Modeling in Engineering
Year:2019 | Volume:17 | Issue:56|Papers Count:33

Pollution is known as one of the important and effective factors on the performance of polymeric insulators. In practice, the deposit contamination on the insulator surface is not uniform completely and is non-uniform contamination. So far, comprehensive research has not been carried out on the effects of different forms of non-uniform contamination on the performance of the insulators. In this paper, the effect of uniform contamination, longitudinal non-uniform pollution and fan-shaped non-uniform pollution in three levels of light, medium and heavy contamination on the potential and electrical field distribution of a 20 kV polymeric insulator using Comsol Multiphysics software have been done and the results have been Analyzed. In longitudinal non-uniform pollution, the severity of pollution in the near of high voltage and ground electrodes regions is heavier than the middle region, and in fan-shaped non-uniform pollution, the severity of pollution in the leeward side region is heavier than the windward side region. The results show that in slightly uniform pollution, the electric field decreases and its amplitude increases with increasing the pollution intensity. In longitudinal non-uniform pollution, electrical potential is almost constant in the near of electrodes and the electric field intensity has been decreased. Also, in the fan-shaped non-uniform pollution, the electric field intensity has been increased in the leeward side region.

The most prominent feature of sheet material forming process is an elastic recovery phenomenon during unloading which leads to springback. Therefore, evaluation of springback is mandatory for production of precise products. In this paper, the effects of temperature, friction coefficient, blank-holder force and sheet thickness on the springback of AL5083-H111 alloy sheet in warm U-bending conditions were investigated by performing experimental tests and numerical method. ABAQUS FEA software was used for numerical simulation. Finally, comparison of experimental and numerical results showed good agreement.

In this article the natural convection of nano-fluid water-copper in a square cavity has been studied numerically. The left wall is maintained at high temperature, right wall is maintained at low temperature and the other walls are adiabatic. The numerical model is based on the SIMPLE algorithm is used to solve the equations of continuity, momentum and energy. The effects of pertinent parameters such as the position and length of the baffle, Rayleigh number and solid volume fraction, on the thermal performance of the cavity are examined. The results showed that, the increase of the Rayleigh number and volume fraction of nanoparticle increased the average Nusselt on both hot and cold walls. The results also showed that the average Nusselt numbers on cold wall increased and on hot wall decreased with increase of the baffle length.

Triple shaft gas turbines are the most gas compressor driven in natural gas compressor station in national Iranian Gas Company. In the recent study, exergy equilibrium formula of each components of gas compressor station specified and several mathematical models made. The model predict different parameters based on environmental and operational conditions. Models made by multivariate linear regression and ANOVA technique that made high precision models. The models results show that how varying the environment and operational condition such compressor inlet temperature, turbine inlet temperature and turbine pressure ratio affect exergy efficiency, fuel consumption, exergy destruction and specific fuel consumption. In this study effects of environmental and operational variables on this parameters and interaction of this variable on each other surveyed. Results showed that variation in each variables has no effect in slope of net output power variation due to change in other variables, whereas compressor inlet temperature and pressure ratio in exergy efficiency model, turbine inlet temperature and pressure ratio in fuel consumption model and turbine and compressor inlet temperature in specific fuel consumption model have interaction on their model's response

In the warm season, the performance of double skin facades has a significant dependence on the faç ade design details and climatic conditions. On the other hand, using the double skin facades can increase the building cooling load. In order to eliminate this problem, two different approaches have attracted the intrest of engineers: solar energy storage and preventing the solar radiation from entering the building by using shading devices. Therefore, in the recent years, the idea of using double skin facades with plants has been proposed in order to decrease the summer energy consumption of buildings. In this study, a thermal performance analysis has been performed by considering a high-rise building with the plants double skin faç ade in Tehran climatic conditions. The results indicate that although using the ordinary double skin faç ades can decrease the building’ s energy consumption up to 24. 3% in cold months of the year; it can lead to increase the summer cooling load about 18. 3%. However, by using double skin faç ades with the plants, the building’ s energy consumption in cold and warm seasons may decrease about 21. 4% and 22. 5%, respectively.

