浅谈液压系统模拟实验设备在液压传动课程中应用

本文通过分析《液压与气压传动》在课堂教学过程中存在的问题,通过在课程中应用液压系统模拟实验设备,对课堂教学模式、教学方法、教学手段进行优化,来提高教学质量,并在实际教学中取得了较好的效果。

《物流系统模拟与仿真实验》的教改初探

《物流系统模拟与仿真实验》是培养物流管理专业学生工程控制设计与应用能力、创新能力的一门必修课。本文重点探讨了在《物流系统模拟与仿真实验》教学建设中进行教学内容、教学方法、教学手段等方面的改革内容。

关于加强会计手工模拟实验的思考

会计手工模拟实验是会计学专业实践性教学的一个重要环节。为了培养会计学专业学生的实际动手能力、会计操作技能和职业判断能力,需要加强会计手工模拟实验,并按照会计专业课程开设的先后顺序逐步进行,具体包括加强基础会计手工模拟实验、中级财务会计手工模拟实验、成本会计手工模拟实验、高级财务会计手工模拟实验、会计综合手工模拟实验等。

一种求解条件非线性最优扰动的快速算法及其在台风目标观测中的初步检验

条件非线性最优扰动(CNOP)是Mu等2003年提出的一个新的理论方法,它是线性奇异向量在非线性情形的推广,克服了线性奇异向量不能代表非线性系统最快发展扰动的缺陷,成为非线性系统可预报性和敏感性等研究新的有效工具。然而,由于以往CNOP的求解需要采用伴随技术,计算量相当巨大,限制了该方法的推广应用。为了克服这一困难,本文基于经验正交分解(EOF),提出了一种求解CNOP的快速算法,利用GRAPES区域业务预报模式实现了 CNOP快速计算,并在台风"麦莎"的目标观测研究中得到初步检验,通过观测系统模拟实验(OSSE)检验了该方法确定敏感性区域(瞄准区)的有效性和可行性。试验结果表明,用快速算法求解的CNOP,其净能量随时间快速地发展,而且发展呈非线性。在台风"麦莎"个例的目标观测试验中,用快速算法得到的预报时间为24 h的CNOP可以有效地识别瞄准区,并通过瞄准区内初值的改善,可明显减少目标区域(检验区)内24 h累计降水预报误差。尤其,累计降水预报的这种改进效果能够延伸到更长时间(如72 h),尽管检验时间是设在第24小时。进一步分析发现,24 h累计降水预报误差的减少是通过利用瞄准区内改善的初值改进初始时刻台风暖心结构、高空相对涡度以及水汽条件等而得以实现的。

基于条件非线性最优扰动的目标观测中瞄准区不同引导性变量的影响试验研究

基于GRAPES区域业务预报模式,采用一种快速算法计算出来的条件非线性最优扰动对实际台风个例麦莎(No.0509)开展了目标观测研究,应用数值模式,进行一系列的敏感性试验,讨论了与目标观测设计相关的一些问题,包括确定瞄准区时使用不同的引导性变量对目标观测效果的影响、及瞄准区范围变化对预报效果的影响。文中分别以提高麦莎在检验区(20.125°—35.3125°N,116.8125°—129.75°E)内的24 h海平面气压预报和24 h累积降水量预报为目的,基于条件非线性最优扰动使用了3种不同的引导性变量寻找敏感区(又称瞄准区),对这些敏感区的分布特点和有效性进行了比较和讨论。试验结果表明,在使用的3种引导性变量中,用不同的引导性变量识别的敏感区是有差别的,总体上说,文中使用的3种引导性变量识别的瞄准区对提高预报都是有效的,特别是第2和第3种的效果更好些,且两者识别的瞄准区常显示出类似的特点。文中进一步针对检验区内24 h累积降水量预报误差问题,将前面确定的瞄准区范围扩大相同的幅度,讨论瞄准区范围变化对改进预报的影响。试验结果表明,增加瞄准格点数,有可能使预报效果得到改善,但是试验结果同时也暗示了单纯靠扩大瞄准区的范围未必一定能减小预报误差,这与不同的引导性变量对瞄准区范围大小的敏感性不同有关。

一种基于历史样本投影的三维变分同化方法

对于中尺度数值天气预报来说,初始条件的准确与否已成为影响预报技巧的主要因素之一。现有的大气观测资料在时空分布上的不均匀,以及存在的观测误差,使得我们必须引进资料同化方法,为中尺度数值模式提供最优的初始场。由于传统的三维变分同化(3DVar)方法缺乏模式约束以及背景误差协方差矩阵(B矩阵)不具有流依赖性,因此本文提出一种基于历史样本投影的3DVar(HSP-3DVar)方法,它不仅具有流依赖的B矩阵,而且比传统的3DVar简单易行。为了评价HSP-3DVar的同化性能,我们基于区域暴雨预报模式AREM(Advanced Regional Eta Model)对其进行了观测系统模拟试验(OSSE),结果表明:HSP-3DVar能够有效融合观测信息,模式初值在各层的均方根误差都显著地降低。

