Dissertations / Theses on the topic 'Solar variations'
To see the other types of publications on this topic, follow the link: Solar variations.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Solar variations.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Walker, Catherine C. "Variations of solar wind parameters over a solar cycle : expectations for NASA's Solar TErrestrial RElations Observatory (STEREO) mission /." Connect to online version, 2007. http://ada.mtholyoke.edu/setr/websrc/pdfs/www/2007/226.pdf.
Full text
2
Jonson, Martin. "On density and pressure variations in the solar wind plasma." Thesis, KTH, Rymd- och plasmafysik, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91825.
Full textAbstract:
A study of ACE solar wind data at lAU, for the period from 1998 to early 2005, was conducted. This was done in order to find sudden solar wind pressure enhancements accounting for plasma transfer through the magnetopause. In order to get information about the extent and orientation of the structures found, a correlation of found events to data from the Wind satellite was done. The enhancements considered are those with a relative increase exceeding unity. These are found by applying a 1-hour box-car average to the data set. A part of the event distribution was found to vary at periodicities of 11 years, 140 days, and 29 days. Most of the pressure enhancements found were due to a corresponding increase in plasma density. The transverse extent of most of the structures found was rather large, i.e., of the order of 100 Earth radii and the mean orientation of the plasma fronts were found to lie between the radial direction and that of the Archimedean spiral. The duration of most of the structures was shorter than 1 hour. An investigation of the direction of the GSE Z-component of the magnetic field of the events, showed that there was no predominant orientation.
3
Sharma, Pratibha. "Modeling, Optimization, and Characterization of High Concentration Photovoltaic Systems Using Multijunction Solar Cells." Thesis, Université d'Ottawa / University of Ottawa, 2017. http://hdl.handle.net/10393/35917.
Full textAbstract:
Recent advancements in the development of high-efficiency multijunction solar cells
have led to a renewed interest in the design and implementation of high concentration photovoltaic systems. With the emergence of novel materials and design structures, understanding the operation of multijunction solar cells has become a challenging task. Modeling and simulation hence play an important role in the analysis of such devices. In this dissertation, techniques for accurate optoelectrical modeling of concentrating photovoltaic systems, based on multijunction solar cells, are proposed. A 2-dimensional, distributed circuit model is proposed, parametrized to values obtained by numerical modeling of three multijunction cell designs, namely: a three-junction, lattice matched design, a three-junction lattice-mismatched, inverted metamorphic design, and a four-junction,lattice matched design. Cell performance for all the three designs is evaluated under both
uniform and nonuniform illumination profiles at high concentrations and efficiency enhancement by optimizing finger spacing is proposed. The effect of luminescent coupling from higher bandgap subcells is also determined.Fresnel-lens based, refractive concentrating optical systems are modeled and optimized
using an optical ray-tracing simulator at two different concentrations, with and without
a secondary optical element. The corresponding optical efficiency, acceptance angle, and the degree of nonuniformity are determined for each optical system. An integrated approach,combining optical design with electrical modeling is proposed for optimizing the multijunction solar cell in tandem with the corresponding concentrating optics. The approach is validated by on-sun, acceptance angle measurements, using a three-junction,lattice-matched cell. Also, temperature effects are modeled and are experimentally validated for a three-junction, lattice-matched design. Experimental results with a single-junction, dilute-nitride cell, targeted for four-junction operation, are presented as well. A modified distributed circuit model is used for analysis of temperature effects in a four-junction solar cell, and the results under both uniform and nonuniform temperature profiles are presented.
When implemented, the designs and their corresponding analyses, may result in new
insights into the development of CPV systems, thereby enabling enhanced efficiencies at higher concentrations.
4
Jacobi, Christoph, Norbert Jakowski, Gerhard Schmidtke, and Thomas N. Woods. "Delayed response of the global total electron content to solar EUV variations." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212283.
Full textAbstract:
The ionospheric response to solar extreme ultraviolet (EUV) variability during 2011–2014 is shown by simple proxies based on Solar Dynamics Observatory/Extreme Ultraviolet Variability Experiment solar EUV spectra. The daily proxies are compared with global mean total electron content (TEC) computed from global TEC maps derived from Global Navigation Satellite System dual frequency measurements. They describe about 74% of the intra-seasonal TEC variability. At time scales of the solar rotation up to about 40 days there is a time lag between EUV and TEC variability of about one day, with a tendency to increase for longer time scales.
5
Hood, L. L., and B. E. Soukharev. "Solar induced variations of odd nitrogen: Multiple regression analysis of UARS HALOE data." AMER GEOPHYSICAL UNION, 2006. http://hdl.handle.net/10150/623348.
Full textAbstract:
A linear multiple regression statistical model is applied to estimate the solar induced component of odd nitrogen variability in the stratosphere and lower mesosphere using UARS HALOE data for 1991–2003. Consistent with earlier studies, evidence is obtained for a decadal NOx variation at the highest available latitudes (50° – 70°) that projects positively onto the solar cycle. This variation, which is most statistically significant in the Southern Hemisphere, also correlates positively with the auroral Ap index. It is therefore probably caused by downward transport during the polar night of thermospheric and mesospheric odd nitrogen. In addition, at low latitudes near and above the stratopause, evidence is obtained for an inverse solar cycle NOx variation. It is suggested that this low-latitude response may be caused primarily by increased photolysis of NO under solar maximum conditions. Throughout most of the rest of the stratosphere, no statistically significant response is obtained.
6
Ortiz, Carbonell Ada Natalia. "Solar Irradiance Variations Induced by Faculae and Small Magnetic Elements in the Photosphere." Doctoral thesis, Universitat de Barcelona, 2003. http://hdl.handle.net/10803/733.
Full textAbstract:
The aim of this thesis is the study of the total and spectral solar irradiance variability induced by the presence of small magnetic elements that emerge into the solar photosphere. It is important to study changes in the solar energy output because they reflect the existence of several physical processes in the solar interior, their interpretation helps to understand the solar cycle and because of their influence on the terrestrial climate. The work presented in this thesis is exclusively based on data provided by the SOHO spacecraft, specifically by the VIRGO and MDI instruments.Irradiance variations produced on the solar rotation time-scale are due to the passage of active regions across the solar disk. However, the origin of variations on the solar cycle time-scale is under debate. One of the most controversial aspects is the long-term contribution of the small magnetic elements conforming faculae and the network. Their identification and contrast measurement is difficult and, consequently, their contrast center-to-limb variation (CLV) remains poorly defined in spite of the fact that its knowledge is essential to determine their contribution to variability.
In this work we have studied the contribution of small photospheric magnetic elements (those with a positive contribution to variability), both on short, i.e. solar rotation, and long, i.e. solar cycle, time-scales. By analyzing the evolution of an isolated active region (NOAA AR 7978) during several Carrington rotations, we have evaluated the variations in luminosity induced by this facular region during the 1996 minimum of activity. Simultaneous photometric and magnetic data from the MDI instrument have been combined in order to study the contrast of small scale magnetic features and its dependence both on position and magnetic field, as well as its evolution along the rising phase of solar cycle 23.
The study of the solar variability has required reduction and analysis of the employed MDI and VIRGO data. These data had to be converted from level 0 (raw data) to level 2 (scientifically useful data), since solar variations were hidden by instrumental effects. We developed original algorithms to correct instrument-related effects from the data, such as filter degradation and the variation of the limb darkening with distance. The determination of the contrast of magnetic features also required the development of an algorithm in order to identify the surface distribution of those small features present over the solar disk.
By analyzing irradiance variations induced by the small magnetic features that emerge into the solar photosphere we have concluded that:
· active region faculae and the magnetic network present very different contrast CLV's, therefore, their contributions to irradiance variability are distinct; as a consequence, both contributions need to be taken into account separately when reconstructing variations of the solar irradiance.
· the functional dependence on position and magnetic signal of the facular contrast is time independent; this suggests that the physical properties of the underlying flux tubes do not vary with time.
· network elements are bright over the whole solar disk and have proved to be the dominant population along the solar cycle; this implies that their contribution to long-term irradiance variations is significant and needs to be taken into account.
7
Hood, L. L., and S. Zhou. "Stratospheric effects of 27-day solar ultraviolet variations: The column ozone response and comparisons of solar cycles 21 and 22." AMER GEOPHYSICAL UNION, 1999. http://hdl.handle.net/10150/624008.
Full textAbstract:
Two unresolved observational issues concerning the response of stratospheric ozone to 27-day solar ultraviolet variations are as follows: (1) the amplitude of the column ozone response and whether it is consistent with the predictions of current two-dimensional stratospheric models and (2) whether the ozone profile response in the upper stratosphere differed appreciably during the solar cycle 22 maximum period (around 1990) as compared with the solar cycle 21 maximum period (around 1980). To investigate these issues, two separate 4-year intervals (1979–1982 and 1989–1992) of daily zonal mean Nimbus 7 Total Ozone Mapping Spectrometer, Nimbus 7 solar backscattered ultraviolet (SBUV), and/or NOAA 11 SBUV/2 data for tropical latitudes (30°S to 30°N) are analyzed using cross correlation and cross-spectral and regression methods. The Mg II core-to-wing ratio is employed as a measure of solar UV variations near 200 nm. Results show that the mean tropical column ozone sensitivity (percent change of ozone for a 1% change in solar flux) is 0.09±0.01 at a lag of 4–6 days during both intervals and is approximately consistent with model predictions. Ozone profile sensitivities and phase lags are also in agreement between the two 4-year intervals when statistical uncertainties and differences in data processing algorithms are considered.
8
Hood, L. L. "Lagged response of tropical tropospheric temperature to solar ultraviolet variations on intraseasonal time scales." AMER GEOPHYSICAL UNION, 2016. http://hdl.handle.net/10150/623304.
Full textAbstract:
Correlative and regression analyses of daily ERA-Interim reanalysis data for three separate solarmaximum periods confirm the existence of a temperature response to short-term (mainly ∼27 day) solarultraviolet variations at tropical latitudes in both the lower stratosphere and troposphere. The response,which occurs at a phase lag of 6–10 days after the solar forcing peak, consists of a warming in the lowerstratosphere, consistent with relative downwelling and a slowing of the mean meridional (Brewer-Dobson)circulation, and a cooling in the troposphere. The midtropospheric cooling response is most significant inthe tropical Pacific, especially under positive El Niño–Southern Oscillation conditions and may be relatedto a reduction in the number of Madden-Julian oscillation events that propagate eastward into the centralPacific following peaks in short-term solar forcing.
