Structured estimation of tire forces and the ground slope using SM observers

In agricultural context, the principal cause of serious accidents for all-terrain vehicles(ATVs) is rollover. The most important parameters related to this risk is the ground slope. In this paper, we propose a structured observer to estimate the system states and the longitudinal tire forces using only wheel angular velocities measurement. The robust estimation is based on a second order sliding mode observer. This estimation is then used to build up a ground slope estimation. The algorithm is composed by two cascaded estimators. This structured estimation is then applied to the model of an agricultural vehicle G7(GregoireTM) integrated in the driving simulation environment SCANeRTM-Studio.     

Thumb push forces exertable by free-standing subjects

This study assessed the maximum pushing force that could be exerted by freestanding subjects, using thumbs only, on a small surface located in one of three horizontal positions at nine heights ranging from 13·5 to 169·9 cm above the floor. Each of 102 subjects made nine force exertion trials. Data are given on the cumulative percentages of subjects who could exert various forces at each of the 27 locations. An analysis of variance showed a highly significant effect due to location of the surface and highly significant interactions of location of the surface and trial presentation direction (top-down or bottom-up); of location of the surface and trial presentation pattern; and of location of the surface, trial presentation direction and trial presentation pattern. Maximum forces are exerted at about waist height and are increasingly reduced with increasing distances above and below the optimum location. Right-sided access to pushing surfaces is favoured over left-sided access.     

基于SolidWorks软件下进行螺杆压缩机转子受力计算

利用螺杆压缩机的型线端面数据点及型线的接触线数据点,通过给定螺杆压缩机转子参数,在Solid Works里绘制出对应的三维模拟。利用Solid Works里面自带的Simulation模块,对螺杆压缩机进行有限元分析,计算出转子静态下的气体轴向力和径向力,对螺杆压缩机的设计及轴承选型提供很好的理论依据。本文以一种双螺杆制冷压缩机转子为例,利用本方法计算出螺杆压缩机阴阳转子吸排气端的气体径向及排气端气体轴向力。     

青岛市土地利用动态变化及驱动力探究

以青岛市1990-2006年土地利用统计资料和卫星图片等相关资料为基础,通过土地利用的时空变化模型分析,归纳出了其动态变化规律,即：居民点及工矿用地面积、林地面积、交通用地面积和其他农用地面积大幅度增加,耕地、园地和未利用地则表现为不同程度的减少.在此基础上,进一步分析得出了影响青岛市土地利用类型动态变化的几种主要因素,分别是：地形地貌、区域位置、经济发展、城镇化和工业化以及中央和地方各级政府的宏观政策.     

By Words and Deeds: Racial Steering by Real Estate Agents in the U.S. in 2000

Although prohibited by the federal Fair Housing Act of 1968, studies in the 1980s found that racial steering by real estate agents in the U.S. was still occurring. That legislation was strengthened in 1988, but throughout the 1990s, no study examined whether these tougher strictures helped eliminate steering. In 2000, HUD and the Urban Institute conducted the national Housing Discrimination Study in 20 U.S. metropolitan areas to replicate and extend that earlier work. In this article, we report the results of this latest study, which examined three types of steering and three steering mechanisms, all at three geographic scales. The results indicate that steering of all types is occurring when Black and White homebuyers are involved. In at least 12 to 15% of the cases, agents provided gratuitous commentary that gave more information to White homebuyers and encouraged them to choose homes in areas with more White and fewer poor households. Steering is less prevalent when Hispanic and White buyers are involved. We also found no evidence that steering declined over the last decade, despite the toughening of the federal legislation in 1988. We conclude by discussing the implications for interracial wealth differentials and new fair housing enforcement initiatives.     

Application of shape memory alloy bars in self-centring precast segmental columns as seismic resistance

The objective of this study is to investigate analytically the performance of self-centring precast segmental bridge columns with shape memory alloy (SMA) starter bars under nonlinear static and lateral seismic loading. For this purpose, a 3D finite element model for hybrid post-tensioned bridge column has been developed. The precast post-tensioned segmental bridge columns possessing a central tendon and adequate transverse confinement provided by the steel tube jacketing as self-centring bridge columns have an undesirable high lateral seismic demand due to their low energy dissipation. In order to eliminate this deficiency while keeping the residual displacement small, SMA starter bars are applied in this system. The effect of post-tensioning (PT) forces of the central strands and SMA bar size are investigated. The results indicate that in high seismicity zones, bridge columns with SMA bars at a higher level of PT forces have a superior performance against earthquake loading.     

Large‐Scale Synthesis of a Porous Co3O4 Nanostructure and Its Application in Metastable Intermolecular Composites

Three‐dimensional nanostructured porous Co₃O₄ was synthesized on a silicon substrate via a hydrothermal route in conjunction with annealing treatment. The structure and morphology of the obtained Co₃O₄ samples were systemically examined using field‐emission scanning electron microscopy and X‐ray diffraction. The Co₃O₄ structures were composed of nanosheets forming a pore‐network architecture that promoted Al penetration into its inner regions during deposition resulting in enhanced interfacial contact area, which significantly improve metastable intermolecular composites (MICs) burning rate and the release of energy. The successfully Co₃O₄ was used to synthesize Al/Co₃O₄ based MICs by integration with nano‐Al deposited via thermal evaporation. The heat of reaction of Al/Co₃O₄, particularly the exothermic reaction before Al melting, was greatly enhanced by the Co₃O₄ nanostructures. The Al/Co₃O₄ based MICs were fabricated on a silicon substrate, which is very convenient for integrating MICs with silicon‐based microelectromechanical systems to achieve functional nanoenergetics‐on‐a‐chip.     

Fe2O3-Al纳米铝热剂与超细RDX复合物的制备与性能

采用溶胶-凝胶方法,制备出了纳米铝热剂nano-Fe2O3-Al,并获得了其与超细RDX的复合含能材料nanoFe2O3-Al/SFRDX。采用BET法、SEM、XRD综合表征了nano-Fe2O3-Al的结构,采用TG/DSC联用技术测试了nano-Fe2O3-Al的热性能,结果表明气凝胶铝热剂的反应温度更低;nano-Fe2O3-Al的静电火花感度测试结果表明纳米铝热剂对静电十分敏感。对nano-Fe2O3-Al/SFRDX在无约束条件和密闭条件下的燃烧行为进行了研究,高速相机照片法发现在无约束条件下,nanoFe2O3-Al燃烧高达300 m/s,且nano-Fe2O3-Al/SFRDX具有在无约束条件下由燃烧转为爆轰的趋势。     

A simple approximation to rigid body dynamics for computer animation

Recently, the dynamics of linked articulated rigid bodies has become a valuable tool for making realistic three-dimensional computer animations. An exact treatment of rigid body dynamics, however, is based on rather non-intuitive results from classical mechanics (e.g. the Euler equations for rotating bodies) and it relies heavily on sophisticated numerical schemes to solve (large) sets of coupled non-linear algebraic and differential equations. As a result, articulated rigid bodies are not yet supported by most real-time animation systems. This paper discusses an approach to rigid body dynamics which is based on (both conceptually and algorithmically much simpler) point mechanics; this gives rise to an asymptotically exact numerical scheme (NSI) which is useful in the context of real-time animation, provided that the number of degrees of freedom of the simulated system is not too large. Based on NSI, a second scheme (NS2) is derived which is useful for approximating the motions of linked articulated rigid bodies; NS2 turns out to be sufficiently fast to give at least qualitative results in real-time simulation. In general, the algorithm NS2 is not necessarily (asymptotically) exact, but a quantitative analysis shows that in the absence of reaction forces it conserves angular momentum.