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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.
91

Challenges in medical visualization : an interactive approach to explore the effect of 3-D technology on the visualization of pain

Spyridonis, Fotios January 2011 (has links)
Pain experienced as a result of a disabling medical condition is a frequent problem in the clinical community and can often be present in any individual with this kind of health concern. Such pain is typically characterized by severe implications reflected on both a person‘s personal life, as well as on a country‘s health and economic systems. Research on pain has revealed that patients not only experience several types of pain that could prove to be challenging to address, but also that each individual can interpret the same type, location and severity of this pain in different subjective ways, making the need for more effective pain measurement methods an imperative and troublesome effort. In retrospect, the healthcare field is currently trying to enhance the available medical methods with alternatives that would be more efficient in providing accurate pain assessment. Most efforts revolve around traditional methods of measuring pain characteristics, which typically involve the 2-Dimensional (2-D) representation of the human body, often used to collect information regarding the type and location of pain. However, these 2-D pain drawings can be limited in their ability to efficiently visualize pain characteristics for diagnosis purposes. Nonetheless, patients have been shown to prefer such drawings. This research develops an alternative interactive software solution to help in addressing the aforementioned situation, by employing the capabilities that advancements in 3-Dimension (3-D) technology offer. Subsequently, in the anticipation that limitations of current 2-D pain visualization will be solved, the developed approach facilitates the measurement of pain experiences via a 3-D visualization model of the patient. To ensure that it can effectively perform in real-world medical practice, the 3-D pain drawing is evaluated in this research through real-life case studies that are carried out in designated settings. The research findings have shown that the developed approach can potentially make significant contributions to society, science/technology and healthcare provision, with patients and clinicians suggesting that 3-D technology can be a promising means in the pursuit for more effective pain measurement solutions.
92

Computer generated lighting techniques: the study of mood in an interior visualisation

Marshall, Bronwyn Gillian 21 September 2009 (has links)
Abstract The report investigates computer generated (CG) lighting techniques with a focus on the rendering of interior architectural visualisations. With rapid advancements in CG technology, the demand and expectation for greater photorealism in visualisations are increasing. The tools to achieve this are widely available and fairly easy to apply; however, renderings on a local scale are still displaying functionality and lack visual appeal. The research discusses how design principles and aesthetics can be used effectively to create visual interest and display mood in the visualisation, with strong attention to the elements that are defined as the fundamentals in achieving photorealism. The focus is on a solid understanding of CG lighting techniques and principles in order to achieve high quality, dynamic visualisations. Case studies examine the work of lighting artist James Turrell and 3D artist Jose Pedro Costa and apply the findings to a creative project, encompassing the discussions in the report. The result is the completion of three photorealistic renderings of an interior visualisation, using different CG lighting techniques to convey mood. The research provides a platform for specialisation in the 3D environment and encourages a multidisciplinary approach to learning.
93

Binocular single vision for visual entertainment applications: 雙目單視於視覺娛樂中的應用 / 雙目單視於視覺娛樂中的應用 / CUHK electronic theses & dissertations collection / Binocular single vision for visual entertainment applications: Shuang mu dan shi yu shi jue yu yue zhong de ying yong / Shuang mu dan shi yu shi jue yu yue zhong de ying yong