9
Montenegro, Cristian Fernando Torres. "Modelling of utility-scale PV systems and effects of solar irradiance variations on voltage levels." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-24032017-132931/.
Full textAbstract:
This work presents a dynamic model for utility-scale PV systems. The model is based on a centralized converter topology, which uses a voltage-sourced converter (VSC) to facilitate the exchange of energy between PV generators and the utility grid. The related control system regulates active and reactive power injected by the PV system, based on a current control strategy. Moreover, the model includes a Maximum Power Point Tracking (MPPT) scheme, implemented with the incremental conductance method. Dimensioning of the model is presented as well as simulation cases to validate its performance. Subsequently, the model was used to analyze the effect of variations in solar radiation on a test network with high penetration of photovoltaic generation. Results showed that without proper compensation of reactive power, variations in solar radiation can cause voltage fluctuations outside allowable limits. Thus, in order to mitigate these fluctuations, local control strategies were implemented to allow the exchange of reactive power between the solar farm and the utility grid. Simulations showed that the proposed strategies can mitigate voltage fluctuations at the point of common coupling, improving voltage regulation in the network.Este trabalho apresenta um modelo dinâmico de sistemas fotovoltaicos de grande escala. O modelo é baseado em uma topologia de conversor centralizado, que usa um conversor de fonte de tensão (VSC) para facilitar a troca de energia entre os geradores fotovoltaicos e a rede elétrica. O sistema de controle relacionado regula a energia ativa e reativa injetada pelo sistema fotovoltaico, com base em uma estratégia de controle de corrente. Além disso, o modelo inclui um sistema de rastreamento de ponto de potência máxima (MPPT), implementado com o método da condutância incremental. O dimensionamento do modelo é apresentado, bem como vários casos de simulação para validar o seu desempenho. Posteriormente, o modelo foi utilizado para analisar o efeito das variações na radiação solar sobre uma rede de teste com uma elevada penetração de geração fotovoltaica. Os resultados mostraram que sem uma adequada compensação de energia reativa, as variações na radiação solar podem causar flutuações de tensão fora dos limites permitidos. Assim, a fim de mitigar estas flutuações, estratégias de controle local foram implementadas para permitir a troca de potência reativa entre os sistemas fotovoltaicos e a rede. As simulações mostraram que as estratégias propostas podem mitigar as flutuações de tensão no ponto de acoplamento comum, melhorando a regulação de tensão na rede.
10
Austin, J., L. L. Hood, and B. E. Soukharev. "Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model." COPERNICUS, 2007. http://hdl.handle.net/10150/623329.
Full textAbstract:
The results from three 45-year simulations of a coupled chemistry climate model are analysed for solar cycle influences on ozone and temperature. The simulations include UV forcing at the top of the atmosphere, which includes a generic 27-day solar rotation effect as well as the observed monthly values of the solar fluxes. The results are analysed for the 27-day and 11-year cycles in temperature and ozone. In accordance with previous results, the 27-day cycle results are in good qualitative agreement with observations, particularly for ozone. However, the results show significant variations, typically a factor of two or more in sensitivity to solar flux, depending on the solar cycle.
In the lower and middle stratosphere we show good agreement also between the modelled and observed 11-year cycle results for the ozone vertical profile averaged over low latitudes. In particular, the minimum in solar response near 20 hPa is well simulated. In comparison, experiments of the model with fixed solar phase (solar maximum/solar mean) and climatological sea surface temperatures lead to a poorer simulation of the solar response in the ozone vertical profile, indicating the need for variable phase simulations in solar sensitivity experiments. The role of sea surface temperatures and tropical upwelling in simulating the ozone minimum response are also discussed.
11
Sikkema, Hendrick A. "The role of solar wind pressure variations in the appearance of near-relativistic electrons near geostationary orbit." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ59877.pdf.
Full text
12
Hood, L. L., and S. Zhou. "Stratospheric effects of 27-day solar ultraviolet variations: An analysis of UARS MLS ozone and temperature data." AMER GEOPHYSICAL UNION, 1998. http://hdl.handle.net/10150/624009.
Full textAbstract:
The characteristics of upper stratospheric ozone and temperature responses at low latitudes to short-term solar ultraviolet variations are studied by using 1000 days of UARS microwave limb sounder (MLS) and solar stellar irradiance comparison experiment data. Consistent with previous analyses of Nimbus 7 solar backscattered ultraviolet (SBUV) data, the high-pass-filtered solar flux in the 200-to 205-nm interval is most strongly correlated with MLS ozone measurements at tropical latitudes near 4 hPa with a sensitivity of about 0.4% for each 1% change in the solar flux. Reproducibility tests, power spectral, and coherency estimates support the reality of the observed ozone response at this level. The MLS solar UV/ozone response is significantly reduced at levels above ∼2 hPa as compared to earlier results based on SBUV data. This reduction appears to be a consequence of the ozone diurnal cycle at high altitudes combined with the necessary inclusion of nighttime records in calculating the MLS ozone zonal averages. Some evidence is obtained for an MLS solar UV/temperature response near the stratopause, but coherency tests are negative. Future analyses of independent data records having similar local time coverage as that of Nimbus 7 SBUV are needed to establish more definitively whether any significant change in the upper stratospheric UV response has occurred.
13
Zhou, Shuntai, Alvin J. Miller, and Lon L. Hood. "A partial correlation analysis of the stratospheric ozone response to 27-day solar UV variations with temperature effect removed." AMER GEOPHYSICAL UNION, 2000. http://hdl.handle.net/10150/624005.
Full textAbstract:
Observational detection of upper stratospheric ozone responses to 27-day solar ultraviolet (UV) variations is often inhibited by larger, dynamically induced ozone variations, which result mainly from the temperature dependence of reaction rates controlling the ozone balance. Here we show that partial correlation coefficients of solar UV and tropical upper stratospheric ozone (1–5 hPa) with the temperature effect removed are larger (07–0.8) than are total correlation coefficients of ozone and solar UV (0.4–0.6). The phase lag of ozone relative to solar UV is also increased, and the maximum ozone-UV correlation is obtained at higher altitudes, as compared with correlation analyses using ozone and solar UV data alone. Assuming that temperature variations are not forced by solar UV variations, the ozone sensitivity to solar UV and temperature can be calculated using a linear multiple regression model. The ozone sensitivity to solar UV is generally independent of time periods used for the analysis. However, the magnitude of the ozone sensitivity to temperature at 1–2 hPa increased significantly from solar cycle 21 to solar cycle 22, possibly reflecting long-term changes in the composition of the upper stratosphere.
14
Jenkins, Jon Michael. "Variations in the 13 cm opacity below the main cloud layer in the atmosphere of Venus inferred from Pioneer-Venus radio occultation studies 1978-1987." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/14843.
Full text
15
Sakai, Tadashi. "A Study of Variable Thrust, Variable Specific Impulse Trajectories for Solar System Exploration." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4904.
Full textAbstract:
A study has been performed to determine the advantages and disadvantages of variable thrust and variable specific impulse (Isp) trajectories for solar system exploration.
There have been several numerical research efforts for variable thrust, variable Isp, power-limited trajectory optimization problems. All of these results conclude that variable thrust, variable Isp (variable specific impulse, or VSI) engines are superior to constant thrust, constant Isp (constant specific impulse, or CSI) engines. However, most of these research efforts assume a mission from Earth to Mars, and some of them further assume that these planets are circular and coplanar. Hence they still lack the generality.
This research has been conducted to answer the following questions:
- Is a VSI engine always better than a CSI engine or a high thrust engine for any mission to any planet with any time of flight considering lower propellant mass as the sole criterion?
- If a planetary swing-by is used for a VSI trajectory, is the fuel savings of a VSI swing-by trajectory better than that of a CSI swing-by or high thrust swing-by trajectory?
To support this research, an unique, new computer-based interplanetary trajectory calculation program has been created. This program utilizes a calculus of variations algorithm to perform overall optimization of thrust, Isp, and thrust vector direction along a trajectory that minimizes fuel consumption for interplanetary travel. It is assumed that the propulsion system is power-limited, and thus the compromise between thrust and Isp is a variable to be optimized along the flight path. This program is capable of optimizing not only variable thrust trajectories but also constant thrust trajectories in 3-D space using a planetary ephemeris database. It is also capable of conducting planetary swing-bys.
Using this program, various Earth-originating trajectories have been investigated and the optimized results have been compared to traditional CSI and high thrust trajectory solutions. Results show that VSI rocket engines reduce fuel requirements for any mission compared to CSI rocket engines. Fuel can be saved by applying swing-by maneuvers for VSI engines, but the effects of swing-bys due to VSI engines are smaller than that of CSI or high thrust engines.
16
Lundin, Johan. "EROI of crystalline silicon photovoltaics : Variations under different assumptions regarding manufacturing energy inputs and energy output." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-199639.
Full textAbstract:
Installed photovoltaic nameplate power have been growing rapidly around the worldin the last few years. But how much energy is returned to society (i.e. net energy) by this technology, and which factors contribute the most to the amount of energy returned? The objective of this thesis was to examine the importance of certain inputs and outputs along the solar panel production chain and their effect on the energy return on (energy) investment (EROI) for crystalline wafer-based photovoltaics. A process-chain model was built using publicly available life-cycle inventory (LCI) datasets. This model has been kept simple in order to ensure transparency. Univariate sensitivity analysis for processes and multivariate case studies was then applied to the model. The results show that photovoltaic EROI values are very sensitive to assumptions regarding location and efficiency. The ability of solar panels to deliver net energy in northern regions of the earth is questionable. Solar cell wafer thickness have a large impact on EROI, with thinner wafers requiring less silicon material. Finding an alternative route for production of solar-grade silicon is also found to be of great importance, as is introduction of kerf loss recycling. Equal system sizes have been found to yield an primary EROI between approximately 5.5-19 depending on location and assumptions. This indicates that a generalized absolute EROI for photovoltaics may be of little use for decision-makers. Using the net energy cliff concept in relation to primary EROI found in this thesis shows that primary EROI rarely decreases to less than the threshold of 8:1 in univariate cases. Crystalline photovoltaics under similar system boundaries as those in the thesis model does not necessarily constrain economic growth on an energetic basis.
