Introduction to Mesh Based Generated Lumped Parameter Models for Electromagnetic Problems using Triangular Elements

This paper is an introduction to mesh based generated reluctance network modeling using triangular elements.Many contributions on mesh based generated reluctance networks using rectangular shaped elements have been published,but very few on those generated from a mesh using triangular elements.The use of triangular elements is aimed at extending the application of the approach to any shape of modeled devices.Basic concepts of the approach are presented in the case of electromagnetic devices.The procedure for coding the approach in the case of a flat linear permanent magnet machine is presented.Codes developed under MATLAB environment are also included.

Review on lumped parameter method for modeling the blood flow in systemic arteries

The cardiovascular system is characterized by complex interactions between various control mechanisms and physiological processes. Different approaches are used to provide better diagnostics and physiological understanding, cardiac prosthesis and medical planning. The mathematical description and modelling of the human cardiovascular system plays nowadays an important role in the comprehension of the genesis and development of cardiovascular disorders by providing computer based simulation of dynamic processes in this system. This paper aims to give an overview on lumped parameter models that have been developed by many researchers all over the world, to simulate the blood flow in systemic arteries. Surveying various references we make a review of different approaches to arterial tree modelling and discuss on the applications of such models.

A modified lumped parameter model of distribution transformer winding

The modelling of the distribution transformer winding is the starting point and serves as important basis for the transformer characteristics analysis and the lightning pulse response prediction.A distributed parameters model can depict the winding characteristics accurately,but it requires complex calculations.Lumped parameter model requires less calculations,but its applicable frequency range is not wide.This paper studies the amplitude-frequency characteristics of the lightning wave,compares the transformer modelling methods and finally proposes a modified lumped parameter model,based on the above comparison.The proposed model minimizes the errors provoked by the lumped parameter approximation,and the hyperbolic functions of the distributed parameter model.By this modification it becomes possible to accurately describe the winding characteristics and rapidly obtain the node voltage response.The proposed model can provide theoretical and experimental support to lightning protection of the distribution transformer.

Introduction to Mesh Based Generated Lumped Parameter Models for Electromagnetic Problems

This paper is an introduction to mesh based generated reluctance network modeling.An overview of scientific works which led to the development of this approach is first presented.Basic concepts of the approach are then presented in the case of electromagnetic devices.A step-by-step procedure for coding the approach in the case of a flat linear permanent magnet machine is presented.Codes developed under MATLAB and Scilab environments are also included.

New lumped-mass-stick model based on modal characteristics of structures: development and application to a nuclear containment building

In this study, a new lumped-mass-stick model （LMSM） is developed based on the modal characteristics of a structure such as eigenvalues and eigenvectors. The simplified model, named the ＂frequency adaptive lumped-massstick model,＂ hasonly a small number of stick elements and nodes to provide the same natural frequencies of the structure and is applied to a nuclear containment building. To investigate the numerical performance of the LMSM, a time history analysis is carried out on both the LMSM and the finite element model （FEM） for a nuclear containment building. A comparison of the results shows that the dynamic responses of the LMSM in terms of displacement and acceleration are almost identical to those of the FEM. In addition, the results in terms of floor response spectra at certain elevations are also in good agreement.

Analysis of Do D inkjet printhead performance for printable electronics fabrication using dynamic lumped element modeling and swarm intelligence based optimal prediction

The major challenge in printable electronics fabrication is to effectively and accurately control a drop-on-demand(Do D) inkjet printhead for high printing quality. In this work, an optimal prediction model, constructed with the lumped element modeling(LEM) and the artificial bee colony(ABC) algorithm, was proposed to efficiently predict the combination of waveform parameters for obtaining the desired droplet properties. For acquiring higher simulation accuracy, a modified dynamic lumped element model(DLEM) was proposed with time-varying equivalent circuits, which can characterize the nonlinear behaviors of piezoelectric printhead. The proposed method was then applied to investigate the influences of various waveform parameters on droplet volume and velocity of nano-silver ink, and to predict the printing quality using nano-silver ink. Experimental results show that, compared with two-dimension manual search, the proposed optimal prediction model perform efficiently and accurately in searching the appropriate combination of waveform parameters for printable electronics fabrication.

