Tesi sul tema "Scales of power and management"

The batteries used to power wireless sensor nodes have become a major roadblock for the wide deployment. Harvesting energy from mechanical vibrations using piezoelectric cantilevers provides possible means to recharge the batteries or eliminate them. Raw power harvested from ambient sources should be conditioned and regulated to a desired voltage level before its application to electronic devices. The efficiency and self-powered operation of a power conditioning and management circuit is a key design issue. In this research, we investigate the characteristics of piezoelectric cantilevers and requirements of power conditioning and management circuits. A two-stage conditioning circuit with a rectifier and a DC-DC converter is proposed to match the source impedance dynamically. Several low-power design methods are proposed to reduce power consumption of the circuit including: (i) use of a discontinuous conduction mode (DCM) flyback converter, (ii) constant on-time modulation, and (iii) control of the clock frequency of a microcontroller unit (MCU). The DCM flyback converter behaves as a lossless resistor to match the source impedance for maximum power point tracking (MPPT). The constant on-time modulation lowers the clock frequency of the MCU by more than an order of magnitude, which reduces dynamic power dissipation of the MCU. MPPT is executed by the MCU at intermittent time interval to save power. Experimental results indicate that the proposed system harvests up to 8.4 mW of power under 0.5-g base acceleration using four parallel piezoelectric cantilevers and achieves 72 percent power efficiency. Sources of power losses in the system are analyzed. The diode and the controller (specifically the MCU) are the two major sources for the power loss. In order to further improve the power efficiency, the power conditioning circuit is implemented in a monolithic IC using 0.18-μ­m CMOS process. Synchronous rectifiers instead of diodes are used to reduce the conduction loss. A mixed-signal control circuit is adopted to replace the MCU to realize the MPPT function. Simulation and experimental results verify the DCM operation of the power stage and function of the MPPT circuit. The power consumption of the mixed-signal control circuit is reduced to 16 percent of that of the MCU.
Ph. D.

In recent years the electric power industry has been challenged by a high level of uncertainty and volatility brought on by deregulation and globalization. A power producer must minimize the life cycle cost while meeting stringent safety and regulatory requirements and fulfilling customer demand for high reliability. Therefore, to achieve true system excellence, a more sophisticated system-level decision-making process with a more accurate forecasting support system to manage diverse and often widely dispersed generation units as a single, easily scaled and deployed fleet system in order to fully utilize the critical assets of a power producer has been created as a response. The process takes into account the time horizon for each of the major decision actions taken in a power plant and develops methods for information sharing between them. These decisions are highly interrelated and no optimal operation can be achieved without sharing information in the overall process. The process includes a forecasting system to provide information for planning for uncertainty. A new forecasting method is proposed, which utilizes a synergy of several modeling techniques properly combined at different time-scales of the forecasting objects. It can not only take advantages of the abundant historical data but also take into account the impact of pertinent driving forces from the external business environment to achieve more accurate forecasting results. Then block bootstrap is utilized to measure the bias in the estimate of the expected life cycle cost which will actually be needed to drive the business for a power plant in the long run. Finally, scenario analysis is used to provide a composite picture of future developments for decision making or strategic planning. The decision-making process is applied to a typical power producer chosen to represent challenging customer demand during high-demand periods. The process enhances system excellence by providing more accurate market information, evaluating the impact of external business environment, and considering cross-scale interactions between decision actions. Along with this process, system operation strategies, maintenance schedules, and capacity expansion plans that guide the operation of the power plant are optimally identified, and the total life cycle costs are estimated.

The great innovations of the last century have ushered continuous progress in many areas of technology, especially in the form of miniaturization of electronic circuits. This progress shows a trend towards consistent decreases in power requirements due to miniaturization. According to the ITRS and industry leaders, such as Intel, the challenge of managing and providing power efficiency still persist as scaling down of devices continues. A variety of power sources can be used in order to provide power to low power applications. Few of these sources have favorable characteristics and can be designed to deliver maximum power such as the novel mini notched turbine used as a source in this work. The MiNT is a novel device that can be used as a feasible energy source when integrated into a system and evaluated for power delivery as investigated in this work. As part of this system, a maximum power point tracking system provides an applicable solution for capturing enhanced power delivery for an energy harvesting system. However, power efficiency and physical size are adversely affected by the characteristics and environment of many energy harvesting systems and must also be addressed. To address these issues, an analysis of mini notched turbine, a RF rectenna, and an enhanced maximum power point tracking system is presented and verified using simulations and measurements. Furthermore, mini notched energy harvesting system, RF rectenna energy harvesting system, and enhanced maximum power point tracking system are developed and experimental data analyzed. The enhanced maximum power point tracking system uses a resistor emulation technique and particle swarm optimization (PSO) to improve the power efficiency and reduce the physical size. This new innovative design improves the efficiency of optimized power management circuitry up to 7% compared to conventional power management circuits over a wide range of input power and range of emulated resistances, allowing more power to be harvested from small energy harvesting sources and delivering it to the load such as smart sensors. In addition, this is the first IC design to be implemented and tested for the patented mini notched turbine (MiNT) energy harvesting device. Another advantage of the enhanced power management system designed in this work is that the proposed approach can be utilized for extremely small energy sources and because of that the proposed work is valid for low emulated resistances. and systems with low load resistance Overall, through the successful completion of this work, various energy harvesting systems can have the ability to provide enhanced power management as the IC industry continues to progress toward miniaturization of devices and systems.

In order to run and manage resource-intensive high-performance applications, large-scale computing and storage platforms have been evolving rapidly in various domains in both academia and industry. The energy expenditure consumed to operate and maintain these cloud computing infrastructures is a major factor to influence the overall profit and efficiency for most cloud service providers. Moreover, considering the mitigation of environmental damage from excessive carbon dioxide emission, the amount of power consumed by enterprise-scale data centers should be constrained for protection of the environment.Generally speaking, there exists a trade-off between power consumption and application performance in large-scale computing systems and how to balance these two factors has become an important topic for researchers and engineers in cloud and HPC communities. Therefore, minimizing the power usage while satisfying the Service Level Agreements have become one of the most desirable objectives in cloud computing research and implementation. Since the fundamental feature of the cloud computing platform is hosting workloads with a variety of characteristics in a consolidated and on-demand manner, it is demanding to explore the inherent relationship between power usage and machine configurations. Subsequently, with an understanding of these inherent relationships, researchers are able to develop effective power management policies to optimize productivity by balancing power usage and system performance. In this dissertation, we develop an autonomic power-aware system management framework for large-scale computer systems. We propose a series of techniques including coarse-grain power profiling, VM power modelling, power-aware resource auto-configuration and full-system power usage simulator. These techniques help us to understand the characteristics of power consumption of various system components. Based on these techniques, we are able to test various job scheduling strategies and develop resource management approaches to enhance the systems' power efficiency.

This thesis examines the significance of a micro-level approach to the Israeli-Palestinian water conflict. By rethinking scale of analysis and examining local insecurities, Palestinian experiences reveal how water conflict plays out in latent and discursive ways. In a step-by-step method, I detail the processes and outcomes of the water struggle in the West Bank. First, I show how technical challenges ((i) poor water supply, (ii) antiquated water infrastructure, (iii) failed institutions) are shaped by political imperatives. Second, I show how Palestinians have responded to local water sector challenges: (iv) nonpayment to the Palestinian Water Authority for their water supply, (v) increasing rural to urban migration by Palestinian farmers. As a result, Palestinian society is stuck in cycles of crisis that make the conditions increasingly ungovernable. While Palestinians are stuck in a mode of ungovernability, their position in the peace process with Israel is undermined.

A presente pesquisa analisa a produção do território de conservação sob as influências de diversos atores localizados a diferentes escalas de poder e gestão. A partir da abordagem de Territorialização – Desterritorialização – Reterritorialização, analisa-se a passagem de Chimanimani como uma área comunitária, formada por várias comunidades, cuja identidade encontra-se sacralizada nos diversos locais sagrados da área, para um território de conservação, que implicou na (re)estruturação do espaço para atender ao ecoturismo e a conservação. As transformações que ocorreram e que estão ocorrendo em Chimanimani são parte de um processo global, iniciado nos finais da década de 80 com a introdução dos Programas de Reabilitação Econômica. Estas transformações submeteram o local ao global e deslocaram a comanda da área para outras escalas de poder e gestão. As transformações pelas quais Chimanimani foi passando implicaram numa transição da agricultura como a base de sobrevivência para o ecoturismo. A dependência ao ecoturismo como a atividade que melhor compatibiliza a exploração dos recursos naturais numa área de conservação parece não encontrar um enquadramento na dinâmica da atividade turística em Moçambique, que tem como preferência o turismo de “sol e praia”. Como dinamizar o turismo em áreas de conservação é um desafio para a realidade moçambicana, cujas condições dificultam o desenvolvimento do ecoturismo em áreas distantes da região costeira. Dentro desse dilema, propõe-se o Turismo Social como uma possibilidade para o desenvolvimento do turismo nas áreas de conservação.
This research analyses the production of the conservation territory under influences of various actors located at different scales of power and management. From the approaches Territorialization – Desterritorialization – Reterritorialization, we analyze the transition of Chimanimani as a community area, formed by several communities, whose identity is enshrined in the various sacred sites of area, to a conservation area, which resulted in (re)structuring space to answer conservation and ecotourism. Transformations that occurred and are occurring in Chimanimani are part of an overall process, begun in the late 80’s with the introduction o Economic Rehabilitation Programs. These changes submitted the place to the global and moved the command of the area for other scales of power and management. These transformations which Chimanimani are involved implicated a transition of the agriculture as the survival base for the ecotourism. The dependence on ecotourism as the activity that better reconcile the exploration of natural resources in an area of conservation does not seem to find a framework in the dynamics of tourism in Mozambique, which is preferably tourism “Sun and sand”. How to boost tourism in conservation areas is a challenge for the Mozambican reality, whose conditions make it difficult to ecotourism development in remote areas far from the coastal region. In this dilemma, it is proposed Social Tourism as a possibility for the development of tourism in conservation areas.

Future generation of all-electric ships will be highly dependent on electric power, since every single system aboard such as the drive propulsion, the weapon system, the communication and navigation systems will be electrically powered. Power conversion modules (PCM) will be used to transform and distribute the power as desired in various zone within the ships. As power densities increase at both components and systems-levels, high-fidelity thermal models of those PCMs are indispensable to reach high performance and energy efficient designs. Efficient systems-level thermal management requires modeling and analysis of complex turbulent fluid flow and heat transfer processes across several decades of length scales. In this thesis, a methodology for thermal modeling of complex PCM cabinets used in naval applications is offered. High fidelity computational fluid dynamics and heat transfer (CFD/HT) models are created in order to analyze the heat dissipation from the chip to the multi-cabinet level and optimize turbulent convection cooling inside the cabinet enclosure. Conventional CFD/HT modeling techniques for such complex and multi-scale systems are severely limited as a design or optimization tool. The large size of such models and the complex physics involved result in extremely slow processing time. A multi-scale approach has been developed to predict accurately the overall airflow conditions at the cabinet level as well as the airflow around components which dictates the chip temperature in details. Various models of different length scales are linked together by matching the boundary conditions. The advantage is that it allows high fidelity models at each length scale and more detailed simulations are obtained than what could have been accomplished with a single model methodology. It was found that the power cabinets under the prescribed design parameters, experience operating point airflow rates that are much lower than the design requirements. The flow is unevenly distributed through the various bays. Approximately 90 % of the cold plenum inlet flow rate goes exclusively through Bay 1 and Bay 2. Re-circulation and reverse flow are observed in regions experiencing a lack of flow motion. As a result high temperature of the air flow and consequently high component temperatures are also experienced in the upper bays of the cabinet. A proper orthogonal decomposition (POD) methodology has been performed to develop reduced-order compact models of the PCM cabinets. The reduced-order modeling approach based on POD reduces the numerical models containing 35 x 109 DOF down to less than 20 DOF, while still retaining a great accuracy. The reduced-order models developed yields prediction of the full-field 3-D cabinet within 30 seconds as opposed to the CFD/HT simulations that take more than 3 hours using a high power computer cluster. The reduced-order modeling methodology developed could be a useful tool to quickly and accurately characterize the thermal behavior of any electronics system and provides a good basis for thermal design and optimization purposes.

