فصلنامه مدل سازی در مهندسی
پیاپی 48 (بهار 1396)

Structural vibration control using intelligent materials has received much attention nowadays. These materials due to their high frequency, low weight and volume, easy convert electrical energy into mechanical and vice versa are being used increasingly in the aerospace industry (for example missiles fin, helicopter rotor blades, satellites, etc.), Marine (Noise and Vibration in submarines, ...), sports equipment as well as space trusses. This study deals with the vibration control of a laminated composite beam using smart magnetostrictive layers. The Navier method has been used to solve the vibration problem of simply supported beams. In the following the effect of the magnetostrictive layers thickness, composite lay-up and magnetic field on the vibration behavior of smart beam has been studied.

In this article, the study of the non-Fourier heat conduction in casting sand that is located inside a container under an instantaneous heat flux. According to inefficiencies of Fourier model to model the behavior of this problem due to differences in heat transfer between the phases and the ability of the models based on fractional calculus to model the anomalous behavior in different materials, in this paper, a model based on fractional calculus have been used. This model has recently entered the field of physics. Thermal properties, initial and boundary conditions of the problem is assumed to be known. The governing equations have been solved in a try and error algorithm to find the phase lag and fractional order using an implicit discretization method. The results show that neither the super-diffusion fractional model nor sub-diffusion fractional model can model the heat transfer in the sand. Based on the present results, it can observe also that in the initial moment, sub-diffusion conditions and after that super-diffusion conditions govern on the problem. Using simultaneously sub-diffusion and super-diffusion models, the numerical results are able to cover the experimental data for the temperature distribution within the container.

In JPEG 2000, two fundamental steps in image compression are wavelet transform and bit-planes encoding. In this method, first the wavelet transform of the image is provided, then, depending on the desired compression rate, the number of bit-planes of the wavelet coefficients are coded from most significant bit to the least significant bit. After achieving the desired compression rate, the other less significant bit-planes of wavelet coefficients are disregarded. In applying this method for low contrast image, wavelet coefficients of high frequency regions have small amounts, so these values are reflected in low bit-planes. These low bit-planes are removed during compression in encoder. Hence, JPEG 2000 has limited performance especially in low contrast image compression. In this paper, to improve the performance of JPEG 2000 a preprocessing is performed on the image to increase its contrast. With increasing image contrast, high frequency regions would have higher values in wavelet coefficients. As a result, information of these coefficients is largely preserved at the bit-planes encoding stage. The results show that the proposed preprocessing method improves the performance of JPEG 2000 in terms of compression rate and retrieved image quality. In more detail, for an equal retrieved image quality in the proposed method and JPEG 2000, the proposed method improves the compression rate of JPEG 2000 with an average of about 3.5%.

The main purpose of optimal blasting operation is suitable crushing and prevent undesirable and unwanted phenomena arising from the blasting (ground vibration, flyrock and backbreak). Generally, the parameters affecting the blasting operation divided into two main group controllable (blasting pattern) and uncontrollable (geomechanical properties of rocks) parameters. Controllable parameter can be determined using experimental models. Due to variety of obtained values for controllable parameters from experimental models, it is necessary to use methods with high efficiency. The main reason for not achieving good results in experimental models is engaging a large number of parameters, resulting from blasting. The combination of intelligent and mehta heuristic methods to solve suck problems can be useful. In this study, Delkan iron mine as a case study has a side effects of blasting like as flyrock and backbreak. The main purpose of this paper is making a artificial neural network model as a strong predictor and finding a combination of data using ant colony optimization to minimum the unwanted phenomena. After the Modeling the blast pattern Burden 2.8 m, spacing 3.3 m, hole length 10.2 m, stemming 1.5 m and powder factor is 201 gr/ton. Using this model can lead to a reduction of approximately 42 percent and 62 percent in flyrock and backbreak respectively.

In this paper, an experimental investigation on dynamic viscosity has been performed. Then, Experimental results were compared with classic theoretical models such as, Einstein and Wang models. The results represented that, the results obtained from experimental tests were far away from the theoretical models. Therefor an empirical correlation for predicting the effective dynamic viscosity of Alumina-water nanofluids has proposed and discussed. In this study, there was used from cone and plate Brookfield viscometer and the viscosities of Al2O3-water nanofluids with different solid volume fractions of 0. 05 (5. 0%), 0. 4(4. 0%), 0. 03 (3. 0%), 0. 02(2. 0%), 0. 01 (1. 0%), 0. 005 (0. 5%) and 0. 0025 (0. 25%) is measured at room temperature.

