Science.gov

Sample records for acceptable mechanical performance

  1. Trinity Acceptance Tests Performance Summary.

    SciTech Connect

    Rajan, Mahesh

    2015-12-01

    Ensuring Real Applications perform well on Trinity is key to success. Four components: ASC applications, Sustained System Performance (SSP), Extra-Large MiniApplications problems, and Micro-benchmarks.

  2. Employee Acceptance of BOS and BES Performance Appraisals.

    ERIC Educational Resources Information Center

    Dossett, Dennis L.; Gier, Joseph A.

    Previous research on performance evaluation systems has failed to take into account user acceptance. Employee acceptance of a behaviorally-based performance appraisal system was assessed in a field experiment contrasting user preference for Behavioral Expectations Scales (BES) versus Behavioral Observation Scales (BOS). Non-union sales associates…

  3. ASME PTC 46 -- Acceptance test code for overall plant performance

    SciTech Connect

    Friedman, J.R.; Yost, J.G.

    1999-11-01

    ASME published PTC 46 in 1996 after five years of development. PTC 46 is the first industry standard providing explicit procedures for conducting acceptance tests to determine the overall thermal performance and output of power generating units. It is applicable to any heat cycle power generating unit. This survey paper provides an overview of PTC 46 and discusses how PTC 46 can be used for acceptance testing of new combined cycle and fossil steam power generating units. Several technical papers have been previously presented that provide more detailed information and discussion on the use of PTC 46 in acceptance testing.

  4. Performance-based waste acceptance criteria preliminary baseline assumptions

    SciTech Connect

    Not Available

    1994-10-24

    The Department of Energy`s (DOE`s) strategy for the management of transuranic (TRU) and TRU mixed wastes has focused on the development of the Waste Isolation Pilot Plant (WIPP). The WIPP repository is designated to receive DOE defense wastes that meet the established criteria for acceptance. As a national strategy [DOE, 1993], DOE does not intend to treat candidate wastes unless treatment or processing are necessary to meet the safety, health, and regulatory criteria for transport and disposal at WIPP. The WIPP WAC has evolved over the past 10 years to include criteria and requirements in support of the Waste Characterization program and other related compliance programs. In aggregate, the final health, safety and regulatory criteria for the waste will be documented in the Disposal WAC. This document serves two purposes. First, it familiarizes regulators and stakeholders with the concept of performance based waste acceptance criteria as an augmentation within a final Waste Isolation Pilot Plant (WIPP) Waste Acceptance Criteria. Second, the document preliminarily identifies certain waste characteristics that appear important to the performance assessment process for WIPP; therefore, these could become component characteristics in the Performance Based Waste Acceptance Criteria (PBWAC). Identification of the final PBWAC will be accomplished through iterative runs of the System Prioritization Method (SPM). These iterations will serve to more clearly isolate and identify those waste characteristics that directly and predominately impact on the performance assessment.

  5. The indicator performance estimate approach to determining acceptable wilderness conditions

    NASA Astrophysics Data System (ADS)

    Hollenhorst, Steven; Gardner, Lisa

    1994-11-01

    Using data from a study conducted in the Cranberry Wilderness Area of West Virginia, United States, this paper describes how a modified importance—performance approach can be used to prioritize wilderness indicators and determine how much change from the pristine is acceptable. The approach uses two key types of information: (1) indicator importance, or visitor opinion as to which wilderness indicators have the greatest influence on their experience, and (2) management performance, or the extent to which actual indicator conditions exceed or are within visitor expectations. Performance was represented by calculating indicator performance estimates (IPEs), as defined by standardized differences between actual conditions and visitor preferences for each indicator. The results for each indicator are then presented graphically on a four-quadrant matrix for objective interpretation. Each quadrant represents a management response: keep up the good work, concentrate here, low priority, or possible overkill. The technique allows managers to more systematically and effectively utilize information routinely collected during the limits of acceptable change wilderness planning process.

  6. The deformable secondary mirror of VLT: final electro-mechanical and optical acceptance test results

    NASA Astrophysics Data System (ADS)

    Briguglio, Runa; Biasi, Roberto; Xompero, Marco; Riccardi, Armando; Andrighettoni, Mario; Pescoller, Dietrich; Angerer, Gerald; Gallieni, Daniele; Vernet, Elise; Kolb, Johann; Arsenault, Robin; Madec, Pierre-Yves

    2014-07-01

    The Deformable Secondary Mirror (DSM) for the VLT ended the stand-alone electro-mechanical and optical acceptance process, entering the test phase as part of the Adaptive Optics Facility (AOF) at the ESO Headquarter (Garching). The VLT-DSM currently represents the most advanced already-built large-format deformable mirror with its 1170 voice-coil actuators and its internal metrology based on co-located capacitive sensors to control the shape of the 1.12m-diameter 2mm-thick convex shell. The present paper reports the final results of the electro-mechanical and optical characterization of the DSM executed in a collaborative effort by the DSM manufacturing companies (Microgate s.r.l. and A.D.S. International s.r.l.), INAF-Osservatorio Astrofisico di Arcetri and ESO. The electro-mechanical acceptance tests have been performed in the company premises and their main purpose was the dynamical characterization of the internal control loop response and the calibration of the system data that are needed for its optimization. The optical acceptance tests have been performed at ESO (Garching) using the ASSIST optical test facility. The main purpose of the tests are the characterization of the optical shell flattening residuals, the corresponding calibration of flattening commands, the optical calibration of the capacitive sensors and the optical calibration of the mirror influence functions.

  7. Small, high-pressure ratio compressor mechanical acceptance test, volume 2

    NASA Technical Reports Server (NTRS)

    Metty, G. R.; Shoup, W. I.

    1973-01-01

    The fabrication and mechanical testing of the high-pressure-ratio compressor are reported. Mechanical testing was performed to demonstrate overspeed capability, adequate rotor dynamics, electrical isolation of the gas bearing trunnion mounted diffuser and shroud and the effect of operating parameters (speed and pressure ratio) on clearance of the compressor test rig. The speed range covered was 20 to 120 percent of rated speed (80,000 rpm). Following these tests an acceptance test which consisted of a 5 hour run at 80,000 rpm was made with approximately design impeller to shroud clearances. For Vol. 1, see N73-26483.

  8. Involvement in Extracurricular Activities as Related to Academic Performance, Personality, and Peer Acceptance.

    ERIC Educational Resources Information Center

    Fung, Yee-wang; Wong, Ngai-ying

    1991-01-01

    Reveals findings of a survey of 294 Hong Kong secondary school students. Evaluates relationships among involvement in extracurricular activities, academic performance, personality, and peer acceptance. Concludes that activity involvement is positively related to academic performance, personality, and peer acceptance. Suggests that further research…

  9. Technology Acceptance and Performance: An Investigation into Requisite Knowledge.

    ERIC Educational Resources Information Center

    Marshall, Thomas E.; Byrd, Terry A.; Gardiner, Lorraine R.; Rainer, R. Kelly, Jr.

    2000-01-01

    Describes an empirical study that investigated how knowledge bases contributed to subjects' attitudes and performance in the use of a computer-assisted software engineering (CASE) tool in database design. Identifies requisite knowledge bases and provides alternatives for organization administration to promote more positive attitudes toward…

  10. The role of acceptance and job control in mental health, job satisfaction, and work performance.

    PubMed

    Bond, Frank W; Bunce, David

    2003-12-01

    Acceptance, the willingness to experience thoughts, feelings, and physiological sensations without having to control them or let them determine one's actions, is a major individual determinant of mental health and behavioral effectiveness in a more recent theory of psychopathology. This 2-wave panel study examined the ability of acceptance also to explain mental health, job satisfaction, and performance in the work domain. The authors hypothesized that acceptance would predict these 3 outcomes 1 year later in a sample of customer service center workers in the United Kingdom (N = 412). Results indicated that acceptance predicted mental health and an objective measure of performance over and above job control, negative affectivity, and locus of control. These beneficial effects of having more job control were enhanced when people had higher levels of acceptance. The authors discuss the theoretical and practical relevance of this individual characteristic to occupational health and performance. PMID:14640816

  11. A Comparative Evaluation of the Technical Performance and User Acceptance of Two Prototype Online Catalog Systems.

    ERIC Educational Resources Information Center

    Siegel, Elliot R.; And Others

    1984-01-01

    Describes research strategy and methods of comparative evaluation conducted by the National Library of Medicine to assess user acceptance and technical performance of two prototype patron accessible online catalog systems within same operational environment. User acceptance studies included sample search experiment, comparison search experiment,…

  12. Interrelationships among Employee Participation, Individual Differences, Goal Difficulty, Goal Acceptance, Goal Instrumentality, and Performance.

    ERIC Educational Resources Information Center

    Yukl, Gary A.; Latham, Gary P.

    1978-01-01

    Discussed is a model for goal setting, which is based on Locke's theory that difficult but clear and specific goals, if accepted, will result in higher performance than easy goals, nonspecific goals, or no goals at all. (Author/RK)

  13. Effects of acceptance-based coping on task performance and subjective stress.

    PubMed

    Kishita, Naoko; Shimada, Hironori

    2011-03-01

    This paper examines the interactive effects of acceptance-based coping and job control on task performance, subjective stress, and perceived control. Forty-eight undergraduate and graduate students first participated in brief educational programs based on either acceptance or control coping strategies. They then participated in a 30-min high workload task under either high or low job control conditions. The results demonstrated a significant interactive effect of acceptance-based coping and job control on perceived control and task performance. No such effect was found for subjective stress. We conclude that to improve employees' perceived control and job performance, there should be an increase not only in job control through work redesign, but also in psychological acceptance. PMID:21074000

  14. Discrete carbon nanotubes increase lead acid battery charge acceptance and performance

    NASA Astrophysics Data System (ADS)

    Swogger, Steven W.; Everill, Paul; Dubey, D. P.; Sugumaran, Nanjan

    2014-09-01

    Performance demands placed upon lead acid batteries have outgrown the technology's ability to deliver. These demands, typically leading to Negative Active Material (NAM) failure, include: short, high-current surges; prolonged, minimal, overvoltage charging; repeated, Ah deficit charging; and frequent deep discharges. Research shows these failure mechanisms are attenuated by inclusion of carbon allotropes into the NAM. Addition of significant quantities of carbon, however, produces detrimental changes in paste rheology, leading to lowered industrial throughput. Additionally, capacity, cold-cranking performance, and other battery metrics are negatively affected at high carbon loads. Presented here is Molecular Rebar® Lead Negative, a new battery additive comprising discrete carbon nanotubes (dCNT) which uniformly disperse within battery pastes during mixing. NS40ZL batteries containing dCNT show enhanced charge acceptance, reserve capacity, and cold-cranking performance, decreased risk of polarization, and no detrimental changes to paste properties, when compared to dCNT-free controls. This work focuses on the dCNT as NAM additives only, but early-stage research is underway to test their functionality as a PAM additive. Batteries infused with Molecular Rebar® Lead Negative address the needs of modern lead acid battery applications, produce none of the detrimental side effects associated with carbon additives, and require no change to existing production lines.

  15. Modelling of biogas extraction at an Italian landfill accepting mechanically and biologically treated municipal solid waste.

    PubMed

    Calabrò, Paolo S; Orsi, Sirio; Gentili, Emiliano; Carlo, Meoni

    2011-12-01

    This paper presents the results of the modelling of the biogas extraction in a full-scale Italian landfill by the USEPA LandGEM model and the Andreottola-Cossu approach. The landfill chosen for this research ('Il Fossetto' plant, Monsummano Terme, Italy) had accepted mixed municipal raw waste for about 15 years. In the year 2003 a mechanical biological treatment (MBT) was implemented and starting from the end of the year 2006, the recirculation in the landfill of the concentrated leachate coming from the internal membrane leachate treatment plant was put into practice. The USEPA LandGEM model and the Andreottola-Cossu approach were chosen since they require only input data routinely acquired during landfill management (waste amount and composition) and allow a simplified calibration, therefore they are potentially useful for practical purposes such as landfill gas management. The results given by the models are compared with measured data and analysed in order to verify the impact of MBT on biogas production; moreover, the possible effects of the recirculation of the concentrated leachate are discussed. The results clearly show how both models can adequately fit measured data even after MBT implementation. Model performance was significantly reduced for the period after the beginning of recirculation of concentrated leachate when the probable inhibition of methane production, due to the competition between methanogens and sulfate-reducing bacteria, significantly influenced the biogas production and composition. PMID:21930528

  16. Development of Performance Acceptance Test Guidelines for Large Commercial Parabolic Trough Solar Fields: Preprint

    SciTech Connect

    Kearney, D.; Mehos, M.

    2010-12-01

    Prior to commercial operation, large solar systems in utility-size power plants need to pass a performance acceptance test conducted by the EPC contractor or owners. In lieu of the present absence of engineering code developed for this purpose, NREL has undertaken the development of interim guidelines to provide recommendations for test procedures that can yield results of a high level of accuracy consistent with good engineering knowledge and practice. The fundamental differences between acceptance of a solar power plant and a conventional fossil-fired plant are the transient nature of the energy source and the necessity to utilize an analytical performance model in the acceptance process. These factors bring into play the need to establish methods to measure steady state performance, potential impacts of transient processes, comparison to performance model results, and the possible requirement to test, or model, multi-day performance within the scope of the acceptance test procedure. The power block and BOP are not within the boundaries of this guideline. The current guideline is restricted to the solar thermal performance of parabolic trough systems and has been critiqued by a broad range of stakeholders in CSP development and technology.

  17. Restrictions on TWT Helix Voltage Ripple for Acceptable Notch Filter Performance

    SciTech Connect

    Hyslop, B.

    1984-12-01

    An ac ripple on the helix voltage of the 1-2 GHz TWT's creates FM sidebands that cause amplitude and phase modulation of the microwave TWT output signal. A limit of 16 volts peak-to-peak is required for acceptable superconducting notch filter performance.

  18. A FORTRAN IV Program for Multiple-choice Tests with Predetermined Minimal Acceptable Performance Levels

    ERIC Educational Resources Information Center

    Noe, Michael J.

    1976-01-01

    A Fortran IV multiple choice test scoring program for an IBM 370 computer is described that computes minimally acceptable performance levels and compares student scores to these levels. The program accomodates up to 500 items with no more than nine alternatives from a group of examinees numbering less than 10,000. (Author)

  19. Improving International-Level Chess Players' Performance with an Acceptance-Based Protocol: Preliminary Findings

    ERIC Educational Resources Information Center

    Ruiz, Francisco J.; Luciano, Carmen

    2012-01-01

    This study compared an individual, 4-hr intervention based on acceptance and commitment therapy (ACT) versus a no-contact control condition in improving the performance of international-level chess players. Five participants received the brief ACT protocol, with each matched to another chess player with similar characteristics in the control…

  20. A validation of Amazon Mechanical Turk for the collection of acceptability judgments in linguistic theory.

    PubMed

    Sprouse, Jon

    2011-03-01

    Amazon's Mechanical Turk (AMT) is a Web application that provides instant access to thousands of potential participants for survey-based psychology experiments, such as the acceptability judgment task used extensively in syntactic theory. Because AMT is a Web-based system, syntacticians may worry that the move out of the experimenter-controlled environment of the laboratory and onto the user-controlled environment of AMT could adversely affect the quality of the judgment data collected. This article reports a quantitative comparison of two identical acceptability judgment experiments, each with 176 participants (352 total): one conducted in the laboratory, and one conducted on AMT. Crucial indicators of data quality--such as participant rejection rates, statistical power, and the shape of the distributions of the judgments for each sentence type--are compared between the two samples. The results suggest that aside from slightly higher participant rejection rates, AMT data are almost indistinguishable from laboratory data. PMID:21287108

  1. The Effect of a Summer MCAT Performance Improvement Program on Minority Medical Student Acceptance

    PubMed Central

    Medina, Miguel A.

    1987-01-01

    The effect of a commercial Medical College Admission Test (MCAT) review course on MCAT retake scores and acceptance into medical school for a group of minority students is reported. The review course enhanced MCAT performance in all of the subgroups. The increase in total MCAT score was more pronounced in students with an initial MCAT score below 36 or a high undergraduate total or science grade point average. Results suggest a relationship between MCAT performance and medical school admission. PMID:3625795

  2. Utility-Scale Power Tower Solar Systems: Performance Acceptance Test Guidelines

    SciTech Connect

    Kearney, D.

    2013-03-01

    The purpose of these Guidelines is to provide direction for conducting performance acceptance testing for large power tower solar systems that can yield results of a high level of accuracy consistent with good engineering knowledge and practice. The recommendations have been developed under a National Renewable Energy Laboratory (NREL) subcontract and reviewed by stakeholders representing concerned organizations and interests throughout the concentrating solar power (CSP) community. An earlier NREL report provided similar guidelines for parabolic trough systems. These Guidelines recommend certain methods, instrumentation, equipment operating requirements, and calculation methods. When tests are run in accordance with these Guidelines, we expect that the test results will yield a valid indication of the actual performance of the tested equipment. But these are only recommendations--to be carefully considered by the contractual parties involved in the Acceptance Tests--and we expect that modifications may be required to fit the particular characteristics of a specific project.

  3. MECHANICAL RELIABILITY AND PLANT PERFORMANCE

    EPA Science Inventory

    A two state statistical model is proposed for studying the effect of equipment outages on plant performance. Simulation of lost treatment capacity in an activated sludge treatment system indicates the degree to which BOD violation frequencies are much more sensitive to lost aerat...

  4. Design and performance of AERHA, a high acceptance high resolution soft x-ray spectrometer

    NASA Astrophysics Data System (ADS)

    Chiuzbǎian, Sorin G.; Hague, Coryn F.; Avila, Antoine; Delaunay, Renaud; Jaouen, Nicolas; Sacchi, Maurizio; Polack, François; Thomasset, Muriel; Lagarde, Bruno; Nicolaou, Alessandro; Brignolo, Stefania; Baumier, Cédric; Lüning, Jan; Mariot, Jean-Michel

    2014-04-01

    A soft x-ray spectrometer based on the use of an elliptical focusing mirror and a plane varied line spacing grating is described. It achieves both high resolution and high overall efficiency while remaining relatively compact. The instrument is dedicated to resonant inelastic x-ray scattering studies. We set out how this optical arrangement was judged best able to guarantee performance for the 50 - 1000 eV range within achievable fabrication targets. The AERHA (adjustable energy resolution high acceptance) spectrometer operates with an effective angular acceptance between 100 and 250 μsr (energy dependent) and a resolving power well in excess of 5000 according to the Rayleigh criterion. The high angular acceptance is obtained by means of a collecting pre-mirror. Three scattering geometries are available to enable momentum dependent measurements with 135°, 90°, and 50° scattering angles. The instrument operates on the Synchrotron SOLEIL SEXTANTS beamline which serves as a high photon flux 2 × 200 μm2 focal spot source with full polarization control.

  5. Air Traffic Controller Performance and Acceptability of Multiple UAS in a Simulated NAS Environment

    NASA Technical Reports Server (NTRS)

    Vu, Kim-Phuong L.; Strybel, Thomas; Chiappe, Dan; Morales, Greg; Battiste, Vernol; Shively, Robert Jay

    2014-01-01

    Previously, we showed that air traffic controllers (ATCos) rated UAS pilot verbal response latencies as acceptable when a 1.5 s delay was added to the UAS pilot responses, but a 5 s delay was rated as mostly unacceptable. In the present study we determined whether a 1.5 s added delay in the UAS pilots' verbal communications would affect ATCos interactions with UAS and other conventional aircraft when the number and speed of the UAS were manipulated. Eight radar-certified ATCos participated in this simulation. The ATCos managed a medium altitude sector containing arrival aircraft, en route aircraft, and one to four UAS. The UAS were conducting a surveillance mission and flew at either a "slow" or "fast" speed. We measured both UAS and conventional pilots' verbal communication latencies, and obtained ATCos' acceptability ratings for these latencies. Although the UAS pilot response latencies were longer than those of conventional pilots, the ATCos rated UAS pilot verbal communication latencies to be as acceptable as those of conventional pilots. Because the overall traffic load within the sector was held constant, ATCos only performed slightly worse when multiple UAS were in their sector compared to when only one UAS was in the sector. Implications of these findings for UAS integration in the NAS are discussed.

  6. Design and performance of AERHA, a high acceptance high resolution soft x-ray spectrometer

    SciTech Connect

    Chiuzbăian, Sorin G. Hague, Coryn F.; Brignolo, Stefania; Baumier, Cédric; Lüning, Jan; Avila, Antoine; Delaunay, Renaud; Mariot, Jean-Michel; Jaouen, Nicolas; Polack, François; Thomasset, Muriel; Lagarde, Bruno; Nicolaou, Alessandro; Sacchi, Maurizio

    2014-04-15

    A soft x-ray spectrometer based on the use of an elliptical focusing mirror and a plane varied line spacing grating is described. It achieves both high resolution and high overall efficiency while remaining relatively compact. The instrument is dedicated to resonant inelastic x-ray scattering studies. We set out how this optical arrangement was judged best able to guarantee performance for the 50 − 1000 eV range within achievable fabrication targets. The AERHA (adjustable energy resolution high acceptance) spectrometer operates with an effective angular acceptance between 100 and 250 μsr (energy dependent) and a resolving power well in excess of 5000 according to the Rayleigh criterion. The high angular acceptance is obtained by means of a collecting pre-mirror. Three scattering geometries are available to enable momentum dependent measurements with 135°, 90°, and 50° scattering angles. The instrument operates on the Synchrotron SOLEIL SEXTANTS beamline which serves as a high photon flux 2 × 200 μm{sup 2} focal spot source with full polarization control.

  7. Performance feedback: An exploratory study to examine the acceptability and impact for interdisciplinary primary care teams

    PubMed Central

    2011-01-01

    Background This mixed methods study was designed to explore the acceptability and impact of feedback of team performance data to primary care interdisciplinary teams. Methods Seven interdisciplinary teams were offered a one-hour, facilitated performance feedback session presenting data from a comprehensive, previously-conducted evaluation, selecting highlights such as performance on chronic disease management, access, patient satisfaction and team function. Results Several recurrent themes emerged from participants' surveys and two rounds of interviews within three months of the feedback session. Team performance measurement and feedback was welcomed across teams and disciplines. This feedback could build the team, the culture, and the capacity for quality improvement. However, existing performance indicators do not equally reflect the role of different disciplines within an interdisciplinary team. Finally, the effect of team performance feedback on intentions to improve performance was hindered by a poor understanding of how the team could use the data. Conclusions The findings further our understanding of how performance feedback may engage interdisciplinary team members in improving the quality of primary care and the unique challenges specific to these settings. There is a need to develop a shared sense of responsibility and agenda for quality improvement. Therefore, more efforts to develop flexible and interactive performance-reporting structures (that better reflect contributions from all team members) in which teams could specify the information and audience may assist in promoting quality improvement. PMID:21443806

  8. Diesel Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Tidwell, Joseph

    Several intermediate performance objectives and corresponding criterion measures are listed for each of 12 terminal objectives for a basic diesel mechanics course. The course is designed as a two-semester (2 hour daily) course for 10th graders interested in being diesel service and repair mechanics; it would serve as the first year of a 3-year…

  9. Acceptability of quality reporting and pay for performance among primary health centers in Lebanon.

    PubMed

    Saleh, Shadi S; Alameddine, Mohamad S; Natafgi, Nabil M

    2013-01-01

    Primary health care (PHC) is emphasized as the cornerstone of any health care system. Enhancing PHC performance is considered a strategy to enhance effective and equitable access to care. This study assesses the acceptability of and factors associated with quality reporting among PHC centers (PHCCs) in Lebanon. The managers of 132 Lebanese Ministry of Health PHCCs were surveyed using a cross-sectional design. Managers' willingness to report quality, participate in comparative quality assessments, and endorse pay-for-performance schemes was evaluated. Collected data were matched to the infrastructural characteristics and services database. Seventy-six percent of managers responded to the questionnaire, 93 percent of whom were willing to report clinical performance. Most expressed strong support for peer-performance comparison and pay-for-performance schemes. Willingness to report was negatively associated with the religious affiliation of centers and presence of health care facilities in the catchment area and favorably associated with use of information systems and the size of population served. The great willingness of PHCC managers to employ quality-enhancing initiatives flags a policy priority for PHC stakeholders to strengthen PHCC infrastructure and to enable reporting in an easy, standardized, and systematic way. Enhancing equity necessitates education and empowerment of managers in remote areas and those managing religiously affiliated centers. PMID:24397238

  10. Cassini RTG acceptance test results and RTG performance on Galileo and Ulysses

    SciTech Connect

    Kelly, C.E.; Klee, P.M.

    1997-06-01

    Flight acceptance testing has been completed for the RTGs to be used on the Cassini spacecraft which is scheduled for an October 6, 1997 launch to Saturn. The acceptance test program includes vibration tests, magnetic field measurements, properties (weight and c.g.) and thermal vacuum test. This paper presents The thermal vacuum test results. Three RTGs are to be used, F-2, F-6, and F-7. F-5 is tile back-up RTG, as it was for the Galileo and Ulysses missions launched in 1989 and 1990, respectively. RTG performance measured during the thermal vacuum tests carried out at die Mound Laboratory facility met all specification requirements. Beginning of mission (BOM) and end of mission (EOM) power predictions have been made based on than tests results. BOM power is predicted to be 888 watts compared to the minimum requirement of 826 watts. Degradation models predict the EOM power after 16 years is to be 640 watts compared to a minimum requirement of 596 watts. Results of small scale module tests are also showing. The modules contain couples from the qualification and flight production runs. The tests have exceeded 28,000 hours (3.2 years) and are continuing to provide increased confidence in the predicted long term performance of the Cassini RTGs. All test results indicate that the power requirements of the Cassini spacecraft will be met. BOM and EOM power margins of over five percent are predicted. Power output from telemetry for the two Galileo RTGs are shown from the 1989 launch to the recent Jupiter encounter. Comparisons of predicted, measured and required performance are shown. Telemetry data are also shown for the RTG on the Ulysses spacecraft which completed its planned mission in 1995 and is now in the extended mission.

  11. Cassini RTG acceptance test results and RTG performance on Galileo and Ulysses

    SciTech Connect

    Kelly, C.E.; Klee, P.M.

    1997-12-31

    Flight acceptance testing has been completed for the RTGs to be used on the Cassini spacecraft which is scheduled for an October 6, 1997 launch to Saturn. The acceptance test program includes vibration tests, magnetic field measurements, mass properties (weight and c.g.) and thermal vacuum test. This paper presents the thermal vacuum test results. Three RTGs are to be used, F-2, F-6, and F-7. F-5 is the backup RTG, as it was for the Galileo and Ulysses missions launched in 1989 and 1990, respectively. RTG performance measured during the thermal vacuum tests carried out at the Mound Laboratory facility met all specification requirements. Beginning of mission (BOM) and end of mission (EOM) power predictions have been made based on these tests results. BOM power is predicted to be 888 watts compared to the minimum requirement of 826 watts. Degradation models predict the EOM power after 16 years is to be 640 watts compared to a minimum requirement of 596 watts. Results of small scale module tests are also shown. The modules contain couples from the qualification and flight production runs. The tests have exceeded 28,000 hours (3.2 years) and are continuing to provide increased confidence in the predicted long term performance of the Cassini RTGs. All test results indicate that the power requirements of the Cassini spacecraft will be met. BOM and EOM power margins of over 5% are predicted. Power output from telemetry for the two Galileo RTGs are shown from the 1989 launch to the recent Jupiter encounter. Comparisons of predicted, measured and required performance are shown. Telemetry data are also shown for the RTG on the Ulysses spacecraft which completed its planned mission in 1995 and is now in the extended mission.

  12. Cassini RTG Acceptance Test Results and RTG Performance on Galileo and Ulysses

    DOE R&D Accomplishments Database

    Kelly, C. E.; Klee, P. M.

    1997-06-01

    Flight acceptance testing has been completed for the RTGs to be used on the Cassini spacecraft which is scheduled for an October 6, 1997 launch to Saturn. The acceptance test program includes vibration tests, magnetic field measurements, properties (weight and c.g.) and thermal vacuum test. This paper presents The thermal vacuum test results. Three RTGs are to be used, F 2, F 6, and F 7. F 5 is tile back up RTG, as it was for the Galileo and Ulysses missions launched in 1989 and 1990, respectively. RTG performance measured during the thermal vacuum tests carried out at die Mound Laboratory facility met all specification requirements. Beginning of mission (BOM) and end of mission (EOM) power predictions have been made based on than tests results. BOM power is predicted to be 888 watts compared to the minimum requirement of 826 watts. Degradation models predict the EOM power after 16 years is to be 640 watts compared to a minimum requirement of 596 watts. Results of small scale module tests are also showing. The modules contain couples from the qualification and flight production runs. The tests have exceeded 28,000 hours (3.2 years) and are continuing to provide increased confidence in the predicted long term performance of the Cassini RTGs. All test results indicate that the power requirements of the Cassini spacecraft will be met. BOM and EOM power margins of over five percent are predicted. Power output from telemetry for the two Galileo RTGs are shown from the 1989 launch to the recent Jupiter encounter. Comparisons of predicted, measured and required performance are shown. Telemetry data are also shown for the RTG on the Ulysses spacecraft which completed its planned mission in 1995 and is now in the extended mission.

  13. Astronaut Scott Carpenter tests balance mechanism performance

    NASA Technical Reports Server (NTRS)

    1961-01-01

    Astronaut M. Scott Carpenter's balance mechanism performance is tested by his walking on a narrow board in his bare feet. He is performing this test at the School of Aviation Medicine, Pensicola, Florida (04570); Carpenter walks a straight line by putting one foot directly in front of the other to test his balance (04571).

  14. Utility-Scale Parabolic Trough Solar Systems: Performance Acceptance Test Guidelines, April 2009 - December 2010

    SciTech Connect

    Kearney, D.

    2011-05-01

    Prior to commercial operation, large solar systems in utility-size power plants need to pass a performance acceptance test conducted by the engineering, procurement, and construction (EPC) contractor or owners. In lieu of the present absence of ASME or other international test codes developed for this purpose, the National Renewable Energy Laboratory has undertaken the development of interim guidelines to provide recommendations for test procedures that can yield results of a high level of accuracy consistent with good engineering knowledge and practice. The Guidelines contained here are specifically written for parabolic trough collector systems with a heat-transport system using a high-temperature synthetic oil, but the basic principles are relevant to other CSP systems.

  15. Acceptance Performance Test Guideline for Utility Scale Parabolic Trough and Other CSP Solar Thermal Systems: Preprint

    SciTech Connect

    Mehos, M. S.; Wagner, M. J.; Kearney, D. W.

    2011-08-01

    Prior to commercial operation, large solar systems in utility-size power plants need to pass a performance acceptance test conducted by the engineering, procurement, and construction (EPC) contractor or owners. In lieu of the present absence of ASME or other international test codes developed for this purpose, the National Renewable Energy Laboratory has undertaken the development of interim guidelines to provide recommendations for test procedures that can yield results of a high level of accuracy consistent with good engineering knowledge and practice. Progress on interim guidelines was presented at SolarPACES 2010. Significant additions and modifications were made to the guidelines since that time, resulting in a final report published by NREL in April 2011. This paper summarizes those changes, which emphasize criteria for assuring thermal equilibrium and steady state conditions within the solar field.

  16. Performance deterioration due to acceptance testing and flight loads; JT90 jet engine diagnostic program

    NASA Technical Reports Server (NTRS)

    Olsson, W. J.

    1982-01-01

    The results of a flight loads test of the JT9D-7 engine are presented. The goals of this test program were to: measure aerodynamic and inertia loads on the engine during flight, explore the effects of airplane gross weight and typical maneuvers on these flight loads, simultaneously measure the changes in engine running clearances and performance resulting from the maneuvers, make refinements of engine performance deterioration prediction models based on analytical results of the tests, and make recommendations to improve propulsion system performance retention. The test program included a typical production airplane acceptance test plus additional flights and maneuvers to encompass the range of flight loads in revenue service. The test results indicated that aerodynamic loads, primarily at take-off, were the major cause of rub-indicated that aerodynamic loads, primarily at take-off, were the major cause of rub-induced deterioration in the cold sectin of the engine. Differential thermal expansion between rotating and static parts plus aerodynamic loads combined to cause blade-to-seal rubs in the turbine.

  17. Protein Folding Modulates the Swapped Dimerization Mechanism of Methyl-Accepting Chemotaxis Heme Sensors

    PubMed Central

    Silva, Marta A.; Lucas, Tânia G.; Salgueiro, Carlos A.; Gomes, Cláudio M.

    2012-01-01

    The periplasmic sensor domains GSU0582 and GSU0935 are part of methyl accepting chemotaxis proteins in the bacterium Geobacter sulfurreducens. Both contain one c-type heme group and their crystal structures revealed that these domains form swapped dimers with a PAS fold formed from the two protein chains. The swapped dimerization of these sensors is related to the mechanism of signal transduction and the formation of the swapped dimer involves significant folding changes and conformational rearrangements within each monomeric component. However, the structural changes occurring during this process are poorly understood and lack a mechanistic framework. To address this issue, we have studied the folding and stability properties of two distinct heme-sensor PAS domains, using biophysical spectroscopies. We observed substantial differences in the thermodynamic stability (ΔG = 14.6 kJ.mol−1 for GSU0935 and ΔG = 26.3 kJ.mol−1 for GSU0582), and demonstrated that the heme moiety undergoes conformational changes that match those occurring at the global protein structure. This indicates that sensing by the heme cofactor induces conformational changes that rapidly propagate to the protein structure, an effect which is directly linked to the signal transduction mechanism. Interestingly, the two analyzed proteins have distinct levels of intrinsic disorder (25% for GSU0935 and 13% for GSU0582), which correlate with conformational stability differences. This provides evidence that the sensing threshold and intensity of the propagated allosteric effect is linked to the stability of the PAS-fold, as this property modulates domain swapping and dimerization. Analysis of the PAS-domain shows that disorder segments are found either at the hinge region that controls helix motions or in connecting segments of the β-sheet interface. The latter is known to be widely involved in both intra- and intermolecular interactions, supporting the view that it's folding and stability

  18. Realization and performance of cryogenic selection mechanisms

    NASA Astrophysics Data System (ADS)

    Aitink-Kroes, Gabby; Bettonvil, Felix; Kragt, Jan; Elswijk, Eddy; Tromp, Niels

    2014-07-01

    Within Infra-Red large wavelength bandwidth instruments the use of mechanisms for selection of observation modes, filters, dispersing elements, pinholes or slits is inevitable. The cryogenic operating environment poses several challenges to these cryogenic mechanisms; like differential thermal shrinkage, physical property change of materials, limited use of lubrication, high feature density, limited space etc. MATISSE the mid-infrared interferometric spectrograph and imager for ESO's VLT interferometer (VLTI) at Paranal in Chile coherently combines the light from 4 telescopes. Within the Cold Optics Bench (COB) of MATISSE two concepts of selection mechanisms can be distinguished based on the same design principles: linear selection mechanisms (sliders) and rotating selection mechanisms (wheels).Both sliders and wheels are used at a temperature of 38 Kelvin. The selection mechanisms have to provide high accuracy and repeatability. The sliders/wheels have integrated tracks that run on small, accurately located, spring loaded precision bearings. Special indents are used for selection of the slider/wheel position. For maximum accuracy/repeatability the guiding/selection system is separated from the actuation in this case a cryogenic actuator inside the cryostat. The paper discusses the detailed design of the mechanisms and the final realization for the MATISSE COB. Limited lifetime and performance tests determine accuracy, warm and cold and the reliability/wear during life of the instrument. The test results and further improvements to the mechanisms are discussed.

  19. Auto Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Carter, Thomas G., Sr.

    Several intermediate performance objectives and corresponding criterion measures are listed for each of 14 terminal objectives for a basic automotive mechanics course. The materials were developed for a two-semester course (2 hours daily) designed to provide training in the basic fundamentals in diagnosis and repair including cooling system and…

  20. Gasoline Engine Mechanics. Performance Objectives. Intermediate Course.

    ERIC Educational Resources Information Center

    Jones, Marion

    Several intermediate performance objectives and corresponding criterion measures are listed for each of six terminal objectives presented in this curriculum guide for an intermediate gasoline engine mechanics course at the secondary level. (For the beginning course guide see CE 010 947.) The materials were developed for a two-semester (2 hour…

  1. Gasoline Engine Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Jones, Marion

    Several intermediate performance objectives and corresponding criterion measures are listed for each of five terminal objectives presented in this curriculum guide for a basic gasoline engine mechanics course at the secondary level. (For the intermediate course guide see CE 010 946.) The materials were developed for a two semester (2 hours daily)…

  2. Diesel Mechanics. Performance Objectives. Intermediate Course.

    ERIC Educational Resources Information Center

    Tidwell, Joseph

    Several intermediate performance objectives and corresponding criterion measures are listed for each of six terminal objectives for an intermediate diesel mechanics course (two semesters, 3 hours daily) designed for high school students who upon completion would be ready for an on-the-job training experience in diesel service and repair. Through…

  3. Mechanical performance of aquatic rowing and flying.

    PubMed Central

    Walker, J A; Westneat, M W

    2000-01-01

    Aquatic flight, performed by rowing or flapping fins, wings or limbs, is a primary locomotor mechanism for many animals. We used a computer simulation to compare the mechanical performance of rowing and flapping appendages across a range of speeds. Flapping appendages proved to be more mechanically efficient than rowing appendages at all swimming speeds, suggesting that animals that frequently engage in locomotor behaviours that require energy conservation should employ a flapping stroke. The lower efficiency of rowing appendages across all speeds begs the question of why rowing occurs at all. One answer lies in the ability of rowing fins to generate more thrust than flapping fins during the power stroke. Large forces are necessary for manoeuvring behaviours such as accelerations, turning and braking, which suggests that rowing should be found in slow-swimming animals that frequently manoeuvre. The predictions of the model are supported by observed patterns of behavioural variation among rowing and flapping vertebrates. PMID:11052539

  4. Mechanical excavator performance in Yucca Mountain tuffs

    SciTech Connect

    Ozdemir, L.; Hansen, F.D.

    1991-01-01

    A research effort of four phases is in progress at the Colorado School of Mines. The overall program will evaluate the cutability of welded tuff and other lithologies likely to be excavated at Yucca Mountain in the site characterization process. Several mechanical systems are considered with emphasis given to the tunnel boring machine. The research comprises laboratory testing, linear drag bit and disc cutter tests and potentially large-scale laboratory demonstrations to support potential use of a tunnel boring machine in welded tuff. Preliminary estimates of mechanical excavator performance in Yucca Mountain tuff are presented here. As phases of the research project are completed, well quantified estimates will be made of performance of mechanical excavators in the Yucca Mountain tuffs. 3 refs., 2 tabs.

  5. Mechanical excavator performance in Yucca Mountain tuffs

    SciTech Connect

    Ozdemir, L.; Hansen, F.D.

    1991-12-31

    A research effort of four phases is in progress at the Colorado School of Mines. The overall program will evaluate the cutability of welded tuff and other lithologies likely to be excavated at Yucca Mountain in the site characterization process. Several mechanical systems are considered with emphasis given to the tunnel boring machine. The research comprises laboratory testing, linear drag bit and disc cutter tests, and potentially large-scale lab. demonstrations to support potential use of a tunnel boring machine in welded tuff. Preliminary estimates of mechanical excavator performance in Yucca Mountain tuff are presented here. As phases of the research project are completed, well-quantified estimates will be made of performance of mechanical excavators in the Yucca Mountain tuffs.

  6. Mechanisms to improve the mechanical performance of surgical gloves

    NASA Astrophysics Data System (ADS)

    Watkins, Michelle Hoyt

    1997-11-01

    The use of gloves as a barrier to cross infection in the medical industry has increased substantially due to the heightened awareness of viral transmission, especially the human immunodeficiency virus and the hepatitis B virus. The glove must allow for tactile sensation, comfort and long use times, while providing equally critical mechanical performance. The majority of surgical gloves are made of natural rubber latex which do not give a critical level of cut-resistance or puncture-resistance. Natural rubber latex gloves are also known to cause latex allergy with hypersensitivity reactions ranging from mild skin rashes to more severe bronchial asthma, anaphylactic reactions, and even death. It has been postulated natural rubber latex (NRL) proteins cause these allergic reactions. The research that has been conducted comprises two approaches that have been explored for improving the cut-resistance of surgical gloves. The first method involves an integral fiber-latex structure that possesses the combination of high reversible extensibility, barrier performance and retention of tactile sense. Improvement in mechanical properties in excess of 85% has been achieved as well as an improvement in cut-resistance. The second method involves the incorporation of a low concentration of ultra high molecular weight (UHMW) polyacrylamide. Although the initial premise for using a UHMW polymer was that it would bridge the latex compound particulates to improve strength, an entirely different mechanism for the enhancement of strength was explored through a parallel investigation of the release of proteins from cured natural rubber. However, no mechanism was conclusively identified. To address the allergy aspects of NRL, a thorough examination of the release of naturally-occurring latex proteins from cured natural rubber latex glove material was conducted in order to identify mechanisms for eliminating and/or reducing the potential allergens. The initial study examined the release of

  7. Neurophysiological mechanisms in acceptance and commitment therapy in opioid-addicted patients with chronic pain.

    PubMed

    Smallwood, Rachel F; Potter, Jennifer S; Robin, Donald A

    2016-04-30

    Acceptance and Commitment Therapy (ACT) has been effectively utilized to treat both chronic pain and substance use disorder independently. Given these results and the vital need to treat the comorbidity of the two disorders, a pilot ACT treatment was implemented in individuals with comorbid chronic pain and opioid addiction. This pilot study supported using neurophysiology to characterize treatment effects and revealed that, following ACT, participants with this comorbidity exhibited reductions in brain activation due to painful stimulus and in connectivity at rest. PMID:27107155

  8. ABSL 18650HC Lot Acceptance Test- Ensuring Consistency And Flight Performance

    NASA Astrophysics Data System (ADS)

    Buckle, Rachel; Thwaite, Carl

    2011-10-01

    ABSL manufactures Space batteries using commercial cells. As the battery sizing is based on test data from cells purchased up to 10 years ago, a rigorous programme of testing is carried out to ensure batch consistency, flight quality and any implications for sizing are found early. A Lot Acceptance Test (LAT) is carried out on each new batch of cells purchased. A selection of cells undergo tests on their build quality, environmental tolerance, safety devices and lifetime degradation. This process will be described, along with issues such as setting acceptance criteria, comparison of results between batches, and what happens if a batch fails.

  9. Athletic Performance and Social Behavior as Predictors of Peer Acceptance in Children Diagnosed With Attention-Deficit/Hyperactivity Disorder

    ERIC Educational Resources Information Center

    Lopez-Williams, Andy; Chacko, Anil; Wymbs, Brian T.; Fabiano, Gregory A.; Seymour, Karen E.; Gnagy, Elizabeth M.; Chronis, Andrea M.; Burrows-MacLean, Lisa; Pelham, William E.; Morris, Tracy L.

    2005-01-01

    Sixty-three children between ages 6 and 12 who were enrolled in a summer treatment program for children with attention-deficit/hyperactivity disorder (ADHD) participated in a study designed to measure the relationship between social behaviors, athletic performance, and peer acceptance. Children were assessed on sport-specific skills of three major…

  10. Decoupling as a mechanism of change in mindfulness and acceptance: a literature review.

    PubMed

    Levin, Michael E; Luoma, Jason B; Haeger, Jack A

    2015-11-01

    A growing body of research within the acceptance and mindfulness-based therapies suggests that these treatments may function in part by reducing or eliminating (i.e., decoupling) the normative relationships between internal experiences and other internal/overt behavior. Examples of decoupling effects found in this review include reduced relationships between urges to smoke and smoking behavior, between dysphoric mood and depressive cognitions, and between pain intensity and persistence in a painful task. A literature review identified 44 studies on acceptance and mindfulness that demonstrated decoupling effects. Overall, preliminary evidence for decoupling effects were found across a broad range of problem areas, including substance abuse, depression, eating disorders, overeating, chronic pain, anxiety, relationships, anger, avoidance behavior, and self-harm, with the strongest evidence currently available in the area of substance abuse. However, the review also notes a general lack of replication studies on decoupling effects and the need for more well-powered and controlled research testing specific decoupling hypotheses. PMID:26349756

  11. PERFORMANCE ANALYSIS OF MECHANICAL DRAFT COOLING TOWER

    SciTech Connect

    Lee, S; Alfred Garrett, A; James02 Bollinger, J; Larry Koffman, L

    2009-02-10

    Industrial processes use mechanical draft cooling towers (MDCT's) to dissipate waste heat by transferring heat from water to air via evaporative cooling, which causes air humidification. The Savannah River Site (SRS) has cross-flow and counter-current MDCT's consisting of four independent compartments called cells. Each cell has its own fan to help maximize heat transfer between ambient air and circulated water. The primary objective of the work is to simulate the cooling tower performance for the counter-current cooling tower and to conduct a parametric study under different fan speeds and ambient air conditions. The Savannah River National Laboratory (SRNL) developed a computational fluid dynamics (CFD) model and performed the benchmarking analysis against the integral measurement results to accomplish the objective. The model uses three-dimensional steady-state momentum, continuity equations, air-vapor species balance equation, and two-equation turbulence as the basic governing equations. It was assumed that vapor phase is always transported by the continuous air phase with no slip velocity. In this case, water droplet component was considered as discrete phase for the interfacial heat and mass transfer via Lagrangian approach. Thus, the air-vapor mixture model with discrete water droplet phase is used for the analysis. A series of parametric calculations was performed to investigate the impact of wind speeds and ambient conditions on the thermal performance of the cooling tower when fans were operating and when they were turned off. The model was also benchmarked against the literature data and the SRS integral test results for key parameters such as air temperature and humidity at the tower exit and water temperature for given ambient conditions. Detailed results will be published here.

  12. High performance stepper motors for space mechanisms

    NASA Astrophysics Data System (ADS)

    Sega, Patrick; Estevenon, Christine

    1995-05-01

    Hybrid stepper motors are very well adapted to high performance space mechanisms. They are very simple to operate and are often used for accurate positioning and for smooth rotations. In order to fulfill these requirements, the motor torque, its harmonic content, and the magnetic parasitic torque have to be properly designed. Only finite element computations can provide enough accuracy to determine the toothed structures' magnetic permeance, whose derivative function leads to the torque. It is then possible to design motors with a maximum torque capability or with the most reduced torque harmonic content (less than 3 percent of fundamental). These later motors are dedicated to applications where a microstep or a synchronous mode is selected for minimal dynamic disturbances. In every case, the capability to convert electrical power into torque is much higher than on DC brushless motors.

  13. High performance stepper motors for space mechanisms

    NASA Technical Reports Server (NTRS)

    Sega, Patrick; Estevenon, Christine

    1995-01-01

    Hybrid stepper motors are very well adapted to high performance space mechanisms. They are very simple to operate and are often used for accurate positioning and for smooth rotations. In order to fulfill these requirements, the motor torque, its harmonic content, and the magnetic parasitic torque have to be properly designed. Only finite element computations can provide enough accuracy to determine the toothed structures' magnetic permeance, whose derivative function leads to the torque. It is then possible to design motors with a maximum torque capability or with the most reduced torque harmonic content (less than 3 percent of fundamental). These later motors are dedicated to applications where a microstep or a synchronous mode is selected for minimal dynamic disturbances. In every case, the capability to convert electrical power into torque is much higher than on DC brushless motors.

  14. Bioinspired layered materials with superior mechanical performance.

    PubMed

    Cheng, Qunfeng; Jiang, Lei; Tang, Zhiyong

    2014-04-15

    Nature has inspired researchers to construct structures with ordered layers as candidates for new materials with high mechanical performance. As a prominent example, nacre, also known as mother of pearl, consists of a combination of inorganic plates (aragonite calcium carbonate, 95% by volume) and organic macromolecules (elastic biopolymer, 5% by volume) and shows a unique combination of strength and toughness. Investigations of its structure reveal that the hexagonal platelets of calcium carbonate and the amorphous biopolymer are alternatively assembled into the orderly layered structure. The delicate interface between the calcium carbonate and the biopolymer is well defined. Both the building blocks that make up these assembled layers and the interfaces between the inorganic and organic components contribute to the excellent mechanical property of natural nacre. In this Account, we summarize recent research from our group and from others on the design of bioinspired materials composed by layering various primitive materials. We focus particular attention on nanoscale carbon materials. Using several examples, we describe how the use of different combinations of layered materials leads to particular properties. Flattened double-walled carbon nanotubes (FDWCNTs) covalently cross-linked in a thermoset three-dimensional (3D) network produced the materials with the highest strength. The stiffest layered materials were generated from borate orthoester covalent bonding between adjacent graphene oxide (GO) nanosheets, and the toughest layered materials were fabricated with Al2O3 platelets and chitosan via hydrogen bonding. These new building blocks, such as FDWCNTs and GO, and the replication of the elaborate micro-/nanoscale interface of natural nacre have provided many options for developing new high performance artificial materials. The interface designs for bioinspired layered materials are generally categorized into (1) hydrogen bonding, (2) ionic bonding, and (3

  15. Mechanism of Tennis Racket Spin Performance

    NASA Astrophysics Data System (ADS)

    Kawazoe, Yoshihiko; Okimoto, Kenji; Okimoto, Keiko

    Players often say that some strings provide a better grip and more spin than others, but ball spin did not depend on string type, gauge, or tension in pervious laboratory experiments. There was no research work on spin to uncover what is really happening during an actual tennis impact because of the difficulty of performing the appropriate experiments. The present paper clarified the mechanism of top spin and its improvement by lubrication of strings through the use of high-speed video analysis. It also provided a more detailed explanation of spin behavior by comparing a racket with lubricated strings with the famous “spaghetti” strung racket, which was banned in 1978 by the International Tennis Federation because it used plastic spaghetti tubing over the strings to reduce friction, resulting in excessive ball spin. As the main strings stretch and slide sideways more, the ball is given additional spin due to the restoring force parallel to the string face when the main strings spring back and the ball is released from the strings. Herein, we also showed that the additional spin results in a reduction of shock vibrations of the wrist joint during impact.

  16. A Mindfulness-Acceptance-Commitment-Based Approach to Athletic Performance Enhancement: Theoretical Considerations

    ERIC Educational Resources Information Center

    Gardner, Frank L.; Moore, Zella E.

    2004-01-01

    While traditional cognitive-behavioral skills-training-based approaches to athletic performance enhancement posit that negative thoughts and emotions must be controlled, eliminated, or replaced for athlete-clients to perform optimally, recent evidence suggests that efforts to control, eliminate, or suppress these internal states may actually have…

  17. Hypothesis for the Mechanism of Ascorbic Acid Activity in Living Cells Related to Its Electron-Accepting Properties.

    PubMed

    Pshenichnyuk, Stanislav A; Modelli, Alberto; Lazneva, Eleonora F; Komolov, Alexei S

    2016-05-01

    Electron-accepting properties, and in particular resonance dissociative electron attachment (DEA) to ascorbic acid (AA), are investigated by means of DEA spectroscopy in vacuo. The experimental features are assigned in silico and discussed in relation to expected dissociative electron transfer processes in vivo with the support of density functional theory calculations and the polarizable continuum model. It is shown that formation of the two most abundant AA metabolites in living cells, namely monodehydroascorbic acid and dehydroascorbic acid, can be stimulated by cellular electron transfer to AA under reductive conditions. Prooxidant effects caused by AA are suggested to be mediated by hydroxyl radicals formation via the DEA mechanism. The involvement of excited electronic states under UV-irradiation in plants could open additional DEA channels leading to specific AA activity forbidden under dark state conditions. PMID:27074645

  18. Performance.

    PubMed

    Chambers, David W

    2006-01-01

    High performance is difficult to maintain because it is dynamic and not well understood. Based on a synthesis of many sources, a model is proposed where performance is a function of the balance between capacity and challenge. Too much challenge produces coping (or a crash); excess capacity results in boredom. Over time, peak performance drifts toward boredom. Performance can be managed by adjusting our level of ability, our effort, the opportunity to perform, and the challenge we agree to take on. Coping, substandard but acceptable performance, is common among professionals and its long-term side effects can be debilitating. A crash occurs when coping mechanisms fail. PMID:17020177

  19. The Impact of Trajectory Prediction Uncertainty on Air Traffic Controller Performance and Acceptability

    NASA Technical Reports Server (NTRS)

    Mercer, Joey S.; Bienert, Nancy; Gomez, Ashley; Hunt, Sarah; Kraut, Joshua; Martin, Lynne; Morey, Susan; Green, Steven M.; Prevot, Thomas; Wu, Minghong G.

    2013-01-01

    A Human-In-The-Loop air traffic control simulation investigated the impact of uncertainties in trajectory predictions on NextGen Trajectory-Based Operations concepts, seeking to understand when the automation would become unacceptable to controllers or when performance targets could no longer be met. Retired air traffic controllers staffed two en route transition sectors, delivering arrival traffic to the northwest corner-post of Atlanta approach control under time-based metering operations. Using trajectory-based decision-support tools, the participants worked the traffic under varying levels of wind forecast error and aircraft performance model error, impacting the ground automations ability to make accurate predictions. Results suggest that the controllers were able to maintain high levels of performance, despite even the highest levels of trajectory prediction errors.

  20. INFLUENCE OF FORAGE SPECIES ON PASTURE PERFORMANCE, CARCASS QUALITY, AND CONSUMER ACCEPTABILITY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    British-type steers of predominantly Angus breeding were used to determine the influence of forage species fed during the final 30 to 45 days of finishing on performance, carcass characteristics, and meat quality. Finishing treatments included: 1) Mixed cool season pasture [bluegrass, orchardgrass,...

  1. The Development of Accepted Performance Items to Demonstrate Competence in Literary Braille

    ERIC Educational Resources Information Center

    Lewis, Sandra; D'Andrea, Frances Mary; Rosenblum, L. Penny

    2012-01-01

    Introduction: This research attempted to establish the content validity of several performance statements that are associated with basic knowledge, production, and reading of braille by beginning teachers. Methods: University instructors (n = 21) and new teachers of students with visual impairments (n = 20) who had taught at least 2 braille…

  2. Post-Graduate Performance, an Academic Comparison Evaluating Situating Learning and Law School Acceptance Scores

    ERIC Educational Resources Information Center

    Traverse, Maria A.

    2012-01-01

    Research on post-graduate performance, pertaining to law school graduates, indicates that success in the legal profession is attributable to more than the theoretical content or cognitive knowledge obtained through educational curricula. Research suggests that the combination of creative and analytic thinking skills contributes to a higher rate of…

  3. Tribomaterial factors in space mechanism brake performance

    NASA Technical Reports Server (NTRS)

    Hawthorne, H. M.

    1990-01-01

    The asbestos/phenolic pads of Shuttle Remote Manipulator System (SRMS) brakes are unsuitable for use in long life space mechanisms because their friction decreases on extended sliding in high vacuum. Dehydration of the material and accumulation of wear debris in the conforming interface of this tribosystem induces the permanent friction changes. Other polymer and some ceramic based materials exhibit similar frictional torque behavior due to the development of minimal contact patches by the interfacial debris. In contrast, high friction occurs when other ceramics form many small contacts throughout fine debris beds. Generating this latter interfacial structure during run-in ensures that the in-vacuo friction remains stable thereafter. Such materials with low wear rates are potential candidates for friction elements in SSRMS and similar mechanisms.

  4. Environmental acceptability of high-performance alternatives for depleted uranium penetrators

    SciTech Connect

    Kerley, C.R.; Easterly, C.E.; Eckerman, K.F.

    1996-08-01

    The Army`s environmental strategy for investigating material substitution and management is to measure system environmental gains/losses in all phases of the material management life cycle from cradle to grave. This study is the first in a series of new investigations, applying material life cycle concepts, to evaluate whether there are environmental benefits from increasing the use of tungsten as an alternative to depleted uranium (DU) in Kinetic Energy Penetrators (KEPs). Current military armor penetrators use DU and tungsten as base materials. Although DU alloys have provided the highest performance of any high-density alloy deployed against enemy heavy armor, its low-level radioactivity poses a number of environmental risks. These risks include exposures to the military and civilian population from inhalation, ingestion, and injection of particles. Depleted uranium is well known to be chemically toxic (kidney toxicity), and workplace exposure levels are based on its renal toxicity. Waste materials containing DU fragments are classified as low-level radioactive waste and are regulated by the Nuclear Regulatory Commission. These characteristics of DU do not preclude its use in KEPs. However, long-term management challenges associated with KEP deployment and improved public perceptions about environmental risks from military activities might be well served by a serious effort to identify, develop, and substitute alternative materials that meet performance objectives and involve fewer environmental risks. Tungsten, a leading candidate base material for KEPS, is potentially such a material because it is not radioactive. Tungsten is less well studied, however, with respect to health impacts and other environmental risks. The present study is designed to contribute to the understanding of the environmental behavior of tungsten by synthesizing available information that is relevant to its potential use as a penetrator.

  5. Evaluation of an Intelligent Tutoring System in Pathology: Effects of External Representation on Performance Gains, Metacognition, and Acceptance

    PubMed Central

    Crowley, Rebecca S.; Legowski, Elizabeth; Medvedeva, Olga; Tseytlin, Eugene; Roh, Ellen; Jukic, Drazen

    2007-01-01

    Objective Determine effects of computer-based tutoring on diagnostic performance gains, meta-cognition, and acceptance using two different problem representations. Describe impact of tutoring on spectrum of diagnostic skills required for task performance. Identify key features of student-tutor interaction contributing to learning gains. Design Prospective, between-subjects study, controlled for participant level of training. Resident physicians in two academic pathology programs spent four hours using one of two interfaces which differed mainly in external problem representation. The case-focused representation provided an open-learning environment in which students were free to explore evidence-hypothesis relationships within a case, but could not visualize the entire diagnostic space. The knowledge-focused representation provided an interactive representation of the entire diagnostic space, which more tightly constrained student actions. Measurements Metrics included results of pretest, post-test and retention-test for multiple choice and case diagnosis tests, ratios of performance to student reported certainty, results of participant survey, learning curves, and interaction behaviors during tutoring. Results Students had highly significant learning gains after one tutoring session. Learning was retained at one week. There were no differences between the two interfaces in learning gains on post-test or retention test. Only students in the knowledge-focused interface exhibited significant metacognitive gains from pretest to post-test and pretest to retention test. Students rated the knowledge-focused interface significantly higher than the case-focused interface. Conclusions Cognitive tutoring is associated with improved diagnostic performance in a complex medical domain. The effect is retained at one-week post-training. Knowledge-focused external problem representation shows an advantage over case-focused representation for metacognitive effects and user

  6. Marine Engine Mechanics. Performance Objectives. Intermediate Course.

    ERIC Educational Resources Information Center

    Jones, Marion

    Several intermediate performance objectives and corresponding criterion measures are presented for each of ten terminal objectives for a two-semester course (3 hours daily). This 540-hour intermediate course includes advanced troubleshooting techniques on outboard marine engines, inboard-outboard marine engines, inboard marine engines, boat…

  7. Marine Engine Mechanics. Performance Objectives. Basic Course.

    ERIC Educational Resources Information Center

    Jones, Marion

    Several intermediate performance objectives and corresponding criterion measures are presented for each of six terminal objectives for a two-semester course (2 hours daily) which provides training in the terminology, construction, and function of both two- and four-cycle fuel-air mixture internal combustion engines with emphasis on outboard marine…

  8. Development and Acceptance Testing of the Dual Wheel Mechanism for the Tunable Filter Imager Cryogenic Instrument on the JWST

    NASA Technical Reports Server (NTRS)

    Leckie, Martin; Ahmad, Zakir

    2010-01-01

    The James Webb Space Telescope (JWST) will carry four scientific instruments, one of which is the Tunable Filter Imager (TFI), which is an instrument within the Fine Guidance Sensor. The Dual Wheel (DW) mechanism is being designed, built and tested by COM DEV Ltd. under contract from the Canadian Space Agency. The DW mechanism includes a pupil wheel (PW) holding seven coronagraphic masks and two calibration elements and a filter wheel (FW) holding nine blocking filters. The DW mechanism must operate at both room temperature and at 35K. Successful operation at 35K comprises positioning each optical element with the required repeatability, for several thousand occasions over the five year mission. The paper discusses the results of testing geared motors and bearings at the cryogenic temperature. In particular bearing retainer design and PGM-HT material, the effects of temperature gradients across bearings and the problems associated with cooling mechanisms down to cryogenic temperatures. The results of additional bearing tests are described that were employed to investigate an abnormally high initial torque experienced at cryogenic temperatures. The findings of these tests, was that the bearing retainer and the ball/race system could be adversely affected by the large temperature change from room temperature to cryogenic temperature and also the temperature gradient across the bearing. The DW mechanism is now performing successfully at both room temperature and at cryogenic temperature. The life testing of the mechanism is expected to be completed in the first quarter of 2010.

  9. Flight Crew Workload, Acceptability, and Performance When Using Data Comm in a High-Density Terminal Area Simulation

    NASA Technical Reports Server (NTRS)

    Norman, R. Michael; Baxley, Brian T.; Adams, Cathy A.; Ellis, Kyle K. E.; Latorella, Kara A.; Comstock, James R., Jr.

    2013-01-01

    This document describes a collaborative FAA/NASA experiment using 22 commercial airline pilots to determine the effect of using Data Comm to issue messages during busy, terminal area operations. Four conditions were defined that span current day to future flight deck equipage: Voice communication only, Data Comm only, Data Comm with Moving Map Display, and Data Comm with Moving Map displaying taxi route. Each condition was used in an arrival and a departure scenario at Boston Logan Airport. Of particular interest was the flight crew response to D-TAXI, the use of Data Comm by Air Traffic Control (ATC) to send taxi instructions. Quantitative data was collected on subject reaction time, flight technical error, operational errors, and eye tracking information. Questionnaires collected subjective feedback on workload, situation awareness, and acceptability to the flight crew for using Data Comm in a busy terminal area. Results showed that 95% of the Data Comm messages were responded to by the flight crew within one minute and 97% of the messages within two minutes. However, post experiment debrief comments revealed almost unanimous consensus that two minutes was a reasonable expectation for crew response. Flight crews reported that Expected D-TAXI messages were useful, and employment of these messages acceptable at all altitude bands evaluated during arrival scenarios. Results also indicate that the use of Data Comm for all evaluated message types in the terminal area was acceptable during surface operations, and during arrivals at any altitude above the Final Approach Fix, in terms of response time, workload, situation awareness, and flight technical performance. The flight crew reported the use of Data Comm as implemented in this experiment as unacceptable in two instances: in clearances to cross an active runway, and D-TAXI messages between the Final Approach Fix and 80 knots during landing roll. Critical cockpit tasks and the urgency of out-the window scan made the

  10. UGV acceptance testing

    NASA Astrophysics Data System (ADS)

    Kramer, Jeffrey A.; Murphy, Robin R.

    2006-05-01

    With over 100 models of unmanned vehicles now available for military and civilian safety, security or rescue applications, it is important to for agencies to establish acceptance testing. However, there appears to be no general guidelines for what constitutes a reasonable acceptance test. This paper describes i) a preliminary method for acceptance testing by a customer of the mechanical and electrical components of an unmanned ground vehicle system, ii) how it has been applied to a man-packable micro-robot, and iii) discusses the value of testing both to ensure that the customer has a workable system and to improve design. The test method automated the operation of the robot to repeatedly exercise all aspects and combinations of components on the robot for 6 hours. The acceptance testing process uncovered many failures consistent with those shown to occur in the field, showing that testing by the user does predict failures. The process also demonstrated that the testing by the manufacturer can provide important design data that can be used to identify, diagnose, and prevent long-term problems. Also, the structured testing environment showed that sensor systems can be used to predict errors and changes in performance, as well as uncovering unmodeled behavior in subsystems.

  11. Mechanical performance improvement of electroactive papers

    NASA Astrophysics Data System (ADS)

    Kim, Jaehwan; Seo, Yung B.; Jung, Eunmi

    2001-07-01

    Electro-Active Paper (EAPap) is a paper that produces large displacement with small force under electrical excitation. EAPap is made with a chemically treated paper by bonding thin aluminum foils on both sides of the paper to comprise electrodes. When electric voltage is applied on the electrodes the EAPap produces bending displacement. However, the displacement output has been unstable and degraded with time scale. To improve the bending performance of EAPap, different paper fibers-broad-leaf, needle-leaf, bacteria cellulose and Korean traditional paper, and additive chemicals are tested. It was observed that needle-leaf paper exhibits better results then others. By eliminating the effect of adhesive layer and selecting a proper paper fiber, the displacement output has been stable with long time scale. The operational principle of EAPap is, we believe, based on the electrostriction effect associated with intermolecular interaction of the constituents of the paper. To confirm this result, more investigation of the paper quality should be followed in the beginning of paper manufacturing process. Since EAPaps are quite simple to fabricate and lightweight, various applications including flexible speakers, active sound absorbing materials and smart shape control devices can be possible.

  12. Process for predicting structural performance of mechanical systems

    DOEpatents

    Gardner, David R.; Hendrickson, Bruce A.; Plimpton, Steven J.; Attaway, Stephen W.; Heinstein, Martin W.; Vaughan, Courtenay T.

    1998-01-01

    A process for predicting the structural performance of a mechanical system represents the mechanical system by a plurality of surface elements. The surface elements are grouped according to their location in the volume occupied by the mechanical system so that contacts between surface elements can be efficiently located. The process is well suited for efficient practice on multiprocessor computers.

  13. Process for predicting structural performance of mechanical systems

    DOEpatents

    Gardner, D.R.; Hendrickson, B.A.; Plimpton, S.J.; Attaway, S.W.; Heinstein, M.W.; Vaughan, C.T.

    1998-05-19

    A process for predicting the structural performance of a mechanical system represents the mechanical system by a plurality of surface elements. The surface elements are grouped according to their location in the volume occupied by the mechanical system so that contacts between surface elements can be efficiently located. The process is well suited for efficient practice on multiprocessor computers. 12 figs.

  14. Effect of annealing treatment on the performance of organic photovoltaic devices using SPFGraphene as electron-accepter material

    NASA Astrophysics Data System (ADS)

    Wang, HaiTeng; He, DaWei; Wang, YongSheng; Liu, ZhiYong; Wu, HongPeng; Wang, JiGang; Zhao, Yu

    2012-08-01

    We have researched the performances of organic photovoltaic devices with the bulk heterojunction (BHJ) structure using the organic solution-processable functionalized graphene (SPFGraphene) material as the electron-accepter material and P3OT as the donor material. The structural configuration of the device is ITO/PEDOT:PSS/P3OT:PCBM-SPFGraphene/LiF/Al. Given the P3OT/PCBM (1:1) mixture with 8wt% of SPFGraphene, the open-circuit voltage ( V oc) of the device reaches 0.64 V, a short-circuit current density ( J sc) reaches 5.7 mA/cm2, a fill factor ( FF) reaches 0.42, and the power conversion efficiency ( η) reaches 1.53% at illumination at 100 mW/cm2 AM1.5. We further studied the reason for the device performances improvement. In the P3OT:PCBM-SPFGraphene composite, the SPFGraphene material acts as exciton dissociation sites and provides the transport pathways of the lowest unoccupied molecular orbital (LUMO)-SPFGraphene-Al. Furthermore, adding SPFGraphene to P3OT results in appropriate energetic distance between the highest occupied molecular orbital (HOMO) and LUMO of the donor/acceptor and provides higher exciton dissociation volume mobility of carrier transport. We have researched the effect of annealing treatment for the devices and found that the devices with annealing treatment at 180°C show better performances compared with devices without annealed treatment. The devices with annealed treatment show the best performance, with an enhancement of the power conversion efficiency from 1.53% to 1.75%.

