检索结果-内蒙古大学图书馆

Design minimization of noise in stiffened cylinders due to tonal external excitation

JOURNAL OF AIRCRAFT 1999年第3期36卷 563-570页

作者： Cunefare, KA Crane, SP Engelstad, SP Powell, EA Georgia Inst Technol George W Woodruff Sch Mech Engn Atlanta GA 30332 USA Lockheed Martin Aeronaut Syst Co Dept 73 C2 Marietta GA 30063 USA

A computational design tool was developed to perform a constrained optimization of the acoustic environment within a vibrating cylinder, incorporating finite element and boundary element methods, The tool comprises a UNIX shell script that coordinates an iterative design optimization process integrating a number of programs, the key components of which are MSC/NASTRAN for structural analyses, COMET/Acoustics for acoustic analyses, and CONMIN for nonlinear optimization. In addition to the structure and implementation of the tool, this paper presents the results of a number of trials of the tool applied to stiffened and unstiffened cylinders, considering different formulations of the objective function to be optimized, and for a constant frequency exterior monopole excitation. Models were constructed to investigate longitudinal vs circumferential variations in design properties as well. The results indicate that shell thickness variations tend to dominate interior acoustic response, as compared with stiffener variations. The results further indicate that longitudinal variation is more effective than circumferential variation. Effective longitudinal design variations include shell thickening toward the cylinder midplane or, equally effective, thinning toward the midplane, Effective circumferential designs exhibited periodic variation around the circumference.

关键词： Acoustics Nastran Boundary Element Method Sound Pressure Level MDO Aircraft Structures Structural Element Structural Modeling optimization algorithm Structural optimization

来源：评论

学校读者我要写书评

暂无评论

Optimal structural design based on self-similarity

引用

AIAA JOURNAL 1999年第1期37卷 110-117页

作者： Hanahara, K Tada, Y Kobe Univ Dept Syst & Comp Engn Kobe Hyogo 6578501 Japan

We discuss an application of self-similarity to structural systems from the view point of optimal design, A general recursive formulation that describes the state of a self-similar structure is provided. On the basis of the formulation, it is also shown that the optimization process can be formulated in a similar recursive manner. In this study the resource-based approach is adopted as the optimal design procedure;it is implemented based on the proposed recursive formulation, Minimum weight design of two-dimensional truss structures is conducted to demonstrate the feasibility of the proposed approach. The computational cost and the storage requirement are evaluated;the efficiency of the proposed recursive approach and suitability to the parallel computation are also discussed.

关键词： Structural Design Adaptive Truss Structural System Stiffness Matrices Parallel Computing Young's Modulus optimization algorithm Allowable Stress Structural Element

来源：评论

学校读者我要写书评

暂无评论

Digital audio codec based on the improveda* optimization algorithm of adaptive wavelets and dynamic bits allocation scheme

Digital audio codec based on the improved optimization algor...

引用

3rd International Conference on Signal Processing (ICSP 96)

作者： Xiong, XB Zhao, EY Department of Telecommunications Engineering Beijing University슠of Posts and슠Telecommunications

ISBN: (纸本)7505338900

This paper presents the idea ofa* optimization algorithm of adaptive wavelets that can improve the coding algorithm to decrease the computation complexity to ten percent of that presented in the paper[5]. The full optimization of adaptive wavelets is replaced by the new method, in which the optimization is divided into two cascaded steps. And the entropy-coding-based quantization of side information is adopted so that tile bit rate is significantly reduced because it accounts for a plenty of percent of bit costs. The bit rate can decrease about 15 percent of that presented ill paper [8] by taking the method. It also coordinates with psycho-acoustics model and dynamic bits allocation scheme to make the coding noise inaudible under the condition of the least bits cost.

关键词： digital communication codecs audio coding entropy codes quantisation (signal) adaptive signal processing wavelet transforms optimisation computational complexity digital audio codec optimization algorithm adaptive wavelets dynamic bit allocation coding algorithm computational complexity reduction entropy coding based quantization side information bit rate reduction psychoacoustics model coding noise bit costs

来源：评论

学校读者我要写书评

暂无评论

Neural network parameter extraction with application to flutter signals

引用

JOURNAL OF AIRCRAFT 1998年第1期35卷 165-168页

作者： Lee, BHK Wong, YS Natl Res Council Canada Expt Aerodynam & Aeroelast Grp Inst Aerosp Res Ottawa ON K1A 0R6 Canada Univ Alberta Dept Math Sci Edmonton AB T6G 2G1 Canada

Presents information on a study of aerospace engineering which provides a neural network parameter extraction to analyze flutter signals. Methodology of the study; Results and conclusions of the study.

关键词： Neural Networks Vortex Breakdown optimization algorithm Orthogonal Wavelets Nonlinear Systems Flight Testing Feedforward Adverse Pressure Gradient Steepest Descent Method Signal Processing

来源：评论

学校读者我要写书评

暂无评论

Experiences with automatic differentiation applied to a volume grid generation code

引用

JOURNAL OF AIRCRAFT 1998年第4期35卷 569-573页

作者： Bischof, CH Mauer, A Jones, WT Samareh, J Argonne Natl Lab Div Math & Comp Sci Argonne IL 60439 USA Comp Sci Corp Hampton VA 23666 USA

Automatic differentiation (AD) is a methodology for developing reliable sensitivity-enhanced versions of arbitrary computer programs with little human effort. As such, it can vastly accelerate the use of advanced simulation codes in a multidisciplinary design optimization context because the time for generating and verifying derivative codes is greatly reduced. The application of the recently developed automatic differentiation of C programs (ADIC) prototype tool for ANSI-C programs on the coordinate and sensitivity calculator for multidisciplinary design optimization multiblock three-dimensional volume grid generator are reported. The ADIC-generated code can easily be interfaced with Fortran derivative codes generated with the ADIFOR AD tool for Fortran 77 programs;thus providing efficient sensitivity-enhancement techniques for multilanguage, multidiscipline problems.

