Submitted by Cláudia Bueno (claudiamoura18@gmail.com) on 2016-02-04T14:20:25Z No. of bitstreams: 2 Dissertação - José Ricardo Rodrigues Rocha - 2015.pdf: 9032071 bytes, checksum: f7c5b727e8a6360824bc8a509326ab74 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-02-11T11:36:32Z (GMT) No. of bitstreams: 2 Dissertação - José Ricardo Rodrigues Rocha - 2015.pdf: 9032071 bytes, checksum: f7c5b727e8a6360824bc8a509326ab74 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2016-02-11T11:36:32Z (GMT). No. of bitstreams: 2 Dissertação - José Ricardo Rodrigues Rocha - 2015.pdf: 9032071 bytes, checksum: f7c5b727e8a6360824bc8a509326ab74 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-03-27 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The man has caused changes in the middle through the transformations, occupation and mode-tion of space, which generates the urban climate. Thus, urban studies are neces-sary is because the sums of these changes cause a hydrothermal discomfort and the dif- ferentiation of heat in the urban network, as shown in many studies. Thus, the study of obje-tive was to determine the variation of temperature and relative humidity (maximum and mí-nima) in two small cities in the Brazilian cerrado, Jataí and Caçu (GO). Thus pro-cured to identify the relationships between the physical aspects of the environment (hipsometria, exhibition sheds and land use) with vari-ations in climate issues, in fixed collection points in cities. Both cities are in the middle region South Goiás, Jataí in the micro region of the Southwest of Goias and Caçu in micro-Quirino-polis. It had as methodological basis the theory of urban climate proposed by Monteiro (1976) and Monteiro e Sezarino (1990), abor-giving the thermodynamic subsystem. To collect tempe-rature data and relati-va humidity were used termohigrômetros (HT-4000 and HT-500 model) distributed at 5 points in Caçu and 09 in Jataí, in which were collected every 30 minutes. For producing the maps as hipsometria, exposure of slopes, land use were used GIS Arcgis 10.1. It was found that the absolute maximum operating temperature (44.6 ° C) was recorded in P3 in Caçu at 14h39m, and Jataí showed 43.1°C in P1, at 13h25m, where land use influenced the values between the collection points, and the elevation for the difference between the ci-ties (range of 1.5°C). The lowest values of minimum temperatures also occurred in August, on 28 and 29, rises the performance of a stationary front, where Jataí was 4.9 ° C in P6, with very low rate of construction (1.1%) and high rate of vegetation (81.5%), and is located in valley bottom. In Caçu was recorded 6.4 ° C in P3, this building has a low rate, average grazing rate (11.5%) and vacant land with soil exposure (34.6%). The maximum relative humidity of air occurred in November 2013, and ranged 100-81% between cities, on 5, 8:26 in the performance of the SACZ and ZCOU. The minimum relative humidity values of the air occurred in August, on days 02, 03, 04, 05 09, 18, 28, 29 and 02 days in September, 09, 11 and 13, where the values varied 6-52 % between 13:00 the 17h00mm. From our analysis, we consider that there was influence of urban structure and the physical aspects of hygrothermal behavior between cities. This is because the local densely built and devoid of vegetation showed higher temperatures and lower humidity of the air, while the places with the highest afforestation rate and smaller buildings had lower rates of temperature and relative humidity of the larger air. / O homem vem provocando alterações no meio através das transformações, ocupação e mode-lação do espaço, o qual gera o clima urbano. Desta forma, os estudos urbanos fazem-se neces-sários, pois as somas destas transformações acarretam um desconforto hidrotérmico e a dife-renciação de calor na malha urbana, como já evidenciado em muitos estudos. Com isso, o ob-jetivo do estudo foi verificar a variação da temperatura e umidade relativa do ar (máxima e mínima) em duas cidades de pequeno porte do cerrado brasileiro, Jataí e Caçu (GO). Assim procurou-se identificar as relações entre os aspectos físicos do ambiente (hipsometria, exposi-ção de vertentes e uso do solo) com a variação dos aspectos climáticos, em pontos de coleta fixos nas cidades. Ambas as cidades situam-se na mesorregião Sul Goiano, Jataí na microrre-gião do Sudoeste de Goiás e Caçu na