In this project an experimental setup is designed to investigate the effect of intermittent load patterns in combination with moisture content on cellulose ageing. It is done by exposing groups of samples to different intermittent load patterns with varying frequency. A literature review is done on transformer insulation system and cellulose degradation. Various technical solutions to different aspects of the experimental design are reviewed. The final experimental setup is explained with the primary focus being on the hardware and programming of the controlling system. The controlling system consists of a Data Acquisition (DAQ) system from National Instruments and is programmed in LabVIEW. The controlling system is examined in two investigative tests where it performed satisfactorily. Three load patterns are developed. This project suggests how to prepare the samples and what direct- and indirect tests to apply to the insulation system for future analysis.Over the years, a considerable amount of scientific work has been devoted to understanding paper ageing in order to improve transformer diagnostics and investments for utility owners. However, transformer loading guidelines of today do not take intermittent load in combination with moisture content into account [1] [2]. Previous work suggests that the thermal models may be improved by looking into the effects of moisture content [3].The primary aim of the proposed experimental setup is to investigate whether an intermittent load pattern in combination with moisture content have a considerable detrimental effect on cellulose ageing. The intent is to contribute with new knowledge about transformer diagnostics and long-term possibly improve the current thermal models used for Dynamic Transformer Rating (DTR) which do not take this phenomenon into account. This would in particular benefit transformers with typically intermittent load patterns, e.g. a transformer connected to a wind farm or photovoltaic panels. Increasing renewable energy installations increase the need for developing the thermal models in the transformer loading guidelines to take unconventional load profiles into account. / I det här projektet utformas ett experiment för att undersöka inverkan av intermittenta lastmönster i kombination med fukthalt på åldrande av cellulosa. Detta görs genom att utsätta provgrupper för olika lastmönster med varierande frekvens. En litteraturgenomgång görs på transformatorisoleringssystem och nedbrytning av cellulosa. Olika tekniska lösningar för olika aspekter av experimentets design ses över. Den slutliga utformningen av experimentet förklaras med fokus på hårdvara och programmering av kontrollsystemet. Kontrollsystemet består av ett system för datainsamling från National Instruments och programmeras i LabVIEW. Kontrollsystemet utvärderas i två undersökande test där det förfor på ett tillfredsställande sätt. Tre lastmönster till experimentet har tagits fram. Det här projektet föreslår hur man förbereder proverna och vilka direkta och indirekta test som kan göras för framtida analyser.Under åren har en betydande mängd vetenskapligt arbete ägnats åt att förstå pappersåldring för att förbättra transformatordiagnostik och investeringsunderlaget för nätägare. De industriella standarderna tar dock inte hänsyn till intermittent belastning i kombination med fukthalt [1] [2]. Tidigare arbete föreslår att de termiska modellerna möjligen kan förbättras genom att undersöka effekterna av fukthalt [3].Det huvudsakliga målet med den föreslagna experimentella uppställningen är att undersöka huruvida ett intermittent belastningsmönster i kombination med fukthalt har en betydande inverkan på pappersåldrandet. Föresatsen är att bidra med ny kunskap om transformatordiagnostik och för att om möjligt långsiktigt förbättra de nuvarande termiska modellerna som används till dynamiska lastbarhetsmodeller för transformatorer. Detta skulle särskilt gynna transformatorer med typiskt intermittenta belastningsmönster, t ex en transformator ansluten till en vindkraftpark eller solcellspaneler. Ökande antal av anläggningar för förnybar energi ökar behovet av att utveckla de termiska modellerna för att ta hänsyn till okonventionella lastprofiler.

