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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
361

Study of formation and convective transport of aerosols using optical diagnostic technique

Kim, Tae-Kyun 30 September 2004 (has links)
The characteristics of liquid and solid aerosols have been intensively investigated by means of optical diagnostic techniques. Part I describes the characteristics of liquid aerosol formation formed by heat transfer fluids (HTFs) from bulk liquids. Part II investigates the characteristics of convective transport behavior of solid particles in virtual impactor (VI). The objective of part I is to establish correlations which offer predictions on atomized particle size of HTFs which are widely and commonly used in process industries. There are numerous reports stating that mist explosions formed from leakage cause disastrous accidents in process industries. For safety concerns, the characteristics of mist formation should be known in order to prevent HTFs from catching on fire or exploding. The empirical data on formation of mist are collected by the optical measurement technique, the Fraunhofer diffraction. The Buckingham-PI theorem is applied to establish a correlation between empirical data and representative physical properties of HTFs. Final results of correlations are solved by a statistical method of linear regression. The objective of part II is to investigate the characteristics of convective transport behavior in virtual impactor (VI) which is used to sort polydisperse precursor powder in the process industries of superconductor wire. VI is the device to separate polydisperse particles as a function of particle size by using the difference in inertia between different sizes of particles. To optimize VI performance, the characteristics of convective transport should be identified. This objective is achieved by visualization techniques. The applied visualization techniques are Mie-scattering and laser induced fluorescence (LIF). To investigate analytically, a local Stokes number is introduced in order to offer criteria on predicting the efficiency of VI performance and boundary effect on particle separation. The achieved results can enhance performance and eliminate defects by having knowledge of the behavior of solid particles in VI.
362

Virtual reconstruction of a seventeenth-century Portuguese nau

Wells, Audrey Elizabeth 10 October 2008 (has links)
This interdisciplinary research project combines the fields of nautical archaeology and computer visualization to create an interactive virtual reconstruction of the 1606 Portuguese vessel Nossa Senhora dos Mártires, also known as the Pepper Wreck. Using reconstruction information provided by Dr. Filipe Castro (Texas A&M Department of Anthropology), a detailed 3D computer model of the ship was constructed and filled with cargo to demonstrate how the ship might have been loaded on the return voyage from India. The models are realistically shaded, lighted, and placed into an appropriate virtual environment. The scene can be viewed using the real-time immersive and interactive system developed by Dr. Frederic Parke (Texas A&M Department of Visualization). The process developed to convert the available information and data into a reconstructed 3D model is documented. This documentation allows future projects to adapt this process for other archaeological visualizations, as well as informs archaeologists about the type of data most useful for computer visualizations of this kind.
363

Multilevel multidimensional scaling on the GPU

Ingram, Stephen F. 05 1900 (has links)
We present Glimmer, a new multilevel visualization algorithm for multidimensional scaling designed to exploit modern graphics processing unit (GPU) hard-ware. We also present GPU-SF, a parallel, force-based subsystem used by Glimmer. Glimmer organizes input into a hierarchy of levels and recursively applies GPU-SF to combine and refine the levels. The multilevel nature of the algorithm helps avoid local minima while the GPU parallelism improves speed of computation. We propose a robust termination condition for GPU-SF based on a filtered approximation of the normalized stress function. We demonstrate the benefits of Glimmer in terms of speed, normalized stress, and visual quality against several previous algorithms for a range of synthetic and real benchmark datasets. We show that the performance of Glimmer on GPUs is substantially faster than a CPU implementation of the same algorithm. We also propose a novel texture paging strategy called distance paging for working with precomputed distance matrices too large to fit in texture memory.
364

Motivational visualization for resources-sharing online communities

Sun, Lingling 14 June 2005
As online applications such as online newsgroups, internet game-rooms, online chat-rooms, and peer-to-peer (P2P) resources-sharing systems become popular, online community visualization became a hot research topic. Different forms and metaphors of visualizations focused on various aspects of online communities have been proposed. In this thesis, I propose one prototype of online community visualization which is designed to motivate user contributions in various aspects and stimulate users to participate in the online community more actively. The uneven participation is a well known problem in human society; according to the 80-20 rule, 20% of the people make 80% of contributions, for example, 20% of the employees in a company do 80% of the work. This problem exits in all kinds of online communities, e.g. newsgroups, chat-rooms, but it is particularly crucial for P2P online resources-sharing communities. Such communities do not have a central server and rely solely on the peers not just to provide contributions, but also to ensure the infrastructure. Large P2P file-sharing communities like KaZaA and Limewire can provide the redundancy of peers and resources needed to support the infrastructure and availability of resources. However, when an online community is small, for example, the students in a class, a research group, a department, or a school, the problem of lack of users it is hard to reach a critical mass of user participation, leading to poor service and resource availability, which reduces users interest in participating in the system. To attract users and motivate them to make more contributions into an online resources-sharing community, I propose to use motivational visualization of the community and the contributions of its members. The motivational effect of the visualization is grounded on two theories in social psychology which explain how individuals align their behaviour with each other and with their group (community). In this thesis, I discuss three stages in the design of the visualization and the subsequent redesigns following results from evaluation and user feedback.
365

