سال:1392 | دوره: | شماره: |تعداد مقالات:8

Pollution occurs when the concentration of various chemical or biological constituents exceed a level implying negative impact on amenities, the ecosystem, resources and human health. Oil spills are the serious environmental hazards which often exhibit long-term impacts. The main objective of response to an oil spill is to reduce its impact on nature and human health. This paper allows us to get a comprehensive idea of the oil spill impact in the presence of thermal and concentration buoyancy effects. The governing equations and their associated boundary conditions are first cast into dimensionless form and the resulting equations are then solved analytically using perturbation technique. The effect of various physical parameters such as Grash of number, Prandtl number, Schmidt number and chemical reaction parameter on the velocity, temperature and concentration profile as well as surface skin friction, heat and coefficient of mass transfers are discussed in detail with the help of graphs.

In this paper, a numerical method is developed for solving a linear sixth order boundary value problem (6VBP) by using the hyperbolic uniform spline of order 3 (lower order). There is proved to be first-order convergent. Numerical results confirm the order of convergence predicted by the analysis.

Abstract. This paper analyzes a renewal input working vacations queue with change over times and Bernoulli schedule vacation interruption under (a, c, b) policy. The service and vacation times are exponentially distributed. The server begins service if there are at least c units in the queue and the service takes place in batches with a minimum of size a and a maximum of size b (a⩽c⩽b). The change over periods follow if there are (c-1) customers at vacation completion instant or (a-1) customers at service completion instant. The steady state queue length distributions at arbitrary and pre-arrival epochs are obtained. Performance measures and optimal cost policy are presented with numerical experiences. The genetic algorithm and quadratic fit search method are employed to search the optimal values of some important parameters of the system.

A company or organization requires special unique strategies to achieve organizational goals which not only do bring about macro-and long-term goals, but also create competitive status for the organization. However, developing different strategies will not guarantee the organization’s success, but the implementation of strategy is the most important step in the entire life of strategic management of the organization. The main objective of this study is to provide a classification of environmental barriers in effective implementation of strategies in Asia insurance company. In this research, experts of insurance industry were considered as statistical society, in which the number of managers, senior professionals and experts with more than 3 years of experience in Asia Central Insurance and its branches across Tehran was about 340 which comprised the statistical society of this research. Morgan table was applied for sampling and a number of 181 people were selected as samples to dis- tribute the questionnaires. This study is descriptive-analytical and practical. Data from the questionnaire (the questionnaire study and design of a new questionnaire was prepared with the help of experts) and data analysis software for regression analysis was performed using SPSS 18; in which organization, competitive factors were identified as the most influential environmental factors in implementation of organizational strategies

Abstract. In this paper, we consider the existence of a non-trivial weak solution to a quasi- linear elliptic system involving critical Hardy exponents. The main issue of the paper is to understand the behavior of these Palais-Smale sequences. Indeed, the principal difficulty here is that there is an asymptotic competition between the energy functional carried by the critical nonlinearities. Then by the variational method, we obtain the existence non-trivial week solution for the system.

Abstract. In this paper, we introduce a hybrid approach based on modified neural networks and optimization teqnique to solve ordinary differential equation. Using modified neural net- work makes that training points should be selected over the  open interval (a, b) without training the network in the range of first and end points. Therefore, the calculating volume involving computational error is reduced. In fact, the training points depending on the distance [a, b] selected for training neural networks are converted to similar points in the open interval (a, b) by using a new approach, then the network is trained in these similar areas. In comparison with existing similar neural networks proposed model provides solutions with high accuracy. Numerical examples with simulation results illustrate the effectiveness of the proposed model.

In this paper, we introduce a hybrid approach based on modified neural networks and optimization teqnique to solve ordinary differential equation. Using modified neural net- work makes that training points should be selected over the open interval (a, b) without training the network in the range of first and end points. Therefore, the calculating volume involving computational error is reduced. In fact, the training points depending on the distance [a, b] selected for training neural networks are converted to similar points in the open interval (a, b) by using a new approach, then the network is trained in these similar areas. In comparison with existing similar neural networks proposed model provides solutions with high accuracy. Numerical examples with simulation results illustrate the effectiveness of the proposed model.

Abstract. In this paper, we show that a matrix A∈Mn (C) that has n coneigenvectors, where coneigenvalues associated with them are distinct, is condiagonalizable. And also show that if all coneigenvalues of conjugate-normal matrix A be real, then it is symmetric.