The transmission of power across the GB transmission system, as operated by National Grid, results in inevitable loss of electrical power. Operationally these power losses cannot be eliminated, but they can be reduced by adjustment of the system voltage profile. At present the minimisation of active power losses relies upon a lengthy manually based iterative adjustment process. Therefore the system operator requires the development of advanced optimisation tools to cope with the challenges faced over the next decade, such as achieving the stringent greenhouse gas emission targets laid down by the UK government, while continue to provide an economical, secure and efficient service. To meet these challenges the research presented in this thesis has developed optimisation techniques that can assist control centre engineers by automatically setting up voltage studies that are low loss and low cost. The proposed voltage optimisation techniques have been shown to produce solutions that are secured against 800 credible contingency cases. A prototype voltage optimisation tool has been deployed, which required the development of a series of novel approaches to extend the functionality of an existing optimisation program. This research has lead to the development of novel methods for handling multi-objectives, contradictory shunt switching configurations and selecting all credible contingencies. Studies indicate that a theoretical loss saving of 1.9% is achievable, equivalent to an annual emissions saving of approximately 64,000 tonnes of carbon dioxide. A novel security constrained mixed integer non-linear optimisation technique has also been developed. The proposed method has been shown to be superior to several conventional methods on a wide range of IEEE standard network models and also on a range of large-scale GB network models. The proposed method manages to further reduce active power losses and also satisfies all security constraints.

Trends in battery-operated portable applications require further miniaturization and eventually on-chip integration of power processing circuits along with their optimum power management control circuits, considered as key components in on-chip power subsystems which have a high impact upon the overall system in terms of size and efficiency. On-chip power management subsystems, both in regulation and more sophisticated functionalities as wideband tracking, are ideally based on power switching converters, paradigm of high efficiency circuits. These subsystems, due to their nonlinear switched dynamic nature, can exhibit various instabilities which are mainly classified as slow-scale and fast-scale instabilities, the latter also known as subharmonic oscillations. The prediction of slow-scale instabilities can be carried out by conventional averaged dynamic models, which are derived form a simple mathematical circuit analysis and have a clear design-oriented standpoint, but due to their averaged nature, they fail to predict fast-scale instabilities. Alternatively, the prediction of the overall stability boundaries within the complete design space, encompassing fast-scale subharmonic oscillations, has hitherto been addressed from an analytic standpoint based on the discrete-time model, which are based on complex analysis that yields accurate prediction results but lacks of a circuit standpoint and hence are not aligned with a design-oriented use. In this thesis the effect of different system parameters upon the stability boundaries is explored, demonstrating that trends towards integration, namely the reduction of reactive component size or a decrease of the relative switching frequency compared to the converter natural dynamics leads to the exhibition of fast-scale instabilities. As far as characterization is concerned, a two-fold approach has been considered both exploring the complete parameter design space of the switching regulator and categorizing it in terms of which type of nonlinear dynamic performance the circuit exhibits (design space characterization), as well as providing a novel characterization of the electrical behaviour for the different dynamic modes in terms of electrical performance metrics connatural to a power processing circuit, such as voltage ripple, average switching frequency and spectra (electrical characterization). With the aim of having a design-oriented circuit-based model for predicting subharmonic instabilities, the thesis proposes a novel approach based on considering the ripple component at the PWM modulator input as an index to predict the fast-scale stability boundary -in the particular case of a voltage-mode buck converter in continuous conduction mode, a representative case of widespread use in battery-operated applications-. This ripple-based instability index has been validated both from the instantaneous nonlinear dynamic state equations solved numerically as well as through experimental prototypes. Finally a bridge between the ripple-based index approach and the discrete-time model is established though relating the ripple and the control signal slope at the switching instant. The approach has been extended to the discontinuous conduction-mode and to current-mode control, demonstrating the general purpose of the ripple-based fast-scale instability prediction approach. A design-oriented comprehensive frequency domain model able to concurrently predict both slow scale and fast scale instabilities through the combined application of averaged models and the ripple-based approach closes this part. Complementarily to the prediction of fast-scale stability boundary, fast-scale instability controllers or chaos controllers are studied, first revisiting the operating principle of already existing delay-based controllers, afterwards proposing and analyzing simpler implementation-friendly chaos controllers. Under the integrated power management perspective, the thesis extends them taking into account other power processor metrics such as output ripple or transient response, thereby proposing a novel controller that, apart from improving fast-scale stability boundary, allows reducing reactive components size and the output voltage ripple. Finally, the thesis tackles the fast-scale instabilities in more advanced topologies and functionalities, which are representative of advanced power management circuits. First, for a multilevel converter, demonstrating that its inherent lower ripple behaviour makes it less prone to exhibit fast-scale instabilities and hence a better candidate to integration, and second for a wideband switching power amplifier, exploring its nonlinear dynamic phenomena and demonstrating that in the case of a single-tone modulation with a frequency close to the filter and switching frequencies, the fast scale stability boundary condition for regulation application is a sufficient condition to guarantee stability over the entire reference period for tracking applications.
Les tendències actuals i previsiblement futures en aplicacions portàtils alimentades per bateries requereixen de major miniaturització i finalment de la integració en un sol chip del circuit de processament de potència juntament amb els circuits de control i gestió optima de la energia, considerats com components clau en els subsistemes de potència, els quals tenen un important impacte global en la mida i la eficiència energètica de tot el sistema. El subsistemes de gestió de potència, tant en regulació com en funcionalitats més sofisticades com és el seguiment de senyals de gran ample de banda amb alt rendiment, són idealment basats en convertidors commutats de potència, paradigma de circuits processadors d’energia d’alt rendiment. Aquests subsistemes, degut a la seva natura no lineal, poden exhibir diverses inestabilitats, les quals es poden classificar segons l’escala temporal en escala ràpida o escala lenta. La predicció de les inestabilitats d’escala lenta es duu a terme habitualment mitjançant els models promitjats convencionals, els quals es deriven d’un anàlisi simple del circuit i tenen com a clar objectiu la simplificació del disseny del sistema, però degut a la seva natura promitjada, no permeten predir les inestabilitats d’escala ràpida. Alternativament, la predicció de la frontera complerta d’estabilitat, incloent ambdós tipus d’inestabilitats, s’ha abordat en el passat des d’un punt de vista analític mitjançant els models en temps discret, basats en una desenvolupament matemàtic més complex i acurat, però que resulta en un anàlisis que s’allunya de la perspectiva orientada al disseny del sistema. En aquest tesis, l’efecte dels diferents paràmetres de l’espai de disseny del sistema sobre la frontera d'estabilitat ha estat explorat, demostrant que les tendències cap a la integració, es a dir, la reducció dels components reactius o la reducció de la freqüència de commutació, condueix a una propensió a exhibir inestabilitats dinàmiques d’escala ràpida. Pel que fa a la caracterització d’aquestes inestabilitats, s’ha dut a terme explorant completament l’espai de disseny així com proposant una caracterització en termes de mètriques de circuit processador d’energia elèctrica del diferents modes dinàmics, incloent així el seu impacte en termes d'arrisat de tensió, espectre, i freqüència promig de commutació. Amb l’objectiu de derivar un model orientat al disseny per predir les inestabilitats d’escala ràpida, la tesi proposa un índex basat en la mesura de l’arrisat a la entrada del modulador PWM per predir de forma quantitativa aquestes inestabilitats en mode de control de tensió. Aquest índex ha estat validat mitjançant simulacions numèriques i experimentalment. Addicionalment, la tesi demostra la relació existent entre l’arrisat en el modulador i els mapes en temps discret. La proposta s’ha estès per al mode de conducció discontinua i també pel mode de control per corrent, demostrant així l’aplicabilitat general de la proposta. Finalment, s’ha proposat i estudiat un model complet en el domini de la freqüència, capaç de predir concurrentment els dos tipus de inestabilitats mitjançant l’aplicació conjunta del model promitjat i el model basat en l’arrisat. De forma complementaria a la predicció de les inestabilitats d’escala ràpida, s’han estudiat diversos controladors orientats a modificar el comportament inestable. Primer tot revisant el principi de funcionament del controladors existents, basat majoritàriament en línies de retard i posteriorment proposant i analitzant controladors que tinguin una implementació mes factible en el domini analògic. Sota la perspectiva de la integració en silici dels sistemes de potència, la tesi ha estès l’anàlisi dels controladors tenint en compte altres mètriques com ara l’arrisat de sortida o la resposta transitòria a un canvi de la carga. Així, s’ha proposat un nou controlador, el qual apart de millorar les inestabilitats d’escala ràpida, permet reduir la mida del components reactius i alhora l’arrisat de sortida del convertidor. Finalment, la tesi aborda la caracterització i predicció de les inestabilitats d’escala ràpida en topologies i funcionalitats mes avançades. Primer, per a un convertidor multinivell, demostrant que el seu inherent baix arrissat el fa menys proper a exhibir inestabilitats i per tant un millor candidat a la integració, i seguidament per a un amplificador commutat de gran ample de banda, explorant la seva dinàmica no lineal, i demostrant que en el cas d’un sol to sinusoïdal, la condició d’estabilitat per regulació estableix una condició suficient per garantir l’estabilitat per aplicacions de seguiment.

Building portfolio management on campus and metropolitan scale involves decisions about energy retrofits, energy resource pooling, and investments in shared energy systems, such as district cooling, community PV and wind power, CHP systems, geothermal systems etc. There are currently no tools that help a portfolio/campus manager make these decisions by rapid comparison of variants. The research has developed an energy supply network management tool at the campus scale. The underlying network energy performance (NEP) model uses (1) an existing energy performance toolkit to quantify the energy performance of building energy consumers on hourly basis, and (2) added modules to calculate hourly average energy generation from a wide variety of energy supply systems. The NEP model supports macro decisions at the generation side (decisions about adding or retrofitting campus wide systems) and consumption side (planning of new building design and retrofit measures). It allows testing different supply topologies by inspecting which consumer nodes should connect to which local suppliers and to which global suppliers, i.e. the electricity and gas utility grids. A prototype software implementation allows a portfolio or campus manager to define the demand and supply nodes on campus scale and manipulate the connections between them through a graphical interface. The NEP model maintains the network topology which is represented by a directed graph with the supply and demand nodes as vertices and their connections as arcs. Every change in the graph automatically triggers an update of the energy generation and consumption pattern, the results of which are shown on campus wide energy performance dashboards. The dissertation shows how the NEP model supports decision making with respect to large-scale building energy system design with a case study of the Georgia Tech campus evaluating the following three assertions: 1. The normative calculations at the individual building scale are accurate enough to support the network energy performance analysis 2. The NEP model supports the study of the tradeoffs between local building retrofits and campus wide energy interventions in renewable systems, under different circumstances 3. The NEP approach is a viable basis for routine campus asset management policies.

