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In this paper, we show how to obtain suitable differential charactristics for block ciphers with neural networks. We represent the operations of a block cipher, regarding their differential characteristics, through a directed weighted graph. In this way, the problem of finding the best differential characteristic for a block cipher reduces to the problem of finding the minimum-weight multi-path way between two known nodes in the proposed graph. We applied Hopfield network to find the minimum-weight multi-path way. In this technique, the probability of convergence to a local minimum increases when the number of rounds of the cipher increases. We also applied Boltzmann machine to avoid local minima. We applied these techniques to find 3-round, 4-round and 5-round differential characteristics of Serpent block cipher, and repeated the optimization procedures for each characteristics 100 times. With Hopfield network, we obtained suitable results 100, 20 and 1 times for 3-round, 4-round and 5-round of the Serpent respectively. With Boltzmann machine, we obtained suitable results 100, 99 and 30 times for 3-round, 4-round and 5-round of the Serpent respectively. These results show that simulated annealing help avoiding the many local minima of energy function. We compare the probabilities of our obtained differential characteristics for Serpent with the probabilities of eight differential characteristics previously reported in other papers. The comparison shows that our proposed technique obtains better results in 6 cases, and the same results in 2 cases. We also found a 7-round differential characteristic with a probability of 2-125 with Boltzmann machine. Neglecting the reported Bommerang differential characteristics of Serpent, our obtained 7-round differential characteristic is the first report on a differential characteristic for more than 6 rounds of this cipher. The results of experiments indicate the efficiency of neural networks to find suitable differential characteristics of block ciphers.

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- Natural convection heat transfer in a square cavity induced by heated plate is investigated using the lattice Boltzmann method. A suitable forcing term is represented in the Boltzmann equation. With the representation, the Navier-Stokes equation can be derived from the lattice Boltzmann equation through the Chapman-Enskog expansion. Top and bottom of the cavity are adiabatic; the two vertical walls of the cavity have constant temperatures lower than the plate’s temperature. The flow is assumed to be two-dimensional. Air is chosen as a working fluid (Pr=0.71). The study is performed for different values of Grashof number ranging from 103 to 105 for different aspect ratios and position of heated plate. The effect of the position and aspect ratio of heated plate on heat transfer are discussed. With increase of the Grashof number, heat transfer rate is increased in both vertical and horizontal position of the plate. The obtained results of the lattice Boltzmann method are validated with those presented in the literature.

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There is a full connection between the electrochemical quantities of a fuel cell and the curves of the temperature and primary materials at the catalyst region. These quantities are strongly linked to the mass and heat transfer phenomena in the other regions. In the present paper, the lattice-Bolzmann method, as a microscale model with good computational capabilities in the problems such as the fuel cell, has been utilized to simulate the fluids flow and heat transfer in a two-dimensional cross section of a proton exchange membrane fuel cell including the channel, bipolar plate, gas diffusion layer and catalyst of the cathode and the electrochemical characteristics in the catalyst layer have been analyzed. By representing a method for estimation of the changes in the concentration along the channel, the serpentine arrangement has been modeled. The results reveal the essential role of the bipolar plate on the quantities at the catalyst layer.

