Virtual environment (VE) systems have been touted as exciting new technologies with many varied applications. Today VEs are used in telerobotics, training, simulation, medicine, architecture, and entertainment. The future use of VEs seems limited only by the creativity of its designers. However, as with any developing technology, some difficulties need to be overcome. Certain users of VEs experience negative side effects from being immersed into the graphically rendered virtual worlds. Some side effects that have been observed include: disorientation, headaches, and difficulties with vision. These negative side effects threaten the safety and effectiveness of VE systems. Negative side effects have been found to develop in a variety of environments. The research focus on VE side effects thus far has been on the symptoms and not the causes. The main goals of this research is fourfold: 1) to compare a new measure for side effects with established ones; 2) begin analyzing the causes of side effects with an analysis of head-tracking; 3) to examine any adaptation that may occur within a session and between days of a session; and, 4) to examine possible predictors for users who may experience side effects. An experiment was conducted using two different VEs with either head-tracking on or head-tracking off over four days. A questionnaire, a balance test, a vision test, and magnitude estimations of side effects were used to assess the incidence and severity of sickness experienced in the VEs. Other assessments, including a mental rotation test, perceptual style, and a questionnaire on pre-existing susceptibility to motion sickness were administered. All factors were analyzed to determine what their relationships were with the incidence and severity of negative side effects that result from immersion into the VEs. Results showed that head-tracking induces more negative side effects than no head-tracking. The maze task environment induces more negative side effects than the office task environment. Adaptation did not occur from day to day throughout the four testing sessions. The incidence and severity of negative side effects increased at a constant rate throughout the 30 minute immersive VE sessions, but did not show any significant changes from day to day. No evidence was found for a predictor that would foretell who might be susceptible to motion sickness in VEs. / Master of Science

In Earth-to-Space communications, well-known propagation effects such as path loss and atmospheric loss can lead to fluctuations in the strength of the communications link between a satellite and its ground station. Additionally, a less-often considered effect of shadowing due to the geometry of the satellite and its solar panels can also lead to link degradation. As a result of these anticipated channel impairments, NASA's communication links have been traditionally designed to handle the worst-case impact of these effects through high link margins and static, lower rate, modulation formats. This thesis first characterizes the propagation environment experienced by a software-defined radio on the NASA SCaN Testbed through a full link-budget analysis. Then, the following chapters propose, design, and model a link adaptation algorithm to provide an improved trade-off between data rate and link margin through varying the modulation format as the received signal-to-noise ratio fluctuates. / Master of Science

This study involves seismic monitoring of a deep coal mine. The purpose is to examine the processes responsible for induced seismicity. A seismic network consisting of five three-component short-period seismometers located above the mine recorded the seismic data. The events discussed here occurred from March 1, 2009 until April 7, 2011 during the mining of three longwall panels and the data was telemetered to Blacksburg, Virginia. A correlation equation was developed to relate local magnitude estimated by automatic data processing software in near real-time to seismic moment for well-recorded events. Local magnitude is a relative measure of relative size for a suite of earthquakes, while seismic moment is an objective measure of the actual physical size. Using the calculated seismic moments, we calculated "moment magnitudes" (Mw) for all events, which allowed us to do further studies in terms of their absolute size as a function of both time and space. The results indicate that there are two distinct classes of seismic events at the mine. The first class consists of small (M<=0) earthquakes recorded near the moving mine face. The second class of seismicity occurs in the mined-out "gob" area of the longwall panel at a greater distance behind the moving face. Their occurrence and relation to the mining history, depth of overburden and geology of the roof rocks is a significant interest. Results show that thick overburden due to elevated topography has a positive correlation with the number of seismic events but is not the only controlling factor; other factors include gob size and geological variability. Another important observation is the high seismic attenuation of the rock mass above the mine. This appears to be the result of the fracturing and caving processes associated with the creation of the gob and the resulting subsidence of the ground surface. / Master of Science

