Background. A previous study on performance benefits of joint reduction for animations was made by the authors of this thesis. The results of the study showed that a reduction in joint count is highly beneficial for performance. What that study left out was the perception of Level of Detail (LoD) of animations, and what the Just Noticeable Difference (JND) of a percentage decrease on the joint count would be. Thus motivating a study on peoples’ perception of animation quality. Objectives. The aim is to study the perception of LoD of animations in a game-like environment whilst doing a simple search-and-click task. Aiming to find the JND between animations with a different number of joints while the players are set with a task that does not involve interacting with the characters performing the animation. Methods. A psychophysical experiment was performed using a game implementation in Unity. Unity was chosen because it has easy access to develop scripts and a game environment. Furthermore, it has a marketplace where already made content can be downloaded and reused, which made the user study much easier to create. Results. A total of 85.71% did not see any difference between the different qualities used for the animations. The 14.29% that saw a difference in the animations all saw the difference between the lowest and the one next to the lowest quality animation. Conclusions. Three out of 21 participants were able to see a difference in the lowest animation quality, whilst no one saw any difference in the other qualities. Thus, people were not able to see a density reduction of up to 62.26% fewer joints for the chosen animation. Due to the low number of positive detections in the quality change of the animations, the JND could not be reliably computed.

Joint torque feedback (JTF) is a new and promising means of kinesthetic feedback to provide information to a person or guide them during a motion task. However, little work has been done to apply the torque feedback to a person. This project evaluates the properties of JTF as haptic feedback, starting from the fabrication of a lightweight elbow haptic exoskeleton. A cheap hobby motor and easily accessible hardware are introduced for manufacturing and open-sourced embedded architecture for data logging. The total cost and the weights are $500 and 509g. Also, as the prerequisite step to assess the JTF in guidance, human perceptual ability to detect JTF was quantified at the elbow during all possible static and dynamic joint statuses. JTF slopes per various joint conditions are derived using the Interweaving Staircase Method. For either directional torque feedback, flexional motion requires 1.89-2.27 times larger speed slope, in mNm/(°/s), than the extensional motion. In addition, we find that JTFs during the same directional muscle's isometric contraction yields a larger slope, in mNm/mNm, than the opposing direction (7.36 times and 1.02 times for extension torque and flexion torque). Finally, the guidance performance of the JTF was evaluated in terms of time delay and position error between the directed input and the wearer's arm. When studying how much the human arm travels with JTF, the absolute magnitude of the input shows more significance than the duration of the input (p-values of <0.0001 and 0.001). In the analysis of tracking the pulse input, the highest torque stiffness, 95 mNm/°, is responsible for the smallest position error, 6.102 ± 5.117°, despite the applied torque acting as compulsory stimuli. / Doctor of Philosophy / Joint torque feedback (JTF) is a new and promising means of haptic feedback to provide information to a person or guide them during a motion task. However, little work has been done to apply the torque feedback to a person, such as determining how well humans can detect external torques or how stiff the torque input should be to augment a human motion without interference with the voluntary movement. This project evaluates the properties of JTF as haptic feedback, starting from the fabrication of a lightweight elbow haptic exoskeleton. The novelty of the hardware is that we mask most of the skin receptors so that the joint receptors are primarily what the body will use to detect external sensations. A cheap hobby motor and easily accessible hardware are introduced for manufacturing and open-sourced software architecture for data logging. The total cost and the weight are $500 and 509g. Also, as the prerequisite step to assess the JTF in guidance, human perceptual ability to detect JTF was quantified at the elbow during all possible static and dynamic joint statuses. A psychophysics tool called Interweaving Staircase Method was implemented to derive torque slopes per various joint conditions. For either directional torque feedback, flexional motion requires 1.89-2.27 times larger speed slope, in mNm/(°/s) than the extensional motion. In addition, the muscles' isometric contraction with the aiding direction required a larger slope, in $mathrm{mNm/mNm}$ than the opposing direction (7.36 times and 1.02 times for extension torque and flexion torque). Finally, the guidance performance of the JTF was evaluated in terms of time delay and position error between the directed input and the wearer's arm. When studying how much the human arm travels with JTF, the absolute magnitude of the input shows more significance than the duration of the input (p-values of <0.0001 and 0.001). In the analysis of tracking the pulse input, the highest torque stiffness, 95 mNm/°, is responsible for the smallest position error, 6.102 ± 5.117°, despite the applied torque acting as compulsory stimuli.

