Modeling in Engineering
Year:2023 | Volume:21 | Issue:73|Papers Count:20

Accurate estimation of required effort for software development plays an important role in the success of the software project. This is always a challenging issue due to the intangible nature of the software project. Therefore, a large category of researches have been performed to develop accurate tools to estimate the required efforts for software development. According to the presented papers in related works, the adoption of methods to identify the types of relationship between software project features and features affecting the required effort for software development have a significant impact on effort estimation accuracy increment. In addition, the effectiveness of various features on the software development effort estimation is different. So, the feature effectiveness determination is advantageous in increasing the effort estimation accuracy. This paper presents a new model consisting of sub-models for project features analyzing and it uses a new and accurate heuristic algorithm called Atom Search Optimization (ASO) Algorithm to configure tools and data modeling methods. The presented model in this article is designed in multiple layers and the sub-models are organized in separate layers. The organizations of sub-models are in such a way to increase performance of other layers and ultimately increase the final estimate accuracy. In accuracy evaluation of the proposed model, 3 data sets from real projects are used and the comparisons of the results with different methods are presented. Based on the results, the proposed model leads to significant improvement of final effort estimation accuracy.

This article presents a new energy management strategy (EMS) for optimal power allocation in the battery/supercapacitor hybrid energy storage (HESS) in DC microgrid applications. The proposed system is composed of a semiactive structure where the supercapacitor is directly connected to DC bus. In this structure, since the main purpose of the HESS is to maintain the DC bus voltage at the desired value, controlling the supercapacitor becomes more important. While, in the semi-active structure, there is no control on the supercapacitor. In this paper, by considering the supercapacitor current as a cost function in the optimization problem, this challenge has been solved. Also, in the case of microgrid excess power mode, a new cost function has been considered to charge the battery with a constant current to reduce the charging time and improve its lifespan. Another objective is to increase battery life by responding the supercapacitor to the sudden power changes and drawing a smooth current from the battery. In order to online determination of the optimal global solution, this multi-objective problem has been converted into a single-objective problem by use of the weighted method and then solved using KKT conditions. Therefore, real-time implementation is the main advantage of the proposed method. Finally, using simulation, the performance of the proposed method is compared with an adaptive cutoff frequency filter-based method and fuzzy logic method, in three 24 seconds different scenarios, in terms of the DC bus voltage regulation, the battery peak current, and the battery state of charge (SoC).

Static Synchronous Compensator (STATCOM) is a shunt grid connected converter used for reactive power/current compensation in electrical networks. Owing to its advantages, cascaded H-bridge inverter with unequal capacitive dc links is utilized in STATCOM application in this paper. In STATCOM application, the voltages of capacitors have to be controlled in addition to reactive current/power control. The studied inverter is composed of cascaded H-bridge cells with capacitive and unequal voltages which makes the regulation and balancing the voltages of capacitors, challenging. In this paper, a strategy based on model predictive control is proposed to meet the control objectives. First, the discrete-time model of the inverter is derived to predict the control variables and then a multi-objective cost function is developed. The input of the multi-objective optimization is the inverter switching states and the proposed control method controls the active and reactive power exchanged with the grid and the voltages of capacitors in each cell. Also, it mitigates the switching frequency in the high-voltage cell. The simulation results are provided on a 27-level asymmetric CHB based STATCOM.

The last two years have been the most critical and critical period of the Covid-19 pandemic.This disease has affected most aspects of life around the world. From a clinical point of view, several methods are available for early diagnosis of the disease, but the capabilities of these methods have been limited. As a result, many studies have been conducted to automatically diagnose the disease. Artificial intelligence has provided potential technical solutions to the medical community to make quick diagnosis based on clinical symptoms.In this research, the patient's clinical symptoms (fever, cough, sore throat, shortness of breath, weakness, sense of taste and smell, environment) are examined with the help of a questionnaire,then the input data is examined by one of rule based system or fuzzy system methods, in the fuzzy method with the help of arithmetic meta-heuristic algorithm. The optimized weight parameter is then applied to the data with the optimized weight fuzzy logic. At the end, the output will be shown as healthy person, weak corona, middel corona, high corona. This article is based on several databases, in which about 600 data have been completed by individuals through questionnaires, 2000 data have been published by the World Health Organization for corona patients, and about 400 data have been provided through hospital data. It was observed that in this system, the accuracy rate is equal to 98%, sensitivity is 100%, specificity is 98% and the F- score is 95%.

