Showing 81 results for Roshan
Volume 14, Issue 7 (10-2014)
Abstract
Aerospace Launch Vehicles (ALVs), used for launching artificial satellites and space stations to Earth orbits, usually encounter with failure in navigation systems . In these cases, survival of an ALV during accurate payloads injection in orbits is one of the most critical issues for Guidance and Control systems.An important challenge for safety of Aerospace Launch Vehicle (ALV) is their reliability against all types of faults. There is a requirement for on-board fault detection without deteriorating the performance of ALV. In this paper, a new software sensor is proposed for fault detection and compensation based on symmetrical behavior of the yaw and pitch channels of an ALV. For this purpose, using identification techniques on the yaw channel, a new software sensor is developed as an online rigid dynamic predictor for the pitch channel. The proposed software sensor is employed to generate the residual of estimation error as an indicator of predefined faults. The main novelty of this software sensor is online tuning of the virtual sensor against unforeseen variations in the parameters of the vehicle. Robustness of the new control system in the presence of asymmetric behavior is investigated. The efficiency of the proposed fault tolerant method is illustrated through simulations.
Volume 14, Issue 10 (1-2015)
Abstract
This paper is concerned with design, develop and implementation of a quaternion based attitude control system for a rigid suborbital module which using cold gas thrusters over a short-duration mission. The quaternion controller produces a demand torque, and a pulse-width pulse-frequency (PWPF) modulator determines the necessary thruster fire signals. The effect of disturbances on module attitude has been investigated and the most significant found to be due to misalignment of thrusters effects. The system concept has been evaluated through modeling in Simulink and a rapid prototype hardware-in-the-loop platform and has been found to meet the requirements laid out for a typical module mission. The satisfactory performance of the controllers was illustrated through both numerical and hardware-in-the-loop simulations, where a system of twelve thrusters and load sensors were implemented in the hardware and disturbance effects such as thrust misalignment and sensor noise were studied. The results show the effectiveness of the proposed control method for agile attitude maneuvers of suborbital modules. The results of the HIL simulation were also used for tuning the parameters of the module’s numerical simulation that is to be used for error budgeting analyses.
Volume 14, Issue 13 (First Special Issue 2015)
Abstract
Optimal trajectory planning is an important task which is required in most of guidance missions. This paper introduces a new method that utilizes the most important characteristics of global optimization methods along with a new gradient-based method in a two layered scheme for the trajectory planning. In the first layer to construct a convenient shooting method based algorithm, some of the most important global methods of optimization are used in an information transform structure. Exchanging the information between selected algorithms helps for increasing the efficiency of problem solving. To do this, a comprehensive model for parameterization of the control history is introduced which allows the method to search for the best profile in a variety of different profiles. Results of this layer are transformed to the second layer that uses one of direct methods of solving the optimal control problems. This gradient based method named Radau pseudospectral method using of the results of global methods, completes the optimization process. Finally, developed algorithm is used to find the optimal trajectory of a reentry capsule and effects of the path constraint values on the total heat absorbed is investigated.
Volume 15, Issue 2 (6-2012)
Abstract
Objective: In an attempt to develop safer and more effective gene therapy approaches as a realistic treatment for various forms of cancer, researchers are increasingly using tumor-specific promoters (TSP) to drive the expression of the gene of interest and eradicate cancer cells. In this study, for the first time we introduce the Oct-4 promoter as a cancer-specific promoter with a high efficacy. Methods: We cloned Oct-4 promoter and enhancers into a pGl3 control reporter vector and analyzed the expression of luciferase as a reporter gene in an AGS gastric cell line. Next, we used a suicide-inducing vector that included an Oct-4 promoter and the TK gene in the presence of the non-toxic prodrug, ganciclovir, to eradicate cancer cells. Cells were treated with PI and connexin V. FACS analysis was conducted to assess the effect of the system on cell cycle and apoptosis induction. Results: Under the activity of the Oct-4 promoter, luciferase expression was three-fold higher than the SV40 promoter. The HSV/TK/GCV system activated by the Oct-4 promoter and enhancers induced apoptosis (86.17%) in the AGS cell line. We verified that this system induced S-phase/G2-phase cell cycle arrest in the AGS cell line. Conclusion: These data indicate that the Oct-4 promoter is active in the AGS cell line. Oct-4 gene is expressed in a wide variety of tumors but not in normal cells. Thus, Oct-4 appears to be a promising tumor-specific promoter for numerous tumors.
