Applying the Dynamic Condensation Technique to the Mechanical Structure Finite Element Modeling

Research for applying the technique of dynamic condensation on the mechanical structure dynamic analysis.The tolerance of the mechanical structure dynamic characteristics has been investigated when it is solved with the useful method of mode condensation.The practice shows that computational result of the dynamic characteristics relating to reserved number of mode and the magnitude of the damping,when the freedom of the complicated mechanical structure finite element model be reduced in big amplitude with the mode condensation technique.     

低桩机割再生稻氮肥施用技术研究

为适应再生稻头季低桩机割条件下再生季分蘖生育特性的变化,设置再生季不同氮肥施用量和施用方法。通过观察分析再生季分蘖消长、产量及其构成,研究了再生季氮肥施用技术。结果表明,再生季经济施氮量为180 kg/hm2,采用早施促蘖肥,中期分次施用穗肥和粒肥的方法,可以有效促进有效分蘖的萌发及其穗粒发育,显著提高产量。     

Testing and modal analysis on multi stage planetarygearbox housing of shield tunnelling machine

The finite element model is developed for the multi stage planetary gearbox housing in shield tunnelling machine (STM), and the the eigenvalue problem is solved by using block Lanczos method, and then the low order natural frequencies and corresponding modes are extracted. Based on the theory of experimental modal analysis, the modal testing is made for the gearbox housing by pulse excitation method. The least squares complex frequency domain (LSCF) estimation method is used to analyze the modal data, and the natural characteristics of housing is obtained. According to the modal assurance criterion (MAC), the experimental modal parameters are validated. Modal analysis shows that the experimental data is coincided with analytical results, which indicates the accuracy of the theoretical model and testing method. The coupling sympathetic vibration is disappearing between the gears train and housing, the local vibration is large at the high speed side of gearbox housing, and the torsional mode is outstanding under operating condition. The research results provide theoretical basis and experimental support for the structural optimization of the gearbox of STM.     

Dynamic characteristics of multi-stage planetary gear trains in shield machine cutter drive

A purely torsional dynamic model of multi-stage planetary gear trains is developed to investigate the dynamic characteristics of the transmission system in shield machine cutter drive. In the model,phase difference between mesh stiffness and error among each stage caused by different initial mesh positions is considered,and other factors such as component bearing stiffness,time-varying mesh stiffness and error are considered as well. Inherent characteristic analysis shows there are more unique and diverse vibration modes in multi-stage planetary gear trains than in single-stage planetary gear trains. Through dynamic response analysis,time-domain and frequency-domain response of dynamic meshing force of each stage is obtained. As the frequency of exciting force of medium-speed and high-speed stage is in proximity to the natural frequency of the system,harmonic resonance tends to occur,which needs to be paid great attention to. Dynamic factors of each stage are also computed and prepare the ground for the dynamic optimizing design of planetary gear trains.     

A Method of Analyzing the Parameter Sensitivity of Large Rotor Systems and Its Application

Based upon the eigenvalue sensitivity theory of non-self-adjoit system and the component mode synthesis method,a new technique is developed to analyze the eigenvalue sensitivity to variation of parameters of large rotor-bearing system. As an application, the influence of the journal bearing parameters on the stability of a large domestic turbine-generator set is analyzed and discussed.     

Analysis of Unified Power Flow Controller in Damping Low Frequency Oscillation of Power System

With the development and complication of power system, the problem of low frequency oscillation in electric network becomes obvious. Unified Power Flow Controller is one of the most powerful facilities in Flexible AC Transmission Systems, which can improve the transient stability and damp the low oscillation in power system with suitable control. Considering the characteristics of inverter's output voltage magnitude, adjustment of phase and process of charge and discharge of dc capacitance, the dynamic model of UPFC is proposed by a series of nonlinear differential coefficient equations. Based on UPFC's dynamic model, the linear optimal controller of UPFC with state feedback is proposed. In this way, the low frequency oscillation is damped effectively. A simulation is processed basing the theory.     

基于FMEA的生鲜猪肉冷链物流质量安全控制研究

生鲜猪肉冷链物流具有运作环节多、过程复杂、风险较高等特点,为规范质量管理,降低流程风险,应用故障模式和影响分析(Failure mode and effect analysis,FMEA)方法对生鲜猪肉冷链物流过程进行风险评估。以某生猪屠宰加工企业为例,对生鲜猪肉的屠宰、预冷、冷藏、分割与包装、运输、销售6个冷链环节进行风险分析,识别12个故障模式。依据风险评价准则,由专家小组评价每个失效模式的严重度、发生度和检测度等级,量化风险顺序数。根据风险等级分类,确定高风险故障模式5个、中度风险故障模式4个、低风险故障模式3个,明确各故障模式改进的先后顺序,从而有针对性地制定风险改善措施并实施。基于FMEA,从系统的角度对生鲜猪肉冷链物流进行全面的风险管理,可以有效预防风险,为构建生鲜猪肉安全供应保障体系提供理论依据。     

Responses of Rubber Bearing Isolation Structure Considering Soil-Structure Dynamic Interaction

By means of the substructure approach in the frequency domain, equations of motion of the rubber - isolated structures are established considering the soil-structure dynamic interaction. The seismic responses of two shear-type base-isolated structures with an embedded rigid rectangular foundation are numerically simulated, and the influences of the different rigidities of soil on the effect of the base isolation and the seismic responses of the structure are investigated. It is concluded that rubber bearing isolation can reduce the dynamic characteristics of structures and reduce displacement of floor and basement relative to ground. Meanwhile, considering the dynamic soil-structure interaction may reduce the isolation effect of the rubber-isolated structures and the effect level is in direct proportion to the stiffness of the superstructure and inverse proportion to the stiffness of foundation soil.     