The embedment behavior of dowels in timber structures, as an essential parameter in the design of connections, is the subject of this thesis. There are numerous advantages using timber structures, including sustainability, energy efficiency, and aesthetic appeal. The mechanical performance of connections in timber structures can be affected by environmental variables, such as moisture content. Thus, in the thesis the embedment behavior of dowels in timber, including the embedment strength and elastic and plastic stiffness at various moisture levels was investigated. In addition to different moisture contents, the effects coming along with changing the moisture content, like swelling and shrinkage, in combination with the assembly history were studied. The study investigated the effects of moisture content variations on the embedment behavior of dowels in timber loaded perpendicular to the grain at relative humidity levels of 38%, 65%, and 85% at a temperature of 20◦C. The study also explored the impact of assembly history of the steel dowels on the embedment behavior. The expression ”assembly history” refers the effects of drilling and assembling steel dowels at different times, i.e. if drilling the timber occurs before changing the moisture content or after changing the moisture content.  Full-hole embedment tests were conducted in five different series to cover all three levels of moisture content while taking the assembly history into account. In total, 100 embedment experiments were carried out, with 50 samples of spruce and 50 samples of birch being assessed perpendicular to the grain. In addition, 20 solid timber specimens were exposed to cyclic loading to evaluate the embedment behavior under these conditions. To evaluate the stress on the timber around the dowel, finite-element simulations, using linear-elastic material behavior in combination with volumetric changes due to moisture variation were conducted. Corresponding to the assembly history in the experiments, the situations of moisture variation in presence and absence of the steel dowel for the swelling and shrinkage case were investigated. The experimental results showed that while the elastic and plastic embedment stiffness can be impacted by moisture content only in low MC situations, it can potentially affect embedment strength in both dry and wet conditions. Additionally, the assembly history influences only the plastic stiffness in a low MC condition. Results from cyclic loading have shown no significant difference to embedment strength and stiffness gained from monotonic loading. According to numerical simulations, the tensile normal stress in the direction perpendicular to the load direction is higher than the tension strength for the shrinkage case with the dowel present. This might be explained by using a simple linear elastic material model in the FEM simulation, which causes an overestimation in the stiffness properties. In conclusion, this thesis offers new perspectives and a deeper knowledge of how moisture content, assembly history, and cyclic loading perpendicular to the grain affect the embedment behavior of dowels in timber connections.

Construction on problematic soils is challenging owing to the potential of volume changes due to variation of moisture content. Lime stabilisation can be used to treat problematic soils. The main drawbacks of lime addition to the clayey soils are the need for lengthy curing periods and relatively large quantities of lime for significant improvement and also loss in ductility. Using eco-friendly agricultural and industrial wastes, that can partially be substituted by the material responsible for greenhouse gases such as lime, can overcome these drawbacks and decrease global warming. In the current study, variables controlling the unconfined compressive strength of lime treated clay with a focus on assessing the effects of moisture content were investigated. Furthermore, the effects of adding agricultural waste (Dried Athel Leaves (DAL)) and industrial waste (Silica Fume (SF)) on hydromechanical properties of lime treated clay were assessed. The performance of the treated mixtures was examined based on results attained from unconfined compressive strength, swelling pressure and permeability. Specimens were treated with deferent percentages of lime and cured at different periods and temperatures to observe the strength behaviour. In oedometer tests, the specimens were prepared and tested immediately after compaction. The failure patterns were also studied to better understand the ultimate behaviour of lime stabilised clays. The appearance and presence of cementitious products were identified by using the scanning electron microscope and energy dispersive X-ray spectrometer techniques to elucidate their strength development. The findings indicated that the effect of moisture content is controlled by the clay content and unit weight. The addition of 7% lime to clay caused a remarkable increase in the unconfined compressive strength