فصلنامه مدل سازی در مهندسی
پیاپی 68 (بهار 1401)

Conventional seismic design and reinforcement methods are based on increasing the capacity of the structure. That is, the bearing capacity of the structure is increased by increasing its strength and ductility, which is not possible in the reinforcement of many structures. However, in seismic isolation, by reducing the seismic demand, by reducing the absolute acceleration of the structure and reducing the energy input to the structure, due to increasing the Period and damping in the level of isolation, the structure can be placed in safe areas. Therefore, in this study, the effect of seismic isolators and also the height of structures on different types of soils have been investigated. For this purpose, the effects of seismic isolators in two buildings of 5 and 8 floors in three types of soil S1, S2 and S3 are investigated and evaluated. After validation of the structure and base isolation, behavioral studies were performed, and it was found that the presence of base isolation reduces the maximum displacement of the roof by up to 20% and 80% of maximum base shear in the 5-storey building. Reduction of about 40% of the maximum sliding displacement of the base isolation in the 8-story structure compared to 5 floors has reduced the effect of the base isolation on the maximum displacement in the higher floors.

Companies are always faced with risks in competing to response diversified needs of markets. Determining the probability of occurrence and how to manage and recognize the risks that cause other risks is always a challenge. The purpose of this study is to manage the effect of uncertainty on expected results and increase of product family developing process success through addressing causal risks that have bigger Conditional probability In this article, the risks of each stage of the product family development process are identified by focusing on the grounded theory based on the responses gathered from 18 experts in Iranian automotive industry Also the effect of the variables was determined through fuzzy cognitive map based on the 18 supplementary questionnaire data in these companies. Then, the conditional probability tables were formed and the probability of each variable was calculated systematically with the help of the Bayesian Belief Networks and causal risk of other risks were identified. The results show that the clustering of customers risk, parts design feature technical risk and modularity risk are specified to this process. The model output, also indicates that the needs risk with the probability of (19.7%), requirement risk (10.52%), and parts design feature technical risk (6.32%) As the causal risk with the highest conditional probability of a negative aspect. The executive managers could achieve greater success by focusing on controlling these three risks that act as the root cause of the next step risks , getting more success and make progress with more certainty .

Data centers are the places where servers and IT equipment are installed. In the network and IT, it is hardware that stores the hardware modules such as servers, switches, switches and communication equipment, and UPS and other network equipment. Due to the usual heat release of the orcs, the management of air distribution systems and cooling systems in the data centers are of particular importance to prevent the destruction from excessive heat. the purpose of management of air distribution systems is to solve problems in cooling of data centers, including the minimization of hot air, due to cold weather and removing hot spots, and can also reduce the high cost of cooling systems by removing air circulation problems. in this study, after simulation and analysis of different modes of cooling system design of cooling system, cooling and cooling corridors can be increased from the allowed range and better energy loss and better efficiency and then the return and partitioning of false floors were introduced as supplementary methods. in total, the comparisons were calculated according to an increase of 20 % of the heat from the orcs in the simulated model of

The present paper investigates the electronic and optical behavior of monolayer gallium sulfide as a transition metal monochalcogenide, doped with IV and V group atoms of the periodic table. The calculations are performed in the SIESTA software package based on density functional theory using the exchange correlation function and the generalized gradient approximations. Analysis of the electronic structure of this material shows that the pure gallium sulfide monolayer has an indirect band gap of 2.3 eV. In order to investigate the effects of impurities on this structure, the impurity atoms of groups IV and V were applied in the position of sulfur and gallium atoms. The impurity concentration of doped structures is 1.14%. The simulation results show that the presence of this impurity, depending on the type of impurity atom and its location, leads to a transition from semiconductor to metal, indirect to direct semiconductor or non-magnetic to magnetic state in this structure. For example, when Sb is doped to the gallium sulfide monolayer in the position of the sulfur atom, this system is magnetic with a direct band gap, while its replacement by the gallium atom preserves the semiconductor nature of the indirect band gap structure with less gap energy. In addition to the electronic properties, the optical properties of the alloyed structure were also analyzed. The results show that the GaS structure of the alloyed alloy with elements of the fourth and fifth groups opens the way for nanoelectronics, optoelectronics and spintronics applications.