Always share of damages of non-structural components is a significant share of the total cost of earthquake damages. A simple method for analyzing the response of non-structural members, is use the floor response spectrum. In this method, first behavior of primary structure at the non-structural member nodes regardless of their interaction is determined. Then the response of non-structural members used as input to the analysis result. In this study, six two-dimensional steel moment frame, three, six and twelve-story is modeled. In order to investigate the effect of changing period in the force exerted on non-structural components there are two models, one with more (flexibility) and one with a smaller period (rigid). 7 record ground motion recorded on soil types that respect to the code design of the buildings against earthquakes (Iran standard no. 2800) scale, has been used for time history analysis. The results obtained were compared with suggested values by conventional codes. From this study it was concluded that the focus of energy absorbing of structures is related to the first e and second mode and the height increases, the tendency to absorb energy will be increased. Distribution of amplification factor of seismic response at high (ratio of peak floor acceleration to the peak ground acceleration) to studied frames showed that the amplification factor proposed by Euro code 8 are closer than to be obtained when the period of non-structural component is closer to of the first period of the structure, the phenomenon of resonance occurs and when the structural period increases (tall buildings) effect of higher modes is increased, this means that the resonance mode in the second and third periods will occur.

In the present paper, numerical simulations of laminar forced convection flow and entropy generation analysis in a 2-D duct with two sudden expansions are investigated. These two expansions are created by four inclined backward facing steps and beget the separation flows and vortex regions. The vortex regions have the significant effects on the heat transfer rates and flow irreversibility. The inclination angle of steps is one of effective parameters on the control of the separation flows, heat transfer rates and flow irreversibility. In this paper, after calculation of velocity fields and temperature distributions, the effect of the step inclination angle on the separated flows, Nusselt number, friction coefficient, entropy generation number and Bejan number is studied. To obtain the temperature distributions and velocity fields, the set of governing equations including mass, momentum and energy equations are solved by the finite volume methods and computational fluid dynamic (CFD) techniques. For simulating the inclined surfaces of steps in Cartesian coordinates, the blocked-off method is used. Also, thermodynamic second law analysis is employed to calculate the entropy generation and flow irreversibility. Finally, the effect of the Brickman number on the entropy generation number and Bijan number is investigated graphically.

In this research, SALCHOW algorithm has been developed to solve linear programming problems. In each step SLACHOW moves towards the constrained gradient of the objective function, so that it always remains within the feasible region. This type of generating sequence of feasible solutions on the boundary of the feasible region differs from the behavior of the simplex. Simplex moves on the corners of the feasible region. On the other hand, SALCHOW is also different from interior point methods; because interior point methods generate solutions that are not on the corner points or even borders of feasible region. SALCHOW assigns a set of coefficients to some active constraints for appending to objective function and updating constrained gradient of objective function. Finally at the optimal point, the Lagrange coefficients of the active constraints are found. Computational results are generated by using a set of randomly generated instance problems and a few standard ones from OR-Library. These results show the superiority of SALCHOW over the simplex in these small instances. In other words, the mean time of solving an instance with SALCHOW is a function of the number of decision variables in contrast with Simplex. Runtime of simplex in the average is a function of the number of constraints. The computational errors caused by round off errors in developed code in MATLAB exhibits that our developed code for SALCHOW suffers from cumulative errors; and it obstructs the possibility of judging the definite superiority of SALCHOW over the simplex in solving small instance problems.

Most of the integrated components used in current CMOS integrated circuits (IC) technology are inevitably nonlinear. This issue complicates the matching between such elements, and affects strongly the performance of analog circuits. In data converters, the nonlinearity caused by employing nonlinear transistors lowers the overall resolution and may limit the number of bits to an unacceptable value. It can be demonstrated that the number of the stages that should be calibrated is equal to the difference between the maximum number of bits without calibration and the desired number of bits which should be calibrated. In this article, we modeled the main error sources of the gain factor in pipeline stages. A modified calibration technique is then applied to estimate and to calibrate the nonlinear gain factor of the primitive stages. The effectiveness of the proposed approach is verified through design and calibration of a 14-bit 65MS/s converter in 0. 18µ m standard CMOS technology.

