Wireless mesh network (WMN) is a promising solution for last mile broadband internet access. Mesh nodes or mesh routers are connected via wireless links to form a multi-hop backbone infrastructure and improving throug...
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Wireless mesh network (WMN) is a promising solution for last mile broadband internet access. Mesh nodes or mesh routers are connected via wireless links to form a multi-hop backbone infrastructure and improving throughput is the primary goal. While previous works mainly focused on either link level protocol design or complex mathematical model, in this paper, we investigate the performance gains from jointly optimizing scheduling and routing in a multi-radio, multi-channel and multi-hop wireless mesh network. Then, two optimization objectives are addressed by considering wireless media contention and spatial multiplexing. The first objective is to maximize throughput by exploiting spatial reuse while the second one is to ensure fairness among different links. We design a cross-layer algorithm by considering both MAC layer and network layer. Simulation results show that our joint optimization algorithm can significantly increase throughput as well as fairness. (c) 2011 Elsevier Ltd. All rights reserved.
The paper is focused on decreasing the computational cost of direct statistical modelling for solving the nonlinear Boltzmann equation using the theory of Poisson ensembles. A modification of the method of majorant fr...
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The paper is focused on decreasing the computational cost of direct statistical modelling for solving the nonlinear Boltzmann equation using the theory of Poisson ensembles. A modification of the method of majorant frequency is constructed on this base to simulate the free run of a many-particle system. An optimization of the algorithm of global piecewise-constant solution estimation is applied with respect to the mean-square metric.
In power systems, dynamic economic dispatch (DED) is one of the most significant non-linear problems showing non-convex characteristic because of the valve-point effects. In this study, an enhanced adaptive particle s...
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In power systems, dynamic economic dispatch (DED) is one of the most significant non-linear problems showing non-convex characteristic because of the valve-point effects. In this study, an enhanced adaptive particle swarm optimisation (EAPSO) algorithm is proposed to solve the DED problem where the valve-point effects, ramp-rate limits and transmission power losses are taken into account. In the proposed optimisation algorithm, a mutation technique is devised to prevent premature phenomena and lead the swarm search space much more effectively;also a novel non-linear approach is designed to adjust the inertia weight factor dynamically according to the optimisation process performance. Social and cognitive factors are self-adaptively tuned, so the swarm can search the space smartly for global optimum solution. The efficiency of the proposed method is validated on three popular test systems in the area including 5, 10 and 30 thermal units. The results are compared with most of the other works in the area. The superiority of the method is shown over earlier methods.
This paper discusses a new constitutive model called the high-rate brittle microplane (HRBM) model and also presents the details of a new software package called the Virtual Materials Laboratory (VML). The VML softwar...
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This paper discusses a new constitutive model called the high-rate brittle microplane (HRBM) model and also presents the details of a new software package called the Virtual Materials Laboratory (VML). The VML software package was developed to address the challenges of Fitting complex material models such as the HRBM model to material property test data and to study the behavior of those models under a wide variety of stress- and strain-paths. VML employs Continuous Evolutionary algorithms (CEA) in conjunction with gradient search methods to create automatic fitting algorithms to determine constitutive model parameters. The VML code is used to fit the new HRBM model to a well-characterized conventional strength concrete called WES5000. Finally, the ability of the new HRBM model to provide high-fidelity simulations of material property experiments is demonstrated by comparing HRBM simulations to laboratory material property data.
We discuss two nonsmooth functions on R-n introduced by Nesterov. We show that the first variant is partly smooth in the sense of Lewis and that its only stationary point is the global minimizer. In contrast, we show ...
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We discuss two nonsmooth functions on R-n introduced by Nesterov. We show that the first variant is partly smooth in the sense of Lewis and that its only stationary point is the global minimizer. In contrast, we show that the second variant has 2(n-1) Clarke stationary points, none of them local minimizers except the global minimizer, but also that its only Mordukhovich stationary point is the global minimizer. Nonsmooth optimization algorithms from multiple starting points generate iterates that approximate all 2(n-1) Clarke stationary points, not only the global minimizer, but it remains an open question as to whether the nonminimizing Clarke stationary points are actually points of attraction for optimization algorithms. Published by Elsevier Ltd
The early aim of the automatic generation control is to regulate the power output of the electrical generator within a prescribed area in response to changes in system frequency, tie-line loading, so as to maintain th...
