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abstract: Visual attention (VA) is the study of mechanisms that allow the human visual system (HVS) to selectively process relevant visual information. This work focuses on the subjective and objective evaluation of computational VA models for the distortion-free case as well as in the presence of image distortions. Existing VA models are traditionally evaluated by using VA metrics that quantify the match between predicted saliency and fixation data obtained from eye-tracking experiments on human observers. Though there is a considerable number of objective VA metrics, there exists no study that validates that these metrics are adequate for the evaluation of VA models. This work constructs a VA Quality (VAQ) Database by subjectively assessing the prediction performance of VA models on distortion-free images. Additionally, shortcomings in existing metrics are discussed through illustrative examples and a new metric that uses local weights based on fixation density and that overcomes these flaws, is proposed. The proposed VA metric outperforms all other popular existing metrics in terms of the correlation with subjective ratings. In practice, the image quality is affected by a host of factors at several stages of the image processing pipeline such as acquisition, compression, and transmission. However, none of the existing studies have discussed the subjective and objective evaluation of visual saliency models in the presence of distortion. In this work, a Distortion-based Visual Attention Quality (DVAQ) subjective database is constructed to evaluate the quality of VA maps for images in the presence of distortions. For creating this database, saliency maps obtained from images subjected to various types of distortions, including blur, noise and compression, and varying levels of distortion severity are rated by human observers in terms of their visual resemblance to corresponding ground-truth fixation density maps. The performance of traditionally used as well as recently proposed VA metrics are evaluated by correlating their scores with the human subjective ratings. In addition, an objective evaluation of 20 state-of-the-art VA models is performed using the top-performing VA metrics together with a study of how the VA models’ prediction performance changes with different types and levels of distortions. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2016

Abstract Eddy currents and susceptibility differences are the most important sources that interfere with the quality of MR images in the presence of an artificial macroscopic object in the volume to be imaged. In this study, both of these factors have been examined. The findings show that the RF field is the most important cause of induced eddy currents when gradients with relatively slow slew rates are used. The induced eddy currents amplify or dampen the RF field with the result that the flip angle changes. At the proximal end in the vicinity of the hip prosthesis surface, there have been areas where the flip angle is nearly threefold compared to the reference flip angle. Areas with decreased flip angles have also been found near the surface of the prosthesis top. The incompleteness of the image due to eddy currents manifests as signal loss areas. Two different methods based on MRI were developed to estimate the susceptibility of a cylindrical object. One of them is based on geometrical distortions in SE magnitude images, while the other takes advantage of phase differences in GRE phase images. The estimate value of the Profile™ test hip prosthesis is χ = (170 ± 13) 10-6. A remapping method was selected to correct susceptibility image distortions. Correction was accomplished with pixel shifts in the frequency domain. The magnetic field distortions were measured using GRE phase images. The method was tested by simulations and by imaging a hip prosthesis in a water tank and in a human pelvis. The main limitations of the method described here are the loss of a single-valued correction map with higher susceptibility differences and the problems with phase unwrapping in phase images. Modulation transfer functions (MTF) were exploited to assess the effect of correction procedure. The corrected image of a prosthesis in a human hip after total hip arthroplasty appears to be equally sharp or slightly sharper than the corresponding original images. The computer programs written for this study are presented in an appendix.

