This report summarizes the design of a digital frequency synthesizer for airborne distance measuring equipment. It is the purpose of the frequency synthesizer to provide a stable frequency source for the local oscillator of the airborne receiver and for the power amplifiers in the transmitter chain. The synthesizer is required to furnish a frequency ranging from 260.250 mHz to 287.50 mHz in channel steps of 250 kHz at a power level of +7.0 dBm. the stability of the frequency must be greater than .005% over the temperature range of from minus 45 degrees centigrade to plus 55 degrees centigrade, requiring a crystal controlled source. Digital techniques are employed using two crystal controlled oscillators to synthesize all required channel frequencies. Linear circuits using standard configurations are employed for the oscillators, buffers, and mixers. Primary attention is paid to optimizing the transient characteristics of the synthesizer which employ programmable digital counters to change the division ratio in a phase locked loop. Decoding is provided to interface the modulus of the counters with the aircraft cockpit controls.

Yes / A novel beam-forming module based on Wilkinson power divider technology, including attenuators and phase shifter chips is designed, fabricated and evaluated to be incorporated in a Relay Station connecting it with the Base Station under a 4G network. The proposed module is a 1:8 port circuit, utilizing two substrates, providing approximately 700 MHz bandwidth over 3.5 GHz frequency band and less than −20 dB transmission line coupling. Moreover an external control unit that feeds the beam-forming module with code-words that define the proper amplitude/phase of the excitation currents is established and described. The presented module is connected to a planar array and tested for two beam-forming scenarios, providing satisfactory radiation patterns.

This thesis explores the framing of graphical qualities of the passenger train and the city of Roanoke, Virginia. A passenger train station frames these icons and brings people directly to the train. This framing creates a new icon for the city. An area on the train tracks is revitalized and creates a permeable threshold into and out of the city. / Master of Architecture

To solve traffic congestion in Bangkok, the Bangkok Mass Transit system (BTS) constructed an overhead rail system with 24 stations. The BTS train station, S2, in this study area covers Silom road and obstructs the air pollutant dispersion in a congestion area. The 1: 200 physical model of the buildings along Silom road with the train station, S2, was simulated in this research to determine the air pollutant dispersion in the train station area. A tracer gas (CO₂) was emitted from a simulated line source with emission rates of 0.383, 0.681, 1.293, 2.586, 5.177 and 10.77 mg/min to simulate actual pollutant emission rates. The CO₂ gas was sampled at 55 locations in the model. The Kriging method was used to interpolate the data in the study area. . Emission rates were used to make the difference between measured CO₂ in the model area and ambient CO₂ large enough to be differentiated. Regression Analysis was used to relate analytically the mass emission rate to the CO₂ concentration. The results indicate that the maximum CO concentrations exceed the 30 ppm Bangkok standard along the Southeast side of Silom Road at the passenger platform level. Drivers will acquire more harmful levels of CO than pedestrians at street level, especially near the Southwest end of the train station. NO₂ concentrations do not exceed the standard (0.17 ppm) at street level. The highest predicted VOC is 1.05 ppm. These results may be used in the future for numerical modeling study. / Master of Science

