微型多槽道平板热管传热特性分析及最大传热量预测

对三角形槽道的微型平板热管,进行流动、传热性能的理论分析和模拟.建立了微型平板热管的一维稳态模型,以分析工质在热管内的轴向分布,液体和蒸汽压力、流速的轴向变化,并计算其最大传热量.该模型更精确地考虑了具有互相连通蒸汽空间的平板热管,汽液界面剪切摩擦力对其传热性能影响,模型预测结果与实验数据取得较好的符合,能够更准确地预测微热管的最大传热量.该模型可用来帮助微型多槽道平板热管的结构设计.

平板热管在毛细极限下的传热能力研究

建立了多孔毛细芯结构的平板热管在冷凝段不发生堵塞的情况下流动和传热的理论模型,分析了热管在毛细限下的最大传热量和热阻的变化。结果表明,丝网目数的增加和工作温度的升高会增大热管的传热能力,热管工质为水时的传热性能优于工质为丙酮和乙醇时的情况。

电气介数及其在电力系统关键线路识别中的应用

提出线路的电气介数并将其用于电力系统关键线路识别。该方法基于电路方程,克服了加权介数模型假设母线间潮流只沿最短路径流动的不足,能有效反映各"发电–负荷"节点对对线路的真实利用情况,其物理背景更符合电力系统特点且可考虑不同发电容量及负荷水平的影响。同时提出系统最大传输能力指标,其变化量同已有指标相结合能更全面地反映系统的故障程度。对IEEE-39系统和西北网的计算表明,高电气介数线路往往属于电网的长程连接,具有关键性地位,且电力系统在针对这些线路的攻击下更为脆弱。对蓄意攻击下系统连锁故障过程的追踪也显示最大传输能力指标的必要性,证明该模型比已有模型更为合理有效。

框架结构能量流网络及其初步应用

从考察框架结构在各种荷载条件下的能量流动出发,考虑结构杆件以及节点的能量流动状况,建立框架结构的能量流动网络。比较各杆件和节点的能量流动方向及大小,按图论方法得到框架结构内能量流动的关键路径,即结构的最大传力途径;通过比较拆除不同杆件对结构系统总体应变能影响的大小,确定结构杆件的重要性;通过跟踪结构杆件的破坏顺序以及结构杆件重要性的变化,确定结构最重要破坏模式。对唐山大地震中倒塌的一个3层框架作了分析,结果表明这种方法可以充分考虑结构受不同荷载作用的影响,可以确定框架结构的杆件重要性、最大传力途径以及最重要破坏模式。

基于无迹卡尔曼滤波预测的锅炉吹灰优化

针对锅炉受热面从清洁到产生积灰和结渣导致锅炉传热效率降低等问题,以清洁因子为监测指标,提出一种基于无迹卡尔曼滤波算法的实时吹灰预测方法。采用双指数函数拟合分析清洁因子退化数据,利用无迹卡尔曼滤波算法对模型参数进行更新,并预测清洁因子未来的变化趋势。同时提出一种基于单位时间传热量最大的吹灰优化模型对吹灰时间进行进一步的优化。以某省煤器的清洁因子数据为例,通过与扩展卡尔曼滤波算法进行比较分析发现,所提方法能够更准确地预测吹灰时间,并进行吹灰优化实例计算,验证了所提优化模型的可行性。

纤维吸液芯平板微热管理论分析与验证

设计了一种纤维吸液芯结构平板微热管,利用纤维紧密排列间隙形成微型热管工作流道。对该微热管进行了理论分析建模,建立了质量方程、动量方程和能量方程等。对模型进行了仿真运算,对比了最大传热量与实测结果,从而得出纤维吸液芯微热管的最大传热量。

报文分片对网络的影响

MTU是以太网里的术语,它是数据链路层的一个参数,最大为1500,如果有报文载荷大于MTU,那么这个报文在传送时就会被分片;本文论述了影响报文分片的相关参数及IP分片原理并通过掌握的原理,应用到网络故障的维护工作中来。

Mass Transfer During Osmotic Dehydration Using Acoustic Cavitation

An experimental study on intensifying osmotic dehydration was carried out ina state of nature and with acoustic cavitation of different cavitating intensity (0.5A, 0.7A and0.9A) respectively, in which the material is apple slice of 5mm thickness. The result showed thatacoustic cavitation remarkably enhanced the osmotic dehydration, and the water loss was acceleratedwith the increase of cavitating intensity. The water diffusivity coefficients ranged from1.8x10^(-10)m^2·s^(-1) at 0.5A to 2.6x10^(-10)m^2·s^(-1) at 0.9A, and solute diffusivitycoefficients ranged from 3.5x10^(-11) m^2·s^(-1) at 0.5A to 4.6X10^(-11)m^2·s^(-1) at 0.9A. On thebasis of experiments, a mathematical model was established about mass transfer during osmoticdehydration, and the numerical simulation was carried out. The calculated results agree well withexperimental data, and represent the rule of mass transfer during osmotic dehydration intensified byacoustic cavitation.