O objetivo do estudo foi entender a influência da marca na percepção de sabor do chocolate pelos consumidores. Foram avaliados 16 sujeitos (31,8 anos, ± 4,2 anos, 8 mulheres) medindo suas avaliações sobre os sabores de chocolates de diferentes marcas, com e sem o conhecimento da marca, e também sobre as marcas sem degustação do produto, como expectativa de sabor, utilizando Escalonamento Psicofísico de Estimativa de Magnitude Direta (EMD). Este método obtém do sujeito a sua impressão subjetiva direta do estímulo físico. Um chocolate foi escolhido como referencia (módulo) e recebeu o valor numérico de 100. A tarefa dos sujeitos foi degustar os chocolates, comparando com a degustação do módulo, e atribuir notas de acordo com a diferença de percepção de sabor, se a percepção de sabor fosse duas vezes melhor do que o módulo, ele deveria designar uma nota duas vezes o valor de referência. O procedimento foi o mesmo para as duas outras condições experimentais, marca e sabor conhecendo a marca. O expoente da curva de potência foi utilizado como a quantificação da magnitude da percepção dos sujeitos. O expoente obtido na avaliação somente do chocolate foi de 0,389 (Coeficiente de Correlação de Pearson r2=0,94) enquanto que somente da marca foi de 0,581 (r2=0,96). Teoricamente pode-se determinar o expoente da percepção de sabor com conhecimento da marca que seria 0,389/0,581 = 0,669, sendo que o expoente obtido empiricamente foi de 0,675 (r2=0,92). Assim concluí-se que a utilização da metodologia de Estimativa de Magnitude Direta para quantificar a preferência subjetiva dos sujeitos por chocolates considerando 2 variáveis, sabor e marca, foi bem sucedida. Os resultados sugerem que a associação de marca e sabor contribui para um efeito mais poderoso sobre a decisão sobre quanto o chocolate é mais saboroso. E como o expoente da percepção do sabor sabendo a marca é maior que os outros dois expoentes isolados pode-se sugerir que a marca possui uma grande influência na decisão / The aim of study was understand brand influence on consumer perception of chocolate flavor. 16 subjects (31.8 years, ± 4.2 years, 8 women) were evaluated by measuring their reviews of the flavors of different brands of chocolates, with and without the knowledge of the brand, and also about the brands without tasting the product, as expectation of flavor, using Psychophysical Scaling of Direct Ratio Magnitude Estimation (RME). This method gets the subject direct subjective impression of the physical stimulus. A chocolate was chosen as reference (modulus) and received the numerical value of 100. The task of subjects was tasting the chocolates, compare to the tasting of the module and assign grades according to the difference in taste perception, if perception of flavor was twice better than module, he should assign a score twice the reference value. The procedure was the same for the other two experimental conditions brand and flavor knowing the brand. The exponent of power law was used to quantify the magnitude of the perception of the subjects. The obtained exponent when examining only chocolate was 0.389 (Pearson correlation coefficient r2=0.94) while only the brand was 0.581 (r2=0.96). Theoretically, we can determine the exponent of the perception of flavor with brand awareness that would be 0.389/0.581=0.669, where the exponent obtained empirically was 0.675 (r2=0.92). Thus we conclude that the use of the methodology of Direct Ratio Magnitude Estimation to quantify the subject subjective preference for chocolate, considering two variables, flavor and brand, was successful. The results suggest that the association of brand and flavor makes for a more powerful effect on the decision about how much chocolate is tastier. And as the exponent of flavor perception knowing the brand is bigger than the other two isolates exponents can suggest that the brand has a great influence on the decision