January 2016 (has links)
Due to the eyes’ different positions on the human head, binocular viewing of a scene creates two slightly different images of the scene. Human binocular vision can fuse two images with disparity into a single percept, up to a certain limit. This is known as binocular single vision. The use of two eyes is advantageous because it provide one more display channels. One major advantage of binocular vision is creating the feeling of depth (stereopsis). Besides stereopsis, it has recently been shown that the visual system of human eye can even fuse the color, contrast, and/or contour differences between the left and the right views (dichoptic viewing), in a non-linear fashion. Human eyes can perceive more visual information via binocular single vision. / The popularity of virtual reality and 3D movies leads to the wide availability of binocular display devices. There exists some methods to utilize binocular device to present more visual content via binocular single vision. However, they do not support motion pictures. In this thesis, we propose a method to synthesize temporal consistent and binocularly fusible dichoptic videos. Our resultant videos significantly enhance the visual richness of the original input monocular or stereoscopic videos. It is the first attempt to explore the possibility of utilizing LDR binocular display to present dichoptic videos besides the traditional stereoscopic videos (disparity only). We evaluate our method with several challenging videos, and validate its effectiveness in raising visual richness via user studies. / The second application we explore on binocular single vision is enhancing color discrimination for colorblind individuals. Approximately 250 million people suffer from colorblindness, or color vision deficiency (CVD). They are usually not able to clearly discriminate certain colors. The losing of color information leads to misunderstanding, inconvenience, or even danger in daily life. In this thesis, we propose a new framework to synthesis binocularly fused image pair for CVD individuals. The binocular single percept maximizes the color discrimination and minimizes the binocular discomfort. Note that different CVD individuals can be substantially different in terms of the type and the severity of color blindness. We also propose a new calibration method to measure the severity of different CVD individuals. Our tailor-made color discrimination solution for CVD individual has been evaluated via qualitative experiments and convincing effect is obtained in all cases. / Color vision deficiencies can hardly share the same visual content with normal-vision audiences. Our last work makes effort in proposing the first system that allows CVD and normal-vision audiences to share the same visual content simultaneously. The key that we can achieve this is because the ordinary stereoscopic display (non-autostereoscopic ones) offers users two visual experiences (with and without wearing stereoscopic glasses). By allocating one experience to CVD audiences and another to normalvision audiences, we allow them to share. The core problem is to synthesize an image pair so that when they are presented binocularly, CVD audiences can distinguish the originally indistinguishable colors; and when it is in monocular presentation, normal-vision audiences wouldn’t notice any difference from the original image. We solve the image-pair recoloring problem by optimizing an objective function that minimizes the color deviation for normal-vision audiences while maximizes the color distinguishability and binocular fusibility for CVD audiences. Our method is extensively evaluated via multiple quantitative experiments and user studies. Convincing results are obtained in all our test cases. / 由於人類的雙眼在頭部的位置特點,左右兩眼看到的內容有所差異。人類的雙目視覺能將兩幅稍微不同的圖像合成一個單一的視界。這就是雙目單視(Binocular Single Vision)現象。雙目的同時使用使人類可感知更多的視覺信息,比如深度信息(立體感)。除此之外,最近的生理學研究表明,雙目單視可以在一定範圍內融合左右眼所看到的不同顏色,對比度,甚至內容。這種非線性的融合可以給人類帶來更多的視覺信息。 / 虛擬現實以及3D電影的流行使得雙目立體顯示設備在生活中普遍存在。前沿的研究已開始關注如何通過立體設備和雙目單視現象來提高視覺效果。然而,現有工作都集中在圖片的研究而無法應用於電影視頻之中。本畢業論文提出了一個新穎的基於連續幀的雙目視頻對生成方法。本方法所生成的視頻對將使人們感知到更多的視覺內容。通過應用雙目單視現象,低動態範圍(Low-Dynamic Range)的立體顯示設備將不再局限於提供深度視覺信息。為了驗證所提方法的有效性,我們在一些比較有挑戰性的視頻上驗證了其豐富的視覺感知體驗。 / 本論文對雙目單視的第二個探索是在色覺補償方面。全球大約有2億五千個色盲(或色覺缺陷)人士,他們難以區分某些色彩。色彩區分能力的缺失使得他們在生活中有理解和溝通困難,甚至會有潛在的安全問題。本論文提出了一個新穎的利用雙目單視的色覺補償框架。該框架生成的圖片對將能幫助色覺缺陷人士更好地區分顏色而又沒有任何視覺感知方面的不適。色覺缺陷有不同的種類和程度。為了提高色覺補償效果,本論文進一步提出了一個新的色覺測量方法。通過精準的色覺測量和計算,本文所提的色覺補償框架在所有的測試實驗中取得了顯著的效果。 / 在同時觀看同一內容的時候,色盲人士所理解的視覺信息與色覺正常人士是不一樣的。本論文的最後一項工作是提出了一個同步色覺補償系統。該系統可以在色覺正常人士察覺不到色彩改變的前提下,對色盲人士提供色覺補償。這個系統的關鍵突破在於利用了立體顯示設備(非裸眼立體設備)中的不同觀看模式(戴立體眼鏡與不戴立體眼鏡)。我們將戴立體眼鏡的觀看模式分配給色盲人士用於色覺補償,而色覺正常人士則不戴立體眼鏡直接觀看屏幕上線性合成的圖片對。同步色覺補償系統的關鍵問題在於如何根據一張輸入圖片生成一對輸出圖片(一張對應色盲人士的左眼,另一張對應色盲人士右眼)。輸出的圖片對需要在最大化色盲人士的色覺補償和雙目單視舒適度的同時,最小化對原圖色彩的改變。我們建立了一個數學優化模型來解決這個關鍵問題。通過一些列的實驗和用戶調查,同步色覺補償系統的有效性得到了驗證。 / Shen, Wuyao. / Thesis Ph.D. Chinese University of Hong Kong 2016. / Includes bibliographical references (leaves 135-152). / Abstracts also in Chinese. / Title from PDF title page (viewed on 24, October, 2016). / Shen, Wuyao. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.
94

