Showing 21 results for Mashayekh
Volume 0, Issue 0 (Articles accepted at the time of publication 2024)
Abstract
For decades, both researchers and EFL learners have been interested in native-like pronunciation. While extensive research has delved into a variety of pedagogical approaches and the complexity of English phonology, an unanswered question is how high-proficiency EFL learners achieve the elusive goal of native-like pronunciation in spoken English. To this end, this multiple-case study aimed to explore the multifaceted strategies employed by 15 high-proficiency EFL learners who had mastery in pronunciation and were selected using the maximum variation sampling method. Data was gathered through the use of diaries and in-depth semi-structured interviews. The data was analyzed with NVivo software version 10, and two main themes were extracted: teacher-directed (TD) and self-directed (SD) pronunciation learning strategies. Regarding the TD strategies, some participants (46%) acknowledged actively engaging with structured tasks and assignments facilitated by teachers. They highlighted the role of in-class (36%) and out-of-class (64%) activities in their journey to master pronunciation. The SD strategies were reported by about half of the participants (54%) in their quest for pronunciation mastery, which included self-talk (48%), podcast listening (29%), shadowing (12%), and reading aloud (11%). This study contributes valuable insights into relevant literature and offers evidence of the interconnectedness of TD and SD strategies in pronunciation improvement. The findings have several implications for further research or practice about pronunciation mastery.
Volume 2, Issue 1 (Issue 1 (Tome 2)- 2012)
Abstract
Asbads are a type of windmill with vertical axis which are considered as the oldest windmills in the world. These mills have been constructed in pre-Islamic eras in Sistan and southern part of Khorasan. From a long time ago, Sistan has been considered as the Iran’s store of wheat. Climate and appropriate soil along with the water of big Hirmand River have provided an appropriate situation for agricultural farms and particularly for wheat. As said, Sistan had been known as a wheat store of Iran. 120-day wind of Sistan is a natural feature of Sistan region. In this region, in the second half of warm season, when wheat is being harvested, vigorous winds start to blow. All of these characteristics provide the situation for constructing the Asbads which are considered as a great innovative production. In this regard there are different evidences which show that the oldest windmills are built at the east of Iran and in Sistan area. Main building of Asbad includes a two-storey building in which upper storey is usually open-ended. Moreover half of the building which is subjected to the wind is constructed completely open and the other half is completely enclosed. The part which is behind the wind side is also entirely open. Asbads have had an important role in past people’s livelihood and also is a sample of combination of traditional architecture with the needs of ecology which is considered as eco-friendly energy. Regarding to the Asbads’ unique characteristic, functional and esthetics features, recognizing them is of special importance. The concern in this research is to know how many groups traditional windmills or Asbads in Sistan are divided to, where they spread in Iran and what are the different types of them? More of the Asbads of Iran have been located in east and south-east of Iran where valuable winds blow during the whole year. Different types of 120-day winds blow in north of Sistan and south of Khorasan in second half of warm season. Asbads with traditional and domestic style provide opportunity for residents to utilize renewable energies. Different types of Asbads have spread all over “big Sistan” which are constructed differently according to the circumstances and ability of residents. Due to this fact, some of them have simple and rural forms and the others are more complicated. However, their functions are the same but their sizes and their efficiencies are different. Studies show that we can break Asbads down into the three groups such as simple Asbads, cylinder Asbads and corridor ones.
Volume 2, Issue 2 (6-2014)
Abstract
This research conducted in order to prioritize the effective criteria on development of medicinal plants cultivation in North Khorasan Province using Analytical Hierarchy Process (AHP) and Delphi methods. For this purpose, a list of effective factors offered to delphi group. Analysis of delphi process showed that among 23 offered factors 19 factors, had greater impact on development of medicinal plants cultivation. Hierarchy tree was drawn through grouping of 19 factors into four criteria including economic, promotional-educational services, cultural-social and supportive policies factors. The pair wise comparison questionnaires were then distributed among relevant researchers and experts of the province to get their opinions about the priority of criteria and sub- criteria. The questionnaires were analyzed using Expert Choice software. The result revealed that economic criterion with respective weight of 0.406 had the most impact among four criteria affecting the development of medicinal plants cultivation. The supportive policies (respective weight of 0.275), educational-extension services (respective weight of 0.193) and cultural-social factors (respective weight of 0.125) received the maximum towards the minimum priorities, respectively. The results of synthesis process showed that among the 19 factors, the guaranteed purchase and establishing of pilot fields of medicinal plants, farmers' awareness of comparative advantage of medicinal plants, and the development of processing industries had the maximum towards minimum impacts on development of medicinal plants cultivation.
