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| 2. |
- Jakobsson, S, et al.
(författare)
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Combustion engine optimization: A multiobjective approach
- 2010
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Ingår i: Optimization & Engineering. - : Springer Science and Business Media LLC. - 1389-4420 .- 1573-2924. ; 11:4, s. 533-554
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Tidskriftsartikel (refereegranskat)abstract
- To simulate the physical and chemical processes inside combustion engines is possible by appropriate software and high performance computers. For combustion engines a good design is such that it combines a low fuel consumption with low emissions of soot and nitrogen oxides. These are however partly conflicting requirements. In this paper we approach this problem in a multi-criteria setting which has the advantage that it is possible to estimate the trade off between the different objectives and the decision of the optimal solution is postponed until all possibilities and limitations are known. The optimization algorithm is based on surrogate models and is here applied to optimize the design of a diesel combustion engine.
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| 3. |
- Bagloee, S. A., et al.
(författare)
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A Mixed User-Equilibrium and System-Optimal Traffic Flow for Connected Vehicles Stated as a Complementarity Problem
- 2017
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Ingår i: Computer-Aided Civil and Infrastructure Engineering. - : Wiley. - 1093-9687 .- 1467-8667. ; 32:7, s. 562-580
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Tidskriftsartikel (refereegranskat)abstract
- Connected vehicles (CVs), be they autonomous vehicles or a fleet of cargo carriers or Uber, are a matter of when they become a reality and not if. It is not unreasonable to think that CV technology may have a far-reaching impact, even to the genesis of a completely new traffic pattern. To this end, the literature has yet to address the routing behavior of the CVs, namely traffic assignment problem (TAP) (perhaps it is assumed, they ought to follow the traditional shortest possible paths, known as user equilibrium [UE]). It is possible that real-time data could be derived from the vehicles' communications that in turn could be used to achieve a better traffic circulation. In this article, we propose a mathematical formulation to ensure the CVs are seeking the system optimal (SO) principles, while the remainder continue to pursue the old-fashioned UE pattern. The model is formulated as a nonlinear complementarity problem (NCP). This article contributes to the literature in three distinct ways: (i) mathematical formulation for the CVs' routing, stated as a mixed UE-SO traffic pattern, is proposed; (ii) a variety of realistic features are explicitly considered in the solution to the TAP including road capacity, elastic demand, multiclass and asymmetric travel time; and (iii) formal proof of the existence and uniqueness of the solutions are also presented. The proposed methodology is applied to the networks of Sioux-Falls and Melbourne.
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| 4. |
- Bagloee, S. A., et al.
(författare)
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Minimization of water pumps' electricity usage: A hybrid approach of regression models with optimization
- 2018
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Ingår i: Expert Systems with Applications. - : Elsevier BV. - 0957-4174. ; 107, s. 222-242
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Tidskriftsartikel (refereegranskat)abstract
- Due to pervasive deployment of electricity-propelled water-pumps, water distribution systems (WDSs) are energy-intensive technologies which are largely operated and controlled by engineers based on their judgments and discretions. Hence energy efficiency in the water sector is a serious concern. To this end, this study is dedicated to the optimal operation of the WDS which is articulated as minimization of the pumps' energy consumption while maintaining flow, pressure, and tank water levels at a minimum level, also known as pump scheduling problem (PSP). This problem is proved to be NP-hard (i.e. a difficult problem computationally). We therefore develop a hybrid methodology incorporating machine-learning techniques as well as optimization methods to address real-life and large-sized WDSs. Other main contributions of this research are (i) in addition to fixed-speed pumps, the variable-speed pumps are optimally controlled, (ii) and operational rules such as water allocation rules can also be explicitly considered in the methodology. This methodology is tested using a large dataset in which the results are found to be highly promising. This methodology has been coded as a user-friendly software composed of MS-Excel (as a user interface), MS-Access (a database), MATLAB (for machine-learning), GAMS (with CPLEX solver for solving optimization problem) and EPANET (to solve hydraulic models). (C) 2018 Elsevier Ltd. All rights reserved.
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| 5. |
- Bagloee, S.A., et al.
(författare)
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Minimization of water pumps' electricity usage: a machine-learning approach
- 2017
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Due to pervasive deployment of electricity-propelled water-pumps, water distribution systems (WDSs) are energy-intensive technologies which are largely operated and controlled by engineers based on their judgments and discretions. Hence energy efficiency in the water sector is a serious concern. To this end, this study is dedicated to the optimal operation of the WDS which is articulated as minimization of the pumps’ energy consumption while maintaining flow, pressure, and tank water levels at a minimum level, also known as pump scheduling problem (PSP). This problem is proved to be of the most difficult problem (namely NP-hard). To this end, we develop a hybrid methodology consists of machine learning techniques as well as optimization methods, that is to address real life and large sized WDSs. Other main contributions of this research are (i) also, variable speed pumps can be modeled and optimally controlled, (ii) operational rules such as water allocation rules can also be explicitly considered in the methodology. This methodology is tested using a large sized dataset in which the results are found to be highly promising. This methodology has been coded as a user-friendly software composed of MS-Excel (as a user interface), MS-Access (a database), MATLAB (for machine learning), GAMS (with CPLEX solver for solving optimization problem) and EPANET (to solve hydraulic models).
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| 6. |
- Evgrafov, A., et al.
(författare)
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Stochastic structural topology optimization : Existence of solutions and sensitivity analyses
- 2003
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Ingår i: Zeitschrift für angewandte Mathematik und Mechanik. - : Wiley. - 0044-2267 .- 1521-4001. ; 83:7, s. 479-492
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Tidskriftsartikel (refereegranskat)abstract
- We consider structural topology optimization problems including unilateral constraints arising from, for example, non-penetration conditions in contact mechanics or non-compression conditions for elastic ropes. To construct more realistic models and to hedge off possible failures or an inefficient behaviour of optimal structures, we allow parameters (for example, loads) defining the problem to be stochastic. The resulting nonsmooth stochastic optimization problem is an instance of stochastic mathematical programs with equilibrium constraints (SMPEC), or stochastic bilevel programs. The existence as well as the continuity of optimal solutions with respect to the lower bounds on the design variables are established. The question of continuity of the optimal solutions with respect to small changes in the probability measure is analysed. For a subclass of the problems considered the answer is affirmative, thus establishing the robustness of optimal solutions. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.
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| 10. |
- Patriksson, Alexandra, et al.
(författare)
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A direct comparison of protein structure in the gas and solution phase - the Trp-cage
- 2007
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 111:46, s. 13147-13150
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics simulations of zwitterions of the Trp-cage protein in the gas phase show that the most stable ion in vacuo has preserved the charge locations acquired in solution. A direct comparison of the gas and solution-phase structures reveals that, despite the similarity in charge location, there is significant difference in the structures, with a substantial increase in hydrogen bonds and exposure of hydrophobic parts in the gas phase. The structure of the salt bridge in the gas phase is also much more stable than in the (experimental) solution structure.
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