microrregião de Quirinópolis. Teve-se como base meto-dológica a teoria do clima urbano proposta por Monteiro (1976) e de Monteiro e Sezarino (1990), abordando o subsistema termodinâmico. Para a coleta dos dados de temperatura e umi-dade relativa do ar foram utilizados termohigrômetros (modelo HT-4000 e HT-500) distribuí-dos em 5 pontos em Caçu e 09 em Jataí, em que foram coletados a cada 30 minutos. Para a confecção dos mapas como: hipsometria, exposição das vertentes, uso da terra foram utilizados SIG Arcgis 10.1. Constatou-se que o valor máximo absoluto de temperatura (44,6°C) foi regis-trado no P3, em Caçu, às 14h39m, e Jataí apresentou 43,1°C no P1, às 13h25m, em que o uso do solo influenciou os valores entre os pontos de coleta, e a altitude para a diferença entre as cidades (amplitude de 1,5°C). Os menores valores de temperaturas mínimas também ocorreram em agosto, nos dias 28 e 29, sobe a atuação de uma frente estacionária, em que Jataí teve 4,9°C no P6, com muito baixa taxa de construção (1,1%) e alta taxa de vegetação (81,5%), além de ser localizado em fundo de vale. Em Caçu foi registrado 6,4°C, no P3, este possui baixa taxa de construção, média taxa de pastagem (11,5%) e terrenos vagos com exposição do solo (34,6%). A umidade relativa do ar máxima ocorreu em novembro de 2013, sendo que oscilou de 100 a 81% entre as cidades, nos dias 5, 8 e 26 sob a atuação das ZCAS e ZCOU. Os valores mínimos de umidade relativa do ar ocorreram em agosto, nos dias 02, 03, 04, 05 09, 18, 28 e 29 e em setembro nos dias 02, 09, 11 e 13, em que os valores oscilaram de 6 a 52%, entre 13h00m as 17h00mm. A partir das análises, consideramos que houve influência da estrutura urbana e os aspectos físicos no comportamento higrotérmico entre as cidades. Isso devido os locais densamente construído e desprovidos de vegetação apresentaram maiores temperaturas e menores umidades relativa do ar, enquanto que, os locais com maior taxa de arborização e menores taxas de construções tiveram temperatura menores e umidade relativa do ar maiores.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2014-09-23T16:55:23Z No. of bitstreams: 2 Dissertação -Andreia Medeiros de Lima.pdf: 5430810 bytes, checksum: 357ae214fb5b84c650b1d337efdb073c (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Jaqueline Silva (jtas29@gmail.com) on 2014-09-23T18:30:49Z (GMT) No. of bitstreams: 2 Dissertação -Andreia Medeiros de Lima.pdf: 5430810 bytes, checksum: 357ae214fb5b84c650b1d337efdb073c (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2014-09-23T18:30:49Z (GMT). No. of bitstreams: 2 Dissertação -Andreia Medeiros de Lima.pdf: 5430810 bytes, checksum: 357ae214fb5b84c650b1d337efdb073c (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2013-03-14 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The objective of the research was to analyze the rainfall on a the regional scale and compare the temperature, air relative humidity and rain at local scale at points outside of semideciduous seasonal forests (FES) and inside the FES, on the area of Barra dos Coqueiros and Caçu hydropower plants (UHEs), in the lower course of the Rio Claro river e, in the cities of Cachoeira Alta and Caçu, in the state of Goiás. The rainfall data were obtained from four rainfall stations of the National Water Agency (ANA), (Cachoeira Alta, Itarumã, Quirinópolis and Pombal) between 1977-2011 and experiment points out of semideciduous seasonal forests (FES), with measurement of temperature and relative humidity and rainfall and inside the FES with temperature and relative humidity of September 2011 to September 2012.The methodological procedures were performed at regional, local and microclimate, with calculation of standard years, statistical calculations, analysis of land use, exposure of the slopes and comparison of climatic elements between points outside and inside the FES, starting from a point reference. On a regional scale, in 35 years of averages of the four seasons, we identified that 66% were standard years rainy, tending to rainy and habitual; the spatial variability of rainfall shows higher concentration northwest and southwest basins and climate trends indicated a trends of increase in stations and Cachoeira Alta Pombal and decrease in Itarumã and Quirinópolis. On a local scale, in relation to land use, the total area of 965 km2 of the two basins, it was found