Search published articles


Showing 350 results for It

Mojtaba Nowrouzifasih, Anwar Mahmoodi, Reza Maihami,
Volume 0, Issue 0 (10-2024)
Abstract

The demand for green products has increased in the past few years due to the heightened awareness of environmental issues and the increasing use of green products by consumers. Thus, choosing the best strategy for green product manufacturers is essential. At the same time, producers and retailers are likely to have their decisions influenced by government actions. In this study, we attempt to determine the product's price and greenness within two competitive supply chains. The study investigates the pricing of two substitutable and green products in which each supply chain produces a green product. Using Nash and Stackelberg Game models, we determine how supply chains and their members interact. A Nash model involves two competing supply chains with equal power, within each supply chain, however, there is a Stackelberg competition between the retailer and the manufacturer. The Stackelberg model assumes that one of the supply chains is the market leader. The results show that with increasing government intervention (government's adjustment factor and green level floor for subsidies), regardless of Nash or Stackelberg structures, the green level of the product will increase, and wholesale and retail prices will decrease. Additionally, the price changes in the retailer-Stackelberg structure are greater than those in the manufacturer-Stackelberg structure. Also, by bearing the greenness cost by the manufacturer or retailer, companies can positively impact their profits as well as the level of greenness in their products. When the manufacturer makes an investment in greenness, the retailer and consumer benefit from it, and ultimately become the main force behind the development of green products.
 

F.d. Javanroodi , K. M. Nikbin ,
Volume 17, Issue 3 (9-2006)
Abstract

There is an increasing need to assess the service life of components containing defect which operate at high temperature. This paper describes the current fracture mechanics concepts that are employed to predict cracking of engineering materials at high temperatures under static and cyclic loading. The relationship between these concepts and those of high temperature life assessment methods is also discussed. A model for predicting creep crack growth initiation and growth in terms of C* and the creep uniaxial ductility is presented and it is shown that this model gives good agreement with the experimental results. The effects of cyclic loading on crack growth behaviour are considered and fractography evidence is shown to back a simple cumulative damage concept when dealing with creep/fatigue interaction. Finally a discussion is presented which highlights the important aspect of life assessment methodology for high temperature plant.


M. Haghpanahi, H. Pirali ,
Volume 17, Issue 3 (9-2006)
Abstract

Finite element analysis of a tubular T-joint subjected to various loading conditions including pure axial loading, pure in-plane bending (IPB) and different ratios of axial loading to in-plane bending loading has been carried out. This effort has been established to estimate magnitudes of the peak hot spot stresses (HSS) at the brace/chord intersection and to find the corresponding locations as well, since, in reality, offshore tubular structures are subjected to combined loading, and hence fatigue life of these structures is affected by combined loading. Therefore in this paper, at the first step, stress concentration factors (SCFs) for pure axial loading and in-plane bending loading are calculated using different parametric equations and finite element method (FEM). At the next step, the peak HSS distributions around the brace/chord intersection are presented and verified by the results obtained from the API RP2A Code procedure. Also the locations of the peak hot spot stresses which are the critical points in fatigue life assessment have been predicted. 


M. M. Shokrieh, R. Rafiee ,
Volume 17, Issue 3 (9-2006)
Abstract

The main goal of this research is to extract the full mechanical properties of stitch biax and triax composite materials which are necessary for finite element analysis, based on limited available experimental data and without performing full static characterization tests. Utilized experimental data are limited to elastic modulus of two 0o and 45o directions. Using presented technique and aforementioned data, mechanical properties of unidirectional fabrics of biax and triax are obtained and consequently mechanical properties of biax and triax composites are calculated. Evaluation of the results proved proper performance of the technique in this research.


A. Shidfar, Ali Zakeri,
Volume 17, Issue 4 (11-2006)
Abstract

This paper considers a linear one dimensional inverse heat conduction problem with non constant thermal diffusivity and two unknown terms in a heated bar with unit length. By using the WKB method, the heat flux at the end of boundary and initial temperature will be approximated, numerically. By choosing a suitable parameter in WKB method the ill-posedness of solution will be improved. Finally, a numerical example will be presented.


