Understanding recent decades of coral community change has been hindered by a shortage of long-term monitoring and a lack of tools that provide a lasting record of benthic reef communities. To increase our understanding of Caribbean coral reef dynamics, this dissertation research developed and used innovative technologies involving landscape mosaic images and 3D reef models, to analyze a novel 40 year dataset of coral community health from Andros Island, Bahamas. Historical data from Andros Island (1968-2000) were provided as part of a Cooperative Research and Development Agreement (CRADA) between the University of Miami and the Naval Undersea Warfare Center Division Newport. Long-term monitoring at Andros Island revealed that reef decline was a-typical over recent decades. Coral mortality and disease increased significantly between 1970 and 2000, whereas macroalgal cover did not. To complement studies of coral mortality and disease, the resilience and resistance of individual coral species at Andros were measured from 1972 to 2008. Of the 24 species studied, only three (Siderastrea siderea, Montastraea cavernosa, and Porites astreoides) were resistant to recent disturbance histories, whereas Porites porites was resilient. Further studies using 3D models explored relationships between coral population dynamics and spatial patterns of coral species. Results indicated that the arrangement of dominant coral species and the processes of recruitment, growth, and mortality were non-random over time. In summary, the application of mosaic images and 3D reef models to a previously un-published long-term coral health dataset led to improved understanding of factors controlling past reef communities.

Thesis (Ph.D.)--University of California, Berkeley, 1962. / "UC-34 Physics" -t.p. "TID-4500 (17th Ed.)" -t.p. Includes bibliographical references (p. 65-66).

Thesis (Ph.D.)--University of California, Berkeley, 1962. / "UC-34 Physics" -t.p. "TID-4500 (17th Ed.)" -t.p. Includes bibliographical references (p. 84-86).

Characterization of distortion transfer and generation through fans with distorted inlet conditions enables progress towards designs with improved distortion tolerance. The abruptness of transition from undistorted to distorted total pressure regions at the inlet impacts the induced swirl profile and therefore the distortion transfer and generation. These impacts are characterized using URANS simulations of PBS Rotor 4 geometry under a variety of inlet distortion profiles. A 90° and a 135° sector, both of 15% total pressure distortion, are considered. Variants of each sector size, with decreasing levels of distortion transition abruptness, are each applied to the fan. Fourier-based distortion descriptors are used to quantify levels of distortion transfer and generation at axial locations through the fan, principally at the stator inlet. It is shown that a gradual transition in distortion at the inlet results in decreased levels of distortion transfer and generation. The flow physics resulting in this reduction are explored. URANS simulations involving turbomachinery are complex and often require simplifying assumptions to balance computational costs with accuracy. One assumption removes the need for a nozzle to control nozzle operation condition and replaces it with a static pressure boundary condition located at the stator exit. This assumption is challenged by conducting a series of distorted inlet simulations with a nozzle, which are then compared to a corresponding set of simulations conducted using the exit boundary assumption. Performance parameters for each set of simulations are compared. Performance was observed to be within 1% difference between the two methods, supporting the assumption that a static pressure boundary is adequate for controlling inlet distortion simulations. Finally, full annulus URANS simulations are presented to investigate distortion phase shift in a single stage transonic fan. The fan is subject to a 90° sector inlet total pressure distortion. Simulation results are presented for choke, design, and near-stall operating conditions. Circumferential profiles of swirl, total pressure, total temperature, power, and phase shift are analyzed at 10%, 30%, 50%, 70%, and 90% span. Several metrics for phase shift, which is a measure of the rotational translation of a distortion profile, are presented and compared. Each aims to assist understanding the translational motion of distortion as it passes through the fan. The different metrics used for phase shift are used to analyze distortion phase. Insights from each are presented alongside limitations for each method. A combination of methods is proposed to address their respective limitations.