17
Smirès, Najib. "Contribution des mesures lidar à l'études des variations à long terme de l'état thermique de l'atmosphère moyenne." Paris 6, 1986. http://www.theses.fr/1986PA066434.
Full textAbstract:
On reporte et analyse les données de sept ans de mesures des profils verticaux nocturnes de la température de la stratosphère et la mésosphère (lidar Rayleigh de l'observatoire de Haute Provence). Les corrélations avec le flux solaire F(10,7) ont été calculées pour différentes saisons et comparées aux résultats publiés pour les cycles 20 et 21. Si l'accord est bon pour la mésosphère, la stratosphère semble avoir un comportement diffèrent pour les cycles 20 et 21 ce qui serait dû aux ondes planétaires. La structure thermique de l'atmosphère est reliée aux concentrations en ozone.
18
Foster, Simon Steven. "Reconstruction of solar irradiance variations for use in studies of global climate change : application of recent SoHO observations with historic data from the Greenwich Observatory." Thesis, University of Southampton, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408976.
Full text
19
Rodrigues, Paulo Roberto Grangeiro. "Astrologia e personalidade: o efeito do conhecimento das características do signo solar em variáveis medidas pelo 16 pf." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/47/47134/tde-20092004-172927/.
Full textAbstract:
Nesta Tese replicamos por constructo uma pesquisa européia que encontrou para conhecedores da astrologia médias mais altas em Extroversão entre sujeitos dos signos de Fogo e Ar comparados com sujeitos de Terra e Água, formando um padrão dente-de-serra previsto em função da alternância zodiacal entre signos de Elementos Quentes (Fogo e Ar) e Frios (Terra e Água), como sendo efeito da auto-atribuição, já que a mesma variação não se deu para sujeitos não conhecedores. Também se encontrou, no entanto, maior suscetibilidade à informação vinda de fora sobre sua personalidade para os Quentes, o que não invalidou totalmente a teoria astrológica. Encontrou-se lá, além disso, maior média geral em Extroversão para os conhecedores. Usamos o 16 PF Questionário dos 16 Fatores de Personalidade com 589 sujeitos brasileiros de ambos os sexos, diferenciando entre conhecedores (208) e não conhecedores (381) da astrologia, sendo o conhecimento constituído da crença na astrologia mais a descrição de três características do signo solar. Para estimular a influência da auto-atribuição, foi dada a parte do grupo (266) a sugestão Esta é uma pesquisa sobre astrologia, enquanto para a outra parte (323) foi dito que seria uma pesquisa sobre personalidade. Investigamos variações em função dos Elementos astrológicos, através da Análise de Variância (ANOVA), em todos os fatores do 16 PF, mais Extroversão, Ansiedade e Controle. Não aparecem diferenças significativas para a Extroversão isoladamente, mesmo entre os conhecedores. Os conhecedores se descreveram como tendo significativamente maior Extroversão e maior Ansiedade, comparados aos não conhecedores, sugerindo um locus de controle externo. Confirmou-se no grupo dos conhecedores que a maior média geral em Extroversão é devida aos sujeitos do subgrupo dos signos Quentes, e a maior média em Ansiedade é devida aos sujeitos do subgrupo dos signos Frios, indicando a confirmação da maior suscetibilidade à informação vinda de fora sobre suas personalidades para os Quentes. Investigamos, além disso, se a auto-atribuição de origem astrológica afeta não apenas o autoconceito, mas as habilidades da pessoa, através dos 13 itens da Inteligência do 16 PF. Para o grupo de não conhecedores a Ansiedade foi maior para os Quentes do que para os Frios, segundo seus componentes Estabilidade Emocional e Tensão. Este resultado apontou que a Ansiedade, como fator não intelectivo, induziu uma variação de base astrológica na Inteligência. Sugere-se um fator de suscetibilidade diferenciada ao mundo externo segundo a escala Frio-Quente. São analisadas as possíveis explicações teóricas e implicações desses achados.In this thesis we constructively replicate an european research that found for astrology knowledgeable subjects higher means on Extraversion among subjects of Fire and Air signs, compared with subjects of Earth and Water, compound a saw-tooth pattern due the zodiacal alternation between signs of Hot (Fire and Air) and Cold (Earth and Water) Elements, as an effect of the self-attribution, since the same variation was not found for no knowledgeable subjets. Also was found, however, a difference on susceptibility to information about their personality from outside for the Hots, what didnt invalidate totally the astrological theory. That research found, furthermore, higher mean in Extraversion for that knowledgeable subjects. We applied the 16PF Test Sixteen Personality Factor Questionnaire to 589 brazilian subjects of both sexes, classifying between knowledgeable (208) and no knowledgeable (381) of astrology, being this knowledge constituted by the believe in astrology and by the naming of three characteristics that go with the sunsign. In order to trigger the self-attribution effect, part of the group (266) was given the cue This is a research into astrology, while to the other part was given research into personality. We investigate variations by dependence on the astrological Elements, by the Analysis of Variance (ANOVA), on all the 16 PF factors, more Extraversion, Anxiety and Control. Didn´t appear significant differences to the Extraversion alone, yet among the knowledgeable. The knowledgeable subjects describe theirselves significantly as having higher Extraversion and Anxiety, suggesting an external locus of control, by comparision with the no knowledgeable. It was confirmed that for the knowledgeable the higher general mean in Extraversion is due to the subjects pertaining to the subgroup of the Hot signs, and the higher general mean in Anxiety is due to the subjects pertaining to the subgroup of the Cold signs, indicating a confirmation of the higher susceptibility to information about their personality from outside among the Hots. We investigate, furthermore, if the astrological self-attribution affects not only the self-concept, but also the actual performance, with the 13 items of Intelligence in the 16PF. For the no knowledgeable group the Anxiety was higher for the Hots than to the Colds due to their components Emotional Estability and Tension. This finding pointed to that Anxiety, as a non-intellective factor, induced the astrologically based variation for Intelligence. It is suggested, as much to knowledgeable as to no knowledgeable subjects, a factor of differenciated susceptibility to the outer world due the Cold-Hot scale. Are analysed the possible theoretical explanations and implications of these findings.
20
Byström, André. "Analys av solcellers påverkan pålågspänningsnätets elkvalitet." Thesis, Karlstads universitet, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-84937.
Full textAbstract:
I takt med att Sverige går mot ett mer klimatsmart och hållbart samhälle samtidigt somskatteavdragen på solceller blir mer lönsamma och mindre komplicerat, så har installationer avsolceller genomgått en enorm ökning dem senaste åren. En ökningstakt som väntas fortsätta. Omsedan flertalet kunder väljer att installera solceller i ett svagt område skulle detta kunna leda tillproblem i form spänningsvariationer och överbelastningar i elnätet.Syftet med studien är därför att identifiera de områden där många solelinstallationer kan leda tillproblem, utreda vilka faktorer som är risker för problematiska nät, lista och prioritera nät i behov avåtgärder samt undersöka vilka områden som är troligast att en storskalig installation av solcelleruppstår i först.I studien utfördes en vid analys av Ellevios lågspänningsnät, där spänningsvariationer ochöverbelastning i nätet undersöktes. Tre områden från analysen med låg potential för solcelleranalyserades djupare för att kontrollera mellanliggande näts tillstånd. Mätdata från områden medinstallerade solceller bearbetades för att utgå som referens för hur verklig sol-produktion kan se ut.För att undersöka var framtida solceller kan installeras studerades granskapseffekten ochmedelinkomst per postnummer. Slutligen listades och prioriterades Ellevios nät utefter behov avåtgärder, där prioriteringen utgår från områden med högst konsekvens och vart framtida solcellertroligast uppstår.Resultatet blir en riskvärdering där andel av områden presenteras utifrån sannolikheten att solcelleruppstår och konsekvenser. Analysen visar att den parameter som påverkade flest områden ilågspänningsnätet är spänningsvariation i sammankopplingspunkt. I djupanalysen framgår attmellanliggande nät är lika, om inte mer sårbara för stor installation av solceller. De områdena medinstallerade solceller visar att den individuellt högsta producerade effekten aldrig kommer upp tillden installerade samt att den sammanlagrade effekten för solelproducenterna i ett område hamnarlångt under den installerade effekten.As Sweden moves towards a more climate-smart and sustainable society at the same time as the taxdeductions on solar cells become more profitable and less complicated, installations of solar cellshave undergone an enormous increase in recent years. A rate of increase that is expected tocontinue. If many customers choose to install large solar cells with high power in a weak area, thenthis could lead to problems in the form of voltage variations and overloads in the electricity grid. Thepurpose of the study is therefore to identify the areas where many solar installations can lead toproblems, investigate the factors that are risks for problematic networks, list and prioritize networksin need of measures. As well as to investigate in which areas large-scale installation of solar cells aremost likely to occur in.In the study, a broad analysis was performed of Ellevio's low voltage network, where voltagevariations and overloads in the network were investigated. Three areas from the analysis with lowpotential for solar cells were analyzed more deeply to check the condition of intermediate networks.Measurement data from areas with installed solar cells were processed to be used as a reference forwhat actual solar production can look like. To investigate where future solar cells can be installed,the spatial neighborhood effect and average income by postcode were studied. Finally, Ellevio'snetwork was listed and prioritized according to the need for measures, where the prioritization isbased on areas with the highest consequence and where future solar cells are most likely to arise.The result is a risk assessment where the proportion of areas is presented based on the probabilitythat solar cells arise and consequences. The analysis shows that the parameter that affected mostareas in the low-voltage network is voltage variation in the connection points. The in-depth analysisshows that intermediate networks are similar, if not more vulnerable to large-scale installation ofsolar cells. The areas with installed solar cells show that the individually highest produced powernever reaches the installed one and that the combined power for the solar producers in an area endsup far below the installed power.
