Modares Mechanical Engineering
Year:2018 | Volume:18 | Issue:1 |Papers Count:54

Due to high ability of built-up edge formation during aluminum machining, this study aim to reducing adhesive wear and increasing surface integrity of 5052 aluminum alloy work piece has been focused on creating different surface texture on tungsten carbide cutting tool. For this purpose, four types of micro-grooves such as parallel and perpendicular to cutting edge and also pit and cross mode have been created on rake face by laser machining process. In addition to the types of texture, three methods of cooling-lubrication condition include: dry machining, flood mode without pressure and flood mode with high-pressure along with various holder and cutting inserts (with chip-breaker and without chip-breaker) as well as three levels of cutting speed (fixed feed rate and depth of cut) were considered as process variables. The experimental results obtained from surface roughness survey of the machined parts along with prepared images of optical microscopy from the work piece surface showed that the presence of parallel micro-grooves significantly improves the cooling-lubrication conditions of the tool-chip surface and its effect on numerical reduction of surface roughness value and reduction of density of defective regions on the work piece surface is visible. The prepared images by scanning electron microscope (SEM) of the tool rake face showed that the presence of chip-breaker did not significantly effect on reduction of adhesion wear in the machining of aluminum alloy but micro-texture can be largely improved the adhesion wear area compared to non-textured tool (with chip-breaker or without chip-breaker).

With increasing amount of pollution by thermal power plants in Industrial and developing countries, tend to use small-sized hydroelectric plants increased. In complex terrain regions there are usually a significant height difference between refineries and using place, the pressure can to produce electricity by power plants pressure reducer. The power plant is due to the relatively high initial cost less were used. Gradually, with the possibility of using pump as turbine and reducing the cost of building a micro power plant use the plant was expanded. Therefore, in this study centrifugal pump by CFturbo software was designed and for Numerical analysis of the three-dimensional fluid, the simulation was performed using the CFX software on SST k-w turbulence model. The numerical results were compared with experimental in pump and turbine modes and showed good agreement. In order to increase the efficiency of the turbine pump (reverse pump), the decrease in the thickness of the impeller blades at different flow rates was investigated, which resulted was decrease in the amount of separation phenomenon around blades and causing increase in hydraulic quantities nearby the turbine bep point, but reducing the thickness at the flow rates very lower from bep point, didn’t have great impact at improvement of efficiency, at the bep point reducing the thickness, caused to increase 11.86 and 13.65 percent of the head and torque, and improved efficiency 1.26 percent.

In this paper, the production of anodes of vertical titanium oxide nanotubes is analyzed and optimized by anodizing method. The parameters of the potential difference and the distance between the two electrodes in the anodize process are investigated and the effect of these parameters on morphology and anode structure has been investigated. The produced anodic plates, have been investigated by field-scattering electron microscope, X-ray diffraction spectrometer and radiation diffraction. The results indicate that by increasing the applied voltage from 20 to 50 Volt, the anodized nanotube diameter will increase from 50 to 155 nanometre, and after a certain voltage, the structure of the nanotubes is destroyed and nano / micro porosity is created. Also, by increasing the voltage from 20 to 50 volt, the wall thickness of the nanotubes increases from 20 to 50 nanometre. As the duration of the voltage increases, the length of the nanotubes increases; but the thickness and diameter of the nanotubes remain constant. As the gap between the two electrodes increases from 0.5 to 4.5 CM, the thickness of the walls decreases from 57 to 13 nanometre. Thus, by controlling the above mentioned parameters, the optimum state of the anodized nanotubes can be achieved to obtain a more and faster penetration of lithium ions. The results of this research are very useful in improving the performance of lithium ion batteries.

In this study, effects of zeta potential distribution and geometrical specifications are investigated on mixing efficiency in electroosmotic flows. Flow geometry in this research is a series of converging-diverging microchannels with different diverging ratios. Governing equations including the Navier Stokes equation for fluid flow and the Poisson-Boltzmann equation for internal electrical field are solved numerically in a two-dimensional domain by using the lattice Boltzmann method. Numerical simulations are validated against available analytic solutions for electroosmotic flow in homogeneous straight channels. The response surface methodology (RSM) is then employed to investigate relationship between flow variables and consequently to optimize mixing efficiency and flow rate of the channel. Results indicate that increasing the zeta potential ratio and diverging ratio, leads to increased value of flow rate, while meanwhile it decreases the mixing efficiency. Zeta potential pattern does not affect flow rate considerably, but its effects on mixing efficiency is noticeable. Furthermore, it is found that mixing efficiency and flow rate are more sensitive to zeta potential ratio than diverging ratio. At last, optimum parameters are determined by RSM which are 0.5 for zeta potential ratio, 0.6 for diverging height, and pp-nn pattern for zeta potential distribution, all associated to simultaneously maximized flow rate and mixing efficiency.

In this paper, a C-programming code is produced to introduce the best propulsion system including an internal combustion engine combined with turbochargers. Because the power of internal combustion engine will reduce as the altitude increasing, it is required to use one or more turbochargers in order to compensate the loss of power which is caused by reduced ambient air pressure. For this purpose, a code is written that will be able to introduce the best turbochargers combination including intercoolers, according to the target power and the desired altitude of the UAV flight. In other words, input required parameters of the code is the target power of the engine and desired altitude of flight and output of the code is number and characteristics of the turbochargers with their exact manufacturing company names and also the number of intercoolers required for best performance of propulsion system. It should be noted that, if the turbochargers that is chosen by the program are not available, user can select of the similar turbochargers with similar characteristics without any significant difference in performance of the propulsion system.

The rotational Equations of motion of spacecraft are generally nonlinear, so use of nonlinear control techniques are helpful in real conditions. Feedback linearization theory is a nonlinear control technique which transforms nonlinear system dynamics into a new form that linear control techniques can be applied. Choosing output functions in input-output linearization which is a specific method of feedback linearization, has a significant effect on internal dynamics stability. In this study the kinematic equations of spacecraft motion are expressed by quaternion parameters, these parameters are selected as output functions. Linear quadratic regulator as a linear optimal control law is used to design a controller for linearized system in feedback linearization control and also to design attitude control of spacecraft separately. By considering the actuator constraints on different control methods that are used here, the EULERINT which is the integral of the Euler angles error about the Euler axis, is evaluated. Then, the power and control effort of the actuators are considered for comparison between controllers. The simulation results show that the amount of EULERINT for feedback linearization method is less among the others. Also study of the power and control effort shows that Feedback linearization method is not only quicker but also more efficient and displays better performance of the actuators.