Trends in battery-operated portable applications require further miniaturization and eventually on-chip integration of power processing circuits along with their optimum power management control circuits, considered as key components in on-chip power subsystems which have a high impact upon the overall system in terms of size and efficiency. On-chip power management subsystems, both in regulation and more sophisticated functionalities as wideband tracking, are ideally based on power switching converters, paradigm of high efficiency circuits. These subsystems, due to their nonlinear switched dynamic nature, can exhibit various instabilities which are mainly classified as slow-scale and fast-scale instabilities, the latter also known as subharmonic oscillations. The prediction of slow-scale instabilities can be carried out by conventional averaged dynamic models, which are derived form a simple mathematical circuit analysis and have a clear design-oriented standpoint, but due to their averaged nature, they fail to predict fast-scale instabilities. Alternatively, the prediction of the overall stability boundaries within the complete design space, encompassing fast-scale subharmonic oscillations, has hitherto been addressed from an analytic standpoint based on the discrete-time model, which are based on complex analysis that yields accurate prediction results but lacks of a circuit standpoint and hence are not aligned with a design-oriented use. In this thesis the effect of different system parameters upon the stability boundaries is explored, demonstrating that trends towards integration, namely the reduction of reactive component size or a decrease of the relative switching frequency compared to the converter natural dynamics leads to the exhibition of fast-scale instabilities. As far as characterization is concerned, a two-fold approach has been considered both exploring the complete parameter design space of the switching regulator and categorizing it in terms of which type of nonlinear dynamic performance the circuit exhibits (design space characterization), as well as providing a novel characterization of the electrical behaviour for the different dynamic modes in terms of electrical performance metrics connatural to a power processing circuit, such as voltage ripple, average switching frequency and spectra (electrical characterization). With the aim of having a design-oriented circuit-based model for predicting subharmonic instabilities, the thesis proposes a novel approach based on considering the ripple component at the PWM modulator input as an index to predict the fast-scale stability boundary -in the particular case of a voltage-mode buck converter in continuous conduction mode, a representative case of widespread use in battery-operated applications-. This ripple-based instability index has been validated both from the instantaneous nonlinear dynamic state equations solved numerically as well as through experimental prototypes. Finally a bridge between the ripple-based index approach and the discrete-time model is established though relating the ripple and the control signal slope at the switching instant. The approach has been extended to the discontinuous conduction-mode and to current-mode control, demonstrating the general purpose of the ripple-based fast-scale instability prediction approach. A design-oriented comprehensive frequency domain model able to concurrently predict both slow scale and fast scale instabilities through the combined application of averaged models and the ripple-based approach closes this part. Complementarily to the prediction of fast-scale stability boundary, fast-scale instability controllers or chaos controllers are studied, first revisiting the operating principle of already existing delay-based controllers, afterwards proposing and analyzing simpler implementation-friendly chaos controllers. Under the integrated power management perspective, the thesis extends them taking into account other power processor metrics such as output ripple or transient response, thereby proposing a novel controller that, apart from improving fast-scale stability boundary, allows reducing reactive components size and the output voltage ripple. Finally, the thesis tackles the fast-scale instabilities in more advanced topologies and functionalities, which are representative of advanced power management circuits. First, for a multilevel converter, demonstrating that its inherent lower ripple behaviour makes it less prone to exhibit fast-scale instabilities and hence a better candidate to integration, and second for a wideband switching power amplifier, exploring its nonlinear dynamic phenomena and demonstrating that in the case of a single-tone modulation with a frequency close to the filter and switching frequencies, the fast scale stability boundary condition for regulation application is a sufficient condition to guarantee stability over the entire reference period for tracking applications.
Les tendències actuals i previsiblement futures en aplicacions portàtils alimentades per bateries requereixen de major miniaturització i finalment de la integració en un sol chip del circuit de processament de potència juntament amb els circuits de control i gestió optima de la energia, considerats com components clau en els subsistemes de potència, els quals tenen un important impacte global en la mida i la eficiència energètica de tot el sistema. El subsistemes de gestió de potència, tant en regulació com en funcionalitats més sofisticades com és el seguiment de senyals de gran ample de banda amb alt rendiment, són idealment basats en convertidors commutats de potència, paradigma de circuits processadors d’energia d’alt rendiment. Aquests subsistemes, degut a la seva natura no lineal, poden exhibir diverses inestabilitats, les quals es poden classificar segons l’escala temporal en escala ràpida o escala lenta. La predicció de les inestabilitats d’escala lenta es duu a terme habitualment mitjançant els models promitjats convencionals, els quals es deriven d’un anàlisi simple del circuit i tenen com a clar objectiu la simplificació del disseny del sistema, però degut a la seva natura promitjada, no permeten predir les inestabilitats d’escala ràpida. Alternativament, la predicció de la frontera complerta d’estabilitat, incloent ambdós tipus d’inestabilitats, s’ha abordat en el passat des d’un punt de vista analític mitjançant els models en temps discret, basats en una desenvolupament matemàtic més complex i acurat, però que resulta en un anàlisis que s’allunya de la perspectiva orientada al disseny del sistema. En aquest tesis, l’efecte dels diferents paràmetres de l’espai de disseny del sistema sobre la frontera d'estabilitat ha estat explorat, demostrant que les tendències cap a la integració, es a dir, la reducció dels components reactius o la reducció de la freqüència de commutació, condueix a una propensió a exhibir inestabilitats dinàmiques d’escala ràpida. Pel que fa a la caracterització d’aquestes inestabilitats, s’ha dut a terme explorant completament l’espai de disseny així com proposant una caracterització en termes de mètriques de circuit processador d’energia elèctrica del diferents modes dinàmics, incloent així el seu impacte en termes d'arrisat de tensió, espectre, i freqüència promig de commutació. Amb l’objectiu de derivar un model orientat al disseny per predir les inestabilitats d’escala ràpida, la tesi proposa un índex basat en la mesura de l’arrisat a la entrada del modulador PWM per predir de forma quantitativa aquestes inestabilitats en mode de control de tensió. Aquest índex ha estat validat mitjançant simulacions numèriques i experimentalment. Addicionalment, la tesi demostra la relació existent entre l’arrisat en el modulador i els mapes en temps discret. La proposta s’ha estès per al mode de conducció discontinua i també pel mode de control per corrent, demostrant així l’aplicabilitat general de la proposta. Finalment, s’ha proposat i estudiat un model complet en el domini de la freqüència, capaç de predir concurrentment els dos tipus de inestabilitats mitjançant l’aplicació conjunta del model promitjat i el model basat en l’arrisat. De forma complementaria a la predicció de les inestabilitats d’escala ràpida, s’han estudiat diversos controladors orientats a modificar el comportament inestable. Primer tot revisant el principi de funcionament del controladors existents, basat majoritàriament en línies de retard i posteriorment proposant i analitzant controladors que tinguin una implementació mes factible en el domini analògic. Sota la perspectiva de la integració en silici dels sistemes de potència, la tesi ha estès l’anàlisi dels controladors tenint en compte altres mètriques com ara l’arrisat de sortida o la resposta transitòria a un canvi de la carga. Així, s’ha proposat un nou controlador, el qual apart de millorar les inestabilitats d’escala ràpida, permet reduir la mida del components reactius i alhora l’arrisat de sortida del convertidor. Finalment, la tesi aborda la caracterització i predicció de les inestabilitats d’escala ràpida en topologies i funcionalitats mes avançades. Primer, per a un convertidor multinivell, demostrant que el seu inherent baix arrissat el fa menys proper a exhibir inestabilitats i per tant un millor candidat a la integració, i seguidament per a un amplificador commutat de gran ample de banda, explorant la seva dinàmica no lineal, i demostrant que en el cas d’un sol to sinusoïdal, la condició d’estabilitat per regulació estableix una condició suficient per garantir l’estabilitat per aplicacions de seguiment.

Biomass is projected to account for approximately half of the new energy production required to achieve the 2020 primary energy target in the UK. Combined heat and power (CHP) bioenergy systems are not only a highly efficient method of energy conversion, at smaller-scales a significant proportion of the heat produced can be effectively utilised for hot water, space heating or industrial heating purposes. However, there are many barriers to project development and this has greatly inhibited deployment in the UK. Project viability is highly subjective to changes in policy, regulation, the finance market and the low cost incumbent; a high carbon centralised energy system. Unidentified or unmitigated barriers occurring during the project lifecycle may not only negatively impact on the project but could ultimately lead to project failure. The research develops a decision support system (DSS) for small-scale (500 kWe to 10 MWe) biomass combustion CHP project development and risk management in the early stages of a potential project’s lifecycle. By supporting developers in the early stages of project development with financial, scheduling and risk management analysis, the research aims to reduce the barriers identified and streamline decision-making. A fuzzy methodology is also applied throughout the developed DSS to support developers in handling the uncertain or approximate information often held at the early stages of the project lifecycle. The DSS is applied to a case study of a recently failed (2011) small-scale biomass CHP project to demonstrate its applicability and benefits. The application highlights that the proposed development within the case study was not viable. Moreover, further analysis of the possible barriers with the DSS confirmed that some possible modifications to be project could have improved this, such as a possible change of feedstock to a waste or residue, addressing the unnecessary land lease cost or by increasing heat utilisation onsite. This analysis is further supported by a practitioner evaluation survey that confirms the research contribution and objectives are achieved.

A conceptual dust detection mission, KnightSat III, using pico-scale satellites is analyzed. The purpose of the proposed KnightSat III mission is to aid in the determination of the size, mass, distribution, and number of dust particles in low earth orbits through a low cost and flexible satellite or a formation of satellites equipped with a new dust detector. The analysis of a single satellite mission with an on-board dust detector is described; though this analysis can easily be extended to a formation of pico-scale satellites. Many design aspects of the mission are discussed, including orbit analysis, power management, attitude determination and control, and mass and power budgets. Two of them are emphasized. The first is a new attitude guidance and control method, and the second is the online optimal power scheduling. It is expected that the measurements obtained from this possible future mission will provide insight into the dynamical processes of inner solar system dust, as well as aid in designing proper micro-meteoroid impact mitigation strategies for future man-made spacecraft.
M.S.A.E.
Masters
Mechanical and Aerospace Engineering
Engineering and Computer Science
Aerospace Engineering; Space System Design and Engineering

The task of thermal management in electrical systems has never been simple and has only become more difficult in recent years as the power electronics industry pushes towards devices with higher power densities. At the Center for Power Electronic Systems (CPES), a new approach to power electronic design is being implemented with the Integrated Power Electronic Module (IPEM). It is believed that an IPEM-based design approach will significantly enhance the competitiveness of the U.S. electronics industry, revolutionize the power electronics industry, and overcome many of the technology limits in today's industry by driving down the cost of manufacturing and design turnaround time. But with increased component integration comes the increased risk of component failure due to overheating. This thesis addresses the issues associated with the thermal management of integrated power electronic devices. Two studies are presented in this thesis. The focus of these studies is on the thermal design of a DC-DC front-end power converter developed at CPES with an IPEM-based approach. The first study investigates how the system would respond when the fan location and heat sink fin arrangement are varied in order to optimize the effects of conduction and forced-convection heat transfer to cool the system. The set-up of an experimental test is presented, and the results are compared to the thermal model. The second study presents an improved methodology for the thermal modeling of large-scale electrical systems and their many subsystems. A zoom-in/zoom-out approach is used to overcome the computational limitations associated with modeling large systems. The analysis performed in this paper was completed using I-DEAS©,, a three-dimensional finite element analysis (FEA) program which allows the thermal designer to simulate the affects of conduction and convection heat transfer in a forced-air cooling environment.
Master of Science

