جستجوی مقالات مرتبط با کلیدواژه « two » در نشریات گروه « برق »
تکرار جستجوی کلیدواژه «two» در نشریات گروه «فنی و مهندسی»-
As one of the promising approaches to increase the network capacity, Full-duplex (FD) communications have recently gained a remarkable attention. FD communication enables wireless nodes to simultaneously send and receive data through the same frequency band. Thanks to the recent achievements in the self-interference (SI) cancellation, this type of communication is expected to be potentially utilized in cellular systems, especially in small cell networks. In this paper, we integrate the FD communications into femtocell networks where femtocell users (FUs) share the same spectrum with macro users (MUs). In particular, aiming to maximize the number of admitted FUs in the network and satisfying the target rate for FUs, we jointly study the problem of sub-channel allocation, duplexing-mode selection, and power control for FUs in both uplink (UL) and downlink (DL) transmissions. Moreover, we address the power control problem for macro-tier where the main goal is to minimize the transmission power of prioritized MUs while guaranteeing a target rate for them. To jointly address these problems for both tiers, we propose a distributed algorithm in which FBSs and admitted FUs choose whether to operate in half-duplex (HD) or FD mode so as to meet their target rate. The convergence and performance of the proposed algorithm are evaluated through simulation where it is demonstrated that the average admission ratio of FUs in our proposed distributed scheme surpasses the existing traditional HD approaches.Keywords: Duplexing mode, Full, duplex communication, Half, duplex, OFDMA, Sub, channel allocation, Two, tier networks}
-
For a two-input two-output distillation column with heavy interactions and long dead times, a two-by-two PI/PID controller is designed. The design objectives are good setpoint regulation and appropriate load disturbance rejection. The constraints are on degree of robust stability, control effort as well as peaks of the maximum singular value of sensitivity and complementary sensitivity matrices. As this set of design objectives and constraints is often conflicting, a more flexible control structure, a two-degree-of-freedom scheme, is proposed. The design problem is formulated as a constrained optimization problem and is solved by a powerful random-search optimization technique, the so-called vector-based swarm optimization. Next, the performance of the proposed method in controlling a Wood and Berry distillation column is evaluated and compared with that of several well-known design techniques. Because of using a flexible control structure, a powerful optimization algorithm and a comprehensive set of design requirements, the proposed control strategy performs well in coping with conflicting design objectivesKeywords: Load disturbance rejection, Robustness, Setpoint regulation, Two, degree, of, freedom control structure, Wood, Berry distillation column}
-
The existing relational network data envelopment analysis (DEA) models evaluate the performance of decision making units (DMUs) with precise data. Whereas in the real world applications, there are many supply chain (SC) networks with imprecise and vague figures. This paper develops a relational network DEA model for evaluating the performance of supply chains with fuzzy numbers. The proposed fuzzy model is capable of evaluating the performance of all kinds of network structures. A pair of two-level mathematical program is utilized to convert the fuzzy relational network DEA to a conventional crisp one. For this purpose, the upper and lower bounds of the efficiencies are calculated by α-cut concept. The proposed model is implemented using actual data from the supply chain of an international shipping company in Iran.Keywords: Relational network DEA, Supply chain, Fuzzy data, Efficiency, Two, level mathematical program}
-
