Dissertations / Theses on the topic 'Modulation solaire'

Le rayonnement cosmique, mis en évidence par Viktor Hess en 1912, est composé de particules chargées, créées et possiblement accélérées dans les restes de supernova, et qui se propagent dans la Galaxie. La mesure des flux du rayonnement cosmique permet de mettre des contraintes sur leurs sources et leur transport, mais aussi de se pencher sur le problème de la matière sombre.C'est pour répondre à ces questions qu'a été construit le détecteur AMS-02, mis en place sur la station spatiale internationale depuis mai 2011. Ce détecteur de haute précision mesure l'ensemble des flux de particules du rayonnement cosmique.Le travail proposé dans cette thèse consiste à estimer le flux de protons avec le détecteur AMS-02. L'accent est mis sur la déconvolution des effets de la réponse en énergie du détecteur sur les flux et sur la caractérisation du flux obtenu à haute énergie (au-dessus de 200 GeV/n) avec la mise en évidence d'une cassure spectrale.D'autre part, le soleil émet un plasma qui interagit avec les particules du rayonnement cosmique, modifiant les flux issus de la propagation dans la Galaxie. Cette modification évolue dans le temps en suivant le cycle d'activité solaire et est appelée modulation solaire. Dans ce cadre, nous avons obtenu une nouvelle détermination robuste des flux interstellaires de protons et d'hélium en nous basant sur les données récentes du rayonnement cosmique (incluant AMS-02). Les niveaux de modulation solaire obtenus sont validés avec une seconde analyse réalisée à partir des données des moniteurs à neutrons, détecteurs au sol, qui permettent d'établir des séries en temps du paramètre de modulation depuis les années 50
Cosmic rays (CR) were discovered by Viktor Hess in 1912. Charged CR are synthesized and supposedly accelerated in supernova remnants, then propagate through the Galaxy. CR flux measurement set constraints on CR sources and propagation, but may also bring answers to the dark matter problem.AMS-02 is a high precision particle physics detector placed on the international space station since may 2011. It measures the CR fluxes of many species.This thesis deals with the proton flux estimation measured by the AMS-02 instrument. The focus is set on the unfolding of the instrument energy response impacting the flux, and on the caracterisation of the high-energy spectral break.The Sun produces a plasma which interacts with CR particles, modifying the flux obtained from galactic propagation. This modification evolves through time following the solar activity cycle, and is denoted solar modulation. In this framework, decolving from this effect, a robust determination of the proton and helium interstellar fluxes is obtained using recent high precision CR data including AMS-02. The associated solar modulation levels are cross-checked with a second estimation taken from neutron monitors (ground based detectors) data, allowing solar modulation time series reconstruction from the 50s

Au cours des 3 dernieres decennies, l'heliosismologie s'est revelee un puissant outil d'investigation de la structure interne du soleil, constituant ainsi le plus grand espoir de tester les modeles d'evolution de l'etoile, et en particulier de resoudre l'enigme des neutrinos. Les spectrometres a resonance permettent d'estimer la vitesse des couches solaires par la mesure du decalage doppler de raies d'absorption. Dans le cas d'observation du disque solaire integre, les fluctuations des profils de raie locaux (dans les regions actives par exemple) contribuent pour une part importante au bruit solaire, notamment dans le domaine des basses frequences ou l'existence des modes de gravite est la plus probable. Afin de reduire cette composante de bruit, le spectrometre golf, embarque a bord de la sonde soho en 1995, permettra une mesure en 4 points dans les raies d1 et d2 du sodium, au lieu de 2 habituellement. Une partie de la these est consacree a l'etude des specifications scientifiques de golf. Le transfert du rayonnement dans la cellule a resonance, cur de la detection, est simule, et quelques tests instrumentaux sont presentes. Deux types de contraintes instrumentales sont etablis, selon les proprietes spectrales des sources de bruit, et les stabilites requises sont estimees. L'autre partie de la these est relative aux resultats de la premiere maquette de golf. Les variations des pentes des profils de raie sont etudiees, et une nouvelle technique d'analyse des oscillations solaires est developpee. Une reduction significative du bruit solaire par rapport aux mesures en 2 points est obtenue pour les periodes d'oscillations superieures a 1 heure

En une heure, la Terre reçoit en énergie solaire l’équivalent d’une année de consommation énergétique mondiale. Pour cette raison, les cellules photovoltaïques qui convertissent des photons en électricité, ont un rôle déterminant à jouer dans la transition énergétique imposée par les changements climatiques. Les cellules solaires sensibilisées par des colorants sont une des technologies émergentes qui ont déjà été utilisées à l’échelle industrielle à travers quelques exemples d’intégration aux bâtiments. Elles représentent une alternative esthétique et peu cher comparée aux cellules à silicium. Ces cellules hybrides dites de « Grätzel » utilisent un semi-conducteur inorganique nanostructuré sur lequel est greffé un colorant qui à l’état photo-excité va injecter des électrons dans l’oxyde. Ce sensibilisateur va être régénéré par un couple redox présent dans un électrolyte ou un transporteur de trous moléculaire qui eux-mêmes vont être régénérés à la contre-électrode. Dans ce contexte, ce travail présente les études réalisées sur certains constituants de la cellule (du semi-conducteur jusqu’au système régénérateur du colorant). La majeure partie de cette thèse concerne la synthèse et la caractérisation avancée de nouveaux semi-conducteurs organiques, des colorants ou des transporteurs de trous moléculaires, et l’étude des relations structure/propriétés. En particulier, le remplacement, la substitution ou la rigidification de groupements présents dans ces structures ont été réalisés et leur influence sur les propriétés des nouvelles molécules a été étudiée. Les colorants synthétisés présentent des maxima de la bande d’absorption à plus faible énergie allant de 440 nm à 610 nm. Les niveaux d’énergie de ces nouveaux matériaux organiques ont été déterminés par voltammétrie cyclique et également calculés et localisés par la chimie quantique. Certains composés ont été étudiés par diffraction des rayons X, par analyse thermogravimétrique ou par calorimétrie différentielle à balayage. Après une complète caractérisation, ces matériaux ont été intégrés dans des dispositifs photovoltaïques à colorants en utilisant un électrolyte liquide pour atteindre des efficacités élevées jusqu’à 9,78 % en utilisant un seul colorant et jusqu’à 10,90 % dans le cas de la co-sensibilisation du TiO2 par deux sensibilisateurs. Certains colorants ont également conduit à des efficacités se situant à l’état de l’art à 7,81 % en remplaçant l’électrolyte liquide par un liquide ionique. De plus, certains colorants dans ces mêmes dispositifs ont présenté une excellente stabilité avec une perte comprise entre 7 et 38 % après 7000 heures d’illumination continue à 1000 W.m-2 à 65 °C. Enfin, des premiers tests ont également été réalisés en dispositifs à l’état solide qui ont conduit à une efficacité 4,5 % avec un transporteur de trous de référence ouvrant de nouvelles perspectives d’application après optimisations. En parallèle, les nouveaux transporteurs de trous synthétisés dans ce travail se sont révélés efficaces en cellules à base de pérovskites
During one hour, the Earth receives solar energy which is equivalent to one year of the world energy consumption. For this reason, photovoltaic cells that convert photons to electricity, have a key role to play in the energetic transition imposed by climate change. Dye-sensitized solar cells are one of the emergent technologies that have already been used at the industrial scale in a few examples of building integrating. They represent an esthetic and low-cost alternative compared to silicon solar cells. These hybrid cells also named « Grätzel cells » use a nanostructured inorganic semi-conductor where a dye is grafted onto the surface and acts as a sensitizer. This dye injects electrons after photo-excitation in the oxide. The dye is regenerated by a redox couple present in a liquid electrolyte or a hole transport material that are themselves regenerated by the counter electrode. In this context, this work presents studies about some of the cell constituents (from the semi-conductor to the dye regenerating system). The major part of this thesis concerns the synthesis and the advanced characterization of organic semi-conductors, dyes or hole transport materials, and the study of the structure/properties relations. In particular, the replacement, the substitution, or the rigidification of some functional groups in these structures were achieved and their influence on the properties of the new molecules were studied. The synthesized dyes present maxima of the absorption band at the lowest energy between 440 nm and 610 nm. Energy levels of the new organic materials were determined by cyclic voltammetry and also calculated and localized using the quantum chemistry. Some of the compounds were studied by X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry. After a complete characterization, these materials were integrated in dye-sensitized photovoltaic devices using a liquid electrolyte to achieve high efficiencies up to 9,78 % using a single dye and up to 10,90 % in the case of the co-sensitization of TiO2 with two dyes. Certain dyes have demonstrated state-of-the-art efficiencies at 7,81 % by replacing the liquid electrolyte by an ionic liquid electrolyte. Moreover, the use of some of the dyes in these last devices was carried out and found to have an excellent stability with a loss of initial efficiency included between 7 % and 38 % after 7000 hours of continuous illumination at 1000 W.m-2 at 65 °C. Finally, first tests were also realized in solid state devices that showed an efficiency of 4,5 % with a reference hole transport material opening new application perspectives after optimizations. In parallel, the new synthesized hole transport materials in this work were effective in perovskite-based cells

This work reports a first attempt to measure the solar neutrino annual
flux modulation due to Earth\'s elliptical orbit with the Borexino detector. Borexino is a real-time calorimetric detector for low energy neutrino spectroscopy located in the underground laboratory of Gran Sasso, Italy. The experiment\'s main focus is the direct measurement of the 7Be solar neutrino flux of all flavors via neutrino-electron scattering in an ultra-pure scintillation liquid. The original goal of this work was to quantify sensitivity of the Borexino detector to a 7% peak-to-peak signal variation over the course of a year and study background stability. A Monte-Carlo simulated sample of the expected variation was prepared in two phases of data acquisition, Phase I that spans from May-2007 to May-2010 and Phase II from October-2011 to September-2012. The data was then fitted in the time domain with a sinusoidal function and analyzed with the Lomb-Scargle fast Fourier transformation in the search for significant periodicities between periods of 0.5 and 1.5 years. The search was performed in the energy window dominated by 7Be, [210; 760] keV, and 60-day bins in the case of the fit and 10-bins for the Lomb-Scargle scan. This work also contains study of the post-purification data of Phase II beyond September-2012 with a prediction for the future sensitivity and justification of the achieved background levels.
Ph. D.