Broiler birds have drastically increased in size over the past few decades through improvements in genetic selection. Physical measurements such as surface area, volume and physical dimensions are needed information in the construction of animal facilities and developing management guidelines. The objective of this study was to develop a three-dimensional scanning methodology to characterize surface area and envelope volume of poultry, livestock, and equine using a commercially available 3D digitizer system. The digitizing system used phase shift moiré to capture images of three test cylinders, four fiberglass animal models, and a live broiler bird. These images were spliced into physical models using image processing software. System accuracy (< 2%) was verified with cylinder models. Recommended camera orientations and placements were established with each species by the use of fiberglass models. The methods will have to be fine-tuned for live animals as observed in the live broiler test.

Renewable energy and distributed generation are getting more and more popular, including photovoltaic modules (PV), wind turbines, and fuel cells. The renewable energy sources need the power electronics interface to the utility grid because of different characteristics between the sources and the grid. No matter what renewable energy source is utilized, inverters are essential in the microgrid system. Thanks to flexible modular design, transformerless connection, extended voltage and power output, less maintenance and higher fault tolerance, the cascade inverters are good candidates for utility interface of various renewable energy sources. This dissertation proposes a new type of cascade inverters based on dual-buck topology and phase-shift control scheme. Compared to traditional cascade inverters, they have enhanced system reliability thanks to no shoot-through problems and lower switching loss with the help of using power MOSFETs. With phase-shift control, it theoretically eliminates the inherent current zero-crossing distortion of the single-unit dual-buck type inverter. In addition, phase-shift control can greatly reduce the ripple current or cut down the size of passive components by increasing the equivalent switching frequency. An asymmetrical half-cycle unipolar (AHCU) PWM technique is proposed for dual-buck full-bridge inverter. The proposed approach is to cut down the switching loss of power MOSFETs by half. At the same time, this AHCU PWM leads to current ripple reduction, and thus reducing ripple-related loss in filter components. Therefore, the proposed PWM strategy results in significant efficiency improvement. Additionally, the AHCU PWM also compensates for the zero-crossing distortion problem of dual-buck full-bridge inverter. Several PWM techniques are analyzed and compared, including bipolar PWM, unipolar PWM and phase-shifted PWM, when applied to the proposed cascade dual-buck full-bridge inverter. It has been found out that a PWM combination technique with the use of two out of the three PWMs leads to better performance in terms of less output current ripple and harmonics, no zero-crossing distortion, and higher efficiency. A grid-tie control system is proposed for cascade dual-buck inverter with both active and reactive power flow capability in a wide range under two types of renewable energy and distributed generation sources. Fuel cell power conditioning system (PCS) is Type I system with active power command generated by balance of plant (BOP) of each unit; and photovoltaic or wind PCS is Type II system with active power harvested by each front-end unit through maximum power point tracking (MPPT). Reactive power command is generated by distributed generation (DG) control site for both systems. Selective harmonic proportional resonant (PR) controller and admittance compensation controller are first introduced to cascade inverter grid-tie control to achieve better steady-state and dynamic performances. / Ph. D.

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Shaped Offset Quadrature Phase Shift Keying (SOQPSK) has the advantages of low sidelobes and high detection probability; however, its main lobe has a fixed width set by the number of constellation points. By slightly modifying the modulation scheme, the four constellation points of quadrature shift keying can be changed to M constellation points where M is a power of 2. After this change, the power spectral density (PSD) retains low sidelobes, and the desirable property of being able to detect the signal by integrating over two symbol periods is retained.

No description available.