This paper presents finite element formulation for dynamic analysis of orthotropic plates using two-variable refined plate theory (RPT). Hamilton's principle is employed to obtain the governing equations and the semi-discrete approach is utilized for solving the equations. After constructing spatial weak form equations, a 4-node rectangular plate element with six degrees of freedom (DOFs) per node is introduced for discretization of the domain. An unconditionally stable implicit Newmark scheme is used for temporal discretization. A MATLAB code with capability of modeling both static and dynamic plate problems with various boundary conditions is generated. Several numerical problems are solved and the obtained displacements and stresses are compared with the existing results in the literature. The results demonstrate the accuracy, simplicity and efficiency of present method in dynamic analysis of plate problems.Keywords: Orthotropic, Finite element method, Dynamic Analysis, Two, variable refined plate theory, Rectangular plate element}
-
Since two-wheeled and the self-balancing robot has a complicated and non-linear structure, its model has some uncertainties. These uncertainties cause that the system has an incorrect solution while using the classic methods for controlling of it. In this paper, a new method based on interval analysis is proposed for modeling the optimal control of the two-wheeled and self-balancing robot with interval uncertain parameters which require only lower and upper bounds of uncertain parameters, with no need to know about probability distributions. Since the system has uncertainties in it, controllability is first analyzed based on interval arithmetic. Afterwards, LQR based method based on Pontryagin principle is utilized to solve the problem. Finally, by solving the interval Ricatti equations, the confidence interval for feedback controller has been achieved. Final results are compared with Monte Carlo method and the results demonstrate the effectiveness of the proposed method.Keywords: Optimal control, Interval analysis, LQR, Chebyshev inclusion method, Monte Carlo, Two, Wheeled Self, Balancing Robot}
-
This work concerns with the numerical study of unsteady MHD convection of cobalt-kerosene ferrouid in a linearly heated two-sided cavity and in the presence of constant and alternating magnetic field. An accurate finite volume method is adapted to solve the governing equations for this problem. The fluid flow and heat transfer characteristics are studied for a wide range of Richardson number (0.01Keywords: MHD mixed convection, Ferrofluid, Two, sided cavity, Linearly heating, Time, periodic magnetic field}
-
This paper addresses the problem of designing a supply chain network consisting of suppliers, manufacturers, warehouses, and customers in which all manufacturers belong to a single owner. All players in this chain are performing under uncertainty. The single product of this supply chain needs one strategic and one non-strategic part for its nal assembly. To hedge against uncertainty in supply and demand, the manufacturers tend to take part in a set of suppliers through a portfolio of contracts, and unmet demand will be satis ed by purchasing from spot market with stochastic prices. In addition, demands, supply capacities, and warehouse capacities are stochastic as well, and the problem has been modeled as a two-stage stochastic program with recourse. Then, a hybrid solution strategy based on sample average approximation and accelerated Benders decomposition is proposed to tackle the problem. The proposed strategy is able to obtain good quality solutions for a large number of scenarios and within an acceptable time interval. Computational results show the e ectiveness of the stochastic model as compared to its deterministic counterpart.Keywords: Supply chain network design, Strategic, non, strategic items, Supplier contracts, Uncertainty, Sample average approximation, Two, stage stochastic programming, Benders decomposition}
-
This article deals with a single perishable item, continuous-review, two-echelon serial inventory system consisting of a warehouse and a retailer. Customer demands at the retailer are assumed to be Poisson. All items have a xed shelf life and start aging on their arrival at the retailer. The demand that cannot be met immediately at the retailer is lost. All transportation times are xed. If there is any stock in the warehouse, the lead time for the retailer would be the transportation time from the warehouse. Otherwise, the retailer orders are met with a delay. In this article, using an approximate technique, we rst present a heuristic for nding cost-e ective base stock policy and then develop a simulation-based neighborhood search procedure to modify the quality of the solution. Also, a numerical experiment is carried out to evaluate e ectiveness and accuracy of the procedures. The results reveal that the approximate model performs rather well.Keywords: Inventory, Perishable items, Base stock policy, Lost sales, Two, echelon}