The time-dependent modulation of galactic cosmic rays in the heliosphere is studied by computing intensities using a two-dimensional, time-dependent modulation model. The compound approach of Ferreira and Potgieter (2004), which describes changes in the cosmic ray transport coefficients over a solar cycle, is improved by introducing recent theoretical advances in the model. Computed intensities are compared with Voyager 1 and 2, IMP 8 and Ulysses proton observations in search of compatibility. It is shown that this approach gives realistic cosmic ray proton intensities on a global scale at Earth and along both Voyager spacecraft trajectories. The results show that cosmic ray modulation, in particular during the present polarity cycle, is not just determined by changes in the drift coefficient but is also dependent on changes in the diffusion coefficients. Furthermore, a comparison of computations to observations along the Voyager 1 and Voyager 2 trajectories illustrates that the heliosphere is asymmetrical. Assuming the latter, E > 70 MeV and 133-242 MeV cosmic ray proton intensities along Voyager 1 and 2 trajectories are predicted from 2012 onwards. It is shown that the computed intensities along Voyager 1 can increase with an almost constant rate since the spacecraft is close to the heliopause. However, the model shows that Voyager 2 is still under the influence of temporal solar activity changes because of the relatively large distance to the heliopause when compared to Voyager 1. Along the Voyager 2 trajectory the intensities should remain generally constant for the next few years and then should start to steadily increase. It is also found that without knowing the exact location of heliopause and transport parameters one cannot conclude anything about local interstellar spectra. The effect of a dynamic inner heliosheath width on cosmic ray modulation is also studied by implementing a time-dependent termination shock position in the model. This does not lead to improved compatibility with spacecraft observations so that a time-dependent termination shock along with a time-dependent heliopause position is required. The variation of the heliopause position over a solar cycle is found to be smaller compared to that of the termination shock. The model predicts the heliopause and termination shock positions along Voyager 1 in 2012 at 119 AU and 88 AU respectively and along Voyager 2 at 100 AU and 84 AU respectively.
Thesis (PhD (Space Physics))--North-West University, Potchefstroom Campus, 2013

A two-dimensional (2-D) time-dependent cosmic ray modulation model is used to calculate the modulation of cosmic-ray protons and electrons for 11-and 22-year modulation cycles using a compound approach to describe solar cycle related changes in the transport parameters. The compound approach was developed by Ferreira and Potgieter (2004) and incorporates the concept of propagation diffusion barriers, global changes in the magnetic field, time-dependent gradient, curvature and current-sheet drifts, and other basic modulation mechanisms. By comparing model results with 2.5 GV Ulysses observations, for both protons and electrons, it is shown that the compound approach results in computed intensities on a global scale compatible to observations. The model also computes the expected latitudinal dependence, as measured by the Ulysses spacecraft, for both protons and electrons. This is especially highlighted when computed intensities are compared to observations for the different fast latitude scan (FLS) periods. For cosmic ray protons a significant latitude dependence was observed for the first FLS period which corresponded to solar minimum conditions. For the second, which corresponded to solar maximum, no latitude dependence was observed as was the case for the third FLS period, which again corresponded to moderate to minimum solar activity. For the electrons the opposite occurred with only an observable latitude dependence in intensities for the third FLS period. It is shown that the model results in compatible intensities when compared to observations for these periods. Due to the success of the compound approach, it is also possible to compute charge-sign dependent modulation for 2.5 GV protons and electrons. The electron to proton ratio is presented at Earth and along the Ulysses trajectory. Lastly, it is also shown how the modulation amplitude between solar minimum and maximum depends on rigidity. This is investigated by computing cosmic ray intensities for both protons and electrons, not only at 2:5 GV, but also up to 7:5 GV. A refinement for the compound approach at higher rigidities is proposed.
Thesis (M.Sc. (Space Physics))--North-West University, Potchefstroom Campus, 2011.

Although the quasi-biennial oscillation (QBO) in the equatorial zonal wind is dominantly driven by wave forcing originating in the troposphere, a recent study suggests that certain properties of the QBO may vary slightly on the 11-year solar cycle timescale [Salby and Callaghan, 2000]. Here we report further statistical investigation using both equatorial wind data for levels from 50 to 1 hPa and longterm proxy solar ultraviolet flux time series (10.7-cm solar radio flux and sunspot numbers). Spectral analysis of the solar time series yields evidence for a significant spectral peak at periods between 25 and 30 months, approximately equivalent to the mean QBO period, as had also been noted by earlier authors [Shapiro and Ward, 1962]. Cross-spectral analysis of the 10.7-cm solar radio flux and equatorial zonal wind time series shows significant coherency at the QBO period at all available pressure levels. The phase lag of the wind data relative to the solar flux at the QBO period ranges from 0–1 months near the stratopause (1 hPa) to 20–24 months in the lower stratosphere (50 hPa). The nearly inphase relationship near the stratopause suggests a possible modulation of the QBO at this level by the radiative and photochemical effects of solar ultraviolet variations. The amplitudes of the solar variations at the QBO period tend to be larger under solar maximum than under solar minimum conditions. Composite analysis of the westerly and easterly phases of the equatorial zonal wind shows subtle but consistent differences in the durations of the westerlies and easterlies between solar maximum and minimum conditions.

The Madden-Julian oscillation (MJO), also known as the 30-60day oscillation, is the strongest of the intraseasonal climate oscillations in the tropics and has significant derivative effects on extratropical circulation and intraseasonal climate. It has recently been shown that the stratospheric quasi-biennial oscillation (QBO) modulates the amplitude of the boreal winter MJO such that MJO amplitudes are larger on average during the easterly phase (QBOE) than during the westerly phase (QBOW). A major possible mechanism is the decrease in static stability in the lowermost stratosphere under QBOE conditions resulting from relative upwelling associated with the QBO-induced meridional circulation. Here evidence is presented that tropical upwelling changes related to the 11year solar cycle also modulate the boreal winter MJO. Based on 37.3years of MJO amplitude data, the largest amplitudes and occurrence rates, and the weakest static stabilities in the tropical lower stratosphere, occur during the QBOE phase under solar minimum (SMIN) conditions while the smallest amplitudes and strongest static stabilities occur during the QBOW phase under solar maximum (SMAX) conditions. Conversely, when the QBO and solar forcings are opposed (QBOW/SMIN and QBOE/SMAX), the difference in occurrence rates becomes statistically insignificant. During the coming solar minimum, at least one additional winter in the QBOE/SMIN category should occur (possibly as early as 2017/2018) during which especially large MJO amplitudes are expected and an initial test of these results will be possible. Plain Language Summary An ongoing issue in climate science is the extent to which upper atmospheric processes, including solar forcing, can influence tropospheric climate. It has recently been shown that an internal oscillation of the stratosphere, the quasi-biennial oscillation, can modulate the amplitude and occurrence rate of intraseasonal climate oscillations in the tropical Pacific during northern winter. These intraseasonal oscillations, the most important of which is the 30-60day Madden-Julian oscillation, have significant derivative effects on climate outside of the tropics, including impacts on rainfall events over the continental United States. Here evidence is presented that the amplitude of the Madden-Julian oscillation during northern winter is also modulated by the 11year solar cycle. The modulation is such that amplitudes and occurrence rates are largest under solar minimum conditions when the quasi-biennial oscillation is in its easterly phase and smallest under solar maximum conditions when the quasi-biennial oscillation is in its westerly phase. However, the available time record (37.3years of satellite measurements) is limited. During the coming solar minimum, at least one additional winter in the solar minimum/easterly category should occur (possibly as early as 2017/2018) during which larger-than-average amplitudes are expected and an initial test of the proposed relationship will be possible.

