Stochastic formulation of particle kinetics in wall-bounded two-phase flows

This paper presents a generalized framework of stochastic modeling for particle kinetics in wall-bounded flow. We modified a reflected Brownian motion process and straightforwardly obtained a Kramers equation for particle probability density function (PDF). After the wall effects were accounted for as a drift from zero in the mean displacement and suppression in the diffusivity of a particle, an analytical solution was worked out for PDF. Three distinguishable mechanisms were identified to affect the profile of particle probability distribution: external forces, turbophoresis effect, and wall-drift effect. The proposed formulation covers the Huang et al. (2009) model of a wall that produces electrostatic repulsion force and van der Waals force, as well as Monte-Carlo solutions for the Peter and Barenbrug (2002) model under a variety of relaxation times. Moreover, it successfully reproduces the two patterns of particle concentration profiles observed in experiments of sediment-laden open-channel flows. The strength of the wall-drift effect was found to be connected with the interaction frequency between particle and wall. Further exploration of the relationship among flow turbulence, particle inertia, and particle concentration is worthwhile.     

基于网格的VOD服务整合方案的研究及实现

为了满足人们对多媒体资源的需求,利用网格技术的技术优势,较好地解决传统的单点VOD系统很容易形成服务器的处理器性能、存储空间等方面的瓶颈,阐述了利用网格技术实现多个VOD服务的整合方案,同时对网格系统传统的Portal登录方式进行了改进,为基于网格的视频点播系统的最终用户更方便地登录系统,提供了一个可行的解决途径。该系统已部署到北京邮电大学高性能集群上,为广大师生视频点播服务。     

NBCORS服务网站的建设

NBCORS服务网站是宁波市连续运行卫星定位服务系统建设的窗口和重要组成部分。网站系统由数据库部分和网站部分构成,网站设置了用户注册、中心介绍、动态信息、数据下栽以及用户论坛几个板块,解决了用户使用中遏到的各种问题,为用户提供了交流和学习的技术平台,促进了NBCORS的推广应用。     

A study on integrated design conjugation profiles application analysis of scroll profiles for automobile air conditioning

The research on scroll profiles theory at present mainly is aiming at the single profile and its amelioration or parameter optimization,not aiming at the natural characteristic of the profiles equation of scroll profiles itself.Thus,the intrinsic differential equation bearing on arc-length and tangent direction angle was studied.Using the inherent differential equation and general functional theory,the conversion ideas between the expression of intrinsic differential equation and the expression in Cartesian...     

食品安全与异物检测技术开始流行

异物造成的食品安全问题 在食品加工过程中，经常会遇到异物不经意混入食品中的情况，如金属、玻璃、塑料、昆虫、毛发、木屑、沙石、毛发等。     

相控线阵声场的实验研究

用实验的方法研究了探头的几何尺寸,探头总成中单个换能器的间距,换能器个数,以及探头发射时的激励延迟时间对相控声场的偏转角、声束宽度的影响情况,然后进行了总结、分析。这些实验的分析总结为相控探头的整体结构设计,工作参数的选择提供了实验基础。     

适合于矿井提升的Vacon变频器

本文详细介绍了Vacon变频器在矿井中的应用，该应用方案中Vacon变频器作为特殊的低频电源。Vacon变频器具有可编程功能，编程工具Vacon NC1131-3 Engineerign是一个符合IEC61131-3标准的图形化的编程工具，它可以用来设计Vacon NX特殊的控制逻辑的参数。它包含了基本功能模块和高级功能模块，如各种滤波器，PI控制器和积分器。NC1131-3可以创建参数，故障信息和其他与应用相前的特性。本系统具有较大的实用和推广价值。     

Tensile performance and crack propagation of coated woven fabrics under multiaxial loads

The tensile performance of coated woven fabrics under multiaxial loads is examined in the present study. Two groups of experiments were conducted to investigate the influences of the configuration of the fabric specimen and the loading speed on the multiaxial tensile properties of the fabrics. The configuration of the specimen for the multiaxial tensile tests is identified as gear‐shape with large arm widths. A loading speed of lower than 20 mm/min is suggested to obtain the tensile properties of the coated woven fabrics under multiaxial loads. The tensile performances of coated woven fabrics under uni‐, bi‐, and multiaxial loads were compared. We found that the tensile performances under bi‐ and multiaxial loads are much better than those under uniaxial loads. Therefore, for the application of the coated woven fabrics in lightweight structures, biaxial or multiaxial loading conditions will be necessary. Experiments on the specimens with an initial crack in the center under multiaxial loads show that, by comparison with other loading directions, the tensile properties in warp direction of the coated woven fabrics play an important role in the failure performance and crack propagation under multiaxial loads. To eliminate the dependence on the mechanical properties in warp direction, the balance of the two principle directions of coated woven fabrics should be improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Simulation of dam breach development for emergency treatment of the Tangjiashan Quake Lake in China

The Tangjiashan Quake Lake is the largest quake lake triggered by the 5.12 Wenchuan Earthquake that happened on May 12, 2008 in China, posing high risk of catastrophic flash flood hazards to downstream human life and properties. A physics-based numerical simulation approach is proposed for real-time prediction of dam breach development of the Tangjiashan Quake Lake in the case of emergency treatment. Bed erosion and lateral development of the dam breach are represented through accounting for the underlying physics including selective sediment transport and gravitational collapse. Conceptualized breach erosion model that involves few parameters enables quick calibration based on the monitored hydrological data in emergency analysis where fully geotechnical information about the barrier dam is not available. The process of dam breach development is found to be nonlinear in cascades due to the combined effects of headcutting and bank collapse. The agreement between the simulation results and the observed data shows the applicability of the present approach for emergency analysis of quake lakes. Limitations will arise in the situation where the soil composition of barrier dam is significantly inhomogeneous. Incorporation of circular arc failure for cohesive soil and lateral seepage in bank slope will also enhance its applicability to complex situations.

     

Implementation of AUV local planning in strong sea flow field based on Q-learning

This article investigated the implementation of AUV local planning under the strong sea flow field by integrating Q learning with fuzzy logic method.The dynamics of AUV under the sea flow was analyzed in detail,and thus fuzzy logic behaviors were defined,including a fuzzy behavior which was defined to resist the sea flow by giving an extra angle towards sea flow.This behavior was complemented by two other behaviors,the moving-to-goal behavior and collision avoiding behavior.The recommendations of these three behaviors were integrated through adjustable weighting factors to generate the final motion command for the AUV.And Q-learning was used to adjust the peak point of fuzzy membership function to increase adaptability.Simulation results showed that it improves the adaptability of AUV under different sea flow greatly.