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Accelerating the performance of parallel depth-first-search branch-and-bound algorithm in transportation network design problem
, Article ICORES 2015 - 4th International Conference on Operations Research and Enterprise Systems, Proceedings, 10 January 2015 through 12 January 2015 ; January , 2015 , Pages 359-366 ; 9789897580758 (ISBN) ; Shafahi, Y ; Sharif University of Technology
SciTePress
2015
Abstract
Transportation Network Design Problem (TNDP) aims at selection of a subset of proposed urban projects in budget constraint to minimize the network users' total travel time. This is a well-known resource-intensive problem in transportation planning literature. Application of parallel computing, as a result, can be useful to address the exact solution of TNDP. This paper is going to investigate how the performance of a parallel Branch-and-Bound (B&B) algorithm with Depth-First-Search (DFS) strategy can be accelerated. The paper suggests assigning greedy solutions to idle processors at the start of the algorithm. A greedy solution, considered in this paper, is a budget-wise feasible selection...
Parallelization of the branch-and-bound algorithm in transportation discrete network design problem
, Article Scientia Iranica ; Volume 23, Issue 2 , 2016 , Pages 407-419 ; 10263098 (ISSN) ; Shafahi, Y ; Sharif University of Technology
Sharif University of Technology
2016
Abstract
Transportation Discrete Network Design Problem (TDNDP) aims at choosing a subset of proposed projects to minimize the users' total travel time with respect to a budget constraint. Because TDNDP is a hard combinatorial problem, recent research has widely addressed heuristic approaches and ignored the exact solution. This paper explores how application of parallel computation can affect the performance of an exact algorithm in TDNDP. First, we show that the Branch-and-Bound (B&B) algorithm, proposed by LeBlanc, is well adapted to a parallel design with synchronized Master-Slave (MS) paradigm. Then, we develop a parallel B&B algorithm and implement it with two search strategies of...
A new class of invariants in the lepton sector
, Article Nuclear Physics B ; Volume 811, Issue 1-2 , 2009 , Pages 98-108 ; 05503213 (ISSN) ; Farzan, Y ; Sharif University of Technology
2009
Abstract
We construct a new set of combinations from the mass matrices of the charged leptons and neutrinos that are invariant under basis transformation, hereafter the invariants. We use these invariants to study various symmetries and neutrino mass textures in a basis independent way. In particular, we show that by using these invariants the ansatz such as μ - τ exchange and reflection symmetries, various texture zeros and flavor symmetries can be expressed in a general basis. © 2008 Elsevier B.V. All rights reserved
An analysis of cosmic neutrinos: flavor composition at source and neutrino mixing parameters
, Article Nuclear Physics B ; Volume 821, Issue 1-2 , 2009 , Pages 197-214 ; 05503213 (ISSN) ; Farzan, Y ; Sharif University of Technology
2009
Abstract
We examine the feasibility of deriving neutrino mixing parameters δ and θ13 from the cosmic neutrino flavor composition under the assumption that the flavor ratios of the cosmic neutrinos at the source were Fνe + Fover(ν, ̄)e : Fνμ + Fover(ν, ̄)μ : Fντ + Fover(ν, ̄)τ = 1 : 2 : 0. We analyze various uncertainties that enter the derivation of δ and θ13 from the ratio of the shower-like to μ-tracks events which is the only realistic source of information on the flavor composition at neutrino telescopes such as ICECUBE. We then examine to what extent the deviation of the initial flavor ratio from 1 : 2 : 0 can be tested by measurement of this ratio at neutrino telescopes taking into account...
Effect of VC and (Ta, Nb)C on wear of WC-10Co based cemented carbides
, Article Tribology - Materials, Surfaces and Interfaces ; Volume 3, Issue 1 , 2009 , Pages 31-36 ; 17515831 (ISSN) ; Ganji, Y ; Sharif University of Technology
2009
Abstract
WC-Co cemented carbides, including small angular tungsten carbides particles, are used extensively to improve wear resistance. Some additives can affect mechanical and wear properties of these materials. In this study, the effect of VC and (Ta, Nb)C content on wear of WC- 10Co were considered. The tests were performed at normal load of 230 N and sliding distance of 800 m up to 3200 m. Wear tests were carried out using dry sand/rubber wheel apparatus. Wear rate, standard and modified wear coefficients were calculated. The microstructures of prepared specimens were examined by optical microscopy. The morphological analysis of the worn surfaces was made by SEM. The results show that VC content...