Nowadays, diagnosis of diseases with high precision, high speed, low-cost and non-invasive approaches has become a necessity. In this regard, taking pulse signal is very easy and inexpensive, which due to the availability and feasibility of the process, can be very useful in the rapid diagnosis heart disease. If we can use the appropriate signal processing and intelligent methods in such a way that its accuracy and total cost equal those of other corresponding methods, we can say that we have reached a valuable achievement; in the current study we pursue the same purpose. In the first step, pressure pulse signals of 45 Coronary Arterial Disease (CAD) patients and 45 healthy persons are acquired from the left fingers using Task Force Monitor (TFM). Then the signals are filtered by wavelet transform (db6) and the wrong items are discarded. Then, the features corresponding to the CAD and healthy states are extracted which based on Time Domain Analysis. By choosing the best features, the data of healthy people and patients (CAD) are classified with Support Vector Machine (SVM) classifier by the accuracy rate of more than 85%. Finally, the effect of age on the best feature was investigated. A correlation of less than 5% between the best feature and age was obtained.

Surface engineering in many manufacturing industries plays an important role in improving product performance and increasing the operating time of parts. Pure aluminum has a very high electrical conductivity, good corrosion resistance and strength to weight ratio. However, due to very low hardness and wear resistance, its application is limited. Therefore, this paper is studied may improve the surface properties of pure aluminum using copper and nickel as alloying elements using electric discharge process. The pulse on time and pulse current as input parameters and surface hardness, alloyed layer texture and surface roughness as output parameters have been considered. According to the micro hardness testing results, in this alloying method, the average hardness of the aluminum parts is about more than 8 times and in some parts of the 38.5 Vickers reached up to 450 Vickers, Based on the results of XRD analysis, the formation of intermetallic compounds Al3Ni2, ALCu, and Al4C3 increased surface hardness. The results show that by increasing the pulse on time surface hardness increased and surface roughness becomes greater. Also, Increasing pulse current the surface roughness increasing trend.

In this paper, a new Multiple Model Adaptive Control (MMAC) is proposed to control of the satellite antenna position with time varying input delay. Selecting of adequate delay estimation method and weighting algorithm using delay estimation error are features of proposed controller. Input delay can be effect on the performance of the closed loop system and if delay time is unknown and time varying, the closed loop system will probably be unstable. At these cases, delay time must be identified to adopt control signal. It is assumed that upper bound of the delay time is known. Delay time is divided into several small bounds and then an adequate PI controller is designed for each bound to guarantee closed loop system performance and stability. In the on-line mode, delay time is identified by adequate estimation algorithm and the control signal is constructed by a weighted sum of the designed controllers output. Control signals weights are a function of the absolute error between the estimated and the average delay time in each bound. Performance of the proposed method and stability of closed-loop system is assessed using several simulations of the system. Simulation results confirm the effectiveness of the proposed algorithm with respect to conventional PI controller.

In this work, joining of 4014 Aluminum tube to 7075 rod is studied using magnetic pulse welding process. The effect of impact angle (4, 6 and 8 degrees) and welding voltage (6 and 7 kV) on the joint are investigated. The microstructure of the weld cross section was evaluated using optical and scanning electron microscopy and mechanical properties of the welds were evaluated by micro hardness and tensile tests. The results showed that, for the impact angles of 4 and 6º, the increase of welding voltage from 6 to 7 kV, leads to the change morphology of interfacial from straight to wavy. While, for the impact angle of 8o, the increase of the welding voltage increases local melting and results in the degradation of the interface. At the same angle, increasing the welding voltage increases the hardness due to the higher work hardening and severe plastic deformation. On the other hand, the effect of welding voltage on the hardness is dominant compared to the impact angle. The results of the tensile test showed that, for the low impact angles, increasing the welding voltage increases the shear strength, while, for the higher impact angles, it decreases the shear strength because of creating holes in welding interface. The results showed that joining of aluminum tube/rod with impact angle of 6º and welding voltage of 7 kV leads in uniform and wavy interface with higher shear strength in comparison with other conditions.

The two thermal effects, thermophoresis and photophoresis phenomena that cause particle movements due to thermal gradient through the liquid and thermal gradient through the particle, respectively, have been widely studied over the past years because of their wide range of applications. This thermal gradient can be made by laser beam. There are a few studies concerning these two effects, especially photophoresis, in liquid media. In this paper, these two effects and their induced velocity to particles are studied in liquid media. The affecting parameters on these effects are studied and their effect on particles are determined. Effect of laser parameters like laser power and wavelength in the channel are discussed and the maximum velocity and temperature inside the channel are calculated. Also in the photophoresis part, the effect of parameters like laser power, particle and laser beam diameter is calculated. By considering the existing models for calculation of thermophoretic velocity, Brenner model is chosen as the most accurate model and will be used in calculations. It is also found that the effect of laser wavelength on thermophoretic velocity is more than changing laser power. In the photophoresis part, photophoretic velocity is calculated by using existing analytical models. The calculated velocities of thermophoresis and photophoresis are compared with the experimental values and there is an acceptable matching between them. The results of this paper will be used for designing and making a particle separator tool.

In this study, the effect of surface roughness on fatigue life was investigated in drilling process of AISI4340 steel. Three hole making methods including drilling with and without pre-drill and helical milling were utilized. In order to study the effect of surface roughness and process parameters on fatigue strength, the two main cutting parameters including cutting speed (Vc) and feed rate (fz) were changed at 5 levels using the response surface method. Five main parameter of surface roughness profile including Rz, Rt, Ra, Rq, and Rsm were measured in each experiment. Then, the fatigue life of specimens were obtained using fatigue tests. Regarding the validation experiments, 13 fatigue tests were carried out for each drilling strategy (39 fatigue tests totally). Investigation of surface texture showed the signs of the tool path, scratches by the chip collisions and ploughing on whole surfaces in the conventional drilling. These effects were negligible in other processes. Accordingly, the highest roughness was observed in conventional drilling, drilling with pre-drill and helical milling processes respectively. Also, the fatigue life estimation model based on Rz had the best estimation with an average error of 4.4%. In fact, the fatigue life is more dependent on the difference between adjacent peaks and valleys. It was also observed that a model based on the roughness parameter will decrease the maximum prediction error of the fatigue life from 16.4% to 7.5% compared to a model based on the cutting parameters.

