Dissertations / Theses on the topic 'Generator approach'

Production and consumption of electricity have grown enormously during the last century. No mater what the primary source of energy is, almost all generation of electricity comes from conversion of a rotational movement in a generator. The aim of this thesis is to see how high voltage technology influence production and storage of electricity. Power flow in the generators used to convert mechanical movement to electric energy is analyzed using Poynting‘s vector. The impact of new generator technology for efficient extraction of hydroelectric power is shown. Simulation of a large permanent magnet turbo generator is presented. A flywheel storage system for electric vehicles utilizing high voltage technology is also presented. In pulsed power applications, a cheap method for intermediate storage of energy during milliseconds, which enables an inductive primary storage is presented and experimentally tested.

We explore the direct and inverse problem of thermodynamics in the context of rule-based modelling. The direct problem can be concisely stated as obtaining a set of rewriting rules and their rates from the description of the energy landscape such that their asymptotic behaviour when t → ∞ coincide. To tackle this problem, we describe an energy function as a finite set of connected patterns P and an energy cost function e which associates real values to each of these energy patterns. We use a finite set of reversible graph rewriting rules G to define the qualitative dynamics by showing which transformations are possible. Given G and P, we construct a finite set of rules Gp which i) has the same qualitative transition system as G and ii) when equipped with rates according to e, defines a continuous-time Markov chain that has detailed balance with respect to the invariant probability distribution determined by the energy function. The construction relies on a technique for rule refinement described in earlier work and allows us to represent thermodynamically consistent models of biochemical interaction networks in a concise manner. The inverse problem, on the other hand, is to i) check whether a rule-based model has an energy function that describes its asymptotic behaviour and if so ii) obtain the energy function from the graph rewriting rules and their rates. Although this problem is known to be undecidable in the general case, we find two suitable subsets of Kappa, our rule-based modelling framework of choice, were this question can be answer positively and the form of their energy functions described analytically.

The proposed energy harvesting system intends to harvest vibrational energy via an electromagnetic generator (EMG). The proposed circuit intends to extract maximum power from the EMG by utilizing the maximum power transfer theorem which states that maximum power is transferred to the load when the source resistance equals the load resistance. The proposed circuit is a synchronous split-capacitor boost converter operating in boundary conduction mode (BCM) to achieve impedance matching and therefore maximum power transferred to the load. The circuit topology combines the rectifier and power stage to reduce power loss of the power management integrated circuit (PMIC). The proposed circuit is designed and fabricated in 130 nm BiCMOS technology. The circuit is validated through schematic level simulations and post-layout simulations. The results conclude the proposed circuit and control operates in a manner to achieve BCM.
Master of Science

This thesis deals with the modeling and control of permanent magnet synchronous generator based wind turbines (PMSG-WTs). The PMSG-WTs are widely used in wind energy conversion systems(WECSs), due to their merits such as high reliability, high efficiency, low noise, high torque to weight ratio and fast dynamic response. Usually, a PMSG-WT is connected to the power grid via an AC-DC-AC converter system. The PMSG-WT can rotate at varying speed based on variable wind power input and thus achieve high efficiency as it dose not need to synchronise its rotational speed with the grid frequency. An overview of the modeling of the PMSG-WT is give at first, with conventional vector control (VC) strategies applied for machine-side and grid-side converter. The VC strategy is a popular method widely used in industry due to its decoupled control of active/reactive power, but it may not provide satisfactory performance for the PMSG-WT as it is required to operate at varying speed in an operation envelope with wide operating range rather than one operation point. The feedback linearisation control (FLC) strategy can improve the performance of the VC with a global optimal controller crossing a wide region and variable operation points, but it has weak robustness against parameter uncertainties and external disturbances, and requires full state measurements. To improve performance of the VC and the FLC, nonlinear adaptive controllers (NACs) designed based on FLC and perturbation estimation and their applications in machine-side and grid-side converter control of the PMSG-WT, and speed control of a permanent magnet synchronous motor (PMSM) have been studied. In the design of the proposed NAC, by defining a lumped perturbation term to present coupling nonlinear dynamics, parameter uncertainties, and other unknown disturbance, then a perturbation observer is designed to estimate the perturbation which is used to compensate the real perturbation and realise an adaptive linearising of the original nonlinear system, without requiring the accurate system model and parameters and full state measurements, and still considering all system nonlinearities and unknown time-varying dynamics, such as tower shadow, grid faults and intermittent wind power inputs. In this thesis, the proposed control schemes are applied for control of PMSGWT in Region 2, Region 3 and integration with the grid. A NAC is developed for a PMSG-WT to extract maximum wind power in Region 2. Simulation and experiment studies are carried out to verify the design and results show that the proposed NAC can provide better performance in MPPT and robustness against parameter uncertainties and time-varying wind power inputs, in comparison with a convention VC and FLC. NACs are designed for control of the pitch angle and generator control of a PMSG-WT to limit the extracted power from time varying wind in Region 3. Simulation results of the proposed NACs are compared to a conventional VC and FLC. The fault ride-through capability (FRTC) of the PMSG-WT at different voltage dip’s levels has been enhanced by a novel NAC applied at the grid-side converter. Simulation results have shown that the proposed NAC can provide satisfactory performances with smaller inrush current and voltage overshoots during grid fault and better robustness against uncertainties. A coordinated nonlinear adaptive control (CNAC) of the machine-side and grid-side converter in the PMSG-WT were studied. The NACs are designed based on state and perturbation observers for control of subsystems. Simulation results show that the CNAC can coordinate each other to achieve the objectives of different operating regions and enhance the FRTC of the PMSG-WT. Finally, the proposed control schemes are applied for control of PMSM. NAC is developed for PMSM to track mechanical rotation speed and provide high robustness against system parameter uncertainties and unknown time-varying load disturbances. Simulation results show that the proposed NAC provides better performance and robustness against system parameter uncertainties and unknown time-varying load disturbances, in comparison with a nonlinear controller with an extended nonlinear observer and a conventional VC.

Small combined heat and power generators have the potential to reduce energy consumption and greenhouse gas emissions of residential buildings. Recently, much attention has been given to these units. To date, the majority of studies in this field have concentrated on the steady operational performance of a specific generator type, and the available computer models have largely been theoretical in nature.

The main goal of this study was to evaluate the performance of the latest combined heat and power generators, when integrated into Canadian residential homes. A fair comparison of four 1 kW (electrical) units was made. The combined heat and power units studied were based on PEM fuel cell, solid oxide fuel cell, Stirling Engine, and internal combustion engine energy converters.

This study utilized recent test data in an attempt to evaluate the most efficient method of integrating the combined heat and power units into residential houses. Start-up, shut down, and load change transients were incorporated into the simulations. The impact of load variations due to building thermal envelope differences and varying building heating system equipment was evaluated. The simulations were evaluated using TRNSYS software. The building heat demands were determined with eQuest hourly building simulation software.

All of the combined heat and power units under study were capable of providing a net annual benefit with respect to global energy and greenhouse gas emissions. The fuel cells offer the highest integrated performance, followed closely by the internal combustion engine and lastly the Stirling engine. Annual global energy savings up to 20%, and greenhouse gas savings up to 5. 5 tonnes per year can be achieved compared to the best conventional high efficiency appliances.

Heat demand influences performance greatly. As the thermal output of the generator unit approaches half of the average building thermal demand, the system design becomes critical. The system design is also critical when integrating with a forced air furnace. Only the PEM fuel cell unit produces clear global energy and emissions benefits when operating in the summertime.

This work discusses the implementation of a Unique Ships Grid design that utilizes Energy Storage. This Unique Ships Grid is used to enhance the efficiency of a Construction Single-Hull River Tender previously discussed and assessed by the Army Corps of Engineers and the United States Coast Guard (USCG). This Grid Design is shown to be both in compliance with applicable regulations and reliable due to built-in redundancy. Compliance with regulations and redundancy are both prized by the Maritime Community and the USCG. An applicable Heuristic Design Methodology is provided in conjunction with the Unique Ships Grid. This Design Methodology can be used with a simple load analysis and results in a Load Center breakdown and the sizing of Cables, Generators, Inverter, and required Energy Storage. This design process is shown to provide an inherent margin for growth and safety. This design process is quick and results in values necessary to do a cost analysis, environmental impact survey, and stability analysis (Ship Stability not Electrical Stability).
Master of Science