Volume 9, Issue 20 (Supplementary Issue (Tome 42)- 2005)
Abstract
Study of the relationship between two important variables, emotional intelligence and leadership style, has been the main purpose of this research.
The population under study consists of 266 marketing and sales managers from Mashhad food and automobile industries from which a sample of 73 peaple was drawn. Data was collected by means of two questionnaires, including Weisinger’s emotional intelligence questionnair and Barak’s leadership style questionnair.
Face validity and split half method were used to determine the questionnaires validity and reliability respectively. The result of split half reliability for emotional intelligence and leadership style questionnaires was known to be .083 and .079 respectively, which the results of the research revealed that there is a positive and meaningful relation between emotional intelligence and transformational leadership style, and a negative relation between emotional intelligence and transactional leadership style of the population under study.
Volume 12, Issue 4 (fall 2021)
Abstract
Objective: Premature ovarian failure (POF) is one of the most important reproductive diseases in women under 40 years of age, which affects the quality of life and longevity of these people by causing short-term and long-term complications.
The incidence of POF is a chronic process that takes several years to develop. The patient went through stages such as premature ovarian insufficiency (POI) and decreased ovarian reserve (DOR), in the early stages of the disease decreased ovarian function efficiency (POI) and then with further progression of the disease, the patient decreased ovarian reserve and further reduce their performance. As the disease progresses, the person eventually develops premature and complete ovarian failure, or POF studies have shown that many factors, including surgical trauma, autoimmune diseases, certain drugs, vaccines, and genetic factors, play a role. Genetic studies have shown that several genes are involved in the development of this disease. Part of the regulation of the expression of these genes is the responsibility of small genetic factors called miRNAs.
Materials and Methods: In the present study, bioinformatics information of miRNAs involved in this disease was investigated. For this purpose, genetic databases such as UCSC, NCBI, KEGG, MIRBASE, TARGET SCAN, STRING, etc. were used to access the genes involved in this disease, structural and functional communication, messaging pathways and regulatory miRNA.
Results and Conclusion: The results of this study indicate that three factors, miRNA-187, miRNA-33b and miRNA-33a, are very effective in the development and progression of this disease.
Volume 12, Issue 48 (9-2015)
Abstract
Production and export of Doogh as a Iranian fermented national drink have increased. Contamination of Doogh by yeasts and molds is one of the defects that results in spoilage and increasing the waste of the product. Drying and convertion of Doogh to its powder by spray dryer is one of the method for increasing the shelf life and decreasing the volume and the costs of transportation. In this study Doogh samples with fat content ( 0.5% and 1.5%), dry matter without fat and salt (3.5% and 4.5%) and 0.7% salt were first dried in preliminary tests including inlet air temperature ( 100, 150 and 200 oC), liquid feed flow rate (5,10 and 15 mL min˗1 ) and drying air flow rate ( 400, 600 and 800 L h˗). Best condition were adjusted accordingto the best results of solubility test and were conducted to drying the samples. fat content and dry matter had significant effect on physical, chemical and microbial characteristics of Doogh powder. First and forth formula had highest and lowest solubility. The solubility of first and forth formula was 82.11±0.62% at 25 oC and 63.18±0.33% at 15 oC respectively. Increasing the fat content results in decreasing the solubility, increasing the particle size and the rate of viable starter counts.