The ability to control the flow, is one of the basic needs of Fluid Mechanics that constantly pursued by researchers. One of the new methods in this area, is using Dielectric barrier discharge (DBD) plasma actuators that by injecting momentum into the boundary layer, causing a delay in the phenomenon separation. The main object in this work was to help to optimize the electrical parameters to obtain stranger vortex and more effective ionic wind created by steady and unsteady plasma actuators on the air through the flat plate. For this reason, simulation is done for a flat plate with the compressible 5 m/s velocity airflow. The time averaged velocity profiles of the ionic wind show that averaged velocity come more and the position of the maximum velocity come near the surface by increasing the excitation voltage and frequency. The power, of the vortices that are shed form the unsteady actuator, increases by increasing duty cycle percentage. Our results on the ionic wind velocity on different position on the flat plate indicate that the maximum averaged velocity occurs in downstream of plasma actuator.

The purpose of this paper is to design a control system with a pre-designed algorithm in order to reach a compromise between satellite attitude and thermal control systems. In addition to the indispensable attitude control system, a thermal control system (TCS) is regarded as a substantial subsystem in any given satellite. The latter is commonly used to effectively reduce the internal heat and/or the thermal tensions caused by solar radiations. In this paper, a novel actuators known as fluid momentum controllers (FMCs) have been utilized to simultaneously produce control torques and develop a cooling mechanism by circulating liquid through a ring. In this research, it has been assumed that the satellite’s internal temperature has reached a critical level to the extent that the FMCs are not able to reduce this temperature sufficiently. In such a case, it is possible to mitigate this problem using a combination of both attitude and thermal control subsystems (CATCS). To accomplish this, a thermal model has been employed to yield the temperature of all six sides of the satellite at each time step and a switching algorithm to design an integrated system. This algorithm uses a particular decision making logic to realize the reconciliation of the two subsystems. Also, a sliding mode controller has been used for the three axis stabilization of the satellite. Simulation results of the integrated attitude and thermal control system indicate that it is possible to conduct an appropriate temperature control while saving power and integrating the two subsystems.

Since woven fabrics have uniqe characteristrics such as light weight, flexibility, high strength, etc. and they are also capable to be improved for mechanical properties by nano thechnology, it is expectal to gain more efficient composite using intrinsic properties of the ceramic nanoparticles and proper coating method. The uniqe properties of the nanoparticles such as high elastic modulus, high strength to weight ratio etc. as well as participating in defeat mechanisms agains external loadings, can be of the factors reinforcing the textiles. Al2O3-13%TiO2 coatings were deposited on Kevlar Fabric substrates from nanostructured powders using atmospheric plasma spraying (APS). A complete characterization of the feedstock confirmed its nanostructured nature. Coating microstructures and phase compositions were characterized using SEM, and XRD techniques. The microstructure comprised two clearly differentiated regions. One region, completely fused, consisted mainly of nanometer-sized grains of a-Al2O3 with dissolved Ti+4. The other region, partly fused, retained the microstructure of the starting powder and was principally made up of nanometer -sized grains of g-Al2O3, as confirmed by FESEM. Coatings were in average slightly lower than the values for nanostructured coating. The results of tensile testing on kevlar fabrics before and after coating showed that APS could improve tensile strength up to 60%. High velocity impact test (V50) performed on coated fabrics well indicated that their ballistic limit experienced a significant increase. In addition, the results of V50 showed revealed that APS can decrease final weight of new composite panel compared to plain polyetylen panel with identical protection level.

Container crane is an under-actuated system, which is why it is much more difficult to control such systems. In this paper, partial feedback linearization and sliding mode controllers are employed to control a 2D container crane with varying cable length. Since, the dynamic model of the system cannot present the real one and the system contains some uncertainties, a controller is designed to reduce the effect of model uncertainties and external disturbances. Since the considered system is under-actuated, in order to design controller, first, dynamics of the system is divided into two parts, actuated and under-actuated. Then, stability of the controllers is discussed. An objective function is considered as the combination of integral of absolute error and rate of variation of control signal. The introduced objective function is minimized employing Harmony Search and particle swarm optimization algorithms and optimum values for parameters of the designed controllers are determined to make it possible to compare performance of the mentioned controllers in their optimum conditions. Simulation results show suitable performance of the designed controllers by harmony search algorithm for the 2D crane in the presence of mass uncertainty, actuator disturbances and sensor noises.

In this article, indentation process of thin-walled metal sections with quadrangular cross-section was studied under the applied lateral compressive loading by a rigid cylindrical punch through numerical simulations by the ABAQUS. Based on numerical simulations and by changing one of the parameters and fixing the other parameters, effects of that parameter was investigated on total and specific absorbed energy by the structure. In other words, influences of various geometrical dimensions such as height, width and wall thickness of cross-section, punch diameter, loading rate and also, effects of material were investigated. In each part, physical justifications of the obtained results were presented, based on theoretical and engineering concepts. Comparison of the results showed that in the specimens with the same cross-sectional perimeter, but, with different aspect ratios, the highest ratio of height/width of the cross-section, results in the best energy absorber, in the studied domain. Furthermore, by changing the height and fixing the width of cross-section and the other parameters, when height of the cross-section was selected equal to punch diameter, the maximum value of total and specific absorbed energy was achieved. But, when cross-section width changed and height and the other characteristics remained constant, by reducing the width, energy absorption performance of the structure improved. In addition, numerical simulations showed that total and specific absorbed energy of quadrangular sections are dependent on the second and first power of wall thickness of the cross-section, respectively. Also, in same specimens, by increasing punch diameter, both TAE and SAE increased.

In this study, stabilization attitude control of a rigid satellite with on-off thrusters using pulse-width pulse-frequency (PWPF) modulator is investigated in presence of sensor noise. The preferred regions of the PWPF modulator parameters and stabilization control gain are obtained based on the two performance indices of the fuel consumption and the total number of thruster firings. The analyses include tumbling, detumbling, and stabilization block as an internal loop of the satellite pointing mode. The design parameters are reduced by using the quasi-normalized equations of PWPF modulator. Therefore, the preferred regions are extracted based on search method in terms of grouped parameters, regardless of the value of each parameter, separately. In quasi-normalized form, the computational burden is considerably decreased, especially in the statistical analysis in the presence of sensor noise. The parametric study is carried out with/without sensor noise. The parameters are also tuned using multi-objective optimization with genetic algorithm for stabilization mode without sensor noise. In the presence of sensor noise, the behaviors of the parameters are plotted versus the noise power spectral density. In order to better specify the preferred regions, each quasi-normalized design curve is plotted for a specified value of the input noise power spectral density. The parameters of the satellite attitude control system are suggested to be tuned/optimized within the preferred regions of the parameters in the stabilization loop as an internal loop.

