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Marine transportation is the most conventional method for transportation of natural gas, mostly liquid form; namely, Liquefied Natural Gas (LNG) to international far market. Hereon provide safe transportation of natural gas is very important. In the event of exterior material contact to LNG, swift boiling and exploding anticipated. The paper, investigates thermo physical water contact (0oC as a fluid with higher temperature) with liquid methane (cause the similarity of thermo physical properties to LNG) at low temperature (-162oC). The intensity of heat transfer between water particle and liquefied methane resulted to swift pressure increase in vapor film. It causes the generation and swift growth of methane vapor film which has been resulted from abrupt evaporation and results to liquid methane explosion. In this situation, the intense vapor explosion phenomena, endangers the safety of system. Mathematical model of these phenomena has been developed by assuming saturation condition on interface phase. Then, the effects of different thermo physical parameter changes on vapor film growth have been investigated. Based on the results, in some cases, the vapor pressure pulse created in the film has been more than 3 times the initial pressure, which can endanger the safety of system.

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The cone-penetration test (CPT) is a well-established in situ test in geotechnical engineering for soil classification and estimation of soil properties. In a CPT, a cone shaped penetrometer is pushed into the ground at a constant rate. The resistance on the cone tip is measured and is then related to soil classification and soil properties. In this research, the finite difference analysis of large deformations for the cone penetration testing (CPT) in the cohesive soil have been conducted using FLAC 2D Software. In this modeling, interface elements between penetrometer and soil are considered and it is assumed that the penetrometer materials show rigid behavior in reaction to the soil materials. FLAC provides interfaces that are characterized by Coulomb sliding and/or tensile separation. Interfaces have the properties of friction, cohesion, dilation, normal and shear stiffness, and tensile strength there is an in-situ state of stress in the ground, before any excavation or construction is started. In FLAC 2D, an attempt is made to reproduce this in-situ state by setting initial conditions. Ideally, information about the initial state comes from field measurements. Boundary conditions are modeled as axesymmetry. Horizontal and vertical direction at the bottom boundary and horizontal direction at the vertical boundary of soil model are fixed. Soil behavior follows full elastic–plastic model and Mohr-Coulomb failure criterion. Numerical model is analyzed to achieve mesh convergency at the various grids. The values of cone and frictional resistance have been obtained through software calculations and then compared with the results obtained from cone penetration test at the aluminum melt factory in Lamard, Fars Province. Stress and displacement contours are related for evaluation of the penetration process. Steady state is considered to achieve steady stress range in which the hole diameter is equal with the CPT hole. The numerical modeling results of CPT test by FLAC 2D software shows good agreement with the field tests results. Furthermore, the results have been discussed by using Robertson Chart 1986 and Eslami- Felonious Chart 1997. Charts almost show same profile with the field test results at the aluminum melt factory site.

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Due to high strength and stiffness in comparison with their weights, laminated composite materials are widely used in many structures such as aerospace and naval structures. Therefore, the understanding of their failure mechanisms to predict their mechanical response is of high importance. One of the major aforementioned mechanisms is the delamination which commonly occurs in skin/stiffener joints. In the present paper, a comparative study on the delamination in composite skin/stringer structures under 3 point and 4 point bending loads is performed by the finite element method (FEM) employing the cohesive elements. The detailed effects of stacking sequence on the damage of structure are investigated. A user defined interface element has been implemented in the Ansys software in continuum damage mechanics framework based on the bilinear cohesive zone model. The advantage of this method is the modeling of delamination growth without any requirements to the presence of initial crack and remeshing. Comparison of the obtained results from FEM with that of experiment justifies the capability of the employed model to predict the delamination initiation and propagation. The results indicate that in the 3 point bending load, the damage initiates from the adhesive between skin and stringer, while in 4 point bending load it initiates from the interface elements between skin layers near the adhesive bond. Finally, in order to increase the strength of skin/stringer structures, the results strongly recommends preventing the use of 45 and 90 degrees plies near each other around the adhesive bond.

