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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. Identifying Minimally Acceptable Interpretive Performance Criteria for Screening Mammography1

    PubMed Central

    Sickles, Edward A.; Monsees, Barbara S.; Bassett, Lawrence W.; Brenner, R. James; Feig, Stephen A.; Smith, Robert A.; Rosenberg, Robert D.; Bogart, T. Andrew; Browning, Sally; Barry, Jane W.; Kelly, Mary M.; Tran, Khai A.; Miglioretti, Diana L.

    2010-01-01

    Purpose: To develop criteria to identify thresholds for minimally acceptable physician performance in interpreting screening mammography studies and to profile the impact that implementing these criteria may have on the practice of radiology in the United States. Materials and Methods: In an institutional review board–approved, HIPAA-compliant study, an Angoff approach was used in two phases to set criteria for identifying minimally acceptable interpretive performance at screening mammography as measured by sensitivity, specificity, recall rate, positive predictive value (PPV) of recall (PPV1) and of biopsy recommendation (PPV2), and cancer detection rate. Performance measures were considered separately. In phase I, a group of 10 expert radiologists considered a hypothetical pool of 100 interpreting physicians and conveyed their cut points of minimally acceptable performance. The experts were informed that a physician’s performance falling outside the cut points would result in a recommendation to consider additional training. During each round of scoring, all expert radiologists’ cut points were summarized into a mean, median, mode, and range; these were presented back to the group. In phase II, normative data on performance were shown to illustrate the potential impact cut points would have on radiology practice. Rescoring was done until consensus among experts was achieved. Simulation methods were used to estimate the potential impact of performance that improved to acceptable levels if effective additional training was provided. Results: Final cut points to identify low performance were as follows: sensitivity less than 75%, specificity less than 88% or greater than 95%, recall rate less than 5% or greater than 12%, PPV1 less than 3% or greater than 8%, PPV2 less than 20% or greater than 40%, and cancer detection rate less than 2.5 per 1000 interpretations. The selected cut points for performance measures would likely result in 18%–28% of interpreting

  5. Criteria for Identifying Radiologists with Acceptable Screening Mammography Interpretive Performance based on Multiple Performance Measures

    PubMed Central

    Miglioretti, Diana L.; Ichikawa, Laura; Smith, Robert A.; Bassett, Lawrence W.; Feig, Stephen A.; Monsees, Barbara; Parikh, Jay R.; Rosenberg, Robert D.; Sickles, Edward A.; Carney, Patricia A.

    2014-01-01

    Objective Using a combination of performance measures, we updated previously proposed criteria for identifying physicians whose performance interpreting screening mammograms may indicate suboptimal interpretation skills. Materials and Methods In this Institutional Review Board-approved, HIPAA-compliant study, six expert breast imagers used a method based on the Angoff approach to update criteria for acceptable mammography performance on the basis of combined performance measures: (Group 1) sensitivity and specificity, for facilities with complete capture of false-negative cancers; and (Group 2) cancer detection rate (CDR), recall rate, and positive predictive value of a recall (PPV1), for facilities that cannot capture false negatives, but have reliable cancer follow-up information for positive mammograms. Decisions were informed by normative data from the Breast Cancer Surveillance Consortium (BCSC). Results Updated, combined ranges for acceptable sensitivity and specificity of screening mammography are: (1) sensitivity ≥80% and specificity ≥85% or (2) sensitivity 75–79% and specificity 88–97%. Updated ranges for CDR, recall rate, and PPV1 are: (1) CDR ≥6/1000, recall rate 3–20%, and any PPV1; (2) CDR 4–6/1000, recall rate 3–15%, and PPV1 ≥3%; or (3) CDR 2.5–4/1000, recall rate 5–12%, and PPV1 3–8%. Using the original criteria, 51% of BCSC radiologists had acceptable sensitivity and specificity; 40% had acceptable CDR, recall rate, and PPV1. Using the combined criteria, 69% had acceptable sensitivity and specificity and 62% had acceptable CDR, recall rate, and PPV1. Conclusion The combined criteria improve previous criteria by considering the inter-relationships of multiple performance measures and broaden the acceptable performance ranges compared to previous criteria based on individual measures. PMID:25794100

  6. 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.

  7. Meditation, mindfulness and executive control: the importance of emotional acceptance and brain-based performance monitoring.

    PubMed

    Teper, Rimma; Inzlicht, Michael

    2013-01-01

    Previous studies have documented the positive effects of mindfulness meditation on executive control. What has been lacking, however, is an understanding of the mechanism underlying this effect. Some theorists have described mindfulness as embodying two facets-present moment awareness and emotional acceptance. Here, we examine how the effect of meditation practice on executive control manifests in the brain, suggesting that emotional acceptance and performance monitoring play important roles. We investigated the effect of meditation practice on executive control and measured the neural correlates of performance monitoring, specifically, the error-related negativity (ERN), a neurophysiological response that occurs within 100 ms of error commission. Meditators and controls completed a Stroop task, during which we recorded ERN amplitudes with electroencephalography. Meditators showed greater executive control (i.e. fewer errors), a higher ERN and more emotional acceptance than controls. Finally, mediation pathway models further revealed that meditation practice relates to greater executive control and that this effect can be accounted for by heightened emotional acceptance, and to a lesser extent, increased brain-based performance monitoring.

  8. 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…

  9. 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,…

  10. 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)

  11. 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.

  12. 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.

  13. Product Delivery Expectations: Hanford LAW Product Performance and Acceptance Tanks Focus Area Task

    SciTech Connect

    Holtzscheiter, E.W.

    1999-04-29

    This task has several facets all aimed at providing technical products that will support the immobilization of Hanford's Low Activity Waste. Since this task breaks new ground in developing predictive capability, a review process external to the technical team is critical for acceptance by the technical community and is key to Hanford's Performance Assessment review process.

  14. 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.

  15. 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…

  16. 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)

  17. Sociocognitive self-regulatory mechanisms governing judgments of the acceptability and likelihood of sport cheating.

    PubMed

    d'Arripe-Longueville, Fabienne; Corrion, Karine; Scoffier, Stéphanie; Roussel, Peggy; Chalabaev, Aïna

    2010-10-01

    This study extends previous psychosocial literature (Bandura et al., 2001, 2003) by examining a structural model of the self-regulatory mechanisms governing the acceptability and likelihood of cheating in a sport context. Male and female adolescents (N = 804), aged 15-20 years, took part in this study. Negative affective self-regulatory efficacy influenced the acceptability and likelihood of cheating through the mediating role of moral disengagement, in females and males. Affective efficacy positively influenced prosocial behavior through moral disengagement or through resistive self-regulatory efficacy and social efficacy, in both groups. The direct effects of affective efficacy on beliefs about cheating were only evident in females. These results extend the findings of Bandura et al. (2001, 2003) to the sport context and suggest that affective and resistive self-regulatory efficacy operate in concert in governing adolescents' moral disengagement and transgressive behaviors in sport.

  18. Causal attribution and affective response as mediated by task performance and self-acceptance.

    PubMed

    Green, T D; Bailey, R C; Zinser, O; Williams, D E

    1994-12-01

    Predictions derived from cognitive consistency theories, self-esteem theories, and ego-serving-bias theory concerning how students would make attributional and affective responses to their academic performance were investigated. 202 university students completed a measure of self-acceptance of their college ability and made attributional and affective responses to an hypothetical examination performance. Analyses showed that students receiving positive feedback perceived greater internal causality and responded with greater positive affect than students receiving negative feedback. Self-acceptance did not moderate the attributions or affective reactions. The results supported the ego-serving-bias theory and provided partial support for self-esteem theory. Findings did not support predictions from cognitive-consistency theory.

  19. 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.

  20. Mechanical performance of disposable surgical needle holders.

    PubMed

    Francis, E H; Towler, M A; Moody, F P; McGregor, W; Himel, H N; Rodeheaver, G T; Edlich, R F

    1992-01-01

    The mechanical performance of disposable Webster surgical needle holders supplied by three different surgical instrument companies was determined by recording the forces (clamping moment) applied by the different needle holder jaws to curved surgical needles. This investigation demonstrated that there was a large variability in the mechanical performance of the disposable needle holders supplied by each surgical instrument company. In addition, the mechanical performance of the disposable needle holder of each surgical instrument company was distinctly different.

  1. 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

  2. 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.

  3. 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.

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

    PubMed

    Chiuzbăian, 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 μm(2) focal spot source with full polarization control.

  5. 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.

  6. Acceptance Plan and Performance Measurement Methodology for the ITER Cryoline System

    NASA Astrophysics Data System (ADS)

    Badgujar, S.; Bonneton, M.; Shah, N.; Chalifour, M.; Chang, H.-S.; Fauve, E.; Forgeas, A.; Navion-Maillot, N.; Sarkar, B.

    The cryoline (CL) systemof ITER consists of a complex network of vacuum insulated multi and single process pipe lines distributed over three different areas with a total length of about 5 km. The thermal performance of the CL system will be measured during the final acceptance tests using the ITER cryoplant and cryo-distribution (CD) infrastructure. The method proposed is based on temperature measurementsof a small calibrated cryogenic helium flow through lines. Thecryoplant will be set to establish constant pressure and temperature whereas dedicated heater and valves in the CD will be used to generate stable mass flow rate.

  7. Alberta's Performance-Based Funding Mechanism.

    ERIC Educational Resources Information Center

    Barnetson, Bob

    This paper provides an overview of the performance indicator-based accountability and funding mechanism implemented in the higher education system of Alberta, Canada. The paper defines the terms accountability and regulation, examines the use of performance indicators to demonstrate accountability, and explains how performance indicator-based…

  8. Psychological flexibility and catastrophizing as associated change mechanisms during online Acceptance & Commitment Therapy for chronic pain.

    PubMed

    Trompetter, Hester R; Bohlmeijer, Ernst T; Fox, Jean-Paul; Schreurs, Karlein M G

    2015-11-01

    The underlying mechanisms of the effectiveness of cognitive behavioural interventions for chronic pain need further clarification. The role of, and associations between, pain-related psychological flexibility (PF) and pain catastrophizing (PC) were examined during a randomized controlled trial on internet-based Acceptance & Commitment Therapy (ACT) for chronic pain. We assessed (1) the unique and combined indirect effects of PF and PC on outcomes, and (2) the causality of relations between PF, PC and the primary outcome pain interference in daily life (MPI) during ACT. A total of 238 pain sufferers were allocated to either ACT, a control condition on Expressive Writing, or a waiting list condition. Non-parametric cross-product of coefficients mediational analyses and cross-lagged panel designs were applied. Compared to control conditions, both baseline to post-intervention changes in PF and PC seemed to uniquely mediate baseline to three-month follow-up changes in pain interference and psychological distress. Only PF mediated changes in pain intensity. Indirect effects were twice as large for PF (κ2 = .09-.19) than for PC (κ² PCS = .05-.10). Further assessment of changes during ACT showed, however, that only PF, and not PC, predicted subsequent changes in MPI, while early and late changes in both PF and PC predicted later changes in each other. In conclusion, only PF functioned as a direct, causal working mechanism during ACT, with larger indirect effects that occurred earlier than changes in PC. Additionally, PC may function as an indirect mechanism of change during ACT for chronic pain via its direct influence on PF.

  9. 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…

  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. Mindful acceptance dampens neuroaffective reactions to external and rewarding performance feedback.

    PubMed

    Teper, Rimma; Inzlicht, Michael

    2014-02-01

    Previous research on mindfulness has suggested that individuals high in trait mindfulness show heightened sensitivity to visceral and internally generated stimuli. However, when mindful individuals are exposed to external stimuli-such as pictures or faces-their emotional responses are typically attenuated. In the current study, we tested how trait mindfulness relates to reactivity in response to a different type of external stimulus, namely, performance feedback. Using electroencephalography, we recorded participants' neuroaffective reactions to rewarding, aversive, and neutral feedback, as indexed by the feedback-related negativity (FRN). The FRN is a brain response that peaks approximately 250 ms after feedback presentation, and it is thought to differentiate feedback indicating favorable versus unfavorable outcomes. Our findings suggest trait mindfulness predicts less differentiation of rewarding from neutral feedback, but does not predict brain differentiation of aversive from neutral feedback. This was the case particularly for individuals who scored highly on the "acceptance" facet of mindfulness, a facet that assesses the nonjudgmental acceptance of thoughts and emotions. We discuss the implications of these findings for current theory on mindfulness and emotion regulation.

  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. 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.

  16. 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.

  17. 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)…

  18. 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…

  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. 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…

  1. 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.

  2. 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

  3. Popularity, Social Acceptance, and Aggression in Adolescent Peer Groups: Links with Academic Performance and School Attendance

    ERIC Educational Resources Information Center

    Schwartz, David; Gorman, Andrea Hopmeyer; Nakamoto, Jonathan; McKay, Tara

    2006-01-01

    This article reports a short-term longitudinal study focusing on popularity and social acceptance as predictors of academic engagement for a sample of 342 adolescents (approximate average age of 14). These youths were followed for 4 consecutive semesters. Popularity, social acceptance, and aggression were assessed with a peer nomination …

  4. Mechanical performance of PPy helix tube microactuator

    NASA Astrophysics Data System (ADS)

    Bahrami Samani, Mehrdad; Spinks, Geoffrey M.; Cook, Christopher

    2004-02-01

    Conducting polymer actuators with favourable properties such as linearity, high power density and compliance are of increasing demand in micro applications. These materials generate forces over two times larger than produced by mammalian skeletal muscles. They operate to convert electro chemical energy to mechanical stress and strain. On the other hand, the application of conducting polymers is limited by the lack of a full description of the relation between four essential parameters: stress, strain, voltage and current. In this paper, polypyrrole helix tube micro actuator mechanical characteristics are investigated. The electrolyte is propylene carbonate and the dopant is TBA. PF6. The experiments are both in isotonic and isometric conditions and the input parameters are both electrical and mechanical. A dual mode force and length control and potentiostat / galvanostat are utilized for this purpose. Ultimately, the viscoelastic behaviour of the actuator is presented in this paper by a standard stress relaxation test. The effect of electrical stimulus on mechanical parameters is also explored by cyclic voltametry at different scan rates to obtain the best understanding of the actuation mechanism. The results demonstrate that the linear viscoelastic model, which performed well on conducting polymer film actuators, has to be modified to explain the mechanical behaviour of PPy helix tube fibre micro actuators. Secondly, the changes in mechanical properties of PPy need to be considered when modelling electromechanical behaviour.

  5. Mindfulness and acceptance-based group therapy and traditional cognitive behavioral group therapy for social anxiety disorder: Mechanisms of change.

    PubMed

    Kocovski, Nancy L; Fleming, Jan E; Hawley, Lance L; Ho, Moon-Ho Ringo; Antony, Martin M

    2015-07-01

    The present study investigated mechanisms of change for two group treatments for social anxiety disorder (SAD): cognitive behavioral group therapy (CBGT) and mindfulness and acceptance-based group therapy (MAGT). Participants were treatment completers (n = 37 for MAGT, n = 32 for CBGT) from a randomized clinical trial. Cognitive reappraisal was the hypothesized mechanism of change for CBGT. Mindfulness and acceptance were hypothesized mechanisms of change for MAGT. Latent difference score (LDS) analysis results demonstrate that cognitive reappraisal coupling (in which cognitive reappraisal is negatively associated with the subsequent rate of change in social anxiety) had a greater impact on social anxiety for CBGT than MAGT. The LDS bidirectional mindfulness model (mindfulness predicts subsequent change in social anxiety; social anxiety predicts subsequent change in mindfulness) was supported for both treatments. Results for acceptance were less clear. Cognitive reappraisal may be a more important mechanism of change for CBGT than MAGT, whereas mindfulness may be an important mechanism of change for both treatments.

  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.

  8. 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…

  9. Performance of 5000 students in introductory mechanics

    NASA Astrophysics Data System (ADS)

    Caballero, Marcos; Bujak, Keith; Kohlmyer, Matthew; Catrambone, Richard; Marr, M. Jackson; Schatz, Michael

    2009-11-01

    We present the performance of nearly 5000 students on a standardized assessment of force and motion (Force Concept Inventory) for two fundamentally different physics curricula; a traditional course based on the Knight text and a reform course based on the text of Chabay and Sherwood, Matter and Interactions (M&I). The traditional course is a standard physics curriculum with particular emphasis on constant force motion. The M&I course is a modern approach to physics instruction with computer modeling and an emphasis on the generality and dynamics of Newton's Second Law. We find poorer performance for students who have taken the M&I course as compared to students taking the standard course. This under-performance is consistent despite the superior performance by M&I students on common exam problems in other areas of mechanics. We offer explanations for this consistent under-performance in the realm of force and motion as well as some results from recent work to combat these misconceptions in the M&I course.

  10. 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

  11. 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.

  12. 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

  13. ACCESS: Thermal Mechanical Design, Performance, and Status

    NASA Astrophysics Data System (ADS)

    Kaiser, Mary Elizabeth; Morris, M. J.; McCandliss, S. R.; Rauscher, B. J.; Kimble, R. A.; Kruk, J. W.; Wright, E. L.; Bohlin, R.; Kurucz, R. L.; Riess, A. G.; Pelton, R.; Deustua, S. E.; Dixon, W. V.; Sahnow, D. J.; Benford, D. J.; Gardner, J. P.; Feldman, P. D.; Moos, H. W.; Lampton, M.; Perlmutter, S.; Woodgate, B. E.

    2014-01-01

    Systematic errors associated with astrophysical data used to probe fundamental astrophysical questions, such as SNeIa observations used to constrain dark energy theories, are now rivaling and exceeding the statistical errors associated with these measurements. ACCESS: Absolute Color Calibration Experiment for Standard Stars is a series of rocket-borne sub-orbital missions and ground-based experiments designed to enable improvements in the precision of the astrophysical flux scale through the transfer of absolute laboratory detector standards from the National Institute of Standards and Technology (NIST) to a network of stellar standards with a calibration accuracy of 1% and a spectral resolving power of 500 across the 0.35 - 1.7μm bandpass. Achieving this level of accuracy requires characterization and stability of the instrument and detector including a thermal background that contributes less than 1% to the flux per resolution element in the NIR. We will present the instrument and calibration status with a focus on the thermal mechanical design and associated performance data. The detector control and performance will be presented in a companion poster (Morris, et al). NASA APRA sounding rocket grant NNX08AI65G supports this work.

  14. 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.

  15. The Adaptive Aerosol Delivery System in a Telehealth Setting: Patient Acceptance, Performance and Feasibility

    PubMed Central

    Denyer, John; Dodd, Mary; Dyche, Tony; Webb, Kevin; Weller, Peter; Stableforth, David

    2010-01-01

    Abstract Background The telehealth service is one of the fastest growing healthcare segments. It is increasingly utilizing computer technology and telecommunication equipment to either provide continuous vital sign monitoring or facilitate patient care at home, rather than relying solely on in-person care. Methods We conducted a 6-week open study in nineteen patients with cystic fibrosis enrolled from three centers, to investigate patient perception of a telehealth enabled nebulizer system (Prodose Adaptive Aerosol Delivery [AAD] System), which enabled the doorstep delivery of repeat medication. Results The results showed that patient confidence in the device and perception of ease of use was high with no significant change between the start and end of the trial. Views on the home delivery of medication were split between ‘great’ and ‘inconvenient.’ However, if the delivery system had been more flexible and delivered all the patients' drugs, the majority of patients would have had their medication delivered in this way. Conclusions The trial showed that it was possible to build telehealth technology into an advanced nebulizer system, and that patient acceptance of the technology was unlikely to be a barrier to the adoption of such a telehealth system. PMID:20373906

  16. Using session-by-session measurement to compare mechanisms of action for acceptance and commitment therapy and cognitive therapy.

