Supplier selection using a novel intuitionist fuzzy clustering approach

Supplier selection is a complicated decision-making problem involving multicriteria, alternative and decision makers (DMs). The main purpose of this paper is to demonstrate the use of a clustering-based method to solve a group decision making (GDM) problem and, also to achieve more realistic and homogeneous results. Intuitionistic fuzzy value (IFV) is used to show the decision makers’ preferences and IFN clustering method is utilized to cluster around DM's preferences. Intuitionistic fuzzy weighted geometric (IFWG) is applied to aggregate the obtained clusters. Ranking process is used based on the two indices, score function and accuracy function, to rank the alternatives. Lastly, to demonstrate the efficiency of our proposed method, it is implemented to choose suppliers in a car factory.The strength of the propose approach is considering the group agreement on proposed DMs’ preferences for giving different effect on their judgment. Besides, encountering the qualitative judgment of DMs using IFV concept with score function and the accuracy function for modeling the DMs’ knowledge is the other contribution of this paper.     

Experimental and finite element analysis of EDM process and investigation of material removal rate by response surface methodology

In this study, thermal modeling and finite element simulation of electrical discharge machining (EDM) has been done, taking into account several important aspects such as temperature-dependent material properties, shape and size of the heated zone (Gaussian heat distribution), energy distribution factor, plasma flushing efficiency, and phase change to predict thermal behavior and material removal mechanism in EDM process. Temperature distribution on the cathode has been calculated using ANSYS finite element code, and the effect of EDM parameters on heat distribution along the radius and depth of the workpiece has been obtained. Temperature profiles have been used to calculate theoretical material removal rate (MRR) from the cathode. Theoretically calculated MRRs are compared with the experimental results, making it possible to precisely determine the portion of energy that enters the cathode for AISI H13 tool steel. Also in this paper, the effect of EDM parameters on MRR has been investigated by using the technique of design of experiments and response surface methodology. Finally, a quadratic polynomial regression model has been proposed for MRR, and the accuracy of this model has been checked by means of analysis of residuals.     

Comparison of conventional and spherical reactor for the industrial auto-thermal reforming of methane to maximize synthesis gas and minimize CO2

Auto-thermal reforming (ATR), a combination of exothermic partial oxidation and endothermic steam reforming of methane, is an important process to produce syngas for petrochemical industries. In a commercial ATR unit, tubular fixed bed reactors are typically used. Pressure drop across the tube, high manufacturing costs, and low production capacity are some disadvantages of these reactors. The main propose of this study is to offer an optimized radial flow, spherical packed bed reactor as a promising alternative for overcoming the drawbacks of conventional tubular reactors. In the current research, a one dimensional pseudo-homogeneous model based on mass, energy, and momentum balances is applied to simulate the performance of packed-bed reactors for the production of syngas in both tubular and spherical reactors. In the optimization section, the proposed work explores optimal values of various decision variables that simultaneously maximize outlet molar flow rate of H₂, CO and minimize molar flow rate of CO₂ from novel spherical reactor. The multi-objective model is transformed to a single objective optimization problem by weighted sum method and the single optimum point is found by using genetic algorithm. The optimization results show that the pressure drop in the spherical reactor is negligible in comparison to that of the conventional tubular reactor. Therefore, it is inferred that the spherical reactor can operate with much higher feed flow rate, more catalyst loading, and smaller catalyst particles.     

Effect of the interphase properties on the fracture energy and fatigue behavior of thermoset resins containing spherical fillers

Interphase region in polymer based nanocomposites is a very thin layer that is created between the reinforcing phase and the matrix surface due to reaction forces between the nanoparticles and the matrix. The ability to determine the behavior of the interphase region can facilitate the understanding and prediction of the fracture toughness and fatigue behavior through multiscale modeling. In the present study, by using the fully analytical multiscale hierarchical modeling method, fracture toughness and also fatigue behavior of thermoset resins containing spherical fillers with consideration the influences of the main damage mechanisms and interphase properties (thickness and elastic modulus of the interphase region) were investigated. The novelty of this investigation is that it enables the application of a range of properties to the interphase zone and describes a technique for multiscale modeling based on this interphase zone. The present multiscale approach quantifies the dissipation energy due to main damage mechanisms at the nanoscale and accounts for the emergence of an interphase region as functionally graded (FG) properties surrounding nanofillers. Modeling of FG interphase power-varying properties, the derivation of governing equations, and the evaluation of the findings, all are parts of the achievements of this research. In addition, multiscale analyses have been carried out on fracture energy and fatigue behavior in various fiber volume fractions with and without interphase properties. It was found that the fracture toughness and fatigue behavior are significantly dependent on the interphase elastic properties and thickness. Furthermore, the critical debonding stress and the fracture energy were assessed with various interfacial fracture energy, elastic modulus, and thickness of interphase. Finally, the accuracy of the utilized multiscale approach with consideration of interphase properties was verified by comparing the modeling results with experimental tests on thermoset resins containing spherical fillers.     