One of the major electrical faults of synchronous machines is an interturn short circuit in the stator winding, due to winding insulation failure. A synchronous machine is designed to have electrical and mechanical symmetry in the stator and rotor. An interturn fault in a synchronous machine damages the symmetrical property, thereby inducing abnormal symptoms like varying torque, mechanical vibration, and deviation of stator and rotor terminal currents from their usual waveform. This last symptom is what is studied in this thesis, as an indicator of the presence of an interturn fault. An interturn fault during machine operation can lead to a catastrophic machine failure and consequent long outage, unless it is rapidly detected and the machine shut down. Prevention of such outages is an important concern for machine owners and power system operators. That is why early detection of interturn faults is desirable to prevent such machine failure. Several external sensors can be implemented to detect such interturn fault, which is costly. That is why it is desirable if the interturn fault can be detected by analyzing the measured currents that already are available to a protective relay. In this thesis a simulation approach is presented to observe the pattern and frequency spectrum of rotor field current in presence of a stator inter turn fault. All simulations have been performed using Matlab-based programs written during this thesis work in the Electromagnetic department (ETK) in KTH. The outcome of the thesis is that in the presence of an interturn fault in the stator, several even harmonic components are found in the frequency spectrum of the rotor field current. The presence of these harmonics is not a definitive sign of an interturn fault, as almost the same even harmonics are found in the rotor field current if the stator winding asymmetry is taken into account.
En av de största elektriska felen i synkronmaskiner är en kortslutning mellan varv i statorlindningen, på grund av skadad lindningsisolering. En synkronmaskins konstruktion ger elektrisk och mekanisk symmetri i statorn och rotorn vilket ger en hög effektivitet. Ett varvfel i statorn skadar symmetrin och inducerar onormalt stora strömmarvilket leder till ett tidsvarierande vridmoment, mekanisk vibration, och onormala vågformer av strömmarna vid statorns och rotorns poler. Varvfel under maskinens drift kan snabbt orsaka stora skador, med följd av långa avbrottstider. Förebyggande av sådana avbrott är viktig hos maskinägare och systemansvariga. Därför är snabb detektering av sådana fel, och urdrifttagning av maskinen önskvärd för att minska skadan. Däremot ska detekteringen ha låg sannolikhet att lösa ut i onödan, av annat skäl. Externa sensorer kan användas för att upptäcka sådana fel, men det är tydligt önskvärt om detekteringen kan göras genom att analysera strömmarna som redan mäts av skyddsreläer för synkronmaskiner. I denna avhandling presenteras en metod för att simulera och observera mönster och frekvensspektrum av rotors magnetiseringsström i fall där statorn har varvfel, samt i andra fall som måste kunna skiljas från varvfel. Alla simuleringar har utförts med Matlab hos avdelningen för Elektroteknisk teori och konstruktion (ETK) i Skolan för Elektro- och systemteknik (EES) på KTH.

Ocean wave energy is a promising renewable source to contribute to supplying the world’s energy demand. The Division of Electricity at Uppsala University is developing a technology to capture energy from ocean waves with a wave energy converter (WEC) consisting of a linear permanent magnet generator and a point absorber. The linear generator is placed on sea bed and is driven directly by the floating absorber. Since March 2006, multiple wave energy converters have been deployed on the Swedish west coast outside the town of Lysekil. The technology is verified by long-term operation during at sea and satisfactory reliability of the electricity generation. This thesis focuses on developing advanced control strategies for fully coupled wave energy converters subject to constraints. A nonlinear control strategy is studied in detail for a single WEC subject to constraints under regular and irregular waves. Besides, two coordinated control strategies are developed to investigate the performance of a wave energy farm subject to constraints. The performance of the WECs using these control strategies are investigated in case studies, and optimal PTO damping coefficients are found to maximize the output power. The results show that these control strategies can significantly improve the performance of the WECs, in terms of mean power, compared to a conventional control. Besides these control strategies, a wave-to-wire simulation platform is built to study the power generation control of the WEC subject to constraints.  The wave-to-wire simulation platform allows both nonlinear and linear control force. The results show that there is a good agreement between the desired value and the actual value after advanced control.

