41 |
Uniformidade da irrigação por microaspersão em jardim residencial e por aspersão em campos de golfe e futebol / Uniformity of irrigation by microsprinkler in residential garden and by sprinkler in golf and football fieldsSiqueira, Marta Mitiko Kubota de 15 May 2017 (has links)
Submitted by Neusa Fagundes (neusa.fagundes@unioeste.br) on 2017-09-04T14:42:23Z
No. of bitstreams: 1
Marta_Mitiko2017.pdf: 6466029 bytes, checksum: bea176930ed4aba028576fab986137a4 (MD5) / Made available in DSpace on 2017-09-04T14:42:23Z (GMT). No. of bitstreams: 1
Marta_Mitiko2017.pdf: 6466029 bytes, checksum: bea176930ed4aba028576fab986137a4 (MD5)
Previous issue date: 2017-05-15 / With the cities expansion, investments in recreation areas, development’s facades, parks and sports areas have been significant in urban areas. It can be noticed that the landscaping of these areas usually consists of extensive grassy areas, protecting the soil against erosions, allowing rainwater drainage and avoiding flooding. However, to maintain this landscaping, the manpower for irrigation or the use of some irrigation system is necessary. Thus, considering the water scarcity that affects several regions of the planet, the present study aimed to evaluate irrigation systems by micro sprinklers in a residencial garden and by sprinklers on a golf and a football fields. The assays were performed according to ABNT standards, calculating the Christiansen uniformity coefficient (CU) and distribution uniformity coefficient (DU), with collectors positioned with their base on the lawn. In addition to the irrigation depth data, climate data such as temperature, air humidity, wind speed, and direction were also collected through a mini meteorological station installed near the trials. At the residence garden, the main objective was to evaluate four microsprinklers under five different operating pressures, which varied from 80 to 180 kPa. The microsprinklers were arranged in a grid of 2.50 x 2.50 meter with area of 6.25 m2, among which 25 collectors were placed, spaced 0.50 meters apart. Twenty-five replications were performed with 1 hour of irrigation and the climatic data were obtained every 10 minutes, with the mini meteorological station at 1 meter high. The best results for CUC, CUD and efficiency were obtained in treatment 4 (150 kPa pressure), with values of 81.38, 72.19 and 53.15%, respectively. In all treatments, the climatic factors with the highest level of similarity were between temperature and wind speed. It was identified by the control chart that only treatment 4 was under statistical control. Therefore, it has been found that it is possible to use a service pressure of 150 kPa, lower than the one specified by the catalog (180 kPa) without significant losses of uniformity of water distribution and efficiency of application. In the football field, two parallel lateral lines, 18 meters apart, were installed with five mini cannon type sprinklers on each line with spacing of 18 meters. The tests were performed in two areas, area A being between the first four sprinklers, and area B between the last four sprinklers. The collectors were spaced 2 meters apart, totalizing 81 collectors between the sprinklers in each area. Twenty-five replications were performed with 10 minutes of irrigation, obtaining the climatic data every 5 minutes, with the mini meteorological station at 2 meters high. In both areas, the results for CUC, CUD and efficiency were not significant at the 5% level. Among the climatic factors, relative air humidity and wind speed had the highest level of similarity, with 67.90%. The control graphs of both areas showed that irrigation was under statistical control. These results indicated that uniformity of water distribution and efficiency was maintained along the lateral line. At the golf course, the tests were performed in three different areas called Tee, Fairway, and Green, in which the collectors were distributed among spacers spaced 2 meters apart. At these sites, 25 trials of 12 minutes of irrigation were performed, with the mini meteorological station positioned at 2 meters high and collecting the climatic data every 5 minutes. In the areas of Tee and Fairway, 27 and 84 collectors were placed, respectively, between four sprinklers, and in the area of Green, 138 collectors between five sprinklers. Soil density and