课程文献中心 更多>>

关键词： 斜撑式超越离合器二轴总成   扭转刚度   扭转阻尼   动态传递误差   动载荷   重合度   动态溜滑角  

摘要： 为使斜撑式超越离合器二轴总成具有良好的动态性能,采用集中参数法建立了四自由度横-扭耦合动力学模型,并运用龙格-库塔法对此非线性系统进行了数值求解,分别研究了斜撑式超越离合器扭转刚度和扭转阻尼对齿轮动态传递误差和动载荷的影响,以及齿轮重合度对斜撑式超越离合器动态溜滑角、最大冲击力及稳态接触力的影响。研究结果表明:①系统在较低的激励频率范围内,齿轮动态传递误差和动载荷随离合器扭转刚度增大而减小,而在较高的激励频率范围内变化相反;②齿轮动态传递误差和动载荷随斜撑式超越离合器扭转阻尼增大而减小;③斜撑式超越离合器动态溜滑角、最大冲击力、稳态接触力随齿轮重合度增大而增大。

关键词： 离合器壳体   拨叉轴   润滑   滚针轴承  

摘要： 文章介绍了一种新式的离合器分离机构。用以解决公交车辆在运行过程中频繁换挡、踩离合器,引起的离合器分离机构频繁工作,使得离合器分离拨叉轴和铜衬套之间润滑不良卡滞,以及拨叉轴易疲劳断裂,进而导致离合器不能正常分离现象。

关键词： 后置发动机   角传动   双柔性结构   电磁离合器  

摘要： 介绍新开发的角传动双柔性电磁离合器在搭载大马力发动机后置客车上的应用。阐述了双柔性电磁离合器的结构原理及应用优势;以厦门金龙旅行车有限公司的战略车型——领航者为例,介绍了双柔性电磁离合器在角传动结构布置中的匹配优化:为风扇角传动结构模块化设计提供参考。

关键词： Type 2 diabetes mellitus   Hypothalamus-pituitary-adrenal axis   Cannabinoid receptor 1   Endocannabinoid hydrolase   Rhesus monkey  

摘要： Hypothalamus-pituitary-adrenal (HPA) axis, as the key moderator in energy metabolism, plays an important role in diabetes. The endogenous cannabinoid system (eCBs) involves in neuronal functions, and simultaneously cannabinoid receptors are almost expressed in all regions of the hypothalamus according to a spate of reports. However, few data investigate the changes of eCBs and HPA axis in type 2 diabetes. In this study, five diabetes mellitus rhesus monkeys, five prediabetes rhesus monkeys and five healthy rhesus monkeys were observed. In the present study, we detected cell swelling and necrosis extensively in the paraventricular nucleus (PVN) and neurohypophysis in prediabetes and overt diabetes monkeys. The adrenocorticotropic hormone in the pituitary gland, adrenocorticotropic hormone receptor, and 11 beta-hydroxysteroid dehydrogenase in the adrenal gland were all hyper-secreted and expressed from healthy to overt diabetes. Meanwhile, the cortisol concentration in the adrenal gland was increased along with the progress of diabetes. It could be concluded that hyperfunction of the HPA axis exists in the type 2 Diabetes pathogenesis. However, we also found a weakened expression and secretion of corticotrophin releasing hormone and glucocorticoids receptor in PVN. The expression of corticotropin releasing hormone receptor 1 in pituitary gland decreased in prediabetes monkeys, but increased in overt diabetes monkeys. The downregulation of cannabinoid receptor 1 and upregulation of monoglycerol lipase and fatty acid amide hydrolase in PVN was involved in the pathogenesis of type 2 diabetes. Collectively, we can conclude that changes in endocannabinoid hydrolase and cannabinoid receptor might indicate the effect of downregulation of eCBs. It can be assumed that hyper-function of the HPA axis from healthy to overt diabetes is due to the undermining inhibition of eCBs. However, the regulatory mechanism of eCBs targets on the HPA axis need to be further explored.

