The efficiency of adopting lamination parameters as design variables for the reliability-based optimization of a laminated composite plate subject to in-plane loads is presented. The plate failure is evaluated by the ...
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The efficiency of adopting lamination parameters as design variables for the reliability-based optimization of a laminated composite plate subject to in-plane loads is presented. The plate failure is evaluated by the first-ply failure (FPF) criterion, where the ply failure is evaluated based on the Tsai-Wu criterion. According to the FPF criterion, the laminated plate is modeled as a series system consisting of every ply failure. The system reliability of the composite plate is evaluated by Ditlevsen's bounds. Each ply-failure probability is evaluated by the first-order reliability method, where the material properties and applied loads are treated as random variables. As numerical examples, two types of the reliability-based design are formulated in terms of lamination parameters. One is the reliability-maximized design of the constant-thickness plate. The other is the thickness-minimized design under the reliability constraint. Through numerical calculations, it is shown that the reliability has a single peak and a continuous distribution in the lamination parameter space. Consequently, numerical searching rapidly achieves the optimum solution.
A simple vortex-imaging algorithm using a least-square method is considered. The position and the circulation of a vortex convected in a channel are identified from the time history of pressure at a limited number of ...
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A simple vortex-imaging algorithm using a least-square method is considered. The position and the circulation of a vortex convected in a channel are identified from the time history of pressure at a limited number of points on the wall. The capabilities of the algorithm are demonstrated using two-dimensional direct numerical simulations. A few observer points on one side of the wall are sufficient to detect the position and the circulation of a compact vortex to a reasonable degree of accuracy. An advanced algorithm can even detect two nearby vortices to the same degree of accuracy. Because the algorithm assumes a point vortex solution, the accuracy of the detection deteriorates as the vorticity distribution spreads.
An algorithm on PMD pulse-width compression is proposed. The new algorithm is more efficient than some recent result and is guaranteed to be globally convergent. Also all iteration points are feasible Jones vectors. T...
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An algorithm on PMD pulse-width compression is proposed. The new algorithm is more efficient than some recent result and is guaranteed to be globally convergent. Also all iteration points are feasible Jones vectors. These properties are important since in many situations, PMD control needs to be implemented in real time.
Despite full correction of the corneal astigmatism with toric intraocular lenses, the retinal image is distorted and the lateral image-object magnification is different in different meridians. The purpose of this stud...
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Despite full correction of the corneal astigmatism with toric intraocular lenses, the retinal image is distorted and the lateral image-object magnification is different in different meridians. The purpose of this study is to describe an iteration strategy for tracing an axial pencil of rays through the 'optical system eye' containing astigmatic refractive surfaces with their axes at random to calculate a thick bitoric lens implant which eliminates image distortion. The capabilities of this computing scheme are demonstrated with two clinical examples. We present a mathematically straightforward computer-based strategy for the calculation of thick bitoric eikonic lens implants. The iteration algorithm is initialized with a spherical front and a toric back surface and stepwise decreases the image distortion by adding cylinder lenses to the front lens surface corrected by the toric lens back surface. Total magnification can be modulated by varying the front-to-back surface power of the thick lens.
An aperiodic two-dimensional diffractive optical element (DOE) with subwavelength features as an uniform beam shaper which shapes an input laser beam into an uniform intensity distribution in an observation plane has ...
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ISBN:
(纸本)0819450480
An aperiodic two-dimensional diffractive optical element (DOE) with subwavelength features as an uniform beam shaper which shapes an input laser beam into an uniform intensity distribution in an observation plane has been designed. A rigorous design method combined an iterative optimization algorithm with a rigorous electromagnetic computation --- the finite-difference time-domain (FDTD) method has been proposed. The design method and the FDTD method have been discussed in detail. The simulated results have shown that the DOE designed by this rigorous method can produce an uniform field distribution with flat-top, steep edge and low profile error in an observation plane.
As part of a continuing effort to construct "synthetic velocity" subgrid-scale (SGS) models for large-eddy simulation (LES) techniques utilizing Kolmogorov scaling and discrete dynamic systems (chaotic maps)...