that the greatest change occurred by increasing the area occupied by water in 2009 was 0.6% and in 2011 becomes occupy 7.4%, which represented an increase of 1200%, with loss of native vegetation and habitat. Regarding climatic elements, temperature and relative humidity, on the reference point outside the FES (P1) differences occurred in the absolute maximum temperature of 10.6 °C and the absolute minimum of 7.8 °C, relative humidity was maximum absolute differences less than 1% and the minimum absolute difference of 8%, relative to rainfall, the largest difference was 927 mm. At the point of reference within the FES (P15), the largest difference in maximum air temperature was 10.5 °C and minimum 2.4 °C, the relative humidity was 3% absolute maximum and minimum of 8%. In microclimatic scale, points out the FES, mainly focused on the areas: north, east, west, northwest and southwest, which receive greater insolation showed higher maximum temperatures between 52.7 to 46.9 °C, while the points located within the FES, independent of the exposure of the strands had the absolute maximum temperature between 36.7 to 47.2 ° C and absolute minimum between 3.8 and 6.5 °C. Therefore, the points inside the FES showed dampening effect on the microclimate, and the absolute maximum temperatures and temperature were lower and the minimum absolute and relative humidity were high. / O objetivo da pesquisa foi analisar as chuvas em escala regional e comparar a temperatura, a umidade relativa do ar e a chuva em escala local em pontos fora das Florestas Estacionais Semideciduais (FES) e no interior das FES, na área das bacias das Usinas Hidrelétricas (UHEs) de Barra dos Coqueiros e Caçu, no baixo curso do rio Claro, nos municípios de Cachoeira Alta e Caçu no Estado de Goiás. Os dados de chuva foram obtidos de quatro estações pluviométricas da Agência Nacional das Águas (ANA), (Cachoeira Alta, Itarumã, Quirinópolis e Pombal) entre 1977 a 2011 e do experimento em pontos fora das Florestas Estacionais Semideciduais (FES), com mensuração de temperatura e umidade relativa do ar e chuvas e no interior das FES com temperatura e umidade relativa do ar de setembro de 2011 a setembro de 2012. Os procedimentos metodológicos foram realizados nas escalas regional, local e microclimática, com cálculo dos anos padrão, cálculos estatísticos, análise do uso da terra, exposição das vertentes e comparação dos elementos climáticos entre os pontos fora e interior das FES, partindo de um ponto de referência. Na escala regional, em 35 anos das médias das quatro estações, identificaram-se que 66% foram anos padrão chuvosos, tendentes a chuvosos e habituais; a variabilidade espacial das chuvas apresentou maior concentração a noroeste e sudoeste das bacias e a tendência climática indicou tendência de acréscimo nas estações de Cachoeira Alta e Pombal e decréscimo em Itarumã e Quirinópolis. Na escala local, em relação ao uso do solo, da área total de 965 km2 das duas bacias, verificou-se que a maior mudança ocorreu pelo aumento da área ocupada por água, em 2009 era de 0,6% e em 2011 passa a ocupar 7,4%, o que representou um aumento de 1200%, com perda de vegetação nativa e habitat. Em relação a temperatura e umidade relativa do ar, no ponto de referência fora da FES (P1) ocorreram diferenças na temperatura máxima absoluta de 10,6 °C e na mínima absoluta de 7,8 °C; a umidade relativa máxima absoluta teve diferenças menores de 1% e na mínima absoluta diferenças de 8%; em relação às chuvas, a maior diferença foi de 927 mm. No ponto de referência no interior da FES (P15), a maior diferença na temperatura máxima absoluta foi de 10,5 °C e a mínima 2,4 °C; a umidade relativa do ar máxima absoluta foi 3% e a mínima de 8%. Na escala microclimática, os pontos fora das FES, principalmente os voltados para as vertentes: norte, nordeste, oeste, noroeste e sudoeste, as quais recebem maior insolação, apresentaram temperaturas máximas maiores entre 52,7 a 46,9 °C, enquanto os pontos localizados no interior das FES, independente da exposição das vertentes, tiveram a temperatura máxima absoluta entre 36,7 a 47,2 °C e a mínima absoluta entre 3,8 a 6,5 °C. Assim, os pontos no interior das FES apresentaram efeito atenuador no microclima, sendo que as temperaturas máximas absolutas e a amplitude térmica foram menores e as mínimas absolutas e umidade relativa do ar foram elevadas.