Dans ce travail, nous étudions les propriétés optiques d'hétérostructures III-V par spectroscopie de modulation optique. En particulier, nous nous intéressons au système GaInAs /AlInAs. Dans un premier temps, nous avons développé un ensemble expérimental sensible travaillant dans la gamme 0. 6-1. 8 micromètres et pour des températures variant de 8K à 600K. Nous avons également montré la faisabilité d'un prototype de photoréflectivimètre compact et performant. Nous avons, caractérisé des couches simples d'AlInAs / InP. La réponse de photoréflectivité (PR) nous a permis de mettre en évidence une modulation de composition ainsi et un effet de localisation dans AlInAs. En outre, nous avons déterminé les propriétés fondamentales de puits quantiques de GaInAs / AlInAs : détermination de la discontinuité de bande, qualité des interfaces et du materiau. Enfin, nous avons appliqué cette technique à la mesure de la position du niveau de Fermi de surface dans des structures de type UN+ (couche non dopée / couche dopée n+) AlInAs. Les mêmes types de structures ont été élaborées afin de mesurer le champ piézoélectrique dans un puits contraint de GaInAs / GaAs épitaxié sur un substrat polaire
In this work, we study using modulation spectroscopy the optical properties of III-V semiconductor compounds, especially InAlAs / InGaAs based structures. The first part of the work deals with the development of an experimental set up, whose sensitivity is 10-6. This system works between 8K and 600K, in the spectral range 0. 6 to-1. 8 micrometer. In this part we also show the feasibility of a performing prototype. The second part deals with the characterization of bulk InAlAs / InP layers. Using the temperature dependence of the Photore-flectance (PR) spectra we show the existence of a localization in the InAlAs layer due to some clustering effect. Furthennore, we have studied InGaAs/InAlAs single quantum wells. The PR technique is shown to be a powerful tool to characterize the interface and material quality, interface roughness…, and to give a qualitative determination of conduction band offset in this system. In the last part of this work, we apply the PR in order to measure the surface Fermi level in an InAlAs UN+ ( undoped layer grown on a heavily doped n+ layer) structure. The same structures have been used to measure the piezoelectric field in a InGaAs/GaAs strained SQW grown on a polar <111> GaAs substrate

The solar minimum of 2009 has been identified as an exceptional event with regard to cosmic ray (CR)modulation, since conditions in the heliosphere have reached unprecedented quiet levels. This unique minimum has been observed by the Earth–orbiting satellite, PAMELA, launched in June, 2006, from which vast sets of accurate proton and electron preliminary observations have been made available. These simultaneous measurements from PAMELA provide the ideal opportunity to conduct an in–depth study of CR modulation, in particular charge–sign dependent modulation. In utilizing this opportunity, a three–dimensional, steady–state modulation model was used to reproduce a selection of consecutive PAMELA proton and electron spectra from 2006 to 2009. Thiswas done by assuming full drifts and simplified diffusion coefficients, where the rigidity dependence and absolute value of themean free paths for protons and electrons were sequentially adjusted below 3 GV and 300 MV, respectively. Care has been taken in calculating yearly–averaged current–sheet tilt angle and magnetic field values that correspond to the PAMELA spectra. Following this study where the numerical model was used to investigate the individual effects resulting from changes in the tilt angle, diffusion coefficients, and global drifts, it was found that all these modulation processes played significant roles in contributing to the total increase in CR intensities from 2006 to 2009, as was observed by PAMELA. Furthermore, the effect that drifts has on oppositely charged particles was also evident from the difference between the peak–shaped time profiles of protons and the flatter time profiles of electrons, as is expected for an A < 0 polarity cycle. Since protons, which drift into the heliosphere along the heliospheric current–sheet, haven’t yet reached maximum intensity levels by 2008, their intensities increased notably more than electrons toward the end of 2009. The time and energy dependence of the electron to proton ratios were also studied in order to further illustrate and quantify the effect of drifts during this remarkable solar minimum period.
Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2012.

In the present work, anomalous distortions occurring in the current-voltage characteristic of perovskite solar cells (PSCs), usually called J-V curve hysteresis, are studied by several methods. This includes dynamic direct current (DC) mode J-V experiments and impedance spectroscopy (IS) analyses in dark and under illumination. The J-V curves of PSCs were measured under different conditions showing capacitive hysteretic currents. This is related with low frequency excess capacitance in the IS spectra. These two features are correlated with the response of mobile ions in space charge regions close to the interfaces. The large values of capacitance under illumination in the sub-Hz regime were explained in terms of mobile ions space charges and chemical capacitances assuming a proportionality between the number of ionized/activated mobile ions and the concentration of charge carriers and photon fluence.
En el presente trabajo se estudian por varios métodos las distorsiones anómalas en la característica de corriente-voltaje de las celdas solares de perovskita (PSC), típicamente llamada histéresis de J-V. Esto incluye experimentos dinámicos de J-V en modo de corriente continua (DC) y análisis de espectroscopía de impedancia (IS) en oscuridad y bajo iluminación. Las curvas J-V en oscuridad de las PSCs exhiben corrientes capacitivas, relacionadas con un exceso de capacitancia de baja frecuencia en los espectros de IS. Estas dos características están correlacionadas con la respuesta de iones móviles en regiones espaciales de carga hacia las interfaces. Los grandes valores de capacitancia bajo iluminación a frecuencias por debajo de las unidades de Hz se explicaron en términos de regiones de cargas espaciales de iones móviles y capacitancias químicas, suponiendo una proporcionalidad entre el número de iones móviles ionizados/activados y la concentración de portadores de carga y flujo de fotones.

A time-dependent two-dimensional (2D) modulation model including drifts, the solar wind tennination shock (TS) with diffusive shock acceleration and a heliosheath based on the Parker (1965) transport equation is used to study the modulation of galactic cosmic rays (GCRs) and the anomalous component of cosmic rays (ACRs) in the heliosphere. In particular, the latitude dependence of the TS compression ratio and injection efficiency of the ACRs (source strength) based on the hydrodynamic modeling results of Scherer et al. (2006) is used for the first time in a modulation model. The subsequent effects on differential intensities for both GCRs and ACRs are illustrated, comparing them to the values without a latitude dependence for these parameters. It is found that the latitude dependence of these parameters is important and that it enables an improved description of the modulation of ACRs beyond the TS. With this modeling approach (without fitting observations) to the latitude dependence of the two parameters, it is possible to obtain a TS spectrum for ACRs at a polar angle of B = 55" that qualitatively approximates the main features of the Voyager 1 observations. This positive result has to be investigated further. Additionally, it is shown that the enhancement of the cosmic ray intensity just below the cut-off energy found for the ACR at the TS in an A < 0 magnetic polarity cycle in the equatorial plane with the latitude independent scenario, disappears in this region when the latitude dependence of the compression ratio and injection efficiency is assumed. Subsequent effects of these scenarios are illustrated on the global anisotropy vector of both GCRs and ACRs as the main theme of this work. For this purpose the radial and latitudinal gradients for GCRs and ACRs were accurately computed. The radial and latitudinal anisotropy components were then computed as a function of energy, radial distance and polar angle. It is also the first time that the anisotropy vector is comprehensively calculated in such a global approach to cosmic ray modeling in the heliosphere, in particular for ACRs. It is shown that the anisotropy vector inside (up-stream) and outside (down-stream) the TS behaves in a complicated way, so care must be taken in interpreting it. It is found that the latitude dependence of the two mentioned parameters can alter the direction (sign) of the anisotropy vector. Its behaviour beyond the TS is markedly different from inside the TS, mainly because of the slower solar wind velocity, with less dependence on the magnetic polarity cycles.
Thesis (M.Sc. (Physics))--North-West University, Potchefstroom Campus, 2007.

The K2 mission is targeting large numbers of nearby (d < 100 pc) GKM dwarfs selected from the SUPERBLINK proper motion survey (mu > 40 mas yr(-1), V < 20). Additionally, the mission is targeting low-mass, high proper motion stars associated with the local (d < 500 pc) Galactic halo population also selected from SUPERBLINK. K2 campaigns 0 through 8 monitored a total of 26,518 of these cool main-sequence stars. We used the auto-correlation function to search for fast rotators by identifying short-period photometric modulations in the K2 light curves. We identified 481 candidate fast rotators with rotation periods < 4 days that show light-curve modulations consistent with starspots. Their kinematics show low average transverse velocities, suggesting that they are part of the young disk population. A subset (13) of the fast rotators is found among those targets with colors and kinematics consistent with the local Galactic halo population and may represent stars spun up by tidal interactions in close binary systems. We further demonstrate that the M dwarf fast rotators selected from the K2 light curves are significantly more likely to have UV excess and discuss the potential of the K2 mission to identify new nearby young GKM dwarfs on the basis of their fast rotation rates. Finally, we discuss the possible use of local halo stars as fiducial, non-variable sources in the Kepler fields.