    PubMed

    Forman, Evan M; Chapman, Jason E; Herbert, James D; Goetter, Elizabeth M; Yuen, Erica K; Moitra, Ethan

    2012-06-01

    Debate continues about the extent to which postulated mechanisms of action of cognitive behavior therapies (CBT), including standard CBT (i.e., Beckian cognitive therapy [CT]) and acceptance and commitment therapy (ACT) are supported by mediational analyses. Moreover, the distinctiveness of CT and ACT has been called into question. One contributor to ongoing uncertainty in this arena is the lack of time-varying process data. In this study, 174 patients presenting to a university clinic with anxiety or depression who had been randomly assigned to receive either ACT or CT completed an assessment of theorized mediators and outcomes before each session. Hierarchical linear modeling of session-by-session data revealed that increased utilization of cognitive and affective change strategies relative to utilization of psychological acceptance strategies mediated outcome for CT, whereas for ACT the mediation effect was in the opposite direction. Decreases in self-reported dysfunctional thinking, cognitive "defusion" (the ability to see one's thoughts as mental events rather than necessarily as representations of reality), and willingness to engage in behavioral activity despite unpleasant thoughts or emotions were equivalent mediators across treatments. These results have potential implications for the theoretical arguments behind, and distinctiveness of, CT and ACT.

  17. 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.

  18. 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…

  19. 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…

  20. The Effect of Aptitude and Experience on Mechanical Job Performance.

    ERIC Educational Resources Information Center

    Mayberry, Paul W.; Carey, Neil B.

    1997-01-01

    The validity of the Armed Services Vocational Aptitude Battery (ASVAB) in predicting mechanical job performance was studied with 891 automotive and 522 helicopter mechanics. The mechanical maintenance component of the ASVAB predicted hands-on performance, job knowledge, and training grades quite well, but experience was more predictive of…

  1. Towards more complete specifications for acceptable analytical performance - a plea for error grid analysis.

    PubMed

    Krouwer, Jan S; Cembrowski, George S

    2011-07-01

    Abstract We examine limitations of common analytical performance specifications for quantitative assays. Specifications can be either clinical or regulatory. Problems with current specifications include specifying limits for only 95% of the results, having only one set of limits that demarcate no harm from minor harm, using incomplete models for total error, not accounting for the potential of user error, and not supplying sufficient protocol requirements. Error grids are recommended to address these problems as error grids account for 100% of the data and stratify errors into different severity categories. Total error estimation from a method comparison can be used to estimate the inner region of an error grid, but the outer region needs to be addressed using risk management techniques. The risk management steps, foreign to many in laboratory medicine, are outlined.

  2. 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.

  3. Automotive Mechanics Occupational Performance Survey. Interim Report.

    ERIC Educational Resources Information Center

    Borcher, Sidney D.; Leiter, Paul B.

    The purpose of this federally-funded interim report is to present the results of a task inventory analysis survey of automotive mechanics completed by project staff within the Instructional Systems Design Program at the Center for Vocational and Technical Education. Intended for use in curriculum development for vocational education programs in…

  4. 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.

  5. 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…

  6. 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…

  7. 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

  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. Photocatalytic degradation of rhodamine B by Bi(2)WO(6) with electron accepting agent under microwave irradiation: mechanism and pathway.

    PubMed

    He, Zhong; Sun, Cheng; Yang, Shaogui; Ding, Youchao; He, Huan; Wang, Zhiliang

    2009-03-15

    Bi(2)WO(6) was successfully synthesized by a facile hydrothermal method, and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET. As a result, Bi(2)WO(6) crystals displayed mainly square-plate-like morphologies with a short edge and the average crystalline size was in the range of 50-150 nm. Then microwave-assisted photocatalytic degradation of rhodamine B (RhB) using Bi(2)WO(6) was investigated. The results illustrated that RhB (10 mg/L) was bleached effectively and the removal efficiency was about 94% in 60 min. Effect of electron accepting agent (air, H(2)O(2)) on the degradation efficiency of RhB was also examined. Degradation intermediates of RhB in the presence of H(2)O(2) were identified by LC/MS/MS and GC/MS. All five N-de-ethylated intermediates were monitored by LC/MS/MS easily, and seven organic acids such as succinic acid, benzoic acid, adipic acid, 3-hydroxybenzoic acid, phthalic acid, etc., were also detected by GC/MS. The possible degradation mechanism of RhB in the presence of H(2)O(2) included four processes: N-de-ethylation, chromophore cleavage, opening-ring and mineralization, which coexisted in microwave-assisted photocatalytic system.

  10. 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.

  11. 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.

  12. An evaluation of the performance and acceptability of three LED fluorescent microscopes in Zambia: lessons learnt for scale-up.

    PubMed

    Turnbull, Eleanor R; Kaunda, Kaunda; Harris, Jennifer B; Kapata, Nathan; Muvwimi, Mweemba W; Kruuner, Annika; Henostroza, German; Reid, Stewart E

    2011-01-01

    The World Health Organization recommends the roll-out of light-emitting diode (LED) fluorescent microscopes (FM) as an alternative to light microscopes in resource-limited settings. We evaluated the acceptability and performance of three LED FMs after a short orientation among laboratory technicians from government health centers in Zambia. Sixteen technicians with varied light microscopy experience were oriented to FMs and divided into groups; each group read a different set of 40 slides on each LED FM (Primo Star iLED™, Lumin™, FluoLED™) and on a reference mercury-vapor FM (Olympus BX41TF). Slide reading times were recorded. An experienced FM technician examined each slide on the Olympus BX41TF. Sensitivity and specificity compared to TB culture were calculated. Misclassification compared to the experienced technician and inter-rater reliability between trainees was assessed. Trainees rated microscopes on technical aspects. Primo Star iLED™, FluoLED™ and Olympus BX41TF had comparable sensitivities (67%, 65% and 65% respectively), with the Lumin™ significantly worse (56%; p<0.05). Specificity was low for trainees on all microscopes (75.9%) compared to the experienced technician on Olympus BX41TF (100%). Primo Star iLED™ had significantly less misclassification (21.1% p<0.05) than FluoLED™ (26.5%) and Lumin™ (26.8%) and significantly higher inter-rater reliability (0.611; p<0.05), compared to FluoLED™ (0.523) and Lumin™ (0.492). Slide reading times for LED FMs were slower than the reference, but not significantly different from each other. Primo Star iLED™ rated highest in acceptability measures, followed by FluoLED™ then Lumin™. Primo Star iLED™ was consistently better than FluoLED™ and Lumin™, and performed comparably to the Olympus BX41TF in all analyses, except reading times. The Lumin™ compared least favorably and was thought unacceptable for use. Specificity and inter-rater reliability were low for all microscopes

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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…

  18. Feasibility, performance, and acceptability of the Wisebag™ for potential monitoring of daily gel applicator use in Durban, South Africa

    PubMed Central

    van der Straten, Ariane; Montgomery, Elizabeth; Pillay, Diantha; Cheng, Helen; Naidoo, Anushka; Cele, Zakhele; Naidoo, Kalendri; Hartmann, Miriam; Piper, Jeanna; Nair, Gonasagrie

    2012-01-01

    The Wisebag™, a lunchbag-style container with an electronic events-monitoring system, was designed as a real-time indirect objective measure of microbicide gel use. Due to cost, alternative functionalities (i.e. use of offline and dummy versions) were explored. We conducted a three-arm, double-blinded pilot study among fifty HIV-negative women in Durban, South Africa to assess participant adherence and Wisebag acceptability and performance. Participants were randomized 2:2:1 to Wisebag with online (events transmitted via cellular signal in real-time), offline (events stored in device memory) or inactive “dummy” devices. Participants were instructed to open the Wisebag daily for two weeks, retrieve a study sticker and affix it on a diary card. All participants completed the study. At exit, 94% did not know which device they had received, nor could they differentiate the Wisebag types when presented with the three options. Five offline devices failed (no data recorded). Per Wisebag events, 26% of women were perfectly adherent compared to 48% by self-report and 46% per diary card. Of reported non-adherence, 92% did not open the Wisebag (travelling or forgot) and 22% opened Wisebag >1x/day (curiosity). Participants liked and were comfortable carrying Wisebag. Successful blinding will allow inclusion of offline and/or dummy Wisebags in future study designs. Perfect adherence by opening events was significantly lower than by self-report, highlighting the importance of objective measures of adherence in clinical trials. Additional studies to validate Wisebag data with actual products, with and without SMS and online functionality, in different populations and settings, and in comparison to biomarkers are warranted. PMID:23054042

  19. Energy transfer performance of mechanical nanoresonators coupled with electromagnetic fields

    PubMed Central

    2012-01-01

    We study the energy transfer performance in electrically and magnetically coupled mechanical nanoresonators. Using the resonant scattering theory, we show that magnetically coupled resonators can achieve the same energy transfer performance as for their electrically coupled counterparts or even outperform them within the scale of interest. Magnetic and electric coupling are compared in the nanotube radio, a realistic example of a nano-scale mechanical resonator. The energy transfer performance is also discussed for a newly proposed bio-nanoresonator composed of magnetosomes coated with a net of protein fibers. PMID:23075029

  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. 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

  2. Performance pressure and caffeine both affect cognitive performance, but likely through independent mechanisms.

    PubMed

    Boere, Julia J; Fellinger, Lizz; Huizinga, Duncan J H; Wong, Sebastiaan F; Bijleveld, Erik

    2016-02-01

    A prevalent combination in daily life, performance pressure and caffeine intake have both been shown to impact people's cognitive performance. Here, we examined the possibility that pressure and caffeine affect cognitive performance via a shared pathway. In an experiment, participants performed a modular arithmetic task. Performance pressure and caffeine intake were orthogonally manipulated. Findings indicated that pressure and caffeine both negatively impacted performance. However, (a) pressure vs. caffeine affected performance on different trial types, and (b) there was no hint of an interactive effect. So, though the evidence is indirect, findings suggest that pressure and caffeine shape performance via distinct mechanisms, rather than a shared one.

  3. Infrared observations of the mechanical performance of tennis strings

    NASA Astrophysics Data System (ADS)

    Luong, Minh Phong

    2001-03-01

    The paper aims to illustrate three advantages of infrared thermography as a non-destructive, non-contact and real time technique (a) to detect the occurrence of intrinsic dissipation localization, (b) to observe the progressive damage processes and mechanisms of tennis string failure, and (c) to determine the optimal tension for each type of string. Experimental results evidence a limit of acceptable damage beyond which strings will fail due to the coalescence of defects and/or weakness zones. In addition, owing to the thermomechanical coupling, this technique provides a simple means for evaluating the wear resistance of strings of interest for skilled tennis players who impart on the ball a great amount of spin combined with a high stroke velocity.

  4. 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.

  5. 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…

  6. 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.

  7. Mechanical determinants of 100-m sprint running performance.

    PubMed

    Morin, Jean-Benoît; Bourdin, Muriel; Edouard, Pascal; Peyrot, Nicolas; Samozino, Pierre; Lacour, Jean-René

    2012-11-01

    Sprint mechanics and field 100-m performances were tested in 13 subjects including 9 non-specialists, 3 French national-level sprinters and a world-class sprinter, to further study the mechanical factors associated with sprint performance. 6-s sprints performed on an instrumented treadmill allowed continuous recording of step kinematics, ground reaction forces (GRF), and belt velocity and computation of mechanical power output and linear force-velocity relationships. An index of the force application technique was computed as the slope of the linear relationship between the decrease in the ratio of horizontal-to-resultant GRF and the increase in velocity. Mechanical power output was positively correlated to mean 100-m speed (P < 0.01), as was the theoretical maximal velocity production capability (P < 0.011), whereas the theoretical maximal force production capability was not. The ability to apply the resultant force backward during acceleration was positively correlated to 100-m performance (r (s) > 0.683; P < 0.018), but the magnitude of resultant force was not (P = 0.16). Step frequency, contact and swing time were significantly correlated to acceleration and 100-m performance (positively for the former, negatively for the two latter, all P < 0.05), whereas aerial time and step length were not (all P > 0.21). Last, anthropometric data of body mass index and lower-limb-to-height ratio showed no significant correlation with 100-m performance. We concluded that the main mechanical determinants of 100-m performance were (1) a "velocity-oriented" force-velocity profile, likely explained by (2) a higher ability to apply the resultant GRF vector with a forward orientation over the acceleration, and (3) a higher step frequency resulting from a shorter contact time. PMID:22422028

  8. Mental imagery in music performance: underlying mechanisms and potential benefits.

    PubMed

    Keller, Peter E

    2012-04-01

    This paper examines the role of mental imagery in music performance. Self-reports by musicians, and various other sources of anecdotal evidence, suggest that covert auditory, motor, and/or visual imagery facilitate multiple aspects of music performance. The cognitive and motor mechanisms that underlie such imagery include working memory, action simulation, and internal models. Together these mechanisms support the generation of anticipatory images that enable thorough action planning and movement execution that is characterized by efficiency, temporal precision, and biomechanical economy. In ensemble performance, anticipatory imagery may facilitate interpersonal coordination by enhancing online predictions about others' action timing. Overlap in brain regions subserving auditory imagery and temporal prediction is consistent with this view. It is concluded that individual differences in anticipatory imagery may be a source of variation in expressive performance excellence and the quality of ensemble cohesion. Engaging in effortful musical imagery is therefore justified when artistic perfection is the goal.

  9. Mechanisms to create high performance pseudo-ductile composites

    NASA Astrophysics Data System (ADS)

    Wisnom, M. R.

    2016-07-01

    Current composites normally fail suddenly and catastrophically, which is an undesirable characteristic for many applications. This paper describes work as part of the High Performance Ductile Composite Technology programme (HiPerDuCT) on mechanisms to overcome this key limitation and introduce pseudo-ductility into the failure process.

  10. 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.

  11. Face-induced expectancies influence neural mechanisms of performance monitoring.

    PubMed

    Osinsky, Roman; Seeger, Jennifer; Mussel, Patrick; Hewig, Johannes

    2016-04-01

    In many daily situations, the consequences of our actions are predicted by cues that are often social in nature. For instance, seeing the face of an evaluator (e.g., a supervisor at work) may activate certain evaluative expectancies, depending on the history of prior encounters with that particular person. We investigated how such face-induced expectancies influence neurocognitive functions of performance monitoring. We recorded an electroencephalogram while participants completed a time-estimation task, during which they received performance feedback from a strict and a lenient evaluator. During each trial, participants first saw the evaluator's face before performing the task and, finally, receiving feedback. Therefore, faces could be used as predictive cues for the upcoming evaluation. We analyzed electrocortical signatures of performance monitoring at the stages of cue processing, task performance, and feedback reception. Our results indicate that, at the cue stage, seeing the strict evaluator's face results in an anticipatory preparation of fronto-medial monitoring mechanisms, as reflected by a sustained negative-going amplitude shift (i.e., the contingent negative variation). At the performance stage, face-induced expectancies of a strict evaluation rule led to increases of early performance monitoring signals (i.e., frontal-midline theta power). At the final stage of feedback reception, violations of outcome expectancies differentially affected the feedback-related negativity and frontal-midline theta power, pointing to a functional dissociation between these signatures. Altogether, our results indicate that evaluative expectancies induced by face-cues lead to adjustments of internal performance monitoring mechanisms at various stages of task processing.

  12. Face-induced expectancies influence neural mechanisms of performance monitoring.

    PubMed

    Osinsky, Roman; Seeger, Jennifer; Mussel, Patrick; Hewig, Johannes

    2016-04-01

    In many daily situations, the consequences of our actions are predicted by cues that are often social in nature. For instance, seeing the face of an evaluator (e.g., a supervisor at work) may activate certain evaluative expectancies, depending on the history of prior encounters with that particular person. We investigated how such face-induced expectancies influence neurocognitive functions of performance monitoring. We recorded an electroencephalogram while participants completed a time-estimation task, during which they received performance feedback from a strict and a lenient evaluator. During each trial, participants first saw the evaluator's face before performing the task and, finally, receiving feedback. Therefore, faces could be used as predictive cues for the upcoming evaluation. We analyzed electrocortical signatures of performance monitoring at the stages of cue processing, task performance, and feedback reception. Our results indicate that, at the cue stage, seeing the strict evaluator's face results in an anticipatory preparation of fronto-medial monitoring mechanisms, as reflected by a sustained negative-going amplitude shift (i.e., the contingent negative variation). At the performance stage, face-induced expectancies of a strict evaluation rule led to increases of early performance monitoring signals (i.e., frontal-midline theta power). At the final stage of feedback reception, violations of outcome expectancies differentially affected the feedback-related negativity and frontal-midline theta power, pointing to a functional dissociation between these signatures. Altogether, our results indicate that evaluative expectancies induced by face-cues lead to adjustments of internal performance monitoring mechanisms at various stages of task processing. PMID:26527096

  13. Effect of marinating time and low pH on marinade performance and sensory acceptability of poultry meat.

    PubMed

    Yusop, Salma M; O'Sullivan, Maurice G; Kerry, John F; Kerry, Joseph P

    2010-08-01

    The effects of marinating time (30, 60, 120 and 180 min) and acidic marinade pH (3.0, 3.2, 3.4, 3.6, 3.8, 4.0 and 4.2) on the instrumental and sensory properties of cooked Chinese-style marinated chicken were investigated. With increasing marinating time up to 180 min, a significant (P<0.05) increase in surface redness (a* value) and the dark pink sensory attribute was observed, along with a corresponding decrease in lightness (L* value) and colour penetration. Increased marinating times of 120-180 min were found to produce more acceptable end products with increased scores for colour, aroma and flavour attributes. Marinade uptake was greater at higher marinade pH levels of 3.8, 4.0 and 4.2, with the highest marinade uptake (3.34%) recorded at pH 4.0. As changes to core meat pH were not observed, the effect of marinating time (up to 180 min) and marinade pH on the instrumental and sensory properties of Chinese-style marinated chicken were located principally at the surface of samples. Consumers considered surface colour as contributing to acceptability of marinated chicken to a greater degree compared to colour penetration. PMID:20416811

  14. Effect of marinating time and low pH on marinade performance and sensory acceptability of poultry meat.

    PubMed

    Yusop, Salma M; O'Sullivan, Maurice G; Kerry, John F; Kerry, Joseph P

    2010-08-01

    The effects of marinating time (30, 60, 120 and 180 min) and acidic marinade pH (3.0, 3.2, 3.4, 3.6, 3.8, 4.0 and 4.2) on the instrumental and sensory properties of cooked Chinese-style marinated chicken were investigated. With increasing marinating time up to 180 min, a significant (P<0.05) increase in surface redness (a* value) and the dark pink sensory attribute was observed, along with a corresponding decrease in lightness (L* value) and colour penetration. Increased marinating times of 120-180 min were found to produce more acceptable end products with increased scores for colour, aroma and flavour attributes. Marinade uptake was greater at higher marinade pH levels of 3.8, 4.0 and 4.2, with the highest marinade uptake (3.34%) recorded at pH 4.0. As changes to core meat pH were not observed, the effect of marinating time (up to 180 min) and marinade pH on the instrumental and sensory properties of Chinese-style marinated chicken were located principally at the surface of samples. Consumers considered surface colour as contributing to acceptability of marinated chicken to a greater degree compared to colour penetration.

