modulus values, bonding agent thickness, and loading conditions on the stress distribution in the dentin adjacent to the bonding agent-dentin interface. All calculations were performed with the ANSYS finite element program. The planar shear bond test was modeled as a cylinder of resin-based composite bonded to a cylindrical dentin substrate. The effects of material, geometry and loading variables were determined primarily by use of a three-dimensional structural element. Several runs were also made using an axisymmetric element with harmonic loading and a plane strain element to determine whether two-dimensional analyses yield valid results. Stress calculations using three-dimensional finite element analyses confirmed the presence of large stress concentration effects for all stress components at the bonding agent-dentin interface near the application of the load. The maximum vertical shear stress generally occurs approximately 0.3 mm below the loading site and then decreases sharply in all directions. The stresses reach relatively uniform conditions within about 0.5 mm of the loading site and then increase again as the lower region of the interface is approached. Calculations using various loading conditions indicated that a wire-loop method of loading leads to smaller stress concentration effects, but a shear bond strength determined by dividing a failure load by the cross-sectional area grossly underestimates the true interfacial bond strength. Most dental researchers are using tensile and shear bond tests to predict the effects of process and material variables on the clinical performance of bonding systems but no evidence has yet shown that bond strength is relevant to clinical performance. A critical factor in assessing the usefulness of bond tests is a thorough understanding of the stress states that cause failure in the bond test and then to assess whether these stress states also exist in the clinical situation. Finite element analyses can help to answer this question but much additional work is needed to identify the failure modes in service and to relate these failures to particular loading conditions. The present study represents only a first step in understanding the stress states in the planar shear bond test.

First Results from a Forward, 3-Dimensional Regional Model of a Transpressional San Andreas Fault System

NASA Astrophysics Data System (ADS)

Fitzenz, D. D.; Miller, S. A.

2001-12-01

We present preliminary results from a 3-dimensional fault interaction model, with the fault system specified by the geometry and tectonics of the San Andreas Fault (SAF) system. We use the forward model for earthquake generation on interacting faults of Fitzenz and Miller [2001] that incorporates the analytical solutions of Okada [85,92], GPS-constrained tectonic loading, creep compaction and frictional dilatancy [Sleep and Blanpied, 1994, Sleep, 1995], and undrained poro-elasticity. The model fault system is centered at the Big Bend, and includes three large strike-slip faults (each discretized into multiple subfaults); 1) a 300km, right-lateral segment of the SAF to the North, 2) a 200km-long left-lateral segment of the Garlock fault to the East, and 3) a 100km-long right-lateral segment of the SAF to the South. In the initial configuration, three shallow-dipping faults are also included that correspond to the thrust belt sub-parallel to the SAF. Tectonic loading is decomposed into basal shear drag parallel to the plate boundary with a 35mm yr-1 plate velocity, and East-West compression approximated by a vertical dislocation surface applied at the far-field boundary resulting in fault-normal compression rates in the model space about 4mm yr-1. Our aim is to study the long-term seismicity characteristics, tectonic evolution, and fault interaction of this system. We find that overpressured faults through creep compaction are a necessary consequence of the tectonic loading, specifically where high normal stress acts on long straight fault segments. The optimal orientation of thrust faults is a function of the strike-slip behavior, and therefore results in a complex stress state in the elastic body. This stress state is then used to generate new fault surfaces, and preliminary results of dynamically generated faults will also be presented. Our long-term aim is to target measurable properties in or around fault zones, (e.g. pore pressures, hydrofractures, seismicity catalogs, stress orientation, surface strain, triggering, etc.), which may allow inferences on the stress state of fault systems.

Evaluation of a load cell model for dynamic calibration of the rotor systems research aircraft

NASA Technical Reports Server (NTRS)

Duval, R. W.; Bahrami, H.; Wellman, B.

1985-01-01

The Rotor Systems Research Aircraft uses load cells to isolate the rotor/transmission system from the fuselage. An analytical model of the relationship between applied rotor loads and the resulting load cell measurements is derived by applying a force-and-moment balance to the isolated rotor/transmission system. The model is then used to estimate the applied loads from measured load cell data, as obtained from a ground-based shake test. Using nominal design values for the parameters, the estimation errors, for the case of lateral forcing, were shown to be on the order of the sensor measurement noise in all but the roll axis. An unmodeled external load appears to be the source of the error in this axis.

Dimensionality and measurement invariance in the Satisfaction with Life Scale in Norway.

PubMed

Clench-Aas, Jocelyne; Nes, Ragnhild Bang; Dalgard, Odd Steffen; Aarø, Leif Edvard

2011-10-01

Results from previous studies examining the dimensionality and factorial invariance of the Satisfaction with Life Scale (SWLS) are inconsistent and often based on small samples. This study examines the factorial structure and factorial invariance of the SWLS in a Norwegian sample. Confirmatory factor analysis (AMOS) was conducted to explore dimensionality and test for measurement invariance in factor structure, factor loadings, intercepts, and residual variance across gender and four age groups in a large (N = 4,984), nationally representative sample of Norwegian men and women (15-79 years). The data supported a modified unidimensional structure. Factor loadings could be constrained to equality between the sexes, indicating metric invariance between genders. Further testing indicated invariance also at the strong and strict levels, thus allowing analyses involving group means. The SWLS was shown to be sensitive to age, however, at the strong and strict levels of invariance testing. In conclusion, the results in this Norwegian study seem to confirm that a unidimensional structure is acceptable, but that a modified single-factor model with correlations between error terms of items 4 and 5 is preferred. Additionally, comparisons may be made between the genders. Caution must be exerted when comparing age groups.

Application of the Quadrupole Method for Simulation of Passive Thermography

NASA Technical Reports Server (NTRS)

Winfree, William P.; Zalameda, Joseph N.; Gregory, Elizabeth D.

2017-01-01

Passive thermography has been shown to be an effective method for in-situ and real time nondestructive evaluation (NDE) to measure damage growth in a composite structure during cyclic loading. The heat generation by subsurface flaw results in a measurable thermal profile at the surface. This paper models the heat generation as a planar subsurface source and calculates the resultant temperature profile at the surface using a three dimensional quadrupole. The results of the model are compared to finite element simulations of the same planar sources and experimental data acquired during cyclic loading of composite specimens.

Influence of Implant Positions and Occlusal Forces on Peri-Implant Bone Stress in Mandibular Two-Implant Overdentures: A 3-Dimensional Finite Element Analysis.

PubMed

Alvarez-Arenal, Angel; Gonzalez-Gonzalez, Ignacio; deLlanos-Lanchares, Hector; Brizuela-Velasco, Aritza; Dds, Elena Martin-Fernandez; Ellacuria-Echebarria, Joseba

2017-12-01

The aim of this study was to evaluate and compare the bone stress around implants in mandibular 2-implant overdentures depending on the implant location and different loading conditions. Four 3-dimensional finite element models simulating a mandibular 2-implant overdenture and a Locator attachment system were designed. The implants were located at the lateral incisor, canine, second premolar, and crossed-implant levels. A 150 N unilateral and bilateral vertical load of different location was applied, as was 40 N when combined with midline load. Data for von Mises stress were produced numerically, color coded, and compared between the models for peri-implant bone and loading conditions. With unilateral loading, in all 4 models much higher peri-implant bone stress values were recorded on the load side compared with the no-load side, while with bilateral occlusal loading, the stress distribution was similar on both sides. In all models, the posterior unilateral load showed the highest stress, which decreased as the load was applied more mesially. In general, the best biomechanical environment in the peri-implant bone was found in the model with implants at premolar level. In the crossed-implant model, the load side greatly altered the biomechanical environment. Overall, the overdenture with implants at second premolar level should be the chosen design, regardless of where the load is applied. The occlusal loading application site influences the bone stress around the implant. Bilateral occlusal loading distributes the peri-implant bone stress symmetrically, while unilateral loading increases it greatly on the load side, no matter where the implants are located.

Quantitative and qualitative measure of intralaboratory two-dimensional protein gel reproducibility and the effects of sample preparation, sample load, and image analysis.

PubMed

Choe, Leila H; Lee, Kelvin H

2003-10-01

We investigate one approach to assess the quantitative variability in two-dimensional gel electrophoresis (2-DE) separations based on gel-to-gel variability, sample preparation variability, sample load differences, and the effect of automation on image analysis. We observe that 95% of spots present in three out of four replicate gels exhibit less than a 0.52 coefficient of variation (CV) in fluorescent stain intensity (% volume) for a single sample run on multiple gels. When four parallel sample preparations are performed, this value increases to 0.57. We do not observe any significant change in quantitative value for an increase or decrease in sample load of 30% when using appropriate image analysis variables. Increasing use of automation, while necessary in modern 2-DE experiments, does change the observed level of quantitative and qualitative variability among replicate gels. The number of spots that change qualitatively for a single sample run in parallel varies from a CV = 0.03 for fully manual analysis to CV = 0.20 for a fully automated analysis. We present a systematic method by which a single laboratory can measure gel-to-gel variability using only three gel runs.

Non-contacting Measurement of Oil Film Thickness Between Loaded Metallic Gear Teeth

NASA Astrophysics Data System (ADS)

Cox, Daniel B.; Ceccio, Steven L.; Dowling, David R.

2013-11-01

The mechanical power transmission efficiency of gears is depends on the lubrication condition between gear teeth. While the lubrication levels can be generally predicted, an effective in-situ non-contacting measurement of oil film thicknesses between loaded metallic gear teeth has proved elusive. This study explores a novel oil film thickness measurement technique based on optical fluence, the light energy transmitted between loaded gear teeth. A gear testing apparatus that allowed independent control of gear rotation rate, load torque, and oil flow was designed and built. Film thickness measurements made with 5-inch-pitch-diameter 60-tooth spur gears ranged from 0.3 to 10.2 mil. These results are compared with film thickness measurements made in an earlier investigation (MacConochie and Cameron, 1960), as well as with predictions from two film thickness models: a simple two-dimensional squeezed oil film and the industry-accepted model as described by the American Gear Manufacturers Association (AGMA 925, 2003). In each case, the measured film thicknesses were larger than the predicted thicknesses, though these discrepancies might be attributed to the specifics the experiments and to challenges associated with calibrating the fluence measurements. [Sponsored by General Electric].

ASCENT Program

NASA Technical Reports Server (NTRS)

Brown, Richard; Collier, Gary; Heckenlaible, Richard; Dougherty, Edward; Dolenz, James; Ross, Iain

2012-01-01

The ASCENT program solves the three-dimensional motion and attendant structural loading on a flexible vehicle incorporating, optionally, an active analog thrust control system, aerodynamic effects, and staging of multiple bodies. ASCENT solves the technical problems of loads, accelerations, and displacements of a flexible vehicle; staging of the upper stage from the lower stage; effects of thrust oscillations on the vehicle; a payload's relative motion; the effect of fluid sloshing on vehicle; and the effect of winds and gusts on the vehicle (on the ground or aloft) in a continuous analysis. The ATTACH ASCENT Loads program reads output from the ASCENT flexible body loads program, and calculates the approximate load indicators for the time interval under consideration. It calculates the load indicator values from pre-launch to the end of the first stage.

Platform switching: biomechanical evaluation using three-dimensional finite element analysis.

PubMed

Tabata, Lucas Fernando; Rocha, Eduardo Passos; Barão, Valentim Adelino Ricardo; Assunção, Wirley Goncalves

2011-01-01

The objective of this study was to evaluate, using three-dimensional finite element analysis (3D FEA), the stress distribution in peri-implant bone tissue, implants, and prosthetic components of implant-supported single crowns with the use of the platform-switching concept. Three 3D finite element models were created to replicate an external-hexagonal implant system with peri-implant bone tissue in which three different implant-abutment configurations were represented. In the regular platform (RP) group, a regular 4.1-mm-diameter abutment (UCLA) was connected to regular 4.1-mm-diameter implant. The platform-switching (PS) group was simulated by the connection of a wide implant (5.0 mm diameter) to a regular 4.1-mm-diameter UCLA abutment. In the wide-platform (WP) group, a 5.0-mm-diameter UCLA abutment was connected to a 5.0-mm-diameter implant. An occlusal load of 100 N was applied either axially or obliquely on the models using ANSYS software. Both the increase in implant diameter and the use of platform switching played roles in stress reduction. The PS group presented lower stress values than the RP and WP groups for bone and implant. In the peri-implant area, cortical bone exhibited a higher stress concentration than the trabecular bone in all models and both loading situations. Under oblique loading, higher intensity and greater distribution of stress were observed than under axial loading. Platform switching reduced von Mises (17.5% and 9.3% for axial and oblique loads, respectively), minimum (compressive) (19.4% for axial load and 21.9% for oblique load), and maximum (tensile) principal stress values (46.6% for axial load and 26.7% for oblique load) in the peri-implant bone tissue. Platform switching led to improved biomechanical stress distribution in peri-implant bone tissue. Oblique loads resulted in higher stress concentrations than axial loads for all models. Wide-diameter implants had a large influence in reducing stress values in the implant system.

Application of displacement monitoring system on high temperature steam pipe

NASA Astrophysics Data System (ADS)

Ghaffar, M. H. A.; Husin, S.; Baek, J. E.

2017-10-01

High-energy piping systems of power plants such as Main Steam (MS) pipe or Hot Reheat (HR) pipe are operating at high temperature and high pressure at base and cyclic loads. In the event of transient condition, a pipe can be deflected dramatically and caused high stress in the pipe, yielding to failure of the piping system. Periodic monitoring and walk down can identify abnormalities but limitations exist in the standard walk down practice. This paper provides a study of pipe displacement monitoring on MS pipe of coal-fired power plant to continuously capture the pipe movement behaviour at different load using 3-Dimensional Displacement Measuring System (3DDMS). The displacement trending at Location 5 and 6 (north and south) demonstrated pipes displace less than 25% to that of design movement. It was determined from synchronisation analysis that Location 7 (north) and Location 8 (south) pipe actual movement difference has exceeded the design movement difference. Visual survey at specified locations with significant displacement trending reveals issues of hydraulic snubber and piping interferences. The study demonstrated that the displacement monitoring is able to capture pipe movement at all time and allows engineer to monitor pipe movement behaviour, aids in identifying issue early for remedy action.

Compilation of load spectrum of loader drive axle

NASA Astrophysics Data System (ADS)

Wei, Yongxiang; Zhu, Haoyue; Tang, Heng; Yuan, Qunwei

2018-03-01

In order to study the preparation method of gear fatigue load spectrum for loaders, the load signal of four typical working conditions of loader is collected. The signal that reflects the law of load change is obtained by preprocessing the original signal. The torque of the drive axle is calculated by using the rain flow counting method. According to the operating time ratio of each working condition, the two dimensional load spectrum based on the real working conditions of the drive axle of loader is established by the cycle extrapolation and synthesis method. The two-dimensional load spectrum is converted into one-dimensional load spectrum by means of the mean of torque equal damage method. Torque amplification includes the maximum load torque of the main reduction gear. Based on the theory of equal damage, the accelerated cycles are calculated. In this way, the load spectrum of the loading condition of the drive axle is prepared to reflect loading condition of the loader. The load spectrum can provide reference for fatigue life test and life prediction of loader drive axle.

Development and Characterization of Improved NiTiPd High-Temperature Shape-Memory Alloys by Solid-Solution Strengthening and Thermomechanical Processing

NASA Technical Reports Server (NTRS)

Bigelow, Glen; Noebe, Ronald; Padula, Santo, II; Garg, Anita; Olson, David

2006-01-01

The need for compact, solid-state actuation systems for use in the aerospace, automotive, and other transportation industries is currently motivating research in high-temperature shape-memory alloys (HTSMA) with transformation temperatures greater than 100 C. One of the basic high-temperature alloys investigated to fill this need is Ni(19.5)Ti(50.5)Pd30. Initial testing has indicated that this alloy, while having acceptable work characteristics, suffers from significant permanent deformation (or ratcheting) during thermal cycling under load. In an effort to overcome this deficiency, various solid-solution alloying and thermomechanical processing schemes were investigated. Solid-solution strengthening was achieved by substituting 5at% gold or platinum for palladium in Ni(19.5)Ti(50.5)Pd30, the so-called baseline alloy, to strengthen the martensite and austenite phases against slip processes and improve thermomechanical behavior. Tensile properties, work behavior, and dimensional stability during repeated thermal cycling under load for the ternary and quaternary alloys were compared. The relative difference in yield strength between the martensite and austenite phases and the dimensional stability of the alloy were improved by the quaternary additions, while work output was only minimally impacted. The three alloys were also thermomechanically processed by cycling repeatedly through the transformation range under a constant stress. This so-called training process dramatically improved the dimensional stability in these samples and also recovered the slight decrease in work output caused by quaternary alloying. An added benefit of the solid-solution strengthening was maintenance of enhanced dimensional stability of the trained material to higher temperatures compared to the baseline alloy, providing a greater measure of over-temperature capability.

Aerodynamic and heat transfer analysis of the low aspect ratio turbine

NASA Astrophysics Data System (ADS)

Sharma, O. P.; Nguyen, P.; Ni, R. H.; Rhie, C. M.; White, J. A.

1987-06-01

The available two- and three-dimensional codes are used to estimate external heat loads and aerodynamic characteristics of a highly loaded turbine stage in order to demonstrate state-of-the-art methodologies in turbine design. By using data for a low aspect ratio turbine, it is found that a three-dimensional multistage Euler code gives good averall predictions for the turbine stage, yielding good estimates of the stage pressure ratio, mass flow, and exit gas angles. The nozzle vane loading distribution is well predicted by both the three-dimensional multistage Euler and three-dimensional Navier-Stokes codes. The vane airfoil surface Stanton number distributions, however, are underpredicted by both two- and three-dimensional boundary value analysis.

Maximized gust loads for a nonlinear airplane using matched filter theory and constrained optimization

NASA Technical Reports Server (NTRS)

Scott, Robert C.; Pototzky, Anthony S.; Perry, Boyd, III

1991-01-01

Two matched filter theory based schemes are described and illustrated for obtaining maximized and time correlated gust loads for a nonlinear aircraft. The first scheme is computationally fast because it uses a simple 1-D search procedure to obtain its answers. The second scheme is computationally slow because it uses a more complex multi-dimensional search procedure to obtain its answers, but it consistently provides slightly higher maximum loads than the first scheme. Both schemes are illustrated with numerical examples involving a nonlinear control system.

Maximized gust loads for a nonlinear airplane using matched filter theory and constrained optimization

NASA Technical Reports Server (NTRS)

Scott, Robert C.; Perry, Boyd, III; Pototzky, Anthony S.

1991-01-01

This paper describes and illustrates two matched-filter-theory based schemes for obtaining maximized and time-correlated gust-loads for a nonlinear airplane. The first scheme is computationally fast because it uses a simple one-dimensional search procedure to obtain its answers. The second scheme is computationally slow because it uses a more complex multidimensional search procedure to obtain its answers, but it consistently provides slightly higher maximum loads than the first scheme. Both schemes are illustrated with numerical examples involving a nonlinear control system.

Overview of Aerothermodynamic Loads Definition Study

NASA Technical Reports Server (NTRS)

Povinelli, L. A.

1985-01-01

The Aerothermodynamic Loads Definition were studied to develop methods to more accurately predict the operating environment in the space shuttle main engine (SSME) components. Development of steady and time-dependent, three-dimensional viscous computer codes and experimental verification and engine diagnostic testing are considered. The steady, nonsteady, and transient operating loads are defined to accurately predict powerhead life. Improvements in the structural durability of the SSME turbine drive systems depends on the knowledge of the aerothermodynamic behavior of the flow through the preburner, turbine, turnaround duct, gas manifold, and injector post regions.

Physics Based Model for Online Fault Detection in Autonomous Cryogenic Loading System

NASA Technical Reports Server (NTRS)

Kashani, Ali; Devine, Ekaterina Viktorovna P; Luchinsky, Dmitry Georgievich; Smelyanskiy, Vadim; Sass, Jared P.; Brown, Barbara L.; Patterson-Hine, Ann

2013-01-01

We report the progress in the development of the chilldown model for rapid cryogenic loading system developed at KSC. The nontrivial characteristic feature of the analyzed chilldown regime is its active control by dump valves. The two-phase flow model of the chilldown is approximated as one-dimensional homogeneous fluid flow with no slip condition for the interphase velocity. The model is built using commercial SINDAFLUINT software. The results of numerical predictions are in good agreement with the experimental time traces. The obtained results pave the way to the application of the SINDAFLUINT model as a verification tool for the design and algorithm development required for autonomous loading operation.

Development of an interactive anatomical three-dimensional eye model.

PubMed

Allen, Lauren K; Bhattacharyya, Siddhartha; Wilson, Timothy D

2015-01-01

The discrete anatomy of the eye's intricate oculomotor system is conceptually difficult for novice students to grasp. This is problematic given that this group of muscles represents one of the most common sites of clinical intervention in the treatment of ocular motility disorders and other eye disorders. This project was designed to develop a digital, interactive, three-dimensional (3D) model of the muscles and cranial nerves of the oculomotor system. Development of the 3D model utilized data from the Visible Human Project (VHP) dataset that was refined using multiple forms of 3D software. The model was then paired with a virtual user interface in order to create a novel 3D learning tool for the human oculomotor system. Development of the virtual eye model was done while attempting to adhere to the principles of cognitive load theory (CLT) and the reduction of extraneous load in particular. The detailed approach, digital tools employed, and the CLT guidelines are described herein. © 2014 American Association of Anatomists.

Flexural impact force absorption of mouthguard materials using film sensor system.

PubMed

Reza, Fazal; Churei, Hiroshi; Takahashi, Hidekazu; Iwasaki, Naohiko; Ueno, Toshiaki

2014-06-01

Several methods have been used to measure the impact force absorption capacities of mouthguard materials; however, the relationships among these measurement systems have not been clearly determined. The purpose of the present study was to evaluate the impact force-absorbing capability of materials using a drop-ball system with film sensors and load cells to clarify the relationship between these two sensor systems. Disk-shaped specimens (1, 2, and 3 mm thick) were prepared using three commercial thermoplastic mouthguard materials (Bioplast, Impact Guard, MG 21) and one experimental mouthguard material [mixture of Poly (ethyl methacrylate)]. Impact force was applied by letting a stainless steel ball drop free-fall onto the specimens and then measuring the impact load under each specimen using a film sensor system and a load cell sensor system. The total load measured with the film sensor system decreased with an increase in mouthguard thickness, while almost none of the transmitted impact forces measured with the load cell system were statistically different. The film sensor system was considered to be superior to the load cell system because the maximum stress and stress area could be determined. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Effect of load transients on SOFC operation—current reversal on loss of load

NASA Astrophysics Data System (ADS)

Gemmen, Randall S.; Johnson, Christopher D.

The dynamics of solid oxide fuel cell (SOFC) operation have been considered previously, but mainly through the use of one-dimensional codes applied to co-flow fuel cell systems. In this paper several geometries are considered, including cross-flow, co-flow, and counter-flow. The details of the model are provided, and the model is compared with some initial experimental data. For parameters typical of SOFC operation, a variety of transient cases are investigated, including representative load increase and decrease and system shutdown. Of particular note for large load decrease conditions (e.g., shutdown) is the occurrence of reverse current over significant portions of the cell, starting from the moment of load loss up to the point where equilibrated conditions again provide positive current. Consideration is given as to when such reverse current conditions might most significantly impact the reliability of the cell.

A method for analyzing dynamic stall of helicopter rotor blades

NASA Technical Reports Server (NTRS)

Crimi, P.; Reeves, B. L.

1972-01-01

A model for each of the basic flow elements involved in the unsteady stall of a two-dimensional airfoil in incompressible flow is presented. The interaction of these elements is analyzed using a digital computer. Computations of the loading during transient and sinusoidal pitching motions are in good qualitative agreement with measured loads. The method was used to confirm that large torsional response of helicopter blades detected in flight tests can be attributed to dynamic stall.

Investigation of the three-dimensional flow field within a transonic fan rotor: Experiment and analysis

NASA Technical Reports Server (NTRS)

Pierzga, M. J.; Wood, J. R.

1984-01-01

An experimental investigation of the three dimensional flow field through a low aspect ratio, transonic, axial flow fan rotor has been conducted using an advanced laser anemometer (LA) system. Laser velocimeter measurements of the rotor flow field at the design operating speed and over a range of through flow conditions are compared to analytical solutions. The numerical technique used herein yields the solution to the full, three dimensional, unsteady Euler equations using an explicit time marching, finite volume approach. The numerical analysis, when coupled with a simplified boundary layer calculation, generally yields good agreement with the experimental data. The test rotor has an aspect ratio of 1.56, a design total pressure ratio of 1.629 and a tip relative Mach number of 1.38. The high spatial resolution of the LA data matrix (9 radial by 30 axial by 50 blade to blade) permits details of the transonic flow field such as shock location, turning distribution and blade loading levels to be investigated and compared to analytical results.

Evaluation of the osteogenic differentiation of gingiva-derived stem cells grown on culture plates or in stem cell spheroids: Comparison of two- and three-dimensional cultures.

PubMed

Lee, Sung-Il; Ko, Youngkyung; Park, Jun-Beom

2017-09-01

Three-dimensional cell culture systems provide a convenient in vitro model for the study of complex cell-cell and cell-matrix interactions in the absence of exogenous substrates. The current study aimed to evaluate the osteogenic differentiation potential of gingiva-derived stem cells cultured in two-dimensional or three-dimensional systems. To the best of our knowledge, the present study is the first to compare the growth of gingiva-derived stem cells in monolayer culture to a three-dimensional culture system with microwells. For three-dimensional culture, gingiva-derived stem cells were isolated and seeded into polydimethylsiloxane-based concave micromolds. Alkaline phosphatase activity and alizarin red S staining assays were then performed to evaluate osteogenesis and the degree of mineralization, respectively. Stem cell spheroids had a significantly increased level of alkaline phosphatase activity and mineralization compared with cells from the two-dimensional culture. In addition, an increase in mineralized deposits was observed with an increase in the loading cell number. The results of present study indicate that gingiva-derived stem cell spheroids exhibit an increased osteogenic potential compared with stem cells from two-dimensional culture. This highlights the potential of three-dimensional culture systems using gingiva-derived stem cells for regenerative medicine applications requiring stem cells with osteogenic potential.

Neighborhood community characteristics associated with HIV disease outcomes in a cohort of urban women living with HIV.

PubMed

Burke-Miller, Jane K; Weber, Kathleen; Cohn, Susan E; Hershow, Ronald C; Sha, Beverly E; French, Audrey L; Cohen, Mardge H

2016-10-01

Recent studies have found geographic variations in immune and viral human immunodeficiency virus (HIV) disease outcomes associated with census measures of neighborhood poverty and segregation. Although readily available, such aggregate census measures are not based on health behavior models and provide limited information regarding neighborhood effect pathways. In contrast, survey-based measures can capture specific aspects of neighborhood disadvantage that may better inform community-based interventions. Therefore, the aim of this study is to assess the measurement validity of multi-dimensional survey measures of neighborhood disorder compared with census measures as predictors of HIV outcomes in a cohort of 197 low-income women in a major metropolitan area. The multi-dimensional survey measures were related to each other and to census measures of concentrated poverty and racial segregation, but not so highly correlated as to be uniform. We found notable variation between community areas in women's CD4 levels but there was no corresponding geographic variance in viral load, and relationships between community area measures and viral load disappeared after adjustment for individual characteristics, including HIV treatment adherence. In multilevel models adjusting for individual characteristics including substance use, depression, and HIV treatment adherence, one survey measure of neighborhood disadvantage (poor-quality built environment) and one census measure (racial segregation) were significantly associated with greater likelihood of CD4 < 500 (p < .05).

Structure design and characteristic analysis of micro-nano probe based on six dimensional micro-force measuring principle

NASA Astrophysics Data System (ADS)

Yang, Hong-tao; Cai, Chun-mei; Fang, Chuan-zhi; Wu, Tian-feng

2013-10-01

In order to develop micro-nano probe having error self-correcting function and good rigidity structure, a new micro-nano probe system was developed based on six-dimensional micro-force measuring principle. The structure and working principle of the probe was introduced in detail. The static nonlinear decoupling method was established with BP neural network to do the static decoupling for the dimension coupling existing in each direction force measurements. The optimal parameters of BP neural network were selected and the decoupling simulation experiments were done. The maximum probe coupling rate after decoupling is 0.039% in X direction, 0.025% in Y direction and 0.027% in Z direction. The static measurement sensitivity of the probe can reach 10.76μɛ / mN in Z direction and 14.55μɛ / mN in X and Y direction. The modal analysis and harmonic response analysis under three dimensional harmonic load of the probe were done by using finite element method. The natural frequencies under different vibration modes were obtained and the working frequency of the probe was determined, which is higher than 10000 Hz . The transient response analysis of the probe was done, which indicates that the response time of the probe can reach 0.4 ms. From the above results, it is shown that the developed micro-nano probe meets triggering requirements of micro-nano probe. Three dimension measuring force can be measured precisely by the developed probe, which can be used to predict and correct the force deformation error and the touch error of the measuring ball and the measuring rod.

Three-Dimensional Modeling of Fluid and Heat Transport in an Accretionary Complex

NASA Astrophysics Data System (ADS)

Paula, C. A.; Ge, S.; Screaton, E. J.

2001-12-01

As sediments are scraped off of the subducting oceanic crust and accreted to the overriding plate, the rapid loading causes pore pressures in the underthrust sediments to increase. The change in pore pressure drives fluid flow and heat transport within the accretionary complex. Fluid is channeled along higher permeability faults and fractures and expelled at the seafloor. In this investigation, we examined the effects of sediment loading on fluid flow and thermal transport in the decollement at the Barbados Ridge subduction zone. Both the width and thickness of the Barbados Ridge accretionary complex increase from north to south. The presence of mud diapers south of the Tiburon Rise and an observed southward decrease in heat flow measurements indicate that the increased thickness of the southern Barbados accretionary prism affects the transport of chemicals and heat by fluids. The three-dimensional geometry and physical properties of the accretionary complex were utilized to construct a three-dimensional fluid flow/heat transport model. We calculated the pore pressure change due to a period of sediment loading and added this to steady-state pressure conditions to generate initial conditions for transient simulations. We then examined the diffusion of pore pressure and possible perturbation of the thermal regime over time due to loading of the underthrust sediments. The model results show that the sediment-loading event was sufficient to create small temperature fluctuations in the decollement zone. The magnitude of temperature fluctuation in the decollement was greatest at the deformation front but did not vary significantly from north to south of the Tiburon Rise.

PIC simulations of conical magnetically insulated transmission line with LTD generator: Transition from self-limited to load-limited flow

NASA Astrophysics Data System (ADS)

Liu, Laqun; Wang, Huihui; Guo, Fan; Zou, Wenkang; Liu, Dagang

2017-04-01

Based on the 3-dimensional Particle-In-Cell (PIC) code CHIPIC3D, with a new circuit boundary algorithm we developed, a conical magnetically insulated transmission line (MITL) with a 1.0-MV linear transformer driver (LTD) is explored numerically. The values of switch jitter time of LTD are critical parameters for the system, which are difficult to be measured experimentally. In this paper, these values are obtained by comparing the PIC results with experimental data of large diode-gap MITL. By decreasing the diode gap, we find that all PIC results agree well with experimental data only if MITL works on self-limited flow no matter how large the diode gap is. However, when the diode gap decreases to a threshold, the self-limited flow would transfer to a load-limited flow. In this situation, PIC results no longer agree with experimental data anymore due to the anode plasma expansion in the diode load. This disagreement is used to estimate the plasma expansion speed.

Developing a Magnetic Resonance Imaging measurement of the forces within 3D granular materials under external loads

NASA Astrophysics Data System (ADS)

Elrington, Stefan; Bertrand, Thibault; Frey, Merideth; Shattuck, Mark; O'Hern, Corey; Barrett, Sean

2014-03-01

Granular materials are comprised of an ensemble of discrete macroscopic grains that interact with each other via highly dissipative forces. These materials are ubiquitous in our everyday life ranging in scale from the granular media that forms the Earth's crust to that used in agricultural and pharmaceutical industries. Granular materials exhibit complex behaviors that are poorly understood and cannot be easily described by statistical mechanics. Under external loads individual grains are jammed into place by a network of force chains. These networks have been imaged in quasi two-dimensional and on the outer surface of three-dimensional granular materials. Our goal is to use magnetic resonance imaging (MRI) to detect contact forces deep within three-dimensional granular materials, using hydrogen-1 relaxation times as a reporter for changes in local stress and strain. To this end, we use a novel pulse sequence to narrow the line width of hydrogen-1 in rubber. Here we present our progress to date, and prospects for future improvements.

[Clinical effect of three dimensional human body scanning system BurnCalc in the evaluation of burn wound area].

PubMed

Lu, J; Wang, L; Zhang, Y C; Tang, H T; Xia, Z F

2017-10-20

Objective: To validate the clinical effect of three dimensional human body scanning system BurnCalc developed by our research team in the evaluation of burn wound area. Methods: A total of 48 burn patients treated in the outpatient department of our unit from January to June 2015, conforming to the study criteria, were enrolled in. For the first 12 patients, one wound on the limbs or torso was selected from each patient. The stability of the system was tested by 3 attending physicians using three dimensional human body scanning system BurnCalc to measure the area of wounds individually. For the following 36 patients, one wound was selected from each patient, including 12 wounds on limbs, front torso, and side torso, respectively. The area of wounds was measured by the same attending physician using transparency tracing method, National Institutes of Health (NIH) Image J method, and three dimensional human body scanning system BurnCalc, respectively. The time for getting information of 36 wounds by three methods was recorded by stopwatch. The stability among the testers was evaluated by the intra-class correlation coefficient (ICC). Data were processed with randomized blocks analysis of variance and Bonferroni test. Results: (1) Wound area of patients measured by three physicians using three dimensional human body scanning system BurnCalc was (122±95), (121±95), and (123±96) cm(2,) respectively, and there was no statistically significant difference among them ( F =1.55, P >0.05). The ICC among 3 physicians was 0.999. (2) The wound area of limbs of patients measured by transparency tracing method, NIH Image J method, and three dimensional human body scanning system BurnCalc was (84±50), (76±46), and (84±49) cm(2,) respectively. There was no statistically significant difference in the wound area of limbs of patients measured by transparency tracing method and three dimensional human body scanning system BurnCalc ( P >0.05). The wound area of limbs of patients measured by NIH Image J method was smaller than that measured by transparency tracing method and three dimensional human body scanning system BurnCalc (with P values below 0.05). There was no statistically significant difference in the wound area of front torso of patients measured by transparency tracing method, NIH Image J method, and three dimensional human body scanning system BurnCalc ( F =0.33, P >0.05). The wound area of side torso of patients measured by transparency tracing method, NIH Image J method, and three dimensional human body scanning system BurnCalc was (169±88), (150±80), and (169±86) cm(2,) respectively. There was no statistically significant difference in the wound area of side torso of patients measured by transparency tracing method and three dimensional human body scanning system BurnCalc ( P >0.05). The wound area of side torso of patients measured by NIH Image J method was smaller than that measured by transparency tracing method and three dimensional human body scanning system BurnCalc (with P values below 0.05). (3) The time for getting information of wounds of patients by transparency tracing method, NIH Image J method, and three dimensional human body scanning system BurnCalc was (77±14), (10±3), and (9±3) s, respectively. The time for getting information of wounds of patients by transparency tracing method was longer than that by NIH Image J method and three dimensional human body scanning system BurnCalc (with P values below 0.05). The time for getting information of wounds of patients by three dimensional human body scanning system BurnCalc was close to that by NIH Image J method ( P >0.05). Conclusions: The three dimensional human body scanning system BurnCalc is stable and can accurately evaluate the wound area on limbs and torso of burn patients.

Application of Dynamic Analysis in Semi-Analytical Finite Element Method.

PubMed

Liu, Pengfei; Xing, Qinyan; Wang, Dawei; Oeser, Markus

2017-08-30

Analyses of dynamic responses are significantly important for the design, maintenance and rehabilitation of asphalt pavement. In order to evaluate the dynamic responses of asphalt pavement under moving loads, a specific computational program, SAFEM, was developed based on a semi-analytical finite element method. This method is three-dimensional and only requires a two-dimensional FE discretization by incorporating Fourier series in the third dimension. In this paper, the algorithm to apply the dynamic analysis to SAFEM was introduced in detail. Asphalt pavement models under moving loads were built in the SAFEM and commercial finite element software ABAQUS to verify the accuracy and efficiency of the SAFEM. The verification shows that the computational accuracy of SAFEM is high enough and its computational time is much shorter than ABAQUS. Moreover, experimental verification was carried out and the prediction derived from SAFEM is consistent with the measurement. Therefore, the SAFEM is feasible to reliably predict the dynamic response of asphalt pavement under moving loads, thus proving beneficial to road administration in assessing the pavement's state.

Strain Measurement System Developed for Biaxially Loaded Cruciform Specimens

NASA Technical Reports Server (NTRS)

Krause, David L.

2000-01-01

A new extensometer system developed at the NASA Glenn Research Center at Lewis Field measures test area strains along two orthogonal axes in flat cruciform specimens. This system incorporates standard axial contact extensometers to provide a cost-effective high-precision instrument. The device was validated for use by extensive testing of a stainless steel specimen, with specimen temperatures ranging from room temperature to 1100 F. In-plane loading conditions included several static biaxial load ratios, plus cyclic loadings of various waveform shapes, frequencies, magnitudes, and durations. The extensometer system measurements were compared with strain gauge data at room temperature and with calculated strain values for elevated-temperature measurements. All testing was performed in house in Glenn's Benchmark Test Facility in-plane biaxial load frame.

An analysis of cross-coupling of a multicomponent jet engine test stand using finite element modeling techniques

NASA Technical Reports Server (NTRS)

Schweikhard, W. G.; Singnoi, W. N.

1985-01-01

A two axis thrust measuring system was analyzed by using a finite a element computer program to determine the sensitivities of the thrust vectoring nozzle system to misalignment of the load cells and applied loads, and the stiffness of the structural members. Three models were evaluated: (1) the basic measuring element and its internal calibration load cells; (2) the basic measuring element and its external load calibration equipment; and (3) the basic measuring element, external calibration load frame and the altitude facility support structure. Alignment of calibration loads was the greatest source of error for multiaxis thrust measuring systems. Uniform increases or decreases in stiffness of the members, which might be caused by the selection of the materials, have little effect on the accuracy of the measurements. It is found that the POLO-FINITE program is a viable tool for designing and analyzing multiaxis thrust measurement systems. The response of the test stand to step inputs that might be encountered with thrust vectoring tests was determined. The dynamic analysis show a potential problem for measuring the dynamic response characteristics of thrust vectoring systems because of the inherently light damping of the test stand.

Lift, drag and thrust measurement in a hypersonic impulse facility

NASA Technical Reports Server (NTRS)

Tuttle, S. L.; Mee, D. J.; Simmons, J. M.

1995-01-01

This paper reports the extension of the stress wave force balance to the measurement of forces on models which are non-axisymmetric or which have non-axisymmetric load distributions. Recent results are presented which demonstrate the performance of the stress wave force balance for drag measurement, for three-component force measurement and preliminary results for thrust measurement on a two-dimensional scramjet nozzle. In all cases, the balances respond within a few hundred microseconds.

The actinic UV-radiation budget during the ESCOMPTE campaign 2001: results of airborne measurements with the microlight research aircraft D-MIFU

NASA Astrophysics Data System (ADS)

Junkermann, Wolfgang

2005-03-01

During the ESCOMPTE campaign 2001, the vertical distribution of ultraviolet actinic radiation was investigated with concurrent measurements of ozone, aerosol size distributions, and scattering coefficients using a microlight aircraft as airborne platform. Three-dimensional (3D) measurements were performed on a regional scale in the area between Avignon, Aix-en-Provence, and Marseille up to an altitude of 4000 m a.s.l. The results show a pronounced dependence of the vertical actinic flux distribution on aerosol load and stratification while horizontally no significant variability was observed. Furthermore, investigations under cloudy conditions and in the vicinity of cumulus clouds were performed allowing comparisons with one-dimensional and recently published three-dimensional model results. Cloud effects of scattered convective clouds were often found to be masked by aerosols and the aerosol content was generally the dominating factor controlling radiation transfer.

Behavior of the shape memory alloy NiTi during one-dimensional shock loading

NASA Astrophysics Data System (ADS)

Millett, J. C. F.; Bourne, N. K.; Gray, G. T., III

2002-09-01

The response of alloys based on the intermetallic compound NiTi to high-strain-rate and shock loading conditions has recently attracted attention. In particular, similarities between it, and other shape memory materials such as the alloy U-6%Nb in the propagation of the plastic wave in Taylor cylinders are of significant interest. In this article, the Hugoniot is measured using multiple manganin stress gauges, either embedded between plates of the NiTi alloy, or supported with blocks of polymethylmethacrylate. In this way, the shock stress, shock velocity, and details of the shock wave profile have been gathered. An inflection at lower stresses has been found in the Hugoniot curve (stress-particle velocity), and has been ascribed to the martensitic phase transformation that is characteristic of the shape memory effect in this alloy. In a similar way, the variation of shock velocity with particle velocity has been found to be nonlinear, contrary to other pure metal and alloy systems. Finally, a break in slope in the rising part of the shock profile has been identified as the Hugoniot elastic limit in NiTi. Conversion to the one-dimensional stress equivalent, and comparison to quasistatic data indicates that NiTi exhibits significant strain-rate sensitivity.

Mechanical and thermal buckling analysis of rectangular sandwich panels under different edge conditions

NASA Technical Reports Server (NTRS)

Ko, William L.

1994-01-01

The combined load (mechanical or thermal load) buckling equations were established for orthotropic rectangular sandwich panels under four different edge conditions by using the Rayleigh-Ritz method of minimizing the total potential energy of a structural system. Two-dimensional buckling interaction curves and three-dimensional buckling interaction surfaces were constructed for high-temperature honeycomb-core sandwich panels supported under four different edge conditions. The interaction surfaces provide overall comparison of the panel buckling strengths and the domains of symmetrical and antisymmetrical buckling associated with the different edge conditions. In addition, thermal buckling curves of these sandwich panels are presented. The thermal buckling conditions for the cases with and without thermal moments were found to be identical for the small deformation theory.

Development of basic theories and techniques for determining stresses in rotating turbine or compressor blades

NASA Technical Reports Server (NTRS)

Chien, C. H.; Swinson, W. F.; Turner, J. L.; Moslehy, F. A.; Ranson, W. F.

1980-01-01

A method for measuring in-plane displacement of a rotating structure by using two laser speckle photographs is described. From the displacement measurements one can calculate strains and stresses due to a centrifugal load. This technique involves making separate speckle photographs of a test model. One photograph is made with the model loaded (model is rotating); the second photograph is made with no load on the model (model is stationary). A sandwich is constructed from the two speckle photographs and data are recovered in a manner similar to that used with conventional speckle photography. The basic theory, experimental procedures of this method, and data analysis of a simple rotating specimen are described. In addition the measurement of in-plane surface displacement components of a deformed solid, and the application of the coupled laser speckle interferometry and boundary-integral solution technique to two dimensional elasticity problems are addressed.

Magnetic resonance imaging reveals functional anatomy and biomechanics of a living dragon tree

PubMed Central

Hesse, Linnea; Masselter, Tom; Leupold, Jochen; Spengler, Nils; Speck, Thomas; Korvink, Jan Gerrit

2016-01-01

Magnetic resonance imaging (MRI) was used to gain in vivo insight into load-induced displacements of inner plant tissues making a non-invasive and non-destructive stress and strain analysis possible. The central aim of this study was the identification of a possible load-adapted orientation of the vascular bundles and their fibre caps as the mechanically relevant tissue in branch-stem-attachments of Dracaena marginata. The complex three-dimensional deformations that occur during mechanical loading can be analysed on the basis of quasi-three-dimensional data representations of the outer surface, the inner tissue arrangement (meristem and vascular system), and the course of single vascular bundles within the branch-stem-attachment region. In addition, deformations of vascular bundles could be quantified manually and by using digital image correlation software. This combination of qualitative and quantitative stress and strain analysis leads to an improved understanding of the functional morphology and biomechanics of D. marginata, a plant that is used as a model organism for optimizing branched technical fibre-reinforced lightweight trusses in order to increase their load bearing capacity. PMID:27604526

Neck muscle load distribution in lateral, frontal, and rear-end impacts: a three-dimensional finite element analysis.

PubMed

Hedenstierna, Sofia; Halldin, Peter; Siegmund, Gunter P

2009-11-15

A finite element (FE) model of the human neck was used to study the distribution of neck muscle loads during multidirectional impacts. The computed load distributions were compared to experimental electromyography (EMG) recordings. To quantify passive muscle loads in nonactive cervical muscles during impacts of varying direction and energy, using a three-dimensional (3D) continuum FE muscle model. Experimental and numerical studies have confirmed the importance of muscles in the impact response of the neck. Although EMG has been used to measure the relative activity levels in neck muscles during impact tests, this technique has not been able to measure all neck muscles and cannot directly quantify the force distribution between the muscles. A numerical model can give additional insight into muscle loading during impact. An FE model with solid element musculature was used to simulate frontal, lateral, and rear-end vehicle impacts at 4 peak accelerations. The peak cross-sectional forces, internal energies, and effective strains were calculated for each muscle and impact configuration. The computed load distribution was compared with experimental EMG data. The load distribution in the cervical muscles varied with load direction. Peak sectional forces, internal energies, and strains increased in most muscles with increasing impact acceleration. The dominant muscles identified by the model for each direction were splenius capitis, levator scapulae, and sternocleidomastoid in lateral impacts, splenius capitis, and trapezoid in frontal impacts, and sternocleidomastoid, rectus capitis posterior minor, and hyoids in rear-end impacts. This corresponded with the most active muscles identified by EMG recordings, although within these muscles the distribution of forces and EMG levels were not the same. The passive muscle forces, strains, and energies computed using a continuum FE model of the cervical musculature distinguished between impact directions and peak accelerations, and on the basis of prior studies, isolated the most important muscles for each direction.

Development and validity of an instrumented handbike: initial results of propulsion kinetics.

PubMed

van Drongelen, Stefan; van den Berg, Jos; Arnet, Ursina; Veeger, Dirkjan H E J; van der Woude, Lucas H V

2011-11-01

To develop an instrumented handbike system to measure the forces applied to the handgrip during handbiking. A 6 degrees of freedom force sensor was built into the handgrip of an attach-unit handbike, together with two optical encoders to measure the orientation of the handgrip and crank in space. Linearity, precision, and percent error were determined for static and dynamic tests. High linearity was demonstrated for both the static and the dynamic condition (r=1.01). Precision was high under the static condition (standard deviation of 0.2N), however the precision decreased with higher loads during the dynamic condition. Percent error values were between 0.3 and 5.1%. This is the first instrumented handbike system that can register 3-dimensional forces. It can be concluded that the instrumented handbike system allows for an accurate force analysis based on forces registered at the handle bars. Copyright © 2011 IPEM. Published by Elsevier Ltd. All rights reserved.

Development of a standardized testing system for orthodontic sliding mechanics.

PubMed

Fathimani, Maryam; Melenka, Garrett W; Romanyk, Dan L; Toogood, Roger W; Heo, Giseon; Carey, Jason P; Major, Paul W

2015-01-01

The primary objective of this study was to develop a computer-controlled three-dimensional friction measuring system, the orthodontic friction simulator (OFS). A clinically-based in vitro experiment considering wet and dry friction for conventionally and self-ligated brackets is presented to elucidate debate surrounding sliding mechanics and illustrate capabilities of the OFS. The OFS was designed and manufactured using sound engineering principles and with the primary concern of being able to measure all forces and moments generated during sliding mechanics. This required the implementation of a six-axis load cell. A variety of translation and rotation stages were also incorporated to allow for precise positioning of the bracket relative to the archwire. Once designed and built, the OFS was then used to compare conventional and self-ligation methods in both the wet and dry state. Damon Q brackets and 0.018″ × 0.025″ stainless steel wires were used for all tests with a sample size of n = 65 for each ligation method. Archwires were pulled at a speed of 0.1 mm/s in 11 increments of 0.1 mm. At each increment, the bracket would be rotated 0.5° resulting in a total archwire travel of 1.1 mm and a second-order bracket angle range of 0°-5°. A repeated measures ANOVA was conducted to determine if ligation method and/or addition of moisture effected resulting orthodontic loads. The developed equipment for studying orthodontic sliding mechanics was able to measure forces and moments in all three directions; a capability not previously realized in the literature. Additionally, it was found that passive ligation significantly reduced resistance to sliding, P ≤ 0.05, while the dry/wet state did not. The OFS certainly proved to be an adequate instrument for the scientific evaluation of orthodontic sliding mechanics. It is capable of measuring loads generated in all directions and is a fully automated apparatus allowing for simple and repeatable friction tests to be conducted. Furthermore, the addition of saliva was not found to significantly influence the loads generated during sliding mechanics regardless of ligation method.

Supercritical nonlinear parametric dynamics of Timoshenko microbeams

NASA Astrophysics Data System (ADS)

Farokhi, Hamed; Ghayesh, Mergen H.

2018-06-01

The nonlinear supercritical parametric dynamics of a Timoshenko microbeam subject to an axial harmonic excitation force is examined theoretically, by means of different numerical techniques, and employing a high-dimensional analysis. The time-variant axial load is assumed to consist of a mean value along with harmonic fluctuations. In terms of modelling, a continuous expression for the elastic potential energy of the system is developed based on the modified couple stress theory, taking into account small-size effects; the kinetic energy of the system is also modelled as a continuous function of the displacement field. Hamilton's principle is employed to balance the energies and to obtain the continuous model of the system. Employing the Galerkin scheme along with an assumed-mode technique, the energy terms are reduced, yielding a second-order reduced-order model with finite number of degrees of freedom. A transformation is carried out to convert the second-order reduced-order model into a double-dimensional first order one. A bifurcation analysis is performed for the system in the absence of the axial load fluctuations. Moreover, a mean value for the axial load is selected in the supercritical range, and the principal parametric resonant response, due to the time-variant component of the axial load, is obtained - as opposed to transversely excited systems, for parametrically excited system (such as our problem here), the nonlinear resonance occurs in the vicinity of twice any natural frequency of the linear system; this is accomplished via use of the pseudo-arclength continuation technique, a direct time integration, an eigenvalue analysis, and the Floquet theory for stability. The natural frequencies of the system prior to and beyond buckling are also determined. Moreover, the effect of different system parameters on the nonlinear supercritical parametric dynamics of the system is analysed, with special consideration to the effect of the length-scale parameter.

Biomechanical comparison of anterior cervical plating and combined anterior/lateral mass plating.

PubMed

Adams, M S; Crawford, N R; Chamberlain, R H; Bse; Sonntag, V K; Dickman, C A

2001-01-01

Previous studies showed anterior plates of older design to be inadequate for stabilizing the cervical spine in all loading directions. No studies have investigated enhancement in stability obtained by combining anterior and posterior plates. To determine which modes of loading are stabilized by anterior plating after a cervical burst fracture and to determine whether adding posterior plating further significantly stabilizes the construct. A repeated-measures in vitro biomechanical flexibility experiment was performed to investigate how surgical destabilization and subsequent addition of hardware components alter spinal stability. Six human cadaveric specimens were studied. Angular range of motion (ROM) and neutral zone (NZ) were quantified during flexion, extension, lateral bending, and axial rotation. Nonconstraining, nondestructive torques were applied while recording three-dimensional motion optoelectronically. Specimens were tested intact, destabilized by simulated burst fracture with posterior distraction, plated anteriorly with a unicortical locking system, and plated with a combined anterior/posterior construct. The anterior plate significantly (p<.05) reduced the ROM relative to normal in all modes of loading and significantly reduced the NZ in flexion and extension. Addition of the posterior plates further significantly reduced the ROM in all modes of loading and reduced the NZ in lateral bending. Anterior plating systems are capable of substantially stabilizing the cervical spine in all modes of loading after a burst fracture. The combined approach adds significant stability over anterior plating alone in treating this injury but may be unnecessary clinically. Further study is needed to assess the added clinical benefits of the combined approach and associated risks.

