Numerical simulations for the predator-prey model on surfaces with lumped mass method

Engineering with Computers - The predator-prey model is powerful mathematical tool to describe the dynamics of biological systems and promote research on biological populations. In this paper, we...     

煤焦油加氢裂化集总动力学模型的研究

基于对煤焦油加氢过程分析,建立了煤焦油加氢裂化五集总(煤焦油、汽油、柴油、气体、焦炭)动力学模型。利用煤焦油加氢裂化的实验室小试结果,对加氢反应过程的动力学参数利用MATLAB软件编程进行了回归。结果表明,该模型能很好的预测产品的分布,其计算结果和实验值一致。在此基础上重点讨论了在一定温度下空速、氢油比、氢气的初始压力等操作条件对产品分布的影响,为进一步工艺流程的优化提供了依据。     

A lumped mass vibration model of a slender latticed cantilever

A relatively simple numerical iterative procedure for estimating the normal modes of flexural vibrations of a slender, multipanel latticed cantilever, tapered or straight, is developed. The cantilever is reduced to a N mass system and the influence coefficients are derived with due consideration to the shear flow through the diagonal bracings. Experimental and computer results on a model are compared.     

Including the influence of groundwater exchanges in a lumped rainfall-runoff model

The growing realisation that groundwater and surface water systems are components of connected hydrologic system has in recent years sparked the development of integrated surface–ground water models. In this paper, a version of the IHACRES rainfall-runoff model is presented, in which the CMD module for calculating effective rainfall is coupled to a streamflow-groundwater module, and applied to the Coxs Creek catchment, a variably gaining-losing stream system in Australia. The aim is to determine the capacity for the coupled model to capture the switching off–on behaviour evident in the observed flow record. Model performance can be improved in terms of event prediction, volume of baseflow and the percentile of flow cessation, through manipulation of CMD parameters, however, improvements in some performance criteria come at the expense of performance in others. An analysis of the input rainfall time-series, generated using a standard weighted Thiessen polygon approach, reveals mismatches between observed streamflow events and the occurrence of rainfall, which impose major limits on model performance. The challenge is to develop a simple lumped rainfall-runoff model that has the potential to improve system understanding and allow for meaningful exploration of alternate climate, groundwater extraction and land use change scenarios, given a situation of data poor catchments in many parts of Australia.     

Development of inverse dynamic model for a surgical hybrid parallel robot with equivalent lumped masses

Robotic-assisted surgery is a continuously developing field, as robots have demonstrated clear benefits in the operating room. This paper presents the inverse dynamic model (in the case of using the laparoscope as a surgical instrument) and some characteristics of a 5-DOF hybrid parallel robot designed for minimally invasive surgery. The new inverse dynamic model is obtained using the virtual work method on the basis of dynamically equivalent lumped masses. The simulation and numerical results have been obtained for the experimental model of the developed PARASURG-5M robot, showing that the analytical inverse dynamic model could be used in the control of the robot. Finally, a comparison between the simulation data obtained in Matlab (IDM) with the simulation data through a Multi-body Simulation software (MBS), namely Adams (MBS) has been performed.     

A saliency and Gaussian net model for retinal vessel segmentation

Frontiers of Information Technology & Electronic Engineering - Retinal vessel segmentation is a significant problem in the analysis of fundus images. A novel deep learning structure called the...     

遗传算法在估计催化裂化集总模型参数中的应用

催化裂化集总动力学模型是1种多参数、高耦联的复杂反应动力学模型.用经典的优化算法求解模型参数时,常常需要对模型作一些数学处理,而复杂模型的数学处理相对困难;此外,经典算法的求解结果也常常不尽如人意.为解决这类模型的参数估计问题,以老遗传算法为基础,提出1种以亲子竞争和最优个体保护策略相结合的新遗传算法.新算法采取全局交叉和自适应变异,既保证了最大范围搜索解空间、避免算法在计算初期就陷入局部最优,又能在后期对局部细致搜索,提高了计算精度;克服了老算法随机性大、容易陷入局部最优的缺点.为测试新算法的效果,首先用某多参数复杂模型做测试,结果证明无论是遗传代数相同情况下的计算精度,还是为了达到某一精度而要求的计算代数,新算法都优于老者.然后用于估计催化裂化提升管反应器集总动力学动态模型参数.最后,取工业实际数据验证模型参数,泛化结果表明模型预测值与实际测量值基本吻合,120组数据的平均相对误差为1.71%,证明新算法适用性较好.     

基于耳蜗模型的舰船噪声谱分析

为提取舰船噪声听觉特征,应用被动长波模型对舰船噪声进行了分析,得到噪声信号的二维时空分布。给出了4种一维特征,它们能够分别从不同侧面反映舰船噪声时频幅特征,同时简化了特征的描述方式。大量实验表明：基于听觉模型特征分析结果,较全面地反映了舰船噪声的听觉特征,为被动声纳目标识别提供了新的特征分析方法。     

Active optimal vibration control for a lumped system

A dynamic absorber with active torque generating DC motors has been studied as an actively suppressing vibration system. A typical two-level spring-lumped mass system with slider undergoing internal excitation vibrations has been considered. Both the main mass and the secondary absorber mass have DC servo motors planned to suppress the amplitude of vibration. State variable techniques are used to formulate the complete system and three optimal control schemes are used to control such a system. First, the discrete time optimal disturbance rejection control for a system with known disturbance is considered, in the second approach a digital optimal control for a linear quadratic regulator problem is studied and in the last approach a discrete optimal control with selected system characteristic matrix is investigated. The response of the system obtained from these optimal control approaches are compared with the response without control action first. The performance of these optimal control approaches are also compared and the availability of implementations of them are evaluated.     