  15. Modeling the Mechanical Performance of Die Casting Dies

    SciTech Connect

    R. Allen Miller

    2004-02-27

    The following report covers work performed at Ohio State on modeling the mechanical performance of dies. The focus of the project was development and particularly verification of finite element techniques used to model and predict displacements and stresses in die casting dies. The work entails a major case study performed with and industrial partner on a production die and laboratory experiments performed at Ohio State.

  16. Larval Exposure to the Juvenile Hormone Analog Pyriproxyfen Disrupts Acceptance of and Social Behavior Performance in Adult Honeybees

    PubMed Central

    Fourrier, Julie; Deschamps, Matthieu; Droin, Léa; Alaux, Cédric; Fortini, Dominique; Beslay, Dominique; Le Conte, Yves; Devillers, James; Aupinel, Pierrick; Decourtye, Axel

    2015-01-01

    Background Juvenile hormone (JH) plays an important role in honeybee development and the regulation of age-related division of labor. However, honeybees can be exposed to insect growth regulators (IGRs), such as JH analogs developed for insect pest and vector control. Although their side effects as endocrine disruptors on honeybee larval or adult stages have been studied, little is known about the subsequent effects on adults of a sublethal larval exposure. We therefore studied the impact of the JH analog pyriproxyfen on larvae and resulting adults within a colony under semi-field conditions by combining recent laboratory larval tests with chemical analysis and behavioral observations. Oral and chronic larval exposure at cumulative doses of 23 or 57 ng per larva were tested. Results Pyriproxyfen-treated bees emerged earlier than control bees and the highest dose led to a significant rate of malformed adults (atrophied wings). Young pyriproxyfen-treated bees were more frequently rejected by nestmates from the colony, inducing a shorter life span. This could be linked to differences in cuticular hydrocarbon (CHC) profiles between control and pyriproxyfen-treated bees. Finally, pyriproxyfen-treated bees exhibited fewer social behaviors (ventilation, brood care, contacts with nestmates or food stocks) than control bees. Conclusion Larval exposure to sublethal doses of pyriproxyfen affected several life history traits of the honeybees. Our results especially showed changes in social integration (acceptance by nestmates and social behaviors performance) that could potentially affect population growth and balance of the colony. PMID:26171610

  17. Potentially acceptable substitutes for the chlorofluorocarbons: properties and performance features of HFC-134a, HCFC-123, and HCFC-141b

    NASA Astrophysics Data System (ADS)

    Sukornick, B.

    1989-05-01

    Potentially acceptable substitutes are known for CFC-11 and CFC-12-the most important Chlorofluorocarbons. HFC-134a could replace CFC-12 in airconditioning and refrigeration and both HCFC-123 and HCFC-141b show promise as CFC-11 substitutes. The replacement molecules all have significantly reduced greenhouse and ozone depletion potentials compared to their fully halogenated counterparts. HCFC-123 is theoretically a less efficient blowing agent than CFC-11, but 141b is more efficient. Results from experimental foaming tests confirm these relationships and show that initial insulating values are slightly lower for 141b and 123 than 11. Both substitutes are nonflammable liquids. Based on its physical properties, HFC-134a is an excellent replacement candidate for CFC-12. In addition, it is more thermally stable than CFC-12. A new family of HFC-134a compatible lubricant oils will be required. The estimated coefficient of performance (COP) of 134a is 96 98% that of CFC-12. Subacute toxicity tests show HFC-134a to have a low order of toxicity. HCFC-123 reveals no serious side effects at a concentration of 0.1% in subchronic tests and the inhalation toxicity of 141b is lower than that of CFC-11 based on a 6-h exposure. Chronic tests on all the new candidates will have to be completed for large-scale commercial use. Allied-Signal is conducting process development at a highly accelerated pace, and we plan to begin commercialization of substitutes within 5 years.

  18. Potentially acceptable substitutes for the chlorofluorocarbons: Properties and performance features of HFC-134a, HCFC-123, and HCFC-141b

    SciTech Connect

    Sukornick, B. )

    1989-05-01

    Potentially acceptable substitutes are known for CFC-11 and CFC-12 - the most important chlorofluorocarbons. HFC-134a could replace CFC-12 in air-conditioning and refrigeration and both HCFC-123 and HCFC-141b show promise as CFC-11 substitutes. The replacement molecules all have significantly reduced greenhouse and ozone depletion potentials compared to their fully halogenated counterparts. HCFC-123 is theoretically a less efficient blowing agent than CFC-11, but 141b is more efficient. Results from experimental foaming tests confirm these relationships and show that initial insulating values are slightly lower for 141 b and 123 than 11. Both substitutes are nonflammable liquids. Based on its physical properties, HFC-134a is an excellent replacement candidate for CFC-12. In addition, it is more thermally stable than CFC-12. A new family of HFC-134a compatible lubricant oils will be required. The estimated coefficient of performance (COP) of 134a is 96-98% that of CFC-12. Subacute toxicity tests show HFC-134a to have a low order of toxicity. HCFC-123 reveals no serious side effects at a concentration of 0.1% in subchronic tests and the inhalation toxicity of 141b is lower than that of CFC-11 based on a 6-h exposure. Chronic tests on all the new candidates will have to be completed for large-scale commercial use. Allied-Signal is conducting process development at a highly accelerated pace, and they plan to begin commercialization of substitutes within 5 years.

  19. Infants' Understanding of Actions Performed by Mechanical Devices

    ERIC Educational Resources Information Center

    Boyer, Ty W.; Pan, J. Samantha; Bertenthal, Bennett I.

    2011-01-01

    Recent research suggests that 9-month-old infants tested in a modified version of the A-not-B search task covertly imitate actions performed by the experimenter. The current study examines whether infants also simulate actions performed by mechanical devices, and whether this varies with whether or not they have been familiarized with the devices…

  20. Asbestos exposures of mechanics performing clutch service on motor vehicles.

    PubMed

    Cohen, Howard J; Van Orden, Drew R

    2008-03-01

    A study was conducted to assess historical asbestos exposures of mechanics performing clutch service on motor vehicles. For most of the 20th century, friction components used in brakes and manual transmission clutches contained approximately 25-60% chrysotile asbestos. Since the late 1960s, asbestos exposure assessment studies conducted on mechanics performing brake service have frequently reported levels below the current OSHA permissible exposure limit (PEL) of 0.1 fiber/cc (flcc). Although there is a robust asbestos exposure data set for mechanics performing brake service, there are almost no data for mechanics removing and replacing clutches in manual transmission vehicles. Personal and area airborne asbestos samples were collected during the removal of asbestos-containing clutches from 15 manual transmissions obtained from salvage facilities by an experienced mechanic. Clutch plates and debris were analyzed for asbestos using EPA and ISO published analytical methods. More than 100 personal and area air samples were collected and analyzed for asbestos fibers using NIOSH methods 7400 and 7402. A separate study involved a telephone survey of 16 automotive mechanics who began work prior to 1975. The mechanics were asked about the duration, frequency, and methods used to perform clutch service. Wear debris in the bell housing surrounding clutches had an average of 0.1% chrysotile asbestos by weight, a value consistent with similar reports of brake debris. Asbestos air sampling data collected averaged 0.047 flcc. Mechanics participating in the telephone survey indicated that clutch service was performed infrequently, the entire clutch assembly was normally replaced, and there was no need to otherwise handle the asbestos-containing clutch plates. These mechanics also confirmed that wet methods were most frequently used to clean debris from the bell housing. Combining the asbestos exposure that occurred when mechanics performed clutch service, along with the duration

  1. Dynamic performance of dissipative dielectric elastomers under alternating mechanical load

    NASA Astrophysics Data System (ADS)

    Zhang, Junshi; Chen, Hualing; Sheng, Junjie; Liu, Lei; Wang, Yongquan; Jia, Shuhai

    2014-07-01

    This paper presents a theoretical study about the effect of dissipation on the dynamic performance of a dielectric elastomer membrane subject to a combination of mechanical load and voltage. The thermodynamic dissipative model is given and the equation of motion is deduced by a free energy method. It is found that when the applied mechanical load and voltage are static, the membrane may reach a state of equilibrium after the viscoelastic relaxation. When the voltage is static but the mechanical load is sinusoidal, the membrane will resonate at multiple frequencies. The study result indicates that the viscoelasticity can reduce the natural frequency and increase the mean stretch of the dielectric elastomer. After the power source is cut off, the effect of current leakage on dynamic performance under alternating mechanical load is that the natural frequency increases and the mean stretch reduces.

  2. High-performance computing in structural mechanics and engineering

    SciTech Connect

    Adeli, H.; Kamat, M.P.; Kulkarni, G.; Vanluchene, R.D. Georgia Inst. of Technology, Atlanta Montana State Univ., Bozeman )

    1993-07-01

    Recent advances in computer hardware and software have made multiprocessing a viable and attractive technology. This paper reviews high-performance computing methods in structural mechanics and engineering through the use of a new generation of multiprocessor computers. The paper presents an overview of vector pipelining, performance metrics for parallel and vector computers, programming languages, and general programming considerations. Recent developments in the application of concurrent processing techniques to the solution of structural mechanics and engineering problems are reviewed, with special emphasis on linear structural analysis, nonlinear structural analysis, transient structural analysis, dynamics of multibody flexible systems, and structural optimization. 64 refs.

  3. Rehabilitation Counseling for Athletes Prior to Retirement: A Preventative Approach Using Self-Acceptance To Enhance Performance before and after Retirement.

    ERIC Educational Resources Information Center

    Mills, Brett D.

    This paper suggests that collegiate and professional athletes preparing to retire should be provided with preretirement and postretirement rehabilitation counseling. The counseling should involve a preventative approach centered around self-acceptance, to enhance the athlete's performance before and after retirement. The development of…

  4. Pulse oximetry performance in mechanically ventilated newborn infants.

    PubMed

    Solevåg, Anne L; Solberg, Marianne T; Šaltytė-Benth, Jūratė

    2015-08-01

    Pulse oximetry is widely used to target oxygenation in newborn infants. In a retrospective chart review of 138 mechanically ventilated infants, pulse oximetry overestimated blood oxygen saturation compared to arterial blood gas analyses. Despite improvements in pulse oximeter technology, pulse oximetry performance in sick newborns should still be under scrutiny. PMID:26067867

  5. Implementation of Statistical Process Control: Evaluating the Mechanical Performance of a Candidate Silicone Elastomer Docking Seal

    NASA Technical Reports Server (NTRS)

    Oravec, Heather Ann; Daniels, Christopher C.

    2014-01-01

    The National Aeronautics and Space Administration has been developing a novel docking system to meet the requirements of future exploration missions to low-Earth orbit and beyond. A dynamic gas pressure seal is located at the main interface between the active and passive mating components of the new docking system. This seal is designed to operate in the harsh space environment, but is also to perform within strict loading requirements while maintaining an acceptable level of leak rate. In this study, a candidate silicone elastomer seal was designed, and multiple subscale test articles were manufactured for evaluation purposes. The force required to fully compress each test article at room temperature was quantified and found to be below the maximum allowable load for the docking system. However, a significant amount of scatter was observed in the test results. Due to the stochastic nature of the mechanical performance of this candidate docking seal, a statistical process control technique was implemented to isolate unusual compression behavior from typical mechanical performance. The results of this statistical analysis indicated a lack of process control, suggesting a variation in the manufacturing phase of the process. Further investigation revealed that changes in the manufacturing molding process had occurred which may have influenced the mechanical performance of the seal. This knowledge improves the chance of this and future space seals to satisfy or exceed design specifications.

  6. Flux-pinning mechanisms for improving cryogenic segmented mirror performance

    NASA Astrophysics Data System (ADS)

    Gersh-Range, Jessica; Arnold, William R.; Lehner, David; Stahl, H. Philip

    2015-01-01

    Although large cryogenic space telescopes may provide a means of answering compelling astrophysics questions, the required increase in the primary mirror diameter presents technical challenges. Larger primaries are more flexible, and cryogenic mirrors are typically very lightly damped-the material damping is negligible, and common damping methods break down. To address these challenges, we propose placing flux-pinning mechanisms along the edges of adjacent mirror segments. These mechanisms consist of a collection of magnets and superconductors, and like flexures, they preferentially allow motion in specific degrees of freedom. Motion in nonpreferred degrees of freedom is resisted by a force analogous to a damped spring force, and the stiffness and damping can be adjusted independently. As an example, we consider simple mechanisms consisting of an inexpensive magnet and a single superconductor. These mechanisms provide increasing resistance as the magnet and superconductor-or mirror segments attached to each-come closer to colliding. These mechanisms, with typical stiffness and damping values on the order of 5000 N/m and 5 kg/s, respectively, also provide modest improvements to the mirror performance. Greater gains can be achieved by using stronger magnets or smaller separations, or by placing nonmagnetic conductive materials near the mechanism.

  7. Mechanisms for training security inspectors to enhance human performance

    SciTech Connect

    Burkhalter, H.E.; Sessions, J.C.

    1988-01-01

    The Department of Energy (DOE) has established qualification standards for protective force personnel employed at nuclear facilities (10 CFR Part 1046 (Federal Register)). Training mechanisms used at Los Alamos to enhance human performance in meeting DOE standards include, but are not limited to, the following: for cardio-respiratory training, they utilize distance running, interval training, sprint training, pacing, indoor aerobics and circuit training; for muscular strength, free weights, weight machines, light hand weights, grip strength conditioners, and calistenics are employed; for muscular endurance, participants do high repetitions (15 - 40) using dumbbells, flex weights, resistive rubber bands, benches, and calisthenics; for flexibility, each training session devotes specific times to stretch the muscles involved for a particular activity. These training mechanisms with specific protocols can enhance human performance.

  8. Critical Performance of Turbopump Mechanical Elements for Rocket Engine

    NASA Astrophysics Data System (ADS)

    Takada, Satoshi; Kikuchi, Masataka; Sudou, Takayuki; Iwasaki, Fumiya; Watanabe, Yoshiaki; Yoshida, Makoto

    It is generally acknowledged that bearings and axial seals have a tendency to go wrong compared with other rocket engine elements. And when those components have malfunction, missions scarcely succeed. However, fundamental performance (maximum rotational speed, minimum flow rate, power loss, durability, etc.) of those components has not been grasped yet. Purpose of this study is to grasp a critical performance of mechanical seal and hybrid ball bearing of turbopump. In this result, it was found that bearing outer race temperature and bearing coolant outlet temperature changed along saturation line of liquid hydrogen when flow rate was decreased under critical pressure. And normal operation of bearing was possible under conditions of more than 70,000 rpm of rotational speed and more than 0.2 liter/s of coolant flow rate. Though friction coefficient of seal surface increased several times of original value after testing, the seal showed a good performance same as before.

  9. Caffeine and anaerobic performance: ergogenic value and mechanisms of action.

    PubMed

    Davis, J K; Green, J Matt

    2009-01-01

    The effect caffeine elicits on endurance performance is well founded. However, comparatively less research has been conducted on the ergogenic potential of anaerobic performance. Some studies showing no effect of caffeine on performance used untrained subjects and designs often not conducive to observing an ergogenic effect. Recent studies incorporating trained subjects and paradigms specific to intermittent sports activity support the notion that caffeine is ergogenic to an extent with anaerobic exercise. Caffeine seems highly ergogenic for speed endurance exercise ranging in duration from 60 to 180 seconds. However, other traditional models examining power output (i.e. 30-second Wingate test) have shown minimal effect of caffeine on performance. Conversely, studies employing sport-specific methodologies (i.e. hockey, rugby, soccer) with shorter duration (i.e. 4-6 seconds) show caffeine to be ergogenic during high-intensity intermittent exercise. Recent studies show caffeine affects isometric maximal force and offers introductory evidence for enhanced muscle endurance for lower body musculature. However, isokinetic peak torque, one-repetition maximum and muscular endurance for upper body musculature are less clear. Since relatively few studies exist with resistance training, a definite conclusion cannot be reached on the extent caffeine affects performance. It was previously thought that caffeine mechanisms were associated with adrenaline (epinephrine)-induced enhanced free-fatty acid oxidation and consequent glycogen sparing, which is the leading hypothesis for the ergogenic effect. It would seem unlikely that the proposed theory would result in improved anaerobic performance, since exercise is dominated by oxygen-independent metabolic pathways. Other mechanisms for caffeine have been suggested, such as enhanced calcium mobilization and phosphodiesterase inhibition. However, a normal physiological dose of caffeine in vivo does not indicate this mechanism plays a

  10. Design and performance of a cryogenic iris aperture mechanism

    NASA Astrophysics Data System (ADS)

    de Jonge, C.; Laauwen, W. M.; de Vries, E. A.; Smit, H. P.; Detrain, A.; Eggens, M. J.; Ferrari, L.; Dieleman, P.

    2014-07-01

    A cryogenic iris mechanism is under development as part of the ground calibration source for the SAFARI instrument. The iris mechanism is a variable aperture used as an optical shutter to fine-tune and modulate the absolute power output of the calibration source. It has 4 stainless steel blades that create a near-circular aperture in every position. The operating temperature is 4.5 Kelvin to provide a negligible background to the SAFARI detectors, and `hot spots' above 9K should be prevented. Cryogenic testing proved that the iris works at 4K. It can be used in a broad range of cryogenic optical instruments where optical throughput needs to be controlled. Challenges in the design include the low cooling power available (5mW) and low friction at cryogenic temperatures. The actuator is an `arc-type' rotary voice-coil motor. The use of flexural pivots creates a mono-stable mechanism with a resonance frequency at 26Hz. Accurate and fast position control with disturbance rejection is managed by a PID servo loop using a hall-sensor as input. At 4 Kelvin, the frequency is limited to 4Hz to avoid excess dissipation and heating. In this paper, the design and performance of the iris are discussed. The design was optimized using a thermal, magnetic and mechanical model made with COMSOL Finite Element Analysis software. The dynamical and state-space modeling of the mechanism and the concept of the electrical control are presented. The performance of the iris show good agreement to the analytical and COMSOL modeling.

  11. Control mechanism to prevent correlated message arrivals from degrading signaling no. 7 network performance

    NASA Astrophysics Data System (ADS)

    Kosal, Haluk; Skoog, Ronald A.

    1994-04-01

    Signaling System No. 7 (SS7) is designed to provide a connection-less transfer of signaling messages of reasonable length. Customers having access to user signaling bearer capabilities as specified in the ANSI T1.623 and CCITT Q.931 standards can send bursts of correlated messages (e.g., by doing a file transfer that results in the segmentation of a block of data into a number of consecutive signaling messages) through SS7 networks. These message bursts with short interarrival times could have an adverse impact on the delay performance of the SS7 networks. A control mechanism, Credit Manager, is investigated in this paper to regulate incoming traffic to the SS7 network by imposing appropriate time separation between messages when the incoming stream is too bursty. The credit manager has a credit bank where credits accrue at a fixed rate up to a prespecified credit bank capacity. When a message arrives, the number of octets in that message is compared to the number of credits in the bank. If the number of credits is greater than or equal to the number of octets, then the message is accepted for transmission and the number of credits in the bank is decremented by the number of octets. If the number of credits is less than the number of octets, then the message is delayed until enough credits are accumulated. This paper presents simulation results showing delay performance of the SS7 ISUP and TCAP message traffic with a range of correlated message traffic, and control parameters of the credit manager (i.e., credit generation rate and bank capacity) are determined that ensure the traffic entering the SS7 network is acceptable. The results show that control parameters can be set so that for any incoming traffic stream there is no detrimental impact on the SS7 ISUP and TCAP message delay, and the credit manager accepts a wide range of traffic patterns without causing significant delay.

  12. Investigation of the Mechanical Performance of Compliant Thermal Barriers

    NASA Technical Reports Server (NTRS)

    DeMange, Jeffrey J.; Bott, Robert J.; Dunlap, Patrick H.

    2011-01-01

    Compliant thermal barriers play a pivotal role in the thermal protection systems of advanced aerospace vehicles. Both the thermal properties and mechanical performance of these barriers are critical in determining their successful implementation. Due to the custom nature of many thermal barriers, designers of advanced spacecraft have little guidance as to the design, selection, and implementation of these elements. As part of an effort to develop a more fundamental understanding of the interrelationship between thermal barrier design and performance, mechanical testing of thermal barriers was conducted. Two different types of thermal barriers with several core insulation density levels ranging from 62 to 141 kg/cu m were investigated. Room-temperature compression tests were conducted on samples to determine load performance and assess thermal barrier resiliency. Results showed that the loading behavior of these thermal barriers was similar to other porous, low-density, compliant materials, such as elastomeric foams. Additionally, the insulation density level had a significant non-linear impact on the stiffness and peak loads of the thermal barriers. In contrast, neither the thermal barrier type nor the level of insulation density significantly influenced the room-temperature resiliency of the samples.

  13. Team Assembly Mechanisms Determine Collaboration Network Structure and Team Performance

    PubMed Central

    Guimerà, Roger; Uzzi, Brian; Spiro, Jarrett; Nunes Amaral, Luís A.

    2007-01-01

    Agents in creative enterprises are embedded in networks that inspire, support, and evaluate their work. Here, we investigate how the mechanisms by which creative teams self-assemble determine the structure of these collaboration networks. We propose a model for the self-assembly of creative teams that has its basis in three parameters: team size, the fraction of newcomers in new productions, and the tendency of incumbents to repeat previous collaborations. The model suggests that the emergence of a large connected community of practitioners can be described as a phase transition. We find that team assembly mechanisms determine both the structure of the collaboration network and team performance for teams derived from both artistic and scientific fields. PMID:15860629

  14. A resorbable bicomponent braided ureteral stent with improved mechanical performance.

    PubMed

    Zou, Ting; Wang, Lu; Li, Wenchao; Wang, Wenzu; Chen, Fang; King, Martin W

    2014-10-01

    Bioresorbable ureteral stents have the advantage of eliminating the need for a second removal surgery and hence avoiding certain complications. However the inadequate mechanical performance and lack of control over the rate of resorption limit the use of current prototype designs. This paper focuses on a series of resorbable millimeter-sized stents which were fabricated by a unique combination of braiding and thermal treatment processes. Their mechanical properties where optimized by varying the braided structure and different resorbable components. Five different bicomponent structures were fabricated for the stent with different areas and distributions of poly (glycolic acid) (PGA) and poly (lactic-co-glycolic acid) (PLGA) resorbable yarns. Subsequent thermal treatment then converted the PLGA yarns into areas of continuous PLGA polymer film. The morphology, applied compression resistance and recovery and tensile strength tests were conducted on these prototype stents so as to investigate the relationship between their structures and mechanical properties. By selecting the appropriate resorbable biomaterials and altering the design of the braided structure it was possible to generate different sized areas and distributions of 100% braided yarn and 100% polymer film within the same bicomponent tubular structure. The relative total area of braided yarn to polymer film coverage was different for the five different prototype stents as well as between the external and internal surfaces of the bicomponent stents. This relative coverage of the braided yarn to polymer film played an important role in determining the mechanical performance of the stents, including the compression and recovery behavior as well as the tensile properties and failure morphology. The design of Stent C appeared to have the optimal structure for a resorbable ureteral stent with superior applied compression and tensile properties. PMID:24997428

  15. The physical and mechanical properties of laterite gravels from southeastern Nigeria relative to their engineering performance

    NASA Astrophysics Data System (ADS)

    Okagbue, C. O.

    Laterite gravels are used extensively as aggregates for highway construction, concrete making and fills in SE Nigeria. This paper presents results of laboratory investigations carried out to evaluate the physical and mechanical properties of these gravels. High mechanical strength, as measured by aggregate crushing (AC), and Los Angeles abrasion (LAA) values were found to be significant factors controlling the performance. Results indicate that significant correlations exist between these and specific gravity, water absorption and angularity of the gravels. No clear distinction in physical and mechanical properties could be found between the laterite gravels formed over sandstones and shales, indicating perhaps that effects of parent rock on the physical and mechanical nature of laterite gravels is of secondary importance. It is proposed that laterite gravels with AC and LAA values in the range of 30-40% and 34-45%, respectively and 10% fines value of between 8 and 4 tonnes be used only for medium and light trafficked roads. Those with AC and LAA values of less than 30% and 34%, respectively and 10% fines value of greater than 8 tonnes can be used for heavily trafficked roads, provided that acceptable gradation, plasticity limits (on the fines) and other construction specifications are met.

  16. Mechanical Performance of Rat, Mouse and Mole Spring Traps, and Possible Implications for Welfare Performance

    PubMed Central

    Baker, Sandra E.; Ellwood, Stephen A.; Tagarielli, Vito L.; Macdonald, David W.

    2012-01-01

    Lethal spring traps are widely used for killing small mammals in the UK. Many require government approval, based primarily on humaneness. However, mole traps and break-back traps for rats and mice are exempt; those available vary widely in price and apparent quality. The EU is considering implementing a Trapping Directive that would alter UK legislation, and a recent report advised the EU that trapping legislation should cover all trapped species and encourage improvement of traps. Mechanical trap performance is often used as an indicator of welfare impact. We examined the mechanical evidence for scope to improve the welfare standards of rat, mouse and mole spring traps. We measured mechanical performance among a range of rat, mouse and mole traps. Impact momentum values varied 6-8 fold, and clamping force values 4-5.5 fold, among traps for killing each species. There was considerable overlap in the performance of rat and mouse traps. Trap-opening angle and spring type were related to impact momentum and clamping force in traps for both species. There was no relationship between price and mechanical performance in traps for any species, except talpa mole traps. We are unable to judge the direct welfare impact of the traps tested, but rather the potential welfare threat associated with their exemption from approval. The wide variation in mechanical performance in traps for each species, overlap in performance between rat and mouse traps and increasing availability of weaker plastic rodent traps indicate considerable scope for improving the humaneness of spring traps for rats, mice and moles. We conclude that all such traps should be subject to the UK approval process. New welfare categories might improve trap standards further. Our results could also help improve rodent trap design and assist consumers in selecting more powerful traps. Many thousands of rats, mice and moles might benefit. PMID:22768073

  17. Right heart catheterisation may be cautiously performed through a mechanical valve prosthesis in the tricuspid position.

    PubMed

    Pettit, Stephen; Tsui, Steven; Parameshwar, Jayan

    2016-01-01

    Right heart catheterisation (RHC) may be performed through a mechanical valve prosthesis in the tricuspid position using a partially inflated pulmonary artery flotation catheter. Preprocedural preparation should include an ex vivo trial with an identical valve prosthesis and the type of catheter to be used for the procedure. The operator should expect immediate unloading of the right ventricle due to catheter-associated tricuspid regurgitation, but it is possible to estimate pulmonary vascular resistance using the Fick principle. The risk of catheter entrapment or damage to the prosthetic leaflets during the procedure is likely to be low. This risk may be acceptable to the clinician and the patient if pulmonary vascular resistance must be measured in order to determine eligibility for heart transplantation. PMID:27074812

  18. Mechanical performance of novel bioactive glass containing dental restorative composites

    PubMed Central

    Khvostenko, D.; Mitchell, J. C.; Hilton, T. J.; Ferracane, J. L.; Kruzic, J. J.

    2013-01-01

    Objectives Bioactive glass (BAG) is known to possess antimicrobial properties and release ions needed for remineralization of tooth tissue, and therefore may be a strategic additive for dental restorative materials. The objective of this study was to develop BAG containing dental restorative composites with adequate mechanical properties comparable to successful commercially available composites, and to confirm the stability of these materials when exposed to a biologically challenging environment. Methods Composites with 72 wt.% total filler content were prepared while substituting 0–15% of the filler with ground BAG. Flexural strength, fracture toughness, and fatigue crack growth tests were performed after several different soaking treatments: 24 hours in DI water (all experiments), two months in brain-heart infusion (BHI) media+S. mutans bacteria (all experiments) and two months in BHI media (only for flexural strength). Mechanical properties of new BAG composites were compared along with the commercial composite Heliomolar by two-way ANOVA and Tukey’s multiple comparison test (p≤0.05). Results Flexural strength, fracture toughness, and fatigue crack growth resistance for the BAG containing composites were unaffected by increasing BAG content up to 15% and were superior to Heliomolar after all post cure treatments. The flexural strength of the BAG composites was unaffected by two months exposure to aqueous media and a bacterial challenge, while some decreases in fracture toughness and fatigue resistance were observed. The favorable mechanical properties compared to Heliomolar were attributed to higher filler content and a microstructure morphology that better promoted the toughening mechanisms of crack deflection and bridging. Significance Overall, the BAG containing composites developed in this study demonstrated adequate and stable mechanical properties relative to successful commercial composites. PMID:24050766

  19. In-Orbit Performance of the MWRI Scanning Mechanisms

    NASA Technical Reports Server (NTRS)

    Schmid, Manfred; Jun, Miao; Shuang, Yu

    2014-01-01

    Scanning Equipment supporting the Millimeter Wave Radiometer Instrument (MWRI) are flying in a sunsynchronized orbit of 850-km altitude with an inclination of 98.8 deg on the FY-3 meteorological satellite (FY = Feng Yun, Wind and Cloud). MWRI is a linearly polarized, ten-channel passive Radiometer; it measures precipitation and water clouds, sea ice, snow/water equivalent, drought and flood index, land temperature and soil moisture. Following the FY3-A, the FY3-B Satellite was launched in autumn 2010. Since that time, the Scanning Equipment was continuously operated. During the last three and a half years in orbit, the Scanning Mechanism has executed about 65 million revolutions, while the Scan Compensation Mechanism (SCM) - used for momentum compensation - has already successfully executed more than one billion revolutions. During the commissioning phase of the instrument and during the first operation phase, random torque spikes, which manifested themselves as a motor current increase, were observed in the Scan Drive Mechanism, whereas the Scan Compensation drive operated nominally from the beginning. The result of the root cause investigations performed in order to isolate the issue, and the consequences for the follow-on MWRI equipment which was successfully launched by end of September 2013 (now flying on the FY 3-C Spacecraft), are discussed.

  20. The Effects of a Brief Acceptance-based Behavior Therapy vs. Traditional Cognitive Behavior Therapy for Public Speaking Anxiety: Differential Effects on Performance and Verbal Working Memory

    NASA Astrophysics Data System (ADS)

    Glassman, Lisa Hayley

    Individuals with public speaking phobia experience fear and avoidance that can cause extreme distress, impaired speaking performance, and associated problems in psychosocial functioning. Most extant interventions for public speaking phobia focus on the reduction of anxiety and avoidance, but neglect performance. Additionally, very little is known about the relationship between verbal working memory and social performance under conditions of high anxiety. The current study compared the efficacy of two cognitive behavioral treatments, traditional Cognitive Behavioral Therapy (tCBT) and acceptance-based behavior therapy (ABBT), in enhancing public speaking performance via coping with anxiety. Verbal working memory performance, as measured by the backwards digit span (BDS), was measured to explore the relationships between treatment type, anxiety, performance, and verbal working memory. We randomized 30 individuals with high public speaking anxiety to a 90-minute ABBT or tCBT intervention. As this pilot study was underpowered, results are examined in terms of effect sizes as well as statistical significance. Assessments took place at pre and post-intervention and included self-rated and objective anxiety measurements, a behavioral assessment, ABBT and tCBT process measures, and backwards digit span verbal working memory tests. In order to examine verbal working memory during different levels of anxiety and performance pressure, we gave each participant a backwards digit span task three times during each assessment: once under calm conditions, then again while experiencing anticipatory anxiety, and finally under conditions of acute social performance anxiety in front of an audience. Participants were asked to give a video-recorded speech in front of the audience at pre- and post-intervention to examine speech performance. Results indicated that all participants experienced a very large and statistically significant decrease in anxiety (both during the speech and BDS

  1. Development of a Performance and Processing Property Acceptance Region for Cementitious Low-Level Waste Forms at Savannah River Site - 13174

    SciTech Connect

    Staub, Aaron V.; Reigel, Marissa M.

    2013-07-01

    The Saltstone Production and Disposal Facilities (SPF and SDF) at the Savannah River Site (SRS) have been treating decontaminated salt solution, a low-level aqueous waste stream (LLW) since facility commissioning in 1990. In 2012, the Saltstone Facilities implemented a new Performance Assessment (PA) that incorporates an alternate design for the disposal facility to ensure that the performance objectives of DOE Order 435.1 and the National Defense Authorization Act (NDAA) of Fiscal Year 2005 Section 3116 are met. The PA performs long term modeling of the waste form, disposal facility, and disposal site hydrogeology to determine the transport history of radionuclides disposed in the LLW. Saltstone has been successfully used to dispose of LLW in a grout waste form for 15 years. Numerous waste form property assumptions directly impact the fate and transport modeling performed in the PA. The extent of process variability and consequence on performance properties are critical to meeting the assumptions of the PA. The SPF has ensured performance property acceptability by way of implementing control strategies that ensure the process operates within the analyzed limits of variability, but efforts continue to improve the understanding of facility performance in relation to the PA analysis. A similar understanding of the impact of variability on processing parameters is important from the standpoint of the operability of the production facility. The fresh grout slurry properties (particularly slurry rheology and the rate of hydration and structure formation) of the waste form directly impact the pressure and flow rates that can be reliably processed. It is thus equally important to quantify the impact of variability on processing parameters to ensure that the design basis assumptions for the production facility are maintained. Savannah River Remediation (SRR) has been pursuing a process that will ultimately establish a property acceptance region (PAR) to incorporate

  2. Performance of a hybrid chemical/mechanical heat pump

    NASA Technical Reports Server (NTRS)

    Silvestri, John J.; Scaringe, Robert P.; Grzyll, Lawrence R.

    1990-01-01

    The authors present the design and preliminary results of the performance of a hybrid chemical/mechanical, low-lift (20 C) heat pump. Studies have indicated that this heat pump has several advantages over the traditional single fluid vapor compression (reverse Rankine) heat pump. Included in these benefits are: 1) increased COPc due to the approximation of the cycle to the Lorenz cycle and due to the availability of the heat of solution, along with the heat of vaporization, to provide cooling; and 2) ease of variation in system cooling capacity by changing the fluid composition. The system performance is predicted for a variety of refrigerant-absorbent pairs. Cooling capacity is determined for systems operating with ammonia as the refrigerant and lithium nitrate and sodium thiocyanate as the absorbents and also with water as the refrigerant and magnesium chloride, potassium hydroxide, lithium bromide, sodium hydroxide, and sulfuric acid as the absorbents. Early indications have shown that the systems operating with water as the refrigerant operate at 2-4 times the capacity of the ammonia-refrigerant-based systems. Using existing working fluids in the proposed innovative design, a coefficient-of-performance improvement of 21 percent is possible when compared to the best vapor compression systems analyzed.

  3. The Simplest Flowchart Stating the Mechanisms for Organic Xenobiotics-induced Toxicity: Can it Possibly be Accepted as a "Central Dogma" for Toxic Mechanisms?

    PubMed

    Park, Yeong-Chul; Lee, Sundong; Cho, Myung-Haing

    2014-09-01

    Xenobiotics causing a variety of toxicity in biological systems could be classified as two types, inorganic and organic chemicals. It is estimated that the organic xenobiotics are responsible for approximately 80~90% of chemical-induced toxicity in human population. In the class for toxicology, we have encountered some difficulties in explaining the mechanisms of toxicity caused especially by organic chemicals. Here, a simple flowchart was introduced for explaining the mechanism of toxicity caused by organic xenobiotics, as the central dogma of molecular biology. This flowchart, referred to as a central dogma, was described based on a view of various aspects as follows: direct-acting chemicals vs. indirect-acting chemicals, cytochrome P450-dependent vs. cytochrome P450-independent biotransformation, reactive intermediates, reactivation, toxicokinetics vs. toxicodynamics, and reversibility vs. irreversibility. Thus, the primary objective of this flowchart is to help better understanding of the organic xenobiotics-induced toxic mechanisms, providing a major pathway for toxicity occurring in biological systems. PMID:25343011

  4. "Acceptance of the Limits of Knowability in Oneself and Others": Performative Politics and Relational Ethics in the Primary School Classroom

    ERIC Educational Resources Information Center

    Teague, Laura

    2015-01-01

    This paper takes up Judith Butler's calls to suspend the desire to completely know the other, and discusses these in relation to the pedagogic relationship in the classroom. It draws upon existing accounts of performative reinscription as a politics to disrupt exclusionary schooling practices and discusses these alongside Butler's theories of…

  5. Self-desiccation mechanism of high-performance concrete.

    PubMed

    Yang, Quan-Bing; Zhang, Shu-Qing

    2004-12-01

    Investigations on the effects of W/C ratio and silica fume on the autogenous shrinkage and internal relative humidity of high performance concrete (HPC), and analysis of the self-desiccation mechanisms of HPC showed that the autogenous shrinkage and internal relative humidity of HPC increases and decreases with the reduction of W/C respectively; and that these phenomena were amplified by the addition of silica fume. Theoretical analyses indicated that the reduction of RH in HPC was not due to shortage of water, but due to the fact that the evaporable water in HPC was not evaporated freely. The reduction of internal relative humidity or the so-called self-desiccation of HPC was chiefly caused by the increase in mole concentration of soluble ions in HPC and the reduction of pore size or the increase in the fraction of micro-pore water in the total evaporable water (T(r)/T(te) ratio). PMID:15547958

  6. Fluid Mechanics of a High Performance Racing Bicycle Wheel

    NASA Astrophysics Data System (ADS)

    Mercat, Jean-Pierre; Cretoux, Brieuc; Huat, Francois-Xavier; Nordey, Benoit; Renaud, Maxime; Noca, Flavio

    2013-11-01

    In 2012, MAVIC released the most aerodynamic bicycle wheel on the market, the CXR 80. The french company MAVIC has been a world leader for many decades in the manufacturing of bicycle wheels for competitive events such as the Olympic Games and the Tour de France. Since 2010, MAVIC has been in a research partnership with the University of Applied Sciences in Geneva, Switzerland, for the aerodynamic development of bicycle wheels. While most of the development up to date has been performed in a classical wind tunnel, recent work has been conducted in an unusual setting, a hydrodynamic towing tank, in order to achieve low levels of turbulence and facilitate quantitative flow visualization (PIV). After a short introduction on the aerodynamics of bicycle wheels, preliminary fluid mechanics results based on this novel setup will be presented.

  7. Mechanical Performance of Rotomoulded Wollastonite-Reinforced Polyethylene Composites

    NASA Astrophysics Data System (ADS)

    Yuan, Xiaowen; Easteal, Allan J.; Bhattacharyya, Debes

    This paper describes the development of a new processing technology for rotational moulding of wollastonite microfibre (WE) reinforced polyethylene (PE). Manufacturing wollastonite-polyethylene composites involved blending, compounding by extrusion, and granulating prior to rotational moulding. The properties of the resulting composites were characterised by tensile and impact strength measurements. The results show that tensile strength increases monotonically with the addition of wollastonite fibres, but impact strength is decreased. In addition, the processability is also decreased after adding more than 12 vol% WE because of increased viscosity. The effects of a coupling agent, maleated polyethylene (MAPE), on the mechanical performance and processability were also investigated. SEM analysis reveals good adhesion between the fibre reinforcements and polyethylene matrix at the fracture surface with the addition of MAPE. It is proposed that fillers with small particles with high aspect ratio (such as wollastonite) provide a large interfacial area between the filler and the polymer matrix, and may influence the mobility of the molecular chains.

  8. Mechanisms Responsible for Microwave Properties in High Performance Dielectric Materials

    NASA Astrophysics Data System (ADS)

    Zhang, Shengke

    Microwave properties of low-loss commercial dielectric materials are optimized by adding transition-metal dopants or alloying agents (i.e. Ni, Co, Mn) to tune the temperature coefficient of resonant frequency (tau f) to zero. This occurs as a result of the temperature dependence of dielectric constant offsetting the thermal expansion. At cryogenic temperatures, the microwave loss in these dielectric materials is dominated by electron paramagnetic resonance (EPR) loss, which results from the spin-excitations of d-shell electron spins in exchange-coupled clusters. We show that the origin of the observed magnetically-induced shifts in the dielectric resonator frequency originates from the same mechanism, as described by the Kramers-Kronig relations. The temperature coefficient of resonator frequency, tauf, is related to three material parameters according to the equation, tau f = - (½ tauepsilon + ½ taumu + alphaL), where tauepsilon, taumu , and alphaL are the temperature coefficient of dielectric constant, magnetic permeability, and lattice constant, respectively. Each of these parameters for dielectric materials of interest are measured experimentally. These results, in combination with density functional simulations, developed a much improved understanding of the fundamental mechanisms responsible for tau f. The same experimental methods have been used to characterize in-situ the physical nature and concentration of performance-degrading point defects in the dielectrics of superconducting planar microwave resonators.

  9. Fluid mechanics and spatial performance of face arrays

    SciTech Connect

    Lipfert, F.W.; Daum, M.L.; Hendrey, G.R.; Lewin, K.F.

    1989-05-01

    This report describes the fluid mechanics and aerodynamic performance of the Free Air Carbon dioxide Enrichment (FACE) array tested at Yazoo City, MS, in September 1987. The report describes three fluid mechanical regimes: the near field, dominated by the injection jets; the array itself; and the flow downwind of the array. The distribution of gas inside the array is described by means of multiport CO{sub 2} sampling and perfluorocarbon tracers, at three different heights. For the plant canopy configuration existing at this time, the flow was nearly uniform with height. Although the centerline CO{sub 2} concentration was controlled to well within the design goal, {plus minus}20%, 80% of the time, the variability away from the center was somewhat greater. On average, {plus minus}20% variability was achieved within a 13 m diameter within the 22 m array. The CO{sub 2} concentration downwind of the array was generally down to ambient levels within a distance of 100 m. The dispersion efficiency of the array, as measured by the parameter XAu/Q, compared well with the Brookhaven National Laboratory (BNL) prototype which had been tested on SO{sub 2}. The dispersion was greater during the daytime than at night. Although theoretical calculations indicated that CO{sub 2} interference from the Mississippi Chemical Company (MCC) plant was possible, no definite instances of such interference were identified. 6 refs., 40 figs., 1 tab.

  10. Bay-annulated indigo (BAI) as an excellent electron accepting building block for high performance organic semiconductors

    DOEpatents

    Liu, Yi; He, Bo; Pun, Andrew

    2015-11-24

    A novel electron acceptor based on bay-annulated indigo (BAI) was synthesized and used for the preparation of a series of high performance donor-acceptor small molecules and polymers. The resulting materials possess low-lying LUMO energy level and small HOMO-LUMO gaps, while their films exhibited high crystallinity upon thermal treatment, commensurate with high field effect mobilities and ambipolar transfer characteristics.

  11. Bay-annulated indigo (BAI) as an excellent electron accepting building block for high performance organic semiconductors

    DOEpatents

    Liu, Yi; He, Bo; Pun, Andrew

    2016-04-19

    A novel electron acceptor based on bay-annulated indigo (BAI) was synthesized and used for the preparation of a series of high performance donor-acceptor small molecules and polymers. The resulting materials possess low-lying LUMO energy level and small HOMO-LUMO gaps, while their films exhibited high crystallinity upon thermal treatment, commensurate with high field effect mobilities and ambipolar transfer characteristics.

  12. Is it time to turn our attention toward central mechanisms for post-exertional recovery strategies and performance?

    PubMed Central

    Rattray, Ben; Argus, Christos; Martin, Kristy; Northey, Joseph; Driller, Matthew

    2015-01-01

    Key Points Central fatigue is accepted as a contributor to overall athletic performance, yet little research directly investigates post-exercise recovery strategies targeting the brainCurrent post-exercise recovery strategies likely impact on the brain through a range of mechanisms, but improvements to these strategies is neededResearch is required to optimize post-exercise recovery with a focus on the brain Post-exercise recovery has largely focused on peripheral mechanisms of fatigue, but there is growing acceptance that fatigue is also contributed to through central mechanisms which demands that attention should be paid to optimizing recovery of the brain. In this narrative review we assemble evidence for the role that many currently utilized recovery strategies may have on the brain, as well as potential mechanisms for their action. The review provides discussion of how common nutritional strategies as well as physical modalities and methods to reduce mental fatigue are likely to interact with the brain, and offer an opportunity for subsequent improved performance. We aim to highlight the fact that many recovery strategies have been designed with the periphery in mind, and that refinement of current methods are likely to provide improvements in minimizing brain fatigue. Whilst we offer a number of recommendations, it is evident that there are many opportunities for improving the research, and practical guidelines in this area. PMID:25852568

  13. Chemical and mechanical performance properties for various final waste forms -- PSPI scoping study

    SciTech Connect

    Farnsworth, R.K.; Larsen, E.D.; Sears, J.W.; Eddy, T.L.; Anderson, G.L.

    1996-09-01

    The US DOE is obtaining data on the performance properties of the various final waste forms that may be chosen as primary treatment products for the alpha-contaminated low-level and transuranic waste at the INEL`s Transuranic Storage Area. This report collects and compares selected properties that are key indicators of mechanical and chemical durability for Portland cement concrete, concrete formed under elevated temperature and pressure, sulfur polymer cement, borosilicate glass, and various forms of alumino-silicate glass, including in situ vitrification glass and various compositions of iron-enriched basalt (IEB) and iron-enriched basalt IV (IEB4). Compressive strength and impact resistance properties were used as performance indicators in comparative evaluation of the mechanical durability of each waste form, while various leachability data were used in comparative evaluation of each waste form`s chemical durability. The vitrified waste forms were generally more durable than the non-vitrified waste forms, with the iron-enriched alumino-silicate glasses and glass/ceramics exhibiting the most favorable chemical and mechanical durabilities. It appears that the addition of zirconia and titania to IEB (forming IEB4) increases the leach resistance of the lanthanides. The large compositional ranges for IEB and IEB4 more easily accommodate the compositions of the waste stored at the INEL than does the composition of borosilicate glass. It appears, however, that the large potential variation in IEB and IEB4 compositions resulting from differing waste feed compositions can impact waste form durability. Further work is needed to determine the range of waste stream feed compositions and rates of waste form cooling that will result in acceptable and optimized IEB or IEB4 waste form performance. 43 refs.

  14. Mechanical performance of the standard Orthofix external fixator.

    PubMed

    Chao, E Y; Hein, T J

    1988-07-01

    Static and fatigue tests of the standard Orthofix unilateral external fixator (Orthofix SRL, Verona, Italy) were performed. Under similar fixation configurations, the Orthofix device offered higher bending stiffness in both directions, equal torsional stiffness, and lower axial stiffness when compared to the Hoffmann-Vidal quadrilateral frame with full pins. The bending resistance of the Orthofix ball joint was found to be proportional to its locking cam tightening torque. After applying 2 million loading cycles to the bone ends fixed by the device, the overall stiffness characteristics of the frame did not change significantly. Repetitive manual tightening and loosening of the ball joint caused abrasive wear on the cam and bushing surfaces. The locking position of the cam migrated for a mean of 45 degrees. After 50 cycles of tightening and bending to failure, the ball joint locking strength was reduced by 20% to 25%, but the stiffness did not change. Wear and stripping of the seat of the fixator body locking screw and the pin fixation screw threads were also noted. Based on the test results, the standard Orthofix device could be re-used, but certain fixator components must be inspected and replaced. The ball joint locking cam and fixation screws required periodic tightening during clinical application to prevent loss of frame stiffness under repetitive loading. Modifications of the fixator design are recommended to improve its mechanical performance. PMID:3405906

  15. Investigation of performance and mechanism for chemical laser propulsion

    NASA Astrophysics Data System (ADS)

    Tang, Zhiping; Li, Long

    2013-05-01

    Chemical laser propulsion (CLP) is accompanied by the release of chemical energy in the process of laser propulsion, which can improve laser propulsion performance. In this article the propulsion performance of POM propellant under the constraint of a cylindrical tube-type thruster in atmospheric and nitrogen environments, respectively, has been conducted experimentally. The results indicate that the ablation masses of a single pulse under two gas environments are close, but the momentum coupling coefficient Cm and specific impulse Isp in atmospheric environment are higher than that in nitrogen environment, which demonstrates an exothermic reaction occurred between the ablation product and the environment oxygen. To learn the mechanism of CLP the molecular spectra for ablation products of POM propellant in atmospheric and vacuum environments are measured and analyzed, respectively, and it reveals that the final product in a vacuum is CH2O, while the final products are CO2 and H2O in the atmosphere. Then the chemical reaction, composition and chemical energy release have been confirmed in the atmospheric environment. By using Arrhenius finite rate chemical reaction model with the code Fluent the flow field evolution of ablation product was simulated numerically. The results show the intensity of chemical energy release is related to the contact and mixing degree of the ablation product and the oxygen in the atmosphere, mixing more fully, the chemical energy released more intensively.

  16. New Mechanical Model for the Transmutation Fuel Performance Code

    SciTech Connect

    Gregory K. Miller

    2008-04-01

    A new mechanical model has been developed for implementation into the TRU fuel performance code. The new model differs from the existing FRAPCON 3 model, which it is intended to replace, in that it will include structural deformations (elasticity, plasticity, and creep) of the fuel. Also, the plasticity algorithm is based on the “plastic strain–total strain” approach, which should allow for more rapid and assured convergence. The model treats three situations relative to interaction between the fuel and cladding: (1) an open gap between the fuel and cladding, such that there is no contact, (2) contact between the fuel and cladding where the contact pressure is below a threshold value, such that axial slippage occurs at the interface, and (3) contact between the fuel and cladding where the contact pressure is above a threshold value, such that axial slippage is prevented at the interface. The first stage of development of the model included only the fuel. In this stage, results obtained from the model were compared with those obtained from finite element analysis using ABAQUS on a problem involving elastic, plastic, and thermal strains. Results from the two analyses showed essentially exact agreement through both loading and unloading of the fuel. After the cladding and fuel/clad contact were added, the model demonstrated expected behavior through all potential phases of fuel/clad interaction, and convergence was achieved without difficulty in all plastic analysis performed. The code is currently in stand alone form. Prior to implementation into the TRU fuel performance code, creep strains will have to be added to the model. The model will also have to be verified against an ABAQUS analysis that involves contact between the fuel and cladding.

  17. Improvement of mechanical characteristics and performances with Ni diffusion mechanism throughout Bi-2223 superconducting matrix

    NASA Astrophysics Data System (ADS)

    Sarıtekin, N. K.; Bilge, H.; Kahraman, M. F.; Zalaoǧlu, Y.; Pakdil, M.; Doǧruer, M.; Yıldırım, G.; Oz, M.

    2016-03-01

    This study is interested in the role of diffusion annealing temperature (650-850°C) on the mechanical characteristics and performance of pure and Ni diffused Bi-2223 superconducting materials by means of standard compression tests and Vickers hardness measurements at performed different applied loads in the range of 0.245-2.940N and theoretical calculations. Based on the experimental findings, the mechanical performances improve with increasing annealing temperature up to 700 °C beyond which they degrade drastically due to the increased artificial disorders, cracks and irregular grain orientation distribution. In other words, the penetration of excess Ni inclusions accelerates both the dislocation movement and especially the cracks and voids propagation as a result of the decrement in the Griffith critical crack length. Further, it is to be mentioned here that all the sample exhibit typical indentation size effect (ISE) behavior. In this respect, both the plastic (irreversible) and elastic (reversible) deformations have dominant role on the superconducting structures as a result of the enhancement in the elastic recovery. At the same time elastic modulus, yield strength and fracture toughness parameters are theoretically extracted from the microhardness values. Moreover, the elastic modulus parameters are compared with the experimental values. It is found that the differentiation between the comparison results enhances hastily with the increment in the applied indentation test loads due to the existence of the increased permanent disorders, lattice defects and strains in the stacked layers. Namely, the error level increases away from the actual crystal structure. Additionally, the microhardness values are theoretically analyzed for the change of the mechanical behaviors with the aid of Meyer's law, elastic/plastic deformation and Hays-Kendall approaches for the first time.

  18. Optimizing Opto-mechanical Performance Using Simple Tools and Techniques

    NASA Astrophysics Data System (ADS)

    Krajci, Tom

    2009-05-01

    You just purchased a modest setup for your observatory - perhaps a mass produced Schmidt-Cassegrain on a German equatorial mount. However, optically and mechanically it's not performing as well as you would like. What can you do? Some simple assessments and repairs may make all the difference. Assessments can be as easy as visual inspection of various mount components, such as the tripod, where gaps between components reduce stiffness or allow unexpected shifts when loads change. Some assessments are only slightly more involved. Main mirror flop can be evaluated by aligning the main telescope and finder on a bright star and then slewing to various parts of the sky. Pointing differences between the two will be readily apparent if this problem exists. Most mid-level mounts use worm drives, but often excessive spacing between worm and worm gear produces large, and unnecessary amounts of backlash. Visual inspection of your dovetail mounting system may leave doubts in your mind as to adequate stiffness. Imaging through the entire night may show you that your aluminum tube telescope causes excessive focus shift as temperature drops. Over time, your Schmidt-Cassegrain corrector plate may no longer be securely held by its retaining ring, and the same may apply to the secondary mirror cell. Repairs for these problems are often not difficult if you're mechanically inclined. Gaps in mount components can be eliminated with shims. Combating mirror flop may be the most difficult task. This can involve re-gluing the main mirror and bolting the main mirror cell in a fixed position. Corrector plate and secondary mirror cells can be improved with setscrews and shims - implementing sound kinematic principles. Worm gear spacing can often be adjusted with simple tools. This brief paper can't possibly cover all problems and solutions, but it can give you the proper mindset to looking at your system with a critical eye and implementing simple, inexpensive fixes. You may be pleasantly

  19. Jumping mechanisms and performance of snow fleas (Mecoptera, Boreidae).

    PubMed

    Burrows, Malcolm

    2011-07-15

    Flightless snow fleas (snow scorpion flies, Mecoptera, Boreidae) live as adults during northern hemisphere winters, often jumping and walking on the surface of snow. Their jumping mechanisms and performance were analysed with high speed imaging. Jumps were propelled by simultaneous movements of both the middle and hind pairs of legs, as judged by the 0.2 ms resolution afforded by image rates of 5000 frames s(-1). The middle legs of males represent 140% and the hindlegs 187% of the body length (3.4 mm), and the ratio of leg lengths is 1:1.3:1.7 (front:middle:hind). In preparation for a jump the middle legs and hindlegs were rotated forwards at their coxal joints with the fused mesothorax and metathorax. The first propulsive movement of a jump was the rotation of the trochantera about the coxae, powered by large depressor muscles within the thorax. The acceleration time was 6.6 ms. The fastest jump by a male had a take-off velocity of 1 m s(-1), which required 1.1 μJ of energy and a power output of 0.18 mW, and exerted a force about 16 times its body weight. Jump distances of about 100 mm were unaffected by temperature. This, and the power per mass of muscle requirement of 740 W kg(-1), suggests that a catapult mechanism is used. The elastic protein resilin was revealed in four pads at the articulation of the wing hinge with the dorsal head of the pleural ridge of each middle leg and hindleg. By contrast, fleas, which use just their hindlegs for jumping, have only two pads of resilin. This, therefore, provides a functional reference point for considerations about the phylogenetic relationships between snow fleas and true fleas. PMID:21697428

  20. The Mechanical Performance of Subscale Candidate Elastomer Docking Seals

    NASA Technical Reports Server (NTRS)

    Bastrzyk, Marta B.; Daniels, Christopher C.

    2010-01-01

    The National Aeronautics and Space Administration is developing a Low Impact Docking System (LIDS) for future exploration missions. The mechanism is a new state-of-the-art device for in-space assembly of structures and rendezvous of vehicles. At the interface between two pressurized modules, each with a version of the LIDS attached, a composite elastomer-metal seal assembly prevents the breathable air from escaping into the vacuum of space. Attached to the active LIDS, this seal mates against the passive LIDS during docking operation. The main interface seal assembly must exhibit low leak and outgas values, must be able to withstand various harsh space environments, must remain operational over a range of temperatures from -50 C to 75 C, and perform after numerous docking cycles. This paper presents results from a comprehensive study of the mechanical performance of four candidate subscale seal assembly designs at -50, 23, 50, and 75 C test temperatures. In particular, the force required to fully compress the seal during docking, and that which is required for separation during the undocking operation were measured. The height of subscale main interface seal bulbs, as well as the test temperature, were shown to have a significant effect on the forces the main interface seal of the LIDS may experience during docking and undocking operations. The average force values required to fully compress each of the seal assemblies were shown to increase with test temperature by approximately 50% from -50 to 75 C. Also, the required compression forces were shown to increase as the height of the seal bulb was increased. The seal design with the tallest elastomer seal bulb, which was 31% taller than that with the shortest bulb, required force values approximately 45% higher than those for the shortest bulb, independent of the test temperature. The force required to separate the seal was shown to increase with decreasing temperature after 15 hours of simulated docking. No adhesion

  1. Mechanisms of Microwave Loss Tangent in High Performance Dielectric Materials

    NASA Astrophysics Data System (ADS)

    Liu, Lingtao

    The mechanism of loss in high performance microwave dielectrics with complex perovskite structure, including Ba(Zn1/3Ta2/3)O 3, Ba(Cd1/3Ta2/3)O3, ZrTiO4-ZnNb 2O6, Ba(Zn1/3Nb2/3)O3, and BaTi4O9-BaZn2Ti4O11, has been investigated. We studied materials synthesized in our own lab and from commercial vendors. Then the measured loss tangent was correlated to the optical, structural, and electrical properties of the material. To accurately and quantitatively determine the microwave loss and Electron Paramagnetic Resonance (EPR) spectra as a function of temperature and magnetic field, we developed parallel plate resonator (PPR) and dielectric resonator (DR) techniques. Our studies found a marked increase in the loss at low temperatures is found in materials containing transition metal with unpaired d-electrons as a result of resonant spin excitations in isolated atoms (light doping) or exchange coupled clusters (moderate to high doping); a mechanism that differs from the usual suspects. The loss tangent can be drastically reduced by applying static magnetic fields. Our measurements also show that this mechanism significantly contributes to room temperature loss, but does not dominate. In order to study the electronic structure of these materials, we grew single crystal thin film dielectrics for spectroscopic studies, including angular resolved photoemission spectroscopy (ARPES) experiment. We have synthesized stoichiometric Ba(Cd1/3Ta2/3)O3 [BCT] (100) dielectric thin films on MgO (100) substrates using Pulsed Laser Deposition. Over 99% of the BCT film was found to be epitaxial when grown with an elevated substrate temperature of 635 °C, an enhanced oxygen pressures of 53 Pa and a Cd-enriched BCT target with a 1 mol BCT: 1.5 mol CdO composition. Analysis of ultra violet optical absorption results indicate that BCT has a bandgap of 4.9 eV.

  2. Acceptance speech.

    PubMed

    Carpenter, M

    1994-01-01

    In Bangladesh, the assistant administrator of USAID gave an acceptance speech at an awards ceremony on the occasion of the 25th anniversary of oral rehydration solution (ORS). The ceremony celebrated the key role of the International Centre for Diarrhoeal Disease Research, Bangladesh (ICDDR,B) in the discovery of ORS. Its research activities over the last 25 years have brought ORS to every village in the world, preventing more than a million deaths each year. ORS is the most important medical advance of the 20th century. It is affordable and client-oriented, a true appropriate technology. USAID has provided more than US$ 40 million to ICDDR,B for diarrheal disease and measles research, urban and rural applied family planning and maternal and child health research, and vaccine development. ICDDR,B began as the relatively small Cholera Research Laboratory and has grown into an acclaimed international center for health, family planning, and population research. It leads the world in diarrheal disease research. ICDDR,B is the leading center for applied health research in South Asia. It trains public health specialists from around the world. The government of Bangladesh and the international donor community have actively joined in support of ICDDR,B. The government applies the results of ICDDR,B research to its programs to improve the health and well-being of Bangladeshis. ICDDR,B now also studies acute respiratory diseases and measles. Population and health comprise 1 of USAID's 4 strategic priorities, the others being economic growth, environment, and democracy, USAID promotes people's participation in these 4 areas and in the design and implementation of development projects. USAID is committed to the use and improvement of ORS and to complementary strategies that further reduce diarrhea-related deaths. Continued collaboration with a strong user perspective and integrated services will lead to sustainable development. PMID:12345470

  3. Acceptance speech.

    PubMed

    Yusuf, C K

    1994-01-01

    I am proud and honored to accept this award on behalf of the Government of Bangladesh, and the millions of Bangladeshi children saved by oral rehydration solution. The Government of Bangladesh is grateful for this recognition of its commitment to international health and population research and cost-effective health care for all. The Government of Bangladesh has already made remarkable strides forward in the health and population sector, and this was recognized in UNICEF's 1993 "State of the World's Children". The national contraceptive prevalence rate, at 40%, is higher than that of many developed countries. It is appropriate that Bangladesh, where ORS was discovered, has the largest ORS production capacity in the world. It was remarkable that after the devastating cyclone in 1991, the country was able to produce enough ORS to meet the needs and remain self-sufficient. Similarly, Bangladesh has one of the most effective, flexible and efficient control of diarrheal disease and epidemic response program in the world. Through the country, doctors have been trained in diarrheal disease management, and stores of ORS are maintained ready for any outbreak. Despite grim predictions after the 1991 cyclone and the 1993 floods, relatively few people died from diarrheal disease. This is indicative of the strength of the national program. I want to take this opportunity to acknowledge the contribution of ICDDR, B and the important role it plays in supporting the Government's efforts in the health and population sector. The partnership between the Government of Bangladesh and ICDDR, B has already borne great fruit, and I hope and believe that it will continue to do so for many years in the future. Thank you. PMID:12345479

  4. Mechanical fatigue performance of PCL-chondroprogenitor constructs after cell culture under bioreactor mechanical stimulus.

    PubMed

    Panadero, Juan Alberto; Sencadas, Vitor; Silva, Sonia C M; Ribeiro, Clarisse; Correia, Vitor; Gama, Francisco M; Gomez Ribelles, José Luis; Lanceros-Mendez, Senentxu

    2016-02-01

    In tissue engineering of cartilage, polymeric scaffolds are implanted in the damaged tissue and subjected to repeated compression loading cycles. The possibility of failure due to mechanical fatigue has not been properly addressed in these scaffolds. Nevertheless, the macroporous scaffold is susceptible to failure after repeated loading-unloading cycles. This is related to inherent discontinuities in the material due to the micropore structure of the macro-pore walls that act as stress concentration points. In this work, chondrogenic precursor cells have been seeded in poly-ε-caprolactone (PCL) scaffolds with fibrin and some were submitted to free swelling culture and others to cyclic loading in a bioreactor. After cell culture, all the samples were analyzed for fatigue behavior under repeated loading-unloading cycles. Moreover, some components of the extracellular matrix (ECM) were identified. No differences were observed between samples undergoing free swelling or bioreactor loading conditions, neither respect to matrix components nor to mechanical performance to fatigue. The ECM did not achieve the desired preponderance of collagen type II over collagen type I which is considered the main characteristic of hyaline cartilage ECM. However, prediction in PCL with ECM constructs was possible up to 600 cycles, an enhanced performance when compared to previous works. PCL after cell culture presents an improved fatigue resistance, despite the fact that the measured elastic modulus at the first cycle was similar to PCL with poly(vinyl alcohol) samples. This finding suggests that fatigue analysis in tissue engineering constructs can provide additional information missed with traditional mechanical measurements. PMID:25772257

  5. A summary of the mechanical design, testing and performance of the IMP-H and J attitude control systems

    NASA Technical Reports Server (NTRS)

    Metzger, J. R.

    1974-01-01

    The main aspects of the attitude control system used on both the IMP-H and J spacecraft are presented. The mechanical configuration is described. Information on all the specific components comprising the flight system is provided. The acceptance and qualification testing of both individual components and the installed system are summarized. Functional information regarding the operation and performance in relation to the orbiting spacecraft and its mission is included. Related topics which are discussed are: (1) safety requirements, (2) servicing procedures, (3) anomalous behavior, and (4) pyrotechnic devices.

  6. 46 CFR 54.30-10 - Method of performing mechanical stress relief.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Method of performing mechanical stress relief. 54.30-10 Section 54.30-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS Mechanical Stress Relief § 54.30-10 Method of performing mechanical stress relief. (a) The mechanical stress relief shall...

  7. 46 CFR 54.30-10 - Method of performing mechanical stress relief.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Method of performing mechanical stress relief. 54.30-10... PRESSURE VESSELS Mechanical Stress Relief § 54.30-10 Method of performing mechanical stress relief. (a) The mechanical stress relief shall be carried out in accordance with the following stipulations using water...

  8. 46 CFR 54.30-10 - Method of performing mechanical stress relief.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Method of performing mechanical stress relief. 54.30-10... PRESSURE VESSELS Mechanical Stress Relief § 54.30-10 Method of performing mechanical stress relief. (a) The mechanical stress relief shall be carried out in accordance with the following stipulations using water...

  9. IMPROVING THE PROFICIENCY OF MECHANICAL ACTIVITIES PERFORMED BY UTAH'S AGRICULTURALISTS.

    ERIC Educational Resources Information Center

    JARRETT, VON H.

    THE MAJOR PURPOSES OF THIS STUDY WERE TO--(1) IMPROVE THE CURRICULUM IN AGRICULTURAL MECHANICS FOR THE PREPARATION OF VOCATIONAL AGRICULTURE TEACHERS AT UTAH STATE UNIVERSITY, (2) SERVE AS A GUIDE IN CHANGING AND DEVELOPING FUTURE COURSES IN AGRICULTURAL MECHANICS FOR ALL-DAY STUDENTS, (3) DISCOVER THE NEEDS FOR INSERVICE TRAINING PROGRAMS, AND…

  10. Mechanisms governing the health and performance benefits of exercise

    PubMed Central

    Bishop-Bailey, D

    2013-01-01

    Humans are considered among the greatest if not the greatest endurance land animals. Over the last 50 years, as the population has become more sedentary, rates of cardiovascular disease and its associated risk factors such as obesity, type 2 diabetes and hypertension have all increased. Aerobic fitness is considered protective for all-cause mortality, cardiovascular disease, a variety of cancers, joint disease and depression. Here, I will review the emerging mechanisms that underlie the response to exercise, focusing on the major target organ the skeletal muscle system. Understanding the mechanisms of action of exercise will allow us to develop new therapies that mimic the protective actions of exercise. PMID:24033098

  11. 46 CFR 54.30-10 - Method of performing mechanical stress relief.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Method of performing mechanical stress relief. 54.30-10 Section 54.30-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS Mechanical Stress Relief § 54.30-10 Method of performing mechanical stress relief. (a)...

