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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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In order to utilize robots for industrial tasks, designing a suitable path is necessary.Executing the path by the robot in the presence of obstacles, makes the path planning task a difficult one. In addition, path planning is a time consuming task and needs expertise to define certain path for each industrial job. In this paper, uses Jerk-minimum method, B-Spline curves, via-point, and obstacle avoidance algorithm to automatically generate a suitable and safe path for a simulated 7 degrees of freedom industrial manipulator.A user determines via-points for robot trajectory using a Kinect sensor,then a combination of Jerk-minimum method, B-Spline curves, a path is generated. This path is checked by an obstacle avoidance algorithm,and a final path is generated. The obstacle avoidance algorithm uses the inverse kinematic equation of the robot to modify the robot trajectory. One of the advantages of the proposed method is both to facilitate trajectory planning for the user and to create a smooth trajectory for the robotic arm.

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Simulation and analysis of two phase flow that crosses over tube bundles is crucial in safety analysis and design of kettle reboilers and steam generators. The geometry complexity of the tube bundle flow field increases the difficulty of the conventional numerical analysis. One of the methods to reduce the numerical calculations cost, is to use the porous media theory instead of the complete tube bundle modeling. Drag and tube bundle resistance force equations have been used in the porous media analysis. Based on available experimental results, two tube bundle arrangements have been considered. Due to existence of symmetric geometry and uniform energy source over the tube bundle, the two dimensional symmetric models has been used as well. It was observed that the predicted pressure drop in this research has acceptable adaptation with the experimental results. Meanwhile, by considering different outlet boundary conditions, calculated void fraction is compared to the experimental results and showed better accuracy than similar CFD research. It was observed that the enhancement of the tube bundle thermal power increases the void fraction in the heating area of the reboiler.

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Maintaining and restoring robot balance in the presence of external disturbances is a significant capability for a quadruped robot. This is due the fact that these robots move over uneven terrains which may be themselves the sources of the disturbances. In this article, the balance recovery problem of a quadruped robot after an external disturbance will be investigated. To this end, as first stage, the equations of motion of a whole-body model of a robot and also a constraint elimination method will be proposed. In order to recover robot balance, the desired accelerations will be computed based on the concepts of a PD controller and by using the desired velocities and the positions of the main body. However, these accelerations maybe lead to slip stance feet or lose robot stability. Therefore, an optimization problem will be defined to calculate the admissible accelerations and the contact forces simultaneously. The optimal regulation of the contact forces will be done to distribute the contact forces among all stance legs to avoid feet slippage. Since the stability and the slippage avoidance conditions are formulated as linear constraints, the optimization can be solved as a linear constrained least squares error. To evaluate the effectiveness of the proposed algorithm, it will be examined on a quadruped robot in the simulation in two different case studies: in standing situation and walking gait. Finally, obtained results will be discussed.

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This paper deals with the collision-free path planning of planar parallel robot by avoiding mechanical interferences and obstacle within the workspace. For this purpose, an Artificial Potential Field approach is developed. As the main contribution of this paper, In order to circumvent the local minima problem of the potential fields, a novel approach is proposed which is a combination of Potential Field approach, Fuzzy Logic and also a novel algorithm consisting of Following Obstacle as well as Virtual Obstacle methods, as a hybrid method. Moreover, the inverse kinematic problem of the 3-RRR planar parallel robot is analyzed and then the aforementioned hybrid method is applied to this mechanism in singular-free case. It is worth mentioning that, in this paper, all the probable collisions, i.e., the collision between the mechanism and the obstacles and also among the links, are taken into accounts. Two general cases have been considered in collision-free path planning simulation; the first case considered a mobile robot in several workspaces and the second one was assigned to the 3-RRR planar parallel robot path planning. Results of the simulations, which are implemented in C programming language for the sake of real-time purposes. reveal that for the both cases, the newly proposed hybrid path planning method is efficient enough for the mobile robot, or the end-effector of the planar parallel robot to reach the goal without colliding with the obstacles.

