Math. Comput. Appl., Volume 15, Issue 2 (August 2010) – 15 articles , Pages 156-308

In evaluating decision making units (DMU) by using Data Envelopment Analysis (DEA) technique, it happens that more than one unit got efficiency score one. In such a case there should be some criterion for ranking these DMUs. Up to now, all of DEA model could rank only extreme efficient units. In this paper the authors proposed a method for ranking extreme and non extreme efficient units. Full article

The equations of motion and bending of Euler-Bernoulli beam are formulated using the nonlocal elasticity theory for cantilever microtubules (MTs). The method of differential quadrature (DQ) has been used for numerical modeling. The size effect is taken into consideration using the Eringen’s non-local elasticity theory. Frequencies and deflections of MTs are obtained. Numerical results are presented to show the effect of small-scale effect on bending and vibration of MTs. Full article

A method for vibration analysis of proportional asymmetric plan frame buildings is presented in this paper. The whole structure is idealized as an equivalent shear-torsion beam in this method. The governing differential equations of equivalent shear-torsion beam are formulated using continuum approach and posed in the form of simple storey transfer matrix. By using the storey transfer matrices and point transfer matrices which consider the inertial forces, system transfer matrix is obtained. Natural frequencies can be calculated by applying the boundary conditions. The structural properties of building may change in the proposed method. A numerical example has been solved at the end of study by a program written in MATLAB to verify the presented method. The results of this example display the agreement between the proposed method and the other valid method given in literature. Full article

Independent wire rope core (IWRC) is one of the fundamental components of complex wire ropes. It is a complex geometry and constructed by wrapping wire strands over a straight wire strand. The outer wires of the IWRC are double helical shaped feature which can be only modeled using special treatment. The aims of this paper are to introduce a new technique of modeling wire rope with IWRC and to compare numerical results obtained from this model with available results in the literature. Therefore the model generation for a simple straight strand is explained and accuracy of this model is validated. Furthermore this modeling procedure is adapted to whole wire rope structure considering double helical geometry concept. The proposed rope model gives remarkable results by means of wire by wire analysis scheme. This model is found easier and more effective. The results show good agreement with other available results but with a simpler and more practical approach.Independent wire rope core (IWRC) is one of the fundamental components of complex wire ropes. It is a complex geometry and constructed by wrapping wire strands over a straight wire strand. The outer wires of the IWRC are double helical shaped feature which can be only modeled using special treatment. The aims of this paper are to introduce a new technique of modeling wire rope with IWRC and to compare numerical results obtained from this model with available results in the literature. Therefore the model generation for a simple straight strand is explained and accuracy of this model is validated. Furthermore this modeling procedure is adapted to whole wire rope structure considering double helical geometry concept. The proposed rope model gives remarkable results by means of wire by wire analysis scheme. This model is found easier and more effective. The results show good agreement with other available results but with a simpler and more practical approach. Full article

In today’s severely competitive business environment, reducing replenishment costs has become one of the most important objectives for companies. This study deals with the replenishment problem under the condition of permissible delay in payments. To better reflect real-world business situations, we extend the traditional EOQ model by considering the situations of permissible delay in payments and multi-item replenishment. This study presents both single-item and joint multi-item replenishment models, and develop theorems to solve the problems. The objective of the single-item replenishment policy is to determine the optimal replenishment cycle time for each item while minimizing the total cost. The objective of the joint multi-item replenishment policy is to determine a common optimal replenishment cycle time for all items. Using computational analysis, we illustrate the solution procedures and draw conclusions. The results of this study can serve as a reference for business managers or administrators. Full article

Microarray image processing is a technology for viewing and computationally measuring thousands of genes at the same time. Gene expressions provide information about the cell activity in an organism. Observing a substantial change in gene expressions between the cDNA (complementary DNA) microarray experiments of an organism can be a sign of a disease. The goal of this study is to make a fine distinction against the gene expressions in the microarray image processing. For this reason, two clustering methods have been experimented and compared. In this study we have specifically investigated the segmentation step of the microarray image. Other than the segmentation methods used in commercial packages we have used the clustering techniques. We have applied fuzzy c–means and k-means methods and observed the results. Full article

In this study, a relation between generalized level density and standard level density is derived. Using this relation and Bethe formula of Fermi gas model for standart level density we obtained a generalized nuclear level density formula for nucleus. Generalized level densities were calculated for some nuclei in mass region between 20 and 50 for different q values close to 1. Our results explain experimental data better than those of Gilbert-Cameron (GC) and Rohr, which are two of the leading compilations in evaluating nuclear level density. Full article

In this paper, an efficient simulation model for fuzzy logic controlled brushless direct current motor drives using Matlab/Simulink is presented. The brushless direct current (BLDC) motor is efficiently controlled by Fuzzy logic controller (FLC). The control algorithms, fuzzy logic and PID are compared. Also, the dynamic characteristics of the BLDC motor (i.e. speed and torque) and as well as currents and voltages of the inverter components are easily observed and analyzed by using the developed model. Full article

