International Journal of Engineering, Transactions B: Applications

Resin transfer molding (RTM) is a composite manufacturing process. A preformed fiber is placed in a closed mold and a viscous resin is injected into the mold. In this paper, a model is developed to predict the flow pattern, extent of reaction and temperature change during filling and curing in a thin rectangular mold. A numerical simulation is presented to predict the free surface and its interactions with heat transfer and cure for flow of a shear-thinning resin through the preformed fiber. To verify the model results, the temperature profiles for preformed fiber has been calculated, and compared with the experimental results of the other researchers. The results showed that, the heat dispersion for a viscous fluid saturating a heater fibrous porous media is an important phenomena in RTM process. Also, because of the mold thickness is much less than its in-plane dimensions, the through thickness dispersion (kdyy) has a strong effect on the non-isothermal process.

ParLeda is a software library that provides the basic primitives needed for parallel implementation of computational geometry applications. It can also be used in implementing a parallel application that uses geometric data structures. The parallel model that we use is based on a new heterogeneous parallel model named HBSP which is based on BSP and is introduced here. ParLeda uses two main libraries that are widely used: MPI for its message passing in the parallel environment and LEDA for its data structures and computations. Dynamic load balancing and replicating C++ objects are two key features of this library. This library was implemented after a survey in researches on parallel computational geometry algorithms and selection of their common primitives. Keywords: Computational Geometry, Parallel Processing, Load Balancing, LEDA, MPI, ParLeda. 1

A prismatic beam made of a behaviorally nonlinear material was analyzed under a concentrated load moving with a known velocity on a nonlinear elastic foundation with a reaction the vibration equation of motion was derived using Hamilton principle and Euler Lagrange equation. The amplitude of vibration, circular frequency, bending moment, stress and deflection of the beam can be calculated by the presented solution. Considering the response of the beam, in the sense of its resonance, it was found that there is no critical velocity when the behavior of the beam and foundation material is assumed to be physically nonlinear and there are finite values for the deflection, stress and bending moment of the beam when h = q =w

Bit swapping linear feedback shift register (BS-LFSR) is employed in a conventional linear feedback shirt register (LFSR) to reduce its power dissipation and enhance its performance. In this paper, an enhanced BS-LFSR for low power application is proposed. To achieve low power dissipation, the proposed BS-LFSR introduced the stacking technique to reduce leakage current. In addition, three different architectures to enhance the feedback element used in BS-LFSR was explored. The pass transistor merged with transistor stack method yielded a better reduction in power dissipation compared to pass transistor design and NAND gate design. The BS-LFSR was designed in Mentor Graphic - TSMC Design Kit Environment using 130nm complementary metal oxide semiconductor (CMOS) technology. The proposed 4-bit BS-LFSR achieved an active area of 1241.1588um2 and consumed only 53.8844nW with total power savings of 19.43%. The proposed design showed superiority when compared with the conventional LFSR and related work in reducing power dissipation and area.

Historical monument of Menar-Jonban (shaking tower) is located in the famous city of Isfahan in central Iran. Initial construction of this interesting and unique masonry monument belongs to 700 years ago. This monument has two vibrating circular towers of 7.5 m height. These towers are separated from each other by a distance of 9.2 m and constructed on top of an ancient tomb of 10 m height. When one of the towers is shaken by the human force, the other one immediately starts to vibrate without transmitting any significant vibration to the other parts of the structure. This unique dynamic behavior has become a puzzle to architects and structural engineers for many years. Visitors from all over the world, climbing to the top of one of the towers and by shaking one, cause automatic shaking of the other tower. In this paper, the description of the structure, free and forced vibration tests setup, test results and findings on this unique structure is presented. Moreover, to identify the dynamic characteristics and behavior of this monument, analytical studies have been performed and the results of the various possible mathematical models were compared with measured response for system identification purposes.

Three-factor interaction for the two-level, three-level, and four-level factorial designs was studied. A new technique and formula based on the coefficients of orthogonal polynomial contrast were proposed to calculate the effect of the three-factor interaction The results show that the proposed technique was in agreement with the least squares method. The advantages of the new technique are 1) it is fixed, 2) it is simple and 3) it is easy to apply without the complicated matrix formula of the least squares method. This new technique will also enhance the use of the coefficients of orthogonal contrast when analyzing other experimental designs.

Effects of pH, D2EHPA, Cyanex® 272 and Cyanex® 302 on extraction of zinc, manganese and cobalt from a Zn-Mn-Co-Cd-Ni containing solution at the room temperature was comprehensively investigated. Addition of Cyanex® 302 indicated a left-shifting-effect on the extraction curve of zinc, a right-shifting-effect on the extraction curve of manganese and no effect on the extraction of cobalt. Addition of Cyanex® 272 shifted all three curves to the right. Therefore, the most suitable extractant for separation of zinc from manganese was therefore 0.3-0.3 mixture of D2EHPA and Cyanex® 302, and that for separation of manganese from cobalt was pure D2EHPA. The stoichiometric coefficient for the extraction reaction of zinc (whether using pure D2EHPA or a mixture made of D2EHPA with Cyanex® 272 or Cyanex® 302) was 3. It varied from 4 to 5 for manganese, when the quantity of Cyanex® 302 dissolved in D2EHPA increased from 0 to 100%. Utilizing the above results, a two stage leaching was devised to recover zinc, manganese and cobalt from a complex solution. At the first stage, a 0.6M D2EHPA extractant could recover zinc, and a scrubbing reaction with organic:aqueous (O:A) ratio of 20:1 could wash-out cadmium from the raffinate. In the second stage, the extracting residue was treated with 0.6M D2EHPA for recovery of manganese. This stage was then followed by a one-stage scrubbing of cobalt with O:A ratio of 20:1.

