International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Modern aircraft and space vehicles routinely sense and record vast quantities of information relevant to assessing the vehicles’ health. However, limitations imposed by the bandwidth of telemetry and network connections prevent real-time transmission of the complete data set to central stations for analysis. An online health-management system suitable for bandwidth-limited network environments that enables interrogation of the full data set by ground-based operators is described. The system uses distributed objects organized in a data processing hierarchy linked by a buffered data-management subsystem. Reduced health information is routinely transmitted, but dynamic reports may be requested on demand from any object.

The text of the thesis deals with controlling, monitoring, tracking and analyzing an individual's online activities by another person and the influence of this Internet behavior on its reflection in reality. The theoretical part deals with relevant issues from the field of ethics, psychology, theory of computer communication and theory of privacy and technological supervision. The practical part is focused on qualitative analysis of behavior of individuals living in long distance relationships and their strategies for using new media as a means to control the activity of their faraway partner.

This paper introduces ideas and methods for testing for structural change in linear regression models and presents how these have been realized in an R package called strucchange. It features tests from the generalized fluctuation test framework as well as from the F test (Chow test) framework. Extending standard significance tests it contains methods to fit, plot and test empirical fluctuation processes (like CUSUM, MOSUM and estimates-based processes) on the one hand and to compute, plot and test sequences of F statistics with the supF, aveF and expF test on the other. Thus, it makes powerful tools available to display information about structural changes in regression relationships and to assess their significance. Furthermore it is described how incoming data can be monitored online. / Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"

The classical approach to testing for structural change employs retrospective tests using a historical data set of a given length. Here we consider a wide array of fluctuation-type tests in a monitoring situation - given a history period for which a regression relationship is known to be stable, we test whether incoming data are consistent with the previously established relationship. Procedures based on estimates of the regression coefficients are extended in three directions: we introduce (a) procedures based on OLS residuals, (b) rescaled statistics and (c) alternative asymptotic boundaries. Compared to the existing tests our extensions offer better power against certain alternatives, improved size in finite samples for dynamic models and ease of computation respectively. We apply our methods to two data sets, German M1 money demand and U.S. labor productivity. / Series: Report Series SFB "Adaptive Information Systems and Modelling in Economics and Management Science"

Orientadores: Matthieu Tubino, Glauco Favilla Bauerfeldt / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-22T16:02:39Z (GMT). No. of bitstreams: 1 RochaJunior_JoseGeraldo_D.pdf: 3381652 bytes, checksum: a5f7a7055b03e667d7fafb7571329b76 (MD5) Previous issue date: 2013 / Resumo: O biodiesel é comumente produzido pela transesterificação dos triglicerídeos com o metanol (metanólise) empregando catalisadores alcalinos. Neste trabalho foi investigada a atividade catalítica do NaOCH3, KOCH3, NaOH e do KOH na metanólise do óleo de soja nas temperaturas de 30 à 60 °C, sob agitação de 400 rpm. O progresso desta reação foi monitorado pelas medidas do índice de refração utilizando um refratômetro portátil digital, ao qual foi acoplado uma peça cônica de Teflon® para permitir o monitoramento online das amostras em fluxo contínuo. O método proposto é simples, rápido, barato, não-destrutivo e não requer pré-tratamento complexo. Foi observado que a etapa de mistura dos reagentes consome grande parte do tempo necessário para a conversão. A lei de velocidade da metanólise pôde ser bem representada por uma cinética de ordem zero, com a reação ocorrendo na interface da mistura metanol/óleo. Os catalisadores contendo o potássio promoveram reações mais rápidas do que os seus análogos de sódio, sugerindo que um mecanismo de reação envolvendo a participação de pares iônicos de metóxidos alcalinos como catalisadores seria mais adequado para representar a metanólise do que aquele catalisado pelos íons metóxidos. Em comparação aos metóxidos alcalinos, nas reações em que se empregaram os hidróxidos as suas velocidades são menos sensíveis à variação da temperatura. Neste caso, os sabões formados com os hidróxidos poderiam estar amenizando a influência da temperatura na difusão dos reagentes fazendo com que a velocidade da reação seja menos afetada. A água parece atuar como um inibidor desta reação, por inativação do catalisador, o que se reflete na menor velocidade observada nas reações com os hidróxidos frente às com os metóxidos. Entretanto isto não é percebido à baixas temperaturas, quando o efeito difusional é predominante / Abstract: Biodiesel is commonly produced by the transesterification of triglycerides with methanol (methanolysis) using alkaline catalysts. In this work we investigated the catalytic activity of NaOCH3, KOCH3, NaOH and KOH in methanolysis of soybean oil at temperatures of 30 to 60 °C, under 400 rpm agitation. The progress of the reaction was monitored by measuring the refractive index using a portable digital refractometer, to which was attached a piece conical Teflon® to allow online monitoring of samples at continuous flux. The proposed method is simple, fast, inexpensive, non-destructive and not requires complex pretreatment. It was observed that the step of mixing the reactants consumes much of the time required for conversion. The rate law of methanolysis can be represented by a zero-order kinetics, with the reaction occurring at the interface of methanol / oil. The catalysts containing potassium promoted reactions faster than its analogs sodium, suggesting that a reaction mechanism involving the participation of ionic pairs of alkaline methoxides would be more suitable to represent the methanolysis than that catalyzed by ions methoxides. In reactions that utilized hydroxides their speeds are less sensitive to temperature variation than the alkaline methoxides. In this case, the soaps formed with the hydroxides could be decreasing the influence of temperature on diffusion of the reactants so that the reaction rate is less affected. The water seems to act as an inhibitor of this reaction by inactivation of the catalyst, which is reflected in the lower velocity observed in reactions with hydroxides towards methoxides. However this is not observed at lower temperatures, when the diffusion effect is predominant / Doutorado / Quimica Analitica / Doutor em Ciências