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The early aim of the automatic generation control is to regulate the power output of the electrical generator within a prescribed area in response to changes in system frequency, tie-line loading, so as to maintain the scheduled system frequency and interchange with the other areas with predetermined limits. The purpose of this study is to propose a PID optimised by the lozi map-based chaotic algorithm (LCOA) to solve the load-frequency control (LFC) problem. The PIDs tuned by the LCOA are used in each area for a two-area power system. The simulation results are used to demonstrate the effectiveness and performance of the proposed controller. It is shown that optimised PID is able to solve the LFC problem and also the performance of the system in each area is satisfactory. In addition, a comparative study is carried out between the results obtained from PID tuned by the LCOA and the other optimisation algorithms.
This paper concerns about energy-efficient broadcasts in mobile ad hoc networks, yet in a model where each station moves on the plane with uniform rectilinear motion. Such restriction is imposed to discern which issue...
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This paper concerns about energy-efficient broadcasts in mobile ad hoc networks, yet in a model where each station moves on the plane with uniform rectilinear motion. Such restriction is imposed to discern which issues arise from the introduction of movement in the wireless ad hoc networks. Given a transmission range assignment for a set of n stations S, we provide an polynomial O(n (2))-time algorithm to decide whether a broadcast operation from a source station could be performed or not. Additionally, we study the problem of computing a transmission range assignment for S that minimizes the energy required in a broadcast operation. An O(n (3)log n)-time algorithm for this problem is presented, under the assumption that all stations have equally sized transmission ranges. However, we prove that the general version of such problem is NP-hard and not approximable within a (1-o(1))ln n factor (unless NPaS,DTIME(n (O(log log n)))). We then propose a polynomial time approximation algorithm for a restricted version of that problem.
A multi-objective design optimisation for double primary and secondary winding transformers is presented in the study, with the aim to minimise the deviation between the prescribed and designed short-circuit impedance...
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A multi-objective design optimisation for double primary and secondary winding transformers is presented in the study, with the aim to minimise the deviation between the prescribed and designed short-circuit impedance values. The optimisation process involves the exploitation of the results of an efficient and experimentally validated finite element model for leakage field prediction by the Taguchi method. The model is used in conjunction with evolutionary stochastic and deterministic optimisation algorithms in order to derive the optimal winding configuration that meets the technical requirements for the compound multi-winding short-circuit impedance target value.
As the complexity and amount of medical information keeps increasing, it is difficult to maintain the same quality of care. Therefore, clinical guidelines are used to structure best practices and care, but they also s...
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As the complexity and amount of medical information keeps increasing, it is difficult to maintain the same quality of care. Therefore, clinical guidelines are used to structure best practices and care, but they also support physicians and nurses in the diagnostic and treatment process. Currently, no standardized format exists to represent these guidelines. Translating guidelines into a computer interpretable format can overcome problems in the physicians' workflow and improve clinician's uptake. An engine is proposed to automatically translate and execute clinical guidelines. These guidelines are represented as flowcharts, expressed in either (i) a computer interpretable guideline format or (ii) a UML diagram. A detailed overview of the architecture is presented and algorithms, aiming at grouping several components and distributing the guidelines, are proposed to optimize the execution of the guidelines. The Modified Schofield guideline for the calculation of the calorie need for burn patients was used for evaluation. Results show that the execution of guidelines using the engine is very efficient. Using optimization algorithms the execution times can be lowered. (C) 2012 Elsevier Ltd. All rights reserved.
This research describes a prototype software navigation system that would allow a spacecraft with a small amount of continuous propulsion to navigate low-energy trajectories. First, the desired route is described in t...
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This research describes a prototype software navigation system that would allow a spacecraft with a small amount of continuous propulsion to navigate low-energy trajectories. First, the desired route is described in terms of basic orbit shapes, such as Lyapunov orbits. This sequence of orbit shapes is converted into an itinerary of spatial boundaries that a spacecraft executing the low-energy maneuver will cross in order. A software system then employs a guided optimization algorithm that identifies the thrust angle that will maintain the desired orbit. Using this software as a research tool, simulations have identified low-energy paths that could be used by a spacecraft with an ion drive to perform a Venus flyby within four or five years of its launch from Earth. This approach makes it possible to identify complex low-energy trajectories that rely on the gravitational elTects of different two-body systems (for instance, Earth moon and Earth sun) and to study the utility of continuous propulsion in flying such trajectories from Earth.
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