The present investigation aims to deposit the three different hard facing powder (Triboloy T-700 and PAC 718, and TETCO 41 C) on SS 304L using laser cladding technique. The single and overlapped clad track was deposited using 2 kW laser power system. The optimized laser process parameters and 50% overlap clad track was used to deposit a large surface area. The optimum laser process parameters were finalised using single clad structure study. The cross-sections of the clad layers were used to obtain the microstructure and micro-hardness from different regions namely, clad layer, diffusion layer, and substrate. Throughout the study, the laser power was kept constant i.e. 1.2 kW. For single clad deposition, the scanning speed and powder feed rate varied from 0.3 to 0.5 m/min and 4 to 9 g/min, respectively. T-700 and PAC 718 shows uniform developing micro-structure while METCO 41 C shows the development of mixed dendritic and cellular type microstructure. The Triboloy shows the maximum surface hardness of 534 Hv, 321 Hv for PAC 718, and 294 Hv for METCO 41 C. © 2021 Materials and Energy Research Center. All rights reserved.

As the scaling continues, Carbon Nanotube Field Effect Transistors (CNFET) are considered to be the potential candidates for overcoming the shortcomings associated with the scale of the art Complementary metal–oxide–semiconductor (CMOS) transistors. In this paper a digitally reconfigurable CNFET based biquadratic multifunctional filter employing a CNFET based single Differential Voltage Current Conveyor (DVCC) at 32nm technology node is presented. The circuit utilizes a single CNFET based DVCC block along with the arrangement of few resistors and capacitors. The proposed digitally reconfigurable multifunctional filter circuit is able to obtain programmable low pass, high pass and band pass filter configurations using the same topology. The designed CNFET based multifunctional filter obtains a resonant frequency of the order of GHz. Furthermore, a 3-bit digital control of the designed multifunctional filter parameters i.e. Quality Factor (Qo) and resonant frequency has been made possible using the Current Summing Network (CSN). Sensitivity and comparative analysis has also been performed. The circuit has been simulated at a low voltage supply of 0.9V using Hewlett Simulation Program with Integrated Circuit (HSPIC) environment at 32nm technology node. The simulation results obtained are in sync with the theoretical analysis. © 2021 Materials and Energy Research Center. All rights reserved.

Buried pipes in the modern societies are considered as lifelines with a vital and essential role in the human life cycle. The performance of buried pipes is affected by many factors such as ground surface subsidence. In this paper, the effect of subsidence on pipelines is investigated using a three-dimensional numerical modeling developed in FLAC3D software for four types of most commonly used pipes. The numerical results showed that ductile iron, steel, and polyethylene pipes with a diameter of 200 mm are stable in the presence of ground subsidence whereas the asbestos pipes at depths of 1 and 1.5 m are not stable; and thus should be buried deeper. In this regard, polyethylene pipes with equal diameter are recommended instead of asbestos pipes due to the high excavation and earth-filling costs and also environmental problems involved in the implementation of asbestos pipes.

Plastic injection is a method in which by using an extruder plastic granules are injected in a hole with high pressure. Because of meeting the two flow fronts in this process, a welding line will be made. Along the welding line, the strength of produced part is low; therefore, the position of welding line and its clarity are very important. In this paper, analysis has been done with Fluent and Mold Flow softwares. In addition, verification of these analysis have been done with practical experiments in order to study the effect of injection pressure and temperature on the welding line and its clarity. The materials used in these experiments are ABS and PP. Results show that applying different injection pressures and temperatures affects the strength of the produced part. It is worth noting that both considered polymers are sensitive to pressure at high temperatures. For instance, pressure increase from 45 MPa to 65 MPa at 210 °C results in 35% and 45% reduction in plastic region, respectively. Temperature increase from 170 °C to 210 °C reduces the modulus of elasticity by about 16%. For the ABS polymer, the plastic region increases 13% at the injection pressure of 55 MPa and 65% at the injection pressure of 65 MPa. Temperature increase from 190 °C to 230 °C reduces the elastic modulus by 8%. © 2018 Materials and Energy Research Center. All rights reserved.