gravimetric moisture in the field capacity and permanent wilting point were obtained in the laboratory to calculate the application efficiency. The best results for CUC, CUD and efficiency were obtained in Tee. On the other hand, from the relative depht, it was verified that irrigation in the Fairway was the closest to the required real irrigation, with lower excess water applied. It was detected from the control chart that the irrigation in the Tee was not under control, unlike the other areas. It was identified that the climatic factors of greater similarity were between wind speed and relative air humidity, with 83.79%, obtained in the Fairway. Overall, due to the low value of the process capability index, both in the residential garden, golf course and football field, the irrigations were not able to remain under control over time. However, the application of the techniques used in the present research was important to detect possible irrigation faults, which can be corrected during the process. / Com o crescimento das cidades, investimentos em áreas de lazer, fachadas de empreendimentos, parques e áreas esportivas têm sido representativos nas zonas urbanas. Percebe-se que o paisagismo dessas áreas é normalmente constituído por extensas áreas gramadas, que protegem o solo contra erosões, possibilitando a drenagem de águas pluviais, evitando possíveis inundações. No entanto, para manter esse paisagismo é necessário mão de obra para a rega ou o uso de algum sistema de irrigação. Dessa forma, considerando-se a escassez da água que atinge diversas regiões do planeta, o presente estudo objetivou avaliar os sistemas de irrigação por microaspersão em um jardim residencial e por aspersão em um campo de golfe e futebol. Os ensaios foram realizados de acordo com as normas da ABNT, calculando-se o coeficiente de uniformidade de Christiansen (CUC) e coeficiente de uniformidade de distribuição (CUD), cujos coletores foram posicionados com a sua base sobre o gramado. Além dos dados da lâmina de irrigação, foram coletados dados climáticos como temperatura, umidade relativa do ar, velocidade e direção do vento a partir de uma miniestação meteorológica instalada nas proximidades dos ensaios. No jardim residencial, o principal objetivo foi de avaliar quatro microaspersores sob cinco diferentes pressões de serviço (de 80 a 180 kPa). Os microaspersores foram dispostos numa malha de 2,50 x 2,50 metros com área de 6,25 m2, entre os quais posicionaram-se 25 coletores distanciados de 0,50 metros entre si. Foram realizadas 25 repetições com duração de 1 hora de irrigação e obtidos os dados climáticos a cada 10 minutos, estando a miniestação meteorológica a 1 metro de altura. Os melhores resultados quanto ao CUC, CUD e eficiência foram obtidos pelo tratamento 4 (pressão de 150 kPa), com os valores de 81,38, 72,19 e 53,15%, respectivamente. Em todos os tratamentos, os fatores climáticos com maior nível de similaridade foram entre a temperatura e a velocidade do vento. Identificou-se pelo gráfico de controle que somente o tratamento 4 (pressão de 150 kPa) esteve sob controle estatístico. Assim, verificou-se que é possível utilizar pressão de serviço de 150 kPa, inferior ao especificado pelo catálogo (180 kPa) sem perdas significativas de uniformidade de distribuição de água e eficiência de aplicação. No campo de futebol, foram instaladas duas linhas laterais paralelas e distanciadas em 18 metros, com cinco aspersores do tipo mini canhão em cada linha com espaçamento de 18 metros. Os ensaios foram realizados em duas áreas, estando a área A entre os quatro primeiros aspersores e a área B entre os quatro últimos aspersores. Os coletores foram espaçados de 2 metros, totalizando 81 coletores entre os aspersores em cada área. Foram realizadas 25 repetições com 10 minutos de irrigação, obtendo-se os dados climáticos a cada 5 minutos, com a miniestação meteorológica a 2 metros de altura. Em ambas as áreas, os resultados quanto ao CUC, CUD e eficiência não houve diferença significativa ao nível de 5%. Entre os fatores climáticos, a umidade relativa do ar e a velocidade do vento tiveram o maior nível de similaridade, com 67,90%. Pelo gráfico de controle de ambas as áreas, verificou-se que a irrigação esteve sob controle estatístico. Esses resultados indicaram que a uniformidade de distribuição de água e a eficiência se mantiveram ao