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This paper investigates the leader-follower formation control problem of nonholonomic mobile robots based on backstepping technique composed with the bio-inspired neurodynamics while avoiding collision with obstacles. Kinematics model of robot and nonholonomic constraint are introduced and formation control scheme is formed based on backstepping technique. In order to solve velocity jump in backstepping kinematics model, the bio-inspired neurodynamic approach is used. In most of the previous studies, researches are used separation-bearing approach and also supposed that desired separation and bearing are constant. In this paper this assumption is relaxed and desired separation and bearing are considered to be time varying. Error dynamics equations are derived and a new controller is proposed. Also an auxiliary reference angular velocity control law is proposed to guarantee global asymptotic stability of the followers and local asymptotic stability of the entire formation according to direct method of Lyapunov. A common example of changing the formation is obstacle avoidance, when an obstacle is located within a follower path and is not in its leader path. Time varying functions for desired separation and bearing are chosen and the new controller is developed with its proof of stability. Simulations results reveal that each follower robot can track its real time leader employing the proposed kinematic controller while avoiding obstacles. Furthermore control inputs at the start moment and also while avoiding obstacles, do not contain impractical jumps and are reasonable thanks to integrating bio-inspired neurodynamic with backstepping technique.

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In the pultrusion process, continuous fibers reinforcement in roving forms are drawn through a pultrusion die. Therefore, the fibers reinforcement in the final product are generally oriented in the longitudinal axis. In this research, for manufacturing of composite rods, on the basis of previous studies and researches, the E-glass fiber-polyethylene prepregs were produced firstly. Then due to the Design of Experiments (DOE), the pultruded rods with unidirectional and helically-wound layers were produced by using the prepregs. In this study, mechanism of the pull-winding process is created as a secondary process during the main process to improve the mechanical and physical properties in the other directions. One of the most important issues in the thermoplastics pultrusions is the fibers impregnation quality with the polymer base. The fiber volume fractions of the productions are found by the burn tests. The density of the specimens is found by the liquid displacement method. The microscopic images were taken from cross-section of the pultruded rods to investigate the fiber impregnation and the void distribution. Due to the surveys conducted, the fiber volume fractions in the pultruded rods was increased, using the pull-winding technique, and also the void content of these rods was decreased.

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This paper presents a new method based on machine vision for mobile robots to detect and avoid obstacles in unknown environments. One of the challenges of mobile robots trajectory control in unknown environments is that their obstacle avoidance system to be designed robust to material and shape of the obstacle. In this research a mobile robot equipped with a camera is designed and fabricated. Also an algorithm is proposed and implemented on the robot in order to detect obstacles by image processing and to control the robot trajectory. Three color laser pointers are mounted on the robot with certain angles that emit beams to the ground at ahead of the robot. The received images from camera contain these colored points that their coordinates are determined by image processing. Then position of any possible obstacle is detected using the proposed algorithm and the robot is commanded to avoid obstacles by changing its path. These obstacles can be static or dynamic. Our experimental results show that the proposed method, with a high reliability, has the ability to detect and avoid obstacles with any shape and material whereas other similar methods had restrictions in this regard.

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This paper focused on the vehicle path planning in the highways and complex urban environments. At first, obstacles and road lines have been detected by sensors of the intelligent vehicle, thereupon the vehicle will be find the safe areas using the time distance method developed in this paper. Then, an appropriate path close to the intelligent decisions about human being would be chosen through the developed algorithm. There is the possibility of collision to surrounding vehicles in the areas where changing the lane is needed. Therefore, to prevent collision, a five orders polynomial curve is offered for each lane change maneuver. The reached maneuver is optimized based on the vehicle dynamic and allowed lateral acceleration. Finally, a suitable path to pass quite safely and without any collision through the obstacles is suggested. At the end, two main and different simulation scenarios included the lack of collision is verified by MATLAB software and the obtained path is controlled by the sliding mode controller. These simulations indicated effectiveness of this method. The lateral acceleration is obtained in allowed range for comfort of occupants in these scenarios.

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This paper aims at proposing an algorithm for collision-free motion planning of two wheeled mobile robots. The proposed approach relies on discrete motion planning, convex optimization and receding horizon control (RHC) concepts. The proposed algorithm is employed for motion planning and control of a mobile robot in order to pass through an unknown environment both in simulation and practical implementation. In this regard, CVX package benefited from the Gurobi solver is employed to solve the optimization problem in the simulation. Moreover, in order to perform a collision-free motion planning, corresponding Robot Operating System (ROS) package with the intended mobile robot is employed to cooperate with the provided motion planner package. The provided package utilizes educational license of Gurobi optimizer solely to speed up solving proposed optimization problem and its built in branch and bound for Mixed Linear Integer Programming (MLIP). In order to keep the linear form of the constraints, a combination of the Velocity Obstacle (VO) in the first horizon and Bug method concept for the rest of the horizons is used. Obtained results show the reliability of this algorithm for safe collision avoidance. The reported results reveal this fact that by considering the maximum velocity of the E-puck, obtained computational time is less than 0.004 sec. in each stage which is fast enough for robot motion planning tasks.

