Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Scientific Information Database (SID) - Trusted Source for Research and Academic Resources
Title: 
Author(s): 

Issue Info: 
  • Year: 

    0
  • Volume: 

    20
  • Issue: 

    78/2 (ویژه نامه ریاضی)
  • Pages: 

    -
Measures: 
  • Citations: 

    0
  • Views: 

    1536
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Title: 
Author(s): 

Issue Info: 
  • Year: 

    0
  • Volume: 

    20
  • Issue: 

    78/2 (ویژه نامه ریاضی)
  • Pages: 

    -
Measures: 
  • Citations: 

    0
  • Views: 

    1214
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 1214

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Title: 
Author(s): 

Issue Info: 
  • Year: 

    0
  • Volume: 

    20
  • Issue: 

    78/2 (ویژه نامه ریاضی)
  • Pages: 

    -
Measures: 
  • Citations: 

    0
  • Views: 

    1641
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

View 1641

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    1-8
Measures: 
  • Citations: 

    1
  • Views: 

    1713
  • Downloads: 

    0
Abstract: 

Introduction: In most survival studies for parametric analysis of data is used the weibull model because it is flexibility. In most cases for weibull model is assumed that the shape parameter is constant, although this assumption for some of the data is wrong.Aim: In this study, we present interval censored method for weibull distribution when the shape parameter isn' t constant.Materials and Methods: With simulation of Monte Carlo, we will present advantages of this approach respect to situation that shape parameter is constant. Then in a practical example we would show that how estimates are determined.Results: Estimation of model coefficient, DIC and Hazard ratio were calculated in model with constant and nonconstant shape parameter then were compared. The results indicated that if the shape parameter of distribution isn' t constant. The estimation of covariates coefficients has less bias, more appropriate fit and the results is different respect to shape parameter is constant.Conclusion: Based on the results is better than the saturated model is selected in such a way that does not assume constant shape parameter to be fixed parameter used as the test model, using appropriate criteria to select fit model.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    9-20
Measures: 
  • Citations: 

    0
  • Views: 

    1222
  • Downloads: 

    0
Abstract: 

Introduction: In recent years, the use of copula function for modeling multivariate survival data has been drastically increased. One of multivarite survival data is competing risk data.Aim: The purpose of this study is to introduce bayesian analysis of competing risk data using possitive stable copula function. At the end we used the proposed model on the Diethylstilbestrol clinical trial data. In this clinical trial 506 prostate cancer patients were treated using different dosage of Diethylstilbestrol drug.Materials and Methods: After constructing likelihood function using copula, by choosing appropriate prior distribution for parameters, we obtain the posterior distribution of parameters using the Metropolis-Hastings algorithms and Slice sampling.Result: Fitting bayesian models to the data indicated that the effect of type of treatment on the time of the death from prostate cancer depended on age and weight of the patiens. The results is in line with the clasic methods.Conclustion: The obtained estimation of Tau Kendall correlation coefficien shows less variation in Bayesian model compared with classical model.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    21-28
Measures: 
  • Citations: 

    0
  • Views: 

    917
  • Downloads: 

    0
Abstract: 

Introduction: Suitable definition and realization of functional form of variables is required for a multivariate data analysis where in the number of parameters must be finite. In the study with incomplete data such as survival studies, performing an analysis is constraint to some assumptions, which may be not fulfilling in practical situations. In these cases, artificial neural network (ANN) is recommended which is flexible and distribution free.Aim: This study aim to make a comparison between the predictions of ANN and Weibull regression via a simulation study and based on a real data set example.Material and Method: At first, three random variables was generated from binomial and standardized normal distributions for simulation study. In addition, Weibull survival times were generated based on dependence structure of parameters and independent variables.Afterward, the data was randomly divided into two parts: training and testing data sets.Finally, network performance was assessed by using of least square error of prediction and Bayesian information criterion.Results: Concordance index of ANN and Weibull regression was calculated as 0.812 and 0.785, respectively.Conclusion: The accuracy of ANN prediction was better than that of Weibull prediction.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Author(s): 

YAVARI M.

Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    29-36
Measures: 
  • Citations: 

    0
  • Views: 

    645
  • Downloads: 

    0
Abstract: 

Introduction: The structures as join spaces, generalized permutations and hypervector spacesare investigated.Aim: The aim of this paper is construction of join spaces from generalized permutations and hypervector spaces by usingCorsini’s method.Materials and Methods: In [2], Corsini presented a different method for construction of join spaces from hypergraphs. By using this method and some results about hypervector spaces, Tallini [1], we obtain a lot of examples of join spaces.Results: We define the hyperoperation ∗g on hypervector space (V, +, ο, K) as follows:"x, y ÎV: x *g Y=g(x) Y g(y)where g (x) =o ο x. We show that if V be a strongly right distributive hypervector space, then (V,*g) is a join space and if V be a strongly left distributive hypervector space, then (V,*g) is not a join space.Conclusion: It is shown that the Corsini’s method is a strong way for construction of join spaces.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    37-48
Measures: 
  • Citations: 

    0
  • Views: 

    941
  • Downloads: 

