Kinematic Analysis and Performance Evaluation of Novel PRS Parallel Mechanism

NASA Astrophysics Data System (ADS)

Balaji, K.; Khan, B. Shahul Hamid

2018-02-01

In this paper, a 3 DoF (Degree of Freedom) novel PRS (Prismatic-Revolute- Spherical) type parallel mechanisms has been designed and presented. The combination of striaght and arc type linkages for 3 DOF parallel mechanism is introduced for the first time. The performances of the mechanisms are evaluated based on the indices such as Minimum Singular Value (MSV), Condition Number (CN), Local Conditioning Index (LCI), Kinematic Configuration Index (KCI) and Global Conditioning Index (GCI). The overall reachable workspace of all mechanisms are presented. The kinematic measure, dexterity measure and workspace analysis for all the mechanism have been evaluated and compared.

Improvements in analysis techniques for segmented mirror arrays

NASA Astrophysics Data System (ADS)

Michels, Gregory J.; Genberg, Victor L.; Bisson, Gary R.

2016-08-01

The employment of actively controlled segmented mirror architectures has become increasingly common in the development of current astronomical telescopes. Optomechanical analysis of such hardware presents unique issues compared to that of monolithic mirror designs. The work presented here is a review of current capabilities and improvements in the methodology of the analysis of mechanically induced surface deformation of such systems. The recent improvements include capability to differentiate surface deformation at the array and segment level. This differentiation allowing surface deformation analysis at each individual segment level offers useful insight into the mechanical behavior of the segments that is unavailable by analysis solely at the parent array level. In addition, capability to characterize the full displacement vector deformation of collections of points allows analysis of mechanical disturbance predictions of assembly interfaces relative to other assembly interfaces. This capability, called racking analysis, allows engineers to develop designs for segment-to-segment phasing performance in assembly integration, 0g release, and thermal stability of operation. The performance predicted by racking has the advantage of being comparable to the measurements used in assembly of hardware. Approaches to all of the above issues are presented and demonstrated by example with SigFit, a commercially available tool integrating mechanical analysis with optical analysis.

A Hybrid Approach to Composite Damage and Failure Analysis Combining Synergistic Damage Mechanics and Peridynamics

DTIC Science & Technology

2017-03-30

Composite Damage and Failure Analysis Combining Synergistic Damage Mechanics and Peridynamics 5b. GRANT NUMBER NOOO 14-16-1-21 73 5c. PROGRAM...ES) 8. PERFORMING ORGANIZATION REPORT NUMBER Texas A&M Engineering Experiment Station (TEES) 400 Harvey Mitchell Parkway, Suite 300 M160 1473 I...Failure Analysis Combining Synergistic Damage Mechanics and Peridynamics Award Number N00014-16-1-2173 DOD-NAVY- Office of Naval Research PI: Ramesh

Independent Orbiter Assessment (IOA): Analysis of the mechanical actuation subsystem

NASA Technical Reports Server (NTRS)

Bacher, J. L.; Montgomery, A. D.; Bradway, M. W.; Slaughter, W. T.

1987-01-01

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. This report documents the independent analysis results corresponding to the Orbiter Mechanical Actuation System (MAS) hardware. Specifically, the MAS hardware consists of the following components: Air Data Probe (ADP); Elevon Seal Panel (ESP); External Tank Umbilical (ETU); Ku-Band Deploy (KBD); Payload Bay Doors (PBD); Payload Bay Radiators (PBR); Personnel Hatches (PH); Vent Door Mechanism (VDM); and Startracker Door Mechanism (SDM). The IOA analysis process utilized available MAS hardware drawings and schematics for defining hardware assemblies, components, and hardware items. Each level of hardware was evaluated and analyzed for possible failure modes and effects. Criticality was assigned based upon the severity of the effect for each failure mode.

The Kinematic Analysis of Flat Leverage Mechanism of the Third Class

NASA Astrophysics Data System (ADS)

Zhauyt, A.; Mamatova, G.; Abdugaliyeva, G.; Alipov, K.; Sakenova, A.; Alimbetov, A.

2017-10-01

It is necessary to make link mechanisms calculation to the strength at designing of flat link mechanisms of high class after definition of block diagrams and link linear sizes i.e. it is rationally to choose their forms and to determine the section sizes. The algorithm of the definition of dimension of link mechanism lengths of high classes (MHC) and their metric parameters at successive approach is offered in this work. It this paper educational and research software named GIM is presented. This software has been developed with the aim of approaching the difficulties students usually encounter when facing up to kinematic analysis of mechanisms. A deep understanding of the kinematic analysis is necessary to go a step further into design and synthesis of mechanisms. In order to support and complement the theoretical lectures, GIM software is used during the practical exercises, serving as an educational complementary tool reinforcing the knowledge acquired by the students.

Analysis of Links Positions in Landing Gear Mechanism

NASA Astrophysics Data System (ADS)

Brewczyński, D.; Tora, G.

2014-08-01

This article contains a kinematic analysis of an aircraft chassis mechanism in a range of positions. The mechanism of the chassis is made up of several smaller subsystems with different functions. The first mechanism is used to eject the chassis before landing (touchdown) and fold it to hatchway after the lift off. The second mechanism is designed to perform rotation of the crossover with the wheel, in order to adjust the position of the wheel to fit it in the limited space in the hold. The third mechanism allows movement of the chassis resulting from the change in length of the damper. To determine the position of the following links of the mechanism calculus of vectors was applied in which unit vectors were used to represent the angular position of the links. The aim of the analysis is to determine the angle of convergence and the angle of heel wheels as a function of the variable length of hydraulic cylinder, length of the shock absorber, length of the regulations rods

Kuhn-Tucker optimization based reliability analysis for probabilistic finite elements

NASA Technical Reports Server (NTRS)

Liu, W. K.; Besterfield, G.; Lawrence, M.; Belytschko, T.

1988-01-01

The fusion of probability finite element method (PFEM) and reliability analysis for fracture mechanics is considered. Reliability analysis with specific application to fracture mechanics is presented, and computational procedures are discussed. Explicit expressions for the optimization procedure with regard to fracture mechanics are given. The results show the PFEM is a very powerful tool in determining the second-moment statistics. The method can determine the probability of failure or fracture subject to randomness in load, material properties and crack length, orientation, and location.

Failure Analysis in Space: International Space Station (ISS) Starboard Solar Alpha Rotary Joint (SARJ) Debris Analysis

NASA Technical Reports Server (NTRS)

Long, V. S.; Wright, M. C.; McDanels, S. J.; Lubas, D.; Tucker, B.; Marciniak, P. J.

2010-01-01

This slide presentation reviews the debris analysis of the Starboard Solar Alpha Rotary Joint (SARJ), a mechanism that is designed to keep the solar arrays facing the sun. The goal of this was to identify the failure mechanism based on surface morphology and to determine the source of debris through elemental and particle analysis.

Finite Element Analysis and Vibration Control of Lorry’s Shift Mechanism

NASA Astrophysics Data System (ADS)

Qiangwei, Li

2017-11-01

The transmission is one of the important parts of the automobile’s transmission system, Shift mechanism’s main function of transmission is to adjust the position of the shift fork, toggle the synchronizer’s tooth ring, so that the gears are separated and combined to achieve the shift. Therefore, in order to ensure the reliability and stability of the shift process, the vibration characteristics of the shift mechanism cannot be ignored. The static analysis of the shift fork is carried out, and the stress distribution of the shift fork is obtained according to the operating characteristics of the shift mechanism of the lorry transmission in this paper. The modal analysis of the shift mechanism shows the low-order vibration frequencies and the corresponding modal vibration shapes, and the vibration control analysis is carried out according to the simulation results. The simulation results provide the theoretical basis for the reasonable optimization design of the shift mechanism of the lorry transmission.

46 CFR 54.30-15 - Requirement for analysis and computation.

Code of Federal Regulations, 2010 CFR

2010-10-01

... PRESSURE VESSELS Mechanical Stress Relief § 54.30-15 Requirement for analysis and computation. (a) A stress... mechanical stress relief process. This analysis should include consideration of the local stresses in way of saddles or other supporting structure and additional bending stresses due to the weight of the...

46 CFR 54.30-15 - Requirement for analysis and computation.

Code of Federal Regulations, 2012 CFR

2012-10-01

... PRESSURE VESSELS Mechanical Stress Relief § 54.30-15 Requirement for analysis and computation. (a) A stress... mechanical stress relief process. This analysis should include consideration of the local stresses in way of saddles or other supporting structure and additional bending stresses due to the weight of the...

46 CFR 54.30-15 - Requirement for analysis and computation.

Code of Federal Regulations, 2014 CFR

2014-10-01

... PRESSURE VESSELS Mechanical Stress Relief § 54.30-15 Requirement for analysis and computation. (a) A stress... mechanical stress relief process. This analysis should include consideration of the local stresses in way of saddles or other supporting structure and additional bending stresses due to the weight of the...

46 CFR 54.30-15 - Requirement for analysis and computation.

Code of Federal Regulations, 2013 CFR

2013-10-01

... PRESSURE VESSELS Mechanical Stress Relief § 54.30-15 Requirement for analysis and computation. (a) A stress... mechanical stress relief process. This analysis should include consideration of the local stresses in way of saddles or other supporting structure and additional bending stresses due to the weight of the...

46 CFR 54.30-15 - Requirement for analysis and computation.

Code of Federal Regulations, 2011 CFR

2011-10-01

... PRESSURE VESSELS Mechanical Stress Relief § 54.30-15 Requirement for analysis and computation. (a) A stress... mechanical stress relief process. This analysis should include consideration of the local stresses in way of saddles or other supporting structure and additional bending stresses due to the weight of the...

Proceedings of the NATO-Advanced Study Institute on Computer Aided Analysis of Rigid and Flexible Mechanical Systems. Volume 1: Main lectures

NASA Astrophysics Data System (ADS)

Pereira, Manuel S.; Ambrosio, Jorge A. C.

1993-07-01

During the last few years, major scientific progress has been achieved in fields related to computer aided analysis of multibody systems. In view of this progress and recent developments of computer hardware and general purpose software, there is a need to access the current state of art and results from different schools of thought, with the objective of focussing trends in future research. Going back to 1983 when an important NATO-NSF-ARO Advanced Study Institute on Computer Aided Analysis and Optimization of Mechanical Systems was held at the University of Iowa, one may notice that less then 10 years ago the state of art was mainly dwelling on rigid body dynamics. The interest in the dynamic simulation of mechanical systems has steadily increased in recent years coming mainly from the aerospace and automative industries. The development of multibody system analysis formulations have been more recently motivated with the need to include several features such as: real-time simulation capabilities, highly non-linear control devices, work space path planing, active control of machine flexibilities and reliability and accuracy in the analysis results. The need for accurate and efficient analysis tools for design of large and lightweight mechanical systems has driven many research groups in the challenging problem of flexible systems with an increasing interaction with finite element methodologies. Basic approaches to mechanical systems dynamic analysis have recently been presented in several new text books. These publications demonstrate that both recursive and absolute methods still have their proponents to resolve the redundancy encountered in most mechanical systems.

Operation analysis of a Chebyshev-Pantograph leg mechanism for a single DOF biped robot

NASA Astrophysics Data System (ADS)

Liang, Conghui; Ceccarelli, Marco; Takeda, Yukio

2012-12-01

In this paper, operation analysis of a Chebyshev-Pantograph leg mechanism is presented for a single degree of freedom (DOF) biped robot. The proposed leg mechanism is composed of a Chebyshev four-bar linkage and a pantograph mechanism. In contrast to general fully actuated anthropomorphic leg mechanisms, the proposed leg mechanism has peculiar features like compactness, low-cost, and easy-operation. Kinematic equations of the proposed leg mechanism are formulated for a computer oriented simulation. Simulation results show the operation performance of the proposed leg mechanism with suitable characteristics. A parametric study has been carried out to evaluate the operation performance as function of design parameters. A prototype of a single DOF biped robot equipped with two proposed leg mechanisms has been built at LARM (Laboratory of Robotics and Mechatronics). Experimental test shows practical feasible walking ability of the prototype, as well as drawbacks are discussed for the mechanical design.

Impact of mechanical bowel preparation in elective colorectal surgery: A meta-analysis.

PubMed

Rollins, Katie E; Javanmard-Emamghissi, Hannah; Lobo, Dileep N

2018-01-28

To analyse the effect of mechanical bowel preparation vs no mechanical bowel preparation on outcome in patients undergoing elective colorectal surgery. Meta-analysis of randomised controlled trials and observational studies comparing adult patients receiving mechanical bowel preparation with those receiving no mechanical bowel preparation, subdivided into those receiving a single rectal enema and those who received no preparation at all prior to elective colorectal surgery. A total of 36 studies (23 randomised controlled trials and 13 observational studies) including 21568 patients undergoing elective colorectal surgery were included. When all studies were considered, mechanical bowel preparation was not associated with any significant difference in anastomotic leak rates (OR = 0.90, 95%CI: 0.74 to 1.10, P = 0.32), surgical site infection (OR = 0.99, 95%CI: 0.80 to 1.24, P = 0.96), intra-abdominal collection (OR = 0.86, 95%CI: 0.63 to 1.17, P = 0.34), mortality (OR = 0.85, 95%CI: 0.57 to 1.27, P = 0.43), reoperation (OR = 0.91, 95%CI: 0.75 to 1.12, P = 0.38) or hospital length of stay (overall mean difference 0.11 d, 95%CI: -0.51 to 0.73, P = 0.72), when compared with no mechanical bowel preparation, nor when evidence from just randomized controlled trials was analysed. A sub-analysis of mechanical bowel preparation vs absolutely no preparation or a single rectal enema similarly revealed no differences in clinical outcome measures. In the most comprehensive meta-analysis of mechanical bowel preparation in elective colorectal surgery to date, this study has suggested that the use of mechanical bowel preparation does not affect the incidence of postoperative complications when compared with no preparation. Hence, mechanical bowel preparation should not be administered routinely prior to elective colorectal surgery.

Skeletal mechanism generation for surrogate fuels using directed relation graph with error propagation and sensitivity analysis

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

Niemeyer, Kyle E.; Sung, Chih-Jen; Raju, Mandhapati P.

2010-09-15

A novel implementation for the skeletal reduction of large detailed reaction mechanisms using the directed relation graph with error propagation and sensitivity analysis (DRGEPSA) is developed and presented with examples for three hydrocarbon components, n-heptane, iso-octane, and n-decane, relevant to surrogate fuel development. DRGEPSA integrates two previously developed methods, directed relation graph-aided sensitivity analysis (DRGASA) and directed relation graph with error propagation (DRGEP), by first applying DRGEP to efficiently remove many unimportant species prior to sensitivity analysis to further remove unimportant species, producing an optimally small skeletal mechanism for a given error limit. It is illustrated that the combination ofmore » the DRGEP and DRGASA methods allows the DRGEPSA approach to overcome the weaknesses of each, specifically that DRGEP cannot identify all unimportant species and that DRGASA shields unimportant species from removal. Skeletal mechanisms for n-heptane and iso-octane generated using the DRGEP, DRGASA, and DRGEPSA methods are presented and compared to illustrate the improvement of DRGEPSA. From a detailed reaction mechanism for n-alkanes covering n-octane to n-hexadecane with 2115 species and 8157 reactions, two skeletal mechanisms for n-decane generated using DRGEPSA, one covering a comprehensive range of temperature, pressure, and equivalence ratio conditions for autoignition and the other limited to high temperatures, are presented and validated. The comprehensive skeletal mechanism consists of 202 species and 846 reactions and the high-temperature skeletal mechanism consists of 51 species and 256 reactions. Both mechanisms are further demonstrated to well reproduce the results of the detailed mechanism in perfectly-stirred reactor and laminar flame simulations over a wide range of conditions. The comprehensive and high-temperature n-decane skeletal mechanisms are included as supplementary material with this article. (author)« less

Structure Optimization of Porous Dental Implant Based on 3D Printing

NASA Astrophysics Data System (ADS)

Ji, Fangqiu; Zhang, Chunyu; Chen, Xianshuai

2018-03-01

In this paper, selective laser melting (SLM) technology is used to process complex structures. In combination with the theory of biomedicine, a porous implant with a porous structure is designed to induce bone cell growth. The mechanical strength advantage of SLM was discussed by observing the metallographic structure of SLM specimen with mechanical microscope and mechanical tensile test. The osseointegration of porous implants was observed and analyzed by biological experiments. By establishing a mechanical model, the mechanical properties of the bone implant combined with the jaw bone were studied by the simple mechanical analysis under static multi loading and the finite element mechanical analysis. According to the experimental observation and mechanical research, the optimization suggestions for the structure design of the implant made by SLM technology were put forward.

Determination of the mechanical parameters of rock mass based on a GSI system and displacement back analysis

NASA Astrophysics Data System (ADS)

Kang, Kwang-Song; Hu, Nai-Lian; Sin, Chung-Sik; Rim, Song-Ho; Han, Eun-Cheol; Kim, Chol-Nam

2017-08-01

It is very important to obtain the mechanical paramerters of rock mass for excavation design, support design, slope design and stability analysis of the underground structure. In order to estimate the mechanical parameters of rock mass exactly, a new method of combining a geological strength index (GSI) system with intelligent displacment back analysis is proposed in this paper. Firstly, average spacing of joints (d) and rock mass block rating (RBR, a new quantitative factor), surface condition rating (SCR) and joint condition factor (J c) are obtained on in situ rock masses using the scanline method, and the GSI values of rock masses are obtained from a new quantitative GSI chart. A correction method of GSI value is newly introduced by considering the influence of joint orientation and groundwater on rock mass mechanical properties, and then value ranges of rock mass mechanical parameters are chosen by the Hoek-Brown failure criterion. Secondly, on the basis of the measurement result of vault settlements and horizontal convergence displacements of an in situ tunnel, optimal parameters are estimated by combination of genetic algorithm (GA) and numerical simulation analysis using FLAC3D. This method has been applied in a lead-zinc mine. By utilizing the improved GSI quantization, correction method and displacement back analysis, the mechanical parameters of the ore body, hanging wall and footwall rock mass were determined, so that reliable foundations were provided for mining design and stability analysis.

Mechanical Design of Downhole Tractor Based on Two-Way Self-locking Mechanism

NASA Astrophysics Data System (ADS)

Fang, Delei; Shang, Jianzhong; Luo, Zirong; Wu, Guoheng; Liu, Yiying

2018-03-01

Based on the technology of horizontal well tractor, a kind of downhole tractor was developed which can realize Two-Way self-locking function. Aiming at the needs of horizontal well logging to realize the target of small size, high traction and high reliability, the tractor selects unique heart-shaped CAM as the locking mechanism. The motion principle of telescopic downhole tractor, the design of mechanical structure and locking principle of the locking mechanism are all analyzed. The mathematical expressions of traction are obtained by mechanical analysis of parallel support rod in the locking mechanism. The force analysis and contour design of the heart-shaped CAM are performed, which can lay the foundation for the development of tractor prototype.

[Present status and trend of heart fluid mechanics research based on medical image analysis].

PubMed

Gan, Jianhong; Yin, Lixue; Xie, Shenghua; Li, Wenhua; Lu, Jing; Luo, Anguo

2014-06-01

With introduction of current main methods for heart fluid mechanics researches, we studied the characteristics and weakness for three primary analysis methods based on magnetic resonance imaging, color Doppler ultrasound and grayscale ultrasound image, respectively. It is pointed out that particle image velocity (PIV), speckle tracking and block match have the same nature, and three algorithms all adopt block correlation. The further analysis shows that, with the development of information technology and sensor, the research for cardiac function and fluid mechanics will focus on energy transfer process of heart fluid, characteristics of Chamber wall related to blood fluid and Fluid-structure interaction in the future heart fluid mechanics fields.

Analysis of hydraulic steering system of tracked all-terrain vehicles' articulated mechanism

NASA Astrophysics Data System (ADS)

Meng, Zhongliang; Zang, Hao

2018-04-01

As for the researches on the dynamic characteristics of tracked all-terrain vehicles' articulated mechanism, the hydraulic feature of their steering system needs researching more, apart from the study on mechanical models. According to the maximum pressure required by the steering system of tracked all-terrain vehicle and the principle of the steering system, this paper conducts an analysis of the hydraulic steering system of the articulated mechanism. Based on the structure principle of the steering gear, a simulation model of the tracked all-terrain vehicle turning left is built. When building the simulation model of the steering gear, it makes a simulation analysis, taking the tracked all-terrain vehicle turning left as an example.

Database integration for investigative data visualization with the Temporal Analysis System

NASA Astrophysics Data System (ADS)

Barth, Stephen W.

1997-02-01

This paper describes an effort to provide mechanisms for integration of existing law enforcement databases with the temporal analysis system (TAS) -- an application for analysis and visualization of military intelligence data. Such integration mechanisms are essential for bringing advanced military intelligence data handling software applications to bear on the analysis of data used in criminal investigations. Our approach involved applying a software application for intelligence message handling to the problem of data base conversion. This application provides mechanisms for distributed processing and delivery of converted data records to an end-user application. It also provides a flexible graphic user interface for development and customization in the field.

A framework supporting the development of a Grid portal for analysis based on ROI.

PubMed

Ichikawa, K; Date, S; Kaishima, T; Shimojo, S

2005-01-01

In our research on brain function analysis, users require two different simultaneous types of processing: interactive processing to a specific part of data and high-performance batch processing to an entire dataset. The difference between these two types of processing is in whether or not the analysis is for data in the region of interest (ROI). In this study, we propose a Grid portal that has a mechanism to freely assign computing resources to the users on a Grid environment according to the users' two different types of processing requirements. We constructed a Grid portal which integrates interactive processing and batch processing by the following two mechanisms. First, a job steering mechanism controls job execution based on user-tagged priority among organizations with heterogeneous computing resources. Interactive jobs are processed in preference to batch jobs by this mechanism. Second, a priority-based result delivery mechanism that administrates a rank of data significance. The portal ensures a turn-around time of interactive processing by the priority-based job controlling mechanism, and provides the users with quality of services (QoS) for interactive processing. The users can access the analysis results of interactive jobs in preference to the analysis results of batch jobs. The Grid portal has also achieved high-performance computation of MEG analysis with batch processing on the Grid environment. The priority-based job controlling mechanism has been realized to freely assign computing resources to the users' requirements. Furthermore the achievement of high-performance computation contributes greatly to the overall progress of brain science. The portal has thus made it possible for the users to flexibly include the large computational power in what they want to analyze.

The strength study of the rotating device driver indexing spatial mechanism

NASA Astrophysics Data System (ADS)

Zakharenkov, N. V.; Kvasov, I. N.

2018-04-01

The indexing spatial mechanisms are widely used in automatic machines. The mechanisms maximum load-bearing capacity measurement is possible based on both the physical and numerical models tests results. The paper deals with the driven disk indexing spatial cam mechanism numerical model at the constant angular cam velocity. The presented mechanism kinematics and geometry parameters and finite element model are analyzed in the SolidWorks design environment. The calculation initial data and missing parameters having been found from the structure analysis were identified. The structure and kinematics analysis revealed the mechanism failures possible reasons. The numerical calculations results showing the structure performance at the contact and bending stresses are represented.

The Association of Fever with Total Mechanical Ventilation Time in Critically Ill Patients.

PubMed

Park, Dong Won; Egi, Moritoki; Nishimura, Masaji; Chang, Youjin; Suh, Gee Young; Lim, Chae Man; Kim, Jae Yeol; Tada, Keiichi; Matsuo, Koichi; Takeda, Shinhiro; Tsuruta, Ryosuke; Yokoyama, Takeshi; Kim, Seon Ok; Koh, Younsuck

2016-12-01

This research aims to investigate the impact of fever on total mechanical ventilation time (TVT) in critically ill patients. Subgroup analysis was conducted using a previous prospective, multicenter observational study. We included mechanically ventilated patients for more than 24 hours from 10 Korean and 15 Japanese intensive care units (ICU), and recorded maximal body temperature under the support of mechanical ventilation (MAX(MV)). To assess the independent association of MAX(MV) with TVT, we used propensity-matched analysis in a total of 769 survived patients with medical or surgical admission, separately. Together with multiple linear regression analysis to evaluate the association between the severity of fever and TVT, the effect of MAX(MV) on ventilator-free days was also observed by quantile regression analysis in all subjects including non-survivors. After propensity score matching, a MAX(MV) ≥ 37.5°C was significantly associated with longer mean TVT by 5.4 days in medical admission, and by 1.2 days in surgical admission, compared to those with MAX(MV) of 36.5°C to 37.4°C. In multivariate linear regression analysis, patients with three categories of fever (MAX(MV) of 37.5°C to 38.4°C, 38.5°C to 39.4°C, and ≥ 39.5°C) sustained a significantly longer duration of TVT than those with normal range of MAX(MV) in both categories of ICU admission. A significant association between MAX(MV) and mechanical ventilator-free days was also observed in all enrolled subjects. Fever may be a detrimental factor to prolong TVT in mechanically ventilated patients. These findings suggest that fever in mechanically ventilated patients might be associated with worse mechanical ventilation outcome.

Dynamic mechanical analysis of carbon nanotube-reinforced nanocomposites.

PubMed

Her, Shiuh-Chuan; Lin, Kuan-Yu

2017-06-16

To predict the mechanical properties of multiwalled carbon nanotube (MWCNT)-reinforced polymers, it is necessary to understand the role of the nanotube-polymer interface with regard to load transfer and the formation of the interphase region. The main objective of this study was to explore and attempt to clarify the reinforcement mechanisms of MWCNTs in epoxy matrix. Nanocomposites were fabricated by adding different amounts of MWCNTs to epoxy resin. Tensile test and dynamic mechanical analysis (DMA) were conducted to investigate the effect of MWCNT contents on the mechanical properties and thermal stability of nanocomposites. Compared with the neat epoxy, nanocomposite reinforced with 1 wt% of MWCNTs exhibited an increase of 152% and 54% in Young's modulus and tensile strength, respectively. Dynamic mechanical analysis demonstrates that both the storage modulus and glass transition temperature tend to increase with the addition of MWCNTs. Scanning electron microscopy (SEM) observations reveal that uniform dispersion and strong interfacial adhesion between the MWCNTs and epoxy are achieved, resulting in the improvement of mechanical properties and thermal stability as compared with neat epoxy.

Experimental and Numerical Analysis of Screw Fixation in Anterior Cruciate Ligament Reconstruction

NASA Astrophysics Data System (ADS)

Chizari, Mahmoud; Wang, Bin; Snow, Martyn; Barrett, Mel

2008-09-01

This paper reports the results of an experimental and finite element analysis of tibial screw fixation in anterior cruciate ligament (ACL) reconstruction. The mechanical properties of the bone and tendon graft are obtained from experiments using porcine bone and bovine tendon. The results of the numerical study are compared with those from mechanical testing. Analysis shows that the model may be used to establish the optimum placement of the tunnel in anterior cruciate ligament reconstruction by predicting mechanical parameters such as stress, strain and displacement at regions in the tunnel wall.

Multiscale Thermo-Mechanical Design and Analysis of High Frequency and High Power Vacuum Electron Devices

NASA Astrophysics Data System (ADS)

Gamzina, Diana

Diana Gamzina March 2016 Mechanical and Aerospace Engineering Multiscale Thermo-Mechanical Design and Analysis of High Frequency and High Power Vacuum Electron Devices Abstract A methodology for performing thermo-mechanical design and analysis of high frequency and high average power vacuum electron devices is presented. This methodology results in a "first-pass" engineering design directly ready for manufacturing. The methodology includes establishment of thermal and mechanical boundary conditions, evaluation of convective film heat transfer coefficients, identification of material options, evaluation of temperature and stress field distributions, assessment of microscale effects on the stress state of the material, and fatigue analysis. The feature size of vacuum electron devices operating in the high frequency regime of 100 GHz to 1 THz is comparable to the microstructure of the materials employed for their fabrication. As a result, the thermo-mechanical performance of a device is affected by the local material microstructure. Such multiscale effects on the stress state are considered in the range of scales from about 10 microns up to a few millimeters. The design and analysis methodology is demonstrated on three separate microwave devices: a 95 GHz 10 kW cw sheet beam klystron, a 263 GHz 50 W long pulse wide-bandwidth sheet beam travelling wave tube, and a 346 GHz 1 W cw backward wave oscillator.

Researcher Biographies

Science.gov Websites

interest: mechanical system design sensitivity analysis and optimization of linear and nonlinear structural systems, reliability analysis and reliability-based design optimization, computational methods in committee member, ISSMO; Associate Editor, Mechanics Based Design of Structures and Machines; Associate

Materials properties, loads, and stress analysis, Spartan REM: Appendix A

NASA Technical Reports Server (NTRS)

Marlowe, D. S.; West, E. J.

1984-01-01

The mechanical properties, load tests, and stress analysis of the Spartan Release Engagement Mechanism (REM) is presented. The fracture properties of the components of the unit are also discussed. Detailed engineering drawings are included.

Predicting cell viability within tissue scaffolds under equiaxial strain: multi-scale finite element model of collagen-cardiomyocytes constructs.

PubMed

Elsaadany, Mostafa; Yan, Karen Chang; Yildirim-Ayan, Eda

2017-06-01

Successful tissue engineering and regenerative therapy necessitate having extensive knowledge about mechanical milieu in engineered tissues and the resident cells. In this study, we have merged two powerful analysis tools, namely finite element analysis and stochastic analysis, to understand the mechanical strain within the tissue scaffold and residing cells and to predict the cell viability upon applying mechanical strains. A continuum-based multi-length scale finite element model (FEM) was created to simulate the physiologically relevant equiaxial strain exposure on cell-embedded tissue scaffold and to calculate strain transferred to the tissue scaffold (macro-scale) and residing cells (micro-scale) upon various equiaxial strains. The data from FEM were used to predict cell viability under various equiaxial strain magnitudes using stochastic damage criterion analysis. The model validation was conducted through mechanically straining the cardiomyocyte-encapsulated collagen constructs using a custom-built mechanical loading platform (EQUicycler). FEM quantified the strain gradients over the radial and longitudinal direction of the scaffolds and the cells residing in different areas of interest. With the use of the experimental viability data, stochastic damage criterion, and the average cellular strains obtained from multi-length scale models, cellular viability was predicted and successfully validated. This methodology can provide a great tool to characterize the mechanical stimulation of bioreactors used in tissue engineering applications in providing quantification of mechanical strain and predicting cellular viability variations due to applied mechanical strain.

Storage reliability analysis summary report. Volume 2: Electro mechanical devices

NASA Astrophysics Data System (ADS)

Smith, H. B., Jr.; Krulac, I. L.

1982-09-01

This document summarizes storage reliability data collected by the US Army Missile Command on electro-mechanical devices over a period of several years. Sources of data are detailed, major failure modes and mechanisms are listed and discussed. Non-operational failure rate prediction methodology is given, and conclusions and recommendations for enhancing the storage reliability of devices are drawn from the analysis of collected data.

Follow the Money: A Comprehensive Review of the Funding Mechanisms of Voucher Programs in Six Cases. Informing Policy & Improving Practice Research Brief

ERIC Educational Resources Information Center

Stewart, Molly S.; Moon, Jodi S.

2016-01-01

This comprehensive review is part of a three-part report, Follow the "Money: A Detailed Analysis of the Funding Mechanisms of Voucher Programs in Six Cases"; this review contains the cross-case analysis and findings of the funding mechanisms of voucher programs across five states (Arizona, Indiana, Louisiana, Ohio, and Wisconsin) and the…

Research in nonlinear structural and solid mechanics

NASA Technical Reports Server (NTRS)

Mccomb, H. G., Jr. (Compiler); Noor, A. K. (Compiler)

1981-01-01

Recent and projected advances in applied mechanics, numerical analysis, computer hardware and engineering software, and their impact on modeling and solution techniques in nonlinear structural and solid mechanics are discussed. The fields covered are rapidly changing and are strongly impacted by current and projected advances in computer hardware. To foster effective development of the technology perceptions on computing systems and nonlinear analysis software systems are presented.

The Shock and Vibration Digest. Volume 18, Number 12

DTIC Science & Technology

1986-12-01

practical msthods for fracture mechanics analysis. Linear elastic methods can yield useful results. Elas- dc-plasdc methods are becoming useful with...geometry factors. Fracture mechanics analysis based on linear elastic concepts developed in the 1960s has become established during the last decade as...2) is slightly conservative [2,3]. Materials that ran be treated with linear elastic fracture mechanics usually belong in this category. No

Layerwise mechanics and finite element for the dynamic analysis of piezoelectric composite plates

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.; Heyliger, Paul R.; Hopkins, Dale A.

1996-01-01

Laminate and structural mechanics for the analysis of laminated composite plate structures with piezoelectric actuators and sensors are presented. The theories implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite laminates. Finite-element formulations are developed for the quasi-static and dynamic analysis of smart composite structures containing piezoelectric layers. Comparisons with an exact solution illustrate the accuracy, robustness and capability of the developed mechanics to capture the global and local response of thin and/or thick laminated piezoelectric plates. Additional correlations and numerical applications demonstrate the unique capabilities of the mechanics in analyzing the static and free-vibration response of composite plates with distributed piezoelectric actuators and sensors.

Evaluation of glass transition temperature and dynamic mechanical properties of autopolymerized hard direct denture reline resins.

PubMed

Takase, Kazuma; Watanabe, Ikuya; Kurogi, Tadafumi; Murata, Hiroshi

2015-01-01

This study assessed methods for evaluation of glass transition temperature (Tg) of autopolymerized hard direct denture reline resins using dynamic mechanical analysis and differential scanning calorimetry in addition to the dynamic mechanical properties. The Tg values of 3 different reline resins were determined using a dynamic viscoelastometer and differential scanning calorimeter, and rheological parameters were also determined. Although all materials exhibited higher storage modulus and loss modulus values, and a lower loss tangent at 37˚C with a higher frequency, the frequency dependence was not large. Tg values obtained by dynamic mechanical analysis were higher than those by differential scanning calorimetry and higher frequency led to higher Tg, while more stable Tg values were also obtained by that method. These results suggest that dynamic mechanical analysis is more advantageous for characterization of autopolymerized hard direct denture reline resins than differential scanning calorimetry.

Quantitative Effectiveness Analysis of Solar Photovoltaic Policies, Introduction of Socio-Feed-in Tariff Mechanism (SocioFIT) and its Implementation in Turkey

NASA Astrophysics Data System (ADS)

Mustafaoglu, Mustafa Sinan

Some of the main energy issues in developing countries are high dependence on non-renewable energy sources, low energy efficiency levels and as a result of this high amount of CO2 emissions. Besides, a common problem of many countries including developing countries is economic inequality problem. In the study, solar photovoltaic policies of Germany, Japan and the USA is analyzed through a quantitative analysis and a new renewable energy support mechanism called Socio Feed-in Tariff Mechanism (SocioFIT) is formed based on the analysis results to address the mentioned issues of developing countries as well as economic inequality problem by using energy savings as a funding source for renewable energy systems. The applicability of the mechanism is solidified by the calculations in case of an implementation of the mechanism in Turkey.

Thermogravimetric analysis for the determination of water release rate from microcrystalline cellulose dry powder and wet bead systems.

PubMed

Mayville, Francis C; Wigent, Rodney J; Schwartz, Joseph B

2006-01-01

The purpose of this work was to determine the total amount of water contained in dry powder and wet bead samples of microcrystalline cellulose, MCC, (Avicel PH-101), taken from various stages of the extrusion/marumerization process used to make beads and to determine the kinetic rates of water release from each sample. These samples were allowed to equilibrate in controlled humidity chambers at 25 degrees C. The total amount of water in each sample, after equilibration, was determined by thermogravimetric analysis (TGA) as a function of temperature. The rates of water release from these samples were determined by using isothermal gravimetric analysis (ITGA) as a function of time. Analysis of the results for these studies suggest that water was released from these systems by several different kinetic mechanisms. The water release mechanisms for these systems include: zero order, second order, and diffusion controlled kinetics. It is believed that all three kinetic mechanisms will occur at the same time, however; only one mechanism will be prominent. The prominent mechanism was based on the amount of water present in the sample.

Development of PRIME for irradiation performance analysis of U-Mo/Al dispersion fuel

NASA Astrophysics Data System (ADS)

Jeong, Gwan Yoon; Kim, Yeon Soo; Jeong, Yong Jin; Park, Jong Man; Sohn, Dong-Seong

2018-04-01

A prediction code for the thermo-mechanical performance of research reactor fuel (PRIME) has been developed with the implementation of developed models to analyze the irradiation behavior of U-Mo dispersion fuel. The code is capable of predicting the two-dimensional thermal and mechanical performance of U-Mo dispersion fuel during irradiation. A finite element method was employed to solve the governing equations for thermal and mechanical equilibria. Temperature- and burnup-dependent material properties of the fuel meat constituents and cladding were used. The numerical solution schemes in PRIME were verified by benchmarking solutions obtained using a commercial finite element analysis program (ABAQUS). The code was validated using irradiation data from RERTR, HAMP-1, and E-FUTURE tests. The measured irradiation data used in the validation were IL thickness, volume fractions of fuel meat constituents for the thermal analysis, and profiles of the plate thickness changes and fuel meat swelling for the mechanical analysis. The prediction results were in good agreement with the measurement data for both thermal and mechanical analyses, confirming the validity of the code.

Nuclear rotations

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

Bertsch, G.F.; Janssens, R.V.

1997-07-01

An analysis of the gamma-ray spectra produced using the quantum mechanical rotational energy formula is presented for nuclei with large angular momentum. This analysis is suitable for quantum mechanics, modern physics, or nuclear physics courses. (AIP) {copyright}{ital 1997 American Institute of Physics}

Aero-Mechanical Design Methodology for Subsonic Civil Transport High-Lift Systems

NASA Technical Reports Server (NTRS)

vanDam, C. P.; Shaw, S. G.; VanderKam, J. C.; Brodeur, R. R.; Rudolph, P. K. C.; Kinney, D.

2000-01-01

In today's highly competitive and economically driven commercial aviation market, the trend is to make aircraft systems simpler and to shorten their design cycle which reduces recurring, non-recurring and operating costs. One such system is the high-lift system. A methodology has been developed which merges aerodynamic data with kinematic analysis of the trailing-edge flap mechanism with minimum mechanism definition required. This methodology provides quick and accurate aerodynamic performance prediction for a given flap deployment mechanism early on in the high-lift system preliminary design stage. Sample analysis results for four different deployment mechanisms are presented as well as descriptions of the aerodynamic and mechanism data required for evaluation. Extensions to interactive design capabilities are also discussed.

Analysis of Skylab fluid mechanics science demonstrations

NASA Technical Reports Server (NTRS)

Tegart, J. R.; Butz, J. R.

1975-01-01

The results of the data reduction and analysis of the Skylab fluid mechanics demonstrations are presented. All the fluid mechanics data available from the Skylab missions were identified and surveyed. The significant fluid mechanics phenomena were identified and reduced to measurable quantities wherever possible. Data correlations were performed using existing theories. Among the phenomena analyzed were: static low-g interface shapes, oscillation frequency and damping of a liquid drop, coalescence, rotating drop, liquid films and low-g ice melting. A survey of the possible applications of the results was made and future experiments are recommended.

Proceedings of the Army Symposium on Solid Mechanics. Advances in Solid Mechanics for Design and Analysis Held at Newport, Rhode Island on 1-3 October 1984.

DTIC Science & Technology

1984-10-01

Proceedings of the Army Symposium on Solid Mechanics, 1984 - Advances in Solid Mechanics for Design and Analysis, held at Newport, Rhode Island, 1-3...aie not to he construed as an official Department of the Army position, unless so designated by othei * author/id documents. Menton of any trade names...Starting with the 1972 meeting, papers have been solicited from in-house and contract researchers and designers for the Navy, Air Force, and other

Socioeconomic disparities in the utilization of mechanical thrombectomy for acute ischemic stroke in US hospitals.

PubMed

Brinjikji, W; Rabinstein, A A; McDonald, J S; Cloft, H J

2014-03-01

Previous studies have demonstrated that socioeconomic disparities in the treatment of cerebrovascular diseases exist. We studied a large administrative data base to study disparities in the utilization of mechanical thrombectomy for acute ischemic stroke. With the utilization of the Perspective data base, we studied disparities in mechanical thrombectomy utilization between patient race and insurance status in 1) all patients presenting with acute ischemic stroke and 2) patients presenting with acute ischemic stroke at centers that performed mechanical thrombectomy. We examined utilization rates of mechanical thrombectomy by race/ethnicity (white, black, and Hispanic) and insurance status (Medicare, Medicaid, self-pay, and private). Multivariate logistic regression analysis adjusting for potential confounding variables was performed to study the association between race/insurance status and mechanical thrombectomy utilization. The overall mechanical thrombectomy utilization rate was 0.15% (371/249,336); utilization rate at centers that performed mechanical thrombectomy was 1.0% (371/35,376). In the sample of all patients with acute ischemic stroke, multivariate logistic regression analysis demonstrated that uninsured patients had significantly lower odds of mechanical thrombectomy utilization compared with privately insured patients (OR = 0.52, 95% CI = 0.25-0.95, P = .03), as did Medicare patients (OR = 0.53, 95% CI = 0.41-0.70, P < .0001). Blacks had significantly lower odds of mechanical thrombectomy utilization compared with whites (OR = 0.35, 95% CI = 0.23-0.51, P < .0001). When considering only patients treated at centers performing mechanical thrombectomy, multivariate logistic regression analysis demonstrated that insurance was not associated with significant disparities in mechanical thrombectomy utilization; however, black patients had significantly lower odds of mechanical thrombectomy utilization compared with whites (OR = 0.41, 95% CI = 0.27-0.60, P < .0001). Significant socioeconomic disparities exist in the utilization of mechanical thrombectomy in the United States.

EFFECTS OF COMPOSITION ON THE MECHANICAL PROPERTIES OF NI-CR-MO-CO FILLER METALS.

DTIC Science & Technology

STEEL, WELDING RODS), CHEMICAL ANALYSIS, CARBON ALLOYS , COBALT ALLOYS , CHROMIUM ALLOYS , MOLYBDENUM ALLOYS , NICKEL ALLOYS , MARAGING STEELS...ALUMINUM COMPOUNDS, TITANIUM , NONMETALS, SHIP HULLS, SHIP PLATES, SUBMARINE HULLS, WELDING , WELDS , MECHANICAL PROPERTIES, STATISTICAL ANALYSIS, MICROSTRUCTURE.

A unified approach to the analysis and design of elasto-plastic structures with mechanical contact

NASA Technical Reports Server (NTRS)

Bendsoe, Martin P.; Olhoff, Niels; Taylor, John E.

1990-01-01

With structural design in mind, a new unified variational model has been developed which represents the mechanics of deformation elasto-plasticity with unilateral contact conditions. For a design problem formulated as maximization of the load carrying capacity of a structure under certain constraints, the unified model allows for a simultaneous analysis and design synthesis for a whole range of mechanical behavior.

A perturbation analysis of a mechanical model for stable spatial patterning in embryology

NASA Astrophysics Data System (ADS)

Bentil, D. E.; Murray, J. D.

1992-12-01

We investigate a mechanical cell-traction mechanism that generates stationary spatial patterns. A linear analysis highlights the model's potential for these heterogeneous solutions. We use multiple-scale perturbation techniques to study the evolution of these solutions and compare our solutions with numerical simulations of the model system. We discuss some potential biological applications among which are the formation of ridge patterns, dermatoglyphs, and wound healing.

JPRS Report China.

DTIC Science & Technology

1993-02-01

a socialist market economy, In the final analysis , the market mechanism is a compe- tition mechanism. Enterprises are going to enter the...sensitive to market feedback, and that there is something wrong with the mechanism. It also indicates an incorrect analysis of various factors related to...The Ghundu Group is an enter- prise group at the core of which is the Luoyang Consol- idated Meats Plant . Our current relative success has a lot to

Exploring the molecular mechanisms of Traditional Chinese Medicine components using gene expression signatures and connectivity map.

PubMed

Yoo, Minjae; Shin, Jimin; Kim, Hyunmin; Kim, Jihye; Kang, Jaewoo; Tan, Aik Choon

2018-04-04

Traditional Chinese Medicine (TCM) has been practiced over thousands of years in China and other Asian countries for treating various symptoms and diseases. However, the underlying molecular mechanisms of TCM are poorly understood, partly due to the "multi-component, multi-target" nature of TCM. To uncover the molecular mechanisms of TCM, we perform comprehensive gene expression analysis using connectivity map. We interrogated gene expression signatures obtained 102 TCM components using the next generation Connectivity Map (CMap) resource. We performed systematic data mining and analysis on the mechanism of action (MoA) of these TCM components based on the CMap results. We clustered the 102 TCM components into four groups based on their MoAs using next generation CMap resource. We performed gene set enrichment analysis on these components to provide additional supports for explaining these molecular mechanisms. We also provided literature evidence to validate the MoAs identified through this bioinformatics analysis. Finally, we developed the Traditional Chinese Medicine Drug Repurposing Hub (TCM Hub) - a connectivity map resource to facilitate the elucidation of TCM MoA for drug repurposing research. TCMHub is freely available in http://tanlab.ucdenver.edu/TCMHub. Molecular mechanisms of TCM could be uncovered by using gene expression signatures and connectivity map. Through this analysis, we identified many of the TCM components possess diverse MoAs, this may explain the applications of TCM in treating various symptoms and diseases. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Synthesis and Physical Properties of Poly(Perfluoroalkylether)Urethanes

DTIC Science & Technology

1989-05-30

Differential scanning calorimetry and dynamic mechanical analysis showed that the incorporation of PFEG into the soft segment phase slightly enhanced...for all the polymers, using electron spectroscopy for chemical analysis (ESCA). The dynamic contact angle results indicate that the polymer surfaces...these polymers were evaluated by a variety of techniques. Differential scanning calorimetry and dynamic mechanical analysis showed that the

Kinematic synthesis of bevel-gear-type robotic wrist mechanisms

NASA Astrophysics Data System (ADS)

Lin, Chen-Chou

Bevel-gear-type robotic wrist mechanisms are commonly used in industry. The reasons for their popularity are that they are compact, light-weight, and relatively inexpensive. However, there are singularities in their workspace, which substantially degrade their manipulative performance. The objective of this research is to develop an atlas of three-degree-of-freedom bevel-gear-type wrist mechanisms, and through dimensional synthesis to improve their kinematic performance. The dissertation contains two major parts: the first is structural analysis and synthesis, the other is kinematic analysis and dimensional synthesis. To synthesize the kinematic structures of bevel-gear-type wrist mechanisms, the kinematic structures are separated from their functional considerations. All kinematic structures which satisfy the mobility condition are enumerated in an unbiased, systematic manner. Then the bevel-gear-type wrist mechanisms are identified by applying the functional requirements. Structural analysis shows that a three-degree-of-freedom wrist mechanism usually consists of non-fractionated, two degree-of-freedom epicyclic gear train jointed with the base link. Therefore, the structural synthesis can be simplified into a problem of examining the atlas of non-fractionated, two-degree-of-freedom epicyclic gear trains. The resulting bevel-gear-type wrist mechanism has been categorized and evaluated. It is shown that three-degree-of-freedom, four-jointed wrist mechanisms are promising for further improving the kinematic performance. It is found that a spherical planetary gear train is necessarily imbedded in a three-degree-of-freedom, four-jointed wrist mechanism. Therefore, to study the workspace and singularity problems of three-degree-of-freedom four-jointed spherical wrist mechanisms, we have to study the trajectories of spherical planetary gear trains. The parametric equations of the trajectories and some useful geometric properties for the analysis and synthesis of workplace are derived. The workspace boundary equations can be derived via both geometric consideration and Jacobian analysis. The workspace is divided by inner and outer boundaries into regions of accessibility of zero, two, and four. The design criteria of full workspace and a maximum four-root region are established.

Evolution from a hinge actuator mechanism to an antenna deployment mechanism for use on the European large communications satellite (L-SAT/OLYMPUS)

NASA Technical Reports Server (NTRS)

Death, M. D.

1984-01-01

The evolution of an Antenna Deployment Mechanism (ADM) from a Hinge Actuator Mechanism (HAM) is described as it pertains to the deployment of large satellite antennas. Design analysis and mechanical tests are examined in detail.

The effect of helium-oxygen-assisted mechanical ventilation on chronic obstructive pulmonary disease exacerbation: A systemic review and meta-analysis.

PubMed

Wu, Xu; Shao, Chuan; Zhang, Liang; Tu, Jinjing; Xu, Hui; Lin, Zhihui; Xu, Shuguang; Yu, Biyun; Tang, Yaodong; Li, Shanqun

2018-03-01

Chronic obstructive pulmonary disease (COPD) is often accompanied by acute exacerbations. Patients of COPD exacerbation suffering from respiratory failure often need the support of mechanical ventilation. Helium-oxygen can be used to reduce airway resistance during mechanical ventilation. The aim of this study is to evaluate the effect of helium-oxygen-assisted mechanical ventilation on COPD exacerbation through a meta-analysis. A comprehensive literature search through databases of Pub Med (1966∼2016), Ovid MEDLINE (1965∼2016), Cochrane EBM (1991∼2016), EMBASE (1974∼2016) and Ovid MEDLINE was performed to identify associated studies. Randomized clinical trials met our inclusion criteria that focus on helium-oxygen-assisted mechanical ventilation on COPD exacerbation were included. The quality of the papers was evaluated after inclusion and information was extracted for meta-analysis. Six articles and 392 patients were included in total. Meta-analysis revealed that helium-oxygen-assisted mechanical ventilation reduced Borg dyspnea scale and increased arterial PH compared with air-oxygen. No statistically significant difference was observed between helium-oxygen and air-oxygen as regards to WOB, PaCO 2 , OI, tracheal intubation rates and mortality within hospital. Our study suggests helium-oxygen-assisted mechanical ventilation can help to reduce Borg dyspnea scale. In terms of the tiny change of PH, its clinical benefit is negligible. There is no conclusive evidence indicating the beneficial effect of helium-oxygen-assisted mechanical ventilation on clinical outcomes or prognosis of COPD exacerbation. © 2017 John Wiley & Sons Ltd.

Elucidation of reaction mechanism involved in the formation of LaNiO3 from XRD and TG analysis

NASA Astrophysics Data System (ADS)

Dharmadhikari, Dipti V.; Athawale, Anjali A.

2013-06-01

The present work is focused on the synthesis and elucidation of reaction mechanism involved in the formation of LaNiO3 with the help of X-ray diffraction (XRD) and thermogravimetric (TG) analysis. LaNiO3 was synthesized by hydrothermal method by heating at 160°C under autogenous pressure for 6h. Pure phase product was obtained after calcining the hydrothermally activated product for 6h at 700°C. The various phases of the product obtained after hydrothermal treatment and calcination followed by the formation of pure phase nanocrystalline lanthanum nickel oxide could be determined from XRD analysis of the samples. The reaction mechanism and phase formation temperature has been interpreted by thermogravimetric analysis of the hydrothermally synthesized product and XRD analysis.

An Historical Perspective on the Theory and Practice of Soil Mechanical Analysis.

ERIC Educational Resources Information Center

Miller, W. P.; And Others

1988-01-01

Traces the history of soil mechanical analysis. Evaluates this history in order to place current concepts in perspective, from both a research and teaching viewpoint. Alternatives to traditional separation techniques for use in soils teaching laboratories are discussed. (TW)

Assessment of crack growth in a space shuttle main engine first-stage, high-pressure fuel turbopump blade

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali

1993-01-01

A two-dimensional finite element fracture mechanics analysis of a space shuttle main engine (SSME) turbine blade firtree was performed using the MARC finite element code. The analysis was conducted under combined effects of thermal and mechanical loads at steady-state conditions. Data from a typical engine stand cycle of the SSME were used to run a heat transfer analysis and, subsequently, a thermal structural fracture mechanics analysis. Temperature and stress contours for the firtree under these operating conditions were generated. High stresses were found at the firtree lobes where crack initiation was triggered. A life assessment of the firtree was done by assuming an initial and a final crack size.

Computational mechanics research and support for aerodynamics and hydraulics at TFHRC, year 2 quarter 1 progress report.

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

Lottes, S.A.; Bojanowski, C.; Shen, J.

2012-04-09

The computational fluid dynamics (CFD) and computational structural mechanics (CSM) focus areas at Argonne's Transportation Research and Analysis Computing Center (TRACC) initiated a project to support and compliment the experimental programs at the Turner-Fairbank Highway Research Center (TFHRC) with high performance computing based analysis capabilities in August 2010. The project was established with a new interagency agreement between the Department of Energy and the Department of Transportation to provide collaborative research, development, and benchmarking of advanced three-dimensional computational mechanics analysis methods to the aerodynamics and hydraulics laboratories at TFHRC for a period of five years, beginning in October 2010. Themore » analysis methods employ well-benchmarked and supported commercial computational mechanics software. Computational mechanics encompasses the areas of Computational Fluid Dynamics (CFD), Computational Wind Engineering (CWE), Computational Structural Mechanics (CSM), and Computational Multiphysics Mechanics (CMM) applied in Fluid-Structure Interaction (FSI) problems. The major areas of focus of the project are wind and water effects on bridges - superstructure, deck, cables, and substructure (including soil), primarily during storms and flood events - and the risks that these loads pose to structural failure. For flood events at bridges, another major focus of the work is assessment of the risk to bridges caused by scour of stream and riverbed material away from the foundations of a bridge. Other areas of current research include modeling of flow through culverts to improve design allowing for fish passage, modeling of the salt spray transport into bridge girders to address suitability of using weathering steel in bridges, CFD analysis of the operation of the wind tunnel in the TFHRC wind engineering laboratory. This quarterly report documents technical progress on the project tasks for the period of October through December 2011.« less

Computational mechanics research and support for aerodynamics and hydraulics at TFHRC, year 2 quarter 2 progress report

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

Lottes, S.A.; Bojanowski, C.; Shen, J.

2012-06-28

The computational fluid dynamics (CFD) and computational structural mechanics (CSM) focus areas at Argonne's Transportation Research and Analysis Computing Center (TRACC) initiated a project to support and compliment the experimental programs at the Turner-Fairbank Highway Research Center (TFHRC) with high performance computing based analysis capabilities in August 2010. The project was established with a new interagency agreement between the Department of Energy and the Department of Transportation to provide collaborative research, development, and benchmarking of advanced three-dimensional computational mechanics analysis methods to the aerodynamics and hydraulics laboratories at TFHRC for a period of five years, beginning in October 2010. Themore » analysis methods employ well benchmarked and supported commercial computational mechanics software. Computational mechanics encompasses the areas of Computational Fluid Dynamics (CFD), Computational Wind Engineering (CWE), Computational Structural Mechanics (CSM), and Computational Multiphysics Mechanics (CMM) applied in Fluid-Structure Interaction (FSI) problems. The major areas of focus of the project are wind and water effects on bridges - superstructure, deck, cables, and substructure (including soil), primarily during storms and flood events - and the risks that these loads pose to structural failure. For flood events at bridges, another major focus of the work is assessment of the risk to bridges caused by scour of stream and riverbed material away from the foundations of a bridge. Other areas of current research include modeling of flow through culverts to improve design allowing for fish passage, modeling of the salt spray transport into bridge girders to address suitability of using weathering steel in bridges, CFD analysis of the operation of the wind tunnel in the TFHRC wind engineering laboratory. This quarterly report documents technical progress on the project tasks for the period of January through March 2012.« less

Progress on Fault Mechanisms for Gear Transmissions in Coal Cutting Machines: From Macro to Nano Models.

PubMed

Jiang, Yu; Zhang, Xiaogang; Zhang, Chao; Li, Zhixiong; Sheng, Chenxing

2017-04-01

Numerical modeling has been recognized as the dispensable tools for mechanical fault mechanism analysis. Techniques, ranging from macro to nano levels, include the finite element modeling boundary element modeling, modular dynamic modeling, nano dynamic modeling and so forth. This work firstly reviewed the progress on the fault mechanism analysis for gear transmissions from the tribological and dynamic aspects. Literature review indicates that the tribological and dynamic properties were separately investigated to explore the fault mechanism in gear transmissions. However, very limited work has been done to address the links between the tribological and dynamic properties and scarce researches have been done for coal cutting machines. For this reason, the tribo-dynamic coupled model was introduced to bridge the gap between the tribological and dynamic models in fault mechanism analysis for gear transmissions in coal cutting machines. The modular dynamic modeling and nano dynamic modeling techniques are expected to establish the links between the tribological and dynamic models. Possible future research directions using the tribo dynamic coupled model were summarized to provide potential references for researchers in the field.

Finite Element-Based Mechanical Assessment of Bone Quality on the Basis of In Vivo Images.

PubMed

Pahr, Dieter H; Zysset, Philippe K

2016-12-01

Beyond bone mineral density (BMD), bone quality designates the mechanical integrity of bone tissue. In vivo images based on X-ray attenuation, such as CT reconstructions, provide size, shape, and local BMD distribution and may be exploited as input for finite element analysis (FEA) to assess bone fragility. Further key input parameters of FEA are the material properties of bone tissue. This review discusses the main determinants of bone mechanical properties and emphasizes the added value, as well as the important assumptions underlying finite element analysis. Bone tissue is a sophisticated, multiscale composite material that undergoes remodeling but exhibits a rather narrow band of tissue mineralization. Mechanically, bone tissue behaves elastically under physiologic loads and yields by cracking beyond critical strain levels. Through adequate cell-orchestrated modeling, trabecular bone tunes its mechanical properties by volume fraction and fabric. With proper calibration, these mechanical properties may be incorporated in quantitative CT-based finite element analysis that has been validated extensively with ex vivo experiments and has been applied increasingly in clinical trials to assess treatment efficacy against osteoporosis.

Meta-analysis of chicken--salmonella infection experiments.

PubMed

Te Pas, Marinus F W; Hulsegge, Ina; Schokker, Dirkjan; Smits, Mari A; Fife, Mark; Zoorob, Rima; Endale, Marie-Laure; Rebel, Johanna M J

2012-04-24

Chicken meat and eggs can be a source of human zoonotic pathogens, especially Salmonella species. These food items contain a potential hazard for humans. Chickens lines differ in susceptibility for Salmonella and can harbor Salmonella pathogens without showing clinical signs of illness. Many investigations including genomic studies have examined the mechanisms how chickens react to infection. Apart from the innate immune response, many physiological mechanisms and pathways are reported to be involved in the chicken host response to Salmonella infection. The objective of this study was to perform a meta-analysis of diverse experiments to identify general and host specific mechanisms to the Salmonella challenge. Diverse chicken lines differing in susceptibility to Salmonella infection were challenged with different Salmonella serovars at several time points. Various tissues were sampled at different time points post-infection, and resulting host transcriptional differences investigated using different microarray platforms. The meta-analysis was performed with the R-package metaMA to create lists of differentially regulated genes. These gene lists showed many similarities for different chicken breeds and tissues, and also for different Salmonella serovars measured at different times post infection. Functional biological analysis of these differentially expressed gene lists revealed several common mechanisms for the chicken host response to Salmonella infection. The meta-analysis-specific genes (i.e. genes found differentially expressed only in the meta-analysis) confirmed and expanded the biological functional mechanisms. The meta-analysis combination of heterogeneous expression profiling data provided useful insights into the common metabolic pathways and functions of different chicken lines infected with different Salmonella serovars.