Online monitoring supports plant reliability and performance management by providing real time information about the condition of equipment. However, the intricate geometries and harsh operating environment of coal fired power plant boilers inhibit the ability to do online measurements of all process related variables. A low-cost alternative lies in the possibility of using knowledge about boiler operation to extract information about its condition from standard online process measurements. This approach is evaluated with the aim of enhancing online condition monitoring of a boiler’s convective pass heat exchanger network by respectively using a soft sensor and a data-driven method. The soft sensor approach is based on a one-dimensional thermofluid process model which takes measurements as inputs and calculates unmeasured variables as outputs. The model is calibrated based on design information. The data-driven method is one developed specifically in this study to identify unique fault signatures in measurement data to detect and quantify changes in unmeasured variables. The fault signatures are initially constructed using the calibrated one-dimensional thermofluid process model. The benefits and limitations of these methods are compared at the hand of a case study boiler. The case study boiler has five convective heat exchanger stages, each composed of four separate legs. The data-driven method estimates the average conduction thermal resistance of individual heat exchanger legs and the flue gas temperature at the inlet to the convective pass. In addition to this, the soft sensor estimates the average fluid variables for individual legs throughout the convective pass and therefore provides information better suited for condition prognosis. The methods are tested using real plant measurements recorded during a period which contained load changes and on-load heat exchanger cleaning events. The cleaning event provides some basis for validating the results because the qualitative changes of some unmeasured monitored variables expected during this event are known. The relative changes detected by both methods are closely correlated. The data-driven method is computationally less expensive and easily implementable across different software platforms once the fault signatures have been obtained. Fault signatures are easily trainable once the model has been developed. The soft sensors require the continuous use of the modelling software and will therefore be subject to licencing constraints. Both methods offer the possibility to enhance the monitoring resolution of modern boilers without the need to install any additional measurements. Implementation of these monitoring frameworks can provide a simple and low-cost contribution to optimized boiler performance and reliability management.

The target of this work is the development of a monitoring system for 3D printing by the Fused Deposition Modeling method, which will be able to identify printing error conditions. During the solving process the needed error conditions were identified. Then, an algorithm was programmed to identify the error condition using the criterion. The resulting Monitoring Hardware was implemented in the printer and experimentally verified. A system has been developed that can identify error conditions with an accuracy of 94.7%. The main benefit of this work is the automatic identification of error conditions that stop printing if necessary. This leads to a reduction in scrap and cost savings. In the future, the software could automatically adjust the print parameters when identifying an error condition. This would prevent or completely eliminate the error condition without user intervention.

