A simulation model for the analysis of a cluster-based multiprocessor system

In previous work, a class of cluster-based multiprocessor systems was introduced and analyzed. The analysis was based on an approximate probabilistic model and assumed circuit-switching methodology. It showed that for a higher rate of favourite requests the cluster-based system performs fairly close to the crossbar system and outperforms the typical multiple-bus system (with buses equal to half the number of processors). In this paper we first simulate the cluster-based system based on the analytical model assumptions presented in our earlier work. We then develop a simulation model that relaxes two unrealistic assumptions of the analytical model. The results obtained from the simulation models are compared with those obtained from the approximate analytical model for the cluster-based, crossbar, and multiple-bus systems. We then introduce a packet-switched cluster-based system. The system uses packet-switched single-shared buses to increase the bus utilization and hence the system throughput. A simulation model based on the event-scheduling approach is developed to evaluate the performance of the packet-switched cluster- based system in terms of delay and throughput. The simulation results of the packet-switched cluster-based system are compared with those obtained for the crossbar and multiple-bus systems for both uniform and favourite reference models.

The ATM adaptation layer type 5 (AAL5) is a new adaptation layer protocol for the ATM layer of broadband integrated services digital networks. Among several features, it is unique in the sense that it includes an end-of-packet (EOP) indicator in the header of the ATM cell (the ATM-layer-user-to-ATM-layer-user (AUU) parameter in the payload type (PT) field). It was previously suggested that the use of this indicator may be used to provide a means by which buffer occupancy can be reduced by dropping cells from already incomplete packets (Armitage, 1993). The objective of this paper is to study the performance of this layer and the effectiveness of the EOP indicator. The performance measures of interest are the probability of packet loss and the mean packet delay. An approximate analytical model is constructed in which the blocking of a tagged source is kept track of in an exact manner. The rest of the sources are modeled approximately. The accuracy of the model is enhanced through an iterative approach. A simulation model is also constructed to assess the accuracy of the approximate model.

A biaxial thermomechanical disk test for glassy polymers

Approximate performance/cost analysis of m-level hierarchical multiprocessor systems

A production line is an important class of manufacturing system when large quantities of identical or similar products are to be produced. The performance of a production line is highly influenced by machine failures. When a machine fails, it is then be unavailable during a certain amount of time required to repair it. Analysis of production lines divides into three types: analytical, approximation and simulation models. The analytical and approximation models have assumptions, which make these models unrealistic such as reliable workstations, certain processing distribution, the first workstation cannot be starved and the last workstation cannot be blocked. The main problems in production lines treatment are the calculation of throughput and average levels of buffers because of the great size of state space. An analytical model is reviewed to clarify the limitations to use such treatment in real production lines. Simulation modeling of production lines is considered very important for designers interested in: Workload Allocation Problem (WAP), Server Allocation Problem (SAP), and Buffer Allocation Problem (BAP). This paper studies and analyzes the performance keys, which effect on production lines. A simulation model is developed by using ARENA software and used to analyze and test several bottlenecks that are causing severe congestions in different areas on the production line and could resolve all of these bottlenecks. In this paper, an actual cement production line is used as a case study. After a simulation time of 13 days, a simulation results show the line bottlenecks, workstations utilization, buffer capacities and the line production rate. The outputs clarify redesign of allocation of buffers, which verify an optimum size could be made; it might be taken into consideration when designers implement such lines. Finally modified better workstations utilization, buffer capacities and the line production rate with an increase about 15% of the production rate and economizing of 37 % from buffer capacities

In this paper we consider dual-band GSM networks, where voice and data services are offered to users moving over an area covered with overlapping macrocells and microcells. For this wireless network context we develop simple approximate analytical models of the system dynamics, and we exploit such analytical models for the design and planning of the critical system parameters, with particular attention to the number of traffic channels to be activated within macrocells.

Queueing systems to study the energy consumption of a campus WLAN

In this paper, approximate analytical models are devised for regular deflection networks with arbitrary node connectivity and buffered nodes. The main feature of the proposed models is the capability to handle a large class of distributed routing schemes, which includes, as particular cases, most of the previously considered routing schemes.

The behavior of certain electromagnetic devices or components can be simulated with great detail in software. A drawback of these simulation models is that they are very time consuming. Since the accuracy required for the computational electromagnetic analysis is usually only 2-3 significant digits, an approximate analytic model is sometimes used instead, as noted by Lehmensiek and Meyer in 2001. The most complex model we consider here is a multivariate rational function, which interpolates a number of simulation data. The interpolating rational function is constructed in such a way that it minimizes both the truncation error and the number of simulation data since each evaluation of the simulation model is computationally costly.

