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Soltanifar M.,Islamic Azad University at Semnan | Hosseinzadeh Lotfi F.,Islamic Azad University at Tehran
Computers and Industrial Engineering | Year: 2011

Making optimal use of available resources has always been of interest to humankind, and different approaches have been used in an attempt to make maximum use of existing resources. Limitations of capital, manpower, energy, etc.; have led managers to seek ways for optimally using such resources. In fact, being informed of the performance of the units under the supervision of a manager is the most important task with regard to making sensible decisions for managing them. Data envelopment analysis (DEA) suggests an appropriate method for evaluating the efficiency of homogeneous units with multiple inputs and multiple outputs. DEA models classify decision making units (DMUs) into efficient and inefficient ones. However, in most cases, managers and researchers are interested in ranking the units and selecting the best DMU. Various scientific models have been proposed by researchers for ranking DMUs. Each of these models has some weakness(es), which makes it difficult to select the appropriate ranking model. This paper presents a method for ranking efficient DMUs by the voting analytic hierarchy process (VAHP). The paper reviews some ranking models in DEA and discusses their strengths and weaknesses. Then, we provide the method for ranking efficient DMUs by VAHP. Finally we give an example to illustrate our approach and then the new method is employed to rank efficient units in a real world problem. © 2010 Published by Elsevier Ltd. All rights reserved.

Soltanifar M.,Islamic Azad University at Semnan | Shahghobadi S.,Islamic Azad University at Tehran
Knowledge-Based Systems | Year: 2014

In most data envelopment analysis (DEA) models, the best performers have the full efficient status denoted by unity (or 100), and, from experience, we know that usually plural decision making units (DMUs) have this efficient status. Discriminating between these efficient DMUs is an interesting subject, and a large number of methods have been proposed for fully ranking both efficient and inefficient DMUs. This paper demonstrates the fact that the rank reversal phenomenon may occur in most DEA ranking methods; however, this study introduces some ranking methods which do not follow the procedure and lack this taint. Numerical examples are provided to clearly illustrate the above mentioned phenomenon in some DEA ranking methods. In fact, certain ranking methods are surveyed in DEA focusing on rank preservation and rank reversal phenomena. © 2014 Elsevier B.V. All rights reserved.

Javadi Y.,Islamic Azad University at Semnan | Najafabadi M.A.,Amirkabir University of Technology
Materials and Design | Year: 2013

This paper presents a comparison of contact and immersion waves used to measure residual stresses. The residual stresses are produced due to a dissimilar welding of stainless steel (304) to carbon steel (A106). Longitudinal critically refracted (LCR) wave propagated by 2. MHz contact and immersion ultrasonic transducers is employed to measure the residual stresses. A Finite Element (FE) model of welding process, which is validated by hole-drilling method, is used to verify the ultrasonic results while an acceptable agreement is achieved. The best agreement is observed in the parent material while the maximum difference is measured in the heat affected zone (HAZ). The results show no considerable difference between using contact and immersion transducers in ultrasonic stress measurement of dissimilar joints. © 2013 Elsevier Ltd.

Jahan A.,Islamic Azad University at Semnan | Edwards K.L.,Aston University
Materials and Design | Year: 2013

The selection of the most appropriate material, or combination of materials, is a demanding intellectual process that takes a lot of time and experience. There are a large number of established and newly developed materials, and their associated materials processes, necessitating the simultaneous consideration of many conflicting criteria. This has highlighted the importance of the developing field of multi-criteria decision-making (MCDM) to the material selection process which is especially useful for high technology market where product differentiation and competitive advantage are often achievable with just small gains in material performance. It is clear that decision-making techniques that address target criteria as well as cost and benefit criteria can help engineering designers make better informed choices of materials. Despite the progress has been made in the ranking of materials for target-based criteria, there is no formalized technique for calculating the weighting dependency when target criteria must be taken into account in material selection problems that usually deals with databases. Therefore, to overcome this shortcoming, the strategy of using dependent weightings is extended in this research. Also, an alternative method is proposed to incorporate the correlation, objective, and subjective weightings effectively when there is uncertainty in the importance of three types of weights. This issue is very important for inexperienced designers. The updated procedure is validated through biomedical applications. The first example demonstrates the importance of dependency weighting in amalgam tooth filling material selection and the second one is a hip joint prosthesis material selection problem, which includes target criteria. Furthermore, a model of continuous improvement in product development is outlined, and it is highlighted that the material selection/development is a permanent and endless task for sustainable and profitable growth. © 2013 Elsevier Ltd.

Jahan A.,Islamic Azad University at Semnan | Edwards K.L.,Aston University
Materials and Design | Year: 2013

The problem with supporting decision-making to help choose materials in engineering design is that it needs different tools in different situations. This is because there is actually a range of values for any property of a given material and there are several methods in multi-attribute decision making (MADM) for ranking of alternatives based on interval data. Recently some MADM methods have been updated for materials selection that address target-based criteria, and validated using biomedical implant design applications. When data are not exact and target-based criteria available, the current methods must be modified to show the correct ranking of materials. Therefore, in this research a new VIKOR method for ranking materials with simultaneous availability of interval data and all types of criteria is presented. Three practical examples of materials selection, including biomedical implants, are presented to demonstrate the extended approach and its validity. It is shown that when there are no target criteria, the new method is the same as the conventional method. © 2013 Elsevier Ltd.