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Numerical modeling of compressible two-phase flow is a challenging and important subject in practical cases and research problems. In these problems, mutual effect of shock wave interaction creates a discontinuity in fluid properties and interface of two fluids as a second discontinuity lead to some difficulties in numerical approximations and estimating an accurate interface during hydro-dynamical capturing process. The objective of this research is to increase the accuracy of numerical simulation of two-phase flow using two dimensional five-equation two-fluid model. For this purposes, MUSCL strategy was used for increasing the Godunov numerical scheme accuracy from 1st order to 2nd order. The privilege of this method is high accuracy, low numerical oscillation and low numerical diffusion. The problems considered for the verification of the results are the water-air shock tube, a square bubble with moving interface in a uniform flow and a shock wave with 1.72 Mach having interaction with an air bubble in a water pool. The obtained numerical results showed that, the results that have been obtained by second order accuracy have less diffusion in the two-phase flow interface.

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Explosive welding is used for excellent bonding of similar and dissimilar materials with the wide variety of thicknesses,area dimensions and different thermal and mechanical properties. In this study, an Al/St/Al multilayer sheet was fabricated by explosive welding process and the effects of annealing temperature on the interfacial properties of explosively bonded Al/Cu bimetal have been investigated. For this purpose, hardness changes along the thickness of the samples have been measured, and the thickness and type of intermetallic compounds formed at the joining interface have been explored by means of optical microscopy (OM), scanning electron microscopy (SEM) and also energy dispersive spectroscopy (EDS). By heat treatment of the samples at 300, 350 and 400°C, it was observed that intermetallic layer was formed at the interfaces. The obtained results indicate that, with the increase of the annealing temperature, the thickness of intermetallic compounds has increased and the amount of hardness along the thickness of the joining interface has diminished. In the annealed sample at 300 °C for 60 min, it was observed that intermetallic layers have formed at the interface of Al/St bimetals. These layers consist of the intermetallic compound Al2Fe and its thickness gets to about 35 μm at some points.

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In present work, models that predict contact angle of a droplet with a solid surface, are considered and compared with each other. Two phases were assumed to be Newtonian, incompressible and immiscible fluids. OpenFOAM software is applied to simulate the two phases interface by using Color function VOF (CF-VOF) method. Different models for contact angle of a droplet as Tanner and Yokoi models are implemented in the OpenFOAM. In addition, the dynamics and statics contact angle models were used to compare with recent models in order to choose the best one. The outcome of study shows, even though the static contact angle model is simple to understand, however, it could be the best model to predict the droplet behavior in a wide range of different conditions. The fluid viscosity effect was also considered in different models of the present study. It concluded that the fluid viscosity affects the type of pattern of droplet impact and as viscosity of fluid increases; more energy is needed to uplift the droplet again from the surface. Kelvin-Helmholtz instability (K-H) was also simulated and explained in details which initiates on the interface of two fluids due to velocity differences of droplet and the surrounded air.

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Extended finite element method (X-FEM) has been recently emerged as an approach to implicitly create a discontinuity based on discontinuous partition of unity enrichment (PUM) of the standard finite element approximation spaces. Despite numerous progresses in mesh generating updating of finite element mesh during crack propagation remain extremely heavy and difficult. This problem becomes more complicate, when there are many discontinuities in the finite element domain. However, the extended finite element method (X-FEM) in the combination with level set method (LSM) could overcome this cumbersome issue. In this contribution, predefined cracks and internal boundaries are created using level set functions and also the effects of soft/hard inclusions (interfaces) and voids are considered on crack propagation schemes. In fact, the interaction of crack and heterogeneities are considered. The level set functions are utilized to represent the locations and the evolutions of internal interfaces. In addition, the stress intensity factors for mixed mode crack problems are numerically calculated by using the interaction integral method. Different crack growth paths are simulated automatically for different oriented edge and center cracks and the interactions of internal boundaries on crack propagations are shown. All numerical examples are demonstrated the flexibility and capabilities of X-FEM in the applied fracture mechanics.