The paper discusses the advantages of the bi-stable energy harvester over linear oscillators in the low frequency excitation regime. When excited by low-frequency base motions, a bistable vibration-based energy harvester’s response is characterized by a combination of a slow, and a non-stationary fast component. By decomposing the response of the bi-stable system into fast and slow components, some new physical insights into the dynamical properties of the system are obtained. Properties such as mechanical frequency up-conversion, asymmetry in the bi-stable potential of the system and extraction of the backbone curve are explored. The proposed decomposition is demonstrated and explained via numerical and experimental results. A simple, approximate analytical model, for the bi-stable oscillator is proposed and its ability to detect migration towards different vibration regimes is illustrated. An expression for the power output of the harvester is derived from the analytical solution allowing us to tune the bi-stable potential towards optimum performance. The analytical model sheds light on the occurrences of bifurcations in the response of such nonlinear systems and on the optimal values of potential barrier vs. excitation levels.

The purpose of the study presented here is to establish a finite element (FE) model to simulate the wear process of a polymer-to-polymer sliding system. Two polymer components which are named as slider and ground are operated on the slant-horizontal contact region reciprocally. A total of 3500 cycles was conducted. The sliding wear motion of the real product is simplified into a two-dimensional model for FE simulation. According to the requirement of the actual application, we are interested in one of effects of the wear performance - the horizontal driving force (HDF) which is applied on the slider component to generate the sliding motion [1]. Two commercial polymer materials have been considered in this paper: 33% glass reinforced, heat stabilised black nylon copolymer resin and BK15945% glass reinforced modified polyethylene terephthalate. For the solution of the wear simulation and prediction, the FE analysis software ANSYS and some mathematic wear equations have been used to build an analysis procedure for this polymer contact structure. First, the FE simulation model is applied to gain the contact surface pressure distribution. Then, the mathematical wear equations are used to calculate the wear depth along the wear sliding surface. Next, the contact surface shape with the wear depth datum is modified. Now, a new model with the upgraded geometry is carried out. Repeating the above four analysis steps, the whole wear process will be represented in the simulation model. In this paper, a series of simulations are performed for every 500 operating cycles for a total of 3500 cycles. The major task of ANSYS is to plot the stress and pressure distribution of the fields of contact and the HDF variation with the sliding motion. Both components have been map-meshed and the two-dimensional structure solid element which is designed as PLANE42 in ANSYS is used for the solid body of the model. The contact pair is described by the flexible surface-to-surface contact elements CONTAC172 and the flexible surface-to-surface target element TARGE169. Twenty load steps across the contact surface are setup for gathering the necessary datum (stress, surface pressure, reaction force, etc). To get a better convergence of the iterative solution, two treatments are also configured. First, the calculation algorithm the pure penalty is switched to the augmented Lagrange. Second, the contact stiffness parameter is adjusted to balance the precise result and the acceptable convergence. Furthermore, an approximate method is introduced to simplify the contact geometry of the upgraded model which is generated by applying the wear depth to the original model. Wear equations employed in this paper are proposed by Archard [2] and Yang [3]. The Archard's equation considers the wear in a steady-state and Yang's equation involves the running-in (transient) wear phase. Both of them based on metal materials and have been extended for the application of polymer materials by Ashraf [4]. A number of simulation results are obtained from a sequence of finite element analyses by progressively removing material and are compared with physical testing results. The simulation results of the horizontal force in an operation cycle of 3500, shows that the force increasing along the slant sliding surface and the position where the peak force occurred are very similar to the experiment. The plot of the von-Mises stress distribution from the FE simulation indicates the maximum stress appears at the top of the slant contact surface. Therefore the maximum wear depth should occur at this region. The variation of the peak horizontal force during the 3500 wear cycles demonstrate a dramatic reduction in peak force over the first 1500 cycles, followed by a gradual decrease in the rate of reduction. For subsequent cycles, the force has decreased continually but at a slower rate. It is found that the FE results have the similar trend with the experimental measured results which support the possibility of using the approximate FE simulation model to estimate the wear process in this particular structure. There are several ways to gain more accurate results. First, refine the model mesh and the load steps. Second, abandon the approximate method which is used to simplify the contact surface after wear. It makes the simulation condition more similar to the actual wear status than the approximate model. Third, apply FE simulation for more wear operation cycles. Due to the model simplifications and the input data of the material properties, this simulation model is only effective for this particular product. Further research will be carried out to extend it to more general the application.

A new approximate analytical model is presented for the fatigue crack propagation rate in concrete. The model considers fatigue cracking at all stress levels up to the modulus of rupture. As the bending stress increases, the size of the inelastic zone compared to the crack length increases, and the stress intensity factor no longer controls the stresses in the vicinity of the crack tip, necessitating the use of the path-independent J-integral. At high stress levels fatigue crack propagation becomes nonlinear, and fracture may occur by ultimate strength collapse. Recently Kharlab postulated a hypothesis that enables the prediction of fracture of concrete by a single criterion that considers failure at any stress level for any size beam. An approximate analytical method for fatigue crack propagation in concrete at any stress level is presented. It incorporates the size effect and uses the crack tip opening displacement as the primary criterion upon which the rate of crack propagation is dependent. The model is validated by the published experimental data on concrete fatigue.

We discuss several analytical models for impedances of very short bunches. The approximate analytical models are compared with direct solution of Maxwell's equations.

An analytical model for stress analysis of short fiber composites in power law creep matrix

Analytical and numerical modelling of shear-link device for seismic energy dissipation in frame structures