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optimal-systems
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Seismic protection of LNG tanks with reliability based optimally designed combined rubber isolator and friction damper
, Article Earthquake and Structures ; Volume 16, Issue 5 , 2019 , Pages 523-532 ; 20927614 (ISSN) ; Maghsoudi Barmi, A ; Khaloo, A ; Sharif University of Technology
Techno Press
2019
Abstract
Different types of gas reservoir such as Liquid Natural Gas (LNG) are among the strategic infrastructures, and have great importance for any government or their private owners. To keep the tank and its contents safe during earthquakes especially if the contents are of hazardous or flammable materials; using seismic protection systems such as base isolator can be considered as an effective solution. However, the major deficiency of this system can be the large deformation in the isolation level which may lead to the failure of bearing system. In this paper, as a solution, the efficacy of an optimally designed combined vibration control system, the combined laminated rubber isolator and...
Bi-objective green scheduling in uniform parallel machine environments
, Article Journal of Cleaner Production ; Volume 217 , 2019 , Pages 559-572 ; 09596526 (ISSN) ; AkhavanNiaki, S. T ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Green and sustainability issues are being considered extensively in industry and in the literature. Most of the green-related effects in the manufacturing sector can be modeled by the costs associated with the production machines due to their resource consumption and/or pollutant emission, as a part of the operation cost. Accordingly, taking into account the machine processing costs alongside the other production criteria is one of the main approaches to consider green issues in the production management problems. In the same way, scheduling as one of the major operational problems in the factories can benefit this point of view to involve sustainability aspects. In this paper, the...
Optimization of multiple transmission layouts for minimal energy consumption of a battery electric vehicle
, Article Scientia Iranica ; Volume 26, Issue 4A , 2019 , Pages 2382-2393 ; 10263098 (ISSN) ; Foumani, M. S ; Delkhosh, M ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
Battery Electric Vehicles (BEVs) are a promising solution for reducing the impacts of passenger vehicles on the environment. However, their driving range is restricted due to the limitations of battery technologies. This range can be extended by adoption of multiple-speed transmissions. Most of the comparisons in the related studies are based on non-optimal designs or limited to modal driving cycles. Furthermore, the impact of Power-Split. Continuously Variable Transmission (PS-CVT) layout with type III power How on the power consumption of BEVs has never been examined. In this paper, single-, two-, and three-speed transmissions along with PS-C'VTs with type I and III power flows are...
Optimization of multiple transmission layouts for minimal energy consumption of a battery electric vehicle
, Article Scientia Iranica ; Volume 26, Issue 4A , 2019 , Pages 2382-2393 ; 10263098 (ISSN) ; Saadat Foumani , M ; Delkhosh, M ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
Battery Electric Vehicles (BEVs) are a promising solution for reducing the impacts of passenger vehicles on the environment. However, their driving range is restricted due to the limitations of battery technologies. This range can be extended by adoption of multiple-speed transmissions. Most of the comparisons in the related studies are based on non-optimal designs or limited to modal driving cycles. Furthermore, the impact of Power-Split. Continuously Variable Transmission (PS-CVT) layout with type III power How on the power consumption of BEVs has never been examined. In this paper, single-, two-, and three-speed transmissions along with PS-C'VTs with type I and III power flows are...
A new method for the solution of hybrid analog digital beamforming problems
, Article Optimal Control Applications and Methods ; Volume 41, Issue 5 , 2020 , Pages 1735-1748 ; Reza Marzban, H ; Rastegari, M ; Sharif University of Technology
John Wiley and Sons Ltd
2020
Abstract
By going to millimeter wave (mmWave) we can use large scale MIMO due to short mmWave wavelength to overcome path loss by using beamforming to focus power of signal to the receiver. System structure of mmWave band is different with conventional MIMO because of large scale MIMO which is leading to use many RF-chains. For this reason Hybrid structure have been proposed for large Scale MIMO. By going to Hybrid structure a new issue has been created with phase shifter constraint. In this paper we propose a novel solution to make a hybrid precoding and combing to reach high spectral efficiency. Our problem includes a maximizing Frobenius norm of multiplying five complex matrices. As constraints,...