In the present work, the three dimensional fluid flow inside a hydrocarbon reservoir block along with the fluid flow inside the wellbore of a production well drilled in this reservoir block is numerically simulated. To do this, the single-phase incompressible fluid flow in the hydrocarbon reservoir in terms of Darcy’s law (porous media flow) along with the fluid flow inside the wellbore in terms of Navier-Stokes equations (free flow) are simultaneously solved. The effects of boundary conditions imposed on the faces of the reservoir block, the off-centered wellbore, and the reservoir rock permeability on the fluid flow behavior inside a reservoir block are investigated. In each case, the well index is numerically approximated, using the pressure and velocity distributions in the reservoir block and the wellbore pressure, and compared with analytical well index. The numerical results indicate that the well equivalent radius and also the well index not only depend on the geometrical properties of reservoir block and well bore and the rock absolute permeability, but also depend on the boundary conditions imposed on the reservoir block faces and the well drilling location.

One of the most important factors in reducing the lifetime of PEM fuel cells is heterogeneous current distribution on membrane surface. Since flow field plays an important role in reactants distribution and water depletion and consequently current distribution, hence, in this paper, with development of a lumped model, water and current distributions on membrane surface were evaluated in two different designs. In this model, the flow field is divided into equal segments and connection between segments are created through flow field pattern. In both designs, flow field of anode side was serpentine, but on cathode side, parallel and serpentine flow field were used in first and second design, respectively. Simulations were carried out for different input relative humidity from 0 to 100 in both sides. The results showed that flow field had no significant effect on polarization curve and the second design had a little better performance in high current density. Also, in terms of current distribution, the second design shows a better uniformity, so that in the first design in fully saturated inlet condition, difference between the percentage of current generated between the first and last segments is about 1.57 percent which recehes to 1.45 percent in the second case.

In the present research, the performance of a Tesla microvalve has been studied under the unsteady three dimensional flow. The time averaged of diodicity is the main criteria for the evaluation of the performance of the valve. By simulation and obtaining the velocity and pressure fields within microvalve, changes in operating parameters of valve including total pressure drop and diodicity parameter in the range of various frequencies studied under sinusoidal excitation. The results showed that the amount of diodicity in steady three dimensional with consideration of third dimension is lower with respect to steady two dimensional flow at entire of studied range of Reynolds numbers. Transient effects on microvalve performance in three dimensional is also studied. It is observed that total pressure drop of unsteady case is greater than steady case at both of forward and backward directions. This important result is in a qualitative agreement with simulation results of other researchers which are obtained by two dimensional simulations. Investigation of effect of applied frequency on Tesla microvalve performance at different Reynolds number is another part of this study. The results showed that at the frequencies lower than 100Hz, the performance of the Tesla microvalve is independent of the frequency, however at higher frequencies greater than 100HZ, its performance is improved by increasing the frequency. Microvalve performance is improved and diodicity is increased by increasing of Reynolds number at all frequencies.

In this paper, an analytical path-dependent plastic instability model is proposed for the thin metallic sheets through considering a linear pre-straining path for the both diffuse and localized necking. The model is introduced by extending a modified maximum force (MMFC) that the MMFC considers the strain hardening on the diffuse necking as well as the loading conditions. Also, the vertex criterion will be used to prediction of localized necking. The vertex criterion presented by storen and Rice are usually based on the J2 deformation theory of classical plasticity, which explores the localized necking through the rate discontinuity assumption at the necking band. Both models will be combined with the strain path effect through a linear adoption of an equivalent strain. It will be investigated by applying a pre-strain in the major and minor directions for prediction of the formability in the non-proportional loading. Moreover, a dependent to yield criterion (DYC) - angle is used for prediction of the necking band angle in the vertex theory. Finally, the quadratic Hill criterion is used to investigate the anisotropy effect. The model is verified by experimental results presented by other authors.

In this paper, the method of non-singular backstepping terminal sliding mode (NSBSM) is used to control the motion of an unmanned aerial vehicle (quadrotor). In the first step, the dynamic equations of quadrotor will be derived by considering all of the effective parameters. The purpose of controller is to achieve proper tracking for desirable positions (x, y, z), yaw angle (Y), and sustainability of the roll and pitch angles notwithstanding of external disturbances. In practical, due to the need for complete information about system states, the usage of controlling methods may be limited. Noise is an indispensable part even all the states of system be available. It should be noticed that usage of a large number of sensors in order to measure states, cause the whole system to be complex and expensive in practical. For this purpose, the Extended Kalman Filter (EKF) has been used as an observer. The EKF in the control structure is used as observer states of the system and noise reduction in these modes. Therefore, simultaneous use of the controller-observer is suggested for controlling and estimating quadrotor states. The design method is based on the stability of Lyapunov and also the simulation results show the good performance and robustness of the observer-controller.

The aim of the proposed study is to investigate the size dependent behavior of the micro-bridge gyroscopes under the combined effects of instantaneous DC voltage and harmonic base excitation. To do so, modified couple stress theory is utilized to model the size-dependent behavior of the micro-gyroscope. To avoid resonance, viscous damping is used. Hamilton’s principle is then employed to derive the governing equations of motion. Afterwards, to convert the partial differential equations of motion to ordinary differential equations of motion, a Galerkin based single mode approximation is made. Then fourth-order Range-Kutta method is used to solve the governing equations of motion. To check the accuracy of the present model, the results are then validated through comparison with the available results in the literature and the comparison shows good agreements. In addition to the previous comparison, the present results are the validated through comparison with the results of COMSOL simulation. Furthermore, the effects of different parameters on the dynamic pull-in instability and amplitude of the vibrations are investigated. The observation shows that for the case of the harmonic base excitation, the system will be excited on two frequencies.