Volume 15, Issue 3 (5-2015)
Abstract
Processor memory capacity and update frequency are one of the main restricting constraints in star tracker design and development. In order to decrease the volume of the data required onboard, uniforming the star catalog which is eventually used as pattern recognition database is considered. Three different methods of uniforming the star catalog have been applied. Spherical patches, fixed slope curve and charged particles or Thomson’s problem. After generation of a sphere with uniform distribution of points, a star is assigned to each point according to its spherical distance or best magnitude. In order to evaluate the performance of each method, seven evaluation criteria are defined. Point distribution minimum energy, catalog size, minimum star required for pattern recognition, mean and standard deviation of star distribution in each frame, database size and pattern recognition true recognize percentage. These seven criteria are combined in weighted equation of “average” to choose the best star catalog uniforming method with respect to the star tracker mission. After having implemented the average equation it is demonstrated that uniforming the star catalog using charged particle or Thomson’s problem has better results.
Volume 15, Issue 3 (5-2015)
Abstract
Reaction wheels are angular momentum exchange devices used to stabilize the position of the satellite and maneuvering. This actuator can change the momentum of the satellite to change the attitude of the system. During the process of operation, noise and disturbances arisen from the unbalancing of the wheels lead to inconvenient performance of the reaction wheels. Several works have been presented for active noise cancelation in these devices. But, the practical tools of signal processing such as filter banks and wavelets which used for offline de-noising are samples of very useful noise cancellation methods. If these toolboxes are employed for online de-noising these signal processing approaches are applicable for noisy systems such as reaction wheels. The main challenge of this strategy is delay arisen from the signal processing and this is inevitable. In this paper, a strategy of online wavelet de-noising is designed and proposed for noise cancellation in a reaction wheel. In this regards, for considering the delay compensation the method of Smith predictor is used to lead the delay of the process out of the closed loop control system. The accuracy of this algorithm requires an estimate of the system dynamics and the understanding of the delay system. According to the use of the FIR filter delay can be fully calculated. The recursive least squares used for identification reaction wheel as an estimate of the system.
Volume 15, Issue 3 (10-2012)
Abstract
Objective: Environmental pollution is of major concern today and lead is considered to be one of the most important environmental pollutants. Long-term contact with lead causes harmful effects to humans. This study seeks to determine the effects of Curcuma longa (turmeric extract) consumption and exercise training on glutathione peroxidase and protein carbonyl in kidney and spleen tissues from rats exposed to lead. Methods: We randomly classified 60 male rats into the following six groups of 10 rats per group: 1) control; 2) sham (turmeric extract solvent); 3) lead; 4) training + lead; 5) turmeric extract + lead; and 6) training + lead + turmeric extract. The training program for groups 3 and 6 consisted of running on a level treadmill for 40 sessions (eight weeks at five sessions per week) at a speed of 22 to 15 m/min for 26 to 64 minutes. Turmeric extract (30 mg/kg) was injected three times per week for eight weeks. Amounts of glutathione peroxidase and protein carbonyl were measured by ELISA. Results: The amount of protein carbonyl in the kidney and spleen tissues of the lead group increased compared to the sham, training, combined and extract groups. Rats in the combined, extract and practice groups (F=4.787; P=0.002) had lower levels of protein carbonyl in their kidney and spleen tissues compared to the sham group (F=6.970, P=0.000). Glutathione peroxidase levels in the kidney and spleen tissues were less in the lead group compared to the sham group. However these levels in the training, extract, and combined groups increased compared with the sham group (respectively, in kidney and spleen P=0.051, F=2.466 and P=0/086, F=2.11). Conclusion: Intake of turmeric extract and exercise alone did not cause complete inhibition of the oxidative effects in kidney and spleen tissues. However, exercise and consumption of turmeric extract can be effective in reducing the harmful effects of lead.