21
Nguyen, Thai Chinh [Verfasser], Harald [Akademischer Betreuer] Schuh, Mahdi [Akademischer Betreuer] Alizadeh, Harald [Gutachter] Schuh, Mahdi [Gutachter] Alizadeh, and Lung-Chih [Gutachter] Tsai. "Use of the East Asia GPS receiving network to observe ionospheric VTEC variations, scintillation and EIA features during the Solar Cycle 24 / Thai Chinh Nguyen ; Gutachter: Harald Schuh, Mahdi Alizadeh, Lung-Chih Tsai ; Harald Schuh, Mahdi Alizadeh." Berlin : Technische Universität Berlin, 2021. http://d-nb.info/1231908394/34.
Full text
22
Aoun, Youva. "Evaluation de la sensibilité de l’instrument FCI à bord du nouveau satellite Meteosat Troisième Génération imageur (MTG-I) aux variations de la quantité d’aérosols d’origine désertique dans l’atmosphère." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEM030/document.
Full textAbstract:
Cette thèse porte sur une méthodologie d’estimation des capacités d’un futur instrument spatioporté. Le cas d’étude est l’instrument Flexible Combined Imager (FCI) à bord du futur satellite Meteosat Troisième Génération Imageur (MTG-I), et plus particulièrement ses capacités à détecter des variations de quantité d’aérosols désertiques dans l’atmosphère. Une meilleure connaissance de ces aérosols fait partie des besoins régulièrement exprimés pour l’étude du climat, la prévision météorologique ou l’estimation de la ressource solaire dans des zones arides comme le Sahara. Ce type d’aérosols est abondant dans l’atmosphère. Leurs propriétés physico-chimique les rendent distinguables des autre types d’aérosols comme ceux résultant de la pollution d’origine anthropique, d’autant qu’ils sont émis dans des zones protégées des contaminations par ces autres types. Ils représentent donc un cas d’étude simple pour valider la méthodologie développée dans cette thèse.La méthodologie consiste à réaliser un simulateur de vue du sol par l’instrument, à effectuer de très nombreuses simulations des luminances mesurées par l’instrument sous diverses conditions atmosphériques et de l’albédo du sol, à analyser les résultats de manière à quantifier l’influence de chaque variable dans la variation de la luminance, puis à conclure quant aux capacités de détection grâce un critère de détectabilité prenant en compte les caractéristiques de l’instrument.Le simulateur développé a été validé par confrontation avec des mesures réelles de l’instrument SEVIRI à bord du satellite Meteosat Second Generation. L’innovation principale réside dans l’usage de l’approche d’analyse de sensibilité globale (GSA). Cette dernière quantifie l’influence de chaque variable séparément ainsi que les termes croisés. Elle exploite des fonctions de répartition statistique des variables extraites d’observations, et permet par conséquent d’obtenir une analyse de sensibilité réaliste. La GSA produit aussi des fonctionnelles modélisant l’influence d’une ou plusieurs variables sur la variabilité du signal observé et utilisables pour différentes applications dans la télédétectionThis thesis deals with a methodology to assess the capabilities of future spaceborne instruments. The case study is the Flexible Combined Imager (FCI) of the future Meteosat Third Generation Imaging mission (MTG - I), and in particular its ability to detect variations in load of desert aerosols in a realistically variable atmosphere. A better understanding of the behavior of these aerosols is part of regularly expressed needs for the study of the climate, weather forecast or assessment of the solar resource in arid areas such as the Sahara. This type of aerosols is abundant in the atmosphere. Their physical and chemical properties make them distinguishable from other types of aerosols such as those resulting from anthropogenic pollution, especially as they are emitted in areas protected from contamination by these other types. They therefore represent a simple case study to validate the methodology developed in this thesis.The methodology is to provide a simulator of the view of the instrument to perform a large number of simulations of the radiance measured under different atmospheric conditions and ground albedo, to analyze the results in order to quantify the influence of each variable in the variation of radiance, and then conclude on the capabilities of detection through a test of detectability taking into account the characteristics of the instrument.The developed simulator was validated by comparison against actual measurements of the SEVIRI instruments onboard Meteosat Second Generation satellites. The main innovation lies in the use of the global sensitivity analysis approach (GSA). The latter quantifies the influence of each variable separately as well as their crossed terms. Cumulative distribution functions were computed from actual observations and allow a realistic sensitivity analysis of the instrument. The GSA is also used to compute functional representation of the influence of one or more variables on the variability of the observed signal. The usefulness of such representations is discussed for various applications in remote sensing
23
Chapman, Steven Anthony. "The variation of coronal holes with solar cycle." Thesis, University of Central Lancashire, 2007. http://clok.uclan.ac.uk/20984/.
Full textAbstract:
Coronal holes are commonly known to be the source of the open magnetic flux and the high-speed solar wind. In EUV and X-ray emission lines, coronal holes are seen as the regions with reduced emission due to lower temperatures and electron density than the surrounding quiet sun. Observing the evolution of coronal holes over the course of a solar cycle, can lead to a greater understanding of the evolution of the solar dynamo and can advance our knowledge in forecasting space weather. Synoptic data from the Normal Incidence Spectrometer (NIS), which is part of the Coronal Diagnostic Spectrometer (CDS) onboard the Solar and Heliospheric Observatory (SoHO), have been used in this work to observe the evolution of coronal holes during cycle 23, from mid-1996 through to mid-2007 (solar minimum to solar minimum). Towards the end of 1998, communication with SoHO was recovered after being temporarily lost for several months. On recovery of SoHO, it was noticed that the spectral lines had acquired wings, making the Gaussian profiles broader. This broadening now extends profiles beyond the boundaries of some spectral windows; this prevents a direct measurement of the background of the spectral line. Here, I present a new method of obtaining an estimate of the background for both the NIS bands, as well as alternative values with which to describe the wings of the broadened Gaussian spectral profiles. The new method for the background level shows a considerable improvement over the background level determined by a fitting routine; I demonstrate that the resultant intensity could be over-estimated by up to 30%. Previous studies which investigated the coronal hole area variation were either limited to or concentrated on the poiar coronal holes, or else the models experienced large uncertainties when determining the area of coronal holes close to the solar limb. However, the isotropic nature of the radiation emitted from the low corona does allow for coronal hole areas to be determined at any location on the solar disc, right up to the limb. Imaging the coronal lines Mg ix and Mg x show many dark low-emission regions which belong to filaments and their channels as well as coronal holes. It is not until the temperature has been derived from the ratio of Mg x/Mg ix, that we are able to see coronal holes as the only regions cooler than the surrounding quiet sun. Observing the typical coronal hole temperature through the solar cycle shows that the temperature of the holes varies in phase with the solar activity cycle; with values of 1.17 ± 0.06 MK and 1.09 ± 0.02 MK at solar maximum and near solar minimum, respectively. Using this low-temperature property of coronal holes, an automated method has been developed to distinguish the coronal hole areas using the large Mg x/Mg ix temperature ratio datasets from May 1998 onwards. Prior to this, the Mg x line was not included in the synoptic study; therefore the coronal hole regions were identified manually from Mg ix intensity images. The results show a negative correlation between the synoptic coronal hole area and solar activity; areas of -12% of the total solar surface area are found around solar minimum, where the coronal holes are predominantly found at the polar regions, and this falls to r.6% around solar maximum. The motion of the coronal holes over the solar cycle has also been observed using maps created from the Mg x/Mg ix temperature ratio. It is shown that, in the northern hemisphere, the old-cycle coronal hole leaves the pole in May 1999 and the new opposite polarity polar coronal hole begins to re-establish at the pole from September 2001. The southern hemisphere polar hole vacates the pole in May 2000 and begins to reform in January 2004. This shows that the northern hemisphere polarity reversed first, followed by the southern hemisphere approximately two years later. An interesting behaviour was noticed at the poles when, shortly after a polar coronal hole established, the coronal hole was displaced from the pole. This occurred three times in both hemispheres until the polar coronal holes finally settled in June 2005 (North) and November 2006 (South). These displacements could be due to interactions between holes of opposite and of like polarity at mid-latitudes. Combining the synoptic coronal hole areas with the daily disk-averaged magnetic field data, obtained by Kitt-Peak and SOLIS facilities, the variation of the open magnetic flux over cycle 23 is also presented. Shortly after the old-cycle northern polar coronal hole vacates the polar region, the open flux is shown to steadily increase up until '.2003, approximately two years after solar maximum. . The open flux begins to return to solar minimum levels in January 2004, when both polar coronal holes are attempting to encompass the pole. These events signify that there is a strong connection between the evolution of open flux and the processes involved in reversing the polarity of the Sun.
24
Guo, Huairui. "Variation monitoring, diagnosis and control for complex solar cell manufacturing processes." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280704.
Full textAbstract:
Interest in photovoltaic products has expanded dramatically, but wide-scale commercial use remains limited due to the high manufacturing cost and insufficient efficiency of solar products. Therefore, it is critical to develop effective process monitoring, diagnosing, and control methods for quality and productivity improvement. This dissertation is motivated by this timely need to develop effective process control methods for variation reduction in thin film solar cell manufacturing processes. Three fundamental research issues related to process monitoring, diagnosis, and control have been studied accordingly. The major research activities and the corresponding contributions are summarized as follows: (1) Online SPC is integrated with generalized predictive control (GPC) for the first time for effective process monitoring and control. This research emphasizes on the importance of developing supervisory strategies, in which the controller parameters are adaptively changed based on the detection of different process change patterns using SPC techniques. It has been shown that the integration of SPC and GPC provides great potential for the development of effective controllers especially for a complex manufacturing process with a large time varying delay and different process change patterns. (2) A generic hierarchical ANOVA method is developed for systematic variation decomposition and diagnosis in batch manufacturing processes. Different from SPC, which focuses on variation reduction due to assignable causes, this research aims to reduce inherent normal process variation by assessing and diagnosing inherent variance components from production data. A systematic method of how to use a full factor decomposition model to systematically determine an appropriate nested model structure is investigated for the first time in this dissertation. (3) A Multiscale statistical process monitoring method is proposed for the first time to simultaneously detect mean shift and variance change for autocorrelated data. Three wavelet-based monitoring charts are developed to separately detect process variance change, measurement error variance change, and process mean shift simultaneously. Although the solar cell manufacturing process is used as an example in the dissertation, the developed methodologies are generic for process monitoring, diagnosis, and control in process variation reduction, which are expected to be applicable to various other semiconductor and chemical manufacturing processes.