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In the present paper the problem of designing a flying vehicle trajectory to avoid the collision with Terrain by limiting the flight range in a flight corridor influenced by the shape of the terrain has been investigated. In order to improve the traceability of the designed trajectory, considering the performance characteristics of the aircraft, the effect of two performance parameters including of the maximum rate of climb and the maximum increasing rate of the flight path angle, are considered in the solution algorithm. In this regard, the quantification of the system performance, has been implemented during the definition of different cost functions to minimize the operating time, control effort and vertical acceleration imposing on the aircraft. Mathematical modeling of the terrain which is considered as the route location of the threat, has been implemented using a power polynomial solution for smoothing. Finally, optimal control theory and nonlinear programming approach are utilized to solve the defined problem. The evaluation of case studies and numerical simulations confirmed the effectiveness of the proposed approach to solve the planning problem in flying maneuvers with low altitude requirements for follow and avoidance of direct and indirect environmental hazards.

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The oviposition behaviour and distribution of the eggs of carpophagous Virachola livia Klug (Lepidoptera: Lycaenidae) was studied on pomegranate for six years. Taylor’s power law and Iwao’s mean patchiness regression, and common k proved the aggregated distribution of the eggs on pomegranate fruits. The butterflies tend to oviposit one egg per fruit, indicating the existence of conspecific egg avoidance behaviour. The study showed that the selection of oviposition sites was affected by the part of the fruit body and the cardinal direction of the tree canopy. Results suggest that the oviposition behavior of V. livia and, consequently, the distribution of the eggs may be regulated by the conspecific aggregation and conspecific egg avoidance. It is apparent that the butterfly integrates these two behaviors to maximize the success of its reproduction.

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Following Northridge earthquake, wide spread brittle cracking had been observed in steel moment connection, and this, was in contrast with the philosophy of designing steel moment frames which accounts for dissipating energy by forming plastic hinges at beams. This situation led to the development of improved connections to make them less prone to brittle fracture. However, studies have shown that these new connections, typically known as post-Northridge connections, can still have the tendency to fracture but in a ductile manner when subjected to ultra low cycle fatigue loading. Ultra low cycle fatigue loading consists of limited cycles of loading with large amplitude which induce strains that are several times greater than yielding. Searching the literature, varied methods have been proposed to predict cracking in ductile steel for both monotonic and cyclic loading.
In this research, a micro mechanical model called cyclic void growth model has been applied to predict the instance and location of cracking in the steel structure. For the purpose of predicting the low cycle fatigue failure, finger shaped steel moment type connections with top and bottom cover plates which their experimental data were available, used as a benchmark study. A micro mechanical model is integrated into the ABAQUS finite element program in order to simulate crack initiations in the cover plate welded beam to column connection. For this purpose, a Fortran code is linked with the ABAQUS software for simulating the crack and specifically to predict when and where the crack initiates. By understanding the crack initiation and the location of this crack, a trend line for low cycle fatigue under various constant drift angels are put together. The trend line provides a number of cycles for the crack to initiate by applying the specific drift angle. Therefore, a finite element model of a cover plate welded moment connection was developed and was used in order to simulate cracking in the connection model. Thus, each crack location and the number of cycles to initiate the crack were detected. Utilizing cyclic void micro mechanical model of growth analysis, which is a technique to predict fracture in a ductile material, different cover plate connections were modeled in the steel moment frame, and then their critical points to trigger the crack were identified. Finally, for the finger shaped cover plate moment connection, considering different loading curves data and in order to present the low cycle fatigue life prediction, displacement versus the number of half cycles diagram is produced.
Finite element results demonstrated acceptable agreement with the experimental data. Furthermore, the low cycle fatigue life of connections under loading with constant amplitude is estimated, and S-N curves are proposed. These curves can be applicable for engineering purposes, such as performance based design. Also it is demonstrated that the finger plate joint revealed a good performance against soft cracking in low cycle fatigue compared to a number of previously tested joints. The results of the S-N curve for a constant displacement loading averaged 73% of the lifetime of the initial cracking. Sensitivity analysis with 20% tolerance on the intrinsic parameters of the micro mechanical model showed a maximum change of 15% in the responses.
 