Volume 15, Issue 4 (12-2015)
Abstract
The lateral spreading of mildly sloping ground and the liquefaction induced by earthquakes can cause major destruction to foundations and buildings, mainly as a result of excess pore water pressure generation and softening of the subsoil. During many large earthquakes, soil liquefaction results in ground failures in the form of sand boils, differential settlements, flow slides, lateral spreading and loss of bearing capacity beneath buildings. Such ground failures have inflicted much damage to the built environment and caused significant loss of life. The risk of liquefaction and associated ground deformation can be reduced by various ground improvement methods, including densification, solidification (e.g., cementation), vibro-compaction, drainage, explosive compaction, deep soil mixing, deep dynamic compaction, permeation grouting, jet grouting, piles group and gravel drains or SCs. Nowadays, using pile foundation is one of the popular solution for soils vulnerable to liquefaction. the pile with enough length more than liquefiable soil depth can reduce the large deformation and unacceptble settlements. Liquefaction and lateral deformation of the soil has caused extensive damage to pile foundations during past earthquakes. Several example of significant damages in pile foundation have been reported in the literature from the 1964 Niigata,1983Nihonkai-Chubu,1989 Manjil and 1995 kobe earthquakes. These damage have been observed mainly in coastal areas or sloping ground. evaluation of liquefaction in order to develop the northern and southern ports and implement coastal and offshore structures in Iran is of particular importance due to locating in a high seismic hazard zone and Liquefactable soil in coastal areas. Although, in recent years many studies have been conducted to understand the various aspects of this phenomenon, yet a lot of uncertainties have remained about the lateral deformations of the soil and its effects on deep foundations. In this study, behavior of pile groups (2 × 1, 1 × 3, 2 × 2 and 3 × 3) were evaluated using fully coupled three-dimensional dynamic analysis. Therefore, the influence of effective parameters such as number of piles, ground slope angle on soil and pile behavior has been studied using the finite element software Opensees SP v2.4. results indicate that most of the factors affecting the behavior of the pile, soil are not considered in the current design codes (such as JRA 2002) and these issues indicate the need to revise the current design and analysis methods.Lateral Pressures compared to that of JRA regulations show that these regulations cannot exactly predict pressures on pile and pile groups. Altogether comparing the results of numerical model of this research to various laboratory observations indicate that the use of numerical method can be reliable to predict the behavior of the soil and pile qualitatively and quantitatively using appropriate constitutive model and parameters for soil and pile. Keywords: Liquefaction soil, pile group, fully coupled numerical analysis, multi-surface-plasticity constitutive model.
Volume 15, Issue 11 (1-2016)
Abstract
Considering uncertainties in the design process is one of the most important factors to achieve reasonable and reliable results. In this article, a collaborative structure, which is a multidisciplinary design optimization, is combined with a robust design approach to design an optimum and robust launch vehicle, while considering the effects of uncertainties. First, a liquid-fuel vehicle is designed under two disciplines to send a 1200 kg mass to the 750 km orbit from the earth surface with 50.7◦ orbital inclination, using the collaborative structure. It should be said that the first discipline includes three subsystems that are engine design, geometry design and estimating the mass. Also, the second discipline includes three subsystems that are pitch program, aerodynamic calculations and trajectory simulation. Then, the optimum collaborative output is combined with the robust design in a multi-objective model to achieve the final vehicle configuration. The results show that the calculated mass of the first stage of the project using the collaborative robust design process is 3 tons heavier than the calculated mass using optimum collaborative design approach and the engines working time is increased. The overall size of the launch vehicle is increased too. The outputs of each subsystem have been evaluated and also, the overall results have been compared with another design process, i.e. MDF. This comparison shows the acceptable accuracy of the proposed approach.
Volume 16, Issue 3 (5-2016)
Abstract
In this study, optimum design of composite sandwich structures will be surveyed and presented using hybrid algorithm. Since, most modern payload fairings are constructed of a composite sandwich laminate, in this research the architecture of the fairing structure has been analyzed on the basis of the composite sandwich shell with a flexible core. However, from the geometrical point of view, fairing composed of two conical and cylindrical parts. Therefore, in the first phase, buckling analysis of conical composite sandwich shell has been done by using high-order theories and the obtained equations reduce to the governing equations of cylindrical sandwich shell when the semi-cone angle is set equal to zero. In the second phase, the obtained structure was optimized using hybrid algorithm. Due to the variety and complexity of design variables in composite sandwich structures, designing process leads to difficulties and obstacles in design optimization problems. Since, the most important selected discipline for optimizing the mass specifications of launch vehicle is structure, therefore with relying on optimization of the structure, after completion of optimization process, finally considerable mass reduction i.e. 40 percent comparing to the utilized fairing in this study (Fairing of Safir), will be concluded due to simultaneous changing of material and optimization.
