Military unmanned aerial vehicles (UAVs) perform missions in airspace where one of the mission goals may be radar-detection avoidance. The research conducted aimed at determining optimum flight-path routes that make maximum utilization of UAV terrain masking opportunities and flight range capability in avoiding radar detection. The problem was formulated as one of constrained optimization in three dimensions and advantageous solutions were identified using Algorithm A*. The study conducted extended the substantial existing literature on radar-detection avoidance for UAVs in three significant ways: First, it explicitly modeled prominent terrain cover, such as forests and urban areas, in masking radar detection through the adaptation of a ray-casting technique in order to determine if expanded flight path cells were visible to any nearby radar. Any existing terrain cover masking prospects were exploited by the algorithm to avoid radar detection, in addition to prospects arising for terrain masking through topographical features. Second, it explicitly modeled the trade-off between detection risk and flight-path length by using a weighted average of the total flight-path length and the radar detectable flightpath length as the objective function to be minimized. The relative importance of detection risk and flight-path length is captured by adjusting the weights. Third, a mission planning process was obtained allowing route selection based on the characteristics of a portfolio of parameters and options, including radar detection exposure, the total distance traveled on a respective flight path, and a computed missile shoot-down risk benchmark for each option. The benchmark estimates the likelihood of aircraft destruction from missile impact subsequent to an integrated air defense system detection, acquisition, tracking, and missile launch sequence. The model was further extended to include provisions for preferred altitude ranges, adjustable aircraft climb and descent rate envelopes, fractional detection probability based movement costs (accounting for simultaneous detection by multiple radars), radar horizon masking, and a perspective based ellipsoidal radar cross section model. Resulting routes can be executed at a significantly lower expected cost than the alternative of using a human piloted stealth aircraft that may be required for a similar mission in the absence of intelligent route-planning.

The dual heap virtual implementation provided a new base for memory organization such that the heap storage can be virtually enlarged to include the extremely large disk space. Two simulation models were used to investigate aging in physical space as well as the dual heap implementation. The simulators generated results which measured the ability of each method to detect leaks generate false positives and false negatives. In comparison, the dual heap implementation showed a relatively better performance than the aging algorithm. The dual heap implementation is shown to produce less false positives and less false negatives. It has better capability of detecting memory leaks. Furthermore, dual heap implementation extends the space provide to the main heap such that programs with greedy memory consumption can also benefit from this implementation. The dual heap virtual model of the heap organization is a promising architecture, which at once masks the memory leak problem and extends the heap storage for greedy programs. The introduction and advancement of 64-bit address machine would not reduce the value of the dual virtual heap implementation, for the simple reasons that a large number of legacy programs will continue to run in a 32-bit environment, and for the fact that greedy programs and leaks will drain the heap storage of 64-bit machines as much as they did for the 32-bit machines.

Sound transmission devices have advanced filtering abilities that theoretically protect the ear from harmful Masking noise while amplifying the sounds that need to be heard, such as backup alarms. Therefore, such devices should provide improved signal detection in noise when compared to their passive counterparts. The masked threshold of a vehicular backup alarm was determined for audiometrically normal and non-normal hearers using two types of sound transmission devices and their passive counterparts within pink noise and milling machine noise at intensities of 75, 85, 95 and 105 dBA. Results indicated that the sound transmission devices did not have any statistically significant advantages over the passive devices with respect to masked threshold of a backup alarm. Therefore, it cannot be concluded that these devices offer advantage over similar passive devices with respect to signal detection. Additionally, ratings of comfort and the ability to detect the alarm for each device were gathered. Both scales did not show any significant differences between the two device types. / Master of Science

Title from first page of PDF document. Includes bibliographical references (p. 29-32).