25
Chapana, Randi Synnøve Hegdal. "The Relative Influence of Solar Radiative and Solar Geomagnetic Variation on the Dynamics of the Polar Upper Mesosphere." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18887.
Full textAbstract:
Resent research indicates that there might be a connection between perturbation of the Earth's geomagnetic field caused by solar wind, and the atmospheric circulation. In this project the mesospheric meridional and zonal wind, obtained from the SuperDARN radars Goose Bay, Hankasalmi, Kapuskasing, King Salmon, Kodiak, Pykkvibær, Saskatoon and Stokkseyri in the northern hemisphere was compared with the global Ap index along with the measure for solar radiance, the F10.7 index. Wind data from the SuperDARN radars were available for every hour and geomagnetic and irradiance data for every month. The solar atmospheric tides along with seasonal effects were removed from the wind data and the perturbation of the residual wind due to Ap and F10.7 was used to see if any connection between the mesospheric wind and Ap/F10.7 could be found, and if they influenced the wind in a similar manner. A tendency for more equatorwards and eastwards winds during periods of high geomagnetic activity was found. In addition, this effect was observed to increase with increasing geomagnetic latitude for the zonal wind. Ap and F10.7 often affected the wind in a similar manner, making it hard to distinguish the two. Using linear regression, the correlation between them was found to be high over the timescales of this study.
26
Las, Vergnas Olivier. "Contribution à l'étude des estimations historiques des éclats des étoiles brillantes par des analyses multidimensionnelles." Phd thesis, Université Pierre et Marie Curie - Paris VI, 1990. http://tel.archives-ouvertes.fr/tel-00655551.
Full textAbstract:
Les étoiles brillantes ont-elles des variations séculaires d'éclat ? Bien que plusieurs astronomes aient étudié ce sujet au cours des siècles écoulés, aucune réponse satisfaisante n'y a été donnée. Il y a un siècle, C. Flammarion rassembla les anciennes estimations et les publia dans son ouvrage Les étoiles et les curiosités du ciel. Il était évident de son point de vue qu'un grand nombre d'étoiles avaient eu des variations séculaires. Pickering (1895) et Zinner (1926) publièrent deux autres compilations de catalogues. Ils ne partageaient pas le point de vue de Flammarion, mais ne purent interpréter l'information contenue dans les données. Il n'y a pas eu d'étude plus récente sur ce sujet. De nouvelles méthodes d'analyse -comme l'analyse factorielle des correspondances- ont été créées ces dernières années, qui permettent d'étudier de manière approfondie de grands tableaux de données. La finalité du travail présenté ici est de voir si ces méthodes peuvent nous aider à résoudre ce problème des variations séculaires. La compilation des catalogues originaux permet de constituer un tableau de données intégrant des éléments "signatures" des diverses causes susceptibles d'expliquer les écarts d'éclats (des causes astrophysiques à la non-fiabilité des données). Plusieurs analyses factorielles, utilisant des codages spécifiques des données, comme "l'écart aux valeurs attendues" ou le "codage flou en magnitude entière", créés pour limiter les différences de notations entre les observateurs sont effectuées. Il n'en ressort pas de "signatures" significativement corrélées avec les écarts d'éclats ; en particulier, il n'y a pas d'effet de couleur constaté. Il semble y avoir globalement "mémoire" des éclats d'un catalogue sur l'autre. Seul échape à cette règle, le catalogue de Sir William Herschel, qui est également le seul à contenir des comparaisons d'éclat et non pas des valeurs de magnitude. Cela amène à se demander si il n'aurait pas été protégé de cet effet de "mémoire" à cause de sa différence de notation. Ce travail ne clôt pas la question. Il se termine par la définition de nouvelles analyses à mettre en place : pour tirer des conclusions astrophysiques, il peut être utile de tester des traitements combinant l'analyse factorielle et l'analyse de Fourier. De tels traitements permettront de se débarasser de l'information de phase et d'effectuer des études de corrélation de périodes.
27
Brilliant, Debra. "A study of nitrogen isotopic systematics in lunar soils and breccias." Thesis, n.p, 1999. http://oro.open.ac.uk/19082/.
Full text
28
Hossain, Sonia. "Influence of Climatic Variation on Soybean Yield in Japan and Asia." Kyoto University, 2014. http://hdl.handle.net/2433/189680.
Full textAbstract:
Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第18523号
農博第2080号
新制||農||1026(附属図書館)
学位論文||H26||N4867(農学部図書室)
31409
京都大学大学院農学研究科農学専攻
(主査)教授 白岩 立彦, 教授 奥本 裕, 教授 稲村 達也
学位規則第4条第1項該当
29
Soukharev, B. E., and L. L. Hood. "Solar cycle variation of stratospheric ozone: Multiple regression analysis of long-term satellite data sets and comparisons with models." AMER GEOPHYSICAL UNION, 2006. http://hdl.handle.net/10150/623340.
Full textAbstract:
Previous multiple regression analyses of the solar cycle variation of stratospheric ozone are improved by (1) analyzing three independent satellite ozone data sets with lengths extending up to 25 years and (2) comparing column ozone measurements with ozone profile data during the 1992–2003 period when no major volcanic eruptions occurred. Results show that the vertical structure of the tropical ozone solar cycle response has been consistently characterized by statistically significant positive responses in the upper and lower stratosphere and by statistically insignificant responses in the middle stratosphere (∼28–38 km altitude). This vertical structure differs from that predicted by most models. The similar vertical structure in the tropics obtained for separate time intervals (with minimum response invariably near 10 hPa) is difficult to explain by random interference from the QBO and volcanic eruptions in the statistical analysis. The observed increase in tropical total column ozone approaching the cycle 23 maximum during the late 1990s occurred primarily in the lower stratosphere below the 30 hPa level. A mainly dynamical origin for the solar cycle total ozone variation at low latitudes is therefore likely. The amplitude of the solar cycle ozone variation in the tropical upper stratosphere derived here is somewhat reduced in comparison to earlier results. Additional data are needed to determine whether this upper stratospheric response is or is not larger than model estimates.
30
Hood, L. L. "The solar cycle variation of total ozone: Dynamical forcing in the lower stratosphere." AMER GEOPHYSICAL UNION, 1997. http://hdl.handle.net/10150/624010.
Full textAbstract:
Multiple regression methods are applied to estimate the solar cycle variation of (1) zonal mean ozone as a function of altitude and latitude using a combination of Nimbus 7 solar backscattered ultraviolet (SBUV) and National Oceanic and Atmospheric Administration (NOAA) 11 SBUV/2 ozone profile data for a 15-year period; (2) total ozone as a function of latitude, longitude, and season using Nimbus 7 total ozone mapping spectrometer (TOMS) data for a 13.3-year period; (3) lower stratospheric temperature as a function of latitude, longitude, and season using microwave sounding unit (MSU) Channel 4 data for a 16-year period; and (4) lower stratospheric geopotential height as a function of latitude, longitude, and season in the northern hemisphere using Berlin height data for a 30-year period. According to the SBUV-SBUV/2 data, most (about 85%) of the 1.5–2% solar cycle variation of global mean total column ozone occurs in the lower stratosphere (altitudes < 28 km). Evidence is obtained for a related solar cycle variation of lower stratospheric temperature (50–150 mbar) and geopotential height (30, 50, and 100 mbar) with geographic dependences similar to that of the solar cycle variation of total ozone. Specifically, total ozone, lower stratospheric temperature, and lower stratospheric geopotential height have annual mean solar regression coefficients in the northern hemisphere that reach a maximum near 30°N latitude within a longitude sector extending from approximately 160°E to 250°E. Maximum variations from solar minimum to maximum in this sector are approximately 11 Dobson units, 0.8 K near 100 mbar, and 60 m at 50 mbar, respectively. Seasonal solar regression coefficients tend to be statistically significant over larger areas in summer but have larger amplitudes within limited regions in winter. These geographic similarities between total ozone, lower stratospheric temperature, and geopotential height solar coefficients suggest that changes in lower stratospheric dynamics between solar minimum and maximum may play an important role in driving the observed total ozone solar cycle variation. To test this hypothesis, a simplified perturbation ozone transport model is applied to calculate the expected total ozone variation owing to dynamical forcing for the calculated geopotential height solar coefficients, climatological ozone mixing ratios, and zonal winds. For the summer season during which the solar regression coefficients are significant over the largest area, both the amplitude and latitude dependence of the observed solar cycle ozone variation are approximately consistent with the model estimates.
31
Underhill, Christopher John. "A characterisation of noise sources in BiSON data, and their variation over the solar cycle." Thesis, University of Birmingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549250.
Full text
32
Jones, S. L. "Negating the Yearly Eccentricity Magnitude Variation of Super-synchronous Disposal Orbits due to Solar Radiation Pressure." Thesis, University of Colorado at Boulder, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1539339.
Full textAbstract:
Solar radiation pressure alters satellites' eccentricity by accelerating and decelerating them during each orbit. The accumulated perturbation cancels yearly for geostationary satellites, but meanwhile the perigee radius changes. Disposed satellites must be reorbited higher to compensate, using more fuel. The examined disposal orbit points toward the Sun and uses the satellite's natural eccentricity. This causes the eccentricity vector to only change direction, keeping the perigee radius constant. This thesis verifies this behavior over one year with an analytical derivation and MATLAB simulation, gaining useful insights into its cause. The traditional and proposed disposal orbits are then modeled using NASA's GMAT for more realistic simulations. The proposed orbit's sensitivity to satellite and initialization errors is also examined. Relationships are developed to show these errors' effect on the perigee radius. In conclusion, while this orbit can be used in the short term, margins are necessary to guarantee protection of the geostationary belt.