  12. 46 CFR 54.30-10 - Method of performing mechanical stress relief.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Method of performing mechanical stress relief. 54.30-10 Section 54.30-10 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) MARINE ENGINEERING PRESSURE VESSELS Mechanical Stress Relief § 54.30-10 Method of performing mechanical stress relief. (a)...

  13. ATS-6 engineering performance report. Volume:Program and systems summaries: Mechanical and thermal details

    NASA Technical Reports Server (NTRS)

    Wales, R. O. (Editor)

    1981-01-01

    The overall mission and spacecraft systems, testing, and operations are summarized. The mechanical subsystems are reviewed, encompassing mechanical design requirements; separation and deployment mechanisms; design and performance evaluation; and the television camera reflector monitor. Thermal control and contamination are discussed in terms of thermal control subsystems, design validation, subsystems performance, the advanced flight experiment, and the quartz-crystal microbalance contamination monitor.

  14. Attentional Mechanisms during the Performance of a Subsecond Timing Task

    PubMed Central

    Velázquez-Martínez, David N.

    2016-01-01

    There is evidence that timing processes in the suprasecond scale are modulated by attentional mechanisms; in addition, some studies have shown that attentional mechanisms also affect timing in the subsecond scale. Our aim was to study eye movements and pupil diameter during a temporal bisection task in the subsecond range. Subjects were trained to discriminate anchor intervals of 200 or 800 msec, and were then confronted with intermediate durations. Eye movements revealed that subjects used different cognitive strategies during the bisection timing task. When the stimulus to be timed appeared randomly at a central or 4 peripheral positions on a screen, some subjects choose to maintain their gaze toward the central area while other followed the peripheral placement of the stimulus; some others subjects used both strategies. The time of subjective equality did not differ between subjects who employed different attentional mechanisms. However, differences emerged in the timing variance and attentional indexes (time taken to initial fixation, latency to respond, pupil dilatation and duration and number of fixations to stimulus areas). Timing in the subsecond range seems invariant despite the use of different attentional strategies. Future research should determine whether the selection of attentional mechanisms is related to particular timing tasks or instructions or whether it represents idiosyncratic cognitive “styles”. PMID:27467762

  15. Attentional Mechanisms during the Performance of a Subsecond Timing Task.

    PubMed

    Toscano-Zapién, Anna L; Velázquez-López, Daniel; Velázquez-Martínez, David N

    2016-01-01

    There is evidence that timing processes in the suprasecond scale are modulated by attentional mechanisms; in addition, some studies have shown that attentional mechanisms also affect timing in the subsecond scale. Our aim was to study eye movements and pupil diameter during a temporal bisection task in the subsecond range. Subjects were trained to discriminate anchor intervals of 200 or 800 msec, and were then confronted with intermediate durations. Eye movements revealed that subjects used different cognitive strategies during the bisection timing task. When the stimulus to be timed appeared randomly at a central or 4 peripheral positions on a screen, some subjects choose to maintain their gaze toward the central area while other followed the peripheral placement of the stimulus; some others subjects used both strategies. The time of subjective equality did not differ between subjects who employed different attentional mechanisms. However, differences emerged in the timing variance and attentional indexes (time taken to initial fixation, latency to respond, pupil dilatation and duration and number of fixations to stimulus areas). Timing in the subsecond range seems invariant despite the use of different attentional strategies. Future research should determine whether the selection of attentional mechanisms is related to particular timing tasks or instructions or whether it represents idiosyncratic cognitive "styles". PMID:27467762

  16. Dynamic performance of the mechanism of an automatically deployable ROPS.

    PubMed

    Etherton, J R; Cutlip, R G; Harris, J R; Ronaghi, M; Means, K H; Howard, S

    2002-02-01

    The mechanism for an automatically deployable ROPS (AutoROPS) has been designed and tested. This mechanism is part of an innovative project to provide passive protection against rollover fatality to operators of new tractors used in both low-clearance and unrestricted-clearance tasks. The device is a spring-action, telescoping structure that releases on signal to pyrotechnic squibs that actuate release pins. Upper post motion begins when the release pins clear an internal piston. The structure extends until the piston impacts an elastomeric ring and latches at the top position. In lab tests the two-post structure consistently deployed in less than 0.3 s and latched securely. Static load tests of the telescoping structure and field upset tests of the fully functional AutoROPS have been successfully completed. PMID:12002370

  17. Mechanically Flexible and High-Performance CMOS Logic Circuits.

    PubMed

    Honda, Wataru; Arie, Takayuki; Akita, Seiji; Takei, Kuniharu

    2015-01-01

    Low-power flexible logic circuits are key components required by the next generation of flexible electronic devices. For stable device operation, such components require a high degree of mechanical flexibility and reliability. Here, the mechanical properties of low-power flexible complementary metal-oxide-semiconductor (CMOS) logic circuits including inverter, NAND, and NOR are investigated. To fabricate CMOS circuits on flexible polyimide substrates, carbon nanotube (CNT) network films are used for p-type transistors, whereas amorphous InGaZnO films are used for the n-type transistors. The power consumption and voltage gain of CMOS inverters are <500 pW/mm at Vin = 0 V (<7.5 nW/mm at Vin = 5 V) and >45, respectively. Importantly, bending of the substrate is not found to cause significant changes in the device characteristics. This is also observed to be the case for more complex flexible NAND and NOR logic circuits for bending states with a curvature radius of 2.6 mm. The mechanical stability of these CMOS logic circuits makes them ideal candidates for use in flexible integrated devices. PMID:26459882

  18. Comparison of the mechanical performance of trochanteric fixation devices.

    PubMed

    Hersh, C K; Williams, R P; Trick, L W; Lanctot, D; Athanasiou, K

    1996-08-01

    The transtrochanteric surgical approach to the hip is commonly used, especially for revision hip surgery. Failure of the trochanter to heal can lead to hardware failure, persistent pain, and limp. Rigid internal fixation is needed in this approach to achieve an adequate rate of healing. Newer cable and cable grip systems have been designed to improve trochanteric fixation, but have not been compared to the older Charnley wire fixation techniques. In this study, an in vitro mechanical method previously used to test wire fixation methods was used to compare wire, cable, and cable grip fixation methods. A quasistatic mechanical distraction device was used to compare structural stiffness, load to clinical failure, energy to clinical failure, and maximum load resisted by the fixation devices. The cable grip system was found to be stiffer, to resist a larger load to mechanical failure at 1-cm displacement, and to absorb a greater amount of energy to clinical failure when compared with the other systems. These data suggest that use of the cable grip fixation method should result in improved clinical success compared with the Charnley wire technique. PMID:8769467

  19. Mechanically Flexible and High-Performance CMOS Logic Circuits

    PubMed Central

    Honda, Wataru; Arie, Takayuki; Akita, Seiji; Takei, Kuniharu

    2015-01-01

    Low-power flexible logic circuits are key components required by the next generation of flexible electronic devices. For stable device operation, such components require a high degree of mechanical flexibility and reliability. Here, the mechanical properties of low-power flexible complementary metal–oxide–semiconductor (CMOS) logic circuits including inverter, NAND, and NOR are investigated. To fabricate CMOS circuits on flexible polyimide substrates, carbon nanotube (CNT) network films are used for p-type transistors, whereas amorphous InGaZnO films are used for the n-type transistors. The power consumption and voltage gain of CMOS inverters are <500 pW/mm at Vin = 0 V (<7.5 nW/mm at Vin = 5 V) and >45, respectively. Importantly, bending of the substrate is not found to cause significant changes in the device characteristics. This is also observed to be the case for more complex flexible NAND and NOR logic circuits for bending states with a curvature radius of 2.6 mm. The mechanical stability of these CMOS logic circuits makes them ideal candidates for use in flexible integrated devices. PMID:26459882

  20. Creatine Loading, Resistance Exercise Performance, and Muscle Mechanics.

    ERIC Educational Resources Information Center

    Stevenson, Scott W.; Dudley, Gary A.

    2001-01-01

    Examined whether creatine (CR) monohydrate loading would alter resistance exercise performance, isometric strength, or in vivo contractile properties of the quadriceps femoris muscle compared with placebo loading in resistance-trained athletes. Overall, CR loading did not provide an ergogenic benefit for the unilateral dynamic knee extension…

  1. Mechanical performance of fiberglass sucker-rod strings

    SciTech Connect

    Tripp, H.A.

    1988-08-01

    The natural frequencies of fiberglass sucker-rod strings can be calculated by treating the rod strings as modified spring/mass vibration systems. The ratio of the pumping-unit operating speed to the rod-string natural frequency can then be used as a basis for understanding fiberglass-rod performance and for predicting downhole pump stroke lengths.

  2. Detection of Operator Performance Breakdown as an Automation Triggering Mechanism

    NASA Technical Reports Server (NTRS)

    Yoo, Hyo-Sang; Lee, Paul U.; Landry, Steven J.

    2015-01-01

    Performance breakdown (PB) has been anecdotally described as a state where the human operator "loses control of context" and "cannot maintain required task performance." Preventing such a decline in performance is critical to assure the safety and reliability of human-integrated systems, and therefore PB could be useful as a point at which automation can be applied to support human performance. However, PB has never been scientifically defined or empirically demonstrated. Moreover, there is no validated objective way of detecting such a state or the transition to that state. The purpose of this work is: 1) to empirically demonstrate a PB state, and 2) to develop an objective way of detecting such a state. This paper defines PB and proposes an objective method for its detection. A human-in-the-loop study was conducted: 1) to demonstrate PB by increasing workload until the subject reported being in a state of PB, and 2) to identify possible parameters of a detection method for objectively identifying the subjectively-reported PB point, and 3) to determine if the parameters are idiosyncratic to an individual/context or are more generally applicable. In the experiment, fifteen participants were asked to manage three concurrent tasks (one primary and two secondary) for 18 minutes. The difficulty of the primary task was manipulated over time to induce PB while the difficulty of the secondary tasks remained static. The participants' task performance data was collected. Three hypotheses were constructed: 1) increasing workload will induce subjectively-identified PB, 2) there exists criteria that identifies the threshold parameters that best matches the subjectively-identified PB point, and 3) the criteria for choosing the threshold parameters is consistent across individuals. The results show that increasing workload can induce subjectively-identified PB, although it might not be generalizable-only 12 out of 15 participants declared PB. The PB detection method based on

  3. An empirical examination of the mechanisms mediating between high-performance work systems and the performance of Japanese organizations.

    PubMed

    Takeuchi, Riki; Lepak, David P; Wang, Heli; Takeuchi, Kazuo

    2007-07-01

    The resource-based view of the firm and social exchange perspectives are invoked to hypothesize linkages among high-performance work systems, collective human capital, the degree of social exchange in an establishment, and establishment performance. The authors argue that high-performance work systems generate a high level of collective human capital and encourage a high degree of social exchange within an organization, and that these are positively related to the organization's overall performance. On the basis of a sample of Japanese establishments, the results provide support for the existence of these mediating mechanisms through which high-performance work systems affect overall establishment performance. PMID:17638466

  4. Language interoperability mechanisms for high-performance scientific applications

    SciTech Connect

    Cleary, A; Kohn, S; Smith, S G; Smolinski, B

    1998-09-18

    Language interoperability is a difficult problem facing the developers and users of large numerical software packages. Language choices often hamper the reuse and sharing of numerical libraries, especially in a scientific computing environment that uses a breadth of programming languages, including C, c ++, Java, various Fortran dialects, and scripting languages such as Python. In this paper, we propose a new approach to langauge interoparability for high-performance scientific applications based on Interface Definition Language (IDL) techniques. We investigate the modifications necessary to adopt traditional IDL approaches for use by the scientific community, including IDL extensions for numerical computing and issues involved in mapping IDLs to Fortran 77 and Fortran 90.

  5. Refinement performance and mechanism of an Al-50Si alloy

    SciTech Connect

    Dai, H.S.; Liu, X.F.

    2008-11-15

    The microstructure and melt structure of primary silicon particles in an Al-50%Si (wt.%) alloy have been investigated by optical microscopy, scanning electron microscopy, electron probe micro-analysis and a high temperature X-ray diffractometer. The results show that the Al-50Si alloy can be effectively refined by a newly developed Si-20P master alloy, and the melting temperature is crucial to the refinement process. The minimal overheating degree {delta}T{sub min} ({delta}T{sub min} is the difference between the minimal overheating temperature T{sub min} and the liquidus temperature T{sub L}) for good refinement is about 260 deg. C. Primary silicon particles can be refined after adding 0.2 wt.% phosphorus amount at sufficient temperature, and their average size transforms from 2-4 mm to about 30 {mu}m. The X-ray diffraction data of the Al-50Si melt demonstrate that structural change occurs when the melting temperature varies from 1100 deg. C to 1300 deg. C. Additionally, the relationship between the refinement mechanism and the melt structure is discussed.

  6. The performance and operating mechanism of the ultrasonic scrubber

    NASA Astrophysics Data System (ADS)

    Saylor, J. R.; Ran, W.

    2014-11-01

    An ultrasonic standing wave field is commonly used to levitate drops, facilitating drop studies in several ways. In the typical use of such a standing wave field, drops are simply placed at the node of the field and thereby levitated. However, it is also true that any particles or drops located in the general vicinity of the nodes of an ultrasonic standing wave are drawn toward the nodes where they accrue. We have shown that this effect can be used to create an ``ultrasonic scrubber'', wherein the combination of a fine water mist and an ultrasonic standing wave field is used to remove particles (e.g. particulate pollutants) from a gas flow directed at the field (Ran, Saylor, & Holt, J. Aerosol Sci., 67, 104 (2014)). In this talk details are presented of the operating mechanism responsible for the success of this approach to scrubbing. The results of an experimental study are also presented showing the effect of the gas flow rate and droplet size distribution on the scavenging coefficient for one version of the ultrasonic scrubber. Support from NSF is gratefully acknowledged.

  7. A comparative study of the mechanical performance of Glass and Glass/Carbon hybrid polymer composites at different temperature environments

    NASA Astrophysics Data System (ADS)

    Shukla, M. J.; Kumar, D. S.; Mahato, K. K.; Rathore, D. K.; Prusty, R. K.; Ray, B. C.

    2015-02-01

    Glass Fiber Reinforced Polymer (GFRP) composites have been widely accepted as high strength, low weight structural material as compared to their metallic counterparts. Some specific advanced high performance applications such as aerospace components still require superior specific strength and specific modulus. Carbon Fiber Reinforced Polymer (CFRP) composites exhibit superior specific strength and modulus but have a lower failure strain and high cost. Hence, the combination of both glass and carbon fiber in polymer composite may yield optimized mechanical properties. Further the in-service environment has a significant role on the mechanical performance of this class of materials. Present study aims to investigate the mechanical property of GFRP and Glass/Carbon (G/C hybrid) composites at room temperature, in-situ and ex-situ temperature conditions. In-situ testing at +70°C and +100°C results in significant loss in inter-laminar shear strength (ILSS) for both the composites as compared to room temperature. The ILSS was nearly equal for both the composite systems tested in-situ at +100°C and effect of fiber hybridisation was completely diminished there. At low temperature ex-situ conditioning significant reduction in ILSS was observed for both the systems. Further at -60°C G/C hybrid exhibited 32.4 % higher ILSS than GFRP. Hence this makes G/C hybrid a better choice of material in low temperature environmental applications.

  8. Baby-Crying Acceptance

    NASA Astrophysics Data System (ADS)

    Martins, Tiago; de Magalhães, Sérgio Tenreiro

    The baby's crying is his most important mean of communication. The crying monitoring performed by devices that have been developed doesn't ensure the complete safety of the child. It is necessary to join, to these technological resources, means of communicating the results to the responsible, which would involve the digital processing of information available from crying. The survey carried out, enabled to understand the level of adoption, in the continental territory of Portugal, of a technology that will be able to do such a digital processing. It was used the TAM as the theoretical referential. The statistical analysis showed that there is a good probability of acceptance of such a system.

  9. Branch classification: A new mechanism for improving branch predictor performance

    SciTech Connect

    Chang, P.Y.; Hao, E.; Patt, Y.; Yeh, T.Y.

    1996-04-01

    There is wide agreement that one of the most significant impediments to the performance of current and future pipelined superscalar processors is the presence of conditional branches in the instruction stream. Speculative execution is one solution to the branch problem, but speculative work is discarded if a branch is mispredicted. For it to be effective, speculative work is discarded if a branch is mispredicted. For it to be effective, speculative execution requires a very accurate branch predictor; 95% accuracy is not good enough. This paper proposes branch classification, a methodology for building more accurate branch predictors. Branch classification allows an individual branch instruction to be associated with the branch predictor best suited to predict its direction. Using this approach, a hybrid branch predictor can be constructed such that each component branch predictor predicts those branches for which it is best suited. To demonstrate the usefulness of branch classification, an example classification scheme is given and a new hybrid predictor is built based on this scheme which achieves a higher prediction accuracy than any branch predictor previously reported in the literature.

  10. High-precision cryogenic wheel mechanisms of the JWST/MIRI instrument: performance of the flight models

    NASA Astrophysics Data System (ADS)

    Krause, O.; Müller, F.; Birkmann, S.; Böhm, A.; Ebert, M.; Grözinger, U.; Henning, Th.; Hofferbert, R.; Huber, A.; Lemke, D.; Rohloff, R.-R.; Scheithauer, S.; Gross, T.; Fischer, T.; Luichtel, G.; Merkle, H.; Übele, M.; Wieland, H.-U.; Amiaux, J.; Jager, R.; Glauser, A.; Parr-Burman, P.; Sykes, J.

    2010-07-01

    The Mid Infrared Instrument (MIRI) aboard JWST is equipped with one filter wheel and two dichroic-grating wheel mechanisms to reconfigure the instrument between observing modes such as broad/narrow-band imaging, coronagraphy and low/medium resolution spectroscopy. Key requirements for the three mechanisms with up to 18 optical elements on the wheel include: (1) reliable operation at T = 7 K, (2) high positional accuracy of 4 arcsec, (3) low power dissipation, (4) high vibration capability, (5) functionality at 7 K < T < 300 K and (6) long lifetime (5-10 years). To meet these requirements a space-proven wheel concept consisting of a central MoS2-lubricated integrated ball bearing, a central torque motor for actuation, a ratchet system with monolithic CuBe flexural pivots for precise and powerless positioning and a magnetoresistive position sensor has been implemented. We report here the final performance and lessons-learnt from the successful acceptance test program of the MIRI wheel mechanism flight models. The mechanisms have been meanwhile integrated into the flight model of the MIRI instrument, ready for launch in 2014 by an Ariane 5 rocket.

  11. Energy efficient mechanisms for high-performance Wireless Sensor Networks

    NASA Astrophysics Data System (ADS)

    Alsaify, Baha'adnan

    2009-12-01

    Due to recent advances in microelectronics, the development of low cost, small, and energy efficient devices became possible. Those advances led to the birth of the Wireless Sensor Networks (WSNs). WSNs consist of a large set of sensor nodes equipped with communication capabilities, scattered in the area to monitor. Researchers focus on several aspects of WSNs. Such aspects include the quality of service the WSNs provide (data delivery delay, accuracy of data, etc...), the scalability of the network to contain thousands of sensor nodes (the terms node and sensor node are being used interchangeably), the robustness of the network (allowing the network to work even if a certain percentage of nodes fails), and making the energy consumption in the network as low as possible to prolong the network's lifetime. In this thesis, we present an approach that can be applied to the sensing devices that are scattered in an area for Sensor Networks. This work will use the well-known approach of using a awaking scheduling to extend the network's lifespan. We designed a scheduling algorithm that will reduce the delay's upper bound the reported data will experience, while at the same time keeps the advantages that are offered by the use of the awaking scheduling -- the energy consumption reduction which will lead to the increase in the network's lifetime. The wakeup scheduling is based on the location of the node relative to its neighbors and its distance from the Base Station (the terms Base Station and sink are being used interchangeably). We apply the proposed method to a set of simulated nodes using the "ONE Simulator". We test the performance of this approach with three other approaches -- Direct Routing technique, the well known LEACH algorithm, and a multi-parent scheduling algorithm. We demonstrate a good improvement on the network's quality of service and a reduction of the consumed energy.

  12. Enhancement mechanisms of graphene in nano-58S bioactive glass scaffold: mechanical and biological performance

    PubMed Central

    Gao, Chengde; Liu, Tingting; Shuai, Cijun; Peng, Shuping

    2014-01-01

    Graphene is a novel material and currently popular as an enabler for the next-generation nanocomposites. Here, we report the use of graphene to improve the mechanical properties of nano-58S bioactive glass for bone repair and regeneration. And the composite scaffolds were fabricated by a homemade selective laser sintering system. Qualitative and quantitative analysis demonstrated the successful incorporation of graphene into the scaffold without obvious structural damage and weight loss. The optimum compressive strength and fracture toughness reached 48.65 ± 3.19 MPa and 1.94 ± 0.10 MPa·m1/2 with graphene content of 0.5 wt%, indicating significant improvements by 105% and 38% respectively. The mechanisms of pull-out, crack bridging, crack deflection and crack tip shielding were found to be responsible for the mechanical enhancement. Simulated body fluid and cell culture tests indicated favorable bioactivity and biocompatibility of the composite scaffold. The results suggest a great potential of graphene/nano-58S composite scaffold for bone tissue engineering applications. PMID:24736662

  13. Can we respond mindfully to distressing voices? A systematic review of evidence for engagement, acceptability, effectiveness and mechanisms of change for mindfulness-based interventions for people distressed by hearing voices

    PubMed Central

    Strauss, Clara; Thomas, Neil; Hayward, Mark

    2015-01-01

    Adapted mindfulness-based interventions (MBIs) could be of benefit for people distressed by hearing voices. This paper presents a systematic review of studies exploring this possibility and we ask five questions: (1) Is trait mindfulness associated with reduced distress and disturbance in relation to hearing voices? (2) Are MBIs feasible for people distressed by hearing voices? (3) Are MBIs acceptable and safe for people distressed by hearing voices? (4) Are MBIs effective at reducing distress and disturbance in people distressed by hearing voices? (5) If effective, what are the mechanisms of change through which MBIs for distressing voices work? Fifteen studies were identified through a systematic search (n = 479). In relation to the five review questions: (1) data from cross-sectional studies showed an association between trait mindfulness and distress and disturbance in relation to hearing voices; (2) evidence from qualitative studies suggested that people distressed by hearing voices could engage meaningfully in mindfulness practice; (3) MBIs were seen as acceptable and safe; (4) there were no adequately powered RCTs allowing conclusions about effectiveness to be drawn; and (5) it was not possible to draw on robust empirical data to comment on potential mechanisms of change although findings from the qualitative studies identified three potential change processes; (i) reorientation of attention; (ii) decentring; and (iii) acceptance of voices. This review provided evidence that MBIs are engaging, acceptable, and safe. Evidence for effectiveness in reducing distress and disturbance is lacking however. We call for funding for adequately powered RCTs that will allow questions of effectiveness, maintenance of effects, mechanisms of change and moderators of outcome to be definitively addressed. PMID:26321980

  14. Can we respond mindfully to distressing voices? A systematic review of evidence for engagement, acceptability, effectiveness and mechanisms of change for mindfulness-based interventions for people distressed by hearing voices.

    PubMed

    Strauss, Clara; Thomas, Neil; Hayward, Mark

    2015-01-01

    Adapted mindfulness-based interventions (MBIs) could be of benefit for people distressed by hearing voices. This paper presents a systematic review of studies exploring this possibility and we ask five questions: (1) Is trait mindfulness associated with reduced distress and disturbance in relation to hearing voices? (2) Are MBIs feasible for people distressed by hearing voices? (3) Are MBIs acceptable and safe for people distressed by hearing voices? (4) Are MBIs effective at reducing distress and disturbance in people distressed by hearing voices? (5) If effective, what are the mechanisms of change through which MBIs for distressing voices work? Fifteen studies were identified through a systematic search (n = 479). In relation to the five review questions: (1) data from cross-sectional studies showed an association between trait mindfulness and distress and disturbance in relation to hearing voices; (2) evidence from qualitative studies suggested that people distressed by hearing voices could engage meaningfully in mindfulness practice; (3) MBIs were seen as acceptable and safe; (4) there were no adequately powered RCTs allowing conclusions about effectiveness to be drawn; and (5) it was not possible to draw on robust empirical data to comment on potential mechanisms of change although findings from the qualitative studies identified three potential change processes; (i) reorientation of attention; (ii) decentring; and (iii) acceptance of voices. This review provided evidence that MBIs are engaging, acceptable, and safe. Evidence for effectiveness in reducing distress and disturbance is lacking however. We call for funding for adequately powered RCTs that will allow questions of effectiveness, maintenance of effects, mechanisms of change and moderators of outcome to be definitively addressed. PMID:26321980

  15. Performance Level in Situations of Helplessness Threat and Group Affiliation: Egotistic Mechanisms in Helplessness Deficits.

    ERIC Educational Resources Information Center

    Witkowski, Tomasz

    1997-01-01

    Tests the egotism hypothesis for poor performance following insoluble problems, and investigates the contribution of egotistic mechanisms to performance in perceived group affiliation and helpless threat conditions. Reports that participants in the failure and group-affiliation conditions performed better than others. Observes that this supports…

  16. Fibrous nanocomposites of carbon nanotubes and graphene-oxide with synergetic mechanical and actuative performance.

    PubMed

    Wang, Ranran; Sun, Jing; Gao, Lian; Xu, Chaohe; Zhang, Jing

    2011-08-14

    Fibrous nanocomposites of carbon nanotubes, graphene-oxide or graphene were prepared by a simple coagulation spinning technique exhibiting synergetic enhancement of mechanical strength, electronic conductivity and electrical actuation performance. PMID:21725531

  17. 46 CFR 160.133-7 - Design, construction, and performance of release mechanisms.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 6 2012-10-01 2012-10-01 false Design, construction, and performance of release mechanisms. 160.133-7 Section 160.133-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Release Mechanisms for Lifeboats and Rescue Boats (SOLAS)...

  18. 46 CFR 160.133-7 - Design, construction, and performance of release mechanisms.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 6 2013-10-01 2013-10-01 false Design, construction, and performance of release mechanisms. 160.133-7 Section 160.133-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Release Mechanisms for Lifeboats and Rescue Boats (SOLAS)...

  19. The significance of task significance: Job performance effects, relational mechanisms, and boundary conditions.

    PubMed

    Grant, Adam M

    2008-01-01

    Does task significance increase job performance? Correlational designs and confounded manipulations have prevented researchers from assessing the causal impact of task significance on job performance. To address this gap, 3 field experiments examined the performance effects, relational mechanisms, and boundary conditions of task significance. In Experiment 1, fundraising callers who received a task significance intervention increased their levels of job performance relative to callers in 2 other conditions and to their own prior performance. In Experiment 2, task significance increased the job dedication and helping behavior of lifeguards, and these effects were mediated by increases in perceptions of social impact and social worth. In Experiment 3, conscientiousness and prosocial values moderated the effects of task significance on the performance of new fundraising callers. The results provide fresh insights into the effects, relational mechanisms, and boundary conditions of task significance, offering noteworthy implications for theory, research, and practice on job design, social information processing, and work motivation and performance. PMID:18211139

  20. Effects of Crimping on Mechanical Performance of Nitinol Stent Designed for Femoral Artery: Finite Element Analysis

    NASA Astrophysics Data System (ADS)

    Nematzadeh, F.; Sadrnezhaad, S. K.

    2013-11-01

    Nitinol stents are used to minimize improper dynamic behavior, low twistability, and inadequate radial mechanical strength of femoral artery stents. In this study, finite element method is used to investigate the effect of crimping and Austenite finish temperature ( A f) of Nitinol on mechanical performance of Z-shaped open-cell femoral stent under crimping conditions. Results show that low A f Nitinol has better mechanical and clinical performance due to small chronic outward force, large radial resistive force, and appropriate superelastic behavior.

  1. The Mechanics of Social Capital and Academic Performance in an Indian College

    ERIC Educational Resources Information Center

    Hasan, Sharique; Bagde, Surendrakumar

    2013-01-01

    In this article we examine how social capital affects the creation of human capital. Specifically, we study how college students' peers affect academic performance. Building on existing research, we consider the different types of peers in the academic context and the various mechanisms through which peers affect performance. We test our…

  2. Mother-Child Attachment and Cognitive Performance in Middle Childhood: An Examination of Mediating Mechanisms

    ERIC Educational Resources Information Center

    West, Katara K.; Mathews, Brittany L.; Kerns, Kathryn A.

    2013-01-01

    Although mother-child attachment has been shown to predict cognitive performance, there has been a lack of attention to the mediating mechanisms that explain these associations. In the present study, we investigated relations of early mother-child attachment and cognitive performance in middle childhood (the latter in terms of both academic…

  3. Mechanism of Isoflavone Aglycone's Effect on Cognitive Performance of Senescence-Accelerated Mice

    ERIC Educational Resources Information Center

    Yang, Hong; Jin, Guifang; Ren, Dongdong; Luo, Sijing; Zhou, Tianhong

    2011-01-01

    This study investigated the effect of isoflavone aglycone (IA) on the learning and memory performance of senescence-accelerated mice, and explored its neural protective mechanism. Results showed that SAM-P/8 senescence-accelerated mice treated with IA performed significantly better in the Y-maze cognitive test than the no treatment control (P less…

  4. The Evaluation of Higher Education Expenditure Performance and Investment Mechanism Reform

    ERIC Educational Resources Information Center

    Wang, De; Fu, Meiying

    2009-01-01

    Along with the reform of Chinese Government public finance, higher education belongs to the public product, gradually changes from "fund investment management" to the "expenditure performance management". The evaluation of expenditure performance system becomes the key point of higher education investment mechanism reform. This…

  5. Determination of biogenic amines by high-performance liquid chromatography (HPLC-DAD) in probiotic cow's and goat's fermented milks and acceptance.

    PubMed

    Costa, Marion P; Balthazar, Celso F; Rodrigues, Bruna L; Lazaro, Cesar A; Silva, Adriana C O; Cruz, Adriano G; Conte Junior, Carlos A

    2015-05-01

    This study evaluated the presence of biogenic amines in fermented cow's and goat's milks containing probiotic bacteria, during the first 10 days of chilled storage (4 ± 2°C), when the probiotic strains are most viable. The overall acceptance of both fermented milks, produced using the same starter culture and probiotics, was tested. In both products, the initially high levels of tyramine (560 mg kg(-1) means for both fermented milks), the predominant biogenic amine, increased during the storage period, which may be considered this amine as a quality index for fermented milks. The other principal biogenic amines (putrescine, cadaverine, histamine, and spermidine) were produced on days 1-5 of storage, and thereafter decreased. At the end of the 10th day, these amines, respectively, showed values of fermented cow's milk 20.26, 29.09, 17.97, and 82.07 mg kg(-1); and values of fermented goat's milk 22.92, 29.09, 34.85, and 53.85 mg kg(-1), in fermented cow's and goat's milk. Fermented cow's milk was well accepted compared to fermented goat's milk. The results suggested that the content of biogenic amines may be a criterion for selecting lactic acid bacteria used to produce fermented milks. PMID:25987991

  6. Determination of biogenic amines by high-performance liquid chromatography (HPLC-DAD) in probiotic cow's and goat's fermented milks and acceptance

    PubMed Central

    Costa, Marion P; Balthazar, Celso F; Rodrigues, Bruna L; Lazaro, Cesar A; Silva, Adriana C O; Cruz, Adriano G; Conte Junior, Carlos A

    2015-01-01

    This study evaluated the presence of biogenic amines in fermented cow's and goat's milks containing probiotic bacteria, during the first 10 days of chilled storage (4 ± 2°C), when the probiotic strains are most viable. The overall acceptance of both fermented milks, produced using the same starter culture and probiotics, was tested. In both products, the initially high levels of tyramine (560 mg kg−1 means for both fermented milks), the predominant biogenic amine, increased during the storage period, which may be considered this amine as a quality index for fermented milks. The other principal biogenic amines (putrescine, cadaverine, histamine, and spermidine) were produced on days 1–5 of storage, and thereafter decreased. At the end of the 10th day, these amines, respectively, showed values of fermented cow's milk 20.26, 29.09, 17.97, and 82.07 mg kg−1; and values of fermented goat's milk 22.92, 29.09, 34.85, and 53.85 mg kg−1, in fermented cow's and goat's milk. Fermented cow's milk was well accepted compared to fermented goat's milk. The results suggested that the content of biogenic amines may be a criterion for selecting lactic acid bacteria used to produce fermented milks. PMID:25987991

  7. Freeform solar concentrator with a highly asymmetric acceptance cone

    NASA Astrophysics Data System (ADS)

    Wheelwright, Brian; Angel, J. Roger P.; Coughenour, Blake; Hammer, Kimberly

    2014-10-01

    A solar concentrator with a highly asymmetric acceptance cone is investigated. Concentrating photovoltaic systems require dual-axis sun tracking to maintain nominal concentration throughout the day. In addition to collecting direct rays from the solar disk, which subtends ~0.53 degrees, concentrating optics must allow for in-field tracking errors due to mechanical misalignment of the module, wind loading, and control loop biases. The angular range over which the concentrator maintains <90% of on-axis throughput is defined as the optical acceptance angle. Concentrators with substantial rotational symmetry likewise exhibit rotationally symmetric acceptance angles. In the field, this is sometimes a poor match with azimuth-elevation trackers, which have inherently asymmetric tracking performance. Pedestal-mounted trackers with low torsional stiffness about the vertical axis have better elevation tracking than azimuthal tracking. Conversely, trackers which rotate on large-footprint circular tracks are often limited by elevation tracking performance. We show that a line-focus concentrator, composed of a parabolic trough primary reflector and freeform refractive secondary, can be tailored to have a highly asymmetric acceptance angle. The design is suitable for a tracker with excellent tracking accuracy in the elevation direction, and poor accuracy in the azimuthal direction. In the 1000X design given, when trough optical errors (2mrad rms slope deviation) are accounted for, the azimuthal acceptance angle is +/- 1.65°, while the elevation acceptance angle is only +/-0.29°. This acceptance angle does not include the angular width of the sun, which consumes nearly all of the elevation tolerance at this concentration level. By decreasing the average concentration, the elevation acceptance angle can be increased. This is well-suited for a pedestal alt-azimuth tracker with a low cost slew bearing (without anti-backlash features).

  8. Mechanical Performance and Failure Mechanism of Thick-walled Composite Connecting Rods Fabricated by Resin Transfer Molding Technique

    NASA Astrophysics Data System (ADS)

    Liu, Gang; Luo, Chuyang; Zhang, Daijun; Li, Xueqin; Qu, Peng; Sun, Xiaochen; Jia, Yuxi; Yi, Xiaosu

    2015-08-01

    A resin transfer molding technique was used to fabricate thick-walled composite connecting rods, and then the mechanical performance of the connecting rod was studied experimentally, at the same time the stress and failure index distributions were simulated numerically. The experimental results show that under a tensile load, the connecting rod first cracks near the vertex of the triangle areas at the two ends, and then the damage propagates along the interface between the main bearing beam and the triangle area as well as along the round angle of the triangle area. Whereas under a compressive load, the delamination primarily occurs at the corner of the U-shaped flange, and the final destruction is caused by the fracture of fibers in the main bearing beam. The simulated results reveal that the tensile failure is originated from the delamination at the round angle transition areas of the T-joints, and the failure strength is determined by the interlaminar strength. Whereas the compressive failure is caused by the fracture of fibers in the main bearing beam, and the failure strength of the structure is determined by the longitudinal compressive strength of the composite material. The simulated results are basically consistent with the experimental results. Hence the mechanical performance and failure mechanism of the complicated composite structure are revealed in great detail through the coupling of the two kinds of research methods, which is helpful for the optimal design of composite structures.

  9. The effect of challenge and threat states on performance: An examination of potential mechanisms

    PubMed Central

    Moore, Lee J; Vine, Samuel J; Wilson, Mark R; Freeman, Paul

    2012-01-01

    Challenge and threat states predict future performance; however, no research has examined their immediate effect on motor task performance. The present study examined the effect of challenge and threat states on golf putting performance and several possible mechanisms. One hundred twenty-seven participants were assigned to a challenge or threat group and performed six putts during which emotions, gaze, putting kinematics, muscle activity, and performance were recorded. Challenge and threat states were successively manipulated via task instructions. The challenge group performed more accurately, reported more favorable emotions, and displayed more effective gaze, putting kinematics, and muscle activity than the threat group. Multiple putting kinematic variables mediated the relationship between group and performance, suggesting that challenge and threat states impact performance at a predominately kinematic level. PMID:22913339

  10. The Effects of a Brief Acceptance-Based Behavioral Treatment Versus Traditional Cognitive-Behavioral Treatment for Public Speaking Anxiety: An Exploratory Trial Examining Differential Effects on Performance and Neurophysiology.

    PubMed

    Glassman, Lisa H; Forman, Evan M; Herbert, James D; Bradley, Lauren E; Foster, Elizabeth E; Izzetoglu, Meltem; Ruocco, Anthony C

    2016-09-01

    Individuals with public speaking anxiety (PSA) experience fear and avoidance that can cause extreme distress, impaired speaking performance, and associated problems in psychosocial functioning. Most extant interventions for PSA emphasize anxiety reduction rather than enhancing behavioral performance. We compared the efficacy of two brief cognitive-behavioral interventions, a traditional cognitive-behavior treatment (tCBT) and an acceptance-based behavior treatment (ABBT), on public speaking performance and anxiety in a clinical sample of persons with PSA. The effects of treatment on prefrontal brain activation were also examined. Participants (n = 21) were randomized to 90 min of an ABBT or a tCBT intervention. Assessments took place at pre- and post-treatment and included self-rated anxiety and observer-rated performance measures, a behavioral assessment, and prefrontal cortical activity measurements using functional near-infrared spectroscopy (fNIRS). Exploratory results indicated that participants in the ABBT condition experienced greater improvements in observer-rated performance relative to those in the tCBT condition, while those in the tCBT condition experienced greater reductions in subjective anxiety levels. Individuals in the ABBT condition also exhibited a trend toward greater treatment-related reductions in blood volume in the left dorsolateral prefrontal cortex relative to those who received tCBT. Overall, these findings preliminarily suggest that acceptance-based treatments may free more cognitive resources in comparison with tCBT, possibly resulting in greater improvements in objectively rated behavioral performances for ABBT interventions. PMID:26872958

  11. Optimal design of a main driving mechanism for servo punch press based on performance atlases

    NASA Astrophysics Data System (ADS)

    Zhou, Yanhua; Xie, Fugui; Liu, Xinjun

    2013-09-01

    The servomotor drive turret punch press is attracting more attentions and being developed more intensively due to the advantages of high speed, high accuracy, high flexibility, high productivity, low noise, cleaning and energy saving. To effectively improve the performance and lower the cost, it is necessary to develop new mechanisms and establish corresponding optimal design method with uniform performance indices. A new patented main driving mechanism and a new optimal design method are proposed. In the optimal design, the performance indices, i.e., the local motion/force transmission indices ITI, OTI, good transmission workspace good transmission workspace(GTW) and the global transmission indices GTIs are defined. The non-dimensional normalization method is used to get all feasible solutions in dimensional synthesis. Thereafter, the performance atlases, which can present all possible design solutions, are depicted. As a result, the feasible solution of the mechanism with good motion/force transmission performance is obtained. And the solution can be flexibly adjusted by designer according to the practical design requirements. The proposed mechanism is original, and the presented design method provides a feasible solution to the optimal design of the main driving mechanism for servo punch press.

  12. Computational Bench Testing to Evaluate the Short-Term Mechanical Performance of a Polymeric Stent.

    PubMed

    Bobel, A C; Petisco, S; Sarasua, J R; Wang, W; McHugh, P E

    2015-12-01

    Over the last decade, there has been a significant volume of research focussed on the utilization of biodegradable polymers such as poly-L-lactide-acid (PLLA) for applications associated with cardiovascular disease. More specifically, there has been an emphasis on upgrading current clinical shortfalls experienced with conventional bare metal stents and drug eluting stents. One such approach, the adaption of fully formed polymeric stents has led to a small number of products being commercialized. Unfortunately, these products are still in their market infancy, meaning there is a clear non-occurrence of long term data which can support their mechanical performance in vivo. Moreover, the load carry capacity and other mechanical properties essential to a fully optimized polymeric stent are difficult, timely and costly to establish. With the aim of compiling rapid and representative performance data for specific stent geometries, materials and designs, in addition to reducing experimental timeframes, Computational bench testing via finite element analysis (FEA) offers itself as a very powerful tool. On this basis, the research presented in this paper is concentrated on the finite element simulation of the mechanical performance of PLLA, which is a fully biodegradable polymer, in the stent application, using a non-linear viscous material model. Three physical stent geometries, typically used for fully polymeric stents, are selected, and a comparative study is performed in relation to their short-term mechanical performance, with the aid of experimental data. From the simulated output results, an informed understanding can be established in relation to radial strength, flexibility and longitudinal resistance, that can be compared with conventional permanent metal stent functionality, and the results show that it is indeed possible to generate a PLLA stent with comparable and sufficient mechanical performance. The paper also demonstrates the attractiveness of FEA as a tool

  13. Mechanical Work Performed by the Individual Legs during Uphill and Downhill Walking

    PubMed Central

    Franz, Jason R.; Lyddon, Nicholas E.; Kram, Rodger

    2011-01-01

    Previous studies of the mechanical work performed during uphill and downhill walking have neglected the simultaneous negative and positive work performed by the leading and trailing legs during double support. Our goal was to quantify the mechanical work performed by the individual legs across a range of uphill and downhill grades. We hypothesized that during double support, 1) with steeper uphill grade, the negative work performed by the leading leg would become negligible and the trailing leg would perform progressively greater positive work to raise the center of mass (CoM), and 2) with steeper downhill grade, the leading leg would perform progressively greater negative work to lower the CoM and the positive work performed by the trailing leg would become negligible. 11 healthy young adults (6M/5F, 71.0 ± 12.3 kg) walked at 1.25 m/s on a dual-belt force-measuring treadmill at seven grades (0, ±3, ±6, ±9°). We collected three-dimensional ground reaction forces (GRFs) and used the individual limbs method to calculate the mechanical work performed by each leg. As hypothesized, the trailing leg performed progressively greater positive work with steeper uphill grade, and the leading leg performed progressively greater negative work with steeper downhill grade (p<0.005). To our surprise, unlike level-ground walking, during double support the leading leg performed considerable positive work when walking uphill and the trailing leg performed considerable negative work when walking downhill (p<0.005). To understand how humans walk uphill and downhill, it is important to consider these revealing biomechanical aspects of individual leg function and interaction during double support. PMID:22099148

  14. ATLAS ACCEPTANCE TEST

    SciTech Connect

    J.C. COCHRANE; J.V. PARKER; ET AL

    2001-06-01

    The acceptance test program for Atlas, a 23 MJ pulsed power facility for use in the Los Alamos High Energy Density Hydrodynamics program, has been completed. Completion of this program officially releases Atlas from the construction phase and readies it for experiments. Details of the acceptance test program results and of machine capabilities for experiments will be presented.

  15. Steam generator tube integrity flaw acceptance criteria

    SciTech Connect

    Cochet, B.

    1997-02-01

    The author discusses the establishment of a flaw acceptance criteria with respect to flaws in steam generator tubing. The problem is complicated because different countries take different approaches to the problem. The objectives in general are grouped in three broad areas: to avoid the unscheduled shutdown of the reactor during normal operation; to avoid tube bursts; to avoid excessive leak rates in the event of an accidental overpressure event. For each degradation mechanism in the tubes it is necessary to know answers to an array of questions, including: how well does NDT testing perform against this problem; how rapidly does such degradation develop; how well is this degradation mechanism understood. Based on the above information it is then possible to come up with a policy to look at flaw acceptance. Part of this criteria is a schedule for the frequency of in-service inspection and also a policy for when to plug flawed tubes. The author goes into a broad discussion of each of these points in his paper.

  16. An Evaluation of Controller and Pilot Performance, Workload and Acceptability under a NextGen Concept for Dynamic Weather Adapted Arrival Routing

    NASA Technical Reports Server (NTRS)

    Johnson, Walter W.; Lachter, Joel; Brandt, Summer; Koteskey, Robert; Dao, Arik-Quang; Kraut, Josh; Ligda, Sarah; Battiste, Vernol

    2012-01-01

    In todays terminal operations, controller workload increases and throughput decreases when fixed standard terminal arrival routes (STARs) are impacted by storms. To circumvent this operational constraint, Prete, Krozel, Mitchell, Kim and Zou (2008) proposed to use automation to dynamically adapt arrival and departure routing based on weather predictions. The present study examined this proposal in the context of a NextGen trajectory-based operation concept, focusing on the acceptability and its effect on the controllers ability to manage traffic flows. Six controllers and twelve transport pilots participated in a human-in-the-loop simulation of arrival operations into Louisville International Airport with interval management requirements. Three types of routing structures were used: Static STARs (similar to current routing, which require the trajectories of individual aircraft to be modified to avoid the weather), Dynamic routing (automated adaptive routing around weather), and Dynamic Adjusted routing (automated adaptive routing around weather with aircraft entry time adjusted to account for differences in route length). Spacing Responsibility, whether responsibility for interval management resided with the controllers (as today), or resided with the pilot (who used a flight deck based automated spacing algorithm), was also manipulated. Dynamic routing as a whole was rated superior to static routing, especially by pilots, both in terms of workload reduction and flight path safety. A downside of using dynamic routing was that the paths flown in the dynamic conditions tended to be somewhat longer than the paths flown in the static condition.

  17. Research on the hydration, hardening mechanism, and microstructure of high performance expansive concrete

    SciTech Connect

    Hu Shuguang; Li Yue

    1999-07-01

    High performance expansive fly ash concrete (HPEC) was prepared and the differences of mechanical properties between the high performance concrete and HPEC were compared under free- and confined-curing conditions. By means of XRD and SEM methods, the hydration progress and microstructure of HPEC were investigated. The results show that an expansive agent is useful and the confinement action could improve the microstructure of hardened expansive concrete.

  18. Fatigue performance of medical Ti6Al4V alloy after mechanical surface treatments.

    PubMed

    Sonntag, Robert; Reinders, Jörn; Gibmeier, Jens; Kretzer, J Philippe

    2015-01-01

    Mechanical surface treatments have a long history in traditional engineering disciplines, such as the automotive or aerospace industries. Today, they are widely applied to metal components to increase the mechanical performance of these. However, their application in the medical field is rather rare. The present study aims to compare the potential of relevant mechanical surface treatments on the high cycle fatigue (R = 0.1 for a maximum of 10 million cycles) performance of a Ti6Al4V standard alloy for orthopedic, spinal, dental and trauma surgical implants: shot peening, deep rolling, ultrasonic shot peening and laser shock peening. Hour-glass shaped Ti6Al4V specimens were treated and analyzed with regard to the material's microstructure, microhardness, residual stress depth profiles and the mechanical behavior during fatigue testing. All treatments introduced substantial compressive residual stresses and exhibited considerable potential for increasing fatigue performance from 10% to 17.2% after laser shock peening compared to non-treated samples. It is assumed that final mechanical surface treatments may also increase fretting wear resistance in the modular connection of total hip and knee replacements. PMID:25823001

  19. Fatigue Performance of Medical Ti6Al4V Alloy after Mechanical Surface Treatments

    PubMed Central

    Sonntag, Robert; Reinders, Jörn; Gibmeier, Jens; Kretzer, J. Philippe

    2015-01-01

    Mechanical surface treatments have a long history in traditional engineering disciplines, such as the automotive or aerospace industries. Today, they are widely applied to metal components to increase the mechanical performance of these. However, their application in the medical field is rather rare. The present study aims to compare the potential of relevant mechanical surface treatments on the high cycle fatigue (R = 0.1 for a maximum of 10 million cycles) performance of a Ti6Al4V standard alloy for orthopedic, spinal, dental and trauma surgical implants: shot peening, deep rolling, ultrasonic shot peening and laser shock peening. Hour-glass shaped Ti6Al4V specimens were treated and analyzed with regard to the material’s microstructure, microhardness, residual stress depth profiles and the mechanical behavior during fatigue testing. All treatments introduced substantial compressive residual stresses and exhibited considerable potential for increasing fatigue performance from 10% to 17.2% after laser shock peening compared to non-treated samples. It is assumed that final mechanical surface treatments may also increase fretting wear resistance in the modular connection of total hip and knee replacements. PMID:25823001

  20. Mechanical properties of high performance fibers vis-a-vis applications in flexible structural composites

    NASA Astrophysics Data System (ADS)

    Sharma, Varunesh

    Some of the critical properties of high performance organic fibers and fiber assemblies have been addressed vis-a-vis their applications in flexible structural composites. These include: tensile properties; mechanical properties under complex modes of deformation; creep at high tensile loads; changes in physical properties due to thermo-mechanical/chemical treatments used in manufacturing of reinforced rubber goods. The axial elastic modulus of fibers and tautly twisted filament assemblies of high performance organic polymers have been measured along with their crystalline orientation distributions. Based on well established procedures in continuum mechanics of axially symmetric structures, a quantitative relationship has been derived to relate the axial elastic modulus to the second and fourth moment of average crystalline orientation distribution. The latter was determined by X-ray diffraction measurements with yarns. This model, valid for single-phase materials, has been found to provide an excellent fit of data from twisted yams of aromatic polyamide and highly ordered polyethylene fibers, with a wide range of overall crystalline orientation distributions. An important property of concern in engineering applications of polymeric filament assemblies of high performance organic fibers is creep. In this study, creep deformation data of gel-spun Ultra High Molecular Weight Polyethylne (UHMWPE) SpectraRTM 1000 yams have been fitted to a model obtained through an empirical mechanical analog of the viscoelastic process. The non-linear viscoelastic model composed of stress-dependent non-linear mechanical analogs qualitatively predicted the creep response to a series of step-loads applied on the UHMWPE yarns. To understand the mechanical properties of high performance organic fibers under combined bending and extension, a simple pin-test procedure has been employed to characterize fibers and twisted yarns. The results obtained from the test have been interpreted with

  1. 46 CFR 160.170-7 - Design, construction, and performance of automatic release mechanisms.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 6 2012-10-01 2012-10-01 false Design, construction, and performance of automatic release mechanisms. 160.170-7 Section 160.170-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Davit-Launched Liferaft Automatic Release Hooks...

  2. 46 CFR 160.170-7 - Design, construction, and performance of automatic release mechanisms.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 6 2013-10-01 2013-10-01 false Design, construction, and performance of automatic release mechanisms. 160.170-7 Section 160.170-7 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Davit-Launched Liferaft Automatic Release Hooks...

  3. Derivation of Performance Statements for the Automotive Mechanics Basic Trade Course: Research Documentation.

    ERIC Educational Resources Information Center

    Fox, A. P.; Kuhl, D. H.

    A project was conducted to derive a comprehensive list of the performances of a competence mechanic to satisfy the planning needs of automotive engineering lecturers, curriculum committees, researchers, course designers, and staff developers. A list of 127 tasks together with information about their relative importance and the frequency with which…

  4. Engine Performance (Section C: Emission Control Systems). Auto Mechanics Curriculum Guide. Module 3. Instructor's Guide.

    ERIC Educational Resources Information Center

    Rains, Larry

    This engine performance (emission control systems) module is one of a series of competency-based modules in the Missouri Auto Mechanics Curriculum Guide. Topics of this module's five units are: positive crankcase ventilation (PCV) and evaporative emission control systems; exhaust gas recirculation (EGR); air injection and catalytic converters;…

  5. Articulated, Performance-Based Instruction Objectives Guide for Automotive Mechanics. Final Document. Revised.

    ERIC Educational Resources Information Center

    Henderson, William Edward, Jr.

    Developed during a project designed to provide continuous, performance-based vocational training at the secondary and postsecondary levels, this instructional guide is intended to help teachers implement a laterally and vertically articulated secondary level automotive mechanics program. Introductory materials include descriptions of Automotive…

  6. Improving Performance in Quantum Mechanics with Explicit Incentives to Correct Mistakes

    ERIC Educational Resources Information Center

    Brown, Benjamin R.; Mason, Andrew; Singh, Chandralekha

    2016-01-01

    An earlier investigation found that the performance of advanced students in a quantum mechanics course did not automatically improve from midterm to final exam on identical problems even when they were provided the correct solutions and their own graded exams. Here, we describe a study, which extended over four years, in which upper-level…

  7. Panoptic Performativity and School Inspection Regimes: Disciplinary Mechanisms and Life under Special Measures

    ERIC Educational Resources Information Center

    Perryman, Jane

    2006-01-01

    This paper looks at Ofsted and particularly special measures regimes as part of a disciplinary mechanism. It examines issues such as school effectiveness theories, the increasing powers of Ofsted, and life under special measures and links it to performativity, discipline and surveillance using the metaphor of the panopticon. The change in…

  8. Dynamic model and performance analysis of landing buffer for bionic locust mechanism

    NASA Astrophysics Data System (ADS)

    Chen, Dian-Sheng; Zhang, Zi-Qiang; Chen, Ke-Wei

    2016-06-01

    The landing buffer is an important problem in the research on bionic locust jumping robots, and the different modes of landing and buffering can affect the dynamic performance of the buffering process significantly. Based on an experimental observation, the different modes of landing and buffering are determined, which include the different numbers of landing legs and different motion modes of legs in the buffering process. Then a bionic locust mechanism is established, and the springs are used to replace the leg muscles to achieve a buffering effect. To reveal the dynamic performance in the buffering process of the bionic locust mechanism, a dynamic model is established with different modes of landing and buffering. In particular, to analyze the buffering process conveniently, an equivalent vibration dynamic model of the bionic locust mechanism is proposed. Given the support forces of the ground to the leg links, which can be obtained from the dynamic model, the spring forces of the legs and the impact resistance of each leg are the important parameters affecting buffering performance, and evaluation principles for buffering performance are proposed according to the aforementioned parameters. Based on the dynamic model and these evaluation principles, the buffering performances are analyzed and compared in different modes of landing and buffering on a horizontal plane and an inclined plane. The results show that the mechanism with the ends of the legs sliding can obtain a better dynamic performance. This study offers primary theories for buffering dynamics and an evaluation of landing buffer performance, and it establishes a theoretical basis for studies and engineering applications.

  9. Dynamic model and performance analysis of landing buffer for bionic locust mechanism

    NASA Astrophysics Data System (ADS)

    Chen, Dian-Sheng; Zhang, Zi-Qiang; Chen, Ke-Wei

    2015-10-01

    The landing buffer is an important problem in the research on bionic locust jumping robots, and the different modes of landing and buffering can affect the dynamic performance of the buffering process significantly. Based on an experimental observation, the different modes of landing and buffering are determined, which include the different numbers of landing legs and different motion modes of legs in the buffering process. Then a bionic locust mechanism is established, and the springs are used to replace the leg muscles to achieve a buffering effect. To reveal the dynamic performance in the buffering process of the bionic locust mechanism, a dynamic model is established with different modes of landing and buffering. In particular, to analyze the buffering process conveniently, an equivalent vibration dynamic model of the bionic locust mechanism is proposed. Given the support forces of the ground to the leg links, which can be obtained from the dynamic model, the spring forces of the legs and the impact resistance of each leg are the important parameters affecting buffering performance, and evaluation principles for buffering performance are proposed according to the aforementioned parameters. Based on the dynamic model and these evaluation principles, the buffering performances are analyzed and compared in different modes of landing and buffering on a horizontal plane and an inclined plane. The results show that the mechanism with the ends of the legs sliding can obtain a better dynamic performance. This study offers primary theories for buffering dynamics and an evaluation of landing buffer performance, and it establishes a theoretical basis for studies and engineering applications.

  10. Does mechanical disturbance affect the performance and species composition of submerged macrophyte communities?

    NASA Astrophysics Data System (ADS)

    Zhang, Qian; Xu, Ying-Shou; Huang, Lin; Xue, Wei; Sun, Gong-Qi; Zhang, Ming-Xiang; Yu, Fei-Hai

    2014-05-01

    Submerged macrophyte communities are frequently subjected to disturbance of various frequency and strength. However, there is still little experimental evidence on how mechanical disturbance affects the performance and species composition of such plant communities. In a greenhouse experiment, we constructed wetland communities consisting of five co-occurring clonal submerged macrophyte species (Hydrilla verticillata, Elodea canadensis, Ceratophyllum demersum, Chara fragilis, and Myriophyllum spicatum) and subjected these communities to three mechanical disturbance regimes (no, moderate and strong disturbance). Strong mechanical disturbance greatly decreased overall biomass, number of shoot nodes and total shoot length, and increased species diversity (evenness) of the total community. It also substantially decreased the growth of the most abundant species (H. verticillata), but did not affect growth of the other four species. Our data reveal that strong disturbance can have different effects on different submerged macrophyte species and thus alters the performance and species composition of submerged macrophyte communities.

  11. Numerical analysis of the texture effect on the hydrodynamic performance of a mechanical seal

    NASA Astrophysics Data System (ADS)

    Adjemout, M.; Brunetiere, N.; Bouyer, J.

    2016-03-01

    The purpose of this paper is to analyze the effect of the main geometrical characteristics of texture on the hydrodynamic lubrication of a mechanical seal. A parametric study was carried out in order to improve the performance of a mechanical seal. The numerical model used in this study solves the Reynolds equation coupled with a mass conservative model which takes into account the cavitation phenomenon. It is shown that among the six dimple shapes tested herein, namely cylinder, square, triangle, truncated cone, truncated pyramid, and spherical cap, the triangular dimples placed symmetrically with respect to their bases are more effective for enhancing the hydrodynamic performance of the mechanical seal. The effect of the area and depth ratios is studied and optimized as well. The optimized solution is able to minimize friction and leakage under a range of operating conditions.

  12. Does mechanical disturbance affect the performance and species composition of submerged macrophyte communities?

    PubMed

    Zhang, Qian; Xu, Ying-Shou; Huang, Lin; Xue, Wei; Sun, Gong-Qi; Zhang, Ming-Xiang; Yu, Fei-Hai

    2014-01-01

    Submerged macrophyte communities are frequently subjected to disturbance of various frequency and strength. However, there is still little experimental evidence on how mechanical disturbance affects the performance and species composition of such plant communities. In a greenhouse experiment, we constructed wetland communities consisting of five co-occurring clonal submerged macrophyte species (Hydrilla verticillata, Elodea canadensis, Ceratophyllum demersum, Chara fragilis, and Myriophyllum spicatum) and subjected these communities to three mechanical disturbance regimes (no, moderate and strong disturbance). Strong mechanical disturbance greatly decreased overall biomass, number of shoot nodes and total shoot length, and increased species diversity (evenness) of the total community. It also substantially decreased the growth of the most abundant species (H. verticillata), but did not affect growth of the other four species. Our data reveal that strong disturbance can have different effects on different submerged macrophyte species and thus alters the performance and species composition of submerged macrophyte communities. PMID:24811826

  13. 48 CFR 452.246-70 - Inspection and Acceptance.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 48 Federal Acquisition Regulations System 4 2011-10-01 2011-10-01 false Inspection and Acceptance... Inspection and Acceptance. As prescribed in 446.370, insert the following clause: Inspection and Acceptance... acceptance will be performed at: ___.* (End of clause) * Contracting Officer shall insert...

  14. A Mechanism That Bounds Execution Performance for Process Group for Mitigating CPU Abuse

    NASA Astrophysics Data System (ADS)

    Yamauchi, Toshihiro; Hara, Takayuki; Taniguchi, Hideo

    Secure OS has been the focus of several studies. However, CPU resources, which are important resources for executing a program, are not the object of access control. For preventing the abuse of CPU resources, we had earlier proposed a new type of execution resource that controls the maximum CPU usage [5,6] The previously proposed mechanism can control only one process at a time. Because most services involve multiple processes, the mechanism should control all the processes in each service. In this paper, we propose an improved mechanism that helps to achieve a bound on the execution performance of a process group, in order to limit unnecessary processor usage. We report the results of an evaluation of our proposed mechanism.

  15. CHARACTERIZATION OF MECHANICAL PERFORMANCE OF NT154 SILICON NITRIDE MICROTRUBINE ROTORS

    SciTech Connect

    Lin, Hua-Tay; Ferber, Mattison K; Waters, Shirley B; Kirkland, Timothy Philip

    2006-01-01

    This paper summarizes the results on recent component characterization efforts carried out to verify the mechanical reliability of NT154 silicon nitride microturbine rotors manufactured by Saint-Gobain. Mechanical properties of biaxial discs machined from airfoil as well as hub region of microturbine rotors were evaluated by a ball-on-ring test technique. Results showed that the mechanical properties of specimens from airfoils with as-processed surfaces exhibited lower characteristic strength than those machined from the hub region with as-machined surfaces. The differences in mechanical performance and reliability between as-processed components and simple-shaped test coupons appear to arise mainly from differences in strength limiting flaw type and microstructure verified by detailed electron microscopy analysis.

  16. Wind Evaluation Breadboard: mechanical design and analysis, control architecture, dynamic model, and performance simulation

    NASA Astrophysics Data System (ADS)

    Reyes García-Talavera, Marcos; Viera, Teodora; Núñez, Miguel; Zuluaga, Pablo; Ronquillo, Bernardo; Ronquillo, Mariano; Brunetto, Enzo; Quattri, Marco; Castro, Javier; Hernández, Elvio

    2008-07-01

    The Wind Evaluation Breadboard (WEB) for the European Extremely Large Telescope (ELT) is a primary mirror and telescope simulator formed by seven segments simulators, including position sensors, electromechanical support systems and support structures. The purpose of the WEB is to evaluate the performance of the control of wind buffeting disturbance on ELT segmented mirrors using an electro-mechanical set-up which simulates the real operational constrains applied to large segmented mirrors. The instrument has been designed and developed by IAC, ALTRAN, JUPASA and ESO, with FOGALE responsible of the Edge Sensors, and TNO of the Position Actuators. This paper describes the mechanical design and analysis, the control architecture, the dynamic model generated based on the Finite Element Model and the close loop performance achieved in simulations. A comparison in control performance between segments modal control and actuators local control is also presented.

  17. Effects of competitive pressure on expert performance: underlying psychological, physiological, and kinematic mechanisms.

    PubMed

    Cooke, Andrew; Kavussanu, Maria; McIntyre, David; Boardley, Ian D; Ring, Christopher

    2011-08-01

    Although it is well established that performance is influenced by competitive pressure, our understanding of the mechanisms which underlie the pressure-performance relationship is limited. The current experiment examined mediators of the relationship between competitive pressure and motor skill performance of experts. Psychological, physiological, and kinematic responses to three levels of competitive pressure were measured in 50 expert golfers, during a golf putting task. Elevated competitive pressure increased putting accuracy, anxiety, effort, and heart rate, but decreased grip force. Quadratic effects of pressure were noted for self-reported conscious processing and impact velocity. Mediation analyses revealed that effort and heart rate partially mediated improved performance. The findings indicate that competitive pressure elicits effects on expert performance through both psychological and physiological pathways. PMID:21265862

  18. Acceptance, values, and probability.

    PubMed

    Steel, Daniel

    2015-10-01

    This essay makes a case for regarding personal probabilities used in Bayesian analyses of confirmation as objects of acceptance and rejection. That in turn entails that personal probabilities are subject to the argument from inductive risk, which aims to show non-epistemic values can legitimately influence scientific decisions about which hypotheses to accept. In a Bayesian context, the argument from inductive risk suggests that value judgments can influence decisions about which probability models to accept for likelihoods and priors. As a consequence, if the argument from inductive risk is sound, then non-epistemic values can affect not only the level of evidence deemed necessary to accept a hypothesis but also degrees of confirmation themselves. PMID:26386533

  19. Newbery Medal Acceptance.

    ERIC Educational Resources Information Center

    Freedman, Russell

    1988-01-01

    Presents the Newbery Medal acceptance speech of Russell Freedman, writer of children's nonfiction. Discusses the place of nonfiction in the world of children's literature, the evolution of children's biographies, and the author's work on "Lincoln." (ARH)

  20. Newbery Medal Acceptance.

    ERIC Educational Resources Information Center

    Cleary, Beverly

    1984-01-01

    Reprints the text of Ms. Cleary's Newbery medal acceptance speech in which she gives personal history concerning her development as a writer and her response to the letters she receives from children. (CRH)

  1. Caldecott Medal Acceptance.

    ERIC Educational Resources Information Center

    Provensen, Alice; Provensen, Martin

    1984-01-01

    Reprints the text of the Provensens' Caldecott medal acceptance speech in which they describe their early interest in libraries and literature, the collaborative aspect of their work, and their current interest in aviation. (CRH)

  2. Baseball Throwing Mechanics as They Relate to Pathology and Performance - A Review

    PubMed Central

    Whiteley, Rod

    2007-01-01

    It is a commonly held perception amongst biomechanists, sports medicine practitioners, baseball coaches and players, that an individual baseball player's style of throwing or pitching influences their performance and susceptibility to injury. With the results of a series of focus groups with baseball managers and pitching coaches in mind, the available scientific literature was reviewed regarding the contribution of individual aspects of pitching and throwing mechanics to potential for injury and performance. After a discussion of the limitations of kinematic and kinetic analyses, the individual aspects of pitching mechanics are discussed under arbitrary headings: Foot position at stride foot contact; Elbow flexion; Arm rotation; Arm horizontal abduction; Arm abduction; Lead knee position; Pelvic orientation; Deceleration-phase related issues; Curveballs; and Teaching throwing mechanics. In general, popular opinion of baseball coaching staff was found to be largely in concordance with the scientific investigations of biomechanists with several notable exceptions. Some difficulties are identified with the practical implementation of analyzing throwing mechanics in the field by pitching coaches, and with some unquantified aspects of scientific analyses. Key pointsBiomechanical analyses including kinematic and kinetic analyses allow for estimation of pitching performance and potential for injury.Some difficulties both theoretic and practical exist for the implementation and interpretation of such analyses.Commonly held opinions of baseball pitching authorities are largely held to concur with biomechanical analyses.Recommendations can be made regarding appropriate pitching and throwing technique in light of these investigations. PMID:24149219

  3. Baseball throwing mechanics as they relate to pathology and performance - a review.

    PubMed

    Whiteley, Rod

    2007-01-01

    It is a commonly held perception amongst biomechanists, sports medicine practitioners, baseball coaches and players, that an individual baseball player's style of throwing or pitching influences their performance and susceptibility to injury. With the results of a series of focus groups with baseball managers and pitching coaches in mind, the available scientific literature was reviewed regarding the contribution of individual aspects of pitching and throwing mechanics to potential for injury and performance. After a discussion of the limitations of kinematic and kinetic analyses, the individual aspects of pitching mechanics are discussed under arbitrary headings: Foot position at stride foot contact; Elbow flexion; Arm rotation; Arm horizontal abduction; Arm abduction; Lead knee position; Pelvic orientation; Deceleration-phase related issues; Curveballs; and Teaching throwing mechanics. In general, popular opinion of baseball coaching staff was found to be largely in concordance with the scientific investigations of biomechanists with several notable exceptions. Some difficulties are identified with the practical implementation of analyzing throwing mechanics in the field by pitching coaches, and with some unquantified aspects of scientific analyses. Key pointsBiomechanical analyses including kinematic and kinetic analyses allow for estimation of pitching performance and potential for injury.Some difficulties both theoretic and practical exist for the implementation and interpretation of such analyses.Commonly held opinions of baseball pitching authorities are largely held to concur with biomechanical analyses.Recommendations can be made regarding appropriate pitching and throwing technique in light of these investigations. PMID:24149219

  4. A mechanical argument for the differential performance of coronary artery grafts.

    PubMed

    Prim, David A; Zhou, Boran; Hartstone-Rose, Adam; Uline, Mark J; Shazly, Tarek; Eberth, John F

    2016-02-01

    Coronary artery bypass grafting (CABG) acutely disturbs the homeostatic state of the transplanted vessel making retention of graft patency dependent on chronic remodeling processes. The time course and extent to which remodeling restores vessel homeostasis will depend, in part, on the nature and magnitude of the mechanical disturbances induced upon transplantation. In this investigation, biaxial mechanical testing and histology were performed on the porcine left anterior descending artery (LAD) and analogs of common autografts, including the internal thoracic artery (ITA), radial artery (RA), great saphenous vein (GSV) and lateral saphenous vein (LSV). Experimental data were used to quantify the parameters of a structure-based constitutive model enabling prediction of the acute vessel mechanical response pre-transplantation and under coronary loading conditions. A novel metric Ξ was developed to quantify mechanical differences between each graft vessel in situ and the LAD in situ, while a second metric Ω compares the graft vessels in situ to their state under coronary loading. The relative values of these metrics among candidate autograft sources are consistent with vessel-specific variations in CABG clinical success rates with the ITA as the superior and GSV the inferior graft choices based on mechanical performance. This approach can be used to evaluate other candidate tissues for grafting or to aid in the development of synthetic and tissue engineered alternatives. PMID:26437296

  5. A Flight Prediction for Performance of the SWAS Solar Array Deployment Mechanism

    NASA Technical Reports Server (NTRS)

    Sneiderman, Gary; Daniel, Walter K.

