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Volume 14, Issue 63 (6-2016)
Abstract

Application of combined technology can reduce the disadvantages of each other as compare to their individual process. Osmotic process along with hot air drying and freezing were applied on red beet pieces in this investigation. red beet divided to slices as well as cubes pieces before treatment with citric and ascorbic acids in two levels of 0.1 and 0.3 percent. red beet slices were semi dried in cabinet drier for period of 75 minutes and cubes for 115 minutes and then were placed into polyethylene bags for prior to freezing process in freezer with -25◦C. Different physicochemical characteristics such as acidity, water activity, image processing and texture were evaluated after 2 hour and 30 days. Statistical analysis of data with completely randomized design and SPSS software version 20 during one month preservation showed that cubes pieces of red beet in 0.3 percent of acid solution along with osmotic dehydration has the best and comparable texture, color and quality characteristics as compared to the fresh red beet.     

Volume 15, Issue 1 (3-2015)
Abstract

Lubrication is an essential factor in sheet metal forming processes such as deep drawing in order to reduce friction at contact surfaces, forming load, tool wear rate and increasing of sheet formability. Various metal oxide nanoparticles can be used as additives to create desirable tribological properties in base lubricants because of their unique properties such as specific surface area. In the present study, the conventional lubricant enhanced by alumina nanoparticles (Al2O3) is utilized in deep drawing process in order to improve frictional conditions. The forming load, surface roughness (Ra) and thickness distribution values of the formed cups were assessed to evaluate the performance of the enhanced conventional lubricant with alumina nanoparticles (Al2O3) in comparison to the conventional lubricant and dry forming condition. The obtained results from experimental tests revealed that adding 0.5 wt.% Al2O3 nanoparticles to the conventional lubricant improves lubrication property significantly and reduces forming load by 16.39% and surface roughness by 19.33% compared to the conventional lubricant. Furthermore, it is observed that using lubricant containing nanoparticle additives results in 23.94% improvement in maximum thickness reduction in critical zone.

Volume 15, Issue 4 (7-2013)
Abstract

 Functional response of the female ladybeetle, Hippodamia variegata (Goeze) (Col., Coccinellidae) to varying densities (5, 10, 20, 40, 60 and 80) of third instar nymphs of Aphis gossypii Glover was assessed in a growth chamber (25˚C, 65± ­5% RH and a photoperiod of 16L: 8D h), on the black eyed bean, Vigna unguiculata (L.), in an open patch design. The logistic regression showed a type II functional response for female ladybeetles with the parameters (using Rogers’ model) as follows: a= 0.083±0.011h-1 and Th =0.197±0.040h. The mean time for the predator to be settled in a patch was 36.1±9.25, 26.8±5.81, 17.18±4.71, 8.5±2.12, 3.3± 0.88 and 0.8±0.35 minutes at densities of 5, 10, 20, 40, 60 and 80 third instar nymphs of A. gossypii, respectively. The settlement time decreased as prey density increased. The maximum theoretical predation (T/Th) for the females was 121.475. The proportion of female H. variegata that remained at the end of the experiment and their voracity were dependent on prey density. This may give an indication for the ability of the predator to persevere in the high pest infestations, and thus a high level of control could be expected.

Volume 15, Issue 6 (8-2015)
Abstract

In this article constitutive equations on dynamic behavior of off- axis polymer matrix composites in different strain rates were investigated. Using the Hill Anisotropy and assumptions governing in fiber composites, a model was developed to express the dynamic behavior of polymer matrix composites. Using the flow rules and effective stress and assumptions in fiber composites like non plastic behavior of composites in fiber direction, the Hill parameters were omitted and reduced to one namely a_66 parameter. This model was called2D one- Parameter Plastic Model (also it can be developed for 3D composite layers). This model was developed for off axis composites as well. For each composite with different fiber directions, effective stress- effective strain was introduced. With choosing the right value for parameter a_66 by try and error, all the stress- strain curves were collapsed in to one single curve. Using this model and the experimental static and quasi- static results gathered from different authors (in range of〖 0.01s〗^(-1)), a viscoplastic model was obtained which can predict the polymer composite respond both in static and high strain rate tests (between 400 s^(-1) and 700s^(-1)). Constant parameters in high strain rates in this model were calculated through extrapolating the data in the static test rang. The accuracy of this model was investigated and approved by Split Hopkinson Pressure Bar test. The results showed that the visco plastic model can predict the dynamic respond of composite fibers in high strain rates very well.

