La cartographie de potentiel est couramment utilisée afin de détecter les zones de corrosion à risque dans les ouvrages en béton armé. Cette méthode utilise une électrode de référence positionnée à la surface du béton afin de mesurer la différence de potentiel entre un point à la surface du béton et une connexion au réseau d'armatures. Toutefois, il existe deux inconvénients majeurs à cette technique : la connexion au treillis d'armatures qui nécessite d'y avoir accès et la vérification de sa continuité électrique dans la zone de mesure. Dans le but de ne plus être soumis à ces inconvénients, une nouvelle méthode est proposée. Au lieu de se connecter au treillis, une seconde électrode de référence est utilisée, elle aussi positionnée à la surface du béton étudié. Cette configuration de mesure ne donne plus des potentiels électriques, mais des gradients de potentiel entre les deux électrodes de mesure. Par la mise en place de simulations numériques et d'essais expérimentaux, cette configuration de mesure est étudiée. En ce qui concerne le travail expérimental, deux dalles de béton armé de 3x3x0,15m ont été coulées afin d'être proche des conditions rencontrées sur site. Ensuite que des zones corrodées, dont la taille est contrôlée, sont créées de manière accélérée à l'aide d'un dispositif de migration de chlorures. L'épaisseur d'enrobage de la dalle ayant une influence sur les mesures, il a été choisi de couler deux dalles. La première dalle comporte un treillis dont l'épaisseur d'enrobage est constante alors que la seconde dalle possède une épaisseur d'enrobage variable. En ce qui concerne la modélisation, une étude paramétrique utilisant la méthode des éléments finis est réalisée. Cette modélisation permet l'étude de l'influence de nombreux paramètres tels que la résistivité, la taille de la zone corrodée, l'épaisseur d'enrobage, le procédé de mesure, etc. C'est l'analyse des courants d'échange, mais aussi des cartographies de potentiels et de gradients de potentiel qui permettent la corrélation entre les résultats expérimentaux et de simulation. C'est alors qu'il est possible de conclure sur la faisabilité de cette méthode et de ses avantages par comparaison avec la mesure classique. / Half-cell potential mapping is commonly used to detect corrosion risks in reinforced concrete structures. This method uses a reference electrode positioned on the surface of concrete for measuring potential difference by using a voltmeter connected to the reinforcement. However, there are two major drawbacks in the implementation of this method: the necessity to make an electrical connection to the reinforcement and the electrical continuity of this reinforcement. In order to overcome these disadvantages, a new method is proposed. Instead of using electrical connection to rebar, a second reference electrode is used, also positioned on the surface. These two electrodes configuration gives the electrical potential gradient on the concrete surface. By performing both experimental work and numerical modelling this method configuration is tested. For experimental work, two reinforced concrete slabs (3x3x0.15 meter sized) were cast to be close to actual structural conditions. The corroded areas are created with an accelerated method, using the migration of chloride ions. Corrosion size and localisation are controlled during the experiment. The thickness of the concrete cover has an influence on the measures, for this reason in the first slab reinforcement depth is fixed, while it is variable in the second slab. Concerning modelling, a parametric study using a finite element model is performed. This model allows the study of the influence of several parameters such as resistivity, corroded area size, concrete cover and also the measurement process. It is the analysis of the corrosion current, as well as potential mapping that allows the correlation between the experimental and modelling results. Discussion of both results concludes on the feasibility of this method and confirms its benefits compared to the usual half-cell potential mapping.

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Made available in DSpace on 2014-10-09T12:23:45Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:57:00Z (GMT). No. of bitstreams: 1 00886.pdf: 3186592 bytes, checksum: 02aa449d230c78ebeaa2a6f79a1c56d9 (MD5) / Dissertacao (Mestrado) / IEA/D / Instituto de Quimica, Universidade de Sao Paulo - IQ/USP

The Earth's polar ionosphere is a highly dynamic region of the upper atmosphere, and acts as the closure of the greater magnetospheric current system. This region plays host to many electrodynamic effects that impact terrestrial systems, such as power grids, railroads, and pipelines. These effects are fundamentally related to the currents, electric fields, and conductivity present in the polar ionosphere. Understanding and predicting the electrodynamics of this region is vital to being able to determine the physical impacts on terrestrial systems and provide predictions to government and commercial entities. Empirical models play a key role in the research and forecasting of the solar wind and interplanetary magnetic field's impact on the polar ionosphere, and is an active area of development and research. Recent interest in polar ionospheric conductivity has led to a community-wide campaign to develop our understanding of this portion of the electrodynamic system. Characterizing the interactions between the solar wind and the polar ionosphere is a difficult task, as the region of interest is highly data starved in many respects. In particular, satellite based data products are scarce due to being costly and logistically difficult. Recent advancements in data sources (such as the Swarm and CHAMP satellite missions) as well as continued research into the physical relationships between solar wind and interplanetary magnetic field drivers have provided the opportunity to develop new, novel tools to study this region of interest. In this dissertation, two polar ionosphere models are described in Chapters 3 and 4, along with the original research that their construction has produced in Chapter 1. These two models are combined to provide a foundation for future research in this area, which is described in Chapter 5. / Doctor of Philosophy / The Earth is subjected to a constant bombardment of solar particles and magnetic fields, known as the solar wind. Our planet’s geomagnetic field protects the atmosphere from this bombardment, and directs the plasma from the solar wind into the magnetic poles of the earth. This plasma flows through a region of the atmosphere called the ionosphere, where its energy is then dissipated. This energy has many impacts on the surface of the planet, including driving currents in power grids and generating auroral displays. The polar ionosphere is the fundamental connection between the solar wind and the planet, and being able to predict how and where this connection occurs is vital to studying its nature. This work describes two models of the plasma properties in the polar ionosphere, and provides some description of the original research that these models have garnered.

