Rozprawy doktorskie na temat „Humidity”
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1
Bellmann, C., A. Steinke, T. Frank i 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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Boltshauser, Thomas. "CMOS humidity sensors /". [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10320.
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TABANDEH, SHAHIN. "Advances in Humidity Standards". Doctoral thesis, Politecnico di Torino, 2019. http://hdl.handle.net/11583/2745353.
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Dedic, Haris. "Humidity sensor for car seat". Thesis, University West, Department of Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-785.
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Newton, Mark K. "The initial perception of humidity". Thesis, University of Portsmouth, 2011. https://researchportal.port.ac.uk/portal/en/theses/the-initial-perception-of-humidity(5c072ca2-6291-450a-a7ac-32c9d6ec1cbc).html.
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Wang, Xiaodong. "Electrolyte-based Wireless Humidity Sensor". Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-95372.
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This master thesis was initiated in the Organic Electronics group at Linköping University within a project called ‘Brains & Bricks’. The purpose was to develop a prototype of a wireless humidity sensor with a solid polyelectrolyte as the humidity sensing material. The humidity levels can be estimated from the resonant frequency of a testing circuit. The readings were performed by a wireless method between two coils. Both the testing circuit and the simulation programs were designed in this thesis work. The operating frequency of the sensor was chosen to be in the range of 100 kHz to 200 kHz at which the solid polyelectrolyte, Polystyrene Sulfonic Acid (PSSH), was sensitive to humidity variations. Three different types of humidity sensors were fabricated and tested. These sensor heads promised for printability and low-cost manufacturing. A shift, responding to a humidity variation, in the resonant frequency of the testing circuit was detected by a reader coil which was 1 cm away from a sensor coil. These measurements matched the results simulated by a Matlab program. The feasibility of fabricating a low-cost wireless humidity sensor with a solid polyelectrolyte as humidity sensing material by printing technique was proved in the thesis work. Subsequent research will be continued to develop humidity sensors having a lateral structure and an improved performance.
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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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Keramitsoglou, Iphigenia. "On measurements of upper tropospheric humidity". Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313660.
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Tong, Jingbo. "MEASUREMENT AND MODELING OF HUMIDITY SENSORS". UKnowledge, 2014. http://uknowledge.uky.edu/ece_etds/59.
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Humidity measurement has been increasingly important in many industries and process control applications. This thesis research focus mainly on humidity sensor calibration and characterization. The humidity sensor instrumentation is briefly described. The testing infrastructure was designed for sensor data acquisition, in order to compensate the humidity sensor’s temperature coefficient, temperature chambers using Peltier elements are used to achieve easy-controllable stable temperatures. The sensor characterization falls into a multivariate interpolation problem. Neuron networks is tried for non-linear data fitting, but in the circumstance of limited training data, an innovative algorithm was developed to utilize shape preserving polynomials in multiple planes in this kind of multivariate interpolation problems.
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Sun, Lu. "Laser nano-ablation for humidity detection". Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/64820.
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Nano-scale fabrication of technical materials is one of the biggest challenges in future industrial applications. There is a growing need for components with feature sizes below one micron. The well-established techniques, including e-beam lithography and focused ion beam milling, suffer several limitations, such as expensive apparatus, low fabrication speed and small scale production. Laser nano-ablation, as an efficient implementation method, has offered promising merits in large scale nano-fabrication. First applied to polymers, it offered a one-step fabrication ability with sub-micron structuring resolution. Later, following the pioneering work of Stuke and co-workers, surface treatment of non-polymeric materials, such as crystals, metals and semiconductors was achieved using picosecond and femtosecond laser systems. In this thesis, laser nano-ablation was used to fabricate large scale nano-hole arrays on polyimide films to improve the performance of humidity sensors. A 193 nm ArF pulsed laser system was established, simulated and optically aligned. Hole arrays with 920 nm diameter at the top, 339 nm diameter at the bottom and 451 nm depth were produced using mask projection ablation on polyimide films. Interdigitated polyimide humidity sensors were fabricated, packaged and tested. Based on conformal mapping and partial capacitance, capacitance modelling of interdigitated electrode arrays was built to analyse the capacitance variations with electrode dimensions. A reliable home-made humidity chamber was established for sensor tests. Static and dynamic tests were carried out to characterize the sensor performance. Static tests showed the nano-patterned films can enhance the sensitivity by 7.1% at humidity levels below 68% RH and by 100% at humidity levels higher than 68% RH. In addition, dynamic test showed that the nano-patterned polyimide films are able to improve the response speed by about 20%. Overall, this thesis demonstrates that large-area nano-hole arrays formed by laser ablation can improve the sensitivity and response time of polyimide-based capacitive humidity sensors.