    0
Abstract: 

Introduction: The main problem is determining of utility function to solve Multi Objective Programming (MOP) problem using Genetic Algorithm (GA), and it is used to select and introduce the best population to the objective functions space.Aim: In this paper using Data Envelopment Analysis (DEA) a linear method is proposed to rank extreme and non-extreme efficient Decision Making Units (DMU). In any step of Genetic Algorithm (GA) we use the proposed ranking method to select the best population. This leads to improve GA as a method to solve Multi Objective Programming (MOP). Using numerical examples the proposed ranking method and the modified GA are verified.Material and Method: In order to introduce the proposed method to rank extreme and non-extreme efficient DMUs and modify GA we have used new linear DEA models.Results: To project a particular member to efficient frontier in an example using Arakawa et al. (1998) and Yun et al. (2001) methods at least 20-30 iterations are needed, while using proposed method only one iteration is needed.Conclusion: The proposed method not only reduces the number of GA iterations but also against of the other methods it can be used to solve MOP problems with greater than three objective functions.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    49-60
Measures: 
  • Citations: 

    0
  • Views: 

    1544
  • Downloads: 

    0
Abstract: 

Introduction: Residue Number System is a non-weighted numerical system that parallel computing and high speed, secure and support low power arithmetic. Including system speed and reduce power consumption along with appropriate security. Here the optimum use of techniques discussed in besides increasing the speed and power consumption can be reduced to an extent to identify and correct the error achieved Aim: Optimization system through a combination of numbers has stayed with other numerical systems is possible. Including its systems, the system can be two numbers have stayed level, numbers have stayed One-Hot system and a system extension numbers remain cited. Combining the numerical systems together with a system approach in defining the optimum system will have the numbers have stayed. Numbers have stayed multilevel system advantages such as simplicity in the choice and range of display module series is great.System remained a number of advantages including One-Hot implementation One-Hot circuits, very fast computation speed and layout is very simple and regular. System of numbers needed to create a security redundant is used. Combining these systems together and create numerical numbers stayed two-level system can One-Hot redundant advantages of all three systems can be used together.Results: The first and most important numbers in the system remains complex measure is selected. Using a two-level residue number system quickly became close to this goal because the layers of the system features large dynamic range is easier. Because these system Numbers needed a hot tub in order to implement the type of calculation speed is increase thus reduces delays. Even in the field of system security numbers due to having been an extension module allowing additional system allows a higher security work.Discution: Numbers have stayed One-Hot system suitable for smaller modules, but due to growth in transistor count circuit's ability account for the major modules of the system cannot be practically used. On the other hand stayed in the two-level system of numbers, arithmetic operations are performed in the second level other words, arithmetic operations on small modules is done. Also benefit from the error detection and correction system using the numbers we needed an extension.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    76-82
Measures: 
  • Citations: 

    0
  • Views: 

    1658
  • Downloads: 

    225
Abstract: 

Introduction: Let G be a simple undirected graph over the vertex set V. Let I(G) denotes the edge ideal of G and DG be the simplicial complex whose faces correspond to the independent sets of G. This simplicial complex reflects many nice properties of G. A simplicial complex D is called shellable if the facets can given a linear order F1,…,Ft such that for all 1£t<f£s, there exists some vÎF1\Ft and some LÎ{1,…,f-1} with F1\Ft={v}. A result due to Hochster says that every pure shellable complex is Cohen-Macaulay over every field. A graph is called shellable, if the simplicial complex DG is a shellable simplicial complex.Aim: In this paper we focus on the question of what graphs G have the property that `G is Cohen-Macaulay, i.e. R/I(`G) is Cohen-Macaulay. We prove that the complement of a connected triangle-free graph is pure shellable and consequently Cohen-Macaulay.Methods: By providing an explicit shelling for the facets of D`G, whenever G is a connected triangle-free graph, we show `G, the complement of G, is pure shellable and consequently Cohen-Macaulay.Conclusion: The complement of any connected bipartite graph and any cycle is pure shellable and hence Cohen-Macaulay.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Author(s): 

MIRZAEE F. | LATIFI L.

Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    83-88
Measures: 
  • Citations: 

    0
  • Views: 

    2957
  • Downloads: 

    623
Abstract: 

Introduction: The theory and application of linear and nonlinear delay differential equations is an important subject within physics and applied mathematics.There are several numerical approaches for solving linear and nonlinear delay differential equations.Aim: In this paper, differential transform method (DTM) is applied to numerical solution of linear and nonlinear delay differential equations.Materials and Methods: In this work, we presented simple proofs of the differential transform Theorems and then we applied them to solving linear and nonlinear delay differential equations.Results: Numerical results compared to exact solutions are reported and it is shown that DTM is a reliable tool for the solution of delay differential equations.Conclusion: The present method reduces the computational difficulties of the other traditional methods and all the calculations can be made simple manipulations. Several examples were tested by applying the DTM and the results have shown remarkable performance.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    89-100
Measures: 
  • Citations: 

    1
  • Views: 

    2635
  • Downloads: 