  15. Hypohydration and Human Performance: Impact of Environment and Physiological Mechanisms.

    PubMed

    Sawka, Michael N; Cheuvront, Samuel N; Kenefick, Robert W

    2015-11-01

    Body water losses of >2 % of body mass are defined as hypohydration and can occur from sweat loss and/or diuresis from both cold and altitude exposure. Hypohydration elicits intracellular and extracellular water loss proportionate to water and solute deficits. Iso-osmotic hypovolemia (from cold and high-altitude exposure) results in greater plasma loss for a given water deficit than hypertonic hypovolemia from sweat loss. Hypohydration does not impair submaximal intensity aerobic performance in cold-cool environments, sometimes impairs aerobic performance in temperate environments, and usually impairs aerobic performance in warm-hot environments. Hypohydration begins to impair aerobic performance when skin temperatures exceed 27 °C, and with each additional 1 °C elevation in skin temperature there is a further 1.5 % impairment. Hypohydration has an additive effect on impairing aerobic performance in warm-hot high-altitude environments. A commonality of absolute hypovolemia (from plasma volume loss) combined with relative hypovolemia (from tissue vasodilation) is present when aerobic performance is impaired. The decrement in aerobic exercise performance due to hypohydration is likely due to multiple physiological mechanisms, including cardiovascular strain acting as the 'lynchpin', elevated tissue temperatures, and metabolic changes which are all integrated through the CNS to reduce motor drive to skeletal muscles.

  16. A Proposed Alternative Mechanism of Action for Transmyocardial Revascularization Prefaced by a Review of the Accepted Explanations

    PubMed Central

    Cardarelli, Marcelo

    2006-01-01

    Laser transmyocardial revascularization, a procedure originally intended to simulate the perfusion mechanism of the reptilian heart, has evolved into an effective but poorly understood treatment for angina when traditional revascularization is not an option. Herein, we review the explanations that have been proposed over the years and suggest a new one. We hypothesize that the long-term mechanism of action of transmyocardial revascularization is the redistribution of stresses on the ventricular wall through the creation of fibrous transmyocardial scars, which penetrate the various layers of muscle that surround the left ventricular cavity. The stress redistribution of a load in an otherwise unchanged ventricular wall reduces the wall stress per unit of wall volume, which in turn decreases the workload for the hyperkinetic compensating areas. This reduces both oxygen demand and local metabolite production, lowering the level of angina. PMID:17215963

  17. 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

  18. 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.

  19. 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.

  20. Exemplar models as a mechanism for performing Bayesian inference.

    PubMed

    Shi, Lei; Griffiths, Thomas L; Feldman, Naomi H; Sanborn, Adam N

    2010-08-01

    Probabilistic models have recently received much attention as accounts of human cognition. However, most research in which probabilistic models have been used has been focused on formulating the abstract problems behind cognitive tasks and their optimal solutions, rather than on mechanisms that could implement these solutions. Exemplar models are a successful class of psychological process models in which an inventory of stored examples is used to solve problems such as identification, categorization, and function learning. We show that exemplar models can be used to perform a sophisticated form of Monte Carlo approximation known as importance sampling and thus provide a way to perform approximate Bayesian inference. Simulations of Bayesian inference in speech perception, generalization along a single dimension, making predictions about everyday events, concept learning, and reconstruction from memory show that exemplar models can often account for human performance with only a few exemplars, for both simple and relatively complex prior distributions. These results suggest that exemplar models provide a possible mechanism for implementing at least some forms of Bayesian inference. PMID:20702863

  1. 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.

  2. Integrated design of castings: effect of porosity on mechanical performance

    NASA Astrophysics Data System (ADS)

    Hardin, R. A.; Beckermann, C.

    2012-07-01

    Porosity can significantly reduce the strength and durability of castings in service. An integrated design approach has been developed where casting simulation is combined with mechanical performance simulations. Predictions of the porosity distribution from the casting process simulation are transferred to and used in stress and fatigue life simulations. Thus, the effect of casting quality on service performance can be evaluated. Results of a study are presented where the measured porosity distribution in cast steel specimens is transferred to an elasto-plastic finite-element stress analysis model. Methods are developed to locally reduce the mechanical properties according to the porosity present, without having to resolve individual pores. Plastic deformation is modeled using porous metal plasticity theory. The predictions are compared to tensile measurements performed on the specimens. The complex deformations and the reductions in the ductility of the specimens due to porosity are predicted well. The predicted stresses are transferred to a fatigue analysis code that takes the porosity distribution into account as well. The measured and predicted fatigue lives are also in good agreement. Finally, the results of a case study are presented that illustrate the utility of the present integrated approach in optimizing the design of a steel casting.

  3. 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

  4. Team assembly mechanisms determine collaboration network structure and team performance.

    PubMed

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

    2005-04-29

    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.

  5. 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

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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

  11. "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…

  12. 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.

  13. 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.

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

    SciTech Connect

    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.

  15. 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.

  16. Design of mechanical components for long-term performance

    NASA Technical Reports Server (NTRS)

    Salvinski, R. J.

    1974-01-01

    Review of the results of a NASA program designed to study advanced techniques for determining the long-term performance of rocket engine components. Aging and operational degradation mechanisms of metal valve seats are identified. Characterization of metal valve seat surfaces by optical signature analysis is described. The results of the development of a long-life 'zero leakage' metal valve seal designed to avoid failure by contamination, stress/strain, fatigue, and the deterioration of the surface by wear is reported. An analysis of a specific seat design showed that material strain prevention along all axes would prevent these failures. The design provided for refurbishment of the sealing surfaces during each valve cycle, thereby preventing cumulative surface damage.

  17. 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.

  18. 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.

  19. Mass transfer mechanisms in high-performance membrane dialyzers.

    PubMed

    Yamashita, Akihiro C

    2011-01-01

    Four dialyzers with super-high-flux membrane or high-performance membrane (HPM) with varying packing density of the hollow fiber (PDF) from 29.6 to 53.1% were investigated in aqueous in vitro experiments for the purpose of identifying the mass transfer mechanism for three test solutes. Clearances for relatively small test solutes (creatinine and vitamin B(12)) slowly increased with PDF and reached plateau since mass transfer mechanism of these solutes was diffusion limited. However, since unlike classic high-flux dialyzers a considerable amount of internal filtration ( > 20 ml/min) should occur in super-high-flux dialyzers even under relatively reduced blood and dialysis fluid flow rates, Q(B) = 200 ml/min and Q(D) = 500 ml/min, it should contribute to enhance the rate of mass transfer especially for those solutes that cannot be easily removed by diffusion, such as β(2)-microglobulin or even larger toxic substances. For dialyzers with the HPM a module design becomes even more important for developing novel commercial products.

  20. Determinations of performance and mechanical efficiency in nordic skiing.

    PubMed Central

    Niinimaa, V.; Shephard, R. J.; Dyon, M.

    1979-01-01

    Determinants of performance and mechanical efficiency of effort have been made on a group of ten male nordic skiers, all participants in the University of Toronto ski-team. The oxygen intake at the maximum attainable speed of skiing on a level course averaged 89.6 percent of the maximum oxygen intake observed during uphill treadmill running; the latter (average 63.9 ml.kg-1 min-1) may be compared with values greater than 80 ml.kg1 min-1 for international competitors. Maximum heart rates and respiratory gas exchange ratios were generally lower during skiing than running, and it is suggested that the maximum oxygen intake attained during skiing is limited by the individual's skill. In support of this the more experienced skiers were able to reach close to 100 percent of the treadmill maximum oxygen intake during level skiing. A multiple regression analysis indicated that the skiing speed sustained over a one-hour period was related to experience of skiing, maximum oxygen intake, and the percentage of body fat. Assuming a dynamic friction coefficient of 0.075, a drag area of 0.7 m2 and a drag coefficient of 1.0, the gross mechanical efficiency of the university-class skier averaged a little under 20 percent, with a net efficiency of 21.3 percent. PMID:465911

  1. 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

  2. Correlation of denitrification-accepted fraction of electrons with NAD(P)H fluorescence for Pseudomonas aeruginosa performing simultaneous denitrification and respiration at extremely low dissolved oxygen conditions.

    PubMed

    Chen, Fan; Xia, Qing; Ju, Lu-Kwang

    2004-01-01

    In cystic fibrosis airway infection, Pseudomonas aeruginosa forms a microaerobic biofilm and undergoes significant physiological changes. It is important to understand the bacterium's metabolism at microaerobic conditions. In this work, the culture properties and two indicators (the denitrification-accepted e- fraction and an NAD(P)H fluorescence fraction) for the culture's "fractional approach" to a fully anaerobic denitrifying state were examined in continuous cultures with practically zero DO but different aeration rates. With decreasing aeration, specific OUR decreased while specific NAR and NIR increased and kept Y(ATP/S) relatively constant. P. aeruginosa thus appeared to effectively compensate for energy generation at microaerobic conditions with denitrification. At the studied dilution rate of 0.06 h(-1), the maximum specific OUR was 2.8 mmol O2/g cells-h and the Monod constant for DO, in the presence of nitrate, was extremely low (<0.001 mg/L). The cell yield Y(X/S) increased significantly (from 0.24 to 0.34) with increasing aeration, attributed to a roughly opposite trend of Y(ATP/X) (ATP generation required for cell growth). As for the denitrification-accepted e- fraction and the fluorescence fraction, both decreased with increasing aeration as expected. The two fractions, however, were not directly proportional. The fluorescence fraction changed more rapidly than the e- fraction at very low aeration rates, whereas the opposite was true at higher aeration. The results demonstrated the feasibility of using online NAD(P)H fluorescence to monitor sensitive changes of cellular physiology and provided insights to the shift of e- -accepting mechanisms of P. aeruginosa under microaerobic conditions.

  3. 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.

  4. 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.

  5. A lethal ovitrap-based mass trapping scheme for dengue control in Australia: I. Public acceptability and performance of lethal ovitraps.

    PubMed

    Ritchie, S A; Rapley, L P; Williams, C; Johnson, P H; Larkman, M; Silcock, R M; Long, S A; Russell, R C

    2009-12-01

    We report on the first field evaluation of the public acceptability and performance of two types of lethal ovitrap (LO) in three separate trials in Cairns, Australia. Health workers were able to set standard lethal ovitraps (SLOs) in 75 and 71% of premise yards in the wet and dry season, respectively, and biodegradable lethal ovitraps (BLOs) in 93% of yards. Public acceptance, measured as retention of traps by residents, was high for both trap types, with <9% of traps missing after 4 weeks. Traps retaining water after 4 weeks were 78 and 34% for the two SLO trials and 58% for the BLOs. The 'failure rate' in the 535 BLOs set in the field for 4 weeks was 47%, of which 19% were lost, 51% had holes from probable insect chewing, 23% were knocked over, 7% had dried by evaporation and 1% were split. There was no significant difference in the failure rate of BLOs set on porous (grass, soil and mulch) versus solid (tiles, concrete, wood and stone) substrates. The SLOs and the BLOs were readily acceptable to ovipositing Aedes aegypti L. (Diptera: Culicidae); the mean number of eggs/trap was 6 and 15, for the dry season and wet season SLO trial, respectively, and 15 for the BLO wet season trial. Indeed, 84-94% of premise yards had egg positive SLOs or BLOs. A high percentage of both wet and dry season SLOs (29 and 70%, respectively) and BLOs (62%) that were dry after 4 weeks were egg positive, indicating the traps had functioned. Lethal strips from SLOs and BLOs that had been exposed for 4 weeks killed 83 and 74%, respectively, of gravid Ae. aegypti in laboratory assays. These results indicate that mass trapping schemes using SLOs and BLOs are not rejected by the public and effectively target gravid Ae. aegypti. The impact of the interventions on mosquito populations is described in a companion paper. PMID:19941595

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. Thermal{endash}mechanical performance of extreme ultraviolet lithographic reticles

    SciTech Connect

    Gianoulakis, S.E.; Ray-Chaudhuri, A.K.

    1998-11-01

    Thermal deformation of reticles will likely become an important consideration for all advanced lithography techniques targeting 130 nm features and below. Such effects can contribute to image placement errors and blur. These issues necessitate the need to quantify the reticle distortion, induced by the absorption of illumination power, for candidate substrate and coating materials. To study the impact of various substrate and coating materials on reticle performance, detailed three-dimensional transient thermal and solid mechanical models have been developed and extensively applied to predict total placement errors, residual placement errors, and blur on an extreme ultraviolet lithography (EUVL) reticle during scanning. The thermal model includes a bidirectional scanning heat source representative of the illumination incident on the reticle. The heat loads on the reticle are characteristic of an EUVL engineering test stand with a wafer throughput of twenty 200 mm wafers per hour (assuming 80{percent} die coverage and 68{percent} exposure time). This article includes the results which describe the impact of (1) different substrate materials, (2) various degrees of contact conductance between the reticle and chuck, (3) pattern density and arrangement, and (4) temperature variations across the chuck. {copyright} {ital 1998 American Vacuum Society.}

  11. 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... 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...

  12. 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...

  13. 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... 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...

  14. 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... 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...

  15. Intelligent data layout mechanism for high-performance image retrieval

    NASA Astrophysics Data System (ADS)

    Leung, Kelvin T.; Tao, Wenchao; Yang, Limin; Kimme-Smith, Carolyn; Bassett, Lawrence W.; Valentino, Daniel J.

    1998-06-01

    Trends in medical imaging indicate that the storage requirements for digital medical datasets require a more efficient, scalable storage architecture for large-scale RIS/PACS to support high-speed retrieval for multiple concurrent clients. As storage and networking technologies mature, the cost of applying such technologies in medical imaging has become more economically viable. We propose to take advantage of such economies of scale in technology to provide an effective network workstation storage solution for achieving (1) faster display and navigation response time, (2) higher server throughput and (3) better data storage management. Full-field direct digital mammography presents a challenging problem in the design of digital workstation systems for screening and diagnosis. Due to the spatial and contrast resolution required for mammography, the digital images are large (exceeding 5K X 6K X 14 bits approximately equals 60MB per image) and therefore difficult to display using commercially available technology. We are developing clinically useful methods of storing, displaying and manipulating large digital images in a medical media server using commercial technology. In this paper we propose an Intelligent Grid-based Data Layout Mechanism to optimize the total response time of a reading by minimizing the speed of image access (data I/O time) and the number of data access requests to the server (queueing effects) during the image navigation. A Navigation Threads Model is developed to characterize the performance of many navigation threads involved in the course of performing a reading session. In our grid-based data layout approach, a large 2D direct-digital mammogram image is divided spatially into many small 2D grids and is stored into an array of magnetic disks to provide parallel grid-based readout services to clients. Such a grid- based approach not only provides fine-granularity control, but also provides a means of collecting statistical information about

  16. 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…

  17. Mechanical performance of fiberglass laminates for sucker rod applications

    SciTech Connect

    Gauchel, J.V.

    1985-01-01

    This paper presents the results of a program designed to evaluate the tensile, shear, and tensile/tensile fatigue performance versus temperature of typical FRP pultruded laminates used in sucker rods. The predictability of performance and its sensitivity to process conditions will also be discussed.

  18. 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.

  19. 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 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)...

  20. 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

  1. 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

  2. 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".

  3. 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

  4. Mechanical performance of pyrolytic carbon in prosthetic heart valve applications.

    PubMed

    Cao, H

    1996-06-01

    An experimental procedure has been developed for rigorous characterization of the fracture resistance and fatigue crack extension in pyrolytic carbon for prosthetic heart valve application. Experiments were conducted under sustained and cyclic loading in a simulated biological environment using Carbomedics Pyrolite carbon. While the material was shown to have modest fracture toughness, it exhibited excellent resistance to subcritical crack growth. The crack growth kinetics in pyrolytic carbon were formulated using a phenomenological description. A fatigue threshold was observed below which the crack growth rate diminishes. A damage tolerance concept based on fracture mechanics was used to develop an engineering design approach for mechanical heart valve prostheses. In particular, a new quantity, referred to as the safe-life index, was introduced to assess the design adequacy against subcritical crack growth in brittle materials. In addition, a weakest-link statistical description of the fracture strength is provided and used in the design of component proof-tests. It is shown that the structural reliability of mechanical heart valves can be assured by combining effective flaw detection and manufacturing quality control with adequate damage tolerance design.

  5. Mechanisms of aerobic performance impairment with heat stress and dehydration.

    PubMed

    Cheuvront, Samuel N; Kenefick, Robert W; Montain, Scott J; Sawka, Michael N

    2010-12-01

    Environmental heat stress can challenge the limits of human cardiovascular and temperature regulation, body fluid balance, and thus aerobic performance. This minireview proposes that the cardiovascular adjustments accompanying high skin temperatures (T(sk)), alone or in combination with high core body temperatures (T(c)), provide a primary explanation for impaired aerobic exercise performance in warm-hot environments. The independent (T(sk)) and combined (T(sk) + T(c)) effects of hyperthermia reduce maximal oxygen uptake (Vo(2max)), which leads to higher relative exercise intensity and an exponential decline in aerobic performance at any given exercise workload. Greater relative exercise intensity increases cardiovascular strain, which is a prominent mediator of rated perceived exertion. As a consequence, incremental or constant-rate exercise is more difficult to sustain (earlier fatigue) or requires a slowing of self-paced exercise to achieve a similar sensation of effort. It is proposed that high T(sk) and T(c) impair aerobic performance in tandem primarily through elevated cardiovascular strain, rather than a deterioration in central nervous system (CNS) function or skeletal muscle metabolism. Evaporative sweating is the principal means of heat loss in warm-hot environments where sweat losses frequently exceed fluid intakes. When dehydration exceeds 3% of total body water (2% of body mass) then aerobic performance is consistently impaired independent and additive to heat stress. Dehydration augments hyperthermia and plasma volume reductions, which combine to accentuate cardiovascular strain and reduce Vo(2max). Importantly, the negative performance consequences of dehydration worsen as T(sk) increases.

  6. 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.

  7. 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…

  8. 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

  9. 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.

  10. A comparison between two lingual orthodontic brackets in terms of speech performance and patients' acceptance in correcting Class II, Division 1 malocclusion: a randomized controlled trial

    PubMed Central

    Haj-Younis, Samiha; Khattab, Tarek Z.; Hajeer, Mohammad Y.; Farah, Hassan

    2016-01-01

    ABSTRACT Objective: To compare speech performance and levels of oral impairment between two types of lingual brackets. Methods: A parallel-group randomized controlled trial was carried out on patients with Class II, Division 1 malocclusion treated at the University of Hama School of Dentistry in Hama, Syria. A total of 46 participants (mean age: 22.3 ± 2.3 years) with maxillary dentoalveolar protrusion were randomly distributed into two groups with 23 patients each (1:1 allocation ratio). Either STb (Ormco) or 7th Generation (Ormco) lingual brackets were applied. Fricative sound/s/ spectrograms were analyzed directly before intervention (T0), one week following premolar extraction prior to bracket placement (T1), within 24 hours of bracket bonding (T2), one month after (T3), and three months after (T4) bracket placement. Patients′ acceptance was assessed by means of standardized questionnaires. Results: After bracket placement, significant deterioration in articulation was recorded at all assessment times in the 7th Generation group, and up to T3 in the STb group. Significant intergroup differences were detected at T2 and T3. No statistically significant differences were found between the two groups in reported tongue irritation levels, whereas chewing difficulty was significantly higher in the 7th Generation group one month after bracket placement. Conclusions: 7th Generation brackets have more interaction with sound production than STb ones. Although patients in both groups complained of some degree of oral impairment, STb appliances appeared to be more comfortable than the 7th Generation ones, particularly within the first month of treatment. PMID:27653268

  11. 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.

  12. 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.

  13. 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.