11
Chen, Qiao. "ESA based fiber optical humidity sensor". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/10134.
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Several techniques for measuring humidity are presented. The goal of the study is to use the electrostatic self-assembled monolayer synthesis process to fabricate a Fabry-Parot Cavity based optical fiber humidity sensor. The sensing scheme bases on the refractive index change with relative humidity of the film applied to the end of optical fiber. That is, the change in reflected optical power indicates certain humidity. To achieve this, some chemicals induce on specific coating materials were applied at the end of optical fiber. In this thesis, experimental results are given to prove that the humidity sensor has high sensitive and fast response time. Furthermore, we investigate the potential for the use of human breathing monitoring and air flow rate detection. Results from preliminary tests of each are given.Master of Science
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Jain, Dharamdeep. "Humidity Driven Performance of Biological Adhesives". University of Akron / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=akron1510053266807976.
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Gaikwad, Parikshit S. "Chemically deposited optical fiber humidity sensor". Master's thesis, Mississippi State : Mississippi State University, 2003. http://library.msstate.edu/etd/show.asp?etd=etd-06092003-141607.
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Zhang, Qi [Verfasser]. "Humidity related magnetite alteration / Qi Zhang". Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/122159639X/34.
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Andersson, Sofia. "Late Holocene humidity variability in central Sweden /". Stockholm : Department of Physical Geography and Quaternary Geology, Stockholm University, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-36884.
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Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.At the time of the doctoral defence, the following papers were unpublished and had a status as follows: Paper 1: Submitted. Paper 3: Accepted. Paper 5: In progress. Härtill 5 uppsatser.
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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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McNally, A. P. "Satellite sounding of tropospheric temperature and humidity". Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276585.
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Birley, Joseph Leonard Mark. "An investigation of temperature controlled humidity sensors". Thesis, De Montfort University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393232.
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ESCOBAR, SERGIO GUTIERREZ. "HUMIDITY SENSOR BASED ON MEMS SAW TECHNOLOGY". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29753@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROAGÊNCIA NACIONAL DE PETRÓLEO
Os sistemas micro eletromecânicos são dispositivos na escala dos micras que combinam estruturas mecânicas com circuitos elétricos, e são usados como sensores ou atuadores. Dentro destes dispositivos, estão os de onda superficial acústica (SAW em inglês) que usam variações na velocidade ou percurso de propagação da onda para fazer a detecção da variável a medir. Uma aplicação importante em processos químicos, é no acondicionamento de ambientes, monitorando a umidade. Para isso um sensor SAW comprado, foi coberto em sua superfície com uma camada de um polímero absorvente de vapor de agua. No qual o aumento na massa do polímero na superfície diminui a velocidade da onda. Por tanto o PolyVinyl Álcool foi escolhido para absorver o vapor de agua e foi preparado com 5.6 wt por cento, para ser depositado por meio de spin coating. Então uma serie de experimentos foram feitos numa câmara climática variando tanto a umidade como a temperatura, com o fim de avaliar o comportamento do sensor medindo a sua variação da frequência. Estes resultados foram comparados com um modelo analítico e uma simulação por elementos finitos. O modelo analítico foi presentado por Sielman, o qual determina como muda a densidade e espessura no polímero com a umidade. Estes valores foram substituídos na equação de Wohltjen que dá a variação da frequência de um SAW devido a absorção de gases. Em quanto a simulação por elementos finitos foi feita em Comsol Multiphysics achando a frequência para a qual o SAW ressona, com o aumento da densidade na camada acima do SAW para as umidades inseridas.
