<p>Real world modeling has become a very useful tool when new designs and applications are tested before they are introduced on the market. A field that recently has discovered the possible use of modeling is reliability prediction. The reliability and lifetime of a component has until recently been based on months and years of testing. In order to shorten the test time it is possible to simulate the environmental effect on the components. Another advantage of modeling is that changes of large systems where many different components work together can easily be studied. Without modeling the reliability has to be tested over and over again if the system is redesigned since it is impossible to know how the new change will affect the reliability.</p><p>Since electronic circuits are being made smaller and smaller with the increasing demand of faster technology the circuits are very vulnerable to corrosion. A trend in the automotive industry is also to move the electronic devices from the benign environment in the cab to the hash environment on the driveline or the chassi. The most common way to protect the electronics from the hash environment is to put it into a protective covering, also called Electronic Control Unit (ECU). Even though the ECU is sealed, water can still enter the ECU in several ways and cause serious damages by corrosion. The corrosion rate of a component is among others depending of the environmental humidity and temperature. Knowing the humidity and temperature are therefore very important to be able to eliminate corrosion problems. In order to achieve a better understanding of the physics behind the failure and to improve the reliability of the ECU a model of the temperature and humidity penetration is built in this thesis.</p><p>There are several components in the ECU which all responds differently to water vapour. By measuring the humidity penetration in the ECU while components were added one by one, the physical properties of the components could be determined. Some properties were also determined through additional solubility measurements. The humidity penetration of the ECU is then predicted by inserting these properties into mathematical models in Simulink^Ó.</p><p>The conclusion is that it is possible to model the humidity penetration and the temperature changes in the ECU. After the physical properties of the components were determined, the diffusion model agreed well with measurements. The numerical method used in this thesis has been found to be fast and stable. The length of the time-steps has been varied from a couple of minutes to more than an hour in the numerical model. A few physical properties has to be examined more in detailed and the model is then going to be a good foundation on which corrosion and other damaging processes can be modelled.</p>

<p>QC 20120928</p>

Real world modeling has become a very useful tool when new designs and applications are tested before they are introduced on the market. A field that recently has discovered the possible use of modeling is reliability prediction. The reliability and lifetime of a component has until recently been based on months and years of testing. In order to shorten the test time it is possible to simulate the environmental effect on the components. Another advantage of modeling is that changes of large systems where many different components work together can easily be studied. Without modeling the reliability has to be tested over and over again if the system is redesigned since it is impossible to know how the new change will affect the reliability. Since electronic circuits are being made smaller and smaller with the increasing demand of faster technology the circuits are very vulnerable to corrosion. A trend in the automotive industry is also to move the electronic devices from the benign environment in the cab to the hash environment on the driveline or the chassi. The most common way to protect the electronics from the hash environment is to put it into a protective covering, also called Electronic Control Unit (ECU). Even though the ECU is sealed, water can still enter the ECU in several ways and cause serious damages by corrosion. The corrosion rate of a component is among others depending of the environmental humidity and temperature. Knowing the humidity and temperature are therefore very important to be able to eliminate corrosion problems. In order to achieve a better understanding of the physics behind the failure and to improve the reliability of the ECU a model of the temperature and humidity penetration is built in this thesis. There are several components in the ECU which all responds differently to water vapour. By measuring the humidity penetration in the ECU while components were added one by one, the physical properties of the components could be determined. Some properties were also determined through additional solubility measurements. The humidity penetration of the ECU is then predicted by inserting these properties into mathematical models in SimulinkÓ. The conclusion is that it is possible to model the humidity penetration and the temperature changes in the ECU. After the physical properties of the components were determined, the diffusion model agreed well with measurements. The numerical method used in this thesis has been found to be fast and stable. The length of the time-steps has been varied from a couple of minutes to more than an hour in the numerical model. A few physical properties has to be examined more in detailed and the model is then going to be a good foundation on which corrosion and other damaging processes can be modelled.