Early diagnosis of hypertensive diseases such as cancer plays an essential role in preventing disease progression. The main cause of death from cancer is the reappearance of the disease due to the release of tumor cells in the blood of the patient. Among the various methods that have been devised for monitoring blood in recent years, the techniques based on micro-scale flow have specially been considered. The development of these methods has led to the emergence of microfluidics laboratories on the chips, which their main advantages are low prices and simplicity. Since the particles’ sizes are different in the flow of blood, the direction of these particles in the micro-channels will vary due to the different forces, and therefore they can be analyzed to the design of bio-microchips. In the present study, a two-phase flow containing spherical particles with the dimensions of blood cells was considered, and the forces affecting the particles of this current, including the lift forces and drag forces, were studied using COMSOL software. For this purpose, a micro divergent channel was designed and the effect of ratio of the outlet width to the inlet width (Aspect Ratio) as an effective geometric parameter in the biological particle separation was analyzed. The study of the effect of particle dimensions and various geometric parameters of the channel on bio-particles separation are the main goals of this research. The results show that by increasing the Aspect ratio, focusing of the larger particles would increase at the outlet of micro-channel.

Optimization of the arrangement of turbines with the aim of producing the maximum power in a wind farm is inherently part of continuous and nonlinear problems. In the present study, for the linearization of the Wake constraint and the connection between turbine power are used single Wake and discrete models. Also, the criterion of placing a turbine in another turbine has been applied indirectly and linearly. The proposed mathematical model compares to continuous nonlinear mathematical models, while maintaining the advantage of achieving exact optimum, has a lower runtime and higher stability. Comparison of the results of the present study with the results of previous studies suggests that met heuristics algorithms may not be obtained in absolute optimal answer. In addition to the power output, environmental issues can also affect the arrangement of turbines. As an example, the maximum noise level is applied in the present model. In order to calculate the intensity of sound, Euclidean distance based on the spread of the hemisphere and the effects of atmospheric absorption has been used. According to the results, it can be said that under the conditions under consideration, the noise level can cause a significant reduction in the output power of the wind farm. Therefore, in selecting the field, attention should be paid to the distance to residential areas. In addition, the effect of cell count on the accuracy of the results was investigated. The results show that there is no clear relationship between optimal power and number of cells.

Sudden cardiac arrest and heart diseases are the leading causes of death globally, but cardiopulmonary resuscitation (CPR) may prevent multitude of death if being performed timely and accurately. Since in many cases of cardiac arrest there is not a trained rescuer and conventional CPR method is difficult and may being performed incorrectly, various equipment has been produced for this purpose. In this study, by reviewing of previous important studies on automated chest compression devices and comparing their effectiveness in returning of spontaneous circulation (ROSC), a novel, portable, programmable, flexible and automated chest compression system is introduced. For prototyping of this device, first required data were extracted from studies on CPR, then mechanical components for compression system and chassis, and electronic components for controlling unit were designed and produced. The novel device which is developed in this research could be installed easily and perform the chest compression according to the patient’s condition and guidelines automatically. It also enables chest compression even during patient transport. Furthermore, because of user-friendly design, everybody could use it easily. Eventually comparison between this device and other similar automated devices indicates that this device has more benefits and more reasonable price as well.

Ceramic balls are industrial parts which have special physical and mechanical properties, thus industries paid attention to them. Ceramic balls are produced by powder metallurgy method. They will reach to desired smoothness, roundness and required diameter via grinding, lapping and polishing procedures. The required finishing process for producing ceramics by required level of surface and geometric precision is time consuming and expensive, so making a new economic finishing method is an important issue in production of ceramic balls. In this article a new mechanism for lapping ceramic balls proposed. The proposed mechanism composed from two lap plates. The lower lap plate has an eccentric V-shaped groove and placed out of upper plate rotation center. The cinematic analysis of proposed mechanism carried out and lapping trajectory on surface of ceramic balls evaluated. The results of cinematic analysis and lapping trajectory shows that the proposed mechanism improves the removing rate and roundness of ceramic balls. Generally, the efficiency of lapping ceramic balls procedure for achieving the desired surface smoothness and roundness improved, and by increasing the removal rate, the speed of process increased and thus the finishing time decreased.

The circular hydraulic jump usually forms when a liquid jet impinges on a horizontal flat plate. However, under certain conditions of fluid viscosity, volume flow rate and obstacle height downstream of the jump, the flow changes from super-critical to sub-critical and hydraulic jump changes shape from circular to polygonal. Despite the phenomenon of the hydraulic polygon jump has observed about two decades, the experimental relationship has not been presented to estimate the number of sides of hydraulic polygon jumps. The size and number of sides of a polygonal hydraulic jump depend on various factors such as fluid volume flow rate, jet diameter, fluid height downstream of the jump, and fluid physical properties; in other words, they depend on the dimensionless numbers of Reynolds, Weber, and Bond. Hence, in this study Taguchi analysis, as a Design of Experiment method, was used to investigate the effect of volume flow rate, jet diameter and obstacle height downstream of the jump on the number of the sides of a polygon hydraulic jump and Linear and nonlinear relationships was proposed for estimating the number of the sides of a polygonal hydraulic jump in terms of the above mentioned parameters.

In this paper, the instability of wave motion on the surface of liquid sheet emanating from a swirl injector exposed to inner and outer air streams, before the breakup is considered using the linear instability analysis by a perturbation method. The forces acting on a liquid gas interface in sprays, including surface tension, pressure, inertia force, centrifugal force and viscous force, lead to grow the disturbances originated from inside the injector on the outgoing liquid sheet. Interaction between these forces ultimately breaks up the jet into the ligaments. The linear instability analysis used in the present study is different from prior analysis. A cylindrical liquid sheet has been considered in previous studies but the present study implements the linear instability on a conical annular liquid sheet. Due to the complexity of derived governing equations a semi-analytical and numerical method was utilized in the solution procedure. The present model is capable to solve governing equations for the liquid jet with large range of spray angle. The predicted results compared with the prior studies results and experiments. The results of the current model in comparison with prior models have better accordance with experimental data. Also, the results show that the improved linear theory (the present model) predicts the breakup length better than linear theory.