-
In this paper, a finite element formulation based on two-variable refined plate theory is developed for free vibration analysis of isotropic and orthotropic plates. The two-variable refined plate theory, which can be used for both thin and thick plates, predicts parabolic variation of transverse shear stresses across the plate thickness, satisfies the zero traction condition on the plate surfaces and does not need the shear correction factor. After constructing weak form equations using the Hamilton principle for vibration formulation, a new 4-node rectangular plate element with six-degrees of freedom at each node is introduced for discretization of the domain. The natural frequencies of isotropic plates with different boundary condition and the fundamental natural frequencies of levy type orthotropic plates are obtained. Comparison of results with exact solutions and other common plate theories shows that beside the simplicity of presented finite element formulations, it presents accurate and efficient results. Also the effects of orthotropy ratio, side-to-thickness ratio and types of boundary conditions on the natural frequencies are studied.Keywords: Finite Element Method, Free Vibration, Rectangular Plate Element, Two, Variable Refined Plate Theory}
-
In todays global world preservation technology becomes very important due to rapid changes in environment. To study this concept, in this article we have developed the two warehouse inventory model with the consideration of preservation technology investment Demand rate is treated as linear function of instantaneous stock level. The limited storage area (OW) is used for the storage of the stock. The excess amount of stock than the capacity of the owned warehouse (OW) is stored in the rented warehouse (RW). The holding cost of rented warehouse is greater than the holding cost of owned warehouse (OW) so that stock of rented warehouse (RW) is used first and than the stock of (OW) is consumed. The shortages are allowed and partially backlogged under the effect of inflation. The main aim of this study is to find the optimal vale of total cost function. Numerical illustrations and sensitivity analysis are given at the end of this article.Keywords: Two, warehouse, preservation technology, stock dependent demand, partial backlogging, inflation}
-
This paper is the first study on the impact of ambient temperature on the electrical characteristics and high frequency performances of double gate armchair graphene nanoribbon field effect transistor (GNRFET). The results illustrate that the GNRFET under high temperature (HT-GNRFET) has the highest cut-off frequency, lowest sub-threshold swing, lowest intrinsic delay and power delay product compared with low-temperature GNRFET (LT-GNRFET) and medium-temperature GNRFET (MT-GNRFET). Besides, the LT-GNRFET demonstrates the lowest off-state current and the highest ratios of Ion/Ioff, average velocity and mobile charge. In addition, the LT-GNRFET has the highest gate and quantum capacitances among three aforementioned GNRFETs.Keywords: GNRFET, Ambient Temperature, Non, Equilibrium Green's Function (NEGF), high frequency, Two, Dimensional FET model}
-
Nowadays, Value based Supply Chain Management (VbSCM) is considered as a resource of competitive advantages, and companies with a long term strategic plan find the VbSCM as an effective factor in sustainability. In this context, supply chain network design has a significant impact on all value drivers (i.e. sales, supply chain costs, fixed assets and working capital). This paper proposes a stochastic mixed integer linear programming model for the value-based supply chain network design in which decisions on physical flow (raw materials and finished products) and financial flow are integrated. The proposed model is designed for a four-echelon, multi-commodity, multi-period supply chain and maximizes the value of the company based on the economic value-added concept by making some strategic and tactical decisions affecting the value drivers. Furthermore, a scenario-based two-stage stochastic programming model is developed with a scenario generation method based on Nataf transformation. Also, a computational analysis is done to illustrate performance of the proposed approach.Keywords: Supply chain network design, Value based management, Two, stage stochastic programming, Correlated parameters}
