International Journal of Modeling, Simulation, and Scientific Computing

A grid is a geographically distributed resource sharing environment across multiple organizations. The most typical grid resources are clusters with high performance/cost ratio. In general, these clusters are shared as non-dedicated grid resources since local users may run their jobs simultaneously. Local jobs are usually queued and processed in a batch mode with uncertain waiting time, while grid jobs always require advance reservations with guaranteed resource allocation.

In this paper, we provide quantitative analysis on the impact of advance reservations over queued jobs, in terms of job waiting time and resource utilization, respectively. It is observed that advance reservations will lead to longer job waiting time and lower resource utilization. That is to say, advance reservations should cost more than queued jobs. In this work, based on quantitative experimental results, an empirical formula for cost estimation of advance reservations over queued jobs is presented. It is suggested that compared with queued jobs, advance reservations should be doubly charged to compensate resource utilization loss. If the notice time of an advance reservation is short below a threshold, additional cost should be applied further since queue waiting time is increased.

We establish a new model for seepage of a liquid to a chink in the cracked deformable layer, an initial value problem of nonlinear fractional differential equation with variable coefficients, then design a numerical scheme of order 2 to solve this initial value problem. This new model theoretically explains the operating thickness H of a layer depending on the values of pressure gradient on the whole chink rather than on one point, which is practiced by a large amount of data. Compared with the Dontsov equation, our fractional model considers more aspects of the whole process. The earlier rejected results can also be considered in the display lines of the fractional model.

In this paper, a new fuzzy optimization based on methodology utilizing a modified s-curve membership function has been applied to an industrial production problem in an oil company. The major contribution of this paper is the optimization of a profit function with respect to uncertain resource variables and technological coefficients. Three cases have been thoroughly studied in this paper. Comparative results have been successfully obtained for these three cases. This piece of information will be very important for the decision makers in implementing their decisions in a vague environment. It will be shown that there are many advantages of using the modified s-curve membership to optimize the profit function used by the decision maker; in particular strategic and flexible decisions are facilitated.

Ultra-broadband networks are currently attracting significant interests in employing wireless access and optical fiber access to the home and to the building at symbol rate reaching Gb/s. OFDM is a multicarrier modulation technique and considered to offer significant reduction of the data symbol to be carried per carrier channel, especially in ultra-high speed optical communications with bit rate reaching 100 Gb/s or even higher. This paper thus presents a novel and generic OFDM system employing both MATLAB Simulink and FPGA-based development software platform for simulation as well as hardware implementation for the generation and detection of OFDM signals for wireless and optical communications transmission media. Although the transmission medium is modeled with delay distortion filter in the baseband, this model would be valid for passband signals as the amplitude is represented by complex amplitude whose phase would be the phase of the carrier. The Simulink and hardware models presented hereunder are scalable to much higher speed allowing possible implementation in multi-Giga samples per second electronic processors. The sub-systems of the OFDM transmitter and receiver are presented to demonstrate the feasibility of such models for ultra-wideband communication systems such as wireless access and long haul optical fiber communication backbone networks.

In the present study, forward modeling of high-speed finish milling process has been solved using soft computing. Two different approaches, namely neural network (NN) and fuzzy logic (FL), have been developed to solve the said problem. The performance of NN and FL systems depends on the structure (i.e. number of neurons in the hidden layer, transfer functions, connection weights, etc.) and knowledge base (i.e. rule base and data base), respectively. Here, an approach is proposed to optimize the above-mentioned parameters of NN and FL systems. A binary coded genetic algorithm (GA) has been used for the said purpose. Once optimized, the NN and FL-based models will be able to provide optimal machining parameters online. The developed approaches are found to solve the above problem effectively, and the performances of the developed approaches have been compared among themselves and with that of the results of existing literature.

Plastic deformation of materials is a major source of energy dissipation during external loading. In nano-crystalline (NC) materials, local plastic strain may arise even if the overall external load is below the yield stress of the material because of the grain structure. In this paper, the damping capacity of nano-crystalline materials is modeled by considering the grain structure. First, the grains are modeled by using a composite model. The composite model takes each oriented crystal and its immediate boundary to form a pair. Next, the finite element method in conjunction with the composite model is employed to evaluate the energy dissipation of nano-crystalline material under cyclic loading. The influence of the grain size and the external loading on the energy dissipation is investigated numerically. Energy dissipation in each of the two parts (i.e. grain and grain boundary) is also calculated as an attempt to understand the effect of grain boundary on energy dissipation.

In this paper, a mathematical model for beams with partially delaminated layers is presented to investigate their behavior. In this formulation account is taken of lateral strains. The principal advantage of the element is that it allows the modeling of delamination anywhere in the structure. Numerical results of the present model are presented and its performance is evaluated for static problems.