M.r. Alirezaee, S.a Mir-Hassani,
Volume 17, Issue 4 (11-2006)
Abstract

In the evaluation of non-efficient units by Data Envelopment Analysis (DEA) referenced Decision Making Units (DMU’s) have an important role. Unfortunately DMU’s with extra ordinary output can lead to a monopoly in a reference set, the fact called abnormality due to the outliers' data. In this paper, we introduce a DEA model for evaluating DMU’s under this circumstance. The layer model can result in a ranking for DMU’s and obtain an improving strategy leading to a better layer.


M. Kargari, Z. Rezaee, H. Khademi Zare ,
Volume 18, Issue 3 (11-2007)
Abstract

 Abstract : In this paper a meta-heuristic approach has been presented to solve lot-size determination problems in a complex multi-stage production planning problems with production capacity constraint. This type of problems has multiple products with sequential production processes which are manufactured in different periods to meet customer’s demand. By determining the decision variables, machinery production capacity and customer’s demand, an integer linear program with the objective function of minimization of total costs of set-up, inventory and production is achieved. In the first step, the original problem is decomposed to several sub-problems using a heuristic approach based on the limited resource Lagrange multiplier. Thus, each sub-problem can be solved using one of the easier methods. In the second step, through combining the genetic algorithm with one of the neighborhood search techniques, a new approach has been developed for the sub-problems. In the third step, to obtain a better result, resource leveling is performed for the smaller problems using a heuristic algorithm. Using this method, each product’s lot-size is determined through several steps. This paper’s propositions have been studied and verified through considerable empirical experiments.

 


P. Akhavan, M. Fathian, M. Jafari ,
Volume 18, Issue 3 (11-2007)
Abstract

Abstract: Nowadays knowledge is recognized as an important enabler for competitive advantages and many companies are beginning to establish knowledge management systems. Within the last few years many organizations tried to design a suitable knowledge management system and many of them were successful. This paper is to discover critical success factors (CSF) of knowledge management (KM) and their relationships in an effective way. A qualitative case study technique has been used in this paper for data collection and analysis. In this way, grounded theory (GT) research approach has been selected .The collected data are categorized and analyzed through specific stages of GT. A semantic network has been developed by categorized data showing the relationships between the extracted CSFs and finally a theory has been emerged. The semantic network and the emerged theory show the roadmap of success in KM area for the organizations.

 


A. Arefmanesh, M. Najafi, H. Abdi ,
Volume 18, Issue 4 (12-2007)
Abstract

 Abstract : The meshless local Petrov-Galerkin method with unity as the weighting function has been applied to the solution of the Navier-Stokes and energy equations. The Navier-Stokes equations in terms of the stream function and vorticity formulation together with the energy equation are solved for a driven cavity flow for moderate Reynolds numbers using different point distributions. The L2-norm of the error as a function of the size of the control volumes is presented for different cases and the rate of convergence of the method is established. The results of this study show that the proposed method is applicable in solving a variety of non-isothermal fluid flow problems.

  


H. Ahmadian, S. Nazari , H. Jalali ,
Volume 18, Issue 4 (12-2007)
Abstract

Abstract: The governing equations of motion for a drill string considering coupling between axial, lateral and torsional vibrations are obtained using a Lagrangian approach. The result leads to a set of non-linear equations with time varying coefficients. A fully coupled model for axial, lateral, and torsional vibrations of drill strings is presented. The bit/formation interactions are assumed to be related to the following parameters: bit motion, effects of gyroscopic moments, contact with the borehole wall, axial excitation due to bit/formation interactions, and hydrodynamic damping due to the presence of drilling mud. Simulation results show that parametric resonance and whirling may occur simultaneously within the range of operating conditions of drilling. The contact force between collar and borehole wall is calculated and its behavior is investigated. The dynamic behavior is quite complicated and may become non-periodic, suggesting a chaotic behavior.

  


H. Golestanian ,
Volume 18, Issue 4 (12-2007)
Abstract

Abstract: This paper presents the results of experimental determination of fiber bed permeability variation with porosity. Flow measurement experiments were designed to measure fiber mat permeability for fiber beds with various fiber volume fractions. Woven fiberglass, chopped fiberglass, and carbon fiber mats were used as reinforcements. The effects of reinforcement type and porosity on fiber bed permeability were investigated. Fiber mat permeability of woven mats showed large degrees of anisotropy, whereas chopped fiberglass mats had isotropic permeability. In all cases perform permeability increased with fiber bed porosity. Fiber mat permeability of woven carbon was found to be about four times lower than that of woven fiberglass mats at the same porosity. This lower permeability results in longer injection time and higher manufacturing cost for composite parts made with carbon fiber mats. The results of this investigation could be employed in process/product optimization in Resin Transfer Molding (RTM) processes.