Meta-analysis of Chicken – Salmonella infection experiments

PubMed Central

2012-01-01

Background Chicken meat and eggs can be a source of human zoonotic pathogens, especially Salmonella species. These food items contain a potential hazard for humans. Chickens lines differ in susceptibility for Salmonella and can harbor Salmonella pathogens without showing clinical signs of illness. Many investigations including genomic studies have examined the mechanisms how chickens react to infection. Apart from the innate immune response, many physiological mechanisms and pathways are reported to be involved in the chicken host response to Salmonella infection. The objective of this study was to perform a meta-analysis of diverse experiments to identify general and host specific mechanisms to the Salmonella challenge. Results Diverse chicken lines differing in susceptibility to Salmonella infection were challenged with different Salmonella serovars at several time points. Various tissues were sampled at different time points post-infection, and resulting host transcriptional differences investigated using different microarray platforms. The meta-analysis was performed with the R-package metaMA to create lists of differentially regulated genes. These gene lists showed many similarities for different chicken breeds and tissues, and also for different Salmonella serovars measured at different times post infection. Functional biological analysis of these differentially expressed gene lists revealed several common mechanisms for the chicken host response to Salmonella infection. The meta-analysis-specific genes (i.e. genes found differentially expressed only in the meta-analysis) confirmed and expanded the biological functional mechanisms. Conclusions The meta-analysis combination of heterogeneous expression profiling data provided useful insights into the common metabolic pathways and functions of different chicken lines infected with different Salmonella serovars. PMID:22531008

Tungsten Disulfide Nanotubes Reinforced Biodegradable Polymers for Bone Tissue Engineering

PubMed Central

Lalwani, Gaurav; Henslee, Allan M.; Farshid, Behzad; Parmar, Priyanka; Lin, Liangjun; Qin, Yi-Xian; Kasper, F. Kurtis; Mikos, Antonios G.; Sitharaman, Balaji

2013-01-01

In this study, we have investigated the efficacy of inorganic nanotubes as reinforcing agents to improve the mechanical properties of poly(propylene fumarate) (PPF) composites as a function of nanomaterial loading concentration (0.01-0.2 wt%). Tungsten disulfide nanotubes (WSNTs) were used as reinforcing agents in the experimental groups. Single- and multi- walled carbon nanotubes (SWCNTs and MWCNTs) were used as positive controls, and crosslinked PPF composites were used as baseline control. Mechanical testing (compression and three-point bending) shows a significant enhancement (up to 28-190%) in the mechanical properties (compressive modulus, compressive yield strength, flexural modulus, and flexural yield strength) of WSNT reinforced PPF nanocomposites compared to the baseline control. In comparison to positive controls, at various concentrations, significant improvements in the mechanical properties of WSNT nanocomposites were also observed. In general, the inorganic nanotubes (WSNTs) showed a better (up to 127%) or equivalent mechanical reinforcement compared to carbon nanotubes (SWCNTs and MWCNTs). Sol fraction analysis showed significant increases in the crosslinking density of PPF in the presence of WSNTs (0.01-0.2 wt%). Transmission electron microscopy (TEM) analysis on thin sections of crosslinked nanocomposites showed the presence of WSNTs as individual nanotubes in the PPF matrix, whereas SWCNTs and MWCNTs existed as micron sized aggregates. The trend in the surface area of nanostructures obtained by BET surface area analysis was SWCNTs > MWCNTs > WSNTs. The BET surface area analysis, TEM analysis, and sol fraction analysis results taken together suggest that chemical composition (inorganic vs. carbon nanomaterials), presence of functional groups (such as sulfide and oxysulfide), and individual dispersion of the nanomaterials in the polymer matrix (absence of aggregation of the reinforcing agent) are the key parameters affecting the mechanical properties of nanostructure-reinforced PPF composites, and the reason for the observed increases in the mechanical properties compared to the baseline and positive controls. PMID:23727293

Design and analysis of a keel latch for use on the Hubble Space Telescope

NASA Technical Reports Server (NTRS)

Calvert, John; Stinson, Melanie

1986-01-01

The mechanical design of the keel latch is discussed, as well as the stress analysis of the keel latch. Background information; mechanical design requirements; some of the initial design considerations; the design considerations that led to the selection of the final design; the mechanics of the final design; testing that has been and will be accomplished to verify that design requirements have been met; and future tests are discussed.

Improving the Performance of Heat Insulation Polyurethane Foams by Silica Nanoparticles

NASA Astrophysics Data System (ADS)

Nikje, M. M. Alavi; Garmarudi, A. Bagheri; Haghshenas, M.; Mazaheri, Z.

Heat insulation polyurethane foam materials were doped by silica nano particles, to investigate the probable improving effects. In order to achieve the best dispersion condition and compatibility of silica nanoparticles in the polymer matrix a modification step was performed by 3-aminopropyltriethoxysilane (APTS) as coupling agent. Then, thermal and mechanical properties of polyurethane rigid foam were investigated. Thermal and mechanical properties were studied by tensile machine, thermogravimetric analysis and dynamic mechanical analysis.

An Overview of Promising Grades of Tool Materials Based on the Analysis of their Physical-Mechanical Characteristics

NASA Astrophysics Data System (ADS)

Kudryashov, E. A.; Smirnov, I. M.; Grishin, D. V.; Khizhnyak, N. A.

2018-06-01

The work is aimed at selecting a promising grade of a tool material, whose physical-mechanical characteristics would allow using it for processing the surfaces of discontinuous parts in the presence of shock loads. An analysis of the physical-mechanical characteristics of most common tool materials is performed and the data on a possible provision of the metal-working processes with promising composite grades are presented.

PHARYNGEAL SWALLOWING MECHANICS SECONDARY TO HEMISPHERIC STROKE

PubMed Central

May, Nelson H; Pisegna, Jessica M; Marchina, Sarah; Langmore, Susan E; Kumar, Sandeep; Pearson, William G

2016-01-01

Goals Computational Analysis of Swallowing Mechanics is a method that utilizes multivariate shape change analysis to uncover covariant elements of pharyngeal swallowing mechanics associated with impairment using videofluoroscopic swallowing studies. The goals of this preliminary study were to (1) characterize swallowing mechanics underlying stroke related dysphagia, (2) decipher the impact of left and right hemispheric stroke on pharyngeal swallowing mechanics, and (3) determine pharyngeal swallowing mechanics associated with penetration-aspiration status. Materials and Methods Videofluoroscopic swallowing studies of 18 dysphagic patients with hemispheric infarcts and age and gender matched controls were selected from well-controlled data sets. Patient data including laterality, and penetration-aspiration status was collected. Coordinates mapping muscle group action during swallowing were collected from videos. Multivariate morphometric analyses of coordinates associated with stroke, affected hemisphere, and penetration-aspiration status were performed. Findings Pharyngeal swallowing mechanics differed significantly in the following comparisons: stroke vs. controls (D=2.19, p<.0001); right hemispheric stroke vs. controls (D=3.64, p<.0001); left hemispheric stroke vs. controls (D=2.06, p<.0001); right hemispheric stroke vs. left hemispheric stroke (D=2.89, p<.0001); and penetration-aspiration vs. within normal limits (D=2.25, p<.0001). Differences in pharyngeal swallowing mechanics associated with each comparison were visualized using eigenvectors. Conclusion While current literature focuses on timing changes in stroke-related dysphagia, this data suggests that mechanical changes are also functionally important. Pharyngeal swallowing mechanics differed by affected hemisphere and penetration-aspiration status. Computational Analysis of Swallowing Mechanics can be used to identify patient specific swallowing impairment associated with stroke injury that could help guide rehabilitation strategies to improve swallowing outcomes. PMID:27913200

Computational Methods for Structural Mechanics and Dynamics

NASA Technical Reports Server (NTRS)

Stroud, W. Jefferson (Editor); Housner, Jerrold M. (Editor); Tanner, John A. (Editor); Hayduk, Robert J. (Editor)

1989-01-01

Topics addressed include: transient dynamics; transient finite element method; transient analysis in impact and crash dynamic studies; multibody computer codes; dynamic analysis of space structures; multibody mechanics and manipulators; spatial and coplanar linkage systems; flexible body simulation; multibody dynamics; dynamical systems; and nonlinear characteristics of joints.

Thermo-Mechanical Modeling and Analysis for Turbopump Assemblies

NASA Technical Reports Server (NTRS)

Platt, Mike; Marsh, Matt

2003-01-01

Life, reliability, and cost are strongly impacted by steady and transient thermo-mechanical effect. Design cycle can suffer big setbacks when working a transient stress/deflection issue. Balance between objectives and constrains is always difficult. Requires assembly-level analysis early in the design cycle.

Diesel Mechanics. Ohio's Competency Analysis Profile.

ERIC Educational Resources Information Center

Ohio State Univ., Columbus. Vocational Instructional Materials Lab.

This Ohio Competency Analysis Profile (OCAP), derived from a modified Developing a Curriculum (DACUM) process, is a current comprehensive and verified employer competency program list for diesel mechanics. Each unit (with or without subunits) contains competencies and competency builders that identify the occupational, academic, and employability…

Recreation Vehicle Mechanic. Occupational Analyses Series.

ERIC Educational Resources Information Center

Dean, Ann; Embree, Rick

This analysis covers tasks performed by a recreation vehicle mechanic, an occupational title some provinces and territories of Canada have also identified as recreation vehicle technician and recreation vehicle service technician. A guide to analysis discusses development, structure, and validation method; scope of the occupation; trends; and…

Reference Models for Multi-Layer Tissue Structures

DTIC Science & Technology

2016-09-01

simulation,  finite   element  analysis 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES 19a. NAME OF RESPONSIBLE PERSON USAMRMC...Physiologically realistic, fully specimen-specific, nonlinear reference models. Tasks. Finite element analysis of non-linear mechanics of cadaver...models. Tasks. Finite element analysis of non-linear mechanics of multi-layer tissue regions of human subjects. Deliverables. Partially subject- and

Layerwise Mechanics and Finite Elements for Smart Composite Structures with Piezoelectric Actuators and Sensors

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.; Heyliger, Paul R.; Hopkins, Dale A.

1996-01-01

Recent developments on layerwise mechanics for the analysis of composite laminates and structures with piezoelectric actuators and sensors are reviewed. The mechanics implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite structures. The corresponding finite-element implementations for the static and dynamic analysis of smart piezoelectric composite structures are also summarized. Select application illustrate the accuracy, robustness and capability of the developed mechanics to capture the global and local dynamic response of thin and/or thick laminated piezoelectric plates.

Computational mechanics - Advances and trends; Proceedings of the Session - Future directions of Computational Mechanics of the ASME Winter Annual Meeting, Anaheim, CA, Dec. 7-12, 1986

NASA Technical Reports Server (NTRS)

Noor, Ahmed K. (Editor)

1986-01-01

The papers contained in this volume provide an overview of the advances made in a number of aspects of computational mechanics, identify some of the anticipated industry needs in this area, discuss the opportunities provided by new hardware and parallel algorithms, and outline some of the current government programs in computational mechanics. Papers are included on advances and trends in parallel algorithms, supercomputers for engineering analysis, material modeling in nonlinear finite-element analysis, the Navier-Stokes computer, and future finite-element software systems.

Development of PRIME for irradiation performance analysis of U-Mo/Al dispersion fuel

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

Jeong, Gwan Yoon; Kim, Yeon Soo; Jeong, Yong Jin

A prediction code for the thermo-mechanical performance of research reactor fuel (PRIME) has been developed with the implementation of developed models to analyze the irradiation behavior of U-Mo dispersion fuel. The code is capable of predicting the two-dimensional thermal and mechanical performance of U-Mo dispersion fuel during irradiation. A finite element method was employed to solve the governing equations for thermal and mechanical equilibria. Temperature-and burnup-dependent material properties of the fuel meat constituents and cladding were used. The numerical solution schemes in PRIME were verified by benchmarking solutions obtained using a commercial finite element analysis program (ABAQUS).The code was validatedmore » using irradiation data from RERTR, HAMP-1, and E-FUTURE tests. The measured irradiation data used in the validation were IL thickness, volume fractions of fuel meat constituents for the thermal analysis, and profiles of the plate thickness changes and fuel meat swelling for the mechanical analysis. The prediction results were in good agreement with the measurement data for both thermal and mechanical analyses, confirming the validity of the code. (c) 2018 Elsevier B.V. All rights reserved.« less

On 3-D inelastic analysis methods for hot section components (base program)

NASA Technical Reports Server (NTRS)

Wilson, R. B.; Bak, M. J.; Nakazawa, S.; Banerjee, P. K.

1986-01-01

A 3-D Inelastic Analysis Method program is described. This program consists of a series of new computer codes embodying a progression of mathematical models (mechanics of materials, special finite element, boundary element) for streamlined analysis of: (1) combustor liners, (2) turbine blades, and (3) turbine vanes. These models address the effects of high temperatures and thermal/mechanical loadings on the local (stress/strain)and global (dynamics, buckling) structural behavior of the three selected components. Three computer codes, referred to as MOMM (Mechanics of Materials Model), MHOST (Marc-Hot Section Technology), and BEST (Boundary Element Stress Technology), have been developed and are briefly described in this report.

Thermal and mechanical analysis of PVA / sulfonated carbon nanotubes composite

NASA Astrophysics Data System (ADS)

Yadav, Vikrant; Sharma, Prem P.; Rajput, Abhishek; Kulshrestha, Vaibhav

2018-04-01

Nanocomposites of polyvinyl alcohol (PVA) and sulfonated carbon nanotubes (s-CNT) with enhanced properties were synthesized successfully. Effect of different amount of sulfonated nanotubes on thermal and mechanical properties of resultant nanocomposites derived from s-CNT and PVA were studied. Structural analysis for functionalization of CNT was done by using FTIR spectra. Thermal and mechanical analysis were done by using TGA, DSC and UTM. Nanocomposite containing s-CNT shows higher elastic moduli, higher melting temperature in consort with lower weight loss at same temperature, compared with pristine PVA. The novelty of this work is to use PVA/s-CNT based composites with improved thermomechanical properties in different nanotechnologies.

Study on stainless steel electrode based on dynamic aluminum liquid corrosion mechanism.

PubMed

Hou, Hua; Yang, Ruifeng

2009-01-01

Scanning electrion microscope (SEM) was performed for investigations on the corrosion mechanism of stainless steel electrode in dynamic melting aluminum liquid. Microstructures and composition analysis was made by electron probe analysis (EPA) combined with metallic phase analysis. It can be concluded that the corrosion process is mainly composed of physical corrosion (flowing and scouring corrosion) and chemical corrosion (forming FeAl and Fe2Al5) and the two mechanisms usually exist simultaneously. The corrosion interface thickness is about 10 μm, which is different to usual interface width of hundreds μm in the static melting Al with iron matrix.

Gesellschaft fuer angewandte Mathematik und Mechanik, Scientific Annual Meeting, Universitaet Stuttgart, Federal Republic of Germany, Apr. 13-17, 1987, Reports

NASA Astrophysics Data System (ADS)

Recent experimental, theoretical, and numerical investigations of problems in applied mechanics are discussed in reviews and reports. The fields covered include vibration and stability; the mechanics of elastic and plastic materials; fluid mechanics; the numerical treatment of differential equations; finite and boundary elements; optimization, decision theory, stochastics, and actuarial analysis; applied analysis and mathematical physics; and numerical analysis. Reviews are presented on mathematical applications of geometric-optics methods, biomechanics and implant technology, vibration theory in engineering, the stiffness and strength of damaged materials, and the existence of slow steady flows of viscoelastic fluids of integral type.

NASGRO(registered trademark): Fracture Mechanics and Fatigue Crack Growth Analysis Software

NASA Technical Reports Server (NTRS)

Forman, Royce; Shivakumar, V.; Mettu, Sambi; Beek, Joachim; Williams, Leonard; Yeh, Feng; McClung, Craig; Cardinal, Joe

2004-01-01

This viewgraph presentation describes NASGRO, which is a fracture mechanics and fatigue crack growth analysis software package that is used to reduce risk of fracture in Space Shuttles. The contents include: 1) Consequences of Fracture; 2) NASA Fracture Control Requirements; 3) NASGRO Reduces Risk; 4) NASGRO Use Inside NASA; 5) NASGRO Components: Crack Growth Module; 6) NASGRO Components:Material Property Module; 7) Typical NASGRO analysis: Crack growth or component life calculation; and 8) NASGRO Sample Application: Orbiter feedline flowliner crack analysis.

User-defined Material Model for Thermo-mechanical Progressive Failure Analysis

NASA Technical Reports Server (NTRS)

Knight, Norman F., Jr.

2008-01-01

Previously a user-defined material model for orthotropic bimodulus materials was developed for linear and nonlinear stress analysis of composite structures using either shell or solid finite elements within a nonlinear finite element analysis tool. Extensions of this user-defined material model to thermo-mechanical progressive failure analysis are described, and the required input data are documented. The extensions include providing for temperature-dependent material properties, archival of the elastic strains, and a thermal strain calculation for materials exhibiting a stress-free temperature.

Investigation of Thermophysical Parameters Properties for Enhancing Overpressure Mechanism Estimation. Case Study: Miri Area, West Baram Delta

NASA Astrophysics Data System (ADS)

Adha, Kurniawan; Yusoff, Wan Ismail Wan; Almanna Lubis, Luluan

2017-10-01

Determining the pore pressure data and overpressure zone is a compulsory part of oil and gas exploration in which the data can enhance the safety with profit and preventing the drilling hazards. Investigation of thermophysical parameters such as temperature and thermal conductivity can enhance the pore pressure estimation for overpressure mechanism determination. Since those parameters are dependent on rock properties, it may reflect the changes on the column of thermophysical parameters when there is abnormally in pore pressure. The study was conducted in “MRI 1” well offshore Sarawak, where a new approach method designed to determine the overpressure generation. The study was insisted the contribution of thermophysical parameters for supporting the velocity analysis method, petrophysical analysis were done in these studies. Four thermal facies were identified along the well. The overpressure developed below the thermal facies 4, where the pressure reached 38 Mpa and temperature was increasing significantly. The velocity and the thermal conductivity cross plots shows a linear relationship since the both parameters mainly are the function of the rock compaction. When the rock more compact, the particles were brought closer into contact and making the sound wave going faster while the thermal conductivity were increasing. In addition, the increment of temperature and high heat flow indicated the presence of fluid expansion mechanism. Since the shale sonic velocity and density analysis were the common methods in overpressure mechanism and pore pressure estimation. As the addition parameters for determining overpressure zone, the presence of thermophysical analysis was enhancing the current method, where the current method was the single function of velocity analysis. The presence of thermophysical analysis will improve the understanding in overpressure mechanism determination as the new input parameters. Thus, integrated of thermophysical technique and velocity analysis are important parameters in investigating the overpressure mechanisms and pore pressure estimation during oil and gas exploitation in the future.

NASTRAN as an analytical research tool for composite mechanics and composite structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.; Sullivan, T. L.

1976-01-01

Selected examples are described in which NASTRAN is used as an analysis research tool for composite mechanics and for composite structural components. The examples were selected to illustrate the importance of using NASTRAN as an analysis tool in this rapidly advancing field.

NASA Workshop on Computational Structural Mechanics 1987, part 3

NASA Technical Reports Server (NTRS)

Sykes, Nancy P. (Editor)

1989-01-01

Computational Structural Mechanics (CSM) topics are explored. Algorithms and software for nonlinear structural dynamics, concurrent algorithms for transient finite element analysis, computational methods and software systems for dynamics and control of large space structures, and the use of multi-grid for structural analysis are discussed.

An analysis of the potential legal constraints on the use of mechanical devices to monitor driving restrictions

DOT National Transportation Integrated Search

1979-09-01

An analysis was made of the potential legal constraints on the use of mechanical devices to supervise drinking and driving restrictions. These conceptual devices would be installed on vehicles operated by restricted drivers. Two devices contain psych...

Identification of the mechanism underlying a human chimera by SNP array analysis.

PubMed

Shin, So Youn; Yoo, Han-Wook; Lee, Beom Hee; Kim, Kun Suk; Seo, Eul-Ju

2012-09-01

Human chimerism resulting from the fusion of two different zygotes is a rare phenomenon. Two mechanisms of chimerism have been hypothesized: dispermic fertilization of an oocyte and its second polar body and dispermic fertilization of two identical gametes from parthenogenetic activation, and these can be identified and discriminated using DNA polymorphism. In the present study we describe a patient with chimerism presenting as a true hermaphrodite and applied single nucleotide polymorphism array analysis to demonstrate dispermic fertilization of two identical gametes from parthenogenetic activation as the underlying mechanism at the whole chromosome level. We suggest that application of genotyping array analysis to the diagnostic process in patients with disorders of sex development will help identify more human chimera patients and increase our understanding of the underlying mechanisms. Copyright © 2012 Wiley Periodicals, Inc.

Engineering science and mechanics; Proceedings of the International Symposium, Tainan, Republic of China, December 29-31, 1981. Parts 1 & 2

NASA Astrophysics Data System (ADS)

Hsia, H.-M.; Chou, Y.-L.; Longman, R. W.

1983-07-01

The topics considered are related to measurements and controls in physical systems, the control of large scale and distributed parameter systems, chemical engineering systems, aerospace science and technology, thermodynamics and fluid mechanics, and computer applications. Subjects in structural dynamics are discussed, taking into account finite element approximations in transient analysis, buckling finite element analysis of flat plates, dynamic analysis of viscoelastic structures, the transient analysis of large frame structures by simple models, large amplitude vibration of an initially stressed thick plate, nonlinear aeroelasticity, a sensitivity analysis of a combined beam-spring-mass structure, and the optimal design and aeroelastic investigation of segmented windmill rotor blades. Attention is also given to dynamics and control of mechanical and civil engineering systems, composites, and topics in materials. For individual items see A83-44002 to A83-44061

ICCM/2; Proceedings of the Second International Conference on Composite Materials, Toronto, Canada, April 16-20, 1978

NASA Technical Reports Server (NTRS)

Noton, B. R. (Editor); Signorelli, R. A.; Street, K. N.; Phillips, L. N.

1978-01-01

Composite materials are discussed with reference to their mechanical and physical properties, fatigue and fracture testing and analysis, nondestructive evaluation, fabrication, and commercial applications. Particular papers are presented on such topics as analysis of mechanical strength data from hybrid laminates of glass and graphite fibers, graphite-aluminum composites, the mechanical behavior of molybdenum-reinforced metal composites, and composite laminate application in magnetic fusion energy superconducting magnet systems.

Colloidal Mechanisms of Gold Nanoparticle Loss in Asymmetric Flow Field-Flow Fractionation.

PubMed

Jochem, Aljosha-Rakim; Ankah, Genesis Ngwa; Meyer, Lars-Arne; Elsenberg, Stephan; Johann, Christoph; Kraus, Tobias

2016-10-07

Flow field-flow fractionation is a powerful method for the analysis of nanoparticle size distributions, but its widespread use has been hampered by large analyte losses, especially of metal nanoparticles. Here, we report on the colloidal mechanisms underlying the losses. We systematically studied gold nanoparticles (AuNPs) during asymmetrical flow field-flow fractionation (AF4) by systematic variation of the particle properties and the eluent composition. Recoveries of AuNPs (core diameter 12 nm) stabilized by citrate or polyethylene glycol (PEG) at different ionic strengths were determined. We used online UV-vis detection and off-line elementary analysis to follow particle losses during full analysis runs, runs without cross-flow, and runs with parts of the instrument bypassed. The combination allowed us to calculate relative and absolute analyte losses at different stages of the analytic protocol. We found different loss mechanisms depending on the ligand. Citrate-stabilized particles degraded during analysis and suffered large losses (up to 74%). PEG-stabilized particles had smaller relative losses at moderate ionic strengths (1-20%) that depended on PEG length. Long PEGs at higher ionic strengths (≥5 mM) caused particle loss due to bridging adsorption at the membrane. Bulk agglomeration was not a relevant loss mechanism at low ionic strengths ≤5 mM for any of the studied particles. An unexpectedly large fraction of particles was lost at tubing and other internal surfaces. We propose that the colloidal mechanisms observed here are relevant loss mechanisms in many particle analysis protocols and discuss strategies to avoid them.

Design and Evaluation of a Prosthetic Knee Joint Using the Geared Five-Bar Mechanism.

PubMed

Sun, Yuanxi; Ge, Wenjie; Zheng, Jia; Dong, Dianbiao

2015-11-01

This paper presents the mechanical design, dynamics analysis and ankle trajectory analysis of a prosthetic knee joint using the geared five-bar mechanism. Compared with traditional four-bar or six-bar mechanisms, the geared five-bar mechanism is better at performing diverse movements and is easy to control. This prosthetic knee joint with the geared five-bar mechanism is capable of fine-tuning its relative instantaneous center of rotation and ankle trajectory. The centrode of this prosthetic knee joint, which is mechanically optimized according to the centrode of human knee joint, is better in the bionic performance than that of a prosthetic knee joint using the four-bar mechanism. Additionally, the stability control of this prosthetic knee joint during the swing and stance phase is achieved by a motor. By adjusting the gear ratio of this prosthetic knee joint, the ankle trajectories of both unilateral and bilateral amputees show less deviations from expected than that of the four-bar knee joint.

Thermal–mechanical stress analysis of pressurized water reactor pressure vessel with/without a preexisting crack under grid load following conditions

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

Mohanty, Subhasish; Soppet, William K.; Majumdar, Saurin

In this paper, we present thermal-mechanical stress analysis of a pressurized water reactor pressure vessel and its hot-leg and cold-leg nozzles. Results are presented from thermal and thermal-mechanical stress analysis under reactor heat-up, cool-down, and grid load-following conditions. Analysis results are given with and without the presence of preexisting crack in the reactor nozzle (axial crack in hot leg nozzle). From the model results it is found that the stress-strain states are significantly higher in case of presence of crack than without crack. In conclusion, the stress-strain state under grid load following condition are more realistic compared to the stress-strainmore » state estimated assuming simplified transients.« less

Thermal–mechanical stress analysis of pressurized water reactor pressure vessel with/without a preexisting crack under grid load following conditions

DOE PAGES

Mohanty, Subhasish; Soppet, William K.; Majumdar, Saurin; ...

2016-10-26

In this paper, we present thermal-mechanical stress analysis of a pressurized water reactor pressure vessel and its hot-leg and cold-leg nozzles. Results are presented from thermal and thermal-mechanical stress analysis under reactor heat-up, cool-down, and grid load-following conditions. Analysis results are given with and without the presence of preexisting crack in the reactor nozzle (axial crack in hot leg nozzle). From the model results it is found that the stress-strain states are significantly higher in case of presence of crack than without crack. In conclusion, the stress-strain state under grid load following condition are more realistic compared to the stress-strainmore » state estimated assuming simplified transients.« less

Analysis of a Pediatric Home Mechanical Ventilator Population.

PubMed

Amirnovin, Rambod; Aghamohammadi, Sara; Riley, Carley; Woo, Marlyn S; Del Castillo, Sylvia

2018-05-01

The population of children requiring home mechanical ventilation has evolved over the years and has grown to include a variety of diagnoses and needs that have led to changes in the care of this unique population. The purpose of this study was to provide a descriptive analysis of pediatric patients requiring home mechanical ventilation after hospitalization and how the evolution of this technology has impacted their care. A retrospective, observational, longitudinal analysis of 164 children enrolled in a university-affiliated home mechanical ventilation program over 26 years was performed. Data included each child's primary diagnosis, date of tracheostomy placement, duration of mechanical ventilation during hospitalization that consisted of home mechanical ventilator initiation, total length of pediatric ICU stay, ventilator settings at time of discharge from pediatric ICU, and disposition (home, facility, or died). Univariate, bivariate, and regression analysis was used as appropriate. The most common diagnosis requiring the use of home mechanical ventilation was neuromuscular disease (53%), followed by chronic pulmonary disease (29%). The median length of stay in the pediatric ICU decreased significantly after the implementation of a ventilator ward (70 d [30-142] vs 36 d [18-67], P = .02). The distribution of subjects upon discharge was home (71%), skilled nursing facility (24%), and died (4%), with an increase in the proportion of subjects discharged on PEEP and those going to nursing facilities over time ( P = 0.02). The evolution of home mechanical ventilation has allowed earlier transition out of the pediatric ICU and with increasing disposition to skilled nursing facilities over time. There has also been a change in ventilator management, including increased use of PEEP upon discharge, possibly driven by changes in ventilators and in-patient practice patterns. Copyright © 2018 by Daedalus Enterprises.

A review of recent studies on the mechanisms and analysis methods of sub-synchronous oscillation in wind farms

NASA Astrophysics Data System (ADS)

Wang, Chenggen; Zhou, Qian; Gao, Shuning; Luo, Jia; Diao, Junchao; Zhao, Haoran; Bu, Jing

2018-04-01

This paper reviews the recent studies of Sub-Synchronous Oscillation(SSO) in wind farms. Mechanisms and analysis methods are the main concerns of this article. A classification method including new types of oscillation occurred between wind farms and HVDC systems and oscillation caused by Permanent Magnet Synchronous Generators(PMSG) is proposed. Characteristics of oscillation analysis techniques are summarized.

A Three Dimensional Kinematic and Kinetic Study of the Golf Swing

PubMed Central

Nesbit, Steven M.

2005-01-01

This paper discusses the three-dimensional kinematics and kinetics of a golf swing as performed by 84 male and one female amateur subjects of various skill levels. The analysis was performed using a variable full-body computer model of a human coupled with a flexible model of a golf club. Data to drive the model was obtained from subject swings recorded using a multi-camera motion analysis system. Model output included club trajectories, golfer/club interaction forces and torques, work and power, and club deflections. These data formed the basis for a statistical analysis of all subjects, and a detailed analysis and comparison of the swing characteristics of four of the subjects. The analysis generated much new data concerning the mechanics of the golf swing. It revealed that a golf swing is a highly coordinated and individual motion and subject-to-subject variations were significant. The study highlighted the importance of the wrists in generating club head velocity and orienting the club face. The trajectory of the hands and the ability to do work were the factors most closely related to skill level. Key Points Full-body model of the golf swing. Mechanical description of the golf swing. Statistical analysis of golf swing mechanics. Comparisons of subject swing mechanics PMID:24627665

A three dimensional kinematic and kinetic study of the golf swing.

PubMed

Nesbit, Steven M

2005-12-01

This paper discusses the three-dimensional kinematics and kinetics of a golf swing as performed by 84 male and one female amateur subjects of various skill levels. The analysis was performed using a variable full-body computer model of a human coupled with a flexible model of a golf club. Data to drive the model was obtained from subject swings recorded using a multi-camera motion analysis system. Model output included club trajectories, golfer/club interaction forces and torques, work and power, and club deflections. These data formed the basis for a statistical analysis of all subjects, and a detailed analysis and comparison of the swing characteristics of four of the subjects. The analysis generated much new data concerning the mechanics of the golf swing. It revealed that a golf swing is a highly coordinated and individual motion and subject-to-subject variations were significant. The study highlighted the importance of the wrists in generating club head velocity and orienting the club face. The trajectory of the hands and the ability to do work were the factors most closely related to skill level. Key PointsFull-body model of the golf swing.Mechanical description of the golf swing.Statistical analysis of golf swing mechanics.Comparisons of subject swing mechanics.

Characterization of Solid Polymers, Ceramic Gap Filler, and Closed-Cell Polymer Foam Using Low-Load Test Methods

NASA Technical Reports Server (NTRS)

Herring, Helen M.

2008-01-01

Various solid polymers, polymer-based composites, and closed-cell polymer foam are being characterized to determine their mechanical properties, using low-load test methods. The residual mechanical properties of these materials after environmental exposure or extreme usage conditions determines their value in aerospace structural applications. In this experimental study, four separate polymers were evaluated to measure their individual mechanical responses after thermal aging and moisture exposure by dynamic mechanical analysis. A ceramic gap filler, used in the gaps between the tiles on the Space Shuttle, was also tested, using dynamic mechanical analysis to determine material property limits during flight. Closed-cell polymer foam, used for the Space Shuttle External Tank insulation, was tested under low load levels to evaluate how the foam's mechanical properties are affected by various loading and unloading scenarios.

An Analysis of the Auto Mechanic Occupation.

ERIC Educational Resources Information Center

Conner, Michael; Thoman, LeRoy

The general purpose of the occupational analysis is to provide workable, basic information dealing with the many and varied duties performed in the auto mechanic occupation. It identifies the broad area of skills and knowledge necessary to perform various tasks involved in diagnosis, maintenance, and repair of automotive systems. Selected…

A Computer Code for Dynamic Stress Analysis of Media-Structure Problems with Nonlinearities (SAMSON). Volume III. User’s Manual.

DTIC Science & Technology

NONLINEAR SYSTEMS, LINEAR SYSTEMS, SUBROUTINES , SOIL MECHANICS, INTERFACES, DYNAMICS, LOADS(FORCES), FORCE(MECHANICS), DAMPING, ACCELERATION, ELASTIC...PROPERTIES, PLASTIC PROPERTIES, CRACKS , REINFORCING MATERIALS , COMPOSITE MATERIALS , FAILURE(MECHANICS), MECHANICAL PROPERTIES, INSTRUCTION MANUALS, DIGITAL COMPUTERS...STRESSES, *COMPUTER PROGRAMS), (*STRUCTURES, STRESSES), (*DATA PROCESSING, STRUCTURAL PROPERTIES), SOILS , STRAIN(MECHANICS), MATHEMATICAL MODELS

Computational Analysis of Pharyngeal Swallowing Mechanics in Patients with Motor Neuron Disease: A Pilot Investigation.

PubMed

Garand, K L; Schwertner, Ryan; Chen, Amy; Pearson, William G

2018-04-01

Swallowing impairment (dysphagia) is a common sequela in patients with motor neuron disease (MND). The purpose of this retrospective, observational pilot investigation was to characterize how pharyngeal swallowing mechanics are impacted in patients with MND using a comparison with healthy, non-dysphagic control group. Computational analysis of swallowing mechanics (CASM) was used to determine covariate biomechanics of pharyngeal swallowing from videofluoroscopic assessment in 15 patients with MND and 15 age- and sex-matched healthy controls. Canonical variant analysis with post hoc discriminate function analysis (DFA) was performed on coordinate data mapping functional muscle groups underlying pharyngeal swallowing. Differences in swallowing mechanics associated with group (MND; control), motor neuron predominance (upper; lower), onset (bulbar; spinal), and swallow task (thin, pudding) were evaluated and visualized. Pharyngeal swallowing mechanics differed significantly in patients with MND compared with healthy controls (D = 2.01, p < 0.0001). Post hoc DFA pairwise comparisons suggest differences in pharyngeal swallow mechanics by motor neuron predominance (D = 5.03, p < 0.0001), onset (D = 2.03, p < 0.0001), and swallow task (D = 1.04, p < 0.0001). Pharyngeal swallowing mechanics of patients with MND differ from and are more heterogeneous than healthy controls. These findings suggest patients with MND may compensate reductions in pharyngeal shortening and tongue base retraction by extending the head and neck and increasing hyolaryngeal excursion. This work and further CASM investigations will lead to further insights into development and evaluation of targeted clinical treatments designed to prolong safe and efficient swallowing function in patients with MND.

Validation of Intensive Care and Mechanical Ventilation Codes in Medicare Data.

PubMed

Wunsch, Hannah; Kramer, Andrew; Gershengorn, Hayley B

2017-07-01

To assess the reliability of codes relevant to critically ill patients in administrative data. Retrospective cohort study linking data from Acute Physiology and Chronic Health Evaluation Outcomes, a clinical database of ICU patients with data from Medicare Provider Analysis and Review. We linked data based on matching for sex, date of birth, hospital, and date of admission to hospital. Forty-six hospitals in the United States participating in Acute Physiology and Chronic Health Evaluation Outcomes. All patients in Acute Physiology and Chronic Health Evaluation Outcomes greater than or equal to 65 years old who could be linked with hospitalization records in Medicare Provider Analysis and Review from January 1, 2009, through September 30, 2012. Of 62,451 patients in the Acute Physiology and Chronic Health Evaluation Outcomes dataset, 80.1% were matched with data in Medicare Provider Analysis and Review. All but 2.7% of Acute Physiology and Chronic Health Evaluation Outcomes ICU patients had either an ICU or coronary care unit charge in Medicare Provider Analysis and Review. In Acute Physiology and Chronic Health Evaluation Outcomes, 37.0% received mechanical ventilation during the ICU stay versus 24.1% in Medicare Provider Analysis and Review. The Medicare Provider Analysis and Review procedure codes for mechanical ventilation had high specificity (96.0%; 95% CI, 95.8-96.2), but only moderate sensitivity (58.4%; 95% CI, 57.7-59.1), with a positive predictive value of 89.6% (95% CI, 89.1-90.1) and negative predictive value of 79.7% (95% CI, 79.4-80.1). For patients with mechanical ventilation codes, Medicare Provider Analysis and Review overestimated the percentage with a duration greater than 96 hours (36.6% vs 27.3% in Acute Physiology and Chronic Health Evaluation Outcomes). There was discordance in the hospital discharge status (alive or dead) for only 0.47% of all linked records (κ = 1.00). Medicare Provider Analysis and Review data contain robust information on hospital mortality for patients admitted to the ICU but have limited ability to identify all patients who received mechanical ventilation during a critical illness. Estimates of use of mechanical ventilation in the United States should likely be revised upward.

Research on the energy and ecological efficiency of mechanical equipment remanufacturing systems

NASA Astrophysics Data System (ADS)

Shi, Junli; Cheng, Jinshi; Ma, Qinyi; Wang, Yajun

2017-08-01

According to the characteristics of mechanical equipment remanufacturing system, the dynamic performance of energy consumption and emission is explored, the equipment energy efficiency and emission analysis model is established firstly, and then energy and ecological efficiency analysis method of the remanufacturing system is put forward, at last, the energy and ecological efficiency of WD615.87 automotive diesel engine remanufacturing system as an example is analyzed, the way of energy efficiency improvementnt and environmental friendly mechanism of remanufacturing process is put forward.

Analysis of Growth and Molecular Responses to Ethylene in Etiolated Rice Seedlings.

PubMed

Ma, Biao; Zhang, Jin-Song

2017-01-01

Ethylene plays a key role in various submergence responses of rice plants, but the mechanism of ethylene action remains largely unclear in rice. Regarding the differences between rice and Arabidopsis in ethylene-regulated processes, rice plants may possess divergent mechanisms in ethylene signaling in addition to the conserved aspects. Forward genetic analysis is essential to fully understand the ethylene signaling mechanism in rice. Here, we describe a method for screening ethylene-response mutants and evaluating ethylene responsiveness in etiolated rice seedlings.

MSFC Skylab structures and mechanical systems mission evaluation

NASA Technical Reports Server (NTRS)

1974-01-01

A performance analysis for structural and mechanical major hardware systems and components is presented. Development background testing, modifications, and requirement adjustments are included. Functional narratives are provided for comparison purposes as are predicted design performance criterion. Each item is evaluated on an individual basis: that is, (1) history (requirements, design, manufacture, and test); (2) in-orbit performance (description and analysis); and (3) conclusions and recommendations regarding future space hardware application. Overall, the structural and mechanical performance of the Skylab hardware was outstanding.

An Analysis of a Nationwide Study on Curricular Emphasis in Basic Mechanics

ERIC Educational Resources Information Center

Raville, M. E.; Lnenicka, W. J.

1976-01-01

Discusses a survey of curricular allocations to mechanics in departments and schools of engineering. Tables show trends of coverage of mechanics topics and faculty perceptions of teaching and learning trends. (MLH)

Statistical Analysis on the Mechanical Properties of Magnesium Alloys

PubMed Central

Liu, Ruoyu; Jiang, Xianquan; Zhang, Hongju; Zhang, Dingfei; Wang, Jingfeng; Pan, Fusheng

2017-01-01

Knowledge of statistical characteristics of mechanical properties is very important for the practical application of structural materials. Unfortunately, the scatter characteristics of magnesium alloys for mechanical performance remain poorly understood until now. In this study, the mechanical reliability of magnesium alloys is systematically estimated using Weibull statistical analysis. Interestingly, the Weibull modulus, m, of strength for magnesium alloys is as high as that for aluminum and steels, confirming the very high reliability of magnesium alloys. The high predictability in the tensile strength of magnesium alloys represents the capability of preventing catastrophic premature failure during service, which is essential for safety and reliability assessment. PMID:29113116

Analysis of passive damping in thick composite structures

NASA Technical Reports Server (NTRS)

Saravanos, D. A.

1993-01-01

Computational mechanics for the prediction of damping and other dynamic characteristics in composite structures of general thicknesses and laminations are presented. Discrete layer damping mechanics that account for the representation of interlaminar shear effects in the material are summarized. Finite element based structural mechanics for the analysis of damping are described, and a specialty finite element is developed. Applications illustrate the quality of the discrete layer damping mechanics in predicting the damped dynamic characteristics of composite structures with thicker sections and/or laminate configurations that induce interlaminar shear. The results also illustrate and quantify the significance of interlaminar shear damping in such composite structures.

Performance of the Sleep-Mode Mechanism of the New IEEE 802.16m Proposal for Correlated Downlink Traffic

NASA Astrophysics Data System (ADS)

de Turck, Koen; de Vuyst, Stijn; Fiems, Dieter; Wittevrongel, Sabine; Bruneel, Herwig

There is a considerable interest nowadays in making wireless telecommunication more energy-efficient. The sleep-mode mechanism in WiMAX (IEEE 802.16e) is one of such energy saving measures. Recently, Samsung proposed some modifications on the sleep-mode mechanism, scheduled to appear in the forthcoming IEEE 802.16m standard, aimed at minimizing the signaling overhead. In this work, we present a performance analysis of this proposal and clarify the differences with the standard mechanism included in IEEE 802.16e. We also propose some special algorithms aimed at reducing the computational complexity of the analysis.

Error analysis of mechanical system and wavelength calibration of monochromator

NASA Astrophysics Data System (ADS)

Zhang, Fudong; Chen, Chen; Liu, Jie; Wang, Zhihong

2018-02-01

This study focuses on improving the accuracy of a grating monochromator on the basis of the grating diffraction equation in combination with an analysis of the mechanical transmission relationship between the grating, the sine bar, and the screw of the scanning mechanism. First, the relationship between the mechanical error in the monochromator with the sine drive and the wavelength error is analyzed. Second, a mathematical model of the wavelength error and mechanical error is developed, and an accurate wavelength calibration method based on the sine bar's length adjustment and error compensation is proposed. Based on the mathematical model and calibration method, experiments using a standard light source with known spectral lines and a pre-adjusted sine bar length are conducted. The model parameter equations are solved, and subsequent parameter optimization simulations are performed to determine the optimal length ratio. Lastly, the length of the sine bar is adjusted. The experimental results indicate that the wavelength accuracy is ±0.3 nm, which is better than the original accuracy of ±2.6 nm. The results confirm the validity of the error analysis of the mechanical system of the monochromator as well as the validity of the calibration method.

The influence of ZrO2/20%Y2O3 and Al2O3 deposited coatings to the behavior of an aluminum alloy subjected to mechanical shock

NASA Astrophysics Data System (ADS)

Pintilei, G. L.; Crismaru, V. I.; Abrudeanu, M.; Munteanu, C.; Luca, D.; Istrate, B.

2015-10-01

Aluminum alloys are used in the aerospace industry due to their good mechanical properties and their low density compared with the density of steels. Usually the parts made of aluminum alloys contribute to the structural frame of aircrafts and they must withstand static and variable mechanical loads and also mechanical loads applied in a very short time which determine different phenomenon's in the material behavior then static or fatigue loads. This paper analysis the resilience of a 2024 aluminum alloy subjected to shock loads and the way how a coating can improve its behavior. For improving the behavior two coatings were considered: Al2O3 with 99.5% purity and ZrO2/20%Y2O3. The coatings were deposited on the base material by plasma spraying. The samples with and without coating were subject to mechanical shock to determine the resilience of the materials and the cracks propagation was investigated using SEM analysis. To highlight the physical phenomenon's that appear in the samples during the mechanical shock, explicit finite element analysis were done using Ansys 14.5 software.

Mechanical properties of silicate glasses exposed to a low-Earth orbit

NASA Technical Reports Server (NTRS)

Wiedlocher, David E.; Tucker, Dennis S.; Nichols, Ron; Kinser, Donald L.

1992-01-01

The effects of a 5.8 year exposure to low earth orbit environment upon the mechanical properties of commercial optical fused silica, low iron soda-lime-silica, Pyrex 7740, Vycor 7913, BK-7, and the glass ceramic Zerodur were examined. Mechanical testing employed the ASTM-F-394 piston on 3-ball method in a liquid nitrogen environment. Samples were exposed on the Long Duration Exposure Facility (LDEF) in two locations. Impacts were observed on all specimens except Vycor. Weibull analysis as well as a standard statistical evaluation were conducted. The Weibull analysis revealed no differences between control samples and the two exposed samples. We thus concluded that radiation components of the Earth orbital environment did not degrade the mechanical strength of the samples examined within the limits of experimental error. The upper bound of strength degradation for meteorite impacted samples based upon statistical analysis and observation was 50 percent.

Auditory motion-specific mechanisms in the primate brain

PubMed Central

Baumann, Simon; Dheerendra, Pradeep; Joly, Olivier; Hunter, David; Balezeau, Fabien; Sun, Li; Rees, Adrian; Petkov, Christopher I.; Thiele, Alexander; Griffiths, Timothy D.

2017-01-01

This work examined the mechanisms underlying auditory motion processing in the auditory cortex of awake monkeys using functional magnetic resonance imaging (fMRI). We tested to what extent auditory motion analysis can be explained by the linear combination of static spatial mechanisms, spectrotemporal processes, and their interaction. We found that the posterior auditory cortex, including A1 and the surrounding caudal belt and parabelt, is involved in auditory motion analysis. Static spatial and spectrotemporal processes were able to fully explain motion-induced activation in most parts of the auditory cortex, including A1, but not in circumscribed regions of the posterior belt and parabelt cortex. We show that in these regions motion-specific processes contribute to the activation, providing the first demonstration that auditory motion is not simply deduced from changes in static spatial location. These results demonstrate that parallel mechanisms for motion and static spatial analysis coexist within the auditory dorsal stream. PMID:28472038

Analysis and design of a mechanical system to use with the Ronchi and Fizeau tests

NASA Astrophysics Data System (ADS)

Galán-Martínez, Arturo D.; Santiago-Alvarado, Agustín.; González-García, Jorge; Cruz-Martínez, Víctor M.; Cordero-Dávila, Alberto; Granados-Agustin, Fermin S.; Robledo-Sánchez, Calos

2013-11-01

Nowadays, there is a demand for more efficient opto-mechanical mounts which allow for the implementation of robust optical arrays in a quick and simple fashion. That is to say, mounts are needed which facilitate alignment of the optical components in order to perform the desired movements of each component. Optical testing systems available in the market today are costly, heavy and sometimes require multiple kits depending on the dimensions of the optical components. In this paper, we present the design and analysis of a mechanical system with some interchangeable basic mounts which allow for the application of both Ronchi and Fizeau tests for the evaluation of concave reflective surfaces with a diameter of 2 to 10 cm. The mechanical system design is done using the methodology of product design process, while the analysis is performed using the commercial software SolidWorks.

The research Of Multilayer Thermal Insulation With Mechanical Properties Based On Model Analysis Test

NASA Astrophysics Data System (ADS)

Lianhua, Yin

The heat shield of aircraft is made of the major thrusts structure with multilayer thermal insulation part. For protecting against thermo-radiation from larger thrusting force engine,the heat shield is installed around this engine nearby.The multilayer thermal insulation part with multilayer radiation/reflection structure is made of reflection layer and interval layer.At vacuum condition,these materials is higher heat insulation capability than other material,is applied for lots of pats on aircraft extensively.But because of these material is made of metal and nonmetal,it is impossible to receive it's mechanical properties of materials from mechanical tests.These paper describes a new measure of mechanical properties of materials in the heat shield based on model analysis test.At the requirement for the first order lateral frequency,these measure provide for the FEM analysis foundation on the optimization structure of the heat shield.

3D braid scaffolds for regeneration of articular cartilage.

PubMed

Ahn, Hyunchul; Kim, Kyoung Ju; Park, Sook Young; Huh, Jeong Eun; Kim, Hyun Jeong; Yu, Woong-Ryeol

2014-06-01

Regenerating articular cartilage in vivo from cultured chondrocytes requires that the cells be cultured and implanted within a biocompatible, biodegradable scaffold. Such scaffolds must be mechanically stable; otherwise chondrocytes would not be supported and patients would experience severe pain. Here we report a new 3D braid scaffold that matches the anisotropic (gradient) mechanical properties of natural articular cartilage and is permissive to cell cultivation. To design an optimal structure, the scaffold unit cell was mathematically modeled and imported into finite element analysis. Based on this analysis, a 3D braid structure with gradient axial yarn distribution was designed and manufactured using a custom-built braiding machine. The mechanical properties of the 3D braid scaffold were evaluated and compared with simulated results, demonstrating that a multi-scale approach consisting of unit cell modeling and continuum analysis facilitates design of scaffolds that meet the requirements for mechanical compatibility with tissues. Copyright © 2014 Elsevier Ltd. All rights reserved.

The Mini-Lab Concept as an Alternative to Conventional Oil Analysis

DTIC Science & Technology

1996-04-01

degradation of functionality within the lubricant. 4. Wear Debris Analysis ( Ferrography ) measures the extent, location and mechanisms of wear. 5. Particle...diagnostic tool, as it ( ferrography ) examination of the wear unique~y provides information particles, determine the on the mechanism of wear. nature, extent...extent of wear as well as the state of the lubricant and presence of contaminants. Wear Debris Analysis or Ferrography has been presented has a high

Coastal Benthic Boundary Layer Special Research Program. Program Direction and Workshop Recommendations

DTIC Science & Technology

1992-08-01

Faas, " Analysis of the relationship between acoustic reflectivity and sediment porosity," Geophysics 3 4, 546-553 (1969). M. A. Foda , J. Y.-H. Chang...properties, together with in situ measured mechanical, acoustic and electrical properties, should be subjected to factor analysis . Natural clusters could...properties. The mechanical 1 properties and remotely sensed properties are a matrix of information that can be subjected to factor analysis . One can

Mechanical testing and finite element analysis of orthodontic teardrop loop.

PubMed

Coimbra, Maria Elisa Rodrigues; Penedo, Norman Duque; de Gouvêa, Jayme Pereira; Elias, Carlos Nelson; de Souza Araújo, Mônica Tirre; Coelho, Paulo Guilherme

2008-02-01

Understanding how teeth move in response to mechanical loads is an important aspect of orthodontic treatment. Treatment planning should include consideration of the appliances that will meet the desired loading of the teeth to result in optimized treatment outcomes. The purpose of this study was to evaluate the use of computer simulation to predict the force and the torsion obtained after the activation of tear drop loops of 3 heights. Seventy-five retraction loops were divided into 3 groups according to height (6, 7, and 8 mm). The loops were subjected to tensile load through displacements of 0.5, 1.0, 1.5, and 2.0 mm, and the resulting forces and torques were recorded. The loops were designed in AutoCAD software(2005; Autodesk Systems, Alpharetta, GA), and finite element analysis was performed with Ansys software(version 7.0; Swanson Analysis System, Canonsburg, PA). Statistical analysis of the mechanical experiment results was obtained by ANOVA and the Tukey post-hoc test (P < .01). The correlation test and the paired t test (P < .05) were used to compare the computer simulation with the mechanical experiment. The computer simulation accurately predicted the experimentally determined mechanical behavior of tear drop loops of different heights and should be considered an alternative for designing orthodontic appliances before treatment.

Molecular Engineering for Mechanically Resilient and Stretchable Electronic Polymers and Composites

DTIC Science & Technology

2016-06-08

conjugated polymers and composites by analysis of the structural determinants of the mechanical properties. We developed coarse-grained molecular...dynamics simulations that predicted the mechanical properties of conjugated polymers and polymer -fullerene composites. We elucidated the mechanical...We also determined the effect of cyclic stretching on the microstructure and mechanical properties of conjugated polymers . We used many of

Full-scale 3-D finite element modeling of a two-loop pressurized water reactor for heat transfer, thermal–mechanical cyclic stress analysis, and environmental fatigue life estimation

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

Mohanty, Subhasish; Soppet, William K.; Majumdar, Saurindranath

This paper discusses a system-level finite element model of a two-loop pressurized water reactor (PWR). Based on this model, system-level heat transfer analysis and subsequent sequentially coupled thermal-mechanical stress analysis were performed for typical thermal-mechanical fatigue cycles. The in-air fatigue lives of example components, such as the hot and cold legs, were estimated on the basis of stress analysis results, ASME in-air fatigue life estimation criteria, and fatigue design curves. Furthermore, environmental correction factors and associated PWR environment fatigue lives for the hot and cold legs were estimated by using estimated stress and strain histories and the approach described inmore » US-NRC report: NUREG-6909.« less

Space Station Common Berthing Mechanism, a multi-body simulation application

NASA Technical Reports Server (NTRS)

Searle, Ian

1993-01-01

This paper discusses an application of multi-body dynamic analysis conducted at the Boeing Company in connection with the Space Station (SS) Common Berthing Mechanism (CBM). After introducing the hardware and analytical objectives we will focus on some of the day-to-day computational issues associated with this type of analysis.

Assessment of optimal control mechanism complexity by experimental landscape Hessian analysis: fragmentation of CH2BrI

NASA Astrophysics Data System (ADS)

Xing, Xi; Rey-de-Castro, Roberto; Rabitz, Herschel

2014-12-01

Optimally shaped femtosecond laser pulses can often be effectively identified in adaptive feedback quantum control experiments, but elucidating the underlying control mechanism can be a difficult task requiring significant additional analysis. We introduce landscape Hessian analysis (LHA) as a practical experimental tool to aid in elucidating control mechanism insights. This technique is applied to the dissociative ionization of CH2BrI using shaped fs laser pulses for optimization of the absolute yields of ionic fragments as well as their ratios for the competing processes of breaking the C-Br and C-I bonds. The experimental results suggest that these nominally complex problems can be reduced to a low-dimensional control space with insights into the control mechanisms. While the optimal yield for some fragments is dominated by a non-resonant intensity-driven process, the optimal generation of other fragments maa difficult task requiring significant additionaly be explained by a non-resonant process coupled to few level resonant dynamics. Theoretical analysis and modeling is consistent with the experimental observations.

Re-designing a mechanism for higher speed: A case history from textile machinery

NASA Astrophysics Data System (ADS)

Douglas, S. S.; Rooney, G. T.

The generation of general mechanism design software which is the formulation of suitable objective functions is discussed. There is a consistent drive towards higher speeds in the development of industrial sewing machines. This led to experimental analyses of dynamic performance and to a search for improved design methods. The experimental work highlighted the need for smoothness of motion at high speed, component inertias, and frame structural stiffness. Smoothness is associated with transmission properties and harmonic analysis. These are added to other design requirements of synchronization, mechanism size, and function. Some of the mechanism trains in overedte sewing machines are shown. All these trains are designed by digital optimization. The design software combines analysis of the sewing machine mechanisms, formulation of objectives innumerical terms, and suitable mathematical optimization ttechniques.

[Research progress on mechanical performance evaluation of artificial intervertebral disc].

PubMed

Li, Rui; Wang, Song; Liao, Zhenhua; Liu, Weiqiang

2018-03-01

The mechanical properties of artificial intervertebral disc (AID) are related to long-term reliability of prosthesis. There are three testing methods involved in the mechanical performance evaluation of AID based on different tools: the testing method using mechanical simulator, in vitro specimen testing method and finite element analysis method. In this study, the testing standard, testing equipment and materials of AID were firstly introduced. Then, the present status of AID static mechanical properties test (static axial compression, static axial compression-shear), dynamic mechanical properties test (dynamic axial compression, dynamic axial compression-shear), creep and stress relaxation test, device pushout test, core pushout test, subsidence test, etc. were focused on. The experimental techniques using in vitro specimen testing method and testing results of available artificial discs were summarized. The experimental methods and research status of finite element analysis were also summarized. Finally, the research trends of AID mechanical performance evaluation were forecasted. The simulator, load, dynamic cycle, motion mode, specimen and test standard would be important research fields in the future.

Cumulative (Dis)Advantage and the Matthew Effect in Life-Course Analysis

PubMed Central

Bask, Miia; Bask, Mikael

2015-01-01

To foster a deeper understanding of the mechanisms behind inequality in society, it is crucial to work with well-defined concepts associated with such mechanisms. The aim of this paper is to define cumulative (dis)advantage and the Matthew effect. We argue that cumulative (dis)advantage is an intra-individual micro-level phenomenon, that the Matthew effect is an inter-individual macro-level phenomenon and that an appropriate measure of the Matthew effect focuses on the mechanism or dynamic process that generates inequality. The Matthew mechanism is, therefore, a better name for the phenomenon, where we provide a novel measure of the mechanism, including a proof-of-principle analysis using disposable personal income data. Finally, because socio-economic theory should be able to explain cumulative (dis)advantage and the Matthew mechanism when they are detected in data, we discuss the types of models that may explain the phenomena. We argue that interactions-based models in the literature traditions of analytical sociology and statistical mechanics serve this purpose. PMID:26606386

Ethical challenges in home mechanical ventilation: a secondary analysis.

PubMed

Dybwik, Knut; Nielsen, Erik Waage; Brinchmann, Berit Støre

2012-03-01

The aim of this study was to explore the ethical challenges in home mechanical ventilation based on a secondary analysis of qualitative empirical data. The data included perceptions of healthcare professionals in hospitals and community health services and family members of children and adults using home mechanical ventilation. The findings show that a number of ethical challenges, or dilemmas, arise at all levels in the course of treatment: deciding who should be offered home mechanical ventilation, respect for patient and family wishes, quality of life, dignity and equal access to home mechanical ventilation. Other challenges were the impacts home mechanical ventilation had on the patient, the family, the healthcare services and the allocation of resources. A better and broader understanding of these issues is crucial in order to improve the quality of care for both patient and family and assist healthcare professionals involved in home mechanical ventilation to make decisions for the good of the patient and his or her family.

Computational mechanics research and support for aerodynamics and hydraulics at TFHRC year 1 quarter 4 progress report.

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

Lottes, S.A.; Kulak, R.F.; Bojanowski, C.

2011-12-09

The computational fluid dynamics (CFD) and computational structural mechanics (CSM) focus areas at Argonne's Transportation Research and Analysis Computing Center (TRACC) initiated a project to support and compliment the experimental programs at the Turner-Fairbank Highway Research Center (TFHRC) with high performance computing based analysis capabilities in August 2010. The project was established with a new interagency agreement between the Department of Energy and the Department of Transportation to provide collaborative research, development, and benchmarking of advanced three-dimensional computational mechanics analysis methods to the aerodynamics and hydraulics laboratories at TFHRC for a period of five years, beginning in October 2010. Themore » analysis methods employ well-benchmarked and supported commercial computational mechanics software. Computational mechanics encompasses the areas of Computational Fluid Dynamics (CFD), Computational Wind Engineering (CWE), Computational Structural Mechanics (CSM), and Computational Multiphysics Mechanics (CMM) applied in Fluid-Structure Interaction (FSI) problems. The major areas of focus of the project are wind and water effects on bridges - superstructure, deck, cables, and substructure (including soil), primarily during storms and flood events - and the risks that these loads pose to structural failure. For flood events at bridges, another major focus of the work is assessment of the risk to bridges caused by scour of stream and riverbed material away from the foundations of a bridge. Other areas of current research include modeling of flow through culverts to assess them for fish passage, modeling of the salt spray transport into bridge girders to address suitability of using weathering steel in bridges, CFD analysis of the operation of the wind tunnel in the TFCHR wind engineering laboratory, vehicle stability under high wind loading, and the use of electromagnetic shock absorbers to improve vehicle stability under high wind conditions. This quarterly report documents technical progress on the project tasks for the period of July through September 2011.« less

A Systems Biology Approach for Identifying Hepatotoxicant Groups Based on Similarity in Mechanisms of Action and Chemical Structure.

PubMed

Hebels, Dennie G A J; Rasche, Axel; Herwig, Ralf; van Westen, Gerard J P; Jennen, Danyel G J; Kleinjans, Jos C S

2016-01-01

When evaluating compound similarity, addressing multiple sources of information to reach conclusions about common pharmaceutical and/or toxicological mechanisms of action is a crucial strategy. In this chapter, we describe a systems biology approach that incorporates analyses of hepatotoxicant data for 33 compounds from three different sources: a chemical structure similarity analysis based on the 3D Tanimoto coefficient, a chemical structure-based protein target prediction analysis, and a cross-study/cross-platform meta-analysis of in vitro and in vivo human and rat transcriptomics data derived from public resources (i.e., the diXa data warehouse). Hierarchical clustering of the outcome scores of the separate analyses did not result in a satisfactory grouping of compounds considering their known toxic mechanism as described in literature. However, a combined analysis of multiple data types may hypothetically compensate for missing or unreliable information in any of the single data types. We therefore performed an integrated clustering analysis of all three data sets using the R-based tool iClusterPlus. This indeed improved the grouping results. The compound clusters that were formed by means of iClusterPlus represent groups that show similar gene expression while simultaneously integrating a similarity in structure and protein targets, which corresponds much better with the known mechanism of action of these toxicants. Using an integrative systems biology approach may thus overcome the limitations of the separate analyses when grouping liver toxicants sharing a similar mechanism of toxicity.

Scott Jenne | NREL

Science.gov Websites

Analysis Center. Areas of Expertise Techno-Economic Analysis Mechanical design 3D modeling/CAD Finite element analysis (FEA) Wave energy conversion Thermal power cycle analysis Research Interests Cost

Constitutive formulations for the mechanical investigation of colonic tissues.

PubMed

Carniel, Emanuele Luigi; Gramigna, Vera; Fontanella, Chiara Giulia; Stefanini, Cesare; Natali, Arturo N

2014-05-01

A constitutive framework is provided for the characterization of the mechanical behavior of colonic tissues, as a fundamental tool for the development of numerical models of the colonic structures. The constitutive analysis is performed by a multidisciplinary approach that requires the cooperation between experimental and computational competences. The preliminary investigation pertains to the review of the tissues histology. The complex structural configuration of the tissues and the specific distributions of fibrous elements entail the nonlinear mechanical behavior and the anisotropic response. The identification of the mechanical properties requires to perform mechanical tests according to different loading situations, as different loading directions. Because of the typical functionality of colon structures, the tissues mechanics is investigated by tensile tests, which are performed on taenia coli and haustra specimens from fresh pig colons. Accounting for the histological investigation and the results from the mechanical tests, a specific hyperelastic framework is provided within the theory of fiber-reinforced composite materials. Preliminary analytical formulations are defined to identify the constitutive parameters by the inverse analysis of the experimental tests. Finite element models of the specimens are developed accounting for the actual configuration of the colon structures to verify the quality of the results. The good agreement between experimental and numerical model results suggests the reliability of the constitutive formulations and parameters. Finally, the developed constitutive analysis makes it possible to identify the mechanical behavior and properties of the different colonic tissues. Copyright © 2013 Wiley Periodicals, Inc.

