Non-linear 2-DOF model and centre manifold theory to study limit cycle oscillations caused by drum-brake judder

This paper presents the research on the laws of systematic-parameter dependent variation in the vibration amplitude of drum-brake limit cycle oscillations (LCO). We established a two-degree non-linear dynamic model to describe the low-frequency vibration of the drum brake, applied the centre manifold theory to simplify the system, and obtained the LCO amplitude by calculating the normal form of the simplified system at the Hopf bifurcation point. It is indicated that when the friction coefficient is smaller than the friction coefficient at the bifurcation point, the amplitude decreases; whereas with a friction coefficient larger than the friction coefficient of bifurcation point, LCO occurs. The results suggest that it is applicable to suppress the LCO amplitude by changing systematic parameters, and thus improve the safety and ride comfort when applying brake. These findings can be applied to guiding the design of drum brakes.     

Thermodynamic Analysis and Comparison on Low Temperature CO_2-NH_3 Cascade Refrigeration Cycle

Intheapplicationsofindustrialandcommercialrefrig erationsystem ,iftherequiredrefrigerationtemperatureisverylow ,theconventionalvaporcompressionsystemisdiffi culttomeettherequirementbecausewhenthedifferencebe tweentheevaporatingtemperatureandthecondensingtemper atureissohighthatitishardtofindarefrigeranttomeettheneedsasthecondensingpressureisnottoohighandtheevap oratingpressureisnottoolow .Whentherefrigeratingtemper atureisverylow ,thecascaderefrigerationcycleissuitabletobeused .Itcannotonlysat…     

用Mathematica计算机代数系统求解数理方程

用Mathematica4.0系统软件精确求解了具有定解条件的一维波动方程和一维热传导方程。     

构建自信与实力间的良性循环

以构建自信与实力间的良性循环为目标,针对各个环节中容易打破循环的问题,重点阐述如何引导学生改变不合理的观念,肯定自己,实现自信与实力间的良性循环.     

基于BIM的建设项目全生命周期成本解决方案

现实中存在建设项目运营和维护成本大大高于建设成本的现象,主要是因为我国在采用全生命周期成本管理中,已完工程缺乏完整的历史数据,存在信息共享性差、未来成本估算的风险性和不确定性等问题,从而限制了相关理论在解决全生命周期成本计算中的实际应用．为此提出,利用建筑信息模型作为信息共享平台,各工具软件可通过API接口与之动态集成,数据库与BIM之间的连接将以ODBC为基础,构建基于BIM的建设项目全生命周期成本的解决方案．     

弹性管束换热器传热与阻力特性的实验研究

对弹性管束水-水换热器的传热与阻力特性进行了研究。主要分析了换热器在不同工况下的传热系数的变化规律;研究了弹性管束在管外流体和管内流体的共同诱导作用下,管外和管内对流换热的情况;并对管程和壳程的流动阻力损失进行了实验测量,得出了管程和壳程的阻力损失变化的规律,以及换热器管程阻力损失的计算方法。     

EXPERIMENTAL STUDY ON SEMI-OPEN HEAT PIPES AND ITS APPLICATIONS

ＩＮＴＲＯＤＵＣＴＩＯＮＨｅａｔｐｉｐｅｓａｒｅｗｉｄｅｌｙｕｓｅｄｉｎｗａｓｔｅｈｅａｔｒｅ ｃｏｖｅｒｙｓｙｓｔｅｍｓ.Ｔｒａｄｉｔｉｏｎａｌｇｒａｖｉｔｙｈｅａｔｐｉｐｅ(ＣＨＰ)ｉｓｃｏｍｐｏｓｅｄｏｆｉｎｓｉｄｅｗｏｒｋｉｎｇｆｌｕｉｄａｎｄｏｕｔｓｉｄｅｃｌｏｓｅｄｓｈｅｌｌｗｉｔｈｈｉｇｈｖａｃｕｕｍｓｔａｔｅｉｎ ｓｉｄｅｉｔ.Ｓｏｍｅｐｒｏｂｌｅｍｓｗｅｒｅｆｏｕｎｄｄｕｒｉｎｇｔｈｅｉｎ ｄｕｓｔｒｉａｌａｐｐｌｉｃａｔｉｏｎｓｏｆｃｌｏｓｅｄｈｅａｔｐｉｐｅｓ (Ａｕｅｔａｌ.,2 0 0…     

Hilbert‘s Sixteenth Problem and Its Generalization

This paper deals with Hilbert‘s 16th problem and its generalizations.The configurations of all closed branches of an algebraic curve of degreee n are discussed.The maximum number of sheets for an algebraic equation of degree n and the maximum number of limit cycles for a planar algebraic autonomous system are achieved.The author also considers different generalizations and some related problems.     

微通道内单相水流动与换热的特性研究

微通道传热技术是近几年发展起来的一门新兴的传热技术,具有传热效率高、结构紧凑等优点,是当前流动与传热研究的重要课题。运用计算流体力学程序(CFX)对环形微通道内单相水的流动与换热进行数值模拟,可以形象地描述出管内的流场和温度场,从中分析各种因素对流动与换热所产生的影响。     

CS（17m,4m）与CS（19m,4m）的存在性

一个所谓的v阶k-圈系统，简记为CS(v,k)，是长度为k的无向圈的集合，它的全体无向边恰构成v阶完全图Kv的边的一个分拆。本文利用差方法构造性地给出了CS（17m,4m),m≡9(mod 16)与CS（19m,4m),m≡3(mod 16)的存在性。