Die bipolare Störung ist eine in depressiven und manischen Phasen verlaufende psychiatrische Erkrankung. Zwischen diesen Phasen kehren die Betroffenen zu einer ausgeglichenen Stimmungslage zurück. Dennoch verschlechtert sich der kognitive Allgemeinzustand der Patienten mit zunehmender Erkrankungsdauer und Anzahl der durchlittenen Episoden, was auch in euthymen Phasen erkennbar ist. Lithium ist das Medikament erster Wahl, das zur Behandlung der bipolaren Störung eingesetzt wird. Es zeichnet sich durch seine antimanische, antisuizidale und phasenprophylaktische Wirkung aus. In Zell- und Kleintierstudien konnte zudem gezeigt werden, dass Lithium sich positiv auf die Resilienz von Neuronen auswirkt und eine Zellen-erhaltende Wirkung hat. Im Rahmen dieser multizentrischen Querschnittstudie soll gezeigt werden, dass die neuroprotektiven Eigenschaften von Lithium sich bei einer Langzeitbehandlung auch schützend auf die kognitive Leistungsfähigkeit bipolarer Patienten auswirkt. Um diesen Effekt zu belegen, verglichen wir 3 Gruppen: Patienten mit einer bipolaren Störungvon einer minimalen Erkrankungsdauer von 10 Jahren und minimal 5 Erkrankungsepisoden mit (akut, seit mindestens 2 Jahren) und ohne (insgesamt maximal 3 Monate, vor mindesten 2 Jahren) Lithium-Langzeitbehandlung und gesunde Kontrollprobanden miteinander. Im Rahmen dieser Studie wurden folgende Daten erhoben: Hippokampusvolumen gemessen mit MRT, NAA-Konzentration im DLPFC gemessen mit MRS, Lebensqualität gemessen mit Quality of Well-Being Scale, allgemeine Intelligenz gemessen mit der HAWIE Testbatterie, verbales Lernen und Merkfähigkeit gemessen mit CVLT und frühe visuelle Informationsverarbeitung sowie Reaktionsgeschwindigkeit gemessen mit VBMT. Im Rahmen dieser Dissertation wurden die Ergebnisse der VBMT ausgewertet und interpretiert. Insgesamt wurden die Daten von 142 Studienteilnehmern ausgewertet, von denen 31 Patienten ohne Lithiumbehandlung, 58 mit Lithiumbehandlung und 53 gesunde Kontrollprobanden waren. Entgegengesetzt zur Studienhypothese, schnitten Patienten mit einer Lithiumbehandlung bezüglich Reaktionsgeschwindigkeit und Fehlerquote schlechter bei der VBMT ab, als gesunde Kontrollprobanden, aber auch als Patienten mit einer bipolaren Störung ohne Lithiumbehandlung. Bei der Untersuchung von allgemeiner Intelligenz und verbaler Lern- und Merkfähigkeit konnte kein signifikanter Unterschied zwischen den drei Gruppen gefunden werden. Dennoch wird bei Betrachtung der absoluten Zahlen deutlich, dass auch bei diesen Untersuchungen Patienten schlechter abschneiden als Gesunde und dass Lithiumpatienten tendenziell schlechter abschneiden als Patienten ohne Lithiumbehandlung. Andererseits ergaben die hirnphysiologischen Untersuchungen dieser Studie, dass sowohl die NAA-Konzentration, als neuronaler Marker, und auch das Volumen des Hippokampus bei Patienten mit Lithiumbehandlung größer war, als bei Patienten ohne Lithiumbehandlung. Zwischen den Volumina und den NAA-Levels der Lithiumpatienten und gesunder Probanden gab es keinen Unterschied. Aus diesen Ergebnissen lässt sich schlussfolgern, dass Lithium auch beim Menschen einen Zell-erhaltenden Effekt hat, der sich jedoch nur physiologisch messen lässt und sich nicht auf die neurokognitive Fähigkeit auswirkt. Patienten mit einer Lithiumbehandlung scheinen zwar eine bessere Resilienz ihrer neuronalen Zellen aufzuweisen, haben aber größere kognitive Defizite. Ob diese Defizite kausal mit der Lithiumbehandlung zusammenhängen, lässt sich bei einem einmaligen Messzeitpunkt nicht aussagen. Des Weiteren ist der kognitive Defizit deutlicher bei der Testung der frühen visuellen Informationsverarbeitung und Reaktionsgeschwindigkeit, gemessen mit der VBMT, als bei Merkfähigkeit und allgemeiner Intelligenzleistung zu erkennen. Dies deutet darauf hin, dass die Hirnregionen, welche bei der frühen visuellen Informationsverarbeitung und psychomotorischer Steuerung beteiligt sind, bei bipolaren Patienten stärker als bei Gesunden, und bei Lithiumpatienten stärker als bei Nicht-Lithiumpatienten beeinträchtigt sind.