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This paper examines the dynamic behavior of steel moment-resisting frames with steel-concrete composite beams with welded connections. One story-two bay frames with and without composite beams with rigid and simple connections were modeled with ABAQUS software and analyzed under earthquake accelerations. The distribution pattern of plastic hinges, rotation of plastic beam to column joints, plastic energy dissipation capacities of frame components and crack mechanism of slabs near the interior and exterior connections were studied. The results revealed that the frames with composite beams and welded rigid connections have the lowest values of period, plastic energy dissipation capacity, plastic rotation of joints and early frame mechanism. Failure mechanism in the exterior connection was in the form of concrete pre-tensioning from the starting at the corner of the column stretching in oblique around the edges of the slab. At the interior connections, it was in the form of concentrated compressive stress over the outer flange of the column. Strength and ductility of steel in tension and compression capacity of concrete in steel-concrete beams (composite beams) make this system suitable for long spans and considerable growth in recent years. In Euro Code 8 , rules are stated for mechanisms between concrete slab and steel column in bending and sagging moment modes. The mechanism in bending and sagging moment regions, where concrete slab has enclosed steel column, is shown in Figure 1. In the first mechanism, the compressive stress is applied directly onto the outer side flange of the column. Whereas in the second mechanism, the concrete slab exerts pressure through a 45 degree angle to the column web. The performance of the first mechanism leads to removal of contact friction between the concrete slab and the column. But the second mechanism leads to removal of contact element (Hard Contact) between the concrete slab and the inner core of the column web and flange. Therefore, activation of both mechanisms manifests a better performance of the system. Formation the plastic hinges in frames generally start at the column base, particularly at the middle column and then expand to other members, connections and the concrete slab. In this study, the use of composite beam, instead of steel beam, causes plastic hinges to form in the connections instead of beams. In composite frames with simple connections, due to stress concentration, the major plastic hinges are formed at the welded connections. In these frames, the first plastic hinge is formed earlier than others. But the failure capacity of these frames is higher than rigid ones. In rigid connections, the added rigidity due to enclosure by concrete slab causes initial stiffness for the frame and delays the formation of the first plastic hinge. However, it induces sudden stresses on the welds at the upper part of the beam. Thus will eventually lead to weld rupture and slab failure. This produces early failure in the frames.     On the basis of the observed behavior and supporting theoretical studies, the effects of the bolt tightness on the behavior of double layer space structures have been discussed in the context of design assisted by testing emphasized in Chapter 7 of the Iranian Code of Practice for Space Structures. With due consideration of different aspects of the influence of the degree of bolt tightness on the behavior of joints, members and modules, as well as the overall structural behavior, some practical recommendations have been presented to improve the reliability of structural performance through increasing rigidity and load carrying capacity of such double layer space grid structures, that can be achieved as a result of a proper choice of the bolt tightening procedure.

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In this paper the effects of the inlet fluid temperature on the electro-osmotic flow pattern in a two-dimensional microchannel with constant walls temperature is investigated with solving the governing equations by the Lattice Boltzmann method. The main objective of this research is to study the effects of temperature variations on the distribution of ions and consequently internal electric potential and velocity field. For make possible to use the Boltzmann ion distribution equation, cup mean temperature for every cross section of the microchannel is used. At the used Lattice Boltzmann method, LBGK model for modeling the Boltzmann collision function and the Zou-He boundary conditions method for velocity field has been used. Wang model for solving the Poisson-Boltzmann and He-Chen model for solving the energy equation has been used. The results show that, with increase the temperature difference between the inlet flow and the walls, the electro-osmotic flow rate increases. Also, observed that with decrease the external electric potential and the electric double layer thickness and increase the temperature difference at the inlet zone of the microchannel, a region with return flow is formed which can be used for controlling the internal flow pattern.

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In this paper, steady incompressible flow patterns inside two-dimensional triangle, trapezoidal, semi-circular and arc-square cavities with moving boundaries are studied via lattice Boltzmann method. The effects of geometry of the cavities on flow pattern are also discussed. The effects of Reynolds number on the flow patterns in triangular, semi-circular and arc-square cavities are studied. Also, for arc-square cavity, it can be observed that by changing the size of top and bottom walls which means a change in the size of cut arcs from the circular, different flow patterns are formed. The influences of the side angles at constant Reynolds number on the flow patterns in the trapezoidal cavities are investigated. It is found out that the vortex near the bottom wall of trapezoidal cavity breaks up into two smaller vortices as side angles increase. The obtained results of the lattice Boltzmann method and the presented boundary condition are compared with those presented in the literature. It can be seen that the lattice Boltzmann method is a suitable method for flow simulation in the mentioned cavities.

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Since the lattice Boltzmann method (LBM) originally carries out the simulations on the regular Cartesian lattices; curved boundaries are often approximated as a series of stair steps. The most commonly employed technique for resolving curved boundary problems is extrapolation of macroscopic properties at boundary nodes. Previous investigations have indicated that using more than one equation for extrapolation in boundary condition potentially causes abrupt changes in particle distributions. Therefore, a new curved boundary treatment is introduced to improve computational accuracy of the conventional stair-shaped approximation used in lattice Boltzmann simulations by using a unified equation for extrapolation of macroscopic variables. This boundary condition is not limited to fluid flow and can be extended to other physical fields. The proposed treatment is tested against several well established problems. Numerical results show that the present treatment is of second-order accuracy, and has well-behaved stability characteristics.