The Alpha Magnetic Spectrometer (AMS-02) is a high-energy particle physics detector operating on the International Space Station (ISS) since May 2011. Since its launch, the AMS-02 provided a large amount of data whose precision was never before achieved, opening a new path for the study of cosmic rays (CRs). The first published results of AMS-021-3 show tension with the current understanding of the cosmic ray theory, particularly at higher energies. These tensions are directly linked to many fundamental questions like the dark matter nature, the CR origin and their propagation through the galaxy. This work presents the measurement of the electron flux and the positron flux in primary cosmic rays, based on the data collected between May 2011 and November 2016, an extended data set with respect to the published AMS-02 results.3 The results extend the energy range explored up to 1 TeV for electrons and up to 700 GeV for positrons, being consistent with the published results when using the same data set. A discrepancy between the new measurement and the published flux is observed in the low energy region of the electron flux, while the positron flux is in good agreement. This can be explained by a charge dependent solar modulation effect. This hypothesis was investigated by studying the time evolution of the fluxes, focusing on the energy region below 40 GeV, where an electron and positron flux is computed over 74 time bins of 27 days width, corresponding to the suns rotation period as seen from the Earth. The time dependent analysis confirms hints of charge dependent solar modulation, that are also observed by other independent analysis that have been carried out in parallel within the collaboration.
O Alpha Magnetic Spectrometer (AMS-02) é um experimento de física de partículas instalado na Estação Espacial Internacional (ISS) desde Maio de 2011. Desde seu lançamento, AMS-02 coleta uma quantidade de dados com tal precisão que até então nunca foram jamais vistos, abrindo o caminho para o estudo dos Raios Cósmicos (CRs). Os primeiros resultados publicados pelo AMS-021-3 apresentam tensões com o modelo atual da teoria de CRs, particularmente nas altas energias. Essas tensões são diretamente ligadas a diversas questões fundamentais como a natureza da Matéria Escura (DM), a origem dos CRs e suas propagações pela galáxia. Este trabalho apresenta a medição do fluxo de elétrons e pósitrons em CRs primários, baseando-se nos dados coletados entre Maio de 2011 e Novembro de 2016, período extendido com relação aos resultados públicados pelo AMS-02.3 Os resultados extendem o intervalo de energia explorado para 1 TeV para elétrons e 700 GeV ára pósitrons, consistentes com os resultados públicados usando o mesmo período. Discrepância entre a nova medição e o fluxo públicado é observada na região de baixas energias para o fluxo de elétrons, enquanto o fluxo de pósitrons continua em bom acordo. O resultado pode ser explicado por uma dependência na carga causada pela modulação solar. Tal hipótese é investigada estudando-se a evolução temporal dos fluxos, focando-se no intervao de energia abaixo de 40 GeV, onde um fluxo de elétrons e pósitrons é medido durante 74 intervalos temporais de 27 dias, correspondendo à rotação do sol vista da Terra. A análise dependente do tempo confirma a existência da dependência de carga da modulação solar, também observada por outras análises independentes que foram feitas dentro da colaboração.

Les preuves pour l'existence de la matière noire (MN), sous forme d'une particule inconnue qui rempli les halos galactiques, sont issues d'observations astrophysiques et cosmologiques: son effet gravitationnel est visible dans les rotations des galaxies, des amas de galaxies et dans la formation des grandes structures de l'univers. Une manifestation non-gravitationnelle de sa présence n'a pas encore été découverte. L'une des techniques les plus prometteuse est la détection indirecte de la MN, consistant à identifier des excès dans les flux de rayons cosmiques pouvant provenir de l'annihilation ou la désintégration de la MN dans le halo de la Voie Lactée. Les efforts expérimentaux actuels se focalisent principalement sur une gamme d'énergie de l'ordre du GeV au TeV, où un signal de WIMP (Weakly Interacting Massive Particles) est attendu. L'analyse des mesures récentes et inédites des rayons cosmiques chargés (antiprotons, électrons et positrons) et leurs émissions secondaires et les améliorations des modèles astrophysiques sont présentées.Les données de PAMELA sur les antiprotons contraignent l'annihilation et la désintégration de la MN de manière similaire (et même légèrement meilleurs) que les contraintes les plus fortes venant des rayons gamma, même dans le cas où les énergies cinétiques inférieures à 10 GeV sont écartées. En choisissant des paramètres astrophysiques différents (modèles de propagation et profils de MN), les contraintes peuvent changer d'un à deux ordres de grandeur. Pour exploiter la totalité de la capacité des antiprotons à contraindre la MN, des effets précédemment négligés sont incorporés et se révèlent être importants dans l'analyse des données inédites de AMS-02 : ajouter les pertes d'énergie, la diffusion dans l'espace des moments et la modulation solaire peut modifier les contraintes, même à de hautes masses. Une mauvaise interprétation des données peut survenir si ces effets ne sont pas pris en compte. Avec les flux de protons et d'hélium exposé par AMS-02, le fond astrophysique et ces incertitudes du ratio antiprotons sur protons sont réévalués et comparés aux données inédites de AMS-02. Aucune indication pour un excès n'est trouvé. Une préférence pour un halo confinant plus large et une dépendance en énergie du coefficient de diffusion plus plate apparaissent. De nouvelles contraintes sur l'annihilation et la désintégration de la MN sont ainsi dérivés.Les émissions secondaires des électrons et des positrons peuvent aussi contraindre l'annihilation et la désintégration de la MN dans le halo galactique : le signal radio dû à la radiation synchrotron des électrons et positrons dans le champs magnétique galactique, les rayons gamma des processus de bremsstrahlung avec le gas galactique et de Compton Inverse avec le champs radiatif interstellaire sont considérés. Différentes configurations de champs magnétique galactique et de modèles de propagation et des cartes de gas et de champs radiatif interstellaire améliorés sont utilisées pour obtenir des outils permettant le calculs des émissions synchrotrons et bremsstrahlung venant de MN de type WIMP. Tous les résultats numériques sont incorporés dans la dernière version du Poor Particle Physicist Coookbook for DM Indirect Detection (PPPC4DMID).Une interprétation d'un possible excès dans les données de rayons gamma de Fermi-LAT au centre galactique comme étant dû à l'annihilation de MN en canaux hadronique et leptonique est analysée. Dans une approche de messagers multiples, le calcul des émissions secondaires est amélioré et se révèle être important pour la détermination du spectre pour le canal leptonique. Ensuite, les limites provenant des antiprotons sur l'annihilation en canal hadronique contraignent sévèrement l'interprétation de cet excès comme étant dû à la MN, dans le cas de paramètres de propagation et de modulation solaire standards. Avec un choix plus conservatif de ces paramètres elles s'assouplissent considérablement
Overwhelming evidence for the existence of Dark Matter (DM), in the form of an unknownparticle filling the galactic halos, originates from many observations in astrophysics and cosmology: its gravitational effects are apparent on galactic rotations, in galaxy clusters and in shaping the large scale structure of the Universe. On the other hand, a non-gravitational manifestation of its presence is yet to be unveiled. One of the most promising techniques is the one of indirect detection, aimed at identifying excesses in cosmic ray fluxes which could possibly be produced by DM annihilations or decays in the Milky Way halo. The current experimental efforts mainly focus in the GeV to TeV energy range, which is also where signals from WIMPs (Weakly Interacting Massive Particles) are expected. Focussing on charged cosmic rays, in particular antiprotons, electrons and positrons, as well as their secondary emissions, an analysis of current and forseen cosmic ray measurements and improvements on astrophysical models are presented. Antiproton data from PAMELA imposes contraints on annihilating and decaying DM which are similar to (or even slightly stronger than) the most stringent bounds from gamma ray experiments, even when kinetic energies below 10 GeV are discarded. However, choosing different sets of astrophysical parameters, in the form of propagation models and halo profiles, allows the contraints to span over one or two orders of magnitude. In order to exploit fully the power of antiprotons to constrain or discover DM, effects which were previously perceived as subleading turn out to be relevant especially for the analysis of the newly released AMS-02 data. In fact, including energy losses, diffusive reaccelleration and solar modulation can somewhat modify the current bounds, even at large DM masses. A wrong interpretation of the data may arise if they are not taken into account. Finally, using the updated proton and helium fluxes just released by the AMS-02 experiment, the astrophysical antiproton to proton ratio and its uncertainties are reevaluated and compared to the preliminarly reported AMS-02 measurements. No unambiguous evidence for a significant excess with respect to expectations is found. Yet, some preference for thicker halos and a flatter energy dependence of the diffusion coefficient starts to emerge. New stringed constraints on DM annihilation and decay are derived. Secondary emissions from electrons and positrons can also be used to constrain DM annihilation or decay in the galactic halo. The radio signal due to synchrotron radiation of electrons and positrons on the galactic magnetic field, gamma rays from bremsstrahlung processes on the galactic gas densities and from Inverse Compton scattering processes on the interstellar radiation field are considered. With several magnetic field configurations, propagation scenarios and improved gas density maps and interstellar radiation field, state-of-art tools allowing the computaion of synchrotron and bremssttrahlung radiation for any WIMP DM model are provided. All numerical results for DM are incorporated in the release of the Poor Particle Physicist Coookbook for DM Indirect Detection (PPPC4DMID). Finally, the possible GeV gamma-ray excess identified in the Fermi-LAT data from the Galactic Center in terms of DM annihilation, either in hadronic or leptonic channels is studied. In order to test this tantalizing interprestation, a multi-messenger approach is used: first, the computation of secondary emisison from DM with respect to previous works confirms it to be relevant for determining the DM spectrum in leptonic channels. Second, limits from antiprotons severely constrain the DM interpretation of the excess in the hadronic channel, for standard assumptions on the Galactic propagation parameters and solar modulation. However, they considerably relax if more conservative choices are adopted

Electrical energy is used at approximately the rate of 15 Terawatts world-wide. Generating this much energy has become a primary concern for all nations. There are many ways of generating energy among which the most commonly used are non-renewable and will extinct much sooner than expected. Very active research is going on both to increase the use of renewable energy sources and to use the available energy with more efficiency. Among these sources, solar energy is being considered as the most abundant and has received high attention. The mobile phone has become one of the basic needs of modern life, with almost every human being having one.Individually a mobile phone consumes little power but collectively this becomes very large. This consideration motivated the research undertaken in this masters thesis. The objective of this thesis is to design a model for solar power based charging circuits for mobile phone using Simulink(R). This thesis explains a design procedure of solar power based mobile charger circuit using Simulink(R) which includes the models for the photo-voltaic array, maximum power point tracker, pulse width modulator, DC-DC converter and a battery. The first part of the thesis concentrates on electron level behavior of a solar cell, its structure and its electrical model.The second part is to design an array of solar cells to generate the desired output. Finally, the third part is to design a DC-DC converter which can stabilize and provide the required input to the battery with the help of the maximum power point tracker and pulse width modulation. The obtained DC-DC converter is adjustable to meet the requirements of the battery. This design is aimed at charging a lithium ion battery with nominal voltage of 3.7 V, which can be taken as baseline to charge different types of batteries with different nominal voltages.