Improving beamforming-based methodologies for seismological analysis

Tan, Fengzhou 10 April 2019 (has links)
We improved two beamforming-based methodologies for seismological analysis. The first one is a new Three-Dimensional Phase-Weighted Relative Back Projection (3-D PWBP) method to improve the spatial resolution of Back Projection results. We exploit both phase and amplitude of the seismogram signal to enhance the distinction of correlated signals. Also, we implement a 3-D velocity model to provide more accurate travel times. We vindicate these refinements with several synthetic tests and an analysis of the 1997 Mw 7.2 Zirkuh (Iran) earthquake, which we show ruptured mainly unilaterally southwards at a rupture speed of ∼3.0 km/s along its ∼125 km- long, mostly single-stranded surface rupture. Then, we apply the new method to the more complex case of the 2016 Mw 7.8 Kaikoura (New Zealand) earthquake, which we demonstrate is divided into two major stages separated by a gap of ∼8 s and ∼30–40 km. The overall rupture speed is ∼1.7 km/s and the overall duration is ∼84 s, considerably shorter than some earlier estimates. We see no clear evidence for continuous failure of the subduction interface that underlies the known, surface-rupturing crustal faults, though we cannot rule out its involvement in the second major stage in the northern part of the rupture area. The late (∼80 s) peak in relative energy is likely a high-frequency stopping phase, and the rupture appears to terminate southwest of the offshore Needles fault. The second methodology is a novel workflow for earthquake detection and location, named Seismicity-Scanning based on Navigated Automatic Phase-picking (S-SNAP). By taking a cocktail approach that combines Source-Scanning, Kurtosis-based Phase-picking and the Maximum Intersection location technique into a single integrated workflow, this new method is capable of delineating complex spatiotemporal distributions of seismicity. It is automatic, efficiently providing earthquake locations with high comprehensiveness and accuracy. We apply S-SNAP to a dataset recorded by a dense local seismic array during a hydraulic fracturing operation to test this novel approach and to demonstrate the effectiveness of S-SNAP in comparison to existing methods. Overall, S-SNAP found nearly four times as many high-quality events as a template-matching based catalogue. All events in the previous catalogue are identi- fied with similar epicenter, depth and magnitude, while no false detections are found by visual inspection. / Graduate
95

Métodos de cálculo de coordenadas tridimensionais para o controle de obras de engenharia / 3-D coordinates determination methods to check engineer works