A humidity fiber optic sensor based on phase-shifted (PS) Fiber Bragg gratings (FBG) is demonstrated. Compared to the standard FBG sensors, the peak of the PS-FBG slips into 2 narrow peaks and forms a sharp dip in the middle. As a result, the resolution of the measurement will be higher. The sensors used in the experiments were fabricated by coating the PS-FBG surface with a moisture-sensitive polyimide and is based on the strain effect caused by the swelling of the coating after moisture absorption. The same trend seen in a standard FBG sensor can be achieved, but with higher measurement resolution in environments differing by humidity and temperature. This thesis presents simulation and measurement results, including sensitivity and response time, of the PS-FBG sensor approach for humidity sensing, as compared to the standard FBG sensors. Stability and hysteresis are also discussed.

The isotopic labelling of carbon in tree-rings varies as a function of growth season temperature and relative humidity. The isotopic labelling of oxygen in tree-rings varies as a function of source-water isotopic composition and humidity-dependent evaporative enrichment of leaf water during the growth season. The season of carbon-isotope labelling was identified statistically as late-spring to early-fall (April to October) for temperatures and relative humidity with a three-year weighted (50-30-20) carry-over due mainly to stored photosynthates. The season of oxygen-isotope labelling was identified statistically as a combination of a winter (pDecember to March) source-water signal (temperature-dependent precipitation isotope composition) with a late-spring to early-fall (April to October) humidity signal (evaporative enrichment of leaf water). A two-year carry-over was attributed to the residence time of soil water, but no notable photosynthate carry-over was identified. Carbon- and oxygen- (mechanistic) isotope response surface models were then compared and contrasted to regression-based bivariate and univariate models. It was found that in most cases the isotope response surface models were the best means of predicting isotopic labelling when environmental data are known. The carbon-isotope response surface was used to reconstruct 50-years (AD 1900-1954) of relative humidity data by introducing measured carbon isotope values and instrumental growth season temperature. During the analysis of the oxygen-isotope response surface we found an isotope-temperature relation that appears to reflect circulation-dependent damping. To verify this we introduced scaled values of the North Pacific index as a proxy for this suppression. The coupling of the isotope response surfaces generated a humidity reconstruction that is also thought to be driven by atmospheric circulation. Our reconstruction shows that the fluctuations in temperature range have not exceeded the natural variability in the instrumental record of the 20th century; however, the atmospheric moisture (humidity) reconstruction predicts a directional drying trend in the Peace-Athabasca Delta that appears to reflect increasingly zonal circulation in western Canada over this period.

Fukt i byggnader är svårt att upptäcka och är ett vanligt problem i dag.Att i ett tidigt skede kunna se hur fuktigt det är kan bespara dyrakostnader. En ny produkt som företaget Sensible Solutions har tagitfram är en fuktsensor som kan placeras innanför väggar i till exempelbadrum. Fuktsensorn består av två RFID-taggar där en av taggarna äromsluten i ett fuktabsorberande material. När det fuktabsorberandematerialet drar åt sig fukt kommer den taggen bli svårare att läsa av,vilket indikerar att fukt förekommer. Avläsningen av fuktsensorn skergenom en handhållen RFID-läsare. En marknadsundersökning hargenomförts med hjälp av en litteraturstudie av skriftliga och webbaseradekällor samt intervjuer med potentiella kunder och en befintligkund. Undersökningen fokuserar på byggföretag i Sverige för att ta redapå vilken marknad Sensible Solutions fuktsensor passar in samt vemslutkund är. Marknadsundersökningen innefattar potentiell marknad,en konkurrentanalys, en SWOT-analys samt en kundundersökning.Granskningen har visat att ett intresse för RFID-teknik samt fuktsensornfinns, men ytterligare information är efterfrågad. Produkterna tillrespektive konkurrent har sina för- och nackdelar men Sensible Solutionsprodukt anses vara unik. En möjlighet som SWOT-analysen visarär bland annat att en vidareutveckling av den befintliga produkten samtav nya produkter finns. Sensible Solutions befintliga kund använder idag fuktsensorn i ett pilotprojekt och pekade på fördelen med fuktsensornatt fuktigheten kunde mätas både under och efter byggtid. Enslutsats är att byggföretag är en rimlig marknad för Sensible Solutionsatt inrikta sig på då den tekniska kompetensen finns och likaså intressetför RFID-teknik och fuktsensorer. / Humidity in buildings is a problem that is difficult to detect and is thusa common problem in present day construction. The ability to detecthumidity at an early stage can be of assistance in the prevention ofexpensive costs. A new product developed by the Sensible Solutionscompany is a humidity sensor that can be placed inside walls, in, forexample, bathrooms. The humidity sensor consists of two RFID tags,one of which is enclosed in a moisture-absorbing material and whenmoisture is absorbed the enclosed tag becomes more difficult to read,which indicates that the humidity is higher than an expected value. Thehumidity sensor is read using an RFID handheld mobile computer.Market research has been conducted by collecting of data from writtensources and the Internet and by conducting interviews with existing andpotential customers; the target group for the research is constructioncompanies. The goal for this market research is to find a prospectivemarket for the Sensible Solutions humidity sensor based on theexpectations of the users. The market research dealt with the potentialmarket, a competitor analysis, a SWOT analysis and a customer survey.The audit revealed that an interest in RFID technology and the humiditysensor did exist, but that more information was required. Each of thecompetitors products have their pros and cons but the SensibleSolutions product is considered to be unique. One possibility shown upby the SWOT analysis is that further development of the existingproducts and new products is possible. The humidity sensor is currentlybeing used by a Sensible Solutions customer in a project, to ensure thequality of the construction during and after implementation. Inconclusion, the construction company market is a reasonable one forSensible Solutions to focus on as these companies possess the technicalcompetence and also the necessary interest in RFID technology andhumidity sensors.

