Analysis of tensioned membrane structures considering cable sliding

In routine design of tensioned membrane st ructures, the membrane is gen erally modeled using space membrane elements and the cables by space cable eleme nts, with no sliding allowed between the membrane and the cables. On the other h and, large deflections are expected and sliding between the membrane and the cab les is inevitable. In the present paper, the general finite element code ABAQUS was employed to investigate the influence of cable sliding on membrane surface o n the structural behavior. Three analysis models were devised to fulfill this pu rpose: (1) The membrane element shares nodes with the cable element; (2) The cab le can slide on the membrane surface freely (without friction) and (3) The cable can slide on the membrane surface, but with friction between the cable and the membrane. The sliding problem is modeled using a surface-based contact algorithm . The results from three analysis models are compared, showing that cable slidin g has only little influence on the structure shape and on the stress distributio ns in the membrane. The main influence of cable sliding may be its effect on the dynamic behavior of tensioned membrane structures.     

圆柱蜗杆传动计算机辅助分析与仿真

本文以计算机图学中曲线曲面理论为基础,以数值方法代替解析方法,将三维空间啮合问题简化为三维平面啮合问题,对磨削加工圆柱蜗杆传动的设计,预测并分析各种啮合质量,正确选择各种设计参数等项进行了研究,并形成了相应软件包.     

此情可待成追忆 ——解读《第一次的亲密接触》

《第一次的亲密接触》运用网络时代的语汇，演绎了一个传统的爱情悲剧。它之所以受到当代青年的拥戴，是因为它既承袭了我国的传统文化，又具有时代的亮色，符合当代青年的审美趣味。     

Measurement of contact forces on a kayak ergometer with a sliding footrest–seat complex

Kinematic analysis is done by measurement of the position of bodies, followed by differentiation to get the accelerations of the centres of mass, and it is widely used in sport research. Another common approach is to measure the forces directly. Our intention here is to perform both a kinematic and a kinetic analysis of the same athlete-equipment system, in this case an athlete on a sliding kayak ergometer, with the aim of exploring the errors that may occur with each measurement type. The kayak ergometer with a sliding trolley, instrumented by seven uniaxial force sensors and two goniometers, was placed in a filming area. The instrumentation was validated in the direction of the anteroposterior axis using Newton’s second law. Ten athletes paddled at 92 strokes per minute, following a stationary phase. The comparison between the net force and the time-derivative of the linear momentum indicated a friction level of about 20 N between the trolley and the frame. Other errors came mainly from the inertial parameters of the trunk. A first analysis of contact forces shows a large inter-subject variability, in particular for the forces applied to the footrest and the seat.     

Research on multiculturalism in Canada

Canada announced a policy of multiculturalism in 1971. The goal of the policy was to improve the quality of intercultural relations. Two main elements of the policy were proposed as steps towards achieving this goal: support for the maintenance and development of cultural communities (the cultural component); and promotion of intercultural contact along with the reduction of barriers to such participation (the intercultural component). Research on these issues can provide a basis for the development and implementation of multiculturalism policies and programmes. A review of psychological research on multiculturalism over the past 40 years is summarised. Topics include: knowledge about the multiculturalism policy; acceptance of multiculturalism; acceptance of ethnocultural groups; acceptance of immigrants; discrimination and exclusion; and attachment and identity. Research assessing three hypotheses derived from the policy is also briefly reviewed. Current evidence is that there is widespread support for these features of the multicultural way of living in Canada. Of particular importance for the success of multiculturalism is the issue of social cohesion: is the first component (the promotion of cultural diversity) compatible with the second component (the full and equitable participation and inclusion of all ethnocultural groups in civic society)? If they are compatible, together do they lead to the attainment of the fundamental goal of attaining positive intercultural relations? Current psychological evidence suggests that these two components are indeed compatible, and that when present, they are associated with mutual acceptance among ethnocultural groups in Canada. I conclude that research in Canada supports the continuation of the multiculturalism policy and programmes that are intended to improve intercultural relations.     