  14. Performance of NASA Equation Solvers on Computational Mechanics Applications

    NASA Technical Reports Server (NTRS)

    Storaasli, Olaf O.

    1996-01-01

    This paper describes the performance of a new family of NASA-developed equation solvers used for large-scale (i.e. 551,705 equations) structural analysis. To minimize computer time and memory, the solvers are divided by application and matrix characteristics (sparse/dense, real/complex, symmetric/nonsymmetric, size: in-core/out of core) and exploit the hardware features of current and future computers. In this paper, the equation solvers, which are written in FORTRAN, and are therefore easily transportable, are shown to be faster than specialized computer library routines utilizing assembly code. Twenty NASA structural benchmark models with NASA solver timings reside on World Wide Web with a challenge to beat them.

  15. 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.

  16. Effects of competition on endurance performance and the underlying psychological and physiological mechanisms.

    PubMed

    Cooke, Andrew; Kavussanu, Maria; McIntyre, David; Ring, Christopher

    2011-03-01

    Competition can influence performance, however, the underlying psychological and physiological mechanisms are poorly understood. To address this issue we tested mechanisms underlying the competition-performance relationship. Measures of anxiety, effort, enjoyment, autonomic activity and muscle activity were obtained from 94 participants during a handgrip endurance task completed in individual and competition conditions. Competition improved endurance performance, increased anxiety, effort, enjoyment, heart rate and muscle activity, and decreased heart rate variability, R-wave to pulse interval and pulse amplitude. Enjoyment fully mediated whereas effort and heart rate variability partially mediated the effects of competition on performance. In addition, anxiety moderated the competition-performance relationship; those with lower anxiety performed better in competition. We confirm that competition elicits effects on performance through psychological and physiological pathways, and identify mechanisms that underlie improved endurance performance during competition. PMID:21295108

  17. 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

  18. 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

  19. 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

  20. Offer/Acceptance Ratio.

    ERIC Educational Resources Information Center

    Collins, Mimi

    1997-01-01

    Explores how human resource professionals, with above average offer/acceptance ratios, streamline their recruitment efforts. Profiles company strategies with internships, internal promotion, cooperative education programs, and how to get candidates to accept offers. Also discusses how to use the offer/acceptance ratio as a measure of program…

  1. 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

  2. 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

  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 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…

  5. 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…

  6. 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…

  7. 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

  8. 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.

  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. 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.

  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. 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

  14. Acceptability of BCG vaccination.

    PubMed

    Mande, R

    1977-01-01

    The acceptability of BCG vaccination varies a great deal according to the country and to the period when the vaccine is given. The incidence of complications has not always a direct influence on this acceptability, which depends, for a very large part, on the risk of tuberculosis in a given country at a given time.

  15. ATLAS ACCEPTANCE TEST

    SciTech Connect

    Cochrane, J. C. , Jr.; Parker, J. V.; Hinckley, W. B.; Hosack, K. W.; Mills, D.; Parsons, W. M.; Scudder, D. W.; Stokes, J. L.; Tabaka, L. J.; Thompson, M. C.; Wysocki, Frederick Joseph; Campbell, T. N.; Lancaster, D. L.; Tom, C. Y.

    2001-01-01

    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.

  16. Alterations to movement mechanics can greatly reduce anterior cruciate ligament loading without reducing performance.

    PubMed

    Myers, Casey A; Hawkins, David

    2010-10-19

    Anterior cruciate ligament (ACL) injuries are one of the most common and potentially debilitating sports injuries. Approximately 70% of ACL injuries occur without contact and are believed to be preventable. Jump stop movements are associated with many non-contact ACL injuries. It was hypothesized that an athlete performing a jump stop movement can reduce their peak tibial shear force (PTSF), a measure of ACL loading, without compromising performance, by modifying their knee flexion angle, shank angle, and foot contact location during landing. PTSF was calculated for fourteen female basketball players performing jump stops using their normal mechanics and mechanics modified to increase their knee flexion angle, decrease their shank angle relative to vertical and land more on their toes during landing. Every subject tested experienced drastic reductions in their PTSF (average reduction=56.4%) using modified movement mechanics. The athletes maintained or improved their jump height with the modified movement mechanics (an average increase in jump height of 2.5cm). The hypothesis was supported: modifications to jump stop movement mechanics greatly reduced PTSF and therefore ACL loading without compromising performance. The results from this study identify crucial biomechanical quantities that athletes can easily modify to reduce ACL loading and therefore should be targeted in any physical activity training programs designed to reduce non-contact ACL injuries.

  17. 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.

  18. 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.

  19. 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.

  20. 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

  1. 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

  2. High-level waste-form-product performance evaluation. [Leaching; waste loading; mechanical stability

    SciTech Connect

    Bernadzikowski, T A; Allender, J S; Stone, J A; Gordon, D E; Gould, Jr, T H; Westberry, III, C F

    1982-01-01

    Seven candidate waste forms were evaluated for immobilization and geologic disposal of high-level radioactive wastes. The waste forms were compared on the basis of leach resistance, mechanical stability, and waste loading. All forms performed well at leaching temperatures of 40, 90, and 150/sup 0/C. Ceramic forms ranked highest, followed by glasses, a metal matrix form, and concrete. 11 tables.

  3. 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;…

  4. 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…

  5. 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…

  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. 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…

  8. 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

  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

    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.

  10. 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.

  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 Central

    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. Mechanical parameters as predictors of performance in alpine World Cup slalom racing.

    PubMed

    Supej, M; Kipp, R; Holmberg, H-C

    2011-12-01

    The aims of the present study were to develop a method for classifying slalom skiing performance and to examine differences in mechanical parameters. Eighteen elite skiers were recorded with three-dimensional kinematical measurements and thereafter divided into a higher (HP) and lower performance group, using the ratio between the difference in mechanical energy divided by the mass of the skier and section entrance velocity (Δe(mech)/v(in)). Moreover, the skiers' velocity (v), acceleration (a), center of mass turn radii (R(CM)) and skis' turn radii (R(AMS)), ground reaction forces (GRF) and differential specific mechanical energy [diff(e(mech))] were calculated. v and diff(e(mech)) were different between the performance groups (P<0.001 and <0.05), while no inter-group differences in R(CM), R(AMS), a and GRF were observed. A relationship between R(AMS) and diff(e(mech)) was demonstrated (r=0.58; P<0.001). The highest GRFs were related to the lowest diff(e(mech)) and a was related to GRF (r=-0.60; P<0.001). The Δe(mech)/v(in) predicted the performance over short course sections. The HP skiers skied with a higher v and a similar range of diff(e(mech)). We suggest that shortest R(AMS) and the highest GRFs should be reduced in elite slalom in order to increase performance.

  14. Mechanical design and performance specifications of anthropomorphic prosthetic hands: a review.

    PubMed

    Belter, Joseph T; Segil, Jacob L; Dollar, Aaron M; Weir, Richard F

    2013-01-01

    In this article, we set forth a detailed analysis of the mechanical characteristics of anthropomorphic prosthetic hands. We report on an empirical study concerning the performance of several commercially available myoelectric prosthetic hands, including the Vincent, iLimb, iLimb Pulse, Bebionic, Bebionic v2, and Michelangelo hands. We investigated the finger design and kinematics, mechanical joint coupling, and actuation methods of these commercial prosthetic hands. The empirical findings are supplemented with a compilation of published data on both commercial and prototype research prosthetic hands. We discuss numerous mechanical design parameters by referencing examples in the literature. Crucial design trade-offs are highlighted, including number of actuators and hand complexity, hand weight, and grasp force. Finally, we offer a set of rules of thumb regarding the mechanical design of anthropomorphic prosthetic hands.

  15. 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.

  16. Acceptance procedures: Microfilm printer

    NASA Technical Reports Server (NTRS)

    Lockwood, H. E.

    1973-01-01

    Acceptance tests were made for a special order automatic additive color microfilm printer. Tests include film capacity, film transport, resolution, illumination uniformity, exposure range checks, and color cuing considerations.

  17. 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.

  18. 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

  19. 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.

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

    NASA Technical Reports Server (NTRS)

    Seniderman, 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.

  1. 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.

  2. 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

  3. 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.

  4. Moderators of and Mechanisms underlying Stereotype Threat Effects on Older Adults' Memory Performance

    PubMed Central

    Hess, Thomas M.; Hinson, Joey T.; Hodges, Elizabeth A.

    2009-01-01

    Recent research has suggested that negative stereotypes about aging may have a detrimental influence on older adults' memory performance. This study sought to determine whether stereotype-based influences were moderated by age, education, and concerns about being stigmatized. Possible mechanisms underlying these influences on memory performance were also explored. The memory performance of adults aged 60 to 70 years and 71 to 82 years was examined under conditions designed to induce or eliminate stereotype threat. Threat was found to have a greater impact on performance in the young-old than in the old-old group, whereas the opposite was observed for the effects of stigma consciousness. In both cases, the effects were strongest for those with higher levels of education. Further analyses found little evidence in support of the mediating roles of affective responses or working memory. The only evidence of mediation was found with respect to recall predictions, suggesting a motivational basis of threat effects on performance. These findings highlight the specificity of stereotype threat effects in later adults as well as possible mechanisms underlying such effects. PMID:19280445

  5. 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.

  6. Moderators of and mechanisms underlying stereotype threat effects on older adults' memory performance.

    PubMed

    Hess, Thomas M; Hinson, Joey T; Hodges, Elizabeth A

    2009-01-01

    Recent research has suggested that negative stereotypes about aging may have a detrimental influence on older adults' memory performance. This study sought to determine whether stereotype-based influences were moderated by age, education, and concerns about being stigmatized. Possible mechanisms underlying these influences on memory performance were also explored. The memory performance of adults aged 60 to 70 years and 71 to 82 years was examined under conditions designed to induce or eliminate stereotype threat. Threat was found to have a greater impact on performance in the young-old than in the old-old group, whereas the opposite was observed for the effects of stigma consciousness. In both cases, the effects were strongest for those with higher levels of education. Further analyses found little evidence in support of the mediating roles of affective responses or working memory. The only evidence of mediation was found with respect to recall predictions, suggesting a motivational basis of threat effects on performance. These findings highlight the specificity of stereotype threat effects in later adulthood as well as possible mechanisms underlying such effects.

  7. 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.

  8. 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.

  9. Mechanical Determinants of Faster Change of Direction and Agility Performance in Female Basketball Athletes.

    PubMed

    Spiteri, Tania; Newton, Robert U; Binetti, Molly; Hart, Nicolas H; Sheppard, Jeremy M; Nimphius, Sophia

    2015-08-01

    Change of direction (COD) and agility require the integration of multiple components to produce a faster performance. However, the mechanisms contributing to a faster performance without the confounding factor of athlete expertise or gender is currently unknown. Therefore, the purpose of this study was to assess body composition, strength, and kinetic profile required for a faster COD and agility performance across multiple directional changes. Six faster and 6 slower (n = 12) elite female basketball athletes completed a maximal dynamic back squat; eccentric and concentric only back squat; isometric midthigh pull; whole-body scan to determine lean, fat, and total mass; 505 COD test; T-test; and a multidirectional agility test over in-ground force plates to obtain relevant kinetic measures. Group (faster and slower) by test (2 × 3) multivariate analyses of variance with follow-up analyses of variance were conducted to examine differences between faster and slower groups and each COD and agility test (p ≤ 0.05). Faster athletes during the 505 COD test produced significantly greater vertical force (p = 0.002) and eccentric and isometric strength capacity (p = 0.001). Faster agility and T-test athletes demonstrated significantly shorter contact times (p = 0.001), greater propulsive impulse (p = 0.02), isometric strength, and relative lean mass compared with slower athletes. Differences between faster athletes across each test seem to be attributed to the mechanical demands of the directional change, increasing force and impulse application as the degree of directional change increased. These findings indicate that different mechanical properties are required to produce a faster COD and agility performances, and the importance of a greater strength capacity to enable greater mechanical adjustment through force production and body control, during different directional changes.

  10. 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

  11. Accepting the T3D

    SciTech Connect

    Rich, D.O.; Pope, S.C.; DeLapp, J.G.

    1994-10-01

    In April, a 128 PE Cray T3D was installed at Los Alamos National Laboratory`s Advanced Computing Laboratory as part of the DOE`s High-Performance Parallel Processor Program (H4P). In conjunction with CRI, the authors implemented a 30 day acceptance test. The test was constructed in part to help them understand the strengths and weaknesses of the T3D. In this paper, they briefly describe the H4P and its goals. They discuss the design and implementation of the T3D acceptance test and detail issues that arose during the test. They conclude with a set of system requirements that must be addressed as the T3D system evolves.

  12. 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

  13. 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).

  14. 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.

  15. 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.

  16. 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

  17. Evolutionary and cellular mechanisms regulating intestinal performance of amphibians and reptiles.

    PubMed

    Secor, Stephen M

    2005-04-01

    Vertebrate intestinal tracts possess an array of structural and functional adaptations to the wide diversity of food and feeding habits. In addition to well-described differences in form and function between herbivores and carnivores, the intestine exhibits adaptive plasticity to variation in digestive demand. The capacity to which intestinal performance responds to changes in digestive demands is a product of evolutionary and cellular mechanisms. In this report, I have taken an integrative approach to exploring the mechanisms responsible for the regulation of intestinal performance with feeding and fasting among amphibians and reptiles. Intestinal performance is presented as the total small intestinal capacity to absorb nutrients, quantified as a product of small intestinal mass and mass-specific rates of nutrient uptake. For sit-and-wait foraging snakes and estivating anurans, both of which naturally experience long episodes of fasting, the dramatic downregulation of intestinal morphology and function with fasting reduces energy expenditure during extended fasts. In contrast, frequently-feeding species modestly regulate intestinal performance with fasting and feeding, trading higher basal rates of metabolism during fasting for the frequent expense of upregulating the gut with feeding. Surveying the magnitude by which intestinal uptake capacity is regulated among 26 families of amphibians and reptiles has revealed potentially five lineages that have independently evolved the capacity to widely regulate intestinal performance. The extent to which intestinal performance is downregulated with fasting among amphibians and reptiles, ranging from 0 to 90%, is largely a function of the degree by which mass-specific rates of nutrient transport are depressed, given that loss of intestinal mass with fasting is a common characteristic of vertebrates. In exploring the underlying mechanisms regulating intestinal nutrient uptake, use of the Burmese python has revealed a

  18. 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

  19. Performance comparison and modeling of PZN, PMN, and PZT stacked actuators in a levered flexure mechanism

    NASA Astrophysics Data System (ADS)

    Woody, Shane C.; Smith, Stuart T.

    2004-04-01

    This article presents a theoretical and experimental assessment of a translation stage design based on a piezoelectric actuator and levering mechanism. This mechanism incorporates stacked piezoelectric actuators of dimensions 5×5×5 mm3 with each stack made from ten plates of 0.5 mm thickness pushing against a symmetric lever design with an ideal amplification of 6.05:1. Three different stacks made from PZN, PMN, and PZT were tested in a nominally similar mechanism to produce displacements of 101, 104, and 33 μm, respectively. Because of their different elastic moduli, the fundamental resonances with each respective device were 670, 729, and 759 Hz. Lagrange analysis of a lumped model of the mechanism is used to estimate the fundamental mode natural frequency of the system while a model for "lost motion" is also presented. This system has been assembled and evaluated experimentally to assess the validity of the models. In general, these models are shown to provide a reasonable estimate of the mechanism performance in terms of lost motion while predicting higher values for the fundamental frequency. The deviations from the model are consistent with the uncertainties associated with rigid body assumptions and the unknown compliances of assembly interfaces and suggest directions for future research in the modeling of such systems.

  20. Optimization of the Mechanical and Electrical Performance of a Thermoelectric Module

    NASA Astrophysics Data System (ADS)

    Sarhadi, Ali; Bjørk, Rasmus; Pryds, Nini

    2015-11-01

    Finite-element simulation of a thermoelectric (TE) module was conducted to optimize its geometrical dimensions in terms of mechanical reliability and performance. The TE module consisted of bismuth telluride n- and p-type legs. The geometrical dimensions of the module, i.e., leg length and leg cross-sectional area, were varied, and the corresponding maximum thermal stress, output power, and efficiency of the module obtained. An optimal design for the module was then suggested based on minimizing the thermal stresses and maximizing the performance, i.e., power and efficiency. The optimal dimensions at maximum von Mises stress of 75 MPa were leg length of 2 mm to 2.5 mm and leg width of 1.5 mm to 2 mm, resulting in efficiency of 7.2%. Finally, the influence of solders, i.e., solder material between the leg, the interconnector, and the top ceramic layer, on the induced thermal stresses and module performance was investigated. The results revealed that the transition from elastic to plastic deformation in the solder decreased the induced thermal stresses significantly. Moreover, beyond the elastic limit, the stress magnitude was highly dependent on the magnitude and mechanism of plastic deformation in the module. The present study provides a basis for a unique and new optimization scheme for TE modules in terms of endurance and performance.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Smaller hospitals accept advertising.

    PubMed

    Mackesy, R

    1988-07-01

    Administrators at small- and medium-sized hospitals gradually have accepted the role of marketing in their organizations, albeit at a much slower rate than larger institutions. This update of a 1983 survey tracks the increasing competitiveness, complexity and specialization of providing health care and of advertising a small hospital's services. PMID:10288550

  7. Students Accepted on Probation.

    ERIC Educational Resources Information Center

    Lorberbaum, Caroline S.

    This report is a justification of the Dalton Junior College admissions policy designed to help students who had had academic and/or social difficulties at other schools. These students were accepted on probation, their problems carefully analyzed, and much effort devoted to those with low academic potential. They received extensive academic and…

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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.

  13. 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.

  14. Nonhematological mechanisms of improved sea-level performance after hypoxic exposure.

    PubMed

    Gore, Christopher John; Clark, Sally A; Saunders, Philo U

    2007-09-01

    Altitude training has been used regularly for the past five decades by elite endurance athletes, with the goal of improving performance at sea level. The dominant paradigm is that the improved performance at sea level is due primarily to an accelerated erythropoietic response due to the reduced oxygen available at altitude, leading to an increase in red cell mass, maximal oxygen uptake, and competitive performance. Blood doping and exogenous use of erythropoietin demonstrate the unequivocal performance benefits of more red blood cells to an athlete, but it is perhaps revealing that long-term residence at high altitude does not increase hemoglobin concentration in Tibetans and Ethiopians compared with the polycythemia commonly observed in Andeans. This review also explores evidence of factors other than accelerated erythropoiesis that can contribute to improved athletic performance at sea level after living and/or training in natural or artificial hypoxia. We describe a range of studies that have demonstrated performance improvements after various forms of altitude exposures despite no increase in red cell mass. In addition, the multifactor cascade of responses induced by hypoxia includes angiogenesis, glucose transport, glycolysis, and pH regulation, each of which may partially explain improved endurance performance independent of a larger number of red blood cells. Specific beneficial nonhematological factors include improved muscle efficiency probably at a mitochondrial level, greater muscle buffering, and the ability to tolerate lactic acid production. Future research should examine both hematological and nonhematological mechanisms of adaptation to hypoxia that might enhance the performance of elite athletes at sea level.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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

  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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. Improved mechanical performance of PBO fiber-reinforced bismaleimide composite using mixed O2/Ar plasma

    NASA Astrophysics Data System (ADS)

    Liu, Dong; Chen, Ping; Yu, Qi; Ma, Keming; Ding, Zhenfeng

    2014-06-01

    The mixed O2/Ar plasma was employed to enhance mechanical properties of the PBO/bismaleimide composite. The interlaminar shear strength was improved to 61.6 MPa or by 38.1%, but the composite brittleness increased. The plasma gas compositions exhibited notable effects on the interfacial adhesion strength. XPS results suggested that the mixed plasma presented higher activation effects on the surface chemical compositions than pure gas plasmas and a larger number of oxygen atoms and hydrophilic groups were introduced on the fiber surface due to the synergy effect, but the synergy effect was considerably performed only within the O2 percentage range of 40-60%. The fibers surface was increasingly etched with growing the O2 contents in the plasma, deteriorating the fibers tensile strength. SEM micrographs demonstrated that the composite shear fracture changed from debonding to cohesive failure in the matrices, and the improving mechanisms were discussed.