A guide to onboard checkout. Volume 6: Structures/mechanics

NASA Technical Reports Server (NTRS)

1971-01-01

The structures and mechanical subsystem of a space station are considered. The subsystem includes basic structure (pressurization, equipment support, meteoroid protection, radiators, insulation, and docking interfaces), the docking mechanisms, spacecraft access (hatches, airlocks, and view ports), and antenna deployment mechanisms. Checkout is discussed in terms of reliability, failure analysis, and maintenance.

Pathway Analysis and the Search for Causal Mechanisms

ERIC Educational Resources Information Center

Weller, Nicholas; Barnes, Jeb

2016-01-01

The study of causal mechanisms interests scholars across the social sciences. Case studies can be a valuable tool in developing knowledge and hypotheses about how causal mechanisms function. The usefulness of case studies in the search for causal mechanisms depends on effective case selection, and there are few existing guidelines for selecting…

Acoustic emission spectral analysis of fiber composite failure mechanisms

NASA Technical Reports Server (NTRS)

Egan, D. M.; Williams, J. H., Jr.

1978-01-01

The acoustic emission of graphite fiber polyimide composite failure mechanisms was investigated with emphasis on frequency spectrum analysis. Although visual examination of spectral densities could not distinguish among fracture sources, a paired-sample t statistical analysis of mean normalized spectral densities did provide quantitative discrimination among acoustic emissions from 10 deg, 90 deg, and plus or minus 45 deg, plus or minus 45 deg sub s specimens. Comparable discrimination was not obtained for 0 deg specimens.

Finite Element Creep-Fatigue Analysis of a Welded Furnace Roll for Identifying Failure Root Cause

NASA Astrophysics Data System (ADS)

Yang, Y. P.; Mohr, W. C.

2015-11-01

Creep-fatigue induced failures are often observed in engineering components operating under high temperature and cyclic loading. Understanding the creep-fatigue damage process and identifying failure root cause are very important for preventing such failures and improving the lifetime of engineering components. Finite element analyses including a heat transfer analysis and a creep-fatigue analysis were conducted to model the cyclic thermal and mechanical process of a furnace roll in a continuous hot-dip coating line. Typically, the roll has a short life, <1 year, which has been a problem for a long time. The failure occurred in the weld joining an end bell to a roll shell and resulted in the complete 360° separation of the end bell from the roll shell. The heat transfer analysis was conducted to predict the temperature history of the roll by modeling heat convection from hot air inside the furnace. The creep-fatigue analysis was performed by inputting the predicted temperature history and applying mechanical loads. The analysis results showed that the failure was resulted from a creep-fatigue mechanism rather than a creep mechanism. The difference of material properties between the filler metal and the base metal is the root cause for the roll failure, which induces higher creep strain and stress in the interface between the weld and the HAZ.

Independent Orbiter Assessment (IOA): Assessment of the mechanical actuation subsystem, volume 2

NASA Technical Reports Server (NTRS)

Bradway, M. W.; Slaughter, W. T.

1988-01-01

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine draft failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline that was available. A resolution of each discrepancy from the comparison was provided through additional analysis as required. These discrepancies were flagged as issues, and recommendations were made based on the FMEA data available at the time. This report documents the results of that comparison for the Orbiter Mechanical Actuation System (MAS) hardware. Specifically, the MAS hardware consists of the following components: Air Data Probe (ADP); Elevon Seal Panel (ESP); External Tank Umbilical (ETU); Ku-Band Deploy (KBD); Payload Bay Doors (PBD); Payload Bay Radiators (PBR); Personnel Hatches (PH); Vent Door Mechanism (VDM); and Startracker Door Mechanism (SDM). Criticality was assigned based upon the severity of the effect for each failure mode. Volume 2 continues the presentation of IOA analysis worksheets and contains the potential critical items list, detailed analysis, and NASA FMEA/CIL to IOA worksheet cross reference and recommendations.

Stray light suppression of optical and mechanical system for telescope detection

NASA Astrophysics Data System (ADS)

Wang, Lei; Ma, Wenli

2013-09-01

During telescope detection, there is atmosphere overflow and other stray light affecting the system which leads to background disturbance. Thus reduce the detection capability of the system. So it is very necessary to design mechanical structure to suppress the stray light for the telescope detection system. It can both improve the signal-to-noise and contrast of the object. This paper designs the optical and mechanical structure of the 400mm telescope. And then the main baffle, baffle vane, field stop and coating technology are used to eliminate the effect of stray light on the optical and mechanical system. Finally, software is used to analyze and simulate stray light on the whole optical and mechanical system. Using PST as the evaluating standard, separate and integrated analysis of the suppressing effect of main baffle, baffle vane and field aperture is completed. And also get the results of PST before and after eliminating the stray light. Meanwhile, the results of stray light analysis can be used to guide the design of the optical and mechanical structure. The analysis results demonstrate that reasonable optical and mechanical structure and stray light suppression measure can highly reduce the PST and also improve the detection capability of the telescope system, and the designed outside baffle, inside baffle, vanes and coating technique etc. can decrease the PST approximately 1 to 3 level.

Computational mechanics research and support for aerodynamics and hydraulics at TFHRC, year 1 quarter 3 progress report.

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

Lottes, S.A.; Kulak, R.F.; Bojanowski, C.

2011-08-26

The computational fluid dynamics (CFD) and computational structural mechanics (CSM) focus areas at Argonne's Transportation Research and Analysis Computing Center (TRACC) initiated a project to support and compliment the experimental programs at the Turner-Fairbank Highway Research Center (TFHRC) with high performance computing based analysis capabilities in August 2010. The project was established with a new interagency agreement between the Department of Energy and the Department of Transportation to provide collaborative research, development, and benchmarking of advanced three-dimensional computational mechanics analysis methods to the aerodynamics and hydraulics laboratories at TFHRC for a period of five years, beginning in October 2010. Themore » analysis methods employ well-benchmarked and supported commercial computational mechanics software. Computational mechanics encompasses the areas of Computational Fluid Dynamics (CFD), Computational Wind Engineering (CWE), Computational Structural Mechanics (CSM), and Computational Multiphysics Mechanics (CMM) applied in Fluid-Structure Interaction (FSI) problems. The major areas of focus of the project are wind and water loads on bridges - superstructure, deck, cables, and substructure (including soil), primarily during storms and flood events - and the risks that these loads pose to structural failure. For flood events at bridges, another major focus of the work is assessment of the risk to bridges caused by scour of stream and riverbed material away from the foundations of a bridge. Other areas of current research include modeling of flow through culverts to assess them for fish passage, modeling of the salt spray transport into bridge girders to address suitability of using weathering steel in bridges, vehicle stability under high wind loading, and the use of electromagnetic shock absorbers to improve vehicle stability under high wind conditions. This quarterly report documents technical progress on the project tasks for the period of April through June 2011.« less

["In psychiatry, nothing more degrading can happen to you"].

PubMed

Frajo-Apor, Beatrice; Stippler, Maria; Meise, Ullrich

2011-08-01

OBJECTIVE The subjective view of psychiatric patients on mechanical restraint is to be examined and the necessity of dealing with this issue consciously is to be pointed out. METHODS 14 patients, who experienced mechanical restraint during a stay in a psychiatric hospital, were questioned in a problem-centered, semi-structured interview. Data analysis was based on inductive category formation, using Mayring's qualitative content analysis. RESULTS Mechanical restraint is primarily experienced as stressful or traumatizing. Patients complain about a lack of information, support and response when referring to mechanical restraint. CONCLUSION Reports of patients who have experienced coercive measures should be increasingly integrated into clinical practice. © Georg Thieme Verlag KG Stuttgart · New York.

Thermal-Mechanical Stress Analysis of PWR Pressure Vessel and Nozzles under Grid Load-Following Mode: Interim Report on the Effect of Cyclic Hardening Material Properties and Pre-existing Cracks on Stress Analysis Results

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

Mohanty, Subhasish; Soppet, William; Majumdar, Saurin

This report provides an update on an assessment of environmentally assisted fatigue for light water reactor components under extended service conditions. This report is a deliverable under the work package for environmentally assisted fatigue as part of DOE’s Light Water Reactor Sustainability Program. In a previous report (September 2015), we presented tensile and fatigue test data and related hardening material properties for 508 low-alloys steel base metal and other reactor metals. In this report, we present thermal-mechanical stress analysis of the reactor pressure vessel and its hot-leg and cold-leg nozzles based on estimated material properties. We also present results frommore » thermal and thermal-mechanical stress analysis under reactor heat-up, cool-down, and grid load-following conditions. Analysis results are given with and without the presence of preexisting cracks in the reactor nozzles (axial or circumferential crack). In addition, results from validation stress analysis based on tensile and fatigue experiments are reported.« less

[Coupled Analysis of Fluid-Structure Interaction of a Micro-Mechanical Valve for Glaucoma Drainage Devices].

PubMed

Siewert, S; Sämann, M; Schmidt, W; Stiehm, M; Falke, K; Grabow, N; Guthoff, R; Schmitz, K-P

2015-12-01

Glaucoma is the leading cause of irreversible blindness worldwide. In therapeutically refractory cases, alloplastic glaucoma drainage devices (GDD) are being increasingly used to decrease intraocular pressure. Current devices are mainly limited by fibrotic encapsulation and postoperative hypotension. Preliminary studies have described the development of a glaucoma microstent to control aqueous humour drainage from the anterior chamber into the suprachoroidal space. One focus of these studies was on the design of a micro-mechanical valve placed in the anterior chamber to inhibit postoperative hypotension. The present report describes the coupled analysis of fluid-structure interaction (FSI) as basis for future improvements in the design micro-mechanical valves. FSI analysis was carried out with ANSYS 14.5 software. Solid and fluid geometry were combined in a model, and the corresponding material properties of silicone (Silastic Rx-50) and water at room temperature were assigned. The meshing of the solid and fluid domains was carried out in accordance with the results of a convergence study with tetrahedron elements. Structural and fluid mechanical boundary conditions completed the model. The FSI analysis takes into account geometric non-linearity and adaptive remeshing to consider changing geometry. A valve opening pressure of 3.26 mmHg was derived from the FSI analysis and correlates well with the results of preliminary experimental fluid mechanical studies. Flow resistance was calculated from non-linear pressure-flow characteristics as 8.5 × 10(-3) mmHg/µl  · min(-1) and 2.7 × 10(-3) mmHg/µl  · min(-1), respectively before and after valve opening pressure is exceeded. FSI analysis indicated leakage flow before valve opening, which is due to the simplified model geometry. The presented bidirectional coupled FSI analysis is a powerful tool for the development of new designs of micro-mechanical valves for GDD and may help to minimise the time and cost expended on manufacturing and testing prototypes. Further optimisation of the FSI model is expected to ensure further convergence between the simulation and the results of experimental investigations. Georg Thieme Verlag KG Stuttgart · New York.

3D hierarchical geometric modeling and multiscale FE analysis as a base for individualized medical diagnosis of bone structure.

PubMed

Podshivalov, L; Fischer, A; Bar-Yoseph, P Z

2011-04-01

This paper describes a new alternative for individualized mechanical analysis of bone trabecular structure. This new method closes the gap between the classic homogenization approach that is applied to macro-scale models and the modern micro-finite element method that is applied directly to micro-scale high-resolution models. The method is based on multiresolution geometrical modeling that generates intermediate structural levels. A new method for estimating multiscale material properties has also been developed to facilitate reliable and efficient mechanical analysis. What makes this method unique is that it enables direct and interactive analysis of the model at every intermediate level. Such flexibility is of principal importance in the analysis of trabecular porous structure. The method enables physicians to zoom-in dynamically and focus on the volume of interest (VOI), thus paving the way for a large class of investigations into the mechanical behavior of bone structure. This is one of the very few methods in the field of computational bio-mechanics that applies mechanical analysis adaptively on large-scale high resolution models. The proposed computational multiscale FE method can serve as an infrastructure for a future comprehensive computerized system for diagnosis of bone structures. The aim of such a system is to assist physicians in diagnosis, prognosis, drug treatment simulation and monitoring. Such a system can provide a better understanding of the disease, and hence benefit patients by providing better and more individualized treatment and high quality healthcare. In this paper, we demonstrate the feasibility of our method on a high-resolution model of vertebra L3. Copyright © 2010 Elsevier Inc. All rights reserved.

Current Results and Proposed Activities in Microgravity Fluid Dynamics

NASA Technical Reports Server (NTRS)

Polezhaev, V. I.

1996-01-01

The Institute for Problems in Mechanics' Laboratory work in mathematical and physical modelling of fluid mechanics develops models, methods, and software for analysis of fluid flow, instability analysis, direct numerical modelling and semi-empirical models of turbulence, as well as experimental research and verification of these models and their applications in technological fluid dynamics, microgravity fluid mechanics, geophysics, and a number of engineering problems. This paper presents an overview of the results in microgravity fluid dynamics research during the last two years. Nonlinear problems of weakly compressible and compressible fluid flows are discussed.

Durability Characteristics Analysis of Plastic Worm Wheel with Glass Fiber Reinforced Polyamide.

PubMed

Kim, Gun-Hee; Lee, Jeong-Won; Seo, Tae-Il

2013-05-10

Plastic worm wheel is widely used in the vehicle manufacturing field because it is favorable for weight lightening, vibration and noise reduction, as well as corrosion resistance. However, it is very difficult for general plastics to secure the mechanical properties that are required for vehicle gears. If the plastic resin is reinforced by glass fiber in the fabrication process of plastic worm wheel, it is possible to achieve the mechanical properties of metallic material levels. In this study, the mechanical characteristic analysis of the glass-reinforced plastic worm wheel, according to the contents of glass fiber, is performed by analytic and experimental methods. In the case of the glass fiber-reinforced resin, the orientation and contents of glass fibers can influence the mechanical properties. For the characteristic prediction of plastic worm wheel, computer-aided engineering (CAE) analysis processes such as structural and injection molding analysis were executed with the polyamide resin reinforcement glass fiber (25 wt %, 50 wt %). The injection mold for fabricating the prototype plastic worm wheel was designed and made to reflect the CAE analysis results. Finally, the durability of prototype plastic worm wheel fabricated by the injection molding process was evaluated by the experimental method and the characteristics according to the glass fiber contents.

Durability Characteristics Analysis of Plastic Worm Wheel with Glass Fiber Reinforced Polyamide

PubMed Central

Kim, Gun-Hee; Lee, Jeong-Won; Seo, Tae-Il

2013-01-01

Plastic worm wheel is widely used in the vehicle manufacturing field because it is favorable for weight lightening, vibration and noise reduction, as well as corrosion resistance. However, it is very difficult for general plastics to secure the mechanical properties that are required for vehicle gears. If the plastic resin is reinforced by glass fiber in the fabrication process of plastic worm wheel, it is possible to achieve the mechanical properties of metallic material levels. In this study, the mechanical characteristic analysis of the glass-reinforced plastic worm wheel, according to the contents of glass fiber, is performed by analytic and experimental methods. In the case of the glass fiber-reinforced resin, the orientation and contents of glass fibers can influence the mechanical properties. For the characteristic prediction of plastic worm wheel, computer-aided engineering (CAE) analysis processes such as structural and injection molding analysis were executed with the polyamide resin reinforcement glass fiber (25 wt %, 50 wt %). The injection mold for fabricating the prototype plastic worm wheel was designed and made to reflect the CAE analysis results. Finally, the durability of prototype plastic worm wheel fabricated by the injection molding process was evaluated by the experimental method and the characteristics according to the glass fiber contents. PMID:28809248

What are the mechanics of quantum cognition?

PubMed

Navarro, Daniel Joseph; Fuss, Ian

2013-06-01

Pothos & Busemeyer (P&B) argue that quantum probability (QP) provides a descriptive model of behavior and can also provide a rational analysis of a task. We discuss QP models using Marr's levels of analysis, arguing that they make most sense as algorithmic level theories. We also highlight the importance of having clear interpretations for basic mechanisms such as interference.

An Analysis of the Waste Water Treatment Maintenance Mechanic Occupation.

ERIC Educational Resources Information Center

Clark, Anthony B.; And Others

The general purpose of the occupational analysis is to provide workable, basic information dealing with the many and varied duties performed in the waste water treatment mechanics occupation. The document opens with a brief introduction followed by a job description. The bulk of the document is presented in table form. Twelve duties are broken…

An Analysis of the Diesel Truck Mechanic Occupation.

ERIC Educational Resources Information Center

Kilo, Joseph L.

The general purpose of the occupational analysis is to provide workable, basic information dealing with the many and varied duties performed in the diesel truck mechanic occupation. The document opens with a brief introduction followed by a job description. The bulk of the document is presented in table form. Thirteen duties are broken down into a…

Using High Speed Smartphone Cameras and Video Analysis Techniques to Teach Mechanical Wave Physics

ERIC Educational Resources Information Center

Bonato, Jacopo; Gratton, Luigi M.; Onorato, Pasquale; Oss, Stefano

2017-01-01

We propose the use of smartphone-based slow-motion video analysis techniques as a valuable tool for investigating physics concepts ruling mechanical wave propagation. The simple experimental activities presented here, suitable for both high school and undergraduate students, allows one to measure, in a simple yet rigorous way, the speed of pulses…

Analysis of photometry of luminous hot stars from BRITE

NASA Astrophysics Data System (ADS)

Rybicka, M.

2017-09-01

The hot part of the Hertzsprung-Russell diagram contains many types of variable stars. The driving mechanisms are not yet understood. They can be pulsations, convection, stellar wind, granulation or other processes. The pulsations can be excited by different mechanisms. We will present here the results of the analysis of the BRITE-Constellation photometry of OB stars.

Optimization design and dynamic analysis on the drive mechanisms of flapping-wing air vehicles based on flapping trajectories

NASA Astrophysics Data System (ADS)

Xie, Lingwang; Zhang, Xingwei; Luo, Pan; Huang, Panpan

2017-10-01

The optimization designs and dynamic analysis on the driving mechanism of flapping-wing air vehicles on base of flapping trajectory patterns is carried out in this study. Three different driving mechanisms which are spatial double crank-rocker, plane five-bar and gear-double slider, are systematically optimized and analysed by using the Mat lab and Adams software. After a series debugging on the parameter, the comparatively ideal flapping trajectories are obtained by the simulation of Adams. Present results indicate that different drive mechanisms output different flapping trajectories and have their unique characteristic. The spatial double crank-rocker mechanism can only output the arc flapping trajectory and it has the advantages of small volume, high flexibility and efficient space utilization. Both planar five-bar mechanism and gear-double slider mechanism can output the oval, figure of eight and double eight flapping trajectories. Nevertheless, the gear-double slider mechanism has the advantage of convenient parameter setting and better performance in output double eight flapping trajectory. This study can provide theoretical basis and helpful reference for the design of the drive mechanisms of flapping-wing air vehicles with different output flapping trajectories.

Integrated analysis of error detection and recovery

NASA Technical Reports Server (NTRS)

Shin, K. G.; Lee, Y. H.

1985-01-01

An integrated modeling and analysis of error detection and recovery is presented. When fault latency and/or error latency exist, the system may suffer from multiple faults or error propagations which seriously deteriorate the fault-tolerant capability. Several detection models that enable analysis of the effect of detection mechanisms on the subsequent error handling operations and the overall system reliability were developed. Following detection of the faulty unit and reconfiguration of the system, the contaminated processes or tasks have to be recovered. The strategies of error recovery employed depend on the detection mechanisms and the available redundancy. Several recovery methods including the rollback recovery are considered. The recovery overhead is evaluated as an index of the capabilities of the detection and reconfiguration mechanisms.

Sensitivity to imputation models and assumptions in receiver operating characteristic analysis with incomplete data

PubMed Central

Karakaya, Jale; Karabulut, Erdem; Yucel, Recai M.

2015-01-01

Modern statistical methods using incomplete data have been increasingly applied in a wide variety of substantive problems. Similarly, receiver operating characteristic (ROC) analysis, a method used in evaluating diagnostic tests or biomarkers in medical research, has also been increasingly popular problem in both its development and application. While missing-data methods have been applied in ROC analysis, the impact of model mis-specification and/or assumptions (e.g. missing at random) underlying the missing data has not been thoroughly studied. In this work, we study the performance of multiple imputation (MI) inference in ROC analysis. Particularly, we investigate parametric and non-parametric techniques for MI inference under common missingness mechanisms. Depending on the coherency of the imputation model with the underlying data generation mechanism, our results show that MI generally leads to well-calibrated inferences under ignorable missingness mechanisms. PMID:26379316

How the embryonic chick brain twists.

PubMed

Chen, Zi; Guo, Qiaohang; Dai, Eric; Forsch, Nickolas; Taber, Larry A

2016-11-01

During early development, the tubular embryonic chick brain undergoes a combination of progressive ventral bending and rightward torsion, one of the earliest organ-level left-right asymmetry events in development. Existing evidence suggests that bending is caused by differential growth, but the mechanism for the predominantly rightward torsion of the embryonic brain tube remains poorly understood. Here, we show through a combination of in vitro experiments, a physical model of the embryonic morphology and mechanics analysis that the vitelline membrane (VM) exerts an external load on the brain that drives torsion. Our theoretical analysis showed that the force is of the order of 10 micronewtons. We also designed an experiment to use fluid surface tension to replace the mechanical role of the VM, and the estimated magnitude of the force owing to surface tension was shown to be consistent with the above theoretical analysis. We further discovered that the asymmetry of the looping heart determines the chirality of the twisted brain via physical mechanisms, demonstrating the mechanical transfer of left-right asymmetry between organs. Our experiments also implied that brain flexure is a necessary condition for torsion. Our work clarifies the mechanical origin of torsion and the development of left-right asymmetry in the early embryonic brain. © 2016 The Author(s).

Scaling analysis for the investigation of slip mechanisms in nanofluids

NASA Astrophysics Data System (ADS)

Savithiri, S.; Pattamatta, Arvind; Das, Sarit K.

2011-07-01

The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it.

Scaling analysis for the investigation of slip mechanisms in nanofluids

PubMed Central

2011-01-01

The primary objective of this study is to investigate the effect of slip mechanisms in nanofluids through scaling analysis. The role of nanoparticle slip mechanisms in both water- and ethylene glycol-based nanofluids is analyzed by considering shape, size, concentration, and temperature of the nanoparticles. From the scaling analysis, it is found that all of the slip mechanisms are dominant in particles of cylindrical shape as compared to that of spherical and sheet particles. The magnitudes of slip mechanisms are found to be higher for particles of size between 10 and 80 nm. The Brownian force is found to dominate in smaller particles below 10 nm and also at smaller volume fraction. However, the drag force is found to dominate in smaller particles below 10 nm and at higher volume fraction. The effect of thermophoresis and Magnus forces is found to increase with the particle size and concentration. In terms of time scales, the Brownian and gravity forces act considerably over a longer duration than the other forces. For copper-water-based nanofluid, the effective contribution of slip mechanisms leads to a heat transfer augmentation which is approximately 36% over that of the base fluid. The drag and gravity forces tend to reduce the Nusselt number of the nanofluid while the other forces tend to enhance it. PMID:21791036

A network pharmacology approach to determine the synergetic mechanisms of herb couple for treating rheumatic arthritis.

PubMed

Xu, Xi-Xi; Bi, Jian-Ping; Ping, Li; Li, Ping; Li, Fei

2018-01-01

The purpose of this study was to investigate the therapeutic mechanism(s) of Clematis chinensis Osbeck/ Notopterygium incisum K.C. Ting ex H.T (CN). A network pharmacology approach integrating prediction of ingredients, target exploration, network construction, module partition and pathway analysis was used. This approach successfully helped to identify 12 active ingredients of CN, interacting with 13 key targets (Akt1, STAT3, TNFsf13, TP53, EPHB2, IL-10, IL-6, TNF, MAPK8, IL-8, RELA, ROS1 and STAT4). Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis indicated that CN-regulated pathways were mainly classified into signal transduction and immune system. The present work may help to illustrate the mechanism(s) of action of CN, and it may provide a better understanding of antirheumatic effects.

Molecular analysis of Hsp70 mechanisms in plants and their function in response to stress.

PubMed

Usman, Magaji G; Rafii, Mohd Y; Martini, Mohammad Y; Yusuff, Oladosu A; Ismail, Mohd R; Miah, Gous

2017-04-01

Studying the strategies of improving abiotic stress tolerance is quite imperative and research under this field will increase our understanding of response mechanisms to abiotic stress such as heat. The Hsp70 is an essential regulator of protein having the tendency to maintain internal cell stability like proper folding protein and breakdown of unfolded proteins. Hsp70 holds together protein substrates to help in movement, regulation, and prevent aggregation under physical and or chemical pressure. However, this review reports the molecular mechanism of heat shock protein 70 kDa (Hsp70) action and its structural and functional analysis, research progress on the interaction of Hsp70 with other proteins and their interaction mechanisms as well as the involvement of Hsp70 in abiotic stress responses as an adaptive defense mechanism.

Structural characterization and mechanical performance of calcium phosphate scaffolds and natural bones: a comparative study.

PubMed

Fuentes, Elena; Sáenz de Viteri, Virginia; Igartua, Amaya; Martinetti, Roberta; Dolcini, Laura; Barandika, Gotzone

2010-01-01

The knowledge of the mechanical response of bones and their substitutes is pertinent to numerous medical problems. Understanding the effects of mechanical influence on the body is the first step toward developing innovative treatment and rehabilitation concepts for orthopedic disorders. This was a comparative study of 5 synthetic scaffolds based on porous calcium phosphates and natural bones, with regard to their microstructural, chemical, and mechanical characterizations. The structural and chemical characterizations of the scaffolds were examined by means of X-ray diffraction, scanning electron microscopy, and X-ray spectroscopy analysis. The mechanical characterization of bones and bone graft biomaterials was carried out through compression tests using samples with noncomplex geometry. Analysis of the chemical composition, surface features, porosity, and compressive strength indicates that hydroxyapatite-based materials and trabecular bone have similar properties.

Mechanisms of Hydrocarbon Based Polymer Etch

NASA Astrophysics Data System (ADS)

Lane, Barton; Ventzek, Peter; Matsukuma, Masaaki; Suzuki, Ayuta; Koshiishi, Akira

2015-09-01

Dry etch of hydrocarbon based polymers is important for semiconductor device manufacturing. The etch mechanisms for oxygen rich plasma etch of hydrocarbon based polymers has been studied but the mechanism for lean chemistries has received little attention. We report on an experimental and analytic study of the mechanism for etching of a hydrocarbon based polymer using an Ar/O2 chemistry in a single frequency 13.56 MHz test bed. The experimental study employs an analysis of transients from sequential oxidation and Ar sputtering steps using OES and surface analytics to constrain conceptual models for the etch mechanism. The conceptual model is consistent with observations from MD studies and surface analysis performed by Vegh et al. and Oehrlein et al. and other similar studies. Parameters of the model are fit using published data and the experimentally observed time scales.

Energy localization and frequency analysis in the locust ear.

PubMed

Malkin, Robert; McDonagh, Thomas R; Mhatre, Natasha; Scott, Thomas S; Robert, Daniel

2014-01-06

Animal ears are exquisitely adapted to capture sound energy and perform signal analysis. Studying the ear of the locust, we show how frequency signal analysis can be performed solely by using the structural features of the tympanum. Incident sound waves generate mechanical vibrational waves that travel across the tympanum. These waves shoal in a tsunami-like fashion, resulting in energy localization that focuses vibrations onto the mechanosensory neurons in a frequency-dependent manner. Using finite element analysis, we demonstrate that two mechanical properties of the locust tympanum, distributed thickness and tension, are necessary and sufficient to generate frequency-dependent energy localization.

Incorporating general race and housing flexibility and deadband in rolling element bearing analysis

NASA Technical Reports Server (NTRS)

Davis, R. R.; Vallance, C. S.

1989-01-01

Methods for including the effects of general race and housing compliance and outer race-to-housing deadband (clearance) in rolling element bearing mechanics analysis is presented. It is shown that these effects can cause significant changes in bearing stiffness characteristics, which are of major importance in rotordynamic response of turbomachinery and other rotating systems. Preloading analysis is demonstrated with the finite element/contact mechanics hybrid method applied to a 45 mm angular contact ball bearing.

Mechanical Design and Analysis of LCLS II 2 K Cold Box

NASA Astrophysics Data System (ADS)

Yang, S.; Dixon, K.; Laverdure, N.; Rath, D.; Bevins, M.; Bai, H.; Kaminski, S.; Ravindranath, V.

2017-12-01

The mechanical design and analysis of the LCLS II 2 K cold box are presented. Its feature and functionality are discussed. ASME B31.3 was used to design its internal piping, and compliance of the piping code was ensured through flexibility analysis. The 2 K cold box was analyzed using ANSYS 17.2; the requirements of the applicable codes—ASME Section VIII Division 2 and ASCE 7-10—were satisfied. Seismic load was explicitly considered in both analyses.

Dynamic Analysis of Hammer Mechanism "Twin Hammer" of Impact Wrench

NASA Astrophysics Data System (ADS)

Konečný, M.; Slavík, J.

This paper describes function of the hammer mechanism "Twin hammer" the impact wrench, calculation of dynamic forces exerted on the mechanism and determining the contact pressures between the parts of the mechanism. The modelling of parts was performed in system Pro ENGINEER—standard. The simulation and finding dynamic forces was performed in advanced module Pro ENGINEER—mechanism design and finding contacts pressures in modul Pro ENGENEER—mechanica.

The prognosis of infective endocarditis treated with biological valves versus mechanical valves: A meta-analysis.

PubMed

Tao, Ende; Wan, Li; Wang, WenJun; Luo, YunLong; Zeng, JinFu; Wu, Xia

2017-01-01

Surgery remains the primary form of treatment for infective endocarditis (IE). However, it is not clear what type of prosthetic valve provides a better prognosis. We conducted a meta-analysis to compare the prognosis of infective endocarditis treated with biological valves to cases treated with mechanical valves. Pubmed, Embase and Cochrane databases were searched from January 1960 to November 2016.Randomized controlled trials, retrospective cohorts and prospective studies comparing outcomes between biological valve and mechanical valve management for infective endocarditis were analyzed. The Newcastle-Ottawa Scale(NOS) was used to evaluate the quality of the literature and extracted data, and Stata 12.0 software was used for the meta-analysis. A total of 11 publications were included; 10,754 cases were selected, involving 6776 cases of biological valves and 3,978 cases of mechanical valves. The all-cause mortality risk of the biological valve group was higher than that of the mechanical valve group (HR = 1.22, 95% CI 1.03 to 1.44, P = 0.023), as was early mortality (RR = 1.21, 95% CI 1.02 to 1.43, P = 0.033). The recurrence of endocarditis (HR = 1.75, 95% CI 1.26 to 2.42, P = 0.001), as well as the risk of reoperation (HR = 1.79, 95% CI 1.15 to 2.80, P = 0.010) were more likely to occur in the biological valve group. The incidence of postoperative embolism was less in the biological valve group than in the mechanical valve group, but this difference was not statistically significant (RR = 0.90, 95% CI 0.76 to 1.07, P = 0.245). For patients with prosthetic valve endocarditis (PVE), there was no significant difference in survival rates between the biological valve group and the mechanical valve group (HR = 0.91, 95% CI 0.68 to 1.21, P = 0.520). The results of our meta-analysis suggest that mechanical valves can provide a significantly better prognosis in patients with infective endocarditis. There were significant differences in the clinical features of patients receiving a biological valve compared to patients receiving a mechanical valve. A large, multicenter retrospective study included in our meta-analysis suggested that any mortality risk of the biological valve group was significant higher than that of the mechanical valve group. However, the risk was no different after risk was adjusted. So, we thought the reason for this result may be related to the characteristics of the patient rather than valve dysfunction. It is still necessary to future randomized studies to verify this conclusion.

Mechanical response of silk crystalline units from force-distribution analysis.

PubMed

Xiao, Senbo; Stacklies, Wolfram; Cetinkaya, Murat; Markert, Bernd; Gräter, Frauke

2009-05-20

The outstanding mechanical toughness of silk fibers is thought to be caused by embedded crystalline units acting as cross links of silk proteins in the fiber. Here, we examine the robustness of these highly ordered beta-sheet structures by molecular dynamics simulations and finite element analysis. Structural parameters and stress-strain relationships of four different models, from spider and Bombyx mori silk peptides, in antiparallel and parallel arrangement, were determined and found to be in good agreement with x-ray diffraction data. Rupture forces exceed those of any previously examined globular protein many times over, with spider silk (poly-alanine) slightly outperforming Bombyx mori silk ((Gly-Ala)(n)). All-atom force distribution analysis reveals both intrasheet hydrogen-bonding and intersheet side-chain interactions to contribute to stability to similar extent. In combination with finite element analysis of simplified beta-sheet skeletons, we could ascribe the distinct force distribution pattern of the antiparallel and parallel silk crystalline units to the difference in hydrogen-bond geometry, featuring an in-line or zigzag arrangement, respectively. Hydrogen-bond strength was higher in antiparallel models, and ultimately resulted in higher stiffness of the crystal, compensating the effect of the mechanically disadvantageous in-line hydrogen-bond geometry. Atomistic and coarse-grained force distribution patterns can thus explain differences in mechanical response of silk crystals, opening up the road to predict full fiber mechanics.

A mechanical energy analysis of gait initiation

NASA Technical Reports Server (NTRS)

Miller, C. A.; Verstraete, M. C.

1999-01-01

The analysis of gait initiation (the transient state between standing and walking) is an important diagnostic tool to study pathologic gait and to evaluate prosthetic devices. While past studies have quantified mechanical energy of the body during steady-state gait, to date no one has computed the mechanical energy of the body during gait initiation. In this study, gait initiation in seven normal male subjects was studied using a mechanical energy analysis to compute total body energy. The data showed three separate states: quiet standing, gait initiation, and steady-state gait. During gait initiation, the trends in the energy data for the individual segments were similar to those seen during steady-state gait (and in Winter DA, Quanbury AO, Reimer GD. Analysis of instantaneous energy of normal gait. J Biochem 1976;9:253-257), but diminished in amplitude. However, these amplitudes increased to those seen in steady-state during the gait initiation event (GIE), with the greatest increase occurring in the second step due to the push-off of the foundation leg. The baseline level of mechanical energy was due to the potential energy of the individual segments, while the cyclic nature of the data was indicative of the kinetic energy of the particular leg in swing phase during that step. The data presented showed differences in energy trends during gait initiation from those of steady state, thereby demonstrating the importance of this event in the study of locomotion.

Integrated analysis and design of thick composite structures for optimal passive damping characteristics

NASA Technical Reports Server (NTRS)

Saravanos, D. A.

1993-01-01

The development of novel composite mechanics for the analysis of damping in composite laminates and structures and the more significant results of this effort are summarized. Laminate mechanics based on piecewise continuous in-plane displacement fields are described that can represent both intralaminar stresses and interlaminar shear stresses and the associated effects on the stiffness and damping characteristics of a composite laminate. Among other features, the mechanics can accurately model the static and damped dynamic response of either thin or thick composite laminates, as well as, specialty laminates with embedded compliant damping layers. The discrete laminate damping theory is further incorporated into structural analysis methods. In this context, an exact semi-analytical method for the simulation of the damped dynamic response of composite plates was developed. A finite element based method and a specialty four-node plate element were also developed for the analysis of composite structures of variable shape and boundary conditions. Numerous evaluations and applications demonstrate the quality and superiority of the mechanics in predicting the damped dynamic characteristics of composite structures. Finally, additional development was focused on the development of optimal tailoring methods for the design of thick composite structures based on the developed analytical capability. Applications on composite plates illustrated the influence of composite mechanics in the optimal design of composites and the potential for significant deviations in the resultant designs when more simplified (classical) laminate theories are used.

Renal blood flow dynamics in inbred rat strains provides insight into autoregulation.

PubMed

A Mitrou, Nicholas G; Cupples, William A

2014-01-01

Renal autoregulation maintains stable renal blood flow in the face of constantly fluctuating blood pressure. Autoregulation is also the only mechanism that protects the delicate glomerular capillaries when blood pressure increases. In order to understand autoregulation, the renal blood flow response to changing blood pressure is studied. The steadystate response of blood flow is informative, but limits investigation of the individual mechanisms of autoregulation. The dynamics of autoregulation can be probed with transfer function analysis. The frequency-domain analysis of autoregulation allows investigators to probe the relative activity of each mechanism of autoregulation. We discuss the methodology and interpretation of transfer function analysis. Autoregulation is routinely studied in the rat, of which there are many inbred strains. There are multiple strains of rat that are either selected or inbred as models of human pathology. We discuss relevant characteristics of Brown Norway, Spontaneously hypertensive, Dahl, and Fawn-Hooded hypertensive rats and explore differences among these strains in blood pressure, dynamic autoregulation, and susceptibility to hypertensive renal injury. Finally we show that the use of transfer function analysis in these rat strains has contributed to our understanding of the physiology and pathophysiology of autoregulation and hypertensive renal disease.Interestingly all these strains demonstrate effective tubuloglomerular feedback suggesting that this mechanism is not sufficient for effective autoregulation. In contrast, obligatory or conditional failure of the myogenic mechanism suggests that this component is both necessary and sufficient for autoregulation.

Crystallization processes in Ge{sub 2}Sb{sub 2}Se{sub 4}Te glass

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

Svoboda, Roman, E-mail: roman.svoboda@upce.cz; Bezdička, Petr; Gutwirth, Jan

2015-01-15

Highlights: • Crystallization kinetics of Ge{sub 2}Sb{sub 2}Se{sub 4}Te glass was studied in dependence on particle size by DSC. • All studied fractions were described in terms of the SB autocatalytic model. • Relatively high amount of Te enhances manifestation of bulk crystallization mechanisms. • XRD analysis of samples crystallized under different conditions showed correlation with DSC data. • XRD analysis revealed a new crystallization mechanism indistinguishable by DSC. - Abstract: Differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analysis were used to study crystallization in Ge{sub 2}Sb{sub 2}Se{sub 4}Te glass under non-isothermal conditions as a function of the particlemore » size. The crystallization kinetics was described in terms of the autocatalytic Šesták–Berggren model. An extensive discussion of all aspects of a full-scale kinetic study of a crystallization process was undertaken. Dominance of the crystallization process originating from mechanically induced strains and heterogeneities was confirmed. Substitution of Se by Te was found to enhance the manifestation of the bulk crystallization mechanisms (at the expense of surface crystallization). The XRD analysis showed significant dependence of the crystalline structural parameters on the crystallization conditions (initial particle size of the glassy grains and applied heating rate). Based on this information, a new microstructural crystallization mechanism, indistinguishable by DSC, was proposed.« less

Heterogeneous structure and surface tension effects on mechanical response in pulmonary acinus: A finite element analysis.

PubMed

Koshiyama, Kenichiro; Nishimoto, Keisuke; Ii, Satoshi; Sera, Toshihiro; Wada, Shigeo

2018-01-20

The pulmonary acinus is a dead-end microstructure that consists of ducts and alveoli. High-resolution micro-CT imaging has recently provided detailed anatomical information of a complete in vivo acinus, but relating its mechanical response with its detailed acinar structure remains challenging. This study aimed to investigate the mechanical response of acinar tissue in a whole acinus for static inflation using computational approaches. We performed finite element analysis of a whole acinus for static inflation. The acinar structure model was generated based on micro-CT images of an intact acinus. A continuum mechanics model of the lung parenchyma was used for acinar tissue material model, and surface tension effects were explicitly included. An anisotropic mechanical field analysis based on a stretch tensor was combined with a curvature-based local structure analysis. The airspace of the acinus exhibited nonspherical deformation as a result of the anisotropic deformation of acinar tissue. A strain hotspot occurred at the ridge-shaped region caused by a rod-like deformation of acinar tissue on the ridge. The local structure becomes bowl-shaped for inflation and, without surface tension effects, the surface of the bowl-shaped region primarily experiences isotropic deformation. Surface tension effects suppressed the increase in airspace volume and inner surface area, while facilitating anisotropic deformation on the alveolar surface. In the lungs, the heterogeneous acinar structure and surface tension induce anisotropic deformation at the acinar and alveolar scales. Further research is needed on structural variation of acini, inter-acini connectivity, or dynamic behavior to understand multiscale lung mechanics. Copyright © 2018 Elsevier Ltd. All rights reserved.

Mechanical analysis of carbon fiber reinforced shape memory polymer composite for self-deployable structure in space environment

NASA Astrophysics Data System (ADS)

Hong, Seok Bin; Ahn, Yong San; Jang, Joon Hyeok; Kim, Jin-Gyun; Goo, Nam Seo; Yu, Woong-Ryeol

2016-04-01

Shape memory polymer (SMP) is one of smart polymers which exhibit shape memory effect upon external stimuli. Reinforcements as carbon fiber had been used for making shape memory polymer composite (CF-SMPC). This study investigated a possibility of designing self-deployable structures in harsh space condition using CF-SMPCs and analyzed their shape memory behaviors with constitutive equation model.CF-SMPCs were prepared using woven carbon fabrics and a thermoset epoxy based SMP to obtain their basic mechanical properties including actuation in harsh environment. The mechanical and shape memory properties of SMP and CF-SMPCs were characterized using dynamic mechanical analysis (DMA) and universal tensile machine (UTM) with an environmental chamber. The mechanical properties such as flexural strength and tensile strength of SMP and CF-SMPC were measured with simple tensile/bending test and time dependent shape memory behavior was characterized with designed shape memory bending test. For mechanical analysis of CF-SMPCs, a 3D constitutive equation of SMP, which had been developed using multiplicative decomposition of the deformation gradient and shape memory strains, was used with material parameters determined from CF-SMPCs. Carbon fibers in composites reinforced tensile and flexural strength of SMP and acted as strong elastic springs in rheology based equation models. The actuation behavior of SMP matrix and CF-SMPCs was then simulated as 3D shape memory bending cases. Fiber bundle property was imbued with shell model for more precise analysis and it would be used for prediction of deploying behavior in self-deployable hinge structure.

Mechanisms and situations of anterior cruciate ligament injuries in professional male soccer players: a YouTube-based video analysis.

PubMed

Grassi, Alberto; Smiley, Stephen Paul; Roberti di Sarsina, Tommaso; Signorelli, Cecilia; Marcheggiani Muccioli, Giulio Maria; Bondi, Alice; Romagnoli, Matteo; Agostini, Alessandra; Zaffagnini, Stefano

2017-10-01

Soccer is considered the most popular sport in the world concerning both audience and athlete participation, and the incidence of ACL injury in this sport is high. The understanding of injury situations and mechanisms could be useful as substratum for preventive actions. To conduct a video analysis evaluating the situations and mechanisms of ACL injury in a homogeneous population of professional male soccer players, through a search entirely performed on the YouTube.com Web site focusing on the most recent years. A video analysis was conducted obtaining videos of ACL injury in professional male soccer players from the Web site YouTube. Details regarding injured players, events and situations were obtained. The mechanism of injury was defined on the basis of the action, duel type, contact or non-contact injury, and on the hip, knee and foot position. Thirty-four videos were analyzed, mostly from the 2014-2015 season. Injuries occurred mostly in the first 9 min of the match (26%), in the penalty area (32%) or near the side-lines (44%), and in non-rainy conditions (97%). Non-contact injuries occurred in 44% of cases, while indirect injuries occurred in 65%, mostly during pressing, dribbling or tackling. The most recurrent mechanism was with an abducted and flexed hip, with knee at first degrees of flexion and under valgus stress. Through a YouTube-based video analysis, it was possible to delineate recurrent temporal, spatial and mechanical characteristics of ACL injury in male professional soccer players. Level IV, case series.

A new strategy for earthquake focal mechanisms using waveform-correlation-derived relative polarities and cluster analysis: Application to the 2014 Long Valley Caldera earthquake swarm

USGS Publications Warehouse

Shelly, David R.; Hardebeck, Jeanne L.; Ellsworth, William L.; Hill, David P.

2016-01-01

In microseismicity analyses, reliable focal mechanisms can typically be obtained for only a small subset of located events. We address this limitation here, presenting a framework for determining robust focal mechanisms for entire populations of very small events. To achieve this, we resolve relative P and S wave polarities between pairs of waveforms by using their signed correlation coefficients—a by-product of previously performed precise earthquake relocation. We then use cluster analysis to group events with similar patterns of polarities across the network. Finally, we apply a standard mechanism inversion to the grouped data, using either catalog or correlation-derived P wave polarity data sets. This approach has great potential for enhancing analyses of spatially concentrated microseismicity such as earthquake swarms, mainshock-aftershock sequences, and industrial reservoir stimulation or injection-induced seismic sequences. To demonstrate its utility, we apply this technique to the 2014 Long Valley Caldera earthquake swarm. In our analysis, 85% of the events (7212 out of 8494 located by Shelly et al. [2016]) fall within five well-constrained mechanism clusters, more than 12 times the number with network-determined mechanisms. Of the earthquakes we characterize, 3023 (42%) have magnitudes smaller than 0.0. We find that mechanism variations are strongly associated with corresponding hypocentral structure, yet mechanism heterogeneity also occurs where it cannot be resolved by hypocentral patterns, often confined to small-magnitude events. Small (5–20°) rotations between mechanism orientations and earthquake location trends persist when we apply 3-D velocity models and might reflect a geometry of en echelon, interlinked shear, and dilational faulting.

[Proposed model of vascular trauma by mean of mechanical characterization of endovascular prostheses (stents) based on structural analysis by FEA].

PubMed

Bustamante, John; Uribe, Pablo; Sosa, Mauricio; Valencia, Raúl

2016-01-01

The accumulated evidence on angioplasty techniques with stents has raised a controversy about the factors that influence the final vascular response. Indeed, several studies have shown there might be re-stenosis between 30% to 40% about 6 months after placement, relating to the design of the device as one of the main causes. This paper proposes the functional characterization of endovascular stents, analyzing its mechanical influence in the vascular system and predicting implicit traumatic factors in the vessel. A structural analysis was made for several computational models of endovascular stents using Finite Element Analysis in order to predict the mechanical behavior and the vascular trauma. In this way, the stents were considered as tubular devices composed of multiple links under radial pressure loads, reflecting stress concentration effects. The analysis allowed to visualize how the geometry of stents is adjusted under several load conditions, in order to obtain the response of "solid-solid" interaction between the stent and the arterial wall. Thus, an analysis was performed in order to calculate stress, and a conceptual model that explains its mechanical impact on the stent-vessel interaction, was raised, to infer on the functionality from the design of the devices. The proposed conceptual model allows to determine the relationship between the conditions of mechanical interaction of the stents, and warns about the effects in what would be the operation of the device on the vascular environment. Copyright © 2016 Instituto Nacional de Cardiología Ignacio Chávez. Publicado por Masson Doyma México S.A. All rights reserved.

An Integrated Tool for System Analysis of Sample Return Vehicles

NASA Technical Reports Server (NTRS)

Samareh, Jamshid A.; Maddock, Robert W.; Winski, Richard G.

2012-01-01

The next important step in space exploration is the return of sample materials from extraterrestrial locations to Earth for analysis. Most mission concepts that return sample material to Earth share one common element: an Earth entry vehicle. The analysis and design of entry vehicles is multidisciplinary in nature, requiring the application of mass sizing, flight mechanics, aerodynamics, aerothermodynamics, thermal analysis, structural analysis, and impact analysis tools. Integration of a multidisciplinary problem is a challenging task; the execution process and data transfer among disciplines should be automated and consistent. This paper describes an integrated analysis tool for the design and sizing of an Earth entry vehicle. The current tool includes the following disciplines: mass sizing, flight mechanics, aerodynamics, aerothermodynamics, and impact analysis tools. Python and Java languages are used for integration. Results are presented and compared with the results from previous studies.

The mechanical fingerprint of murine excisional wounds.

PubMed

Pensalfini, Marco; Haertel, Eric; Hopf, Raoul; Wietecha, Mateusz; Werner, Sabine; Mazza, Edoardo

2018-01-01

A multiscale mechanics approach to the characterization of murine excisional wounds subjected to uniaxial tensile loading is presented. Local strain analysis at a physiological level of tension uncovers the presence of two distinct regions within the wound: i) a very compliant peripheral cushion and ii) a core area undergoing modest deformation. Microstructural visualizations of stretched wound specimens show negligible engagement of the collagen located in the center of a 7-day old wound; fibers remain coiled despite the applied tension, confirming the existence of a mechanically isolated wound core. The compliant cushion located at the wound periphery appears to protect the newly-formed tissue from excessive deformation during the phase of new tissue formation. The early remodeling phase (day 14) is characterized by a restored mechanical connection between far field and wound center. The latter remains less deformable, a characteristic possibly required for cell activities during tissue remodeling. The distribution of fibrillary collagens at these two time points corresponds well to the identified heterogeneity of mechanical properties of the wound region. This novel approach provides new insight into the mechanical properties of wounded skin and will be applicable to the analysis of compound-treated wounds or wounds in genetically modified tissue. Biophysical characterization of healing wounds is crucial to assess the recovery of the skin barrier function and the associated mechanobiological processes. For the first time, we performed highly resolved local deformation analysis to identify mechanical characteristics of the wound and its periphery. Our results reveal the presence of a compliant cushion surrounding a stiffer wound core; we refer to this heterogeneous mechanical behavior as "mechanical fingerprint" of the wound. The mechanical response is shown to progress towards that of the intact skin as healing takes place. Histology and multiphoton microscopy suggest that wounded skin recovers its mechanical function via progressive reconnection of the newly-deposited collagen fibers with the surrounding intact matrix. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Efficiency limit factor analysis for the Francis-99 hydraulic turbine

NASA Astrophysics Data System (ADS)

Zeng, Y.; Zhang, L. X.; Guo, J. P.; Guo, Y. K.; Pan, Q. L.; Qian, J.

2017-01-01

The energy loss in hydraulic turbine is the most direct factor that affects the efficiency of the hydraulic turbine. Based on the analysis theory of inner energy loss of hydraulic turbine, combining the measurement data of the Francis-99, this paper calculates characteristic parameters of inner energy loss of the hydraulic turbine, and establishes the calculation model of the hydraulic turbine power. Taken the start-up test conditions given by Francis-99 as case, characteristics of the inner energy of the hydraulic turbine in transient and transformation law are researched. Further, analyzing mechanical friction in hydraulic turbine, we think that main ingredients of mechanical friction loss is the rotation friction loss between rotating runner and water body, and defined as the inner mechanical friction loss. The calculation method of the inner mechanical friction loss is given roughly. Our purpose is that explore and research the method and way increasing transformation efficiency of water flow by means of analysis energy losses in hydraulic turbine.

Mechanical Properties Analysis of 4340 Steel Specimen Heat Treated in Oven and Quenching in Three Different Fluids

NASA Astrophysics Data System (ADS)

Fakir, Rachid; Barka, Noureddine; Brousseau, Jean

2018-03-01

This paper proposes a statistical approach to analyze the mechanical properties of a standard test specimen, of cylindrical geometry and in steel 4340, with a diameter of 6 mm, heat-treated and quenched in three different fluids. Samples were evaluated in standard tensile test to access their characteristic quantities: hardness, modulus of elasticity, yield strength, tensile strength and ultimate deformation. The proposed approach is gradually being built (a) by a presentation of the experimental device, (b) a presentation of the experimental plan and the results of the mechanical tests, (c) anova analysis of variance and a representation of the output responses using the RSM response surface method, and (d) an analysis of the results and discussion. The feasibility and effectiveness of the proposed approach leads to a precise and reliable model capable of predicting the variation of mechanical properties, depending on the tempering temperature, the tempering time and the cooling capacity of the quenching medium.

Effect of surface modified kaolin on properties of polypropylene grafted maleic anhydride

NASA Astrophysics Data System (ADS)

Yang, Ni; Zhang, Zuo-Cai; Ma, Ning; Liu, Huan-Li; Zhan, Xue-Qing; Li, Bing; Gao, Wei; Tsai, Fang-Chang; Jiang, Tao; Chang, Chang-Jung; Chiang, Tai-Chin; Shi, Dean

To achieve reinforcement of mechanical and thermal performances of polypropylene (PP) product, this work aimed at fabrication of surface modified kaolin (M-kaolin) filled polypropylene grafted maleic anhydride (PP-g-MAH) composites with varying contents of fillers and investigation of their mechanical and thermal properties. And the prepared PP-g-MAH/M-kaolin composites were characterized by means of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Fracture analysis by SEM showed M-kaolin particles were well dispersed in the PP-g-MAH matrix. Mechanical behaviors were determined by tensile strength, tensile strain at break and impact strength analysis. Impact strength of PP-g-MAH/2 wt% M-kaolin composites was improved up to 30% comparing with unfilled composites. Thermostability had been found enhanced when M-kaolin added. The results revealed PP-g-MAH/M-kaolin composites showed the optimal thermal and mechanical properties when 2 wt% of M-kaolin was added.

Mechanical analysis of CFRP-steel hybrid composites considering the interfacial adhesion

NASA Astrophysics Data System (ADS)

Jang, Jinhyeok; Sung, Minchang; Han, Sungjin; Shim, Wonbo; Yu, Woong-Ryeol

2017-10-01

Recently, hybrid composites of carbon fiber reinforced plastics (CFRP) and steel have attracted great attention from automotive engineers due to their high potential for lightweight and multi-materials structures. Interestingly, such hybrid composites have demonstrated increased breaking strain, i.e., the breaking strain of CFRP in the hybrid was larger than that of single CFRP. As such the mechanical properties of hybrid composites could not be calculated using the rule of mixture. In addition, such increase is strongly dependent on the adhesion between CFRP and steel. In this study, a numerical analysis model was built to investigate the mechanism behind increased breaking strain of CFRP in the hybrid structure. Using cohesive zone model, the adhesion between CFRP and steel was effectively considered. The numerical results showed that the simulated mechanical behavior of the hybrid composites did not change as much as observed in experimental as the interfacial adhesion varied. We will investigate this discrepancy in detail and will report new analysis method suitable for CFRP and steel hybrid composites.

Development of a High-speed Electromagnetic Repulsion Mechanism for High-voltage Vacuum Circuit Breakers

NASA Astrophysics Data System (ADS)

Tsukima, Mitsuru; Takeuchi, Toshie; Koyama, Kenichi; Yoshiyasu, Hajimu

This paper presents a design and testing of a new high-speed electromagnetic driving mechanism for a high-voltage vacuum circuit breaker (VCB). This mechanism is based on a high-speed electromagnetic repulsion and a permanent magnet spring (PMS). This PMS is introduced instead of the conventional disk spring due to its low spring energy and more suitable force characteristics for VCB application. The PMS has been optimally designed by the 3d non-linear finite-elements magnetic field analysis and investigated its internal friction and eddy-current effect. Furthermore, we calculated the dynamic of this mechanism coupling with the electromagnetic field and circuit analysis, in order to satisfy the operating characteristics—contact velocity, response time and so on, required for the high-speed VCB. A prototype VCB, which was built based on the above analysis shows sufficient operating performance. Finally, the short circuit interruption tests were carried out with this prototype breaker, and we have been able to verify its satisfying performance.

Origami-inspired building block and parametric design for mechanical metamaterials

NASA Astrophysics Data System (ADS)

Jiang, Wei; Ma, Hua; Feng, Mingde; Yan, Leilei; Wang, Jiafu; Wang, Jun; Qu, Shaobo

2016-08-01

An origami-based building block of mechanical metamaterials is proposed and explained by introducing a mechanism model based on its geometry. According to our model, this origami mechanism supports response to uniaxial tension that depends on structure parameters. Hence, its mechanical properties can be tunable by adjusting the structure parameters. Experiments for poly lactic acid (PLA) samples were carried out, and the results are in good agreement with those of finite element analysis (FEA). This work may be useful for designing building blocks of mechanical metamaterials or other complex mechanical structures.

Thermal-Mechanical Cyclic Test of a Composite Cryogenic Tank for Reusable Launch Vehicles

NASA Technical Reports Server (NTRS)

Messinger, Ross; Pulley, John

2003-01-01

This viewgraph presentation provides an overview of thermal-mechanical cyclic tests conducted on a composite cryogenic tank designed for reusable launch vehicles. Topics covered include: a structural analysis of the composite cryogenic tank, a description of Marshall Space Flight Center's Cryogenic Structure Test Facility, cyclic test plans and accomplishments, burst test and analysis and post-testing evaluation.

KENNEDY SPACE CENTER, FLA. - Jeff Thon, an SRB mechanic with United Space Alliance, tests a technique for vertical solid rocket booster propellant grain inspection. The inspection of segments is required as part of safety analysis.

NASA Image and Video Library

2003-09-11

KENNEDY SPACE CENTER, FLA. - Jeff Thon, an SRB mechanic with United Space Alliance, tests a technique for vertical solid rocket booster propellant grain inspection. The inspection of segments is required as part of safety analysis.

Elucidation of wear mechanisms by ferrographic analysis

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.

1981-01-01

The use of ferrographic analysis in conjunction with light and scanning electron microscopy is described for the elucidation of wear mechanisms taking place in operating equipment. Example of adhesive wear, abrasive wear, corrosive wear, rolling element fatigue, lubricant breakdown, and other wear modes are illustrated. In addition, the use of magnetic solutions to precipitate nonmagnetic debris from aqueous and nonaqueous fluids is described.

Postmodeling Sensitivity Analysis to Detect the Effect of Missing Data Mechanisms

ERIC Educational Resources Information Center

Jamshidian, Mortaza; Mata, Matthew

2008-01-01

Incomplete or missing data is a common problem in almost all areas of empirical research. It is well known that simple and ad hoc methods such as complete case analysis or mean imputation can lead to biased and/or inefficient estimates. The method of maximum likelihood works well; however, when the missing data mechanism is not one of missing…

Individual Participant Data Meta-Analysis of Mechanical Workplace Risk Factors and Low Back Pain

PubMed Central

Shannon, Harry S.; Wells, Richard P.; Walter, Stephen D.; Cole, Donald C.; Côté, Pierre; Frank, John; Hogg-Johnson, Sheilah; Langlois, Lacey E.

2012-01-01

Objectives. We used individual participant data from multiple studies to conduct a comprehensive meta-analysis of mechanical exposures in the workplace and low back pain. Methods. We conducted a systematic literature search and contacted an author of each study to request their individual participant data. Because outcome definitions and exposure measures were not uniform across studies, we conducted 2 substudies: (1) to identify sets of outcome definitions that could be combined in a meta-analysis and (2) to develop methods to translate mechanical exposure onto a common metric. We used generalized estimating equation regression to analyze the data. Results. The odds ratios (ORs) for posture exposures ranged from 1.1 to 2.0. Force exposure ORs ranged from 1.4 to 2.1. The magnitudes of the ORs differed according to the definition of low back pain, and heterogeneity was associated with both study-level and individual-level characteristics. Conclusions. We found small to moderate ORs for the association of mechanical exposures and low back pain, although the relationships were complex. The presence of individual-level OR modifiers in such an area can be best understood by conducting a meta-analysis of individual participant data. PMID:22390445

Continuum Damage Mechanics Models for the Analysis of Progressive Failure in Open-Hole Tension Laminates

NASA Technical Reports Server (NTRS)

Song, Kyonchan; Li, Yingyong; Rose, Cheryl A.

2011-01-01

The performance of a state-of-the-art continuum damage mechanics model for interlaminar damage, coupled with a cohesive zone model for delamination is examined for failure prediction of quasi-isotropic open-hole tension laminates. Limitations of continuum representations of intra-ply damage and the effect of mesh orientation on the analysis predictions are discussed. It is shown that accurate prediction of matrix crack paths and stress redistribution after cracking requires a mesh aligned with the fiber orientation. Based on these results, an aligned mesh is proposed for analysis of the open-hole tension specimens consisting of different meshes within the individual plies, such that the element edges are aligned with the ply fiber direction. The modeling approach is assessed by comparison of analysis predictions to experimental data for specimen configurations in which failure is dominated by complex interactions between matrix cracks and delaminations. It is shown that the different failure mechanisms observed in the tests are well predicted. In addition, the modeling approach is demonstrated to predict proper trends in the effect of scaling on strength and failure mechanisms of quasi-isotropic open-hole tension laminates.

Preparation, characterization and dynamical mechanical properties of dextran-coated iron oxide nanoparticles (DIONPs).

PubMed

Can, Hatice Kaplan; Kavlak, Serap; ParviziKhosroshahi, Shahed; Güner, Ali

2018-03-01

Dextran-coated iron oxide nanoparticles (DIONPs) with appropriate surface chemistry exhibit many interesting properties that can be exploited in a variety of biomedical applications such as magnetic resonance imaging (MRI) contrast enhancement, tissue repair, hyperthermia, drug delivery and in cell separation. This paper reports the experimental detail for preparation, characterization and investigation of thermal and dynamical mechanical characteristics of the dextran-coated Fe 3 O 4 magnetic nanoparticles. In our work, DIONPs were prepared in a 1:2 ratio of Fe(II) and Fe(III) salt in the HCl solution with NaOH at given temperature. The obtained dextran-coated iron-oxide nanoparticles structure-property correlation was characterized by spectroscopic methods; attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and XRD. Coating dextran on the iron-oxide proof of important peaks can be seen from the ATR-FTIR. Dramatic crystallinity increment can be observed from the XRD pattern of the iron-oxide dextran nanoparticles. The thermal analysis was examined by differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA) and differential thermal analysis (DTA). Dynamical mechanical properties of dextran nanoparticles were analysed by dynamic mechanical analysis (DMA). Thermal stability of the iron oxide dextran nanoparticles is higher than that of the dextran.