A avaliação objetiva da qualidade de imagens é de especial importância em diversas aplicações, por exemplo na compressão de imagens, onde pode ser utilizada para regular a taxa que deve ser empregada para que haja a máxima compressão (permitindo perda de dados) sem comprometer a qualidade final; outro exemplo é na inserção de marcas dágua, isto é, introdução de informações descritivas utilizadas para atestar a autenticidade de uma imagem, que devem ser invisíveis para o observador. O SSIM (Structural SIMilarity) é uma métrica de avaliação objetiva da qualidade de imagens de referência completa projetada para imagens em tons de cinza. Esta dissertação investiga sua aplicação na avaliação de imagens coloridas. Para tanto, inicialmente é feito um estudo do SSIM utilizando quatro diferentes espaços de cores RGB, YCbCr, L&#945;&#946; e CIELAB. O SSIM é primeiramente calculado nos canais individuais desses espaços de cores. Em seguida, com inspiração no trabalho desenvolvido em (1) são testadas formas de se combinar os valores SSIM obtidos para cada canal em um valor único os chamados SSIM Compostos. Finalmente, a fim de buscar melhores correlações entre SSIM e avaliação subjetiva, propomos a utilização da mínima diferença de cor perceptível, calculada utilizando o espaço de cores CIELAB, conjuntamente com o SSIM. Para os testes são utilizados três bancos de dados de imagens coloridas, LIVE, IVC e TID, a fim de se conferir consistência aos resultados. A avaliação dos resultados é feita utilizando as métricas empregadas pelo VQEG (Video Quality Experts Group) para a avaliação da qualidade de vídeos, com uma adaptação. As conclusões do trabalho sugerem que os melhores resultados para avaliação da qualidade de imagens coloridas usando o SSIM são obtidas usando os canais de luminância dos espaços de cores YCbCr, L&#945;&#946; e especialmente o CIELAB. Também se concluiu que a utilização da mínima diferença de cor perceptível contribui para o melhoramento dos resultados da avaliação objetiva. / Objective image quality evaluation is of special interest in many image applications, for example for image compression, where it can be used to control the rate in order to keep a tradeoff between lost of data and image quality; another example is in the application of watermarks, i.e., introduction of descriptive information used to guarantee the authenticity of an image, that must be invisible to the observer who looks at the image. SSIM (Structural SIMilarity) index is a full-reference image quality assessment metric developed to evaluate gray images. This work investigates the application of SSIM in the evaluation of color images. Therefore, four different color spaces are tested RGB, YCbCr, L&#945;&#946; e CIELAB. Initially SSIM is calculated individually for each one of color spaces channels. Then, inspired in (1), the results of the SSIM in the individual channels are combined in a unique result the so called Composite SSIM. Finally, in order to improve the correlations between, calculated using CIELAB color space, together with SSIM. Three color image databases, LIVE, IVC and TID, were employed in the tests in order to confer solidity to the results. The evaluation of the results is made using VQEG (Video Quality Experts Group) methodology, developed for video quality evaluation with an adaptation regarding the time dimension that does not exist in the image domain. The conclusions from the work were that SSIM performs better in the evaluation of color images when applied to luminance channel of YCbCr, L&#945;&#946; and especially to CIELAB color spaces. It was also concluded that the use of just noticeable difference concept improve objective assessment results.