Svenska Aerogel AB has developed the material Quartzene® which is of the typeprecipitated silica and contains calcium - magnesium silicate ((Ca, Mg) SiO3). Thematerial is used for molecular filtration of contaminated air. Qartzene™, which is inpellet form, is porous and has a high internal surface which is a requirement for themolecular filtration. With the use of various impregnations, filtration can affect thedesired outcome. As an example Quartzene® can be impregnated with Potassiumhydroxide and clear the air of Sulfur dioxide, SO2 (Svenska Aerogel AB, n.d).Svenska Aerogel AB has developed Quartzene® further and new areas of application hasarosee, one of these areas is how the material function within dehumidification. Thepurpose of this study is to research and analyze how different impregnation salts effecthow Quartzene® function in terms of moisture absorption and moisture desorption.Quartzene® is a hygroscopic material, which is a material that easily absorbs and exudatesmoisture from the air. Materials with high porosity absorb moisture by adsorption andcapillary condensation. A hygroscopic material strives for equilibrium with ambientenvironment which is illustrated in a sorption curve where moisture absorption is set inrelation to relative humidity. In this study the jar method is used to measure moistureabsorption, this is shown with the use of sorption curves. The jar method uses saturatesalt solutions to create environments whit a set relative humidity. Quartzene® – pellets areplaced in jars and weighed at regular intervals to determine the moisture absorption.The results of this study indicate that impregnations affect the way that Quartzene®function in terms of moisture absorption and moisture desorption. Some of theimpregnations affect the material to absorb more moisture than Quartzene® that has notbeen impregnated, while others affect the material to absorb less moisture. The resultsalso show that sodium – based impregnation gives similar results as Quartzene® that hasnot been impregnated.

Understanding the mechanisms for fatigue crack initiation and propagation in micron-scale silicon (Si) is of great importance to assess and improve the reliability of Si based microelectromechanical systems (MEMS) in harsh environments. Accordingly, this investigation studies the fatigue properties of 10-micron-thick single-crystal Si (SCSi) films using kHz-frequency resonating structures under fully-reversed loading. Overall, the stress plays a major role on the fatigue properties: decreasing the stress amplitude from ~3-3.5 GPa to ~1.5-2 GPa results in an increase in lifetime from 10² to 10¹⁰ cycles, and a decrease in degradation rate by 4-5 orders of magnitude. In addition to stress, the influences of resonant frequency (4 vs. 40 kHz) and environment (30°C, 50%RH vs. 80°C, 30%RH and 80°C, 90%RH) on the resulting S-N curves and resonant frequency evolution are thoroughly investigated. In the high- to very high-cycle fatigue (HCF/VHCF) regime, both the frequency and environment strongly affect the fatigue properties. Damage accumulation rates are significantly higher in harsh environments. In 80°C, 90%RH the rates exceed by one to two orders of magnitude the values at 30°C, 50%RH for similar stress amplitudes. The separate influence of humidity, affecting the adsorbed water layer thickness, is also highlighted at 80°C: the decrease rates are measured up to one order of magnitude lower at 30%RH than at 90%RH. Moreover, a strong influence of frequency is detected. These observations bring further evidence supporting reaction-layer fatigue as a viable description of the HCF/VHCF behavior of micron-scale Si.