Volume 13, Issue 3 (11-2013)
Abstract
A novel chemical solution deposition approach is reported for the deposition of nickel catalyst, which is a required step for the growth of carbon nanotubes (CNTs). In this work, after catalyst coating, vertically aligned CNTs have been grown on the silicon oxide and silicon surfaces. The results were studied using field emission scanning electron microscopy (SEM), Raman and X-ray diffraction. This technique has a high selectivity over the size of the catalyst nanoparticles, which results in the simple controlling of the average diameter of grown CNTs in the range of 30 to 150 nm. In addition, this approach leads to a more conformal coating on the surface of the sample in comparison with traditional vacuum-based deposition techniques, enabling the growth of CNTs on highly rough surfaces. The proposed catalyst deposition technique is a fast, inexpensive and simple Nickel catalyst deposition method that can significantly facilitate the growth process of CNTs
Volume 13, Issue 14 (Second Special Issue 2014)
Abstract
In this paper, the process of joining Ti-3Al-2.5V titanium alloy thin sheets by means of micro-plasma arc welding (MPAW) is reported. An experimental set-up was developed using traditional gas tungsten arc welding apparatus and a home-built torch for butt welding of coupon specimens. The specimens were welded under controlled welding parameters, such as voltage, current, travel speed and shielding gas flow rate. An appropriate set of parameters for MPAW process was examined by mechanical properties tests and microstructure characterization. Mechanical tests including tensile test, bending test and micro-hardness evaluation across the weld line generally show that if suitable welding parameters are used, the tensile strength of the welded specimen is well comparable with that of the base metal while its hardness increased at the fusion zone (FZ). The bending test revealed that using appropriate welding parameters, no crack or notch appeared at the welded joint. Fractography, X-ray diffraction and metallograpghy were also performed to study the microstructure evolution. SEM images of the fracture surface presented characteristics of ductile rupture. Studies on microstructure morphology of the specimens at the FZ and HAZ reveal occurrence of phase transformation from high temperature phase to acicular phase
Volume 14, Issue 13 (First Special Issue 2015)
Abstract
In this paper, the Finite Cell Method (FCM) is used to predict the ductile damage and crack evolution in ductile materials under small strains and nonlinear isotropic hardening conditions. In the first step, a fully coupled elastic-plastic-damage model based on modified Lemaitre ductile damage model was developed and implemented into FCM implicit codes. Also the effect of micro-crack closure, which may dramatically decrease the rate of damage growth under compression, was incorporated and its computational implementation was discussed. The FCM is the result of combining the p-version finite element and fictitious domain methods, and has been shown to be effective in solving problems with complicated geometries for which the meshing procedure can be quite expensive. It, therefore, combines fast and simple mesh generation with a high convergence rate inherited from p-FEM. The performance of the FCM and damage model is verified by means of numerical examples and the results were compared with exprimental observation. The results showed that modified Lemaitre damage model can be used as a quick and accurate tool to predict ductile damage and fracture in metal forming processes.
Volume 16, Issue 2 (9-2013)
Abstract
Objective: The prevalence of respiratory allergies, especially those induced by fungi such as Alternaria alternata, has dramatically increased over the past decade. This increase has caused major health problems worldwide. This study aimed to investigate the role of A. alternata in the etiology of allergic asthma, by using the skin prick test and assessment of IgE specific to the fungus in the patient's sera. Methods: This study enrolled 202 patients with allergic asthma, aged 12 to 83 years. Participants included 40.1% males and 59.9% females who were enrolled after recording demographic information. A skin prick test with the whole cellextract of A. alternata was performed on the epidermis of the patients' forearms. Histamine and normal saline were used as positive and negative controls, respectively. Serum levels of IgE specific for A. alternata were measured for all patients using the ImmunoCAP Phadiatop method in which the specific A. alternata allergen cocktail that connected to the solid phase reacted to IgE antibodies in each patient's sera. Data were analyzed by analysis of variance and chi-square tests. Results: Among 202 patients with allergic asthma, 14 (6.93%) had mild asthma, 73 (36.10%) were moderate asthmatics and 115 (56.90%) had severe asthma. In total, 14 (6.93%) patients were positive for both the skin test and IgE specific to A. alternata, 35 (17.33%) had negative specific IgE and positive skin test results, and 36 (17.82%) had a positive specific IgE and negative skin test. A total of 117 (57.92%) patients were negative for both tests. Conclusion: The results of this study showed the presence of IgE specific for A. alternata in 50 of 202 (24.75%) patients diagnosed with allergic asthma. The skin prick test was successfully used as a screening test. The results were further confirmed by solid-phase immunoassay of the IgE specific for A. alternata crude allergenic extract.
Volume 17, Issue 10 (1-2018)
Abstract
One of the main challenges of simulating virtual objects by haptic devices is instability, especially in simulating stiff objects. In this paper, a stability criterion for a haptic device is derived using Lyapunov approach. The haptic device is modeled as a mass and viscous friction, which has to simulate the touching a virtual environment (VE) with specified stiffness and damping. Dynamic equations and state-space equations are derived with assumption of small values of sampling time, time delay and virtual damping. A Lyapunov function is proposed, consisting of summation of kinetic and potential energy of the system, plus two unknown terms. Each one of these two unknown terms is a function of one system states (i.e. position and velocity). These two functions are determined so that, from one side the Lyapunov function be positive definite, and from the other side the stability criterion is reached with putting time derivation of the Lyapunov function negative. The stability condition determined by this method is a linear criterion between maximum permissible virtual stiffness, virtual damping of the VE, physical damping of the haptic device, sampling time and time delay, and is consistent with the results of previous researches with linear methods. The importance of the presented analysis in this paper is that this method can be extended by adding new terms to the Lyapunov function, to remove some limitations and to take into account nonlinear effects. Presented criterion and its results are verified by experiments on KUKA robot.