Dynamic cone penetration tests in granular media: Determination of the tip's dynamic load-penetration curve

NASA Astrophysics Data System (ADS)

Escobar, E.; Benz, M.; Gourvès, R.; Breul, P.

2013-06-01

In this article a two-dimensional discrete numerical model, realized in PFC2D, is presented. This model is used in the dynamic penetration tests in a granular medium. Its objective being the validation of the measurement technique offered by Panda 3® (Benz et al. 2011) which is designed to calculate the tip's load-penetration curve for each impact in the soil where different parameters are used. To do so, we have compared the results obtained by calculation during the impacts to those measured directly in the model of a penetrometer through the installation of the gauges at the cone.

Structural weights analysis of advanced aerospace vehicles using finite element analysis

NASA Technical Reports Server (NTRS)

Bush, Lance B.; Lentz, Christopher A.; Rehder, John J.; Naftel, J. Chris; Cerro, Jeffrey A.

1989-01-01

A conceptual/preliminary level structural design system has been developed for structural integrity analysis and weight estimation of advanced space transportation vehicles. The system includes a three-dimensional interactive geometry modeler, a finite element pre- and post-processor, a finite element analyzer, and a structural sizing program. Inputs to the system include the geometry, surface temperature, material constants, construction methods, and aerodynamic and inertial loads. The results are a sized vehicle structure capable of withstanding the static loads incurred during assembly, transportation, operations, and missions, and a corresponding structural weight. An analysis of the Space Shuttle external tank is included in this paper as a validation and benchmark case of the system.

Physics based model for online fault detection in autonomous cryogenic loading system

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

Kashani, Ali; Ponizhovskaya, Ekaterina; Luchinsky, Dmitry

2014-01-29

We report the progress in the development of the chilldown model for a rapid cryogenic loading system developed at NASA-Kennedy Space Center. The nontrivial characteristic feature of the analyzed chilldown regime is its active control by dump valves. The two-phase flow model of the chilldown is approximated as one-dimensional homogeneous fluid flow with no slip condition for the interphase velocity. The model is built using commercial SINDA/FLUINT software. The results of numerical predictions are in good agreement with the experimental time traces. The obtained results pave the way to the application of the SINDA/FLUINT model as a verification tool formore » the design and algorithm development required for autonomous loading operation.« less

A Fast Proceduere for Optimizing Thermal Protection Systems of Re-Entry Vehicles

NASA Astrophysics Data System (ADS)

Ferraiuolo, M.; Riccio, A.; Tescione, D.; Gigliotti, M.

The aim of the present work is to introduce a fast procedure to optimize thermal protection systems for re-entry vehicles subjected to high thermal loads. A simplified one-dimensional optimization process, performed in order to find the optimum design variables (lengths, sections etc.), is the first step of the proposed design procedure. Simultaneously, the most suitable materials able to sustain high temperatures and meeting the weight requirements are selected and positioned within the design layout. In this stage of the design procedure, simplified (generalized plane strain) FEM models are used when boundary and geometrical conditions allow the reduction of the degrees of freedom. Those simplified local FEM models can be useful because they are time-saving and very simple to build; they are essentially one dimensional and can be used for optimization processes in order to determine the optimum configuration with regard to weight, temperature and stresses. A triple-layer and a double-layer body, subjected to the same aero-thermal loads, have been optimized to minimize the overall weight. Full two and three-dimensional analyses are performed in order to validate those simplified models. Thermal-structural analyses and optimizations are executed by adopting the Ansys FEM code.

The design and validation of a magnetic resonance imaging-compatible device for obtaining mechanical properties of plantar soft tissue via gated acquisition.

PubMed

Williams, Evan D; Stebbins, Michael J; Cavanagh, Peter R; Haynor, David R; Chu, Baocheng; Fassbind, Michael J; Isvilanonda, Vara; Ledoux, William R

2015-10-01

Changes in the mechanical properties of the plantar soft tissue in people with diabetes may contribute to the formation of plantar ulcers. Such ulcers have been shown to be in the causal pathway for lower extremity amputation. The hydraulic plantar soft tissue reducer (HyPSTER) was designed to measure in vivo, rate-dependent plantar soft tissue compressive force and three-dimensional deformations to help understand, predict, and prevent ulcer formation. These patient-specific values can then be used in an inverse finite element analysis to determine tissue moduli, and subsequently used in a foot model to show regions of high stress under a wide variety of loading conditions. The HyPSTER uses an actuator to drive a magnetic resonance imaging-compatible hydraulic loading platform. Pressure and actuator position were synchronized with gated magnetic resonance imaging acquisition. Achievable loading rates were slower than those found in normal walking because of a water-hammer effect (pressure wave ringing) in the hydraulic system when the actuator direction was changed rapidly. The subsequent verification tests were, therefore, performed at 0.2 Hz. The unloaded displacement accuracy of the system was within 0.31%. Compliance, presumably in the system's plastic components, caused a displacement loss of 5.7 mm during a 20-mm actuator test at 1354 N. This was accounted for with a target to actual calibration curve. The positional accuracy of the HyPSTER during loaded displacement verification tests from 3 to 9 mm against a silicone backstop was 95.9% with a precision of 98.7%. The HyPSTER generated minimal artifact in the magnetic resonance imaging scanner. Careful analysis of the synchronization of the HyPSTER and the magnetic resonance imaging scanner was performed. With some limitations, the HyPSTER provided key functionality in measuring dynamic, patient-specific plantar soft tissue mechanical properties. © IMechE 2015.

Three-Dimensional Nonlinear Finite Element Analysis and Microcomputed Tomography Evaluation of Microgap Formation in a Dental Implant Under Oblique Loading.

PubMed

Jörn, Daniela; Kohorst, Philipp; Besdo, Silke; Borchers, Lothar; Stiesch, Meike

2016-01-01

Since bacterial leakage along the implant-abutment interface may be responsible for peri-implant infections, a realistic estimation of the interface gap width during function is important for risk assessment. The purpose of this study was to compare two methods for investigating microgap formation in a loaded dental implant, namely, microcomputed tomography (micro-CT) and three-dimensional (3D) nonlinear finite element analysis (FEA); additionally, stresses to be expected during loading were also evaluated by FEA. An implant-abutment complex was inspected for microgaps between the abutment and implant in a micro-CT scanner under an oblique load of 200 N. A numerical model of the situation was constructed; boundary conditions and external load were defined according to the experiment. The model was refined stepwise until its load-displacement behavior corresponded sufficiently to data from previous load experiments. FEA of the final, validated model was used to determine microgap widths. These were compared with the widths as measured in micro-CT inspection. Finally, stress distributions were evaluated in selected regions. No microgaps wider than 13 μm could be detected by micro-CT for the loaded implant. FEA revealed gap widths up to 10 μm between the implant and abutment at the side of load application. Furthermore, FEA predicted plastic deformation in a limited area at the implant collar. FEA proved to be an adequate method for studying microgap formation in dental implant-abutment complexes. FEA is not limited in gap width resolution as are radiologic techniques and can also provide insight into stress distributions within the loaded complex.

Scalable loading of a two-dimensional trapped-ion array

PubMed Central

Bruzewicz, Colin D.; McConnell, Robert; Chiaverini, John; Sage, Jeremy M.

2016-01-01

Two-dimensional arrays of trapped-ion qubits are attractive platforms for scalable quantum information processing. Sufficiently rapid reloading capable of sustaining a large array, however, remains a significant challenge. Here with the use of a continuous flux of pre-cooled neutral atoms from a remotely located source, we achieve fast loading of a single ion per site while maintaining long trap lifetimes and without disturbing the coherence of an ion quantum bit in an adjacent site. This demonstration satisfies all major criteria necessary for loading and reloading extensive two-dimensional arrays, as will be required for large-scale quantum information processing. Moreover, the already high loading rate can be increased by loading ions in parallel with only a concomitant increase in photo-ionization laser power and no need for additional atomic flux. PMID:27677357

Bearing-Load Modeling and Analysis Study for Mechanically Connected Structures

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.

2006-01-01

Bearing-load response for a pin-loaded hole is studied within the context of two-dimensional finite element analyses. Pin-loaded-hole configurations are representative of mechanically connected structures, such as a stiffener fastened to a rib of an isogrid panel, that are idealized as part of a larger structural component. Within this context, the larger structural component may be idealized as a two-dimensional shell finite element model to identify load paths and high stress regions. Finite element modeling and analysis aspects of a pin-loaded hole are considered in the present paper including the use of linear and nonlinear springs to simulate the pin-bearing contact condition. Simulating pin-connected structures within a two-dimensional finite element analysis model using nonlinear spring or gap elements provides an effective way for accurate prediction of the local effective stress state and peak forces.

Static stability of a three-dimensional space truss. M.S. Thesis - Case Western Reserve Univ., 1994

NASA Technical Reports Server (NTRS)

Shaker, John F.

1995-01-01

In order to deploy large flexible space structures it is necessary to develop support systems that are strong and lightweight. The most recent example of this aerospace design need is vividly evident in the space station solar array assembly. In order to accommodate both weight limitations and strength performance criteria, ABLE Engineering has developed the Folding Articulating Square Truss (FASTMast) support structure. The FASTMast is a space truss/mechanism hybrid that can provide system support while adhering to stringent packaging demands. However, due to its slender nature and anticipated loading, stability characterization is a critical part of the design process. Furthermore, the dire consequences surely to result from a catastrophic instability quickly provide the motivation for careful examination of this problem. The fundamental components of the space station solar array system are the (1) solar array blanket system, (2) FASTMast support structure, and (3) mast canister assembly. The FASTMast once fully deployed from the canister will provide support to the solar array blankets. A unique feature of this structure is that the system responds linearly within a certain range of operating loads and nonlinearly when that range is exceeded. The source of nonlinear behavior in this case is due to a changing stiffness state resulting from an inability of diagonal members to resist applied loads. The principal objective of this study was to establish the failure modes involving instability of the FASTMast structure. Also of great interest during this effort was to establish a reliable analytical approach capable of effectively predicting critical values at which the mast becomes unstable. Due to the dual nature of structural response inherent to this problem, both linear and nonlinear analyses are required to characterize the mast in terms of stability. The approach employed herein is one that can be considered systematic in nature. The analysis begins with one and two-dimensional failure models of the system and its important components. From knowledge gained through preliminary analyses a foundation is developed for three-dimensional analyses of the FASTMast structure. The three-dimensional finite element (FE) analysis presented here involves a FASTMast system one-tenth the size of the actual flight unit. Although this study does not yield failure analysis results that apply directly to the flight article, it does establish a method by which the full-scale mast can be evaluated.

Static stability of a three-dimensional space truss

NASA Astrophysics Data System (ADS)

Shaker, John F.

1995-05-01

In order to deploy large flexible space structures it is necessary to develop support systems that are strong and lightweight. The most recent example of this aerospace design need is vividly evident in the space station solar array assembly. In order to accommodate both weight limitations and strength performance criteria, ABLE Engineering has developed the Folding Articulating Square Truss (FASTMast) support structure. The FASTMast is a space truss/mechanism hybrid that can provide system support while adhering to stringent packaging demands. However, due to its slender nature and anticipated loading, stability characterization is a critical part of the design process. Furthermore, the dire consequences surely to result from a catastrophic instability quickly provide the motivation for careful examination of this problem. The fundamental components of the space station solar array system are the (1) solar array blanket system, (2) FASTMast support structure, and (3) mast canister assembly. The FASTMast once fully deployed from the canister will provide support to the solar array blankets. A unique feature of this structure is that the system responds linearly within a certain range of operating loads and nonlinearly when that range is exceeded. The source of nonlinear behavior in this case is due to a changing stiffness state resulting from an inability of diagonal members to resist applied loads. The principal objective of this study was to establish the failure modes involving instability of the FASTMast structure. Also of great interest during this effort was to establish a reliable analytical approach capable of effectively predicting critical values at which the mast becomes unstable. Due to the dual nature of structural response inherent to this problem, both linear and nonlinear analyses are required to characterize the mast in terms of stability. The approach employed herein is one that can be considered systematic in nature. The analysis begins with one and two-dimensional failure models of the system and its important components. From knowledge gained through preliminary analyses a foundation is developed for three-dimensional analyses of the FASTMast structure. The three-dimensional finite element (FE) analysis presented here involves a FASTMast system one-tenth the size of the actual flight unit. Although this study does not yield failure analysis results that apply directly to the flight article, it does establish a method by which the full-scale mast can be evaluated.

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

Koh, J. H.; Robertson, A.; Jonkman, J.

Need to modify simulated system behavior to the measured data, but the tower wind loads improved the comparison for nonoperating conditions. the SWAY system in both turbine operating and nonoperating conditions. Mixed results were observed when comparing the simulated system behavior to the measured data, but the tower wind loads improved the comparison for nonoperating conditions. without the new tower-load capability to examine its influence on the response characteristics of the system. This is important in situations when the turbine is parked in survival conditions. The simulation results were then compared to measured data from the SWAY system in bothmore » turbine operating and nonoperating conditions. Mixed results were observed when comparing the simulated system behavior to the measured data, but the tower wind loads improved the comparison for nonoperating conditions.« less

Dynamics of Individual cilia to external loading- A simple one dimensional picture

NASA Astrophysics Data System (ADS)

Swaminathan, Vinay; Hill, David; Superfine, R.

2008-10-01

From being called the cellular janitors to swinging debauchers, cilia have captured the fascinations of researchers for over 200 years. In cystic fibrosis and chronic obstructive pulmonary disease where the cilia loses it's function, the protective mucus layer in the lung thickens and mucociliary clearance breaks down, leading to inflammation along the airways and an increased rate of infection. The mechanistic understanding of mucus clearance depends on a quantitative assessment of the axoneme dynamics and the maximum force the cilia are capable of generating and imparting to the mucus layer. Similar to the situation in molecular motors, detailed quantitative measurements of dynamics under applied load conditions are expected to be essential in developing predictive models. Based on our measurements of the dynamics of individual ciliary motion in the human bronchial epithelial cell under the application of an applied load, we present a simple one dimensional model for the axoneme dynamics and quantify the axoneme stiffness, the internal force generated by the axoneme, the stall force and show how the dynamics sheds insight on the time dependence of the internal force generation. The internal force generated by the axoneme is related to the ability of cilia to propel fluids and to their potential role in force sensing.

Combined Loadings and Cross-Dimensional Loadings Timeliness of Presentation of Financial Statements of Local Government

NASA Astrophysics Data System (ADS)

Muda, I.; Dharsuky, A.; Siregar, H. S.; Sadalia, I.

2017-03-01

This study examines the pattern of readiness dimensional accuracy of financial statements of local government in North Sumatra with a routine pattern of two (2) months after the fiscal year ends and patterns of at least 3 (three) months after the fiscal year ends. This type of research is explanatory survey with quantitative methods. The population and the sample used is of local government officials serving local government financial reports. Combined Analysis And Cross-Loadings Loadings are used with statistical tools WarpPLS. The results showed that there was a pattern that varies above dimensional accuracy of the financial statements of local government in North Sumatra.

Effect of impeded medial longitudinal arch drop on vertical ground reaction force and center of pressure during static loading.

PubMed

Chen, Shing-Jye; Gielo-Perczak, Krystyna

2011-01-01

Arch supports commonly used to alleviate foot pain can impede the normal drop of medial longitudinal arch (MLA) thereby altering its function. The purpose of the study was to examine the effect of using arch supports on vertical ground reaction force (GRF) and center of pressure (COP) during simulated midstance while the foot was statically loaded. Ten healthy young subjects were recruited. Two dimensional (2D) analysis of the MLA was captured for both barefoot (BF) and arch support conditions before and after loading via a custom made weight loading apparatus. The foot was loaded and positioned to simulate the midstance phase of walking. Two-dimensional reflective markers demarcated the MLA and captured with the loaded foot on a force platform. The impeded MLA drop was compared between the unloaded BF, loaded BF and loaded arch support conditions. The vertical GRF, the anterior-posterior and the medial-lateral COP displacements were also measured in response to the impeded MLA by the arch supports. The arch supports impeded the MLA drop (p<0.05) and shifted the COP toward the medial side (p<0.05), specifically for the rearfoot (calcaneal segment region), but no changes were determined for the vertical GRF (p>0.05). The impedance of MLA drop by the arch support altered the pattern of the ML COP shift in the rearfoot region. The use of arch supports may not relieve painful foot conditions that are associated with excessive calcaneal eversion indicated by altering COP shifts in localized foot regions.

Simulating Fatigue Crack Growth in Spiral Bevel Gears

NASA Technical Reports Server (NTRS)

Spievak, Lisa E.; Wawrzynek, Paul A.; Ingraffea, Anthony R.

2000-01-01

The majority of helicopter transmission systems utilize spiral bevel gears to convert the horizontal power from the engine into vertical power for the rotor. Due to the cyclical loading on a gear's tooth, fatigue crack propagation can occur. In rotorcraft applications, a crack's trajectory determines whether the gear failure will be benign or catastrophic for the aircraft. As a result, the capability to predict crack growth in gears is significant. A spiral bevel gear's complex shape requires a three dimensional model of the geometry and cracks. The boundary element method in conjunction with linear elastic fracture mechanics theories is used to predict arbitrarily shaped three dimensional fatigue crack trajectories in a spiral bevel pinion under moving load conditions. The predictions are validated by comparison to experimental results. The sensitivity of the predictions to variations in loading conditions and crack growth rate model parameters is explored. Critical areas that must be understood in greater detail prior to predicting more accurate crack trajectories and crack growth rates in three dimensions are identified.

Mechanical and thermal buckling analysis of sandwich panels under different edge conditions

NASA Technical Reports Server (NTRS)

Ko, William L.

1993-01-01

By using the Rayleigh-Ritz method of minimizing the total potential energy of a structural system, combined load (mechanical or thermal load) buckling equations are established for orthotropic rectangular sandwich panels supported under four different edge conditions. Two-dimensional buckling interaction curves and three dimensional buckling interaction surfaces are constructed for high-temperature honeycomb-core sandwich panels supported under four different edge conditions. The interaction surfaces provide easy comparison of the panel buckling strengths and the domains of symmetrical and antisymmetrical buckling associated with the different edge conditions. Thermal buckling curves of the sandwich panels also are presented. The thermal buckling conditions for the cases with and without thermal moments were found to be identical for the small deformation theory. In sandwich panels, the effect of transverse shear is quite large, and by neglecting the transverse shear effect, the buckling loads could be overpredicted considerably. Clamping of the edges could greatly increase buckling strength more in compression than in shear.

Phase-sensitive two-dimensional neutron shearing interferometer and Hartmann sensor

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

Baker, Kevin

2015-12-08

A neutron imaging system detects both the phase shift and absorption of neutrons passing through an object. The neutron imaging system is based on either of two different neutron wavefront sensor techniques: 2-D shearing interferometry and Hartmann wavefront sensing. Both approaches measure an entire two-dimensional neutron complex field, including its amplitude and phase. Each measures the full-field, two-dimensional phase gradients and, concomitantly, the two-dimensional amplitude mapping, requiring only a single measurement.

Three-dimensional boron particle loaded thermal neutron detector

DOEpatents

Nikolic, Rebecca J.; Conway, Adam M.; Graff, Robert T.; Kuntz, Joshua D.; Reinhardt, Catherine; Voss, Lars F.; Cheung, Chin Li; Heineck, Daniel

2014-09-09

Three-dimensional boron particle loaded thermal neutron detectors utilize neutron sensitive conversion materials in the form of nano-powders and micro-sized particles, as opposed to thin films, suspensions, paraffin, etc. More specifically, methods to infiltrate, intersperse and embed the neutron nano-powders to form two-dimensional and/or three-dimensional charge sensitive platforms are specified. The use of nano-powders enables conformal contact with the entire charge-collecting structure regardless of its shape or configuration.

A prediction model for lift-fan simulator performance. M.S. Thesis - Cleveland State Univ.

NASA Technical Reports Server (NTRS)

Yuska, J. A.

1972-01-01

The performance characteristics of a model VTOL lift-fan simulator installed in a two-dimensional wing are presented. The lift-fan simulator consisted of a 15-inch diameter fan driven by a turbine contained in the fan hub. The performance of the lift-fan simulator was measured in two ways: (1) the calculated momentum thrust of the fan and turbine (total thrust loading), and (2) the axial-force measured on a load cell force balance (axial-force loading). Tests were conducted over a wide range of crossflow velocities, corrected tip speeds, and wing angle of attack. A prediction modeling technique was developed to help in analyzing the performance characteristics of lift-fan simulators. A multiple linear regression analysis technique is presented which calculates prediction model equations for the dependent variables.

Global surface pressure measurements of static and dynamic stall on a wind turbine airfoil at low Reynolds number

NASA Astrophysics Data System (ADS)

Disotell, Kevin J.; Nikoueeyan, Pourya; Naughton, Jonathan W.; Gregory, James W.

2016-05-01

Recognizing the need for global surface measurement techniques to characterize the time-varying, three-dimensional loading encountered on rotating wind turbine blades, fast-responding pressure-sensitive paint (PSP) has been evaluated for resolving unsteady aerodynamic effects in incompressible flow. Results of a study aimed at demonstrating the laser-based, single-shot PSP technique on a low Reynolds number wind turbine airfoil in static and dynamic stall are reported. PSP was applied to the suction side of a Delft DU97-W-300 airfoil (maximum thickness-to-chord ratio of 30 %) at a chord Reynolds number of 225,000 in the University of Wyoming open-return wind tunnel. Static and dynamic stall behaviors are presented using instantaneous and phase-averaged global pressure maps. In particular, a three-dimensional pressure topology driven by a stall cell pattern is detected near the maximum lift condition on the steady airfoil. Trends in the PSP-measured pressure topology on the steady airfoil were confirmed using surface oil visualization. The dynamic stall case was characterized by a sinusoidal pitching motion with mean angle of 15.7°, amplitude of 11.2°, and reduced frequency of 0.106 based on semichord. PSP images were acquired at selected phase positions, capturing the breakdown of nominally two-dimensional flow near lift stall, development of post-stall suction near the trailing edge, and a highly three-dimensional topology as the flow reattaches. Structural patterns in the surface pressure topologies are considered from the analysis of the individual PSP snapshots, enabled by a laser-based excitation system that achieves sufficient signal-to-noise ratio in the single-shot images. The PSP results are found to be in general agreement with observations about the steady and unsteady stall characteristics expected for the airfoil.

Two-dimensional array of cold-electron bolometers for high-sensitivity polarization measurements

NASA Astrophysics Data System (ADS)

Kuzmin, L. S.

2012-01-01

A new concept of a two-dimensional array of cold-electron bolometers with distributed dipole antennas in the focal plane for high-sensitivity polarization measurements is proposed. The concept gives a unique combination of high polarization resolution due to a large uniforms array of cold-electron bolometers and optimal matching with junction field effect transistor (JFET) amplifiers because of flexibility in direct-current connections. The noise characteristics are improved due to arriving-signal power distribution among numerous cold-electron bolometers and an increase in their response. This should lead to a significant increase in the sensitivity and dynamic range compared with competing alternative bolometer technologies. The reliability of the twodimensional array significantly increases due to a series-parallel connection of a large number of cold-electron bolometers. High polarization resolution should be ensured due to uniform covering of a substrate by a two-dimensional array over a large area and the absence of the beam compression to small lumped elements. The fundamental sensitivity limit of the cold-electron bolometer array is smaller than photon noise which is considered to be the ultimate level restricted by the background radiation. Estimates of noise of bolometers with the JFET reading system show the possibility of realizing the ultimate sensitivity below the photon-noise level 5 ・10-17 W/Hz1/2 at a frequency of 350 GHz for an optical load with a power of 5 pW. These parameters correspond to the requirements to the receiving system of a BOOMERanG balloon telescope.

Development and verification of global/local analysis techniques for laminated composites

NASA Technical Reports Server (NTRS)

Thompson, Danniella Muheim; Griffin, O. Hayden, Jr.

1991-01-01

A two-dimensional to three-dimensional global/local finite element approach was developed, verified, and applied to a laminated composite plate of finite width and length containing a central circular hole. The resulting stress fields for axial compression loads were examined for several symmetric stacking sequences and hole sizes. Verification was based on comparison of the displacements and the stress fields with those accepted trends from previous free edge investigations and a complete three-dimensional finite element solution of the plate. The laminates in the compression study included symmetric cross-ply, angle-ply and quasi-isotropic stacking sequences. The entire plate was selected as the global model and analyzed with two-dimensional finite elements. Displacements along a region identified as the global/local interface were applied in a kinematically consistent fashion to independent three-dimensional local models. Local areas of interest in the plate included a portion of the straight free edge near the hole, and the immediate area around the hole. Interlaminar stress results obtained from the global/local analyses compares well with previously reported trends, and some new conclusions about interlaminar stress fields in plates with different laminate orientations and hole sizes are presented for compressive loading. The effectiveness of the global/local procedure in reducing the computational effort required to solve these problems is clearly demonstrated through examination of the computer time required to formulate and solve the linear, static system of equations which result for the global and local analyses to those required for a complete three-dimensional formulation for a cross-ply laminate. Specific processors used during the analyses are described in general terms. The application of this global/local technique is not limited software system, and was developed and described in as general a manner as possible.

Two-dimensional measures of accuracy in navigational systems

DOT National Transportation Integrated Search

1987-03-31

Two-dimensional measures generally used to depict the accuracy of radiolocation and navigation systems are described in the report. Application to the NAVSTAR Global Positioning System (GPS) is considered, with a number of geometric illustrations.

High-resolution velocimetry in energetic tidal currents using a convergent-beam acoustic Doppler profiler

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

Sellar, Brian; Harding, Samuel F.; Richmond, Marshall C.

An array of convergent acoustic Doppler velocimeters has been developed and tested for the high resolution measurement of three-dimensional tidal flow velocities in an energetic tidal site. This configuration has been developed to increase spatial resolution of velocity measurements in comparison to conventional acoustic Doppler profilers (ADPs) which characteristically use diverging acoustic beams emanating from a single instrument. This is achieved using converging acoustic beams with a sample volume at the focal point of 0.03 m 3. The array is also able to simultaneously measure three-dimensional velocity components in a profile throughout the water column, and as such is referredmore » to herein as a converging-beam acoustic Doppler profiler (CADP). Mid-depth profiling is achieved through integration of the sensor platform with the operational Alstom 1MW DeepGen-IV Tidal Turbine. This proof-of-concept paper outlines system configuration and comparison to measurements provided by co-installed reference instrumentation. Comparison of CADP to standard ADP velocity measurements reveals a mean difference of 8 mm/s, standard deviation of 18 mm/s, and order-of-magnitude reduction in realizable length-scale. CADP focal point measurements compared to a proximal single-beam reference show peak cross-correlation coefficient of 0.96 over 4.0 s averaging period and a 47% reduction in Doppler noise. The dual functionality of the CADP as a profiling instrument with a high resolution focal point make this configuration a unique and valuable advancement in underwater velocimetry enabling improved turbulence, resource and structural loading quantification and validation of numerical simulations. Alternative modes of operation have been implemented including noise-reducing bi-static sampling. Since waves are simultaneously measured it is expected that derivatives of this system will be a powerful tool in wave-current interaction studies.« less

Transient three-dimensional startup side load analysis of a regeneratively cooled nozzle

NASA Astrophysics Data System (ADS)

Wang, Ten-See

2009-07-01

The objective of this effort is to develop a computational methodology to capture the side load physics and to anchor the computed aerodynamic side loads with the available data by simulating the startup transient of a regeneratively cooled, high-aspect-ratio nozzle, hot-fired at sea level. The computational methodology is based on an unstructured-grid, pressure-based, reacting flow computational fluid dynamics and heat transfer formulation, and a transient inlet history based on an engine system simulation. Emphases were put on the effects of regenerative cooling on shock formation inside the nozzle, and ramp rate on side load reduction. The results show that three types of asymmetric shock physics incur strong side loads: the generation of combustion wave, shock transitions, and shock pulsations across the nozzle lip, albeit the combustion wave can be avoided with sparklers during hot-firing. Results from both regenerative cooled and adiabatic wall boundary conditions capture the early shock transitions with corresponding side loads matching the measured secondary side load. It is theorized that the first transition from free-shock separation to restricted-shock separation is caused by the Coanda effect. After which the regeneratively cooled wall enhances the Coanda effect such that the supersonic jet stays attached, while the hot adiabatic wall fights off the Coanda effect, and the supersonic jet becomes detached most of the time. As a result, the computed peak side load and dominant frequency due to shock pulsation across the nozzle lip associated with the regeneratively cooled wall boundary condition match those of the test, while those associated with the adiabatic wall boundary condition are much too low. Moreover, shorter ramp time results show that higher ramp rate has the potential in reducing the nozzle side loads.

Photovoltaic power converter system with a controller configured to actively compensate load harmonics

DOEpatents

de Rooij, Michael Andrew; Steigerwald, Robert Louis; Delgado, Eladio Clemente

2008-12-16

Photovoltaic power converter system including a controller configured to reduce load harmonics is provided. The system comprises a photovoltaic array and an inverter electrically coupled to the array to generate an output current for energizing a load connected to the inverter and to a mains grid supply voltage. The system further comprises a controller including a first circuit coupled to receive a load current to measure a harmonic current in the load current. The controller includes a second circuit to generate a fundamental reference drawn by the load. The controller further includes a third circuit for combining the measured harmonic current and the fundamental reference to generate a command output signal for generating the output current for energizing the load connected to the inverter. The photovoltaic system may be configured to compensate harmonic currents that may be drawn by the load.

Coherent Lidar Turbulence Measurement for Gust Load Alleviation

NASA Technical Reports Server (NTRS)

Bogue, Rodney K.; Ehernberger, L. J.; Soreide, David; Bagley, Hal

1996-01-01

Atmospheric turbulence adversely affects operation of commercial and military aircraft and is a design constraint. The airplane structure must be designed to survive the loads imposed by turbulence. Reducing these loads allows the airplane structure to be lighter, a substantial advantage for a commercial airplane. Gust alleviation systems based on accelerometers mounted in the airplane can reduce the maximum gust loads by a small fraction. These systems still represent an economic advantage. The ability to reduce the gust load increases tremendously if the turbulent gust can be measured before the airplane encounters it. A lidar system can make measurements of turbulent gusts ahead of the airplane, and the NASA Airborne Coherent Lidar for Advanced In-Flight Measurements (ACLAIM) program is developing such a lidar. The ACLAIM program is intended to develop a prototype lidar system for use in feasibility testing of gust load alleviation systems and other airborne lidar applications, to define applications of lidar with the potential for improving airplane performance, and to determine the feasibility and benefits of these applications. This paper gives an overview of the ACLAIM program, describes the lidar architecture for a gust alleviation system, and describes the prototype ACLAIM lidar system.

A two-dimensional analytical model for groundwater flow in a leaky aquifer extending finite distance under the estuary

NASA Astrophysics Data System (ADS)

Chuang, Mo-Hsiung; Hung, Chi-Tung; -Yen Lin, Wen; Ma, Kuo-chen

2017-04-01

In recent years, cities and industries in the vicinity of the estuarine region have developed rapidly, resulting in a sharp increase in the population concerned. The increasing demand for human activities, agriculture irrigation, and aquaculture relies on massive pumping of water in estuarine area. Since the 1950s, numerous studies have focused on the effects of tidal fluctuations on groundwater flow in the estuarine area. Tide-induced head fluctuation in a two-dimensional estuarine aquifer system is complicated and rather important in dealing with many groundwater management or remediation problems. The conceptual model of the aquifer system considered is multi-layered with estuarine bank and the leaky aquifer extend finite distance under the estuary. The solution of the model describing the groundwater head distribution in such an estuarine aquifer system and subject to the tidal fluctuation effects from estuarine river is developed based on the method of separation of variables along with river boundary. The solutions by Sun (Sun H. A two-dimensional analytical solution of groundwater response to tidal loading in an estuary, Water Resour. Res. 1997; 33:1429-35) as well as Tang and Jiao (Tang Z. and J. J. Jiao, A two-dimensional analytical solution for groundwater flow in a leaky confined aquifer system near open tidal water, Hydrological Processes, 2001; 15: 573-585) can be shown to be special cases of the present solution. On the basis of the analytical solution, the groundwater head distribution in response to estuarine boundary is examined and the influences of leakage, hydraulic parameters, and loading effect on the groundwater head fluctuation due to tide are investigated and discussed. KEYWORDS: analytical model, estuarine river, groundwater fluctuation, leaky aquifer.

Smith machine counterbalance system affects measures of maximal bench press throw performance.

PubMed

Vingren, Jakob L; Buddhadev, Harsh H; Hill, David W

2011-07-01

Equipment with counterbalance weight systems is commonly used for the assessment of performance in explosive resistance exercise movements, but it is not known if such systems affect performance measures. The purpose of this study was to determine the effect of using a counterbalance weight system on measures of smith machine bench press throw performance. Ten men and 14 women (mean ± SD: age, 25 ± 4 years; height, 173 ± 10 cm; weight, 77.7 ± 18.3 kg) completed maximal smith machine bench press throws under 4 different conditions (2 × 2; counterbalance × load): with or without a counterbalance weight system and using 'light' or 'moderate' net barbell loads. Performance variables (peak force, peak velocity, and peak power) were measured using a linear accelerometer attached to the barbell. The counterbalance weight system resulted in significant (p < 0.001) reductions in measures of peak force (mean difference ± standard error: light: -112 ± 20 N; moderate: -140 ± 23 N), peak velocity (light: -0.49 ± 0.10 m·s; moderate: -0.33 ± 0.07 m·s), and peak power (light: -220 ± 43 W; moderate: -143 ± 28 W) compared with no counterbalance system for both load conditions. Load condition did not affect absolute or percentage reductions from the counterbalance weight system for any variable. In conclusion, the use of a counterbalance weight system reduces accelerometer-based performance measures for the bench press throw exercise at light and moderate loads. This reduction in measures is likely because of an increase in the external resistance during the movement, which results in a discrepancy between the manually input and the actual value for external load. A counterbalance weight system should not be used when measuring performance in explosive resistance exercises with an accelerometer.

[On evaluating the robot-based experimental system for biomechanical experiment of human knee].

PubMed

Deng, Guoyong; Tian, Lianfang; Bai, Bo; Sun, Hui

2010-02-01

This is a report on how we use the hybrid force-displacement control method to load the human knee and analyze the effect and value of our robot experimental system through the biomechanical experiments of total meniscal resection of human knee. The whole robot control system can load continuously on the specimens, thus overcoming the shortcomings of the traditional loading methods which can only load discretely. In the meantime, by using the robot-based testing system, the force (torque) of the specimens and the spatial position under the force can be measured in real-time, which overcomes the shortcomings caused by the separation of force (torque) measurement from displacement measurement and so greatly improves the measurement accuracy.

Crack surface roughness in three-dimensional random fuse networks

NASA Astrophysics Data System (ADS)

Nukala, Phani Kumar V. V.; Zapperi, Stefano; Šimunović, Srđan

2006-08-01

Using large system sizes with extensive statistical sampling, we analyze the scaling properties of crack roughness and damage profiles in the three-dimensional random fuse model. The analysis of damage profiles indicates that damage accumulates in a diffusive manner up to the peak load, and localization sets in abruptly at the peak load, starting from a uniform damage landscape. The global crack width scales as Wtilde L0.5 and is consistent with the scaling of localization length ξ˜L0.5 used in the data collapse of damage profiles in the postpeak regime. This consistency between the global crack roughness exponent and the postpeak damage profile localization length supports the idea that the postpeak damage profile is predominantly due to the localization produced by the catastrophic failure, which at the same time results in the formation of the final crack. Finally, the crack width distributions can be collapsed for different system sizes and follow a log-normal distribution.

Three-dimensional nonlinear responses to impact loads on free-span pipeline: Torsional coupling and load steps

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

Chung, J.S.; Huttelmaier, H.P.; Cheng, B.R.

1995-12-31

For a heavy object falling on a free-span pipeline, this study assesses three-dimensional (3-D) pipe-span responses with the torsional ({theta}x-) coupling of a pipeline through the biaxial (y) bending responses. The static pipe-span equilibrium is achieved with its self-weight and buoyancy and the external torsional moment induced by the cross-flow (y-directional) current on the sagged pipe span. Load steps taken for 2 different sequences of applying static loads induced different pipe deformations, and the pipe twists in entirely different pattern. The two types of impact loads are applied in the vertical (z-) direction to excite the pipe span in itsmore » static equilibrium: (1) triangular impulse loading and (2) ramp loading. Boundary condition of the span supports is ``fixed-fixed`` at both ends in both displacement and rotation. 3-D coupled axial (x-), bending (y- and z-) and torsional ({theta}x-) responses, both state and dynamic, to the z-directional impact loadings, are modeled and analyzed by a nonlinear FEM method for a 16-in pipeline. The 3-D responses are compared with 2-D responses. The comparison shows significant torsional vibrations caused by the cross-flow current, especially for longer spans. The torsional ({theta}x-) coupling is very sensitive to the time-step size in achieving numerical stability and accuracy, particularly for the ramp loading and for a shorter span. For very large impact loads, the response frequencies differ from the fundamental frequencies of the span, exhibiting beatings and strong bending-to-axial and to-twist couplings. Also, the eigenvalues for the linear system are not necessarily the resonance frequencies for these nonlinear coupled responses.« less

Unsteady loads due to propulsive lift configurations. Part B: Pressure and velocity measurements in a three dimensional wall jet

NASA Technical Reports Server (NTRS)

Catalano, G. D.; Morton, J. B.; Humphris, R. R.

1978-01-01

The effects of increasing the velocity ratio, lambda sub j were explored. The quantities measured include the width of the mixing region, the mean velocity field, turbulent intensities and time scales. In addition, wall and static pressure velocity correlations and coherences are presented. The velocity measurements were made using a laser Doppler velocimeter with a phase locked loop processor. The fluctuating pressures were monitored using condenser type microphones.

Reactive-transport simulation of phosphorus in the sewage plume at the Massachusetts Military Reservation, Cape Cod, Massachusetts

USGS Publications Warehouse

Parkhurst, David L.; Stollenwerk, Kenneth G.; Colman, John A.

2003-01-01

The subsurface transport of phosphorus introduced by the disposal of treated sewage effluent to ground-infiltration disposal beds at the Massachusetts Military Reservation on western Cape Cod was simulated with a three-dimensional reactive-transport model. The simulations were used to estimate the load of phosphorus transported to Ashumet Pond during operation of the sewage-treatment plant?from 1936 to 1995?and for 60 years following cessation of sewage disposal. The model accounted for spatial and temporal changes in water discharge from the sewage-treatment plant, ground-water flow, transport of associated chemical constituents, and a set of chemical reactions, including phosphorus sorption on aquifer materials, dissolution and precipitation of iron- and manganese-oxyhydroxide and iron phosphate minerals, organic carbon sorption and decomposition, cation sorption, and irreversible denitrification. The flow and transport in the aquifer were simulated by using parameters consistent with those used in previous flow models of this area of Cape Cod, except that numerical dispersion was much larger than the physical dispersion estimated in previous studies. Sorption parameters were fit to data derived from phosphorus sorption and desorption laboratory column experiments. Rates of organic carbon decomposition were adjusted to match the location of iron concentrations in an anoxic iron zone within the sewage plume. The sensitivity of the simulated load of phosphorus transported to Ashumet Pond was calculated for a variety of processes and input parameters. Model limitations included large uncertainties associated with the loading of the sewage beds, the flow system, and the chemistry and sorption characteristics in the aquifer. The results of current model simulations indicate a small load of phosphorus transported to Ashumet Pond during 1965?85, but this small load was particularly sensitive to model parameters that specify flow conditions and the chemical process by which non-desorbable phosphorus is incorporated in the sediments. The uncertainties were large enough to make it difficult to determine whether loads of phosphorus transported to Ashumet Pond in the 1990s were greater or less than loads during the previous two decades. The model simulations indicate substantial discharge of phosphorus to Ashumet Pond after about 1965. After the period 2000?10 the simulations indicate that the load of phosphorus transported to Ashumet Pond decreases continuously, but the load of phosphorus remains substantial for many decades. The current simulations indicate a peak in phosphorus discharge to Ashumet Pond of about 1,000 kilograms per year during the 1990s; however, comparisons of simulated phosphorus concentrations with measured concentrations in 1993 indicate that the peak in phosphorus load transported to Ashumet Pond may be larger and moving more quickly in the model simulations than in the aquifer. The results of the three-dimensional reactive-transport simulations are consistent with the loading history, experimental laboratory data, and field measurements. The results of the simulations adequately reproduce the spatial distribution of phosphorus concentrations measured in 1993, the magnitude of changes in phosphorus concentration with time in a profile near the disposal beds following cessation of sewage disposal, the observed iron zone in the sewage plume, the approximate flow of treated sewage effluent into Ashumet Valley, and laboratory-column data for phosphorus sorption and desorption.

A multi scale multi-dimensional thermo electrochemical modelling of high capacity lithium-ion cells

NASA Astrophysics Data System (ADS)

Tourani, Abbas; White, Peter; Ivey, Paul

2014-06-01

Lithium iron phosphate (LFP) and lithium manganese oxide (LMO) are competitive and complementary to each other as cathode materials for lithium-ion batteries, especially for use in electric vehicles. A multi scale multi-dimensional physic-based model is proposed in this paper to study the thermal behaviour of the two lithium-ion chemistries. The model consists of two sub models, a one dimensional (1D) electrochemical sub model and a two dimensional (2D) thermo-electric sub model, which are coupled and solved concurrently. The 1D model predicts the heat generation rate (Qh) and voltage (V) of the battery cell through different load cycles. The 2D model of the battery cell accounts for temperature distribution and current distribution across the surface of the battery cell. The two cells are examined experimentally through 90 h load cycles including high/low charge/discharge rates. The experimental results are compared with the model results and they are in good agreement. The presented results in this paper verify the cells temperature behaviour at different operating conditions which will lead to the design of a cost effective thermal management system for the battery pack.

Three-dimensional fracture instability of a displacement-weakening planar interface under locally peaked nonuniform loading

NASA Astrophysics Data System (ADS)

Uenishi, Koji

2018-06-01

We consider stability of fracture on a three-dimensional planar interface subjected to a loading stress that is locally peaked spatially, the level of which increases quasi-statically in time. Similar to the earlier study on the two-dimensional case (Uenishi and Rice, 2003; Rice and Uenishi, 2010), as the loading stress increases, a crack, or a region of displacement discontinuity (opening gap in tension or slip for shear fracture), develops on the interface where the stress is presumed to decrease according to a displacement-weakening constitutive relation. Upon reaching the instability point at which no further quasi-static solution for the extension of the crack on the interface exists, dynamic fracture follows. For the investigation of this instability point, we employ a dimensional analysis as well as an energy approach that gives a Rayleigh-Ritz approximation for the dependence of crack size and maximum displacement discontinuity on the level and quadratic shape of the loading stress distribution. We show that, if the linear displacement-weakening law is applied and the crack may be assumed of an elliptical form, the critical crack size at instability is independent of the curvature of the loading stress distribution and it is of the same order for all two- and three-dimensional cases.

Methods of video and shearography inspection

NASA Technical Reports Server (NTRS)

Lansing, Matthew D.; Bullock, Michael W.; Gnacek, William J.

1995-01-01

The goal of this research effort was to study methods of video image correlation and electronic shearography for nondestructive evaluation of aerospace components. Methods of physical load application must be developed before interrogations with these methods may be used to qualify hardware. To that end, inspection procedures were developed for a variety of aerospace components and material systems. Experiments were also conducted from which the relationship between the control settings of the electronic shearography apparatus may be related to flaw detectability. A short feasibility study was conducted to determine the applicability of electronic shearography to the determination of the stress intensity factor of a Mode 1 crack tip by measurement of the localized zone of three dimensional plasticity

Damage assessment in a sandwich panel based on full-field vibration measurements

NASA Astrophysics Data System (ADS)

Seguel, F.; Meruane, V.

2018-03-01

Different studies have demonstrated that vibration characteristics are sensitive to debonding in composite structures. Nevertheless, one of the main restrictions of vibration measurements is the number of degrees of freedom that can be acquired simultaneously, which restricts the size of the damage that can be identified. Recent studies have shown that it is possible to use high-speed three-dimensional (3-D) digital image correlation (DIC) techniques for full-field vibration measurements. With this technique, it is possible to take measurements at thousands of points on the surface of a structure with a single snapshot. The present article investigates the application of full-field vibration measurements in the debonding assessment of an aluminium honeycomb sandwich panel. Experimental data from an aluminium honeycomb panel containing different damage scenarios is acquired by a high-speed 3-D DIC system; four methodologies to compute damage indices are evaluated: mode shape curvatures, uniform load surface, modal strain energy and gapped smoothing.

Application of Dynamic Analysis in Semi-Analytical Finite Element Method

PubMed Central

Oeser, Markus

2017-01-01

Analyses of dynamic responses are significantly important for the design, maintenance and rehabilitation of asphalt pavement. In order to evaluate the dynamic responses of asphalt pavement under moving loads, a specific computational program, SAFEM, was developed based on a semi-analytical finite element method. This method is three-dimensional and only requires a two-dimensional FE discretization by incorporating Fourier series in the third dimension. In this paper, the algorithm to apply the dynamic analysis to SAFEM was introduced in detail. Asphalt pavement models under moving loads were built in the SAFEM and commercial finite element software ABAQUS to verify the accuracy and efficiency of the SAFEM. The verification shows that the computational accuracy of SAFEM is high enough and its computational time is much shorter than ABAQUS. Moreover, experimental verification was carried out and the prediction derived from SAFEM is consistent with the measurement. Therefore, the SAFEM is feasible to reliably predict the dynamic response of asphalt pavement under moving loads, thus proving beneficial to road administration in assessing the pavement’s state. PMID:28867813

Tilted orthodontic micro implants: a photoelastic stress analysis.

PubMed

Çehreli, Seçil; Özçırpıcı, Ayça Arman; Yılmaz, Alev

2013-10-01

The aim of this study was to examine peri-implant stresses around orthodontic micro implants upon torque-tightening and static load application by quasi-three-dimensional photoelastic stress analysis. Self-tapping orthodontic micro implants were progressively inserted into photoelastic models at 30, 45, 70, and 90 degrees and insertion torques were measured. Stress patterns (isochromatic fringe orders) were recorded by the quasi-three-dimensional photoelastic method using a circular polariscope after insertion and 250 g static force application. Torque-tightening of implants generated peri-implant stresses. Upon insertion, 90 degree placed implants displayed the lowest and homogeneous stress distribution followed by 30, 70, and 45 degree tilted implants. Static loading did not dramatically alter stress fields around the implants tested. The highest alteration in stress distribution was observed for the 90 degree placed implant, while 70 degree tilted implant had the lowest stresses among tilted implants. Torque-tightening of orthodontic micro implants creates a stress field that is not dramatically altered after application of static lateral moderate orthodontic loads, particularly at the cervical region of tilted implants.

Evaluation of comprehensive multidimensional separations using reversed-phase, reversed-phase liquid chromatography/mass spectrometry for shotgun proteomics.

PubMed

Nakamura, Tatsuji; Kuromitsu, Junro; Oda, Yoshiya

2008-03-01

Two-dimensional liquid-chromatographic (LC) separation followed by mass spectrometric (MS) analysis was examined for the identification of peptides in complex mixtures as an alternative to widely used two-dimensional gel electrophoresis followed by MS analysis for use in proteomics. The present method involves the off-line coupling of a narrow-bore, polymer-based, reversed-phase column using an acetonitrile gradient in an alkaline mobile phase in the first dimension with octadecylsilanized silica (ODS)-based nano-LC/MS in the second dimension. After the first separation, successive fractions were acidified and dried off-line, then loaded on the second dimension column. Both columns separate peptides according to hydrophobicity under different pH conditions, but more peptides were identified than with the conventional technique for shotgun proteomics, that is, the combination of a strong cation exchange column with an ODS column, and the system was robust because no salts were included in the mobile phases. The suitability of the method for proteomics measurements was evaluated.

Shortcut loading a Bose–Einstein condensate into an optical lattice

NASA Astrophysics Data System (ADS)

Zhou, Xiaoji; Jin, Shengjie; Schmiedmayer, Jörg

2018-05-01

We present an effective and fast (few microseconds) procedure for transferring a Bose–Einstein condensate from the ground state in a harmonic trap into the desired bands of an optical lattice. Our shortcut method is a designed pulse sequence where the time duration and the interval in each step are fully optimized in order to maximize robustness and fidelity of the final state with respect to the target state. The atoms can be prepared in a single band with even or odd parity, and superposition states of different bands can be prepared and manipulated. Furthermore, we extend this idea to the case of two-dimensional or three-dimensional optical lattices where the energies of excited states are degenerate. We experimentally demonstrate various examples and show very good agreement with the theoretical model. Efficient shortcut methods will find applications in the preparation of quantum systems, in quantum information processing, in precise measurement and as a starting point to investigate dynamics in excited bands.

Stress Distribution in Single Dental Implant System: Three-Dimensional Finite Element Analysis Based on an In Vitro Experimental Model.

PubMed

Rezende, Carlos Eduardo Edwards; Chase-Diaz, Melody; Costa, Max Doria; Albarracin, Max Laurent; Paschoeto, Gabriela; Sousa, Edson Antonio Capello; Rubo, José Henrique; Borges, Ana Flávia Sanches

2015-10-01

This study aimed to analyze the stress distribution in single implant system and to evaluate the compatibility of an in vitro model with finite element (FE) model. The in vitro model consisted of Brånemark implant; multiunit set abutment of 5 mm height; metal-ceramic screw-retained crown, and polyurethane simulating the bone. Deformations were recorded in the peri-implant region in the mesial and distal aspects, after an axial 300 N load application at the center of the occlusal aspect of the crown, using strain gauges. This in vitro model was scanned with micro CT to design a three-dimensional FE model and the strains in the peri-implant bone region were registered to check the compatibility between both models. The FE model was used to evaluate stress distribution in different parts of the system. The values obtained from the in vitro model (20-587 με) and the finite element analysis (81-588 με) showed agreement among them. The highest stresses because of axial and oblique load, respectively were 5.83 and 40 MPa for the cortical bone, 55 and 1200 MPa for the implant, and 80 and 470 MPa for the abutment screw. The FE method proved to be effective for evaluating the deformation around single implant. Oblique loads lead to higher stress concentrations.

Advanced Software for Analysis of High-Speed Rolling-Element Bearings

NASA Technical Reports Server (NTRS)

Poplawski, J. V.; Rumbarger, J. H.; Peters, S. M.; Galatis, H.; Flower, R.

2003-01-01

COBRA-AHS is a package of advanced software for analysis of rigid or flexible shaft systems supported by rolling-element bearings operating at high speeds under complex mechanical and thermal loads. These loads can include centrifugal and thermal loads generated by motions of bearing components. COBRA-AHS offers several improvements over prior commercial bearing-analysis programs: It includes innovative probabilistic fatigue-life-estimating software that provides for computation of three-dimensional stress fields and incorporates stress-based (in contradistinction to prior load-based) mathematical models of fatigue life. It interacts automatically with the ANSYS finite-element code to generate finite-element models for estimating distributions of temperature and temperature-induced changes in dimensions in iterative thermal/dimensional analyses: thus, for example, it can be used to predict changes in clearances and thermal lockup. COBRA-AHS provides an improved graphical user interface that facilitates the iterative cycle of analysis and design by providing analysis results quickly in graphical form, enabling the user to control interactive runs without leaving the program environment, and facilitating transfer of plots and printed results for inclusion in design reports. Additional features include roller-edge stress prediction and influence of shaft and housing distortion on bearing performance.

Aeroelastic loads prediction for an arrow wing. Task 3: Evaluation of the Boeing three-dimensional leading-edge vortex code

NASA Technical Reports Server (NTRS)

Manro, M. E.

