课程文献中心 更多>>

关键词： 人字齿轮   高重合度   动态性能   抛物线修形   遗传算法   噪音  

摘要： 对人字齿轮传动进行高重合度设计的分析,基于人字齿轮副承载接触分析技术,针对人字齿轮传动中主动小齿轮轴向浮动安装的特点,综合考虑齿轮时变啮合刚度、啮合冲击激励及误差激励等因素的影响,采用集中质量法建立了考虑修形的人字齿轮副弯-扭-轴耦合非线性振动模型,推导了系统无量纲运动微分方程,求解得到齿轮传动系统的振动加速度。以齿轮的振动加速度均方根值为优化的目标函数,针对该类复杂实际工程优化设计中适应值计算费时的缺点,提出了一种改进的具有适应值预测机制的遗传算法,优化得到了人字齿轮的基本设计参数及修形参数,提高了计算效率,通过实例分析验证了该优化方法的有效性。对加工的人字齿轮在减振降噪试验台上进行带载试验,对比优化前后的噪音分贝值,进一步验证了该优化方法对齿轮副减振降噪具有一定作用。

关键词： 分置式双离合自动变速器   动力学模型   参数设计   AVL   Cruise仿真  

摘要： 为解决双离合器自动变速器的双离合器总成模块难于生产制造的问题,提出了一种新型的分置式双离合器自动变速器技术方案,分析了该方案的结构特点和工作原理;建立了该变速器的动力学模型,并分析了变速器起步和换挡过程的运动学关系;然后根据整车参数的要求,对变速器主要参数进行了设计;利用AVL Cruise仿真软件,建立整车动力传动系统模型,并进行了整车性能仿真,仿真结果表明:该设计方案的变速器不仅满足了车辆设计要求,而且与普通的双离合器自动变速器相比,在最高车速、最大爬坡度、加速时间、循环工况油耗方面的性能差距在2.5%以内。因此,该分置式双离合器自动变速器设计方案的双离合器模块克服了双离合器自动变速器的双离合器总成难于生产制造的缺陷,具有较好的应用和参考价值。

关键词： Childhood trauma   Adolescent   HPA-axis   Cortisol   PITUITARY-ADRENAL AXIS   NEUROENDOCRINE STRESS REACTIVITY   CORTISOL AWAKENING RESPONSE   SALIVARY CORTISOL   MALTREATED CHILDREN   LIFE STRESS   EXPOSURE   DEPRESSION   IMPACT   VIOLENCE  

摘要： Studies examining the association between childhood trauma exposure and neuroendocrine functioning have returned inconsistent findings. To date, few studies have accounted for the role exposure to different types of childhood trauma may have on different neuroendocrine adaptations, and no study has examined this association using multiple indices of hypothalamic pituitary adrenal axis (HPA-axis) functioning. The purpose of this study was to characterize the unique associations between exposure to physical abuse, emotional abuse, and non-intentional trauma, and multiple indices of HPA-axis functioning. Methods: A community sample of 138 youth (aged 9-16) completed the Socially Evaluated Cold Pressor Task (SE-CPT) while their parents completed the Early Trauma Inventory (ET!). All youth then collected 4 diurnal salivary cortisol samples at home across 2 consecutive weekdays. Results: High reported exposure to non-intentional trauma was associated with intact diurnal regulation but elevated cortisol at bedtime, physical abuse was associated with faster reactivity to acute stress, and emotional abuse was associated with delayed recovery of cortisol following acute stress. Taken together, there was a heterogeneous relationship among different indices of HPA-axis functioning and trauma subtype. Discussion: Different types of childhood trauma exposure are related to distinct anomalies in HPA-axis functioning. This study underscores the importance of research incorporating multiple indices of HPA-axis functioning to inform our understanding of the underlying neuroendocrine dysregulation that may later lead to stress-related psychopathology. (C) 2015 Elsevier Ltd. All rights reserved.

关键词： Clutch Characteristics   Clutch Torque   Kiss Point   Clutch Temperature   Real-world Driver  

摘要： Efficient concepts for controlling automated friction clutches in dual-clutch transmissions use the clutch characteristic as a quasi-steady-state model of clutch behaviour. However, the transfer behaviour of the clutch changes while driving, thus necessitating continuous adaptation of the clutch characteristic. IAV has developed a new process for adapting clutch characteristics using selected methods of system identification with subsequent testing in real-world driving.

关键词： Avian assemblages   David Lack   macroecological approach   normalized difference vegetation index   number of eggs   Philip Nelson Ashmole   SPATIAL STRUCTURE   BIRDS   PRODUCTIVITY   REPRODUCTION   PREDATION   EVOLUTION   PATTERNS   GRADIENT   COST  

摘要： AimTo separate the effect of overall resource level from the effect of seasonality on avian clutch size to test Ashmole's hypothesis that birds have larger clutch sizes in seasonal environments due to high per capita food availability during the breeding season. LocationSouth Africa and Lesotho. MethodsWe used a large-scale environmental gradient to test the effects of maximum resource availability and resource seasonality (estimated by the normalized difference vegetation index) on clutch size variation among local passerine assemblages (25kmx25km grid cells). The importance of maximum resource availability was distinguished from the importance of resource seasonality by using multivariate general additive models and by subsetting the data so that variation in one of these parameters was minimized. Spatial autocorrelation was controlled for by using spatial generalized least squares. ResultsAssemblage mean clutch size showed a hump-shaped relationship with maximum resource availability but an increase with resource seasonality. When the variation in maximum resource availability was fixed, clutch size increased with increasing seasonality, but it decreased with increasing maximum resource availability when we fixed the variation in seasonality. These results hold for all feeding guilds except granivores, for which we found opposite patterns. The patterns were much less pronounced when family membership was controlled for, indicating that the overall trends are mostly driven by variation between families. Main conclusionsAlthough clutch size can be affected by many factors related to environmental productivity and its variation, Ashmole's hypothesis provides the most parsimonious explanation of the observed patterns: geographical patterns in mean clutch size across bird assemblages seem to be driven by variation of per capita food availability determined by seasonal variation of population density.

关键词： 磁流变液   离合器   线圈绕向   磁路   输出转矩  

摘要： 以圆筒型磁流变离合器的线圈绕组为研究对象,应用ANSYS软件仿真并分析了离合器中的单级绕组、双级同向绕组、双级异向绕组和外圆筒中部加隔磁环的双级同向绕组的磁路。此外,分析了绕组型式对离合器输出转矩的影响。

关键词： 手扶拖拉机   离合器   跑偏   原因   预防  

摘要： 手扶拖拉机在工作中常见的故障有很多。本文分析了手扶拖拉机离合器分离轴承早期损坏、拖拉机跑偏的原因及预防方法。

关键词： MIRA   工程技术   离合器   测力仪   踏板力   Windows   分析软件包   上海  

摘要： 该测量仪由MIRA独家研发和销售，用于测量、记录和分析对离合器的运行和操作感觉影响最大的参数。为了获取和分析完整的离合器系统数据，MIRA的工程专家开发了一套高效且易干使用的基于Windows的分析软件包。该软件可以记录熄火点、接合点和分离点等信息，并能够计算和显示调节、效率、迟滞、最大力和行程等离合器特性，帮助用户确定和测量离合器在工作时的属性。

关键词： 石碴车   离合器   破坏   改进  

摘要： 离合器是K13石碴车卸货传动系统中,风动与手动相互转换的重要零件,其受力很大,极易损坏,以前制造的离合器有多个缺陷。经过改进后,效果很好,离合器破坏的情况几乎没再发生,使用单位反映很好。