نشریه مهندسی مکانیک مدرس
سال هجدهم شماره 6 (شهریور 1397)

Present study proposes a new multidimensional artificially characteristic-based (MACB) scheme for simulation of combined convection flows. Multidimensional characteristic structure for energy propagation in incompressible flow is derived for the first time. Four pseudo-waves are selected and equations are discretized along them to observe the physical behavior of domain. Viscous fluxes are computed by variables derivatives at the cell interfaces and for time discretization, a 4th-order Runge-Kutta method was used. According to the new scheme, two-dimensional flow with heat transfer in a square cavity and forced convection around a circular cylinder are solved for a wide range of Reynolds and Grashof numbers. Also, for comparison purposes, the CB scheme with averaging for energy equation is used. It was found that MACB has remarkable faster convergence in comparison with CB scheme and averaging methods. Also, by using MACB scheme, maximum permissible CFL number can be increased 80 percent in comparison to CB scheme. At higher Richardson numbers, the conventional flux averaging was failed to converge properly while MACB scheme presents the most rapid convergence. The computed results of MACB scheme are in good agreement with the benchmark solutions.

Lower extremity exoskeleton a motion assistive technology, has been developed in recent years. Generation of gait pattern is a fundamental topic in design of these robots. A usual approach in most of exoskeletons is to use a pre-recorded pattern used as look up table. There are some deficiencies in this method, including data storage limitation and poor regulation according to walking parameters. Therefore, it is required to modeling human walking pattern to use in exoskeletons. There are simple models for walking of healthy person and humanoid robots. Nevertheless, using these models may cause injury to joints of the patient or damage to robot motors due to physical limitation of the user’s body. In this paper, the physical limitations are represented as mathematical constraints. Considering these constraints, appropriate models are proposed for position of the joints. Then, inverse kinematics equations are used to generate joints angles. In this work, the model parameters consist of stride length and height, walking speed and length of user thigh and shin. The performance of the model is evaluated by implementing on Exoped robot. Satisfaction and convenience of the users demonstrates the good performance of the model.

Today, with increasing consumption of non-renewable energy sources, scientists are looking for an alternative for these resources. The Stirling engine is one of the ideas that have recently attracted engineers' attention. The purpose of this study is to optimize the output power and stability of a beta type free-piston Stirling engine. In this regard, at first by deriving the thermodynamic and dynamic equations of the system and combining them, the governing equations are obtained including the nonlinear function of the pressure loss in heat exchangers. The governing nonlinear equations are solved and for the purpose of validation, simulation results obtained in this study are compared with experimental and simulation results presented in the literature. In free-piston Stirling engines, increasing the output power by keeping their stability is very important. Therefore, by performing parametric study, the parameters with more effects on the output power and stability are determined and considered as optimization variables. In order to perform multi-objective optimization of output power and stability of the free-piston Stirling engine, a proper objective function is selected and one of the methods in genetic algorithm is employed using optimization software Modefrontier. Finally, values of variables, before and after optimization and also, percentage of improvements in output power and stability of the free-piston Stirling engine are presented.

In this paper, the mixing efficiency in electroosmotic flow inside a micromixer is simulated numerically for different states of non-uniform wall Zeta potential. The geometry of flow is a two-dimensional channel between two parallel plates and the flow is assumed to be incompressible, steady and laminar. The governing equations, including a Laplace equation for the distribution of external electric potential, a Poisson equation for the distribution of electric double layer potential, the Nernst-Planck equation for the distribution of ions concentration, the species convection-diffusion equation, the modified Navier-Stokes equations for the fluid flow field, have been solved using the finite volume numerical method. In order to validate the numerical results, the analytical results of an ideal electroosmotic flow in where throughout the walls are charged is compared with the obtained numerical results. The numerical results show that, by linear-ascending, linear-descending and parabolic changes of the wall Zeta potential at the middle length of the microchannel, the mixing efficiency increases compared to a constant Zeta potential. For the cases of linear changing of Zeta potential, the mixing efficiency increases to 86% and for parabolic change of Zeta potential the mixing efficiency increases to 75%, while the Zeta potential is constant at middle length the maximum of mixing efficiency increases to 64%. In the case that only the upper wall at middle length is charged, the results show that a vortex region is created in the flow. This vortex region causes a maximum (100%) mixing efficiency.

