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http://iranjournals.nlai.ir/2127/
Feed provided by scientiairanica. Click to visit.Robust optimization for the resource-constrained multi-project scheduling problem with ...
http://iranjournals.nlai.ir/2127/article_666257_88059.html
This paper studies the multi-project scheduling problem which involves multiple projects with different importance weight; with predefined assigned due dates; with activities that have uncertain durations; and with renewable resources that are constrained. The resource sharing policy is applied to share the resources among projects. Due to the environmental rapid changes and also the uniqueness of projects, the probability distribution function of uncertain durations cannot be estimated with confidence. Besides, the multi-project scheduling problem with its large scale investment dictates a conservative approach to deal with the existing uncertainty. Therefore, the Robust Resource-Constrained Multi-Project Scheduling Problem (RRCMPSP) is studied in this paper while the maximum total weighted tardiness of the projects should be minimized. A scenario-relaxation algorithm is implemented which results in optimal solutions for the RRCMPSP. The aim is to find an optimal structure containing all the projects in such a way that it transfers the resources between the activities based on the resource sharing policy while the maximum weighted differences between the projects finish times and their assigned due dates will be minimum.Fri, 31 Jan 2020 20:30:00 +0100A multi-stage stochastic programming model for sustainable closed-loop supply chain network ...
http://iranjournals.nlai.ir/2127/article_666258_88059.html
This paperproposes a multi-objective, multi-stage programming model to design a sustainable closed-loop supply chain network considering financial decisions. A multi-product, sustainable closed-loop plastic supply chain network design problem which encompasses economic, environmental and social objectives is modeled in a mathematical manner. The decisions to be made are concerned with location of facilities; the flow of products, loans to take and investments to make. Uncertainty issue is about demand of customers and investment's rate of return. The decision making model is formulated as a multi-objective, multi-stage mixed integer linear programming problem and is solved by implementing path formulation and augmented Ɛ-constraint methods. Computational analysis, is provided based on the subject company to determine the significance of the proposed model and the efficiency regarding integrating financial decisions with supply chain network design decisions.Fri, 31 Jan 2020 20:30:00 +0100Extended TOPSIS method for multi-criteria group decision-making problems under cubic ...
http://iranjournals.nlai.ir/2127/article_666259_88059.html
The objective of this work is to present a novel multi-criteria group decision making (MCGDM) method under cubic intuitionistic fuzzy (CIF) environment by integrating extended TOPSIS method. In the existing studies, the uncertainties which are present in the data are handled either an interval-valued intuitionistic fuzzy sets (IVIFS) or an intuitionistic fuzzy set (IFS) information, which may lose some useful information of alternatives. On the other hand, CIF set (CIFS) handles the uncertainties by considering both the IVIFS and IFS instantaneously. Thus, motivated by this, in the present work, we presented some series of distance measures between the pairs of CIFSs and investigated their various relationship. Further, under this environment, a group decision-making method based on the proposed measure is presented by taking the different priority pairs of the decision makers. A practical example is provided to verify the developed approach and to demonstrate its practicality and feasibility, we compared their results with the several existing approaches results.Fri, 31 Jan 2020 20:30:00 +0100Resilient supplier selection and order allocation under uncertainty
http://iranjournals.nlai.ir/2127/article_666260_88059.html
Increasing the number of disasters around the world will decrease the performance of the supply chain. The decision makers should design resilience supply chain network which could encounter with disruptions. This paper develops an integrated resilience model of supplier selection and order allocation. Resiliency measures including quality, delivery, technology, continuity, environmental competences are explored for determining the Resilience Weight of suppliers. Fuzzy DEMATEL and ANP methods are applied to find overall performance of each supplier. Then, the developed mathematical model maximizes overall performance of suppliers while minimizes total cost of network. The proposed mathematical model helps the decision makers to select supplier and allocate the optimum order quantities by considering shortage. Since the disruptive incidents are inevitable events in real world problems, the impact of disruptions on suppliers, manufactures and retailers has been considered in the proposed model. Inherent uncertainties of parameters are taken into account to increase the compatibility of the approach with realistic environments. To tackle the uncertainty and multi-objectiveness of the proposed model, interval Method and TH aggregation function is adapted. The proposed model is validated through application to a real case study in a furniture company. Results demonstrate the usefulness and applicability of the proposed model.Fri, 31 Jan 2020 20:30:00 +0100A joint determination of production cycle length, maintenance policy, and control chart ...