longo da linha lateral. No campo de golfe, os ensaios foram realizados em três áreas diferentes denominadas Tee, Fairway e Green, nas quais os coletores foram distribuídos entre os aspersores, distanciados em 2 metros. Nesses locais, foram realizados 25 ensaios de 12 minutos de irrigação, com a miniestação meteorológica posicionada a 2 metros de altura e coleta dos dados climáticos a cada 5 minutos. Nas áreas do Tee e do Fairway foram colocados respectivamente 27 e 84 coletores entre quatro aspersores e na área do Green, 138 coletores entre cinco aspersores. A densidade do solo e a umidade gravimétrica na capacidade de campo e ponto de murcha permanente foram obtidas em laboratório para o cálculo da irrigação real necessária. Os melhores resultados quanto ao CUC, CUD e eficiência foram obtidos no Tee. Por outro lado, a partir da lâmina relativa verificou-se que irrigação no Fairway foi a mais próxima da irrigação real necessária, com menor excesso de água aplicada. Detectou-se, a partir do gráfico de controle que a irrigação no Tee esteve fora de controle, ao contrário das demais áreas. Identificou-se que os fatores climáticos de maior similaridade foram entre a velocidade do vento e umidade relativa do ar, com 83,79%, obtida no Fairway. De forma geral, devido ao baixo valor do índice de capacidade do processo, tanto no jardim residencial quanto nos campos de golfe e de futebol, as irrigações não foram capazes de se manter sob controle ao longo do tempo. Entretanto, as aplicações das técnicas utilizadas na presente pesquisa foram importantes para detectar possíveis falhas na irrigação, que podem ser corrigidas durante o processo.
|
42 |
Sambandet mellan radarsignaler och fukthalt i en lättbetongkonstruktionGellerstedt, Jennifer, Westman, Simon January 2017 (has links)
Fukt i byggnader är vanligt och kan leda till skador. Fukten kan ge upphov till mögel och röta, vilket inte är bra för människors hälsa. Fukten kan också påverka olika egenskaper hos byggnadsmaterialen såsom hållfasthet, värmeisoleringsförmåga och ge dimensionsförändringar. Eftersom höga fukthalter kan ha en stor påverkan på materialen är det viktigt att upptäcka och fastställa problemet i ett tidigt skede. Syfte och mål med den här rapporten är att se om det finns ett samband mellan radarsignaler och fukthalt och avgöra om radarteknik är en användbar metod för att mäta fukthalt i ett byggnadselement. I det här arbetet har litteraturstudier, mätningar och analyser gjorts. Materialet som använts är lättbetong som byggts upp till fyra väggar i två olika tjocklekar, två stora och två små väggar. De stora testväggarna användes för radarmätningar och de små som provväggar till den gravimetriska metoden. Väggarna byggdes upp i ett tält där relativa luftfuktigheten (RF) och temperatur kunde styras. I början av experimentet var RF i tältet inställt på 98-99 % och temperaturen på 22 °C som därefter reglerats för att torka ut väggarna. Mätningar har utförts med radar och den gravimetriska metoden parallellt, där den sistnämnda gjorts genom att väga provväggarnas lättbetongblock vid samma tillfällen som radarmätningarna. Provväggarnas lättbetongblock torkades därefter i torkningsugn i 105 °C för att fastställa dess torrdensitet. Insamlade data från radarmätningarna har bearbetats av Radarbolagets personal. Resultaten för de olika metoderna har därefter analyserats och jämförts för att se om det finns ett samband. Resultaten från studien visar att det finns ett samband mellan fukthalt och signalerna från radarmätningarna. Fukthalten kan bestämmas på en lättbetongvägg med en felmarginal på ± 4 kgH20/m3 material, vilket motsvarar cirka 4 %. Det går att få ett bra resultat med radarmätning, metoden är däremot komplicerad men det kan finnas värde för fortsatta studier på flerskiktade konstruktioner för att avgöra om tekniken kan vara användbar för befintliga byggnadskonstruktioner. / Moisture in buildings is common and can lead to damage. The moisture can cause moldand rot, which is not good for human health. The moisture can also affect different properties of the building materials such as strength, thermal insulation and dimensional changes. Because high moisture levels can have a major impact on the materials, it is important to detect and fix the problem at an early stage. The purpose and aim of this report is to see if there is a correlation between