Orientador: Eliane Mauerberg-de-Castro / Banca: José Aparecido da Silva / Banca: Afonso Antonio Machado / Banca: Catia Mary Volp / Banca: Edison Duarte / Resumo: A imagem corporal refere-se a experiências humanas incorporadas ao longo da vida sobre seu próprio corpo. É um construto multifacetado que une a percepção e as atitudes das pessoas, especialmente as preocupações e atitudes relacionadas à aparência física (Cash, Maikkula & Yamamiya, 2004). Quando distorcida, a representação da imagem corporal pode levar o indivíduo a riscos, tais como transtornos alimentares e depressão (Smolak, 2002), que estão entre os principais e mais sérios problemas clínicos encontrados em meninas adolescentes e mulheres jovens na atualidade (Shroff & Thompson, 2006). O objetivo geral deste estudo foi avaliar aspectos comportamentais e perceptivos da imagem corporal de meninas adolescentes com distúrbio de imagem corporal (GCD) e sem distúrbio de imagem corporal (GSD). Especificamente identificar se parâmetros comportamentais (i.e., nível de satisfação com o próprio corpo) são distintos entre os grupos; verificar em tarefa com silhuetas e em tarefa com imagens do próprio corpo a consistência dos sub-componentes afetivo, cognitivo e perceptivo de ambos os grupos; avaliar se parâmetros perceptivos (i.e., expoente da função psicofísica de potência e magnitude do erro no julgamento de dimensões do próprio corpo) diferem entre os grupos; verificar se parâmetros perceptivos são diferentes entre tarefas que incluem imagens da própria pessoa, de pessoa desconhecida e de estímulo neutro (i.e., projeção frontal de um cubo) e se estas possíveis diferenças ocorrem para ambos os grupos; se fatores como distúrbio de imagem, transtorno alimentar e IMC predizem o nível de insatisfação do próprio corpo e se predizem a magnitude do erro no julgamento de dimensões do próprio corpo. Para tanto, 43 participantes do GSD e 10 participantes do GCD responderam a testes e inventários (BSQ, EAT, escala de silhuetas e escala da imagem própria)... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Body image is a multi-dimensional construct that combines perceptions and attitudes about the body, particularly those that relate to physical appearance (Cash, Maikkula & Yamamiya, 2004). When body image perception is disturbed-most common amongst teenage girls (Shroff & Thompson, 2006), serious health risks may result, which include eating disorders and depression (Smolak, 2002). The purpose of this study was to assess the behavioral and perceptual aspects of body image in adolescent females with and without body image distortion, (BID) and (NBI). Specifically, it was to identify whether or not behavioral parameters are distinct between groups. The study attempted to verify, in both groups, levels of consistency in sub-components: affective, cognitive and perceptual, using tasks that portrayed the individual's own body as well as a stranger's body. Also assessed was whether or not perceptual parameters could it be determined, and whether or not perceptual parameters are different for tasks that include an individual's own body image versus those tasks that include a stranger's body image and a task with a neutral image. If differences existed between groups, the study attempted to assess whether or not body image disturbance, presence of eating disorder and BMI-body mass index (IMC) predicted levels of individual body dissatisfaction and magnitude of error when the individuals judged the dimensions of their own bodies. Forty-three participants comprised the NBI group, and ten participants comprised the BID group. In order to establish the behavioral components of body image, individuals in both groups were asked to complete questionnaires and inventories (BSQ, EAT, silhouette scale, SIL, and own body image scale, OBI). Also, psychophysical tasks were used to assess the perceptual components of body image. Results of the behavioral aspects related to body image showed that... (Complete abstract click electronic access below) / Doutor

Made available in DSpace on 2014-06-11T19:30:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-04-06Bitstream added on 2014-06-13T19:19:36Z : No. of bitstreams: 1 paula_ai_dr_rcla.pdf: 1264548 bytes, checksum: f5f07951ceae1ba51d882db3847be6b2 (MD5) / A imagem corporal refere-se a experiências humanas incorporadas ao longo da vida sobre seu próprio corpo. É um construto multifacetado que une a percepção e as atitudes das pessoas, especialmente as preocupações e atitudes relacionadas à aparência física (Cash, Maikkula & Yamamiya, 2004). Quando distorcida, a representação da imagem corporal pode levar o indivíduo a riscos, tais como transtornos alimentares e depressão (Smolak, 2002), que estão entre os principais e mais sérios problemas clínicos encontrados em meninas adolescentes e mulheres jovens na atualidade (Shroff & Thompson, 2006). O objetivo geral deste estudo foi avaliar aspectos comportamentais e perceptivos da imagem corporal de meninas adolescentes com distúrbio de imagem corporal (GCD) e sem distúrbio de imagem corporal (GSD). Especificamente identificar se parâmetros comportamentais (i.e., nível de satisfação com o próprio corpo) são distintos entre os grupos; verificar em tarefa com silhuetas e em tarefa com imagens do próprio corpo a consistência dos sub-componentes afetivo, cognitivo e perceptivo de ambos os grupos; avaliar se parâmetros perceptivos (i.e., expoente da função psicofísica de potência e magnitude do erro no julgamento de dimensões do próprio corpo) diferem entre os grupos; verificar se parâmetros perceptivos são diferentes entre tarefas que incluem imagens da própria pessoa, de pessoa desconhecida e de estímulo neutro (i.e., projeção frontal de um cubo) e se estas possíveis diferenças ocorrem para ambos os grupos; se fatores como distúrbio de imagem, transtorno alimentar e IMC predizem o nível de insatisfação do próprio corpo e se predizem a magnitude do erro no julgamento de dimensões do próprio corpo. Para tanto, 43 participantes do GSD e 10 participantes do GCD responderam a testes e inventários (BSQ, EAT, escala de silhuetas e escala da imagem própria)... / Body image is a multi-dimensional construct that combines perceptions and attitudes about the body, particularly those that relate to physical appearance (Cash, Maikkula & Yamamiya, 2004). When body image perception is disturbed—most common amongst teenage girls (Shroff & Thompson, 2006), serious health risks may result, which include eating disorders and depression (Smolak, 2002). The purpose of this study was to assess the behavioral and perceptual aspects of body image in adolescent females with and without body image distortion, (BID) and (NBI). Specifically, it was to identify whether or not behavioral parameters are distinct between groups. The study attempted to verify, in both groups, levels of consistency in sub-components: affective, cognitive and perceptual, using tasks that portrayed the individual’s own body as well as a stranger’s body. Also assessed was whether or not perceptual parameters could it be determined, and whether or not perceptual parameters are different for tasks that include an individual’s own body image versus those tasks that include a stranger’s body image and a task with a neutral image. If differences existed between groups, the study attempted to assess whether or not body image disturbance, presence of eating disorder and BMI-body mass index (IMC) predicted levels of individual body dissatisfaction and magnitude of error when the individuals judged the dimensions of their own bodies. Forty-three participants comprised the NBI group, and ten participants comprised the BID group. In order to establish the behavioral components of body image, individuals in both groups were asked to complete questionnaires and inventories (BSQ, EAT, silhouette scale, SIL, and own body image scale, OBI). Also, psychophysical tasks were used to assess the perceptual components of body image. Results of the behavioral aspects related to body image showed that... (Complete abstract click electronic access below)