North American porcupine (Erethizon dorsatum) feeding scars on trees were used as an index of past porcupine abundance in the Bas St. Laurent region of eastern Quebec, Canada. The frequency distribution of scars revealed that porcupine populations have fluctuated regularly over the past 130 years in the Bas St. Laurent region, with superimposed periodicities of 11 and 22 years. This porcupine population cycle has closely followed the 11 and 22-year solar activity cycles. An analysis of local temperature and precipitation data revealed a close relationship between fluctuations in annual precipitation and both the solar cycle and the porcupine cycle. These results suggest that the solar cycle has sufficiently important effects on the climate along the southern shore of the St. Lawrence estuary to influence terrestrial ecosystem functioning to the point of setting the rhythm of porcupine population fluctuations. This is the strongest available evidence of a top-down cascading effect of solar variability on ecological systems at the decadal time scale and local spatial scale. These results confirm and extend those obtained by others at greater temporal and spatial scales and provide exciting opportunities for future research on the extensively debated topic of solar variability and its impact on our planet.

In this dissertation, we study the optical property of 2D graded photonic super-crystals (GPSCs) for photon management. We focused primarily on manipulation and control of light by using the newly discovered GPSCs which present great opportunity for electromagnetic wave control in photonic devices. The GPSC has been used to explore the superior capability of improving the light extraction efficiency of OLEDs. The enhancement of extraction efficiency has been explained in term of destructive interference of surface plasmon resonance and out-coupling of surface plasmon through phase matching provided by GPSC and verified by e-field intensity distributions. A large light extraction efficiency up to 75% into glass substrate has been predicted through simulation. We also study the light trapping enhancement in GPSCs. Broadband, wide incident angle, and polarization independent light trapping enhancement is achieved in silicon solar cells patterned with the GPSCs. In addition, novel 2D GPSCs were fabricated using holographic lithography through the interference lithography by two sets of multiple beams arranged in a cone geometry using a spatial light modulator (SLM). Finally, we also report a fabrication of GPSCs with a super-cell size of 12a×12a by using e-beam lithography. Diffraction pattern from GPSCs reveals unique diffraction properties. In an application aspect, light emitting diode arrays can be replaced by a single light emitting diode shinning onto the diffraction pattern for a uniform fluorescence.

Shortage of drinking water in most parts of the world has been a growing concern in recent times. The situation has been getting worse in underdeveloped and developing countries due to sudden explosion in population growth and the growth in the industries. The natural resources for potable water are limited and unless a feasible solution is obtained in the near future, the ‘concern situation’ may turn into a ‘panic situation’. A possible solution for the shortage in drinking water is to use water from inexhaustible sources such as oceans and seas and make it potable using desalination process. However, the process of desalination is an energy intensive process which the poor countries can not afford. In recent times, the cost of fossil fuels has been skyrocketing. With the crude oil costing more than Rs.5200 (US$120) a barrel as on September 2008, even the rich countries like USA and the countries in the European Union are feeling the pinch of the energy cost. Alternate energy sources such as solar, wind, geo-thermal, hydrogen etc., have become the order of the day. These sources are renewable and are environmental friendly. More than one third of the populations of the world live in coastal areas. These areas get abundant amount of solar energy throughout the year. Utilization of this energy in desalination process would solve drinking water problem to a very great extent. However, construction of centralized desalination plants requires large amount of capital which the poor countries can ill-afford. An alternate solution would be to construct decentralized smaller plants that would require smaller capital to construct and easier to maintain. If the energy requirement is tapped from renewable sources such as solar, then the operational cost also becomes affordable for the poor countries. By taking care of the water requirement of the coastal areas through this process, one may save large amounts of money in transporting potable water from interior areas to the coastal areas. There would be enough water for the people living in the interior areas. The water bed level in the interior areas would gradually increase, thereby reducing the drinking water concerns significantly. In this thesis, a small scale stand alone power generation system for the desalination process is proposed that is suitable to provide clean potable water from sources such as sea water or brackish water. Solar energy is proposed as a source of energy for the proposed desalination system. This source is available in plenty in arid and semi-arid areas. It is free and is also friendlier to the environment. It is proposed to use solar energy in thermal form to obtain energy equivalent of ‘latent heat of vaporization’ for the vaporization process and in electrical form for operating the dc machines and electronic control units that are integral parts of the desalination system. The proposed desalination unit can be built as small as possible even to feed a single household’s requirement and hence can be conceptualized as decentralized units. These units would require considerably less capital to build, and would require minimum maintenance. The desalination process is based on flash evaporation wherein a heated liquid is subjected to a pressure reduction by passing through a throttling device resulting in an initially superheated state. In the proposed desalination process, the traditional flash evaporator is extended to include continuous dynamic pressure modulation to obtain an optimal flow rate for a specified energy input. The cost function or the performance index for optimization is defined as the ratio of flow rate to the energy spent. The optimal flow rate occurs at a specific chamber pressure for a given inlet water temperature. By operating at optimal pressure, significant energy is saved for a specific flow rate. This principle is validated experimentally and the results are presented and discussed in the thesis. This proposed scheme along with hybrid energy input will prove to be an attractive solution for community drinking water problem. A system needs to have a mathematical representation in order to predict the dynamic behavior of the system. This thesis proposes the bond graph method of modeling the physical system wherein the energy flow across the electrical, thermal and the hydraulic domains are included. A system may comprise of several subsystems and the energy flow in each subsystem may be in a different domain. A desalination system is such a system wherein the energy flow in subsystems is in different domains such as electrical, thermal and hydraulics. The bond graph approach is best suited for modeling of such systems where the power/energy flow across domains can be easily and seamlessly integrated. The thesis proposes a fifth order dynamic model of a single stage flash evaporation with pressure modulation using the bond graph approach. The proposed model incorporates the effects of chamber pressure variation, the entropy flow from the chamber due to conduction, convection, radiation and also the thermal dynamics of the water bodies in the evaporation, condensation and collection chambers. The proposed model is simulated in MATLAB/Simulink environment. The simulation results are compared with the experimental results to validate the model. This proposed model can be used for both analysis and synthesis of a desalination system. The desalination system is a complex system wherein multiple energy domains are involved. The thesis presents a systematic process for the design of the desalination system. Design of the desalination system involves design of multi domain subsystems. The design becomes much more complex if the energy source to run the system is solar/ hybrid solar based. The energy budget has to be carefully evaluated considering the worst case conditions for the availability of solar energy. Hence, the information on the quantum of solar energy available at any location is a critical parameter needed for design of the desalination system. A generic method of developing a solar insolation model for a specific region such as the Indian sub-continent is proposed in this thesis along with the validation of the model by comparing measured value with the values that are obtained from the model. As the insolation model is dependent on the water vapor content in the vertical column at the location, the methodology is further applied to develop a model for estimating the precipitated water vapor content in a vertical column for any location. The model is validated by comparing the computed values to the measured values. The thesis further presents the design and selection of the balance of the system. The selection of the balance of the system includes sizing of solar thermal plate collectors such as flat plate for pre-heating and paraboloid for vaporization, solar PV panels for operating pumps, actuator and control units, and battery for backup source for night loads and during ‘no-sun days’, criteria of selecting centrifugal pump for circulating condensation water, vacuum pump for dynamic pressure modulation and selecting linear actuator for Sun tracking of the paraboloid concentrator. A discussion on the electronic circuits used in the control scheme is presented in this thesis. This includes the circuit for maximum power point tracking, circuit for DC-DC conversion, circuit for pressure modulation, circuit for speed control of linear actuator, and finally the circuit for water level limiter. A discussion on the life cycle costing is also presented in this thesis. This is an important parameter that refers to the accumulated worth of all the costs related to building and operating the desalination plant during its life span. It is emphasized that the objective of the design process is to minimize the life cycle cost while meeting other performance requirements. Thus, life cycle costing is an essential part of the design cycle. The design methodology and the approach used to design the desalination system are implemented in the form of a toolbox in the MATLAB environment. The various functions of the toolbox are highlighted by a detailed step by step presentation of the design modules in the thesis. The modules form the components of the design toolbox for designing the proposed desalination system.