Thermal Integration of Sulfuric Acid and Continuous Catalyst Regeneration of Naphtha Reforming Plants

An optimal reactor design is proposed that simultaneously improves the naphtha reforming reactor performance and increases sulfur trioxide production. In this new configuration, the naphtha reforming process as an endothermic reaction is coupled with the oxidation reaction of sulfur dioxide, which is an exothermic reaction. The differential evolution optimization technique is applied to maximize the produced amounts and yields of aromatics and hydrogen. The results obtained with the optimized thermally coupled reactor are compared with those of the conventional and thermally coupled reactors, proving the superiority of the proposed configuration.     

Improving the Mechanical Properties of Poly Methyl Methacrylate Nanocomposites for Dentistry Applications Reinforced with Different Nanoparticles

Properties of poly methyl methacrylate are improved using different nanoparticles for denture applications and the best combination is selected using multi-criteria decision-making methods. For these purposes, poly methyl methacrylate is melt compounded with TiO₂, SiO₂, and Al₂O₃ nanoparticles and then injection molded. The results of mechanical tests revealed that by addition of TiO₂ and SiO₂, the impact strengths of poly methyl methacrylate were increased 229 and 62%, respectively. Also, the results indicated a significant improvement in Young’s modulus and hardness. The implementation of multi-criteria decision-making methods illustrated that TiO₂ nanoparticles are the best candidate for improving the properties of poly methyl methacrylate for dental applications.     

Balancing Scattering Channels: A Panoscopic Approach toward Zero Temperature Coefficient of Resistance Using High‐Entropy Alloys

Designing alloys with an accurate temperature‐independent electrical response over a wide temperature range, specifically a low temperature coefficient of resistance (TCR), remains a big challenge from a material design point of view. More than a century after their discovery, Constantan (Cu–Ni) and Manganin (Cu–Mn–Ni) alloys remain the top choice for strain gauge applications and high‐quality resistors up to 473–573 K. Here, an average TCR is demonstrated that is up to ≈800 times smaller in the temperature range 5–300 K and >800 times smaller than for any of these standard materials over a wide temperature range (5 K < T < 1200 K). This is achieved for selected compositions of Al_xCoCrFeNi high‐entropy alloys (HEAs), for which a strong correlation of the ultralow TCR is established with the underlying microstructure and its local composition. The exceptionally low electron–phonon coupling expected in these HEAs is crucial for developing novel devices, e.g., hot‐electron detectors, high‐Q resonant antennas, and materials in gravitational wave detectors.     

Buckling of a functionally graded coated solid subjected to sliding contact loading

This paper investigates the buckling of a bi-layered material with functionally graded coating including a pre-existing interface crack. In order to investigate this phenomenon which is of particular interest to the tribological community, the stresses due to sliding cylindrical loading were determined. Solutions for stresses are obtained by use of Fourier transform technique. These stress fields under such loading are strongly affected by various parameters such as friction coefficient, indenter tip radius, film thickness, etc. Therefore, to assess the coating strength reliably, the mechanical stress field developed by mixed normal and tangential surface pressure was analyzed by considering the affected parameters. The mechanical properties of the FG coating are assumed to vary exponentially through the thickness. On the basis of stress analysis, a satisfactory framework was developed to study the buckling of FG coatings. An interface crack was assumed to model the actually occurring flaws in such coated systems, and the critical buckling stress was obtained.     

Fatigue life prediction of friction stir spot welds based on cyclic strain range with hardness distribution and finite element analysis

The main aim of the present study is to investigate the fatigue behavior of single friction stir spot welds (FSSW) using strain-based modified Morrow’s damage equation. The correlation between microhardness, cyclic material constants, and mechanical strength of different zones around the FSSW are assumed to be proportional to the base material hardness. Experimental fatigue tests of friction stir spot welded specimens have been carried out using a constant amplitude load control servo-hydraulic fatigue testing machine. ANSYS finite element code has been used to simulate a single tensile shear friction stir spot welded joint, and non-linear elastic-plastic finite element analysis has been employed to obtain the values of local equivalent stress and strain near the notch roots of the joints. The results based on the numerical predictions have been compared with the experimental fatigue test data. It has been shown that the strain-based approach does a very good job for estimating the fatigue life of friction stir spot welded joints.