1983-01-01

Two separated flow computer programs and a semiempirical method for incorporating the experimentally measured separated flow effects into a linear aeroelastic analysis were evaluated. The three dimensional leading edge vortex (LEV) code is evaluated. This code is an improved panel method for three dimensional inviscid flow over a wing with leading edge vortex separation. The governing equations are the linear flow differential equation with nonlinear boundary conditions. The solution is iterative; the position as well as the strength of the vortex is determined. Cases for both full and partial span vortices were executed. The predicted pressures are good and adequately reflect changes in configuration.

Performance Estimation for Two-Dimensional Brownian Rotary Ratchet Systems

NASA Astrophysics Data System (ADS)

Tutu, Hiroki; Horita, Takehiko; Ouchi, Katsuya

2015-04-01

Within the context of the Brownian ratchet model, a molecular rotary system that can perform unidirectional rotations induced by linearly polarized ac fields and produce positive work under loads was studied. The model is based on the Langevin equation for a particle in a two-dimensional (2D) three-tooth ratchet potential of threefold symmetry. The performance of the system is characterized by the coercive torque, i.e., the strength of the load competing with the torque induced by the ac driving field, and the energy efficiency in force conversion from the driving field to the torque. We propose a master equation for coarse-grained states, which takes into account the boundary motion between states, and develop a kinetic description to estimate the mean angular momentum (MAM) and powers relevant to the energy balance equation. The framework of analysis incorporates several 2D characteristics and is applicable to a wide class of models of smooth 2D ratchet potential. We confirm that the obtained expressions for MAM, power, and efficiency of the model can enable us to predict qualitative behaviors. We also discuss the usefulness of the torque/power relationship for experimental analyses, and propose a characteristic for 2D ratchet systems.

Io's Plasma Environment During the Galileo Flyby: Global Three-Dimensional MHD Modeling with Adaptive Mesh Refinement

NASA Technical Reports Server (NTRS)

Combi, M. R.; Kabin, K.; Gombosi, T. I.; DeZeeuw, D. L.; Powell, K. G.

1998-01-01

The first results for applying a three-dimensional multimedia ideal MHD model for the mass-loaded flow of Jupiter's corotating magnetospheric plasma past Io are presented. The model is able to consider simultaneously physically realistic conditions for ion mass loading, ion-neutral drag, and intrinsic magnetic field in a full global calculation without imposing artificial dissipation. Io is modeled with an extended neutral atmosphere which loads the corotating plasma torus flow with mass, momentum, and energy. The governing equations are solved using adaptive mesh refinement on an unstructured Cartesian grid using an upwind scheme for AHMED. For the work described in this paper we explored a range of models without an intrinsic magnetic field for Io. We compare our results with particle and field measurements made during the December 7, 1995, flyby of to, as published by the Galileo Orbiter experiment teams. For two extreme cases of lower boundary conditions at Io, our model can quantitatively explain the variation of density along the spacecraft trajectory and can reproduce the general appearance of the variations of magnetic field and ion pressure and temperature. The net fresh ion mass-loading rates are in the range of approximately 300-650 kg/s, and equivalent charge exchange mass-loading rates are in the range approximately 540-1150 kg/s in the vicinity of Io.

Comparative Study of 3-Dimensional Woven Joint Architectures for Composite Spacecraft Structures

NASA Technical Reports Server (NTRS)

Jones, Justin S.; Polis, Daniel L.; Segal, Kenneth N.

2011-01-01

The National Aeronautics and Space Administration (NASA) Exploration Systems Mission Directorate initiated an Advanced Composite Technology (ACT) Project through the Exploration Technology Development Program in order to support the polymer composite needs for future heavy lift launch architectures. As an example, the large composite structural applications on Ares V inspired the evaluation of advanced joining technologies, specifically 3D woven composite joints, which could be applied to traditionally manufactured barrel segments. Implementation of these 3D woven joint technologies may offer enhancements in damage tolerance without sacrificing weight. However, baseline mechanical performance data is needed to properly analyze the joint stresses and subsequently design/down-select a preform architecture. Six different configurations were designed and prepared for this study; each consisting of a different combination of warp/fill fiber volume ratio and preform interlocking method (z-fiber, fully interlocked, or hybrid). Tensile testing was performed for this study with the enhancement of a dual camera Digital Image Correlation (DIC) system which provides the capability to measure full-field strains and three dimensional displacements of objects under load. As expected, the ratio of warp/fill fiber has a direct influence on strength and modulus, with higher values measured in the direction of higher fiber volume bias. When comparing the z-fiber weave to a fully interlocked weave with comparable fiber bias, the z-fiber weave demonstrated the best performance in two different comparisons. We report the measured tensile strengths and moduli for test coupons from the 6 different weave configurations under study.

Computational strategies for three-dimensional flow simulations on distributed computer systems

NASA Technical Reports Server (NTRS)

Sankar, Lakshmi N.; Weed, Richard A.

1995-01-01

This research effort is directed towards an examination of issues involved in porting large computational fluid dynamics codes in use within the industry to a distributed computing environment. This effort addresses strategies for implementing the distributed computing in a device independent fashion and load balancing. A flow solver called TEAM presently in use at Lockheed Aeronautical Systems Company was acquired to start this effort. The following tasks were completed: (1) The TEAM code was ported to a number of distributed computing platforms including a cluster of HP workstations located in the School of Aerospace Engineering at Georgia Tech; a cluster of DEC Alpha Workstations in the Graphics visualization lab located at Georgia Tech; a cluster of SGI workstations located at NASA Ames Research Center; and an IBM SP-2 system located at NASA ARC. (2) A number of communication strategies were implemented. Specifically, the manager-worker strategy and the worker-worker strategy were tested. (3) A variety of load balancing strategies were investigated. Specifically, the static load balancing, task queue balancing and the Crutchfield algorithm were coded and evaluated. (4) The classical explicit Runge-Kutta scheme in the TEAM solver was replaced with an LU implicit scheme. And (5) the implicit TEAM-PVM solver was extensively validated through studies of unsteady transonic flow over an F-5 wing, undergoing combined bending and torsional motion. These investigations are documented in extensive detail in the dissertation, 'Computational Strategies for Three-Dimensional Flow Simulations on Distributed Computing Systems', enclosed as an appendix.

Computational strategies for three-dimensional flow simulations on distributed computer systems

NASA Astrophysics Data System (ADS)

Sankar, Lakshmi N.; Weed, Richard A.

1995-08-01

This research effort is directed towards an examination of issues involved in porting large computational fluid dynamics codes in use within the industry to a distributed computing environment. This effort addresses strategies for implementing the distributed computing in a device independent fashion and load balancing. A flow solver called TEAM presently in use at Lockheed Aeronautical Systems Company was acquired to start this effort. The following tasks were completed: (1) The TEAM code was ported to a number of distributed computing platforms including a cluster of HP workstations located in the School of Aerospace Engineering at Georgia Tech; a cluster of DEC Alpha Workstations in the Graphics visualization lab located at Georgia Tech; a cluster of SGI workstations located at NASA Ames Research Center; and an IBM SP-2 system located at NASA ARC. (2) A number of communication strategies were implemented. Specifically, the manager-worker strategy and the worker-worker strategy were tested. (3) A variety of load balancing strategies were investigated. Specifically, the static load balancing, task queue balancing and the Crutchfield algorithm were coded and evaluated. (4) The classical explicit Runge-Kutta scheme in the TEAM solver was replaced with an LU implicit scheme. And (5) the implicit TEAM-PVM solver was extensively validated through studies of unsteady transonic flow over an F-5 wing, undergoing combined bending and torsional motion. These investigations are documented in extensive detail in the dissertation, 'Computational Strategies for Three-Dimensional Flow Simulations on Distributed Computing Systems', enclosed as an appendix.

Instrument for controlling the application of mechanical loads to biological and bicompatible test subjects

DOEpatents

Lintilhac, Phillip M.; Vesecky, Thompson B.

1995-01-01

Apparatus and methods are disclosed facilitating the application of forces and measurement of dimensions of a test subject. In one arrangement the test subject is coupled to a forcing frame and controlled forces applied thereto. Force applied to the test subject is measured and controlled. A dimensional characteristic of the test subject, such as growth, is measured by a linear variable differential transformer. The growth measurement data can be used to control the force applied. The transducer module receives force and dimensional data from the forcing frame. The transducer module is a separate, microprocessor-based unit that communicates the test data to a controller unit that controls the application of force to the test subject and receives the test data from the transducer module for force control, storage, and/or communication to the user.

Instrument for controlling the application of mechanical loads to biological and bicompatible test subjects

DOEpatents

Lintilhac, P.M.; Vesecky, T.B.

1995-09-19

An apparatus and methods are disclosed facilitating the application of forces and measurement of dimensions of a test subject. In one arrangement the test subject is coupled to a forcing frame and controlled forces applied thereto. Force applied to the test subject is measured and controlled. A dimensional characteristic of the test subject, such as growth, is measured by a linear variable differential transformer. The growth measurement data can be used to control the force applied. The transducer module receives force and dimensional data from the forcing frame. The transducer module is a separate, microprocessor-based unit that communicates the test data to a controller unit that controls the application of force to the test subject and receives the test data from the transducer module for force control, storage, and/or communication to the user. 8 figs.

A Generalized Hydrodynamic-Impact Theory for the Loads and Motions of Deeply Immersed Prismatic Bodies

NASA Technical Reports Server (NTRS)

Markey, Melvin F.

1959-01-01

A theory is derived for determining the loads and motions of a deeply immersed prismatic body. The method makes use of a two-dimensional water-mass variation and an aspect-ratio correction for three-dimensional flow. The equations of motion are generalized by using a mean value of the aspect-ratio correction and by assuming a variation of the two-dimensional water mass for the deeply immersed body. These equations lead to impact coefficients that depend on an approach parameter which, in turn, depends upon the initial trim and flight-path angles. Comparison of experiment with theory is shown at maximum load and maximum penetration for the flat-bottom (0 deg dead-rise angle) model with bean-loading coefficients from 36.5 to 133.7 over a wide range of initial conditions. A dead-rise angle correction is applied and maximum-load data are compared with theory for the case of a model with 300 dead-rise angle and beam-loading coefficients from 208 to 530.

NASTRAN computer system level 12.1

NASA Technical Reports Server (NTRS)

Butler, T. G.

1971-01-01

Program uses finite element displacement method for solving linear response of large, three-dimensional structures subject to static, dynamic, thermal, and random loadings. Program adapts to computers of different manufacture, permits up-dating and extention, allows interchange of output and input information between users, and is extensively documented.

Characterizing the uncertainty in holddown post load measurements

NASA Technical Reports Server (NTRS)

Richardson, J. A.; Townsend, J. S.

1993-01-01

In order to understand unexpectedly erratic load measurements in the launch-pad supports for the space shuttle, the sensitivities of the load cells in the supports were analyzed using simple probabilistic techniques. NASA engineers use the loads in the shuttle's supports to calculate critical stresses in the shuttle vehicle just before lift-off. The support loads are measured with 'load cells' which are actually structural components of the mobile launch platform which have been instrumented with strain gauges. Although these load cells adequately measure vertical loads, the horizontal load measurements have been erratic. The load measurements were simulated in this study using Monte Carlo simulation procedures. The simulation studies showed that the support loads are sensitive to small deviations in strain and calibration. In their current configuration, the load cells will not measure loads with sufficient accuracy to reliably calculate stresses in the shuttle vehicle. A simplified model of the holddown post (HDP) load measurement system was used to study the effect on load measurement accuracy for several factors, including load point deviations, gauge heights, and HDP geometry.

Large-area photogrammetry based testing of wind turbine blades

NASA Astrophysics Data System (ADS)

Poozesh, Peyman; Baqersad, Javad; Niezrecki, Christopher; Avitabile, Peter; Harvey, Eric; Yarala, Rahul

2017-03-01

An optically based sensing system that can measure the displacement and strain over essentially the entire area of a utility-scale blade leads to a measurement system that can significantly reduce the time and cost associated with traditional instrumentation. This paper evaluates the performance of conventional three dimensional digital image correlation (3D DIC) and three dimensional point tracking (3DPT) approaches over the surface of wind turbine blades and proposes a multi-camera measurement system using dynamic spatial data stitching. The potential advantages for the proposed approach include: (1) full-field measurement distributed over a very large area, (2) the elimination of time-consuming wiring and expensive sensors, and (3) the need for large-channel data acquisition systems. There are several challenges associated with extending the capability of a standard 3D DIC system to measure entire surface of utility scale blades to extract distributed strain, deflection, and modal parameters. This paper only tries to address some of the difficulties including: (1) assessing the accuracy of the 3D DIC system to measure full-field distributed strain and displacement over the large area, (2) understanding the geometrical constraints associated with a wind turbine testing facility (e.g. lighting, working distance, and speckle pattern size), (3) evaluating the performance of the dynamic stitching method to combine two different fields of view by extracting modal parameters from aligned point clouds, and (4) determining the feasibility of employing an output-only system identification to estimate modal parameters of a utility scale wind turbine blade from optically measured data. Within the current work, the results of an optical measurement (one stereo-vision system) performed on a large area over a 50-m utility-scale blade subjected to quasi-static and cyclic loading are presented. The blade certification and testing is typically performed using International Electro-Technical Commission standard (IEC 61400-23). For static tests, the blade is pulled in either flap-wise or edge-wise directions to measure deflection or distributed strain at a few limited locations of a large-sized blade. Additionally, the paper explores the error associated with using a multi-camera system (two stereo-vision systems) in measuring 3D displacement and extracting structural dynamic parameters on a mock set up emulating a utility-scale wind turbine blade. The results obtained in this paper reveal that the multi-camera measurement system has the potential to identify the dynamic characteristics of a very large structure.

Lifetime prediction for the subsurface crack propagation using three-dimensional dynamic FEA model

NASA Astrophysics Data System (ADS)

Yin, Yuan; Chen, Yun-Xia; Liu, Le

2017-03-01

The subsurface crack propagation is one of the major interests for gear system research. The subsurface crack propagation lifetime is the number of cycles remaining for a spall to appear, which can be obtained through either stress intensity factor or accumulated plastic strain analysis. In this paper, the heavy loads are applied to the gear system. When choosing stress intensity factor, the high compressive stress suppresses Mode I stress intensities and severely reduces Mode II stress intensities in the heavily loaded lubricated contacts. Such that, the accumulated plastic strain is selected to calculate the subsurface crack propagation lifetime from the three-dimensional FEA model through ANSYS Workbench transient analysis. The three-dimensional gear FEA dynamic model with the subsurface crack is built through dividing the gears into several small elements. The calculation of the total cycles of the elements is proposed based on the time-varying accumulated plastic strain, which then will be used to calculate the subsurface crack propagation lifetime. During this process, the demonstration from a subsurface crack to a spall can be uncovered. In addition, different sizes of the elements around the subsurface crack are compared in this paper. The influences of the frictional coefficient and external torque on the crack propagation lifetime are also discussed. The results show that the lifetime of crack propagation decreases significantly when the external load T increasing from 100 N m to 150 N m. Given from the distributions of the accumulated plastic strain, the lifetime shares no significant difference when the frictional coefficient f ranging in 0.04-0.06.

Measuring spatial variability in soil characteristics

DOEpatents

Hoskinson, Reed L.; Svoboda, John M.; Sawyer, J. Wayne; Hess, John R.; Hess, J. Richard

2002-01-01

The present invention provides systems and methods for measuring a load force associated with pulling a farm implement through soil that is used to generate a spatially variable map that represents the spatial variability of the physical characteristics of the soil. An instrumented hitch pin configured to measure a load force is provided that measures the load force generated by a farm implement when the farm implement is connected with a tractor and pulled through or across soil. Each time a load force is measured, a global positioning system identifies the location of the measurement. This data is stored and analyzed to generate a spatially variable map of the soil. This map is representative of the physical characteristics of the soil, which are inferred from the magnitude of the load force.

A development of two-dimensional birefringence distribution measurement system with a sampling rate of 1.3 MHz

NASA Astrophysics Data System (ADS)

Onuma, Takashi; Otani, Yukitoshi

2014-03-01

A two-dimensional birefringence distribution measurement system with a sampling rate of 1.3 MHz is proposed. A polarization image sensor is developed as core device of the system. It is composed of a pixelated polarizer array made from photonic crystal and a parallel read out circuit with a multi-channel analog to digital converter specialized for two-dimensional polarization detection. By applying phase shifting algorism with circularly-polarized incident light, birefringence phase difference and azimuthal angle can be measured. The performance of the system is demonstrated experimentally by measuring actual birefringence distribution and polarization device such as Babinet-Soleil compensator.

Computational methods for frictional contact with applications to the Space Shuttle orbiter nose-gear tire: Comparisons of experimental measurements and analytical predictions

NASA Technical Reports Server (NTRS)

Tanner, John A.

1996-01-01

A computational procedure is presented for the solution of frictional contact problems for aircraft tires. A Space Shuttle nose-gear tire is modeled using a two-dimensional laminated anisotropic shell theory which includes the effects of variations in material and geometric parameters, transverse-shear deformation, and geometric nonlinearities. Contact conditions are incorporated into the formulation by using a perturbed Lagrangian approach with the fundamental unknowns consisting of the stress resultants, the generalized displacements, and the Lagrange multipliers associated with both contact and friction conditions. The contact-friction algorithm is based on a modified Coulomb friction law. A modified two-field, mixed-variational principle is used to obtain elemental arrays. This modification consists of augmenting the functional of that principle by two terms: the Lagrange multiplier vector associated with normal and tangential node contact-load intensities and a regularization term that is quadratic in the Lagrange multiplier vector. These capabilities and computational features are incorporated into an in-house computer code. Experimental measurements were taken to define the response of the Space Shuttle nose-gear tire to inflation-pressure loads and to inflation-pressure loads combined with normal static loads against a rigid flat plate. These experimental results describe the meridional growth of the tire cross section caused by inflation loading, the static load-deflection characteristics of the tire, the geometry of the tire footprint under static loading conditions, and the normal and tangential load-intensity distributions in the tire footprint for the various static vertical-loading conditions. Numerical results were obtained for the Space Shuttle nose-gear tire subjected to inflation pressure loads and combined inflation pressure and contact loads against a rigid flat plate. The experimental measurements and the numerical results are compared.

Simplified two-dimensional microwave imaging scheme using metamaterial-loaded Vivaldi antenna

NASA Astrophysics Data System (ADS)

Johari, Esha; Akhter, Zubair; Bhaskar, Manoj; Akhtar, M. Jaleel

2017-03-01

In this paper, a highly efficient, low-cost scheme for two-dimensional microwave imaging is proposed. To this end, the AZIM (anisotropic zero index metamaterial) cell-loaded Vivaldi antenna is designed and tested as effective electromagnetic radiation beam source required in the microwave imaging scheme. The designed antenna is first individually tested in the anechoic chamber, and its directivity along with the radiation pattern is obtained. The measurement setup for the imaging here involves a vector network analyzer, the AZIM cell-loaded ultra-wideband Vivaldi antenna, and other associated microwave components. The potential of the designed antenna for the microwave imaging is tested by first obtaining the two-dimensional reflectivity images of metallic samples of different shapes placed in front of the antenna, using the proposed scheme. In the next step, these sets of samples are hidden behind wooden blocks of different thicknesses and the reflectivity image of the test media is reconstructed by using the proposed scheme. Finally, the reflectivity images of various dielectric samples (Teflon, Plexiglas, permanent magnet moving coil) along with the copper sheet placed on a piece of cardboard are reconstructed by using the proposed setup. The images obtained for each case are plotted and compared with the actual objects, and a close match is observed which shows the applicability of the proposed scheme for through-wall imaging and the detection of concealed objects.

Development of a Shipboard Remote Control and Telemetry Experimental System for Large-Scale Model’s Motions and Loads Measurement in Realistic Sea Waves

PubMed Central

Jiao, Jialong; Ren, Huilong; Adenya, Christiaan Adika; Chen, Chaohe

2017-01-01

Wave-induced motion and load responses are important criteria for ship performance evaluation. Physical experiments have long been an indispensable tool in the predictions of ship’s navigation state, speed, motions, accelerations, sectional loads and wave impact pressure. Currently, majority of the experiments are conducted in laboratory tank environment, where the wave environments are different from the realistic sea waves. In this paper, a laboratory tank testing system for ship motions and loads measurement is reviewed and reported first. Then, a novel large-scale model measurement technique is developed based on the laboratory testing foundations to obtain accurate motion and load responses of ships in realistic sea conditions. For this purpose, a suite of advanced remote control and telemetry experimental system was developed in-house to allow for the implementation of large-scale model seakeeping measurement at sea. The experimental system includes a series of technique sensors, e.g., the Global Position System/Inertial Navigation System (GPS/INS) module, course top, optical fiber sensors, strain gauges, pressure sensors and accelerometers. The developed measurement system was tested by field experiments in coastal seas, which indicates that the proposed large-scale model testing scheme is capable and feasible. Meaningful data including ocean environment parameters, ship navigation state, motions and loads were obtained through the sea trial campaign. PMID:29109379

Development and application of 3-D foot-shape measurement system under different loads

NASA Astrophysics Data System (ADS)

Liu, Guozhong; Wang, Boxiong; Shi, Hui; Luo, Xiuzhi

2008-03-01

The 3-D foot-shape measurement system under different loads based on laser-line-scanning principle was designed and the model of the measurement system was developed. 3-D foot-shape measurements without blind areas under different loads and the automatic extraction of foot-parameter are achieved with the system. A global calibration method for CCD cameras using a one-axis motion unit in the measurement system and the specialized calibration kits is presented. Errors caused by the nonlinearity of CCD cameras and other devices and caused by the installation of the one axis motion platform, the laser plane and the toughened glass plane can be eliminated by using the nonlinear coordinate mapping function and the Powell optimized method in calibration. Foot measurements under different loads for 170 participants were conducted and the statistic foot parameter measurement results for male and female participants under non-weight condition and changes of foot parameters under half-body-weight condition, full-body-weight condition and over-body-weight condition compared with non-weight condition are presented. 3-D foot-shape measurement under different loads makes it possible to realize custom-made shoe-making and shows great prosperity in shoe design, foot orthopaedic treatment, shoe size standardization, and establishment of a feet database for consumers and athletes.

The effect of implant number and position on the stress behavior of mandibular implant retained overdentures: A three-dimensional finite element analysis.

PubMed

Topkaya, Tolga; Solmaz, Murat Yavuz

2015-07-16

The present study evaluated the effects of ball anchor abutment attached to implants with a 4.30 mm diameter and 11 mm insert length on stress distribution in a patient without any remaining teeth in the lower jaw. In the study, the stress analysis was performed for five different configurations (2 with 4 implant-supported and 3 with 2 implant-supported) and three different loading types using ANSYS Workbench software. The stresses measured in the 4 implant-supported models were lower compared to the stresses measured in the 2 implant-supported models. The stresses on the implants intensified on the cervical region of the implants. When the effects of the loading sites on the stress were examined, the loading on the first molar tooth produced the highest stresses on the implants. Copyright © 2015 Elsevier Ltd. All rights reserved.

Precision and accuracy of 3D lower extremity residua measurement systems

NASA Astrophysics Data System (ADS)

Commean, Paul K.; Smith, Kirk E.; Vannier, Michael W.; Hildebolt, Charles F.; Pilgram, Thomas K.

1996-04-01

Accurate and reproducible geometric measurement of lower extremity residua is required for custom prosthetic socket design. We compared spiral x-ray computed tomography (SXCT) and 3D optical surface scanning (OSS) with caliper measurements and evaluated the precision and accuracy of each system. Spiral volumetric CT scanned surface and subsurface information was used to make external and internal measurements, and finite element models (FEMs). SXCT and OSS were used to measure lower limb residuum geometry of 13 below knee (BK) adult amputees. Six markers were placed on each subject's BK residuum and corresponding plaster casts and distance measurements were taken to determine precision and accuracy for each system. Solid models were created from spiral CT scan data sets with the prosthesis in situ under different loads using p-version finite element analysis (FEA). Tissue properties of the residuum were estimated iteratively and compared with values taken from the biomechanics literature. The OSS and SXCT measurements were precise within 1% in vivo and 0.5% on plaster casts, and accuracy was within 3.5% in vivo and 1% on plaster casts compared with caliper measures. Three-dimensional optical surface and SXCT imaging systems are feasible for capturing the comprehensive 3D surface geometry of BK residua, and provide distance measurements statistically equivalent to calipers. In addition, SXCT can readily distinguish internal soft tissue and bony structure of the residuum. FEM can be applied to determine tissue material properties interactively using inverse methods.

Effect of passive polarizing three-dimensional displays on surgical performance for experienced laparoscopic surgeons.

PubMed

Smith, R; Schwab, K; Day, A; Rockall, T; Ballard, K; Bailey, M; Jourdan, I

2014-10-01

Although the potential benefits of stereoscopic laparoscopy have been recognized for years, the technology has not been adopted because of poor operator tolerance. Passive polarizing projection systems, which have revolutionized three-dimensional (3D) cinema, are now being trialled in surgery. This study was designed to see whether this technology resulted in significant performance benefits for skilled laparoscopists. Four validated laparoscopic skills tasks, each with ten repetitions, were performed by 20 experienced laparoscopic surgeons, in both two-dimensional (2D) and 3D conditions. The primary outcome measure was the performance error rate; secondary outcome measures were time for task completion, 3D motion tracking (path length, motion smoothness and grasping frequency) and workload dimension ratings of the National Aeronautics and Space Administration (NASA) Task Load Index. Surgeons demonstrated a 62 per cent reduction in the median number of errors and a 35 per cent reduction in median performance time when using the passive polarizing 3D display compared with the 2D display. There was a significant 15 per cent reduction in median instrument path length, an enhancement of median motion smoothness, and a 15 per cent decrease in grasper frequency with the 3D display. Participants reported significant reductions in subjective workload dimension ratings of the NASA Task Load Index following use of the 3D displays. Passive polarizing 3D displays improved both the performance of experienced surgeons in a simulated setting and surgeon perception of the operative field. Although it has been argued that the experience of skilled laparoscopic surgeons compensates fully for the loss of stereopsis, this study indicates that this is not the case. Surgical relevance The potential benefits of stereoscopic laparoscopy have been known for years, but the technology has not been adopted because of poor operator tolerance. The first laparoscopic operation was carried out using a prototype passive polarizing laparoscopic system in 2010. This is new three-dimensional (3D) technology offers a real option for 3D laparoscopic surgery where previous systems have failed. This study is the first to have been carried out using this technology. It is essential that new technologies are adopted only when there is robust evidence to support their use. Currently, there are concerns about the use of robotic technologies and whether advantages exist for patient care. If there are advantages, 3D must be playing a significant role. If so, perhaps the technology under investigation here offers potential to a greater spectrum of surgeons, as well as being a more affordable option. © 2014 BJS Society Ltd. Published by John Wiley & Sons Ltd.

Measuring heterogenous stress fields in a 3D colloidal glass

NASA Astrophysics Data System (ADS)

Lin, Neil; Bierbaum, Matthew; Bi, Max; Sethna, James; Cohen, Itai

Glass in our common experience is hard and fragile. But it still bends, yields, and flows slowly under loads. The yielding of glass, a well documented yet not fully understood flow behavior, is governed by the heterogenous local stresses in the material. While resolving stresses at the atomic scale is not feasible, measurements of stresses at the single particle level in colloidal glasses, a widely used model system for atomic glasses, has recently been made possible using Stress Assessment from Local Structural Anisotropy (SALSA). In this work, we use SALSA to visualize the three dimensional stress network in a hard-sphere glass during start-up shear. By measuring the evolution of this stress network we identify local-yielding. We find that these local-yielding events often require only minimal structural rearrangement and as such have most likely been ignored in previous analyses. We then relate these micro-scale yielding events to the macro-scale flow behavior observed using bulk measurements.

Femoral loading mechanics in the Virginia opossum, Didelphis virginiana: torsion and mediolateral bending in mammalian locomotion.

PubMed

Gosnell, W Casey; Butcher, Michael T; Maie, Takashi; Blob, Richard W

2011-10-15

Studies of limb bone loading in terrestrial mammals have typically found anteroposterior bending to be the primary loading regime, with torsion contributing minimally. However, previous studies have focused on large, cursorial eutherian species in which the limbs are held essentially upright. Recent in vivo strain data from the Virginia opossum (Didelphis virginiana), a marsupial that uses a crouched rather than an upright limb posture, have indicated that its femur experiences appreciable torsion during locomotion as well as strong mediolateral bending. The elevated femoral torsion and strong mediolateral bending observed in D. virginiana might result from external forces such as a medial inclination of the ground reaction force (GRF), internal forces deriving from a crouched limb posture, or a combination of these factors. To evaluate the mechanism underlying the loading regime of opossum femora, we filmed D. virginiana running over a force platform, allowing us to measure the magnitude of the GRF and its three-dimensional orientation relative to the limb, facilitating estimates of limb bone stresses. This three-dimensional analysis also allows evaluations of muscular forces, particularly those of hip adductor muscles, in the appropriate anatomical plane to a greater degree than previous two-dimensional analyses. At peak GRF and stress magnitudes, the GRF is oriented nearly vertically, inducing a strong abductor moment at the hip that is countered by adductor muscles on the medial aspect of the femur that place this surface in compression and induce mediolateral bending, corroborating and explaining loading patterns that were identified in strain analyses. The crouched orientation of the femur during stance in opossums also contributes to levels of femoral torsion as high as those seen in many reptilian taxa. Femoral safety factors were as high as those of non-avian reptiles and greater than those of upright, cursorial mammals, primarily because the load magnitudes experienced by opossums are lower than those of most mammals. Thus, the evolutionary transition from crouched to upright posture in mammalian ancestors may have been accompanied by an increase in limb bone load magnitudes.

Strain Gage Loads Calibration Testing of the Active Aeroelastic Wing F/A-18 Aircraft

NASA Technical Reports Server (NTRS)

Lokos, William A.; Olney, Candida D.; Chen, Tony; Crawford, Natalie D.; Stauf, Rick; Reichenbach, Eric Y.; Bessette, Denis (Technical Monitor)

2002-01-01

This report describes strain-gage calibration loading through the application of known loads of the Active Aeroelastic Wing F/A-18 airplane. The primary goal of this test is to produce a database suitable for deriving load equations for left and right wing root and fold shear; bending moment; torque; and all eight wing control-surface hinge moments. A secondary goal is to produce a database of wing deflections measured by string potentiometers and the onboard flight deflection measurement system. Another goal is to produce strain-gage data through both the laboratory data acquisition system and the onboard aircraft data system as a check of the aircraft system. Thirty-two hydraulic jacks have applied loads through whiffletrees to 104 tension-compression load pads bonded to the lower wing surfaces. The load pads covered approximately 60 percent of the lower wing surface. A series of 72 load cases has been performed, including single-point, double-point, and distributed load cases. Applied loads have reached 70 percent of the flight limit load. Maximum wingtip deflection has reached nearly 16 in.

Predicting dynamic knee joint load with clinical measures in people with medial knee osteoarthritis.

PubMed

Hunt, Michael A; Bennell, Kim L

2011-08-01

Knee joint loading, as measured by the knee adduction moment (KAM), has been implicated in the pathogenesis of knee osteoarthritis (OA). Given that the KAM can only currently be accurately measured in the laboratory setting with sophisticated and expensive equipment, its utility in the clinical setting is limited. This study aimed to determine the ability of a combination of four clinical measures to predict KAM values. Three-dimensional motion analysis was used to calculate the peak KAM at a self-selected walking speed in 47 consecutive individuals with medial compartment knee OA and varus malalignment. Clinical predictors included: body mass; tibial angle measured using an inclinometer; walking speed; and visually observed trunk lean toward the affected limb during the stance phase of walking. Multiple linear regression was performed to predict KAM magnitudes using the four clinical measures. A regression model including body mass (41% explained variance), tibial angle (17% explained variance), and walking speed (9% explained variance) explained a total of 67% of variance in the peak KAM. Our study demonstrates that a set of measures easily obtained in the clinical setting (body mass, tibial alignment, and walking speed) can help predict the KAM in people with medial knee OA. Identifying those patients who are more likely to experience high medial knee loads could assist clinicians in deciding whether load-modifying interventions may be appropriate for patients, whilst repeated assessment of joint load could provide a mechanism to monitor disease progression or success of treatment. Copyright © 2010 Elsevier B.V. All rights reserved.

Numerical investigation of road salt impact on an urban wellfield.

PubMed

Bester, M L; Frind, E O; Molson, J W; Rudolph, D L

2006-01-01

The impact of road salt on a wellfield in a complex glacial moraine aquifer system is studied by numerical simulation. The moraine underlies an extensive urban and industrial landscape, which draws its water supply from >20 wellfields, several of which are approaching or have exceeded the drinking water limit for chloride. The study investigates the mechanisms of road salt infiltration, storage, and transport in the subsurface and assesses the effectiveness of mitigation measures designed to reduce the impact. The three-dimensional transport model accounts for increases in salt loading, as well as growth of the urbanized area and road network over the past 50 years. The simulations, which focus on one impacted wellfield, show chloride plumes originating mainly at arterial roads and migrating through aquitard windows into the water supply aquifers. The results suggest that the aquifer system contains a large and heterogeneously distributed mass of chloride and that concentrations in the aquifer can be substantially higher than the concentrations in the well water. Future impact scenarios indicate that although the system responds rapidly to reductions in salt loading, the residual chloride mass may take decades to flush out, even if road salting were discontinued. The implications with respect to urban wellfields in typical snow-belt areas are discussed.

A system for extracting 3-dimensional measurements from a stereo pair of TV cameras

NASA Technical Reports Server (NTRS)

Yakimovsky, Y.; Cunningham, R.

1976-01-01

Obtaining accurate three-dimensional (3-D) measurement from a stereo pair of TV cameras is a task requiring camera modeling, calibration, and the matching of the two images of a real 3-D point on the two TV pictures. A system which models and calibrates the cameras and pairs the two images of a real-world point in the two pictures, either manually or automatically, was implemented. This system is operating and provides three-dimensional measurements resolution of + or - mm at distances of about 2 m.

Photovoltage detection of edge magnetoplasmon oscillations and giant magnetoplasmon resonances in a two-dimensional hole system

NASA Astrophysics Data System (ADS)

Mi, Jian; Wang, Jianli; Pfeiffer, Loren N.; West, Ken W.; Baldwin, Kirk W.; Zhang, Chi

In our high mobility p-type AlGaAs/GaAs two-dimensional hole samples, we originally observe the B - periodic oscillation induced by microwave (MW) in photovoltage (PV) measurements. In the frequency range of our measurements (5 - 40 GHz), the period is inversely proportional to the microwave frequency (f). The distinct oscillations come from the edge magnetoplasmon (EMP) in the high quality heavy hole system. Simultaneously, we observe the giant plasmon resonance signals in our measurements on the shallow two-dimensional hole system (2DHS).

Halo vest instrumentation

NASA Astrophysics Data System (ADS)

Huston, Dryver R.; Krag, Martin

1996-05-01

The halo vest is a head and neck immobilization system that is often used on patients that are recovering from cervical trauma or surgery. The halo vest system consists of a rigid halo that is firmly attached to the skull, an upright support structure for stabilization and immobilization, and a torso-enveloping vest. The main purpose of this study was to measure the forces that are carried by the halo-vest structure as the subject undergoes various activities of daily living and external loading for different vest designs. A tethered strain gage load cell based instrumentation system was used to take these load measurements on ten different subjects. Three different halo-vest systems were evaluated. The primary difference between the vests was the amount of torso coverage and the use of shoulder straps. The loads were measured, analyzed and used to compare the vests and to create a model of halo-vest-neck mechanics. Future applications of this technology to standalone data logging, pin-load measuring and biofeedback applications are discussed.

Granular dynamics under shear with deformable boundaries

NASA Astrophysics Data System (ADS)

Geller, Drew; Backhaus, Scott; Ecke, Robert

2015-03-01

Granular materials under shear develop complex patterns of stress as the result of granular positional rearrangements under an applied load. We consider the simple planar shear of a quasi two-dimensional granular material consisting of bi-dispersed nylon cylinders confined between deformable boundaries. The aspect ratio of the gap width to total system length is 50, and the ratio of particle diameter to gap width is about 10. This system, designed to model a long earthquake fault with long range elastic coupling through the plates, is an interesting model system for understanding effective granular friction because it essentially self tunes to the jamming condition owing to the hardness of the grains relative to that of the boundary material, a ratio of more than 1000 in elastic moduli. We measure the differential strain displacements of the plates, the inhomogeneous stress distribution in the plates, the positions and angular orientations of the individual grains, and the shear force, all as functions of the applied normal stress. There is significant stick-slip motion in this system that we quantify through our quantitative measurements of both the boundary and the grain motion, resulting in a good characterization of this sheared 2D hard sphere system.

Design and Fabrication of an Instrumented Handrim to Measure the Kinetic and Kinematic Information by the Hand of User for 3D Analysis of Manual Wheelchair Propulsion Dynamics

PubMed Central

Mallakzadeh, Mohammadreza; Akbari, Hossein

2014-01-01

The repetitious nature of propelling a wheelchair has been associated with the high incidence of injury among manual wheelchair users (MWUs), mainly in the shoulder, elbow and wrist. Recent literature has found a link between handrim biomechanics and risk of injury to the upper extremity. The valid measurement of three-dimensional net joint forces and torques, however, can lead to a better understanding of the mechanisms of injury, the development of prevention techniques, and the reduction of serious injuries to the joints. In this project, an instrumented wheel system was developed to measure the applied loads dynamically by the hand of the user and the angular position of the wheelchair user's hand on the handrim during the propulsion phase. The system is composed of an experimental six-axis load cell, and a wireless eight channel data logger mounted on a wheel hub. The angular position of the wheel is measured by an absolute magnetic encoder. The angular position of the wheelchair user's hand on the handrim during the propulsion phase (ɸ) or point of force application (PFA) is calculated by means of a new-experimental method using 36 pairs of infrared emitter/receiver diodes mounted around the handrim. In this regard, the observed data extracted from an inexperienced able-bodied subject pushed a wheelchair with the instrumented handrim are presented to show the output behavior of the instrumented handrim. The recorded forces and torques were in agreement with previously reported magnitudes. However, this paper can provide readers with some technical insights into possible solutions for measuring the manual wheelchair propulsion biomechanical data. PMID:25426429

Design and Fabrication of an Instrumented Handrim to Measure the Kinetic and Kinematic Information by the Hand of User for 3D Analysis of Manual Wheelchair Propulsion Dynamics.

PubMed

Mallakzadeh, Mohammadreza; Akbari, Hossein

2014-10-01

The repetitious nature of propelling a wheelchair has been associated with the high incidence of injury among manual wheelchair users (MWUs), mainly in the shoulder, elbow and wrist. Recent literature has found a link between handrim biomechanics and risk of injury to the upper extremity. The valid measurement of three-dimensional net joint forces and torques, however, can lead to a better understanding of the mechanisms of injury, the development of prevention techniques, and the reduction of serious injuries to the joints. In this project, an instrumented wheel system was developed to measure the applied loads dynamically by the hand of the user and the angular position of the wheelchair user's hand on the handrim during the propulsion phase. The system is composed of an experimental six-axis load cell, and a wireless eight channel data logger mounted on a wheel hub. The angular position of the wheel is measured by an absolute magnetic encoder. The angular position of the wheelchair user's hand on the handrim during the propulsion phase (ɸ) or point of force application (PFA) is calculated by means of a new-experimental method using 36 pairs of infrared emitter/receiver diodes mounted around the handrim. In this regard, the observed data extracted from an inexperienced able-bodied subject pushed a wheelchair with the instrumented handrim are presented to show the output behavior of the instrumented handrim. The recorded forces and torques were in agreement with previously reported magnitudes. However, this paper can provide readers with some technical insights into possible solutions for measuring the manual wheelchair propulsion biomechanical data.

Vegetated land cover near residence is associated with ...

EPA Pesticide Factsheets

Abstract Background: Greater exposure to urban green spaces has been linked to reduced risks of depression, cardiovascular disease, diabetes and premature death. Alleviation of chronic stress is a hypothesized pathway to improved health. Previous studies linked chronic stress with biomarker-based measures of physiological dysregulation known as allostatic load. This study aimed to assess the relationship between vegetated land cover near residences and allostatic load. Methods: This cross-sectional population-based study involved 204 adult residents of the Durham-Chapel Hill, North Carolina metropolitan area. Exposure was quantified using high-resolution metrics of trees and herbaceous vegetation within 500 m of each residence derived from the U.S. Environmental Protection Agency’s EnviroAtlas land cover dataset. Eighteen biomarkers of immune, neuroendocrine, and metabolic functions were measured in serum or saliva samples. Allostatic load was defined as a sum of biomarker values dichotomized at specific percentiles of sample distribution. Regression analysis was conducted using generalized additive models with two-dimensional spline smoothing function of geographic coordinates, weighted measures of vegetated land cover allowing decay of effects with distance, and geographic and demographic covariates. Results: An inter-quartile range increase in distance-weighted vegetated land cover was associated with 37% (46%; 27%) reduced allostatic load; significantly

A three-dimensional finite element model for biomechanical analysis of the hip.

PubMed

Chen, Guang-Xing; Yang, Liu; Li, Kai; He, Rui; Yang, Bin; Zhan, Yan; Wang, Zhi-Jun; Yu, Bing-Nin; Jian, Zhe

2013-11-01

The objective of this study was to construct a three-dimensional (3D) finite element model of the hip. The images of the hip were obtained from Chinese visible human dataset. The hip model includes acetabular bone, cartilage, labrum, and bone. The cartilage of femoral head was constructed using the AutoCAD and Solidworks software. The hip model was imported into ABAQUS analysis system. The contact surface of the hip joint was meshed. To verify the model, the single leg peak force was loaded, and contact area of the cartilage and labrum of the hip and pressure distribution in these structures were observed. The constructed 3D hip model reflected the real hip anatomy. Further, this model reflected biomechanical behavior similar to previous studies. In conclusion, this 3D finite element hip model avoids the disadvantages of other construction methods, such as imprecision of cartilage construction and the absence of labrum. Further, it provides basic data critical for accurately modeling normal and abnormal loads, and the effects of abnormal loads on the hip.

A detailed study of gold-nanoparticle loaded cells using X-ray based techniques for cell-tracking applications with single-cell sensitivity

NASA Astrophysics Data System (ADS)

Astolfo, Alberto; Arfelli, Fulvia; Schültke, Elisabeth; James, Simon; Mancini, Lucia; Menk, Ralf-Hendrik

2013-03-01

In the present study complementary high-resolution imaging techniques on different length scales are applied to elucidate a cellular loading protocol of gold nanoparticles and subsequently its impact on long term and high-resolution cell-tracking utilizing X-ray technology. Although demonstrated for malignant cell lines the results can be applied to non-malignant cell lines as well. In particular the accumulation of the gold marker per cell has been assessed quantitatively by virtue of electron microscopy, two-dimensional X-ray fluorescence imaging techniques and X-ray CT with micrometric and sub-micrometric resolution. Moreover, utilizing these techniques the three dimensional distribution of the incorporated nanoparticles, which are sequestered in lysosomes as a permanent marker, could be determined. The latter allowed elucidation of the gold partition during mitosis and the cell size, which subsequently enabled us to define the optimal instrument settings of a compact microCT system to visualize gold loaded cells. The results obtained demonstrate the feasibility of cell-tracking using X-ray CT with compact sources.

Three-dimensional shape measurement system applied to superficial inspection of non-metallic pipes for the hydrocarbons transport

NASA Astrophysics Data System (ADS)

Arciniegas, Javier R.; González, Andrés. L.; Quintero, L. A.; Contreras, Carlos R.; Meneses, Jaime E.

2014-05-01

Three-dimensional shape measurement is a subject that consistently produces high scientific interest and provides information for medical, industrial and investigative applications, among others. In this paper, it is proposed to implement a three-dimensional (3D) reconstruction system for applications in superficial inspection of non-metallic pipes for the hydrocarbons transport. The system is formed by a CCD camera, a video-projector and a laptop and it is based on fringe projection technique. System functionality is evidenced by evaluating the quality of three-dimensional reconstructions obtained, which allow observing the failures and defects on the study object surface.

A three-dimensional `Kaiser damage-memory' effect through true-triaxial loading

NASA Astrophysics Data System (ADS)

Meredith, P. G.; Browning, J.; Harland, S. R.; Healy, D.; Stuart, C.; Mitchell, T. M.

2017-12-01

Microcrack damage leading to failure in rocks evolves in response to differential loading. The vast majority of experimental studies investigate damage evolution, the `Kaiser damage-memory' effect, and rock failure using conventional triaxial stress states (σ1 > σ2 = σ3). Such stress states develop a crack population that displays cylindrical transverse isotropy. However, in nature the stress state is in general truly triaxial (σ1 > σ2 > σ3) and experiments that utilise such loading conditions can generate crack populations that display planar transverse isotropy which in turn influences properties such as permeability and strength. We investigate the evolution of crack damage under both conventional and true triaxial stress conditions using results from measurements made on cubic samples of sandstone deformed in three orthogonal directions with independently controlled stress paths. We have measured, simultaneously with stress and strain, the changes in ultrasonic compressional and shear wave velocities in the three principal directions, together with the bulk acoustic emission (AE) output. Changes in acoustic wave velocities are associated with both elastic closure and opening of pre-existing cracks, and the inelastic formation of new cracks. By contrast, AE is only associated with the inelastic growth of new crack damage and as such, we use the onset of AE to determine the initiation of new crack damage. By mapping these damage onsets under both conventional triaxial and true triaxial sequential cyclic loading, we have shown that `damage envelopes' evolve dynamically and can be pushed closer to the failure envelope. Whether a stress state has been `visited' before is key to determining and understanding damage states. Crack damage populations can be generated with multiple orientations depending on the arrangement of loading directions and hence principal stress directions. The sequential cyclic loading tests show that further damage in any one population commences only when the previous maximum differential stress `seen' by that population is exceeded. Understanding anisotropic damage is important for applying the results of true-triaxial tests and hence better replicating natural fractured systems.

ASTROP2-LE: A Mistuned Aeroelastic Analysis System Based on a Two Dimensional Linearized Euler Solver

NASA Technical Reports Server (NTRS)

Reddy, T. S. R.; Srivastava, R.; Mehmed, Oral

2002-01-01

An aeroelastic analysis system for flutter and forced response analysis of turbomachines based on a two-dimensional linearized unsteady Euler solver has been developed. The ASTROP2 code, an aeroelastic stability analysis program for turbomachinery, was used as a basis for this development. The ASTROP2 code uses strip theory to couple a two dimensional aerodynamic model with a three dimensional structural model. The code was modified to include forced response capability. The formulation was also modified to include aeroelastic analysis with mistuning. A linearized unsteady Euler solver, LINFLX2D is added to model the unsteady aerodynamics in ASTROP2. By calculating the unsteady aerodynamic loads using LINFLX2D, it is possible to include the effects of transonic flow on flutter and forced response in the analysis. The stability is inferred from an eigenvalue analysis. The revised code, ASTROP2-LE for ASTROP2 code using Linearized Euler aerodynamics, is validated by comparing the predictions with those obtained using linear unsteady aerodynamic solutions.

Linear and nonlinear dynamic analysis of redundant load path bearingless rotor systems

NASA Technical Reports Server (NTRS)

Murthy, V. R.

1985-01-01

The bearingless rotorcraft offers reduced weight, less complexity and superior flying qualities. Almost all the current industrial structural dynamic programs of conventional rotors which consist of single load path rotor blades employ the transfer matrix method to determine natural vibration characteristics because this method is ideally suited for one dimensional chain like structures. This method is extended to multiple load path rotor blades without resorting to an equivalent single load path approximation. Unlike the conventional blades, it isk necessary to introduce the axial-degree-of-freedom into the solution process to account for the differential axial displacements in the different load paths. With the present extension, the current rotor dynamic programs can be modified with relative ease to account for the multiple load paths without resorting to the equivalent single load path modeling. The results obtained by the transfer matrix method are validated by comparing with the finite element solutions. A differential stiffness matrix due to blade rotation is derived to facilitate the finite element solutions.

A servo controlled gradient loading triaxial model test system for deep-buried cavern.

PubMed

Chen, Xu-guang; Zhang, Qiang-yong; Li, Shu-cai

2015-10-01

A servo controlled gradient loading model test system is developed to simulate the gradient geostress in deep-buried cavern. This system consists of the gradient loading apparatus, the digital servo control device, and the measurement system. Among them, the gradient loading apparatus is the main component which is used for exerting load onto the model. This loading apparatus is placed inside the counterforce wall/beam and is divided to several different loading zones, with each loading zone independently controlled. This design enables the gradient loading. Hence, the "real" geostress field surrounding the deep-buried cavern can be simulated. The loading or unloading process can be controlled by the human-computer interaction machines, i.e., the digital servo control system. It realizes the automation and visualization of model loading/unloading. In addition, this digital servo could control and regulate hydraulic loading instantaneously, which stabilizes the geostress onto the model over a long term. During the loading procedure, the collision between two adjacent loading platens is also eliminated by developing a guide frame. This collision phenomenon is induced by the volume shrinkage of the model when compressed in true 3D state. In addition, several accurate measurements, including the optical and grating-based method, are adopted to monitor the small deformation of the model. Hence, the distortion of the model could be accurately measured. In order to validate the performance of this innovative model test system, a 3D geomechanical test was conducted on a simulated deep-buried underground reservoir. The result shows that the radial convergence increases rapidly with the release of the stress in the reservoir. Moreover, the deformation increases with the increase of the gas production rate. This observation is consistence with field observation in petroleum engineering. The system is therefore capable of testing deep-buried engineering structures.

Aeroacoustic theory for noncompact wing-gust interaction

NASA Technical Reports Server (NTRS)

Martinez, R.; Widnall, S. E.

1981-01-01

Three aeroacoustic models for noncompact wing-gust interaction were developed for subsonic flow. The first is that for a two dimensional (infinite span) wing passing through an oblique gust. The unsteady pressure field was obtained by the Wiener-Hopf technique; the airfoil loading and the associated acoustic field were calculated, respectively, by allowing the field point down on the airfoil surface, or by letting it go to infinity. The second model is a simple spanwise superposition of two dimensional solutions to account for three dimensional acoustic effects of wing rotation (for a helicopter blade, or some other rotating planform) and of finiteness of wing span. A three dimensional theory for a single gust was applied to calculate the acoustic signature in closed form due to blade vortex interaction in helicopters. The third model is that of a quarter infinite plate with side edge through a gust at high subsonic speed. An approximate solution for the three dimensional loading and the associated three dimensional acoustic field in closed form was obtained. The results reflected the acoustic effect of satisfying the correct loading condition at the side edge.

Estimation of three-dimensional radar tracking using modified extended kalman filter

NASA Astrophysics Data System (ADS)

Aditya, Prima; Apriliani, Erna; Khusnul Arif, Didik; Baihaqi, Komar

2018-03-01

Kalman filter is an estimation method by combining data and mathematical models then developed be extended Kalman filter to handle nonlinear systems. Three-dimensional radar tracking is one of example of nonlinear system. In this paper developed a modification method of extended Kalman filter from the direct decline of the three-dimensional radar tracking case. The development of this filter algorithm can solve the three-dimensional radar measurements in the case proposed in this case the target measured by radar with distance r, azimuth angle θ, and the elevation angle ϕ. Artificial covariance and mean adjusted directly on the three-dimensional radar system. Simulations result show that the proposed formulation is effective in the calculation of nonlinear measurement compared with extended Kalman filter with the value error at 0.77% until 1.15%.

A solution procedure for behavior of thick plates on a nonlinear foundation and postbuckling behavior of long plates

NASA Technical Reports Server (NTRS)

Stein, M.; Stein, P. A.

1978-01-01

Approximate solutions for three nonlinear orthotropic plate problems are presented: (1) a thick plate attached to a pad having nonlinear material properties which, in turn, is attached to a substructure which is then deformed; (2) a long plate loaded in inplane longitudinal compression beyond its buckling load; and (3) a long plate loaded in inplane shear beyond its buckling load. For all three problems, the two dimensional plate equations are reduced to one dimensional equations in the y-direction by using a one dimensional trigonometric approximation in the x-direction. Each problem uses different trigonometric terms. Solutions are obtained using an existing algorithm for simultaneous, first order, nonlinear, ordinary differential equations subject to two point boundary conditions. Ordinary differential equations are derived to determine the variable coefficients of the trigonometric terms.