Dynamic Performance of a Semi-Submersible Platform Subject to Wind and Waves

By applying experimental and numerical simulations, the motion performance of a semi-submersible platform with mooring positoning system under combined actions of wind and waves is studied. The numerical simulation is conducted by the method of nonlinear time domain coupled analysis, and the mooring forces are calculated by the piecewise extrapolating method. The scale in the model experiment is 1:100, and the mooring system of the model is designed with the method of equivalent water-depth truncation by comparing the numerical and the experimental results, the platform motion and mooring forces subject to wind and waves are investigated. The results indicate that the numerically simulated mooring forces agree well with the experimental results in static equivalent field, but show some difference in dynamic equivalent field; the numerically simulated platform motions coincide well with the experimental results. The maximum motion of the platform under operating conditions is 20.5 m. It means that the horizontal displacement is 2% less than the water depth, which satisfies the operating requirements.

Study on Diffusion of Hydrocarbons in FAU and MFI Zeolites by Molecular Simulation and Related Experiments

The diffusion of C4-24 alkanes, aromatics and cycloalkanes in FAU and MFI zeolites were studied systemati- cally by molecular simulation. The basic data on diffusion energy barriers and the diffusion characteristics of alkanes, cyclo- alkanes and aromatics in FAU and MFI zeolites were obtained. It was found out that the 12-member-ring openings between the two adjacent super cages limited the diffusion of hydrocarbons in FAU zeolites, and the hydrocarbon molecules diffused more easily in the intersections of MFI zeolite channels than in the straight channels between the intersections. It was more difficult for the molecules to diffuse in the sinusoidal channel of the MFI zeolite than in the straight channel because of the atoms at the comer of sinusoidal channel. The diffusion of three kinds of C6 alkanes was studied by gravity sorption method. The simulation results were well consistent with the experimental results, indicating that the simulation results were con- vincing.

SATVPC:Secure-agent-based trustworthy virtual private cloud model in open computing environments

Private clouds and public clouds are turning mutually into the open integrated cloud computing environment,which can aggregate and utilize WAN and LAN networks computing,storage,information and other hardware and software resources sufficiently,but also bring a series of security,reliability and credibility problems.To solve these problems,a novel secure-agent-based trustworthy virtual private cloud model named SATVPC was proposed for the integrated and open cloud computing environment.Through the introduction of secure-agent technology,SATVPC provides an independent,safe and trustworthy computing virtual private platform for multi-tenant systems.In order to meet the needs of the credibility of SATVPC and mandate the trust relationship between each task execution agent and task executor node suitable for their security policies,a new dynamic composite credibility evaluation mechanism was presented,including the credit index computing algorithm and the credibility differentiation strategy.The experimental system shows that SATVPC and the credibility evaluation mechanism can ensure the security of open computing environments with feasibility.Experimental results and performance analysis also show that the credit indexes computing algorithm can evaluate the credibilities of task execution agents and task executor nodes quantitatively,correctly and operationally.

Cloud Seedability Study with a Dual-Model System

In this research, one-dimensional stratiform a novel dual-model system, cold cloud model （1DSC） coupled to Weather Research and Forecast （WRF） model （WRF-1DSC for short）, was employed to investigate the effects of cloud seeding by silver iodide （AgI） on rain enhancement. Driven by changing environmental conditions extracted from the WRF model, WRF-1DSC could be used to assess the cloud seeding effects quantitatively. The employment of WRF- 1DSC, in place of a one-dimen- sional two-moment cloud seeding model applied to a three-dimensional mesoscale cloud-resolving model, was found to result in massive reduction of computational resources. Numerical experiments with WRF-1DSC were conducted for a real stratiform precipitation event ob- served on 4-5 July 2004, in Northeast China. A good agreement between the observed and modeled cloud system ensured the ability of WRF-1DSC to simulate the observed precipitation process efficiently. Sensitivity tests were performed with different seeding times, locations, and amounts. Experimental results showed that the optimum seeding effect （defined as the percentage of rain enhancement or rain enhancement rate） could be achieved through proper seeding at locations of maximum cloud water content when the updraft was strong. The optimum seeding effect was found to increase by 5.61% when the cloud was seeded at 5.5 km above ground level around 2300 UTC 4 July 2004, with the maximum AgI mixing ratio （As） equaling 15 ng kg-1. On the other hand, for an overseeded cloud, a significant reduction occurred in the accumulated precipitation （-12.42%） as Xs reached 100 ng kg^-1. This study demonstrates the potential of WRF- 1DSC in determining the optimal AgI seeding strategy in practical operations of precipitation enhancement.

New One-Way Line for Electric Transmission System

There are three well known types of wire lines for transmitting electrical energy or information. The first type is ordinary two wires line （below A-Line）. The second type is so-called single-wire line, where ground plays the role instead of second wire. Polyphase systems belong to the third type, three phase system is the most popular among them. The purpose of this article is another attempt to build a one-wired （without ground） system--the transmission of electrical energy. In this paper an original idea of building such a system is justified, the results of simulations and laboratory modeling are presented. It is shown that the proposed method can reduce the cost of electric transmission lines, the losses in them and significantly reduce interferences.