 


Mohsen Faizi, Farhang Mozaffar , Mehdi Khakzand,
Volume 18, Issue 6 (7-2007)
Abstract

  In this paper, authors tackle three very important questions that need to be answered if a theory of design is to be constructed. The first is what designers do, Which we attempt to illustrate with the help of case studies and theories of design practice. The second question is what guides designers. Here, authors try to present some of the proposed normative positions about design, to show the similarities and differences between positions and a framework of how they can be categorized. The main (third) question is how the design thinking process can be represented drawing upon on a review of recent studies of design practice and designer's creativity.

  One approach to design thinking is to extract the features of the designers' strategic knowledge, for which comparative studies between expert designers and novices are useful. Also, controlled experimental studies may be adopted in order to understand the nature of the idea generation process.

Finally, the methods of research and representation of design thinking in order to gain a deeper understanding of the designers' creativity are proposed .
Fatemeh Mehdizadeh Saradj,
Volume 18, Issue 6 (7-2007)
Abstract

When a specific building is examined and analysed for its architectural merits, it is the visible, superficial aspects, which are considered, for example: aesthetics, function, spatial relationships, and landscape. One of the most important invisible factors that should be considered in the design process is the safety of buildings against natural hazards, particularly against earthquakes. While the provision of earthquake resistance is accomplished through structural means, the architectural designs and decisions play a major role in determining the seismic performance of a building. In other words, the seismic design is a shared architectural and engineering responsibility, which stems from the physical relationship between architectural forms and structural systems. It is economic to incorporate earthquake resistance in the stage of design than to add it later in the structural calculation or strengthening after completion. In addition, a building with proper earthquake-proof design will be more effective against earthquakes than the one with complementary strengthening. This paper will demonstrate that evidence for this lies in many historical buildings, which have withstood earthquakes throughout the hundreds of years without having been reinforced with special material. The fact is that the master builder or Mimar (traditional architect) of historic buildings was simultaneously designing the architecture as well as choosing the suitable form, proportion, and material for the best structural performance.
Asghar Mohammad Moradi , Mahdi Akhtarkavan,
Volume 18, Issue 6 (7-2007)
Abstract

The present paper will investigate the specific elements of architectural design based on Islamic beliefs, by taking Iranian Architectural values and vernacular climate design methods into consideration. This research will assess the spirit of experimental elements, created by the inhabitants, according to recent scientific findings. The main concentration will be on the physical design of rural areas in hot, arid and sunny regions of Iran in order to have active and healthy environments and to emphasize on transferring all these sustainable values to the future.
R. Farnoosh, B. Zarpak ,
Volume 19, Issue 1 (3-2008)
Abstract

Abstract: Stochastic models such as mixture models, graphical models, Markov random fields and hidden Markov models have key role in probabilistic data analysis. In this paper, we used Gaussian mixture model to the pixels of an image. The parameters of the model were estimated by EM-algorithm.

  In addition pixel labeling corresponded to each pixel of true image was made by Bayes rule. In fact, a new numerically method was introduced for finding the maximum a posterior estimation by using EM-algorithm and Gaussians mixture distribution. In this algorithm, we were made a sequence of priors, posteriors were made and then converged to a posterior probability that is called the reference posterior probability. Maximum a posterior estimated can determine by the reference posterior probability which can make labeled image. This labeled image shows our segmented image with reduced noises. We presented this method in several experiments.


R. Tavakkoli-Moghaddam, M. Aryanezhad, H. Kazemipoor , A. Salehipour ,
Volume 19, Issue 1 (3-2008)
Abstract

Abstract : A tandem automated guided vehicle (AGV) system deals with grouping workstations into some non-overlapping zones , and assigning exactly one AGV to each zone. This paper presents a new non-linear integer mathematical model to group n machines into N loops that minimizes both inter and intra-loop flows simultaneously. Due to computational difficulties of exact methods in solving our proposed model, a threshold accepting (TA) algorithm is proposed. To show its efficiency, a number of instances generated randomly are solved by this proposed TA and then compared with the LINGO solver package employing the branch-and-bound (B/B) method. The related computational results show that our proposed TA dominates the exact algorithm when the size of instances grows.