http://iranjournals.nlai.ir/2127/article_666261_88059.html
Statistical process monitoring, maintenance policy, and production cycle length usually have been investigated separately while they are three dependent aspects in the industrial systems. Moreover, most of the papers that integrated simultaneously these aspects, suffer from three major drawbacks as follows: (1) Optimizing the production cost without considering the time value of money to simplify the model; (2) Considering the fixed shift size while it is a random variable in the real condition; (3) Economic design of control charts ignoring the statistical properties that lead to reduce the control chart power, extremely. To eliminate these weaknesses, this paper presents an integrated model of production cycle length, maintenance policy, and economic-statistical design considering the time value of money and the stochastic shift size. Furthermore, to maintain the reliability of the system at an acceptable level, the presented model uses non-uniform sampling. Finally, three comparative studies on the main contributions are presented to illustrate the advantages of the model and a sensitivity analysis is implemented on the several parameters to extend insights into the matter.Fri, 31 Jan 2020 20:30:00 +0100Economic evaluation of investment projects under uncertainty: A probability theory perspective
http://iranjournals.nlai.ir/2127/article_666262_88059.html
In the current competitive economy, the investors are facing increased uncertainty while evaluating new investment projects. This uncertainty caused from existence of insufficient information, oscillating markets, unstable economic conditions, obsolescence of technology and so on, and hence uncertainty is inevitable in reality. In such conditions, the deterministic models, while easy to use, do not perfectly represent the real situations and might lead to misleading decisions. When the cash flows for an uncertain investment project, over a number of future periods, are discounted using the traditional deterministic approaches, it may not provide investors with an accurate estimation of the project value. Therefore, this paper utilizes the probability theory tools to derive closed-form probability distribution function (PDF) and related expressions of the net present worth (NPW), as a useful and frequently used criterion, for cost-benefit evaluation of projects. The random cash flows follow normal, uniform or exponential distributions in our analysis. The probability distribution function of the NPW is an important tool that helps investors to accurately estimate the probability of being economic for projects, and hence, it is important tool for investment decision-making under uncertainty.Fri, 31 Jan 2020 20:30:00 +0100Partnership of contractors in cooperative game theory approach to project resource management
http://iranjournals.nlai.ir/2127/article_666263_88059.html
It is accepted that project breakdown into several independent subprojects can help to have a successful and effective project management. On the other hand, it can lead to inefficiently use of some renewable resources, and increase the total project cost and time. This article studies the benefits of the horizontal partnering among contractors assigned to subprojects through the sharing renewable resources and proposes a model based on cooperative game theory to solve it. The improvement of the net present value of the project is considered as the benefit of the cooperation among contractors. Therefore, a mixed-integer non-linear programming (MINLP) model is developed for the resource constrained project scheduling with objective function of maximizing the net present value (NPV) of each coalition. Seven widely used cooperative game theory solution methods are used to solve the benefit (NPV) allocation problem and then the stability criteria are suggested to find the best allocation scheme. Finally, an example is represented to more comprehensively illustrate the problem.Fri, 31 Jan 2020 20:30:00 +0100A novel fuzzy multi-objective method for supplier selection and order allocation problem using ...
http://iranjournals.nlai.ir/2127/article_666264_88059.html
This paper introduces a supplier selection and order allocation problem in a single-buyer-multi-supplier supply chain in which appropriate suppliers are selected and orders allocated to them. Transportation costs, quantity discount, fuzzy type uncertainty and some practical constraints are taken into account in the problem. The problem is formulated as a bi-objective model to minimize annual supply chain costs and to maximize the annual purchasing value. The fuzzy weights of suppliers, which are the output of one of the supplier evaluation methods, are considered in the second objective function. Then, we propose a novel fuzzy multi-objective programming method for obtaining Pareto solutions. The method is the extension of a single-objective method exist in the literature. This method is based on the decision maker's degree of satisfaction from each fuzzy objectives considering the fulfillment level of fuzzy constraints. In the proposed method, the problem remains multi-objective and, unlike existing methods, does not transformed into a single-objective model. At the last stage of proposed method, the fuzzy results are compared with an index, and decision maker can identify the appropriate or inappropriate solutions. To solve the problem, non-dominated sorting genetic algorithm (NSGA II) is designed and computational results are presented using numerical examples.Fri, 31 Jan 2020 20:30:00 +0100Optimizing decisions on under- and out-of-warranty products in a finite planning horizon
http://iranjournals.nlai.ir/2127/article_666265_88059.html
