一种接地网雷电流冲击数值模型模拟的计算方法

通过傅里叶级数对双指数函数的雷电流进行分解,得到各个频率分量.在此频域特性的基础上提出一种计算接地参数的等效模型,利用电路的节点电压法得出接地网雷电冲击数值模型模拟的计算方法.根据该方法运用MATLAB进行编程,将运行的结果与权威的接地分析软件CDEGS的结果相比较,证明了提出的计算方法正确、可行.     

可变网格下江河截流数学模型研究

在江河截流过程中,随着戗堤的移动,龙口处河床及河岸边界条件不断变化,给截流设计中的水力计算带来了很大困难.本文将可变网格的计算方法应用到江河截流数值模拟中,克服了传统采用固定网格下的数学模型在计算时,难以随截流戗堤的移动动态调整计算边界的困难,使得在计算过程中,计算网格随龙口戗堤的移动而移动,为研究龙口附近的水力参数提供了一种新的计算途径.以三峡工程大江截流为模型计算实例,对截流过程中水力参数变化进行了模拟,并与物理模型结果及天然实测资料进行了对比,结果吻合较好,表明所建模型能较好的模拟不同龙口宽度时水力参数的变化规律,可为截流施工设计提供必要的科学依据.     

A model for human skin impedance during surface functional neuromuscular stimulation.

A new mathematical model for the bulk electrical impedance of human skin is presented. In particular this model describes the impedance of skin during surface functional neuromuscular stimulation (FNS) with square stimulation pulses. Experimental data are presented that illustrate the nonlinear dynamic properties of human skin during current and voltage controlled stimulation. Model predictions are compared to experimental data, measured under both constant voltage and constant current transcutaneous stimulation. It is found that this model captures a variety of nonlinear time-varying effects observed in the skin impedance when stimulating with either protocol. This model may be used as part of large neuromusculoskeletal models or in the more accurate modeling of transcutaneous FNS, which is currently the most common clinical implementation of FNS.     

基于元胞自动机的电网隐性故障传播模型关键线路识别方法

有效辨识电网中关键线路对优化电网结构、减少电网连锁故障具有重大意义。为此,考虑电网线路隐性故障,建立了基于元胞自动机理论的电网隐性故障模型,并在此基础上提出了一种综合考虑线路两端负荷量、线路故障频率和线路邻居数量的电网关键线路辨识方法。以IEEE39节点系统为算例,识别了该节点系统的关键线路,并通过与别的方法对比验证了该模型的合理性及其电网关键线路辨识方法的有效性。该模型和方法能为电网连锁故障模型和脆弱性评估提供新的参考。     

A three-dimensional finite element model of the transibial residual limb and prosthetic socket to predict skin temperatures.

Amputees who wear prosthetic limbs often experience discomfort from blisters and sores due to mechanical insult; these skin conditions are exacerbated by elevated skin temperatures and excessive perspiration within the prosthetic socket. The goal of this study was to create a tool for developing new prostheses that accommodate varying thermal loads arising from everyday activities. A three-dimensional thermal model of a transtibial residual limb and prosthesis was constructed using the finite element (FE) method. Transverse computerized tomography (CT) scans were used to specify the geometry of the residual limb and socket. Thermal properties from the literature were assigned to both biological tissue and prosthetic socket elements. The purpose of this work was to create a model that would aid in testing the effect of new prosthesis designs on skin temperature. To validate its output, the model was used to predict the skin temperature distribution in a common prosthetic socket system (silicone liner, wool sock, and carbon fiber socket) at rest with no mechanical loading. Skin temperatures were generally elevated near muscle and decreased anteriorly and at the distal end. Experimental temperature measurements taken at the skin-prosthesis interface of five human subjects were used to validate the model. Data extracted from the thermal model at anterior, posterior, lateral, and medial locations were typically within one standard deviation of experimental results; the mean temperatures were within 0.3 degree C for each section and were within 0.1 degree C overall.     

Analysis of cavitation dynamics during pulsed laser tissue ablationby optical on-line monitoring

Flashlamp pumped mid-IR laser systems emitting in the 2-3-μm wavelength range are widely used for various medical applications, especially for tissue ablation. Explosive evaporation is inevitably associated with this process due to the short pulse durations of these laser systems and the high absorption of tissue and water in this spectral regime. Tissue displacement and dissection occur in liquid environment as a consequence of the induced cavitation. Depending on the application these processes might enhance the tissue ablation but can also cause adverse tissue effects. The ablation dynamics were investigated by evaluating the change in reflected probe-light intensity re-emitted from the application fiber tip. The ablated cavity and the signal was correlated to fast-flash photographs of the event. Based on this reflection signal a water/tissue discrimination system is introduced which can widely support medical laser applications. In laser sclerostomy ab externo, for example, this approach can be used as a feedback system to automatically control the ablation process. With such a system, adverse effects to adjacent tissue in the anterior chamber of the eye can be minimized     

基于XGBoost算法的智能电网信息攻击识别模型

智能电网在遭受信息攻击后,如何根据量测数据的变化规律,准确识别电力系统遭受的攻击类型是提高电网安全防御的有效手段,本文提出一种基于Extreme Gradient Boosting (XGBoost)算法的智能电网信息攻击识别模型。首先,基于kmeans-smote设计电力数据过采样方法,对量测数据进行平衡处理,解决攻击事件样本的不平衡问题。然后,提出最大相关-最小冗余(MRMR)特征选择方法,提取信息攻击事件最优表征特征子集,降低数据维度并提升信息攻击的识别效率。最后,设计XGBoost分类器,对3种攻击状态和正常状态进行分类识别,采用准确率、召回率等指标评估模型的识别性能。经仿真实验验证,本文提出的信息攻击识别模型显著提升了智能电网信息攻击的识别精度,且具有较好的泛化性。     