Lenses in virtual reality headsets make it possible to put displays close to users' eyes and they provide users with wider field of view. However, they also distort the displayed image. Providing we know the lens distortion properties, it is possible to compensate for the distortion by displaying an image that is distorted in the opposite way. This thesis focuses on measurement of the distortion for an arbitrarily complex lens, while also considering chromatic aberration. A system capable of measuring of the distortion using just a camera attached to the virtual reality headset is designed and implemented. It is based on pattern detection and comparison of relative positions of points on the display and their correspondences in the distorted image. The result is a 2D distortion map that can be used to transform images such that they appear undistorted to the virtual reality headset users.

Anorexia Nervosa (AN) is a severe and complex psychiatric disorder characterized by significantly low body weight, an intense fear of gaining weight, and a distorted body image. Despite otherwise successful treatments, body image distortions are often persistent and are considered a critical factor in the persistence, development, and relapse of AN. The present review outlines the current literature on tactile distance processing in AN to investigate and discuss its proposed role in the persistence and development of a distorted body image. The discussion of literature further discusses its implications for cognitive neuroscience since AN patients display similar symptoms as patients diagnosed with body image-related neuropsychiatric disorders with damage to the parietal lobe. The evidence suggests that individuals with AN have poorer tactile distance estimation than controls but do not differ regarding tactile detection. This review outlines the current literature, identifies gaps within the methodology, and proposes novel directions for future research.

When a camera system in a car is mounted behind the windshield, light rays will be refracted by the windshield. The distortion can be significant, especially for wide field-of-view cameras. Traditional approaches handle the windshield distortion along with the calibration that calculates the intrinsic and extrinsic parameters. However, these approaches do not handle the windshield distortion explicitly, and to understand the image formation, it brings to understand more about the windshield distortion effect. In this thesis, data is collected from a camera system viewed with and without the windshield. The windshield distortion effect has been studied by varying the windshield’s tilt and the camera’s setup. Points are then found in both images and matched. From this, a distortion difference is calculated and analyzed. Next, a preliminary model of the windshield distortion effect is presented and evaluated. The results show that the model works well for all cases and the two windshields considered in this thesis.

Encoding hieroglyphic texts is time-consuming. If a text already exists as hand-written transcription, there is an alternative, namely OCR. Off-the-shelf OCR systems seem difficult to adapt to the peculiarities of Ancient Egyptian. Presented is a proof-of-concept tool that was designed to digitize texts of Urkunden IV in the hand-writing of Kurt Sethe. It automatically recognizes signs and produces a normalized encoding, suitable for storage in a database, or for printing on a screen or on paper, requiring little manual correction. The encoding of hieroglyphic text is RES (Revised Encoding Scheme) rather than (common dialects of) MdC (Manuel de Codage). Earlier papers argued against MdC and in favour of RES for corpus development. Arguments in favour of RES include longevity of the encoding, as its semantics are font-independent. The present study provides evidence that RES is also much preferable to MdC in the context of OCR. With a well-understood parsing technique, relative positioning of scanned signs can be straightforwardly mapped to suitable primitives of the encoding.

Encoding hieroglyphic texts is time-consuming. If a text already exists as hand-written transcription, there is an alternative, namely OCR. Off-the-shelf OCR systems seem difficult to adapt to the peculiarities of Ancient Egyptian. Presented is a proof-of-concept tool that was designed to digitize texts of Urkunden IV in the hand-writing of Kurt Sethe. It automatically recognizes signs and produces a normalized encoding, suitable for storage in a database, or for printing on a screen or on paper, requiring little manual correction. The encoding of hieroglyphic text is RES (Revised Encoding Scheme) rather than (common dialects of) MdC (Manuel de Codage). Earlier papers argued against MdC and in favour of RES for corpus development. Arguments in favour of RES include longevity of the encoding, as its semantics are font-independent. The present study provides evidence that RES is also much preferable to MdC in the context of OCR. With a well-understood parsing technique, relative positioning of scanned signs can be straightforwardly mapped to suitable primitives of the encoding.