Comparison of mechanical energy profiles of passive and active below-knee prostheses: a case study.

PubMed

Takahashi, Kota Z; Horne, John R; Stanhope, Steven J

2015-04-01

With the recent technological advancements of prosthetic lower limbs, there is currently a great desire to objectively evaluate existing prostheses. Using a novel biomechanical analysis, the purpose of this case study was to compare the mechanical energy profiles of anatomical and two disparate prostheses: a passive prosthesis and an active prosthesis. An individual with a transtibial amputation who customarily wears a passive prosthesis (Elation, Össur) and an active prosthesis (BiOM, iWalk, Inc.) and 11 healthy subjects participated in an instrumented gait analysis. The total mechanical power and work of below-knee structures during stance were quantified using a unified deformable segment power analysis. Active prosthesis generated greater peak power and total positive work than passive prosthesis and healthy anatomical limbs. The case study will enhance future efforts to objectively evaluate prosthetic functions during gait in individuals with transtibial amputations. A prosthetic limb should closely replicate the mechanical energy profiles of anatomical limbs. The unified deformable (UD) analysis may be valuable to facilitate future clinical prescription and guide fine adjustments of prosthetic componentry to optimize gait outcomes. © The International Society for Prosthetics and Orthotics 2014.

Independent Orbiter Assessment (IOA): Assessment of the mechanical actuation subsystem, volume 1

NASA Technical Reports Server (NTRS)

Bradway, M. W.; Slaughter, W. T.

1988-01-01

The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA approach features a top-down analysis of the hardware to determine draft failure modes, criticality, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the proposed Post 51-L NASA FMEA/CIL baseline that was available. A resolution of each discrepancy from the comparison was provided through additional analysis as required. These discrepancies were flagged as issues, and recommendations were made based on the FMEA data available at the time. This report documents the results of that comparison for the Orbiter Mechanical Actuation System (MAS) hardware. Specifically, the MAS hardware consists of the following components: Air Data Probe (ADP); Elevon Seal Panel (ESP); External Tank Umbilical (ETU); Ku-Band Deploy (KBD); Payload Bay Doors (PBD); Payload Bay Radiators (PBR); Personnel Hatches (PH); Vent Door Mechanism (VDM); and Startracker Door Mechanism (SDM). Criticality was assigned based upon the severity of the effect for each failure mode.

Analysis of Parallelogram Mechanism used to Preserve Remote Center of Motion for Surgical Telemanipulator

NASA Astrophysics Data System (ADS)

Trochimczuk, R.

2017-02-01

This paper presents an analysis of a parallelogram mechanism commonly used to provide a kinematic remote center of motion in surgical telemanipulators. Selected types of parallel manipulator designs, encountered in commercial and laboratory-made designs described in the medical robotics literature, will serve as the research material. Among other things, computer simulations in the ANSYS 13.0 CAD/CAE software environment, employing the finite element method, will be used. The kinematics of the solution of manipulator with the parallelogram mechanism will be determined in order to provide a more complete description. These results will form the basis for the decision regarding the possibility of applying a parallelogram mechanism in an original prototype of a telemanipulator arm.

[The emergence of obstetrical mechanism: From Lucy to Homo sapiens].

PubMed

Frémondière, P; Thollon, L; Marchal, F

2017-03-01

The evolutionary history of modern birth mechanism is now a renewed interest in obstetrical papers. The purpose of this work is to review the literature in paleo-obstetrical field. Our analysis focuses on paleo-obstetrical hypothesis, from 1960 to the present day, based on the reconstruction of fossil pelvis. Indeed, these pelvic reconstructions usually provide an opportunity to make an obstetrical assumption in our ancestors. In this analysis, we show that modern birth mechanism takes place during the emergence of our genus 2 million years ago. References are made to human specificities related to obstetrical mechanism: exclusive bipedalism, increase of brain size at birth, metabolic cost of the pregnancy and deep trophoblastic implantation. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

High-Throughput Assessment of Cellular Mechanical Properties.

PubMed

Darling, Eric M; Di Carlo, Dino

2015-01-01

Traditionally, cell analysis has focused on using molecular biomarkers for basic research, cell preparation, and clinical diagnostics; however, new microtechnologies are enabling evaluation of the mechanical properties of cells at throughputs that make them amenable to widespread use. We review the current understanding of how the mechanical characteristics of cells relate to underlying molecular and architectural changes, describe how these changes evolve with cell-state and disease processes, and propose promising biomedical applications that will be facilitated by the increased throughput of mechanical testing: from diagnosing cancer and monitoring immune states to preparing cells for regenerative medicine. We provide background about techniques that laid the groundwork for the quantitative understanding of cell mechanics and discuss current efforts to develop robust techniques for rapid analysis that aim to implement mechanophenotyping as a routine tool in biomedicine. Looking forward, we describe additional milestones that will facilitate broad adoption, as well as new directions not only in mechanically assessing cells but also in perturbing them to passively engineer cell state.

The mechanism distinguishability problem in biochemical kinetics: the single-enzyme, single-substrate reaction as a case study.

PubMed

Schnell, Santiago; Chappell, Michael J; Evans, Neil D; Roussel, Marc R

2006-01-01

A theoretical analysis of the distinguishability problem of two rival models of the single enzyme-single substrate reaction, the Michaelis-Menten and Henri mechanisms, is presented. We also outline a general approach for analysing the structural indistinguishability between two mechanisms. The approach involves constructing, if possible, a smooth mapping between the two candidate models. Evans et al. [N.D. Evans, M.J. Chappell, M.J. Chapman, K.R. Godfrey, Structural indistinguishability between uncontrolled (autonomous) nonlinear analytic systems, Automatica 40 (2004) 1947-1953] have shown that if, in addition, either of the mechanisms satisfies a particular criterion then such a transformation always exists when the models are indistinguishable from their experimentally observable outputs. The approach is applied to the single enzyme-single substrate reaction mechanism. In principle, mechanisms can be distinguished using this analysis, but we show that our ability to distinguish mechanistic models depends both on the precise measurements made, and on our knowledge of the system prior to performing the kinetics experiments.

Thermomechanical analysis and durability of commercial micro-porous polymer Li-ion battery separators

NASA Astrophysics Data System (ADS)

Love, Corey T.

2011-03-01

Static and dynamic thermomechanical analysis was performed with a dynamic mechanical analyzer (DMA) to identify thermal and mechanical transitions for commercially available polymer separators under mechanical loading. Clear transitions in deformation mode were observed at elevated temperatures. These transitions identified the onset of separator "shutdown" which occurred at temperatures below the polymer melting point. Mechanical loading direction was critical to the overall integrity of the separator. Anisotropic separators (Celgard 2320, 2400 and 2500) were mechanically limited when pulled in tensile in the transverse direction. The anisotropy of these separators is a result of the dry technique used to manufacture the micro-porous membranes. Separators prepared using the wet technique (Entek Gold LP) behaved more uniformly, or biaxially, where all mechanical properties were nearly identical within the separator plane. The information provided by the DMA can also be useful for predicting the long-term durability of polymer separators in lithium-ion batteries exposed to electrolyte (solvent and salt), thermal fluctuations and electrochemical cycling. Small losses in mechanical integrity were observed for separators exposed to the various immersion environments over the 4-week immersion time.

Mechanically activated synthesis of PZT and its electromechanical properties

NASA Astrophysics Data System (ADS)

Liu, X.; Akdogan, E. K.; Safari, A.; Riman, R. E.

2005-08-01

Mechanical activation was successfully used to synthesize nanostructured phase-pure Pb(Zr0.7Ti0.3)O3 (PZT) powders. Lead zirconium titanium (PbZrTi) hydrous oxide precursor, synthesized from chemical co-precipitation, was mechanically activated in a NaCl matrix. The synthesized PZT particles were characterized by using X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, laser-light diffraction, and nitrogen adsorption. Thermogravimetric analysis and differential thermal analysis were used to monitor dehydration and phase transformation of PbZrTi hydrous oxide precursor during mechanical activation. The best mechanical activation conditions corresponded to mechanically activating PbZrTi hydrous oxide precursor in a NaCl matrix with a NaCl/precursor weight ratio of 4:1 for 8 h. These conditions resulted in a dispersible phase-pure PZT powder with a median secondary-particle size of ˜110 nm. The properties of PZT 70/30 from mechanically activated powder, as measured on discs sintered at 1150 °C for 2 h, were found to be in close conformity to those obtained by a conventional mixed oxide solid state reaction route.

LV dyssynchrony as assessed by phase analysis of gated SPECT myocardial perfusion imaging in patients with Wolff-Parkinson-White syndrome.

PubMed

Chen, Chun; Li, Dianfu; Miao, Changqing; Feng, Jianlin; Zhou, Yanli; Cao, Kejiang; Lloyd, Michael S; Chen, Ji

2012-07-01

The purpose of this study was to evaluate left ventricular (LV) mechanical dyssynchrony in patients with Wolff-Parkinson-White (WPW) syndrome pre- and post-radiofrequency catheter ablation (RFA) using phase analysis of gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). Forty-five WPW patients were enrolled and had gated SPECT MPI pre- and 2-3 days post-RFA. Electrophysiological study (EPS) was used to locate accessory pathways (APs) and categorize the patients according to the AP locations (septal, left and right free wall). Electrocardiography (ECG) was performed pre- and post-RFA to confirm successful elimination of the APs. Phase analysis of gated SPECT MPI was used to assess LV dyssynchrony pre- and post-RFA. Among the 45 patients, 3 had gating errors, and thus 42 had SPECT phase analysis. Twenty-two patients (52.4%) had baseline LV dyssynchrony. Baseline LV dyssynchrony was more prominent in the patients with septal APs than in the patients with left or right APs (p < 0.05). RFA improved LV synchrony in the entire cohort and in the patients with septal APs (p < 0.01). Phase analysis of gated SPECT MPI demonstrated that LV mechanical dyssynchrony can be present in patients with WPW syndrome. Septal APs result in the greatest degree of LV mechanical dyssynchrony and afford the most benefit after RFA. This study supports further investigation in the relationship between electrical and mechanical activation using EPS and phase analysis of gated SPECT MPI.

Mechanical characterization of metallic nanowires by using a customized atomic microscope

NASA Astrophysics Data System (ADS)

Celik, Emrah

A new experimental method to characterize the mechanical properties of metallic nanowires is introduced. An accurate and fast mechanical characterization of nanowires requires simultaneous imaging and testing of nanowires. However, there exists no practical experimental procedure in the literature that provides a quantitative mechanical analysis and imaging of the nanowire specimens during mechanical testing. In this study, a customized atomic force microscope (AFM) is placed inside a scanning electron microscope (SEM) in order to locate the position of the nanowires. The tip of the atomic force microscope cantilever is utilized to bend and break the nanowires. The nanowires are prepared by electroplating of nickel ions into the nanoscale pores of the alumina membranes. Force versus bending displacement responses of these nanowires are measured experimentally and then compared against those of the finite element analysis and peridynamic simulations to extract their mechanical properties through an inverse approach. The average elastic modulus of nickel nanowires, which are extracted using finite element analysis and peridynamic simulations, varies between 220 GPa and 225 GPa. The elastic modulus of bulk nickel published in the literature is comparable to that of nickel nanowires. This observation agrees well with the previous findings on nanowires stating that the elastic modulus of nanowires with diameters over 100nm is similar to that of bulk counterparts. The average yield stress of nickel nanowires, which are extracted using finite element analysis and peridynamic simulations, is found to be between 3.6 GPa to 4.1 GPa. The average value of yield stress of nickel nanowires with 250nm diameter is significantly higher than that of bulk nickel. Higher yield stress of nickel nanowires observed in this study can be explained by the lower defect density of nickel nanowires when compared to their bulk counterparts. Deviation in the extracted mechanical properties is investigated by analyzing the major sources of uncertainty in the experimental procedure. The effects of the nanowire orientation, the loading position and the nanowire diameter on the mechanical test results are quantified using ANSYS simulations. Among all of these three sources of uncertainty investigated, the nanowire diameter has been found to have the most significant effect on the extracted mechanical properties.

Mechanisms of ketamine on mice hippocampi shown by gas chromatography-mass spectrometry-based metabolomic analysis.

PubMed

Lian, Bin; Xia, Jinjun; Yang, Xun; Zhou, Chanjuan; Gong, Xue; Gui, Siwen; Mao, Qiang; Wang, Ling; Li, Pengfei; Huang, Cheng; Qi, Xunzhong; Xie, Peng

2018-06-13

In the present study, we used a gas chromatography-mass spectrometry-based metabolomics method to evaluate the effects of ketamine on mice hippocampi. Multivariate statistical analysis and ingenuity pathway analysis were then used to identify and explore the potential mechanisms and biofunction of ketamine. Compared with the control (CON) group, 14 differential metabolites that involved amino acid metabolism, energy metabolism, and oxidative stress metabolism were identified. After combination with 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline-2,3-dione (NBQX) administration, six of the 14 metabolites remained significantly differentially expressed between the ketamine (KET) and KET+NBQX groups, including glycine, alanine, glutamine, aspartic acid, myoinositol, and ascorbate, whereas no difference was found in the levels of the other eight metabolites between the KET and KET+NBQX groups, including phosphate, 4-aminobutyric acid, urea, creatine, L-malic acid, galactinol, inosine, and aminomalonic. Our findings indicate that ketamine exerts antidepressant effects through an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid inhibition-dependent mechanism and a mechanism not affected by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid inhibition. Which provides further insight into the therapeutic mechanisms of ketamine in the hippocampus.

A Mid-Layer Model for Human Reliability Analysis: Understanding the Cognitive Causes of Human Failure Events

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

Stacey M. L. Hendrickson; April M. Whaley; Ronald L. Boring

The Office of Nuclear Regulatory Research (RES) is sponsoring work in response to a Staff Requirements Memorandum (SRM) directing an effort to establish a single human reliability analysis (HRA) method for the agency or guidance for the use of multiple methods. As part of this effort an attempt to develop a comprehensive HRA qualitative approach is being pursued. This paper presents a draft of the method’s middle layer, a part of the qualitative analysis phase that links failure mechanisms to performance shaping factors. Starting with a Crew Response Tree (CRT) that has identified human failure events, analysts identify potential failuremore » mechanisms using the mid-layer model. The mid-layer model presented in this paper traces the identification of the failure mechanisms using the Information-Diagnosis/Decision-Action (IDA) model and cognitive models from the psychological literature. Each failure mechanism is grouped according to a phase of IDA. Under each phase of IDA, the cognitive models help identify the relevant performance shaping factors for the failure mechanism. The use of IDA and cognitive models can be traced through fault trees, which provide a detailed complement to the CRT.« less

Revisiting an old concept: the coupled oscillator model for VCD. Part 2: implications of the generalised coupled oscillator mechanism for the VCD robustness concept.

PubMed

Nicu, Valentin Paul

2016-08-03

Using two illustrative examples it is shown that the generalised coupled oscillator (GCO) mechanism implies that the stability of the VCD sign computed for a given normal mode is not reflected by the magnitude of the ratio ζ between the rotational strength and dipole strength of the respective mode, i.e., the VCD robustness criterium proposed by Góbi and Magyarfalvi. The performed VCD GCO analysis brings further insight into the GCO mechanism and also into the VCD robustness concept. First, it shows that the GCO mechanism can be interpreted as a VCD resonance enhancement mechanism, i.e. very large VCD signals can be observed when the interacting molecular fragments are in favourable orientation. Second, it shows that the uncertainties observed in the computed VCD signs are associated to uncertainties in the relative orientation of the coupled oscillator fragments and/or to uncertainties in the predicted nuclear displacement vectors, i.e. not uncertainties in the computed magnetic dipole transition moments as was originally assumed. Since it is able to identify such situations easily, the VCD GCO analysis can be used as a VCD robustness analysis.

Systematic study of imidazoles inhibiting IDO1 via the integration of molecular mechanics and quantum mechanics calculations.

PubMed

Zou, Yi; Wang, Fang; Wang, Yan; Guo, Wenjie; Zhang, Yihua; Xu, Qiang; Lai, Yisheng

2017-05-05

Indoleamine 2,3-dioxygenase 1 (IDO1) is regarded as an attractive target for cancer immunotherapy. To rationalize the detailed interactions between IDO1 and its inhibitors at the atomic level, an integrated computational approach by combining molecular mechanics and quantum mechanics methods was employed in this report. Specifically, the binding modes of 20 inhibitors was initially investigated using the induced fit docking (IFD) protocol, which outperformed other two docking protocols in terms of correctly predicting ligand conformations. Secondly, molecular dynamics (MD) simulations and MM/PBSA free energy calculations were employed to determine the dynamic binding process and crucial residues were confirmed through close contact analysis, hydrogen-bond analysis and binding free energy decomposition calculations. Subsequent quantum mechanics and nonbonding interaction analysis were carried out to provide in-depth explanations on the critical role of those key residues, and Arg231 and 7-propionate of the heme group were major contributors to ligand binding, which lowed a great amount of interaction energy. We anticipate that these findings will be valuable for enzymatic studies and rational drug design. Copyright © 2017. Published by Elsevier Masson SAS.

A mid-layer model for human reliability analysis : understanding the cognitive causes of human failure events.

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

Shen, Song-Hua; Chang, James Y. H.; Boring,Ronald L.

2010-03-01

The Office of Nuclear Regulatory Research (RES) at the US Nuclear Regulatory Commission (USNRC) is sponsoring work in response to a Staff Requirements Memorandum (SRM) directing an effort to establish a single human reliability analysis (HRA) method for the agency or guidance for the use of multiple methods. As part of this effort an attempt to develop a comprehensive HRA qualitative approach is being pursued. This paper presents a draft of the method's middle layer, a part of the qualitative analysis phase that links failure mechanisms to performance shaping factors. Starting with a Crew Response Tree (CRT) that has identifiedmore » human failure events, analysts identify potential failure mechanisms using the mid-layer model. The mid-layer model presented in this paper traces the identification of the failure mechanisms using the Information-Diagnosis/Decision-Action (IDA) model and cognitive models from the psychological literature. Each failure mechanism is grouped according to a phase of IDA. Under each phase of IDA, the cognitive models help identify the relevant performance shaping factors for the failure mechanism. The use of IDA and cognitive models can be traced through fault trees, which provide a detailed complement to the CRT.« less

Computerized structural mechanics for 1990's: Advanced aircraft needs

NASA Technical Reports Server (NTRS)

Viswanathan, A. V.; Backman, B. F.

1989-01-01

The needs for computerized structural mechanics (CSM) as seen from the standpoint of the aircraft industry are discussed. These needs are projected into the 1990's with special focus on the new advanced materials. Preliminary design/analysis, research, and detail design/analysis are identified as major areas. The role of local/global analyses in these different areas is discussed. The lessons learned in the past are used as a basis for the design of a CSM framework that could modify and consolidate existing technology and include future developments in a rational and useful way. A philosophy is stated, and a set of analyses needs driven by the emerging advanced composites is enumerated. The roles of NASA, the universities, and the industry are identified. Finally, a set of rational research targets is recommended based on both the new types of computers and the increased complexity the industry faces. Computerized structural mechanics should be more than new methods in structural mechanics and numerical analyses. It should be a set of engineering applications software products that combines innovations in structural mechanics, numerical analysis, data processing, search and display features, and recent hardware advances and is organized in a framework that directly supports the design process.

Improved strength of silk fibers in Bombyx mori trimolters induced by an anti-juvenile hormone compound.

PubMed

Guo, Kaiyu; Dong, Zhaoming; Zhang, Yan; Wang, Dandan; Tang, Muya; Zhang, Xiaolu; Xia, Qingyou; Zhao, Ping

2018-05-01

Bombyx mori silk fibers with thin diameters have advantages of lightness and crease-resistance. Many studies have used anti-juvenile hormones to induce trimolters in order to generate thin silk; however, there has been comparatively little analysis of the morphology, structure and mechanical properties of trimolter silk. This study induced two kinds of trimolters by appling topically anti-juvenile hormones and obtained thin diameter silk. Scanning electron microscope (SEM), FTIR analysis, tensile mechanical testing, chitin staining were used to reveal that the morphology, conformation and mechanical property of the trimolter silk. Cocoon of trimolters were highly densely packed by thinner fibers and thus had small apertures. We found that the conformation of trimolter silk fibroin changed and formed more β-sheet structures. In addition, analysis of mechanical parameters yielded a higher Young's modulus and strength in trimolter silk than in the control. By chitin staining of silk gland, we postulated that the mechanical properties of trimolters' silk was enhanced greatly during to the structural changes of silk gland. We induced trimolters by anti-juvenile hormones and the resulting cocoons were more closely packed and had smaller silk fiber diameters. We found that the conformation of trimolters silk fibroin had a higher content of β-sheet structures and better mechanical properties. Our study revealed the structures and mechanical properties of trimolter silk, and provided a valuable reference to improve silk quality by influencing molting in silkworms. Copyright © 2018 Elsevier B.V. All rights reserved.

Learning mechanisms to limit medication administration errors.

PubMed

Drach-Zahavy, Anat; Pud, Dorit

2010-04-01

This paper is a report of a study conducted to identify and test the effectiveness of learning mechanisms applied by the nursing staff of hospital wards as a means of limiting medication administration errors. Since the influential report ;To Err Is Human', research has emphasized the role of team learning in reducing medication administration errors. Nevertheless, little is known about the mechanisms underlying team learning. Thirty-two hospital wards were randomly recruited. Data were collected during 2006 in Israel by a multi-method (observations, interviews and administrative data), multi-source (head nurses, bedside nurses) approach. Medication administration error was defined as any deviation from procedures, policies and/or best practices for medication administration, and was identified using semi-structured observations of nurses administering medication. Organizational learning was measured using semi-structured interviews with head nurses, and the previous year's reported medication administration errors were assessed using administrative data. The interview data revealed four learning mechanism patterns employed in an attempt to learn from medication administration errors: integrated, non-integrated, supervisory and patchy learning. Regression analysis results demonstrated that whereas the integrated pattern of learning mechanisms was associated with decreased errors, the non-integrated pattern was associated with increased errors. Supervisory and patchy learning mechanisms were not associated with errors. Superior learning mechanisms are those that represent the whole cycle of team learning, are enacted by nurses who administer medications to patients, and emphasize a system approach to data analysis instead of analysis of individual cases.

Analysis and Characterization of the Mechanical Structure for the I-Tracker of the Mu2e Experiment

NASA Astrophysics Data System (ADS)

De Lorenzis, L.; Grancagnolo, F.; L'Erario, A.; Maffezzoli, A.; Miccoli, A.; Rella, S.; Spedicato, M.; Zavarise, G.

2014-03-01

The design of a tracking detector for electrons in a magnetic field consisting of a drift chamber is discussed. The chosen materials for its construction must be light to minimize the effects of the subatomic particles interactions with the chamber walls. Low-density materials and very thin wall thicknesses are therefore needed. From a mechanical engineering point of view, it is important to analyse the drift chamber structure and define the conditions to which it is subject in terms of both mechanical loads and geometric constraints. The analysis of the structural response of the drift chamber has been performed through the Finite Element Method (FEM) as implemented in the commercial software ANSYS and its interface for the analysis for composite structures ACP (Ansys Composite Pre/Post).

Occupational Contact Dermatitis in Mechanics and Repairers Referred for Patch Testing: Retrospective Analysis From the North American Contact Dermatitis Group 1998-2014.

PubMed

Warshaw, Erin M; Hagen, Solveig L; Sasseville, Denis; Maibach, Howard I; DeKoven, Joel G; Belsito, Donald V; Fowler, Joseph F; Zug, Kathryn A; Taylor, James S; Mathias, C G Toby; Fransway, Anthony F; DeLeo, Vincent A; Marks, James G; Pratt, Melanie D; Zirwas, Matthew J; Storrs, Frances J

Contact dermatoses are common in mechanic and repair occupations. This study aimed to (1) estimate the prevalence of occupationally related contact dermatitis among mechanics/repairers patch tested from 1998 to 2014 by the North American Contact Dermatitis Group, (2) characterize responsible allergens and irritants, and their sources, and (3) compare results among 3 occupational subgroups (mechanics, electrical/electronic, and other). A cross-sectional analysis of patients patch tested by the North American Contact Dermatitis Group between 1998 and 2014. Of 38,784 patients patch tested, 691 (1.8%) were mechanics/repairers. Male sex (93.5%) and hand involvement (59.5%) were common overall. Occupationally related skin disease was more prevalent among vehicle and mobile equipment mechanics/repairers (52.7%) and other mechanics/repairers (41.4%) than electrical/electronic equipment mechanics/repairers (21.3%). Overall, carba mix, thiuram mix, and methylchloroisothiazolone/methylisothiazolone were the most common occupation-related clinically relevant allergens. Gloves, automotive vehicles, solvents, oils, lubricants, and fuels were the most common sources of responsible allergens. Common occupationally related allergens included rubber accelerators and the preservative methylchloroisothiazolone/methylisothiazolone.

Jet-A reaction mechanism study for combustion application

NASA Technical Reports Server (NTRS)

Lee, Chi-Ming; Kundu, Krishna; Acosta, Waldo

1991-01-01

Simplified chemical kinetic reaction mechanisms for the combustion of Jet A fuel was studied. Initially, 40 reacting species and 118 elementary chemical reactions were chosen based on a literature review. Through a sensitivity analysis with the use of LSENS General Kinetics and Sensitivity Analysis Code, 16 species and 21 elementary chemical reactions were determined from this study. This mechanism is first justified by comparison of calculated ignition delay time with the available shock tube data, then it is validated by comparison of calculated emissions from the plug flow reactor code with in-house flame tube data.

Advances and trends in computational structural mechanics

NASA Technical Reports Server (NTRS)

Noor, A. K.

1986-01-01

Recent developments in computational structural mechanics are reviewed with reference to computational needs for future structures technology, advances in computational models for material behavior, discrete element technology, assessment and control of numerical simulations of structural response, hybrid analysis, and techniques for large-scale optimization. Research areas in computational structural mechanics which have high potential for meeting future technological needs are identified. These include prediction and analysis of the failure of structural components made of new materials, development of computational strategies and solution methodologies for large-scale structural calculations, and assessment of reliability and adaptive improvement of response predictions.

Sequential allosteric mechanism of ATP hydrolysis by the CCT/TRiC chaperone is revealed through Arrhenius analysis

PubMed Central

Gruber, Ranit; Levitt, Michael; Horovitz, Amnon

2017-01-01

Knowing the mechanism of allosteric switching is important for understanding how molecular machines work. The CCT/TRiC chaperonin nanomachine undergoes ATP-driven conformational changes that are crucial for its folding function. Here, we demonstrate that insight into its allosteric mechanism of ATP hydrolysis can be achieved by Arrhenius analysis. Our results show that ATP hydrolysis triggers sequential ‟conformational waves.” They also suggest that these waves start from subunits CCT6 and CCT8 (or CCT3 and CCT6) and proceed clockwise and counterclockwise, respectively. PMID:28461478

Sequential allosteric mechanism of ATP hydrolysis by the CCT/TRiC chaperone is revealed through Arrhenius analysis.

PubMed

Gruber, Ranit; Levitt, Michael; Horovitz, Amnon

2017-05-16

Knowing the mechanism of allosteric switching is important for understanding how molecular machines work. The CCT/TRiC chaperonin nanomachine undergoes ATP-driven conformational changes that are crucial for its folding function. Here, we demonstrate that insight into its allosteric mechanism of ATP hydrolysis can be achieved by Arrhenius analysis. Our results show that ATP hydrolysis triggers sequential ‟conformational waves." They also suggest that these waves start from subunits CCT6 and CCT8 (or CCT3 and CCT6) and proceed clockwise and counterclockwise, respectively.

Using high speed smartphone cameras and video analysis techniques to teach mechanical wave physics

NASA Astrophysics Data System (ADS)

Bonato, Jacopo; Gratton, Luigi M.; Onorato, Pasquale; Oss, Stefano

2017-07-01

We propose the use of smartphone-based slow-motion video analysis techniques as a valuable tool for investigating physics concepts ruling mechanical wave propagation. The simple experimental activities presented here, suitable for both high school and undergraduate students, allows one to measure, in a simple yet rigorous way, the speed of pulses along a spring and the period of transverse standing waves generated in the same spring. These experiments can be helpful in addressing several relevant concepts about the physics of mechanical waves and in overcoming some of the typical student misconceptions in this same field.

Analysis of Mechanical and Thermogravimetric Properties of Composite Materials Based on PVA/MWCNT and Styrene-Acrylic Copolymer/MWCNT

NASA Astrophysics Data System (ADS)

Volynets, N. I.; Poddubskaya, O. G.; Demidenko, M. I.; Lyubimov, A. G.; Kuzhir, P. P.; Suslyaev, V. I.; Pletnev, M. A.; Zicans, Janis

2017-08-01

Mechanical and thermogravimetric properties of polymer composite materials with various concentrations of multiwalled carbon nanotubes effectively shielding radiation in the radio frequency (20 Hz - 1 MHz) and microwave (26-36 GHz) frequency ranges are studied. As a matrix, widely available polymeric materials, such as polyvinyl acetate and styrene-acrylate, were used in the form of dispersions. From the analysis of the obtained experimental data, it was shown that the introduction of carbon nanotubes into the polymer matrix makes it possible to increase mechanical properties and thermal stability of composite materials.

Gesellschaft fuer angewandte Mathematik und Mechanik, Annual Scientific Meeting, Universitaet Regensburg, Regensburg, West Germany, April 16-19, 1984, Proceedings

NASA Astrophysics Data System (ADS)

Problems in applied mathematics and mechanics are addressed in reviews and reports. Areas covered are vibration and stability, elastic and plastic mechanics, fluid mechanics, the numerical treatment of differential equations (general theory and finite-element methods in particular), optimization, decision theory, stochastics, actuarial mathematics, applied analysis and mathematical physics, and numerical analysis. Included are major lectures on separated flows, the transition regime of rarefied-gas dynamics, recent results in nonlinear elasticity, fluid-elastic vibration, the new computer arithmetic, and unsteady wave propagation in layered elastic bodies.

Analysis of rolling contact spall life in 440 C steel bearing rims

NASA Technical Reports Server (NTRS)

Bastias, P. C.; Bhargava, V.; Bower, A. P.; Du, J.; Gupta, V.; Hahn, G. T.; Kulkarni, S. M.; Kumar, A. M.; Leng, X.; Rubin, C. A.

1991-01-01

The results of a two year study of the mechanisms of spall failure in the HPOTP bearings are described. The objective was to build a foundation for detailed analyses of the contact life in terms of: cyclic plasticity, contact mechanics, spall nucleation, and spall growth. Since the laboratory rolling contact testing is carried out in the 3 ball/rod contact fatigue testing machine, the analysis of the contacts and contact lives produced in this machine received attention. The results from the experimentally observed growth lives are compared with calculated predictions derived from the fracture mechanics calculations.

The initiation, propagation, and effect of matrix microcracks in cross-ply and related laminates

NASA Technical Reports Server (NTRS)

Nairn, John A.; Hu, Shoufeng; Liu, Siulie; Bark, Jong

1991-01-01

Recently, a variational mechanics approach was used to determine the thermoelastic stress state in cracked laminates. Described here is a generalization of the variational mechanics techniques to handle other cross-ply laminates, related laminates, and to account for delaminations emanating from microcrack tips. Microcracking experiments on Hercules 3501-6/AS4 carbon fiber/epoxy laminates show a staggered cracking pattern. These results can be explained by the variational mechanics analysis. The analysis of delaminations emanating from microcrack tips has resulted in predictions about the structural and material variables controlling competition between microcracking and delamination failure modes.

Research in progress in applied mathematics, numerical analysis, fluid mechanics, and computer science

NASA Technical Reports Server (NTRS)

1994-01-01

This report summarizes research conducted at the Institute for Computer Applications in Science and Engineering in applied mathematics, fluid mechanics, and computer science during the period October 1, 1993 through March 31, 1994. The major categories of the current ICASE research program are: (1) applied and numerical mathematics, including numerical analysis and algorithm development; (2) theoretical and computational research in fluid mechanics in selected areas of interest to LaRC, including acoustics and combustion; (3) experimental research in transition and turbulence and aerodynamics involving LaRC facilities and scientists; and (4) computer science.

Insight into the novel inhibition mechanism of apigenin to Pneumolysin by molecular modeling

NASA Astrophysics Data System (ADS)

Niu, Xiaodi; Yang, Yanan; Song, Meng; Wang, Guizhen; Sun, Lin; Gao, Yawen; Wang, Hongsu

2017-11-01

In this study, the mechanism of apigenin inhibition was explored using molecular modelling, binding energy calculation, and mutagenesis assays. Energy decomposition analysis indicated that apigenin binds in the gap between domains 3 and 4 of PLY. Using principal component analysis, we found that binding of apigenin to PLY weakens the motion of domains 3 and 4. Consequently, these domains cannot complete the transition from monomer to oligomer, thereby blocking oligomerisation of PLY and counteracting its haemolytic activity. This inhibitory mechanism was confirmed by haemolysis assays, and these findings will promote the future development of an antimicrobial agent.

An Analysis of Agricultural Mechanics Safety Practices in Agricultural Science Laboratories.

ERIC Educational Resources Information Center

Swan, Michael K.

North Dakota secondary agricultural mechanics instructors were surveyed regarding instructional methods and materials, safety practices, and equipment used in the agricultural mechanics laboratory. Usable responses were received from 69 of 89 instructors via self-administered mailed questionnaires. Findings were consistent with results of similar…

Mechanisms of Diagonal-Shear Failure in Reinforced Concrete Beams analyzed by AE-SiGMA

NASA Astrophysics Data System (ADS)

Ohno, Kentaro; Shimozono, Shinichiro; Sawada, Yosuke; Ohtsu, Masayasu

Serious shear failures in reinforced concrete (RC) structures were reported in the Hanshin-Awaji Earthquake. In particular, it was demonstrated that a diagonal-shear failure could lead to disastrous damage. However, mechanisms of the diagonal-shear failure in RC beams have not been completely clarified yet. In this study, the diagonal-shear failure in RC beams is investigated, applying acoustic emission (AE) method. To identify source mechanisms of AE signals, SiGMA (Simplified Green's functions for Moment tensor Analysis) procedure was applied. Prior to four-point bending tests of RC beams, theoretical waveforms were calculated to determine the optimal arrangement of AE sensors. Then, cracking mechanisms in experiments were investigated by applying the SiGMA procedure to AE waveforms. From results of the SiGMA analysis, dominant motions of micro-cracks are found to be of shear crack in all the loading stages. As the load increased, the number of tensile cracks increased and eventually the diagonal-shear failure occurred in the shear span. Prior to final failure, AE cluster of micro-cracks was intensely observed in the shear span. To classify AE sources into tensile and shear cracks, AE parameter analysis was also applied. As a result, most of AE hits are classified into tensile cracks. The difference between results obtained by the AE parameter analysis and by the SiGMA analysis is investigated and discussed.

Deflection Analysis of the Space Shuttle External Tank Door Drive Mechanism

NASA Technical Reports Server (NTRS)

Tosto, Michael A.; Trieu, Bo C.; Evernden, Brent A.; Hope, Drew J.; Wong, Kenneth A.; Lindberg, Robert E.

2008-01-01

Upon observing an abnormal closure of the Space Shuttle s External Tank Doors (ETD), a dynamic model was created in MSC/ADAMS to conduct deflection analyses of the Door Drive Mechanism (DDM). For a similar analysis, the traditional approach would be to construct a full finite element model of the mechanism. The purpose of this paper is to describe an alternative approach that models the flexibility of the DDM using a lumped parameter approximation to capture the compliance of individual parts within the drive linkage. This approach allows for rapid construction of a dynamic model in a time-critical setting, while still retaining the appropriate equivalent stiffness of each linkage component. As a validation of these equivalent stiffnesses, finite element analysis (FEA) was used to iteratively update the model towards convergence. Following this analysis, deflections recovered from the dynamic model can be used to calculate stress and classify each component s deformation as either elastic or plastic. Based on the modeling assumptions used in this analysis and the maximum input forcing condition, two components in the DDM show a factor of safety less than or equal to 0.5. However, to accurately evaluate the induced stresses, additional mechanism rigging information would be necessary to characterize the input forcing conditions. This information would also allow for the classification of stresses as either elastic or plastic.

Computed tomography-based finite element analysis to assess fracture risk and osteoporosis treatment

PubMed Central

Imai, Kazuhiro

2015-01-01

Finite element analysis (FEA) is a computer technique of structural stress analysis and developed in engineering mechanics. FEA has developed to investigate structural behavior of human bones over the past 40 years. When the faster computers have acquired, better FEA, using 3-dimensional computed tomography (CT) has been developed. This CT-based finite element analysis (CT/FEA) has provided clinicians with useful data. In this review, the mechanism of CT/FEA, validation studies of CT/FEA to evaluate accuracy and reliability in human bones, and clinical application studies to assess fracture risk and effects of osteoporosis medication are overviewed. PMID:26309819

Multidisciplinary analysis and design of printed wiring boards

NASA Astrophysics Data System (ADS)

Fulton, Robert E.; Hughes, Joseph L.; Scott, Waymond R., Jr.; Umeagukwu, Charles; Yeh, Chao-Pin

1991-04-01

Modern printed wiring board design depends on electronic prototyping using computer-based simulation and design tools. Existing electrical computer-aided design (ECAD) tools emphasize circuit connectivity with only rudimentary analysis capabilities. This paper describes a prototype integrated PWB design environment denoted Thermal Structural Electromagnetic Testability (TSET) being developed at Georgia Tech in collaboration with companies in the electronics industry. TSET provides design guidance based on enhanced electrical and mechanical CAD capabilities including electromagnetic modeling testability analysis thermal management and solid mechanics analysis. TSET development is based on a strong analytical and theoretical science base and incorporates an integrated information framework and a common database design based on a systematic structured methodology.

Delamination and debonding of materials

NASA Technical Reports Server (NTRS)

Johnson, W. S. (Editor)

1985-01-01

The general topics consist of stress analysis, mechanical behavior, and fractography/NDI of composite laminates. Papers are presented on a dynamic hybrid finite-element analysis for interfacial cracks in composites, energy release rate during delamination crack growth in composite laminates, matrix deformation and fracture in graphite-reinforced epoxies, and the role of delamination and damage development on the strength of thick notched laminates. In addition, consideration is given to a new ply model for interlaminar stress analysis, a fracture mechanics approach for designing adhesively bonded joints, the analysis of local delaminations and their influence on composite laminate behavior, and moisture and temperature effects on the mixed-mode delamination fracture of unidirectional graphite/epoxy.

3D Material Response Analysis of PICA Pyrolysis Experiments

NASA Technical Reports Server (NTRS)

Oliver, A. Brandon

2017-01-01

The PICA decomposition experiments of Bessire and Minton are investigated using 3D material response analysis. The steady thermoelectric equations have been added to the CHAR code to enable analysis of the Joule-heated experiments and the DAKOTA optimization code is used to define the voltage boundary condition that yields the experimentally observed temperature response. This analysis has identified a potential spatial non-uniformity in the PICA sample temperature driven by the cooled copper electrodes and thermal radiation from the surface of the test article (Figure 1). The non-uniformity leads to a variable heating rate throughout the sample volume that has an effect on the quantitative results of the experiment. Averaging the results of integrating a kinetic reaction mechanism with the heating rates seen across the sample volume yield a shift of peak species production to lower temperatures that is more significant for higher heating rates (Figure 2) when compared to integrating the same mechanism at the reported heating rate. The analysis supporting these conclusions will be presented along with a proposed analysis procedure that permits quantitative use of the existing data. Time permitting, a status on the in-development kinetic decomposition mechanism based on this data will be presented as well.

Guidelines for Proof Test Analysis

NASA Technical Reports Server (NTRS)

Chell, G. G.; McClung, R. C.; Kuhlman, C. J.; Russell, D. A.; Garr, K.; Donnelly, B.

1999-01-01

These guidelines integrate state-of-the-art elastic-plastic fracture mechanics (EPFM) and proof test implementation issues into a comprehensive proof test analysis procedure in the form of a road map which identifies the types of data, fracture mechanics based parameters, and calculations needed to perform flaw screening and minimum proof load analyses of fracture critical components. Worked examples are presented to illustrate the application of the road map to proof test analysis. The state-of-the art fracture technology employed in these guidelines is based on the EPFM parameter, J, and a pictorial representation of a J fracture analysis, called the failure assessment diagram (FAD) approach. The recommended fracture technology is validated using finite element J results, and laboratory and hardware fracture test results on the nickel-based superalloy Inconel 718, the aluminum alloy 2024-T3511, and ferritic pressure vessel steels. In all cases the laboratory specimens and hardware failed by ductile mechanisms. Advanced proof test analyses involving probability analysis and multiple-cycle proof testing (MCPT) are addressed. Finally, recommendations are provided on how to account for the effects of the proof test overload on subsequent service fatigue and fracture behaviors.

Expression and mutational analysis of Cip/Kip family in early glottic cancer.

PubMed

Kim, D-K; Lee, J H; Lee, O J; Park, C H

2015-02-01

Genetic alteration of cyclin-dependent kinase inhibitors has been associated with carcinogenesis mechanisms in various organs. This study aimed to evaluate the expression and mutational analysis of Cip/Kip family cyclin-dependent kinase inhibitors (p21CIP1/WAF1, p27KIP1 and p57KIP2) in early glottic cancer. Expressions of Cip/Kip family and p53 were determined by quantitative reverse transcription polymerase chain reaction and densitometry. For the analysis of p21 inactivation, sequence alteration was assessed using single-strand conformational polymorphism polymerase chain reaction. Additionally, the inactivation mechanism of p27 and p57 were investigated using DNA methylation analysis. Reduced expression of p27 and p57 were detected in all samples, whereas the expression of p21 was incompletely down-regulated in 6 of 11 samples. Additionally, single-strand conformational polymorphism polymerase chain reaction analysis showed the p53 mutation at exon 6. Methylation of p27 and p57 was detected by DNA methylation assay. Our results suggest that the Cip/Kip family may have a role as a molecular mechanism of carcinogenesis in early glottic cancer.

Validation of a new method for finding the rotational axes of the knee using both marker-based roentgen stereophotogrammetric analysis and 3D video-based motion analysis for kinematic measurements.

PubMed

Roland, Michelle; Hull, M L; Howell, S M

2011-05-01

In a previous paper, we reported the virtual axis finder, which is a new method for finding the rotational axes of the knee. The virtual axis finder was validated through simulations that were subject to limitations. Hence, the objective of the present study was to perform a mechanical validation with two measurement modalities: 3D video-based motion analysis and marker-based roentgen stereophotogrammetric analysis (RSA). A two rotational axis mechanism was developed, which simulated internal-external (or longitudinal) and flexion-extension (FE) rotations. The actual axes of rotation were known with respect to motion analysis and RSA markers within ± 0.0006 deg and ± 0.036 mm and ± 0.0001 deg and ± 0.016 mm, respectively. The orientation and position root mean squared errors for identifying the longitudinal rotation (LR) and FE axes with video-based motion analysis (0.26 deg, 0.28 m, 0.36 deg, and 0.25 mm, respectively) were smaller than with RSA (1.04 deg, 0.84 mm, 0.82 deg, and 0.32 mm, respectively). The random error or precision in the orientation and position was significantly better (p=0.01 and p=0.02, respectively) in identifying the LR axis with video-based motion analysis (0.23 deg and 0.24 mm) than with RSA (0.95 deg and 0.76 mm). There was no significant difference in the bias errors between measurement modalities. In comparing the mechanical validations to virtual validations, the virtual validations produced comparable errors to those of the mechanical validation. The only significant difference between the errors of the mechanical and virtual validations was the precision in the position of the LR axis while simulating video-based motion analysis (0.24 mm and 0.78 mm, p=0.019). These results indicate that video-based motion analysis with the equipment used in this study is the superior measurement modality for use with the virtual axis finder but both measurement modalities produce satisfactory results. The lack of significant differences between validation techniques suggests that the virtual sensitivity analysis previously performed was appropriately modeled. Thus, the virtual axis finder can be applied with a thorough understanding of its errors in a variety of test conditions.

Investigating the different mechanisms of genotoxic and non-genotoxic carcinogens by a gene set analysis.

PubMed

Lee, Won Jun; Kim, Sang Cheol; Lee, Seul Ji; Lee, Jeongmi; Park, Jeong Hill; Yu, Kyung-Sang; Lim, Johan; Kwon, Sung Won

2014-01-01

Based on the process of carcinogenesis, carcinogens are classified as either genotoxic or non-genotoxic. In contrast to non-genotoxic carcinogens, many genotoxic carcinogens have been reported to cause tumor in carcinogenic bioassays in animals. Thus evaluating the genotoxicity potential of chemicals is important to discriminate genotoxic from non-genotoxic carcinogens for health care and pharmaceutical industry safety. Additionally, investigating the difference between the mechanisms of genotoxic and non-genotoxic carcinogens could provide the foundation for a mechanism-based classification for unknown compounds. In this study, we investigated the gene expression of HepG2 cells treated with genotoxic or non-genotoxic carcinogens and compared their mechanisms of action. To enhance our understanding of the differences in the mechanisms of genotoxic and non-genotoxic carcinogens, we implemented a gene set analysis using 12 compounds for the training set (12, 24, 48 h) and validated significant gene sets using 22 compounds for the test set (24, 48 h). For a direct biological translation, we conducted a gene set analysis using Globaltest and selected significant gene sets. To validate the results, training and test compounds were predicted by the significant gene sets using a prediction analysis for microarrays (PAM). Finally, we obtained 6 gene sets, including sets enriched for genes involved in the adherens junction, bladder cancer, p53 signaling pathway, pathways in cancer, peroxisome and RNA degradation. Among the 6 gene sets, the bladder cancer and p53 signaling pathway sets were significant at 12, 24 and 48 h. We also found that the DDB2, RRM2B and GADD45A, genes related to the repair and damage prevention of DNA, were consistently up-regulated for genotoxic carcinogens. Our results suggest that a gene set analysis could provide a robust tool in the investigation of the different mechanisms of genotoxic and non-genotoxic carcinogens and construct a more detailed understanding of the perturbation of significant pathways.

Investigating the Different Mechanisms of Genotoxic and Non-Genotoxic Carcinogens by a Gene Set Analysis

PubMed Central

Lee, Won Jun; Kim, Sang Cheol; Lee, Seul Ji; Lee, Jeongmi; Park, Jeong Hill; Yu, Kyung-Sang; Lim, Johan; Kwon, Sung Won

2014-01-01

Based on the process of carcinogenesis, carcinogens are classified as either genotoxic or non-genotoxic. In contrast to non-genotoxic carcinogens, many genotoxic carcinogens have been reported to cause tumor in carcinogenic bioassays in animals. Thus evaluating the genotoxicity potential of chemicals is important to discriminate genotoxic from non-genotoxic carcinogens for health care and pharmaceutical industry safety. Additionally, investigating the difference between the mechanisms of genotoxic and non-genotoxic carcinogens could provide the foundation for a mechanism-based classification for unknown compounds. In this study, we investigated the gene expression of HepG2 cells treated with genotoxic or non-genotoxic carcinogens and compared their mechanisms of action. To enhance our understanding of the differences in the mechanisms of genotoxic and non-genotoxic carcinogens, we implemented a gene set analysis using 12 compounds for the training set (12, 24, 48 h) and validated significant gene sets using 22 compounds for the test set (24, 48 h). For a direct biological translation, we conducted a gene set analysis using Globaltest and selected significant gene sets. To validate the results, training and test compounds were predicted by the significant gene sets using a prediction analysis for microarrays (PAM). Finally, we obtained 6 gene sets, including sets enriched for genes involved in the adherens junction, bladder cancer, p53 signaling pathway, pathways in cancer, peroxisome and RNA degradation. Among the 6 gene sets, the bladder cancer and p53 signaling pathway sets were significant at 12, 24 and 48 h. We also found that the DDB2, RRM2B and GADD45A, genes related to the repair and damage prevention of DNA, were consistently up-regulated for genotoxic carcinogens. Our results suggest that a gene set analysis could provide a robust tool in the investigation of the different mechanisms of genotoxic and non-genotoxic carcinogens and construct a more detailed understanding of the perturbation of significant pathways. PMID:24497971

Computer aided analysis and optimization of mechanical system dynamics

NASA Technical Reports Server (NTRS)

Haug, E. J.

1984-01-01

The purpose is to outline a computational approach to spatial dynamics of mechanical systems that substantially enlarges the scope of consideration to include flexible bodies, feedback control, hydraulics, and related interdisciplinary effects. Design sensitivity analysis and optimization is the ultimate goal. The approach to computer generation and solution of the system dynamic equations and graphical methods for creating animations as output is outlined.

A variational principle for compressible fluid mechanics: Discussion of the multi-dimensional theory

NASA Technical Reports Server (NTRS)

Prozan, R. J.

1982-01-01

The variational principle for compressible fluid mechanics previously introduced is extended to two dimensional flow. The analysis is stable, exactly conservative, adaptable to coarse or fine grids, and very fast. Solutions for two dimensional problems are included. The excellent behavior and results lend further credence to the variational concept and its applicability to the numerical analysis of complex flow fields.

Practical Applications of Fracture Mechanics

DTIC Science & Technology

1980-05-01

Department British AerospaceRoyal Aircraft Establishment Manchester DivisioFarnborough, Hampshire United Kingdom n U nited K ingdom Anit e r Kin1o Francis...Bulkhead (Grange) 385 (6) Crack Propagation Analysis of Flat Stiffened Pa,"is (Schwarmann) 3-88 (7) Crack Propagation Analysis of Pressurized Fusel:. e ...modeling basis for microcrack growth. Major issues as to the applicability of fracture mechanic. e ,"thodoloqy, surface retardation due to machining

Influence of natural fibers on the phase transitions in high-density polyethylene composites using dynamic mechanical analysis

Treesearch

Mehdi Tajvidi; Robert H. Falk; John C. Hermanson; Colin Felton

2003-01-01

Dynamic mechanical analysis was employed to evaluate the performance of various natural fibers in high-density polyethylene composites. Kenaf, newsprint, rice hulls, and wood flour were sources of fiber. Composites were made at 25 percent and 50 percent by weight fiber contents. Maleic anhydride modified polyethylene was also added at 1:25 ratio to the fiber....

Effects of Crimped Fiber Paths on Mixed Mode Delamination Behaviors in Woven Fabric Composites

DTIC Science & Technology

2016-09-01

continuum finite - element models. Three variations of a plain-woven fabric architecture—each of which had different crimped fiber paths—were considered... Finite - Element Analysis Fracture Mechanics Fracture Toughness Mixed Modes Strain Energy Release Rate 16. SECURITY...polymer FB Fully balanced laminate FEA Finite - element analysis FTCM Fracture toughness conversion mechanism G Shear modulus GI, GII, GIII Mode

Influence of Aluminum Passivation on the Reaction Mechanism: Flame Propagation Studies

DTIC Science & Technology

2009-01-01

synthesis and characterization of Al nanoparticles without an oxide shell is presented in refs 15- 18. In summary, SEM, thermogravimetric analysis (TGA) and...al.1 examined the oxidation behavior of ultrafine grain aluminum powder using Rutherford back- scattering spectrometry, thermogravimetric analysis , and...to opposite predictions in nanoparticle design. The diffusion mechanism suggests that the reduction Dr complete elimination of the oxide shell will

In situ MEMS testing: correlation of high-resolution X-ray diffraction with mechanical experiments and finite element analysis.

PubMed

Schifferle, Andreas; Dommann, Alex; Neels, Antonia

2017-01-01

New methods are needed in microsystems technology for evaluating microelectromechanical systems (MEMS) because of their reduced size. The assessment and characterization of mechanical and structural relations of MEMS are essential to assure the long-term functioning of devices, and have a significant impact on design and fabrication. Within this study a concept for the investigation of mechanically loaded MEMS materials on an atomic level is introduced, combining high-resolution X-ray diffraction (HRXRD) measurements with finite element analysis (FEA) and mechanical testing. In situ HRXRD measurements were performed on tensile loaded single crystal silicon (SCSi) specimens by means of profile scans and reciprocal space mapping (RSM) on symmetrical (004) and (440) reflections. A comprehensive evaluation of the rather complex XRD patterns and features was enabled by the correlation of measured with simulated, 'theoretical' patterns. Latter were calculated by a specifically developed, simple and fast approach on the basis of continuum mechanical relations. Qualitative and quantitative analysis confirmed the admissibility and accuracy of the presented method. In this context [001] Poisson's ratio was determined providing an error of less than 1.5% with respect to analytical prediction. Consequently, the introduced procedure contributes to further going investigations of weak scattering being related to strain and defects in crystalline structures and therefore supports investigations on materials and devices failure mechanisms.

In situ MEMS testing: correlation of high-resolution X-ray diffraction with mechanical experiments and finite element analysis

PubMed Central

Schifferle, Andreas; Dommann, Alex; Neels, Antonia

2017-01-01

Abstract New methods are needed in microsystems technology for evaluating microelectromechanical systems (MEMS) because of their reduced size. The assessment and characterization of mechanical and structural relations of MEMS are essential to assure the long-term functioning of devices, and have a significant impact on design and fabrication. Within this study a concept for the investigation of mechanically loaded MEMS materials on an atomic level is introduced, combining high-resolution X-ray diffraction (HRXRD) measurements with finite element analysis (FEA) and mechanical testing. In situ HRXRD measurements were performed on tensile loaded single crystal silicon (SCSi) specimens by means of profile scans and reciprocal space mapping (RSM) on symmetrical (004) and (440) reflections. A comprehensive evaluation of the rather complex XRD patterns and features was enabled by the correlation of measured with simulated, ‘theoretical’ patterns. Latter were calculated by a specifically developed, simple and fast approach on the basis of continuum mechanical relations. Qualitative and quantitative analysis confirmed the admissibility and accuracy of the presented method. In this context [001] Poisson’s ratio was determined providing an error of less than 1.5% with respect to analytical prediction. Consequently, the introduced procedure contributes to further going investigations of weak scattering being related to strain and defects in crystalline structures and therefore supports investigations on materials and devices failure mechanisms. PMID:28533825

Constitutive model of friction stir weld with consideration of its inhomogeneous mechanical properties

NASA Astrophysics Data System (ADS)

Zhang, Ling; Min, Junying; Wang, Bin; Lin, Jianping; Li, Fangfang; Liu, Jing

2016-03-01

In practical engineering, finite element(FE) modeling for weld seam is commonly simplified by neglecting its inhomogeneous mechanical properties. This will cause a significant loss in accuracy of FE forming analysis, in particular, for friction stir welded(FSW) blanks due to the large width and good formability of its weld seam. The inhomogeneous mechanical properties across weld seam need to be well characterized for an accurate FE analysis. Based on a similar AA5182 FSW blank, the metallographic observation and micro-Vickers hardness analysis upon the weld cross-section are performed to identify the interfaces of different sub-zones, i.e., heat affected zone(HAZ), thermal-mechanically affected zone(TMAZ) and weld nugget(WN). Based on the rule of mixture and hardness distribution, a constitutive model is established for each sub-zone to characterize the inhomogeneous mechanical properties across the weld seam. Uniaxial tensile tests of the AA5182 FSW blank are performed with the aid of digital image correlation(DIC) techniques. Experimental local stress-strain curves are obtained for different weld sub-zones. The experimental results show good agreement with those derived from the constitutive models, which demonstrates the feasibility and accuracy of these models. The proposed research gives an accurate characterization of inhomogeneous mechanical properties across the weld seam produced by FSW, which provides solutions for improving the FE simulation accuracy of FSW sheet forming.

Parametric Design and Mechanical Analysis of Beams based on SINOVATION

NASA Astrophysics Data System (ADS)

Xu, Z. G.; Shen, W. D.; Yang, D. Y.; Liu, W. M.

2017-07-01

In engineering practice, engineer needs to carry out complicated calculation when the loads on the beam are complex. The processes of analysis and calculation take a lot of time and the results are unreliable. So VS2005 and ADK are used to develop a software for beams design based on the 3D CAD software SINOVATION with C ++ programming language. The software can realize the mechanical analysis and parameterized design of various types of beams and output the report of design in HTML format. Efficiency and reliability of design of beams are improved.

Thermal Degradation Mechanism of a Thermostable Polyester Stabilized with an Open-Cage Oligomeric Silsesquioxane

PubMed Central

Gozalbo, Ana; Mestre, Sergio; Sanz, Vicente

2017-01-01

A polyester composite was prepared through the polymerization of an unsaturated ester resin with styrene and an open-cage oligomeric silsesquioxane with methacrylate groups. The effect of the open-cage oligomeric silsesquioxane on the thermal stability of the thermostable polyester was studied using both thermogravimetric analysis and differential thermal analysis. The results showed that the methacryl oligomeric silsesquioxane improved the thermal stability of the polyester. The decomposition mechanism of the polyester/oligomer silsesquioxane composite was proposed by Fourier transform infrared spectroscopy (FTIR) analysis of the volatiles. PMID:29295542

Anti-wear Mechanism Analysis of Nano-CaCO3 Additives

NASA Astrophysics Data System (ADS)

Xu, Zhen; Sun, Junfeng

2018-06-01

In this paper, the wear test was carried on with cylinder piston by the wear test device, receiving the results of the piston ring wear and abrasive characteristics by monitoring the wear process, the thesis analysis and put forward the nano-CaCO3 lubricating oil additive anti wear mechanism by the ferrography analysis technology, and provide the technical reference for the relevant measures to reduce wear and the friction, and provide reference value for further study on the related theories of reducing wear and reducing friction.

Fluid mechanics and mass transfer in melt crystal growth: Analysis of the floating zone and vertical Bridgman processes

NASA Technical Reports Server (NTRS)

Brown, R. A.

1986-01-01

This research program focuses on analysis of the transport mechanisms in solidification processes, especially one of interest to the Microgravity Sciences and Applications Program of NASA. Research during the last year has focused on analysis of the dynamics of the floating zone process for growth of small-scale crystals, on studies of the effect of applied magnetic fields on convection and solute segregation in directional solidification, and on the dynamics of microscopic cell formation in two-dimensional solidification of binary alloys. Significant findings are given.

Portfolio optimization problem with nonidentical variances of asset returns using statistical mechanical informatics.

PubMed

Shinzato, Takashi

2016-12-01

The portfolio optimization problem in which the variances of the return rates of assets are not identical is analyzed in this paper using the methodology of statistical mechanical informatics, specifically, replica analysis. We defined two characteristic quantities of an optimal portfolio, namely, minimal investment risk and investment concentration, in order to solve the portfolio optimization problem and analytically determined their asymptotical behaviors using replica analysis. Numerical experiments were also performed, and a comparison between the results of our simulation and those obtained via replica analysis validated our proposed method.

Portfolio optimization problem with nonidentical variances of asset returns using statistical mechanical informatics

NASA Astrophysics Data System (ADS)

Shinzato, Takashi

2016-12-01

The portfolio optimization problem in which the variances of the return rates of assets are not identical is analyzed in this paper using the methodology of statistical mechanical informatics, specifically, replica analysis. We defined two characteristic quantities of an optimal portfolio, namely, minimal investment risk and investment concentration, in order to solve the portfolio optimization problem and analytically determined their asymptotical behaviors using replica analysis. Numerical experiments were also performed, and a comparison between the results of our simulation and those obtained via replica analysis validated our proposed method.

Agricultural Science and Mechanics I & II. Task Analyses. Competency-Based Education.

ERIC Educational Resources Information Center

Henrico County Public Schools, Glen Allen, VA. Virginia Vocational Curriculum Center.

This task analysis guide is intended to help teachers and administrators develop instructional materials and implement competency-based education in the agricultural science and mechanics courses. Section 1 contains a validated task inventory for agricultural science and mechanics I and II. For each task, applicable information pertaining to…

Photoredox Catalysis: The Need to Elucidate the Photochemical Mechanism.

PubMed

Marchini, Marianna; Bergamini, Giacomo; Cozzi, Pier Giorgio; Ceroni, Paola; Balzani, Vincenzo

2017-10-09

The photocatalytic mechanism reported in a recent Communication to produce the radical anion of pyrenes postulates a highly endergonic electron transfer process. An analysis of the thermodynamics is reported together with the proposal of an alternative thermodynamically feasible mechanism. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Selected physical and mechanical properties of moso bamboo (Phyllostachys pubescens)

Treesearch

H.Q. Yu; Z.H. Jiang; C.Y. Hse; T.F. Shupe

2008-01-01

Selected physical and mechanical properties of moso bamboo (Phyllostachys pubescens). Selected physical and mechanical properties of 4?6 year old moso bamboo (Phyllostachys pubescens) grown in Zhejiang, China were investigated at different vertical and horizontal positions. Two way analysis of variance and Tukey?s mean comparison...