Induction machine drives with various configurations are getting a lot of attention in several industrial applications. Due to this increasing demand in industrial applications, the significance of developing effective control approaches for obtaining a high dynamic performance from the induction machine drives became essential. Up to the present time, the control of induction machine drives using power converters has been based on the principle of mean value, using pulse width modulation with linear controllers in a cascaded structure. Recent research works have demonstrated that it is possible to use Predictive Control to control induction machine drives with the use of power converters, without using modulators and linear controllers. This new approach will have a strong impact on control in power electronics in coming decades. The advantages of Predictive Control are noticed through the ability to consider a multi-objective case within the model, easy inclusion of non-linearities within the model, simple treatment of system constraints, easy of digital implementation, and flexibility of including modifications and extension of control horizons according to the required applications. Upon this, the research presented in this thesis concerns with developing different control topologies for various configurations of induction machine drives based on finite control set model predictive control (FCS-MPC) principle, which actuates directly the switch states of the voltage source inverter (VSI). In addition, for enhancing the robustness of the induction machine drives, different sensorless approaches are utilized and tested for validations. The first topology of induction machine drives that has been studied is the induction motor (IM) drive. An effective model predictive direct torque control (MP DTC) approach is used to control the torque and stator flux of the motor through the utilization of an effective cost function, through which the understanding and comparing implementation variants and studying convergence and stability issues can be easily investigated. The speed sample effect on the control variants and overall performance of the proposed MP DTC is analyzed, which enables the understanding of the real base principle of DTC, as well as why and when it works well. Two different sensorless procedures for estimating the speed and rotor position are used by the proposed MP DTC approach; the first utilizes a model reference adaptive system (MRAS) observer, while the other exploits the prediction step during the implementation of proposed MP DTC to get the speed information through performing a linear extrapolation of the speed values starting from the last two estimated samples. Extensive simulation and experimental tests have been carried out to validate the effectiveness of both sensorless approaches in achieving precise tracking of speed commands for a wide range of variations. For enhancing the robustness of proposed MP DTC, the stator flux as a control variable is replaced with controlling the flow of the reactive power through the induction motor drive. As the reactive power is a measured quantity compared with the estimated value of stator flux, thus, the sensitivity of the control against parameters variation is limited, and this confirmed through the obtained results from both simulation and experimental tests. In addition, an effective alternative approach to the MP DTC is presented, which based on controlling the instantaneous values of the active and reactive powers of the IM drive based on model predictive principle, instead of controlling the torque and flux as in MP DTC. This technique has the advantage that all controlled variables are became measured quantities (active and reactive powers), thus the estimation problems that commonly present in classic DTC schemes are effectively limited. For the last two control approaches (MP DTC reactive power control, and MP IPCactive and reactive power control), the sensorless that utilizes the predictive feature is also adopted. Obtained results via simulation and experiments confirm the feasibility of the two alternatives control procedures in obtaining a robust dynamic response of IM drive. To limit the accompanied ripple contents in the controlled values of electromagnetic torque and stator flux of induction motor, an effective ripple reduction technique has been presented. The technique is based on the derivation of the optimal value for the weighting factor (w_f) used in the cost function. A detailed mathematical derivation of the optimal value of w_f is introduced based on the analysis of torque and flux ripples behaviors. The proposed ripple reduction technique has been validated via simulation utilizing Matlab/Simulink software, and experimentally tested using a fast control prototyping dSpace 1104 board. In addition, the prediction step based sensorless approach is adopted during implementation. The performance of the IM drive using the proposed approach is compared with the results obtained from MP DTC approach that uses an arbitrary value of w_f. The comparison confirms the validity of the proposed ripple reduction procedure in reducing the ripple contents in the controlled variables while preserving the permissible computation burdens during the implementation. The FCS-MPC principle is also utilized to control the current of induction motor as an alternative to classic field oriented control (FOC), the proposed model predictive current control (MPCC) approach belongs to the class of the hysteresis predictive control (for limiting the switching frequency) as the MPCC is triggered by the exceeding of the error of a given threshold. In addition, a sensorless drive is achieved by including an effective Luenberger observer (LO) for precise estimation of rotor flux vector together with stator current, speed and load torque. The stator currents are estimated to eliminate the accompanied noise in their values when they are directly measured, thus the currents noise during prediction is limited. An effective pole placement procedure for the selection of observer gains has been adopted. The procedure is based on shifting the poles of the observer to the left of the motor poles in the complex (s-plane) with low imaginary part, so that the stability of the observer is enhanced for wide speed range. The feasibility of the sensorless MPCC for IM drive is confirmed through the obtained simulation and experimental results. The second topology of induction machine drives that has been studied is the doubly fed induction motor (DFIM) drive. An effective model predictive direct torque control (MP DTC) algorithm is developed for controlling the torque and rotor flux of DFIM drive. In addition, an effective sensorless approach is presented, which estimates the speed and rotor position in an explicit way without the need for involving the flux in the estimation process, thus the effect of parameters variation on the overall performance of the sensorless observer is effectively limited, this has been approved through the obtained results that are performed for a wide speed range from sub-synchronous to super-synchronous speed operation. During the operation, the stator resistance and magnetizing inductance values are changed from their original values to study the variation effect on the observer performance. Matlab/Simulink software and a prototyping dSpace 1104 control board are used to validate the effectiveness of proposed sensorless MP DTC approach through simulation and experiments, respectively. The results proof the robustness of the proposed sensorless approach and its ability to achieve precise estimation of the speed and rotor position. The third topology of induction machine drives that has been studied is the doubly fed induction generator (DFIG). A detailed analytical derivation for the proposed model predictive direct power control (MP DPC) approach for DFIG is presented, which as a sequence considered as a transposed control approach from the MP DTC used before for doubly fed induction motor (DFIM). A sensorless approach based on model reference adaptive system (MRAS) observer is adopted for estimating the speed and rotor position. Both simulation using Matlab/Simulink software and experimental test using a prototyping dSpace 1104 control board have tested the dynamic performance of the drive. Obtained results affirm the feasibility of the proposed MP DPC approach in achieving a decoupled control of active and reactive powers for DFIG. In summary, it can be said that the proposed model predictive control approaches have proved their ability in achieving high dynamic performance for different topologies of induction machine drives. In addition, the proposed sensorless techniques have confirmed their effectiveness for a wide range of speed variations. All of this are approved and validated through extensive simulation and experimental tests.
Gli azionamenti con machine ad induzione (macchine asincrone nelle loro varie configurazioni), stanno riacquistando molta attenzione in diverse applicazioni industriali. A causa di questo crescente interesse applicativo, è diventato di essenziale importanza lo sviluppo di efficaci tecniche di controllo per ottenere dagli azionamenti in questione elevate prestazioni dinamiche. Fino ad oggi, il controllo degli azionamenti con macchina a induzione alimentati da convertitori di potenza è basato sul “principio del valore medio” delle grandezze in commutazione, utilizzando la modulazione di larghezza di impulsi con controllori lineari in una struttura a cascata. Recenti ricerche hanno dimostrato che è possibile utilizzare il Controllo Predittivo per controllare gli azionamenti con macchina a induzione, con l'utilizzo di convertitori di potenza senza utilizzare modulatori e controllori lineari. Questo nuovo approccio avrà un forte impatto sul controllo dell'elettronica di potenza nei prossimi decenni. I vantaggi del Controllo Predittivo derivano dalla possibilità di perseguire problemi multi-obiettivo, di includere facile le non linearità all'interno del modello, di trattare in modo semplice i vincoli di sistema, nonché dalla facilità di implementazione digitale e dalla flessibilità di includere modifiche ed estensioni al controllo secondo le applicazioni richieste. Inlinea con tutto ciò, la ricerca presentata in questa tesi riguarda lo sviluppo di diverse topologie di controllo per varie configurazioni di azionamenti con macchine a induzione, basate sul principio di Controllo Predittivo a modello con insieme finito degli stati di controllo (Finite Control Set Model Predictive Control - FCS-MPC), che definisce direttamente l’assetto dell'inverter di tensione (VSI). Inoltre, per aumentare la robustezza degli azionamenti, vengono proposti e sperimentati diversi approcci senza sensori elettromeccanici (sensorless). La prima topologia studiata di azionamenti con macchina a induzione (IM) è l'azionamento con motore a gabbia. Il controllo diretto di coppia (DTC) è aggiornato in termini di controllo predittivo a modello (MP DTC) e usato per controllare la coppia e il flusso statorico attraverso l'utilizzo di una efficace funzione di costo attraverso la quale è anche possibile facilmente comprendere e confrontare le varianti di implementazione e studiare i problemi di convergenza e di stabilità. Viene analizzato l'effetto della velocità sulle diverse versioni di controllo e sulle prestazioni complessive del MP DTC proposto; ciò consente di comprendere appieno il principio del DTC, nonché perché e quando esso funzioni bene. Vengono utilizzate due diverse procedure di stima della posizione e della velocità del rotore nel MP DTC proposto; il primo utilizza uno stimatore adattivo con modello di riferimento (MRAS), mentre l'altro sfrutta la stessa fase di predizione del MP DTC proposto per ottenere le informazioni sulla velocità effettuando infine un'estrapolazione lineare dei valori di velocità a partire dagli ultimi due campioni stimati. Sono state eseguite numerose prove in simulazione e sperimentali per convalidare l'efficacia di entrambi gli approcci sensorless nell’ottenere un preciso inseguimento del comando di velocità per una vasta gamma di situazioni. Per migliorare la robustezza del MP DTC proposto rispetto alle variazioni parametriche, il controllo del flusso dello statore viene sostituito con quello della potenza reattiva assorbita dal motore ad induzione; di conseguenza la sensibilità del controllo alle variazioni dei parametri è limitata e ciò è confermato attraverso i risultati ottenuti sia dalla simulazione che dalle prove sperimentali. Inoltre, viene presentato un ulteriore efficace approccio alternativo per il MP DTC, basato sul principio del controllo predittivo a modello dei valori istantanei delle potenze attive e reattive dell'azionamento, invece di controllare la coppia e il flusso come nell’usuale MP DTC. Questa variante ha il vantaggio che tutte le variabili controllate sono divenute quantità misurate (potenze attive e reattive) e quindi i problemi di stima comunemente presenti nei classici schemi DTC sono efficacemente limitati. Per gli ultimi due approcci di controllo (controllo di coppia e di potenza reattiva e controllo di potenza attiva e reattiva) viene anche adottato la stima della velocità rotorica che sfrutta la funzione predittiva del controllo. I risultati ottenuti attraverso la simulazione e la sperimentazione confermano la fattibilità delle due procedure alternative di controllo per ottenere una risposta dinamica robusta dell’azionamento con IM. Per limitare il ripple che accompagna gli andamenti controllati della coppia e del flusso statorico del motore, è stata presentata una tecnica efficace di riduzione della sua ampiezza. La tecnica è basata sull’impiego di un valore ottimale per il fattore di ponderazione w_f utilizzato nella funzione di costo per sommare i due contributi che la definiscono. Viene introdotta una derivazione matematica dettagliata del valore ottimale di w_f attraverso l'analisi dei comportamenti dell’ondulazione di coppia e del flusso. La tecnica di riduzione del ripple proposta è stata verificata tramite la simulazione usando il software Matlab/Simulink e sperimentalmente utilizzando la scheda di rapida prototipazione del controllo dSpace 1104. Ancora, l'implementazione adotta l'approccio sensorless basato sulla fase di predizione. Le prestazioni dell’azionamento con IM utilizzando quest’ultimo approccio proposto sono confrontate con i risultati ottenuti con l'approccio MP DTC che utilizza invece un valore arbitrario di w_f. Il confronto conferma la validità della procedura di riduzione del ripple nelle variabili controllate mantenendo nel contempo gli oneri di calcolo entro i limiti consentiti per l'implementazione. Il principio FCS-MPC è anche utilizzato per controllare la corrente del motore di induzione come alternativa al controllo classico ad orientamento di campo (Field Oriented Control -FOC). L'approccio proposto di controllo di corrente di tipo predittivo (Model Predictive Current Control - MPCC) appartiene alla classe del controllo predittivo ad isteresi (per limitare il frequenza di commutazione) in quanto il MPCC viene attivato dal raggiungimento dell’errore di corrente di una determinata soglia. In questo caso, la caratteristica sensorless dell’azionamento è ottenuta includendo un efficace osservatore Luenberger (LO) per una precisa stima del vettore del flusso del rotore insieme alla coppia di carico e alla velocità. È stata adottata una efficace procedura di allocazione dei poli per la selezione dei guadagni dell'osservatore; la procedura si basa sul posizionamento dei poli dell'osservatore a sinistra di quelli del motore nel complesso (piano di s) con una ridotta parte immaginaria, in modo che la stabilità dell'osservatore sia migliorata in un'ampia gamma di velocità. La fattibilità dell'azionamento sensorless con MPCC è ancora confermata attraverso la simulazione e i risultati sperimentali. La seconda topologia degli azionamenti con macchina a induzione che è stata studiata è l'azionamento con motore ad anelli con rotore alimentato da invertitore e statore da rete (Doubly Fed Induction Motor DFIM). È stato sviluppato un efficace algoritmo predittivo a modello (MP DTC) per il controllo dinamico della coppia e del flusso di rotore dell'azionamento DFIM. Inoltre, viene presentato un approccio efficace di soluzione sensorless che valuta la velocità e la posizione del rotore in modo esplicito senza la necessità di coinvolgere la stima del flusso nel processo di predizione; di conseguenza l'effetto delle variazioni dei parametri sulle prestazioni complessive dell'osservatore di posizione e velocità è sensibilmente limitato. Questo è stato provato attraverso i risultati ottenuti con test eseguiti in un'ampia gamma di velocità, dal sub-sincronismo a velocità super-sincrona. Durante l'operazione, la resistenza dello statore e i valori di induttanza di magnetizzazione sono stati modificati rispetto ai valori reali per studiare l'effetto di variazioni parametriche sulle prestazioni dell'osservatore. Anche in questo caso, il software Matlab/Simulink e una scheda di controllo dSpace 1104 sono stati utilizzati per convalidare l'efficacia dell'approccio sensorless del MP DTC per l’azionamento. I risultati dimostrano la robustezza del controllo sensorless proposto e la sua capacità di ottenere una precisa stima della posizione e della velocità del rotore. La terza topologia di azionamenti con macchina a induzione che è stata studiata è quella del generatore ad induzione con rotore avvolto (DFIG) e invertitore sul rotore. Viene presentata una derivazione analitica dettagliata del controllo predittivo diretto di potenza (MP DPC) per DFIG, che trasferisce ed estende l’approccio di controllo del MP DTC citato prima per il motore a induzione a doppia alimentazione (DFIM). Una soluzione sensorless ancora basata sull'osservatore adattivo a modello di riferimento (MRAS) è adottato per stimare la velocità e la posizione del rotore. Sia le simulazioni usando il software Matlab/Simulink che i test sperimentali utilizzando la scheda dSpace 1104 hanno mostrato le elevate prestazioni dinamiche dell'azionamento. I risultati ottenuti confermano la fattibilità del metodo MP DPC proposto per ottenere un controllo disaccoppiato di potenze attive e reattive per DFIG. In sintesi, si può dire che l'utilizzo proposto del controllo predittivo a modello ha dimostrato la sua capacità di ottenere elevate prestazioni dinamiche per le diverse topologie degli azionamenti con macchina ad induzione considerati. Inoltre, le tecniche sensorless proposte hanno confermato la loro efficacia per una vasta gamma di velocità. Tutto questo è stato verificato e validato attraverso una vasta attività analisi simulativa e di sperimentazione in laboratorio.

