In some environments, there is a serious mismatch between the perceived (psychoacoustic) urgency of a warning and its situational urgency. In addition, many auditory warnings are not detectable within their environments. This research examined several prominent pulse parameters which affect the perceived urgency and detection time of auditory warning signals. These elements included pulse format (multitone sequential, multitone simultaneous, and rising sawtooth frequency-modulated pulse formats), pulse level (65 dBC and 79 dBC), and time between pulses (0 ms, 150 ms, and 300 ms). The environments of interest were those settings with steady-state broadband machinery noise. Conditions included a loading task which presented additional attentional demands upon the subject during the signal detection task. Free-modulus magnitude estimation quantified the relationship between auditory signal parameters and changes in perceived urgency. The method of paired comparisons was used to compare the perceived urgency of the auditory stimuli. Simple reaction time measured signal detectability. Signal effects were analyzed using a multivariate approach. Results indicated that there was a small but statistically significant relationship between perceived urgency and detection time. As perceived urgency increased, detection time decreased. Both perceived urgency and detection time were influenced by pulse level and format. The higher pulse level resulted in a greater perceived urgency of the signal and shorter detection time. Sequential signals were rated as less urgent than the other pulse formats, and subjects took longer to detect their occurrence. Under most conditions, there was no significant difference in the perceived urgency or detection time of simultaneous and frequency-modulated pulses. Time between pulses (inter-pulse interval) affected only perceived urgency, not detection time. The shorter the time between pulses, the greater the perceived urgency of the signal. / Ph. D.

Rain and other precipitation cause attenuation and depolarization of high frequency satellite signals. Some characteristics of rain can be measured by dual-polarized radar. These characteristics can then be used to predict the effects of the rain on satellite-path propagation. This thesis describes briefly the theory of radar and satellite link measurements. Methods for calibrating the equipment and deriving actual experimental values from measured power are presented in detail. A set of computer programs to approximately predict radar and link values from measured rain rate are developed. Predicted and measured values may then be compared by a researcher to evaluate system operation and assess the importance of the event data. A discussion of the use of sampled data and these comparisons concludes the report. / Master of Science

The advent of spectrum sharing has increased the need for robust interference rejection methods. The Citizens Broadband Radio Service (CBRS) band is soon to be occupied by LTE waveforms and License Assisted Access (LAA) will have LTE signals coexisting with other signals in the 5 GHz band. In anticipation of this need, we present a method for interference rejection of cyclostationary signals, which can also help avoid interference through better detection of low power co-channel signals. The method proposed in this thesis consists of a frequency-shift (FRESH) filter which acts as a whitening filter, canceling the interference by exploiting its cyclostationarity. It learns the cyclostationary characteristics of the interferer blindly, through a property restoration algorithm which aims to drive the spectrum to white noise. The property restoration algorithm, inspired by the constant modulus algorithm (CMA), is applied to each frequency bin to determine the optimal coefficients for the proposed CMA FRESH whitening filter (CFW). The performance of the CFW in interference rejection is compared to a time-invariant version, and proposed use cases are analyzed. The use cases consist of the rejection of a high powered, wider bandwidth interferer which is masking the signal-of-interest (SOI). The interferer is rejected blindly, with no knowledge of its characteristics. We analyzed signal detection performance in the case that the SOI is another user with much lower power, for multiple types of SOIs ranging from BPSK to OFDM. We also deal with the case that the SOI is to be received and demodulated; we recover it and compare resulting bit error rates to state of the art FRESH filters. The results show significantly better signal detection and recovery. / Master of Science / Wireless communication is complicated by the fact that multiple radios may be attempting to transmit at the same frequency, time and location concurrently. This scenario may be a due to malicious intent by certain radios (jamming), or mere confusion due to a lack of knowledge that another radio is transmitting in the same channel. The latter scenario is more common due to congested wireless spectrum, as the number of devices increases exponentially. In either case, interference results. We present a novel interference rejection method in this work, one that is blind to the properties of the interferer and adapts to cancel it. It follows the philosophy of property restoration as extolled by the constant modulus algorithm (CMA) and is a frequency shift (FRESH) filter, hence the name. The process of restoring the wireless spectrum to white noise is what makes it a whitening filter, and is also how it adapts to cancel interference. Such a filter has myriad possible uses, and we examine the use case of rejecting interference to detect or recover the signal-of-interest (SOI) that we are attempting to receive. We present performance results in both cases and compare with conventional time-invariant filters and state of the art FRESH filters.