Results of the first complete static calibration of the RSRA rotor-load-measurement system

NASA Technical Reports Server (NTRS)

Acree, C. W., Jr.

1984-01-01

The compound Rotor System Research Aircraft (RSRA) is designed to make high-accuracy, simultaneous measurements of all rotor forces and moments in flight. Physical calibration of the rotor force- and moment-measurement system when installed in the aircraft is required to account for known errors and to ensure that measurement-system accuracy is traceable to the National Bureau of Standards. The first static calibration and associated analysis have been completed with good results. Hysteresis was a potential cause of static calibration errors, but was found to be negligible in flight compared to full-scale loads, and analytical methods have been devised to eliminate hysteresis effects on calibration data. Flight tests confirmed that the calibrated rotor-load-measurement system performs as expected in flight and that it can dependably make direct measurements of fuselage vertical drag in hover.

Comparison of FRF measurements and mode shapes determined using optically image based, laser, and accelerometer measurements

NASA Astrophysics Data System (ADS)

Warren, Christopher; Niezrecki, Christopher; Avitabile, Peter; Pingle, Pawan

2011-08-01

Today, accelerometers and laser Doppler vibrometers are widely accepted as valid measurement tools for structural dynamic measurements. However, limitations of these transducers prevent the accurate measurement of some phenomena. For example, accelerometers typically measure motion at a limited number of discrete points and can mass load a structure. Scanning laser vibrometers have a very wide frequency range and can measure many points without mass-loading, but are sensitive to large displacements and can have lengthy acquisition times due to sequential measurements. Image-based stereo-photogrammetry techniques provide additional measurement capabilities that compliment the current array of measurement systems by providing an alternative that favors high-displacement and low-frequency vibrations typically difficult to measure with accelerometers and laser vibrometers. Within this paper, digital image correlation, three-dimensional (3D) point-tracking, 3D laser vibrometry, and accelerometer measurements are all used to measure the dynamics of a structure to compare each of the techniques. Each approach has its benefits and drawbacks, so comparative measurements are made using these approaches to show some of the strengths and weaknesses of each technique. Additionally, the displacements determined using 3D point-tracking are used to calculate frequency response functions, from which mode shapes are extracted. The image-based frequency response functions (FRFs) are compared to those obtained by collocated accelerometers. Extracted mode shapes are then compared to those of a previously validated finite element model (FEM) of the test structure and are shown to have excellent agreement between the FEM and the conventional measurement approaches when compared using the Modal Assurance Criterion (MAC) and Pseudo-Orthogonality Check (POC).

Analysis of interlaminar stresses in symmetric and unsymmetric laminates under various loadings

NASA Astrophysics Data System (ADS)

Leger, C. A.; Chan, W. S.

1993-04-01

A quasi-three-dimensional finite-element model is developed to investigate the interlaminar stresses in a composite laminate under combined loadings. An isoparametric quadrilateral element with eight nodes and three degrees of freedom per node is the finite element used in this study. The element is used to model a composite laminate cross section loaded by tension, torsion, transverse shear, and both beam and chord bending which are representative of loading in a helicopter rotor system. Symmetric and unsymmetric laminates are examined with comparisons made between the interlaminar stress distributions and magnitudes for each laminate. Unsymmetric results are compared favorably to limited results found in literature. The unsymmetric interlaminar normal stress distribution in a symmetric laminate containing a free edge delamination is also examined.

Non-linear programming in shakedown analysis with plasticity and friction

NASA Astrophysics Data System (ADS)

Spagnoli, A.; Terzano, M.; Barber, J. R.; Klarbring, A.

2017-07-01

Complete frictional contacts, when subjected to cyclic loading, may sometimes develop a favourable situation where slip ceases after a few cycles, an occurrence commonly known as frictional shakedown. Its resemblance to shakedown in plasticity has prompted scholars to apply direct methods, derived from the classical theorems of limit analysis, in order to assess a safe limit to the external loads applied on the system. In circumstances where zones of plastic deformation develop in the material (e.g., because of the large stress concentrations near the sharp edges of a complete contact), it is reasonable to expect an effect of mutual interaction of frictional slip and plastic strains on the load limit below which the global behaviour is non dissipative, i.e., both slip and plastic strains go to zero after some dissipative load cycles. In this paper, shakedown of general two-dimensional discrete systems, involving both friction and plasticity, is discussed and the shakedown limit load is calculated using a non-linear programming algorithm based on the static theorem of limit analysis. An illustrative example related to an elastic-plastic solid containing a frictional crack is provided.

John F. Kennedy Space Center's Wireless Hang Angle Instrumentation System

NASA Technical Reports Server (NTRS)

Kohler, Jeff

2009-01-01

The technology is a high-precision, wireless inclinometer. The system was designed for monitoring the suspension angle of the Orbiter vehicle during loading onto the Solid Rocket Boosters of the Space Shuttle. Originally, operators manually measured the alignment of the Orbiter with a hand-held inclinometer on a nonrigid surface. The measurement was open to interpretation by the loader. If the Orbiter is misaligned, it can crush ball joints and delay the loading while repairs are made. With this system, the Orbiter can be loaded without damage and without manual measurement.

Design and two dimensional cascade test of a jet-flap turbine stator blade with ratio of axial chord to spacing of 0.5

NASA Technical Reports Server (NTRS)

Stabe, R. G.

1971-01-01

A jet-flap blade was designed for a velocity diagram typical of the first-stage stator of a jet engine turbine and was tested in a simple two-dimensional cascade of six blades. The principal measurements were blade surface static pressure and cross-channel surveys of exit total pressure, static pressure, and flow angle. The results of the experimental investigation include blade loading, exit angle, flow, and loss data for a range of exit critical velocity ratios and three jet flow conditions.

Revised Geometric Measure of Entanglement in Infinite Dimensional Multipartite Quantum Systems

NASA Astrophysics Data System (ADS)

Wang, Yinzhu; Wang, Danxia; Huang, Li

2018-05-01

In Cao and Wang (J. Phys.: Math. Theor. 40, 3507-3542, 2007), the revised geometric measure of entanglement (RGME) for states in finite dimensional bipartite quantum systems was proposed. Furthermore, in Cao and Wang (Commun. Theor. Phys. 51(4), 613-620, 2009), the authors obtained the revised geometry measure of entanglement for multipartite states including three-qubit GHZ state, W state, and the generalized Smolin state in the presence of noise and the two-mode squeezed thermal state, and defined the Gaussian geometric entanglement measure. In this paper, we generalize the RGME to infinite dimensional multipartite quantum systems, and prove that this measure satisfies some necessary properties as a well-defined entanglement measure, including monotonicity under local operations and classical communications.

Analytical and experimental study of sleeper SAT S 312 in slab track Sateba system

NASA Astrophysics Data System (ADS)

Guigou-Carter, C.; Villot, M.; Guillerme, B.; Petit, C.

2006-06-01

In this paper, a simple prediction tool based on a two-dimensional model is developed for a slab track system composed of two rails with rail pads, sleepers with sleeper pads, and a concrete base slab. The track and the slab are considered as infinite beams with bending stiffness, loss factor and mass per unit length. The track system is represented by its impedance per unit length of track and the ground by its line input impedance calculated using a two-dimensional elastic half-space ground model based on the wave approach. Damping of each track component is modelled as hysteretic damping and is taken into account by using a complex stiffness. The unsprung mass of the vehicle is considered as a concentrated mass at the excitation point on the rail head. The effect of the dynamic stiffness of the sleeper pads on the vibration isolation is studied in detail, the vibration isolation provided by the track system being quantified by an insertion gain in dB per one-third octave band. The second part of this paper presents an experimental test rig used to measure the dynamic stiffness of the sleeper pads on a full width section of the track (two rails). The experimental set-up is submitted to vertical as well as horizontal static loads (via hydraulic jacks) and an electrodynamic shaker is used for dynamic excitation of the system. The determination of the dynamic stiffness of the sleeper pads is based on the approach called the "direct method". The limitations of the experimental set-up are discussed. The measurement results for one type of sleeper pad are presented.

Design of an Ultra-Efficient GaN High Power Amplifier for Radar Front-Ends Using Active Harmonic Load-Pull

NASA Technical Reports Server (NTRS)

Thrivikraman, Tushar; Hoffman, James

2012-01-01

This work presents a new measurement technique, mixed-signal active harmonic load-pull (MSALP) developed by Anterverta-mw in partnership with Maury Microwave, that allows for wide-band ultra-high efficiency amplifiers to be designed using GaN technology. An overview of the theory behind active load-pull is presented and why load-pull is important for high-power device characterization. In addition, an example procedure is presented that outlines a methodology for amplifier design using this measurement system. Lastly, measured results of a 10W GaN amplifier are presented. This work aims to highlight the benefit of using this sophisticated measurement systems for to optimize amplifier design for real radar waveforms that in turn will simplify implementation of space-based radar systems

Data Report on Post-Irradiation Dimensional Change of AGC-1 Samples

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

William Windes

This report summarizes the initial dimensional changes for loaded and unloaded AGC-1 samples. The dimensional change for all samples is presented as a function of dose. The data is further presented by graphite type and applied load levels to illustrate the differences between graphite forming processes and stress levels within the graphite components. While the three different loads placed on the samples have been verified [ ref: Larry Hull’s report] verification of the AGC-1 sample temperatures and dose levels are expected in the summer of 2012. Only estimated dose and temperature values for the samples are presented in this reportmore » to allow a partial analysis of the results.« less

Static calibration of the RSRA active-isolator rotor balance system

NASA Technical Reports Server (NTRS)

Acree, C. W., Jr.

1987-01-01

The Rotor Systems Research Aircraft (RSRA) active-isolator system is designed to reduce rotor vibrations transmitted to the airframe and to simultaneously measure all six forces and moments generated by the rotor. These loads are measured by using a combination of load cells, strain gages, and hydropneumatic active isolators with built-in pressure gages. The first static calibration of the complete active-isolator rotor balance system was performed in l983 to verify its load-measurement capabilities. Analysis of the data included the use of multiple linear regressions to determine calibration matrices for different data sets and a hysteresis-removal algorithm to estimate in-flight measurement errors. Results showed that the active-isolator system can fulfill most performance predictions. The results also suggested several possible improvements to the system.

Development of a patient-specific 3D dose evaluation program for QA in radiation therapy

NASA Astrophysics Data System (ADS)

Lee, Suk; Chang, Kyung Hwan; Cao, Yuan Jie; Shim, Jang Bo; Yang, Dae Sik; Park, Young Je; Yoon, Won Sup; Kim, Chul Yong

2015-03-01

We present preliminary results for a 3-dimensional dose evaluation software system ( P DRESS, patient-specific 3-dimensional dose real evaluation system). Scanned computed tomography (CT) images obtained by using dosimetry were transferred to the radiation treatment planning system (ECLIPSE, VARIAN, Palo Alto, CA) where the intensity modulated radiation therapy (IMRT) nasopharynx plan was designed. We used a 10 MV photon beam (CLiX, VARIAN, Palo Alto, CA) to deliver the nasopharynx treatment plan. After irradiation, the TENOMAG dosimeter was scanned using a VISTA ™ scanner. The scanned data were reconstructed using VistaRecon software to obtain a 3D dose distribution of the optical density. An optical-CT scanner was used to readout the dose distribution in the gel dosimeter. Moreover, we developed the P DRESS by using Flatform, which were developed by our group, to display the 3D dose distribution by loading the DICOM RT data which are exported from the radiotherapy treatment plan (RTP) and the optical-CT reconstructed VFF file, into the independent P DRESS with an ioniz ation chamber and EBT film was used to compare the dose distribution calculated from the RTP with that measured by using a gel dosimeter. The agreement between the normalized EBT, the gel dosimeter and RTP data was evaluated using both qualitative and quantitative methods, such as the isodose distribution, dose difference, point value, and profile. The profiles showed good agreement between the RTP data and the gel dosimeter data, and the precision of the dose distribution was within ±3%. The results from this study showed significantly discrepancies between the dose distribution calculated from the treatment plan and the dose distribution measured by a TENOMAG gel and by scanning with an optical CT scanner. The 3D dose evaluation software system ( P DRESS, patient specific dose real evaluation system), which were developed in this study evaluates the accuracies of the three-dimensional dose distributions. Further applications of the system utility are expected to result from future studies.

Influence of Thickness and Contact Surface Geometry of Condylar Stem of TMJ Implant on Its Stability

NASA Astrophysics Data System (ADS)

Arabshahi, Zohreh; Kashani, Jamal; Kadir, Mohammed Rafiq Abdul; Azari, Abbas

The aim of this study is to examine the effect thickness and contact surface geometry of condylar stem of TMJ implant on its stability in total reconstruction system and evaluate the micro strain resulted in bone at fixation screw holes in jaw bone embedded with eight different designs of temporomandibular joint implants. A three dimensional model of a lower mandible of an adult were developed from a Computed Tomography scan images. Eight different TMJ implant designs and fixation screws were modeled. Three dimensional finite element models of eight implanted mandibles were analyzed. The forces assigned to the masticatory muscles for incisal clenching were applied consisting of nine important muscular loads. In chosen loading condition, The results indicated that the anatomical curvature contact surface design of TMJ implant can moderately improve the stability and the strain resulted in fixation screw holes in thinner TMJ implant was diminished in comparison with other thicknesses.

Fiber pushout test: A three-dimensional finite element computational simulation

NASA Technical Reports Server (NTRS)

Mital, Subodh K.; Chamis, Christos C.

1990-01-01

A fiber pushthrough process was computationally simulated using three-dimensional finite element method. The interface material is replaced by an anisotropic material with greatly reduced shear modulus in order to simulate the fiber pushthrough process using a linear analysis. Such a procedure is easily implemented and is computationally very effective. It can be used to predict fiber pushthrough load for a composite system at any temperature. The average interface shear strength obtained from pushthrough load can easily be separated into its two components: one that comes from frictional stresses and the other that comes from chemical adhesion between fiber and the matrix and mechanical interlocking that develops due to shrinkage of the composite because of phase change during the processing. Step-by-step procedures are described to perform the computational simulation, to establish bounds on interfacial bond strength and to interpret interfacial bond quality.

An Evaluation Technique for an F/A-18 Aircraft Loads Model Using F/A-18 Systems Research Aircraft Flight Data

NASA Technical Reports Server (NTRS)

Olney, Candida D.; Hillebrandt, Heather; Reichenbach, Eric Y.

2000-01-01

A limited evaluation of the F/A-18 baseline loads model was performed on the Systems Research Aircraft at NASA Dryden Flight Research Center (Edwards, California). Boeing developed the F/A-18 loads model using a linear aeroelastic analysis in conjunction with a flight simulator to determine loads at discrete locations on the aircraft. This experiment was designed so that analysis of doublets could be used to establish aircraft aerodynamic and loads response at 20 flight conditions. Instrumentation on the right outboard leading edge flap, left aileron, and left stabilator measured the hinge moment so that comparisons could be made between in-flight-measured hinge moments and loads model-predicted values at these locations. Comparisons showed that the difference between the loads model-predicted and in-flight-measured hinge moments was up to 130 percent of the flight limit load. A stepwise regression technique was used to determine new loads derivatives. These derivatives were placed in the loads model, which reduced the error to within 10 percent of the flight limit load. This paper discusses the flight test methodology, a process for determining loads coefficients, and the direct comparisons of predicted and measured hinge moments and loads coefficients.

Parameter Optimization and Operating Strategy of a TEG System for Railway Vehicles

NASA Astrophysics Data System (ADS)

Heghmanns, A.; Wilbrecht, S.; Beitelschmidt, M.; Geradts, K.

2016-03-01

A thermoelectric generator (TEG) system demonstrator for diesel electric locomotives with the objective of reducing the mechanical load on the thermoelectric modules (TEM) is developed and constructed to validate a one-dimensional thermo-fluid flow simulation model. The model is in good agreement with the measurements and basis for the optimization of the TEG's geometry by a genetic multi objective algorithm. The best solution has a maximum power output of approx. 2.7 kW and does not exceed the maximum back pressure of the diesel engine nor the maximum TEM hot side temperature. To maximize the reduction of the fuel consumption, an operating strategy regarding the system power output for the TEG system is developed. Finally, the potential consumption reduction in passenger and freight traffic operating modes is estimated under realistic driving conditions by means of a power train and lateral dynamics model. The fuel savings are between 0.5% and 0.7%, depending on the driving style.

Evaluation of Stress Distribution in Magnetic Materials Using a Magnetic Imaging System

NASA Astrophysics Data System (ADS)

Lo, C. C. H.; Paulsen, J. A.; Jiles, D. C.

2004-02-01

The feasibility of detecting stress distribution in magnetic materials by magnetic hysteresis and Barkhausen effect measurements has been evaluated using a newly developed magnetic imaging system. The system measured hysteresis loops and Barkhausen effect signals with the use of a surface sensor that was scanned over the material. The data were converted into a two-dimensional image showing spatial variations of the magnetic properties from which mechanical conditions of the materials can be inferred. In this study a nickel plate machined into a shear-beam load cell configuration was used. By applying a stress along the neutral axis, various stress patterns such as shear stress and stress concentration could be produced in different regions of the sample. The scanned images of magnetic properties such as coercivity and rms value of Barkhausen effect signal exhibited patterns similar to the stress distribution calculated using finite element model (FEM), in particular in the regions where a high stress level and a high stress gradient existed. For direct comparison, images of magnetic properties were simulated based on the results of FEM stress calculation and experimental calibration of the magnetomechanical effect. The simulated images were found to closely resemble the scanned images, indicating the possibility of measuring stress distribution by mapping magnetic properties using the magnetic imaging system.

Three-dimensional innate mobility of the human foot bones under axial loading using biplane X-ray fluoroscopy

PubMed Central

Hosoda, Koh; Shimizu, Masahiro; Ikemoto, Shuhei; Nagura, Takeo; Seki, Hiroyuki; Kitashiro, Masateru; Imanishi, Nobuaki; Aiso, Sadakazu; Jinzaki, Masahiro; Ogihara, Naomichi

2017-01-01

The anatomical design of the human foot is considered to facilitate generation of bipedal walking. However, how the morphology and structure of the human foot actually contribute to generation of bipedal walking remains unclear. In the present study, we investigated the three-dimensional kinematics of the foot bones under a weight-bearing condition using cadaver specimens, to characterize the innate mobility of the human foot inherently prescribed in its morphology and structure. Five cadaver feet were axially loaded up to 588 N (60 kgf), and radiographic images were captured using a biplane X-ray fluoroscopy system. The present study demonstrated that the talus is medioinferiorly translated and internally rotated as the calcaneus is everted owing to axial loading, causing internal rotation of the tibia and flattening of the medial longitudinal arch in the foot. Furthermore, as the talus is internally rotated, the talar head moves medially with respect to the navicular, inducing external rotation of the navicular and metatarsals. Under axial loading, the cuboid is everted simultaneously with the calcaneus owing to the osseous locking mechanism in the calcaneocuboid joint. Such detailed descriptions about the innate mobility of the human foot will contribute to clarifying functional adaptation and pathogenic mechanisms of the human foot. PMID:29134100

Modeling and Analysis Tools for Linear and Nonlinear Mechanical Systems Subjected to Extreme Impulsive Loading

DTIC Science & Technology

2015-03-23

SAMPE, Long Beach, CA, 2008. [28] N Hu and H Fukunaga. A new approach for health monitoring of composite structures through identification of impact...Bernard H Minster . Hysteresis and two- dimensional nonlinear wave propagation in berea sandstone. Journal of Geo- physical Research: Solid Earth (1978–2012

In situ calibration of neutron activation system on the large helical device

NASA Astrophysics Data System (ADS)

Pu, N.; Nishitani, T.; Isobe, M.; Ogawa, K.; Kawase, H.; Tanaka, T.; Li, S. Y.; Yoshihashi, S.; Uritani, A.

2017-11-01

In situ calibration of the neutron activation system on the Large Helical Device (LHD) was performed by using an intense 252Cf neutron source. To simulate a ring-shaped neutron source, we installed a railway inside the LHD vacuum vessel and made a train loaded with the 252Cf source run along a typical magnetic axis position. Three activation capsules loaded with thirty pieces of indium foils stacked with total mass of approximately 18 g were prepared. Each capsule was irradiated over 15 h while the train was circulating. The activation response coefficient (9.4 ± 1.2) × 10-8 of 115In(n, n')115mIn reaction obtained from the experiment is in good agreement with results from three-dimensional neutron transport calculations using the Monte Carlo neutron transport simulation code 6. The activation response coefficients of 2.45 MeV birth neutron and secondary 14.1 MeV neutron from deuterium plasma were evaluated from the activation response coefficient obtained in this calibration experiment with results from three-dimensional neutron calculations using the Monte Carlo neutron transport simulation code 6.

Dynamic Fracture Properties of Rocks Subjected to Static Pre-load Using Notched Semi-circular Bend Method

NASA Astrophysics Data System (ADS)

Chen, Rong; Li, Kang; Xia, Kaiwen; Lin, Yuliang; Yao, Wei; Lu, Fangyun

2016-10-01

A dynamic load superposed on a static pre-load is a key problem in deep underground rock engineering projects. Based on a modified split Hopkinson pressure bar test system, the notched semi-circular bend (NSCB) method is selected to investigate the fracture initiation toughness of rocks subjected to pre-load. In this study, a two-dimensional ANSYS finite element simulation model is developed to calculate the dimensionless stress intensity factor. Three groups of NSCB specimen are tested under a pre-load of 0, 37 and 74 % of the maximum static load and with the loading rate ranging from 0 to 60 GPa m1/2 s-1. The results show that under a given pre-load, the fracture initiation toughness of rock increases with the loading rate, resembling the typical rate dependence of materials. Furthermore, the dynamic rock fracture toughness decreases with the static pre-load at a given loading rate. The total fracture toughness, defined as the sum of the dynamic fracture toughness and initial stress intensity factor calculated from the pre-load, increases with the pre-load at a given loading rate. An empirical equation is used to represent the effect of loading rate and pre-load force, and the results show that this equation can depict the trend of the experimental data.

The prediction of rotor rotational noise using measured fluctuating blade loads

NASA Technical Reports Server (NTRS)

Hosier, R. N.; Pegg, R. J.; Ramakrishnan, R.

1974-01-01

In tests conducted at the NASA Langley Research Center Helicopter Rotor Test Facility, simultaneous measurements of the high-frequency fluctuating aerodynamic blade loads and far-field radiated noise were made on a full-scale, nontranslating rotor system. After their characteristics were determined, the measured blade loads were used in an existing theory to predict the far-field rotational noise. A comparison of the calculated and measured rotational noise is presented with specific attention given to the effect of blade loading coefficients, chordwise loading distributions, blade loading phases, and observer azimuthal position on the predictions.

Association of Post-Saline Load Plasma Aldosterone Levels With Left Ventricular Hypertrophy in Primary Hypertension.

PubMed

Catena, Cristiana; Verheyen, Nicolas D; Url-Michitsch, Marion; Kraigher-Krainer, Elisabeth; Colussi, GianLuca; Pilz, Stefan; Tomaschitz, Andreas; Pieske, Burkert; Sechi, Leonardo A

2016-03-01

Left ventricular hypertrophy (LVH) is an independent risk factor for cardiovascular morbidity in hypertension. Current evidence suggests a contribution to LVH of plasma aldosterone levels that are inappropriately elevated for the salt status. The aim of this study was to investigate whether inappropriate modulation of aldosterone production by a saline load is associated with left ventricular (LV) mass in hypertensive patients. In 90 hypertensive patients free of clinically relevant cardiovascular complications in whom secondary forms of hypertension were ruled out, we performed a standard intravenous saline load (0.9% NaCl, 2 l in 4 hours) with measurement of plasma aldosterone and active renin at baseline and end of infusion. Bi-dimensional echocardiography was performed for the assessment of cardiac morphology and function. LVH was present in 19% of patients who had significantly worse renal function and higher body mass, blood pressure, and plasma aldosterone levels measured both at baseline and after the saline load than patients without LVH. LV mass was directly related to age, body mass, systolic blood pressure, duration of hypertension, baseline, and post-saline load plasma aldosterone levels and inversely to glomerular filtration. Multivariate regression analysis showed independent correlation of LV mass with body mass, systolic blood pressure, and plasma aldosterone levels measured after intravenous saline load, but not at baseline. In patients with hypertension, aldosterone levels measured after intravenous saline load are related to LV mass independent of age, body mass, and blood pressure, suggesting that limited ability of salt to modulate aldosterone production could contribute to LVH. © American Journal of Hypertension, Ltd 2015. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Shake Test Results and Dynamic Calibration Efforts for the Large Rotor Test Apparatus

NASA Technical Reports Server (NTRS)

Russell, Carl R.

2014-01-01

A shake test of the Large Rotor Test Apparatus (LRTA) was performed in an effort to enhance NASAscapability to measure dynamic hub loads for full-scale rotor tests. This paper documents the results of theshake test as well as efforts to calibrate the LRTA balance system to measure dynamic loads.Dynamic rotor loads are the primary source of vibration in helicopters and other rotorcraft, leading topassenger discomfort and damage due to fatigue of aircraft components. There are novel methods beingdeveloped to reduce rotor vibrations, but measuring the actual vibration reductions on full-scale rotorsremains a challenge. In order to measure rotor forces on the LRTA, a balance system in the non-rotatingframe is used. The forces at the balance can then be translated to the hub reference frame to measure therotor loads. Because the LRTA has its own dynamic response, the balance system must be calibrated toinclude the natural frequencies of the test rig.

Preconditioning of mesenchymal stromal cells toward nucleus pulposus-like cells by microcryogels-based 3D cell culture and syringe-based pressure loading system.

PubMed

Zeng, Yang; Feng, Siyu; Liu, Wei; Fu, Qinyouen; Li, Yaqian; Li, Xiaokang; Chen, Chun; Huang, Chenyu; Ge, Zigang; Du, Yanan

2017-04-01

To precondition mesenchymal stromal/stem cells (MSCs) with mechanical stimulation may enhance cell survival and functions following implantation in load bearing environment such as nucleus pulposus (NP) in intervertebral disc (IVD). In this study, preconditioning of MSCs toward NP-like cells was achieved in previously developed poly (ethylene glycol) diacrylate (PEGDA) microcryogels (PMs) within a syringe-based three-dimensional (3D) culture system which provided a facile and cost-effective pressure loading approach. PMs loaded with alginate and MSCs could be incubated in a sealable syringe which could be air-compressed to apply pressure loading through a programmable syringe pump. Expression levels of chondrogenic marker genes SOX9, COL II, and ACAN were significantly upregulated in MSCs when pressure loading of 0.2 MPa or 0.8 MPa was implemented. Expression levels of COL I and COL X were downregulated when pressure loading was applied. In a nude mouse model, MSCs loaded in PMs mechanically stimulated for three days were subcutaneously injected using the same culture syringe. Three weeks postinjection, more proteoglycans (PGs) were deposited and more SOX9 and COL II but less COL I and COL X were stained in 0.2 MPa group. Furthermore, injectable MSCs-loaded PMs were utilized in an ex vivo rabbit IVD organ culture model that demonstrated the leak-proof function and enhanced cell retention of PMs assisted cell delivery to a load bearing environment for potential NP regeneration. This microcryogels-based 3D cell culture and syringe-based pressure loading system represents a novel method for 3D cell culture with mechanical stimulation for better function. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 507-520, 2017. © 2015 Wiley Periodicals, Inc.

Nonplanar wing load-line and slender wing theory

NASA Technical Reports Server (NTRS)

Deyoung, J.

1977-01-01

Nonplanar load line, slender wing, elliptic wing, and infinite aspect ratio limit loading theories are developed. These are quasi two dimensional theories but satisfy wing boundary conditions at all points along the nonplanar spanwise extent of the wing. These methods are applicable for generalized configurations such as the laterally nonplanar wing, multiple nonplanar wings, or wing with multiple winglets of arbitrary shape. Two dimensional theory infers simplicity which is practical when analyzing complicated configurations. The lateral spanwise distribution of angle of attack can be that due to winglet or control surface deflection, wing twist, or induced angles due to multiwings, multiwinglets, ground, walls, jet or fuselage. In quasi two dimensional theory the induced angles due to these extra conditions are likewise determined for two dimensional flow. Equations are developed for the normal to surface induced velocity due to a nonplanar trailing vorticity distribution. Application examples are made using these methods.

Modeling of Permeability Structure Using Pore Pressure and Borehole Strain Monitoring

NASA Astrophysics Data System (ADS)

Kano, Y.; Ito, H.

2011-12-01

Hydraulic or transport property, especially permeability, of the rock affect the behavior of the fault during earthquake rupture and also interseismic period. The methods to determine permeability underground are hydraulic test utilizing borehole and packer or core measurement in laboratory. Another way to know the permeability around a borehole is to examine responses of pore pressure to natural loading such as barometric pressure change at surface or earth tides. Using response to natural deformation is conventional method for water resource research. The scale of measurement is different among in-situ hydraulic test, response method, and core measurement. It is not clear that the relationship between permeability values form each method for an inhomogeneous medium such as a fault zone. Supposing the measurement of the response to natural loading, we made a model calculation of permeability structure around a fault zone. The model is 2 dimensional and constructed with vertical high-permeability layer in uniform low-permeability zone. We assume the upper and lower boundaries are drained and no-flow condition. We calculated the flow and deformation of the model for step and cyclic loading by numerically solving a two-dimensional diffusion equation. The model calculation shows that the width of the high-permeability zone and contrast of the permeability between high- and low- permeability zones control the contribution of the low-permeability zone. We made a calculation with combinations of permeability and fault width to evaluate the sensitivity of the parameters to in-situ measurement of permeability. We applied the model calculation to the field results of in-situ packer test, and natural response of water level and strain monitoring carried out in the Kamioka mine. The model calculation shows that knowledge of permeability in host rock is also important to obtain permeability of fault zone itself. The model calculations help to design long-term pore pressure monitoring, in-situ hydraulic test, and core measurement using drill holes to better understand fault zone hydraulic properties.

Measurement of the internal stress and electric field in a resonating piezoelectric transformer for high-voltage applications using the electro-optic and photoelastic effects

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

VanGordon, James A.; Kovaleski, Scott D., E-mail: kovaleskis@missouri.edu; Norgard, Peter

The high output voltages from piezoelectric transformers are currently being used to accelerate charged particle beams for x-ray and neutron production. Traditional methods of characterizing piezoelectric transformers (PTs) using electrical probes can decrease the voltage transformation ratio of the device due to the introduction of load impedances on the order of hundreds of kiloohms to hundreds of megaohms. Consequently, an optical diagnostic was developed that used the photoelastic and electro-optic effects present in piezoelectric materials that are transparent to a given optical wavelength to determine the internal stress and electric field. The combined effects of the piezoelectric, photoelastic, and electro-opticmore » effects result in a time-dependent change the refractive indices of the material and produce an artificially induced, time-dependent birefringence in the piezoelectric material. This induced time-dependent birefringence results in a change in the relative phase difference between the ordinary and extraordinary wave components of a helium-neon laser beam. The change in phase difference between the wave components was measured using a set of linear polarizers. The measured change in phase difference was used to calculate the stress and electric field based on the nonlinear optical properties, the piezoelectric constitutive equations, and the boundary conditions of the PT. Maximum stresses of approximately 10 MPa and electric fields of as high as 6 kV/cm were measured with the optical diagnostic. Measured results were compared to results from both a simple one-dimensional (1D) model of the piezoelectric transformer and a three-dimensional (3D) finite element model. Measured stresses and electric fields along the length of an operating length-extensional PT for two different electrical loads were within at least 50 % of 3D finite element simulated results. Additionally, the 3D finite element results were more accurate than the results from the 1D model for a wider range of electrical load impedances under test.« less

Measurement of the internal stress and electric field in a resonating piezoelectric transformer for high-voltage applications using the electro-optic and photoelastic effects.

PubMed

VanGordon, James A; Kovaleski, Scott D; Norgard, Peter; Gall, Brady B; Dale, Gregory E

2014-02-01

The high output voltages from piezoelectric transformers are currently being used to accelerate charged particle beams for x-ray and neutron production. Traditional methods of characterizing piezoelectric transformers (PTs) using electrical probes can decrease the voltage transformation ratio of the device due to the introduction of load impedances on the order of hundreds of kiloohms to hundreds of megaohms. Consequently, an optical diagnostic was developed that used the photoelastic and electro-optic effects present in piezoelectric materials that are transparent to a given optical wavelength to determine the internal stress and electric field. The combined effects of the piezoelectric, photoelastic, and electro-optic effects result in a time-dependent change the refractive indices of the material and produce an artificially induced, time-dependent birefringence in the piezoelectric material. This induced time-dependent birefringence results in a change in the relative phase difference between the ordinary and extraordinary wave components of a helium-neon laser beam. The change in phase difference between the wave components was measured using a set of linear polarizers. The measured change in phase difference was used to calculate the stress and electric field based on the nonlinear optical properties, the piezoelectric constitutive equations, and the boundary conditions of the PT. Maximum stresses of approximately 10 MPa and electric fields of as high as 6 kV/cm were measured with the optical diagnostic. Measured results were compared to results from both a simple one-dimensional (1D) model of the piezoelectric transformer and a three-dimensional (3D) finite element model. Measured stresses and electric fields along the length of an operating length-extensional PT for two different electrical loads were within at least 50 % of 3D finite element simulated results. Additionally, the 3D finite element results were more accurate than the results from the 1D model for a wider range of electrical load impedances under test.

Comparative Study of 3-Dimensional Woven Joint Architectures for Composite Spacecraft Structures

NASA Technical Reports Server (NTRS)

Jones, Justin S.; Polis, Daniel L.; Rowles, Russell R.; Segal, Kenneth N.

2011-01-01

The National Aeronautics and Space Administration (NASA) Exploration Systems Mission Directorate initiated an Advanced Composite Technology (ACT) Project through the Exploration Technology Development Program in order to support the polymer composite needs for future heavy lift launch architectures. As an example, the large composite structural applications on Ares V inspired the evaluation of advanced joining technologies, specifically 3D woven composite joints, which could be applied to segmented barrel structures needed for autoclave cured barrel segments due to autoclave size constraints. Implementation of these 3D woven joint technologies may offer enhancements in damage tolerance without sacrificing weight. However, baseline mechanical performance data is needed to properly analyze the joint stresses and subsequently design/down-select a preform architecture. Six different configurations were designed and prepared for this study; each consisting of a different combination of warp/fill fiber volume ratio and preform interlocking method (Z-fiber, fully interlocked, or hybrid). Tensile testing was performed for this study with the enhancement of a dual camera Digital Image Correlation (DIC) system which provides the capability to measure full-field strains and three dimensional displacements of objects under load. As expected, the ratio of warp/fill fiber has a direct influence on strength and modulus, with higher values measured in the direction of higher fiber volume bias. When comparing the Z-fiber weave to a fully interlocked weave with comparable fiber bias, the Z-fiber weave demonstrated the best performance in two different comparisons. We report the measured tensile strengths and moduli for test coupons from the 6 different weave configurations under study.

On the impact of multi-axial stress states on trailing edge bondlines in wind turbine rotor blades

NASA Astrophysics Data System (ADS)

Noever Castelos, Pablo; Balzani, Claudio

2016-09-01

For a reliable design of wind turbine systems all of their components have to be designed to withstand the loads appearing in the turbine's lifetime. When performed in an integral manner this is called systems engineering, and is exceptionally important for components that have an impact on the entire wind turbine system, such as the rotor blade. Bondlines are crucial subcomponents of rotor blades, but they are not much recognized in the wind energy research community. However, a bondline failure can lead to the loss of a rotor blade, and potentially of the entire turbine, and is extraordinarily relevant to be treated with strong emphasis when designing a wind turbine. Modern wind turbine rotor blades with lengths of 80 m and more offer a degree of flexibility that has never been seen in wind energy technology before. Large deflections result in high strains in the adhesive connections, especially at the trailing edge. The latest edition of the DNV GL guideline from end of 2015 demands a three-dimensional stress analysis of bondlines, whereas before an isolated shear stress proof was sufficient. In order to quantify the lack of safety from older certification guidelines this paper studies the influence of multi-axial stress states on the ultimate and fatigue load resistance of trailing edge adhesive bonds. For this purpose, detailed finite element simulations of the IWES IWT-7.5-164 reference wind turbine blades are performed. Different yield criteria are evaluated for the prediction of failure and lifetime. The results show that the multi-axial stress state is governed by span-wise normal stresses. Those are evidently not captured in isolated shear stress proofs, yielding non-conservative estimates of lifetime and ultimate load resistance. This finding highlights the importance to include a three-dimensional stress state in the failure analysis of adhesive bonds in modern wind turbine rotor blades, and the necessity to perform a three-dimensional characterization of adhesive materials.

NASA Tech Briefs, February 2005

NASA Technical Reports Server (NTRS)

2005-01-01

Topics discussed include: Instrumentation for Sensitive Gas Measurements; Apparatus for Testing Flat Specimens of Thermal Insulation; Quadrupole Ion Mass Spectrometer for Masses of 2 to 50 Da; Miniature Laser Doppler Velocimeter for Measuring Wall Shear; Coherent Laser Instrument Would Measure Range and Velocity; Printed Microinductors for Flexible Substrates; Digital Receiver for Microwave Radiometry; Printed Antennas Made Reconfigurable by Use of MEMS Switches; Traffic-Light-Preemption Vehicle-Transponder Software Module; Intersection-Controller Software Module; Central-Monitor Software Module; Estimating Effects of Multipath Propagation on GPS Signals; Parallel Adaptive Mesh Refinement Library; Predicting Noise From Aircraft Turbine-Engine Combustors; Generating Animated Displays of Spacecraft Orbits; Diagnosis and Prognosis of Weapon Systems; Training Software in Artificial-Intelligence Computing Techniques; APGEN Version 5.0; Single-Command Approach and Instrument Placement by a Robot on a Target; Three-Dimensional Audio Client Library; Isogrid Membranes for Precise, Singly Curved Reflectors; Nickel-Tin Electrode Materials for Nonaqueous Li-Ion Cells; Photocatalytic Coats in Glass Drinking-Water Bottles; Fast Laser Shutters With Low Vibratory Disturbances; Series-Connected Buck Boost Regulators; Space Physics Data Facility Web Services; Split-Resonator, Integrated-Post Vibratory Microgyroscope; Blended Buffet-Load-Alleviation System for Fighter Airplane; Gifford-McMahon/Joule-Thomson Refrigerator Cools to 2.5 K; High-Temperature, High-Load-Capacity Radial Magnetic Bearing; Fabrication of Spherical Reflectors in Outer Space; Automated Rapid Prototyping of 3D Ceramic Parts; Tissue Engineering Using Transfected Growth-Factor Genes; Automation of Vapor-Diffusion Growth of Protein Crystals; Atom Skimmers and Atom Lasers Utilizing Them; Gears Based on Carbon Nanotubes; Patched Off-Axis Bending/Twisting Actuators for Thin Mirrors; and Improving Control in a Joule-Thomson Refrigerator.

Collaborated measurement of three-dimensional position and orientation errors of assembled miniature devices with two vision systems

NASA Astrophysics Data System (ADS)

Wang, Xiaodong; Zhang, Wei; Luo, Yi; Yang, Weimin; Chen, Liang

2013-01-01

In assembly of miniature devices, the position and orientation of the parts to be assembled should be guaranteed during or after assembly. In some cases, the relative position or orientation errors among the parts can not be measured from only one direction using visual method, because of visual occlusion or for the features of parts located in a three-dimensional way. An automatic assembly system for precise miniature devices is introduced. In the modular assembly system, two machine vision systems were employed for measurement of the three-dimensionally distributed assembly errors. High resolution CCD cameras and high position repeatability precision stages were integrated to realize high precision measurement in large work space. The two cameras worked in collaboration in measurement procedure to eliminate the influence of movement errors of the rotational or translational stages. A set of templates were designed for calibration of the vision systems and evaluation of the system's measurement accuracy.

Load Asymmetry Observed During Orion Main Parachute Inflation

NASA Technical Reports Server (NTRS)

Morris, Aaron L.; Taylor, Thomas; Olson, Leah

2011-01-01

The Crew Exploration Vehicle Parachute Assembly System (CPAS) has flight tested the first two generations of the Orion parachute program. Three of the second generation tests instrumented the dispersion bridles of the Main parachute with a Tension Measuring System. The goal of this load measurement was to better understand load asymmetry during the inflation process of a cluster of Main parachutes. The CPAS Main parachutes exhibit inflations that are much less symmetric than current parachute literature and design guides would indicate. This paper will examine loads data gathered on three cluster tests, quantify the degree of asymmetry observed, and contrast the results with published design guides. Additionally, the measured loads data will be correlated with videos of the parachute inflation to make inferences about the shape of the parachute and the relative load asymmetry. The goal of this inquiry and test program is to open a dialogue regarding asymmetrical parachute inflation load factors.

Position Between Trunk and Pelvis During Gait Depending on the Gross Motor Function Classification System.

PubMed

Sanz-Mengibar, Jose Manuel; Altschuck, Natalie; Sanchez-de-Muniain, Paloma; Bauer, Christian; Santonja-Medina, Fernando

2017-04-01

To understand whether there is a trunk postural control threshold in the sagittal plane for the transition between the Gross Motor Function Classification System (GMFCS) levels measured with 3-dimensional gait analysis. Kinematics from 97 children with spastic bilateral cerebral palsy from spine angles according to Plug-In Gait model (Vicon) were plotted relative to their GMFCS level. Only average and minimum values of the lumbar spine segment correlated with GMFCS levels. Maximal values at loading response correlated independently with age at all functional levels. Average and minimum values were significant when analyzing age in combination with GMFCS level. There are specific postural control patterns in the average and minimum values for the position between trunk and pelvis in the sagittal plane during gait, for the transition among GMFCS I-III levels. Higher classifications of gross motor skills correlate with more extended spine angles.

Development and validation of a computational model of the knee joint for the evaluation of surgical treatments for osteoarthritis

PubMed Central

Mootanah, R.; Imhauser, C.W.; Reisse, F.; Carpanen, D.; Walker, R.W.; Koff, M.F.; Lenhoff, M.W.; Rozbruch, S.R.; Fragomen, A.T.; Dewan, Z.; Kirane, Y.M.; Cheah, Pamela A.; Dowell, J.K.; Hillstrom, H.J.

2014-01-01

A three-dimensional (3D) knee joint computational model was developed and validated to predict knee joint contact forces and pressures for different degrees of malalignment. A 3D computational knee model was created from high-resolution radiological images to emulate passive sagittal rotation (full-extension to 65°-flexion) and weight acceptance. A cadaveric knee mounted on a six-degree-of-freedom robot was subjected to matching boundary and loading conditions. A ligament-tuning process minimised kinematic differences between the robotically loaded cadaver specimen and the finite element (FE) model. The model was validated by measured intra-articular force and pressure measurements. Percent full scale error between EE-predicted and in vitro-measured values in the medial and lateral compartments were 6.67% and 5.94%, respectively, for normalised peak pressure values, and 7.56% and 4.48%, respectively, for normalised force values. The knee model can accurately predict normalised intra-articular pressure and forces for different loading conditions and could be further developed for subject-specific surgical planning. PMID:24786914

Development and validation of a computational model of the knee joint for the evaluation of surgical treatments for osteoarthritis.

PubMed

Mootanah, R; Imhauser, C W; Reisse, F; Carpanen, D; Walker, R W; Koff, M F; Lenhoff, M W; Rozbruch, S R; Fragomen, A T; Dewan, Z; Kirane, Y M; Cheah, K; Dowell, J K; Hillstrom, H J

2014-01-01

A three-dimensional (3D) knee joint computational model was developed and validated to predict knee joint contact forces and pressures for different degrees of malalignment. A 3D computational knee model was created from high-resolution radiological images to emulate passive sagittal rotation (full-extension to 65°-flexion) and weight acceptance. A cadaveric knee mounted on a six-degree-of-freedom robot was subjected to matching boundary and loading conditions. A ligament-tuning process minimised kinematic differences between the robotically loaded cadaver specimen and the finite element (FE) model. The model was validated by measured intra-articular force and pressure measurements. Percent full scale error between FE-predicted and in vitro-measured values in the medial and lateral compartments were 6.67% and 5.94%, respectively, for normalised peak pressure values, and 7.56% and 4.48%, respectively, for normalised force values. The knee model can accurately predict normalised intra-articular pressure and forces for different loading conditions and could be further developed for subject-specific surgical planning.

Quantifying entrainment in pyroclastic density currents from the Tungurahua eruption, Ecuador: Integrating field proxies with numerical simulations

NASA Astrophysics Data System (ADS)

Benage, M. C.; Dufek, J.; Mothes, P. A.

2016-07-01

The entrainment of air into pyroclastic density currents (PDCs) impacts the dynamics and thermal history of these highly mobile currents. However, direct measurement of entrainment in PDCs is hampered due to hazardous conditions and opaqueness of these flows. We combine three-dimensional multiphase Eulerian-Eulerian-Lagrangian calculations with proxies of thermal conditions preserved in deposits to quantify air entrainment in PDCs at Tungurahua volcano, Ecuador. We conclude that small-volume PDCs develop a particle concentration gradient that results in disparate thermal characteristics for the concentrated bed load (>600 to ~800 K) and the overlying dilute suspended load (~300-600 K). The dilute suspended load has effective entrainment coefficients 2-3 times larger than the bed load. This investigation reveals a dichotomy in entrainment and thermal history between two regions in the current and provides a mechanism to interpret the depositional thermal characteristics of small-volume but frequently occurring PDCs.

Sonic-boom-induced building structure responses including damage.

NASA Technical Reports Server (NTRS)

Clarkson, B. L.; Mayes, W. H.

1972-01-01

Concepts of sonic-boom pressure loading of building structures and the associated responses are reviewed, and results of pertinent theoretical and experimental research programs are summarized. The significance of sonic-boom load time histories, including waveshape effects, are illustrated with the aid of simple structural elements such as beams and plates. Also included are discussions of the significance of such other phenomena as three-dimensional loading effects, air cavity coupling, multimodal responses, and structural nonlinearities. Measured deflection, acceleration, and strain data from laboratory models and full-scale building tests are summarized, and these data are compared, where possible, with predicted values. Damage complaint and claim experience due both to controlled and uncontrolled supersonic flights over communities are summarized with particular reference to residential, commercial, and historic buildings. Sonic-boom-induced building responses are compared with those from other impulsive loadings due to natural and cultural events and from laboratory simulation tests.

Three-Dimensional Root Phenotyping with a Novel Imaging and Software Platform1[C][W][OA

PubMed Central

Clark, Randy T.; MacCurdy, Robert B.; Jung, Janelle K.; Shaff, Jon E.; McCouch, Susan R.; Aneshansley, Daniel J.; Kochian, Leon V.

2011-01-01

A novel imaging and software platform was developed for the high-throughput phenotyping of three-dimensional root traits during seedling development. To demonstrate the platform’s capacity, plants of two rice (Oryza sativa) genotypes, Azucena and IR64, were grown in a transparent gellan gum system and imaged daily for 10 d. Rotational image sequences consisting of 40 two-dimensional images were captured using an optically corrected digital imaging system. Three-dimensional root reconstructions were generated and analyzed using a custom-designed software, RootReader3D. Using the automated and interactive capabilities of RootReader3D, five rice root types were classified and 27 phenotypic root traits were measured to characterize these two genotypes. Where possible, measurements from the three-dimensional platform were validated and were highly correlated with conventional two-dimensional measurements. When comparing gellan gum-grown plants with those grown under hydroponic and sand culture, significant differences were detected in morphological root traits (P < 0.05). This highly flexible platform provides the capacity to measure root traits with a high degree of spatial and temporal resolution and will facilitate novel investigations into the development of entire root systems or selected components of root systems. In combination with the extensive genetic resources that are now available, this platform will be a powerful resource to further explore the molecular and genetic determinants of root system architecture. PMID:21454799

Prediction of equibiaxial loading stress in collagen-based extracellular matrix using a three-dimensional unit cell model.

PubMed

Susilo, Monica E; Bell, Brett J; Roeder, Blayne A; Voytik-Harbin, Sherry L; Kokini, Klod; Nauman, Eric A

2013-03-01

Mechanical signals are important factors in determining cell fate. Therefore, insights as to how mechanical signals are transferred between the cell and its surrounding three-dimensional collagen fibril network will provide a basis for designing the optimum extracellular matrix (ECM) microenvironment for tissue regeneration. Previously we described a cellular solid model to predict fibril microstructure-mechanical relationships of reconstituted collagen matrices due to unidirectional loads (Acta Biomater 2010;6:1471-86). The model consisted of representative volume elements made up of an interconnected network of flexible struts. The present study extends this work by adapting the model to account for microstructural anisotropy of the collagen fibrils and a biaxial loading environment. The model was calibrated based on uniaxial tensile data and used to predict the equibiaxial tensile stress-stretch relationship. Modifications to the model significantly improved its predictive capacity for equibiaxial loading data. With a comparable fibril length (model 5.9-8μm, measured 7.5μm) and appropriate fibril anisotropy the anisotropic model provides a better representation of the collagen fibril microstructure. Such models are important tools for tissue engineering because they facilitate prediction of microstructure-mechanical relationships for collagen matrices over a wide range of microstructures and provide a framework for predicting cell-ECM interactions. Copyright © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Test and Analysis of Sub-Components of Aluminum-Lithium Alloy Cylinders

NASA Technical Reports Server (NTRS)

Haynie, Waddy T.; Chunchu, Prasad B.; Satyanarayana, Arunkumar; Hilburger, Mark W.; Smith, Russell W.

2012-01-01

Integrally machined blade-stiffened panels subjected to an axial compressive load were tested and analyzed to observe the buckling, crippling, and postcrippling response of the panels. The panels were fabricated from aluminum-lithium alloys 2195 and 2050, and both alloys have reduced material properties in the short transverse material direction. The tests were designed to capture a failure mode characterized by the stiffener separating from the panel in the postbuckling range. This failure mode is attributed to the reduced properties in the short transverse direction. Full-field measurements of displacements and strains using three-dimensional digital image correlation systems and local measurements using strain gages were used to capture the deformation of the panel leading up to the failure of the panel for specimens fabricated from 2195. High-speed cameras were used to capture the initiation of the failure. Finite element models were developed using an isotropic strain-hardening material model. Good agreement was observed between the measured and predicted responses for both alloys.

Length and Dimensional Measurements at NIST

PubMed Central

Swyt, Dennis A.

2001-01-01

This paper discusses the past, present, and future of length and dimensional measurements at NIST. It covers the evolution of the SI unit of length through its three definitions and the evolution of NBS-NIST dimensional measurement from early linescales and gage blocks to a future of atom-based dimensional standards. Current capabilities include dimensional measurements over a range of fourteen orders of magnitude. Uncertainties of measurements on different types of material artifacts range down to 7×10−8 m at 1 m and 8 picometers (pm) at 300 pm. Current work deals with a broad range of areas of dimensional metrology. These include: large-scale coordinate systems; complex form; microform; surface finish; two-dimensional grids; optical, scanning-electron, atomic-force, and scanning-tunneling microscopies; atomic-scale displacement; and atom-based artifacts. PMID:27500015

Observable measure of quantum coherence in finite dimensional systems.

PubMed

Girolami, Davide

2014-10-24

Quantum coherence is the key resource for quantum technology, with applications in quantum optics, information processing, metrology, and cryptography. Yet, there is no universally efficient method for quantifying coherence either in theoretical or in experimental practice. I introduce a framework for measuring quantum coherence in finite dimensional systems. I define a theoretical measure which satisfies the reliability criteria established in the context of quantum resource theories. Then, I present an experimental scheme implementable with current technology which evaluates the quantum coherence of an unknown state of a d-dimensional system by performing two programmable measurements on an ancillary qubit, in place of the O(d2) direct measurements required by full state reconstruction. The result yields a benchmark for monitoring quantum effects in complex systems, e.g., certifying nonclassicality in quantum protocols and probing the quantum behavior of biological complexes.