Volume 15, Issue 7 (9-2015)
Abstract

One of the most important issues in the review of cold roll forming process of metals is estimation of required torque. The optimum production line can be designed by determining the effective parameters on torque. Some of these parameters are sheet material and thickness, bending angle, lubrication conditions, rolls rotational speed and distance of the stands. The aim of this study is to predict amount of required torque considering the factors influencing torque, including thickness, yield strength, sheet width and forming angle using artificial neural network. So the forming process was 3D simulated in a finite element code. Simulation results showed that with increase of yield strength, thickness and forming angle, applied torque on rolls will increase. Also the increase in sheet width -assuming constant web length- will decrease the torque needed for forming. The effects of thickness and sheet width were experimentally investigated which verified the results obtained by finite element analysis. A feed-forward back-propagation neural network was created. The comparison between the experimental results and ANN results showed that the trained network could predict the required torque adequately.

Volume 16, Issue 3 (5-2016)
Abstract

Widespread use in the machining procedures in producing industrial pieces, optimization of this procedure is one of most subjects that attract researchers interest. Finite element analysis based techniques are available to simulate cutting processes. Success and reliability of numerical models are heavily dependent upon work material flow stress models in function of strain, strain rate and temperatures. One of the most accurate and most useful equations are presented, the fundamental equation Johnson-Cook is. The basic equations for modeling the behavior of each material, is needed to determine the equation coefficients.The model parameters are determined by fitting the data from both quasi-static compression tests at law strain rates and machining tests at high strain rates. After getting result from the equation, its accuracy being checked either in compression tests or in machining tests by simulation with Abaqus software and its results are compared with the results of machining tests. Studies show the correctness of the equation in determining the dynamic behavior of 5083 alloy is established. Therefore, this equation can be used for modeling the behavior of the selected alloy in other shaping processes, and can be used its results.

Volume 16, Issue 6 (8-2016)
Abstract

Steam jet ejectors are the essential part in refrigeration and air conditioning, desalination, petroleum refining, petrochemical and chemical industries. A greater understanding of flow physic inside an ejector plays an important role in its performance improvement. In this study, analytical algorithm is developed for design of steam ejectors. The algorithm gives the flow ratio (motive to suction flow rate) as a function of the expansion ratio and the pressures of the entrained vapor, motive steam and compressed vapor. The compression ratio and back pressure variations were studied in ejector flow ratio with expansion ratio of 5 and 50. It showed that compression ratio increase by increasing the flow ratio. Also in a similar flow rate, compression ratio for ejector with expansion ratio of 50 is greater than compression ratio in the ejector with expansion ratio of 50, due to more vacuum in the case with expansion ratio 50. Then, the code results were compared with experimental results that showed appreciate agreement with other results. Finally, Mach number variations from nozzle exit to discharge diffuser were obtained by code. Results showed that the pressurized condition causes the lowering of expansion angle, thus resulting in smaller jet core and larger effective area. The expanded wave is further accelerated at a lower Mach number. Therefore, the momentum of the jet core is reduced. However, the enlarged effective area allows a larger amount of secondary fluid to be entrained.

Volume 16, Issue 8 (10-2016)
Abstract

Differences in the persons’ individual parameters such as age, gender, weight, height and basal metabolic rate have a significant effect on the human body thermoregulation. Therefore, using the human thermal models that developed on the basis of large humanity population cannot lead to accurate results for specific individuals. Because, the individual parameters have not been considered in standard thermal comfort models and also available individual and local models are so complicated in applications; nowadays, the necessity of developing a simple and accurate individualized model is felt. In this study, some physiological parameters such as: body fat percentage, subcutaneous fat layer thickness, body heat capacity coefficient and tissue conductive resistances have been modeled from readily-available external measurement of individuals and these parameters are incorporated into three node-model algorithm structure to predict individual variations in thermal response between individuals. Three-node thermal comfort model is based on Gagge’s standard model that has been accurately estimated thermal sensation of the bare and clothed parts of the body. The model has been verified against the analytical and experimental results where a good agreement was found. In conclusion, the results indicate that the mean error in prediction of skin temperature is decreased from 1.2℃ for three-node model to 0.4℃ for the new individual model.