Given the continuing deployment of total quality control and total quality management initiatives by organizations, employees have seen changes in their work environment. Furthermore, the impact of downsizing has resulted in operators becoming responsible for the quality of their own processes. This study tested the impact of various display alternatives of control chart data on decision performance and mental workload.  The control charts were shown as multiple two dimensional displays, a composite two dimensional display, and a composite three dimensional perspective display. Multiple two dimensional displays were found to have significantly higher decision accuracy and decision confidence ratings than either composite displays. No significant difference in decision accuracy and decision confidence ratings was found among the composite displays. The type of display did not have a significant effect on decision time. Mental workload was also found to be significantly affected by the type of display used. Multiple two dimensional displays imposed significantly lower levels of mental workload than either composite display. No significant difference in mental workload was found among the composite displays. These results indicated that multiple two dimensional displays should be used when control chart data from multiple processes must be displayed. / Master of Science

No description available.

Every day we are exposed to huge amounts of visual stimuli (scenes). However, i tis not yet clear how accurately these scenes are stored and remembered, and what is the role of detail relative to the memory for the whole image. More specifically, to what extent the details are remembered and to what extent we extrapolate the unseen content from the presented details. We used fragmented scenes (broken to 4x4 grids) to investigate this question. Fragmented scenes were composed of three different theme categories (indoor, natural, man-made), each with different number of presented patches (3, 5 and 8). Our main research question is, whether there is any relationship between the number of presented patches and the ability to recognize which patches were presented and which were not (but still patches from the same photograph). In analysis we focus on Signal Detection Theory characteristics, mainly memory sensitivity (d') and bias. We run two experiments and in both the highest scores for (d') were for 3 patches (Exp.1: d'(n3) = 0,67; Exp.2: d'(n3) = 0,66) with bias towards negative answers (Exp.1: c(n3) = 0,27; Exp.2: c(n3) = 0,16). For 5 and 8 patches the (d') was lower (Exp.1: d'(n5) = 0,35; d'(n8) = 0,34; Exp.2: d'(n5) = 0,39; d'(n8) = 0,41) and in the same time bias was towards positive answers...

published_or_final_version / Speech and Hearing Sciences / Master / Master of Science in Audiology

