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1
Pretlove, Stephen Edward Charles. "Predicting relative humidity in UK dwellings." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555004.
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Mould growth affects a significant proportion of dwellings in the UK and Europe. The house dust mite is also known to inhabit most dwellings and is one of the key factors affecting the health of the occupants. One of the key variables affecting mould growth and house dust mite populations is relative humidity. The relative humidity in a dwelling is dependent upon both the moisture levels and the temperature. The ability to assess the impact of different interventions on the relative humidity depends upon the ability to model both the internal temperature and the internal vapour pressure. This thesis develops, tests and assesses the impact of four combined moisture and thermal models which predict micro-environmental relative humidity. Two thermal models are tested, the BREDEM-8 monthly model, and the BREDEM-12 seasonal model. To each of these, two moisture models have been integrated including Loudon's steady-state moisture model and Jones' admittance moisture model. The BREDEM-8 Loudon model has been shown to be the most accurate model for predicting the airspace relative humidity in 36 dwellings during the heating season. The BREDEM-8 Loudon model has then undergone further development and testing and the applications of the model are investigated. A variable infiltration calculation has been implemented and tested within the BREDEM-8 Loudon model and the results show no improvement in the model prediction accuracy. Surface relative humidity calculations have also been incorporated for all dwelling surfaces, including cold bridges, and the significance of predicting surface conditions has been evaluated. The impact of fuel poverty is tested using simple versions of the BREDEM-8 Loudon model which have been adapted to account for situations where the expenditure available for fuel is limited and where the heating system is inadequately sized. Finally, a Mould Index has been developed which indicates the risk of mould growing on the coldest surfaces in a dwelling and various interventions in dwelling design and use are tested against this index and against the Affordable Warmth Index which defines the affordability of a particular dwelling. The results demonstrate a number of significant limitations in the current British Standard for condensation in buildings, BS 5250: 1989. It has been shown that the geographical and seasonal variations in internal relative humidity are significant, and that the highest relative humidity is unlikely to coincide with the coldest period of the year. It has also been shown that the modelling of surface conditions is critical in the assessment of mould growth in dwellings. Sensitivity studies carried out on the BREDEM-8 Loudon model have shown the most significant variables affecting the relative humidity predictions are the demand temperature, the heating pattern, the number of occupants, the ventilation rate and the level of insulation. The adequate sizing of the heating system and the ability of the occupants to afford to heat the dwelling to a comfortable temperature have been shown to be essential. It has also been shown that a change in the dwelling design or use may improve the affordability but may also lead to an increased risk from mould growth.
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Bellmann, C., A. Steinke, T. Frank, and G. Gerlach. "Humidity micro switch based on humidity-sensitive polymers." SPIE, 2015. https://tud.qucosa.de/id/qucosa%3A35030.
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We present recent results on a binary threshold sensor based on the binary zero-power sensor (BIZEPS) platform which is able to use the energy provided directly from the measured relative humidity of the ambient air to mechanically switch an electrical micro contact. This zero-power switch behavior is realized by using the humidity-sensitive volume swelling of a polymer layer as the detection element deflecting a mechanically deformable silicon boss structure, thus closing the electrical contacts of the switch. For the humidity-sensitive sensor switch considered here, a humidity-sensitive hydrogel blend of poly(vinyl alcohol) and poly(acryl acid) was used. The sensitive part affected by the measurand is completely separated from the electrical part, thus providing long-term stability. By using an inverse silicone stamping technique the polymer layer with a thickness of about 15 μm was patterned on test structures possessing a thin silicon flexure plate of 5 mm x 5 mm in size and 20 μm in thickness. Reproducible deformations of up to 15 … 24 μm has been measured. Investigations of the swelling kinetics showed for several discrete relative humidity values a saturation of the water load. The time to reach this saturation state is reduced from 5 hours down to approx. 20 min by increasing the relative humidity beyond the threshold value of 70% r.H. A significant influence of the temperature to the humidity load could not be observed.
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McCarthy, Mark Paul. "Observed variability of tropical tropospheric relative humidity." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.419846.
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Tyrell, James W. G. "The influence of relative humidity on interparticle force." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/844097/.
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Forces acting between individual grains in a powder can have a critical and controlling effect on powder bulk behaviour. Operations such as powder flow, fluidisation, compaction, agglomeration and mixing are all influenced significantly by the intensity of interparticle forces. This is especially true when the particle size falls below around 100 mum at which point the surface forces outweigh the force due to gravity acting on a single particle. Studies of cohesion using bulk powder samples are of limited use because it is difficult to decouple the fundamental mechanisms of interparticle force from other contributions to cohesion such as variations in the powder microstructure, or geometric interlocking of individual particles. A review of the relevant literature has unearthed conflicting evidence associated with the influence of relative humidity (RH) on both bulk powder cohesion and interparticle force. Therefore there is a need for experimental force studies at the scale of the individual particle to identify the fundamental mechanisms that prevail and resolve some of the apparent uncertainty that currently exists. A custom built force instrument, incorporating Atomic Force Microscope (AFM) technology, was designed, constructed and commissioned. This instrument was used to quantify the interactions between particles of around 40 mum in diameter and flat surfaces as a function of the relative humidity of the surrounding air. Interactions between soda-lime glass surfaces, gold surfaces and amorphous quartz surfaces were studied. Striking results were obtained on soda-lime glass surfaces upon decreasing the RH from > 70% to around 40%. At this point the glass surfaces suddenly exhibited a strong repulsion upon approach. The range of this repulsion was observed at separation distances as great as 250 nm. Once the surfaces were brought into contact the strong repulsion was accompanied by a very large force of adhesion. This strong repulsion and associated peak value of adhesion was not observed at other RH values and was specific to desorption rather than adsorption. Force curves for gold and quartz surfaces showed no such repulsion and peak adhesion. It is thought that the critical humidity coincides with the formation of a complete monolayer of adsorbed water molecules. A number of possible explanations have been offered for the effect and its uniqueness to soda-lime glass in the present experiments. Theoretical calculations of adhesion force have been performed based on the concept of capillary meniscus formation. Calculations give values of around 17000 nN for a sphere 40 mum in diameter and a contact angle of 20°. These values are somewhat larger than measured values in all cases apart from peak adhesion. It is thought that at low humidities there is insufficient water adsorbed to overcome the effect of surface roughness. Contact occurs at asperities, which reduces the expected contact area and hence leads to an adhesive force that is lower than predicted. At humidities > 80% the experiments show evidence of capillary elongation upon surface separation. This implies that the surface adsorbed film is mobile with bulk liquid being drawn into the bridge under the action of the surface tension force. The associated increase in bridge volume and the change in bridge curvature with I elongation will tend to equalise the Laplace pressure inside the bridge and therefore give a value of adhesion that is lower than predicted.
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Newnum, Justin Dale. "The effects of relative humidity on respirator performance." Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/861.
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Švarc, Vojtěch. "Stínící efekt oxidové izolační vrstvy na povrchový potenciál měřený pomocí Kelvinovy sondové mikroskopie." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231956.
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The diploma thesis deals with the experimental study of shielding effect of oxide isolating layer on surface potential measured by Kelvin Probe Force Microscopy. For the study of surface potential were created Au/SiO2 based nanostructures by Electron Beam Lithography, Atomic Layer Deposition and Multilayer Deposition. Surface potential was measured depending on the relative humidity and thickness of oxide isolating layer.
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Zhang, Qing. "Creep properties of cementitious materials : effect of water and microstructure : An approach by microindentation." Phd thesis, Université Paris-Est, 2014. http://pastel.archives-ouvertes.fr/pastel-00996571.
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Cementitious materials such as concrete, cement and gypsum are widely used in construction, as the raw materials of which they are made are abundant on Earth. Such trend is unlikely to change in the coming decades. But these materials suffer from creep. The creep of cementitious materials is a complex issue. On one hand, in cementitious materials creep is often coupled with other phenomena such as drying, hydration and cracking, and can be influenced by various parameters such as temperature, level of stress, water content and mix design. On the other hand, measuring creep by traditional macroscopic creep testing is time-consuming (creep test on concrete is recommended to be carried out over several months in order to provide a reliable characterization of long-term creep) and tedious, since experimental parameters need to be well controlled over extensive periods of time. This thesis studied microindentation at the scale of cement paste or gypsum plaster for the assessment of long-term basic creep properties of cementitious materials, by comparing creep functions obtained by minutes-long microindentation testing with those obtained with macroscopic creep experiments which lasted up to years. For cement paste, the comparison was made at the scale of concrete with the aid of upscaling tools. The study validated that minutes-long microindentation testing can provide a measurement of the long-term creep properties of cementitious materials. With the validated indentation technique, we studied the effect of microstructure (i.e., the distribution and the spatial organization of phases) and of water on long-term basic creep of cementitious materials. The effect of microstructure was studied on materials such as C3S pastes and C2S pastes as well as on compacts of synthetic C-S-H, portlandite (CH) and their mixtures prepared by compaction of powders. For all samples considered, we identified the right micromechanical model that allows predicting the results. The choice of micromechanical model was consistent with microstructural observations. The effect of relative humidity was studied by conditioning and testing some of those materials (i.e., C3S paste, compact of C-S-H, and compact of CH) in various relative humidities ranging from 11% to 94%. Relative humidity had a significant effect on creep: for all materials tested, a greater humidity led to a greater creep. The compact of portlandite was the most sensitive to relative humidity, probably because creep occurs at interfaces between portlandite crystals. For C3S paste, a linear relation was identified between long-term creep properties and water content at relative humidities ranging from 11% to 75%.Finally, we proposed micromechanical models that allow predicting long-term basic creep properties of cementitious materials with a wide range of volume fraction of crystalline phase and over a wide range of relative humidities
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Guo, William X. "Influence of relative humidity on the stress relaxation of sucrose compacts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ51526.pdf.