Micro electromechanical systems (MEMS) are devices that combine mechanical structures with electrical circuits at the micro scale, to function as sensors or actuators. One type of MEMS are the surface acoustic waves (SAW) devices, which uses the surface wave velocity or propagation path variations to measure the variable of interest. One important application in chemical processes is related to environment condition control, specifically humidity measurement. With that purpose, a commercial SAW was purchased and coated with a polymer layer in its surface. The PolyVynil Alcohol (PVA) was chosen to be the sensing layer in the SAW due to water vapor absorption properties, that increases the mass over the surface and decrease the wave velocity, leading to sense this humidity changes. 5.6wt per cent PVA solution was prepared and deposited through spin coating. Therefore, a series of tests were carried out in a climatic chamber, varying the humidity and temperature conditions, with the aim to analyze the sensor behavior by measuring its frequency shift. These results were compared with an analytical model and a finite element simulation. The analytical model presented by Sielman determines how the polymer density changes with humidity. These density values were inserted into the Wohltjen equation, which gives the frequency shift of the SAW due to gas absorption. Regarding the finite element simulation, it was carried out in the Comsol Multiphysics software, by solving the different resonating frequencies as a function of the increase in the polymer density due to the insets of humidity values.
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Kottayil, Ajil. "Satellite and radiosonde measurements of atmospheric humidity". Licentiate thesis, Luleå tekniska universitet, Rymdteknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17792.
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This licentiate thesis is based on two papers which are related to the study ofatmospheric humidity. The first paper mainly focuses on a non linear method forretrieving atmospheric humidity from infrared sounder satellite measurements basedon fuzzy clustering which could potentially improve the retrieval accuracy. The mainaim of this study was to provide a better first guess humidity profile for physicalretrieval algorithms which can further improve retrieval accuracy. This method hasbeen compared against linear and non linear regression retrievals which are the gen-erally used methods to get the first guess profile. The results reveal that the retrievalaccuracy is better for the new method as compared to the conventional methods.Generally, the accuracy of the humidity measurements of radiosonde is poor in theupper troposphere (UT) and is worse for day time measurements due to solar heatingof the humidity sensor. Several methods have been developed to correct the humiditymeasurements of radiosondes in the UT. The second paper presents a detailed analysisof the implications of these corrections and depicts how important they are for satellitevalidation. The corrections have been applied separately for daytime and nighttimeradiosonde measurements and their effects have been quantified by comparing againstthe coinciding satellite measurements in the infrared and microwave spectral rangeused for humidity measurements.Godkänd; 2012; 20111213 (ajikot); LICENTIATSEMINARIUM Ämnesområde: Rymdteknik/Space Engineering Examinator: Professor Stefan Buehler, Institutionen för system- och rymdteknik, Luleå tekniska universitet Diskutant: Docent Patrick Eriksson, Institutionen för rymd- och geovetenskap, Chalmers tekniska högskola, Göteborg Tid: Fredag den 3 februari 2012 kl 10.00 Plats: Sal C, Rymdcampus Kiruna, Luleå tekniska universitet
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Majundar, Pradip. "Analysis of desiccant cooling systems using advanced desiccant matrix structure". access full-text online access from Digital Dissertation Consortium, 1986. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?8707884.
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Charoensupaya, Dhanes. "Experimental and analytical investigations of composite desiccant structures and low humidity adsorption". access full-text online access from Digital Dissertation Consortium, 1986. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?8707873.
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Okcan, Burak. "Humidity Sensors Using Mems And Standard Cmos Technologies". Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1124106/index.pdf.
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This thesis presents the development of humidity sensors using surface
micromachining and standard CMOS processes. Two types of humidity sensors are
designed and implemented. The first one is a capacitive humidity sensor with a
polyimide film as the humidity sensitive dielectric layer. The second sensor is a
thermal conductivity based humidity sensor, which measures the amount of humidity
using the difference between the thermal conductivity of the air and the water vapor.