A avaliação objetiva da qualidade de imagens é de especial importância em diversas aplicações, por exemplo na compressão de imagens, onde pode ser utilizada para regular a taxa que deve ser empregada para que haja a máxima compressão (permitindo perda de dados) sem comprometer a qualidade final; outro exemplo é na inserção de marcas dágua, isto é, introdução de informações descritivas utilizadas para atestar a autenticidade de uma imagem, que devem ser invisíveis para o observador. O SSIM (Structural SIMilarity) é uma métrica de avaliação objetiva da qualidade de imagens de referência completa projetada para imagens em tons de cinza. Esta dissertação investiga sua aplicação na avaliação de imagens coloridas. Para tanto, inicialmente é feito um estudo do SSIM utilizando quatro diferentes espaços de cores RGB, YCbCr, L&#945;&#946; e CIELAB. O SSIM é primeiramente calculado nos canais individuais desses espaços de cores. Em seguida, com inspiração no trabalho desenvolvido em (1) são testadas formas de se combinar os valores SSIM obtidos para cada canal em um valor único os chamados SSIM Compostos. Finalmente, a fim de buscar melhores correlações entre SSIM e avaliação subjetiva, propomos a utilização da mínima diferença de cor perceptível, calculada utilizando o espaço de cores CIELAB, conjuntamente com o SSIM. Para os testes são utilizados três bancos de dados de imagens coloridas, LIVE, IVC e TID, a fim de se conferir consistência aos resultados. A avaliação dos resultados é feita utilizando as métricas empregadas pelo VQEG (Video Quality Experts Group) para a avaliação da qualidade de vídeos, com uma adaptação. As conclusões do trabalho sugerem que os melhores resultados para avaliação da qualidade de imagens coloridas usando o SSIM são obtidas usando os canais de luminância dos espaços de cores YCbCr, L&#945;&#946; e especialmente o CIELAB. Também se concluiu que a utilização da mínima diferença de cor perceptível contribui para o melhoramento dos resultados da avaliação objetiva. / Objective image quality evaluation is of special interest in many image applications, for example for image compression, where it can be used to control the rate in order to keep a tradeoff between lost of data and image quality; another example is in the application of watermarks, i.e., introduction of descriptive information used to guarantee the authenticity of an image, that must be invisible to the observer who looks at the image. SSIM (Structural SIMilarity) index is a full-reference image quality assessment metric developed to evaluate gray images. This work investigates the application of SSIM in the evaluation of color images. Therefore, four different color spaces are tested RGB, YCbCr, L&#945;&#946; e CIELAB. Initially SSIM is calculated individually for each one of color spaces channels. Then, inspired in (1), the results of the SSIM in the individual channels are combined in a unique result the so called Composite SSIM. Finally, in order to improve the correlations between, calculated using CIELAB color space, together with SSIM. Three color image databases, LIVE, IVC and TID, were employed in the tests in order to confer solidity to the results. The evaluation of the results is made using VQEG (Video Quality Experts Group) methodology, developed for video quality evaluation with an adaptation regarding the time dimension that does not exist in the image domain. The conclusions from the work were that SSIM performs better in the evaluation of color images when applied to luminance channel of YCbCr, L&#945;&#946; and especially to CIELAB color spaces. It was also concluded that the use of just noticeable difference concept improve objective assessment results.