In this paper, we consider a manufacturer that produces products in a finite horizon time and sells products with non-renewing free replacement warranty policy. The manufacturer is responsible to provide spare parts for failed products, whether the products are under or out of warranty. Previous research on warranty optimization has focused on maximizing manufacturer profit without considering the spare part market for out-of-warranty products. This study proposes a novel nonlinear model that maximizes manufacturer profit by optimization of price, warranty length and spare part inventory for under- and out-of-warranty products in a manufacturing/remanufacturing system. Due to the model’s unique structure, we propose a new two-stage approach that combines metaheuristic and an exact method, in which the first stage is to determine product’s prices and warranty length with metaheuristic algorithm and in the second stage the remaining inventory related problem is transferred to a Minimum Cost Network Flow Problem which is solved for spare part inventory control. To illustrate the effectiveness of the suggested method, the model is solved for a case study of Iranian SANAM electronic company with two different metaheuristic algorithms and a sensitivity analysis is conducted to study the effect of various parameters on the optimal solution.Fri, 31 Jan 2020 20:30:00 +0100Application of AG method and its improvement to nonlinear damped oscillators
http://iranjournals.nlai.ir/2127/article_666266_88059.html
In this paper, a new and innovative semi analytical technique, namely Akbari-Ganji’s method (AGM), is employed for solving three nonlinear damped oscillatory systems. Applying this method to nonlinear problems is very simple because in solving process only a trial solution, the main differential equation and its derivatives are required. The analytical solutions obtained by the AGM are utilized to study the impact of amplitude on nonlinear frequency and damping ratio. It is found that the AGM leads to acceptable results for the problems considered in this paper. Also, in order to obtain a more accurate solution, instead of using a trial solution with higher-order terms which may result in complicated and time consuming mathematical calculations, the solution obtained by AGM is improved via variational iteration method (VIM). The usefulness and effectiveness of the approach is demonstrated through comparison of the obtained results with those achieved by the numerical method. Hence, the AGM can be applied to nonlinear problems consisting of significant nonlinear damping terms and, if necessary, can be easily improved.Fri, 31 Jan 2020 20:30:00 +0100Modeling particle deposition in the respiratory system during successive respiratory cycles
http://iranjournals.nlai.ir/2127/article_666267_88059.html
In this study, using a 5-lobe symmetric model, total, lobar and generational particle deposition in the lungs during successive cycles is investigated. It has been found that for the particle size between 0.05 and 2 μm and the tidal volumes greater than 1000 ml, considering the effect of successive cycles predicted more deposition fraction per cycle compared to a single cycle up to about 16 percent. The mentioned range of tidal volume is related to light or heavy physical activities. So, it can be understood that people exposed to particulate matter within the mentioned size range, when acting physically, are at more health risk compared not only to the resting state, but also to the same state calculations based on a single cycle. Finally, total and generational remaining mass fraction suspended in the respiratory tract after the completion of each cycle is calculated. This remaining mass fraction turned out to be negligible except for particles between 0.05 and 2 μm.Fri, 31 Jan 2020 20:30:00 +0100Estimation of mixed-mode fracture parameters by gene expression programming
http://iranjournals.nlai.ir/2127/article_666268_88059.html
The linear elastic fracture phenomenon has been characterized with stress intensity factors (SIFs). In this study a general function is obtained in order to predict the fracture parameters. Numerical calculation of the SIFs in a mixed-mode condition is a cumbersome task. In this research, more than 6800 numerical analyses using extended finite element method are conducted to simulate the fracture problem. States are considered for a plate with an arbitrary edge or center crack. Mixed mode SIFs were calculated using of interaction integral. Then, Gene Expression Programming (GEP) method is utilized to extraction of a function. Results show acceptable correlations between numerical calculations and genetic programming functions. R-square (R2) values are in a range of 0.91 to 0.96 that guarantees the accuracy of the inferred functions.Fri, 31 Jan 2020 20:30:00 +0100Improving heat transfer in a triplex tube heat exchanger containing phase-change materials by ...
http://iranjournals.nlai.ir/2127/article_666269_88059.html
Heat thermal energy storage is a technique to improve thermal efficiency through reducing discrepancy between energy demand and supply. Latent heat thermal energy storage as a kind of thermal energy storage method has drawn considerable attention from researchers due to its high thermal energy density and constant operating temperature. This study numerically investigates the melting process in a triplex tube heat exchanger containing phase change material (PCM) RT82. A two-dimensional numerical model has been generated using the Ansys Fluent 16 software program to simulate melting process. In this study, conduction and natural convection have been considered. Selected arrangements of rectangular fins, including lengths and positions, were selected according to heat distribution while the total area of fins was kept constant. This new strategy was done to improve heat transfer in PCM which would result in decreasing its melting time. The select optimized model in this article reduces meting time to 28.4% in comparison with the model in Ref. [1]. Numerical results have been validated by numerical and experimental results of this reference and there has been a proper agreement between them.Fri, 31 Jan 2020 20:30:00 +0100Studying buckling of composite rods made of hybrid carbon fiber/carbon nanotube-reinforced ...