The EU has proposed an ambitious goal to achieve widespread E-mobility in both the electrical and commercial sectors. To accomplish this, a substantial number of DC fast-charging stations must be built. These power converters, installed in the DC fast-charging stations (DCFC), differ from traditional DCDC converters as they exhibit high power density, reaching tens of kilowatts. In contrast to traditional non-isolated power converters, isolated power converters offer ideal galvanic isolation, providing protection to both the local power grid and electric vehicles. Among the DC power converters designed for industrial applications, the LLC resonant converters and DAB converters (Dual Active Bridge) have gained significant popularity. When compared to LLC converters, DAB converters demonstrate a more flexible input and output power range, as well as a higher power density. Considering these advantages, a 10kW bidirectional DAB power converter has been designed for the purpose of fulfilling the requirements of this thesis project. The thesis is organized into four distinct parts. The first part focuses on conducting a comprehensive literature review to explore the challenges prevalent in the current electrical field. Various DC-DC topologies are compared based on different factors, including component analysis, controllability, safety considerations, and cost-effectiveness. By examining these aspects, potential solutions for Electric Vehicles (EVs) are identified. In the second part, a specific DC-DC converter with a power rating of 10kW is chosen, utilizing the DAB (Dual Active Bridge) topology. The selection is based on the analysis conducted in the literature review. The thesis delves into the issues and technical challenges associated with this choice, such as reactive power, peak current, zero-voltage switching (ZVS), and phase shift modulation. These topics are thoroughly explored and discussed within the literature study. The second part of the thesis involves the establishment of a DAB model, incorporating mathematical equations and physical derivations. This modeling and design section discusses the energy conversion process, starting from fundamental physical formulas and extending to the overall system setup. Utilizing the proposed model, a control method called SPS (Single Phase Shift) modulation is implemented in the circuit to achieve closed-loop control. Within this part, the relationship between current, voltage, and output power is derived and utilized for the design of a PI closed controller. To address challenges associated with SPS control, such as reactive power elimination and peak current suppression, an EPS (Enhanced Phase Shift) control scheme is introduced. The EPS control scheme not only fulfills the basic requirement of power transfer but also optimizes the system’s overall efficiency. In the third part of the thesis, a simulation is developed to validate the accuracy of the proposed DAB model and control methods. Simulations are implemented using Simulink, a widely used software for dynamic system modeling and simulation. Various aspects of the system are evaluated through the simulation, including the leakage inductor current, voltage waveforms on both the primary and secondary sides and output power. These parameters are plotted and analyzed to assess the performance of the DAB model and control methods. Additionally, loss and efficiency analyses are conducted using PLECS, a simulation platform that specializes in power electronics systems. By inputting the datasheet information of the switches and transformer, PLECS enables the evaluation of losses and efficiency within the system. This analysis provides valuable insights into the performance and energy efficiency of the proposed DAB-based converter. In the final part of the thesis, conclusions are drawn based on the theoretical findings and simulation results obtained throughout the study. These conclusions reflect the overall outcomes and implications of the research conducted. Furthermore, the future work section outlines the tasks that remain unfinished or areas that can be explored in subsequent studies. This section serves as a guide for future researchers, highlighting potential directions for further investigation and improvement in the field of DAB-based DC-DC converters for E-mobility applications. By presenting the conclusions and future work, the thesis provides a comprehensive summary of the research conducted, its contributions, and potential avenues for future research and development. / EU har föreslagit ett ambitiöst mål för att uppnå utbredd e-mobilitet inom både den elektriska och kommersiella sektorn. För att åstadkomma detta måste ett stort antal DC snabbladdningsstationer byggas. Dessa effektomvandlare, installerade i DC-snabbladdningsstationerna (DCFC), skiljer sig från traditionella DC-DC-omvandlare eftersom de uppvisar hög effekttäthet och når tiotals kilowatt. I motsats till traditionella icke-isolerade kraftomvandlare erbjuder isolerade kraftomvandlare