Volume 16, Issue 10 (1-2017)
Abstract

This paper presents the control of a quadrotor using nonlinear approaches based on the experimentally measured sensors data. The main goal is the control and closed loop simulation of a quadrotor using feedback linearization and sliding mode algorithms. First, a nonlinear model of quadrotor is derived using Newton-Euler equations. To have a more realistic simulation the sensors noise performance were measured using a setup. sensors data was measured under on engines. Since the experimental data for sensor had error and noise, a Kalman filter was used to reduce sensors noise effect. Results demonstrate good performance for Kalman filter and controllers. Results showed that feedback linearization and sliding mode controllers performance was good but angles changes were smoother on feedback linearization controller. With increasing uncertainty, feedback linearization performance was away desired mode from this aspect The time to reach the goal situation while increasing uncertainty was no significant impact on the performance of sliding mode controller.Thus feedback linearization controller added PID is Appropriate to Maintain the quadrotor attitude while sliding mode controller has better performance to angles change and transient situations.

Volume 16, Issue 10 (1-2017)
Abstract

Super alloys due to special features such as high resistance to corrosion and heat, have the ability to maintain mechanical and chemical properties at extremely high temperatures which used in various industries, especially in the aerospace industry. On the other hand, very low heat transfer coefficient, high toughness with work hardening in these alloys caused the machining of them is seriously challenged. In the present study, the effect of cutting parameters on surface roughness of A286 superalloy has been studied in different lubrication conditions. Response surface method experimental design was used to plan experiments. In order to investigate the effects of machining parameters and conditions of lubrication on the surface roughness, Two factors - cutting speed and feed rate- on three levels and minimum quantity lubrication conditions and wet method are considered as the main parameters too. In order to investigate the Tool wear and workpiece surface quality, the images of Scanning Electron Microscope and optical microscope are used. The results show that using of the minimum quantity method of lubricant is caused to increase cooling-lubrication fluid particles penetrating power to the cutting zone and improves the process by reducing the surface roughness. It was observed that with increasing feed rate in fixed cutting speed, numerical values of surface roughness in Ra criterion are taken apart for different lubrication circumstances and its value for the minimum quantity method of lubricant is less, which shows the superiority of this method over the wet method.

Volume 16, Issue 90 (August 2019)
Abstract

In recent years, synchronous with the development and diversification of bread production, have expanded various processing methods, as well as the co processes (additives). One of the traditional products that have been welcomed by consumers for many years in eastern Asia due to the simplicity of raw materials and ease of using is roti bread. Therefore, in the present study, has been investigated the use of baking methods, such as hot-electric plates and rotary oven and compare them with the traditional method and so on is evaluated using of guar, carboxymethyl cellulose (CMC) and Carrageenan hydrocolloids (each one 0.5%) in roti bread formulation in a completely randomized double factorial arrangement test (P≤0.05). The results of this study clearly showed that application of hot-electric plates for baking along with addition of both CMC and guar gum in the formulation, had effect on the moisture content and crust L* value and in this regard the effect of CMC gum was higher than guar gum. Also, based on the results, it was found that the sample produced by the hot-electric plates containing CMC gum had the least firmness of the texture during 2 and 72 hours after baking, as well as one week after baking (P≤0.05). Finally, tasting the samples, the panelists introduced the samples produced with hot-electric plates containing CMC gum and samples produced with hot-electric plates containing guar gum as the best samples.
 

Volume 17, Issue 1 (4-2014)
Abstract

Objective: microRNAs (miRNAs) are noncoding RNAs that function as key regulators of diverse biological activities such as cellular metabolism, cell proliferation and cell cycle regulation. Recent studies have indicated the high potential of these small molecules to control stem cell differentiation into desired cells. The aim of present study is to investigate the possible effect of let-7f on expression of hepatic nuclear factor 4 alpha (HNF4a) and some hepatic specific factors such as albumin (ALB), alpha fetoprotein (AFP), cytokeratin18 (CK18) and cytokeratin19 (CK19) in human adipose tissue derived stem cells (hADSCs). Methods: ADSCs were isolated from human adipose tissue using collagenase type I and were transduced by recombinant lentiviruses that contained human inhibitor let-7f and Scramble (negative control). Afterward, the expressions of HNF4a, ALB, AFP, CK18 and CK19 were evaluated by Real-time PCR at different time points. Results: Transduction efficiency of lentiviral vectors into ADSCs was more than 80% as judged by the expression of the GFP reporter gene. Real-time PCR analysis revealed that inhibition of let-7f in hADSCs resulted in significant up regulation of hepatic specific genes compared with the negative control. The expression level of HNF4a also increased in experimental cells at day 14, which supported the suppression of HNF4a expression by let-7f. Conclusion: The results of this study identified let-7f as a negative regulator of HNF4a expression in hADSCs and increased the expression of hepatocyte specific factors through silencing of let-7f. Therefore, suppression of let-7f could be a considerable tool for hepatic differentiation of hADSCs.