Thesis (Ph. D.)--Computing, Georgia Institute of Technology, 2007.
Calton Pu, Committee Chair ; Ling Liu, Committee Member ; Karsten Schwan, Committee Member ; Olin Shivers, Committee Member ; Donald F. Ferguson, Committee Member.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Curricular reorientation based on the Thematic Approach Freirean (TAF) articulated approach to Science, Technology and Society (STS) are possibilities, so that the linear curriculum, preparatory and fragmented schools is questioned and, for that to happen, it is essential to invest in the formation of educators. Thus, the research problem of this research is: What are the possibilities and challenges faced by educators Sciences (Biology, Physics and Chemistry), a public school in Santa Maria, to use the thematic approach in their classes, especially in structuring and implementing the theme "Arroio Cadena: Santa Postcard Maria? "?. In terms of research problem detailing, three objectives were assumed: Discuss how it came to Theme Generator to be developed from the study of Reality (SR); Develop a training collective and interdisciplinary process with educators, aimed at construction / reconstruction of the curriculum through the use of articulated TAF to focus STS; Investigate the possibilities and challenges encountered in the training process and in the development and implementation of educational design / learning. The survey was implemented in the State Preparatory High School Don Antonio Reis, in the city of Santa Maria / RS, during the year 2014. The theoretical reference used in the research is based on the TAF, following the steps of the Three Pedagogical Moments (3PM) as structuring the curriculum, assumptions of the educator Paulo Freire and ideals of focus STS and Latin American Thought in Science Technology and Society (LATSTS). The research was developed in different phases and in the first, It is made explicit the process for obtaining generator theme, from SR, and in the second, the formation process aiming at Thematic Approach (TA). With qualitative approach, the instruments used in the first phase were: document analysis of the school's pedagogical project; research in local newspapers; informal conversations with: Brazilian Institute of Geography and Statistics (BIGS), health post, prefecture, city planning institute and military brigade; interview with students, teachers, directive team and local community. In the second phase, the instruments used were: questionnaire on the first meeting of the formative process, daily researcher, recordings of the encounters of the formative process, teaching projects / elaborate learning, daily educators, interviews with educators and students. As a synthesis of research results initially is discussed as the generator theme emerged: Arroio Cadena: Postcard of Santa Maria? . Just after are discussed two emerging categories of analysis of the whole process using the Text Analysis Discourse (DTA) as methodology: Possibilities of an curricular reorientation the perspective of TA and Challenges of a curricular reorientation the perspective of TA In possibilities, are characteristics such as: interdisciplinary work and the extension of the collective work in school (school and local community), the contributions of the formative process in professional walk of educators, the shift in attitude and dialogue constructed between educator-students and awakening to a culture of participation. In the category of challenges, emerging problems related to the lack of time for interdisciplinary planning, the resistance of students in work developed and yet, the conceptual approach rooted in the concepts and practices.
Reorientações curriculares baseadas na Abordagem Temática Freireana (ATF) articulada ao enfoque Ciência- Tecnologia-Sociedade (CTS) são possibilidades, para que o currículo linear, propedêutico e fragmentado das escolas seja problematizado e, para que isso aconteça, é fundamental investir na formação dos educadores. Assim, o problema de investigação desta pesquisa é: Quais as possibilidades e desafios encontrados por educadores de Ciências (Biologia, Física e Química), de uma escola pública de Santa Maria, ao utilizarem a Abordagem Temática em suas aulas, especialmente na estruturação e implementação do tema Arroio Cadena: Cartão Postal de Santa Maria? . Em termos de detalhamento do problema de pesquisa, três objetivos foram assumidos: Discutir como se chegou ao Tema Gerador a ser desenvolvido, a partir do Estudo da Realidade (ER); Desenvolver um processo formativo coletivo e interdisciplinar com educadores, com vistas à construção/reconstrução do currículo, através da utilização da ATF articulada ao enfoque CTS; Investigar as possibilidades e desafios encontrados no processo formativo e na elaboração e implementação do projeto de ensino/aprendizagem. A pesquisa foi implementada na Escola Estadual de Ensino Médio Dom Antônio Reis, do município de Santa Maria/RS, durante o ano de 2014. O referencial teórico utilizado na pesquisa está fundamentado na ATF, que segue as etapas dos Três Momentos Pedagógicos (3MP) como estruturantes de currículos, pressupostos do educador Paulo Freire e nos ideais do enfoque CTS e do Pensamento Latino Americano em Ciência-Tecnologia-Sociedade (PLACTS). A pesquisa foi desenvolvida em diferentes fases, sendo que, na primeira, é explicitado o processo para obtenção do tema gerador, a partir do ER, e, na segunda, o processo formativo com vistas à Abordagem Temática (AT). Com cunho qualitativo, os instrumentos utilizados na primeira fase foram: análise documental do Projeto Pedagógico da escola; pesquisas em jornais locais; conversas informais com: Instituto Brasileiro de Geografia e Estatística (IBGE), posto de saúde, prefeitura, Instituto de planejamento da cidade e brigada militar; entrevista com educandos, educadores, equipe diretiva e comunidade local. Já na segunda fase, os instrumentos utilizados foram: questionário referente ao primeiro encontro do processo formativo, diários da pesquisadora, gravações dos encontros do processo formativo, projetos de Ensino/Aprendizagem elaborados, diários dos educadores, entrevista com os educadores e educandos. Como síntese dos resultados da investigação, inicialmente, é discutido como emergiu o tema gerador: Arroio Cadena: Cartão Postal de Santa Maria? . Logo após, são discutidas duas categorias emergentes da análise de todo o processo, utilizando a Análise Textual Discursiva (ATD) como metodologia: Possibilidades de uma reorientação curricular na perspectiva da AT e Desafios de uma reorientação curricular na perspectiva da AT. Nas possibilidades, encontram-se características como: o trabalho interdisciplinar e a ampliação do trabalho coletivo na escola (comunidade escolar e local), as contribuições do processo formativo na caminhada profissional dos educadores, a mudança de postura e o diálogo construído entre educador-educandos e o despertar para uma cultura de participação. Na categoria dos desafios, emergem problemas relacionados com a falta de tempo para o planejamento interdisciplinar, as resistências dos educandos no trabalho desenvolvido e, ainda, a abordagem conceitual enraizada nas concepções e práticas.