  


A. Seifoddin, H.a. Salimi , A. Seyed Esfahani ,
Volume 19, Issue 1 (3-2008)
Abstract

Abstract: Innovations, commercialized by new or old established firms, located at the core of industrial renewal process. The innovation concept has suffered transformations, along with the evolution of the models that try to explain and understand the innovation process. The innovative process corresponds to all activities that generate technological changes and the dynamic interaction between them, not necessarily being novelties. Linier model, Chain-Linked Model and National Innovation Systems (NIS) Approach, are three models that have developed for innovation process. Innovation process can be viewed as evolutionary process. One can recognize some mechanism for innovation evolution. These are grouped into two classes those that increase configurations variation and those that decrease it. Emergence of knowledge, knowledge flow and recombination are the mechanism to increase variation of configuration. Internal and external selections are the mechanism to selecting. Innovation operators are evolutionary operators that create new combinations of configuration and increase variation. This paper develops an evolutionary cycle in innovation process and extends evolutionary mechanisms of innovation.

  


M.b Aryanezhad , A. Roghanian ,
Volume 19, Issue 1 (3-2008)
Abstract

Abstract: Bi-level programming, a tool for modeling decentralized decisions, consists of the objective(s) of the leader at its first level and that is of the follower at the second level. Three level programming results when second level is itself a bi-level programming. By extending this idea it is possible to define multi-level programs with any number of levels. Supply chain planning problems are concerned with synchronizing and optimizing multiple activities involved in the enterprise, from the start of the process, such as procurement of the raw materials, through a series of process operations, to the end, such as distribution of the final product to customers.  Enterprise-wide supply chain planning problems naturally exhibit a multi-level decision network structure, where for example, one level may correspond to a local plant control/scheduling/planning problem and another level to a corresponding plant-wide planning/network problem. Such a multi-level decision network structure can be mathematically represented by using “multi-level programming” principles. This paper studies a “bi-level linear multi-objective decision making” model in with “interval” parameters and presents a solution method for solving it this method uses the concepts of tolerance membership function and multi-objective multi-level optimization when all parameters are imprecise and interval .

  


Rahman Farnoosh, Behnam Zarpak,
Volume 19, Issue 1 (3-2008)
Abstract

  Stochastic models such as mixture models, graphical models, Markov random fields and hidden Markov models have key role in probabilistic data analysis. In this paper, we have learned Gaussian mixture model to the pixels of an image. The parameters of the model have estimated by EM-algorithm.

  In addition pixel labeling corresponded to each pixel of true image is made by Bayes rule. In fact, we introduce a new numerically method of finding maximum a posterior estimation by using EM-algorithm and Gaussians mixture distribution. In this algorithm, we have made a sequence of priors, posteriors and they converge to a posterior probability that is called the reference posterior probability. Maximum a posterior estimated can determine by the reference posterior probability that will make labeled image. This labeled image shows our segmented image with reduced noises. We show this method in several experiments.


.a. Seifoddin, M. H. Salimi , M. M. Syed Esfahani,
Volume 19, Issue 1 (3-2008)
Abstract

Innovations, commercialized by new or old established firms, located at the core of industrial renewal process. The innovation concept has suffered transformations, along with the evolution of the models that try to explain and understand the innovation process. The innovative process corresponds to all activities that generate technological changes and the dynamic interaction between them, not necessarily being novelties. Linier model, Chain-Linked Model and National Innovation Systems (NIS) Approach, are three models that have developed for innovation process. Innovation process can be viewed as evolutionary process. One can recognize some mechanism for innovation evolution. These are grouped into two classes those that increase configurations variation and those that decrease it. Emergence of knowledge, knowledge flow and recombination are the mechanism to increase variation of configuration. Internal and external selections are the mechanism to selecting. Innovation operators are evolutionary operators that create new combinations of configuration and increase variation. This paper develops an evolutionary cycle in innovation process and extends evolutionary mechanisms of innovation.



Page 1 from 18    
First
Previous
1
...