During the quasar era (redshifts between 1 and 3) Radio Galaxies (RGs) have been claimed to have substantially influenced the growth and evolution of large scale structures in the universe. In this dissertation I test the robustness of these exciting claims. In order to probe the impacts in more detail, good theoretical models for such RG systems are required. With this motivation, I seek to develop an essentially analytical model for the evolution of Fanaroff-Riley Class II radio galaxies both as they age individually and as their numbers vary with cosmological epoch. To do so, I first compare three sophisticated semi-analytical models for the dynamical and radio lobe power evolution of FR II galaxies, those given by Kaiser, Dennett-Thorpe & Alexander (1997, KDA), Blundell, Rawlings, & Willott (1999, BRW) and Manolakou & Kirk (2002, MK). I perform multi-dimensional Monte Carlo simulations leading to virtual radio surveys. The predictions of each model for redshift, radio power (at 151 MHz), linear size and spectral index are then compared with data. The observational samples are the low frequency radio surveys, 3CRR, 6CE and 7CRS, which are flux-limited and redshift complete. I next perform extensive statistical tests to compare the distributions of model radio source parameters and those of the observational samples. The statistics used are the 1-Dimensional and 2-Dimensional Kolmogorov-Smirnov (K-S) tests and the 4-variable Spearman partial rank correlation coefficient. I search for and describe the "best" parameters for each model. I then produced modifications to each of the three original models, and extensively compare the original and the modified model performances in fitting the data. The key result of my dissertation is that using the Radio Luminosity Function of Willott et al. (2001) as the redshift birth function of radio sources, the KDA and MK models perform better than the BRW models in fitting the 3CRR, 6CE and 7CRS survey data when using K-S based statistical tests, and the KDA model provides the best fits to the correlation coefficients. However, no pre-existing or modified model can provide adequate fits for the spectral indices. I also calculate the volume fraction of the relevant universe filled by the generations of radio galaxies over the quasar era. This volume filling factor is not as large as estimated earlier. Nonetheless, the allowed ranges of various model parameters produce a rather wide range of astrophysically interesting relevant volume fraction values. I conclude that the expanding RGs born during the quasar era may still play significant roles in the cosmological history of the universe.

Geomagnetically Induced Currents (GIC's) in B. C. Hydro's 500 kV transmission system have in the past been responsible for the generation of harmonics of 60 Hz, system voltage drops, and misoperation of relay units. Characterization of the associated magnetic storms' spatial scales would further the understanding of GIC generation in the area, and allow advanced warning of potential problems in future power transmission projects. Data collected in 1984 at four substations were analysed to determine lateral variations in geomagnetically induced earth surface electric fields. Inversion techniques were employed to find a variety of solutions that would reproduce the data. Results suggested that the magnetic storms were larger than the area monitored, and that resultant electric fields seen by a large portion of the transmission grid were uniform. Departures from this uniformity in other portions of the electric field models were felt either to be due to earth induction effects, or in some cases, to be artifacts of the data analysis techniques. An experiment designed to determine the controlling factors behind GIC's is outlined. Considerable effort would be required to explicitly determine all electric fields affecting the transmission system
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

In an office building in the US the office equipment uses about 7% of the total electricity use. Eventhough this is a low number, there is still a reason to save more energy, especially since one third of theenergy savings are lost when power management is not enabled.The core in the project ”Power Management Controls” is to develop a voluntary standard, The UserInterface Standard, that manufacturers of office equipment can use as a reference when they developnew equipment and design new interfaces. The interface is an important part of the use of powermanagement and doing this should increase the use of power management and save more energy. Theinterfaces are ofter hidden or inconsistent and confusing, which makes it harder for the user tounderstand power management. A more consistent interface makes it easier for the user to understandthe meaning of an interface and power management itselfThe standard consists of six different parts, which describe what can be done to achieve a consistentinterface. The standard also describes the part of the project called Dynamic Behavior. This part isconcentrating on the interfaces and the behavior of the device over time, which is important for the userto understand.The purpose of this degree project is to study and participate in the project ”Power ManagementControls”, and to understand what is being done to save more energy.

Raters have been shown to react differently to performance evaluation formats. However, reactions to a new and promising format, frame-of-reference scales (FORS), remains untested. This experiment found that FORS users reacted more positively compared to standard scale users overall, and results were attributable to perceived accuracy and fairness.

Recent developments in energy harvesting techniques allowed implementation of completely autonomous biosensor nodes. However, an energy harvesting device generally demands a customized power management unit (PMU) in order to provide the adequate voltage supply for the biosensor. One of the key blocks within this PMU is a regulation DC-DC converter. In this Master Thesis, the most relevant switched-capacitor DC-DC converter topologies that are suitable for biosensors are compared. The topology that can achieve the best efficiency and has the minimum area is chosen and designed. In order to maintain the supply voltage of the biosensor constant when the input voltage and the output current vary, a traditional Pulse-Frequency-Modulation (PFM) control is employed. An ultra-low-power PFM control circuit is designed to operate in weak inversion region. The post-layout simulations show that the designed DC-DC converter can provide an output voltage of 900mV when the output current varies between 5μA and 40μA. Additionally, the post layout simulations of the entire system, which includes the DC-DC converter and PFM control, show that the selected topology can achieve 87% peak efficiency, when the control losses are included. The main advantages of the proposed topology are its smaller chip area and its high efficiency during processing ultra-low power levels.

Printed electronics and low power radio has evolved significantly in recent years. This has made it possible to implement electronic worn on the body or clothing. Printed batteries internal resistance is much higher compared to regular batteries. Unless a battery power management circuit is used, the radio peak current makes that the terminal voltage may drop to a level below the specified supply voltage for the radio, causing operation failure. A large capacitor solves this but a large surface mounted capacitor can be both larger and heavier than the integrated radio circuit. A trade-o_ must be done. Voltage regulation is necessary since the battery voltage is higher than the supply voltage for the radio. Design of capacitor, battery and low-dropout regulator were simulated in the shape of function and life length in LTSpice. The results were compared between theory, simulation and radio measurements.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 137-145).
Power management circuits perform a wide range of vital tasks for electronic systems including DC-DC conversion, energy harvesting, battery charging and protection as well as dynamic voltage scaling. The impact of the efficiency of the power management circuits is highly profound for ultra-low power systems such as implantable, ingestible or wearable devices. Typically the size of the system for such applications does not allow the integration of a large energy storage device. Therefore, extreme energy efficiency of the power management circuits is critical for extended operation time. In addition, flexibility and small form factor are desirable to conform to the human body and reduce the system's over all size. Thus, this thesis presents highly efficient and miniature power converters for multiple applications using architecture and circuit level optimization as well as emerging technologies. The first part presents a power management IC (PMIC) featuring an integrated reconfigurable switched capacitor DC-DC converter using on-chip ferroelectric caps in 130 nm CMOS process. Digital pulse frequency modulation and gain selection circuits allow for efficient output voltage regulation. The converter utilizes four gain settings (1, 2/3, 1/2, 1/3) to support an output voltage of 0.4 V to 1.1 V from 1.5 V input while delivering load current of 20 [mu]A to 1 mA. The PMIC occupies 0.366 mm² and achieves a peak efficiency of 93% including the control circuit overhead at a load current of 500 [mu]A. The second part presents a solar energy harvesting system with 3.2 nW overall quiescent power. The chip integrates self-startup, battery management, supplies 1 V regulated rail with a single inductor and supports power range of 10 nW to 1 [mu]W. The control circuit is designed in an asynchronous fashion that scales the effective switching frequency of the converter with the level of the power transferred. The ontime of the converter switches adapts dynamically to the input and output voltages for peak-current control and zero-current switching. The system has been implemented in 180 nm CMOS process. For input power of 500 nW, the proposed system achieves an efficiency of 82%, including the control circuit overhead, while charging a battery at 3 V from 0.5 V input. The third part focuses on developing an energy harvesting system for an ingestible device using gastric acid. An integrated switched capacitor DC-DC converter is designed to efficiently power sensors and RF transmitter with a 2.5 V regulated voltage rail. A reconfigurable Dickson topology with four gain settings (3, 4, 6, 10) is used to support a wide input voltage range from 0.3 V to 1.1 V. The converter is designed in 65 nm CMOS process and achieves a peak efficiency of 80% in simulation for output power of 2 [mu]W. The last part focuses on flexible circuit design using Molybdenum Disulfide (MoS₂), one of the emerging 2D materials. A computer-aided design flow is developed for MoS₂-based circuits supporting device modeling, circuit simulation and parametric cell-based layout - which paves the road for the realization of large-scale flexible MoS₂ systems.
by Dina Reda El-Damak.
Ph. D.

Cross-cultural factors affect the cognitive processes engaged in by subjects to respond to rating scales. By using a sequential explanatory strategy of mixed-method research design, this study investigates four cultural groups in the software industry (n=92) - Israelis, Latinos, Romanians, and Americans — to investigate cultural effects on the thought processes used by respondents performing selected verbal (ordinal) and numeric (interval) scales.

Cluster analysis of the qualitative data identified four main response styles used by subjects – Extremes, Midpoint, Range, and Refiners. While the clusters did not differ in their demographics, when evaluating their cognitive processes against the theory of Tourangeau, Rips, and Rasinski (2000), clusters used different cognitive processes. Specifically, Refiners and Midpoint were more likely to adjust their responses during the Judgment stage before responding.

The findings of this research identified that values as acquired through life experience (i.e., leadership position) and demographics (i.e., gender, age, and educational level) rather than basic culture play a key role in the cognitive processes used by subjects to respond to scales. These factors affected scale preference, response style, cognitive processes, and even generated sentiments and emotions. Focusing on cultural values rather than cultural practices is a key need to yield valid survey results.

While some of the subjects are oblivious to the cultural effects discussed in this study, those effects have theoretical and practical implications for surveys conducted by multi-national organizations and business leaders. Furthermore, identifying and handling cross-cultural differences described in this study can be used to train leaders in cross-cultural environments.