http://iranjournals.nlai.ir/2127/article_666270_88059.html
In this paper, the buckling behavior of rods made of carbon fiber/carbon nanotube-reinforced polyimide (CF/CNT-RP) under the action of axial load is investigated based on a multiscale finite element method. A dual-step procedure is first adopted to couple the influences of micro- and nano-scale in order to obtain the equivalent elastic properties of CF/CNT-RP for various volume fractions of CF and CNT. The interphase effect between CNTs and the polymer matrix is taken into consideration. Also, dispersion of CF/CNT into the polymer matrix is assumed to be random. Then, rods with square and circular cross sections are considered whose stability characteristics are analyzed. The finite element modeling is performed using two models including a 3D brick model and a 2D beam model. Selected numerical results are given to study the effects of volume fraction of CNT/CF, interphase and geometrical properties on the axial buckling response of multiscale composite rods.Fri, 31 Jan 2020 20:30:00 +0100Intelligent navigation of a self-fabricated biped robot using a regression controller
http://iranjournals.nlai.ir/2127/article_666271_88059.html
With increasing demand towards use of biped robots in industrial automation and other related applications, navigation and path planning has emerged as one of the most challenging research topic over the last few decades. In this paper, a novel navigational controller is designed and implemented in a self-fabricated biped robot. After fabricating the biped equipped with a large set of sensors, a regression controller is implemented in it for obstacle avoidance and path optimization purpose. The obstacle distances detected by the sensory network of the biped are fed as input parameters to the regression controller and the output obtained from the controller is the necessary heading angle required to avoid the obstacles present randomly in the environment. The biped is tested in a simulation environment for obstacle avoidance and target following behaviour. Along with that, to validate the simulation results, a real-time experimental set up is designed under laboratory conditions. The results obtained from both the environments are compared in terms of navigational parameters and a good agreement between them is observed. Being a relatively new area of research, the navigation of bipeds can serve as a pioneer act towards industrial automation.Fri, 31 Jan 2020 20:30:00 +0100Adaptive control of a cable-actuated parallel manipulator mounted on a platform with ...
http://iranjournals.nlai.ir/2127/article_666272_88059.html
Cable-actuated parallel Manipulators (CPMs) are widely employed for object handling applications. In order to displace the carried object along the ground to an unlimited distance, the CPMs can be mounted on wheeled mobile robots (WMRs). The derivation of the dynamic equations of motion for this integrated system is presented using Lagrange method. Since in load carrying task, the inertia of the moving load is the main source of uncertainty, an adaptive control approach is considered for the CPM, whereas the WMR uses a feedback linearized sliding mode approach. In order to maintain the end-effector of the CPM in within its relative workspace in the WMR frame, the convergence rate in the two controllers should be similar. Decentralization of the control law can be accomplished if the inertia of the CPM motors are negligible compared with the other inertias of the system. This assumption is shown to be applicable if an introduced index is small enough to have noticeable effect on the tracking error.Fri, 31 Jan 2020 20:30:00 +0100Numerical and experimental study of the effect of the process parameters on the void evolution ...
http://iranjournals.nlai.ir/2127/article_666273_88059.html
Elimination of defects such as voids and internal cavities is required in metal forming processes to avoid premature failure of mechanical components during service. In this paper, the effect of different parameters on the void closure behavior is studied in the cold extrusion of rods. A three dimensional nonlinear dynamic finite element model is developed for this purpose. Experiments are also performed on aluminum samples to verify the accuracy of the finite element model. Results of the developed model are in good agreement with experimental findings. It is observed that voids contract in all directions during the direct extrusion which is in contrast to some other metal forming processes like forging and rolling. Effect of parameters such as die semi-angle, friction coefficient and void location on the void evolution is systematically investigated and discussed. The results of this study can help industries using metal extrusion for optimized design and control of the process to reduce voids and porosity and increase the strength of their product.Fri, 31 Jan 2020 20:30:00 +0100Analysis of change in the state of hydraulic drive of machines in operation according to the ...
http://iranjournals.nlai.ir/2127/article_666274_88059.html
Technical diagnostics is a sphere of knowledge embracing theory, methods and means for defining the technical state of the objects. It is necessary for provision of security, functional reliability and efficiency of the technical object operation, as well as for reduction of the costs for its technical maintenance and reduction of the idle time losses caused by failures and premature shutdowns for maintenance. Therefore the objective of the paper is to analyze the change in the state of hydraulic drive of machines while in operation according to the diagnostic results. In order to achieve the set objective the authors used various experimental methods. The paper considers mutual influence of maintenance and technical diagnostics of hydrostatic drives of construction, track and some other mobile machines. It is shown that introduction of technical diagnostics allows transferring from the system of planned preventive repairs to the system of servicing the machines according to their actual technical state, which allows completely using the resource of a series of expensive aggregates. The authors described several main basic characteristics of change in the volume effectiveness of the hydraulic sets while in operation.Fri, 31 Jan 2020 20:30:00 +0100Effect of processing time on microstructure of surface and corrosion resistance of coatings ...