One of the most important problems that energy absorbers as thin-walled structures have been considered by designers, is the amount of energy absorption and the initial peak crushing load. In this paper, the crashworthiness of end capped circular aluminum tubes under axial compression is investigated. In this design, in order to reduce the initial maximum crushing load, holes were created in the outer surface of the adsorbent with specified distances along the tube. The presence of annular holes as a imperfection in the absorber prevents the sudden load applied to the main structure and the occupants. In this study, using numerical simulation by ABAQUS software, the effect of the presence of holes, angle and direction of applied oblique load has been studied on the crashworthiness of end capped tubes. Also, in order to validate the numerical simulation results, a number of experimental tests were performed which showed good agreement. The results showed that the applied oblique load with an angle of 10 degree and the opposite direction of the holes is effective on the state of collapse, energy absorption and reduction of initial peak load, and the angles of 20, 30 and 40 degree do not have significant changes in initial peak force and energy absorption.

Among thorax tumors, lung tumors move mainly due to respiration. In order to enhance the precision of radiotherapy, one solution is estimating tumor motion from external motion of chest wall and abdomen regions. For this aim, consistent prediction models are constructed and then implemented for real time tumor motion tracking. In these models, clustering of database extracted from tumor motion and chest wall motion has non-negligible effect which has been taken into account in this work. In this investigation, motion database of fifteen patients with lung cancer who were treated by means of Cyberknife Synchrony system at Georgetown University hospital, has been used. Two subtractive and fuzzy C-means as common available clustering strategies have been employed in order to investigate their quantitative effects, in a comparative fashion. Final analyzed results show that the average targeting error of prediction models (difference between tumor position estimated by model and actual position of tumor) over all patients are 6.5 and 7.5 mm implementing subtractive and fuzzy C-means clustering, respectively. Moreover, using fuzzy C-means algorithm, tumor tracking is done with more stability. Since, breathing phenomena has high degree of variations, motion data clustering has an important role on the accuracy of prediction model performance by determining model parameters while constructing at pre-treatment step and while updating the model during the treatment.

The stability of the training process in the identification of nonlinear systems is one of the foremost issues in control research. This paper studies the training stability of an interval type 2 adaptive neuro-fuzzy Inference system (IT2ANFIS) as an identifier through a newfound Lyapunov function. Lyapunov stability analysis is conducted on the training of IT2ANFIS, when the premise and the consequent of the system are trained with the gradient descent algorithm and the Kalman Filter, respectively. Therefore, using the proposed stability analysis, the permissible limits for the adjustable parameters of the algorithms are applied to the algorithms to maintain the stability of the identification process. According to the stability analysis of this study, wide ranges of adaptive limits are obtained for the adjustable parameters of the algorithms. Besides, the simulation results show that when the permissible limits are chosen based on the proposed stability analysis, the identification process is stable with acceptable performance. The proposed method outperforms other methods in terms of root mean square error, simulation time, and its less stagnation in the trap of local minimums when it is utilized in the training of the Mackey-Glass chaotic time series and a nonlinear plant with stochastic data sets.

In this work, Nusselt number and friction factor in the tube side of car radiator which is a type of fin and tube heat exchanger are experimentally determined. Two types of nanofluids including water-Al2O3 and water-CuO are used and experimental results are performed for three nanoparticles volumetric concentration (PVC) and for Reynolds number in the range of 3000-15000. The results show that, both Nusselt number and friction factor increases in the case of nanofluid compared with the base fluid and this increase is higher in the CuO nanofluid. For example, at Re=3000, 1.92%, 15.08% and 22.46% improvement in Nusselt number are observed for Al2O3 nanofluid compared with base fluid respectively for PVC=0.025, 0.050 and 0.075. The mentioned improvement for CuO nanofluid are obtain 10.89%, 35.50% and 46.11%, respectively. In addition, at Re=3000, 15.27%, 9.64% and 13.80% increases in friction factor are observed for Al2O3 nanofluid compared with base fluid respectively for PVC=0.025, 0.050 and 0.075. The mentioned increases for CuO nanofluid are obtain 7.71%, 13.97% and 19.59%, respectively. Then, correlations for Nusselt number and friction factor with acceptable precision are derived.