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Gurnagul, N. (Norayr). "Some effects of relative humidity on the porous structure of paper." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74013.
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Mooney, J. P. "The effect of relative humidity on mycotoxin production by Penicillium viridicum." Thesis, University of Strathclyde, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382428.
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Smith, Megan Schwenker. "An Investigation into CaDNA Conformation as a Function of Relative Humidity." University of Toledo / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1279122399.
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Aung, Tin. "Effect of relative humidity on peanut (Arachis hypogaea L.) seed deterioration /." The Ohio State University, 1991. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487687959966447.
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Talbot, Collin. "Effects of relative humidity on the fluorescence of uranine (disodium fluorescein)." Oklahoma City : [s.n.], 2009.
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Mooiweer, Wiesje. "The dependence of aerosol scattering on relative humidity and particulate composition." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1798481061&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Johari, Houri. "Development of MEMS Sensors for Measurements of Pressure, Relative Humidity, and Temperature." Digital WPI, 2003. https://digitalcommons.wpi.edu/etd-theses/815.
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Continued demands for better control of the operating conditions of structures and processes have led to the need for better means of measuring temperature (T), pressure (P), and relative humidity (RH). One way to satisfy this need is to use MEMS technology to develop a sensor that will contain, in a single package, capabilities to simultaneously measure T, P, and RH of its environment. Because of the advantages of MEMS technology, which include small size, low power, very high precision, and low cost, it was selected for use in this thesis. Although MEMS sensors that individually measure T, P, and RH exist, there are no sensors that combine all three measurements in a single package. In this thesis, a piezoresistive pressure sensor and capacitive humidity sensor were developed to operate in the range, of 0 to 2 atm and 0% to 100%, respectively. Finally, a polysilicon resistor temperature sensor, which can work in the range of -50ºC to 150ºC, was analyzed. Multimeasurement capability will make this sensor particularly applicable for point-wise mapping of environmental conditions for advanced process control. In this thesis, the development of sensors for such an integrated device is outlined. Selected results, based on the use of analytical, computational, and experimental solutions (ACES) methodology, particularly suited for the development of MEMS sensors, are presented for the pressure, relative humidity, and temperature sensors.
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Costa, Junior Juvenil Severino da. "Sensor de umidade microeletrônico fabricado em substrato de alumina e baseado na detecção do ponto de orvalho." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259033.
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Orientador: Fabiano FruettDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: Sensores de umidade relativa do ar estão sendo cada vez mais utilizados em sistemas de controle e aquisição de dados. Estes sensores são facilmente encontrados em estufas, automóveis, refrigeradores, equipamentos médicos, eletrodomésticos, instrumentos de precisão e outros. Mais recentemente, com o crescimento do mercado agrícola no Brasil, a demanda por sensores de umidade vem crescendo substancialmente. Este trabalho e dedicado ao estudo de um sistema sensor de umidade por detecção de ponto de orvalho utilizando uma ponte de impedância. A ponte de impedância foi microfabricada diretamente sobre um substrato de alumina que compõe uma pastilha Peltier. Um termistor também micro fabricado no mesmo substrato fornece o sinal necessário para a detecção do ponto de orvalho. A face fria da pastilha Peltier e resfriada ate alcançar a temperatura do ponto de orvalho do ar ao seu redor. Este resfriamento resulta na saturação do vapor de d'água presente no ar, fazendo com que gotículas de água condensem sobre o substrato de alumina. A condensação de água sobre os eletrodos da ponte de impedância causa um desbalanceamento que gera um sinal de controle para a pastilha Peltier. As temperaturas no limiar de condensação e ambiente são utilizadas no calculo da umidade relativa. Este sensor de umidade foi projetado para que alguns requisitos com relação a resistência contra contaminantes e baixa histerese fossem alcançados
Abstract: Sensors for relative humidity are being increasingly used in control systems and data acquisition. These sensors are easily found in greenhouses, cars, weather equipment, medical equipment, appliances, etc.. More recently, with the growth of the agricultural market in Brazil, the demand for humidity sensors has been growing substantially. This work is dedicated to the study of a humidity sensor for dew point detection using an impedance bridge. The impedance bridge was microfabricated directly on an alumina substrate that comprises a Peltier device. A thermistor also microfabricated on the same substrate control the temperature of the Peltier device to the threshold where the dew point produces the saturation of water vapor in the air. The cold face of the Peltier device is cooled until it reaches the dew point temperature. This cooling results in saturation of water vapor in the air, around the side of the Peltier device causing water droplets to condense on the alumina substrate. Water condensation on the electrodes of the impedance bridge causes an imbalance that generates a control signal to the Peltier device. The temperatures measured at the threshold of condensation along with ambient temperature are used to calculate the relative humidity. This sensor was designed to fulfill some requirements related to resistence to contaminants and low hysteresis
Mestrado
Eletrônica, Microeletrônica e Optoeletrônica
Mestre em Engenharia Elétrica
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Gouveia, Rubia Figueredo. "Padrões eletrostaticos em uma superficie de silica : um modelo para o acumulo de cargas eletricas em isolantes." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250289.
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Orientador: Fernando GalembeckDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Atualmente muitas tecnologias importantes são baseadas nos princípios eletrostáticos, como por exemplo, a pintura eletrostática, a reciclagem de termoplásticos e a eletrofotografia. No entanto, mesmo considerando todo o desenvolvimento da eletrostática, ainda existem muitas questões importantes não respondidas, quando se considera a eletrização de materiais isolantes. Na maioria dos casos não se conhece quais são as espécies portadoras de cargas, nem como elas podem ser detectadas e identificadas. Trabalhos anteriores deste laboratório mostraram que os portadores de cargas em látexes são íons simples (K, RSO4, etc). Neste trabalho foram estudados os padrões eletrostáticos criados em uma superfície de sílica, recoberta por um conjunto de eletrodos interdigitados de ouro. As amostras foram preparadas utilizando técnicas microlitográficas e sua superfície foi investigada usando as microscopias de força atômica (AFM) e de varredura de potencial elétrico (SEPM). Foram obtidos padrões eletrostáticos reprodutíveis; a aplicação de uma diferença de potencial elétrico entre os eletrodos produz padrões de potenciais elétricos que desaparecem rapidamente quando os eletrodos são curto-circuitados e aterrados. O tempo de relaxação desses padrões foi de aproximadamente 10 minutos sob umidade de 70% e eles são fortemente influenciados pela umidade relativa da atmosfera, apresentando um tempo de decaimento superior a 1 hora, quando a superfície é exposta a uma umidade relativa de 10%. Os resultados são interpretados usando um modelo simples baseado na quimisorção de espécies presentes na atmosfera acompanhada de reações eletródicas, podendo ser aplicado a outros isolantes.
Abstract: Many current important technologies are based on electrostatic principles, as for instance electrostatic painting, polymer recycling and photocopying. However, even considering its long history, there are still many open questions in the study of electric phenomena in insulators. For instance, how can charge carriers in insulators be detected, identified and quantified? In this laboratory the examination of latexes showed that the charge carriers are K e RSO4 ions. This work describes reproducible electric potential patterns created on silica surfaces, covered with sets of interdigitated parallel gold electrodes by using microlithography techniques. The patterns are detected by concurrent atomic force microscopy (AFM) and scanning electric potential microscopy (SEPM). The images were acquired while electrodes were biased and also after they were all short-circuited and grounded, producing reproducible electrostatic patterns. Characteristic times for pattern formation and relaxation are in the order of 10 minutes at 70% relative humidity and they are strongly influenced by the relative humidity of the atmosphere, showing a relaxation time in the order of 1 hour, when the surface is under 10% RH. The results are interpreted using a model based on the chemisorption of atmospheric water and electrochemical activity at the silica surface. The sum up, this work describes a new approach to the study of the electrification of insulator surfaces that produces reproducible results and can be applied to many other cases.
Mestrado
Físico-Química
Mestre em Química
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Poderoso, Fabiana Maria Gonçalves de Lima. "Impacto do ambiente do incubatório na produção de pintos de corte." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256837.