ABSTRACT EFFECTIVENESS OF CONCEPTUAL CHANGE INSTRUCTION ON OVERCOMING STUDENTS&#039 / MISCONCEPTIONS OF ELECTRIC FIELD, ELECTRIC POTENTIAL AND ELECTRIC POTENTIAL ENERGY AT TENTH GRADE LEVEL VATANSEVER, Orhan MS, Department of Secondary Science and Mathematics Education Supervisor: Dr. Mehmet Sancar December 2006, 107 pages The purpose of this study was to investigate the effectiveness of the conceptual change text based instruction over traditionally designed physics instruction to overcome tenth grade students&amp / #8217 / misconceptions on electric field, electric potential and electric potential energy concepts. To provide conceptual change, conceptual change texts (CCT) were developed by the researcher. An Electric Potential and Electric Potential Energy Concept Test (EPEPECT) which consists of 10-items was developed and used to examine students&amp / #8217 / probable misconceptions. Physics Attitude Scale (PATS) was administered to the students to obtain valid information concerning how conceptual change text based instruction effect students&amp / #8217 / attitudes toward physics. The subjects of this study included two tenth grade level classes from TED Ankara College Private High School in Ankara, Turkey, and a total of 37 students&amp / #8217 / scores were used for the statistical analysis. Students from one of the classes that were randomly assigned participated in traditional instruction and referred as the control group. Students from the other class participated in CCT based instruction and referred as the experimental group. EPEPECT and PATS had been administrated to both groups on two different occasions as pretest and posttest. According to the results of the study, statistically significant differences were found between conceptual change instruction and traditional method. Students taught with CCI showed a better scientific conception related to electric field, electric potential and electric potential energy and elimination of misconceptions than the students taught with traditionally designed physics instruction (TDPI). However, CCI did not increase the students&amp / #8217 / attitudes toward physics as school subject more than TDPI did. That is, conceptual change instruction was not effective in improving positive attitudes toward physics.

No description available.

Anisotropic thermoelectric effects can be measured in certain materials. Anisotropy can also be simulated using a repeated, layered structure of two materials cut at an angle. Various aspect ratios and angles of inclination are investigated in device geometry in order to maximize the thermopower. Eddy currents have been shown to occur in thermoelectric devices, and evidence of these currents are revealed in finite element analysis of the artificially synthesized anisotropic Peltier effect.

No description available.