In this paper elastic mechanical stress analysis for a 2D-FGM thick hollow cylinder with finite length have been conducted in which the material properties distributions are following a new developed material model according to the Mori-Tanaka scheme. This cylinder is subjected to internal or external non-uniform pressure loading and finite element method with third order Lagrange shape functions have been utilized to analyze the problem. Verification has been performed with a simplified study in which the results have been extracted by utilizing MLPG method. The results show that the stresses obtained from external pressure loading is higher than its counterpart stresses related to the internal pressure. Furthermore, normalized effective stresses according to the metallic volume fraction along the horizontal center line have significant change by nz variation. Also, normalized effective stresses on the center point of the cylinder wall have been increased by increasing of nr. Finally, it has been demonstrated that the minimum value of the maximum normalized effective stresses for both internal and external pressure loading are related to material distribution of nr=20 and nz=0. 1. It means that the ceramic 2 (Si3N4) rich cylinder wall has the lowest value of normalized effective stress.

This paper presents an economic order quantity model (EOQ) for growing items. In this inventory system, a buyer orders those items such as livestock and poultry, after a period of time grow and reach their ideal weight. Then, the company slaughters and sells items to customers. Shortage is not allowed and the order number must be integer values. Due to this, we have an integer non-linear programming problem and assumed that the items with a linear approximation grow and after reaching to the ideal weight become ready for consumption. We proved that the proposed model is a convex programming problem to obtain an optimal solution regardless of the integer of the order. Then, according to the value obtained, a solution algorithm for integer optimal solution is developed. At the end, we use a hypothetical numerical example to explain and express the proposed model and solution method. Also, we've done a sensitivity analysis showing the impact of each parameter on the objective function and order quantity values.

In this paper, the stress intensity factor (SIF) in the opening mode I is investigated in cracked beams with the I-shaped cross sections under axial loading. In cracked cross sections, a couple is made due to shifting the two centroids, or in the other word due to a misalignment between the axes of the axial force. The analysis is carried out through two analytical and numerical approaches. In analytical approach, a mathematical model for SIF is proposed via the theory of the energy release rate in the region around the crack. This model is adapted by considering the moment of the couple. It is presented in two situations in terms of the crack location including the crack in a part of the flange, and the crack in the flange and a part of the web. In numerical approach, geometric and material characteristics and type of loading are modeled by using Abaqus software; then SIF values of the I-shaped cracked beam are determined. In the presented numerical solution, two methods of C-integral and X-FEM are employed to model the crack. The validity of proposed equations is confirmed by the comparison between the presented results of numerical and analytical approaches.

According to recent studies, beam-column connections in concrete structures are highly important since failure in these parts, as the main elements of force transmission in the building, causes the destruction and instability of the entire structure. The use of high performance fiber reinforced cementitious composites (HPFRCC) is one of the new methods to make beam-column connections. These materials include cement mortar with fine aggregates and fiber. They have high pre-failure cracking and energy absorption capabilities due to exhibiting strain hardening behavior under tensile loading, which can lead to the formation of structures with higher resistance and ductility than the conventional concrete structures. In this paper, following the introduction of HPFRCC materials, the impact of using HPFRCC materials on improving the beam-column connection performance was studied. To this end, the results of experimental studies by Chao at the University of Michigan were used as the basis for verification of finite element model. Accordingly, the effects of different connection parameters on the connection performance were examined in the base model individually or in combination. The results of nonlinear finite element models analysis indicated that the ductility ratio of HC-B0-C711. 2 and HC-B0-C355. 6 models is higher than other models. Thus, their ductility ratio appears to be 50. 1% higher than the base connection. In addition, the maximum resistance of the HC-BS50 connection is greater than all other models so that its maximum resistance is 4. 6 % more than the base connection.