    1999-01-01

    The focus of this paper is a comparison of ground-based solar array deployment tests with the on-orbit deployment. The discussion includes a summary of the mechanisms involved and the correlation of a dynamics model with ground based test results. Some of the unique characteristics of the mechanisms are explained through the analysis of force and angle data acquired from the test deployments. The correlated dynamics model is then used to predict the performance of the system in its flight application.

  6. The relationship between the clinical performance and large deformation mechanical behavior of retrieved UHMWPE tibial inserts.

    PubMed

    Kurtz, S M; Rimnac, C M; Pruitt, L; Jewett, C W; Goldberg, V; Edidin, A A

    2000-02-01

    Many aspects of the proposed relationship between material properties and clinical performance of UHMWPE components remain unclear. In this study, we explored the hypothesis that the clinical performance of tibial inserts is directly related to its large-deformation mechanical behavior measured near the articulating surface. Retrieval analysis was performed on three conventional UHMWPE and three Hylamer-M tibial components of the same design and manufacturer. Samples of material were then obtained from the worn regions of each implant and subjected to mechanical characterization using the small punch test. Statistically significant relationships were observed between the metrics of the small punch test and the total damage score and the burnishing damage score of the implants. We also examined the near-surface morphology of the retrievals using transmission electron microscopy. TEM analysis revealed lamellar alignment at and below the wear surfaces of the conventional UHMWPE retrievals up to a maximum depth of approximately 8 microm, consistent with large-deformation crystalline plasticity. The depth of the plasticity-induced damage layer varied not only between the retrievals, but also between the conventional UHMWPE and Hylamer-M components. Thus, the results of this study support the hypothesis that the clinical performance of UHMWPE tibial inserts is related to the large-deformation mechanical behavior measured near the articulating surface. PMID:10646945

  7. Wearing knee wraps affects mechanical output and performance characteristics of back squat exercise.

    PubMed

    Lake, Jason P; Carden, Patrick J C; Shorter, Kath A

    2012-10-01

    The aim of this study was to investigate the effects of wearing knee wraps on mechanical output and performance characteristics of back squat exercise. Ten resistance trained men (back squat 1 repetition maximum [1RM]: 160.5 ± 18.4 kg) performed 6 single back squats with 80% 1RM, 3 wearing knee wraps, 3 without. Mechanical output was obtained from ground reaction force, performance characteristics from digitized motion footage obtained from a single high-speed digital camera. Wearing knee wraps led to a 39% reduction (0.09 compared with 0.11 m, p = 0.037) in horizontal barbell displacement that continued during the lifting phase. Lowering phase vertical impulse remained within 1% across conditions; however, the lowering phase was performed 45% faster (1.13 compared with 1.57 seconds). This demonstrated that vertical force applied to the center of mass during the lowering phase was considerably larger and was likely a consequence of the generation and storage of elastic energy within the knee wrap. Subsequent vertical impulse applied to the center of mass was 10% greater (192 compared with 169 N·s, p = 0.018). Mechanical work involved in vertically displacing the center of mass was performed 20% faster and was reflected by a 10% increase in peak power (2,121 compared with 1,841 W, p = 0.019). The elastic properties of knee wraps increased mechanical output but altered back squat technique in a way that is likely to alter the musculature targeted by the exercise and possibly compromise the integrity of the knee joint. Knee wraps should not be worn during the strength and condition process, and perceived weakness in the knee joint should be assessed and treated. PMID:22995993

  8. Energy Saving Melting and Revert Reduction Technology (E-SMARRT): Mechanical Performance of Dies

    SciTech Connect

    R. Allen Miller, Principal Investigator; Kabiri-Bamoradian, Contributors: Khalil; Delgado-Garza, Abelardo; Murugesan, Karthik; Ragab, Adham

    2011-09-13

    As a net shape process, die casting is intrinsically efficient and improvements in energy efficiency are strongly dependent on design and process improvements that reduce scrap rates so that more of the total consumed energy goes into acceptable, usable castings. A casting that is distorted and fails to meet specified dimensional requirements is typically remelted but this still results in a decrease in process yield, lost productivity, and increased energy consumption. This work focuses on developing, and expanding the use of, computer modeling methods that can be used to improve the dimensional accuracy of die castings and produce die designs and machine/die setups that reduce rejection rates due to dimensional issues. A major factor contributing to the dimensional inaccuracy of the casting is the elastic deformations of the die cavity caused by the thermo mechanical loads the dies are subjected to during normal operation. Although thermal and die cavity filling simulation are widely used in the industry, structural modeling of the die, particularly for managing part distortion, is not yet widely practiced. This may be due in part to the need to have a thorough understanding of the physical phenomenon involved in die distortion and the mathematical theory employed in the numerical models to efficiently model the die distortion phenomenon. Therefore, two of the goals of this work are to assist in efforts to expand the use of structural modeling and related technologies in the die casting industry by 1) providing a detailed modeling guideline and tutorial for those interested in developing the necessary skills and capability and 2) by developing simple meta-models that capture the results and experience gained from several years of die distortion research and can be used to predict key distortion phenomena of relevance to a die caster with a minimum of background and without the need for simulations. These objectives were met. A detailed modeling tutorial was

  9. Improving the mechanical performance of wood fiber reinforced bio-based polyurethane foam

    NASA Astrophysics Data System (ADS)

    Chang, Li-Chi

    Because of the environmental impact of fossil fuel consumption, soybean-based polyurethane (PU) foam has been developed as an alternative to be used as the core in structural insulated panels (SIPs). Wood fibers can be added to enhance the resistance of foam against bending and buckling in compression. The goal of this work is to study the effect of three modifications: fiber surface treatment, catalyst choice, and mixing method on the compression performance of wood fiber-reinforced PU foam. Foams were made with a free-rising process. The compression performance of the foams was measured and the foams were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray computed tomography (CT). The foam reinforced with alkali-treated fibers had improved compression performance. The foams made with various catalysts shared similar performance. The foam made using a mechanical stirrer contained well-dispersed fibers but the reinforcing capability of the fibers was reduced.

  10. Performance acceptance test of a portable instrument to detect uranium in water at the DOE Advanced Waste Water Treatment Plant, Fernald, Ohio

    SciTech Connect

    Anderson, M.S.; Weeks, S.J.

    1997-03-28

    The Eppendorf-Biotronik Model IC 2001-2, a portable field ruggedized ion chromatography instrument, was rigorously tested at the DOE Advanced Waste Water Treatment Plant, Fernald, Ohio. This instrument rapidly detected the uranium concentration in water, and has a detection limit in the low ppb range without using the sample concentrating feature. The test set of samples analyzed included: ``Real World`` water samples from the AWWT containing uranium concentrations in the 9--110 ppb range, a sample blank, and a performance evaluation sample. The AWWT samples contained sets of both raw water and acid-preserved water samples. Selected samples were analyzed in quadruplicate to asses the instrument`s precision, and these results were compared with the results from an off-site confirmatory laboratory to assess the instrument`s accuracy. Additional comparisons with on-site laboratory instruments, Chemcheck KPA-11 and Scintrex UA-3 are reported. Overall, the Eppendorf-Biotronik IC 2001-2 performed exceptionally well providing a detection limit in the low ppb region (< 10 ppb) and giving rapid (< 5 minutes) accurate and reproducible analytical results for the AWWT, ``real world``, water samples with uranium concentrations in the region of interest (10--40 ppb). The per sample operating cost for this instrument is equivalent to the per sample cost for the currently used KPA. The time required to analyze a sample and provide a result is approximately the same for the CI 2001-2, KPA, and Scintrex instruments.

  11. Virtual Team Governance: Addressing the Governance Mechanisms and Virtual Team Performance

    NASA Astrophysics Data System (ADS)

    Zhan, Yihong; Bai, Yu; Liu, Ziheng

    As technology has improved and collaborative software has been developed, virtual teams with geographically dispersed members spread across diverse physical locations have become increasingly prominent. Virtual team is supported by advancing communication technologies, which makes virtual teams able to largely transcend time and space. Virtual teams have changed the corporate landscape, which are more complex and dynamic than traditional teams since the members of virtual teams are spread on diverse geographical locations and their roles in the virtual team are different. Therefore, how to realize good governance of virtual team and arrive at good virtual team performance is becoming critical and challenging. Good virtual team governance is essential for a high-performance virtual team. This paper explores the performance and the governance mechanism of virtual team. It establishes a model to explain the relationship between the performance and the governance mechanisms in virtual teams. This paper is focusing on managing virtual teams. It aims to find the strategies to help business organizations to improve the performance of their virtual teams and arrive at the objectives of good virtual team management.

  12. Effect of Heat Treatment on Mechanical Properties and Corrosion Performance of Cold-Sprayed Tantalum Coatings

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Vidyasagar, V.; Jyothirmayi, A.; Joshi, S. V.

    2016-04-01

    The cold-spray technique is of significant interest to deposit refractory metals with relatively high melting point for a variety of demanding applications. In the present study, mechanical properties of cold-sprayed tantalum coatings heat treated at different temperatures were investigated using microtensile testing, scratch testing, and nanoindentation. The corrosion performance of heat-treated coatings was also evaluated in 1 M KOH solution, and potentiodynamic polarization as well as impedance spectroscopy studies were carried out. Assessment of structure-property correlations was attempted based on microstructure, porosity, and intersplat bonding state, together with mechanical and corrosion properties of the heat-treated cold-sprayed tantalum coatings. Coatings annealed at 1500 °C, which is very close to the recrystallization temperature of tantalum, were found to perform almost as bulk tantalum, with exciting implications for various applications.

  13. Predictive performance of microarray gene signatures: impact of tumor heterogeneity and multiple mechanisms of drug resistance

    PubMed Central

    A’Hern, Roger; Bidard, Francois-Clement; Lemetre, Christophe; Swanton, Charles; Shen, Ronglai; Reis-Filho, Jorge S.

    2014-01-01

    Gene signatures have failed to predict responses to breast cancer therapy in patients to date. In this study, we used bioinformatic methods to explore the hypothesis that the existence of multiple drug resistance mechanisms in different patients may limit the power of gene signatures to predict responses to therapy. Additionally, we explored whether sub-stratification of resistant cases could improve performance. Gene expression profiles from 1,550 breast cancers analyzed with the same microarray platform were retrieved from publicly available sources. Gene expression changes were introduced in cases defined as sensitive or resistant to a hypothetical therapy. In the resistant group, up to five different mechanisms of drug resistance causing distinct or overlapping gene expression changes were generated bioinformatically, and their impact on sensitivity, specificity and predictive values of the signatures was investigated. We found that increasing the number of resistance mechanisms corresponding to different gene expression changes weakened the performance of the predictive signatures generated, even if the resistance-induced changes in gene expression were sufficiently strong and informative. Performance was also affected by cohort composition and the proportion of sensitive versus resistant cases or resistant cases that were mechanistically distinct. It was possible to improve response prediction by sub-stratifying chemotherapy-resistant cases from actual datasets (non-bioinformatically-perturbed datasets), and by using outliers to model multiple resistance mechanisms. Our work supports the hypothesis that the presence of multiple resistance mechanisms to a given therapy in patients limits the ability of gene signatures to make clinically-useful predictions. PMID:24706696

  14. Effect of angular stability and other locking parameters on the mechanical performance of intramedullary nails.

    PubMed

    Hoffmann, Stefanie; Gerber, Claus; von Oldenburg, Geert; Kessler, Manuel; Stephan, Daniel; Augat, Peter

    2015-04-01

    To extend the indications of intramedullary nails for distal or proximal fractures, nails with angle stable locking options have been developed. Studies on the mechanical efficacy of these systems have been inconsistent likely due to confounding variables such as number, geometry, or orientation of the screws, as well as differences in the loading mode. Therefore, the aim of this study was to quantify the effect of angular stability on the mechanical performance of intramedullary nails. The results could then be compared with the effects of various locking screw parameters and loading modes. A generic model was developed consisting of artificial bone material and titanium intramedullary nail that provided the option to systematically modify the locking screw configuration. Using a base configuration, the following parameters were varied: number of screws, distance and orientation between screws, blocking of screws, and simulation of freehand locking. Tension/compression, torsional, and bending loads were applied. Stiffness and clearance around the zero loading point were determined. Angular stability had no effect on stiffness but completely blocked axial clearance (p=0.003). Simulation of freehand locking reduced clearance for all loading modes by at least 70% (p<0.003). The greatest increases in torsional and bending stiffness were obtained by increasing the number of locking screws (up to 80%, p<0.001) and by increasing the distance between them (up to 70%, p<0.001). In conclusion, our results demonstrate that the mechanical performance of IM nailing can be affected by various locking parameters of which angular stability is only one. While angular stability clearly reduces clearance of the screw within the nail, mechanical stiffness depends more on the number of screws and their relative distance. Thus, optimal mechanical performance in IM nailing could potentially be obtained by combining angular stability with optimal arrangement of locking screws. PMID

  15. Reliability performance of titanium sputter coated Ni-Ti arch wires: mechanical performance and nickel release evaluation.

    PubMed

    Anuradha, P; Varma, N K Sapna; Balakrishnan, Avinash

    2015-01-01

    The present research was aimed at developing surface coatings on NiTi archwires capable of protection against nickel release and to investigate the stability, mechanical performance and prevention of nickel release of titanium sputter coated NiTi arch wires. Coated and uncoated specimens immersed in artificial saliva were subjected to critical evaluation of parameters such as surface analysis, mechanical testing, element release, friction coefficient and adhesion of the coating. Titanium coatings exhibited high reliability on exposure even for a prolonged period of 30 days in artificial saliva. The coatings were found to be relatively stable on linear scratch test with reduced frictional coefficient compared to uncoated samples. Titanium sputtering adhered well with the Ni-Ti substrates at the molecular level, this was further confirmed by Inductive coupled plasma emission spectroscopy (ICPE) analysis which showed no dissolution of nickel in the artificial saliva. Titanium sputter coatings seem to be promising for nickel sensitive patients. The study confirmed the superior nature of the coating, evident as reduced surface roughness, friction coefficient, good adhesion and minimal hardness and elastic modulus variations in artificial saliva over a given time period. PMID:26484557

  16. Effect of mechanical surface treatments on fatigue performance of titanium alloys

    SciTech Connect

    Wagner, L.

    1999-07-01

    Generally, mechanical surface treatments induce high dislocation densities in near-surface regions. Due to the local plastic deformation, residual stresses are developed and the surface topography is changed. The effect of these parameters on the fatigue performance after shot peening is illustrated for Ti-6Al-4V. Results on the influence of shot peening and roller-burnishing on {alpha}-, ({alpha}+{beta})- and metastable-{beta}-alloys are compared and contrasted.

  17. MICROSTRUCTURE AND MECHANICAL PROPERTY PERFORMANCE OF COMMERCIAL GRADE API PIPELINE STEELS IN HIGH PRESSURE GASEOUS HYDROGEN

    SciTech Connect

    Stalheim, Mr. Douglas; Boggess, Todd; San Marchi, Chris; Jansto, Steven; Somerday, Dr. B; Muralidharan, Govindarajan; Sofronis, Prof. Petros

    2010-01-01

    The continued growth of the world s developing countries has placed an ever increasing demand on traditional fossil fuel energy sources. This development has lead to increasing research and development of alternative energy sources. Hydrogen gas is one of the potential alternative energy sources under development. Currently the most economical method of transporting large quantities of hydrogen gas is through steel pipelines. It is well known that hydrogen embrittlement has the potential to degrade steel s mechanical properties when hydrogen migrates into the steel matrix. Consequently, the current pipeline infrastructure used in hydrogen transport is typically operated in a conservative fashion. This operational practice is not conducive to economical movement of significant volumes of hydrogen gas as an alternative to fossil fuels. The degradation of the mechanical properties of steels in hydrogen service is known to depend on the microstructure of the steel. Understanding the levels of mechanical property degradation of a given microstructure when exposed to hydrogen gas under pressure can be used to evaluate the suitability of the existing pipeline infrastructure for hydrogen service and guide alloy and microstructure design for new hydrogen pipeline infrastructure. To this end, the 2 Copyright 2010 by ASME microstructures of relevant steels and their mechanical properties in relevant gaseous hydrogen environments must be fully characterized to establish suitability for transporting hydrogen. A project to evaluate four commercially available pipeline steels alloy/microstructure performance in the presences of gaseous hydrogen has been funded by the US Department of Energy along with the private sector. The microstructures of four pipeline steels were characterized and then tensile testing was conducted in gaseous hydrogen and helium at pressures of 800, 1600 and 3000 psi. Based on measurements of reduction of area, two of the four steels that performed the best

  18. An Integrated Signaling-Encryption Mechanism to Reduce Error Propagation in Wireless Communications: Performance Analyses

    SciTech Connect

    Olama, Mohammed M; Matalgah, Mustafa M; Bobrek, Miljko

    2015-01-01

    Traditional encryption techniques require packet overhead, produce processing time delay, and suffer from severe quality of service deterioration due to fades and interference in wireless channels. These issues reduce the effective transmission data rate (throughput) considerably in wireless communications, where data rate with limited bandwidth is the main constraint. In this paper, performance evaluation analyses are conducted for an integrated signaling-encryption mechanism that is secure and enables improved throughput and probability of bit-error in wireless channels. This mechanism eliminates the drawbacks stated herein by encrypting only a small portion of an entire transmitted frame, while the rest is not subject to traditional encryption but goes through a signaling process (designed transformation) with the plaintext of the portion selected for encryption. We also propose to incorporate error correction coding solely on the small encrypted portion of the data to drastically improve the overall bit-error rate performance while not noticeably increasing the required bit-rate. We focus on validating the signaling-encryption mechanism utilizing Hamming and convolutional error correction coding by conducting an end-to-end system-level simulation-based study. The average probability of bit-error and throughput of the encryption mechanism are evaluated over standard Gaussian and Rayleigh fading-type channels and compared to the ones of the conventional advanced encryption standard (AES).

  19. Evaluation of mechanical properties and durability performance of HDPE-wood composites

    SciTech Connect

    Tazi, M.; Erchiqui, F.; Kaddami, H.; Bouazara, M.; Poaty, B.

    2015-05-22

    The objective of this work is to evaluate the mechanical properties and durability performance of bio-composite materials made from sawdust and thermoplastic polymer (HDPE). For the preparation of the composites, sawdust in different proportions with Maleic Anhydride grafted Polyethylene (MAPE) as the coupling agent was used. The thermal and mechanical properties were successively characterized. The results indicate that adding wood fillers to a polymer matrix increases the degree of crystallinity and improves the tensile strength and ductility of composites. On the contrary, resistance to water absorption decreases as a function of the wood fillers. Scanning electron microscopy (SEM) was used to analyze morphological structure alteration when exposed to intense weathering. The biodegradability of bio-composites up to 97 days was also investigated; the results indicate that, by increasing the filler content, the amount of weight loss increased as well. In other words, even though the addition of sawdust to thermoplastic polymer improves the mechanical performance of a composite material, it also accelerates the biodegradation rate of the composite. An optimum amount of filler content might compromise the effect of biodegradation and mechanical properties of composite materials.

  20. Evaluation of mechanical properties and durability performance of HDPE-wood composites

    NASA Astrophysics Data System (ADS)

    Tazi, M.; Erchiqui, F.; Kaddami, H.; Bouazara, M.; Poaty, B.

    2015-05-01

    The objective of this work is to evaluate the mechanical properties and durability performance of bio-composite materials made from sawdust and thermoplastic polymer (HDPE). For the preparation of the composites, sawdust in different proportions with Maleic Anhydride grafted Polyethylene (MAPE) as the coupling agent was used. The thermal and mechanical properties were successively characterized. The results indicate that adding wood fillers to a polymer matrix increases the degree of crystallinity and improves the tensile strength and ductility of composites. On the contrary, resistance to water absorption decreases as a function of the wood fillers. Scanning electron microscopy (SEM) was used to analyze morphological structure alteration when exposed to intense weathering. The biodegradability of bio-composites up to 97 days was also investigated; the results indicate that, by increasing the filler content, the amount of weight loss increased as well. In other words, even though the addition of sawdust to thermoplastic polymer improves the mechanical performance of a composite material, it also accelerates the biodegradation rate of the composite. An optimum amount of filler content might compromise the effect of biodegradation and mechanical properties of composite materials

  1. Flexible thick-film glucose biosensor: influence of mechanical bending on the performance.

    PubMed

    Chuang, Min-Chieh; Yang, Yang-Li; Tseng, Ta-Feng; Chou, Tzuyang; Lou, Shyh-Liang; Wang, Joseph

    2010-04-15

    The influence of the bending-induced mechanical stress of flexible Nafion/GOx/carbon screen-printed electrodes (SPEs) upon the performance of such glucose biosensors has been examined. Surprisingly, such flexible enzyme/polymer-SPEs operate well following a severe bending-induced mechanical stress (including a 180 degrees pinch), and actually display a substantial sensitivity enhancement following their mechanical bending. The bending-induced sensitivity enhancement is observed only for the amperometric detection of the glucose substrate but not for measurements of hydrogen peroxide, catechol or ferrocyanide at coated or bare SPEs. These (and additional) data indicate that the bending effect is associated primarily with changes in the biocatalytic activity. Such sensitivity enhancement is more pronounced at elevated glucose levels, reflecting the bending-induced changes in the biocatalytic reaction. Factors affecting the bending-induced changes in the performance are examined. While our data clearly indicate that flexible enzyme/polymer-SPEs can tolerate a severe mechanical stress and hold promise as wearable glucose biosensors, delivering the sample to the active sensor surface remains the major challenge for such continuous health monitoring. PMID:20188880

  2. Mechanical performance and ultrasonic properties of cemented gangue backfill with admixture of fly ash.

    PubMed

    Wu, Di; Zhang, Yongliang; Liu, Yucheng

    2016-01-01

    Cemented gangue backfill (CGB) is prepared by mixing cement, coal gangue and water. Fly ash from the combustion of coal is commonly utilized as admixture to improve the mechanical performance and fluidity of CGB, as well as to reduce cost of preparing CGB. Uniaxial compressive strength (UCS) is one of the most commonly used indicators for evaluating the mechanical performance of CGB. Ultrasonic testing, which is a non-destructive measurement, can also be applied to determine the mechanical properties of cementitious materials such as CGB. So this paper investigates the UCS and ultrasonic pulse velocity (UPV) of CGB prepared at different fly ash dosage (19, 20 and 21 wt.%) and solid content (76.5, 77.5 and 78.5 wt.%), versus curing periods of 3-28 days. The UCS and UPV values of CGB increase with increasing fly ash dosage and solid content. In order to find out the correlation between the UCS and UPV values of CGB, different types (linear, logarithmic, exponential and power) of curve fitting are conducted on the CGB samples made at different solid content. An exponential relationship with the correlation coefficient of 0.959 appears to exist between the UCS and UPV for CGB samples. This obtained exponential relationship is validated to be available by performing the t- and F- tests. The results acquired by this paper are capable of providing guidance for utilizing UPV test to estimate the strength of underground CGB structures. PMID:26320702

  3. Phthalonitrile-Based Carbon Foam with High Specific Mechanical Strength and Superior Electromagnetic Interference Shielding Performance.

    PubMed

    Zhang, Liying; Liu, Ming; Roy, Sunanda; Chu, Eng Kee; See, Kye Yak; Hu, Xiao

    2016-03-23

    Electromagnetic interference (EMI) performance materials are urgently needed to relieve the increasing stress over electromagnetic pollution problems arising from the growing demand for electronic and electrical devices. In this work, a novel ultralight (0.15 g/cm(3)) carbon foam was prepared by direct carbonization of phthalonitrile (PN)-based polymer foam aiming to simultaneously achieve high EMI shielding effectiveness (SE) and deliver effective weight reduction without detrimental reduction of the mechanical properties. The carbon foam prepared by this method had specific compressive strength of ∼6.0 MPa·cm(3)/g. High EMI SE of ∼51.2 dB was achieved, contributed by its intrinsic nitrogen-containing structure (3.3 wt% of nitrogen atoms). The primary EMI shielding mechanism of such carbon foam was determined to be absorption. Moreover, the carbon foams showed excellent specific EMI SE of 341.1 dB·cm(3)/g, which was at least 2 times higher than most of the reported material. The remarkable EMI shielding performance combined with high specific compressive strength indicated that the carbon foam could be considered as a low-density and high-performance EMI shielding material for use in areas where mechanical integrity is desired. PMID:26910405

  4. Sodium effects on mechanical performance and consideration in high temperature structural design for advanced reactors

    NASA Astrophysics Data System (ADS)

    Natesan, K.; Li, Meimei; Chopra, O. K.; Majumdar, S.

    2009-07-01

    Sodium environmental effects are key limiting factors in the high temperature structural design of advanced sodium-cooled reactors. A guideline is needed to incorporate environmental effects in the ASME design rules to improve the performance reliability over long operating times. This paper summarizes the influence of sodium exposure on mechanical performance of selected austenitic stainless and ferritic/martensitic steels. Focus is on Type 316SS and mod.9Cr-1Mo. The sodium effects were evaluated by comparing the mechanical properties data in air and sodium. Carburization and decarburization were found to be the key factors that determine the tensile and creep properties of the steels. A beneficial effect of sodium exposure on fatigue life was observed under fully reversed cyclic loading in both austenitic stainless steels and ferritic/martensitic steels. However, when hold time was applied during cyclic loading, the fatigue life was significantly reduced. Based on the mechanical performance of the steels in sodium, consideration of sodium effects in high temperature structural design of advanced fast reactors is discussed.

  5. Mechanics and molecular filtration performance of graphyne nanoweb membranes for selective water purification

    NASA Astrophysics Data System (ADS)

    Lin, Shangchao; Buehler, Markus J.

    2013-11-01

    Two-dimensional carbon materials such as the 2D nanoweb-like graphyne membrane are promising as molecular sieves for energy and environmental applications. Based on the application of water purification - the removal of contaminants from wastewater and seawater - here we use molecular dynamics (MD) simulations to investigate the interplay between mechanical forces, filtration mechanisms, and overall performance for graphyne membranes with different pore sizes. We carry out biaxial tensile tests and verify the superior mechanical robustness and tolerance of graphyne membranes against possible deformations from the membrane installation process. A possible ultimate stress in excess of 15 GPa and an ultimate strain of 1.2-2.7% are determined. We also demonstrate their excellent filtration performance with barrier-free water permeation and perfect rejection of the representative contaminants considered here, including divalent heavy metal salts (copper sulfate), hydrophobic organic chemicals (benzene and carbon tetrachloride), and inorganic monovalent salts (sodium chloride). We find that graphtriyne, with an effective pore diameter of 3.8 Å, exhibits an optimal purification performance, because the contaminant rejection rate is more sensitive to pore size than water permeability. In addition, we find that the hydrophobic graphyne membranes exhibit higher rejection rates for hydrophilic contaminants compared to the hydrophobic ones. This size exclusion effect is a result of the larger hydrated radii of hydrophilic species due to stronger interactions between them and water molecules. Finally, we find that the maximum deformation of graphtriyne at the ultimate strain before material failure has only a minor impact on its filtration performance. One of the advantages of using graphyne for water purification is that no chemical functionalization or defects need to be introduced, which maintains the structural integrity of the membrane, and possibly, the long-term device

  6. Mechanics and molecular filtration performance of graphyne nanoweb membranes for selective water purification.

    PubMed

    Lin, Shangchao; Buehler, Markus J

    2013-12-01

    Two-dimensional carbon materials such as the 2D nanoweb-like graphyne membrane are promising as molecular sieves for energy and environmental applications. Based on the application of water purification - the removal of contaminants from wastewater and seawater - here we use molecular dynamics (MD) simulations to investigate the interplay between mechanical forces, filtration mechanisms, and overall performance for graphyne membranes with different pore sizes. We carry out biaxial tensile tests and verify the superior mechanical robustness and tolerance of graphyne membranes against possible deformations from the membrane installation process. A possible ultimate stress in excess of 15 GPa and an ultimate strain of 1.2-2.7% are determined. We also demonstrate their excellent filtration performance with barrier-free water permeation and perfect rejection of the representative contaminants considered here, including divalent heavy metal salts (copper sulfate), hydrophobic organic chemicals (benzene and carbon tetrachloride), and inorganic monovalent salts (sodium chloride). We find that graphtriyne, with an effective pore diameter of 3.8 Å, exhibits an optimal purification performance, because the contaminant rejection rate is more sensitive to pore size than water permeability. In addition, we find that the hydrophobic graphyne membranes exhibit higher rejection rates for hydrophilic contaminants compared to the hydrophobic ones. This size exclusion effect is a result of the larger hydrated radii of hydrophilic species due to stronger interactions between them and water molecules. Finally, we find that the maximum deformation of graphtriyne at the ultimate strain before material failure has only a minor impact on its filtration performance. One of the advantages of using graphyne for water purification is that no chemical functionalization or defects need to be introduced, which maintains the structural integrity of the membrane, and possibly, the long-term device

  7. Heliox breathing equally influences respiratory mechanics and cycling performance in trained males and females

    PubMed Central

    Wilkie, Sabrina S.; Dominelli, Paolo B.; Sporer, Benjamin C.; Koehle, Michael S.

    2014-01-01

    In this study we tested the hypothesis that inspiring a low-density gas mixture (helium-oxygen; HeO2) would minimize mechanical ventilatory constraints and preferentially increase exercise performance in females relative to males. Trained male (n = 11, 31 yr) and female (n = 10, 26 yr) cyclists performed an incremental cycle test to exhaustion to determine maximal aerobic capacity (V̇o2max; male = 61, female = 56 ml·kg−1·min−1). A randomized, single-blinded crossover design was used for two experimental days where subjects completed a 5-km cycling time trial breathing humidified compressed room air or HeO2 (21% O2:balance He). Subjects were instrumented with an esophageal balloon for the assessment of respiratory mechanics. During the time trial, we assessed the ability of HeO2 to alleviate mechanical ventilatory constraints in three ways: 1) expiratory flow limitation, 2) utilization of ventilatory capacity, and 3) the work of breathing. We found that HeO2 significantly reduced the work of breathing, increased the size of the maximal flow-volume envelope, and reduced the fractional utilization of the maximal ventilatory capacity equally between men and women. The primary finding of this study was that inspiring HeO2 was associated with a statistically significant performance improvement of 0.7% (3.2 s) for males and 1.5% (8.1 s) for females (P < 0.05); however, there were no sex differences with respect to improvement in time trial performance (P > 0.05). Our results suggest that the extent of sex-based differences in airway anatomy, work of breathing, and expiratory flow limitation is not great enough to differentially affect whole body exercise performance. PMID:25429095

  8. Mechanisms Underlying Age- and Performance-related Differences in Working Memory

    PubMed Central

    Daffner, Kirk R.; Chong, Hyemi; Sun, Xue; Tarbi, Elise C.; Riis, Jenna L.; McGinnis, Scott M.; Holcomb, Phillip J.

    2011-01-01

    This study took advantage of the subsecond temporal resolution of ERPs to investigate mechanisms underlying age- and performance-related differences in working memory. Young and old subjects participated in a verbal n-back task with three levels of difficulty. Each group was divided into high and low performers based on accuracy under the 2-back condition. Both old subjects and low-performing young subjects exhibited impairments in preliminary mismatch/match detection operations (indexed by the anterior N2 component). This may have undermined the quality of information available for the subsequent decision-making process (indexed by the P3 component), necessitating the appropriation of more resources. Additional anterior and right hemisphere activity was recruited by old subjects. Neural efficiency and the capacity to allocate more resources to decision-making differed between high and low performers in both age groups. Under low demand conditions, high performers executed the task utilizing fewer resources than low performers (indexed by the P3 amplitude). As task requirements increased, high-performing young and old subjects were able to appropriate additional resources to decision-making, whereas their low-performing counterparts allocated fewer resources. Higher task demands increased utilization of processing capacity for operations other than decision-making (e.g., sustained attention) that depend upon a shared pool of limited resources. As demands increased, all groups allocated additional resources to the process of sustaining attention (indexed by the posterior slow wave). Demands appeared to have exceeded capacity in low performers, leading to a reduction of resources available to the decision-making process, which likely contributed to a decline in performance. PMID:20617886

  9. ASR DIAGNOSIS BY PETROGRAPHIC INVESTIGATION AND EVALUATION OF MECHANICAL PERFORMANCE OF ASR DETERIORATED PRETENSIONED PC BEAM

    NASA Astrophysics Data System (ADS)

    Tomiyama, Jun; Yamada, Kazuo; Kaneda, Kazuo; Iraha, Shigeo; Oshiro, Takeshi

    ASR diagnosis and evaluation of load carrying capacity have been performed on the pre-tensioned PC beam which was cut out of a national high way bridge. The bridge was replaced lately after 25years service due to ASR deterioration. Comprehensive investigations such as crack measurement, material strength test, petrographic investigation, beam bending test have been performed on the deteriorated beam. Cracks have been observed on all sides and the appearance has been classified as severe deterioration grade. Petrographic investigation concluded that the reacted mineral was mainly reactive cristobalite contained in andesite of fine aggregates and EPMA investigation found that the reaction seemed to be the final stage. The late expansive ASR has been superimposed by cryptocrystalline quartz in coarse aggregates and it is still in progress. Deteriorated concrete cores with no visual crack have reduced only 10% of compressive strength compared with design strength, but significant loss has been observed on the elastic modulus. The static bending load test on the deteriorated test beam showed 95% of design load capacity indicating that the visual deterioration on surfaces has affected slight damages at this moment. But loss of bending rigidity has been appeared on the deteriorated beam .after bending cracks have started. This comprehensive study including the petrographic diagnosis and the appraisal on mechanical performance of the deteriorated beam conclude that there is a possibility of ASR deterioration in progress and further loss of mechanical performance though the beam had some margin for loading capacity at this moment.

  10. High-Performance Buildings – Value, Messaging, Financial and Policy Mechanisms

    SciTech Connect

    McCabe, Molly

    2011-02-22

    At the request of the Pacific Northwest National Laboratory, an in-depth analysis of the rapidly evolving state of real estate investments, high-performance building technology, and interest in efficiency was conducted by HaydenTanner, LLC, for the U.S. Department of Energy (DOE) Building Technologies Program. The analysis objectives were • to evaluate the link between high-performance buildings and their market value • to identify core messaging to motivate owners, investors, financiers, and others in the real estate sector to appropriately value and deploy high-performance strategies and technologies across new and existing buildings • to summarize financial mechanisms that facilitate increased investment in these buildings. To meet these objectives, work consisted of a literature review of relevant writings, examination of existing and emergent financial and policy mechanisms, interviews with industry stakeholders, and an evaluation of the value implications through financial modeling. This report documents the analysis methodology and findings, conclusion and recommendations. Its intent is to support and inform the DOE Building Technologies Program on policy and program planning for the financing of high-performance new buildings and building retrofit projects.

  11. Bond stress-slip mechanisms in high-performance fiber-reinforced cement composites

    NASA Astrophysics Data System (ADS)

    Guerrero Z., Aydee Patricia

    This research covers integrated experimental and analytical investigations of the mechanisms that influence the fiber pull-out versus slip response of typical fibers used in the production of fiber reinforced cementitious composites, in order to improve their mechanical performance. The fibers investigated include smooth steel fibers, hooked steel fibers, Torex twisted steel fibers and PVA (polyvinyl alcohol) fibers. Torex is a newly developed steel fiber, of general polygonal shape, that is twisted along its longitudinal axis to improve the mechanical component of bond. PVA fibers, currently used as replacement for asbestos fibers, have good mechanical properties and are believed to develop an adhesive or chemical bond component with cement matrices. Matrix parameters investigated comprised four different additives (fly ash, metakaolin, PVA polymer and latex) and the fineness of the sand. The experimental program included two types of tests, a single fiber pull-out test and a tensile test on notched prisms, considered an indirect test to measure bond. The first test was used when the fiber diameter exceeded 200 microns. The second test was primarily carried out for PVA fibers with a diameter in the range of 11 to 50 microns. Closed-loop control was used in the notched prism tests where the rate of crack opening at the notch controlled the machine displacement. Also in these tests, three different volume fractions of fibers were investigated for each parameter in order to back-calculate the bond strength. The analytical program includes three parts: (1) a study to model the contribution of the hook to the mechanical component of bond in hooked steel fibers, (2) a study to back-calculate adhesive-frictional bond of fine PVA fibers from the stress versus crack opening response of notched tensile prisms, and (3) a study to model the effect of twisting on the mechanical contribution of bond in Torex steel fibers. This last model utilizes a finite element code (based on

  12. Fiber Reinforcement Architectures of PMCs on the Hygrothermal-Mechanical Performance for Aeropropulsion Applications

    NASA Technical Reports Server (NTRS)

    Shin, Eugene; Thesken, John; Sutter, James; Chuang, Kathy; Juhas, John; Veverka, A.; Inghram, L.; Burke, C.; Fink, J. E.; Arendt, C.

    2003-01-01

    A rigid lightweight sandwich support structure, for the combustor chamber of a new generation liquid propellant rocket engine, was designed and fabricated using Polymer Matric Composite (PMC) facesheet on a Ti honeycomb or Carbon foam core. The facesheet consisted of high stiffness carbon fiber, M40JB, and high temperature Polyimides, such as PMR-11-50 and HFPE-II. Six different fiber architectures; 4HS woven fabric, uni-fabric, woven-uni hybrid, stitched woven fabric, stitched uni-fabric and tri-axial braided structures have been investigated for optimum stiffness-thickness-weight-performance design criteria for the hygrothermal-mechanical propulsion service exposure conditions including rapid heating up to 200 F/sec, maximum operating temperature of 600 F, internal pressure up to 100 psi. An extensive property and performance database including dry-wet mechanical properties at both 25 F and 600 F in various loading modes, thermal and physical properties including blistering onset condition was developed for fiber architecture down-selection and design guidelines. Various optimized process methods including vacuum bag compression molding, solvent assistant RTM (SaRTM), resin film infusion (RFI) were utilized for PMC panel fabrication depending on the architecture type. In the case of stitched woven fabric architecture, the optimal stitch pattern was chosen in terms of stitch density and yarn size, based on both in-plane mechanical properties and blistering performance. Potential reduction of the in-plane properties transverse to the line of stitching was also evaluated. Attempt to correlate the experimental results with theoretical micro-mechanics predictions will be presented.

  13. Performance predictions for mechanical excavators in Yucca Mountain tuffs; Yucca Mountain Site Characterization Project

    SciTech Connect

    Ozdemir, L.; Gertsch, L.; Neil, D.; Friant, J.

    1992-09-01

    The performances of several mechanical excavators are predicted for use in the tuffs at Yucca Mountain: Tunnel boring machines, the Mobile Miner, a roadheader, a blind shaft borer, a vertical wheel shaft boring machine, raise drills, and V-Moles. Work summarized is comprised of three parts: Initial prediction using existing rock physical property information; Measurement of additional rock physical properties; and Revision of the initial predictions using the enhanced database. The performance predictions are based on theoretical and empirical relationships between rock properties and the forces-experienced by rock cutters and bits during excavation. Machine backup systems and excavation design aspects, such as curves and grades, are considered in determining excavator utilization factors. Instanteous penetration rate, advance rate, and cutter costs are the fundamental performance indicators.

  14. Micro-electro-mechanically tunable metamaterial with enhanced electro-optic performance

    SciTech Connect

    Pitchappa, Prakash; Pei Ho, Chong; Lin, Yu-Sheng; Lee, Chengkuo; Kropelnicki, Piotr; Singh, Navab; Huang, Chia-Yi

    2014-04-14

    We experimentally demonstrate a micro-electro-mechanically tunable metamaterial with enhanced electro-optical performance by increasing the number of movable cantilevers in the symmetrical split ring resonator metamaterial unit cell. Simulations were carried out to understand the interaction of the incident terahertz radiation with out-of-plane deforming metamaterial resonator. In order to improve the overall device performance, the number of released cantilever in a unit cell was increased from one to two, and it was seen that the tunable range was doubled and the switching contrast improved by a factor of around five at 0.7 THz. This simple design approach can be adopted for a wide range of high performance electro-optical devices such as continuously tunable filters, modulators, and electro-optic switches to enable future photonic circuit applications.

  15. Acceptance Test Plan for ANSYS Software

    SciTech Connect

    CREA, B.A.

    2000-10-25

    This plan governs the acceptance testing of the ANSYS software (Full Mechanical Release 5.5) for use on Project Word Management Contract (PHMC) computer systems (either UNIX or Microsoft Windows/NT). There are two phases to the acceptance testing covered by this test plan: program execution in accordance with the guidance provided in installation manuals; and ensuring results of the execution are consistent with the expected physical behavior of the system being modeled.

  16. Acceptance Test Report for 241-U compressed air system

    SciTech Connect

    Freeman, R.D.

    1994-10-20

    This Acceptance Test Report (ATR) documents the results of acceptance testing of a newly upgraded compressed air system at 241-U Farm. The system was installed and the test successfully performed under work package 2W-92-01027.

  17. Examination of mechanisms underlying enhanced memory performance in action video game players: a pilot study

    PubMed Central

    Li, Xianchun; Cheng, Xiaojun; Li, Jiaying; Pan, Yafeng; Hu, Yi; Ku, Yixuan

    2015-01-01

    Previous studies have shown enhanced memory performance resulting from extensive action video game playing. The mechanisms underlying the cognitive benefit were investigated in the current study. We presented two types of retro-cues, with variable intervals to memory array (Task 1) or test array (Task 2), during the retention interval in a change detection task. In Task 1, action video game players demonstrated steady performance while non-action video game players showed decreased performance as cues occurred later, indicating their performance difference increased as the cue-to-memory-array intervals became longer. In Task 2, both participant groups increased their performance at similar rates as cues presented later, implying the performance difference in two groups were irrespective of the test-array-to-cue intervals. These findings suggested that memory benefit from game plays is not attributable to the higher ability of overcoming interference from the test array, but to the interactions between the two processes of protection from decay and resistance from interference, or from alternative hypotheses. Implications for future studies were discussed. PMID:26136720

  18. Examination of mechanisms underlying enhanced memory performance in action video game players: a pilot study.

    PubMed

    Li, Xianchun; Cheng, Xiaojun; Li, Jiaying; Pan, Yafeng; Hu, Yi; Ku, Yixuan

    2015-01-01

    Previous studies have shown enhanced memory performance resulting from extensive action video game playing. The mechanisms underlying the cognitive benefit were investigated in the current study. We presented two types of retro-cues, with variable intervals to memory array (Task 1) or test array (Task 2), during the retention interval in a change detection task. In Task 1, action video game players demonstrated steady performance while non-action video game players showed decreased performance as cues occurred later, indicating their performance difference increased as the cue-to-memory-array intervals became longer. In Task 2, both participant groups increased their performance at similar rates as cues presented later, implying the performance difference in two groups were irrespective of the test-array-to-cue intervals. These findings suggested that memory benefit from game plays is not attributable to the higher ability of overcoming interference from the test array, but to the interactions between the two processes of protection from decay and resistance from interference, or from alternative hypotheses. Implications for future studies were discussed. PMID:26136720

  19. Accept or divert?

    PubMed

    Angelucci, P A

    1999-09-01

    Stretching scarce resources is more than a managerial issue. Should you accept the patient to an understaffed ICU or divert him to another facility? The intense "medical utility" controversy focuses on a situation that critical care nurses now face every day. PMID:10614370

  20. Approaches to acceptable risk

    SciTech Connect

    Whipple, C.

    1997-04-30

    Several alternative approaches to address the question {open_quotes}How safe is safe enough?{close_quotes} are reviewed and an attempt is made to apply the reasoning behind these approaches to the issue of acceptability of radiation exposures received in space. The approaches to the issue of the acceptability of technological risk described here are primarily analytical, and are drawn from examples in the management of environmental health risks. These include risk-based approaches, in which specific quantitative risk targets determine the acceptability of an activity, and cost-benefit and decision analysis, which generally focus on the estimation and evaluation of risks, benefits and costs, in a framework that balances these factors against each other. These analytical methods tend by their quantitative nature to emphasize the magnitude of risks, costs and alternatives, and to downplay other factors, especially those that are not easily expressed in quantitative terms, that affect acceptance or rejection of risk. Such other factors include the issues of risk perceptions and how and by whom risk decisions are made.

  1. 1984 Newbery Acceptance Speech.

    ERIC Educational Resources Information Center

    Cleary, Beverly

    1984-01-01

    This acceptance speech for an award honoring "Dear Mr. Henshaw," a book about feelings of a lonely child of divorce intended for eight-, nine-, and ten-year-olds, highlights children's letters to author. Changes in society that affect children, the inception of "Dear Mr. Henshaw," and children's reactions to books are highlighted. (EJS)

  2. Why was Relativity Accepted?

    NASA Astrophysics Data System (ADS)

    Brush, S. G.

    Historians of science have published many studies of the reception of Einstein's special and general theories of relativity. Based on a review of these studies, and my own research on the role of the light-bending prediction in the reception of general relativity, I discuss the role of three kinds of reasons for accepting relativity (1) empirical predictions and explanations; (2) social-psychological factors; and (3) aesthetic-mathematical factors. According to the historical studies, acceptance was a three-stage process. First, a few leading scientists adopted the special theory for aesthetic-mathematical reasons. In the second stage, their enthusiastic advocacy persuaded other scientists to work on the theory and apply it to problems currently of interest in atomic physics. The special theory was accepted by many German physicists by 1910 and had begun to attract some interest in other countries. In the third stage, the confirmation of Einstein's light-bending prediction attracted much public attention and forced all physicists to take the general theory of relativity seriously. In addition to light-bending, the explanation of the advance of Mercury's perihelion was considered strong evidence by theoretical physicists. The American astronomers who conducted successful tests of general relativity became defenders of the theory. There is little evidence that relativity was `socially constructed' but its initial acceptance was facilitated by the prestige and resources of its advocates.

  3. High temperature mechanical performance of a hot isostatically pressed silicon nitride

    SciTech Connect

    Wereszczak, A.A.; Ferber, M.K.; Jenkins, M.G.; Lin, C.K.J.

    1996-01-01

    Silicon nitride ceramics are an attractive material of choice for designers and manufacturers of advanced gas turbine engine components for many reasons. These materials typically have potentially high temperatures of usefulness (up to 1400{degrees}C), are chemically inert, have a relatively low specific gravity (important for inertial effects), and are good thermal conductors (i.e., resistant to thermal shock). In order for manufacturers to take advantage of these inherent properties of silicon nitride, the high-temperature mechanical performance of the material must first be characterized. The mechanical response of silicon nitride to static, dynamic, and cyclic conditions at elevated temperatures, along with reliable and representative data, is critical information that gas turbine engine designers and manufacturers require for the confident insertion of silicon nitride components into gas turbine engines. This final report describes the high-temperature mechanical characterization and analyses that were conducted on a candidate structural silicon nitride ceramic. The high-temperature strength, static fatigue (creep rupture), and dynamic and cyclic fatigue performance were characterized. The efforts put forth were part of Work Breakdown Structure Subelement 3.2.1, {open_quotes}Rotor Data Base Generation.{close_quotes} PY6 is comparable to other hot isostatically pressed (HIPed) silicon nitrides currently being considered for advanced gas turbine engine applications.

  4. Workshop on rock mechanics issues in repository design and performance assessment

    SciTech Connect

    1996-04-01

    The Center for Nuclear Waste Regulatory Analyses organized and hosted a workshop on ``Rock Mechanics Issues in Repository Design and Performance Assessment`` on behalf its sponsor the U.S. Nuclear Regulatory Commission (NRC). This workshop was held on September 19- 20, 1994 at the Holiday Inn Crowne Plaza, Rockville, Maryland. The objectives of the workshop were to stimulate exchange of technical information among parties actively investigating rock mechanics issues relevant to the proposed high-level waste repository at Yucca Mountain and identify/confirm rock mechanics issues important to repository design and performance assessment The workshop contained three technical sessions and two panel discussions. The participants included technical and research staffs representing the NRC and the Department of Energy and their contractors, as well as researchers from the academic, commercial, and international technical communities. These proceedings include most of the technical papers presented in the technical sessions and the transcripts for the two panel discussions. Selected papers have been indexed separately for inclusion the Energy Science and Technology Database.

  5. 2013 SYR Accepted Poster Abstracts.

    PubMed

    2013-01-01

    SYR 2013 Accepted Poster abstracts: 1. Benefits of Yoga as a Wellness Practice in a Veterans Affairs (VA) Health Care Setting: If You Build It, Will They Come? 2. Yoga-based Psychotherapy Group With Urban Youth Exposed to Trauma. 3. Embodied Health: The Effects of a Mind�Body Course for Medical Students. 4. Interoceptive Awareness and Vegetable Intake After a Yoga and Stress Management Intervention. 5. Yoga Reduces Performance Anxiety in Adolescent Musicians. 6. Designing and Implementing a Therapeutic Yoga Program for Older Women With Knee Osteoarthritis. 7. Yoga and Life Skills Eating Disorder Prevention Among 5th Grade Females: A Controlled Trial. 8. A Randomized, Controlled Trial Comparing the Impact of Yoga and Physical Education on the Emotional and Behavioral Functioning of Middle School Children. 9. Feasibility of a Multisite, Community based Randomized Study of Yoga and Wellness Education for Women With Breast Cancer Undergoing Chemotherapy. 10. A Delphi Study for the Development of Protocol Guidelines for Yoga Interventions in Mental Health. 11. Impact Investigation of Breathwalk Daily Practice: Canada�India Collaborative Study. 12. Yoga Improves Distress, Fatigue, and Insomnia in Older Veteran Cancer Survivors: Results of a Pilot Study. 13. Assessment of Kundalini Mantra and Meditation as an Adjunctive Treatment With Mental Health Consumers. 14. Kundalini Yoga Therapy Versus Cognitive Behavior Therapy for Generalized Anxiety Disorder and Co-Occurring Mood Disorder. 15. Baseline Differences in Women Versus Men Initiating Yoga Programs to Aid Smoking Cessation: Quitting in Balance Versus QuitStrong. 16. Pranayam Practice: Impact on Focus and Everyday Life of Work and Relationships. 17. Participation in a Tailored Yoga Program is Associated With Improved Physical Health in Persons With Arthritis. 18. Effects of Yoga on Blood Pressure: Systematic Review and Meta-analysis. 19. A Quasi-experimental Trial of a Yoga based Intervention to Reduce Stress and

  6. A Mechanical Fish to Emulate the Fast-Start Performance of Pike

    NASA Astrophysics Data System (ADS)

    Feng, Chengcheng; Modarres-Sadeghi, Yahya

    2010-11-01

    A northern pike is capable of achieving an instantaneous acceleration of 25g, far greater than that achieved by any manmade vehicle. In order to understand the secrets behind achieving such high accelerations, we have built a mechanical fish to emulate the motion of a pike, a fast-start specialist. A live pike bends its body into a C-shaped curve and then uncoils it very quickly to send a traveling wave along its body in order to achieve high acceleration. We have designed a mechanical fish whose motion is accurately controlled by servo motors, to emulate the fast-start by bending its body to a C-shape from its original straight position, and then back to its straight position. An earlier design of a mechanical fish, which could start from an initial C-shaped curve, shed two vortex rings downstream, resulting in a transfer of energy from the fish to water, and therefore, a reaction force from the fluid to the fish. A maximum acceleration of around 4g was achieved in that design. Our new design adds an additional motion to the sequence by first bending the fish from its straight position into a C-shaped curve. Furthermore, this new mechanical fish is designed to be adjustable in swimming pattern, tail shape, tail rigidity, and body rigidity, making it possible to study the influence of all of these parameters on the fast-start performance.

  7. A New Mechanical Loading Configuration for Maximizing The Performance of Dielectric Elastomer Generators

    NASA Astrophysics Data System (ADS)

    Shian, Samuel; Huang, Jiangshui; Suo, Zhigang; Clarke, David

    2013-03-01

    Electrical energy can be generated from mechanical deformations using dielectric elastomers but currently achieved energy densities and conversion efficiencies are still small. In this presentation, we demonstrate that significant improvements, an energy density over 500 mJ/g and up to 10% in efficiency, can be produced using VHB elastomers by altering the mechanical loading geometry. A major limitation is viscous losses in the VHB elastomer indicating that higher efficiencies with other elastomers will be attainable. The basic concept of mechanical energy harvesting with a dielectric elastomer sheet is a straightforward electromechanical cycle leading to a voltage step-up: a sheet is stretched, electrical charge at low voltage is placed on either side using compliant electrodes, the stretch is released causing the sheet's initial thickness and area to be recovered increasing the charge potential which can then be harvested. Integral to maximizing the energy conversion is the amount of mechanical energy that can be stored elastically and the amount of capacitance change in the elastomer sheet during stretching. We show that these factors can be maximized by equi-biaxial loading. Details of our dielectric elastomer generator will be described as well as the procedures we use for quantifying its performance.

  8. Effect of different supplementary cementitious materials on mechanical properties of high performance concrete

    SciTech Connect

    Khatri, R.P.; Sirivivatnanon, V. . Div. of Building, Construction and Engineering); Gross, W. . Readymix Group)

    1995-01-01

    High performance concrete prepared from general purpose (GP) portland cement and various supplementary cementitious materials are increasingly finding their use in construction worldwide. This study was undertaken to compare mechanical properties as well as fresh concrete properties of concretes containing silica fume, ground granulated blast furnace slag (slag), fly ash and GP portland cement. The aim of the study was to enable evaluation of the suitability of a particular binder system for an application based on fresh concrete properties and mechanical properties. Concrete mixes were prepared with GP portland cement, high slag cement and slag cement, and also mixes were prepared with the addition of silica fume and fly ash. The work focused on concrete mixes having a fixed water/binder ratio of 0.35 and a constant total binder content of 430 kg/m[sup 3]. Apart from measuring fresh concrete properties, the mechanical properties evaluated were development of compressive strength, flexural strength, elastic modulus, and strain due to creep and drying shrinkage. Results indicated that the addition of silica fume to GP portland cement concrete marginally decreased the workability of the concrete but significantly improved the mechanical properties. However, the effect of addition of silica fume to high slag cement concrete was less pronounced.

  9. Mechanical and Electrical Performance of Thermally Stable Au-ZnO films

    SciTech Connect

    Schoeppner, Rachel L.; Goeke, Ronald S.; Moody, Neville R.; Bahr, David F.

    2015-03-28

    The mechanical properties, thermal stability, and electrical performance of Au–ZnO composite thin films are determined in this work. The co-deposition of ZnO with Au via physical vapor deposition leads to grain refinement over that of pure Au; the addition of 0.1 vol.% ZnO reduces the as-grown grain size by over 30%. The hardness of the as-grown films doubles with 2% ZnO, from 1.8 to 3.6 GPa as measured by nanoindentation. Films with ZnO additions greater than 0.5% show no significant grain growth after annealing at 350 °C, while pure gold and smaller additions do exhibit grain growth and subsequent mechanical softening. Films with 1% and 2% ZnO show a decrease of approximately 50% in electrical resistivity and no change in hardness after annealing. A model accounting for both changes in the interface structure between dispersed ZnO particles and the Au matrix captures the changes in mechanical and electrical resistivity. Furthermore, the addition of 1–2% ZnO co-deposited with Au provides a method to create mechanically hard and thermally stable films with a resistivity less than 80 nΩ-m. Our results complement previous studies of other alloying systems, suggesting oxide dispersion strengthened (ODS) gold shows a desirable hardness–resistivity relationship that is relatively independent of the particular ODS chemistry.

  10. Performance and mechanism of FeSb2 as negative electrode for Na-ion batteries

    NASA Astrophysics Data System (ADS)

    Darwiche, Ali; Toiron, Matthieu; Sougrati, Moulay T.; Fraisse, Bernard; Stievano, Lorenzo; Monconduit, Laure

    2015-04-01

    For the first time, cycling capability and life analysis of the FeSb2/Na battery are tested. Thanks to an appropriate carboxymethyl cellulose/carbon formulation, this electrode exhibits excellent electrochemical performances as negative electrode material for Sodium-Ion Batteries (SIB), sustaining a reversible capacity exceeding 540 and 440 mAh/g over more than 130 cycles at a current of 36 and 300 mA/g, respectively. Such performances overtake those of Sb in terms of cyclability under high rate, one of the best negative electrodes reported to date for SIB. In situ X-ray diffraction and low temperature Mössbauer spectroscopy analyses indicate that the reaction mechanism of the first sodiation of FeSb2 is based on a conversion reaction, leading to the formation of a very efficient Na3Sb/metallic Fe0 nanosized electrode with an excellent capacity retention at relatively high rate. The reaction mechanism after the first discharge is based on a reversible alloying reaction (2Na3Sb ↔ 2Sb + 6Na), where iron is no more involved. The role of Fe appears however to be crucial in the excellent cycling performances, likely due to the increase of the electronic conductivity brought both by its nanosized nature and its homogenous distribution in the electrode.

  11. The mechanical performances and the metrology system of the European ALMA antenna

    NASA Astrophysics Data System (ADS)

    Rampini, F.; Marchiori, G.; Biasi, R.; Stanghellini, S.; Ghedin, L.

    2010-07-01

    The Atacama Large Millimeter Array (ALMA) consists of a large number of 12 m diameter antennas that will operate up to 950GHz. The mechanical performances in terms of surface accuracy, pointing stability and residual delay are very tight. The antennas must work at full performances in free air during night and day with also the request to observe the sun. The mechanical performances are affected by all the not repeatable error sources and in particular by the temperature variations and wind component blowing from different directions. The design of the antenna has been done in order to have a very light and stiff structure, in particular all the elevation structure is in carbon fibre with also a very low thermal expansion coefficient, but to achieve the ALMA specification, two different systems able to predict the above error sources have been implemented in the control of the antenna. The first system is composed by a determined number of thermal sensors distributed in the alidade of the antenna (is the only part in steel ) and compensates the elevation axis deformation due to the temperature variation by means of a deformation matrix. The second system is based on two high accuracy inclinometers with a very short recovery time opportunely placed on the antenna and correct the wind induced errors. These innovative systems and instruments have been design and tested in the prototype antenna to the production phase.

  12. Mechanical performance of artificial pneumatic muscles to power an ankle-foot orthosis.

    PubMed

    Gordon, Keith E; Sawicki, Gregory S; Ferris, Daniel P

    2006-01-01

    We developed a powered ankle-foot orthosis that uses artificial pneumatic muscles to produce active plantar flexor torque. The purpose of this study was to quantify the mechanical performance of the orthosis during human walking. Three subjects walked at a range of speeds wearing ankle-foot orthoses with either one or two artificial muscles working in parallel. The orthosis produced similar total peak plantar flexor torque and network across speeds independent of the number of muscles used. The orthosis generated approximately 57% of the peak ankle plantar flexor torque during stance and performed approximately 70% of the positive plantar flexor work done during normal walking. Artificial muscle bandwidth and force-length properties were the two primary factors limiting torque production. The lack of peak force and work differences between single and double muscle conditions can be explained by force-length properties. Subjects altered their ankle kinematics between conditions resulting in changes in artificial muscle length. In the double muscle condition greater plantar flexion yielded shorter artificial muscles lengths and decreased muscle forces. This finding emphasizes the importance of human testing in the design and development of robotic exoskeleton devices for assisting human movement. The results of this study outline the mechanical performance limitations of an ankle-foot orthosis powered by artificial pneumatic muscles. This orthosis could be valuable for gait rehabilitation and for studies investigating neuromechanical control of human walking. PMID:16023126

  13. Selective crystallization of regioregularity controlled polythiophene for enhancing mechanical stability and electronic performance

    NASA Astrophysics Data System (ADS)

    Kim, Hyeong Jun; Yu, Hojeong; Kim, Jae Han; Kim, Jin-Sung; Kim, Taek Soo; Oh, Joon Hak; Kim, Bumjoon

    Considering the many potential applications of organic electronics in portable electronic devices, it is of great importance to develop an electro-active material that possesses mechanical stability and high electronic performance. Coexistence of both properties, however, is very difficult to achieve because good electronic performance is associated with long conjugation length, and high crystallinity often results in stiffness and brittleness. Herein, we utilize P3HT with two different regioregularities: high RR (98%) P3HT has high electronic properties but poor mechanical resilience, and low RR P3HT (68%) exhibits high elasticity and ductility but poor electronic performance. Selective crystallization of high RR P3HT induced by solution assembly allows construction of percolated networks of high RR P3HT nanowires (NWs) embedded in low RR P3HT matrix. Only 5 wt% high RR P3HT is required to reach a hole mobility comparable to that of high RR P3HT, and high RR NWs embedded in film exhibits 20 times higher elongation at break. Selective self-assembly allows us to overcome the fragile nature of highly crystalline conjugated polymers without losing their electronic properties.

  14. Selective crystallization of regioregularity controlled polythiophene for enhancing mechanical stability and electronic performance

    NASA Astrophysics Data System (ADS)

    Kim, Hyeong Jun; Yu, Hojeong; Kim, Jae-Han; Kim, Jin-Sung; Kim, Taek Soo; Oh, Joon Hak; Kim, Bumjoon

    Considering the many potential applications of organic electronics in portable electronic devices, it is of great importance to develop an electro-active material that possesses mechanical stability and high electronic performance. Coexistence of both properties, however, is very difficult to achieve because good electronic performance is associated with long conjugation length, and high crystallinity often results in stiffness and brittleness. Herein, we utilize P3HT with two different regioregularities: high RR (98) P3HT has high electronic properties but poor mechanical resilience, and low RR P3HT (68) exhibits high elasticity and ductility but poor electronic performance. Selective crystallization of high RR P3HT induced by solution assembly allows construction of percolated networks of high RR P3HT nanowires (NWs) embedded in low RR P3HT matrix. Only 5 wt high RR P3HT is required to reach a hole mobility comparable to that of high RR P3HT, and high RR NWs embedded in film exhibits 20 times higher elongation at break. Selective self-assembly allows us to overcome the fragile nature of highly crystalline conjugated polymers without losing their electronic properties.

  15. Microbial community succession mechanism coupling with adaptive evolution of adsorption performance in chalcopyrite bioleaching.

    PubMed

    Feng, Shoushuai; Yang, Hailin; Wang, Wu

    2015-09-01

    The community succession mechanism of Acidithiobacillus sp. coupling with adaptive evolution of adsorption performance were systematically investigated. Specifically, the μmax of attached and free cells was increased and peak time was moved ahead, indicating both cell growth of Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans was promoted. In the mixed strains system, the domination courses of A. thiooxidans was dramatically shortened from 22th day to 15th day, although community structure finally approached to the normal system. Compared to A. ferrooxidans, more positive effects of adaptive evolution on cell growth of A. thiooxidans were shown in either single or mixed strains system. Moreover, higher concentrations of sulfate and ferric ions indicated that both sulfur and iron metabolism was enhanced, especially of A. thiooxidans. Consistently, copper ion production was improved from 65.5 to 88.5 mg/L. This new adaptive evolution and community succession mechanism may be useful for guiding similar bioleaching processes. PMID:25978855

  16. The nano-mechanical signature of Ultra High Performance Concrete by statistical nanoindentation techniques

    SciTech Connect

    Sorelli, Luca Constantinides, Georgios; Ulm, Franz-Josef; Toutlemonde, Francois

    2008-12-15

    Advances in engineering the microstructure of cementitious composites have led to the development of fiber reinforced Ultra High Performance Concretes (UHPC). The scope of this paper is twofold, first to characterize the nano-mechanical properties of the phases governing the UHPC microstructure by means of a novel statistical nanoindentation technique; then to upscale those nanoscale properties, by means of continuum micromechanics, to the macroscopic scale of engineering applications. In particular, a combined investigation of nanoindentation, scanning electron microscope (SEM) and X-ray Diffraction (XRD) indicates that the fiber-matrix transition zone is relatively defect free. On this basis, a four-level multiscale model with defect free interfaces allows to accurately determine the composite stiffness from the measured nano-mechanical properties. Besides evidencing the dominant role of high density calcium silicate hydrates and the stiffening effect of residual clinker, the suggested model may become a useful tool for further optimizing cement-based engineered composites.

