This thesis serves to provide a conceptual mission design for a Titan-orbiting stellar occultation mission. Titan has a significant atmosphere much like Earth's. An improved understanding of Titan's atmosphere could provide valuable information about the evolution of Earth's climate. Titan's atmosphere is known to be in a state of superrotation, wherein the atmosphere rotates significantly faster than the surface beneath. The details of the creation and sustainment of this extreme state on Titan in terms of angular momentum exchange remain unknown despite current theories and models. These unknowns, alongside inconsistencies between current models with observations from the Cassini mission, call for an urgent need for Titan atmospheric observations able to resolve atmospheric waves. The science objectives driving the mission design include maximizing the number of measurements, the latitude versus longitude coverage, the latitude versus local solar time coverage, and the mission duration. These measurement needs can be met by a Titan orbiter utilizing a refractive stellar occultation technique. Refractive stellar occultation observes starlight bending through an atmosphere as stars set behind a body. The observed bending profile can be inverted to infer density, temperature, and pressure profiles. This research uses Systems Tool Kit (STK) as a simulation tool to predict measurement coverage for various orbits. The orbital radius was determined to be the driving independent variable which set all other design variables, including the orbital plane which was uniquely selected for a given orbital radius to maximize the number of occultations. The results of this study show that a lower orbital radius is desired as this produces the best combination of measurement number and distribution. This orbital plane should be closely aligned with the Milky Way galactic plane to see the most stars occult. For the lowest sustainable orbital altitude, Low Titan Orbit (LTO) at 1200 km, the orbital plane should be nearly polar to maximize the number of occultations and latitude coverage. The optimal orbit selection (defined by orbital elements a = 3775 km, e = 0, i = 85 degrees, Ω = 87 degrees, ω = 0 degrees, and ν = 0 degrees) for a single satellite can produce nearly 400 stellar occultation opportunities per orbit and provide full latitude versus longitude coverage. A single satellite shows gaps in latitude versus local solar time coverage at mid-latitudes normal to the satellite ground track which may inhibit the diagnosis of the angular momentum flux associated with thermal tides. If necessary, a second satellite in an orbit orthogonal to the first is suggested to close coverage gaps to provide full local time coverage over a Titan day. The optimal orbit selection of this second satellite (defined by orbital elements a = 3775 km, e = 0, i = 5.3 degrees, Ω = 5.9 degrees, ω = 0 degrees, and ν = 0 degrees) provides an additional 343 occultation opportunities per orbit and increases latitude versus local solar time coverage by a factor of 1.5. The understanding of Titan's Earth-like atmosphere could provide insight into climate evolution here on Earth. This concept proposes a novel approach to improving this understanding. / Master of Science / This thesis serves to provide a conceptual mission design for a Titan-orbiting stellar occultation mission. Titan, one of Saturn's 82 moons, has a significant atmosphere much like Earth's. An improved understanding of Titan's atmosphere could provide valuable information about the evolution of Earth's climate. Titan's atmosphere is known to be in a state of superrotation, wherein the atmosphere rotates significantly faster than the surface beneath. The details of the creation and sustainment of this extreme state on Titan remain unknown despite current theories and models. These unknowns, alongside inconsistencies between current models with observations from the Cassini mission, call for an urgent need for Titan atmospheric observation. The science objectives driving the mission design include maximizing the number of measurements, the latitude versus longitude coverage, the latitude versus local solar time coverage (on a 24-hour scale), and the mission duration. These measurement needs can be met by a Titan orbiter utilizing a refractive stellar occultation technique. Refractive stellar occultation observes starlight bending through an atmosphere as stars set behind a body. The observed bending profile can be inverted to infer density, temperature, and pressure profiles. This research uses a simulation tool to predict measurement coverage for various orbits. The radius of the orbit was determined to be the driving independent variable which set all other design variables, including the orbital plane which was uniquely selected for a given orbital radius to maximize the number of occultations. The results of this study show that a lower orbital radius is desired as this produces the best combination of measurement number and distribution. This orbital plane should be closely aligned with the Milky Way galactic plane to see the most stars occult. For the lowest sustainable orbital altitude, Low Titan Orbit (LTO) at 1200 km, the orbital plane should be nearly polar to maximize the number of occultations and latitude coverage. The optimal orbit selection for a single satellite can produce nearly 400 stellar occultation opportunities per orbit and provide full latitude versus longitude coverage. A single satellite shows gaps in latitude versus local solar time coverage at mid-latitudes normal to the satellite ground track which may inhibit the diagnosis of atmospheric waves tied to Titan's night and day cycle. If necessary, a second satellite in an orbit orthogonal to the first is suggested to close coverage gaps to provide full local time coverage over a Titan day. The optimal orbit selection of this second satellite provides an additional 343 occultation opportunities per orbit and increases latitude versus local solar time coverage by a factor of 1.5. The understanding of Titan's Earth-like atmosphere could provide insight into climate evolution here on Earth. This concept proposes a novel approach to improving this understanding.

