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Minimizing expected discounted cost in a queueing loss model with discriminating arrivals
, Article European Journal of Operational Research ; Volume 282, Issue 2 , 2020 , Pages 593-601 ; Ross, S ; Sharif University of Technology
Elsevier B.V
2020
Abstract
We consider a queuing loss system with heterogeneous skill based servers and Poisson arrivals. We first assume that each arrival has a vector (X1,…,Xn) of independent binary random variables with Xi=1 if server i is eligible to serve that arrival. The service time at server i is exponential with rate μi. Arrivals finding no servers that are both idle and eligible to serve them are lost. Assuming the system incurs a cost of one unit for each lost customer, our goal is to find the optimal policy for assigning arrivals to idle and eligible servers so as to minimize the expected discounted cost of the system. Later, we generalize our model by considering k server pools where each pool i is...
Experimental and Theoretical Investigation on Losses and One Dimensional Modeling of The Centrifugal Compressor
, M.Sc. Thesis Sharif University of Technology ; Hajilouy Benisi, Ali (Supervisor)
Abstract
Centrifugal compressors have wide applications in the turbochargers, aircraft propulsion and petrochemical industry. Therefore it is important to design high efficiency centrifugal compressor. Knowledge of compressor performance at different conditions, energy losses and the contribution of each component of compressor in efficiency losses have of great importance.
In this research, different loss models of the centrifugal compressor were reviewed and investigated. Then 1D codes were developed based on the loss models, and performance characteristics of S2B Schweitzer and GT4082 Garret compressors at different conditions were achieved. In order to evaluate the modeling results,...
In this research, different loss models of the centrifugal compressor were reviewed and investigated. Then 1D codes were developed based on the loss models, and performance characteristics of S2B Schweitzer and GT4082 Garret compressors at different conditions were achieved. In order to evaluate the modeling results,...
A generalized total least squares algorithm for RSS-based localization with unknown path-loss model parameters
, Article 24th Iranian Conference on Electrical Engineering, ICEE 2016, 10 May 2016 through 12 May 2016 ; 2016 , Pages 521-524 ; 9781467387897 (ISBN) ; Danaee, M. R ; Bayat, S ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2016
Abstract
Node localization is of paramount importance to different wireless sensor network (WSN) applications. This paper investigates the received signal strength (RSS) based localization problem with unknown path-loss model parameters. Most works in RSS localization assume the transmit power and path-loss exponent (PLE) are known that is not a realistic assumption in some cases. However this paper, assumes the transmit power and the PLE are both unknown and a novel algorithm for sensor location is proposed. The algorithm is based on the generalized total least-squares (GTLS) method and gives an explicit solution for the localization problem. The performance of the proposed method is compared with...
Experimental and Theoretical Investigation on Losses and Modeling Axial Flow Turbine
, M.Sc. Thesis Sharif University of Technology ; Hajilouy-Benisi, Ali (Supervisor)
Abstract
Prediction of axial flow turbine’s performance with different operating conditions due to the high costs and lack of reliable empirical data is always under developing. In this type of turbine, fluid flow is three-dimensional, viscous and highly turbulent. Nowadays, although a relatively detailed picture of the flow field can be obtained by the computational and numerical tools, but using of appropriate loss models in one-dimensional modeling for the performance prediction as well as optimization of the turbine in initial design phases, is a common trend.
In the current study, aerodynamic losses in the axial flow turbine are investigated. Several loss models for the axial flow turbines...
In the current study, aerodynamic losses in the axial flow turbine are investigated. Several loss models for the axial flow turbines...
Optimal Drive for Brushless Doubly Fed Induction Generator
, M.Sc. Thesis Sharif University of Technology ; Oraee Mirzamani, Hashem (Supervisor)
Abstract
In this thesis, losses of steady state operation of brushless doubly-fed induction machines (BDFM) are analyzed and optimized. Since the final objective of engineering systems is economic advantage, after brief introduction to BDFM, economic model of wind farms is presented and BDFM benefits and deficits are studied. Among BDFM’s research topics, power density and efficiency were recognized of most importance, according to the economic model. In absence of analytical model of core loss for BDFM, a maximum torque per ampere optimization for BDFM is presented, including torque equation derivation, optimal current angle extraction and machine design objective function calculation. The...
