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Moisture content profiles and surface phenomena during drying of woodRosenkilde, Anders January 2002 (has links)
<p>Timber drying is one of the most important processes whenmanufacturing sawn timber products. The drying processinfluences deformations, surface checking, discoloration andhence, the product quality and the manufacturing costs.Research in this field is of great importance for the woodindustry since the industrial drying process always needs to beimproved as market demands increases and new wood products aredeveloped.</p><p>The aim of the present thesis was to investigate themoisture transport behaviour in wood based on measurementsduring drying from fresh condition down to end use moisturecontent. The behaviour near the surface interface has beenspecifically investigated since it is of great importance forthe theoretical description of the drying process. Furthermore,studies based on measurements in the wood surface layer duringdrying are not easy to find in the literature. The reason forthat is probably that it is very difficult to make accuratemoisture measurements with high spatial or temporal resolutionwithout disturbing the drying process.</p><p>Measurements of moisture content profiles in Scots pineheartwood and sapwood during drying have been performed byusing three different methods. The first was a destructivemethod where the wood samples are sliced with a knife intoseveral smaller pieces. The moisture content in each piece wasdetermined with the dry weight method. The second method usedis non-destructive and it utilises a medical CT-scanner thathas been adapted for drying experiments. The samples are driedin-situ the scanner through the whole experiment. TheCT-scanner measures density and the moisture content arecalculated according to existing methods developed by otherscientists. The third method was also non-destructive and itutilises a Magnetic Resonance Imaging, MRI, technique. Withthis technique the amount of water in the wood sample ismeasured directly even though it has to be calibrated tomoisture content.</p><p>The surface emission factor, S, or surface resistance, 1/S,has been studied by performing sorption experiments with MDF ina narrow moisture content range. The experiment was evaluatedusing a simple diffusion model that includes a surface emissionfactor S. The experimental result was compared with resultscalculated using well established boundary layer theories.</p><p>Measurements of moisture content profiles in the wood bulkshowed an expected Fickian behaviour at moisture contents belowthe fibre saturation point. Above the fibre saturation pointalmost flat moisture profiles were observed. This behaviour wasnot expected and it is not possible to simulate this behaviourwith the existing drying models since they usually assume thatthere is a gradient in the moisture profile over the wholemoisture content range. From the moisture profiles thediffusion coefficients were determined over a moisture contentranging from 8 to 30%. The values for heartwood and sapwood areapproximately equal in radial and tangential direction tograin. Furthermore, the diffusion values in longitudinaldirection are much higher as expected.</p><p>The sorption experiments with MDF gave a greater surfaceresistance compared with the calculation that was based onboundary layer theory. The ratio was three or higher. Thisimplied that there was a greater resistance in the surfacelayer. In addition, this was not well described in theliterature even though a few recent published studiesexist.</p><p>High resolution measurements in the surface layer of woodshowed behaviour similar to that observed in the bulk wood. Theresults showed the very early development of a dry zone closeto the surface interface. In that zone or shell the moisturecontent was below the FSP even though the bulk moisture contentwas far above the FSP. At the end of the experiments themoisture content in the surface layer (0300 µm)nearly reached the equilibrium moisture content even though thebulk moisture content still was much higher.</p><p><b>Keywords:</b>Computer tomography, Diffusion, Magneticresonance, Moisture measurements, Moisture profiles, Surfaceemission, Wood drying</p>
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Effects of moisture on the breakdown strength and lifetime of low permittivity dielectric for nanometer scale interconnectsChoi, Soo Young, doctor of materials science and engineering 13 June 2011 (has links)
Advanced integrated circuit (IC) technology has implemented new materials for necessary and timely performance improvements. New materials are now required at both the front-end-of-line (FEoL) and back-end-of-line (BEoL) of the device because simple dimensional scaling with standard materials has come with performance costs that negate dimensional scaling performance improvements. At the FEoL, high-[kappa]/metal gate processes are being developed to reduce gate oxide leakage. At the BEoL, Cu-based metallization and low-[kappa] dielectric materials have been developed to reduce BEoL contribution to RC-propagation delay. Cu-based metallization has required change in integration strategy, which has led to concerns about new material reliability performance. Furthermore, continuing pressure to improve device performance requires that a new, more advanced low-[kappa] dielectric be used, which are mechanically and electrically inferior. These performance demands and greater reliability concerns must be balanced. This kind of balance requires that better