The performance of several Database Management Systems (DBMSs) and Data Stream Management Systems (DSMSs) queries is dominated by the cost of the sorting algorithm. Sorting is an integral component of most database management systems. Stable sorting algorithms play an important role in DBMS queries since such operations requires stable sorting outputs. In this paper, we present a new stable sorting algorithm for internal sorting that scans an unsorted input array of length n and arranges it into m sorted sub-arrays. By using the m-way merge algorithm, the sorted m subarrays will be merged into the final output sorted array. The proposed algorithm keeps the stability of the keys intact. The scanning process requires linear time complexity (O(n)) in the best case, and O(n log m) in the worst case, and the m-way merge process requires O (n log m) time complexity. The proposed algorithm has a time complexity of O (n log m) element comparisons. The performed experimental results have shown that the proposed algorithm outperforms other stable sorting algorithms that are designed for join-based queries. Full article

In this paper Pade Embedded Differential Transformation is proposed for the solution of higher order nonlinear or linear Ordinary Differential Equations (ODE’s). The proposed approach provides a better iterative procedure to find the spectrum of the analytic solutions compared to the classical differential transformation. Illustrative examples are presented to show the preciseness and effectiveness of the proposed method. Full article

This paper outlines a comparison of the couplings of He’s and Adomian’s polynomials with correction functional of variational iteration method (VIM) to investigate a solution of Flierl-Petviashivili (FP) equation which plays a very important role in mathematical physics, engineering and applied sciences. These elegant couplings give rise to two modified versions of VIM which are very efficient in solving initial and boundary value problems of diversified nature. Moreover, we also introduces a new transformation which is required for the conversion of the Flierl-Petviashivili equation to a first order initial value problem and a reliable framework designed to overcome the difficulty of the singular point at x = 0. The proposed modified versions are applied to the reformulated first order initial value problem which gives the solution in terms of transformed variable. The desired series of solution is obtained by making use of the inverse transformation. It is observed that the modification based on He’s polynomials is much easier to implement and is more user friendly. Full article

The stability of asphalt concrete under the effects of freezing and thawing was studied experimentally, and the experimental test results were modelled using fuzzy logic and statistical methods. The stability was investigated experimentally using the Marshall and ultrasound methods. Asphalt core samples 10 cm in diameter were alternately frozen (–20°C for 16 hr) and thawed (16°C for 8 hr) for 5, 10, 15, 20, 25, and 30 cycles to simulate daily winter conditions. The stability of asphalt concrete at the laboratory environment temperature of 17°C was used as a reference. The results showed that the stability of asphalt core samples exposed to freezing and thawing increased, and this increase varied between 22.7% and 19.2% for 5- and 30-day cycles, respectively. By using Fuzzy Logic and statistical methods, prediction models were constituted based on freezing-thawing cycle, bitumen ratio, saturated unit volume weight, volume of voids, air dry unit volume weight to predict the Stability of asphalt concrete which could not be determined with experimental. The experimental results, the fuzzy logic model, and the statistical results showed good correlations. For the stability of asphalt core samples, the correlation coefficient was R² = 0.88 for the fuzzy logic model and R² = 1.0 for the statistical method. Based on the results of this study, it is clear that both the fuzzy logic and statistical methods can be used to model the stability of asphalt concrete under various freezing and thawing conditions. Full article

Adaptive control technique is used to design suitable controllers to synchronize two different coupled chaotic systems with uncertainties. The information signal hidden in chaotic signal is transmitted and then successfully recovered at the receiver once synchronization is achieved. Different chaotic systems with uncertainties are chosen respectively as the transmitter and receiver systems to ensure higher security in communication. Numerical simulation examples verify the effectiveness of the proposed method. Full article

In this paper, we concentrate on the internal blocking problem related to Omega Network which is a type of Multistage Interconnection Networks (MINs). We introduce a new algorithm to alleviate the internal blocking problem, the function of this look-ahead algorithm is to decide which packet to block in case of internal blocking. The performance results indicate that the introduced algorithm decreases the internal blocking problem significantly. Since the computations involved in the introduced algorithm are so little, it can be implemented in real time effectively. Full article

Prediction of traffic-flow in Istanbul has been a great concern for planners of the city. Istanbul as being one of the most crowded cities in the Europe has a rural population of more than 10 million. The related transportation agencies in Istanbul continuously collect data through many ways thanks to improvements in sensor technology and communication systems which allow to more closely monitor the condition of the city transportation system. Since monitoring alone cannot improve the safety or efficiency of the system, those agencies actively inform the drivers continuously through various media including television broadcasts, internet, and electronic display boards on many locations on the roads. Currently, the human expertise is employed to judge traffic-flow on the roads to inform the public. There is no reliance on past data and human experts give opinions only on the present condition without much idea on what will be the likely events in the next hours. Historical events such as school-timings, holidays and other periodic events cannot be utilized for judging the future traffic-flows. This paper makes a preliminary attempt to change scenario by using artificial neural networks (ANNs) to model the past historical data. It aims at the prediction of the traffic volume based on the historical data in each major junction in the city. ANNs have given very encouraging results with the suggested approach explained in the paper. Full article