In today's competitive dynamic world/markets, providing a desirable framework for exploring future perspectives is a crucial challenge to support robust decision making and proper policy making. This research proposes a novel framework that develops plausible future energy scenarios through the Fuzzy Cognitive Map (FCM) technique. As a new method in scenario planning, FCM model attempts to present a set of rational, reliable and credible plausible scenarios together with analyzing dynamic behaviors of parameters. The integrated FCM-based approach encompasses STEEP analysis to identify parameters, Cross Impact Analysis (CIA) to determine key drivers, Morphological analysis for scenario selection, and FCM model to develop semi-quantitative scenarios. This new approach for scenario development brings together the benefits of both quantitative and qualitative analysis and it is not limited to the investigation of few pre-defined scenario drivers. As a research case, the proposed methodology is examined to detect plausible trends for Iran's oil production in the post sanction era. The implemented FCM simulations indicate that in three scenarios oil production increases and growth will be significant in the first two scenarios. The fourth projection is the most pessimistic scenario that can be imagined in the post-sanction era where the country faces massive investment backlogs.

In open pit mines the loaders and hauls choice, allocation and dispatching of trucks is one of the most important and complicated operational processes. That’ s optimization results in great thrifts. For the analysis of this type of examples, simulation is a powerful tool. One of the basic points in the topic of simulation models is the presentment of optimization. Simulation based optimization methods are often one objective. In this Thesis it has been objected to use the multi objective forms of these methods. The considered goals are minimizing of operational cost and maximizing of production. Meta heuristic algorithms which is chosen for this issue Multi-Objective-Particle-Swarm-Optimization (MOPSO). For simulation we have used Arena’ s software and for optimization used MATLAB software. The results of proposal methods implementation on Sungun mine’ s loading and hauling fleet, shows that with the administration of obtained scenarios it is possible to maximize the current production of the mine 2. 5 times and to reduce the operational costs of production up to 23%

Anomaly detection means detecting samples that are different from the normal samples in the dataset. One of the great challenges in this area is finding labeled data, especially for the abnormal categories. In this paper, we propose a method that uses normal data to detect anomalies. This method is based on established neural networks which are called automated encoder and are considered in deep learning studies. An automated encoder reproduces its input as output and reconstruction deviation to rate anomalies. We have used LSTM blocks to construct encoder instead of using ordinary neurons. In fact, these blocks are a category of recurring neural networks that are specialized in discovering and fetching time and proximity dependencies. The result of employing an automated encoder using LSTM blocks to detect point anomalies shows that this approach has been promising and successful in extracting the normal data’ s internal model and also detecting anomalous data. The AUC factor of the model, in almost all cases, is better than the AUC of an ordinary automated encoder and One Class Support Vector Machine (OC-SVM).

According to the positive results of low salinity water (LSW) flooding to recover incremental oil, different studies have been performed to investigate the combination of LSW and other enhanced oil recovery (EOR) methods. Combination of polymer flooding and LSW could be one of the most effective EOR methods. Taking into account the strength and weakness of each individual method, one can take advantage of the synergism between polymer and LSW: presence of polymer improves oil sweep efficiency and LSW decreases polymer adsorption and alters rock wettability to more water-wet. In this paper, we applied fractional flow theory to investigate the performance of polymer-associated low salinity water (LSP) flooding as an EOR method in sandstone reservoirs. Also, application of LSP flooding to recover incremental oil was compared to that of high and low salinity water flooding. The results showed that as LSP was injected into the given sandstone reservoir, there is a delay in water breakthrough time to as much as 0. 75 PV. Also, oil recovery duet to the LSP injection increased from 38% to 77% as compared to high salinity water flooding after 1 PV injection. Fractional flow analyses showed that the incremental oil obtained by LSP is mainly due to the presence of two distinct water saturation shock front.

Ever increasing development of wireless devices and wireless networks have increased the value of spectral space. Many efforts have been conducted to increase spectral utilization. The radio environment mapping opens new gates for developing low cost wireless devices. In this paper, a new method is proposed for increasing spectral utilization in distributed networks. In this method distributed Kalman filter, which is modified to increase estimation accuracy, is used to estimate position, velocity and power of primary transmitters. These data are used to select spectrum holes optimally and increase spectral utilization compared to centralized methods. Obtained r esults are evaluated through practical implementations and simulations. Innovations of this research include introducing and employing a linear model for estimating position of a transmitter using received power in line of sight (LoS) and non-line of sight (NLS) conditions, modifying extended kalman filter and implementation of distributed spectrum sensing; advantages of this method are illustrated compared to centralized methods.