Yes / Many visual effects are believed to be processed at several functional and anatomical levels of cortical processing. Determining if and how the levels contribute differentially to these effects is a leading problem in visual perception and visual neuroscience. We review and analyze a combination of extant psychophysical findings in the context of neurophysiological and brain-imaging results. Specifically using findings relating to visual illusions, crowding, and masking as exemplary cases, we develop a theoretical rationale for showing how relative levels of cortical processing contributing to these effects can already be deduced from the psychophysically determined functions relating respectively the illusory, crowding and masking strengths to the contrast of the illusion inducers, of the flankers producing the crowding, and of the mask. The wider implications of this rationale show how it can help to settle or clarify theoretical and interpretive inconsistencies and how it can further psychophysical, brain-recording and brain-imaging research geared to explore the relative functional and cortical levels at which conscious and unconscious processing of visual information occur. Our approach also allows us to make some specific predictions for future studies, whose results will provide empirical tests of its validity.

The study investigated the effects of noise, one of the major environmental stressors, on speech perception and spoken word comprehension. Three tasks were employed – listening span, listening comprehension, and shadowing – in order to find out to what extent different types of background noise affected speech perception and encoding into working verbal memory, as well as spoken word comprehension. Six types of maskers were used – (1) single babble masker in English, (2) single babble masker in Mandarin, (3) multi babble masker in Greek and (4) construction site noise, (5) narrow-band speech signal emulating phone effect and (6) reverberated speech signal. These could be categorized as energetic (2, 3, and 4), informational (1) and signal degradation (6 and 7) noise maskers. The study found that general speech perception and specific word comprehension are not equally affected by the different noise maskers – if shadowing is considered primarily a task relying on speech perception, with the other two tasks considered to rely on working memory, word comprehension and semantic inference. The results indicate that informational masking is most detrimental to speech perception, while energetic masking and sound degradation are most detrimental to spoken word comprehension. The results imply that masking categories must be used with caution, since not all maskers belonging to one category had the same effect on performance. Finally, introducing a noise component to any memory task, particularly to speech perception and spoken word recognition tasks, adds another cognitively stimulating real-life dimension to them. This could be beneficial to students training to become interpreters helping them to get accustomed to working in a noisy environment, an inevitable part of this profession. A final study explored the effects of noise on automatic speech recognition. The same types of noise as in the human studies were tested on two automatic speech recognition programs: Otter and Ava. This technology was originally developed as an aid for the deaf and hard of hearing. However, their application has since been extended to a broad range of fields, including education, healthcare and finance. The analysis of the transcripts created by the two programs found speech to text technology to be fairly resilient to the degradation of the speech signal, while mechanical background noise still presented a serious challenge to this technology. / Dissertation / Doctor of Philosophy (PhD) / The study investigated the effects of noise, one of the major environmental stressors, on speech perception and spoken word comprehension. Throughout three different tasks (listening span task, in which participants were asked to recall a certain number of items from a list; listening comprehension task, in which listeners needed to demonstrate understanding of the incoming speech; and shadowing, in which listeners were required to listen and simultaneously repeat aloud the incoming speech), various types of background noise were presented in order to find out which ones would cause more disruptions to the two cognitive processes. The study found that general speech perception and specific word comprehension are not equally affected by the different noise maskers – provided that shadowing is considered primarily a task relying on speech perception, with the other two tasks considered to rely on working memory, word comprehension and semantic inference, or the way the listener combines and synthesizes information from different parts of a text (or speech) in order to establish its meaning. The results indicate that understandable background speech is most detrimental to speech perception, while any type of noise, if loud enough, as well as degraded target speech signal are most detrimental to spoken word comprehension. Finally, introducing a noise component to these tasks, adds another cognitively stimulating real-life dimension, which could potentially be beneficial to students of interpreting by getting them accustomed to working in a noisy environment, an inevitable part of this profession. Another field of application is the optimization of speech recognition software. In the last study, the same types of noise as used in the first studies were tested on two automatic speech recognition programs. This technology was originally developed as an aid for the deaf and hard of hearing. However, its application has since been extended to a broad range of fields including education, healthcare and finance. The analysis of the transcripts created by the two programs found speech to text technology to be fairly resilient to a degraded speech signal, while mechanical background noise still presented a serious challenge to this technology.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / The Bit Rate Agile Onboard Telemetry Formatting (BRAOTF) system was developed by Killdeer Mountain Manufacturing to address increasing demands on the efficiency of telemetry systems. The BRAOTF thins and reorders data streams, adjusting the bit rate of a pulse code modulation (PCM) stream using a bit-locked loop to match the desired information rate exactly. The BRAOTF accomplishes the adjustment in hardware, synthesizing a clock whose operating frequency is derived from the actual timing of the input format. Its firmware manages initialization and error management. Testing has confirmed that the BRAOTF implementation meets its design goals.