by 363%. The incorporation of 2% DAL and 5% SF within lime treated clay further increased the strength by 6% and 33% respectively after curing of 28 days at 20 °c in comparison with those attained by lime treatment only. The improvement of the strength of the lime­ treated clay augmented with both wastes continued in long term. Temperature and lime content have positive effects on the improvement of strength, however, increasing lime content to 11% negatively affected the strength of lime treated specimens with 2% DAL. The formation of cementitious products was observed in SEM images and detected quantitatively through EDS analysis. The results of the recorded oedometric tests for lime-DAL and lime-SF mixtures revealed that incorporation of the 2% DAL and 5% SF reduced the clay swelling pressures by 25% and 10% compared to that attained by lime treatment only resulting in total reductions of 93.6% and 68% from that recorded on untreated clay. In addition, the impermeable clay transformed into permeable material by adding DAL and SF. Of the two types of wastes considered in this research, DAL demonstrated more superior improving capability. A further study was conducted to develop ANN model based on collated laboratory data for the prediction of the UCS values of lime treated soils. The promising outcomes of this research suggest that the drawbacks of lime stabilisation can be overcome by the addition of agricultural and industrial wastes. Consequently, the findings attained could be considered in future practice standards with regards to the requirement of lime stabilisation. / Ministry of Higher Education and Scientific Research in Libya

No description available.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25269号 / 工博第5228号 / 新制||工||1997(附属図書館) / 京都大学大学院工学研究科都市環境工学専攻 / (主査)教授 西村 文武, 教授 米田 稔, 教授 松田 知成 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

Krypgrunder i någon form har använts som grundkonstruktion i Sverige under långtid. Förr var det torpargrunder som med tiden blev isolerade krypgrunder och plintgrunder. Gemensamt för krypgrundskonstruktioner som är ventilerade med utomhusluft är att under sommarhalvåret blir det förhöjda relativa ånghalter. Syftet med fallstudien är att studera en uteluftsventilerad konstruktion med välisolerat bjälklag och markisolering. Konstruktionen är nedgrävd och ventilationen i grunden sker via en tunn spalt under marknivå. Luftspaltens temperatur och relativa ånghalt är av intresse för att avgöra om det finns risken för mögel i konstruktionen. En simulering av värmeflödet mellan byggnad och mark genomförs i COMSOLMultiphysics 5.5 för att avgöra temperaturfördelningen i konstruktionen. Temperaturfördelningen ligger som grund för fastställandet av relativ ånghalt i konstruktionens luftspalt. Simuleringen använder klimatdata för ett typår i Gävle. Simuleringen visar att det är höga temperaturer i luftspalten året runt. Detta ger enrelativ ånghalt som månadsmedel på 37–77% under ett år. Den höga temperaturen iluftspalten bidrar till att hålla konstruktionen torr då kritisk relativ ånghalt, 75–80%, inte överstigs under en längre period. Resultat är förvånansvärt positivt med en låg risk för mögeltillväxt i konstruktionen.Det finns många antaganden framförallt vilket luftflöde som återfinns i luftspalten.För att validera resultaten i arbetet så bör mätningar genomföras på de två prototyphus som existerar. / Crawl spaces in some form have been used as foundations in Sweden for a long time.In the past, it was uninsulated crawl spaces that eventually evolved into insulatedcrawl spaces and open plinth foundations. An increased relative humidity during thesummer is a common problem for crawl spaces that are ventilated with outdoor air. The purpose of the case study is to study an outdoor ventilated structure with wellinsulated floor and ground insulation. The construction is below ground level andthe ventilation takes place via a thin air gap below ground level. The temperatureand relative humidity in the air gap are of interest to determine if there is a risk ofmould growth in the design. A simulation of the heat flow between the building and the ground is carried out inCOMSOL Multiphysics 5.5 to determine the temperature distribution in the design.The temperature distribution is the basis for the determination of relative vaporcontent in the air gap of the structure.The simulation uses climate data for a typicalyear in Gävle. The simulation shows a high temperature in the air gap which gives a relative vaporcontent as a monthly average of 37–77% during a year. The high temperature in theair gap contributes to keeping the structure dry when critical relative humidity, 75–80%, is not exceeded for a longer period of time. The results are surprisingly positive with a low risk of mold growth in the construction.There are many assumptions, in particular, which airflow is found in the airgap. In order to validate the results in the work, measurements should be made onthe two prototype houses that exist.