HTS transformers leakage flux and short circuit force mitigation through optimal design of auxiliary windings
, Article Cryogenics ; Volume 110 , September , 2020 ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Mitigation and control of leakage fluxes and short circuit forces needs much more attention, for a high-temperature superconducting (HTS) transformer, than for a conventional one. Different methods such as the application of auxiliary windings, multi-segment winding, and flux diverter have been presented in the literatures for leakage magnetic field reduction in HTS transformers. In this paper, for the first time, optimal design of auxiliary windings has been performed for a 132/13.8 kV, 50 MVA three phase core type HTS transformer. Genetic algorithm (GA) has been used for the optimization process. Induced current in auxiliary windings which is inversely proportional to the leakage fluxes...
Optimal design of flux diverter using genetic algorithm for axial short circuit force reduction in HTS transformers
, Article IEEE Transactions on Applied Superconductivity ; Volume 30, Issue 1 , January , 2020 ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
The appealing advantages of high-temperature superconducting (HTS) power transformers over conventional ones have attracted transformer manufacturing companies, power companies, research institutes, and universities worldwide to conduct research and development in this field. Unfortunately, HTS transformers are more vulnerable to mechanical stresses than conventional transformers. The results of the interaction between current carrying windings and leakage magnetic fluxes are the electromagnetic forces, which act on transformer windings. Under short circuit events, these forces are remarkable, and, therefore, catastrophic failure of transformer may arise. Flux-diverter applications have been...
An algorithm for numerical nonlinear optimization: fertile field algorithm (FFA)
, Article Journal of Ambient Intelligence and Humanized Computing ; Volume 11, Issue 2 , 2020 , Pages 865-878 ; Khodaygan, S ; Sharif University of Technology
Springer
2020
Abstract
Nature, as a rich source of solutions, can be an inspirational guide to answer scientific expectations. Seed dispersal mechanism as one of the most common reproduction method among the plants is a unique technique with millions of years of evolutionary history. In this paper, inspired by plants survival, a novel method of optimization is presented, which is called Fertile Field Algorithm. One of the main challenges of stochastic optimization methods is related to the efficiency of the searching process for finding the global optimal solution. Seeding procedure is the most common reproduction method among all the plants. In the proposed method, the searching process is carried out through a...
Leakage-aware battery lifetime analysis using the calculus of variations
, Article IEEE Transactions on Circuits and Systems I: Regular Papers ; Volume 67, Issue 12 , June , 2020 , Pages 4829-4841 ; Safaei, B ; Ejlali, A ; Chen, J.-J ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2020
Abstract
Due to non-linear factors such as the rate capacity and the recovery effect, the shape of the battery discharge curve plays a significant role in the overall lifetime of the batteries. Accordingly, this paper proposes a simple heuristic battery-aware speed scheduling policy for periodic and non-periodic real-time tasks in Dynamic Voltage Scaling (DVS) systems with non-negligible leakage/static power. A set of comprehensive analysis has been conducted to compare the battery efficiency of the proposed policies with an optimal solution, which could be derived via the Calculus of Variations (CoV). These evaluations have taken into account both periodic and non-periodic tasks in DVS-based...
Multi-objective optimal design of stiffened laminated composite cylindrical shell with piezoelectric actuators
, Article International Journal on Interactive Design and Manufacturing ; Volume 14, Issue 2 , January , 2020 , Pages 595-611 ; Bohlooly, M ; Sharif University of Technology
Springer
2020
Abstract
The stiffeners and piezoelectric actuators are used in many aerospace structures as an auxiliary layer with laminated composites. A question then arises as to whether we can estimate the percentage of these materials in an efficient design. Due to the high computational cost, it is not easy to answer through numerical solutions. The objective of this paper is concurrently to maximize the buckling load and minimize the weight of the cylindrical shell. To reach this aim, a multi-objective optimization problem is developed based on the closed-form solutions of thermal/mechanical buckling and weight of the piezolaminated shell with eccentric/concentric stiffener. The Non-dominated Sorting...
