بایگانی برچسب برای: Optimization

Real-time railway traffic management optimization[taliem.ir]

Real-time railway traffic management optimization and imperfect information: preliminary studies

Railway traffic is often perturbed by unexpected events and appropriate train routing and scheduling shall be applied to minimize delay propagation. A number algorithms for this routing and scheduling problem have been proposed in the literature and they have been tested in different traffic situations. Nonetheless, their performance are almost always studied considering perfect knowledge of future traffic conditions, which is almost impossible to achieve in reality. In this paper, we propose an experimental analysis assessing the usefulness of these algorithms in case of imperfect information. We consider RECIFE-MILP as a traffic management algorithm and advanced or delayed train entrance times in the control area as the source of imperfect information. The results show that the application of traffic management optimization allows outperforming the firstcome-first-served management strategy even if the actual traffic conditions are not perfectly known by the optimization algorithm.
Optimal Roadside Units Placement in Urban Areas for Vehicular Networks[taliem.ir]

Optimal Roadside Units Placement in Urban Areas for Vehicular Networks

The most important component of a vehicular ad hoc network (VANET), besides VANET-enabled vehicles, is roadside units (RSUs). The effectiveness of a VANET largely depends on the density and location of these RSUs. During the initial stages of VANET, it will not be possible to deploy a large number of RSUs either due to the low market penetration of VANET-enabled vehicles or due to the deployment cost of RSUs. There is, therefore, a need to optimally place a limited number of RSUs in a given region in order to achieve maximum performance. In this paper, we present two different optimization methods for placement of a limited number of RSUs in an urban region: an analytical Binary Integer Programming (BIP) method and a novel Balloon Expansion Heuristic (BEH) method. BIP method utilizes branch and bound approach to find an optimal analytical solution whereas BEH method uses balloon expansion analogy to find an optimal or near optimal solution. Our evaluations show that both methods perform optimally or near optimally compared with the exhaustive method. Further, BEH method is more versatile and performs better than BIP method in terms of computational cost and scalability.
Unit commitment by dynamic programming for[taliem.ir]

Unit commitment by dynamic programming for microgrid operational planning optimization and emission reduction

This paper presents a 24 hour ahead microgrid power planning using the approach of unit commitment by dynamic programming. The studied system comprises twelve PVbased active generators with embedded storage and three micro gas turbines. Based on the prediction of the energy available from the PV generator, the storage availability, the micro turbine emission characteristics and the load prediction, a central energy management system calculates a 24-hour ahead plan of the power references for three micro gas turbines and the active generators in order to minimize the CO2 equivalent emissions of the gas turbines.
Optimized Design Considering the Mass Influence of an Axial[taliem.ir]

Optimized Design Considering the Mass Influence of an Axial Flux Permanent-Magnet Synchronous Generator With Concentrated Pole Windings

In this paper, the efficiency optimization of an axial flux permanent-magnet synchronous generator with concentrated pole windings is examined for a 3.6 kW/2000 rpm combined heat and power application. Because the efficiency of the machine is important, specific measures are taken in order to reduce losses in the machine: thin laminated grain oriented material in the teeth, concentrated pole windings, and segmented magnets. A study of the influence of a limited set of geometry parameters on the efficiency of this type of machine is done, using both analytical and finite-element methods. In the analytical as well as in the finite- element model, the inherent 3-D geometry of the axial flux machine is approximated by multiple 2-D models at different radii in circumferential direction. Afterwards, the influence of mass on the optimal values of the geometry parameters and the efficiency is considered, and it is found that mass can be seriously decreased with only a small reduction in efficiency. Finally, the results of both methods are compared with measurements on a prototype to evaluate their validity.
Optimizing the durability and service life of self-consolidating concrete[taliem.ir]

Optimizing the durability and service life of self-consolidating concrete containing metakaolin using statistical analysis

This paper utilizes the statistical design of experiments approach to optimize the mixture design of selfconsolidating concrete (SCC) incorporating metakaolin (MK). The factors studied were total binder content, percentage of MK, water-to-binder ratio, and curing conditions. The results obtained from the developed statistical models were exploited to determine the most significant factors affecting the chloride permeability and the expected service life (calculated using Fick’s second law of diffusion) of the tested mixtures. The developed models were also used to optimize the level of each response variable to minimize the chloride permeability, and to maximize the expected service life of the developed high performance SCC mixture. The results yielded an optimum SCC mixture with MK which achieved the lowest chloride permeability compared to counterpart SCC mixtures containing fly ash, slag, and silica fume. The results also showed that MK replacement proved to be the most significant variable affecting the chloride permeability, decline of permeability over time, and the service life of the tested mixtures
A model for concurrent maintenance of bridge elements[taliem.ir]

A model for concurrent maintenance of bridge elements

Maintenance activities on existing bridges are important for bridge safety and management. However, maintenance activities cause traffic jams and detours, and thus increase user costs. To reduce user costs resulting from maintenance activities while maintaining bridge elements in good condition, we introduce the concept of “concurrent element maintenance.” The concurrent maintenance concept attempts to integrate maintenance timings of different elements of a bridge to reduce user costs over the bridge's life cycle. The proposed model adopts constraint programming as the search algorithm for optimizing the maintenance strategy of any bridge .An example using real data for a reinforced concrete highway bridge is presented. Sensitivity analysis of the discount rate investigates its influence on the life-cycle cost. The results demonstrate that the proposed model is effective for reducing the user costs as well as the total life-cycle costs