Wood products play a key role in the transformation to a more sustainable society based on renewable bio-based resources, together with the positive effects on climate mitigation by replacing fossil fuels. However, to increase the use of forest fuel in practice it is important to understand the effects of handling and storage on its quality and removal of nutrients from the forest. This thesis addresses these effects with special focus on a comparative evaluation of the traditional dried-stacked with “new” and to some extent more controversial fresh-stacked methods for extraction of logging residues from Norway spruce (Picea abies (L.) Karst). The results indicate that a normal extraction of logging residues will leave at least 20% of logging residues at the clear-felled area, in accordance with Swedish Forest Agency recommendations. However, the results also indicate that the ambition of the dried-stacked method to leave the majority of the needles well spread over the clear-felled area does not meet these recommendations. In fact, the harvesting operation is more important than the extraction method, with respect to how much logging residues (nutrients) being left in the forest. The results also show that the quality of fuel yielded by the two handling methods differs only to minor extent, indicating that other factors have stronger effects, where “dried-stacked” and “fresh-stacked” logging residues from different clear-felling areas is often similar. Generally, logging residues stored over summer (regardless method), seem to provide sufficiently dry forest fuel, with a needle content of about 5–10%. There is a clear correlation between drying and effective loss of needles from twigs, but the loss does not necessarily mean that the needles will remain in the forest.  However, needle color (green or brown) is not a strong indicator for a reduction in needle content. Acceptance of the fresh-stacked method would provide opportunities for the development of new technologies, more efficient use of machinery throughout the whole year, reduced costs, shorter lead times and increased amounts of logging residues extracted from each clear-felled area. This is mainly because it would enable extraction at optimal times from a logistical, financial and/or forestry perspectives. Written in English with summary and conclusion in Swedish. / Skogen och dess produkter har en nyckelroll i omställningen till ett framtida hållbart samhälle eftersom användande av träråvara har en positiv effekt på klimatet, t.ex. genom träbyggande eller att fossila bränslen ersätts med bioenergi. Men för att kunna ta tillvara mer skogsbränsle i form av grenar och toppar (grot) från bestånd dominerade av gran (Picea abies (L.) Karst) är det viktigt att förstå hur hanteringen påverkar såväl bränslekvalitet som bortförsel av näringsämnen från skogen. Denna avhandling belyser hanteringens effekter på bränslekvalitet och näringsförluster genom att jämföra den traditionella metoden (skotning av torkad grot, ”brunrisskotning”), med den ”nya” och till viss del ifrågasatta skotningen av färsk grot (”grönrisskotning”). Resultatet visar att ett normalt grot-uttag kommer att lämna minst 20 % av groten kvar på hygget, helt i linje med Skogsstyrelsens rekommendationer. Däremot uppfylls inte rekommendationerna med avseende på att lämna merparten av barren väl spridda på hygget, detta trots att det är ambitionen med den traditionella hyggestorkningen av grot. Hur mycket grot (och således näringsämne) som lämnas kvar på hygget påverkas i själva verket mer av hur avverkningen utförs, än när groten skotas ihop. Resultatet visar också en skillnad i bränslekvalitet mellan de båda beskrivna hanteringsmetoderna. Denna skillnad är dock så liten att andra faktorer sannolikt påverkar mer än hanteringsmetoden. Hyggestorkad grot från ett enskilt hygge i södra Sverige, kan i verkligheten ofta vara ganska likt färskskotad grot från ett annat hygge. Grot som har lagrats över sommaren kan alltså förväntas ha torkat tillräckligt, samt ha en barrandel på ca 5–10 % oavsett hanteringsmetod. Det verkar också finnas ett klart samband mellan torkning och att barren släpper från kvisten, men det betyder inte nödvändigtvis att barren blir kvar i skogen. Hur som helst, barrens färg (gröna eller bruna) är inte en rättvisande indikator på avbarrning. Om skotning av färsk grot accepteras ger det möjligheter för utveckling av ny teknik, effektivare användning av maskinresurser över hela året, minskade kostnader, kortare ledtider, samt möjligt ökat grot-uttag från enskilda hyggen. Detta beror främst på att det skulle vara möjligt att utföra grot-uttaget när det passar bäst ur ett logistiskt, ekonomiskt och/eller skogligt perspektiv. Skriven på engelska, men med sammanfattning och slutsatser på svenska / <p><strong>Tidigare handledare har också varit:</strong></p><p>Thomas Thörnqvist, Professor, Linnéuniversitetet</p><p>Dick Dandberg, Professor, Linnéuniversitetet</p><p>Åsa Blom, Docent, Linnéuniversitetet</p><p><strong>Sammanläggningsavhandlingen består av totalt fyra Paper:</strong></p><p>Paper I</p><p>Nilsson, B., Blom, Å., Thörnqvist, T. 2013. The influence of two different handling methods on the moisture content and composition of logging residues. <em>Biomass and Bioenergy</em>, 52, 34–42.