Modelling and simulation of moving contact line problems with wetting effects

This paper presents a numerical scheme for computing moving contact line flows with wetting effects. The numerical scheme is based on Arbitrary Lagrangian Eulerian (ALE) finite elements on moving meshes. In the computations, the wetting effects are taken into account through a weak enforcement of the prescribed equilibrium contact angle into the model equations. The equilibrium contact angle is included in the variational form of the model by replacing the curvature with Laplace Beltrami operator and integration by parts. This weak implementation allows that the contact angle determined by the numerical scheme differs from the equilibrium value and develops a certain dynamics. The Laplace Beltrami operator technique with an interface/boundary resolved mesh is well-suited for describing the dynamic contact angle observed in experiments. We consider the spreading and the pendant liquid droplets to investigate this implementation of the contact angle. It is shown that the dynamic contact angle tends to the prescribed equilibrium contact angle when time goes to infinity. However, the dynamics of the contact angle is influenced by the slip at the moving contact line. This work has been partially supported by the German Research Foundation (DFG) through the grant To143/9.     

蠕虫扫描策略和流量模拟方法研究

对蠕虫扫描策略及其传播效率进行了深入分析;并提出了"带宽限制型 部分预定义目标地址列表 基于路由扫描 随机均匀扫描"的快速扫描策略.分析了各种蠕虫传播过程模拟方法和蠕虫流量模拟方法的优劣;并从统计意义上建立了"延迟限制型"蠕虫的周期性突发的扫描流量模型,结合混合层次模拟方法,能够为蠕虫模拟、检测和应对技术提供基础,同时减少了蠕虫模拟的复杂性.     

Modelling the software development process using an expert simulation system having fuzzy logic

This paper describes an intelligent computerized tool designed to aid managers of software development projects in planning, managing and controlling the development process of medium- to large-scale software projects. Systems dynamics is used to model and simulate the dynamic process of software development. The software development process is affected by some imprecise and vague variables that are treated as fuzzy variables. The simulation model is integrated with two expert systems. The fuzzy input variables to the system dynamics simulation model are handled by an input expert system having fuzzy logic. This expert system is designed to check the consistency of input variables. The simulation results are analysed by an output expert system having fuzzy logic. This expert system is designed to make recommendations based on experimentation with the simulation model.     

Application of modified geometry of face gear drive

An enhanced approach for the application of longitudinal plunging in the manufacturing of a double crowned pinion of a face gear drive has been investigated, with the purpose of reducing the sensitivity of the gear drive to misalignments. The process of manufacturing is based on a modification of the movements applied to the grinding disk during the generation of the surfaces of the pinion, consisting in the introduction of a tilt of the plane that contains the planar trajectory performed by the center of the disk. Tooth contact analysis and stress analysis have been considered to simulate the contact and meshing of the gear tooth surfaces and to calculate the evolution of contact and bending stresses of the gear drive along the cycle of meshing. The performed research proves that an appropriate choice of the machine tool settings permits the avoidance of edge contact, in presence of misalignment as well, without a high reduction of the contact ratio. The results are illustrated with numerical examples.     

Modelling and simulation of a catalytic membrane reactor

A catalytic membrane reactor modelling is established through mass balance equations in different control volumes. Two different strategies were followed to solve the parabolic differential system representing the mass balance. The orthogonal collocation method in two spatial dimensions is first used to solve the elliptic form of the equation corresponding to steady state. Secondly, a structural approximation method, i.e. finite difference method is used to solve the global dynamic system. The approximation problem is studied by using some convergence results of discretising approximation of a linear continuous operator in a Banach space. The two approximation methods give sound modelling of this new type of reactor for numerical solutions study and approximative structure study.     

Modelling and simulation of a lighting control system

The objective of this paper was to regulate the amount of illumination in a room at a constant level, irrespective of the disturbances from outside such as weather conditions or the use of blinds to avoid the glare risk. In order to produce a model of the lighting system in our project, the supply voltage to the lamp dimmer circuits was varied stepwise and the resulting response – measured by the light sensors – was captured with a data-acquisition board. A nonlinear static characteristic in series with a linear 3rd order dynamic system was obtained from this experiment. The model was then used to implement and to validate a lighting system simulator, which was then further used to design, tune, test and evaluate efficient lighting controllers. The control design was rather challenging because the system is highly nonlinear and because undesired interaction occurs between multiple illumination zones in a big office room. The main benefits are a higher level of comfort and a continuous saving of energy.     