A Task-Centered Visualization Design Environment and a Method for Measuring the Complexity of Visualization Designs

Suo, Xiaoyuan 17 July 2009 (has links)
Recent years have seen a growing interest in the emerging area of computer security visualization which is about developing visualization methods to help solve computer security problems. In this thesis, we will first present a method for measuring the complexity of information visualization designs. The complexity is measured in terms of visual integration, number of separable dimensions for each visual unit, the complexity of interpreting the visual attributes, number of visual units, and the efficiency of visual search. This method is designed to better assist fellow developers to quickly evaluate multiple design choices, potentially enables computer to automatically measure the complexity of visualization data. We will also analyze the design space of network security visualization. Our main contribution is a new taxonomy that consists of three dimensions – data, visualizations, and tasks. Each dimension is further divided into hierarchical layers, and for each layer we have identified key parameters for making major design choices. This new taxonomy provides a comprehensive framework that can guide network security visualization developers to systematically explore the design space and make informed design decisions. It can also help developers or users systematically evaluate existing network security visualization techniques and systems. Finally it helps developers identify gaps in the design space and create new techniques. Taxonomy showed that most of the existing computer security visualization programs are data centered. However, some studies have shown that task centered visualization is perhaps more effective. To test this hypothesis, we propose a task centered visualization design framework, in which tasks are explicitly identified and organized and visualizations are constructed for specific tasks and their related data parameters. The center piece of this framework is a task tree which dynamically links the raw data with automatically generated visualization. The task tree serves as a high level interaction technique that allows users to conduct problem solving naturally at the task level, while still giving end users flexible control over the visualization construction. This work is currently being extended by building a prototype visualization system based on a Task-centered Visualization Design Architecture.
366

ParaViewGeo: Open source visualization for geoscience

Maynard, Robert 23 September 2008 (has links)
Robert Maynard, lead developer for E2V0 (MIRARCO), describes ParaViewGeo - a version of ParaView that they have modified heavily to support data modelling and visualization in the mining and geoscience fields - as well as the open source development process used by E2V0.
367

Automated Annotation and Visualization of Rhetorical Figures

Gawryjolek, Jakub Jan 11 May 2009 (has links)
Linguistic annotation provides additional information asserted with a particular purpose in a document or other piece of information. It is widely used in various fields, from computing and bioinformatics, through imaging, to law and linguistics. There is also a clear distinction between what is communicated through the written/spoken natural language and how this is passed on. A new problem of linguistic annotation is the annotation of classical rhetorical figures --- patterns of text in which a characteristic syntactic form modifies the standard meanings of words, and leads to a change or an extension of meaning. Rhetoric studies the effectiveness of language comprehensively, including its emotional impact, as much as its propositional content. The annotation of rhetorical figures is therefore important not only for the linguistic point of view, but also for discovering different styles of writing, purpose and effect of written documents, and for better natural language understanding in general. The purpose of this thesis is the automated annotation of rhetorical figures. In the thesis we primarily focus on the figures of repetition, which include the repetition of words, phrases, and clauses. Additionally, we also describe the work we have done on the detection and annotation of figures of parallelism, as well as those that pertain more to the semantics than to the syntax, or positioning. We have developed a rhetorical figure annotation tool dubbed JANTOR (Java ANnotation Tool Of Rhetoric), which enables manual and automated annotation of files in HTML format. We have applied a lexicalized probabilistic context-free grammar parser for the recognition of the figures of repetition. We also describe a simple parse tree distance used for calculating the difference between similarly structured phrases, which is necessary for the recognition of some of the figures of parallelism. Moreover, we have applied the semantic relationships contained in the WordNet lexical database and extended Porter stemmer algorithm for finding derivationally related words. Finally, we present a method for finding pairs of words which are ordinarily contradictory, which is crucial for detecting the interesting figure of speech: oxymoron. For this purpose typed dependency grammars together with WordNet are used. The experiments we have conducted on the detection of selected subset of rhetorical figures have yielded very promising results. Lastly, we present the visualization of the occurrences of the figures and comparison between 14 American presidents' inaugural addresses including the most recent one by President Barack Obama. The provocative results of this comparison show that a) automated analysis of meaningful rhetorical information is possible and tractable, and b) help us with understanding what creates a successful orator.
368

