路试充分发出平均减速度可取信范围分析

当我们使用便携式制动性能测试仪来检验涉案车辆制动性能,为什么有时获得的充分发出的平均减速度（MFDD,mean fully developed deceleration）值会大于重力加速度g,这些较大的MFDD值与《便携式制动性能测试仪校准规范》中的测量范围是否相冲突,这些检测值在车速等运算中是否可以被采信,路试检验MFDD的有效范围是什么,鉴定业界对这些问题有着诸多争议和不同答案。本文旨在对路面摩擦系数进行讨论,并利用达朗贝尔原理建立车辆制动受力模型,从而证明高于g的充分发出的平均减速度在路试检验中可以成立,并确认了该值的可以取信范围0~l1h×g。     

重新认识光的半波损失及牛顿环中心暗斑

通过对菲涅耳反射系数的讨论, 重新认识光的 “半波损失”,指出一些大学物理教科书中在光的“半波损失”认识上的误区,重新解释了牛顿环中心暗斑的“半波损失”现象。     

收入差距拉大:构建和谐社会的阻梗

改革开放实行的差异性发展政策,形成了部分地区、部分企业和部分人的率先发展,而政策调整的滞后,使得经济发展水平的差异硬化为明显的社会差异,随着经济的进一步发展,富者愈富、穷者更穷,社会的分化和差距越来越大,收入分配差距目前已经达到可以容忍的上限。改革发展的成果不能惠及到社会的各个方面,弱势群体的心理失衡和行为失范以及由此可能导致的社会动荡,可能成为我们构建和谐社会的阻梗,疏通这一阻梗应当成为我们建设和谐社会的重要任务。     

Validation of Walkway Tribometers: Establishing a Reference Standard*

Abstract: Tribometers are mechanical devices used to measure walkway coefficient of friction (COF) for the purpose of assessing slip risk. The purpose of this study was to define a tribometer reference standard and use it to assess the performance of various tribometers. Eighty subjects were randomly assigned to walk across one of four wet walkway surfaces (polished black granite, porcelain, vinyl composition tile, and ceramic tile) to establish the relative slipperiness of each surface. Eleven tribometers were subsequently used to measure and rank the COF of all four surfaces. Our results revealed that only four of the 11 tribometers (Wessex pendulum, Sigler pendulum, Mark II, and Mark III) met our compliance criteria by both correctly ranking all four surfaces and differentiating between surfaces of varying degrees of slipperiness. Our protocol demonstrates that human gait‐based measures of slipperiness can be used to create reference standards against which tribometer measurements can be validated.     

小波子空间的抽样定理

本文首先介绍了古典仙农抽样定理,然后回顾了小波分析和多尺度分析的历史;接着,从低通滤波器系数和小波的角度刻画了小波子空间中抽样定理成立的一个充要条件,并研究了它们的对称性。     

典型电动两轮车倒地滑动摩擦系数实验研究

目的 为获得典型电动两轮车倒地滑动摩擦系数,研究倒地滑行速度、路面干湿、路面材料以及电动两轮车结构等因素对电动两轮车倒地滑动摩擦系数的影响.方法 采用实车牵引法测试了“标准”和“非标”两种类型电动两轮车在四种常见路面上的0～50km/h速度区间内的倒地滑动摩擦系数.结果 电动两轮车在实验混凝土路面倒地滑动摩擦系数为0....     

城乡居民收入分配现状及其对策的思考

建国以来 ,我党一直在为提高人民的生活水平而努力 ,其中有很多宝贵的经验和深刻的教训 ,特别是 1978年改革开放以来 ,我国居民个人收入总量急剧增加。然而 ,居民收入分配差距也在不断扩大。本文列举了居民收入分配差距不断拉大的几种主要原因 ,并且根据我国收入差距演变的情况 ,提出了适合我国国情的对策 ,以求实现缩小居民收入差距 ,达到共同富裕的目的。     

Wind-drag estimation in a traffic accident involving a motor scooter and a tractor-trailer

This case report describes a noncontact traffic accident involving a motor scooter and a tractor-trailer with a focus on the wind-drag effect. We used load cells to measure the drag force acting on a substantially similar motor scooter when a substantially similar tractor-trailer passes by it, taking into consideration various speeds of the tractor-trailer and distances between the two vehicles. A three-dimensional steady-state flow analysis was also performed by using the CFX program for computational fluid dynamics to examine the streamlines and the pressure distribution around the tractor-trailer at various speeds. From the experiment, for a separation distance of 1.0 m (3.28 ft) and a speed of 90 km/h (55.9 mph), the maximum resultant drag force is 124.5 N (28 lb); this constitutes a degree of force that could abruptly disrupt the stability in maneuvering by an operator who is unaware of the approaching tractor-trailer. In addition, a single equation that relates the tractor-trailer speed to the drag force that acts on the motor scooter was derived on the basis of the Reynolds number (Re) and the wind-drag coefficient (C(d)): C(d) = 1.298 × 10(-7) Re.     

The role of center of mass kinematics in predicting peak utilized coefficient of friction during walking

Slips frequently occur when the friction required between the foot and floor exceeds available surface slip resistance. To date, the ability to identify variables that predict an individual's friction needs during walking, or utilized coefficient of friction (COFU), remains limited. Understanding COFU in the context of pedestrian/walkway accidents is important as individuals who demonstrate higher COFU are at a greater risk of slipping. This study determined if whole body center of mass (CM) kinematics were predictive of peak COFU during walking. Ground reaction forces and kinematic data were recorded simultaneously as subjects walked. Stepwise regression analysis determined that the combination of the subject's CM-to-center-of-pressure angle and CM anterior (i.e., forward) velocity predicted 62% of the variance in peak COFU during weight acceptance (p < 0.001). The identified relationships between CM kinematics and peak COFU provide insight into how gait and individual anthropometric characteristics may increase risk for slip initiation.