O uso lesivo de bebidas alcoólicas é o terceiro maior fator mundial de risco de doenças e incapacitação. O álcool pode causar várias alterações no Sistema Nervoso Central (SNC), dentre elas, a diminuição do processamento de informações visuais. Alguns estudos avaliam as alterações nos processos perceptuais durante a Síndrome de Abstinência do Álcool (SAA) por meio da ilusão visual da máscara côncava. Essa ilusão exemplifica o fenômeno ilusório de inversão visual da profundidade de uma máscara humana oca, que é percebida como convexa. Foi encontrado um possível desequilíbrio entre os componentes bottom-up e top-down da percepção visual provocado pelo álcool, capaz de prejudicar a capacidade do indivíduo de perceber essa ilusão. Entretanto, a presente pesquisa investiga uma hipótese alternativa, e sugere que a redução na frequência de respostas de inversão pode resultar de mudanças de critérios para emitir as repostas e não em alterações perceptuais. Para isso, foram utilizados os parâmetros da Teoria da Detecção de Sinal (TDS) aplicada à psicofísica. Participaram da pesquisa 20 indivíduos saudáveis, 20 com SAA leve e 20 com SAA moderada. Eles realizaram duas tarefas experimentais de observação monocular dos lados côncavo e convexo, alternadamente, de uma máscara da face humana de tamanho reduzido. Na tarefa de confidence rating, foram julgadas a concavidade ou convexidade da máscara e o grau de certeza nas respostas, com certeza ou com dúvida. Na tarefa de escolha forçada entre duas alternativas (2AFC), as máscaras foram apresentadas aos pares alternados e o participante identificava o lado côncavo. A análise dos resultados revelou que os indivíduos com SAA moderada apresentaram maiores escores para os índices de sensibilidade R-index, Az, e da, na tarefa de confidence rating, apontando para uma capacidade significativamente maior de identificação e discriminação dos lados côncavo e convexo da máscara. Isto reflete um prejuízo significativo na capacidade destes indivíduos em perceber a ilusão da máscara côncava. Não houve diferença entre os grupos de indivíduos saudáveis e com SAA leve. Entretanto, os grupos com SAA apresentaram um maior grau de certeza em seus julgamentos comparativamente ao grupo controle. Resultados semelhantes para o grupo com SAA moderada foram encontrados na tarefa de escolha forçada para os índices d e taxa de acerto, indicando maior capacidade desses indivíduos em discriminar os dois lados da máscara. Todos os participantes apresentaram critérios de decisão moderados na tarefa de confidence rating. Os indivíduos saudáveis, na tarefa de escolha forçada, se mostraram tão capazes quanto os com SAA moderada na discriminação dos dois lados da máscara. Os indivíduos saudáveis, na tarefa de escolha forçada, se mostraram tão capazes quanto os com SAA moderada na discriminação dos dois lados da máscara. Entretanto, supõe-se que esses resultados foram provenientes de estratégias inesperadas por esses indivíduos em seus julgamentos, prejudicando a validade interna dos resultados; e representam um viés de pesquisa importante. As análises apontam para um possível desequilíbrio, já relatado em estudos anteriores, entre os componentes bottom-up e top-down da percepção visual, provocado pelo álcool, que impede o SNC de corrigir hipóteses perceptuais ambíguas. / The harmful use of alcoholic beverages is the third largest worldwide risk factor for illness and disability. Alcohol can cause several changes in the Central Nervous System (CNS), among them, the decrease in the processing of visual information. Some studies evaluate changes in perceptual processes during Alcohol Withdrawal Syndrome (AWS) through the hollow face illusion. Its exemplifies the illusory visual depth inversion of a hollow human mask, which is perceived as convex. A possible imbalance was found between the bottomup and top-down components of visual perception caused by alcohol, which could impair the individual\'s ability to perceive the illusion. However, the present research investigates an alternative hypothesis, and suggests that the reduction in the frequency of inversion responses may result from changes in the criteria to issue responses rather than on perceptual