http://iranjournals.nlai.ir/2127/article_666275_88059.html
In this study, the effect of coating processing time on microstructure of surface and corrosion resistance of coatings resulted by plasma electrolytic oxidation (PEO) was investigated on substrate of TiAl6V4 alloy. The coating processes in hydroxyapatite nano-powder electrolytic were carried out in same conditions of constant voltage of 600V and three different times of 125, 250 and 350 seconds. Studying the microstructure of coatings identified that the coating formed in 125 (s) had more compact and steady structure with fine surface cavities and less porosity. X-ray diffraction pattern of coating demonstrates that this coating is consists of oxide phases of titanium (rutile and anatase) and hydroxyapatite. Also, the study of corrosion resistance of coatings by Potentiodynamic polarization and electrochemical impedance spectroscopy in corrosive solution of chloride sodium 3.5% showed that the coating formed in 125 s has the most noble corrosion resitance potential and the least ICorr and finally the highest resistance to corrosion.Fri, 31 Jan 2020 20:30:00 +0100Parameter converting method for bifurcation analysis of nonlinear dynamical systems
http://iranjournals.nlai.ir/2127/article_666276_88059.html
For detecting behavior of a dynamical system, bifurcation analysis is necessary with respect to change in parameters of system. In this work, based on the solution of ordinary differential equations from initial value and parameters, a simple method is presented, which can efficiently reveal different bifurcations of system. In addition to its simplicity, this method does not required to have deep physical and mathematical understanding of the problem, and because of its high precision and the speed of solutions, does not need to reduce the order of models in many complex problems or problems with high degrees of freedom. This method is named parameter converting method (PCM), which has two steps. In the first step the parameter is varied as a function of time and in the second step, time is expressed as inverse of this assumed function. With this method bifurcation and amplitude-frequency diagrams and hidden attractors of some complex dynamics will be analyzed and the sensitivity of the multi potential well systems to initial conditions is studied. With this algorithm, a simple way to find the domain of high-energy orbit in bistable systems is obtained.Fri, 31 Jan 2020 20:30:00 +0100Modeling, control, and simulation of a SCARA PRR-type robot manipulator
http://iranjournals.nlai.ir/2127/article_666277_88059.html
In this study, a SCARA PRR-type robot manipulator is designed and implemented. Firstly, the SCARA robot was designed according to the mechanical calculations. Then, forward and inverse kinematic equations of the robot are derived by using D-H parameters and analytical methods. The software is developed according to obtain cartesian velocities from joint velocities and joint velocities from cartesian velocities. The trajectory planning is designed using the calculated kinematic equations and the simulation is performed in MATLAB VRML environment. A stepping motor is used for prismatic joint of the robot, and servo motors are used for revolute joints. While most of the SCARA robot studies focus on RRP-type servo control strategy, this work focuses PRR-type and both stepper and servo control structures. The objects in the desired points of the workspace are picked and placed to another desired point synchronously with the simulation. So the performance of the robot is examined experimentally.Fri, 31 Jan 2020 20:30:00 +0100Comparative study of damage behavior of synthetic and natural fiber-reinforced brittle ...
http://iranjournals.nlai.ir/2127/article_666278_88059.html
In the present study, comparative study on the damage behaviour of Glass-Epoxy (GE), Jute-Epoxy (JE) laminates with [0/90]s orientation and Jute-Rubber-Jute (JRJ) sandwich is carried out using ABAQUS/CAE finite element software. The GE, JE laminate and JRJ sandwich with thickness of 2 mm is impacted by a hemispherical shaped impactor at a velocity of 2.5 m/s. The mechanisms in which the brittle laminate gets damaged are analyzed using Hashin’s 2D failure criteria and flexible composites are analysed by ductile damage mechanism. The energy absorbed and the incipient point of each laminate was compared. It was observed from the results that there is no evidence of delamination in JRJ as opposed to GE and JE. The compliant nature of rubber contributes in absorbing more energy and it is slightly higher than GE. Also it was observed that there is no incipient point in JRJ sandwich which means there is no cracking of matrix since rubber is elastic material. Thus the JRJ material can be a better substitute for GE laminate in low velocity applications. The procedure proposed for the analysis in the present study can serve as benchmark method in modelling the impact behaviour of composite structures in further investigations.Fri, 31 Jan 2020 20:30:00 +0100Design of mixed flow pump impeller blade using mean streamline theory and its analysis
http://iranjournals.nlai.ir/2127/article_666279_88059.html
