汽车排气消声器设计应用

文章根据消声器的消声原理,将消声器典型结构组合应用到CN100排气消声器的设计中,分别设计了2个前消声器方案和2个后消声器方案。经过对消声量的模拟计算,初步优选了前消声器方案2。而因为2个后消声器方案模拟计算结果接近,故通过制造前消声器和后消声器的样件,并将前消声器方案与2个后消声器方案组合进行对比试验,以确定后消声器方案。试验结果表明,后消声器方案1优于后消声器方案2,因此CN100排气消声器确定为前消声器方案2和后消声器方案1。同时试验结果表明,CN100排气消声器的排气背压、尾管口噪声达到了设计目标,有效地解决了发动机排气噪声,为整车加速行驶通过噪声提供了良好的贡献值。     

汽车排气消声器的数值模拟分析

排气消声器的数值模拟涉及流体动力学、结构动力学以及声学等多个学科的知识,同时又与发动机耦合在一起。文章利用传递矩阵法,建立了CN100排气消声器与发动机的联合模型,对CN100排气消声器的性能进行了一维数值模拟。数值模拟结果证明:文中提交的2个方案,初步满足CN100尾管噪声与排气背压的设计要求。     

汽车排气消声器的数值模拟分析

排气消声器的数值模拟涉及流体动力学、结构动力学以及声学等多个学科的知识,同时又与发动机耦合在一起。文章利用传递矩阵法,建立了CN100排气消声器与发动机的联合模型,对CN100排气消声器的性能进行了一维数值模拟。数值模拟结果证明：文中提交的2个方案,初步满足CN100尾管噪声与排气背压的设计要求。     

汽车排气消声器性能研究与设计开发分析

随着社会进步不断的加快,人民生活质量不断的提高,基本上很多家庭都拥有一辆汽车。汽车方便了人民的生活,但是汽车排气噪声却困扰着居民,汽车排气噪声作为最主要的汽车噪声源,它严重影响人民的休息,危及人民的健康。如何有效的控制排气噪声是当务之急,安装排气消声器就是目前最有效、最实用的方法。排气消声器不仅能阻碍声音传播,而且允许气流通过,并且还能增加排气阻力,是一种非常实用有效的降低噪音装置。本文将对汽车排气消声器性能的研究和设计开发进行分析。     

基于虚拟计算的汽车排气系统声学性能研究

针对某车型排气系统消声器的开发设计受到发动机及整车资源的限制,难以在规定时限内达到噪声目标要求的问题,文章采用数值仿真方法进行先期方案评估,利用边界条件建立系统声学仿真模型,使用一维计算流体力学的有限体积法进行模拟分析,并通过试验验证方法的有效性和实用性。此方法能够实现排气系统消声器的提前开发,减少项目后期试验频次,并为开发排气系统消声器提供一种新的方法。     

汽车消声器声学性能仿真分析与优化

基于传递导纳和声学有限元的相关理论,利用LMS Virtual Lab声学软件,仿真计算了消声器的插入损失和传递损失,随后通过在内部隔板上增开小孔的方法对原消声器进行了优化,并分析了不同孔径对消声性能的影响。优化结果表明,在消声器隔板上开孔可以使消声器在低频范围内的消声性能得到显著提高,进而为消声器的研发设计提供了理论基础。     

内燃叉车排气消声器结构分析及改进

内燃叉车在工作时会产生较大的噪声,噪声源主要来自车身结构噪声和底盘系统噪声,噪声不但会对周边环境产生污染,而且还会对长时间工作在这种环境中的驾驶员的身心健康产生严重的伤害,因此对内燃叉车进行降噪研究意义重大。排气消声器是降低内燃叉车噪音的有效途径之一,文章主要就排气消声器的结构和分析等问题进行了研究探讨。     

某纯电动商用车怠速工况低噪声设计

针对某纯电动商用车怠速工况噪声大的问题,采用分部运转法,确定主要噪声源,并结合激励源特性,分析噪声源的频率特性,为低噪声设计提供理论及实验依据。针对空压机低频窄带噪声,分别设计谐振腔、扩张室消声器,降低进风口噪声;并通过增加进气引管,使声源远离驾驶室,进一步降低室内外噪声;设计冷却风扇四级调速,减少风扇启动的占空比,降低怠速噪声。测试结果显示,采用噪声优化方法及装置后,噪声明显降低,效果明显。     

煤矿风井噪声治理

对煤矿风井排风口噪声严重超标的原因进行分析,通过实际测量,计算消声量,拿出治理方案,采用聚氨脂喷涂新工艺治理达标,通过运用新工艺,新材料,新的治理方法为煤矿风井噪声治理,排风道的设计提供新的途径。     

常州火车站空调系统设计

常州火车站是沪宁高铁上的一座最大火车站,也是一座按照最新铁道部旅客站房设计细节要求进行设计的典型中型站房。文章对该站空调系统的设计进行了详细介绍,包括室内温度、湿度、噪声、新风量设计参数的选定、集中空调系统形式的确定(尤其是大空间气流组织的形式,以及按细则要求而采取的送风方式)、夏热冬冷地区冷热源方案的选择,以及为减少站房噪声而采取的消声隔振措施和技术,此外,还对该站的集中空调系统自动控制内容进行了详细的阐述。     

基于凌阳单片机控制的语音小车

本设计利用凌阳SPCE061A单片机控制四相步进电机,完成智能小车前轮的连杆传动,带动前轮转向;并通过单片机控制功率放大电路,带动后轮共轴直流电机,完成正转倒转功能;其间的各种行进控制用语音识别来完成,包括前进,后退,停止,左转,右转。在智能车的前端装有两个光线传感器,可以通过对左右光线的变化识别是否将要碰撞前方障碍物,进而反馈到单片机进行转向控制,完成躲避障碍物的功能。     

Procedures to determine optimum two-stage sampling plans by attributes

Summary In order to compare two sampling plans we use the minimax regret principle, i.e. the minimax principle applied to regret functions. It is shown that among all two-stage sampling plans there exists an optimum sampling plan which can be computed with the aid of a procedure presented in this paper; furthermore another procedure is described how to obtain an approximately optimum two-stage sampling plan in a more direct way. Finally only those two-stage sampling plans are regarded which satisfy an additional condition; among these sampling plans an optimum one exists and is to be determined, too.     

