Effect of Interdependency among Supplier Selection Criteria on Supplier Selection in the Automotive Industry

Most organizations prefer to outsource their activities which are not cost-efficient. The proper supplier selection requires all criteria to be clearly identified and investigated. Previous studies indicate that interdependencies exist among the criteria of supplier selection, and this may have an effect on the rankings of suppliers. In this study, six criteria for supplier selection (Cost, Quality, Delivery Reliability, Flexibility and Responsiveness, Professionalism, and Long-Term Relationship) were identified through literature and the interdependencies among them were investigated. A questionnaire was developed to identify weights for the criteria and sub-criteria of supplier selection and to identify the interdependencies among them. One set of this questionnaire was sent to three companies (two in Malaysia and one in Iran) related to automotive industry. Five expert decision makers in each Malaysian company answered the questionnaire and six in Iran. The supplier selection evaluation was done under two conditions, with and without considering interdependencies. An Analytic Hierarchy Process (AHP) method was used when the criteria were assumed independent. For interdependencies, Analytic Network Process (ANP) and a hybrid Modified TOPSIS (Technique for Order Performance by Similarity to Ideal Solution) were used. A trial version of Super Decisions 1.6.0 software was used to develop all the three methods. The optimal ordering quantity was then determined by means of a multi-objective decision making (MODM) technique named Preemptive Goal Programming (PGP) aimed to maximize the Total Value of Purchasing (TVP) and to minimize the Total Cost of Purchasing (TCP) using a trial version of Win QSB 1.0 as a linear programming software. Findings from the model show that by considering the interdependencies, the optimal ordering quantities have been changed. Based on this fact, in all three companies the hybrid Modified TOPSIS is more effective than ANP and AHP methods. The results for PROTON show that the hybrid Modified TOPSIS had the optimal TVP of 2,542 units, while the values for AHP and ANP were 1,609 and 1,515 units respectively. However, all three methods present the TCP value of 306,575 US Dollars. This trend was also seen in the other two companies. The results showed that interdependencies existed among the criteria and they influence the decision of supplier selection. The study was conducted for one particular product. Similar methods can be used to identify the best supplier selection with other products and other manufacturing industries

Fabrication and Characterization of Dextrin-g-Polypyrrole/Graphene Oxide Nanocomposite for Effective Removal of Pb (II) and Methylene Blue Dye from Aqueous Solutions

Dextrin-g-polypyrrole/graphene oxides (PDGP/GO) nanocomposite was synthesized using in-situ polymerization and direct blending of PDGP and graphene oxide nanoparticles. The products were named nanocomposite 1 and nanocomposite 2, respectively. The prepared nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy. Surface morphology and structure of nanocomposites were investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The performance of the synthesized nanocomposites in removing Pb (II) and methylene blue dye from aqueous solutions was evaluated. The effect of pH, adsorbent dosage, contact time and contaminant concentration on Pb (II) and methylene blue uptake capacity was studied. On the other hand, the percentage removal of Pb (II) metal ion by nanocomposite 2 (96%) was higher than that of nanocomposite 1 (88%). The optimum condition for effective removal of methylene blue dye by nanocomposite 1 (94%) and nanocomposite 2 (98%) could be obtained at pH 8, nanocomposite dosage of 100 mg, contact time of 60 min and methylene blue concentration of 80 mg/L. Langmuir and Freundlich isotherm models, pseudo-first-order and pseudo-second-order kinetics equations and thermodynamic models were used to determine the mechanism of Pb (II) and methylene blue adsorption on the nanocomposite 2.  The results showed that the Langmuir isotherm, pseudo-first-order kinetic and spontaneous adsorption were suitable models for Pb (II) sorption on nanocomposite 2, while the Freundlich isotherm, pseudo-second-order kinetic and spontaneous adsorption were suitable models for methylene blue dye removal. Therefore, the PDGP/GO nanocomposite prepared by direct blending could be considered as a promising adsorbent for Pb (II) and methylene blue removal from aqueous solutions

Investigating the Patterns of Attention Performance in Children With Mathematical Learning Disorder, With Using “Test of Everyday Attention for Children”

Objective Mathematical learning disorder is a type of neurodevelopmental disorder detected by three types of working memory deficits, procedural and visual-spatial problems. The limited capacity of attention and a lot of environmental stimuli have encountered children with learning disorders with the problems. Since attention is one of the most important cognitive functions in the development of mathematics learning, it is important to recognize and evaluate a variety of attention deficits in this group of disorders. Therefore, considering to the three-factor model of Manly, based on sustained attention, selective attention, and control attention, in this study difference of patterns of attention in children with mathematical learning disorder using &ldquo;Test of Everyday Attention for Children&rdquo; was investigated. Materials & Methods The present study was a descriptive-analytic study in a community of students aged 7-11 years with a learning disorder in Tehran, Iran. The selection was based on the early diagnosis of learning disorder with psychiatric and the standard intelligence scores of the Wechsler test in the academic records. Accordingly, 17 male and female students aged 7-11 years with the mathematical disorder were selected from five public learning centers in Tehran and 17 normal children were matched in age and gender. Initially, the demographic information questionnaire was completed by families. Then A version of &ldquo;Test of everyday attention for children&rdquo; was taken by the researcher during the standard period in the calming room. Accordingly, two groups with a mathematical learning disorder and normal peers were compared in three domains of sustained attention, selective, control in &ldquo;Test of Everyday Attention for Children.&rdquo; Results The results of the Shapiro-Wilk test indicated that the distribution of values of all variables, except &ldquo;sky search dual task&rdquo; (sustained attention) and the speed of &ldquo;creatures counting&rdquo; (control attention), have a normal distribution in the learning disorder group (P>0.05). While the values of variables such as &ldquo;Score&rdquo; (sustained attention), &ldquo;Opposite worlds&rdquo;, accuracy of &ldquo;creatures counting&rdquo; (control attention), and &ldquo;walk don&rsquo;t walk&rdquo;(sustained attention) do not follow a normal distribution in the control group (P<0.05). In sustained attention and control attention domains, the results of the nonparametric tests indicated that have a significant difference in two groups in the subtests of &ldquo;Score&rdquo;, &ldquo;walk don&rsquo;t walk&rdquo;, &ldquo;sky search dual task&rdquo;, &ldquo;creatures counting&rdquo; and &quot;opposite worlds.&quot; Homogeneity of variances with the Leven test, reports that equality of variances. Accordingly, the results of independent t-test indicated that children with mathematical learning disorder were worse than the control group in the &quot;Code Transition&quot; and &ldquo;Score Dual Task&quot; subtests. In the domain of selective attention, the results of independent t-test indicated that significant difference in the subtests of &quot;map mission&quot; and the speed and accuracy of &quot;sky search&quot; in the two groups. Therefore, all domains of sustained and control attention (P<0.001) and selective attention (P<0.05) were significantly different in the two groups. Conclusion The results demonstrate that children with mathematical learning disorders were significantly worse than their normal peers in all three domains. Findings indicated that &ldquo;Test of Everyday Attention for Children&rdquo; has the potential to evaluate the attention deficits in mathematical learning disorder as compared with normal peers. Therefore, it can be an appropriate tool for the evaluation in this group