changes. The parameters of the Signal Detection Theory (SDT) applied to psychophysics allow this analysis. Twenty healthy subjects, 20 with mild AWS and 20 with moderate AWS participated in the study. They performed two experimental tasks of monocular observation of concave and convex sides, alternately, of a reduced size human face mask. In the task of confidence rating, the concavity or convexity of the mask and the degree of certainty in the answers were judged: certainly or with doubt. In the task of forced choice between two alternatives (2AFC), the masks were presented in alternating pairs and the participant identified the concave side. The analysis of the results revealed that individuals with moderate AWS presented higher scores for the sensitivity index scores R-index, Az, and da, pointing to a significantly greater capacity of identification and discrimination of the concave and convex sides of the mask. This reflects a significant impairment in the ability of these individuals to perceive the hollow face illusion. There was no difference between healthy individuals and with mild AWS. However, all groups with AWS presented a greater degree of certainty in their judgments compared to the control group. Similar results for the group with moderate AWS were found in the task of forced choice to the indices d and hit rate, indicating a greater ability of these individuals to discriminate both sides of the mask. Healthy subjects, on the task of forced choice, showed themselves to be as capable as those with moderate AWS in discriminating both sides of the mask. However, it supposed that these results were from unexpected strategies used by these individuals in their judgments, impairing the internal validity of the results, and represented an important research bias. The analyzes point to a possible imbalance, already reported in previous studies, between the bottom-up and top-down components of visual perception, caused by alcohol, which inhibits the CNS from correcting ambiguous perceptual hypotheses.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2009. / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Includes bibliographical references (leaves 264-277). / The lateral line system on fish has been found to aid in schooling behavior, courtship communication, active and passive hydrodynamic imaging, and prey detection. The most widely used artificial prey stimulus has been the vibrating sphere, which some fish are able to detect even when the signal velocities to its lateral line are orders of magnitude smaller than background current velocities. It is not clear how the fish are able to extract this signal. This thesis uses a series of computational fluid dynamic (CFD) simulations, matched with recent experiments, to quantify the effects of 3D fish body parts on the received dipole signals, and to determine signal detection abilities of the lateral line system in background flow conditions. An approximation is developed for the dipole induced, oscillatory, boundary layer velocity profile over the surface of a fish. An analytic solution is developed for the case when the surface is a wall, and is accurate at points of maximal surface tangential velocity. Results indicate that the flow outside a thin viscous layer remains potential in nature, and that body parts, such as fins, do not significantly affect the received dipole signal in still water conditions. In addition, the canal lateral line system of the sculpin is shown to be over 100 times more sensitive than the superficial lateral line system to high frequency dipole stimuli. Analytical models were developed for the Mottled Sculpin canal and superficial neuromast motions, in response to hydrodynamic signals. When the background flow was laminar, the neuromast motions induced by the stimulus signal at threshold had a spectral peak larger than spectral peaks resulting from the background flow induced motions. / (cont.) When the turbulence level increased, the resulting induced neuromast motions had dominant low frequency oscillations. For fish using the signal encoding mechanisms of phase-locking or spike rate increasing, signal masking should occur. / by Mark Andrew Rapo. / Ph.D.