The KiK-net ground motion database is used to develop ground motion prediction equations for Arias Intensity (I_a), 5-95% Significant Duration (Ds_5-95), and 5-75% Significant Duration (Ds_5-75). Relationships are developed both for shallow crustal earthquakes and subduction zone earthquakes (hypocentral depth less than 45 km). The models developed consider site amplification using V_S30 and the depth to a layer with V_S=800 m/s (h₈₀₀). We observe that the site effect for I_α is magnitude dependent. For Ds_5-95 and Ds_5-75, we also observe strong magnitude dependency in distance attenuation. We compare the results with previous GMPEs for Japanese earthquakes and observe that the relationships are similar. The results of this study also allow a comparison between earthquakes in shallow-crustal regions, and subduction regions. This comparison shows that Arias Intensity has similar magnitude and distance scaling between both regions and generally Arias Intensity of shallow crustal motions are higher than subduction motions. On the other hand, the duration of shallow crustal motions are longer than subduction earthquakes except for records with large distance and small magnitude causative earthquakes. Because small shallow crustal events saturate with distance, ground motions with large distances and small magnitudes have shorter duration for shallow crustal events than subduction earthquakes. / This thesis presents the development of new Ground Motion Prediction Equations (GMPEs) for the prediction of the duration and the Arias Intensity of earthquake strong motions. . Arias Intensity is an index for the energy in the ground motion. The GMPEs are based on the Japanese KiK-net database. Based on the causative earthquake source, source to site path, and site properties, GMPEs give estimation of the mean and standard deviation of the parameters. This information is necessary for conducting probabilistic seismic hazard analyses. The characteristics of the ground motions with the same magnitude and source to site distance vary amongst different tectonic regimes. For this reason, we develop different GMPEs for earthquakes from different tectonic regimes (subduction zone and shallow crustal earthquakes). The primary motivation for this research is that no existing GMPEs for duration are directly applicable to subduction-zone earthquakes. In addition, because the same stations recorded both types of events, we can directly compare the effect of tectonic environment on the selected ground motion parameters. The estimation of mean duration and mean Arias intensity made by this study show while magnitude and distance scaling of Arias Intensity is the same for shallow crustal and subduction earthquakes, the tectonic regime has a significant effect on duration of ground motion.

The key goal in this work is to enable a flexible ground station that is not constrained to a particular mission or set of hardware. In addition, with the concepts and software produced in this thesis, it will play a significant role in educating engineers and students by providing critical infrastructure and a sandbox for ground station operations. Key pieces of software were developed in this work to create a flexible and robust software-defined ground station. Several digital transmission modes were developed in order to allow communication between the ground station and common amateur radio CubeSats and SmallSats. In order to handle distributed tasks and process at a ground station with multiple servers and controllers, a specialized actor framework was written in Python for ease of use. Actors have the ability to send messages to one another over a network, and they maintain their own memory in order to avoid synchronization problems that come with sharing memory. In addition to the software developed in this work, a novel Peer-to-Peer (P2P) protocol for a network of ground stations is proposed in order to increase coverage and access to spacecraft without requiring centralized server infrastructure. This protocol provides the method to scale the developed software architecture beyond a single ground station. Since the Virginia Tech Ground Station (VTGS) will have many concurrent processes running across multiple servers, it was necessary to apply the actor model in order to simplify the design of the system. The purpose of this thesis is to describe the developed software for the VTGS as well as the P2P protocol for a larger network of ground stations. There are three primary repositories: planck-dsp, gr-vtgs, and pystation. The planck-dsp library and gr-vtgs Out-of-tree (OOT) make up the primary digital signal processing and communications toolboxes, where GNU Radio serves as the scheduler for signal processing blocks used in flow graphs. The pystation module is the extensible software actor framework that connects various systems both locally and remotely. It is also responsible for scheduling and handling ground station requests. While the software was primarily created for the VTGS, it is general enough to apply to other ground station implementations. / Master of Science

For a successful CubeSat mission, it is imperative to schedule events in a fashion that will generate maximum useful science data. Intuitive uplink commanding software is required for the Lower Atmosphere/Ionosphere Coupling Experiment (LAICE) CubeSat to ensure best results. The ground station up-link software is created with this aim in mind. This will make the operation center for the LAICE project efficient. This will also help in evaluating the effect of a particular schedule on LAICE instrument interface board (LIIB) before sending the commands to it. The interactive User Interface (UI) that makes the entire process intuitive guides the user to create an uplink schedule without any human error. The control software creates the command sequence taking in to account all the limitations and specification of the systems and instruments on LAICE. These data are backed up in an efficient format in Virginia Tech’s database for future processing. This web-based application ensures a smooth scheduling process without any errors. Assistive flight-ready software is provided on the flight computer on the LAICE CubeSat to upload the correct uplink sequence to the LIIB. / Master of Science