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Orientador: Irenilza de Alencar Nääs, Marta dos Santos BarachoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola
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Resumo: No Brasil, a avicultura é uma atividade relativamente nova, apesar de ter seu início na década de 30, como atividade fornecedora de subproduto, o esterco para os cafezais, se tornando uma atividade econômica produtora de proteína de alto valor biológico, somente a partir da década de 60. Hoje ocupa um lugar privilegiado na economia mundial devido ao trabalho de muitos profissionais ligados à atividade, sendo os principais pontos que ocorreram grandes melhorias: avanço tecnológico nas áreas de produção, nutrição e sanidade, permitindo uma melhora significativa nos índices zootécnicos. O incubatório é o local onde se obtêm o produto final, ou seja, do pintainho de um dia, tem a responsabilidade de disponibilizar aos produtores, pintos de qualidade para maximizar o desempenho das aves a campo. O presente trabalho teve como objetivo geral avaliar a influência da temperatura e da umidade relativa do ar no ambiente do incubatório, sobre as respostas da taxa de eclosão durante o processo de incubação e nascimento. Os dados de temperatura e umidade relativa do ar foram registrados em uma das salas das incubadoras e em uma das salas de nascedouro do Incubatório São José no município de Amparo - SP e analisados com relação ao índice de eclosão dos ovos incubados que foi analisado no dia do nascimento dos pintos. Foram rastreadas 48 bandejas, tendo capacidade de 96 ovos cada bandeja, até o nascimento desses pintos, sendo estas divididas seis quadrantes na incubadora sendo oito bandejas em cada quadrante classificadas como lotes e após foram monitoradas na sala de nascedouro que foi dividida em quatro quadrantes. Os dados foram submetidos à análise estatística descritiva por lote e análise de comparação de médias, através do teste F na ANOVA e do teste não-paramétrico de Kruskal-Wallis. Os resultados obtidos foram: a temperatura do ambiente influenciou o descarte total de ovos no 14º dia de incubação (de 35.9ºC à 37.0°C) e no 21º de incubação (de 37,0 °C à 37,3 °C) e, comparados com a idade das matrizes (42 semanas e 56 semanas), identificou-se que a matriz mais velha obteve maior número de descartes nas variáveis analisadas como: ovos inférteis, mortalidade de 0 a 7 dias e ovos quebrados, a serem o volume maior do total de ovos descartados. E, somente houve influência da umidade relativa do ar aos 21 dias de incubação ( de 52,2% à 62%). Conclui-se que houve influência do ambiente térmico e da idade da matriz no descarte total de ovos no processo de incubação
Abstract: Poultry science is responsible for studying the birds. In Brazil poultry production is a relatively new activity, although had its beginning in the 30's decade as an activity that supplied waste which was used in coffee production. It became an economical activity that produces protein of high biological value just after the decade of 60. Today Brazil occupies a privileged place in the world's economy due to the work of several professionals connected to this activity. The areas were the greatest technological improvements occurred are: production, nutrition and health, allowing significant enhancement in animal production indexes. The hatchery is the place where the final product is obtained, the one day old pullet, and that has the responsibility of given the producers high quality chicks in order to maximize their performance in the field. The objective of this research is to evaluate the influence of ambient temperature and relative humidity of the air in the hatchery on the response during the process in both incubator and hatcher. Air temperature and relative humidity data will be registered in a incubator and hatcher at the Incubatório São José, county of Amparo - SP and they will be analyzed with relation to the hatcher index at the first day. Forty eight trays with 96 eggs each were screened trays until the birth of these chicks. The hatchery was divided in six quarters and eight incubator trays in each quadrant were classified as lots and they were monitored after the hatcher room, which was divided into four quadrants. The data were analyzed by descriptive statistics and analysis of batch mean comparison, using the F test in ANOVA and nonparametric Kruskal-Wallis. The obtained results were: the temperature of the environment influenced the discarding total egg on day 14 of incubation and 21 of incubation and compared with age of the array, we identified that it took the variables as: infertile eggs, mortality 0-7 days and broken eggs, to be the bulk of total eggs discarded. There was only influence of relative humidity at 21 days of incubation. It is concluded that there was influence of thermal environment and age of female breeder in total egg discarding in the process of incubation
Mestrado
Construções Rurais e Ambiencia
Mestre em Engenharia Agrícola
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Smolinski, Steven P. "Marine boundary layer depth and relative humidity estimates using multispectral satellite measurements." Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23069.
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A technique is presented to estimate surface relative humidity and boundary layer depth from multispectral satellite measurements using the AVHRR sensor on TIROS-N generation satellites. A sensitivity study quantifies the effect of a combination of input measurement errors of sea-surface temperature, optical depth and total water vapor used in the technique to produce outputs of surface relative humidity and boundary layer depth under simulated conditions and model atmospheres. Technique verification is then accomplished with satellite data compared to ship and aircraft vertical soundings and sea-surface temperature measurements. The root mean square differences between the surface relative humidity/boundary layer depth satellite-measured estimates and verified measurements are 6% and 75 m respectively. Finally, synoptic-scale mapping of the surface relative humidity and boundary layer depth fields based on the satellite derived estimates is accomplished with monochromatic and color enhanced satellite images. Horizontal variability of surface relative humidity and boundary layer depth on the order of kilometers can be visually detected from these images. Keywords: Remote sensing; MABL(Marine Boundary Layer); Marine atmospheres; Air ocean interface; Advanced very high resolution radiometers; Theses. (edc)
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Thai, Minh Quan. "Modélisation micromécanique et simulation numérique du fluage des bétons avec prise en compte de l'endommagement et des effets thermo-hydriques." Phd thesis, Université Paris-Est, 2012. http://tel.archives-ouvertes.fr/tel-00788439.
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Le béton est un matériau hétérogène complexe dont les déformations comportent une partie différée qui est affectée par un grand nombre de facteurs tels que la température, l'humidité relative et l'évolution de la microstructure. La prise en compte des déformations différées et en particulier du fluage est indispensable dans le calcul des ouvrages en béton tels que ceux destinés à stocker des déchets radioactifs. Ce travail de thèse a pour objectifs : (1) de développer un modèle de fluage simple et robuste pour le béton en faisant appel à la micromécanique et en tenant compte de l'endommagement et des effets thermiques et hydriques ; (2) d'implanter numériquement le modèle développé dans un code de calcul par éléments finis de façon à pouvoir simuler le comportement d'éléments de structure simples en béton. Pour atteindre ce double objectif, le travail est scindé en trois parties. Dans la première partie, le matériau cimentaire est à l'échelle microscopique supposé être constitué d'une matrice viscoélastique linéaire caractérisée par un modèle de Maxwell généralisé et de phases particulaires représentant les granulats élastiques et les pores. Le schéma micromécanique de Mori-Tanaka, la transformée de Laplace-Carson et son inversion sont alors utilisés pour obtenir dans l'espace temporel des estimations analytiques ou numériques de ses paramètres mécaniques et hydromécaniques. Ensuite, le modèle micromécanique de fluage obtenu est couplé au modèle d'endommagement de Mazars via le concept de pseudo-déformations introduit par Schapery. Les paramètres intervenant dans le modèle viscoélastique endommageable ainsi établi sont systématiquement identifiés à l'aide de données expérimentales. Enfin, la prise en compte des effets de la température et de l'humidité relative dans le modèle viscoélastique endommageable est basée sur la méthode du temps équivalent ; l'efficacité de cette approche est démontrée et discutée dans le cas de chargements simples de fluage
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Jacquot, Bruno. "Etanchéité des matériaux pour obturations radiculaires et coronaires en odontologie : approche physico-chimique." Thesis, Montpellier 1, 2011. http://www.theses.fr/2011MON12201/document.
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Ce travail de thèse est scindé en 4 parties. La première partie est une approche originale en odontologie par modélisation de la pénétration de colorants à l'interface des matériaux pour obturation radiculaire. Les deux situations extrêmes ont été envisagées. Lorsque l'interface est remplie uniquement par de l'air à pression atmosphérique, la pénétration s'effectue par capillarité. Lorsque l'interface est remplie d'eau, la pénétration s'effectue par diffusion. Les différentes équations physiques qui régissent ces phénomènes ont été déterminées. Les différents paramètres d'influence ont été quantifiés. La seconde partie et la troisième partie est une revue de littérature critique concernant l'influence de l'humidité relative et de la température du milieu buccal sur l'adhérence et l'étanchéité des matériaux adhésifs pour obturation coronaire. Une corrélation a été recherchée entre les études de laboratoire et les études cliniques. La quatrième partie est la mise au point d'un modèle permettant d'évaluer la pénétration de l'eau liquide et de l'eau gazeuse à la surface des matériaux adhésifs utilisés en odontologie. L'analyse de surface est réalisée par Spectroscopie Raman et le degré de conversion de ces résines méthacryliques est quantifié. La couche d'inhibition par l'oxygène de l'air est caractérisée en épaisseur et en degré de conversion. Une comparaison est effectuée entre les composites d'obturation, les composites flow et différents systèmes adhésifs amélo-dentinairesThis thesis is divided into 4 partsThe first part is an original approach in dentistry by modeling the penetration of dyes at the interface of root filling materials. The two extreme situations were considered. When the interface is filled only with air at atmospheric pressure, the penetration is by capillary action. When the interface is filled with water, the penetration is by diffusion. The different physical equations governing these phenomena have been determined. The influence of the various parameters were quantified. The second part and third part are a review of critical literature on the influence of relative humidity and temperature of the oral environment on adhesion and sealing material for sealing coronary adhesives. A correlation was sought between laboratory studies and clinical trials.The fourth part is the development of a model to assess the penetration of liquid water and water vapor on the surface of the adhesive materials used in dentistry. Surface analysis is carried out by Raman spectroscopy and the degree of conversion of the methacrylate resins is quantified. Layer inhibition by oxygen is characterized by thickness and degree of conversion. A comparison is made between the composite filling, the composite flow and various adhesive systems enamel-dentin
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Lee, Lizabeth. "Monitoring of Indoor Relative Humidity Levels in Residential Dwellings: A Sensor Network Application." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/270.