Numerical study on maximum rebound ratio in blasting wave propagation along radian direction normal to joints

In the process of 2-D compressional wave propagation in a rock mass with multiple parallel joints along the radian direction normal to the joints, the maximum possible wave amplitude corresponding to the points between the two adjacent joints in the joint set is controlled by superposition of the multiple transmitted and the reflected waves, measured by the maximum rebound ratio. Parametric studies on the maximum rebound ratio along the radian direction normal to the joints were performed in universal distinct element code. The results show that the maximum rebound ratio is influenced by three factors, i.e., the normalized normal stiffness of joints, the ratio of joint spacing to wavelength and the joint from which the wave rebounds. The relationship between the maximum rebound ratio and the influence factors is generalized into five charts. Those charts can be used as the prediction model for estimating the maximum rebound ratio.

Influence of Zeotropic Mixtures' Temperature Gliding on the Performance of Heat Transfer in Condenser or Evaporator

Many zeotropic refrigerant mixtures are proposed as alternatives to some chlorofluorocar-bons (CFCs) and hydrochlorofluorocarbons ( HCFCs). An advantage of zeotropic mixtures is the possibility of reduction in entropy generation by matching the temperature glidings of refrigerant and heat-transfer fluid in both condenser and evaporator. Zeotropic mixtures are compared with pure re-frigerants to evaluate their exergetic losses. On the other hand, the special phenomena which result from temperature gliding are proved by experiments. A simple equation is obtained, to evaluate dif-ferent zeotropic mixtures' exergetic losses. The maximum flow rate of heat-transfer fluids is found in order that refrigerants phase change can be completed. Lastly, some examples of zeotropic mix-tures ( R407C, R405A and R414B) are given, and their exergetic losses and maximum flow rate of heat-transfer fluids in condenser are forecasted.

Fast method for spreading sequence estimation of DSSS signal based on maximum likelihood function

To estimate the spreading sequence of the direct sequence spread spectrum (DSSS) signal, a fast algorithm based on maximum likelihood function is proposed, and the theoretical derivation of the algorithm is provided. By simplifying the objective function of maximum likelihood estimation, the algorithm can realize sequence synchronization and sequence estimation via adaptive iteration and sliding window. Since it avoids the correlation matrix computation, the algorithm significantly reduces the storage requirement and the computation complexity. Simulations show that it is a fast convergent algorithm, and can perform well in low signal to noise ratio (SNR).

A method of searching fault propagation paths in mechatronic systems based on MPPS model

In view of the structure and action behavior of mechatronic systems,a method of searching fault propagation paths called maximum-probability path search(MPPS)is proposed,aiming to determine all possible failure propagation paths with their lengths if faults occur.First,the physical structure system,function behavior,and complex network theory are integrated to define a system structural-action network(SSAN).Second,based on the concept of SSAN,two properties of nodes and edges,i.e.,the topological property and reliability property,are combined to define the failure propagation property.Third,the proposed MPPS model provides all fault propagation paths and possible failure rates of nodes on these paths.Finally,numerical experiments have been implemented to show the accuracy and advancement compared with the methods of Function Space Iteration(FSI)and the algorithm of Ant Colony Optimization(ACO).

On-line estimation of concentration parameters in fermentation processes

It has long been thought that bioprocess, with their inherent measurement difficulties and complex dynamics, posed almost insurmountable problems to engineers. A novel software sensor is proposed to make more effective use of those meas- urements that are already available, which enable improvement in fermentation process control. The proposed method is based on mixtures of Gaussian processes (GP) with expectation maximization (EM) algorithm employed for parameter estimation of mixture of models. The mixture model can alleviate computational complexity of GP and also accord with changes of operating condition in fermentation processes, i.e., it would certainly be able to examine what types of process-knowledge would be most relevant for local models’ specific operating points of the process and then combine them into a global one. Demonstrated by on-line estimate of yeast concentration in fermentation industry as an example, it is shown that soft sensor based state estimation is a powerful technique for both enhancing automatic control performance of biological systems and implementing on-line moni- toring and optimization.

Unknown State Transmission Using GHZ States via Collective Noise Channel

Two protocols for transmitting an unknown single-photon state and an unknown non-maximally entangledEPR state are presented by using the quantum channel of three-phonton GHZ (Greenberger-Horne-Zeilinger) state,which can be realized with unitary success probability when collective noise is taken into account.The protocols canalso be generalized to transmit multi-photon state or to realize quantum communication in collective noise channel.