In this research about 450 cases of 3D shear walls are considered with different shapes and heights. L, T and H-shape walls are studied. They are nonlinearly analyzed in Abaqus using a micro-model, i.e. the finite element modeling and analysis. A meso-modeling approach using fiber elements is also examined in Opensees. It is shown that the meso-model is both accurate enough and much faster than the micro modeling approach. To go further, a macro-model is developed in bending in which the nonlinear behavior is assumed to be concentrated at the base of the wall using a rotational spring. The axial force, shape of the cross section, percentage of the longitudinal reinforcement and the aspect ratio of the wall are recognized to be the main parameters defining characteristics of the rotational spring. Using regression, semi-analytical formulas are suggested for rapid determination of the moment-rotation curve of the rotational spring. Comparison with micro-model and available experimental results confirm the good accuracy of the developed macro-model.

Highly ordered mesoporous MCM-41silica with hexagonal structure was synthesized using extracted amorphous silica from sedge (Carex riparia) ash. Obtained mesoporous materials functionalized by 3-(Aminopropyl) trimethoxysilane (APTMS) and their structures characterized by means of X-ray diffraction (XRD), nitrogen adsorption-desorption, thermogravimetric analysis (TGA) and Fourier transform infrared (FT-IR) spectroscopy. The synthesized material were applied for adsorption of Cd(II) metal ions from aqueous solution in batch and fixed bed column systems. Batch adsorption process was carried out to evaluate initial ion concentrations, sorbent dose, contact time, pH and temperature. The equilibrium data were analyzed using the Langmuir and Freundlich isotherm by nonlinear regression analysis. The kinetics study reviled that data from the experiments fitted well to the pseudo-second order equation than pseudo-first order. Thermodynamic parameters reviled that the adsorption process strongly depended on temperature and the adsorption capacity increased by increasing the temperature of the system, indicating the endothermic behavior and spontaneous nature of adsorption. For continuous adsorption experiments, NH2-MCM-41 adsorbent was used and breakthrough curves were analyzed at different bed heights, flow rates and initial metal ion concentrations. Thomas and bed depth service time (BDST) models were used to determine the kinetic constants and to predict the breakthrough curves of each component.

Wire-Electric Discharge (WED) Machining is one of the most suitable machining techniques for machining hard-to-cut materials such as Titanium, with precision. It is of utmost importance to optimize the control parameters to achieve the desired levels of machining performance characteristics. Considering this goal, this research investigates the effects of current, pulse on time (Ton) and pulse off time (Toff) on the material removal rate, surface roughness and kerf width of WED machined Ti-6Al-4V. The results of optimization showed that, current – 5.19 A, Ton – 20 µs, Toff – 30 µs, is the optimized settings for machining of Ti-6Al-4V alloy using molybdenum electrode for the best machining performance. Based on the analysis of grey relational grades, the order of influence of the control parameter is ranked as: Ton – I, Toff – II and Current – III. The efficacy of GRA based approach was evaluated through confirmation experiments wherein the theoretical predictions showed errors < 3%.

A B S T R A C T Clostridium ljungdahlii is a strictly anaerobic acetogene known for its ability to ferment a wide var iety of substrates to ethanol and acetate. This bacterium presents a complex anaerobic metabolism including the acetogenic and solventogenic phases. In this study, the effect of various carbon sources on triggering the metabolic shift toward solventogenesis was considered. The bacterium was grown on fructose, glucose, acetate and ethanol in batch cultures. The fermentation results demonstrated that fructose improved ethanol prod uction (27.1 mM) over acetate (26.3 mM), but glucose was predominantly metabolized to acetate. The bacterial cells were able to either utilize or produce ethanol (25 mM) probably through different metabolic pathways. The presence of acetate as the carbon source in the culture shifted the metabolic pathway of the cells toward solventogenic phase, but the amount ethanol formation was not considerable (3.5 mM). It was also atte mpted to improve ethanol production yield by varying the fructose concentration (1 to11 g/L) in the batch culture. Under the conditions of substrate depletion or high fructose concentrations, the cell growth declined and the metabolic pathway of C. ljungdahlii was unable to switch from acetogenesis to solventogenesis. The fructose concentration of 5 g/L was found as the suitable concentration to yield an ethanol to acetate molar ratio of 1:1.

In the current work, the seismic analysis of bent region in buried pipes is performed, and effects of soil properties and modeling methods on pipe's response are investigated. To do this task, beam, beamshell finite element modeling, and a continuum shell FE model of a 90-degree elbow are employed. In the beam model, the pipe is simulated by beam elements while combined shell-beam elements are used for the continuum shell finite element model. The surrounding soil is simulated by nonlinear springs and solid elements; moreover, soil hardening behavior and soil-pipe slippage are considered in the models. In addition, an equivalent boundary condition has been employed at the end of each elbow leg to simulate far field effects more closely. From these analyses, it can be revealed that axial strain at bends is larger in stiffer soil due to smaller slippage. In addition, a full three dimensional soil-pipe interaction using continuum shell FE model causes a substantial increase of elbow strain.