In comparison with Si-based converters, the emerging Medium Voltage (MV) SiC-based converters can achieve higher blocking voltage capability, lower on-resistance, faster switching speed with less switching related losses and run under higher temperature. Thus, theoretically, it can achieve much higher power density, which becomes very promising for future power transmission and distribution. However, in order to achieve the desired high power density, insulation system of the MV SiC-based converter must be compact. Therefore, challenges for the insulation system gradually appeared, as the insulation size becomes smaller and the Electric field (E-field) intensity significantly increases. Under such high E-field intensity, it is necessary and important to eliminate Partial Discharge (PD) for such power converters, since the converter system is vulnerable to PDs. Developing an insulation design, assessment and online monitoring method to help reach a compact and PD free insulation system for MV SiC-based converters is a goal of this work. General insulation design and assessment guidelines based on experimental PD investigation and physics-based model –Experimental PD investigation is completed for internal void discharge, surface discharge, and point discharge representative coupons under square excitations. Based on the data and the existing knowledge about PD mechanisms, widely accepted PD models are selected. Using these physics-based models, simulation results can demonstrate the major features observed in the experiments. With the experimental data and valid PD models, several general insulation design and assessment guidelines are proposed, which could be further applied during converter prototypes development. Partial Discharge elimination methodology and design examples – By using the laminated bus as the design example, internal void evaluation and analysis method is demonstrated. Then, targeting the internal PD-free design with reasonable insulation thickness, several insulation improvement methods are applied and experimentally verified by using representative coupons. After understanding the possible ways for evaluating and eliminating internal voids, a PCB-based planar bus is designed and fabricated, which shows great insulation improvement after experimental verification. In order to eliminate PDs in the air and shrink the insulation distance, three ways for managing E-field distribution in air are demonstrated by three examples. First, by using the interconnections among the power modules, Rogowski-based current-sensing board, and the laminated bus as an example, E-field distribution can be estimated by Finite Element Analysis (FEA) and its management can be achieved by geometrical modifications. Second, for the one-turn inductor, a methodology is demonstrated that builds a coaxial insulation structure with proper termination technology in order to squeeze air out of the insulation system. Finally, E-field shielding technology is applied along the heatsink edges in order to make the E-field distribution uniform and to shrink the insulation distance between the heatsink and the cooling system. After improving the insulation, this work shrinks the converter unit size by around 50% while maintaining its PD-free status under normal operation conditions. Besides the significant increase in power density and weight reduction, the entire converter system has less ringing and better current-sharing performance due to reductions of the parasitic inductance. Partial Discharge online monitoring via acoustic and photon detection methods –Targeting the online monitoring and even localization of surface discharge for power converter applications, two novel types of sensors have been proposed and fabricated. In order to verify the concepts, one example with experimental results has been given for each type of sensor. The experimental data demonstrates that such sensors can be placed inside the converter and online monitoring can be realized for surface or corona discharges by capturing either the acoustic signal or the photons that are generated by discharge events. / Doctor of Philosophy / A unproper designed insulation system can take more than 50% volume of Medium Voltage (MV) SiC-based converters and have significant internal or external Partial Discharge (PD), which can not only accelerate the insulation aging but also risk to multiple aspects of the converter system. Therefore, developing an insulation design, assessment and online monitoring method to help reach a compact and PD free insulation system for MV SiC-based converters is a goal of this work. Experimental PD investigation is completed for internal void discharge, surface discharge, and point discharge representative coupons under square excitations. Several general insulation design and assessment guidelines are proposed based on the experimental PD investigation and physics-based explanations, which are further applied during converter prototypes development. Then, PD elimination methodology is developed and demonstrated by design examples. By using the laminated bus as an example, internal void evaluation and analysis method is demonstrated. Then, targeting the internal PD-free design with reasonable insulation thickness, several insulation improvement methods are applied and experimentally verified by using representative coupons. In order to eliminate PDs in air and shrink the insulation distance, three ways for managing E-field distribution in air are demonstrated by three examples. First, by using the interconnections among the power modules, Rogowski-based current-sensing board, and the laminated bus as an example, E-field distribution can be estimated by Finite Element Analysis (FEA) and its management can be achieved by geometrical modifications. Second, for the one-turn inductor, a coaxial insulation structure with proper termination technology in order to squeeze air out of the insulation system is demonstrated. Finally, E-field shielding technology is applied along the heatsink edges in order to make the E-field distribution uniform and to shrink the insulation distance between the heatsink and the cooling system. After improving the insulation, this work shrinks the converter unit size by around 50% while maintaining its PD-free status under normal operation conditions. Besides the significant increase in power density and weight reduction, the entire converter system has less ringing and better current-sharing performance due to reductions of the parasitic inductance. Targeting the PD online monitoring for power converter applications, two novel types of sensors have been proposed and fabricated. In order to verify the concepts, one example with experimental results has been given for each type of sensor. The experimental data demonstrates that such sensors can be placed inside the converter and online monitoring can be realized for surface or corona discharges by capturing either the acoustic signal or the photons that are generated by discharge events.