Moreira, Attus Pereira 09 December 1998 (has links)
O presente trabalho propõe duas novas metodologias para a determinação de coordenadas tridimensionais visando o emprego no controle de obras de engenharia. Os dois métodos propostos fundamentam-se na concepção de um ponto fixo, visível simultaneamente por todos os aparelhos envolvidos no processo e em uma direção de orientação. O primeiro método tem como princípio básico a minimização de uma função matemática, definida pelo somatório das distâncias entre as linhas de visadas dos aparelhos e o alvo. O segundo fundamenta-se no ajustamento pelo Método dos Mínimos Quadrados, aplicado às equações de erros, que são determinadas em função das coordenadas do centro ótico de cada aparelho e dos ângulos zenitais e azimutais medidos. Esse segundo método proporciona, ao mesmo tempo, que sejam estimadas as precisões dos elementos envolvidos no cálculo das coordenadas do alvo e, ainda, ajusta os valores iniciais das coordenadas do centro ótico dos aparelhos. Ambos os métodos podem ser empregados para a verificação de recalques ou deslocamentos estruturais nas provas de carga em obras de engenharia. Os resultados obtidos comprovam que os métodos propostos determinam coordenadas tridimensionais com maior precisão que os principais métodos apresentados na revisão da literatura e podem ser empregados no controle de obras de engenharia. / The purpose of this work is to present new methodologies to determine 3-D coordinates to check engineer works. The two proposed methods are well-founded on a conception of a fixed point and a direction that are proposed. This fixed point must be visible by all surveying equipments envolved in the process to determine 3-D coordinates. The first method presented in this work is based on a mathematic function that must be minimized and this function is defined by the sum of the distances of the target and the sightlines from the surveying equipments directed to the target. The second method presented is based on the L.S.M. adjustment process. This method uses the errors equations that are functions of the 3-D coordinates of the optic center of the surveying equipments envolved in this process. It also uses the azimuth and zenith angles related to the target measured. This method provides at the same time, a way to estimate the precisions of ali elements envolved in 3-D coordinates determination calculus of the target and it also provides the adjustment of the 3-D coordinates of the optic centers of the surveying equipments used to measure the angles. The conception of the orientation point provides more flexibility in a performance of these two methods. The two methods can be employed to check structural displacements and pressing down in charge experiments in engineer works. The results presented in this work validate that these two proposed methods determine 3-D coordinates with more precision and accuracy than the main methods presented in literature revision and may be able to check engineer works.
96

Métodos de cálculo de coordenadas tridimensionais para o controle de obras de engenharia / 3-D coordinates determination methods to check engineer works

Attus Pereira Moreira 09 December 1998 (has links)
O presente trabalho propõe duas novas metodologias para a determinação de coordenadas tridimensionais visando o emprego no controle de obras de engenharia. Os dois métodos propostos fundamentam-se na concepção de um ponto fixo, visível simultaneamente por todos os aparelhos envolvidos no processo e em uma direção de orientação. O primeiro método tem como princípio básico a minimização de uma função matemática, definida pelo somatório das distâncias entre as linhas de visadas dos aparelhos e o alvo. O segundo fundamenta-se no ajustamento pelo Método dos Mínimos Quadrados, aplicado às equações de erros, que são determinadas em função das coordenadas do centro ótico de cada aparelho e dos ângulos zenitais e azimutais medidos. Esse segundo método proporciona, ao mesmo tempo, que sejam estimadas as precisões dos elementos envolvidos no cálculo das coordenadas do alvo e, ainda, ajusta os valores iniciais das coordenadas do centro ótico dos aparelhos. Ambos os métodos podem ser empregados para a verificação de recalques ou deslocamentos estruturais nas provas de carga em obras de engenharia. Os resultados obtidos comprovam que os métodos propostos determinam coordenadas tridimensionais com maior precisão que os principais métodos apresentados na revisão da literatura e podem ser empregados no controle de obras de engenharia. / The purpose of this work is to present new methodologies to determine 3-D coordinates to check engineer works. The two proposed methods are well-founded on a conception of a fixed point and a direction that are proposed. This fixed point must be visible by all surveying equipments envolved in the process to determine 3-D coordinates. The first method presented in this work is based on a mathematic function that must be minimized and this function is defined by the sum of the distances of the target and the sightlines from the surveying equipments directed to the target. The second method presented is based on the L.S.M. adjustment process. This method uses the errors equations that are functions of the 3-D coordinates of the optic center of the surveying equipments envolved in this process. It also uses the azimuth and zenith angles related to the target measured. This method provides at the same time, a way to estimate the precisions of ali elements envolved in 3-D coordinates determination calculus of the target and it also provides the adjustment of the 3-D coordinates of the optic centers of the surveying equipments used to measure the angles. The conception of the orientation point provides more flexibility in a performance of these two methods. The two methods can be employed to check structural displacements and pressing down in charge experiments in engineer works. The results presented in this work validate that these two proposed methods determine 3-D coordinates with more precision and accuracy than the main methods presented in literature revision and may be able to check engineer works.
97

