电压型变频调速系统负载扰动的研究

本文利用坐标轴系的变换,推导出控制对象异步电动机的数学模型,进而推导出电压型交-直-交变频调速系统受负载扰动的主回路动态结构图。据此结构图,在模拟机上对电压型变频调速系统进行了负载扰动的分析和研究,在满足扰动性能指标的情况下,能够选择调节器的最佳参数。     

基于夹点技术的Einstein循环制冷系统优化

针对制冷系统性能较低的缺点,基于系统现行换热网络,分析Einstein循环制冷系统的工作原理,利用夹点技术 对其进行分析改造。应用问题表格法确定出夹点的位置,计算各换热器的热负荷。研究结果表明：系统优化后,输入系 统的热公用工程量和冷公用工程量分别降低了12.5%和48. 1%,系统能效系数CCOP提高了14. 3%。夹点技术优化提升 Einstein循环制冷系统性能效果显著,取得较好的节能效果。     

基于FWD荷载下的沥青路面实测动力响应分析

沥青路面基于高度条件和重载作用,其受力状态以及静载模式下的受力条件都会产生极大差异。通过试验分析基于动载激励条件下沥青路面的动态响应规律,在此基础上分析沥青路面的损害机理。为研究动态荷载作用下沥青路面的实测动力响应,基于实际工程,构筑了3种典型的沥青路面,采用FWD(落锤式弯沉仪)分析沥青路面的动态弯沉盆特性,通过动态应变传感器,得到基于动态荷载下的层底弯拉应变响应。结果表明：沥青路面结构的动态响应随FWD荷载的变化表现出非线性特性,3种沥青路面结构的面层底具有较低的应变状态,且几乎不对路面累计疲劳造成损伤,相对于横向应变,具有较大的纵向应变能力。     

Caregiving Load and Respite Service Use: A Comparison between Older Caregivers and Younger Caregivers

Study aims were to explore differences in predictors of respite care use between older (aged 65+) and younger caregivers (aged 18–64 years), and associations between caregiving load and respite care use using multivariate logistic regression analysis and unpaid caregiver (n= 10,500) data from the 2009 California Health Interview Survey. Caregiving load comprised number of care recipients, weekly hours in caregiving, and caregiving duration. Variables with a significant association with respite care for older caregivers were female gender, income, and health insurance. For younger caregivers, respite care use associations were with ethnicity, caregiving relationship, education, and availability of substitute help.     

Theoretical aspects of extinction by inbreeding depression

Populational extinction due to inbreeding depression is analyzed with simple population genetic and population ecological models. Two alternative genetic mechanisms of inbreeding depression, i.e. recessive deleterious genes and overdominant genes, are assumed in separate analyses in order to examine their relative importance. With both mechanisms the population size and the coefficient of inbreeding are maintained at stable equilibria if there is no non-genetic demographic disturbance or stress. With a certain amount of demographic disturbance the population declines rapidly due to interaction between the decrease of population size and the increase of inbreeding coefficient. Such rapid extinction occurs with both genetic mechanisms. However, in the case of overdominant genes extinction happens only if the equilibrium population size is small and the selection coefficient is large such that segregation load is large. In nature, extinction due to overdominant genes is considered to be much less likely than extinction due to recessive deleterious genes.     

动压气膜轴承间隙平面流动的数值分析

基于计算流体动力学中的SIMPLEC算法，从流动模拟分析的角度对动压气膜轴承的工作机理，包括气体可压缩性、轴承间隙大小、轴颈偏心率及轴承运行线速度的作用等作了分析．结果表明，减小轴承的间隙、提高偏心率和线速度可以使间隙内压力增大，从而提高轴承的承载能力．本文的结果为动压气膜轴承的设计计算和三维轴承的计算提供了基础．     

基于认知心理学的高效视觉信息加工可视化策略

决策剧场是一种辅助决策者面对复杂问题进行群决策的新技术结合体。通过专家团队对复杂问题建立数学模型,并运用计算机进行可视化模拟,呈现不同决策所产生的结果,提高决策质量。如何优化决策剧场中可视化呈现的效果,使决策者能够高效加工视觉信息,成为决策剧场研究中的基础性问题。文章结合认知心理学的有关成果,通过以降低决策者认知负载为目标的研究,生成了四条可视化策略。在此基础上,基于人视觉信息加工特点,生成了另外四条可视化策略。以上策略将用于指导可视化技术对于事件模拟仿真的实现。     

轴向力对简支梁弯曲与振动的影响

应用伽辽金法,分析了简支梁在纵向、横向荷载作用下的弯曲与振动问题,讨论了轴向力对简支梁的弯曲参数与振动参数的影响,给出了计算结果并与精确解进行了比较.     

运动负荷、负荷量、负荷强度概念及内涵的讨论与分析

多年来,无论是运动训练学以及各种有关运动训练方面的研究,当提到运动负荷时,无一例外的认为其结构是——负荷量与负荷强度。本文通过分析认为;运动负荷与运动负荷量在概念上有重复之嫌,且运动负荷量与运动负荷强度不是同一层次的概念,因为强度本身就是量。同时提出运动负荷的构成因素之一是运动量而不是负荷量。