Voluntary actions affect subsequent perception. For example, an action that precedes an auditory stimulus is perceived to have occurred later in time than is actually the case, while the auditory stimulus is perceived earlier in time. This effect is known as intentional binding. Current literature regarding action effects focuses on perception of a single sensory modality while the effects on perception of multiple modalities remain largely unknown. The present thesis explored how actions influenced the timing of perceived multisensory events. Additionally, this thesis investigated differences in voluntary compared to involuntary actions on subsequent perception. In Chapter 2, action effects on perceived onsets of visual and tactile stimuli were explored. This question was extended to other bimodal pairs, including audiovisual and audiotactile, in Chapter 3. Lastly, in Chapter 4, action effects on temporal resolution were investigated. In all the experiments, participants performed a chosen or a fixed button press that followed a bimodal temporal order judgment (TOJ) task. To investigate the influence of spatial proximity between actions and stimuli on binding, in Chapters 2 and 3, each stimulus modality appeared on different sides. In Chapter 4, the critical stimuli appeared at the same location, either close to or far from the preceding action, to explore the effect of action on temporal resolution. The present data provide evidence that actions affect the perceived onsets of multisensory events in an idiosyncratic manner, depending on the subsequent stimuli. Actions appear to preferentially bind to vision, then touch, and lastly, audition, but actions do not always bind to subsequent stimuli. Furthermore, actions degrade temporal resolution of bimodal stimuli. Lastly, the type of action, whether chosen or fixed, did not impact the degree of binding. Together, these data contribute to the action-perception literature, illustrating that our behaviours dynamically affect how we perceive the world. / Dissertation / Doctor of Philosophy (PhD)

Dans les sociétés industrialisées, les humains sont exposés à multiples sources de mouvements vibratoires. Jusqu'à présent, l’analyse de l'effet des stimuli vibratoire dans son ensemble a été bien développée, plus précisément en ce qui concerne le seuil de perception. Au cours des dernières années, diverses études ont analysé l'influence de certains facteurs.Cependant, l'effet d'une des composantes du stimulus sur la perception d'autres composants a été rarement rapporté. Dans ce cas, très peu d'information a été trouvée dans la littérature. Dans les deux études trouvées, le seuil absolu a été réévalué en considérant un second signal sinusoïdal. La valeur du seuil était plus élevée que ce qui a été estimé avec le stimulus simple. L'augmentation du seuil a été attribuée à l'effet de masquage. Basé sur ces observations, cette étude examine l'existence de l'effet de masquage dans les vibrations vertical du corps entière. Afin d'examiner l'effet de masquage, la différence entre le seuil absolu et le seuil masqué est nécessaire. Deux types de stimuli ont été utilisés : le stimulus masquage et le stimulus de test. Le masque est un signal de bruit à bande étroite entre 10 et 20 Hz, à trois niveaux d'amplitude différents. La sélection du stimulus de masque a été basée sur le modèle de masquage largement étudié dans certains domaines tels que l'acoustique, le domaine visuel et vibrotactile. Le stimulus de test est un signal sinusoïdale d'amplitude modulée à six fréquences différentes (30, 35, 40, 50, 60, 80 Hz. L'effet de la fréquence sur le seuil absolu estimé est similaire à ce qui a été indiqué par d'autres études. La détection du stimulus en présence du signal de masquage a été empêchée. Par conséquent, il est certainement clair que le phénomène de masquage a eu lieu. Les valeurs des seuils masqués étaient considérablement plus élevées que ceux correspondant aux seuils absolus. Le seuil décroît en fonction de la fréquence de test et l'effet de masque est plus important à haute qu’à faible niveau d'intensité du masque. Le démasquage est lié à l’écart entre les fréquences des signaux masquant et de test. Lorsque l’écart est faible, prévaut la reconnaissance de l’augmentation de l’intensité globale d'énergie. Si l’écart augmente, la discrimination des signaux prédomine. / In industrialized societies, humans are exposed to multiple sources of vibratory motions. To date, the analyses of the impact of vibratory stimuli as a whole have been well developed, more precisely with respect to perception threshold. Along recent years various studies have been analyzed the influence of some factors involved.However, the effect of one component of the stimulus in to perception of other components has been rarely reported. In this case, little information was found in the literature. In two studies found, the absolute threshold was revalued by integrating a second sinusoidal signal. The threshold value was higher that which has been estimated with the simple stimulus. The increase of threshold has been attributed to a masking effect. Based on these remarks, this study investigates the existence of masking effect for vertical whole body vibration, in particular to sitting position. To examine the masking effect, the difference between absolute and masked thresholds is required. Two types of stimuli have been used: the masking and the test stimulus. The masker is a narrow-band noise from 10 to 20 Hz at three different magnitude levels. The selection of mask stimulus was based on the masking model widely studied in acoustic, visual and vibrotactile areas. The test stimulus is a sinusoidal modulated amplitude signal at six different frequencies (30, 35, 40, 50, 60, 80 Hz). The frequency dependence of the absolute threshold estimated is similar to the results presented in other studies. The stimulus detection in the presence of the masking signal has been prevented. Therefore, it is certainly clear that the masking phenomenon occurred. The masked thresholds values were considerably higher than those absolute thresholds. The threshold decreases as a function of test frequency and the mask effect is more important at high than at low intensity masker levels. The unmasking is related to the difference between the mask and test signals frequencies. When the difference is small, the recognition of the increase in the overall energy intensity predominates. However, if the difference increases, then the discrimination of signals is dominant.