Legendre series for the identification of non-linear lumped systems

An operational matrix for the integration of a shifted Legendre vector is applied to the parameter identification of time-invariant non-linear lumped systems with and without noise, proper shape having been given to the non-linear terms. A new approach is developed which is simple, accurate and computationally convenient.     

A lumped Galerkin method for solving the Burgers equation

A numerical solution of the one-dimensional Burgers equation is obtained using a lumped Galerkin method with quadratic B-spline finite elements. The scheme is implemented to solve a set of test problems with known exact solutions. Results are compared with published numerical and exact solutions. The proposed scheme performs well. A linear stability analysis shows the scheme to be unconditionally stable.     

A lumped circuit model for a nonlinear inductor exhibiting dynamic hysteresis loops and its application to the electric circuits

Previously, modeling magnetodynamic fields, taking into account dynamic hysteresis loops, was proposed for predicting three-dimensional magnetodynamic fields in electromagnetic devices. This method is now applied to work out the lumped circuit model for a nonlinear inductor exhibiting dynamic hysteresis loops. This lumped circuit model for a nonlinear inductor is introduced into the simulation models for typical nonlinear circuits, whose dynamic hysteresis loops as well as current responses are calculated and compared with experimental measurements. Good agreement is obtained.     

Dynamic selection of actuators for lumped and distributed parameter systems

The theory of relaxed controls is used to solve the problem of selection, at each instant of time, of one out of many actuators in order to obtain a desired result. For lumped parameter systems it is shown that there exist optimal solutions for the problem involving the minimization of a quadratic cost functional. Necessary conditions for optimality are established and a numerical algorithm to determine the optimal solution is proposed. The method developed for lumped parameter systems is extended to distributed systems and, in particular, to the problem of Optimal allocation of actuators.     

A Boussinesq model for pressure and flow velocity waves in arterial segments

We derive a nonlinear model for the pressure and flow velocity wave propagation in an arterial segment. We then study the transmission and reflection of pulses at bifurcation. We observe a linear dependence of the transmitted speeds to the incoming speeds, and similarly for the reflected speeds. We propose a method for validating the numerical results obtained from this model against real data.     

Observability conditions for a class of mixed distributed and lumped parameter systems

Observability of a class of mixed distributed and lumped parameter systems with respect to physically realizable measurements is studied. Measurements are made either on the lumped subsystem or at interior points of the spatial domain. In both cases algebraic observability conditions are determined and the results applied to a transportation lag system.     

Recursive methods for parameter estimation of linear lumped systems using Hermite polynomials

A recursive method for estimation of the parameters of a linear lumped parameter system is developed. An example is given to illustrate the algorithm, and results of the estimation in the presence of white noise are also given.     

Cad compatible accurate models of microwave passive lumped elements for mmic applications

This article presents accurate measurement-based models derived from measured S-parameters of passive circuit elements which include inductors, thin-film resistors, interdigital and MIM capacitors, via holes, and airbridges for use in the computer-aided design of monolithic microwave integrated circuits (MMICs). The thru-reflect-line (TRL) calibration method is employed to accurately measure the S-parameters of the passive elements. Some of the models are scalable for different substrate thicknesses and substrate dielectric constant values as they are based on microstrip line theory. © 1994 John Wiley & Sons, Inc.     

Algebraic and topological aspects of the regulator problem for lumped linear systems

The regulator problem with robustness is solved for systems modelled by rational transfer matrices. A topology for possibly unstable plants is presented. A necessary and sufficient condition is derived for the existence of a proper controller which provides internal stability and output regulation throughout an open neighbourhood of the plant. A characterization of all such controllers is determined.     

Diagnosis and optimization of a power distribution network by extracting its parasitic inductances and building a lumped circuit model

Design of power distribution networks (PDNs) in high speed digital circuit has become a more challenging task in view of decreasing supply voltages and increasing transient currents. The parasitic inductance of a PDN is the most crucial parameter that limits high frequency performance. In this paper, a specific PDN on printed circuit board (PCB), with multiple supply voltages, is diagnosed and optimized. A simple method is developed to extract the parasitic inductances of the PDN by examining the Y parameters. An equivalent lumped circuit model is built to interpret the input impedance curve of the PDN. Based on this model, a simpler circuit model is presented. Predictions based on the simple circuit model are in agreement with the field simulated performance of the whole structure and with measured results. The performance of the PDN can be improved by optimizing segmentation and distribution of power planes along with strategic placement of decoupling capacitors. It is crucial for PDN design to decrease the parasitic inductance between power/ground pads on PCB and their junction points to PDN power/ground pairs.