</p><p>Paper II</p><p>Nilsson, B., Nilsson, D., Thörnqvist, T. 2015. Distributions and losses of logging residues at clear-felled areas during extraction for bioenergy: Comparing dried- and fresh-stacked method. <em>Forests</em>, 6, 4212–4227.</p><p>Paper III</p><p>Nilsson, D., Nilsson, B., Thörnqvist, T., Bergh, J. 2016. Amount of nutrients extracted and left behind at the clear-felled area using the fresh- and dried-stacked method of logging residue extraction. Submitted to <em>Scandinavian Journal of Forest Research </em>(2016-11-01).</p><p>Paper IV</p><p>Nilsson, B., Lerman, P. 2016. Experimental study of relations between defoliation, moisture content and color change in logging residues. Department of Forestry and Wood Technology, Linnaeus University, Växjö, Sweden. <em>Manuscript</em>.</p>

This thesis consists of two essays that each discuss a major component of the post-harvest management of maize in sub-Saharan Africa: drying and storage. The first essay uses cross-country data about on-farm storage decisions between 2013 and 2015 to assess the severity of storage loss in the absence of improved storage technologies. We find that while losses are low, farmers report on average that they lose more than expected and sell earlier than originally intended at harvest. Additionally, we look for evidence that farmers use adaptation strategies for the purpose of mitigating storage loss and find that storage chemicals are effective at both reducing loss and increasing storage duration. The second essay introduces a third-party moisture testing service to traders in western Kenya to elicit willingness to pay for external quality verification using two moisture detection devices, a low-cost hygrometer and a commercial grade moisture meter. We find that while traders value the moisture meter service more, the hygrometer service is more profitable for potential service providers. Further, when offered a chance to purchase the hygrometer device at/around market price ($2.50), only 15% of traders accepted the offer, suggesting that a service provider model is a viable way to make moisture testing more widely accessible and standard practice in the future.

O objetivo deste trabalho é avaliar a influência da variação do teor de umidade no valor do módulo de resiliência (MR) de um solo argiloso de subleito, tendo em vista que este parâmetro é muito susceptível à variações climáticas ambientais. Foram realizados ensaios triaxiais cíclicos para se estimar o módulo de resiliência de corpos de prova ensaiados em diversas condições de umidade. Verificou-se que o MR é influenciado pela tensão desvio, de forma que aquele aumenta com o acréscimo desta. Constatou-se que os corpos de prova moldados na Wot e submetidos a trajetórias de secagem e umedecimento alcançaram valores de MR superiores e inferiores, respectivamente, ao se comparar com o MR de corpos de prova ensaiados na Wot. Este fato foi também observado para os corpos de prova moldados com massa específica seca máxima, em teores de umidade abaixo e acima do teor ótimo. Determinou-se, ainda, a sucção no solo através do método do papel filtro e levantou-se a sua curva característica. Verificou-se que à medida que a umidade aumenta, a sucção diminui. Observou-se que o valor do MR aumenta com o aumento da sucção no solo. Este crescimento é tanto maior quanto maior seja a tensão desvio aplicada. Foi possível determinar a relação entre o MR, a tensão desvio e o módulo tangente inicial (Eo), proveniente dos ensaios de compressão simples. Relacionou-se, também, o Eo e a sucção no solo. / The aim of this work is to evaluate the influence of moisture content variation in resilient modulus value (MR) of a subgrade clayey soil, considering that this parameter is very susceptible to environmental climatic variations. Cyclic triaxial tests were performed to acess resilient modulus of specimens tested in several moisture conditions. lt has been verified that MR is influenced by deviator stress, so that the former increases with the latter increases. lt has been confirmed that specimens molded in Wot and submited to a drying and moistening route reached MR values higher and lower, respectively, to compare with MR of specimens tested in Wot. This fact was also observed for the specimens molded with dry density, in moisture contents below and above of optimum moisture content. lt has been also determined the soil suction using filter paper method and it has been built its characteristic curve. lt has been verified that when moisture increases, the suction decreases. lt has been observed that MR value increases with the soil suction increase. This increase is as bigger as bigger the applied deviator stress be. lt was possible to determine the relationship between MR, deviator stress and parameters from compressive strength tests. lt has been related parameters from compressive strength tests and soil suction.