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In this paper, natural convection heat transfer inside an enclosure which is partially filled with porous layer is reported using lattice Boltzmann method. Generalized equations in modeling flow in porous media have been employed which are coupled with the lattice Boltzmann formulation of the momentum and energy equations. The present study investigates the effect of position of porous layer on heat transfer rate for different dimensionless parameters, such as Rayleigh number, Darcy number and porosity of the porous layer. In addition, a modified Rayleigh number is presented as an effective parameter which affects the degree of penetration of the fluid into the porous layers. The obtained results showed that the heat transfer rate in the case of vertical layer is more than that of horizontal porous layers.

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Abstract- In this paper, two-dimensional natural convection heat transfer in semi ellipse cavities is investigated using lattice Boltzmann method. The Prandtl number is taken as 0.71 that corresponds to that of air. Heat transfer and flow pattern are predicted at various Rayleigh numbers ranging from 104 to 106 for different aspect ratios. By increasing of the aspect ratio, the heat transfer rate in the cavity is increased for low Rayleigh numbers, but it is decreased for high Rayleigh numbers. The obtained results of the lattice Boltzmann method are validated with those presented in the literature and show that the lattice Boltzmann method can simulate heat transfer and flow pattern in complex cavities. Analysis of heat transfer in a semi-ellipse cavity using second order boundary condition on curved surfaces is among the novelties of the present work.

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In the present study, the motion and deformation of a red blood cell in the incompressible viscous flow is simulated using the lattice Boltzmann method combined with the immersed boundary method. The lattice Boltzmann method is used to solve the flow field, whereas the immersed boundary method is used to simulate the dynamics of the red blood cell. The red blood cell is considered as an elastic boundary immersed in the fluid domain. The main advantage of the lattice Boltzmann method is that it solves only an algebraic equation. In the immersed boundary method the fluid domain is descretized using a regular Eulerian grid, while the immersed boundary is represented in the Lagrangian coordinates. The Eulerian grid points would not necessarily coincide with the Lagrangian points. The fluid- immersed boundary interaction is modeled using an appropriate form of delta function. The effects of the no-slip condition are taken into account via a forcing term added to the Navier-Stokes Equations (here the lattice Boltzmann equation). In the present study, the tank-treading motion of a red blood cell in the viscous shear flow is simulated. The results are found to be in good agreement with the available experimental and numerical ones.

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Two-phase flow modeling has been the subject of many investigations. However, fewer studies are corresponded for two-phase flow within a porous medium, because of additional complications. In this paper, two-phase flow with the density and viscosity ratio of 1, within a porous medium is simulated by Shan and Chen model. Due to inherent limitations and weaknesses of this approach in an independent control of surface tension, investigation of parameters such as Reynolds number, Froude and Weber is not applicable. However, porous medium parameters such as Darcy number and contact angle could be studied by changing the porous medium and contact angle. Competition between opposing forces against the drop and the capillary effect because of increasing the number of particles in the porous media is described using the Darcy number. Also the effect of the contact angle between liquid-gas phases and the solid surface is evaluated on the droplet penetration inside the porous medium.

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In the present work a new lattice Boltzmann (LB) framework has been developed to study the electroosmotic flows in a 2-D flat microchannel. The governing equations are presented in the continuum model, while a set of equivalent equations in LB model is introduced and solved numerically. In particular, the Poisson and the Nernst–Planck (NP) equations are solved by two new lattice evolution methods. In the analysis of electroosmotic flows, when the convective effects are not negligible or the Electric Double Layers (EDLs) have overlap, the NP equations must be employed to determine the ionic distribution throughout the microchannel. The results of these new models have been validated by available analytical and numerical results. The new framework has also been used to examine the electroosmotic flows in single and parallel heterogeneous microchannels.

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In this study, the collision of two drops using Lattice Boltzmann numerical method in two-phase flow has been investigated. The simulation for incompressible fluid is based on the model represented by Lee. The prominent feature of this model is to simulate fluids with high density ratios. Thus, the model has easily been compared with experimental results and its validity has been investigated. Using this simulation, the variation of non-dimensional parameters such as Weber number, Reynolds number, Impact parameter, density ratio, kinematic viscosity ratio, diameter ratio and velocity ratio of two drops were studied. Considering the results, it was shown that the Reynolds number, density ratio and relative velocity ratio have no effect on separation or coalescence of drops collision; while the variation of Weber number, Impact Parameter and kinematic viscosity ratio results in separation or coalescence. Moreover, by increase in Weber number, Reynolds number or density ratio or decrease in kinematic viscosity, the number of oscillations and the time needed to reach equilibrium increases. Likewise, the amplitude of oscillation and the deformation of the drops increase when the Weber number, Reynolds number or density ratio rise or the kinematic viscosity lowers.