Profit in Mass Media Industries： A Phenomenology of Contradiction Between Public Interest and Profit Orientation

In this paper, the resaerchers analyze phenomenology of competitiveness in media communication market which is being observed as a theoretical, cultural, communicative, and social process of relationship of mass media industries and profit-oriented economy. The impact of globalization, government regulation, and technology has put attention to the importance of media not only as information and entertainment resources but also as economic units. The objective of economic units is to maximize profit; production costs must be lower than income from sales. Also, media must cover their costs and create returns to be able to develop respectively invest in new sources like employees, technology, marketing, etc.. In the article we will focus on economic problems which are specific for mass media, media industry, and media market. We define factors that significantly influence the reasoning behind profit orientation of institutions in public interest.

HAS Dynamic Buffer-Driven Resource Management to Enhance QoE in Mobile Network

Hypertext transfer protocol(HTTP) adaptive streaming(HAS) plays a key role in mobile video transmission. Considering the multi-segment and multi-rate features of HAS, this paper proposes a buffer-driven resource management(BDRM) method to enhance HAS quality of experience(QoE) in mobile network. Different from the traditional methods only focusing on base station side without considering the buffer, the proposed method takes both station and client sides into account and end user's buffer plays as the drive of whole schedule process. The proposed HAS QoE influencing factors are composed of initial delay, rebuffering and quality level. The BDRM method decomposes the HAS QoE maximization problem into client and base station sides separately to solve it in multicell and multi-user video playing scene in mobile network. In client side, the decision is made based on buffer probe and rate request algorithm by each user separately. It guarantees the less rebuffering events and decides which HAS segment rate to fetch. While, in the base station side, the schedule of wireless resource is made to maximize the quality level of all access clients and decides the final rate pulled from HAS server. The drive of buffer and twice rate request schemes make BDRMtake full advantage of HAS's multi-segment and multi-rate features. As to the simulation results, compared with proportional fair(PF), Max C/I and traditional HAS schedule(THS) methods, the proposed BDRM method decreases rebuffering percent to 1.96% from 11.1% with PF and from 7.01% with THS and increases the mean MOS of all users to 3.94 from 3.42 with PF method and from 2.15 with Max C/I method. It also guarantees a high fairness with 0.98 from the view of objective and subjective assessment metrics.

Elitism-based immune genetic algorithm and its application to optimization of complex multi-modal functions

A novel immune genetic algorithm with the elitist selection and elitist crossover was proposed, which is called the immune genetic algorithm with the elitism （IGAE）. In IGAE, the new methods for computing antibody similarity, expected reproduction probability, and clonal selection probability were given. IGAE has three features. The first is that the similarities of two antibodies in structure and quality are all defined in the form of percentage, which helps to describe the similarity of two antibodies more accurately and to reduce the computational burden effectively. The second is that with the elitist selection and elitist crossover strategy IGAE is able to find the globally optimal solution of a given problem. The third is that the formula of expected reproduction probability of antibody can be adjusted through a parameter r, which helps to balance the population diversity and the convergence speed of IGAE so that IGAE can find the globally optimal solution of a given problem more rapidly. Two different complex multi-modal functions were selected to test the validity of IGAE. The experimental results show that IGAE can find the globally maximum/minimum values of the two functions rapidly. The experimental results also confirm that IGAE is of better performance in convergence speed, solution variation behavior, and computational efficiency compared with the canonical genetic algorithm with the elitism and the immune genetic algorithm with the information entropy and elitism.

Study on quality evaluation model in multi-station assembly processes

Based on features of dimension variation propagation in multi-station assembly processes,a new quality evaluation model of assembly processes is established. Firstly,the error source of multi-station assembly system is analyzed,the relationship of dimension variation propagation in multi-station assembly processes is studied and the state equation for variation propagation is constructed too. Then,the feature parameters which influence variation propagation and accumulation in multi-station assembly processes are found to evaluate quality characteristic of the assembly system. Through the derivation of equation on dimension variation propagation,station coefficient matrices which are combined and conversed to determine the max eigenvalue are educed. The max eigenvalue is multiplied by the weight coefficient to establish the quality evaluation model in multi-station assembly processes. Furthermore,assembly variation indexes are proposed to judge of the assembly technology process. Finally,through the practical example,the application of the model and assembly variation indexes are presented.

Arrangement Strategy of Ground Heat Exchanger with Groundwater

The orientation strategy of side pipe and the heat transfer performance of six ground heat exchangers(GHEs) were optimized by numerical simulation,with soil being treated as a porous medium.An experiment on the heat transfer of four GHEs was carried out in 2010.Results indicate that the velocity field is disturbed by GHEs.The optimal orientation strategy of side pipe is that the upward pipe is located upstream and the downward pipe downstream.The space between GHEs should be appropriately adjusted,depending on the direction and flow velocity.Groups of GHEs should be installed perpendicular to the mainstream in a single row,but if the acreage does not meet the requirements,GHEs should be installed in staggered multiple rows.Fewer GHEs parallel to the mainstream strengthen the heat transfer.Moreover,numerical results agree well with the test data,with the maximum relative error being less than 7.7%.