40 CFR 92.116 - Engine output measurement system calibrations.

Code of Federal Regulations, 2010 CFR

2010-07-01

... spaced torque values as indicated by the master load-cell for each in-use range used. (v) The in-use torque measurement must be within 2 percent of the torque measured by the master system for each load... the calibration equipment described in this section. (2) The engine flywheel torque feedback signals...

One dimensional wavefront distortion sensor comprising a lens array system

DOEpatents

Neal, Daniel R.; Michie, Robert B.

1996-01-01

A 1-dimensional sensor for measuring wavefront distortion of a light beam as a function of time and spatial position includes a lens system which incorporates a linear array of lenses, and a detector system which incorporates a linear array of light detectors positioned from the lens system so that light passing through any of the lenses is focused on at least one of the light detectors. The 1-dimensional sensor determines the slope of the wavefront by location of the detectors illuminated by the light. The 1 dimensional sensor has much greater bandwidth that 2 dimensional systems.

One dimensional wavefront distortion sensor comprising a lens array system

DOEpatents

Neal, D.R.; Michie, R.B.

1996-02-20

A 1-dimensional sensor for measuring wavefront distortion of a light beam as a function of time and spatial position includes a lens system which incorporates a linear array of lenses, and a detector system which incorporates a linear array of light detectors positioned from the lens system so that light passing through any of the lenses is focused on at least one of the light detectors. The 1-dimensional sensor determines the slope of the wavefront by location of the detectors illuminated by the light. The 1 dimensional sensor has much greater bandwidth that 2 dimensional systems. 8 figs.

Analysis of Ninety Degree Flexure Tests for Characterization of Composite Transverse Tensile Strength

NASA Technical Reports Server (NTRS)

OBrien, T. Kevin; Krueger, Ronald

2001-01-01

Finite element (FE) analysis was performed on 3-point and 4-point bending test configurations of ninety degree oriented glass-epoxy and graphite-epoxy composite beams to identify deviations from beam theory predictions. Both linear and geometric non-linear analyses were performed using the ABAQUS finite element code. The 3-point and 4-point bending specimens were first modeled with two-dimensional elements. Three-dimensional finite element models were then performed for selected 4-point bending configurations to study the stress distribution across the width of the specimens and compare the results to the stresses computed from two-dimensional plane strain and plane stress analyses and the stresses from beam theory. Stresses for all configurations were analyzed at load levels corresponding to the measured transverse tensile strength of the material.

Deflection-Based Aircraft Structural Loads Estimation with Comparison to Flight

NASA Technical Reports Server (NTRS)

Lizotte, Andrew M.; Lokos, William A.

2005-01-01

Traditional techniques in structural load measurement entail the correlation of a known load with strain-gage output from the individual components of a structure or machine. The use of strain gages has proved successful and is considered the standard approach for load measurement. However, remotely measuring aerodynamic loads using deflection measurement systems to determine aeroelastic deformation as a substitute to strain gages may yield lower testing costs while improving aircraft performance through reduced instrumentation weight. With a reliable strain and structural deformation measurement system this technique was examined. The objective of this study was to explore the utility of a deflection-based load estimation, using the active aeroelastic wing F/A-18 aircraft. Calibration data from ground tests performed on the aircraft were used to derive left wing-root and wing-fold bending-moment and torque load equations based on strain gages, however, for this study, point deflections were used to derive deflection-based load equations. Comparisons between the strain-gage and deflection-based methods are presented. Flight data from the phase-1 active aeroelastic wing flight program were used to validate the deflection-based load estimation method. Flight validation revealed a strong bending-moment correlation and slightly weaker torque correlation. Development of current techniques, and future studies are discussed.

Deflection-Based Structural Loads Estimation From the Active Aeroelastic Wing F/A-18 Aircraft

NASA Technical Reports Server (NTRS)

Lizotte, Andrew M.; Lokos, William A.

2005-01-01

Traditional techniques in structural load measurement entail the correlation of a known load with strain-gage output from the individual components of a structure or machine. The use of strain gages has proved successful and is considered the standard approach for load measurement. However, remotely measuring aerodynamic loads using deflection measurement systems to determine aeroelastic deformation as a substitute to strain gages may yield lower testing costs while improving aircraft performance through reduced instrumentation weight. This technique was examined using a reliable strain and structural deformation measurement system. The objective of this study was to explore the utility of a deflection-based load estimation, using the active aeroelastic wing F/A-18 aircraft. Calibration data from ground tests performed on the aircraft were used to derive left wing-root and wing-fold bending-moment and torque load equations based on strain gages, however, for this study, point deflections were used to derive deflection-based load equations. Comparisons between the strain-gage and deflection-based methods are presented. Flight data from the phase-1 active aeroelastic wing flight program were used to validate the deflection-based load estimation method. Flight validation revealed a strong bending-moment correlation and slightly weaker torque correlation. Development of current techniques, and future studies are discussed.

Edge delamination of composite laminates subject to combined tension and torsional loading

NASA Technical Reports Server (NTRS)

Hooper, Steven J.

1990-01-01

Delamination is a common failure mode of laminated composite materials. Edge delamination is important since it results in reduced stiffness and strength of the laminate. The tension/torsion load condition is of particular significance to the structural integrity of composite helicopter rotor systems. Material coupons can easily be tested under this type of loading in servo-hydraulic tension/torsion test stands using techniques very similar to those used for the Edge Delamination Tensile Test (EDT) delamination specimen. Edge delamination of specimens loaded in tension was successfully analyzed by several investigators using both classical laminate theory and quasi-three dimensional (Q3D) finite element techniques. The former analysis technique can be used to predict the total strain energy release rate, while the latter technique enables the calculation of the mixed-mode strain energy release rates. The Q3D analysis is very efficient since it produces a three-dimensional solution to a two-dimensional domain. A computer program was developed which generates PATRAN commands to generate the finite element model. PATRAN is a pre- and post-processor which is commonly used with a variety of finite element programs such as MCS/NASTRAN. The program creates a sufficiently dense mesh at the delamination crack tips to support a mixed-mode fracture mechanics analysis. The program creates a coarse mesh in those regions where the gradients in the stress field are low (away from the delamination regions). A transition mesh is defined between these regions. This program is capable of generating a mesh for an arbitrarily oriented matrix crack. This program significantly reduces the modeling time required to generate these finite element meshes, thus providing a realistic tool with which to investigate the tension torsion problem.

C-shaped specimen plane strain fracture toughness tests. [metallic materials

NASA Technical Reports Server (NTRS)

Buzzard, R. T.; Fisher, D. M.

1977-01-01

Test equipment, procedures, and data obtained in the evaluation of C-shaped specimens are presented. Observations reported on include: specimen preparation and dimensional measurement; modifications to the standard ASTM E 399 displacement gage, which permit punch mark gage point engagement; and a measurement device for determining the interior and exterior radii of ring segments. Load displacement ratios were determined experimentally which agreed with analytically determined coefficients for three different gage lengths on the inner surfaces of radially-cracked ring segments.

Multi-Dimensional Calibration of Impact Dynamic Models

NASA Technical Reports Server (NTRS)

Horta, Lucas G.; Reaves, Mercedes C.; Annett, Martin S.; Jackson, Karen E.

2011-01-01

NASA Langley, under the Subsonic Rotary Wing Program, recently completed two helicopter tests in support of an in-house effort to study crashworthiness. As part of this effort, work is on-going to investigate model calibration approaches and calibration metrics for impact dynamics models. Model calibration of impact dynamics problems has traditionally assessed model adequacy by comparing time histories from analytical predictions to test at only a few critical locations. Although this approach provides for a direct measure of the model predictive capability, overall system behavior is only qualitatively assessed using full vehicle animations. In order to understand the spatial and temporal relationships of impact loads as they migrate throughout the structure, a more quantitative approach is needed. In this work impact shapes derived from simulated time history data are used to recommend sensor placement and to assess model adequacy using time based metrics and orthogonality multi-dimensional metrics. An approach for model calibration is presented that includes metric definitions, uncertainty bounds, parameter sensitivity, and numerical optimization to estimate parameters to reconcile test with analysis. The process is illustrated using simulated experiment data.

Thermal Analysis on Cryogenic Liquid Hydrogen Tank on an Unmanned Aerial Vehicle System

NASA Technical Reports Server (NTRS)

Wang, Xiao-Yen; Harpster, George; Hunter, James

2007-01-01

Thermal analyses are performed on the liquid hydrogen (LH2) tank designed for an unmanned aerial vehicle (UAV) powered by solar arrays and a regenerative proton-exchange membrane (PEM) fuel cell. A 14-day cruise mission at a 65,000 ft altitude is considered. Thermal analysis provides the thermal loads on the tank system and the boiling-off rates of LH2. Different approaches are being considered to minimize the boiling-off rates of the LH2. It includes an evacuated multilayer insulation (MLI) versus aerogel insulation on the LH2 tank and aluminum versus stainless steel spacer rings between the inner and outer tank. The resulting boil-off rates of LH2 provided by the one-dimensional model and three-dimensional finite element analysis (FEA) on the tank system are presented and compared to validate the results of the three-dimensional FEA. It concludes that heat flux through penetrations by conduction is as significant as that through insulation around the tank. The tank system with MLI insulation and stainless steel spacer rings result in the lowest boiling-off rate of LH2.

Finite state modeling of aeroelastic systems

NASA Technical Reports Server (NTRS)

Vepa, R.

1977-01-01

A general theory of finite state modeling of aerodynamic loads on thin airfoils and lifting surfaces performing completely arbitrary, small, time-dependent motions in an airstream is developed and presented. The nature of the behavior of the unsteady airloads in the frequency domain is explained, using as raw materials any of the unsteady linearized theories that have been mechanized for simple harmonic oscillations. Each desired aerodynamic transfer function is approximated by means of an appropriate Pade approximant, that is, a rational function of finite degree polynomials in the Laplace transform variable. The modeling technique is applied to several two dimensional and three dimensional airfoils. Circular, elliptic, rectangular and tapered planforms are considered as examples. Identical functions are also obtained for control surfaces for two and three dimensional airfoils.

Comparing the influence of crestal cortical bone and sinus floor cortical bone in posterior maxilla bi-cortical dental implantation: a three-dimensional finite element analysis.

PubMed

Yan, Xu; Zhang, Xinwen; Chi, Weichao; Ai, Hongjun; Wu, Lin

2015-05-01

This study aimed to compare the influence of alveolar ridge cortical bone and sinus floor cortical bone in sinus areabi-cortical dental implantation by means of 3D finite element analysis. Three-dimensional finite element (FE) models in a posterior maxillary region with sinus membrane and the same height of alveolar ridge of 10 mm were generated according to the anatomical data of the sinus area. They were either with fixed thickness of crestal cortical bone and variable thickness of sinus floor cortical bone or vice versa. Ten models were assumed to be under immediate loading or conventional loading. The standard implant model based on the Nobel Biocare implant system was created via computer-aided design software. All materials were assumed to be isotropic and linearly elastic. An inclined force of 129 N was applied. Von Mises stress mainly concentrated on the surface of crestal cortical bone around the implant neck. For all the models, both the axial and buccolingual resonance frequencies of conventional loading were higher than those of immediate loading; however, the difference is less than 5%. The results showed that bi-cortical implant in sinus area increased the stability of the implant, especially for immediately loading implantation. The thickness of both crestal cortical bone and sinus floor cortical bone influenced implant micromotion and stress distribution; however, crestal cortical bone may be more important than sinus floor cortical bone.

Design of Raft Foundations for High-Rise Buildings on Jointed Rock

NASA Astrophysics Data System (ADS)

Justo, J. L.; García-Núñez, J.-C.; Vázquez-Boza, M.; Justo, E.; Durand, P.; Azañón, J. M.

2014-07-01

This paper presents calculations of displacements and bending moments in a 2-m-thick reinforced-concrete foundation slab using three-dimensional finite-element software. A preliminary paper was presented by Justo et al. (Rock Mech Rock Eng 43:287-304, 2010). The slab is the base of a tower of 137 m height above foundation, supported on jointed and partly weathered basalt and scoria. Installation of rod extensometers at different depths below foundation allowed comparison between measured displacements and displacements calculated using moduli obtained from rock classification systems and three material models: elastic, Mohr-Coulomb and hardening (H). Although all three material models can provide acceptable results, the H model is preferable when there are unloading processes. Acceptable values of settlement may be achieved with medium meshing and an approximate distribution of loads. The absolute values of negative bending moments (tensions below) increase as the rock mass modulus decreases or when the mesh is refined. The paper stresses the importance of adequately representing the details of the distribution of loads and the necessity for fine meshing to obtain acceptable values of bending moments.

Automated validation of a computer operating system

NASA Technical Reports Server (NTRS)

Dervage, M. M.; Milberg, B. A.

1970-01-01

Programs apply selected input/output loads to complex computer operating system and measure performance of that system under such loads. Technique lends itself to checkout of computer software designed to monitor automated complex industrial systems.

Characterization of Akiyama probe applied to dual-probes atomic force microscope

NASA Astrophysics Data System (ADS)

Wang, Hequn; Gao, Sitian; Li, Wei; Shi, Yushu; Li, Qi; Li, Shi; Zhu, Zhendong

2016-10-01

The measurement of nano-scale line-width has always been important and difficult in the field of nanometer measurements, while the rapid development of integrated circuit greatly raises the demand again. As one kind of scanning probe microscope (SPM), atomic force microscope (AFM) can realize quasi three-dimensional measurement, which is widely used in nanometer scale line-width measurement. Our team researched a dual-probes atomic force microscope, which can eliminate the prevalent effect of probe width on measurement results. In dual-probes AFM system, a novel head are newly designed. A kind of self-sensing and self-exciting probes which is Nanosensors cooperation's patented probe—Akiyama probe, is used in this novel head. The Akiyama probe applied to dual-probe atomic force microscope is one of the most important issues. The characterization of Akiyama probe would affect performance and accuracy of the whole system. The fundamental features of the Akiyama probe are electrically and optically characterized in "approach-withdraw" experiments. Further investigations include the frequency response of an Akiyama probe to small mechanical vibrations externally applied to the tip and the effective loading force yielding between the tip and the sample during the periodic contact. We hope that the characterization of the Akiyama probe described in this paper will guide application for dual-probe atomic force microscope.

Thermal and Structural Performance of Woven Carbon Cloth For Adaptive Deployable Entry and Placement Technology

NASA Technical Reports Server (NTRS)

Arnold, James O.; Peterson, Keith H.; Yount, Bryan C.; Schneider, Nigel; Chavez-Garcia, Jose

2013-01-01

Arcjet testing and analysis of a three-dimensional (3D) woven carbon fabric has shown that it can be used as a thermal protection system and as a load bearing structural component for a low ballistic coefficient hypersonic decelerator called ADEPT (Adaptive Deployable Entry and Placement Technology). Results of arcjet tests proved that the 3D woven carbon fabric can withstand flight-like heating while under flight-like biaxial mechanical loads representative of those encountered during shallow entry flight path angles into the atmosphere of Venus. Importantly, the arcjet test results have been used to extend a preliminary material thermal response model based on previous testing of the same 3D woven carbon fabric under uni-axial mechanical loading.

Studying Hardness Meter Spring Strength to Understand Hardness Distribution on Body Surfaces.

PubMed

Arima, Yoshitaka

2017-10-01

For developing a hardness multipoint measurement system for understanding hardness distribution on biological body surfaces, we investigated the spring strength of the contact portion main axis of a biological tissue hardness meter (product name: PEK). We measured the hardness of three-layered sheets of six types of gel sheets (90 mm × 60 mm × 6 mm) constituting the acupuncture practice pads, with PEK measurements of 1.96 N, 2.94 N, 3.92 N, 4.90 N, 5.88 N, 6.86 N, 7.84 N, 8.82 N, and 9.81 N of the main axis spring strength. We obtained measurements 10 times for the gel sheets and simultaneously measured the load using a digital scale. We measured the hardness distribution of induration embedded and breast cancer palpation models, with a main axis with 1.96 N, 4.90 N, and 9.81 N spring strengths, to create a two-dimensional Contour Fill Chart. Using 4.90 N spring strength, we could obtain measurement loads of ≤3.0 N, and the mean hardness was 5.14 mm. This was close to the median of the total measurement range 0.0-10.0 mm, making the measurement range the largest for this spring strength. We could image the induration of the induration-embedded model regardless of the spring strength. Overall, 4.90 N spring strength was best suited for imaging cancer in the breast cancer palpation model. Copyright © 2017. Published by Elsevier B.V.

Hamstrings Stiffness and Landing Biomechanics Linked to Anterior Cruciate Ligament Loading

PubMed Central

Blackburn, J. Troy; Norcross, Marc F.; Cannon, Lindsey N.; Zinder, Steven M.

2013-01-01

Context: Greater hamstrings stiffness is associated with less anterior tibial translation during controlled perturbations. However, it is unclear how hamstrings stiffness influences anterior cruciate ligament (ACL) loading mechanisms during dynamic tasks. Objective: To evaluate the influence of hamstrings stiffness on landing biomechanics related to ACL injury. Design: Cross-sectional study. Setting: Research laboratory. Patients or Other Participants: A total of 36 healthy, physically active volunteers (18 men, 18 women; age = 23 ± 3 years, height = 1.8 ± 0.1 m, mass = 73.1 ± 16.6 kg). Intervention(s): Hamstrings stiffness was quantified via the damped oscillatory technique. Three-dimensional lower extremity kinematics and kinetics were captured during a double-legged jump-landing task via a 3-dimensional motion-capture system interfaced with a force plate. Landing biomechanics were compared between groups displaying high and low hamstrings stiffness via independent-samples t tests. Main Outcome Measure(s): Hamstrings stiffness was normalized to body mass (N/m·kg−1). Peak knee-flexion and -valgus angles, vertical and posterior ground reaction forces, anterior tibial shear force, internal knee-extension and -varus moments, and knee-flexion angles at the instants of each peak kinetic variable were identified during the landing task. Forces were normalized to body weight, whereas moments were normalized to the product of weight and height. Results: Internal knee-varus moment was 3.6 times smaller in the high-stiffness group (t22 = 2.221, P = .02). A trend in the data also indicated that peak anterior tibial shear force was 1.1 times smaller in the high-stiffness group (t22 = 1.537, P = .07). The high-stiffness group also demonstrated greater knee flexion at the instants of peak anterior tibial shear force and internal knee-extension and -varus moments (t22 range = 1.729–2.224, P < .05). Conclusions: Greater hamstrings stiffness was associated with landing biomechanics consistent with less ACL loading and injury risk. Musculotendinous stiffness is a modifiable characteristic; thus exercises that enhance hamstrings stiffness may be important additions to ACL injury-prevention programs. PMID:24303987

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.

Server-based Approach to Web Visualization of Integrated Three-dimensional Brain Imaging Data

PubMed Central

Poliakov, Andrew V.; Albright, Evan; Hinshaw, Kevin P.; Corina, David P.; Ojemann, George; Martin, Richard F.; Brinkley, James F.

2005-01-01

The authors describe a client-server approach to three-dimensional (3-D) visualization of neuroimaging data, which enables researchers to visualize, manipulate, and analyze large brain imaging datasets over the Internet. All computationally intensive tasks are done by a graphics server that loads and processes image volumes and 3-D models, renders 3-D scenes, and sends the renderings back to the client. The authors discuss the system architecture and implementation and give several examples of client applications that allow visualization and analysis of integrated language map data from single and multiple patients. PMID:15561787

Development of a finite element based delamination analysis for laminates subject to extension, bending, and torsion

NASA Technical Reports Server (NTRS)

Hooper, Steven J.

1989-01-01

Delamination is a common failure mode of laminated composite materials. This type of failure frequently occurs at the free edges of laminates where singular interlaminar stresses are developed due to the difference in Poisson's ratios between adjacent plies. Typically the delaminations develop between 90 degree plies and adjacent angle plies. Edge delamination has been studied by several investigators using a variety of techniques. Recently, Chan and Ochoa applied the quasi-three-dimensional finite element model to the analysis of a laminate subject to bending, extension, and torsion. This problem is of particular significance relative to the structural integrity of composite helicopter rotors. The task undertaken was to incorporate Chan and Ochoa's formulation into a Raju Q3DG program. The resulting program is capable of modeling extension, bending, and torsional mechanical loadings as well as thermal and hygroscopic loadings. The addition of the torsional and bending loading capability will provide the capability to perform a delamination analysis of a general unsymmetric laminate containing four cracks, each of a different length. The solutions obtained using this program are evaluated by comparing them with solutions from a full three-dimensional finite element solution. This comparison facilitates the assessment of three dimensional affects such as the warping constraint imposed by the load frame grips. It wlso facilitates the evaluation of the external load representation employed in the Q3D formulation. Finally, strain energy release rates computed from the three-dimensional results are compared with those predicted using the quasi-three-dimensional formulation.

Data-Driven Residential Load Modeling and Validation in GridLAB-D

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

Gotseff, Peter; Lundstrom, Blake

Accurately characterizing the impacts of high penetrations of distributed energy resources (DER) on the electric distribution system has driven modeling methods from traditional static snap shots, often representing a critical point in time (e.g., summer peak load), to quasi-static time series (QSTS) simulations capturing all the effects of variable DER, associated controls and hence, impacts on the distribution system over a given time period. Unfortunately, the high time resolution DER source and load data required for model inputs is often scarce or non-existent. This paper presents work performed within the GridLAB-D model environment to synthesize, calibrate, and validate 1-second residentialmore » load models based on measured transformer loads and physics-based models suitable for QSTS electric distribution system modeling. The modeling and validation approach taken was to create a typical GridLAB-D model home that, when replicated to represent multiple diverse houses on a single transformer, creates a statistically similar load to a measured load for a given weather input. The model homes are constructed to represent the range of actual homes on an instrumented transformer: square footage, thermal integrity, heating and cooling system definition as well as realistic occupancy schedules. House model calibration and validation was performed using the distribution transformer load data and corresponding weather. The modeled loads were found to be similar to the measured loads for four evaluation metrics: 1) daily average energy, 2) daily average and standard deviation of power, 3) power spectral density, and 4) load shape.« less

Communication requirements of sparse Cholesky factorization with nested dissection ordering

NASA Technical Reports Server (NTRS)

Naik, Vijay K.; Patrick, Merrell L.

1989-01-01

Load distribution schemes for minimizing the communication requirements of the Cholesky factorization of dense and sparse, symmetric, positive definite matrices on multiprocessor systems are presented. The total data traffic in factoring an n x n sparse symmetric positive definite matrix representing an n-vertex regular two-dimensional grid graph using n exp alpha, alpha not greater than 1, processors are shown to be O(n exp 1 + alpha/2). It is O(n), when n exp alpha, alpha not smaller than 1, processors are used. Under the conditions of uniform load distribution, these results are shown to be asymptotically optimal.

Large deflection analysis of a pre-stressed annular plate with a rigid boss under axisymmetric loading

NASA Astrophysics Data System (ADS)

Su, Y. H.; Chen, K. S.; Roberts, D. C.; Spearing, S. M.

2001-11-01

The large deflection analysis of a pre-stressed annular plate with a central rigid boss subjected to axisymmetric loading is presented. The factors affecting the transition from plate behaviour to membrane behaviour (e.g. thickness, in-plane tension and material properties) are studied. The effect of boss size and pre-tension on the effective stiffness of the plate are investigated. The extent of the bending boundary layers at the edges of the plate are quantified. All results are presented in non-dimensional form. The design implications for microelectromechanical system components are assessed.

Computational Methods for Frictional Contact With Applications to the Space Shuttle Orbiter Nose-Gear Tire

NASA Technical Reports Server (NTRS)

Tanner, John A.

1996-01-01

A computational procedure is presented for the solution of frictional contact problems for aircraft tires. A Space Shuttle nose-gear tire is modeled using a two-dimensional laminated anisotropic shell theory which includes the effects of variations in material and geometric parameters, transverse-shear deformation, and geometric nonlinearities. Contact conditions are incorporated into the formulation by using a perturbed Lagrangian approach with the fundamental unknowns consisting of the stress resultants, the generalized displacements, and the Lagrange multipliers associated with both contact and friction conditions. The contact-friction algorithm is based on a modified Coulomb friction law. A modified two-field, mixed-variational principle is used to obtain elemental arrays. This modification consists of augmenting the functional of that principle by two terms: the Lagrange multiplier vector associated with normal and tangential node contact-load intensities and a regularization term that is quadratic in the Lagrange multiplier vector. These capabilities and computational features are incorporated into an in-house computer code. Experimental measurements were taken to define the response of the Space Shuttle nose-gear tire to inflation-pressure loads and to inflation-pressure loads combined with normal static loads against a rigid flat plate. These experimental results describe the meridional growth of the tire cross section caused by inflation loading, the static load-deflection characteristics of the tire, the geometry of the tire footprint under static loading conditions, and the normal and tangential load-intensity distributions in the tire footprint for the various static vertical loading conditions. Numerical results were obtained for the Space Shuttle nose-gear tire subjected to inflation pressure loads and combined inflation pressure and contact loads against a rigid flat plate. The experimental measurements and the numerical results are compared.

Grid oscillators

NASA Technical Reports Server (NTRS)

Popovic, Zorana B.; Kim, Moonil; Rutledge, David B.

1988-01-01

Loading a two-dimensional grid with active devices offers a means of combining the power of solid-state oscillators in the microwave and millimeter-wave range. The grid structure allows a large number of negative resistance devices to be combined. This approach is attractive because the active devices do not require an external locking signal, and the combining is done in free space. In addition, the loaded grid is a planar structure amenable to monolithic integration. Measurements on a 25-MESFET grid at 9.7 GHz show power-combining and frequency-locking without an external locking signal, with an ERP of 37 W. Experimental far-field patterns agree with theoretical results obtained using reciprocity.

3D Magnetic Field Analysis of a Turbine Generator Stator Core-end Region

NASA Astrophysics Data System (ADS)

Wakui, Shinichi; Takahashi, Kazuhiko; Ide, Kazumasa; Takahashi, Miyoshi; Watanabe, Takashi

In this paper we calculated magnetic flux density and eddy current distributions of a 71MVA turbine generator stator core-end using three-dimensional numerical magnetic field analysis. Subsequently, the magnetic flux densities and eddy current densities in the stator core-end region on the no-load and three-phase short circuit conditions obtained by the analysis have good agreements with the measurements. Furthermore, the differences of eddy current and eddy current loss in the stator core-end region for various load conditions are shown numerically. As a result, the facing had an effect that decrease the eddy current loss of the end plate about 84%.

A multiscale 3D finite element analysis of fluid/solute transport in mechanically loaded bone

PubMed Central

Fan, Lixia; Pei, Shaopeng; Lucas Lu, X; Wang, Liyun

2016-01-01

The transport of fluid, nutrients, and signaling molecules in the bone lacunar–canalicular system (LCS) is critical for osteocyte survival and function. We have applied the fluorescence recovery after photobleaching (FRAP) approach to quantify load-induced fluid and solute transport in the LCS in situ, but the measurements were limited to cortical regions 30–50 μm underneath the periosteum due to the constrains of laser penetration. With this work, we aimed to expand our understanding of load-induced fluid and solute transport in both trabecular and cortical bone using a multiscaled image-based finite element analysis (FEA) approach. An intact murine tibia was first re-constructed from microCT images into a three-dimensional (3D) linear elastic FEA model, and the matrix deformations at various locations were calculated under axial loading. A segment of the above 3D model was then imported to the biphasic poroelasticity analysis platform (FEBio) to predict load-induced fluid pressure fields, and interstitial solute/fluid flows through LCS in both cortical and trabecular regions. Further, secondary flow effects such as the shear stress and/or drag force acting on osteocytes, the presumed mechano-sensors in bone, were derived using the previously developed ultrastructural model of Brinkman flow in the canaliculi. The material properties assumed in the FEA models were validated against previously obtained strain and FRAP transport data measured on the cortical cortex. Our results demonstrated the feasibility of this computational approach in estimating the fluid flux in the LCS and the cellular stimulation forces (shear and drag forces) for osteocytes in any cortical and trabecular bone locations, allowing further studies of how the activation of osteocytes correlates with in vivo functional bone formation. The study provides a promising platform to reveal potential cellular mechanisms underlying the anabolic power of exercises and physical activities in treating patients with skeletal deficiencies. PMID:27722020

Cognitive Load and Attentional Demands during Objects' Position Change in Real and Digital Environments

ERIC Educational Resources Information Center

Zacharis, Georgios K.; Mikropoulos, Tassos Anastasios; Kalyvioti, Katerina

2016-01-01

Studies showed that two-dimensional (2D) and three-dimensional (3D) educational content contributes to learning. Although there were many studies with 3D stereoscopic learning environments, only a few studies reported on the differences between real, 2D, and 3D scenes, as far as cognitive load and attentional demands were concerned. We used…

Lumped versus distributed thermoregulatory control: results from a three-dimensional dynamic model.

PubMed

Werner, J; Buse, M; Foegen, A

1989-01-01

In this study we use a three-dimensional model of the human thermal system, the spatial grid of which is 0.5 ... 1.0 cm. The model is based on well-known physical heat-transfer equations, and all parameters of the passive system have definite physical values. According to the number of substantially different areas and organs, 54 spatially different values are attributed to each physical parameter. Compatibility of simulation and experiment was achieved solely on the basis of physical considerations and physiological basic data. The equations were solved using a modification of the alternating direction implicit method. On the basis of this complex description of the passive system close to reality, various lumped and distributed parameter control equations were tested for control of metabolic heat production, blood flow and sweat production. The simplest control equations delivering results on closed-loop control compatible with experimental evidence were determined. It was concluded that it is essential to take into account the spatial distribution of heat production, blood flow and sweat production, and that at least for control of shivering, distributed controller gains different from the pattern of distribution of muscle tissue are required. For sweat production this is not so obvious, so that for simulation of sweating control after homogeneous heat load a lumped parameter control may be justified. Based on these conclusions three-dimensional temperature profiles for cold and heat load and the dynamics for changes of the environmental conditions were computed. In view of the exact simulation of the passive system and the compatibility with experimentally attainable variables there is good evidence that those values extrapolated by the simulation are adequately determined. The model may be used both for further analysis of the real thermoregulatory mechanisms and for special applications in environmental and clinical health care.

Development of a 3D numerical methodology for fast prediction of gun blast induced loading

NASA Astrophysics Data System (ADS)

Costa, E.; Lagasco, F.

2014-05-01

In this paper, the development of a methodology based on semi-empirical models from the literature to carry out 3D prediction of pressure loading on surfaces adjacent to a weapon system during firing is presented. This loading is consequent to the impact of the blast wave generated by the projectile exiting the muzzle bore. When exceeding a pressure threshold level, loading is potentially capable to induce unwanted damage to nearby hard structures as well as frangible panels or electronic equipment. The implemented model shows the ability to quickly predict the distribution of the blast wave parameters over three-dimensional complex geometry surfaces when the weapon design and emplacement data as well as propellant and projectile characteristics are available. Considering these capabilities, the use of the proposed methodology is envisaged as desirable in the preliminary design phase of the combat system to predict adverse effects and then enable to identify the most appropriate countermeasures. By providing a preliminary but sensitive estimate of the operative environmental loading, this numerical means represents a good alternative to more powerful, but time consuming advanced computational fluid dynamics tools, which use can, thus, be limited to the final phase of the design.

A novel three-dimensional large-pore mesoporous carbon matrix as a potential nanovehicle for the fast release of the poorly water-soluble drug, celecoxib.

PubMed

Zhang, Yanzhuo; Wang, Hong; Li, Chuanjun; Sun, Baoxiang; Wang, Yu; Wang, Siling; Gao, Cunqiang

2014-04-01

A novel mesocellular carbon foam (MSU-FC) with a large pore size and a three-dimensional porous structure for the oral delivery of poorly water-soluble drugs was prepared. The goal of this study was to improve in vitro dissolution and in vivo absorption of celecoxib (CEB), a model drug, by means of novel carbon-based nanoparticles prepared from the MSU-FC matrix. The MSU-FC matrix was synthesized by an inverse replica templating method using mesocellular silica template. A solvent immersion/evaporation method was used to load the drug molecules. The drug-loaded nanoparticles were characterized for morphology, surface area, particle size, mesoporous structure, crystallinity, solubility and dissolution. The effect of MSU-FC on cell viability was measured using the MTT conversion assay. Furthermore, the oral bioavailability of CEB-loaded MSU-FC in fasted rats was compared with that of the marketed product. Our results demonstrate that CEB incorporation into the prepared MSU-FC resulted in an approximately 9-fold increase in aqueous solubility in comparison with crystalline CEB. MSU-FC produced accelerated immediate release of CEB in comparison with crystalline CEB (pure CEB powder or marketed formulation) and the drug-loaded conventional mesoporous carbon particles. The relative bioavailability of CEB for CEB-loaded MSU-FC was 172%. In addition, MSU-FC nanoparticles exhibited very low toxicity. The MSU-FC nanomatrix has been shown to be a promising drug delivery vehicle for improving the dissolution and biopharmaceutical characteristics of poorly water-soluble drugs.

Experimental multiphysical characterization of an SMA driven, camber morphing owl wing section

NASA Astrophysics Data System (ADS)

Stroud, Hannah R.; Leal, Pedro B. C.; Hartl, Darren J.

2018-03-01

In the context of aerospace engineering, morphing structures are useful in their ability to change the outer mold line (OML) while improving or maintaining certain aerodynamic performance metrics. Skin-based morphing is of particular interest in that it minimizes installation volume. Shape memory alloys (SMAs) have a high force to volume ratio that makes them a suitable choice for skin-based morphing. Because the thermomechanical properties of SMAs are coupled, strain can be generated via a temperature variation; this phenomenon is used as the actuation method. Therefore, it is necessary to determine the interaction of the system not only with aerodynamic loads, but with thermal loads as well. This paper describes the wind tunnel testing and in situ thermomechanical analysis of an SMA actuated, avian inspired morphing wing. The morphing wing is embedded with two SMA composite actuators and consists of a foam core enveloped in a fiberglass-epoxy composite. As the SMA wire is heated, the actuator contracts, morphing the wing from the original owl OML to a highly cambered, high lift OML. Configuration characteristics are analyzed in situ using simultaneous three dimensional digital image correlation (DIC) and infrared thermography, thereby coupling strain and thermal measurements. This method of testing allows for the nonintrusive, multiphysical data acquisition of each actuator separately and the system as a whole.

Dynamic characterization of small fibers based on the flexural vibrations of a piezoelectric cantilever probe

NASA Astrophysics Data System (ADS)

Zhang, Xiaofei; Ye, Xuan; Li, Xide

2016-08-01

In this paper, we present a cantilever-probe system excited by a piezoelectric actuator, and use it to measure the dynamic mechanical properties of a micro- and nanoscale fiber. Coupling the fiber to the free end of the cantilever probe, we found the dynamic stiffness and damping coefficient of the fiber from the resonance frequency and the quality factor of the fiber-cantilever-probe system. The properties of Bacillus subtilis fibers measured using our proposed system agreed with tensile measurements, validating our method. Our measurements show that the piezoelectric actuator coupled to cantilever probe can be made equivalent to a clamped cantilever with an effective length, and calculated results show that the errors of measured natural frequency of the system can be ignored if the coupled fiber has an inclination angle of alignment of less than 10°. A sensitivity analysis indicates that the first or second resonant mode is the sensitive mode to test the sample’s dynamic stiffness, while the damping property has different sensitivities for the first four modes. Our theoretical analysis demonstrates that the double-cantilever probe is also an effective sensitive structure that can be used to perform dynamic loading and characterize dynamic response. Our method has the advantage of using amplitude-frequency curves to obtain the dynamic mechanical properties without directly measuring displacements and forces as in tensile tests, and it also avoids the effects of the complex surface structure and deformation presenting in contact resonance method. Our method is effective for measuring the dynamic mechanical properties of fiber-like one-dimensional (1D) materials.

Biomechanical Assessment of the Canadian Integrated Load Carriage System using Objective Assessment Measures

DTIC Science & Technology

2001-05-01

UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADPO 11004 TITLE: Biomechanical Assessment of the Canadian Integrated Load...ADP010987 thru ADPO11009 UNCLASSIFIED 21-1 Biomechanical Assessment of the Canadian Integrated Load Carriage System using Objective Assessment Measures Joan...CANADA, B3J 2X4 Summary The purpose of this study was to provide an overview of contributions by biomechanical testing to the design of the final

Prediction and modeling of the two-dimensional separation characteristic of a steam generator at a nuclear power station with VVER-1000 reactors

NASA Astrophysics Data System (ADS)

Parchevsky, V. M.; Guryanova, V. V.

2017-01-01

A computational and experimental procedure for construction of the two-dimensional separation curve (TDSC) for a horizontal steam generator (SG) at a nuclear power station (NPS) with VVER-reactors. In contrast to the conventional one-dimensional curve describing the wetness of saturated steam generated in SG as a function of the boiler water level at one, usually rated, load, TDSC is a function of two variables, which are the level and the load of SGB that enables TDSC to be used for wetness control in a wide load range. The procedure is based on two types of experimental data obtained during rated load operation: the nonuniformity factor of the steam load at the outlet from the submerged perforated sheet (SPS) and the dependence of the mass water level in the vicinity of the "hot" header on the water level the "cold" end of SG. The TDSC prediction procedure is presented in the form of an algorithm using SG characteristics, such as steam load and water level as the input and giving the calculated steam wetness at the output. The zoneby-zone calculation method is used. The result is presented in an analytical form (as an empirical correlation) suitable for uploading into controllers or other controls. The predicted TDSC can be used during real-time operation for implementation of different wetness control scenarios (for example, if the effectiveness is a priority, then the minimum water level, minimum wetness, and maximum turbine efficiency should be maintained; if safety is a priority, then the maximum level at the allowable wetness and the maximum water inventory should be kept), for operation of NPS in controlling the frequency and power in a power system, at the design phase (as a part of the simulation complex for verification of design solutions), during construction and erection (in developing software for personnel training simulators), during commissioning tests (to reduce the duration and labor-intensity of experimental activities), and for training.

Development of a magneto-rheological fluid based hybrid actuation system

NASA Astrophysics Data System (ADS)

John, Shaju

A hybrid hydraulic actuation system is proposed as an active pitch link for rotorcraft applications. Such an active pitch link can be used to implement Individual Blade Control (IBC) techniques for vibration and noise reduction, in addition to providing primary control for the helicopter. Conventional technologies like electric motors and hydraulic actuators have major disadvantages when it come to applications on a rotating environment. Centralized hydraulic system require the use of mechanically complex hydraulic slip rings and electric motors have high precision mechanical moving parts that make them unattractive in application with high centrifugal load. The high energy density of smart materials can be used to design hydraulic actuators in a compact package. MagnetoRheological (MR) fluids can be used as the working fluid in such a hybrid hydraulic actuation system to implement a valving system with no moving parts. Thus, such an actuation system can be theoretically well-suited for application in a rotating environment. To develop an actuation system based on an active material stack and MR fluidic valves, a fundamental understanding of the hydraulic circuit is essential. In order to address this issue, a theoretical model was developed to understand the effect of pumping chamber geometry on the pressure losses in the pumping chamber. Three dimensional analytical models were developed for steady and unsteady flow and the results were correlated to results obtained from Computation Fluid Dynamic simulation of fluid flow inside the pumping chamber. Fundamental understanding regarding the pressure losses in a pumping chamber are obtained from the modeling process. Vortices that form in the pumping chamber (during intake) and the discharge tube (during discharge) are identified as a major cause of pressure loss in the chamber. The role of vortices during dynamic operation is also captured through a frequency domain model. Extensive experimental studies were conducted on a hybrid hydraulic system driven by a pump (actuated by a 2" long and 1/4" diameter Terfenol-D rod) and a Wheatstone bridge network of MR fluidic valves. The Wheatstone bridge network is used to provide bi-directionality to the load. Through a variety of experimental studies, the main performance metrics of the actuation system, like output power, blocked force, maximum no-load velocity and efficiency, are obtained. The actuation system exhibits a blocked force of 30 N and a maximum no-load velocity of 50 mm/s. Extensive bi-directional tests were also done for cases of no-load, inertial load and spring load to establish the frequency bandwidth of the actuator. The actuation system can output a stroke of 9 mm at an output actuator frequency of 4 Hz. An analytical model was developed to predict the performance of the hybrid hydraulic actuation system. A state space representation of the system was derived using equations derived from the control volume considerations. The results of the analytical model show that the model predicts the frequency peak of the system to within 20 Hz of the actual resonance frequency. In the third part of this dissertation, the effectiveness of the hybrid hydraulic actuation system is evaluated in a rotating environment. A piezoelectric stack that is driven by three PI-804.10 stacks was attached at the end of a spin bar. After balancing the spin bar using a counterweight, the spin bar is spun to an RPM of 300. This simulates a centrifugal loading of 400 g, which is slightly higher than the full-scale centrifugal loads experienced by a pitch link on a UH-60. The performance of the actuator was measured in terms of velocity of an output cylinder shaft. Since some deterioration of performance was expected at 300 RPM, the output cylinder was redesigned to include roller bearings to support the excess force. Through no load and load tests, the effectiveness of the current hybrid actuation system design was shown as the performance of the system did not deteriorate in performance with greater centrifugal acceleration.

The biomechanical strength of a hardware-free femoral press-fit method for ACL bone-tendon-bone graft fixation.

PubMed

Arnold, M P; Burger, L D; Wirz, D; Goepfert, B; Hirschmann, M T

2017-04-01

The purpose was to investigate graft slippage and ultimate load to failure of a femoral press-fit fixation technique for anterior cruciate ligament (ACL) reconstruction. Nine fresh-frozen knees were used. Standardized harvesting of the B-PT-B graft was performed. The femora were cemented into steel rods, and a tunnel was drilled outside-in into the native ACL footprint and expanded using a manual mill bit. The femoral bone block was fixed press-fit. To pull the free end of the graft, it was fixed to a mechanical testing machine using a deep-freezing technique. A motion capture system was used to assess three-dimensional micro-motion. After preconditioning of the graft, 1000 cycles of tensile loading were applied. Finally, an ultimate load to failure test was performed. Graft slippage in mm ultimate load to failure as well as type of failure was noted. In six of the nine measured specimens, a typical pattern of graft slippage was observed during cyclic loading. For technical reasons, the results of three knees had to be discarded. 78.6 % of total graft slippage occurred in the first 100 cycles. Once the block had settled, graft slippage converged to zero, highlighting the importance of initial preconditioning of the graft in the clinical setting. Graft slippage after 1000 cycles varied around 3.4 ± 3.2 mm (R = 1.3-9.8 mm) between the specimens. Ultimate loading (n = 9) revealed two characteristic patterns of failure. In four knees, the tendon ruptured, while in five knees the bone block was pulled out of the femoral tunnel. The median ultimate load to failure was 852 N (R = 448-1349 N). The implant-free femoral press-fit fixation provided adequate primary stability with ultimate load to failure pull forces at least equal to published results for interference screws; hence, its clinical application is shown to be safe.

A Dielectric-Filled Waveguide Antenna Element for 3D Imaging Radar in High Temperature and Excessive Dust Conditions.

PubMed

Xu, Ding; Li, Zhiping; Chen, Xianzhong; Wang, Zhengpeng; Wu, Jianhua

2016-08-22

Three-dimensional information of the burden surface in high temperature and excessive dust industrial conditions has been previously hard to obtain. This paper presents a novel microstrip-fed dielectric-filled waveguide antenna element which is resistant to dust and high temperatures. A novel microstrip-to-dielectric-loaded waveguide transition was developed. A cylinder and cuboid composite structure was employed at the terminal of the antenna element, which improved the return loss performance and reduced the size. The proposed antenna element was easily integrated into a T-shape multiple-input multiple-output (MIMO) imaging radar system and tested in both the laboratory environment and real blast furnace environment. The measurement results show that the proposed antenna element works very well in industrial 3D imaging radar.

A calibration procedure for load cells to improve accuracy of mini-lysimeters in monitoring evapotranspiration

NASA Astrophysics Data System (ADS)

Misra, R. K.; Padhi, J.; Payero, J. O.

2011-08-01

SummaryWe used twelve load cells (20 kg capacity) in a mini-lysimeter system to measure evapotranspiration simultaneously from twelve plants growing in separate pots in a glasshouse. A data logger combined with a multiplexer was used to connect all load cells with the full-bridge excitation mode to acquire load-cell signal. Each load cell was calibrated using fixed load within the range of 0-0.8 times the full load capacity of load cells. Performance of all load cells was assessed on the basis of signal settling time, excitation compensation, hysteresis and temperature. Final calibration of load cells included statistical consideration of these effects to allow prediction of lysimeter weights and evapotranspiration over short-time intervals for improved accuracy and sustained performance. Analysis of the costs for the mini-lysimeter system indicates that evapotranspiration can be measured economically at a reasonable accuracy and sufficient resolution with robust method of load-cell calibration.

Dealing with periodical loads and harmonics in operational modal analysis using time-varying transmissibility functions

NASA Astrophysics Data System (ADS)

Weijtjens, Wout; Lataire, John; Devriendt, Christof; Guillaume, Patrick

2014-12-01

Periodical loads, such as waves and rotating machinery, form a problem for operational modal analysis (OMA). In OMA only the vibrations of a structure of interest are measured and little to nothing is known about the loads causing these vibrations. Therefore, it is often assumed that all dynamics in the measured data are linked to the system of interest. Periodical loads defy this assumption as their periodical behavior is often visible within the measured vibrations. As a consequence most OMA techniques falsely associate the dynamics of the periodical load with the system of interest. Without additional information about the load, one is not able to correctly differentiate between structural dynamics and the dynamics of the load. In several applications, e.g. turbines and helicopters, it was observed that because of periodical loads one was unable to correctly identify one or multiple modes. Transmissibility based OMA (TOMA) is a completely different approach to OMA. By using transmissibility functions to estimate the structural dynamics of the system of interest, all influence of the load-spectrum can be eliminated. TOMA therefore allows to identify the modal parameters without being influenced by the presence of periodical loads, such as harmonics. One of the difficulties of TOMA is that the analyst is required to find two independent datasets, each associated with a different loading condition of the system of interest. This poses a dilemma for TOMA; how can an analyst identify two different loading conditions when little is known about the loads on the system? This paper tackles that problem by assuming that the loading conditions vary continuously over time, e.g. the changing wind directions. From this assumption TOMA is developed into a time-varying framework. This development allows TOMA to not only cope with the continuously changing loading conditions. The time-varying framework also enables the identification of the modal parameters from a single dataset. Moreover, the time-varying TOMA approach can be implemented in such a way that the analyst no longer has to identify different loading conditions. For these combined reasons the time-varying TOMA is less dependent on the user and requires less testing time than the earlier TOMA-technique.

Three-Axis Distributed Fiber Optic Strain Measurement in 3D Woven Composite Structures

NASA Technical Reports Server (NTRS)

Castellucci, Matt; Klute, Sandra; Lally, Evan M.; Froggatt, Mark E.; Lowry, David

2013-01-01

Recent advancements in composite materials technologies have broken further from traditional designs and require advanced instrumentation and analysis capabilities. Success or failure is highly dependent on design analysis and manufacturing processes. By monitoring smart structures throughout manufacturing and service life, residual and operational stresses can be assessed and structural integrity maintained. Composite smart structures can be manufactured by integrating fiber optic sensors into existing composite materials processes such as ply layup, filament winding and three-dimensional weaving. In this work optical fiber was integrated into 3D woven composite parts at a commercial woven products manufacturing facility. The fiber was then used to monitor the structures during a VARTM manufacturing process, and subsequent static and dynamic testing. Low cost telecommunications-grade optical fiber acts as the sensor using a high resolution commercial Optical Frequency Domain Reflectometer (OFDR) system providing distributed strain measurement at spatial resolutions as low as 2mm. Strain measurements using the optical fiber sensors are correlated to resistive strain gage measurements during static structural loading. Keywords: fiber optic, distributed strain sensing, Rayleigh scatter, optical frequency domain reflectometry

Modeling power flow in the induction cavity with a two dimensional circuit simulation

NASA Astrophysics Data System (ADS)

Guo, Fan; Zou, Wenkang; Gong, Boyi; Jiang, Jihao; Chen, Lin; Wang, Meng; Xie, Weiping

2017-02-01

We have proposed a two dimensional (2D) circuit model of induction cavity. The oil elbow and azimuthal transmission line are modeled with one dimensional transmission line elements, while 2D transmission line elements are employed to represent the regions inward the azimuthal transmission line. The voltage waveforms obtained by 2D circuit simulation and transient electromagnetic simulation are compared, which shows satisfactory agreement. The influence of impedance mismatch on the power flow condition in the induction cavity is investigated with this 2D circuit model. The simulation results indicate that the peak value of load voltage approaches the maximum if the azimuthal transmission line roughly matches the pulse forming section. The amplitude of output transmission line voltage is strongly influenced by its impedance, but the peak value of load voltage is insensitive to the actual output transmission line impedance. When the load impedance raises, the voltage across the dummy load increases, and the pulse duration at the oil elbow inlet and insulator stack regions also slightly increase.

Three-dimensional elastic-plastic finite-element analysis of fatigue crack propagation

NASA Technical Reports Server (NTRS)

Goglia, G. L.; Chermahini, R. G.

1985-01-01

Fatigue cracks are a major problem in designing structures subjected to cyclic loading. Cracks frequently occur in structures such as aircraft and spacecraft. The inspection intervals of many aircraft structures are based on crack-propagation lives. Therefore, improved prediction of propagation lives under flight-load conditions (variable-amplitude loading) are needed to provide more realistic design criteria for these structures. The main thrust was to develop a three-dimensional, nonlinear, elastic-plastic, finite element program capable of extending a crack and changing boundary conditions for the model under consideration. The finite-element model is composed of 8-noded (linear-strain) isoparametric elements. In the analysis, the material is assumed to be elastic-perfectly plastic. The cycle stress-strain curve for the material is shown Zienkiewicz's initial-stress method, von Mises's yield criterion, and Drucker's normality condition under small-strain assumptions are used to account for plasticity. The three-dimensional analysis is capable of extending the crack and changing boundary conditions under cyclic loading.

A unified theory for laminated plates

NASA Astrophysics Data System (ADS)

Guiamatsia Tafeuvoukeng, Irene

A literature survey on plate and beam theories show how the advent of the finite element method and the variational method circa 1940 have been a great stimulant for the research in this field. The initial thin plate formulation has been incrementally expanded to treat the isotropic thick plate, the anisotropic single layer, and then laminated plates. It appears however that current formulations still fall into one of two categories: (1) The formulation is tailored for a specific laminate and/or loading case; (2) or the formulation is too complicated to be of practical relevance. In this work a new unifying approach to laminated plate formulation is presented. All laminated plates, including sandwich panels, subjected to any surface load and with any boundary conditions are treated within a single model. In addition, the fundamental behavior of the plate as a two-dimensional structural element is explained. The novel idea is the introduction of fundamental state solutions, which are analytical far field stress and strain solutions of the laminated plate subjected to a set of hierarchical primary loads, the fundamental loads. These loads are carefully selected to form a basis of the load space, and corresponding solutions are superposed to obtain extremely accurate predictions of the three dimensional solution. six,y,z =aklx,y sikl z where i = 1,..., 6; 1=1,...,l max is a substate of the kth fundamental state k=1,2,3,... Typically, a fundamental state solution is expressed as a through-thickness function (z), while the amplitudes of each fundamental load are found from two dimensional finite element solution as a function of in-plane coordinates (x,y). Three major contributions are produced in this work: (1) A complete calibration of the plate as a two-dimensional structure is performed with pure bending and constant shear fundamental states. (2) There are four independent ways to apply a constant shear resultant on a plate, as opposed to one for a beam. This makes it impossible to define a unique 2 x 2 transverse shear stiffness matrix. Therefore the traditional problem of the shear correction factor loses all relevance. It is however shown that an explicit transverse constitutive relation can be obtained for isotropic-layered laminates or single-layers. (3) Higher accuracy, three-dimensional solutions are obtained using a two-dimensional finite element model with a complexity level (degrees of freedom) similar to the Reissner-Mindlin plate. The proof of concept is realized using Pagano solution for rectangular plates under sinusoidal load, for a sandwich panel. Additional comparisons are also performed for four and six-layer symmetric and antisymmetric laminates, between the new plate theory results and full three-dimensional finite element solutions.

