检索结果-内蒙古大学图书馆

Developing a prototype concurrent design tool for composite topside structures

NAVAL ENGINEERS JOURNAL 1997年第3期109卷 279-290页

作者： Dirlik, S Hambric, S Azarm, S Marquardt, M Hellman, A Bartlett, S Castelli, V Steve Dirlik:began his career at the Naval Surface Warfare Center Carderock Division in 1981 as an aerospace engineer co-op student. He completed his bachelor of science degree in aeropace and ocean engineering from Virginia Polytechnic Institute and State University in 1985 and his master of science degree in aerospace engineering from the University of Maryland in 1990. Mr. Dirlik recently completed a master of science program in applied physics at The Johns Hopins University and currently works in the Radar Cross Section and Target Physics Branch of the Signatures Directorate at the Naval Surface Warfare Center Corderoke Division. He has worked on Navy low observable programs since 1990. Stephen Hambric:is a research associate at the Applied Research Laboratory at The Pennsylvania State University. He received his B. S. and M.S. degree in mechanical engineering from Virginia Polytechnic Institute and State University and his D. Sc. in mechnical engineering from the George Washington University. He has worked on several computer aided multidiscikplinary design and optimization projects over the years including an automated propeller design system and a structural acoustic optimization capability. Dr. Shpour Azarm:is currently working as an associate professor with the Design and Manufacturing Group of the Department of Mechanical Engineering at the University of maryland at College Park. Dr Azarm's expertise is in the areas of optimization-based designed and concurrent design and optimization of multidisciplinary systems. He was a consultant at Black & Decker Corporation (summer 1996) and worked as a Navy senior summer faculty fellow (summer 1995) and a NASA summer faculty fellow (summer 1994). He was a visiting scientist at NASA Langley Research Center for Multidisciplinary Analysis and Applied Structural Optimzatiom at the University of Siegen in Germany (spring 1992) and the Design Institute of the Technical University of Denmark (summer 1990). Dr Azarm was an associate technical editor of the ASME Jour

A prototype concurrent engineering tool has been developed for the preliminary design of composite topside structures for modern navy warships. This tool, named GELS for the Concurrent Engineering of Layered Structures, provides designers with an immediate assessment of the impacts of their decisions on several disciplines which are important to the performance of a modern naval topside structure, including electromagnetic interference effects (EMI), radar cross section (RCS), structural integrity, cost, and weight. Preliminary analysis modules in each of these disciplines are integrated to operate from a common set of design variables and a common materials database. Performance in each discipline and an overall fitness function for the concept are then evaluated. A graphical user interface (GUI) is used to define requirements and to display the results from the technical analysis modules. Optimization techniques, including feasible sequential quadratic programming (FSQP) and exhaustive search are used to modify the design variables to satisfy all requirements simultaneously. The development of this tool, the technical modules, and their integration are discussed noting the decisions and compromises required to develop and integrate the modules into a prototype conceptual design tool.

关键词： Warships

来源：评论

学校读者我要写书评

暂无评论

The symbiotic relationship between computer graphics and colour imaging

The symbiotic relationship between computer graphics and col...

引用

Final program and Proceedings of the 4th IS and T/SID Color Imaging Conference: Color Science, Systems and Applications

作者： Greenberg, Donald P. Program of Computer Graphics Cornell University Ithaca NY United States

Our goal is to develop physically based lighting models and perceptually based rendering procedures for computer graphics that will allow synthetic images to be generated that are visually and measurably indistinct from real-world images. The research implies the symbiotic relationship which could exist between computer graphics and digital imaging. This presentation describes how work at Cornell's program of computer graphics is attempting to achieve this goal.

关键词： Color image processing

来源：评论

学校读者我要写书评

暂无评论

A model of visual adaptation for realistic image synthesis 96

A model of visual adaptation for realistic image synthesis

引用

23rd Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1996

作者： Ferwerda, James A. Pattanaik, Sumanta N. Shirley, Peter Greenberg, Donald P. Program of Computer Graphics 580 Frank H. T. Rhodes Hall Cornell University IthacaNY14853 United States

ISBN: (纸本)0897917464

In this paper we develop a computational model of visual adaptation for realistic image synthesis based on psychophysical experiments. The model captures the changes in threshold visibility, color appearance, visual acuity, and sensitivity over time that are caused by the visual system's adaptation mechanisms. We use the model to display the results of global illumination simulations illuminated at intensities ranging from daylight down to starlight. The resulting images better capture the visual characteristics of scenes viewed over a wide range of illumination levels. Because the model is based on psychophysical data it can be used to predict the visibility and appearance of scene features. This allows the model to be used as the basis of perceptually-based error metrics for limiting the precision of global illumination computations. © 1996 ACM.