-
امروزه استفاده از سامانه های ژل های پلیمری برای جلوگیری از تولید آب اضافی از چاه های تولیدی نفت، به طور گسترده ای در جهان به کار گرفته می شود. کارآمدی این مواد در محیط متخلخل در گرو پارامترهای متعددی از جمله ترکیب مواد سازنده و شرایط محیطی ژل پلیمر است. از این رو بررسی جامع پارامترهای تاثیر گذار و شناسایی اثر متقابل آنها به منظور افزایش بهره وری سامانه ژل پلیمر، امری لازم الاجراست. لذا در این تحقیق از روش آماری و جامع فاکتوریل جزئی در دو سطح، به منظور بررسی پارامترهای موثر بر زمان بندش ژل پلیمری متشکل از پلی اکریل آمید سولفونه و عامل شبکه کننده استات کروم III استفاده شد تا علاوه بر انجام تعداد آزمایش های بهینه با کمترین هزینه و درکوتاهترین زمان، موثرترین عوامل از میان هشت پارامتر pH، غلظت کلرید کلسیم، نسبت عامل شبکه کننده به کوپلیمر، غلظت کلرید سدیم، غلظت کوپلیمر، سدیم لاکتیت، نانو رس و تیوریا، در کنترل زمان بندش ژل های پلیمری با انجام 32 آزمایش بطری، شناسایی شده و با مدلسازی فرآیند، شرایط بهینه در جهت بهبود فرآیند ایجاد گردد. مدل ارائه شده در این تحقیق با قابلیت پیش بینی زمان بندش ژل بر اساس پارامترهای مورد بررسی، دارای درجه اطمینان 99% است. نتایج نشان داد سدیم لاکتیت، غلظت کوپلیمر، نانو رس، تیوریا و نسبت غلظت عامل شبکه کننده به کوپلیمر به ترتیب پارامترهای اصلی تاثیرگذار بر زمان بندش ژل بوده و همچنین در میان تمامی اثرات متقابل بین پارامترها، اثر متقابل سدیم لاکتیت و نسبت غلظت عامل شبکه کننده به کوپلیمر بیشترین سهم را در کنترل زمان بندش ژل دارد.
کلید واژگان: ژل پلیمر, مدلسازی, زمان بندش ژل, روش فاکتوریل جزئی, پارامتر اصلی, اثر متقابل بین پارامترها}A system of Polymer gel is widely used in oil production wells in order to reduce unwanted water production. The efficiency of these systems in porous media depended on various parameters such as the composition concentration and the media condition of the polymer gels performance. So it is necessary to study the effective parameters and their interactions in order to increase the efficiency of systems of polymer gels. Therefore، in this research، two-level factorial design as a statistical method was used to study the effective parameters on the gelation time of polymer gel containing sulfonated polyacrylamide copolymer and chromium triacetate as crosslinker to not only reduce the number of experiments in the lowest time and cost، but also present the most effective parameters among the eight studied parameters (pH، CaCl2 concentration، crosslinker/co-polymer ratio، NaCl concentration، co-polymer concentration، sodium lactate، nanoclay and thiouria) on gelation time of polymer gels using 32 bottle testing experiment and finally by modeling the process، the optimum condition is presented. The presented model in 99% significant to predict the gelation time of the polymer gel based on the effective parameters. The results showed that sodium lactate، co-polymer concentration، nanoclay، thiouria and crosslinker/co-polymer ratio are the main effects respectively. Also، among the interactions between parameters، the interaction of sodium lactate and crosslinker/co-polymer ratio has the most effect on the gelation time of the hydrogel.Keywords: Polymer gels, Modeling, Gelation time, Two, level factorial design, Main effect, Interaction} -
A finite element formulation based on two-variable refined plate theory has been developed in this paper and has been implemented for bending analysis of isotropic and orthotropic plates. The two-variable refined plate theory can be used for thin and thick plates and predicts parabolic variation of transverse shear stresses across the plate thickness. In this theory the zero traction condition on the plate surfaces is satisfied without using shear correction factor. The governing equations have been derived using the principle of minimum potential energy. After constructing weak form equations، a new 4-node rectangular plate element with six degrees of freedom at each node has been used for discretization of the domain. The finite element code is written in MATLAB and some benchmark problems have been solved. Comparison of results with exact solution and other common plate theories shows the accuracy and efficiency of presented finite element formulation.
