Molecular dynamics simulation of compressible hot/cold moving lid-driven microcavity flow

Hard-sphere molecular dynamics simulations of lid-driven microcavity gas flow with various subsonic speeds and lid temperatures are conducted. Simulations with faster and colder lids show streamlines of stronger primary vortices. Variations of mass and energy centers with respect to lid speed and temperature are examined. Center of energy is less sensitive to employed lid conditions than center of gravity is. Although moving lid imparts energy into fluid, due to change of impingement rates on the walls of fixed temperature, average energy within the cavity seems quite insensitive to the subsonic lid speed. Behavior of compressibility at both top corners is observed even at low Mach numbers widely considered within incompressible flow region. While high Knudsen number causes considerable property slips near the lid, two-dimensional pressure, density, and temperature plots of excellent quality are generated. Results are promising in use of molecular dynamics simulations for compressible vortex flow analyses while providing insights for understanding microfluidics and nanofluidics in context of molecular mass, momentum and heat transfer in microscale and nanoscale systems.     

Failure Analysis of Two-Dimensional Carbon-Epoxy Composite Plate Pinned Joint

The aim of this study is to investigate failure strength and failure mode of a mechanically fastened carbon-epoxy composite plate of arbitrary orientation. The failure load and the failure mode are analyzed numerically and experimentally. The numerical method includes two steps. First, the stress distribution in the plate is calculated by the use of finite-element method. Second, the failure load and the failure mode are predicted by means of Tsai-Hill and fiber tensile-compressive failure criteria. A computer program was developed which can be used to calculate the failure load, the failure mode, and the propagation of failure. The distance-to-diameter, E/D , and width-to-diameter, W/D , ratios in the plate are changed from 1 to 5 and 2 to 5, respectively. It is found that full bearing strength is developed when E/D and W/D ratios are equal to or greater than 4.     

Immediate Antecedents of Cigarette Smoking in Smokers With and Without Posttraumatic Stress Disorder: A Preliminary Study.

Using ambulatory methods for 1 day of monitoring, the authors of this study investigated the association between smoking and situational cues in 63 smokers with posttraumatic stress disorder (PTSD) and 32 smokers without PTSD. Generalized estimating equations contrasted 682 smoking and 444 nonsmoking situations by group status. Smoking was strongly related to craving, positive and negative affect, PTSD symptoms, restlessness, and several situational variables among PTSD smokers. For non-PTSD smokers, the only significant antecedent variables for smoking were craving, drinking coffee, being alone, not being with family, not working, and being around others who were smoking. These results are consistent with previous ambulatory findings regarding mood in smokers but also underscore that, in certain populations, mood and symptom variables may be significantly associated with ad lib smoking. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A haar wavelet approximation for two-dimensional time fractional reaction–subdiffusion equation

Engineering with Computers - In this study, we established a wavelet method, based on Haar wavelets and finite difference scheme for two-dimensional time fractional reaction–subdiffusion...     

Impact and post impact behavior of layer fabric composites

In this study, the effect of impact and post impact behavior of E-glass/epoxy composite plates having different layer fabrics were investigated by considering energy profile diagram and the related load–deflection curves. Different impact energies (5 J–60 J)were subjected to the plates consisting of eight layers of plain weave (1D), double (2D) and triple (3D) layer fabrics. The impact tests were continued until complete perforation of layer fabrics. The damage modes and damage processes of layer fabrics under varied impact energies were also discussed. At the end of the impact tests, the damaged samples were mounted into a compression apparatus to determine the Compression After Impact (CAI) strength of layer fabric samples. The results of these impact and post impact tests showed that contact force occurring between the impactor and the composite specimen increased and the CAI strength reduced by increasing the impact energy. The objective of this study was to determine the perforation threshold of E-glass/epoxy composite plates having different layer fabrics as plain weave (1D), double (2D), and triple (3D) layer fabrics.     

Bayesian Computations for a Class of Reliability Growth Models

In this article, we consider the development and analysis of both attribute- and variable-data reliability growth models from a Bayesian perspective. We begin with an overview of a Bayesian attribute-data reliability growth model and illustrate how this model can be extended to cover the variable-data growth models as well. Bayesian analysis of these models requires inference over ordered regions, and even though closed-form results for posterior quantities can be obtained in the attribute-data case, variable-data models prove difficult. In general, when the number of test stages gets large, computations become burdensome and, more importantly, the results may become inaccurate due to computational difficulties. We illustrate how the difficulties in the posterior and predictive analyses can be overcome using Markov-chain Monte Carlo methods. We illustrate the implementation of the proposed models by using examples from both attribute and variable reliability growth data.     