碩士
國立成功大學
光電科學與工程學系
100
In this study, we prepared the poly(3-hexylthiophene) (P3HT):Indene -C60 Bisadduct (IC60BA) blend films-based polymer bulk heterojunction (BHJ) solar cells by the co-solvent methods. The host solvent was 1,2-dichlorobenzene (DCB), and mixed with dichloromethane (DCM) or chloroform (CF) as co-solvents. For P3HT, DCM and CF are poor and good solvents, respectively. To investigate the effects of co-solvents on microstructure of the active layers, the P3HT:IC60BA films were characterized by absorption spectroscopy, Raman spectroscopy, photoluminescence spectroscopy, atomic force microscopy (AFM) and X-ray diffraction (XRD). The correlation between the microstructural properties of the active layers and photovoltaic properties of the polymer BHJ solar cells was discussed. For the photovoltaic properties of the solar cells made by the DCM:DCB co-solvents with the volume fraction of DCM (fm) was below 50%, we observed that the fill factor (F.F.) decreased when the fm was increased, while increasing short-circuit current density (Jsc) and power conversion efficiency. When the fm is below 50%, the increased in JSC can be attributed to higher absorbance arising from thickness contributions. When the fm is higher than 50 %, however, we observed a reduction in the JSC, reflecting the decreased probability of charge carriers transport to the right electrodes due to largely increasing active layer thickness. Above-motioned observations still hold true for the solar cells made by the CF:DCB co-solvents. Microstructural analysis results revealed that the crystalline P3HT in the P3HT:IC60BA blend films were not affected by changing the composition of the DCM:DCB co-solvents. In contrast, we observed more amorphous P3HT contents and smaller grain size of the films made by the CF:DCB co-solvents, thereby poor carrier transport and increased probability of carrier recombination. This provides a reasonable basis for the lower F.F. and Jsc of the solar cells. Finally, we have demonstrated a P3HT:IC60BA blends-based solar cell with high power conversion efficiency of 5.23 % by using the DCM:DCB co-solvent with fm of 50 %

碩士
國立中興大學
電機工程學系所
102
Optimization the quality of i-layer can improve the optical, structural and electrical properties of a-Si:H p-i-n solar cell. In this thesis, a-Si:H thin-film solar cells were fabricated using 13.56 MHz plasma enhanced chemical vapor deposition (PECVD) technique by modulation initial gas flow for i-layer deposition. Changing the initial gas flow can control the inital plasma chemistry to alter the initial growth of the i-layer. The influence of this change on the performance of a-Si:H p-i-n solar cells were investigated. The initial gas flow control were divided into two modes (a) pre-treatment SiH4 gas flow. This mode was controlled using H2 fill up vacuum chamber to reache the target pressure, then feeding SiH4 gas in a few second before ignition the plasma. (b) Gradually increased SiH4 gas flow. The SiH4 gas flow was gradually increased before and after plasma ignition. The results of pre-treatment SiH4 gas flow showed that the effects of changing the waiting time were no substantial influence on the performance of the solar cells. The results of gradually increasing SiH4 gas flow showed that increasing the waiting and delay time could increase the open-circuit voltage (Voc) and fill factory (FF). Gradually increasing SiH4 gas changed the hydrogen dilution ratio, which had the functions of hydrogen passivation on the surface of the p-layer, and reduction the high dissociation of SiH4 in plasma. The film density could be increased and the defects would be reduced. Increasing the watting and delay time of gradually increasing of SiH4 gas flow could improve the performance of solar cells. The solar cell fabricated by watting time (-79s) and delay time (+104s) could obtain the energy conversion effiency of 7.05 %, Voc of 0.873 V, short-circuit current density of 11.62 mA/cm2, and FF of 69.5 %.

碩士
國立中興大學
光電工程研究所
99
In this study, 13.56 MHz plasma-enhanced chemical vapor deposition (PECVD) with pulse-wave modulation of RF plasma is used to fabricate hydrogenated amorphous silicon (a-Si:H) single i-layer by changing total gas flow, and a-Si:H/hydrogenated protocrystalline silicon (a-Si:H/pc-Si:H) multilayer i-layer by SiH4 pulse-wave adding method of p-i-n silicon thin-film solar cells. 　　The total gas flow of (50, 100, 150 and 200 sccm) is used to fabricate single i-layer of solar cells. Increasing total gas flow, the density of large molecules of Si-related radicals in chamber starts to increase with increasing the supply of SiH4. The deposition of there radicals can induce more defect densities in the film, thus, the ideal factor, fill factor and energy conversion efficiency of solar cells are decreased. Suitable total gas flow shall be carefully selected to obtain high energy conversion efficiency of solar cells. 　　Using SiH4 pulse-wave adding method to fabricate a-Si:H/pc-Si:H multilayer i-layer solar cells, A-sublayer is an a-Si:H film and B-sublayer is a pc-Si:H film, which is deposited by residue of SiH4, and the total gas flow is fixed at 50 and 200 sccm, respectively. The influence of deposition time of B-sublayer on electrical properties of solar cells is investigated. 　　For total gas flow of 50 sccm series, the current density, fill factor and energy conversion efficiency of a-Si:H/pc-Si:H multilayer solar cells are decreased as B-sublayer deposition time increased. The concentration of residue SiH4 in the chamber is gradually decreased and the hydrogen gas flow is constant. Thus, the hydrogen dilution ratio is increased, and the structure of the film is gradually changed from amorphous to protocrystalline structure. The current density, fill factor and energy conversion efficiency of solar cells are decreased as the thickness of B-sublayer with protocrystalline structure increased. 　　For total gas flow of 200 sccm series, due to high flow, the SiH4 residence time is shortened, the B-sublayer thickness is very thin that the structure can not be changed to protocrystalline structure, therefore, the electrical properties of solar cells is less affected by inserting of B-sublayer.

Until recently, numerical modulation models for the solar modulation of cosmic rays have been based primarily on finite difference approaches; however, models based on the solution of an appropriate set of stochastic differential equations have become increasingly popular. This study utilises such a spatially three-dimensional and time-stationary model, based on that of Strauss et al. (2011b). The remarkable numerical stability and powerful illustrative capabilities of this model are utilised extensively and in a distinctly comparative fashion to enable new insights into the processes of modulation. The model is refined to provide for both the Smith-Bieber (Smith and Bieber, 1991) and Jokipii-Kota (Jokipii and Kota, 1989) modifcations to the Parker heliospheric magnetic field (Parker, 1958) and the implications for modulation are investigated. During this investigation it is conclusively illustrated that the Parker field is most conducive to drift dominated modulation, while the Jokipii-Kota and Smith-Bieber modifcations are seen to induce successively larger contributions from diffusive processes. A further refinement to the model is the incorporation of a different profile for the heliospheric current sheet. This profile is defined by its latitudinal extent given by Kota and Jokipii (1983), as opposed to the profile given by Jokipii and Thomas (1981). An extensive investigation into current sheet related matters is launched, illustrating the difference between these current sheet geometries, the associated drift velocity fields and the effect on modulation. At high levels of solar activity, such that the current sheet enters deep enough into the polar regions, the profile of Kota and Jokipii (1983) is found to significantly reduce the effective inward (outward) drifts of positively (negatively) charged particles during A > 0 polarity cycles. The analogous effect is true for A < 0 polarity cycles and the overall effect is of such an extent that the A > 0 and A < 0 solutions are found to coincide at the highest levels of solar activity to form a closed loop. This is a result that has never before been achieved without having to scale down the drift coefficient to zero at solar maximum, as was done by e.g. Ndiitwani et al. (2005). Furthermore, it is found that the drift velocity fields associated with these two current sheet profiles lead to significant differences in modulation even at such low levels of solar activity where no difference in the geometries of these profiles are yet in evidence. The model is finally applied to reproduce four observed galactic proton spectra, selected from PAMELA measurements (Adriani et al., 2013) during the atypical solar minimum of 2006 to 2009; a new proton local interstellar spectrum was employed. The results are found to be in accordance with that found by other authors and in particular Vos (2011), i.e. the diffusion was required to consistently increase from 2006 to 2009 and, in addition, the rigidity dependence below ~ 3 GV was required to change over this time so that the spectra became increasingly softer.
MSc (Space Physics), North-West University, Potchefstroom Campus, 2015

碩士
國立中興大學
電機工程學系所
98
In this thesis, 13.56 MHz plasma-enhanced chemical vapor deposition (PECVD) with pulse modulation of RF plasma is used to fabricate the single-layer, hydrogenated protocrystal silicon/hydrogenated amorphous silicon (pc-Si:H/a-Si:H) multilayer and graded-layer intrinsic films of p-i-n silicon thin film solar cells by constant, periodic and gradual variation of the hydrogen dilution ratio (R = H2/SiH4). Single-layer intrinsic films are deposited by R change from 4 to 28 and fixed the thickness at 300 nm. Pc-Si:H/a-Si:H multilayer intrinsic films are fabricated with R from 6 to 28 for pc-Si:H as A sublayers (fixed at 20 nm), and with R = 4 for a-Si:H as the B sublayers (fixed at 10 nm). The total thickness of the pc-Si:H/a-Si:H multilayer intrinsic film is 300 nm with a period of 30 nm and 10 periods. The a-Si:H to pc-Si:H (or pc-Si:H to a-Si:H) graded-layer intrinsic films are fabricated by gradually change the hydrogen dilution ratio from R = 4 to 28 or R = 28 to 4. The optical band gap of single-layer films is increased, but the absorption coefficient and the film density are decreased as the hydrogen dilution ratio is increased. For pc-Si:H/a-Si:H multilayer films, absorption coefficient and film density are decreased due to the increasing of pc-Si:H layer hydrogen dilution ratio, and the structures gradually change to protocrystal structure. The short-circuit current density, fill factor and energy conversion efficiency of single-layer and pc-Si:H/a-Si:H multilayer intrinsic films solar cells are decreased due to the increasing of hydrogen dilution ratio. For the graded-layer intrinsic film solar cells, increasing the number of grading layers and the total thickness of i-layer can increase the short-circuit current density and the energy conversion efficiency. Single-layer intrinsic film solar cells have high energy conversion, but low stability. The pc-Si:H/a-Si:H multilayer intrinsic film solar cells have high stability. The energy conversion efficiency of graded-layer intrinsic film solar cells are between those of single-layer and pc-Si:H/a-Si:H multilayer intrinsic film solar cell, but its stability compared with single-layer film solar cell is significantly improved. In conclusion, pc-Si:H/a-Si:H multilayer and graded intrinsic films structures can improve the stability of solar cells.