Volume 17, Issue 2 (3-2017)
Abstract

Motion and deformation of the drop falling in an immiscible fluid has become a benchmark problem in fluid mechanics and has a wide range of application in petroleum, medicine processing, metals extraction, power plant and heat exchanger. In this paper, an exact analytical solution of a falling viscous drop at low Reynolds number is investigated. Analytical solution for both internal and external flows is obtained using the perturbation method. The Reynolds numbers and capillary are considered as the perturbation parameters. Drop’s shape remains spherical for sufficient small ones. The falling drop’s shape at Newtonian phase, deforms from its spherical shape as its volume increases. Inertial forces, surface tension, normal components stresses have the most influence on the falling drop’s shape. Drop’s deformation is due to the forces at the interfaces acting between two fluids. By volume increase of the falling drop, normal components stresses overcome to the surface tension and cause a dimple at the bottom drops in addition to the inertial force enhancement. For small non-dimensional parameters (Reynolds number and capillary) drop’s deformation is exactly similar to a sphere and then by increase in Reynolds number and capillary, the drop’s shape alters and cause a dimple at the bottom drops. Analytical solution show suitable agreement in terminal velocity and drop shape estimation with experimental results.

Volume 17, Issue 5 (12-2017)
Abstract

Space grids are highly modular structures assembled from components that are almost exclusively factory fabricated. The components therefore, are usually produced with high dimensional accuracy, with a high quality of surface finish and they are generally easily transportable, requiring little further work except assembly on site. Because of their modular nature, space grids may be extended without difficulty and even taken down and reassembled elsewhere. One of the most popular types of connectors that are widely used in the construction of double layer grids is the MERO system. The Mero KK space truss system, the first commercially available, is still considered to be one of the most elegant solutions for the construction of space grid structures. The elegance and simplicity of the Mero system means that it is not only used in buildings but also for shop displays and exhibition stands using lightweight materials. Circular tube members are connected to cast ‘ball’ joints at the nodes by a single concealed bolt for each tube. A double layer grid is combination of prefabricated tetrahedral, octahedral or skeleton pyramids or inverted pyramids having triangular, square or hexagonal basis with top and bottom members normally not lying in the same vertical plane. The connector is an extremely important part of a grid design. The type of connector depends primarily on the connecting technique, whether it is bolting, welding, or applying special mechanical connectors. It is also affected by the shape of the members. This system is multidirectional system allowing up to fourteen tubular members together at various angles. The system consists of tubular elements that are connected together by means of a MERO connector. The ball is located at the intersection of the longitudinal axes of tubular elements. The longitudinal axis of tabular element and all the constituent parts of its end connectors are along together. This axis is referred to as axis of member. The MERO system had only one type of standard joint, a sphere with 18 threaded holes and machined bearing surfaces at angles of 45, 60 and 90° to each other. A model of MERO connector is presented in this paper for double layer grid structure. The internal forces in the members of double layer grid are found using SAP software. These forces are applied as pressures on the MERO connector. The deflection and rotation patterns of the connector are studied under different loading conditions using the ABAQUS software. The forces to be applied on the connector are calculated using of displacementg control.
In order to take into account the connector effects in structural analysis, their behavior under combined load should be predicted. In double-layer grids that are an important family of space structures, the main internal forces are axial forces. In the present study, to determine the force-displacement relationship of MERO jointing system, some tensile, compressive and bending simulation tests were carried out on a connector of this type using 3D finite element method. The obtained force-displacement and moment- rotation relationship were used under different load. The results of the finite element simulation with experimental results have a good match. It was also found that in both compressive and tensile loading, the ball came to the plastic stage. Compressive axial force increases the flexural stiffness of the connection and with increasing compressive force decreases the elastic bending moment.