In order to use and control Shape Memory Alloy (SMA) actuators, it is essential to measure its state variables to be used as the feedback in the control loop. The wire temperature is one of critical state variables need to be fed back. However, measuring this variable is difficult and usually contains some noises and delay. Therefore, it is desirable to estimate this variable instead of measuring it. Thermoelectric model is one of the most common models used to estimate the SMA wire temperature. This model calculates the SMA wire temperature based on its input electric current. In this paper, first three unknown parameters of thermoelectric model are estimated using Extended Kalman filter (EKF) and the wire temperature is calculated based on the identified model. The parameter estimation and temperature calculation are performed on a practical SMA actuator. Then, in order to eliminate the effects of environmental disturbances and the thermoelectric model inaccuracies, the temperature is estimated using EKF. In this method, all measurable data such as the input current, the strain and stress of the SMA wire are used in the temperature estimation. The estimator combines the information obtained from both thermoelectric and Brinson models and the measurement data. This method is used for online temperature estimation of the SMA wire on a practical SMA actuator. The results show that the estimated temperature matches the actual wire temperature with high precision. Furthermore, the temperature estimation using EKF is more accurate than the estimates of the thermoelectric model.

In this paper, the design of predictive functional controller based on Laguerre functions to track the load changes in Pressurized Water Reactor (PWR) nuclear power stations has been considered. Since, despite of out-performance of predictive controllers in industrial applications, their implementation implies high computational complexity for constrained large scale systems, in this paper, the design of model predictive controller with low computational complexity was considered. For this purpose, at first, the order of PWR model was reduced via Balanced Truncation method. Then, due to low computational complexity and high performance of predictive functional controllers, we dealt with the design of predictive functional controllers based on Laguerre functions. In this context, the Laguerre polynomial scaling parameter was determined by minimizing integral square error. Then, due to mechanical constraints, some specific constraints were applied to the control effort and its changes, and the Quadratic Programming method was used for solving the constrained model predictive control problem and consequently, designing the control effort signal. Also, in order to show the efficiency of the proposed core power control method, the system response in the presence of disturbance is investigated. It is shown that, by using predictive functional controller on a reduced order model, in addition to the decrease of the computation volume, the performance of the core power control to track load changes in presence of external disturbance is well done.

Controller design for non-linear multi-input, multi-output systems, such as unmanned quadrotor vehicles, has always been a challenging issue due to the strong interconnection between state variables and highly nonlinear dynamic equations. In addition, quadrotor is an under-actuated non-linear dynamic device. Due to being under-actuated for moving in the horizontal direction, the combination of changes in the speed of the existing quadruple operators should be used. So that, by creating the angle between the quadrotor hypothetical plane and the horizon surface, the device can be forced to move in the longitudinal or transverse direction. Therefore, in the quadrotor control system, two nested control loops are required. An outer loop to determine the appropriate angle of the device relative to the horizon for horizontal movements and an inner loop that is required to angle of the device panel is equal to this angle. In this paper, a fuzzy hybrid super-twisting sliding mode non-linear controller for controlling a sample quadrotor is designed. For this purpose, a fuzzy controller in the outer loop and a super twisting sliding mode controller in inner loop are used. An important advantage of this strategy is that it optimizes the horizontal speed of the device. If the distance from the target is too high, the angle of the device panel also increases, and if the distance is reduced, the angle also decreases. As a result, the device reaches the target with the desired speed. The performed simulation results confirmed this fact.

In this paper, Global sensitivity analysis of predicted strain from clamped–clamped beam magnetic shape memory alloy based energy harvester with PAWN method is presented. In the selected model MSMA units attached to the roots of clamped-clamped beam while coil wrapped around MSMA. A shock load is applied to a proof mass in the middle of the beam. As a result of beam vibration a longitudinal strain is produced in the MSMA and beam. There are limits to harvest energy from this model and one of them is the strain applied to the MSMA. As the strain increases with respect to the applied pre-strain, the MSMA exits the compression region and causes the model to fail. When strain exceeds limits also affect the predicted result. Thus PAWN method as an efficient and easy way for global sensitivity analysis of the inputs has been taken into account. Then the model is analyzed with introduced method to determine the effect of each input on the output. In the following, due to the importance of the harvested voltage, the sensitivity analysis and ranking of inputs are performed. Moreover, using two-sample Kolmogorov-Smirnov test it is shown that for design and optimization of model with respect to strain one can fix thickness, width and length of MSMA while studying model in corresponding maximums and minimums and also with respect to RMS voltage and similar test the width of the beam can be fixed.

In recent years, the use of insulation polymers in various fields has expanded. Therefore, Considering the importance and application of these polymers in various industries, their behavioral characteristics, including thermal properties evaluating their performance and the optimized and efficient use of them is necessary. The study also estimates that radiant and conductive properties of zirconia ceramic foam as an insulating polymer using inverse heat transfer method are discussed. Heat transfer method used in this paper is conjugate gradient method. The control volume numerical methods for solving the energy and radiation are used. The problem of inverse heat transfer is solved for estimation of radiation-conduction parameters by considering two modes, single sensors and two sensors and taking into account different initial guesses. For solving the inverse problem, the data used for direct solving are used and by entering some error, these data are used in the inverse solution. The results show that conjugate gradient algorithm for calculating the properties of radiative and conductive thermal insulation polymer gives acceptable results and also with the increasing number of sensors, parameters are estimated accurately using the conjugate gradient algorithm increases.

This paper considers the issue of precise control of robotic manipulators in the presence of dynamic uncertainties along with hard nonlinear perturbation such as friction using Modified Transpose Effective Jacobian and model based friction compensator. In order to model friction in robot joints, The LuGre friction model has been used and its unknown parameters have been identified by a bio-inspired optimization algorithm called Cuttlefish. By comparing Cuttlefish with other meta-heuristic algorithms such as Glowworm swarm optimization, its superiorities have been proved. After accurate identification of model parameters and determine frictions function, using Modified Transpose Effective Jacobian and model-based friction compensator, a two link planar manipulator has been controlled experimentally. Furthermore in order to compare the controller performance with other methods, the mentioned manipulator has been controlled using computed torque controller and transpose Jacobian besides Adaptive Radial Based Function Neural Network friction compensators. Experimental results offer the Modified Transpose effective Jacobian control method has privileges for better tracking control with more accuracy and better friction compensating as well as better robustness against dynamic uncertainties with lower computational efforts.