One of the most important sources of volatile organic compounds is chemical solvent manufacturing. In addition to causing a lot of pollution to the environment, these organic materials are also economically harmful due to waste. For this reason, removing organic matter from industrial water or wastewater, as well as retrieving them, is an important issue. In this paper, the simulation of the process of separating volatile organic material from water by using nano-fiber membrane has been investigated. COMSOL Multiphysics software was used for numerical simulation of the system. By simulating in different conditions, it is possible to evaluate the performance of a membrane process in the removal of various pollutants. Finally, in order to evaluate the accuracy of the results of the simulation, the results of laboratory experiments by Feng et al. Were used. The simulation results show that after five hours, the concentration of chloroform at 60 ° C was reduced from 1157 to 400 ppm. At 23 ° C, the amount of organic matter lost from 1347 to 1080 ppm. The difference in gradient variations in these two temperatures is mainly due to the change in the Henry coefficient in the VLE, which increases with increasing temperature and improves the chlorophyll penetration inside the membrane and consequently improves its removal rate. Comparing the variations in the concentration of feed inside the tank at these two temperatures indicates that the simulations are very suitable for laboratory simulations with a relative difference of 11%.

A social network consists of some people who are related to each other through some similarities. The emergence and evolution of these networks and increasing rate of using them is the major cause for social network analysis to be a hot research topic. Using various algorithms, each network can be divided into some communities. So, each community includes some members of the social network. Community detection is one of the most important and fundamental tasks in network analysis. It is a step towards understanding the patterns and characteristics of the complex systems they represent. In this paper, the state of the art algorithms for community detection are categorized into six categories (spectral clustering and centrality, quality function, Label propagation, Structure, Closeness, link clustering) based on their definition of the community and modelling the concept of overlapping (existence of the nodes with membership in multiple communities). Next, these methods are implemented on various datasets and compared to each other. It is obvious from the results of performance measures, even in this small collection of data sets, no algorithm can be considered as the best community detection method for all kinds of networks.

Generating a production schedule that will provide optimal operating strategies without all technical and operational constraints is not practical. Creating such models with considering NPV as objective function result to oversize mathematical problems which needs more CPU time. This paper developed a multi-index clustering algorithm to reduce the size of the large-scale mathematical problems by reducing the number of decisions variables. By the way the presented algorithm remove dependency to weight importance coefficients and marks the planning with minimum error and significant reduction in the size of the model and solving time. In application and comparison of the presented clustering technique, 2478 extraction block aggregated in first step in 10 clusters, and in second step in 40 and finally in 109 clusters. By using CPLEX and MATLAB the MILP models of clusters and extraction block created to evaluate the clustering technique. The results show that CPU time has 86% reduction whereas the NPV only show 1. 8% difference between clusters and block models.

Efficient combustion in the Scramjet combustors depends on the proper air-fuel mixing. Sufficient mixing between the supersonic airstream and the fuel jet is critical for designing of scramjet engines, and this is due to the very short residence timescale for the mixture in supersonic flows. The fluid residence time is only about of the order of milliseconds in a scramjet engine, and therefore injection and spreading of the fuel is an important issue. In this paper staged transverse injection of sonic circular jets into supersonic crossflows behind a step has been studied numerically. In comparison with parallel injection, Transverse injection provides better fuel penetration with sufficient mixing and heat release but imposes larger stagnation pressure loss. Three-dimensional Reynolds Averaged Navier-Stokes equations and k-ω sst turbulence model and the perfect gas equation have been solved by using Fluent software. The results of the numerical solution are compared and validated with available experimental data. Numerical results showed good agreement with the experimental values. The simulations correctly captured the location and shape of the main flow features. The flow filed consists of various shock waves such as bow shocks, separation-induced shocks, and barrel shocks. Results showed that Mach disc height of the second injector is larger than first injector that is due to the stagnation pressure loss of the first injection.