Value based seismic design of structures using performance assessment by the endurance time method
, Article Structure and Infrastructure Engineering ; Volume 16, Issue 10 , January , 2020 , Pages 1397-1415 ; Estekanchi, H. E ; Sharif University of Technology
Taylor and Francis Ltd
2020
Abstract
A framework for optimal seismic design of structures, considering maximum value as the design objective, is introduced. In this framework, the value parameter incorporates a comprehensive set of performance indicators. Decision indicators are mapped into equivalent economic values and are directly involved in the design process. This approach leads to optimal assignment of the available resources to meet infrastructure requirements. The construction cost and the risk of seismic consequences are considered as the value components. FEMA-P58 methodology is utilized in estimation of the seismic consequences including the repair cost, repair time, injuries and casualties. Endurance Time method is...
Optimum seismic design of steel framed-tube and tube-in-tube tall buildings
, Article Structural Design of Tall and Special Buildings ; Volume 29, Issue 14 , 2020 ; Estekanchi, H. E ; Moosavian, H ; Sharif University of Technology
John Wiley and Sons Ltd
2020
Abstract
The relatively large number of structural elements and the variety of design code requirements complicate the design process of tall buildings. This process is exacerbated when the target is to obtain the seismic code-compliant optimal design with minimum weight. The present paper aims at providing a practical methodology for the optimal design of steel tall building structures considering the constraints imposed by typical building codes. The applicability of the proposed approach is demonstrated through the determination of the optimal seismic design for 20-, 40-, and 60-story buildings with a framed tube as well as a tube-in-tube system. Such a design gives rise to a basis for the fair...
A comparison of two estimators for solutions to greedy algorithm in scheduling depletable sources
, Article International Conference on Risk Management and Engineering Management, Toronto, ON, 18 April 2008 through 18 April 2008 ; 2008 , Pages 80-85 ; 9780978348458 (ISBN) ; Azizi, E ; Kianfar, F ; Sharif University of Technology
2008
Abstract
There are many depletable resource planning problems associated with convex cost function. The Greedy algorithm has been used to find the optimal solution for such problems. But exploiting that algorithm requires a large bulk of computations to find the optimal solution. Thus, in this paper we have established two piecewise linear estimators for the convex cost function: an inner intersection of the function values and an outer tangent. A practical experiment was conducted to compare the performance of the two presented estimators and it was observed that the outer tangent performs more efficiently than the inner intersection. The execution time of the Greedy Algorithm and the estimation...
Optimal multi-objective resource allocation for d2d underlaying cellular networks in uplink communications
, Article IEEE Access ; Volume 9 , 2021 , Pages 114153-114166 ; 21693536 (ISSN) ; Jalali, J ; Khalili, A ; Mili, M.R ; Wittevrongel, S ; Steendam, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
In this paper, we study a resource allocation problem in orthogonal frequency division multiple access (OFDMA)-based Device-to-Device (D2D) communications. To this end, we propose a multi-objective optimization problem (MOOP) framework, which jointly maximizes the sum rate of D2D users (DUs) and cellular users (CUs) in uplink communications and minimizes the total transmit power. The proposed problem formulation takes into account the minimum data-rates and the maximum transmitted power budget for both DUs and CUs. We transform this MOOP into a single-objective optimization problem (SOOP) using the weighted sum method and then propose an approach to solve this SOOP via a monotonic approach...
Minimization of Non-repeatable Runout (NRRO) in High-Speed Spindle Bearings
, Article SAE 2021 Automotive Technical Papers, WONLYAUTO 2021, 1 January 2021 ; Issue 2021 , 2021 ; 01487191 (ISSN) ; Khodaygan, S ; Sharif University of Technology
SAE International
2021
Abstract
The production with high quality at the lowest production time can be a key means to success in the competitive environment of manufacturing companies. Therefore, in recent years, the need for extra precise and high-speed machine tools has been impressively increased in manufacturing applications. One of the main sources of errors in the motion of high-speed spindles is the occurrence of non-repetitive runouts (NRRO) in the bearing. The NRRO can be caused by some factors such as the form of balls, the waviness of rings, the number of balls, and the permutation of one or two balls in the ball bearing. In this paper, a Taguchi-based approach is proposed for the optimal design of high-speed...
