Exploring invariant sets and invariant measures

We propose a method to explore invariant measures of dynamical systems. The method is based on numerical tools which directly compute invariant sets using a subdivision technique, and invariant measures by a discretization of the Frobenius-Perron operator. Appropriate visualization tools help to analyze the numerical results and to understand important aspects of the underlying dynamics. This will be illustrated for examples provided by the Lorenz system. (c) 1997 American Institute of Physics.     

Nonlinear imaging and THz diagnostic tools in the service of Cultural Heritage

We present the use of novel nonlinear imaging, terahertz time-domain spectroscopy and imaging as powerful diagnostic tools for studies of works of art. It is shown that nonlinear imaging offers precise in-depth information, while terahertz imaging can reveal hidden objects and uncover information on highly absorbing organic compounds whose visualization is difficult in other parts of the spectrum.     

Uniform Manifold Approximation and Projection Analysis of Soccer Players

In professional soccer, the choices made in forming a team lineup are crucial for achieving good results. Players are characterized by different skills and their relevance depends on the position that they occupy on the pitch. Experts can recognize similarities between players and their styles, but the procedures adopted are often subjective and prone to misclassification. The automatic recognition of players’ styles based on their diversity of skills can help coaches and technical directors to prepare a team for a competition, to substitute injured players during a season, or to hire players to fill gaps created by teammates that leave. The paper adopts dimensionality reduction, clustering and computer visualization tools to compare soccer players based on a set of attributes. The players are characterized by numerical vectors embedding their particular skills and these objects are then compared by means of suitable distances. The intermediate data is processed to generate meaningful representations of the original dataset according to the (dis)similarities between the objects. The results show that the adoption of dimensionality reduction, clustering and visualization tools for processing complex datasets is a key modeling option with current computational resources.     

Probing the QCD critical point with relativistic heavy-ion collisions

We utilize an event-by-event relativistic hydrodynamic calculation performed at a number of different incident beam energies to investigate the creation of hot and dense QCD matter near the critical point. Using state-of-the-art analysis and visualization tools we demonstrate that each collision event probes QCD matter characterized by a wide range of temperatures and baryo-chemical potentials, making a dynamical response of the system to the vicinity of the critical point very difficult to isolate above the background.     

Matlab在大学物理教学中的辅助应用

以(线性和非线性)谐振子的求解过程为例,分析如何在大学物理的教学过程中引入Matlab计算工具.利用Matlab的符号计算和数值模拟两方面的强大功能,引导学生如何处理基本物理问题,体现了Matlab的可视化和简洁性对大学物理教学的辅助作用,激发学生学习的热情,提高大学物理教学的整体效率和质量.     

弹上激光接收机的光谱响应特性检测研究

检测该系统能采集和分析相关测试数据,能显示、保存和打印最终测试结果。由于使用了选进的编程开发软件和虚拟仪器技术,使系统能成为检测激光接收器光谱参数的测试系统。测试结果证明,这种方法实用、方便,测量精度高。     

Filming the invisible – time-resolved visualization of compressible flows

Essentially all processes in gasdynamics are invisible to the naked eye as they occur in a transparent medium. The task to observe them is further complicated by the fact that most of these processes are also transient, often with characteristic times that are considerably below the threshold of human perception. Both difficulties can be overcome by combining visualization methods that reveal changes in the transparent medium, and high-speed photography techniques that “stop” the motion of the flow. The traditional approach is to reconstruct a transient process from a series of single images, each taken in a different experiment at a different instant. This approach, which is still widely used today, can only be expected to give reliable results when the process is reproducible. Truly time-resolved visualization, which yields a sequence of flow images in a single experiment, has been attempted for more than a century, but many of the developed camera systems were characterized by a high level of complexity and limited quality of the results. Recent advances in digital high-speed photography have changed this situation and have provided the tools to investigate, with relative ease and in sufficient detail, the true development of a transient flow with characteristic time scales down to one microsecond. This paper discusses the potential and the limitations one encounters when using density-sensitive visualization techniques in time-resolved mode. Several examples illustrate how this approach can reveal and explain a number of previously undetected phenomena in a variety of highly transient compressible flows. It is demonstrated that time-resolved visualization offers numerous advantages which normally outweigh its shortcomings, mainly the often-encountered loss in resolution. Apart from the capability to track the location and/or shape of flow features in space and time, adequate time-resolved visualization allows one to observe the development of deliberately introduced near-isentropic perturbation wavelets. This new diagnostic tool can be used to qualitatively and quantitatively determine otherwise inaccessible thermodynamic properties of a compressible flow.     