Study on Lumped Kinetic Model for FDFCC I. Establishment of Model

According to the process features and the reaction mechanism of FDFCC technology, its two reaction subsystems, one for heavy oil riser reactor, the other for gasoline riser reactor, were respec-tively studied. Correspondingly, a 12-lump kinetic model for heavy oil FCC and a 9-lump kinetic model for gasoline catalytic upgrading were presented. Based on this work, mathematical correlation of the lumps in the feeds and products involved in the reaction subsystems and those of the overall reaction system were analyzed in detail. Then, a combined kinetic model for FDFCC, which was based on the data recovered from a commercial unit, was put forward. The reaction performance embodied by the kinetic constants for the combined model of FDFCC was in accordance with catalytic cracking reaction mechanism. The model-calculated values were close to the data obtained in commercial scale. The model was easy to be applied in practice and could also provide some theoretical groundwork for further re-search on kinetic model for FDFCC.

An improved lumped parameter model predicting attenuation of earmuff with air leakage

Since air leakage is inevitable when earmuffs are worn improperly or together with safety glasses in factory or military,it is required to be considered to accurately predict earmuff attenuation.Besides unwanted air leakage,under controlled air leakage is introduced to earmuff to achieve adjustable attenuations in different signal-to-noise ratios(SNRs)and balance between attenuation and speech intelligibility.This work is to develop an improved lumped parameter model(LPM)to predict earmuff attenuation with consideration of air leakage.Air leakage paths are introduced into conventional LPM without air leakage,and air leakage path impedance is analytically described by Maa’s microperforated tube impedance.Earmuff passive attenuation behavior can be analytically described and analyzed with the improved LPM.Finally,the validity of improved LPM is verified experimentally.The results indicate that the improved LPM can predict earmuff attenuation with air leakage,and air leakage deteriorates earmuff attenuation and turns resonance frequency higher.

Lumped Parameter Mass Flow Rate and Pressure Control Characteristics Model for High-Speed Pneumatic PWM on/off Valve

Aiming at solving the problem of strong coupling characteristic of the key parameters of high-speed pneumatic pulse width modulation( PWM) on / off valve, a general lumped parameter mathematical model based on the valves time periods was well developed. With this model,the mass flow rate and dynamic pressure characteristics of constant volumes controlled by high-speed pneumatic PWM on /off valves was well described. A variable flow rate coefficient model was proposed to substitute for the constant one used in most of the prior works to investigate PWM on /off valves' dynamical pressure response, and a formula for disclosing the inherent relationship among the PWM command signal,static mass flow rate,and sonic conductance of the valve was newly derived.Finally,an extensive set of analytical experimental comparisons were implemented to verify the validity of the proposed mathematica model. With the proposed model, PWM on /off valves' characteristics,such as mass flow rate,step pressure response of the valve control system,mean pressure and ripple amplitude,not only in the linear range,but also in the nonlinear range can be wel predicted; Good agreement between measured and calculated results was obtained,which proved that the model is helpful for designing a control strategy in a closed loop control system.

A Lumped Kinetic Model for Low-and Medium-Temperature Coal Tar Hydrocracking Process

A five-lump kinetic model for hydrocracking of coal tar is proposed to simulate the product distribution on the basis of the experimental data of coal tar in a laboratory fixed-bed downflow reactor with a Ni/Mo catalyst at a temperature of 360―380°C.The kinetic model includes 5 lumps,viz.:unreacted coal tar,diesel,gasoline,gas,and coke.The product distribution predicted and measured were compared and analyzed,indicating that the kinetic model in this research is suitable for the hydrocracking process of coal tar.Meanwhile,the hydrocracking mechanism of coal tar was further analyzed on the basis of the kinetic model.During the entire hydrocracking process of coal tar,the diesel fraction served as an intermediate component of the reaction.