  8. 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.

  9. 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.

  10. 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.

  11. 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

  12. 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)

  13. 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.

  14. 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.

  15. Defect analysis and mechanical performance of plasma-deposited thin films on flexible polycarbonate substrates

    NASA Astrophysics Data System (ADS)

    Patel, Rakhi P.; Wolden, Colin A.

    2013-03-01

    A simple solvent-etch based technique is developed to visualize and quantify defects in transparent thin films deposited on flexible polymer substrates. This approach is used to characterize defects in as-deposited films and to monitor their evolution as a function of applied and repetitive bending. Thin films investigated include sputtered indium tin oxide (ITO) and alumina-silicone nanolaminates fabricated by plasma-enhanced chemical vapor deposition. It is shown that the use of nanolaminate architectures reduces the defect density by two orders of magnitude relative to a single alumina layer. The pinhole density increases when nanolaminates are subjected to applied stress, and at a critical density of ˜10/mm2 the isolated defects coalesce into macroscopic cracks. In the case of ITO an optimum film thickness is identified that balances electronic performance with mechanical integrity. Conductivity correlates with defect density, and the films displayed very similar performance under tensile and compressive strain. A critical radius of curvature of 0.75 in. was identified, but films cycled below the threshold strain demonstrated robust performance, with only negligible changes in resistivity through 2000 bending cycles. The strong performance under strain is attributed to the amorphous nature of the sputtered ITO.

  16. 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

  17. 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

  18. 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

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

    DOE PAGES

    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. Performance of mechanical filters and respirators for capturing nanoparticles--limitations and future direction.

    PubMed

    Mostofi, Reza; Wang, Bei; Haghighat, Fariborz; Bahloul, Ali; Jaime, Lara

    2010-01-01

    There is an increasing concern about the health hazard posed to workers exposed to inhalation of nanoparticles. Inhaling nanoparticles possess an occupational hazard due to elevated amount emitted to the atmosphere and working environment. Nanoparticles have potential toxic properties: the high particle surface area, number concentration, and surface reactivity. Inhalation, the most common route of nanoparticle exposure, has been shown to cause adverse effects on pulmonary functions and the deposited particles in the lung can be translocated to the blood system by passing through the pulmonary protection barriers. Filtration is the simplest and most common method of aerosol control. It is widely used in mechanical ventilation and respiratory protection. However, concerns have been raised regarding the effectiveness of the filters for capturing nanoparticles. This paper reviews the literature on the filtration performance of mechanical filters and respirators against nanoparticles. It includes the discussion about filtration mechanisms, theoretical models, affecting factors of the filtration efficiency, and testing protocols for respirator and filter certification. PMID:20562505

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

    PubMed

    Valashani, Seyed Mohammad Mirkhalaf; Barthelat, Francois

    2015-03-30

    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%.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. 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.

  7. 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.

  8. Characterization and performance evaluation of a vertical seismic isolator using link and crank mechanism

    NASA Astrophysics Data System (ADS)

    Tsujiuchi, N.; Ito, A.; Sekiya, Y.; Nan, C.; Yasuda, M.

    2016-09-01

    In recent years, various seismic isolators have been developed to prevent earthquake damage to valuable art and other rare objects. Many seismic isolators only defend against horizontal motions, which are the usual cause of falling objects. However, the development of a seismic isolator designed for vertical vibration is necessary since such great vertical vibration earthquakes as the 2004 Niigata Prefecture Chuetsu Earthquake have occurred, and their increased height characteristics are undesirable. In this study, we developed a vertical seismic isolator that can be installed at a lower height and can support loads using a horizontal spring without requiring a vertical spring. It has a mechanism that combines links and cranks. The dynamic model was proposed and the frequency characteristics were simulated when the sine waves were the input. Shaking tests were also performed. The experimental value of the natural frequency was 0.57 Hz, and the theoretical values of the frequency characteristics were close to the experimental values. In addition, we verified this vertical seismic isolator's performance through shaking tests and simulation for typical seismic waves in Japan. We verified the seismic isolation's performance from the experimental result because the average reduction rate of the acceleration was 0.21.

  9. 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.

  10. 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…

  11. 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

  12. Stunting delays maturation of triceps surae mechanical properties and motor performance in prepubertal children.

    PubMed

    Paiva, Maria das Graças; Souza, Thaysa O L; Canon, Francis; Pérot, Chantal; Xavier, Luciana C C; Ferraz, Karla M; Osório, Mônica M; Manhães-de-Castro, Raul; Lambertz, Daniel

    2012-12-01

    Malnutrition can lead to possible irreversible consequences in the development of muscle function and some of them are yet poorly characterized. The present study evaluated the mechanical properties of the triceps surae and motor performance in stunted (S) and eutrophic (E) prepubertal children (9 years ± 6 months). Height-for-age ratio was used as indicator of stunting due to early malnutrition, according to the World Health Organization. Torque was determined by maximal voluntary contractions (MVC) and musculotendinous (MT) stiffness was achieved through quick-release tests to obtain MT stiffness index (SI(MT)) and passive stiffness (K (p)) from linear MT stiffness-torque relationships. Percutaneous supramaximal electrically elicited contractions determined twitch torque (Pt) and electromechanical delay (EMD). Motor performance was evaluated by balance test. S group presented significantly lower MVC and a trend of lower Pt values indicating lower capacities to develop force under voluntary or induced conditions. Significantly higher SI(MT) and EMD values were observed, while K (p) and motor performance in balance were significantly lower. Higher SI(MT) values have been reported previously in youngest prepubertal children, indicating that immature activation capacities can mask MT stiffness assessment during voluntary contractions, taking into consideration the higher EMD values as a measure of muscle stiffness contribution. Lower K (p) may indicate a delay in the maturation of tendinous tissue in S group, influencing motor performance in balance. The present study shows that malnutrition leads to adaptation of intrinsic MT elastic properties, but depends on the level of the observed structure.

  13. 48 CFR 28.203 - Acceptability of individual sureties.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... surety for a surety previously determined to be unacceptable. (e) When evaluating individual sureties... to accepting the bid guarantee and payment and performance bonds. (g) Evidence of possible...

  14. 48 CFR 28.203 - Acceptability of individual sureties.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... surety for a surety previously determined to be unacceptable. (e) When evaluating individual sureties... to accepting the bid guarantee and payment and performance bonds. (g) Evidence of possible...

  15. 48 CFR 28.203 - Acceptability of individual sureties.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... surety for a surety previously determined to be unacceptable. (e) When evaluating individual sureties... to accepting the bid guarantee and payment and performance bonds. (g) Evidence of possible...

  16. 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.

  17. Enhanced mechanical performance of biocompatible hemicelluloses-based hydrogel via chain extension.

    PubMed

    Qi, Xian-Ming; Chen, Ge-Gu; Gong, Xiao-Dong; Fu, Gen-Que; Niu, Ya-Shuai; Bian, Jing; Peng, Feng; Sun, Run-Cang

    2016-09-16

    Hemicelluloses are widely used to prepare gel materials because of their renewability, biodegradability, and biocompatibility. Here, molecular chain extension of hemicelluloses was obtained in a two-step process. Composite hydrogels were prepared via free radical graft copolymerization of crosslinked quaternized hemicelluloses (CQH) and acrylic acid (AA) in the presence of crosslinking agent N,N'-methylenebisacrylamide (MBA). This chain extension strategy significantly improved the mechanical performance of the resulting hydrogels. The crosslinking density, compression modulus, and swelling capacities of hydrogels were tuned by changing the AA/CQH and MBA/CQH contents. Moreover, the biocompatibility test suggests that the hemicelluloses-based hydrogels exhibited no toxicity to cells and allowed cell growth. Taken together, these properties demonstrated that the composite hydrogels have potential applications in the fields of water absorbents, cell culture, and other functional biomaterials.

  18. 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.

  19. 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).

  20. 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.

  1. Enhanced mechanical performance of biocompatible hemicelluloses-based hydrogel via chain extension

    PubMed Central

    Qi, Xian-Ming; Chen, Ge-Gu; Gong, Xiao-Dong; Fu, Gen-Que; Niu, Ya-Shuai; Bian, Jing; Peng, Feng; Sun, Run-Cang

    2016-01-01

    Hemicelluloses are widely used to prepare gel materials because of their renewability, biodegradability, and biocompatibility. Here, molecular chain extension of hemicelluloses was obtained in a two-step process. Composite hydrogels were prepared via free radical graft copolymerization of crosslinked quaternized hemicelluloses (CQH) and acrylic acid (AA) in the presence of crosslinking agent N,N’-methylenebisacrylamide (MBA). This chain extension strategy significantly improved the mechanical performance of the resulting hydrogels. The crosslinking density, compression modulus, and swelling capacities of hydrogels were tuned by changing the AA/CQH and MBA/CQH contents. Moreover, the biocompatibility test suggests that the hemicelluloses-based hydrogels exhibited no toxicity to cells and allowed cell growth. Taken together, these properties demonstrated that the composite hydrogels have potential applications in the fields of water absorbents, cell culture, and other functional biomaterials. PMID:27634095

  2. 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.

  3. 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.

  4. 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.

  5. Enhanced mechanical performance of biocompatible hemicelluloses-based hydrogel via chain extension.

    PubMed

    Qi, Xian-Ming; Chen, Ge-Gu; Gong, Xiao-Dong; Fu, Gen-Que; Niu, Ya-Shuai; Bian, Jing; Peng, Feng; Sun, Run-Cang

    2016-01-01

    Hemicelluloses are widely used to prepare gel materials because of their renewability, biodegradability, and biocompatibility. Here, molecular chain extension of hemicelluloses was obtained in a two-step process. Composite hydrogels were prepared via free radical graft copolymerization of crosslinked quaternized hemicelluloses (CQH) and acrylic acid (AA) in the presence of crosslinking agent N,N'-methylenebisacrylamide (MBA). This chain extension strategy significantly improved the mechanical performance of the resulting hydrogels. The crosslinking density, compression modulus, and swelling capacities of hydrogels were tuned by changing the AA/CQH and MBA/CQH contents. Moreover, the biocompatibility test suggests that the hemicelluloses-based hydrogels exhibited no toxicity to cells and allowed cell growth. Taken together, these properties demonstrated that the composite hydrogels have potential applications in the fields of water absorbents, cell culture, and other functional biomaterials. PMID:27634095

  6. 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

  7. 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

  8. 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

  9. 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

  10. 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.

  11. 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.

  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. A review on removing pharmaceutical contaminants from wastewater by constructed wetlands: design, performance and mechanism.

    PubMed

    Li, Yifei; Zhu, Guibing; Ng, Wun Jern; Tan, Soon Keat

    2014-01-15

    This paper presents a comprehensive review of the current state of research activities on the application of constructed wetlands for removing pharmaceutical contaminants from wastewater. The focus of the review was placed on the application of constructed wetlands as an alternative secondary wastewater treatment system or as a wastewater polishing treatment system. The design parameters of the reported constructed wetlands including the physical configuration, hydraulic mode, vegetation species, and targeting pharmaceuticals were summarized. The removal efficiencies of pharmaceuticals under different conditions in the wetlands were evaluated at the macroscopic level. In addition, the importance of the three main components of constructed wetlands (substrate, plants and microbes) for pharmaceutical removal was analyzed to elucidate the possible removal mechanisms involved. There is a general consensus among many researchers that constructed wetlands hold great potential of being used as an alternative secondary wastewater treatment system or as a wastewater polishing treatment system for the removal of pharmaceuticals, but relevant reported studies are scarce and are not conclusive in their findings. Current knowledge is limited on the removal efficiencies of pharmaceuticals in constructed wetlands, the removal mechanisms involved, the toxicity to constructed wetlands caused by pharmaceuticals, and the influences of certain important parameters (configuration design, hydraulic mode, temperature and seasonality, pH, oxygen and redox potential, etc.). This review promotes further research on these issues to provide more and better convincing evidences for the function and performance of larger laboratory-scale, pilot-scale or full-scale constructed wetlands.

  14. Evaluation of the flocculation and de-flocculation performance and mechanism of polymer flocculants.

    PubMed

    Ponou, Josiane; Ide, Tomohito; Suzuki, Akiko; Tsuji, Hideyuki; Wang, Li Pang; Dodbiba, Gjergj; Fujita, Toyohisa

    2014-01-01

    Understanding the interaction mechanism between polymeric flocculants and solid particles in two oppositely charged solutions: bentonite and calcium fluoride, is of great practical and fundamental importance. In this work, inorganic flocculants based on aluminum(III) or iron(III); cationic, anionic and non-ionic organic flocculants were used. The solution pH, which highly influenced the flocculation performance of the system, has been used as a function of turbidity removal, sediment volume and velocity. Results show that the flocculation of inorganic polymers does not depend on the zeta potential but on the solution pH, contrary for cationic and anionic polymers. Non-ionic polymer was independent on both. By varying the final pH of the heterogeneous solution formed of flocs-liquid, it was found for inorganic polymers, the optimum condition of pH < 3 to separate inorganic flocculant particles from flocs. Inductively coupled plasma atomic emission spectrometer and X-ray fluorescence analysis proved the reversibility of flocculation process by indicating the concentration of flocculant representative atom (Al or Fe) in the flocs and in the emerging solutions when the flocculation was optimized and the reversibility was effective. As results, weak forces were suggested as responsible for inorganic polymers flocculation where electrostatic interaction and hydrogen bonds may enroll the mechanism of organic flocculants.

  15. 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

  16. 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

  17. Evaluation of the flocculation and de-flocculation performance and mechanism of polymer flocculants.

    PubMed

    Ponou, Josiane; Ide, Tomohito; Suzuki, Akiko; Tsuji, Hideyuki; Wang, Li Pang; Dodbiba, Gjergj; Fujita, Toyohisa

    2014-01-01

    Understanding the interaction mechanism between polymeric flocculants and solid particles in two oppositely charged solutions: bentonite and calcium fluoride, is of great practical and fundamental importance. In this work, inorganic flocculants based on aluminum(III) or iron(III); cationic, anionic and non-ionic organic flocculants were used. The solution pH, which highly influenced the flocculation performance of the system, has been used as a function of turbidity removal, sediment volume and velocity. Results show that the flocculation of inorganic polymers does not depend on the zeta potential but on the solution pH, contrary for cationic and anionic polymers. Non-ionic polymer was independent on both. By varying the final pH of the heterogeneous solution formed of flocs-liquid, it was found for inorganic polymers, the optimum condition of pH < 3 to separate inorganic flocculant particles from flocs. Inductively coupled plasma atomic emission spectrometer and X-ray fluorescence analysis proved the reversibility of flocculation process by indicating the concentration of flocculant representative atom (Al or Fe) in the flocs and in the emerging solutions when the flocculation was optimized and the reversibility was effective. As results, weak forces were suggested as responsible for inorganic polymers flocculation where electrostatic interaction and hydrogen bonds may enroll the mechanism of organic flocculants. PMID:24647191

  18. Explanation of the mechanism by which CAD assistance improves diagnostic performance when reading CT images

    NASA Astrophysics Data System (ADS)

    Matsumoto, Toru; Wada, Shinichi; Yamamoto, Shinji; Murao, Kohei; Furukawa, Akira; Endo, Masahiro; Matsumoto, Mitsuomi; Sone, Shusuke

    2006-03-01

    The purpose of our research is to make clear the mechanism that a reader (physician or radiological technologist) effectively identify abnormal findings in CT images of lung cancer screening by using with CAD system. A method guessing the 2X2 decision matrix between reader / CAD and reader / reader with CAD was investigated. We suppose the next scene to be it. At first, a reader judges whether abnormal findings per one patient per one CT image are present (1) or absent (0) without CAD results. The second, a reader judges whether abnormal findings are present (1) or absent (0) with CAD results. We expresses the correlation between diagnoses by a reader and CAD system for abnormal cases and for normal cases by following formula using phi correlation coefficient:φ=(cd-ab)/√(a+c)(b+d)(b+c)(a+d). a,b,c,d: 2X2 decision matrix parameters. If TPR1=(a+c)/n, TPR2=(b+c)/n and TPR3=(a+b+c)/n for abnormal cases, TPR3=TPR1+TPR2 - TPR1×TRR2 - φ√TPR1(1-TPR1)TPR2(1-TPR2). Therefore, a=n (TPR3 - TPR1), b=n (TPR3 - TPR2), c=n (TPR1 + TPR2 -TPR3), d=n (1.0 - TPR3). This theory was applied for the experimental data. The 41 students interpreted the same CT images [no training]. A second interpretation was performed after they had been instructed on how to interpret CT images [training], and third was assisted by a virtual CAD [training + CAD]. The mechanism that makes up for a good point of a reader and a CAD with CAD in interpreting CT images was theoretically and experimentally investigated. We concluded that a method guessing the decision matrix (2X2) between a reader and a CAD decided the "presence" or "absence" of abnormal findings explain the improvement mechanism of diagnostic performance with CAD system.

  19. 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.

  20. 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.

  1. Mechanisms for enhanced performance of platinum-based electrocatalysts in proton exchange membrane fuel cells.

    PubMed

    Su, Liang; Jia, Wenzhao; Li, Chang-Ming; Lei, Yu

    2014-02-01

    As a new generation of power sources, fuel cells have shown great promise for application in transportation. However, the expensive catalyst materials, especially the cathode catalysts for oxygen reduction reaction (ORR), severely limit the widespread commercialization of fuel cells. Therefore, this review article focuses on platinum (Pt)-based electrocatalysts for ORR with better catalytic performance and lower cost. Major breakthroughs in the improvement of activity and durability of electrocatalysts are discussed. Specifically, on one hand, the enhanced activity of Pt has been achieved through crystallographic control, ligand effect, or geometric effect; on the other hand, improved durability of Pt-based cathode catalysts has been realized by means of the incorporation of another noble metal or the morphological control of nanostructures. Furthermore, based on these improvement mechanisms, rationally designed Pt-based nanoparticles are summarized in terms of different synthetic strategies such as wet-chemical synthesis, Pt-skin catalysts, electrochemically dealloyed nanomaterials, and Pt-monolayer deposition. These nanoparticulate electrocatalysts show greatly enhanced catalytic performance towards ORR, aiming not only to outperform the commercial Pt/C, but also to exceed the US Department of Energy 2015 technical target ($30/kW and 5000 h).

  2. 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.

