Frequency-warped autoregressive modeling and filtering

This thesis consists of an introduction and nine articles. The articles are related to the application of frequency-warping techniques to audio signal processing, and in particular, predictive coding of wideband audio signals. The introduction reviews the literature and summarizes the results of the articles. Frequency-warping, or simply warping techniques are based on a modification of a conventional signal processing system so that the inherent frequency representation in the system is changed. It is demonstrated that this may be done for basically all traditional signal processing algorithms. In audio applications it is beneficial to modify the system so that the new frequency representation is close to that of human hearing. One of the articles is a tutorial paper on the use of warping techniques in audio applications. Majority of the articles studies warped linear prediction, WLP, and its use in wideband audio coding. It is proposed that warped linear prediction would be particularly attractive method for low-delay wideband audio coding. Warping techniques are also applied to various modifications of classical linear predictive coding techniques. This was made possible partly by the introduction of a class of new implementation techniques for recursive filters in one of the articles. The proposed implementation algorithm for recursive filters having delay-free loops is a generic technique. This inspired to write an article which introduces a generalized warped linear predictive coding scheme. One example of the generalized approach is a linear predictive algorithm using almost logarithmic frequency representation.reviewe

The Telecommunications and Data Acquisition Report

Deep Space Network advanced systems, very large scale integration architecture for decoders, radar interface and control units, microwave time delays, microwave antenna holography, and a radio frequency interference survey are among the topics discussed

Resolving the global distribution of sawfishes (family Pristidae) using environmental DNA

The imperiled status of sawfishes globally has warranted the development of robust and reliable tools to study them. Madalyn Cooper developed a non-invasive detection method harnessing environmental DNA and applied the method in a survey of coastal and riverine habitats in the global tropics and subtropics where the sawfishes face risk of extinction. The methods and findings of Madalyn's PhD are significant for agencies and practitioners working toward the management and conservation of sawfish populations, and furthers the application of eDNA methods for rare and threatened species

Gastrointestinal symbionts of wild chimpanzees and sympatric colobus monkeys living in close proximity of humans in Liberia and Uganda

Dissertação de Mestrado Integrado em Medicina VeterináriaEsta dissertação teve como objetivo principal caracterizar a fauna de simbiontes de chimpanzés (Pan troglodytes), e colobos pretos e brancos (Colobus sp.) de diferentes localidades Africanas (Parque Nacional de Sapo, na Libéria e em Bulindi, no Uganda), comparar resultados entre eles e estudos prévios e teorizar sobre as possíveis implicações zoonóticas dos simbiontes encontrados. Recorrendo a técnicas de coprologia como sedimentação MIF modificada e a flutuação de Sheather, e um teste de imunofluorescência direta para deteção de oocistos de Crypstosporidium e cistos de Giardia, 47 amostras fecais preservadas de chimpanzé e 15 de colobos pretos e brancos foram examinadas. Os protozoários detetados incluíram Troglodytella abrassarti, Entamoeba spp., Blastocystis sp. e Iodamoeba buetschlii; e nematodes, Trichuris sp, Colobenterobius sp., strongylideos e várias larvas de nematodes. Todas as amostras foram negativas no teste de imunofluorescência directa. Em geral, o espectro de simbiontes encontrado no presente estudo está de acordo com o que é regularmente descrito em estudos que abordam chimpanzés e colobos pretos e brancos de vida selvagem. Contudo, pequenos microrganismos aquáticos denominados Rotifera ou rotíferos foram observados pela primeira vez em amostras fecais de chimpanzé e colobos pretos e brancos. Considerando o contato próximo entre os primatas estudados e seres humanos, é importante realizar futuras pesquisas recorrendo a técnicas moleculares nos simbiontes assinalados por este trabalho e avaliar o seu real potencial zoonótico.ABSTRACT - Gastrointestinal symbionts of wild chimpanzees and sympatric colobus monkeys living in close proximity of humans in Liberia and Uganda - This dissertation aimed to characterize the symbiont fauna of chimpanzees (Pan troglodytes) and black and white colobus (Colobus sp.) from different African localities, (Sapo National Park in Liberia and Bulindi in Uganda), compare results between them and previous studies, and theorize about possible zoonotic implications of the found symbionts. Using coprologic techniques as modified MIF sedimentation and Sheather’s flotation, and a direct immunofluorescence teste for detection of Crypstosporidium oocysts and Giardia cysts, 47 chimpanzee and 15 black and white colobus preserved fecal samples were examined. Detected protozoans included Troglodytella abrassarti, Entamoeba spp., Blastocystis sp. and Iodamoeba buetschlii; and nematodes, Trichuris sp., Colobenterobius sp., strongylids and various nematodes larvae. All samples were negative for the direct immunofluorescence test. Overall, the spectrum of symbionts found in the present study is in accordance with what is regularly described in studies addressing the free ranging chimpanzees and black and white colobus. However, small aquatic microorganisms denominated Rotifera or rotifers were observed for the first time in chimpanzee and in black and white colobus faecal samples. Considering the close contact between the studied primates and humans, it is important to conduct further research using molecular techniques in the found symbionts to assess the real zoonotic potential.N/