understanding of the extrinsic threats to device reliability be understood and is the general area of interest for this work. In particular, this study examines the extent of degradation found in low-[kappa] dielectric when it is exposed to ambient moisture and the potential impact of this degradation on intrinsic reliability performance under electrical stress. The integration method is described for low-[kappa] dielectric processing so that potential damages during process can be explained. Local damages can allow moisture incorporation at the expense of additional dielectric performance and reliability degradation. The molecular form of moisture incorporation into low-[kappa] dielectric and potential process methods to reduce moisture incorporation are also discussed. The electrical reliability performance is shown using interdigitated structures through voltage ramped dielectric breakdown study of inter-metal dielectric (IMD). Clear evidence of dielectric degradation is found after extreme moisture incorporation. Moisture penetration impact is also examined on the long-term reliability of integrated low-[kappa] dielectric using time-dependent dielectric breakdown (TDDB). Results show a dramatic change in the observed field acceleration parameter through moisture exposure that is not easily explained in a standard way according to proposed dielectric breakdown models for low-[kappa] dielectrics. A simple modification of the thermochemical [Epsilon]-model is proposed to explain the results. / text
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Modeling soil moisture from real-time weather dataOjo, Emmanuel R. 21 December 2011 (has links)
Extreme variability of rainfall during the growing season in the Prairies underlies the need to improve means of quantifying the amount of soil moisture available for plant growth in real time. This study was conducted to modify and validate the Versatile Soil Moisture Budget (VSMB) for estimating volumetric soil water content. A network of soil moisture hydra probes and weather stations were installed for continuous soil moisture monitoring and real-time weather data collection at 13 sites across Central and Western Manitoba during the 2009 and 2010 growing seasons. The data from the probes were validated and calibrated. Both the laboratory and field validations showed that the root mean square error of the default factory calibration increased with increasing clay content of the soil. Outputs from these probes were used to test the modified VSMB model. The model was most effective at simulating soil water content at the surface layers.
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Soil water content and corn yield response to grass and grass-legume mixture winter cover crops in east central IndianaNielsen, Kerry E. 04 May 2013 (has links)
Cover crops may be used as a management tool in modifying soil water content, helping lower agriculture’s impact on water quality and lead to greater crop yields. During the 2012 growing season, a field study was conducted in Albany, IN to determine: 1) the impact of cover crops on soil moisture throughout the growing season and 2) cover crops’ influence on corn (Zea mays) yield. Treatments of a monoculture of annual ryegrass (Lolium multiflorum) (AR), a mixture of annual ryegrass (Lolium multiflorum), crimson clover (Trifolium incarnatum), and groundhog radish (Raphanus sativus) (MIX), were compared with a no cover crop control (CTRL) in a randomized complete block design, with blocks positioned in moderately well drained (MWD) and poorly drained (PD) soils. Cover crop treatments were similar to each other in accelerating moisture removal before the corn growing season, resulting in soil profiles that were 47% drier in the MWD soil and 22% drier in the PD soil than controls. Abnormally hot and dry weather conditions made water availability a limiting factor and decreased the relative importance of soil nitrogen while corn was growing. In the MWD soils, corn grown after MIX treatments had 21% higher yields than CTRL treatments and 11% higher yields than AR treatments due to increased subsoil water usage. Corn grain yields in PD soils were related to surface moisture conservation, leading to 3-5% higher yields in MIX and AR treatments. Implications for improved field trafficability, reduced runoff and tile drainage flow, and enhanced water availability to crops are discussed. / Department of Natural Resources and Environmental Management
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Modeling soil moisture from real-time weather dataOjo, Emmanuel R. 21 December 2011 (has links)
Extreme variability of rainfall during the growing season in the Prairies underlies the need to improve means of quantifying the amount of soil moisture available for plant growth in real time. This study was conducted to modify and validate the Versatile Soil Moisture Budget (VSMB) for estimating volumetric soil water content. A network of soil moisture hydra probes and weather stations were installed for continuous soil moisture monitoring and real-time weather data collection at 13 sites across Central and Western Manitoba during the 2009 and 2010 growing seasons. The data from the probes were validated and calibrated. Both the laboratory and field validations showed that the root mean square error of the default factory calibration increased with increasing clay content of the soil. Outputs from these probes were used to test the modified VSMB model. The model was most effective at simulating soil water content at the surface layers.