Transnationalisation within School Education:The Interconnection between Actors, Structures and Mechanisms

ERIC Educational Resources Information Center

Schneider, Claudia

2017-01-01

The current literature of school education, transnationalisation and migration explores actors, structures and social mechanisms, however, tends to focus on these analytical levels separately. This article advocates a more explicit analysis of the interconnections of structures, actors and mechanisms within and across schools and wider national…

In vivo effects of metal ions on conformation and mechanical performance of silkworm silks.

PubMed

Wang, Xin; Li, Yi; Liu, Qingsong; Chen, Quanmei; Xia, Qingyou; Zhao, Ping

2017-03-01

The mechanism of silk fiber formation is of particular interest. Although in vitro evidence has shown that metal ions affect conformational transitions of silks, the in vivo effects of metal ions on silk conformations and mechanical performance are still unclear. This study explored the effects of metal ions on silk conformations and mechanical properties of silk fibers by adding K + and Cu 2+ into the silk fibroin solutions or injecting them into the silkworms. Aimed by CD analysis, FTIR analysis, and mechanical testing, the conformational and mechanical changes of the silks were estimated. By using BION Web Server, the interactions of K + and N-terminal of silk fibroin were also simulated. We presented that K + and Cu 2+ induced the conformational transitions of silk fibroin by forming β-sheet structures. Moreover, the mechanical parameters of silk fibers, such as strength, toughness and Young's modulus, were also improved after K + or Cu 2+ injection. Using BION Web Server, we found that potassium ions may have strong electrostatic interactions with the negatively charged residues. We suggest that K + and Cu 2+ play crucial roles in the conformation and mechanical performances of silks and they are involved in the silk fiber formation in vivo. Our results are helpful for clarifying the mechanism of silk fiber formation, and provide insights for modifying the mechanical properties of silk fibers. Copyright © 2016 Elsevier B.V. All rights reserved.

46 CFR 154.448 - Calculations.

Code of Federal Regulations, 2011 CFR

2011-10-01

... similar vessel. (d) A tank buckling analysis considering the maximum construction tolerance. (e) A finite element analysis using the loads determined under § 154.406. (f) A fracture mechanics analysis using the...

46 CFR 154.448 - Calculations.

Code of Federal Regulations, 2010 CFR

2010-10-01

... similar vessel. (d) A tank buckling analysis considering the maximum construction tolerance. (e) A finite element analysis using the loads determined under § 154.406. (f) A fracture mechanics analysis using the...

46 CFR 154.448 - Calculations.

Code of Federal Regulations, 2014 CFR

2014-10-01

... similar vessel. (d) A tank buckling analysis considering the maximum construction tolerance. (e) A finite element analysis using the loads determined under § 154.406. (f) A fracture mechanics analysis using the...

46 CFR 154.448 - Calculations.

Code of Federal Regulations, 2013 CFR

2013-10-01

... similar vessel. (d) A tank buckling analysis considering the maximum construction tolerance. (e) A finite element analysis using the loads determined under § 154.406. (f) A fracture mechanics analysis using the...

46 CFR 154.448 - Calculations.

Code of Federal Regulations, 2012 CFR

2012-10-01

... similar vessel. (d) A tank buckling analysis considering the maximum construction tolerance. (e) A finite element analysis using the loads determined under § 154.406. (f) A fracture mechanics analysis using the...

Micro-finite-element method to assess elastic properties of trabecular bone at micro- and macroscopic level.

PubMed

Rieger, R; Auregan, J C; Hoc, T

2018-03-01

The objective of the present study is to assess the mechanical behavior of trabecular bone based on microCT imaging and micro-finite-element analysis. In this way two methods are detailed: (i) direct determination of macroscopic elastic property of trabecular bone; (ii) inverse approach to assess mechanical properties of trabecular bone tissue. Thirty-five females and seven males (forty-two subjects) mean aged (±SD) 80±11.7 years from hospitals of Assistance publique-Hôpitaux de Paris (AP-HP) diagnosed with osteoporosis following a femoral neck fracture due to a fall from standing were included in this study. Fractured heads were collected during hip replacement surgery. Standardized bone cores were removed from the femoral head's equator by a trephine in a water bath. MicroCT images acquisition and analysis were performed with CTan ® software and bone volume fraction was then determined. Micro-finite-element simulations were per-formed using Abaqus 6.9-2 ® software in order to determine the macroscopic mechanical behaviour of the trabecular bone. After microCT acquisition, a longitudinal compression test was performed and the experimental macroscopic Young's Modulus was extracted. An inverse approach based on the whole trabecular bone's mechanical response and micro-finite-element analysis was performed to determine microscopic mechanical properties of trabecular bone. In the present study, elasticity of the tissue was shown to be similar to that of healthy tissue but with a lower yield stress. Classical histomorphometric analysis form microCT imaging associated with an inverse micro-finite-element method allowed to assess microscopic mechanical trabecular bone parameters. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

Stress and strain analysis from dynamic loads of mechanical hand using finite element method

NASA Astrophysics Data System (ADS)

Hasanuddin, Iskandar; Husaini; Syahril Anwar, M.; Yudha, B. Z. Sandy; Akhyar, Hasan

2018-05-01

This research discusses the distribution of stress and strain due to the dynamic loads of mechanical hand. The stress and strain that occur on mechanical hand are the main concern for comparing the value of finite element analysis (FEA) and calculating for its material properties. The stress and strain analysis are done with a loading condition. The given loading condition is dynamic. The loading input condition in the simulation of using hydraulic hand dynamometer is from the grip strength measurement of ten samples. The form of the given loading to the mechanical hand is the increment value with a maximum of 708 N/m2 within 1 minute. The amount of maximum stress (von Mises) simulation is 1.731 x 105 Pa, and the amount of maximum strain is 7.441 x 10-7. The amount of maximum reaction force is 5.864 x 10-2 N, while the amount of maximum displacement that occurs on the distal part is 1.223 x 10 m. Based on the analysis, the maximum stress and strain were found both to occur at the extension part. The result of this study has shown that the stress and strain still occur far below from the yield strength and the shear strength from the material AISI 1010. It can be concluded that the mechanical hand is durable for the given loading and can hold an object with a minimum diameter of 45 mm.

Architectural measures of the cancellous bone of the mandibular condyle identified by principal components analysis.

PubMed

Giesen, E B W; Ding, M; Dalstra, M; van Eijden, T M G J

2003-09-01

As several morphological parameters of cancellous bone express more or less the same architectural measure, we applied principal components analysis to group these measures and correlated these to the mechanical properties. Cylindrical specimens (n = 24) were obtained in different orientations from embalmed mandibular condyles; the angle of the first principal direction and the axis of the specimen, expressing the orientation of the trabeculae, ranged from 10 degrees to 87 degrees. Morphological parameters were determined by a method based on Archimedes' principle and by micro-CT scanning, and the mechanical properties were obtained by mechanical testing. The principal components analysis was used to obtain a set of independent components to describe the morphology. This set was entered into linear regression analyses for explaining the variance in mechanical properties. The principal components analysis revealed four components: amount of bone, number of trabeculae, trabecular orientation, and miscellaneous. They accounted for about 90% of the variance in the morphological variables. The component loadings indicated that a higher amount of bone was primarily associated with more plate-like trabeculae, and not with more or thicker trabeculae. The trabecular orientation was most determinative (about 50%) in explaining stiffness, strength, and failure energy. The amount of bone was second most determinative and increased the explained variance to about 72%. These results suggest that trabecular orientation and amount of bone are important in explaining the anisotropic mechanical properties of the cancellous bone of the mandibular condyle.

Mortality prediction of head Abbreviated Injury Score and Glasgow Coma Scale: analysis of 7,764 head injuries.

PubMed

Demetriades, Demetrios; Kuncir, Eric; Murray, James; Velmahos, George C; Rhee, Peter; Chan, Linda

2004-08-01

We assessed the prognostic value and limitations of Glasgow Coma Scale (GCS) and head Abbreviated Injury Score (AIS) and correlated head AIS with GCS. We studied 7,764 patients with head injuries. Bivariate analysis was performed to examine the relationship of GCS, head AIS, age, gender, and mechanism of injury with mortality. Stepwise logistic regression analysis was used to identify the independent risk factors associated with mortality. The overall mortality in the group of head injury patients with no other major extracranial injuries and no hypotension on admission was 9.3%. Logistic regression analysis identified head AIS, GCS, age, and mechanism of injury as significant independent risk factors of death. The prognostic value of GCS and head AIS was significantly affected by the mechanism of injury and the age of the patient. Patients with similar GCS or head AIS but different mechanisms of injury or ages had significantly different outcomes. The adjusted odds ratio of death in penetrating trauma was 5.2 (3.9, 7.0), p < 0.0001, and in the age group > or = 55 years the adjusted odds ratio was 3.4 (2.6, 4.6), p < 0.0001. There was no correlation between head AIS and GCS (correlation coefficient -0.31). Mechanism of injury and age have a major effect in the predictive value of GCS and head AIS. There is no good correlation between GCS and head AIS.

COMPUTATIONAL ANALYSIS OF SWALLOWING MECHANICS UNDERLYING IMPAIRED EPIGLOTTIC INVERSION

PubMed Central

Pearson, William G.; Taylor, Brandon K; Blair, Julie; Martin-Harris, Bonnie

2015-01-01

Objective Determine swallowing mechanics associated with the first and second epiglottic movements, that is, movement to horizontal and full inversion respectively, in order to provide a clinical interpretation of impaired epiglottic function. Study Design Retrospective cohort study. Methods A heterogeneous cohort of patients with swallowing difficulties was identified (n=92). Two speech-language pathologists reviewed 5ml thin and 5ml pudding videofluoroscopic swallow studies per subject, and assigned epiglottic component scores of 0=complete inversion, 1=partial inversion, and 2=no inversion forming three groups of videos for comparison. Coordinates mapping minimum and maximum excursion of the hyoid, pharynx, larynx, and tongue base during pharyngeal swallowing were recorded using ImageJ software. A canonical variate analysis with post-hoc discriminant function analysis of coordinates was performed using MorphoJ software to evaluate mechanical differences between groups. Eigenvectors characterizing swallowing mechanics underlying impaired epiglottic movements were visualized. Results Nineteen of 184 video-swallows were rejected for poor quality (n=165). A Goodman-Kruskal index of predictive association showed no correlation between epiglottic component scores and etiologies of dysphagia (λ=.04). A two-way analysis of variance by epiglottic component scores showed no significant interaction effects between sex and age (f=1.4, p=.25). Discriminant function analysis demonstrated statistically significant mechanical differences between epiglottic component scores: 1&2, representing the first epiglottic movement (Mahalanobis distance=1.13, p=.0007); and, 0&1, representing the second epiglottic movement (Mahalanobis distance=0.83, p=.003). Eigenvectors indicate that laryngeal elevation and tongue base retraction underlie both epiglottic movements. Conclusion Results suggest that reduced tongue base retraction and laryngeal elevation underlie impaired first and second epiglottic movements. The styloglossus, hyoglossus and long pharyngeal muscles are implicated as targets for rehabilitation in dysphagic patients with impaired epiglottic inversion. PMID:27426940

A Bioreactor to Identify the Driving Mechanical Stimuli of Tissue Growth and Remodeling.

PubMed

van Kelle, Mathieu A J; Oomen, Pim J A; Bulsink, Jurgen A; Janssen-van den Broek, Marloes W J T; Lopata, Richard G P; Rutten, Marcel C M; Loerakker, Sandra; Bouten, Carlijn V C

2017-06-01

Tissue growth and remodeling are essential processes that should ensure long-term functionality of tissue-engineered (TE) constructs. Even though it is widely recognized that these processes strongly depend on mechanical stimuli, the underlying mechanisms of mechanically induced growth and remodeling are only partially understood. It is generally accepted that cells sense mechanical changes and respond by altering their surroundings, by means of extracellular matrix growth and remodeling, in an attempt to return to a certain preferred mechanical homeostatic state. However, the exact mechanical cues that trigger cells to synthesize and remodel their environment remain unclear. To identify the driving mechanical stimuli of these processes, it is critical to be able to temporarily follow the mechanical state of developing tissues under physiological loading conditions. Therefore, a novel "versatile tissue growth and remodeling" (Vertigro) bioreactor was developed that is capable of tissue culture and mechanical stimulation for a prolonged time period, while simultaneously performing mechanical testing. The Vertigro's unique two-chamber design allows easy, sterile handling of circular 3D TE constructs in a dedicated culture chamber, while a separate pressure chamber facilitates a pressure-driven dynamic loading regime during culture. As a proof-of-concept, temporal changes in the mechanical state of cultured tissues were quantified using nondestructive mechanical testing by means of a classical bulge test, in which the tissue displacement was tracked using ultrasound imaging. To demonstrate the successful development of the bioreactor system, compositional, structural, and geometrical changes were qualitatively and quantitatively assessed using a series of standard analysis techniques. With this bioreactor and associated mechanical analysis technique, a powerful toolbox has been developed to quantitatively study and identify the driving mechanical stimuli of engineered tissue growth and remodeling.

Deciphering the mechanisms of binding induced folding at nearly atomic resolution: The Φ value analysis applied to IDPs.

PubMed

Gianni, Stefano; Dogan, Jakob; Jemth, Per

2014-01-01

The Φ value analysis is a method to analyze the structure of metastable states in reaction pathways. Such a methodology is based on the quantitative analysis of the effect of point mutations on the kinetics and thermodynamics of the probed reaction. The Φ value analysis is routinely used in protein folding studies and is potentially an extremely powerful tool to analyze the mechanism of binding induced folding of intrinsically disordered proteins. In this review we recapitulate the key equations and experimental advices to perform the Φ value analysis in the perspective of the possible caveats arising in intrinsically disordered systems. Finally, we briefly discuss some few examples already available in the literature.

Finite Element Analysis of New Crankshaft Automatic Adjustment Mechanism of Pumping Unit

NASA Astrophysics Data System (ADS)

Wu, Jufei; Wang, Qian

2017-12-01

In this paper, the crankshaft automatic adjustment mechanism designed on CYJY10-4.2-53HF pumping unit is used as the research object. The simulation of the friction and bending moment of the crank is carried out by ANSYS Workbench, and the finite element simulation results are compared with the theoretical calculation results to verify the theoretical calculation. The final result is that the finite element analysis of the friction of the crank is basically consistent with the theoretical calculation; The analysis and calculation of the stress and deformation about the two kinds of ultimate conditions of the guide platform are carried out too; The dynamic state analysis of the mechanism is carried out to obtain the vibration modes and natural frequencies of the vibration of the different parts of the counterweight under the condition of no preload force so that the frequency of the array can avoid the natural frequency, and can effectively avoid the resonance phenomenon, and for different modes we can improve the stiffness of the structure.

Investigation on de-trapping mechanisms related to non-monotonic kink pattern in GaN HEMT devices

NASA Astrophysics Data System (ADS)

Sharma, Chandan; Laishram, Robert; Amit, Rawal, Dipendra Singh; Vinayak, Seema; Singh, Rajendra

2017-08-01

This article reports an experimental approach to analyze the kink effect phenomenon which is usually observed during the GaN high electron mobility transistor (HEMT) operation. De-trapping of charge carriers is one of the prominent reasons behind the kink effect. The commonly observed non-monotonic behavior of kink pattern is analyzed under two different device operating conditions and it is found that two different de-trapping mechanisms are responsible for a particular kink behavior. These different de-trapping mechanisms are investigated through a time delay analysis which shows the presence of traps with different time constants. Further voltage sweep and temperature analysis corroborates the finding that different de-trapping mechanisms play a role in kink behavior under different device operating conditions.

Optimization evaluation of cutting technology based on mechanical parts

NASA Astrophysics Data System (ADS)

Wang, Yu

2018-04-01

The relationship between the mechanical manufacturing process and the carbon emission is studied on the basis of the process of the mechanical manufacturing process. The formula of carbon emission calculation suitable for mechanical manufacturing process is derived. Based on this, a green evaluation method for cold machining process of mechanical parts is proposed. The application verification and data analysis of the proposed evaluation method are carried out by an example. The results show that there is a great relationship between the mechanical manufacturing process data and carbon emissions.

Mechanical, Thermal and Dynamic Mechanical Properties of PP/GF/xGnP Nanocomposites

NASA Astrophysics Data System (ADS)

Ashenai Ghasemi, F.; Ghorbani, A.; Ghasemi, I.

2017-03-01

The mechanical, thermal, and dynamic mechanical properties of ternary nanocomposites based on polypropylene, short glass fibers, and exfoliated graphene nanoplatelets were studied. To investigate the mechanical properties, uniaxial tensile and Charpy impact tests were carried out. To study the crystallinity of the compositions, a DSC test was performed. A dynamic mechanical analysis was used to characterize the storage modulus and loss factor (tan δ). The morphology of the composites was studied by a scanning electron microscope (SEM). The results obtained are presented in tables and graphics.

Analytical techniques and instrumentation: A compilation

NASA Technical Reports Server (NTRS)

1974-01-01

Technical information on developments in instrumentation is arranged into four sections: (1) instrumentation for analysis; (2) analysis of matter; (3) analysis of electrical and mechanical phenomena; and (4) structural analysis. Patent information for two of the instruments described is presented.

Outgas analysis of mechanical cryocoolers for long lifetime

NASA Astrophysics Data System (ADS)

Sato, Yoichi; Shinozaki, Keisuke; Sawada, Kenichiro; Sugita, Hiroyuki; Mitsuda, Kazuhisa; Yamasaki, Noriko Y.; Nakagawa, Takao; Tsunematsu, Shoji; Otsuka, Kiyomi; Kanao, Kenichi; Yoshida, Seiji; Narasaki, Katsuhiro

2017-12-01

Mechanical cryocoolers for space applications are required to have high reliability to achieve long-term operation in orbit. ASTRO-H (Hitomi), the 6th Japanese X-ray astronomy mission, has a major scientific instrument onboard-the Soft X-ray Spectrometer (SXS) with several 20K-class two-stage Stirling (2ST) coolers and a 4K-class Joule Thomson (JT) cooler, which must operate for 3 years to ensure the lifetime of liquid helium as a cryogen for cooling of its detectors [1,2]. Other astronomical missions such as SPICA [3,4], LiteBIRD [5], and Athena [6] also have top requirements for these mechanical cryocoolers, including a 1K-class JT cooler to be operated for more than 3-5 years with no cryogen system. The reliability and lifetime of mechanical cryocoolers are generally understood to depend on (1) mechanical wear of the piston seal and valve seal, and (2) He working gas contaminated by impurity outgases, mainly H2O and CO2 released from the materials in the components of the cryocoolers. The second factor could be critical relative to causing blockage in the JT heat exchanger plumbing and the JT orifice or resulting in blockage in the Stirling regenerator and thereby degrading its performance. Thus, reducing the potential for outgassing in the cryocooler design and fabrication process, and predicting the total amount of outgases in the cryocooler are very important to ensure cryocooler lifetime and cooling performance in orbit. This paper investigates the outgas analysis of the 2ST and the 1K/4K-JT coolers for achieving a long lifetime. First, gas analysis was conducted for the materials and components of the mechanical cryocoolers, focusing on non-metallic materials as impurity gas sources. Then gas analysis of the mechanical wear effect of the piston seal materials and linear ball bearings was investigated. Finally, outgassing from a fully assembled cryocooler was measured to evaluate whether the outgas reduction process works properly to meet the requirement levels.

Improved ethanol yield and reduced minimum ethanol selling price (MESP) by modifying low severity dilute acid pretreatment with deacetylation and mechanical refining: 2) Techno-economic analysis

PubMed Central

2012-01-01

Background Our companion paper discussed the yield benefits achieved by integrating deacetylation, mechanical refining, and washing with low acid and low temperature pretreatment. To evaluate the impact of the modified process on the economic feasibility, a techno-economic analysis (TEA) was performed based on the experimental data presented in the companion paper. Results The cost benefits of dilute acid pretreatment technology combined with the process alternatives of deacetylation, mechanical refining, and pretreated solids washing were evaluated using cost benefit analysis within a conceptual modeling framework. Control cases were pretreated at much lower acid loadings and temperatures than used those in the NREL 2011 design case, resulting in much lower annual ethanol production. Therefore, the minimum ethanol selling prices (MESP) of the control cases were $0.41-$0.77 higher than the $2.15/gallon MESP of the design case. This increment is highly dependent on the carbohydrate content in the corn stover. However, if pretreatment was employed with either deacetylation or mechanical refining, the MESPs were reduced by $0.23-$0.30/gallon. Combing both steps could lower the MESP further by $0.44 ~ $0.54. Washing of the pretreated solids could also greatly improve the final ethanol yields. However, the large capital cost of the solid–liquid separation unit negatively influences the process economics. Finally, sensitivity analysis was performed to study the effect of the cost of the pretreatment reactor and the energy input for mechanical refining. A 50% cost reduction in the pretreatment reactor cost reduced the MESP of the entire conversion process by $0.11-$0.14/gallon, while a 10-fold increase in energy input for mechanical refining will increase the MESP by $0.07/gallon. Conclusion Deacetylation and mechanical refining process options combined with low acid, low severity pretreatments show improvements in ethanol yields and calculated MESP for cellulosic ethanol production. PMID:22967479

Optical performance assessment under environmental and mechanical perturbations in large, deployable telescopes

NASA Astrophysics Data System (ADS)

Folley, Christopher; Bronowicki, Allen

2005-09-01

Prediction of optical performance for large, deployable telescopes under environmental conditions and mechanical disturbances is a crucial part of the design verification process of such instruments for all phases of design and operation: ground testing, commissioning, and on-orbit operation. A Structural-Thermal-Optical-Performance (STOP) analysis methodology is often created that integrates the output of one analysis with the input of another. The integration of thermal environment predictions with structural models is relatively well understood, while the integration of structural deformation results into optical analysis/design software is less straightforward. A Matlab toolbox has been created that effectively integrates the predictions of mechanical deformations on optical elements generated by, for example, finite element analysis, and computes optical path differences for the distorted prescription. The engine of the toolbox is the real ray-tracing algorithm that allows the optical surfaces to be defined in a single, global coordinate system thereby allowing automatic alignment of the mechanical coordinate system with the optical coordinate system. Therefore, the physical location of the optical surfaces is identical in the optical prescription and the finite element model. The application of rigid body displacements to optical surfaces, however, is more general than for use solely in STOP analysis, such as the analysis of misalignments during the commissioning process. Furthermore, all the functionality of Matlab is available for optimization and control. Since this is a new tool for use on flight programs, it has been verified against CODE V. The toolbox' functionality, to date, is described, verification results are presented, and, as an example of its utility, results of a thermal distortion analysis are presented using the James Webb Space Telescope (JWST) prescription.

A global sensitivity analysis approach for morphogenesis models.

PubMed

Boas, Sonja E M; Navarro Jimenez, Maria I; Merks, Roeland M H; Blom, Joke G

2015-11-21

Morphogenesis is a developmental process in which cells organize into shapes and patterns. Complex, non-linear and multi-factorial models with images as output are commonly used to study morphogenesis. It is difficult to understand the relation between the uncertainty in the input and the output of such 'black-box' models, giving rise to the need for sensitivity analysis tools. In this paper, we introduce a workflow for a global sensitivity analysis approach to study the impact of single parameters and the interactions between them on the output of morphogenesis models. To demonstrate the workflow, we used a published, well-studied model of vascular morphogenesis. The parameters of this cellular Potts model (CPM) represent cell properties and behaviors that drive the mechanisms of angiogenic sprouting. The global sensitivity analysis correctly identified the dominant parameters in the model, consistent with previous studies. Additionally, the analysis provided information on the relative impact of single parameters and of interactions between them. This is very relevant because interactions of parameters impede the experimental verification of the predicted effect of single parameters. The parameter interactions, although of low impact, provided also new insights in the mechanisms of in silico sprouting. Finally, the analysis indicated that the model could be reduced by one parameter. We propose global sensitivity analysis as an alternative approach to study the mechanisms of morphogenesis. Comparison of the ranking of the impact of the model parameters to knowledge derived from experimental data and from manipulation experiments can help to falsify models and to find the operand mechanisms in morphogenesis. The workflow is applicable to all 'black-box' models, including high-throughput in vitro models in which output measures are affected by a set of experimental perturbations.

IBiSA_Tools: A Computational Toolkit for Ion-Binding State Analysis in Molecular Dynamics Trajectories of Ion Channels.

PubMed

Kasahara, Kota; Kinoshita, Kengo

2016-01-01

Ion conduction mechanisms of ion channels are a long-standing conundrum. Although the molecular dynamics (MD) method has been extensively used to simulate ion conduction dynamics at the atomic level, analysis and interpretation of MD results are not straightforward due to complexity of the dynamics. In our previous reports, we proposed an analytical method called ion-binding state analysis to scrutinize and summarize ion conduction mechanisms by taking advantage of a variety of analytical protocols, e.g., the complex network analysis, sequence alignment, and hierarchical clustering. This approach effectively revealed the ion conduction mechanisms and their dependence on the conditions, i.e., ion concentration and membrane voltage. Here, we present an easy-to-use computational toolkit for ion-binding state analysis, called IBiSA_tools. This toolkit consists of a C++ program and a series of Python and R scripts. From the trajectory file of MD simulations and a structure file, users can generate several images and statistics of ion conduction processes. A complex network named ion-binding state graph is generated in a standard graph format (graph modeling language; GML), which can be visualized by standard network analyzers such as Cytoscape. As a tutorial, a trajectory of a 50 ns MD simulation of the Kv1.2 channel is also distributed with the toolkit. Users can trace the entire process of ion-binding state analysis step by step. The novel method for analysis of ion conduction mechanisms of ion channels can be easily used by means of IBiSA_tools. This software is distributed under an open source license at the following URL: http://www.ritsumei.ac.jp/~ktkshr/ibisa_tools/.

D2 Delta Robot Structural Design and Kinematics Analysis

NASA Astrophysics Data System (ADS)

Yang, Xudong; wang, Song; Dong, Yu; Yang, Hai

2017-12-01

In this paper, a new type of Delta robot with only two degrees of freedom is proposed on the basis of multi - degree - of - freedom delta robot. In order to meet our application requirements, we have carried out structural design and analysis of the robot. Through SolidWorks modeling, combined with 3D printing technology to determine the final robot structure. In order to achieve the precise control of the robot, the kinematics analysis of the robot was carried out. The SimMechanics toolbox of MATLAB is used to establish the mechanism model, and the kinematics mathematical model is used to simulate the robot motion control in Matlab environment. Finally, according to the design mechanism, the working space of the robot is drawn by the graphic method, which lays the foundation for the motion control of the subsequent robot.

Skeletal Mechanism Generation of Surrogate Jet Fuels for Aeropropulsion Modeling

NASA Astrophysics Data System (ADS)

Sung, Chih-Jen; Niemeyer, Kyle E.

2010-05-01

A novel implementation for the skeletal reduction of large detailed reaction mechanisms using the directed relation graph with error propagation and sensitivity analysis (DRGEPSA) is developed and presented with skeletal reductions of two important hydrocarbon components, n-heptane and n-decane, relevant to surrogate jet fuel development. DRGEPSA integrates two previously developed methods, directed relation graph-aided sensitivity analysis (DRGASA) and directed relation graph with error propagation (DRGEP), by first applying DRGEP to efficiently remove many unimportant species prior to sensitivity analysis to further remove unimportant species, producing an optimally small skeletal mechanism for a given error limit. It is illustrated that the combination of the DRGEP and DRGASA methods allows the DRGEPSA approach to overcome the weaknesses of each previous method, specifically that DRGEP cannot identify all unimportant species and that DRGASA shields unimportant species from removal.

In vivo measurement of mechanical properties of human long bone by using sonic sound

NASA Astrophysics Data System (ADS)

Hossain, M. Jayed; Rahman, M. Moshiur; Alam, Morshed

2016-07-01

Vibration analysis has evaluated as non-invasive techniques for the in vivo assessment of bone mechanical properties. The relation between the resonant frequencies, long bone geometry and mechanical properties can be obtained by vibration analysis. In vivo measurements were performed on human ulna as a simple beam model with an experimental technique and associated apparatus. The resonant frequency of the ulna was obtained by Fast Fourier Transformation (FFT) analysis of the vibration response of piezoelectric accelerometer. Both elastic modulus and speed of the sound were inferred from the resonant frequency. Measurement error in the improved experimental setup was comparable with the previous work. The in vivo determination of bone elastic response has potential value in screening programs for metabolic bone disease, early detection of osteoporosis and evaluation of skeletal effects of various therapeutic modalities.

The prognosis of infective endocarditis treated with biological valves versus mechanical valves: A meta-analysis

PubMed Central

Tao, Ende; Wan, Li; Wang, WenJun; Luo, YunLong; Zeng, JinFu; Wu, Xia

2017-01-01

Objective Surgery remains the primary form of treatment for infective endocarditis (IE). However, it is not clear what type of prosthetic valve provides a better prognosis. We conducted a meta-analysis to compare the prognosis of infective endocarditis treated with biological valves to cases treated with mechanical valves. Methods Pubmed, Embase and Cochrane databases were searched from January 1960 to November 2016.Randomized controlled trials, retrospective cohorts and prospective studies comparing outcomes between biological valve and mechanical valve management for infective endocarditis were analyzed. The Newcastle-Ottawa Scale(NOS) was used to evaluate the quality of the literature and extracted data, and Stata 12.0 software was used for the meta-analysis. Results A total of 11 publications were included; 10,754 cases were selected, involving 6776 cases of biological valves and 3,978 cases of mechanical valves. The all-cause mortality risk of the biological valve group was higher than that of the mechanical valve group (HR = 1.22, 95% CI 1.03 to 1.44, P = 0.023), as was early mortality (RR = 1.21, 95% CI 1.02 to 1.43, P = 0.033). The recurrence of endocarditis (HR = 1.75, 95% CI 1.26 to 2.42, P = 0.001), as well as the risk of reoperation (HR = 1.79, 95% CI 1.15 to 2.80, P = 0.010) were more likely to occur in the biological valve group. The incidence of postoperative embolism was less in the biological valve group than in the mechanical valve group, but this difference was not statistically significant (RR = 0.90, 95% CI 0.76 to 1.07, P = 0.245). For patients with prosthetic valve endocarditis (PVE), there was no significant difference in survival rates between the biological valve group and the mechanical valve group (HR = 0.91, 95% CI 0.68 to 1.21, P = 0.520). Conclusion The results of our meta-analysis suggest that mechanical valves can provide a significantly better prognosis in patients with infective endocarditis. There were significant differences in the clinical features of patients receiving a biological valve compared to patients receiving a mechanical valve. A large, multicenter retrospective study included in our meta-analysis suggested that any mortality risk of the biological valve group was significant higher than that of the mechanical valve group. However, the risk was no different after risk was adjusted. So, we thought the reason for this result may be related to the characteristics of the patient rather than valve dysfunction. It is still necessary to future randomized studies to verify this conclusion. PMID:28407024

Transient thermal, hydraulic, and mechanical analysis of a counter flow offset strip fin intermediate heat exchanger using an effective porous media approach

NASA Astrophysics Data System (ADS)

Urquiza, Eugenio

This work presents a comprehensive thermal hydraulic analysis of a compact heat exchanger using offset strip fins. The thermal hydraulics analysis in this work is followed by a finite element analysis (FEA) to predict the mechanical stresses experienced by an intermediate heat exchanger (IHX) during steady-state operation and selected flow transients. In particular, the scenario analyzed involves a gas-to-liquid IHX operating between high pressure helium and liquid or molten salt. In order to estimate the stresses in compact heat exchangers a comprehensive thermal and hydraulic analysis is needed. Compact heat exchangers require very small flow channels and fins to achieve high heat transfer rates and thermal effectiveness. However, studying such small features computationally contributes little to the understanding of component level phenomena and requires prohibitive computational effort using computational fluid dynamics (CFD). To address this issue, the analysis developed here uses an effective porous media (EPM) approach; this greatly reduces the computation time and produces results with the appropriate resolution [1]. This EPM fluid dynamics and heat transfer computational code has been named the Compact Heat Exchanger Explicit Thermal and Hydraulics (CHEETAH) code. CHEETAH solves for the two-dimensional steady-state and transient temperature and flow distributions in the IHX including the complicating effects of temperature-dependent fluid thermo-physical properties. Temperature- and pressure-dependent fluid properties are evaluated by CHEETAH and the thermal effectiveness of the IHX is also calculated. Furthermore, the temperature distribution can then be imported into a finite element analysis (FEA) code for mechanical stress analysis using the EPM methods developed earlier by the University of California, Berkeley, for global and local stress analysis [2]. These simulation tools will also allow the heat exchanger design to be improved through an iterative design process which will lead to a design with a reduced pressure drop, increased thermal effectiveness, and improved mechanical performance as it relates to creep deformation and transient thermal stresses.

Meta-analysis of high-latitude nitrogen-addition and warming studies implies ecological mechanisms overlooked by land models

DOE PAGES

Bouskill, N. J.; Riley, W. J.; Tang, J. Y.

2014-12-11

Accurate representation of ecosystem processes in land models is crucial for reducing predictive uncertainty in energy and greenhouse gas feedbacks with the climate. Here we describe an observational and modeling meta-analysis approach to benchmark land models, and apply the method to the land model CLM4.5 with two versions of belowground biogeochemistry. We focused our analysis on the aboveground and belowground responses to warming and nitrogen addition in high-latitude ecosystems, and identified absent or poorly parameterized mechanisms in CLM4.5. While the two model versions predicted similar soil carbon stock trajectories following both warming and nitrogen addition, other predicted variables (e.g., belowgroundmore » respiration) differed from observations in both magnitude and direction, indicating that CLM4.5 has inadequate underlying mechanisms for representing high-latitude ecosystems. On the basis of observational synthesis, we attribute the model–observation differences to missing representations of microbial dynamics, aboveground and belowground coupling, and nutrient cycling, and we use the observational meta-analysis to discuss potential approaches to improving the current models. However, we also urge caution concerning the selection of data sets and experiments for meta-analysis. For example, the concentrations of nitrogen applied in the synthesized field experiments (average = 72 kg ha -1 yr -1) are many times higher than projected soil nitrogen concentrations (from nitrogen deposition and release during mineralization), which precludes a rigorous evaluation of the model responses to likely nitrogen perturbations. Overall, we demonstrate that elucidating ecological mechanisms via meta-analysis can identify deficiencies in ecosystem models and empirical experiments.« less

Meta-analysis of high-latitude nitrogen-addition and warming studies implies ecological mechanisms overlooked by land models

NASA Astrophysics Data System (ADS)

Bouskill, N. J.; Riley, W. J.; Tang, J. Y.

2014-12-01

Accurate representation of ecosystem processes in land models is crucial for reducing predictive uncertainty in energy and greenhouse gas feedbacks with the climate. Here we describe an observational and modeling meta-analysis approach to benchmark land models, and apply the method to the land model CLM4.5 with two versions of belowground biogeochemistry. We focused our analysis on the aboveground and belowground responses to warming and nitrogen addition in high-latitude ecosystems, and identified absent or poorly parameterized mechanisms in CLM4.5. While the two model versions predicted similar soil carbon stock trajectories following both warming and nitrogen addition, other predicted variables (e.g., belowground respiration) differed from observations in both magnitude and direction, indicating that CLM4.5 has inadequate underlying mechanisms for representing high-latitude ecosystems. On the basis of observational synthesis, we attribute the model-observation differences to missing representations of microbial dynamics, aboveground and belowground coupling, and nutrient cycling, and we use the observational meta-analysis to discuss potential approaches to improving the current models. However, we also urge caution concerning the selection of data sets and experiments for meta-analysis. For example, the concentrations of nitrogen applied in the synthesized field experiments (average = 72 kg ha-1 yr-1) are many times higher than projected soil nitrogen concentrations (from nitrogen deposition and release during mineralization), which precludes a rigorous evaluation of the model responses to likely nitrogen perturbations. Overall, we demonstrate that elucidating ecological mechanisms via meta-analysis can identify deficiencies in ecosystem models and empirical experiments.

LV dyssynchrony as assessed by phase analysis of gated SPECT myocardial perfusion imaging in patients with Wolff-Parkinson-White syndrome

PubMed Central

Chen, Chun; Miao, Changqing; Feng, Jianlin; Zhou, Yanli; Cao, Kejiang; Lloyd, Michael S.; Chen, Ji

2013-01-01

Purpose The purpose of this study was to evaluate left ventricular (LV) mechanical dyssynchrony in patients with Wolff-Parkinson-White (WPW) syndrome pre- and post-radiofrequency catheter ablation (RFA) using phase analysis of gated single photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI). Methods Forty-five WPW patients were enrolled and had gated SPECT MPI pre- and 2–3 days post-RFA. Electrophysiological study (EPS) was used to locate accessory pathways (APs) and categorize the patients according to the AP locations (septal, left and right free wall). Electrocardiography (ECG) was performed pre- and post-RFA to confirm successful elimination of the APs. Phase analysis of gated SPECT MPI was used to assess LV dyssynchrony pre- and post-RFA. Results Among the 45 patients, 3 had gating errors, and thus 42 had SPECT phase analysis. Twenty-two patients (52.4 %) had baseline LV dyssynchrony. Baseline LV dyssynchrony was more prominent in the patients with septal APs than in the patients with left or right APs (p<0.05). RFA improved LV synchrony in the entire cohort and in the patients with septal APs (p<0.01). Conclusion Phase analysis of gated SPECT MPI demonstrated that LV mechanical dyssynchrony can be present in patients with WPW syndrome. Septal APs result in the greatest degree of LV mechanical dyssynchrony and afford the most benefit after RFA. This study supports further investigation in the relationship between electrical and mechanical activation using EPS and phase analysis of gated SPECT MPI. PMID:22532253

Analysis of the Transition in Deformation Mechanisms in Superplastic 5083 Aluminum Alloys by Orientation Imaging Microscopy

DTIC Science & Technology

2001-09-01

Analysis of the Transition in Deformation Mechanisms in Superplastic 5083 Aluminum Alloys by Orientation Imaging Microscopy 6. AUTHOR( S ) Harrell...James W. 5. FUNDING NUMBERS 7. PERFORMING ORGANIZATION NAME( S ) AND ADDRESS(ES) Naval Postgraduate School Monterey, CA 93943-5000 8. PERFORMING...ORGANIZATION REPORT NUMBER 9. SPONSORING / MONITORING AGENCY NAME( S ) AND ADDRESS(ES) General Motors Corp., Research and Development Center

Three Dialogs: A Framework for the Analysis and Assessment of Twenty-First-Century Literacy Practices, and Its Use in the Context of Game Design within "Gamestar Mechanic"

ERIC Educational Resources Information Center

Games, Ivan Alex

2008-01-01

This article discusses a framework for the analysis and assessment of twenty-first-century language and literacy practices in game and design-based contexts. It presents the framework in the context of game design within "Gamestar Mechanic", an innovative game-based learning environment where children learn the Discourse of game design. It…

Computational structural mechanics methods research using an evolving framework

NASA Technical Reports Server (NTRS)

Knight, N. F., Jr.; Lotts, C. G.; Gillian, R. E.

1990-01-01

Advanced structural analysis and computational methods that exploit high-performance computers are being developed in a computational structural mechanics research activity sponsored by the NASA Langley Research Center. These new methods are developed in an evolving framework and applied to representative complex structural analysis problems from the aerospace industry. An overview of the methods development environment is presented, and methods research areas are described. Selected application studies are also summarized.

[The role of plastic shock absorbers in dental implantation].

PubMed

Szücs, A; Divinyi, T; Belina, K; Vörös, G

1999-01-01

The mechanical behaviour of different plastics (PE, PP, PI, PA, ABS, POM) was examined by static and dynamic loading. Detection of microdeformations and photoelastic stress analysis served as the examination method. According to the results, polyethylene is unsuitable, however the other plastics, with clauses, are suitable as shock absorbers. Apart from the mechanical investigation photoelastic stress analysis also revealed the benefit of osseointegration in force transmission to the bone.

Fracture Mechanics Analysis for Short Cracks.

DTIC Science & Technology

1987-08-27

McClintock (Ref. 3), Rice (Ref. 4) and Hutchinson (Ref. 5). EPFM is applicable and needed especially for high toughness and low strength materials wherein...The development of LEFM has been followed by the development of elastic- plastic fracture mechanics ( EPFM ) with the pioneering work of Hult and...predict growth of these short cracks, as application of long crack fatigue growth analysis will not be applicable and failures may not be predicted. In

Demonstration of spectral calibration for stellar interferometry

NASA Technical Reports Server (NTRS)

Demers, Richard T.; An, Xin; Tang, Hong; Rud, Mayer; Wayne, Leonard; Kissil, Andrew; Kwack, Eug-Yun

2006-01-01

A breadboard is under development to demonstrate the calibration of spectral errors in microarcsecond stellar interferometers. Analysis shows that thermally and mechanically stable hardware in addition to careful optical design can reduce the wavelength dependent error to tens of nanometers. Calibration of the hardware can further reduce the error to the level of picometers. The results of thermal, mechanical and optical analysis supporting the breadboard design will be shown.

Analysis of small crack behavior for airframe applications

NASA Technical Reports Server (NTRS)

Mcclung, R. C.; Chan, K. S.; Hudak, S. J., Jr.; Davidson, D. L.

1994-01-01

The small fatigue crack problem is critically reviewed from the perspective of airframe applications. Different types of small cracks-microstructural, mechanical, and chemical-are carefully defined and relevant mechanisms identified. Appropriate analysis techniques, including both rigorous scientific and practical engineering treatments, are briefly described. Important materials data issues are addressed, including increased scatter in small crack data and recommended small crack test methods. Key problems requiring further study are highlighted.

Impact resistance of fiber composites - Energy-absorbing mechanisms and environmental effects

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.

1985-01-01

Energy absorbing mechanisms were identified by several approaches. The energy absorbing mechanisms considered are those in unidirectional composite beams subjected to impact. The approaches used include: mechanic models, statistical models, transient finite element analysis, and simple beam theory. Predicted results are correlated with experimental data from Charpy impact tests. The environmental effects on impact resistance are evaluated. Working definitions for energy absorbing and energy releasing mechanisms are proposed and a dynamic fracture progression is outlined. Possible generalizations to angle-plied laminates are described.

Impact resistance of fiber composites: Energy absorbing mechanisms and environmental effects

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.

1983-01-01

Energy absorbing mechanisms were identified by several approaches. The energy absorbing mechanisms considered are those in unidirectional composite beams subjected to impact. The approaches used include: mechanic models, statistical models, transient finite element analysis, and simple beam theory. Predicted results are correlated with experimental data from Charpy impact tests. The environmental effects on impact resistance are evaluated. Working definitions for energy absorbing and energy releasing mechanisms are proposed and a dynamic fracture progression is outlined. Possible generalizations to angle-plied laminates are described.

Sample Manipulation System for Sample Analysis at Mars

NASA Technical Reports Server (NTRS)

Mumm, Erik; Kennedy, Tom; Carlson, Lee; Roberts, Dustyn

2008-01-01

The Sample Analysis at Mars (SAM) instrument will analyze Martian samples collected by the Mars Science Laboratory Rover with a suite of spectrometers. This paper discusses the driving requirements, design, and lessons learned in the development of the Sample Manipulation System (SMS) within SAM. The SMS stores and manipulates 74 sample cups to be used for solid sample pyrolysis experiments. Focus is given to the unique mechanism architecture developed to deliver a high packing density of sample cups in a reliable, fault tolerant manner while minimizing system mass and control complexity. Lessons learned are presented on contamination control, launch restraint mechanisms for fragile sample cups, and mechanism test data.

Dynamic analysis of six-bar mechanical press for deep drawing

NASA Astrophysics Data System (ADS)

Mitsi, S.; Tsiafis, I.; Bouzakis, K. D.

2017-02-01

This paper analyzes the dynamical behavior of a six-bar linkage used in mechanical presses for metal forming such as deep drawing. In the under study mechanism, a four-bar linkage is connected to a slider through an articulated binary link. The motion of the six-bar linkage is studied by kinematic analysis developing an analytical method. Furthermore, using an iterative method and d’ Alembert’s principle, the joint forces and drive moment are evaluated considering joint frictions. The simulation results obtained with a MATLAB program are validated by comparing the theoretical values of the input moment with the ones obtained from the conservation of energy law.

Mechanics analysis of the multi-point-load process for the thin film solar cell

NASA Astrophysics Data System (ADS)

Wang, Zhiming; Wei, Guangpu; Gong, Zhengbang

2008-02-01

The main element of thin film solar cell is silicon. Because of the special mechanical characteristic of silicon, the method of loading pressure on the thin film solar cell and the value of pressure is the key problem which must be solved during the manufacturing of thin film solar cell. This paper describes the special mechanical characteristic of silicon, discussed the test method overall; value of pressure on thin film solar cell; the elements and the method of load by ANSYS finite element, according to these theory analysis, we obtained the key conclusion in the actual operation, these result have a great meaning in industry.

Dynamical mechanical characteristic simulation and analysis of the low voltage switch under vibration and shock conditions

NASA Astrophysics Data System (ADS)

Miao, Xiaodan; Han, Feng

2017-04-01

The low voltage switch has widely application especially in the hostile environment such as large vibration and shock conditions. In order to ensure the validity of the switch in the hostile environment, it is necessary to predict its mechanical characteristic. In traditional method, the complex and expensive testing system is build up to verify its validity. This paper presented a method based on finite element analysis to predict the dynamic mechanical characteristic of the switch by using ANSYS software. This simulation could provide the basis for the design and optimization of the switch to shorten the design process to improve the product efficiency.

Mechanical design and analysis of a low beta squeezed half-wave resonator

NASA Astrophysics Data System (ADS)

He, Shou-Bo; Zhang, Cong; Yue, Wei-Ming; Wang, Ruo-Xu; Xu, Meng-Xin; Wang, Zhi-Jun; Huang, Shi-Chun; Huang, Yu-Lu; Jiang, Tian-Cai; Wang, Feng-Feng; Zhang, Sheng-Xue; He, Yuan; Zhang, Sheng-Hu; Zhao, Hong-Wei

2014-08-01

A superconducting squeezed type half-wave resonator (HWR) of β=0.09 has been developed at the Institute of Modern Physics, Lanzhou. In this paper, a basic design is presented for the stiffening structure for the detuning effect caused by helium pressure and Lorentz force. The mechanical modal analysis has been investigated the with finite element method (FEM). Based on these considerations, a new stiffening structure is proposed for the HWR cavity. The computation results concerning the frequency shift show that the low beta HWR cavity with new stiffening structure has low frequency sensitivity coefficient df/dp and Lorentz force detuning coefficient KL, and stable mechanical properties.

Monogenic Mouse Models of Autism Spectrum Disorders: Common Mechanisms and Missing Links

PubMed Central

Hulbert, Samuel W.; Jiang, Yong-hui

2016-01-01

Autism Spectrum Disorders (ASDs) present unique challenges in the fields of genetics and neurobiology because of the clinical and molecular heterogeneity underlying these disorders. Genetic mutations found in ASD patients provide opportunities to dissect the molecular and circuit mechanisms underlying autistic behaviors using animal models. Ongoing studies of genetically modified models have offered critical insight into possible common mechanisms arising from different mutations, but links between molecular abnormalities and behavioral phenotypes remain elusive. The challenges encountered in modeling autism in mice demand a new analytic paradigm that integrates behavioral analysis with circuit-level analysis in genetically modified models with strong construct validity. PMID:26733386

Fractography and estimates of fracture origin size from fracture mechanics

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

Quinn, G.D.; Swab, J.J.

1996-12-31

Fracture mechanics should be used routinely in fractographic analyses in order to verify that the correct feature has been identified as the fracture origin. This was highlighted in a recent Versailles Advanced Materials and Standards (VAMAS) fractographic analysis round robin. The practice of using fracture mechanics as an aid to fractographic interpretation is codified in a new ASTM Standard Practice. Conversely, very good estimates for fracture toughness often come from fractographic analysis of strength tested specimens. In many instances however, the calculated flaw size is different from the empirically-measured flaw size. This paper reviews the factors which may cause themore » discrepancies.« less

Prediction of properties of intraply hybrid composites

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.

1979-01-01

Equations based on the mixtures rule are presented for predicting the physical, thermal, hygral, and mechanical properties of unidirectional intraply hybrid composites (UIHC) from the corresponding properties of their constituent composites. Bounds were derived for uniaxial longitudinal strengths, tension, compression, and flexure of UIHC. The equations predict shear and flexural properties which agree with experimental data from UIHC. Use of these equations in a composites mechanics computer code predicted flexural moduli which agree with experimental data from various intraply hybrid angleplied laminates (IHAL). It is indicated, briefly, how these equations can be used in conjunction with composite mechanics and structural analysis during the analysis/design process.

Finite element cochlea box model - Mechanical and electrical analysis of the cochlea

NASA Astrophysics Data System (ADS)

Nikolic, Milica; Teal, Paul D.; Isailovic, Velibor; Filipović, Nenad

2015-12-01

The primary role of the cochlea is to transform external sound stimuli into mechanical vibrations and then to neural impulses which are sent to the brain. A simplified cochlea box model was developed using the finite element method. Firstly, a mechanical model of the cochlea was analyzed. The box model consists of the basilar membrane and two fluid chambers - the scala vestibuli and scala tympani. The third chamber, the scala media, was neglected in the mechanical analysis. The best agreement with currently available analytical and experimental results was obtained when behavior of the fluid in the chambers was described using the wave acoustic equation and behavior of the basilar membrane was modeled with Newtonian dynamics. The obtained results show good frequency mapping. The second approach was to use an active model of the cochlea in which the Organ of Corti was included. The operation of the Organ of Corti involves the generation of current, caused by mechanical vibration. This current in turn causes a force applied to the basilar membrane, creating in this way an active feedback mechanism. A state space representation of the electro-mechanical model from existing literature was implemented and a first comparison with the finite element method is presented.

Terahertz mechanical vibrations in lysozyme: Raman spectroscopy vs modal analysis

NASA Astrophysics Data System (ADS)

Carpinteri, Alberto; Lacidogna, Giuseppe; Piana, Gianfranco; Bassani, Andrea

2017-07-01

The mechanical behaviour of proteins is receiving an increasing attention from the scientific community. Recently it has been suggested that mechanical vibrations play a crucial role in controlling structural configuration changes (folding) which govern proteins biological function. The mechanism behind protein folding is still not completely understood, and many efforts are being made to investigate this phenomenon. Complex molecular dynamics simulations and sophisticated experimental measurements are conducted to investigate protein dynamics and to perform protein structure predictions; however, these are two related, although quite distinct, approaches. Here we investigate mechanical vibrations of lysozyme by Raman spectroscopy and linear normal mode calculations (modal analysis). The input mechanical parameters to the numerical computations are taken from the literature. We first give an estimate of the order of magnitude of protein vibration frequencies by considering both classical wave mechanics and structural dynamics formulas. Afterwards, we perform modal analyses of some relevant chemical groups and of the full lysozyme protein. The numerical results are compared to experimental data, obtained from both in-house and literature Raman measurements. In particular, the attention is focused on a large peak at 0.84 THz (29.3 cm-1) in the Raman spectrum obtained analyzing a lyophilized powder sample.

Mechanical Network in Titin Immunoglobulin from Force Distribution Analysis

PubMed Central

Wilmanns, Matthias; Gräter, Frauke

2009-01-01

The role of mechanical force in cellular processes is increasingly revealed by single molecule experiments and simulations of force-induced transitions in proteins. How the applied force propagates within proteins determines their mechanical behavior yet remains largely unknown. We present a new method based on molecular dynamics simulations to disclose the distribution of strain in protein structures, here for the newly determined high-resolution crystal structure of I27, a titin immunoglobulin (IG) domain. We obtain a sparse, spatially connected, and highly anisotropic mechanical network. This allows us to detect load-bearing motifs composed of interstrand hydrogen bonds and hydrophobic core interactions, including parts distal to the site to which force was applied. The role of the force distribution pattern for mechanical stability is tested by in silico unfolding of I27 mutants. We then compare the observed force pattern to the sparse network of coevolved residues found in this family. We find a remarkable overlap, suggesting the force distribution to reflect constraints for the evolutionary design of mechanical resistance in the IG family. The force distribution analysis provides a molecular interpretation of coevolution and opens the road to the study of the mechanism of signal propagation in proteins in general. PMID:19282960

Mechanical instability and titanium particles induce similar transcriptomic changes in a rat model for periprosthetic osteolysis and aseptic loosening.

PubMed

Amirhosseini, Mehdi; Andersson, Göran; Aspenberg, Per; Fahlgren, Anna

2017-12-01

Wear debris particles released from prosthetic bearing surfaces and mechanical instability of implants are two main causes of periprosthetic osteolysis. While particle-induced loosening has been studied extensively, mechanisms through which mechanical factors lead to implant loosening have been less investigated. This study compares the transcriptional profiles associated with osteolysis in a rat model for aseptic loosening, induced by either mechanical instability or titanium particles. Rats were exposed to mechanical instability or titanium particles. After 15 min, 3, 48 or 120 h from start of the stimulation, gene expression changes in periprosthetic bone tissue was determined by microarray analysis. Microarray data were analyzed by PANTHER Gene List Analysis tool and Ingenuity Pathway Analysis (IPA). Both types of osteolytic stimulation led to gene regulation in comparison to unstimulated controls after 3, 48 or 120 h. However, when mechanical instability was compared to titanium particles, no gene showed a statistically significant difference (fold change ≥ ± 1.5 and adjusted p-value ≤ 0.05) at any time point. There was a remarkable similarity in numbers and functional classification of regulated genes. Pathway analysis showed several inflammatory pathways activated by both stimuli, including Acute Phase Response signaling, IL-6 signaling and Oncostatin M signaling. Quantitative PCR confirmed the changes in expression of key genes involved in osteolysis observed by global transcriptomics. Inflammatory mediators including interleukin (IL)-6, IL-1β, chemokine (C-C motif) ligand (CCL)2, prostaglandin-endoperoxide synthase (Ptgs)2 and leukemia inhibitory factor (LIF) showed strong upregulation, as assessed by both microarray and qPCR. By investigating genome-wide expression changes we show that, despite the different nature of mechanical implant instability and titanium particles, osteolysis seems to be induced through similar biological and signaling pathways in this rat model for aseptic loosening. Pathways associated to the innate inflammatory response appear to be a major driver for osteolysis. Our findings implicate early restriction of inflammation to be critical to prevent or mitigate osteolysis and aseptic loosening of orthopedic implants.

Mechanism of extracellular ion exchange and binding-site occlusion in the sodium-calcium exchanger

PubMed Central

Lee, ChangKeun; Huang, Yihe; Faraldo-Gómez, José D.; Jiang, Youxing

2016-01-01

Na+/Ca2+ exchangers utilize the Na+ electrochemical gradient across the plasma membrane to extrude intracellular Ca2+, and play a central role in Ca2+ homeostasis. Here, we elucidate their mechanisms of extracellular ion recognition and exchange through a structural analysis of the exchanger from Methanococcus jannaschii (NCX_Mj) bound to Na+, Ca2+ or Sr2+ in various occupancies and in an apo state. This analysis defines the binding mode and relative affinity of these ions, establishes the structural basis for the anticipated 3Na+:1Ca2+ exchange stoichiometry, and reveals the conformational changes at the onset of the alternating-access transport mechanism. An independent analysis of the dynamics and conformational free-energy landscape of NCX_Mj in different ion-occupancy states, based on enhanced-sampling molecular-dynamics simulations, demonstrates that the crystal structures reflect mechanistically relevant, interconverting conformations. These calculations also reveal the mechanism by which the outward-to-inward transition is controlled by the ion-occupancy state, thereby explaining the emergence of strictly-coupled Na+/Ca2+ antiport. PMID:27183196

A review on recent contribution of meshfree methods to structure and fracture mechanics applications.

PubMed

Daxini, S D; Prajapati, J M

2014-01-01

Meshfree methods are viewed as next generation computational techniques. With evident limitations of conventional grid based methods, like FEM, in dealing with problems of fracture mechanics, large deformation, and simulation of manufacturing processes, meshfree methods have gained much attention by researchers. A number of meshfree methods have been proposed till now for analyzing complex problems in various fields of engineering. Present work attempts to review recent developments and some earlier applications of well-known meshfree methods like EFG and MLPG to various types of structure mechanics and fracture mechanics applications like bending, buckling, free vibration analysis, sensitivity analysis and topology optimization, single and mixed mode crack problems, fatigue crack growth, and dynamic crack analysis and some typical applications like vibration of cracked structures, thermoelastic crack problems, and failure transition in impact problems. Due to complex nature of meshfree shape functions and evaluation of integrals in domain, meshless methods are computationally expensive as compared to conventional mesh based methods. Some improved versions of original meshfree methods and other techniques suggested by researchers to improve computational efficiency of meshfree methods are also reviewed here.

Quasi-Static Indentation Analysis of Carbon-Fiber Laminates.

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

Briggs, Timothy; English, Shawn Allen; Nelson, Stacy Michelle

2015-12-01

A series of quasi - static indentation experiments are conducted on carbon fiber reinforced polymer laminates with a systematic variation of thicknesses and fixture boundary conditions. Different deformation mechanisms and their resulting damage mechanisms are activated b y changing the thickn ess and boundary conditions. The quasi - static indentation experiments have been shown to achieve damage mechanisms similar to impact and penetration, however without strain rate effects. The low rate allows for the detailed analysis on the load response. Moreover, interrupted tests allow for the incremental analysis of various damage mechanisms and pr ogressions. The experimentally tested specimens aremore » non - destructively evaluated (NDE) with optical imaging, ultrasonics and computed tomography. The load displacement responses and the NDE are then utilized in numerical simulations for the purpose of model validation and vetting. The accompanying numerical simulation work serves two purposes. First, the results further reveal the time sequence of events and the meaning behind load dro ps not clear from NDE . Second, the simulations demonstrate insufficiencies in the code and can then direct future efforts for development.« less

Parametric analysis of a shape memory alloy actuated arm

NASA Astrophysics Data System (ADS)

Wright, Cody; Bilgen, Onur

2016-04-01

Using a pair of antagonistic Shape Memory Allow (SMA) wires, it may be possible to produce a mechanism that replicates human musculoskeletal movement. The movement of interest is the articulation of the elbow joint actuated by the biceps brachii muscle. In an effort to understand the bio-mechanics of the arm, a single degree of freedom crankslider mechanism is used to model the movement of the arm induced by the biceps brachii muscle. First, a purely kinematical analysis is performed on a rigid body crank-slider. Force analysis is also done modeling the muscle as a simple linear spring. Torque, rocking angle, and energy are calculated for a range of crank-slider geometries. The SMA wire characteristics are experimentally determined for the martensite detwinned and full austenite phases. Using the experimental data, an idealized actuator characteristic curve is produced for the SMA wire. Kinematic and force analyses are performed on the nonlinear wire characteristic curve and a linearized wire curve; both cases are applied to the crankslider mechanism. Performance metrics for both cases are compared, followed by discussion.

A simple and inexpensive image analysis technique to study the effect of disintegrants concentration and diluents type on disintegration.

PubMed

Berardi, Alberto; Bisharat, Lorina; Blaibleh, Anaheed; Pavoni, Lucia; Cespi, Marco

2018-06-20

Tablets disintegration is often the result of a size expansion of the tablets. In this study, we quantified the extent and direction of size expansion of tablets during disintegration, using readily available techniques, i.e. a digital camera and a public domain image analysis software. After validating the method, the influence of disintegrants concentration and diluents type on kinetics and mechanisms of disintegration were studied. Tablets containing diluent, disintegrant (sodium starch glycolate-SSG, crospovidone-PVPP or croscarmellose sodium-CCS) and lubricant were prepared by direct compression. Projected area and aspect ratio of the tablets were monitored using image analysis techniques. The developed method could describe the kinetics and mechanisms of disintegration qualitatively and quantitatively. SSG and PVPP acted purely by swelling and shape recovery mechanisms. Instead, CCS worked by a combination of both mechanisms, the extent of which changed depending on its concentration and the diluent type. We anticipate that the method described here could provide a framework for the routine screening of tablets disintegration using readily available equipment. Copyright © 2018. Published by Elsevier Inc.

Comparing DNA damage-processing pathways by computer analysis of chromosome painting data.

PubMed

Levy, Dan; Vazquez, Mariel; Cornforth, Michael; Loucas, Bradford; Sachs, Rainer K; Arsuaga, Javier

2004-01-01

Chromosome aberrations are large-scale illegitimate rearrangements of the genome. They are indicative of DNA damage and informative about damage processing pathways. Despite extensive investigations over many years, the mechanisms underlying aberration formation remain controversial. New experimental assays such as multiplex fluorescent in situ hybridyzation (mFISH) allow combinatorial "painting" of chromosomes and are promising for elucidating aberration formation mechanisms. Recently observed mFISH aberration patterns are so complex that computer and graph-theoretical methods are needed for their full analysis. An important part of the analysis is decomposing a chromosome rearrangement process into "cycles." A cycle of order n, characterized formally by the cyclic graph with 2n vertices, indicates that n chromatin breaks take part in a single irreducible reaction. We here describe algorithms for computing cycle structures from experimentally observed or computer-simulated mFISH aberration patterns. We show that analyzing cycles quantitatively can distinguish between different aberration formation mechanisms. In particular, we show that homology-based mechanisms do not generate the large number of complex aberrations, involving higher-order cycles, observed in irradiated human lymphocytes.

