Changes of China’s Status in the Global System and Its Influencing Factors:A Multiple Contact Networks Perspective

Clarifying China’s position in the global system is an important logical basis for developing national diplomacy.Although much research has been done on China’s development status,most studies have been based on country comparisons or institutional en-vironment.In today’s networked era in which the global economy,trade,personnel,and information are closely connected,studies on China’s global position and its status changes and influencing factors in multiple contact networks are still insufficient.In this study,from the perspective of diverse global contact networks,we constructed economic,cultural,and political influence indices to explore the changes and influencing factors on China’s status in the global system from 2005 to 2018.The results show that during the study period,China’s global influence in the fields of economic ties,cultural exchanges,and political contacts increased significantly,but its influ-ence in the fields of cultural exchanges and political contacts lagged far economic ties.The pattern of China’s economic influence on various economies around the world has shown a transformation from an‘upright pyramid’to an‘inverted pyramid’structure.The proportion of these economies in low-influence zones has decreased from more than 60%in 2005 to less than 20%in 2018.China’s cultural and political influence on various economies around the world has increased significantly;however,for the former,the percentage of high-influence areas is still less than 20%,whereas for the latter the percentage of these economies in medium-and high-influence areas is still less than 50%.Analyses such as a scatter plot matrix show that geographical proximity,economic globalization,close cooperation with developing countries,and a proactive and peaceful foreign policy are important factors in improving China’s status in the diverse global network system.

新型内啮合S型齿轮啮合效率计算与分析

为了准确计算新型内啮合S型齿轮的啮合效率,引入了考虑轮齿表面滑差、润滑油状况及时变载荷等因素的弹流润滑时变摩擦模型;分析啮合齿面润滑机制,通过轮齿接触分析(Tooth ContactAnalysis,TCA)及轮齿承载接触分析,计算了啮合齿面滑动摩擦因数及摩擦损失功率;在此基础上,获得内啮合S型齿轮啮合周期内的瞬时啮合效率和平均啮合效率,并给出了计算实例。研究结果表明,在相同设计参数下,新型内啮合S型齿轮较渐开线齿轮有更高的啮合效率;经螺旋线修形后,新型内啮合S型齿轮的啮合效率有所提高且随修形量的增大而增大。

一种基于Hertz非线性的法向接触力模型

基于Hertz理论建立非线性动力学方程,并结合能量法,推导了两球接触过程中最大变形量的表达式,获得了新的粘滞阻尼因子,提出一种改进的法向接触力模型。并针对该模型与几种常见的同类型法向接触力模型,实例分析了相对速度与变形量随时间的变化关系,以及相同实例下不同恢复系数下法向接触力、相对速度与变形量之间的关系,获得了各模型输入与计算的恢复系数的变化关系,结果表明:改进的法向接触力模型在保证正确性的前提下,具有足够的精度与适用范围。

鄂北S井区盒8上亚段砂体叠置类型及其对气藏分布的影响

为明确鄂北S井区盒8上亚段地层砂体叠置类型及其与气藏分布的关系,通过岩心观察、测井解释等方法对研究区盒8上亚段沉积微相类型、砂体的垂向叠置及侧向接触关系进行深入研究,再结合试气资料探讨不同砂体叠置类型的气藏分布特征。结果表明:鄂北S井区盒8上亚段为曲流河三角洲平原亚相,有利砂体对应的沉积微相类型为边滩与河道充填微相;砂体垂向叠置类型可划分为分离式、叠加式、切叠式、替代式,侧向接触关系可划分为间湾接触、堤岸接触、对接式、侧切式、替代式;鄂北S井区盒8上亚段砂体垂向叠置类型主要为侧向切叠式和替代式,增加了砂体在侧向上的连通性;盒8上亚段砂体侧向接触关系主要为侧切式,提升了砂体侧向上的连通程度,气藏储存关系较好;单一、孤立存在的砂体,其连通性较差,整体的含气性也较差。该研究对寻找低渗透背景下产能高、潜力大的砂体分布区具有重要指导意义。

基于Adams与RecurDyn的机械结构Hertz接触仿真对比分析

接触仿真是让多体动力学仿真软件能够更加真实的模拟机械系统的运动状态和受力情况的重要环节之一。为了得到多体动力学仿真软件Adams和RecurDyn在进行机械结构的Hertz接触问题仿真时的区别,对比了两种软件接触仿真的算法,运用Creo2.0建立了两种经典机构的虚拟样机,并针对某型越障小车的定轴轮系进行数字化建模,对这三种机构的Hertz接触问题分别运用Adams和RecurDyn进行了仿真,得到了运动状态曲线和接触力曲线,对比了仿真结果。仿真结果给进行Hertz接触问题分析的学者提供了参考。