关键词： MDO Computer Programs Computing Wing Root High Speed Civil Transport Fuselages Source Transformation CFD Analysis Aeroplane optimization algorithm

来源：评论

学校读者我要写书评

暂无评论

A neural network approach to rapid thin film characterization

A neural network approach to rapid thin film characterizatio...

引用

Conference on Flatness, Roughness, and Discrete Defects Characterization for Computer Disks, Wafers, and Flat Panel Displays II

作者： Jakatdar, N Niu, XH Spanos, CJ Univ Calif Berkeley Dept Elect Engn & Comp Sci Berkeley CA 94720 USA

ISBN: (纸本)0819427144

A novel approach for thin film thickness and optical constant extraction from spectral reflectance data is presented here. This methodology combines the global minimization abilities of Adaptive Simulated Annealing with the high computational efficiency of Neural Networks to solve complex characterization problems in real time. The optical constants of many thin films such as Polysilicon are a function of the processing conditions and hence the real time measurement of these parameters could possibly be used in real time or run to run process control applications.

关键词： spectroscopic reflectometry Neural Networks Adaptive Simulated Annealing process control Forouhi-Bloomer optimization algorithm characteristic matrix photolithography thin films

来源：评论

学校读者我要写书评

暂无评论

Comparison ofa* optimization algorithms for aerodynamic shape design

引用

AIAA JOURNAL 1997年第8期35卷 1413-1415页

作者： Obayashi, S Tsukahara, T Tohoku University Sendai 980-77 Japan

Compares threea* optimization algorithms and evaluates their performance when applied to airfoil design. Gradient-based method; Simulated annealing; Genetic algorithm; Airfoild design using approximation method.

关键词： optimization algorithm Aerodynamic Performance Direct Numerical Simulation Laminar Boundary Layer Freestream Velocity Particle Image Velocimetry Search algorithm Convective Boundary Condition Navier Stokes Equations Energy Conservation

来源：评论

学校读者我要写书评

暂无评论

Periodic optimal cruise for a hypersonic vehicle with constraints

引用

JOURNAL OF SPACECRAFT AND ROCKETS 1997年第2期34卷 165-171页

作者： Chuang, CH Morimoto, H Georgia Institute of Technology Atlanta Georgia 30332-0150

A new approach is presented to solve periodic optimal control problems, As an application of the approach, fuel-optimal periodic control problems for a hypersonic vehicle are solved. The model of the vehicle was constructed by using numerical data and figures from available space plane literature. In particular, heating-rate and load-factor constraints are considered to make this model more realistic than other previous models. These constraints increase the difficulty in obtaining a numerical solution and also increase the sensitivity to the initial guess for convergence. By assuming the shape of an altitude profile as a sinusoidal function of range and by using a bang-bang thrust control, a suboptimal solution is obtained for the vehicle without any constraints. This suboptimal solution serves as a very good initial guess for the optimal solution generated by the minimizing-boundary-condition method. The optimal solution shows a fuel saving of 8.12 % over the steady-state cruise, with a maximum heating rate of 1202.4 W/cm(2), and with a maximum load factor of 8.27. Constraints for a heating rate and a load factor are then added to the problem. With a maximum heating rate of 400 W/cm(2), the fuel saving reduces to 2.45%. With a load factor of 7, the fuel saving does not change much from the nonconstrained solution, An optimal periodic-cruise solution with maximum heating rate of 1158.0 W/cm(2) and simultaneously with maximum load factor of 7 is also determined with a fuel saving of 8.09%.

关键词： Hypersonic Vehicles Transversality Condition Angle of Attack Aerodynamic Force Fuel Consumption Nonlinear Programming Lagrange Multipliers Dynamic Pressure Scramjet Engines optimization algorithm

来源：评论

学校读者我要写书评

暂无评论

Evaluation of practical solutions for onboard aircraft four-dimensional guidance

引用

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1997年第5期20卷 1052-1054页

作者： Hagelauer, P MoraCamino, F Laboratoire d’ Analyse et d’ Architecture des Systemes 31077 Toulouse France

A theoretical analysis of the time-constrained cruise optimization problem shows that existing solutions are based on two main assumptions. The first is to consider that the optimal speed profile can be approximated by the constant-cost-index (CI)-speed profile. The second is to consider that the altitude profile is frozen when a time constraint is introduced. A dynamic-programming-based approach shows that the optimization of the altitude-shift points can lead to additional fuel savings of several percent for particular time constaints. The constant-CI assumption is argued to be valid because the speed profiles generated by both approaches on identical altitude profiles lead to simlar total fuel burn. (AIAA)

关键词： Airbus A340 Trajectory optimization Mach Number Cruise Altitude optimization algorithm Nonlinear Feedback Aircraft Dynamics Fuel Consumption Computing Airspace

来源：评论

学校读者我要写书评

暂无评论

Minimum drag control allocation

引用

JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 1997年第1期20卷 190-193页

作者： Durham, WC Bolling, JG Bordignon, KA Virginia Polytechnic Institute and State University Blacksburg Virginia 24061

While direct control allocation constitutes a powerful approach to the solution of three-moment multiple-control problems, it is here shown that it can be straightforwardly modified to account for a larger, four-objective multiple control problem. Drag is considered as the fourth objective, which the allocation was instructed to minimize. The application was a fully nonlinear F-18 simulation. (AIAA)

关键词： Control Surfaces Angle of Attack Pitching Moment Fuzzy Control Air Data Computer Aeroplane Sideslip Nonlinear Dynamic Inversion optimization algorithm Conservation of Energy

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：