Estimating activity patterns using spatio-temporal data of cell phone networks
, Article International Journal of Urban Sciences ; Volume 22, Issue 2 , 2018 , Pages 162-179 ; 12265934 (ISSN) ; Shafahi, Y ; Sharif University of Technology
Routledge
2018
Abstract
The tendency towards using activity-based models to predict trip demand has increased dramatically over recent years. However, these models have suffered from insufficient data for calibration, and the intrinsic problems of traditional methods impose the need to search for better alternatives. This paper discusses ways to process cell phone spatio-temporal data in a manner that makes it comprehensible for traffic interpretations and proposes methods on how to infer urban mobility and activity patterns from the aforementioned data. The movements of each subscriber are described by a sequence of stops and trips, and each stop is labelled by an activity. The types of activities are estimated...
Estimating activity patterns using spatio-temporal data of cell phone networks
, Article International Journal of Urban Sciences ; 2017 , Pages 1-18 ; 12265934 (ISSN) ; Shafahi, Y ; Sharif University of Technology
2017
Abstract
The tendency towards using activity-based models to predict trip demand has increased dramatically over recent years. However, these models have suffered from insufficient data for calibration, and the intrinsic problems of traditional methods impose the need to search for better alternatives. This paper discusses ways to process cell phone spatio-temporal data in a manner that makes it comprehensible for traffic interpretations and proposes methods on how to infer urban mobility and activity patterns from the aforementioned data. The movements of each subscriber are described by a sequence of stops and trips, and each stop is labelled by an activity. The types of activities are estimated...
Model of sustainable development of energy system, case of Hamedan
, Article Energy Policy ; Volume 104 , 2017 , Pages 66-79 ; 03014215 (ISSN) ; Saboohi, Y ; Sharif University of Technology
Elsevier Ltd
2017
Abstract
Sustainable economic growth and improvement of the social welfare depend upon the sufficient supply of energy resources, while the utilization of energy resources is one of the main factors of environmental degradation. This research is involved with development of a sustainable energy system model and a new method for sustainability assessment. This model represents the flow of energy from primary resources through processing, conversion, and end-use technologies in an optimization framework where the useful energy demand in various social and economic sectors is met. The impact of energy supply and consumption chain on the environment at each level of energy system is also embedded in the...
Planning for investment in energy innovation: Developing an analytical tool to explore the impact of knowledge flow
, Article International Journal of Energy Economics and Policy ; Volume 8, Issue 2 , 2018 , Pages 7-19 ; 21464553 (ISSN) ; Saboohi, Y ; Sharif University of Technology
Econjournals
2018
Abstract
The major objective of this study is to provide an analytical tool to identify the role of investment on innovation in the process of new technologies development. To achieve this goal, a model of knowledge flow is developed and the effects of national and international knowledge spillovers are investigated. Results show that when knowledge spillovers are modelled in the Nordic countries, the required investment on domestic energy R&D decreases and the cumulative knowledge increases to 10.7 billion USD by 2030. This is a significant economic potential for technological innovation which can be considered for both energy researchers and energy planners. Finally, some important policy insights...
Vehicle identification sensors location problem for large networks
, Article Journal of Intelligent Transportation Systems: Technology, Planning, and Operations ; 2018 ; 15472450 (ISSN) ; Shafahi, Y ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
Finding the optimal location for sensors is a key problem in flow estimation. There are several location models that have been developed recently for vehicle identification (ID) sensors. However, these location models cannot be applied to large networks because there are many constraints and integer variables. Based on a property of the location problem for vehicle ID sensors, given the initial vehicle ID sensors that are pre-installed and fixed on the network, this article presents a solution that greatly reduces the size of this location problem. An applied example demonstrates that when 8% of the arcs from a real network that are randomly selected have a vehicle ID sensor, the reductions...