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Box-columns are suitable members for structures with moment frames in two directions but performing the internal continuity plate in them causes some practical troubles. Details of the new proposal to alleviate this problem in box-columns is CONXL connection. This connection includes a set of Collar Flange Top (CFT), Collar Flange Bottom (CFB), Collar Corner Top (CCT), Collar Corner Bottom (CCB) and when the depth of the beams is more than 460 mm, Collar Corner Middle (CCM), Collar Web Extension (CWX) (only in the face of beam to column connection) and also a set of diagonal pre-tensioned high strength bolts (45 degrees angle), which collectively make up CONXL node. The bolts and collars performance make up a rigid diaphragm around the column. All collar flanges top and bottom are connected to the beam by means of groove welding with complete joint penetration, and the connection of collar web extension to the beams and that of collars corner to the column walls is made by fillet weld; collar corners are connected to each other through groove weld in factory and the pieces are just assembled in worksite. The objectives of presenting these details are industrializing, removing weld in workplace, removing continuity plate, enhancing quality, speeding up the construction, and simplifying the inspection. Through the distribution of force among collar systems, forces are transmitted from beams to the columns. The aim of this study is to numerically study the seismic behavior of CONXL connection without filler concrete of columns and to reduce the number of collar bolts with different arrangements. In order to reach this purpose, the numerical results of specimens; RBS and Kaiser bolted bracket (KBB) connection are compared to experimental results to verify the modeling and analyzing and good agreement is observed between numerical and experimental data. Afterward nine specimens of CONXL moment connections in box-columns not filled with concrete whit axial force in single, planer and bi-axial loading conditions with different arrangement of bolts are studied and their performances are evaluated. Results showed that seismic behavior of specimens with beam section depths equal or less than W30 series under cyclic loading, even with reducing the number of bolts to 16 numbers, is suitable in the over 0.04 radian rotations. Also, use of 16 numbers of bolts in connections with W30 series of beams, when it would be appropriate that use for corner connections (Single sided loading), and the specifications of ASTM-A36 for beams material to be used. Also, whatever the position of bolts to be outer than in collar flanges, axial strain in the bolts shank is bigger and its slip is less. The optimal position of the bolts is near the middle of the collar flanges. The results also showed that seismic behavior of all specimens with columns without concrete filling is appropriate and the column will remain without any remarkable local buckling in over 0.04 radian inter-story drift angle.

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In this paper, the immersed boundary-lattice Boltzmann method has been employed to simulate non-Newtonian flow around curve boundaries. The pressure base lattice Boltzmann equations have been used to solve the Eulerian domain to estimate proper pressure gradient in the Poiseuille flow. In addition Immersed boundary method (IBM) utilizes a discrete set of force density is also used to represent the effect of boundary on flow domain. In addition to simulate the real physical dominate problem and study the right effects of non-Newtonian fluid properties, scaling parameters have been introduced to notice the relationship between physical and lattice variables. At First, the capability of present method is examined for simulating the power-law fluid flow around a confined circular cylinder and the results show good agreement with previous study. In the following, the power-law fluid flow around elliptical cylinder in a channel is investigated for three aspect ratios eta=1,1.5,2 and for 5

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In present paper the Inamuro Model based on free energy approach of the Lattice Boltzmann Method (LBM) was used to simulate the motion of bubble and coalescence of two bubbles under buoyancy force. By combining the Tanaka and Inamuro models, three-dimensional model of Inamuro was used in two-dimension for decreasing the computational cost. Firstly it was ensured that the surface tension effect and Laplace low for two density ratio 50 and 1000 were properly implemented. Secondly in next step, effect of governing dimensionless numbers problem such as Etvos number and Morton number on Reynolds number and terminal shape of bubble were investigated. Different flow patterns in various dimensionless numbers were obtained and by changing the dimensionless number, terminal change of bubble’s shape was seen. Finally, motion of two bubbles and terminal shape of coalescence of two bubbles were studied in different dimensionless number, which shape of first bubble was same to single bubble, but it was seen that second bubble experienced various shapes due to its location in wake of first bubble and less difference pressure on two sides of this bubble.