A soft-segmentation visualization scheme for magnetic resonance images

Prevalent visualization tools exploit gray value distribution in images through modified histogram equalization and matching technique, referred to as the window width/window level-based method, to improve visibility and enhance diagnostic value. The window width/window level tool is extensively used in magnetic resonance (MR) images to highlight tissue boundaries during image interpretation. However, the identification of different regions and distinct boundaries between them based on gray-level distribution and displayed intensity levels is extremely difficult because of the large dynamic range of tissue intensities inherent in MR images. We propose a soft-segmentation visualization scheme to generate pixel partitions from the histogram of MR image data using a connectionist approach and then generate selective visual depictions of pixel partitions using pseudo color based on an appropriate fuzzy membership function. By applying the display scheme in clinical examples in this study, we could demonstrate additional overlapping regions between distinct tissue types in healthy and diseased areas (in the brain) that could help improve the tissue characterization ability of MR images.     

Dynamical Analysis of the Dow Jones Index Using Dimensionality Reduction and Visualization

Time-series generated by complex systems (CS) are often characterized by phenomena such as chaoticity, fractality and memory effects, which pose difficulties in their analysis. The paper explores the dynamics of multidimensional data generated by a CS. The Dow Jones Industrial Average (DJIA) index is selected as a test-bed. The DJIA time-series is normalized and segmented into several time window vectors. These vectors are treated as objects that characterize the DJIA dynamical behavior. The objects are then compared by means of different distances to generate proper inputs to dimensionality reduction and information visualization algorithms. These computational techniques produce meaningful representations of the original dataset according to the (dis)similarities between the objects. The time is displayed as a parametric variable and the non-locality can be visualized by the corresponding evolution of points and the formation of clusters. The generated portraits reveal a complex nature, which is further analyzed in terms of the emerging patterns. The results show that the adoption of dimensionality reduction and visualization tools for processing complex data is a key modeling option with the current computational resources.     

Virtual cisternoscopy of intracranial vessels: a novel visualization technique using virtual reality

This paper introduces a different visualization method which we call “virtual cisternoscopy” using 3D MRA data sets. Virtual cisternoscopy uses well known tools, such as perspective volume rendering (pVR), fly-through techniques, and interactive visualization and combines them to a new approach featuring motion to resolve spatial relationships of intracranial vessels and vascular malformations. With a dedicated flight protocol extraluminal topography of intracranial arteries was analyzed using pVR. For evaluation of difficult vascular malformations extraluminal views are necessary. Therefore, movies of pVR views were produced simulating virtual tracks of neurosurgical flexible endoscopes, by flying around the intracranial vessels and vascular malformations within the cisterns. Endoluminal views were acquired additionally for precise evaluation of cases with complex vessel topography. Two healthy volunteers and three patients were examined. Comparing MIP and pVR images relevant advantages of pVR were found, such as depth information, perspective, lighting, and color. In contrast to MIP and source images of the MRA data set, virtual cisternoscopy of an aneurysm of the left middle cerebral artery demonstrated clearly an early origin of an artery in the region of the aneurysm neck/sac. In this case only virtual cisternoscopy led to the correct therapeutical decision. In a newborn, the type of a vein of Galen aneurysmal malformation could only be evaluated reliably by means of virtual cisternoscopy. The third case of a patient with a clipped aneurysm was evaluated more easily with virtual cisternoscopy than with DSA. In conclusion, virtual cisternoscopy may improve the pretherapeutical visualization of intracranial vascular malformations.     

International nanotechnology development in 2003: Country,institution, and technology field analysis based on USPTO patent database

Nanoscale science and engineering (NSE) have seen rapid growth and expansion in new areas in recent years. This paper provides an international patent analysis using the U.S. Patent and Trademark Office (USPTO) data searched by keywords of the entire text: title, abstract, claims, and specifications. A fraction of these patents fully satisfy the National Nanotechnology Initiative definition of nanotechnology (which requires exploiting specific phenomena and direct manipulation at the nanoscale), while others only make use of NSE tools and methods of investigation. In previous work we proposed an integrated patent analysis and visualization framework of patent content mapping for the NSE field and of knowledge flow pattern identification until 2002. In this paper, the results are updated for 2003, and the new trends are presented.     

Recurrence plots of experimental data: To embed or not to embed?