This study applied dual processing theory, the theory of working memory, and the theory of cue summation to examine how the video and audio in a television news story interact with or against each other when the story uses pull quote graphics to convey key information to viewers. Using eye-tracking, the study produced visual depictions of exactly what viewers look at on the screen when the words in the reporter's voice track match the text in the pull quote graphic verbatim, when the reporter summarizes the text in the graphic, and when the reporter's voice track ignores the text in the pull quote. The study tested the effect on recall when viewers were presented with these three story conditions—high redundancy, medium redundancy, and low redundancy, respectively. Key findings included the following: first, that stories with low redundancy resulted in lower recall and memory sensitivity scores (a measure of memory strength) than pull quotes that the reporter either summarized or read verbatim on the air. Second, it was found that neither high-redundancy nor medium-redundancy stories were superior or inferior to the other when looking at the effect on recall and memory sensitivity. And finally, in high-, medium-, and low-redundancy conditions, subjects stated that they relied more on the reporter's narration than the pull quote to get information. The study states possible implications for news producers and reporters and suggests future research in the broadcast television news industry.

This study applied dual processing theory, the theory of working memory, and the theory of cue summation to examine how the video and audio in a television news story interact with or against each other when the story uses pull quote graphics to convey key information to viewers. Using eye-tracking, the study produced visual depictions of exactly what viewers look at on the screen when the words in the reporter's voice track match the text in the pull quote graphic verbatim, when the reporter summarizes the text in the graphic, and when the reporter's voice track ignores the text in the pull quote. The study tested the effect on recall when viewers were presented with these three story conditions—high redundancy, medium redundancy, and low redundancy, respectively. Key findings included the following: first, that stories with low redundancy resulted in lower recall and memory sensitivity scores (a measure of memory strength) than pull quotes that the reporter either summarized or read verbatim on the air. Second, it was found that neither high-redundancy nor medium-redundancy stories were superior or inferior to the other when looking at the effect on recall and memory sensitivity. And finally, in high-, medium-, and low-redundancy conditions, subjects stated that they relied more on the reporter's narration than the pull quote to get information. The study states possible implications for news producers and reporters and suggests future research in the broadcast television news industry.

University of Macau / Faculty of Science and Technology / Department of Electrical and Electronics Engineering

In todays society, a growing number of users are demanding more sophisticated services from wireless communication devices. In order to meet these rising demands, it has been proposed to increase the capacity of the wireless channel by using more than one antenna at the transmitter and receiver, thereby creating multiple-input multiple-output (MIMO) channels. Using MIMO communication techniques is a promising way to improve wireless communication technology because in a rich-scattering environment the capacity increases linearly with the number of antennas. However, increasing the number of transmit antennas also increases the complexity of detection at an exponential rate. So while MIMO channels have the potential to greatly increase the capacity of wireless communication systems, they also force a greater computational burden on the receiver. Even suboptimal MIMO detectors that have relatively low complexity, have been shown to achieve unprecedented high spectral efficiency. However, their performance is far inferior to the optimal MIMO detector, meaning they require more transmit power. The fact that the optimal MIMO detector is an impractical solution due to its prohibitive complexity, leaves a performance gap between detectors that require reasonable complexity and the optimal detector. The objective of this research is to bridge this gap and provide new solutions for managing the inherent performance-complexity trade-off in MIMO detection. The optimally-ordered decision-feedback (BODF) detector is a standard low-complexity detector. The contributions of this thesis can be regarded as ways to either improve its performance or reduce its complexity - or both. We propose a novel algorithm to implement the BODF detector based on noise-prediction. This algorithm is more computationally efficient than previously reported implementations of the BODF detector. Another benefit of this algorithm is that it can be used to easily upgrade an existing linear detector into a BODF detector. We propose the partial decision-feedback detector as a strategy to achieve nearly the same performance as the BODF detector, while requiring nearly the same complexity as the linear detector. We propose the family of Chase detectors that allow the receiver to trade performance for reduced complexity. By adapting some simple parameters, a Chase detector may achieve near-ML performance or have near-minimal complexity. We also propose two new detection strategies that belong to the family of Chase detectors called the B-Chase and S-Chase detectors. Both of these detectors can achieve near-optimal performance with less complexity than existing detectors. Finally, we propose the double-sorted lattice-reduction algorithm that achieves near-optimal performance with near-BODF complexity when combined with the decision-feedback detector.

The objective of this research work is to develop reliable and power-efficient synchronization algorithms for continuous phase modulation (CPM). CPM is a bandwidth and power efficient signaling scheme suitable for wireless and mobile communications. Binary CPM schemes have been widely used in many commercial and military systems. CPM with multilevel symbol inputs, i.e., M-ary CPM, can achieve a higher data rate than binary CPM. However, the use of M-ary CPM has been limited due to receiver complexity and synchronization problems. In the last decade, serially concatenated CPM (SCCPM) has drawn more attention since this turbo-like coded scheme can achieve near Shannon-limit performance by performing iterative demodulation/decoding. Note that SCCPM typically operates at a low signal-to-noise ratio, which makes reliable and power-efficient synchronization more challenging. In this thesis, we propose a novel timing and phase recovery technique for CPM. Compared to existing maximum-likelihood estimators, the proposed data-aided synchronizer can achieve a better acquisition performance when a preamble is short or channel model errors are present. We also propose a novel adaptive soft-input soft-output (A-SISO) module for iterative detection with parameter uncertainty. In contrast to the existing A-SISO algorithms using linear prediction, the parameter estimation in the proposed structure is performed in a more general least-squares sense. Based on this scheme, a family of fixed-interval A-SISO algorithms are utilized to implement blind iterative phase synchronization for SCCPM. Moreover, the convergence characteristics of iterative phase synchronization and detection are analyzed by means of density evolution. Particularly, an oscillatory convergence behavior is observed when cycle slips occur during phase tracking. In order to reduce performance degradation due to this convergence fluctuation, design issues, including delay depth of the proposed algorithms, iteration-stopping criteria and interleaver size, are also discussed. Finally, for completeness of the study on phase synchronization, we investigate the error probability performance of noncoherently detected full-response CPM, which does not require channel (or phase) estimation.