Broadening the mind: Beneficial effects of sojourn experiences and contact with visiting international students on prospective teachers’ motivation to avoid prejudiced behavior

Opportunities for intergroup contact are particularly important for prospective teachers because they bear responsibility for an ethnically diverse student population. Using data from a sample of 330 students inscribed in Austrian university colleges of teacher education, we investigated the long-term effects of international student exchange on prospective teachers’ motivation to avoid prejudiced behavior (MAPB). Both sojourning and domestic students’ friendships with visiting international students (VIS) were evaluated as potential instances of naturally occurring intergroup contact that can affect students’ MAPB. Sojourning students had an increased MAPB even nine months after returning to their home country. No effect was found for domestic students’ friendships with VIS. Possibly, the quality of these friendships was insufficient to result in long-term prejudice reduction. Implications of these results are discussed, and the need to advance interventions that are appropriate to improve domestic students’ contact with VIS is ascertained.     

Examining the effect of perceived group norms on the indirect relationship between intergroup contact and anti-Muslim prejudice among white Americans

Prior studies have found that normative group pressure plays a significant role in shaping prejudice-related attitudes. The present paper examined the role of perceived group norms on the indirect relationship between intergroup contact and anti-Muslim prejudice in a cross-sectional sample of 428 non-Hispanic White American adults, the racial group with the strongest anti-Muslim sentiment. To begin, we tested the indirect relationship between intergroup contact and anti-Muslim prejudice via perceived realistic and symbolic threats as well as intergroup anxiety. Next, we tested whether these mediation effects were conditional on whether group norms were perceived as tolerant or intolerant. We employed Process Macro to test these hypotheses. Our data confirmed (partial) mediation of the contact-prejudice relationship via threat perceptions and intergroup anxiety. Moreover, the moderated mediation analysis showed that while the mediation effects of threat perceptions were not conditional on perceived group norms, the mediation effect of intergroup anxiety was. Specifically, for respondents with perceived intolerant norms, negative intergroup contact demonstrated a stronger relationship with anti-Muslim prejudice through intergroup anxiety compared to respondents with perceived tolerant norms. Furthermore, given the possible bidirectionality of the contact-prejudice relationship, we tested an alternative model examining whether perceived intolerant norms mediate the effect of prejudice on contact. Our data supported this hypothesis, fitting a model that prejudice creates the intolerant group norms that in turn leads to negative contact with Muslims. The alternative model in fact showed a better fit to the data than the proposed model. This study advances theories of contact, integrated threats, and group norm theory to the context of intergroup relations with Muslims. Our findings provide support for the notion of changing the normative climate, and equally promoting positive intergroup contact, with the goal of enhancing relations between Muslim and non-Muslim individuals.     

浅析运动队内部人际交往的管理效能

本文以加强运动队科学管理的角度出发,对运动队内部人际交往的意义、功能和如何完善管理效能等进行了研究,可供各运动队参考。     

Investigation on the factors influencing the thickness distribution of superplastic-formed components

In the superplastic sheet forming process, the uniformity of the sheet's final thickness distribution is vital for ensuring the good mechanical quality of the formed components. The influences of the component shape and the contact friction on the final thickness distribution were investigated in this work by using finite element method on a series of axisymmetric models. It was concluded that shape optimization and friction elimination are required to get uniform thickness distribution, and eventually to improve the mechanical quality of the formed components. The constitutive equation of the Ti-6Al-4V superplastic material was also determined on the basis of experimental data.     

The optimal object posture that minimizes contact forces in grasping

Because of the ill-posedness of grasping, one feasible method must be selected from possible strategies. Among many factors, this paper focuses on the posture of an object: which object direction is best when it is grasped. Then, the object is assumed to be held with three points where the contact forces can be generated in any directions. To evaluate the object posture, the norm of contact force vector consisting of the normal and tangential forces is selected. Consequently, the contact force becomes minimal when the center of mass of the grasped object and the centroid of the triangle composed by three contact points are aligned in the gravitational direction.