In this paper, a sandwich beam of a SMP material which have a corrugated core is studied. The corrugated core is from a polymeric material. Structures with corrugated profiles show higher stiffness-to-mass ratio in the transverse to corrugation direction compared to flat structures. As a result, the beam with corrugation along the transverse direction is stiffer than the one with corrugation along the beam length. The flexural behavior of the composite corrugated beam is studied employing a developed constitutive model for SMP and the Euler-Bernoulli beam theory. The constitutive model utilized is in integral form and is discretized employing finite difference scheme. To verify the results of the Euler-Bernoulli beam theory and finite difference method, finite element models of different corrugated sections have been simulated in a 3D finite element program. The results demonstrate that the developed model for the composite beam presented in this study predicts the behavior of the beam successfully. The sandwich beam with different corrugated cores (triangular, sinusoidal and trapezoidal shapes) are compared with each other. Also, results show that the shape fixity is decreased a little, like any other reinforcing method. This decrease in shape fixity results in increase of load capacity in composite beams. The stress-free strain recovery and constrained stress-recovery cycles are both studied.

This study was conducted to investigate the simultaneous effect of individual and physiological characteristics of subjects on the hands thermal response under severe cold stimulation. So, the hands’ transient thermal responses of 89 male students was evaluated by thermography imaging technique. Then, by applying statistical analysis methods, experimental relationships have been developed to estimate the thermal response time of the subjects with different individual and physiological conditions. The results showed that among the 9 individual and physiological parameters (age, vascular fat, muscle percentage, fat percentage, body mass index, systolic blood pressure, diastolic blood pressure, heart rate and fasting time), only there are four independent parameters of internal fat, body mass index, systolic blood pressure and fasting time have a significant relation with the response time. Also, using a multivariate linear regression, a relationship has been developed to estimate the thermal response time of the subjects against cold stimulation. This relationship indicates that the response time of the obese can be up to 20% higher than that of the lean subjects. In addition, the results shows that for each one hour after the last meal, the thermal response of the body is slower about 1%.

How to provide sustainable and clean sources of energy is probably the most vital question of our world today. The population growth and technology development are leading to an increase in the world energy demand and fast depletion of fuel resources. Our environment is facing critical challenges and there are serious uncertainties with the future availability of fossil fuel. The only possible remedy is to increase the share of clean and renewable energies in total energy use and to make our technology more energy efficient. Marine and offshore renewable energies are from the cleanest types that are available from the boundless energy of fluid flow in the oceans, seas, rivers and channels. In the present study, the wave energy absorption in a channel has been studied. A plate with infinite length and finite width and thickness that is placed at the bottom of a channel has been investigated to absorb the energy of gravity waves. The plate is on a viscoelastic foundation which displays linear behavior. The coupled equations of fluid and plate have been investigated to calculate the vibration characteristics of fluid surface and plate. Subsequently, a proper analysis has been done for the plate's ability to absorb wave energy.

This paper presents an improved approach for handling stress constraints in minimum weight topological design. The Finite Element Method (FEM) and the material model of Solid Isotropic Material with Penalization (SIMP) are used to formulate the topology optimization problem. To evaluate the stress values in elements, the von Mises stresses are calculated at the so called super-convergent Gauss quadrature points. To reduce the time and computational cost, a clustering approach is here adopted and the P -norm integrated stress constraints are used. Doing this, a large number of local constraints are replaced with a few global ones and consequently the stress constraint sensitivities are calculated by using the adjoint method. The employed formulation as well as a complete explanation of the sensitivity analysis is provided. Due to the complexity of the topology optimization problem in the presence of stress constraints, the Method of Moving Asymptotes (MMA) is here employed. To demonstrate the performance and capability of the procedure, a couple of plane stress elasticity problems are taken into consideration. The resulted layouts indicate the superiority of the approach in generating acceptable and practical topological designs.

Ceramic matrix composites (CMCs) are a new class of high technology materials which can be utilized as a replacement for metallic super-alloys. CMCs have a vast array of applications in modern industries due to their upstanding properties, including low density, relatively high hardness and fracture toughness, and high corrosion and wear resistance. Extremely high hardness and inhomogeneous structure of CMCs cause unstable process and high grinding forces and temperature. This research was conducted in order to overcome the grinding challenges of these composites by recognizing and analyzing the effects of main process parameters comprising cutting speed, feed speed, and depth of cut on the grinding forces, specific energy, and grinding force ratio in three different environments including dry, wet and MQL grinding. To evaluate the significance of input parameters and their influence on the responses and also to derive predicting equations, Analysis of Variance (ANOVA) was employed. It was concluded that MQL technique is the most efficient cooling-lubrication method where implementation of this process reduces the tangential grinding force by 38.88% and normal grinding force by 31.16%, relative to dry grinding; however, the amount of force reduction in wet grinding is 34.22% for tangential grinding force and 24.81% for normal grinding force, relative to dry grinding. In addition, increase of cutting speed leads to reduced grinding forces and force ratio and higher amounts of specific energy, and also increase of feed speed and depth of cut cause higher grinding forces and force ratio and lower amounts of specific energy.

In this paper, a robust linear quadratic regulator (LQR) based Reinforcement learning method is designed for a four degree of freedom inverted pendulum. The considered system contains a four degree of freedom inverted pendulum with a concentrated mass at the tip of it. The bottom of inverted pendulum is moved in x-y plane in x and y directions. For tracking control of two angles of inverted pendulum, two plane forces are applied in x and y directions at the bottom of pendulum. The governing equations of the system are derived using the Lagrange method and then a robust linear quadratic regulator (LQR) based Reinforcement learning controller is designed. The inverted pendulum is learned for a range of different angles, different lengths and different masses. The parametric uncertainties are defined as various lengths and masses of inverted pendulum and the disturbances are defined as impact and continuous forces which are applied on the inverted pendulum. After learning, the controller can learn online the system for any arbitrary angle, length, mass or disturbance which are not learned in the defined range. Numerical results show that the good performance of the reinforcement learning controller for the inverted pendulum in the presence of structural and parametric uncertainties, impact and continuous disturbances and sensor noises.