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Bolt joints play an important role in the industries, so the estimation of fatigue life of bolts is an essential task. The aim of present study is estimation of fatigue life of connection bolts of two flanges in reinforced cylindrical shell with cutout. Two groups of data are needed for mentioned bolt: fatigue properties of bolt and value of stress of bolt due to applying load to structure. So, two paths have been gone. First, the fatigue properties of bolt have been measured in laboratory according to ISO 3800 standard. For this purpose a specific fixture was designed and manufactured which provided testing different bolts. By doing fatigue experiments, the fatigue properties of mentioned bolt such as fatigue limit and Basquin’s equation constants (fatigue strength coefficient and fatigue strength exponent) have been measured. Fracture mechanism and fracture surface have been investigated, too. Afterward, in the next step the value of stress in bolt that is subjected to mix loading has been calculated by using of FE modeling. Because of problem complexities, cost of three dimensional analysis of this problem increases, so analysis of the problem has been performed by shell-to-solid sub-modeling technique. At the end, by calculating the nominal stress of bolt from FE modeling and using fatigue properties witch obtained from experiments, life of the mentioned bolt has been estimated.

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In this paper an analytical approach for determining load distribution in single-column multi-bolt composite joints by considering elastic nonlinear behavior of the composite materials is presented. Load distribution was calculated by writing the governing equations of the motion. This closed form solution is an integration of spring-based models with nonlinear behavior of composite plate materials. Developed method is capable to calculate taken load by each bolt and its displacement by simultaneous solving of governing equilibrium equations of the system. This manuscript specifically focused on the influence of composite material nonlinearity on the load distribution of single bolted composite joints. For this purpose, load changes versus displacement are plotted by taking into account both the linear and nonlinear material behavior. The achieved results via suggested solution revealed that displacements were increased upto 2.5-5 percent in comparison with the results of linear method available in the literature. In addition, due to the manufacturing tolerances, bolt–hole clearances can vary within allowable limits and fits. Therefore the effect of bolt hole-clearance on the composite joints with linear and nonlinear material properties was also investigated.

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Emulsion consists of drops of one liquid dispersed into another immiscible liquid, is a novel technique for producing monodisperse droplets. The aim of this research is using the Lattice Boltzmann Method (LBM) to simulate two-phase flows in micro-channels to access the emulsification process. To this approach, The Index-Function Model proposed by He, is used to simulate drop formation in emulsification process in a co-flowing micro-channel with a complex geometry and three inlets. The simulation is performed to investigate the mechanism of drop generation due to dripping and jetting modes and the mode between them. Index function model, which is a new reliable model to evaluate two-phase flows, is applied to track the motion and deformation of the interface between the two immiscible fluids. Accuracy of our results is examined by two well-known basic analytical models including Relaxation of a rectangular drop and coalescence of two static droplets. Our results indicate good agreements with analytical data. The dimensionless numbers such as Capillary and Velocity ratio were used. The Capillary number is one of the most important dimensionless numbers in determination of fluid flow characteristics in micro-channels. The simulations reproduce dripping, widening jetting and narrowing jetting simultaneously in a coflowing microchannel in agreement with the experimental ones. This indicates that index function LBM model has a good accuracy and high stability to simulate this kind of flow.

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In the present Paper, solution methods for simulating compressible flows and shock wave simulation by using Lattice Boltzmann Method(LBM) and simulation of shock wave in the bubble with a moving boundary is evaluated. The standard LBM is found to be incapable of predicting compressible flows and confront instabilities in high Mach number flows. But with some efforts that has been made in recent years, new models for stable solutions of the compressible equations are established. Modified Lax–Wendroff finite difference scheme that has stabale solutions has been used for discretizing Lattice Boltzmann equation. In this study models based on the compressible Euler and compressible multispeed Navier-Stokes to simulate compressible lattice Boltzmann method have been used. The dynamics of compressible bubble busing Rayleigh-Plesset equation have been obtained. Simulation of shock wave in the bubble with other computational fluid dynamics methods has been carried out, However, due to the weakness of the Lattice Boltzmann method for compressible flow, no effort to study the physic of this phenomena has been done with this method. The purpose of this simulation is to achieve a distribution of thermodynamic properties through the radius while collapsing and eventually forming the Sonoluminescence phenomena that caused by the collision of shock waves in the center of the bubble to one other,with lattice boltzmann method.