Volume 16, Issue 96 (February 2020)
Abstract
Fermentation is one of the oldest techniques in food preservation, this process is defined as the biological activity of microorganisms to improve sensory, organoleptic and nutritional properties and produce a range of metabolites that inhibit the growth of unwanted microbial flora. As a result, fermented products have a shelf life substantially higher than raw materials and also have very beneficial effects on health. In this research, ginger in 4 and 8 % levels and yogurt whey in 0 and 3 % levels, were added to the carrots and evaluated during of 0,4, 8, 16, 24 and 32 days of fermentation. The results showed that by adding 4% ginger, pH, mold and yeast count and L* index decreased, acidity, total count, lactic acid count, a* and b* color indexes and overall acceptance increased. In contrast, the addition of 8% ginger had a negative effect on the studied parameters and decreased the overall acceptance and enumeration of lactic acid bacteria. Addition of yogurt (3%) decreased pH, mold and yeast count and L* index, but increased acidity, total count also color indices a* and b* and overall acceptance. In the non-yogurt and non-ginger sample from the beginning to the end of the storage period, pH, total count and mold and yeast counts increased steadily, and overall acidity and acceptance decreased. Whereas in the samples containing ginger and yogurt, the pH and count of mold and yeast decreased as the fermentation time increased to the 16th day and overall count increased, lactic acid bacteria, acidity and total acceptance. According to the results of this study, using 4% ginger, 3% yogurt and 16 days fermentation time to increase shelf life and lactic acid bacteria and improve the sensory characteristics of fermented carrots.
Volume 17, Issue 1 (3-2017)
Abstract
Development of wave energy convertors (WEC) is one of the main challenges that naval architectures have encountered, recently. One of the most important approaches before construction of WECs is the evaluation of their conceptual models in computational fluid dynamics (CFD) software. Therefore, in the current article, an innovative model of wave energy convertor is presented and hydrodynamic performance of proposed model in Persian Gulf has been examined. For accurate simulation of dynamics of WEC, mesh morphing technique is utilized. Since the presented WEC is an innovative design and there is no experimental result for validation purpose, it is tried to verify the numerical setup using similar experimental problems which have the various characteristics of the considered problem. Then, several different geometries including flat and foil pedals, and big and small semi-spherical pedals as a part of WEC have been analyzed, numerically. Small semi-spherical pedal has been determined as the best possible geometry. Number of pedals has been another parameter which has been studied and eight pedals model has been recognized as optimum choice. Finally, optimum WEC has been simulated in nine different waves and the results have been presented.
Ali Shakoor, K. Yazdjerdi, A. Kamanah, Gh. Roshan, M. Ramazanzadah,
Volume 17, Issue 2 (6-2010)
Abstract
This paper tries to systematically survey, with taking theoretical view on geomorphic basin and its changes into account. The purpose of this research is to determine the balance and stability of geomorphic basins from the past to present and then to future. Consequently, it tries to determine the balance between energy and input-output materials for example (rainfall , solar radiation, tectonics and neotectonics …) to the basin based cybernetics (including geomorphic, topographic and geological state) and also to calculate energy and material balance considering positive and negative entropy at basin level. Based on the findings, which is the outcome of cybernetic resultant between form and process in basin, we can determine stability and type of balance in the basin. In this paper, emphasis has been put only on rainfall (express of the energy exponent). However, it first discusses Kor Basin Geomorphic locations and Energy-Material Entropy on its surface and then Quantity form of energy (Isolated & Potential Energy). Considering geomorphic state of the basin, we can determine the best planning method from all systems (planning, risk management and crisis management) for basin that neither requires a great cost nor causes disturbance in stability and geomorphic balance while being the optimal process. In Kor geo planning, we are encountering and determining two dimentions: (Y dimension, for geomorphic change for example throughput topogeraphy geradient formations on Kor Basin and X dimension, for rainfall discharge range on Kor Basin rivers out let only and only on fiat paper surface), but in Kor geo management, we represent at least three – dimensional ordered, for example topogeraphy gradient for Y coordinate and rivers discharge quantity for X coordinate and absolution geography location (for space point Z coordinate). Consequently, Kor River Basin can be studied based on two scientific metod : I . Planning & II , Management .