Force system generated by elastic archwires with vertical V bends: a three-dimensional analysis.

PubMed

Upadhyay, Madhur; Shah, Raja; Peterson, Donald; Asaki, Takafumi; Yadav, Sumit; Agarwal, Sachin

2017-04-01

Our previous understanding of V-bend mechanics is primarily from two-dimensional (2D) analysis of archwire bracket interactions in the second order. These analyses do not take into consideration the three-dimensional (3D) nature of orthodontic appliances involving the third order. To quantify the force system generated in a 3D two bracket set up involving the molar and incisors with vertical V-bends. Maxillary molar and incisor brackets were arranged in a dental arch form and attached to load cells capable of measuring forces and moments in all three planes (x, y, and z) of space. Symmetrical V-bends (right and left sides) were placed at 11 different locations along rectangular beta-titanium archwires of various sizes at an angle of 150degrees. Each wire was evaluated for the 11 bend positions. Specifically, the vertical forces (Fz) and anterio-posterior moments (Mx) were analysed. Descriptive statistics were used to interpret the results. With increasing archwire size, Fz and Mx increased at the two brackets (P < 0.05). The vertical forces were linear and symmetric in nature, increasing in magnitude as the bends moved closer to either bracket. The Mx curves were asymmetric and non-linear displaying higher magnitudes for molar bracket. As the bends were moved closer to either bracket a distinct flattening of the incisor Mx curve was noted, implying no change in its magnitude. This article provides critical information on V-bend mechanics involving second order and third order archwire-bracket interactions. A model for determining this force system is described that might allow for easier translation to actual clinical practice. © The Author 2016. Published by Oxford University Press on behalf of the European Orthodontic Society. All rights reserved. For permissions, please email: journals.permissions@oup.com

Wave Phase-Sensitive Transformation of 3d-Straining of Mechanical Fields

NASA Astrophysics Data System (ADS)

Smirnov, I. N.; Speranskiy, A. A.

2015-11-01

It is the area of research of oscillatory processes in elastic mechanical systems. Technical result of innovation is creation of spectral set of multidimensional images which reflect time-correlated three-dimensional vector parameters of metrological, and\\or estimated, and\\or design parameters of oscillations in mechanical systems. Reconstructed images of different dimensionality integrated in various combinations depending on their objective function can be used as homeostatic profile or cybernetic image of oscillatory processes in mechanical systems for an objective estimation of current operational conditions in real time. The innovation can be widely used to enhance the efficiency of monitoring and research of oscillation processes in mechanical systems (objects) in construction, mechanical engineering, acoustics, etc. Concept method of vector vibrometry based on application of vector 3D phase- sensitive vibro-transducers permits unique evaluation of real stressed-strained states of power aggregates and loaded constructions and opens fundamental innovation opportunities: conduct of continuous (on-line regime) reliable monitoring of turboagregates of electrical machines, compressor installations, bases, supports, pipe-lines and other objects subjected to damaging effect of vibrations; control of operational safety of technical systems at all the stages of life cycle including design, test production, tuning, testing, operational use, repairs and resource enlargement; creation of vibro-diagnostic systems of authentic non-destructive control of anisotropic characteristics of materials resistance of power aggregates and loaded constructions under outer effects and operational flaws. The described technology is revolutionary, universal and common for all branches of engineering industry and construction building objects.

Unsteady Thick Airfoil Aerodynamics: Experiments, Computation, and Theory

NASA Technical Reports Server (NTRS)

Strangfeld, C.; Rumsey, C. L.; Mueller-Vahl, H.; Greenblatt, D.; Nayeri, C. N.; Paschereit, C. O.

2015-01-01

An experimental, computational and theoretical investigation was carried out to study the aerodynamic loads acting on a relatively thick NACA 0018 airfoil when subjected to pitching and surging, individually and synchronously. Both pre-stall and post-stall angles of attack were considered. Experiments were carried out in a dedicated unsteady wind tunnel, with large surge amplitudes, and airfoil loads were estimated by means of unsteady surface mounted pressure measurements. Theoretical predictions were based on Theodorsen's and Isaacs' results as well as on the relatively recent generalizations of van der Wall. Both two- and three-dimensional computations were performed on structured grids employing unsteady Reynolds-averaged Navier-Stokes (URANS). For pure surging at pre-stall angles of attack, the correspondence between experiments and theory was satisfactory; this served as a validation of Isaacs theory. Discrepancies were traced to dynamic trailing-edge separation, even at low angles of attack. Excellent correspondence was found between experiments and theory for airfoil pitching as well as combined pitching and surging; the latter appears to be the first clear validation of van der Wall's theoretical results. Although qualitatively similar to experiment at low angles of attack, two-dimensional URANS computations yielded notable errors in the unsteady load effects of pitching, surging and their synchronous combination. The main reason is believed to be that the URANS equations do not resolve wake vorticity (explicitly modeled in the theory) or the resulting rolled-up un- steady flow structures because high values of eddy viscosity tend to \\smear" the wake. At post-stall angles, three-dimensional computations illustrated the importance of modeling the tunnel side walls.

[Contrast of Z-Pinch X-Ray Yield Measure Technique].

PubMed

Li, Mo; Wang, Liang-ping; Sheng, Liang; Lu, Yi

2015-03-01

Resistive bolometer and scintillant detection system are two mainly Z-pinch X-ray yield measure techniques which are based on different diagnostic principles. Contrasting the results from two methods can help with increasing precision of X-ray yield measurement. Experiments with different load material and shape were carried out on the "QiangGuang-I" facility. For Al wire arrays, X-ray yields measured by the two techniques were largely consistent. However, for insulating coating W wire arrays, X-ray yields taken from bolometer changed with load parameters while data from scintillant detection system hardly changed. Simulation and analysis draw conclusions as follows: (1) Scintillant detection system is much more sensitive to X-ray photons with low energy and its spectral response is wider than the resistive bolometer. Thus, results from the former method are always larger than the latter. (2) The responses of the two systems are both flat to Al plasma radiation. Thus, their results are consistent for Al wire array loads. (3) Radiation form planar W wire arrays is mainly composed of sub-keV soft X-ray. X-ray yields measured by the bolometer is supposed to be accurate because of the nickel foil can absorb almost all the soft X-ray. (4) By contrast, using planar W wire arrays, data from scintillant detection system hardly change with load parameters. A possible explanation is that while the distance between wires increases, plasma temperature at stagnation reduces and spectra moves toward the soft X-ray region. Scintillator is much more sensitive to the soft X-ray below 200 eV. Thus, although the total X-ray yield reduces with large diameter load, signal from the scintillant detection system is almost the same. (5) Both Techniques affected by electron beams produced by the loads.

Strain measurement using a Brillouin optical time domain reflectometer for development of aircraft structure health monitoring system

NASA Astrophysics Data System (ADS)

Shimizu, Takayuki; Yari, Takashi; Nagai, Kanehiro; Takeda, Nobuo

2001-07-01

We conducted theoretical and experimental approaches for applying Brillouin optical time domain reflectometer (BOTDR) to aircraft and spacecraft structure health monitoring system. Firstly, distributed strain was measured by BOTDR under 3-point bending test and a spatial resolution was enhanced up to 0.5m using Brillouin spectrum analysis and processing though the device used in this experiment had a spatial resolution of 2m normally. Secondly, dynamic strain measurement was executed under cyclic loading conditions. Brillouin spectrum measured under dynamic conditions is equivalent to superposed spectrum using many spectra measured under static loading conditions. As the measured spectrum was decomposed into many spectra in static loading state, the strain amplitude and its ratio could be estimated. Thirdly, strain and temperature could be measured independently using combined system of BOTDR and fiber Bragg grating (FBG) with wavelength division multiplexing (WDM). Additionally, the application of BOTDR sensing system was shown for a prototype carbon fiber reinforced plastic (CFRP) liquid hydrogen (LH2) tank under cryogenic condition.

Computational knee ligament modeling using experimentally determined zero-load lengths.

PubMed

Bloemker, Katherine H; Guess, Trent M; Maletsky, Lorin; Dodd, Kevin

2012-01-01

This study presents a subject-specific method of determining the zero-load lengths of the cruciate and collateral ligaments in computational knee modeling. Three cadaver knees were tested in a dynamic knee simulator. The cadaver knees also underwent manual envelope of motion testing to find their passive range of motion in order to determine the zero-load lengths for each ligament bundle. Computational multibody knee models were created for each knee and model kinematics were compared to experimental kinematics for a simulated walk cycle. One-dimensional non-linear spring damper elements were used to represent cruciate and collateral ligament bundles in the knee models. This study found that knee kinematics were highly sensitive to altering of the zero-load length. The results also suggest optimal methods for defining each of the ligament bundle zero-load lengths, regardless of the subject. These results verify the importance of the zero-load length when modeling the knee joint and verify that manual envelope of motion measurements can be used to determine the passive range of motion of the knee joint. It is also believed that the method described here for determining zero-load length can be used for in vitro or in vivo subject-specific computational models.

Turbidity-controlled sampling for suspended sediment load estimation

Treesearch

Jack Lewis

2003-01-01

Abstract - Automated data collection is essential to effectively measure suspended sediment loads in storm events, particularly in small basins. Continuous turbidity measurements can be used, along with discharge, in an automated system that makes real-time sampling decisions to facilitate sediment load estimation. The Turbidity Threshold Sampling method distributes...

Left ventricular mechanics in isolated mild mitral stenosis: a three dimensional speckle tracking study.

PubMed

Poyraz, Esra; Öz, Tuğba Kemaloğlu; Zeren, Gönül; Güvenç, Tolga Sinan; Dönmez, Cevdet; Can, Fatma; Güvenç, Rengin Çetin; Dayı, Şennur Ünal

2017-09-01

In a fraction of patients with mild mitral stenosis, left ventricular systolic function deteriorates despite the lack of hemodynamic load imposed by the dysfunctioning valve. Neither the predisposing factors nor the earlier changes in left ventricular contractility were understood adequately. In the present study we aimed to evaluate left ventricular mechanics using three-dimensional (3D) speckle tracking echocardiography. A total of 31 patients with mild rheumatic mitral stenosis and 27 healthy controls were enrolled to the study. All subjects included to the study underwent echocardiographic examination to collect data for two- and three-dimensional speckle-tracking based stain, twist angle and torsion measurements. Data was analyzed offline with a echocardiographic data analysis software. Patients with rheumatic mild MS had lower global longitudinal (p < 0.001) circumferential (p = 0.02) and radial (p < 0.01) strain compared to controls, despite ejection fraction was similar for both groups [(p = 0.45) for three dimensional and (p = 0.37) for two dimensional measurement]. While the twist angle was not significantly different between groups (p = 0.11), left ventricular torsion was significantly higher in mitral stenosis group (p = 0.03). All strain values had a weak but significant positive correlation with mitral valve area measured with planimetry. Subclinical left ventricular systolic dysfunction develops at an early stage in rheumatic mitral stenosis. Further work is needed to elucidate patients at risk for developing overt systolic dysfunction.

Multi-range force sensors utilizing shape memory alloys

DOEpatents

Varma, Venugopal K.

2003-04-15

The present invention provides a multi-range force sensor comprising a load cell made of a shape memory alloy, a strain sensing system, a temperature modulating system, and a temperature monitoring system. The ability of the force sensor to measure contact forces in multiple ranges is effected by the change in temperature of the shape memory alloy. The heating and cooling system functions to place the shape memory alloy of the load cell in either a low temperature, low strength phase for measuring small contact forces, or a high temperature, high strength phase for measuring large contact forces. Once the load cell is in the desired phase, the strain sensing system is utilized to obtain the applied contact force. The temperature monitoring system is utilized to ensure that the shape memory alloy is in one phase or the other.

Transient Three-Dimensional Side Load Analysis of Out-of-Round Film Cooled Nozzles

NASA Technical Reports Server (NTRS)

Wang, Ten-See; Lin, Jeff; Ruf, Joe; Guidos, Mike

2010-01-01

The objective of this study is to investigate the effect of nozzle out-of-roundness on the transient startup side loads. The out-of-roundness could be the result of asymmetric loads induced by hardware attached to the nozzle, asymmetric internal stresses induced by previous tests and/or deformation, such as creep, from previous tests. The rocket engine studied encompasses a regeneratively cooled thrust chamber and a film cooled nozzle extension with film coolant distributed from a turbine exhaust manifold. The computational methodology is based on an unstructured-grid, pressure-based computational fluid dynamics formulation, and a transient inlet history based on an engine system simulation. Transient startup computations were performed with the out-of-roundness achieved by four degrees of ovalization of the nozzle: one perfectly round, one slightly out-of-round, one more out-of-round, and one significantly out-of-round. The computed side load physics caused by the nozzle out-of-roundness and its effect on nozzle side load are reported and discussed.

Three-Dimensional Flow Separation Induced by a Model Vocal Fold Polyp

NASA Astrophysics Data System (ADS)

Stewart, Kelley C.; Erath, Byron D.; Plesniak, Michael W.

2012-11-01

The fluid-structure energy exchange process for normal speech has been studied extensively, but it is not well understood for pathological conditions. Polyps and nodules, which are geometric abnormalities that form on the medial surface of the vocal folds, can disrupt vocal fold dynamics and thus can have devastating consequences on a patient's ability to communicate. A recent in-vitro investigation of a model polyp in a driven vocal fold apparatus demonstrated that such a geometric abnormality considerably disrupts the glottal jet behavior and that this flow field adjustment was a likely reason for the severe degradation of the vocal quality in patients. Understanding of the formation and propagation of vortical structures from a geometric protuberance, and their subsequent impact on the aerodynamic loadings that drive vocal fold dynamic, is a critical component in advancing the treatment of this pathological condition. The present investigation concerns the three-dimensional flow separation induced by a wall-mounted prolate hemispheroid with a 2:1 aspect ratio in cross flow, i.e. a model vocal fold polyp. Unsteady three-dimensional flow separation and its impact of the wall pressure loading are examined using skin friction line visualization and wall pressure measurements. Supported by the National Science Foundation, Grant No. CBET-1236351 and GW Center for Biomimetics and Bioinspired Engineering (COBRE).

Comparison of one-dimensional probabilistic finite element method with direct numerical simulation of dynamically loaded heterogeneous materials

NASA Astrophysics Data System (ADS)

Robbins, Joshua; Voth, Thomas

2011-06-01

Material response to dynamic loading is often dominated by microstructure such as grain topology, porosity, inclusions, and defects; however, many models rely on assumptions of homogeneity. We use the probabilistic finite element method (WK Liu, IJNME, 1986) to introduce local uncertainty to account for material heterogeneity. The PFEM uses statistical information about the local material response (i.e., its expectation, coefficient of variation, and autocorrelation) drawn from knowledge of the microstructure, single crystal behavior, and direct numerical simulation (DNS) to determine the expectation and covariance of the system response (velocity, strain, stress, etc). This approach is compared to resolved grain-scale simulations of the equivalent system. The microstructures used for the DNS are produced using Monte Carlo simulations of grain growth, and a sufficient number of realizations are computed to ensure a meaningful comparison. Finally, comments are made regarding the suitability of one-dimensional PFEM for modeling material heterogeneity. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Establishment of the optimum two-dimensional electrophoresis system of ovine ovarian tissue.

PubMed

Jia, J L; Zhang, L P; Wu, J P; Wang, J; Ding, Q

2014-08-26

Lambing performance of sheep is the most important economic trait and is regarded as a critic factoring affecting the productivity in sheep industry. Ovary plays the most roles in lambing trait. To establish the optimum two-dimensional electrophoresis system (2-DE) of ovine ovarian tissue, the common protein extraction methods of animal tissue (trichloroacetic acid/acetone precipitation and direct schizolysis methods) were used to extract ovine ovarian protein, and 17-cm nonlinear immobilized PH 3-10 gradient strips were used for 2-DE. The sample handling, loading quantity of the protein sample, and isoelectric focusing (IEF) steps were manipulated and optimized in this study. The results indicate that the direct schizolysis III method, a 200-μg loading quantity of the protein sample, and IEF steps II (20°C active hydration, 14 h→500 V, 1 h→1000 V 1 h→1000-9000 V, 6 h→80,000 VH→500 V 24 h) are optimal for 2-DE analysis of ovine ovarian tissue. Therefore, ovine ovarian tissue proteomics 2-DE was preliminarily established by the optimized conditions in this study; meanwhile, the conditions identified herein could provide a reference for ovarian sample preparation and 2-DE using tissues from other animals.

Skeletal Structural Consequences of Reduced Gravity Environments

NASA Technical Reports Server (NTRS)

Ruff, Christropher B.

1999-01-01

The overall goal of this project is to provide structurally meaningful data on bone loss after exposure to reduced gravity environments so that more precise estimates of fracture risk and the effectiveness of countermeasures in reducing fracture risk can be developed. The project has three major components: (1) measure structural changes in the limb bones of rats subjected to complete and partial nonweightbearing, with and without treatment with ibandronate and periodic full weightbearing; (2) measure structural changes in the limb bones of human bedrest subjects, with and without treatment with alendronate and resistive exercise, and Russian cosmonauts flying on the Mir Space Station; and (3) validate and extend the 2-dimensional structural analyses currently possible in the second project component (bedrest and Mir subjects) using 3-dimensional finite element modeling techniques, and determine actual fracture-producing loads on earth and in space.

Electromagnetic Forces in a Hybrid Magnetic-Bearing Switched-Reluctance Motor

NASA Technical Reports Server (NTRS)

Morrison, Carlos R.; Siebert, Mark W.; Ho, Eric J.

2008-01-01

Analysis and experimental measurement of the electromagnetic force loads on the hybrid rotor in a novel hybrid magnetic-bearing switched-reluctance motor (MBSRM) have been performed. A MBSRM has the combined characteristics of a switched-reluctance motor and a magnetic bearing. The MBSRM discussed in this report has an eight-pole stator and a six-pole hybrid rotor, which is composed of circular and scalloped lamination segments. The hybrid rotor is levitated using only one set of four stator poles, while a second set of four stator poles imparts torque to the scalloped portion of the rotor, which is driven in a traditional switched reluctance manner by a processor. Static torque and radial force analysis were done for rotor poles that were oriented to achieve maximum and minimum radial force loads on the rotor. The objective is to assess whether simple one-dimensional magnetic circuit analysis is sufficient for preliminary evaluation of this machine, which may exhibit strong three-dimensional electromagnetic field behavior. Two magnetic circuit geometries, approximating the complex topology of the magnetic fields in and around the hybrid rotor, were employed in formulating the electromagnetic radial force equations. Reasonable agreement between the experimental and the theoretical radial force loads predictions was obtained with typical magnetic bearing derating factors applied to the predictions.

JT9D engine diagnostics. Task 2: Feasibility study of measuring in-service flight loads. [747 aircraft performance

NASA Technical Reports Server (NTRS)

Kafka, P. G.; Skibo, M. A.; White, J. L.

1977-01-01

The feasibility of measuring JT9D propulsion system flight inertia loads on a 747 airplane is studied. Flight loads background is discussed including the current status of 747/JT9D loads knowledge. An instrumentation and test plan is formulated for an airline-owned in-service airplane and the Boeing-owned RA001 test airplane. Technical and cost comparisons are made between these two options. An overall technical feasibility evaluation is made and a cost summary presented. Conclusions and recommendations are presented in regard to using existing inertia loads data versus conducting a flight test to measure inertia loads.

NASA experiments onboard the controlled impact demonstration

NASA Technical Reports Server (NTRS)

Hayduk, R. J.; Alfaro-Bou, E.; Fasanella, E. L.

1985-01-01

The structural crashworthiness tests conducted by NASA on the December 1, 1984 controlled impact demonstration are discussed. The components and locations of the data acquisition and photographic systems developed by NASA to evaluate impact loads throughout the aircraft structure and the transmission of loads into the dummies are described. The effectiveness of the NASA designed absorbing seats and the vertical, longitudinal, and transverse impact loads are measured. Data that is extremely applicable to crash dynamics structural research was obtained by the data acquisition system and very low load levels were measured for the NASA energy absorbing seats.

Parsimonious description for predicting high-dimensional dynamics

PubMed Central

Hirata, Yoshito; Takeuchi, Tomoya; Horai, Shunsuke; Suzuki, Hideyuki; Aihara, Kazuyuki

2015-01-01

When we observe a system, we often cannot observe all its variables and may have some of its limited measurements. Under such a circumstance, delay coordinates, vectors made of successive measurements, are useful to reconstruct the states of the whole system. Although the method of delay coordinates is theoretically supported for high-dimensional dynamical systems, practically there is a limitation because the calculation for higher-dimensional delay coordinates becomes more expensive. Here, we propose a parsimonious description of virtually infinite-dimensional delay coordinates by evaluating their distances with exponentially decaying weights. This description enables us to predict the future values of the measurements faster because we can reuse the calculated distances, and more accurately because the description naturally reduces the bias of the classical delay coordinates toward the stable directions. We demonstrate the proposed method with toy models of the atmosphere and real datasets related to renewable energy. PMID:26510518

Evaluation of load carriage systems used by active duty police officers: Relative effects on walking patterns and perceived comfort.

PubMed

Ramstrand, Nerrolyn; Zügner, Roland; Larsen, Louise Bæk; Tranberg, Roy

2016-03-01

This study aimed to examine the effects of two different load carriage systems on gait kinematics, temporospatial gait parameters and self-reported comfort in Swedish police. 21 active duty police officers were recruited for this crossover study design. Biomechanical and self-report data was collected on two testing occasions. On occasion 1, three dimensional kinematic data was collected while police wore a/no equipment (control), b/their standard issues belt and ballistic protection vest and c/a load bearing vest with ballistic protection vest. Police then wore the load bearing vest for a minimum of 3 months before the second testing occasion. The load bearing vest was associated with a significant reduction in range of motion of the trunk, pelvis and hip joints. Biomechanical changes associated with the load bearing vest appeared to reduce with increased wear time. In both the standard issue belt condition and the load bearing vest condition, police walked with the arms held in a significantly greater degree of abduction. Self-report data indicated a preference for the load bearing vest. The two load carriage designs tested in this study were found to significantly alter gait kinematics. The load bearing vest design was associated with the greatest number of kinematic compensations however these reduced over time as police became more accustomed to the design. Results from this study do not support selection of one load carriage design over the other and providing individuals with the option to choose a load carriage design is considered appropriate. Copyright © 2015 Elsevier Ltd and The Ergonomics Society. All rights reserved.

Rigorous joining of advanced reduced-dimensional beam models to three-dimensional finite element models

NASA Astrophysics Data System (ADS)

Song, Huimin

In the aerospace and automotive industries, many finite element analyses use lower-dimensional finite elements such as beams, plates and shells, to simplify the modeling. These simplified models can greatly reduce the computation time and cost; however, reduced-dimensional models may introduce inaccuracies, particularly near boundaries and near portions of the structure where reduced-dimensional models may not apply. Another factor in creation of such models is that beam-like structures frequently have complex geometry, boundaries and loading conditions, which may make them unsuitable for modeling with single type of element. The goal of this dissertation is to develop a method that can accurately and efficiently capture the response of a structure by rigorous combination of a reduced-dimensional beam finite element model with a model based on full two-dimensional (2D) or three-dimensional (3D) finite elements. The first chapter of the thesis gives the background of the present work and some related previous work. The second chapter is focused on formulating a system of equations that govern the joining of a 2D model with a beam model for planar deformation. The essential aspect of this formulation is to find the transformation matrices to achieve deflection and load continuity on the interface. Three approaches are provided to obtain the transformation matrices. An example based on joining a beam to a 2D finite element model is examined, and the accuracy of the analysis is studied by comparing joint results with the full 2D analysis. The third chapter is focused on formulating the system of equations for joining a beam to a 3D finite element model for static and free-vibration problems. The transition between the 3D elements and beam elements is achieved by use of the stress recovery technique of the variational-asymptotic method as implemented in VABS (the Variational Asymptotic Beam Section analysis). The formulations for an interface transformation matrix and the generalized Timoshenko beam are discussed in this chapter. VABS is also used to obtain the beam constitutive properties and warping functions for stress recovery. Several 3D-beam joint examples are presented to show the convergence and accuracy of the analysis. Accuracy is accessed by comparing the joint results with the full 3D analysis. The fourth chapter provides conclusions from present studies and recommendations for future work.

Deflection Measurements of a Thermally Simulated Nuclear Core Using a High-Resolution CCD-Camera

NASA Technical Reports Server (NTRS)

Stanojev, B. J.; Houts, M.

2004-01-01

Space fission systems under consideration for near-term missions all use compact. fast-spectrum reactor cores. Reactor dimensional change with increasing temperature, which affects neutron leakage. is the dominant source of reactivity feedback in these systems. Accurately measuring core dimensional changes during realistic non-nuclear testing is therefore necessary in predicting the system nuclear equivalent behavior. This paper discusses one key technique being evaluated for measuring such changes. The proposed technique is to use a Charged Couple Device (CCD) sensor to obtain deformation readings of electrically heated prototypic reactor core geometry. This paper introduces a technique by which a single high spatial resolution CCD camera is used to measure core deformation in Real-Time (RT). Initial system checkout results are presented along with a discussion on how additional cameras could be used to achieve a three- dimensional deformation profile of the core during test.

A geometrically exact formulation for three-dimensional numerical simulation of the umbilical cable in a deep-sea ROV system

NASA Astrophysics Data System (ADS)

Quan, Wei-cai; Zhang, Zhu-ying; Zhang, Ai-qun; Zhang, Qi-feng; Tian, Yu

2015-04-01

This paper proposes a geometrically exact formulation for three-dimensional static and dynamic analyses of the umbilical cable in a deep-sea remotely operated vehicle (ROV) system. The presented formulation takes account of the geometric nonlinearities of large displacement, effects of axial load and bending stiffness for modeling of slack cables. The resulting nonlinear second-order governing equations are discretized spatially by the finite element method and solved temporally by the generalized- α implicit time integration algorithm, which is adapted to the case of varying coefficient matrices. The ability to consider three-dimensional union action of ocean current and ship heave motion upon the umbilical cable is the key feature of this analysis. The presented formulation is firstly validated, and then three numerical examples for the umbilical cable in a deep-sea ROV system are demonstrated and discussed, including the steady configurations only under the action of depth-dependent ocean current, the dynamic responses in the case of the only ship heave motion, and in the case of the combined action of the ship heave motion and ocean current.

Helicopter rotor rotational noise predictions based on measured high-frequency blade loads

NASA Technical Reports Server (NTRS)

Hosier, R. N.; Ramakrishnan, R.

1974-01-01

In tests conducted at the Langley helicopter rotor test facility, simultaneous measurements of up to 200 harmonics of the fluctuating aerodynamic blade surface pressures and far-field radiated noise were made on a full-scale nontranslating rotor system. After their characteristics were determined, the measured blade surface pressures were converted to loading coefficients and used in an existing theory to predict the far-field rotational noise. A comparison of the calculated and measured noise shows generally good agreement up to 300 to 600 Hz, depending on the discreteness of the loading spectrum. Specific attention is given to the effects of the blade loading coefficients, chordwise loading distributions, blade loading phases, and observer azimuthal position on the calculations.

Stress and stability of plate-screw fixation and screw fixation in the treatment of Schatzker type IV medial tibial plateau fracture: a comparative finite element study.

PubMed

Huang, Xiaowei; Zhi, Zhongzheng; Yu, Baoqing; Chen, Fancheng

2015-11-25

The purpose of this study is to compare the stress and stability of plate-screw fixation and screw fixation in the treatment of Schatzker type IV medial tibial plateau fracture. A three-dimensional (3D) finite element model of the medial tibial plateau fracture (Schatzker type IV fracture) was created. An axial force of 2500 N with a distribution of 60% to the medial compartment was applied to simulate the axial compressive load on an adult knee during single-limb stance. The equivalent von Mises stress, displacement of the model relative to the distal tibia, and displacement of the implants were used as the output measures. The mean stress value of the plate-screw fixation system was 18.78 MPa, which was significantly (P < 0.001) smaller than that of the screw fixation system. The maximal value of displacement (sum) in the plate-screw fixation system was 2.46 mm, which was lower than that in the screw fixation system (3.91 mm). The peak stress value of the triangular fragment in the plate-screw fixation system model was 42.04 MPa, which was higher than that in the screw fixation model (24.18 MPa). But the mean stress of the triangular fractured fragment in the screw fixation model was significantly higher in terms of equivalent von Mises stress (EVMS), x-axis, and z-axis (P < 0.001). This study demonstrated that the load transmission mechanism between plate-screw fixation system and screw fixation system was different and the stability provided by the plate-screw fixation system was superior to the screw fixation system.

Three-Dimensional Stress Fields and Slip Systems for Single Crystal Superalloy Notched Specimens

NASA Technical Reports Server (NTRS)

Magnan, Shannon M.; Throckmorton, David (Technical Monitor)

2002-01-01

Single crystal superalloys have become increasingly popular for turbine blade and vane applications due to their high strength, and creep and fatigue resistance at elevated temperatures. The crystallographic orientation of a single crystal material greatly affects its material properties, including elastic modulus, shear modulus, and ductility. These directional properties, along with the type of loading and temperature, dictate an anisotropic response in the yield strength, creep resistance, creep rupture ductility, fatigue resistance, etc. A significant amount of research has been conducted to determine the material properties in the <001> orientation, yet the material properties deviating from the <001> orientation have not been assessed for all cases. Based on the desired application and design criteria, a crystal orientation is selected to yield the maximum properties. Currently, single crystal manufacturing is able to control the primary crystallographic orientation within 15 of the target orientation, which is an acceptable deviation to meet both performance and cost guidelines; the secondary orientation is rarely specified. A common experiment is the standard load-controlled tensile test, in which specimens with different orientations can be loaded to observe the material response. The deformation behavior of single-crystal materials under tension and compression is known to be a function of not only material orientation, but also of varying microdeformation (i.e. dislocation) mechanisms. The underlying dislocation motion causes deformation via slip, and affects the activation of specific slip systems based on load and orientation. The slip can be analyzed by observing the visible traces left on the surface of the specimen from the slip activity within the single crystal material. The goal of this thesis was to predict the slip systems activated in three-dimensional stress fields of a notched tensile specimen, as a function of crystal orientation, using finite element analysis without addressing microstructural deformation mechanisms that govern their activation. Out of three orientations tested, the specimen with a [110] load orientation and a [001] growth direction had the lowest maximum resolved shear stress; this specimen orientation appears to be the best design candidate for a tensile application.

Stereo Imaging Velocimetry

NASA Technical Reports Server (NTRS)

McDowell, Mark (Inventor); Glasgow, Thomas K. (Inventor)

1999-01-01

A system and a method for measuring three-dimensional velocities at a plurality of points in a fluid employing at least two cameras positioned approximately perpendicular to one another. The cameras are calibrated to accurately represent image coordinates in world coordinate system. The two-dimensional views of the cameras are recorded for image processing and centroid coordinate determination. Any overlapping particle clusters are decomposed into constituent centroids. The tracer particles are tracked on a two-dimensional basis and then stereo matched to obtain three-dimensional locations of the particles as a function of time so that velocities can be measured therefrom The stereo imaging velocimetry technique of the present invention provides a full-field. quantitative, three-dimensional map of any optically transparent fluid which is seeded with tracer particles.

Flux agreement above a Scots pine plantation

NASA Astrophysics Data System (ADS)

Gay, L. W.; Vogt, R.; Bernhofer, Ch.; Blanford, J. H.

1996-03-01

The surface energy exchange of 12m high Scots pine plantation at Hartheim, Germany, was measured with a variety of methods during a 11-day period of fine weather in mid-May 1992. Net radiation and rate of thermal storage were measured with conventional net radiometers, soil heat flux discs and temperature-based storage models. The turbulent fluxes discussed in this report were obtained with an interchanging Bowen ratio energy budget system (BREB, at 14 m), two one-propeller eddy correlation systems (OPEC systems 1 and 2 at 17m), a 1-dimensional sonic eddy correlation system (SEC system 3) at 15 m, all on one “low” tower, and a 3-dimensional sonic eddy correlation system (SEC system 22) at 22 m on the “high” tower that was about 46 m distant. All systems measured sensible and latent heat (H and LE) directly, except for OPEC systems 1 and 2 which estimated LE as a residual term in the surface energy balance. Closure of turbulent fluxes from the two SEC systems was around 80% for daytime and 30% for night, with closure of 1-dimensional SEC system 3 exceeding that of 3-dimensional SEC system 22. The night measurements of turbulent fluxes contained considerable uncertainty, especially with the BREB system where measured gradients often yielded erroneous fluxes due to problems inherent in the method (i.e., computational instability as Bowen's ratio approaches -1). Also, both eddy correlation system designs (OPEC and SEC) appeared to underestimate |H| during stable conditions at night. In addition, both sonic systems (1- and 3-dimensional) underestimated |LE| during stable conditions. The underestimate of |H| at night generated residual estimates of OPEC LE containing a “phantom dew” error that erroneously decreased daily LE totals by about 10 percent. These special night problems are circumvented here by comparing results for daytime periods only, rather than for full days. To summarize, turbulent fluxes on the low tower from OPEC system 2 and the adjacent SEC system 3 were in reasonable agreement, while the BREB system appeared to overestimate H and underestimate LE; H and LE measured by SEC system 22 on the high tower were lower than from OPEC and SEC3 on the low tower. The turbulent flux measurements tended to converge, but the data exhibit unexplained differences between days, between systems, and between locations.

Morphologic Characteristics Help Explain the Gender Difference in Peak Anterior Cruciate Ligament Strain During a Simulated Pivot Landing

PubMed Central

Lipps, David B.; Oh, Youkeun K.; Ashton-Miller, James A.; Wojtys, Edward M.

2015-01-01

Background Gender differences exist in anterior cruciate ligament (ACL) cross-sectional area and lateral tibial slope. Biomechanical principles suggest that the direction of these gender differences should induce larger peak ACL strains in females under dynamic loading. Hypothesis Peak ACL relative strain during a simulated pivot landing is significantly greater in female ACLs than male ACLs. Study Design Controlled laboratory study. Methods Twenty cadaveric knees from height- and weight-matched male and female cadavers were subjected to impulsive 3-dimensional test loads of 2 times body weight in compression, flexion, and internal tibial torque starting at 15° of flexion. Load cells measured the 3-dimensional forces and moments applied to the knee, and forces in the pretensioned quadriceps, hamstring, and gastrocnemius muscle equivalents. A novel, gender-specific, nonlinear spring simulated short-range and longer range quadriceps muscle tensile stiffness. Peak relative strain in the anteromedial bundle of the ACL (AM-ACL) was measured using a differential variable reluctance transducer, while ACL cross-sectional area and lateral tibial slope were measured using magnetic resonance imaging. A repeated-measures Mann-Whitney signed-rank test was used to test the hypothesis. Results Female knees exhibited 95% greater peak AM-ACL relative strain than male knees (6.37% [22.53%] vs 3.26% [11.89%]; P = .004). Anterior cruciate ligament cross-sectional area and lateral tibial slope were significant predictors of peak AM-ACL relative strain (R2 = .59; P = .001). Conclusion Peak AM-ACL relative strain was significantly greater in female than male knees from donors of the same height and weight. This gender difference is attributed to a smaller female ACL cross-sectional area and a greater lateral tibial slope. Clinical Relevance Since female ACLs are systematically exposed to greater strain than their male counterparts, training and injury prevention programs should take this fact into consideration. PMID:21917612

Residual Strength Analyses of Monolithic Structures

NASA Technical Reports Server (NTRS)

Forth, Scott (Technical Monitor); Ambur, Damodar R. (Technical Monitor); Seshadri, B. R.; Tiwari, S. N.

2003-01-01

Finite-element fracture simulation methodology predicts the residual strength of damaged aircraft structures. The methodology uses the critical crack-tip-opening-angle (CTOA) fracture criterion to characterize the fracture behavior of the material. The CTOA fracture criterion assumes that stable crack growth occurs when the crack-tip angle reaches a constant critical value. The use of the CTOA criterion requires an elastic- plastic, finite-element analysis. The critical CTOA value is determined by simulating fracture behavior in laboratory specimens, such as a compact specimen, to obtain the angle that best fits the observed test behavior. The critical CTOA value appears to be independent of loading, crack length, and in-plane dimensions. However, it is a function of material thickness and local crack-front constraint. Modeling the local constraint requires either a three-dimensional analysis or a two-dimensional analysis with an approximation to account for the constraint effects. In recent times as the aircraft industry is leaning towards monolithic structures with the intention of reducing part count and manufacturing cost, there has been a consistent effort at NASA Langley to extend critical CTOA based numerical methodology in the analysis of integrally-stiffened panels.In this regard, a series of fracture tests were conducted on both flat and curved aluminum alloy integrally-stiffened panels. These flat panels were subjected to uniaxial tension and during the test, applied load-crack extension, out-of-plane displacements and local deformations around the crack tip region were measured. Compact and middle-crack tension specimens were tested to determine the critical angle (wc) using three-dimensional code (ZIP3D) and the plane-strain core height (hJ using two-dimensional code (STAGS). These values were then used in the STAGS analysis to predict the fracture behavior of the integrally-stiffened panels. The analyses modeled stable tearing, buckling, and crack branching at the integral stiffener using different values of critical CTOA for different material thicknesses and orientation. Comparisons were made between measured and predicted load-crack extension, out-of-plane displacements and local deformations around the crack tip region. Simultaneously, three-dimensional capabilities to model crack branching and to monitor stable crack growth of multiple cracks in a large thick integrally-stiffened flat panels were implemented in three-dimensional finite element code (ZIP3D) and tested by analyzing the integrally-stiffened panels tested at Alcoa. The residual strength of the panels predicted from STAGS and ZP3D code compared very well with experimental data. In recent times, STAGS software has been updated with new features and now one can have combinations of solid and shell elements in the residual strength analysis of integrally-stiffened panels.

[The physiological classification of human thermal states under high environmental temperatures].

PubMed

Bobrov, A F; Kuznets, E I

1995-01-01

The paper deals with the physiological classification of human thermal states in a hot environment. A review of the basic systems of classifications of thermal states is given, their main drawbacks are discussed. On the basis of human functional state research in a broad range of environmental temperatures the system of evaluation and classification of human thermal states is proposed. New integral one-dimensional multi-parametric criteria for evaluation are used. For the development of these criteria methods of factor, cluster and canonical correlation analyses are applied. Stochastic nomograms capable of identification of human thermal state for different intensity of influence are given. In this case evaluation of intensity is estimated according to one-dimensional criteria taking into account environmental temperature, physical load and time of man's staying in overheating conditions.

Biological Movement and Laws of Physics.

PubMed

Latash, Mark L

2017-07-01

Living systems may be defined as systems able to organize new, biology-specific, laws of physics and modify their parameters for specific tasks. Examples include the force-length muscle dependence mediated by the stretch reflex, and the control of movements with modification of the spatial referent coordinates for salient performance variables. Low-dimensional sets of referent coordinates at a task level are transformed to higher-dimensional sets at lower hierarchical levels in a way that ensures stability of performance. Stability of actions can be controlled independently of the actions (e.g., anticipatory synergy adjustments). Unintentional actions reflect relaxation processes leading to drifts of corresponding referent coordinates in the absence of changes in external load. Implications of this general framework for movement disorders, motor development, motor skill acquisition, and even philosophy are discussed.

Three-dimensional visual guidance improves the accuracy of calculating right ventricular volume with two-dimensional echocardiography

NASA Technical Reports Server (NTRS)

Dorosz, Jennifer L.; Bolson, Edward L.; Waiss, Mary S.; Sheehan, Florence H.

2003-01-01

Three-dimensional guidance programs have been shown to increase the reproducibility of 2-dimensional (2D) left ventricular volume calculations, but these systems have not been tested in 2D measurements of the right ventricle. Using magnetic fields to identify the probe location, we developed a new 3-dimensional guidance system that displays the line of intersection, the plane of intersection, and the numeric angle of intersection between the current image plane and previously saved scout views. When used by both an experienced and an inexperienced sonographer, this guidance system increases the accuracy of the 2D right ventricular volume measurements using a monoplane pyramidal model. Furthermore, a reconstruction of the right ventricle, with a computed volume similar to the calculated 2D volume, can be displayed quickly by tracing a few anatomic structures on 2D scans.

Atmospheric electron flux at airplane altitude

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

Enomoto, R.; Chiba, J.; Ogawa, K.

1991-12-01

We have developed a new detector to systematically measure the cosmic-ray electron flux at airplane altitudes. We loaded a lead-glass-based electron telescope onto a commercial cargo airplane. The first experiment was carried out using the air route between Narita (Japan) and Sydney (Australia); during this flight we measured the electron flux at various altitudes and latitudes. The thresholds of the electron energies were 1, 2, and 4 GeV. The results agree with a simple estimation using one-dimensional shower theory. A comparison with a Monte Carlo calculation was made.

A Novel Method for Quantifying Human In Situ Whole Brain Deformation under Rotational Loading Using Sonomicrometry.

PubMed

Alshareef, Ahmed; Giudice, J Sebastian; Forman, Jason; Salzar, Robert S; Panzer, Matthew B

2018-03-01

Traumatic brain injuries (TBI) are one of the least understood injuries to the body. Finite element (FE) models of the brain have been crucial for understanding concussion and for developing injury mitigation systems; however, the experimental brain deformation data currently used to validate these models are limited. The objective of this study was to develop a methodology for the investigation of in situ three-dimensional brain deformation during pure rotational loading of the head, using sonomicrometry. Sonomicrometry uses ultrasonic pulses to measure the dynamic distances between piezoelectric crystals implanted in any sound-transmitting media. A human cadaveric head-neck specimen was acquired 14 h postmortem and was instrumented with an array of 32 small sonomicrometry crystals embedded in the head: 24 crystals were implanted in the brain, and 8 were fixed to the inner skull. A dynamic rotation was then applied to the head using a closed-loop controlled test device. Four pulses with different severity levels were applied around three orthogonal anatomical axes of rotation. A repeated test of the highest severity rotation was conducted in each axis to assess repeatability. All tests were completed within 56 h postmortem. Overall, the combined experimental and sonomicrometry methods were demonstrated to reliably and repeatedly capture three-dimensional dynamic deformation of an intact human brain. These methods provide a framework for using sonomicrometry to acquire multidimensional experimental data required for FE model development and validation, and will lend insight into the deformations sustained by the brain during impact.

Advanced one-dimensional optical strain measurement system, phase 4

NASA Technical Reports Server (NTRS)

Lant, Christian T.

1992-01-01

An improved version of the speckle-shift strain measurement system was developed. The system uses a two-dimensional sensor array to maintain speckle correlation in the presence of large off-axis rigid body motions. A digital signal processor (DSP) is used to calculate strains at a rate near the RS-170 camera frame rate. Strain measurements were demonstrated on small diameter wires and fibers used in composite materials research. Accurate values of Young's modulus were measured on tungsten wires, and silicon carbide and sapphire fibers. This optical technique has measured surface strains at specimen temperatures above 750 C and has shown the potential for measurements at much higher temperatures.

A Hydrostatic Bearing Test System for Measuring Bearing Load Using Magnetic-Fluid Lubricants.

PubMed

Weng, Huei Chu; Chen, Lu-Yu

2016-05-01

This paper conducts a study on the design of a hydrostatic bearing test system. It involves the determination of viscous properties of magnetic-fluid lubricants. The load of a hydrostatic thrust bearing using a water-based magnetite nanofluid of varying volume flow rate is measured under an applied external induction field via the test system. Results reveal that the presence of nanoparticles in a carrier liquid would cause an enhanced bearing load. Such an effect could be further magnified by increasing the lubricant volume flow rate or the external induction field strength.

Evaluating mental workload of two-dimensional and three-dimensional visualization for anatomical structure localization.

PubMed

Foo, Jung-Leng; Martinez-Escobar, Marisol; Juhnke, Bethany; Cassidy, Keely; Hisley, Kenneth; Lobe, Thom; Winer, Eliot

2013-01-01

Visualization of medical data in three-dimensional (3D) or two-dimensional (2D) views is a complex area of research. In many fields 3D views are used to understand the shape of an object, and 2D views are used to understand spatial relationships. It is unclear how 2D/3D views play a role in the medical field. Using 3D views can potentially decrease the learning curve experienced with traditional 2D views by providing a whole representation of the patient's anatomy. However, there are challenges with 3D views compared with 2D. This current study expands on a previous study to evaluate the mental workload associated with both 2D and 3D views. Twenty-five first-year medical students were asked to localize three anatomical structures--gallbladder, celiac trunk, and superior mesenteric artery--in either 2D or 3D environments. Accuracy and time were taken as the objective measures for mental workload. The NASA Task Load Index (NASA-TLX) was used as a subjective measure for mental workload. Results showed that participants viewing in 3D had higher localization accuracy and a lower subjective measure of mental workload, specifically, the mental demand component of the NASA-TLX. Results from this study may prove useful for designing curricula in anatomy education and improving training procedures for surgeons.

Sex-based differences in lifting technique under increasing load conditions: A principal component analysis.

PubMed

Sheppard, P S; Stevenson, J M; Graham, R B

2016-05-01

The objective of the present study was to determine if there is a sex-based difference in lifting technique across increasing-load conditions. Eleven male and 14 female participants (n = 25) with no previous history of low back disorder participated in the study. Participants completed freestyle, symmetric lifts of a box with handles from the floor to a table positioned at 50% of their height for five trials under three load conditions (10%, 20%, and 30% of their individual maximum isometric back strength). Joint kinematic data for the ankle, knee, hip, and lumbar and thoracic spine were collected using a two-camera Optotrak motion capture system. Joint angles were calculated using a three-dimensional Euler rotation sequence. Principal component analysis (PCA) and single component reconstruction were applied to assess differences in lifting technique across the entire waveforms. Thirty-two PCs were retained from the five joints and three axes in accordance with the 90% trace criterion. Repeated-measures ANOVA with a mixed design revealed no significant effect of sex for any of the PCs. This is contrary to previous research that used discrete points on the lifting curve to analyze sex-based differences, but agrees with more recent research using more complex analysis techniques. There was a significant effect of load on lifting technique for five PCs of the lower limb (PC1 of ankle flexion, knee flexion, and knee adduction, as well as PC2 and PC3 of hip flexion) (p < 0.005). However, there was no significant effect of load on the thoracic and lumbar spine. It was concluded that when load is standardized to individual back strength characteristics, males and females adopted a similar lifting technique. In addition, as load increased male and female participants changed their lifting technique in a similar manner. Copyright © 2016. Published by Elsevier Ltd.

Fluid–Structure Interaction Analysis of Papillary Muscle Forces Using a Comprehensive Mitral Valve Model with 3D Chordal Structure

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

Toma, Milan; Jensen, Morten Ø.; Einstein, Daniel R.

2015-07-17

Numerical models of native heart valves are being used to study valve biomechanics to aid design and development of repair procedures and replacement devices. These models have evolved from simple two-dimensional approximations to complex three-dimensional, fully coupled fluid-structure interaction (FSI) systems. Such simulations are useful for predicting the mechanical and hemodynamic loading on implanted valve devices. A current challenge for improving the accuracy of these predictions is choosing and implementing modeling boundary conditions. In order to address this challenge, we are utilizing an advanced in-vitro system to validate FSI conditions for the mitral valve system. Explanted ovine mitral valves weremore » mounted in an in vitro setup, and structural data for the mitral valve was acquired with *CT. Experimental data from the in-vitro ovine mitral valve system were used to validate the computational model. As the valve closes, the hemodynamic data, high speed lea et dynamics, and force vectors from the in-vitro system were compared to the results of the FSI simulation computational model. The total force of 2.6 N per papillary muscle is matched by the computational model. In vitro and in vivo force measurements are important in validating and adjusting material parameters in computational models. The simulations can then be used to answer questions that are otherwise not possible to investigate experimentally. This work is important to maximize the validity of computational models of not just the mitral valve, but any biomechanical aspect using computational simulation in designing medical devices.« less

Fluid-Structure Interaction Analysis of Papillary Muscle Forces Using a Comprehensive Mitral Valve Model with 3D Chordal Structure.

PubMed

Toma, Milan; Jensen, Morten Ø; Einstein, Daniel R; Yoganathan, Ajit P; Cochran, Richard P; Kunzelman, Karyn S

2016-04-01

Numerical models of native heart valves are being used to study valve biomechanics to aid design and development of repair procedures and replacement devices. These models have evolved from simple two-dimensional approximations to complex three-dimensional, fully coupled fluid-structure interaction (FSI) systems. Such simulations are useful for predicting the mechanical and hemodynamic loading on implanted valve devices. A current challenge for improving the accuracy of these predictions is choosing and implementing modeling boundary conditions. In order to address this challenge, we are utilizing an advanced in vitro system to validate FSI conditions for the mitral valve system. Explanted ovine mitral valves were mounted in an in vitro setup, and structural data for the mitral valve was acquired with [Formula: see text]CT. Experimental data from the in vitro ovine mitral valve system were used to validate the computational model. As the valve closes, the hemodynamic data, high speed leaflet dynamics, and force vectors from the in vitro system were compared to the results of the FSI simulation computational model. The total force of 2.6 N per papillary muscle is matched by the computational model. In vitro and in vivo force measurements enable validating and adjusting material parameters to improve the accuracy of computational models. The simulations can then be used to answer questions that are otherwise not possible to investigate experimentally. This work is important to maximize the validity of computational models of not just the mitral valve, but any biomechanical aspect using computational simulation in designing medical devices.

Effect of thermal stresses on the mechanism of tooth pain.

PubMed

Oskui, Iman Z; Ashtiani, Mohammed N; Hashemi, Ata; Jafarzadeh, Hamid

2014-11-01

Daily hot and cold thermal loadings on teeth may result in structural deformation, mechanical stress, and pain signaling. The aim of this study was to compare the adverse effects of hot and cold beverages on an intact tooth and, then, to provide physical evidence to support the hydrodynamic theory of tooth pain sensation mechanism. Three-dimensional finite element analysis was performed on a premolar model subjected to hot and cold thermal loadings. Elapsed times for heat diffusion and stress detection at the pulp-dentin junction were calculated as measures of the pain sensation. Extreme tensile stress within the enamel resulted in damage in cold loadings. Also, extreme values of stress at the pulpal wall occurred 21.6 seconds earlier than extreme temperatures in hot and cold loadings. The intact tooth was remarkably vulnerable to cold loading. Earlier changes in mechanical stress rather than temperature at the pulp-dentin junction indicate that the dental pain caused by hot or cold beverages may be based on the hydrodynamic theory. Copyright © 2014 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

Residual Strength Predictions with Crack Buckling

NASA Technical Reports Server (NTRS)

Dawicke, D. S.; Gullerud, A. S.; Dodds, R. H., Jr.; Hampton, R. W.

1999-01-01

Fracture tests were conducted on middle crack tension, M(T), and compact tension, C(T), specimens of varying widths, constructed from 0.063 inch thick sheets of 2024-T3 aluminum alloy. Guide plates were used to restrict out-of-plane displacements in about half of the tests. Analyses using the three-dimensional, elastic-plastic finite element code WARP3D simulated the tests with and without guide plates using a critical CTOA fracture criterion. The experimental results indicate that crack buckling reduced the failure loads by up to 40%. Using a critical CTOA value of 5.5 deg., the WARP3D analyses predicted the failure loads for the tests with guide plates within +/- 10% of the experimentally measured values. For the M(T) tests without guide plates, the WARP3D analyses predicted the failure loads for the 12 and 24 inch tests within 10%, while over predicting the failure loads for the 40 inch wide tests by about 20%.