This thesis consists of two different research problems. In the first one, the aim is to model and simulate a solar-powered, single-effect, absorption refrigeration system using a flat-plate solar collector and LiBr-H2O mixture as the working fluid. The cooling capacity and the coefficient of performance of the system are analyzed by varying all independent parameters, namely: evaporator pressure, condenser pressure, mass flow rate, LiBr concentration, and inlet generator temperature. The cooling performance of the system is compared with conventional vapor-compression systems for different refrigerants (R-134a, R-32, and R-22). The cooling performance is also assessed for a typical year in Tampa, Florida. Higher COP values are obtained for a lower LiBr concentration in the solution. The effects of evaporator and condenser pressures on the cooling capacity and cooling performance are found to be negligible. The LiBr-H2O solution shows higher cooling performance compared to other mixtures under the same absorption cooling cycle conditions. For typical year in Tampa, Florida, the model shows a constant coefficient of performance of 0.94. In the second problem, a numerical model is developed for a typical food retail store refrigeration/HVAC system to study the effects of indoor space conditions on supermarket energy consumption. Refrigerated display cases are normally rated at a store environment of 24ºC (75ºF) and a relative humidity of 55%. If the store can be maintained at lower relative humidity, significant quantities of refrigeration energy, defrost energy and anti-sweat heater energy can be saved. The numerical simulation is performed for a typical day in a standard store for each month of the year using the climate data for Tampa, Florida. This results in a 24 hour variation in the store relative humidity. Using these calculated hourly values of relative humidity for a typical 24 hour day, the store relative humidity distribution is calculated for a full year. The annual average supermarket relative humidity is found to be 51.1%. It is shown that for a 5% reduction in store relative humidity that the display case refrigeration load is reduced by 9.25%, and that results in total store energy load reduction of 4.84%. The results show good agreement with available experimental data.

Recent failures and severe corrosion distress of post-tensioned (PT) bridges in Florida have revealed corrosion of the 7-wire strands in tendons. Post-tensioned duct assemblies are fitted with multiple 7-wire steel strands and ducts are subsequently filled with grout. During construction, the length of time from the moment in which the strands have been inserted into the ducts, until the ducts are grouted, is referred to as the `ungrouted' period. During this phase, the steel strands are vulnerable to corrosion and consequently the length of this period is restricted (typically to 7 days) by construction guidelines. This investigation focuses on determining the extent of corrosion that may take place during that period, but limited to strands that were in the unstressed condition. Visual inspections and tensile testing were used to identify trends in corrosion development. Corrosion induced cracking mechanisms were also investigated via wire bending and metallographic cross section evaluation. Corrosion damage on unstressed strands during ungrouted periods of durations in the order of those otherwise currently prescribed did not appear to seriously degrade mechanical performance as measured by standardized tests. However the presence of stress in the ungrouted period, as is normally the case, may activate other mechanisms (e.g., EAC) that require further investigation. As expected in the unstressed condition, no evidence of transverse cracking was observed.

Continuously reinforced concrete pavement (CRCP) is a portland cement concrete (PCC) pavement structure with a continuous longitudinal steel layout. CRCP is forming a major portion of PCC roadway systems in the state of Texas due to its low life cycle cost, ease of maintenance, and durable nature. While the overall performance of CRCP is proven to be excellent, some performance problems are still found as a form of distresses such as punchout and spalling. The current pavement design guide states that these distresses are closely related with the early-age behavior characteristics of CRCP, and various measures are underway to develop to improve the long-term performance of CRCP in terms of initial material design and use, structural design, and quality control. Understanding the current issues that pavement engineers and researchers face, the primary objective of this dissertation research focuses on sound understanding of the early-age structural behavior characteristics of CRCP and its effect on the long-term performance to provide reliable design and analysis criteria for CRCP. To achieve this main objective, characterizing the early-age structural response in CRCP was a core task of this study. For this purpose, a zero-stress temperature (ZST), one of the design and construction variables considered to have most significant effects on CRCP behavior and performance, was evaluated. As a beginning point of the entire framework, a series of field experiments were conducted in four new PCC pavement construction projects in the state of Texas to evaluate the actual structural response in early-age CRCP since a laboratory experiment would have a critical limitation in simulating the restraint conditions that exist in actual CRCP. To