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Applications of aluminium and magnesium castings have been increased, as a result of increasing demand for the light weight components in various sectors of industries, in recent years. In this work an Al/Mg bimetal was prepared by casting Al melt into a cylindrical Mg bush, with 35 mm height and 76 and 84 inner and outer inner diameter, rotating at 1200 and 1600 revolutions per minute (rpm), 0.9, 1.6 and 2.7 melt-to-solid volume ratio and 30, 120, 150 and 200 oC preheating temperature, respectively. Vertical centrifugal casting process was selected for producing samples. In this process melt is under effect of centrifugal, coriolis and gravity forces during filling. Difference between shrinkage of Al and Mg led to the formation of mechanical bond in the interface. The results of scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis showed that concentration gradient changes from Mg to Al side in such a way that three sub layers including Al3Mg2 and Al12Mg17 intermetallics plus eutectic microstructure (Al12Mg17 and δ), were formed, based on aluminium and magnesium phase diagram, in the interface

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Using the soft fingers increases stability and dexterity in object grasping and manipulation. This is because of the enlarged contact interface between soft fingers and object. Although slippage phenomenon has a crucial role in robust grasping and stable manipulation, in the most of previous researches in the field of finger manipulation, it is assumed that the slippage between finger and object does not occur. In this paper, slippage dynamic modeling in object grasping and manipulation using soft fingers is studied. Because of the enlarged contact interface between soft fingers and object, a frictional moment along with tangential frictional force and normal force is applied on the contact interface. Therefore, a novel method for dynamic modeling of planar slippage using the concept of Friction Limit Surface is presented. In this method, equality and inequality relations of different states of planar contact is rewritten in the form of a single second-order differential equation with variable coefficients. These coefficients are determined based on the slippage conditions. This kind of dynamic modeling of contact forces can be used for designing the controllers to cancel the undesired slippage. The method is used in study of slippage analysis of a three-link soft finger manipulating a rigid object on a horizontal surface. In order to increase the accuracy of dynamic modeling of soft finger, dynamics of soft tip is integrated with the dynamic of finger linkage. Dynamic behavior of this system is shown in the numerical simulations.

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Due to the influence of Internet and mobile service in every part of our lives in addition to pervasive demand for them, next generation wireless networks should be able to address different kind of objectives or demands. New generation of cellular networks must achieve high user quality of experience (QoE) in order to satisfy the user demands and survive in market. To meet this demands, drastic revision need to be made in previous network architecture. This paper reviews some of the key technologies which are emerged to improve future network architecture and meet the demands of users, especially in Fifth generation (5G) cellular network. In this paper, the prime focus is on the air interface of 5G
which includes millimeter wave communication, multiple access technologies, carrier aggregation (CA), and massive Multiple-Input Multiple-Output (MIMO).

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In electromagnetic motors, increase in output torque leads to increase in rotor inertia. Various robotics applications, especially haptic interfaces, oblige convenient dynamic performances of electromagnetic motors which are strongly in turn influenced by the rotor’s inertia. In the present paper, a robust control method for a viscous hybrid actuator is developed which supplies a desired varying torque while maintaining a constant low inertia. This hybrid actuator includes two dc motors with the shafts coupled through a rotational damper using a viscous non-contact coupler. This coupling method is based on Eddy current to provide the required performances. The large far motor eliminates or reduces the inertial forces and external dynamics effects on the actuator. The small near motor provides the desired output torque. Since the system is essentially linear, the applied robust control method is based on Hꝏ and parametric uncertainties and physical constraints including motors’ voltages saturation, rotary damper’s speed saturation, fastest user’s speed and acceleration applied to the actuator and force sensor noise are considered in its design. Also the robust method of µ-synthesis for the system in presence of parameteric uncertainties and other physical constraints are studied. The implementation of the controller on a 1 dof haptic interface model validate the achievement of the desired performances.