The electric potential changes under uniaxial loading in some minerals and rocks have long been recognized. To daylight the electrical response of some minerals and rocks against applied stress, both theoretical studies and laboratory experiments are conducted. Some theories are also proposed by different researchers, in order to explain the electric potential variations. However, the mechanisms leading to electrical potential generation have not been fully explained yet. In the explanation of electric potential changes observed in rocks, type of the observed rock and the rock forming minerals in the rock fabric play an important role. One theory is based on the fundamentals of piezoelectricity only. However the relation between the stress state and the electric generation is not fully understood. This thesis aims to make a further contribution to the studies on understanding the electric potential change in rocks, containing quartz, which is a common piezoelectric mineral, under uniaxial loading conditions. Three types of rocks, namely quartz-sandstone, granite and granodiorite, are tested, and the stress and electric potential (EP) variations are recorded during the uniaxial loading experiments in a continuous manner. The experiments are conducted at three different loading rates, in order to investigate the effect of loading rate on the electrification mechanism. Also step loading experiments are conducted. Results indicated that, application of uniaxial stress creates a clear change in the EP responses of three quartz bearing rock types. The possible relationships between the EP generation and the level of applied stress are investigated based on the initial and final potential values (EPinitial, EPfinal), the potential just before the time of failure (EPUCS), the spike-like potential jump at the time of failure (&amp / #8710 / V), which are derived from the recorded data of the experiments.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O objetivo do presente trabalho é comparar, do ponto de vista elétrico, a membrana do neurônio ganglionar com a da célula de neuroblastoma, analisando os efeitos das cargas fixas sobre o potencial elétrico nas superfícies da bicamada lipídica e também sobre o comportamento do perfil de potencial através da membrana, considerando as condiçõesfísico-químicas do estado de repouso e do estado de potencial de ação. As condições para a ocorrência dos referidos estados foram baseadas em valores numéricos de parâmetros elétricos e químicos, característicos dessas células, obtidos na literatura. O neurônio ganglionar exemplifica um neurônio sadio, e a célula de neuroblastoma, que é uma célula tumoral, exemplifica um neurônio patológico, alterado por esta condição. O neuroblastoma é um tumor que se origina das células da crista neural (neuroblastos), que é uma estrutura embrionária que dá origem a muitas partes do sistema nervoso, podendo surgir em diversos locais do organismo, desde a região do crânio até a área mais inferior da coluna. O modelo adotado para simular a membrana de neurônio inclui: (a) as distribuições espaciais de cargas elétricas fixas no glicocálix e na rede de proteínas citoplasmáticas; (b) as distribuições de cargas na solução eletrolítica dos meios externo e interno; e (c) as cargas superficiais da bicamada lipídica. Os resultados que obtivemos mostraram que, nos estados de repouso e de ação, os potenciais superficiais da bicamada interno (ÁSbc) e externo (ÁSgb) da célula de neuroblastoma não sofrem alteração mensurável, quando a densidade de carga na superfície interna (QSbc) torna-se 50 vezes mais negativa, tanto para uma densidade de carga na superfície externa da bicamada nula (QSgb = 0), como para um valor de QSgb 6= 0. Porém, no estado de repouso, uma leve queda em ÁSbc do neur^onio ganglionar pode ser observada com este nível de variação de carga, sendo que ÁSgb do neurônio ganglionar é mais negativo quando QSgb = 1=1100 e/A2. No estado de ação, para QSgb = 0, o aumento da negatividade de QSbc não provoca alteração detectável de ÁSbc e ÁSgb para os dois neurônios. Quando consideramos QSgb = 1=1100 e/A2, ÁSgb do neurônio ganglionar se torna mais negativo, não se observando variações detectáveis nos potenciais superficiais da célula de neuroblastoma. Tanto no repouso quanto no estado de ação, ÁSgb das duas células não sofre variação sensível com o aumento da negatividade da carga fixa distribuída espacialmente no citoplasma. Já a ÁSbc sofre uma queda gradativa nos dois tipos celulares; porém, no estado de ação, esta queda é mais rápida. Descobrimos diferenças importantes nos perfis de potencial das duas células, especialmente na região do glicocálix. / The aim of our work is to compare, from the electrical point of view, the ganglion neuron membrane with the neuroblastoma cell's membrane, analyzing the effects of fixed charges on the electric potential of the surfaces of the lipidic bilayer and on the behavior of the potential profile across the membrane, considering the physicochemical conditions of the resting state and of the action potential state. The conditions for the occurrence of these states were defined, based on numerical values of electrical and chemical parameters of these cells, obtained in the literature. The ganglion neuron portrays a healthy neuron,and the neuroblastoma cell, which is a tumor cell, represents a pathologic neuron, different from the ganglion cell, due to this condition. A neuroblastoma is a tumor, originated from neural crest cells (neuroblasts), which is an embryonic structure that gives rise to many parts of the nervous system and can arise in various body sites, from the region of the skull all the way to the lower spinal column area.The model used to simulate the neuron membrane includes: (a) the spatial distribution of the fixed electric charges on the glycocalyx and on the network of cytoplasmic proteins; (b) the distribution of the charges in the electrolytic solution of outer and inner resources; and (c) the surface charges of the lipidic bilayer. The results we obtained show that, in the resting and action states, the inner (ÁSbc) and outer (ÁSgb) surface potential of neuroblastoma cells do not change measurably, when the charge density on the inner surface (QSbc) becomes 50 times more negative, for both null charge density on the outer surface (QSgb = 0) and for QSgb 6= 0. However, a slight drop in ÁSbc of a ganglion neuron can be observed with this level of charge variation, but ÁSgb of ganglion neuron is more negative when QSgb = 1=1100 e/A2. At action potential state, for QSgb = 0, the negative increase of QSbc does not measurably change ÁSbc and ÁSgb , for both neurons. When we consider QSgb = 1=1100 e/A2, for the ganglion neuron ÁSgb becomes more negative, with no significant detectable changes in the neuroblastoma cell's surface potentials. At the resting and action states, ÁSgb of both cells does not undergo substantial changes with the negative increasing of fixed charges uniformly distributed in the cytoplasm. However,ÁSbc undergoes a gradual decrease in both cell types, although for the action state, this fall is faster. We discovered important dierences among the potential profile of the two cells, especially in the glicocalyx region.