Given the importance of blade design in effective performance of the mixed flow pump, the present work demonstrates the designing of the mixed flow pump impeller blade using almost unexplored Mean stream line theory. The Mean stream line theory, though been used sparingly but has found to give comparable results to that of other templates of design. The design process has been carried out in AUTOCAD 2013 and Solid Works Premium 2014 software. The analysis for equivalent stress, equivalent elastic strain, Total deformation and the directional deformation have been carried out in ANSYS 2014 for different construction material of the blade i.e., stainless steel, titanium alloy, bronze, and copper alloy. Total deformation was found to be maximum for impeller blade made from titanium alloy whereas the equivalent stress and strain was least for titanium alloyed impeller blade. Further, a comparison analysis has been carried out for the equivalent stresses in blade designed using mean stream line theory and free vortex theory. It was observed that the equivalent stress in impeller blade designed using free vortex theory was lesser than that designed using mean stream line theory.Fri, 31 Jan 2020 20:30:00 +0100Assessment of Mechanical and Durability Properties of Concrete Containing PET Waste
http://iranjournals.nlai.ir/2127/article_666280_88059.html
Plastic waste is a silent threat to the environment, and their disposal is a serious issue. To sort out this issue, many efforts were made to reuse the plastic waste, but no significant results were achieved. On the contrary, concrete being the widely used construction material is facing problem due to unavailability of ingredient material (sand and coarse aggregate). In this study PET (polyethylene terephthalate) aggregates manufactured from the waste un-washed PET bottles in shredded form were used to partially replace fine aggregate and coarse aggregate in concrete in various percentages (0%, 5%, 10%, 15% and 20%). Various tests like workability, compressive strength, flexural strength, water permeability, abrasion resistance, dynamic and static modulus of elasticity were performed. The micro-structural analysis of the specimens was carried out using an optical microscope. It was found that the workability, compressive strength, flexural strength, dynamic and static modulus of elasticity decreased with the increasing amount of PET waste in concrete. Water permeability of concrete was found to increase with increasing amount of PET waste. In both the cases, i.e., when fine and coarse aggregates were replaced with PET waste, an improvement in the abrasion resistance of concrete was found.Fri, 31 Jan 2020 20:30:00 +0100Numerical investigation of Cover Plate in RCS connections
http://iranjournals.nlai.ir/2127/article_666281_88059.html
Due to the growing popularity of Reinforced Concrete column with Steel beam (RCS) moment frame system in recent years, there are lots of publications about the performance of this structural system. In this paper, fifteen RCS joints with practical details are studied using a verified finite element method. Joint details of the models include Cover Plate, Additional Bearing Plate, Steel Doubler Plate, and joint stirrups. The results show that Cover Plate can be used instead of a combination of steel doubler plate and joint stirrups; it improves the joint performance by increasing the confinement of joint region and contributing to joint shear strength.Fri, 31 Jan 2020 20:30:00 +0100Attitude-Based Conflict Management for Resolving Disputes over Water Quality of the Seymareh ...
http://iranjournals.nlai.ir/2127/article_666282_88059.html
A strategic negotiation methodology for managing complex water-related conflicts is presented in order to consider the decision makers' attitudes. The developed approach systematically exploits the Graph Model for Conflict Resolution (GMCR) as an analytical and practical technique, and helps decision makers find the most beneficial outcomes for negotiating their disputes, assuming the competing needs, wants, and attitudes of decision makers. A real case study of a water-related dispute in Iran is used to demonstrate the implementation of the developed methodology and to emphasize the significance of decision makers' attitudes in identifying feasible negotiation outcomes for resolving complex disputes. In fact, the developed attitude-oriented methodology proposes an innovative engineering approach to help stakeholders address a wide range of conflicts, especially in complex water disputes in developing countries where human factors such as attitude play a significant role. The research can also help decision makers with the shortcomings of conventional decision making systems, such as original GMCR, through incorporating attitudes into conflict resolution tools in order to better clarify needs and interests, obtain equilibrium results, and generate more equitable solutionsFri, 31 Jan 2020 20:30:00 +0100Seismic Behavior of Chevron Concentrically Braced Frames with Weak Beam
http://iranjournals.nlai.ir/2127/article_666283_88059.html
Concentrically braced frames provide ductility and imparted seismic energy dissipation through yielding of tension braces and buckling of compression braces. In braced frames with chevron configuration, difference of actions in tension and buckled brace results in considerable unbalanced force at brace-beam intersection, which is addressed in modern seismic design provisions. In this paper, effect of flexural capacity of beam to carry this unbalanced force and consequently seismic behavior of braced frame is investigated by finite element analysis. Two-story and four-story chevron braced frames were modeled in ABAQUS software and studied by means of nonlinear cyclic pushover and nonlinear response history analysis methods. Results showed that inadequate flexural strength of the beams reduce lateral stiffness and strength of braced frame significantly as lateral drift increases; therefore, concentration of lateral deformation in one story may cause formation of soft and weak story. Furthermore, seismic behavior of chevron braced frame and two-story X braced frames were compared.Fri, 31 Jan 2020 20:30:00 +0100On the measurement of transverse shear stress in a rectangular open channel using an optimal ...