Volume 17, Issue 2 (3-2017)
Abstract
In this paper, conceptual design of a General Aviation Aircraft (GAA) is explained as a multi-objective Multidisciplinary Design Optimization (MDO). In the early sizing phase, preliminary aircraft configuration is defined based on a predetermined requirements and statistical Study. Afterwards, conceptual design disciplines are developed and integrated based on Multidisciplinary Design Feasibility (MDF) structure to improve the aircraft performance. The MDF loop is established by implementing a multidisciplinary analysis which includes disciplines as engine selection, weight and sizing, aerodynamics, performance and stability. In this design process, Constraints and algorithms are considered based on the Gudmundsson design approach. Design variables are selected carefully using sensitivity analysis on design objectives (i.e. reducing the weight and increasing the range). In order to obtain a feasible design, static stability constraints are considered. The NSGA-II multi-objective evolutionary optimization algorithm is utilized to demonstrate a set of possible answers in the form of the Pareto front. By selecting different engines and illustrating the Pareto fronts resulted from optimization process, the feasibility and effectiveness of rapid GAA conceptual design is demonstrated.
Volume 17, Issue 3 (5-2017)
Abstract
In today’s world, using of biogas is increasing due to its methane content, renewability, and low price. Solid oxide fuel cell is one of the best energy conversion technologies, in order to use biogas and it has a high potential to integrate with the gas turbine. In this paper, solid oxide fuel cell-gas turbine hybrid system, which is fed by biogas is modeled with respect to energy and economic aspects. Maximization of electrical energy efficiency and minimization of total investment cost are objective functions, which are considered to find the optimal design variables of the hybrid system. First, each component of the hybrid system is modeled and validated individually. Then, in order to optimize the hybrid system, multi objective optimization via NSGAII is implemented and optimal values of design parameters of the hybrid system were calculated. Optimal point is obtained using Euclidian non-dimensionalization and LINMAP decision making method in Pareto front. So, optimal design values are 66 percent and 175227.4 $, which are electrical energy efficiency and total investment cost, respectively. In optimal point Levelized unit cost is 6.3 cent per kWh. Finally, in order to determine the effect of design parameters on the objective functions, sensitivity of each design parameters were analyzed using Sobol's sensitivity analysis method. Results show that compressor pressure ratio has the maximum effect on electrical energy efficiency. Furthermore, turbine isentropic efficiency and fuel cell current have the maximum effect on the total investment cost.
Volume 17, Issue 6 (8-2017)
Abstract
In this paper the problem of optimal multiple-burn injection of a satellite into geostationary orbit using an upper stage with a limited thrust and restart capability, and comparison with sub-optimal case is considered. The goal is finding thrust vector angle, times of the engine firings and optimal duration of active phases of the upper stage so as to minimize fuel consumption and to meet desired boundary conditions. The contribution of this research is developing an accurate and rapid convergence algorithm for solving multiple-burn trajectory for satellite injection into geostationary orbit. To solve the multipoint boundary value problem, an improved indirect shooting method with high performance and modified Newton’s method is presented and used for optimal solution. Moreover, the novel method presented for multi burn problem, not only has very good accuracy, but also, it converges very fast to the desired end conditions. Various flight sequences with multiple burns are considered and the optimal trajectory with minimum fuel consumption criteria, for each flight sequence is derived. The verification and validation of the proposed algorithm is made via comparison with references. Finally, the results of optimal solutions are compared with the results of sub-optimal solution which its thrust direction is aligned to the velocity vector direction.