radar and moisture content and determine whether radar technology is a useful method of measuring moisture contentin a building element. In this work, literature studies, measurements and analyzes have been made. The material used is lightweight concrete that is built up to four walls in two different thicknesses, two large and two small walls. The large test-walls were used for radar measurements and the small ones as sample-walls for the gravimetric method. The walls were built in a tent where relative humidity (RF) and temperature could be controlled. At the beginning of the experiment, the RF in the tent was set to 98-99 % and the temperature of 22 °C, which was then regulated to dry out the walls. Measurements have been made with radar and the gravimetric method in parallel, where the latter was made by weighing the sample-walls light concrete blocks at the same time as the radar measurements. The blocks of the sample walls were then dried in an oven at 105 °C to determine drydensity. The collected data from the radar measurements have been processed by the Radarbolaget’s personnel. The results for the different methods have then been analyzed and compared to see if there is a relationship. The results from the study show that there is a connection between moisture content and the signals from the radar measurements. The moisture content can be determined on a light concrete wall with a margin of error of ± 4 kgH20/m3material, which corresponds to about 4 %. It is possible to get a good result with radar measurement. However, the method is complicated, but there may be value for further studies on multilayered structures to determine whether the technology can be useful for existing building constructions.
|
43 |
Fine particle emissions from biomass cookstoves : Evaluation of a new laboratory setup and comparison of three appliancesGarcìa Lòpez, Natxo January 2017 (has links)
It is estimated that around three billion people globally rely on traditional usage of biomass to cover their daily energy needs, which causes health and social inequality problems and contributes to global warming. Thus, the study of particle emissions from cookstoves provides important information that can help improve global welfare. This study aims to (a) evaluate a new laboratory setup for measurement of particle emissions from cookstoves and (b) use this setup to compare the particle emissions from three cookstove appliances that cover the whole spectra of used technologies, namely a 3-stone fire, an improved cookstove and a gasifier stove. Emissions of total suspended particles (TSP), fine particles (≤ 2500 nm) and other emission components such as carbon dioxide were measured. Results from this study show that the new laboratory setup is appropriate to measure and investigate fine particle emissions from cookstoves as well as cookstove efficiency. Further, it also shows that the 3-stone fire was the cookstove with the highest emission factor of all, followed by the rocket stove and the gasifier stove respectively. The analysis of the data obtained from the transient particle measurement provided some information on the particle size and the soot and salt contained in the overall emitted particles. Finally, some suggestions such as continuous measurements of background particle and CO2 levels are recommended. Additionally, further research ideas are also proposed.
|
44 |
Reduction of iron ore fines in the Ifcon furnaceLourens, Leon 19 August 2008 (has links)
This work involved an investigation into the mechanisms governing the reduction of material in the solids bed of the Ifcon® process. Thermo gravimetric analyses were done to investigate the influence of various operational parameters on the rate of solid state reduction. The experiments were modeled, and model predictions were compared to experimental results. Kinetic data was analised and the reduction rate constants were calculated. The rate constants were used as inputs to a model, which describes the reduction behaviour and temperature profile in a composite solids bed (similar to that in the Ifcon® process). High temperature reduction- and melting tests were done in an 150 kW induction furnace, to simulate final reduction in a solids bed. The temperature profile through the solids bed was measured and results were compared to model predictions. Finally the extent to which solid state reduction occurs in the solids bed was estimated as a function of production rate. / Dissertation (MEng (Metallurgical Engineering))--University of Pretoria, 2008. / Materials Science and Metallurgical Engineering / unrestricted