An Experiment to Improve the Model of Lumped Element Circuit

The model of lumped element circuit ignores the finite time of signals to propagate around a circuit. However, using modern oscilloscope, the time of nanoseconds in a circuit can be measured. Then the speed of alternating electricity can be obtained in a RL circuit. A typical RL circuit is formed by a power source, wire, resistance and inductance. The basic formula is: U(t)=I(t)R+LdI(t)/dt. It can be derived from the Ohm’s law and Kirchhoff laws. Based on our experimental results, this paper has discussed the new explanation of this equation in a RL circuit. As a result, the speed of alternating electricity is greater than light in a special RL circuit. The model of lumped element circuit can be improved when considering the finite time of signals.

LUMPED-PARAMETER MODEL OF MASS TRANSFER IN HEMODIALYZER WITH ULTRAFILTRATION

1 INTRODUCTIONHemodialysis with ultrafiltration,also called hemodiafiltration(HDF),is a main methodof treatment for patients with chronic renal failure.The HDF procedure providesadequate removals of both small and middle molecular weight toxic substamces fromuremic blood,which is not possible by dialysis or ultrafiltration alone.According toclinical experience[1],the HDF procedure is well accepied by the patients,and thetreatment time is reduced by using it.

Study on Lumped Kinetic Model for FDFCC Ⅱ.Validation and Prediction of Model

On the basis of formulating the 9-lump kinetic model for gasoline catalytic upgrading and the 12-lump kinetic model for heavy oil FCC,this paper is aimed at development of a combined kinetic model fora typical FDFCC process after analyzing the coupled relationship and combination of these two models.Themodel is also verified by using commercial data,the results of which showed that the model can betterpredict the product yields and their quality,with the relative errors between the main products of the unit andcommercial data being less than five percent.Furthermore,the combined model is used to predict andoptimize the operating conditions for gasoline riser and heavy oil riser in FDFCC.So this paper can offersome guidance for the processing of FDFCC and is instructive to model research and development of suchmulti-reactor process and combined process.

Development of basic technique to improve seismic response accuracy of tributary area-based lumped-mass stick models

Although a detailed finite element(FE) model provides more precise results, a lumped-mass stick(LMS) model is preferred because of its simplicity and rapid computational time. However, the reliability of LMS models has been questioned especially for structures dominated by higher modes and seismic inputs. Normally, the natural frequencies and dynamic responses of a LMS model based on tributary area mass consideration are different from the results of the FE model. This study proposes a basic updating technique to overcome these discrepancies; the technique employs the identical modal response, D(t), to the detailed FE model. The parameter D(t) is a time variable function in the dynamic response composition and it depends on frequency and damping ratio for each mode, independent of the structure's mode shapes. The identical response D(t) for each mode is obtained from the frequency adaptive LMS model; the adaptive LMS model which can provide identical modal frequencies as the detailed FE model. Theoretical backgrounds and formulations of the updating technique are proposed. To validate the updating technique, two types of structures(a symmetric straight column and an unsymmetric T-shaped structure) are considered. From the seismic response results including base shear and base moment, the updating technique considerably improves the seismic response accuracy of the tributary area-based LMS model.

A Numerical Simulation of Air Flow in the Human Respiratory System Based on Lung Model

The lung is an important organ that takes part in the gas exchange process. In the study of gas transport and exchange in the human respiratory system, the complicated process of advection and diffusion (AD) in airways of human lungs is considered. The basis of a lumped parameter model or a transport equation is modeled during the inspiration process, when oxygen enters into the human lung channel. The quantitative measurements of oxygen are detached and the model equation is solved numerically by explicit finite difference schemes. Numerical simulations were made for natural breathing conditions or normal breathing conditions. The respiratory flow results for the resting conditions are found strongly dependent on the AD effect with some contribution of the unsteadiness effect. The contour of the flow rate region is labeled and AD effects are compared with the variation of small intervals of time for a constant velocity when breathing is interrupted for a negligible moment.

基于磁热耦合法的非对称混合磁极永磁电机热分析

针对传统内置永磁电机损耗高、发热量大的问题,提出非对称混合磁极永磁电机拓扑结构.介绍非对称混合磁极永磁电机的拓扑结构,对比分析两者的电磁特性与损耗分布特性.针对非对称混合磁极永磁电机分布式绕组的结构特点,对绕组进行等效处理,确定等效导热系数,建立集中参数热网络模型.建立单向磁热耦合模型,计算电机各部件的温度分布,验证了热网络模型的正确性.考虑到温度对永磁材料的影响,建立双向磁热耦合模型,对比分析不同电流密度对电机温升的影响规律.试制一台样机并搭建温升试验平台进行温升试验,验证了新型拓扑结构的有效性与合理性以及磁热双向耦合法计算结果的准确性.