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Indoor Air Quality is an increasing concern in the world today. The mere presence of people in a building or residence can significantly alter indoor air quality. Relative humidity over the range of normal indoor temperatures (66 - 80 degrees Farenheit) has been linked both directly and indirectly to various health and structural problems. The purpose of this project was to discover whether residential dwellings might benefit from an indoor humidification system. The project consisted of the deployment of three separate sensor networks consisting of 12 tmote sky modules manufactured by the Moteiv corporation, each equipped with a temperature and humidity sensor manufactured by Sensirion. Each tmote sky module continuously transmitted the raw data readings to a base station to be processed. The lifetime of each network was approximately four days of continuous data transmission. The results verified the hypothesis that relative humidity levels have a significant affect on the indoor environment and can be linked to the health and structural problems reported by the occupants of each monitored residence. Based on the project findings residential dwellings would benefit from an indoor humidification system, given the symptoms associated with relative humidity level problems exist.
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Watson, David William. "Monitoring moisture movement within modified concretes." Thesis, Heriot-Watt University, 1997. http://hdl.handle.net/10399/641.
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Fan, Mizi. "Dimensional instability of cement bonded particleboard : understanding its occurrence and reducing its magnitude." Thesis, Bangor University, 1997. https://research.bangor.ac.uk/portal/en/theses/dimensional-instability-of-cement-bonded-particleboard--understanding-its-occurrence-and-reducing-its-magnitude(ce649ec2-90ed-4914-8412-4af2e67e749f).html.
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Tapias, Camacho Mauricio Alberto. "Particle model for crushable aggregates which includes size, time and relative humidity effects." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/404622.
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This thesis presents a study of the mechanical behaviour of coarse-crushable aggregates, using the discrete element method (DEM). A novel DEM model has been developed taking into account particle breakage, the influence of the relative humidity, time-dependent behaviour and the effect of particle size.
A criterion of particle breakage has been proposed based in fracture mechanics and the theory of subcritical crack propagation. Three theoretical models for the crack propagation are proposed taking into account the relative humidity.
Pyramidal macroparticles, which behave like clumps and can break, were selected for the DEM model, in view of the results of the analysis performed on the effect of particle shape. The model has been implemented using the commercial software PFC3D, through the incorporation of functions programmed in FISH language.
The proposed DEM model is mainly based on three parameters: the inter-granular contact stiffness (kn), the inter-particle friction (μ) and the fracture toughness of the material (Kc). It also takes into account the surface roughness of the particles through the solid angle describing contact stresses (θ0) and the yield stress of the aggregates (σy).
In order to calibrate the parameters of the model, some laboratory tests were performed. The basic (φb) and mineral (φm) friction angles were determined by means of shear tests using Tilt table test and a Direct shear cell. Contact stiffness tests in one-directional compression on prismatic specimens allowed the determination of kn. θ0 was found by means of an estimation of mean roughness (Ra) and by microscope examination of grain surfaces.
The calibration of the DEM parameters was also carried out by means of a back analysis oedometer tests and experimental data. Compressibility, the evolution of grain size distribution curves and the calculation of breakage indices helped to perform the calibration.
Additionally, several oedometer tests were performed on a brittle-crushable material -sugar cubes- in order to investigate the mechanisms of breakage. Two types of arrangements were used to obtain two very different initial void ratios: 0.80 and 0.20. Two mechanisms of breakage were determined: Comminution crushing and particle splitting. An analysis of time-dependent behaviour was also carried
out. These considerations were taken into account in the DEM model.
Blind numerical triaxial tests were also performed using parameters previously calibrated in the back analysis of oedometer tests. The prediction was quite accurate and it shows the capability of the DEM model developed to reproduce the constitutive behaviour of crushable aggregates compared with experimental results from the literature.
The DEM simulations of the oedometer and triaxial tests were consistent and accurate. The influence of the relative humidity on the mechanical behaviour, particle size effects, time-dependent behaviour and the evolution of the grain size distribution were well reproduced.Esta tesis presenta un estudio del comportamiento mecánico de los agregados gruesos a partir de la modelación numérica utilizando el método de Elementos Discretos (DEM). Se ha desarrollado un novedoso modelo DEM que tiene en cuenta la rotura de las partículas, la humedad relativa, la influencia del tiempo y el efecto del tamaño de las partículas.Se propone un criterio de rotura de partículas con base en la mecánica de fracturas y la teoría de propagación subcrítica de grietas. Tres modelos teóricos para la propagación de grietas se proponen teniendo en cuenta la influencia de la humedad relativa.Después de realizar un análisis de sensibilidad de formas de las partículas, para el modelo DEM se seleccionaron macropartículas con formas piramidales que se comportan como clumps (totalmente rígidas) y pueden romper. El modelo ha sido implementado utilizando el software comercial PFC3D, mediante la incorporación de funciones programadas en lenguaje FISH.El modelo DEM propuesto trabaja principalmente con tres parámetros: la rigidez de los contactos (kn), la fricción entre las partículas (µ) y la tenacidad de Fractura del material (Kc). También tiene en cuenta la rugosidad superficial de las partículas a través del parámetro ¿o (ángulo sólido-solid angle) y la tensión de fluencia de los agregados.Con el fin de calibrar los parámetros del modelo se realizaron algunos ensayos de laboratorio. Para la estimación de µ: ensayos para determinar el ángulo de fricción básico y mineral de los agregados a partir de ensayos de corte utilizando la Mesa Inclinada y el Corte Directo. Para la determinación de kn: ensayos de Rigidez de Contactos a partir de compresión uni-direccional sobre muestras prismáticas con uno de sus extremos de forma piramidal apoyado sobre una superficie plana. Para la determinación de ¿o: estimación de la Rugosidad media (Ra) medida a partir de observaciones con el microscopio.La calibración de los parámetros del modelo DEM también se llevó a cabo a partir de un análisis retrospectivo (back analysis) de los ensayos numéricos edométricos comparados con datos experimentales ¿realizando un análisis de sensibilidad de diferentes parámetros-. Se tuvieron en cuenta la compresibilidad, la evolución de las curvas granulométricas y el cálculo de índices de rotura.Adicionalmente, con el fin de investigar sobre los mecanismos de rotura, se realizaron ensayos edométricos sobre un material frágil: cubos de azúcar. Se utilizaron dos tipos de arreglos de los cubos obteniéndose dos relaciones de vacíos iniciales muy diferentes: 0.80 y 0.20. Se determinaron dos mecanismos de rotura: Rotura local (comminution crushing) y divisiones en dos partes que se aproximaron a mitades (particle splitting). Así mismo se realizó un análisis del comportamiento en el tiempo. Estas consideraciones fueron tenidas en cuenta en el modelo DEM.También se ejecutaron ensayos triaxiales numéricos con los parámetros calibrados previamente en los ensayos edométricos y se compararon con resultados experimentales de la literatura. La predicción del comportamiento fue bastante acertada mostrando de esta forma la fiabilidad del modelo desarrollado. Las simulaciones DEM de los ensayos edométricos y triaxiales fueron consistentes y bastante ajustadas con los resultados experimentales. La influencia de la humedad relativa en el comportamiento mecánico, el efecto del tamaño de las partículas, el comportamiento dependiente del tiempo y la evolución de la curvas de distribución granulométrica fueron bien reproducidas.
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Mamo, Bayou Million. "The effect of natural fencerows on local standardized windspeed, temperature and relative humidity." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0019/MQ29455.pdf.
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Willard, Eric Hillman Tharsing. "Temperature and relative humidity gradients of intermittent and perennial tributaries in Northern California." [Chico, Calif. : California State University, Chico], 2009. http://hdl.handle.net/10211.4/108.
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NiaziEsfyani, Sadegh. "The role of relative humidity and aerosol composition in airborne respiratory virus survival." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/214025/1/Sadegh_NiaziEsfyani_Thesis.pdf.