The satellites on the ground during construction and transportation, in launching stage and operation in space are under various types of dynamic loads, including high and low frequency vibrational loads, acoustics, shock, impact, etc., each of which can be an important source in the creation of stress on the satellite. The satellite components should be designed in such a way that can continue to operate while facing these situations. Electronic boards, in particular their solder joints, are critical components of satellites. Therefore, investigation of damage in design process of boards have great importance. Loading pattern on the satellite during its operation is usually random which considered as quasi-static load. Improvement of the design of the satellite against the weaknesses shown while facing different loads is essential, and given the fact that it is time consuming and costly to carry out laboratory tests, the use of analytical methods for checking the strength and lifetime of the structure can be very useful. In this research, random vibrations environment is equivalent to pseudo-static loads, and using the multilayer plate theory, the stresses in solder joints and failure of joints under this loading will be investigated. Also, the effect of parameters such as electronic board width and the boundary condition of the printed circuit board on the solder joints' stress will be considered in analytical solution.

Applying membranes with especial geometries and fouling characteristics has been an area of research and a subject of interest in membrane science community. While a considerable part of fouling happenings are originated from chaotic roots such as Brownian motions, the remainders can be scheduled to approach on desired filtration features. Here in this study the somehow invisible features of progressive fouling which is the case for novel micro-engineered membranes was realized in some details. The problem of progressive fouling was considered as a result of dead-ended filtration of non-colloidal particles over a vertically extended pore geometry. It was shown that, in this filtration apparatus, due to a serialized activation and deactivation of flow passages, progressive fouling can change its seat with other more flow resistive classical types of surface and pore blockings and control filtration path more apparently. Results was considered for different amounts of pore extension and porosities. It was found that employing an especial set of pore extension length and porosity make it feasible to derive manageable filtration processes with high levels of purification and permeation performances.

In this paper free and forced vibrations analysis of a viscoelastic nonlinear nano rotating beam by considering surface effects is investigated. Using Hamilton principle and Gurtin Murdoch theory, the equations of motion are obtained and discretized by Galerkin method. Using the multiple time scales method the equations of motion are solved. In free vibrations analysis, the analytical expressions for amplitude and phase are obtained. In forced vibrations analysis the steady state solution are obtained. The effect of surface effect, damping coefficients, dimensions of cross section area, external excitation amplitude etc. on frequency response curves are investigated. It is seen that in free vibrations, by increasing surface stress the amplitude of the system decreased, and by increasing surface density or elasticity it is increased. Also, by increasing internal and external damping coefficients free vibration amplitude is decreased. In forced vibrations, it is seen that considering surface effect the amplitude of the system is decreased and the first bifurcation point is obviously changed. By increasing internal and external damping coefficients the amplitude is decreased and the first bifurcation point occur in frequencies near the natural frequency. It is seen that for two different dimensions of cross section with same area, amplitude and the loci of the bifurcation points are changed. By increasing the amplitude of external excitation the amplitude of response is increased the bifurcation points occur in frequencies far away from natural frequency. So, considering the surface effects for free and forced vibrations analysis of the nano rotating beams is mandatory.

The use of biomass by means of gasification to produce bio fuels and reducing the environmental impact of fossil fuels has been the focus of many researchers in recent years. In the present study, the computational fluid dynamics method is used to predict the process of gasification inside a downdraft gasifier. Recent studies have shown that although many studies have been carried out by various researchers to maximize the cold gas efficiency in the gasification process, so far, no study has been done to minimize the emission of pollutants as one of the other important design parameters along with the increase of cold gas efficiency. So, in this study, the effect of changing the equivalence ratio as design variable on the gasification efficiency as well as the amount of pollutant produced simultaneously is investigated. Also, in this study, CO/CO2 and H2 /H2O molar ratios are considered as another objective function in selecting the optimal process point. In order to verify the validity of the results, the simulation data was compared with the experimental results and the previous numerical study, and a good agreement was shown between their comparison. The results of this study show that in the ratio of 0.64, the rate of production of nitrogen oxides relative to cold gas efficiency is optimal considering the maximum production of CO/CO2 and H2/H2O molar ratios . This point is the optimal point. Under the working conditions of the gasification process.