Keywords: Finite Element Method, Two, Variable Plate Theory, Rectangular Plate Element, Orthotropic Plate} -
حذف نویز ضربه ای از تصاویر دیجیتالی مبتنی بر تخمین توزیع مکانی نویزهاهدف از این پژوهش ارائه روشی جهت شناسایی و حذف نویزهای تک ضربه ای روشن و تیره می باشد. در این پژوهش جهت شناسایی نویزهای تک ضربه ای در تصویر نویزدار دو الگوریتم آشکارساز معرفی شده است. روش پیشنهادی در این پژوهش یک پروسه تکراری می باشد که هر تکرار شامل سه مرحله است. روش ارائه شده می تواند بر مبنای هر دو الگوریتم آشکارساز معرفی شده جهت شناسایی نویزهای ضربه ای کار کند. در این تحقیق جهت بررسی روش پیشنهادی نویزهای تک ضربه ای با سه نوع توزیع متفاوت مدلسازی و به تصویر اصلی اضافه شده است و تصویر بازسازی شده با تصویر اصلی مورد مقایسه قرار گرفته است. جهت ارزیابی نویزهای شناسایی شده توسط الگوریتم های آشکارساز پیشنهادی و کیفیت تصاویر بازسازی شده به ترتیب از شاخص صحت کلی و شاخص نسبت اوج سیگنال به نویز استفاده شده است. نتایج ارزیابی ها نشان می دهند که روش پیشنهادی بر مبنای دو الگوریتم آشکارساز معرفی شده به مراتب بهتر از روش فیلترینگ دو عبوری میانه می باشد و نسبت به یکی از روش های معرفی شده قبلی یعنی فیلترینگ دو عبوری میانه توافقی نتایج بهتری ارائه داده است. کیفیت تصاویر بازسازی شده توسط روش پیشنهادی بیش تر از روش فیلترینگ دو عبوری میانه و دو عبوری میانه توافقی می باشد. این افزایش کیفیت بطور میانگین و به ترتیب معادل با افزایش 5/37 و 4/17 دسیبل در شاخص نسبت اوج سیگنال به نویز می باشد.
کلید واژگان: نویز تک ضربه ای, الگوریتم آشکارساز نویز, فیلترینگ دو عبوری میانه, فیلترینگ دو عبوری میانه توافقی, شاخص نسبت اوج سیگنال به نویز, شاخص صحت کلی}UniPolar impulse noise removing from digital images based on estimation of noises spatial distributionThis article introduces a method to detect and remove unipolar impulse noises from digital images. In this study, proposed method is a repetitive procedure which each repeat contain three steps. Also, proposed method can be based on two detection algorithms that are introduced to detect unipolar impulse noises. In this research, unipolar impulse noises with 3 different distribution types are modeled and added to original image to produce noised image. Then, image is reconstructed based on proposed method from produced noised image. Finally, reconstructed image is evaluated in comparison to original image. Detected noises by introduced algorithms are evaluated by Overall Accuracy index. Also, quality of the reconstructed image is evaluated by Peak Signal to Noise Ratio (PSNR) index. Evaluation results are shown that proposed method based on two detection algorithms is better than regular and adaptive two-pass median filters. Quality of the reconstructed images by proposed method is high than results of regular and adaptive two-pass median filters. The average enhancement in quality is equivalent with increasement 5.37 and 4.17 decibels in PSNR index respectively.Keywords: Unipolar Impulse Noise, Noise Detection Algorithm, Two, Pass Median Filter (TPMF), Adaptive Two, Pass Median Filter (ATPMF), Peak Signal to Noise Ratio (PSNR) Index, Overall Accuracy (OA) Index.} -
Coriolis mass flow meters are one of the most accurate tools to measure the mass flow in the industry. However, two-phase mode (gas-liquid) may cause severe operating difficulties as well as decreasing certitude in measurement. This paper presents a method based on fuzzy systems to correct the error and improve the reliability of these sensors in the presence of two-phase model fluid. Definite available flow meter parameters are given to designed fuzzy system as inputs, and error is estimated as its output. In the proposed method, to decrease the number of rules, data are clustered using K-means clustering algorithm. The ability of this method in error correction is shown by testing it on real experimental data and compared with the least square method.Keywords: Coriolis mass flow meter, Reliability, Two, phase mode, Clustering, Fuzzy systems}
-