O sistema visual é considerado o mais complexo de todos os sistemas sensoriais do ser humano. O objetivo da visão é construir uma representação dos objetos extraindo informações do ambiente, transformando-as em um código neural que origina a percepção. A compreensão dos fatores sensoriais que alteram a percepção é necessária para uma teoria adequada da percepção visual. Evidências sobre os efeitos do contexto ambiental ainda são limitadas, mas sabe-se que alterações no plano de fundo, criação de lacunas e mudanças de textura alteram a percepção de profundidade. Esse estudo teve como objetivo principal investigar quais fatores sensoriais básicos alteram a estimativa de magnitude (EM) de tamanho de círculos nos sujeitos saudáveis, verificando se existiu correlação entre a variação de parâmetros do estímulo físico com os respectivos julgamentos para diferentes condições visuais, além da possibilidade de desenvolver um instrumento para avaliação de algumas psicopatologias. O método da EM se refere a um procedimento no qual o observador faz um julgamento numérico direto de uma magnitude psicológica de uma série de percepções. Para isso, desenvolvemos um programa de computador como uma ferramenta psicofísica para medidas de EM que nos permitiu gerar 15 diferentes condições experimentais separadas em quatro protocolos (P1, P2, P3 e P4). O projeto consistiu em dois blocos: (1) de experimentos básicos, cujo objetivo foi abordar como elementos sensoriais visuais básicos interferiram no julgamento para estímulos simples, usando o P2, cujas variáveis luminância e o P4 no qual a disposição espacial para diferenças na lateralização do processamento visual foram alteradas; e (2) de exploração metodológica, que buscou manipular o valor de referência (P1) e a indução de sensações de profundidade (P3). Foram avaliados 78 indivíduos típicos (m = 27,55, dp = 4,69) com nível superior completo ou incompleto, todos com visão normal ou devidamente corrigida, distribuídos aleatoriamente em os quatro grupos 8 experimentais. Os protocolos 1 e 2 apresentaram os resultados mais satisfatórios que nos permitirão a utilização do programa em indivíduos com psicopatologias para investigação de diferenças da população normal. Ainda que os protocolos 3 e 4 tenham gerado dados controversos, levou-se em consideração que se tratou de um estudo de investigação metodológica, cuja continuidade nos permitirá uma melhor contribuição teórica alcançada com a retomada de estudos no campo da Psicofísica Clássica, principalmente devido a escassez de publicações nas últimas décadas acerca do tema aqui proposto / The visual system is considered the most complex human sensory system. The purpose of the vision is to create a representation of the objects by gathering information of the environment and converting it into a neural code that generates perception. The comprehension of sensory factors that influence the perception is necessary to an adequate theory of visual perception. Evidences about the effects of the context remain still limited, but it is known that some facts such as variations on backgrounds, creation of gaps and texture changes modify the perception of depth. This study aimed to investigate which are the basic sensory factors that change the Magnitude Estimation (ME) of the size of circles in healthy subjects, in order to verify if there was a correlation between parameter variations of physical stimulus and its respective judgments about different visual condition, in addition to the possibility of development of a screening test to assess some psychopathologies. The ME method is the procedure in which the observer makes a direct numeric judgment of a psychological magnitude of a series of perceptions. For this purpose, we developed a computer software which was used as a psychophysical tool in order to measure ME that allowed us to generate 15 different experimental conditions allocated into four protocols (P1, P2, P3 and P4). The project was composed of two blocs: (1) basic experiments, in whichthe objective was to investigate how basic sensory visual elements interfere on the judgment of simple stimulus, using P2 in which the variable luminance was changed and P4 in which spatial position to evaluate differences on lateralization of visual process was altered; and (2) methodological exploration, that aimed to manipulate the reference value (P1) and the induction of depth sensory perception (P3). Seventy-eight healthy subjects were tested (m = 27.55, sd = 4.69), that had a complete or incomplete graduation course, they all had normal or corrected-to-normal visual acuity, and they were randomly distributed into the four experimental groups. The protocols 1 and 2 10 had shown the most satisfactory results that will allow us to use the software in people with psychopathologies in attention to screen differences of the general population. Despite the protocols 3 and 4 had generated controversial data, it is important to consider this as a study about methodological investigation, and its follow up will lead us to an improvement of the theoretical contribution reached by the recovery of Classic Psychophysics experiments, mainly due to the last decades lack of publishing about this purposed topic

By studying the frequency domain of seismic signals generated by earthquakes, the source parameters can be recovered, i.e., the seismic moment (M0) and the stress drop (Δσ). This method is an advantage especially since if the source parameters are calculated from the time domain a full waveform inversion is needed, therefore this procedure facilitates the computation. Besides, the moment magnitude (Mw) can be calculated from the seismic moment and, in turn, the local magnitude (ML) can be obtained by using an algorithm that matches different ranges of moment magnitude with their corresponding local magnitude. In the present thesis, small to moderate earthquakes in Northern Sweden have been used to develop a code that calculates the source parameters through the fitting of five different spectral models and, this way, discerns which model obtains the best determination of the parameters. These models have been chosen in a way that we can also extract information about the attenuation. The different models are; the Brune spectral model, Boatwright spectral model, Boatwright spectral model with a fixed fall-off rate, a general form of the spectral model with quality factor equal to 1000 and a general form of the spectral model with quality factor equal to 600. Among these models, the Boatwright model with fixed fall-off rate equal to 2, has been found to give the best fit to the data used in this thesis. This might be due to the regional conditions which are the low attenuation in the crust of northern Fennoscandia and the short hypocentral distances of the studied earthquakes. The earthquakes studied in the present thesis have shown a range of magnitudes from ML 4.2 to -0.2 with radius of an assumed circular fault ranging from 269 m to 66 m.

No description available.