Psychiatric diagnoses as contemporaneous risk factors for suicide attempts among adolescents and young adults: Developmental changes.

The purpose of this prospective, naturalistic study was to examine the relationships between suicide attempts and contemporaneous psychiatric disorders, and developmental changes in these relationships from adolescence to young adulthood. The sample consisted of 180 adolescents, 12–19 years of age at hospitalization, repeatedly assessed for up to 13 years (n = 1,825 assessments). Semistructured psychiatric diagnostic instruments were administered at repeated assessments to assess psychiatric disorders and suicide attempts. After controlling for demographic variables and prehospitalization suicide attempts, most contemporaneous psychiatric disorders (major depressive disorder [MDD], dysthymic disorder, generalized anxiety disorder [GAD], panic disorder, attention-deficit/hyperactivity disorder [AD/HD], conduct disorder, and substance use disorder [SUD]) were related to increased risk of attempts. The relationship between suicide attempts and MDD, GAD, AD/HD, and SUD strengthened as participants got older. MDD, dysthymic disorder, GAD, and panic disorder were more commonly associated with repeat than 1st-time suicide attempts. In sum, most major psychiatric disorders are associated with increased risk for suicide attempts, but the strength of the relationships between these disorders and attempts changes over the course of development. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Bearing strength of carbon epoxy laminates under static and dynamic loading

An experimental study has been carried out to investigate both the static and dynamic bearing strengths of a pinned-joint carbon epoxy composite plate with [0°/45°/−45°/90°]_S and [90°/45°/−45°/0°]_S stacking configurations. The static and dynamic experiments have been carried out according to the ASTM D953 standards and ASTM STP 749, respectively [ASTM D 953-D, Standard Test method for Bearing Strength of Plastics, ASTM Designation. 342; Joining of Composite Materials, ASTM STP 749, American Society for Testing and Materials (1981) 131]. The ratio of the edge distance to the pin diameter (E/D), and that of the width to the pin diameter (W/D) of the specimens were varied to obtain the static bearing strength and the S–N fatigue curve. The experiments show that the static bearing strengths reach their upper limit when E/D and W/D ratios are equal to or greater than 4 for both [0°/45°/−45°/90°]_S and [90°/45°/−45°/0°]_S stacking sequences. The fatigue strength, on the other hand, reduces by up to 65% as E/D and W/D ratios increase for both stacking configurations.     

Effect of Valsalva Maneuver on QT Dispersion in Hemodialysis Patients

Increased QT dispersion seems to be related to an increased risk of arrhythmia and sudden death, a common cause of mortality in hemodialysis (HD) patients. Increase in sympathetic tone has been documented in HD patients. In this study, we aimed to investigate the effect of changes in the autonomic tone on QT dispersion (QTd) in HD patients. Twenty HD patients (M/F 13/7; age, mean ±SD, 28 ± 10 years) and 22 age‐ and sex‐matched healthy controls (M/F 12/10; age, 30 ± 10 years) were included. The patients were dialyzed three‐times weekly; time on dialysis was 17 ± 8 months. The QT durations were measured from 12 lead surface EKGs and were corrected for RR intervals. Corrected maximum (QT_c max) and minimum (QT_cmin) QT intervals and their difference (QT _c d) were recorded. The effect of the Valsalva maneuver in the release phase on QT _c intervals and dispersion was assessed. The HD patients had prolonged values compared to controls: QT _c d, 59 ± 17 ms versus 35 ± 7 ms, p < 0.001; QT _c max, 458 ± 41 ms versus 397 ± 21 ms, p < 0.001; and QT _c min, 398 ± 36 ms versus 362 ± 25 ms, p < 0.001. After the Valsalva maneuver no changes were observed in controls: QT _c max, 397 ± 21 ms versus 396 ± 22 ms, p = 0.9; QT _c min, 362 ± 24 ms versus 358 ± 19 ms, p = 0.5; and QT _c d, 35 ± 7 ms versus 38 ± 10 ms, p = 0.15. Whereas, in HD patients all values were significantly shortened: QT_cmax, 458 ± 41 ms versus 427 ± 35 ms, p = 0.003; QT_c min, 398 ± 36 ms versus 379 ± 34 ms, p = 0.04; and QT_c d, 59 ± 17 ms versus 48 ± 15 ms, p = 0.01. The decrease in QTmax was more prominent than the decrease in QTmin, hence QT dispersion was significantly decreased after the Valsalva maneuver, but differences from controls were still significant. In conclusion, increased sympathetic activity may have a role in the prolonged QT duration and increased QT dispersion in HD patients.