33
Theys, Céline. "Détection et caractérisation de variations dans des signaux non stationnaires : application à des signaux SONAR." Nice, 1993. http://www.theses.fr/1993NICE4676.
Full textAbstract:
Le sujet de ce mémoire s'inscrit dans le cadre de l'étude des signaux non stationnaires. A partir d'un problème réel qui est la détection de trajets multiples dans des signaux résultant d'une émission SONAR dans la direction d'une cible, plusieurs facettes du traitement du signal sont examinées. Après une première étape préalable de localisation du signal utile dans la récurrence totale, plusieurs méthodes de traitement des signaux non stationnaires sont développées dans le but de suivre la fréquence instantanée du signal puis de détecter et de caractériser les non stationnarités rapides dues à l'arrivée des trajets multiples. On étudie, dans un premier temps, des méthodes paramétriques dédiées au suivi des variations lentes dans le but d'estimer en ligne la fréquence instantanée du signal. Cette étude mettant en évidence des non stationnarités plus rapides, nous nous sommes orientés vers des méthodes séquentielles de détection de rupture, ce qui constitue la partie la plus développée et la plus novatrice de ce mémoire. En particulier, on propose deux solutions spécifiques pour détecter un saut dans les caractéristiques d'un signal sinunoi͏̈dal. La première solution proposée est originale par la mise en équations d'état d'un signal subissant un saut de phase et/ou d'amplitude. A partir de ce modèle du signal perburbé, on peut soit appliquer l'algorithme GLR de Willsky à partir des innovations du filtre de Kalman associé, soit simplifier ce test en le calculant directement à partir des observations. Cette solution étant, cependant, très lourde en calculs, une seconde solution est développée et calculée à partir de l'approche locale permettant de détecter un saut d'amplitude, de phase initiale ou de fréquence. Cette solution d'écriture complexe est très intéressante car on montre que l'expression du détecteur est simplifiable si l'on connait le type de saut, ce qui permet d'estimer l'amplitude du changement. Des simulations sur des signaux synthétiques permettent d'étudier les performances de ces différents algorithmes. Enfin, ils ont été appliqués à la détection de trajets multiples dans le signal réel sous-marin
34
Rogers, Hannah Mallalieu. "Labile Ligand Variation in Polyazine-Bridged Ruthenium/Rhodium Supramolecular Complexes Providing New Insight into Solar Hydrogen Production from Water." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/64364.
Full textAbstract:
Mixed-metal supramolecular complexes containing one or two RuII light absorbing subunits coupled through polyazine bridging ligands to a RhIII reactive metal center were prepared for use as photocatalysts for the production of solar H2 fuel from H2O. The electrochemical, photophysical, and photochemical properties upon variation of the monodentate, labile ligands coordinated to the Rh reactive metal center were investigated.
Bimetallic complexes [(Ph2phen)2Ru(dpp)RhX2(Ph2phen)]3+ (Ph2phen = 4,10-diphenyl-1,10-phenanthroline; dpp = 2,3-bis(2-pyridyl)pyrazine; X = Br- or Cl-) were prepared using a building block approach, allowing for selective component choice. The identity of the halide coordinated to Rh did not impact the light absorbing or excited state properties of the structural motif. However, the o-donating ability of the halides modulated the Rh-based cathodic electrochemistry and required the use of multiple pathways to explain the reduction of Rh by two electrons. Regardless of halide identity, the bimetallic complex possessed a Ru-based HOMO (highest occupied molecular orbital) and Rh-based LUMO (lowest unoccupied molecular orbital) important for photoinitiated electron collection at Rh. As a photocatalyst for H2 evolution, the X = Br- complex produced nearly 30% more H2 than the X = Cl- analogue. H2 production experiments with added halide suggested that ion pairing with halides played a major role in catalyst deactivation, which provided evidence for the importance of component selection for photocatalyst design.
New trimetallic complex [{(bpy)2Ru(dpp)}2Ru(OH)2](PF6)5 (bpy = 2,2'-bipyridine) was prepared for comparison to halide analogues [{(bpy)2Ru(dpp)}2RhX2](PF6)5 (X = Br- or Cl-). The synthesis of a halide-free supramolecule containing OH- ligands afforded an ideal system to further examine the impact of the ligands at the reactive metal center on H2 photocatalysis. Electrochemistry results revealed that while the identity of the ligands at Rh did modulate the Rh-based reduction potential, all three complexes possessed a Ru-based HOMO and Rh-based LUMO. The light absorbing properties were not impacted by the identity of the monodentate ligands at Rh; however, the excited state properties did vary upon changing the ligands at Rh. The hydroxo trimetallic complex functioned as a photocatalyst for H2 production in organic solvent, producing nearly double the amount of H2 as the highest performing Br-' trimetallic complex in DMF solvent. Interestingly, H2 production studies in high dielectric aqueous solvent revealed no discrepancies in H2 evolution upon variation of the ligands at Rh, which further supported the ion pairing phenomenon realized for the bimetallic motif.
Variation of the labile ligands coordinated to the Rh reactive metal center in RuIIRhIII multimetallic supramolecules provided important insight about the large impact of small structural variation on H2 photocatalysis. Electrochemical, photophysical, and photochemical studies of new RuIIRhIII complexes afforded a deeper understanding of the molecular processes important for the design of new complexes applicable to solar fuel production schemes.Ph. D.
35
Cook, Daniel A. "Variational and active surface techniques for acoustic and electromagnetic imaging." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53522.
Full textAbstract:
This research seeks to expand the role of variational and adjoint processing methods into segments of the sonar, radar, and nondestructive testing communities where they have not yet been widely introduced. First, synthetic aperture reconstruction is expressed in terms of the adjoint operator. Many, if not all, practical imaging modalities can be traced back to this general result, as the adjoint is the foundation for backprojection-type algorithms.
Next, active surfaces are developed in the context of the Helmholtz equation for the cases of opaque scatterers (i.e., with no interior field) embedded in free space, and penetrable scatterers embedded in a volume which may be bounded. The latter are demonstrated numerically using closed-form solutions based on spherical harmonics. The former case was chosen as the basis for a laboratory experiment using Lamb waves in an aluminum plate. Lamb wave propagation in plates is accurately described by the Helmholtz equation, where the field quantity is the displacement potential. However, the boundary conditions associated with the displacement potential formulation of Lamb waves are incompatible with the shape gradient derived for the Helmholtz equation, except for very long or very short wavelengths.
Lastly, optical flow is used to solve a new and unique problem in the field of synthetic aperture sonar. Areas of acoustic focusing and dilution attributable to refraction can sometimes resemble the natural bathymetry of the ocean floor. The difference is often visually indistinguishable, so it is desirable to have a means of detecting these transient refractive effects without having to repeat the survey. Optical flow proved to be effective for this purpose, and it is shown that the parameters used to control the algorithm can be linked to known properties of the data collection and scattering physics.
36
Eppanapelli, Lavan Kumar. "Investigation of wind potential variation at three measurement sites based on atmospheric stability and power production." Thesis, KTH, Kraft- och värmeteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-136935.
Full textAbstract:
As tapping energy from wind expands rapidly worldwide, it is a common procedure to locate a practicable site to extract energy from abundant wind flow by building wind farms. Comprehensive understanding of wind resource at a site is important to perform the main activities say, wind flow modeling, wind turbines micro siting, annual energy yield calculation and cost of energy estimation. Wind measuring campaigns involve using of measuring instruments such as meteorological tower instrumented with anemometers, wind vanes and temperature sensors; remote sensing devices such as SoDAR, LiDAR. These meteorological devices provide detailed information on wind behavior with respect to the height, time and temperature. These systems were proven in providing promising wind measurements even though they are susceptible to certain weather conditions. The study progressed by focusing on the wind behavior at three locations to investigate the possible factors that varies the wind character. A location with one met mast and two AQ500 SoDAR systems was considered for this project where one AQ500 is 800m away and other AQ500 is 5515m away from the point of Met mast. The location is contemplated as a decent approach to the spatial analysis of the wind resource as there is a large scope to analyze the wind character between two nearby sites and two faraway sites. Monostatic 3-beam SoDAR systems from AQ System, Sweden and 100m meteorological tower with instruments are used in this project work for collecting the wind data. One-year worth of wind data at standard 10min intervals has been collected from the three systems. This report outlines the theoretical description of project location, AQ500 SoDAR and Met mast. A detailed explanation of the data quality control and filtering methods are discussed along with respective reasons. The conclusion is drawn after performing the statistical analysis between wind speed and other parameters such as turbulent intensity, wind direction, thermal stability and temperature. Mat lab is used for computing and analyzing the wind data from three systems.
37
Towfie, Nazley. "Dynamic variation of hydrogen dilution during hot-wire chemical vapour deposition of silicon thin films." Thesis, University of the Western Cape, 2013. http://hdl.handle.net/11394/3813.
Full textAbstract:
It has been debated that among all the renewable energy alternatives, only solar energy offers sufficient resources to meet energy demands. Silicon thin film solar cells are at the frontier of commercial solar technology. Hot wire chemical vapour deposition (HWCVD) is the technique of choice for silicon thin film deposition due to the absence of ion bombardment and its independence toward geometry or electromagnetic properties of the substrate, as seen by plasma enhanced chemical vapour deposition (PECVD). With the implementation of nanostructures in a
multi-band gap tandem solar cell, considerable improvement has been achieved over the single junction solar cells. Defect assisted tunnelling processes at the junctions between individual solar cells in a tandem structure solar cell largely affect the efficiency of these solar cells. In this contribution, the investigation toward the improvement of silicon thin films for tandem solar cell application is initiated. This study reports on the effects of hydrogen dilution and deposition time on six silicon thin films deposited at six specific deposition regimes. The thin film properties are investigated via X-Ray diffraction analysis, Raman spectroscopy, Fourier transform infra-red spectroscopy, elastic recoil detection analysis, scanning and transmission electron microscopy and UV-visible spectroscopy. This investigation revealed the dominating etching effect of atomic hydrogen with
the increase in hydrogen dilution and a bonded hydrogen content (CH) exceeding 10 at.% for each of the six thin films. The optically determined void volume fraction and static refractive index remain constant, for each thin film, with the change in CH. A new deposition procedure, utilising the deposition conditions of the previously investigated thin films, is performed by HWCVD to deposit two silicon thin films. This deposition procedure involved either increasing (protocol 1) or decreasing (protocol 2) hydrogen dilution during deposition. Structural and optical variation with depth was observed for the dynamically deposited silicon thin films, with nano-voids existing across the entire cross section and bond angle variations which are indicative of good structural order. The optical absorption curves differ for the two silicon thin films whereas the optical density remains constant for both.>Magister Scientiae - MSc
38
Kübler, Svea. "Evaluation of the Variation in Operating Point for a Solar-Driven Gas-Yurbine and its Influence on the Performance of the Machine." Thesis, KTH, Energiteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-72489.