O sistema visual é considerado o mais complexo de todos os sistemas sensoriais do ser humano. O objetivo da visão é construir uma representação dos objetos extraindo informações do ambiente, transformando-as em um código neural que origina a percepção. A compreensão dos fatores sensoriais que alteram a percepção é necessária para uma teoria adequada da percepção visual. Evidências sobre os efeitos do contexto ambiental ainda são limitadas, mas sabe-se que alterações no plano de fundo, criação de lacunas e mudanças de textura alteram a percepção de profundidade. Esse estudo teve como objetivo principal investigar quais fatores sensoriais básicos alteram a estimativa de magnitude (EM) de tamanho de círculos nos sujeitos saudáveis, verificando se existiu correlação entre a variação de parâmetros do estímulo físico com os respectivos julgamentos para diferentes condições visuais, além da possibilidade de desenvolver um instrumento para avaliação de algumas psicopatologias. O método da EM se refere a um procedimento no qual o observador faz um julgamento numérico direto de uma magnitude psicológica de uma série de percepções. Para isso, desenvolvemos um programa de computador como uma ferramenta psicofísica para medidas de EM que nos permitiu gerar 15 diferentes condições experimentais separadas em quatro protocolos (P1, P2, P3 e P4). O projeto consistiu em dois blocos: (1) de experimentos básicos, cujo objetivo foi abordar como elementos sensoriais visuais básicos interferiram no julgamento para estímulos simples, usando o P2, cujas variáveis luminância e o P4 no qual a disposição espacial para diferenças na lateralização do processamento visual foram alteradas; e (2) de exploração metodológica, que buscou manipular o valor de referência (P1) e a indução de sensações de profundidade (P3). Foram avaliados 78 indivíduos típicos (m = 27,55, dp = 4,69) com nível superior completo ou incompleto, todos com visão normal ou devidamente corrigida, distribuídos aleatoriamente em os quatro grupos 8 experimentais. Os protocolos 1 e 2 apresentaram os resultados mais satisfatórios que nos permitirão a utilização do programa em indivíduos com psicopatologias para investigação de diferenças da população normal. Ainda que os protocolos 3 e 4 tenham gerado dados controversos, levou-se em consideração que se tratou de um estudo de investigação metodológica, cuja continuidade nos permitirá uma melhor contribuição teórica alcançada com a retomada de estudos no campo da Psicofísica Clássica, principalmente devido a escassez de publicações nas últimas décadas acerca do tema aqui proposto / The visual system is considered the most complex human sensory system. The purpose of the vision is to create a representation of the objects by gathering information of the environment and converting it into a neural code that generates perception. The comprehension of sensory factors that influence the perception is necessary to an adequate theory of visual perception. Evidences about the effects of the context remain still limited, but it is known that some facts such as variations on backgrounds, creation of gaps and texture changes modify the perception of depth. This study aimed to investigate which are the basic sensory factors that change the Magnitude Estimation (ME) of the size of circles in healthy subjects, in order to verify if there was a correlation between parameter variations of physical stimulus and its respective judgments about different visual condition, in addition to the possibility of development of a screening test to assess some psychopathologies. The ME method is the procedure in which the observer makes a direct numeric judgment of a psychological magnitude of a series of perceptions. For this purpose, we developed a computer software which was used as a psychophysical tool in order to measure ME that allowed us to generate 15 different experimental conditions allocated into four protocols (P1, P2, P3 and P4). The project was composed of two blocs: (1) basic experiments, in whichthe objective was to investigate how basic sensory visual elements interfere on the judgment of simple stimulus, using P2 in which the variable luminance was changed and P4 in which spatial position to evaluate differences on lateralization of visual process was altered; and (2) methodological exploration, that aimed to manipulate the reference value (P1) and the induction of depth sensory perception (P3). Seventy-eight healthy subjects were tested (m = 27.55, sd = 4.69), that had a complete or incomplete graduation course, they all had normal or corrected-to-normal visual acuity, and they were randomly distributed into the four experimental groups. The protocols 1 and 2 10 had shown the most satisfactory results that will allow us to use the software in people with psychopathologies in attention to screen differences of the general population. Despite the protocols 3 and 4 had generated controversial data, it is important to consider this as a study about methodological investigation, and its follow up will lead us to an improvement of the theoretical contribution reached by the recovery of Classic Psychophysics experiments, mainly due to the last decades lack of publishing about this purposed topic