In the present research, combustion species detection in methane/air flame is carried out based on Flame Emission Spectroscopy (FES). Experimental investigation is performed on a test rig equipped with measurement devices to get the flame emission of a perforated burner which is one of most popular burners used in condensation boilers. Combustion species H2O*, OH*, CH* and C2* are detected from their chemiluminescence The emission of OH* radical was investigated for different equivalence ratios (Φ) and burner powers showing an intensity peak in the range of Φ between 0.77 to 0.85 that corresponds to the maximum heat release rate. Emission of H2O* was also investigated leading to its maximum at Φ=0.82 which shows the most complete combustion equation for different burner powers. The similar experiment showed that OH*/CH* intensity ratio was independent of burner power as is confirmed by previous researchers. One could infer equivalence ratio from the flame emission. Burner surface temperature was also targeted by an infrared thermometer with the purpose of finding the maximum surface temperature of 415 to 420oC which happened at nearly Φ=0.82 for all burner powers. Finding equivalence ratio of the burner by using its natural emission and improving its efficiency by the method of investigating combustion specifications relating to heat release rate is the basis of this work.

Now a days gas turbines are widely used in the transportation and energy industry. According to Combustion of fossil fuels in these engine, environmental concerns have increased due to production of nitrogen oxides and carbon monoxide. Various methods have been offered to reduce the emission of pollutants. One of these methods is adding steam or water to the combustion chamber to reduce the flame temperature. Different methods can be applied to add steam to the combustion chamber, in this study, the steam is added to the diffuser and premixed with air into the combustion chamber. Steam addition influences the combustion process inside the combustion chamber, which should be considered during the combustion chamber design process. Therefore, a model for the conceptual design of the chamber geometry and the effect of adding steam on it will be presented. For this purpose, the data from an actual combustion chamber will be used to compare results of geometry design by using this model and to study the influence of steam on the chamber geometry. To investigate the combustion chamber performance, the chemical reactor network method for combustion modeling will be used. First, with this procedure an annular conventional combustion chamber will be modeled without steam addition and the results of this method will be compared with the actual data of this combustor. Then the effect of adding steam on the performance will be investigated. The study will show adding steam is an effective way to reduce the flame temperature and emission of pollutants.

Elastomers are a group of polymeric materials that have unique properties, including time-dependent behavior and time-independent, the mechanical behavior of this material is affected by various factors. In this study, the effect of increasing the silica nanoparticles and strain rates in two quasi-static and dynamic states on the tensile behavior of HDPE / POE has been investigated. For this purpose, an elastomeric material was first created with 40% HDPE and 60% POE mixing ratio. Then with increasing Nano silica particles, 4 sample types including 3 samples 0.7%, 1% and 1.4%, and one sample of HDPE/POE was fabricated. The samples were loaded at strain rate of 0.04 1⁄s, 0.07 1⁄s , 0.1 1⁄s , 0.14 1⁄s , 0.17 1⁄s in a quasi-static tensile state. In dynamic mode, tensile load with a strain rate of 160 1⁄s and 100 1⁄s was applied to the specimens using a new fixture designed on the low velocity impact test machine (Drop weight impact test machine). In the dynamic loading, the behavior of the elastomeric material is extremely dependent on the strain rate, with increasing the strain rate the level of stress and forces in both quasi-static and dynamic loads will be increase. The increase in force levels in dynamic loading is much more than static. Also, the new designed mechanism provides access to dynamic tensile data at different strain rates in a low velocity impact machine. On the other hand, with increasing Nano silica percentage, the tensile strength of the samples is noticeably increased.