Full text
39
Didelot, Aurélien. "Films d’oxydes de vanadium thermochromes dopés aluminium obtenus après un recuit d’oxydation-cristallisation pour applications dans le solaire thermique." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0307/document.
Full textAbstract:
Ces travaux sont issus d’une thèse CIFRE et de la collaboration entre la société Viessmann Faulquemont et le laboratoire de recherche l’Institut Jean Lamour. Ayant pour objectif de fortement réduire les problèmes liés aux hautes températures de stagnation dans les panneaux solaires thermiques, nous présentons une nouvelle génération d’absorbeur solaire intelligent à base de dioxyde de vanadium. Le dioxyde de vanadium, noté VO2, est un matériau présentant une transition métal-isolant (MIT) à une température critique (Tc) de 68°C. Cette transition s’accompagne d’une modification de la structure cristallographique. Le VO2 se trouve sous une forme monoclinique VO2(M) à basse température, et sous une forme rutile VO2(R) à haute température. Ce changement de structure s’accompagne d’une forte modification des propriétés optiques. La synthèse de ces films est réalisée à partir d’une couche de vanadium métallique déposée par pulvérisation. Un recuit d’oxydation-cristallisation est ensuite effectué pour obtenir une couche d’environ 400 nm de dioxyde de vanadium. Afin d’optimiser et d’augmenter la variation d’émissivité (Δε), la température et la durée du recuit sont étudiées. Dans un second temps, un dopage aluminium est réalisé afin d’augmenter l’effet de la transition thermochrome. Après optimisation, le passage au niveau industriel est un succès et des prototypes de taille 1 sont réalisés à partir de la couche thermochrome et de la couche standard afin d’être comparés dans des conditions normales d’utilisationThis work is a CIFRE thesis between VIESSMANN Faulquemont SAS society and the laboratory Institut Jean Lamour. In order to strongly reduce the problems associated with high stagnation temperature, we present a new generation of solar absorbent layers based on a smart thermochromic vanadium dioxide thin film. Vanadium dioxide (VO2) is a material which exhibit a metal insulator transition (MIT) at a critical temperature of 68°C (Tc). The transition is accompanied by a change in crystallographic structure VO2(M), while a rutile-like structure VO2(R) is obtained at high temperature. This structural change induces a drastic modification of the optical properties. The synthesis of vanadium-based films is performed using magnetron sputtering. We proceed to a subsequent annealing in air to form crystalline films of about 400 nm thickness. In order to increase the thermochromic effect of our thin film (Δε) we study the temperature and duration of the annealing. In a second time we try to increase the emissivity switch between the low and high temperature phase by adding an aluminum doping. After optimization, scale up have been successfully done and the optimized parameters have been used to build a prototype of thermochromic selective layer that has been compared to the standard industrial solar absorber
40
Tenholt, Frederik Josef [Verfasser], Julia [Gutachter] Tjus, and Horst [Gutachter] Fichtner. "Studying the temporal variation of the cosmic-ray sun shadow : comparison of IceCube data with models of the solar magnetic field / Frederik Tenholt ; Gutachter: Julia Tjus, Horst Fichtner ; Fakultät für Physik und Astronomie." Bochum : Ruhr-Universität Bochum, 2020. http://d-nb.info/1205976329/34.
Full text
41
Tenholt, Frederik [Verfasser], Julia [Gutachter] Tjus, and Horst [Gutachter] Fichtner. "Studying the temporal variation of the cosmic-ray sun shadow : comparison of IceCube data with models of the solar magnetic field / Frederik Tenholt ; Gutachter: Julia Tjus, Horst Fichtner ; Fakultät für Physik und Astronomie." Bochum : Ruhr-Universität Bochum, 2020. http://d-nb.info/1205976329/34.
Full text
42
Antoine, Joseph. "Synthèse par pulvérisation cathodique de pérovskites thermochromes comme couche sélective "haute performance" d'absorbeurs solaires thermiques." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0273.
Full textAbstract:
Ces travaux de thèse ont porté sur l’étude du système LaCoO3 élaboré sous forme de couches minces par pulvérisation cathodique magnétron réactive. La première partie de ce travail est dédiée à l’étude des paramètres de synthèse permettant l’obtention d’un film homogène cristallin. Les influences sur la transition thermochrome des paramètres de traitement thermique et de la pression de dépôt sont discutées. Nous avons montré qu’il était possible de contrôler le rapport entre les phases cubique et rhomboédrique ainsi que la taille des cristallites en optimisant les paramètres de synthèse. Dans une seconde partie, nous avons étudié en détail les changements de propriétés de nos échantillons à l’aide du rayonnement synchrotron et de la microscopie électronique en transmission. Nos mesures ont montré que la phase cubique et la taille de cristallites influent le spin des atomes de cobalt et donc sur la nature des liaisons Co-O. Nous avons mis en évidence qu’une microstructure fine et une phase rhomboédrique augmentent l’effet thermochrome et l’amplitude optique de la transition grâce à une augmentation de la densité de population au niveau de Fermi et une diminution du gap optiqueThe present PhD work is focused on the study of the LaCoO3 system deposited as a thin film by reactive magnetron sputtering. The first part of this work is dedicated to the influence of the deposition parameters on the film structure. The influences of heat treatment parameters and deposition total pressure on the thermochromic transition are discussed. We have shown that it is possible to control the ratio between the cubic and rhombohedral phases as well as the size of the crystallites through the control of our parameters. In a second part, we studied in detail the properties changes using synchrotron radiation and transmission electron microscopy. Our measurements have shown that the cubic phase and the crystallites size influence the spin of cobalt atoms and therefore the nature of the Co-O bonds. We have shown that a fine microstructure and a rhombohedral phase increase the thermochromic effect and the optical switch of the transition thanks to an increase in the population density at the Fermi level and a decrease of the optical gap
43
Jovan, Bajčetić. "Modelovanje uticaja intenzivnih promena Sunčevog zračenja na prostiranje radio talasa." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2017. https://www.cris.uns.ac.rs/record.jsf?recordId=102468&source=NDLTD&language=en.
Full textAbstract:
Ova disertacija predstavlja rezultate istraživanja uticaja dve vrsteintenzivnih promena Sunčevog zračenja na prostiranje radio talasa. Prvi deoprikazanih rezultata odnosi se na efekte neperiodičnih zračenja u X-opsegutalasnih dužina u toku trajanja Sunčevog X-flera. Izvršeno je modelovanjekarakteristika jonizovane sredine D-sloja jonosfere u toku celokupnogtrajanja efekata dodatne energije jonizacije i karakteristika prostiranjaradio talasa određenih frekvencijskih opsega u okviru navedene sredine.Drugi deo rezultata prikazuje periodičnu promenu nivoa prijemnog signalausmerene mikrotalasne radio komunikacije koja nastaje u toku jutarnjihčasova. Pokazano je da ova promena ima visok stepen korelisanosti sapromenama vrednosti geomagnetskog polja i da je uzrokuje pojava Sunca nahorizontu. Na osnovu rezultata dobijenih merenjem je predložen model kojiopisuje trend navedene promene u jutarnjim časovima.This thesis presents the research results of intensive solar radiation variationinfluence on radio propagation. The first part of presented results is related to theeffects of non-periodic radiation within X-ray wavelength during Solar X-flare.Modelling of ionosphere D-layer medium is performed during all time duration ofadditional ionization energy, as well as radio propagation characteristics within thismedium. The second part of the measured results presents periodic variation ofreceiving microwave radio signal level of experimental Line-of-site communicationduring the morning hours. It is shown that this variation is highly correlated withgeomagnetic field component values variation and that is caused by the Sunappearance on the horizon. Based on the experimentally collected results, the modelthat describes this variation during morning hours is proposed.
44
Juwono, Alamsyah M. "Cosmic ray solar diurnal and sidereal variations." Thesis, 1997. https://eprints.utas.edu.au/20379/1/whole_JuwonoAlamsyahM1997_thesis.pdf.
Full textAbstract:
Data from underground cosmic ray observatories at Cambridge and
Liapootah, Tasmania and Mawson, Antarctica, have been studied to
determine the amplitudes of Solar Diurnal Variations for period of 11 years,
1982-1992, for Cambridge and Mawson observatories, and for 1992-1993 for
Liapootah observatory. The amplitudes are estimated for either monthly
average or yearly average, for ground based and free space as well. The
monthly Solar Diurnal Variations have been shown to be contaminated by
Sidereal component, and by using method of the sinusoidal fittings, the
amplitudes of Solar Diurnal Variation and the Sidereal component of the
variation have been extracted. The results of extracting the monthly Solar
Diurnal Variations are (0.104 ± 0.004 %), (0.116 ± 0.006 %) for Cambridge,
(0.090 ± 0.004 %) for Mawson and (0.060 ± 0.008 %) for Liapootah. The
amplitudes of Sidereal component contaminating the Solar Diurnal Variations
also have been found. These sidereal amplitudes are (0.043 ± 0.006 %) and
(0.022 ± 0.008 %) for Cambridge, (0.019 ± 0.006 %) for Mawson and
(0.0067 ± 0.012 %) for Liapootah.
By using the Sidereal Variation component as detected in a deep
underground station at Poatina as reference, i.e. that it is assumed to be purely
galactic, the percentage of the Sidereal component detected by one of
Cambridge's telescope which is due to North-South Anisotropy has been
estimated. The result is that about 72% of total 0.043% Sidereal component
detected in that telescope is due to North-South Anisotropy, and the other
28% is of galactic origin.
