Journal of Operational Research in its Applications
Year:2006 | Volume:2 | Issue:7|Papers Count:8

Here we study the space pendulums, derive their equations of motion and solve them for different initial conditions. Space pendulum is a model for many physical and engineering problems. For example tower cranes while moving a load can be modeled by a space pendulum. In this article the equations of motion for a tower crane are derived using Lagrangian method. Then the numerical solutions (for the general condition) and the analytic solutions (by simplifying assumptions) are presented. Finally the effect of the radial velocity of pendulum on its maximum deviation from equilibrium is studied.

Nowadays microstrip antennas have found lots of applications in the world of local area networks due to their unique characteristics. They are widely used in the most recent documents of the European Telecommunication Standards Institute (ETSI) such as High Performance Local Area Network (Hiperlan) type 1 and 2. One example of such a usage is to utilize the microstrip antennas as a conformal structure which attaches to the case of a Personal Computer to establish a Point to Point or Point to Multi Point wireless communication between a series of networked computers. In this paper a circular microstrip patch antenna with an omni directional radiation pattern has been proposed which is mainly working on the desired TM01 mode of propagation (with a negligible spurious radiation in the vertical axis). Other specifications of the proposed structure are: operating frequency of 5GHz, 3 to 4 dB Gain and %7.13 of bandwidth according to the Voltage Standing Wave Ratio of less than 2.

Data envelopment analysis (DEA) is a non-parametric technique to measuring the relative efficiency of decision-making units (DMU) that in this technique using of multiple input and multiple outputs is possible. In the DEA model efficiency of (DMU) calculate by making of appropriate linear programming models.In this paper we consider fuzzy DEA (FDEA) based on (1-a) statistical confidence interval and transform it to interval linear programming problem and solve theme's with Noor's method and a solution is present for the solve the problem in over the confidence interval (1-a) of level. We will use the new ranking method discussed in this paper to ordering DMU's. We will give example and solve them.

Data envelopment analysis DEA exactly evaluates the efficiency score by using the mathematical models. As the evaluation has done by mathematical models do not achieve exact results, so many papers have suggested for modification of these models. As we know basic models in such as CCR envelopment model or multiplier model of that construct an efficiency frontier and based on this frontier, efficiency score is evaluated. Basic models in DEA such as CCR -envelopment model or multiplier model construct an efficiency frontier based on observed DMUs and evaluation on each DMU is done by comparing with this frontier. This frontier may be a weak or strong one. The procedure proposed by Zhu, Morita and Chen (2003) maintain the efficient frontier while evaluating each DMU in Fc È NFc .Since this modified method according to SCSC solutions, considers several hypothetical hyper planes as a frontier, it is capable of solving a variety of problems. So it is suggested that, efficiency measure for a DMU or its projection which is located on a weak efficient frontier, can be obtained by bounds that reached by SCSC solutions. It can be done only by solving the problem once. This method have been developed to deal with the number of problems which would be solved and evaluate efficiency score for all observed DMUs same as the procedure proposed by Zhu, Morita and Chen.

In many real application of DEA, the model presented, are designed to obtain an aggregatete efficiency score. However there are situations that the decision making units can be separated into different components in which each component consumes inputs to produce outputs. In this case some of inputs are shared among components. In this paper, we present a DEA-like to determine the aggregate efficiency of decision making units a companying with component measure.

This paper introduces the Qn graphs followed by some properties of these graphs. Next the paper presents an algorithm to draw the networks, the Dm divisions of an integer positive.

Structural properties of CaTiO3 have been calculated by first principles in framework of density functional theory. This is done by solving many body problem Schrodinger equations. Analytical solving of many body problems is very hard than we should use computational methods with the aim of some useful pakage such as WIEN and VASP. In this paper we have calculated band structure and some of electronic properties of CaTiO3. The results are in good agreement with expriment.

This paper discusses the way of selecting the best alternative in a group decision makingenvironment. For this purpose, each decision maker defines the weights vector of the ranks using pairwise comparisons and a mathematical model similar to the one in Data Envelopment Analysis (DEA) is developed. At first, a CCR type model is developed in which decision making units have one input (equal to one) and some outputs .(16 ,17 ,18) Then, some constraints will be added to the model in order to meet the requirements in such a way that it can be applied in a preferential voting system. Finally, some new objective functions will be added to the model in order to apply the majority decision rule. The resulted multi-objective function is converted in to a multi-objective linear programming model from which the optimal solution is obtained. It worth noting that some useful information can be obtained from the above mentioned model.