The capacitive humidity sensor is fabricated by three mask process, where the
humidity sensitive polyimide layer is sandwiched between two metal electrodes. The
bottom electrode is designed in a heater resistor shape, which provides humidity
measurement at high relative humidity levels where there is the risk of water
condensation. Characterization results show that the fabricated sensor tracks the
humidity change with a sensitivity of 145fF/%RH, with nonlinearity less than 0.2%. The hysteresis of the sensor is 2.57% RH. The sensor is hybrid connected to a
switched capacitor readout circuit, which dissipates 1.75mW power. The measured
sensitivity of the hybrid module is 19.4mV/%RH with nonlinearity less than 0.2%.
Operation of the integrated heater is also verified by monitoring the resistance versus
temperature and resistance versus power characteristics.
The thermal conductivity based humidity sensor is implemented using
thermally isolated p-n junction diodes obtained by standard CMOS and post-CMOS
bulk silicon micromachining processes. Thermal isolation is achieved by anisotropic
bulk silicon etching using electrochemical etch stop technique in a TMAH solution.
One of the suspended diodes is sealed and has a fixed thermal conductance, while the
other one is exposed to the ambient and has humidity dependent thermal
conductancetherefore, they provide different diode voltages when they are heated with same biasing currents. The difference between the diode voltages are converted into current through a monolithic transconductance amplifier, and this current is integrated by a switched capacitor integrator to obtain an amplified output signal. The measured temperature sensitivity of the diodes is -1.3mV/K within 150º
C to 250º
C range at 100µ
A bias level. Relative humidity sensitivity of the sensor is 14.3mV/%RH, 26mV/%RH, and 46.9mV/%RH for 20º
C, 30º
C, and 40º
C ambient temperature respectively with a nonlinearity less than 0.3%. The measured hysteresis of the sensor is less than 1% at 20º
C and 30º
C ambient temperature conditions. The sensor operates from a 5V supply and dissipates 1.38mW power.
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Spindura, Jillian. "The response of poly (vinyl alcohol) to humidity". Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365748.
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陳國柱 i Kwok-chu Timmy Chan. "Calcium sulphate hemihydrate: effect of humidity in storage". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B21129526.
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Foster, Gary Marc. "Mechanical properties of coil coatings under controlled humidity". Thesis, University of Exeter, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.559098.
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This thesis deals with the determination of the effect of controlled relative humidity (RH) on the mechanical properties of coil coatings. The coil coatings studied were based on polyester/melamine technology. The study employed mechanical and dynamic mechanical analysis, using modified environmental chambers, to measure the effects of controlled RH on a range of mechanical parameters. Of particular interest was the effect of controlled RH on the minimum forming temperature of the coil coated metallic panels. This is the temperature below which the coating would fracture. A description has been given of the modifications made to both a mechanical tester and a Dynamic Mechanical Analyser (DMA), which allowed controlled RH experiments to be performed under isothermal or thermal scanning conditions. Comparison of this study with published work showed that some experimental data in the literature could be erroneous due to lack of, or inappropriate, RH conditioning prior to testing. The results showed a good correlation for both free film and coated metal samples between the glass transition temperature (Tg) and the brittle-tough transition (Tbt). A reduction of both the Tg and the Tbt of up to 15°C were found as the controlled RH was increased. A controlled RH and environmentally instrumented slow-draw cupping device was constructed to measure the behaviour of coil coatings on aluminium (Al) and hot dip galvanised steel (HDG-steel) substrates. The importance of indentation depth during the cupping test and the difference between the substrates was emphasised. Fracture mechanics was employed to study differences in performance.
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Bownass, David Casson. "Passive fibre-optic humidity sensing for telecommunications networks". Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/1191.
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Svensson, Andreas. "Humidity Structures in the Marine Atmospheric Boundary Layer". Thesis, Uppsala universitet, Luft-, vatten och landskapslära, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-302863.