The attachment system is activated when a threat is perceived in the environment. Attachment style differences moderate the levels of this activation. Whereas anxiously attached people are more hypervigilant to attachment-related stress, avoidant people have an ability to suppress their attachment related thoughts under stressful conditions. The aim of the present study was to investigate whether the subliminal presentation of threat and attachment figure primes interfere with the cognitive task performance of participants with different attachment styles. It was hypothesized that anxious participants would perform worse than secure and avoidant participants under both conditions of attachment-related threat and attachment figure primes. Avoidant participants were expected to perform poorly only when a threat prime is followed by an attachment figure prime. The securely attached participants were expected to perform better than the other attachment groups. University students (N = 225) filled out a questionnaire package including the measures of attachment figure names (WHOTO), attachment anxiety and avoidance (The Experiences in Close Relationships, ECR) / and they were administered computerized Signal Detection and Stroop tasks representing cognitive attentional performance in the laboratory. The results showed that attachment avoidance was a significant predictor of decreased cognitive performance, and attachment anxiety makes people vulnerable to cognitive performance decline only under certain circumstances of attachment system activation. Attachment security was identified to make individuals immune to the effects of threat or attachment figure availability priming on cognitive performance. The findings were discussed considering previous work and implications for cultural differences.

Wireless relay can be utilized to extend signal coverage, achieve spatial diversity by user cooperation, or shield mobile terminals from adverse channel conditions over the direct link. In a two-hop multi-input-multi-output (MIMO) amplify-and-forward (AF) relay system, the overall noise at the destination station (DS) consists of the colored noise forwarded from the relay station (RS) and the local white noise. We propose blind noise correlation estimation at the DS by utilizing statistics of the broadband relay channel over the RS-DS hop, which effectively improves signal detection at the DS. For further performance improvement, we also propose to estimate the two cascaded MIMO relay channels over the source-RS and the RS-DS links at the DS based on the overall channel between the source and the DS and the amplifying matrix applied at the RS. To cancel cross-talk interference at a channel-reuse-relay-station (CRRS), we utilize the random forwarded signals of the CRRS as equivalent pilots for local coupling channel estimation and achieve a much higher post signal-to-interference ratio (SIR) than the conventional dedicated pilots assisted cancellers without causing any in-band interference at the DS. When an OFDM-based RS is deployed on a high-speed train to shield mobile terminals from the high Doppler frequency over the direct link, inter-subchannel interference (ICI) mitigation is required at the RS. By utilizing statistics of the channel between the base station and the train, we develop both full-rate and reduced-rate OFDM transmission with inherent ICI self-cancellation via transmit and/or receive preprocessing, which achieve significant performance improvement over the existing ICI self-cancellation schemes.

This paper introduces a high-gain, low-noise band-pass filter system for detection/amplification of small signals. In addition, related theory and methodology are described for a specific design implementation. Simulation and experimental results are presented and discussed. The purpose of the implemented design was to construct a band-pass filter system with 102 dB gain and with an output noise level of less than 0.8V. The design of the high-gain band-pass filter system was achieved mainly with the help of Filter Pro, LTSpice IV, and Multisim 12. The thesis provides important support for the project Marker Locator and constitutes a valuable reference for future active filter system design and small signal detection/amplification. / Marker Locator