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The elastic behavior of an edge dislocation located inside the core of a core-shell nanowire which is embedded in an infinite matrix is studied within the surface/interface elasticity theory. The corresponding boundary value problem is solved exactly by using complex potential functions and Laurent series expansion. An important parameter so-called interface characteristic parameter which has the dimension of length and is a combination of the interface moduli enters the formulations. The stress field of the dislocation, image force acting on the dislocation, and the dislocation strain energy is calculated by considering the interface effect. The stress field of the dislocation is shown as contour plots and the results are compared with classical case. The image forces acting on the dislocation are studied in details and it is shown that they depend on the interface characteristic parameter, nanowire dimension, dislocation orientation, and dislocation distance from the interface. Moreover, the repelling and attracting effects of the interface parameter on the image force are discussed. The equilibrium position of the dislocation is also studied. The dislocation strain energy in the interface elasticity framework is only slightly different from that of traditional elasticity when the dislocation is placed in the central region of the core and reaches its maximum value when it is located near the core–shell interface.

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Individuals with high levels of disability like patients with cervical spinal cord injury, are highly dependant on their relatives for daily life needs. Hence, this problem decreases the quality of life of this individuals and their relatives. New technologies such as robotics have the potential to help these kind of patients and give them some degree of independence. The first step in design and implementation of robots which have the capability of helping disabled people is to design a user interface that can receive user’s commands and transfer these commands into the robot environment. In this paper, a haptic user interface has been designed and implemented to serve patients with cervical spinal cord injury. In this user interface, user’s head angles have been extracted using a gyroscope sensor and then transferred into the computer simulation environment in which the robotic arm is graphically simulated and the user can control the arm using his/her head movements through a novel control pattern. A haptic unit has also designed and implemented to produce resistive torques against head movements to help user to physically sense the weight of gripped objects and the collision of the robotic arm with obstacles. The performance of haptic user interface evaluated using three sets of tests subject to two healthy individuals. Finally, obstacle collision detection tests was 100 percent successfully while heavy and light object recognition tests were 83 percent and heavy, medium and light object recognition tests were 72 percent successful.

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Coatings are used in various industries in order to improve the surface properties of materials. Delamination of coatings from their substrate, at the root of channel cracks, is one of the common failure modes in these structures. In this paper, discrete element method is used in order to simulate the initiation and propagation of damages, caused by the mismatch between the thermal expansion coefficients of coating and substrate. Coating and substrate are considered to be brittle elastic in which, substrate is stiffer than the coating, but the thermal expansion coefficient of coating is considered to be much greater than substrate. The interface properties are also considered to be the geometric average between the coating and substrate. Temperature reduction is applied to the whole structure as loading. The effect of elastic mismatch and coating thickness was investigated. The results showed that, by increasing the elastic mismatch and decreasing the coating thickness, the temperature reduction, need to delamination initiation at the interface, increased. Also, changing in the damage propagation pattern was happened by changing in the elastic mismatch. In coatings with high elastic mismatch, damage propagation was happened inside them but by increasing the stiffness, damage propagation happened at the interface.

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In this study, the effect of delamination interface fiber angle orientation on the initiation and propagation fracture toughness of plain woven composites with stacking sequences of [012//012], [011/30//0/011] and [011/45//0/011] under mode I loading were investigated. These stacking sequences are chosen in order to eliminate the effect of the remote ply orientation on the delamination behavior of the double cantilever beam (DCB) specimens. Samples were manufactured by the wet hand lay-up method and fracture tests were conducted on specimens using the universal testing machine (SANTAM STM-150) according to ASTM standard. The experimental results showed that the interface ply orientation had a negligible effect on magnitudes of the initiation and propagation fracture toughness of plain woven composites due to delamination propagation in the resin-fiber interface of delamination interface. Experimental investigations of the fracture surface have shown the effect of different mechanisms on the delamination propagation, which crack propagation in the resin-fiber interface is one of the main mechanisms for increasing the fracture toughness in these specimens. In addition, the experimental evidence revealed that the fiber bridging was not the main mechanism of increasing fracture toughness during the delamination propagation, unlike the unidirectional DCB specimens.