In this paper, the effect of various parameters on out-of-phase thermo-mechanical fatigue (OP-TMF) lifetime of A356.0 cast aluminum alloy is investigated. The studied parameters include maximum temperature, dwell time, and the thermo-mechanical loading factor. OP-TMF tests are conducted considering realistic running conditions of diesel engine cylinder heads. The maximum temperature varies between 200 to 275°C and the thermo-mechanical loading factor, which is the ratio of mechanical strain to thermal strain, is considered between 75 to 150%. The dwell time (or holding time) changes between 5 to 180 sec. at maximum temperature. The fracture surfaces of specimens are studied using Scanning electron microscope (SEM). These SEM images reveal that A356.0 alloy has a ductile behavior. The cyclic softening phenomenon is also observed during stress-strain hysteresis loops. The TMF tests results demonstrate that the dwell time bears no significant effect upon the lifetime. However, large influences for maximum temperature and the thermo-mechanical loading factor are depicted in the lifetime of A356.0 alloy.

In the present study, the influences of cold rolling and annealing time on the fatigue crack propagation behavior of AA5052 aluminum alloy were investigated. The alloy sheet was cold-rolled under different rolling reductions, i.e., 0, 15, 30, and 45%. A 45% as-rolled specimen was then annealed at 370°C under different annealing times, i.e., for 2, 4, and 6 h. The microstructure evolutions after the cold rolling and annealing treatments were also examined using optical microscopy whereas the fatigue crack propagation behavior was characterized by using a fatigue test. Results showed that severely elongated grains were observed with increasing the rolling reduction. The elongated microstructures were changed into equaxial structures due to recrystallization during annealing treatment. The fatigue life was decreased drastically by increasing the rolling reduction but increased significantly with increasing annealing time. The fatigue life of the alloy was reduced by 93% when cold-rolled up to 45%. On the other hand, the fatigue life of the 45% rolled samples was increased significantly by 412% when annealed at 370ºC for 6 h. © 2021 Materials and Energy Research Center. All rights reserved.

Precast prestreesed concrete braces are a new method for seismic strength of Concrete Structures which has the following benefits: a) no wet concrete work in construction site b) no bolt or anchorage to the existing frame c) easy to apply d) short construction period e) low construction cost; to evaluate seismic performance of strengthened structure. A model consist of existing frame and concrete braces were created using ABAQUS (nonlinear-finite element) software. Comparison existing and strengthened frame showed that braces are effective in lateral drift decreasing. Study concrete compressive strength on seismic behavior of brace showed that when compression strength of brace is lower than existing frame; retrofitting system has low stiffness and wasn’t effective in reducing lateral drift. But, in specimen with compressive strength ratio (brace to frame) two times or more, braces showed high strength and stiffness. © 2018 Materials and Energy Research Center. All rights reserved.

Gelatin is considered as a partially degraded product of collagen and it is a biodegradable polymer which can be used to produce scaffolds for tissue engineering. Three-dimensional, porous gelatin scaffolds were fabricated by thermally induced phase separation and freeze-drying method. Their porous structure and pore size were characterized by scanning electron microscopy. Scaffolds with different pore sizes were obtained by adjusting the concentration of the gelatin solution. Scaffolds with 3.75% (w/v) gelatin and 5% (w/v) gelatin produced pores ranging from 100 to 450µm. The average pore size increased with an increase in gelatin concentration. The properties of the scaffolds in terms of water uptake were studied. The results showed that when the concentration of the gelatin solution was changed from 3.75% to 5%, the water absorption of the fabricated scaffolds decreased by 104%. The increment in the concentration of gelatin induced a reduction in water uptake in the scaffolds produced. © 2018 Materials and Energy Research Center. All rights reserved.

Optimum design of sound absorbers with optimum thickness and maximum sound absorption has always been an important issue to noise control. The purpose of this paper is an achievement of optimum design for micro-perforated panel (MPP) and its combination with a porous material and air gap to obtain maximum sound absorption with maximum overall thickness up to about 10 cm in the frequency range of (20-500 Hz), (500-2000 Hz) and (2000-10000 Hz). For this purpose, the genetic algorithm is proposed as an effective technique to solve the optimization problem. By using the precise theoretical models (i.e. simplified Allard's model and Atalla et al.’s model) to calculate the acoustic characteristics of each layer consisting of MPP, porous material, and airgap, we obtained more precise optimized structures. The transfer matrix method has been used to investigate the sound absorption of structures. To verify the operation of the programmed genetic algorithm, the results obtained from the optimization of the MPP absorber are compared with others that show the accuracy and efficiency of this method. After ensuring the accuracy of the proposed programmed genetic algorithm with more precise theoretical models to achieve the characteristics of each layer, new structures were obtained that have a much better sound absorption coefficient in the desired frequency range than the previous structures. The results show that the sound absorption coefficient can be reached to 0.67, 0.96, and 0.96 in the mentioned first, second, and third frequency range, respectively by optimum design parameter choosing of a composite structure. © 2022 Materials and Energy Research Center. All rights reserved.