In this paper, a new simulation method (quasi-three-dimensional) is introduced to model devices based on inertial and Magnus forces. Simulations were computed using the COMSOL software. The experiments were performed using micro channels made by lithography method out of PDMS and glass slides. The use of quasi-three-dimensional simulation method made the simulation time much shorter. Results showed with increasing the particle diameter and the flow Reynolds number in microchannels, particles reach their equilibrium positions faster and with changing aspect ratio of channel, equilibrium position of particles changed and different steady state patterns were observed. In expansion-contraction channels, increasing the particle diameter also increases the channel efficiency. But increasing the flow rate to reach its optimum of 3.5ml/min enhances the efficiency and then, increasing flow rate beyond it, would not have a positive effect on efficiency anymore. Also with changing geometry of expansion section from rectangle to circle, the capture efficiency reached 0.86. Experimental results also confirm the accuracy of the simulation results and 19 micrometer particles are trapped in the wide part of the channel and 10 micrometer particles come out of it.

Due to the carcinogenic nature of diesel particles, these particles will pose a serious threat to human health. In order to meet this challenge, the attention of researchers and government agencies around the world is focused on achieving an economical and safe technology to control these particles. Given that electrostatic precipitators are one of the most important treatment technologies, this paper deals with the mathematical modeling of a cylindrical electrostatic precipitator and the prediction of the collection efficiency of diesel conductive particles in its various conditions. This sediment consists of a grounded cylinder with a circular cross-section and an excited electrode with negative direct current voltage installed in the center of the cylinder. Using the analytical response of Poisson equations and current conservation, ion spatial charge density, electric potential distribution and electrical volume forces in the electrostatic precipitator channel will be calculated. In this paper, COMSOL software is used for three-dimensional modeling of cylindrical electrostatic precipitators and solving turbulent air flow equations considering volume electric force. The particle charge and motion equations have been implemented in COMSOL software using particle routing physics and the results have been analyzed.

Considering that the traction system is main factor of energy consumption in the train, and amount of force required for moving the train is directly related to its speed, therefore, the optimal profile selection for the speed of the train movement, in the path between the stations and the design of the controller for accurate tracing The optimal profile of the train speed, can be a determinant of the amount of energy consumed. Control of a train includes the non-linear, uncertainty and external disturbances terms that should be considered in the design of control rules. In this thesis, we present a control strategy for tracking optimal profile of train speed, based on the fuzzy sliding mode control (FSMC). The main motive of use the Sliding Mode Control (SMC), in non-linear systems, its resistance to parametric uncertainties, unmodeled dynamics, external disturbances and as well as the simplicity of its design. However, the occurrence of chattering phenomenon is the most important limiting factors the use of this control method. In this thesis to remove the chattering, fuzzy control is used to estimate the reaching control signal and the stability of the entire system is also guaranteed on the basis of the Lyapunov stability theorem Numerical simulations using the nonlinear dynamics model of the train, despite the uncertainty and disturbance, and comparing it with the conventional SMC, show the effectiveness of the FSMC method in tracing the optimal train speed profile.

The pressure-driven water transport inside the nanochannel formed by GE bilayers is studied via molecular dynamics simulation. The drift of water was carried out by using an external force. The effect of changing the external force on the fluid and the geometry of the channel on flow rate, density distribution and diffusion coefficient were studied. The simulations show that water is the layer structure when it passes through the nanochannel. Also, with the increase of external force applied on water molecules, the velocity of the flow has increased. By changing the pressure difference, the permeability and the water flow rate increase. As the pressure difference increases from 100 to 500 MPa, the flow rate increases more than 45 times. The results also showed that in a given cross-sectional area, the square nanochannel has the highest flow rate. This study paves the way for the design and application of graphene-based nanomaterials in nanofiltration and water treatment technologies in the future.