Probabilistic seismic performance assessment of optimally designed highway bridge isolated by ordinary unbonded elastomeric bearings
, Article Engineering Structures ; Volume 247 , 2021 ; 01410296 (ISSN) ; Khansefid, A ; Khaloo, A ; Ehteshami Moeini, M ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
Following the idea of using unbonded isolators to eliminate the tensile stress and providing a cost-effective isolation system, recent experimental research has shown ordinary unbonded steel reinforced elastomeric bearings (SREBs) as an attractive option for seismic isolation of highway bridges. The focus of current research work is on the evaluation of the seismic vulnerability of a highway bridge isolated by unbonded SREBs through developing fragility curves of the structure. This assessment considers parameters playing a key role in the isolation system behavior, namely the friction coefficient, as well as the isolator aging effects. In this regard, a typical three-span highway bridge is...
A novel design and performance optimization methodology for hydraulic Cross-Flow turbines using successive numerical simulations
, Article Renewable Energy ; Volume 169 , 2021 , Pages 1402-1421 ; 09601481 (ISSN) ; Durali, M ; Khakrand, M. H ; Hoghooghi, H ; Sharif University of Technology
Elsevier Ltd
2021
Abstract
This paper introduces a new methodology for designing and optimizing the performance of hydraulic Cross-Flow turbines for a wide range of operating conditions. The methodology is based on a one-step approach for the system-level design phase and a three-step, successive numerical analysis approach for the detail design phase. Compared to current design methodologies, not only does this approach break down the process into well-defined steps and simplify it, but it also has the advantage that once numerical simulations are conducted for a single turbine, most of the results can be used for an entire class of Cross-Flow turbines. In this paper, after a discussion of the research background, we...
Optimal design of truss structures with frequency constraints: a comparative study of DE, IDE, LSHADE, and CMAES algorithms
, Article Engineering with Computers ; 2021 ; 01770667 (ISSN) ; Mesbahi, P ; Moosavian, N ; Daliri, H ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2021
Abstract
The present study examines the performance of three powerful methods including the original differential evolution (DE), the improved differential evolution (IDE), and the winner of the CEC-2014 competition, LSHADE, in addition to the covariance matrix adaptation evolution strategy (CMAES) for size optimization of truss structures under natural frequency constraints. Despite the abundant researches on novel meta-heuristic algorithms in the literature, the application of CMAES, one of the most powerful and reliable optimization algorithms, on the optimal solution of the truss structures has received scant attention. For consistent comparison between these algorithms, four stopping criteria...
CorrIndex: A permutation invariant performance index
, Article Signal Processing ; Volume 195 , 2022 ; 01651684 (ISSN) ; Comon, P ; Jutten, C ; Babaie Zadeh, M ; Sharif University of Technology
Elsevier B.V
2022
Abstract
Permutation and scaling ambiguities are relevant issues in tensor decomposition and source separation algorithms. Although these ambiguities are inevitable when working on real data sets, it is preferred to eliminate these uncertainties for evaluating algorithms on synthetic data sets. As shown in the paper, the existing performance indices for this purpose are either greedy and unreliable or computationally costly. In this paper, we propose a new performance index, called CorrIndex, whose reliability can be proved theoretically. Moreover, compared to previous performance indices, it has a low computational cost. Theoretical results and computer experiments demonstrate these advantages of...
A new scheme for the development of IMU-based activity recognition systems for telerehabilitation
, Article Medical Engineering and Physics ; Volume 108 , 2022 ; 13504533 (ISSN) ; Eslaminia, A. R ; Bakhshayesh, P. R ; Ejtehadi, M ; Alibiglou, L ; Behzadipour, S ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Wearable human activity recognition systems (HAR) using inertial measurement units (IMU) play a key role in the development of smart rehabilitation systems. Training of a HAR system with patient data is costly, time-consuming, and difficult for the patients. This study proposes a new scheme for the optimal design of HARs with minimal involvement of the patients. It uses healthy subject data for optimal design for a set of activities used in the rehabilitation of PD1 patients. It maintains its performance for individual PD subjects using a single session data collection and an adaptation procedure. In the optimal design, several classifiers (i.e. NM, k-NN, MLP with RBF as a hidden layer, and...