  17. Mechanical Performance and Parameter Sensitivity Analysis of 3D Braided Composites Joints

    PubMed Central

    Wu, Yue; Nan, Bo; Chen, Liang

    2014-01-01

    3D braided composite joints are the important components in CFRP truss, which have significant influence on the reliability and lightweight of structures. To investigate the mechanical performance of 3D braided composite joints, a numerical method based on the microscopic mechanics is put forward, the modeling technologies, including the material constants selection, element type, grid size, and the boundary conditions, are discussed in detail. Secondly, a method for determination of ultimate bearing capacity is established, which can consider the strength failure. Finally, the effect of load parameters, geometric parameters, and process parameters on the ultimate bearing capacity of joints is analyzed by the global sensitivity analysis method. The results show that the main pipe diameter thickness ratio γ, the main pipe diameter D, and the braided angle α are sensitive to the ultimate bearing capacity N. PMID:25121121

  18. Preparation of bacterial cellulose/graphene nanosheets composite films with enhanced mechanical performances.

    PubMed

    Shao, Wei; Wang, Shuxia; Liu, Hui; Wu, Jimin; Zhang, Rui; Min, Huihua; Huang, Min

    2016-03-15

    Graphene has been considered to be a promising nanofiller material for building polymeric nanocomposites because it has large specific surface area and unique mechanical property. In the study, BC/graphene composites were prepared by a simple blending method. The resulting structure and thermal stability of the composites were investigated by several techniques including TEM, SEM, XRD, TG and Raman spectrum. These results indicate graphene nanosheets were successfully impregnated and uniformly dispersed in the BC matrix. Water contact angles result showed that the addition of graphene decreased hydrophilic property since water contact angle of BC increased from 51.2° to 84.3° with 4wt% graphene added. The mechanical performances of BC/graphene composites were highly evaluated. When compared to pristine BC, the incorporation of 4wt% graphene improved the tensile strength from 96MPa to 155MPa and Young's modulus from 369MPa to 530MPa, respectively. PMID:26794749

  19. Mechanical performance and parameter sensitivity analysis of 3D braided composites joints.

    PubMed

    Wu, Yue; Nan, Bo; Chen, Liang

    2014-01-01

    3D braided composite joints are the important components in CFRP truss, which have significant influence on the reliability and lightweight of structures. To investigate the mechanical performance of 3D braided composite joints, a numerical method based on the microscopic mechanics is put forward, the modeling technologies, including the material constants selection, element type, grid size, and the boundary conditions, are discussed in detail. Secondly, a method for determination of ultimate bearing capacity is established, which can consider the strength failure. Finally, the effect of load parameters, geometric parameters, and process parameters on the ultimate bearing capacity of joints is analyzed by the global sensitivity analysis method. The results show that the main pipe diameter thickness ratio γ, the main pipe diameter D, and the braided angle α are sensitive to the ultimate bearing capacity N. PMID:25121121

  20. Integrated physiological mechanisms of exercise performance, adaptation, and maladaptation to heat stress.

    PubMed

    Sawka, Michael N; Leon, Lisa R; Montain, Scott J; Sonna, Larry A

    2011-10-01

    This article emphasizes significant recent advances regarding heat stress and its impact on exercise performance, adaptations, fluid electrolyte imbalances, and pathophysiology. During exercise-heat stress, the physiological burden of supporting high skin blood flow and high sweating rates can impose considerable cardiovascular strain and initiate a cascade of pathophysiological events leading to heat stroke. We examine the association between heat stress, particularly high skin temperature, on diminishing cardiovascular/aerobic reserves as well as increasing relative intensity and perceptual cues that degrade aerobic exercise performance. We discuss novel systemic (heat acclimation) and cellular (acquired thermal tolerance) adaptations that improve performance in hot and temperate environments and protect organs from heat stroke as well as other dissimilar stresses. We delineate how heat stroke evolves from gut underperfusion/ischemia causing endotoxin release or the release of mitochondrial DNA fragments in response to cell necrosis, to mediate a systemic inflammatory syndrome inducing coagulopathies, immune dysfunction, cytokine modulation, and multiorgan damage and failure. We discuss how an inflammatory response that induces simultaneous fever and/or prior exposure to a pathogen (e.g., viral infection) that deactivates molecular protective mechanisms interacts synergistically with the hyperthermia of exercise to perhaps explain heat stroke cases reported in low-risk populations performing routine activities. Importantly, we question the "traditional" notion that high core temperature is the critical mediator of exercise performance degradation and heat stroke. Published 2011. This article is a U.S. Government work and is in the public domain in the USA. PMID:23733692

  1. COMBINE*: An integrated opto-mechanical tool for laser performance modeling

    NASA Astrophysics Data System (ADS)

    Rehak, M.; Di Nicola, J. M.

    2015-02-01

    Accurate modeling of thermal, mechanical and optical processes is important for achieving reliable, high-performance high energy lasers such as those at the National Ignition Facility [1] (NIF). The need for this capability is even more critical for high average power, high repetition rate applications. Modeling the effects of stresses and temperature fields on optical properties allows for optimal design of optical components and more generally of the architecture of the laser system itself. Stresses change the indices of refractions and induce inhomogeneities and anisotropy. We present a modern, integrated analysis tool that efficiently produces reliable results that are used in our laser propagation tools such as VBL [5]. COMBINE is built on and supplants the existing legacy tools developed for the previous generations of lasers at LLNL but also uses commercially available mechanical finite element codes ANSYS or COMSOL (including computational fluid dynamics). The COMBINE code computes birefringence and wave front distortions due to mechanical stresses on lenses and slabs of arbitrary geometry. The stresses calculated typically originate from mounting support, vacuum load, gravity, heat absorption and/or attending cooling. Of particular importance are the depolarization and detuning effects of nonlinear crystals due to thermal loading. Results are given in the form of Jones matrices, depolarization maps and wave front distributions. An incremental evaluation of Jones matrices and ray propagation in a 3D mesh with a stress and temperature field is performed. Wavefront and depolarization maps are available at the optical aperture and at slices within the optical element. The suite is validated, user friendly, supported, documented and amenable to collaborative development. * COMBINE stands for Code for Opto-Mechanical Birefringence Integrated Numerical Evaluations.

  2. Analyzing the fast-start performance of northern pike using a mechanical fish

    NASA Astrophysics Data System (ADS)

    Modarres-Sadeghi, Yahya; Feng, Chengcheng; Bonafilia, Brian; Costain, Andrew

    2011-11-01

    The northern pike is able to achieve an instantaneous acceleration of 245 m/s2 through a two-stage motion. In the first stage the fish curls its body into either a C-shaped or an S-shaped curve (preparatory stage), and in the second stage uncurls it very quickly (propulsive stage) generating high accelerations due to the vortices shed from its tail. We have built a mechanical fish, based on the body profile of a pike, which is capable of performing this two-stage fast-start motion. Movement is governed by servo motors, which pull on cables attached to certain ribs, bending the fish into a C- or an S-shape. The degree of bending and timing of strokes can be controlled, and the fish can perform either a propulsive stroke only or a full stroke consisting of both the preparatory stage and the propulsive stage. The mechanical fish is capable of achieving peak accelerations of around 4 m/s2. We use this fish in order to study the influence of various variables on the observed acceleration. Although the maximum accelerations observed in our mechanical fish are smaller than those of a live fish, the form of the measured acceleration signal as function of time is quite similar to that of a live fish. The hydrodynamic efficiencies are observed to be around 12%, and it is shown that the majority of the thrust is produced at the rear part of the mechanical fish--similarly to the live fish.

  3. Effect of Bonder at Skin/Core Interface on the Mechanical Performances of Sandwich Structures Used in Marine Industry

    NASA Astrophysics Data System (ADS)

    Borsellino, C.; Calabrese, L.; di Bella, G.

    2007-11-01

    The present work is aimed to extend the knowledge of mechanical properties of sandwich structures used for marine applications focusing on the possibility to increase the performances of such structures by adding a bonder at the skin/core interface. Therefore, three sandwich structures that are utilised in different structural components of a yacht were realised by manual lay-up. The mechanical characterisation was performed by flatwise compressive, edgewise compressive and three point flexural tests. The tests execution has allowed both to determine the mechanical performances and to understand the fracture mechanisms that take place when the bonder is added in the stacking sequence of the samples.

  4. The acceptability of ending a patient's life

    PubMed Central

    Guedj, M; Gibert, M; Maudet, A; Munoz, S; Mullet, E; Sorum, P

    2005-01-01

    Objectives: To clarify how lay people and health professionals judge the acceptability of ending the life of a terminally ill patient. Design: Participants judged this acceptability in a set of 16 scenarios that combined four factors: the identity of the actor (patient or physician), the patient's statement or not of a desire to have his life ended, the nature of the action as relatively active (injecting a toxin) or passive (disconnecting life support), and the type of suffering (intractable physical pain, complete dependence, or severe psychiatric illness). Participants: 115 lay people and 72 health professionals (22 nurse's aides, 44 nurses, six physicians) in Toulouse, France. Main measurements: Mean acceptability ratings for each scenario for each group. Results: Life ending interventions are more acceptable to lay people than to the health professionals. For both, acceptability is highest for intractable physical suffering; is higher when patients end their own lives than when physicians do so; and, when physicians are the actors, is higher when patients have expressed a desire to die (voluntary euthanasia) than when they have not (involuntary euthanasia). In contrast, when patients perform the action, acceptability for the lay people and nurse's aides does not depend on whether the patient has expressed a desire to die, while for the nurses and physicians unassisted suicide is more acceptable than physician assisted suicide. Conclusions: Lay participants judge the acceptability of life ending actions in largely the same way as do healthcare professionals. PMID:15923476

  5. Computer acceptance of older adults.

    PubMed

    Nägle, Sibylle; Schmidt, Ludger

    2012-01-01

    Even though computers play a massive role in everyday life of modern societies, older adults, and especially older women, are less likely to use a computer, and they perform fewer activities on it than younger adults. To get a better understanding of the factors affecting older adults' intention towards and usage of computers, the Unified Theory of Acceptance and Usage of Technology (UTAUT) was applied as part of a more extensive study with 52 users and non-users of computers, ranging in age from 50 to 90 years. The model covers various aspects of computer usage in old age via four key constructs, namely performance expectancy, effort expectancy, social influences, and facilitating conditions, as well as the variables gender, age, experience, and voluntariness it. Interestingly, next to performance expectancy, facilitating conditions showed the strongest correlation with use as well as with intention. Effort expectancy showed no significant correlation with the intention of older adults to use a computer. PMID:22317258

  6. Determining Performance Acceptability of Electrochemical Oxygen Sensors

    NASA Technical Reports Server (NTRS)

    Gonzales, Daniel

    2012-01-01

    A method has been developed to screen commercial electrochemical oxygen sensors to reduce the failure rate. There are three aspects to the method: First, the sensitivity over time (several days) can be measured and the rate of change of the sensitivity can be used to predict sensor failure. Second, an improvement to this method would be to store the sensors in an oxygen-free (e.g., nitrogen) environment and intermittently measure the sensitivity over time (several days) to accomplish the same result while preserving the sensor lifetime by limiting consumption of the electrode. Third, the second time derivative of the sensor response over time can be used to determine the point in time at which the sensors are sufficiently stable for use.

  7. Evaluation of the Mechanical Performance of Self-Piercing Rivets in Friction Stir Welded Structures

    SciTech Connect

    Stephens, Elizabeth V.; Grant, Glenn J.; Davies, Richard W.; Wazny, Scott; Kaunitz, Leon; Fulbright, Brian; Waldron, D.

    2005-04-01

    This paper presents the coupon performance data of friction stir welded tailor welded blanks (TWBs) joined to a monolithic aluminum sheet by self-piercing rivets (SPRs). Uniaxial tensile tests were performed to characterize the joint strength and the total energy absorption capability of the TWB/monolithic joint assemblies. Cyclic fatigue tests were also conducted to characterize the fatigue behavior and failure mechanisms of the jointed assemblies. It was found that the static and fatigue strength of the TWB/monolithic assembly was approximately 30 percent less in all loading configurations tested in comparison to a common monolithic sheet SPR assembly. The total energy absorbed by the TWB/monolithic sheet assemblies was also found to be 30 percent less than the monolithic sheet assemblies in cross tension loading. In lap shear loading, the total energy absorbed was comparable.

  8. Anatomy of a Nanoscale Conduction Channel Reveals the Mechanism of a High-Performance Memristor

    NASA Astrophysics Data System (ADS)

    Miao, Feng; Strachan, John Paul; Yang, J. Joshua; Yi, Wei; Goldfarb, Ilan; Zhang, M.-X.; Torrezan, Antonio C.; Eschbach, Peter; Kelley, Ronald D.; Medeiros-Ribeiro, Gilberto; Williams, R. Stanley

    2012-02-01

    Two major challenges for resistance memory devices (memristors) based on conductivity changes in oxide materials are better performance and understanding of the microscopic picture of the switching. After researchers' relentless pursuit for years, tantalum oxide-based memristors have rapidly risen to be the top candidate, showing fast speed, high endurance and excellent scalability. While the microscopic picture of these devices remains obscure, by employing a precise method for locating and directly visualizing the conduction channel, here we observed a nanoscale channel consisting of an amorphous Ta(O) solid solution surrounded by crystalline Ta2O5. Structural and chemical analyses of the channel combined with temperature dependent transport measurements revealed a unique resistance switching mechanism: the modulation of the channel elemental composition, and thus the conductivity, by the cooperative influence of drift, diffusion and thermophoresis, which seem to enable the high switching performance observed. (Miao*, Strachan*, Yang* et al., Advanced Materials. DOI: 10.1002/adma201103379 (2011))

  9. Acceptability of human risk.

    PubMed Central

    Kasperson, R E

    1983-01-01

    This paper has three objectives: to explore the nature of the problem implicit in the term "risk acceptability," to examine the possible contributions of scientific information to risk standard-setting, and to argue that societal response is best guided by considerations of process rather than formal methods of analysis. Most technological risks are not accepted but are imposed. There is also little reason to expect consensus among individuals on their tolerance of risk. Moreover, debates about risk levels are often at base debates over the adequacy of the institutions which manage the risks. Scientific information can contribute three broad types of analyses to risk-setting deliberations: contextual analysis, equity assessment, and public preference analysis. More effective risk-setting decisions will involve attention to the process used, particularly in regard to the requirements of procedural justice and democratic responsibility. PMID:6418541

  10. Thermal and Mechanical Performance of a Carbon/Carbon Composite Spacecraft Radiator

    NASA Technical Reports Server (NTRS)

    Kuhn, Jonathan; Benner, Steve; Butler, Dan; Silk, Eric

    1999-01-01

    Carbon-carbon composite materials offer greater thermal efficiency, stiffness to weight ratio, tailorability, and dimensional stability than aluminum. These lightweight thermal materials could significantly reduce the overall costs associated with satellite thermal control and weight. However, the high cost and long lead-time for carbon-carbon manufacture have limited their widespread usage. Consequently, an informal partnership between government and industrial personnel called the Carbon-Carbon Spacecraft Radiator Partnership (CSRP) was created to foster carbon-carbon composite use for thermally and structurally demanding space radiator applications. The first CSRP flight opportunity is on the New Millennium Program (NMP) Earth Orbiter-1 (EO-1) spacecraft, scheduled for launch in late 1999. For EO-1, the CSRP designed and fabricated a Carbon-Carbon Radiator (CCR) with carbon-carbon facesheets and aluminum honeycomb core, which will also serve as a structural shear panel. While carbon-carbon is an ideal thermal candidate for spacecraft radiators, in practice there are technical challenges that may compromise performance. In this work, the thermal and mechanical performance of the EO-1 CCR is assessed by analysis and testing. Both then-nal and mechanical analyses were conducted to predict the radiator response to anticipated launch and on-orbit loads. The thermal model developed was based on thermal balance test conditions. The thermal analysis was performed using SINDA version 4.0. Structural finite element modeling and analysis were performed using SDRC/1-DEAS and UAI/NASTRAN, respectively. In addition, the CCR was subjected to flight qualification thermal/vacuum and vibration tests. The panel meets or exceeds the requirements for space flight and demonstrates promise for future satellite missions.

  11. Age and Acceptance of Euthanasia.

    ERIC Educational Resources Information Center

    Ward, Russell A.

    1980-01-01

    Study explores relationship between age (and sex and race) and acceptance of euthanasia. Women and non-Whites were less accepting because of religiosity. Among older people less acceptance was attributable to their lesser education and greater religiosity. Results suggest that quality of life in old age affects acceptability of euthanasia. (Author)

  12. Improving performance in quantum mechanics with explicit incentives to correct mistakes

    NASA Astrophysics Data System (ADS)

    Brown, Benjamin R.; Mason, Andrew; Singh, Chandralekha

    2016-06-01

    An earlier investigation found that the performance of advanced students in a quantum mechanics course did not automatically improve from midterm to final exam on identical problems even when they were provided the correct solutions and their own graded exams. Here, we describe a study, which extended over four years, in which upper-level undergraduate students in a quantum physics course were given four identical problems in both the midterm exam and final exam. Approximately half of the students were given explicit incentives to correct their mistakes in the midterm exam. In particular, they could get back up to 50% of the points lost on each midterm exam problem. The solutions to the midterm exam problems were provided to all students in both groups but those who corrected their mistakes were provided the solution after they submitted their corrections to the instructor. The performance on the same problems on the final exam suggests that students who were given incentives to correct their mistakes significantly outperformed those who were not given an incentive. The incentive to correct the mistakes had greater impact on the final exam performance of students who had not performed well on the midterm exam.

  13. Optimal control simulations reveal mechanisms by which arm movement improves standing long jump performance.

    PubMed

    Ashby, Blake M; Delp, Scott L

    2006-01-01

    Optimal control simulations of the standing long jump were developed to gain insight into the mechanisms of enhanced performance due to arm motion. The activations that maximize standing long jump distance of a joint torque actuated model were determined for jumps with free and restricted arm movement. The simulated jump distance was 40 cm greater when arm movement was free (2.00 m) than when it was restricted (1.60 m). The majority of the performance improvement in the free arm jump was due to the 15% increase (3.30 vs. 2.86 m/s) in the take-off velocity of the center of gravity. Some of the performance improvement in the free arm jump was attributable to the ability of the jumper to swing the arms backwards during the flight phase to alleviate excessive forward rotation and position the body segments properly for landing. In restricted arm jumps, the excessive forward rotation was avoided by "holding back" during the propulsive phase and reducing the activation levels of the ankle, knee, and hip joint torque actuators. In addition, swinging the arm segments allowed the lower body joint torque actuators to perform 26 J more work in the free arm jump. However, the most significant contribution to developing greater take-off velocity came from the additional 80 J work done by the shoulder actuator in the jump with free arm movement. PMID:15992805

  14. Mechanical strength of porous nickel plates containing lithium and their performance as the cathode for MCFC

    NASA Astrophysics Data System (ADS)

    Kim, Seung-Goo; Yoon, Sung Pil; Han, Jonghee; Nam, Suk Woo; Lim, Tae-Hoon; Oh, In-Hwan; Hong, Seong-Ahn

    To improve the mechanical properties of MCFC cathode materials, pre-lithiated porous nickel plates containing 1-5 mol% of lithium were fabricated by the tape casting method, and the microstructures, mechanical properties, and performance was examined. The microstructure and pore distribution was not changed until the lithum content reached 3 mol%. The sample containing 5 mol% of lithium had patch structure on the skeleton and a smaller volume of primary pores. XRD analysis showed that lithium-containing porous nickel plates can easily form solid solutions without any undesirable byproducts after the oxidation. Both the bending strength and Young's modulus of the porous plates increased with the increase of lithium content. The average bending strengths of the samples containing 1, 3, and 5 mol% of lithium were 1.29, 1.33, and 1.49 kgf/mm 2 which were 2.9, 3.0, and 3.4 times higher than that of pure porous nickel plate. The Young's modulus increased up to 1.35 kgf/mm in the case of the 5 mol% lithium containing sample that is 5.4 times higher than that of pure porous nickel plate. The OCV of single cells using pre-lithiated cathodes were between 1.065 and 1.067 V, and comparable cell performance was obtained for 500 h of single cell operation.

  15. Optimization of the dye-sensitized solar cell performance by mechanical compression

    NASA Astrophysics Data System (ADS)

    Meen, Teen Hang; Tsai, Jenn Kai; Tu, Yu Shin; Wu, Tian Chiuan; Hsu, Wen Dung; Chang, Shoou-Jinn

    2014-09-01

    In this study, the P25 titanium dioxide (TiO2) nanoparticle (NP) thin film was coated on the fluorine-doped tin oxide (FTO) glass substrate by a doctor blade method. The film then compressed mechanically to be the photoanode of dye-sensitized solar cells (DSSCs). Various compression pressures on TiO2 NP film were tested to optimize the performance of DSSCs. The mechanical compression reduces TiO2 inter-particle distance improving the electron transport efficiency. The UV-vis spectrophotometer and electrochemical impedance spectroscopy (EIS) were employed to quantify the light-harvesting efficiency and the charge transport impedance at various interfaces in DSSC, respectively. The incident photon-to-current conversion efficiency was also monitored. The results show that when the DSSC fabricated by the TiO2 NP thin film compressed at pressure of 279 kg/cm2, the minimum resistance of 9.38 Ω at dye/TiO2 NP/electrolyte interfaces, the maximum short-circuit photocurrent density of 15.11 mA/cm2, and the photoelectric conversion efficiency of 5.94% were observed. Compared to the DSSC fabricated by the non-compression of TiO2 NP thin film, the overall conversion efficiency is improved over 19.5%. The study proves that under suitable compression pressure the performance of DSSC can be optimized.

  16. Comparison of Co(2+) adsorption by chitosan and its triethylene-tetramine derivative: Performance and mechanism.

    PubMed

    Liao, Bing; Sun, Wei-Yi; Guo, Na; Ding, Sang-Lan; Su, Shi-Jun

    2016-10-20

    A cross-linked chitosan derivative (CCTS) was synthesized via cross-linking of epichlorohydrin and grafting of triethylene-tetramine. The adsorption performance and capacity of the raw chitosan (CTS) and its derivative were also investigated for removal of Co(2+) from aqueous solution. A maximum adsorbed amount of 30.45 and 59.51mg/g was obtained for CTS and CCTS, respectively under the optimized conditions. In addition, the adsorption kinetics for the adsorption of Co(2+) by CTS and CCTS were better described by the pseudo second-order equation. The adsorption isotherm of CCTS was well fitted by the Langmuir equation, but the data of the adsorption of Co(2+) onto CTS followed Freundlich and Sips isotherms better. Furthermore, the adsorbent still exhibited good adsorption performance after five regeneration cycles. Finally, Co(2+) removal mechanisms, including physical, chemical, and electrostatic adsorption, were discussed based on microstructure analysis and adsorption kinetics and isotherms. Chemical adsorption was the main adsorption method among these mechanisms. PMID:27474539

  17. Optimization of the dye-sensitized solar cell performance by mechanical compression

    PubMed Central

    2014-01-01

    In this study, the P25 titanium dioxide (TiO2) nanoparticle (NP) thin film was coated on the fluorine-doped tin oxide (FTO) glass substrate by a doctor blade method. The film then compressed mechanically to be the photoanode of dye-sensitized solar cells (DSSCs). Various compression pressures on TiO2 NP film were tested to optimize the performance of DSSCs. The mechanical compression reduces TiO2 inter-particle distance improving the electron transport efficiency. The UV–vis spectrophotometer and electrochemical impedance spectroscopy (EIS) were employed to quantify the light-harvesting efficiency and the charge transport impedance at various interfaces in DSSC, respectively. The incident photon-to-current conversion efficiency was also monitored. The results show that when the DSSC fabricated by the TiO2 NP thin film compressed at pressure of 279 kg/cm2, the minimum resistance of 9.38 Ω at dye/TiO2 NP/electrolyte interfaces, the maximum short-circuit photocurrent density of 15.11 mA/cm2, and the photoelectric conversion efficiency of 5.94% were observed. Compared to the DSSC fabricated by the non-compression of TiO2 NP thin film, the overall conversion efficiency is improved over 19.5%. The study proves that under suitable compression pressure the performance of DSSC can be optimized. PMID:25276109

  18. Optimization of the dye-sensitized solar cell performance by mechanical compression.

    PubMed

    Meen, Teen Hang; Tsai, Jenn Kai; Tu, Yu Shin; Wu, Tian Chiuan; Hsu, Wen Dung; Chang, Shoou-Jinn

    2014-01-01

    In this study, the P25 titanium dioxide (TiO2) nanoparticle (NP) thin film was coated on the fluorine-doped tin oxide (FTO) glass substrate by a doctor blade method. The film then compressed mechanically to be the photoanode of dye-sensitized solar cells (DSSCs). Various compression pressures on TiO2 NP film were tested to optimize the performance of DSSCs. The mechanical compression reduces TiO2 inter-particle distance improving the electron transport efficiency. The UV-vis spectrophotometer and electrochemical impedance spectroscopy (EIS) were employed to quantify the light-harvesting efficiency and the charge transport impedance at various interfaces in DSSC, respectively. The incident photon-to-current conversion efficiency was also monitored. The results show that when the DSSC fabricated by the TiO2 NP thin film compressed at pressure of 279 kg/cm(2), the minimum resistance of 9.38 Ω at dye/TiO2 NP/electrolyte interfaces, the maximum short-circuit photocurrent density of 15.11 mA/cm(2), and the photoelectric conversion efficiency of 5.94% were observed. Compared to the DSSC fabricated by the non-compression of TiO2 NP thin film, the overall conversion efficiency is improved over 19.5%. The study proves that under suitable compression pressure the performance of DSSC can be optimized. PMID:25276109

  19. Mechanical and Electrical Performance of Thermally Stable Au-ZnO films

    DOE PAGESBeta

    Schoeppner, Rachel L.; Goeke, Ronald S.; Moody, Neville R.; Bahr, David F.

    2015-03-28

    The mechanical properties, thermal stability, and electrical performance of Au–ZnO composite thin films are determined in this work. The co-deposition of ZnO with Au via physical vapor deposition leads to grain refinement over that of pure Au; the addition of 0.1 vol.% ZnO reduces the as-grown grain size by over 30%. The hardness of the as-grown films doubles with 2% ZnO, from 1.8 to 3.6 GPa as measured by nanoindentation. Films with ZnO additions greater than 0.5% show no significant grain growth after annealing at 350 °C, while pure gold and smaller additions do exhibit grain growth and subsequent mechanicalmore » softening. Films with 1% and 2% ZnO show a decrease of approximately 50% in electrical resistivity and no change in hardness after annealing. A model accounting for both changes in the interface structure between dispersed ZnO particles and the Au matrix captures the changes in mechanical and electrical resistivity. Furthermore, the addition of 1–2% ZnO co-deposited with Au provides a method to create mechanically hard and thermally stable films with a resistivity less than 80 nΩ-m. Our results complement previous studies of other alloying systems, suggesting oxide dispersion strengthened (ODS) gold shows a desirable hardness–resistivity relationship that is relatively independent of the particular ODS chemistry.« less

  20. A laser-engraved glass duplicating the structure, mechanics and performance of natural nacre.

    PubMed

    Valashani, Seyed Mohammad Mirkhalaf; Barthelat, Francois

    2015-04-01

    Highly mineralized biological materials such as nacre (mother of pearl), tooth enamel or conch shell boast unique and attractive combinations of stiffness, strength and toughness. The structures of these biological materials and their associated mechanisms are now inspiring new types of advanced structural materials. However, despite significant efforts, no bottom up fabrication method could so far match biological materials in terms of microstructural organization and mechanical performance. Here we present a new 'top down' strategy to tackling this fabrication problem, which consists in carving weak interfaces within a brittle material using a laser engraving technique. We demonstrate the method by fabricating and testing borosilicate glasses containing nacre-like microstructures infiltrated with polyurethane. When deformed, these materials properly duplicate the mechanisms of natural nacre: combination of controlled sliding of the tablets, accompanied with geometric hardening, strain hardening and strain rate hardening. The nacre-like glass is composed of 93 volume % (vol%) glass, yet 700 times tougher and breaks at strains as high as 20%. PMID:25822595

  1. Analog performance of vertical nanowire TFETs as a function of temperature and transport mechanism

    NASA Astrophysics Data System (ADS)

    Martino, Marcio Dalla Valle; Neves, Felipe; Ghedini Der Agopian, Paula; Martino, João Antonio; Vandooren, Anne; Rooyackers, Rita; Simoen, Eddy; Thean, Aaron; Claeys, Cor

    2015-10-01

    The goal of this work is to study the analog performance of tunnel field effect transistors (TFETs) and its susceptibility to temperature variation and to different dominant transport mechanisms. The experimental input characteristic of nanowire TFETs with different source compositions (100% Si and Si1-xGex) has been presented, leading to the extraction of the Activation Energy for each bias condition. These first results have been connected to the prevailing transport mechanism for each configuration, namely band-to-band tunneling (BTBT) or trap assisted tunneling (TAT). Afterward, this work analyzes the analog behavior, with the intrinsic voltage gain calculated in terms of Early voltage, transistor efficiency, transconductance and output conductance. Comparing the results for devices with different source compositions, it is interesting to note how the analog trends vary depending on the source characteristics and the prevailing transport mechanisms. This behavior results in a different suitability analysis depending on the working temperature. In other words, devices with full-Silicon source and non-abrupt junction profile present the worst intrinsic voltage gain at room temperature, but the best results for high temperatures. This was possible since, among the 4 studied devices, this configuration was the only one with a positive intrinsic voltage gain dependence on the temperature variation.

  2. Assessment of Mechanical Performance of Bone Architecture Using Rapid Prototyping Models

    NASA Astrophysics Data System (ADS)

    Saparin, Peter; Woesz, Alexander; Thomsen, Jasper S.; Fratzl, Peter

    2008-06-01

    The aim of this on-going research project is to assess the influence of bone microarchitecture on the mechanical performance of trabecular bone. A testing chain consist-ing of three steps was established: 1) micro computed tomography (μCT) imaging of human trabecular bone; 2) building of models of the bone from a light-sensitive polymer using Rapid Prototyping (RP); 3) mechanical testing of the models in a material testing machine. A direct resampling procedure was developed to convert μCT data into the format of the RP machine. Standardized parameters for production and testing of the plastic models were established by use of regular cellular structures. Next, normal, osteoporotic, and extreme osteoporotic vertebral trabecular bone architectures were re-produced by RP and compression tested. We found that normal architecture of vertebral trabecular bone exhibit behaviour characteristic of a cellular structure. In normal bone the fracture occurs at much higher strain values that in osteoporotic bone. After the fracture a normal trabecular architecture is able to carry much higher loads than an osteoporotic architecture. However, no statistically significant differences were found in maximal stress during uniaxial compression of the central part of normal, osteoporotic, and extreme osteoporotic vertebral trabecular bone. This supports the hypothesis that osteoporotic trabecular bone can compensate for a loss of trabeculae by thickening the remaining trabeculae in the loading direction (compensatory hypertrophy). The developed approach could be used for mechanical evaluation of structural data acquired non-invasively and assessment of changes in performance of bone architecture.

  3. Effects of oxygen and weak magnetic field on Fe(0)/bisulfite system: performance and mechanisms.

    PubMed

    Xiong, Xinmei; Gan, Jinhong; Zhan, Wei; Sun, Bo

    2016-08-01

    The performance and mechanisms of 4-nitrophenol (4-NP) degradation by the Fe(0)/bisulfite system were systematically investigated for the first time. The evidences presented in this study verified that O2 was a crucial factor that affected the mechanism of Fe(0)/bisulfite-driven 4-NP degradation. In the Fe(0)/bisulfite/O2 system, Fe(0) acted as a supplier of Fe(2+) to catalyze bisulfite oxidation that induced a chain reaction to produce reactive radicals for 4-NP degradation. While under N2 purging condition, bisulfite worked as a specified reductant that facilitated the transformation of Fe(3+) to nascent Fe(2+) ions, which principally accounted for the reductive removal of 4-NP. The application of a weak magnetic field (WMF) efficiently improved the removal rate of 4-NP and did not alter the mechanisms in both Fe(0)/bisulfite/O2 and Fe(0)/bisulfite/N2 processes. The secondary radicals, HO(·), SO4 (·-), and SO5 (·-), were considered as the most possible active oxidants contributing to the oxidative removal of 4-NP and even partial mineralization under an oxic condition. Compared with anoxic conditions, the performance removal of 4-NP by the WMF-Fe(0)/bisulfite/O2 system showed less pHini dependence. To facilitate the application of WMF-Fe(0)/bisulfite/O2 technology in real practice, premagnetization of Fe(0) was employed to combine with bisulfite/O2 and proved to be an effective and applicable method for 4-NP removal. PMID:27184150

  4. W-026, transuranic waste (TRU) glovebox acceptance test report

    SciTech Connect

    Leist, K.J.

    1998-03-11

    On July 18, 1997, the Transuranic (TRU) glovebox was tested using glovebox acceptance test procedure 13021A-86. The primary focus of the glovebox acceptance test was to examine control system interlocks, display menus, alarms, and operator messages. Limited mechanical testing involving the drum ports, hoists, drum lifter, compacted drum lifter, drum tipper, transfer car, conveyors, sorting table, lidder/delidder device and the TRU empty drum compactor were also conducted. As of February 25, 1998, 10 of the 102 test exceptions that affect the TRU glovebox remain open. These items will be tracked and closed via the WRAP Master Test Exception Database. As part of Test Exception resolution/closure the responsible individual closing the Test Exception performs a retest of the affected item(s) to ensure the identified deficiency is corrected, and, or to test items not previously available to support testing. Test exceptions are provided as appendices to this report.

  5. WRAP low level waste (LLW) glovebox acceptance test report

    SciTech Connect

    Leist, K.J.

    1998-02-17

    In June 28, 1997, the Low Level Waste (LLW) glovebox was tested using glovebox acceptance test procedure 13031A-85. The primary focus of the glovebox acceptance test was to examine control system interlocks, display menus, alarms, and operator messages. Limited mechanical testing involving the drum ports, hoists, drum lifter, compacted drum lifter, drum tipper, transfer car, conveyors, lidder/delidder device and the supercompactor were also conducted. As of November 24, 1997, 2 of the 131 test exceptions that affect the LLW glovebox remain open. These items will be tracked and closed via the WRAP Master Test Exception Database. As part of Test Exception resolution/closure the responsible individual closing the Test Exception performs a retest of the affected item(s) to ensure the identified deficiency is corrected, and, or to test items not previously available to support testing. Test Exceptions are provided as appendices to this report.

  6. 5 CFR 531.409 - Acceptable level of competence determinations.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 5 Administrative Personnel 1 2010-01-01 2010-01-01 false Acceptable level of competence... REGULATIONS PAY UNDER THE GENERAL SCHEDULE Within-Grade Increases § 531.409 Acceptable level of competence... delegated shall determine which employees are performing at an acceptable level of competence. (b) Basis...

  7. Acceptance test procedure for shuttle actuators simulator (elevon subsystem)

    NASA Technical Reports Server (NTRS)

    Barr, J.

    1976-01-01

    The acceptance test procedure is described for the Lockheed Electronics Elevon Servoactuator Simulator to be used in the Shuttle Avionics Integration Laboratory (SAIL). The intent of this acceptance test procedure is to comply with the technical Shuttle Actuators Simulator Requirements. Acceptance tests will be performed on each Elevon Servoactuator Simulator.

  8. 5 CFR 531.409 - Acceptable level of competence determinations.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 5 Administrative Personnel 1 2012-01-01 2012-01-01 false Acceptable level of competence... REGULATIONS PAY UNDER THE GENERAL SCHEDULE Within-Grade Increases § 531.409 Acceptable level of competence... delegated shall determine which employees are performing at an acceptable level of competence. (b) Basis...

  9. 5 CFR 531.409 - Acceptable level of competence determinations.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 5 Administrative Personnel 1 2013-01-01 2013-01-01 false Acceptable level of competence... REGULATIONS PAY UNDER THE GENERAL SCHEDULE Within-Grade Increases § 531.409 Acceptable level of competence... delegated shall determine which employees are performing at an acceptable level of competence. (b) Basis...

  10. 5 CFR 531.409 - Acceptable level of competence determinations.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 5 Administrative Personnel 1 2014-01-01 2014-01-01 false Acceptable level of competence... REGULATIONS PAY UNDER THE GENERAL SCHEDULE Within-Grade Increases § 531.409 Acceptable level of competence... delegated shall determine which employees are performing at an acceptable level of competence. (b) Basis...

  11. Sandwich structures for high temperature applications: Microstructural development and mechanical performance

    NASA Astrophysics Data System (ADS)

    Azarmi, Fardad

    There has been a great deal of interest in the development of sandwich structures as viable engineering constructions. It is due to their unique structural, physical, and mechanical characteristics such as light weight, high strength to weight ratio, high bending stiffness, excellent thermal and acoustical insulation. Although the service temperature for most applications of sandwich structures is low, the outstanding properties make sandwich constructions attractive for use in high temperature service conditions as well. The overall performance of sandwich constructions depends on the material properties of skin and core, and their geometrical characteristics. An investigation of the characteristics of sandwich structures suitable for high temperature application is presented. The objective of the investigation was to develop a process for producing sandwich structures by depositing alloy 625 skins on Ni foam cores using air plasma spraying (APS), and to characterize the structure and mechanical behavior of the constituents and the sandwich structure. The experimental investigation consisted of optimization of deposition process parameters, microstructural and mechanical characterization of sandwich constituents and testing of mechanical performance of sandwich structures under flexural loading conditions. The responses of the as-received foam, as-sprayed coating, and as-fabricated sandwich structure to heat treatment were investigated. Available analytical models and numerical simulations linking the mechanical properties of the Ni alloy foam, the alloy 625 coating, and the sandwich structure to their physical properties and microstructures were compared with the results of mechanical testing to understand the behavior of the sandwich structure in terms of the properties of the constituents. An empirical model was developed to predict deposition parameters which simultaneously minimize the oxide content and the porosity in the alloy 625 coating. The optimum

  12. Quiet eye and the Bereitschaftspotential: visuomotor mechanisms of expert motor performance.

    PubMed

    Mann, Derek T Y; Coombes, Steven A; Mousseau, Melanie B; Janelle, Christopher M

    2011-08-01

    Concurrent exploration of the Bereitschaftspotential (BP) and quiet eye period (QE) was implemented to assess potential mechanisms underlying psychomotor skills that differentiate expert and near-expert performers. Twenty golfers were classified by their USGA handicap rating as either a high handicap (HH; near-expert) or low handicap (LH; expert) to permit skill-based inferences. Participants completed 90 trials during which QE duration, BP activity, and putting performance were recorded. The application of single-subject analyses illustrated that LH golfers were more accurate and less variable in their performance than the HH group. Systematic differences in QE duration and BP were also observed, with experts exhibiting a prolonged quiet eye period and greater cortical activation in the right-central region compared with non-experts. A significant association between cortical activation and QE duration was also noted. The results of this investigation lend support to the motor programming/preparation function of the QE period. Practical and theoretical implications are presented and suggestions for future empirical work provided. PMID:21465225

  13. Mechanical-biological treatment: performance and potentials. An LCA of 8 MBT plants including waste characterization.

    PubMed

    Montejo, Cristina; Tonini, Davide; Márquez, María del Carmen; Astrup, Thomas Fruergaard

    2013-10-15

    In the endeavour of avoiding presence of biodegradable waste in landfills and increasing recycling, mechanical-biological treatment (MBT) plants have seen a significant increase in number and capacity in the last two decades. The aim of these plants is separating and stabilizing the quickly biodegradable fraction of the waste as well as recovering recyclables from mixed waste streams. In this study the environmental performance of eight MBT-based waste management scenarios in Spain was assessed by means of life cycle assessment. The focus was on the technical and environmental performance of the MBT plants. These widely differed in type of biological treatment and recovery efficiencies. The results indicated that the performance is strongly connected with energy and materials recovery efficiency. The recommendation for upgrading and/or commissioning of future plants is to optimize materials recovery through increased automation of the selection and to prioritize biogas-electricity production from the organic fraction over direct composting. The optimal strategy for refuse derived fuel (RDF) management depends upon the environmental compartment to be prioritized and the type of marginal electricity source in the system. It was estimated that, overall, up to ca. 180-190 kt CO2-eq. y(-1) may be saved by optimizing the MBT plants under assessment. PMID:23850761

  14. Influence of drive and timing mechanisms on breathing pattern and ventilation during mental task performance.

    PubMed

    Wientjes, C J; Grossman, P; Gaillard, A W

    1998-09-01

    Assessment of multiple respiratory measures may provide insight into how behavioral demands affect the breathing pattern. This is illustrated by data from a study among 44 subjects, in which tidal volume, respiration rate, minute ventilation and indices of central drive and timing mechanisms were assessed via inductive plethysmography, in addition to end-tidal PCO2. After a baseline, three conditions of a memory comparison task were presented. The first two conditions differed only with regard to the presence or absence of feedback of performance (NFB and FB). In the third 'all-or-nothing' (AON) condition, subjects only received a monetary bonus, if their performance exceeded that of the previous two conditions. Minute ventilation increased from baseline to all task conditions, and from NFB and FB to AON. Respiration rate increased in all task conditions, but there were no differences between task conditions. Tidal volume decreased during NFB, but was equal to baseline during FB and AON. Of the respiratory control indices, inspiratory flow rate covaried much more closely with minute ventilation than duty cycle. The task performance induced a minor degree of hyperventilation. The discussion focusses on how behavioral demands affect respiratory control processes to produce alterations in breathing pattern and ventilation. PMID:9792484

  15. Effect of pulsed plasma nitriding on mechanical and tribological performance of Ck45 steel.

    PubMed

    Rastkar, A R; Kiani, A; Alvand, F; Shokri, B; Amirzadeh, M

    2011-06-01

    We studied the mechanical properties and wear performance of AISI 1045 (Ck45) carbon steel under the influence of pulsed plasma nitriding. The treatments were performed at temperatures of 500 and 550 degrees C in N2:H2 gas ratios of 1:3 and 3:1 and the working pressure of 10 mbar for 1 to 4 hours. Samples were examined by X-ray diffraction, optical, electron and atomic force microscopy, microhardness tests, roughness measurements and wear tests. Nitride layers were mainly composed of epsilon-(Fe2-3N) or gamma'-(Fe4N) depending on the gas ratio and/or temperature and time. When the nitriding time is increased, the composition of the compound layer varies from monophase gamma'-(Fe4N) to the two phase of epsilon-(Fe2-3N) and gamma'-(Fe4N). The highest thickness and hardness of the layers were obtained at 550 degrees C in the N2:H2 gas ratios of 3:1 for 4 h. The topographical evolution and surface roughness of the samples showed that all the roughness parameters increase with increasing the temperature. The friction coefficient of all samples was higher than that of untreated material. Wear performance of all nitrided samples was significantly better than that of untreated material. PMID:21770190

  16. An Evaluation of the Corrosion and Mechanical Performance of Interstitially Surface-Hardened Stainless Steel

    NASA Astrophysics Data System (ADS)

    Jones, Jennifer L.; Koul, Michelle G.; Schubbe, Joel J.

    2014-06-01

    A surface hardening technique called "interstitial hardening" is commercially available, whereby interstitial carbon atoms are introduced into stainless steel surfaces without the formation of carbides. Surface hardening of machine elements such as impellors or fasteners would improve performance regarding cavitation and galling resistance, and has intensified interest in this process. However, there remains a need to characterize and validate the specific performance characteristics of the hardened materials. This paper describes experimental testing conducted on 316L stainless steel that has been surface hardened using available commercial techniques, using carbon as the interstitial atom. The corrosion performance of the hardened surface is assessed using electrochemical potentiodynamic testing to determine the breakdown potential in 3.5 wt.% NaCl solution to identify the most promising method. The hardness and thickness of the surface-hardened layer is characterized and compared using metallography and microhardness profiling. Corrosion fatigue and slow strain rate testing of untreated, hardened, and damaged, hardened surfaces exposed to ASTM seawater is conducted. Finally, critical galling stresses are determined and compared. Post-test examination of damage attempts to identify mechanisms of material failure and characterize how corrosion-assisted cracks initiate and grow in surface-hardened materials.

  17. High acceptance recoil polarimeter

    SciTech Connect

    The HARP Collaboration

    1992-12-05

    In order to detect neutrons and protons in the 50 to 600 MeV energy range and measure their polarization, an efficient, low-noise, self-calibrating device is being designed. This detector, known as the High Acceptance Recoil Polarimeter (HARP), is based on the recoil principle of proton detection from np[r arrow]n[prime]p[prime] or pp[r arrow]p[prime]p[prime] scattering (detected particles are underlined) which intrinsically yields polarization information on the incoming particle. HARP will be commissioned to carry out experiments in 1994.

  18. Dogmatism, Self-Acceptance, and Acceptance of Others Among Spanish and American Students

    ERIC Educational Resources Information Center

    Gonzalez-Tamayo, Eulogy

    1974-01-01

    A cross cultural study of 16-year-olds in Spain and the United States assesses the extent to which open or closed societies effect performance on the Dogmatism Scale, and the Acceptance of Self and Others Attitude Scale. (JH)

  19. Flight Performance Handbook for Orbital Operations: Orbital Mechanics and Astrodynamics Formulae, Theorems, Techniques, and Applications

    NASA Technical Reports Server (NTRS)

    Ambrosio, Alphonso; Blitzer, Leon; Conte, S.D.; Cooper, Donald H.; Dergarabedian, P.; Dethlefsen, D.G.; Lunn, Richard L.; Ireland, Richard O.; Jensen, Arnold A.; Kang, Garfield; Levy, Ezra C.; Liu, Anthony; Marcus, Silvia R.; Mickelwait, A.B.; Moe, Kenneth; Moe, Mildred M.; Pitton, A.R.; Scheuer, Ernest M.; Tompkins, E.H.; Weiser, Peter B.; Whitford, R.K.; Wolverton, R.W.

    1961-01-01

    This handbook provides parametric data useful both to the space vehicle designer and mission analyst. It provides numerical and analytical relationships between missions and gross vehicle characteristics as a function of performance parameters. The effects of missile constraints and gross guidance limitations plus operational constraints such as launch site location, tracking net location, orbit visibility and mission on trajectory and orbit design parameters are exhibited. The influence of state-of- the-art applications of solar power as compared to future applications of nuclear power on orbit design parameters, such as eclipse time, are among the parameters included in the study. The principal aim, however, is in providing the analyst with useful parametric design information to cover the general area of earth satellite missions in the region of near-earth to cislunar space and beyond and from injection to atmospheric entry and controlled descent. The chapters are organized around the central idea of orbital operations in the 1961-1969 era with emphasis on parametric flight mechanics studies for ascent phase and parking orbits, transfer maneuvers, rendezvous maneuver, operational orbit considerations, and operational orbit control. The results are based almost entirely on the principles of flight and celestial mechanics. Numerous practical examples have been worked out in detail. This is especially important where it has been difficult or impossible to represent all possible variations of the parameters. The handbook contains analytical formulae and sufficient textual material to permit their proper use. The analytic methods consist of both exact and rapid, approximate methods. Scores of tables, working graphs and illustrations amplify the mathematical models which, together with important facts and data, cover the engineering and scientific applications of orbital mechanics. Each of the five major chapters are arranged to provide a rapid review of an entire

  20. An Empirical Examination of the Mechanisms Mediating between High-Performance Work Systems and the Performance of Japanese Organizations

    ERIC Educational Resources Information Center

    Takeuchi, Riki; Lepak, David P.; Wang, Heli; Takeuchi, Kazuo

    2007-01-01

    The resource-based view of the firm and social exchange perspectives are invoked to hypothesize linkages among high-performance work systems, collective human capital, the degree of social exchange in an establishment, and establishment performance. The authors argue that high-performance work systems generate a high level of collective human…

  1. Surface moisture measurement system hardware acceptance test report

    SciTech Connect

    Ritter, G.A., Westinghouse Hanford

    1996-05-28

    This document summarizes the results of the hardware acceptance test for the Surface Moisture Measurement System (SMMS). This test verified that the mechanical and electrical features of the SMMS functioned as designed and that the unit is ready for field service. The bulk of hardware testing was performed at the 306E Facility in the 300 Area and the Fuels and Materials Examination Facility in the 400 Area. The SMMS was developed primarily in support of Tank Waste Remediation System (TWRS) Safety Programs for moisture measurement in organic and ferrocyanide watch list tanks.

  2. Unexpected behavior of irradiated spider silk links conformational freedom to mechanical performance.

    PubMed

    Perea, G Belén; Solanas, Concepción; Plaza, Gustavo R; Guinea, Gustavo V; Jorge, Inmaculada; Vázquez, Jesús; Pérez Mateos, Jorge M; Marí-Buyé, Núria; Elices, Manuel; Pérez-Rigueiro, José

    2015-06-28

    Silk fibers from Argiope trifasciata and Nephila inaurata orb-web weaving spiders were UV irradiated to modify the molecular weight of the constituent proteins. Fibers were characterized either as forcibly silked or after being subjected to maximum supercontraction. The effect of irradiation on supercontraction was also studied, both in terms of the percentage of supercontraction and the tensile properties exhibited by irradiated and subsequently supercontracted fibers. The effects of UV exposure at the molecular level were assessed by polyacrylamide gel electrophoresis and mass spectrometry. It is shown that UV-irradiated fibers show a steady decrease in their main tensile parameters, most notably, tensile strength and strain. The combination of the mechanical and biochemical data suggests that the restricted conformational freedom of the proteins after UV irradiation is critical in the reduction of these properties. Consequently, an adequate topological organization of the protein chains emerges as a critical design principle in the performance of spider silk. PMID:25994594

  3. Influence of Molecular Weight on the Mechanical Performance of a Thermoplastic Glassy Polyimide

    NASA Technical Reports Server (NTRS)

    Nicholson, Lee M.; Whitley, Karen S.; Gates, Thomas S.; Hinkley, Jeffrey A.

    1999-01-01

    Mechanical Testing of an advanced thermoplastic polyimide (LaRC-TM-SI) with known variations in molecular weight was performed over a range of temperatures below the glass transition temperature. The physical characterization, elastic properties and notched tensile strength were all determined as a function of molecular weight and test temperature. It was shown that notched tensile strength is a strong function of both temperature and molecular weight, whereas stiffness is only a strong function of temperature. A critical molecular weight (Mc) was observed to occur at a weight-average molecular weight (Mw) of approx. 22000 g/mol below which, the notched tensile strength decreases rapidly. This critical molecular weight transition is temperature-independent. Furthermore, inelastic analysis showed that low molecular weight materials tended to fail in a brittle manner, whereas high molecular weight materials exhibited ductile failure. The microstructural images supported these findings.

  4. Design considerations in mechanical face seals for improved performance. II - Lubrication

    NASA Technical Reports Server (NTRS)

    Ludwig, L. P.; Greiner, H. F.

    1977-01-01

    The importance of sealing technology in the U.S. industrial chemical-orientated society in regard to maintenance and environmental contamination is pointed out. It is stated that seal performance (leakage, life) is directly related to seal lubrication, which is a mechanism not well understood. Current thinking in regard to seal lubrication is reviewed, the effect of energy dissipation in the thin lubricating film separating the sealing faces is pointed out, and the results of vaporization due to heating are illustrated. Also, hydrodynamic lubrication is reviewed, and an inherent tendency for the seal to operate with angular misalignment is pointed out. Recent work on hydrostatic effects is summarized and the conditions for seal instability are discussed. Four different modes of seal lubrication are postulated with the mode type being a strong function of speed and pressure.

  5. Thermal contact algorithms in SIERRA mechanics : mathematical background, numerical verification, and evaluation of performance.

    SciTech Connect

    Copps, Kevin D.; Carnes, Brian R.

    2008-04-01

    We examine algorithms for the finite element approximation of thermal contact models. We focus on the implementation of thermal contact algorithms in SIERRA Mechanics. Following the mathematical formulation of models for tied contact and resistance contact, we present three numerical algorithms: (1) the multi-point constraint (MPC) algorithm, (2) a resistance algorithm, and (3) a new generalized algorithm. We compare and contrast both the correctness and performance of the algorithms in three test problems. We tabulate the convergence rates of global norms of the temperature solution on sequentially refined meshes. We present the results of a parameter study of the effect of contact search tolerances. We outline best practices in using the software for predictive simulations, and suggest future improvements to the implementation.

  6. Parallel Performance Analysis between Free Response Environments and the Force Concept Inventory in Introductory Mechanics Courses

    NASA Astrophysics Data System (ADS)

    Bobbitt, Nicole; Wade, Aaron; Prayaga, Chandra

    2013-03-01

    This paper reports our attempts to: 1) create a problem solving situation that folds in both kinematics and force discussions 2) find a way to model and predict common thought processes that cause typical misconceptions identified by the Force Concept Inventory (FCI). Two pen and paper test questions were designed with these goals in mind, both broken into specific elements to arrive at a quantifiable fragmentation of the necessary thought processes required to solve the problem. These results were compared to pre- and post-FCI data to analyze the common misconceptions as defined by FCI. The data was analysed using factor analysis to group performance across the two environments. Two styles of grading were used to highlight the effectiveness of this method. Ultimately this, and any future questions, would become a tool in the classroom to pinpoint the critical ideas with which a typical student struggles during an introductory mechanics course.

  7. Thrust chamber life prediction. Volume 1: Mechanical and physical properties of high performance rocket nozzle materials

    NASA Technical Reports Server (NTRS)

    Esposito, J. J.; Zabora, R. F.

    1975-01-01

    Pertinent mechanical and physical properties of six high conductivity metals were determined. The metals included Amzirc, NARloy Z, oxygen free pure copper, electroformed copper, fine silver, and electroformed nickel. Selection of these materials was based on their possible use in high performance reusable rocket nozzles. The typical room temperature properties determined for each material included tensile ultimate strength, tensile yield strength, elongation, reduction of area, modulus of elasticity, Poisson's ratio, density, specific heat, thermal conductivity, and coefficient of thermal expansion. Typical static tensile stress-strain curves, cyclic stress-strain curves, and low-cycle fatigue life curves are shown. Properties versus temperature are presented in graphical form for temperatures from 27.6K (-410 F) to 810.9K (1000 F).

  8. Charge storage mechanisms in electrochemical capacitors: Effects of electrode properties on performance

    NASA Astrophysics Data System (ADS)

    Dupont, Madeleine F.; Donne, Scott W.

    2016-09-01

    The capacitive behaviour of four commonly studied electrochemical capacitor systems has been analyzed using the step potential electrochemical spectroscopy (SPECS) method. Electrode-electrolyte combinations with different charge storage mechanisms were characterized, including activated carbon in aqueous (H2SO4) and organic (TEABF4 in acetonitrile) electrolytes, manganese dioxide (Na2SO4) and anhydrous ruthenium oxide (H2SO4). The SPECS method was used to separate the charge storage contributions from double layer capacitance (CDL) and diffusion-limited pseudo-capacitance (CD) at scan rates ranging from 0.08 to 125 mV/s. The relative contributions from each process are related to the physicochemical properties of the electrode. Additionally, the effects of these electrode properties on the overall performance of each system, in terms of specific power and energy, are identified.

  9. Flotation performances and adsorption mechanism of α-hydroxyoctyl phosphinic acid to cassiterite

    NASA Astrophysics Data System (ADS)

    Li, Fangxu; Zhong, Hong; Zhao, Gang; Wang, Shuai; Liu, Guangyi

    2015-10-01

    In this paper, the flotation performances and adsorption mechanism of α-hydroxyoctyl phosphinic acid (HPA) to cassiterite were investigated by adsorption experiments, micro-flotation tests, zeta potential measurements, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses. The micro-flotation results indicated that compared with styrene phosphonic acid (SPA), diphosphonic acid (DPA), benzohydroxamic acid (BHA) and salicylhydroxamic acid (SHA), HPA exhibited excellent collecting power to cassiterite and superior selectivity against magnetite or hematite over a wide pH range. The results of adsorption experiments and zeta potential deduced that HPA chemisorb on cassiterite surfaces. The results of FTIR inferred HPA chemisorb onto cassiterite surfaces through its P and O atoms with the P-H and O-H bonds broken. XPS analysis further demonstrated HPA react with Sn species by formation of Sn-O-P and Sn-P bond.

  10. Mechanisms Underlying the Bioindicator Notion: Spatial Association between Individual Sexual Performance and Community Diversity

    PubMed Central

    Laiolo, Paola; Bañuelos, María J.; Blanco-Fontao, Beatriz; García, Mónica; Gutiérrez, Gloria

    2011-01-01

    The bioindicator notion is an appealing concept that has received more support in applied than in basic ecology, mostly due to the difficulty in deriving general ecological rules applicable to all target organisms. However, recognizing the mechanisms that determine the association between a particular species and the well-being of many other species is important for understanding the functioning of ecosystems and the relationship among different biological levels. We examined here the processes at the individual level that cause an association between species performance and biodiversity value, by analyzing attributes that can be studied in a variety of animals with sexual reproduction, namely breeding site selection and condition-dependent sexual signals. Our study model was the Capercaillie, an indicator of forest functioning and diversity, and the associated bird community, used here as a surrogate of broader forest biodiversity. At a regional scale Capercaillie occurrence was not associated with the most diverse forest patches, but at the scale of male spring territories the sexual display grounds (arenas) were located in the oldest and less disturbed forest portions, which also hosted the richest local bird communities. Social mechanisms and conspecific cueing likely concurred with habitat-driven processes in determining the long-term persistence of traditional display grounds, which were appealing to many other species because of their structural composition. Characteristics of male vocal display that honestly advertize male quality (low frequencies and rapid song rates) were significantly correlated with high diversity values, resulting in a spatial association between individual and community performances. Costly or risky activities such as reproductive or social behaviors, which more than other attributes match gradients in habitat quality, are therefore contributing to functionally connect individuals with ecosystem health. PMID:21818374

  11. Jumping mechanisms and performance in beetles. I. Flea beetles (Coleoptera: Chrysomelidae: Alticini).

    PubMed

    Nadein, Konstantin; Betz, Oliver

    2016-07-01

    The present study analyses the anatomy, mechanics and functional morphology of the jumping apparatus, the performance and the kinematics of the natural jump of flea beetles (Coleoptera: Chrysomelidae: Galerucinae: Alticini). The kinematic parameters of the initial phase of the jump were calculated for five species from five genera (average values from minimum to maximum): acceleration 0.91-2.25 (×10(3)) m s(-2), velocity 1.48-2.80 m s(-1), time to take-off 1.35-2.25 ms, kinetic energy 2.43-16.5 µJ, G: -force 93-230. The jumping apparatus is localized in the hind legs and formed by the femur, tibia, femoro-tibial joint, modified metafemoral extensor tendon, extensor ligament, tibial flexor sclerite, and extensor and flexor muscles. The primary role of the metafemoral extensor tendon is seen in the formation of an increased attachment site for the extensor muscles. The rubber-like protein resilin was detected in the extensor ligament, i.e. a short, elastic element connecting the extensor tendon with the tibial base. The calculated specific joint power (max. 0.714 W g(-1)) of the femoro-tibial joint during the jumping movement and the fast full extension of the hind tibia (1-3 ms) suggest that jumping is performed via a catapult mechanism releasing energy that has beforehand been stored in the extensor ligament during its stretching by the extensor muscles. In addition, the morphology of the femoro-tibial joint suggests that the co-contraction of the flexor and the extensor muscles in the femur of the jumping leg is involved in this process. PMID:27385755

  12. Effect of Clay Amounts on Morphology and Mechanical Performances in Multiscale PET Composites

    NASA Astrophysics Data System (ADS)

    Barbosa, C. N.; Chabert, F.; Nassiet, V.; Viana, J. C.; Pereira, P.

    2011-05-01

    This work presents an investigation of the properties of poly(ethylene terephthalate)/glass fibres/nanoclay multiscale composites. The aim is to demonstrate the effect of adding various clay amounts on the morphology and mechanical performance of multiscale PET composites. Multiscale composites were prepared by adding 0.5, 1.0, 3.0, and 5.0 wt% of Cloisite15A montmorillonite: Initially, a masterbatch of pure PET blended with 10 wt% of Cloisite15A was obtained in a co-rotating twin screw extruder. The multiscale composites were then blended, via mechanical mixing, and injection moulded by adding the masterbatch to the glass fibre reinforced matrix. The morphological and mechanical characterizations of all compounds are discussed. X-ray diffraction (XRD) and transmission electron microscopy (TEM) revealed that the characteristic (001) peak of the nanocomposite obtained by extrusion (masterbatch) shifted to the lower angle region stating an intercalated structure. However, the subsequent injection moulding process changed the morphological structure of the multiscale nanocomposites reducing the basal distance mostly for small loadings of nanoclay. The addition of nanoclay to PET matrices increases the degree of crystallinity, the clay platelets possibly playing the role of nucleating agent, as revealed by DSC and FTIR. The time relaxation spectra broaden as seen by DMA, as the ratio of clay/polymer interfaces increases. The yield stress of composites with 0.5 and 1 wt% of C15A content are enhanced. For more than 3% of nanoclay, the yield stress decreases. The Young's modulus is increased when adding C15 nanoclay. Indeed, clay exfoliation was not attained, but the intercalated particle dispersion improved the stiffness properties of PET/glass fibres/nanoclay composites.

  13. Microstructure and Mechanical Performance of Friction Stir Spot-Welded Aluminum-5754 Sheets

    NASA Astrophysics Data System (ADS)

    Pathak, N.; Bandyopadhyay, K.; Sarangi, M.; Panda, Sushanta Kumar

    2013-01-01

    Friction stir spot welding (FSSW) is a recent trend of joining light-weight sheet metals while fabricating automotive and aerospace body components. For the successful application of this solid-state welding process, it is imperative to have a thorough understanding of the weld microstructure, mechanical performance, and failure mechanism. In the present study, FSSW of aluminum-5754 sheet metal was tried using tools with circular and tapered pin considering different tool rotational speeds, plunge depths, and dwell times. The effects of tool design and process parameters on temperature distribution near the sheet-tool interface, weld microstructure, weld strength, and failure modes were studied. It was found that the peak temperature was higher while welding with a tool having circular pin compared to tapered pin, leading to a bigger dynamic recrystallized stir zone (SZ) with a hook tip bending towards the upper sheet and away from the keyhole. Hence, higher lap shear separation load was observed in the welds made from circular pin compared to those made from tapered pin. Due to influence of size and hardness of SZ on crack propagation, three different failure modes of weld nugget were observed through optical cross-sectional micrograph and SEM fractographs.

  14. Insights into the Mechanism and Kinetics of Thermo-Oxidative Degradation of HFPE High Performance Polymer.

    PubMed

    Kunnikuruvan, Sooraj; Parandekar, Priya V; Prakash, Om; Tsotsis, Thomas K; Nair, Nisanth N

    2016-06-01

    The growing requisite for materials having high thermo-oxidative stability makes the design and development of high performance materials an active area of research. Fluorination of the polymer backbone is a widely applied strategy to improve various properties of the polymer, most importantly the thermo-oxidative stability. Many of these fluorinated polymers are known to have thermo-oxidative stability up to 700 K. However, for space and aerospace applications, it is important to improve its thermo-oxidative stability beyond 700 K. Molecular-level details of the thermo-oxidative degradation of such polymers can provide vital information to improve the polymer. In this spirit, we have applied quantum mechanical and microkinetic analysis to scrutinize the mechanism and kinetics of the thermo-oxidative degradation of a fluorinated polymer with phenylethenyl end-cap, HFPE. This study gives an insight into the thermo-oxidative degradation of HFPE and explains most of the experimental observations on the thermo-oxidative degradation of this polymer. Thermolysis of C-CF3 bond in the dianhydride component (6FDA) of HFPE is found to be the rate-determining step of the degradation. Reaction pathways that are responsible for the experimentally observed weight loss of the polymer is also scrutinized. On the basis of these results, we propose a modification of HFPE polymer to improve its thermo-oxidative stability. PMID:27187246

  15. Subjective Significance Shapes Arousal Effects on Modified Stroop Task Performance: A Duality of Activation Mechanisms Account.

    PubMed

    Imbir, Kamil K

    2016-01-01

    Activation mechanisms such as arousal are known to be responsible for slowdown observed in the Emotional Stroop and modified Stroop tasks. Using the duality of mind perspective, we may conclude that both ways of processing information (automatic or controlled) should have their own mechanisms of activation, namely, arousal for an experiential mind, and subjective significance for a rational mind. To investigate the consequences of both, factorial manipulation was prepared. Other factors that influence Stroop task processing such as valence, concreteness, frequency, and word length were controlled. Subjective significance was expected to influence arousal effects. In the first study, the task was to name the color of font for activation charged words. In the second study, activation charged words were, at the same time, combined with an incongruent condition of the classical Stroop task around a fixation point. The task was to indicate the font color for color-meaning words. In both studies, subjective significance was found to shape the arousal impact on performance in terms of the slowdown reduction for words charged with subjective significance. PMID:26869974

  16. Subjective Significance Shapes Arousal Effects on Modified Stroop Task Performance: A Duality of Activation Mechanisms Account

    PubMed Central

    Imbir, Kamil K.

    2016-01-01

    Activation mechanisms such as arousal are known to be responsible for slowdown observed in the Emotional Stroop and modified Stroop tasks. Using the duality of mind perspective, we may conclude that both ways of processing information (automatic or controlled) should have their own mechanisms of activation, namely, arousal for an experiential mind, and subjective significance for a rational mind. To investigate the consequences of both, factorial manipulation was prepared. Other factors that influence Stroop task processing such as valence, concreteness, frequency, and word length were controlled. Subjective significance was expected to influence arousal effects. In the first study, the task was to name the color of font for activation charged words. In the second study, activation charged words were, at the same time, combined with an incongruent condition of the classical Stroop task around a fixation point. The task was to indicate the font color for color-meaning words. In both studies, subjective significance was found to shape the arousal impact on performance in terms of the slowdown reduction for words charged with subjective significance. PMID:26869974

  17. Citizens' quality councils: an innovative mechanism for monitoring and providing social endorsement of healthcare providers' performance?

    PubMed

    Ruelas, Enrique

    2006-01-01

    In recent years, under the influence of continuing improvement and total quality strategies, efforts to improve the quality of healthcare have been generated from within each healthcare organization. External mechanisms, such as accreditation, that drive quality improvement from without, have existed for much longer. However, these accreditation systems incorporated the need to demonstrate the existence of continuing improvement processes as a standard barely 10 years ago; thus, the external mechanism included the development of internal processes as yet another requirement. As Dobrow, Langer, Angus and Sullivan state in the lead article, the existence of a whole evidence-based culture that has spread the concern about quality is beyond doubt; I would add that it has also intensified this concern. Several factors have contributed to this trend, which now seems irreversible. On the one hand, as the paper points out, one of these factors is the growing requirement to allocate resources according to performance. On the other, there is the growing evidence of errors committed by health systems that cause harm to patients. The latter has created increasing demand for reliable information, conceived not only to allow the detection of these situations, but also to invest greater reliability in the health systems in the eyes of patients and general public. In both cases, however, the question remains: Who defines and who measures quality levels in such a way that the information is credible? PMID:16651858

  18. Efficient removal of fluoride by hierarchical MgO microspheres: Performance and mechanism study

    NASA Astrophysics Data System (ADS)

    Jin, Zhen; Jia, Yong; Luo, Tao; Kong, Ling-Tao; Sun, Bai; Shen, Wei; Meng, Fan-Li; Liu, Jin-Huai

    2015-12-01

    Hierarchical MgO microspheres assembled by numerous porous nanoplates were successfully obtained by annealing the precursors of magnesium carbonate hydroxide hydrate synthesized through a facile and cost-effective hydrothermal process at low temperature. The as-prepared products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Brunauer-Emmett-Teller measurements. The fluoride removal performance of the hierarchical MgO microspheres was investigated. The adsorption isotherm could be well fitted in Freundlich model, and the adsorption capacity was over 115.5 mg/g at pH 7. The absorbent also showed high fluoride removal ability in a wide pH range of 2-10, which is favorable for practical application. The effect of co-existing anions on fluoride removal was also investigated. The result indicated that the fluoride adsorption capacity was influenced when carbonate, bicarbonate and phosphate existed above the concentration of 50 mg/g. In addition, the adsorption mechanism was investigated by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. A novel hydroxyl and carbonate co-exchange mechanism has been proposed for the first time. It can be found that fluoride ions could replace the surface carbonates which formed by the reaction of MgO and the adsorbed CO2 molecules, and then anchored on the MgO surface.