Three-dimensional graphene-polypyrrole hybrid electrochemical actuator

NASA Astrophysics Data System (ADS)

Liu, Jia; Wang, Zhi; Zhao, Yang; Cheng, Huhu; Hu, Chuangang; Jiang, Lan; Qu, Liangti

2012-11-01

The advancement of mechanical actuators benefits from the development of new structural materials with prominent properties. A novel three-dimensional (3D) hydrothermally converted graphene and polypyrrole (G-PPy) hybrid electrochemical actuator is presented, which is prepared via a convenient hydrothermal process, followed by in situ electropolymerization of pyrrole. The 3D pore-interconnected G-PPy pillar exhibits strong actuation responses superior to pure graphene and PPy film. In response to the low potentials of +/-0.8 V, the saturated strain of 3D G-PPy pillar can reach a record of 2.5%, which is more than 10 times higher than that of carbon nanotube film and about 3 times that of unitary graphene film under an applied potential of +/-1.2 V. Also, the 3D G-PPy actuator exhibits high actuation durability with high operating load as demonstrated by an 11 day continuous measurement. Finally, a proof-of-concept application of 3D G-PPy as smart filler for on/off switch is also demonstrated, which indicates the great potential of the 3D G-PPy structure developed in this study for advanced actuator systems.The advancement of mechanical actuators benefits from the development of new structural materials with prominent properties. A novel three-dimensional (3D) hydrothermally converted graphene and polypyrrole (G-PPy) hybrid electrochemical actuator is presented, which is prepared via a convenient hydrothermal process, followed by in situ electropolymerization of pyrrole. The 3D pore-interconnected G-PPy pillar exhibits strong actuation responses superior to pure graphene and PPy film. In response to the low potentials of +/-0.8 V, the saturated strain of 3D G-PPy pillar can reach a record of 2.5%, which is more than 10 times higher than that of carbon nanotube film and about 3 times that of unitary graphene film under an applied potential of +/-1.2 V. Also, the 3D G-PPy actuator exhibits high actuation durability with high operating load as demonstrated by an 11 day continuous measurement. Finally, a proof-of-concept application of 3D G-PPy as smart filler for on/off switch is also demonstrated, which indicates the great potential of the 3D G-PPy structure developed in this study for advanced actuator systems. Electronic supplementary information (ESI) available: Experimental setup for fabrication of G-PPy hybrid structure, and movie showing the on/off response of G-PPy filler. See DOI: 10.1039/c2nr32699j

A Mechanism for the Loading-Unloading Substorm Cycle Missing in MHD Global Magnetospheric Simulation Models

NASA Technical Reports Server (NTRS)

Klimas, A. J.; Uritsky, V.; Vassiliadis, D.; Baker, D. N.

2005-01-01

Loading and consequent unloading of magnetic flux is an essential element of the substorm cycle in Earth's magnetotail. We are unaware of an available global MHD magnetospheric simulation model that includes a loading- unloading cycle in its behavior. Given the central role that MHD models presently play in the development of our understanding of magnetospheric dynamics, and given the present plans for the central role that these models will play in ongoing space weather prediction programs, it is clear that this failure must be corrected. A 2-dimensional numerical driven current-sheet model has been developed that incorporates an idealized current- driven instability with a resistive MHD system. Under steady loading, the model exhibits a global loading- unloading cycle. The specific mechanism for producing the loading-unloading cycle will be discussed. It will be shown that scale-free avalanching of electromagnetic energy through the model, from loading to unloading, is carried by repetitive bursts of localized reconnection. Each burst leads, somewhat later, to a field configuration that is capable of exciting a reconnection burst again. This process repeats itself in an intermittent manner while the total field energy in the system falls. At the end of an unloading interval, the total field energy is reduced to well below that necessary to initiate the next unloading event and, thus, a loading-unloading cycle results. It will be shown that, in this model, it is the topology of bursty localized reconnection that is responsible for the appearance of the loading-unloading cycle.

Chaos in quantum steering in high-dimensional systems

NASA Astrophysics Data System (ADS)

He, Guang Ping

2018-04-01

Quantum steering means that in some bipartite quantum systems the local measurements on one side can determine the state of the other side. Here we show that in high-dimensional systems there exists a specific entangled state which can display a kind of chaos effect when being adopted for steering. That is, a subtle difference in the measurement results on one side can steer the other side into completely orthogonal states. Moreover, by expanding the result to infinite-dimensional systems, we find two sets of states for which, contrary to common belief, even though their density matrices approach being identical, the steering between them is impossible. This property makes them very useful for quantum cryptography.

Feasibility of solid oxide fuel cell dynamic hydrogen coproduction to meet building demand

NASA Astrophysics Data System (ADS)

Shaffer, Brendan; Brouwer, Jacob

2014-02-01

A dynamic internal reforming-solid oxide fuel cell system model is developed and used to simulate the coproduction of electricity and hydrogen while meeting the measured dynamic load of a typical southern California commercial building. The simulated direct internal reforming-solid oxide fuel cell (DIR-SOFC) system is controlled to become an electrical load following device that well follows the measured building load data (3-s resolution). The feasibility of the DIR-SOFC system to meet the dynamic building demand while co-producing hydrogen is demonstrated. The resulting thermal responses of the system to the electrical load dynamics as well as those dynamics associated with the filling of a hydrogen collection tank are investigated. The DIR-SOFC system model also allows for resolution of the fuel cell species and temperature distributions during these dynamics since thermal gradients are a concern for DIR-SOFC.

A low-cost and portable realization on fringe projection three-dimensional measurement

NASA Astrophysics Data System (ADS)

Xiao, Suzhi; Tao, Wei; Zhao, Hui

2015-12-01

Fringe projection three-dimensional measurement is widely applied in a wide range of industrial application. The traditional fringe projection system has the disadvantages of high expense, big size, and complicated calibration requirements. In this paper we introduce a low-cost and portable realization on three-dimensional measurement with Pico projector. It has the advantages of low cost, compact physical size, and flexible configuration. For the proposed fringe projection system, there is no restriction to camera and projector's relative alignment on parallelism and perpendicularity for installation. Moreover, plane-based calibration method is adopted in this paper that avoids critical requirements on calibration system such as additional gauge block or precise linear z stage. What is more, error sources existing in the proposed system are introduced in this paper. The experimental results demonstrate the feasibility of the proposed low cost and portable fringe projection system.

Three Dimensional Vibration Characteristics of the Permanent Magnet-HTSC Magnetic Bearing

NASA Astrophysics Data System (ADS)

Ohashi, Shunsuke

The three dimensional vibration of the rotor in a HTSC-permanent magnet bearing system is studied. We have developed the magnetic bearing system which can revolve up to 12,000rpm, and three dimensional vibration of the rotor is measured with laser displacement sensors. To consider the rotor vibration under the mechanical resonance state, static lateral and vertical pinning force of the magnetic bearing is measured. From the results, resonance frequency is given. There are two factors of mechanical resonance caused by the magnetic bearing. One is lateral equivalent spring and the other is vertical one. Influence of the resonance caused by the lateral spring is large, and that by the vertical one is small. Three dimensional vibration of the rotor position around the mechanical resonance frequency is measured. Because revolution of the rotor increases lateral force to the center, resonance frequency given from the free revolution experiment becomes larger than that from pinning force measurement.

Selection considerations between ZERODUR® and silicon carbide for dimensionally-stable spaceborne optical telescopes in two-earth-orbits

NASA Astrophysics Data System (ADS)

Hull, Tony; Westerhoff, Thomas; Weidmann, Gunter

2015-09-01

A key consideration in defining a space telescope mission is definition of the optical materials. This selection defines both the performance of the system and system complexity and cost. Optimal material selection for system stability must consider the thermal environment and its variation. Via numerical simulations, we compare the thermal and structural-mechanical behavior of ZERODUR® and SiC as mirror substrates for telescope assemblies in space. SiC has significantly larger CTE values then ZERODUR®, but also its thermal diffusivity k/(ρcp) is larger, and that helps to homogenize thermal gradients in the mirror. Therefore it is not obvious at first glance which material performs with better dimensional stability under realistic unsteady, inhomogeneous thermal loads. We specifically examine the telescope response to transient, gradient driving, thermal environments representative of low- and high-earth- orbits.

Multidisciplinary Design Optimization of A Highly Flexible Aeroservoelastic Wing

NASA Astrophysics Data System (ADS)

Haghighat, Sohrab

A multidisciplinary design optimization framework is developed that integrates control system design with aerostructural design for a highly-deformable wing. The objective of this framework is to surpass the existing aircraft endurance limits through the use of an active load alleviation system designed concurrently with the rest of the aircraft. The novelty of this work is two fold. First, a unified dynamics framework is developed to represent the full six-degree-of-freedom rigid-body along with the structural dynamics. It allows for an integrated control design to account for both manoeuvrability (flying quality) and aeroelasticity criteria simultaneously. Secondly, by synthesizing the aircraft control system along with the structural sizing and aerodynamic shape design, the final design has the potential to exploit synergies among the three disciplines and yield higher performing aircraft. A co-rotational structural framework featuring Euler--Bernoulli beam elements is developed to capture the wing's nonlinear deformations under the effect of aerodynamic and inertial loadings. In this work, a three-dimensional aerodynamic panel code, capable of calculating both steady and unsteady loadings is used. Two different control methods, a model predictive controller (MPC) and a 2-DOF mixed-norm robust controller, are considered in this work to control a highly flexible aircraft. Both control techniques offer unique advantages that make them promising for controlling a highly flexible aircraft. The control system works towards executing time-dependent manoeuvres along with performing gust/manoeuvre load alleviation. The developed framework is investigated for demonstration in two design cases: one in which the control system simply worked towards achieving or maintaining a target altitude, and another where the control system is also performing load alleviation. The use of the active load alleviation system results in a significant improvement in the aircraft performance relative to the optimum result without load alleviation. The results show that the inclusion of control system discipline along with other disciplines at early stages of aircraft design improves aircraft performance. It is also shown that structural stresses due to gust excitations can be better controlled by the use of active structural control systems which can improve the fatigue life of the structure.

A novel multi-dimensional absolute distance measurement system using a basic frequency modulated continuous wave radar and an external cavity laser with trilateration metrology

NASA Astrophysics Data System (ADS)

Xiong, Xingting; Qu, Xinghua; Zhang, Fumin

2018-01-01

We propose and describe a novel multi-dimensional absolute distance measurement system. This system incorporates a basic frequency modulated continuous wave (FMCW) radar and an second external cavity laser (ECL). Through the use of trilateration, the system in our paper can provide 3D resolution inherently range. However, the measured optical path length differences (OPD) is often variable in industrial environments and this will causes Doppler effect, which has greatly impact on the measurement result. With using the second ECL, the system can correct the Doppler effect to ensure the precision of absolute distance measurement. Result of the simulation will prove the influence of Doppler effect.

Development of sensitized pick coal interface detector system

NASA Technical Reports Server (NTRS)

Burchill, R. F.

1982-01-01

One approach for detection of the coal interface is measurement of pick cutting loads and shock through the use of pick strain gage load cells and accelerometers. The cutting drum of a long wall mining machine contains a number of cutting picks. In order to measure pick loads and shocks, one pick was instrumented and telemetry used to transmit the signals from the drum to an instrument-type tape recorder. A data system using FM telemetry was designed to transfer cutting bit load and shock information from the drum of a longwall shearer coal mining machine to a chassis mounted data recorder. The design of components in the test data system were finalized, the required instruments were assembled, the instrument system was evaluated in an above-ground simulation test, and an underground test series to obtain tape recorded sensor data was conducted.

Spin-oscillator model for the unzipping of biomolecules by mechanical force.

PubMed

Prados, A; Carpio, A; Bonilla, L L

2012-08-01

A spin-oscillator system models unzipping of biomolecules (such as DNA, RNA, or proteins) subject to an external force. The system comprises a macroscopic degree of freedom, represented by a one-dimensional oscillator, and internal degrees of freedom, represented by Glauber spins with nearest-neighbor interaction and a coupling constant proportional to the oscillator position. At a critical value F(c) of an applied external force F, the oscillator rest position (order parameter) changes abruptly and the system undergoes a first-order phase transition. When the external force is cycled at different rates, the extension given by the oscillator position exhibits a hysteresis cycle at high loading rates, whereas it moves reversibly over the equilibrium force-extension curve at very low loading rates. Under constant force, the logarithm of the residence time at the stable and metastable oscillator rest position is proportional to F-F(c) as in an Arrhenius law.

Rotor redesign for a highly loaded 1800 ft/sec tip speed fan. 1: Aerodynamic and mechanical design report

NASA Technical Reports Server (NTRS)

Norton, J. M.; Tari, U.; Weber, R. M.

1979-01-01

A quasi three dimensional design system and multiple-circular-arc airfoil sections were used to design a fan rotor. An axisymmetric intrablade flow field calculation modeled the shroud of an isolated splitter and radial distribution. The structural analysis indicates that the design is satisfactory for evaluation of aerodynamic performance of the fan stage in a test facility.

Automated acoustic intensity measurements and the effect of gear tooth profile on noise

NASA Technical Reports Server (NTRS)

Atherton, William J.; Pintz, Adam; Lewicki, David G.

1987-01-01

Acoustic intensity measurements were made at NASA Lewis Research Center on a spur gear test apparatus. The measurements were obtained with the Robotic Acoustic Intensity Measurement System developed by Cleveland State University. This system provided dense spatial positioning, and was calibrated against a high quality acoustic intensity system. The measured gear noise compared gearsets having two different tooth profiles. The tests evaluated the sound field of the different gears for two speeds and three loads. The experimental results showed that gear tooth profile had a major effect on measured noise. Load and speed were found to have an effect on noise also.

Ultracold atoms in an optical lattice one millimeter from air

NASA Astrophysics Data System (ADS)

Jervis, Dylan; Edge, Graham; Trotzky, Stefan; McKay, David; Thywissen, Joseph

2013-05-01

Over the past decade, ultracold atoms in optical lattices have shown to be versatile systems able to realize canonical Hamiltonians of condensed matter. High-resolution in-situ imaging of ultracold clouds has furthermore enabled thermometry, equation of state measurements, direct measurement of fluctuations, and unprecedented control. We report on microscopy of ultracold bosons and fermions in a novel configuration where the atoms are harmonically trapped 800 microns away from a 200 micron-thick vacuum window. This window also serves as a retro-reflecting mirror for an optical lattice, into which the atoms can be loaded. Two additional transverse standing waves complete the three-dimensional lattice setup. In free space, we have shown that laser cooling with 405 nm light, on the open 4S1/2-5P3/2 transition, allows for temperatures below the Doppler temperature of the 4S1/2-4P3/2 cycling transition at 767 nm. Microscopy with 405 nm light furthermore reduces the diffraction limit of in-situ imaging.

Radicals and Reservoirs in the GMI Chemistry and Transport Model: Comparison to Measurements

NASA Technical Reports Server (NTRS)

Douglass, Anne R.; Stolarski, Richard S.; Strahan, Susan E.; Connell, Peter S.

2004-01-01

We have used a three-dimensional chemistry and transport model (CTM), developed under the Global Modeling Initiative (GMI), to carry out two simulations of the composition of the stratosphere under changing halogen loading for 1995 through 2030. The two simulations differ only in that one uses meteorological fields from a general circulation model while the other uses meteorological fields from a data assimilation system. A single year's winds and temperatures are repeated for each 36-year simulation. We compare results from these two simulations with an extensive collection of data from satellite and ground-based measurements for 1993-2000. Comparisons of simulated fields with observations of radical and reservoir species for some of the major ozone-destroying compounds are of similar quality for both simulations. Differences in the upper stratosphere, caused by transport of total reactive nitrogen and methane, impact the balance among the ozone loss processes and the sensitivity of the two simulations to the change in composition.

Anticipatory effects on anterior cruciate ligament loading during sidestep cutting.

PubMed

Weinhandl, Joshua T; Earl-Boehm, Jennifer E; Ebersole, Kyle T; Huddleston, Wendy E; Armstrong, Brian S R; O'Connor, Kristian M

2013-07-01

A key to understanding potential anterior cruciate ligament injury mechanisms is to determine joint loading characteristics associated with an injury-causing event. However, direct measurement of anterior cruciate ligament loading during athletic tasks is invasive. Thus, previous research has been unable to study the association between neuromuscular variables and anterior cruciate ligament loading. Therefore, the purpose of this study was to determine the influence of movement anticipation on anterior cruciate ligament loading using a musculoskeletal modeling approach. Twenty healthy recreationally active females were recruited to perform anticipated and unanticipated sidestep cutting. Three-dimensional kinematics and kinetics of the right leg were calculated. Muscle, joint and anterior cruciate ligament forces were then estimated using a musculoskeletal model. Dependent t-tests were conducted to investigate differences between the two cutting conditions. ACL loading significantly increased during unanticipated sidestep cutting (p<0.05). This increase was primarily due to a significant increase in the sagittal plane ACL loading, which contributed 62% of the total loading. Frontal plane ACL loading contributed 26% and transverse plane ACL loading contributed 12%. These results suggest that anterior cruciate ligament loading resulted from a multifaceted interaction of the sagittal plane shear forces (i.e., quadriceps, hamstrings, and tibiofemoral), as well as the frontal and transverse plane knee moments. Additionally, the results of this study confirm the hypothesis in the current literature that unanticipated movements such as sidestep cutting increase anterior cruciate ligament loading. Copyright © 2013 Elsevier Ltd. All rights reserved.

Comparison of Building Loads Analysis and System Thermodynamics (BLAST) Computer Program Simulations and Measured Energy Use for Army Buildings.

DTIC Science & Technology

1980-05-01

engineering ,ZteNo D R RPTE16 research w 9 laboratory COMPARISON OF BUILDING LOADS ANALYSIS AND SYSTEM THERMODYNAMICS (BLAST) AD 0 5 5,0 3COMPUTER PROGRAM...Building Loads Analysis and System Thermodynamics (BLAST) computer program. A dental clinic and a battalion headquarters and classroom building were...Building and HVAC System Data Computer Simulation Comparison of Actual and Simulated Results ANALYSIS AND FINDINGS

Lyapunov exponents for infinite dimensional dynamical systems

NASA Technical Reports Server (NTRS)

Mhuiris, Nessan Mac Giolla

1987-01-01

Classically it was held that solutions to deterministic partial differential equations (i.e., ones with smooth coefficients and boundary data) could become random only through one mechanism, namely by the activation of more and more of the infinite number of degrees of freedom that are available to such a system. It is only recently that researchers have come to suspect that many infinite dimensional nonlinear systems may in fact possess finite dimensional chaotic attractors. Lyapunov exponents provide a tool for probing the nature of these attractors. This paper examines how these exponents might be measured for infinite dimensional systems.

Frequency-Switchable Microfluidic CSRR-Loaded QMSIW Band-Pass Filter Using a Liquid Metal Alloy

PubMed Central

Eom, Seunghyun; Memon, Muhammad Usman; Lim, Sungjoon

2017-01-01

In this paper, we have proposed a frequency-switchable complementary split-ring resonator (CSRR)-loaded quarter-mode substrate-integrated-waveguide (QMSIW) band-pass filter. For frequency switching, a microfluidic channel and liquid metal are used. The liquid metal used is eutectic gallium-indium (EGaIn), consisting of 24.5% indium and 75.5% gallium. The microfluidic channels are built using the elastomer polydimethylsiloxane (PDMS) and three-dimensional-printed microfluidic channel frames. The CSRR-loaded QMSIW band-pass filter is designed to have two states. Before the injection of the liquid metal, the measured center frequency and fractional bandwidths are 2.205 GHz and 6.80%, respectively. After injection, the center frequency shifts from 2.205 GHz to 2.56 GHz. Although the coupling coefficient is practically unchanged, the fractional bandwidth changes from 6.8% to 9.38%, as the CSRR shape changes and the external quality factor decreases. After the removal of the liquid metal, the measured values are similar to the values recorded before the liquid metal was injected. The repeatability of the frequency-switchable mechanism is, therefore, verified. PMID:28350355

Particle tracking experiments in match-index-refraction porous media.

PubMed

Lachhab, Ahmed; Zhang, You-Kuan; Muste, Marian V I

2008-01-01

A low-cost, noninvasive, three-dimensional (3D), particle tracking velocimetry system was designed and built to investigate particle movement in match-index-refraction porous media. Both a uniform load of the glass beads of the same diameter and a binary load of the glass beads of two diameters were used. The purpose of the experiments is to study the effect of the two loads on the trajectories, velocity distribution, and spreading of small physical particles. A total of 35 particles were released and tracked in the uniform load and 46 in the binary load. The 3D trajectory of each particle was recorded with two video camcorders and analyzed. It is found that the particle's velocity, trajectory, and spreading are very sensitive to its initial location and that the smaller pore size or heterogeneity in the binary load increases the particles' velocity and enhances their spreading as compared with the uniform load. The experiments also verified the previous finding that the distribution of the particle velocities are lognormal in the longitudinal direction and Gaussian in two transverse directions and that the particle spreading is much larger along the longitudinal direction than along the traverse directions.

Cognitive Load Measurement in a Virtual Reality-based Driving System for Autism Intervention

PubMed Central

Zhang, Lian; Wade, Joshua; Bian, Dayi; Fan, Jing; Swanson, Amy; Weitlauf, Amy; Warren, Zachary; Sarkar, Nilanjan

2016-01-01

Autism Spectrum Disorder (ASD) is a highly prevalent neurodevelopmental disorder with enormous individual and social cost. In this paper, a novel virtual reality (VR)-based driving system was introduced to teach driving skills to adolescents with ASD. This driving system is capable of gathering eye gaze, electroencephalography, and peripheral physiology data in addition to driving performance data. The objective of this paper is to fuse multimodal information to measure cognitive load during driving such that driving tasks can be individualized for optimal skill learning. Individualization of ASD intervention is an important criterion due to the spectrum nature of the disorder. Twenty adolescents with ASD participated in our study and the data collected were used for systematic feature extraction and classification of cognitive loads based on five well-known machine learning methods. Subsequently, three information fusion schemes—feature level fusion, decision level fusion and hybrid level fusion—were explored. Results indicate that multimodal information fusion can be used to measure cognitive load with high accuracy. Such a mechanism is essential since it will allow individualization of driving skill training based on cognitive load, which will facilitate acceptance of this driving system for clinical use and eventual commercialization. PMID:28966730

Cognitive Load Measurement in a Virtual Reality-based Driving System for Autism Intervention.

PubMed

Zhang, Lian; Wade, Joshua; Bian, Dayi; Fan, Jing; Swanson, Amy; Weitlauf, Amy; Warren, Zachary; Sarkar, Nilanjan

2017-01-01

Autism Spectrum Disorder (ASD) is a highly prevalent neurodevelopmental disorder with enormous individual and social cost. In this paper, a novel virtual reality (VR)-based driving system was introduced to teach driving skills to adolescents with ASD. This driving system is capable of gathering eye gaze, electroencephalography, and peripheral physiology data in addition to driving performance data. The objective of this paper is to fuse multimodal information to measure cognitive load during driving such that driving tasks can be individualized for optimal skill learning. Individualization of ASD intervention is an important criterion due to the spectrum nature of the disorder. Twenty adolescents with ASD participated in our study and the data collected were used for systematic feature extraction and classification of cognitive loads based on five well-known machine learning methods. Subsequently, three information fusion schemes-feature level fusion, decision level fusion and hybrid level fusion-were explored. Results indicate that multimodal information fusion can be used to measure cognitive load with high accuracy. Such a mechanism is essential since it will allow individualization of driving skill training based on cognitive load, which will facilitate acceptance of this driving system for clinical use and eventual commercialization.

A functional video-based anthropometric measuring system

NASA Technical Reports Server (NTRS)

Nixon, J. H.; Cater, J. P.

1982-01-01

A high-speed anthropometric three dimensional measurement system using the Selcom Selspot motion tracking instrument for visual data acquisition is discussed. A three-dimensional scanning system was created which collects video, audio, and performance data on a single standard video cassette recorder. Recording rates of 1 megabit per second for periods of up to two hours are possible with the system design. A high-speed off-the-shelf motion analysis system for collecting optical information as used. The video recording adapter (VRA) is interfaced to the Selspot data acquisition system.

In vivo tibiofemoral cartilage-to-cartilage contact area of females with medial osteoarthritis under acute loading using MRI.

PubMed

Shin, Choongsoo S; Souza, Richard B; Kumar, Deepak; Link, Thomas M; Wyman, Bradley T; Majumdar, Sharmila

2011-12-01

To investigate the effect of acute loading on in vivo tibiofemoral contact area changes in both compartments, and to determine whether in vivo tibiofemoral contact area differs between subjects with medial knee osteoarthritis (OA) and healthy controls. Ten subjects with medial knee OA (KL3) and 11 control subjects (KL0) were tested. Coronal three-dimensional spoiled gradient-recalled (3D-SPGR) and T(2) -weighted fast spin-echo FSE magnetic resonance imaging (MRI) of the knee were acquired under both unloaded and loaded conditions. Tibiofemoral cartilage contact areas were measured using image-based 3D models. Tibiofemoral contact areas in both compartments significantly increased under loading (P < 0.001) and the increased contact area in the medial compartment was significantly larger than in the lateral compartment (P < 0.05). Medial compartment contact area was significantly larger in KL3 subjects than KL0 subjects, both at unloaded and loaded conditions (P < 0.05). Contact areas measured from 3D-SPGR and T(2) -weighted FSE images were strongly correlated (r = 0.904). Females with medial OA increased tibiofemoral contact area in the medial compartment compared to healthy subjects under both unloaded and loaded conditions. The contact area data presented in this study may provide a quantitative reference for further cartilage contact biomechanics such as contact stress analysis and cartilage biomechanical function difference between osteoarthritic and healthy knees. Copyright © 2011 Wiley Periodicals, Inc.

Dimensional Analysis of Impulse Loading Resulting from Detonation of Shallow-Buried Charges

DTIC Science & Technology

2013-01-01

lines running along the floor, floor-bolted seats , ammunition storage racks, power-train lines, etc.). MMMS 9,3 368 Traditionally, the floor-rupture...The power of dimensional analysis is that the functional relations offered are generalized, i.e. the effect of geometrical, kinematic , ambient, loading... ejected vdet Explosive detonation velocity L/T A new quantity added which controls the time of sand-overburden bubble burst Charge/plate positioning

A CFD analysis of blade row interactions within a high-speed axial compressor

NASA Astrophysics Data System (ADS)

Richman, Michael Scott

Aircraft engine design provides many technical and financial hurdles. In an effort to streamline the design process, save money, and improve reliability and performance, many manufacturers are relying on computational fluid dynamic simulations. An overarching goal of the design process for military aircraft engines is to reduce size and weight while maintaining (or improving) reliability. Designers often turn to the compression system to accomplish this goal. As pressure ratios increase and the number of compression stages decrease, many problems arise, for example stability and high cycle fatigue (HCF) become significant as individual stage loading is increased. CFD simulations have recently been employed to assist in the understanding of the aeroelastic problems. For accurate multistage blade row HCF prediction, it is imperative that advanced three-dimensional blade row unsteady aerodynamic interaction codes be validated with appropriate benchmark data. This research addresses this required validation process for TURBO, an advanced three-dimensional multi-blade row turbomachinery CFD code. The solution/prediction accuracy is characterized, identifying key flow field parameters driving the inlet guide vane (IGV) and stator response to the rotor generated forcing functions. The result is a quantified evaluation of the ability of TURBO to predict not only the fundamental flow field characteristics but the three dimensional blade loading.

Fracture Mechanical Analysis of Open Cell Ceramic Foams Under Thermal Shock Loading

NASA Astrophysics Data System (ADS)

Settgast, C.; Abendroth, M.; Kuna, M.

2016-11-01

Ceramic foams made by replica techniques containing sharp-edged cavities, which are potential crack initiators and therefore have to be analyzed using fracture mechanical methods. The ceramic foams made of novel carbon bonded alumina are used as filters in metal melt filtration applications, where the filters are exposed to a thermal shock. During the casting process the filters experience a complex thermo-mechanical loading, which is difficult to measure. Modern numerical methods allow the simulation of such complex processes. As a simplified foam structure an open Kelvin cell is used as a representative volume element. A three-dimensional finite element model containing realistic sharp-edged cavities and three-dimensional sub-models along these sharp edges are used to compute the transient temperature, stress and strain fields at the Kelvin foam. The sharp edges are evaluated using fracture mechanical methods like the J-integral technique. The results of this study describe the influence of the pore size, relative density of the ceramic foam, the heat transfer and selected material parameters on the fracture mechanical behaviour.

Blade Row Interaction Effects on the Performance of a Moderately Loaded NASA Transonic Compressor Stage

NASA Technical Reports Server (NTRS)

VanZante, Dale E.; To, Wai-Ming; Chen, Jen-Ping

2003-01-01

Blade row interaction effects on loss generation in compressors have received increased attention as compressor work-per-stage and blade loading have increased. Two dimensional Laser Doppler Velocimeter measurements of the velocity field in a NASA transonic compressor stage show the magnitude of interactions in the velocity field at the peak efficiency and near stall operating conditions. The experimental data are presented along with an assessment of the velocity field interactions. In the present study the experimental data are used to confirm the fidelity of a three-dimensional, time-accurate, Navier Stokes calculation of the stage using the MSU-TURBO code at the peak efficiency and near stall operating conditions. The simulations are used to quantify the loss generation associated with interaction phenomena. At the design point the stator pressure field has minimal effect on the rotor performance. The rotor wakes do have an impact on loss production in the stator passage at both operating conditions. A method for determining the potential importance of blade row interactions on performance is presented.

Dimensionality of the 9-item Utrecht Work Engagement Scale revisited: A Bayesian structural equation modeling approach.

PubMed

Fong, Ted C T; Ho, Rainbow T H

2015-01-01

The aim of this study was to reexamine the dimensionality of the widely used 9-item Utrecht Work Engagement Scale using the maximum likelihood (ML) approach and Bayesian structural equation modeling (BSEM) approach. Three measurement models (1-factor, 3-factor, and bi-factor models) were evaluated in two split samples of 1,112 health-care workers using confirmatory factor analysis and BSEM, which specified small-variance informative priors for cross-loadings and residual covariances. Model fit and comparisons were evaluated by posterior predictive p-value (PPP), deviance information criterion, and Bayesian information criterion (BIC). None of the three ML-based models showed an adequate fit to the data. The use of informative priors for cross-loadings did not improve the PPP for the models. The 1-factor BSEM model with approximately zero residual covariances displayed a good fit (PPP>0.10) to both samples and a substantially lower BIC than its 3-factor and bi-factor counterparts. The BSEM results demonstrate empirical support for the 1-factor model as a parsimonious and reasonable representation of work engagement.

Finite-element simulation of blood perfusion in muscle tissue during compression and sustained contraction.

PubMed

Vankan, W J; Huyghe, J M; Slaaf, D W; van Donkelaar, C C; Drost, M R; Janssen, J D; Huson, A

1997-09-01

Mechanical interaction between tissue stress and blood perfusion in skeletal muscles plays an important role in blood flow impediment during sustained contraction. The exact mechanism of this interaction is not clear, and experimental investigation of this mechanism is difficult. We developed a finite-element model of the mechanical behavior of blood-perfused muscle tissue, which accounts for mechanical blood-tissue interaction in maximally vasodilated vasculature. Verification of the model was performed by comparing finite-element results of blood pressure and flow with experimental measurements in a muscle that is subject to well-controlled mechanical loading conditions. In addition, we performed simulations of blood perfusion during tetanic, isometric contraction and maximal vasodilation in a simplified, two-dimensional finite-element model of a rat calf muscle. A vascular waterfall in the venous compartment was identified as the main cause for blood flow impediment both in the experiment and in the finite-element simulations. The validated finite-element model offers possibilities for detailed analysis of blood perfusion in three-dimensional muscle models under complicated loading conditions.

Transition paths in single-molecule force spectroscopy

NASA Astrophysics Data System (ADS)

Cossio, Pilar; Hummer, Gerhard; Szabo, Attila

2018-03-01

In a typical single-molecule force spectroscopy experiment, the ends of the molecule of interest are connected by long polymer linkers to a pair of mesoscopic beads trapped in the focus of two laser beams. At constant force load, the total extension, i.e., the end-to-end distance of the molecule plus linkers, is measured as a function of time. In the simplest systems, the measured extension fluctuates about two values characteristic of folded and unfolded states, with occasional transitions between them. We have recently shown that molecular (un)folding rates can be recovered from such trajectories, with a small linker correction, as long as the characteristic time of the bead fluctuations is shorter than the residence time in the unfolded (folded) state. Here, we show that accurate measurements of the molecular transition path times require an even faster apparatus response. Transition paths, the trajectory segments in which the molecule (un)folds, are properly resolved only if the beads fluctuate more rapidly than the end-to-end distance of the molecule. Therefore, over a wide regime, the measured rates may be meaningful but not the transition path times. Analytic expressions for the measured mean transition path times are obtained for systems diffusing anisotropically on a two-dimensional free energy surface. The transition path times depend on the properties both of the molecule and of the pulling device.

A Dielectric-Filled Waveguide Antenna Element for 3D Imaging Radar in High Temperature and Excessive Dust Conditions

PubMed Central

Xu, Ding; Li, Zhiping; Chen, Xianzhong; Wang, Zhengpeng; Wu, Jianhua

2016-01-01

Three-dimensional information of the burden surface in high temperature and excessive dust industrial conditions has been previously hard to obtain. This paper presents a novel microstrip-fed dielectric-filled waveguide antenna element which is resistant to dust and high temperatures. A novel microstrip-to-dielectric-loaded waveguide transition was developed. A cylinder and cuboid composite structure was employed at the terminal of the antenna element, which improved the return loss performance and reduced the size. The proposed antenna element was easily integrated into a T-shape multiple-input multiple-output (MIMO) imaging radar system and tested in both the laboratory environment and real blast furnace environment. The measurement results show that the proposed antenna element works very well in industrial 3D imaging radar. PMID:27556469

Three-dimensional flow characteristics of aluminum alloy in multi-pass equal channel angular pressing

NASA Astrophysics Data System (ADS)

Jin, Young-Gwan; Son, Il-Heon; Im, Yong-Taek

2010-06-01

Experiments with a square specimen made of commercially pure aluminum alloy (AA1050) were conducted to investigate deformation behaviour during a multi-pass Equal Channel Angular Pressing (ECAP) for routes A, Bc, and C up to four passes. Three-dimensional finite element numerical simulations of the multi-pass ECAP were carried out in order to evaluate the influence of processing routes and number of passes on local flow behaviour by applying a simplified saturation model of flow stress under an isothermal condition. Simulation results were investigated by comparing them with the experimentally measured data in terms of load variations and microhardness distributions. Also, transmission electron microscopy analysis was employed to investigate the microstructural changes. The present work clearly shows that the three-dimensional flow characteristics of the deformed specimen were dependent on the strain path changes due to the processing routes and number of passes that occurred during the multi-pass ECAP.

Investigation of Portevin-Le Chatelier effect in 5456 Al-based alloy using digital image correlation

NASA Astrophysics Data System (ADS)

Cheng, Teng; Xu, Xiaohai; Cai, Yulong; Fu, Shihua; Gao, Yue; Su, Yong; Zhang, Yong; Zhang, Qingchuan

2015-02-01

A variety of experimental methods have been proposed for Portevin-Le Chatelier (PLC) effect. They mainly focused on the in-plane deformation. In order to achieve the high-accuracy measurement, three-dimensional digital image correlation (3D-DIC) was employed in this work to investigate the PLC effect in 5456 Al-based alloy. The temporal and spatial evolutions of deformation in the full field of specimen surface were observed. The large deformation of localized necking was determined experimentally. The distributions of out-of-plane displacement over the loading procedure were also obtained. Furthermore, a comparison of measurement accuracy between two-dimensional digital image correlation (2D-DIC) and 3D-DIC was also performed. Due to the theoretical restriction, the measurement accuracy of 2D-DIC decreases with the increase of deformation. A maximum discrepancy of about 20% with 3D-DIC was observed in this work. Therefore, 3D-DIC is actually more essential for the high-accuracy investigation of PLC effect.

Linear and nonlinear interpretation of the direct strike lightning response of the NASA F106B thunderstorm research aircraft

NASA Technical Reports Server (NTRS)

Rudolph, T. H.; Perala, R. A.

1983-01-01

The objective of the work reported here is to develop a methodology by which electromagnetic measurements of inflight lightning strike data can be understood and extended to other aircraft. A linear and time invariant approach based on a combination of Fourier transform and three dimensional finite difference techniques is demonstrated. This approach can obtain the lightning channel current in the absence of the aircraft for given channel characteristic impedance and resistive loading. The model is applied to several measurements from the NASA F106B lightning research program. A non-linear three dimensional finite difference code has also been developed to study the response of the F106B to a lightning leader attachment. This model includes three species air chemistry and fluid continuity equations and can incorporate an experimentally based streamer formulation. Calculated responses are presented for various attachment locations and leader parameters. The results are compared qualitatively with measured inflight data.

Algorithm for loading shot noise microbunching in multi-dimensional, free-electron laser simulation codes

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

Fawley, William M.

We discuss the underlying reasoning behind and the details of the numerical algorithm used in the GINGER free-electron laser(FEL) simulation code to load the initial shot noise microbunching on the electron beam. In particular, we point out that there are some additional subtleties which must be followed for multi-dimensional codes which are not necessary for one-dimensional formulations. Moreover, requiring that the higher harmonics of the microbunching also be properly initialized with the correct statistics leads to additional complexities. We present some numerical results including the predicted incoherent, spontaneous emission as tests of the shot noise algorithm's correctness.

Prediction of clinical depression scores and detection of changes in whole-brain using resting-state functional MRI data with partial least squares regression

PubMed Central

Shimizu, Yu; Yoshimoto, Junichiro; Takamura, Masahiro; Okada, Go; Okamoto, Yasumasa; Yamawaki, Shigeto; Doya, Kenji

2017-01-01

In diagnostic applications of statistical machine learning methods to brain imaging data, common problems include data high-dimensionality and co-linearity, which often cause over-fitting and instability. To overcome these problems, we applied partial least squares (PLS) regression to resting-state functional magnetic resonance imaging (rs-fMRI) data, creating a low-dimensional representation that relates symptoms to brain activity and that predicts clinical measures. Our experimental results, based upon data from clinically depressed patients and healthy controls, demonstrated that PLS and its kernel variants provided significantly better prediction of clinical measures than ordinary linear regression. Subsequent classification using predicted clinical scores distinguished depressed patients from healthy controls with 80% accuracy. Moreover, loading vectors for latent variables enabled us to identify brain regions relevant to depression, including the default mode network, the right superior frontal gyrus, and the superior motor area. PMID:28700672

A new method for registration of heterogeneous sensors in a dimensional measurement system

NASA Astrophysics Data System (ADS)

Zhao, Yan; Wang, Zhong; Fu, Luhua; Qu, Xinghua; Zhang, Heng; Liu, Changjie

2017-10-01

Registration of multiple sensors is a basic step in multi-sensor dimensional or coordinate measuring systems before any measurement. In most cases, a common standard is used to be measured by all sensors, and this may work well for general registration of multiple homogeneous sensors. However, when inhomogeneous sensors detect a common standard, it is usually very difficult to obtain the same information, because of the different working principles of the sensors. In this paper, a new method called multiple steps registration is proposed to register two sensors: a video camera sensor (VCS) and a tactile probe sensor (TPS). In this method, the two sensors measure two separated standards: a chrome circle on a reticle and a reference sphere with a constant distance between them, fixed on a steel plate. The VCS captures only the circle and the TPS touches only the sphere. Both simulations and real experiments demonstrate that the proposed method is robust and accurate in the registration of multiple inhomogeneous sensors in a dimensional measurement system.

Center of mass trajectory and orientation to ankle and knee in sagittal plane is maintained with forward lean when backpack load changes during treadmill walking.

PubMed

Caron, Robert R; Wagenaar, Robert C; Lewis, Cara L; Saltzman, Elliot; Holt, Kenneth G

2013-01-04

Maintaining the normal shape and amplitude of the vertical trajectory of the center of mass (COM) during stance has been shown to maximize the efficiency of unloaded gait. Kinematic adaptations to load carriage, such as forward lean have yet to be understood in relation to COM movement. The purpose of this study is to better understand how load impacts the vertical COM(TSYS) trajectory and to clarify the impact of forward lean as it relates to the dynamics of sagittal plane COM(TSYS) movement during stance with changing load. 17 subjects walked on treadmill at a constant preferred walking velocity while nine different loads ranging from 12.5% to 40% bodyweight were systematically added and removed from a backpack. Kinematic data were collected using an Optotrak, three-dimensional motion analysis system and used to estimate position of the COM as well as segment and COM-to-joint vector orientation angles. The shape and amplitude of the COM vertical trajectory was maintained across all loaded conditions. The orientations of COM-to-ankle and -knee vectors were maintained in all loaded conditions except the heaviest load (40% BW). Results suggest that forward lean changed linearly with changes in load to maintain the COM-to-ankle and -knee vector orientations. COM vertical trajectory was maintained by a combination of invariants including lower-limb segment angles and a constant direction of toe-off impulse vector. The kinematic invariants found suggest a simplified control mechanism by which the system limits degrees of freedom and potentially minimizes torque about lower-extremity joints with added load. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biomechanical evaluation of nursing tasks in a hospital setting.

PubMed

Jang, R; Karwowski, W; Quesada, P M; Rodrick, D; Sherehiy, B; Cronin, S N; Layer, J K

2007-11-01

A field study was conducted to investigate spinal kinematics and loading in the nursing profession using objective and subjective measurements of selected nursing tasks observed in a hospital setting. Spinal loading was estimated using trunk motion dynamics measured by the lumbar motion monitor (LMM) and lower back compressive and shear forces were estimated using the three-dimensional (3D) Static Strength Prediction Program. Subjective measures included the rate of perceived physical effort and the perceived risk of low back pain. A multiple logistic regression model, reported in the literature for predicting low back injury based on defined risk groups, was tested. The study results concluded that the major risk factors for low back injury in nurses were the weight of patients handled, trunk moment, and trunk axial rotation. The activities that required long time exposure to awkward postures were perceived by nurses as a high physical effort. This study also concluded that self-reported perceived exertion could be used as a tool to identify nursing activities with a high risk of low-back injury.

Permeability hysterisis of limestone during isotropic compression.

PubMed

Selvadurai, A P S; Głowacki, A

2008-01-01

The evolution of permeability hysterisis in Indiana Limestone during application of isotropic confining pressures up to 60 MPa was measured by conducting one-dimensional constant flow rate tests. These tests were carried out either during monotonic application of the confining pressure or during loading-partial unloading cycles. Irreversible permeability changes occurred during both monotonic and repeated incremental compression of the limestone. Mathematical relationships are developed for describing the evolution of path-dependent permeability during isotropic compression.

Thermal loading of natural streams

USGS Publications Warehouse

Jackman, Alan P.; Yotsukura, Nobuhiro

1977-01-01

The impact of thermal loading on the temperature regime of natural streams is investigated by mathematical models, which describe both transport (convection-diffusion) and decay (surface dissipation) of waste heat over 1-hour or shorter time intervals. The models are derived from the principle of conservation of thermal energy for application to one- and two-dimensional spaces. The basic concept in these models is to separate water temperature into two parts, (1) excess temperature due to thermal loading and (2) natural (ambient) temperature. This separation allows excess temperature to be calculated from the models without incoming radiation data. Natural temperature may either be measured in prototypes or calculated from the model. If use is made of the model, however, incoming radiation is required as input data. Comparison of observed and calculated temperatures in seven natural streams shows that the models are capable of predicting transient temperature regimes satisfactorily in most cases. (Woodard-USGS)

Medium change based image estimation from application of inverse algorithms to coda wave measurements

NASA Astrophysics Data System (ADS)

Zhan, Hanyu; Jiang, Hanwan; Jiang, Ruinian

2018-03-01

Perturbations worked as extra scatters will cause coda waveform distortions; thus, coda wave with long propagation time and traveling path are sensitive to micro-defects in strongly heterogeneous media such as concretes. In this paper, we conduct varied external loads on a life-size concrete slab which contains multiple existing micro-cracks, and a couple of sources and receivers are installed to collect coda wave signals. The waveform decorrelation coefficients (DC) at different loads are calculated for all available source-receiver pair measurements. Then inversions of the DC results are applied to estimate the associated distribution density values in three-dimensional regions through kernel sensitivity model and least-square algorithms, which leads to the images indicating the micro-cracks positions. This work provides an efficiently non-destructive approach to detect internal defects and damages of large-size concrete structures.

Electronic transport in low dimensions: Carbon nanotubes and mesoscopic silver wires

NASA Astrophysics Data System (ADS)

Ghanem, Tarek Khairy

This thesis explores the physics of low-dimensional electronic conductors using two materials systems, carbon nanotubes (CNTs) and lithographically-defined silver nanowires. In order to understand the intrinsic electronic properties of CNTs, it is important to eliminate the contact effects from the measurements. Here, this is accomplished by using a conductive-tip atomic force microscope cantilever as a local electrode in order to obtain length dependent transport properties. The CNT-movable electrode contact is fully characterized, and is largely independent of voltage bias conditions, and independent of the contact force beyond a certain threshold. The contact is affected by the fine positioning of the cantilever relative to the CNT due to parasitic lateral motion of the cantilever during the loading cycle, which, if not controlled, can lead to non-monotonic behavior of contact resistance vs. force. Length dependent transport measurements are reported for several metallic and semiconducting CNTs. The resistance versus length R(L) of semiconducting CNTs is linear in the on state. For the depleted state R(L) is linear for long channel lengths, but non-linear for short channel lengths due to the long depletion lengths in one-dimensional semiconductors. Transport remains diffusive under all depletion conditions, due to both low disorder and high temperature. The study of quantum corrections to classical conductivity in mesoscopic conductors is an essential tool for understanding phase coherence in these systems. A long standing discrepancy between theory and experiment regards the phase coherence time, which is expected theoretically to grow as a power law at low temperatures, but is experimentally found to saturate. The origins of this saturation have been debated for the last decade, with the main contenders being intrinsic decoherence by zero-point fluctuations of the electrons, and decoherence by dilute magnetic impurities. Here, the phase coherence time in quasi-one-dimensional silver wires is measured. The phase coherence times obtained from the weak localization correction to the conductivity at low magnetic field show saturation, while those obtained from universal conductance fluctuations at high field do not. This indicates that, for these samples, the origin of phase coherence time saturation obtained from weak localization is extrinsic, due to the presence of dilute magnetic impurities.

Transition Documentation on a Three-Element High-Lift Configuration at High Reynolds Numbers: Analysis

NASA Technical Reports Server (NTRS)

Bertelrud, Arild; Anders, J. B. (Technical Monitor)

2002-01-01

A 2-D high-lift system experiment was conducted in August of 1996 in the Low Turbulence Pressure Tunnel at NASA Langley Research Center, Hampton, VA. The purpose of the experiment was to obtain transition measurements on a three element high-lift system for CFD code validation studies. A transition database has been created using the data from this experiment. The present report contains the analysis of the surface hot film data in terms of the transition locations on the three elements. It also includes relevant information regarding the pressure loads and distributions and the wakes behind the model to aid in the interpretation of the transition data. For some of the configurations the current pressure data has been compared with previous wind tunnel entries of the same model. The methodology used to determine the regions of transitional flow is outlined and each configuration tested has been analyzed. A discussion of interference effects, repeatability, and three-dimensional effects on the data is included.

Relaxation of creep strain in paper

NASA Astrophysics Data System (ADS)

Mustalahti, Mika; Rosti, Jari; Koivisto, Juha; Alava, Mikko J.

2010-07-01

In disordered, viscoelastic or viscoplastic materials a sample response exhibits a recovery phenomenon after the removal of a constant load or after creep. We study experimentally the recovery in paper, a quasi-two-dimensional system with intrinsic structural disorder. The deformation is measured by using the digital image correlation (DIC) method. By the DIC we obtain accurate displacement data and the spatial fields of deformation and recovered strains. The averaged results are first compared to several heuristic models for viscoelastic polymer materials in particular. The most important experimental quantity is the permanent creep strain, and we analyze whether it is non-zero by fitting the empirical models of viscoelasticity. We then present in more detail the spatial recovery behavior results from DIC, and show that they indicate a power-law-type relaxation. We outline results on variation from sample to sample and collective, spatial fluctuations in the recovery behavior. An interpretation is provided for the relaxation in the general context of glassy, interacting systems with barriers.

Mechanical Strength of the Proximal Femur After Arthroscopic Osteochondroplasty for Femoroacetabular Impingement: Finite Element Analysis and 3-Dimensional Image Analysis.

PubMed

Oba, Masatoshi; Kobayashi, Naomi; Inaba, Yutaka; Choe, Hyonmin; Ike, Hiroyuki; Kubota, So; Saito, Tomoyuki

2018-06-21

To examine the influence of femoral neck resection on the mechanical strength of the proximal femur in actual surgery. Eighteen subjects who received arthroscopic cam resection for cam-type femoroacetabular impingement (FAI) were included. Finite element analyses (FEAs) were performed to calculate changes in simulative fracture load between pre- and postoperative femur models. The finite element femur models were constructed from computed tomographic images; thus, the models represented the shape of the original femur, including the bone resection site. Three-dimensional image analysis of the bone resection site was performed to identify morphometric factors that affect strength in the postoperative femur model. Four oblique sagittal planes running perpendicular to the femoral neck axis were used as reference planes to measure the bone resection site. At the transcervical reference plane, both the bone resection depth and the cross-sectional area at the resection site correlated strongly with postoperative changes in the simulated fracture load (R 2  = 0.6, P = .0001). However, only resection depth was significantly correlated with the simulated fracture load at the reference plane for the head-neck junction. The resected bone volume did not correlate with the postoperative changes in the simulated fracture load. The results of our FEA suggest that the bone resection depth measured at the head-neck junction and transcervical reference plane correlates with fracture risk after osteochondroplasty. By contrast, bone resection at more proximal areas did not have a significant effect on the postoperative femur model strength in our FEA. The total volume of resected bone was also not significantly correlated with postoperative changes in femur model strength. This biomechanical study using FEA suggest that there is a risk of femoral neck fracture after arthroscopic cam resection, particularly when the resected lesion is located distally. Copyright © 2018 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Damage Assessment of Composite Structures Using Digital Image Correlation

NASA Astrophysics Data System (ADS)

Caminero, M. A.; Lopez-Pedrosa, M.; Pinna, C.; Soutis, C.

2014-02-01

The steady increase of Carbon-Fiber Reinforced Polymer (CFRP) Structures in modern aircraft will reach a new dimension with the entry into service of the Boeing 787 and Airbus 350. Replacement of damaged parts will not be a preferable solution due to the high level of integration and the large size of the components involved. Consequently the need to develop repair techniques and processes for composite components is readily apparent. Bonded patch repair technologies provide an alternative to mechanically fastened repairs with significantly higher performance, especially for relatively thin skins. Carefully designed adhesively bonded patches can lead to cost effective and highly efficient repairs in comparison with conventional riveted patch repairs that cut fibers and introduce highly strained regions. In this work, the assessment of the damage process taking place in notched (open-hole) specimens under uniaxial tensile loading was studied. Two-dimensional (2D) and three-dimensional (3D) Digital Image Correlation (DIC) techniques were employed to obtain full-field surface strain measurements in carbon-fiber/epoxy T700/M21 composite plates with different stacking sequences in the presence of an open circular hole. Penetrant enhanced X-ray radiographs were taken to identify damage location and extent after loading around the hole. DIC strain fields were compared to finite element predictions. In addition, DIC techniques were used to characterise damage and performance of adhesively bonded patch repairs in composite panels under tensile loading. This part of work relates to strength/stiffness restoration of damaged composite aircraft that becomes more important as composites are used more extensively in the construction of modern jet airliners. The behaviour of bonded patches under loading was monitored using DIC full-field strain measurements. Location and extent of damage identified by X-ray radiography correlates well with DIC strain results giving confidence to the technique for structural health monitoring of bonded patches.

Use of Guided Acoustic Waves to Assess the Effects of Thermal-Mechanical Cycling on Composite Stiffness

NASA Technical Reports Server (NTRS)

Seale, Michael D.; Madaras, Eric I.