Introduction : World poultry meat consumption consists of three major segments: broilers, turkeys, and other poultry which includes spent egg layers, spent breeder hens/males, ducks, geese, guinea-fowl, pheasants, quail, ratites, ostriches and emus. Broilers clearly dominate the world poultry consumption contributing about 70 percent to the world poultry market. Turkeys account for about eight percent while other poultry provides the balance of 22 percent (Roenick, 1998). The world broiler industry has been, and continues to be a very dynamic industry. It has been typified with unprecedented growth in terms of production. In 1961, the world produced 6.5 billion broilers. By 1990, the total annual production was a little over 27 billion broilers and by 1996, total world production had grown to 35.3 billion (Van der Sluis., 1999). This represents a fivefold increase in 35 years, and it has not stopped growing since, with world production surpassed 38 billion in 1998 (Van der Sluis., 1999). In Africa the human population was estimated to be 819.9 million, while the total poultry population of the continent was estimated as 1.133 million chickens, 15 million ducks and seven million turkeys in 1998. Production scale being 1.781701 metric tones (MT) of hen eggs, 2.269000 MT of chickens’ meat, 32.824MT of turkey meat and 52.989MT of duck meat (Gueye, 2000). Commercial poultry products are also imported and exported. For example, 12.000 metric tons of poultry meat was estimated to have been exported from South Africa in 1999, whereas 87.000 and 10.000 metric tons of poultry meat was imported into South Africa and Egypt, respectively (Gueye, 2000). In South Africa poultry production is moving toward the 21st century with the potential for increased development being greater than any other sector of the agricultural industry. The small-scale to medium-scale or semi-commercial farmer is becoming a role-player that needs to be serviced by the poultry industry (Fourie, 2000). The industry will have to take up the challenges that are facing an entrepreneur starting with a poultry venture. The poultry industry has developed from a humble beginning at the turn of the century into a multi-million Rand enterprise where protein is provided through the commercial and small marketing sector (Fourie, 2000). Some of the larger commercial companies market three million birds per week. It is estimated that the commercial company sector is responsible for 75 to 85 percent of production and marketing of white meat in this country whereas the small-scale and medium-scale or semi commercial poultry production enterprises provide 20 to 25 percent of the white meat through the sales of slaughtered and live poultry sale to rural, peri-urban and urban settlements (Fourie., 2000). Small-scale and semi-commercial broiler production is developed by entrepreneurs who buy day-old chicks from the big commercial hatcheries, rear them to the age of five to eight weeks and sell them through a marketing network or small outlets. The small-scale consist of farmers who reared 100 t0 1000 chickens per batch and semi-commercial consist of farmers who reared 1000 to 5000 chickens per batch. These types of farmers acquire very little technical backup in terms of a training and services center where assistance is available every day of the week. The broiler industry requires birds that are of commercial crosses selected for their ability to grow very fast and produce a good quality carcass in the shortest time frame. The small farmers purchase broiler stock, as the day-old chicks from commercial hatcheries and reared them up to six to eight weeks before slaughtered or sold as live chickens. The selling of live chickens through a network outlets system is becoming an industry that is growing at a steady pace, as household food security is becoming important to communities (Fourie, 2000). The price of feed is the single most expensive item on the list of expenses of a farmer because of their financial constraints. The small-scale and semicommercial broiler farmer is faced with the problem of buying small quantities of feed at an inflated price. The problem can be alleviated by groups of small farmers joining co-operative and buying feeds in bulk from suppliers and redistributing to small farmers. The community co-operative can once again play a major role in the distribution of small amounts of feed to its member. The biggest challenge is to provide training with a “hands on” approach. It will be ideal to have a training center where small farmers can be trained in all aspects of poultry production. The training facility will have to operate as a fully operational poultry unit with no risks to bio-security of a commercial enterprise. Training will have to be provided in aspects like hatchery, housing, broilers and record management depending on the farmer’s needs. There is also a need for the research on broiler performance under small-scale and semi commercial farming. Research in this sector of poultry production should look in appropriate feeds, feeding, technology, genotype and performance of genotypes under the system. Emphasis in this study will be on growth patterns and performance of the Ross hybrids as a modern broiler under small-scale and semi commercial management condition. Aspect of the environment such as age, type of feeds and feeding methods, housing, seasons, lighting and genotype will be taken into consideration. The result of the study will provide a realistic database for mathematical modeling of production response and guideline for management planning in small-scale and semi-commercial management condition. Also this result will be important to broiler breeders, to determine the suitability of the modern broiler to small-scale and semi commercial management conditions. The objective of the study was to evaluate the mathematical model that could describe the performance of broilers under the small-scale and semi-commercial management conditions.

The global marketplace, with its complexity, immediacy, and ubiquitous disruptions places almost impossible demands on its leaders and its leadership ranks. For many years, a top, perennial contender for the “what keeps CEOs up at night” list has been a severe lack in both the quantity and quality of effective leaders. The war for talent has been figuratively bloody and literally protracted. Leadership development and coaching modalities abound, but demand appears to be much greater than the supply of effective and measurable solutions. Nowhere does there appear to be a scalable approach to accelerate into this demand curve.

This descriptive phenomenological inquiry explores the lived experiences of 16 leaders who participated in an experimental Facilitated Peer-group Coaching experience (FPC). FPC is a coaching methodology where participants work on both their own leadership development and the development of their peers. Participants learn to coach and develop each other with the assistance of a trained facilitator. Subjects in this study responded to 20 face-to-face interview questions designed to identify their thoughts, perceptions, feelings and perspectives. The findings and conclusions of this study revealed five developmental fields that catalyze and empower leadership growth. These fields include creating community, self-exploration and illumination, the community mirror, leadership development, and organizational business results. Those fields comprise an ecosystem that presents opportunities for global organizations, coaches and coaching organizations, and academic scholarship.

Power law relationships are ubiquitous in ecology, and complex systems in general, and can be used as metrics to describe many aspects of ecosystem structure and function. While ecological interactions and processes predominantly occur at the individual level of biological organisation, currently, most ecological studies aim to estimate “typical” ecosystem behaviour over large spatial and temporal scales. This disconnect results in the under- appreciation of ecosystem dynamics that are potentially important for developing ecological theory and ecosystem modelling. The research presented herein aims to estimate within-ecosystem dynamics, as quantified by power law relationships, to test whether expected ecological dynamics can be captured effectively at smaller scales. I show that Taylor’s power law, a metric of aggregation, varies systematically, both spatially and temporally within the North Sea fish community, with the abiotic environment when populations were considered as cohorts of individual body sizes. By combining estimates of the power law distribution of body size in fish with stable isotopes that can be used to infer trophic interactions, I show that seasonal trends in fish movement patterns and the incorporation of pulsed phytoplankton production can be quantified in a highly dynamic estuarine environment. Estimates of the in situ community predator-prey mass ratio, which describes trophic behaviour, and the apparent trophic transfer efficiency are then derived and shown to exhibit strong seasonal variation, indicative of an estuarine food web that is temporally variable. Finally, I quantify the degree of individual specialisation, a mechanism by which intraspecific competition is modulated, in the diet of a commercially important but over-exploited fish species to inform conservation efforts. This work shows that ecological dynamics can be captured by a range of ecosystem metrics and that, therefore, small scale behaviours can be tested for empirically to direct ecosystem models and theory.

The evolution of hand-held devices and portable machines started the increase in demand for reliable, secure, and faster means of communication from wireless LAN infrastructures. This has lead to an enormous increase in the size of networks, which in turn has increased the cost and power consumption of access points and switches in the network infrastructure. While managing demand, networks become underutilized with less traffic demands and over utilized with more traffic demands. This research tends to discuss the best designs for maximum efficiency in terms of power and cost while retaining the best user experience. Designs were mainly evaluated based on the benefits of a centralized structure and a non-centralized structure. Furthermore, in order to understand the differences and make centralized structure more efficient in terms of power and cost, a new algorithm was designed with convex hull approach and was also implemented in the emulator kind of network testbed generating outstanding results and evaluations. The algorithm proposed in this thesis and the resulting design, if implemented in the future, could mean 60 percent additional savings in power consumption and costs.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Electrical Engineering and Computer Science.

Energy is a critical resource in all types of computing systems from servers, where energy costs dominate data centre expenses and carbon footprints, to embedded systems, where the system's battery life limits the device's functionality. In their efforts to reduce the energy use of these system's hardware manufacturers have implemented features which allow a reduced energy consumption under software control. This thesis shows that managing these settings is a more complex problem than previously considered. Where much (but not all) of the previous academic research investigates unrealistic scenarios, this thesis presents a solution to managing the power on varying hardware. Instead of making unrealistic assumptions, we extract a model from empirical data and characterise that model. Our models estimate the effect of different power management settings on the behaviour of the hardware platform, taking into account the workload, platform and environmental characteristics, but without any kind of a-priori knowledge of the specific workloads being run. These models encapsulate a system's knowledge of the platform. We also developed a \emph{generalised energy-delay} policy which allows us to quickly express the instantaneous importance of both performance and energy to the system. It allows us to select a power management strategy from a number of options. This thesis shows, by evaluation on a number of platforms, that our implementation, Koala, can accurately meet energy and performance goals. In some cases, our system saves 26\% of the system-level energy required for a task, while losing only 1\% performance. This is nearly 46\% of the dynamic energy. Taking advantage of all energy-saving opportunities requires detailed platform, workload and environmental information. Given this knowledge, we reach the exciting conclusion that near optimal power management is possible on real operating systems, with real platforms and real workloads.

This thesis investigates the development of a dispatch/pricing model to examine the effect of maintaining voltage stability margins on spot prices, and also presents models for voltage stability constrained reactive power planning. We develop an AC OPF primal problem incorporating both multiple generator contingency constraints and multiple voltage stability margin contingency constraints. Active and reactive power trade off functions for the generators and the opportunity cost of foregoing active power generation to provide increased reactive power are considered. The objective is to minimise costs while maintaining the capability to deal with pre-defined contingency events. The dual of the primal problem is analysed to determine generation, reserve and demand price equations, which are examined to establish the effects on active and reactive power spot prices of generator contingency constraints and voltage stability margin contingency constraints. We also develop a voltage stability constrained and contingency constrained reactive power planning model. This uses a non-linear mixed integer programming algorithm to efficiently formulate and solve the VAR planning problem. Next, a statistical approximation procedure simplifying the voltage stability constrained planning model is presented. An equation of the locus of the PoCs is developed using statistical regression methods and used to simplify the full MINLP model. Finally, a preventive/corrective control model is developed to guard against voltage instability while taking into account the load-shed dynamics.

Near-field wireless power transfer (WPT) technology facilitates the energy autonomy of heterogeneous systems, significantly augmenting complementary metal-oxide-semiconductor field-effect-transistor (CMOS) technology. In low-power wearable devices, existing power conditioning integrated circuits do not maximize the power factor (PF) for rectification and power conversion efficiency (PCE) due to multiple conversion. Additionally, there is no core power management for the entire power flow. The majority of the research focuses on active rectifiers, which reduce the turn-on voltage for rectification. Certain studies target the output voltage regulation via feedback to the transmitter or direct battery charging without power maximization. Firstly, this study investigates a high-power factor WPT front-end circuit that is namely the mono-periodic switching rectifier (MPSR) and implemented in a 0.18µm 1.8V/5V CMOS process. Integrated phase synchronizers are used to align the waveshape of a wirelessly-coupled sinusoidal voltage source in a receiving coil to the corresponding conducting current. Using this approach, the PF can be increased from roughly 0.6 to unity without requiring any wireless or wired feedback to the transmitter. The proposed MPSR can also provide AC-DC rectification, and step up and down the sinusoidal voltage source's peak amplitude using a pulse-width modulator. Measured voltage conversion ratios range between 0.73X and 2X, and the PF can be boosted up to unity. Secondly, the wireless power system-on-chip (WPower-SoC) is proposed and implemented in a 0.18µm 1.8V/3.3V CMOS process. The WPower-SoC integrating power management can provide rectification, output voltage regulation, and battery charging. Additionally, the implementation of feedforward envelope detection (FED) can reduce the variation in a wireless power link and improve load transient responses. Simulated results demonstrate that 5% of the output voltage regulation is improved when an output load changes. Moreover, the FED reduces approximately 40% of the transient response time. Overshoot and undershoot voltages are decreased by 23% and 26.5%, respectively. The measured output voltage regulates at 3.42V and can supply output power up to 342mW. A temperature sensor as part of the power management core remains active when the WPT receivers enter sleep mode to prolong the battery usage time. In the final part of this study, a nano-watt high-accuracy temperature sensing core is implemented in a 0.18µm 1.8V/3.3V CMOS process that can self-compensate the temperature shift without the need for additional compensating techniques that consume extra power.

