Application of fuzzy optimal selection of similar slopes to the evaluation of slope stability

The numerical calculation method is widely used in the evaluation of slope stability,but it cannot take the randomness and fuzziness into account that exist in rock and soil engineering objectively.The fuzzy optimization theory is thus introduced to the evaluation of slope stability by this paper and a method of fuzzy optimal selection of similar slopes is put forward to analyze slope stability.By comparing the relative membership degrees that the evaluated object sample of slope is similar to the source samples of which the stabilities are detected clearly,the source sample with the maximal relative membership degree will be chosen as the best similar one to the object sample,and the stability of the object sample can be evaluated by that of the best similar source sample.In the process many uncertain influential factors are considered and characteristics and knowledge of the source samples are obtained.The practical calculation indicates that it can achieve good results to evaluate slope stability by using this method.     

Influence of Lithological Characters of Coal Bearing Formation on Stability of Roof of Coal Seams

Lithology is one of the important factors influencing the stability of roof of coal seams. In order to investigate this, the phenomenon of underground pressure and distribution of pressure were studied by using the local observation and simulation test with similar materials. The observation results show that the distance of initial weighting and periodic weighting of the mudstone roof is shorter than that of sandstone roofs. The sandstone roof with a high strength has a longer distance of initial weighting and periodic weighting, the abutment stress on the working face is big and the height of caving and fracture zone is high. The peak point of abutment stress in the sandstone roof is near to the working face and the pressure bump is inclined to occur. The result is contrary to that in case of the mudstone roof with a low strength. While in the transition zone of nipped sandstone, roof rock-mass is broken and is poor in stability, therefore, it is difficult to hold the roof.     

Research on dynamic stability rotational speed range of rolling projectiles with different characteristics

Traditional dynamic stability analyses of the rolling projectiles are mainly based on solving the systems＇ transfer functions or angular motion＇ s homogeneous equations to obtain their charac- teristic roots. The solving processes of these methods are complex and lacking further analysis of the results. To solve this problem, Routh stability criterion is introduced to determine the stability of rolling missiles based on the transfer function model, and an important advantage of this method is that it is unnecessary to solve the system＇ s characteristic equation. Rotational speed ranges satisfy- ing the dynamic stability of rolling projectiles with four different characteristics are acquired, and the correctness of analysis results is verified by computing the system＇ s root locus. The analysis results show that the relation between stability and rotational speed for static stable missiles is opposite to that for spin-stabilized projectiles, and the relative size of gyroscopic effect and Magnus effect has an extremely important influence on the trend of the stability of the system with increasing rotational speed.     

Incrusting structure of nanosized Fe_3O_4 particles in magnetic fluids

Magnetic fluids have important applications in high-technical fields especially in the area of lubrication and sealing due to their good properties of flow-ability as well as magnetism[1—4]. A magnetic fluid mainly consists of three parts——nanosized magnetic particles, base liquid, and surfactant. The strong magnetism and long-term stability are the basic criteria to judge the quality of magnetic fluids as well as the key factors guaranteeing their good applications[5—9]. The incrusting of…     

Stability and reliability of pit slopes in surface mining combined with underground mining in Tonglushan mine

Slope stability is of critical importance in the process of surface-underground mining combination. The influence of underground mining on pit slope stability was mainly discussed, and the self-stabilization of underground stopes was also studied. The random finite element method was used to analyze the probability of the rock mass stability degree of both pit slopes and underground stopes. Meanwhile, 3D elasto-plastic finite element method was used to research into the stress, strain and rock mass failure resulting from mining. The results of numerical simulation indicate that the mining of the underground test stope has certain influence on the stability of the pit slope, but the influence is not great. The safety factor of pit slope is decreased by 0.06, and the failure probability of the pit slope is increased by 1.84%. In addition, the strata yielding zone exists around the underground test stope. The results basically conform to the information coming from the field monitoring.     

Robust adaptive cross-coupling position control of biaxial motion system

The stability and synchronous performance are usually hard to be improved simultaneously in the biaxial cross-coupling position motion control system.Based on analyzing the characteristics of the cross-coupling control system,a robust adaptive cross-coupling control strategy is proposed.To restrict influences of destabilizing factors and improve both of stability and synchronous performance,the strategy forces dual axes to track the same reference model using Narendra adaptive control theory.And then,a robust parameters adaptive law is proposed.The stability analysis of the proposed strategy is conducted by applying Lyapunov stability theory.Related simulations and experiments indicate that the proposed strategy can improve synchronous performance and stability simultaneously.     