A recurrence plot is a visualization tool for analyzing experimental data. These plots often reveal correlations in the data that are not easily detected in the original time series. Existing recurrence plot analysis techniques, which are primarily application oriented and completely quantitative, require that the time-series data first be embedded in a high-dimensional space, where the embedding dimension d(E) is dictated by the dimension d of the data set, with d(E)>/=2d+1. One such set of recurrence plot analysis tools, recurrence quantification analysis, is particularly useful in finding locations in the data where the underlying dynamics change. We have found that for certain low-dimensional systems the same results can be obtained with no embedding. (c) 1998 American Institute of Physics.     

面向LAMOST的天体光谱离群数据挖掘系统研究

在宇宙中寻求未知天体是人类探索宇宙奥妙所追求的目标之一,离群数据挖掘是发现未知天体光谱数据的一种有效途径。文章首先以VC++和Oracle9i为开发工具,设计与实现了面向LAMOST的恒星光谱离群数据挖掘系统,并给出了其软件体系结构和模块功能。其次,对基于中值滤波器的恒星光谱数据预处理、基于距离的恒星光谱数据聚类、基于距离支持度的恒星光谱数据离群数据挖掘、基于主分量分析法PCA的恒星光谱数据离群数据的三维可视化等主要关键技术进行了详细描述。最后,基于SDSS恒星光谱数据的运行结果表明,利用该系统寻找天体光谱离群数据是可行的,从而为寻找未知的、特殊的天体光谱数据提供了一种新途径。     

Fast free-surface detection and level-set function definition in SPH solvers

The present paper proposes a novel algorithm to detect the free-surface in particle simulations, both in two and three dimensions. Since the proposed algorithms are based on SPH interpolations their implementation does not require complex geometrical procedures. Thus the free-surface detection can be easily embedded in SPH solvers, without a significant increase of the CPU time. Throughout this procedure accurate normal vectors to the free-surface are made available. Then it is possible to define a level-set function algorithm which is presented in detail. The latter allows in-depth analyses of three-dimensional free-surface simulations by using standard visualization tools, including internal features of the flow. The algorithms proposed for detecting free-surface particles and defining the level-set function are validated on simple and complex two- and three-dimensional flow simulations. The usefulness of the proposed procedures to post-process and analyze complex flows are illustrated on realistic examples.     

A visualization study of the near-wall behaviors of an oblique plate at different angles of attack

Abstract  

A combined method of oil flow visualization and smoke visualization with a laser sheet was conducted on an oblique plate with 64° sweep under different angles of attack. The oil flow visualization results reveal the characteristics of the flow pattern on the upper surface of the oblique plate, including the formation of separation, reattachment lines and the variation of these lines when the angle of attack changes. The smoke visualization results show the vortex structure above the oblique plate so as to demonstrate and interpret the flow pattern captured in the oil flow visualization.     

Technology of automobile and visualization studies

Computer simulation and visualization techniques for automotive studies are reviewed through the history of computer-aided visualization techniques to celebrate the 10th anniversary of Journal of Visualization. Future direction of visualization study is also mentioned through the introduction of up-to-dated numerical visualizations.     

Visualization of scientific arts and some examples of applications

In this paper, implementation and visualization of scientific arts are described using some examples of application in subject research areas, such as sculpture, archeology, fine arts and information aesthetics, which have been discussed through the Scientific Art Session at FLUCOME9, Tallahassee, Florida, 2007–9. In the application to sculpture, stereo visualization techniques, such as anaglyph stereo visualization and integral imaging technique, are introduced to realize the three-dimensional geometry of sculpture to enhance visual impact on the art. The second application is the flow visualization technique for archeology, where the vortices behind the river stones are studied to understand the origin of patterns on Jomon pottery. Interestingly, such vortex patterns also appear in the paintings of fine arts. The third example is the visualization of information aesthetics, where the Web information, such as public media and stock market, are visualized through scientific techniques. These examples of visualization of scientific arts provide the present state of the art in interdisciplinary visualization.     

VisAct: a visualization design system based on semantic actions

Current visualization design toolkits help users to explore data and create visualizations. However, most of these systems do not record the executed actions during the visualization construction process with semantic context. In this paper, we present VisAct, a visualization design system based on semantic actions, that helps average users to construct visualizations step by step. Our system contributes a set of action-based visualization components and a high-level grammar for semantic actions. VisAct also guides the visualization construction process and provides an action tracker for history management and data collection. We demonstrate the usability of VisAct by visualizations and a plugin application. Finally, we conduct a user study to evaluate the efficiency and effectiveness of our system.