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This thesis presents and tests a novel hypothesis that attempts to predict the relative humidity (RH) dependent survival of airborne respiratory viruses in protein-enriched saline aerosols. The hypothesis proposed that virus-laden respiratory aerosols exist in either an effloresced (solid) or deliquesced (liquid) state, depending on the ambient air RH and that the survival of viruses embedded in such aerosols changes with that state. Experiments confirmed as predicted, that rhinovirus and influenza virus exhibited a V-shaped surviving fraction dependence on RH. Implications concerning the survival of these viruses under seasonal conditions are discussed along with strategies to control indoor airborne infection.
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Wright, Jonathon S. "Influences of Tropical Deep Convection on Upper Tropospheric Humidity." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11573.
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Godoy, Charlotte. "Filtration d’aérosols de suie en présence de vapeur et/ou de gouttelettes d’eau." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0287.
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L'épuration de l'air contaminé par les particules générées par de nombreux procédés industriels fait le plus souvent appel à la filtration au moyen de médias filtrants. Ces équipements collectifs de protection des personnes et de l’environnement sont éprouvés en termes d’efficacité initiale mais leur comportement au cours du temps reste difficilement prévisible. Ce constat est d’autant plus vrai lorsque ces dispositifs sont confrontés à un aérosol diphasique constitué de particules solides et liquides. Ces situations peuvent notamment être rencontrées lors de l’usinage de métaux, l’épandage de pesticides ou encore lors d’incendie dans des zones confinées comme les centrales nucléaires. L'étude proposée visera à établir les performances d’un média fibreux vis à vis d’aérosols diphasiques composés de particules solides nanostructurées et de gouttelettes (submicroniques ou microniques). Si la filtration d’aérosols solides ou d’aérosols liquides seuls est relativement bien documentée dans la littérature, aucune étude ne s’est intéressée à cette problématique d’aérosols diphasiques (surtout en termes de colmatage). Pour de forts ratios solide/liquide, l’évolution temporelle de la perte de charge devrait se rapprocher de celle d’un filtre soumis à des aérosols solides, à savoir une augmentation quasi-linéaire au cours du temps. Dans le cas d’un aérosol majoritairement constitué de gouttelettes, une stabilisation de la perte de charge, caractérisée par un état d’équilibre entre le débit massique de gouttelettes collectées et le débit de liquide drainé sur la face aval du filtre, pourrait être envisagée. Mais quid de l’évolution de la perte de charge entre ces deux extremums ? La détermination de l’évolution temporelle de l’efficacité de collecte est tout aussi incertaine et de plus se heurte à un véritable verrou métrologique. Une mesure fine et fiable de la concentration et de la distribution granulométrique d’un aérosol constitué d’agglomérats nanostructurés est déjà relativement complexe. La présence de gouttelettes rendra la mesure d’autant plus difficile car pourrait être à l’origine d’une modification de la distribution granulométrique des particules solides au cours de leur transport (impaction, condensation). De plus, la caractérisation d’un aérosol diphasique nécessitera le couplage de différents granulomètres basés sur des principes de mesure différents de façon à faire la distinction entre les particules liquides et solides. L’objectif de cette thèse a ainsi pour but de pallier l’absence de connaissance sur la filtration d’aérosols diphasiques dans une double optique de protection des personnes et de l’environnementOne of the most frequently used methods to purify air contaminated by particles, in many industrial processes, is filter media. These collective equipment for protecting people and the environment are proven in terms of initial efficiency, but their behavior over time remains difficult to predict. This is all the more noticeable when these devices are confronted with a biphasic aerosol composed of solid and liquid particles. These situations can be encountered during metals machining, pesticides spreading or even during fires in confined areas such as nuclear power plants. The proposed study will aim to establish the performance of a fibrous media with respect to biphasic aerosols with nanostructured solid particles and droplets (submicron or micron-sized). If the filtration of solid aerosols or liquid aerosols is relatively well documented in the literature, no study has been interested in this problem of biphasic aerosols. For high solid / liquid ratios, the time course of the pressure drop should be close to solid aerosols filtration evolution, ie a quasi-linear increase over time. In the case of an aerosol predominantly made up of droplets, a constant pressure drop overtime, characterized by a state of equilibrium between the mass flow rate of collected droplets and the flow rate of liquid drained on the downstream face of the filter, could be considered . But what about the evolution of the pressure drop between these two extremes? The determination of the temporal evolution of the collection efficiency is also uncertain and should be regarded as a real metrological challenge
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Tabor, Kimberly Lane. "Succession and Development Studies on Carrion Insects of Forensic Importance." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11188.
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Forensic entomological field and laboratory studies were conducted to obtain data currently missing or conflicting in the literature. The first goal of this project was to identify and qualitatively assess the major taxa of forensic importance in southwest Virginia. Carcasses of the domestic pig, Sus scrofa L., were placed in field conditions and allowed to decompose until they reached the advanced stage of decay. Over 50 taxa were collected and identified, with Phormia regina, Phaenicia coeruleiviridis, Phaenicia sericata, Calliphora spp., Sarcophaga utilis, Musca domestica, Hydrotaea leucostoma, Stearibia nigriceps, Prochyliza xanthostoma, and Meroplius minutus among the most commonly observed fly species, and Creophilis maxillosus, Platydracus maculosus, Aleochara lata, Oiceoptoma noveboracense, Necrodes surinamensis, and Necrophila americana among the most commonly observed beetle species.
The second objective of this study was to analyze successional patterns of taxa collected and identified in the carrion-insect succession studies. Occurrence matrices were constructed for the successional patterns of insect taxa during 21 sampling intervals in the spring and eight intervals in the summer studies. Permutation analyses of the occurrence matrices showed that the successional patterns of insect taxa were similar between spring 2001 and 2002 (P = 0.001) and between summer 2001 and 2002 (P = 0.007). Results indicated that the successional patterns appear to be typical for the seasonal periods.
The third objective of this study was to analyze the effects of antemortem ingestion of ethanol by pigs on insect successional patterns and development rates. Pigs were dosed with a mixture of 95% ethanol and saline. Blood samples were collected immediately prior to euthanasia. The carcasses then were placed at an open
field site and allowed to decompose. Insect samples were collected from carcasses for ten days post-mortem and the collected data were used to develop occurrence matrices. Permutation analysis to test the null hypothesis of no similarity between successional patterns of taxa from treated and untreated pigs showed that the successional patterns were similar. Loin meat from the carcasses was used as a rearing medium for field development studies of the black blow fly, Phormia regina. Development rates of 3rd instar P. regina maggots feeding on meat from treated pigs were significantly different from development rates of maggots feeding on meat from untreated pigs. No significant differences were detected in 1st and 2nd instars.
Finally, the effect of relative humidity (RH) on egg hatch time and percent hatch rate of Phormia regina and Phaenicia coeruleiviridis was tested using saturated salt solutions. The global ANOVA of mean hatch times and percent hatch was found to be significant for P. regina at 20°C and 30°C and P. coerulieviridis at 20°C among RH levels at á = 0.05. T-test (LSD comparisons) results detected significant differences between some but not all RH levels within all three data series tested. Percent hatch observed varied widely, depending on the RH level. Of the levels tested, the lowest RH where hatch rate was observed was 53% (20°C) for P. coeruleiviridis, where only 1% of the eggs hatched. At 90+% RH, almost all of the eggs hatched for both species.Ph. D.
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Ozsan, Burcu. "Effect Of Relative Humidity Of Reactant Gases On Proton Exchange Membrane Fuel Cell Performance." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614375/index.pdf.
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Fuel cells are expected to play a major role in the economy of this century and for the foreseeable future. The use of hydrogen and fuel cells can address critical challenges in all energy sectors like commercial, residential, industrial, and transportation. Fuel cells are electrochemical devices that convert energy of a chemical reaction directly into electrical energy by combining hydrogen fuel with oxygen from air. If hydrogen is used as fuel, only byproducts are heat and water.
The objective of this thesis is to investigate the effect of operating temperature and relative humidity (RH) of reactant gases on proton exchange membrane (PEM) fuel cell performance by adjusting the operation temperature of the fuel cell and humidification temperature of the reactant gases.
In this study, the effect of the different operating parameters on the performance of single proton exchange membrane (PEM) fuel cell have been studied experimentally using pure hydrogen on the anode side and air on the cathode side. Experiments with different fuel cell operating temperatures, different air and hydrogen humidification temperatures have been carried out. The experimental results are presented in the form of polarization curves, which show the effects of the various operating parameters on the performance of the PEM fuel cell. The polarization curves data have been fit to a zero dimensional model, and the effect of the fuel cell operation and humidification temperatures on the kinetic parameters and the cell resistance have been determined.