expand this core task to various parametric categories, a computer-aided parametric simulation was performed using valid numerical models. Based on data sets obtained from the parametric investigation, a statistical model to quantify the early-age structural response of CRCP was proposed to implement in codes of practice and pavement design guides. A secondary task was to identify a correlation between the early-age structural response and the long-term performance of CRCP structures. Since the experimental and analytical investigations tended to provide quite localized information for the time-dependent behavior of CRCP, the overall performance of CRCP could not be properly identified solely based on those results. To overcome this limitation, extensive field condition surveys were performed in seven different old CRCP sections with known material and early-age temperature history to find the implications of early-age behavior characteristics on the long-term performance of CRCP from a macroscopic point of view. It is expected that this research effort will provide pavement engineers and researchers with useful information to understand the actual time-dependent behavior of CRCP and a solid foundation to improve the sustainability of CRCP structures. / text

Single-walled carbon nanotubes are naturally-forming nanostructures that have attracted considerable recent research interest due to their unique opto-electronic properties and comparative ease of fabrication. Two-thirds of nanotube species are semiconductors due to symmetry conditions imposed by their pseudo-one-dimensional tubular structure, and exhibit band-gap photoluminescence when isolated from their environment. Despite their elegant structural simplicity, fundamental properties of carbon nanotubes, such as their intrinsic quantum efficiency, non-linear excitonic recombination mechanisms, and the role of environmental effects, continue to be disputed in the literature. The design of an apparatus capable of observing nanotube photoluminescence is presented, along with conclusive proof of the observation of a single (9,8)-chirality nanotube in the form of spectral, spatial, and polarization-dependent measurements. The dependance of the excitation and emission spectra of a single nanotube on the excitation intensity is explored and the emission spectra found to be described by a Gaussian peak function, in contrast to previously-reported results. The unexpected ability to cause redshifts in the emission spectrum via the ambient humidity is discovered, which has consequences on experimental best practices. Photoluminescence quantum efficiencies are measured to be 4±2% and 13±6% for two different nanotubes. This is at the high end of the range for comparable literature results, and supports the validity of a recent literature value for the effective atomic absorption coefficient for carbon, AC=1.6×10^−3nm^2, which is ten times greater than previous literature values. Pulsed power dependence studies show that the PL emission undergoes ‘hard’ saturation at an excitation intensity of 0.5×10^12photons/pulse/cm2, which is at least 100 times lower than previous reports and provides insight into non-linear decay dynamics. A novel theoretical model is developed to explain this saturation process, which yields an absorption co-efficient of AC=1.2±0.3×10^−3nm^2 as a fit parameter. Time-resolved photoluminescence dynamics are explored using femtosecond excitation correlation spectroscopy. Results suggest that the one-body decay processes are bi-exponential, with time constants of 31±4ps and 313±61ps, but also highlight the limitations of this technique in observing the expected very rapid (~1 ps) two-body Auger recombination process. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2008-09-26 16:23:40.81

The active ventilation of grain with the optimum drying regimen was the main issue of the work. The moisture of the harvested grain in Lithuania often exceeds the conditional one. Thus the grain should by dried before the storage. The active ventilation is mostly used in Lithuania to dry the grain, it was the topical point in this work. There was analyzed meteorology of the topical months, were maked the calculating equations, whitch we can prognosticate these meteorological facts: temperature and relative humidity. The maked mathematical model defines metathesis moisture‘s between ambient air flow and grain. Also there were the algorithm of model‘s realisation‘s and the computer programme with Visual basic 6.0 maked. Adequacy of mathematical model‘s was rated with results of experimental researches and calculated results.

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. / To help PEMFC development and large scale commercialization, several studies deal with reducing costs and increasing durability while trying to improve performances and to understand physical phenomena involved. This study focuses on developing gas diffusion media which operates at low relative humidity, more particularly it deals with the influence of the structure of gas diffusion media on performances. Thanks to a process different from those used for currently commercialized gas diffusion layers, the structure of the media is more easily modified. According to the manufacturing parameters chosen, different physical and chemical properties will be obtained and thus different performances. A model is used to help analyze these differences and consequently allow the link between manufacturing parameters and physical properties and performances.