Business Process Management (BPM) is management technique which seeks to constantly innovate business processes to improve customer service while reducing costs. It is introduced into organisations alongside software called Business Process Management Systems (BPMS). BPM monitors and measures processes to find opportunities for improvement of these processes. The system enables the capture of business processes by rendering them as process models; these are used to link to information, to deliver this information to staff, to automate tasks where possible, and to turn tasks into work flows which appear on manager's and staff's desktops as 'to do' lists. This thesis presents a case study of the implementation of BPM and a BPMS into a large insurance company in New Zealand. The initial research objective was to identify critical success factors (CSF's) for BPM and use Action Research (AR) in conjunction with ethnography to track the presence of the CSF's and to develop strategies to compensate for any lack in CSF's. The pilot BPM project in the organisation was successful, although it did require radical change in the business unit. However, the BPM project failed to embed BPM techniques in the rest of the organisation and was ultimately cancelled. At this point the research objective shifted to understanding the forms of power and resistance that had emerged over the course of the implementation. To understand these, a theoretical framework was developed with Rescherian process philosophy as its ontological foundation and Foucauldian concepts of power/knowledge as its epistemological foundation. The axiological foundation is that the self-formed in this processual reality is formed in the grid of power relations in which it is situated. The key findings of the research are that the concepts of culture and values are not sufficient to explain the forms of resistance that emerge when BPM and its associated Information Systems (IS) are implemented. Instead, a processual analysis using Foucauldian concepts of power and resistance proved to be a richer and more explanatory framework. This analysis found that the insurance industry is a technique of bio-power. This form of power relies on techniques of pastoral power to produce ethical, self-regulating, risk-managing subjects, both consumers and suppliers of risk mitigation products. These subjects are seen as self-governing, guided by conscience, and capable of unique responses to situations so that the manager is primarily a coach. BPM, on the other hand, is a technique of disciplinary power which produces disciplined, docile, utile subjects. These subjects are seen as requiring the three elements of hierarchical observation, normalising judgment and examination to ensure productivity and quality so that the manager is primarily an enforcer. These two forms of managerial subjectivity are opposed so that the introduction of the form of disciplinary power relations required by BPM generated resistance from the existing predominant forms of pastoral power. Ultimately this predominant form of power successfully resisted the introduction of disciplinary power. I suggest that this framework may prove useful for predicting resistance in future BPM projects.

This dissertation examines the politics of knowledge in collaborative watershed governance institutions of the Klamath River Basin of Northern California and Southern Oregon. The waters of the Klamath are shared between farmers, fisherfolk, indigenous communities, hydro-electric facilities and one of the most biologically diverse eco-regions in the United States. Since 1986, the watershed has provided the primary spatial unit for resolving resource conflict by coordinating agency and citizen science, guiding integrated resource management and cultivating a shared sense of place and belonging among Klamath watershed inhabitants. For nearly three decades, the Klamath Basin has served as a laboratory for experiments in “watershed democracy”- a form of hydrologically-grounded political association that attempts to facilitate the direct participation of all watershed inhabitants in knowledge production, deliberation and collective action at the watershed scale. Through the idiom of watershed democracy, I connect empirical research on the outcomes of nearly three decades of community-based natural resource management in the Klamath with theoretical debates waged over the last century and a half regarding the question of scale in environmental science, democratic governance and natural resource management.

In this dissertation, I analyze the watershed as a scale of knowledge production, a site of democratic deliberation and a unit of environmental governance. I investigate whether the watershed is the most appropriate socio- spatial unit for representing people and place in the Klamath, paying particular attention to the impact of collaborative watershed governance arenas on the ability of Karuk Tribal members to participate in knowledge-production and decision- making for natural resource management in their ancestral territory in northern California.

Through participatory research with the Karuk Tribe’s Department of Natural Resources, participant observation, document analysis and interviews with Federal, State, Tribal and local agency scientists and representatives, I follow knowledge and policy-making processes across a diverse range of institutions engaged in Klamath watershed governance. Combining participatory research and participant observation with theoretical insights from political ecology, science and technology studies (STS) and indigenous studies scholarship, I evaluate the processes and outcomes of collaborative watershed-based governance according to its impacts on local watershed ecosystems and communities. Drawing on the theoretical framework of “co-production”, I analyze the mutually constitutive relations between watershed science, watershed governance institutions, the materialities of Klamath watershed-ecosystems and the distributions of resource benefits and burdens in Klamath communities. I follow Klamath experiments in watershed democracy negotiate the basic terms of political life such as property, territory, sovereignty and the public good, as well as the material conditions and flows of watershed resources and the patterns of access to, ownership in and distribution of these resources.

While the Klamath experiements in collaborative environmental governance at the watershed scale have opened up oppportunities for Karuk representatives to participate in knowledge production and decision-making, the watershed scale has itself constrained the focus of integrated resource management, limiting the kinds of knowledge that can pattern as reliable and the types of restoration and management projects that can issue from Klamath collaborative governance forums. I demonstrate how Karuk representatives have both leveraged and critiqued the watershed as a way of conceptualizing Klamath watershed-ecological processes and as a socio-spatial unit for approaching ecological restoration and cultural revitalization in their ancestral territory. Watershed science and watershed governance forums were sometimes leveraged by Karuk representatives to substantiate Karuk sovereignty and resource rights and at times rejected for not being able to convey distinct Karuk epistemologies, ontologies and cosmologies. I demonstrate how collaborative watershed management forums have struggled to render different types of indigenous, local and scientific knowledge commensurable and have instead provoked debates about how to produce knowledge about nature in ways that are appropriate for the local community and its ecosystems.

I draw attention to the cultural politics of scale to critique watershed-centric management and search for alternative ways of representing the multiple scales through which Klamath inhabitants understand and value nature. I compare watershed-based governance with two other emerging scales of democratic resource governance- firesheds and foodsheds- in their abilities to bring together diverse forms of environmental knowledge around multiple nested scales of social and ecological processes. Firesheds are emerging areas of community-based fire management patterned according to the way fire burns across the western Klamath landscape. Foodsheds are another emerging form of community-based resource governance taking shape in the Klamath around the spatial and temporal characteristics of food resources and their associated management practices in forest ecosystems. Comparing watersheds, firesheds and foodsheds opens up the question of scale in collaborative environmental governance by highlighting tensions among different ways of producing knowledge, managing resources and acting collectively at different bioregional scales in the Klamath.

Against watershed-centric approaches to ecological democracy, I argue for deliberative multi-scalar approaches to implementing collaborative environmental governance, cultural revitalization and watershed-ecosystem restoration in the Klamath. Multi-scalar perspectives can accommodate multiple ways of making knowledge while avoiding homogenizing diverse situated perspectives into a single way of seeing Klamath eco-cultural landscapes. I argue for “democratizing scale” in order to define an appropriate scalar framework for producing knowledge, representing human values and making decisions about the management of natural resources. Collaborative environmental governance requires an accompanying democratization of scale to accommodate the myriad ways of knowing nature and making a living in Klamath watershed-ecosystems. Scalar formations that are produced through deliberative democratic processes can provide more inclusive grounds than watersheds for democratic environmental governance and multispecies world-making.

Disruption Tolerant Networks (DTNs) are mobile wireless networks that are designed to work in highly-challenged environments where the density of nodes is insufficient to support direct end-to-end communication. Recent efforts in DTNs have shown that mobility provides a powerful means for delivering messages in such highly-challenging environments. Unfortunately, many mobility scenarios depend on untethered devices with limited energy supplies. Without careful management, depleted energy supplies will degrade network connectivity and counteract the robustness gained by mobility. A primary concern is the energy consumed by wireless communications because the wireless interface is one of the largest energy consumers in mobile devices whether they are actively communicating or just listening. However, mobile devices exhibit a tension between saving energy and providing connectivity through opportunistic encounters. In order to pass messages, the device must discover communication opportunities with other nodes. At the same time, energy can be conserved by ``sleeping,' i.e., turning off or disabling the wireless interfaces. However, if the wireless interface is asleep, the node cannot discover other nodes for communication. Thus, power management in DTNs must balance the discovery of other nodes while aggressively sleeping the radio during the remaining periods. In this thesis, we first develop a power management framework for a single radio architecture that allows a node to save energy while discovering communication opportunities. The framework is tailored to the available knowledge about network connectivity over time. Further, the framework supports explicit trade-offs between energy savings and connectivity, so network operators can choose, for example, to conserve energy at the cost of reduced message delivery performance. We next examine the possibility of using a hierarchical radio architecture in which nodes are equipped with two complementary radios: a long-range, high-power radio and a short-range, low-power radio. In this architecture, energy can be conserved by using the low-power radio to discover communication opportunities with other nodes and waking the high-power radio to undertake the data transmission. However, the short range of the low-power radio may result in missing communication opportunities. Thus, we develop a generalized power management framework in which both radios support the discovery. In addition, we incorporate the knowledge of traffic load and network dynamics and devise approximation algorithms to control the sleep/wake-up cycling of the radios to provide maximum energy conservation while discovering enough communication opportunities to handle the expected traffic load. Finally, we investigate the Message Ferrying (MF) routing paradigm as a means to save energy while trading off data delivery delay. In MF, special nodes called ferries move around the deployment area to deliver messages for nodes. While this routing paradigm has been developed mainly to deliver messages in partitioned networks, here we explore its use in a connected MANET. The reliance on the movement of the ferries to deliver messages increases the delivery delay if a network is not partitioned. However, delegating message delivery to the ferries provides the opportunity for nodes to save energy by aggressively putting their radios to sleep when ferries are far away. To exploit this feature, we present a power management framework, in which nodes switch their power management modes based on the knowledge of ferry location.

