مجله بین المللی محاسبات و مدل سازی ریاضی
سال چهارم شماره 2 (Spring 2014)

This paper proposes mathematical modeling and analysis of ferrofluid lubricated newly designed slider bearing having convex pad (surface or plate) stator with two porous layers attached to the slider. The problem considers the effect of slip velocity proposed by Sparrow et. al.[1] and modified by Shah et. al.[2] at the film-porous interface. The squeeze velocity V=−which appears when the upper impermeable plate approach to the lower one, is also considered here for study. The magnetic field is assumed to be oblique to the lower plate. From the Reynolds’s equation of the above model, expressions for dimensionless form of pressure and load carrying capacity are obtained. The expression for the dimensionless load carrying capacity is then solved numerically to examine its possible effect on the designed bearing system.

Small Area estimation is a technique used to estimate parameters of subpopulations with small sample sizes. Small area estimation is needed in obtaining information on a small area, such as sub-district or village. Generally, in some cases, small area estimation uses parametric modeling. But in fact, a lot of models have no linear relationship between the small area average and the covariate. This problem requires a non-parametric approach to solve, such as Kernel approach and Local Polynomial Regression (LPR). The purpose of this study is comparing the results of small area estimation using Kernel approach and LPR. Data used in this study are generated by simulation results using R language. Simulation data obtained by generating function m (x) are linear and quadratic pattern. The criteria used to compare the results of the simulation are Absolute Relative Bias (ARB), Mean Square Error (MSE), Generalized Cross Validation (GCV), and risk factors. The simulation results showed: 1) Kernel gives smaller relative bias than LPR does on both linear and quadratic data pattern. The relative bias obtained by Kernel tends to be more stable and consistent than the relative bias resulted by LPR, (2) the Kernel MSE is smaller than the LPR MSE either on linear or quadratic pattern in any combination treatment, (3) the value of GCV and the risk factors in Kernel are smaller than these in LPR in any combination of the simulated data patterns, (4) on non parametric data, for both linear data pattern and quadratic data pattern, Kernel methods provide better estimation compared to LPR.

In many of the studies concerning Accelerated life testing (ALT), the log linear function between life and stress which is just a simple re-parameterization of the original parameter of the life distribution is used to obtain the estimates of original parameters but from the statistical point of view, it is preferable to work with the original parameters instead of developing inferences for the parameters of the log-linear link function. In this paper the geometric process is used to estimate the parameters of Pareto Distribution with type-II censored data in constant stress accelerated life testing. Assuming that the lifetimes under increasing stress levels form a geometric process, estimates of the parameters are obtained by using the maximum likelihood method. In addition, asymptotic confidence interval estimates of the parameters using Fisher information matrix are also obtained. The statistical properties of estimates of the parameters and the confidence intervals are illustrated by a Simulation study.

Play is often episodic and mission-centric, with a series of challenges culminating in a final puzzle or enemy that must be overcome. Multiple missions played with the same characters may be related to each other in a plot arc of escalating challenges. The exact tone, structure, pace and end (if any) vary from game to game depending on the needs and preferences of the players, as in [9]. «THE CHANCE ELEMENT in thousands of indoor games is introduced by a variety of simple random-number generators. The most popular of such devices, ever since the time of ancient Egypt, have been cubical Dice. Cubical, Because of their symmetry, any of the five regular solids can be and have been used as gaming dice, but the cube has certain obvious advantages over the other four solids. It is the easiest to make, its six sides accommodate a set of numbers neither too large nor too small, and it rolls easily enough but not too easily», as in [1], [2]. In our proposed Dice Finder game problem, user can see the different dice number''s on screen from 1 to 6. Using the property of Dice that “Opposite sides of a dice add up to seven”, user has to find that correct number of dice out all of that, for which one condition is true.

A single server finite population queueing model with compulsory server vacation and with fixed batch service has been considered. For this model the system steady state probabilities are obtained. Some performance measures are calculated and numerical examples are also given.

Priority queues have a great importance in the study of computer communication networks in which different types of traffic require different quality of service standards. The discrete-time non-preemptive priority queuing model with priority jumps is proposed in this paper. On the basis of probability generating functions mean system contents and mean queuing delay characteristics are obtained. The effect of jumping mechanism is analysed which clearly shows that the queuing system provides better results when the fraction of class-1 arrivals in the overall traffic mix is small.

In this paper, we consider the step fixed-charge transportation problem (FCTP) in which a step fixed cost, sometimes called a setup cost, is incurred if another related variable assumes a nonzero value. In order to solve the problem, two metaheuristic, a spanning tree-based genetic algorithm (GA) and a spanning tree-based memetic algorithm (MA), are developed for this NP-hard problem. For comparing GA and MA, twenty eight problems with different specifics have been generated at random and then the quality of the proposed algorithms was evaluated using the relative percentage deviation (RPD) method. Finally, based on RPD method, we investigate the impact of increasing the problem size on the performance of our proposed algorithms.