While humans can separate a sound of interest amidst a cacophony of contending sounds in an echoic environment, machine-based methods lag behind in solving this task. This thesis thus aims at improving performance of audio separation algorithms when they are informed i.e. have access to source location information. These locations are assumed to be known a priori in this work, for example by video processing. Initially, a multi-microphone array based method combined with binary time-frequency masking is proposed. A robust least squares frequency invariant data independent beamformer designed with the location information is utilized to estimate the sources. To further enhance the estimated sources, binary time-frequency masking based post-processing is used but cepstral domain smoothing is required to mitigate musical noise. To tackle the under-determined case and further improve separation performance at higher reverberation times, a two-microphone based method which is inspired by human auditory processing and generates soft time-frequency masks is described. In this approach interaural level difference, interaural phase difference and mixing vectors are probabilistically modeled in the time-frequency domain and the model parameters are learned through the expectation-maximization (EM) algorithm. A direction vector is estimated for each source, using the location information, which is used as the mean parameter of the mixing vector model. Soft time-frequency masks are used to reconstruct the sources. A spatial covariance model is then integrated into the probabilistic model framework that encodes the spatial characteristics of the enclosure and further improves the separation performance in challenging scenarios i.e. when sources are in close proximity and when the level of reverberation is high. Finally, new dereverberation based pre-processing is proposed based on the cascade of three dereverberation stages where each enhances the twomicrophone reverberant mixture. The dereverberation stages are based on amplitude spectral subtraction, where the late reverberation is estimated and suppressed. The combination of such dereverberation based pre-processing and use of soft mask separation yields the best separation performance. All methods are evaluated with real and synthetic mixtures formed for example from speech signals from the TIMIT database and measured room impulse responses.

A practical model is proposed for predicting the detectability of targets at arbitrary locations in the visual field, in arbitrary gray-scale backgrounds, and under photopic viewing conditions. The major factors incorporated into the model include: (i) the optical point spread function of the eye, (ii) local luminance gain control (Weber's law), (iii) the sampling array of retinal ganglion cells, (iv) orientation and spatial-frequency dependent contrast masking, (iv) broadband contrast masking, (vi) and efficient response pooling. The model is tested against previously reported threshold measurements on uniform backgrounds (the ModelFest data set and data from Foley et al. 2007), and against new measurements reported here for several ModelFest targets presented on uniform, 1/f noise, and natural backgrounds, at retinal eccentricities ranging from 0 to 10 deg. Although the model has few free parameters, it is able to account quite well for all the threshold measurements. / text