Volume 17, Issue 7 (9-2017)
Abstract

Machining processes are the most important method to production in the industry. In these processes, the friction in tool-chip surface during the machining is one of the affecting factors on surface quality of work piece. The generated heat by friction, augment the tool wear mechanism and increase the wear rate of cutting edge which leads to reduction the surface quality. The high talent of aluminum to built-up edge formation during machining has the undesirable effect on the surface quality. In the present study in order to improvement the cooling-lubrication conditions in machining of 6061 aluminum alloy, a new cutting tool with creating micro-grooves on its rake face was developed to achieve the improving of cutting fluid transfer to machining zone and reducing the friction between tool-chip surface. Two types of micro-grooves have been created by laser machining process. Specimens by changing the machining parameters and types of the applying of cutting fluid to machining zone were machined. The experimental results obtained from surface roughness survey and prepared images of work piece surface by scanning electron microscope (SEM) and optical microscope showed that by creating the micro-grooves, the delivery conditions of cutting fluid to machining zone has improved and its effect to reduction of surface roughness is clearly visible. By comparison the results of two micro-grooves showed that direction of grooves is the most important parameters in its design, so that the perpendicular texture is not only improves the surface quality but also increase the surface roughness compared to non-texture tool.

Volume 17, Issue 9 (11-2017)
Abstract

In this paper, steady motion of non-Newtonian falling drop through a Newtonian fluid at low Reynolds number is investigated analytically. Here, the Upper Convected Maxwell model (UCM) is used for drop phase and Newtonian model is considered for external fluid. During the past few decades, studies relating to non-Newtonian instabilities especially those involving free surfaces are amongst the most striking. These types of studies can be used to optimize design processes in, for example, the petroleum and medicine related processes, metal extraction, and paint and power-plant related fields. Analytical solution is obtained using the perturbation method. Reynolds and Deborah numbers are used to linearize the equations governing the problem in analytical method. Deborah number indicates the elastic effect of drop. The drag force increases by the growth of the elastic effect of non-Newtonian Drop’s. The non-Newtonian drop loses its shape and exchanges to an oblate form. Increment in Deborah number enhances the dimple at the bottom of the drop and results in an increment in its drag force and as a consequence its terminal velocity decreases. A hole is created at the rear of the drop due to the presence of inertia force and focus of normal component of stress at the rear of the drop. The novelty of this study is to consider the convection (non-linear) term of the momentum equations which was neglected in the previous studies due to the creeping flow.

Volume 17, Issue 106 (December 2020)
Abstract

Resistant starch type III as a dietary fiber is included in the prebiotic composition. It can be used to enrich low-calorie, gluten-free diets for celiac patients. The aim of this study was to investigate the possibility of improving the quantitative and qualitative properties of gluten free rice cake via replacement rice flour by resistant starch type III at levels of 0, 5, 10, 15, 20, 25 and 30%. Physicochemical, textural and sensory properties of the product were evaluated in a completely randomized design (P˂0.05). The results showed that replacing the rice flour by resistant starch in the gluten free rice cake formulation reduced the specific gravity of batter and increased the moisture content of the final product. Also, by replacing rice flour by resistant starch up to 20%, the height, specific volume and porosity of the final product increased and then decreased. On the other hand, the sample containing 20% resistant starch had the lowest firmness at 2h, 3 and 7 days after production. In addition, the results showed that 25 and 30% replacements of the resistant starch in gluten-free rice cake formulation by rice flour, the L* value of the crust and crumb increased and the a* and b* were reduced. Finally, the panelists by evaluating the sensory properties such as shape, color, texture firmness and softness, taste and overall acceptance the sample containing 80% rice flour and 20% resistant starch type III introduced as the best sample. Therefore, according to the results of the physicochemical and sensory evaluation, replacement of 20% rice flour by resistant starch type III in gluten free cake formulation can produce a lower calorie product suitable for celiac patient.

Volume 17, Issue 107 (January 2021)
Abstract

In this study, three levels of flour extraction rate (80, 88 and 96 %) and amylase and xylanase (50ppm) were used in barbari bread. The moisture, specific volume, porosity, firmness (2, 24 and 72 hours after baking), crust color and sensory properties of breads were evaluated. The result showed, the moisture and a* value were increased and firmness (during 72 hours) and L* value were decreased by increasing flour extraction rate. The sample containing 80% extraction rate and amylase and xylanase had the highest specific volume and porosity. Amylase and xylanase had the positive effect on texture, specific volume, porosity and sensory properties of bread. The flour extraction rate and enzymes didn’t have significant effect (P<0.05) on b* value of samples. Finally, the evaluation of sensory properties showed the samples containing 80 and 88 % extraction rate and enzymes had the highest overall acceptability.  
 

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