Vehicle identification sensors location problem for large networks
, Article Journal of Intelligent Transportation Systems: Technology, Planning, and Operations ; Volume 23, Issue 4 , 2019 , Pages 389-402 ; 15472450 (ISSN) ; Shafahi, Y ; Sharif University of Technology
Taylor and Francis Inc
2019
Abstract
Finding the optimal location for sensors is a key problem in flow estimation. There are several location models that have been developed recently for vehicle identification (ID) sensors. However, these location models cannot be applied to large networks because there are many constraints and integer variables. Based on a property of the location problem for vehicle ID sensors, given the initial vehicle ID sensors that are pre-installed and fixed on the network, this article presents a solution that greatly reduces the size of this location problem. An applied example demonstrates that when 8% of the arcs from a real network that are randomly selected have a vehicle ID sensor, the reductions...
A survey on exergy, energy and environmental analysis of sulfur recovery unit in case of five intensified configurations
, Article Chemical Papers ; Volume 73, Issue 6 , 2019 , Pages 1529-1539 ; 03666352 (ISSN) ; Tavan, Y ; Sharif University of Technology
Springer International Publishing
2019
Abstract
In this study, a combination of energy and exergy analysis is applied for the industrial sulfur recovery unit (SRU) in commercial simulation software. The data of energy and exergy are obtained from the simulator and Excel (for physical and chemical exergy), respectively. In doing so, five intensified SRU configurations namely: (1) hot gas bypass (2) acid gas bypass (3) inlet stream preheating (4) acid gas enrichment and (5) oxygen (air) enrichment are compared in terms of energy production, reaction furnace temperature, sulfur recovery and pollutant emission into environment. Then, irreversibility in these five arrangements is compared and all the proposed methods show higher useful exergy...
Energy supply transformation pathways in Iran to reduce GHG emissions in line with the Paris Agreement
, Article Energy Strategy Reviews ; Volume 32 , 2020 ; Saboohi, Y ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Extensive dependence of the national economy on wasteful fossil fuel use as well as limited access to the international financial markets and the best available techniques over the strict economic sanctions period have hindered Iran from developing a sustainable energy system. By considering the reversal order, the present study investigated the least-cost options for improving energy efficiency and reducing GHG emissions in the energy supply sector. The essential purpose of this research work is to increase the evidence base necessary to inform policy and strategy discussions within Iran and related communities concerning the choice of GHG emissions reduction. Applying ARDL approach to...
A new wave equation for MHD instabilities in aluminum reduction cells
, Article TMS 2007 Annual Meeting and Exhibition, Orlando, FL, 25 February 2007 through 1 March 2007 ; 2007 , Pages 345-349 ; 01470809 (ISSN) ; 0873396596 (ISBN); 9780873396592 (ISBN) ; Saboohi, Y ; Sharif University of Technology
2007
Abstract
To overcome the problem of magneto hydrodynamic instabilities at the aluminum-cryolite interface in aluminum reduction cells, the use of a simple and efficient model has been suggested. In this paper a new model for evaluation of magneto hydrodynamic instabilities in aluminum reduction cells is proposed. This model is in the form of a wave equation for interfacial oscillations and is constructed based on Shallow Water approximation and linear stability analysis. In this model two terms for linear friction in each molten layer of aluminum and cryolite has been considered and also Lorentz forces in cryolite layer have not been neglected. By accounting of these additional terms in our model,...