Analysis of lateral stability of I-section aluminum beams

This paper focuses on the lateral buckling of laterally-unrestrained aluminum beams subjected to a concentrated, uniformly loading and pure-bending action. The design methods of lateral stability of aluminum beams in the current codes are discussed. The influence of material property on the lateral buckling of aluminum beams is investigated with finite element analysis (FEA) methods. Some numerical examples are given, and the results from current codes are compared with the FEA solutions. The design method on lateral stability of steel beams specified in the Chinese standard GB 50017-2003 is modified to calibrate the stability factors of aluminum beams according to the European code, British code, and American code, and the modified method is verified by FEA results. Through comparison with the available test results, the modified design method for overall stability of aluminum bending members is proposed in this paper and proved applicable in the design of lateral stability of aluminum beams.     

Research on anti-contact fatigue performance of grease containing nano SbSbS4 particles

The rise of nano-technology has recently madenano-tribology a rapidly developing area of study[1].Nano-tribology is the mostup-to-date partof tribology[2].Nanoparticles as an additive to grease can create a solid-liquid fluid lubricant, which surprisingly improves the ca-pability of the grease. Manyscholars have investigated thefriction and wear capability of nano-additives[3-8].SbSbS4is a type of extreme pressure and anti-frictionadditive with excellent capabilities. The addition of asmall …     

Design and Trafficability Study of Flexible Wheel for Planetary Exploration Rover

To reduce sending costs, a flexible wheel configuration is proposed. The wheel is made of titanium alloy （Ti-6Al-4V） in consideration of the planetary environment factors （i. e. strong radiation, big temperature differences, high vacuum）, and mass constraint of launch vehicle. The advantages of the proposed wheel involves the potential for： ① small sending volume and mass, ② large deployed area and volume to reduce wheel loading, ③ a damping effect to smooth motion on rough terrain. To study the trafficability and tractive performance of the wheel concept, the drawbar pull and driven torque were calculated based on simplified model of terramechanics formulations. The results show that the wheel possesses sufficient drawbar pull to negotiate all types of soil stratums listed in this contribution.     

Stability analysis and controller design of T-S fuzzy systems with time-delay under imperfect premise matching

The issue of the stability and controller design of Takagi-Sugeno(T-S) fuzzy control systems with time-delay is investigated under imperfect premise matching when the T-S fuzzy time-delay model and fuzzy controller do not share the same membership functions.A new stability criterion which contains the information of membership functions is derived.The new stability criterion is less conservative,and enhances the design flexibility.Two numerical examples are presented to illustrate the conservativeness and effectiveness of the proposed method.     

磁悬浮硬盘转子机电耦合动力学模型

磁悬浮硬盘转子系统由定子、转子、电磁作动器、传感器、控制器和放大器等部件组成。为了研究磁悬浮硬盘转子的动力学特性，不仅要建立转子的动力学模型，还要将定子和磁力轴承的动力学模型融入到转子模型之中。提出了一种基于状态空间的统一的动力学模型，它包含了机、电、磁、控制系统之间的耦合关系，这个统一的动力学模型能够用于磁悬浮转子系统的稳定性、极限转速、动态响应等特性分析。     

水轮发电机组转子-轴承系统横向振动特性分析

将非线性Capone油膜力模型与考虑电机磁极对数分布的不平衡磁拉力模型相结合,建立了水轮发电机组转子-轴承系统非线性动力学模型。基于Matlab语言程序采用4阶5级Runge-Kutta法对系统进行了数值分析计算。研究了在考虑与不考虑不平衡磁拉力的情况下,轴承长径比、转子质量偏心及轴颈间隙等参数的变化对转子轴心轨迹以及频域特性的影响。数值结果表明,同轴承长径比及转子质量偏心相比,轴颈间隙是影响系统轴心轨迹和频域特性的主要因素。相关结论可为进一步研究水轮发电机组在电磁和机械等结构参数共同作用下的运动特性提供部分参考。     

水电机组水力系统和调速器控制规律对电力系统稳定的影响

水电机组的动态过渡过程是一个水力系统、机械系统和电气系统间的相互影响、相互制约的复杂过渡过程.通过对水电机组复杂非线性模型的仿真研究,探讨了水电机组引水系统的水击效应和水轮机调速器控制规律对电力系统稳定的影响.研究结果表明:由于水击作用的影响,原动机的自动调节会恶化系统阻尼,使转子摇摆曲线的衰减速度明显减慢,水轮机调速器的微分作用对单机-无穷大电网的稳定是不利的,并入电网运行的水电机组调速器应采用PI控制规律.     

