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Showing 9 results for Akhoundi


Volume 7, Issue 1 (Winter 2019)
Abstract

Aims: Green algae (Chlorophyta), as a diverse group of algae, has almost omnipresent distribution in the Caspian Sea and plays an important role in ecosystem functioning. The aim of this study was to investigate the spatial and temporal distribution and biomass trend of planktonic green microalgae (Chlorophyta) in southeast of the Caspian Sea.
Materials & Methods: This experimental study was performed by sampling water from south of the Caspian Sea in Mazandaran province during the winter 2015 and summer 2016. Water sampling was done along two half-lines perpendicular to the estuaries of "Tajan" and "Babolrood" rivers in 8 stations and 4 depths (less than 1, 5, 10, and 20 m) in the euphotic zone, at 8 stations along the linear transects. Settlement method was applied to the preserved samples in formaldehyde 4%, in order to the qualitative and quantitative analysis of phytoplankton. The biomass of Chlorophyta was calculated, using the geometric shape method. The data were statistically analyzed, using PRIMER 6 and SPSS 19 software and the diagrams were drawn by Excel 2013.
Findings: Of total 29 identified Chlorophyta species, 28 species were present in the summer with the highest abundance of Chlorella sp. (1395×105±671×104 N/m3) and, 19 species were observed during the winter, with the highest abundance of Binuclearia sp. (456×105±155×104 N/m3). Binuclearia sp. also showed the highest biomass in both seasons.
Conclusion: The diversity of Chlorophyta is influenced by seasonal variations. Estuaries are the richest stations in terms of abundance and biomass of planktonic Chlorophyta in summer.
 


Volume 10, Issue 2 (10-2020)
Abstract

Creation of capacity concentrates on understanding obstacles halting people, governments, and organizations from the realization of development goals. It also makes them achieve results of consistent development. The goal of this study is to propose a conceptual analysis of elements and results of organizational capacity building in higher education to respond to expectations of the society. The directionality of this research is developmental and its methodology is content analysis using an analogy approach concentrating on words, inspections, and precision in the text in order to analyze, describe, explain, and interpret the texts through creating primary codes and coding. The statistical population of this project involves academic scholars and the set of documents and papers related to the questions and variables in this study. 13 samples chosed through Snowball sampling. In this section, semi - structured interview method was used to collect data. To assess the accuracy of findings we used theoretical validation through the points posed by the scholars in the field known as the specialist committee to assess as well as Cohen's kappa coefficient for assurance of accuracy of study method and data collection in the intended phenomenon. By confirmation of the focal group and the estimation of the coefficient 0.761, the research findings had the ability to validate and trust. Results showed that organizational capacity building contains five major concepts of strategic, structural, systemic and procedural, cultural, resources and infrastructures development and a social responsiveness concept as the outcome of the phenomenon under investigations. Therefore, it is suggested to study individual analysis and environmental analysis levels in creating capacity.   

Volume 10, Issue 3 (Summer 2022)
Abstract

Aims: Monitoring variations in macroalgal assemblages is a crucial issue for the preservation and management program of coastal waters. This study was conducted to determine the seasonal and spatial distribution patterns, and composition of macroalgal communities along the eastern coasts of Qeshm Island, Iran.
Materials & methods: Seasonal sampling was conducted at three different sites of different tidal levels on the eastern coasts of Qeshm Island. Random samples of macroalgae were collected at three stations, seasonally. The species were identified and the dry weight of each species was used to calculate the macroalgae abundance. The Species richness and the Diversity indices were calculated to evaluate the distribution pattern and composition of the macroalgal community.
Findings: As a result, 51 species (4 Chlorophyta, 21 Phaeophyta, and 26 Rhodophyta) were identified. The seasonal and spatial dominant species were found to be Padina sp. and Hypnea sp., and a distribution pattern was seen to have increasing macroalgal biomass from the upper to lower intertidal level. The sampling sites shared more than 50% similarity of their macroalgal species, indicating a relatively homogeneous distribution. The highest (18.1±4.3 gr drywt m-2) and lowest (8.27±2.1 gr drywt m-2) mean of total seaweed biomass were recorded in winter and summer, respectively.
Conclusion: The assemblage composition of macroalgae significantly differs between hot and cold seasons, and there was no substantial compositional variation of seaweeds communities along the tidal gradient. The macroalgal distribution was largely homogeneous with no significant difference among the research areas at sampling seasons.

Mojtaba Nabipour, Amir Hossein Behravesh, Behnam Akhoundi,
Volume 17, Issue 1 (3-2017)
Abstract

This paper presents an experimental study on the effects of printing parameters on the tensile strength of the polymer-metal composites printed via Fused Deposition Modeling (FDM) technique .In the recent years, 3D printer systems have been widely employed in various industries. FDM is one of the most widely used 3D printer systems worldwide due to its simplicity and lower cost. Although extensive research works have been carried out in the area of 3D printing, less efforts have been reported in developing new materials and their use in FDM process. The materials utilized in this study consisted of Cu particles in ABS polymeric matrix with a constant 25 wt.% of metal powder. The filament production line was implemented to accustom with the manufacturing process. The printing variables were selected as nozzle (orifice) diameter, layer height, fill pattern and nozzle temperature that were examined in three levels. Taguchi method was employed to find the optimal FDM process parameters. The main effect, signal-to- noise ratio and analysis of variance were employed to analyze the process parameters in order to achieve optimum tensile strength of the composite material specimens. Finally, the specimens were produce at the optimized parameters to confirm the tests and method.