Computation of rarefied gaseous flows in micro to nano scale channels with slip to transient regimes using general second-order quadratic elements
, Article Proceedings of the 6th International Conference on Nanochannels, Microchannels, and Minichannels, ICNMM2008, 23 June 2008 through 25 June 2008, Darmstadt ; Issue PART A , 2008 , Pages 55-64 ; 0791848345 (ISBN); 9780791848340 (ISBN) ; Daghighi, Y ; Sharif University of Technology
2008
Abstract
A new finite-volume-based finite-element method using the quadratic elements is developed in the present study, to analyze the flow in micro and nano sizes with higher-order slip boundary conditions. The method is applied to gaseous flow in micro and nanoscale-channels. The developed method is carried out over a wide range of Knudsen numbers, which cover not only the continuum slip flow regime with 0≤Kn≤0.1 but also it entire the range of transient regime with 0.1
A numerical method for solving nth-order boundary-value problems
, Article Applied Mathematics and Computation ; Volume 196, Issue 2 , 2008 , Pages 889-897 ; 00963003 (ISSN) ; Jalilian, Y ; Sharif University of Technology
2008
Abstract
In this paper, we consider the solution of an nth order boundary-value problem. We solve this problem by changing the problem to a system of two integral-differential equations and using the variational iteration method. By giving three examples and comparing with the other methods, the efficiency of the method will be shown. © 2007 Elsevier Inc. All rights reserved
A combined upper bound and finite element model for prediction of velocity and temperature fields during hot rolling process
, Article International Journal of Mechanical Sciences ; Volume 50, Issue 9 , 2008 , Pages 1423-1431 ; 00207403 (ISSN) ; Mahmoodkhani, Y ; Sharif University of Technology
Elsevier Ltd
2008
Abstract
In this work, velocity field and temperature distribution during hot strip rolling are predicted, employing a combined upper bound and finite element analysis. At first, a velocity field is proposed utilizing the principle of volume constancy, and then the velocity field is modified by means of upper bound theorem. At the same time, a thermal-finite element analysis is utilized to determine temperature distribution within the metal as well as to calculate the flow stress of deforming material. The model is capable of considering the effects of different factors on temperature and velocity distributions such as rolling speed and interface heat transfer coefficient. In order to verify the...
Evaluation of the optimal performance of passenger vehicle by integrated energy-environment-economic modeling
, Article International Journal of Environmental Science and Technology ; Volume 4, Issue 2 , 2007 , Pages 189-196 ; 17351472 (ISSN) ; Saboohi, Y ; Sharif University of Technology
CEERS
2007
Abstract
Analysis of multi dimensional interactions of flow of energy in passenger vehicle is a complex task that necessitates development and utilization of analytical tools. Development of analytical tools with high complexity is usually based on conclusions of many concepts and theories from different scientific disciplines. In this approach, Passenger vehicle is supposed to be organized in the form of a firm and appears in the market that oriented towards establishing an effective energy supply system which may be identified as delivering the product (person kilometer or tone kilometer) with minimum operation costs. To this end, an optimization model named power software founded on theory of firm...
Local graph clustering with network lasso
, Article IEEE Signal Processing Letters ; Volume 28 , 2021 , Pages 106-110 ; 10709908 (ISSN) ; Sarcheshmehpour, Y ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2021
Abstract
We study the statistical and computational properties of a network Lasso method for local graph clustering. The clusters delivered by nLasso can be characterized elegantly via network flows between cluster boundaries and seed nodes. While spectral clustering methods are guided by a minimization of the graph Laplacian quadratic form, nLasso minimizes the total variation of cluster indicator signals. As demonstrated theoretically and numerically, nLasso methods can handle very sparse clusters (chain-like) which are difficult for spectral clustering. We also verify that a primal-dual method for non-smooth optimization allows to approximate nLasso solutions with optimal worst-case convergence...
An inverse f(R) gravitation for cosmic speed up, and dark energy equivalent
, Article Modern Physics Letters A ; Volume 23, Issue 23 , 2008 , Pages 1929-1937 ; 02177323 (ISSN) ; Sobouti, Y ; Sharif University of Technology
2008
Abstract
To explain the cosmic speed up, brought to light by the recent SNIa and CMB observations, we propose the following: (a) In a spacetime endowed with a FRW metric, we choose an empirical scale factor that best explains the observations. (b) We assume a modified gravity, generated by an unspecified field Lagrangian, f(R). (c) We use the adopted empirical scale factor to work back retroactively to obtain f(R), hence the term "Inverse f(R)". (d) Next we consider the classic GR and a conventional FRW universe that, in addition to its known baryonic content, possesses a hypothetical "Dark Energy" component. We compare the two scenarios and find the density, the pressure, and the equation of the...