Monolayer WS2 offers great promise for use in optical devices due to its direct bandgap and high photoluminescence intensity. In this way, large-area and high-quality materials are essential for the implementation of technological applications. In this research, we Synthesize the WS2 monolayer under controlled temperature conditions and characterize the films using Fourier-transform infrared spectroscopy (FTIR), Raman, x-ray photoelectron spectroscopies, and scanning electron microscope (SEM). The results show that with the introduction of argon gas as a carrier, the quality of the layer improves, and the growth level of WS2 increases, and as a result, the films show an average coating thickness of 43 nm. By controlling the growth temperature and timely entry of argon-carrying gas, the WO3 precursor is more effectively reduced and the oxidative etching of the synthesized monolayers is protected. The addition of hydrogen more effectively reduces the WO3 precursor and protects against oxidative etching of the synthesized monolayers. The obtained results indicate the complete synthesis of a two-dimensional structure (2D) of a single layer with sheets consisting of a crystal size of about 26 nm with a thickness of about 43 nm.

Recently, a method for multi-exposure images fusion based on structural decomposition of images into three parts including signal strength, signal structure and signal mean has been introduced. In this paper, we seek to use this decomposition, for images fusion in other fields, including multimodal medical, multi-focus, and infrared and visible images. To increase the fusion quality, besides the introduction of the proposed weighting factor in the structural decomposition, contourlet transformation and the pyramidal structure have also been used. First, each of the K input images are represented into low frequency and high frequency subbands, by using contourlet transform. Then, all the corresponding subbands (resulting from the same scales and directions) are fused with each other, separately and in an iterative process. In this iterative process, first, a separate pyramid structure (including approximation and detail layers) is created for each of the corresponding K subbands. These layers are obtained by the down-sampling of subbands and structural separation based on the proposed new weighting factor. Then, the fusion is performed in the reverse direction of the pyramidal structure and the fused image of the K corresponding subband is obtained. By repeating this process, the fused image will be obtained for all the corresponding subbands. At the end, the final fused image is obtained by the inverse contourlet transformation on the fused images of the subbands. Several visual and quantitative comparisons, with 7 common methods in this field, have been made. In the visual aspect, the proposed method shows the highest quality.

In most applications of wireless sensor networks, it is not possible to charge the nodes' batteries, so the protocols designed for these networks must be as energy-efficient as possible. Clustering is one of the main approaches to designing energy-efficient and scalable protocols for wireless sensor networks. The use of clusters reduces the communication overhead caused by data transmission as well as energy consumption and wave interference between nodes. Despite the importance of clustering in wireless sensor networks, no criteria have yet been proposed to evaluate the quality of clusters derived from clustering algorithms. This paper defines several criteria for evaluating the quality of clusters formed in different clustering protocols. Then, these criteria are combined using fuzzy logic. With the help of the resulting fuzzy criterion, the quality of clusters formed in different clustering algorithms can be better compared. Finally, the correctness and feasibility of this fuzzy evaluation criterion have been verified by simulating three applied protocols and comparing the metrics evaluation results with what is actually happening.

