Shear performance analysis of a heavy-duty universal hinged cast steel support

This paper presents the shear performance analysis of a heavy-duty universal hinged cast steel support with the largest bearing capacity. The effect of 9 parameters ( 52 specimens) ,i. e. height of the upper support,depth of the ring of the upper support,depth of the top plate of the bottom support,height of the ribs of the bottom support,depth of the ribs of the bottom support,bolt hole diameter,number of the ribs of the bowl,depth of the ribs of the bowl,and yield strength of the material,were analyzed with a 3-dimensional elastic-plastic finite element model in which the nonlinearities of geometry,material and contact were all considered. Analysis shows that height of the upper support,depth of the ring of the upper support and yield strength of the material have a great effect on the mechanical performance of the support. Height of the upper support has the largest effect on performance price ratio of the support,and the maximum effect can be up to 160% . Depth of the top plate of the bottom support,height of the ribs of the bottom support and depth of the ribs of the bottom support have a medium effect on performance price ratio of the support,and the effect is within the limit of 15% 19% .     

Measurement methods on the complexity of network

Based on the size of network and the number of paths in the network,we proposed a model of topology complexity of a network to measure the topology complexity of the network. Based on the analyses of the effects of the number of the equipment,the types of equipment and the processing time of the node on the complexity of the network with the equipment-constrained,a complexity model of equipment-constrained network was constructed to measure the integrated complexity of the equipment-constrained network. The algorithms for the two models were also developed. An automatic generator of the random single label network was developed to test the models. The results show that the models can correctly evaluate the topology complexity and the integrated complexity of the networks.     

Identification the Motion Error of Machine Tool Based on the Correlation Analysis

Machine tool has been widely used in the production of the military and civilian.The machining precision of the workpiece is the direct reflection for the machining performance of machine tool.With the improvement for requirement of the machining precision,improving the accuracy of machining is becoming important.Guideway and spindle are the key motion components that decided the shape,the relative position and the surface roughness of the workpiece.In order to adapt to the requirements of the workpiece machining,this paper analyzes the errors of guideway and spindle that affect the accuracy of the processing,establishes the motion relations for every errors of guideway in machining process,identifies the regular for the straightness,bending of the guideway and rotating error of spindle that influences the workpiece surface.Finally,according to the correlation analysis of the measured and the simulation results,the motion error of machine tool is identified,which lays the foundation for improving the accuracy of machine tool in next step.     

Calculation on the pitch angle of rocker of a rocker lunar rover in uneven terrain and path planning

For the concerted motion of rocker lunar rover, the pitch angle of rocker of a rocker lunar rover in uneven terrain must be calculated. According to the character of passive shape-shifting adaptive suspension of rocker lunar rover, the model of rocker lunar rover and the model of terrain were both simplified. The pitch angle of rocker was calculated using forward solving, reverse solving and the method of offsetting the curve of terrain re- spectively. Because of the banishment of the nonlinearity of equation sets of calculation by reverse solving, the calculation of the pitch angle based on reverse solving was programmed by means of MATLAB. Simulations were carried out by means of ADAMS. The result verified the validity of the calculation based on reverse solving. It provides the theoretical foundation for motion planning and path planning of rocker lunar rover. As applications of the calculation of pitch angle of rocker, the multi-attribute decision making of path based on the concerted motion planning and the predictive control on lunar rover based on the Markov prediction model were introduced.     

R-T instability model of magnetic fluid and its numerical simulations

The Rayleigh-Taylor(R-T) instability of ferrofluid has been the subject of recent research,because of its implications on the stability of stellar.By neglecting the viscosity and rotation of magnetic fluid,and assuming that the magnetic particles are irrotational and temperature insensitive,we obtain a simplified R-T instability model of magnetic fluid.For the interface tracing,we use five-order weighted essentially non-oscillatory(WENO) scheme to spatial direction and three-order TVD R-K method to time direction on the uniform mesh,respectively.If the direction of the external magnetic field is the same as that of gravity,the velocities of the interface will be increased.But if the direction of the external magnetic field is in opposition to the direction of gravity,the velocities of the interface will be decreased.When the direction of the external magnetic field is perpendicular to the direction of gravity,the symmetry of the interface will be destroyed.Because of the action which is produced by perpendicular external magnetic field,there are other bubbles at the boudaries which parallel the direction of gravity.When we increase the magnetic susceptibility of the magnetic fluids,the effects of external magnetic fields will be more distinct for the interface tracing.     