Computer aided design of 3D of renewable energy platform for Togo's smart grid power system infrastructure

Komlanvi, Moglo January 2018 (has links)
The global requirement for sustainable energy provision will become increasingly important over the next fifty years as the environmental effects of fossil fuel use become apparent. Therefore, the issues surrounding integration of renewable energy supplies need to be considered carefully. The focus of this work was the development of an innovative computer aided design of a 3 Dimensional renewable energy platform for Togo’s smart grid power system infrastructure. It demonstrates its validation for industrial, commercial and domestic applications. The Wind, Hydro, and PV system forming our 3 Dimensional renewable energy power generation systems introduces a new path for hybrid systems which extends the system capacities to include, a stable and constant clean energy supply, a reduced harmonic distortion, and an improved power system efficiency. Issues requiring consideration in high percentage renewable energy systems therefore includes the reliability of the supply when intermittent sources of electricity are being used, and the subsequent necessity for storage and back-up generation The adoption of Genetic algorithms in this case was much suited in minimizing the THD as the adoption of the CHB-MLI was ideal for connecting renewable energy sources with an AC grid. Cascaded inverters have also been proposed for use as the main traction drive in electric vehicles, where several batteries or ultra-capacitors are well suited to serve as separate DC sources. The simulation done in various non-linear load conditions showed the proportionality of an integral control based compensating cascaded passive filter thereby balancing the system even in non-linear load conditions. The measured total harmonic distortion of the source currents was found to be 2.36% thereby in compliance with IEEE 519-1992 and IEC 61000-3 standards for harmonics This work has succeeded in developing a more complete tool for analysing the feasibility of integrated renewable energy systems. This will allow informed decisions to be made about the technical feasibility of supply mix and control strategies, plant type, sizing and storage sizing, for any given area and range of supply options. The developed 3D renewable energy platform was examined and evaluated using CAD software analysis and a laboratory base mini test. The initial results showed improvements compared to other hybrid systems and their existing control systems. There was a notable improvement in the dynamic load demand and response, stability of the system with a reduced harmonic distortion. The derivatives of this research therefore proposes an innovative solution and a path for Togo and its intention of switching to renewable energy especially for its smart grid power system infrastructure. It demonstrates its validation for industrial, commercial and domestic applications.
98

Automated 3-D segmentation and analysis of retinal optical coherence tomography images

Garvin, Mona Kathryn 01 January 2008 (has links)
Optical coherence tomography (OCT) is becoming an increasingly important modality for the noninvasive assessment of a variety of ocular diseases such as glaucoma, diabetic macular edema, and age-related macular degeneration. Even though individual layers of the retina are visible on OCT images, current commercial quantitative assessment is limited to measuring the thickness of only one layer. Because each intraretinal layer may be affected differently by disease, an intraretinal layer segmentation approach is needed to enable quantification of individual layer properties, such as thickness or texture. Furthermore, with the latest generation of OCT scanner systems producing true volumetric image data, processing these images using 3-D methods is important for maximal extraction of image information. In this thesis, an optimal 3-D graph search approach for the intraretinal layer segmentation of OCT images is presented. It is built upon the optimal 3-D multiple surface graph-theoretic approach presented by Li et al. (K. Li, X. Wu, D. Z. Chen, and M. Sonka, "Optimal surface segmentation in volumetric images - a graph-theoretic approach," IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 28, no. 1, pp. 119-134, 2006). In this method, multiple surfaces can be found simultaneously by transforming the 3-D segmentation problem into finding a minimum-cost closed set in a corresponding vertex-weighted geometric graph. However, the original formulation of this approach did not incorporate varying feasibility constraints or true regional information, two extensions that would aid in the intraretinal layer segmentation of OCT images. Thus, the major contributions of this thesis include: 1) extending the optimal 3-D graph-theoretic segmentation approach to allow for the incorporation of varying feasibility constraints and regional information, 2) developing a method for learning varying constraints and cost functions from examples for use in the approach, 3) developing and validating a method for the 3-D segmentation of intraretinal layers in both time-domain and spectral-domain OCT images (achieving error rates comparable to that of multiple human experts), and 4) analyzing layer thickness properties in normal subjects and in patients with anterior ischemic optic neuropathy (AION).
99

