柴油机各缸工作不均匀程度对性能的影响分析

利用飞轮处的瞬时转速信号来间接估计柴油机的各缸工作不均匀程度,结合基于电磁阀的时间控制式电控燃油喷射系统,实现了柴油机各缸工作不均匀程度的闭环反馈控制。在此基础上,通过台架试验分析了各缸工作不均匀程度和发动机性能之间的关系。结果表明,在发动机的大负荷工况下,各缸工作不均匀程度对发动机的经济性和烟度排放影响显著,从而验证了实现柴油机分缸均匀性实时检测和闭环控制的重要性。     

应用于发动机缸体缸盖中的消失模铸造技术

消失模铸造技术是把涂有耐火材料的泡沫塑料模样放入砂箱,高温使泡沫热解“消失”而获得铸件的一项精确成形的铸造技术。其技术在汽车中的应用十分广泛,尤其在发动机的缸体缸盖中的应用更是发展迅速。消失模铸造技术铸件精度高、灵活设计、生产清洁、制造成本低等特点显著。比传统的砂型铸造技术有更高的技术含量,用于气缸盖和气缸体等生产更加复杂、更加精确的高难度铸件,能充分体现出这种铸造技术的优越性和经济效益。     

Towards On-line Automated Semantic Scoring of English-Chinese Translation

Described and exemplified a semantic scoring system of students' on-line English-Chinese translation. To achieve accurate assessment, the system adopted a comprehensive method which combines semantic scoring with keyword matching scoring. Four kinds of words-verbs, adjectives, adverbs and "the rest" including nouns, pronouns, idioms, prepositions, etc., are identified after parsing. The system treats different words tagged with different part of speech differently. Then it calculated the semantic similarity between these words of the standard versions and those of students' translations by the distinctive differences of the semantic features of these words with the aid of HowNet. The first semantic feature of verbs and the last semantic features of adjectives and adverbs are calculated. "The rest" is scored by keyword matching. The experiment results show that the semantic scoring system is applicable in fulfilling the task of scoring students' on-line English-Chinese translations.     

沉入式无底圆筒结构基底压力试验研究

采用模型试验,以实测筒内、外土压力和筒底压力为依据,探讨内填料和地基土与圆筒筒壁间摩阻力的调整及其变化规律。在此基础上,提出了沉入式无底圆筒结构基底压力的计算方法。     

发动机气缸盖气缸体一体化三维模拟研究

应用三维有限元方法,在发动机开发的布置设计阶段,建立发动机气缸盖气缸体的一体化模型,并进行详细的温度场分布和结构耐久性计算。在温度场分析中,引入水套CFD计算结果作为输入条件,并考虑材料的非线性温度效应,计算符合实际工况的温度分布。利用温度场的计算结果,进而进行结构分析,在考虑气缸垫材料非线性行为和各部件接触非线性的基础上,进行多个工况模拟,考察气缸盖气缸体的应力情况和疲劳安全系数,同时对气缸垫压力分布和缸套变形进行分析。     

机动车行人保护发射装置研究

本文以行人保护测试系统发射装置为研究对象，采用高速液压弹射控制技术，分别阐述了发射装置的构成、高速液压缸的结构设计、高速液压发射的控制原理及电气控制系统。最后通过对各种冲击模型的实际测试进行了验证，结果表明：其发射速度稳定、准确、可靠，达到了试验要求。该装置可缓解目前国内行人保护测试设备主要依赖进口的局面，形成了采用高速液压缸进行行人保护试验测试设备的专有技术。     

Trapped waves within the blocking frequency under compressed sea ice and two-dimensional current

