Immune evolutionary algorithm is proposed based on the evolutionary principle in the immune system. In the algorithm, two new parameters of expansion radius and mutation radius are defined to construct a small neighbo...
详细信息
ISBN:
(纸本)0780378652
Immune evolutionary algorithm is proposed based on the evolutionary principle in the immune system. In the algorithm, two new parameters of expansion radius and mutation radius are defined to construct a small neighborhood and a large neighborhood. Then expansion and mutation operations are designed to perform local and global search respectively by using the two neighborhoods, thus, two-level neighborhood search mechanism is realized. The results of multi-modal function optimization show that the algorithm has nice global and local searching performances. The algorithm is employed to design a neuro-fuzzy controller for real-time control of an inverted pendulum. In order to avoid the combinatorial explosion of fuzzy rules due to multivariable inputs, state variable synthesis scheme is suggested to reduce the number of fuzzy rules. Experimental results show that the designed controller can control actual inverted pendulum successfully.
When Simulated Annealng (SA) is applied to continuous optimization problems, the design of the neighborhood used in SA becomes important. Many experiments are necessary to determine an appropriate neighborhood range i...
详细信息
ISBN:
(纸本)9781424400225
When Simulated Annealng (SA) is applied to continuous optimization problems, the design of the neighborhood used in SA becomes important. Many experiments are necessary to determine an appropriate neighborhood range in each problem, because the neighborhood range corresponds to distance in Euclidean space and is decided arbitrarily. We propose Multi-point Simulated Annealing with Adaptive Neighborhood (MSA/AN) for continuous optimization problems, which determines the appropriate neighborhood range automatically. The proposed method provides a neighborhood range from the distance and the design variables of two search points, and generates candidate solutions using a probability distribution based on this distance in the neighborhood, and selects the next solutions from them based on the energy. In addition, a new acceptance judgment is proposed for multi-point SA based on the Metropolis criterion. The proposed method shows good performance in solving typical test problems.
Design optimization using high-fidelity computational fluid dynamics simulations is becoming increasingly popular, sustaining the desire to make these methods more computationally efficient. A reduction in problem dim...
详细信息
Design optimization using high-fidelity computational fluid dynamics simulations is becoming increasingly popular, sustaining the desire to make these methods more computationally efficient. A reduction in problem dimensions as a result of improved parameterization techniques is a common contributor to this efficiency. The focus of this paper is on the high-fidelity aerodynamic design of airfoil shapes. A multifidelity design search method is presented which uses a parameterization of the airfoil pressure distribution followed by inverse design, giving a reduction in the number of design variables used in optimization. Although an expensive analysis code is used in evaluating airfoil performance, computational cost is reduced by using a low-fidelity code in the inverse design process. This method is run side by side with a method which is considered to be a current benchmark in design optimization. The two methods are described in detail, and their relative performance is compared and discussed. The newly presented method is found to converge towards the optimum design significantly more quickly than the benchmark method, providing designs with greater performance for a given computational expense.
This paper investigates the ability of the largest producer in an electricity market to manipulate both the electricity and emission allowances markets to its advantage. A Stackelberg game to analyze this situation is...
详细信息
This paper investigates the ability of the largest producer in an electricity market to manipulate both the electricity and emission allowances markets to its advantage. A Stackelberg game to analyze this situation is constructed in which the largest firm plays the role of the leader, while the medium-sized firms are treated as Cournot followers with price-taking fringes that behave competitively in both markets. Since there is no explicit representation of the best-reply function for each follower, this Stackelberg game is formulated as a large-scale mathematical program with equilibrium constraints. The best-reply functions are implicitly represented by a set of nonlinear complementarity conditions. Analysis of the computed solution for the Pennsylvania-New Jersey-Maryland electricity market shows that the leader can gain substantial profits by withholding allowances and driving up NOx allowance costs for rival producers. The allowances price is higher than the corresponding price in the Nash-Cournot case, although the electricity prices are essentially the same.
Power consumption has gained much saliency in circuit design recently. One design problem is modelled as "Under a timing constraint, to minimize power as much as possible". Previous research regarding this p...
详细信息
ISBN:
(纸本)0780394518
Power consumption has gained much saliency in circuit design recently. One design problem is modelled as "Under a timing constraint, to minimize power as much as possible". Previous research regarding this problem focused on either minimizing dynamic power by gate sizing, or reducing leakage power by dual threshold voltage assignment on non-critical path. However, given a timing constraint, an optimization algorithm must be able to utilize gate sizing and threshold-voltage assignment interchangeably, in order to minimize total power consumption including dynamic and leakage power in active mode and leakage power in idle mode. We find that switching-activity of a gate plays an important role in making decision as to choosing gate sizing or threshold-voltage assignment for performance improvement. For high switching-activity gates, threshold-voltage assignment should be used while for low switching-activity gates, gate sizing should be utilized. We develop an algorithm to perform gate sizing and threshold-voltage assignment simultaneously taking switching activity into consideration. The results show that under the same timing constraint, our circuits have 16.26%, and 18.53%, improvement of total power as compared to the original circuits for the cases where the percentage of active time are 100%, and 50%, respectively.
A hybrid trajectory optimization procedure for a class of solar-electric-propulsion, gravity-assist, outer-planet missions is presented. The parameter space of a target mission is often nonconvex and a calculus-of-var...