Link layer protocol performance of indoor infrared wireless communications

The increasing deployment of portable computers and mobile devices leads to an increasing demand for wireless connections. Infrared presentsseveral advantagesover radio for indoor wireless connectivity but infrared link quality is affected by ambient infrared noise and by low power transmission levels due to eye safety limitations. The Infrared Data Association (IrDA) has developed the widely used IrDA 1.x protocol standard for short range, narrow beam, point to point connections.IrDA addressedthe requirement for indoor multipoint connectivity with the development of the Advanced Infrared (AIr) protocol stack. This work analyses infrared link layer design based on IrDA proposals for addressing link layer topics and suggests implementation issues and protocol modifications that improve the operation of short range infrared connections. The performance of optical wireless links is measuredby the utilization, which can be drawn at the data link layer. A new mathematical model is developed that reaches a simple equation that calculates IrDA 1.x utilization. The model is validated by comparing its outcome with simulation results obtained using the OPNET modeler. The mathematical model is employed to study the effectiveness on utilization of physical and link layer parameters.The simple equation gives insights for the optimum control of the infrared link for maximum utilization. By differentiating the utilization equation, simple formulas are derived for optimum values of the window and frame size parameters. Analytical results indicate that significant utilization increase is observed if the optimum values are implemented, especially for high error rate links. A protocolimprovement that utilizes special Supervisory frames (S-frames) to pass transmission control is proposed to deal with delays introduced by F-timer expiration. Results indicate that employing the special S-frame highly improves utilization when optimum window and frame size values are implemented. The achieved practical utilization increase for optimum parameter implementation is confirmed by meansof simulation. AIr protocol trades speedfor range by employing Repetition Rate (RR) coding to achieve the increased transmission range required for wireless LAN connectivity. AIr employs the RTS/CTS medium reservation scheme to cope with hidden stations and CSMA/CA techniques with linear contention window (CW) adjustment for medium access. A mathematical model is developed for the AIr collision avoidance (CA) procedures and validated by comparing analysis with simulation results. The model is employed to examine the effectiveness of the CA parameters on utilization. By differentiating the utilization equation, the optimum CW size that maximises utilization as a function of the number of the transmitting stations is derived. The proposed linear CW adjustment is very effective in implementing CW values close to optimum and thus minimizing CA delays. AIr implements a Go-Back-N retransmission scheme at high or low level to cope with transmission errors. AIr optionally implements a Stop-and-Wait retransmission scheme to efficiently implement RR coding. Analytical models for the AIr retransmission schemes are developed and employed to compare protocol utilization for different link parametervalues. Finally, the effectiveness of the proposedRR coding on utilization for different retransmission schemes is explored

Network coded wireless architecture

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 183-197).Wireless mesh networks promise cheap Internet access, easy deployment, and extended range. In their current form, however, these networks suffer from both limited throughput and low reliability; hence they cannot meet the demands of applications such as file sharing, high definition video, and gaming. Motivated by these problems, we explore an alternative design that addresses these challenges. This dissertation presents a network coded architecture that significantly improves throughput and reliability. It makes a simple yet fundamental switch in network design: instead of routers just storing and forwarding received packets, they mix (or code) packets' content before forwarding. We show through practical systems how routers can exploit this new functionality to harness the intrinsic characteristics of the wireless medium to improve performance. We develop three systems; each reveals a different benefit of our network coded design. COPE observes that wireless broadcast naturally creates an overlap in packets received across routers, and develops a new network coding algorithm to exploit this overlap to deliver the same data in fewer transmissions, thereby improving throughput. ANC pushes network coding to the signal level, showing how to exploit strategic interference to correctly deliver data from concurrent senders, further increasing throughput. Finally, MIXIT presents a symbol-level network code that exploits wireless spatial diversity, forwarding correct symbols even if they are contained in corrupted packets to provide high throughput reliable transfers. The contributions of this dissertation are multifold. First, it builds a strong connection between the theory of network coding and wireless system design. Specifically, the systems presented in this dissertation were the first to show that network coding can be cleanly integrated into the wireless network stack to deliver practical and measurable gains. The work also presents novel algorithms that enrich the theory of network coding, extending it to operate over multiple unicast flows, analog signals, and soft-information.(cont.) Second, we present prototype implementations and testbed evaluations of our systems. Our results show that network coding delivers large performance gains ranging from a few percent to several-fold depending on the traffic mix and the topology. Finally, this work makes a clear departure from conventional network design. Research in wireless networks has largely proceeded in isolation, with the electrical engineers focusing on the physical and lower layers, while the computer scientists worked up from the network layer, with the packet being the only interface. This dissertation pokes a hole in this contract, disposing of artificial abstractions such as indivisible packets and point-to-point links in favor of a more natural abstraction that allows the network and the lower layers to collaborate on the common objectives of improving throughput and reliability using network coding as the building block. At the same time, the design maintains desirable properties such as being distributed, low-complexity, implementable, and integrable with the rest of the network stack.by Sachin Rajsekhar Katti.Ph.D

A Bibliography of Sign Languages, 2008-2017

This concise bibliography on Sign Languages was compiled on the occasion of the 20th international Congress of Linguists in Cape Town, South Africa, in July 2018. The selection of titles is drawn from the Linguistic Bibliography and gives an overview of scholarship on Sign language over the past 10 years. The introduction is by Myriam Vermeerbergen (KU Leuven & Stellenbosch University) and Anna-Lena Nilsson (NTNU – Norwegian University of Science and Technology) gives an overview of the most recent developments in the field