O objetivo do estudo foi entender a influência da marca na percepção de sabor do chocolate pelos consumidores. Foram avaliados 16 sujeitos (31,8 anos, ± 4,2 anos, 8 mulheres) medindo suas avaliações sobre os sabores de chocolates de diferentes marcas, com e sem o conhecimento da marca, e também sobre as marcas sem degustação do produto, como expectativa de sabor, utilizando Escalonamento Psicofísico de Estimativa de Magnitude Direta (EMD). Este método obtém do sujeito a sua impressão subjetiva direta do estímulo físico. Um chocolate foi escolhido como referencia (módulo) e recebeu o valor numérico de 100. A tarefa dos sujeitos foi degustar os chocolates, comparando com a degustação do módulo, e atribuir notas de acordo com a diferença de percepção de sabor, se a percepção de sabor fosse duas vezes melhor do que o módulo, ele deveria designar uma nota duas vezes o valor de referência. O procedimento foi o mesmo para as duas outras condições experimentais, marca e sabor conhecendo a marca. O expoente da curva de potência foi utilizado como a quantificação da magnitude da percepção dos sujeitos. O expoente obtido na avaliação somente do chocolate foi de 0,389 (Coeficiente de Correlação de Pearson r2=0,94) enquanto que somente da marca foi de 0,581 (r2=0,96). Teoricamente pode-se determinar o expoente da percepção de sabor com conhecimento da marca que seria 0,389/0,581 = 0,669, sendo que o expoente obtido empiricamente foi de 0,675 (r2=0,92). Assim concluí-se que a utilização da metodologia de Estimativa de Magnitude Direta para quantificar a preferência subjetiva dos sujeitos por chocolates considerando 2 variáveis, sabor e marca, foi bem sucedida. Os resultados sugerem que a associação de marca e sabor contribui para um efeito mais poderoso sobre a decisão sobre quanto o chocolate é mais saboroso. E como o expoente da percepção do sabor sabendo a marca é maior que os outros dois expoentes isolados pode-se sugerir que a marca possui uma grande influência na decisão / The aim of study was understand brand influence on consumer perception of chocolate flavor. 16 subjects (31.8 years, ± 4.2 years, 8 women) were evaluated by measuring their reviews of the flavors of different brands of chocolates, with and without the knowledge of the brand, and also about the brands without tasting the product, as expectation of flavor, using Psychophysical Scaling of Direct Ratio Magnitude Estimation (RME). This method gets the subject direct subjective impression of the physical stimulus. A chocolate was chosen as reference (modulus) and received the numerical value of 100. The task of subjects was tasting the chocolates, compare to the tasting of the module and assign grades according to the difference in taste perception, if perception of flavor was twice better than module, he should assign a score twice the reference value. The procedure was the same for the other two experimental conditions brand and flavor knowing the brand. The exponent of power law was used to quantify the magnitude of the perception of the subjects. The obtained exponent when examining only chocolate was 0.389 (Pearson correlation coefficient r2=0.94) while only the brand was 0.581 (r2=0.96). Theoretically, we can determine the exponent of the perception of flavor with brand awareness that would be 0.389/0.581=0.669, where the exponent obtained empirically was 0.675 (r2=0.92). Thus we conclude that the use of the methodology of Direct Ratio Magnitude Estimation to quantify the subject subjective preference for chocolate, considering two variables, flavor and brand, was successful. The results suggest that the association of brand and flavor makes for a more powerful effect on the decision about how much chocolate is tastier. And as the exponent of flavor perception knowing the brand is bigger than the other two isolates exponents can suggest that the brand has a great influence on the decision

Current research in the field of numerical cognition reveals strong behavioral interactions and similar processing mechanisms for the perceptions of space, time, and number; which is generally believed to indicate that these dimensions share a common metric for representation in the brain. These three dimensions of magnitude––analog, ratio dependent representations of space, time, and number––are essential for interaction with the environment, and provide a conceptual basis on which further perceptual experience enhances the discrimination of distance, speed, numerosity, quantity, and size. Basic, approximate and non-verbal conceptions of spatial navigation, temporal orienting, and numerical computations have been found in human adults and children, as well as non-human animals, while the employment of discrete measures seems to be a consequence of a verbally and culturally mediated ontogenetic shift exclusive to humans (e.g. Feigenson, Libertus, and Halberda, 2013). This thesis investigates the link between nature and nurture, in an attempt to find the key factor that ultimately induces the ontogenetic shift from approximate to exact representations of space, time, and number. An extensive theoretical review is performed, based on both neuroscientific and cross-cultural data, where I propose that cultural and linguistic mediation is as vital to the representational advancement of numerical cognition as our biologically predisposed magnitude system. The neuroscientific approach is strongly based on a leading––but controversial––theory in the field of numerical cognition, ATOM (Walsh, 2003), which suggests that both human and non-human animals possess a generalized magnitude system with fully shared representational mechanisms for space, time, and number. To further illustrate the assumed theoretical stance of ATOM, an exploratory fMRI study with a single participant is performed, with results closely resembling those argued by Walsh (2003).