A theoretical analysis of vertical dynamic response of large-diameter pipe piles in layered soil

Considering the viscous damping of the soil and soil-pile vertical coupled vibration, a computational model of large-diameter pipe pile in layered soil was established. The analytical solution in frequency domain was derived by Laplace transformation method. The responses in time domain were obtained by inverse Fourier transformation. The results of the analytical solution proposed agree well with the solutions in homogenous soil. The effects of the shear modulus and damping coefficients of the soil at both outer and inner sides of the pipe pile were researched. The results indicate that the shear modulus of the outer soil has more influence on velocity admittance than the inner soil. The smaller the shear modulus, the larger the amplitude of velocity admittance. The velocity admittance weakened by the damping of the outer soil is more obvious than that weakened by the damping of the inner soil. The displacements of the piles with the same damping coefficients of the outer soil have less difference. Moreover, the effects of the distribution of soil layers are analyzed. The results indicate that the effect of the upper soil layer on dynamic response of the pipe pile is more obvious than that of the bottom soil layer. A larger damping coefficient of the upper layer results in a smaller velocity admittance. The dynamic response of the pipe pile in layered soil is close to that of the pipe pile in homogenous soil when the properties of the upper soil layer are the same.     

Stress characteristics of surrounding rocks for inner water exosmosis in high-pressure hydraulic tunnels

Seepage and stress redistribution are the main factors affecting the stability of surrounding rock in high-pressure hydraulic tunnels.In this work,the effects of the seepage field were firstly simplified as a seepage factor acting on the stress field,and the equilibrium equation of high pressure inner water exosmosis was established based on physical theory.Then,the plane strain theory was used to solve the problem of elasticity,and the analytic expression of surrounding rock stress was obtained.On the basis of criterion of Norway,the influences of seepage,pore water pressure and buried depth on the characteristics of the stress distribution of surrounding rocks were studied.The analyses show that the first water-filling plays a decisive role in the stability of the surrounding rock; the influence of seepage on the stress field around the tunnel is the greatest,and the change of the seepage factor is approximately consistent with the logarithm divergence.With the effects of the rock pore water pressure,the circumferential stress shows the exchange between large and small,but the radial stress does not.Increasing the buried depth can enhance the arching effect of the surrounding rock,thus improving the stability.     

A novel orientation measurement using optical sensor for spherical motor

The measurement of spherical rotor orientation is crucial to the close-loop control of spherical motors. This paper presents a novel method for the measuring of three-degree-of-freedom (DOF) rotor orientation of spherical motors using optical sensors. The spatial orientation of spherical rotor is output in the form of ZXZ Euler angles. Firstly, the structure of the measuring system composed of optical sensors and the patterns on the rotor surface are presented, and the operational principle of recognizing intersection points between the optical ring detectors and the latitude/longitude on the rotor surface is illustrated. The analytical model of input-output characteristic is established for the measuring system of three-DOF rotor orientation. Afterwards, the effect of parameters of the optical ring detectors on the linearity, sensitivity, resolving power and measuring range of the measuring system is analyzed using the analytical model. Finally, the feasibility of the measurement is validated through experiments of prototype measuring system. The analysis is expected to be a basis for the design parameter optimization of the orientation measuring system of a PM spherical motor.     

Failure analysis of polycrystalline diamond compact cutters for breaking rock by bending waves theory

The breakage mechanism of the polycrystalline diamond compact（PDC） cutters was analyzed by the energy theory of bending waves. The cutting tests of granite block were conducted on a multifunctional testing device by using the cutter at three kinds of negative fore angles of 30°, 45°and 60°. The results show that, when the edge of the PDC layer is broken, the layer of tungsten cobalt is broken a little under the angle of 30°, while the layer of tungsten cobalt is broken continuously under the angle of 60°, their maximum depths are about 2 and 7 mm respectively in the two cases. The eccentric distance mainly depends on the negative fore angle of the cutter. When the cutter thrusts into the rock under an attack angle of 60°, the energy of bending waves reaches the maximum since the eccentric distance is the maximum. So the damage of cutter is the most serious. This test result is consistent with the conclusion of theoretical analysis well. The eccentric distance from the axial line of cutter to the point of action between the rock and cutter has great effect on the breakage of the cutter. Thus during the process of cutting, the eccentric distance should be reduced to improve the service life of PDC cutters.     