Rosenbrock-based coupled time integration method and its convergence analysis

Real-time substructring testing is under rapid development. is a hybrid computational-experimental technique, and its challenge is to ensure that the numerical substructure and the experimental substructure interact in real time, which requires efficient numerical integration methods. With this mind, based on the Rosenbrock real-time integrator, a coupled time integration method is proposed which enables completely parallel computation. By virtue of a Single-DoF split-mass test problem, stability and accuracy analyses are performed theoretically for the coupled method. Moreover, numerical simulations on a Three-DoF split-mass system are conducted to further investigate the convergence and other properties of the coupled method. The theoretical analysis and the numerical simulations reveal that the method exhibits favourable stability and second order accuracy. Compared with direct time integration methods, the proposed method is more suitable for Real-Time Substructuring Tests of complicated structures and relevant hybrid simulations.     

Applying hybrid dynamic substructure synthetic method to dynamic analysis for tower crane

This paper presents a dynamic hybrid substructure synthetic method for tower crane dynamic analysis. This method employs the transfer matrix method and the flexibility degree method respectively to formulate the vibration mathematical models of the tower body and tower top system substructures in the hoisting luffing plane. Based on the motion of the substructures in the interface and the dynamic harmonize condition, the frequency equations are established. Then the program is designed according to the mathematical models and firstly applied to the dynamic analysis of the QTZ63 tower crane in the construction site and the parameter identification of attached device and tower body. The test results show that the value calculated by the above method is quite approximate to the instrument measured value, which can meet the engineering requirements. Further study has found that , for the flexible long-distance attached tower crane, the method that introduces dynamic load coefficient for statics analysis of tower cranes is unprecise enough since there exist errors.This paper suggests to conduct site test and identification of the rigidity coefficient of attached device of the tower crane for the accident prevention of tower crane collapse by timely take measures.     

模式识别的斜拉桥损伤诊断动力指纹与识别算法

为有效并准确诊断出斜拉桥损伤,对基于模式识别的斜拉桥损伤诊断方法进行了研究。选取易于测试出的低阶模态频率和部分关键点竖向振型数据为动力指纹,无需模态扩展或模型缩聚。研究并采用全因子设计进行动力指纹库的创建,可精确评估设定的损伤因子及其交互作用对损伤识别结果的影响。设计并增加了带随机误差的动力指纹库样本集。编制了基于Matlab的模式识别的多种算法,重点研究了精确度高的多层感知器识别算法及其提高该算法预测准确率的装袋集成算法。最后给出一座单塔双跨双索面斜拉桥的多种识别算法的损伤诊断过程和结果,得到一种可包容测试随机误差的高精确度斜拉桥损伤诊断评估模型。     

Analysis of a multimode transmission line model of the shielding effectiveness of enclosures with apertures

The equivalent transmission line method is extended to multi-transverse electric modes of cavity which are introduced by aperture coupling, and it is used to analyze the shielding effectiveness of rectangular enclosures with apertures. The multimode transmission line method is verified by HFSS(High Frequency Structure Simulator). The results show that higher-order mode is essential to obtain an accurate shielding effectiveness of rectangular enclosure on wide frequency domain. Below the frequency of 1 GHz, nearer to the slot, the impact of higher-order mode on the shielding effectiveness is greater in the place mear the slot. Higher-order mode leads to a better shielding effectiveness.     

TOPSIS法综合评价宁夏中部干旱带五种风蚀环境抗风蚀性能

针对宁夏中部干旱带土壤风蚀严重、沙尘暴频发等生态问题,分别选择典型压砂农田、沙质旱作传统翻耕农田、人工灌木林地、封育草场和流动沙地5种风蚀环境为研究对象,利用TOPSIS法综合评价不同风蚀环境抗风蚀性能。结果表明:灌木林地的抗风蚀性能最强,其Ci值为0.674257,其次为压砂农田、封育草场;抗风蚀性能最弱的是翻耕农田、流动沙地,Ci值分别为0.087007和0.003552。可见翻耕农田和流动沙地是当地主要沙尘来源。     

Junction stiffness analysis and vibration noise prediction of wind power speed-increase gearbox

In order to study the vibration characteristics and radiation noise of wind power speed-increase gearbox, a torsional vibration model of wind power speed-increase gearbox is established based on the analysis of supporting stiffness of bearing and contact stiffness of gear pairs. By solving the vibration differential equation with the help of Matlab, the frequency and corresponding vibration mode are obtained. With taking stiffness excitation, error exaction and meshing impact exaction into account, the dynamic finite element model of speed-increase gearbox is set up, and the dynamic response simulation is carried out. Regarding vibration displacement of the nodes on gearbox surface as boundary condition, an acoustic boundary element model of speed-increase gearbox is built. The surface acoustic pressure of gearbox and the radiation noise of field points are solved by the direct boundary element method. The results show that there is a great difference between torsion frequency and excitation frequency of wind power speed-increase gearbox, and so the resonance doesn't occur. The maximum structural noise and radiation noise mainly appear near the double octave of the gears meshing frequency of high-speed grade.     