关键词： Visibility

来源：评论

学校读者我要写书评

暂无评论

COLLISION DETECTION FOR INTERACTIVE graphics APPLICATIONS

引用

IEEE TRANSACTIONS ON VISUALIZATION AND computer graphics 1995年第3期1卷 218-230页

作者： HUBBARD, PM Program of Computer Graphics Cornell University Ithaca NY USA

Collision detection and response are important for interactive graphics applications such as vehicle simulators and virtual reality. Unfortunately, previous collision-detection algorithms are too slow for interactive use. This paper presents a new algorithm for rigid or articulated objects that meets performance goals through a form of time-critical computing. The algorithm supports progressive refinement, detecting collisions between successively tighter approximations to object surfaces as the application allows it more processing time. The algorithm uses simple four-dimensional geometry to approximate motion, and hierarchies of spheres to approximate three-dimensional surfaces at multiple resolutions. In a sample application, the algorithm allows interactive performance that is not possible with a good previous algorithm. In particular, the new algorithm provides acceptable accuracy while maintaining a steady and high frame rate, which in some cases improves on the previous algorithm's rate by more than two orders of magnitude.

关键词： COLLISION DETECTION TIME-CRITICAL COMPUTING REAL-TIME PERFORMANCE INTERACTION 4 DIMENSIONS APPROXIMATION

来源：评论

学校读者我要写书评

暂无评论

Three-dimensional reconstruction and volume rendering of intravascular ultrasound slices imaged on a curved arterial path 1st

Three-dimensional reconstruction and volume rendering of int...

引用

1st International Conference on computer Vision, Virtual Reality, and Robotics in Medicine, CVRMed 1995

作者： Lengyel, Jed Greenberg, Donald P. Yeung, Alan Alderman, Edwin Popp, Richard Program of Computer Graphics Cornell University IthacaNY14853 United States Cardiovascular Medicine Division Stanford University School of Medicine StanfordCA94305 United States

ISBN: (纸本)9783540591207

Past techniques for three-dimensional reconstruction of intravascular ultrasound have assumed that the ultrasound slices are parallel and that the vessel being imaged is straight. These assumptions result in distortions of vessel and lesion geometry. To properly reconstruct the volume data for a curved artery, the position and orientation of the transducer must be known or calculated. We use angiography to recover the geometry of the artery centerline, which is then used as a coordinate system to position the ultrasound slices. To estimate the registration of the slices, several landmark sites are selected by the physician and imaged over a complete heart cycle. Continuous pullbacks are then used to sample between the landmark sites, yielding a three-dimensional volume data set. Standard volume rendering techniques require data on a regular grid. We present new sampling and rendering techniques that handle the oriented ultrasound slices positioned along the curved artery. © Springer-Verlag Berlin Heidelberg 1995.

关键词： Ultrasonics

来源：评论

学校读者我要写书评

暂无评论

Assembly Maintainability Study with Motion Planning

Assembly Maintainability Study with Motion Planning

引用

IEEE International Conference on Robotics and Automation (ICRA)

作者： Hsuan Chang Tsai-Yen Li Computer Graphics & Systems Program GE Corporate Research and Development Center Schenectady NY USA

ISBN: (纸本)0780319656

Maintainability is an important issue in design where the accessibility of certain parts is determined for routine maintenance. In the past its study has been largely manual and labor intensive. Either by using physical mockup or computer animation with CAD models of a design, the task relies on a human to provide an access path for the part. In this paper, the authors present an automated approach to replace this manual process. By applying results from and developing extensions to research in motion planning and other fields, the authors demonstrate that an automated maintainability study system is feasible. The authors describe general extensions needed to adapt robotic motion planning techniques in maintainability studies. The authors show results from applying such a system to two classes of industrial application problems.

关键词： Assembly Force sensors Fingers Animation Application software Tendons Grasping Motion control computer graphics Research and development

来源：评论

学校读者我要写书评

暂无评论

Visual navigation of large environments using textured clusters 95

Visual navigation of large environments using textured clust...