Energy efficiency enhancement of two-way amplifier forward relaying with channel estimation error

In order to save energy consumption of two-way amplifier forward(AF) relaying with channel estimation error, an energy efficiency enhancement scheme is proposed in this work. Firstly, through the analysis of two-way AF relaying mode with channel estimation error, the resultant instantaneous SNRs at end nodes is obtained. Then, by using a high SNR approximation, outage possibility is acquired and its simple closed-form expression is represented. Specially, for using the energy resource more efficiently, a low-complexity power allocation and transmission mode selection policy is proposed to enhance the energy efficiency of two-way AF relay system. Finally, relay priority region is identified in which cooperative diversity energy gain can be achieved. The computer simulations are presented to verify our analytical results, indicating that the proposed policy outperforms direct transmission by an energy gain of 3 dB at the relative channel estimation error less than 0.001. The results also show that the two-way AF relaying transmission loses the two-way AF relaying transmission loses its superiority to direct transmission in terms of energy efficiency when channel estimation error reaches 0.03.

Reservoir Inflow Estimation Using Remote Sensing, GIS and Geosimulation

RS （remote sensing） applications to hydrological problem solving have successfully transitioned from being experimental to operational in the last couple of years, and information gathered through these technologies can facilitate water resource procedures. Patterns from RS imagery can be translated into a deterministic distribution of input data over a wide area on a pixel-by-pixel basis. This paper presents the implementation of different methodologies of integrating satellite-derived information from RS, and GIS （geographic information system） visualization and simulation capabilities in improving hydrologic estimation processes.

Modeling active worm propagation on the P2P network

This paper analyzes the characteristics of the Peer-to-Peer （P2P） active worm and its attacking mechanism, and then proposes a mathematical model of propagation of the P2P active worm applying Epidemiology. Based on the analysis on the protocols of realistic P2P systems, a software which can be used to simulate the P2P network environment and the propagation of P2P active worm is imple- mented in this paper. A large number of simulation experiments are performed using the developed simulation software. The results from these simulation experiments validate the proposed model, which means that the model can be used to analyze the spreading behaviors of the P2P active worm and predict its trend.

Simulation of Reductive Dechlorination Processes in a Lab-Scale Anaerobic Biobarrier with Enriched TCP Dechlorinating Consortium

In order to design and predict the dechlorination processes for remediating the halogenated aromatic com- pounds in the biobarrier system applied in situ, an anaerobic continuous-flow column was set up with the introduction of an enriched 2, 4, 6-trichlorophenol （TCP） reductive dechlorinating consortium. The fates of TCP and its metabo- lites were simulated according to the first-order sequential dechlorination kinetic model. The enriched TCP anaerobic dechlorinating consortium dechlorinated 100 p.mol/L TCP to 4-chlorophenol （4-CP） via 2,4-dichlorophenol （DCP） in 10 d. The consortium was predominated with the phylum of Firmicutes and Bacteroidetes, based on the PCR- denaturing gradient gel electrophoresis （DGGE） analysis. After the consortium was applied to the colunm, the ex- perimental data in the steady state were fitted by the least square method, and the first-order dechlorination kinetic constants from TCP to 2,4-DCP, from 2,4-DCP to 4-CP and from 4-CP to phenol, were 1.58 d-1, 2.23 d 1 and 0.206 d-1, respectively. According to the fitting results, the required biobarrier width for the complete remediation of TCP, 2,4- DCP and 4-CP were 126 cm, 130 cm and 689 cm, respectively. The dechlorination/degradation of 4-CP must be in- creased when the technology is applied to the real site.

Social Network Impacts on Stock Market： An Experimental View

In this paper, the authors present a method to construct a simulation experiment system which used to prove how social network affects the stock market. The authors construct a model considered of three main stock market effect factors： cognitive factors, social factors and economic factors. In the simulation system, free-scale social network is generated for information relations among investors in stock market. The authors simulate the organization information propaganda processes and generate stock related news. The generated news contains economy factors and sudden events. Stockholders cooperate with the related stockholders in their social network, and make stock exchange decision based on this news and their cognitive understanding of this news. Simulation results shows that the social network news propaganda effect stock prices. If social network in stock market have circles, the news affection will be amplified.

The Choice of Model of External Load in Problem of Synthesis of Adequate Mathematical Description

The problem of mathematical simulation of motion of dynamic systems characteristics and their coincidence with real experimental data which correspond to these characteristics is investigated in this paper. Mathematical description of process will be named as adequate mathematical description if the results of mathematical simulation by the help of this description coincide with experiment with inaccuracy of initial data. The synthesis of such description is very important at mathematical modeling and forecast of motion of real physical phenomena. The specified problem is still poorly investigated and hardly adapted to formalization. The requirements to the adequate mathematical description of dynamic system are considered for the case when mathematical description of dynamic systems is represented by linear system of the ordinary differential equations. In this paper the mathematical model of process is given a priori with inexact parameters and then the models of external loads are being determined for which the results of simulation coincide with experiment. The methods of obtaining of the steady models of external loads are suggested. The example of the adequate description construction of the main mechanical line dynamics of rolling mill is given.