|
45 |
Correlação temporal da fotocontagem em germinação de trigo (Triticum aestivum) com o perfil gravimétrico local = Temporal correlations of photon-counts in wheat (Triticum aestivum) germination with the local gravimetric pattern / Temporal correlations of photon-counts in wheat (Triticum aestivum) germination with the local gravimetric patternMoraes, Thiago Alexandre, 1986- 22 August 2018 (has links)
Orientador: Cristiano de Mello Gallep / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Tecnologia / Made available in DSpace on 2018-08-22T03:28:54Z (GMT). No. of bitstreams: 1
Moraes_ThiagoAlexandre_M.pdf: 12211625 bytes, checksum: 5e27e2aac5dfc12de0ee782b7b6a33bc (MD5)
Previous issue date: 2013 / Resumo: A emissão fotônica ultrafraca proveniente de plântulas de trigo foi mensurada em várias séries de testes sob condições constantes, no interior de câmara escura. Grãos brasileiros também foram transportados e testados na Alemanha, em séries simultâneas realizadas paralelamente a séries conduzidas tanto no Brasil quanto na Alemanha. As plântulas em ambos os países apresentaram ritmos semicircadianos, coincidentes e em sincronia com os ritmos da variação da aceleração gravimétrica local, produzidos pelos movimentos lunissolares. São apresentadas análises matemáticas a respeito destas sincronias e coincidências. Em mais de 80% do período de testes considerados o coeficiente local de correlação de Pearson entre os dois parâmetros revelou relação significante (P>0,7). Com o uso da transformada rápida de Fourier foram evidenciadas as similaridades entre as componentes temporais de oscilação do parâmetro fotônico e as encontradas no parâmetro gravimétrico. As fases da lua e a época do ano possivelmente produzem influências relevantes no desenvolvimento das plântulas. Os resultados encontrados sustentam a hipótese de que os processos envolvidos com a emissão fotônica em plântulas de trigo sejam regulados pelos ritmos de variação gravimétrica, produzidos pelos movimentos lunissolares. A técnica de detecção de emissão fotônica espontânea se mostrou uma ferramenta inovadora e útil para estudos biofísicos e cronobiológicos / Abstract: The ultra-weak photon emission from wheat seedling was measured in several series of tests under constant conditions inside a dark chamber. Brazilian seeds were also transported and tested in Germany, with simultaneous series conducted both in Brazil and in Germany. The seedlings showed, in both countries, semi-circadian rhythms coincident and in synchrony with the rhythms of local gravimetric variations of acceleration produced by lunisolar movements. Mathematical analysis of these synchronies and coincidences are presented. The local Pearson correlation coefficient between the two parameters showed a significant relationship (P> 0.7) in more than 80% of the considered testing period. The rhythmic similarities between the biophotonic oscillation and the gravimetric parameter were done by fast Fourier transform. The phases of the moon and the time of year possibly produce relevant influences on development of seedlings. The results support the hypothesis that processes involved with biophoton emission in wheat seedlings may be regulated by variations on the gravimetric rhythms in accordance to lunisolar movements. Further studies are desirable in order to look for the physiological origin of this phenomenon. The spontaneous ultra-weak photon emission detection technique proved to be a new and useful tool for chrono-biological and biophysical studies / Mestrado / Tecnologia e Inovação / Mestre em Tecnologia
|
46 |
Studies on Electrochemical Properties of Composites of Black Phosphorous and Graphite for Use in Li-ion Batteries / リチウムイオン電池用黒リンと黒鉛コンポジットの電気化学特性に関する研究Ju, Yuhang 23 March 2023 (has links)
京都大学 / 新制・課程博士 / 博士(工学) / 甲第24633号 / 工博第5139号 / 新制||工||1982(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 阿部 竜, 教授 作花 哲夫 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM
|
47 |
Effect of Fullerene Nano-spheres on Evaporation Kinetics of FluidsWang, Wenhu 15 December 2011 (has links)
No description available.