The effects of weigh-in-motion (WIM) systems on traffic operations and weight enforcement were compared and evaluated. The systems studied included high speed WIM, medium speed WIM and conventional static scales alone. The major measurements of effectiveness were traffic delay, queue, and the avoidance rate for overweight vehicles. Four weighing facilities from both the eastern and western United States were chosen as the real life bases for the study. Queuing theories, probability and statistics were the major methodologies employed in the study. The characteristics of queuing systems, such as traffic arrival patterns, weight enforcement processing time distribution, and capacity of the static scales at each weigh station were determined through field data collection at weigh stations. The proportion of the vehicle population directed to the static scale by WIM screening was analyzed, based on WIM accuracy and truck weight distributions at or near each weigh facility. By considering delay, queue, and the avoidance rate of overweight vehicles comprehensively, optimal weighing systems are proposed for different V/C ratios, i.e., the ratio of traffic volume at a specific site to the actual capacity of the static scale. When the V/C ratio is less than 1, a weighing facility using a static scale alone is most cost effective; when the V/C ratio is between 1 and 1.5, a medium speed WIM is suggested. High speed WIM is recommended only when the V/C ratio is larger than 1.5. / Master of Science

International Telemetering Conference Proceedings / October 25-28, 1999 / Riviera Hotel and Convention Center, Las Vegas, Nevada / In 1998, AlliedSignal Technical Services (ATSC) installed three fully autonomous 13-meter satellite tracking systems for the Integrated Program Office of the National Oceanic and Atmospheric Administration (NOAA) at the Command and Data Acquisition Station near Fairbanks, Alaska. These systems track and command NOAA Polar Orbiting Weather Satellites and Defense Meteorological Satellites. Each tracking system operates for extended periods of time with little intervention other than periodic scheduling contacts. Schedule execution initiates equipment configuration, including establishing the RF communications link to the satellite. Station autonomy is achieved through use of a robust scheduler that permits remote users and the System Administrator to request pass activities for any of the supported missions. Spacecraft in the mission set are scheduled for normal operations according to the priority they have been assigned. Once the scheduler resolves conflicts, it builds a human-readable control script that executes all required support activities. Pass adds or deletes generate new schedule scripts and can be performed in seconds. The systems can be configured to support CCSDS and TDM telemetry processing, but the units installed at Fairbanks required only telemetry and command through-put capabilities. Received telemetry data is buffered on disk-storage for immediate, post-pass playback, and also on tape for long-term archiving purposes. The system can autonomously support up to 20 spacecraft with 5 different configuration setups each. L-Band, S-Band and X-Band frequencies are supported.

A técnica de localização móvel utilizando o sistema celular recebeu especial atenção por parte de empresas fabricantes e operadoras de telecomunicações, devido à necessidade de se cumprir as exigências estabelecidas para chamadas de serviços de emergência e outros serviços de apelo comercial. Neste trabalho são analisados os principais métodos de localização propostos na literatura, incluindo, para cada um, a formulação matemática envolvida no cálculo da localização, os principais algoritmos utilizados e suas limitações. É analisada, também, a modelagem do canal de propagação no ambiente celular baseada na proposta do relatório do COST 259. A partir desta análise pode ser encontrada uma correlação entre o atraso médio do sinal e o seu espalhamento, que motivou sua utilização em um novo algoritmo para estimativa de localização. Esse novo algoritmo, particularmente eficiente para os casos em que uma ou mais estações rádio-bases não apresentam visada direta com a unidade móvel (NLoS), é apresentado neste trabalho, e diversos resultados de simulação são analisados, comparando-se o seu desempenho com outros algoritmos amplamente aceitos e reconhecidos. Para melhorar a estimativa de posição final, a filtragem de Kalman também é aplicada ao algoritmo proposto. / The mobile location technique using the cellular system received a special attention from the telecommunication manufacturers and operators, regarding the need of accomplishing the established demands by the emergency service calls and other commercial ones. This study analyzes the main location methods proposed in the literature, including, in each one, the mathematical formulation involved in the location calculus, the main used algorithms and their limitations. Also, it is analyzed the modeling of the propagation channel based on a cellular environment proposed in COST 259 report. After this analysis we can find a correlation between the signal mean delay and its delay spread, which motivated the use of a new algorithm for location estimative. A new algorithm, especially efficient for the cases where one or more base stations don\'t have Line-of-Sight (NLoS) with mobile station, is presented and several simulation results are analyzed and compared with other algorithms widely accepted and recognized. In order to improve the final position estimation, the Kalman filtering is also applied to the new proposed algorithm.