水溶液一步法制备铜基Cu_(2)S微纳米结构及其超疏水性能

无需任何模板、表面活性剂或添加剂,通过廉价、简洁、易操作的水溶液一步法,将预处理的铜箔浸渍于一定浓度的CH_(3)CSNH_(2)溶液中,室温条件下反应,得到了具有微-纳米双尺寸粗糙结构的硫化亚铜超疏水薄膜。结果表明,铜基底上生成的硫化亚铜微-纳米双尺度粗糙结构表面对水的静态接触角高达171°,水滴滚动角低至3.5°,具有优异的超疏水性能。

Analysis and Numerical Simulation of Rolling Contact between Sphere and Cone

In non-conforming rolling contact, the contact stress is highly concentrated in the contact area. However, there are some limitations of the special contact model and stress model used for the theoretical study of the phenomenon, and this has prevented in-depth analysis of the associated friction, wear, and failure. This paper is particularly aimed at investigating the area of rolling contact between a sphere and a cone, for which purpose the boundary is determined by the Hertz theory and the geometries of the non-conforming surfaces. The phenomenon of stick-slip contact is observed to occur in the contact area under the condition of no-full-slip（Q 〈 μ·P）. Using the two-dimensional rolling contact theory developed by CARTER, the relative positions of the stick and slip regions and the distribution of the tangential force over the contact area are analyzed. Furthermore, each stress component is calculated based on the Mc Ewen theory and the idea of narrow band. The stress equations for the three-dimensional rolling contact between the sphere and the cone are obtained by the principle of superposition, and are used to perform some numerical simulations. The results show that the stress components have a large gradient along the boundary between the stick and slip regions, and that the maximum stress is inversely proportional to the contact coefficient and proportional to the friction coefficient. A new method for investigating the stress during non-classical three-dimensional rolling contact is proposed as a theoretical foundation for the analysis of the associated friction, wear, and failure.

媒介接触下青年群体自主产品消费意愿的形成机理研究——基于S-O-R理论

培养青年群体自主产品消费意愿是实施扩大内需战略与深化供给侧结构性改革有机结合的有力抓手。基于S-O-R(刺激—有机体—反应)这一环境心理学理论,从“爱国情感”和“政府信任”两大路径出发构建媒介接触下的自主产品消费意愿模型,并将媒介细分为主流媒体和非主流媒体展开对比研究。基于结构方程模型的验证发现,主流媒体和社交媒体刺激了消费者的爱国情感和政府信任,最终影响自主产品消费意愿,且爱国情感路径下的作用更为突出。

基于Hertz接触理论的整体叶盘百页轮抛光材料去除深度建模研究

为了揭示复杂曲面百页轮抛光的材料去除机理,假设磨粒凸出高度服从正态分布,通过Hertz接触理论得到了接触区的抛光压力分布模型,然后基于弹塑性接触理论进行单颗磨粒受力分析,结合百页轮表面磨粒凸出高度分布函数建立了磨粒切入深度模型。在此基础上,综合主轴转速、进给速度和磨粒切削沟槽形状等确定了单颗磨粒的材料去除体积,并通过沿抛光轨迹积分的方法建立了材料去除深度模型。实验结果表明,材料去除深度的预测值与实验值的最大偏差和平均偏差分别为4.85%和2.95%,验证了所建材料去除深度模型的正确性和有效性。

Modeling and Experiment on Contact Stiffness and Accuracy Analysis of Ball Linear Guide Feed Unit

The contact stiffness and the error analysis have an important effect on the manufacture and the optimization of Ball Linear Guide Feed Unit( BLGFU). In order to analyze the contact stiffness and linear errors or angle errors of BLGFU,in this paper,the contact stress and deformation mechanics between the ball and rail is analyzed. Based on Hertz theory of contact and theory of the multi-body system,a model of the contact stiffness considering the changes in contact angle is established. With the increasing of the external load,the varying trend of the contact deformation can be obtained. Therefore, the motion accuracy degradation of the BLGFU can be analyzed. By using a special experimental device and test system of the rolling linear guide worktable,the horizontal contact stiffness and the vertical linear stiffness are obtained,respectively. By comparing the contact stiffness of the experiment dates and the simulation results,the variation tendency of two curves is consisted and the difference between the measured values and the theoretical values is less than 18%. It is obvious that the model of the contact stiffness considering changes of contact angle has accuracy and feasibility. Thus,while external force point locating at different positions; the contact stiffness and the accuracy analysis of the BLGFU are proved validity by simulations.