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Avaliação dos resultados obtidos no equipamento Moisture Management Tester (MMT) comparativamente a outros métodos de medida de gerenciamento de umidade / Evaluation of results obtained in Moisture Management Tester equipment (MMT) compared to other moisture management methods of measurement.Fernanda Gomes de Vasconcelos 23 June 2016 (has links)
O conforto é um aspecto muito importante ao se tratar de vestuário, por isso cada vez mais estão sendo desenvolvidos tecidos com características específicas para proporcionar conforto nas mais diversas situações de uso. Dentro desse contexto, o conforto térmico fisiológico tem papel fundamental e um dos seus pontos chave é a capacidade dos têxteis de gerenciar a umidade proporcionada pelo processo de suor do corpo. O equipamento Moisture Management Tester (MMT) foi desenvolvido para possibilitar uma avaliação prática e confiável dessa propriedade dos tecidos e permite calcular um índice que reflete a capacidade global de gestão de umidade (OMMC) das amostras analisadas. O objetivo desse trabalho é realizar uma avaliação dos resultados obtidos no equipamento MMT em tecidos de malha fabricados com diversos tipos de fios e de contexturas e comparar os resultados com outros métodos de medida de gerenciamento de umidade, para verificar a eficácia do equipamento em quantificar a diferença de comportamento entre os tecidos analisados. Através da análise estatística concluiu-se que a metodologia utilizada no MMT possui uma divisão mais equilibrada da influência dos fatores para os resultados encontrados, sendo mais fiel ao que acontece com o tecido na pratica, com resultados mais representativos, pois todos os fatores que interferem nos resultados são consideração de maneira equilibrada / Comfort is a very important aspect related to garments, that is why fabrics containing specific characteristics to provide comfort in all kinds of situations are being developed. Within this context, the physiological thermal comfort plays a crucial role and one of his key points is the ability of textile to manage moisture provided by the body sweat process. The Moisture Management Tester (MMT) methodology was developed to enable a practical and reliable evaluation of this property of fabrics and allows the calculation of an index that reflects the overall moisture management capacity (OMMC) of the samples. The objective of this was to provide an evaluation of the results obtained on MMT on different types of yarn and knits compared to other moisture management methods of measurement, and intending to verify the effectiveness of the equipment to quantify the difference in behavior among the analyzed fabrics. Through statistical analysis, it was concluded that the methodology used in MMT has a more balanced division of the factors influence in founded results, seen as more faithful to what happens to fabric in practice, with more representative results because all factors that interfere in the results are considered in a balanced way
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Moisture content profiles and surface phenomena during drying of woodRosenkilde, Anders January 2002 (has links)
Timber drying is one of the most important processes whenmanufacturing sawn timber products. The drying processinfluences deformations, surface checking, discoloration andhence, the product quality and the manufacturing costs.Research in this field is of great importance for the woodindustry since the industrial drying process always needs to beimproved as market demands increases and new wood products aredeveloped. The aim of the present thesis was to investigate themoisture transport behaviour in wood based on measurementsduring drying from fresh condition down to end use moisturecontent. The behaviour near the surface interface has beenspecifically investigated since it is of great importance forthe theoretical description of the drying process. Furthermore,studies based on measurements in the wood surface layer duringdrying are not easy to find in the literature. The reason forthat is probably that it is very difficult to make accuratemoisture measurements with high spatial or temporal resolutionwithout disturbing the drying process. Measurements of moisture content profiles in Scots pineheartwood and sapwood during drying have been performed byusing three different methods. The first was a destructivemethod where the wood samples are sliced with a knife intoseveral smaller pieces. The moisture content in each piece wasdetermined with the dry weight method. The second method usedis non-destructive and it utilises a medical CT-scanner thathas been adapted for drying experiments. The samples are driedin-situ the scanner through the whole experiment. TheCT-scanner measures density and the moisture content arecalculated according to existing methods developed by otherscientists. The third method was also non-destructive and itutilises a Magnetic Resonance Imaging, MRI, technique. Withthis technique