Determination of elastic mechanical characteristics of surface coatings from analysis of signals obtained by impulse excitation

NASA Astrophysics Data System (ADS)

Nyaguly, E.; Craştiu, I.; Deac, S.; Gozman-Pop, C.; Drăgănescu, G.; Bereteu, L.

2018-01-01

Most of the surface coatings are based on the synthetic polymers, which are substances composed from very large molecules that form tough, flexible, adhesive films when applied to surfaces. The other components of surface coverings materials are pigments that provide colour, opacity, gloss and other properties. Surface coatings are two-phase composite materials: constitute a polymer matrix on the one side, and on the other side of the pigments and additives dispersed in the matrix. Their role is not only aesthetically but also to ensure anticorrosive protection or even improve some mechanical properties of coated surfaces. In this paper it will follow, starting from the mechanical properties of the substrate, the metallic sheet in general, to determine the new properties of the assembly of substrate and the two coating layers, also the determination of mechanical properties of the layers. From the analysis of vibroacoustic signals obtained by the impulse excitation of the sample, one can determine the elasticity modulus. These results come to validate the results based on finite element analysis (FEA) of the same samples.

Mechanism of extracellular ion exchange and binding-site occlusion in a sodium/calcium exchanger

DOE PAGES

Liao, Jun; Marinelli, Fabrizio; Lee, Changkeun; ...

2016-05-16

Na +/Ca 2+ exchangers utilize the Na + electrochemical gradient across the plasma membrane to extrude intracellular Ca 2+, and play a central role in Ca 2+ homeostasis. Here, we elucidate their mechanisms of extracellular ion recognition and exchange through a structural analysis of the exchanger from Methanococcus jannaschii (NCX_Mj) bound to Na +, Ca 2+ or Sr 2+ in various occupancies and in an apo state. This analysis defines the binding mode and relative affinity of these ions, establishes the structural basis for the anticipated 3:1Na +/Ca 2+ exchange stoichiometry, and reveals the conformational changes at the onset ofmore » the alternating-access transport mechanism. An independent analysis of the dynamics and conformational free-energy landscape of NCX_Mj in different ion-occupancy states, based on enhanced-sampling molecular-dynamics simulations, demonstrates that the crystal structures reflect mechanistically relevant, interconverting conformations. Lastly, these calculations also reveal the mechanism by which the outward-to-inward transition is controlled by the ion-occupancy state, thereby explaining the emergence of strictly-coupled Na +/Ca 2+ antiport.« less

ANALYSIS OF 2,3,7,8-TCDD TUMOR PROMOTION ACTIVITY ...

EPA Pesticide Factsheets

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) has a high estimated cancer potency in animals which has been reasoned to imply that TCDD might be carcinogenic to man. The animal cancer data show that TCDD can act in a solitary manner causing tumors without the participation of other known factors. owever, there exist animal cancer data indicating that TCDD can act as a tumor-promoting compound. This analysis examines which type of carcinogen and which mechanism best characterize TCDD cancer activity. It is suggested that TCDD acts by a hormonal mechanism to cause cancer in solitary manner, at low doses, in two species, and in a number of different organs, including rare sites. These observations in toto characterize TCDD as a complete carcinogen, which by definition encompasses both initiation and promotion carcinogenic activities. This analysis examines which type of carcinogen and which mechanism best characterize TCDD cancer activity. It is suggested that TCDD acts by a hormonal mechanism to cause cancer in solitary manner, at low doses, in two species, and in a number of different organs, including rare sites

Global Conformational Selection and Local Induced Fit for the Recognition between Intrinsic Disordered p53 and CBP

PubMed Central

Yu, Qingfen; Ye, Wei; Wang, Wei; Chen, Hai-Feng

2013-01-01

The transactivation domain (TAD) of tumor suppressor p53 can bind with the nuclear coactivator binding domain (NCBD) of cyclic-AMP response element binding protein (CBP) and activate transcription. NMR experiments demonstrate that both apo-NCBD and TAD are intrinsic disordered and bound NCBD/TAD undergoes a transition to well folded. The recognition mechanism between intrinsic disordered proteins is still hotly debated. Molecular dynamics (MD) simulations in explicit solvent are used to study the recognition mechanism between intrinsic disordered TAD and NCBD. The average RMSD values between bound and corresponding apo states and Kolmogorov-Smirnov P test analysis indicate that TAD and NCBD may follow an induced fit mechanism. Quantitative analysis indicates there is also a global conformational selection. In summary, the recognition of TAD and NCBD might obey a local induced fit and global conformational selection. These conclusions are further supported by high-temperature unbinding kinetics and room temperature landscape analysis. These methods can be used to study the recognition mechanism of other intrinsic disordered proteins. PMID:23555731

Prognostic Analysis System and Methods of Operation

NASA Technical Reports Server (NTRS)

MacKey, Ryan M. E. (Inventor); Sneddon, Robert (Inventor)

2014-01-01

A prognostic analysis system and methods of operating the system are provided. In particular, a prognostic analysis system for the analysis of physical system health applicable to mechanical, electrical, chemical and optical systems and methods of operating the system are described herein.

Thermal diffusivity study of aged Li-ion batteries using flash method

NASA Astrophysics Data System (ADS)

Nagpure, Shrikant C.; Dinwiddie, Ralph; Babu, S. S.; Rizzoni, Giorgio; Bhushan, Bharat; Frech, Tim

Advanced Li-ion batteries with high energy and power density are fast approaching compatibility with automotive demands. While the mechanism of operation of these batteries is well understood, the aging mechanisms are still under investigation. Investigation of aging mechanisms in Li-ion batteries becomes very challenging, as aging does not occur due to a single process, but because of multiple physical processes occurring at the same time in a cascading manner. As the current characterization techniques such as Raman spectroscopy, X-ray diffraction, and atomic force microscopy are used independent of each other they do not provide a comprehensive understanding of material degradation at different length (nm 2 to m 2) scales. Thus to relate the damage mechanisms of the cathode at mm length scale to micro/nanoscale, data at an intermediate length scale is needed. As such, we demonstrate here the use of thermal diffusivity analysis by flash method to bridge the gap between different length scales. In this paper we present the thermal diffusivity analysis of an unaged and aged cell. Thermal diffusivity analysis maps the damage to the cathode samples at millimeter scale lengths. Based on these maps we also propose a mechanism leading to the increase of the thermal diffusivity as the cells are aged.

BATMAN-TCM: a Bioinformatics Analysis Tool for Molecular mechANism of Traditional Chinese Medicine.

PubMed

Liu, Zhongyang; Guo, Feifei; Wang, Yong; Li, Chun; Zhang, Xinlei; Li, Honglei; Diao, Lihong; Gu, Jiangyong; Wang, Wei; Li, Dong; He, Fuchu

2016-02-16

Traditional Chinese Medicine (TCM), with a history of thousands of years of clinical practice, is gaining more and more attention and application worldwide. And TCM-based new drug development, especially for the treatment of complex diseases is promising. However, owing to the TCM's diverse ingredients and their complex interaction with human body, it is still quite difficult to uncover its molecular mechanism, which greatly hinders the TCM modernization and internationalization. Here we developed the first online Bioinformatics Analysis Tool for Molecular mechANism of TCM (BATMAN-TCM). Its main functions include 1) TCM ingredients' target prediction; 2) functional analyses of targets including biological pathway, Gene Ontology functional term and disease enrichment analyses; 3) the visualization of ingredient-target-pathway/disease association network and KEGG biological pathway with highlighted targets; 4) comparison analysis of multiple TCMs. Finally, we applied BATMAN-TCM to Qishen Yiqi dripping Pill (QSYQ) and combined with subsequent experimental validation to reveal the functions of renin-angiotensin system responsible for QSYQ's cardioprotective effects for the first time. BATMAN-TCM will contribute to the understanding of the "multi-component, multi-target and multi-pathway" combinational therapeutic mechanism of TCM, and provide valuable clues for subsequent experimental validation, accelerating the elucidation of TCM's molecular mechanism. BATMAN-TCM is available at http://bionet.ncpsb.org/batman-tcm.

Mechanical design, analysis, and laboratory testing of a dental implant with axial flexibility similar to natural tooth with periodontal ligament.

PubMed

Pektaş, Ömer; Tönük, Ergin

2014-11-01

At the interface between the jawbone and the roots of natural teeth, a thin, elastic, shock-absorbing tissue, called the periodontal ligament, forms a cushion which provides certain flexibility under mechanical loading. The dental restorations supported by implants, however, involve comparatively rigid connections to the jawbone. This causes overloading of the implant while bearing functional loading together with neighboring natural teeth, which leads to high stresses within the implant system and in the jawbone. A dental implant, with resilient components in the upper structure (abutment) in order to mimic the mechanical behavior of the periodontal ligament in the axial direction, was designed, analyzed in silico, and produced for mechanical testing. The aims of the design were avoiding high levels of stress, loosening of the abutment connection screw, and soft tissue irritations. The finite element analysis of the designed implant revealed that the elastic abutment yielded a similar axial mobility with the natural tooth while keeping stress in the implant at safe levels. The in vitro mechanical testing of the prototype resulted in similar axial mobility predicted by the analysis and as that of a typical natural tooth. The abutment screw did not loosen under repeated loading and there was no static or fatigue failure. © IMechE 2014.

Deducing Reaction Mechanism: A Guide for Students, Researchers, and Instructors

ERIC Educational Resources Information Center

Meek, Simon J.; Pitman, Catherine L.; Miller, Alexander J. M.

2016-01-01

An introductory guide to deducing the mechanism of chemical reactions is presented. Following a typical workflow for probing reaction mechanism, the guide introduces a wide range of kinetic and mechanistic tools. In addition to serving as a broad introduction to mechanistic analysis for students and researchers, the guide has also been used by…

Fracture control methods for space vehicles. Volume 2: Assessment of fracture mechanics technology for space shuttle applications

NASA Technical Reports Server (NTRS)

Ehret, R. M.

1974-01-01

The concepts explored in a state of the art review of those engineering fracture mechanics considered most applicable to the space shuttle vehicle include fracture toughness, precritical flaw growth, failure mechanisms, inspection methods (including proof test logic), and crack growth predictive analysis techniques.

Circulating tumour DNA profiling reveals heterogeneity of EGFR inhibitor resistance mechanisms in lung cancer patients

PubMed Central

Chabon, Jacob J.; Simmons, Andrew D.; Lovejoy, Alexander F.; Esfahani, Mohammad S.; Newman, Aaron M.; Haringsma, Henry J.; Kurtz, David M.; Stehr, Henning; Scherer, Florian; Karlovich, Chris A.; Harding, Thomas C.; Durkin, Kathleen A.; Otterson, Gregory A.; Purcell, W. Thomas; Camidge, D. Ross; Goldman, Jonathan W.; Sequist, Lecia V.; Piotrowska, Zofia; Wakelee, Heather A.; Neal, Joel W.; Alizadeh, Ash A.; Diehn, Maximilian

2016-01-01

Circulating tumour DNA (ctDNA) analysis facilitates studies of tumour heterogeneity. Here we employ CAPP-Seq ctDNA analysis to study resistance mechanisms in 43 non-small cell lung cancer (NSCLC) patients treated with the third-generation epidermal growth factor receptor (EGFR) inhibitor rociletinib. We observe multiple resistance mechanisms in 46% of patients after treatment with first-line inhibitors, indicating frequent intra-patient heterogeneity. Rociletinib resistance recurrently involves MET, EGFR, PIK3CA, ERRB2, KRAS and RB1. We describe a novel EGFR L798I mutation and find that EGFR C797S, which arises in ∼33% of patients after osimertinib treatment, occurs in <3% after rociletinib. Increased MET copy number is the most frequent rociletinib resistance mechanism in this cohort and patients with multiple pre-existing mechanisms (T790M and MET) experience inferior responses. Similarly, rociletinib-resistant xenografts develop MET amplification that can be overcome with the MET inhibitor crizotinib. These results underscore the importance of tumour heterogeneity in NSCLC and the utility of ctDNA-based resistance mechanism assessment. PMID:27283993

Experimental measurement and modeling analysis on mechanical properties of incudostapedial joint

PubMed Central

Zhang, Xiangming

2011-01-01

The incudostapedial (IS) joint between the incus and stapes is a synovial joint consisting of joint capsule, cartilage, and synovial fluid. The mechanical properties of the IS joint directly affect the middle ear transfer function for sound transmission. However, due to the complexity and small size of the joint, the mechanical properties of the IS joint have not been reported in the literature. In this paper, we report our current study on mechanical properties of human IS joint using both experimental measurement and finite element (FE) modeling analysis. Eight IS joint samples with the incus and stapes attached were harvested from human cadaver temporal bones. Tension, compression, stress relaxation and failure tests were performed on those samples in a micro-material testing system. An analytical approach with the hyperelastic Ogden model and a 3D FE model of the IS joint including the cartilage, joint capsule, and synovial fluid were employed to derive mechanical parameters of the IS joint. The comparison of measurements and modeling results reveals the relationship between the mechanical properties and structure of the IS joint. PMID:21061141

Experimental measurement and modeling analysis on mechanical properties of incudostapedial joint.

PubMed

Zhang, Xiangming; Gan, Rong Z

2011-10-01

The incudostapedial (IS) joint between the incus and stapes is a synovial joint consisting of joint capsule, cartilage, and synovial fluid. The mechanical properties of the IS joint directly affect the middle ear transfer function for sound transmission. However, due to the complexity and small size of the joint, the mechanical properties of the IS joint have not been reported in the literature. In this paper, we report our current study on mechanical properties of human IS joint using both experimental measurement and finite element (FE) modeling analysis. Eight IS joint samples with the incus and stapes attached were harvested from human cadaver temporal bones. Tension, compression, stress relaxation and failure tests were performed on those samples in a micro-material testing system. An analytical approach with the hyperelastic Ogden model and a 3D FE model of the IS joint including the cartilage, joint capsule, and synovial fluid were employed to derive mechanical parameters of the IS joint. The comparison of measurements and modeling results reveals the relationship between the mechanical properties and structure of the IS joint.

The criterion for time symmetry of probabilistic theories and the reversibility of quantum mechanics

NASA Astrophysics Data System (ADS)

Holster, A. T.

2003-10-01

Physicists routinely claim that the fundamental laws of physics are 'time symmetric' or 'time reversal invariant' or 'reversible'. In particular, it is claimed that the theory of quantum mechanics is time symmetric. But it is shown in this paper that the orthodox analysis suffers from a fatal conceptual error, because the logical criterion for judging the time symmetry of probabilistic theories has been incorrectly formulated. The correct criterion requires symmetry between future-directed laws and past-directed laws. This criterion is formulated and proved in detail. The orthodox claim that quantum mechanics is reversible is re-evaluated. The property demonstrated in the orthodox analysis is shown to be quite distinct from time reversal invariance. The view of Satosi Watanabe that quantum mechanics is time asymmetric is verified, as well as his view that this feature does not merely show a de facto or 'contingent' asymmetry, as commonly supposed, but implies a genuine failure of time reversal invariance of the laws of quantum mechanics. The laws of quantum mechanics would be incompatible with a time-reversed version of our universe.

Combining instruction prefetching with partial cache locking to improve WCET in real-time systems.

PubMed

Ni, Fan; Long, Xiang; Wan, Han; Gao, Xiaopeng

2013-01-01

Caches play an important role in embedded systems to bridge the performance gap between fast processor and slow memory. And prefetching mechanisms are proposed to further improve the cache performance. While in real-time systems, the application of caches complicates the Worst-Case Execution Time (WCET) analysis due to its unpredictable behavior. Modern embedded processors often equip locking mechanism to improve timing predictability of the instruction cache. However, locking the whole cache may degrade the cache performance and increase the WCET of the real-time application. In this paper, we proposed an instruction-prefetching combined partial cache locking mechanism, which combines an instruction prefetching mechanism (termed as BBIP) with partial cache locking to improve the WCET estimates of real-time applications. BBIP is an instruction prefetching mechanism we have already proposed to improve the worst-case cache performance and in turn the worst-case execution time. The estimations on typical real-time applications show that the partial cache locking mechanism shows remarkable WCET improvement over static analysis and full cache locking.

Combining Instruction Prefetching with Partial Cache Locking to Improve WCET in Real-Time Systems

PubMed Central

Ni, Fan; Long, Xiang; Wan, Han; Gao, Xiaopeng

2013-01-01

Caches play an important role in embedded systems to bridge the performance gap between fast processor and slow memory. And prefetching mechanisms are proposed to further improve the cache performance. While in real-time systems, the application of caches complicates the Worst-Case Execution Time (WCET) analysis due to its unpredictable behavior. Modern embedded processors often equip locking mechanism to improve timing predictability of the instruction cache. However, locking the whole cache may degrade the cache performance and increase the WCET of the real-time application. In this paper, we proposed an instruction-prefetching combined partial cache locking mechanism, which combines an instruction prefetching mechanism (termed as BBIP) with partial cache locking to improve the WCET estimates of real-time applications. BBIP is an instruction prefetching mechanism we have already proposed to improve the worst-case cache performance and in turn the worst-case execution time. The estimations on typical real-time applications show that the partial cache locking mechanism shows remarkable WCET improvement over static analysis and full cache locking. PMID:24386133

Regression-based statistical mediation and moderation analysis in clinical research: Observations, recommendations, and implementation.

PubMed

Hayes, Andrew F; Rockwood, Nicholas J

2017-11-01

There have been numerous treatments in the clinical research literature about various design, analysis, and interpretation considerations when testing hypotheses about mechanisms and contingencies of effects, popularly known as mediation and moderation analysis. In this paper we address the practice of mediation and moderation analysis using linear regression in the pages of Behaviour Research and Therapy and offer some observations and recommendations, debunk some popular myths, describe some new advances, and provide an example of mediation, moderation, and their integration as conditional process analysis using the PROCESS macro for SPSS and SAS. Our goal is to nudge clinical researchers away from historically significant but increasingly old school approaches toward modifications, revisions, and extensions that characterize more modern thinking about the analysis of the mechanisms and contingencies of effects. Copyright © 2016 Elsevier Ltd. All rights reserved.

Changes in frontal plane dynamics and the loading response phase of the gait cycle are characteristic of severe knee osteoarthritis application of a multidimensional analysis technique.

PubMed

Astephen, J L; Deluzio, K J

2005-02-01

Osteoarthritis of the knee is related to many correlated mechanical factors that can be measured with gait analysis. Gait analysis results in large data sets. The analysis of these data is difficult due to the correlated, multidimensional nature of the measures. A multidimensional model that uses two multivariate statistical techniques, principal component analysis and discriminant analysis, was used to discriminate between the gait patterns of the normal subject group and the osteoarthritis subject group. Nine time varying gait measures and eight discrete measures were included in the analysis. All interrelationships between and within the measures were retained in the analysis. The multidimensional analysis technique successfully separated the gait patterns of normal and knee osteoarthritis subjects with a misclassification error rate of <6%. The most discriminatory feature described a static and dynamic alignment factor. The second most discriminatory feature described a gait pattern change during the loading response phase of the gait cycle. The interrelationships between gait measures and between the time instants of the gait cycle can provide insight into the mechanical mechanisms of pathologies such as knee osteoarthritis. These results suggest that changes in frontal plane loading and alignment and the loading response phase of the gait cycle are characteristic of severe knee osteoarthritis gait patterns. Subsequent investigations earlier in the disease process may suggest the importance of these factors to the progression of knee osteoarthritis.

Analysis and Evaluation of Deployment Mechanism of a Tiny Rover in a Microgravity by Drop Tower Experiments

NASA Astrophysics Data System (ADS)

Nagaoka, Kenji; Yano, Hajime; Yoshimitsu, Tetsuo; Yoshida, Kazuya; Kubota, Takashi; Adachi, Tadashi; Kurisu, Masamitsu; Yatsunami, Hiroyuki; Kuroda, Yoji

This presentation introduces the analysis and evaluation of a deployment mechanism of a tiny rover by ZARM drop tower experiments. The mechanism is installed on the MINERVA-II2 system in the Hayabusa-2 project performed by JAXA. The MINERVA-II2 system includes a small exploration rover, and the rover will be released from the Hayabusa-2 spacecraft to the asteroid surface. After the rover lands on the surface, it will move over the surface and conduct scientific measurements. To achieve such a challenging mission, the deployment mechanism of the rover is one of the significant components. In particular, controlling the rover's landing velocity against the asteroid surface is required with high-reliability mechanism. In the MINERVA-II2 system, a reliable deployment mechanism using a metal spring is installed. By the simple mechanism, the rover's releasing velocity will be controlled within a required value. Although the performance evaluation and analysis are necessary before launch, it is difficult to experiment the deployment performance three-dimensionally on ground. In the MINERVA-II2 project, with the cooperation of ZARM, DLR and JAXA, we conducted microgravity experiments using a ZARM drop tower to examine the deployment performance in a three-dimensional microgravity. During the experiments, motion of the deployment mechanism and the rover were captured by an external camera mounted on the dropping chamber. After the drop, we analyzed the rover's releasing velocity based on image processing of the camera data. The experimental results confirmed that the deployment mechanism is feasible and reliable for controlling the rover's releasing velocity. In addition to the experiments, we analyzed a mechanical friction resistance of the mechanism from a theoretical viewpoint. These results contribute to design of spring stiffness and feedback to the development of the MINERVA-II2 flight model. Finally, the drop tower experiments were accomplished based on the agreement on the Hayabusa-2 project by DLR-JAXA. The chamber for the experiments was used, which was developed by the Hayabusa-2 project. In the experiments, we received technical and operations supports from ZARM. We sincerely express our acknowledgement to ZARM, DLR and JAXA.

Mechanics of inter-modal tunneling in nonlinear waveguides

NASA Astrophysics Data System (ADS)

Jiao, Weijian; Gonella, Stefano

2018-02-01

In this article, we investigate the mechanics of nonlinearly induced inter-modal energy tunneling between flexurally-dominated and axially-dominated modes in phononic waveguides. Special attention is devoted to elucidating the role played by the coupling between axial and flexural degrees of freedom in the determination of the available mode hopping conditions and the associated mechanisms of deformation. Waveguides offer an ideal test bed to investigate the mechanics of nonlinear energy tunneling, due to the fact that they naturally feature, even at low frequencies, families of modes (flexural and axial) that are intrinsically characterized by extreme complementarity. Moreover, thanks to their geometric simplicity, their behavior can be explained by resorting to intuitive structural mechanics models that effectively capture the dichotomy and interplay between flexural and axial mechanisms. After having delineated the fundamental mechanics of flexural-to-axial hopping using the benchmark example of a homogeneous structure, we adapt the analysis to the case of periodic waveguides, in which the complex dispersive behavior due to periodicity results in additional richness of mode hopping mechanisms. We finally extend the analysis to periodic waveguides with internal resonators, in which the availability of locally-resonant bandgaps implies the possibility to activate the resonators even at relatively low frequencies, thus increasing the degree of modal complementarity that is available in the acoustic range. In this context, inter-modal tunneling provides an unprecedented mechanism to transfer conspicuous packets of energy to the resonating microstructure.

Course of Weaning from Prolonged Mechanical Ventilation after Cardiac Surgery

PubMed Central

Herlihy, James P.; Koch, Stephen M.; Jackson, Robert; Nora, Hope

2006-01-01

In order to determine the temporal pattern of weaning from mechanical ventilation for patients undergoing prolonged mechanical ventilation after cardiac surgery, we performed a retrospective review of 21 patients' weaning courses at our long-term acute care hospital. Using multiple regression analysis of an estimate of individual patients' percentage of mechanical ventilator support per day (%MVSD), we determined that 14 of 21 patients (67%) showed a statistically significant quadratic or cubic relationship between time and %MVSD. These patients showed little or no improvement in their ventilator dependence until a point in time when, abruptly, they began to make rapid progress (a “wean turning point”), after which they progressed to discontinuation of mechanical ventilation in a relatively short period of time. The other 7 patients appeared to have a similar weaning pattern, although the data were not statistically significant. Most patients in the study group weaned from the ventilator through a specific temporal pattern that is newly described herein. Data analysis suggested that the mechanism for the development of a wean turning point was improvement of pulmonary mechanics rather than improvement in gas exchange or respiratory load. Although these observations need to be confirmed by a prospective trial, they may have implications for weaning cardiac surgery patients from prolonged mechanical ventilation, and possibly for weaning a broader group of patients who require prolonged mechanical ventilation. PMID:16878611

High-Frequency Oscillatory Ventilation Use and Severe Pediatric ARDS in the Pediatric Hematopoietic Cell Transplant Recipient.

PubMed

Rowan, Courtney M; Loomis, Ashley; McArthur, Jennifer; Smith, Lincoln S; Gertz, Shira J; Fitzgerald, Julie C; Nitu, Mara E; Moser, Elizabeth As; Hsing, Deyin D; Duncan, Christine N; Mahadeo, Kris M; Moffet, Jerelyn; Hall, Mark W; Pinos, Emily L; Tamburro, Robert F; Cheifetz, Ira M

2018-04-01

The effectiveness of high-frequency oscillatory ventilation (HFOV) in the pediatric hematopoietic cell transplant patient has not been established. We sought to identify current practice patterns of HFOV, investigate parameters during HFOV and their association with mortality, and compare the use of HFOV to conventional mechanical ventilation in severe pediatric ARDS. This is a retrospective analysis of a multi-center database of pediatric and young adult allogeneic hematopoietic cell transplant subjects requiring invasive mechanical ventilation for critical illness from 2009 through 2014. Twelve United States pediatric centers contributed data. Continuous variables were compared using a Wilcoxon rank-sum test or a Kruskal-Wallis analysis. For categorical variables, univariate analysis with logistic regression was performed. The database contains 222 patients, of which 85 subjects were managed with HFOV. Of this HFOV cohort, the overall pediatric ICU survival was 23.5% ( n = 20). HFOV survivors were transitioned to HFOV at a lower oxygenation index than nonsurvivors (25.6, interquartile range 21.1-36.8, vs 37.2, interquartile range 26.5-52.2, P = .046). Survivors were transitioned to HFOV earlier in the course of mechanical ventilation, (day 0 vs day 2, P = .002). No subject survived who was transitioned to HFOV after 1 week of invasive mechanical ventilation. We compared subjects with severe pediatric ARDS treated only with conventional mechanical ventilation versus early HFOV (within 2 d of invasive mechanical ventilation) versus late HFOV. There was a trend toward difference in survival (conventional mechanical ventilation 24%, early HFOV 30%, and late HFOV 9%, P = .08). In this large database of pediatric allogeneic hematopoietic cell transplant subjects who had acute respiratory failure requiring invasive mechanical ventilation for critical illness with severe pediatric ARDS, early use of HFOV was associated with improved survival compared to late implementation of HFOV, and the subjects had outcomes similar to those treated only with conventional mechanical ventilation. Copyright © 2018 by Daedalus Enterprises.

Kinetic analysis of a Michaelis-Menten mechanism in which the enzyme is unstable.

PubMed Central

Garrido-del Solo, C; García-Cánovas, F; Havsteen, B H; Varón-Castellanos, R

1993-01-01

A kinetic analysis of the Michaelis-Menten mechanism is made for the cases in which the free enzyme, or the enzyme-substrate complex, or both, are unstable, either spontaneously or as a result of the addition of a reagent. The explicit time-course equations of all of the species involved has been derived under conditions of limiting enzyme concentration. The validity of these equations has been checked by using numerical simulations. An experimental design and a kinetic data analysis allowing the evaluation of the parameters and kinetic constants are recommended. PMID:8373361

Network Analysis Reveals the Recognition Mechanism for Mannose-binding Lectins

NASA Astrophysics Data System (ADS)

Zhao, Yunjie; Jian, Yiren; Zeng, Chen; Computational Biophysics Lab Team

The specific carbohydrate binding of mannose-binding lectin (MBL) protein in plants makes it a very useful molecular tool for cancer cell detection and other applications. The biological states of most MBL proteins are dimeric. Using dynamics network analysis on molecular dynamics (MD) simulations on the model protein of MBL, we elucidate the short- and long-range driving forces behind the dimer formation. The results are further supported by sequence coevolution analysis. We propose a general framework for deciphering the recognition mechanism underlying protein-protein interactions that may have potential applications in signaling pathways.

Echocardiographic Evaluation of Left Atrial Mechanics: Function, History, Novel Techniques, Advantages, and Pitfalls.

PubMed

Leischik, Roman; Littwitz, Henning; Dworrak, Birgit; Garg, Pankaj; Zhu, Meihua; Sahn, David J; Horlitz, Marc

2015-01-01

Left atrial (LA) functional analysis has an established role in assessing left ventricular diastolic function. The current standard echocardiographic parameters used to study left ventricular diastolic function include pulsed-wave Doppler mitral inflow analysis, tissue Doppler imaging measurements, and LA dimension estimation. However, the above-mentioned parameters do not directly quantify LA performance. Deformation studies using strain and strain-rate imaging to assess LA function were validated in previous research, but this technique is not currently used in routine clinical practice. This review discusses the history, importance, and pitfalls of strain technology for the analysis of LA mechanics.

Computational fluid mechanics utilizing the variational principle of modeling damping seals

NASA Technical Reports Server (NTRS)

Abernathy, J. M.; Farmer, R.

1985-01-01

An analysis for modeling damping seals for use in Space Shuttle main engine turbomachinery is being produced. Development of a computational fluid mechanics code for turbulent, incompressible flow is required.

Wear mechanisms of the biotribological nanocomposite a-C : H coatings implanted by metallic nanoparticles.

PubMed

Major, L; Janusz, M; Lackner, J M; Kot, M; Dyner, M; Major, B

2017-10-01

Recently, to reduce the residual stress and increase the mechanical properties of a-C:H coatings, metallic nanoparticles have been implanted into their structure. In the present work, to improve the properties of the coating, metallic nanoparticles, including Cu, Nb, Ta, Zr, AgPt and Ag, were inserted into the a-C:H structure. The applied biological and mechanical analysis allowed the optimal biotribological parameters to be indicated for the potential application as protective coatings for metallic medical tools. Wear mechanisms operating at the small length of the designed biotribological coating, such as a-C:H implanted by Zr nanoparticles, were studied by means of transmission electron microscopy (TEM). The TEM analysis confirmed very good coating adhesion to the metallic substrate. © 2017 The Authors Journal of Microscopy © 2017 Royal Microscopical Society.

Theoretical and experimental analysis of the reaction mechanism of MrTPS2, a triquinane-forming sesquiterpene synthase from chamomile.

PubMed

Hong, Young J; Irmisch, Sandra; Wang, Selina C; Garms, Stefan; Gershenzon, Jonathan; Zu, Liansuo; Köllner, Tobias G; Tantillo, Dean J

2013-09-27

Terpene synthases, as key enzymes of terpene biosynthesis, have garnered the attention of chemists and biologists for many years. Their carbocationic reaction mechanisms are responsible for the huge variety of terpene structures in nature. These mechanisms are amenable to study by using classical biochemical approaches as well as computational analysis, and in this study we combine quantum-chemical calculations and deuterium-labeling experiments to elucidate the reaction mechanism of a triquinane forming sesquiterpene synthase from chamomile. Our results suggest that the reaction from farnesyl diphosphate to triquinanes proceeds through caryophyllyl and presilphiperfolanyl cations and involves the protonation of a stable (-)-(E)-β-caryophyllene intermediate. A tyrosine residue was identified that appears to be involved in the proton-transfer process. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of electron beam irradiation on thermal and mechanical properties of epoxy polymer

NASA Astrophysics Data System (ADS)

Nguyen, A. T.; Visakh, P. M.; Nazarenko, O. B.; Chandran, C. S.; Melnikova, T. V.

2017-01-01

This study investigates the thermal and mechanical properties of epoxy polymer after exposure to different doses of electron beam irradiation. The epoxy polymer was prepared using epoxy-diane resin ED-20 cured by polyethylenepolyamine. The irradiation of the samples was carried out with doses of 30, 100 and 300 kGy. The effects of doses on thermal and mechanical properties of the epoxy polymer were investigated by the methods of thermal gravimetric analysis, tensile test, and dynamic mechanical analysis. The thermal properties of the epoxy polymer slightly increased after irradiation at the heating in air. The tensile strength and Young’s modulus of the epoxy polymer increased by the action of electron beam up to dose of 100 kGy and then decreased. The elongation at break decreased with increasing the irradiation dose.

Behavior analysis and mechanism: One is not the other

PubMed Central

Morris, Edward K.

1993-01-01

Behavior analysts have been called mechanists, and behavior analysis is said to be mechanistic; that is, they are claimed to be aligned with the philosophy of mechanism. What this means is analyzed by (a) examining standard and specialized dictionary and encyclopedia definitions and descriptions of mechanism and its cognates and (b) reviewing contemporary representations of the mechanistic worldview in the literature on the philosophy of psychology. Although the term mechanism and its cognates are sometimes an honorific (e.g., “natural science”), their standard meanings, usages, and functions in society, science, psychology, and philosophy do not aptly characterize the discipline. These terms mischaracterize how behavior analysts conceptualize (a) the behavior of their subjects and the individuals with whom they work and (b) their own behavior as scientists. Discussion is interwoven throughout about the nature of terms and definitions in science. PMID:22478129

Top-Down Targeted Proteomics Reveals Decrease in Myosin Regulatory Light-Chain Phosphorylation That Contributes to Sarcopenic Muscle Dysfunction.

PubMed

Gregorich, Zachery R; Peng, Ying; Cai, Wenxuan; Jin, Yutong; Wei, Liming; Chen, Albert J; McKiernan, Susan H; Aiken, Judd M; Moss, Richard L; Diffee, Gary M; Ge, Ying

2016-08-05

Sarcopenia, the loss of skeletal muscle mass and function with advancing age, is a significant cause of disability and loss of independence in the elderly and thus, represents a formidable challenge for the aging population. Nevertheless, the molecular mechanism(s) underlying sarcopenia-associated muscle dysfunction remain poorly understood. In this study, we employed an integrated approach combining top-down targeted proteomics with mechanical measurements to dissect the molecular mechanism(s) in age-related muscle dysfunction. Top-down targeted proteomic analysis uncovered a progressive age-related decline in the phosphorylation of myosin regulatory light chain (RLC), a critical protein involved in the modulation of muscle contractility, in the skeletal muscle of aging rats. Top-down tandem mass spectrometry analysis identified a previously unreported bis-phosphorylated proteoform of fast skeletal RLC and localized the sites of decreasing phosphorylation to Ser14/15. Of these sites, Ser14 phosphorylation represents a previously unidentified site of phosphorylation in RLC from fast-twitch skeletal muscle. Subsequent mechanical analysis of single fast-twitch fibers isolated from the muscles of rats of different ages revealed that the observed decline in RLC phosphorylation can account for age-related decreases in the contractile properties of sarcopenic fast-twitch muscles. These results strongly support a role for decreasing RLC phosphorylation in sarcopenia-associated muscle dysfunction and suggest that therapeutic modulation of RLC phosphorylation may represent a new avenue for the treatment of sarcopenia.

Mechanism reduction for multicomponent surrogates: A case study using toluene reference fuels

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

Niemeyer, Kyle E.; Sung, Chih-Jen

Strategies and recommendations for performing skeletal reductions of multicomponent surrogate fuels are presented, through the generation and validation of skeletal mechanisms for a three-component toluene reference fuel. Using the directed relation graph with error propagation and sensitivity analysis method followed by a further unimportant reaction elimination stage, skeletal mechanisms valid over comprehensive and high-temperature ranges of conditions were developed at varying levels of detail. These skeletal mechanisms were generated based on autoignition simulations, and validation using ignition delay predictions showed good agreement with the detailed mechanism in the target range of conditions. When validated using phenomena other than autoignition, suchmore » as perfectly stirred reactor and laminar flame propagation, tight error control or more restrictions on the reduction during the sensitivity analysis stage were needed to ensure good agreement. In addition, tight error limits were needed for close prediction of ignition delay when varying the mixture composition away from that used for the reduction. In homogeneous compression-ignition engine simulations, the skeletal mechanisms closely matched the point of ignition and accurately predicted species profiles for lean to stoichiometric conditions. Furthermore, the efficacy of generating a multicomponent skeletal mechanism was compared to combining skeletal mechanisms produced separately for neat fuel components; using the same error limits, the latter resulted in a larger skeletal mechanism size that also lacked important cross reactions between fuel components. Based on the present results, general guidelines for reducing detailed mechanisms for multicomponent fuels are discussed.« less

Static and Dynamic Mechanical Characteristics of Ionic Liquid Modified MWCNT-SBR Composites: Theoretical Perspectives for the Nanoscale Reinforcement Mechanism.

PubMed

Abraham, Jiji; Thomas, Jince; Kalarikkal, Nandakumar; George, Soney C; Thomas, Sabu

2018-02-01

Well-dispersed, robust, mechanicaly long-term stable functionalized multiwalled carbon nanotube (f-MWCNT)-styrene butadiene rubber (SBR) nanocomposites were fabricated via a melt mixing route with the assistance of ionic liquid as a dispersing agent. The mechanical properties of f-MWCNT/SBR vulcanizates were compared over a range of loadings, and it was found that the network morphology was highly favorable for mechanical performance with enlarged stiffness. A comparative investigation of composite models found that modified Kelly-Tyson theory gave an excellent fit to tensile strength data of the composites considering the effect of the interphase between polymer and f-MWCNT. Dynamic mechanical analysis highlighted the mechanical reinforcement due to the improved filler-polymer interactions which were the consequence of proper dispersion of the nanotubes in the SBR matrix. Effectiveness of filler, entanglement density, and adhesion factor were evaluated to get an in depth understanding of the reinforcing mechanism of modified MWCNT. The amount of polymer chains immobilized by the filler surface computed from dynamic mechanical analysis further supports a substantial boost up in mechanics. The Cole-Cole plot shows an imperfect semicircular curve representing the heterogeneity of the system and moderately worthy filler polymer bonding. The combined results of structural characterizatrion by Raman spectroscopy, cure characteristics, mechanical properties, and scanning and transmission electron microscopy (SEM, TEM) confirm the role of ionic liquid modified MWCNT as a reinforcing agent in the present system.

Mechanism reduction for multicomponent surrogates: A case study using toluene reference fuels

DOE PAGES

Niemeyer, Kyle E.; Sung, Chih-Jen

2014-11-01

Strategies and recommendations for performing skeletal reductions of multicomponent surrogate fuels are presented, through the generation and validation of skeletal mechanisms for a three-component toluene reference fuel. Using the directed relation graph with error propagation and sensitivity analysis method followed by a further unimportant reaction elimination stage, skeletal mechanisms valid over comprehensive and high-temperature ranges of conditions were developed at varying levels of detail. These skeletal mechanisms were generated based on autoignition simulations, and validation using ignition delay predictions showed good agreement with the detailed mechanism in the target range of conditions. When validated using phenomena other than autoignition, suchmore » as perfectly stirred reactor and laminar flame propagation, tight error control or more restrictions on the reduction during the sensitivity analysis stage were needed to ensure good agreement. In addition, tight error limits were needed for close prediction of ignition delay when varying the mixture composition away from that used for the reduction. In homogeneous compression-ignition engine simulations, the skeletal mechanisms closely matched the point of ignition and accurately predicted species profiles for lean to stoichiometric conditions. Furthermore, the efficacy of generating a multicomponent skeletal mechanism was compared to combining skeletal mechanisms produced separately for neat fuel components; using the same error limits, the latter resulted in a larger skeletal mechanism size that also lacked important cross reactions between fuel components. Based on the present results, general guidelines for reducing detailed mechanisms for multicomponent fuels are discussed.« less

Study of the effect of gamma irradiation on a commercial polycyclooctene I. Thermal and mechanical properties

NASA Astrophysics Data System (ADS)

García-Huete, N.; Laza, J. M.; Cuevas, J. M.; Vilas, J. L.; Bilbao, E.; León, L. M.

2014-09-01

A gamma radiation process for modification of commercial polymers is a widely applied technique to promote new physical, chemical and mechanical properties. Gamma irradiation originates free radicals able to induce chain scission or recombination of radicals, which induces annihilation, branching or crosslinking processes. The aim of this work is to research the structural, thermal and mechanical changes induced on a commercial polycyclooctene (PCO) when it is irradiated with a gamma source of 60Co at different doses (25-200 kGy). After gamma irradiation, gel content was determined by Soxhlet extraction in cyclohexane. Furthermore, thermal properties were evaluated before and after Soxhlet extraction by means of Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC), as well as mechanical properties were measured by Dynamic Mechanical Thermal Analysis (DMTA). The results showed the variations of the properties depending on the irradiation dose. Finally, a first approach to evaluate qualitatively the shape memory behaviour of all irradiated PCO samples was performed by a visually monitoring shape recovery process.

Evaluation of consolidation method on mechanical and structural properties of ODS RAF steel

NASA Astrophysics Data System (ADS)

Frelek-Kozak, M.; Kurpaska, L.; Wyszkowska, E.; Jagielski, J.; Jozwik, I.; Chmielewski, M.

2018-07-01

In the present work, the effects of the fabrication method on mechanical and structural properties of 12%Cr, 2%W, 0.25%Ti, 0.25%Y2O3 steels were investigated. Materials obtained by Spark Plasma Sintering (SPS), Hot Isostatic Pressing (HIP) and Hot Extrusion (HE) methods were studied. The microstructure was characterized by using Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction analysis (EBSD). Mechanical properties of the studied samples were evaluated by using Vickers micro hardness HV0.1, Small Punch Test (SPT) and nanoindentation (NI) methods. The analysis revealed that samples manufactured via HIP and SPS processes exhibit very similar properties, whereas SPS method produces material with slightly lower hardness. In addition, significantly lower mechanical properties of the specimens after HE process were observed. The study described in this article addresses also the problems of mechanical parameters measured in micro- and nano-scale experiments and aims to identify possible pitfalls related to the use of various manufacturing technologies.

Grid indentation analysis of mechanical properties of composite electrodes in Li-ion batteries

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

Vasconcelos, Luize Scalco de; Xu, Rong; Li, Jianlin

We report that electrodes in commercial rechargeable batteries are microscopically heterogeneous materials. The constituent components, including active materials, polymeric binders, and porous conductive matrix, often have large variation in their mechanical properties, making the mechanical characterization of composite electrodes a challenging task. In a model system of LiNi 0.5Mn 0.3Co 0.2O 2 cathode, we employ the instrumented grid indentation to determine the elastic modulus and hardness of the constituent phases. The approach relies on a large array of nanoindentation experiments and statistical analysis of the resulting data provided that the maximum indentation depth is carefully chosen. The statistically extracted propertiesmore » of the active particles and the surrounding medium are in good agreement with the tests of targeted indentation at selected sites. Lastly, the combinatory technique of grid indentation and statistical deconvolution represents a fast and reliable route to quantify the mechanical properties of composite electrodes that feed the parametric input for the mechanics models.« less

Grid indentation analysis of mechanical properties of composite electrodes in Li-ion batteries

DOE PAGES

Vasconcelos, Luize Scalco de; Xu, Rong; Li, Jianlin; ...

2016-03-09

We report that electrodes in commercial rechargeable batteries are microscopically heterogeneous materials. The constituent components, including active materials, polymeric binders, and porous conductive matrix, often have large variation in their mechanical properties, making the mechanical characterization of composite electrodes a challenging task. In a model system of LiNi 0.5Mn 0.3Co 0.2O 2 cathode, we employ the instrumented grid indentation to determine the elastic modulus and hardness of the constituent phases. The approach relies on a large array of nanoindentation experiments and statistical analysis of the resulting data provided that the maximum indentation depth is carefully chosen. The statistically extracted propertiesmore » of the active particles and the surrounding medium are in good agreement with the tests of targeted indentation at selected sites. Lastly, the combinatory technique of grid indentation and statistical deconvolution represents a fast and reliable route to quantify the mechanical properties of composite electrodes that feed the parametric input for the mechanics models.« less

Fracture mechanics evaluation of heavy welded structures

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

Sprung, I.; Ericksson, C.W.; Zilberstein, V.A.

1982-05-01

This paper describes some applications of nondestructive examination (NDE) and engineering fracture mechanics to evaluation of flaws in heavy welded structures. The paper discusses not only widely recognized linear elastic fracture mechanics (LEFM) analysis, but also methods of the elastic-plastic fracture mechanics (EPFM), such as COD, J-integral, and Failure Assessment Diagram. Examples are given to highlight the importance of interaction between specialists providing input and the specialists performing the analysis. The paper points out that the critical parameters for as-welded structures when calculated by these methods are conservative since they are based on two pessimistic assumptions: that the magnitude ofmore » residual stress is always at the yield strength level, and that the residual stress always acts in the same direction as the applied (mechanical) stress. The suggestion is made that it would be prudent to use the COD or the FAD design curves for a conservative design. The appendix examines a J-design curve modified to include residual stresses.« less

Effect of electron beam irradiation on thermal and mechanical properties of aluminum based epoxy composites

NASA Astrophysics Data System (ADS)

Visakh, P. M.; Nazarenko, O. B.; Sarath Chandran, C.; Melnikova, T. V.; Nazarenko, S. Yu.; Kim, J.-C.

2017-07-01

The epoxy resins are widely used in nuclear and aerospace industries. The certain properties of epoxy resins as well as the resistance to radiation can be improved by the incorporation of different fillers. This study examines the effect of electron beam irradiation on the thermal and mechanical properties of the epoxy composites filled with aluminum nanoparticles at percentage of 0.35 wt%. The epoxy composites were exposed to the irradiation doses of 30, 100 and 300 kGy using electron beam generated by the linear electron accelerator ELU-4. The effects of the doses on thermal and mechanical properties of the aluminum based epoxy composites were investigated by the methods of thermal gravimetric analysis, tensile test, and dynamic mechanical analysis. The results revealed that the studied epoxy composites showed good radiation resistance. The thermal and mechanical properties of the aluminum based epoxy composites increased with increasing the irradiation dose up to 100 kGy and decreased with further increasing the dose.

Analysis of parameters for technological equipment of parallel kinematics based on rods of variable length for processing accuracy assurance

NASA Astrophysics Data System (ADS)

Koltsov, A. G.; Shamutdinov, A. H.; Blokhin, D. A.; Krivonos, E. V.

2018-01-01

A new classification of parallel kinematics mechanisms on symmetry coefficient, being proportional to mechanism stiffness and accuracy of the processing product using the technological equipment under study, is proposed. A new version of the Stewart platform with a high symmetry coefficient is presented for analysis. The workspace of the mechanism under study is described, this space being a complex solid figure. The workspace end points are reached by the center of the mobile platform which moves in parallel related to the base plate. Parameters affecting the processing accuracy, namely the static and dynamic stiffness, natural vibration frequencies are determined. The capability assessment of the mechanism operation under various loads, taking into account resonance phenomena at different points of the workspace, was conducted. The study proved that stiffness and therefore, processing accuracy with the use of the above mentioned mechanisms are comparable with the stiffness and accuracy of medium-sized series-produced machines.

Mechanical relaxation in a Zr-based bulk metallic glass: Analysis based on physical models

NASA Astrophysics Data System (ADS)

Qiao, J. C.; Pelletier, J. M.

2012-08-01

The mechanical relaxation behavior in a Zr55Cu30Ni5Al10 bulk metallic glass is investigated by dynamic mechanical analysis in both temperature and frequency domains. Master curves can be obtained for the storage modulus G' and for the loss modulus G'', confirming the validity of the time-temperature superposition principle. Different models are discussed to describe the main (α) relaxation, e.g., Debye model, Havriliak-Negami (HN) model, Kohlrausch-Williams-Watt (KWW) model, and quasi-point defects (QPDs) model. The main relaxation in bulk metallic glass cannot be described using a single relaxation time. The HN model, the KWW model, and the QPD theory can be used to fit the data of mechanical spectroscopy experiments. However, unlike the HN model and the KWW model, some physical parameters are introduced in QPD model, i.e., atomic mobility and correlation factor, giving, therefore, a new physical approach to understand the mechanical relaxation in bulk metallic glasses.

Applications of FEM and BEM in two-dimensional fracture mechanics problems

NASA Technical Reports Server (NTRS)

Min, J. B.; Steeve, B. E.; Swanson, G. R.

1992-01-01

A comparison of the finite element method (FEM) and boundary element method (BEM) for the solution of two-dimensional plane strain problems in fracture mechanics is presented in this paper. Stress intensity factors (SIF's) were calculated using both methods for elastic plates with either a single-edge crack or an inclined-edge crack. In particular, two currently available programs, ANSYS for finite element analysis and BEASY for boundary element analysis, were used.

Kinetics and mechanism of the oxidation process of two-component Fe-Al alloys

NASA Technical Reports Server (NTRS)

Przewlocka, H.; Siedlecka, J.

1982-01-01

The oxidation process of two-component Fe-Al alloys containing up to 7.2% Al and from 18 to 30% Al was studied. Kinetic measurements were conducted using the isothermal gravimetric method in the range of 1073-1223 K and 1073-1373 K for 50 hours. The methods used in studies of the mechanism of oxidation included: X-ray microanalysis, X-ray structural analysis, metallographic analysis and marker tests.

UTD analysis of electromagnetic scattering by flat structures. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Sikta, F. A.; Peters, L., Jr.

1981-01-01

The different scattering mechanisms that contribute to the radar cross of finite flat plates were identified and analyzed. The geometrical theory of diffraction, the equivalent current and the corner diffraction are used for this study. A study of the cross polarized field for a monopole mounted on a plate is presented, using novel edge wave mechanism in the analysis. The results are compared with moment method solutions as well as measured data.

Availability analysis of mechanical systems with condition-based maintenance using semi-Markov and evaluation of optimal condition monitoring interval

NASA Astrophysics Data System (ADS)

Kumar, Girish; Jain, Vipul; Gandhi, O. P.

2018-03-01

Maintenance helps to extend equipment life by improving its condition and avoiding catastrophic failures. Appropriate model or mechanism is, thus, needed to quantify system availability vis-a-vis a given maintenance strategy, which will assist in decision-making for optimal utilization of maintenance resources. This paper deals with semi-Markov process (SMP) modeling for steady state availability analysis of mechanical systems that follow condition-based maintenance (CBM) and evaluation of optimal condition monitoring interval. The developed SMP model is solved using two-stage analytical approach for steady-state availability analysis of the system. Also, CBM interval is decided for maximizing system availability using Genetic Algorithm approach. The main contribution of the paper is in the form of a predictive tool for system availability that will help in deciding the optimum CBM policy. The proposed methodology is demonstrated for a centrifugal pump.

3-D inelastic analysis methods for hot section components (base program). [turbine blades, turbine vanes, and combustor liners

NASA Technical Reports Server (NTRS)

Wilson, R. B.; Bak, M. J.; Nakazawa, S.; Banerjee, P. K.

1984-01-01

A 3-D inelastic analysis methods program consists of a series of computer codes embodying a progression of mathematical models (mechanics of materials, special finite element, boundary element) for streamlined analysis of combustor liners, turbine blades, and turbine vanes. These models address the effects of high temperatures and thermal/mechanical loadings on the local (stress/strain) and global (dynamics, buckling) structural behavior of the three selected components. These models are used to solve 3-D inelastic problems using linear approximations in the sense that stresses/strains and temperatures in generic modeling regions are linear functions of the spatial coordinates, and solution increments for load, temperature and/or time are extrapolated linearly from previous information. Three linear formulation computer codes, referred to as MOMM (Mechanics of Materials Model), MHOST (MARC-Hot Section Technology), and BEST (Boundary Element Stress Technology), were developed and are described.

In vivo measurement of mechanical properties of human long bone by using sonic sound

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

Hossain, M. Jayed, E-mail: zed.hossain06@gmail.com; Rahman, M. Moshiur, E-mail: razib-121@yahoo.com; Alam, Morshed

Vibration analysis has evaluated as non-invasive techniques for the in vivo assessment of bone mechanical properties. The relation between the resonant frequencies, long bone geometry and mechanical properties can be obtained by vibration analysis. In vivo measurements were performed on human ulna as a simple beam model with an experimental technique and associated apparatus. The resonant frequency of the ulna was obtained by Fast Fourier Transformation (FFT) analysis of the vibration response of piezoelectric accelerometer. Both elastic modulus and speed of the sound were inferred from the resonant frequency. Measurement error in the improved experimental setup was comparable with themore » previous work. The in vivo determination of bone elastic response has potential value in screening programs for metabolic bone disease, early detection of osteoporosis and evaluation of skeletal effects of various therapeutic modalities.« less

Validation of Slosh Model Parameters and Anti-Slosh Baffle Designs of Propellant Tanks by Using Lateral Slosh Testing

NASA Technical Reports Server (NTRS)

Perez, Jose G.; Parks, Russel, A.; Lazor, Daniel R.

2012-01-01

The slosh dynamics of propellant tanks can be represented by an equivalent mass-pendulum-dashpot mechanical model. The parameters of this equivalent model, identified as slosh mechanical model parameters, are slosh frequency, slosh mass, and pendulum hinge point location. They can be obtained by both analysis and testing for discrete fill levels. Anti-slosh baffles are usually needed in propellant tanks to control the movement of the fluid inside the tank. Lateral slosh testing, involving both random excitation testing and free-decay testing, are performed to validate the slosh mechanical model parameters and the damping added to the fluid by the anti-slosh baffles. Traditional modal analysis procedures were used to extract the parameters from the experimental data. Test setup of sub-scale tanks will be described. A comparison between experimental results and analysis will be presented.

Controlled hydrostatic pressure stress downregulates the expression of ribosomal genes in preimplantation embryos: a possible protection mechanism?

PubMed

Bock, I; Raveh-Amit, H; Losonczi, E; Carstea, A C; Feher, A; Mashayekhi, K; Matyas, S; Dinnyes, A; Pribenszky, C

2016-04-01

The efficiency of various assisted reproductive techniques can be improved by preconditioning the gametes and embryos with sublethal hydrostatic pressure treatment. However, the underlying molecular mechanism responsible for this protective effect remains unknown and requires further investigation. Here, we studied the effect of optimised hydrostatic pressure treatment on the global gene expression of mouse oocytes after embryonic genome activation. Based on a gene expression microarray analysis, a significant effect of treatment was observed in 4-cell embryos derived from treated oocytes, revealing a transcriptional footprint of hydrostatic pressure-affected genes. Functional analysis identified numerous genes involved in protein synthesis that were downregulated in 4-cell embryos in response to hydrostatic pressure treatment, suggesting that regulation of translation has a major role in optimised hydrostatic pressure-induced stress tolerance. We present a comprehensive microarray analysis and further delineate a potential mechanism responsible for the protective effect of hydrostatic pressure treatment.

Static and Dynamic Mechanical Properties of Graphene Oxide-Incorporated Woven Carbon Fiber/Epoxy Composite

NASA Astrophysics Data System (ADS)

Adak, Nitai Chandra; Chhetri, Suman; Kim, Nam Hoon; Murmu, Naresh Chandra; Samanta, Pranab; Kuila, Tapas

2018-03-01

This study investigates the synergistic effects of graphene oxide (GO) on the woven carbon fiber (CF)-reinforced epoxy composites. The GO nanofiller was incorporated into the epoxy resin with variations in the content, and the CF/epoxy composites were manufactured using a vacuum-assisted resin transfer molding process and then cured at 70 and 120 °C. An analysis of the mechanical properties of the GO (0.2 wt.%)/CF/epoxy composites showed an improvement in the tensile strength, Young's modulus, toughness, flexural strength and flexural modulus by 34, 20, 83, 55 and 31%, respectively, when compared to the CF/epoxy composite. The dynamic mechanical analysis of the composites exhibited an enhancement of 56, 114 and 22% in the storage modulus, loss modulus and damping capacity (tan δ), respectively, at its glass transition temperature. The fiber-matrix interaction was studied using a Cole-Cole plot analysis.

The Evolution of In-Grain Misorientation Axes (IGMA) During Deformation of Wrought Magnesium Alloy AZ31

NASA Astrophysics Data System (ADS)

Chun, Y. B.; Davies, C. H. J.

Understanding deformation mechanisms is a prerequisite for the development of more formable magnesium alloys. We have developed a novel approach based on analysis of in-grain misorientation axes which allows identification of the dominant slip system for a large number of grains. We investigated the effects of orientations and temperatures on active deformation mechanisms during the rolling of AZ31, including slip, deformation twinning and deformation banding. The IGMA analysis suggests that increasing rolling temperature promotes activation of prism slip which enhances the rollability of the plate favorably oriented for this slip mode. The approach also reveals an orientation-dependent occurrence of deformation banding and its crystallographic relationship with parent grain. It is concluded that IGMA analysis can be effectively used to study deformation mechanism in hcp metals, and can be used as a criterion for validating some crystal plasticity models.

Thermo-mechanically coupled fracture analysis of shape memory alloys using the extended finite element method

NASA Astrophysics Data System (ADS)

Hatefi Ardakani, S.; Ahmadian, H.; Mohammadi, S.

2015-04-01

In this paper, the extended finite element method is used for fracture analysis of shape memory alloys for both cases of super elastic and shape memory effects. Heat generation during the forward and reverse phase transformations can lead to temperature variation in the material because of strong thermo-mechanical coupling, which significantly influences the SMA mechanical behavior. First, the stationary crack mode is studied and the effects of loading rate on material behavior in the crack tip are examined. Then, the crack propagation analysis is performed in the presence of an initial crack by adopting a weighted averaging criterion, where the direction of crack propagation is determined by weighted averaging of effective stresses at all the integration points in the vicinity of the crack tip. Finally, several numerical examples are analyzed and the obtained results are compared with the available reference results.

Physicochemical, mechanical and thermal properties of chitosan films with and without sorbitol.

PubMed

Liu, Mei; Zhou, Yibin; Zhang, Yang; Yu, Chen; Cao, Shengnan

2014-09-01

The effect of sorbitol on the physicochemical, mechanical and thermal properties of chitosan films with different degrees of deacetylation (DD; i.e., DD85% and DD95%) was investigated. The thickness, moisture content (MC), water solubility (WS) and water-vapor permeability (WVP) of the films were evaluated. Sorbitol addition reduced MC, increased WS and significantly (p<0.01) reduced WVP of both film types. DD95% films had lower MC and WVP, and higher WS than DD85% films. Static (thermomechanical analysis) and dynamic (dynamic mechanical analysis) tests indicated that sorbitol increased the strain and decreased stress for both DD films, but DD95% could sustain higher strain and DD85% could sustain higher stress. Thermogravimetrics analysis and differential scanning calorimetry showed that sorbitol elicited a lower degradation temperature for both films, and that DD95% films exhibited higher thermal stability than DD85% films. Copyright © 2014 Elsevier B.V. All rights reserved.

Recent advances in the study of age-related hearing loss - A Mini-Review

PubMed Central

Kidd, Ambrose R; Bao, Jianxin

2013-01-01

Hearing loss is a common age-associated affliction that can result from the loss of hair cells and spiral ganglion neurons (SGNs) in the cochlea. Although hair cells and SGNs are typically lost in the same cochlea, recent analysis suggests that they can occur independently, via unique mechanisms. Research has identified both environmental and genetic factors that contribute to degeneration of cochlear cells. Additionally, molecular analysis has identified multiple cell signaling mechanisms that likely contribute to pathological changes that result in hearing deficiencies. These analyses should serve as useful primers for future work, including genomic and proteomic analysis, to elucidate the mechanisms driving cell loss in the aging cochlea. Significant progress in this field has occurred in the past decade. As our understanding of aging-induced cochlear changes continues to improve, our ability to offer medical intervention will surely benefit the growing elderly population. PMID:22710288

NASA Contractor Report: Guidelines for Proof Test Analysis

NASA Technical Reports Server (NTRS)

Chell, G. G.; McClung, R. C.; Kuhlman, C. J.; Russell, D. A.; Garr, K.; Donnelly, B.

1997-01-01

These Guidelines integrate state-of-the-art Elastic-Plastic Fracture Mechanics (EPFM) and proof test implementation issues into a comprehensive proof test analysis procedure in the form of a Road Map which identifies the types of data, fracture mechanics based parameters, and calculations needed to perform flaw screening and minimum proof load analyses of fracture critical components. Worked examples are presented to illustrate the application of the Road Map to proof test analysis. The state-of-the-art fracture technology employed in these Guidelines is based on the EPFM parameter, J, and a pictorial representation of a J fracture analysis, called the Failure Assessment Diagram (FAD) approach. The recommended fracture technology is validated using finite element J results, and laboratory and hardware fracture test results on the nickel-based superalloy IN-718, the aluminum alloy 2024-T351 1, and ferritic pressure vessel steels. In all cases the laboratory specimens and hardware failed by ductile mechanisms. Advanced proof test analyses involving probability analysis and Multiple Cycle Proof Testing (MCPT) are addressed. Finally, recommendations are provided on to how to account for the effects of the proof test overload on subsequent service fatigue and fracture behaviors.

Magnetic resonance elastography (MRE) in cancer: Technique, analysis, and applications

PubMed Central

Pepin, Kay M.; Ehman, Richard L.; McGee, Kiaran P.