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The importance of environmental issues has increased the use of biodegradable polymers which nowadays have become among main components in medical and biological applications. In the present study, a new combined method of fused filament fabrication (FFF) and batch foaming was introduced to improve the properties of poly lactic acid. For this purpose, FFF samples were produced with infill percentages of 100, 80 and 60 and then, foamed in batch process. Due to the importance and effect of the void fraction on structural and mechanical performance as well as the biodegradability of materials with porous structure, especially for medical purposes, void fraction and impact strength were evaluated. The results showed that the void fractions of FFF samples were 3%, 13% and 25% in infill percentages of 100, 80 and 60, respectively while after the foaming they reached to 14%, 19% and 30%. The findings revealed that the impact strength of FFF foamed samples was improved compared to FFF solid samples. For samples with 100 infill percentage, the impact strength improved from 207 to 506 J/m² due to the foaming procedure with nano-sized cells created by the batch foaming.

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The condition of non-liability in insurance has been less considered by researchers and existing laws. The ambiguity of the conditions of these terms and  referral of the condition of these terms to the private conditions of the insurance policy, due to the extension of insurance contracts and the superior trading power of insurance companies, is criticized, often to the detriment of the insurers and beneficiaries of the insurance policy Ends. However, according to legal basis, it is possible to cancel the condition of non-responsibility for the main obligation of the insurer, but this ambiguity continues with the insurer's underwriting obligations. Also, in cases where the condition of non-liability is minor, although such a condition is subject to the principal obligation, considering that such a condition does not eliminate the overall effect of the insurance contract, it is not possible to invalidate or insert the insurance contract. But in general, the referral of the status of the condition of non-responsibility to private conditions has created opportonities for misuse. For this reason, reform of existing laws and regulations seems to be necessary from this perspective.
 

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According to the information view, the main function of accounting is to provide information and thus reduce uncertainty. So, the high internal information environment quality (IIEQ) reduces the corporate declared tax disagreement by tax auditors due to facilitating tax planning coordination between different departments of the company and providing documents to tax authorities. The purpose of this study is to investigate the impact of IIEQ on tax risk reduction in listed companies in Tehran Stock Exchange (TSE) by applying data collected from 136 companies during the years 2009 to 2015. For this purpose, the difference between the corporate declared and certain tax due to the uncertainty about the confirmation of the declared tax is taken as a tax risk. The results show that environmental uncertainty increases tax risk. Moreover, income quality, income forecasting accuracy, and financial reporting quality and transparency reduce tax risk. Corporate governance quality, is also effective for tax risk reduction. These findings highlight the importance of environmental conditions, measurement process, financial reporting and internal monitoring for tax risk reduction. On the other hand, based on the research findings, companies with lower tax rates have higher tax risks; but conservatism and asset returns don’t make sense for tax risk. Moreover, tax risk is higher in larger companies, and financial leverage, also, increases tax risk. The findings provide new evidence of the IIEQ impact on the corporate tax planning. These findings can be useful in assessing corporate tax risk based on its IIEQ.

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Under articles 37 and 48 of the United Nations Convention on Contracts for the International Sale of Goods (CISG), the seller is entitled to cure the lack of conformity of the goods due to specific circumstances. The same legal establishment has been accepted in the Article 7-1-4 0f the Unidroit Principles of International Commercial Contracts (UPICC).
Anticipating the seller’s right to cure, one controversial issue raised is the status of the buyer's right to avoidance. Subsequently, the question arisen is whether the seller's right to cure is prior or the buyer's right to avoidance. While there are various interpretations of Article 48 leading to disagreements, in UPICC, the buyer has no right to avoidance in case of seller’s cure under Article 7-1-4. Similarly, according to general principals including Article 478 of the Civil Code in Iranian legal system, the buyer has no right to terminate if the seller is ready to cure.
To conclude, we can say the seller’s right to cure from the perspective of the doctrine, judicial precedent, legal and economic analysis has priority over buyer’s right to avoidance.

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In recent years, advancements in driver assistance technology have significantly minimized the impact of human error on traffic accidents. The development of these systems is of great interest, especially for critical and accident-causing maneuvers such as critical lane change on the highway. One of the important parts of automatic lane change is the motion planning. In this research, taking into account the criteria of collision avoidance and feasibility of the path, an algorithm for the motion planning is proposed. The main innovation of the present research is that the dynamic limits and stability margins of the vehicle have been converted into quantitative criteria and considered in the motion planning. To evaluate the performance of the motion planning algorithm, the complete model of the car is used in the Carsim-Simulink software. Also, to follow the designed path, an integrated longitudinal-lateral control has been designed and implemented. The simulation results show that the proposed method provides a more accurate assessment of the trajectory dynamic feasibility in high-speed critical lane change maneuvers compared to the previous methods. This issue is especially evident for critical maneuvers where the lateral acceleration of the trajectory is more dominant than the longitudinal acceleration.