Myxococcus xanthus, a Gram-negative bacterium with a developmental cycle, displays a type IV pili (TFP) mediated surface motility known as social (S) gliding. Beside the polarly localized TFP, the fibril or extracellular polysaccharide (EPS) is also required for S-motility to function. It is proposed that S-motility, along with the related bacterial twitching motility in other species, is powered by TFP retraction. EPS is proposed to anchor and trigger such retractions in M. xanthus. EPS production is known to be regulated by TFP and the Dif signal transduction pathway. Two genetic screens were performed previously to identify additional genes important for EPS production. The first was for the isolation of pilA suppressors, the second for the identification of mutants underproducing EPS in a difA suppressor background. Both screens identified transposon insertions at the stk locus. In particular, StkA, a DnaK homolog, was identified as a possible negative regulator of EPS production by a stkA transposon insertion that suppressed a pilA mutation. A stkB transposon insertion was found to have diminished EPS production in a difA suppressor background. In this study, in-frame deletion mutants of the five genes at the stk locus, stkY, stkZ, stkA, stkB and stkC, were constructed and examined. In addition, mutations of rbp and bskL, two genes downstream of the stk locus, were constructed. Like transposon insertions, the stkA in-frame deletion resulted in overproduction of EPS. The stkB and to a less extent the stkC mutants underproduced EPS. Mutations in the other genes had no obvious effects on EPS production. Genetic epistasis suggests that StkA functions downstream of TFP and upstream of the Dif sensory proteins in EPS regulation in M. xanthus. Epistasis analysis involving stkB was inconclusive. It is unresolved whether StkB plays a role in the biosynthesis or the regulation of EPS production in M. xanthus. / Master of Science

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International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper details the interaction of a small satellite with a space network and estimates the number of contacts and duration of contacts between the small, spin-stabilized satellite and a TDRS satellite. The simulations were performed using Satellite Tool Kit (STK) version 3.0, an orbital analysis software program. STK was configured for the four vehicles representing the spin-stabilized satellite and three TDRS satellites, TDRS East, West, and TDRS Zone of Exclusion. A set of simulations were run in which the spinstabilized satellite was given orbital elements corresponding to an orbital altitude between 600 km and 1200 km. The orbital inclination angle for the set of simulations was also varied from 20° through 100° along with the antenna cone angle of 10° through 40° to account for the effective beamwidths. In each of the simulations, the access to each TDRS satellite in the SN constellation was examined as a function of orbital altitude, orbital inclination angle, and antenna cone angle.