Recent increase in performance of High Performance Computing (HPC) systems has been followed by even higher increase in power consumption. Power draw of modern supercomputers leads to very high operating costs and reliability concerns. Furthermore, it has negative consequences on the environment. Accordingly, over the last decade there have been many works dealing with power/energy management in HPC systems. Since CPUs accounts for a high portion of the total system power consumption, our work aims at CPU power reduction. Dynamic Voltage Frequency Scaling (DVFS) is a widely used technique for CPU power management. Running an application at lower frequency/voltage reduces its power consumption. However, frequency scaling should be used carefully since it has negative effects on the application performance. We argue that the job scheduler level presents a good place for power management in an HPC center having in mind that a parallel job scheduler has a global overview of the entire system. In this thesis we propose power-aware parallel job scheduling policies where the scheduler determines the job CPU frequency, besides the job execution order. Based on the goal, the proposed policies can be classified into two groups: energy saving and power budgeting policies. The energy saving policies aim to reduce CPU energy consumption with a minimal job performance penalty. The first of the energy saving policies assigns the job frequency based on system utilization while the other makes job performance predictions. While for less loaded workloads these policies achieve energy savings, highly loaded workloads suffer from a substantial performance degradation because of higher job wait times due to an increase in load caused by longer job run times. Our results show higher potential of the DVFS technique when applied for power budgeting. The second group of policies are policies for power constrained systems. In contrast to the systems without a power limitation, in the case of a given power budget the DVFS technique even improves overall job performance reducing the average job wait time. This comes from a lower job power consumption that allows more jobs to run simultaneously. The first proposed policy from this group assigns CPU frequency using the job predicted performance and current power draw of already running jobs. The other power budgeting policy is based on an optimization problem which solution determines the job execution order, as well as power distribution among jobs selected for execution. This policy fully exploits available power and leads to further performance improvements. The last contribution of the thesis is an analysis of the DVFS technique potential for energyperformance trade-off in current and future HPC systems. Ongoing changes in technology decrease the DVFS applicability for energy savings but the technique still reduces power consumption making it useful for power constrained systems. In order to analyze DVFS potential, a model of frequency scaling impact on MPI application execution time has been proposed and validated against measurements on a large-scale system. This parametric analysis showed for which application/platform characteristic, frequency scaling leads to energy savings.
El aumento de rendimiento que han experimentado los sistemas de altas prestaciones ha venido acompañado de un aumento aún mayor en el consumo de energía. El consumo de los supercomputadores actuales implica unos costes muy altos de funcionamiento. Estos costes no tienen simplemente implicaciones a nivel económico sino también implicaciones en el medio ambiente. Dado la importancia del problema, en los últimos tiempos se han realizado importantes esfuerzos de investigación para atacar el problema de la gestión eficiente de la energía que consumen los sistemas de supercomputación. Dado que la CPU supone un alto porcentaje del consumo total de un sistema, nuestro trabajo se centra en la reducción y gestión eficiente de la energía consumida por la CPU. En concreto, esta tesis se centra en la viabilidad de realizar esta gestión mediante la técnica de Dynamic Voltage Frequency Scalingi (DVFS), una técnica ampliamente utilizada con el objetivo de reducir el consumo energético de la CPU. Sin embargo, esta técnica puede implicar una reducción en el rendimiento de las aplicaciones que se ejecutan, ya que implica una reducción de la frecuencia. Si tenemos en cuenta que el contexto de esta tesis son sistemas de alta prestaciones, minimizar el impacto en la pérdida de rendimiento será uno de nuestros objetivos. Sin embargo, en nuestro contexto, el rendimiento de un trabajo viene determinado por dos factores, tiempo de ejecución y tiempo de espera, por lo que habrá que considerar los dos componentes. Los sistemas de supercomputación suelen estar gestionados por sistemas de colas. Los trabajos, dependiendo de la política que se aplique y el estado del sistema, deberán esperar más o menos tiempo antes de ser ejecutado. Dado las características del sistema objetivo de esta tesis, nosotros consideramos que el Planificador de trabajo (o Job Scheduler), es el mejor componente del sistema para incluir la gestión de la energía ya que es el único punto donde se tiene una visión global de todo el sistema. En este trabajo de tesis proponemos un conjunto de políticas de planificación que considerarán el consumo energético como un recurso más. Estas políticas decidirán que trabajo ejecutar, el número de cpus asignadas y la lista de cpus (y nodos) sino también la frecuencia a la que estas cpus se ejecutarán. Estas políticas estarán orientadas a dos objetivos: reducir la energía total consumida por un conjunto de trabajos y controlar en consumo puntual de un conjunto puntual para evitar saturaciones del sistema en aquellos centros que puedan tener una capacidad limitada (permanente o puntual). El primer grupo de políticas intentará reducir el consumo total minimizando el impacto en el rendimiento. En este grupo encontramos una primera política que asigna la frecuencia de las cpus en función de la utilización del sistema y una segunda que calcula una estimación de la penalización que sufrirá el trabajo que va a empezar para decidir si reducir o no la frecuencia. Estas políticas han mostrado unos resultados aceptables con sistemas poco cargados, pero han mostrado unas pérdidas de rendimiento significativas cuando el sistema está muy cargado. Estas pérdidas de rendimiento no han sido a nivel de incremento significativo del tiempo de ejecución de los trabajos, pero sí de las métricas de rendimiento que incluyen el tiempo de espera de los trabajos (habituales en este contexto). El segundo grupo de políticas, orientadas a sistemas con limitaciones en cuanto a la potencia que pueden consumir, han mostrado un gran potencial utilizando DVFS como mecanismo de gestión. En este caso, comparado con un sistema que no incluya esta gestión, han demostrado mejoras en el rendimiento ya que permiten ejecutar más trabajos de forma simultánea, reduciendo significativamente el tiempo de espera de los trabajos. En este segundo grupo proponemos una política basada en el rendimiento del trabajo que se va a ejecutar y una segunda que considera la asignación de todos los recursos como un problema de optimización lineal. Esta última política es la contribución más importante de la tesis ya que demuestra un buen comportamiento en todos los casos evaluados. La última contribución de la tesis es un estudio del potencial de DVFS como técnica de gestión de la energía en un futuro próximo, en función de un estudio de las características de las aplicaciones, de la reducción de DVFS en el consumo de la CPU y del peso de la CPU dentro de todo el sistema. Este estudio indica que la capacidad de DVFS de ahorrar energía será limitado pero sigue mostrando un gran potencial de cara al control del consumo energético.

Monitoring parameters characterizing water quality, such as temperature, pH and concentrations of heavy metals in natural waters, is often followed by transmitting the data to remote receivers using telemetry systems. Such systems are commonly powered by batteries, which can be inconvenient at times because batteries have a limited lifetime and have to be recharged or replaced periodically to ensure that sufficient energy is available to power the electronics. To avoid these inconveniences, we have designed and tested a self-renewable power source, a microbial fuel cell, which has the potential to eliminate the need for batteries to power electrochemical sensors used to monitor water quality and small telemetry systems used to transmit the data acquired by these sensors. To demonstrate the utility of the microbial fuel cell, we have combined it with low-power, high-efficiency electronic circuitry providing a stable power source for wireless data transmission. To generate enough power for the telemetry system, energy produced by the microbial fuel cell was stored in an ultracapacitor and used in short bursts when needed. Since powering commercial components of electronic circuits requires 5 Volts, and our cell was able to deliver a maximum of 2.1 V, we used a DC-DC converter to increase the potential. The DC-DC converter powered the transmitter, which gathered the data from the sensor and transmitted them to a receiver. To demonstrate the utility of the system, we initially measured temporal variations in temperature followed by the implementation of a chemical sensor to measure copper and lead concentrations in water; this data was then wirelessly transmitted to a remote receiver.

One of the unique characteristics of wireless sensor networks (WSNs) is that sensor nodes have very constrained resources. Typical sensor nodes have lower computing power, communication bandwidth, and smaller memory than other wireless devices, and operate on limited capacity batteries. Hence power efficiency is very important in WSNs because power failure of some sensor nodes may lead to total network failure. In many cases the WSNs have to operate in harsh environments without human intervention for expended period time. Thus, much research on reducing or minimizing the power consumption, and thereby increasing the network lifetime, has been performed at each layer of the network layers. In this dissertation we approach three important issues related power management in WSNs: routing, time synchronization, and medium access control (MAC). We first discuss the effect of selecting routing protocols on the lifetime of the WSNs. The maximum and minimum bounds of the lifetime with respect to the routing protocols are derived. The routing protocols corresponding to the bounds are also presented. The simulation results show that the choice of the routing protocol has very little impact on the lifetime of the network and that simple routing protocols such as shortest path routing perform very close to the the maximum bound of the lifetime of the network. Next, we propose a simple and accurate time synchronization protocol that can be used a a fundamental component of other synchronization-based protocols in WSNs. Analytical bounds on the synchronization errors of proposed protocol are discussed. The implementation results on Mica2 and Telos motes show that proposed time synchronization protocol outperforms existing ones in terms of the precision and required resources. Finally, we model the power consumption of WSN MAC protocols. We derive analytically the power consumption of well known MAC protocols for WSNs, and analyze and compare their performance. We validate the models by measuring the power consumption on Mica 2 motes and comparing those measured power consumption with the analytical results.

Coordinated Power Management in Heterogeneous Processors Indrani Paul 164 pages Directed by Dr. Sudhakar Yalamanchili With the end of Dennard scaling, the scaling of device feature size by itself no longer guarantees sustaining the performance improvement predicted by Moore’s Law. As industry moves to increasingly small feature sizes, performance scaling will become dominated by the physics of the computing environment and in particular by the transient behavior of interactions between power delivery, power management and thermal fields. Consequently, performance scaling must be improved by managing interactions between physical properties, which we refer to as processor physics, and system level performance metrics, thereby improving the overall efficiency of the system. The industry shift towards heterogeneous computing is in large part motivated by energy efficiency. While such tightly coupled systems benefit from reduced latency and improved performance, they also give rise to new management challenges due to phenomena such as physical asymmetry in thermal and power signatures between the diverse elements and functional asymmetry in performance. Power-performance tradeoffs in heterogeneous processors are determined by coupled behaviors between major components due to the i) on-die integration, ii) programming model and the iii) processor physics. Towards this end, this thesis demonstrates the needs for coordinated management of functional and physical resources of a heterogeneous system across all major compute and memory elements. It shows that the interactions among performance, power delivery and different types of coupling phenomena are not an artifact of an architecture instance, but is fundamental to the operation of many core and heterogeneous architectures. Managing such coupling effects is a central focus of this dissertation. This awareness has the potential to exert significant influence over the design of future power and performance management algorithms. The high-level contributions of this thesis are i) in-depth examination of characteristics and performance demands of emerging applications using hardware measurements and analysis from state-of-the-art heterogeneous processors and high-performance GPUs, ii) analysis of the effects of processor physics such as power and thermals on system level performance, iii) identification of a key set of run-time metrics that can be used to manage these effects, and iv) development and detailed evaluation of online coordinated power management techniques to optimize system level global metrics in heterogeneous CPU-GPU-memory processors.

Les Piles à Combustible Microbiennes (PCMs) mettent en oeuvre le métabolisme de micro-organismes et utilisent de la matière organique pour générer de l'énergie électrique. Les applications potentielles incluent le traitement d'eau usée autonome en énergie, les bio-batteries, et le grappillage d'énergie ambiante. Les PCMs sont des équipements basse-tension et basse-puissance dont le comportement est influencé par la vitesse à laquelle l'énergie électrique est récupérée. Dans cette thèse, on étudie des méthodes pour récupérer l'énergie électrique de façon efficace. La tension à laquelle l'énergie est récupérée des PCMs influence leur fonctionnement et leurs performances électriques. La puissance délivrée est maximum pour une tension spécifique (environ 1/3 de la tension en circuit-ouvert). Les PCMs ont été testées à ce point en utilisant une charge contrôlée automatiquement qui inclut un algorithme de recherche de puissance maximale. Un tel outil a été utilisé pour évaluer la puissance maximum, la vitesse de consommation du combustible, le rendement Coulombic et le rendement de conversion de 10 PCMs à chambre unique de 1.3 L, construites de façon similaire. Bien que d'autres choix structurels et opératoires peuvent permettre d'améliorer ces performances, ces résultats ont étudié pour la première fois les performances des PCMs en condition de production d'énergie de point de puissance maximal et les PCMs ont été testées avec des conditions de récupération d'énergie réalistes. Récupérer un maximum d'énergie des PCMs est la ligne directrice de ce rapport. Cela est rendu possible par des circuits dédiés de gestion de l'énergie qui embarquent un contrôle contre-réactif pour réguler la tension des PCMs à une valeur de référence qui est égale à une fraction de leur tension en circuit ouvert. Deux scénarios typiques sont développés dans la suite. Une application critique des PCMs concerne le grappillage autonome de petites énergies, pour alimenter des équipements électroniques basse-puissance (e.g. capteurs sans fil). Dans ce cas, les contraintes basse-puissance et basse-tension imposées par les PCMs nécessitent des fonctionnalités de démarrage autonomes. L'oscillateur d'Armstrong, composé d'inductances couplées à fort rapport d'enroulement et d'un interrupteur normalement-fermé permet d'élever des tensions de façon autonome à partir de sources basse-tension continues comme les PCMs. Ce circuit a été associé à des convertisseurs d'électronique de puissance AC/DC et DC/DC pour réaliser respectivement un élévateur-de-tension et une unité de gestion de l'énergie (UGE) auto-démarrante basée sur une architecture flyback. La première est adaptée pour les puissances inférieures à 1 mW, alors que la seconde peut être dimensionnée pour des niveaux de puissance de quelques mW et permet de mettre en oeuvre une commande qui recherche le point de puissance maximal du générateur. Une seconde application d'intérêt concerne le cas où de l'énergie est récupérée depuis plusieurs PCMs. L'association série peut être utilisée pour élever la tension de sortie mais elle peut avoir des conséquences négatives en terme de performances à cause des non-uniformités entre cellules. Cet aspect peut être résolu avec des circuits d'équilibrage de tension. Trois de ces circuits ont été analysés et évalués. Le circuit " complete disconnection " déconnecte une cellule défectueuse de l'association pour s'assurer qu'elle ne diminue pas le rendement global. Le circuit " switched-capacitor " transfère de l'énergie depuis les MFCs fortes vers les faibles pour équilibrer les tensions de toutes les cellules de l'association. Le circuit " switched-MFCs " connecte les PCMs en parallèle et en série de façon alternée. Chacune des trois méthodes peut être mise en oeuvre à bas prix et à haut rendement, la plus efficace étant la " switched-capacitor " qui permet de récupérer plus de 85 % de la puissance maximum idéale d'une association très largement non uniforme

Algorithms are essential for solving many important problems, including in power systems control, where they can allow the connection of new demand and generation whilst deferring or avoiding the need for network reinforcement. However, in many problem domains no algorithm always delivers the best performance for all problems, so better performance can be achieved by using algorithm selection to select the best algorithms for each problem. This work applies algorithm selection to power systems control, with power flow management using generator curtailment examined as a representative power systems control task. The first half of this work focuses on whether potential performance benefits are available if algorithms are selected optimally for each network state. Five power flow management algorithms are implemented, which use diverse approaches such as optimal power flow, constraint satisfaction, power flow sensitivity factors, and linear programming. Four case study power systems – an 11 kV radial distribution system, a 33 kV meshed distribution system, the IEEE 14-bus system, and the IEEE 57-bus system – are used to test the algorithms over a extensive range of network states. None of the algorithms give the most effective performance for every state, in terms of minimising either the number or energy of overloads, whilst minimising curtailment. By optimally selecting algorithms for each state there are potential performance benefits for three of the four case study systems In the second half of this work, algorithm selection systems (selectors) are created in order to exploit and deliver the observed potential performance benefits of per-state algorithm selection. Existing techniques for creating algorithm selectors are adapted and extended for the power flow management application, which includes the development of a training method that allows selectors to consider two objectives simultaneously. The selectors created take measurements of network state as input and use machine learning models to make algorithm selection decisions. The models either directly predict which algorithm is likely to be the most effective, or predict the performance of each algorithm, with the algorithm with the most effective predicted performance then being selected. Both of these approaches are shown to be effective in creating algorithm selectors for power flow management that deliver statistically significant performance benefits. In some cases, the selectors are able to match the optimum performance that could be achieved by selecting between the algorithms.