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In the present paper, a new penalization method is proposed for implementation of the rigid surfaces on the Navier-Stokes equations in the vorticity-stream function formulation. In this method, a rigid body is considered as a region in the fluid flow, where the time is stopped. Therefore, by stopping the fluid particles, this region plays the role of a rigid body. In this regard, a new transformation is introduced and applied to the governing equations and a set of modified equations are obtained. Then, in the modified equations, the time dilation of the solid region is approached to infinity, while the time dilation of the fluid region remains In the article, the physical and mathematical properties of modified equations are investigated and satisfaction of the no-slip and no-penetration conditions are justified. Then, a suitable numerical algorithm is presented for solving the modified equations. In the proposed algorithm, the modified equation is time integrated via the Crank–Nicolson method, and the spatial discretization with the second-order finite differencing on a uniform Cartesian grid. The method is applied to the fluid flow around a square obstacle placed in a channel, the sudden flow perpendicular to a thin flat plate, and the flow around a circular cylinder. The results show that the no-slip and no-penetration conditions are satisfied accurately, while the flow fields are also high level of accuracy.
 

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With increasing urban population, the need for underground spaces increases and deep excavation is an inevitable affair in civil projects. deep tunnels and large buildings require deep excavations, which is a must use some techniques for stabilize it. grouted soil nail is a popular reinforcement to stabilize slopes, excavations and retaining walls. This method has been introduced to Hong Kong in the mid-1980s and has become an alternative solution to the conventional slope stabilizing methods such as compaction, earth retaining structure, or reduced inclination of the slope, etc. this method is based on sewing the potential failure wedge of soil on the stable soil using some inactive (un-prestressed) elements. the shear strength-displacement behavior at the interface between the grouted nail and surrounding soil is an important parameter in design of various geotechnical engineering projects, for example, soil nails, retaining walls, shallow foundations, pile foundations, etc. in soil nail system, the most common method to measure the interface shear strength is pullout test. It is also possible to determine the interface strength based on the development of resistance between soil and grout in direct shear tests. However, accurate perception of the shear behavior in the connection area of the soil and grout is essential to reach an optimum design. In other words, the interaction between soil and grouted nail is necessary to design an optimum soil nail system. the most common method for determination grouted soil interface resistance is pullout test but there is another experiment that can yield acceptable results. The current study investigates the interface shear behavior between cement-grout and granular soil in direct shear test with different grout pressures ( up to bar) and different overburden pressures ( up to 300 kPa). For this purpose, a number of direct shear tests are performed by modifying of the standard shear box for injection of grout. “Firozkooh” sand is used in this study. The soil is compacted to the relative density of % and the slurry is sprayed with pressure on its surface. Furthermore, results of two pullout tests were used for verification. These pullout test have already been presented in another study with different normal stress and grout pressure. it is shown that the results of direct shear test and pullout test at interface are similar. this may indicate the proper function of direct shear test as a suitable choice alongside pullout test. It was observed that shear stress–displacement curves of the soil-grout interface in direct shear tests are similar to the soil-soil tests; which are classified under different grouting pressures. In addition, increasing grout pressure increases shear strength by increasing the angle of friction and bonding of soil and slurry. The effect of adhesion is dominant. it is shown that The interface shear stress under different grouting pressures is greater than the shear stress of soil under the same normal stresses. it is shown that grouting pressure and normal stress have influence on the behavior of soil-cement interface. Therefore, interface shear strength increases with increase in overburden and injection pressure. The variation of the interface shear strength is approximately linear versus grouting pressure. Finally, a formula is proposed for interface shear strength considering grouting pressure.

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In order to improve the intelligent mechanized harvesting ability of small green vegetables, a self-propelled small green vegetables intelligent combine harvester was designed according to its planting mode and agronomic requirements. It can simultaneously meet the requirements of mechanized harvesting operations for cutting, clamping and conveying, and collecting of small green vegetables. Additionally, this model adopts the electric drive chassis of the pure electric drive intelligent battery management system based on BMS technology, which realizes the intelligent balance matching of power. The harvester adopts the intelligent control system controlled by PLC to automatically detect the walking speed of the machine, the height of the cutter and the transmission speed, etc., so as to realize the rapid matching of each working part. It was found that the proportion of electricity consumption of the harvester in two hours was 23%, with an average harvesting efficiency of 0.16 hm²/h. Besides, the average loss rate was 4.22% during the normal operation of the harvester. This study provides a reference basis for the intelligent mechanized harvesting of small green vegetables.