The energy absorbing capability is one of the most important aspects of crushing behavior of a structure subjected to axial impact. In this paper, a simple practical method is introduced to enhance the crushing behavior of this kind of structure. The dynamic explicit simulation of axial impact of metallic energy absorbing thin-walled tubes with special shaped cross-section is provided using LS-DYNA software. The effect of change in the corners bluntness of non-circular tubes on their energy absorbing capability has been studied. Moreover, the mean crushing force, the maximum deformation, and the mass specific energy absorption (MSEA ) of the tubes were compared. Results show that the energy absorbing capability can be significantly improved by choosing proper bluntness of the corners for quasi-triangle- and quasi-square shaped tubes. Furthermore, results show an improvement in the energy absorbing capability of quasisquare shaped tubes even in comparison with circular one.

Progressive collapse is a kind of failure in which whole or large part of a structure collapses when a local damage occurs and distributes to other parts. Earthquake inspections indicate that structural element can be damaged during earthquakes and this initial damage distributes to the other parts, so seismic progressive collapse is proposed as a research issue. As the earthquake induced progressive collapse could occur in any building independent of the number of stories, in this work, seismic progressive collapse of a one-story steel building was investigated. The effect of variation in the number and length of spans in both directions was also studied. Based on the obtained results, by decreasing the spans length and number in the direction of lateral loading compared with its perpendicular direction, the behavior of the structure becomes more critical. Furthermore, failure pattern of the structure under seismic progressive collapse was investigated. The results showed that collapse pattern is in a way that the damaged frame as well as the nearby frames has the most participation in supporting lateral deformations, and by distancing away from the damaged frame, deformation of the frames decreases. At the end, non-linear dynamic column removal analysis was carried out and the obtained results showed differences between the behavior of the structure under seismic progressive collapse and sudden column removal analyses.

Energy absorbers are used to reduce accident induced damages. Thin-walled energy absorbers are widely used in modern industries due to their high efficiency and ease of manufacturing. In this study, thin-walled stainless steel structures in quasi-hemisphere geometry were subjected under quasi-static loading using Santam 150KN apparatus. Experimental results were compared with the results of numerical simulations by LS-DYNA and it was shown that there is a good agreement between experimental and numerical results. Two different collapse types in radial and circumferential directions were observed. Also, the multi-cell quasi-hemisphere specimens from 3 to 6 cells were numerically investigated and it is observedthat increasing the number of cells increases the absorbed energy. Increasing the thickness of the quasi-hemisphere sample in smaller diameter specimens is more effective. The results showed that Six-cell specimen with the largest diameter and the minimum thickness has the most increase of Specific Absorbed Energy (SAE) with respect to simple section.

Most existing power converters and industrial motor drive systems draw non-sinusoidal currents from the supply. Non-sinusoidal currents contained harm harmonics disturb the power supply which it causes serious concern for reliability. Other equipments that use the same power supply are adversely affected. This paper suggests the operation and performance of a new modified AC/DC converter that allows bi-directional power flow. It also provides improved power factor and reduces harmonic magnitude and disturbance to the supply by system. The bi-directional feature allows recovery of regenerative energy of loads, back to the power supply and the converters. The proposed converter has high potential for industrial applications, such as electronically controlled traction system, lifts and generally industrial motor drive systems which can increase overall efficiency and reliability.

The effect of squeeze casting process parameters on wear behavior of AC2A aluminium alloy was primarily investigated in this experimental study. Five process parameters, namely squeeze pressure, pouring temperature, die temperature, die material and compression time, each at four levels were chosen and sixteen experimental runs based on L16 orthogonal array were performed. From analysis of variance (ANOVA) and F-test, it was observed that squeeze pressure, die temperature and compression time were the parameters making significant improvement in wear resistance. A mathematical model relating the effect of significant parameters with wear behavior was developed for the process using nonlinear regression analysis with the help of MINITAB software. Taguchi method, Microsoft XL Solver and MATLAB genetic algorithm were employed to optimize the process. The result show that parametric conditions obtained through the optimization tools exhibit about 20% enhancement in wear resistance compared to gravity casting condition.

This paper develops Order Acceptance for an Integrated Production-Distribution Problem in which Batch Delivery is implemented. The aim of this problem is to coordinate: (1) rejecting some of the orders (2) production scheduling of the accepted orders and (3) batch delivery to maximize Total Net Profit. A Mixed Integer Programming is proposed for the problem. In addition, a hybrid meta-heuristic algorithm is developed. For a quick exploration around a solution, a Local search is proposed. Two simple heuristics for initial population and a heuristic for batching are proposed. Besides, data is generated to evaluate the performance of algorithms and compare with each other based on comprehensive experiments.

Memories are most important building blocks in many digital systems. As the integrated circuits requirements are growing, the test circuitry must grow as well. There is a need for more efficient test techniques with low power and high speed. Many memory built in self-test techniques have been proposed to test memories. Compared with combinational and sequential circuits memory testing utilizes more amount of power. Test circuitry is intensively used for memory testing. This may cause excessive power consumption during memory testing. Sophisticated and efficient techniques with less overhead on power must be needed. Regarding memories, power consumption is very much high during testing when compared with normal functional mode. March test algorithms are popular testing techniques used for memory testing. Power consumption during testing can be reduced by reducing the switching activity in test circuitry. A new test technique is proposed in this paper to reduce power consumption in test mode by reducing the switching activity in Built in Self-Test circuitry. Address sequencing in the address decoder is changed in such a way that it reduces switching activity.