A follower load as a muscle control mechanism to stabilize the lumbar spine

Kim, Byeong Sam 01 December 2011 (has links)
Study Design: Computational analyses using optimization finite element (FE) models. Objective: To determine the spinal muscle forces (MFs) creating compressive follower loads (CFL) in the lumbar spine in various sagittal postures and to investigate if such MFs can maintain the spinal stability. Summary of Background Data: Biomechanical loads are known closely associated with spinal disorders. Normal spinal loads, however, remains poorly understood due to the lack of knowledge of the MF control mechanism for normal biomechanical functions. Methods: 3-D optimization and FE models of the spinal system (trunk, lumbar spine, sacrum, pelvis, and 232 muscles) were developed and validated using reported experimental data. Optimization models were used to determine the MFs creating CFLs in the lumbar spine in various sagittal postures from 10 extension to 40 flexion. The deformation of the lumbar spine under these MFs and trunk weight was predicted from FE models. The stable lumbar spine deformation was determined by the resultant trunk sway < 10 mm. Results: Optimization solutions of MFs, CFLs, and follower load path (FLP) location were feasible for all studied postures. The FE predictions clearly demonstrated that MFs creating CFLs along the base spinal curve connecting the geometrical centers or along a curve in its vicinity (within anterior or posterior shift by 2 mm) produce the stable deformation of the lumbar spine in the neutral standing and flexed postures, whereas the MFs creating the smallest CFLs resulted in the unstable deformation. In case of extended postures, however, it was not possible to find the CFL creating MFs that produce stable deformation of the extended spine. Conclusion: The results of this study demonstrated the feasibility for spinal muscles to stabilize the spine via the CFL mechanism.
100

Micro-Autoradiographic Fusion Tomography

Merker, James 07 April 2008 (has links)
Two-dimensional (2-D) micro-autoradiography is typically used to identify the location of a radio-labeled ligand bound to a cellular target in tissue sections. Data, such as a histological image, combined with the autoradiographic data provide a spatial relationship of the radiolabel to cellular structures. However, the disadvantage of 2-D imaging is that it only provides a local distribution of the radiolabel within a tissue slice, and not a volumetric regional distribution in the structure of interest. The development of 3-D autoradiographic/histological visualizations would provide important information not otherwise apparent, such as the ability to visualize the distribution of the labeled agents in subcutaneous tissue. We plan to obtain digital micro-autoradiographic images and fuse them to their corresponding histological images using commercially available software. We plan to create a series of 2-D fused images. This series of 2-D fused images will then form a basis for creating 3-D visualization of autoradiographic/histological images using another commercially available software. These type of fused 3-D images, which we will refer to as micro-autoradiographic fusion tomography (MAFT), are not currently available. We will illustrate the use of MAFT with the distribution of vascular endothelial growth factor (VEGF) in subcutaneous tissue. [14C]-VEGF will be injected into rat subcutaneous tissue. VEGF has been found to stimulate angiogenesis, or the growth of new blood vessels, which could prove beneficial by aiding the function of an implantable blood glucose sensor. The diffusion coefficient for VEGF in subcutaneous tissue has not yet been characterized. MAFT would be an ideal technique to use for this type of study. My thesis will address the following specific aims: 1) To label the nicotine receptors in adult and adolescent rat brains, and to obtain digital micro-autoradiographic images and histological images; 2) To fuse a 2-D digital micro-autoradiographic image with a 2-D histological image; 3) To create a 3-D image from a series of 2-D fusion images; and 4) To assess the increased information value obtained using MAFT.

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