New geometry of face worm gear drives with conical and cylindrical worms: generation,simulation of meshing,and stress analysis

New geometry of face worm gear drives with conical and cylindrical worms is proposed. The generation of the face worm gear is based on application of a tilted head-cutter (grinding tool) instead of application of a hob applied at present. The generation of a conjugated worm is based on application of a tilted head-cutter (grinding tool) as well. The bearing contact of the gear drive is localized and is oriented longitudinally. A predesigned parabolic function of transmission errors for reduction of noise and vibration is provided. The stress analysis of the gear drive is performed, the contacting model is designed automatically. The developed theory is illustrated with numerical examples.     

Modelling and simulation of a group of mobile robots

In this paper the mathematical background of the developed robot soccer simulator is presented. It involves robot and ball dynamic behaviour and focuses mainly on their collisions study. Vital parts of the simulator are explained and modelled in more detail, beginning with the simple model of ball and robot motion and continuing with a more complex approximate collisions models, where the real robot shape is taken into consideration. Some new ideas of collision formulation, realization and real robot shape inclusion are used. The implementation of the simulator is described and advantages for the usage of the realistic simulator are stated.     

On the drive train design of gear coupled manipulators

A systematic methodology for the drive train design of gear coupled manipulators is developed. The approach is based on the idea that the generalized inertia forces contribution to the system's dynamic equations can be divided into the contribution of the virtual open-loop chain and that of the drive train. It is shown that the contribution of the drive train to the system's dynamic equations is a function of the orientations of its rotational axes and the orientations of joints. Conditions to determine these orientations such that the drive train can have configuration-invariant contribution to the system's dynamic equations are derived. From the design conditions, mechanical details of the drive train such as the choice of actuator locations, the arrangements of the drive train and joints, the compatibility between orientations of joints and rotational axes of the drive train can be determined accordingly. This approach, together with the developed design methods for the serial type manipulators, provides a complete design methodology in designing new robots or improving the dynamic performance of existing ones. © 1998 John Wiley & Sons, Inc.     

面向对象的蠕虫仿真方法研究

本文首先分析了网络蠕虫的特征行为,从宏观和微观两个层次对蠕虫进行了研究,并指出借助仿真实验来研究蠕虫的方法的优势所在;然后通过对仿真环境的构造的分析和对仿真动力来源的介绍,详细阐述了蠕虫仿真的基本过程;最后给出面向对象的网络蠕虫仿真的基本思路与方法。     

Modelling and simulation of a copper electrolysis cell group

The energy consumption of the copper electrolysis process is relatively high. Electrical disturbances – like contact failures and short circuits – even increase the energy consumption and also reduce the quality of copper produced. To better understand and improve the process, a computationally feasible and reliable model of copper electrolysis cell group is of great importance. In this paper a multiphysical FEM model of copper electrolysis cell group is presented. A number of simplifications are proposed to make the model computationally feasible.     

Computer aided analysis on the meshing behavior of a height-modified dual-torus double-enveloping toroidal worm drive

A flank modification methodology is proposed for the double-enveloping toroidal worm drive and a novel type of the dual-torus double-enveloping toroidal worm drive (the DTT worm drive) is developed. Because the height variation of the tool relative to the position during generating an unmodified worm is the unique modification parameter, this novel type of worm drive can be named as the height-modified DTT worm drive. Based on a strict meshing analysis, the selection principle of the modification style is recommended. A systematic and thorough study is conducted on the meshing behavior of the height-modified DTT worm pair by means of a computer simulation. The investigation results show that the height-modified DTT worm drive has favorable meshing performance.     

Vibration analysis of a contact slider/gimbal of a flexible disk drive

 To design contact-type gimbal system for a newly developed removable flexible disk drive called Card size flexible disk drive (CFDD) (Shinpuku et al., 2001; Ryoson et al., 2001), the gimbal's vibration characteristics in the disk-rotation direction were measured and simulated using FEM. To determine the relationship between vibration and friction in the head disk interface (HDI), a hard disk was also used. The friction characteristics were inserted into the FEM model based on the results. The gimbal was modified to suppress vibration amplitude to half in both simulation and experiment. Received: 5 July 2001/Accepted: 1 November 2001 Paper presented at the 12th Annual Symposium on Information Storage and Processing Systems, Santa Clara, CA, USA, 28–29 June, 2001.     