The occurrences of accidents on the railways are inevitable in today's world and the factors which may cause it, except the atmospheric and accidental ones, are identified and preventable as well. Therefore, these factors can be investigated and useful actions can be performed in order to reduce these accidents. The main impetus of the present research is the statistical analysis of the causes of railway accidents in Iran. Our achievement illustrates that except the train collision accidents with vehicles, all the accidents vary upon a sixth order curve which means the instability and unpredictability of the railway accidents during the last years. According to the performed studies, it is clarified that the railway accidents during the 10 years from 2000 to 2010 haven't had a stable flow and have been under fluctuations and each of the kinds and causes of the accidents has their own contribution to the occurrence of these railway related happenings. Based on the analyses, derailment is the major factor of the various railway accidents and it includes about 55% of these accidents. Damage to people and collisions with non-rail vehicles are place in the second category. Hereupon, efforts must be made by providing the necessary equipment for the simple access of the people beyond the lines such as pedestrian bridges in order to reduce the railway accidents.

The paper seeks to highlight and analyze the relationship between the occupants’ displacements of chest and pelvis and the deceleration of vehicle in frontal crash accidents. A testing scheme including 5 groups of dynamic tests was devised and conducted. Totally, 5 kinds of acceleration pulses were employed to simulate the real crash. The experimental finding indicates that the integral values and shapes of vehicle’s deceleration pulses can influence the occupants’ chest and pelvis displacements to some extent; thus, having effects on the risks of secondary collisions between occupants and the vehicle. How the deceleration pulses of vehicle influence the secondary collision is also clarified in the paper by a comprehensive comparison of testing results between different groups. Further research can be carried out on optimization of deceleration pulses of vehicle in the frontal collisions and on how to reduce the risks of secondary collisions based on the findings. © 2021 Materials and Energy Research Center. All rights reserved.

This paper presents a set of linearized equations which was derived for the motion, relative to an elliptical reference orbit, of an object influenced by J2 perturbation terms. Approximate solution for simulations was used to compare these equations and the linearized keplerian equations to the exact equations. The inclusion of the linearized perturbations in the derived equations increased the high accuracy of the solution significantly in the out of orbit plane direction, while the accuracy within the orbit plane remained roughly unchanged. In fact, it will be determined whether the inclusion of this disturbance provides a significant increase in accuracy over Melton's problem. Because of replacing approximate terms (e, M) in this solution, for continues accuracy increase of time-varying parameters containing θ(t) and RO(t), this solution could be useful in the element-errors evaluation and analysis of orbital multiple rendezvous missions, that are involved to the short-period terms.

In this paper, we present a new model for calculating the capacitance of MEMS sensor with corrugated diaphragm. In this work, the effect of residual stress is considered on deflection of diaphragm and capacitance of sensor. First, a new analytical analyzes have been carried out to derive mathematic expression for central deflection of corrugated diaphragm and its relationship with residual stress. Then, the capacitance and sensitivity of sensor using corrugated diaphragm with residual stress are calculated under bias voltage and pressure. The analytical results are compared with simulation using a Finite Element Method (FEM). The results show that the new analytical model is very close with simulation results.

Accurate determination of the pull-in, or the collapse voltage is critical in the design process. In this paper an analytical method is presented that provides a more accurate determination of the pull-in voltage for MEMS capacitive devices with clamped square diaphragm. The method incorporates both the linearized modle of the electrostatic force and the nonlinear deflection model of a clamped square diaphragm. The capacitor structure has been designed using a low stress doped poly silicon diaphragm with a proposed thickness of 0.8 μm and an area of 2.4 mm2, an air gap of 3.0 μm, and a 1.0 μm thick back plate. The value of pull-in voltage calculated using equation is about 6.85V and the finite element analysis (FEA) results show that the pull-in occurs at 6.75V. The resulting pull-in voltage and deflection profile of the diaphragm are in close agreement with finite element analysis results.

Thermoplastic elastomer (TPE) based on polyamid 6 (PA6)/ acrylonitrile-butadiene rubber (NBR) containing 5 wt % nanoclay (Closite 30B) have been prepared via friction stir process (FSP). In this study, the essential work of fracture (EWF) approach was employed to investigate the fracture behavior of PA6/NBR nanocompsites. Also, the modulus strength of specimens was modeled by response surface methodology (RSM), considering three input variables including rotational speed (ω), traverse speed (S), and shoulder temperature (T). Thus, a quadratic mathematical model between input variables (ω, S and T) and response (modulus strength) of PA6/NBR/clay nanocomposites was achieved. Moreover, the morphology of the PA6/NBR blends containing 5 wt % was investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that a sample of PA6/NBR thermoplastic elastomer (TPE) containing 5 wt % nanoclay at maximum tensile strength exhibited the maximum specific essential work of fracture (we) and specific non-essential work of fracture (wp). Also, the results of RSM method demonstrate that the optimum condition of the process including rotational speed (ω), traverse speed (S), and shoulder temperature (T) were 1200 rpm, 25mm/min, and 146°C, respectively. Thus, under optimum condition, maximum modulus strength of 658 MPa was obtained. © 2021 Materials and Energy Research Center. All rights reserved.

