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Ahmadi I.,Islamic Azad University at Khorasgan
Turkish Journal of Agriculture and Forestry | Year: 2013

To examine the effects of different geometries and mass specifications of a tractor operating across irregular sloping grounds on the lateral stability of this machine, a dynamic model was developed. In the proposed model, overturn and skid instabilities were studied and the tractor stability indexes were formulated (i.e. TSIoverturn and TSIskid). Using a modified Excel spreadsheet package employing the parameters of the model, the TSIs were then determined. Finally, the effects of variation in the parameters of the model on TSIs were evaluated. The results of the analyses indicate that changing the tractor mass moment of inertias about the x- and y-axes had no influence on TSIskid, whereas increasing the tractor mass moment of inertias about the x-axis by 71% led to a 2.5% reduction of TSIoverturn and increasing the tractor mass moment of inertias about the y-axis by 71% led to a 1.8% reduction of TSIoverturn. However, increasing the wheel-ground coefficient of friction from 0.34 to 0.84 improved TSI by up to 27%. Moreover, the effect of tractor wheel track width and the height of its center of gravity on TSIoverturn was greater than the effect of the tractor wheel base on this stability index. Therefore, the best strategy for stabilizing a tractor against overturn is to lower the tractor's center of gravity and increase the tractor's wheel track width simultaneously. © TÜBİTAK. Source

Eghbalsaied S.,Islamic Azad University at Khorasgan
Tropical Animal Health and Production | Year: 2011

This study was aimed to assess genetic parameters for 13 traits in heifers and first-parity Holstein dairy cows. Data consisted of calving and insemination dates of 14,707 Holstein dairy cows in Isfahan province of Iran. Reproductive traits included age at first service (AFS), first service to conception (FSTC), gestation length (GL), age at first calving (AFC), calving to first service (CTFS), days open (DO), calving interval (CI), number of services per conception (NS), and non-return rate at 56 days (NRR). Model equations were optimized using GLM procedure in SAS package following genetic analysis using animal models in ASREML software. Minimum and maximum departure from normal distribution for phenotypic records belonged to AFS, NRR, GL, DO, CI and AFC, NS, FSTC, CTFS, respectively. Estimated heritability varied from 0.002 (NRR) to 0.184 (GL) in heifers and from 0.003 (NRR) to 0.153 (GL) in first-parity cows. AFS, CTFS, and GL were noticeably heritable compared to other assessed traits. Estimated absolute additive genetic correlations were in the range of 0.01 (NRR and AFS) and 0.99 (NRR and NS) in heifers and 0.07 (GL and CI) to 1 (FSTC and CI) in cows. Additive genetic correlations were antagonistic between AFS and other traits, except AFC. Interestingly, NRR which has been included in sire catalogs had the highest average absolute genetic associations with other traits. © 2010 Springer Science+Business Media B.V. Source

Hadi-Vencheh A.,Islamic Azad University at Khorasgan | Mokhtarian M.N.,Islamic Azad University at Mobarakeh
Expert Systems with Applications | Year: 2011

This paper proposes a new fuzzy MCDM (FMCDM) approach based on centroid of fuzzy numbers for ranking of alternatives. The FMCDM approach allows decision makers (DMs) to evaluate alternatives using linguistic terms such as very high, high, slightly high, medium, slightly low, low, very low or none rather than precise numerical values, allows them to express their opinions independently, and also provides an algorithm to aggregate the assessments of alternatives. Three numerical examples are investigated using the FMCDM approach to illustrate its applications. It is shown that the FMCDM approach offers a flexible, practical and effective way of group decision making. © 2010 Elsevier Ltd. All rights reserved. Source

Hadi-Vencheh A.,Islamic Azad University at Khorasgan | Mohamadghasemi A.,Islamic Azad University
Expert Systems with Applications | Year: 2011

In order to efficiently control the inventory items and determine the suitable ordering policies for them, multi-criteria ABC inventory classification, which is one of the most common techniques of production and inventory control, is used. In this classification, other criteria in addition to annual dollar usage are taken into account and then the items are classified in three classes with different ordering policies, based on their priority. In this paper, we propose an integrated fuzzy analytic hierarchy process-data envelopment analysis (FAHP-DEA) for multiple criteria ABC inventory classification. The proposed FAHP-DEA methodology uses the FAHP to determine the weights of criteria, linguistic terms such as Very High, High, Medium, Low and Very Low to assess each item under each criterion, the data envelopment analysis (DEA) method to determine the values of the linguistic terms, and the simple additive weighting (SAW) method to aggregate item scores under different criteria into an overall score for each item. The integrated FAHP-DEA methodology is illustrated using a real case study. © 2010 Elsevier Ltd. All rights reserved. Source

Hadi-Vencheh A.,Islamic Azad University at Khorasgan
International Journal of Computer Integrated Manufacturing | Year: 2011

Supplier evaluation and selection problem has been studied extensively. Various decision-making approaches have been proposed to tackle the problem. In contemporary supply chain management, the performance of potential suppliers is evaluated against multiple criteria rather than considering a single factor-cost. This article proposes a new weighted nonlinear model to solve the multiple criteria supplier-selection problem. The proposed model not only incorporates multiple criteria for supplier selection but also maintains the effects of weights in the final solution. An illustrative example is presented to compare the proposed model and those in the literature. © 2011 Taylor & Francis. Source

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