The purpose of this article is finding the optimal path with minimum effort to move the end-effector of the three cable spatial robot in work space. For this work, first, kinematic and dynamic modeling is done of the three cable spatial robot. Then simulation and results extraction are done by both direct and indirect methods. Based on of indirect solution method is the calculus of variations. Optimality necessary condition is given in order to minimize the torque between the two points and is extracted using the pontryagin minimum principle. This optimality condition is formed a boundary value problem of two-point, which can be solved using numerical algorithms. Direct method is created by combining a metaheuristic optimization method, a polynomial interpolation and the robot equations. This article is used the metaheuristic method of triangular optimizer algorithm and the polynomial interpolation of four degree. This new combination created with the polynomial of four degree, instead of using the intermediate values of the path as design variables, specified constants of polynomial puts the design variable in order to path optimization. The indirect method gives the exact response, but extraction of optimality condition its, is the difficult in terms of calculations mathematical. While the direct method gives the approximate response without algebraic calculations. Finally, two examples are done with direct method and indirect method. The results comparisons are show the appropriate efficiency of the suggested direct method.

The main object of current study is investigation of influence and role of symmetric and asymmetric vortices formation and number of them on the pressure drop and losses of flow in gradual expansions. For creating symmetric and asymmetric vortices, laminar flow of Newtonian fluid is simulated in a channel with a planar gradual expansion for the expansion ratio of 1:3. Discretization of the governing equations is performed with utilization finite volume method (FVM) in two-dimensional. Also, the velocity and pressure are coupled based on the PISO algorithm on a collocated mesh. To study effect of vortices, analyze and calculation of pressure and loss coefficients has been done for a wide range of expansion angles and in different Reynolds numbers . Therefore, to assess the validity of this study, results from the expansion angle of 90° are compared with past researches, which is in very good agreement with previous studies. Streamlines and pressure contours for the analysis and understanding of flow dynamics is depicted. To investigate the role of symmetry and non-symmetric of vortices and the effect of the number of vortices, graphs of pressure changes on the central line of the channel, pressure and loss coefficients have been traced and analyzed as a function of expansion angle and Reynolds number. The remarkable point in this study is that the pressure and loss coefficients in the expansion angle of 53 degrees are independent of the Reynolds number for fluid flow through the planar gradual expansion channel.

In this paper, chirality effect on the buckling behavior of SWCNTs has been investigated. In order to explore the effect of chiral angle, all structures are used with the same length and diameter but different chiral angles. For modeling of chemical bonds between carbon atoms, potential energy of molecular mechanics theory and strain energies of a 3D beam element have been equalized. After calculating the element properties, the node coordinates have been determined using a computer code developed in MATLAB software. Then, ANSYS software is used to study the chirality effects on axial and torsional buckling load. Results show that the chiral angle has no significant influence on critical axial force. However, chiral angle is an effective parameter in torsional buckling. Chiral angle of 19.11 degree has the maximum critical torsional moment among all structures. In counter-clock-wise loading condition, chiral angle of 9.64 degree has the minimum critical torsional moment. Also, the direction of twisting (cw or ccw) is important and the difference between cw and ccw critical torsional moment reaches its maximum value for chiral angle of 15.48 degree.

In this paper, an experimental study carried out to investigate the turbulent convective heat transfer performance of low concentration of COOH-functionalize MWCNT/water nanofluid flowing through a circular tube. The effect of solid concentration from 0.0005 to 0.01 on convective heat transfer studied at Reynolds number in the range between 5000 to 27000.Also Thermal conductivity and dynamic viscosity of nanofluid has been measured experimentally in various temperatures and solid volume fractions. It is observed that both thermal conductivity and dynamic viscosity of nanofluid strongly depend on temperature and solid concentration. Therefore two new correlations as a function of temperature and concentration were proposed for predict the thermal conductivity of functionalized MWCNTs/water nanofluid.
In addition,Heat transfer coefficient, Nusselt number, pressure drop and thermal performance factor of nanofluid were presented for different volume fractions. The experimental results clearly indicate that increase in both heat transfer coefficient and Thermal performance factor is obtained by increasing solid concentration. In average, 78% increase in heat transfer coefficient, 36.5% increase in average Nusselt number and 27.3% penalty in pressure drop was observed at the highest concentration of MWCNTs in water abstract.