The existence of trapped modes due to a horizontal submerged rigid cylinder placed below a compressed ice-covered surface is shown to exist within the frequency band of wave blocking by employing linearized water wave theory and with the inclusion of the effects of a two-dimensional current and the obliqueness of the propagating wave. A new modified multipole expansion method catering to the multiple propagating modes is proposed. The impact of different choices of propagating modes at a fixed frequency within the above-mentioned band on the trapped modes is detailed. Multiple trapped modes whose number depends on the direction and magnitude of the current exist within the frequency band. Out of the three choices of current types considered, while two of them result in the generation of trapped modes for all three possible choices of the propagating wave, the remaining one shows that only one propagating mode can generate a trapped wave. A break in the continuous spectrum of the trapped mode frequency due to the wave blocking and at the point of inflexion is presented. There exists a region of angle of propagation within which an abundance of the trapped mode is shown. The surface profiles for different angles of propagation and choices of propagating modes are illustrated graphically. The trapped modes associated with a higher angle of propagation decay at a faster rate.     

Intelligent VIV control of 2DOF sprung cylinder in laminar shear-thinning and shear-thickening cross-flow based on self-tuning fuzzy PID algorithm

A self-tuning fuzzy PID (ST-FPID) control scheme is implemented within a joint interactive (Matlab/Simulink/Fluent) co-simulation framework for effective two degrees of freedom (2DOF) vortex-induced vibration (VIV) control of an elastically-mounted circular cylinder in laminar cross-flow of incompressible non-Newtonian power-law fluids based on the control action of a single transverse force actuator. The model-free controller, which systematically tunes the control parameters online in real time based on given rules, is well-known to be highly advantageous over the previously employed conventional PID controllers. It is particularly capable of handling the intricate non-linear dynamic effects inherent in the complex fluid rheology of non-Newtonian flow past the cylinder in presence of unmodeled system dynamics, high parametric uncertainties, diverse operational conditions, and time-varying external disturbances and control signals. Extensive numerical simulations reveal that the complex shear-thinning and shear-thickening behaviors of fluid viscosity can substantially influence the cylinder dynamic response, applied hydrodynamic forces, and flow structure. In particular, effectiveness and high performance of the adopted ST-FPID control strategy in substantial suppression of the high amplitude coupled 2DOF VIV of the elastically-mounted cylinder at selected critical reduced velocities in the lock-in region are established for a wide range of power-law index parameters (e.g., up to 83% reduction in RMS value of cylinder cross-flow displacement and up to 35% reduction in RMS value of cylinder in-line displacement for n=1and U* = 5 at Re = 100). Also, the vigorous action of the error-driven ST-FPID controller in forcing the high strength vortex shedding patterns of the uncontrolled cylinder out of the lock-in condition into the classical von Kármán vortex street of 2S-type mode of moderately weaker strengths is verified.     

基于可调储液缸的再生制动电液分配控制策略

为满足低成本小型电动车的再生制动需求，本文提出了一种在传统真空助力制动系统的基础上增设一套活塞式可调储液缸的再生制动系统，并设计相应的电液分配控制策略。首先再生制动电液分配策略根据辨识的制动意图和再生制动力约束对再生制动力进行合理分配；其次设计踏板解耦决策策略，确定了可调储液缸不同的工作阶段和对应的目标活塞位移；最后采用双闭环可调储液缸控制策略完成精确的主动储液控制。基于dSPCAE搭建了实车试验平台进行算法测试，结果表明，设计的电液分配控制策略能保证该制动系统在0.15g以下的减速度范围内实现良好的再生制动电液协同控制效果。     

An improved method for estimating internal solitary waves force on small circular cylindrical structures

Theoretically calculation and laboratory experiments were performed to investigate the horizontal force exerted by internal solitary wave (ISW) on small circular cylindrical structures. Improvement in calculation of drag force and inertia force by introducing two-drag-coefficient method and spatial derivative of velocity into the calculation of force by eigenfunction was made based on systematically study on theoretical foundations. Particle image velocimetry (PIV) method and high precision force sensor were used to measure the velocity and force exerted by ISW, respectively. ISW waveform was traced by analyzing image frames follow grayscale threshold method. For the first time, components of horizontal force were calculated from PIV data, which show good agreement with theoretical one. Moreover, series comparisons between experimental data and calculational results were carried out to examine the proposed method. The results show ideal accuracy of the method and significant improvement comparing to the traditional method.