碩士
國立中興大學
電機工程學系所
103
In this thesis, intrinsic hydrogenated amorphous silicon (a-Si:H) thin films i-layers and p-i-n solar cells were fabricated by 13.56 MHz plasma-enhanced chemical vapor deposition (PECVD) with pulse-wave modulation plasma and hydrogen dilution (R = H2/SiH4) methods. The optical properties of dielectric constants (real part: 1 and imaginary part: 2), refractive index (n), extinction coefficient (k), absorption coefficient () and optical energy gap (Eg) of the a-Si:H i layers were measured by spectroscopic ellipsometry (SE). The dark current-voltage (I-V), photo I-V and quantum efficiency (QE) of the a-Si:H p-i-n solar cells were measured by I-V and QE instruments The plasma turn-on time (ton), plasma turn-off time (toff), and the periods of the pulsed-wave plasma was 5 and 10 ms, 1, 5, 10, 20, and 30 ms, and 240000 cycles, respectively. The R ratio was 5 and 10. Modulation R, ton and toff to fabricated a-Si:H i-layers, the variation of  , n,  , and Eg was less than approximately 4.4 %, which indicated that the optical properties of the films were no significantly changed. However, using these a-Si:H i-layers for p-i-n solar cells, the variation of open-circuit voltage (Voc), short-circuit density (Jsc) was within 6 %, and the variation of fill factor (FF) was much higher up to 8 to 11 %. The variation of the energy efficiency was 11 ~ 18%. The most important factor to reduce the efficiency was FF. The small variation of the optical properties of a-Si:H i-layer could not correspond to the large variation of the I-V characteristics. The large variation of FF indicated that the possible reason for reduction of energy efficiency was due to oxygen contamination. Inserting a low oxygen contamination a-Si:H i-layer deposited by short toff time at the p/i interface could improve FF and  of the solar cell. In this study, the highest efficiency solar cell was fabricated by R = 5, ton = 10 ms, toff = 1 ms, and the , FF, Jsc and Voc was 7.12 %, 68 %, 12.53 mA/cm2 and 0.84 V, respectively.

The modulation of galactic cosmic ray (GCR) Carbon in a north-south asymmetrical heliosphere is studied, using a two-dimensional numerical model that contains a solar wind termination shock (TS), a heliosheath, as well as particle drifts and diffusive shock re-acceleration of GCRs. The asymmetry in the geometry of the heliosphere is incorporated in the model by assuming a significant dependence on heliolatitude of the thickness of the heliosheath. As a result, the model allows comparisons of modulation in the north and south hemispheres during both magnetic polarity cycles of the Sun, and from solar minimum to moderate maximum conditions. When comparing the computed spectra between polar angles of 55o (approximating the Voyager 1 direction) and 125o (approximating the Voyager 2 direction), it is found that at kinetic energies E < 1:0 GeV/nuc the effects of the assumed asymmetry in the geometry of the heliosphere on the modulated spectra are insignificant up to 60 AU from the Sun, but become increasingly more significant with larger radial distances to reach a maximum inside the heliosheath. In contrast, with E > 1:0 GeV/nuc, these effects remained insignificant throughout the heliosphere even very close to the heliopause (HP). However, when the enhancement of both polar and radial perpendicular diffusion coefficients off the equatorial plane is assumed to differ from heliographic pole to pole, reflecting different modulation conditions between the two hemispheres, major differences in the computed intensities between the two Voyager directions are obtained throughout the heliosphere. The model is further improved by incorporating new information about the HP location and the relevant heliopause spectrum for GCR Carbon at E < 200 MeV/nuc based on the recent Voyager 1 observations. When comparing the computed solutions at the Earth with ACE observations taken during different solar modulation conditions, it is found that it is possible for the level of modulation at the Earth, when solar activity changes from moderate maximum conditions to solar minimum conditions, to exceed the total modulation between the HP and the Earth during solar minimum periods. In the outer heliosphere, reasonable compatibility with the corresponding Voyager observations is established when drifts are scaled down to zero in the heliosheath in both polarity cycles. The effects of neglecting drifts in the heliosheath are found to be more significant than neglecting the enhancement of polar perpendicular diffusion. Theoretical expressions for the scattering function required for the reduction of the drift coefficient in modulation studies are illustrated and implemented in the numerical model. It is found that when this scattering function decreases rapidly over the poles, the computed A < 0 spectra are higher than the A > 0 spectra at all energies at Earth primarily because of drifts, which is unexpected from a classical drift modeling point of view. Scenarios of this function with strong decreases over the polar regions seem realistic at and beyond the TS, where the solar wind must have a larger latitudinal dependence.
PhD (Space Physics), North-West University, Potchefstroom Campus, 2015

碩士
國立中央大學
照明與顯示科技研究所
101
The production of silicon solar cells can use many methods, commonly used high-temperature diffusion and ion implantation to form a PN junction. The activation temperature of dopant is above 900oC for high-temperature diffusion and ion implantation methods, it will consume much energy of these manufacture technologies. In this thesis for the fabrication technology of c-Si solar cells, we can grow epitaxial-like silicon thin films with dopants at low temperatures (<200oC) by ECRCVD. It will diminish issues of energy consumption, as compared with the traditional high-temperature diffusion process. For the study of epitaxial-like silicon thin films with dopants, we modulate the recipes of ECRCVD, such as microwave power, working pressure, dilution ratio of process gas, and thickness to investigate their structural and electronic characteristics. The thickness and crystalline fraction of the boron-doped thin films were measured by spectroscopic ellipsometry (SE), and their electrical properties such as mobility, concentration, and resistivity were measured by Hall effect measurement. Under the condition of low microwave power and high working pressure, the carrier concentration, and resistivity of a boron-doped epitaxial-like Si thin film with 7 nm thickness is 1.6x1019(cm-3), and 6.7x10-3(Ω-cm), the crystallinity is about 79%. Furthermore, we can control the carrier concentration varied between 2.2x1017 and 2.3x1020(cm-3) under the modulation of process gas dilution ratio. The c-Si solar cell was fabricated with the structure : ITO / epi-Si:H (p+) / c-Si(n) / μc-Si:H (n+). Doped with a high carrier concentration and a low resistivity of the thin thickness that will reduce the solar light incident on the front of the absorption. The low electrical properties of silicon thin film solar cells can be reduced series resistance, and doped silicon thin films with different silicon solar cell research in the photoelectric conversion characteristics. We modulate the doping gas ratio, microwave power, and working pressure to obtain various carrier concentrations of emitter thin films. When the carrier concentration is above 8x1019 cm-3, the 560 mV of Voc and 35 mA/cm2 of Jsc can be achieved in the performance of solar cells. Therefore, this study can be in the plane n-type FZ (100) silicon substrate optimum solar cell characteristics: Voc = 560.4mV, Jsc = 37.69 mA/cm2, FF = 73.3%, finally resulting in the efficiency of solar source AM1.5 in 1 cm2 area was 16.23%.

碩士
國立清華大學
化學工程學系所
105
In this work, we have used combined in-situ grazing-incidence X-ray scattering, X-ray diffraction, and X-ray photoemission spectroscopy, to resolve the intermediate structure and crystallization kinetics of CH3NH3PbI3-xClx perovskite. After spin-cast from a DMF solution, the precursor PbCl2 and MAI of 3:1 molar ratio would preferentially form an intermediate phase (CH3NH3)2Pb(Cl2I2)·CH3NH3I in the early stage of high temperature (ca. 110 。C) annealing. The resolved intermediate structure (L1) comprises layers of 2-D ordered lead-halide octahedra intercalated with MAI layers, and could direct 3-D perovskite formation during prolong annealing, in a two-stage formation process. At 110 。C, formation of highly oriented L1 phase dominates over randomly oriented perovskite formation in the first stage; in the second stage, oriented perovskite crystals are formed mainly from the L1-templated conversion. Kinetic competition and conversion between the L1 phase and perovskite formation in the two-stage process are elucidated by Avrami analysis and the corresponding activation energy Ea extracted. The Avrami exponent n = 1 is obtained for the direct formation of perovskite in the first stage with Ea1 =180 kJ/mol, whereas n = 3.5 and Ea2 = 66 kJ/mol are obtained for the perovskite crystals formed from L1-templated conversion. The L1 phase is of a close Ea value of 124 kJ/mol, supporting the proposed L1-to-perovskite conversion. In the second part of the study, we have used inorganic nanocrystals of PbS surrounded with MAI as embedded crystallization nuclei to enhance nucleation-dominated formation of the intermediate phase. With PbS nanocrystals mixed into the perovskite precursor solution, the hence spin-cast precursor film is found to have substantially enhanced perovskite crystallization rate owing to fast formation and conversion of the L1 phase at 110 。C annealing. Correspondingly observed are improved crystallinity, orientation along vertical direction, and surface coverage of perovskite. These lead to an enchantment in PCE to 17% from the 14% for a pristine case, proving the concept of using cryptographically aligned nanocrystals as seeded crystallization nuclei.