Volume 18, Issue 1 (may 2018)
Abstract
Large-scale spatial skeletal structures belong to a special kind of 3D structures widely used in exhibition centers, supermarkets, sport stadiums, airports, etc., to cover large surfaces without intermediate columns. Space structures are often categorized as grids, domes and barrel vaults. Double layer grid structures are classical instances of prefabricated space structures and also the most popular forms which are frequently used nowadays.Topology optimization of large-scale skeletal structures has been recognized as one of the most challenging tasks in structural design. In topology optimization of these structures with discrete cross-sectional areas, the performance of meta-heuristic optimization algorithms can be increased if they are combined with continuous-based topology optimization methods. In this article, a hybrid methodology combining evolutionary structural optimization (ESO) and harmony search algorithm (HSA) methods is proposed for topologyoptimization of double layer grid structures subject to vertical load. In the present methodology, which is called ESO-HSA method, the size optimization of double layer grid structures is first performed by the ESO. Then, the outcomes of the ESO are used to improve the HSA. In fact, a sensitivity analysis is carried out using an optimization method (ESO) to determine more important members based on the cross-sectional areas of members. Then, the obtained optimum cross-sectional areas of members are used to enhance the HSA through two modifications. Structural weight is minimized against constraints on the displacements of nodes, internal stresses and element slenderness ratio. In topology optimization of double layer grid structures, the geometry of the structure, support locations and coordinates of nodes are fixed and this structure is assumed as a ground structure. Presence/absence of bottom nodes, and element cross-sectional areas are selected as design variables. In topology optimization of the ground structure, tabulating of nodes is carried out based on structural symmetry: this leads to reduce complexity of design space and nodes are removed in groups of 8, 4 or 1. The presence or absence of each node group is determined by a variable (topology variable) which takes the value of 1 and 0 for the two cases, respectively. The ground structure is assumed to be supported at the perimeter nodes of the bottom grid. Therefore, these supported nodes will not be removed from the ground structure. In order to achieve a practical structure, the existence of nodes in the top grid will not be considered as a variable. This causes the load bearing areas of top layer nodes to remain constant. Also, discrete variables are used to optimize the cross-sectional area of structural members. These variables are selected from pipe sections with specified thickness and outer diameter. Therefore, in topology optimization problem, the number of design variables is the summation of the number of compressive and tensile element types and the number of topology variables. The proposed approach is successfully tested in topology optimization problem of double layer grid structure. In particular, ESO-HSA is very competitive with other metaheuristic methods recently published in literature and can always find the best design overall. Also, it is determined that HSA method can find better answer in the topology optimization of large-scale skeletal structures, in comparison to optimum structures attained by the GSA and ICA.
Volume 18, Issue 7 (11-2018)
Abstract
Recently, the phase field approach has gained popularity as a versatile tool for simulating crack propagation. The purpose of this study is to employ the capabilities of the phase field method for crack growth modeling in complex structures such as porous media. The phase field method does not need predefined cracks and it can simulate curvilinear crack path. This goal is accomplished by replacing the sharp discontinuities with a scalar damage phase field parameter representing the diffuse crack topology. To simulate brittle fracture in this study, the equations of elastic displacement field and fracture phase field are first introduced. Afterwards, using the weak form of the equations, the staggered solution of the equations is performed. To implement the equations in the finite element method, the Abaqus software with User Element Subroutine (UEL) is used. Given that the bone structure is somehow a porous structure, a representative volume element of the bone is selected for phase field simulation. In order to verify the developed model, the tensile test of the single edge notched specimen has been simulated. Subsequently, crack propagation in a porous media with different porosities under tensile loading was simulated. The simulation results illustrate the capability of the phase field method in predicting crack growth in geometrically complex structures. In addition, the load-carrying capacity or the strength of the porous structure continuously decreases with increasing porosity and noteworthy is that such a strength is suddenly decreased around a critical porosity value.