In this paper, a novel technique for the design of two-channel Quadrature Mirror Filter (QMF) banks with linear phase in frequency domain is presented. To satisfy the exact reconstruction condition of the filter bank, low-pass prototype filter response in pass-band, transition band and stop band is optimized using unconstrained indirect update optimization method. The objective function is formulated as a weighted sum of pass-band error and stop-band residual energy of low-pass prototype filter, and the square error of the distortion transfer function of the QMF bank at the quadrature frequency. The performance of the proposed algorithm is evaluated in terms of Peak Reconstruction Error (PRE), mean square error in pass-band and stop-band regions and stop-band edge attenuation. Design examples are included to illustrate the performance of the proposed algorithm and the quality of the filter banks that can be designed.Keywords: Nearly Perfect, Reconstruction, Optimization, Phase Distortion, Two, Channel Filter Banks}
-
Natural convection of a nano uid consisted of water and SiO2 in a square enclosure cavity have been studied numerically. The sidewalls are maintained at di erent constant temperatures and the other walls are thermally insulated. Two-phase mixture model has been used to investigate the hydrodynamic and thermal behaviors of the nano uid for various inclination angles of enclosure ranging from = -60 to = 60, for Rayleigh numbers varying from 103 to 07 and for volume fraction = 0 - 6%. The governing equations in a two-dimensional space are solved numerically using the nitevolume approach. The results show that the average Nusselt number increases with growth of both Rayleigh number and the volume fraction of the nanoparticles. Moreover, inclination angle can be a control parameter for nano uid lled enclosure, and the angle, in which the maximum average Nusselt number occurs for various values of Rayleigh numbers and volume fraction, is obtained.Keywords: Nanofluids, Two, phase mixture model, Natural convection, Inclination angle, Enclosure}
-
The fault rupture propagation phenomenon, spreading from the base rock through different layers of soil, is a matter of concern in many natural and man-made soil structures. The focus of this paper is to investigate reverse fault rupture propagation through two layers of sand deposits by means of numerical modeling. For this purpose, analyses are carried out for different permutations of the three typical materials: dense sand, medium dense sand and loose sand, considering five fault dip angles, 30, 45, 60, 75 and 90 degrees. The validity of numerical model was verified by simulating an experimental model of homogeneous soil layer subjected to reverse faulting. Further to the general trends found in fault rupture propagation in a single layer of soil, special attentions are devoted to the refraction of fault path in the interface of two materials as well as its concavity in the continuation. Moreover, four patterns of fault rapture propagation in two-layered sands, depending on their arrangements and fault dip angles, were concluded from the results.
Keywords: Fault Rupture propagation, Numerical modeling, Two, layered sand, Rupture refraction} -
In this paper for the first time, a circuit model for multi-finger I-gate body-contacted silicon-on-insulator MOSFET is presented. The model parameters are adjusted using simulation of a 45 nm SOI nMOSFET. Using the model, typical body voltage for a 35 finger device is obtained and applied to the transistor. The threshold voltage and drain current are obtained for the first transistor and center ones in the multi-finger structure. The drain induced barrier lowering of the center transistor is increased by 30% and off-current 40 times than that of the first transistor. Simulation results verified the I-gate body contact model in lack of controlling the body voltage comparing with the conventional body contacts e.g. H-gate.Keywords: Silicon, on, Insulator MOSFET, I, gate Body Contact, Two, Dimensional Device Simulation, Body Resistance, Drain Induced Barrier Lowering}
نکته
- نتایج بر اساس تاریخ انتشار مرتب شده‌اند.
- کلیدواژه مورد نظر شما تنها در فیلد کلیدواژگان مقالات جستجو شده‌است. به منظور حذف نتایج غیر مرتبط، جستجو تنها در مقالات مجلاتی انجام شده که با مجله ماخذ هم موضوع هستند.
- در صورتی که می‌خواهید جستجو را در همه موضوعات و با شرایط دیگر تکرار کنید به صفحه جستجوی پیشرفته مجلات مراجعه کنید.
©2000-2024 magiran.com All Rights Reserved.