引用

Proceedings of the 1995 symposium on Interactive 3D graphics

作者： Paulo W. C. Maciel Peter Shirley Department of Computer Science Lindley Hall Indiana University Bloomington Indiana Program of Computer Graphics Cornell University Ithaca New York

ISBN: (纸本)9780897917360

A visual navigation system is described which uses texture mapped primitives to represent clusters of objects to maintain high and approximately constant frame rates. In cases where there are more unoccluded primitives inside the viewing frustum than can be drawn in real-time on the workstation, this system ensures that each visible object, or a cluster that includes it, is drawn in each frame. The system supports the use of traditional “level-of-detail” representations for individual objects, and supports the automatic generation of a certain type of level-of-detail for objects and clusters of objects. The concept of choosing a representation from among those associated with an object that accounts for the direction from which the object is viewed is also supported. The level-of-detail concept is extended to the whole model and the entire scene is stored as a hierarchy of levels-of-detail that is traversed top-down to find a good representation for a given viewpoint. This system does not assume that visibility information can be extracted from the model and is thus especially suited for outdoor environments.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Bounds and error estimates for radiosity 94

Bounds and error estimates for radiosity

引用

Proceedings of the Annual Conference on computer graphics

作者： Lischinski, Dani Smits, Brian Greenberg, Donald P. Program of Computer Graphics Cornell University

ISBN: (纸本)9780897916677

We present a method for determining a posteriori bounds and estimates for local and total errors in radiosity solutions. The ability to obtain bounds and estimates for the total error is crucial fro reliably judging the acceptability of a solution. Realistic estimates of the local error improve the efficiency of adaptive radiosity algorithms, such as hierarchical radiosity, by indicating where adaptive refinement is ***, we describe a hierarchical radiosity algorithm that computes conservative lower and upper bounds on the exact radiosity function, as well as on the approximate solution. These bounds account for the propagation of errors due to interreflections, and provide a conservative upper bound on the error. We also describe a non-conservative version of the same algorithm that is capable of computing tighter bounds, from which more realistic error estimates can be obtained. Finally, we derive an expression for the effect of a particular interaction on the total error. This yields a new error-driven refinement strategy for hierarchical radiosity, which is shown to be superior to brightness-weighted refinement.

关键词： importance hierarchical radiosity global illumination adaptive refinement a posteriori error bounds and estimates

来源：评论

学校读者我要写书评

暂无评论

A clustering algorithm for radiosity in complex environments 94

A clustering algorithm for radiosity in complex environments

引用

21st Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1994

作者： Smits, Brian Arvo, James Greenberg, Donald Program of Computer Graphics Cornell University 580 ETC Building IthacaNY14853 United States

ISBN: (纸本)0897916670

We present an approach for accelerating hierarchical radiosity by clustering objects. Previous approaches constructed effective hierarchies by subdividing surfaces, but could not exploit a hierarchical grouping on existing surfaces. This limitation resulted in an excessive number of initial links in complex environments. Initial linking is potentially the most expensive portion of hierarchical radiosity algorithms, and constrains the complexity of the environments that can be simulated. The clustering algorithm presented here operates by estimating energy transfers between collections of objects while maintaining reliable error bounds on each transfer. Two methods of bounding the transfers are employed with different tradeoffs between accuracy and time. In contrast with the O(s2) time and space complexity of the initial linking in previous hierarchical radiosity algorithms, the new methods have complexities of O(slogs) and O(s) for both time and space. Using these methods we have obtained speedups of two orders of magnitude for environments of moderate complexity while maintaining comparable accuracy. © ACM 1994.

关键词： Clustering algorithms

来源：评论

学校读者我要写书评

暂无评论

The irradiance Jacobian for partially occluded polyhedral sources 94

The irradiance Jacobian for partially occluded polyhedral so...

引用

21st Annual Conference on computer graphics and Interactive Techniques, SIGGRAPH 1994

作者： Arvo, James Program of Computer Graphics Cornell University 580 Engineering and Theory Center Building IthacaNY14853 United States

ISBN: (纸本)0897916670

The irradiance at a point on a surface due to a polyhedral source of uniform brightness is given by a well-known analytic formula. In this paper we derive the corresponding analytic expression for the irradiance Jacobian, the derivative of the vector representation of irradiance. Although the result is elementary for unoccluded sources, within penumbrae the irradiance Jacobianmust incorporate more information about blockers than either the irradiance or vector irradiance. The expression presented here holds for any number of polyhedral blockers and requires only a minor extension of standard polygon clipping to evaluate. To illustrate its use, three related applications are briefly described: direct computation of isolux contours, finding local irradiance extrema, and iso-meshing. Isolux contours are curves of constant irradiance acrossasurface that can be followed using a predictor-corrector method based on the irradiance Jacobian. Similarly, local extrema can be found using a descent method. Finally, iso-meshing is a new approach to surface mesh generation that incorporates families of isolux contours. © ACM 1994.

关键词： Mesh generation

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：