集总与多体耦合人车模型的振动特性仿真

为了更好地分析车辆行驶时人体的振动情况以及更好地评价人体的动态舒适性,通过COMSOL软件建立了集总参数与多体耦合人-椅-车动力学模型。利用滤波白噪声法建立随机路面时域模型作为人车系统的振动输入,对不同路面等级和车速下的人体振动响应进行时域和频域仿真分析。根据ISO 2631-1:1997(E)计算垂向和纵向人体头部以及臀部的加速度均方根值,以此来评价人体乘坐舒适性。研究结果表明,路面等级越低、车速越高,人体乘坐舒适性越差。提出的集总与多体耦合人-椅-车振动模型可以比较精确地计算出坐姿人体垂向、纵向的振动响应,有助于对车辆乘坐舒适性进行评价。

体外反搏对典型冠状动脉疾病作用效果的集中参数建模仿真

目的 研究增强型体外反搏(enhanced external counter pulsation,EECP)疗法对典型冠脉血管病及微血管心绞痛的血流动力学影响。方法 使用集中参数建模方法,建立包含导管动脉与心肌微循环的右优势型冠脉生理模型。分别仿真单支狭窄、三支狭窄及微血管心绞痛等病理情况。建立EECP干预模型,结合上述病理模型,仿真EECP对病理模型的血流动力学作用。结果 建立的冠脉生理模型、病理模型及EECP干预模型仿真结果与相关文献中的实验数据相符合。EECP对3种病理情况都有改善冠脉血流的效果。对单支狭窄,EECP在左主干冠脉狭窄程度达到80%~85%之后便无法使血流恢复正常水平。对三支狭窄,若3条分支狭窄程度有1支超过90%,则无法使用EECP治疗。对微血管心绞痛,EECP有效的临界情况是充血心肌血流量>1.03 mL/(min·g)、冠状动脉血流储备>1.64。结论 建立的EECP干预冠脉血管病模型符合预期,所获仿真数据对EECP的临床操作具有一定参考价值。

考虑柱体摇摆效应的殿堂式木结构古建筑非线性地震反应分析

为了准确描述半刚性榫卯连接柱架在地震作用下的动力性能,采用非线性转动弹簧以模拟柱体在地震作用下的摇摆行为,基于柱体、榫卯节点及斗栱的非线性恢复力模型,提出了单层殿堂式木结构地震分析的集中质量简化分析模型,进行了地震作用下的结构动力响应时程分析。通过计算时程曲线与振动台试验结果的对比分析发现,未考虑柱体摇摆的计算值与试验值的误差较大,考虑摇摆效应的整体结构时程曲线计算峰值与柱架的实际位移峰值误差相对较小,且峰值出现的时间基本相同。基于简化模型进一步进行了参数分析,结果表明:竖向荷载可以显著降低殿堂式木结构的地震位移响应;柱高越大,结构的地震位移响应越大;结构的地震位移响应随着榫卯节点转动刚度的增大而显著降低;斗栱数量的增加提高了整体结构的抗侧刚度,从而降低了结构的地震位移响应。研究结果可为木结构古建筑在地震作用下的性能评估提供计算依据。

海上风电打桩系统动力学建模与冲击动力特性分析

基于LS-DYNA建立3500 kJ海上风电打桩系统拒桩工况下的有限元模型,基于应力波原理分析打桩系统内部能量的传递和各部件的动力学响应。同时基于牛顿碰撞理论建立打桩系统的集中参数模型,该模型综合考虑各部件的质量和刚度,和有限元模型的分析结果较吻合。从而在该集中参数模型的基础上,分别分析替打刚度、替打和锤质量比、替打环刚度对打桩系统冲击力的影响规律,表明冲击力的主要影响参数为替打刚度。