In this paper, the axisymmetric actuator disk method (2D) with acceptable accuracy and low computational cost based on computational fluid dynamics have been adopted to study the flow behavior around the horizontal wind turbine rotor and the wake. For this sake, a C code is developed as a self-developed user-defined function (UDF) in commercial software package ANSYS FLUENT. The rotor is modeled as a virtual disc and its effect is added to the Navier-Stokes equations as a sink term. The results obtained for the 5 MW NREL wind turbine in this study show the appropriate accuracy and speed-up. The interaction of two wind turbines in the wind farm has been investigated. The results depict that the output power and thrust of the downstream rotor due to the presence of an upstream turbine drop up to 88% and 57%, respectively. Also, radial distribution of the downstream rotor power shows that at a closer distance, the middle part of the blade has a larger contribution to power generation. Further, the effect of downstream rotor on the upstream rotor performance is up to 1.5% and 0.7% reduction in power and thrust respectively.

In recent years, the use of Gas Turbine-Modular Helium Reactor (GT-MHR) which operates in accordance with closed Brayton cycle with helium fluid as working fluid has attracted researchers’ attention because of its high efficiency, high reactor safety, being economical, and low maintenance costs. In the present study, a combined system, including GT-MHR cycle, Kalina cycle and Ammonia-water absorption cycle is investigated with respect to energy, exergy, and exergoeconomic. As the bottoming cycle, Kalina cycle and absorption cycle are used in order to avoid energy wasted by gas turbine cycle and to increase efficiency of energy conversion. The results of the simulated model show that, in the basic input mode, the overall work is 304462 kW, the overall exergy destruction is 289766kW and the overall exergy efficeincy of cogeneration cycle is 0.689kW. Also reactor, turbine and compressor in helium cycle are the component to which more attention should be paid with respect to exergoeconomic because the highest amount of cost rate is related to these components. At the end, parametric analysis is carried out in order to evaluate the effect of the changing pressure ratio of helium compressor, input temperature of helium compressor, input pressure and temperature of turbine and mass fraction of the base mode of the Kalina cycle on the output parameters.

The semi-analytical method (SAM) is an approach that computationally efficient and easy to implement. That's why this method often used for the sensitivity analysis of finite element models. However, SAM is not without defect especially in problems that rigid body motions are relatively large reveals severe inaccuracy. Such errors outcome from the pseudo load vector calculated by differentiation using the finite difference method. In the present paper, a new semi-analytical approach based on complex variables is proposed to compute the sensitivity of nonlinear finite element models. This method combines the complex variable method with the discrete sensitivity analysis to obtain the response sensitivity accurately and efficiently. The current approach maintains the computational efficiency of the semi-analytical method with higher accuracy. In addition, the current approach is insensitive to the choice of step size, a feature that simplifies its use in practical problems. The method can be used to nonlinear finite elements only requires minor modifications to existing finite element codes. In this paper, the authors demonstrate that the discrete sensitivity analysis and the complex variable method are equivalent and solve the same equation. Finally, the accuracy of the method is investigated through the various numerical examples by comparing by other methods and will show that this method is reliable and independent of step size.

Along with improvement of technology and need for access to energy resources, existence of pipelines such as gas, oil and water pipes is vital for our lives. These pipes will be eroded and damaged over time. With the prediction of the defects and tracking of pipeline paths, the probability of sudden damages is greatly reduced. In this paper, at first various non-destructive methods of monitoring the pipelines are investigated and it is shown that the laser method is the most comprehensive and non-destructive inspection method and then the background of the chosen method is examined. Also, the hardware aspect of the system and the proper layout of the laser sensors are determined on the system. After that a complete mathematical model and an algorithm is proposed for it which can be used to analyze the data obtained from the simulation of laser sampling creates image of the pipe internal surface and using this method identifies the defects found at the pipe surface. In the fourth section, a pipe with specific geometric deflection is examined based on the proposed method and algorithm and its results show the correctness of the proposed method.