  19. Void fraction instrument acceptance test procedure

    SciTech Connect

    Pearce, K.L.

    1994-09-15

    This acceptance test procedure (ATP) was written to test the void fraction instrument (VFI) and verify that the unit is ready for field service. The procedure verifies that the mechanical and electrical features (not specifically addressed in the software ATP) and software alarms are operating as designed.

  20. W-087 Acceptance test procedure. Revision 1

    SciTech Connect

    Joshi, A.W.

    1997-06-10

    This Acceptance Test Procedure/Operational Test Procedure (ATP/OTP) has been prepared to demonstrate that the Electrical/Instrumentation and Mechanical systems function as required by project criteria and to verify proper operation of the integrated system including the interlocks.

  1. Performance of nanoscale metallic multilayer systems under mechanical and thermal loading

    NASA Astrophysics Data System (ADS)

    Economy, David Ross

    Reports of nanoscale metallic multilayers (NMM) performance show a relatively high strength and radiation damage resistance when compared their monolithic components. Hardness of NMMs has been shown to increase with increasing interfacial density (i.e. decreasing layer thickness). This interface density-dependent behavior within NMMs has been shown to deviate from Hall-Petch strengthening, leading to higher measured strengths during normal loading than those predicted by a rule of mixtures. To fully understand why this occurs, other researchers have looked at the influence of the crystal structures of the component layers, orientations, and compositions on deformation processes. Additionally, a limited number of studies have focused on the structural stability and possible performance variation between as-deposited systems and those exposed to mechanical and thermal loading. This dissertation identified how NMM as-deposited structures and performance are altered by mechanical loading (sliding/wear contact) and/or thermal (such as diffusion, relaxation) loading. These objectives were pursued by tracking hardness evolution during sliding wear and after thermal loading to as-deposited stress and mechanical properties. Residual stress progression was also examined during thermal loading and supporting data was collected to detail structural and chemical changes. All of these experimental observations were conducted using Cu/Nb NMMs with 2 nm, 20 nm, or 100 nm thick individual layers deposited with either 1 microm or 10 microm total thicknesses with two geometries (Cu/Nb and Nb/Cu) on (100) Si. Wear boxes were performed on Cu/Nb NMM using a nanoindentation system with a 1 microm conical diamond counterface. After nano-wear deformation, the hardness of the deformed regions significantly rose with respect to as-deposited measurements, which further increased with greater wear loads. Additionally, NMMs with thinner layers showed less volume loss as measured by laser

  2. A novel collector 2-ethyl-2-hexenoic hydroxamic acid: Flotation performance and adsorption mechanism to ilmenite

    NASA Astrophysics Data System (ADS)

    Xu, Haifeng; Zhong, Hong; Tang, Qing; Wang, Shuai; Zhao, Gang; Liu, Guangyi

    2015-10-01

    In this paper, a novel collector, 2-ethyl-2-hexenoic hydroxamic acid (EHHA) was prepared and characterized by elemental analysis, infrared, 1H NMR, 13C NMR and mass spectra. The flotation performance and adsorption mechanism of EHHA to ilmenite were investigated by micro-flotation tests, density functional theory (DFT) calculations, FTIR spectra, zeta potential and solution chemistry analyses. The micro-flotation results indicated that EHHA exhibited superior flotation performance compared to isooctyl hydroximic acid (IOHA) and octyl hydroxamic acid (OHA), and floated out 84.03% ilmenite at pH 8.0 with 250 mg/L dosage. The analyses of FTIR spectra and zeta potential demonstrated that EHHA might chemisorb onto ilmenite surfaces by form of five-membered chelates. The solution chemistry analyses further inferred that at pH 6.3-10.5, both Fe and Ti species on ilmenite surfaces could chelate EHHA. DFT calculation results implied EHHA owned the strongest affinity to ilmenite among the three C8 hydroximic acids. To discern the sharply improving floatability of ilmenite at pH 8-10, a schematic co-adsorption molecule-ion model of EHHA on ilmenite surfaces was suggested.

  3. Mechanically switchable solid inhomogeneous phantom for performance tests in diffuse imaging and spectroscopy.

    PubMed

    Pifferi, Antonio; Torricelli, Alessandro; Cubeddu, Rinaldo; Quarto, Giovanna; Re, Rebecca; Sekar, Sanathana K V; Spinelli, Lorenzo; Farina, Andrea; Martelli, Fabrizio; Wabnitz, Heidrun

    2015-12-01

    A mechanically switchable solid inhomogeneous phantom simulating localized absorption changes was developed and characterized. The homogeneous host phantom was made of epoxy resin with black toner and titanium dioxide particles added as absorbing and scattering components, respectively. A cylindrical rod, movable along a hole in the block and made of the same material, has a black polyvinyl chloride cylinder embedded in its center. By varying the volume and position of the black inclusion, absorption perturbations can be generated over a large range of magnitudes. The phantom has been characterized by various time-domain diffuse optics instruments in terms of absorption and scattering spectra, transmittance images, and reflectance contrast. Addressing a major application of the phantom for performance characterization for functional near-infrared spectroscopy of the brain, the contrast was measured in reflectance mode while black cylinders of volumes from ≈20  mm3 to ≈270  mm3 were moved in lateral and depth directions, respectively. The new type of solid inhomogeneous phantom is expected to become a useful tool for routine quality check of clinical instruments or implementation of industrial standards provided an experimental characterization of the phantom is performed in advance. PMID:26220211

  4. Heat insulation performance, mechanics and hydrophobic modification of cellulose-SiO2 composite aerogels.

    PubMed

    Shi, Jianjun; Lu, Lingbin; Guo, Wantao; Zhang, Jingying; Cao, Yang

    2013-10-15

    Cellulose-SiO2 composite hydrogel was prepared by combining the NaOH/thiourea/H2O solvent system and the immersion method with controlling the hydrolysis-fasculation rate of tetraethyl orthosilicate (TEOS). The hydrophobic composite aerogels were obtained through the freeze-drying technology and the cold plasma modification technology. Composite SiO2 could obviously reduce the thermal conductivity of cellulose aerogel. The thermal conductivity could be as low as 0.026 W/(mK). The thermal insulation mechanism of the aerogel material was discussed. Composite SiO2 reduced hydrophilicity of cellulose aerogel, but environmental humidity had a significant influence on heat insulation performance. After hydrophobic modification using CCl4 as plasma was conducted, the surface of composite aerogel was changed from hydrophilic to hydrophobic and water contact angle was as high as 132°. The modified composite aerogel still kept good heat insulation performance. This work provided a foundation for the possibility of applying cellulose-SiO2 composite aerogel in the insulating material field. PMID:23987346

  5. Mechanically switchable solid inhomogeneous phantom for performance tests in diffuse imaging and spectroscopy

    NASA Astrophysics Data System (ADS)

    Pifferi, Antonio; Torricelli, Alessandro; Cubeddu, Rinaldo; Quarto, Giovanna; Re, Rebecca; Sekar, Sanathana K. V.; Spinelli, Lorenzo; Farina, Andrea; Martelli, Fabrizio; Wabnitz, Heidrun

    2015-12-01

    A mechanically switchable solid inhomogeneous phantom simulating localized absorption changes was developed and characterized. The homogeneous host phantom was made of epoxy resin with black toner and titanium dioxide particles added as absorbing and scattering components, respectively. A cylindrical rod, movable along a hole in the block and made of the same material, has a black polyvinyl chloride cylinder embedded in its center. By varying the volume and position of the black inclusion, absorption perturbations can be generated over a large range of magnitudes. The phantom has been characterized by various time-domain diffuse optics instruments in terms of absorption and scattering spectra, transmittance images, and reflectance contrast. Addressing a major application of the phantom for performance characterization for functional near-infrared spectroscopy of the brain, the contrast was measured in reflectance mode while black cylinders of volumes from ≈20 mm3 to ≈270 mm3 were moved in lateral and depth directions, respectively. The new type of solid inhomogeneous phantom is expected to become a useful tool for routine quality check of clinical instruments or implementation of industrial standards provided an experimental characterization of the phantom is performed in advance.

  6. Mechanical behavior and fatigue performance of SMA short fiber reinforced MMC

    NASA Astrophysics Data System (ADS)

    Al-Matar, Basem Jawad

    The mechanical behavior and performance of Shape Memory Alloy (SMA) short fiber NiTi reinforced Al was experimentally investigated for monotonic and fatigue test Al 6061 NiTi-SiC T6 was superior to unreinforced materials as well as to the reinforced Al T4. Taya three-dimensional model was performed on the monotonic tensile test at room temperature. It showed good agreement with experimental results. In order to utilize the compressive criterion for SMA, the NiTi reinforced Al composite was cooled at -10°C and prestrained at 1.2%. Beyond this limit composite suffered from damage. The net enhancement of SMA effect was around 10 MPa on composite yield stress. Results showed that the elastic constant for the composite did not change with loading and unloading suggesting that the inelastic behavior is plasticity. Further investigation on the inelastic behavior model as damage and/or plasticity by evaluating Poisson's ratio during loading was carried out by Adaptive Image Correlation Technique for Full-Field Strain Measurement. Poisson's ratio increased from around 0.33 to 0.5 demonstrating that it is plasticity that is responsible for the inelastic behavior. Scanning electron microscopy was also used and confirmed model results. The overall damage-behavior was quantified in terms of the post fatigue failure strength for low-cycle fatigue tests. Power law model was best to fit experimental findings.

  7. Variation in the shape and mechanical performance of the lower jaws in ceratopsid dinosaurs (Ornithischia, Ceratopsia).

    PubMed

    Maiorino, Leonardo; Farke, Andrew A; Kotsakis, Tassos; Teresi, Luciano; Piras, Paolo

    2015-11-01

    Ceratopsidae represents a group of quadrupedal herbivorous dinosaurs that inhabited western North America and eastern Asia during the Late Cretaceous. Although horns and frills of the cranium are highly variable across species, the lower jaw historically has been considered to be relatively conservative in morphology. Here, the lower jaws from 58 specimens representing 21 ceratopsoid taxa were sampled, using geometric morphometrics and 2D finite element analysis (FEA) to explore differences in morphology and mechanical performance across Ceratopsoidea (the clade including Ceratopsidae, Turanoceratops and Zuniceratops). Principal component analyses and non-parametric permuted manovas highlight Triceratopsini as a morphologically distinct clade within the sample. A relatively robust and elongate dentary, a larger and more elongated coronoid process, and a small and dorso-ventrally compressed angular characterize this clade, as well as the absolutely larger size. By contrast, non-triceratopsin chasmosaurines, Centrosaurini and Pachyrhinosaurini have similar morphologies to each other. Zuniceratops and Avaceratops are distinct from other taxa. No differences in size between Pachyrhinosaurini and Centrosaurini are recovered using non-parametric permuted anovas. Structural performance, as evaluated using a 2D FEA, is similar across all groups as measured by overall stress, with the exception of Triceratopsini. Shape, size and stress are phylogenetically constrained. A longer dentary as well as a long coronoid process result in a lower jaw that is reconstructed as relatively much more stressed in triceratopsins. PMID:26467240

  8. Effect of Board Thickness on Sn-Ag-Cu Joint Interconnect Mechanical Shock Performance

    NASA Astrophysics Data System (ADS)

    Lee, Tae-Kyu; Xie, Weidong

    2014-12-01

    The mechanical stability of solder joints with Sn-Ag-Cu alloy joints on various board thicknesses was investigated with a high G level shock environment. A test vehicle with three different board thicknesses was used for board drop shock performance tests. These vehicles have three different strain and shock level condition couples per board, and are used to identify the joint stability and failure modes based on the board responses. The results revealed that joint stability is sensitive to board thickness. The board drop shock test showed that the first failure location shifts from the corner location near the standoff to the center with increased board thickness due to the shock wave response. From analysis of the thickness variation and failure cycle number, the strain rate during the pulse strain cycle is the dominant factor, which defines the life cycle number per board thickness, and not the maximum strain value. The failure location shift and the shock performance differentiation are discussed from the perspective of maximum principal strain, cycle frequency and strain rate per cycle.

  9. Using a new incentive mechanism to improve wastewater sector performance: the case study of Italy.

    PubMed

    De Gisi, Sabino; Petta, Luigi; Farina, Roberto; De Feo, Giovanni

    2014-01-01

    The system of "Service Objectives", introduced by the Italian National Strategic Framework 2007-2013, is an innovative results-oriented programme concerning 4 thematic areas (education, care for the elderly and children, management of municipal solid wastes and integrated water service) in which the Ministry of Economic Development and eight Southern Italy districts are involved. The system was initially associated to an incentive mechanism which provided subsidies for a total amount of EUR 3 billion from the national Underdeveloped Areas Fund, according to the achievement of specific targets set for 11 service indicators in 2013. The indicators used for the integrated water service refer to the efficiency in water supply service as well as the coverage of wastewater treatment service. The aim of the study is to describe the activities carried out in Italy by the ENEA Agency in order to define a new performance indicator for wastewater treatment service taking into account the appropriateness and efficiency of existing plants equipment and, consequently, evaluating economic incentives. The proposed procedure takes into account both wastewater treatment demand and quality of wastewater treatment service offered to citizens. Input data, provided by the National Institute of Statistics (ISTAT), were elaborated in order to define appropriate parameters, with a multi-criteria analysis being used to define the new performance indicator. The applicability of the proposed procedure was verified considering all the 8 Southern Italy and Island districts (Abruzzo, Molise, Campania, Apulia, Basilicata, Calabria, Sicily and Sardinia) involved in the programme. The obtained results show that the quality of municipal wastewater may influence the calculation of the incentive amount. The performance indicators defined in this work might be conveniently extended to other contexts similar to the assessed geographical area (Southern Italy and Islands). PMID:24291582

  10. Nanofiber reinforcement of a geopolymer matrix for improved composite materials mechanical performance

    NASA Astrophysics Data System (ADS)

    Rahman, AKM Samsur

    Geopolymers have the potential to cross the process performance gap between polymer matrix and ceramic matrix composites (CMC), enabling high temperature capable composites that are manufactured at relatively low temperatures. Unfortunately, the inherently low toughness of these geopolymers limits the performance of the resulting fiber reinforced geopolymer matrix composites. Toughness improvements in composites can be addressed through the adjustments in the fiber/matrix interfacial strength and through the improvements in the inherent toughness of the constituent materials. This study investigates the potential to improve the inherent toughness of the geopolymer matrix material through the addition of nanofillers, by considering physical dimensions, mechanical properties, reinforcing capability and interfacial bond strength effects. A process optimization study was first undertaken to develop the ability to produce consistent, neat geopolymer samples, a critical precursor to producing nano-filled geopolymer for toughness evaluation. After that, single edge notched bend beam fracture toughness and un-notched beam flexural strength were evaluated for silicon carbide, alumina and carbon nanofillers reinforced geopolymer samples treated at various temperatures in reactive and inert environments. Toughness results of silicon carbide and carbon nanofillers reinforced geopolymers suggested that with the improved baseline properties, high aspect ratio nanofillers with high interfacial bond strength are the most capable in further improving the toughness of geopolymers. Among the high aspect ratio nanofillers i.e. nanofibers, 2vol% silicon carbide whicker (SCW) showed the highest improvement in fracture toughness and flexural strength of ~164% & ~185%, respectively. After heat treatment at 650 °C, SCW reinforcement was found to be effective, with little reduction in the performance, while the performance of alumina nanofiber (ANF) reinforced geopolymer significantly

  11. Mesoporous silica nanoparticles loading doxorubicin reverse multidrug resistance: performance and mechanism

    NASA Astrophysics Data System (ADS)

    Shen, Jianan; He, Qianjun; Gao, Yu; Shi, Jianlin; Li, Yaping

    2011-10-01

    Multidrug resistance (MDR) is one of the major obstacles for successful chemotherapy in cancer. One of the effective approaches to overcome MDR is to use nanoparticle-mediated drug delivery to increase drug accumulation in drug resistant cancer cells. In this work, we first report that the performance and mechanism of an inorganic engineered delivery system based on mesoporous silica nanoparticles (MSNs) loading doxorubicin (DMNs) to overcome the MDR of MCF-7/ADR (a DOX-resistant and P-glycoprotein (P-gp) over-expression cancer cell line). The experimental results showed that DMNs could enhance the cellular uptake of doxorubicin (DOX) and increase the cell proliferation suppression effect of DOX against MCF-7/ADR cells. The IC50 of DMNs against MCF-7/ADR cells was 8-fold lower than that of free DOX. However, an improved effect of DOX in DMNs against MCF-7 cells (a DOX-sensitive cancer cell line) was not found. The increased cellular uptake and nuclear accumulation of DOX delivered by DMNs in MCF-7/ADR cells was confirmed by confocal laser scanning microscopy, and could result from the down-regulation of P-gp and bypassing the efflux action by MSNs themselves. The cellular uptake mechanism of DMNs indicated that the macropinocytosis was one of the pathways for the uptake of DMNs by MCF-7/ADR cells. The in vivo biodistribution showed that DMNs induced a higher accumulation of DOX in drug resistant tumors than free DOX. These results suggested that MSNs could be an effective delivery system to overcome multidrug resistance.

  12. High mechanical performance of Areva upgraded fuel assemblies for PWR in USA

    SciTech Connect

    Gottuso, Dennis; Canat, Jean-Noel; Mollard, Pierre

    2007-07-01

    The merger of the product portfolios of the former Siemens and Framatome fuel businesses gave rise to a new family of PWR products which combine the best features of the different technologies to enhance the main performance of each of the existing products. In this way, the technology of each of the three main fuel assembly types usually delivered by AREVA NP, namely Mark-BW{sup TM}, HTP{sup TM} and AFA 3G{sup TM} has been enriched by one or several components from the others which contributes to improve their robustness and to enhance their performance. The combined experience of AREVA's products shows that the ROBUST FUELGUARD{sup TM}, the HMP{sup TM} end grid, the MONOBLOC{sup TM} guide tube, a welded structure, M5{sup R} material for every zirconium component and an upper QUICK-DISCONNECT{sup TM} are key features for boosting fuel assembly robustness. The ROBUST FUELGUARD benefits from a broad experience demonstrating its high efficiency in stopping debris. In addition, its mechanical strength has been enhanced and the proven blade design homogenizes the downstream flow distribution to strongly reduce excitation of fuel rods. The resistance to rod-to-grid fretting resistance of AREVA's new products is completed by the use of a lower HMP grid with 8 lines of contact to insure low wear. The Monobloc guide tube with a diameter maximized to strengthen the fuel assembly stiffness, excludes through its uniform outer geometry any local condition which could weaken guide tube straightness. The application of a welded cage to all fuel assemblies of the new family of products in combination with stiffer guide tubes and optimized hold-down assures each fuel assembly enhanced resistance to distortion. The combination of these features has been widely demonstrated as an effective method to reduce the risk of incomplete RCCA insertion and significantly reduce assembly distortion. Thanks to its enhanced performance, M5 alloy insures that all fuel assemblies in the family

  13. Acceptance of dying: a discourse analysis of palliative care literature.

    PubMed

    Zimmermann, Camilla

    2012-07-01

    The subject of death denial in the West has been examined extensively in the sociological literature. However, there has not been a similar examination of its "opposite", the acceptance of death. In this study, I use the qualitative method of discourse analysis to examine the use of the term "acceptance" of dying in the palliative care literature from 1970 to 2001. A Medline search was performed by combining the text words "accept or acceptance" with the subject headings "terminal care or palliative care or hospice care", and restricting the search to English language articles in clinical journals discussing acceptance of death in adults. The 40 articles were coded and analysed using a critical discourse analysis method. This paper focuses on the theme of acceptance as integral to palliative care, which had subthemes of acceptance as a goal of care, personal acceptance of healthcare workers, and acceptance as a facilitator of care. For patients and families, death acceptance is a goal that they can be helped to attain; for palliative care staff, acceptance of dying is a personal quality that is a precondition for effective practice. Acceptance not only facilitates the dying process for the patient and family, but also renders care easier. The analysis investigates the intertextuality of these themes with each other and with previous texts. From a Foucauldian perspective, I suggest that the discourse on acceptance of dying represents a productive power, which disciplines patients through apparent psychological and spiritual gratification, and encourages participation in a certain way to die. PMID:22513246

  14. Mechanical performance of spider orb webs is tuned for high-speed prey.

    PubMed

    Sensenig, Andrew T; Kelly, Sean P; Lorentz, Kimberly A; Lesher, Brittany; Blackledge, Todd A

    2013-09-15

    Spiders in the Orbiculariae spin orb webs that dissipate the mechanical energy of their flying prey, bringing the insects to rest and retaining them long enough for the spider to attack and subdue their meals. Small prey are easily stopped by webs but provide little energetic gain. While larger prey offer substantial nourishment, they are also challenging to capture and can damage the web if they escape. We therefore hypothesized that spider orb webs exhibit properties that improve their probability of stopping larger insects while minimizing damage when the mechanical energy of those prey exceeds the web's capacity. Large insects are typically both heavier and faster flying than smaller prey, but speed plays a disproportionate role in determining total kinetic energy, so we predicted that orb webs may dissipate energy more effectively under faster impacts, independent of kinetic energy per se. We used high-speed video to visualize the impact of wooden pellets fired into orb webs to simulate prey strikes and tested how capture probability varied as a function of pellet size and speed. Capture probability was virtually nil above speeds of ~3 m s(-1). However, successful captures do not directly measure the maximum possible energy dissipation by orb webs because these events include lower-energy impacts that may not significantly challenge orb web performance. Therefore, we also compared the total kinetic energy removed from projectiles that escaped orb webs by breaking through the silk, asking whether more energy was removed at faster speeds. Over a range of speeds relevant to insect flight, the amount of energy absorbed by orb webs increases with the speed of prey (i.e. the rates at which webs are stretched). Orb webs therefore respond to faster - and hence higher kinetic energy - prey with better performance, suggesting adaptation to capture larger and faster flying insect prey. This speed-dependent toughness of a complex structure suggests the utility of the

  15. Fleet Performance of Project 100,000 Personnel in the Aviation Structural Mechanic S (Structures) Rating. Final Report.

    ERIC Educational Resources Information Center

    Mayo, George D.

    The fleet performance of a small group of Project 100,000 (low aptitude) personnel was assessed by means of an evaluation form completed by their supervisors after the men had been on board for approximately seven months. The men had previously been trained for the Navy rating, Aviation Structural Mechanic S (Structures), AMS. The performance of…

  16. The case for improved HEPA-filter mechanical performance standards revisited

    SciTech Connect

    Ricketts, C.I.; Smith, P.R.

    1997-08-01

    Under benign operating conditions, High Efficiency Particulate Air (HEPA) filter units serve as reliable and relatively economical components in the air cleaning systems of nuclear facilities worldwide. Despite more than four decades of filter-unit evaluation and improvements, however, the material strength characteristics of the glass fiber filter medium continue to ultimately limit filter functional reliability. In worst-case scenarios involving fire suppression, loss-of-coolant accidents (LOCA`s), or exposure to shock waves or tornado induced flows, rupture of the filter medium of units meeting current qualification standards cannot be entirely ruled out. Even under so-called normal conditions of operation, instances of filter failure reported in the literature leave open questions of filter-unit reliability. Though developments of filter units with improved burst strengths have been pursued outside the United States, support for efforts in this country has been comparatively minimal. This despite user requests for filters with greater moisture resistance, for example. Or the fact that conventional filter designs result in not only the least robust component to be found in a nuclear air cleaning system, but also the one most sensitive to the adverse effects of conditions deviating from those of normal operation. Filter qualification-test specifications of current codes, standards, and regulatory guidelines in the United States are based primarily upon research performed in a 30-year period beginning in the 1950`s. They do not seem to reflect the benefits of the more significant developments and understanding of filter failure modes and mechanisms achieved since that time. One overseas design, based on such knowledge, has proven reliability under adverse operating conditions involving combined and serial challenges. Its widespread use, however, has faltered on a lack of consensus in upgrading filter performance standards. 34 refs., 2 figs., 3 tabs.

  17. A single intake of capsiate improves mechanical performance and bioenergetics efficiency in contracting mouse skeletal muscle.

    PubMed

    Kazuya, Yashiro; Tonson, Anne; Pecchi, Emilie; Dalmasso, Christiane; Vilmen, Christophe; Fur, Yann Le; Bernard, Monique; Bendahan, David; Giannesini, Benoît

    2014-05-15

    Capsiate is known to increase whole body oxygen consumption possibly via the activation of uncoupling processes, but its effect at the skeletal muscle level remains poorly documented and conflicting. To clarify this issue, gastrocnemius muscle function and energetics were investigated in mice 2 h after a single intake of either vehicle (control) or purified capsiate (at 10 or 100 mg/kg body wt) through a multidisciplinary approach combining in vivo and in vitro measurements. Mechanical performance and energy pathway fluxes were assessed strictly noninvasively during a standardized electrostimulation-induced exercise, using an original device implementing 31-phosphorus magnetic resonance spectroscopy, and mitochondrial respiration was evaluated in isolated saponin-permeabilized fibers. Compared with control, both capsiate doses produced quantitatively similar effects at the energy metabolism level, including an about twofold decrease of the mitochondrial respiration sensitivity for ADP. Interestingly, they did not alter either oxidative phosphorylation or uncoupling protein 3 gene expression at rest. During 6 min of maximal repeated isometric contractions, both doses reduced the amount of ATP produced from glycolysis and oxidative phosphorylation but increased the relative contribution of oxidative phosphorylation to total energy turnover (+28 and +21% in the 10- and 100-mg groups, respectively). ATP cost of twitch force generation was further reduced in the 10- (-35%) and 100-mg (-45%) groups. Besides, the highest capsiate dose also increased the twitch force-generating capacity. These data present capsiate as a helpful candidate to enhance both muscle performance and oxidative phosphorylation during exercise, which could constitute a nutritional approach for improving health and preventing obesity and associated metabolic disorders. PMID:24644244

  18. Hanford Site Solid Waste Acceptance Criteria

    SciTech Connect

    MCDOWELL, A.K.; TRINER, G.C.

    2002-03-28

    DOE Order 435.1 requires that each treatment, storage, and/or disposal facility (referred to in this document as TSD unit) that manages low-level or transuranic (TRU) waste (including mixed waste and TSCA PCB waste) maintain waste acceptance criteria. These criteria must address the various requirements to operate the TSD unit in compliance with applicable safety and environmental requirements. This document sets forth the baseline criteria for acceptance of waste at TSD units operated by WMP. The criteria for each TSD unit have been established to ensure that waste accepted can be managed in a manner that is within the operating requirements of the unit, including environmental regulations, DOE Orders, permits, technical safety requirements, waste analysis plans, performance assessments, and other applicable requirements. Revisions to the acceptance criteria document require an Unreviewed Safety Question review to document that the changes are consistent with current applicable safety analysis. Acceptance criteria apply to the following TSD units: the Low-Level Burial Grounds (LLBG) including both the nonregulated portions of the LLBG and trenches 31 and 34 of the 218-W-5 Burial Ground for mixed waste disposal; Central Waste Complex (CWC); Waste Receiving and Processing (WRAP) Facility; and T-Plant facility. Waste from all generators, both from the Hanford Site and from offsite facilities, must comply with these criteria. Exceptions can be granted as provided in Section 1.6. Specific waste streams could have additional requirements based on the identified TSD pathway. These requirements are communicated in the waste specification records (WSRds) and/or waste stream profile sheet approvals. The Hanford Site manages nonradioactive waste through direct shipments to offsite contractors. The waste acceptance requirements of the offsite TSD facility must be met for these nonradioactive wastes. This document does not address the acceptance requirements of these offsite

  19. Sonic boom acceptability studies

    NASA Astrophysics Data System (ADS)

    Shepherd, Kevin P.; Sullivan, Brenda M.; Leatherwood, Jack D.; McCurdy, David A.

    1992-04-01

    The determination of the magnitude of sonic boom exposure which would be acceptable to the general population requires, as a starting point, a method to assess and compare individual sonic booms. There is no consensus within the scientific and regulatory communities regarding an appropriate sonic boom assessment metric. Loudness, being a fundamental and well-understood attribute of human hearing was chosen as a means of comparing sonic booms of differing shapes and amplitudes. The figure illustrates the basic steps which yield a calculated value of loudness. Based upon the aircraft configuration and its operating conditions, the sonic boom pressure signature which reaches the ground is calculated. This pressure-time history is transformed to the frequency domain and converted into a one-third octave band spectrum. The essence of the loudness method is to account for the frequency response and integration characteristics of the auditory system. The result of the calculation procedure is a numerical description (perceived level, dB) which represents the loudness of the sonic boom waveform.

  20. Sonic boom acceptability studies

    NASA Technical Reports Server (NTRS)

    Shepherd, Kevin P.; Sullivan, Brenda M.; Leatherwood, Jack D.; Mccurdy, David A.

    1992-01-01

    The determination of the magnitude of sonic boom exposure which would be acceptable to the general population requires, as a starting point, a method to assess and compare individual sonic booms. There is no consensus within the scientific and regulatory communities regarding an appropriate sonic boom assessment metric. Loudness, being a fundamental and well-understood attribute of human hearing was chosen as a means of comparing sonic booms of differing shapes and amplitudes. The figure illustrates the basic steps which yield a calculated value of loudness. Based upon the aircraft configuration and its operating conditions, the sonic boom pressure signature which reaches the ground is calculated. This pressure-time history is transformed to the frequency domain and converted into a one-third octave band spectrum. The essence of the loudness method is to account for the frequency response and integration characteristics of the auditory system. The result of the calculation procedure is a numerical description (perceived level, dB) which represents the loudness of the sonic boom waveform.

  1. Effects of welding on weldment mechanical performance in two austenitic steels

    SciTech Connect

    Strum, M.J.

    1982-06-01

    The effect of autogenous gas-tungsten arc-welding on the mechanical performance of two austenitic steels has been evaluated for cable jackets of force-cooled superconductor coils. The original candidate material was Nitronic 40, a nitrogen-strengthened stainless steel. The in-situ reaction heat treatment at 700/sup 0/C necessary for the formation of the superconducting A15 phase results in severe degradation of the cryogenic tensile ductility in the weld metal. The search for an alternate material led to JBK-75, a modified A-286 type ..gamma..' precipitation hardening iron-based superalloy. Observations of a tensile strength mismatch between base metal and the weaker weld metal in JBK-75 prompted a study into the aging response in weldments of this alloy. Localized strain through slip step traces show an easy path of deformation within the solidification structure. Weldment strength varies with grain size. It was found that through post-weld annealing treatments at 950/sup 0/C, prior to aging, weldment hardness levels can be matched. However, although increased strength levels are obtained in the weld metal, concomitant decreases in base metal strengths are suffered, presumably due to observed grain growth. 24 figures, 9 tables.

  2. A novel preterm respiratory mechanics active simulator to test the performances of neonatal pulmonary ventilators

    NASA Astrophysics Data System (ADS)

    Cappa, Paolo; Sciuto, Salvatore Andrea; Silvestri, Sergio

    2002-06-01

    A patient active simulator is proposed which is capable of reproducing values of the parameters of pulmonary mechanics of healthy newborns and preterm pathological infants. The implemented prototype is able to: (a) let the operator choose the respiratory pattern, times of apnea, episodes of cough, sobs, etc., (b) continuously regulate and control the parameters characterizing the pulmonary system; and, finally, (c) reproduce the attempt of breathing of a preterm infant. Taking into account both the limitation due to the chosen application field and the preliminary autocalibration phase automatically carried out by the proposed device, accuracy and reliability on the order of 1% is estimated. The previously indicated value has to be considered satisfactory in light of the field of application and the small values of the simulated parameters. Finally, the achieved metrological characteristics allow the described neonatal simulator to be adopted as a reference device to test performances of neonatal ventilators and, more specifically, to measure the time elapsed between the occurrence of a potentially dangerous condition to the patient and the activation of the corresponding alarm of the tested ventilator.

  3. [Mechanism and performance of a membrane bioreactor for treatment of toluene vapors].

    PubMed

    Ye, Qi-hong; Wei, Zai-shan; Xiao, Pan; Li, Hua-qin; Zhang, Zai-li; Fan, Qin-juan

    2012-08-01

    The performance of a membrane bioreactor for treatment of toluene as a model pollutant is presented. Effects of toluene inlet concentration, residence time, spray density and pH of liquid phase on the toluene removal rate were evaluated. The experimental results showed that the toluene removal efficiency reached 99%. The optimal pH, residence time and spray density were 7.2, 6.4 s and 2.5 m3 x (m2 x h)(-1), respectively. The gas-phase biodegradation intermediate products were acetaldehyde acid (C2H2O3) and vinyl formic acid (C3H4O2), which were identified by means of gas chromatography/mass spectrometry (GC/MS). The mechanism of toluene degradation using a membrane bioreactor can be described as the combination of mass transfer from hollow fiber membrane to biofilm and biological degradation. Toluene (C6H5CH3) and oxygen diffused from the gas phase to the wet layer of the biofilm and were then consumed by the microbial communities. Toluene was oxidized to the intermediate organic products such as acetaldehyde acid (C2H2O3) and vinyl formic acid (C3H4O2), and the intermediate products were then converted to CO2 and H2O through continuous biological oxidation reactions. PMID:23213872

  4. Mechanical properties testing of candidate polymer matrix materials for use in high performance composites

    NASA Technical Reports Server (NTRS)

    Zimmerman, R. S.; Adams, D. F.

    1985-01-01

    The mechanical properties of four candidate neat resin systems for use in graphite/epoxy composites are characterized. This includes tensile and shear stiffnesses and strengths, coefficients of thermal and moisture expansion, and fracture toughness. Tests are conducted on specimens in the dry state and moisture-saturated, at temperatures of 23C, 82C and 121C. The neat resins tested are Hexcel HX-1504, Narmco 5245-C, American Cyanamid CYCOM 907, and Union Carbide ERX-4901A (MDA). Results are compared with those obtained for four other epoxy resins tested in a prior program, i.e., Hercules 3502, 2220-1, and 2220-3, and Ciba-Geigy Fibredux 914, as well as with available Hercules 3501-6 data. Scanning electron microscopic examination of fracture surfaces is performed to permit the correlation of observed failure modes with the environmental test conditions. A finite element micromechanics analysis is used to predict unidirectional composite response under various test conditions, using the measured neat resin properties as input data.

  5. The heterotrophic-combined-with-autotrophic denitrification process: performance and interaction mechanisms.

    PubMed

    Xu, Guihua; Feng, Cuijie; Fang, Fang; Chen, Shaohua; Xu, Yuanjian; Wang, Xingzu

    2015-01-01

    In this work, the interaction mechanisms between an autotrophic denitrification (AD) and heterotrophic denitrification (HD) process in a heterotrophic-autotrophic denitrification (HAD) system were investigated, and the performance of the HAD system under different S/Ac(-) molar ratios was also evaluated. The results demonstrated that the heterotrophic-combined-with-autotrophic denitrification process is a promising technology which can remove chemical oxygen demand (COD), sulfide and nitrate simultaneously. The reduction rate of NO(3)(-) to NO(2)(-) by the HD process was much faster than that of reducing NO(2)(-) to N₂, while the reduction rate of NO(3)(-) to NO(2)(-) by the AD process was slower than that of NO(2)(-) to N₂. Therefore, the AD process could use the surplus NO(2)(-) produced by the HD process. This could alleviate the NO(2)(-)-N accumulation and increase the denitrification rate. In addition, the inhibition effects of acetate on AD bacteria and sulfide on HD were observed, and the inhibition was compensated by the promotion effects on NO(2)(-). Therefore, the processes of AD and HD seem to react in parallel, without disturbing each other, in our HAD system. PMID:25909732

  6. In Vitro Biocompatibility and Mechanical Performance of Titanium Doped High Calcium Oxide Metaphosphate-Based Glasses

    PubMed Central

    Abou Neel, Ensanya A.; Chrzanowski, Wojciech; Georgiou, George; Dalby, Matthew J.; Knowles, Jonathan C.

    2010-01-01

    This study challenged to produce phosphate-based glasses (PBG) for the treatment of osseous defects. The glasses contained, among other components, 40 mol% CaO and 1–5 mol% TiO2. The mechanical performance and in vitro biocompatibility using both human osteosarcoma and primary osteoblasts were carried out. Incorporation of TiO2 into PBG had no significant effect on strength and modulus. These glasses encouraged attachment and maintained high viability of osteosarcoma cells similar to the positive control surface. Cells grown directly (on glasses) or indirectly (in the presence of glass extracts) showed similar proliferation pattern to the positive control cells with no significant effect of TiO2 detected. Increasing TiO2 content, however, has a profound effect on cytoskeleton organization and spreading and maturation of primary osteoblasts. It is believed that TiO2 might have acted as a chemical cue-modulating cells response, and hence the substrates supported maturation/mineralization of the primary osteoblasts. PMID:21350644

  7. In vitro biocompatibility and mechanical performance of titanium doped high calcium oxide metaphosphate-based glasses.

    PubMed

    Abou Neel, Ensanya A; Chrzanowski, Wojciech; Georgiou, George; Dalby, Matthew J; Knowles, Jonathan C

    2010-01-01

    This study challenged to produce phosphate-based glasses (PBG) for the treatment of osseous defects. The glasses contained, among other components, 40 mol% CaO and 1-5 mol% TiO(2). The mechanical performance and in vitro biocompatibility using both human osteosarcoma and primary osteoblasts were carried out. Incorporation of TiO(2) into PBG had no significant effect on strength and modulus. These glasses encouraged attachment and maintained high viability of osteosarcoma cells similar to the positive control surface. Cells grown directly (on glasses) or indirectly (in the presence of glass extracts) showed similar proliferation pattern to the positive control cells with no significant effect of TiO(2) detected. Increasing TiO(2) content, however, has a profound effect on cytoskeleton organization and spreading and maturation of primary osteoblasts. It is believed that TiO(2) might have acted as a chemical cue-modulating cells response, and hence the substrates supported maturation/mineralization of the primary osteoblasts. PMID:21350644

  8. Mechanical performance of hybrid polyester composites reinforced Cloisite 30B and kenaf fibre

    NASA Astrophysics Data System (ADS)

    Bonnia, N. N.; Surip, S. N.; Ratim, S.; Mahat, M. M.

    2012-06-01

    Hybridization of rubber toughened polyester-kenaf nanocomposite was prepared by adding various percentage of kenaf fiber with 4% Cloisite 30B in unsaturated polyester resin. Composite were prepared by adding filler to modified polyester resin subsequently cross-linked using methyl ethyl ketone peroxide and the accelerator cobalt octanoate 1%. Three per hundred rubbers (phr) of liquid natural rubber (LNR) were added in producing this composite. This composite expected to be applied in the interior of passenger cars and truck cabins. This is a quality local product from a combination of good properties polyester and high performance natural fiber, kenaf that is suitable for many applications such as in automotive sector and construction sector. The mechanical and thermal properties of composite were characterized using Durometer Shore-D hardness test, Izod impact test, Scanning electron microscopy, thermogravimetry (TGA) and differential scanning calorimetry (DSC). Result shows that addition of LNR give good properties on impact, flexural and hardness compare to without LNR composite. DSC curve shows that all composition of composites is fully cured and good in thermal properties. Addition of higher percentage of kenaf will lead the composite to elastic behavior and decrease the toughened properties of the composite. Hybrid system composite showed the flexural properties within the flexural properties of kenaf - polyester and Cloisite 30B.

  9. The effect of palmitate and lactate on mechanical performance and metabolism of cat and rat myocardium.

    PubMed Central

    Drake-Holland, A J; Elzinga, G; Noble, M I; ter Keurs, H E; Wempe, F N

    1983-01-01

    Fourteen isolated ejecting hearts were perfused with a suspension of red cells in Tyrode solution. In five hearts comparison was made between glucose alone as substrate and glucose plus free fatty acid (palmitate). In five hearts the effect of additional lactate was studied. In the remaining hearts no substrate changes were made (controls). There were only transient changes in cardiac output of the hearts (at fixed mean aortic pressure) when the perfusion media were switched from one to another. There were no consistent steady-state changes in myocardial oxygen consumption, mean external power, efficiency, cardiac output or coronary blood flow associated with any of the changes in substrate consumption. Thus we were unable to confirm an increase in oxygen consumption and decrease in efficiency associated with either free fatty acid or lactate as substrates. Isolated rat trabeculae were deprived of exogenous substrate; their mechanical performance remained constant for approximately 10 min. Subsequent deterioration was restored by any of the three exogenous substrates. We conclude that there is no oxygen wasting effect of these substrates as has previously been postulated, nor any deleterious effect of changing exogenous or endogenous carbohydrate or lipid substrate. Images Fig. 2 PMID:6887017

  10. Hill's equation of muscle performance and its hidden insight on molecular mechanisms.

    PubMed

    Seow, Chun Y

    2013-12-01

    Muscles shorten faster against light loads than they do against heavy loads. The hyperbolic equation first used by A.V. Hill over seven decades ago to illustrate the relationship between shortening velocity and load is still the predominant method used to characterize muscle performance, even though it has been regarded as purely empirical and lacking precision in predicting velocities at high and low loads. Popularity of the Hill equation has been sustained perhaps because of historical reasons, but its simplicity is certainly attractive. The descriptive nature of the equation does not diminish its role as a useful tool in our quest to understand animal locomotion and optimal design of muscle-powered devices like bicycles. In this Review, an analysis is presented to illustrate the connection between the historic Hill equation and the kinetics of myosin cross-bridge cycle based on the latest findings on myosin motor interaction with actin filaments within the structural confines of a sarcomere. In light of the new data and perspective, some previous studies of force-velocity relations of muscle are revisited to further our understanding of muscle mechanics and the underlying biochemical events, specifically how extracellular and intracellular environment, protein isoform expression, and posttranslational modification of contractile and regulatory proteins change the interaction between myosin and actin that in turn alter muscle force, shortening velocity, and the relationship between them. PMID:24277600

  11. [Performance and Mechanism of Ferric Tannate in the Removal of Inorganic Nitrogen from Wastewater].

    PubMed

    Zhang, Rui-na; Li, Lin; Liu, Jun-xin

    2015-11-01

    A novel adsorbent material-ferric tannate was synthesized, and performances and mechanisms of NH4(+) -N, NO2(-) -N and NO3(-) -N were investigated via batch adsorption experiments. The results indicated that ferric tannate exhibited preferential adsorption for NH4(+) -N and NO2(-) -N. When the mass ratios of ferric tannate to NH4(+) -N and ferric tannate to NO2(-) -N were both 200, the removal efficiencies were both higher than 95%. The adsorption behaviors were analyzed with adsorption kinetic models, Langmuir and Freundlich isotherm adsorption models, and Weber-Morris equation. The results implied that NH4(+) -N and NO2(-) -N were adsorbed on the surface of ferric tannate in the forms of monolayer and multilayer, respectively. The pseudo-second order kinetic model was more suitable to describe the adsorption processes, and the external particle diffusion and surface adsorption played the key roles in the adsorption process. NH: -N could be combined with negative oxygen ions which distributed on the external surface of ferric tannate by the electrostatic interaction, whereas NO2(-) -N could be combined with ferric ions in ferric tannate by the electrostatic interaction and coordination. The present study provided scientific evidence for the application of ferric tannate as a potential adsorbent in the future. PMID:26911001

  12. Neural representations and mechanisms for the performance of simple speech sequences

    PubMed Central

    Bohland, Jason W.; Bullock, Daniel; Guenther, Frank H.

    2010-01-01

    Speakers plan the phonological content of their utterances prior to their release as speech motor acts. Using a finite alphabet of learned phonemes and a relatively small number of syllable structures, speakers are able to rapidly plan and produce arbitrary syllable sequences that fall within the rules of their language. The class of computational models of sequence planning and performance termed competitive queuing (CQ) models have followed Lashley (1951) in assuming that inherently parallel neural representations underlie serial action, and this idea is increasingly supported by experimental evidence. In this paper we develop a neural model that extends the existing DIVA model of speech production in two complementary ways. The new model includes paired structure and content subsystems (cf. MacNeilage, 1998) that provide parallel representations of a forthcoming speech plan, as well as mechanisms for interfacing these phonological planning representations with learned sensorimotor programs to enable stepping through multi-syllabic speech plans. On the basis of previous reports, the model’s components are hypothesized to be localized to specific cortical and subcortical structures, including the left inferior frontal sulcus, the medial premotor cortex, the basal ganglia and thalamus. The new model, called GODIVA (Gradient Order DIVA), thus fills a void in current speech research by providing formal mechanistic hypotheses about both phonological and phonetic processes that are grounded by neuroanatomy and physiology. This framework also generates predictions that can be tested in future neuroimaging and clinical case studies. PMID:19583476

  13. Acceptance Priority Ranking & Annual Capacity Report

    SciTech Connect

    2004-07-31

    The Nuclear Waste Policy Act of 1982, as amended (the Act), assigns the Federal Government the responsibility for the disposal of spent nuclear fuel and high-level waste. Section 302(a) of the Act authorizes the Secretary to enter into contracts with the owners and generators of commercial spent nuclear fuel and/or high-level waste. The Standard Contract for Disposal of Spent Nuclear Fuel and/or High-Level Radioactive Waste (Standard Contract) established the contractual mechanism for the Department's acceptance and disposal of spent nuclear fuel and high-level waste. It includes the requirements and operational responsibilities of the parties to the Standard Contract in the areas of administrative matters, fees, terms of payment, waste acceptance criteria, and waste acceptance procedures. The Standard Contract provides for the acquisition of title to the spent nuclear fuel and/or high-level waste by the Department, its transportation to Federal facilities, and its subsequent disposal.

  14. AIR CLEANING FOR ACCEPTABLE INDOOR AIR QUALITY

    EPA Science Inventory

    The paper discusses air cleaning for acceptable indoor air quality. ir cleaning has performed an important role in heating, ventilation, and air-conditioning systems for many years. raditionally, general ventilation air-filtration equipment has been used to protect cooling coils ...

  15. Association of Ego Defense Mechanisms with Academic Performance, Anxiety and Depression in Medical Students: A Mixed Methods Study

    PubMed Central

    Waqas, Ahmed; Malik, Aamenah; Muhammad, Umer; Khan, Sarah; Mahmood, Nadia

    2015-01-01

    Background: Ego defense mechanisms are unconscious psychological processes that help an individual to prevent anxiety when exposed to a stressful situation. These mechanisms are important in psychiatric practice to assess an individual’s personality dynamics, psychopathologies, and modes of coping with stressful situations, and hence, to design appropriate individualized treatment. Our study delineates the relationship of ego defense mechanisms with anxiety, depression, and academic performance of Pakistani medical students. Methods: This cross-sectional study was done at CMH Lahore Medical College and Fatima Memorial Hospital Medical and Dental College, both in Lahore, Pakistan, from December 1, 2014 to January 15, 2015. Convenience sampling was used and only students who agreed to take part in this study were included. The questionnaire consisted of three sections: 1) Demographics, documenting demographic data and academic scores on participants’ most recent exams; 2) Hospital Anxiety and Depression Scale (HADS); and 3) Defense Style Questionnaire-40 (DSQ-40). The data were analyzed with SPSS v. 20. Mean scores and frequencies were calculated for demographic variables and ego defense mechanisms. Bivariate correlations, one-way ANOVA, and multiple linear regression were used to identify associations between academic scores, demographics, ego defense mechanisms, anxiety, and depression. Results: A total of 409 medical students participated, of whom 286 (70%) were females and 123 (30%) were males. Mean percentage score on the most recent exams was 75.6% in medical students. Bivariate correlation revealed a direct association between mature and neurotic ego defense mechanisms and academic performance, and an indirect association between immature mechanisms and academic performance. One-way ANOVA showed that moderate levels of anxiety (P < .05) and low levels of depression (P < .05) were associated with higher academic performance. Conclusion: There was a

  16. 46 CFR 164.023-11 - Acceptance tests.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 6 2014-10-01 2014-10-01 false Acceptance tests. 164.023-11 Section 164.023-11 Shipping...: SPECIFICATIONS AND APPROVAL MATERIALS Thread for Personal Flotation Devices § 164.023-11 Acceptance tests. (a) Performance testing. Manufacturers shall ensure that the performance tests described in § 164.023-7 (a) or...

  17. Contributions and mechanisms of action of graphite nanomaterials in ultra high performance concrete

    NASA Astrophysics Data System (ADS)

    Sbia, Libya Ahmed

    Ultra-high performance concrete (UHPC) reaches high strength and impermeability levels by using a relatively large volume fraction of a dense binder with fine microstructure in combination with high-quality aggregates of relatively small particle size, and reinforcing fibers. The dense microstructure of the cementitions binder is achieved by raising the packing density of the particulate matter, which covers sizes ranging from few hundred nanometers to few millimeters. The fine microstructure of binder in UHPC is realized by effective use of pozzolans to largely eliminate the coarse crystalline particles which exist among cement hydrates. UHPC incorporates (steel) fibers to overcome the brittleness of its dense, finely structured cementitious binder. The main thrust of this research is to evaluate the benefits of nanmaterials in UHPC. The dense, finely structure cementitious binder as well as the large volume fraction of the binder in UHPC benefit the dispersion of nanomaterials, and their interfacial interactions. The relatively close spacing of nanomaterials within the cementitious binder of UHPC enables them to render local reinforcement effects in critically stressed regions such as those in the vicinity of steel reinforcement and prestressing strands as well as fibers. Nanomaterials can also raise the density of the binder in UHPC by extending the particle size distribution down to the few nanometers range. Comprehensive experimental studies supported by theoretical investigations were undertake in order to optimize the use of nanomaterials in UHPC, identity the UHPC (mechanical) properties which benefit from the introduction of nanomaterials, and define the mechanisms of action of nanomaterials in UHPC. Carbon nanofiber was the primary nanomaterial used in this investigation. Some work was also conducted with graphite nanoplates. The key hypotheses of the project were as follows: (i) nanomaterials can make important contributions to the packing density of the

  18. Performance enhancement of zero valent iron based systems using depassivators: Optimization and kinetic mechanisms.

    PubMed

    Ansaf, Karim Vayalunkal Karottu; Ambika, Selvaraj; Nambi, Indumathi Manivannan

    2016-10-01

    The long-term ability of Zero-Valent Iron (ZVI) in contaminant removal relies on the effectiveness of iron to serve as electron donor, which makes it a versatile remediation material. However, the formation of oxide and hydroxide layers results in passive layer on ZVI surface during contaminant removal hinders its reactivity. The focus of this research was to evaluate the performance of corrosive agents such as acetic acid (HAc), aluminium sulphate (Alum) and potassium chloride (KCl) as depassivators to overcome passivation for sustainability and longevity. Batch experiments using seven combinations of the above chemicals were conducted to optimize the dosage of depassivators based on passive layer removal. The influence of depassivators in catalytic activity of ZVI in removing Cr(6+) was evaluated. The passive layer on ZVI particles was characterized using Scanning Electron Microscopy (SEM) and confirmed by Energy-Dispersive X-ray spectroscopy (EDAX) analysis. The major mechanisms in passive layer removal was found to be H(+) ion embrittlement followed by uniform depassivation when [HAc] was used and pitting corrosion when [Alum] and [KCl]were used. All the seven sets of chemicals enabled depassivation, but considering the criteria of maximum depassivation, catalytic activity and long term reactivity the depassivation treatments were effective in order as [HAc-Alum] > [HAc-Alum-KCl] >[HAc] > [Alum] > [HAc-KCl] > [KCl] > [Alum-KCl]. The kinetic rate of ZVI using [HAc-Alum] and [Alum] was relatively unchanged over the pH range of 4-10, made it suitable for ex-situ remediation. This insignificant influence of initial pH in catalytic activity of ZVI along with the improvement in longevity and sustainability makes it suitable for effective water treatment applications. The present work has successfully demonstrated that chemical depassivation can restore considerable reactivity of ZVI in the existing permeable reactive barriers. PMID:27395028

  19. Superior mechanical performance of highly porous, anisotropic nanocellulose-montmorillonite aerogels prepared by freeze casting.

    PubMed

    Donius, Amalie E; Liu, Andong; Berglund, Lars A; Wegst, Ulrike G K

    2014-09-01

    Directionally solidified nanofibrillated cellulose (NFC)-sodium-montmorillonite (MMT) composite aerogels with a honeycomb-like pore structure were compared with non-directionally frozen aerogels with equiaxed pore structure and identical composition and found to have superior functionalities. To explore structure-property correlations, three different aerogel compositions of 3wt% MMT, and 0.4wt%, 0.8wt%, and 1.2wt% NFC, respectively, were tested. Young׳s modulus, compressive strength and toughness were found to increase with increasing NFC content for both architectures. The modulus increased from 25.8kPa to 386kPa for the isotropic and from 2.13MPa to 3.86MPa for the anisotropic aerogels, the compressive yield strength increased from 3.3kPa to 18.0kPa for the isotropic and from 32.3kPa to 52.5kPa for the anisotropic aerogels, and the toughness increased from 6.3kJ/m(3) to 24.1kJ/m(3) for the isotropic and from 22.9kJ/m(3) to 46.2kJ/m(3) for the anisotropic aerogels. The great range of properties, which can be achieved through compositional as well as architectural variations, makes these aerogels highly attractive for a large range of applications, for which either a specific composition, or a particular pore morphology, or both are required. Finally, because NFC is flammable, gasification experiments were performed, which revealed that the inclusion of MMT increased the heat endurance and shape retention functions of the aerogels dramatically up to 800°C while the mechanical properties were retained up to 300°C. PMID:24905177

  20. Process for controlling morphology and improving thermal-mechanical performance of high performance interpenetrating and semi-interpenetrating polymer networks

    NASA Technical Reports Server (NTRS)

    Pater, Ruth H. (Inventor); Hansen, Marion G. (Inventor)

    1997-01-01

    In the process of the present invention, a non-polar, aprotic solvent is removed from an oligomer/polymer solution by freeze-drying in order to produce IPNs and semi-IPNs. By thermally quenching the solution to a solid in a short length of time, the size of the minor constituent-rich regions is greatly reduced as they are excluded along with the major constituent from the regions of crystallizing solvent. The use of this process sequence of controlling phase morphology provides IPNs and semi-IPNs with improved fracture toughness, microcracking resistance, and other physical-mechanical properties as compared to IPNs and semi-IPNs formed when the solvent is evaporated rather than sublimed.

  1. Process for controlling morphology and improving thermal mechanical performance of high performance interpenetrating and semiinterpenetrating polymer networks

    NASA Technical Reports Server (NTRS)

    Pater, Ruth H. (Inventor); Hansen, Marion G. (Inventor)

    1998-01-01

    In the process of the present invention, a non-polar, aprotic solvent is removed from an oligomer/polymer solution by freeze-drying in order to produce IPNs and semi-IPNs. By thermally quenching the solution to a solid in a short length of time, the size of the minor constituent-rich regions is greatly reduced as they are excluded along with the major constituent from the regions of crystallizing solvent. The use of this process sequence of controlling phase morphology provides IPNs and semi-IPNs with improved fracture toughness, microcracking resistance, and other physical-mechanical properties as compared to IPNs and semi-IPNs formed when the solvent is evaporated rather than sublimed.

  2. 30 CFR 870.16 - Acceptable payment methods.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 30 Mineral Resources 3 2011-07-01 2011-07-01 false Acceptable payment methods. 870.16 Section 870... § 870.16 Acceptable payment methods. (a) If you owe total quarterly reclamation fees of $25,000 or more...) If you pay more than $25,000 by a method other than an electronic fund transfer mechanism approved...

  3. Not Accepted by the Family: "Being Difficult" or "Being Different"?

    ERIC Educational Resources Information Center

    Komter, Aafke; Voorpostel, Marieke; Pels, Trees

    2011-01-01

    Using data from the Netherlands Kinship Panel Study (NKPS) and combining a quantitative approach and a qualitative approach (N = 8,148 and n = 43, respectively), this study investigates the mechanisms associated with a lack of acceptance by one's family. From the total NKPS sample, 12.1% did not feel (entirely) accepted by their family. The…

  4. 30 CFR 870.16 - Acceptable payment methods.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 30 Mineral Resources 3 2010-07-01 2010-07-01 false Acceptable payment methods. 870.16 Section 870... § 870.16 Acceptable payment methods. (a) If you owe total quarterly reclamation fees of $25,000 or more...) If you pay more than $25,000 by a method other than an electronic fund transfer mechanism approved...

  5. 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.

  6. 46 CFR 160.133-7 - Design, construction, and performance of release mechanisms.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... by reference, see § 160.133-5 of this subpart); (3) 46 CFR part 159; and (4) This subpart. (b) Each... accordance with 46 CFR 8.220, the U.S. Navy, or the national body where the release mechanism is constructed... mechanism, must be in accordance with 46 CFR part 58, subpart 58.30, with hose and fittings in...

  7. Physiologic correlates to background noise acceptance

    NASA Astrophysics Data System (ADS)

    Tampas, Joanna; Harkrider, Ashley; Nabelek, Anna

    2001-05-01

    Acceptance of background noise can be evaluated by having listeners indicate the highest background noise level (BNL) they are willing to accept while following the words of a story presented at their most comfortable listening level (MCL). The difference between the selected MCL and BNL is termed the acceptable noise level (ANL). One of the consistent findings in previous studies of ANL is large intersubject variability in acceptance of background noise. This variability is not related to age, gender, hearing sensitivity, personality, type of background noise, or speech perception in noise performance. The purpose of the current experiment was to determine if individual differences in physiological activity measured from the peripheral and central auditory systems of young female adults with normal hearing can account for the variability observed in ANL. Correlations between ANL and various physiological responses, including spontaneous, click-evoked, and distortion-product otoacoustic emissions, auditory brainstem and middle latency evoked potentials, and electroencephalography will be presented. Results may increase understanding of the regions of the auditory system that contribute to individual noise acceptance.

  8. W-026, acceptance test report manipulator system

    SciTech Connect

    Watson, T.L.

    1997-04-15

    The purpose of the WRAP Manipulator System Acceptance Test Plan (ATP) is to verify that the 4 glovebox sets of WRAP manipulator components, including rail/carriage, slave arm, master controller and auxiliary equipment, meets the requirements of the functional segments of 14590 specification. The demonstration of performance elements of the ATP are performed as a part of the Assembly specifications. Manipulator integration is integrated in the performance testing of the gloveboxes. Each requirement of the Assembly specification will be carried out in conjunction with glovebox performance tests.

  9. Mechanism of fatigue performance enhancement in a laser sintered superhard nanoparticles reinforced nanocomposite followed by laser shock peening

    NASA Astrophysics Data System (ADS)

    Lin, Dong; Ye, Chang; Liao, Yiliang; Suslov, Sergey; Liu, Richard; Cheng, Gary J.

    2013-04-01

    This study investigates the fundamental mechanism of fatigue performance enhancement during a novel hybrid manufacturing process, which combines laser sintering of superhard nanoparticles integrated nanocomposites and laser shock peening (LSP). Through laser sintering, TiN nanoparticles are integrated uniformly into iron matrix to form a nanocomposite layer near the surface of AISI4140 steel. LSP is then performed on the nanocomposite layer to generate interaction between nanoparticles and shock waves. The fundamental mechanism of fatigue performance enhancement is discussed in this paper. During laser shock interaction with the nanocomposites, the existence of nanoparticles increases the dislocation density and also helps to pin the dislocation movement. As a result, both dislocation density and residual stress are stabilized, which is beneficial for fatigue performance.

  10. Self-Reported Acceptance of Social Anxiety Symptoms: Development and Validation of the Social Anxiety-Acceptance and Action Questionnaire

    ERIC Educational Resources Information Center

    MacKenzie, Meagan B.; Kocovski, Nancy L.

    2010-01-01

    Mindfulness and acceptance-based interventions have been used in social anxiety treatments with initial success. Further research requires the psychometrically sound measurement of mechanisms of change associated with these treatments. This research was conducted to develop and evaluate such a measure, the Social Anxiety-Acceptance and Action…

  11. Accepters and Rejecters of Counseling.

    ERIC Educational Resources Information Center

    Rose, Harriett A.; Elton, Charles F.

    Personality differences between students who accept or reject proffered counseling assistance were investigated by comparing personality traits of 116 male students at the University of Kentucky who accepted or rejected letters of invitation to group counseling. Factor analysis of Omnibus Personality Inventory (OPI) scores to two groups of 60 and…

  12. Cone penetrometer acceptance test report

    SciTech Connect

    Boechler, G.N.

    1996-09-19

    This Acceptance Test Report (ATR) documents the results of acceptance test procedure WHC-SD-WM-ATR-151. Included in this report is a summary of the tests, the results and issues, the signature and sign- off ATP pages, and a summarized table of the specification vs. ATP section that satisfied the specification.

  13. Neural mechanisms underlying paradoxical performance for monetary incentives are driven by loss aversion.

    PubMed

    Chib, Vikram S; De Martino, Benedetto; Shimojo, Shinsuke; O'Doherty, John P

    2012-05-10

    Employers often make payment contingent on performance in order to motivate workers. We used fMRI with a novel incentivized skill task to examine the neural processes underlying behavioral responses to performance-based pay. We found that individuals' performance increased with increasing incentives; however, very high incentive levels led to the paradoxical consequence of worse performance. Between initial incentive presentation and task execution, striatal activity rapidly switched between activation and deactivation in response to increasing incentives. Critically, decrements in performance and striatal deactivations were directly predicted by an independent measure of behavioral loss aversion. These results suggest that incentives associated with successful task performance are initially encoded as a potential gain; however, when actually performing a task, individuals encode the potential loss that would arise from failure. PMID:22578508

  14. Effect of tow alignment on the mechanical performance of 3D woven textile composites

    NASA Technical Reports Server (NTRS)

    Norman, Timothy L.; Allison, Patti; Baldwin, Jack W.; Gracias, Brian K.; Seesdorf, Dave

    1993-01-01

    Three-dimensional (3D) woven preforms are currently being considered for use as primary structural components. Lack of technology to properly manufacture, characterize and predict mechanical properties, and predict damage mechanisms leading to failure are problems facing designers of textile composite materials. Two material systems with identical specifications but different manufacturing approaches are investigated. One manufacturing approach resulted in an irregular (nonuniform) preform geometry. The other approach yielded the expected preform geometry (uniform). The objectives are to compare the mechanical properties of the uniform and nonuniform angle interlock 3D weave constructions. The effect of adding layers of laminated tape to the outer surfaces of the textile preform is also examined. Damage mechanisms are investigated and test methods are evaluated.

  15. Computational performance of Free Mesh Method applied to continuum mechanics problems.

    PubMed

    Yagawa, Genki

    2011-01-01

    The free mesh method (FMM) is a kind of the meshless methods intended for particle-like finite element analysis of problems that are difficult to handle using global mesh generation, or a node-based finite element method that employs a local mesh generation technique and a node-by-node algorithm. The aim of the present paper is to review some unique numerical solutions of fluid and solid mechanics by employing FMM as well as the Enriched Free Mesh Method (EFMM), which is a new version of FMM, including compressible flow and sounding mechanism in air-reed instruments as applications to fluid mechanics, and automatic remeshing for slow crack growth, dynamic behavior of solid as well as large-scale Eigen-frequency of engine block as applications to solid mechanics. PMID:21558753

  16. Computational performance of Free Mesh Method applied to continuum mechanics problems

    PubMed Central

    YAGAWA, Genki

    2011-01-01

    The free mesh method (FMM) is a kind of the meshless methods intended for particle-like finite element analysis of problems that are difficult to handle using global mesh generation, or a node-based finite element method that employs a local mesh generation technique and a node-by-node algorithm. The aim of the present paper is to review some unique numerical solutions of fluid and solid mechanics by employing FMM as well as the Enriched Free Mesh Method (EFMM), which is a new version of FMM, including compressible flow and sounding mechanism in air-reed instruments as applications to fluid mechanics, and automatic remeshing for slow crack growth, dynamic behavior of solid as well as large-scale Eigen-frequency of engine block as applications to solid mechanics. PMID:21558753

  17. Ion beam sputtering coatings on large substrates: toward an improvement of the mechanical and optical performances.

    PubMed

    Cimma, Bernard; Forest, Danièle; Ganau, Patrick; Lagrange, Bernard; Mackowski, Jean-Marie; Michel, Christophe; Montorio, Jean-Luc; Morgado, Nazario; Pignard, Renée; Pinard, Laurent; Remillieux, Alban

    2006-03-01

    Large mirrors (ø350 mm) having extremely low optical loss (absorption, scattering, wavefront) were coated for the VIRGO interferometer. The new generation of mirrors needs to have a better wavefront and lower mechanical loss. To improve the component wavefront, the corrective coating technique was used. By doping the tantalum pentoxide layers, we improved, for the first time to our knowledge, the multilayer mechanical loss. The first results are discussed. PMID:16539246

  18. Confidence versus Performance as an Indicator of the Presence of Alternative Conceptions and Inadequate Problem-Solving Skills in Mechanics

    ERIC Educational Resources Information Center

    Potgieter, Marietjie; Malatje, Esther; Gaigher, Estelle; Venter, Elsie

    2010-01-01

    This study investigated the use of performance-confidence relationships to signal the presence of alternative conceptions and inadequate problem-solving skills in mechanics. A group of 33 students entering physics at a South African university participated in the project. The test instrument consisted of 20 items derived from existing standardised…

  19. Effects of the Badge Mechanism on Self-Efficacy and Learning Performance in a Game-Based English Learning Environment

    ERIC Educational Resources Information Center

    Yang, Jie Chi; Quadir, Benazir; Chen, Nian-Shing

    2016-01-01

    A growing number of studies have been conducted on digital game-based learning (DGBL). However, there has been a lack of attention paid to individuals' self-efficacy and learning performance in the implementation of DGBL. This study therefore investigated how the badge mechanism in DGBL enhanced users' self-efficacy in the subject domain of…

  20. Reward and Visual Feedback Relative to the Performance and Mechanical Efficiency of High School Girls in the Standing Broad Jump.

    ERIC Educational Resources Information Center

    Zebas, Carole J.