La théorie des valeurs extrêmes étudie la probabilité de survenance d'événements extrêmes, tels les inondations, les sécheresses ou encore les crises financières. Une part importante de cette théorie repose sur les théorèmes limites, comme celui des valeurs extrêmes, ou de Pickands-Balkema-de Haan. Afin d'appliquer ces théorèmes avec précision et approcher raisonnablement la loi des données extrêmes, inconnue en général, par son modèle limite, il faut pouvoir quantifier la vitesse de convergence de ces théorèmes. Une façon de faire est d'utiliser l'approche par générateur de la méthode de Stein. Aussi, dans cette thèse nous introduisons et étudions une famille de semi-groupes de Markov spécialement construits pour admettre les lois d'extremum comme mesure invariante. Pour ce faire, la définition choisie repose sur une formule de Mehler, elle-même conséquence des relations de stabilité satisfaites par les lois max-stables. L'avantage principal de cette construction est que les semi-groupes ainsi définis disposent automatiquement de propriétés similaires à celles du semi-groupe d'Ornstein-Uhlenbeck (propriété de commutation, inégalité de Poincaré, identités de covariance, etc.). Nous appliquons ensuite ces résultats à l'obtention de bornes générales sur les distance à une loi d'extremum, puis nous spécialisons ces bornes dans différents contextes pour obtenir des taux explicites. Enfin le dernier chapitre porte sur les processus de Poisson dont la mesure intensité satisfait une propriété d'homogénéité. Nous étudions comment les propriétés bien connues de ces processus se traduisent en nouveaux résultats pour les lois max-stables, éclairant ainsi d'une autre manière le contenu des chapitres précédents
Extreme value theory deals with the probability of occurrence of extreme events, such as floods, droughts or financial crises. An important part of that theory relies on limit theorems, such as the extreme value theorem, or the Pickands-Balkeman-de Hann theorem. In order to apply those theorems accurately and approximate efficiently the usually unknown distribution of the extreme data by its limit model, one needs to quantify the speed of convergence of those theorems. A manner of doing so is to use the generator approach of Stein's method. That is why in this thesis we construct a family of Markov semi-groups whose invariant measure is an extreme-value distribution. We do so via a Mehler's formula, which relies itself on the stability property satisfied by max-stable distributions. Thanks to this definition, the semi-groups satisfy similar properties to the Ornstein-Uhlenbeck (commutation rule, Poincaré's inequality, covariance identities, etc.). We then proceed to apply those results to the generator approach of Stein's method to deduce rates of convergence to extreme-value distributions in various settings. The last chapter focuses on Poisson processes whose intensity measure satisfies an homogeneity assumption and how their standard properties translate into new results for max-stable distributions, thus shedding a new light on the contents of the previous chapters

Anomaly detection is an important issue in data mining and analysis, with applications in almost every area in science, technology and business that involves data collection. The development of general anomaly detection techniques can therefore have a large impact on data analysis across many domains. In spite of this, little work has been done to consolidate the different approaches to the subject. In this report, this deficiency is addressed in the target domain of temporal machine-generated data. To this end, new theory for comparing and reasoning about anomaly detection tasks and methods is introduced, which facilitates a problem-oriented rather than a method-oriented approach to the subject. Using this theory as a basis, the possible approaches to anomaly detection in the target domain are discussed, and a set of interesting anomaly detection tasks is highlighted. One of these tasks is selected for further study: the detection of subsequences that are anomalous with regards to their context within long univariate real-valued sequences. A framework for relating methods derived from this task is developed, and is used to derive new methods and an algorithm for solving a large class of derived problems. Finally, a software implementation of this framework along with a set of evaluation utilities is discussed and demonstrated

Poetry is a unique artifact of the human language faculty, with its defining feature being a strong unity between content and form. Contrary to the opinion that the automatic generation of poetry is a relatively easy task, we argue that it is in fact an extremely difficult task that requires intelligence, world and linguistic knowledge, and creativity. We propose a model of poetry generation as a state space search problem, where a goal state is a text that satisfies the three properties of meaningfulness, grammaticality, and poeticness. We argue that almost all existing work on poetry generation only properly addresses a subset of these properties. In designing a computational approach for solving this problem, we draw upon the wealth of work in natural language generation (NLG). Although the emphasis of NLG research is on the generation of informative texts, recent work has highlighted the need for more flexible models which can be cast as one end of a spectrum of search sophistication, where the opposing end is the deterministically goal-directed planning of traditional NLG. We propose satisfying the properties of poetry through the application to NLG of evolutionary algorithms (EAs), a wellstudied heuristic search method. MCGONAGALL is our implemented instance of this approach. We use a linguistic representation based on Lexicalized Tree Adjoining Grammar (LTAG) that we argue is appropriate for EA-based NLG. Several genetic operators are implemented, ranging from baseline operators based on LTAG syntactic operations to heuristic semantic goal-directed operators. Two evaluation functions are implemented: one that measures the isomorphism between a solution’s stress pattern and a target metre using the edit distance algorithm, and one that measures the isomorphism between a solution’s propositional semantics and a target semantics using structural similarity metrics. We conducted an empirical study using MCGONAGALL to test the validity of employing EAs in solving the search problem, and to test whether our evaluation functions adequately capture the notions of semantic and metrical faithfulness. We conclude that our use of EAs offers an innovative approach to flexible NLG, as demonstrated by its successful application to the poetry generation task.

The dynamics of the atmosphere and ocean are dominated by slowly evolving, large-scale motions. However, fast, small-scale motions in the form of inertia-gravity waves are ubiquitous. These waves are of great importance for the circulation of the atmosphere and oceans, mainly because of the momentum and energy they transport and because of the mixing they create upon breaking. So far the study of inertia-gravity waves has answered a number of questions about their propagation and dissipation, but many aspects of their generation remain poorly understood. The interactions that take place between the slow motion, termed balanced or vortical motion, and the fast inertia-gravity wave modes provide mechanisms for inertia-gravity wave generation. One of these is the instability of balanced flows to gravity-wave-like perturbations; another is the so-called spontaneous generation in which a slowly evolving solution has a small gravity-wave component intrinsically coupled to it. In this thesis, we derive and study a simple model of inertia-gravity wave generation which considers the evolution of a small-scale, small amplitude perturbation superimposed on a large-scale, possibly time-dependent °ow. The assumed spatial-scale separation makes it possible to apply a WKB approach which models the perturbation to the flow as a wavepacket. The evolution of this wavepacket is governed by a set of ordinary differential equations for its position, wavevector and its three amplitudes. In the case of a uniform flow (and only in this case) the three amplitudes can be identifed with the amplitudes of the vortical mode and the two inertia-gravity wave modes. The approach makes no assumption on the Rossby number, which measures the time-scale separation between the balanced motion and the inertia-gravity waves. The model that we derive is first used to examine simple time-independent flows, then flows that are generated by point vortices, including a point-vortex dipole and more complicated flows generated by several point vortices. Particular attention is also paid to a flow with uniform vorticity and elliptical streamlines which is the standard model of elliptic instability. In this case, the amplitude of the perturbation obeys a Hill equation. We solve the corresponding Floquet problem asymptotically in the limit of small Rossby number and conclude that the inertia-gravity wave perturbation grows with a growth rate that is exponentially small in the Rossby number. Finally, we apply the WKB approach to a flow obtained in a baroclinic lifecycle simulation. The analysis highlights the importance of the Lagrangian time dependence for inertia-gravity wave generation: rapid changes in the strain field experienced along wavepacket trajectories (which coincide with fluid-particle trajectories in our model) are shown to lead to substantial wave generation.

Philosophiae Doctor - PhD
Sequencing an HIV quasispecies with next generation sequencing technologies yields a dataset with significant amplification bias and errors resulting from both the PCR and sequencing steps. Both the amplification bias and sequencing error can be reduced by labelling each cDNA (generated during the reverse transcription of the viral RNA to DNA prior to PCR) with a random sequence tag called a Primer ID (PID). Processing PID data requires additional computational steps, presenting a barrier to the uptake of this method. MotifBinner is an R package designed to handle PID data with a focus on resolving potential problems in the dataset. MotifBinner groups sequences into bins by their PID tags, identifies and removes false unique bins, produced from sequencing errors in the PID tags, as well as removing outlier sequences from within a bin. MotifBinner produces a consensus sequence for each bin, as well as a detailed report for the dataset, detailing the number of sequences per bin, the number of outlying sequences per bin, rates of chimerism, the number of degenerate letters in the final consensus sequences and the most divergent consensus sequences (potential contaminants). We characterized the ability of the PID approach to reduce the effect of sequencing error, to detect minority variants in viral quasispecies and to reduce the rates of PCR induced recombination. We produced reference samples with known variants at known frequencies to study the effectiveness of increasing PCR elongation time, decreasing the number of PCR cycles, and sample partitioning, by means of dPCR (droplet PCR), on PCR induced recombination. After sequencing these artificial samples with the PID approach, each consensus sequence was compared to the known variants. There are complex relationships between the sample preparation protocol and the characteristics of the resulting dataset. We produce a set of recommendations that can be used to inform sample preparation that is the most useful the particular study. The AMP trial infuses HIV-negative patients with the VRC01 antibody and monitors for HIV infections. Accurately timing the infection event and reconstructing the founder viruses of these infections are critical for relating infection risk to antibody titer and homology between the founder virus and antibody binding sites. Dr. Paul Edlefsen at the Fred Hutch Cancer Research Institute developed a pipeline that performs infection timing and founder reconstruction. Here, we document a portion of the pipeline, produce detailed tests for that portion of the pipeline and investigate the robustness of some of the tools used in the pipeline to violations of their assumptions.