2015-01-01

Tissue mechanical properties are significantly altered with the development of cancer. Magnetic resonance elastography (MRE) is a noninvasive technique capable of quantifying tissue mechanical properties in vivo. This review describes the basic principles of MRE and introduces some of the many promising MRE methods that have been developed for the detection and characterization of cancer, evaluation of response to therapy, and investigation of the underlying mechanical mechanisms associated with malignancy. PMID:26592944

Global reduced mechanisms for methane and hydrogen combustion with nitric oxide formation constructed with CSP data

NASA Astrophysics Data System (ADS)

Massias, A.; Diamantis, D.; Mastorakos, E.; Goussis, D. A.

1999-06-01

Reduced mechanisms for methane-air and hydrogen-air combustion including NO formation have been constructed with the computational singular perturbation (CSP) method using the fully automated algorithm described by Massias et al. The analysis was performed on solutions of unstrained adiabatic premixed flames with detailed chemical kinetics described by GRI 2.11 for methane and a 71-reaction mechanism for hydrogen including NOx formation. A 10-step reduced mechanism for methane has been constructed which reproduces accurately laminar burning velocities, flame temperatures and mass fraction distributions of major species for the whole flammability range. Many steady-state species are also predicted satisfactorily. This mechanism is an improvement over the seven-step set of Massias et al, especially for rich flames, because the use of HCNO, HCN and C2H2 as major species results in a better calculation of prompt NO. The present 10-step mechanism may thus also be applicable to diffusion flames. A five-step mechanism for lean and hydrogen-rich combustion has also been constructed based on a detailed mechanism including thermal NO. This mechanism is accurate for a wide range of the equivalence ratio and for pressures as high as 40 bar. For both fuels, the CSP algorithm automatically pointed to the same steady-state species as those identified by laborious analysis or intuition in the literature and the global reactions were similar to well established previous methane-reduced mechanisms. This implies that the method is very well suited for the study of complex mechanisms for heavy hydrocarbon combustion.

Mechanisms of Feeding Deterrence by Ziziphins.

DTIC Science & Technology

1985-05-30

number) e mechanism of feeding deterrence by ziziphins for sout rn armyworms ( Spodoptera eridania ; Lepidoptera:Noctuidae) was investigated using bo long... Spodoptera eridania , to investigate the mechanisms of feeding deterrence by ziziphins extracted from the leaves of • .Ziziphus jujuba. Evaluation...Videotape Analysis of Feeding Suppression in the Southern Armyworm ( Spodoptera eridania ; Lepidoptera: Noctuidae) Produced by Extracts of the

Location uncertainty and the tri-areal design

Treesearch

Francis A. Roesch

2007-01-01

The U.S. Department of Agriculture Forest Service Forest Inventory and Analysis Program (FIA) uses a field plot design that incorporates multiple sample selection mechanisms. Not all of the five FIA units currently use the entire suite of available sample selection mechanisms. These sampling selection mechanisms could be described in a number of ways with respect to...

An Analysis of Applied Mechanics Contest for Senior High School Students in Taiwan

ERIC Educational Resources Information Center

Chen, Nelson Cheng-Chih; Chen, Ching-Hao; Lin, Ming-chun

2008-01-01

The applied mechanics education contest hosted by STAM (Society of Theoretical Applied Mechanics) has been held in Taiwan for several years. The contest pattern has been changed from a simple written test to an experiment-oriented test after the NSTM (National Science and Technology Museum) proceeded to hold the competition in 2005. The major…

Analysis and Synthesis of Adaptive Neural Elements and Assemblies

DTIC Science & Technology

1992-12-14

network, a learning rule (activity-dependent neuromodulation ), which has been proposed as a cellular mechanism for classical conditioning , was...activity-dependent neuromodulation ), which has been proposed as a cellular mechanism for classical conditioning, was demonstrated to support many...network, a learning rule (activity-dependent neuromodulation ), which has been proposed as a cellular mechanism for classical conditioning, was

Mechanical performance of hemp fiber polypropylene composites at different operating temperatures

Treesearch

Mehdi Tajvidi; Nazanin Motie; Ghonche Rassam; Robert H. Falk; Colin Felton

2010-01-01

In order to quantify the effect of temperature on the mechanical properties of hemp fiber polypropylene composites, formulations containing 25% and 40% (by weight) hemp fiber were produced and tested at three representative temperatures of 256, 296, and 336 K. Flexural, tensile, and impact tests, as well as dynamic mechanical analysis, were performed and the reduction...

The Operation Mechanisms of External Quality Assurance Frameworks of Foreign Higher Education and Implications for Graduate Education

ERIC Educational Resources Information Center

Lin, Mengquan; Chang, Kai; Gong, Le

2016-01-01

The higher education quality evaluation and assurance frameworks and their operating mechanisms of countries such as the United Kingdom, France, and the United States show that higher education systems, traditional culture, and social background all impact quality assurance operating mechanisms. A model analysis of these higher education quality…

Location uncertainty and the tri-areal design

Treesearch

Francis A. Roesch

2005-01-01

The U.S. Department of Agriculture Forest Service Forest Inventory and Analysis Program (FTA) uses a field plot design that incorporates multiple sample selection mechanisms. Not all of the five FIA units currently use the entire suite of available sample selection mechanisms. These sampling selection mechanisms could be described in a number of ways with respect to...

Computer-aided analysis of star shot films for high-accuracy radiation therapy treatment units

NASA Astrophysics Data System (ADS)

Depuydt, Tom; Penne, Rudi; Verellen, Dirk; Hrbacek, Jan; Lang, Stephanie; Leysen, Katrien; Vandevondel, Iwein; Poels, Kenneth; Reynders, Truus; Gevaert, Thierry; Duchateau, Michael; Tournel, Koen; Boussaer, Marlies; Cosentino, Dorian; Garibaldi, Cristina; Solberg, Timothy; De Ridder, Mark

2012-05-01

As mechanical stability of radiation therapy treatment devices has gone beyond sub-millimeter levels, there is a rising demand for simple yet highly accurate measurement techniques to support the routine quality control of these devices. A combination of using high-resolution radiosensitive film and computer-aided analysis could provide an answer. One generally known technique is the acquisition of star shot films to determine the mechanical stability of rotations of gantries and the therapeutic beam. With computer-aided analysis, mechanical performance can be quantified as a radiation isocenter radius size. In this work, computer-aided analysis of star shot film is further refined by applying an analytical solution for the smallest intersecting circle problem, in contrast to the gradient optimization approaches used until today. An algorithm is presented and subjected to a performance test using two different types of radiosensitive film, the Kodak EDR2 radiographic film and the ISP EBT2 radiochromic film. Artificial star shots with a priori known radiation isocenter size are used to determine the systematic errors introduced by the digitization of the film and the computer analysis. The estimated uncertainty on the isocenter size measurement with the presented technique was 0.04 mm (2σ) and 0.06 mm (2σ) for radiographic and radiochromic films, respectively. As an application of the technique, a study was conducted to compare the mechanical stability of O-ring gantry systems with C-arm-based gantries. In total ten systems of five different institutions were included in this study and star shots were acquired for gantry, collimator, ring, couch rotations and gantry wobble. It was not possible to draw general conclusions about differences in mechanical performance between O-ring and C-arm gantry systems, mainly due to differences in the beam-MLC alignment procedure accuracy. Nevertheless, the best performing O-ring system in this study, a BrainLab/MHI Vero system, and the best performing C-arm system, a Varian Truebeam system, showed comparable mechanical performance: gantry isocenter radius of 0.12 and 0.09 mm, respectively, ring/couch rotation of below 0.10 mm for both systems and a wobble of 0.06 and 0.18 mm, respectively. The methodology described in this work can be used to monitor mechanical performance constancy of high-accuracy treatment devices, with means available in a clinical radiation therapy environment.

Missing continuous outcomes under covariate dependent missingness in cluster randomised trials

PubMed Central

Diaz-Ordaz, Karla; Bartlett, Jonathan W

2016-01-01

Attrition is a common occurrence in cluster randomised trials which leads to missing outcome data. Two approaches for analysing such trials are cluster-level analysis and individual-level analysis. This paper compares the performance of unadjusted cluster-level analysis, baseline covariate adjusted cluster-level analysis and linear mixed model analysis, under baseline covariate dependent missingness in continuous outcomes, in terms of bias, average estimated standard error and coverage probability. The methods of complete records analysis and multiple imputation are used to handle the missing outcome data. We considered four scenarios, with the missingness mechanism and baseline covariate effect on outcome either the same or different between intervention groups. We show that both unadjusted cluster-level analysis and baseline covariate adjusted cluster-level analysis give unbiased estimates of the intervention effect only if both intervention groups have the same missingness mechanisms and there is no interaction between baseline covariate and intervention group. Linear mixed model and multiple imputation give unbiased estimates under all four considered scenarios, provided that an interaction of intervention and baseline covariate is included in the model when appropriate. Cluster mean imputation has been proposed as a valid approach for handling missing outcomes in cluster randomised trials. We show that cluster mean imputation only gives unbiased estimates when missingness mechanism is the same between the intervention groups and there is no interaction between baseline covariate and intervention group. Multiple imputation shows overcoverage for small number of clusters in each intervention group. PMID:27177885

Missing continuous outcomes under covariate dependent missingness in cluster randomised trials.

PubMed

Hossain, Anower; Diaz-Ordaz, Karla; Bartlett, Jonathan W

2017-06-01

Attrition is a common occurrence in cluster randomised trials which leads to missing outcome data. Two approaches for analysing such trials are cluster-level analysis and individual-level analysis. This paper compares the performance of unadjusted cluster-level analysis, baseline covariate adjusted cluster-level analysis and linear mixed model analysis, under baseline covariate dependent missingness in continuous outcomes, in terms of bias, average estimated standard error and coverage probability. The methods of complete records analysis and multiple imputation are used to handle the missing outcome data. We considered four scenarios, with the missingness mechanism and baseline covariate effect on outcome either the same or different between intervention groups. We show that both unadjusted cluster-level analysis and baseline covariate adjusted cluster-level analysis give unbiased estimates of the intervention effect only if both intervention groups have the same missingness mechanisms and there is no interaction between baseline covariate and intervention group. Linear mixed model and multiple imputation give unbiased estimates under all four considered scenarios, provided that an interaction of intervention and baseline covariate is included in the model when appropriate. Cluster mean imputation has been proposed as a valid approach for handling missing outcomes in cluster randomised trials. We show that cluster mean imputation only gives unbiased estimates when missingness mechanism is the same between the intervention groups and there is no interaction between baseline covariate and intervention group. Multiple imputation shows overcoverage for small number of clusters in each intervention group.

Finite element analysis (FEA) analysis of the preflex beam

NASA Astrophysics Data System (ADS)

Wan, Lijuan; Gao, Qilang

2017-10-01

The development of finite element analysis (FEA) has been relatively mature, and is one of the important means of structural analysis. This method changes the problem that the research of complex structure in the past needs to be done by a large number of experiments. Through the finite element method, the numerical simulation of the structure can be used to achieve a variety of static and dynamic simulation analysis of the mechanical problems, it is also convenient to study the parameters of the structural parameters. Combined with a certain number of experiments to verify the simulation model can be completed in the past all the needs of experimental research. The nonlinear finite element method is used to simulate the flexural behavior of the prestressed composite beams with corrugated steel webs. The finite element analysis is used to understand the mechanical properties of the structure under the action of bending load.

Comparison of microCT and an inverse finite element approach for biomechanical analysis: Results in a MSC therapeutic system for fracture healing

PubMed Central

Weis, Jared A.; Granero-Moltó, Froilán; Myers, Timothy J.; Longobardi, Lara; Spagnoli, Anna; Miga, Michael I.

2013-01-01

An important concern in the study of fracture healing is the ability to assess mechanical integrity in response to candidate therapeutics in small-animal systems. In recent reports, it has been proposed that microCT image-derived densitometric parameters could be used as a surrogate for mechanical property assessment. Recently, we have proposed an inverse methodology that iteratively reconstructs the modulus of elasticity of the lumped soft callus/hard callus region by integrating both intrinsic mechanical property (from biomechanical testing) and geometrical information (from microCT) within an inverse finite element analysis (FEA) to define a callus quality measure. In this paper, data from a therapeutic system involving mesenchymal stem cells is analyzed within the context of comparing traditional microCT densitometric and mechanical property metrics. In addition, a novel multi-parameter regression microCT parameter is analyzed as well as our inverse FEA metric. The results demonstrate that the inverse FEA approach was the only metric to successfully detect both longitudinal and therapeutic responses. While the most promising microCT-based metrics were adequate at early healing states, they failed to track late-stage mechanical integrity. In addition, our analysis added insight to the role of MSCs by demonstrating accelerated healing and was the only metric to demonstrate therapeutic benefits at late-stage healing. In conclusion, the work presented here indicates that microCT densitometric parameters are an incomplete surrogate for mechanical integrity. Additionally, our inverse FEA approach is shown to be very sensitive and may provide a first-step towards normalizing the often challenging process of assessing mechanical integrity of healing fractures. PMID:22766379

What has finite element analysis taught us about diabetic foot disease and its management? A systematic review.

PubMed

Telfer, Scott; Erdemir, Ahmet; Woodburn, James; Cavanagh, Peter R

2014-01-01

Over the past two decades finite element (FE) analysis has become a popular tool for researchers seeking to simulate the biomechanics of the healthy and diabetic foot. The primary aims of these simulations have been to improve our understanding of the foot's complicated mechanical loading in health and disease and to inform interventions designed to prevent plantar ulceration, a major complication of diabetes. This article provides a systematic review and summary of the findings from FE analysis-based computational simulations of the diabetic foot. A systematic literature search was carried out and 31 relevant articles were identified covering three primary themes: methodological aspects relevant to modelling the diabetic foot; investigations of the pathomechanics of the diabetic foot; and simulation-based design of interventions to reduce ulceration risk. Methodological studies illustrated appropriate use of FE analysis for simulation of foot mechanics, incorporating nonlinear tissue mechanics, contact and rigid body movements. FE studies of pathomechanics have provided estimates of internal soft tissue stresses, and suggest that such stresses may often be considerably larger than those measured at the plantar surface and are proportionally greater in the diabetic foot compared to controls. FE analysis allowed evaluation of insole performance and development of new insole designs, footwear and corrective surgery to effectively provide intervention strategies. The technique also presents the opportunity to simulate the effect of changes associated with the diabetic foot on non-mechanical factors such as blood supply to local tissues. While significant advancement in diabetic foot research has been made possible by the use of FE analysis, translational utility of this powerful tool for routine clinical care at the patient level requires adoption of cost-effective (both in terms of labour and computation) and reliable approaches with clear clinical validity for decision making.

atBioNet--an integrated network analysis tool for genomics and biomarker discovery.

PubMed

Ding, Yijun; Chen, Minjun; Liu, Zhichao; Ding, Don; Ye, Yanbin; Zhang, Min; Kelly, Reagan; Guo, Li; Su, Zhenqiang; Harris, Stephen C; Qian, Feng; Ge, Weigong; Fang, Hong; Xu, Xiaowei; Tong, Weida

2012-07-20

Large amounts of mammalian protein-protein interaction (PPI) data have been generated and are available for public use. From a systems biology perspective, Proteins/genes interactions encode the key mechanisms distinguishing disease and health, and such mechanisms can be uncovered through network analysis. An effective network analysis tool should integrate different content-specific PPI databases into a comprehensive network format with a user-friendly platform to identify key functional modules/pathways and the underlying mechanisms of disease and toxicity. atBioNet integrates seven publicly available PPI databases into a network-specific knowledge base. Knowledge expansion is achieved by expanding a user supplied proteins/genes list with interactions from its integrated PPI network. The statistically significant functional modules are determined by applying a fast network-clustering algorithm (SCAN: a Structural Clustering Algorithm for Networks). The functional modules can be visualized either separately or together in the context of the whole network. Integration of pathway information enables enrichment analysis and assessment of the biological function of modules. Three case studies are presented using publicly available disease gene signatures as a basis to discover new biomarkers for acute leukemia, systemic lupus erythematosus, and breast cancer. The results demonstrated that atBioNet can not only identify functional modules and pathways related to the studied diseases, but this information can also be used to hypothesize novel biomarkers for future analysis. atBioNet is a free web-based network analysis tool that provides a systematic insight into proteins/genes interactions through examining significant functional modules. The identified functional modules are useful for determining underlying mechanisms of disease and biomarker discovery. It can be accessed at: http://www.fda.gov/ScienceResearch/BioinformaticsTools/ucm285284.htm.

Metabolomics Coupled with Multivariate Data and Pathway Analysis on Potential Biomarkers in Gastric Ulcer and Intervention Effects of Corydalis yanhusuo Alkaloid

PubMed Central

Shuai, Wang; Yongrui, Bao; Shanshan, Guan; Bo, Liu; Lu, Chen; Lei, Wang; Xiaorong, Ran

2014-01-01

Metabolomics, the systematic analysis of potential metabolites in a biological specimen, has been increasingly applied to discovering biomarkers, identifying perturbed pathways, measuring therapeutic targets, and discovering new drugs. By analyzing and verifying the significant difference in metabolic profiles and changes of metabolite biomarkers, metabolomics enables us to better understand substance metabolic pathways which can clarify the mechanism of Traditional Chinese Medicines (TCM). Corydalis yanhusuo alkaloid (CA) is a major component of Qizhiweitong (QZWT) prescription which has been used for treating gastric ulcer for centuries and its mechanism remains unclear completely. Metabolite profiling was performed by high-performance liquid chromatography combined with time-of-flight mass spectrometry (HPLC/ESI-TOF-MS) and in conjunction with multivariate data analysis and pathway analysis. The statistic software Mass Profiller Prossional (MPP) and statistic method including ANOVA and principal component analysis (PCA) were used for discovering novel potential biomarkers to clarify mechanism of CA in treating acid injected rats with gastric ulcer. The changes in metabolic profiling were restored to their base-line values after CA treatment according to the PCA score plots. Ten different potential biomarkers and seven key metabolic pathways contributing to the treatment of gastric ulcer were discovered and identified. Among the pathways, sphingophospholipid metabolism and fatty acid metabolism related network were acutely perturbed. Quantitative real time polymerase chain reaction (RT-PCR) analysis were performed to evaluate the expression of genes related to the two pathways for verifying the above results. The results show that changed biomarkers and pathways may provide evidence to insight into drug action mechanisms and enable us to increase research productivity toward metabolomics drug discovery. PMID:24454691

Cognitive Issues in Learning Advanced Physics: An Example from Quantum Mechanics

NASA Astrophysics Data System (ADS)

Singh, Chandralekha; Zhu, Guangtian

2009-11-01

We are investigating cognitive issues in learning quantum mechanics in order to develop effective teaching and learning tools. The analysis of cognitive issues is particularly important for bridging the gap between the quantitative and conceptual aspects of quantum mechanics and for ensuring that the learning tools help students build a robust knowledge structure. We discuss the cognitive aspects of quantum mechanics that are similar or different from those of introductory physics and their implications for developing strategies to help students develop a good grasp of quantum mechanics.

Prediction and Estimation of Scaffold Strength with different pore size

NASA Astrophysics Data System (ADS)

Muthu, P.; Mishra, Shubhanvit; Sri Sai Shilpa, R.; Veerendranath, B.; Latha, S.

2018-04-01

This paper emphasizes the significance of prediction and estimation of the mechanical strength of 3D functional scaffolds before the manufacturing process. Prior evaluation of the mechanical strength and structural properties of the scaffold will reduce the cost fabrication and in fact ease up the designing process. Detailed analysis and investigation of various mechanical properties including shear stress equivalence have helped to estimate the effect of porosity and pore size on the functionality of the scaffold. The influence of variation in porosity was examined by computational approach via finite element analysis (FEA) and ANSYS application software. The results designate the adequate perspective of the evolutionary method for the regulation and optimization of the intricate engineering design process.

Design and analysis of an underactuated anthropomorphic finger for upper limb prosthetics.

PubMed

Omarkulov, Nurdos; Telegenov, Kuat; Zeinullin, Maralbek; Begalinova, Ainur; Shintemirov, Almas

2015-01-01

This paper presents the design of a linkage based finger mechanism ensuring extended range of anthropomorphic gripping motions. The finger design is done using a path-point generation method based on geometrical dimensions and motion of a typical index human finger. Following the design description, and its kinematics analysis, the experimental evaluation of the finger gripping performance is presented using the finger 3D printed prototype. The finger underactuation is achieved by utilizing mechanical linkage system, consisting of two crossed four-bar linkage mechanisms. It is shown that the proposed finger design can be used to design a five-fingered anthropomorphic hand and has the potential for upper limb prostheses development.

The effects of multiple repairs on Inconel 718 weld mechanical properties

NASA Technical Reports Server (NTRS)

Russell, C. K.; Nunes, A. C., Jr.; Moore, D.

1991-01-01

Inconel 718 weldments were repaired 3, 6, 9, and 13 times using the gas tungsten arc welding process. The welded panels were machined into mechanical test specimens, postweld heat treated, and nondestructively tested. Tensile properties and high cycle fatigue life were evaluated and the results compared to unrepaired weld properties. Mechanical property data were analyzed using the statistical methods of difference in means for tensile properties and difference in log means and Weibull analysis for high cycle fatigue properties. Statistical analysis performed on the data did not show a significant decrease in tensile or high cycle fatigue properties due to the repeated repairs. Some degradation was observed in all properties, however, it was minimal.

Preliminary Analysis of the General Performance and Mechanical Behavior of Irradiated FeCrAl Base Alloys and Weldments

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

Gussev, Maxim N.; Field, Kevin G.; Briggs, Samuel A.

The iron-based, iron-chromium-aluminum (FeCrAl) alloys are promising, robust materials for deployment in current and future nuclear power plants. This class of alloys demonstrates excellent performance in a range of environments and conditions, including high-temperature steam (>1000°C). Furthermore, these alloys have the potential to have prolonged survival under loss-of-coolant accident (LOCA) conditions compared to the more traditional cladding materials that are either Zr-based alloys or austenitic steels. However, one of the issues associated with FeCrAl alloys is cracking during welding. The present project investigates the possibility of mitigating welding-induced cracking via alloying and precise structure control of the weldments; in themore » frame work of the project, several advanced alloys were developed and are being investigated prior to and after neutron irradiation to provide insight into the radiation tolerance and mechanical performance of the weldments. The present report provides preliminary results on the post-irradiation characterization and mechanical tests performed during United States Fiscal Year (FY) 2016. Chapter 1 provides a general introduction, and Chapter 2 describes the alloy compositions, welding procedure, specimen geometry and manufacturing parameters. Also, a brief discussion of the irradiation at the High Flux Isotope Reactor (HFIR) is provided. Chapter 3 is devoted to the analysis of mechanical tests performed at the hot cell facility; tensile curves and mechanical properties are discussed in detail focusing on the irradiation temperature. Limited fractography results are also presented and analyzed. The discussion highlights the limitations of the testing within a hot cell. Chapter 4 underlines the advantages of in-situ testing and discusses the preliminary results obtained with newly developed miniature specimens. Specimens were moved to the Low Activation Materials Development and Analysis (LAMDA) laboratory and prepared for mechanical tests. Tensile tests were conducted at LAMDA using a modern digital image correlation approach allowing for strain distribution analysis. Plastic strain initiation and necking are discussed in detail; a concept of strain rate maps is also introduced and discussed. Follow-on SEM-EBSD and FIBTEM analysis is planned.« less

Study on force mechanism for therapeutic effect of pushing manipulation with one-finger meditation base on similarity analysis of force and waveform.

PubMed

Fang, Lei; Fang, Min; Guo, Min-Min

2016-12-27

To reveal the force mechanism for therapeutic effect of pushing manipulation with one-finger meditation. A total of 15 participants were recruited in this study and assigned to an expert group, a skilled group and a novice group, with 5 participants in each group. Mechanical signals were collected from a biomechanical testing platform, and these data were further observed via similarity analysis and cluster analysis. Comparing the force waveforms of manipulation revealed that the manipulation forces were similar between the expert group and the skilled group (P>0.05). The mean value of vertical force was 9.8 N, and 95% CI rang from 6.37 to 14.70 N, but there were significant differences compared with the novice group (P<0.05). The result of overall similarity coefficient cluster analysis showed that two kinds of manipulation forces curves were existed between the expert group and the skilled group. Pushing manipulation with one-finger meditation is a kind of light stimulation manipulation on the acupoint, and force characteristics of double waveforms continuously alternated during manual operation.

Collapse Mechanism Analysis in the Design of Superstructure Vehicle

NASA Astrophysics Data System (ADS)

Mohd Nor, M. K.

2016-11-01

The EU directive 2001/85/EC is an official European text which describes the specifications for “single deck class II and III vehicles” required to be approved by the regulation UN/ECE no.66 (R66). To prevent the catastrophic consequences by occupant during an accident, the Malaysian government has reinforced the same regulation upon superstructure construction. This paper discusses collapse mechanism analysis of a superstructure vehicle using a Crash D nonlinear analysis computer program based on this regulation. The analysis starts by hand calculation to define the required energy absorption by the chosen structure. Simple calculations were then performed to define the weakest collapse mechanism after undesirable collapse modes are eliminated. There are few factors highlighted in this work to pass the regulation. Using the selected cross section, Crash D simulation showed a good result. Generally, the deformation is linearly correlates to the energy absorption for the structure with low stiffness. Failure of critical members such as vertical lower side wall must be avoided to sustain safety of the passenger compartment and prevent from severe and fatal injuries to the trapped occupant.

Nonlinear analysis of collapse mechanism in superstructure vehicle

NASA Astrophysics Data System (ADS)

Nor, M. K. Mohd; Ho, C. S.; Ma'at, N.

2017-04-01

The EU directive 2001/85/EC is an official European text which describes the specifications for "single deck class II and III vehicles" required to be approved by the regulation UN/ECE no.66 (R66). To prevent the catastrophic consequences by occupant during an accident, the Malaysian government has reinforced the same regulation upon superstructure construction. This paper discusses collapse mechanism analysis of a superstructure vehicle using a Crash D nonlinear analysis computer program based on this regulation. The analysis starts by hand calculation to define the required energy absorption by the chosen structure. Simple calculations were then performed to define the weakest collapse mechanism after undesirable collapse modes are eliminated. There are few factors highlighted in this work to pass the regulation. Using the selected cross section, Crash D simulation showed a good result. Generally, the deformation is linearly correlates to the energy absorption for the structure with low stiffness. Failure of critical members such as vertical lower side wall must be avoided to sustain safety of the passenger compartment and prevent from severe and fatal injuries to the trapped occupant.

Integrated modeling analysis of a novel hexapod and its application in active surface

NASA Astrophysics Data System (ADS)

Yang, Dehua; Zago, Lorenzo; Li, Hui; Lambert, Gregory; Zhou, Guohua; Li, Guoping

2011-09-01

This paper presents the concept and integrated modeling analysis of a novel mechanism, a 3-CPS/RPPS hexapod, for supporting segmented reflectors for radio telescopes and eventually segmented mirrors of optical telescopes. The concept comprises a novel type of hexapod with an original organization of actuators hence degrees of freedom, based on a swaying arm based design concept. Afterwards, with specially designed connecting joints between panels/segments, an iso-static master-slave active surface concept can be achieved for any triangular and/or hexagonal panel/segment pattern. The integrated modeling comprises all the multifold sizing and performance aspects which must be evaluated concurrently in order to optimize and validate the design and the configuration. In particular, comprehensive investigation of kinematic behavior, dynamic analysis, wave-front error and sensitivity analysis are carried out, where, frequently used tools like MATLAB/SimMechanics, CALFEM and ANSYS are used. Especially, we introduce the finite element method as a competent approach for analyses of the multi-degree of freedom mechanism. Some experimental verifications already performed validating single aspects of the integrated concept are also presented with the results obtained.

Causation mechanism analysis for haze pollution related to vehicle emission in Guangzhou, China by employing the fault tree approach.

PubMed

Huang, Weiqing; Fan, Hongbo; Qiu, Yongfu; Cheng, Zhiyu; Xu, Pingru; Qian, Yu

2016-05-01

Recently, China has frequently experienced large-scale, severe and persistent haze pollution due to surging urbanization and industrialization and a rapid growth in the number of motor vehicles and energy consumption. The vehicle emission due to the consumption of a large number of fossil fuels is no doubt a critical factor of the haze pollution. This work is focused on the causation mechanism of haze pollution related to the vehicle emission for Guangzhou city by employing the Fault Tree Analysis (FTA) method for the first time. With the establishment of the fault tree system of "Haze weather-Vehicle exhausts explosive emission", all of the important risk factors are discussed and identified by using this deductive FTA method. The qualitative and quantitative assessments of the fault tree system are carried out based on the structure, probability and critical importance degree analysis of the risk factors. The study may provide a new simple and effective tool/strategy for the causation mechanism analysis and risk management of haze pollution in China. Copyright © 2016 Elsevier Ltd. All rights reserved.

Development and application of computer assisted optimal method for treatment of femoral neck fracture.

PubMed

Wang, Monan; Zhang, Kai; Yang, Ning

2018-04-09

To help doctors decide their treatment from the aspect of mechanical analysis, the work built a computer assisted optimal system for treatment of femoral neck fracture oriented to clinical application. The whole system encompassed the following three parts: Preprocessing module, finite element mechanical analysis module, post processing module. Preprocessing module included parametric modeling of bone, parametric modeling of fracture face, parametric modeling of fixed screw and fixed position and input and transmission of model parameters. Finite element mechanical analysis module included grid division, element type setting, material property setting, contact setting, constraint and load setting, analysis method setting and batch processing operation. Post processing module included extraction and display of batch processing operation results, image generation of batch processing operation, optimal program operation and optimal result display. The system implemented the whole operations from input of fracture parameters to output of the optimal fixed plan according to specific patient real fracture parameter and optimal rules, which demonstrated the effectiveness of the system. Meanwhile, the system had a friendly interface, simple operation and could improve the system function quickly through modifying single module.

Dynamics of mechanical feedback-type hydraulic servomotors under inertia loads

NASA Technical Reports Server (NTRS)

Gold, Harold; Otto, Edward W; Ransom, Victor L

1953-01-01

An analysis of the dynamics of mechanical feedback-type hydraulic servomotors under inertia loads is developed and experimental verification is presented. The analysis, which is developed in terms of two physical parameters, yields direct expressions for the following dynamic responses: (1) the transient response to a step input and the maximum cylinder pressure during the transient and (2) the variation of amplitude attenuation and phase shift with the frequency of a sinusoidally varying input. The validity of the analysis is demonstrated by means of recorded transient and frequency responses obtained on two servomotors. The calculated responses are in close agreement with the measured responses. The relations presented are readily applicable to the design as well as to the analysis of hydraulic servomotors.

Behaviour and Analysis of Mechanically Fastened Joints in Composite Structures

DTIC Science & Technology

1988-03-01

Safety Factors for Use When Designing bolted Joints In GRP," Composites , April 1979, pp. M376. 93. Dastln, S., "Joining and Machining Techniques... MACHINE SPACER LOCKmm STEEL PLATE FASTENER 203 mm OR DOWEL FiN EXTENSOMETER EXTENSOMETER TGAUGE LENGTH ATTACHMENT COMPOSITE - PLATE 31 mm p NOTE: NOT TO...No.427 Behaviour and Analysis of Mechanically Fastened Joints in Composite Structures DTIC CXVTflUTION STATEME~r £ELECTE Approved fm Vubhc sIlam l JUL

Energy spectrum analysis - A model of echolocation processing. [in animals

NASA Technical Reports Server (NTRS)

Johnson, R. A.; Titlebaum, E. L.

1976-01-01

The paper proposes a frequency domain approach based on energy spectrum analysis of the combination of a signal and its echoes as the processing mechanism for the echolocation process used by bats and other animals. The mechanism is a generalized wide-band one and can account for the large diversity of wide-band signals used for orientation. The coherency in the spectrum of the signal-echo combination is shown to be equivalent to correlation.

Microwave power transmission system studies. Volume 3, section 8: Mechanical systems and flight operations

NASA Technical Reports Server (NTRS)

Maynard, O. E.; Brown, W. C.; Edwards, A.; Haley, J. T.; Meltz, G.; Howell, J. M.; Nathan, A.

1975-01-01

The efforts and recommendations associated with preliminary design and concept definition for mechanical systems and flight operations are presented. Technical discussion in the areas of mission analysis, antenna structural concept, configuration analysis, assembly and packaging with associated costs are presented. Technology issues for the control system, structural system, thermal system and assembly including cost and man's role in assembly and maintenance are identified. Background and desired outputs for future efforts are discussed.

Impact of new computing systems on computational mechanics and flight-vehicle structures technology

NASA Technical Reports Server (NTRS)

Noor, A. K.; Storaasli, O. O.; Fulton, R. E.

1984-01-01

Advances in computer technology which may have an impact on computational mechanics and flight vehicle structures technology were reviewed. The characteristics of supersystems, highly parallel systems, and small systems are summarized. The interrelations of numerical algorithms and software with parallel architectures are discussed. A scenario for future hardware/software environment and engineering analysis systems is presented. Research areas with potential for improving the effectiveness of analysis methods in the new environment are identified.

[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.

Understanding the Mechanism of Thermotolerance Distinct From Heat Shock Response Through Proteomic Analysis of Industrial Strains of Saccharomyces cerevisiae*

PubMed Central

Shui, Wenqing; Xiong, Yun; Xiao, Weidi; Qi, Xianni; Zhang, Yong; Lin, Yuping; Guo, Yufeng; Zhang, Zhidan; Wang, Qinhong; Ma, Yanhe

2015-01-01

Saccharomyces cerevisiae has been intensively studied in responses to different environmental stresses such as heat shock through global omic analysis. However, the S. cerevisiae industrial strains with superior thermotolerance have not been explored in any proteomic studies for elucidating the tolerance mechanism. Recently a new diploid strain was obtained through evolutionary engineering of a parental industrial strain, and it exhibited even higher resistance to prolonged thermal stress. Herein, we performed iTRAQ-based quantitative proteomic analysis on both the parental and evolved industrial strains to further understand the mechanism of thermotolerant adaptation. Out of ∼2600 quantifiable proteins from biological quadruplicates, 193 and 204 proteins were differentially regulated in the parental and evolved strains respectively during heat-stressed growth. The proteomic response of the industrial strains cultivated under prolonged thermal stress turned out to be substantially different from that of the laboratory strain exposed to sudden heat shock. Further analysis of transcription factors underlying the proteomic perturbation also indicated the distinct regulatory mechanism of thermotolerance. Finally, a cochaperone Mdj1 and a metabolic enzyme Adh1 were selected to investigate their roles in mediating heat-stressed growth and ethanol production of yeasts. Our proteomic characterization of the industrial strain led to comprehensive understanding of the molecular basis of thermotolerance, which would facilitate future improvement in the industrially important trait of S. cerevisiae by rational engineering. PMID:25926660

Effect of Heliox on Respiratory Outcomes during Rigid Bronchoscopy in Term Lambs.

PubMed

Sowder, Justin C; Dahl, Mar Janna; Zuspan, Kaitlin R; Albertine, Kurt H; Null, Donald M; Barneck, Mitchell D; Grimmer, J Fredrik

2018-03-01

Objective To (1) compare physiologic changes during rigid bronchoscopy during spontaneous and mechanical ventilation and (2) evaluate the efficacy of a helium-oxygen (heliox) gas mixture as compared with room air during rigid bronchoscopy. Study Design Crossover animal study evaluating physiologic parameters during rigid bronchoscopy. Outcomes were compared with predicted computational fluid analysis. Setting Simulated ventilation via computational fluid dynamics analysis and term lambs undergoing rigid bronchoscopy. Methods Respiratory and physiologic outcomes were analyzed in a lamb model simulating bronchoscopy during foreign body aspiration to compare heliox with room air. The main outcome measures were blood oxygen saturation, heart rate, blood pressure, partial pressure of oxygen, and partial pressure of carbon dioxide. Computational fluid dynamics analysis was performed with SOLIDWORKS within a rigid pediatric bronchoscope during simulated ventilation comparing heliox with room air. Results For room air, lambs desaturated within 3 minutes during mechanical ventilation versus normal oxygen saturation during spontaneous ventilation ( P = .01). No improvement in respiratory outcomes was seen between heliox and room air during mechanical ventilation. Computational fluid dynamics analysis demonstrates increased turbulence within size 3.5 bronchoscopes when comparing heliox and room air. Meaningful comparisons could not be made due to the intolerance of the lambs to heliox in vivo. Conclusion During mechanical ventilation on room air, lambs desaturate more quickly during rigid bronchoscopy on settings that should be adequate. Heliox does not improve ventilation during rigid bronchoscopy.

Quantitative assessment of soft tissue deformation using digital speckle pattern interferometry: studies on phantom breast models.

PubMed

Karuppanan, Udayakumar; Unni, Sujatha Narayanan; Angarai, Ganesan R

2017-01-01

Assessment of mechanical properties of soft matter is a challenging task in a purely noninvasive and noncontact environment. As tissue mechanical properties play a vital role in determining tissue health status, such noninvasive methods offer great potential in framing large-scale medical screening strategies. The digital speckle pattern interferometry (DSPI)-based image capture and analysis system described here is capable of extracting the deformation information from a single acquired fringe pattern. Such a method of analysis would be required in the case of the highly dynamic nature of speckle patterns derived from soft tissues while applying mechanical compression. Soft phantoms mimicking breast tissue optical and mechanical properties were fabricated and tested in the DSPI out of plane configuration set up. Hilbert transform (HT)-based image analysis algorithm was developed to extract the phase and corresponding deformation of the sample from a single acquired fringe pattern. The experimental fringe contours were found to correlate with numerically simulated deformation patterns of the sample using Abaqus finite element analysis software. The extracted deformation from the experimental fringe pattern using the HT-based algorithm is compared with the deformation value obtained using numerical simulation under similar conditions of loading and the results are found to correlate with an average %error of 10. The proposed method is applied on breast phantoms fabricated with included subsurface anomaly mimicking cancerous tissue and the results are analyzed.

Kinematic analysis of crank -cam mechanism of process equipment

NASA Astrophysics Data System (ADS)

Podgornyj, Yu I.; Skeeba, V. Yu; Martynova, T. G.; Pechorkina, N. S.; Skeeba, P. Yu

2018-03-01

This article discusses how to define the kinematic parameters of a crank-cam mechanism. Using the mechanism design, the authors have developed a calculation model and a calculation algorithm that allowed the definition of kinematic parameters of the mechanism, including crank displacements, angular velocities and acceleration, as well as driven link (rocker arm) angular speeds and acceleration. All calculations were performed using the Mathcad mathematical package. The results of the calculations are reported as numerical values.

Traffic management mechanism for intranets with available-bit-rate access to the Internet

NASA Astrophysics Data System (ADS)

Hassan, Mahbub; Sirisena, Harsha R.; Atiquzzaman, Mohammed

1997-10-01

The design of a traffic management mechanism for intranets connected to the Internet via an available bit rate access- link is presented. Selection of control parameters for this mechanism for optimum performance is shown through analysis. An estimate for packet loss probability at the access- gateway is derived for random fluctuation of available bit rate of the access-link. Some implementation strategies of this mechanism in the standard intranet protocol stack are also suggested.

The relationships between deformation mechanisms and mechanical properties of additively manufactured porous biomaterials.

PubMed

Kadkhodapour, J; Montazerian, H; Darabi, A Ch; Zargarian, A; Schmauder, S

2017-06-01

Modulating deformation mechanism through manipulating morphological parameters of scaffold internal pore architecture provides potential to tailor the overall mechanical properties under physiological loadings. Whereas cells sense local strains, cell differentiation is also impressed by the elastic deformations. In this paper, structure-property relations were developed for Ti6-Al-4V scaffolds designed based on triply periodic minimal surfaces. 10mm cubic scaffolds composed of 5×5×5 unit cells formed of F-RD (bending dominated) and I-WP (stretching dominated) architectures were additively manufactured at different volume fractions and subjected to compressive tests. The first stages of deformation for stretching dominated structure, was accompanied by bilateral layer-by-layer failure of unit cells owing to the buckling of micro-struts, while for bending dominated structure, namely F-RD, global shearing bands appeared since the shearing failure of struts in the internal architecture. Promoted mechanical properties were found for stretching dominated structure since the global orientation of struts were parallel to loading direction while inclination of struts diminished specific properties for bending dominated structure. Moreover, elastic-plastic deformation was computationally studied by applying Johnson-Cook damage model to the voxel-based models in FE analysis. Scaling analysis was performed for mechanical properties with respect to the relative density thereby failure mechanism was correlated to the constants of power law describing mechanical properties. Copyright © 2016 Elsevier Ltd. All rights reserved.

Comparison of the Long-Term Outcomes of Mechanical and Bioprosthetic Aortic Valves　- A Propensity Score Analysis.

PubMed

Minakata, Kenji; Tanaka, Shiro; Tamura, Nobushige; Yanagi, Shigeki; Ohkawa, Yohei; Okonogi, Shuichi; Kaneko, Tatsuo; Usui, Akihiko; Abe, Tomonobu; Shimamoto, Mitsuomi; Takahara, Yoshiharu; Yamanaka, Kazuo; Yaku, Hitoshi; Sakata, Ryuzo

2017-07-25

The aim of this study was to assess the long-term outcomes of aortic valve replacement (AVR) with either mechanical or bioprosthetic valves according to age at operation.Methods and Results:A total of 1,002 patients (527 mechanical valves and 475 bioprosthetic valves) undergoing first-time AVR were categorized according to age at operation: group Y, age <60 years; group M, age 60-69 years; and group O, age ≥70 years). Outcomes were compared on propensity score analysis (adjusted for 28 variables). Hazard ratio (HR) was calculated using the Cox regression model with adjustment for propensity score with bioprosthetic valve as a reference (HR=1). There were no significant differences in overall mortality between mechanical and bioprosthetic valves for all age groups. Valve-related mortality was significantly higher for mechanical valves in group O (HR, 2.53; P=0.02). Reoperation rate was significantly lower for mechanical valves in group Y (HR, 0.16; P<0.01) and group M (no events for mechanical valves). Although the rate of thromboembolic events was higher in mechanical valves in group Y (no events for tissue valves) and group M (HR, 9.05; P=0.03), there were no significant differences in bleeding events between all age groups. The type of prosthetic valve used in AVR does not significantly influence overall mortality.

Mechanical vs. manual cleaning of hospital beds: a prospective intervention study.

PubMed

Hopman, J; Nillesen, M; de Both, E; Witte, J; Teerenstra, S; Hulscher, M; Voss, A

2015-06-01

Cleaning regimens for hospital beds were evaluated in the context of a rising prevalence of highly resistant micro-organisms and increasing financial pressure on healthcare systems. Dutch hospitals have to choose between standardized, mechanical bed-washers advised in national guidance and manual cleaning. To evaluate the quality of mechanical and manual bed-cleaning regimens. The multi-faceted analysis of bed-cleaning regimens consisted of three steps. In Step 1, the training of the domestic service team was evaluated. In Step 2, the cleaning quality of manual and mechanical regimens was assessed. Soiled beds, obtained at random, from different departments were evaluated using microbiological analysis (N = 40) and ATP (N = 20). ATP and microbiological contamination were measured in five predetermined locations on all beds. In Step 3, manual cleaning was introduced over a two-month pilot study at the surgical short-stay unit, and beds from other departments were processed according to the 'gold standard' mechanical cleaning. ATP levels were evaluated in three locations on 300 beds after cleaning. Training was found to improve the quality of cleaning significantly. Mechanical cleaning resulted in significantly lower ATP levels than manual cleaning. Mechanical cleaning shows less variation and results in consistently lower ATP levels than manual cleaning. Copyright © 2015 The Healthcare Infection Society. Published by Elsevier Ltd. All rights reserved.

Mechanical Design of a 4-Stage ADR for the PIPER mission

NASA Technical Reports Server (NTRS)

James, Bryan L.; Kimball, Mark O.; Shirron, Peter J.; Sampson, Michael A.; Letmate, Richard V.; Jackson, Michael L.

2017-01-01

The four 1,280 bolometer detector arrays that will fly on the balloon borne PIPER mission will be cooled by a 4-stage adiabatic demagnetization refrigerator (ADR). Two of the three mechanically independent ADR assemblies provide thermal isolation to their salt pills through Kevlar suspensions while the other provides thermal isolation to its salt pill through the use of bellows and Vespel material. The ADR integrates with the detector arrays and it sits in a large bucket Dewar containing superfluid liquid helium. This paper will describe the complex mechanical design of the PIPER ADR, and summarize the mechanical analysis done to validate the design.The four 1,280 bolometer detector arrays that will fly on the balloon borne PIPER mission will be cooled by a 4-stage adiabatic demagnetization refrigerator (ADR). Two of the three mechanically independent ADR assemblies provide thermal isolation to their salt pills through Kevlar suspensions while the other provides thermal isolation to its salt pill through the use of bellows and Vespel material. The ADR integrates with the detector arrays and it sits in a large bucket Dewar containing superfluid liquid helium. This paper will describe the complex mechanical design of the PIPER ADR, and summarize the mechanical analysis done to validate the design.

Mono- and tri-ester hydrogenolysis using tandem catalysis. Scope and mechanism

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

Lohr, Tracy L.; Li, Zhi; Assary, Rajeev S.

The scope and mechanism of thermodynamically leveraged ester RC(O)O–R' bond hydrogenolysis by tandem metal triflate + supported Pd catalysts are investigated both experimentally and theoretically by DFT and energy span analysis.

Computer models and output, Spartan REM: Appendix B

NASA Technical Reports Server (NTRS)

Marlowe, D. S.; West, E. J.

1984-01-01

A computer model of the Spartan Release Engagement Mechanism (REM) is presented in a series of numerical charts and engineering drawings. A crack growth analysis code is used to predict the fracture mechanics of critical components.

Mono- and tri-ester hydrogenolysis using tandem catalysis. Scope and mechanism

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

Lohr, Tracy L.; Li, Zhi; Assary, Rajeev S.

2016-01-01

The scope and mechanism of thermodynamically leveraged ester RC(O)O–R' bond hydrogenolysis by tandem metal triflate + supported Pd catalysts are investigated both experimentally and theoretically by DFT and energy span analysis.

SPACEBAR: Kinematic design by computer graphics

NASA Technical Reports Server (NTRS)

Ricci, R. J.

1975-01-01

The interactive graphics computer program SPACEBAR, conceived to reduce the time and complexity associated with the development of kinematic mechanisms on the design board, was described. This program allows the direct design and analysis of mechanisms right at the terminal screen. All input variables, including linkage geometry, stiffness, and applied loading conditions, can be fed into or changed at the terminal and may be displayed in three dimensions. All mechanism configurations can be cycled through their range of travel and viewed in their various geometric positions. Output data includes geometric positioning in orthogonal coordinates of each node point in the mechanism, velocity and acceleration of the node points, and internal loads and displacements of the node points and linkages. All analysis calculations take at most a few seconds to complete. Output data can be viewed at the scope and also printed at the discretion of the user.

Music preferences of mechanically ventilated patients participating in a randomized controlled trial.

PubMed

Heiderscheit, Annie; Breckenridge, Stephanie J; Chlan, Linda L; Savik, Kay

2014-01-01

Mechanical ventilation (MV) is a life-saving measure and supportive modality utilized to treat patients experiencing respiratory failure. Patients experience pain, discomfort, and anxiety as a result of being mechanically ventilated. Music listening is a non-pharmacological intervention used to manage these psychophysiological symptoms associated with mechanical ventilation. The purpose of this secondary analysis was to examine music preferences of 107 MV patients enrolled in a randomized clinical trial that implemented a patient-directed music listening protocol to help manage the psychophysiological symptom of anxiety. Music data presented includes the music genres and instrumentation patients identified as their preferred music. Genres preferred include: classical, jazz, rock, country, and oldies. Instrumentation preferred include: piano, voice, guitar, music with nature sounds, and orchestral music. Analysis of three patients' preferred music received throughout the course of the study is illustrated to demonstrate the complexity of assessing MV patients and the need for an ongoing assessment process.

Effects of aging on the structural, mechanical, and thermal properties of the silicone rubber current transformer insulation bushing for a 500 kV substation.

PubMed

Wang, Zhigao; Zhang, Xinghai; Wang, Fangqiang; Lan, Xinsheng; Zhou, Yiqian

2016-01-01

In order to analyze the cracking and aging reason of the silicone rubber current transformer (CT) insulation bushing used for 8 years from a 500 kV alternating current substation, characteristics including Fourier transform infrared (FTIR) spectroscopy, mechanical properties analysis, hardness, and thermo gravimetric analysis have been carried out. The FTIR results indicated that the external surface of the silicone rubber CT insulation bushing suffered from more serious aging than the internal part, fracture of side chain Si-C bond was much more than the backbone. Mechanical properties and thermal stability results illustrated that the main aging reasons were the breakage of side chain Si-C bond and the excessive cross-linking reaction of the backbone. This study can provide valuable basis for evaluating degradation mechanism and aging state of the silicone rubber insulation bushing in electric power field.

Finite element fatigue analysis of rectangular clutch spring of automatic slack adjuster

NASA Astrophysics Data System (ADS)

Xu, Chen-jie; Luo, Zai; Hu, Xiao-feng; Jiang, Wen-song

2015-02-01

The failure of rectangular clutch spring of automatic slack adjuster directly affects the work of automatic slack adjuster. We establish the structural mechanics model of automatic slack adjuster rectangular clutch spring based on its working principle and mechanical structure. In addition, we upload such structural mechanics model to ANSYS Workbench FEA system to predict the fatigue life of rectangular clutch spring. FEA results show that the fatigue life of rectangular clutch spring is 2.0403×105 cycle under the effect of braking loads. In the meantime, fatigue tests of 20 automatic slack adjusters are carried out on the fatigue test bench to verify the conclusion of the structural mechanics model. The experimental results show that the mean fatigue life of rectangular clutch spring is 1.9101×105, which meets the results based on the finite element analysis using ANSYS Workbench FEA system.

Mechanical properties of experimental composites with different calcium phosphates fillers.

PubMed

Okulus, Zuzanna; Voelkel, Adam

2017-09-01

Calcium phosphates (CaPs)-containing composites have already shown good properties from the point of view of dental restorative materials. The purpose of this study was to examine the crucial mechanical properties of twelve hydroxyapatite- or tricalcium phosphate-filled composites. The raw and surface-treated forms of both CaP fillers were applied. As a reference materials two experimental glass-containing composites and one commercial dental restorative composite were applied. Nano-hardness, elastic modulus, compressive, flexural and diametral tensile strength of all studied materials were determined. Application of statistical methods (one-way analysis of variance and cluster agglomerative analysis) allowed for assessing the similarities between examined materials according to the values of studied parameters. The obtained results show that in almost all cases the mechanical properties of experimental CaPs-composites are comparable or even better than mechanical properties of examined reference materials. Copyright © 2017 Elsevier B.V. All rights reserved.

Additive Manufacturing of PLA and CF/PLA Binding Layer Specimens via Fused Deposition Modeling

NASA Astrophysics Data System (ADS)

Li, Yuhang; Gao, Shiyou; Dong, Rongmei; Ding, Xuebing; Duan, Xiaoxi

2018-02-01

As one of the most popular additive manufacturing techniques, fused deposition modeling (FDM) is successfully applied in aerospace, automotive, architecture, and other fields to fabricate thermoplastic parts. Unfortunately, as a result of the limited nature of the mechanical properties and mass in raw materials, there is a pressing need to improve mechanical properties and reduce weight for FDM parts. Therefore, this paper presents an experiment of a special polylactic acid (PLA) and carbon fiber (CF)/PLA-laminated experimental specimen fabricated using the FDM process. The mechanical properties and mass analysis of the new composites for the PLA and CF/PLA binding layer specimen are investigated experimentally. Through the experimental analysis, one can conclude that the mass of laminated specimen is lighter than the CF/PLA specimen, and the tensile and flexural mechanical properties are higher than the pure PLA specimen.

[Lung-brain interaction in the mechanically ventilated patient].

PubMed

López-Aguilar, J; Fernández-Gonzalo, M S; Turon, M; Quílez, M E; Gómez-Simón, V; Jódar, M M; Blanch, L

2013-10-01

Patients with acute lung injury or acute respiratory distress syndrome (ARDS) admitted to the ICU present neuropsychological alterations, which in most cases extend beyond the acute phase and have an important adverse effect upon quality of life. The aim of this review is to deepen in the analysis of the complex interaction between lung and brain in critically ill patients subjected to mechanical ventilation. This update first describes the neuropsychological alterations occurring both during the acute phase of ICU stay and at discharge, followed by an analysis of lung-brain interactions during mechanical ventilation, and finally explores the etiology and mechanisms leading to the neurological disorders observed in these patients. The management of critical patients requires an integral approach focused on minimizing the deleterious effects over the short, middle or long term. Copyright © 2012 Elsevier España, S.L. y SEMICYUC. All rights reserved.

Improving aluminum particle reactivity by annealing and quenching treatments: Synchrotron X-ray diffraction analysis of strain

DOE PAGES

McCollum, Jena; Pantoya, Michelle L.; Tamura, Nobumichi

2015-11-06

In bulk material processing, annealing and quenching metals such as aluminum (Al) can improve mechanical properties. On a single particle level, affecting mechanical properties may also affect Al particle reactivity. Our study examines the effect of annealing and quenching on the strain of Al particles and the corresponding reactivity of aluminum and copper oxide (CuO) composites. Micron-sized Al particles were annealed and quenched according to treatments designed to affect Al mechanical properties. Furthermore, synchrotron X-ray diffraction (XRD) analysis of the particles reveals that thermal treatment increased the dilatational strain of the aluminum-core, alumina-shell particles. Flame propagation experiments also show thermalmore » treatments effect reactivity when combined with CuO. An effective annealing and quenching treatment for increasing aluminum reactivity was identified. Our results show that altering the mechanical properties of Al particles affects their reactivity.« less

Experiments and kinematics analysis of a hand rehabilitation exoskeleton with circuitous joints.

PubMed

Zhang, Fuhai; Fu, Yili; Zhang, Qinchao; Wang, Shuguo

2015-01-01

Aiming at the hand rehabilitation of stroke patients, a wearable hand exoskeleton with circuitous joint is proposed. The circuitous joint adopts the symmetric pinion and rack mechanism (SPRM) with the parallel mechanism. The exoskeleton finger is a serial mechanism composed of three closed-chain SPRM joints in series. The kinematic equations of the open chain of the finger and the closed chains of the SPRM joints were built to analyze the kinematics of the hand rehabilitation exoskeleton. The experimental setup of the hand rehabilitation exoskeleton was built and the continuous passive motion (CPM) rehabilitation experiment and the test of human-robot interaction force measurement were conducted. Experiment results show that the mechanical design of the hand rehabilitation robot is reasonable and that the kinematic analysis is correct, thus the exoskeleton can be used for the hand rehabilitation of stroke patients.

Interactive mechanism of working environments and construction behaviors with cognitive work analysis: an elevator installation case study.

PubMed

Wang, Yanqing; Chong, Heap-Yih; Liao, Pin-Chao; Ren, Hantao

2017-09-25

Unsafe behavior is a leading factor in accidents, and the working environment significantly affects behaviors. However, few studies have focused on detailed mechanisms for addressing unsafe behaviors resulting from environmental constraints. This study aims to delineate these mechanisms using cognitive work analysis (CWA) for an elevator installation case study. Elevator installation was selected for study because it involves operations at heights: falls from heights remain a major cause of construction worker mortality. This study adopts a mixed research approach based on three research methodology stages. This research deconstructs the details of the working environment, the workers' decision-making processes, the strategies chosen given environmental conditions and the conceptual model for workers' behaviors, which jointly depict environment-behavior mechanisms at length. By applying CWA to the construction industry, environmental constraints can easily be identified, and targeted engineering suggestions can be generated.

Creep-Fatigue Failure Diagnosis

PubMed Central

Holdsworth, Stuart

2015-01-01

Failure diagnosis invariably involves consideration of both associated material condition and the results of a mechanical analysis of prior operating history. This Review focuses on these aspects with particular reference to creep-fatigue failure diagnosis. Creep-fatigue cracking can be due to a spectrum of loading conditions ranging from pure cyclic to mainly steady loading with infrequent off-load transients. These require a range of mechanical analysis approaches, a number of which are reviewed. The microstructural information revealing material condition can vary with alloy class. In practice, the detail of the consequent cracking mechanism(s) can be camouflaged by oxidation at high temperatures, although the presence of oxide on fracture surfaces can be used to date events leading to failure. Routine laboratory specimen post-test examination is strongly recommended to characterise the detail of deformation and damage accumulation under known and well-controlled loading conditions to improve the effectiveness and efficiency of failure diagnosis. PMID:28793676

Music preferences of mechanically ventilated patients participating in a randomized controlled trial

PubMed Central

Heiderscheit, Annie; Breckenridge, Stephanie J.; Chlan, Linda L.; Savik, Kay

2014-01-01

Mechanical ventilation (MV) is a life-saving measure and supportive modality utilized to treat patients experiencing respiratory failure. Patients experience pain, discomfort, and anxiety as a result of being mechanically ventilated. Music listening is a non-pharmacological intervention used to manage these psychophysiological symptoms associated with mechanical ventilation. The purpose of this secondary analysis was to examine music preferences of 107 MV patients enrolled in a randomized clinical trial that implemented a patient-directed music listening protocol to help manage the psychophysiological symptom of anxiety. Music data presented includes the music genres and instrumentation patients identified as their preferred music. Genres preferred include: classical, jazz, rock, country, and oldies. Instrumentation preferred include: piano, voice, guitar, music with nature sounds, and orchestral music. Analysis of three patients’ preferred music received throughout the course of the study is illustrated to demonstrate the complexity of assessing MV patients and the need for an ongoing assessment process. PMID:25574992

Investigation of the mechanism of impurity assisted nanoripple formation on Si induced by low energy ion beam erosion

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

Koyiloth Vayalil, Sarathlal, E-mail: sarathlal.koyilothvayalil@desy.de; UGC-DAE Consortium for Scientific Research, University Campus, Khandwa Road, Indore 452017; Gupta, Ajay

A detailed mechanism of the nanoripple pattern formation on Si substrates generated by the simultaneous incorporation of pure Fe impurities at low energy (1 keV) ion beam erosion has been studied. To understand and clarify the mechanism of the pattern formation, a comparative analysis of the samples prepared for various ion fluence values using two complimentary methods for nanostructure analysis, atomic force microscopy, and grazing incidence small angle x-ray scattering has been done. We observed that phase separation of the metal silicide formed during the erosion does not precede the ripple formation. It rather concurrently develops along with the ripple structure.more » Our work is able to differentiate among various models existing in the literature and provides an insight into the mechanism of pattern formation under ion beam erosion with impurity incorporation.« less

Mechanisms of Evolution in High-Consequence Drug Resistance Plasmids

PubMed Central

He, Susu; Chandler, Michael; Varani, Alessandro M.; Hickman, Alison B.; Dekker, John P.

2016-01-01

ABSTRACT The dissemination of resistance among bacteria has been facilitated by the fact that resistance genes are usually located on a diverse and evolving set of transmissible plasmids. However, the mechanisms generating diversity and enabling adaptation within highly successful resistance plasmids have remained obscure, despite their profound clinical significance. To understand these mechanisms, we have performed a detailed analysis of the mobilome (the entire mobile genetic element content) of a set of previously sequenced carbapenemase-producing Enterobacteriaceae (CPE) from the National Institutes of Health Clinical Center. This analysis revealed that plasmid reorganizations occurring in the natural context of colonization of human hosts were overwhelmingly driven by genetic rearrangements carried out by replicative transposons working in concert with the process of homologous recombination. A more complete understanding of the molecular mechanisms and evolutionary forces driving rearrangements in resistance plasmids may lead to fundamentally new strategies to address the problem of antibiotic resistance. PMID:27923922

Repellents Inhibit P450 Enzymes in Stegomyia (Aedes) aegypti

PubMed Central

Jaramillo Ramirez, Gloria Isabel; Logan, James G.; Loza-Reyes, Elisa; Stashenko, Elena; Moores, Graham D.

2012-01-01

The primary defence against mosquitoes and other disease vectors is often the application of a repellent. Despite their common use, the mechanism(s) underlying the activity of repellents is not fully understood, with even the mode of action of DEET having been reported to be via different mechanisms; e.g. interference with olfactory receptor neurones or actively detected by olfactory receptor neurones on the antennae or maxillary palps. In this study, we discuss a novel mechanism for repellence, one of P450 inhibition. Thirteen essential oil extracts from Colombian plants were assayed for potency as P450 inhibitors, using a kinetic fluorometric assay, and for repellency using a modified World Health Organisation Pesticide Evaluations Scheme (WHOPES) arm-in cage assay with Stegomyia (Aedes) aegypti mosquitoes. Bootstrap analysis on the inhibition analysis revealed a significant correlation between P450-inhibition and repellent activity of the oils. PMID:23152795

Characterization of Nanocomposites by Thermal Analysis

PubMed Central

Corcione, Carola Esposito; Frigione, Mariaenrica

2012-01-01

In materials research, the development of polymer nanocomposites (PN) is rapidly emerging as a multidisciplinary research field with results that could broaden the applications of polymers to many different industries. PN are polymer matrices (thermoplastics, thermosets or elastomers) that have been reinforced with small quantities of nano-sized particles, preferably characterized by high aspect ratios, such as layered silicates and carbon nanotubes. Thermal analysis (TA) is a useful tool to investigate a wide variety of properties of polymers and it can be also applied to PN in order to gain further insight into their structure. This review illustrates the versatile applications of TA methods in the emerging field of polymer nanomaterial research, presenting some examples of applications of differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMTA) and thermal mechanical analysis (TMA) for the characterization of nanocomposite materials.