Nitrate contamination of water resources and the growing concentration of nitrate endanger human health and the environment and considering its reduction strategies from water resources is important. The aim of this study was to investigate the possibility of granular activated carbon from grape wood coated with iron nanoparticles to remove nitrate from aqueous solutions. The results showed that more than 99% of the nitrate was removed from the solution using granular activated carbon/nanoparticles zero valence iron (GAC/NZVI). The nitrate adsorption process by GAC followed the Freundlich isotherm (R² = 0.95) and NZVI and GAC/NZVI followed Langmuir isotherm (R² = 0.96). Furthermore, the kinetic studies of all three adsorbents in the nitrate adsorption showed the highest correlation with the pseudo-second order equation. According to the results of this study, it can be stated that activated carbon derived from grape wood coated by iron nanoparticles as a relatively cheap and abundant adsorbent is efficient in nitrate removal from water. © 2018 Materials and Energy Research Center. All rights reserved.

The structural and bleaching properties of nitric acid-activated Nteje clay was studied to investigate its ability to serve as an alternative to the high cost imported bleaching earth. The clay was mined, sundried, grinded, and reacted with different concentrations of nitric acid, ranging from 2 mol.L -1 to 15 mol.L-1. The un-activated and activated samples were characterized to study the structural effects of the activation process. The activated samples were employed in bleaching palm oil under controlled conditions of the process variables. The characterization results showed that the surface area, cation exchange capacity (CEC), and oil retention properties of the activated samples were affected by the activation reaction. The surface area increased to about 4 times (288.8 m2.g-1) the initial value (68.5 m2.g-1), while the CEC decreased from 154 to 65 meg.100-1g-1 with acid activation. The bleaching studies revealed that the activated clay samples adsorbed color pigments from palm oil more than the un-treated clay sample, with the bleaching efficiency of the sample activated using 13 mol.L-1 HNO3 increased from 37.82 % to 89.76 %. This study has shown that nitric acid can be employed favourably in activation of Nteje clay to improve its bleaching ability. It is also concluded that the activated samples can serve as an alternative to the imported bleaching earths.

Municipal and industrial wastewater contain a lot of contaminants. The major contaminants of concern are heavy metals. Heavy metals are known to be toxic, non-biodegradable and have a long half-life. The release of untreated wastewater containing heavy metals can cause serious problems to human, plants and animals. In this study, activated carbon was developed from sugarcane bagasse and its effectiveness in adsorbing lead ions from wastewater was examined. Batch adsorption experiments were carried out to investigate the effects of pH and initial lead concentration on the adsorption process. The batch adsorption test showed that extent of lead adsorption by sugarcane bagasse activated carbon (SCBA) was dependent to pH and initial lead concentrations. The optimum pH for lead adsorption was found to be pH 5.0. Removal of lead decreases with the increase in initial metal concentrations. The adsorption of lead ions onto SCBA follows a pseudo-second-order reaction model. The rate limiting step is a chemisorption or chemical adsorption that involves van der Waals forces through electrons exchange between the SCBA and lead ions.

Curcumin is the natural bio-active component of turmeric (Curcuma longa L.) with known therapeutic properties; nevertheless, its biological applications are limited due to its poor bioavailability. To overcome this limitation, curcumin was conjugated with silica nanoparticles. Curcumin was separated from turmeric by microwave-assisted extraction and silica nanoparticles were developed from rice husk. Conjugation of curcumin with silica nanoparticles was performed through ultrasound-assisted wet impregnation. XRD, FTIR and UV-visible analyses confirmed the successful synthesis of the conjugate; the drug loading in the nanoparticle was 39% as determined by HPLC analysis. TEM and AFM analyses indicated the spherical morphology of the conjugate with average particle size of 85.9 nm. The cell killing activity of the conjugate was tested against HeLa, MCF-7 and Saos-2 cancer cell lines and normal fibroblast cell line using MTT assay. The silica:curcumin conjugate was effective for destruction of cancerous cells, especially HeLa cells, with minimum side effects on healthy fibroblasts. © 2018 Materials and Energy Research Center. All rights reserved.

Project success is assessed based on various criteria, every one of which enjoys a different level of importance from the beneficiaries and decision makers. Time and cost are the most important objectives and criteria for assessing project success. On the other hand, reducing the risk of finishing activities by the predetermined deadlines should be taken into account. Having formulated the problem as a multi-objective planning one, the present study aims to minimize the project completion time as well as maximizing the net present value and project flexibility by taking into accounts the resource constraints and precedence relations. Here, the flexibility of the project is calculated by considering a free float for each activity and maximizing the sum of these flotation times. Moreover, the performance of each activity may be possible in various states of using resources (mode) which can change the project completion time and cost. Owing to the complexity of the problem, the Multi Objective Simulated Annealing Meta-Heuristic Algorithm is used to solve the proposed model. For accrediting the algorithm, four benchmark problems were considered. Since the algorithm performed well in finding the optimal answers to the benchmark problems, it was used to find the optimal answer of large scale problems. © 2018 Materials and Energy Research Center. All Rights Reserved.