Distribution network reconfiguration is one of the well-known and effective strategies in the distribution networks which performs by the status management of the network switches in order to obtain a new optimal configuration for the feeders. This study formulates multi-objective distribution feeder reconfiguration in the presence of distributed generators and capacitors. Common objective functions in the Distribution network reconfiguration problem include power losses and voltage deviations, which are important goals in traditional distribution systems. Usually, less attention has been paid to the reliability and voltage security target functions. Therefore, the main objectives of this study are to improve the reliability and maintenance of voltage by solving the problem of Distribution network reconfiguration. The inherent complexities of the distribution network rearrangement problem have made it a serious challenge to provide a practical and robust solution to overcome the complexities of this problem, therefore, the improved gravitational search optimization algorithm to solve this problem Has been. In order to show the efficiency of the proposed method, it has been tested on a 33-bus test system.and the results are compared with theresults of using other evolutionary algorithms, such as particleswarm optimization and shuffled frog leaping

In this paper, the Smoothed Particle Hydrodynamics (SPH) method with dynamic boundary condition has been used to simulate 3D Fluid flow in the centrifugal pump. Severe fluctuations in the field of pressure and velocity is one of the major problems in this method. In this paper, the fluctuations have been corrected using Delta and Shift algorithms. The simulation was numerically performed with real fluid viscosity (laminar and turbulence). Validation of this method indicated that in the case of real fluid viscosity, the Delta and Shift algorithms should be used simultaneously to obtain good agreement with the experimental data. To validate the pump results, a comparison was made between the numerical outputs and the performance curves of pump EN 125-315 of Pumpiran Company under relatively similar conditions. The results of this comparison showed that the error of simulation of pump head, consumption power and efficiency values compared with experimental data were about 12, 5.5 and 16 percent, respectively.

The blades moving in a circular path have many industrial applications, these include their use in some turbomachines. In more modern turbo machines, such as jet engine compressors, the flow conditions are completely incompressible. On the other hand, 2-D study of the flow around these blades, which shows many characteristics of the flow and to simplify the matter, it is usually unavoidable. In this regard, the simulation method LES and RANS in order to simulate the flow around the NACA0012 airfoil, different modes of fixed and rotating airfoil with opposite attack angle and 3-D impeller mode have been implemented. Lift coefficient, drag coefficient, torque and mass flow of S-A, RNG, SST, RSM and LES models are compared. Among the turbulence methods, the best result for Lift coefficient, drag coefficient and torque coefficient and mass flow of LES method is obtained. In according to, adding "the work of centrifugal forces and Coriolis acceleration" to Momentum equation, a better and more accurate convergence has been achieved compared to the works of others.

In this article, the analysis of the flow field and forced convection heat transfer of non-Newtonian fluids inside the channel with spindle-shaped obstacles is discussed. At first, after checking the governing equations and the boundary conditions of the problem, the grid independency has been evaluated. Then, the results of the present study have been validated for two cases of the Newtonian and non-Newtonian fluids with previous similar works. The effects of various parameters such as the effect of the arrangement of spindle obstacles, the effect of the obstacles diameter and the effect of the obstacles length have been investigated. Also, the effect of different power indexes of non-Newtonian fluid and its effect on drag coefficient and Nusselt number have been investigated. By examining the results, it was found that for all the mentioned parameters, the staggered arrangement of the spindle obstacles had a higher heat transfer rate than the ordered arrangement. The results of this research revealed that with the increase in the diameter and length of the obstacles, the amount of heat transfer from the obstacles decreases. Also, by increasing the diameter of obstacles, the pressure and friction drag coefficients increases. Finally, by examining the behavior of the non-Newtonian fluid of the power-law model, it was found that with the increase of the power index, the Nusselt number decreased and for shear thinning non-Newtonian fluids (n<1) less friction and pressure drops were obtained.

Considering the increasing use of nanotubes in various industries, it is of great importance to investigate the mechanical properties of these nanostructures. Today, due to the extraordinary properties that nanotubes have shown in various sciences, they have attracted the attention of many scientists. Boron nitride nanotubes are a form of boron nitride that are structurally very similar to carbon nanotubes. Many studies have been done to achieve the mechanical properties of these materials, and scientists have achieved this with different methods. But finding an easy and simple solution has always been the focus of many scientists who are still trying to achieve it. In this study, the molecular mechanics and solid mechanics properties of boron nitride nanotubes have been studied using a mechanical model to predict Young's modulus; and a spatial structure consisting of a unit cell has been used to describe the mechanical response of boron nitride nanotubes to applied loading. According to this assumption, a new unit cell, named mechanical unit cell, is introduced here to make a boron nitride plate or wall of boron nitride nanotubes. The analytical research presented in this research provides a simple method for predicting the Young's modulus of boron nitride nanotubes, and the obtained results are in good agreement with experimental and theoretical data.