Consumer-generated reviews play an important role in online purchase decisions for many consumers. However, the quality and helpfulness of online reviews varies significantly. In addition, the helpfulness of different consumer-generated reviews is not disclosed to consumers unless they carefully analyze the overwhelming number of available contents. Therefore, it is of vital importance to develop predictive models that can evaluate online product reviews efficiently and then display the most useful reviews to consumers, in order to assist them in making purchase decisions. This thesis examines the problem of building computational models for predicting whether a consumer-generated review is helpful based on consumers' online votes on other reviews (where a consumer's vote on a review is either HELPFUL or UNHELPFUL), with the aim of suggesting the most suitable products and vendors to consumers.In particular, we propose in this thesis three different helpfulness prediction approaches for consumer-generated reviews. Our entropy-based approach is relatively simple and suitable for applications requiring simple recommendation engine with fully-voted reviews. However, our entropy-based approach, as well as the existing approaches, lack a general framework and are all limited to utilizing fully-voted reviews. We therefore present a probabilistic helpfulness prediction framework to overcome these limitations. To demonstrate the versatility and flexibility of this framework, we propose an EM-based model and a logistic regression-based model. We show that the EM-based model can utilize reviews voted by a very small number of voters as the training set, and the logistic regression-based model is suitable for real-time helpfulness predicting of consumer-generated reviews. To our best knowledge, this is the first framework for modeling review helpfulness and measuring the goodness of models. Although this thesis primarily considers the problem of review helpfulness prediction, the presented probabilistic methodologies are, in general, applicable for developing recommender systems that make recommendation based on other forms of user-generated contents.

Thesis (MSc (Mathematical Sciences))-- University of Stellenbosch, 2010.
ENGLISH ABSTRACT: We investigate the suitability of applying some of the probabilistic and automata theoretic ideas, that have been extremely successful in the areas of speech and natural language processing, to the area of musical style imitation. By using music written in a certain style as training data, parameters are calculated for (visible and hidden) Markov models (of mixed, higher or first order), in order to capture the musical style of the training data in terms of mathematical models. These models are then used to imitate two instrument music in the trained style.
AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek die toepasbaarheid van probabilitiese en outomaatteoretiese konsepte, wat uiters suksesvol toegepas word in die gebied van spraak en natuurlike taal-verwerking, op die gebied van musiekstyl nabootsing. Deur gebruik te maak van musiek wat geskryf is in ’n gegewe styl as aanleer data, word parameters vir (sigbare en onsigbare) Markov modelle (van gemengde, hoër- of eerste- orde) bereken, ten einde die musiekstyl van die data waarvan geleer is, in terme van wiskundige modelle te beskryf. Hierdie modelle word gebruik om musiek vir twee instrumente te genereer, wat die musiek waaruit geleer is, naboots.

The goal of this project was to understand ethnic and generational differences in attitudes towards caregiving and expected burden while taking into consideration factors such as gender, generation, familism, and acculturation. One hundred and sixteen young adults (ages 18-25) and 93 middle-age adults (ages 38-62) were enrolled in the study. Participants included European Americans, African Americans, and Hispanics. Using moderation analysis, two hypotheses were investigated: 1) Ethnicity relates to attitudes towards caregiving, moderated by gender, generation, familism, and acculturation. 2) Ethnicity and expected burden relate to each other, moderated by gender, generation, familism, and acculturation. Familism emerged as a moderator in the relationship between ethnicity and expected burden. Results suggested that the strength of the relationship between being African American and expecting burden was less for those with moderate familism (R =.078), slightly higher for low familism (R = .176), and the highest for high familism (R= .261). Additional results indicated that the strength of the relationship between being Hispanic, as opposed to being European American, and expected burden, was higher for middle-aged adults (R =.23) when compared to young adults (R =.19). The current findings lend support to the recently established idea that familism is not protective against burden as it increases one's sense of obligation towards family (Knight & Sayegh, 2010).

Pharmaceutical Sciences
Ph.D.
In drug discovery there are several approaches to lead generation and one traditional approach involves the synthesis and screening of a structurally diverse compound library against a number of biological targets to identify high affinity lead compounds. The use of a `privileged' structure-based compound library represents a viable approach that could lead to drug like lead compounds. Privileged structures are defined as those ligand substructures that may be used to generate high affinity leads for more than one type of receptor. Examples of privileged structures include phenyl substituted monocycles such as biphenyls, diphenyl methane derivatives, 1,4-dihydropyridines, fused ring systems such as chromones, quinoxalines, quinazolines, 2-benzoxazolones, indoles, benzimidazoles and benzofurans. There are several instances in the literature describing the development of compound libraries based on privileged structures with reportedly high hit rates. Privileged structure based approaches has been used with notable success in the identification of high affinity ligands especially for G-protein coupled receptors (GPCRs). The scaffold 2-aminothiazole (fused and non-fused) may be considered a privileged structure because of its occurrence in a wide variety of pharmaceuticals. The scaffold is found in antibacterials, anti-inflammatory agents, glutamate transporter (GLT-1) modulators, serotonin and muscarinic ligands. The present study involves the synthesis of a 2-aminothiazole (fused and non-fused) based compound library (60 compounds) by incorporating bioactive fragments shown to produce hits in the biological targets of interest. Microwave assisted organic synthesis (MAOS) has been employed at key steps of scaffold synthesis as well as in Suzuki coupling to generate the target aminothiazoles. Preliminary biological screening has resulted in the identification of some promising lead compounds. Trifluoromethoxy substituted aminothiazoles were found to be potent antimicrobials with MIC values in the range of 4-16 microgram/ml. Furanone based aminothiazoles showed affinity for muscarinic receptors. Piperidine based aminothiazoles showed greater than 90% of control (8-OH-DPAT) specific agonist response at the 5-HT1A receptor subtype. The Clog P values of the most potent antimicrobials were found to be in the range of 4.5-6.2 indicating the high lipophilicity of the compounds. High lipophilicity is known to cause solubility issues that may hamper future development. Therefore in an effort to make compounds with intermediate lipophilicity, the phenyl core of the potent aminothiazoles will be replaced with pyridine core using literature procedures (Pyridine core containing aminothiazoles showed Clog P < 4). Future plans include expanding the library, improving the yields of compounds and to evaluate the compounds as modulators of glutamate transporter (GLT-1). The work could be extended to include other privileged structures such as 2-aminooxazole, 2-aminobenzoxazole, 2-aminoimidazole and 2-aminobenzimidazole. These mono and bicyclic heterocyles may be considered bioisosteres of 2-aminothiazole.
Temple University--Theses

The process of designing a floorplan is highly iterative and requires extensive human labor. Currently, there are a number of computer programs that aid humans in floorplan design. These programs, however, are limited in their inability to fully automate the creative process. Such automation would allow a professional to quickly generate many possible floorplan solutions, greatly expediting the process. However, automating this creative process is very difficult because of the many implicit and explicit rules a model must learn in order create viable floorplans. In this paper, we propose a method of floorplan generation using two machine learning models: a sequential model that generates rooms within the floorplan, and a graph-based model that finds adjacencies between generated rooms. Each of these models can be altered such that they are each capable of producing a floorplan independently; however, we find that the combination of these models outperforms each of its pieces, as well as a statistic-based approach.

Humans are not often very skilled in asking good questions because of their inconsistent mind in certain situations. Thus, Question Generation (QG) and Question Answering (QA) became the two major challenges for the Natural Language Processing (NLP), Natural Language Generation (NLG), Intelligent Tutoring System, and Information Retrieval (IR) communities, recently. In this thesis, we consider a form of Sentence-to-Question generation task where given a sentence as input, the QG system would generate a set of questions for which the sentence contains, implies, or needs answers. Since the given sentence may be a complex sentence, our system generates elementary sentences from the input complex sentences using a syntactic parser. A Part of Speech (POS) tagger and a Named Entity Recognizer (NER) are used to encode necessary information. Based on the subject, verb, object and preposition information, sentences are classified in order to determine the type of questions to be generated. We conduct extensive experiments on the TREC-2007 (Question Answering Track) dataset. The scenario for the main task in the TREC-2007 QA track was that an adult, native speaker of English is looking for information about a target of interest. Using the given target, we filter out the important sentences from the large sentence pool and generate possible questions from them. Once we generate all the questions from the sentences, we perform a recall-based evaluation. That is, we count the overlap of our system generated questions with the given questions in the TREC dataset. For a topic, we get a recall 1.0 if all the given TREC questions are generated by our QG system and 0.0 if opposite. To validate the performance of our QG system, we took part in the First Question Generation Shared Task Evaluation Challenge, QGSTEC in 2010. Experimental analysis and evaluation results along with a comparison of different participants of QGSTEC'2010 show potential significance of our QG system.
x, 125 leaves : ill. ; 29 cm

The solution of generation scheduling (GS) problems involves the determination of the unit commitment (UC) and economic dispatch (ED) for each generator in a power system at each time interval in the scheduling period. The solution procedure requires the simultaneous consideration of these two decisions. In recent years researchers have focused much attention on new solution techniques to GS. This paper proposes the application of a variety of genetic algorithm (GA) based approaches and investigates how these techniques may be improved in order to more quickly obtain the optimum or near optimum solution for the GS problem. The results obtained show that the GA-based hybrid approach offers an effective alternative for solving realistic GS problems within a realistic timeframe.