GSM has changed the face of communication and information exchange, much as the Internet did. With the advances made in the mobile technology arena, new opportunities are created. Mobile Commerce (m-Commerce) is one such opportunity. Each new advance in technology brings with it associated risks. This dissertation focuses on the risks involved with m-Commerce for the banking industry. This dissertation provides a detailed overview of basic services that any m-Commerce application should provide to the banking industry. These principles provide the foundation for securing any financial transaction over untrusted networks. Several mechanisms to provide these services are also discussed. Examples of such mechanisms include hash functions, Message Authentication Codes and Digital Signatures. The security of GSM networks has come under attack in the past. This is largely due to the fact that the GSM consortium opted to develop their security technologies in secret, rather than in the public domain. This dissertation aims to evaluate the security offered by GSM and assess potential attacks in order to further understand risks associated with m-Commerce applications over GSM. In recent years there have been significant additions to the GSM enabling technology family. The arrival of the SIM Application Toolkit and the Wireless Application Protocol promised to again change the face of commerce. Although market acceptance of these technologies proved to be initially slow, usage is set to increase exponentially within the next couple of years. A detailed analysis of these enabling technologies is presented in the dissertation. Possible attacks on these technologies are discussed in the latter part or this document. Based on the findings of the research, some changes to either the application architectures or the processing of the data have been suggested in order to enhance the security offered by these services. It is not the intent of this dissertation to redesign these applications, but to rather leverage off the current technologies in order to enable secure m-Commerce over these channels. This dissertation provides a detailed overview of basic services that any m-Commerce application should provide to the banking industry. These principles provide the foundation for securing any financial transaction over untrusted networks. Several mechanisms to provide these services are also discussed. Examples of such mechanisms include hash functions, Message Authentication Codes and Digital Signatures. The security of GSM networks has come under attack in the past. This is largely due to the fact that the GSM consortium opted to develop their security technologies in secret, rather than in the public domain. This dissertation aims to evaluate the security offered by GSM and assess potential attacks in order to further understand risks associated with m Commerce applications over GSM. In recent years there have been significant additions to the GSM enabling technology family. The arrival of the SIM Application Toolkit and the Wireless Application Protocol promised to again change the face of commerce. Although market acceptance of these technologies proved to be initially slow, usage is set to increase exponentially within the next couple of years. A detailed analysis of these enabling technologies is presented in the dissertation. Possible attacks on these technologies are discussed in the latter part or this document. Based on the findings of the research, some changes to either the application architectures or the processing of the data have been suggested in order to enhance the security offered by these services. It is not the intent of this dissertation to redesign these applications, but to rather leverage off the current technologies in order to enable secure m-Commerce over these channels. / Dissertation (M.Sc (Electronics))--University of Pretoria, 2005. / Electrical, Electronic and Computer Engineering / unrestricted

A considerable part of the research in computer science is dedicated to speech recognition as the speech-controlled systems become useful in many applications. One of them is the keyword spotting which makes possible to find words in audio data. Such a detector is developed at BUT Faculty of Information Technology. The goal of this work is to propose a network interface to this keyword detector based on client/server architecture. Client connects to the server and sends audio data. Server runs keyword detector with this received data and sends the result of keyword spotting back to client. Finally client visualizes the result and interact with user.

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Práce uvádí základní informace o průmyslové sběrnici AS-Interface a popisuje její funkce. Dále se zabývá rozšířením stávajícího FTZ AS-Interface Slave Simulátoru o dotykový display, který značně usnadní ovládání tohoto simulačního nástroje. Je zde nastíněn návrh a řešení uživatelského dotykového rozhraní k tomuto simulátoru s použitím Amulet LCD modulu STK 480272C. Vývoj tohoto rozhraní je proveden pomocí GEMstudia, softwaru firmy Amulet Technologies a grafických programů. Dále tato studie pojednává o softwarové úpravě FTZ AS-i Slave Smilulátoru. Jedná se o úpravu řídícího FPGA v jazyce VHDL zajišťující komunikaci s dotykovým displejem. Poslední kapitola se týká problematiky spojené s návrhem uživatelsky přívětivé aplikace.