2000-01-01

The introduction of new, advanced composite materials into aviation systems requires it thorough understanding of the long-term effects of combined thermal and mechanical loading. As part of a study to evaluate the effects of thermal-mechanical cycling, it guided acoustic (Lamb) wave measurement system was used to measure the bending and out-of-plane stiffness coefficients of composite laminates undergoing thermal-mechanical loading. The system uses a pulse/receive technique that excites an antisymmetric Lamb mode and measures the time-of-flight over a wide frequency range. Given the material density and plate thickness, the bending and out-of-plane shear stiffnesses are calculated from a reconstruction of the velocity dispersion curve. A series of 16 and 32-ply composite laminates were subjected to it thermal-mechanical loading profile in load frames equipped with special environmental chambers. The composite systems studied were it graphite fiber reinforced amorphous thermoplastic polyimide and it graphite fiber reinforced bismaleimide thermoset. The samples were exposed to both high and low temperature extremes its well as high and low strain profiles. The bending and out-of-plane stiffnesses for composite sample that have undergone over 6,000 cycles of thermal-mechanical loading are reported. The Lamb wave generated elastic stiffness results have shown decreases of up to 20% at 4,936 loading cycles for the graphite/thermoplastic samples and up to 64% at 4,706 loading cycles for the graphite/thermoset samples.

Biomechanical analysis of low back load when sneezing.

PubMed

Hasegawa, Tetsuya; Katsuhira, Junji; Matsudaira, Ko; Iwakiri, Kazuyuki; Maruyama, Hitoshi

2014-09-01

Although sneezing is known to induce low back pain, there is no objective data of the load generated when sneezing. Moreover, the approaches often recommended for reducing low back pain, such as leaning with both hands against a wall, are not supported by objective evidence. Participants were 12 healthy young men (mean age 23.25 ± 1.54 years) with no history of spinal column pain or low back pain. Measurements were taken using a three-dimensional motion capture system and surface electromyograms in three experimental conditions: normal for sneezing, characterized by forward trunk inclination; stand, in which the body was deliberately maintained in an upright posture when sneezing; and table, in which the participants leaned with both hands on a table when sneezing. We analyzed and compared the intervertebral disk compressive force, low back moment, ground reaction force, trunk inclination angle, and co-contraction of the rectus abdominis and erector spinae muscles in the three conditions. The intervertebral disk compressive force and ground reaction force were significantly lower in the stand and table conditions than in the normal condition. The co-contraction index value was significantly higher in the stand condition than in the normal and table conditions. When sneezing, body posture in the stand or table condition can reduce load on the low back compared with body posture in the normal sneezing condition. Thus, placing both hands on a table or otherwise maintaining an upright body posture appears to be beneficial for reducing low back load when sneezing. Copyright © 2014 Elsevier B.V. All rights reserved.

Time-dependent behavior of porcine periodontal ligament: A combined experimental, numeric in-vitro study.

PubMed

Knaup, Thomas Johannes; Dirk, Cornelius; Reimann, Susanne; Keilig, Ludger; Eschbach, Meike; Korbmacher-Steiner, Heike; Bourauel, Christoph

2018-01-01

The aim of this study was to analyze the time-dependent in-vitro behavior of the periodontal ligament (PDL) by determining the material parameters using specimens of porcine jawbone. Time-dependent material parameters to be determined were expected to complement the results from earlier biomechanical studies. Five mandibular deciduous porcine premolars were analyzed in a combined experimental-numeric study. After selecting suitable specimens (excluding root resorption) and preparing the measurement system, the specimens were deflected by a distance of 0.2 mm at loading times of 0.2, 0.5, 1, 2, 5, 10, and 60 seconds. The deflection of the teeth was determined via a laser optical system, and the resulting forces and torques were measured. To create the finite element models, a microcomputed tomography scanner was used to create 3-dimensional x-ray images of the samples. The individual structures (tooth, PDL, bone) of the jaw segments were reconstructed using a self-developed reconstruction program. A comparison between experiment and simulation was conducted using the results from finite element simulations. Via iterative parameter adjustments, the material parameters (Young's modulus and Poisson's ratio) of the PDL were assessed at different loading velocities. The clinically observed effect of a distinct increase in force during very short periods of loading was confirmed. Thus, a force of 2.6 N (±1.5 N) was measured at the shortest stress duration of 0.2 seconds, and a force of 1.0 N (±0.5 N) was measured at the longest stress duration of 60 seconds. The numeric determination of the material parameters showed bilinear behavior with a median value of the first Young's modulus between 0.06 MPa (2 seconds) and 0.04 MPa (60 seconds), and the second Young's modulus between 0.30 MPa (10 seconds) and 0.20 MPa (60 seconds). The ultimate strain marking the transition from the first to the second Young's modulus remained almost unchanged with a median value of 6.0% for all loading times. A combined experimental-numeric analysis is suitable for determining the material properties of the PDL. Microcomputed tomography allows high-precision recordings with only minimum effort. This study confirms the assumption of time dependency and nonlinearity of previous studies. Copyright © 2017 American Association of Orthodontists. Published by Elsevier Inc. All rights reserved.

An FMM-FFT Accelerated SIE Simulator for Analyzing EM Wave Propagation in Mine Environments Loaded With Conductors

PubMed Central

Sheng, Weitian; Zhou, Chenming; Liu, Yang; Bagci, Hakan; Michielssen, Eric

2018-01-01

A fast and memory efficient three-dimensional full-wave simulator for analyzing electromagnetic (EM) wave propagation in electrically large and realistic mine tunnels/galleries loaded with conductors is proposed. The simulator relies on Muller and combined field surface integral equations (SIEs) to account for scattering from mine walls and conductors, respectively. During the iterative solution of the system of SIEs, the simulator uses a fast multipole method-fast Fourier transform (FMM-FFT) scheme to reduce CPU and memory requirements. The memory requirement is further reduced by compressing large data structures via singular value and Tucker decompositions. The efficiency, accuracy, and real-world applicability of the simulator are demonstrated through characterization of EM wave propagation in electrically large mine tunnels/galleries loaded with conducting cables and mine carts. PMID:29726545

Proceedings of the ISTVS (International Society for Terrain-Vehicle Systems) Workshop on Measurement and Evaluation of Tire Performance under Winter Conditions, Alta, Utah, 11-14 April 1983.

DTIC Science & Technology

1985-09-01

Transducers capable of measuring electro-hydraulic control system which fore-aft and vertical load on a driven controls the brake system to deactivate tire...power. * axle allows design of all load-carrying - System logic power. ENGINE I EXTERNAL COMPARTMENT COMPONENTS CAB Brake Levelin system I trans... brake con- The TWS DAS was designed to 1) pro- trol system . vide onboard data sampling and filtering, A simplified truck operational flow chart 2) make

Three-dimensional analyses of ultrasonic scaler oscillations.

PubMed

Lea, Simon C; Felver, Bernhard; Landini, Gabriel; Walmsley, A Damien

2009-01-01

It is stated that the oscillation patterns of dental ultrasonic scalers are dependent upon whether the instrument is of a magnetostrictive or piezoelectric design. These patterns are then linked to differences in root surface debridement in vitro. Piezoelectric (A, P) and magnetostrictive (Slimline, TFI-3) ultrasonic scalers (three of each) were evaluated, loaded (100 g/200 g) and unloaded with a 3D laser vibrometer. Loads were applied to the probe tips via teeth mounted in a load-measuring device. Elliptical motion was demonstrated for all probes under loaded and unloaded conditions. Loading flattened the elliptical motion along the length of the probe. Unloaded, Slimline tip 1 was significantly different to tips 2 and 3 (p<0.0001). There were no differences between the A-tips (p>0.207). All TFI-3 tips were different to each other (p<0.0001). P-tips 1 and 2 were different to each other (p=0.046). Loaded, Slimline tips were different to each other (p<0.001). There were no differences between the P probes (p>0.867). Generator power increased all Slimline and P tip vibrations (p<0.0001). Probe oscillation patterns are independent of ultrasound production mechanism and are dependent upon probe shape and generator power. Loaded probes oscillated with an elliptical pattern.

Computational Knee Ligament Modeling Using Experimentally Determined Zero-Load Lengths

PubMed Central

Bloemker, Katherine H; Guess, Trent M; Maletsky, Lorin; Dodd, Kevin

2012-01-01

This study presents a subject-specific method of determining the zero-load lengths of the cruciate and collateral ligaments in computational knee modeling. Three cadaver knees were tested in a dynamic knee simulator. The cadaver knees also underwent manual envelope of motion testing to find their passive range of motion in order to determine the zero-load lengths for each ligament bundle. Computational multibody knee models were created for each knee and model kinematics were compared to experimental kinematics for a simulated walk cycle. One-dimensional non-linear spring damper elements were used to represent cruciate and collateral ligament bundles in the knee models. This study found that knee kinematics were highly sensitive to altering of the zero-load length. The results also suggest optimal methods for defining each of the ligament bundle zero-load lengths, regardless of the subject. These results verify the importance of the zero-load length when modeling the knee joint and verify that manual envelope of motion measurements can be used to determine the passive range of motion of the knee joint. It is also believed that the method described here for determining zero-load length can be used for in vitro or in vivo subject-specific computational models. PMID:22523522

Dynamic Response of Reinforced Soil Systems. Volume 2. Appendices

DTIC Science & Technology

1993-03-01

by a burster slab. These protection measures are costly, time consuming to construct, and sensitive to multiple strikes. Soil has been used to...load--deflection behavior of the reinforced soi I Dynamic puilout tests were then performed using the same parameters as the static tests. A standard...system was capable cf loading the sample in just a few micro-seconds to simulate a blast load. Dynamic load-deflection behavior was characterized and

Effect of therapeutic insoles on the medial longitudinal arch in patients with flatfoot deformity: a three-dimensional loading computed tomography study.

PubMed

Kido, Masamitsu; Ikoma, Kazuya; Hara, Yusuke; Imai, Kan; Maki, Masahiro; Ikeda, Takumi; Fujiwara, Hiroyoshi; Tokunaga, Daisaku; Inoue, Nozomu; Kubo, Toshikazu

2014-12-01

Insoles are frequently used in orthotic therapy as the standard conservative treatment for symptomatic flatfoot deformity to rebuild the arch and stabilize the foot. However, the effectiveness of therapeutic insoles remains unclear. In this study, we assessed the effectiveness of therapeutic insoles for flatfoot deformity using subject-based three-dimensional (3D) computed tomography (CT) models by evaluating the load responses of the bones in the medial longitudinal arch in vivo in 3D. We studied eight individuals (16 feet) with mild flatfoot deformity. CT scans were performed on both feet under non-loaded and full-body-loaded conditions, first with accessory insoles and then with therapeutic insoles under the same conditions. Three-dimensional CT models were constructed for the tibia and the tarsal and metatarsal bones of the medial longitudinal arch (i.e., first metatarsal bone, cuneiforms, navicular, talus, and calcaneus). The rotational angles between the tarsal bones were calculated under loading with accessory insoles or therapeutic insoles and compared. Compared with the accessory insoles, the therapeutic insoles significantly suppressed the eversion of the talocalcaneal joint. This is the first study to precisely verify the usefulness of therapeutic insoles (arch support and inner wedges) in vivo. Copyright © 2014 Elsevier Ltd. All rights reserved.

Contact-coupled impact of slender rods: analysis and experimental validation

PubMed Central

Tibbitts, Ira B.; Kakarla, Deepika; Siskey, Stephanie; Ochoa, Jorge A.; Ong, Kevin L.; Brannon, Rebecca M.

2013-01-01

To validate models of contact mechanics in low speed structural impact, slender rods were impacted in a drop tower, and measurements of the contact and vibration were compared to analytical and finite element (FE) models. The contact area was recorded using a novel thin-film transfer technique, and the contact duration was measured using electrical continuity. Strain gages recorded the vibratory strain in one rod, and a laser Doppler vibrometer measured speed. The experiment was modeled analytically on a one-dimensional spatial domain using a quasi-static Hertzian contact law and a system of delay differential equations. The three-dimensional FE model used hexahedral elements, a penalty contact algorithm, and explicit time integration. A small submodel taken from the initial global FE model economically refined the analysis in the small contact region. Measured contact areas were within 6% of both models’ predictions, peak speeds within 2%, cyclic strains within 12 με (RMS value), and contact durations within 2 μs. The global FE model and the measurements revealed small disturbances, not predicted by the analytical model, believed to be caused by interactions of the non-planar stress wavefront with the rod’s ends. The accuracy of the predictions for this simple test, as well as the versatility of the diagnostic tools, validates the theoretical and computational models, corroborates instrument calibration, and establishes confidence that the same methods may be used in experimental and computational study of contact mechanics during impact of more complicated structures. Recommendations are made for applying the methods to a particular biomechanical problem: the edge-loading of a loose prosthetic hip joint which can lead to premature wear and prosthesis failure. PMID:24729630

Evaluation of 16 measures of mental workload using a simulated flight task emphasizing mediational activity

NASA Technical Reports Server (NTRS)

Wierwille, W. W.; Rahimi, M.; Casali, J. G.

1985-01-01

As aircraft and other systems become more automated, a shift is occurring in human operator participation in these systems. This shift is away from manual control and toward activities that tap the higher mental functioning of human operators. Therefore, an experiment was performed in a moving-base flight simulator to assess mediational (cognitive) workload measurement. Specifically, 16 workload estimation techniques were evaluated as to their sensitivity and intrusion in a flight task emphasizing mediational behavior. Task loading, using navigation problems presented on a display, was treated as an independent variable, and workload-measure values were treated as dependent variables. Results indicate that two mediational task measures, two rating scale measures, time estimation, and two eye behavior measures were reliably sensitive to mediational loading. The time estimation measure did, however, intrude on mediational task performance. Several of the remaining measures were completely insensitive to mediational load.

A simple method for quantifying jump loads in volleyball athletes.

PubMed

Charlton, Paula C; Kenneally-Dabrowski, Claire; Sheppard, Jeremy; Spratford, Wayne

2017-03-01

Evaluate the validity of a commercially available wearable device, the Vert, for measuring vertical displacement and jump count in volleyball athletes. Propose a potential method of quantifying external load during training and match play within this population. Validation study. The ability of the Vert device to measure vertical displacement in male, junior elite volleyball athletes was assessed against reference standard laboratory motion analysis. The ability of the Vert device to count jumps during training and match-play was assessed via comparison with retrospective video analysis to determine precision and recall. A method of quantifying external load, known as the load index (LdIx) algorithm was proposed using the product of the jump count and average kinetic energy. Correlation between two separate Vert devices and three-dimensional trajectory data were good to excellent for all jump types performed (r=0.83-0.97), with a mean bias of between 3.57-4.28cm. When matched against jumps identified through video analysis, the Vert demonstrated excellent precision (0.995-1.000) evidenced by a low number of false positives. The number of false negatives identified with the Vert was higher resulting in lower recall values (0.814-0.930). The Vert is a commercially available tool that has potential for measuring vertical displacement and jump count in elite junior volleyball athletes without the need for time-consuming analysis and bespoke software. Subsequently, allowing the collected data to better quantify load using the proposed algorithm (LdIx). Copyright © 2016 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

[Three-dimensional stress analysis of periodontal ligament of mandible incisors fixed bridge abutments under dynamic loads by finite element method].

PubMed

Ma, Da; Tang, Liang; Pan, Yan-Huan

2007-12-01

Three-dimensional finite method was used to analyze stress and strain distributions of periodontal ligament of abutments under dynamic loads. Finite element analysis was performed on the model under dynamic loads with vertical and oblique directions. The stress and strain distributions and stress-time curves were analyzed to study the biomechanical behavior of periodontal ligament of abutments. The stress and strain distributions of periodontal ligament under dynamic load were same with the static load. But the maximum stress and strain decreased apparently. The rate of change was between 60%-75%. The periodontal ligament had time-dependent mechanical behaviors. Some level of residual stress in periodontal ligament was left after one mastication period. The stress-free time under oblique load was shorter than that of vertical load. The maximum stress and strain decrease apparently under dynamic loads. The periodontal ligament has time-dependent mechanical behaviors during one mastication. There is some level of residual stress left after one mastication period. The level of residual stress is related to the magnitude and the direction of loads. The direction of applied loads is one important factor that affected the stress distribution and accumulation and release of abutment periodontal ligament.

40 CFR 89.307 - Dynamometer calibration.

Code of Federal Regulations, 2014 CFR

2014-07-01

... instructions for initial start-up and basic operating adjustments. (b) Check the dynamometer torque measurement... transfer standard may be used to verify the torque measurement system. (1) The master load-cell and read... master load-cell for each in-use range used. (5) The in-use torque measurement must be within 2 percent...

NASA Tech Briefs, April 2005

NASA Technical Reports Server (NTRS)

2005-01-01

Gas-Tolerant Device Senses Electrical Conductivity of Liquid Nanoactuators Based on Electrostatic Forces on Dielectrics Replaceable Microfluidic Cartridges for a PCR Biosensor CdZnTe Image Detectors for Hard-X-Ray Telescopes High-Aperture-Efficiency Horn Antenna Full-Circle Resolver-to-Linear-Analog Converter Continuous, Full-Circle Arctangent Circuit Advanced Three-Dimensional Display System Automatic Focus Adjustment of a Microscope Topics covered include: FastScript3D - A Companion to Java 3D; Generating Mosaics of Astronomical Images; Simulating Descent and Landing of a Spacecraft; Simulating Vibrations in a Complex Loaded Structure; Rover Sequencing and Visualization Program; Software Template for Instruction in Mathematics; Support for User Interfaces for Distributed Systems; Nanostructured MnO2-Based Cathodes for Li-Ion/Polymer Cells; Multi-Layer Laminated Thin Films for Inflatable Structures; Two-Step Laser Ranging for Precise Tracking of a Spacecraft; Growing Aligned Carbon Nanotubes for Interconnections in ICs; Multilayer Composite Pressure Vessels; Texturing Blood-Glucose-Monitoring Optics Using Oxygen Beams; Fault-Tolerant Heat Exchanger; Atomic Clock Based on Opto-Electronic Oscillator; Microfocus/Polycapillary-Optic Crystallographic X-Ray Sys; Depth-Penetrating Luminescence Thermography of Thermal- Barrier Coatings; One-Dimensional Photonic Crystal Superprisms; Measuring Low-Order Aberrations in a Segmented Telescope; Mapping From an Instrumented Glove to a Robot Hand; Application of the Hilbert-Huang Transform to Financial Data; Optimizing Parameters for Deep-Space Optical Communication; and Low-Shear Microencapsulation and Electrostatic Coating.

[Three-dimensional finite element analysis on cell culture membrane under mechanical load].

PubMed

Guo, Xin; Fan, Yubo; Song, Jinlin; Chen, Junkai

2002-01-01

A three-dimensional finite element model of the cell culture membrane was developed in the culture device under tension state made by us. The magnitude of tension and the displacement distribution in the membrane made of silicon rubber under different hydrostatic load were obtained by use of FEM analysis. A comparative study was made between the numerical and the experimental results. These results can serve as guides to the related cellular mechanical research.

Delayed elasticity in Zerodur® at room temperature

NASA Astrophysics Data System (ADS)

Pepi, John W.; Golini, Donald

1991-12-01

Much has been written about structural relaxation, viscous flow, delayed elasticity, hysteresis, and other dimensional stability phenomena of glass and ceramics at elevated temperatures. Less has been documented about similar effects at room temperature. The time dependent phenomenon of delayed elasticity exhibited by Zerodur has been studied at room temperature and is presented here. Using a high-performance mechanical profilometer, a delayed strain on the order of 1 percent is realized over a period of a few weeks, under low stress levels. An independent test using optical interferometry validates the results. A comparison of Corning ULE silica glass is also made. The effect is believed to be related to the alkali oxide content of the glass ceramic and rearrangement of the ion groups within the structure during stress. The effect, apparent under externally applied load, is elastic and repeatable, that is, no hysteresis of permanent set, as measured at elevated temperature, is evidenced within measurement capabilities. Nonetheless, it must be accounted for in determining the magnitude of distortion under load (delayed elastic creep) and upon load removal (delayed elastic recovery). This is particularly important for large lightweight optics which might undergo large strain during fabrication and environmental loading, such as experienced in gravity release or in dynamic control of active optics.

Three-dimensional hysteresis compensation enhances accuracy of robotic artificial muscles

NASA Astrophysics Data System (ADS)

Zhang, Jun; Simeonov, Anthony; Yip, Michael C.

2018-03-01

Robotic artificial muscles are compliant and can generate straight contractions. They are increasingly popular as driving mechanisms for robotic systems. However, their strain and tension force often vary simultaneously under varying loads and inputs, resulting in three-dimensional hysteretic relationships. The three-dimensional hysteresis in robotic artificial muscles poses difficulties in estimating how they work and how to make them perform designed motions. This study proposes an approach to driving robotic artificial muscles to generate designed motions and forces by modeling and compensating for their three-dimensional hysteresis. The proposed scheme captures the nonlinearity by embedding two hysteresis models. The effectiveness of the model is confirmed by testing three popular robotic artificial muscles. Inverting the proposed model allows us to compensate for the hysteresis among temperature surrogate, contraction length, and tension force of a shape memory alloy (SMA) actuator. Feedforward control of an SMA-actuated robotic bicep is demonstrated. This study can be generalized to other robotic artificial muscles, thus enabling muscle-powered machines to generate desired motions.

Squid-based CW NMR system for measuring the magnetization of helium-3 films

NASA Astrophysics Data System (ADS)

White, Kevin Spencer

This thesis describes the design and construction of a SQUID-based CW NMR system together with its application in a study of the two dimensional magnetism of 3He. 3He provides an exemplary system for the study of two-dimensional magnetism. Two-dimensional 3He films of varying coverages may be formed by plating 3He on relatively uniform two-dimensional substrates, such as GTA Grafoil and ZYX graphite substrates. At coverages above approximately 20 atoms/nm. 2 on these substrates, the second layer of 3He exhibits a strong ferromagnetic ordering tendency. The ferromagnetic ordering presents as a rapid onset of measured magnetization that becomes independent of the applied magnetic field as film temperatures approach 1 mK. Very low applied magnetic fields are used to probe the ferromagnetic ordering in order to minimize masking of the measured magnetization and to stay within the available bandwidth of the SQUID. Commensurate with the ferromagnetic ordering, the NMR linewidth increases dramatically at these coverages and temperatures. An increasing linewidth equates to a short decay time with respect to pulsed NMR probing of the two-dimensional 3He magnetization. The decay times at these coverages and temperatures become so short that they fall below the minimum recovery time necessary for a SQUID-based pulsed NMR system to recover from the relatively large tipping pulse and acquire meaningful data. To address this problem, we have designed a SQUID-based CW NMR system to leverage as much of an already-existing pulsed NMR system as possible but allow accurate measurement of the rapid onset of ferromagnetic ordering of the 3He films below the approximate 1 mK temperature limit of the pulsed NMR system.

Characterization of three-dimensional anisotropic heart valve tissue mechanical properties using inverse finite element analysis.

PubMed

Abbasi, Mostafa; Barakat, Mohammed S; Vahidkhah, Koohyar; Azadani, Ali N

2016-09-01

Computational modeling has an important role in design and assessment of medical devices. In computational simulations, considering accurate constitutive models is of the utmost importance to capture mechanical response of soft tissue and biomedical materials under physiological loading conditions. Lack of comprehensive three-dimensional constitutive models for soft tissue limits the effectiveness of computational modeling in research and development of medical devices. The aim of this study was to use inverse finite element (FE) analysis to determine three-dimensional mechanical properties of bovine pericardial leaflets of a surgical bioprosthesis under dynamic loading condition. Using inverse parameter estimation, 3D anisotropic Fung model parameters were estimated for the leaflets. The FE simulations were validated using experimental in-vitro measurements, and the impact of different constitutive material models was investigated on leaflet stress distribution. The results of this study showed that the anisotropic Fung model accurately simulated the leaflet deformation and coaptation during valve opening and closing. During systole, the peak stress reached to 3.17MPa at the leaflet boundary while during diastole high stress regions were primarily observed in the commissures with the peak stress of 1.17MPa. In addition, the Rayleigh damping coefficient that was introduced to FE simulations to simulate viscous damping effects of surrounding fluid was determined. Copyright © 2016 Elsevier Ltd. All rights reserved.

Ultrahigh resolution optical coherence elastography using a Bessel beam for extended depth of field

NASA Astrophysics Data System (ADS)

Curatolo, Andrea; Villiger, Martin; Lorenser, Dirk; Wijesinghe, Philip; Fritz, Alexander; Kennedy, Brendan F.; Sampson, David D.

2016-03-01

Visualizing stiffness within the local tissue environment at the cellular and sub-cellular level promises to provide insight into the genesis and progression of disease. In this paper, we propose ultrahigh-resolution optical coherence elastography, and demonstrate three-dimensional imaging of local axial strain of tissues undergoing compressive loading. The technique employs a dual-arm extended focus optical coherence microscope to measure tissue displacement under compression. The system uses a broad bandwidth supercontinuum source for ultrahigh axial resolution, Bessel beam illumination and Gaussian beam detection, maintaining sub-2 μm transverse resolution over nearly 100 μm depth of field, and spectral-domain detection allowing high displacement sensitivity. The system produces strain elastograms with a record resolution (x,y,z) of 2×2×15 μm. We benchmark the advances in terms of resolution and strain sensitivity by imaging a suitable inclusion phantom. We also demonstrate this performance on freshly excised mouse aorta and reveal the mechanical heterogeneity of vascular smooth muscle cells and elastin sheets, otherwise unresolved in a typical, lower resolution optical coherence elastography system.

Probabilistic structural analysis methods for space propulsion system components

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1986-01-01

The development of a three-dimensional inelastic analysis methodology for the Space Shuttle main engine (SSME) structural components is described. The methodology is composed of: (1) composite load spectra, (2) probabilistic structural analysis methods, (3) the probabilistic finite element theory, and (4) probabilistic structural analysis. The methodology has led to significant technical progress in several important aspects of probabilistic structural analysis. The program and accomplishments to date are summarized.

Advances in solid polymer electrolyte fuel cell technology with low-platinum-loading electrodes

NASA Technical Reports Server (NTRS)

Srinivasan, Supramaniam; Ticianelli, E. A.; Derouin, C. R.; Redondo, A.

1987-01-01

The Gemini Space program demonstrated the first major application of fuel cell systems. Solid polymer electrolyte fuel cells were used as auxiliary power sources in the spacecraft. There has been considerable progress in this technology since then, particularly with the substitution of Nafion for the polystyrene sulfonate membrane as the electrolyte. Until recently the performance was good only with high platinum loading (4 mg/sq cm) electrodes. Methods are presented to advance the technology by (1) use of low platinum loading (0.35 mg/sq cm) electrodes; (2) optimization of anode/membrane/cathode interfaces by hot pressing; (3) pressurization of reactant gases, which is most important when air is used as cathodic reactant; and (4) adequate humidification of reactant gases to overcome the water management problem. The high performance of the fuel cell with the low loading of platinum appears to be due to the extension of the three dimensional reaction zone by introduction of a proton conductor, Nafion. This was confirmed by cyclic voltammetry.

Validation Tests of Fiber Optic Strain-Based Operational Shape and Load Measurements

NASA Technical Reports Server (NTRS)

Bakalyar, John A.; Jutte, Christine

2012-01-01

Aircraft design has been progressing toward reduced structural weight to improve fuel efficiency, increase performance, and reduce cost. Lightweight aircraft structures are more flexible than conventional designs and require new design considerations. Intelligent sensing allows for enhanced control and monitoring of aircraft, which enables increased structurally efficiency. The NASA Dryden Flight Research Center (DFRC) has developed an instrumentation system and analysis techniques that combine to make distributed structural measurements practical for lightweight vehicles. Dryden's Fiber Optic Strain Sensing (FOSS) technology enables a multitude of lightweight, distributed surface strain measurements. The analysis techniques, referred to as the Displacement Transfer Functions (DTF) and Load Transfer Functions (LTF), use surface strain values to calculate structural deflections and operational loads. The combined system is useful for real-time monitoring of aeroelastic structures, along with many other applications. This paper describes how the capabilities of the measurement system were demonstrated using subscale test articles that represent simple aircraft structures. Empirical FOSS strain data were used within the DTF to calculate the displacement of the article and within the LTF to calculate bending moments due to loads acting on the article. The results of the tests, accuracy of the measurements, and a sensitivity analysis are presented.

Coaxial-type water load for measuring high voltage, high current and short pulse of a compact Marx system for a high power microwave source

NASA Astrophysics Data System (ADS)

Han, Jaeeun; Kim, Jung-ho; Park, Sang-duck; Yoon, Moohyun; Park, Soo Yong; Choi, Do Won; Shin, Jin Woo; So, Joon Ho

2009-11-01

A coaxial-type water load was used to measure the voltage output from a Marx generator for a high power microwave source. This output had a rise time of 20 ns, a pulse duration of a few hundred ns, and an amplitude up to 500 kV. The design of the coaxial water load showed that it is an ideal resistive divider and can also accurately measure a short pulse. Experiments were performed to test the performance of the Marx generator with the calibrated coaxial water load.

Time-domain measurement of terahertz frequency magnetoplasmon resonances in a two-dimensional electron system by the direct injection of picosecond pulsed currents

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

Wu, Jingbo; Mayorov, Alexander S.; Wood, Christopher D.

2016-02-29

We have investigated terahertz (THz) frequency magnetoplasmon resonances in a two-dimensional electron system through the direct injection of picosecond duration current pulses. The evolution of the time-domain signals was measured as a function of magnetic field, and the results were found to be in agreement with calculations using a mode-matching approach for four modes observed in the frequency range above 0.1 THz. This introduces a generic technique suitable for sampling ultrafast carrier dynamics in low-dimensional semiconductor nanostructures at THz frequencies.

The design and analysis of single flank transmission error tester for loaded gears

NASA Technical Reports Server (NTRS)

Bassett, Duane E.; Houser, Donald R.

1987-01-01

To strengthen the understanding of gear transmission error and to verify mathematical models which predict them, a test stand that will measure the transmission error of gear pairs under design loads has been investigated. While most transmission error testers have been used to test gear pairs under unloaded conditions, the goal of this report was to design and perform dynamic analysis of a unique tester with the capability of measuring the transmission error of gears under load. This test stand will have the capability to continuously load a gear pair at torques up to 16,000 in-lb at shaft speeds from 0 to 5 rpm. Error measurement will be accomplished with high resolution optical encoders and the accompanying signal processing unit from an existing unloaded transmission error tester. Input power to the test gear box will be supplied by a dc torque motor while the load will be applied with a similar torque motor. A dual input, dual output control system will regulate the speed and torque of the system. This control system's accuracy and dynamic response were analyzed and it was determined that proportional plus derivative speed control is needed in order to provide the precisely constant torque necessary for error-free measurement.

Experimental investigation of commercial small diameter dental implants in porcine mandibular segments.

PubMed

Hasan, Istabrak; Heinemann, Friedhelm; Schwegmann, Monika; Keilig, Ludger; Stark, Helmut; Bourauel, Christoph

2017-02-01

Small diameter (mini) dental implants have become more popular in recent years as alternatives to classical implant treatment in clinical cases with critical bony situations. However, an in-depth scientific analysis of the mechanical and biomechanical effects of small diameter implants has not yet been published. The aim of the present study was to investigate experimentally different commercial mini implants by measuring their displacements under immediate loading. Twelve commercially available mini implants were measured. Implants were inserted into porcine mandibular segments and loaded by means of a predefined displacement of 0.5 mm of the loading system. The implants were loaded at an angle of 30° to the implant long axis using the self-developed biomechanical hexapod measurement system. Implant displacements were registered. The experimental results were compared to the numerical ones from a previous study. Measured implant displacements were within the range of 39-194 μm. A large variation in the displacements was obtained among the different implant systems due to the different designs and thread profiles. Comparing experimental and numerical results, the displacements that were obtained numerically were within the range of 79-347 μm. The different commercial mini implants showed acceptable primary stability and could be loaded immediately after their insertion.

Model studies of laser absorption computed tomography for remote air pollution measurement

NASA Technical Reports Server (NTRS)

Wolfe, D. C., Jr.; Byer, R. L.

1982-01-01

Model studies of the potential of laser absorption-computed tomography are presented which demonstrate the possibility of sensitive remote atmospheric pollutant measurements, over kilometer-sized areas, with two-dimensional resolution, at modest laser source powers. An analysis of this tomographic reconstruction process as a function of measurement SNR, laser power, range, and system geometry, shows that the system is able to yield two-dimensional maps of pollutant concentrations at ranges and resolutions superior to those attainable with existing, direct-detection laser radars.

Biomechanical performance of rigid compared to dynamic anterior cervical plating: analysis of adjacent upper and lower level compressive forces.

PubMed

Connor, David E; Shamieh, Khader Samer; Ogden, Alan L; Mukherjee, Debi P; Sin, Anthony; Nanda, Anil

2012-12-01

Dynamic anterior cervical plating is well established as a means of enhancing graft loading and subsequent arthrodesis. Current concerns center on the degree of adjacent-level stress induced by these systems. The aim of this study was to evaluate and compare the load transferred to adjacent levels for single-level anterior cervical discectomy and fusion utilizing rigid compared to dynamic anterior plating systems. Nine cadaveric adult human cervical spine specimens were subjected to range-of-motion testing prior to and following C5-C6 anterior cervical discectomy and fusion procedures. Interbody grafting was performed with human fibula tissue. Nondestructive biomechanical testing included flexion/extension and lateral bending loading modes. A constant displacement of 5mm was applied in each direction and the applied load was measured in newtons (N). Specimens were tested in the following order: intact, following discectomy, after rigid plating, then after dynamic plating. Adjacent level (C4-C5 [L(S)] and C6-C7 [L(I)]) compressive forces were measured using low profile load cells inserted into each disc space. The measured load values for plating systems were then normalized using values measured for the intact specimens. Mean loads transferred to L(S) and L(I) during forced flexion in specimens with rigid plating were 23.47 N and 8.76 N, respectively; while the corresponding values in specimens with dynamic plating were 18.55 N and 1.03 N, respectively. Dynamic plating yielded no significant change at L(I) and a 21.0% decrease in load at L(S) when compared with rigid plating, although the difference was not significant. The observed trend suggests that dynamic plating may diminish superior adjacent level compressive stresses. Copyright © 2012 Elsevier Ltd. All rights reserved.

Wind tunnel analysis of the aerodynamic loads on rolling stock over railway embankments: the effect of shelter windbreaks.

PubMed

Avila-Sanchez, Sergio; Pindado, Santiago; Lopez-Garcia, Oscar; Sanz-Andres, Angel

2014-01-01

Wind-flow pattern over embankments involves an overexposure of the rolling stock travelling on them to wind loads. Windbreaks are a common solution for changing the flow characteristic in order to decrease unwanted effects induced by the presence of cross-wind. The shelter effectiveness of a set of windbreaks placed over a railway twin-track embankment is experimentally analysed. A set of two-dimensional wind tunnel tests are undertaken and results corresponding to pressure tap measurements over a section of a typical high-speed train are herein presented. The results indicate that even small-height windbreaks provide sheltering effects to the vehicles. Also, eaves located at the windbreak tips seem to improve their sheltering effect.

Wind Tunnel Analysis of the Aerodynamic Loads on Rolling Stock over Railway Embankments: The Effect of Shelter Windbreaks

PubMed Central

Avila-Sanchez, Sergio; Lopez-Garcia, Oscar; Sanz-Andres, Angel

2014-01-01

Wind-flow pattern over embankments involves an overexposure of the rolling stock travelling on them to wind loads. Windbreaks are a common solution for changing the flow characteristic in order to decrease unwanted effects induced by the presence of cross-wind. The shelter effectiveness of a set of windbreaks placed over a railway twin-track embankment is experimentally analysed. A set of two-dimensional wind tunnel tests are undertaken and results corresponding to pressure tap measurements over a section of a typical high-speed train are herein presented. The results indicate that even small-height windbreaks provide sheltering effects to the vehicles. Also, eaves located at the windbreak tips seem to improve their sheltering effect. PMID:25544954

Applications to car bodies - Generalized layout design of three-dimensional shells

NASA Technical Reports Server (NTRS)

Fukushima, Junichi; Suzuki, Katsuyuki; Kikuchi, Noboru

1993-01-01

We shall describe applications of the homogenization method, formulated in Part 1, to design layout of car bodies represented by three-dimensional shell structures based on a multi-loading optimization.

Numerical assessment of bone remodeling around conventionally and early loaded titanium and titanium-zirconium alloy dental implants.

PubMed

Akça, Kıvanç; Eser, Atılım; Çavuşoğlu, Yeliz; Sağırkaya, Elçin; Çehreli, Murat Cavit

2015-05-01

The aim of this study was to investigate conventionally and early loaded titanium and titanium-zirconium alloy implants by three-dimensional finite element stress analysis. Three-dimensional model of a dental implant was created and a thread area was established as a region of interest in trabecular bone to study a localized part of the global model with a refined mesh. The peri-implant tissues around conventionally loaded (model 1) and early loaded (model 2) implants were implemented and were used to explore principal stresses, displacement values, and equivalent strains in the peri-implant region of titanium and titanium-zirconium implants under static load of 300 N with or without 30° inclination applied on top of the abutment surface. Under axial loading, principal stresses in both models were comparable for both implants and models. Under oblique loading, principal stresses around titanium-zirconium implants were slightly higher in both models. Comparable stress magnitudes were observed in both models. The displacement values and equivalent strain amplitudes around both implants and models were similar. Peri-implant bone around titanium and titanium-zirconium implants experiences similar stress magnitudes coupled with intraosseous implant displacement values under conventional loading and early loading simulations. Titanium-zirconium implants have biomechanical outcome comparable to conventional titanium implants under conventional loading and early loading.

Development and Validation of a Bioreactor System for Dynamic Loading and Mechanical Characterization of Whole Human Intervertebral Discs in Organ Culture

PubMed Central

Walter, BA; Illien-Junger, S; Nasser, P; Hecht, AC; Iatridis, JC

2014-01-01

Intervertebral disc (IVD) degeneration is a common cause of back pain, and attempts to develop therapies are frustrated by lack of model systems that mimic the human condition. Human IVD organ culture models can address this gap, yet current models are limited since vertebral endplates are removed to maintain cell viability, physiological loading is not applied, and mechanical behaviors are not measured. This study aimed to (i) establish a method for isolating human IVDs from autopsy with intact vertebral endplates, and (ii) develop and validate an organ culture loading system for human or bovine IVDs. Human IVDs with intact endplates were isolated from cadavers within 48 hours of death and cultured for up to 21 days. IVDs remained viable with ~80% cell viability in nucleus and annulus regions. A dynamic loading system was designed and built with the capacity to culture 9 bovine or 6 human IVDs simultaneously while applying simulated physiologic loads (maximum force: 4kN) and measuring IVD mechanical behaviors. The loading system accurately applied dynamic loading regimes (RMS error <2.5N and total harmonic distortion <2.45%), and precisely evaluated mechanical behavior of rubber and bovine IVDs. Bovine IVDs maintained their mechanical behavior and retained >85% viable cells throughout the 3 week culture period. This organ culture loading system can closely mimic physiological conditions and be used to investigate response of living human and bovine IVDs to mechanical and chemical challenges and to screen therapeutic repair techniques. PMID:24725441

Axial calibration methods of piezoelectric load sharing dynamometer

NASA Astrophysics Data System (ADS)

Zhang, Jun; Chang, Qingbing; Ren, Zongjin; Shao, Jun; Wang, Xinlei; Tian, Yu

2018-06-01

The relationship between input and output of load sharing dynamometer is seriously non-linear in different loading points of a plane, so it's significant for accutately measuring force to precisely calibrate the non-linear relationship. In this paper, firstly, based on piezoelectric load sharing dynamometer, calibration experiments of different loading points are performed in a plane. And then load sharing testing system is respectively calibrated based on BP algorithm and ELM (Extreme Learning Machine) algorithm. Finally, the results show that the calibration result of ELM is better than BP for calibrating the non-linear relationship between input and output of loading sharing dynamometer in the different loading points of a plane, which verifies that ELM algorithm is feasible in solving force non-linear measurement problem.

Measurements and modelling of base station power consumption under real traffic loads.

PubMed

Lorincz, Josip; Garma, Tonko; Petrovic, Goran

2012-01-01

Base stations represent the main contributor to the energy consumption of a mobile cellular network. Since traffic load in mobile networks significantly varies during a working or weekend day, it is important to quantify the influence of these variations on the base station power consumption. Therefore, this paper investigates changes in the instantaneous power consumption of GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System) base stations according to their respective traffic load. The real data in terms of the power consumption and traffic load have been obtained from continuous measurements performed on a fully operated base station site. Measurements show the existence of a direct relationship between base station traffic load and power consumption. According to this relationship, we develop a linear power consumption model for base stations of both technologies. This paper also gives an overview of the most important concepts which are being proposed to make cellular networks more energy-efficient.

Coupled CFD/CSD Analysis of an Active-Twist Rotor in a Wind Tunnel with Experimental Validation

NASA Technical Reports Server (NTRS)

Massey, Steven J.; Kreshock, Andrew R.; Sekula, Martin K.

2015-01-01

An unsteady Reynolds averaged Navier-Stokes analysis loosely coupled with a comprehensive rotorcraft code is presented for a second-generation active-twist rotor. High fidelity Navier-Stokes results for three configurations: an isolated rotor, a rotor with fuselage, and a rotor with fuselage mounted in a wind tunnel, are compared to lifting-line theory based comprehensive rotorcraft code calculations and wind tunnel data. Results indicate that CFD/CSD predictions of flapwise bending moments are in good agreement with wind tunnel measurements for configurations with a fuselage, and that modeling the wind tunnel environment does not significantly enhance computed results. Actuated rotor results for the rotor with fuselage configuration are also validated for predictions of vibratory blade loads and fixed-system vibratory loads. Varying levels of agreement with wind tunnel measurements are observed for blade vibratory loads, depending on the load component (flap, lag, or torsion) and the harmonic being examined. Predicted trends in fixed-system vibratory loads are in good agreement with wind tunnel measurements.

Measurements and Modelling of Base Station Power Consumption under Real Traffic Loads †

PubMed Central

Lorincz, Josip; Garma, Tonko; Petrovic, Goran

2012-01-01

Base stations represent the main contributor to the energy consumption of a mobile cellular network. Since traffic load in mobile networks significantly varies during a working or weekend day, it is important to quantify the influence of these variations on the base station power consumption. Therefore, this paper investigates changes in the instantaneous power consumption of GSM (Global System for Mobile Communications) and UMTS (Universal Mobile Telecommunications System) base stations according to their respective traffic load. The real data in terms of the power consumption and traffic load have been obtained from continuous measurements performed on a fully operated base station site. Measurements show the existence of a direct relationship between base station traffic load and power consumption. According to this relationship, we develop a linear power consumption model for base stations of both technologies. This paper also gives an overview of the most important concepts which are being proposed to make cellular networks more energy-efficient. PMID:22666026

Non-destructive and three-dimensional measurement of local strain development during tensile deformation in an aluminium alloy

NASA Astrophysics Data System (ADS)

Kobayashi, M.; Miura, H.; Toda, H.

2015-08-01

Anisotropy of mechanical responses depending on crystallographic orientation causes inhomogeneous deformation on the mesoscopic scale (grain size scale). Investigation of the local plastic strain development is important for discussing recrystallization mechanisms, because the sites with higher local plastic strain may act as potential nucleation sites for recrystallization. Recently, high-resolution X-ray tomography, which is non-destructive inspection method, has been utilized for observation of the materials structure. In synchrotron radiation X-ray tomography, more than 10,000 microstructural features, like precipitates, dispersions, compounds and hydrogen pores, can be observed in aluminium alloys. We have proposed employing these microstructural features as marker gauges to measure local strains, and then have developed a method to calculate the three-dimensional strain distribution by tracking the microstructural features. In this study, we report the development of local plastic strain as a function of the grain microstructure in an aluminium alloy by means of this three-dimensional strain measurement technique. Strongly heterogeneous strain development was observed during tensile loading to 30%. In other words, some parts of the sample deform little whereas another deforms a lot. However, strain in the whole specimen was keeping harmony. Comparing the microstructure with the strain concentration that is obtained by this method has a potential to reveal potential nucleation sites of recrystallization.

A fuzzy-logic antiswing controller for three-dimensional overhead cranes.

PubMed

Cho, Sung-Kun; Lee, Ho-Hoon

2002-04-01

In this paper, a new fuzzy antiswing control scheme is proposed for a three-dimensional overhead crane. The proposed control consists of a position servo control and a fuzzy-logic control. The position servo control is used to control crane position and rope length, and the fuzzy-logic control is used to suppress load swing. The proposed control guarantees not only prompt suppression of load swing but also accurate control of crane position and rope length for simultaneous travel, traverse, and hoisting motions of the crane. Furthermore, the proposed control provides practical gain tuning criteria for easy application. The effectiveness of the proposed control is shown by experiments with a three-dimensional prototype overhead crane.

Finite element analysis of steady and transiently moving/rolling nonlinear viscoelastic structure. II - Shell and three-dimensional simulations

NASA Technical Reports Server (NTRS)

Kennedy, Ronald; Padovan, Joe

1987-01-01

In a three-part series of papers, a generalized finite element solution strategy is developed to handle traveling load problems in rolling, moving and rotating structure. The main thrust of this section consists of the development of three-dimensional and shell type moving elements. In conjunction with this work, a compatible three-dimensional contact strategy is also developed. Based on these modeling capabilities, extensive analytical and experimental benchmarking is presented. Such testing includes traveling loads in rotating structure as well as low- and high-speed rolling contact involving standing wave-type response behavior. These point to the excellent modeling capabilities of moving element strategies.

Combined particle-image velocimetry and force analysis of the three-dimensional fluid-structure interaction of a natural owl wing.

PubMed

Winzen, A; Roidl, B; Schröder, W

2016-04-01

Low-speed aerodynamics has gained increasing interest due to its relevance for the design process of small flying air vehicles. These small aircraft operate at similar aerodynamic conditions as, e.g. birds which therefore can serve as role models of how to overcome the well-known problems of low Reynolds number flight. The flight of the barn owl is characterized by a very low flight velocity in conjunction with a low noise emission and a high level of maneuverability at stable flight conditions. To investigate the complex three-dimensional flow field and the corresponding local structural deformation in combination with their influence on the resulting aerodynamic forces, time-resolved stereoscopic particle-image velocimetry and force and moment measurements are performed on a prepared natural barn owl wing. Several spanwise positions are measured via PIV in a range of angles of attack [Formula: see text] 6° and Reynolds numbers 40 000 [Formula: see text] 120 000 based on the chord length. Additionally, the resulting forces and moments are recorded for -10° ≤ α ≤ 15° at the same Reynolds numbers. Depending on the spanwise position, the angle of attack, and the Reynolds number, the flow field on the wing's pressure side is characterized by either a region of flow separation, causing large-scale vortical structures which lead to a time-dependent deflection of the flexible wing structure or wing regions showing no instantaneous deflection but a reduction of the time-averaged mean wing curvature. Based on the force measurements the three-dimensional fluid-structure interaction is assumed to considerably impact the aerodynamic forces acting on the wing leading to a strong mechanical loading of the interface between the wing and body. These time-depending loads which result from the flexibility of the wing should be taken into consideration for the design of future small flying air vehicles using flexible wing structures.

Dimensional Analysis Applied to Electricity and Mechanics.

ERIC Educational Resources Information Center

Thomas, G.

1979-01-01

Suggests an alternative system of measurement to be used in engineering, which provides theoretical insight and leads to definitions of dual and analogous physical quantities. The system is based on the notion that the dimensional product of three fundamental quantities should be energy. (GA)

Sinking and fit of abutment of locking taper implant system

PubMed Central

Moon, Seung-Jin; Kim, Hee-Jung; Son, Mee-Kyoung

2009-01-01

STATEMENT OF PROBLEM Unlike screw-retention type, fixture-abutment retention in Locking taper connection depends on frictional force so it has possibility of abutment to sink. PURPOSE In this study, Bicon® Implant System, one of the conical internal connection implant system, was used with applying loading force to the abutments connected to the fixture. Then the amount of sinking was measured. MATERIAL AND METHODS 10 Bicon® implant fixtures were used. First, the abutment was connected to the fixture with finger force. Then it was tapped with a mallet for 3 times and loads of 20 kg corresponding to masticatory force using loading application instrument were applied successively. The abutment state, slightly connected to the fixture without pressure was considered as a reference length, and every new abutment length was measured after each load's step was added. The amount of abutment sinking (mm) was gained by subtracting the length of abutment-fixture under each loading condition from reference length. RESULTS It was evident, that the amount of abutment sinking in Bicon® Implant System increased as loads were added. When loads of 20 kg were applied more than 5 - 7 times, sinking stopped at 0.45 ± 0.09 mm. CONCLUSION Even though locking taper connection type implant shows good adaption to occlusal force, it has potential for abutment sinking as loads are given. When locking taper connection type implant is used, satisfactory loads are recommended for precise abutment location. PMID:21165262

Using NASTRAN to solve symmetric structures with nonsymmetric loads

NASA Technical Reports Server (NTRS)

Butler, T. G.

1982-01-01

A method for computation of reflective dihedral symmetry in symmetrical structures under nonsymmetric loads is described. The method makes it possible to confine the analysis to a half, a quarter, or an octagonal segment. The symmetry of elastic deformation is discussed, and antisymmetrical deformation is distinguished from nonsymmetrical deformation. Modes of deformation considered are axial, bending, membrane, and torsional deformation. Examples of one and two dimensional elements are presented and extended to three dimensional elements. The method of setting up a problem within NASTRAN is discussed. The technique is applied to a thick structure having quarter symmetry which was modeled with polyhedra and subjected to five distinct loads having varying degrees of symmetry.

Combined Effect of Piezoviscous Dependency and Non-Newtonian Couple Stress on Squeeze-Film Porous Annular Plate

NASA Astrophysics Data System (ADS)

Vasanth, K. R.; Hanumagowda, B. N.; Santhosh Kumar, J.

2018-04-01

Squeeze film investigations focus upon film pressure, load bearing quantity and the minimum thickness of film. The combined effect of pressure viscous dependent and non- Newtonian couple stress in porous annular plate is studied. The modified equations of one dimensional pressure, load bearing quantity, non dimensional squeeze time are obtained. The conclusions obtained in the study are found to be in very good agreement compared to the previous results which are published. The load carrying capacity is increased due to the variation in the pressure dependent viscosity and also due to the couple stress effect. Finally this results in change in the squeeze film timings.

40 CFR 86.333-79 - Dynamometer calibration.

Code of Federal Regulations, 2013 CFR

2013-07-01

... basic operating adjustments. (b) Check the dynamometer torque measurement for each range used by the... or transfer standard may be used to verify the in-use torque measurement system. (1) The master load... master load-cell for each in-use range used. (5) The in-use torque measurement must be within 2 percent...

40 CFR 86.333-79 - Dynamometer calibration.

Code of Federal Regulations, 2012 CFR

2012-07-01

... basic operating adjustments. (b) Check the dynamometer torque measurement for each range used by the... or transfer standard may be used to verify the in-use torque measurement system. (1) The master load... master load-cell for each in-use range used. (5) The in-use torque measurement must be within 2 percent...

40 CFR 86.333-79 - Dynamometer calibration.

Code of Federal Regulations, 2011 CFR

2011-07-01

... basic operating adjustments. (b) Check the dynamometer torque measurement for each range used by the... or transfer standard may be used to verify the in-use torque measurement system. (1) The master load... master load-cell for each in-use range used. (5) The in-use torque measurement must be within 2 percent...

40 CFR 89.307 - Dynamometer calibration.

Code of Federal Regulations, 2013 CFR

2013-07-01

... torque measurement for each range used by the following method: (1) Warm up the dynamometer following the... transfer standard may be used to verify the torque measurement system. (1) The master load-cell and read... master load-cell for each in-use range used. (5) The in-use torque measurement must be within 2 percent...