the amount of water in the wood sample ismeasured directly even though it has to be calibrated tomoisture content. The surface emission factor, S, or surface resistance, 1/S,has been studied by performing sorption experiments with MDF ina narrow moisture content range. The experiment was evaluatedusing a simple diffusion model that includes a surface emissionfactor S. The experimental result was compared with resultscalculated using well established boundary layer theories. Measurements of moisture content profiles in the wood bulkshowed an expected Fickian behaviour at moisture contents belowthe fibre saturation point. Above the fibre saturation pointalmost flat moisture profiles were observed. This behaviour wasnot expected and it is not possible to simulate this behaviourwith the existing drying models since they usually assume thatthere is a gradient in the moisture profile over the wholemoisture content range. From the moisture profiles thediffusion coefficients were determined over a moisture contentranging from 8 to 30%. The values for heartwood and sapwood areapproximately equal in radial and tangential direction tograin. Furthermore, the diffusion values in longitudinaldirection are much higher as expected. The sorption experiments with MDF gave a greater surfaceresistance compared with the calculation that was based onboundary layer theory. The ratio was three or higher. Thisimplied that there was a greater resistance in the surfacelayer. In addition, this was not well described in theliterature even though a few recent published studiesexist. High resolution measurements in the surface layer of woodshowed behaviour similar to that observed in the bulk wood. Theresults showed the very early development of a dry zone closeto the surface interface. In that zone or shell the moisturecontent was below the FSP even though the bulk moisture contentwas far above the FSP. At the end of the experiments themoisture content in the surface layer (0300 µm)nearly reached the equilibrium moisture content even though thebulk moisture content still was much higher. Keywords:Computer tomography, Diffusion, Magneticresonance, Moisture measurements, Moisture profiles, Surfaceemission, Wood drying / <p>NR 20140805</p>
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Determinação do teor de umidade em madeiras por meio de medidores elétricos / not availableWaldemir Rodrigues 02 July 1999 (has links)
A madeira quando seca é um excelente isolante elétrico, porém quando a umidade da madeira aumenta, essa característica diminui fazendo com que esta passe a conduzir a corrente elétrica. A determinação do teor de umidade permite um controle do custo de produção e qualidade da madeira, além de facilitar a utilização de tratamentos preservativos e pintura. O método de determinação do teor de umidade com o uso de estufa é o método mais exato, e por esta razão é utilizado como padrão para calibrar outras técnicas. Por outro lado, a verificação do teor de umidade por meio da estufa é muito demorado e danifica parte do componente a ser analisado. O objetivo deste trabalho é propor uma metodologia para calibrar medidores elétricos de umidade, utilizando espécies de dicotiledôneas nativas e coníferas de florestamento. Na experimentação realizada foi possível constatar que apesar da menor precisão na determinação de teores de umidade, o método que utiliza medidores de umidade do tipo resistência, permite com algumas correções, a obtenção de valores confiáveis para o controle de umidade de peças de madeira serrada. Para isso foram desenvolvidas expressões obtidas por meio de análise de regressão linear que possibilitam fazer as correções necessárias nas leituras realizadas com o medidor elétrico do tipo resistência. / Wood when dry is an excellent electric insulating material. However when the moisture content of wood increases, that feature decreases, which makes it conduct electric current. Determining the moisture content allows the control of the production cost and the quality of the timber, and also facilitates the use of preservative treatments and painting. The method for the determination of the moisture content using the kiln is the most exact method, and therefore it is used as standard to calibrate other techniques. On the other hand, the verification of the moisture content by means of the kiln takes toe much time and damages part of the component to be analyzed. The aim of this work is to propose a methodology to gauge electric moisture meters using species of tropical and forestation hardwood and softwood. The experiments made it possible to verify that, even having less accuracy in determining the moisture content, the method based on moisture electric meters allows, with some adjustments, a reliable data acquisition for the control of moisture content of sawed lumber. For this matter, equations were developed by means of linear regression analysis allowing the necessary corrections of the readings carried out with the electric measurer of the resistance type.