A Dynamic Coupled Magnetosphere-Ionosphere-Ring Current Model

Pembroke, Asher 16 September 2013 (has links)
In this thesis we describe a coupled model of Earth's magnetosphere that consists of the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamics (MHD) simulation, the MIX ionosphere solver and the Rice Convection Model (RCM). We report some results of the coupled model using idealized inputs and model parameters. The algorithmic and physical components of the model are described, including the transfer of magnetic field information and plasma boundary conditions to the RCM and the return of ring current plasma properties to the LFM. Crucial aspects of the coupling include the restriction of RCM to regions where field-line averaged plasma-beta <=1, the use of a plasmasphere model, and the MIX ionosphere model. Compared to stand-alone MHD, the coupled model produces a substantial increase in ring current pressure and reduction of the magnetic field near the Earth. In the ionosphere, stronger region-1 and region-2 Birkeland currents are seen in the coupled model but with no significant change in the cross polar cap potential drop, while the region-2 currents shielded the low-latitude convection potential. In addition, oscillations in the magnetic field are produced at geosynchronous orbit with the coupled code. The diagnostics of entropy and mass content indicate that these oscillations are associated with low-entropy flow channels moving in from the tail and may be related to bursty bulk flows and bubbles seen in observations. As with most complex numerical models, there is the ongoing challenge of untangling numerical artifacts and physics, and we find that while there is still much room for improvement, the results presented here are encouraging. Finally, we introduce several new methods for magnetospheric visualization and analysis, including a fluid-spatial volume for RCM and a field-aligned analysis mesh for the LFM. The latter allows us to construct novel visualizations of flux tubes, drift surfaces, topological boundaries, and bursty-bulk flows.
369

Visualization techniques in Logistics : Case study on the strategy development for logistics network in Internet of Things era

Zhang, Jie, Wu, Jingbo January 2011 (has links)
Twenty years ago, if someone said that every object could have its own identity, no one would agree and some might even think that was crazy. However, it turns out that the wild imagination is possible today. With the help of the Internet of Things (IoT), it is convenient to identify any objects with RFID (Radio Frequency Identification) and control the objects via the Internet. In the near future, people will even make the IoT network visible, thus all the information on the Internet can become dynamic and much easier to understand than numbers to be.   At the moment, Guiyang Municipal Science &amp; Technology Bureau is planning to design and apply visualization technique to logistics, the focus of Guizhou Provincial logistic network in the IoT era. This is a good opportunity for different kinds of enterprises in theGuizhoudistrict or even in the whole country.   This thesis focuses on three problems, namely, discussion on the use of visualization techniques in IoT, the necessary preparation of manufacturing industry to join in the visible IoT and measures available that the government can adopt. The exploratory case study in this thesis is about the visualization technique in IoT in manufacturing industry in theGuizhouProvince. A company was selected for the case study to explore the situation inGuizhouProvince. The related information was collected through interviews with relevant personnel and observation in the company. To bring a clear view of the situation and provide enterprises with information for reference, SWOT analysis is adopted to evaluate the strength and weakness in both the internal and external environment. Those measures that government can take to promote its development include unification in standards, support in research and development of technology and emphasis on personal privacy.   The conclusion shows that the use of visualization techniques in IoT can promote information transmission both in effectiveness and efficiency, and control the supply chain as well as special processes in an efficient way. Discussions have been conducted on four techniques which are able to realize visualization, including GPS, RFID, bar code and machine vision. The preparation that needs to be done in a progressive way, of manufacturing enterprises mainly involves three aspects: equipment, system, and management; which have been discussed in detail in this study. Only totally combining the three aspects, not a single one can be omitted, can enterprises achieve the goal of growth in benefit and costs reduction through the use of IoT. Due to immaturity of the emerging network and technology, in the future, the IoT still has a long way to go. Certainly, we should not ignore the followed huge benefit and improvement that IoT can bring.
370

Visualization of Weather Data : Temperature trend visualization

Liu, Jiayi January 2012 (has links)
Weather data are huge. Traditional visualization techniques are limited to show temperature trends. Pixel-based approaches could be used to visualize the huge amount of weather data and in process show the temperature trends. A prototype using this approach is built to make temperature data more understandable in changing trends. It is implemented using a 2D representation and many popular interaction techniques. It is a lightweight and reusable tool to visualize temperatures.

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