L'objectif de ce travail consiste à appliquer des techniques de contrôle optimal pour améliorer la performance des lois de gestion d'énergie. Plus précisément, les techniques étudiées sont les solutions de viscosité de l'équation de Hamilton-Jacobi, des méthodes level-set pour l'étude de l'atteignabilité, la programmation dynamique stochastique, la programmation dynamique stochastique duale et les contraintes en probabilité. En premier lieu, ce document débute avec la présentation des outils techniques et modèles nécessaires à l'étude de l'optimisation des lois de gestion d'énergie au sein des véhicules hybrides. En deuxième lieu, nous regardons la synthèse des lois de gestion d'énergie en prenant compte des incertitudes dans le profil de vitesse du véhicule. Dans un premier moment, cette étude porte sur l'utilisation de la programmation dynamique stochastique. Dans un second moment, la programmation dynamique stochastique duale est analysée. Ensuite, nous introduisons une formulation du problème de contrôle optimal avec des contraintes en probabilités, visant la synthèse de lois plus flexibles. En troisième lieu, des résultats théoriques sur l'étude de l'atteignabilité des systèmes hybrides sont démontrés. L'ensemble des états atteignables est caractérisé par une fonction valeur. Nous démontrons ensuite que cette fonction valeur est l'unique solution d'un système d'inégalités quasi-variationnelles dans le sens de la viscosité. Aussi, nous montrons la convergence d'une classe de schémas numériques permettant le calcul de cette fonction valeur. Visant à approfondir l'étude sur l'atteignabilité, nous nous intéressons à une formulation de la dynamique hybride en temps discret, ce qui amène à l'utilisation d'un algorithme directement basé sur la programmation dynamique pour caractériser la fonction valeur
The purpose of the this work is to apply optimal control techniques to enhance the performance of the power management of hybrid vehicles. More precisely, the techniques concerned are viscosity solutions of Hamilton-Jacobi equations, level set methods in reachability analysis, stochastic dynamic programming, stochastic dual dynamic programming and chance constrained optimal control. This document starts by presenting the necessary technical background and models for the study of optimal power management of hybrid vehicles. The synthesis of efficient power management strategies for hybrid vehicles accounting for uncertainty in the vehicle speed is studied next. This is done via a stochastic dynamic algorithm, at a first time, and then by a stochastic dual dynamic programming algorithm. In addition, we introduce a chance constrained optimal control problem that can be used to synthesize more flexible optimal control strategies. We detail a dynamic programming principle in a form that can be readily used for the numerical synthesis of optimal feedback using a dynamic programming algorithm. Later, theoretical results regarding the reachability analysis of hybrid systems are obtained. The reachability set of a continuous-time hybrid system is characterized by a value function via a level set approach. Furthermore, we show that the value function of a hybrid optimal control problem is the unique solution of a system of quasi-variational inequalities in the viscosity sense. Then, we prove the convergence of a class of numerical schemes for the computation of the value function. As a further step in the reachability analysis, we study of the discrete-time dynamical system and the discrete-time optimal control problem for the reachability analysis of hybrid systems. Here, the focus is on a discrete-time modeling of the hybrid system, which leads to dynamic programming principle, which can be used to characterize the value function. Lastly, we describe the construction of a stochastic model of the speed profile for electric vehicles

Répondre aux exigences de la conception de puces basse consommation constitue un véritable défi pour l’industrie des semi-conducteurs. Au cours de ces dernières années, de nouvelles méthodologies ont été développées pour aider les ingénieurs à traiter la complexité croissante des puces. L’une de ces méthodologies traite l'unification des descriptions dites power-intent dans la norme IEEE-1801 en définissant un langage standard structuré pour annoter le power-intent dans la description des circuits. Tout en permettant de nombreuses améliorations lors de la conception, la vérification et la mise en œuvre de circuits à faible consommation d'énergie, la norme amène également de nouveaux défis, en particulier son intégration dans les flots de conception existants. Nous présentons l'évolution d'un flot de conception traditionnel vers un flot de conception intégrant des stratégies pour la basse consommation et exploitant d'une synthèse à l’état de l’art. Dans cette thèse, nous soulignons les raisons et les choix qui ont donné forme au flot de conception actuel, et qui nous amènent aux défis rencontrés aujourd'hui.Cette thèse propose deux méthodologies intégrant la gestion du power-intent dans les flots existants pour faire face aux problèmes rencontrés dans l’industrie. Plus spécifiquement, il aborde le domaine de l'optimisation au niveau RTL au travers de cette thèse CIFRE (partenariat académique – industriel). Tout d'abord, nous présentons une méthodologie de vérification de la cohérence entre une description UPF (IEEE-1801) et les langages de description matérielle (HDL). Cette méthodologie a été mise en œuvre et validée par un outil, spécifiquement développé, qui nous a servi de preuve de concept. Enfin, nous avons étendu nos recherches en proposant une méthode automatisée préservant la cohérence du power-intent entre une description UPF et RTL lors de la modification du design. Nous avons présenté et modélisé les principes théoriques d’une optimisation RTL et ses effets de bord dans les descriptions de power-intent. Cette méthodologie est accompagnée d'une pléthore de cas d’usage décrivant les étapes pour préserver chaque spécification du power-intent
Meeting the requirements of low-power design is a real challenge in the semiconductor industry. In the past few years, new methodologies have been introduced to help engineers dealing with the growing complexity of chip design. One of such methodologies is the unification of power-intent descriptions into the IEEE-1801 standard, defining a structured standard language to annotate power-intent to a design. While enabling many improvements in low-power design, verification and implementation, the standard also introduces new challenges, in particular its integration into existing design flows. We present the evolution from a traditional design flow to a power-aware design flow, accompanied by a state-of-art low-power design synthesis. In this PhD work, we highlight the reasons and choices that shaped the current design flow, contributing to the challenges seen today.This thesis proposes two methodologies to cope with the issues commonly faced by the industry while integrating power-intent management into existing flows. More specifically, it addresses the field of RTL design optimizations, due to the industrial context of this CIFRE PhD (academical–industrial partnership). First, we present a tool agnostic methodology highly correlating UPF (IEEE-1801) and Hardware Description Languages (HDL) in order to track power-intent inconsistencies due to modifications in either of the descriptions. The consistency check methodology is validated by the implementation of a proof-of-concept tool. Finally, we extend the research by proposing an automation methodology preserving a consistent power-intent between UPF and RTL when modifying the design. We model and present the theoretical principles of RTL optimizations and their effects in the power-intent descriptions. This methodology is accompanied by a plethora of small, but comprehensive, use cases, depicting the steps to preserve each of the main power-intent specifications

Unmanned Air Vehicles (UAVs) are becoming more widely used in both military and civilian applications. Some of the largest UAVs have power systems equivalent to that of a military strike jet making power management an important aspect of their design. As they have developed, the amount of power needed for loads has increased. This has placed increase strain on the on-board generators and a need for higher reliability. In normal operation these generators are sized to be able to power all on-board systems with out overheating. Under abnormal operating conditions these generators may start to overheat, causing the loss of the generator's power output. The research presented here aims to answer two main questions: 1) Is it possible to predict when an overheat fault will occur based on the expected power usage defined by mission profiles? 2) Can an overheat fault be prevented while still allowing power to be distributed to necessary loads to allow mission completion? This is achieved by a load management algorithm, which adjusts the load profile for a mission, by either displacing the load to spare generators, or resting the generator to cool it down. The result is that for non-catastrophic faults the faulty generator does not need to be fully shut down and missions can continue rather than having to be aborted. This thesis presents the development of the load management system including the algorithm, prediction method and the models used for prediction. Ultimately, the algorithms developed are tested on a generator test rig. The main contribution of this work is the design of a prognostic load management algorithm. Secondary contributions are the use of a lumped parameter thermal model within a condition monitoring application, and the creation of a system identification model to describe the thermal dynamics of a generator.

The main target of this thesis is to summarize and explain the specifics of power markets and test application of models, which might be used especially in risk management area. Thesis starts with definition of market subjects, typology of traded contracts and description of market development with focus on Czech Republic. Thesis continues with development of theoretical concepts of short term/spot electricity markets and potential link between spot and forward electricity markets. After deriving of those microeconomic fundamental models we continue with stochastic models (Jump Diffusion Mean Reverting process and Extreme Value Theory) in order to depict patterns of spot and forward power contracts price volatility. Last chapter deals with credit risk specifics of power trading and develops model (using concept known as Credit Value Adjustment) to compare economic efficiency of OTC and exchange power trading. Developed and described models are tested on selected power markets, again with focus on Czech power market data set.

This thesis presents methods for voltage management in distribution systems with high photovoltaic (PV) power production. The high PV penetration leads to both new challenges such as voltage profile violation and reverse power flow, and also new opportunities. Traditionally, the voltage control in the distribution network is achieved by common devices in the networks such as capacitor banks, static synchronous compensators (STATCOMs) and on-load tap changers (OLTCs). This thesis has considered existing reactive power capable solar PV inverters together with STATCOMs to provide voltage support for the distribution network. In this thesis, two effective coordination methods using the STATCOM and PV inverters are developed in order to study their interaction and how they together can stabilize the voltage level. Data from existing low-voltage (LV) and medium-voltage (MV) networks are used for a case study. The first control method is developed for LV network’s voltage control by means of PV inverter and STATCOM. The second control method is developed for both LV and MV networks’ voltage control, where reactive power control in PV inverters and STATCOMs are used in the LV network and only STATCOMs in the MV network. The control methods follow a hierarchical structure where reactive power compensation using PV inverters are prioritized. The STATCOMs, first in the LV and thereafter in the MV network in the second control method, are used only when the PV inverters are not able to provide or consume enough reactive power. This is beneficial due to the significant reduction in numbers of STATCOMs and their operation. The simulation results indicate that the proposed method is able to control both the over- and undervoltage situations for the test distribution networks. It is also shown that reactive power supply at night by the PV inverters can be an important resource for effective voltage regulation by using the proposed coordinated voltage control method.