Nos dias atuais, há muitos casos em que sistemas de potência estão operando perto dos seus limites de estabilidade devido a restrições econômicas e leis ambientais. A estabilidade de tensão é uma matéria de muita pesquisa e interesse devido a que é considerado como uma das maiores ameaças na segurança dos sistemas. Uma prevenção exitosa de colapso do sistema baseia-se na precisão do método, a simplicidade dos índices, e muito baixo tempo de computação. Este trabalho apresenta uma rede Perceptron Multicamada (PMC) como proposta para monitoramento em tempo real da estabilidade de tensão de sistemas de potência usando como principais dados de entrada medidas obtidas do sistema SCADA. Os dados de treinamento são obtidos com cálculos de fluxo de potência continuado. A rede Perceptron Multicamadas é apresentada como um aproximador universal de funções, que diminui o tempo computacional dos métodos convencionais como o fluxo de potência continuado. Por fim, a topologia da rede PMC proposta é avaliada com o sistema de 30 barras do IEEE, e os resultados em relação ao tempo de computação e precisão são comparados com o método de fluxo de potência continuado. / Nowadays, many power systems are operating near their limits of stability due to economic restrictions and environmental laws. Voltage stability is a subject of great interest because it is considered one of the greatest threats for power systems security. The keys to preventing blackouts are the accuracy of the method, speed indication, and low computation time. This work presents a Multi-layer Perceptron (PMC) network as a proposal for real-time monitoring of voltage stability in power systems using input data obtained from the SCADA system. The training data are obtained by running Continuation Power Flow (CPF) routine. The multi-layer Perceptron network is presented as a universal approximator, reducing the computation time of conventional methods such as the Finally, the proposed PMC network is evaluated in the IEEE 30-bus system. Computation time and accuracy are compared with the continuation power flow method.

Nos dias atuais, há muitos casos em que sistemas de potência estão operando perto dos seus limites de estabilidade devido a restrições econômicas e leis ambientais. A estabilidade de tensão é uma matéria de muita pesquisa e interesse devido a que é considerado como uma das maiores ameaças na segurança dos sistemas. Uma prevenção exitosa de colapso do sistema baseia-se na precisão do método, a simplicidade dos índices, e muito baixo tempo de computação. Este trabalho apresenta uma rede Perceptron Multicamada (PMC) como proposta para monitoramento em tempo real da estabilidade de tensão de sistemas de potência usando como principais dados de entrada medidas obtidas do sistema SCADA. Os dados de treinamento são obtidos com cálculos de fluxo de potência continuado. A rede Perceptron Multicamadas é apresentada como um aproximador universal de funções, que diminui o tempo computacional dos métodos convencionais como o fluxo de potência continuado. Por fim, a topologia da rede PMC proposta é avaliada com o sistema de 30 barras do IEEE, e os resultados em relação ao tempo de computação e precisão são comparados com o método de fluxo de potência continuado. / Nowadays, many power systems are operating near their limits of stability due to economic restrictions and environmental laws. Voltage stability is a subject of great interest because it is considered one of the greatest threats for power systems security. The keys to preventing blackouts are the accuracy of the method, speed indication, and low computation time. This work presents a Multi-layer Perceptron (PMC) network as a proposal for real-time monitoring of voltage stability in power systems using input data obtained from the SCADA system. The training data are obtained by running Continuation Power Flow (CPF) routine. The multi-layer Perceptron network is presented as a universal approximator, reducing the computation time of conventional methods such as the Finally, the proposed PMC network is evaluated in the IEEE 30-bus system. Computation time and accuracy are compared with the continuation power flow method.