Volume 17, Issue 12 (2-2018)
Abstract
In this research, High Order Expansions method implementation in order to obtain an optimal solution for an unmanned aerial vehicle continuous maneuver problem is studied. The main goal of this research, is to describe a specific approach to solve nonlinear optimal control problems using series expansions and algebraic matrix Riccati equation in order to obtain solutions with better performance. Based on this, the state feedback control with different powers is used for optimal commands calculations. Clearly, the control command would be high order and closed-loop; it has been shown it results in a superior performance in smooth nonlinear problems. In this research, in addition to the implementation of High Order Expansions method and its usage, a different approach of dealing with optimal control problem based on this method has been given. Continuous maneuver of an unmanned aerial vehicle problem is solved for investigating the performance of the proposed method. In this example, the High Order Expansions up to and including the third order are used and two different flight scenarios are simulated. By investigating the result of the solution to this problem, the superior performance of the third order optimal command with respect to the first order is illustrated.
Volume 17, Issue 100 (june 2020)
Abstract
Abstract
Free radicals cause many diseases in human. Antioxidants reduce the risk of cardiovascular disease and stroke by neutralizing free radicals and on the other hand, prevent progression of cancer. The natural antioxidant enhances antioxidant properties of plasma to prevent diseases such as heart disease, cancer, and stroke. Plants are a rich source of secondary compounds, which are the most important natural antioxidants.
In this study, Fumaria vaillanti aqueous, methanol and ethanol extracts were used to determine the anticancer effect of extracts on Breast Cancer Cells Lines BT-474, MDA-MB_231 after 24, 48 and 72h.
The highest percentage of cell death, according to the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) technique, has been reported in the aqueous extract on MDA-MB-231 cells after 72 hours at with IC50 of 2 μg / ml.
The results of this study indicate that Fumaria vaillanti shows a significant antioxidant and cell toxicity effect and full potential of extracts can be realized by further studies on animal models and subsequent trials.
Volume 17, Issue 104 (October 2020)
Abstract
Oils and fats under the influence of several factors such as oxygen, light, heat, metal ions and enzyme are oxidized. Use of synthetic antioxidants due to the possibility of toxicity and carcinogenicity, has been under questioned. The aim of this study was to optimize the extraction conditions of Ajowan seed extracts and evaluate their antioxidant properties. In this study Ajowan seed under different concentration of solvents (water and ethanol in 0, 50 and 100% concentration), extraction time (0.25, 12 and 24 hours) and different temperatures (20, 50, 80 °C) were prepared. The optimal extraction conditions were defined by response surface methods and extraction was performed at the optimum condition. Then different concentrations (0.2, 0.4 and 0.6%) of optimum extracts were prepared and added to the non- containing antioxidant soybean oil. All treatments were kept under 90 °C for 5 days. Acidic value, peroxide value and
thiobarbituric acid (TBA) were performed on each treatment in every day. Data analysis showed that addition of water to the solvent increased phenolic compounds extracts and antioxidant activity. According to the results of the thermal stability of soybean oil, the best results were related to BHT and other higher concentrations of ethanolic extracts. The results of the present study showed that the ethanolic extracts of Ajowan seed can be used as natural antioxidants in the formulation of edible oils.
Volume 17, Issue 106 (December 2020)
Abstract
Abstract
Ovarian cancer is one of the deadliest cancers in women causing abnormal cancerous cells that can spread and metastasize to other parts of the body. Secondary metabolites are highly variable in terms of structural and chemical properties and they are very important for plants survival. In this study, the extracts of two plants using three different solvents (water, ethanol 80% and methanol 80%) and water bath extraction method were obtained. phenolic compounds of extracts were determined by Folin Sioculto method. DPPH (2, 2-Diphenyl-1-picrylhydrazyl) and FRAP (Ferric reducing ability of plasma) methods were performed for determination of antioxidant properties. The amount of phenolic compounds in two plants was higher in 80% methanol solvent and the most antioxidant activities were observed in water solvent of extracts. Water solvent had the highest antioxidant activity and was selected to investigate the anti-cancer properties of extracts on ovarian cancer cells. Water extract of Ocimum basilicum within72 hours had the highest cytotoxic effect with an IC50 value of 1.105 ± 0.001 mg / ml. In study of antimicrobial activity by disc diffusion method, the highest antibacterial properties were only in ethanol extracts of two plants. In the measurement of MIC and MBC, ethanol and methanol extracts of Ocimum basilicum and water and ethanol extracts in Imatiens walleriana had the most inhibitory and bactericide effects.