http://iranjournals.nlai.ir/2127/article_666284_88059.html
The laboratory studies have been carried out in this research. Determining the sensitivity analysis of the Preston tube diameter in shear stress, four Preston tubes with external diameters of 3.2, 3.9, 4.7 and 6.3 mm were used. The aspect ratios of 2.86 to 13.95 were examined. For measuring the pressure difference of the Preston tube a 200 millibar differential pressure transducer with 0.01 accuracy of the original scale was used. Laboratory results demonstrated that Preston tubes with a diameter of 3.9 mm present the minimum difference in the average value of the shear stress resulting from the Bechert and Patel calibration equations. Therefore, using the Preston tube with an optimal diameter, transverse distribution of shear stress in channels bed and wall were determined. The outcome of this part of study is two dimensionless relationships for determining the local shear stress both in the bed and wall. These relationships are a function of the aspect ratio B/H and the bed relative coordinates b/B in cross section and Z/H sidewall. The survey showed that the dimensionless bed shear stress distribution is considerably influenced by the aspect ratio. The transverse distribution of wall shear stress is independent from the aspect ratio for B/H3.Fri, 31 Jan 2020 20:30:00 +0100Developing a new algorithm (G-JPSO) for optimal control of pumps in water distribution networks
http://iranjournals.nlai.ir/2127/article_666285_88059.html
Meta-heuristic methods have been widely used for solving complex problems recently. Among these methods, JPSO is regarded as a promising algorithm. However, in order to achieve more robust performance, the probability to solve the graph-based problems is modified by changing the jumping nature of this algorithm and a new algorithm called G-JPSO is presented which is evaluated by solving Fletcher-Powell function and optimal control of pumps in water distribution network problems. In addition to reduction of electricity cost and the problem limitations such as minimum required pressure in each node, minimum and maximum height of tanks, should also be considered. Moreover, another limitation was performed on the objective function which includes the maximum times of turning the pumps on and off. In order to determine the pumps optimal operation, an optimization-simulation model based on the optimization algorithms G-JPSO and JPSO is developed. This proposed model is used for determination of optimal operation program of Van Zyl distribution network. The comparison carried out between the results of our proposed algorithm and those of the similar algorithms including ant colony, genetic and JPSO shows the high ability of the presented algorithm in finding solutions near the optimal solutions with reasonable computation costs.Fri, 31 Jan 2020 20:30:00 +0100Experimental behavior of circular foundations on oil contaminated sand
http://iranjournals.nlai.ir/2127/article_666286_88059.html
This paper studies the behavior of circular footings placed on the gasoil and kerosene-contaminated soil. The ultimate objective of this study is to determine the effect that oil contamination has on the sand bearing capacity. The contaminated sand layers were mixed with different levels of between 1 and 4 percent of gasoil and kerosene contamination. The influence of the contamination depth and type of contamination was examined in this study. Laboratory tests were conducted on small scale models and performed in load-controlled manner. The results showed that the contamination can influence the load-settlement curves and lead to a reduction in its load-bearing capacity. An increase in the depth and percentage of contamination decreased the bearing capacity. Some formulas have been provided in which by knowing the depth and percentage of contamination one can predict the third bearing capacity factor of a circular foundationFri, 31 Jan 2020 20:30:00 +0100Soil behavior around the stub abutment of an integral bridge and buried piles in the ...
http://iranjournals.nlai.ir/2127/article_666287_88059.html
The change in the deck length under temperature load affects the upper part of integral bridge abutments and causes abutments rotation. The deck contraction makes the abutment move away from the backfill and causes a failure wedge. To prevent the failure wedge, a new method has been proposed. In this method, the inhibition of integral bridges under contraction is done by cables connected from each abutment to the buried piles outside the bridge along the abutments. In the analysis, the behaviour of soil around the abutment and buried piles is an important parameter which has a great influence on the results. In this paper, the soil behaviour around a laterally loaded stub abutment and buried piles was studied on laboratory stub abutment models using the PIV (particle image velocimetry) method. The PIV analysis was carried out to obtain the deformation pattern and shear strains of the soil around the stub abutment and buried piles. The effects of piles number and soil – pile interaction on the soil deformation pattern were investigated. The results showed that the use of buried piles connected by the cable avoided creating a failure wedge in the backfill.Fri, 31 Jan 2020 20:30:00 +0100Optimal location of stone column for stabilization of sand slope: An experimental and 3D ...
http://iranjournals.nlai.ir/2127/article_666288_88059.html
Utilization of numerical and analytical methods to stabilize earth slopes applying piles or stone columns is subject commonly discussed by numerous researchers. Various researchers have practiced optimization of the location of pile or stone column, to stabilize earth slope through numerical and analytical approaches. Their efforts have led to various results raising the question of what the optimal place for installation of a pile or stone column is. It is look like that no experimental studies are conducted in this regard; the point which is discussed in this article. Experimental study conducted in this article is new topic and it can solve the problem caused by varying and sometimes contradictory results of numerical analyses to find the optimal pile (or stone column) location. In this article, an experimental study is conducted for two-layer sand earth slope, which is saturated through precipitation and failure after saturation over time. Installing stone columns in different locations and saturating the earth slope through precipitation, rational acceptable results were obtained that can appropriately assist designers. All of the experimental models were modeled and compared using the 3D finite difference method (3D FDM), which are compliant with each other.Fri, 31 Jan 2020 20:30:00 +0100Improvement in the structure of fire alarm systems' alarm bell stop switch
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Fire alarm systems are essentially installed in specific firefighting equipment and serve as one of important alarm equipments which senses fire early. The main goal of the study is to find methods for improving the structure of fire alarm needs. This study is about false alarms of fire indicating equipment in fire alarm systems. It is found that false alarms false alarms by fire alarm systems are constantly occurring and fire safety manager is neglecting his duty of work by turning alarm bell stop switch on even during usual times. To prevent this, the alarm bell stop switch should be changed into an automatically resettable manual operation type so that it can automatically reset to its original state even though fire safety manager turns the switch on. As a result, aid in correcting fire safety managers' wrongful practices by making the alarm bell ring whenever an actual fire occurs, and ultimately reduce false alarms by eliminating fundamental causes when false alarms occur.Fri, 31 Jan 2020 20:30:00 +0100Structural control of RC buildings subjected to near-fault ground motions in terms of tuned ...
