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...     

A lumped conceptual model to simulate groundwater level time-series

Lumped, conceptual groundwater models can be used to simulate groundwater level time-series quickly and efficiently without the need for comprehensive modelling expertise. A new model of this type, AquiMod, is presented for simulating groundwater level time-series in unconfined aquifers. Its modular design enables users to implement different model structures to gain understanding about controls on aquifer storage and discharge. Five model structures are evaluated for four contrasting aquifers in the United Kingdom. The ability of different model structures and parameterisations to replicate the observed hydrographs is examined. AquiMod simulates the quasi-sinusoidal hydrographs of the relatively uniform Chalk and Sandstone aquifers most efficiently. It is least efficient at capturing the flashy hydrograph of a heterogeneous, fractured Limestone aquifer. The majority of model parameters demonstrate sensitivity and can be related to available field data. The model structure experiments demonstrate the need to represent vertical aquifer heterogeneity to capture the storage–discharge dynamics efficiently.     

Three-dimensional reconstruction of moving arterial beds from digital subtraction angiography

A system for three-dimensional reconstruction of dynamic (moving) vascular bed structures has been developed and is described. Input images are obtained from two-view (bi-plane or ECG correlated) X-ray angiograms. A target structure consisting of vessel branch points (nodes) and lines between the branch points is entered on the first of a sequence of images in one view. The movement of the nodes is indicated on subsequent images and on the images of the second view. The target is linearly warped according to the motion of the node points. Automatic edge detection (with subsequent operator correction) is used to detect centerlines and edges of vessels. Three-dimensional reconstruction is accomplished using a distance minimizing point matching technique. Finally, angle-corrected densitometric methods are used to refine the vessel cross section. Standard shaded surface display techniques are then used to display the moving arterial bed. Flow measurements are obtained by tracking the leading edge of the bolus down the three-dimensional arterial tree.     

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.     

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。     

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.     

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.     

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...     

Topological semantics for lumped parameter systems modeling

Behaviors of many engineering systems are described by lumped parameter models that encapsulate the spatially distributed nature of the system into networks of lumped elements; the dynamics of such a network is governed by a system of ordinary differential and algebraic equations. Languages and simulation tools for modeling such systems differ in syntax, informal semantics, and in the methods by which such systems of equations are generated and simulated, leading to numerous interoperability challenges. Logical extensions of SysML aim specifically at unifying a subset of the underlying concepts in such languages.We propose to unify semantics of all such systems using standard notions from algebraic topology. In particular, Tonti diagrams classify all physical theories in terms of physical laws (topological and constitutive) defined over a pair of dual cochain complexes and may be used to describe different types of lumped parameter systems. We show that all possible methods for generating the corresponding state equations within each physical domain correspond to paths over Tonti diagrams. We further propose a generalization of Tonti diagram that captures the behavior and supports canonical generation of state equations for multi-domain lumped parameter systems.The unified semantics provides a basis for greater interoperability in systems modeling, supporting automated translation, integration, reuse, and numerical simulation of models created in different authoring systems and applications. Notably, the proposed algebraic topological semantics is also compatible with spatially and temporally distributed models that are at the core of modern CAD and CAE systems.     

集中质量-弹簧碰撞模型在汽车被动安全预研阶段的应用

为在车身开发的概念设计阶段明确车辆前碰的安全性目标加速度波形,提出以乘员伤害值确定整车正面碰撞波形的方法,建立包括驾乘人员的车辆集中质量-弹簧(Lumped Mass-Spring,LMS)模型.为确保LMS模型的有效性,将整车有限元模型仿真结果与运动学特性计算结果对比.通过对比前碰加速度波形、刚性墙力以及前舱总的压溃位移,对LMS模型的有效性进行验证.以乘员胸部的乘约效率为优化目标,基于已验证的LMS模型进行关键参数的试验设计分析,从而为车辆前结构的碰撞安全性能设计提供参考.     

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.     

Actively-controlled beds for ambulances

During transportation by ambulance, a patient is exposed to inertial acceleration when an ambulance decelerates or turns a corner. Such acceleration often gives a patient physical stress such as blood pressure variation or body sway, which causes strong pain, feeling of discomfort or sometimes critical damage for seriously injured persons. To reduce this undesirable effect of the acceleration, the authors developed the actively-controlled bed （ACB） which controls the posture of a stretcher in real time to reduce foot-to-head and lateral acceleration acting on a supine person. This paper describes development of the ACB, including control system design and performance evaluation. The control system is designed by Zakian＇s framework, which comprises the principle of matching and the method of inequalities, so that the design specifications on the tracking error and the motor torque are satisfied. From the results of driving experiments and simulation, it is estimated that the ACB can reduce the acceleration acting on a patient by 65% in the foot-to-head direction and by 75% in the lateral direction.     

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.     

一种并行LSTM-FCN模型在船舶航迹预测中的应用

航迹预测是保障船舶航行安全、提高海洋交通管制效能、高效搜索海面目标的关键技术.为提高船舶航迹预测精确度,针对航迹特征多维度的特点,提出一种并行LSTM-FCN(parallel LSTM-FCN, PLSTM-FCN)模型.该模型有效结合LSTM模型对时间序列数据长期趋势预测的优势和全卷积网络(FCN)模型擅于提取时间序列数据细节变化规律的特点,通过并行结构设计保证相同训练效率下提取特征参数翻倍,实现较高精确度的高维航迹数据特征提取和趋势预测.基于动态时间规整算法和拉依达准则的船舶历史航迹数据预处理方法,可提高PLSTMFCN模型从不同类型船舶历史航迹中深度学习航行趋势和转弯细节的效率.基于船舶自动识别系统(AIS)数据的仿真实验结果表明, PLSTM-FCN模型对多维特征船舶航迹预测的精确度明显优于传统循环神经网络.     

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.