The isotopic labelling of carbon in tree-rings varies as a function of growth season temperature and relative humidity. The isotopic labelling of oxygen in tree-rings varies as a function of source-water isotopic composition and humidity-dependent evaporative enrichment of leaf water during the growth season. The season of carbon-isotope labelling was identified statistically as late-spring to early-fall (April to October) for temperatures and relative humidity with a three-year weighted (50-30-20) carry-over due mainly to stored photosynthates. The season of oxygen-isotope labelling was identified statistically as a combination of a winter (pDecember to March) source-water signal (temperature-dependent precipitation isotope composition) with a late-spring to early-fall (April to October) humidity signal (evaporative enrichment of leaf water). A two-year carry-over was attributed to the residence time of soil water, but no notable photosynthate carry-over was identified. Carbon- and oxygen- (mechanistic) isotope response surface models were then compared and contrasted to regression-based bivariate and univariate models. It was found that in most cases the isotope response surface models were the best means of predicting isotopic labelling when environmental data are known. The carbon-isotope response surface was used to reconstruct 50-years (AD 1900-1954) of relative humidity data by introducing measured carbon isotope values and instrumental growth season temperature. During the analysis of the oxygen-isotope response surface we found an isotope-temperature relation that appears to reflect circulation-dependent damping. To verify this we introduced scaled values of the North Pacific index as a proxy for this suppression. The coupling of the isotope response surfaces generated a humidity reconstruction that is also thought to be driven by atmospheric circulation. Our reconstruction shows that the fluctuations in temperature range have not exceeded the natural variability in the instrumental record of the 20th century; however, the atmospheric moisture (humidity) reconstruction predicts a directional drying trend in the Peace-Athabasca Delta that appears to reflect increasingly zonal circulation in western Canada over this period.

Humidity sensors are one of the most widely used sensors in commercial and industrial applications for environmental monitoring and controlling. Although related technology have been studied intensively, humidity sensing in harsh environments still remains a challenge. The inability of current humidity sensors to operate in high temperature environments is generally due to the degradation of the sensing films caused by high temperature, high humidity level, and/or contamination. Our goal is the design and fabrication of a humidity sensor that is capable of working under high temperatures and in a condensing environment. The targeted application of this sensor is in the polymer electrolyte membrane (PEM) fuel cell, where humidity control is crucial for performance optimization. In this work, ordered macroporous silicon is thoroughly studied as a humidity sensing layer. In addition to the advantages of traditional porous silicon for gas sensing (high resistance to high temperature and good compatibility with current IC fabrication process), the ordered macroporous silicon used in these experiment has uniform pore size, pore shape and distribution. All the vertical aligned pores can be opened to the environment at both ends, which can significantly increase the efficiency of gas diffusion and adsorption. Moreover, this special structure opens the door to uniform surface modifications for sensing enhancement. Both ordered macroporous silicon based heterostructure and self-supporting membrane are fabricated and investigated as a humidity sensor. Heterostructure sensors with different thin film surface coatings including bare Si, thermally grown SiO2, atom layer deposited ZnO, HfO2, and Ta2O5 are characterized. Post micro-fabrication is achieved on this ordered porous structure without affecting the material and its sensing properties. It has been proven that the ordered macroporous silicon with Ta2O5 surface coating shows the best sensing property due to its ultra-hydrophilic surface. The sensor shows high sensitivity, fast response times, small hysteresis, and extraordinary stability and repeatability under high temperatures and in condensing environment. It demonstrates great potential and advantages over existing commercial humidity sensors in the fuel cell application field. In addition to ordered macroporous silicon, well aligned 1D ZnO nanorods/nanowires -another widely used nanostructure in gas sensing- is also investigated as humidity sensing materials. Both vertically and laterally aligned nanorods/nanowires are fabricated and tested against humidity changes. The sensors shows increasing resistance to increasing relative humidity, which is contrary to most published works so far. Possible mechanisms have been proposed in this thesis and future work has been suggested for further study. To the best of our knowledge, this work is the first to use ordered macroporous silicon and well aligned 1D ZnO nanorods/nanowires for humidity sensing.