Jahan A.,Islamic Azad University at Semnan | Bahraminasab M.,Islamic Azad University at Semnan | Edwards K.L.,Aston University
Materials and Design | Year: 2012

Ranking and selection of the optimal material is an important stage in the engineering design process. However, most of the methods proposed for ranking in materials selection have tended to focus on cost and benefit criteria, with target values receiving much less attention in spite of their importance in many practical decision-making problems such as selecting materials to best match the properties of human tissue in biomedical engineering applications. In response to this perceived gap, the development of a new normalization technique is considered in this paper that provides an extension of the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method and objective weighting in materials selection. There are four example cases included to validate the accuracy of outcomes from the proposed model. It is believed that the proposed decision-making model is suitable for linking to material databases and has the potential to enhance the efficiency of computer-aided materials selection systems. © 2011 Elsevier Ltd.

Rafiee R.,University of Tehran | Heidarhaei M.,Islamic Azad University at Semnan
Composite Structures | Year: 2012

The main goal of this research is to predict Young's modulus of carbon nanotubes using a full non-linear finite element model. Spring elements are used to simulate molecular interactions in atomic structure of carbon nanotube. All interactions are simulated non-linearly. A parametric study is performed to investigate effects of chirality and diameter on the Young's modulus of single walled carbon nanotubes. Unlike the results of presented linear finite element models, the results of current model imply on independency of Young's modulus from chirality and diameter. Obtained results from this study are in a good agreement with experimental observations and published data. © 2012 Elsevier Ltd.

Kahouei M.,Semnan University of Medical Sciences | Zadeh J.M.,Semnan University of Medical Sciences | Roghani P.S.,Islamic Azad University at Semnan
International Journal of Medical Informatics | Year: 2015

In a developing country like Iran, wasting economic resources has a number of negative consequences. Therefore, it is crucial that problems of introducing new electronic systems be identified and addressed early to avoid failure of the programs. The purpose of this study was to evaluate head nurses' and supervisors' perceptions about the efficiency of the electronic patient record (EPR) system and its impact on nursing management tasks in order to provide useful recommendations. Methods: This descriptive study was performed in teaching hospitals affiliated to Semnan University of Medical Sciences, Iran. An anonymous self-administered questionnaire was developed. Head nurses and supervisors were included in this study. Results: It was found that the EPR system was immature and was not proportionate to the operational level. Moreover, few head nurses and supervisors agreed on the benefits of the EPR system on the performance of their duties such as planning, organizing, budgeting, and coordinating. Conclusion: It is concluded that in addition to the technical improvements, the social and cultural factors should be considered to improve the acceptability of electronic systems through social marketing in the different aspects of nursing management. It is essential that health information technology managers emphasize on training head nurses and supervisors to design technology corresponding to their needs rather than to accept poorly designed technology. © 2015 Elsevier Ireland Ltd.

Rostamiyan Y.,Islamic Azad University at Sari | Hamed Mashhadzadeh A.,Islamic Azad University at Semnan | SalmanKhani A.,K. N. Toosi University of Technology
Materials and Design | Year: 2014

Epoxy resins have tight three-dimensional molecular network structures; because of this reason, these materials are brittle in nature and have pore resistance in front of crack propagation. In the present study, to overcome this issue, the optimized mixture proportions of epoxy-based hybrid nanocomposite with different composition of nano silica as nano reinforcement, high-impact polystyrene as thermoplastic phase and hardener were determined by applying the simplex-centroid mixture design method to achieve the ultimate tensile, flexural, compression and impact strength. Results revealed that the best mixture occurs in 2.67wt.% of HIPS, 4.01wt.% of nano SiO2 and 28phr of hardener. Experimental results indicate that new ternary nanocomposite improved ultimate tensile, compression and impact strength up to 59.5%, 45% and 414% compared to those of the neat epoxy resin respectively, although they did not show enhanced flexural strength. The tensile and flexural elongations at break were improved up to 71% and 83% larger than those of neat epoxy, respectively, but compression strain did not change considerably. Correlation between the morphology of the nanocomposite and its mechanical properties was noted when using the SEM technique. EDX analysis used to indicate homogeneous combination of Silica nano particles in matrix and show solvent evaporated completely under vacuum situation. © 2013 Elsevier Ltd.

Bahraminasab M.,Islamic Azad University at Semnan | Jahan A.,Islamic Azad University at Semnan
Materials and Design | Year: 2011

The increasing trend of total knee replacement (TKR) revision surgery, which is associated with aseptic loosening, makes it a challenging research subject. The concern of loosening can be partially improved by selecting the optimal materials for TKR components. Therefore, this paper considers selection of the best material among the set of alternatives for femoral component of TKR through the multi-criteria decision making approach. The comprehensive VIKOR method was used to select the optimum material, and a systematic technique for sensitivity analysis of weights was introduced to find more reliable results. The obtained ranking order suggested the use of new materials over the existing ones. Porous and dense NiTi shape memory alloys were ranked first and second respectively. © 2011 Elsevier Ltd.

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