idealisk galvanisk isolering, vilket ger skydd för både det lokala elnätet och elfordon. Bland likströmsomvandlarna som är designade för industriella applikationer har LLC-resonantomvandlarna och DABomvandlarna (Dual Active Bridge) vunnit betydande popularitet. Jämfört med LLC-omvandlare uppvisar DAB-omvandlare ett mer flexibelt in- och uteffektområde, såväl som en högre effekttäthet. Med tanke på dessa fördelar har en 10kW dubbelriktad DAB-effektomvandlare designats för att uppfylla kraven i detta examensarbete. Avhandlingen är organiserad i fyra distinkta delar. Den första delen fokuserar på att genomföra en omfattande litteraturgenomgång för att utforska de utmaningar som råder inom det nuvarande elektriska området. Olika DCDC-topologier jämförs baserat på olika faktorer, inklusive komponentanalys, kontrollerbarhet, säkerhetsöverväganden och kostnadseffektivitet. Genom att undersöka dessa aspekter identifieras potentiella lösningar för elektriska fordon (EV). I den andra delen väljs en specifik DC-DC-omvandlare med en märkeffekt på 10kW, som använder DAB-topologin (Dual Active Bridge). Urvalet baseras på den analys som gjorts i litteraturöversikten. Avhandlingen fördjupar sig i de problem och tekniska utmaningar som är förknippade med detta val, såsom reaktiv effekt, toppström, nollspänningsomkoppling (ZVS) och fasskiftsmodulering. Dessa ämnen utforskas och diskuteras grundligt inom litteraturstudien. Den andra delen av examensarbetet omfattar upprättandet av en DAB-modell, innefattande matematiska ekvationer och fysiska härledningar. Det här avsnittet om modellering och design diskuterar energiomvandlingsprocessen, med start från grundläggande fysiska formler och sträcker sig till den övergripande systemuppställningen. Genom att använda den föreslagna modellen implementeras en styrmetod som kallas SPS-modulering (Single Phase Shift) i kretsen för att uppnå sluten-loop-styrning. Inom denna del härleds förhållandet mellan ström, spänning och uteffekt och används för konstruktionen av en sluten PI-regulator. För att ta itu med utmaningar förknippade med SPS-kontroll, såsom eliminering av reaktiv effekt och undertryckning av toppström, introduceras ett EPS-kontrollschema (Enhanced Phase Shift). EPS-kontrollsystemet uppfyller inte bara det grundläggande kravet på kraftöverföring utan optimerar också systemets totala effektivitet. I den tredje delen av avhandlingen utvecklas en simulering för att validera noggrannheten hos den föreslagna DAB-modellen och styrmetoderna. Simuleringar implementeras med Simulink, en mycket använd programvara för dynamisk systemmodellering och simulering. Olika aspekter av systemet utvärderas genom simuleringen, inklusive läckans induktorström, spänningsvågformer på både primär- och sekundärsidan och uteffekt. Dessa parametrar plottas och analyseras för att bedöma prestandan hos DABmodellen och styrmetoderna. Dessutom genomförs förlust- och effektivitetsanalyser med hjälp av PLECS, en simuleringsplattform som är specialiserad på kraftelektroniksystem. Genom att mata in databladsinformationen för switcharna och transformatorn, möjliggör PLECS utvärdering av förluster och effektivitet i systemet. Denna analys ger värdefulla insikter om prestandan och energieffektiviteten hos den föreslagna DAB-baserade omvandlaren. I den sista delen av uppsatsen dras slutsatser baserat på de teoretiska fynden och simuleringsresultat som erhållits genom studien. Dessa slutsatser speglar de övergripande resultaten och konsekvenserna av den genomförda forskningen. Vidare skisserar det framtida arbetsavsnittet de uppgifter som förblir oavslutade eller områden som kan utforskas i efterföljande studier. Det här avsnittet fungerar som en guide för framtida forskare, och lyfter fram potentiella riktningar för ytterligare undersökningar och förbättringar inom området DAB-baserade DC-DC-omvandlare för e-mobilitetstillämpningar. Genom att presentera slutsatserna och det framtida arbetet ger avhandlingen en omfattande sammanfattning av den forskning som bedrivs, dess bidrag och potentiella vägar för framtida forskning och utveckling.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / The Nova HYPERMOD demodulator operates in three modes, the classic pulse-code modulation/frequency modulation (PCM/FM), sometimes known as continuous phase frequency shift keying (CPFSK) mode, shaped offset quadrature phase shift keying (SOQPSK) mode, and continuous phase modulation (CPM) mode. Of interest to this paper is SOQPSK mode which is a waveform similar to the Advanced Range Telemetry (ARTM) Tier I waveform, Feher’s Quadrature Phase Shift Keying, B version (FQPSK-B) revision (Rev) A1. Also considered is another variant, FQPSK-JR. This paper will outline the cross compatibility and resynchronization speed of these waveforms based upon ARTM-adopted demodulator performance tests. The results of these laboratory tests comparing the HYPERMOD demodulator, the enhanced Tier I demodulator, and the current Tier I reference demodulator, both from RF Networks, will be presented.