Mathematical and Computational Applications

1320 KiB

Open AccessArticle

Flow Analysis and Determination of Drag Forces for Spikes of Crops

by S. Kırmacı and M. Pakdemirli

Math. Comput. Appl. 2012, 17(1), 83-91; https://doi.org/10.3390/mca17010083 - 01 Apr 2012

Viewed by 1026

In this work, flow analysis and drag forces of spikes of crops are investigated. A control volume is constructed to calculate drag forces and coefficients of spikes of wheats (Triticum durum, Triticum aestivum) for various velocities. In addition, drag forces corresponding to different [...] Read more.

In this work, flow analysis and drag forces of spikes of crops are investigated. A control volume is constructed to calculate drag forces and coefficients of spikes of wheats (Triticum durum, Triticum aestivum) for various velocities. In addition, drag forces corresponding to different orientation angles are determined for spikes of bread wheats. Spikes without awns are drawn using UNIGRAPHICS program in order to computationally analyze the flow. The drawings are inserted into ANSYS ICEM-CFD program and drag forces and coefficients are determined. Full article

364 KiB

Open AccessArticle

Exact Solvability of Stochastic Differential Equations Driven by Finite Activity Levy Processes

by Ismail Iyigunler, Mine Çağlar and Gazanfer Ünal

Math. Comput. Appl. 2012, 17(1), 68-82; https://doi.org/10.3390/mca17010068 - 01 Apr 2012

Cited by 4 | Viewed by 1112

Abstract

We consider linearizing transformations of the one-dimensional nonlinear stochastic differential equations driven by Wiener and compound Poisson processes, namely finite activity Levy processes. We present linearizability criteria and derive the required transformations. We use a stochastic integrating factor method to solve the linearized [...] Read more.

We consider linearizing transformations of the one-dimensional nonlinear stochastic differential equations driven by Wiener and compound Poisson processes, namely finite activity Levy processes. We present linearizability criteria and derive the required transformations. We use a stochastic integrating factor method to solve the linearized equations and provide closed-form solutions. We apply our method to a number ofstochastic differential equations including Cox-Ingersoll-Ross short-term interest rate model, log-mean reverting asset pricing model and geometric Ornstein- Uhlenbeck equation all with additional jump terms. We use their analytical solutions to illustrate the accuracy of the numerical approximations obtained from Euler and Maghsoodi discretization schemes. The means of the solutions are estimated through Monte Carlo method. Full article

260 KiB

Open AccessArticle

On the Stability of Delay Population Dynamics Related with Allee Effects

by O. A. Gumus and H. Kose

Math. Comput. Appl. 2012, 17(1), 56-67; https://doi.org/10.3390/mca17010056 - 01 Apr 2012

Cited by 3 | Viewed by 1044

Abstract

In recent years, many scientists have focus on the studies of the Allee effect in population dynamics. This paper presents the stability analysis of equilibrium points of population dynamics with Allee effect which occurs at low population density. Full article

297 KiB

Open AccessArticle

The Investigation of 130,132Te by IBM-2

by Sait İnan, Nureddin Türkan and İsmail Maraş

Math. Comput. Appl. 2012, 17(1), 48-55; https://doi.org/10.3390/mca17010048 - 01 Apr 2012

Cited by 2 | Viewed by 973

Abstract

In this study, we determined the most appropriate Hamiltonian that is needed for present calculations of nuclei in the A 130 region by interacting boson model. The second version of interacting boson model (IBM-2) has been widely used for describing the quadrupole collective [...] Read more.

In this study, we determined the most appropriate Hamiltonian that is needed for present calculations of nuclei in the A 130 region by interacting boson model. The second version of interacting boson model (IBM-2) has been widely used for describing the quadrupole collective states of the medium heavy nuclei. The proton and neutron variables are distinguished when this version of the model is applied. Because it is important to describe the proton and neutron variables explicitely. Using the best-fitted values of parameters in the Hamiltonian of the IBM-2, we have calculated energy levels and B(E2) values for 130,132Te. The results were compared with the previous experimental and theoretical data and it is observed that they are in good agreement. Some B(E2) values that are still not known so far are stated and the set of parameters used in these calculations is the best approximation that has been carried out so far. It has turned out that the interacting boson approximation (IBA) is fairly reliable for the calculation of spectra in the entire set of such Te isotopes. Full article

86 KiB

Open AccessArticle

Computation Approaches for Parameter Estimation of Weibull Distribution

by Yunn-Kuang Chu and Jau-Chuan Ke

Math. Comput. Appl. 2012, 17(1), 39-47; https://doi.org/10.3390/mca17010039 - 01 Apr 2012

Cited by 23 | Viewed by 1423

Abstract

This paper examines the estimation comparison of two methods for Weibull parameters, one is the maximum likelihood method and the other is the least squares method. A numerical simulation study is carried out to understand performance of the two methods. Based on sample [...] Read more.