The fuel cell has been operated with 1.2 and 2 stoichiometry ratio for hydrogen and air, respectively. Fuel cell performance was detected at different fuel cell operation temperatures changing from 60 to 80 ºC, and relative humidity of the entering gases changing from 20 to 100 % for air and 50 % and 100 % for hydrogen. Tests were performed in a PEM fuel cell test station. The highest performance of 275 mA/cm2 at 0.6 V and 650 mA/cm2 at 0.4 V was obtained for 50 % RH air with a constant 100 % relative humidity of hydrogen for working at atmospheric pressure and 60 oC fuel cell temperature. However, the highest performance of 230 mA/cm2 at 0.6 V for 50 % RH of air with a constant 100 % relative humidity of hydrogen and the highest performance of 530 mA/cm2 at 0.4 V for both 70 % RH and 100% RH air with a constant 100 % relative humidity of hydrogen was obtained for working at atmospheric pressure and 70 oC fuel cell temperature. Besides, the highest performance of 200 mA/cm2 at 0.6 V and 530 mA/cm2 at 0.4 V was obtained for 100 % RH air with a constant 100 % RH of hydrogen for working at atmospheric pressure and 80 oC fuel cell temperature.
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Bell, Ryan D. "Impact of Relative Humidity on the Biology of Pardosa milvina Hentz, 1844 (Araneae: Lycosidae)." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243917682.
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Quaas, Johannes. "Evaluating the “critical relative humidity” as a measure of subgrid-scale variability of humidity in general circulation model cloud cover parameterizations using satellite data." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-177265.
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A simple way to diagnose fractional cloud cover in general circulation models is to relate it to the simulated relative humidity, and allowing for fractional cloud cover above a “critical relative humidity” of less than 100%. In the formulation chosen here, this is equivalent to assuming a uniform “top-hat” distribution of subgrid-scale total water content with a variance related to saturation. Critical relative humidity has frequently been treated as a “tunable” constant, yet it is an observable. Here, this parameter, and its spatial distribution, is examined from Atmospheric Infrared Sounder (AIRS) satellite retrievals, and from a combination of relative humidity from the ECMWF Re-Analyses (ERA-Interim) and cloud fraction obtained from CALIPSO lidar satellite data. These observational data are used to evaluate results from different simulations with the ECHAM general circulation model (GCM). In sensitivity studies, a cloud feedback parameter is analyzed from simulations applying the original parameter choice, and applying parameter choices guided by the satellite data. Model sensitivity studies applying parameters adjusted to match the observations show larger positive cloud-climate feedbacks, increasing by up to 30% compared to the standard simulation.
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Chovanec, Jan. "Meteorologická měření." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217479.
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The achievement of this thesis is to design functional equipment which is able to measure the basic meteorological variables as air temperature, humidity and barometric pressure. In order to measure relative humidity completed with temperature, an intelligent sensor manufactured by Intersema Inc., MS5534B, was chosen. Relative humidity is measured by a capacitance sensor Humirel HS1101LF. The measured data are stored in anon-volatile memory. Data can be downloaded to a computer file via serial port or they can be online displayed on the computer screen via the wireless Bluetooth connection. Because the equipment is supposed to be used for the external measurement without the connection to electricity, low power consumption was considered as a most important parameter as well as good weather protection.
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Irvine, Douglas A. "Control of temperature, relative humidity and carbon dioxide for reduced ventilation in commercial potato storages." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/mq23352.pdf.
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Altaf, Kazim. "Investigation of the effect of relative humidity on additive manufactured polymers by depth sensing indentation." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8567.
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Additive manufacturing methods have been developed from rapid prototyping techniques and are now being considered as alternatives to conventional techniques of manufacturing. Stereolithography is one of the main additive methods and is considered highly accurate and consistent. Polymers are used as stereolithography materials and exhibit features such as high strength-to-weight ratio, corrosion resistance, ease of manufacturing and good thermal and electrical resistance properties. However, they are sensitive to environmental factors such as temperature, moisture and UV light, with moisture being identified as one of the most important factors that affect their properties. Moisture generally has an adverse effect on the mechanical properties of polymers. Investigation of the effects of moisture on polymers can be carried out using a number of experimental techniques; however, the benefits of the depth sensing indentation method over bulk tests include its ability to characterise various mechanical properties in a single test from only a small volume of material and the investigation of spatial variation in mechanical properties near the surface. The aim of this research was to investigate the effects of varying relative humidity on the indentation behaviour of stereolithography polymers and to develop a modelling methodology that can predict this behaviour under various humidities. It was achieved by a combination of experimental and numerical methods. Depth sensing indentation experiments were carried out at 33.5 %, 53.8 %, 75.3 % and 84.5 % RH (relative humidity) and 22.5 °C temperature to investigate the effects of varying humidity on the micron scale properties of the stereolithography resin, Accura 60. In order to minimise the effects of creep on the calculated properties, appropriate loading and unloading rates with suitable dwell period were selected and indentation data was analysed using the Oliver and Pharr method (1992). A humidity control unit fitted to the machine was used to condition the samples and regulate humidity during testing. Samples were also preconditioned at 33.5 %, 53.8 %, 75.3 % and 84.5 % RH using saturated salt solutions and were tested at 33.5 % RH using humidity control unit. It was seen that properties such as indentation depth increased and contact iv hardness and contact modulus decreased with increasing RH. The samples conditioned and tested using the humidity control unit at high RH showed a greater effect of moisture than the preconditioned samples tested at 33.5 % RH. This was because the samples preconditioned at high RH exhibited surface desorption of moisture when tested at ambient RH, resulting in some recovery of the mechanical properties. In order to investigate these further, tests were performed periodically on saturated samples after drying. Ten days drying of samples conditioned for five days at 84.5 % RH provided significant, though not complete, recovery in the mechanical properties. These tests confirmed that Accura 60 is highly hygroscopic and its mechanical properties are a function of RH and removal of moisture leads to a significant recovery of the original mechanical properties.
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Vohra, Amit. "Photocatalytic disinfection of indoor air effect of relative humidity and surface roughness of photocatalytic reactor /." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013032.
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Weeks, Brian, and Paul Baker. "Survivability of the Subterranean Termite Heterotermes aureus When Exposed to Different Temperatures and Relative Humidity." College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/216629.
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Survivability of Heterotermes aureus (Snyder) was tested under varying temperature and relative humidity regimes in laboratory incubators over seven day periods. Initial tests showed that RH had a strong influence on H. aureus survival. Survival was significantly higher (P<.05) at 90% RH than 50% RH when held at a constant temperature of 29.4°C. Four temperatures were tested at a constant RH of 90%. Survival was highest at temperatures of 19.4°C (91.8%) and 21.1°C (97.3%). Survival was significantly lower for the higher ranger temperatures of 29.4°C (91.2%) and 32.2°C (69.2%).
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Cardona, Allison Leanne. "The frequency of tropopause-level thick and thin cirrus clouds as observed by CALIPSO and the relationship to relative humidity and outgoing longwave radiation." Texas A&M University, 2008. http://hdl.handle.net/1969.1/85992.
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Thin cirrus clouds play an important radiative role in the earth's atmosphere and
climate system, yet are one of the least understood components of the climate system.
With the use of data from Cloud-Aerosol Lidar and Infrared Pathfinder Satellite
Observations (CALIPSO), thin cirrus and thick cloud distributions in the tropics are
analyzed at 121, 100, and 82 hPa. Observations obtained between December 2006 and
November 2007 show that thin cirrus between 30°N and 30°S occur in close proximity
to regions of intense convection and are positively correlated with low values of
outgoing longwave radiation (OLR).
In conjunction with the CALIPSO data, water vapor data from the Earth
Observing System (EOS) Microwave Limb Sounder (MLS), OLR data provided by the
NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, from their Web site at
http://www.cdc.noaa.gov/, and linearly interpolated NCEP reanalysis temperature data
were used. These data were used to examine how thick and thin cirrus cloud fractions at
121-hPa and 100-hPa are related to relative humidity with respect to ice (RHI), temperature, and OLR. Our observations show that both RHI and convection play
important roles in the development and maintenance of thick and thin cirrus clouds at the
pressure levels of interest. The highest fractions of clouds are almost always seen within
OLR values representative of convection and at relatively high values of RHI. However,
when peaks in cloud fraction are found above the convective threshold, higher RHI
values are needed than are needed when convection is responsible for the formation and
maintenance of these clouds.
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Santos, Helena Paula Aguiar Vicente dos. "Espectro de esporos de fungos alergisantes na atmosfera de Lisboa." Master's thesis, ISA/UTL, 2011. http://hdl.handle.net/10400.5/4103.
Full textAbstract:
Mestrado em Engenharia Florestal e dos Recursos Naturais - Instituto Superior de AgronomiaSpectrum of allergenic fungal spores in the atmosphere of Lisbon Outdoor airborne fungal spores may cause respiratory allergic diseases in humans. The genera Alternaria and Cladosporium are referred by several authors as the most common and prevalent allergenic fungi distributed in atmosphere. Monitoring of these fungi and the knowledge on the influence of climate on their distribution and abundance are important contributions to the elaboration of calendars of occurrence. The present work aimed at analyzing the seasonal variation in the concentration of spores of both fungal species and establishing relationships between meteorological parameters and their dynamics. The samples were collected in the city of Lisbon, between February 2009 and February 2011, with a volumetric Hirst-type trap. The assessment of effects of meteorological parameters was determined through multiple linear regression and application of the AIC criteria. Results confirmed the permanence of both fungi with a distinct predominance for Cladosporium. The highest concentrations of spores occurred in the months of June and July. Temperature and relative humidity of atmosphere were found to be the parameters best correlated with the abundance of those fungal spores in the atmosphere. Continuing of studies of this kind was considered to be recommendable to improve knowledge on the occurrence of these fungal spores in atmosphere.