急性ST段抬高型心肌梗死患者救治与降压达标的相关性研究

目的分析急性ST段抬高型心肌梗死(ST-elevation myocardial infarction,STEMI)救治时间节点与降压达标的相关性。方法选择CCU于2017年2月至2018年8月收治的行急诊经皮冠状动脉介入术(PCI)的STEMI患者374例,采用统一调查问卷收集资料,根据合并高血压情况分为高血压组168例和非高血压组206例。依据高血压组血压控制达标情况,分为达标组(75例)和未达标组(93例),分析2组间的差异,Logistic回归分析降压达标与首次医疗接解(S-to-FMC)、D-to-B、总缺血时间(TIT)的相关性。结果STEMI患者中高血压患者的检出率44.9%;2、3级高血压患者占92.7%;高血压组与非高血压组比较,2组S-to-FMC、D-to-B、TIT差异无统计学意义(P>0.05);降压达标组S-to-FMC、TIT时间显著低于非达标组(P<0.05)。结论降压达标患者的获益不仅是在降压本身及重要脏器的保护作用,与心血管事件的及时救治有一定的相关性,降压达标的STEMI患者院前延迟时间、心肌总缺血时间缩短,有助于改善患者的预后。

An experimental method for quantitative analysis of real contact area based on the total reflection optical principle

The simulation of real contact area between materials is foundationally important for the contact mechanics of mechanical structures. The Greenwood and Williamson(GW) model and the Majumdar(MB) model are the basic models in this field, which are widely accepted and proven to be valid in many experiments and engineering. Although the contact models have evolved considerably in recent years, the verifications of the models are most based on the indirect methods such as electrical conductivity and contact stiffness, because of the lack of effective methods to directly measure the variation of contact surface. In this paper, the total reflection(TR) method is introduced into the verification of contact models.An experiment system based on TR method is constructed to measure the real contact area of two PMMA specimens. The comparison analysis between the results of experiment and models suggests that the experiment result has the same trend with simulation, the MB model has better agreement with the experimental result because this method can take into account the variation of radius and the merging of asperities, while the GW model has a huge deviation because of the dependence on resolution and the lack of considering the variation of radius and asperity's merging process. Taking the interaction of asperities into account could give a better result that is closer to the experiment. Our results and analysis prove that the experimental methods in this paper could be used as a more direct and valid method to quantitatively measure the real contact area and to verify the contact models.

Direct contacts of microglia on myelin sheath and Ranvier’s node in the corpus callosum in rats

Over the recent years, it has been found that microglia pseudopodia contact synapses, detect sick ones and prune them, even in adult animals. Myelinated nerves also carry out plasticity in which microglia remove myelin debris by phagocytosis. However, it remains unknown whether microglia explore structures on nerve fibers, such as Ranvier’s node(RN) or myelin sheath, before they become debris. By double or triple staining RNs or myelin sheathes and microglia in healthy rat corpus callosum, this study unveiled direct contacts of microglia pseudopodia with RNs and with para-and inter-nodal myelin sheathes, which was then verified by electron microscopic observations. Our data indicated that microglia also explore unmyelinated nerve fibers. Furthermore, we used the animals with matured white matter;therefore, microglia may be actively involved in plasticity of matured white matter tracts as it does for synapse pruning, instead of only passively phagocytize myelin debris.

深水S型铺管的管道形态与内力计算程序开发

深水海底管线的铺设主要采用S型铺管的方式,在铺管船船尾设有托管架以支撑和保护管道,并控制管道入水的角度,保证管道安全。依托某深水铺管船项目,根据S型管道的特点,将其分为上弯段、中间段和下弯段三部分进行力学分析;利用MATLAB软件编写程序,计算不同铺设工况下的管道形态和内力,以OFFPIPE的计算结果为参照,验证本程序的可靠性和准确性。针对在实际铺管过程中并不能保证管道与每个托辊都接触的问题,在程序中设定指定托辊不接触的情况。计算结果表明,该工况下管道在后一个托辊处将受到较大弯矩作用,可能引起失效,应引起关注。

Aggregate gradation design of asphalt mixture with stone-to-stone contact based on fuller's model