Nowadays, nano-precision positioning stages, have a special position and are used in a variety of applications, such as taking pictures and taking particles of the surface. In this paper,some observers for a nano-precision positioning platform are designed based on three different types of neural networks. The simulated platform was designed at Sharif University of Technology and, based on the system's final requirement for the feedback signal for use in the control rule, neural network observers were designed. In previous studies, the comsol model of the positioning system has been obtained. At this step, the neural network has used the Comsol model and the system has been trained for a sum of a number of sinusoidal functions, and its generalizability has been investigated for ramp input. Neural networks used include, respectively, a multi-layer perceptron network, a radial basis function network and a support vector regression network. By performing simulations, it has been seen that the multi-layer perceptron network and the radial basis function network yielded a good response with low error, but the support vector regression network has a relatively high error.

For determination of the fracture parameters of self-compacting lightweight concrete (SCLC) size effect and work of fracture methods were used. For considering the behavior of concrete in different strengths, two mixes with water to cement (W/C) ratios of 0.42 and 0.47 were utilized. At first, the workability of the concrete was investigated and, after ensuring their self-compacting properties, the mechanical properties of the hardened concrete were determined. Then, by using the above-mentioned methods and conducting three-point bending tests on 30 beams, concrete fracture parameters, and crack-tip opening displacement were achieved. The results showed that with increasing W/C ratio from 0.42 to 0.47, the initial and total fracture energies, and fracture toughness decreased by 39.4%, 33.4% and 25.3%, respectively. The effect of the W/C ratio on the fracture parameters of this type of concrete was discussed. Furthermore, several empirical relations have been proposed that by the use of them and only by the determination of the compressive strength, the initial fracture energy, total fracture energy, the ratio of energies to each other, and fracture toughness can be determined. Then, by using the fracture parameters, the mechanical properties of the concrete and the extended finite-element method, the crack propagation was modeled. The results showed that this method has high accuracy in the numerical solution of the fracture problems as well as the efficiency of the obtained parameters for determining the behavior of self-compacting lightweight concrete.

Glass-reinforced phenolic laminates show a low resistance to delamination. Toughening of the matrix resin with a polymeric interlayer is among the method used to improve the delamination strength. In this research Polyvinyl butyral(PVB) nanoweb with the fiber diameter of 300-600 nanometer were used as an interlayer in a 14-layer glass reinforced phenolic composite. A hybrid nanoweb consists of PVB nanoweb reinforced with pyrolytic carbon and carbon nanotube (CNT) were also prepared and used as the interlayer. Mode I and Mode II delamination tests were conducted on the samples according to the related ASTM standard test method. The results showed that PVB interlayer improves the delamination strength of the composites by 13.6% and 13.8%. for mode I and Mode II, respectively. Also, with the hybrid nanoweb, better improvement in the fracture toughness was achieved. In the hybrid nanowebs, CNTs at the optimum amount has a greater effect on the Mode I fracture (49% improvement in GIc), while the pyrolytic carbon mainly affected the Mode II fracture toughness by 38% improvement in GIIc. Morphological studies carried out by SEM microscopy showed that crack deviation is the dominant mechanism for toughening of the polymeric matrix which results in the delay in fracture initiation and increase of the crack length and in doing so enhances the fracture toughness of the laminates.

Laser percussion drilling is one of the advanced drilling processes that its numerous advantages have extended the applications of this process. This study focuses on experimental investigation of laser percussion drilling using Nd:YAG laser on titanium alloy Ti6Al4V sheets with various thickness which is widely used in industry. In this paper the effects of the input parameters peak power, pulse width, frequency, assist gas type, gas pressure and sheet thickness on the most important process outputs include hole entrance diameter, hole exit diameter, hole taper angle, hole entrance circularity and hole exit circularity were studied. Statistical analysis was employed to analyze the experimental data and significant parameters in each response are presented. For conducting the experiments “Design of Experiments” method and for modelling “Response Surface Methodology” were used. The results obtained show that sheet thickness affects all outputs. After that frequency and pulse width, peak power and assist gas type respectively are the most significant parameters influence process outputs. Gas pressure only affects the hole entrance circularity. For this alloy to achieve a hole with high quality, it is recommended to work at lower peak power and frequency, shorter pulse width and higher assist gas pressure with Nitrogen as assist gas.