Volume 19, Issue 1 (7-2015)
Abstract
Many companies are dependent on purchasing the required professional services (such as managerial, marketing, accounting, legal, and IT services) from specialist contractors. The contract between such contractors and clients forms an agency relationship, so the agency theory may be used to regulate the relationship between them. However, since the abstract knowledge is the subject of exchange between the client and professional service provider and there is a knowledge asymmetry between these two parties, the application of agency theory as it is used for traditional owner-manager agency relationship is not possible for principal-professional agent relations. In this article, we expand the agency theory to be applicable in such agency relationships. We suggest that a combination of behavior-based and outcome-based contracts be employed in principal-professional agent relationships, if possible. Moreover, we discuss why it is very hard or even impossible to have a direct control over professional service contractor and to measure the outcomes of its services. We finally propose two alternative mechanisms (1-trust and self-control, and 2-indirect control) for reducing opportunistic behaviors and solving some agency problems occurring in principal-professional agent relations.
Volume 19, Issue 125 (July 2022)
Abstract
The aim of this study was to investigate the effect of different ratios of starter and kind of probiotic culture on the physicochemical, textural, microbial and sensory properties of probiotic soy cheese. Different ratios of starter (50% thermophilic + 50% mesophilic , 25% thermophilic + 75% mesophilic, 75% thermophilic + 25% mesophilic) with different species of probiotic bacteria (Lactobacillus acidophilus, Lactobacillus casei and Bifidobacterium lactis were used to produce probiotic soy cheese. The results were analyzed in a completely randomized design consisting of 12 treatments with 3 replications using two-way analysis of variance. The means were compared by Duncan's multiple range test at 5% probability level. The results showed that treatment 10 (cheese sample containing starter compound (75% thermophilic + 25% mesophilic) + Lactobacillus acidophilus probiotic bacterium) had the lowest pH and the highest acidity. The highest amount of acetic acid was related to treatment 12 (cheese sample containing starter compound (75% thermophilic + 25% mesophilic) + Bifidobacterium lactis probiotic bacterium). In all samples of probiotic soy cheese, the population of probiotic bacteria was in the range of 7-8 log cfu / g. Treatment 6 (cheese sample containing starter compound (25% thermophilic + 75% mesophilic) + Lactobacillus acidophilus probiotic bacterium) had the highest hardness, cohesiveness and tissue springiness, also treatment 6 had the highest sensory quality score, therefore this sample the best treatment was selected. Overall, the results showed that probiotic soy cheese is a suitable environment for the growth of probiotic bacteria and the production of a functional product.
Volume 19, Issue 125 (July 2022)
Abstract
Today, special attention is paid to the use of bioactive peptides in the production of functional foods and drugs. In the present study, isolation and evaluation of bioactive properties of peptides derived from enzymatic hydrolysis of soy whey were investigated. For enzymatic hydrolysis of soy whey protein, two types of enzymes, ficin and trypsin, were used at temperatures of 37 °C and 45 °C and at times of 2 and 4 hours. Then, the obtained protein hydrolysates were separated by reverse phase- high performance liquid chromatography and the obtained fractions were collected for biological activity. Statistical analysis of hydrolysis degree results was conducted by factorial method. One-way analysis of variance was used to analyze the results of the bioactive properties of peptides. The means were compared by Duncan's multiple range test at 5% probability level. Based on the results, peptide fractions had good antioxidant activity and also showed antimicrobial effect against Escherichia coli and Staphylococcus aureus. The T4F7 fraction (the seventh fraction obtained from trypsin-prepared protein hydrolyzate at 45 °C for 4 hours) had the highest antioxidant and antimicrobial properties. Therefore, this fraction was considered as the superior fraction. Electrophoregram of separation of peptide components in the selected bioactive peptide fraction (T4F7) showd that the presence of peptides with a molecular mass often of about 5 to 10 kDa and Less than 50 kDa is the main cause of desirable antioxidant properties in this treatment. Therefore, soy whey peptide can be used as a functional ingredient and natural preservative in food products.
Volume 20, Issue 5 (May 2020)
Abstract
Diseases such as heart and brain attacks, which sometimes lead to movement disorders in people, has raised with an increasing community age. Nowadays, medical scientists replaced rehabilitation robots instead of traditional therapeutic methods. Design and implementation of a low-cost and home-like usable device for a patient was the primary goal of this research. In this study, a robot which consisted of cable and springs for movement in the transverse plane of the human body was introduced. For this purpose, stiffness and free length of springs were achieved by an optimization process, firstly. Afterward, static and dynamic workspace calculated to identify robot mechanical characteristic. At the end, controllability of the system in different paths in two conditions of presence and absence of the patient's hand was investigated and verified by the results obtained by the built device. Dynamic and static workspace indicates that a patient can do exercises with the help of the designed robot. Also, the control results and the obtained results from the implemented device test shows the stability of the control system and its ability to eliminate possible error occurring in the path.