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The turbulence structure over the sea was studied with the emphasis on humidity. The data sets used came from the island of Östergarnsholm outside Gotland in the Baltic Sea. The study included spectral and quadrant analyses of the wind, temperature and humidity parameters from one measuring level. The wave state of the sea was deduced from data from a wave rider buoy anchored 4 km from the site.Two turbulence instruments for humidity were compared, the MIUU instrument (hot wire) and an open pass infrared gas analyser from LI-COR. The comparison showed that the LI-COR instrument resolved the high frequency fluctuations of the humidity better. The unstable cospectra of the sensible and latent heat fluxes were studied and categorised. It was found that many cospectra have two or more maxima. The higher frequency maxima gained influence when the stratification became near neutral.The quadrant analyses showed that the structures of humidity flux were similar to those of the heat flux. The sources of the flux were studied using different ratios. The ratio between events of moist updrafts and dry downdrafts were extensively studied. It was shown that the events of moist updrafts were more dominating during swell than during growing sea. When the results of the spectral and quadrant analyses were combined, it was shown that the smaller sized eddies of heat dominate the events of warm updrafts and that the large eddies dominate the cold downdrafts. The bulk transfer number for moisture, the Dalton number (CE), was found to be almost constant with stratification for unstable runs. The mean value was calculated to (1.0±0.3)·10-3.Målet för denna studie var turbulensstrukturer över hav med särskild tonvikt på fuktigheten. I denna studie har använts observationer från en mast på ön Östergarns-holm, strax öster om Gotland. Arbetet innefattar spektral- och kvadrantanalys av vind, temperatur och fuktighet från en mätnivå. Havets aktuella tillstånd mättes med en vågboj förtöjd 4 km från masten. Två turbulensinstrument för fuktighet jämfördes, MIUU-instrumentet (varmtråds-instrument) och ett instrument från företaget LI-COR som mäter infraröd absorption. Jämförelsen visade att LI-COR-instrumentet löser upp de högfrekventa fuktighets-fluktuationerna bättre. Instabila cospektra för sensibelt och latent värmeflöde studerades och kategoriserades. Det visade sig att många cospektra hade två eller flera maxima. Det högfrekventa maximumet fick ökad betydelse när skiktningen blev nära neutral. Kvadrantanalyserna visade att strukturerna för värme- och fuktighetsflödet är liknande. Källan för flödena studerades med hjälp av olika kvoter. Av särskilt intresse var kvoten mellan tillfällen med fuktiga uppvindar och torra nedvindar. Det visade sig att tillfällen med fuktiga uppvindar var mer dominerande vid dyning än vid upp-byggande vågor. När resultaten från spektral- och kvadrantanalysen kombinerades, visade det sig att de små virvlarna med värme dominerar vid tillfällen med varma uppvindar och att de stora virvlarna dominerar vid kalla nedvindar. Utbyteskoefficienten CE för fuktighet, även kallad Dalton-talet, är nästan konstant för de instabila fallen. Medelvärdet av CE beräknades till (1,0±0,3)·10-3.
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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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Chan, Kwok-chu Timmy. "Calcium sulphate hemihydrate effect of humidity in storage /". Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21129526.
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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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Glass, Laurie. "Preterm Infant Incubator Humidity Levels: A Systematic Review". ScholarWorks, 2019. https://scholarworks.waldenu.edu/dissertations/7650.
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Numerous scholars have reported that inconsistent incubator humidity in the neonatal intensive care unit (NICU) requires attention. Evidence synthesis was needed to assist the identification of optimal incubator humidity levels and duration to decrease transepidermal water loss (TEWL) and the potential for infection. The purpose of this doctoral project was to appraise and synthesize the evidence of preterm outcomes related to incubator humidity. The practice-focused question addressed what patient outcomes were impacted by incubator humidity level and duration in premature infants < 32 0/7 weeks cared for in the NICU. The foundation of this project was the Joanna Briggs Institute method for systematic reviews. Mefford’s theory of health promotion for the preterm infant was used to address the wholeness of the preterm infant’s body system. Evidence was classified using the Johns Hopkins evidence-based practice levels and quality of evidence. The search was conducted in 8 databases, and citation searching was used to identify 340 articles, 12 of which met the inclusion criteria. The evidence demonstrates that the practice of incubator humidity is warranted; however, it does not come without risks. Microbial growth was increased in high levels of incubator humidity. Unnecessary TEWL was prevented by lowering high levels of incubator humidity after the 1st week, improving skin barrier formation. Incubator humidity of 60%–70% in the 1st week was effective in preventing TEWL in infants born ≥ 26 weeks; however, future research is needed for infants < 26 weeks. When optimal levels and duration of incubator humidity are achieved, positive social change will occur from the improved outcomes of the smallest neonatal patients.