In this research, a closed-loop green supply chain network is designed under uncertain conditions. In the proposed model, four objective functions including minimizing network costs, minimizing greenhouse gas emissions, minimizing production-technical risk, and minimizing the time of sending products to customers are considered simultaneously. Using the proposed network, it is possible to manage the flow of raw materials, first-hand products, and return products between facilities, production planning for each production center, how to allocate products to each facility, determine the number of manpower required for employment and training in each production center, how to allocate machinery and equipment, as well as time management by determining the minimum acceptable time to send products to customers so that the network has the least cost, the least amount of greenhouse gas emissions from the operational processes of facilities and transportation and has made strategic decisions with the least production-technical risk and the least time possible. In this research, to increase the efficiency of the model, parameters such as the amount of return product, recycling rate, and destruction are considered indefinitely and fuzzy logic is used to eliminate the uncertainty. Finally, due to the breadth of the model, the model is validated using a genetic algorithm. The result of the validation indicates the efficiency of the proposed model in optimizing the closed-loop green supply chain network.

In this paper, the simulation of the displacement enclosure of the H-151 furnace unit of the distillation unit in the Isfahan refinery is carried out by using computational fluid dynamics (CFD). This simulation involves simultaneous investigation of fluid flow inside the tubes of displacement enclosure and the flue gas flow of convection section through the tubes as well as displacement enclosure gas flow by adding additional tubes in a two-dimensional state. Grid independency study was done for tube and displacement enclosure and the best grid with numbers of 315000 and 67024 were chosen for tube and displacement enclosure, respectively. The error of temperature and velocity diagrams for tubes with grid numbers 315000 were 0.021% and 0.0569% and for displacement enclosure with grid numbers, 67024 were 0.0712% and 0.0254%, respectively. The velocity and temperature diagrams for the tube, displacement enclosure, and displacement enclosure with additional tubes were obtained and examined. The results show that the flow at the beginning of the tube is turbulent. The fluid velocity inside the tube has been developed from 1.4 meters due to the large length of the tube. The comparison of the results obtained from the displacement enclosure with/without additional tubes has been shown that the temperature and velocity of the gas passing through the tubes are reduced by using additional tubes.

In this paper, the optimal allocation of renewable energy resources is presented with the aim of minimizing cost of power losses and reliability improvement considering generation and load uncertainty using new approach named information gap decision theory (IGDT). Decision variables include location, size and power factor of renewable resources, also the maximum uncertainty radius of generation and load using improved salp swarm algorithm (ISSA). In the ISSA method, the performance of traditional salp swarm algorithm is improved to increase convergence speed and accuracy using evolutionary differential operators. The problem is implemented as deterministic and IGDT-based methods on 33 bus-IEEE networks with risk aversion. In the wind turbine scenario, the results showed that for the 33 bus network in the deterministic method that is increased by 20% in IGDT, the network load is increased by 7.61% and wind turbine generation is decreased by 44.06%. Also, compared to the deterministic method, the losses cost and reliability cost increased by 20.87% and 4.58%, respectively and the net saving is decreased by 6.33%.

Currently, infrared photodetectors have attracted lots of attentions due to the wide range of industrial and non-industrial application. In this paper, a new hubrid metal-semiconductor-metal thin film infrared photodetector based on plasmonic nanostructure and ring shape optical lens has been proposed that leads to higher optical absorption. The finite difference time domain method (FDTD) is used to thoroughly investigate the interaction of proposed structure with near infrared incident wave (1.1-1.7 µm). Optical lens concentrate the incoming light on gold nanodisk array and increases the electric field magnitude on the nanodisk array. Gold nanodisk array with optimized geometrical structure leads to excitation of surface plasmon polariton and results in very high local field point inside the indium gallium arsenide layer. So, the photocarrier generation rate enhances and the structure shows higher photocurrent. According to the simulation results, proposed structure indicates 105% absorption enhancement and 140% photocurrent enhancement compared to simple photodetector strcuture.