Graphs have been successfully employed in avariety of problems and applications, being the object of study in modeling, analysis and construction of visual representations. While different approaches exist for graph visualization,most of them suffer from the severe clutter when the number of nodes or edges is large. Among the approaches that handle such problem, edge bundling techniques attained relative success on improving the quality of the visual representations by bending and aggregating edges in order to produce an organized layout. Despite this success, most of the exiting techniques create edge bundles based only on the visual space information, that is, there is no explicit connection between the edge bundling layout and the original data. There fore, these techniques generates less meaningful bundles and may lead users to misinterpret the data. This masters research presents a novel edge bundling technique based on the similarity relationships among vertices. We developed such technique based on two assumptions. First, it supports the hypothesis that edge bundling can better represent the data when there is an inherent connection between the proximity among the elements in the information space and the proximity between edges in the edge bundling layout. We address this question by presenting a similarity bundling framework, that considers the similarity between vertices when performing the edges bending. To guide the bundling, we create a similarity hierarchy, called backbone. This is based on a multilevel partition of the data, which groups edges of similar vertices. Second, we also support that a multiscale representation improves the visual and complexity scalability of bundling layouts. We present a multiscale edge bundling, which allows an overview plus detailed exploration, coarsening or revealing the bundling at different levelsof the same visualization. Our evaluation framework shows that our backbone produces a balanced hierarchy with a good representation of similarity relationships among vertices. Moreover, the edge bundling layout guided by the backbone reduces the visual clutter and surpass state-of-the-art techniques in displaying global and local edge patterns.
Grafos são empregados com sucesso em uma grande variedade de problemas e aplicações, sendo objeto de estudo na modelagem, análise e na construção de representações visuais. Embora existam diferentes formas para a visualização de grafos, a maioria delas sofrem pela desorganização do espaço visual quando o número de vértices ou arestas é alto. Entre as abordagens que lidam com este problema, as técnicas de agrupamentos visuais de arestas obtiveram sucesso na melhora da representação visual pelo encurvamento e agrupamento de arestas que aperfeiçoam a organização da representação. Apesar deste sucesso, a maioria das técniques criam grupos de arestas baseados apenas na informação do espaço visual, não existindo conexão explícita entre o desenho no espaço visual e o conjunto de dados original. Dessa forma, estas técnicas produzem agrupamentos de arestas com baixa significância e podem levar o usuário a uma interpretação incorreta da informação. Esta pesquisa de mestrado apresenta uma nova técnica de agrupamento visual de arestas baseado nas relações de similaridade entre os vértices. Nós desenvolvemos esta técnica com base em duas premissas. Primeiro, ela defende a hipótese que a representação por agrupamento de arestas pode representar melhor o conjunto de dados se existir uma conexão inerente entre a proximidade dos elementos no espaço de informação e a proximidade entre arestas no desenho de arestas agrupadas. Nós atendemos esta questão apresentando um arcabouço para o agrupamento de arestas baseado em similaridade, que considera a similaridade entre vértices para realizar o encurvamento das arestas. Para guiar este encurvamento, nós criamos uma estrutura de similaridade, denominada backbone. Esta estrutura é baseada em um particionamento multi-nível do conjunto de dados, que agrupa arestas de vértices similares. A segunda premissa, nós também defendemos que uma representação multiescala melhora a escalabilidade computacional e visual da representação visual de arestas agrupadas. Nós apresentamos um agrupamento visual multi-nível de arestas que permite uma exploração generalizada e detalhada, revelando detalhes em múltiplos níveis da visualização. Nosso processo de avaliação mostra que a construção do backbone produz uma hierarquia balanceada e com boa representação das relações de similaridade entre os vértices. Além disso, a visualização com arestas guiadas pelo backbone reduz a desordem visual e melhora as técnicas do estado-da-arte na identificação de padrões de arestas globais e locais.

The thesis is focused on multiparametric diagnostic of generators at the Dukovany nuclear power plant. One generator was chosen for the thesis and it was examined especially from the practical point of view. The thesis describes current state of the issue with focus on noise diagnostics, vibrodiagnostics and electrodiagnostics. The emphasis is on the system approach of the solution. In the practical part an experiment is designed, described and evaluated. Attention is paid to the conclusions of the performed vibrodiagnostics and noise diagnostics. Data sets are evaluated separately and the relationship between the two diagnostic methods is analyzed. Furthermore, the data set from electrodiagnostics is evaluated and dependencies of electrical diagnostic quantities on other quantities are described. Trends in electrical diagnostic quantities are also monitored. Conclusions and recommendations are formulated at the end of the thesis. It is stated that using multiparametric diagnostics to assess the status of generators in power plants is still in its beginning and that the conclusions of the submitted thesis will contribute to the developmnet in this area.

Liquid combustible fossil fuel empowers global society, yet is a non-renewable entity with time-constrained limits to supply. Advanced generation biofuel derived from microalgae could feasibly yield more than conventional biofuel crops, utilise non-agricultural land or the sea and remediate atmospheric carbon dioxide and anthropogenic waste. However, technical and economical limits have so far prevented the successful implementation of microalgae biofuels. This thesis exemplifies how apparently disconnected technologies are able to become united in their provision for the growth and processing of microalgae. In so doing, it employs unique experimental methodology which unites inter- disciplinary themes with the proposition to cultivate and process microalgae biomass in a manner which has never been done before. The novelty of this endeavour presents a unique set of challenges, reasoning and results with implications for future creative research and investigation. The philosophical approach to conception and achievement of the laboratory work intercedes with entirely new methodology. Selected examples of such methodology follow. In chapter 3, a newly developed bio-composite gel disk was processed aligning a new design of apparatus for a geotextile puncture resistance test. In chapter 3, a novel formulation for harvesting microalgae is described. In chapter 5, a modified methodology of the preceding chapter is used to investigate seawater ion remediation via ionic and density phase separation. Chapter 6 integrates waste components from 5 different industries, namely dairy farming, anaerobic digestion, brewing, steel slag aggregates and coal power combustion with no previously known unification of such technologies in scientific literature. Chapter 7 assesses the lipid quality of biomass harvested by the novel formulation of chapter 3, before and after exposure to hydrothermal liquefaction. Chapter 8 extrapolates findings from the thesis to define an economic appraisal and suggest a cost saving process.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Hoje em dia é incontável o volume aplicações desenvolvidas para a World Wide Web. Essas aplicações possuem interfaces com o usuário que devem ser capazes de se adaptar a diversas situações de uso, mudanças de contexto e conteúdo e ainda ser compatíveis com vários navegadores e dispositivos. Além disso, o projeto e a manutenção de interfaces que necessitam de adaptações em função das regras de negócio da aplicação demandam boa parte do esforço exigido durante do ciclo de vida do desenvolvimento de uma aplicação. Para auxiliar no projeto dessas interfaces, algumas UIDL s (User Interfaces Description Languages) foram propostas com o intuito de oferecer um nível de abstração para que o projetista não precise focar a atenção em aspectos mais concretos durante o desenvolvimento de uma interface. Esse trabalho apresenta uma proposta para modelagem e geração de interfaces de aplicações web baseadas em regras de produção. Essas regras definem critérios para as situações de: acionamento de uma interface, seleção dos elementos que participam da composição abstrata e do mapeamento dos widgets concretos que serão utilizados na etapa de renderização. Essa proposta contempla um método para modelagem das interfaces, uma arquitetura de implementação e um ambiente de autoria e execução dos modelos de interface. Também será apresentada uma arquitetura para construção de widgets concretos, uma máquina de interpretação e renderização de interfaces. O objetivo geral da proposta é conseguir projetar interfaces mais sensíveis aos dados e aos contextos de uso, cobrir certas situações de adaptação e gerar interfaces mais flexíveis e reutilizáveis.
Today there is a countless number of applications developed for the World Wide Web. These applications have user interfaces that should be able to adapt to several usage scenarios, content and context changes and also to be compatible with multiple browsers and devices. Furthermore, the design and maintenance of interfaces that need adjustments depending on the business rules of the application require much effort during the development life cycle of an application. In order to assist in the design of these interfaces, some UIDL s (User Interface Description Languages) have been proposed aiming at providing a level of abstraction so that the designer does not need to immediately focus attention on concrete aspects during the development of an interface. This work presents a proposal for modeling and generating interfaces of web applications based on production rules. These rules define criteria for situations determining the activation of an interface; for the selection the elements that participate in the abstract composition and also for the mapping of specific widgets that will be used in the rendering stage. The proposal contemplates a method for modeling interfaces, an implementation architecture and a framework for authoring and execution of the proposed interface models. An architecture is also presented for building widgets as well as a concrete interface interpretation and rendering machine from a hierarchy specification. The overall goal of the proposal is to design interfaces more responsive to data and contexts of use, including situations of adaptation, generating more flexible and reusable interfaces.

Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2001.
Includes bibliographical references (leaves 78-81).
This thesis discusses the design and implementation of Hyperscore, a computer-assisted composition system intended for users of all musical backgrounds. Hyperscore presents a unique graphical interface which takes input in the form of freehand drawing. The strokes in the drawing are mapped to structural and gestural elements in the music, allowing the user to describe the large scale-structure of a piece visually. Hyperscore's graphical notation also enables the depiction of musical ideas on a detailed level. Additional annotations around a main curve indicate the placement and emphasis of selected motives. These motives are short melodic fragments that are either composed by the user or selected from a set of pre-composed material. Changing qualitative aspects of the annotations such as texture and shape let the user alter different musical parameters. The ultimate goal of Hyperscore is to provide an intuitive, interactive graphical environment for creating and editing compositions.
by Mary Farbood.
S.M.

Thesis advisor: Eric Dearing
Increasing evidence indicates that exposure to poverty in early childhood may undermine neural growth that is critical to developing executive functions (EF) and, in turn, emotional and behavioral regulation (Blair et al. 2011; Kim et al., 2013; Raver et al., 2013). There is, however, also increasing evidence indicating that high-quality Early Childhood Education (ECE) (a) buffers children from risks associated with early exposure to poverty and (b) supports healthy socio-emotional development (Bierman et al., 2008; Raver, 2002; Yoshikawa et al., 2013). One line of this intervention work has focused on two-generation programs that pair high-quality ECE with supports for parents that are designed to improve parenting and the home environment. Although evidence on two-generation programs is mixed (Grindal et al., 2016; Neville et al., 2013), it is clear that much of the risk of poverty is relayed to children through their homes, and parenting is among the most critical influences on child emotional and behavioral self-regulation in infancy and early childhood (Bradley & Corwyn, 2004; Calkins & Johnson, 1998; Calkins et al., 1998). The present study builds on existing theoretical and empirical prior work indicating that children’s EF skills are important precursors to emotional and behavioral regulation that may be best promoted when addressed in both classroom and home contexts. Specifically, the present study uses a randomized design to evaluate the effects of classroom-based activities that target children’s executive functioning and the value added by training parents to better support their children’s EFs. Children were evaluated pre- and post-intervention on EF skills and prosocial and adaptive problem-solving behavior. In general, few significant effects of either the child training or the added parent component were evident. These findings are discussed with special attention to the fact that fidelity of implementation of the classroom and parent trainings was low, with less than half of teachers incorporating games at least once a week and only 13 percent of parents attending the trainings. In addition, implications for future empirical work as well as policy and practice are discussed with special attention given to further inquiry into the malleability of EF
Thesis (PhD) — Boston College, 2017
Submitted to: Boston College. Lynch School of Education
Discipline: Counseling, Developmental and Educational Psychology

The need for Intelligent advice, help and tutoring, generated automatically by computers is widely accepted. Recently, efforts to achieve these requirements have focused upon research into user models and improved user-machine interaction. This thesis develops a mechanism for detecting when an individual has a problem with the computer system, and identifies the nature of his problem. The method uses Plan Recognition to suggest plans that a user may be following. A Chart Parser is used to achieve this plan recognition task. This technique is capable of detecting multiple, interleaved and incomplete plans, without prior knowledge of the user's intended goals. A model of the user's beliefs is developed for the UNIX operating system. This model is capable of representing misconceptions that users possess about the domain. The combination of these techniques and heuristics to suggest when the user is experiencing difficulty, enables the computer to initiate the advice process and determine the basis for the advice.

Thesis (M.S.)--West Virginia University, 1999.
Title from document title page. Document formatted into pages; contains xi, 125 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 108-111).

Thesis (M.S.)--University of Florida, 2001.
Title from title page of source document. Document formatted into pages; contains x, 73 p.; also contains graphics. Includes vita. Includes bibliographical references.

Objective of these four first chapters is to have a complete understanding of the supramolecular organisation of several complementary modules able to form 2-D networks first in solution using optical spectroscopy measurements as function of solvent polarity , concentration and temperature, and then on solid surface using microscopy techniques such as STM, AFM and TEM. The last chapter presents another type of supramolecular material for application in solar cells technology involving fullerenes and OPV systems. We describes the photoinduced energy and electron process using transient absorption experiments. All these systems provide an exceptional example for the potential of the supramolecular approach as an alternative to the restricted lithographic method for the fabrication of adressable molecular devices.

Objective of these four first chapters is to have a complete understanding of the supramolecular organisation of several complementary modules able to form 2-D networks first in solution using optical spectroscopy measurements as function of solvent polarity , concentration and temperature, and then on solid surface using microscopy techniques such as STM, AFM and TEM. The last chapter presents another type of supramolecular material for application in solar cells technology involving fullerenes and OPV systems. We describes the photoinduced energy and electron process using transient absorption experiments. All these systems provide an exceptional example for the potential of the supramolecular approach as an alternative to the restricted lithographic method for the fabrication of adressable molecular devices.

In this dissertation, we propose a novel distributed approach to the control of generators in the electric grid. Specifically, we consider the problem of the optimal economic dispatch of generator; we present a simple, distributed algorithm, which adjusts the power-frequency set-points of generators to correct for power imbalances arising from generation and load fluctuations. In this algorithm each generator independently adjusts its real-power output based on its estimate of the aggregate power imbalance in the network; such as an estimate can be independently obtained by each generator through local measurements of the frequency deviation on the grid. Eventually, over the course of network operation, the distributed algorithm achieves the equal-marginal-cost power allocation among generators while driving the power imbalance exponentially to zero. In the absence of power losses, we prove the eventual optimality of the distributed algorithm under mild assumptions (strict convexity and positivity of cost functions) and present simulation results to compare its performance with traditional (centralized) dispatch algorithms. Furthermore, we present numerical simulation results that show that the distributed algorithm performs well even in the presence of power losses and other constraints. We argue that distributed control methods are especially attractive for electric grids with smart meters and other advanced capabilities at the end node and grids with high penetration of alternative energy generators and we identify interesting open problems for future work in this area.

L'émergence des transformateurs piézoélectriques coïncident avec le développement dans les années 1950 des céramiques ferroélectriques appartenant à la famille cristalline des pérovskites qui n'ont cessé de s'améliorer depuis. Outre la compacité dont bénéficie ces structures, les transformateurs piézoélectriques offrent des performances remarquables en terme de gain en tension et rendement utiles pour des applications nécessitant une adaptation de tension ou une isolation galvanique, parfaitement dédiés aux applications de faibles puissances à haut rendement. Toutefois, les transformateurs piézoélectriques peuvent être déviés de leurs applications premières. En effet, la dernière décennie a été marquée par l'apparition de générateur de plasma par effet piézoélectrique utilisant principalement des architectures de type transformateur. Pourtant, si quelques applications usuelles illustrent parfaitement cette interaction, la compréhension des phénomènes physiques qui en sont à l'origine reste à approfondir. L'objectif de cette thèse est d'en expliquer les fondements par une approche méthodique. Ce travail s'articule autour de plusieurs étapes comprenant la mise en oeuvre d'une méthode systématique de la modélisation analytique d'un transformateur piézoélectrique, de l'étude de la carte de champ produit par un transformateur ainsi qu'une étude expérimentale vue des bornes en guise de premières investigations. La modélisation analytique est basée sur l'exploitation du Principe de Moindre Action (PMA). A partir de la théorie linéaire de la piézoélectricité, un modèle général applicable à toutes les géométries de transformateur, exploitant des modes de couplage piézoélectrique multiples, est proposé. Son caractère multimodal est par ailleurs mis en exergue. Cette modélisation est appliquée à une structure classique de transformateur piézoélectrique de type Rosen et les résultats obtenus sont validés d'une part par une identification numérique, issue d'un logiciel de calcul par éléments finis, et d'autre part par une caractérisation expérimentale. La modélisation analytique précédente ne tient pas compte dans sa mise en oeuvre de l'influence de l'environnement dans lequel évolue le transformateur piézoélectrique. Afin de caractériser le potentiel électrique produit, un modèle numérique 2D du champ électrique environnant est proposé selon la méthode des différences finies. Ce modèle est basé sur une extension du modèle analytique précédemment développé incluant les pertes mécaniques afin de quantifier le potentiel électrique de surface. Même si l'influence du plasma est négligée en première approximation, la modélisation permet de mettre en lumière les zones de fort champ correspondant aux zones de décharges luminescentes observées expérimentalement. Finalement, afin de valider le concept de générateur de plasma piézoélectrique, une caractérisation vue des bornes du transformateur piézoélectrique de type Rosen a été entreprise. Une étude systématique du déclenchement de la décharge plasma en fonction du niveau de tension et de la pression environnante a été menée. Cette part expérimentale de l'étude constitue une approche pionnière pour qualifier le comportement électromécanique du transformateur et a ainsi permis de mettre en évidence des comportements non linéaires issus de ce mode de fonctionnement atypique qu'est la génération de décharges de surface par effet piézoélectrique.