Volume 22, Issue 3 (5-2022)
Abstract

Graphic Statics is a visual analysis and calculation method to find the type and amount of internal forces in structures, which achieves this importance away from computational difficulties and only with a geometric approach focused on two reciprocal diagrams of form and force. In this paper, arched trusses based on Warren type are analyzed using graphic statics. For this purpose, the parametric model of form and force diagrams were programmed in the Grasshopper parametric plugin. Parametrization has also provided the ability to find and analyze any different types of free-form trusses based on the type of warren truss. To measure the validity of the method and the accuracy of the algorithm written in the Grasshopper add-on, the numerical results obtained from several samples of arched trusses under different loads have been compared with the finite element computational method. The results of the validation simulations indicate the high accuracy and speed of the proposed algorithm.

Fatemeh Negahdari, Behnam Akhoundi,
Volume 22, Issue 10 (October 2022)
Abstract

In orthopedic surgery, the drilling process is used to internally fix the fracture zone. During bone drilling, if the temperature exceeds the limit of 47 °C, it results in altered bone alkaline phosphatase nature, occurrence of thermal necrosis, non-fixation and inadequate bone fusion In order to investigate the effective parameters of the drilling process, after three-dimensional modeling of the femur bone in Mimics software and determination of bone coefficients based on the Johnson-Cook model, numerical simulation of the cortical and trabecular bone oblique drilling process have been performed. The drilling process was performed in both normal and high speed modes based on reverse heat transfer theory using DEFORM-3D software. The results of numerical simulation after validation with experimental results showed that this theory is capable of estimating the temperature and heat flux in this process and the occurrence of necrosis in both processes (normal and high speed) is imminent. The temperature in the drilling area of the trabecular bone is higher than the cortical bone at all speeds and feed rates and the axial force of the trabecular bone is less than the cortical bone at all speeds and feed rates. The optimum point leading to the minimum temperature in normal drilling of trabecular and cortical bone is the feed rate of 150 mm/min and the rotational speed of 2000 rpm. This optimum point is obtained in the high-speed drilling of trabecular and cortical bone at the feed rate of 150 mm/min and rotational speed of 4,000 rpm and 7,000 rpm. 
Majid Elyasi, Vahid Modanloo, Hossein Talebi Ghadikolaee, Farzad Ahmadi Khatir, Behnam Akhoundi,
Volume 23, Issue 4 (April 2023)
Abstract

Thin-walled tube bending is one of the important processes for manufacturing parts in the automotive and aerospace industries. This paper investigates the effect of heat treatment on the bendability of thin-walled tubes made of AA6063 alloy. With the hydro rotary draw bending process, the cross-section ovality of the as-received, annealed, and artificial aged tubes has been examined at different fluid pressures. In the experiments, the tube diameter to tube thickness ratio was 13.88. Also, the critical bending ratio was 1.6, and the bending angle was 90 degrees. By examining the results, it has been found that heat treatment and fluid pressure had an important effect on the quality of the bent tubes. By increasing the fluid pressure to 3.6 MPa, critical cross-section ovality has decreased in all specimens. The maximum decrease of cross-section ovality is obtained in the annealed sample by 49%. Also, in the artificially aged specimens, the critical cross-section ovality decreases by about 45%. It has also been observed that at a pressure of 3.6 MPa, the critical cross-section ovality of the annealed sample has improved by 19% compared to the artificially aged specimens.

 
Vahid Modanloo, Ahmad Mashayekhi, Behnam Akhoundi,
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.
Reza Zanganeh, Amin Safi Jahanshahi, Behnam Akhoundi,
Volume 24, Issue 4 (April 2024)
Abstract

With the emergence and expansion of additive manufacturing processes, especially the fused deposition modeling process, extensive research has been conducted on these processes. One important research area is strengthening the printed parts by the fused deposition modeling method. One of the main areas of research is related to the strengthening of printed parts by the fused deposition modeling method. This process enables the production of complex structures and the customization of parts. On the other hand, polylactic acid material is one of the main materials used in this process, which has been noticed over other materials due to its biocompatibility and biodegradability properties. In this research, the effect of annealing heat treatment on the compressive strength and modulus of porous samples has been investigated with the approach of using them in tissue engineering as a scaffold for bone tissue. The samples are 3D printed with wiggle, grid, and honeycomb patterns and with filling percentages of 40, 70, and maximum. In addition, the effect of two parameters, the extrusion width, and the layer height, has also been investigated. To create porous structures with interconnected porosities, the pattern of filling in each layer is rotated to a certain extent, and this causes the introduction of new porous structures that can have wide applications such as being used as scaffolds in tissue engineering. After evaluating the compressive mechanical properties of the samples, the same samples were heat treated, and then their compressive mechanical properties were also evaluated. The obtained results show that the maximum compressive strength and modulus occur in the sample with an extrusion width of 0.6 mm, layer height of 0.25 mm, wiggle filling pattern, and maximum filling percentage. The values ​​of compressive strength and modulus for the non-heat-treated sample are equal to 84.51 MPa and 2.28 GPa respectively and for the heat-treated sample, it is equal to 105.44 MPa and 2.29 GPa respectively.

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