反拱法碳纤维加固RC梁的数值模拟分析

采用动力设备将钢筋混凝土梁向上反拱一定的弧度,然后在梁的下部外贴碳纤维布（CFRP）,待碳纤维布养护完全后,卸载,此时后加的碳纤维布与原钢筋混凝土梁同时进入工作状态。作者采用分析软件ANSYS模拟此过程,通过与直接用碳纤维布加固RC梁进行比较,得出反拱法加固RC梁能有效提高其承载能力,对类似工程具有一定的借鉴意义。     

安县晓坝镇震后新建场址主要岩土工程问题及对策

安县晓坝镇处于＂5.12＂汶川大地震极重灾区,受灾严重,不具备重建条件,需选址重建。在野外详细调查的基础上,通过现场勘查和室内试验,深入研究了晓坝镇灾后新建场址的主要岩土工程问题。研究表明,新建场址主要土层为粉质粘土和淤泥质土,属高压缩性软弱土;地下水埋深浅,对基础施工和地基土承载力影响大;建筑场地类别Ⅱ类,属抗震不利地段。提出了深层水泥土搅拌法和换填地基两种软基处理方案,以及加强地基基础抗震设计等措施。     

New CFD Validation Method with Application to Verify Computations of Near Wall Flows

For high Re number flows, a new computational fluid dynamics (CFD) validation method, namely, wall-surface compatibility criteria method and also called Gaos criteria, is proposed to verify near wall flows. As examples, Gaos criteria method and other two CFD verification methods (analytic solutions method and grid convergence analysis) are used to verify FLUENTs near wall flows solutions for two-dimensional incompressible laminar stagnation-point flows. The exact solution of the Navier-Stokes equations for laminar stagnation-point flows satisfy accurately all Gaos criteria, numerical simulations of laminar stagnation-point flows show that when physical parameters (the pressure coefficient and the Stanton number at wall surface) achieve convergence with more and more fine-screen grid, a part of Gaos criteria are not satisfied.     

烟气冷凝热能回收利用装置烟气流动方式优化研究

烟气冷凝热能回收利用装置中烟气的分布与流动对换热起着重要作用,为优化烟气冷凝热能回收利用装置,保证烟气能够在装置中分布均匀、充分换热,分别设计两种烟气流动方式,采用CFD软件Fluent模拟了烟气冷凝热能回收利用装置中的流场及温度场,并将其分别应用于实际工程进行现场实测.结果表明,采用渐变断面设计的烟气流动方式,烟气在换热面上分布更均匀,更有利于强化换热,阻力更小,节能率比采用等高断面最大可提高3.25%,可有效降低和消除噪音.     

Sintering technology for micro heat pipe with sintered wick

In order to study reasonable sintering technological parameters and appropriate copper powder size range of micro heat pipe (MHP) with the sintered wick, the forming principle of copper powders in wicks and MHP’s heat transfer capabilities were first analyzed, then copper powders with different cell sizes and dispersions were sintered in RXL-12-11 resistance furnace under the protection of the hydrogen at different sintering temperatures for different durations of sintering time, and finally the sintered wicks’ scanning electron microscope (SEM) images and their heat transfer capabilities were analyzed. The results indicate that the wick sintered with copper powders of larger cell size or smaller size range has better sintering properties and larger heat transfer capabilities; and that the increase of either sintering temperatures or sintering time also helps to improve the wick’s sintering properties and heat transfer capabilities, and the former affects more obviously than the latter. Considering both its manufacturing cost and performance requirements, it is recommended that copper powders with the size range of 140–170 μm are sintered at 900–950°C for 30–60 min in practical manufacturing. In addition, two approaches to improve wick’s porosity are also proposed through theoretical analysis, which suggests that the larger the wick’s porosity, the better the heat transfer capabilities of the MHP.     

Prediction-based energy-efficient target tracking protocol in wireless sensor networks

A prediction based energy-efficient target tracking protocol in wireless sensor networks (PET) was proposed for tracking a mobile target in terms of sensing and communication energy consumption. In order to maximize the lifetime of a wireless sensor network (WSN), the volume of messages and the time for neighbor discovery operations were minimized. The target was followed in a special region known as a face obtained by planarization technique in face-aware routing. An election process was conducted to choose a minimal number of appropriate sensors that are the nearest to the target and a wakeup strategy was proposed to wakeup the appropriate sensors in advance to track the target. In addition, a tracking algorithm to track a target step by step was introduced. Performance analysis and simulation results show that the proposed protocol efficiently tracks a target in WSNs and outperforms some existing protocols of target tracking with energy saving under certain ideal situations.     

Status of research on biogenic coalbed gas generation mechanisms

Biogenic coalbed gas,how it is generated and the geochemical characteristics of the gas are gaining global attention.The ways coalbed gas is generated,the status of research on the generation mechanism and the methods of differentiating between biogenic gasses are discussed.The generation of biogenic coalbed methane is consistent with anaerobic fermentation theory.Commercial biogenic coalbed gas reservoirs are mainly generated by the process of CO2 reduction.The substrates used by the microbes living in the coal include organic compounds,CO2,H2 and acetate.The production ratio and quantity of biogenic coalbed methane depend on the exposed surface area,the solubility and permeability of the coal and the microbial concentration in the coal seam.It is generally believed that biogenic coalbed gas has a value for σ13C1＜-5.5%,C1/C1+＞0.95.The H isotope ratio is controlled by both the environment and the generation mechanism:typically σD1＜-20%.Biogenic methane formed by CO2 reduction has more σD1 than that formed by acetate fermentation.     

Static solution on four-region spherial cavity expansion model in a pressure sensitive medium

Spherical cavity expansion model is often used to study the mechanic characteristics of pressure sensitive mediums. The most important one we do in the paper is that we construct a four-region model with σθ≠0 in damage region,which is different from what Satapathy did before and is more reasonable. By adopting this model,different constitutive equations were constructed by different method-elastic mechanics in elastic region,damage mechanics and fracture mechanics in damage region,and macro-micro mechanics theory in plastic region. Then using Durban's self-similarity assumption,the control differential equations with boundary conditions were established,and the static numerical solution of stress field and displacement field in the three different regions of elastic,damage and plastic area were discussed respectively. Results showed that this four-region model can describe precisely the mechanic characteristics of pressure sensitive mediums under initial pressure.     

Asymptotical mean square stability of cellular neural networks with random delay

In this paper,the asymptotical mean-square stability analysis problem is considered for a class of cellular neural networks (CNNs) with random delay. Compared with the previous work,the delay is modeled by a continuous-time homogeneous Markov process with a finite number of states. The main purpose of this paper is to establish easily verifiable conditions under which the random delayed cellular neural network is asymptotic mean-square stability. By using some stochastic analysis techniques and Lyapunov-Krasovskii functional,some conditions are derived to ensure that the cellular neural networks with random delay is asymptotical mean-square stability. A numerical example is exploited to show the vadlidness of the established results.     

基于TCN的地铁列车控制方案的研究

本文针对地铁车厢内控制设备分散的问题,设计了基于TCNRTP的地铁列车控制网络系统。采用NS2网络模拟软件构建的虚拟网络环境,编写消息数据传输层协议,通过测试列控网络的通信效率,得出了影响通信效率的因素;通过配置列控通信设备的基本功能和设定装置运行参数达到配置网络化通信的目的。