碩士
國立中興大學
電機工程學系
87
The influences of different pulse ON/OFF ratio and power of the pulse modulation of RF power on the properties of a-Si:H films and p-i-n solar cells were studied. Six different pulse ON/OFF ratio (CW, 3/1, 2/1, 1/1, 1/2, and 1/3) and four different power (35W, 40W, 50W, and 60W) were used to deposit a-Si:H films and the i layer of p-i-n solar cells . The characteristics of a-Si:H film and p-i-n solar cells were measured using FTIR spectrometer, UV-VIS-NIR spectrometer, I-V measurement and AFM. A-Si:H films deposited with low pulse ON/OFF ratio (1/3) have the characteristics of low effective deposition rate, low microstructure R ratio, small roughness, low activation energy and optical bandgap, and have a lower photo-conductivity decay rate. With power increasing from 35W to 60W, the effective deposition, microstructure R ratio, roughness, activation energy, photo-conductivity, and optical bandgap of a-Si:H films increased. The p-i-n solar cell, which a-Si:H i-layer deposited with low pulse ON/OFF ratio (1/3), has the characteristics of low open-circuit voltage (Voc), high short-circuit current density (Jsc), high fill factor (FF), low series resistance (Rs ; Rs*), and high shunt resistance (Rsh*). The p-i-n solar cell, which a-Si:H i-layer deposited with low power (35W), has the characteristics of low open-circuit voltage (Voc), high short-circuit current density (Jsc), high fill factor (FF), low series resistance (Rs ; Rs*), and high shunt resistance (Rsh*). Low pulse ON/OFF ratio and low RF peak power of the pulse modulation of RF power can deposited good quality a-Si:H films and good performance p-i-n solar cells.

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia
O desenvolvimento da eletrónica de potência, o aumento do preço da energia e a imposição de restrições ambientais levou à aposta na produção de energia a partir de fontes renováveis, como o vento e o sol. Os sistemas híbridos de energia renovável são uma solução interessante quando as condições locais são favoráveis ao nível do vento e da irradiação solar, pois tira partido da complementaridade existente entre o vento e o sol. Estes sistemas podem estar ligados à rede elétrica ou funcionar em modo isolado. São constituídos por dois sistemas de energia renovável (eólico e solar fotovoltaico) e pelo sistema de armazenamento de energia, onde são todos ligados a um barramento DC.Nesta dissertação é implementado o sistema híbrido de energia renovável, excluindo o sistema eólico, quando ligado à rede elétrica. Todos os subsistemas de energia partilham um barramento DC, o qual é ligado a um barramento AC por intermédio de um conversor DC-AC. O sistema solar fotovoltaico e o sistema de armazenamento de energia são também ligados a este barramento DC através de conversores DC-DC. Assim, o objetivo deste trabalho consiste em controlar os fluxos de potência que ocorrem no sistema híbrido de energia renovável. Para tal, é desenvolvido e implementado uma estratégia de controlo que permita controlar os conversores DC-DC e o conversor DC-AC, com o propósito de produzir e armazenar energia, extrair a potência máxima dos painéis e fornecer/absorver energia para/da rede com um fator de potência unitário.É realizado o dimensionamento dos conversores DC-DC, bem como a modelação e análise no domínio da frequência, de forma a projetar os controladores das malhas de corrente. Para o conversor DC-AC é realizada a modelação e o projeto dos controladores das malhas de corrente e tensão de forma a controlar a tensão do barramento DC e controlar de forma independente, a potência ativa e reativa, tal que o fator de potência seja unitário.O sistema híbrido de energia renovável é implementado em Matlab/Simulink, e é realizado o estudo da dinâmica do sistema. Por fim, implementa-se experimentalmente o sistema de forma a validar os métodos de controlo implementados em ambiente de simulação e analisa-se a sua dinâmica. Nos testes experimentais, todos os algoritmos de controlo foram implementados numa plataforma digital da dSpace.
The development of power electronics technology, the increasing of the energy price and environmental regulations more stringent, led that renewable energy, such as wind and solar, became more attractive. The hybrid renewable energy systems can be a viable solution when the local conditions are favourable to the level of wind and solar irradiation. The photovoltaic energy and wind energy are complementary. These systems, that can work in standalone or grid connected mode, consist in two renewable energy systems (wind and solar photovoltaic) and by energy storage system. All the systems are sharing a common DC bus. In these thesis is implemented the hybrid renewable system, without the wind system, in a grid connected mode. So, the shared DC bus is connected to AC bus by a DC-AC converter. The solar photovoltaic system and energy storage are also connected to the common DC bus by DC-DC converters.Therefore, the goal of this work is the control of power flow that occurs inside the hybrid renewable energy system. So, a control strategy that enable the control of the DC-DC converters as well as the DC-AC converter is developed and implemented. This control strategy aims to, regulate the production and storage of energy levels, the extraction of the maximum power from photovoltaic panels and send/receive energy to/from the grid with unit power factor.The components of DC-DC converters are calculated, from the modulation and analysis in frequency domain are design the controller current loop. From the modulation and the design of the DC-AC convertor are design the controller to voltage and current loop, so that, the voltage in DC bus is control and the active and reactive power are control separated to obtain a unit power factor. The hybrid renewable energy system is implemented in Matlab/Simulink and the study of the system dynamic is performed. Finally, the experimental implementation and a global study of system dynamic are made by implementing the control developed in simulation.In the experimental tests, all control algorithms were implemented on a digital platform from dSpace.

Dissertação de mestrado em Engenharia Eletrónica Industrial e de Computadores
Atualmente, a utilização de cargas não lineares é cada vez mais frequente. Estas, originam problemas de qualidade de energia elétrica (QEE), resultando em várias consequências, como falhas em equipamentos eletrónicos, podendo causar prejuízos elevados em diversos setores. Os filtros ativos de potência, que também podem fazer interface com fontes de energia renovável, apresentam-se como uma boa solução para mitigar estes problemas. Nesta dissertação de mestrado apresentam-se as topologias de filtros ativos de potência, tendo sido simulada uma topologia de Filtro Ativo Paralelo do Tipo Fonte de Corrente. Nesta simulação, para além do inversor fonte de corrente (Current-Source Inverter - CSI), implementou-se um algoritmo baseado na Teoria p-q, bem como a técnica de modulação vetorial (Space-Vector Modulation - SVM). Estas técnicas foram as escolhidas para efetuar o controlo e a modulação do Filtro Ativo Paralelo do Tipo Fonte de Corrente. Nesta dissertação é ainda efetuado um estudo sobre o estado da arte dos conversores CC-CC utilizados em sistemas solares fotovoltaicos, e sobre os sistemas de controlo aplicáveis aos mesmos. Tendo em conta as características do sistema, foi selecionado o conversor CC-CC push-pull, sendo o mesmo simulado e implementado. Nesta dissertação é realizado o dimensionamento e a construção do transformador de alta-frequência deste conversor CC-CC. São ainda apresentadas as placas do andar de potência e o sistema de controlo, desenvolvido no DSP TMS320F28335 da Texas Instruments. A presente dissertação de mestrado apresenta também os testes realizados ao transformador de alta-frequência e ao conversor CC-CC push-pull a operar isoladamente. São ainda apresentados resultados experimentais para a operação de todas as placas desenvolvidas.
Nowadays, the use of no-linear loads in industry and by general consumers is increasingly common. This situation causes Power Quality problems, resulting in various consequences, such as flaws in electronic equipment, which may cause revenue losses in several sectors. Besides that, Power Quality problems contributes to the increase of efficiency losses in domestic and industrial equipment, and also in the electrical installations. The Active Power Filters, which can be incorporated with Renewable Energy solutions, are a good solution to mitigate these problems. In this Master Thesis are presented the main topologies of Active Power Filters, with Current-Source Shunt Active Power Filter being simulated. In this simulation, in addition to the Current-Source Inverter, an algorithm based on the p-q Theory and the Space Vector Modulation technique was implemented. These techniques were chosen to control and modulate the Current-Source Shunt Active Power Filter. In this work, it is also made a study about the state of the art of DC-DC Converters used in Photovoltaic Solar Systems, and the control systems that can be applied to them. Considering the characteristics of the system, the DC-DC Push Pull Converter has been selected, where it is simulated and implemented. In this Master Thesis the design and construction of the high-frequency transformer of this converter was developed. The power stage boards and the control system, implemented in the Texas Instruments microcontroller DSP TMS320F28335, are also developed and presented. This work also presents the tests performed for the developed high-frequency transformer and DC-DC Push Pull Converter. Experimental results of all developed circuits are presented.