This paper examines the estimation comparison of two methods for Weibull parameters, one is the maximum likelihood method and the other is the least squares method. A numerical simulation study is carried out to understand performance of the two methods. Based on sample root mean square errors, we make a comparison between the two computation approaches. We find that the least squares method significantly outperforms the maximum likelihood when the sample size is small. Full article

411 KiB

Open AccessArticle

Bayesian Estimator of a Change Point in the Hazard Function

by Durdu Karasoy

Math. Comput. Appl. 2012, 17(1), 29-38; https://doi.org/10.3390/mca17010029 - 01 Apr 2012

Viewed by 1059

Abstract

This article presents a new approach for obtaining the change point in the hazard function. The proposed approach is developed with the Bayesian estimator. Using a simulation study, mean value and mean square error (MSE) of proposed estimator are obtained and compared with [...] Read more.

This article presents a new approach for obtaining the change point in the hazard function. The proposed approach is developed with the Bayesian estimator. Using a simulation study, mean value and mean square error (MSE) of proposed estimator are obtained and compared with the mean and MSE of traditional estimators. It is showed that the proposed estimator is more efficient than the traditional estimators in many cases. Furthermore, a numerical example is discussed to demonstrate the practice of the proposed estimator. Full article

184 KiB

Open AccessArticle

Application of (G'/G)-Expansion Method to the Compound KdV–Burgers-Type Equations

by Mustafa MIZRAK and Abdulkadir ERTAŞ

Math. Comput. Appl. 2012, 17(1), 18-28; https://doi.org/10.3390/mca17010018 - 01 Apr 2012

Cited by 1 | Viewed by 1160

Abstract

In this Letter, the (G'/G) -expansion method is proposed to seek exact solutions of nonlinear evolution equations. For illustrative examples, we choose the compound KdV-Burgers equation, the compound KdV equation, the KdV-Burgers equation, the mKdV equation. The power of the employed [...] Read more.

In this Letter, the (G'/G) -expansion method is proposed to seek exact solutions of nonlinear evolution equations. For illustrative examples, we choose the compound KdV-Burgers equation, the compound KdV equation, the KdV-Burgers equation, the mKdV equation. The power of the employed method is confirmed. Full article

570 KiB

Open AccessArticle

Population Based Procedural Artificial City Generation Using Beta Distribution

by Baha Sen, Abdullah Çavusoġlu, Haldun Göktas and Nesrin Aydin

Math. Comput. Appl. 2012, 17(1), 9-17; https://doi.org/10.3390/mca17010009 - 01 Apr 2012

Viewed by 1107

Abstract

Artificial city generation on computer graphics platforms introduce several problems from the point of view of the application programmer. Especially in the cases where the product is aimed for virtual reality applications, this becomes more important since the target is achieving city layouts [...] Read more.

Artificial city generation on computer graphics platforms introduce several problems from the point of view of the application programmer. Especially in the cases where the product is aimed for virtual reality applications, this becomes more important since the target is achieving city layouts akin to the real cities. The same is valid for the civil engineers where the layouts of the blocks/cities are determined in advance of the construction. An important parameter for artificial cities is the determination of the population distribution over the cities which in turn affect the overall appearance of the city or the blocks forming it. In this study, the Beta distribution has been used to disperse artificial city populations over the city blocks to generate cities that do not look to regular. The system uses HTF based maps and the produced 3D cities are quite realistic when compared to the similar products. Full article

166 KiB

Open AccessArticle

A Method for Discriminating Efficient Candidates with Ranked Voting Data by Common Weights

by Gholamreza Jahanshahloo, Farhad Hosseinzadeh Lotfi, Masomeh Khanmohammadi and Mansoureh Kazemimanesh

Math. Comput. Appl. 2012, 17(1), 1-8; https://doi.org/10.3390/mca17010001 - 01 Apr 2012

Cited by 7 | Viewed by 1233

Abstract

Ranked voting data arise when voters select and rank more than one candidate with an order of preference. Cook et al.[1] introduced data envelopment analysis (DEA) to analyze ranked voting data. Obata et al.[2] proposed a new method that did not use information [...] Read more.

Ranked voting data arise when voters select and rank more than one candidate with an order of preference. Cook et al.[1] introduced data envelopment analysis (DEA) to analyze ranked voting data. Obata et al.[2] proposed a new method that did not use information obtained from inefficient candidates to discriminate efficient candidates. Liu et al.[3] ranked efficient DMUs on the DEA frontier with common weights. They proposed a methodology to determine one common set of weights for the performance indices of all DMUs. Then, these DMUs were ranked according to the efficiency score weighted by the common set of weights. In this paper, we use one common set of weights for ranked voting data. Full article

Journal Menu

Journal Browser

Math. Comput. Appl., Volume 17, Issue 1 (April 2012) – 9 articles , Pages 1-91

Further Information

Guidelines

MDPI Initiatives

Follow MDPI