    This study focuses on changes occurring in selected mechanical components of high school girls performing the standing broad jump, and collects data pertaining to the effects of monetary reward and videotape feedback upon the following components: (a) distance jumped, (b) maximum angle of knee flexion, (c) maximum angle of hip flexion, (d) hip…

  1. Risk assessment of maintenance operations: the analysis of performing task and accident mechanism.

    PubMed

    Carrillo-Castrillo, Jesús A; Rubio-Romero, Juan Carlos; Guadix, Jose; Onieva, Luis

    2015-01-01

    Maintenance operations cover a great number of occupations. Most small and medium-sized enterprises lack the appropriate information to conduct risk assessments of maintenance operations. The objective of this research is to provide a method based on the concepts of task and accident mechanisms for an initial risk assessment by taking into consideration the prevalence and severity of the maintenance accidents reported. Data were gathered from 11,190 reported accidents in maintenance operations in the manufacturing sector of Andalusia from 2003 to 2012. By using a semi-quantitative methodology, likelihood and severity were evaluated based on the actual distribution of accident mechanisms in each of the tasks. Accident mechanisms and tasks were identified by using those variables included in the European Statistics of Accidents at Work methodology. As main results, the estimated risk of the most frequent accident mechanisms identified for each of the analysed tasks is low and the only accident mechanisms with medium risk are accidents when lifting or pushing with physical stress on the musculoskeletal system in tasks involving carrying, and impacts against objects after slipping or stumbling for tasks involving movements. The prioritisation of public preventive actions for the accident mechanisms with a higher estimated risk is highly recommended. PMID:25179119

  2. The effect of body mechanics education on the work performance of fruit warehouse workers.

    PubMed

    Holmes, Wendy; Lam, Pui-Yan; Elkind, Pamela; Pitts, Kathy

    2008-01-01

    Agriculture is one of the nation's more hazardous occupations, and injury prevention among agricultural workers is a focus of safety and education programs nationwide. This research project investigated the effectiveness of a culturally appropriate body mechanics education program for fruit warehouse workers in Washington State. The purpose of the body mechanics education program was to promote correct ergonomic behavior among migrant and seasonal fruit warehouse workers. Participants received instruction in proper body mechanics by viewing a videotaped Spanish-language theatre program (with English subtitles) followed by a demonstration and practice of correct lifting techniques and selected stretches for injury prevention. A written pre- and post-test to assess body mechanics knowledge and an evaluation of lifting methods were administered at the time of the training and again two weeks later. The results indicated culturally appropriate body mechanics education is an effective intervention for increasing knowledge and promoting correct lifting techniques. However, further research is indicated to examine the significance of supervised and individualized, job-specific practice on affecting more lasting changes in work-related body mechanics and lifting behaviors. PMID:19127017

  3. Evaluating the trade-off between mechanical and electrochemical performance of separators for lithium-ion batteries: Methodology and application

    NASA Astrophysics Data System (ADS)

    Plaimer, Martin; Breitfuß, Christoph; Sinz, Wolfgang; Heindl, Simon F.; Ellersdorfer, Christian; Steffan, Hermann; Wilkening, Martin; Hennige, Volker; Tatschl, Reinhard; Geier, Alexander; Schramm, Christian; Freunberger, Stefan A.

    2016-02-01

    Lithium-ion batteries are in widespread use in electric vehicles and hybrid vehicles. Besides features like energy density, cost, lifetime, and recyclability the safety of a battery system is of prime importance. The separator material impacts all these properties and requires therefore an informed selection. The interplay between the mechanical and electrochemical properties as key selection criteria is investigated. Mechanical properties were investigated using tensile and puncture penetration tests at abuse relevant conditions. To investigate the electrochemical performance in terms of effective conductivity a method based on impedance spectroscopy was introduced. This methodology is applied to evaluate ten commercial separators which allows for a trade-off analysis of mechanical versus electrochemical performance. Based on the results, and in combination with other factors, this offers an effective approach to select suitable separators for automotive applications.

  4. An Update on the Mechanical and EM Performance of the Composite Dish Verification Antenna (DVA-1) for the SKA

    NASA Technical Reports Server (NTRS)

    Lacy, G. E.; Fleming, M.; Baker, L.; Imbriale, W.; Cortes-Medellin, G.; Veidt, B.; Hovey, G. J.; DeBoer, D.

    2012-01-01

    This paper will give an overview of the unique mechanical and optical design of the DVA-1 telescope. The rim supported carbon fibre reflector surfaces are designed to be both low cost and have high performance under wind, gravity, and thermal loads. The shaped offset Gregorian optics offer low and stable side lobes along with a large area at the secondary focus for multiple feeds with no aperture blockage. Telescope performance under ideal conditions as well as performance under gravity, wind, and thermal loads will be compared directly using calculated radiation patterns for each of these operating conditions.

  5. Hierarchical assembly strategy and multiscale structural origin of exceptional mechanical performance in nacre

    NASA Astrophysics Data System (ADS)

    Huang, Zaiwang

    Nacre (mother of pearl) is a self-assembled hierarchical nanocomposite in possession of exquisite multiscale architecture and exceptional mechanical properties. Previous work has shown that the highly-ordered brick-mortar-like structure in nacre is assembled via epitaxial growth and the aragonite platelets are pure single-crystals. Our results challenge this conclusion and propose that nacre's individual aragonite platelets are constructed with highly-aligned aragonite nanoparticles mediated by screw dislocation and amorphous aggregation. The underlying physics mechanism why the aragonite nanoparticles choose highly-oriented attachment as its crystallization pathway is rationalized in terms of thermodynamics. The aragonite nanoparticle order-disorder transformation can be triggered by high temperature and mechanical deformation, which in turn confirms that the aragonite nanoparticles are basic building blocks for aragonite platelets. Particularly fascinating is the fracture toughness enhancement of nacre through exquisitely collecting mechanically inferior calcium carbonate (CaCO3) and biomolecules. The sandwich-like microarchitecture with a geometrically staggered arrangement can induce crack deflection along its biopolymer interface, thus significantly enhancing nacre's fracture toughness. Our new findings ambiguously demonstrate that, aside from crack deflection, the advancing crack can invade aragonite platelet, leaving a zigzag crack propagation pathway. These unexpected experimental observations disclose, for the first time, the inevitable structural role of aragonite platelets in enhancing nacre's fracture toughness. Simultaneously, the findings that the crack propagates in a zigzag manner within individual aragonite platelets overturn the previously well-established wisdom that considers aragonite platelets as brittle single-crystals. Moreover, we investigated the dynamical mechanical response of nacre under unixial compression. Our results show that the

  6. Parkinson's Disease-Related Impairments in Body Movement, Coordination and Postural Control Mechanisms When Performing 80° Lateral Gaze Shifts.

    PubMed

    Bonnet, Cédrick T; Delval, Arnaud; Defebvre, Luc

    2015-09-01

    We investigated early signs of Parkinson's disease-related impairment in mediolateral postural control. Thirty-six participants (18 Hoehn & Yahr stage 2 patients in the off-drug condition and 18 healthy controls) were studied in a stationary gaze condition and when performing 80° lateral gaze shifts at 0.125 and 0.25 Hz. Body sway, coordination and postural control mechanisms were analyzed. All participants performed the visual tasks adequately. The patients were not unstable in the stationary gaze condition. In both groups, mediolateral ankle- and hip-based postural control mechanisms were significantly more active under gaze shift conditions than under the stationary gaze condition. As expected, the patients exhibited significantly greater angular movements of the lower back and significantly lower angular movements of the head (relative to controls) when performing gaze shifts. When considering linear displacements (rather than angular movements), the patients exhibited significantly greater displacements of the lower back and lower, slower displacements of the head than controls under gaze shift conditions. Relative to controls, the patients performed "en block" body movements. Overall, our results show that the patients' ankle- and hip-based mediolateral postural control mechanisms did not adapt to the difficulty of the visual task being performed. PMID:25423653

  7. Seeing the same thing differently: mechanisms that contribute to assessor differences in directly-observed performance assessments.

    PubMed

    Yeates, Peter; O'Neill, Paul; Mann, Karen; Eva, Kevin

    2013-08-01

    Assessors' scores in performance assessments are known to be highly variable. Attempted improvements through training or rating format have achieved minimal gains. The mechanisms that contribute to variability in assessors' scoring remain unclear. This study investigated these mechanisms. We used a qualitative approach to study assessors' judgements whilst they observed common simulated videoed performances of junior doctors obtaining clinical histories. Assessors commented concurrently and retrospectively on performances, provided scores and follow-up interviews. Data were analysed using principles of grounded theory. We developed three themes that help to explain how variability arises: Differential Salience-assessors paid attention to (or valued) different aspects of the performances to different degrees; Criterion Uncertainty-assessors' criteria were differently constructed, uncertain, and were influenced by recent exemplars; Information Integration-assessors described the valence of their comments in their own unique narrative terms, usually forming global impressions. Our results (whilst not precluding the operation of established biases) describe mechanisms by which assessors' judgements become meaningfully-different or unique. Our results have theoretical relevance to understanding the formative educational messages that performance assessments provide. They give insight relevant to assessor training, assessors' ability to be observationally "objective" and to the educational value of narrative comments (in contrast to numerical ratings). PMID:22581567

  8. Reduced order modeling of mechanical degradation induced performance decay in lithium-ion battery porous electrodes

    DOE PAGESBeta

    Barai, Pallab; Smith, Kandler; Chen, Chien -Fan; Kim, Gi -Heon; Mukherjee, Partha P.

    2015-06-17

    In this paper, a one-dimensional computational framework is developed that can solve for the evolution of voltage and current in a lithium-ion battery electrode under different operating conditions. A reduced order model is specifically constructed to predict the growth of mechanical degradation within the active particles of the carbon anode as a function of particle size and C-rate. Using an effective diffusivity relation, the impact of microcracks on the diffusivity of the active particles has been captured. Reduction in capacity due to formation of microcracks within the negative electrode under different operating conditions (constant current discharge and constant current constantmore » voltage charge) has been investigated. At the beginning of constant current discharge, mechanical damage to electrode particles predominantly occurs near the separator. As the reaction front shifts, mechanical damage spreads across the thickness of the negative electrode and becomes relatively uniform under multiple discharge/charge cycles. Mechanical degradation under different drive cycle conditions has been explored. It is observed that electrodes with larger particle sizes are prone to capacity fade due to microcrack formation. Finally, under drive cycle conditions, small particles close to the separator and large particles close to the current collector can help in reducing the capacity fade due to mechanical degradation.« less

  9. Reduced order modeling of mechanical degradation induced performance decay in lithium-ion battery porous electrodes

    SciTech Connect

    Barai, Pallab; Smith, Kandler; Chen, Chien -Fan; Kim, Gi -Heon; Mukherjee, Partha P.

    2015-06-17

    In this paper, a one-dimensional computational framework is developed that can solve for the evolution of voltage and current in a lithium-ion battery electrode under different operating conditions. A reduced order model is specifically constructed to predict the growth of mechanical degradation within the active particles of the carbon anode as a function of particle size and C-rate. Using an effective diffusivity relation, the impact of microcracks on the diffusivity of the active particles has been captured. Reduction in capacity due to formation of microcracks within the negative electrode under different operating conditions (constant current discharge and constant current constant voltage charge) has been investigated. At the beginning of constant current discharge, mechanical damage to electrode particles predominantly occurs near the separator. As the reaction front shifts, mechanical damage spreads across the thickness of the negative electrode and becomes relatively uniform under multiple discharge/charge cycles. Mechanical degradation under different drive cycle conditions has been explored. It is observed that electrodes with larger particle sizes are prone to capacity fade due to microcrack formation. Finally, under drive cycle conditions, small particles close to the separator and large particles close to the current collector can help in reducing the capacity fade due to mechanical degradation.

  10. Composition, structure and mechanical properties define performance of pulmonary surfactant membranes and films.

    PubMed

    Parra, Elisa; Pérez-Gil, Jesús

    2015-01-01

    The respiratory surface in the mammalian lung is stabilized by pulmonary surfactant, a membrane-based system composed of multiple lipids and specific proteins, the primary function of which is to minimize the surface tension at the alveolar air-liquid interface, optimizing the mechanics of breathing and avoiding alveolar collapse, especially at the end of expiration. The goal of the present review is to summarize current knowledge regarding the structure, lipid-protein interactions and mechanical features of surfactant membranes and films and how these properties correlate with surfactant biological function inside the lungs. Surfactant mechanical properties can be severely compromised by different agents, which lead to surfactant inhibition and ultimately contributes to the development of pulmonary disorders and pathologies in newborns, children and adults. A detailed comprehension of the unique mechanical and rheological properties of surfactant layers is crucial for the diagnostics and treatment of lung diseases, either by analyzing the contribution of surfactant impairment to the pathophysiology or by improving the formulations in surfactant replacement therapies. Finally, a short review is also included on the most relevant experimental techniques currently employed to evaluate lung surfactant mechanics, rheology, and inhibition and reactivation processes. PMID:25260665

  11. Hanford Site solid waste acceptance criteria

    SciTech Connect

    Ellefson, M.D.

    1998-07-01

    Order 5820.2A requires that each treatment, storage, and/or disposal facility (referred to in this document as TSD unit) that manages low-level or transuranic waste (including mixed waste and TSCA PCB waste) maintain waste acceptance criteria. These criteria must address the various requirements to operate the TSD unit in compliance with applicable safety and environmental requirements. This document sets forth the baseline criteria for acceptance of radioactive waste at TSD units operated by WMH. The criteria for each TSD unit have been established to ensure that waste accepted can be managed in a manner that is within the operating requirements of the unit, including environmental regulations, DOE Orders, permits, technical safety requirements, waste analysis plans, performance assessments, and other applicable requirements. Acceptance criteria apply to the following TSD units: the Low-Level Burial Grounds (LLBG) including both the nonregulated portions of the LLBG and trenches 31 and 34 of the 218-W-5 Burial Ground for mixed waste disposal; Central Waste Complex (CWC); Waste Receiving and Processing Facility (WRAP); and T Plant Complex. Waste from all generators, both from the Hanford Site and from offsite facilities, must comply with these criteria. Exceptions can be granted as provided in Section 1.6. Specific waste streams could have additional requirements based on the 1901 identified TSD pathway. These requirements are communicated in the Waste Specification Records (WSRds). The Hanford Site manages nonradioactive waste through direct shipments to offsite contractors. The waste acceptance requirements of the offsite TSD facility must be met for these nonradioactive wastes. This document does not address the acceptance requirements of these offsite facilities.

  12. Automotive Tune-up and Performance; Automotive Mechanics 3: 9047.02.

    ERIC Educational Resources Information Center

    Dade County Public Schools, Miami, FL.

    This document presents an outline for a 135-hour course designed to help students become employable and provide them with the skills, knowledge, attitudes, and values necessary for performing the required services in automotive tune up and performance. Such services are critical and must be exact to meet Federal Emission Control Standards. The…

  13. The effects of incentive framing on performance decrements for large monetary outcomes: behavioral and neural mechanisms.

    PubMed

    Chib, Vikram S; Shimojo, Shinsuke; O'Doherty, John P

    2014-11-01

    There is a nuanced interplay between the provision of monetary incentives and behavioral performance. Individuals' performance typically increases with increasing incentives only up to a point, after which larger incentives may result in decreases in performance, a phenomenon known as "choking." We investigated the influence of incentive framing on choking effects in humans: in one condition, participants performed a skilled motor task to obtain potential monetary gains; in another, participants performed the same task to avoid losing a monetary amount. In both the gain and loss frame, the degree of participants' behavioral loss aversion was correlated with their susceptibility to choking effects. However, the effects were markedly different in the gain and loss frames: individuals with higher loss aversion were susceptible to choking for large prospective gains and not susceptible to choking for large prospective losses, whereas individuals with low loss aversion choked for large prospective losses but not for large prospective gains. Activity in the ventral striatum was predictive of performance decrements in both the gain and loss frames. Moreover, a mediation analysis revealed that behavioral loss aversion hindered performance via the influence of ventral striatal activity on motor performance. Our findings indicate that the framing of an incentive has a profound effect on an individual's susceptibility to choking effects, which is contingent on their loss aversion. Furthermore, we demonstrate that the ventral striatum serves as an interface between incentive-driven motivation and instrumental action, regardless of whether incentives are framed in terms of potential losses or gains. PMID:25378151

  14. On the Development and Mechanics of Delayed Matching-to-Sample Performance

    ERIC Educational Resources Information Center

    Kangas, Brian D.; Berry, Meredith S.; Branch, Marc N.

    2011-01-01

    Despite its frequent use to assess effects of environmental and pharmacological variables on short-term memory, little is known about the development of delayed matching-to-sample (DMTS) performance. This study was designed to examine the dimensions and dynamics of DMTS performance development over a long period of exposure to provide a more…

  15. A Model for Sustainable Building Energy Efficiency Retrofit (BEER) Using Energy Performance Contracting (EPC) Mechanism for Hotel Buildings in China

    NASA Astrophysics Data System (ADS)

    Xu, Pengpeng

    Hotel building is one of the high-energy-consuming building types, and retrofitting hotel buildings is an untapped solution to help cut carbon emissions contributing towards sustainable development. Energy Performance Contracting (EPC) has been promulgated as a market mechanism for the delivery of energy efficiency projects. EPC mechanism has been introduced into China relatively recently, and it has not been implemented successfully in building energy efficiency retrofit projects. The aim of this research is to develop a model for achieving the sustainability of Building Energy Efficiency Retrofit (BEER) in hotel buildings under the Energy Performance Contracting (EPC) mechanism. The objectives include: • To identify a set of Key Performance Indicators (KPIs) for measuring the sustainability of BEER in hotel buildings; • To identify Critical Success Factors (CSFs) under EPC mechanism that have a strong correlation with sustainable BEER project; • To develop a model explaining the relationships between the CSFs and the sustainability performance of BEER in hotel building. Literature reviews revealed the essence of sustainable BEER and EPC, which help to develop a conceptual framework for analyzing sustainable BEER under EPC mechanism in hotel buildings. 11 potential KPIs for sustainable BEER and 28 success factors of EPC were selected based on the developed framework. A questionnaire survey was conducted to ascertain the importance of selected performance indicators and success factors. Fuzzy set theory was adopted in identifying the KPIs. Six KPIs were identified from the 11 selected performance indicators. Through a questionnaire survey, out of the 28 success factors, 21 Critical Success Factors (CSFs) were also indentified. Using the factor analysis technique, the 21 identified CSFs in this study were grouped into six clusters to help explain project success of sustainable BEER. Finally, AHP/ANP approach was used in this research to develop a model to

  16. Mechanical Design of a Performance Test Rig for the Turbine Air-Flow Task (TAFT)

    NASA Technical Reports Server (NTRS)

    Forbes, John C.; Xenofos, George D.; Farrow, John L.; Tyler, Tom; Williams, Robert; Sargent, Scott; Moharos, Jozsef

    2004-01-01

    To support development of the Boeing-Rocketdyne RS84 rocket engine, a full-flow, reaction turbine geometry was integrated into the NASA-MSFC turbine air-flow test facility. A mechanical design was generated which minimized the amount of new hardware while incorporating all test and instrumentation requirements. This paper provides details of the mechanical design for this Turbine Air-Flow Task (TAFT) test rig. The mechanical design process utilized for this task included the following basic stages: Conceptual Design. Preliminary Design. Detailed Design. Baseline of Design (including Configuration Control and Drawing Revision). Fabrication. Assembly. During the design process, many lessons were learned that should benefit future test rig design projects. Of primary importance are well-defined requirements early in the design process, a thorough detailed design package, and effective communication with both the customer and the fabrication contractors.

  17. Smart Multifunctional Fluids for Lithium Ion Batteries: Enhanced Rate Performance and Intrinsic Mechanical Protection

    NASA Astrophysics Data System (ADS)

    Ding, Jie; Tian, Tongfei; Meng, Qing; Guo, Zaiping; Li, Weihua; Zhang, Peng; Ciacchi, Fabio T.; Huang, Jewel; Yang, Wenrong

    2013-08-01

    Lithium ion batteries are attractive power sources for the consumer electronics market and are being aggressively developed for road transportation. Nevertheless, issues with safety and reliability need to be solved prior to the large-scale uptake of these batteries. There have recently been significant development and assessment of materials with resistance to mechanical abuse, with the aims of reinforcing the battery and preventing puncturing during a crash. Most of the work on battery mechanical safety has concentrated on the external packaging of batteries, with little attention being paid to the enclosed electrolyte. We report on smart multifunctional fluids that act as both highly conductive electrolytes and intrinsic mechanical protectors for lithium ion batteries. These fluids exhibit a shear thickening effect under pressure or impact and thus demonstrate excellent resistance to crushing. Also, the fluids show higher ionic conductivities and comparable redox stability windows to the commercial liquid electrolytes.

  18. Smart multifunctional fluids for lithium ion batteries: enhanced rate performance and intrinsic mechanical protection.

    PubMed

    Ding, Jie; Tian, Tongfei; Meng, Qing; Guo, Zaiping; Li, Weihua; Zhang, Peng; Ciacchi, Fabio T; Huang, Jewel; Yang, Wenrong

    2013-01-01

    Lithium ion batteries are attractive power sources for the consumer electronics market and are being aggressively developed for road transportation. Nevertheless, issues with safety and reliability need to be solved prior to the large-scale uptake of these batteries. There have recently been significant development and assessment of materials with resistance to mechanical abuse, with the aims of reinforcing the battery and preventing puncturing during a crash. Most of the work on battery mechanical safety has concentrated on the external packaging of batteries, with little attention being paid to the enclosed electrolyte. We report on smart multifunctional fluids that act as both highly conductive electrolytes and intrinsic mechanical protectors for lithium ion batteries. These fluids exhibit a shear thickening effect under pressure or impact and thus demonstrate excellent resistance to crushing. Also, the fluids show higher ionic conductivities and comparable redox stability windows to the commercial liquid electrolytes. PMID:23962885

  19. Automated Transportation Management System (ATMS) V2.0 logistics module PBI acceptance criteria

    SciTech Connect

    Weidert, R.S.

    1995-02-28

    This document defines the acceptance criteria for the Automated Transportation Management System V2.0 Logistics Module Performance Based Incentive (PBI). This acceptance criteria will be the primary basis for the generation of acceptance test procedures. The purpose of this document is to define the minimum criteria that must be fulfilled to guarantee acceptance of the Logistics Module.

  20. Performance degradation mechanisms and modes in terrestrial photovoltaic arrays and technology for their diagnosis

    NASA Technical Reports Server (NTRS)

    Noel, G. T.; Sliemers, F. A.; Derringer, G. C.; Wood, V. E.; Wilkes, K. E.; Gaines, G. B.; Carmichael, D. C.

    1978-01-01

    Accelerated life-prediction test methodologies have been developed for the validation of a 20-year service life for low-cost photovoltaic arrays. Array failure modes, relevant materials property changes, and primary degradation mechanisms are discussed as a prerequisite to identifying suitable measurement techniques and instruments. Measurements must provide sufficient confidence to permit selection among alternative designs and materials and to stimulate widespread deployment of such arrays. Furthermore, the diversity of candidate materials and designs, and the variety of potential environmental stress combinations, degradation mechanisms and failure modes require that combinations of measurement techniques be identified which are suitable for the characterization of various encapsulation system-cell structure-environment combinations.

  1. [Successful Treatment of Repeated Bilateral Middle Cerebral Artery Occlusion by Performing Mechanical Thrombectomy in a Patient with Trousseau Syndrome].

    PubMed

    Inoue, Satoshi; Fujita, Atsushi; Mizowaki, Takashi; Uchihashi, Yoshito; Kuroda, Ryuichi; Urui, Seishirou; Kurihara, Eiji; Kohmura, Eiji

    2016-06-01

    We report a patient with Trousseau syndrome who presented with repeated acute middle cerebral artery (MCA) occlusion, which was successfully treated by performing mechanical thrombectomy. A 66-year-old man with a lung lesion and abdominal lymph node swelling experienced a sudden onset of left hemiparesis. Magnetic resonance angiography (MRA) revealed a right MCA occlusion. Perfusion-weighted imaging revealed reduced cerebral blood flow in the right MCA territory. Complete recanalization of the occluded vessel was achieved by performing mechanical thrombectomy, and his symptoms remarkably disappeared. Twenty days after the procedure, he experienced right hemiparesis and total aphasia. MRA revealed a left MCA occlusion, which was located on the contralateral side of the first occlusion. The second mechanical thrombectomy was successfully performed, and complete recanalization was successfully achieved. Right hemiparesis improved after the procedure. Histological examination of the retrieved clots revealed coagulated fibrin and platelets. Cytodiagnosis of pleural effusion revealed adenocarcinoma, and he was diagnosed with lung adenocarcinoma and cancerous pleurisy. Trousseau syndrome was the presumed primary cause of the patient's tendency for thrombogenesis. To the best of our knowledge, there were no reports regarding the repeated use of mechanical thrombectomy for patients with bilateral MCA occlusion caused by Trousseau syndrome. Neuroendovascular therapy can offer good neurological outcomes even in patients with malignant lesions. PMID:27270149

  2. 5 CFR 531.409 - Acceptable level of competence determinations.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... REGULATIONS PAY UNDER THE GENERAL SCHEDULE Within-Grade Increases § 531.409 Acceptable level of competence... competence in his or her current position, and the employee has not been given a performance rating in any... acceptable level of competence, the within-grade increase will be granted retroactively to the beginning...

  3. Structural acceptance criteria Remote Handling Building Tritium Extraction Facility

    SciTech Connect

    Mertz, G.

    1999-12-16

    This structural acceptance criteria contains the requirements for the structural analysis and design of the Remote Handling Building (RHB) in the Tritium Extraction Facility (TEF). The purpose of this acceptance criteria is to identify the specific criteria and methods that will ensure a structurally robust building that will safely perform its intended function and comply with the applicable Department of Energy (DOE) structural requirements.

  4. 46 CFR 164.013-5 - Acceptance tests.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 6 2014-10-01 2014-10-01 false Acceptance tests. 164.013-5 Section 164.013-5 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) EQUIPMENT, CONSTRUCTION, AND MATERIALS...) § 164.013-5 Acceptance tests. Manufacturers shall ensure that the performance and identification...

  5. UH-1 Helicopter Mechanic (MOS 67N20) Job Description Survey: Performance of Specific Maintenance Tasks.

    ERIC Educational Resources Information Center

    Schulz, Russel E.; And Others

    The report is the second of two describing the results of a world-wide survey of the maintenance activities of UH-1 helicopter mechanics for the purpose of studying the relationships among job requirements, training, and manpower considerations for aviation maintenance. A summary of the results of the first report is included. The survey…

  6. 46 CFR 160.170-7 - Design, construction, and performance of automatic release mechanisms.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... recommendation on testing Part 1/8.2 (incorporated by reference, see § 160.170-5 of this subpart). (3) 46 CFR... recognized by the Commandant in accordance with 46 CFR 8.220, the U.S. Navy, or the national body where the... hydraulic system, if used to activate the release mechanism, must be in accordance with 46 CFR part...

  7. Musical experience shapes top-down auditory mechanisms: evidence from masking and auditory attention performance.

    PubMed

    Strait, Dana L; Kraus, Nina; Parbery-Clark, Alexandra; Ashley, Richard

    2010-03-01

    A growing body of research suggests that cognitive functions, such as attention and memory, drive perception by tuning sensory mechanisms to relevant acoustic features. Long-term musical experience also modulates lower-level auditory function, although the mechanisms by which this occurs remain uncertain. In order to tease apart the mechanisms that drive perceptual enhancements in musicians, we posed the question: do well-developed cognitive abilities fine-tune auditory perception in a top-down fashion? We administered a standardized battery of perceptual and cognitive tests to adult musicians and non-musicians, including tasks either more or less susceptible to cognitive control (e.g., backward versus simultaneous masking) and more or less dependent on auditory or visual processing (e.g., auditory versus visual attention). Outcomes indicate lower perceptual thresholds in musicians specifically for auditory tasks that relate with cognitive abilities, such as backward masking and auditory attention. These enhancements were observed in the absence of group differences for the simultaneous masking and visual attention tasks. Our results suggest that long-term musical practice strengthens cognitive functions and that these functions benefit auditory skills. Musical training bolsters higher-level mechanisms that, when impaired, relate to language and literacy deficits. Thus, musical training may serve to lessen the impact of these deficits by strengthening the corticofugal system for hearing. PMID:20018234

  8. Engine Performance (Section B: Fuel and Exhaust Systems). Auto Mechanics Curriculum Guide. Module 3. Instructor's Guide.

    ERIC Educational Resources Information Center

    Rains, Larry

    This module is the third of nine modules in the competency-based Missouri Auto Mechanics Curriculum Guide. Six units cover: fuel supply systems; carburetion; carburetor service; gasoline engine electronic fuel injection; diesel fuel injection; and exhaust systems and turbochargers. Introductory materials include a competency profile and…

  9. Performance of mechanical thinners for bloom or green fruit thinning in peaches

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Removal of excess fruits (thinning) is one of the most time consuming and costly operations in a peach orchard. A mechanical aid to assist in peach thinning would be a significant advancement for peach growers. A cooperative study between Penn State University and the USDA-ARS, Appalachian Fruit R...

  10. Relation of Three Mechanisms of Working Memory to Children's Complex Span Performance

    ERIC Educational Resources Information Center

    Magimairaj, Beula; Montgomery, James; Marinellie, Sally; McCarthy, John

    2009-01-01

    There is a paucity of research examining the relative contribution of the different mechanisms of working memory (short-term storage [STM], processing speed) to children's complex memory span. This study served to replicate and extend the few extant studies that have examined the issue. In this study, the relative contribution of three mechanisms…

  11. Mechanical property and biological performance of electrospun silk fibroin-polycaprolactone scaffolds with aligned fibers.

    PubMed

    Yuan, Han; Shi, Hongfei; Qiu, Xushen; Chen, Yixin

    2016-01-01

    The mechanical strength, biocompatibility, and sterilizability of silk fibroin allow it to be a possible candidate as a natural bone regenerate material. To improve mechanical character and reinforce the cell movement induction, silk fibroin (SF)-polycaprolactone (PCL) alloy was fabricated by electrospinning techniques with a rotating collector to form aligned fibrous scaffolds and random-oriented scaffolds. The scanning electron microscope image of the scaffold and the mechanical properties of the scaffold were investigated by tensile mechanical tests, which were compared to random-oriented scaffolds. Furthermore, mesenchymal stem cells were planted on these scaffolds to investigate the biocompatibility, elongation, and cell movement in situ. Scanning electron microscopy shows that 91% fibers on the aligned fibroin scaffold were distributed between the dominant direction ±10°. With an ideal support for stem cell proliferation in vitro, the aligned fibrous scaffold induces cell elongation at a length of 236.46 ± 82 μm and distribution along the dominant fiber direction with a cell alignment angle at 6.57° ± 4.45°. Compared with random-oriented scaffolds made by artificial materials, aligned SF-PCL scaffolds could provide a moderate mesenchymal stem cell engraftment interface and speed up early stage cell movement toward the bone defect. PMID:26588014

  12. Global Microwave Imager (GMI) Spin Mechanism Assembly Design, Development, and Performance Test Results

    NASA Technical Reports Server (NTRS)

    Kubitschek, Michael; Woolaway, Scott; Guy, Larry; Dayton, Chris; Berdanier, Barry; Newell, David; Pellicciotti, Joseph W.

    2011-01-01

    The GMI Spin Mechanism Assembly (SMA) is a precision bearing and power transfer drive assembly mechanism that supports and spins the Global Microwave Imager (GMI) instrument at a constant rate of 32 rpm continuously for the 3 year plus mission life. The GMI instrument will fly on the core Global Precipitation Measurement (GPM) spacecraft and will be used to make calibrated radiometric measurements at multiple microwave frequencies and polarizations. The GPM mission is an international effort managed by the National Aeronautics and Space Administration (NASA) to improve climate, weather, and hydro-meteorological predictions through more accurate and frequent precipitation measurements [1]. Ball Aerospace and Technologies Corporation (BATC) was selected by NASA Goddard Space Flight Center (GSFC) to design, build, and test the GMI instrument. The SMA design has to meet a challenging set of requirements and is based on BATC space mechanisms heritage and lessons learned design changes made to the WindSat BAPTA mechanism that is currently operating on-orbit and has recently surpassed 8 years of Flight operation.

  13. Effects of Fiber Reinforcement Architecture on the Hygrothermal-Mechanical Performance of Polyimide Matrix Composites for Aeropropulsion Applications

    NASA Technical Reports Server (NTRS)

    Shin, E. Eugene; Thesken, John C.; Sutter, James K.; Chuang, Kathy; Juhas, John; Veverka, Adrienne; Inghram, Linda; Papadopoulos, Demetrios; Burke, Chris; Scheiman, Dan

    2003-01-01

    A lightweight sandwich support structure, for the combustor chamber of a new generation liquid propellant rocket engine, was designed and fabricated using a polymer matrix composite (PMC) facesheet on a Ti honeycomb core. The PMC facesheet consisted of high stiffness carbon fiber, M40JB, and high temperature Polyimides, such as PMR-II-50 and HFPE-II-52. Six different fiber architectures; four harness satin (4HS) woven fabric, uni-tape, woven-uni hybrid, stitched woven fabric, stitched uni-tape and triaxial braided structures have been investigated for optimum stiffness-thickness-weight-hygrothermal performance design criteria for the hygrothermal-mechanical propulsion service exposure conditions including rapid heating up to 200 F/sec, maximum operating temperature of 600 F, internal pressure up to 100 psi. One of the specific objectives in this study is to improve composite blistering resistance in z-direction at minimum expense of in-plane mechanical properties. An extensive property-performance database including dry-wet mechanical properties at various temperatures, thermal-physical properties, such as blistering onset condition was generated for fiber architecture down-selection and design guidelines. Various optimized process methods such as vacuum bag compression molding, solvent assistant resin transfer molding (SaRTM), resin film infusion (RFI) and autoclaving were utilized for PMC panel fabrication depending on the architecture type. In the case of stitched woven fabric architecture, the stitch pattern in terms of stitch density and yarn size was optimized based on both in-plane mechanical properties and blistering performance. Potential reduction of the in-plane properties transverse to the line of stitching was also evaluated. Efforts have been made to correlate the experimental results with theoretical micro-mechanics predictions. Changes in deformation mechanism and failure sequences in terms of fiber architecture will be discussed.

  14. Differences in HIV vaccine acceptability between genders.

    PubMed

    Kakinami, Lisa; Newman, Peter A; Lee, Sung-Jae; Duan, Naihua

    2008-05-01

    The development of safe and efficacious preventive HIV vaccines offers the best long-term hope of controlling the AIDS pandemic. Nevertheless, suboptimal uptake of safe and efficacious vaccines that already exist suggest that HIV vaccine acceptability cannot be assumed, particularly among communities most vulnerable to HIV. The present study aimed to identify barriers and motivators to future HIV vaccine acceptability among low socioeconomic, ethnically diverse men and women in Los Angeles County. Participants completed a cross-sectional survey assessing their attitudes and beliefs regarding future HIV vaccines. Hypothetical HIV vaccine scenarios were administered to determine HIV vaccine acceptability. Two-sided t-tests were performed, stratified by gender, to examine the association between vaccine acceptability and potential barriers and motivators. Barriers to HIV vaccine acceptability differed between men and women. For women, barriers to HIV vaccine acceptability were related to their intimate relationships (p<0.05), negative experiences with health care providers (p<0.05) and anticipated difficulties procuring insurance (p<0.01). Men were concerned that the vaccine would weaken the immune system (p<0.005) or would affect their HIV test results (p<0.05). Motivators for women included the ability to conceive a child without worrying about contracting HIV (p<0.10) and support from their spouse/significant other for being vaccinated (p<0.10). Motivators for men included feeling safer with sex partners (p<0.05) and social influence from friends to get vaccinated (p<0.005). Family support for HIV immunization was a motivator for both men and women (p<0.10). Gender-specific interventions may increase vaccine acceptability among men and women at elevated risk for HIV infection. Among women, interventions need to focus on addressing barriers due to gendered power dynamics in relationships and discrimination in health care. Among men, education that addresses fears

  15. Energy Efficiency Investments in Public Facilities - Developing a Pilot Mechanism for Energy Performance Contracts (EPCs) in Russia

    SciTech Connect

    Evans, Meredydd; Roshchanka, Volha; Parker, Steven A.; Baranovskiy, Aleksandr

    2012-02-01

    : Russian public sector buildings tend to be very inefficient, which creates vast opportunities for savings. This report overviews the latest developments in the Russian legislation related to energy efficiency in the public sector, describes the major challenges the regulations pose, and proposes ways to overcome these challenges. Given Russia’s limited experience with energy performance contracts (EPCs), a pilot project can help test an implementation mechanism. This paper discusses how EPCs and other mechanisms can help harness energy savings opportunities in Russia in general, and thus, can be applicable to any Russian region.

  16. Lignocellulose Nanofiber-Reinforced Polystyrene Produced from Composite Microspheres Obtained in Suspension Polymerization Shows Superior Mechanical Performance.

    PubMed

    Ballner, Daniel; Herzele, Sabine; Keckes, Jozef; Edler, Matthias; Griesser, Thomas; Saake, Bodo; Liebner, Falk; Potthast, Antje; Paulik, Christian; Gindl-Altmutter, Wolfgang

    2016-06-01

    A facile approach to obtaining cellulose nanofiber-reinforced polystyrene with greatly improved mechanical performance compared to unreinforced polystyrene is presented. Cellulose nanofibers were obtained by mechanical fibrillation of partially delignified wood (MFLC) and compared to nanofibers obtained from bleached pulp. Residual hemicellulose and lignin imparted amphiphilic surface chemical character to MFLC, which enabled the stabilization of emulsions of styrene in water. Upon suspension polymerization of styrene from the emulsion, polystyrene microspheres coated in MFLC were obtained. When processed into polymer sheets by hot-pressing, improved bending strength and superior impact toughness was observed for the polystyrene-MFLC composite compared to the un-reinforced polystyrene. PMID:27163488

  17. Accepted scientific research works (abstracts).

    PubMed

    2014-01-01

    These are the 39 accepted abstracts for IAYT's Symposium on Yoga Research (SYR) September 24-24, 2014 at the Kripalu Center for Yoga & Health and published in the Final Program Guide and Abstracts. PMID:25645134

  18. L-286 Acceptance Test Record

    SciTech Connect

    HARMON, B.C.

    2000-01-14

    This document provides a detailed account of how the acceptance testing was conducted for Project L-286, ''200E Area Sanitary Water Plant Effluent Stream Reduction''. The testing of the L-286 instrumentation system was conducted under the direct supervision

  19. Effect of expansive admixtures on the shrinkage and mechanical properties of high-performance fiber-reinforced cement composites.

    PubMed

    Choi, Won-Chang; Yun, Hyun-Do

    2013-01-01

    High-performance fiber-reinforced cement composites (HPFRCCs) are characterized by strain-hardening and multiple cracking during the inelastic deformation process, but they also develop high shrinkage strain. This study investigates the effects of replacing Portland cement with calcium sulfoaluminate-based expansive admixtures (CSA EXAs) to compensate for the shrinkage and associated mechanical behavior of HPFRCCs. Two types of CSA EXA (CSA-K and CSA-J), each with a different chemical composition, are used in this study. Various replacement ratios (0%, 8%, 10%, 12%, and 14% by weight of cement) of CSA EXA are considered for the design of HPFRCC mixtures reinforced with 1.5% polyethylene (PE) fibers by volume. Mechanical properties, such as shrinkage compensation, compressive strength, flexural strength, and direct tensile strength, of the HPFRCC mixtures are examined. Also, crack width and development are investigated to determine the effects of the EXAs on the performance of the HPFRCC mixtures, and a performance index is used to quantify the performance of mixture. The results indicate that replacements of 10% CSA-K (Type 1) and 8% CSA-J (Type 2) considerably enhance the mechanical properties and reduce shrinkage of HPFRCCs. PMID:24376382

  20. Effect of Expansive Admixtures on the Shrinkage and Mechanical Properties of High-Performance Fiber-Reinforced Cement Composites

    PubMed Central

    Choi, Won-Chang; Yun, Hyun-Do

    2013-01-01

    High-performance fiber-reinforced cement composites (HPFRCCs) are characterized by strain-hardening and multiple cracking during the inelastic deformation process, but they also develop high shrinkage strain. This study investigates the effects of replacing Portland cement with calcium sulfoaluminate-based expansive admixtures (CSA EXAs) to compensate for the shrinkage and associated mechanical behavior of HPFRCCs. Two types of CSA EXA (CSA-K and CSA-J), each with a different chemical composition, are used in this study. Various replacement ratios (0%, 8%, 10%, 12%, and 14% by weight of cement) of CSA EXA are considered for the design of HPFRCC mixtures reinforced with 1.5% polyethylene (PE) fibers by volume. Mechanical properties, such as shrinkage compensation, compressive strength, flexural strength, and direct tensile strength, of the HPFRCC mixtures are examined. Also, crack width and development are investigated to determine the effects of the EXAs on the performance of the HPFRCC mixtures, and a performance index is used to quantify the performance of mixture. The results indicate that replacements of 10% CSA-K (Type 1) and 8% CSA-J (Type 2) considerably enhance the mechanical properties and reduce shrinkage of HPFRCCs. PMID:24376382

  1. Breathing air trailer acceptance test report

    SciTech Connect

    Kostelnik, A.J.

    1996-02-12

    This Acceptance Test Report documents compliance with the requirements of specification WHC-S-0251, Rev.0 and ECNs 613530 and 606113. The equipment was tested according to WHC-SD-WM-ATP-104. The equipment tested is a Breathing Air Supply Trailer purchased as a design and fabrication procurement activity. The ATP was written by the Seller and was performed by the Seller with representatives of the Westinghouse Hanford Company witnessing portions of the test at the Seller`s location.

  2. Isolating the neural mechanisms of interference during continuous multisensory dual-task performance.

    PubMed

    Kasper, Ryan W; Cecotti, Hubert; Touryan, Jon; Eckstein, Miguel P; Giesbrecht, Barry

    2014-03-01

    The need to engage in multiple tasks simultaneously is often encountered in everyday experience, but coordinating between two or more tasks can lead to impaired performance. Typical investigations of multitasking impairments have focused on the performance of two tasks presented in close temporal proximity on discrete trials; however, such paradigms do not match well with the continuous performance situations more typically encountered outside the laboratory. As a result, the stages of information processing that are affected during multisensory continuous dual tasks and how these changes in processing relate to behavior remain unclear. To address these issues, participants were presented simultaneous rapid visual and auditory stimulus sequences under three conditions: attend visual only, attend auditory only, and dual attention (attend both visual and auditory). Performance, measured in terms of response time and perceptual sensitivity (d'), revealed dual-task impairments only in the auditory task. Neural activity, measured by the ERP technique, revealed that both early stage sensory processing and later cognitive processing of the auditory task were affected by dual-task performance, but similar stages of processing of the visual task were not. Critically, individual differences in neural activity at both early and late stages of information processing accurately rank-ordered individuals based on the observed difference in behavioral performance between the single and dual attention conditions. These results reveal relationships between behavioral performance and the neural correlates of both early and late stage information processing that provide key insights into the complex interplay between the brain and behavior when multiple tasks are performed continuously. PMID:24047391

  3. Tuning mechanical performance of poly(ethylene glycol) and agarose interpenetrating network hydrogels for cartilage tissue engineering

    PubMed Central

    Rennerfeldt, DA; Renth, AN; Talata, Z; Gehrke, SH; Detamore, MS

    2013-01-01

    Hydrogels are attractive for tissue engineering applications due to their incredible versatility, but they can be limited in cartilage tissue engineering applications due to inadequate mechanical performance. In an effort to address this limitation, our team previously reported the drastic improvement in the mechanical performance of interpenetrating networks (IPNs) of poly(ethylene glycol) diacrylate (PEG-DA) and agarose relative to pure PEG-DA and agarose networks. The goal of the current study was specifically to determine the relative importance of PEG-DA concentration, agarose concentration, and PEG-DA molecular weight in controlling mechanical performance, swelling characteristics, and network parameters. IPNs consistently had compressive and shear moduli greater than the additive sum of either single network when compared to pure PEG-DA gels with a similar PEG-DA content. IPNs withstood a maximum stress of up to 4.0 MPa in unconfined compression, with increased PEG-DA molecular weight being the greatest contributing factor to improved failure properties. However, aside from failure properties, PEG-DA concentration was the most influential factor for the large majority of properties. Increasing the agarose and PEG-DA concentrations as well as the PEG-DA molecular weight of agarose/PEG-DA IPNs and pure PEG-DA gels improved moduli and maximum stresses by as much as an order of magnitude or greater compared to pure PEG-DA gels in our previous studies. Although the viability of encapsulated chondrocytes was not significantly affected by IPN formulation, glycosaminoglycan (GAG) content was significantly influenced, with a 12-fold increase over a three-week period in gels with a lower PEG-DA concentration. These results suggest that mechanical performance of IPNs may be tuned with partial but not complete independence from biological performance of encapsulated cells. PMID:23932504

  4. Critical length scales and strain localization govern the mechanical performance of multi-layer graphene assemblies

    NASA Astrophysics Data System (ADS)

    Xia, Wenjie; Ruiz, Luis; Pugno, Nicola M.; Keten, Sinan

    2016-03-01

    Multi-layer graphene assemblies (MLGs) or fibers with a staggered architecture exhibit high toughness and failure strain that surpass those of the constituent single sheets. However, how the architectural parameters such as the sheet overlap length affect these mechanical properties remains unknown due in part to the limitations of mechanical continuum models. By exploring the mechanics of MLG assemblies under tensile deformation using our established coarse-grained molecular modeling framework, we have identified three different critical interlayer overlap lengths controlling the strength, plastic stress, and toughness of MLGs, respectively. The shortest critical length scale Lsc governs the strength of the assembly as predicted by the shear-lag model. The intermediate critical length Lpc is associated with a dynamic frictional process that governs the strain localization propensity of the assembly, and hence the failure strain. The largest critical length scale LTc corresponds to the overlap length necessary to achieve 90% of the maximum theoretical toughness of the material. Our analyses provide the general guidelines for tuning the constitutive properties and toughness of multilayer 2D nanomaterials using elasticity, interlayer adhesion energy and geometry as molecular design parameters.Multi-layer graphene assemblies (MLGs) or fibers with a staggered architecture exhibit high toughness and failure strain that surpass those of the constituent single sheets. However, how the architectural parameters such as the sheet overlap length affect these mechanical properties remains unknown due in part to the limitations of mechanical continuum models. By exploring the mechanics of MLG assemblies under tensile deformation using our established coarse-grained molecular modeling framework, we have identified three different critical interlayer overlap lengths controlling the strength, plastic stress, and toughness of MLGs, respectively. The shortest critical length scale

  5. Validation and acceptance of synthetic infrared imagery

    NASA Astrophysics Data System (ADS)

    Smith, Moira I.; Bernhardt, Mark; Angell, Christopher R.; Hickman, Duncan; Whitehead, Philip; Patel, Dilip

    2004-08-01

    This paper describes the use of an image query database (IQ-DB) tool as a means of implementing a validation strategy for synthetic long-wave infrared images of sea clutter. Specifically it was required to determine the validity of the synthetic imagery for use in developing and testing automatic target detection algorithms. The strategy adopted for exploiting synthetic imagery is outlined and the key issues of validation and acceptance are discussed in detail. A wide range of image metrics has been developed to achieve pre-defined validation criteria. A number of these metrics, which include post processing algorithms, are presented. Furthermore, the IQ-DB provides a robust mechanism for configuration management and control of the large volume of data used. The implementation of the IQ-DB is reviewed in terms of its cardinal point specification and its central role in synthetic imagery validation and EOSS progressive acceptance.

  6. Performance of a TiN-coated monolithic silicon pin-diode array under mechanical stress

    NASA Astrophysics Data System (ADS)

    VanDevender, B. A.; Bodine, L. I.; Myers, A. W.; Amsbaugh, J. F.; Howe, M. A.; Leber, M. L.; Robertson, R. G. H.; Tolich, K.; Van Wechel, T. D.; Wall, B. L.

    2012-05-01

    The Karlsruhe Tritium Neutrino Experiment (KATRIN) will detect tritium β-decay electrons that pass through its electromagnetic spectrometer with a highly segmented monolithic silicon pin-diode focal-plane detector (FPD). This pin-diode array will be on a single piece of 500-μm-thick silicon, with contact between titanium nitride (TiN)-coated detector pixels and front-end electronics made by spring-loaded pogo pins. The pogo pins will exert a total force of up to 50 N on the detector, deforming it and resulting in mechanical stress up to 50 MPa in the silicon bulk. We have evaluated a prototype pin-diode array with a pogo-pin connection scheme similar to the KATRIN FPD. We find that pogo pins make good electrical contact to TiN and observe no effects on detector resolution or reverse-bias leakage current which can be attributed to mechanical stress.

  7. Size and rate effects on mechanical behavior of ultra high performance concrete

    NASA Astrophysics Data System (ADS)

    Lim, Boon Him

    Cor-Tuf, broadly characterize as a reactive powder concrete is a type of cementitious material. Cementitious materials have been observed to exhibit a strain-rate dependent mechanical behavior. The mechanical behavior of cementitious materials can also depend significantly on specimen sizes. Therefore it is crucial to determine the behavior of Cor-Tuf with different specimen sizes for high-rate applications. For this purpose, split Hopkinson pressure bar (SHPB), also known as Kolsky bar was utilized to determine the dynamic behavior of Cor-Tuf for different specimen sizes under uniaxial dynamic compression loading at different strain rates. It was observed that as strain rate increases the compressive strength decreases for the small specimen. However for specimens at larger diameter, the compressive strength was observed to be rate independent. The Young's modulus decreases as strain rate increases for all specimen sizes. However the critical strain and energy absorption per unit volume was observed to increase as the strain rate increases.

  8. Description of the performances of a thermo-mechanical energy harvester using bimetallic beams

    NASA Astrophysics Data System (ADS)

    Arnaud, A.; Boughaleb, J.; Monfray, S.; Boeuf, F.; Cugat, O.; Skotnicki, T.

    2016-06-01

    Many recent researches have been focused on the development of thermal energy harvesters using thermo-mechanical or thermo-electrical coupling phenomena associated to a first-order thermodynamic transition. In the case of the bimetallic strip heat engine, the exploitation of the thermo-mechanical instability of bimetallic membranes placed in a thermal gradient enables to convert heat into kinetic energy. This paper is a contribution to the modeling and the comprehension of these heat engines. By restraining the study to the simply-supported bimetallic beams and using a Ritz approximation of the beam shape, this paper aims to give an analytical solution to the first mode of the composite beams and then to evaluate the efficiency of the harvesters exploiting these kinds of instability.

  9. Microstructural Characterization and Mechanical Performance of Hot Work Tool Steel Processed by Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Holzweissig, Martin Joachim; Taube, Alexander; Brenne, Florian; Schaper, Mirko; Niendorf, Thomas

    2015-04-01

    Microstructural characterization of hot work tool steel processed by selective laser melting was carried out. The findings shed light on the interrelationship between processing parameters and the microstructural evolution. It was found that the microstructure after layer-wise processing partially consists of metastable-retained austenite which transforms to martensite in a subsequent tensile test. This improves the mechanical properties of the hot work tool steel enabling direct application.

  10. Mechanical Design of a Performance Test Rig for the Turbine Air-Flow Task (TAFT)

    NASA Technical Reports Server (NTRS)

    Xenofos, George; Forbes, John; Farrow, John; Williams, Robert; Tyler, Tom; Sargent, Scott; Moharos, Jozsef

    2003-01-01

    To support development of the Boeing-Rocketdyne RS84 rocket engine, a fill-flow, reaction turbine geometry was integrated into the NASA-MSFC turbine air-flow test facility. A mechanical design was generated which minimized the amount of new hardware while incorporating all test and instrUmentation requirements. This paper provides details of the mechanical design for this Turbine Air-Flow Task (TAFT) test rig. The mechanical design process utilized for this task included the following basic stages: Conceptual Design. Preliminary Design. Detailed Design. Baseline of Design (including Configuration Control and Drawing Revision). Fabrication. Assembly. During the design process, many lessons were learned that should benefit future test rig design projects. Of primary importance are well-defined requirements early in the design process, a thorough detailed design package, and effective communication with both the customer and the fabrication contractors. The test rig provided steady and unsteady pressure data necessary to validate the computational fluid dynamics (CFD) code. The rig also helped characterize the turbine blade loading conditions. Test and CFD analysis results are to be presented in another JANNAF paper.

  11. Critical length scales and strain localization govern the mechanical performance of multi-layer graphene assemblies.

    PubMed

    Xia, Wenjie; Ruiz, Luis; Pugno, Nicola M; Keten, Sinan

    2016-03-17

    Multi-layer graphene assemblies (MLGs) or fibers with a staggered architecture exhibit high toughness and failure strain that surpass those of the constituent single sheets. However, how the architectural parameters such as the sheet overlap length affect these mechanical properties remains unknown due in part to the limitations of mechanical continuum models. By exploring the mechanics of MLG assemblies under tensile deformation using our established coarse-grained molecular modeling framework, we have identified three different critical interlayer overlap lengths controlling the strength, plastic stress, and toughness of MLGs, respectively. The shortest critical length scale L governs the strength of the assembly as predicted by the shear-lag model. The intermediate critical length L is associated with a dynamic frictional process that governs the strain localization propensity of the assembly, and hence the failure strain. The largest critical length scale L corresponds to the overlap length necessary to achieve 90% of the maximum theoretical toughness of the material. Our analyses provide the general guidelines for tuning the constitutive properties and toughness of multilayer 2D nanomaterials using elasticity, interlayer adhesion energy and geometry as molecular design parameters. PMID:26935048

  12. The disinfection performance and mechanisms of Ag/lysozyme nanoparticles supported with montmorillonite clay.

    PubMed

    Jiang, Jing; Zhang, Chang; Zeng, Guang-Ming; Gong, Ji-Lai; Chang, Ying-Na; Song, Biao; Deng, Can-Hui; Liu, Hong-Yu

    2016-11-01

    The fabrication of montmorillonite (Mt) decorated with lysozyme-modified silver nanoparticles (Ag/lyz-Mt) was reported. The lysozyme (lyz) was served as both reducing and capping reagent. Coupling the bactericidal activity of the lyz with AgNPs, along with the high porous structure and large specific surface area of the Mt, prevented aggregation of AgNPs and promoted nanomaterial-bacteria interactions, resulting in a greatly enhanced bactericidal capability against both Gram positive and Gram negative bacteria. This paper systematically elucidated the bactericidal mechanisms of Ag/lyz-Mt. Direct contact between the Ag/lyz-Mt surface and the bacterial cell was essential to the disinfection. Physical disruption of bacterial membrane was considered to be one of the bactericidal mechanisms of Ag/lyz-Mt. Results revealed that Ag(+) was involved in the bactericidal activity of Ag/lyz-Mt via tests conducted using Ag(+) scavengers. A positive ROS (reactive oxygen species) scavenging test indirectly confirmed the involvement of ROS (O2(-), H2O2, and OH) in the bactericidal mechanism. Furthermore, the concentrations of individual ROS were quantified. Results showed that Ag/lyz-Mt nanomaterial could be a promising bactericide for water disinfection. PMID:27318738

  13. FIB-etching of polymer/metal laminates and its effect on mechanical performance.

    PubMed

    Faber, Enne; Vellinga, Willem P; De Hosson, Jeff T M

    2014-12-01

    This paper investigates the adhesive interface in a polymer/metal (polyethylene terephthalate/steel) laminate that is subjected to uniaxial strain. Cross-sections perpendicular to such interfaces were created with a focused ion beam and imaged with scanning electron microscopy during straining in the electron microscope. During in situ straining, glide steps formed by the steel caused traction at the interface and initiated crazes in the polyethylene terephthalate (PET). These crazes readily propagated along the free surface of the PET layer. Similar crazing has not been previously encountered in laminates that were pre-strained or in numerical calculations. The impact of focused ion beam treatments on mechanical properties of the polymer/metal laminate system was therefore investigated. It was found that mechanical properties such as toughness of PET are dramatically influenced by focused ion beam etching. It was also found that this change in mechanical properties has a different effect on the pre-strained and in situ strained samples. PMID:25381755

  14. Effects of simulated on-fire processing conditions on the microstructure and mechanical performance of Q345R steel

    NASA Astrophysics Data System (ADS)

    Peng, Yi-chao; Xu, Hao-hao; Zhang, Mai-cang

    2016-01-01

    A series of simulated on-fire processing experiments on Q345R steel plates was conducted, and the plates' Brinell hardness, tensile strength, and impact energy were tested. Microstructure morphologies were systematically analyzed using a scanning electron microscope with the aim of investigating the effect of the steel's microstructure on its performance. All examined performance parameters exhibited a substantial decrease in the cases of samples heat-treated at temperatures near 700°C. However, although the banded structure decreased with increasing treatment temperature and holding time, it had little effect on the performance decline in fact. Further analysis revealed that pearlite degeneration near 700°C, which was induced by the interaction of both subcritical annealing and conventional spherical annealing, was the primary reason for the degradation behavior. Consequently, some nonlinear mathematical models of different mechanical performances were established to facilitate processing adjustments.

  15. [When do bad apples not spoil the barrel? Negative relationships in teams, team performance, and buffering mechanisms].

    PubMed

    de Jong, Jeroen P; Curşeu, Petru L; Leenders, Roger Th A J

    2014-05-01

    The study of negative relationships in teams has primarily focused on the impact of negative relationships on individual team member attitudes and performance in teams. The mechanisms and contingencies that can buffer against the damaging effects of negative relationships on team performance have received limited attention. Building on social interdependence theory and the multilevel model of team motivation, we examine in a sample of 73 work teams the team-level attributes that foster the promotive social interaction that can neutralize the adverse effect of negative relationships on team cohesion and, consequently, on team performance. The results indicate that high levels of team-member exchange as well as high task-interdependence attenuate how team cohesion and team performance suffer from negative relationships. Implications for research and practice are discussed. PMID:24661274

  16. Mechanical and physiological evaluation of exercise performance in elite national rowers.

    PubMed

    Mahler, D A; Nelson, W N; Hagerman, F C

    1984-07-27

    We describe the scientific basis for evaluating the biomechanics and associated physiological requirements of exercise performance in elite national rowers. Computer-assisted analysis of high-speed cinematography has demonstrated that efficiency in rowing is related to the relative proximity between peak force and the perpendicular position of the oar. Physiological testing has indicated that near maximal levels of oxygen consumption are required during "all out" rowing, involving both aerobic and anaerobic metabolism. Serial testing has been performed on elite oarsmen throughout the year in order to evaluate the individual benefits of a training program and to establish guidelines for future training. Successful application of the scientific analysis of rowing performance requires that the athlete, coach, and investigator work closely together in an effort to increase the average velocity of the boat. PMID:6737640

  17. Small wind turbine performance evaluation using field test data and a coupled aero-electro-mechanical model

    NASA Astrophysics Data System (ADS)

    Wallace, Brian D.

    A series of field tests and theoretical analyses were performed on various wind turbine rotor designs at two Penn State residential-scale wind-electric facilities. This work involved the prediction and experimental measurement of the electrical and aerodynamic performance of three wind turbines; a 3 kW rated Whisper 175, 2.4 kW rated Skystream 3.7, and the Penn State designed Carolus wind turbine. Both the Skystream and Whisper 175 wind turbines are OEM blades which were originally installed at the facilities. The Carolus rotor is a carbon-fiber composite 2-bladed machine, designed and assembled at Penn State, with the intent of replacing the Whisper 175 rotor at the off-grid system. Rotor aerodynamic performance is modeled using WT_Perf, a National Renewable Energy Laboratory developed Blade Element Momentum theory based performance prediction code. Steady-state power curves are predicted by coupling experimentally determined electrical characteristics with the aerodynamic performance of the rotor simulated with WT_Perf. A dynamometer test stand is used to establish the electromechanical efficiencies of the wind-electric system generator. Through the coupling of WT_Perf and dynamometer test results, an aero-electro-mechanical analysis procedure is developed and provides accurate predictions of wind system performance. The analysis of three different wind turbines gives a comprehensive assessment of the capability of the field test facilities and the accuracy of aero-electro-mechanical analysis procedures. Results from this study show that the Carolus and Whisper 175 rotors are running at higher tip-speed ratios than are optimum for power production. The aero-electro-mechanical analysis predicted the high operating tip-speed ratios of the rotors and was accurate at predicting output power for the systems. It is shown that the wind turbines operate at high tip-speeds because of a miss-match between the aerodynamic drive torque and the operating torque of the wind

  18. Influence of mechanical properties of alginate-based substrates on the performance of Schwann cells in culture.

    PubMed

    Ning, Liqun; Xu, Yitong; Chen, Xiongbiao; Schreyer, David J

    2016-06-01

    In tissue engineering, artificial tissue scaffolds containing living cells have been studied for tissue repair and regeneration. Notably, the performance of these encapsulated-in-scaffolds cells in terms of cell viability, proliferation, and expression of function during and after the scaffold fabrication process, has not been well documented because of the influence of mechanical, chemical, and physical properties of the scaffold substrate materials. This paper presents our study on the influence of mechanical properties of alginate-based substrates on the performance of Schwann cells, which are the major glial cells of peripheral nervous system. Given the fact that alginate polysaccharide hydrogel has poor cell adhesion properties, in this study, we examined several types of cell-adhesion supplements and found that alginate covalently modified with RGD peptide provided improved cell proliferation and adhesion. We prepared alginate-based substrates for cell culture using varying alginate concentrations for altering their mechanical properties, which were confirmed by compression testing. Then, we examined the viability, proliferation, morphology, and expression of the extracellular matrix protein laminin of Schwann cells that were seeded on the surface of alginate-based substrates (or 2D culture) or encapsulated within alginate-based substrates (3D cultures), and correlated the examined cell performance to the alginate concentration (or mechanical properties) of hydrogel substrates. Our findings suggest that covalent attachment of RGD peptide can improve the success of Schwann cell encapsulation within alginate-based scaffolds, and provide guidance for regulating the mechanical properties of alginate-based scaffolds containing Schwann cells for applications in peripheral nervous system regeneration and repair. PMID:27012482

  19. High performance radial p-n junction solar cell based on silicon nanopillar array with enhanced decoupling mechanism

    NASA Astrophysics Data System (ADS)

    Dou, Bingfei; Jia, Rui; Li, Haofeng; Chen, Chen; Ding, Wuchang; Meng, Yanlong; Xing, Zhao; Liu, Xinyu; Ye, Tianchun

    2012-10-01

    High performance radial p-n junction solar cells based on silicon nanopillar array were synthesized from p-type silicon substrates and compared with planar cell. These radial p-n junction cells exhibited considerable higher short-circuit current, due to their unique carriers' decoupling mechanism. After the electrode enhancement via light induced plating, a best efficiency of near 12% was achieved for radial p-n junction solar cell, which is better than the planar control cell.

  20. A Comparative Numerical Study on the Performances and Vortical Patterns of Two Bioinspired Oscillatory Mechanisms: Undulating and Pure Heaving

    PubMed Central

    Ebrahimi, Mohsen; Abbaspour, Madjid

    2015-01-01

    The hydrodynamics and energetics of bioinspired oscillating mechanisms have received significant attentions by engineers and biologists to develop the underwater and air vehicles. Undulating and pure heaving (or plunging) motions are two significant mechanisms which are utilized in nature to provide propulsive, maneuvering, and stabilization forces. This study aims to elucidate and compare the propulsive vortical signature and performance of these two important natural mechanisms through a systematic numerical study. Navier-Stokes equations are solved, by a pressure-based finite volume method solver, in an arbitrary Lagrangian-Eulerian (ALE) framework domain containing a 2D NACA0012 foil moving with prescribed kinematics. Some of the important findings are (1) the thrust production of the heaving foil begins at lower St and has a greater growing slope with respect to the St; (2) the undulating mechanism has some limitations to produce high thrust forces; (3) the undulating foil shows a lower power consumption and higher efficiency; (4) changing the Reynolds number (Re) in a constant St affects the performance of the oscillations; and (5) there is a distinguishable appearance of leading edge vortices in the wake of the heaving foil without observable ones in the wake of the undulating foil, especially at higher St. PMID:27057133

  1. A Comparative Numerical Study on the Performances and Vortical Patterns of Two Bioinspired Oscillatory Mechanisms: Undulating and Pure Heaving.

    PubMed

    Ebrahimi, Mohsen; Abbaspour, Madjid

    2015-01-01

    The hydrodynamics and energetics of bioinspired oscillating mechanisms have received significant attentions by engineers and biologists to develop the underwater and air vehicles. Undulating and pure heaving (or plunging) motions are two significant mechanisms which are utilized in nature to provide propulsive, maneuvering, and stabilization forces. This study aims to elucidate and compare the propulsive vortical signature and performance of these two important natural mechanisms through a systematic numerical study. Navier-Stokes equations are solved, by a pressure-based finite volume method solver, in an arbitrary Lagrangian-Eulerian (ALE) framework domain containing a 2D NACA0012 foil moving with prescribed kinematics. Some of the important findings are (1) the thrust production of the heaving foil begins at lower St and has a greater growing slope with respect to the St; (2) the undulating mechanism has some limitations to produce high thrust forces; (3) the undulating foil shows a lower power consumption and higher efficiency; (4) changing the Reynolds number (Re) in a constant St affects the performance of the oscillations; and (5) there is a distinguishable appearance of leading edge vortices in the wake of the heaving foil without observable ones in the wake of the undulating foil, especially at higher St. PMID:27057133

  2. Thermosetting polyimide resin matrix composites with interpenetrating polymer networks for precision foil resistor chips based on special mechanical performance requirements

    NASA Astrophysics Data System (ADS)

    Wang, X. Y.; Ma, J. X.; Li, C. G.; Wang, H. X.

    2014-04-01

    Based on interpenetrating networks (IPNs) different macromolecular materials such as epoxy, phenolic, and silicone resin were chosen to modify thermosetting polyimide (TSPI) resin to solve the lack of performance when used for protecting precision foil resistor chips. Copolymerization modification, controlled at curing stage, was used to prepare TSPI composites considering both performance and process requirements. The mechanical properties related to trimming process were mainly studied due to the special requirements of the regularity of scratch edges caused by a tungsten needle. The analysis on scratch edges reveals that the generation and propagation of microcracks caused by scratching together with crack closure effect may lead to regular scratch traces. Experiments show that the elongation at break of TSPI composites is the main reason that determines the special mechanical properties. The desired candidate materials should have proper hardness and toughness, and the specific mechanical data are that the mean elongation at break and tensile strength of polymer materials are in the range of 9.2-10.4% and 100-107 MPa, respectively. Possible reasons for the effect of the modifiers chosen on TSPI polymers, the reaction mechanisms on modified TSPI resin and the IPN structure in TSPI composite polymers were discussed based on IR and TG analysis.

  3. Electromagnetic, mechanical and thermal performance analysis of the CFETR magnet system

    NASA Astrophysics Data System (ADS)

    Ren, Yong; Zhu, Jiawu; Gao, Xiang; Shen, Fengshun; Chen, Siming

    2015-09-01

    The Chinese Fusion Engineering Test Reactor (CFETR) superconducting magnet system was designed by the National Integration Design Group for Magnetic Confinement Fusion Reactor. The CFETR magnet system consists mainly of a central solenoid (CS) coil with six modules, 16 toroidal field (TF) coils, 8 poloidal field (PF) coils, and a set of correction coils (CC). The electromagnetic stresses and stored magnetic energy are huge on the CFETR magnets since they experience both large current densities and high magnetic field. The electromagnetic, structural and thermal performance needs to be evaluated to ensure that the magnetic field, stress, and hot spot temperature of the magnet system are within the allowed criteria. The evaluation of the electromagnetic performance of the CFETR superconducting magnet system under normal operation and fault conditions was performed. The two-dimensional finite element method was adopted to analyse the stress/strain behaviour of the CFETR CS coils. In addition, the thermal-hydraulic behaviour on quench propagation performance of the CFETR CS and TF coils was analysed to evaluate the hot spot temperature of the cable and the helium pressure inside a jacket during a quench.