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A Correlation of Humus with Water Content and Crop Rotation in San Saba and Denton Clays, Denton County, TexasCulwell, John Walton 08 1900 (has links)
A study of the humus content and the water content of San Saba clay and Denton clay. Studies show that the physical properties of soil are conducive to moisture retention and the availability of moisture to plants.
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Hjälpmedel för fuktsäkert byggande : Utvärdering av ByggaF / Instruments for moisture proof construction : Evaluation of ByggaFJohansson, Björn, Stenfeldt, Filip January 2013 (has links)
För att efterleva Regeringens miljöpolitik har Boverket tilldelats ansvaret för miljömålet God bebyggd miljö. Boverket är en myndighet som arbetar för Riksdagens miljömål och skall vid behov förslå åtgärder för miljöarbetets utveckling. I Boverkets Byggregler finns krav som måste följas för att uppnå ett fuktsäkert byggande. Som förslag på hur dessa krav ska uppnås nämns Svensk Byggindustriers metod ByggaF – Metod för fuktsäkert byggande. ByggaF är en dokumentsamling med mallar, checklistor, kontrollpunkter och rutiner. Dessa dokument kan då ligga till grund för att upprätta en metod som säkerställer fuktsäkerheten under alla byggskeden. Skadefall har studerats i syfte att påvisa hur ByggaF fungerar och nyttan i att använda det. I samtliga av de behandlade fallen har kopplingar kunnat finnas till ByggaF, som kan förhindra problematiken. På så vis har dess täckningsgrad bekräftats. Kontakt har upprättats med flertalet aktörer i branschen för att få en uppfattning om hur metoden har tagits emot i branschen efter att den lanserades år 2007. Utifrån intervjuerna uppfattas att de flesta entreprenörer hört talas om metoden men inte använt den själva. Däremot har fuktsakkunniga använt den som underlag för att ta fram egna interna fuktsäkerhetsplaner. På grund av det används den av entreprenörer indirekt. Hos beställare ställs ByggaF som ett krav om man väljer att miljöcertifiera i Silver- eller Guldklass hos Miljöbyggnad. Annars ställs det oftast inte tillräckligt med krav på fuktsäkerhetsmetoder. / Included in Boverkets Byggregler are a number of demands that must be fulfilled in order to achieve a moisture safe construction. One of the suggestions on how to fulfil these demands is to use the method developed by Svensk Byggindustri, ByggaF – Method for moisture safe construction. In order to work according to the government’s environmental politics, Boverket has been given the responsibility to fulfil the aims of God bebyggd miljö, it is also their work to ensure that operations and establishments fulfil and reaches the goals that have been set by the Swedish government. ByggaF is a collection of documents including templates, check lists, control points and routines; these documents can be used during the whole building process to create a method which ensures that the moisture safety is withheld. It has been investigated whether or not cases of moisture damages could have been prevented with the proper use of ByggaF. In all the cases that have been studied, ByggaF could have been used to prevent mistakes and problems and by this, the efficiency and importance of the documents has been proven. Several major actors within the field have been contacted in order to gain a larger understanding about how the method has been perceived and utilized since its launch in 2007. In general most of the entrepreneurs has heard of the method but never used it themselves. However, moisture specialist from major construction operations, have utilized ByggaF in order to develop internal moisture safety routines, therefor ByggaF is indirectly used by the entrepreneurs. ByggaF would, for constructors, be a requirement if one desires an environmental certification in either the gold or the silver category within the framework of Miljöbyggnad. Normally there are not enough requirements set regarding methods for moisture safety.
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