<p>  </p> <p>The prevalence of obesity and type 2 diabetes has increased worldwide over the last decades. Sugar-sweetened beverages are especially problematic in the development of obesity and type 2 diabetes. Although the proportion of Americans consuming SSB regularly has been steadily declining, added sugar intake still remains above recommendations by the Dietary Guidelines for Americans and World Health Organization. However, alternatives to SSB exist on the market. For many years, the primary alternatives to SSB were low-calorie sweetened beverages, with sweetness replacers such as aspartame or sucralose. In recent years, options that are less sweet or unsweetened (instead of alternatively sweetened) have become increasingly available. These less-sweet beverages are available in similar packaging and at similar cost as SSB. Thus, these less-sweet beverages may be ideal options to reduce added sugar in the diet. However, few studies have tested switching consumers from SSB to less-sweet beverages (rather than low-calorie sweetened beverages or plain water), and thus the acceptability and implications of this dietary change are minimally documented. In this work, we tested less sweet soda-like beverages and unsweetened sparkling waters for potential to replace SSB. First, we showed that small reductions in sweetness in cola-flavored sodas are noticeable to individuals, meaning that any switch from SSB to less-sweet options will likely need to be overt to the consumer. Next, we conducted a 12-week intervention with adolescents, which showed that replacing SSBs with unsweetened sparkling waters leads to increased liking of less-sweet sodas and shifts in the ideal level of sweetness towards lower sugar concentrations. Building on these results, our final study shows that even just 2 weeks is enough time to induce these changes in acceptance of less sweetness in sodas, if a consumer prefers the higher concentrations of sugar at the beginning of the intervention (a “sweet liker”). Future studies are needed to evaluate how replacing SSB with less sweet options, leading to shifts in sweetness preference, might influence overall diet and risks for diet-related chronic diseases.</p>

This dissertation presents research in the development and use of a multi-modal visual and haptic virtual model in higher education. The model, named Chemical Force Feedback (CFF), represents molecular recognition through the example of protein-ligand docking, and enables students to simultaneously see and feel representations of the protein and ligand molecules and their force interactions. The research efforts have been divided between educational research aspects and development of haptic feedback techniques. The CFF model was evaluated in situ through multiple data-collections in a university course on molecular interactions. To isolate possible influences of haptics on learning, half of the students ran CFF with haptics, and the others used the equipment with force feedback disabled. Pre- and post-tests showed a significant learning gain for all students. A particular influence of haptics was found on students reasoning, discovered through an open-ended written probe where students' responses contained elaborate descriptions of the molecular recognition process. Students' interactions with the system were analyzed using customized information visualization tools. Analysis revealed differences between the groups, for example, in their use of visual representations on offer, and in how they moved the ligand molecule. Differences in representational and interactive behaviours showed relationships with aspects of the learning outcomes. The CFF model was improved in an iterative evaluation and development process. A focus was placed on force model design, where one significant challenge was in conveying information from data with large force differences, ranging from very weak interactions to extreme forces generated when atoms collide. Therefore, a History Dependent Transfer Function (HDTF) was designed which adapts the translation of forces derived from the data to output forces according to the properties of the recently derived forces. Evaluation revealed that the HDTF improves the ability to haptically detect features in volumetric data with large force ranges. To further enable force models with high fidelity, an investigation was conducted to determine the perceptual Just Noticeable Difference (JND) in force for detection of interfaces between features in volumetric data. Results showed that JNDs vary depending on the magnitude of the forces in the volume and depending on where in the workspace the data is presented.