  3. Flocculation performance and mechanism of graphene oxide for removal of various contaminants from water.

    PubMed

    Yang, Zhen; Yan, Han; Yang, Hu; Li, Haibo; Li, Aimin; Cheng, Rongshi

    2013-06-01

    The application of nanomaterials in water treatment plants has attracted significant attention recently. This study investigates the possibility of using graphene oxide (GO) as a novel flocculant to remove contaminants with different surface charges from water, including two particulate ones (kaolin and hematite) and two soluble ones (humic acid (HA) and cationic light yellow 7GL dye (7GL)). The flocculation performances of traditional polyaluminum chloride (PAC) and original graphite were also tested for comparison. Fractal theory was applied to evaluate the floc properties and explore the flocculation mechanism in combination with zeta potential measurements. For negatively charged contaminants, kaolin and HA, GO was observed to remove these contaminants successfully via the sweeping flocculation effect under acidic and neutral conditions. However, GO was less efficient than PAC. For positively charged contaminants, hematite and 7GL, the flocculation performances of GO were significantly improved than those of PAC via patching effect for hematite suspension and charge neutralization effect for 7GL solution. The results highlighted the extensive potential applicability of GO as a suitable flocculant in water treatment.

  4. Improving Arithmetic Performance with Number Sense Training: An Investigation of Underlying Mechanism

    PubMed Central

    Park, Joonkoo; Brannon, Elizabeth M.

    2014-01-01

    A nonverbal primitive number sense allows approximate estimation and mental manipulations on numerical quantities without the use of numerical symbols. In a recent randomized controlled intervention study in adults, we demonstrated that repeated training on a non-symbolic approximate arithmetic task resulted in improved exact symbolic arithmetic performance, suggesting a causal relationship between the primitive number sense and arithmetic competence. Here, we investigate the potential mechanisms underlying this causal relationship. We constructed multiple training conditions designed to isolate distinct cognitive components of the approximate arithmetic task. We then assessed the effectiveness of these training conditions in improving exact symbolic arithmetic in adults. We found that training on approximate arithmetic, but not on numerical comparison, numerical matching, or visuo-spatial short-term memory, improves symbolic arithmetic performance. In addition, a second experiment revealed that our approximate arithmetic task does not require verbal encoding of number, ruling out an alternative explanation that participants use exact symbolic strategies during approximate arithmetic training. Based on these results, we propose that nonverbal numerical quantity manipulation is one key factor that drives the link between the primitive number sense and symbolic arithmetic competence. Future work should explore implications from this finding that training young children on approximate arithmetic tasks even before they solidify the symbolic number understanding may be fruitful for improving readiness for math education. PMID:25044247

  5. Neural network approach for a combined performance and mechanical health monitoring of a gas turbine engine

    NASA Astrophysics Data System (ADS)

    Barad, Sanjay G.; P. V., Ramaiah; R. K., Giridhar; Krishnaiah, G.

    2012-02-01

    Traditionally independent diagnostics methods were employed for health monitoring of system. These exhibited an overall satisfactory performance, but with a limited effectiveness range. A discipline that has emerged in recent years is that of an information (or data) fusion, which allows interweaving of different methods with different effectiveness ranges, to produce a wider and more reliable coverage of diagnosis. It is a multidisciplinary domain wherein, data from the various domain is blended together to arrive at a more reliable monitoring. The present paper brings out a Neural Network (NN) based approach for executing this task of combined health monitoring viz. mechanical and performance, with an example case study pertaining to a developmental power turbine. The various parameters used along with the trending methodologies both for steady state and transient operations are brought out. In addition, the influences of various parameters that can lead to deviations in the response are also discussed. The whole process of executing this task is put forward in a rather simple manner. The results accrued have been well corroborated with the findings on dismantling of the turbine.

  6. US EPR Tests Performed to confirm the Mechanical and Hydraulic Design of the Vessel Internals

    SciTech Connect

    Dolleans, Philippe; Chambrin, Jean-Luc; Muller, Thierry

    2006-07-01

    The EPR is an Evolutionary high-Power Reactor which is based on the best French and German experience of the past twenty years in plant design construction and operation. In the present detailed engineering phase of the plant under construction in Finland (Okiluoto 3) or scheduled in France (Flamanville 3), a few actions are still ongoing mainly to complement equipment validation files. Design and validation of the main EPR components were performed within Framatome ANP's engineering teams and its two Technical Centers located in France and Germany, which develop state of the art methods in the field of thermo hydraulic testing. The Reactor Pressure Vessel internals are mainly derived from components already implemented on presently operating plants, but they differ in some features from the design used in French N4 or German Konvoi. The aim of this paper is to present the tests performed to confirm the hydraulic and mechanical design of the EPR vessel internals. - Four different mock-ups are presented to illustrate these tests: - JULIETTE for the reactor pressure vessel lower internals; - ROMEO for the reactor pressure vessel upper internals; - MAGALY for the design of the skeleton-type control rod guide assembly; - HYDRAVIB for the vibratory response of the reactor pressure vessel lowers internals. (authors)

  7. 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.

  8. 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

  9. 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

  10. 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

  11. WRAP low level waste restricted waste management (LLW RWM) glovebox acceptance test report

    SciTech Connect

    Leist, K.J.

    1997-11-24

    On April 22, 1997, the Low Level Waste Restricted Waste Management (LLW RWM) glovebox was tested using acceptance test procedure 13027A-87. Mr. Robert L. Warmenhoven served as test director, Mr. Kendrick Leist acted as test operator and test witness, and Michael Lane provided miscellaneous software support. The primary focus of the glovebox acceptance test was to examine glovebox control system interlocks, operator Interface Unit (OIU) menus, alarms, and messages. Basic drum port and lift table control sequences were demonstrated. OIU menus, messages, and alarm sequences were examined, with few exceptions noted. Barcode testing was bypassed, due to the lack of installed equipment as well as the switch from basic reliance on fixed bar code readers to the enhanced use of portable bar code readers. Bar code testing was completed during performance of the LLW RWM OTP. Mechanical and control deficiencies were documented as Test Exceptions during performance of this Acceptance Test. These items are attached as Appendix A to this report.

  12. 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.

  13. Comparison of human turning gait with the mechanical performance of lower limb prosthetic transverse rotation adapters.

    PubMed

    Flick, K C; Orendurff, M S; Berge, J S; Segal, A D; Klute, G K

    2005-04-01

    Given the importance of minimizing transverse plane shear stress on soft tissue, several transverse rotational adapters (TRAs) are available for incorporation in lower limb prostheses. This study compares kinetic and kinematic data from human subjects during straight and turning gaits to the mechanical performance of several TRAs. Physiological data were collected from three individuals walking straight and turning at self-selected speeds around a 1 m radius circle. The average peak torques and range of motion for normal subjects while turning were 8.2 Nm and 26 degrees (outside leg), 11.8Nm and 20 degrees (inside leg), and 11.4 Nm and 20 degrees (right leg) during straight gait. Each TRA was mechanically tested without axial loading in a servo-hydraulic material testing system (MTS) over its rotational range at 0.5 dergrees/s and 60 degrees/s. The TRAs with axial compression were also tested at 0.5 degrees/s under a 736N (75kg mass) axial load. Applying these torques to the different TRAs yielded 3 to 35 degrees rotation, depending on the elastomer installed. Some TRAs had nearly constant stiffness, while others stiffened with rotation. The TRAs also varied in their average maximum stiffness from 0.4Nm/degree to 2.7Nm/degrees. Normal subjects exhibit interior vs. exterior asymmetrical torques and displacements; however, only one of the TRAs is designed to allow asymmetrical stiffness, and none have asymmetric ranges. Prosthetists and physicians can use these data to better interpret amputees' qualitative remarks and to prescribe the correct TRA and/or elastomer. This information also forms a basis for further design and development of novel torque absorbing prosthetic adapters.

  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. 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

  16. 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.

  17. 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.

  18. Performance of a low cost MBT prior to landfilling: study of the biological treatment of size reduced MSW without mechanical sorting.

    PubMed

    Lornage, R; Redon, E; Lagier, T; Hébé, I; Carré, J

    2007-01-01

    In France, the interest in Mechanical Biological Treatment (MBT) prior to landfilling is actually growing. In the absence of acceptance criteria for the waste to be landfilled, an alternative to the intensive, high-technology MBT can only find its place in the French context if it shows substantial benefits from an environmental, economic or operational point of view. This paper presents an experiment of low-cost MBT of size reduced MSW without material splitting. The performance of an experimental, pilot-scale mechanical and biological treatment process has been studied on 37.5 Mg of raw municipal solid waste. The mechanical process has been kept simple with only coarse shredding and no material recovery. The biological treatment, which was a low-cost forced aeration process, was monitored for 25 weeks. The biogas production potential of the waste was reduced by 90% to 19 NL kgDM(-1). The initial AT4 index of 82.9 mg O2 gDM(-1) decreased to 16.0 mg O2 gDM(-1). After 25 weeks of aerobic treatment, the dry mass loss reached 37%, while the mass of waste going to landfill was reduced by 28%. The average performances of the process were explained by the biological process itself, which was not optimal, and also by the characteristics of the input waste. The high particle size of the treated waste and the high content of slowly biodegradable matter (such as paper and cardboard) may both be significant drawbacks for the biological stabilisation of waste.

  19. 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.

  20. 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.

  1. Mechanisms of differential pollen donor performance in wild radish, Raphanus sativus (Brassicaceae).

    PubMed

    Marshall, D L; Diggle, P K

    2001-02-01

    In order to understand the characters on which sexual selection might operate in plants, it is critical to assess the mechanisms by which pollen competition and mate choice occur. To address this issue we measured a number of postpollination characters, ranging from pollen germination and pollen tube growth to final seed paternity, in wild radish. Crosses were performed using four pollen donors on a total of 16 maternal plants (four each from four families). Maternal plants were grown under two watering treatments to evaluate the effects of maternal tissue on the process of mating. The four pollen donors differed significantly in number of seeds sired and differed overall in the mating characters measured. However, it was difficult to associate particular mechanistic characters with ability to sire seeds, perhaps because of interactions among pollen donors within styles or among pollen donors and maternal plants. The process of pollen tube growth and fertilization differed substantially among maternal watering treatments, with many early events occurring more quickly in stressed plants. Seed paternity, however, was somewhat more even among pollen donors used on stressed maternal plants, suggesting that when maternal tissue is more competent, mating is slowed and is more selective.

  2. Cr(VI) Adsorption on Red Mud Modified by Lanthanum: Performance, Kinetics and Mechanisms

    PubMed Central

    Cui, You-Wei; Li, Jie; Du, Zhao-Fu; Peng, Yong-Zhen

    2016-01-01

    Water pollution caused by the highly toxic metal hexavalent chromium (Cr(VI)) creates significant human health and ecological risks. In this study, a novel adsorbent was used to treat Cr(VI)-containing wastewater; the adsorbent was prepared using red mud (RM) generated from the alumina production industry and the rare earth element lanthanum. This study explored adsorption performance, kinetics, and mechanisms. Results showed that the adsorption kinetics of the RM modified by lanthanum (La-RM), followed the pseudo-second-order model, with a rapid adsorption rate. Cr(VI) adsorption was positively associated with the absorbent dose, pH, temperature, and initial Cr(VI) concentration; coexisting anions had little impact. The maximum Cr(VI) adsorption capacity was 17.35 mg/g. Cr(VI) adsorption on La-RM was a mono-layer adsorption pattern, following the Langmuir isotherm model. Thermodynamic parameters showed the adsorption was spontaneous and endothermic. The adsorption of Cr(VI) on La-RM occurred as a result of LaOCl formation on the RM surface, which in turn further reacted with Cr(VI) in the wastewater. This study highlighted a method for converting industrial waste into a valuable material for wastewater treatment. The novel absorbent could be used as a potential adsorbent for treating Cr(VI)-contaminating wastewater, due to its cost-effectiveness and high adsorption capability. PMID:27658113

  3. 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

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. Placebo mechanisms across different conditions: from the clinical setting to physical performance

    PubMed Central

    Pollo, Antonella; Carlino, Elisa; Benedetti, Fabrizio

    2011-01-01

    Although the great increase in interest in the placebo phenomenon was spurred by the clinical implications of its use, the progressive elucidation of the neurobiological and pharmacological mechanisms underlying the placebo effect also helps cast new light on the relationship between mind (and brain) and body, a topic of foremost philosophical importance but also a major medical issue in light of the complex interactions between the brain on the one hand and body functions on the other. While the concept of placebo can be a general one, with a broad definition generally applicable to many different contexts, the description of the cerebral processes called into action in specific situations can vary widely. In this paper, examples will be given where physiological or pathological conditions are altered following the administration of an inert substance or verbal instructions tailored to induce expectation of a change, and explanations will be offered with details on neurotransmitter changes and neural pathways activated. As an instance of how placebo effects can extend beyond the clinical setting, data in the physical performance domain and implications for sport competitions will also be presented and discussed. PMID:21576136

  9. Protein supplementation for military personnel: a review of the mechanisms and performance outcomes.

    PubMed

    McLellan, Tom M

    2013-11-01

    Protein supplement use is common among athletes, active adults, and military personnel. This review provides a summary of the evidence base that either supports or refutes the ergogenic effects associated with different mechanisms that have been proposed to support protein supplementation. It was clear that if carbohydrate delivery was optimal either during or after an acute bout of exercise that additional protein will not increase exercise capacity. Evidence was also weak to substantiate use of protein supplements to slow the increase in brain serotonin and onset of central fatigue. It was also evident that additional research is warranted to test whether the benefits of protein supplements for enhancing recovery of fluid balance after exercise will affect subsequent work in the heat. In contrast, with repeated exercise, use of protein supplementation was associated with reductions in muscle soreness and often a faster recovery of muscle function due to reductions in protein degradation. There was also good supportive evidence for long-term benefits of protein supplementation for gains in muscle mass and strength through accelerated rates of protein synthesis, as long as the training stimulus was of sufficient intensity, frequency, and duration. However, studies have not examined the impact of protein supplements under the combined stress of a military environment that includes repeated bouts of exercise with little opportunity for feeding and recovery, lack of sleep, and exposure to extreme environments. Both additional laboratory and field research is warranted to help provide evidence-based guidance for the choice of protein supplements to enhance soldier performance.

  10. 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.

  11. 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...

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. Traits, properties, and performance: how woody plants combine hydraulic and mechanical functions in a cell, tissue, or whole plant.

    PubMed

    Lachenbruch, Barbara; McCulloh, Katherine A

    2014-12-01

    This review presents a framework for evaluating how cells, tissues, organs, and whole plants perform both hydraulic and mechanical functions. The morphological alterations that affect dual functionality are varied: individual cells can have altered morphology; tissues can have altered partitioning to functions or altered cell alignment; and organs and whole plants can differ in their allocation to different tissues, or in the geometric distribution of the tissues they have. A hierarchical model emphasizes that morphological traits influence the hydraulic or mechanical properties; the properties, combined with the plant unit's environment, then influence the performance of that plant unit. As a special case, we discuss the mechanisms by which the proxy property wood density has strong correlations to performance but without direct causality. Traits and properties influence multiple aspects of performance, and there can be mutual compensations such that similar performance occurs. This compensation emphasizes that natural selection acts on, and a plant's viability is determined by, its performance, rather than its contributing traits and properties. Continued research on the relationships among traits, and on their effects on multiple aspects of performance, will help us better predict, manage, and select plant material for success under multiple stresses in the future.

  20. 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.

  1. 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…

  2. 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.

  3. Dissolution test acceptance sampling plans.

    PubMed

    Tsong, Y; Hammerstrom, T; Lin, K; Ong, T E

    1995-07-01

    The U.S. Pharmacopeia (USP) general monograph provides a standard for dissolution compliance with the requirements as stated in the individual USP monograph for a tablet or capsule dosage form. The acceptance rules recommended by USP have important roles in the quality control process. The USP rules and their modifications are often used as an industrial lot release sampling plan, where a lot is accepted when the tablets or capsules sampled are accepted as proof of compliance with the requirement. In this paper, the operating characteristics of the USP acceptance rules are reviewed and compared to a selected modification. The operating characteristics curves show that the USP acceptance rules are sensitive to the true mean dissolution and do not reject a lot or batch that has a large percentage of tablets that dissolve with less than the dissolution specification.

  4. Study on preparation and mechanical performance of TPU/nonwoven composites

    NASA Astrophysics Data System (ADS)

    Sun, X. C.; Xi, B. J.

    2016-07-01

    In order to study the influence of resin content and layer sequence parameters on the mechanical properties of TPU/non-woven composite materials synthesized by moulding pressing technology. The effects of the resin content and layer sequence on composites were discussed. Through experiments and theoretical analysis, it was revealed how resin content, layer sequence impact on mechanical properties of composite. The mechanics properties of TPU/non-woven composite materials are improved. The process is pressure 0.5 MPa, temperature 110 °C and time 120s min. The melting of the TPU infiltrated into the fabric and filled the space between the fibers.

  5. Neural Mechanisms Underlying Paradoxical Performance for Monetary Incentives Are Driven by Loss Aversion

    PubMed Central

    Chib, Vikram S.; De Martino, Benedetto; Shimojo, Shinsuke; O'Doherty, John P.

    2012-01-01

    Summary 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

  6. 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

  7. Performance comparisons of naturally and mechanically ventilated solar-assisted nurseries

    SciTech Connect

    Milanuk, M.; Bodman, G.R.; DeShazer, J.A.; Schulte, D.

    1983-12-01

    When combined with solar floor heating and careful management, naturally ventilated swine nurseries can result in energy savings and comparable pig responses to mechanically ventilated nurseries of the current design that were also solar assisted.

  8. 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.

  9. 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…

  10. 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…

  11. A Plan to Organize Performance Based Auto Mechanics Programs and Derive Learning Content. Information Series Number Four. A Project Report.

    ERIC Educational Resources Information Center

    West, Bill R.; Brannock, Dennis

    A plan was created for organizing and deriving the learning content of a multi-occupational, performance based vocational education (PBVE) Indiana high school auto mechanics program in vehicle repair. Three surveys were conducted. First, 498 businesses were surveyed to determine existing vehicle repair job titles in Indiana and ways to group these…

  12. 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…

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Extending the Technology Acceptance Model: Policy Acceptance Model (PAM)

    NASA Astrophysics Data System (ADS)

    Pierce, Tamra

    There has been extensive research on how new ideas and technologies are accepted in society. This has resulted in the creation of many models that are used to discover and assess the contributing factors. The Technology Acceptance Model (TAM) is one that is a widely accepted model. This model examines people's acceptance of new technologies based on variables that directly correlate to how the end user views the product. This paper introduces the Policy Acceptance Model (PAM), an expansion of TAM, which is designed for the analysis and evaluation of acceptance of new policy implementation. PAM includes the traditional constructs of TAM and adds the variables of age, ethnicity, and family. The model is demonstrated using a survey of people's attitude toward the upcoming healthcare reform in the United States (US) from 72 survey respondents. The aim is that the theory behind this model can be used as a framework that will be applicable to studies looking at the introduction of any new or modified policies.

  20. 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.

  1. Decoupling congestion control and error control mechanisms in TCP and evaluating their performance over broadband satellite networks

    NASA Astrophysics Data System (ADS)

    Wang, Lina; Gu, Xuemai

    2004-04-01

    In this paper, we propose a novel method to better evaluate the performance of TCP over broadband satellite networks. We decouple the most crucial parts of TCP that impact its performance in broadband satellite environments, namely congestion control and error control mechanisms. And then we re-design these two function blocks and make them become two individual parts. With these re-designed modules, we have investigated the interactions between various currently existing TCP congestion control and error control schemes, as well as their impact on TCP performance over a geostationary broadband satellite link with long propagation delay and high bit error rate. Simulation results have shown that some combinations of different congestion control and error control mechanisms can waste satellite link bandwidth with large numbers of retransmission packets and unnecessary retransmission packets. And the modified TCP NewReno implementation can avoid high amount of retransmissions and unnecessary retransmissions.

  2. 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.