Today, piezoelectric micro-beams are widely used in atomic and friction force microscopies, thermal scanning microscopy, and biomass measurement due to their flexible structure, sensitivity to molecular and atomic forces, and very fast response. Due to the small displacements of these micro-beams, their complete vibrating analysis and studying their behavior can play a key role in their measurement precision and optimal design. For this reason, first the numerical Runge-Kutta method (based on the discontinuous beam model) as well as the finite element method was employed to solve the differential equation governing the piezoelectric micro-beams motion by considering geometrical discontinuities. Then, the sensitivity analysis was conducted to determine the effects of each micro-beams geometric parameter on the main parameters of the vibratory motion. The sensitivity analysis was conducted using Sobol method which is based on the output data variance. According to the obtained results, both the discontinuous cantilever model and the finite element model exhibited acceptable accuracy in calculating the natural frequency as well as the resonance amplitude of this type of micro-beams. Also, the results obtained from the sensitivity analysis showed that the first mode of the vibratory MC motion was the most suitable mode for nanoparticle surface topography.

This research has been investigated water pressure drop through the multistage industrial orifices that are installed into a pipe in 1300 MW Arak-Shazand Thermal Power Plant. Whereas having turbulence flow done simulating model was standard . In order to reach a specific water pressure drop with a specific water flow rate, the optimum design is implemented based on the composition of orifice stage’s number along with changing the diameter of the holes and number’s. Finally to verification of simulation’s results, it will be compared with results of experimental test that is done with multistage orifices installed into a pipe. That could be illustrated good adjustment with together. Also this pressure drop lead to increase the percentage’s opening spray control valves that has extreme influence to decrease corrosion and better work of control valves.

Hot water distribution for different purposes is one of the most important factors which have not been studied in solar water heater design. The main goal in the solar water heater installation is to receive the maximum solar radiation on a unit surface of the solar collector without considering the hot water distribution. In order to achieve the maximum solar absorption with higher efficiency, the optimum collector orientation can be determined by modification of basic solar calculations using consumption time interval and storage tank temperature. The effect of latitude, longitude and altitude on the optimum collector orientation is well investigated in classical solar calculations but the optimal collector performance is also dependent on several other factors concerning the hot water distribution. The main objective of the paper is the simultaneously optimization of design parameters such as collector direction and storage tank capacity by consideration of the consumption pattern. The results show increasing up to 7% in annual energy saving and 1.5% in economic saving.

With respect to the height to width ratio, the concrete shear walls are divided into two categories of cantilever and short shear walls. Cantilever shear walls with the aspect ratio greater than 2 demonstrate flexural behavior while short shear walls with the aspect ratio smaller than to 2 exhibit shear behavior. In this study the behavior of short reinforced concrete shear walls are investigated using the nonlinear finite element software ATENA 3D. The failure mode and the ultimate and residual shear resistance of the short shear walls, as well as the affecting parameters such as the magnitude of the axial force, the compression strength of concrete and yield strength of reinforcements are studied. It is resulted that the magnitude of axial forces has significance effect on the ductile behavior of short shear walls.

The objective of this study is to investigate the adequacy of Artificial Neural Networks (ANN) as a method to determine the dynamic response of fluid in elevated water tanks. For this purpose, an ANN models were proposed to estimate the hydrodynamic pressure in bottom of container and sloshing of water surface. ANN models were developed, trained and tested in a based MATLAB program. Nonlinear dynamic analysis using Finite Element Application (FEA) based ANSYS was used to generate training and testing set of ANN models. In the ANN models, a multilayer perceptron (MLP) with a back-propagation (BP) algorithm was employed using a scaled conjugate gradient. The data used in the ANN model are arranged in a format of three input parameters that cover the time history of earthquake horizontal acceleration, container ceiling displacement and base shear force.The performance of the new ANN model is compared with ANSYS results. The comparison indicates that the ANN model has strong potential to estimate hydrodynamic pressure. It was demonstrated that the neural network based approach is highly successful to estimate response of fluid subjected to earthquake without using complex fluid elements.

In this paper optimal design and effectiveness assessment of active multiple tuned mass dampers (AMTMDs) in reducing the vibration of nonlinear hysteretic structures has been studied. For active control of nonlinear structures the Newmark-based instantaneous optimal control algorithm has been used. Optimal parameters of AMTMDs and weighting matrices of active control performance index have been determined based on minimization of the maximum required control force of ATMDs to below the maximum drift of structure to a specified limit. For solving the optimization problem which includes a large number of variables, genetic algorithm (GA) has been applied. For numerical simulation, an eight–storey shear frame with bilinear hysteretic behavior subjected to white noise excitation and for different values of MTMDs mass ratio and ATMDs number, optimal AMTMDs have been designed. Also the efficiency of the AMTMDs mechanism under both near-fault and far-fault earthquakes has been tested. The results of numerical simulations show the effectiveness of the proposed method in designing AMTMDs on nonlinear structures. Also, it has been concluded that using AMTMDs could be effective in mitigating the damage of nonlinear structures which the amount of reduction depends on the input earthquake characteristics, AMTMDs mass ratio and ATMDs number.