This paper investigates the parametric excitation of a micro-pipe conveying fluid suspended between two symmetric electrodes. Electrostatically actuated micro-pipes may become unstable when the exciting voltage is greater than the pull-in value. It is demonstrated that the parametric excitation of a micro-pipe by periodic (ac) voltages may have a stabilizing effect and permit an increase of the steady (dc) component of the actuation voltage beyond the pull-in value. Mathieu type equation of the system is obtained by applying Taylor series expansion and Galerkin method to the nonlinear partial differential equation of motion. Floquet theory is used to extract the transition curves and stability margins in physical parameters space (Vdc-Vac). In addition, the stability margins are plotted in flow velocity and excitation amplitude space (u-Vac space). The results depict that the micro-pipe remains stable even if the flow velocity is more than the critical value for a certain dc voltage. For instance, in absence of the (ac) component, it is shown that pull-in voltages associated to critical velocities 3 and 6 are 14.06 and 5.4 volt, respectively. However, transition curves show that superimposing an (ac) component with forcing frequency ω=10 increases the pull-in voltage beyond these values. Furthermore, for the present pull-in voltages the critical velocities 3 and 6 could be increases with imposing some (ac) component. These results are discussed in detail in simulation results section where the transion curves are ploted quantitatively.

The present work demonstrates the successful application of a simple active vibration control procedure based on structural dynamics. Based on theories of mathematical and structural dynamics, the appropriate locations of sensor and actuator of smart structure were predicted. Also, the optimum value of actuator force which controls the structural vibrations is quickly formulated so that the first damping coordinates becomes critical. The validity and efficiency of the proposed method have been investigated by active vibration suppression of some classic structural models. The results showed the ability of suggested active control processes in suppression of the unwanted structural vibrations.

Soft robotics using Pneumatic Network actuators (Pneu-Net) is a developing field that has a promising future for variety of applications involving delicate operations such as biomedical assistance. The interaction between geometry and the performance of the actuator is an important topic which has been studied by many researchers in this field. However, there is a lack of investigation on the relationship between gripping capability and geometrical parameters of soft actuators. Especially, there is a need to shed more light on the effects of wall thicknesses on the gripping force developed. In the present study, a semi-cylindrical chambered PneuNet soft actuator is numerically investigated to evaluate the effects of pressure and wall thickness variations on its performance characteristics. The results revealed that increasing the restraining layer thickness (RLT) aids the bending capability of the actuator whereas increasing the chamber wall thickness reduces it. Therefore, maximum bending of the actuator is achieved at the combinations of minimum wall thickness and maximum RLT. At these geometrical configurations of maximum bending, the deformation-pressure relationships followed a sigmoidal function and tended towards linearity with increasing wall thickness and decreasing RLT. The gripping force showed an exponential increase with increasing working pressures and wall thicknesses. The maximum gripping force increased cubically with increasing wall thicknesses at their respective maximum working pressures, which was modeled using a polynomial regression model (R2=99.79%).

A modified method for satellite attitude control system in presence of novel actuators is proposed in this paper. The attitude control system is composed of three fluidic momentum controller (FMC) actuators that are used to control Euler angles and their dynamics is considered in satellite attitude equations as well. L1 adaptive control is utilized for satellite three-axial stabilization. A significant characteristic of L1 adaptive control structure is that robustness is guaranteed in presence of fast adaptation. The main achievement of this controller is that the error norm is inversely proportional to the square root of adaptation gains. Therefore, large values of gains provides some advantages. The proposed L1 adaptive control is designed based on simplified attitude dynamic equations without satellite coupling effects, and then it is placed on coupled nonlinear equations. Next, the impact of available delay on FMC actuators is investigated. Simulation results suggest that the system remains stable with the assumption of actuators time delay, but it experiences some oscillations in Euler angles, control inputs and angular velocities. In order to solve this problem, a modified L1 adaptive control system including a predictive observer with high estimation speed is used. Finally, it is recognized that the available oscillations are reduced even when the actuator time delay increases and thus the control system's performance improves. © 2018 Materials and Energy Research Center. All rights reserved.

In many signal processing applications, such as EEG analysis, the non-stationary signal is often required to be segmented into small epochs. This is accomplished by drawing the boundaries of signal at time instances where its statistical characteristics, such as amplitude and/or frequency, change. In the proposed method, the original signal is initially decomposed into signals with different frequency bands using wavelet transform. The fractal dimension of the decomposed signal is calculated in a sliding window and the results are used as a feature for adaptive segmentation. A criterion is introduced in this paper to choose a proper length for the sliding window. Performance of the proposed method is compared with that of three other existing segmentation methods using synthetic and real EEG data. Simulation results show the high efficiency of the proposed method in signal segmentation.