  3. Reduced order modeling of mechanical degradation induced performance decay in lithium-ion battery porous electrodes

    DOE PAGES

    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

  4. Characterization for the performance of capacitive switches activated by mechanical shock

    PubMed Central

    Younis, Mohammad I.; Alsaleem, Fadi M; Miles, Ronald; Su, Quang

    2009-01-01

    This paper presents experimental and theoretical investigation of a new concept of switches (triggers) that are actuated at or beyond a specific level of mechanical shock or acceleration. The principle of operation of the switches is based on dynamic pull-in instability induced by the combined interaction between electrostatic and mechanical shock forces. These switches can be tuned to be activated at various shock and acceleration thresholds by adjusting the DC voltage bias. Two commercial off-the-shelf capacitive accelerometers operating in air are tested under mechanical shock and electrostatic loading. A single-degree-of-freedom model accounting for squeeze-film damping, electrostatic forces, and mechanical shock is utilized for the theoretical investigation. Good agreement is found between simulation results and experimental data. Our results indicate that designing these new switches to respond quasi-statically to mechanical shock makes them robust against variations in shock shape and duration. More importantly, quasi-static operation makes the switches insensitive to variations in damping conditions. This can be promising to lower the cost of packaging for these switches since they can operate in atmospheric pressure with no hermetic sealing or costly package required. PMID:21720493

  5. 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.

  6. 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…

  7. 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.

  8. 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

  9. 46 CFR 164.023-11 - Acceptance tests.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...), as appropriate, are performed on a minimum of five samples in each of the lightest and darkest colors... 46 Shipping 6 2010-10-01 2010-10-01 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....

  10. 10 CFR 36.41 - Construction monitoring and acceptance testing.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... IRRADIATORS Design and Performance Requirements for Irradiators § 36.41 Construction monitoring and acceptance... foundations to verify that their construction meets design specifications. (c) Pool integrity. For pool... 10 Energy 1 2012-01-01 2012-01-01 false Construction monitoring and acceptance testing....

  11. 10 CFR 36.41 - Construction monitoring and acceptance testing.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... IRRADIATORS Design and Performance Requirements for Irradiators § 36.41 Construction monitoring and acceptance... foundations to verify that their construction meets design specifications. (c) Pool integrity. For pool... 10 Energy 1 2014-01-01 2014-01-01 false Construction monitoring and acceptance testing....

  12. 10 CFR 36.41 - Construction monitoring and acceptance testing.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... IRRADIATORS Design and Performance Requirements for Irradiators § 36.41 Construction monitoring and acceptance... foundations to verify that their construction meets design specifications. (c) Pool integrity. For pool... 10 Energy 1 2011-01-01 2011-01-01 false Construction monitoring and acceptance testing....

  13. 10 CFR 36.41 - Construction monitoring and acceptance testing.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... IRRADIATORS Design and Performance Requirements for Irradiators § 36.41 Construction monitoring and acceptance... foundations to verify that their construction meets design specifications. (c) Pool integrity. For pool... 10 Energy 1 2013-01-01 2013-01-01 false Construction monitoring and acceptance testing....

  14. 10 CFR 36.41 - Construction monitoring and acceptance testing.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... IRRADIATORS Design and Performance Requirements for Irradiators § 36.41 Construction monitoring and acceptance... foundations to verify that their construction meets design specifications. (c) Pool integrity. For pool... 10 Energy 1 2010-01-01 2010-01-01 false Construction monitoring and acceptance testing....

  15. 48 CFR 28.203-3 - Acceptance of real property.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 48 Federal Acquisition Regulations System 1 2010-10-01 2010-10-01 false Acceptance of real... Acceptance of real property. (a) Whenever a bond with a security interest in real property is submitted, the..., () performance bond, () or payment bond obligations as an individual surety on solicitation/contract...

  16. 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...

  17. 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...

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. 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.

  4. Viking GC/MS mechanisms design and performance. [for analyzing samples of Martian surface

    NASA Technical Reports Server (NTRS)

    Chase, C. P.; Weilbach, A. O.

    1976-01-01

    The Viking Lander gas chromatograph/mass spectrometer will analyze pyrolyzed samples of the Martian surface for organic content. The surface-sample loader and pyrolyzer assembly (SSPLA) is described, along with the major problems encountered during design and testing. Three mechanisms were developed to implement the required SSLPA functions: (1) a soil loader that forces soil from a filled rotating funnel into each of three ovens located on a carriage, (2) a Geneva drive for rotating and precisely indexing the ovens to receive sample, and (3) a toggle-clamp mechanism for sealing the ovens by forcing circular double knife edges into gold sealing surfaces.

  5. 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

  6. 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

  7. Mechanical work performed by individual limbs of transfemoral amputees during step-to-step transitions: Effect of walking velocity.

    PubMed

    Bonnet, Xavier; Villa, Coralie; Fodé, Pascale; Lavaste, Francois; Pillet, Hélène

    2014-01-01

    The greater metabolic demand during the gait of people with a transfemoral amputation limits their autonomy and walking velocity. Major modifications of the kinematic and kinetic patterns of transfemoral amputee gait quantified using gait analysis may explain their greater energy cost. Donelan et al. proposed a method called the individual limb method to explore the relationships between the gait biomechanics and metabolic cost. In the present study, we applied this method to quantify mechanical work performed by the affected and intact limbs of transfemoral amputees. We compared a cohort of six active unilateral transfemoral amputees to a control group of six asymptomatic subjects. Compared to the control group, we found that there was significantly less mechanical work produced by the affected leg and significantly more work performed by the unaffected leg during the step-to-step transition. We also found that this mechanical work increased with walking velocity; the increase was less pronounced for the affected leg and substantial for the unaffected leg. Finally, we observed that the lesser work produced by the affected leg was linked to the increase in the hip flexion moment during the late stance phase, which is necessary for initiating knee flexion in the affected leg. It is possible to quantify the mechanical work performed during gait by people with a transfemoral amputation, using the individual limb method and conventional gait laboratory equipment. The method provides information that is useful for prosthetic fitting and rehabilitation.

  8. [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

  9. 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.

  10. Whole shaft visibility and mechanical performance for active MR catheters using copper-nitinol braided polymer tubes

    PubMed Central

    Kocaturk, Ozgur; Saikus, Christina E; Guttman, Michael A; Faranesh, Anthony Z; Ratnayaka, Kanishka; Ozturk, Cengizhan; McVeigh, Elliot R; Lederman, Robert J

    2009-01-01

    Background Catheter visualization and tracking remains a challenge in interventional MR. Active guidewires can be made conspicuous in "profile" along their whole shaft exploiting metallic core wire and hypotube components that are intrinsic to their mechanical performance. Polymer-based catheters, on the other hand, offer no conductive medium to carry radio frequency waves. We developed a new "active" catheter design for interventional MR with mechanical performance resembling braided X-ray devices. Our 75 cm long hybrid catheter shaft incorporates a wire lattice in a polymer matrix, and contains three distal loop coils in a flexible and torquable 7Fr device. We explored the impact of braid material designs on radiofrequency and mechanical performance. Results The incorporation of copper wire into in a superelastic nitinol braided loopless antenna allowed good visualization of the whole shaft (70 cm) in vitro and in vivo in swine during real-time MR with 1.5 T scanner. Additional distal tip coils enhanced tip visibility. Increasing the copper:nitinol ratio in braiding configurations improved flexibility at the expense of torquability. We found a 16-wire braid of 1:1 copper:nitinol to have the optimum balance of mechanical (trackability, flexibility, torquability) and antenna (signal attenuation) properties. With this configuration, the temperature increase remained less than 2°C during real-time MR within 10 cm horizontal from the isocenter. The design was conspicuous in vitro and in vivo. Conclusion We have engineered a new loopless antenna configuration that imparts interventional MR catheters with satisfactory mechanical and imaging characteristics. This compact loopless antenna design can be generalized to visualize the whole shaft of any general-purpose polymer catheter to perform safe interventional procedures. PMID:19674464

  11. 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…

  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. 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…

  14. Physics Problem Solving: Student Performance Analysis on Mechanics Problems Requiring Diagrammatic Visualisation.

    ERIC Educational Resources Information Center

    Prendergast, Wilfred Francis

    This study investigated problem solving skills in mechanics problems that required the use of diagrams. These skills were examined in two ways. First, the study examined student problem solving skills using solution scripts from the Western Australian Tertiary Admission Examination in physics. Solution attempts by students in the 1978 and 1979…

  15. 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…

  16. 46 CFR 160.133-7 - Design, construction, and performance of release mechanisms.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... compatible or insulated with suitable non-porous materials. Provisions must also be made to prevent loosening...) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Release Mechanisms... recommendation on testing, Part 1/6.9 (incorporated by reference, see § 160.133-5 of this subpart); (3) 46...

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

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ...-porous materials. Provisions must also be made to prevent loosening or tightening resulting from...) EQUIPMENT, CONSTRUCTION, AND MATERIALS: SPECIFICATIONS AND APPROVAL LIFESAVING EQUIPMENT Release Mechanisms... by reference, see § 160.133-5 of this subpart); (3) 46 CFR part 159; and (4) This subpart. (b)...

  18. 46 CFR 160.170-7 - Design, construction, and performance of automatic release mechanisms.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 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 58... recommendation on testing Part 1/8.2 (incorporated by reference, see § 160.170-5 of this subpart). (3) 46...

  19. 46 CFR 160.133-7 - Design, construction, and performance of release mechanisms.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... recognized by the Commandant in accordance with 46 CFR 8.220, the U.S. Navy, or the national body where the... recommendation on testing, Part 1/6.9 (incorporated by reference, see § 160.133-5 of this subpart); (3) 46 CFR... persons wearing immersion suits; (2) Each release mechanism should be designed following standard...

  20. Confidence versus Performance as an Indicator of the Presence of Alternative Conceptions and Inadequate Problem-Solving Skills in Mechanics

    NASA Astrophysics Data System (ADS)

    Potgieter, Marietjie; Malatje, Esther; Gaigher, Estelle; Venter, Elsie

    2010-07-01

    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 tests from literature, each of which was followed by a self-reported measure of confidence of students in the correctness of their answers. Data collected for this study included students' responses to multiple-choice questions and open-ended explanations for their chosen answers. Fixed response physics and confidence data were logarithmically transformed according to the Rasch model to linear measures of performance and confidence. The free response explanations were carefully analysed for accuracy of conceptual understanding. Comparison of these results with raw score data and transformed measures of performance and confidence allowed a re-evaluation of the model developed by Hasan, Bagayoko, and Kelley in 1999 for the detection of alternative conceptions in mechanics. Application of this model to raw score data leads to inaccurate conclusions. However, application of the Hasan hypothesis to transformed measures of performance and confidence resulted in the accurate identification of items plagued by alternative conceptions. This approach also holds promise for the differentiation between over-confidence due to alternative conceptions or due to inadequate problem-solving skills. It could become a valuable tool for instructional design in mechanics.

  1. 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

  2. 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

  3. 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.

  4. 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.

  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. Tuning mechanical performance of poly(ethylene glycol) and agarose interpenetrating network hydrogels for cartilage tissue engineering.

    PubMed

    Rennerfeldt, Deena A; Renth, Amanda N; Talata, Zsolt; Gehrke, Stevin H; Detamore, Michael S

    2013-11-01

    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.

  7. 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

  8. 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.

  9. 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.

  10. 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.

  11. [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

  12. Anatomy of a nanoscale conduction channel reveals the mechanism of a high-performance memristor.

    PubMed

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

    2011-12-15

    By employing a precise method for locating and directly imaging the active switching region in a resistive random access memory (RRAM) device, a nanoscale conducting channel consisting of an amorphous Ta(O) solid solution surrounded by nearly stoichiometric Ta(2) O(5) is observed. Structural and chemical analysis of the channel combined with temperature-dependent transport measurements indicate a unique resistance switching mechanism.

  13. 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

    2016-03-28

    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(C)(S) governs the strength of the assembly as predicted by the shear-lag model. The intermediate critical length L(C)(P) 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(C)(T) 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

  14. 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

    2016-03-28

    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(C)(S) governs the strength of the assembly as predicted by the shear-lag model. The intermediate critical length L(C)(P) 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(C)(T) 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.

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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

  20. Direct correlation of single-molecule properties with bulk mechanical performance for the biomimetic design of polymers.

    PubMed

    Chung, Jaeyoon; Kushner, Aaron M; Weisman, Adam C; Guan, Zhibin

    2014-11-01

    For rational design of advanced polymeric materials, it is critical to establish a clear mechanistic link between the molecular structure of a polymer and the emergent bulk mechanical properties. Despite progress towards this goal, it remains a major challenge to directly correlate the bulk mechanical performance to the nanomechanical properties of individual constituent macromolecules. Here, we show a direct correlation between the single-molecule nanomechanical properties of a biomimetic modular polymer and the mechanical characteristics of the resulting bulk material. The multi-cyclic single-molecule force spectroscopy (SMFS) data enabled quantitative derivation of the asymmetric potential energy profile of individual module rupture and re-folding, in which a steep dissociative pathway accounted for the high plateau modulus, while a shallow associative well explained the energy-dissipative hysteresis and dynamic, adaptive recovery. These results demonstrate the potential for SMFS to serve as a guide for future rational design of advanced multifunctional materials.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. Molecular dynamics study of binding energies, mechanical properties, and detonation performances of bicyclo-HMX-based PBXs.

    PubMed

    Qiu, Ling; Xiao, Heming

    2009-05-15

    To investigate the effect of polymer binders on the monoexplosive, molecular dynamics simulations were performed to study the binding energies, mechanical properties, and detonation performances of the bicyclo-HMX-based polymer-bonded explosives (PBXs). The results show that the binding energies on different crystalline surfaces of bicyclo-HMX decrease in the order of (010)>(100)>(001). On each crystalline surface, binding properties of different polymers with the same chain segment are different from each other, while those of the polymers in the same content decrease in the sequence of PVDF>F(2311)>F(2314) approximately PCTFE. The mechanical properties of a dozen of model systems (elastic coefficients, various moduli, Cauchy pressure, and Poisson's ratio) have been obtained. It is found that mechanical properties are effectively improved by adding small amounts of fluorine polymers, and the overall effect of fluorine polymers on three crystalline surfaces of bicyclo-HMX changes in the order of (010)>(001) approximately (100). In comparison with the base explosive, detonation performances of the PBXs decrease slightly, but they are still superior to TNT. These suggestions may be useful for the formulation design of bicyclo-HMX-based PBXs.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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

  20. 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.

  1. The effect of ductile innerlayers on the mechanical performance of fiber-reinforced composite materials

    SciTech Connect

    Hsu, Meng-Bor.

    1990-01-01

    The effects of ductile innerlayers on the mechanical behavior of unidirectional fiber reinforced composites were studied. Two fiber systems were used as the reinforcement; a monofilament system and a roving system. The ductile innerlayer materials were applied on fiber surfaces using coating equipment that was first designed for monofilament coating. For composites reinforced by rovings, problems such as nonuniform fiber distribution and resin starvation in spaces between closely packed filaments arise from the coating process. Even with these problems, improvement in transverse tensile strength, longitudinal compressive strength, flexural fatigue resistance, and fatigue endurance limit were achieved. For monofilament systems, properties such as flexural strength, interlaminar shear strength, and transverse tensile strength are improved by the application of ductile innerlayers. Three mechanisms were shown to be responsible for the improvements: by acting as a spacer and preventing fiber-fiber contact; local ductility is provided near the fiber-matrix interface and lowering stress concentrations; and healing surface flaws in large diameter fiber systems, thus increasing fiber strength.

  2. 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

  3. Math-Fact Retrieval as the Cognitive Mechanism Underlying Gender Differences in Math Test Performance.

    PubMed

    Royer; Tronsky; Chan; Jackson; Marchant

    1999-07-01

    Males from select populations receive better scores on standardized math achievement tests than females. The research reported in this article evaluates the hypothesis that the reason for these differences is that males are faster at retrieving basic math facts. Studies 1-3 demonstrate that math-fact retrieval predicts performance on math achievement tests with students in grades 5-8 and in college. Studies 4-6 show that males and females in grades 2-8 and in college have different patterns of math-fact retrieval performance and that males at the high positive end of the retrieval distribution are faster than comparable females. Study 5 also demonstrates that math-fact retrieval varies in three populations (Anglo-American, Chinese-American, Hong Kong Chinese) and that speed of retrieval improves with practice. Studies 7-9 tested the hypothesis that males are faster than females on retrieval tasks in general. Study 7 showed that there were no gender differences on simple retrieval tasks, and Studies 8 and 9 showed that females were slightly faster than males on verbal-processing tasks. The General Discussion indicates that the math-fact retrieval hypothesis is consistent with previous research. It also relates the math-fact retrieval hypothesis to theories of cognitive performance and introduces the practice and engagement hypothesis. This hypothesis explains the origin of gender differences in math and reading and relates those differences to the existing literature on gender differences in academic performance. The article concludes with a description of needed future research and a discussion of the educational implications of the math-fact retrieval hypothesis. Copyright 1999 Academic Press.

  4. 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.

  5. Environmentally induced mechanical feedback in locomotion: frog performance as a model.

    PubMed

    Aerts, Peter; Nauwelaerts, Sandra

    2009-12-01

    At first glance, the strategy for generating propulsive impulses for both jumping and swimming in frogs is quite similar. Both modes rely on powerful extension of the hind limbs. However, in Rana esculenta (the semi-aquatic green frog), propulsive impulses for jumping were found to be much larger than those generated during swimming [Nauwelaerts and Aerts, 2003. Propulsive impulses as a covarying performance measure in the comparison of the kinematics of swimming and jumping in frogs. J. Exp. Biol. 206, 4341-4351]. The hypothesis that differences in propulsive impulse between swimming and jumping are largely caused by specific environmental constraints rather than being due to changes in motor control is tested in the present study. To assess this question, the actuator of a simple mathematical model, mimicking a frog with symmetrically kicking hind limbs, is first tuned to perform frog-like jumps. Next, the same actuator activation is applied to drive the model in an 'aquatic environment'. Despite the entirely identical activation, the resulting in silico propulsive swimming impulse was less than half that produced during jumping, just as observed in vivo. Although duration of limb extension is similar for both locomotor modes (both in vivo and in silico), this conspicuous difference in model behaviour is entirely explained by the actuator working at different positions along its force-velocity curve. These findings suggest that the same environmentally induced effects are also involved in real swimming and jumping as well, thus explaining the apparent difference in performance level.

  6. Optimum Design of Thin Walled Tube on the Mechanical Performance of Super Lock Nut

    NASA Astrophysics Data System (ADS)

    Noda, Nao-Aki; Xiao, Yang; Kuhara, Masahiro; Saito, Kinjiro; Nagawa, Masato; Yumoto, Atsushi; Ogasawara, Ayako

    The bolts and nuts are widely used in various fields as important joining elements with long history. However, loosening induced by the vibration and external loads is still a big problem. For example, the loosening sometimes causes very serious accident without notice. This paper deals with a special nut named “Super Lock Nut (SLN)” which can prevent loosening effectively. There is a thin walled tube between the upper and lower threads, which can be deformed along the axial direction so that the phase difference of lower and upper threads is produced and SLN is developed. This phase difference induces the contrary forces on the surfaces of the upper and lower threads, which bring out the anti-loosening performance. In this study, the anti-loosening performance is analyzed and realized with the finite element method. Moreover, the anti-loosening performances under various phase difference of lower and upper threads are compared and finally best dimensions for SLN are examined.

  7. [Acceptance check and quality control of SPECT].