Aerodynamic Design Methodology for Changing Axial Compressor Capacity
, M.Sc. Thesis Sharif University of Technology ; Ghorbanian, Kaveh (Supervisor)
Abstract
Axial compressor design is a very complex and expensive process. In general, for design and development of a new axial compressor, manufacturing companies usually intend to employ an existing and successful axial compressor as an starting point and modify and upgrade it. In this regard, dimensional scaling is a common method for derivative axial compressors. The goal of dimensional scaling is to get a different capacitywhile minimizing the development time and cost. In this thesis, theNASA eight stage transonic axial flow compressor is chosen as the base model for dimensional scaling to lower and upper size of its original dimension. The scaled compressor is analyzed with a quasi 2-D code....
Load Sharing Control among Parallel Inverters for Achiving Maximum Efficiency
, M.Sc. Thesis Sharif University of Technology ; Mokhtari, Hossein (Supervisor)
Abstract
Regarding increasing rate of electrical energy demand, paucity of fossil fuels and the pollution stemmed from burning them, using renewable energy is inevitable. For transmitting the generated electrical energy to grid, power electronics converters are used. Inverters and back-to-back converters are some of these converters. Inverters and back-to-back converters are used in connecting photovoltaic power plants and wind systems to grid respectively. Because of technological limitation, converters are paralleled with others at high power transmitting. Paralleling converters has other merits such as increasing system reliability through redundancy and repairing defective converter without...
Probabilistic Modeling Framework for Predicting Seismic Failure and Damage of Electrical Substations
, M.Sc. Thesis Sharif University of Technology ; Haj Kazem Kashani, Hamed (Supervisor) ; Mahsouli, Mojtaba (Supervisor)
Abstract
The increasing dependence of urban communities on infrastructure highlights the importance of resilience in the event of natural disasters, including earthquakes. Every society is made up of various infrastructures such as water supply, electricity, transportation, hospitals and so on.Every infrastructure to serve the community depends directly or indirectly on the electricity infrastructure.The power supply infrastructure consists of three main systems of electricity generation, transmission and distribution. Power substations, as nodes of the transmission and distribution network, are considered to be very vital nodes that it is important to maintain their serviceability after severe...
Analysis of axial turbines behavior by means of comparing experimental and theoretical results
, Article 44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Hartford, CT, 21 July 2008 through 23 July 2008 ; June , 2008 ; 9781563479434 (ISBN) ; Hajilouy Benisi, A ; Sharif University of Technology
2008
Abstract
Estimation of efficiency of axial flow gas turbines under variety of conditions i.e. different speed and pressure ratio has been hampered by lack of reliable experimental data and experiments cost. Because the flow in an axial turbine is complex and many mechanisms of the flow losses in turbine have not been known well, loss models are necessary not only in the preliminary process of mean line prediction, but also in the further process of through flow calculation in the simulation and optimization of turbines. Present study has been carried out using 1-D modeling. Simulation computer code is prepared for one-stage axial turbine based on Ainley&Mathieson method with some modifications in the...
State Plane Analysis and Optimization of CLLC Resonant Converter for Bidirectional EV Charger
, Ph.D. Dissertation Sharif University of Technology ; Tahami, Farzad (Supervisor) ; Schanen, Jean-Luc (Supervisor)
Abstract
As more renewables step in, the ongoing change will be drastic for the electrical grid. The energy sector must find new ways to balance energy production and consumption. Electric vehicle (EV) batteries are by far the most cost-efficient form of energy storage since they require no additional investments in hardware. A bidirectional EV charger is a new technology that enables energy to be pushed back to the power grid and auxiliary loads from the battery. The electrical requirements of the EV charger are examined in detail to find an appropriate power electronics converter to meet all the requirements. The CLLC resonant converter is a promising candidate for high efficient, bidirectional...
Thermal degradation behavior and kinetic analysis of ultra high molecular weight polyethylene based multi-walled carbon nanotube nanocomposites prepared via in-situ polymerization
, Article Journal of Macromolecular Science, Part A: Pure and Applied Chemistry ; Volume 49, Issue 9 , 2012 , Pages 749-757 ; 10601325 (ISSN) ; Saadatabadi, A. R ; Khorasheh, F ; Sharif University of Technology
T&F
2012
Abstract
Thermal degradation behavior of multi-wall carbon nanotubes (MWCNTs)/ultra high molecular weight polyethylene (UHMWPE) nanocomposites, with different nanotubes contents (0.5, 1.5 and 3.5 wt%) prepared via in-situ polymerization technique have been investigated using thermal gravimetric analysis (TGA). TGA spectra revealed that these nanocomposites had enhanced thermal stability and no significant mass loss (<0.4 wt%) occurred up to 350°C. Thermal degradation of these UHMWPE/MWCNT nanocomposites was investigated in terms of parameters such as the onset temperature of degradation (T 10), the decomposition temperature at 50% wt loss (T 50), the degradation temperature of maximum rate of the...