Research on remote hydro-generator sets diagnosis system

A type of remote monitoring and diagnosis system is brought forward which based on Matlab Web Server.Firstly,wavelet packet decomposition is introduced to acquire energy features of which reflect hydrogenerator sets performance to be Feature Parameter.Then these Feature Parameters can be adopted as BP Neural Network input variable to realize fault diagnosis.Most of all,it is the first time to adopt Matlab Web Server to hydro-generator sets faults diagnosis field to implement distributed remote monitoring and diagnosis system.Therefore,remote diagnosis application is independent from the OS used on server side.There is no need for software maintenance by clients.And clients can finish remote diagnosis by Web Browser and without installation of Matlab-software.Client users can monitor and diagnose hydro-generator sets by Browser.Finally,further research work is pointed out such as hydro-generator sets fault modeling,accelerating BP Neural Network learning speed and convergence property,improving data transfer speed of Matlab Web Server to meet the needs of real-time diagnosis for hydropower generator sets.     

Nonlinear dynamic behavior of rubbing rotor under interaction between bending and torsional vibrations

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转子临界转速的求解方法比较

工程中的各种高速转子都需要确定其临界转速,以确保其在安全的转速范围工作,不发生共振.以一种实验型转子为研究对象,分别采用解析法和基于ANSYS的有限元法对其临界转速进行求解;再利用实验测量的方法测得该转子的临界转速值;把用解析法和有限元法计算所求得的数值与用实验所得实测值进行比较和分析,考查解析法和有限元法计算的准确性、可行性.结果表明基于ANSYS的有限元法对转子临界转速的计算准确性高,计算方便,为工程上其它转子临界转速的求解提供方法依据.     

非线性轴承-转子系统的不平衡响应分析

由于轴承转子系统支承油膜非线性恢复力的作用，使得作用在轴承上的转子的不平衡响应行为比较复杂，用修正的短轴承理论模型对一个实际的轴承转子进行了动力学分析计算，得出了在一定的不平衡下，各种转速的不平衡响应，特别是计算出了半频和倍频出现的分叉点，计算结果表明，轴承－转子系统的半频涡动分叉点与转子转速，转子上所受载荷和不平衡大小均有关系。     

某涡扇发动机转子系统稳定裕度及其灵敏度分析

某型涡扇发动机转子系统由3个单转子系统构成。将该三转子系统在耦合处分开,把耦合力作为单个转子上的外力,并利用集总参数法和各节点的振动微分方程表达式建立单个转子的振动方程。利用各转子间耦合部件的总体耦合矩阵将单个转子的振动方程耦合在一起,建立了整个三转子系统的振动微分方程。通过求解整个系统的振动微分方程,得到整个系统所有模态的对数衰减率,并进一步求出系统的稳定裕度和其灵敏度。研究结论表明：提高高压转子轴承的阻尼和高压转子的弯曲刚度可以有效提高系统的稳定裕度;联轴器的存在和转子转速的提高都会降低转子系统的稳定裕度。     

偏心量对转子-轴承-密封耦合系统非线性振动特性影响的分析

转子偏心量是直接关系转子系统运行稳定性的一个重要因素,将迷宫密封力模型和capone圆轴承非线性油膜力模型相结合,建立了具有非线性转子-轴承-密封耦合系统的动力学模型,研究了转子-轴承-密封耦合系统在不同的偏心量下的非线性动力学行为。针对转速对耦合系统动态响应进行了仿真计算,给出了四个不同转子偏心量下系统轴颈和圆盘随转速变化的响应分叉图,以及典型转速下的Poincare截面图。研究发现随着不平衡量增加,系统出现了混沌运动,但在较大不平衡量时,随着转速的增加,系统在混沌运动后最终呈现同频周期运动,这表明较大的不平衡量反而有助于增加系统稳定的作用。还给出了系统在特定转速下偏心量变化影响下的分岔图,并分析了变化的平衡量下系统对应着复杂的非线性运动。数值计算表明,转子转速、偏心量都是影响系统动力学行为的重要因素,随着转速和偏心量的变化,系统呈现单周期运动、拟周期运动、混沌运动等复杂的动力学行为,具有很强的非线性特征。并且这些结果为实验中偏心量的选择提供了有利的依据。     

Calculations of the bounds on limit cycle oscillations in nonlinear aeroelastic systems based on equivalent linearization

The nonlinear aeroelastic system of an airfoil with an external store was investigated,with emphasis on the bounds of limit cycle oscillations(LCOs).Based on the equivalent linearization,an approach was proposed to calculate the bounds on LCOs over the full flight envelope.The bounds are determined directly without solving LCOs one by one as the flow speed varies.The presented approach can provide us with the maximal LCO amplitudes and the lower threshold for flow speed beyond which LCOs may arise.Numerical examples show that the obtained bounds are in nice agreement with numerical simulation results.The speed threshold can be predicted to a relative error less than 0.1%,and the maximal LCO amplitude to about 3%.The influences of the system parameters on the speed threshold for speed were investigated efficiently by the proposed approach.