In this paper, a numerical method is used to solve the one-dimensional inverse heat transfer problem, which is a combination of punctuation with wavelet collocation method and Tikhonov's method of stabilization. In order to validation of the heat transfer problem, the input data is used as including noise data ranging from 1 to 5%. Also, in this study, the Haar functions, in addition to estimating the unknown functions, are also used to reduce output noise. From the results, two main advantages of the repeated method have been proven, first, the precision of this method in estimating the unknown boundary condition and the second processing speed due to the lack of need for wavelet functions to be collocated at low intervals. This suggests that this method is also high speed. According to the obtained results it can be admitted that the present method maintains its sustainability with small error in input data.

In recent years, because of the increased social concerns about the environment, the reverse logistics concept has been linked to waste management. In fact, municipal solid waste management can be considered as one of the reverse logistics issues in managing the supply chain. In this research, a model for the design of a supply chain network of reverse logistic for municipal soild waste is presented. Using the two objective of profit and biological functions, we have tried to consider two dimensions of sustainable development. The economic objective function examines the maximization of profit and the environmental objective function examines the minimization of co2 due to waste transportation and landfill storage. The proposed model is able to determine the optimal number and the location of facilities and materials flow between nodes at different levels of the network in order to achieve simultaneous economic and environmental goals. The ɛ-constraint Methods has been used to solve a multi-objective model. Also, in order to reduce the problem space and monitor the potential locations of the supply chain network facility, an effective ranking method such as data envelopment analysis is presented. The present study has been used as an applied research data from the waste management organization of Shiraz Municipality and the proposed model has been solved in GAMS software.

Supply chain network resilience is a serious challenge in the supply chain management. The existing researches in the literature focused on creating resilience in design of new supply chain networks, and creating resilience in supply chain has not been addressed in previous studies. This research investigated supply chain network redesign to make supply chain resilience. For this purpose a mixed integer linear programing model is developed considering two existing risk mitigation strategies, consisting of “ the extra capacity” and “ the emergency stock” , and a new strategy called "two-phase facility". The proposed “ two-phase strategy” is applied in two echelons of distribution centers and retailers. Eventually, numerical experiments have been conducted to evaluate and compare the performance of the resilient and non-resilient supply chain networks as well as to compare the efficiency of risk mitigation strategies. Results revealed that resilient supply chain enjoys 4. 5% and 5. 5% higher performance in compared with non-resilient supply chain in terms of supply capability and profit, respectively.

The conventional boost and buck boost converter have low voltage gain. The voltage gain of the conventional converters is limited considering the issues such as parasitic resistance and because of this issues, high step up dc-dc converter must be used. In this paper, new transformerless high step-up buck boost and boost converters with low stress on the switch are proposed. In this converters only one active switch are used, which makes the control scheme simple as well as reducing the switching power loss. The voltage gain of the proposed converters is higher than the conventional boost and buck boost converters. The proposed converters expand the continues conduction mode (CCM) operation region. Proposed converters have low voltage stress on the active switch, low conduction loss and high efficiency. The proposed converters can be operated in the continuous conduction mode (CCM) and the discontinuous conduction mode (DCM). In this paper, different operation modes of the proposed converter, calculation of the voltage gain, the currents that flow through the components and efficiency are provided. To prove the correct operation of the proposed converters, simulation results in PSCAD software are provided.

Evaluation of concrete strength is one of the important issues in the concrete industry and concrete structures. In most cases, during construction, samples of concrete are picked up and after curing, according to the existing standards, they are subjected to uniaxial compression and based on the applied force, the strength of the concrete is determined. Minimum strength of concrete can be predicted but in many cases, due to reasons such as lack of proper implementation, concrete strength in structure with design strength is different. Core drilling is one of the accepted in-situ tests for measuring the strength of concrete that is a destructive method. Providing a non-destructive method that can estimate the strength of concrete in a structure in many cases is a remedial. In this research, by providing concrete samples with different mix design, in addition to studying the effect of mixing ratios on concrete strength and ultrasound wave velocity, a relationship between concrete strength and ultrasonic wave velocity is presented. Also, a comprehensive relationship is presented to estimate the strength of concrete considering water to cement ratio and the ratio of fine aggregate to course aggregate.