    PubMed

    Sun, L M; Liu, C B

    2001-05-01

    This paper explains the testing of SPECT, especially the new SPECT with double digital detector and spiral scanning frames that has been introduced to China recently, in the acceptance check, proceeding from the physical functions of the system to its mechanical functions, to the NEMA standard functions, and then to the computer hardware specified in the contract. A brief introduction is also given of the quality control of SPECT in terms of its spatial resolution, energy resolution, spatial linearity, sensitivity, and center of rotation. PMID:12583289

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. Influences of carbon nanofillers on mechanical performance of epoxy resin polymer

    NASA Astrophysics Data System (ADS)

    Singh, Shraddha; Srivastava, V. K.; Prakash, Rajiv

    2015-03-01

    The influence of multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GnPs) on epoxy resin was investigated to compare their mechanical properties. MWCNT/epoxy resin and GnP/epoxy resin composites were compared with each other for their tensile strength, compressive strength, Charpy Impact and Izod impact energy with the variation of weight percentage ratio of nanofiller ranging from 0.5, 1.0, 2.0 and 3.0, respectively. The result shows that GnP/epoxy resin composite gave better tensile and compressive strength compared to MWCNT/epoxy resin composite whereas Izod impact energy, Charpy impact energy and dynamic fracture toughness of MWCNT/epoxy resin composite resulted in better impact resistance than the GnP/epoxy resin composite. Thermal stability and microstructural properties of composites were measured using Thermogravimetric analysis (TGA), transmission electron microscope (TEM) and scanning electron microscope (SEM).

  15. 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

  16. 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

  17. 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

  18. Acceptance test report, inlet air filter and control station pressure decay leak test

    SciTech Connect

    Tuck, J.A., Fluor Daniel Hanford

    1997-02-11

    This is the acceptance test report for pressure decay leak tests performed on Tank Farm primary ventilation system inlet air filter and control stations, following their installation in the field and prior to acceptance for beneficial use.

  19. 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

  20. Mechanical properties of high performance concrete made with high calcium high sulfate fly ash

    SciTech Connect

    Zhang, Y.; Sun, W.; Shang, L.

    1997-07-01

    A high calcium fly ash with high SO{sub 3} content was used to produce high performance concrete. In all the mixes, the fly ash contents of 50% and 60% by weight were applied. Although fly ash cement pastes showed severe volume instability and poor pore structure development, mortars and concretes incorporating high mass high calcium fly ash exhibited good performance in both fresh and hardened state as those with low calcium fly ash did. The 3d and 28d compressive strength of mortars reached 25.2--42.2MPa respectively with the water binder ratio varying from 0.30 to 0.24. What is noticeable is that all the mortars and concretes showed good strength developing tendency with the 90d compressive strength up to 67.3--85.5MPa. This investigation reveals once more the fact that some materials which are not up to standard can still play a special role so long as the components are carefully chosen and proportions properly designed.

  1. Operation mechanism of high performance organic permeable base transistors with an insulated and perforated base electrode

    NASA Astrophysics Data System (ADS)

    Kaschura, Felix; Fischer, Axel; Klinger, Markus P.; Doan, Duy Hai; Koprucki, Thomas; Glitzky, Annegret; Kasemann, Daniel; Widmer, Johannes; Leo, Karl

    2016-09-01

    The organic permeable base transistor is a vertical transistor architecture that enables high performance while maintaining a simple low-resolution fabrication. It has been argued that the charge transport through the nano-sized openings of the central base electrode limits the performance. Here, we demonstrate by using 3D drift-diffusion simulations that this is not the case in the relevant operation range. At low current densities, the applied base potential controls the number of charges that can pass through an opening and the opening is the current limiting factor. However, at higher current densities, charges accumulate within the openings and in front of the base insulation, allowing for an efficient lateral transport of charges towards the next opening. The on-state in the current-voltage characteristics reaches the maximum possible current given by space charge limited current transport through the intrinsic semiconductor layers. Thus, even a small effective area of the openings can drive huge current densities, and further device optimization has to focus on reducing the intrinsic layer thickness to a minimum.

  2. 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.

  3. Two-dimensional confined jet thrust vector control: Operating mechanisms and performance

    NASA Astrophysics Data System (ADS)

    Caton, Jeffrey L.

    1989-03-01

    An experimental investigation of two-dimensional confined jet thrust vector control nozzles was performed. Thrust vector control was accomplished by using secondary flow injection in the diverging section of the nozzle. Schlieren photographs and video tapes were used to study flow separation and internal shock structures. Nozzle performance parameters were determined for nozzle flow with and without secondary flows. These parameters included nozzles forces, vector angles, thrust efficiencies, and flow switching response times. Vector angles as great as 18 degrees with thrust efficiencies of 0.79 were measured. Several confined jet nozzles with variations in secondary flow port design were tested and results were compared to each other. Converging-diverging nozzles of similar design to the confined jet nozzles were also tested and results were compared to the confined jet nozzle results. Existing prediction models for nozzle side to axial force ratio were evaluated. A model for nozzle total forces based on shock losses that predicted values very close to actual results was developed.

  4. 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.

  5. Optimization of the mechanical performance of bacterial cellulose/poly(L-lactic) acid composites.

    PubMed

    Quero, Franck; Nogi, Masaya; Yano, Hiroyuki; Abdulsalami, Kovo; Holmes, Stuart M; Sakakini, Bahij H; Eichhorn, Stephen J

    2010-01-01

    Understanding the nature of the interface between nanofibers and polymer resins in composite materials is challenging because of the complexity of interactions that may occur between fibers and between the matrix and the fibers. The ability to select the most efficient amount of reinforcement for stress transfer, making a saving on both cost and weight, is also a key part of composite design. The use of Raman spectroscopy to investigate micromechanical properties of laminated bacterial cellulose (BC)/poly(l-lactic) acid (PLLA) resin composites is reported for the first time as a means for understanding the fundamental stress-transfer processes in these composites, but also as a tool to select appropriate processing and volume fraction of the reinforcing fibers. Two forms of BC networks are investigated, namely, one cultured for 3 days and another for 6 days. The mechanical properties of the latter were found to be higher than the former in terms of Young's modulus, stress at failure, and work of fracture. However, their specific Young's moduli (divided by density) were found to be similar. Young's modulus and stress at failure of transparent predominantly amorphous PLLA films were found to increase by 100 and 315%, respectively, for an 18% volume fraction of BC fibers. BC networks cultured for 3 days were shown to exhibit enhanced interaction with PLLA because of their higher total surface area compared, as measured by nitrogen adsorption, to the material cultured for 6 days. This enhanced interaction is confirmed by using the Raman spectroscopic approach, whereby larger band shift rates, of a peak initially located at 1095 cm(-1), with respect to both strain and stress, are observed, which is a quantitative measure of enhanced stress transfer. Thermal analysis (differential scanning calorimetry) and electron microscopy imaging (scanning electron microscopy) of the samples also confirms the enhanced coupling between the resin and the BC networks cultured for 3 days

  6. 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

  7. User acceptance of mobile commerce: an empirical study in Macau

    NASA Astrophysics Data System (ADS)

    Lai, Ivan K. W.; Lai, Donny C. F.

    2014-06-01

    This study aims to examine the positive and negative factors that can significantly explain user acceptance of mobile commerce (m-commerce) in Macau. A technology acceptance model for m-commerce with five factors is constructed. The proposed model is tested using data collected from 219 respondents. Confirmatory factor analysis is performed to examine the reliability and validity of the model, and structural equation modelling is performed to access the relationship between behaviour intention and each factor. The acceptance of m-commerce is influenced by factors including performance expectancy, social influence, facilitating conditions and privacy concern; while effort expectancy is insignificant in this case. The results of the study are useful for m-commerce service providers to adjust their strategies for promoting m-commerce services. This study contributes to the practice by providing a user technology acceptance model for m-commerce that can be used as a foundation for future research.

  8. 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.

  9. 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

  10. Imaginary Companions and Peer Acceptance

    ERIC Educational Resources Information Center

    Gleason, Tracy R.

    2004-01-01

    Early research on imaginary companions suggests that children who create them do so to compensate for poor social relationships. Consequently, the peer acceptance of children with imaginary companions was compared to that of their peers. Sociometrics were conducted on 88 preschool-aged children; 11 had invisible companions, 16 had personified…

  11. Acceptance of Others (Number Form).

    ERIC Educational Resources Information Center

    Masters, James R.; Laverty, Grace E.

    As part of the instrumentation to assess the effectiveness of the Schools Without Failure (SWF) program in 10 elementary schools in the New Castle, Pa. School District, the Acceptance of Others (Number Form) was prepared to determine pupil's attitudes toward classmates. Given a list of all class members, pupils are asked to circle a number from 1…

  12. W-025, acceptance test report

    SciTech Connect

    Roscha, V.

    1994-10-04

    This acceptance test report (ATR) has been prepared to establish the results of the field testing conducted on W-025 to demonstrate that the electrical/instrumentation systems functioned as intended by design. This is part of the RMW Land Disposal Facility.

  13. Euthanasia Acceptance: An Attitudinal Inquiry.

    ERIC Educational Resources Information Center

    Klopfer, Fredrick J.; Price, William F.

    The study presented was conducted to examine potential relationships between attitudes regarding the dying process, including acceptance of euthanasia, and other attitudinal or demographic attributes. The data of the survey was comprised of responses given by 331 respondents to a door-to-door interview. Results are discussed in terms of preferred…

  14. Helping Our Children Accept Themselves.

    ERIC Educational Resources Information Center

    Gamble, Mae

    1984-01-01

    Parents of a child with muscular dystrophy recount their reactions to learning of the diagnosis, their gradual acceptance, and their son's resistance, which was gradually lessened when he was provided with more information and treated more normally as a member of the family. (CL)

  15. Acceptance and Commitment Therapy: Introduction

    ERIC Educational Resources Information Center

    Twohig, Michael P.

    2012-01-01

    This is the introductory article to a special series in Cognitive and Behavioral Practice on Acceptance and Commitment Therapy (ACT). Instead of each article herein reviewing the basics of ACT, this article contains that review. This article provides a description of where ACT fits within the larger category of cognitive behavior therapy (CBT):…

  16. Who accepts first aid training?

    PubMed

    Pearn, J; Dawson, B; Leditschke, F; Petrie, G; Nixon, J

    1980-09-01

    The percentage of individuals trained in first aid skills in the general community is inadequate. We report here a study to investigate factors which influence motivation to accept voluntary training in first aid. A group of 700 randomly selected owners of inground swimming pools (a parental high-risk group) was offered a course of formal first aid instruction. Nine per cent attended the offered training course. The time commitment involved in traditional courses (eight training nights spread over four weeks) is not a deterrent, the same percentage accepting such courses as that who accept a course of one night's instruction. Cost is an important deterrent factor, consumer resistance rising over 15 cost units (one cost unit = the price of a loaf of bread). The level of competent first aid training within the community can be raised by (a) keeping to traditional course content, but (b) by ensuring a higher acceptance rate of first aid courses by a new approach to publicity campaigns, to convince prospective students of the real worth of first aid training. Questions concerning who should be taught first aid, and factors influencing motivation, are discussed.

  17. 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

  18. 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

  19. 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.

  20. 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

  1. Mechanical and in vitro biological performance of graphene nanoplatelets reinforced calcium silicate composite.

    PubMed

    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

  2. Cellulose Nanofibers as a Modifier for Rheology, Curing and Mechanical Performance of Oil Well Cement

    NASA Astrophysics Data System (ADS)

    Sun, Xiuxuan; Wu, Qinglin; Lee, Sunyoung; Qing, Yan; Wu, Yiqiang

    2016-08-01

    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.

  3. Mechanical performance of encapsulated restorative glass-ionomer cements for use with Atraumatic Restorative Treatment (ART)

    PubMed Central

    MOLINA, Gustavo Fabián; CABRAL, Ricardo Juan; MAZZOLA, Ignacio; BRAIN LASCANO, Laura; FRENCKEN, Jo. E.

    2013-01-01

    The Atraumatic Restorative Treatment (ART) approach was suggested to be a suitable method to treat enamel and dentine carious lesions in patients with disabilities. The use of a restorative glass-ionomer with optimal mechanical properties is, therefore, very important. Objective: To test the null-hypotheses that no difference in diametral tensile, compressive and flexural strengths exists between: (1) The EQUIA system and (2) The Chemfil Rock (encapsulated glass-ionomers; test materials) and the Fuji 9 Gold Label and the Ketac Molar Easymix (hand-mixed conventional glass-ionomers; control materials); (3) The EQUIA system and Chemfil Rock. Material and Methods: Specimens for testing flexural (n=240) and diametral tensile (n=80) strengths were prepared according to standardized specifications; the compressive strength (n=80) was measured using a tooth-model of a class II ART restoration. ANOVA and Tukey B tests were used to test for significant differences between dependent and independent variables. Results: The EQUIA system and Chemfil Rock had significantly higher mean scores for all the three strength variables than the Fuji 9 Gold Label and Ketac Molar Easymix (α=0.05). The EQUIA system had significant higher mean scores for diametral tensile and flexural strengths than the Chemfil Rock (α=0.05). Conclusion: The two encapsulated high-viscosity glass-ionomers had significantly higher test values for diametral tensile, flexural and compressive strengths than the commonly used hand-mixed high-viscosity glass-ionomers. PMID:23857657

  4. Animal studies on the role of sleep in memory: from behavioral performance to molecular mechanisms.

    PubMed

    Havekes, Robbert; Meerlo, Peter; Abel, Ted

    2015-01-01

    Although the exact functions of sleep remain a topic of debate, several hypotheses propose that sleep benefits neuronal plasticity, which ultimately supports brain function and cognition . For over a century, researchers have applied a wide variety of behavioral, electrophysiological, biochemical, and molecular approaches to study how memory processes are promoted by sleep and perturbed by sleep loss. Interestingly, experimental studies indicate that cognitive impairments as a consequence of sleep deprivation appear to be most severe with learning and memory processes that require the hippocampus , which suggests that this brain region is particularly sensitive to the consequences of sleep loss. Moreover, recent studies in laboratory rodents indicate that sleep deprivation impairs hippocampal neuronal plasticity and memory processes by attenuating intracellular cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) signaling. Attenuated cAMP-PKA signaling can lead to a reduced activity of the transcription factor cAMP response element binding protein (CREB) and ultimately affect the expression of genes and proteins involved in neuronal plasticity and memory formation. Pharmacogenetic experiments in mice show that memory deficits following sleep deprivation can be prevented by specifically boosting cAMP signaling in excitatory neurons of the hippocampus. Given the high incidence of sleep disturbance and sleep restriction in our 24/7 society, understanding the consequences of sleep loss and unraveling the underlying molecular mechanisms is of great importance.

  5. 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.

  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.

  7. 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

  8. Animal studies on the role of sleep in memory: from behavioral performance to molecular mechanisms.

    PubMed

    Havekes, Robbert; Meerlo, Peter; Abel, Ted

    2015-01-01

    Although the exact functions of sleep remain a topic of debate, several hypotheses propose that sleep benefits neuronal plasticity, which ultimately supports brain function and cognition . For over a century, researchers have applied a wide variety of behavioral, electrophysiological, biochemical, and molecular approaches to study how memory processes are promoted by sleep and perturbed by sleep loss. Interestingly, experimental studies indicate that cognitive impairments as a consequence of sleep deprivation appear to be most severe with learning and memory processes that require the hippocampus , which suggests that this brain region is particularly sensitive to the consequences of sleep loss. Moreover, recent studies in laboratory rodents indicate that sleep deprivation impairs hippocampal neuronal plasticity and memory processes by attenuating intracellular cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) signaling. Attenuated cAMP-PKA signaling can lead to a reduced activity of the transcription factor cAMP response element binding protein (CREB) and ultimately affect the expression of genes and proteins involved in neuronal plasticity and memory formation. Pharmacogenetic experiments in mice show that memory deficits following sleep deprivation can be prevented by specifically boosting cAMP signaling in excitatory neurons of the hippocampus. Given the high incidence of sleep disturbance and sleep restriction in our 24/7 society, understanding the consequences of sleep loss and unraveling the underlying molecular mechanisms is of great importance. PMID:25680961

  9. 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

  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. Performance improvement of smooth impact drive mechanism at low voltage utilizing ultrasonic friction reduction

    NASA Astrophysics Data System (ADS)

    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.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  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 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.

  19. The role of incline, performance level, and gender on the gross mechanical efficiency of roller ski skating

    PubMed Central

    Sandbakk, Øyvind; Hegge, Ann Magdalen; Ettema, Gertjan

    2013-01-01

    The ability to efficiently utilize metabolic energy to produce work is a key factor for endurance performance. The present study investigated the effects of incline, performance level, and gender on the gross mechanical efficiency during roller ski skating. Thirty-one male and nineteen female elite cross-country skiers performed a 5-min submaximal session at approximately 75% of VO2peak on a 5% inclined treadmill using the G3 skating technique. Thereafter, a 5-min session on a 12% incline using the G2 skating technique was performed at a similar work rate. Gross efficiency was calculated as the external work rate against rolling friction and gravity divided by the metabolic rate using gas exchange. Performance level was determined by the amount of skating FIS points [the Federation of International Skiing (FIS) approved scoring system for ski racing] where fewer points indicate a higher performance level. Strong significant correlations between work rate and metabolic rate within both inclines and gender were revealed (r = −0.89 to 0.98 and P < 0.05 in all cases). Gross efficiency was higher at the steeper incline, both for men (17.1 ± 0.4 vs. 15.8 ± 0.5%, P < 0.05) and women (16.9 ± 0.5 vs. 15.7 ± 0.4%, P < 0.05), but without any gender differences being apparent. Significant correlations between gross efficiency and performance level were found for both inclines and genders (r = −0.65 to 0.81 and P < 0.05 in all cases). The current study demonstrated that cross-country skiers of both genders used less metabolic energy to perform the same amount of work at steeper inclines, and that the better ranked elite male and female skiers skied more efficiently. PMID:24155722

  20. Rapid increase in training load affects markers of skeletal muscle damage and mechanical performance.

    PubMed

    Kamandulis, Sigitas; Snieckus, Audrius; Venckunas, Tomas; Aagaard, Per; Masiulis, Nerijus; Skurvydas, Albertas

    2012-11-01

    The aim of this study was to monitor the changes in indirect markers of muscle damage during 3 weeks (9 training sessions) of stretch-shortening (drop jump) exercise with constant load alternated with steep increases in load. Physically active men (n = 9, mean age 19.1 years) performed a program involving a rapid stepwise increase in the number of jumps, drop height, and squat depth, and the addition of weight. Concentric, isometric maximal voluntary contraction (MVC), and stimulated knee extension torque were measured before and 10 minutes after each session. Muscle soreness and plasma creatine kinase activity were assessed after each session. Steep increments in stretch-shortening exercise load in sessions 4 and 7 amplified the postexercise decrease in stimulated muscle torque and slightly increased muscle soreness but had a minimal effect on the recovery of MVC and stimulated torque. Maximal jump height increased by 7.8 ± 6.3% (p < 0.05), 11.4 ± 3.3% (p < 0.05), and 12.8 ± 3.6% (p < 0.05) at 3, 10, and 17 days after the final training session, respectively. Gains in isometric knee extension MVC (7.9 ± 8.2%) and 100-Hz-evoked torque (9.9 ± 9.6%) (both p < 0.05) were observed within 17 days after the end of the training. The magnitude of improvement was greater after this protocol than that induced by a continuous constant progression loading pattern with small gradual load increments in each training session. These findings suggest that plyometric training using infrequent but steep increases in loading intensity and volume may be beneficial to athletic performance. PMID:22158097