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As part of a continuing effort to construct "synthetic velocity" subgrid-scale (SGS) models for large-eddy simulation (LES) techniques utilizing Kolmogorov scaling and discrete dynamic systems (chaotic maps), focus is centered on constructing the chaotic maps from experimental data to demonstrate consistency of the modeling approach with basic physics. Although such efforts have been made previously, all of them used a linear combination of logistic maps to fit one-dimensional experimental data. A two-dimensional chaotic map derived directly from the Navier-Stokes equations is employed, and the bifurcation parameters of this map are determined to best fit two-dimensional experimental velocity data. A genetic algorithm is used as the optimization tool to obtain the required least-squares fit of the time series for a point in a two-dimensional flow behind a turbulator. Results compare reasonably well with the experimental time series, implying that two-dimensional chaotic maps provide viable candidates for producing temporal fluctuations in synthetic-velocity SGS models for LES and additionally as part of real-time control mechanisms.
A methodology whereby the optimal set of design tolerances is assigned to the dimensions of a general mechanical assembly, is developed and tested. The manufacturing cost is minimized, while the design is constrained ...
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A methodology whereby the optimal set of design tolerances is assigned to the dimensions of a general mechanical assembly, is developed and tested. The manufacturing cost is minimized, while the design is constrained to a specified probability of meeting functional requirements, called the yield of the design. An analytical relationship for the assembly yield surface is generally unknown, and use is made of response surface approximations in the optimization algorithm. Yield values are determined at design space points through Monte Carlo simulations, seen as the response surface experiments. The methodology is benchmarked on example problems from the literature, and the optimum compares superior to published results.
A new methodology is developed to find the optimal aerodynamic performance of a turbine cascade. A boundary-layer coupled Euler algorithm and a genetic algorithm are linked within an automated optimization loop. The m...
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A new methodology is developed to find the optimal aerodynamic performance of a turbine cascade. A boundary-layer coupled Euler algorithm and a genetic algorithm are linked within an automated optimization loop. The multiparameter objective function is based on the blade loading. For a given inlet Mach number and baseline cascade geometry, the flow inlet and exit angles, the blade thickness and the solidity are optimized by a robust genetic algorithm. First, the Sanz subcritical turbine cascade is selected as the baseline cascade and is used for How solver validation. Second, the baseline cascade parameters are modified to yield the maximum tangential blade force. Finally, the effects of different crossover techniques, random number seeds, and population sizes on the performance of the genetic algorithm are studied. It is shown that the maximum blade loading is achieved for a higher flow turning, a wider pitch, and a thicker cascade.
A coevolutionary architecture for distributed optimization of complex coupled systems is presented. This architecture is inspired by the phenomena of coevolutionary adaptation occurring in ecological systems. The focu...
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A coevolutionary architecture for distributed optimization of complex coupled systems is presented. This architecture is inspired by the phenomena of coevolutionary adaptation occurring in ecological systems. The focus of this research is to develop flexible design architectures for addressing the organizational and computational challenges involved in optimization of large-scale multidisciplinary systems. In the proposed design architecture the optimization procedure is modeled as the process of coadaptation between sympatric species in an ecosystem. Each species is entrusted with the task of improving subdomain specific objectives and the satisfaction of subdomain constraints. Coupling compatibility constraints are accommodated via implicit generalized Jacobi iteration, which enables the application of the proposed architecture to systems with arbitrary coupling bandwidth between the disciplines, without an increase in the problem size. A domain decomposition approach is presented for distributed structural optimization to construct a class of test problems. Numerical studies are presented to demonstrate that convergence to an optimal solution satisfying the subdomain and coupling compatibility constraints can be readily achieved.
An optimization algorithm is proposed for choosing the parameters of a Fourier flat-top interleaver. The requirement for identical response in both the bar and cross states requires that the intensity coupling ratio f...
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An optimization algorithm is proposed for choosing the parameters of a Fourier flat-top interleaver. The requirement for identical response in both the bar and cross states requires that the intensity coupling ratio for the first coupler must be 1:1. The second and third couplers will depend on the linewidth of each channel. Calculations for typical situations are carried out and the insertion loss for input spectra of different linewidths are also investigated for an interleaver optimized for a typical application. (C) 2002 Society of Photo-Optical Instrumentation Engineers.
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