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The present work focuses on a posteriori, equilibrium based, reconstruction of transverse stress profiles in the finite element analysis of FSDT laminated plates. The accuracy of this reconstruction depends on accuracy of the firs...
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The present work focuses on a posteriori, equilibrium based, reconstruction of transverse stress profiles in the finite element analysis of FSDT laminated plates. The accuracy of this reconstruction depends on accuracy of the first and second-order derivatives of the plate stress resultants, which is not guaranteed by most available low-order plate finite elements. To cure this trouble, two different strategies, based on the Recovery by Compatibility in Patches procedure, are here proposed and compared. Numerical results of typical reconstructed transverse stress profiles are presented showing the effectiveness of the proposed approach.
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The recovery of the stress gradient in finite elements problems is a widely discussed topic with many applications in the design process. The stress gradient is related to the second derivative (Hessian) of the nodal displacements...
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The recovery of the stress gradient in finite elements problems is a widely discussed topic with many applications in the design process. The stress gradient is related to the second derivative (Hessian) of the nodal displacements and numerical techniques are required for its calculation. Particular difficulties are encountered in the reconstruction of the stress gradient in the boundary regions of the domain. This is of particular concern in most applications, especially in mechanical components, where the maximum values of stresses are often located in these regions and the stress gradient has a strong influence on the fatigue life of the component. This paper presents a comparison between some already published, partially modified, recovery techniques and a different approach based on radial basis function networks. The aim of the paper is to compare the performances of the different approaches for a number of element types with particular focus on the boundary regions. Some examples of mechanical interest are considered.
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Creep and relaxation phenomena are being observed in shape memory alloys, not only at high temperatures but also at room temperature, due to their martensitic transformation. Transformation-induced creep and stress relaxation in s...
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Creep and relaxation phenomena are being observed in shape memory alloys, not only at high temperatures but also at room temperature, due to their martensitic transformation. Transformation-induced creep and stress relaxation in shape memory alloys occur due to temperature variations during loading and unloading cycles. In this work, a one-dimensional fully coupled thermomechanical model was employed to develop a continuum framework for studying these behaviors in shape memory alloy wires. A decrease or increase in stress was observed during forward or reverse transformation at a constant amount of strain, showing the stress relaxation and stress recovery, respectively. Similarly, the model predicts that strain increases or decreases when stress is held fixed in the course of forward or reverse transformation, meaning the phenomena of creep and creep recovery, respectively. This model provides the ability of investigating the effects of different ambient temperatures, strain rates, applied stresses and strains, and wire radii on the creep and relaxation responses of shape memory alloys. Relaxation and creep experiments at different ambient temperatures and loading or unloading rates were also done on NiTi wires, and the theoretical predictions were shown to be in a good agreement with the empirical observations.
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Work-related stress is considered one of the biggest health and safety challenges among the member states of the European Union. A critical factor is recovery between periods of stress. The primary purpose of this study was to inv...
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Work-related stress is considered one of the biggest health and safety challenges among the member states of the European Union. A critical factor is recovery between periods of stress. The primary purpose of this study was to investigate whether a brief behaviorally oriented stress-recovery management intervention delivered in an individual setting could reduce stress symptoms among individuals with high levels of perceived stress. A single-subject experimental design with multiple baselines across three individuals was used. The results indicate, with at least moderate experimental control, a temporal relation between the start of the intervention and beneficial changes from baseline in continuous self-recordings of stress symptoms. The changes were maintained at 1-year and 5-year follow-up assessments. Also, self-reporting inventories measuring perceived stress, worry, anxiety, depression, burnout, type A behavior, unwinding and recuperation from work stress, and insomnia showed overall changes in beneficial directions at post-assessment, as well as the two follow-up assessments. The results indicate that a behaviorally oriented stress-recovery management intervention delivered in an individual setting can reduce stress symptoms in individuals with high levels of perceived stress. However, for firm conclusions to be drawn, further research is needed.
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Young athletes in intensive training settings are confronted with a series of daily stressors although they have a smaller and less flexible coping repertoire than adults. Moreover, previous studies neglected the multivariate natu...
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Young athletes in intensive training settings are confronted with a series of daily stressors although they have a smaller and less flexible coping repertoire than adults. Moreover, previous studies neglected the multivariate nature of coping. Therefore, the purpose of the current study was to first identify coping profiles of young athletes in response to daily stressors related to their competitive sport involvement. Second, the study examined: (a) if such profiles were similar across the three waves, (b) how many participants belonged to the same profile along the three waves, and (c) whether individuals from distinct profiles differed on burnout, stress, and recovery. One hundred and forty-seven young table-tennis players involved in intensive training settings completed the CICS, RESTQ-Sport, and ABQ three times during a 2-month period. Cluster analyses indicated three similar clusters across the three waves: task-oriented coping, distraction-and disengagement-oriented coping, and low coping profiles. The distribution of athletes significantly varied across waves. Burnout, stress, and recovery significantly differed across the coping profiles. Athletes from the task-oriented coping profile were characterized by the best psychological adjustment (high scores of recovery and low scores of stress and burnout). In contrast, athletes from the distraction-and disengagement-oriented coping profile were characterized by the worst psychological adjustment (high scores of stress and burnout and low scores of recovery). These findings highlighted that the coping profiles allow examining coping within a holistic approach, teasing out the complex associations with key outcomes, such as burnout, stress, and recovery.