In this study, special attention has been paid to modeling of the interface between the sheet metals in prediction of forming limit diagram (FLD) of two-layer sheets. In the present work, a two-layer sheet consists of 1.35 mm steel sheet and 0.45 mm copper sheet has been used. This two-layer sheet has been made by explosive welding method. To determine the FLD, numerical method has been used by applying ABAQUS finite element software. For this purpose, the so called Nakazima method has been simulated. The criteria used for determining the failure in steel and copper layers was GTN model. Also, in order to determine the failure in interface between the layers, the traction-separation law was used. For modeling the interface, cohesive elements were used. In order to verify the results, Nakazima tests were performed. The simulations and experimental works were done for both side directions of the sheets. The results indicate that the FLDs obtained by the numerical modeling are in good agreement with the experimental results.

In this paper a modified Godunov-type wave propagation algorithm is utilised for the modelling of falling water wave over a dry bed. The defined numerical model is well-balanced and is capable to treat the influx/efflux source terms and also the friction term within the flux-differencing of the finite volume neighbouring cells. Additionally, the method employs a rather simple HLLE wave speed for the propagation over dry-state. First the efflux flow from the bed of a reservoir is analyzed. Then, the entrance of falling water wave from the middle and edge sides of the reservoir over a dry bottom is simulated. In order to validate the achieved numerical results for the non-hydrostatic pressure situations a dimensionless number based upon the inflow velocity, the slot length and the falling height is introduced. The obtained results of the defined numerical solver are then compared with the numerical prediction of the STAR-CD which is a commercial Navier-Stokes package. The numerical results demonstrate that the introduced flux-wave solver is able to simulate the falling water waves over the dry-state for a given range of the dimensionless number.

In this paper, a linear dynamic model of simply supported Above-Ground pipeline during pigging process has been developed and verified by experimental tests. The PIG (Pipeline Inspection Gadget), is an internal moving sprung mass pushed by the fluid pressure, which itself act as a flowing varying mass. The governing equations of motion for the system including the pipeline, moving PIG as a moving vibrational sub-system, and flowing fluid with varying mass were obtained using Hamilton’s principle. Then, the extracted equations were discretized and solved via finite element method. Modal parameters of the pipeline system were calculated during intermittent passage of PIG through the pipe under different fluid flow rates, and their variations were extracted. Validation of the model was carried out using an experimental setup, including a 2.5 meter length Carbon Steel pipe, a simple bi-directional PIG with rubber discs and a centrifugal pump, connected to a control valve, providing required fluid pressure to push the PIG through the pipe. Using data acquisition system to acquire the vibration signals, and employing experimental modal analysis, frequency responses of the system at different points were obtained and the modal parameters were extracted and compared to that of the simulated model. A comparable results have been achieved between theoretical and experimental methods. Also variation of the system natural frequency versus speed and position of PIG in the pipe, were investigated. Moreover, the displacement of the mid-span of considered pipe during pigging process has been obtained using suggested theoretical model.

The size of database and minimum number of visible stars in the field of view of star sensor are two important, influential and contradictory parameters that should be considered in design of star sensor. In this regard, the purpose of this paper is to unify the database using the uniform distribution of points on the celestial sphere with the triangulation method. For this purpose, the choice of the suitable star catalog, minimum suitable magnitude and elimination of double stars are the other steps of the uniformity process that is carried out in this study. Thus, the results of the investigations showed that Delaunay's triangulation method is faster and more accurate than the geodesic grid. Also, by simulating and performing Monte Carlo tests to count the number of stars observed in the different FOVs of a typical sensor, it was found that Delaunay's triangulation leads to a significant reduction of the probability of viewing the high density of the catalog stars in the field of view, so that the probability of observation more than 25 stars in all possible FOVs has reached to zero. On the other hand, for observing 4 or more than 4 stars at a confidence level more than 95% in non-uniform catalog, the field of view needs to be at least 12.5 degrees, while in uniform database; this field is slightly increased to more than 13 degrees. In other words, uniformity has increased the minimum field of view needed to see the minimum number of required stars.