Based on Fuller＇s model, a gradation design is presented for the load-carrying capacity of an asphalt mixture with stone-to-stone contact. The coarse aggregate gradation, fine aggregate and filler gradation are respectively designed for their different effects on an asphalt mixture with stone-to-stone contact. The equation of coarse aggregate gradation is deduced from the Fuller＇s model. Fine aggregate gradation is calculated by using Fuller＇s equation. The asphalt mixture with the 16 mm maximum size of aggregate is verified. When the coefficient of coarse aggregate gradation is 0.35 and fine aggregate gradation is 0.25, the volume parameters of asphalt mixture meet the technical specifications. Moreover, the high temperature stability and crack resistance at low temperature are all well.

Finite Element Analysis of Elastic-Plastic Contact Mechanic Considering the Effect of Contact Geometry and Material Properties

Each surface of roughness has different shape of asperity which is modeled with various shapes of analytical models. In this paper, the differences among various models of shape of asperity investigate using the Finite Element Method (FEM) and various analytical models. The contact stresses in rough surfaces are calculated analytically using various asperity shape models. Finite element analysis is also carried out assuming three types of material properties namely, the linear, the elastic-perfect plastic and the elastic-nonlinear hardening. The analytical results are compared with the results obtained by the finite element method. The results illustrate for using a deterministic approach which the numerical models are suitable. In hertz model, the result of force is very big in interface of causing deformation plastic, while Model Zhao has almost same result with FEM nonlinear property model. It is observed that the results obtained from Zhao’s model are generally in a better agreement with the results obtained from various finite element models especially in elastic-plastic and plastic zones, hence it may be concluded that Zhao’s model can be used for analyzing the rough surfaces in contact mechanics.

Understanding the Properties of Silicon Solar Cells Aluminium Contact Layers and Its Effect on Mechanical Stability

As the thickness of silicon solar wafer and solar cells becomes thinner, the cells are subjected to high stress due to the thermal coefficient mismatch induced by metallization process. Handling and bowing problems associated with thinner wafers become increasingly important, as these can lead to cells cracking and thus to high yield losses. The goal of this work to provide experimental understanding of Al rear side microstructure development and mechanical properties as well as correlate the obtained results with fracture behaviour of the cell. It is shown that the aluminium back contact has a complex microstructure, consisting of five main components: 1) the back surface field layer;2) a eutectic layer;3) spherical (3 - 5 μm) hypereutectic Al-Si particles surrounded by a thin aluminium oxide layer (200 nm);4) a bis- muth-silicate glass matrix;and 5) pores (14 vol%). It was concluded that the eutectic layer thickness and waviness depends on Al particle size, amount of Al paste and textured surface roughness of silicon wafers. The Young’s modulus of the Al-Si particles is estimated by nano-indentation and the overall Young’s modulus is estimated on the basis of bowing measurements and found to be ~43 GPa. It was found, that there is a relation between aluminium paste composition, eutectic layer thickness, mechanical strength and bowing of solar cells. Three main parameters were found to affect the mechanical strength of mc-silicon solar cells with an aluminium contact layer, namely the eutectic layer thickness and uniformity, the Al layer thickness (which results from the Al particle size and its distribution), and the amount of porosity and the bismuth glass fraction.

Frictional contact problem for elastic-viscoplastic materials with thermal effect

A dynamic contact problem for elastic-viscoplastic materials with thermal effects is investigated. The contact is bilateral, and the friction is modeled with Tresca＇s friction law with heat exchange. A variational formulation of the model is derived, and the existence of a unique weak solution is proved. The proofs are based on the classical result of nonlinear first order evolution inequalities, the equations with monotone operators, and the fixed point arguments. Finally, the continuous dependence of the solution on the friction yield limit is studied.

Counterformal contacts of full toroidal continuously variable transmission

The point and the line contacts of a toroidal continuously variable transmission (CVT) are studied. The contact shapes between the roller and input and output disks are formulated by using the classical Hertz contact theory. Based on the formulated equations, different system factors affecting the maximum Hertz stress in the elliptical and strip contacts of the full toroidal CVT are explored, which include the properties of the contacting material (Young’s modulus), operating condition (pushing load) and geometrical parameters (aspect cavity ratio, aspect roller ratio). The comparative results reveal the relations between the maximum Hertz stress and the speed ratio in the form of graphs. These graphs give useful information for designer to know the maximum Hertz stress during operation in such systems.

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