  4. Understanding the role of dip-coating process parameters in the mechanical performance of polymer-coated bioglass robocast scaffolds.

    PubMed

    Motealleh, Azadeh; Eqtesadi, Siamak; Perera, Fidel Hugo; Pajares, Antonia; Guiberteau, Fernando; Miranda, Pedro

    2016-12-01

    The effect of different dip-coating variables-solvent, deposition temperature and polymer concentration-on the mechanical performance of polycaprolactone-coated 45S5 bioglass robocast scaffolds is systematically analyzed in this work. The reproducible geometry of the scaffolds produced by this additive manufacturing technique makes them an optimal model system and facilitates the analysis. The results suggest that the mechanical performance of the hybrid scaffolds is improved monotonically with polymer concentration, but this concentration cannot be increased indefinitely if the macroporosity interconnectivity, and thus the scaffold׳s capacity to promote tissue ingrowth, are to be preserved. An optimal concentration, and therefore viscosity (~1-4Pas in the present case), exists for any given set of process variables (scaffold geometry and material, polymer, solvent and process temperature) that yields coatings with optimal reinforcement and minimal reduction of scaffold functionality. Solvent and process temperature do not directly affect the strengthening provided by the polymeric coating. However they can determine the maximum concentration at the critical viscosity, and thereby the maximum achievable mechanical performance of the resulting hybrid scaffold. PMID:27522314

  5. Performance prediction of mechanical excavators from linear cutter tests on Yucca Mountain welded tuffs; Yucca Mountain Site Characterization Project

    SciTech Connect

    Gertsch, R.; Ozdemir, L.

    1992-09-01

    The performances of mechanical excavators are predicted for excavations in welded tuff. Emphasis is given to tunnel boring machine evaluations based on linear cutting machine test data obtained on samples of Topopah Spring welded tuff. The tests involve measurement of forces as cutters are applied to the rock surface at certain spacing and penetrations. Two disc and two point-attack cutters representing currently available technology are thus evaluated. The performance predictions based on these direct experimental measurements are believed to be more accurate than any previous values for mechanical excavation of welded tuff. The calculations of performance are predicated on minimizing the amount of energy required to excavate the welded tuff. Specific energy decreases with increasing spacing and penetration, and reaches its lowest at the widest spacing and deepest penetration used in this test program. Using the force, spacing, and penetration data from this experimental program, the thrust, torque, power, and rate of penetration are calculated for several types of mechanical excavators. The results of this study show that the candidate excavators will require higher torque and power than heretofore estimated.

  6. Design considerations in mechanical face seals for improved performance. I - Basic configurations

    NASA Technical Reports Server (NTRS)

    Ludwig, L. P.; Greiner, H. F.

    1977-01-01

    Basic assembly configurations of the mechanical face seal are described and some advantages associated with each are listed. The various forms of seal components (the primary seal, secondary seal, etc.) are illustrated, and functions pointed out. The technique of seal pressure balancing and its application is described; and the concept of the PV factor, its different forms and limitations are discussed. Brief attention is given to seal lubrication since it is covered in detail in a companion paper. Finally, the operating conditions for various applications of low pressure seals (aircraft transmissions) are listed, and the seal failure mode of a particular application is discussed.

  7. Design considerations in mechanical face seals for improved performance. 1: Basic configurations

    NASA Technical Reports Server (NTRS)

    Ludwig, L. P.; Greiner, H. F.

    1977-01-01

    Basic assembly configurations of the mechanical face seal are described and some advantages associated with each are listed. The various forms of seal components are illustrated, and functions pointed out. The technique of seal pressure balancing and its application are described; and the concept of the PV factor, its different forms and limitations are discussed. Brief attention is given to seal lubrication since it is covered in detail in a companion paper. Finally, the operating conditions for various applications of low pressure seals (aircraft transmissions) are listed, and the seal failure mode of a particular application is discussed.

  8. Acceptance Test Procedure for New Pumping Instrumentation & Control Skid V

    SciTech Connect

    KOCH, M.R.

    2000-08-14

    This Acceptance Test Procedure (ATP) provides for the inspection and testing of the new Pumping Instrumentation and Control (PIC) skid designated as ''V''. The ATP will be performed after the construction of the PIC skid in the fabrication shop.

  9. Radioisotope Thermoelectric Generator F7 Flight Unit Acceptance Buy Off

    SciTech Connect

    1997-02-20

    These are viewgraphs from the subject presentation. The LMMS E-7 history is outlined; Qualification and use of the F-7 GPHS-RTG for the Cassini mission; and the F-7 acceptance test program and performance are described.

  10. Enhanced Mechanical Performance of Bio-Inspired Hybrid Structures Utilising Topological Interlocking Geometry

    NASA Astrophysics Data System (ADS)

    Djumas, Lee; Molotnikov, Andrey; Simon, George P.; Estrin, Yuri

    2016-05-01

    Structural composites inspired by nacre have emerged as prime exemplars for guiding materials design of fracture-resistant, rigid hybrid materials. The intricate microstructure of nacre, which combines a hard majority phase with a small fraction of a soft phase, achieves superior mechanical properties compared to its constituents and has generated much interest. However, replicating the hierarchical microstructure of nacre is very challenging, not to mention improving it. In this article, we propose to alter the geometry of the hard building blocks by introducing the concept of topological interlocking. This design principle has previously been shown to provide an inherently brittle material with a remarkable flexural compliance. We now demonstrate that by combining the basic architecture of nacre with topological interlocking of discrete hard building blocks, hybrid materials of a new type can be produced. By adding a soft phase at the interfaces between topologically interlocked blocks in a single-build additive manufacturing process, further improvement of mechanical properties is achieved. The design of these fabricated hybrid structures has been guided by computational work elucidating the effect of various geometries. To our knowledge, this is the first reported study that combines the advantages of nacre-inspired structures with the benefits of topological interlocking.

  11. Functionalization of titanium with chitosan via silanation: evaluation of biological and mechanical performances.

    PubMed

    Renoud, Pauline; Toury, Bérangère; Benayoun, Stéphane; Attik, Ghania; Grosgogeat, Brigitte

    2012-01-01

    Complications in dentistry and orthopaedic surgery are mainly induced by peri-implant bacterial infections and current implant devices do not prevent such infections. The coating of antibacterial molecules such as chitosan on its surface would give the implant bioactive properties. The major challenge of this type of coating is the attachment of chitosan to a metal substrate. In this study, we propose to investigate the functionalization of titanium with chitosan via a silanation. Firstly, the surface chemistry and mechanical properties of such coating were evaluated. We also verified if the coated chitosan retained its biocompatibility with the peri-implant cells, as well as its antibacterial properties. FTIR and Tof-SIMS analyses confirmed the presence of chitosan on the titanium surface. This coating showed great scratch resistance and was strongly adhesive to the substrate. These mechanical properties were consistent with an implantology application. The Chitosan-coated surfaces showed strong inhibition of Actinomyces naeslundii growth; they nonetheless showed a non significant inhibition against Porphyromonas gingivalis after 32 hours in liquid media. The chitosan-coating also demonstrated good biocompatibility to NIH3T3 fibroblasts. Thus this method of covalent coating provides a biocompatible material with improved bioactive properties. These results proved that covalent coating of chitosan has significant potential in biomedical device implantation. PMID:22859940

  12. Enhanced Mechanical Performance of Bio-Inspired Hybrid Structures Utilising Topological Interlocking Geometry

    PubMed Central

    Djumas, Lee; Molotnikov, Andrey; Simon, George P.; Estrin, Yuri

    2016-01-01

    Structural composites inspired by nacre have emerged as prime exemplars for guiding materials design of fracture-resistant, rigid hybrid materials. The intricate microstructure of nacre, which combines a hard majority phase with a small fraction of a soft phase, achieves superior mechanical properties compared to its constituents and has generated much interest. However, replicating the hierarchical microstructure of nacre is very challenging, not to mention improving it. In this article, we propose to alter the geometry of the hard building blocks by introducing the concept of topological interlocking. This design principle has previously been shown to provide an inherently brittle material with a remarkable flexural compliance. We now demonstrate that by combining the basic architecture of nacre with topological interlocking of discrete hard building blocks, hybrid materials of a new type can be produced. By adding a soft phase at the interfaces between topologically interlocked blocks in a single-build additive manufacturing process, further improvement of mechanical properties is achieved. The design of these fabricated hybrid structures has been guided by computational work elucidating the effect of various geometries. To our knowledge, this is the first reported study that combines the advantages of nacre-inspired structures with the benefits of topological interlocking. PMID:27216277

  13. Sea Cucumber-Inspired Autolytic Hydrogels Exhibiting Tunable High Mechanical Performances, Repairability, and Reusability.

    PubMed

    Gao, Fei; Zhang, Yinyu; Li, Yongmao; Xu, Bing; Cao, Zhiqiang; Liu, Wenguang

    2016-04-13

    Inspired by stimuli-responsive remarkable changes in consistency (hardening, softening, autolysis) of sea cucumbers, we synthesized a supramolecular polymer(SP) hydrogel directly by photoinitiated aqueous polymerization of N-acryloyl 2-glycine monomer bearing one amide and one carboxyl group on the side chain. The SP hydrogels doped with Ca(2+) demonstrated excellent mechanical properties-high tensile strength (∼1.3 MPa), large stretchability (up to 2300%), high compressive strength (∼10.8 MPa), and good toughness (∼1000 J m(-2)) due to cooperative hydrogen bonding interactions from amide and carboxyl together with Ca(2+) cross-linking. Responding to the change in pH and Ca(2+) concentration, the hydrogels could modulate their network stability and mechanical properties: at pH3.0 and higher Ca(2+) content, the hydrogel formed low swelling network which was stiff and stable; in alkaline or neutral buffer with lower content of or without Ca(2+), the hydrogel formed a highly swollen transient network, which was soft and eventually autolyzed. The reversible multiple noncovalent bonds enabled the hydrogels to achieve thermoplasticity, self-healability, and reusability. Notably, distinct formulations of hydrogels could be welded together under heating to form a gradient hydrogel. In vitro cytotoxicity assay and subcutaneous implantation indicated that the SP hydrogels were biocompatible and autolytic in vivo. The SP hydrogels may find applications as temporary biodevices for intestinal drug delivery or for injectable filling in assisting suturing small vessels. PMID:27014865

  14. Numerical Investigation of the Performance of Three Hinge Designs of Bileaflet Mechanical Heart Valves

    PubMed Central

    Simon, Hélène A.; Ge, Liang; Sotiropoulos, Fotis

    2010-01-01

    Thromboembolic complications (TECs) of bileaflet mechanical heart valves (BMHVs) are believed to be due to the nonphysiologic mechanical stresses imposed on blood elements by the hinge flows. Relating hinge flow features to design features is, therefore, essential to ultimately design BMHVs with lower TEC rates. This study aims at simulating the pulsatile three-dimensional hinge flows of three BMHVs and estimating the TEC potential associated with each hinge design. Hinge geometries are constructed from micro-computed tomography scans of BMHVs. Simulations are conducted using a Cartesian sharp-interface immersed-boundary methodology combined with a second-order accurate fractional-step method. Leaflet motion and flow boundary conditions are extracted from fluid–structure-interaction simulations of BMHV bulk flow. The numerical results are analyzed using a particle-tracking approach coupled with existing blood damage models. The gap width and, more importantly, the shape of the recess and leaflet are found to impact the flow distribution and TEC potential. Smooth, streamlined surfaces appear to be more favorable than sharp corners or sudden shape transitions. The developed framework will enable pragmatic and cost-efficient preclinical evaluation of BMHV prototypes prior to valve manufacturing. Application to a wide range of hinges with varying design parameters will eventually help in determining the optimal hinge design. PMID:20571852

  15. Simulation of mechanical performance limits and failure of carbon nanotube composites

    NASA Astrophysics Data System (ADS)

    Jensen, Benjamin D.; Wise, Kristopher E.; Odegard, Gregory M.

    2016-02-01

    The mechanical properties of carbon nanotube (CNT) fiber composites are steadily approaching those of traditional carbon fiber composites. This work is focused on establishing a plausible upper bound on these properties by modeling the elastic deformations, yield, and fracture of idealized CNT composites using reactive molecular dynamics. Amorphous carbon (AC) was used for the matrix material because of its structural simplicity and physical compatibility with the CNT fillers. Three different arrangements of CNTs in the simulation cell were investigated: a single-wall nanotube (SWNT) array, a multi-wall nanotube (MWNT) array, and a SWNT bundle system. The SWNT and MWNT array systems are clearly idealizations, but the SWNT bundle system is a step closer to real systems in which individual tubes aggregate into large assemblies. Chemical crosslinking was modeled by adding bonds between the CNTs and AC to explore the balance between weakening the CNTs and improving fiber-matrix load transfer. The simulation results reported here clarify the impact of CNT dispersion, the extent of crosslinking, and CNT-templated matrix structuring on the mechanical properties of CNT composites.

  16. Functionalization of Titanium with Chitosan via Silanation: Evaluation of Biological and Mechanical Performances

    PubMed Central

    Renoud, Pauline; Toury, Bérangère; Benayoun, Stéphane; Attik, Ghania; Grosgogeat, Brigitte

    2012-01-01

    Complications in dentistry and orthopaedic surgery are mainly induced by peri-implant bacterial infections and current implant devices do not prevent such infections. The coating of antibacterial molecules such as chitosan on its surface would give the implant bioactive properties. The major challenge of this type of coating is the attachment of chitosan to a metal substrate. In this study, we propose to investigate the functionalization of titanium with chitosan via a silanation. Firstly, the surface chemistry and mechanical properties of such coating were evaluated. We also verified if the coated chitosan retained its biocompatibility with the peri-implant cells, as well as its antibacterial properties. FTIR and Tof-SIMS analyses confirmed the presence of chitosan on the titanium surface. This coating showed great scratch resistance and was strongly adhesive to the substrate. These mechanical properties were consistent with an implantology application. The Chitosan-coated surfaces showed strong inhibition of Actinomyces naeslundii growth; they nonetheless showed a non significant inhibition against Porphyromonas gingivalis after 32 hours in liquid media. The chitosan-coating also demonstrated good biocompatibility to NIH3T3 fibroblasts. Thus this method of covalent coating provides a biocompatible material with improved bioactive properties. These results proved that covalent coating of chitosan has significant potential in biomedical device implantation. PMID:22859940

  17. Enhanced Mechanical Performance of Bio-Inspired Hybrid Structures Utilising Topological Interlocking Geometry.

    PubMed

    Djumas, Lee; Molotnikov, Andrey; Simon, George P; Estrin, Yuri

    2016-01-01

    Structural composites inspired by nacre have emerged as prime exemplars for guiding materials design of fracture-resistant, rigid hybrid materials. The intricate microstructure of nacre, which combines a hard majority phase with a small fraction of a soft phase, achieves superior mechanical properties compared to its constituents and has generated much interest. However, replicating the hierarchical microstructure of nacre is very challenging, not to mention improving it. In this article, we propose to alter the geometry of the hard building blocks by introducing the concept of topological interlocking. This design principle has previously been shown to provide an inherently brittle material with a remarkable flexural compliance. We now demonstrate that by combining the basic architecture of nacre with topological interlocking of discrete hard building blocks, hybrid materials of a new type can be produced. By adding a soft phase at the interfaces between topologically interlocked blocks in a single-build additive manufacturing process, further improvement of mechanical properties is achieved. The design of these fabricated hybrid structures has been guided by computational work elucidating the effect of various geometries. To our knowledge, this is the first reported study that combines the advantages of nacre-inspired structures with the benefits of topological interlocking. PMID:27216277

  18. Topographical mapping system for radiological and hazardous environments acceptance testing

    SciTech Connect

    Armstrong, G.A.; Dochat, G.R.

    1997-12-01

    During the summer of 1996, the Topographical Mapping System (TMS) for hazardous and radiological environments and its accompanying three-dimensional (3-D) visualization tool, the Interactive Computer-Enhanced Remote-Viewing System (ICERVS), were delivered to Oak Ridge National Laboratory (ORNL). ORNL and Mechanical Technology, Inc., performed final acceptance testing of the TMS during the next eight months. The TMS was calibrated and characterized during this period. This paper covers the calibration, characterization, and acceptance testing of the TMS. Development of the TMS and ICERVS was initiated by the US Department of Energy (DOE) for the purpose of characterization and remediation of underground storage tanks (USTs) at DOE sites across the country. DOE required a 3-D, topographical mapping system suitable for use in hazardous and radiological environments. The intended application is the mapping of the interior of USTs as part of DOE`s waste characterization and remediation efforts and to obtain baseline data on the content of the storage tank interiors as well as data on changes in the tank contents and levels brought about by waste remediation steps. Initially targeted for deployment at the Hanford Washington site, the TMS is designed to be a self-contained, compact, and reconfigurable system that is capable of providing rapid, variable-resolution mapping information in poorly characterized workspaces with a minimum of operator intervention.

  19. Topographical mapping system for radiological and hazardous environments acceptance testing

    NASA Astrophysics Data System (ADS)

    Armstrong, Gary A.; Dochat, G. R.

    1997-09-01

    During the summer of 1996, the topographical mapping system (TMS) for hazardous and radiological environments and its accompanying three-dimensional (3-D) visualization tool, the interactive computer-enhanced remote-viewing system (ICERVS), were delivered to Oak Ridge National Laboratory (ORNL). ORNL and Mechanical Technology, Inc., performed final acceptance testing of the TMS during the next eight months. The TMS was calibrated and characterized during this period. This paper covers the calibration, characterization, and acceptance testing of the TMS. Development of the TMS and the ICERVS was initiated by the U.S. Department of Energy (DOE) for the purpose of characterization and remediation of underground storage tanks (USTs) at DOE sites across the country. DOE required a 3-D, topographical mapping system suitable for use in hazardous and radiological environments. The intended application is the mapping of the interior of USTs as part of DOE's waste characterization and remediation efforts and to obtain baseline data on the content of the storage tank interiors as well as data on changes in the tank contents and levels brought about by waste remediation steps. Initially targeted for deployment at the Hanford Washington site, the TMS is designed to be a self-contained, compact, reconfigurable system that is capable of providing rapid, variable-resolution mapping information in poorly characterized workspaces with a minimum of operator intervention.

  20. Hybrid Cleaning Technology for Enhanced Post-Cu/Low-Dielectric Constant Chemical Mechanical Planarization Cleaning Performance

    NASA Astrophysics Data System (ADS)

    Ramachandran, Manivannan; Cho, Byoung-Jun; Kwon, Tae-Young; Park, Jin-Goo

    2013-05-01

    During chemical mechanical planarization (CMP), a copper/low-k surface is often contaminated by abrasive particles, organic materials and other additives. These contaminants need to be removed in the subsequent cleaning process with minimum material loss. In this study, a dilute amine-based alkaline cleaning solution is used along with physical force in the form of megasonic energy to remove particles and organic contaminants. Tetramethylammonium hydroxide (TMAH) and monoethanolamine (MEA) are used as an organic base and complexing agent, respectively, in the proposed solution. Ethanolamine acts as a corrosion inhibitor in the solution. Organic residue removal was confirmed through contact angle measurements and X-ray photoelectron spectroscopy analysis. Electrochemical studies showed that the proposed solution increases protection against corrosion, and that the hybrid cleaning technology resulted in higher particle removal efficiency from both the copper and low-k surfaces.

  1. Controlled Thermal-Mechanical Processing of Tubes and Pipes for Enhanced Manufacturing and Performance

    SciTech Connect

    Kolarik, Robert V.

    2005-11-11

    The Alloy Steel Business of The Timken Company won an award for the controlled thermo-mechanical processing (CTMP) project and assembled a strong international public/private partnership to execute the project. The premise of the CTMP work was to combine Timken's product understanding with its process expertise and knowledge of metallurgical and deformation fundamentals developed during the project to build a predictive process design capability. The CTMP effort succeeded in delivering a pc-based capability in the tube optimization model, with a virtual pilot plant (VPP) feature to represent the desired tube making process to predict the resultant microstructure tailored for the desired application. Additional tasks included a system for direct, online measurement of grain size and demonstration of application of CTMP via robotically enhanced manufacturing.

  2. Parallel Performance Analysis between Free Response Environments and the Force Concept Inventory in Introductory Mechanics Courses

    NASA Astrophysics Data System (ADS)

    Bobbitt, Nicole; Wade, Aaron; Prayaga, Chandra

    2012-02-01

    This paper reports our attempts to: 1) find a way to model and predict common thought processes that cause typical misconceptions identified by the Force Concept Inventory (FCI), 2) create a problem solving situation that folds in both kinematics and force discussions, and 3) accurately assess the students' ability to interpret a kinematic graph. Two pen and paper test questions were designed with these goals in mind, both broken into specific elements, not only to allow for partial credit, but also to arrive at a quantifiable fragmentation of the necessary thought processes required to solve the problem. These results were compared to pre- and post-FCI data to analyze the common misconceptions as defined by FCI and their correlation to mistakes in the thought processes in answering the designed questions. Ultimately this, and any future questions, would become a tool in the classroom to pinpoint the critical ideas with which a typical student struggles during a mechanics course.

  3. Characterization of HTPB-based solid fuel formulations: Performance, mechanical properties, and pollution

    NASA Astrophysics Data System (ADS)

    DeLuca, L. T.; Galfetti, L.; Maggi, F.; Colombo, G.; Merotto, L.; Boiocchi, M.; Paravan, C.; Reina, A.; Tadini, P.; Fanton, L.

    2013-12-01

    Features such as safety, low-cost, and throttleability make hybrid rocket engines an attractive option for suborbital flights and space exploration missions in general. While the domain of possible liquid oxidizers is well characterized, the choice of a suitable solid fuel is still a matter of investigation. Space Propulsion Laboratory (SPLab) at Politecnico di Milano has developed a series of proprietary techniques to evaluate, on a relative grading, the quality of innovative solid fuels while visualizing at the same time their flame structure. But a serious alert was recently notified that soot emission from hydrocarbon fuels has the potential to contribute to global climate change. In this paper, HTPB polymer has been taken as baseline and characterized at laboratory level in terms of ballistic properties, mechanical testing, and thermochemical calculations.

  4. The Great Reduction of a Carbon Nanotube's Mechanical Performance by a Few Topological Defects.

    PubMed

    Zhu, Liyan; Wang, Jinlan; Ding, Feng

    2016-06-28

    It is widely believed that carbon nanotubes (CNTs) can be employed to produce superstrong materials with tensile strengths of up to 50 GPa. Numerous efforts have, however, led to CNT fibers with maximum strengths of only a few GPa. Here we report that, due to different mechanical responses to the tensile loading of disclination topological defects in the CNT walls, a few of these topological defects are able to greatly decrease the strength of the CNTs, by up to an order of magnitude. This study reveals that even nearly perfect CNTs cannot be used to build exceptionally strong materials, and therefore synthesizing flawless CNTs is essential for utilizing the ideal strength of CNTs. PMID:27251448

  5. Interplay between electrical and mechanical domains in a high performance nonlinear energy harvester

    NASA Astrophysics Data System (ADS)

    Mallick, Dhiman; Amann, Andreas; Roy, Saibal

    2015-12-01

    This paper reports a comprehensive experimental characterization and modeling of a compact nonlinear energy harvester for low frequency applications. By exploiting the interaction between the electrical circuitry and the mechanical motion of the device, we are able to improve the power output over a large frequency range. This improvement is quantified using a new figure of merit based on a suitably defined ‘power integral (P f)’ for nonlinear vibrational energy harvesters. The developed device consists of beams with fixed-guided configuration which produce cubic monostable nonlinearity due to stretching strain. Using a high efficiency magnetic circuit a maximum output power of 488.47 μW across a resistive load of 4000 Ω under 0.5g input acceleration at 77 Hz frequency with 9.55 Hz of bandwidth is obtained. The dynamical characteristics of the device are theoretically reproduced and explained by a modified nonlinear Duffing oscillator model.

  6. Multilayer Roll-Bonded Sandwich: Processing, Mechanical Performance, and Bioactive Behavior

    SciTech Connect

    Palkowski H.; Stanic V.; Carrado, A.

    2012-03-30

    Multifunctionality and improving the properties of materials make it necessary to use hybrid systems such as combinations of metals with polymers. Their applications can be found in all areas where light weight and improved and adapted mechanical properties as well as high functionality are needed. Moreover, tailored types of hybrids can be interesting for biomedical applications, as under specific conditions they show, e.g., good strength combined with high elasticity. Herein, we present preliminary tests on the biomimetic behavior of AISI SS316L/polypropylene copolymer/AISI SS316L sandwich. Biomimetic coatings were produced by inducing a calcium phosphate layer in a way similar to the process of natural bone formation. Knowledge of the formability of three-layered sandwich sheets and their biomimetic behavior is presented.

  7. SOLID OXIDE FUEL CELL CATHODES: Polarization Mechanisms and Modeling of the Electrochemical Performance

    NASA Astrophysics Data System (ADS)

    Fleig, Jurgen

    2003-08-01

    Several recent experimental and numerical investigations have contributed to the improved understanding of the electrochemical mechanisms taking place at solid oxide fuel cell (SOFC) cathodes and yielded valuable information on the relationships between alterable parameters (geometry/material) and the cathodic polarization resistance. Efforts to reduce the polarization resistance in SOFCs can benefit from these results, and some important aspects of the corresponding studies are reviewed. Experimental results, particularly measurements using geometrically well-defined Sr-doped LaMnO3 (LSM) cathodes, are discussed. In regard to simulations, the different levels of sophistication used in SOFC electrode modeling studies are summarized and compared. Exemplary simulations of mixed conducting cathodes that show the capabilities and limits of different modeling levels are described.

  8. Evaluation of changes in microstructure and mechanical performance of metals via electrical resistivity measurements

    NASA Astrophysics Data System (ADS)

    Omari, Mohammad Ahmad

    This work focuses on experimental study of cross-property connections that link up effective linear elastic and electrical conductive properties of heterogeneous materials. Such connections are especially useful when one property (electrical conductivity) is easier to measure than the other (elastic constants). Also, take advantages from the easy of measure electrical resistance to study the microstructural changes, and then compare results with different methods like microscopy and other published methods. Mechanical and electrical properties of different specimens under both fatigue and quasi-static loading were investigated, combined with the analysis of microstructural changes produced by such loading. Two different types of metals (stainless steel 304 and Titanium CP-2) have been cut from sheets and then subjected to two different type of loading: cyclic loading (up to 80000 cycles) at several values of maximal stress sigmamax and then quasi-static loading. At low values of sigmamax as well as at the low number of cycles no significant changes in mechanical properties and mild decrease in electrical conductivity (approximately uniform over the specimen) have been observed. The latter can be explained by generation cluster of new dislocations that can be seen in photo images in the form of black dots. As the number of cycles and sigmamax grow up, reduction in Young's modulus and in ultimate strength of the specimens take place. This reduction is accompanied by local decrease in electrical conductivity due to formation of the microcracks. Changes in Young's modulus and electrical conductivity at high values of sigma max. (higher than the yield limit) follow the theoretically predicted cross-property connection for microcracked materials. Qualitative correlation between strength reduction and maximum value of local resistivity across the specimen has been observed at qualitative level.

  9. Corrosion and mechanical performance of AZ91 exposed to simulated inflammatory conditions.

    PubMed

    Brooks, Emily K; Der, Stephanie; Ehrensberger, Mark T

    2016-03-01

    Magnesium (Mg) and its alloys, including Mg-9%Al-1%Zn (AZ91), are biodegradable metals with potential use as temporary orthopedic implants. Invasive orthopedic procedures can provoke an inflammatory response that produces hydrogen peroxide (H2O2) and an acidic environment near the implant. This study assessed the influence of inflammation on both the corrosion and mechanical properties of AZ91. The AZ91 samples in the inflammatory protocol were immersed for three days in a complex biologically relevant electrolyte (AMEM culture media) that contained serum proteins (FBS), 150 mM of H2O2, and was titrated to a pH of 5. The control protocol immersed AZ91 samples in the same biologically relevant electrolyte (AMEM & FBS) but without H2O2 and the acid titration. After 3 days all samples were switched into fresh AMEM & FBS for an additional 3-day immersion. During the initial immersion, inflammatory protocol samples showed increased corrosion rate determined by mass loss testing, increased Mg and Al ion released to solution, and a completely corroded surface morphology as compared to the control protocol. Although corrosion in both protocols slowed once the test electrolyte solution was replaced at 3 days, the samples originally exposed to the simulated inflammatory conditions continued to display enhanced corrosion rates as compared to the control protocol. These lingering effects may indicate the initial inflammatory corrosion processes modified components of the surface oxide and corrosion film or initiated aggressive localized processes that subsequently left the interface more vulnerable to continued enhanced corrosion. The electrochemical properties of the interfaces were also evaluated by EIS, which found that the corrosion characteristics of the AZ91 samples were potentially influenced by the role of intermediate adsorption layer processes. The increased corrosion observed for the inflammatory protocol did not affect the flexural mechanical properties of the AZ91

  10. Defining acceptable conditions in wilderness

    NASA Astrophysics Data System (ADS)

    Roggenbuck, J. W.; Williams, D. R.; Watson, A. E.

    1993-03-01

    The limits of acceptable change (LAC) planning framework recognizes that forest managers must decide what indicators of wilderness conditions best represent resource naturalness and high-quality visitor experiences and how much change from the pristine is acceptable for each indicator. Visitor opinions on the aspects of the wilderness that have great impact on their experience can provide valuable input to selection of indicators. Cohutta, Georgia; Caney Creek, Arkansas; Upland Island, Texas; and Rattlesnake, Montana, wilderness visitors have high shared agreement that littering and damage to trees in campsites, noise, and seeing wildlife are very important influences on wilderness experiences. Camping within sight or sound of other people influences experience quality more than do encounters on the trails. Visitors’ standards of acceptable conditions within wilderness vary considerably, suggesting a potential need to manage different zones within wilderness for different clientele groups and experiences. Standards across wildernesses, however, are remarkably similar.

  11. From requirements to acceptance tests

    NASA Technical Reports Server (NTRS)

    Baize, Lionel; Pasquier, Helene

    1993-01-01

    From user requirements definition to accepted software system, the software project management wants to be sure that the system will meet the requirements. For the development of a telecommunication satellites Control Centre, C.N.E.S. has used new rules to make the use of tracing matrix easier. From Requirements to Acceptance Tests, each item of a document must have an identifier. A unique matrix traces the system and allows the tracking of the consequences of a change in the requirements. A tool has been developed, to import documents into a relational data base. Each record of the data base corresponds to an item of a document, the access key is the item identifier. Tracing matrix is also processed, providing automatically links between the different documents. It enables the reading on the same screen of traced items. For example one can read simultaneously the User Requirements items, the corresponding Software Requirements items and the Acceptance Tests.

  12. Physical effects of mechanical design parameters on photon sensitivity and spatial resolution performance of a breast-dedicated PET system

    PubMed Central

    Spanoudaki, V. C.; Lau, F. W. Y.; Vandenbroucke, A.; Levin, C. S.

    2010-01-01

    Purpose: This study aims to address design considerations of a high resolution, high sensitivity positron emission tomography scanner dedicated to breast imaging. Methods: The methodology uses a detailed Monte Carlo model of the system structures to obtain a quantitative evaluation of several performance parameters. Special focus was given to the effect of dense mechanical structures designed to provide mechanical robustness and thermal regulation to the minuscule and temperature sensitive detectors. Results: For the energies of interest around the photopeak (450–700 keV energy window), the simulation results predict a 6.5% reduction in the single photon detection efficiency and a 12.5% reduction in the coincidence photon detection efficiency in the case that the mechanical structures are interspersed between the detectors. However for lower energies, a substantial increase in the number of detected events (approximately 14% and 7% for singles at a 100–200 keV energy window and coincidences at a lower energy threshold of 100 keV, respectively) was observed with the presence of these structures due to backscatter. The number of photon events that involve multiple interactions in various crystal elements is also affected by the presence of the structures. For photon events involving multiple interactions among various crystal elements, the coincidence photon sensitivity is reduced by as much as 20% for a point source at the center of the field of view. There is no observable effect on the intrinsic and the reconstructed spatial resolution and spatial resolution uniformity. Conclusions: Mechanical structures can have a considerable effect on system sensitivity, especially for systems processing multi-interaction photon events. This effect, however, does not impact the spatial resolution. Various mechanical structure designs are currently under evaluation in order to achieve optimum trade-off between temperature stability, accurate detector positioning, and minimum

  13. Acceptance Probability (P a) Analysis for Process Validation Lifecycle Stages.

    PubMed

    Alsmeyer, Daniel; Pazhayattil, Ajay; Chen, Shu; Munaretto, Francesco; Hye, Maksuda; Sanghvi, Pradeep

    2016-04-01

    This paper introduces an innovative statistical approach towards understanding how variation impacts the acceptance criteria of quality attributes. Because of more complex stage-wise acceptance criteria, traditional process capability measures are inadequate for general application in the pharmaceutical industry. The probability of acceptance concept provides a clear measure, derived from specific acceptance criteria for each quality attribute. In line with the 2011 FDA Guidance, this approach systematically evaluates data and scientifically establishes evidence that a process is capable of consistently delivering quality product. The probability of acceptance provides a direct and readily understandable indication of product risk. As with traditional capability indices, the acceptance probability approach assumes that underlying data distributions are normal. The computational solutions for dosage uniformity and dissolution acceptance criteria are readily applicable. For dosage uniformity, the expected AV range may be determined using the s lo and s hi values along with the worst case estimates of the mean. This approach permits a risk-based assessment of future batch performance of the critical quality attributes. The concept is also readily applicable to sterile/non sterile liquid dose products. Quality attributes such as deliverable volume and assay per spray have stage-wise acceptance that can be converted into an acceptance probability. Accepted statistical guidelines indicate processes with C pk > 1.33 as performing well within statistical control and those with C pk < 1.0 as "incapable" (1). A C pk > 1.33 is associated with a centered process that will statistically produce less than 63 defective units per million. This is equivalent to an acceptance probability of >99.99%. PMID:26024723

  14. The MAGNEX large acceptance spectrometer

    SciTech Connect

    Cavallaro, M.; Cappuzzello, F.; Cunsolo, A.; Carbone, D.; Foti, A.

    2010-03-01

    The main features of the MAGNEX large acceptance magnetic spectrometer are described. It has a quadrupole + dipole layout and a hybrid detector located at the focal plane. The aberrations due to the large angular (50 msr) and momentum (+- 13%) acceptance are reduced by an accurate hardware design and then compensated by an innovative software ray-reconstruction technique. The obtained resolution in energy, angle and mass are presented in the paper. MAGNEX has been used up to now for different experiments in nuclear physics and astrophysics confirming to be a multipurpose device.

  15. Lattice Boltzmann investigation of acoustic damping mechanism and performance of an in-duct circular orifice.

    PubMed

    Ji, Chenzhen; Zhao, Dan

    2014-06-01

    In this work, three-dimensional numerical simulations of acoustically excited flow through a millimeter-size circular orifice are conducted to assess its noise damping performance, with particular emphasis on applying the lattice Boltzmann method (LBM) as an alternative computational aeroacoustics tool. The model is intended to solve the discrete lattice Boltzmann equation (LBE) by using the pseudo-particle based technique. The LBE controls the particles associated with collision and propagation over a discrete lattice mesh. Flow variables such as pressure, density, momentum, and internal energy are determined by performing a local integration of the particle distribution at each time step. This is different from the conventional numerical investigation attempting to solve Navier-Stokes (NS) equations by using high order finite-difference or finite-volume methods. Compared with the conventional NS solvers, one of the main advantages of LBM may be a reduced computational cost. Unlike frequency domain simulations, the present investigation is conducted in time domain, and the orifice damping behavior is quantified over a broad frequency range at a time by forcing an oscillating flow with multiple tones. Comparing the numerical results with those obtained from the theoretical models, large eddy simulation, and experimental measurements, good agreement is observed. PMID:24907789

  16. Algorithms for thermal and mechanical contact in nuclear fuel performance analysis

    SciTech Connect

    Hales, J. D.; Andrs, D.; Gaston, D. R.

    2013-07-01

    The transfer of heat and force from UO{sub 2} pellets to the cladding is an essential element in typical nuclear fuel performance modeling. Traditionally, this has been accomplished in a one-dimensional fashion, with a slice of fuel interacting with a slice of cladding. In this manner, the location at which the transfer occurs is set a priori. While straightforward, this limits the applicability and accuracy of the model. We propose finite element algorithms for the transfer of heat and force where the location for the transfer is not predetermined. This enables analysis of individual fuel pellets with large sliding between the fuel and the cladding. The simplest of these approaches is a node on face constraint. Heat and force are transferred from a node on the fuel to the cladding face opposite. Another option is a transfer based on quadrature point locations, which is applied here to the transfer of heat. The final algorithm outlined here is the so-called mortar method, with applicability to heat and force transfer. The mortar method promises to be a highly accurate approach which may be used for a transfer of other quantities and in other contexts, such as heat from cladding to a CFD mesh of the coolant. This paper reviews these approaches, discusses their strengths and weaknesses, and presents results from each on simplified nuclear fuel performance models. (authors)

  17. Solventless, curable fluid oligomeric systems for high performance microwave, acoustical and mechanical applications

    NASA Technical Reports Server (NTRS)

    Lefave, G. M.; Stanton, Leo; Foreman, Jim

    1994-01-01

    While establishing the basis for a 'Technology 2000' product plan several years ago we plugged in the usual factors contributing toward product success: price/performance justifiable; profitable, warranting high quality maintenance, enhancement, and specific property improvement; narrow inventory requirements; and raw material integrable backwards with easily variable properties (molecular weight, functionality, and isomer control). We resolved this by selecting radical functional, low molecular weight polybutadiene liquid polymers. Encouraged by the need for solid rocket binders, several companies embarked on various perceptions of binder performance requirements over four decades ago. Initially dominated by progress of liquid polysulfides, soon a few settled primarily upon polybutadiene based binders. Such an approach in a few instances was exploited quite viably with a series of functional group terminated liquid polybutadienes: hydroxyl, mercaptan, carboxyl, vinyl, and amine. Good results are obtained for oligomers, liquid polymers, and their hybrids. The only significant limits on compounded products has been solvent resistance and oxidative sensitivity, unless sufficient proportion of sulfide or nitrile moiety is incorporated. For convenience, they have been grouped under the trademarks Nylane, Seamax, Oligomax, and Castomax.

  18. Choking under pressure: the neuropsychological mechanisms of incentive-induced performance decrements

    PubMed Central

    Yu, Rongjun

    2015-01-01

    In contrast to the assumption of efficiency wage models, which state that wage incentives should be positively correlated with productivity, high incentives may produce performance decrements in real life scenarios. Such a “choking under pressure” phenomenon exemplifies how psychological stress can profoundly shape human behavior, for good or for bad. Previous theories suggest that individual choking under pressure because that high pressure may distract individuals’ attention away from the task (the distraction account), raise the attention paid to step-by-step skill processes (the explicit monitoring account), or elevate the arousal in general (the over-arousal account). Recent neuroimaging studies have shown that several brain regions implicated in motivation and top-down control of attention also play a key role in stress-induced choking, supporting for the over-arousal and distraction theories of choking. This review aims to identify psychological factors that determine choking and the neural underpinnings of these processes. Insights into how incentives influence performance may aid engineering training regimens and interventions that equip individuals to better handle high-stakes-induced psychological stress, and to thrive under stress. PMID:25713517

  19. Choking under pressure: the neuropsychological mechanisms of incentive-induced performance decrements.

    PubMed

    Yu, Rongjun

    2015-01-01

    In contrast to the assumption of efficiency wage models, which state that wage incentives should be positively correlated with productivity, high incentives may produce performance decrements in real life scenarios. Such a "choking under pressure" phenomenon exemplifies how psychological stress can profoundly shape human behavior, for good or for bad. Previous theories suggest that individual choking under pressure because that high pressure may distract individuals' attention away from the task (the distraction account), raise the attention paid to step-by-step skill processes (the explicit monitoring account), or elevate the arousal in general (the over-arousal account). Recent neuroimaging studies have shown that several brain regions implicated in motivation and top-down control of attention also play a key role in stress-induced choking, supporting for the over-arousal and distraction theories of choking. This review aims to identify psychological factors that determine choking and the neural underpinnings of these processes. Insights into how incentives influence performance may aid engineering training regimens and interventions that equip individuals to better handle high-stakes-induced psychological stress, and to thrive under stress. PMID:25713517

  20. Effect of operating frequency and phase angle on performance of Alpha Stirling cryocooler driven by a novel compact mechanism

    NASA Astrophysics Data System (ADS)

    Sant, K. D.; Bapat, S. L.

    2015-12-01

    Amongst the mechanical cryocoolers in use, Stirling cycle cryocoolers exhibit the desirable features such as high efficiency, low specific power consumption, small size and mass and large mean time before failure. Stirling cycle cryocooler of Alpha configuration exhibits better theoretical performance as compared to Gamma. However, the theory could not be put into practice due to unavailability of compatible drive mechanism for Alpha cryocooler providing large stroke to diameter ratio. The concept of novel compact drive mechanism can be made functional to operate miniature Alpha Stirling cryocoolers. It allows the use of multicylinder system while converting rotary motion to reciprocating. This permits the drive mechanism to be employed for driving different configurations of Stirling cryocooler simultaneously. This drive is capable of providing large stroke to diameter ratio compared to other drive mechanisms generally in use for the purpose. A stroke to diameter ratio of three is chosen in the present work and the drive dimensions are calculated for four piston-cylinder arrangements with 90° phase difference between adjacent arrangements providing two Alpha Stirling cryocoolers working simultaneously. It has to be noted that the coolers operate at half the frequency of the motor used. As the two coolers operate at phase difference of 180°, during compression stroke of one unit, the suction stroke occurs for the other unit. Due to power output of second unit, the combined peak torque requirement falls by 26.81% below the peak torque needed when one unit is operated separately. This allows for use of a comparatively lower torque motor. The practicability of the drive ensuring smooth operation of the system is decided based on comparison between torque availability from the motor and torque requirement of the complete unit. The second order method of cyclic (or thermodynamic) analysis provides a simple computational procedure useful for the design of Stirling

  1. Effect of cellulosic fiber scale on linear and non-linear mechanical performance of starch-based composites.

    PubMed

    Karimi, Samaneh; Abdulkhani, Ali; Tahir, Paridah Md; Dufresne, Alain

    2016-10-01

    Cellulosic nanofibers (NFs) from kenaf bast were used to reinforce glycerol plasticized thermoplastic starch (TPS) matrices with varying contents (0-10wt%). The composites were prepared by casting/evaporation method. Raw fibers (RFs) reinforced TPS films were prepared with the same contents and conditions. The aim of study was to investigate the effects of filler dimension and loading on linear and non-linear mechanical performance of fabricated materials. Obtained results clearly demonstrated that the NF-reinforced composites had significantly greater mechanical performance than the RF-reinforced counterparts. This was attributed to the high aspect ratio and nano dimension of the reinforcing agents, as well as their compatibility with the TPS matrix, resulting in strong fiber/matrix interaction. Tensile strength and Young's modulus increased by 313% and 343%, respectively, with increasing NF content from 0 to 10wt%. Dynamic mechanical analysis (DMA) revealed an elevational trend in the glass transition temperature of amylopectin-rich domains in composites. The most eminent record was +18.5°C shift in temperature position of the film reinforced with 8% NF. This finding implied efficient dispersion of nanofibers in the matrix and their ability to form a network and restrict mobility of the system. PMID:27339322

  2. Laccase-catalyzed decolorization of malachite green: performance optimization and degradation mechanism.

    PubMed

    Yang, Jie; Yang, Xiaodan; Lin, Yonghui; Ng, Tzi Bun; Lin, Juan; Ye, Xiuyun

    2015-01-01

    Malachite green (MG) was decolorized by laccase (LacA) of white-rot fungus Cerrena sp. with strong decolorizing ability. Decolorization conditions were optimized with response surface methodology. A highly significant quadratic model was developed to investigate MG decolorization with LacA, and the maximum MG decolorization ratio of 91.6% was predicted under the conditions of 2.8 U mL(-1) LacA, 109.9 mg L(-1) MG and decolorization for 172.4 min. Kinetic studies revealed the Km and kcat values of LacA toward MG were 781.9 mM and 9.5 s(-1), respectively. UV-visible spectra confirmed degradation of MG, and the degradation mechanism was explored with liquid chromatography-mass spectrometry (LC-MS) analysis. Based on the LC-MS spectra of degradation products, LacA catalyzed MG degradation via two simultaneous pathways. In addition, the phytotoxicity of MG, in terms of inhibition on seed germination and seedling root elongation of Nicotiana tabacum and Lactuca sativa, was reduced after laccase treatment. These results suggest that laccase of Cerrena was effective in decolorizing MG and promising in bioremediation of wastewater in food and aquaculture industries. PMID:26020270

  3. Cellulose Nanofibers as a Modifier for Rheology, Curing and Mechanical Performance of Oil Well Cement.

    PubMed

    Sun, Xiuxuan; Wu, Qinglin; Lee, Sunyoung; Qing, Yan; Wu, Yiqiang

    2016-01-01

    The influence of nanocellulose on oil well cement (OWC) properties is not known in detail, despite recent advances in nanocellulose technology and its related composite materials. The effect of cellulose nanofibers (CNFs) on flow, hydration, morphology, and strength of OWC was investigated using a range of spectroscopic methods coupled with rheological modelling and strength analysis. The Vom-Berg model showed the best fitting result of the rheology data. The addition of CNFs increased the yield stress of OWC slurry and degree of hydration value of hydrated CNF-OWC composites. The flexural strength of hydrated OWC samples was increased by 20.7% at the CNF/OWC ratio of 0.04 wt%. Excessive addition of CNFs into OWC matrix had a detrimental effect on the mechanical properties of hydrated CNF-OWC composites. This phenomenon was attributed to the aggregation of CNFs as observed through coupled morphological and elemental analysis. This study demonstrates a sustainable reinforcing nano-material for use in cement-based formulations. PMID:27526784

  4. Cellulose Nanofibers as a Modifier for Rheology, Curing and Mechanical Performance of Oil Well Cement

    PubMed Central

    Sun, Xiuxuan; Wu, Qinglin; Lee, Sunyoung; Qing, Yan; Wu, Yiqiang

    2016-01-01

    The influence of nanocellulose on oil well cement (OWC) properties is not known in detail, despite recent advances in nanocellulose technology and its related composite materials. The effect of cellulose nanofibers (CNFs) on flow, hydration, morphology, and strength of OWC was investigated using a range of spectroscopic methods coupled with rheological modelling and strength analysis. The Vom-Berg model showed the best fitting result of the rheology data. The addition of CNFs increased the yield stress of OWC slurry and degree of hydration value of hydrated CNF-OWC composites. The flexural strength of hydrated OWC samples was increased by 20.7% at the CNF/OWC ratio of 0.04 wt%. Excessive addition of CNFs into OWC matrix had a detrimental effect on the mechanical properties of hydrated CNF-OWC composites. This phenomenon was attributed to the aggregation of CNFs as observed through coupled morphological and elemental analysis. This study demonstrates a sustainable reinforcing nano-material for use in cement-based formulations. PMID:27526784

  5. Laccase-Catalyzed Decolorization of Malachite Green: Performance Optimization and Degradation Mechanism

    PubMed Central

    Yang, Jie; Yang, Xiaodan; Lin, Yonghui; Ng, Tzi Bun; Lin, Juan; Ye, Xiuyun

    2015-01-01

    Malachite green (MG) was decolorized by laccase (LacA) of white-rot fungus Cerrena sp. with strong decolorizing ability. Decolorization conditions were optimized with response surface methodology. A highly significant quadratic model was developed to investigate MG decolorization with LacA, and the maximum MG decolorization ratio of 91.6% was predicted under the conditions of 2.8 U mL-1 LacA, 109.9 mg L-1 MG and decolorization for 172.4 min. Kinetic studies revealed the Km and kcat values of LacA toward MG were 781.9 mM and 9.5 s-1, respectively. UV–visible spectra confirmed degradation of MG, and the degradation mechanism was explored with liquid chromatography–mass spectrometry (LC-MS) analysis. Based on the LC-MS spectra of degradation products, LacA catalyzed MG degradation via two simultaneous pathways. In addition, the phytotoxicity of MG, in terms of inhibition on seed germination and seedling root elongation of Nicotiana tabacum and Lactuca sativa, was reduced after laccase treatment. These results suggest that laccase of Cerrena was effective in decolorizing MG and promising in bioremediation of wastewater in food and aquaculture industries. PMID:26020270

  6. The mechanical performance of weft-knitted/electrospun bilayer small diameter vascular prostheses.

    PubMed

    Xie, Yu; Guan, Ying; Kim, Soo-Hyun; King, Martin W

    2016-08-01

    Cardiovascular disease (CVD) accounts for a significant mortality rate worldwide. Autologous vessels, such as the saphenous vein and the internal mammary artery, are currently the gold standard materials for by-pass surgery. However, they may not always be available due to aging, previous harvesting or the pre-existing arterial disease. Synthetic commercial ePTFE and polyester (PET) are not suitable for small diameter vascular grafts (<6mm), mainly due to their poor circumferential compliance, rapid thrombus formation and low endothelialization. In order to reduce thrombogenicity and improve cell proliferation, we developed a collagen/elastin knitted/electrospun bilayer graft made of biodegradable and biocompatible poly(lactic acid) (PLA) and poly(lactide-co-caprolactone) (PLCL) polymers to mimic the multilayer structure of native arteries. We also designed the prostheses to provide some of the required mechanical properties. While the bilayer structure had excellent circumferential tensile strength, bursting strength and suture retention resistance, the radial compliance did not show any observable improvement. PMID:27111627

  7. The European Robotic Arm: A High-performance Mechanism Finally on Its Way to Space

    NASA Technical Reports Server (NTRS)

    Cruijssen, H. J.; Ellenbroek, M.; Henderson, M.; Petersen, H.; Verzijden, P.; Visser, M.

    2014-01-01

    This paper describes the design and qualification of the European Robotic Arm (ERA), which is planned to be launched by the end of 2015. After years of changes, a shift of launcher and new loads, launch preparation is underway. The European Robotic Arm ERA has been designed and manufactured by Dutch Space and its subcontractors such as Astrium, SABCA and Stork with key roles for the mechanical aspects. The arm was originally designed to be launched by the STS (mounted on a Russian module for the ISS) in 2001. However, due to delays and the STS disaster, a shift was made to the Russian Proton rocket. ERA will be launched on the Multipurpose Laboratory Module (MLM). This module, which is now planned for launch to the ISS in 2015, will carry the ERA. The symmetrical design of the arm with a complete 3 degree-of-freedom wrist and general-purpose end effector on both sides, allows ERA to relocate on the station by grappling a new base point and releasing the old one, and move to different working locations.

  8. N-(6-(hydroxyamino)-6-oxohexyl) decanamide collector: Flotation performance and adsorption mechanism to diaspore

    NASA Astrophysics Data System (ADS)

    Deng, Lanqing; Wang, Shuai; Zhong, Hong; Liu, Guangyi

    2015-08-01

    In this paper, a novel surfactant, N-(6-(hydroxyamino)-6-oxohexyl)decanamide (NHOD) was synthesized and used as a collector for flotation separation of diaspore and aluminosilicate minerals. The adsorption mechanism of NHOD onto diaspore was also investigated by FTIR spectra, zeta potential measurement and XPS. The flotation results demonstrated that NHOD exhibited superior collecting power to diaspore and selectivity against kaolinite and illite and could effectively realize flotation recovery of diaspore from bauxite ores contained aluminosilicate minerals under neutral conditions. The results of XPS, FTIR spectra and zeta potential illustrated that at around pH 7.0, NHOD might chemisorb on diaspore surfaces through Alsbnd O coordination bonds formed by binding its sbnd C(dbnd O)NHOH or sbnd C(dbnd O)NHsbnd chelate groups with aluminum atoms on diaspore surfaces. NHOD's unique properties, such as characteristic bond patterns onto diaspore surfaces, two hydrophobic groups, and intermolecular hydrogen bonds between neighboring NHOD molecules coated on diaspore surfaces, rendered it to be a superior flotation collector for diaspore.

  9. Testing of elastomeric liners used in limb prosthetics: classification of 15 products by mechanical performance.

    PubMed

    Sanders, Joan E; Nicholson, Brian S; Zachariah, Santosh G; Cassisi, Damon V; Karchin, Ari; Fergason, John R

    2004-03-01

    The mechanical properties of 15 elastomeric liner products used in limb prosthetics were evaluated under compressive, frictional, shear, and tensile loading conditions. All testing was conducted at load levels comparable to interface stress measurements reported on transtibial amputee subjects. For each test configuration, materials were classified into four groups based on the shapes of their response curves. For the 15 liners tested, there were 10 unique classification sets, indicating a wide range of unique materials. In general, silicone gel liners classified within the same groups thus were quite similar to each other. They were of lower compressive, shear, and tensile stiffness than the silicone elastomer products, consistent with their lightly cross-linked, high-fluid content structures. Silicone elastomer products better spanned the response groups than the gel liners, demonstrating a wide range of compressive, shear, and tensile stiffness values. Against a skin-like material, a urethane liner had the highest coefficient of friction of any liner tested, although coefficients of friction values for most of the materials were higher than interface shear:pressure ratios measured on amputee subjects using Pelite liners. The elastomeric liner material property data and response groupings provided here can potentially be useful to prosthetic fitting by providing quantitative information on similarities and differences among products. PMID:15558371

  10. Performance improvement of smooth impact drive mechanism at low voltage utilizing ultrasonic friction reduction.

    PubMed

    Cheng, Tinghai; Lu, Xiaohui; Zhao, Hongwei; Chen, Dong; He, Pu; Wang, Liang; Zhao, Xilu

    2016-08-01

    The smooth impact drive mechanism (SIDM) actuator is traditionally excited by a saw-tooth wave, but it requires large input voltages for high-speed operation and load capacity. To improve the output characteristic of the SIDM operating at low input voltage, a novel driving method based on ultrasonic friction reduction technology is proposed in this paper. A micro-amplitude sinusoidal signal with high frequency is applied to the rapid deformation stage of the traditional saw-tooth wave. The proposed driving method can be realized by a composite waveform that includes a driving wave (D-wave) and a friction regulation wave (FR-wave). The driving principle enables lower input voltage to be used in normal operation, and the principle of the proposed driving method is analyzed. A prototype of the SIDM is fabricated, and its experimental system is established. The tested results indicate that the actuator has suitable velocity and load characteristics while operating at lower input voltage, and the load capacity of the actuator is 2.4 times that of an actuator excited by a traditional saw-tooth driving wave. PMID:27587153

  11. Mechanical and In Vitro Biological Performance of Graphene Nanoplatelets Reinforced Calcium Silicate Composite

    PubMed Central

    Mehrali, Mehdi; Moghaddam, Ehsan; Seyed Shirazi, Seyed Farid; Baradaran, Saeid; Mehrali, Mohammad; Latibari, Sara Tahan; Metselaar, Hendrik Simon Cornelis; Kadri, Nahrizul Adib; Zandi, Keivan; Osman, Noor Azuan Abu

    2014-01-01

    Calcium silicate (CaSiO3, CS) ceramic composites reinforced with graphene nanoplatelets (GNP) were prepared using hot isostatic pressing (HIP) at 1150°C. Quantitative microstructural analysis suggests that GNP play a role in grain size and is responsible for the improved densification. Raman spectroscopy and scanning electron microscopy showed that GNP survived the harsh processing conditions of the selected HIP processing parameters. The uniform distribution of 1 wt.% GNP in the CS matrix, high densification and fine CS grain size help to improve the fracture toughness by ∼130%, hardness by ∼30% and brittleness index by ∼40% as compared to the CS matrix without GNP. The toughening mechanisms, such as crack bridging, pull-out, branching and deflection induced by GNP are observed and discussed. The GNP/CS composites exhibit good apatite-forming ability in the simulated body fluid (SBF). Our results indicate that the addition of GNP decreased pH value in SBF. Effect of addition of GNP on early adhesion and proliferation of human osteoblast cells (hFOB) was measured in vitro. The GNP/CS composites showed good biocompatibility and promoted cell viability and cell proliferation. The results indicated that the cell viability and proliferation are affected by time and concentration of GNP in the CS matrix. PMID:25229540

  12. GIOTTO's antenna de-spin mechanism: Ots lubrication and thermal vacuum performance

    NASA Technical Reports Server (NTRS)

    Todd, M. J.; Parker, K.

    1987-01-01

    Except in the near Earth phase of GIOTTO's mission to Comet Halley, the HGA (high gain antenna) on board GIOTTO was the only designed means of up/down communications. The spacecraft spin stabilization required that the HGA be despun at the same rotational rate of nominally 15 rpm in order to keep the HGA pointing accurately to a Earth. A dual servomotor despin mechanism was designed and built by SEP of France for this purpose. The expected thermal environment suggested that dry lubrication was preferable to wet for the ball bearings but there existed no relevant data on the torque noise spectrum of candidate solid lubricants. Therefore ad hoc torque noise tests were run with two solid lubricants: ion plated lead film plus lead bronze cage (retainer) and a PTFE composite cage only. The lead lubrication showed the better spectrum up to the mission lifetime point so it was selected for continued test over some 20 times the Halley mission life, with periodic torque spectrum monitoring. The spectrum remained well within the pointing error budget over the 100 million revolutions covered.

  13. Electromagnetic induction moisture measurement system acceptance test plan

    SciTech Connect

    Vargo, G.F., Westinghouse Hanford

    1996-08-01

    The purpose of this acceptance test plan (ATP) is to verify that the mechanical, electrical and software features of the ElectroMagnetic Induction (EMI) probe are operating as designed,and that the unit is ready for field service. The accepted EMI and Surface Moisture Measurement Systems (SMMS) will be used primarily in support of Tank Waste Remediation System (TWRS) Safety Programs for moisture measurement of organic and ferrocyanide watch list tanks.

  14. Opto-mechanical Analyses for Performance Optimization of Lightweight Grazing-incidence Mirrors

    NASA Technical Reports Server (NTRS)

    Roche, Jacqueline M.; Kolodziejczak, Jeffery J.; Odell, Stephen L.; Elsner, Ronald F.; Weisskopf, Martin C.; Ramsey, Brian; Gubarev, Mikhail V.

    2013-01-01

    New technology in grazing-incidence mirror fabrication and assembly is necessary to achieve subarcsecond optics for large-area x-ray telescopes. In order to define specifications, an understanding of performance sensitivity to design parameters is crucial. MSFC is undertaking a systematic study to specify a mounting approach, mirror substrate, and testing method. Lightweight mirrors are typically flimsy and are, therefore, susceptible to significant distortion due to mounting and gravitational forces. Material properties of the mirror substrate along with its dimensions significantly affect the distortions caused by mounting and gravity. A parametric study of these properties and their relationship to mounting and testing schemes will indicate specifications for the design of the next generation of lightweight grazing-incidence mirrors. Here we report initial results of this study.

  15. Design considerations in mechanical face seals for improved performance. 2: Lubrication

    NASA Technical Reports Server (NTRS)

    Ludwig, L. P.; Greiner, H. F.

    1977-01-01

    The importance of sealing technology in our industrial, chemical-oriented society in regard to maintenance and environmental contamination is pointed out. It is stated that seal performance (leakage, life) is directly related to seal lubrication. Current thinking in regard to seal lubrication is reviewed; the effect of energy dissipation in the thin lubricating film separating the sealing faces is pointed out, and the results of vaporization due to heating are illustrated. Also, hydrodynamic lubrication is reviewed, and an inherent tendency for the seal to operate with angular misalignment is shown. Recent work on hydrostatic effects is summarized and the conditions for seal instability are discussed. Four different modes of seal lubrication are postulated with the mode type being a strong function of speed and pressure.

  16. Aerodynamic performance investigation of advanced mechanical suppressor and ejector nozzle concepts for jet noise reduction

    NASA Technical Reports Server (NTRS)

    Wagenknecht, C. D.; Bediako, E. D.

    1985-01-01

    Advanced Supersonic Transport jet noise may be reduced to Federal Air Regulation limits if recommended refinements to a recently developed ejector shroud exhaust system are successfully carried out. A two-part program consisting of a design study and a subscale model wind tunnel test effort conducted to define an acoustically treated ejector shroud exhaust system for supersonic transport application is described. Coannular, 20-chute, and ejector shroud exhaust systems were evaluated. Program results were used in a mission analysis study to determine aircraft takeoff gross weight to perform a nominal design mission, under Federal Aviation Regulation (1969), Part 36, Stage 3 noise constraints. Mission trade study results confirmed that the ejector shroud was the best of the three exhaust systems studied with a significant takeoff gross weight advantage over the 20-chute suppressor nozzle which was the second best.

  17. Highly conductive and flexible polymer composites with improved mechanical and electromagnetic interference shielding performances

    NASA Astrophysics Data System (ADS)

    Chen, Mengting; Zhang, Ling; Duan, Shasha; Jing, Shilong; Jiang, Hao; Luo, Meifang; Li, Chunzhong

    2014-03-01

    New flexible and conductive materials (FCMs) comprising a quartz fiber cloth (QFC) reinforced multi-walled carbon nanotubes (MWCNTs)-carbon aerogel (QMCA) and poly(dimethylsiloxane) (PDMS) have been successfully prepared. The QMCA-PDMS composite with a very low loading of MWCNTs (~1.6 wt%) demonstrates enhanced performance in tensile strength (129.6 MPa), modulus (3.41 GPa) and electromagnetic interference (EMI) shielding efficiency (SE) (~16 dB in X-band (8.2-12.4 GHz) region). Compared to the QC (where MWCNTs were simply deposited on the QFCs without forming aerogel networks) based PDMS composite, a ~120%, 330% and 178% increase of tensile strength, modulus, and EMI SE was obtained, respectively. Moreover, the EMI SE of the QMCA-PDMS composite can further reach 20 dB (a SE level needed for commercial applications) with only 2 wt% MWCNTs. Furthermore, the conductivity of the QMCA-PDMS laminate can reach 1.67 S cm-1 even with very low MWCNTs (1.6 wt%), which still remains constant even after 5000 times bending and exhibits an increase of ~170% than that of MWCNT-carbon aerogel (MCA)-PDMS at 20% strain. Such intriguing performances are mainly attributed to their unique networks in QMCA-PDMS composites. In addition, these features can also protect electronics against harm from external forces and EMI, giving the brand-new FCMs huge potential in next-generation devices, like E-skin, robot joints and so on.New flexible and conductive materials (FCMs) comprising a quartz fiber cloth (QFC) reinforced multi-walled carbon nanotubes (MWCNTs)-carbon aerogel (QMCA) and poly(dimethylsiloxane) (PDMS) have been successfully prepared. The QMCA-PDMS composite with a very low loading of MWCNTs (~1.6 wt%) demonstrates enhanced performance in tensile strength (129.6 MPa), modulus (3.41 GPa) and electromagnetic interference (EMI) shielding efficiency (SE) (~16 dB in X-band (8.2-12.4 GHz) region). Compared to the QC (where MWCNTs were simply deposited on the QFCs without forming

  18. Opto-mechanical Analyses for Performance Optimization of Lightweight Grazing-incidence Mirrors

    NASA Technical Reports Server (NTRS)

    Roche, Jacqueline; Kolodsiejczak, Jeffrey; Odell, Stephen; Elsner, Ronald; Weisskopf, Martin; Ramsey, Brian; Gubarev, Mikhail

    2013-01-01

    New technology in grazing-incidence mirror fabrication and assembly is necessary to achieve sub-arcsecond optics for large-area x-ray telescopes. In order to define specifications, an understanding of performance sensitivity to design parameters is crucial. MSFC is undertaking a systematic study to specify a mounting approach, mirror substrate, and testing method. Because the lightweight mirrors are typically flimsy, they are susceptible to significant distortion due to mounting and gravitational forces. Material properties of the mirror substrate along with its thickness and dimensions significantly affect the distortions caused by mounting and gravity. A parametric study of these properties and their relationship to mounting and testing schemes will indicate specifications for the design of the next generation of lightweight grazing-incidence mirrors. Initial results will be reported.

  19. Opto-Mechanical Analyses for Performance Optimization of Lightweight Grazing-Incidence Mirrors

    NASA Technical Reports Server (NTRS)

    Roche, Jacqueline; Kolodziejczak, Jeff; Odell, Steve; Eisner, Ronald; Ramsey, Brian; Gubarev, Mikhail

    2013-01-01

    New technology in grazing-incidence mirror fabrication and assembly is necessary to achieve sub-arcsecond optics for large-area x-ray telescopes. In order to define specifications, an understanding of performance sensitivity to design parameters is crucial. MSFC is undertaking a systematic study to specify a mounting approach, mirror substrate, and testing method. Because the lightweight mirrors are typically flimsy, they are susceptible to significant distortion due to mounting and gravitational forces. Material properties of the mirror substrate along with its thickness and dimensions significantly affect the distortions caused by mounting and gravity. A parametric study of these properties and their relationship to mounting and testing schemes will indicate specifications for the design of the next generation of lightweight grazing-incidence mirrors. Initial results will be reported.

  20. Nanowire templated semihollow bicontinuous graphene scrolls: designed construction, mechanism, and enhanced energy storage performance.

    PubMed

    Yan, Mengyu; Wang, Fengchao; Han, Chunhua; Ma, Xinyu; Xu, Xu; An, Qinyou; Xu, Lin; Niu, Chaojiang; Zhao, Yunlong; Tian, Xiaocong; Hu, Ping; Wu, Hengan; Mai, Liqiang

    2013-12-01

    Graphene scrolls have been widely investigated for applications in electronics, sensors, energy storage, etc. However, graphene scrolls with tens of micrometers in length and with other materials in their cavities have not been obtained. Here nanowire templated semihollow bicontinuous graphene scroll architecture is designed and constructed through "oriented assembly" and "self-scroll" strategy. These obtained nanowire templated graphene scrolls can achieve over 30 μm in length with interior cavities between the nanowire and scroll. It is demonstrated through experiments and molecular dynamic simulations that the semihollow bicontinuous structure construction processes depend on the systemic energy, the curvature of nanowires, and the reaction time. Lithium batteries based on V3O7 nanowire templated graphene scrolls (VGSs) exhibit an optimal performance with specific capacity of 321 mAh/g at 100 mA/g and 87.3% capacity retention after 400 cycles at 2000 mA/g. The VGS also shows a high conductivity of 1056 S/m and high capacity of 162 mAh/g at a large density of 3000 mA/g with only 5 wt % graphene added which are 27 and 4.5 times as high as those of V3O7 nanowires, respectively. A supercapacitor made of MnO2 nanowire templated graphene scrolls (MGSs) also shows a high capacity of 317 F/g at 1A/g, which is over 1.5 times than that of MnO2 nanowires without graphene scrolls. These excellent energy storage capacities and cycling performance are attributed to the unique structure of the nanowire templated graphene scroll, which provides continuous electron and ion transfer channels and space for free volume expansion of nanowires during cycling. This strategy and understanding can be used to synthesize other nanowire templated graphene scroll architectures, which can be extended to other fabrication processes and fields. PMID:24219156