International Journal of Modeling, Simulation, and Scientific Computing

One topology widely known for use in high-voltage high-power converter in medical equipment is the Series Loaded Resonant (SLR) converter. As the power level required by medical equipment increases, there is a need to parallel the SLR converter for improved efficiency and performance. This paper presents the development of a circuit model for paralleled SLR converter to aid circuit designers evaluate circuit performance before the actual hardware is implemented. Each section of the circuit is modeled individually using sinusoidal approximation and circuit network methods. The derived model is then extended to include the parallel connection of the converter. The validity of the model is then tested by using computer simulation and hardware setup to demonstrate the converter's switching waveforms, output voltage and efficiency. Results from both simulation and hardware show good agreement, which demonstrate the validity of the derived model and its usefulness in the initial design of the converter.

The object of this paper is to propose a model to simulate steady and unsteady cavitating flows. In the engineering practice, cavitation flow is often modeled as a single-phase flow (mixture), where the cavitation area is handled as an area with the pressure lower than the vapor pressure. This approach always leads to the result, and the requirement of computer time is many times lower in comparison with multiphase flow models. The Reynolds-averaged Navier–Stokes equations are solved for the mixture of liquid and vapor, which is considered as a single-phase with variable density. The vaporization and condensation processes are controlled by barocline low. A transport equation with source terms is implanted in the code Computational Fluid Dynamics (CFD) to compute the volume fraction of the vapor. The CFD code used is ANSYS CFX. The influence of numerical and the physical parameters are presented. The numerical results are compared to previous experimental measures. For steady flow, a SST turbulence model is adopted and LES for the unsteady flow.

Computational grids have the potential for solving large-scale scientific applications using heterogeneous and geographically distributed resources. In addition to the challenges of managing and scheduling these applications, reliability challenges arise because of the unreliable nature of grid infrastructure. Two major problems that are critical to the effective utilization of computational resources are efficient scheduling of jobs and providing fault tolerance in a reliable manner. This paper addresses these problems by combining the checkpoint replication based fault tolerance mechanism with minimum total time to release (MTTR) job scheduling algorithm. TTR includes the service time of the job, waiting time in the queue, transfer of input and output data to and from the resource. The MTTR algorithm minimizes the response time by selecting a computational resource based on job requirements, job characteristics, and hardware features of the resources. The fault tolerance mechanism used here sets the job checkpoints based on the resource failure rate. If resource failure occurs, the job is restarted from its last successful state using a checkpoint file from another grid resource. Globus ToolKit is used as the grid middleware to set up a grid environment and evaluate the performance of the proposed approach. The monitoring tools Ganglia and Network Weather Service are used to gather hardware and network details, respectively. The experimental results demonstrate that, the proposed approach effectively schedule the grid jobs with fault-tolerant way thereby reduces TTR of the jobs submitted in the grid. Also, it increases the percentage of jobs completed within specified deadline and making the grid trustworthy.

In the present work, an efficient partial domain, intrinsic, enriched element-free Galerkin criterion has been extended to simulate the cracks lying in nonconvex domains. According to this criterion, only a part of the domain near the crack tip has been enriched. A linear ramp function has been used to avoid the sudden truncation of the enrichment effect. Some cases of cracks lying in convex as well as in nonconvex domains have been solved by both full and partial domain enrichment criteria under plane stress conditions. For the cracks lying in convex domain, the results obtained by full domain enrichment criterion are found in good agreement with those obtained by partial domain enrichment criterion, whereas for cracks lying in nonconvex domain, the results obtained by full domain enrichment criterion are found to be misleading. The partial domain enrichment not only accurately simulates the cracks in nonconvex domains but also reduces the computational cost of the method.

Water impact is one of the most critical phenomena from the viewpoint of the structural design of ships and offshore structures. The impact force can impose a large load with high local pressure on the body surface. On the other hand, determination of the maximum impact force during impact and acting point itself is very important in the design of floats.

In this paper, the water entry of a two-dimensional wedge section is considered. This study is carried out in the framework of a potential-flow assumption. In particular, water impact on a dropping wedge with a constant velocity is pursued analytically by using the Schwartz–Christoffel conformal mapping. In order to determine a position of the wedge where the instantaneous effective force is largest during the impact, a particular equation is introduced here for the first time. The pressure distribution and maximum impact force are also calculated. The obtained results are compared against other numerical and experimental works and favorable agreement is displayed.

In this paper, a very efficient and easy-to-use successive linearization approach for solving nonlinear differential equations is proposed. The implementation of the method is demonstrated by solving three nonlinear differential equations of different complexities arising in heat transfer. New closed form explicit analytic solutions of some of the governing nonlinear equations are obtained and compared with the results of the proposed method and with numerical solutions from the MATLAB in-built routine bvp4c.

Most control strategies for networked control systems (NCS) assume that system model is known "a priori" which is, however, impractical in many industrial applications. To obtain the model of First Order Plus Dead Time type plant for networked control, this paper concentrates on model identification under the networked control environment. Ideal-relay feedback-based networked identification scheme is proposed here along with the new packet-based real-time queuing protocol to identify the plant's critical parameters, which takes into account the effect of nondeterministic factors such as network-induced delay, data packet disordering, and limited data packet loss between the sensor and controller as well as the controller and the actuator. Experimental results show that the proposed networked identification scheme can effectively overcome the impact of various network-induced nondeterministic factors for ideal-relay-based model identification in NCS.