|
48 |
Synthesis and characterization of novel hybrid organic-inorganic materials / Syntes och karakterisering av nya hybrida organiska-oorganiska materialBlomdahl, Emil January 2021 (has links)
Efterfrågan på bättre och mer hållbart material ökar. Mer effektivt material kommer att behövas för att möta den ökande, globala efterfrågan. Hybrida organiska-oorganiska material är en typ av material som har varit av stort intresse nyligen, och kan beskrivas som en typ av material som består av både organiska och oorganiska komponenter. Denna avhandling har fokuserat på hybrida organiska-oorganiska material inspirerade av den klassiska perovskitstrukturen ABX3, där komponent A är en organisk katjon, komponent B är en divalent metalkatjon och komponent X är en anjon. Hybrida organiska-oorganiska material som är utgår från den klassiska perovskitstrukturen kan ha olika funktionella egenskaper och en bred variation av tänkbara applikationer. Några exempel på dessa egenskaper och möjliga applikationer inkluderar god fotokonduktivitet för solceller, utmärkt emissionsegenskaper för ljusdioder och justerbara dielektriska egenskaper för elektroniska växlar och sensorer. De fysiska egenskaperna av det hybrida organiska-oorganiska materialet beror på kristallstrukturen av materialet, som i sig bestäms av valet av komponenter. På grund av de många möjligheter av organiska och oorganiska komponenter så finns det möjlighet att syntetisera helt nya hybrida organiska-oorganiska föreningar som kan ha nya eller förbättrade fysiska egenskaper. Nuvarande hybrida organiska-oorganiska material som utgår från perovskitstrukturen använder huvudsakligen bly som divalent metalkatjon, och det beror på att den ger den bästa funktionella effekten. Blys toxicitet är dock en stor nackdel för nuvarande blybaserade hybrid oorganiska material. Möjligheten att ersätta bly med en annan divalent metall har undersökts under detta projekt. I denna avhandling så har den organiska katjonen cyclohexylammonium (CHA) varit i fokus som den organiska komponenten. Målet med detta examensarbete var att designa, syntetisera och karakterisera nytt hybrid organisk-oorganiskt material. De hybrida organiska-oorganiska föreningarna CHAZnBr3 och (CHA)2ZnBr4 syntetiserades för den första gången, så vitt författaren vet, och kommer vara i fokus i denna avhandling. De två nya hybrida organiska-oorganiska föreningarna blev strukturellt karakteriserade med X-ray Diffraction (XRD) och termiskt karakteriserade med Thermal Gravimetric Analysis (TGA) och Differential Scanning Calorimetry (DSC). Den första föreningen, CHAZnBr3, kunde bestämmas att vara ortorombisk vid 298 K. Föreningen bestämdes vara termisk stabil upp till 490 K, och genomgår en fasövergång vid 445 K. Den andra föreningen, (CHA)2ZnBr4, kunde inte bestämmas strukturellt vid varken 100 K eller 298 K. Föreningen bestämdes vara termisk stabil upp till 490 K, och genomgår en fasövergång vid 230 K. Ytterligare karakterisering krävs för att bättre förstå egenskaperna hos dessa föreningar och deras möjliga användningsområden. / The demand for better and more sustainable material is increasing. More efficient materials will be needed to meet the growing global need. Hybrid organic-inorganic materials are one type of materials that have been of great interest recently, which can be described as a class of materials that mix organic and inorganic components. This thesis focused on hybrid organic-inorganic materials inspired by the classical perovskite crystal structure ABX3, where component A is an organic cation, component B is a divalent metal cation and component X is an anion. Hybrid organic-inorganic materials based on the classical perovskite structure may have various functional properties and may have a broad range of potential applications. Some examples of those properties as well as some and possible applications include good photoconductivity and power conversion efficiency for photovoltaic devices, excellent emission properties for light emitting diodes and tunable dielectric properties for electronic switches and sensors. The physical properties of the hybrid organic-inorganic material are determined by the crystal structure of the material, which in turn will be decided by the choice of components. With the many possible choices for organic and inorganic components, there is an opportunity to synthesize completely new hybrid organic-inorganic compounds that may display new or superior physical properties. Current hybrid organic-inorganic materials based on the perovskite crystal structure mainly use lead as the divalent metal, since it currently gives the best performance. The toxicity of lead is a major drawback for current lead-based hybrid organic-inorganic materials. The possibility to replace lead with another divalent metal has been explored during this project. For this thesis, the organic cation cyclohexylammonium (CHA) has been of focus as the organic component. The aim of this thesis was to design, synthesize and characterize novel hybrid organic-inorganic compounds. The hybrid organic-inorganic compounds CHAZnBr3 and (CHA)2ZnBr4 were synthesized for the first time, to the best of our knowledge, and will be the focus of this thesis. The two new hybrid organic-inorganic compounds were structurally characterized by X-ray Diffraction (XRD) and thermally characterized by Thermal Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The first compound, CHAZnBr3, could be determined to be orthorhombic at 298 K. The compound was found to be thermally stable up 490 K, and to undergo a phase transition at 445 K. The second compound, (CHA)2ZnBr4, could not be fully structurally solved at either 100 K or 298 K. The compound was found to be thermally stable up to 490 K, and to undergo a phase transition at 230 K. Further characterization will be needed to better understand the properties of these two compounds and their possible applications.