关键词： 126-kV horseshoe-type vacuum interrupter (VI)   maximum arcing contact gap   minimum arcing contact gap   opening velocity design method   vacuum arcs  

摘要： The objective of this paper is to determine arcing contact gap of a 126-kV horseshoe-type bipolar axial magnetic field vacuum interrupter. Drawn arc experiments were carried out in a demountable vacuum. Experimental current ranged from 12-to 40-kA rms. Based on the vacuum arc behavior, minimum arcing contact gap D-1 and maximum arcing contact gap D-2 were defined. When average opening speed within 20 mm (v(1)) was 1.9, 2.3, and 2.6 m/s, D-1 was determined as 15.3, 16.8, and 14.3 mm, respectively. In addition, D-1 reflected a peak effect with v1. When average opening speed within 40 mm (v(2)) was 2.6, 2.7, and 2.8 m/s, D-2 was determined as 38.5, 36.7, and 36.1 mm, respectively. Uncontrollable arc mode appeared when current was higher than 32 kA with arc duration of 9 ms. The critical contact gap to avoid uncontrollable arc mode decreased as a liner function of arc current. Based on the experimental results, quantitative design method of three-interval opening velocity for the 126-kV horseshoe-type vacuum circuit breaker was proposed. For short-circuit current interruption test duty T100s, lower limit value of v(1) and upper limit value of v(2) were determined as 2.5 and 2.9 m/s with a prospective minimum arcing time of 7 ms.

关键词： body size   Gopherus polyphemus   mating system   microsatellites   reproductive success  

摘要： In many vertebrates, body size is an important driver of variation in male reproductive success. Larger, more fit individuals are more likely to dominate mating opportunities, skewing siring success and resulting in lower effective population sizes and genetic diversity. The mating system of the gopher tortoise (Gopherus polyphemus) has been characterized as both female-defense and scramble-competition polygyny. Mating systems are typically not fixed and can be influenced by factors such as population density, demographic structure, and environmental conditions;however, most populations will have a predominant strategy that results from local conditions. We assessed how male body size influences patterns of paternity and reproductive success in a natural population of gopher tortoises in Florida, United States. Using microsatellites, we assigned parentage of 220 hatchlings from 31 nests collected during 2 reproductive seasons. Larger males were significantly more likely to sire offspring and sired more offspring than smaller males;however, the likelihood of a clutch being multiply sired was unrelated to male body size. We also found evidence of mate fidelity across years. Although paternity patterns in this high-density population are more consistent with defense polygyny, female monopoly by males was incomplete, with both large and small males contributing to multiply sired clutches. Additional behavioral data are needed to clarify the role of female mate selection in paternity outcomes. The context-dependence of mating systems underscores the need to compare parentage patterns across populations and to recognize the potential for more than 1 strategy to be employed within a single population.

关键词： TBK1   ubiquitination   deubiquitination   degradation   innate immunity  

摘要： Ubiquitination and deubiquitination are important post-translational regulatory mechanisms responsible for fine tuning the antiviral signaling. In this study, we identified a deubiquitinase, the ubiquitin-specific peptidase 7/herpes virus associated ubiquitin-specific protease (USP7/HAUSP) as an important negative modulator of virus-induced signaling. Overexpression of USP7 suppressed Sendai virus and polyinosinic-polycytidylic acid and poly(deoxyadenylic-deoxythymidylic)-induced ISRE and IFN- activation, and enhanced virus replication. Knockdown or knockout of endogenous USP7 expression had the opposite effect. Coimmunoprecipitation assays showed that USP7 physically interacted with tripartite motif (TRIM)27. This interaction was enhanced after SeV infection. In addition, TNF receptor-associated factor family member-associated NF-kappa-B-binding kinase (TBK)-1 was pulled down in the TRIM27-USP7 complex. Overexpression of USP7 promoted the ubiquitination and degradation of TBK1 through promoting the stability of TRIM27. Knockout of endogenous USP7 led to enhanced TRIM27 degradation and reduced TBK1 ubiquitination and degradation, resulting in enhanced type I IFN signaling. Our findings suggest that USP7 acts as a negative regulator in antiviral signaling by stabilizing TRIM27 and promoting the degradation of ***, J., Chen, H.-Y., Peng, S.-J., Meng, J.-L., Wang, Y., Zhou, Y., Qian, X.-P., Sun, X.-Y., Pang, X.-W., Zhang, Y., Zhang, J. USP7-TRIM27 axis negatively modulates antiviral type I IFN signaling.

关键词： 汽车   两冲程发动机   手动变速器   越野车   离合器   卡丁车   驾驶   欧宝  

摘要： 我从四岁开始驾驶，最初只是开那些使用两冲程发动机和惯性离合器无档可换的小型越野车，到了五岁便开始驾驶卡丁车。我第一次开的合法街国是欧宝Monza，当时只有七岁。那辆Monza用手动变速器，我不大看得清车外情况，幸好有祖父陪伴在侧。

关键词： 说课   平面四杆机构   教材   机械设计基础  

摘要： 以"平面四杆机构的基本特性"为例,从说教材、说学情、说教法和说教学过程四个方面设计说课内容,为广大青年教师进行说课教学活动提供参考。