This study presents a simple process for producing resistance-based humidity sensors utilizing dopamine (DA) coated gold nano-particles (AuNPs) as the sensing material. The sensing material for typical humidity sensors are solid state metal oxides, graft-polymers or salt-doped polymers. However, these humidity sensors may suffer from low sensing response or slow time response since water molecules have to diffuse into the sensing materials to induce the electrical property changes. Alternatively, AuNPs have large surface area for water molecule absorption and can be potentially for high performance humidity sensing. Nevertheless, the surface property of AuNPs is hydrophobic and needs to be modified. In this regards, this work uses a highly hydrophilic molecule of dopamine to modify the surface of AuNP into hydrophilic to enhance the humidity sensing performance. Highly hydrophilic bio-molecule of dopamine is physically bonded onto 4-6 nm AuNPs to enhance the humidity sensing performance. Results show that the DA coated AuNPs have nice humidity sensing responses in the measuring range of 20-90%RH. The measured resistance response shows >1500 times greater than the sensor using the same AuNPs without DA coating. The developed humidity sensor shows rapid time responses for water absorption (13 s) and desorption (30 s), respectively. Moreover, a 3-day long-term measurement at low, medium and high humidity ranges also shows the good stability of the developed sensor. The method developed in this study provides a simple and low-cost method to produce high-performance humidity sensors with DA-coated AuNPs.

Causative influences that impact the separation of Ae. aegypti and Ae. albopictus populations in different geographic areas were determined, as well as how they are affected by the abiotic conditions as seen in the habitats they frequent in Texas. The eggs of Ae. albopictus and Ae. aegypti collected from McAllen and Brownsville, Texas, and laboratory populations of these two species were subjected to 25 different temperature and relative humidity conditions for up to three months. In most treatments, Ae. aegypti eggs had a greater percent hatch than Ae. albopictus, regardless of temperature or relative humidity. With an increase in relative humidity, the percent hatch for both species increased, but at the higher temperatures of 32° and 35°C the amount of time the eggs were exposed to those temperatures had a greater negative effect on the percent hatch than did the positive effect of increase in relative humidity. The surface area, volume and surface-area-to-volume ratio of Ae. aegypti and Ae. albopictus eggs with and without the chorionic egg pad, and the size of the chorionic egg pad were calculated for fifty eggs of each species of mosquito from populations collected in McAllen and Brownsville and from the laboratory populations. Ae. aegypti had a larger egg volume, and a larger surface area; but, it is likely their larger egg pad compensates for this high surface-area-to-volume ratio by holding moisture along the egg’s surface and that the egg pad is associated with the high desiccation resistance seen in Ae. aegypti eggs. Development rates for both species of mosquitoes from populations collected in Galveston and Brownsville, Texas, and laboratory populations were produced by measuring the development time from a hatched egg to the adult at seven temperatures. The temperature optima (28°-33°C) were similar for all populations; however, the rate of development for Ae. aegypti was significantly faster at the temperature optima. It is likely that this faster development rate in the Ae. aegypti population helps to maintain a population in climates that have this range of temperatures given that Ae. albopictus is a superior competitor in the larval and adult stages.