Parallel robots are widely used in many industrial and medical applications. Reconfigurable parallel robots could be defined as a group of parallel robots that can have different geometries, thus obtaining different degrees of freedom derived from the basic structure. These robots have some disadvantages like having erratic workspace and singular points in the workspace. These limitations should be studied for proper usage of parallel manipulators. This paper presents the kinematics and workspace analysis of a 3DOF parallel reconfigurable robot. This robot has two different configurations. The first configuration is a Tricept robot (3UPS-PU) and the second is a fully Spherical robot (3UPS-S). The kinematic equations are derived based on the geometry of the system and then Jacobian matrices are determined via velocity loop closure analysis. The kinematic model is verified by the results obtained from robot simulation in ADAMS software. Then, the workspace of the robot is determined by considering the kinematic constraints.

Thermal energy storage systems can reduce the need for energy during peak demand times. In this system, energy is stored during non-peak times and is used during peak demand times. In this research, the performance of the energy storage system in connection with the cooling tower as a sole cooling source of radiant ceiling system has been assessed. Since the performance of the cooling tower depends on the environmental conditions, the performance of the cited cooling system has been investigated in different climate zones. The performance of this system has been evaluated in four cities of Tehran, Shiraz, Tabriz and Bandar Abbas, which are representative of temperate and humid, hot and dry, cold and hot and humid climates respectively. The results presented that by storing the chilled water which is produced by the cooling tower in non-peak hours and using this water in peak hours, the maximum COP of the cooling system could increase to 8.5, 14, 12 and 10 in cities of Tehran, Shiraz, Tabriz and Bandar Abbas, respectively. Furthermore, it can be seen that after implementation of the mentioned cooling system, the chilled water temperature of radiant ceiling system is at least 2 to 3°C lower than the temperature of the water which is provided by the tower in majority of occupant attendance hours, especially during peak demand times. The results indicated that the proposed cooling system in Tehran with a temperate climate is able to provide thermal comfort conditions in 90% of attendance times.

A huge part of the thermal energy consumed in energy industries is lost after exiting the process. Some of this waste heat can be recovered by various methods such as generating electrical energy, generating hot air for the production process or providing hot water. In Iran, the cement industry has always been far from the optimal use of resources, including energy, due to the existence of energy subsidies. In this research, the heat loss from the baking system of Nireez white cement plant as a model industry of the country to evaluate the simultaneous production of heat and electricity by using the organic Rankine cycle that generates electric power has been investigated in Span Plus V12 software. This evaluation is done to calculate the heat loss, including the mass and energy balance on the cooking system, as well as the energy balance on the pre-cooking system. The heat energy obtained enters the Rankine cycle and is converted into energy by the turbine. The results show that 635 kilowatts of electrical energy was produced from energy recycling, which leads to the elimination of 317.5 kg/hour of greenhouse gas.

In this study, molecular dynamics simulation was used to investigate the modification of quartz surface with adsorption of polystyrene and graphene nanoparticles. The simulations were performed on the super-hydrophilic quartz (001) surface. Polystyrene nanoparticles in three different percentages of surface coverage (5, 7, and 10) and one, two, four, and six layers’ graphene nano-sheets were created and adsorbed on the quartz surface. Then, contact angle, dipole moments, and intermolecular and intermolecular interactions between different nano-particles, quartz surface as a super hydrophilic substrate, and water molecules in the nano droplets were measured as the indicators of surface wettability. Analysis of the simulation results showed that the net and uncovered surface of quartz tolerates a high and asymmetric distribution of partial charge, causing a severe surface stress and intense hydrophilic behavior of the mineral surface. However, with the adsorption of polystyrene and graphene nanoparticles, the wettability behavior of the surface was changed to hydrophobic. Besides, changes in the surface energy due to nanoparticle adsorption, led to extensive changes in the dipole moment arrangement of water molecules on the quartz surface.