详细信息
A hybrid trajectory optimization procedure for a class of solar-electric-propulsion, gravity-assist, outer-planet missions is presented. The parameter space of a target mission is often nonconvex and a calculus-of-variations-based optimization algorithm suffers difficulties efficiently exploring this space. A hybrid procedure using a genetic algorithm to drive a calculus-of-variations program is developed to automate searching over a reduced parameter space. Employing the hybrid procedure, the delivered mass profiles of a Uranus and Pluto mission are generated more quickly than by using the calculus-of-variations optimization algorithm alone.
The solution of the minimum-state (MS) approximation of the unsteady aerodynamic forces is brought in this work into the form of a nonlinear optimization problem. This new formulation takes as design variables all of ...
详细信息
The solution of the minimum-state (MS) approximation of the unsteady aerodynamic forces is brought in this work into the form of a nonlinear optimization problem. This new formulation takes as design variables all of the aerodynamic lag terms (known also as aerodynamic roots) as well as the two matrices that directly operate on these lag terms. This new formulation enables the explicit determination of the remaining matrices that form the MS approximation, and it does not require enforcing any equality constraints. Furthermore, it also permits the derivation of simple analytical expressions for the gradients of the least-square (LS)-type objective function. This combination of explicit expressions for both the gradients and some of the unknown matrices leads to a dramatic reduction in computational labor. It is also shown that by appropriately scaling the tabulated aerodynamic matrix a significantly accelerated rate of convergence is obtained during the process of optimization, whereas a general weighting scheme might considerably slow down this convergence. It is also shown that the preceding scaling of the tabulated aerodynamic matrix can also significantly reduce the computational labor required by current methods of solution that are based on iterative LS analysis. The new formulation presented in this work leads to better results (i.e., lower values for the objective function) than those obtained using current iterative LS-based methods that use preassumed values for the aerodynamic lag terms. At the same time, the computer CPU time required by these two methods of solution is of the same order, with only slightly higher CPU values needed for the new formulation. On the other hand, current methods based on iterative LS analysis that attempt to optimize the aerodynamic roots rather than use preassumed values need extensive added computational labor to the extent that makes them practically unattractive.
In this paper,a new fast mode-selection ap-proach is *** algorithm combines the proposed approaches of mode pre-decision and precise large-small mode decision,by selecting the best mode ***-perimental results show tha...
详细信息
In this paper,a new fast mode-selection ap-proach is *** algorithm combines the proposed approaches of mode pre-decision and precise large-small mode decision,by selecting the best mode ***-perimental results show that the proposed approach can re-duce the computational cost of full search and fast multi-block motion estimation by 80%and 45%,respec-tively,with similar visual quality and bit *** proposed algorithm also reduces by 75%the computational cost of the large-small mode isolation algorithm for low-motion sequence coding,and with 0.06 PSNR gain and 3.7%re-duction in bit rate.
A real-time optimization controller is developed to steer a linear time-varying control system to closed-loop trajectories that optimize a cost functional of interest. When advantage is taken of the differential flatn...
详细信息
A real-time optimization controller is developed to steer a linear time-varying control system to closed-loop trajectories that optimize a cost functional of interest. When advantage is taken of the differential flatness of the linear systems, a basis function approach is used to parameterize the open-loop trajectories of the system and to approximate the optimal solution of the finite time optimal control problem. An adaptive optimization method is used to formulate the real-time optimization scheme. The problem is posed as a real-time optimal trajectory generation problem in which the approximate optimal trajectories are computed using an extremum-seeking approach. The control algorithm provides tracking of the approximate optimal trajectories. Two optimal control problems are considered to demonstrate the application of the technique. It is shown that the technique can be successfully implemented in real time.
作者：
Li, WKrist, SCampbell, RNASA
Langley Res Ctr Aeronaut Syst Anal Branch Syst Anal Concept Directorate Hampton VA 23681 USA NASA
Langley Res Ctr Configurat Aerodynam Branch Res & Technol Directorate Hampton VA 23681 USA
A modified profile optimization method using a smoothest shape modification strategy (POSSEM) is developed for airfoil shape optimization in a preliminary design environment. POS EM is formulated to overcome two techn...
详细信息
A modified profile optimization method using a smoothest shape modification strategy (POSSEM) is developed for airfoil shape optimization in a preliminary design environment. POS EM is formulated to overcome two technical difficulties frequently encountered when conducting multipoint airfoil optimization within a high-resolution design space: the generation of undesirable optimal airfoil shapes and significant degradation in the off-design performance. To demonstrate the usefulness or POSSEM in a preliminary design environment, a design competition was conducted with the objective of improving a fairly well-designed baseline airfoil at four transonic flight conditions without incurring any off-design performance degradation. Independently, two designs were generated from the inverse design tool CDISC, while a third design was generated from POSSEM, using over 200 control points of a cubic B-spline curve representation of the airfoil as design variables for the shape optimization. Pros and cons of all of the airfoil designs are documented along with in-depth analyses of simulation results. The POSSEM design exhibits a fairly smooth curvature and no degradation in the off-design performance. Moreover, it has the lowest average drag at the design conditions among the three airfoil designs, as evaluated from each of three different flow solvers.
暂无评论