    184
Abstract: 

Introduction: Orlicz and Birnbaum considered spaces of functions with growth properties different from the power type growth control, provided by the Lp -norm. This generalization found many applications in differential and integral equations with kernels of non-power types. A more abstract approach was given by Nakano in connection with the theory of order spaces. His point of view was generalized by Musielak and Orlicz (1950) who defined what is now commonly known as modular spaces.Aim: Banach's fixed point theorem is the first and famous fact in the fixed point theory. As an application, one can constructive a solution of an ordinary differential equations. The propose of this paper is to establish some analogues of Banach’s fixed point theorem for contractive mappings and mention an application in modular spaces.Material and Method: the existence of a fixed point for mappings satisfying a contractive condition of integral type in modular spaces is studied. Moreover, we extend the contractive conditions of integral type to solve an integral equation in Musielak-Orlicz space. Our method is based on constructing a contractive operator of integral type in such way, it has a fixed point. This fixed point can be considered as a solution of the integral equation.Results: Some fixed point theorems in modular spaces are presented. Moreover, as an application of these theorems, the existence of a solution of an integral equation in Musielak-Orlicz space, is proved.Conclusion: one can consider an integral equation in the modular spaces and can find a solution of it. This shows that one can solve integral equations in a space where members has growth properties different from the power type growth control, provided by the Lp -norm.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    101-108
Measures: 
  • Citations: 

    0
  • Views: 

    988
  • Downloads: 

    137
Abstract: 

Introduction: In the evaluation of Decision Making Units (DMUs) using Data Envelopment Analysis (DEA) models, more than one DMU may be identified as efficient. So ranking them is necessary for Decision Makers (DM). One of the main problems in ranking DMUs, by using Data Envelopment Analysis, is the ranking of non-extreme efficient DMUs. Most of the existing methods can only rank extreme DMUs.Aim: In this paper, we propose a method to rank non-extreme DMUs in Tv.Materials and Methods: We rank non-extreme DMUs by finding a positive convex combination (with the best score) of extreme efficient DMUs located on the minimum face containing the non-extreme DMU.Results: Our proposed method can rank all efficient DMUs in 3 steps: at first, extreme and non-extreme efficient DMUs must be identified (It can be done by AP model). Ranking related score for each extreme DMU can be attained by one of the existing ranking methods that can rank extreme DMUs. Then for obtaining ranking related score for non-extreme DMU, we consider the face with minimum dimension, containing the non-extreme DMU. At last, by solving a model or its dual, and based on the ranking related scores of extreme efficient DMUs located on the minimum face containing the non-extreme DMU, a ranking related score for non-extreme DMUs can be obtained.Conclusion: Although, we rarely have got observed non-extreme efficient DMUs, we must theoretically be able to rank them, because, all virtual efficient DMUs are almost non-extreme. Our method can rank non-extreme efficient DMUs as same as extreme efficient DMUs.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Author(s): 

ABBASBANDY S. | HAJJARI T.

Issue Info: 
  • Year: 

    2011
  • Volume: 

    20
  • Issue: 

    78/2 (MATHEMATICS ISSUE)
  • Pages: 

    109-117
Measures: 
  • Citations: 

    0
  • Views: 

    2695
  • Downloads: 

    268
Abstract: 

Introduction: In many applications, ranking of fuzzy numbers is an important component of the decision process. Many authors have investigated the use of fuzzy sets in ranking alternatives and they have studied different methods of raking fuzzy sets. Particularly, the ranking of fuzzy numbers. In a paper by Cheng [A new approach for ranking fuzzy numbers by distance method, Fuzzy Sets and Systems 95 (1998) 307-317], a centroid-based distance method was suggested for ranking fuzzy numbers, both normal and non-normal. The method utilizes the Euclidean distances from the origin to the centroid point of each fuzzy numbers to compare and rank the fuzzy numbers. It is found that the mentioned method could not rank fuzzy numbers correctly. For example, it cannot rank fuzzy numbers when they have the same centroid point. Some other researches such as Chu and Tsao' s, Wang and Lee and Deng et al. tried to overcome the shortcoming of the inconsistency of Cheng's method but their methods still have drawback.Aim: In this paper, we want to indicate these problems of Cheng's distance, Chu and Tsao's area and Wang and Lee's revised method and then we will propose an improvement method, which can avoid these problems for ranking fuzzy numbers.Materials and Methods: In point of our view, every fuzzy number may lead to zero, positive or negative real number. To overcome with this subject, we first introduce the sign function. By connecting the sign function, corrected centroid point formulas and Cheng’s distance method, the improvement method will be presented.Results: The proposed method includes all situations of fuzzy numbers to rank them correctly. Therefore, it improves the distance method of Cheng as well.Conclusion: In order to overcomes the shortcoming in Cheng's distance method, Chu and Tsao's formulae and new revised method by Wang and Lee, a sign function was introduced and composed an improvement strategy of Cheng’s distance. In this work those method are considered, which utilized the centroid points. The improved method can effectively rank various fuzzy numbers and their images. Thus, the method is superior to Cheng' distance, Chu and Tsao's area and Wang and Lee's revised method.

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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