Abstract- The optimal power flow (OPF) is one of the key tools in the planning and operation of power systems. However, due to extensive using of the renewable energy sources especially, wind generation in the electric energy generation, application of this tool encounter with a major challenge. Uncertainty in the available wind generation level rooted in forecast error necessitates the change in the modeling and solution method of OPF problem. In this research work, Locational Marginal Price (MCP) as an important parameter in the market-based power systems is modeled in the context of optimal power flow problem and its probability density function is computed using a new point estimation method. The proposed point estimation method approximate the desired probability characteristics using their a few moments. Apart from that the proposed method guarantees the feasibility of the obtained estimated points, as the significant advantage, it notably outperforms the conventional point estimation methods in the required time and approximation accuracy aspects. Application of the obtained results is discussed from practical point of view as well. Effectiveness of the proposed method is examined on the 9-bus and 24-bus IEEE test systems together with realistic 118-bus power system and its advantages in accuracy and quickness with respect to the other methods are shown.

Speech emotion recognition is a relatively new field of research that could plays an important role in man-machine interaction. In this paper we use from two new spectral features for the automatic recognition of human affective information from speech. These features are extracted from the spectrogram of speech signal by image processing techniques. Also we study the effects of gender information on speech emotion recognition. Hierarchical SVM base classifiers are designed to classify speech signals according to their emotional states. Classifiers are optimized by the Fisher Discriminant Ratio (FDR) to classify the most separable classes at the upper nodes, which can reduce the classification error. The proposed algorithm tested on the well known Berlin database for the male and female speakers separately and in combination. The overall recognition rate of 43.4% is obtained for the coeducational speakers. The results show the 39.46% improvement when the gender information is used.

Proper coordination between distance relays and overcurrent in the power system is one of the most important issues for security and stability of system. This paper presents a new method for optimal distance and directional overcurrent relays coordination by considering high set element and different characteristics for all overcurrent relays by using genetic optimization algorithm. Using high set element with the change in coordination constraints provides possibility of adjusting the second zone time of distance relays with constant and classical value. The proposed method is applied to 8-bus and the IEEE 30-bus test systems and simulation results, show usefulness of this method in reducing operation time of protection system.

One of the most important aspects of designing a supply chain is the matter of supplier selection. It’s a complicated issue because suppliers should satisfy some criteria and ranking those leads to a MCDM problem. Therefore, a structured and systematic approach is required to solve this problem. In this article, we address supplier selection problem in advertising industry and propose two new criteria. Correspondingly, in order to evaluate suppliers in the industry a hybrid approach is proposed which combines fuzzy AHP with fuzzy TOPSIS techniques. Each method has its cons and pros we try to use the advantages of the both methods in the proposed hybrid approach. On the other hand, the related parameters in this decision making problem are qualitative. Some errors could happen in transformation of the qualitative parameters to quantitative ones. Accordingly, in transforming procedure we use fuzzy theory to reduce these errors.

This paper determines the location of bank branches under competitive conditions with different attractive conditions. Finding an optimum location of branches depends on many factors and these problems are known as NP-hard problems. Despite being approximate methods, meta-heuristic algorithms seem suitable tools for solving NP-hard problems. In this paper, Genetic Algorithm (GA), Simulated Annealing (SA) and Cuckoo Optimization Algorithm (COA) are applied for finding the best location of bank branches. From marketing point of view, the aim is to attract more customers while the number of attracted persons to a new branch should be acceptable. The new methods have capability to find the optimum location of new branches under competitive conditions. The location of a new branch should be as far away as possible from branches of the same bank. The other condition is that the total number of customers for the new branch should not be less than a specified number, while the new branch should not attract customers of old branches of the same bank more than a threshold. To fulfill this propose a part of the Tabriz city was selected for implementation. Finally, to evaluate quality and accuracy of the algorithms, several iterations with different seeds are performed. The results of statistical and final tests indicate that the accuracy and convergence speed of Cuckoo Optimization Algorithm are more than the Simulated Annealing and Genetic Algorithms in finding optimal location of bank branches under competitive conditions.