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Larish, Whitney Anne. "Heterogeneous reaction and kinetics of acetic acid on components of mineral dust aerosol." Thesis, University of Iowa, 2014. https://ir.uiowa.edu/etd/1351.
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Ribeyre, Quentin. "Influence de l'humidité de l'air sur la perte de charge d'un dépôt nanostructuré." Thesis, Université de Lorraine, 2015. http://www.theses.fr/2015LORR0056/document.
Full textAbstract:
Dans l’industrie, des systèmes de protection collectifs doivent être mis en œuvre pour protéger aussi bien les travailleurs que l’environnement. Des filtres à fibres sont généralement disposés dans les circuits de ventilation générale pour capter ces particules en suspension dans l’air. Les performances de ces media fibreux en termes d’efficacité de collecte et consommation énergétique sont relativement bien documentées lors de leur fonctionnement dans des conditions standards (humidité et température ambiantes). Cependant, peu d’études s’intéressent à l’interaction de l’humidité de l’air avec un dépôt composé de particules nanostructurées collectées par ces media filtrants et son incidence sur l’évolution de la perte de charge. Le travail de thèse a donc consisté dans un premier temps à la mesure d’isothermes de sorption de quatre poudres nanostructurées. Un modèle semi-prédictif d’adsorption-condensation basé sur le modèle GAB et la loi de Kelvin a ensuite été proposé. La seconde partie de l’étude a permis de décrire expérimentalement la variation de perte de charge et d’épaisseur d’un milieu poreux, formé par ces mêmes particules nanostructurées, pour différentes valeurs d’humidité. Grâce à la variation d’épaisseur du milieu déterminée par trigonométrie laser et au modèle d’adsorption-condensation, la porosité pour chaque valeur d’humidité relative a pu être calculée. En incorporant les valeurs de porosité et d’épaisseur dans trois modèles de perte de charge, il a été possible de représenter de façon satisfaisante les résultats expérimentaux. Enfin, une analyse rhéologique des poudres est proposée pour quantifier leur augmentation de cohésion sous humiditéAir quality has emerged as a major public environmental and health issue. Almost all fine particles in the air are man-made or manufactured and there are many questions regarding the impact of ultrafine (<100nm) particles on human health. Thus, in most cases, institutions use large-scale protection equipment to protect workers. These institutions often use particulate air filters placed within the flow of general ventilation. Almost all of the available data corresponds to standard ambient air conditions. Despite this, few studies focus on the interaction of water moisture on the deposit formed by these accumulated nanoparticles and the impact on the pressure drop. The first part of this study consists of the measurement of sorption isotherms of four nanostructured powders. A semi-predictive sorption model based on the theory of the multimolecular adsorption (described by the GAB equation) and on the capillary condensation (Kelvin’s law) was developed. The second part of the study experimentally describes the thickness and pressure drop variation of a porous medium formed by these nanostructured particles for different values of humidity. Through the thickness variation of the media - determined by laser trigonometry - and adsorption-condensation model, the porosity for each humidity value has been calculated. Following this, three pressure drop models available in the literature have been modified by introducing cake thickness and porosity variation according to relative humidity. This allows us to model the experimental data for all the samples. Finally, a rheological analysis of powders is proposed to quantify the cohesion changes under moisture conditions
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Schladitz, Alexander. "Parametrization of relative humidity- and wavelength-dependent optical properties of mixed Saharan dust and marine aerosol." Doctoral thesis, Universitätsbibliothek Leipzig, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-70494.
Full textAbstract:
Aerosol particles interact with sunlight through scattering and absorption and have therefore a direct radiative effect. Hygroscopic aerosol particles take up water and are able to grow in size below 100% relative humidity, which involves the change of optical properties and the direct radiative effect. The change of aerosol optical properties for aerosol mixtures under humidification is presently not well understood, especially for the largest particle sources worldwide. The present PhD-thesis quantifies wavelength- and humidity-dependent aerosol optical properties for a mixture of Saharan mineral dust and marine aerosol. For quantification, an aerosol model was developed, which based on in-situ measurements of microphysical and optical properties at Cape Verde. With this model, aerosol optical properties were calculated from the dry state up to 90% relative humidity. To validate the model, a measure of the total extenuated light from particles under ambient conditions was used. Finally, the humidity dependence of aerosol optical properties for marine aerosol, Saharan dust aerosol, and a mixture of both species was described by two empirical equations. With the wavelength of the incident visible solar radiation, relative humidity, and dry dust volume fraction, the humidity dependence of optical properties can be calculated from tabulated values. To calculate radiative effects, aerosol optical properties were used as input parameters for global circulation models including radiative transfer. Due to the complexity of aerosol related processes, they have been treated implicitly, meaning in parameterized form. For modelling purposes, the present PhD-thesis provides a solution to include humidity effects of aerosol optical propertiesAerosolpartikel wechselwirken durch Streu- und Absorptionsprozesse mit der einfallenden Sonnenstrahlung und haben somit einen direkten Strahlungseffekt. Bei relativen Feuchten bis 100% können Aerosolpartikel aufquellen und somit ihre Größe ändern. Im Zuge des Aufquellens, ändern sich die optischen Eigenschaften und somit auch der direkte Strahlungseffekt der Aerosolpartikel. Speziell für Mischungen von verschiedenen Aerosolspezies ist die Änderung der optischen Eigenschaften des Aerosols durch Feuchte Einfuss noch nicht ausreichend verstanden. Gegenstand der vorliegenden Arbeit ist daher die Quantifizierung der wellenlängen- und feuchteabhängigen optischen Eigenschaften einer Mischung von Saharastaub- und marinen Aerosol. Die zur Quantifizierung notwendigen Daten wurden im Rahmen einer Feldmessung von mikrophysikalischen- und optischen Aerosol-Eigenschaften auf den Kapverdischen Inseln gesammelt. Auf Grundlage dieser Messungen wurde ein Aerosol-Modell entwickelt. Dieses Modell wurde daraufhin verwendet, um Berechnungen von optischen Aerosol-Eigenschaften bei relativen Feuchten bis 90% durchzuführen. Eine Messung der Lichtschwächung durch Aerosolpartikel unter Umgebungsbedingungen wurde verwandt, um das Modell bei Umgebungsfeuchten zu validieren. Die Wellenlängen- und Feuchteabhängigkeit der optischen Eigenschaften des Aerosols wurde parametrisiert und konnte anhand von zwei Parametergleichungen bestimmt werden. Unter Benutzung von tabellierten Werten und der Wellenlänge des einfallenden sichtbaren Sonnenlichtes, der relativen Feuchte, sowie der Staubvolumenfraktion, kann die Feuchteabhängigkeit von wichtigen Aerosol-optischen Eigenschaften für Saharastaub, marinen Aerosol und einer Mischung aus beiden Komponenten bestimmt werden. Globale Zirkulationsmodelle, die auch eine Berechnung von Strahlungseffekten durch Aerosolpartikel beinhalten, nutzen Aerosol-optische Eigenschaften als Eingabeparameter. Durch zunehmende Komplexitiät zur Beschreibung von Wechselwirkungen in der Atmosphäre, sind einfache Parametrisierungen unabdingbar. Die vorliegende Arbeit liefert daher einen wichtigen Beitrag für die Modellierung von Strahlungseffekten durch Aerosolpartikel und somit zum Verständnis des Strahlungshaushaltes der Erde
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Crimm, Robert Prentiss. "Experimental apparatus for measuring moisture transfer in porous materials subject to relative humidity and temperature differences." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-01122010-020146/.
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Marks, Marguerite Colasurdo. "Incorporating Chemical Activity and Relative Humidity Effects in Regional Air Quality Modeling of Organic Aerosol Formation." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/1511.
Full textAbstract:
Atmospheric particulate matter is known to have significant effects on human health, visibility, and global climate. The magnitudes of these effects, however, depend in complex ways on chemical composition, relative humidity, temperature, phase state, and other parameters. Current regional air quality models such as CMAQ (Community Multiscale Air Quality model) ignore many of these considerations, and consider that the formation of secondary organic aerosol (SOA) can be calculated by assuming thermodynamic ideality in the organic particulate matter (OPM) phase as well as negligible uptake of water into the OPM phase. Theoretical predictions and model simulations considering non-ideality and water uptake show that the standard model assumptions can lead to large errors in predicted SOA mass, and that the magnitude of these errors is sensitive to the composition of the OPM phase.