A powerful two-phase lattice Boltzmann model with the ability of modeling high density ratio is applied to simulate a rising bubble striking a porous obstacle. This model is able to simulate immiscible two-phase flow with density ratio of 1000 and result in desirable mass conservation. In present research, a porous obstacle is posed in two-phase flow domain, bounce back and wetting boundary conditions at walls and corners is discussed and showed that after implementation of obstacle boundary conditions, mass conservation of the model is preserved. Accuracy and ability of the model firstly examined by some basic problems. Next, striking of a rising bubble with 1000 density ratio to a porous obstacle is simulated and the effect of contact angle, Eotvos number and porosity ratio in deformation and passing of the bubble from the obstacle is investigated systematically. Different porosity ratios and contact angles, result in different bubble behavior striking the porous obstacle; In low porosity ratios and low contact angles, the bubble remains below the obstacle. At high contact angles, the hydrophobicity of the obstacle surface draws the bubble into the porosities, and the bubble moves to the top of the obstacle and stays on the top surface of the obstacle. In other cases, the bubble completely passes through the obstacle and separates it. Mass conservation error of bubble passing the porous obstacle is of order of 10-11 which is completely desirable.

Nowadays, using of virtual reality in surgical training is taken consideration due to safety, reproducibility, lower cost and other benefits. The various presented method for virtual surgery have attempt to make it more real and also make it online. This paper presents a new methodology for the deformation of soft tissue by drawing an analogy between cellular neural network (CNN) and elastic and viscoelastic equations. Viscoelastic model has been resulted from collection between Navier-Cauchi equations and Kelvin-Voigt model. Furthermore, a haptic system for viscoelastic modeling of soft tissue deformation is presented. The displacement created at a point by external force is released throughout the tissue via the cellular neural network. Because this method needs to cubic meshing, a new meshing algorithm is designed that executed offline. Indeed a collision detection algorithm is used to detect collision between tool and cells that executed inside the main algorithm and force feedback using the force model provided by the neural network and the haptic interface. This algorithm is implemented on a 3d liver model and executed online.

The purpose of this work is to provide a model in lattice Boltzmann method for D simulating thermal rarified gas flows. The study model is a microchannel with a square cross section. The magnetic field flux was created by the magnets on two facing walls. The electrodes are embedded on the walls adjacent to that of the magnets and DC voltage is applied at both ends. Compressible fluid behavior is compared in slip (Kn =0.15) and transient (Kn =0.1) regimes. There are assumptions of laminar and steady flow. Newtonian fluid is electrically and magnetically conductive. Slip and temperature jump on the microchannel walls are considered and the effects of electric double layer thickness and changes of Hartmann number are studied. Since the ionic process is non-isothermal, energy equation is coupled with that of the velocity and the magnetic field and the effects of interaction forces of Lorentz, electric and electrothermal have been entered into Boltzmann equations in separate terms. The outcomes show the interaction between an axial electric field and a transverse magnetic field results in three-dimensional nature of the flow. Navier-Maxwell second order slip boundary condition imposed on the electromagnetic channel walls plays an important role in the vortices formation and the temperature distribution across the channel goes out of the symmetric state. Mass flow rate loss along the channel, resulting from the fluid rarefaction, and pressure deviation from linearity, across and along the channel axis because of the compressibility, was observed

In this paper, a novel model predictive control method is presented for controlling a boiler-turbine system as an uncertain nonlinear system. In the proposed method, type-2 fuzzy system is used to cope with steady state error or bias appeared in the predictive control method due to the effects of model mismatch. For this purpose, using a piece-wise linear model of the system and considering the constraints in the system and the control signal, a predictive controller is designed to solve a constrained optimization problem. . In the presented control scheme, a type-2 fuzzy supervisor is used to adjust the reference input signal according to the system conditions. It has been shown that utilizing type-2 fuzzy system in the predictive control method, instead of type-1 fuzzy system, leads to satisfactory results. The proposed method is applied to the nonlinear model of the boiler-turbine system and the simulation results show the effectiveness of this method compared with the existing fuzzy predictive control methods, especially for the conditions in which the model uncertainty is present.