Times of Maximum for monthly Solar Diurnal Variation detected by the
two observatories, Cambridge and Mawson, are also discussed. The results
show that in the ground-based observation Time of Maximum of Mawson
tends to be later than those of Cambridge. Free Space analysis shows that
there is good similarity among Times of Maximum of the monthly Solar
Diurnal Variations detected by the two telescopes at Cambridge and one at
Mawson, which in turn exhibits that cosmic ray particles which are detected
in polar regions may undergo different magnetic bending than those detected
in lower latitude regions. The free space analysis also gives the estimates of
free space amplitudes of the Solar Diurnal Variations for corresponding Solar
Diurnal Variation amplitudes as they observed in the ground.
Yearly Solar Diurnal Variations at Cambridge and Mawson have also been
studied. The wave-forms of the yearly plots during period of 1982-1993 show
that they are consistent with the long-term modulations, either 11-year or 22-
year modulation. In this case it is shown that the cosmic rays detected in those
two observatories during 1985/1986 underwent a minor depression, i.e. a
situation when 11-year and 22-year modulation waves are superposing with
one out of phase to the other.
The last part of this study concerns on North-South Asymmetry of the
sidereal variation. Data from vertical telescope at Liapootah are used for this purpose. The 1992-1993 data of Liapootah have been compared to data from
the vertical telescope at Matsushiro underground station. The result of the
Sidereal Variation of (0.040 ± 0.007 %) from Liapootah is significantly larger
than that found from Matsushiro which is (0.026 ± 0.008 %). This result
confirms what previously reported by Munakata et al. (1994). Sidereal
Variations from other telescope components of Liapootah station have also
been studied. They are plotted against the latitudes of viewing of
corresponding telescopes, to examine the presumption that there is NorthSouth
Asymmetry of Sidereal Variation. The result of the plotting supports
the presumption, and it exhibits that the line of symmetry may lie somewhere
between equator and 20C S.
45
Shepherd, Simon J., S. I. Zharkov, and Valentina V. Zharkova. "Prediction of Solar Activity from Solar Background Magnetic Field Variations in Cycles 21-23." Thesis, 2014. http://hdl.handle.net/10454/10790.
Full textAbstract:
yesA comprehensive spectral analysis of both the solar background magnetic field (SBMF) in cycles 21-23 and the sunspot magnetic field in cycle 23 reported in our recent paper showed the presence of two principal components (PCs) of SBMF having opposite polarity, e. g., originating in the northern and southern hemispheres, respectively. Over a duration of one solar cycle, both waves are found to travel with an increasing phase shift toward the northern hemisphere in odd cycles 21 and 23 and to the southern hemisphere in even cycle 22. These waves were linked to solar dynamo waves assumed to form in different layers of the solar interior. In this paper, for the first time, the PCs of SBMF in cycles 21-23 are analyzed with the symbolic regression technique using Hamiltonian principles, allowing us to uncover the underlying mathematical laws governing these complex waves in the SBMF presented by PCs and to extrapolate these PCs to cycles 24-26. The PCs predicted for cycle 24 very closely fit (with an accuracy better than 98%) the PCs derived from the SBMF observations in this cycle. This approach also predicts a strong reduction of the SBMF in cycles 25 and 26 and, thus, a reduction of the resulting solar activity. This decrease is accompanied by an increasing phase shift between the two predicted PCs (magnetic waves) in cycle 25 leading to their full separation into the opposite hemispheres in cycle 26. The variations of the modulus summary of the two PCs in SBMF reveals a remarkable resemblance to the average number of sunspots in cycles 21-24 and to predictions of reduced sunspot numbers compared to cycle 24: 80% in cycle 25 and 40% in cycle 26.
46
Ho, Wan-chien, and 何萬謙. "Variations of ionospheric neutral densities in response to solar activity." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/71310393180035983666.
Full textAbstract:
碩士國立中央大學
太空科學研究所
102
This thesis focuses on the studies of variations of neutral densities at a height of 410 Km in response to solar activity. It use solar radiation indices F10.7 and EUV to linearly fit neutral density measured by the Challenging Minisatellite Payload (CHAMP) satelliteduring the period 2003 - 2008. Aclearly phase delay in solar radiation and neutral density have been found when we were doing data analysis. It's also pointed out that neutral density variation has a time delay with solar radiation in the previous papers. In this study, we could get a conclusion that the time delay is one day during 2003 to 2008. In doing the linear regression,the result from multiple parameters is almost the same as that from single parameter. And, because of the more completeness of the observations of F10.7 than EUV, we decide to use F10.7 index to be the main parameter in the following studies. To compare original data of neutral density with the fitted data has a significant difference in the period of low solar activity. The difference has high relation with Kp index. Additional linear regression is required for these differences with Kp index.The results indicate that solar radiation is a dominate factor in the variations of neutral densities in the period of high solar activity, and geomagnetic activity produced by the solar wind becomes important in the low solar activity. The difference between original data of neutral density with the fitted data has a period of 130 days, which can be attributed to the satellite orbit.Removement of this component can increase the correlation coefficient of the original data the fitted data up to 0.95. But this effect is only important in the period near solar minimum.
47
Zharkova, Valentina V., Simon J. Shepherd, E. Popova, and Sergei I. Zharkov. "Heartbeat of the Sun from Principal Component Analysis and prediction of solar activity on a millenium timescale." 2015. http://hdl.handle.net/10454/11803.
Full textAbstract:
yesWe derive two principal components (PCs) of temporal magnetic field variations over the solar cycles 21–24 from full disk magnetograms covering about 39% of data variance, with σ = 0.67. These PCs are attributed to two main magnetic waves travelling from the opposite hemispheres with close frequencies and increasing phase shift. Using symbolic regeression analysis we also derive mathematical formulae for these waves and calculate their summary curve which we show is linked to solar activity index. Extrapolation of the PCs backward for 800 years reveals the two 350-year grand cycles superimposed on 22 year-cycles with the features showing a remarkable resemblance to sunspot activity reported in the past including the Maunder and Dalton minimum. The summary curve calculated for the next millennium predicts further three grand cycles with the closest grand minimum occurring in the forthcoming cycles 26–27 with the two magnetic field waves separating into the opposite hemispheres leading to strongly reduced solar activity. These grand cycle variations are probed by α − Ω dynamo model with meridional circulation. Dynamo waves are found generated with close frequencies whose interaction leads to beating effects responsible for the grand cycles (350–400 years) superimposed on a standard 22 year cycle. This approach opens a new era in investigation and confident prediction of solar activity on a millenium timescale.
48
Gong, Bin. "Variations of Jovian aurora induced by changes in solar wind dynamic pressure." Thesis, 2005. http://hdl.handle.net/1911/18908.
Full textAbstract:
The jovian aurora contains a persistent main oval encircling each magnetic pole, which is associated with the upward field-aligned currents in the corotation enforcement current system. It has been suggested by two recent studies that the brightness of the main oval should become temporarily dimmer ∼ 1 hr after arrival of a shock wave in the solar wind, compressing the magnetosphere abruptly, because the difference between the angular velocity of the plasma in the magnetosphere and the rigid planetary rotational speed becomes smaller. But recent observations at Jupiter and Saturn have reported the opposite: the auroral oval brightens, and moves poleward, after the arrival of a solar wind shock. In this thesis, I will quantitatively include the flywheel effect of the neutral gas in the ionosphere in the coupling current system to explain this discrepancy and show that the corotation enforcement current should reverse and strengthen after a compression, and thereby temporarily cause the main oval to become brighter and move poleward. I will also show the differences between the night side and the day side in steady state and after a compression event by applying two different magnetic field models fitted from observations, and try to qualitatively explain the dawn-dusk asymmetry by introducing a region-1 current system analogous to that at Earth, which arises from the detailed interaction between solar wind and magnetosphere. Generally, I expect the day side sector of the main oval to brighten more than the night side sector, and the dawn sector to brighten more than the dusk sector.
49
Huang, Guan-Han, and 黃冠瀚. "Constructing Solar Synoptic Maps to Study The Temporal Variations of Coronal Holes." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/09312845136150154268.
Full textAbstract:
碩士國立中央大學
太空科學研究所
104
Synoptic maps are approximations of the full surface of the sun. We construct synoptic maps from CR2099 to CR2158 to study the dark regions on the EUV image called coronal holes. The data are retrieved from Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager onboard Solar Dynamics Obervatory. Each synoptic map contains 48 central meridian images arranged in time series. Dark regions are extracted by the thresholding routines. A dark region is identified as a coronal hole if its magnetic field skewness exceeds 0.35. The sun is divided into north-polar (65° to 90°), mid-low latitude (-65° to 65°) and south-polar (-90° to -65°) region. Each region the area and unsigned flux of coronal holes are calculated and discussed. The result shows that mid-low latitude holes occupy 5% the area of mid-low latitude region, with unsigned flux 0.8×10^22 Mx. South-polar holes occupy 30% the area of the south polar region, with unsigned flux 0.4×10^22 Mx. Since south-polar region is much smaller than the mid-low latitude region, the magnetic field is stronger in south-polar holes than in mid-low latitude holes. In addition, we combine synoptic maps with Real-Time Solar Wind measurements on Advanced Composition Explorer, and try to trace fast solar wind particles from 1 AU back to the solar surface. The result shows that 48% of fast solar wind sources are close to the center of coronal holes.
50
Xu, Daoxiang, and 徐道翔. "A performance study of the cut solar cell base on shunt resistance variations." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/47405445508914458761.
Full textAbstract:
碩士聖約翰科技大學
電機工程系碩士班
100
This paper developed a detection method of cut solar cell. First using MATLAB software to simulate solar cell equivalent circuit mathematical model to understand the impact of solar cell equivalent circuit the shunt resistance change of the I-V curve. Established shunt resistance change will affect the slope of the curve near the short-circuit current in the I-V curve. On this basis, design level slope curve test method and reverse voltage test method, respectively use the solar cells irradiated (level curve slope test method) and unirradiated (reverse voltage test method) the shunt resistance characteristics, to achieve detection of cut solar cell performance. Finally comparison of measurement results and make recommendations.