Volume 20, Issue 6 (12-2020)
Abstract
A suitable design is one design can achieve to its aims with minimum cost and needing to less computing time. In civil engineering due to survey of large scale structures and large number of design variables, it is so hard achieving to such design only based on experience and therefore optimization methods came to help designer as useful tools in order to find an economic and efficient design. Structural optimization can be defined as a process of dealing with the optimal design of various structures. Ausual objective function is the weight of the structure. In general, there are three main categories in structural optimization applications, namely, size, topology and geometry (shape) optimization.Cellular automata (CA) is a computationally efficient and robust tool to simply implement complex computations. As CA is simple to be implemented and can deal with complex problems without extensive mathematical computations, it is widely used in various fields of science and engineering.In recent years, various meta-heuristic inspired optimization methods have been developed.Almost all of metaheuristic algorithms come up with an idea of employing a particular process or event in nature as a source of inspiration for the development of optimization algorithm. The Cuttlefish algorithm is inspired based on the color changing behavior of cuttlefish to find the optimal solution. The patterns and colors seen in cuttlefish are produced by reflected light from different layers of cells including (chromatophores, leucophores and iridophores) stacked together, and it is the combination of certain cells at once that allows cuttlefish to possess such a large array of patterns and colors.In this article, cuttlefish algorithm (CFA)combined with cellular automata (CA) and were used for optimization truss structures.First, cellular automata and the Moor neighboring cells are defined and to the number ofsquares of the cell number ofcellular automata lattice( )is selected from the best population. Then, the variables vector and their objective function of selected population are placed in each cell of the cellular automata.In a Moor neighboring, nine cells are compared to each other and the best answer ( )is selected and that is used to create new population.Finally, the best person in thenew population will be selected and itreplacedwith the worst person in the cellular automata, and thus the cellular automatais updated. Some benchmark numerical examples were solved using the CFA and CA-CFA algorithms, and the results of the numerical examples showed that the enhanced algorithm performancesbetter in size and topology optimization of truss structures than cuttlefish algorithm and other methods introduced in the literature. Finally, it can be concluded that the convergence speed of the improved algorithm compared with previous approaches is higher and its ability to achieve the desired values is better too.
Volume 21, Issue 2 (9-2017)
Abstract
Problem definition is the most vital and important step in system dynamics approach. It is the basis for other steps of dynamic modeling and one of the main conditions in the effectiveness of modeling and its success. Considering its importance, there is scant literature on process of problem definition and attributes as well as indicators of dynamic problems. With aims to explain the problem definition, this article creates problem definition framework through the systematic and structured process by extracting the indicators and factors that determine a dynamic problem. At this point all the articles listed at the first two rounds of system dynamics research conferences in 1976 and 1981 and also 33 around of the system dynamics conference from 1983 to 2015 as well as the Journal of System Dynamics Review (SDR) and scientific databases include Elsevier, Wiley, Springer and Emerald were examined. Finally, a framework was designed with 6 indicators including structure of the problem, problem`s stakeholders, border of problem, problem complexity, dynamics and nature of the problem, which altogether consists of 24 indexes. A comprehensive framework for the diagnosis of dynamics problem is main finding of this paper.
Volume 23, Issue 9 (September 2023)
Abstract
In addition to the need for lightweight properties, the metallic bipolar plates in the PEM fuel cells should work in a humid and acidic environment. Due to its low density and excellent corrosion resistance, titanium is a proper candidate for manufacturing bipolar plates. In this paper, the manufacturing of bipolar plates made of commercially pure titanium with an initial thickness of 0.1 mm was investigated using the stamping process. A four-channel die with a parallel flow field was used in the experiments. To estimate the formability of microchannels of the bipolar plates, the response surface method, genetic algorithm, and adaptive neural fuzzy inference system were employed. Die clearance, stamping speed, and friction coefficient between the sheet and die were considered input variables, whereas the die filling rate was as output. The designed experiments using the response surface method were used to train the meta-heuristic techniques. The results showed that the regression model obtained from the response surface method predicts the die filling rate with acceptable accuracy. Furthermore, the coefficients of the equation obtained from the regression have been improved using the genetic algorithm and the error rate has been reduced by about 53%. Finally, an adaptive neural fuzzy inference system was used to predict the die filling. The results showed that the proposed system is very feasible and approximates the maximum filling rate with high accuracy.