Constructal optimization of cylindrical heat sources with forced convection based on entransy dissipation rate minimization

Based on constructal theory and entransy theory,the optimal designs of constant-and variable-cross-sectional cylindrical heat sources are carried out by taking dimensionless equivalent resistance minimization as optimization objective.The effects of the cylindrical height,the cylindrical shape and the ratio of thermal conductivity of the fin to that of the heat source are analyzed.The results show that when the volume of the heat source is fixed,there exists an optimal ratio of the center-to-centre distance of the fin and the heat source to the cylinder radius which leads to the minimum dimensionless equivalent thermal resistance.With the increase in the height of the cylindrical heat source and the ratio of thermal conductivity,the minimum dimensionless equivalent thermal resistance decreases gradually.For the heat source model with inverted variable-cross-sectional cylinder,there exist an optimal ratio of the center-to-centre distance of the fin and the heat source to the cylinder radius and an optimal radius ratio of the smaller and bigger circles of the cylindrical fin which lead to a double minimum dimensionless equivalent thermal resistance.Therefore,the heat transfer performance of the cylindrical heat source is improved by adopting the cylindrical model with variable-cross-section.The optimal constructs of the cylindrical heat source based on the minimizations of dimensionless maximum thermal resistance and dimensionless equivalent thermal resistance are different.When the thermal security is ensured,the optimal construct of the cylindrical heat source based on minimum equivalent thermal resistance can provide a new alternative scheme for the practical design of heat source.The results obtained herein enrich the work of constructal theory and entransy theory in the optimal design field of the heat sources,and they can provide some guidelines for the designs of practical heat source systems.     

减少反馈策略和联合编码策略下的多播资源分配

针对传统的多播策略中,系统吞吐量受限于多播组中最差用户的信道增益的问题,提出一种基于减少反馈策略和联合编码策略下的多播资源分配算法.采用分层编码与里所(RS)码的联合编码策略,进行数据的分层和补偿丢失的数据包.对传输的不同层的数据采用不同的反馈策略来降低上行反馈负载,并且将资源分配问题建模为最优化问题,为了减轻计算复杂度,又提出了次优化的能保证多播组服务质量的比例公平子载波分配算法与注水功率分配算法(WF-Q).为进一步降低复杂度,采用新的增加固定功率的分配算法(IFP-Q).仿真结果表明,提出的反馈策略明显减少了上行反馈负载,并且联合的编码策略能进一步提高系统性能.     

Turbo码在无线视频传输的误码保护及方案

由于无线信道的时变、高误码等特性,要求信道编码方式有较强的抗误码能力,而且能够自适应无线信道状态的变化。码率匹配删余Turbo码能实现这样的编码要求,并使用tr-s交织器,使其对视频流进行保护。本文介绍了Turbo码在移动通信信道的应用,并讨论了新的自适应调制及不等差错保护方案。     

基于自适应分割和非规则LDPC的图像编码

为了提高图像在无线信道上的传输效率和抵御误码的能力，提出了一种基于自适应分割和非规则低密度奇偶检验（low-density parity check, LDPC）码的联合信源信道编码（JSCC）方案.针对自适应分割能够把图像分割成不同重要级别的图像子块、非规则LDPC中高度数的比特节点比低度数比特节点有更强的纠错能力的特点，研究了把自适应图像分割和非规则LDPC结合起来的联合信源信道编码的算法；自适应分割后不同重要性级别的图像子块，采用非规则LDPC编码，获得了不等错误保护（unequal error protection, UEP）. 仿真结果表明,该方案能够显著地提高无线图像的传输质量和传输效率，与采用等错误保护（equal error protection, EEP）策略的JPEG图像相比，在信噪比Eb/N0=1.6 dB时，重建图像的峰值信噪比(PSNR)有17.78 dB 的改善.     

Channel Coding Techniques for VHF-Mobile Radio System and Its DSP Implementation

Forastronglyvaryingtransmissionenviron ment,anadaptivemulti rate(AMR)speechcodec hasbeenadoptedforsourcecodingonVHF mobile radiosystem,justasin3GPPsystem.TheAMRen codedbitsofthespeechcoderarecomposedofbits withvaryingimportanceforthereconstructionof originalspeech.Duetothedifferenceofeachbitson sourcesignificantinformation,unequalerrorprotec tion(UEP)adoptedinthechannelprotectionof speechcoderhasbeenextensivelystudied[1,2].Theapplicationofrate compatiblepunctured convolutional(RCPC)for…     

无线Mesh网络功率控制与信道分配联合优化

针对无线Mesh网络网关节点和网络链路承载的负载不均问题,择优选择网关节点,并设计链路权重,构建以网络加权吞吐量为优化目标的资源分配模型.在构建的资源分配模型下,提出一种基于Q学习和差分进化的联合功率控制与信道分配算法（QDJPCA）.该算法通过获取功率控制的反馈结果,采用基于多重变异和自适应交叉因子的差分进化算法进行信道分配;针对每次迭代产生的信道分配结果,采用基于状态聚类和状态修正的Q学习算法实现功率控制.NS-3仿真结果表明,QDJPCA能够有效求解所提资源分配模型,在优先保证网关负载均衡和高负载链路吞吐量性能的基础上提升网络整体性能.     