|
49 |
Nineteenth century concrete in Seguin, Texas: construction materials & techniquesHunter, Sarah Beth 12 September 2014 (has links)
This investigation centers on early concrete technology used in Seguin, Texas, during the mid-19th century. Over the course of fifty years, more than ninety concrete structures were built in Seguin. Over the last century, these have dwindled to twenty extant structures. Much of the previous Seguin concrete era research has focused on the historical narrative and architectural description. This study aims to answer questions that
previous research has not — it investigated the raw materials used in making Seguin’s concrete. The results provide new information about the Seguin concrete structures, providing guidance for their long-term maintenance.
The materials analysis uses instrumental techniques such as scanning electron microscopy, energy dispersive x-ray spectroscopy, and x-ray diffraction to determine the
chemical composition and crystalline structure of the cement binder from several extant structures in Seguin. Gathering both qualitative and quantitative data for the binder
allowed us to identify the raw materials used in the concrete and better understand the construction methods. Studying the materials and methods increased our understanding
of these historic structures and will inform future preservation efforts. / text
|
50 |
Structural and thermogravimetric studies of alkali metal amides and imidesLowton, Rebecca L. January 1999 (has links)
This work presents an in-depth study of the crystal structures and hydrogen sorption potential of the Li - N - H and Li - Na - N - H systems. The structures of the materials have been studied using X-ray and neutron diffraction, Raman spectroscopy and inelastic neutron scattering. The behavior of the materials during heating was studied using variable temperature X-ray diffraction, intelligent gravimetric analysis in conjunction with neutron diffraction, intelligent gravimetric analysis combined with mass spectrometry and differential scanning calorimetry. The role of cation disorder in the Li - N - H (D) system has been explored, indicating that crystallographic ordering of the Li<sup>+</sup> ions within lithium amide and lithium imide significantly affects the hydrogen sorption properties of the materials. Order-disorder transitions were observed both during hydrogen desorption from ordered LiNH<sub>2</sub> and during deuterium adsorption on ordered Li<sub>2</sub>ND. Such transitions were not observed in disordered samples of the materials. The intrinsic disorder and the stoichiometry of Li - N - H(D) materials was shown to depend strongly on the techniques used during their synthesis. Studies regarding the synthesis, crystal chemistry and decomposition properties of the mixed Li / Na amides are presented. Two distinct mixed Li / Na amides of formulae Li<sub>3</sub>Na(NH<sub>2</sub>)<sub>4</sub> and LiNa<sub>2</sub>(NH<sub>2</sub>)<sub>3</sub> were observed in the LiNH<sub>2</sub> / NaNH<sub>2</sub> phase space. Na was also seen to be soluble in LiNH<sub>2</sub>, forming sodium-doped LiNH<sub>2</sub> . Li<sub>3</sub>Na(NH<sub>2</sub>)<sub>4</sub> and Na-doped LiNH<sub>2</sub> were found to exhibit significant cation non-stoichiometry, whereas LiNa<sub>2</sub>(NH<sub>2</sub>)<sub>4</sub> was shown to exist as a line phase material. Thermogravimetric and calorimetric studies of the mixed Li / Na amides suggested that these materials decompose primarily with loss of H<sub>2</sub>.
|
Page generated in 0.0647 seconds