In this article, in order to provide energy absorption in thin-walled conical tubes under the inversion process, a new model of a multi-component conical absorber with a spherical cap is presented. For this purpose, by creating edges, a conical tube with a long length is divided into smaller components with different lengths and diameters. When the tube is subjected to axial loading, the process of deformation and dissipate of energy in this energy absorber is divided into two stages. The first stage is deformation of the spherical cap and the second stage is free inversion of each part of the conical inside next part. In other words, free inversion is formed by curling the edge of the components and then moving the tube wall downward. Therefore, the loss of energy absorption occurs with the bending of the spherical cap, the curling of the components edge and the circumferential contraction in the tube wall of each component. In this study, by using numerical simulation ABAQUS software, the effect of geometrical parameters, including cap type, number of conical components and semi-apical angle, on crashworthiness characteristics of the multi-component conical tubes are investigated. Also, in order to investigate the accuracy of the numerical simulation, some experimental tests were performed, which have obtained acceptable results. The results show that the proposed absorber model can be a suitable alternative for energy absorbers under the progressive buckling process.

In this article, the laminar flow of an incompressible and viscoelastic fluid inside a channel with porous walls has been investigated using optimal asymptotic homotopy method (OHAM). The flow inside the channel is considered steady and the Darcy model is used to simulate the effects of drag on the flow caused by the porous medium. The governing equations of the problem are converted into non-linear ordinary differential equations and solved. To prove the correctness of the solution, some of the results have been compared with the obtained numerical results. The effects of Darcy number, Deborah number and Reynolds number on the velocity distribution are analyzed. Based on the comparison, the ability and high accuracy of this method to solve the problem has been determined. Finally, it can be concluded that this method can be used as a reliable method to solve the internal flow of fluid inside a channel with a porous wall.

Two new higher order version of WENO schemes are introduces and problems are solved to investigate problems containing shocks and disturbances in compressible flow. The solver is capable of solving conservation laws using WENO scheme of up to 7th order. The scheme is a recently developed version of the WENO-η-z method with a modified Global Smoothness Indicator (GSI) of 12th order of accuracy, aimed to decrease numerical dissipation over critical points. The code is primarily investigated trough solving several 1D and 2D problems, including the Sod’s shock tub, Lax’s problem, the Shu-Osher problem, which some are presented here as verification. The 2-D shock-bobble interaction and Richtmyer-Meshkov instability are solved as problems including shocks and disturbances, in which proposed methods are compared with both original WENO- η-z and two similarly modified methodes from recent literature. In these problems, the introduced scheme shows lower dissipation in comparison with the original versions, while having more acceptable stability and symmetry against other modifien versions.

Male infertility as an effective factor can affect the lives of infertile couples. Sperm morphology is an important step in evaluating and examining semen in male infertility. The lack of samples of sperm head abnormalities compared to natural sperm samples can make the classification of sperm head images into an imbalanced classification problem. With the inability of common classification algorithms, capsule neural networks (CapsNet) provide a suitable platform for designing imbalanced classification models compared to other deep networks. Also, Generative Adversarial Networks (GANs) help improve the imbalanced classification of images by producing appropriate artificial samples. To this end, in this paper a new architecture is introduced based on CapsNet and GAN to evaluate the imbalanced classification of human sperm images. Reviewing and comparing the proposed model with other deep learning models in the balanced and imbalanced classification of human sperm images showed the superiority of the proposed model. Investigating the general methods of increasing data with the proposed model to increase data, it was concluded that the general methods have less resistance to reducing the number of data than the proposed model. Balanced classification of human sperm images was done by proposed model with 98.1 % accuracy. The proposed model also maintained a high sensitivity to the minority to the majority of 1:25, indicating its proper performance in the imbalanced classification of sperm images.