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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. Source

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. Source

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. Source

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. Source

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. Source

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