Modelling, simulation and control in a data-rich environment

This paper describes the use and potential use of mathematical modelling, computer simulation, real-time parameter identification and adaptive feedback control techniques in data-rich clinical environments. We consider a system to be operating in a data-rich environment when measurements of system inputs and outputs are frequently available. Two particular application examples which illustrate the power of these techniques will be examined. The first example that will be described involves the development and testing of a real-time adaptive controller for simultaneous regulation of mean arterial pressure and cardiac output using two drugs. The second application of these techniques involves the real-time control of electrical stimulation for the functional use of paralyzed muscles in neuroprosthetic devices.     

Modelling and dynamic simulation of a parabolic trough power plant

Investigational dynamic simulations of an existing 50 MW_el parabolic trough solar thermal power plant in Spain are carried out during clear days and slightly cloudy periods. This work is the first research, which presents a detail dynamic model of a parabolic trough power plant. Besides the thermal energy storage system and solar field, the developed model describes the heat transfer fluid and steam/water paths in detail. Advanced control circuits, including drum level, economiser water bypass, attemperator and steam bypass controllers are also included. The parabolic trough power plant is modelled using Advanced Process Simulation Software (APROS). The comparison between the simulation results and measured data is documented, showing a reliable prediction of the real behaviour of the investigated solar power plant. The validated model offers a possibility for accurate simulation of further operation processes of the real plant.     

Face-gear drive with spur involute pinion: geometry,generation by a worm,stress analysis

A face-gear drive with a spur involute pinion is considered. The generation of the face gear is based on application of a grinding or cutting worm whereas the conventional method of generation is based on application of an involute shaper. The authors have developed an analytical approach for determination of: (i) the worm thread surface, (ii) avoidance of singularities of the worm thread surface, (iii) dressing of the worm, and (iv) determination of stresses of the face-gear drive. A computer program is developed for simulation of meshing and contact of the pinion and face gear. Correction of machine-tool settings is proposed for reduction of the shift of the bearing contact caused by misalignment. An automatic development of the model of five contacting teeth has been proposed for stress analysis. Numerical examples for illustration of the developed theory are provided.     

具有permutation扫描特征的多态蠕虫传播实验仿真*

大部分蠕虫建模工作都是基于相对简单的随机扫描蠕虫,而且蠕虫的形态是相对固定的。随着蠕虫技术的显著提高,在传播方式上出现了较高级的传播方式如permutation扫描,同时出现了能改变蠕虫形态的多态变形技术。为了更好地理解该类型蠕虫的传播特性,首先研究permutation扫描技术,然后构建实验模拟具有permutation扫描特性的多态蠕虫传播。分析当环境中不存在IDS时,各类蠕虫数目和被感染主机的运行情况,当环境中存在IDS时,各参数对多态蠕虫传播过程的影响。最后在仿真的基础上对蠕虫传播的动力学机制进行了总结,对防御方法进行了初步探讨。     

Modelling and simulation of porous immersed boundaries

The immersed boundary method has been used to simulate a wide range of fluid–structure interaction problems from biology and engineering, wherein flexible solid structures deform in response to a surrounding incompressible fluid flow. We generalize the IB method to handle porous membranes by incorporating an additional transmembrane flux that obeys Darcy’s law. An approximate analytical solution is derived that clearly illustrates the effect of porosity on the immersed boundary motion. Numerical simulations in two dimensions are used to validate the analytical results and to illustrate the motion of more general porous membrane dynamics.     

Modelling and distributed simulation of asynchronous hardware

Synchronous VLSI design is approaching a critical point, with clock distribution becoming an increasingly costly and complicated issue and power consumption rapidly emerging as a major concern. Hence, recently, there has been a resurgence of interest in asynchronous digital design techniques as they promise to liberate VLSI systems from clock skew problems, offer the potential for low power and high performance and encourage a modular design philosophy which makes incremental technological migration a much easier task. This activity has revealed a need for modelling and simulation techniques suitable for the asynchronous design style. Contributing to the quest for modelling and simulation techniques suitable for asynchronous design, and motivated by the increasing debate regarding the potential of CSP for this purpose, this paper investigates the suitability of occam, a CSP-based programming language, for the modelling and simulation of complex asynchronous systems. A generic modelling framework is introduced and issues arising from the parallel semantics of CSP/occam when the latter is employed to perform simulation are addressed.