Controlling Strategy Research on Batteries Imbalance

In order to increase using time of the batteries, and improve the hybrid electrical vehicles' economical and dynamic performance. By analyzing imbalance instances of the batteries, the battery characteristic mode of batteries imbalance dynamic performance is built, and the energy diffluent charge and discharge modes about controlling batteries imbalance degrees are put forward. Consequently, the energy diffluent charge and discharge controlling strategys of batteries imbalance degrees are advanced, and simulation calculation is processed, good-result is received.     

Perturbation Analysis of Complex Modes for Vibration System with Viscous Damping and Its Application

The sensitivity characteristics of the undamped natural frequencies and complex mode shapes of vibration system with the non-proportional viscous damping with respect to structural mass, stiffness and damping modifications are analyzed in this paper using the matrix perturbation of complex modes. The general principles for the selectivity of the design and the most sensitive positions of the structural perturbation modifications are shown thereby. This is of importance to a great computational savings in the dynamic characteristic improvement of large or complex structures. By the dynamic characteristic sensitivity analysis of a test device type RDT-1,the optimal structural design for its especial requirement of dynamic characteristics is obtained easily and the principles presented in this paper are confirmed by the numerical results of perturbation analysis.     

Numerical Prediction of Frequency of Delaminated Advanced Grid Stiffened plate

The paper aims to investigate natural frequency of delaminated advanced grid stiffened composite plates by hump resonance method.The composite laminated plate element and the rib element are adapted to simulate the laminated plate and the ribs.Based on the composite laminated plate and beam element model considering first-order shear effect,a damping model on the basis of Rayleigh damping model in conjunction with Adams' strain energy method(MSE) and a Hertz nonlinear dynamic contact model to avoid the overlap and penetration phenomenon between the upper and lower sub-laminates at the delaminated region.A numerical analysis method of dynamic response for the delaminated composite plates is carried out by precise time-integration method,and then the natural frequencies are achieved when the dynamic deflections reach the hump peak.For the frequency-domain analysis provided in the former research papers,it is a difficult problem to avoid the embedded phenomenon in the mode shapes at the delamination zone,while in the current time-domain analysis,the embedded phenomenon can be successfully overcome by using nonlinear contact model.By vibration excitation test,the specimens were excited by different excited frequency and the amplitude frequency response characteristics obtained are used to extract the frequency.The extracted frequencies of the narrow delaminated composite plates measured,which agrees well with the predicted natural frequencies.     

种植方式调控早稻生长研究进展

种植方式多样性是中国水稻生产主要特点之一，对于应对多变的种植环境，提高水稻综合生产能力和保障国家粮食安全具有重要作用。为了揭示不同种植方式下早稻生长发育特性和高产形成特征，本文阐述了我国目前早稻生产和种植方式发展现状，归纳了不同种植方式对早稻根系生长、养分吸收、干物质积累、茎蘖动态、生育期变化、产量和品质形成，以及经济和生态效益的影响，并认为今后可以从不同种植方式下早稻生育进程的内在机理、稻田杂草群落组成及其物种多样性和稻田土壤矿质元素流失特征展开探究。     

Structural Optimum of Main Tower- Frame of Mast Crane

Taking the Structural optimum of main metal frame of mast- crane as a sample,this paper discussed the method of Structural optimization of common middle & high flexibility metal tower- frame by dynamic programming.The method of dynamic programming applied to the structural optimum was deducted and the minimum weight design method of tower- frame was practiced The paper gave up the traditional interactive way of choosing type of material,combining with the concrete example,changed the data- table looking up into formula solution,shifting with one by one into directly sieving within selected types,artificially fixing up composed rods into automaticaliy arranging them through the way of maximum twist moment of inertia,thus,accelerate optimization and offered a short way for artificial structural analysis and calculation.     

Low frequency oscillation restraint in power systems that include asynchronized turbogenerators

Yangtze River is abundant of water and can provide enough water as cooling and heating source for water source heat pumps (WSHP). A pair of contrast experiments with open loop system and close loop system of WSHP were finished in order to get the heat pump's COP, the system's COP and the distribution of water temperature in the heat exchanger etc. This paper compared the characteristic and the COP of these two kinds of system. The heat pump's COP of the open loop system and close loop System are 3.08 and 3.77 respectively, and the system's COP are 2.83 and 2.80 respectively. At last, applications of open loop system and close loop System of WSHP at Yangtze River were analyzed and the key problem for attention was pointed out in the paper. 