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The Acute Recovery and Stress Scale (ARSS) and the Short Recovery and Stress Scale were first established in German for the purposes of monitoring athletes' current recovery-stress states in an economical and multidimensional mann...
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The Acute Recovery and Stress Scale (ARSS) and the Short Recovery and Stress Scale were first established in German for the purposes of monitoring athletes' current recovery-stress states in an economical and multidimensional manner. The aim of this paper is to document the development and initial validation of the English versions of these two psychometric monitoring tools. A total of 267 English-speaking athletes from a variety of team and individual sports participated in the study. The English versions demonstrated satisfactory internal consistency for both instruments (Cronbach of .74-.89). Furthermore, good model fit was found for the eight scales of the ARSS, matching the structure and results of the German counterparts. Correlations among and between the scales reciprocate the theoretical constructs of stress and recovery, supporting the construct validity of the scales. Correlation coefficients within stress and recovery ranged between r(s)=.29 and .68. The correlations between stress and recovery varied between r(s)=-.29 and -.64. These constructs were further supported by correlations with the scores of the Recovery-Stress Questionnaire for Athletes, thereby showing convergent validity. The findings demonstrate initial validity and reliability of the two measures and reflect the results of the German versions. However, further research is needed before applying these scales in practical settings.
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Cortisol (C) and testosterone (T) are impacted significantly by prolonged endurance exercise with inverse responses. Increases in C are witnessed concurrently with decrements in T, possibly impacting recovery. This study was condu...
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Cortisol (C) and testosterone (T) are impacted significantly by prolonged endurance exercise with inverse responses. Increases in C are witnessed concurrently with decrements in T, possibly impacting recovery. This study was conducted to assess the dynamics of C and free T (fT) concentration and recovery time following an exhaustive endurance exercise session (EES).
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A model to predict the evolution of dislocation density following hot deformation is presented in this article. The model is validated by stress relaxation experiments on austenite at various temperatures. It is found that the act...
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A model to predict the evolution of dislocation density following hot deformation is presented in this article. The model is validated by stress relaxation experiments on austenite at various temperatures. It is found that the activation energy for self-diffusion is the rate-controlling parameter determining the evolution of dislocation density, and hence the recovery rate. A methodology to control the softening experienced by high-temperature alloys is proposed.
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Acute whole-body hyperthermia (WBH) increases blood markers concentration of stress, impairs motor drive to exercising muscles, and decreases resistance to neuromuscular fatigability. The functional natural residual consequences o...
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Acute whole-body hyperthermia (WBH) increases blood markers concentration of stress, impairs motor drive to exercising muscles, and decreases resistance to neuromuscular fatigability. The functional natural residual consequences of WBH on neuromuscular functions remain unclear. We aimed to investigate the effects of residual WBH on voluntary and electrically induced ankle plantar flexor contractility properties, motor drive transmission (reflexes), muscle torque steadiness, resistance to neuromuscular fatigability, and markers of stress as the body temperature recovers naturally to normothermia. WBH was induced by Finnish sauna bathing in 16 apparently healthy young (24 4 years) adult men. Motor performance was monitored before and 2 h after the sauna, and immediately after submaximal exercise (120 s at 50% of maximal voluntary contraction). Markers of stress were monitored before and 2 h after the sauna. Finnish sauna exposure induced moderate to severe WBH (rectal temperature, 38.5-39.6 degrees C). At 2 h after the sauna, rectal temperature had recovered to the preheating level (preheating 37.11 +/- 0.33 degrees C versus postheating 37.00 +/- 0.29 degrees C, p > .05). Post-sauna recovery was accompanied by slowed salivary free cortisol diurnal kinetics, whereas noradrenaline, dopamine, and serotonin did not persist into the 2 h recovery after the sauna. Although recovery to normothermia after a sauna led to a greater acceleration of muscle contractility properties and decreased muscle steadiness, sustained isometric submaximal contraction did not provoke greater neuromuscular fatigability.
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This is a short overview of the principles of a novel development in surgery called enhanced recovery after surgery (ERAS) programs. This is an evidence-based approach to perioperative care that has shown to reduce complications a...
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This is a short overview of the principles of a novel development in surgery called enhanced recovery after surgery (ERAS) programs. This is an evidence-based approach to perioperative care that has shown to reduce complications and recovery time by 30-50%. The main mechanism is reduction of the stress reactions to the operation. These principles have been shown to be particularly well suited for the compromised patient and hence very good for the elderly people who often have co-morbidities and run a higher risk of complications.
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