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61.
The paper considers vulnerable multi-state series-parallel systems operating under influence of external impacts. Both the external impacts and internal failures affect system survivability, which is determined as the probability of meeting a given demand. The external impacts are characterized by several destructive factors affecting the system or its parts simultaneously.In order to increase the system's survivability a multilevel protection against the destructive factors can be applied to its subsystems. In such systems, the protected subsystems can be destroyed only if all of the levels of their protection are destroyed.The paper presents an algorithm for evaluating the survivability of series-parallel systems with arbitrary configuration of multilevel protection against multiple destructive factor impacts. The algorithm is based on a composition of Boolean and the Universal Generating Function techniques.Illustrative examples are presented.  相似文献   
62.
许家新 《油气井测试》2003,12(4):20-22,35
经对冷43块深层块状普通稠油水驱注水5个试验井组开展的稳定同位素示踪测试,利用中子活化技术分析样品,采用先进的示踪剂定量分析与流动模拟相互结合的方法,以示踪数值模拟为手段,评价了油井连通、油层平面及纵向上的非均质性、隔层的封隔性等因素对水驱控制程度及动用状况的影响,通过优化注水推进方向及速度,强化动态调整措施,提高了稳产基础。  相似文献   
63.
Survival of patients on hemodialysis remains poor, but the benefits of increasing urea clearance have probably been maximized within our current treatment schedules. Long dialysis sessions (8 hr) produce impressive outcomes, with mortality 53% to 55% lower than conventional schedules. Even increasing from 4 to 5 hr may improve survival. Increased frequency of dialysis (6 times weekly) produces impressive reductions in left ventricular mass and could conceivably be implemented in‐center. Preliminary data suggest a 61% reduction in mortality with increased frequency. Nightly dialysis combines longer sessions with increased frequency and has produced remarkable clinical gains in blood pressure, left ventricular mass, serum phosphate, and sleep apnea. However, the data are mainly from case series and impact on mortality remains unknown. Expansion of home hemodialysis would be necessary for this modality to grow. Convective therapies remove middle molecules more effectively, and observational data suggest hemodiafiltration has the potential to improve mortality by 35% to 36%. Hemodiafiltration has the advantage of being relatively easy to implement. The uremic milieu is complex and further investigation of the underlying pathophysiology is needed to inform future dialysis interventions. The survival data above are from observational studies, and hence benefits are likely to be exaggerated. Randomized trials of dialysis interventions are desperately needed. They remain difficult to perform, because of the complexity of both the patient population and the interventions, and because of limited available funding.  相似文献   
64.
Prepulse inhibition (PPI) refers to a reduction in the startle response to a strong sensory stimulus when this stimulus is preceded by a weaker stimulus--the prepulse. PPI reflects a nonlearned sensorimotor gating mechanism and also shows a robust gender difference, with women exhibiting lower PPI than men. The present study examined the eyeblink startle responses to acoustic stimuli of 59 healthy heterosexual and homosexual men and women. Homosexual women showed significantly masculinized PPI compared with heterosexual women, whereas no difference was observed in PPI between homosexual and heterosexual men. These data provide the first evidence for within-gender differences in basic sensorimotor gating mechanisms and implicate the known neural substrates of PPI in human sexual orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
65.
Risk factors affecting the course of posttraumatic stress disorder (PTSD) are poorly understood. As part of a larger study on characterizing exposure to herbicides in Vietnam, the authors investigated this issue in a random sample of 1,377 American Legionnaires who had served in Southeast Asia during the Vietnam War and were followed over a 14-year period. High combat exposure, perceived negative community attitudes at homecoming, minority race, depression symptoms at Time 1, and more anger at Time 1 predicted a more chronic course. Community involvement at Time 1 was protective and associated with decreased risk at Time 2. Discomfort in disclosing Vietnam experiences was associated with an increased risk for developing PTSD but did not predict its course. Combat exposure predicted PTSD course more strongly than any other risk factor. Findings suggest recovery from PTSD is significantly influenced by perceived social support. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
66.
水热合成纳米氧化锡粉体工艺因素研究   总被引:1,自引:0,他引:1  
以SnCl4·5H2O和氨水为原料,通过正交实验并借助于XRD、TEM等手段,研究了前驱物浓度、反应温度、保温时间和氨水滴加速率等工艺因素对水热合成纳米SnO2粉体的影响。  相似文献   
67.
Sperm competition occurs when the sperm of multiple males concurrently occupy the reproductive tract of a female and compete to fertilize an egg. We used a questionnaire to investigate psychological responses to the risk of sperm competition for 237 men in committed, sexual relationships. As predicted, a man who spends a greater (relative to a man who spends a lesser) proportion of time apart from his partner since the couple's last copulation reported (a) greater sexual interest in his partner, (b) greater distress in response to his partner's sexual rejection, and (c) greater sexual persistence in response to his partner's sexual rejection. All effects were independent of total time since the couple's last copulation and the man's relationship satisfaction. Discussion addresses limitations of the current research and situates the current results within the broader comparative literature on adaptation to sperm competition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
68.
The 2004 Gold Medal Award for Life Achievement in the Application of Psychology was awarded to Edwin A. Fleishman, for his significant contributions to the science and applications of psychology, which he has sustained over his remarkable career. He is cited for his research, which has had a profound influence on our understanding of human capabilities, their measurement, their development, and their application in the world of work. Through his many influential leadership roles, as president of the International Association of Applied Psychology and three divisions of the American Psychological Association, and as editor of the Journal of Applied Psychology, he has helped shape our profession. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
69.
The ability to accurately and reliably predict whether an older adult will commit suicide has eluded clinicians and researchers. A random national sample of psychologists who work with older adults was surveyed regarding their perception of 36 risk factors for completed suicide and indirect self-destructive behavior in older adults. This study produced a profile of psychologists' assessment and treatment practices when working with suicidal older adults. Determining what psychologists consider to be the most salient risk factors for completed suicide is important in identifying a minimum standard that clinicians should follow when assessing older adults. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
70.
76 mm口径EFP成形过程数值模拟及影响因素研究   总被引:10,自引:1,他引:9  
周翔  龙源  岳小兵 《弹道学报》2003,15(2):59-63
采用LS-DYNA3D对76mm口径药型罩爆炸成型弹丸(EFP)的成形过程进行了数值模拟,模拟结果与实验数据基本吻合.通过数值模拟着重分析了装药长径比L/D、壳体厚度、药型罩壁厚对EFP速度的影响规律,得到了有关EFP成形速度公式,得出EFP速度随L/D的增大而增大,随药型罩厚度增大而减小,受装药外壳厚度影响不大.  相似文献   
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