The SOA module in CMAQ v4.7.1 has been revised in this work to allow consideration of the effects of both non-ideality and water uptake. First, a reasonable specific surrogate structure was assigned to each of the lumped products assumed to be produced by reaction of the different precursor hydrocarbons considered in CMAQ (e.g., isoprene, benzene, and toluene). Second, the CMAQ code was modified to allow iterative calculation (at each point in space and time) of the gas/particle partitioning coefficient for each of the SOA-forming products and for water. Third, model simulations were performed for the Eastern US at a resolution of 36-km x 36-km for late summer 2006, under a range of relative humidity conditions.
When compared with an appropriate base case, the modified code produced increases in SOA ranging from 0.17 to 0.51 micrograms per cubic meter. The average change was 0.30 micrograms per cubic meter, corresponding to a 37% increase in SOA formation. Incorporation of phase separation effects would likely lead to further increases in predicted SOA levels.
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Testa, F. "INFLUENCE OF ATMOSPHERIC TEMPERATURE AND RELATIVE HUMIDITY ON BULK MILK SOMATIC CELL COUNT IN DAIRY HERDS." Doctoral thesis, Università degli Studi di Milano, 2012. http://hdl.handle.net/2434/168080.
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The production loss and health issues due to the presence of high bulk milk tank somatic cell count in dairy herds makes it essential to implement a consistent effort to maintain this indicator at levels below those required by law. For veterinary practitioners, providing evidence-based advice to clients in order to reduce risk factors of increasing somatic cell count is a difficult task. Statistical Process Control tools allow to verify with statistical certainty when process performance is improving, staying the same, or getting worse and they can be used in dairy farms. The main purpose of the project was to improve understanding in bulk milk somatic cell count variation related to daily temperature and relative humidity, and to build a model which could be predictive of future performance of somatic cell count. Daily bulk milk samples of thirteen commercial dairy farms included in the study were collected and data on daily mean temperature and relative humidity were used. Statistical analysis was performed using Generalized Additive Mixed Models to assess the impact of climatic variables on somatic cell count. We could describe a regression model which shows that the effect of temperature on response appears approximately linear while the one of humidity varies in a more complex way. The model fits well for all herds except one, and explanations are provided. The model constitutes a solid basis for further study of the relationship between daily temperature and humidity, and daily bulk milk somatic cell count. It will allow to set up a quality control on dairy farm using atmospheric temperature and humidity data. Hence it will be possible to provide evidence-based advice to dairy farmers with the use of control charts created on the basis of our statistical model.
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Jonquille, Jenny. "Développement de couches de diffusion de piles PEMFC pour un fonctionnement à faible humidité relative." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00631359.
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Afin de favoriser la commercialisation à grande échelle des piles à combustible PEMFC, de nombreuses études sont menées dans le but de réduire les coûts et d'augmenter la durée de vie tout en améliorant les performances et de comprendre les phénomènes physiques mis en jeu. Cette étude se concentre sur le développement de couches de diffusion pour un fonctionnement à faible humidité relative, en particulier sur l'influence de la structure du support de diffusion sur les performances. Grâce à un procédé de fabrication différent de ceux utilisés pour les produits actuellement commercialisés, la structure des supports est plus aisément modifiée. Ainsi, selon les paramètres de fabrication choisis, les propriétés physico-chimiques associées donnent accès à des niveaux de performances différents. Le modèle d'analyse mis en place permet d'expliquer ces différences observées. Par conséquent, il permet de relier les paramètres de fabrication aux propriétés physiques et aux performances en pile.
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Domenegueti, José Francisco Miras. "Sensor de umidade e vácuo baseado na reflexão interna." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-09092014-113655/.
Full textAbstract:
No presente trabalho propomos a utilização de uma técnica refratométrica baseada na determinação do ângulo crítico para o desenvolvimento de um sensor de umidade relativa e, no mesmo escopo de aplicação, um medidor de vácuo primário. A técnica proposta tira vantagem da diferença de fase adquirida pelas componentes paralela e perpendicular de um feixe luminoso, linearmente polarizado, passando por reflexão interna, para produzir um laser de HeNe sintonizável, um polarizador, um prisma semicilíndrico de índice de refração conhecido fabricado em vidro tipo flint, um analisador, um mínimo de intensidade, facilmente detectável no perfil refletido correspondendo à posição do ângulo crítico. Desenvolvemos um estudo acerca dos principais aspectos teóricos envolvidos no fenômeno da reflexão total interna, onde realizamos algumas simulações buscando avaliar as variações da posição angular do ângulo crítico a partir de alterações no índice de refração. A montagem básica utilizada nos experimentos consiste de um CCD linear e de um computador, onde as informações coletadas pelo CCD foram tratadas por meio de um programa de aquisição de dados desenvolvido na plataforma LabVIEWTM. O programa empregado permite o acompanhamento das variações do perfil refletido da base do prisma ponto a ponto, ou seja, é possível acompanhar toda a dinâmica de evolução do índice de refração da amostra analisada em tempo real. Para confirmação da efetividade da técnica, realizamos medidas da variação do índice de refração de amostras gasosas em função da umidade relativa e da pressão. O sistema demonstrou sensibilidade suficiente para acompanhar mudanças da ordem de 10-5em unidades do índice de refração.In the present work we propose the use of a refractometric technique based on the determination of the critical angle for the development of a relative humidity sensor and, in the same application scope, a primary vacuum gauge. The proposed technique takes advantage of the phase difference acquired by the parallel and perpendicular components of a, linearly polarized, light beam undergoing internal reflection, to produce an easily detectable intensity minimum in the reflected profile corresponding to the position of the critical angle. We develop a study about the main theoretical aspects involved in the total internal reflection phenomenon, where we perform some simulations aiming to evaluate the variations of the critical angle angular position from changes on the refractive index. The basic set up used in the experiments consist of a HeNe tunable laser, a polarizer, a semi-cylindrical prism with known refractive index made of flint glass type, a analyzer, a linear CCD and a computer, where the information collected by de CCD were treated by means of a data acquisition program developed on the LabVIEWTM platform. The used program allows the point-by-point monitoring of the changes of the profile reflected from the prism base, in other words, one can monitor all the evolution dynamics of the refractive index of the analyzed sample in real time. To confirm the effectiveness of the technique, we perform measurements of changes of the refractive index of gaseous samples as function of the relative humidity and the pressure. The system has shown enough sensitivity to track changes of the order of 10-5 in units of the index of refraction.
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Junior, Sergio Serafini. "O microclima de uma vereda degradada: estudo de caso no Parque Estadual Veredas do Peruaçu - MG." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/8/8135/tde-08102010-110002/.
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O Bioma Cerrado, ao longo da história de ocupação pelo homem, vem sendo explorado em detrimento da redução de sua biodiversidade. Dentre as várias características típicas da vegetação do cerrado, nesta tese, um maior destaque é dado às veredas que se alinham ao sistema hidrográfico acompanhando seu traçado e formando um corredor de cobertura vegetal de porte arbóreo, muito utilizado pela fauna local como fonte de alimentação, reprodução e abrigo, favorecendo o fluxo gênico local, como parte do processo natural de manutenção dos ecossistemas ali presente formadores do Bioma Cerrado. Em vista da importância da preservação ambiental do cerrado, foi criado o Parque Estadual Veredas do Peruaçu que está localizado na região norte de Minas Gerais, onde também, estão instaladas propriedades rurais que concentram suas atividades na exploração agrícola e pecuária. Neste contexto, o próprio rio Peruaçu configura-se como o limite geográfico entre esta Unidade de Conservação e as propriedades rurais ali próximas que, frequentemente, o ultrapassam como forma de ampliação de suas áreas produtivas, além da caça e corte de madeira para produção de carvão, comprometendo a preservação dos ambientes de veredas ali existentes, modificando também as características microclimáticas daquele ambiente, verificada na área de estudo, através da coleta de dados, quando verificou-se que aqueles ambientes modificados pela ação antrópica apresentaram temperatura do ar (°C) mais altas e umidade relativa do ar (%) menor.The Cerrado, throughout the history of occupation by man, has been deployed at the expense of reduced its biodiversity. Among the various characteristics of the vegetation cerrado, in this thesis, a greater emphasis is given to paths that line the river system following its track and forming a corridor of vegetation cover trees, often used by local wildlife as source of food, shelter and reproduction, favoring local gene flow, as part of the natural maintenance of ecosystems present there trainers Cerrado. In view of the importance of environmental preservation cerrado was created State Park Trails Peruaçu which is located in the northern region of Minas Gerais, where also rural properties that are installed focus their activities on the farm and livestock. In this context, the river itself Peruaçu configures itself as the geographical boundary between this unit and Conservation farms near here that often the excess as a way of expanding their areas productive than hunting and logging production coal, jeopardizing the preservation of environments paths that exist there, also changing the microclimatic characteristics of that environment, observed in the study area, through data collection, when it was found that these modified environments by human action were air temperature (° C) higher and relative humidity (%) lower.