In this study, the refractive index of pure alcohols and binary alcohol mixtures were investigated experimentally and theoretically. In the experimental approach, a refractometer was used to measure the refractive index of the samples. Aa artificial neural network in form of a multilayer perceptron was also used to model and predict the measured refractive data. The input parameters of the network included temperature, molecular weight, the group contributions of CH3, CH2 and OH for the pure materials and for the binary mixtures the additional parameters of mole fractions, molecular weight and group contributions of both components have to be considered. The refractive index of the pure or binary alcohol mixture consist the only output parameter of the network. 70% of the experimental data were considered for train, 15% for test and 15% for the validation of the neural network. The optimum neural architecture for the pure compounds consisted of 10 neurons in the hidden layer with 0. 08457 mean absolute relative error and the optimum network for binary mixtures consisted of 12 neurons in the hidden layer with 0. 07121 absolute relative error. Comparison of the results showed a good agreement between the experimental data and the neural network outputs and the high accuracy of the model.

Since the distribution of actual tensions in aircraft components is one of the most important inputs for carrying out aircraft design and survey research, the present study analyzes the strength of the horizontal stabilizer torque box structure of the aircraft. For this purpose, the exact geometric model of torque box construction components has been manufactured using the CATIA® software and has been transferred to the ABAQUS® software for static analysis. After modification of the geometric model and the aerodynamic load extraction, using the plane loading curves, a finite element model is constructed. Then appropriate boundary conditions and properties of the material of the components are allocated and finally, the stresses of the structural components and horizontal stabilizer are obtained. The structure of the torque box, with a large part of the forces involved on the tail of the aircraft, which has all a control level and is in different angles of change, can withstand a critical structure. After presenting the results of the static analysis, critical components of the torque box structure under aerodynamic forces have been investigated and evaluated for the remaining lifetime. Regarding the unequal nature of parts, the criterion of criticality based on the stress ratio on the piece is based on stress tolerance of the piece. Accordingly, given the lower supply tension in the second main rack, this piece was introduced as a critical piece.

Today, with advancements of engineering sciences in the medical field, the use of robotic rehabilitation systems for treating motor disabilities has been widely considered. There are some robotic systems for mechanical rehabilitation and revival of motion pattern of stroke patients. In this research, the main purpose is to designing a new robotic system with one degree of freedom (DOF) to move lower legs of patient without any physiotherapist’ s help during rehabilitation. For presented model of system, an optimal kinematic design according to the normal pattern of human motion has been performed. Also, the equations of motion for rehabilitation system have been extracted and the minimum torque of the actuator of the mechanism with solution of inverse dynamic problem has been obtained. In next step, the prototype of orthosis is fabricated and its function is tested on a healthy subject. The experiments show that the proposed device provides optimum simulated motion for the user. In addition, the results of test of heart beat indicate a significant reduction in heart rate and energy consumption of user during using orthosis system comparing to normal motion (without device).

By installing the smart sensor and early detection of minor failures, the predictive maintenance can be added to the periodic maintenance. The purpose of this paper is to present a new preventive and predictive maintenance Markov model. For this at the first step, the various types of equipment failures are analysed. Therefore, a mathematical model is presented to calculate the rates of failures at various levels. In addition, the effect of smart sensor instalation on these failure rates has been modelled. In this modelling, the failure probability of the sensor is also considered. The equipment failures are classified into four levels of failure. The most importants failures rates are the outage failure rate and emergency failure rate. In the second step, a new Integrated preventive and predictive maintenance Markov model to consider the effect of smart sensor installation on equipments in maintenance process is presented. By installing the smart sensor, a number of high severity failures are early identified and corrected by emergency outages. So the frequency of going to major maintenance, the lifetime and maintenance costs in the new Markov model is improved with respect to the preventive maintenance model. At the third step, the failures of 400 kv and 132 kv power transformers of Khorasan Regional Electricity Company (KREC) were studied. The simulation results show that with new Markov model, the outage rates of 400 kv and 132 kv transformers are reduced by 74. 12% and 54. 51%, respectively, and the lifetimes are increased 28. 4 and 20. 4, respectively