无线信道下视频传输的组合式差错控制机制

为减轻无线信道差错对视频传输质量的影响,针对现有前向纠错技术多采用多参数RS编码方式的局限性,提出一种新的组合式差错控制机制,首先联合信源采用交错式控制建立基于对视频重建影响程度的Q oS映射;然后采用非均等差错防护确立基于typeⅢ-HARQ的CRC-RS组合式差错机制;最后提出自适应帧长及组包算法进行有效的CRC传输,以最大化利用无线带宽资源。通过仿真结果可以看出,系统在失真度和功率损耗的改善上都有很大的优势。     

基于用户分簇的物理层增强安全多播算法

物理层安全技术是无线网络技术中一项重要的关键技术。在大量多播用户和窃听用户共存的场景中,针对传统物理层安全技术中在波束赋形下增加人工噪声时不能很好地应用于多播传输的问题,提出了一种基于多播用户分簇策略下的物理层增强安全多播算法。首先,具有相近信道矢量的多播用户被分为同一个多播簇,不同的多播簇分配不同的子载波传输多播数据;其次,基于多播用户分簇策略的结果,提出了通过采用联合功率分配和波束赋形设计算法,最大化整个多播系统的安全多播速率;最后,为了降低算法的计算复杂度,提出了新的搜索算法处理联合功率分配和波束赋形设计算法。仿真结果显示：与传统安全多播算法相比,基于多播用户分簇策略的物理层增强安全多播算法不但能够获得更高的多播安全传输速率,而且其计算复杂度也大大低于采用遍历搜索的传统安全多播算法。     

Resource allocation scheme for video transmissions in cognitive radio networks

Considering SUs with multiple radios, this paper discusses the cross-layer resource allocation problem for video transmissions in cognitive radio networks. Because of the coupling relationship between radio and channel, this paper proposes a new conflict graph based on the link-radio-channel, and models the resource allocation problem into an optimization problem. The constraints ensure the conflict-free and interference-free video transmissions, and provide flow routing and rate allocation for video services based on the feature of scalable video coding streams. The objective function achieves the network-level throughput maximization with fairness consideration. Simulation results show that the multi-radio transmission could gain a higher throughput. Also, the proposed scheme could provide fairness resource allocation, and use resource efficiently based on the feature of video services.     

多播系统中基于多用户分集的资源分配

针对无线多播系统中传输速率受限于多播组中最差用户信道容量的问题,提出一种组内资源分配算法.在考虑用户之间不同速率需求的前提下,对多播组内用户进行子载波分配和功率分配,来最大化多播系统归一化速率.子载波分配算法利用每个子载波上多播用户之间的多用户分集,将子载波分配给该子载波上性能较好的多个用户.功率分配算法采用基于梯度的功率分配方式对各子载波上所分配的功率做局部优化,进一步提高多播系统的传输速率.仿真结果表明,与传统多播组内资源分配方案相比,显著提升多播系统的归一化速率.     

面向链接的资源分配与QoS保障联合跨层算法

为了在无线蜂窝网络中向各物理链路上具有不同速率以及延时要求的多条数据链接提供最优化的资源分配以及服务质量(QoS)保障,设计了一种面向链接的资源分配与QoS保障联合算法.基于跨层设计思想,将目标建模为接入控制、速率分配以及资源分配3个子问题.来自物理层的信道状态信息、来自媒体接入控制（MAC）层的队列状态信息、来自应用层的速率及延时请求信息在系统模型中得到了综合的考虑.子问题可以分别通过贪婪算法及凸规划算法顺序地进行求解,从而得出每条数据链接上最优的资源及功率分配值,而这些结果将通过特定的接口反馈到各个层次模块中去.仿真结果表明,该算法能够解决模型面临的问题,并且比层次式协议栈中的算法更加有效地利用了网络资源