Evaluating Form and Functionality of Pay‐for‐Performance Plans: The Relative Incentive and Sorting Effects of Merit Pay,Bonuses, and Long‐Term Incentives

Using two‐year longitudinal data from a large sample of US employees from a service‐related organization, the present study investigates the relative effects of three forms of pay‐for‐performance (PFP) plans on employees’ job performance (incentive effects) and voluntary turnover (sorting effects). The study differentiates between three forms of pay: merit pay, individual‐based bonuses, and long‐term incentives. By definition, these PFP plans have different structural elements that distinguish them from each other (i.e., pay plan form) and different characteristics (functionality), such as the degree to which pay and performance are linked and the size of the rewards, which can vary both within and across plan types. Our results provide evidence that merit raises have larger incentive and sorting effects than bonuses and long‐term incentives in multi‐PFP plan environments where the three PFP plans are operating simultaneously. Only merit pay has both incentive and sorting effects among the three PFP plans. The implications for the PFP‐related theory, as well as for the design and implementation of PFP plans, are discussed. © 2015 Wiley Periodicals, Inc.     

Small asymmetric fractional factorial plans for main effects and specified two-factor interactions

Fractional factorial plans represented by orthogonal arrays of strength two are known to be optimal in a very strong sense under a model that includes the mean and all the main effects, when all interactions are assumed to be absent. When a fractional factorial plan given by an orthogonal array of strength two is not saturated, one might think of entertaining some two-factor interactions also in the model. In such a situation, it is of interest to examine which of the two-factor interactions can be estimated via a plan represented by an orthogonal array, as also to study the overall efficiency of the plan when some interactions are in the model alongwith the mean and all main effects. In this paper, an attempt has been made to examine these issues by considering some practically useful plans for asymmetric (mixed level) factorials with small number of runs.     

The AQL and RQL of the attributes sampling plans in MIL-STD-1916

Since 1996, the Department of Defense-USA has adopted MIL-STD-1916 (Military Standard-1916) sampling plans instead of the traditional MIL-STD-105E (Military Standard-105E) sampling plans. MIL-STD-1916 emphasizes on an effective prevention-based strategy quality system. Its attributes sampling plans are based on “zero accept one reject” as criteria of judgment. In this paper, the lot sizes are regrouped from original 11 groups into 18 new groups such that 100% inspection and sampling plan could be clearly separated. The relationship between fraction nonconforming and probability of acceptance for each verification level (VL) and lot size is investigated. The acceptable quality level (AQL) and rejectabe quality level (RQL) for each VL and lot size are also investigated. The results of this research provide user friendly tables as guidance for both supplier and customer.     

某水电站拦鱼电栅设计

文章介绍了某水电站拦鱼电栅的总体设计方案、布置方案比较和主要计算过程,分析了拦鱼电栅布置形式的特点。     

货物配装和车辆路径问题的一种联合求解方法

货物配装和车辆路径问题(VRP)都是NP难问题,启发式算法是求解此类问题的常用方法。求解单配送中心多车型的货物配送问题,需要改进传统遗传算法:首先采用双层结构表示染色体,车辆数无需事先确定;然后对随机产生的客户序列,利用三叉树算法进行货物配装确定每辆车的配装方案,从而可以知道每个客户的货物装车顺序;依据先装后卸的原则,可得每辆车的客户装车顺序的逆序便是每辆车的客户配送顺序;最终得到货物配装方案和配送方案。基于此思想,通过Java编程验证了一个实例,证明算法切实可行,对实际作业有一定借鉴作用。     

In Pursuit of Time: Business Plan Sequencing,Duration and Intraentrainment Effects on New Venture Viability

In this study, we examine three under‐explored dimensions of the temporal relationship between formal written business plans and the achievement of new venture viability. First, we theorize and investigate the effects of plan sequencing; arguing that a business plan written early on in new venture development increases the prospects of venture viability. Second, we examine plan duration effects, and argue that there is a curvilinear relationship between spending time on a plan and achieving venture viability. Finally, we investigate plan intraentrainment effects (synchronization with other gestation activities). We theorize that if plans are synchronized with other gestation activities, venture viability is more likely. Using longitudinal data and controlling for truncation and endogeneity issues, we find that it is beneficial to plan early but that this is contingent on how long a founder spent on a plan and whether or not a plan is intraentrained with other gestation activities.     

DETERMINANTS OF PUBLIC PENSION PLAN INVESTMENT RETURN. The role of fund value maximization and public choice theory

Public pension plans are a major type of institutional owner during the new era of investor capitalism, yet little is known about them. Based upon fund value maximization (FVM) and public choice theory (PCT), we develop hypotheses on the determinants of plan performance as measured by plan annual investment return. FVM espouses that the plan's fund or investment portfolio will be invested to maximize return for a given level of risk, while PCT holds that agency costs are significant in the public sector, and will have a negative effect on plan return. Using biennial pension plan data for 1992–96 for several hundred plans, we found that fund value maximization has a much greater influence on plan performance, but that plan performance is also subject to agency costs associated with public choice theory.