Shewanella oneidensis est une bactérie aquatique capable de chimiotactisme, c'est-à-dire d'orienter sa nage en réponse aux signaux qu'elle perçoit. Mon travail de thèse s'est focalisé sur l'étude du système chimiotactique de cette bactérie. Mon premier objectif a été d'identifier de nouveaux substrats induisant une réponse chimiotactique ainsi que les chimiorécepteurs les détectant. Une approche à haut débit utilisant une banque de substrats, couplée à une recherche de substrats plus spécifiques, a permis d'identifier de nouveaux signaux. Nous avons confirmé que S. oneidensis est attirée par les accepteurs alternatifs d'électrons ainsi que par certains métaux. Nous avons montré qu'elle est attirée par le malate et le chromate et repoussée par le nickel et le cobalt. Nous avons identifié deux MCPs potentiellement impliqués dans la détection du malate et un dans la détection du chromate.Mon second objectif a été de comprendre le rôle du système chimiotactique dans la formation d'un biofilm flottant : la pellicule. Nous avons montré que le développement de la pellicule est un processus en trois étapes déclenché par la détection de l'oxygène en condition statique, probablement par aérotactisme. Nous avons mis en évidence l'implication inattendue du chimiotactisme dans la formation de la pellicule. En effet des mutants délétés de gènes codant pour des éléments du système chimiotactique ne forment pas de pellicule normale. Le développement de la pellicule met en jeu d'autres signaux chimiotactiques, générés au sein de la pellicule, qui pourraient intervenir dans la localisation des cellules et l'homogénéisation de la pellicule au cours de sa maturation. / Shewanella oneidensis is an aquatic bacterium capable of chemotaxis, meaning that it can change its direction in response to detected signals. My thesis focused on the study of the chemotaxis system of this bacterium.The first objective of my thesis was to identify new substrates inducing a chemotactic response and the chemoreceptors involved in their detection. A high-throughput technique involving a library of solutes coupled with a search of more specific compounds allowed to identify new signals. We confirmed that S. oneidensis is attracted toward alternative electron acceptors and by several metals. We showed that S. oneidensis is attracted toward malate and also chromate. Finally, we identified two repellents, nickel and cobalt. After construction of deletion mutants, we identified two MCPs potentially involved in malate detection and one in chromate detection.The second objective of my thesis was to understand the role of the chemotaxis system in the formation of a floating biofilm: the pellicle. We first characterized the pellicle development through time, revealing that it is a three-step process. We then highlighted the unexpected role of the chemotaxis system in pellicle formation. Indeed mutants deleted of genes coding for chemotaxis elements are not able to form a pellicle or form an abnormal one. We showed that oxygen is the main signal triggering pellicle formation in static condition and that it is probably detected through aerotaxis. Pellicle development also involves other chemotactic signals produced in the pellicle which could be used in the localization of cells at the air-liquid interface but also in the homogenization of the pellicle.

A ocorrência de um estímulo auditivo imediatamente antes de um estímulo alvo visual reduz o tempo de reação em dezenas de milisegundos, um efeito atribuído a atenção temporal automática. O presente estudo investigou se este efeito é resultante de uma facilitação de mecanismos sensoriais. Dois experimentos foram realizados. No primeiro, foi realizada uma tarefa de tempo de reação simples por meio da resposta a estímulos alvos visuais com variações em sua detectabilidade. Esperava-se que o tamanho do efeito facilitador pudesse aumentar com o aumento da dificuldade de detecção do alvo. No segundo experimento foi realizada uma tarefa de acurácia. Os dados foram analisados pela teoria de detecção de sinais. Esperava-se que o estímulo precedente possibilitasse o aumento da detectabilidade do alvo e redução do critério de resposta. No primeiro experimento, não houve influência do estímulo precedente no aumento da detectabilidade do alvo. Os resultados do segundo experimento indicaram haver influência do estímulo precedente no aumento da detectabilidade do alvo e redução do critério pra a resposta. Esses resultados reforçam a teoria de que a atenção temporal automática facilita o processamento sensorial. / The occurrence of an auditory stimulus immediately before a visual target stimulus shortens reaction time by tens of milliseconds, an effect attributed to automatic temporal expectation. The present study investigated whether this effect results from a facilitation of sensory mechanisms. Two experiments were performed. In the first one the volunteers performed a simple reaction time task. They responded to visual targets which differ in detectability. It was expected that the size of the facilitatory effect would increase with the difficulty of target detection. In the second experiment the volunteers performed an accuracy task. Its data were analyzed on basis of signal detection theory. It was expected that the warning stimulus would increase the detectability of the target and lower the criterion to respond. The results of the first experiment did not indicate any influence of target detectability. The results of the second experiment indicate that both the detectability of the target and the criterion to respond were affected by the warning stimulus. These results provide support to the idea that automatic temporal expectancy facilitates sensory processing.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 336-341. / by David John Rossi. / Ph.D.