Na construção de rodovias, as condições de umidade e densidade observadas na compactação são, geralmente, próximas daquelas correspondentes ao pico da curva de compactação obtida no ensaio Proctor. É sabido que variações ambientais no decorrer da vida do pavimento podem alterar, de maneira significativa, a umidade do subleito e dos seus componentes e assim, as suas propriedades resilientes. O objetivo principal desta pesquisa é avaliar a influência da variação da umidade pós-compactação no módulo de resiliência de solos de rodovias do interior paulista a partir de resultados de ensaios de laboratório. Foram coletados e caracterizados setenta e três solos, e, dentre estes, selecionados trinta para a etapa de estudo da variação da umidade pós-compactação, após a realização de ensaios MCT, difração de raios-x, microscopia eletrônica de varredura e azul de metileno para determinação da gênese. Os solos selecionados apresentam características distintas quanto à gênese, sendo metade laterítico e metade não-laterítico. Os corpos-de-prova foram compactados na umidade ótima e submetidos a processos de secagem e umedecimento e, posteriormente, realizados ensaios triaxiais cíclicos. Os resultados permitiram a modelagem do 'M IND.R' em função do estado de tensão para diferentes umidades e a avaliação da competência de alguns modelos matemáticos nesta representação. Estudou-se a influência da gênese e da granulometria sobre o valor do 'M IND.R' e avaliou-se a conseqüência da variação da umidade sobre este para solos lateríticos e não-lateríticos. Determinou-se uma expressão para estimar a variação do 'M IND.R' com a variação da umidade a partir do parâmetro k1, independentemente do estado de tensão. Pesquisou-se a existência de relações entre os parâmetros de regressão do modelo composto e os resultados dos ensaios de compressão simples e as propriedades físicas dos solos, de forma a permitir a estimativa do módulo de resiliência a partir do resultado de ensaios mais simples. Investigou-se a possibilidade de se utilizar as relações entre a variação do módulo tangente inicial com a variação da umidade para estimar os efeitos sobre o 'M IND.R'. / On road construction, the field compaction conditions are usually close to those determined from Proctor tests. Environmental variations may lead to changes in the pavement moisture and also changing its resilient properties. The main objective of this research is to study the influence of post-compaction moisture content variation on the resilient modulus of soils from São Paulo state pavements, using laboratory tests. To accomplish this objective, seventy three soils samples were collected and characterized. Among them, thirty samples were selected, after four different tests were carried out to determine the soils genesis, to study the post-compaction moisture content variation. Half of these selected soils are lateritic ones, and the other half are non-lateritic soils. The specimens were compacted at optimum moisture content and submitted to drying and moistening processes prior cyclic triaxial test to be carried out. The results allowed the resilient modulus modeling as a function at the stress state and the performance evaluation of five different models. The genesis and grain size distribution influence on the resilient modulus values were studied. The effects of moisture content variations on lateritic and non-lateritic soils were investigated. An expression to estimate the resilient modulus variations with the moisture variations was determined, independently of the stress state. The existence of relations of the compound model regression parameters with the results of unconfined compressive strength and soil properties were studied. The possibility of using the initial tangent modulus variations with the moisture variations to estimate the effects on the resilient modulus were also investigated.