Analysis and control of the vibration of doubly fed wind turbine

NASA Astrophysics Data System (ADS)

Yu, Manye; Lin, Ying

2017-01-01

The fault phenomena of the violent vibration of certain doubly-fed wind turbine were researched comprehensively, and the dynamic characteristics, load and fault conditions of the system were discussed. Firstly, the structural dynamics analysis of wind turbine is made, and the dynamics mold is built. Secondly, the vibration testing of wind turbine is done with the German test and analysis systems BBM. Thirdly, signal should be analyzed and dealt with. Based on the experiment, spectrum analysis of the motor dynamic balance can be made by using signal processing toolbox of MATLAB software, and the analysis conclusions show that the vibration of wind turbine is caused by dynamic imbalance. The results show that integrating mechanical system dynamics theory with advanced test technology can solve the vibration problem more successfully, which is important in vibration diagnosis of mechanical equipment.

Integration mechanisms and hospital efficiency in integrated health care delivery systems.

PubMed

Wan, Thomas T H; Lin, Blossom Yen-Ju; Ma, Allen

2002-04-01

This study analyzes integration mechanisms that affect system performances measured by indicators of efficiency in integrated delivery systems (IDSs) in the United States. The research question is, do integration mechanisms improve IDSs' efficiency in hospital care? American Hospital Association's Annual Survey (1998) and Dorenfest's Survey on Information Systems in Integrated Healthcare Delivery Systems (1998) were used to conduct the study, using IDS as the unit of analysis. A covariance structure equation model of the effects of system integration mechanisms on IDS performance was formulated and validated by an empirical examination of IDSs. The study sample includes 973 hospital-based integrated health care delivery systems operating in the United States, carried in the list of Dorenfests Survey on Information Systems in Integrated Health care Delivery Systems. The measurement indicators of system integration mechanisms are categorized into six related domains: informatic integration, case management, hybrid physician-hospital integration, forward integration, backward integration, and high tech medical services. The multivariate analysis reveals that integration mechanisms in system operation are positively correlated and positively affect IDSs' efficiency. The six domains of integration mechanisms account for 58.9% of the total variance in hospital performance. The service differentiation strategy such as having more high tech medical services have much stronger influences on efficiency than other integration mechanisms do. The beneficial effects of integration mechanisms have been realized in IDS performance. High efficiency in hospital care can be achieved by employing proper integration strategies in operations.

Computation and Communication Evaluation of an Authentication Mechanism for Time-Triggered Networked Control Systems

PubMed Central

Martins, Goncalo; Moondra, Arul; Dubey, Abhishek; Bhattacharjee, Anirban; Koutsoukos, Xenofon D.

2016-01-01

In modern networked control applications, confidentiality and integrity are important features to address in order to prevent against attacks. Moreover, network control systems are a fundamental part of the communication components of current cyber-physical systems (e.g., automotive communications). Many networked control systems employ Time-Triggered (TT) architectures that provide mechanisms enabling the exchange of precise and synchronous messages. TT systems have computation and communication constraints, and with the aim to enable secure communications in the network, it is important to evaluate the computational and communication overhead of implementing secure communication mechanisms. This paper presents a comprehensive analysis and evaluation of the effects of adding a Hash-based Message Authentication (HMAC) to TT networked control systems. The contributions of the paper include (1) the analysis and experimental validation of the communication overhead, as well as a scalability analysis that utilizes the experimental result for both wired and wireless platforms and (2) an experimental evaluation of the computational overhead of HMAC based on a kernel-level Linux implementation. An automotive application is used as an example, and the results show that it is feasible to implement a secure communication mechanism without interfering with the existing automotive controller execution times. The methods and results of the paper can be used for evaluating the performance impact of security mechanisms and, thus, for the design of secure wired and wireless TT networked control systems. PMID:27463718

BATMAN-TCM: a Bioinformatics Analysis Tool for Molecular mechANism of Traditional Chinese Medicine

NASA Astrophysics Data System (ADS)

Liu, Zhongyang; Guo, Feifei; Wang, Yong; Li, Chun; Zhang, Xinlei; Li, Honglei; Diao, Lihong; Gu, Jiangyong; Wang, Wei; Li, Dong; He, Fuchu

2016-02-01

Traditional Chinese Medicine (TCM), with a history of thousands of years of clinical practice, is gaining more and more attention and application worldwide. And TCM-based new drug development, especially for the treatment of complex diseases is promising. However, owing to the TCM’s diverse ingredients and their complex interaction with human body, it is still quite difficult to uncover its molecular mechanism, which greatly hinders the TCM modernization and internationalization. Here we developed the first online Bioinformatics Analysis Tool for Molecular mechANism of TCM (BATMAN-TCM). Its main functions include 1) TCM ingredients’ target prediction; 2) functional analyses of targets including biological pathway, Gene Ontology functional term and disease enrichment analyses; 3) the visualization of ingredient-target-pathway/disease association network and KEGG biological pathway with highlighted targets; 4) comparison analysis of multiple TCMs. Finally, we applied BATMAN-TCM to Qishen Yiqi dripping Pill (QSYQ) and combined with subsequent experimental validation to reveal the functions of renin-angiotensin system responsible for QSYQ’s cardioprotective effects for the first time. BATMAN-TCM will contribute to the understanding of the “multi-component, multi-target and multi-pathway” combinational therapeutic mechanism of TCM, and provide valuable clues for subsequent experimental validation, accelerating the elucidation of TCM’s molecular mechanism. BATMAN-TCM is available at http://bionet.ncpsb.org/batman-tcm.

Non-strictly black body spectrum from the tunnelling mechanism

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

Corda, Christian, E-mail: cordac.galilei@gmail.com

2013-10-15

The tunnelling mechanism is widely used to explain Hawking radiation. However, in many cases the analysis used to obtain the Hawking temperature only involves comparing the emission probability for an outgoing particle with the Boltzmann factor. Banerjee and Majhi improved this approach by explicitly finding a black body spectrum associated with black holes. Their result, obtained using a reformulation of the tunnelling mechanism, is in contrast to that of Parikh and Wilczek, who found an emission probability that is compatible with a non-strictly thermal spectrum. Using the recently identified effective state for a black hole, we solve this contradiction viamore » a slight modification of the analysis by Banerjee and Majhi. The final result is a non-strictly black body spectrum from the tunnelling mechanism. We also show that for an effective temperature, we can express the corresponding effective metric using Hawking’s periodicity arguments. Potential important implications for the black hole information puzzle are discussed. -- Highlights: •We review an important result by Banerjee and Majhi on the tunnelling mechanism in the framework of Hawking radiation. •This result is in contrast to another result reported by Parikh and Wilczek. •We introduce the effective state of a black hole. •We explain the contrast via a slight modification of the analysis by Banerjee and Majhi. •We discuss potential important implications for the black hole information puzzle.« less

Underlying Mechanisms of Cooperativity, Input Specificity, and Associativity of Long-Term Potentiation Through a Positive Feedback of Local Protein Synthesis.

PubMed

Hao, Lijie; Yang, Zhuoqin; Lei, Jinzhi

2018-01-01

Long-term potentiation (LTP) is a specific form of activity-dependent synaptic plasticity that is a leading mechanism of learning and memory in mammals. The properties of cooperativity, input specificity, and associativity are essential for LTP; however, the underlying mechanisms are unclear. Here, based on experimentally observed phenomena, we introduce a computational model of synaptic plasticity in a pyramidal cell to explore the mechanisms responsible for the cooperativity, input specificity, and associativity of LTP. The model is based on molecular processes involved in synaptic plasticity and integrates gene expression involved in the regulation of neuronal activity. In the model, we introduce a local positive feedback loop of protein synthesis at each synapse, which is essential for bimodal response and synapse specificity. Bifurcation analysis of the local positive feedback loop of brain-derived neurotrophic factor (BDNF) signaling illustrates the existence of bistability, which is the basis of LTP induction. The local bifurcation diagram provides guidance for the realization of LTP, and the projection of whole system trajectories onto the two-parameter bifurcation diagram confirms the predictions obtained from bifurcation analysis. Moreover, model analysis shows that pre- and postsynaptic components are required to achieve the three properties of LTP. This study provides insights into the mechanisms underlying the cooperativity, input specificity, and associativity of LTP, and the further construction of neural networks for learning and memory.

Investigation of abrupt degradation of drain current caused by under-gate crack in AlGaN/GaN high electron mobility transistors during high temperature operation stress

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

Zeng, Chang; Liao, XueYang; Li, RuGuan

2015-09-28

In this paper, we investigate the degradation mode and mechanism of AlGaN/GaN based high electron mobility transistors (HEMTs) during high temperature operation (HTO) stress. It demonstrates that there was abrupt degradation mode of drain current during HTO stress. The abrupt degradation is ascribed to the formation of crack under the gate which was the result of the brittle fracture of epilayer based on failure analysis. The origin of the mechanical damage under the gate is further investigated and discussed based on top-down scanning electron microscope, cross section transmission electron microscope and energy dispersive x-ray spectroscopy analysis, and stress simulation. Basedmore » on the coupled analysis of the failure physical feature and stress simulation considering the coefficient of thermal expansion (CTE) mismatch in different materials in gate metals/semiconductor system, the mechanical damage under the gate is related to mechanical stress induced by CTE mismatch in Au/Ti/Mo/GaN system and stress concentration caused by the localized structural damage at the drain side of the gate edge. These results indicate that mechanical stress induced by CTE mismatch of materials inside the device plays great important role on the reliability of AlGaN/GaN HEMTs during HTO stress.« less

Computation and Communication Evaluation of an Authentication Mechanism for Time-Triggered Networked Control Systems.

PubMed

Martins, Goncalo; Moondra, Arul; Dubey, Abhishek; Bhattacharjee, Anirban; Koutsoukos, Xenofon D

2016-07-25

In modern networked control applications, confidentiality and integrity are important features to address in order to prevent against attacks. Moreover, network control systems are a fundamental part of the communication components of current cyber-physical systems (e.g., automotive communications). Many networked control systems employ Time-Triggered (TT) architectures that provide mechanisms enabling the exchange of precise and synchronous messages. TT systems have computation and communication constraints, and with the aim to enable secure communications in the network, it is important to evaluate the computational and communication overhead of implementing secure communication mechanisms. This paper presents a comprehensive analysis and evaluation of the effects of adding a Hash-based Message Authentication (HMAC) to TT networked control systems. The contributions of the paper include (1) the analysis and experimental validation of the communication overhead, as well as a scalability analysis that utilizes the experimental result for both wired and wireless platforms and (2) an experimental evaluation of the computational overhead of HMAC based on a kernel-level Linux implementation. An automotive application is used as an example, and the results show that it is feasible to implement a secure communication mechanism without interfering with the existing automotive controller execution times. The methods and results of the paper can be used for evaluating the performance impact of security mechanisms and, thus, for the design of secure wired and wireless TT networked control systems.

BATMAN-TCM: a Bioinformatics Analysis Tool for Molecular mechANism of Traditional Chinese Medicine

PubMed Central

Liu, Zhongyang; Guo, Feifei; Wang, Yong; Li, Chun; Zhang, Xinlei; Li, Honglei; Diao, Lihong; Gu, Jiangyong; Wang, Wei; Li, Dong; He, Fuchu

2016-01-01

Traditional Chinese Medicine (TCM), with a history of thousands of years of clinical practice, is gaining more and more attention and application worldwide. And TCM-based new drug development, especially for the treatment of complex diseases is promising. However, owing to the TCM’s diverse ingredients and their complex interaction with human body, it is still quite difficult to uncover its molecular mechanism, which greatly hinders the TCM modernization and internationalization. Here we developed the first online Bioinformatics Analysis Tool for Molecular mechANism of TCM (BATMAN-TCM). Its main functions include 1) TCM ingredients’ target prediction; 2) functional analyses of targets including biological pathway, Gene Ontology functional term and disease enrichment analyses; 3) the visualization of ingredient-target-pathway/disease association network and KEGG biological pathway with highlighted targets; 4) comparison analysis of multiple TCMs. Finally, we applied BATMAN-TCM to Qishen Yiqi dripping Pill (QSYQ) and combined with subsequent experimental validation to reveal the functions of renin-angiotensin system responsible for QSYQ’s cardioprotective effects for the first time. BATMAN-TCM will contribute to the understanding of the “multi-component, multi-target and multi-pathway” combinational therapeutic mechanism of TCM, and provide valuable clues for subsequent experimental validation, accelerating the elucidation of TCM’s molecular mechanism. BATMAN-TCM is available at http://bionet.ncpsb.org/batman-tcm. PMID:26879404

Hostile Attribution Bias Mediates the Relationship Between Structural Variations in the Left Middle Frontal Gyrus and Trait Angry Rumination

PubMed Central

Wang, Yueyue; Zhu, Wenfeng; Xiao, Mingyue; Zhang, Qin; Zhao, Yufang; Zhang, Hao; Chen, Xu; Zheng, Yong; Xia, Ling-Xiang

2018-01-01

Angry rumination is a common mental phenomenon which may lead to negative social behaviors such as aggression. Although numerous neuroimaging studies have focused on brain area activation during angry rumination, to our knowledge no study has examined the neuroanatomical and cognitive mechanisms of this process. In this study, we conducted a voxel-based morphometry analysis, using a region of interest analysis to identify the structural and cognitive mechanisms underlying individual differences in trait angry rumination (as measured by the Angry Rumination Scale) in a sample of 82 undergraduate students. We found that angry rumination was positively correlated with gray matter density in the left middle frontal gyrus (left-MFG), which is implicated in inhibition control, working memory, and emotional regulation. The mediation analysis further revealed that hostile attribution bias (as measured by the Social Information Processing–Attribution Bias Questionnaire) acted as a cognitive mechanism underlying the positive association between the left-MFG gray matter density and trait angry rumination. These findings suggest that hostile attribution bias may contribute to trait angry rumination, while the left-MFG may play an important role in the development of hostile attribution bias and trait angry rumination. The study reveals the brain mechanisms of trait angry rumination and plays a role in revealing the cognitive mechanisms of the development of trait angry rumination. PMID:29695990

Investigation of allosteric modulation mechanism of metabotropic glutamate receptor 1 by molecular dynamics simulations, free energy and weak interaction analysis

NASA Astrophysics Data System (ADS)

Bai, Qifeng; Yao, Xiaojun

2016-02-01

Metabotropic glutamate receptor 1 (mGlu1), which belongs to class C G protein-coupled receptors (GPCRs), can be coupled with G protein to transfer extracellular signal by dimerization and allosteric regulation. Unraveling the dimer packing and allosteric mechanism can be of great help for understanding specific regulatory mechanism and designing more potential negative allosteric modulator (NAM). Here, we report molecular dynamics simulation studies of the modulation mechanism of FITM on the wild type, T815M and Y805A mutants of mGlu1 through weak interaction analysis and free energy calculation. The weak interaction analysis demonstrates that van der Waals (vdW) and hydrogen bonding play an important role on the dimer packing between six cholesterol molecules and mGlu1 as well as the interaction between allosteric sites T815, Y805 and FITM in wild type, T815M and Y805A mutants of mGlu1. Besides, the results of free energy calculations indicate that secondary binding pocket is mainly formed by the residues Thr748, Cys746, Lys811 and Ser735 except for FITM-bound pocket in crystal structure. Our results can not only reveal the dimer packing and allosteric regulation mechanism, but also can supply useful information for the design of potential NAM of mGlu1.

Exploring Newtonian Mechanics in a Conceptually-Integrated Digital Game: Comparison of Learning and Affective Outcomes for Students in Taiwan and the United States

ERIC Educational Resources Information Center

Clark, Douglas B.; Nelson, Brian C.; Chang, Hsin-Yi; Martinez-Garza, Mario; Slack, Kent; D'Angelo, Cynthia M.

2011-01-01

This study investigates the potential of a digital game that overlays popular game-play mechanics with formal physics representations and terminology to support explicit learning and exploration of Newtonian mechanics. The analysis compares test data, survey data, and observational data collected during implementations in Taiwan and the United…

INSAT-2A and 2B development mechanisms

NASA Technical Reports Server (NTRS)

Sathyanarayan, M. N.; Rao, M. Nageswara; Nataraju, B. S.; Viswanatha, N.; Chary, M. Laxmana; Balan, K. S.; Murthy, V. Sridhara; Aller, Raju; Kumar, H. N. Suresha

1994-01-01

The Indian National Satellite (INSAT) 2A and 2B have deployment mechanisms for deploying the solar array, two C/S band antenna reflectors and a coilable lattice boom with sail. The mechanisms have worked flawlessly on both satellites. The configuration details, precautions taken during the design phase, the test philosophy, and some of the critical analysis activities are discussed.

Multilevel semantic analysis and problem-solving in the flight-domain

NASA Technical Reports Server (NTRS)

Chien, R. T.

1982-01-01

The use of knowledge-base architecture and planning control; mechanisms to perform an intelligent monitoring task in the flight domain is addressed. The route level, the trajectory level, and parts of the aerodynamics level are demonstrated. Hierarchical planning and monitoring conceptual levels, functional-directed mechanism rationalization, and using deep-level mechanism models for diagnoses of dependent failures are discussed.

Modeling, Analysis, and Optimization Issues for Large Space Structures.

DTIC Science & Technology

1983-02-01

There are numerous opportunities - provided by new advances in computer hardware, firmware, software , CAD/CAM systems, computational algorithms and...Institute Department of Mechanical Engineering Dept. of Civil Engineering & Mechanics Troy, NY 12181 Drexel University Philadelphia, PA 19104 Dr...Mechanical Engineering Hampton, VA 23665 Washington, DC 20059 Dr. K. T. Alfriend Mr. Siva S. Banda Department of the Navy Flight Dynamics LaboratoryNaval

Enhancing the Connection to Undergraduate Engineering Students: A Hands-On and Team-Based Approach to Fluid Mechanics

ERIC Educational Resources Information Center

Wei, Tie; Ford, Julie

2015-01-01

This article provides information about the integration of innovative hands-on activities within a sophomore-level Fluid Mechanics course at New Mexico Tech. The course introduces students to the fundamentals of fluid mechanics with emphasis on teaching key equations and methods of analysis for solving real-world problems. Strategies and examples…

Stereoselective Degradation and Molecular Ecological Mechanism of Chiral Pesticides Beta-Cypermethrin in Soils with Different pH Values.

PubMed

Yang, Zhong-Hua; Ji, Guo-Dong

2015-12-15

For decades, pesticides have been widely used for agricultural activities around the world, and the environmental problems caused by these compounds have raised widespread concern. However, the different enantioselective behaviors of chiral pesticide enantiomers are often ignored. Here, the selective degradation patterns and mechanisms of chiral pesticide enantiomers were successfully investigated for the first time in the soils of three cultivation areas with different pH values. Beta-cypermethrin was chosen as the target analyte. We found that the degradation rates of the four isomers of beta-cypermethrin were different. We used stepwise regression equations between degradation rates and functional genes to quantitatively study their relationships. Quantitative response analysis revealed that different isomers have different equations even under identical conditions. The results of path analysis showed that a single functional gene can make different direct and indirect contributions to the degradation of different isomers. Finally, the high-throughput technology was used to analysis the genome of the three tested soils and then compared the main microbial communities in them. We have successfully devised a method to investigate the molecular biological mechanisms of the selective degradation behavior of chiral compounds, thus enabling us to better understand these mechanisms.

Integrated network analysis reveals potentially novel molecular mechanisms and therapeutic targets of refractory epilepsies

PubMed Central

Liu, Guangming; Wang, Yiwei; Zhao, Pengyao; Zhu, Yizhun; Yang, Xiaohan; Zheng, Tiezheng; Zhou, Xuezhong; Jin, Weilin; Sun, Changkai

2017-01-01

Epilepsy is a complex neurological disorder and a significant health problem. The pathogenesis of epilepsy remains obscure in a significant number of patients and the current treatment options are not adequate in about a third of individuals which were known as refractory epilepsies (RE). Network medicine provides an effective approach for studying the molecular mechanisms underlying complex diseases. Here we integrated 1876 disease-gene associations of RE and located those genes to human protein-protein interaction (PPI) network to obtain 42 significant RE-associated disease modules. The functional analysis of these disease modules showed novel molecular pathological mechanisms of RE, such as the novel enriched pathways (e.g., “presynaptic nicotinic acetylcholine receptors”, “signaling by insulin receptor”). Further analysis on the relationships between current drug targets and the RE-related disease genes showed the rational mechanisms of most antiepileptic drugs. In addition, we detected ten potential novel drug targets (e.g., KCNA1, KCNA4-6, KCNC3, KCND2, KCNMA1, CAMK2G, CACNB4 and GRM1) located in three RE related disease modules, which might provide novel insights into the new drug discovery for RE therapy. PMID:28388656

Upscaling Cement Paste Microstructure to Obtain the Fracture, Shear, and Elastic Concrete Mechanical LDPM Parameters.

PubMed

Sherzer, Gili; Gao, Peng; Schlangen, Erik; Ye, Guang; Gal, Erez

2017-02-28

Modeling the complex behavior of concrete for a specific mixture is a challenging task, as it requires bridging the cement scale and the concrete scale. We describe a multiscale analysis procedure for the modeling of concrete structures, in which material properties at the macro scale are evaluated based on lower scales. Concrete may be viewed over a range of scale sizes, from the atomic scale (10 -10 m), which is characterized by the behavior of crystalline particles of hydrated Portland cement, to the macroscopic scale (10 m). The proposed multiscale framework is based on several models, including chemical analysis at the cement paste scale, a mechanical lattice model at the cement and mortar scales, geometrical aggregate distribution models at the mortar scale, and the Lattice Discrete Particle Model (LDPM) at the concrete scale. The analysis procedure starts from a known chemical and mechanical set of parameters of the cement paste, which are then used to evaluate the mechanical properties of the LDPM concrete parameters for the fracture, shear, and elastic responses of the concrete. Although a macroscopic validation study of this procedure is presented, future research should include a comparison to additional experiments in each scale.

Metabolomics study on the hepatoprotective effect of scoparone using ultra-performance liquid chromatography/electrospray ionization quadruple time-of-flight mass spectrometry.

PubMed

Zhang, Aihua; Sun, Hui; Dou, Shengshan; Sun, Wenjun; Wu, Xiuhong; Wang, Ping; Wang, Xijun

2013-01-07

Scoparone is an important constituent of Yinchenhao (Artemisia annua L.), a famous medicinal plant, and displayed bright prospects in the prevention and therapy of liver injury. However, the precise molecular mechanism of hepatoprotective effects has not been comprehensively explored. Here, metabolomics techniques are the comprehensive assessment of endogenous metabolites in a biological system and may provide additional insight into the mechanisms. The present investigation was designed to assess the effects and possible mechanisms of scoparone against carbon tetrachloride-induced liver injury. Ultra-performance liquid chromatography/electrospray ionization quadruple time-of-flight mass spectrometry (UPLC/ESI-Q-TOF/MS) combined with pattern recognition approaches including principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) were integrated to discover differentiating metabolites. Results indicate five ions in the positive mode as differentiating metabolites. Functional pathway analysis revealed that the alterations in these metabolites were associated with primary bile acid biosynthesis, pyrimidine metabolism. Of note, scoparone has a potential pharmacological effect through regulating multiple perturbed pathways to the normal state. Our findings also showed that the robust metabolomics techniques are promising for getting biomarkers and clarifying mechanisms of disease, highlighting insights into drug discovery.

Upscaling Cement Paste Microstructure to Obtain the Fracture, Shear, and Elastic Concrete Mechanical LDPM Parameters

PubMed Central

Sherzer, Gili; Gao, Peng; Schlangen, Erik; Ye, Guang; Gal, Erez

2017-01-01

Modeling the complex behavior of concrete for a specific mixture is a challenging task, as it requires bridging the cement scale and the concrete scale. We describe a multiscale analysis procedure for the modeling of concrete structures, in which material properties at the macro scale are evaluated based on lower scales. Concrete may be viewed over a range of scale sizes, from the atomic scale (10−10 m), which is characterized by the behavior of crystalline particles of hydrated Portland cement, to the macroscopic scale (10 m). The proposed multiscale framework is based on several models, including chemical analysis at the cement paste scale, a mechanical lattice model at the cement and mortar scales, geometrical aggregate distribution models at the mortar scale, and the Lattice Discrete Particle Model (LDPM) at the concrete scale. The analysis procedure starts from a known chemical and mechanical set of parameters of the cement paste, which are then used to evaluate the mechanical properties of the LDPM concrete parameters for the fracture, shear, and elastic responses of the concrete. Although a macroscopic validation study of this procedure is presented, future research should include a comparison to additional experiments in each scale. PMID:28772605

Application of fault tree approach for the causation mechanism of urban haze in Beijing--Considering the risk events related with exhausts of coal combustion.

PubMed

Huang, Weiqing; Fan, Hongbo; Qiu, Yongfu; Cheng, Zhiyu; Qian, Yu

2016-02-15

Haze weather has become a serious environmental pollution problem which occurs in many Chinese cities. One of the most critical factors for the formation of haze weather is the exhausts of coal combustion, thus it is meaningful to figure out the causation mechanism between urban haze and the exhausts of coal combustion. Based on above considerations, the fault tree analysis (FAT) approach was employed for the causation mechanism of urban haze in Beijing by considering the risk events related with the exhausts of coal combustion for the first time. Using this approach, firstly the fault tree of the urban haze causation system connecting with coal combustion exhausts was established; consequently the risk events were discussed and identified; then, the minimal cut sets were successfully determined using Boolean algebra; finally, the structure, probability and critical importance degree analysis of the risk events were completed for the qualitative and quantitative assessment. The study results proved that the FTA was an effective and simple tool for the causation mechanism analysis and risk management of urban haze in China. Copyright © 2015 Elsevier B.V. All rights reserved.

High performance light-colored nitrile-butadiene rubber nanocomposites.

PubMed

Lei, Yanda; Guo, Baochun; Chen, Feng; Zhu, Lixin; Zhou, Wenyou; Jia, Demin

2011-12-01

High mechanical performance nitrile-butadiene rubber (NBR) with light color was fabricated by the method of in situ formation of zinc disorbate (ZDS) or magnesium disorbate (MDS). The in situ formed ZDS and its polymerization via internal mixing was confirmed by X-ray diffaraction. The mechanical properties, ageing resistance, morphology and the dynamic mechanical analysis were fully studied. It was found that with increasing loading of metallic disorbate both the curing rate and the ionic crosslink density was largely increased. The modulus, tensile strength and tear strength were largely increased. With a comparison between internal mixing and opening mixing, the mechanical performance for the former one was obviously better than the latter one. The high performance was ascribed to the finely dispersion nano domains with irregular shape and obscure interfacial structures. Except for the NBR vulcanizate with a high loading of MDS, the others' ageing resistance with incorporation of these two metallic disorbate was found to be good. Dynamic mechanical analysis (DMA) showed that, with increasing loading of metallic disorbate, the highly increased storage modulus above -20 degrees C, the up-shifted glass transition temperature (Tg) and the reduced mechanical loss were ascribed to strengthened interfacial interactions.

Mechanics and pathomechanics in the overhead athlete.

PubMed

Kibler, W Ben; Wilkes, Trevor; Sciascia, Aaron

2013-10-01

Optimal performance of the overhead throwing task requires precise mechanics that involve coordinated kinetic and kinematic chains to develop, transfer, and regulate the forces the body needs to withstand the inherent demands of the task and to allow optimal performance. These chains have been evaluated and the basic components, called nodes, have been identified. Impaired performance and/or injury, the DTS, is associated with alterations in the mechanics that are called pathomechanics. They can occur at multiple locations throughout the kinetic chain. They must be evaluated and treated as part of the overall problem. Observational analysis of the mechanics and pathomechanics using the node analysis method can be useful in highlighting areas of alteration that can be evaluated for anatomic injury or altered physiology. The comprehensive kinetic chain examination can evaluate sites of kinetic chain breakage, and a detailed shoulder examination can assess joint internal derangement of altered physiology that may contribute to the pathomechanics. Treatment of the DTS should be comprehensive, directed toward restoring physiology and mechanics and optimizing anatomy. This maximizes the body’s ability to develop normal mechanics to accomplish the overhead throwing task. Copyright © 2013 Elsevier Inc. All rights reserved.

Thermo-mechanical analysis of an internal cooling system with various configurations of a combustion liner after shell

NASA Astrophysics Data System (ADS)

Moon, Hokyu; Kim, Kyung Min; Park, Jun Su; Kim, Beom Seok; Cho, Hyung Hee

2015-12-01

The after-shell section, which is part of the gas turbine combustion liner, is exposed to the hottest combustion gas. Various cooling schemes have been applied to protect against severe thermal load. However, there is a significant discrepancy in the thermal expansion with large temperature differences, resulting in thermo-mechanical crack formation. In this study, to reduce combustion liner damage, thermo-mechanical analysis was conducted on three after-shell section configurations: inline-discrete divider wall, staggered divider wall, and swirler wall arrays. These array components are well-known heat-transfer enhancement structures in the duct. In the numerical analyses, the heat transfer characteristics, temperature and thermo-mechanical stress distribution were evaluated using finite volume method and finite element method commercial codes. As a result, we demonstrated that the temperature and the thermo-mechanical stress distribution were readily dependent on the structural array for cooling effectiveness and structural support in each modified cooling system. Compared with the reference model, the swirler wall array was most effective in diminishing the thermo-mechanical stress concentration, especially on the inner ring that is vulnerable to crack formation.

Cofilin Increases the Bending Flexibility of Actin Filaments: Implications for Severing and Cell Mechanics

PubMed Central

McCullough, Brannon R.; Blanchoin, Laurent; Martiel, Jean-Louis; De La Cruz, Enrique M.

2009-01-01

We determined the flexural (bending) rigidities of actin and cofilactin filaments from a cosine correlation function analysis of their thermally driven, two-dimensional fluctuations in shape. The persistence length of actin filaments is 9.8 µm, corresponding to a flexural rigidity of 0.040 pN µm2. Cofilin binding lowers the persistence length ∼5-fold to a value of 2.2 µm and the filament flexural rigidity to 0.0091 pN µm2. That cofilin-decorated filaments are more flexible than native filaments despite an increased mass indicates that cofilin binding weakens and redistributes stabilizing subunit interactions of filaments. We favor a mechanism in which the increased flexibility of cofilin-decorated filaments results from the linked dissociation of filament-stabilizing ions and reorganization of actin subdomain 2 and as a consequence promotes severing due to a mechanical asymmetry. Knowledge of the effects of cofilin on actin filament bending mechanics, together with our previous analysis of torsional stiffness, provide a quantitative measure of the mechanical changes in actin filaments associated with cofilin binding, and suggest that the overall mechanical and force-producing properties of cells can be modulated by cofilin activity. PMID:18617188

Effect of fabrication processes on mechanical properties of glass fiber reinforced polymer composites for 49 meter (160 foot) recreational yachts

NASA Astrophysics Data System (ADS)

Kim, Dave (dea-wook); Hennigan, Daniel John; Beavers, Kevin Daniel

2010-03-01

Polymer composite materialsoffer high strength and stiffness to weight ratio, corrosion resistance, and total life cost reductions that appeal to the marine industry. The advantages of composite construction have led to their incorporation in U.S. yacht hull structures over 46 meters (150 feet) in length. In order to construct even larger hull structures, higher quality composites with a lower cost production techniques need to be developed. In this study, the effect of composite hull fabrication processes on mechanical properties of glass fiber reinforced plastic(GFRP) composites is presented. Fabrication techniques used in this study are hand lay-up (HL), vacuum infusion (VI), and hybrid (HL+VI) processes. Mechanical property testing includes: tensile, compressive, and ignition loss sample analysis. Results demonstrate that the vacuum pressure implemented during composite fabrication has an effect on mechanical properties. The VI processed GFRP yields improved mechanical properties in tension/compression strengths and tensile modulus. The hybrid GFRP composites, however, failed in a sequential manor, due to dissimilar failure modes in the HL and VI processed sides. Fractography analysis was conducted to validate the mechanical property testing results

Mechanical biocompatibility of highly deformable biomedical materials.

PubMed

Mazza, Edoardo; Ehret, Alexander E

2015-08-01

Mismatch of mechanical properties between highly deformable biomedical materials and adjacent native tissue might lead to short and long term health impairment. The capability of implants to deform at the right level, i.e. similar to the macroscopic mechanical response of the surrounding biological materials, is often associated with dissimilar microstructural deformation mechanisms. This mismatch on smaller length scales might lead to micro-injuries, cell damage, inflammation, fibrosis or necrosis. Hence, the mechanical biocompatibility of soft implants depends not only on the properties and composition of the implant material, but also on its organization, distribution and motion at one or several length scales. The challenges related to the analysis and attainment of mechanical biocompatibility are illustrated with two examples: prosthetic meshes for hernia and pelvic repair and electrospun scaffolds for tissue engineering. For these material systems we describe existing methods for characterization and analysis of the non-linear response to uniaxial and multiaxial stress states, its time and history dependence, and the changes in deformation behavior associated with tissue in-growth and material resorption. We discuss the multi-scale deformation behavior of biomaterials and adjacent tissue, and indicate major interdisciplinary questions to be addressed in future research. Copyright © 2015 Elsevier Ltd. All rights reserved.

Influence of the grade on the variability of the mechanical properties of polypropylene waste.

PubMed

Jmal, Hamdi; Bahlouli, Nadia; Wagner-Kocher, Christiane; Leray, Dimitri; Ruch, Frédéric; Munsch, Jean-Nicolas; Nardin, Michel

2018-05-01

The prior properties of recycled polypropylene depend on the origin of waste deposits and its chemical constituents. To obtain specific properties with a predefine melt flow index of polypropylene, the suppliers of polymer introduce additives and fillers. However, the addition of additives and/or fillers can modify strongly the mechanical behaviour of recycled polypropylene. To understand the impact of the additives and fillers on the quasi-static mechanical behaviour, we consider, in this study, three different recycled polypropylenes with three different melt flow index obtained from different waste deposits. The chemical constituents of the additives and filler contents of the recycled polypropylenes are determined through thermo-physico-chemical analysis. Tensile and bending tests performed at different strain rates allow identifying the mechanical properties such as the elastic modulus, the yield stress, the maximum stress, and the failure mechanisms. The results obtained are compared with non-recycled polypropylene and with few researches to explain the combined effect of additives. Finally, a post-mortem analysis of the samples was carried out to make the link between the obtained mechanical properties and microstructure. Copyright © 2018 Elsevier Ltd. All rights reserved.

A mechanism for efficient debugging of parallel programs

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

Miller, B.P.; Choi, J.D.

1988-01-01

This paper addresses the design and implementation of an integrated debugging system for parallel programs running on shared memory multi-processors (SMMP). The authors describe the use of flowback analysis to provide information on causal relationships between events in a program's execution without re-executing the program for debugging. The authors introduce a mechanism called incremental tracing that, by using semantic analyses of the debugged program, makes the flowback analysis practical with only a small amount of trace generated during execution. The extend flowback analysis to apply to parallel programs and describe a method to detect race conditions in the interactions ofmore » the co-operating processes.« less

Scaled boundary finite element simulation and modeling of the mechanical behavior of cracked nanographene sheets

NASA Astrophysics Data System (ADS)

Honarmand, M.; Moradi, M.

2018-06-01

In this paper, by using scaled boundary finite element method (SBFM), a perfect nanographene sheet or cracked ones were simulated for the first time. In this analysis, the atomic carbon bonds were modeled by simple bar elements with circular cross-sections. Despite of molecular dynamics (MD), the results obtained from SBFM analysis are quite acceptable for zero degree cracks. For all angles except zero, Griffith criterion can be applied for the relation between critical stress and crack length. Finally, despite the simplifications used in nanographene analysis, obtained results can simulate the mechanical behavior with high accuracy compared with experimental and MD ones.

Practical results from a mathematical analysis of guard patrols

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

Indusi, Joseph P.

1978-12-01

Using guard patrols as a primary detection mechanism is not generally viewed as a highly efficient detection method when compared to electronic means. Many factors such as visibility, alertness, and the space-time coincidence of guard and adversary presence all have an effect on the probability of detection. Mathematical analysis of the guard patrol detection problem is related to that of classical search theory originally developed for naval search operations. The results of this analysis tend to support the current practice of using guard forces to assess and respond to previously detected intrusions and not as the primary detection mechanism. 6more » refs.« less

AtomicJ: An open source software for analysis of force curves

NASA Astrophysics Data System (ADS)

Hermanowicz, Paweł; Sarna, Michał; Burda, Kvetoslava; Gabryś, Halina

2014-06-01

We present an open source Java application for analysis of force curves and images recorded with the Atomic Force Microscope. AtomicJ supports a wide range of contact mechanics models and implements procedures that reduce the influence of deviations from the contact model. It generates maps of mechanical properties, including maps of Young's modulus, adhesion force, and sample height. It can also calculate stacks, which reveal how sample's response to deformation changes with indentation depth. AtomicJ analyzes force curves concurrently on multiple threads, which allows for high speed of analysis. It runs on all popular operating systems, including Windows, Linux, and Macintosh.

Thermal Structure Analysis of SIRCA Tile for X-34 Wing Leading Edge TPS

NASA Technical Reports Server (NTRS)

Milos, Frank S.; Squire, Thomas H.; Rasky, Daniel J. (Technical Monitor)

1997-01-01

This paper will describe in detail thermal/structural analyses of SIRCA tiles which were performed at NASA Ames under the The Tile Analysis Task of the X-34 Program. The analyses used the COSMOS/M finite element software to simulate the material response in arc-jet tests, mechanical deflection tests, and the performance of candidate designs for the TPS system. Purposes of the analysis were to verify thermal and structural models for the SIRCA tiles, to establish failure criteria for stressed tiles, to simulate the TPS response under flight aerothermal and mechanical load, and to confirm that adequate safety margins exist for the actual TPS design.

Bending nanowire growth in solution by mechanical disturbance.

PubMed

Wang, Chao; Wei, Yujie; Jiang, Hongyuan; Sun, Shouheng

2010-06-09

The effect of mechanical disturbance on one-dimensional nanocrystal growth in solution phase is investigated by controlled growth of Au nanowires with and without stirring. While a static growth leads to straight, single-crystal Au nanowires, the mechanic disturbance by stirring tends to bend the nanowire growth, yielding nanowire kinks abundant in various types of crystal defects including dislocations, twin boundaries, and grain boundaries. Mechanical modeling and analysis is introduced to elucidate the nanowire growth mechanisms in these two conditions. The provided fundamental understanding of crystal defect formation at nanoscale could be applied to guide the development of advanced nanomaterials with shape control and unique mechanical properties.

Small, high pressure ratio compressor: Aerodynamic and mechanical design

NASA Technical Reports Server (NTRS)

Bryce, C. A.; Erwin, J. R.; Perrone, G. L.; Nelson, E. L.; Tu, R. K.; Bosco, A.

1973-01-01

The Small, High-Pressure-Ratio Compressor Program was directed toward the analysis, design, and fabrication of a centrifugal compressor providing a 6:1 pressure ratio and an airflow rate of 2.0 pounds per second. The program consists of preliminary design, detailed areodynamic design, mechanical design, and mechanical acceptance tests. The preliminary design evaluate radial- and backward-curved blades, tandem bladed impellers, impeller-and diffuser-passage boundary-layer control, and vane, pipe, and multiple-stage diffusers. Based on this evaluation, a configuration was selected for detailed aerodynamic and mechanical design. Mechanical acceptance test was performed to demonstrate that mechanical design objectives of the research package were met.

Design and development aspects of flexure mechanism for high precision application

NASA Astrophysics Data System (ADS)

Sollapur, Shrishail B.; Patil, M. S.; Deshmukh, S. P.

2018-04-01

Planer XY Flexurel Mechanisms has various applications in precision motion mechanisms. A flexural mechanism generates relative motion between fixed support and motion stage using flexibility of material. This mechanism offers zero backlash, frictionless motion and high order repeatability. It is relatively compact in design as compared to rigid link mechanism. The merits of using flexure is complete mechanism can be from single monolith. Modelling of flexural mechanism to provide accurate scanning of comparatively larger range at a higher speed. Static Analysis of mechanism is carried out on FEA tool to determine static deflection of motion stage. Further Mechanism is actuated with the help of weight pan and weights. The resultant displacement is measured on Dial Gauge Indicator. Experimental set-up consists of Flexural mechanism, Dial Gauge, Weight Pan and Weights, Pulley, String, Small metal strip, Optical Bread Board etc. Further experimental Results and Analytical Results are compared and minimum deviation is found.

Molecular mechanisms of protein aggregation from global fitting of kinetic models.

PubMed

Meisl, Georg; Kirkegaard, Julius B; Arosio, Paolo; Michaels, Thomas C T; Vendruscolo, Michele; Dobson, Christopher M; Linse, Sara; Knowles, Tuomas P J

2016-02-01

The elucidation of the molecular mechanisms by which soluble proteins convert into their amyloid forms is a fundamental prerequisite for understanding and controlling disorders that are linked to protein aggregation, such as Alzheimer's and Parkinson's diseases. However, because of the complexity associated with aggregation reaction networks, the analysis of kinetic data of protein aggregation to obtain the underlying mechanisms represents a complex task. Here we describe a framework, using quantitative kinetic assays and global fitting, to determine and to verify a molecular mechanism for aggregation reactions that is compatible with experimental kinetic data. We implement this approach in a web-based software, AmyloFit. Our procedure starts from the results of kinetic experiments that measure the concentration of aggregate mass as a function of time. We illustrate the approach with results from the aggregation of the β-amyloid (Aβ) peptides measured using thioflavin T, but the method is suitable for data from any similar kinetic experiment measuring the accumulation of aggregate mass as a function of time; the input data are in the form of a tab-separated text file. We also outline general experimental strategies and practical considerations for obtaining kinetic data of sufficient quality to draw detailed mechanistic conclusions, and the procedure starts with instructions for extensive data quality control. For the core part of the analysis, we provide an online platform (http://www.amylofit.ch.cam.ac.uk) that enables robust global analysis of kinetic data without the need for extensive programming or detailed mathematical knowledge. The software automates repetitive tasks and guides users through the key steps of kinetic analysis: determination of constraints to be placed on the aggregation mechanism based on the concentration dependence of the aggregation reaction, choosing from several fundamental models describing assembly into linear aggregates and fitting the chosen models using an advanced minimization algorithm to yield the reaction orders and rate constants. Finally, we outline how to use this approach to investigate which targets potential inhibitors of amyloid formation bind to and where in the reaction mechanism they act. The protocol, from processing data to determining mechanisms, can be completed in <1 d.

Nanostructure and molecular mechanics of spider dragline silk protein assemblies

PubMed Central

Keten, Sinan; Buehler, Markus J.

2010-01-01

Spider silk is a self-assembling biopolymer that outperforms most known materials in terms of its mechanical performance, despite its underlying weak chemical bonding based on H-bonds. While experimental studies have shown that the molecular structure of silk proteins has a direct influence on the stiffness, toughness and failure strength of silk, no molecular-level analysis of the nanostructure and associated mechanical properties of silk assemblies have been reported. Here, we report atomic-level structures of MaSp1 and MaSp2 proteins from the Nephila clavipes spider dragline silk sequence, obtained using replica exchange molecular dynamics, and subject these structures to mechanical loading for a detailed nanomechanical analysis. The structural analysis reveals that poly-alanine regions in silk predominantly form distinct and orderly beta-sheet crystal domains, while disorderly regions are formed by glycine-rich repeats that consist of 31-helix type structures and beta-turns. Our structural predictions are validated against experimental data based on dihedral angle pair calculations presented in Ramachandran plots, alpha-carbon atomic distances, as well as secondary structure content. Mechanical shearing simulations on selected structures illustrate that the nanoscale behaviour of silk protein assemblies is controlled by the distinctly different secondary structure content and hydrogen bonding in the crystalline and semi-amorphous regions. Both structural and mechanical characterization results show excellent agreement with available experimental evidence. Our findings set the stage for extensive atomistic investigations of silk, which may contribute towards an improved understanding of the source of the strength and toughness of this biological superfibre. PMID:20519206

Nanostructure and molecular mechanics of spider dragline silk protein assemblies.

PubMed

Keten, Sinan; Buehler, Markus J

2010-12-06

Spider silk is a self-assembling biopolymer that outperforms most known materials in terms of its mechanical performance, despite its underlying weak chemical bonding based on H-bonds. While experimental studies have shown that the molecular structure of silk proteins has a direct influence on the stiffness, toughness and failure strength of silk, no molecular-level analysis of the nanostructure and associated mechanical properties of silk assemblies have been reported. Here, we report atomic-level structures of MaSp1 and MaSp2 proteins from the Nephila clavipes spider dragline silk sequence, obtained using replica exchange molecular dynamics, and subject these structures to mechanical loading for a detailed nanomechanical analysis. The structural analysis reveals that poly-alanine regions in silk predominantly form distinct and orderly beta-sheet crystal domains, while disorderly regions are formed by glycine-rich repeats that consist of 3₁-helix type structures and beta-turns. Our structural predictions are validated against experimental data based on dihedral angle pair calculations presented in Ramachandran plots, alpha-carbon atomic distances, as well as secondary structure content. Mechanical shearing simulations on selected structures illustrate that the nanoscale behaviour of silk protein assemblies is controlled by the distinctly different secondary structure content and hydrogen bonding in the crystalline and semi-amorphous regions. Both structural and mechanical characterization results show excellent agreement with available experimental evidence. Our findings set the stage for extensive atomistic investigations of silk, which may contribute towards an improved understanding of the source of the strength and toughness of this biological superfibre.

Frictional healing of quartz gouge under hydrothermal conditions: 2. Quantitative interpretation with a physical model

NASA Astrophysics Data System (ADS)

Nakatani, Masao; Scholz, Christopher H.

2004-07-01

The companion paper by [2004] shows that a hydrothermal frictional healing mechanism results from local solution transfer. Here we evaluate this mechanism with the model of [1994], which assumes that the healing occurs by stress-driven asperity creep. The absence of a clear temperature dependence of the healing parameter b in the narrow tested range of 100-200°C is consistent with the model's prediction. The analysis also indicates that the mechanism involves a high stress assist parameter Ωσ = 200 kJ/mol, which is consistent with the contact stress being the indentation hardness, σ ˜ 10 GPa, and the activation volume Ω being the molar volume, both of which are reasonable. For this to be consistent with the observed temperature enhanced kinetics of healing also requires that the activation energy exceed 200 kJ/mol. This is much higher than the 20-70 kJ/mol known for low contact stress pressure solution. The analysis of several previously published studies of hydrothermal healing of hard silicates yielded the same results. Hence, if the underlying process is stress driven, it must have a different mechanism at high stress than at low stress. Alternatively, a solution transfer mechanism driven by something other than stress could be the underlying mechanism, but this is inconsistent with other aspects of our experimental results. On the other hand, the same analysis of phenomena that are independently inferred to proceed under relatively low contact stress yielded the parameter values consistent with low-stress pressure solution.

Auxetic coronary stent endoprosthesis: fabrication and structural analysis.

PubMed

Amin, Faisal; Ali, Murtaza Najabat; Ansari, Umar; Mir, Mariam; Minhas, Muhammad Asim; Shahid, Wakeel

2015-07-04

Cardiovascular heart disease is one of the leading health issues in the present era and requires considerable health care resources to prevent it. The present study was focused on the development of a new coronary stent based on novel auxetic geometry which enables the stent to exhibit a negative Poisson's ratio. Commercially available coronary stents have isotropic properties, whereas the vascular system of the body shows anisotropic characteristics. This results in a mismatch between anisotropic-isotropic properties of the stent and arterial wall, and this in turn is not favorable for mechanical adhesion of the commercially available coronary stents with the arterial wall. It is believed that an auxetic coronary stent with inherent anisotropic mechanical properties and negative Poisson's ratio will have good mechanical adhesion with the arterial wall. The auxetic design was obtained via laser cutting, and surface treatment was performed with acid pickling and electropolishing, followed by an annealing process. In vitro mechanical analysis was performed to analyze the mechanical performance of the auxetic coronary stent. Scanning electronic microscopy (SEM) was used to determine the effects of fabrication processes on the topography of the auxetic stent. The elastic recoil (3.3%) of the in vitro mechanical analysis showed that the auxetic stent design effectively maintained the luminal patency of the coronary artery. Also, the auxetic coronary stent showed no foreshortening, therefore it avoids the problem of stent migration, by expanding in both the radial and longitudinal directions. By virtue of its synclastic behavior, the auxetic stent bulges outward when it is radially expanded through an inflated balloon.

Biomechanical analysis of ankle ligamentous sprain injury cases from televised basketball games: Understanding when, how and why ligament failure occurs.

PubMed

Panagiotakis, Emmanouil; Mok, Kam-Ming; Fong, Daniel Tik-Pui; Bull, Anthony M J

2017-12-01

Ankle sprains due to landing on an opponent's foot are common in basketball. There is no analysis to date that provides a quantification of this injury mechanism. The aim of this study was to quantify the kinematics of this specific injury mechanism and relate this to lateral ankle ligament biomechanics. Case series. The model-based image-matching technique was used to quantify calcaneo-fibular-talar kinematics during four ankle inversion sprain injury incidents in televised NBA basketball games. The four incidents follow the same injury pattern in which the players of interest step onto an opponent's foot with significant inversion and a diagnosed ankle injury. A geometric analysis was performed to calculate the in vivo ligament strains and strain rates for the anterior talofibular ligament (ATFL) and the calcaneofibular ligament (CFL). Despite the controlled selection of cases, the results show that there are two distinct injury mechanisms: sudden inversion and internal rotation with low levels of plantarflexion; and a similar mechanism without internal rotation. The first of these mechanisms results in high ATFL and CFL strains, whereas the second of these strains the CFL in isolation. The injury mechanism combined with measures of the ligament injury in terms of percentage of strain to failure correlate directly with the severity of the injury quantified by return-to-sport. The opportunity to control excessive internal rotation through proprioceptive training and/or prophylactic footwear or bracing could be utilised to reduce the severity of common ankle injuries in basketball. Copyright © 2017 Sports Medicine Australia. Published by Elsevier Ltd. All rights reserved.

The Child's Demystification of Psychological Defense Mechanisms: A Structural and Developmental Analysis.

ERIC Educational Resources Information Center

Chandler, Michael J.; And Others

1978-01-01

Explored the relationships between the cognitive developmental level of preoperational, concrete operational, and formal operational children (N=10) and their success in interpreting and explaining each of eight commonly described mechanisms of psychological defense. (JMB)

Prevalence of clinically important traumatic brain injuries in children with minor blunt head trauma and isolated severe injury mechanisms.

PubMed

Nigrovic, Lise E; Lee, Lois K; Hoyle, John; Stanley, Rachel M; Gorelick, Marc H; Miskin, Michelle; Atabaki, Shireen M; Dayan, Peter S; Holmes, James F; Kuppermann, Nathan

2012-04-01

To determine the prevalence of clinically important traumatic brain injuries (TBIs) with severe injury mechanisms in children with minor blunt head trauma but with no other risk factors from the Pediatric Emergency Care Applied Research Network (PECARN) TBI prediction rules (defined as isolated severe injury mechanisms). Secondary analysis of a large prospective observational cohort study. Twenty-five emergency departments participating in the PECARN. Children with minor blunt head trauma and Glasgow Coma Scale scores of at least 14. Treating clinicians completed a structured data form that included injury mechanism (severity categories defined a priori). Clinically important TBIs were defined as intracranial injuries resulting in death, neurosurgical intervention, intubation for more than 24 hours, or hospital admission for at least 2 nights. We investigated the rate of clinically important TBIs in children with either severe injury mechanisms or isolated severe injury mechanisms. Of the 42,412 patients enrolled in the overall study, 42,099 (99%) had injury mechanisms recorded, and their data were included for analysis. Of all study patients, 5869 (14%) had severe injury mechanisms, and 3302 (8%) had isolated severe injury mechanisms. Overall, 367 children had clinically important TBIs (0.9%; 95% CI, 0.8%-1.0%). Of the 1327 children younger than 2 years with isolated severe injury mechanisms, 4 (0.3%; 95% CI, 0.1%-0.8%) had clinically important TBIs, as did 12 of the 1975 children 2 years or older (0.6%; 95% CI, 0.3%-1.1%). Children with isolated severe injury mechanisms are at low risk of clinically important TBI, and many do not require emergent neuroimaging.

Differential proteomics analysis to identify proteins and pathways associated with male sterility of soybean using iTRAQ-based strategy.

PubMed

Li, Jiajia; Ding, Xianlong; Han, Shaohuai; He, Tingting; Zhang, Hao; Yang, Longshu; Yang, Shouping; Gai, Junyi

2016-04-14

To further elucidate the molecular mechanism of cytoplasmic male sterility (CMS) in soybean, a differential proteomic analysis was completed between the CMS line NJCMS1A and its maintainer NJCMS1B using iTRAQ-based strategy. As a result, 180 differential abundance proteins (DAPs) were identified, of which, 60 were down-regulated and 120 were up-regulated in NJCMS1A compared with NJCMS1B. Bioinformatic analysis showed that 167 DAPs were annotated in 41 Gene Ontology functional groups, 106 DAPs were classified into 20 clusters of orthologous groups of protein categories, and 128 DAPs were enrichment in 53 KEGG pathways. Fifteen differential level proteins/genes with the same expression pattern were identified in the further conjoint analysis of DAPs and the previously reported differential expression genes. Moreover, multiple reaction monitoring test, qRT-PCR analysis and enzyme activity assay validated that the iTRAQ results were reliable. Based on functional analysis of DAPs, we concluded that male sterility in NJCMS1A might be related to insufficiencies in energy supply, unbalance of protein synthesis and degradation, disruption of flavonoid synthesis, programmed cell death, abnormalities of substance metabolism, etc. These results might facilitate our understanding of the molecular mechanisms behind CMS in soybean. Soybean is an important global crop that provides protein and oil. Heterosis is a significantly potential approach to increase the yield of soybean. Cytoplasmic male sterility (CMS) plays a vital role in the production of hybrid seeds. However, the genetic and molecular mechanisms of male sterility in soybean still need to be further elucidated. In the present paper, a differential proteomic analysis was carried out and the results showed that several key proteins involved in key pathways were associated with male sterility in soybean. This work provides a new insight to understand the genetic and molecular mechanisms underlying CMS in soybean. Copyright © 2016 Elsevier B.V. All rights reserved.

Proteomics and bioinformatics analysis of altered protein expression in the placental villous tissue from early recurrent miscarriage patients.

PubMed

Pan, Hai-Tao; Ding, Hai-Gang; Fang, Min; Yu, Bin; Cheng, Yi; Tan, Ya-Jing; Fu, Qi-Qin; Lu, Bo; Cai, Hong-Guang; Jin, Xin; Xia, Xian-Qing; Zhang, Tao

2018-01-01

Recurrent miscarriage (RM) affects 5% of women, it has an adverse emotional impact on women. Because of the complexities of early development, the mechanism of recurrent miscarriage is still unclear. We hypothesized that abnormal placenta leads to early recurrent miscarriage (ERM). The aim of this study was to identify ERM associated factors in human placenta villous tissue using proteomics. Investigation of these differences in protein expression in parallel profiling is essential to understand the comprehensive pathophysiological mechanism underlying recurrent miscarriage (RM). To gain more insight into mechanisms of recurrent miscarriage (RM), a comparative proteome profile of the human placenta villous tissue in normal and RM pregnancies was analyzed using iTRAQ technology and bioinformatics analysis used by Ingenuity Pathway Analysis (IPA) software. In this study, we employed an iTRAQ based proteomics analysis of four placental villous tissues from patients with early recurrent miscarriage (ERM) and four from normal pregnant women. Finally, we identified 2805 proteins and 79,998 peptides between patients with RM and normal matched group. Further analysis identified 314 differentially expressed proteins in placental villous tissue (≥1.3-fold, Student's t-test, p < 0.05); 209 proteins showed the increased expression while 105 proteins showed decreased expression. These 314 proteins were analyzed by Ingenuity Pathway Analysis (IPA) and were found to play important roles in the growth of embryo. Furthermore, network analysis show that Angiotensinogen (AGT), MAPK14 and Prothrombin (F2) are core factors in early embryonic development. We used another 8 independent samples (4 cases and 4 controls) to cross validation of the proteomic data. This study has identified several proteins that are associated with early development, these results may supply new insight into mechanisms behind recurrent miscarriage. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ageing management of french NPP civil work structures

NASA Astrophysics Data System (ADS)

Gallitre, E.; Dauffer, D.

2011-04-01

This paper presents EDF practice about concrete structure ageing management, from the mechanisms analysis to the formal procedure which allows the French company to increase 900 MWe NPP lifetime until 40 years; it will also introduce its action plan for 60 years lifetime extension. This practice is based on a methodology which identifies every ageing mechanism; both plants feedback and state of the art are screened and conclusions are drawn up into an "ageing analysis data sheet". That leads at first to a collection of 57 data sheets which give the mechanism identification, the components that are concerned and an analysis grid which is designed to assess the safety risk. This analysis screens the reference documents describing the mechanism, the design lifetime hypotheses, the associated regulation or codification, the feedback experiences, the accessibility, the maintenance actions, the repair possibility and so one. This analysis has to lead to a conclusion about the risk taking into account monitoring and maintenance. If the data sheet conclusion is not clear enough, then a more detailed report is launched. The technical document which is needed, is a formal detailed report which summarizes every theoretical knowledge and monitoring data: its objective is to propose a solution for ageing management: this solution can include more inspections or specific research development, or additional maintenance. After a first stage on the 900 MWe units, only two generic ageing management detailed reports have been needed for the civil engineering part: one about reactor building containment, and one about other structures which focuses on concrete inflating reactions. The second stage consists on deriving this generic analysis (ageing mechanism and detailed reports) to every plant where a complete ageing report is required (one report for all equipments and structures of the plant, but specific for each reactor). This ageing management is a continuous process because the 57 generic data sheets set is updated every year and the detailed generic reports every five years. After this 40 year lifetime extension, EDF is preparing a 60 years lifetime action plan which includes R&D actions, specific industrial studies and also monitoring improvements.

CYP2C19 progress curve analysis and mechanism-based inactivation by three methylenedioxyphenyl compounds.

PubMed

Salminen, Kaisa A; Meyer, Achim; Imming, Peter; Raunio, Hannu

2011-12-01

Several in vitro criteria were used to assess whether three methylenedioxyphenyl (MDP) compounds, the isoquinoline alkaloids bulbocapnine, canadine, and protopine, are mechanism-based inactivators of CYP2C19. The recently reported fluorometric CYP2C19 progress curve analysis approach was applied first to determine whether these alkaloids demonstrate time-dependent inhibition. In this experiment, bulbocapnine, canadine, and protopine displayed time dependence and saturation in their inactivation kinetics with K(I) and k(inact) values of 72.4 ± 14.7 μM and 0.38 ± 0.036 min(-1), 2.1 ± 0.63 μM and 0.18 ± 0.015 min(-1), and 7.1 ± 2.3 μM and 0.24 ± 0.021 min(-1), respectively. Additional studies were performed to determine whether other specific criteria for mechanism-based inactivation were fulfilled: NADPH dependence, irreversibility, and involvement of a catalytic step in the enzyme inactivation. CYP2C19 activity was not significantly restored by dialysis when it had been inactivated by the alkaloids in the presence of a NADPH-regenerating system, and a metabolic-intermediate complex-associated increase in absorbance at approximately 455 nm was observed. In conclusion, the CYP2C19 progress curve analysis method revealed time-dependent inhibition by these alkaloids, and additional experiments confirmed its quasi-irreversible nature. This study revealed that the CYP2C19 progress curve analysis method is useful for identifying novel mechanism-based inactivators and yields a wealth of information in one run. The alkaloids bulbocapnine, canadine, and protopine, present in herbal medicines, are new mechanism-based inactivators and the first MDP compounds exhibiting quasi-irreversible inactivation of CYP2C19.

Influence of Grain Size on Mechanical Responses in Beta Ti-12Mo Alloy Demonstrating Concurrent Twinning-Induced Plasticity/Transformation-induced Plasticity Effects

NASA Astrophysics Data System (ADS)

Zhang, D. C.; Xue, Q.; Lei, J. F.; Ma, Y. J.; Yang, R.; Wang, C.

2018-06-01

Metastable β Ti-12Mo wt pct alloys with controllable grain sizes are successfully produced, and the effect of grain size on mechanical responses has been thoroughly investigated. It is found that target alloys possess concurrent twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP) features. Mechanisms governing mechanical properties through well-manipulated tensile experiments, detailed microstructure analysis, as well as strong correlations between triggering stress and twinning/phase transformation are offered.