基于格子玻尔兹曼方法的流域汇流数值模型

本文利用Lattice Boltzmann Method方法分析了坡面水流和河道水流运动方程圣维南方程的特点,提出了流域汇流过程的LBM数值模型,此模型在汇流过程中将地貌因素与水动力扩散相结合以描述坡面水流运动,很好解决了坡面水流的流量分配问题。利用此模型生成的单位线对抚河南城流域14场洪水进行了汇流计算,结果表明所提出的汇流模型用于流域汇流计算具有较好的精度。本研究对于分析坡面水流运动、汇流机制、土壤侵蚀、泥沙输移等诸多领域,具有重要的理论意义。     

Integration of distributed energy resources into low voltage grid: A market-based multiperiod optimization model

This paper develops a multiperiod optimization model for an interconnected micro grid with hierarchical control that participates in wholesale energy market to maximize its benefit (i.e. revenues-costs). In addition to the operational constraints of distributed energy resources (DER) including both inter-temporal and non-inter-temporal types, the adequacy and steady-state security constraints of micro grid and its power losses are incorporated in the optimization model. In the presented model, DER are integrated into low voltage grid considering both technical and economical aspects. This integration as a micro grid can participate in wholesale energy market as an entity with dual role including producer and consumer based on the direction of exchanged power. The developed model is evaluated by testing on a micro grid considering different cases and the results are analyzed.     

A conceptual model of power supply for the integrated grid of high-speed railway transport in Russia

The strategy of railway-transport development in Russia until 2030 and beyond involves the application of new technologies ensuring the competitiveness of Russian railways, which act as one of the key growth factors of the economy and its system-forming sector in the transportation industry of Russia. The article discusses the main factors and breakthrough technologies on the basis of which an integrated grid of high-speed railway connection is created. Paramount importance is given to increasing the speed of passenger and freight trains, combining high-speed railway lines into a single grid to provide an agglomeration effect, mobility, energy efficiency, and environmental safety. One of the priorities is the factor of reliable and safe power supply of competitive railway connections, for which a conceptual model of railway power supply is developed.     

A numerical analysis of forced vibrations of a poroelastic model of a gas turbine blade

Matters relating to application of the theory of saturated porous media for analyzing the dynamic characteristics of structural elements of power equipment are considered. Calculations of the resonance frequencies and vibration modes of a gas turbine blade having a transpiration cooling system made in the form of a set of rectilinear pores are presented.     

基于粗糙径向基神经网络的电网故障诊断新模型

在一种属性约简方法的基础上,利用粗糙集和径向基网络的优势,将二者充分融合,构建了一种电网故障诊断新模型,并对其进行了改造.通过对电网故障诊断算例的仿真实验比较表明,该模型减少了识别的主观因素,简化了网络结构,并且识别效果明显,分类能力强,具有很强的容错性和解释性,有很广阔的应用前景.     

基于粗糙径向基神经网络的电网故障诊断新模型

在一种属性约简方法的基础上,利用粗糙集和径向基网络的优势,将二者充分融合,构建了一种电网故障诊断新模型,并对其进行了改造。通过对电网故障诊断算例的仿真实验比较表明,该模型减少了识别的主观因素,简化了网络结构,并且识别效果明显,分类能力强,具有很强的容错性和解释性,有很广阔的应用前景。     

中温反应过程中石灰石颗粒化学反应的数值研究

在晶粒模型的基础上建立了用于描述中温烟气(450∽1050℃)石灰石脱硫过程的数学模型。通过该模型的程序计算可以更好地了解中温区域内石灰石脱硫反应的进程和反应机理,准确地模拟石灰石的热解过程,以及温度和粒径对热解率的影响程度,从而为中温烟气脱硫技术在我国环保应用提供了理论基础。     

基于变化量模式的继电保护一体化整定计算全网精细模型分层管理方法

为适应特高压交直流混联电网所带来的电网运行方式转变,满足国家电网一体化整定计算的需求,有必要针对统一的互联电网建立起全网精细模型,并能基于全网精细模型进行分层管理、维护和应用。提出了一种基于变化量模式的多级电网精细模型分层管理方法。该方法充分考虑了各级电网模型交互过程中不同阶段的特点,采用不同的方法来保证电网模型的准确性,提高电网模型的生成和维护效率。通过在继电保护一体化整定计算平台中开发应用所述方法来管理国、分、省三级调度的继电保护整定计算数据模型,验证了该方法的正确性及实用性。     

Pressure wave propagation in arteries. A model with radialdilatation for simulating the behavior of a real artery

The authors solve the equation of pressure wave propagation in an artery with radial dilatation to give an analytic solution of wave propagation in an elastic vessel for more generalized conditions. This will serve as a complementary solution to work that is based on the assumption that the radial dilatation of the arterial wall is small. The authors' solution is important for physiological studies because it simulates the behavior of a real artery. To confirm the authors' analytic solution, experiments were performed in tubes with different elastic constants