In submerged-arc welding, flux is produced through bonding so that alloying element can be added to Weld Metal. In this method, mineral ingredients and alloying elements are milled and mixed with glue in appropriate proportions. Once the drying of the pellets is complete in air, they are baked at 350 degree centigrade and broken up by using a sieve to attain the desired particle size (0.3-1 mm). The various content of Cr, Mo and Cr-Mo was added to bonded flux. Addition of alloying elements was done through flux and slag-weld metal reactions. Mechanical properties were studied by means of Longitudinal Tensile, Hardness and Charpy V-notch tests. Microstructure was studied by means of Optical and Scanning Electron Microscope. The addition of 0.4 wt. % Mo increased the volume fraction of Acicular Ferrite (AF) to 87%. The Ultimate Tensile Strength (UTS) increased by 20% and Impact Toughness (IT) decreased by 25%. Cr affected AF content less than Mo. The addition of 0.4 wt. % Cr increased the volume fraction of AF to 57%. The UTS almost did not change and IT decreased by 35%. Further increase in Cr content led to increase of Ferrite with Second Alloyed phase that strongly impaired IT (60%). The highest proportion of AF (95%) obtained in 0.28 wt. %Cr and 0.35 wt. % Mo. In this specimen UTS increased by 20% (100 Mpa) and Impact Toughness was decreased by 15% (20 J).

One of the usual and useful techniques for the flow field measurement in open channels is Acoustic Doppler Velocimeter (ADV). Physical presence of ADV probe and its holding system against flow disturb natural flow pattern which can change turbulent flow structure. Thus, the error of the Acoustic Doppler Velocimeter is consist of its intrinsic error and the physical presence of ADV against flow. To study this issue in this paper, flow field in an open-channel is measured using Particle Image Velocimetry (PIV) technique and side-looking ADV probe. The results show that sreamwise velocity obtained from both methods are in good agreement and on average, there is 5 percent difference, while vertical and lateral components of velocity are considerably different. Also, comparison of sreamwise and lateral turbulence intensities and the Reynolds shear stress shows lower differences for measured points near the water surface and the differences increase approaching to the bed.

Reduction in warm up time of engine reduces fuel consumption and emissions. The hot spots of IC engine are near the exhaust valves and between the cylinders space which need the maximum value of cooling. Coolant at inlet of the block, having a temperature lower than the cylinder head. As a result, the block cooling is more than necessary value to ensure that maximum temperature in the cylinder head is lower that critical value. Reduction in coolant flow rate is associated with block temperature rise, reduction of brake specific fuel consumption and HC and CO emissions. On the other hand, increasing the cylinder head temperature causes problems such as an increase in the production of NOx. One method to solve this problem, is separate cooling of block and cylinder head. In this method, the coolant at the outlet the pump, is divided into two separate paths one for the block and one for cylinder head, and thus, the flow rate which required for cooling each part must be set separately. In this study, to calculate the warm up time, the cooling circuit of national engine has been modeled. To validate, the numerical results of pressure loss of coolant in the engine water jacket, radiator flow rate and warm up time have been compared with the results of the cooling test. At last, the influence of separation of block and cylinder head cooling circuit of engine on warm up time has been studied. Results show 15 percent reduction in warm-up time.

In this paper, finite element modeling of friction welding of two ASTM A106-B and AISI 4140 dissimilar pipes is investigated. The effect of the friction welding parameters including rotation speed, friction pressure, friction time, forging pressure and forging time on the axial shortening are investigated using a fractional factorial design method. Because of the extreme material deformation, an innovative remeshing technique was scripted in Abaqus CAE to prevent the creation of distorted elements.27 models were solved and 3 validation experimental tests were carried out. Results showed that increasing the all parameters cause larger axial shortening. Friction pressure with 33.9% had the most effect on the axial shortening. Moreover, an increase in forging pressure and forging time has a limited effect on the axial shortening. After about 2 seconds from the beginning of the welding, the temperature of the interface becomes steady at about 1250oC. The validation tests revealed that the simulation error was about 5.6% which shows a good agreement between the finite element results and the experimental data.

An ejector-expansion refrigeration cycle employing N2O is studied in this paper and thermodynamic and exergy analysis is carried out to find out the effect of some key factor within the system and draw a comparison between this model and the others employing the same refrigerant and also CO2. Furthermore, the model developed in this study was validated by the same model proposed in other studies for CO2 as working fluid within the three types of these cycles, vapor-compression refrigeration cycle (VCRC), internal heat exchanger cycle (IHEC) and ejector-expansion refrigeration cycle (EERC). The results for N2O showed that the ejector entrainment ratio, one of the important parameters in ejector-expansion cycles representing the proportion of vapor and liquid in the outlet of ejector noticeably varies with high-side pressure of the cycle, just opposite the variation of vapor at the outlet of the ejector. The results show that Ejector-Expansion Refrigeration Cycle obviously has the highest maximum coefficient of performance and exergy efficiency by about 12% and 14% more than Internal Heat Exchanger Cycle; meanwhile these are about 15% and 16.5% higher than Vapor-Compression Refrigeration Cycle ones, respectively. Moreover, the total exergy destruction in N2O ejector-expansion cycle is 63.3% and 54% less than IHEC and VCRC and the exergy destructed in expansion process within EERC is 19.39% and 40.497% of total destruction less than IHEC and VCRC. Furthermore, the highest COP for vapor-compression refrigeration, internal heat exchanger and ejector-expansion refrigeration cycles is corresponding to the high side pressure of 7.328 MPa, while this value for CO2 refrigeration cycle is about 8.5 MPa.

Density currents flow due to the density difference between the current and surrounding environment. An important category of density currents is called turbidity currents, which density difference created as a result of suspended solid particle presence in fluid. In the present study, it is tried to use both Eulerian-Eulerian and Eulerian-Lagrangian methods, to take advantage of each one. In this way, the larger particle that have a more effective role in sedimentation mechanism due to the more falling velocity are calculated as Lagrangian and smaller particles by the Eulerian method. In order to obtain a criterion for particle assortment, seven currents with different particle sizes in the Eulerian-Eulerian model have been numerically simulated in a simple channel and it is compared with no particle case, and also the Eulerian-Eulerian method has been verified with experimental results and identified when the particle sizes is less than 12 micron, the sedimentation process is not appreciable, and the presence effect of these kind of particle can be ignored. Therefore, the Eulerian-Eulerian method is a suitable method for this case. The Eulerian-Lagrangian method validation has been performed with experimental results. Finally, the current inside the channel with a spectrum of particle dimensions is simulated and described the results by the proposed method (the combination of two methods). To perform numerical simulations, the development of open-source Open FOAM codes has been used to take into account the effect of particle. Due to the current’s turbulence, a Large Eddy Simulation method has been used for turbulent modeling.