http://iranjournals.nlai.ir/2127/article_666290_88059.html
To design a proper structure against earthquake in modern systems, control systems are of special importance. Added passive tuned mass damper is one of such systems which will be discussed in this paper. In this regard, the effect of adding this damper to a 10-floor concrete structure under six near-fault earthquakes is investigated. To do this, a code has been written in MATLAB which receives ground motion record of the occurring earthquake as well as the structure specifications such as matrix of mass, stiffness and damping as an input. As output, it presents time-history of responses for top floor, a diagram for the floor displacement and drift of the structure at the time that the top floor has reached the maximum displacement. Also, these diagrams are compared both when the added damper is present and absent. It is observed that the added passive control of TMD is highly effective in the reduction of structure response against earthquake which in turn depends on the properties of the earthquake and therefore should be chosen based on the site seismic conditions.Fri, 31 Jan 2020 20:30:00 +0100Pulse extraction of pulse-like ground motions based on particle swarm optimization algorithm
http://iranjournals.nlai.ir/2127/article_666291_88059.html
Considering the devastating effects of near-fault earthquakes, seismologists and engineers have, qualitatively and quantitatively, represented the strong velocity pulse of near-fault ground motions using models including physical parameters associated with the wave propagation process. In some mathematical models, the derivation of physical parameters is required to fit time history and response spectrum of the simulated record to the actual record through trial and error process, which limits the scope of these models. In the current study, the particle swarm optimization (PSO) algorithm is replaced with the trial and error procedure. In this way, an automatic and quantitative process with the minimal judgment of the analyst is prepared to extract a wide range of pulselike records. Then, the proposed approach is applied to simulate and represent mathematically a set of 91 pulselike records from the Next Generation Attenuation (NGA) project ground motion library. The obtained results show that a velocity pulse of each pulselike record could be extracted using the proposed approach, and it can therefore be considered as a powerful tool in pulse parametric studies and the relationship between velocity pulse and structure’s response.Fri, 31 Jan 2020 20:30:00 +0100Water flow stabilization using submerged weir for draft-tube reaction hydraulic turbine
http://iranjournals.nlai.ir/2127/article_666292_88059.html
In turbine practice engineering, draft tube downstream running under extreme water flow pressure and velocity. This is causing a vibrations and pressure variation during different operation frequencies. The practical challenge of obtaining a stabilized water flow is ongoing domain of research. In this paper, a proposition of initiating submerged weir in the downstream of draft tube reaction turbine is inspected. The main goal of this research is to reduce the water flow pressure variation, velocity and shear distribution in accordance to the upstream water level influence. Two types of turbines including vertical Kaplan and Francis turbine units are examined. ANSYS CFX software tool is used to build three-dimension (3D) numerical models for the Kaplan and Francis turbines with building a submerged weir at the outlet of the draft tubes at three deferent height suggestions. The influence of the proposed submerged weir is studied the flow through these turbines by considering the dimensions of their components including the penstock with inlets, spiral casing, shafts and blades, and the draft tube with outlets. The findings of this research were tremendous proposition to solve the problem of negative pressure pulsation in draft tube of Kaplan and Francis turbines types.Fri, 31 Jan 2020 20:30:00 +0100Smart-home electrical energy scheduling system using multi-objective antlion optimizer and ...
http://iranjournals.nlai.ir/2127/article_666293_88059.html
Smart-home energy-management-systems (SHEMSs) are widely used for energy management in smart buildings. Energy management in smart homes is an arduous task and necessitates efficient scheduling of appliances in buildings. Scheduling of smart appliances is usually enmeshed by various and sometimes contradictory criteria which should be considered concurrently in the scheduling process. Multi-criteria decision-making (MCDM) techniques are able to select the most suitable alternative among copious ones. This paper tailors a comprehensive framework which merges MCDM techniques with evolutionary multi-objective optimization (EMOO) techniques for selecting the most proper schedule for appliances by creating a trade-off between optimization criteria. A Multi-Objective Ant Lion Optimizer (MOALO) is tailored and tested on a smart home case study to detect all the Pareto solutions. A benchmark instance of the appliance scheduling is solved employing the proposed methodology, Shannon’s entropy technique is employed to find the objectives’ corresponding weights, and afterward, the acquired Pareto optimal solutions are ranked utilizing the Evidential Reasoning (ER) method. By inspecting the efficiency of every solution considering multiple criteria such as unsafety, electricity cost, delay, Peak Average Ratio, and CO2 emission, the proposed approach confirms its effectiveness in enhancing the method for smart appliance scheduling.Fri, 31 Jan 2020 20:30:00 +0100