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Tse, Oi Ling. "Development of humidity sensor based on fluorimetric optode membrane". HKBU Institutional Repository, 1999. http://repository.hkbu.edu.hk/etd_ra/191.
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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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Kharaz, Ahmad H. "Humidity sensing by optically interfacing with spectrally absorptive materials". Thesis, Brunel University, 1999. http://bura.brunel.ac.uk/handle/2438/5197.
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The measurement of humidity is rapidly increasing in importance in physical, chemical and biological processes as industry attempts to improve quality and production rates by better control of relative humidity (RH). A novel optical fibre humidity sensor suitable for use in an optical fibre multi-point distributed sensing system has been developed, thus for the first time allowing multipoint measurements of humidity along an optical fibre which can be distributed within an industrial plant or machine without the need for electrical power supplies. The novel point sensor is based on the principle of using the absorption spectrum of a colorimetric reagent (cobalt chloride) immobilised on the surface of the core of a multimode optical fibre by employing a thin gelatin film. The single point sensor has an insertion loss of less than 0.2 dB. Two-wavelength detection is employed to provide referencing to eliminate common mode intensity variation. The basic design, construction and testing of an experimental sensor in the humidity region 20 to 80% RH and temperature range 25 to 50 °C is described. Resolution and Repeatability can be better than 2% RH with a time constant of 0.5 second. A two-wavelength optical time domain reflectometer (OTDR) has been developed and a four-sensor network has been built. The resolution of measurement on the network can be better than 4% RH, but because of noise in the OTDR the resolution value is dependent on averaging time in the instrument.
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Tashtoush, Nehad M. "SAW humidity sensor and an environmental electronic nose system". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq25915.pdf.
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Xu, Lina. "Optical fiber humidity sensor based on evanescent wave scattering". MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07092004-112625/.
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An optical fiber humidity sensor has been devised using a porous sol-gel silica (PSGS) coating as a transducer. Evanescent wave scattering (EWS) in the PSGS coating. PSGS particles are highly hydrophilic and have a strong tendency to absorb water molecules from the surrounding environment. The absorbed water molecules form a thin layer on the inner surface of the pores inside the porous silica and enhance EWS, from which an indicatory signal can be obtained. The humidity sensor presented in this thesis has a fast response, is reversible, low cost, and has a broad dynamic relative humidity range from 3.6?0-6% to 100% or humidity range from 1.2ppm to 30000ppm. Because of its multiple advantages, including immunity to electromagnetic interference, resistance to corrosive environments, and high sensitivity, this humidity sensor has various applications. In soil moisture sensing, this humidity sensor can avoid the interference caused by compounds in soil water. For electrical transformer moisture sensing, this humidity sensor can avoid the effect of electromagnetic fields.
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Feng, Yi. "Printed RFID Humidity Sensor Tags for Flexible Smart Systems". Doctoral thesis, KTH, Industriell och Medicinsk Elektronik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-162152.
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Radio frequency identification (RFID) and sensing are two key technologies enabling the Internet of Things (IoT). Development of RFID tags augmented with sensing capabilities (RFID sensor tags) would allow a variety of new applications, leading to a new paradigm of the IoT. Chipless RFID sensor technology offers a low-cost solution by eliminating the need of an integrated circuit (IC) chip, and is hence highly desired for many applications. On the other hand, printing technologies have revolutionized the world of electronics, enabling cost-effective manufacturing of large-area and flexible electronics. By means of printing technologies, chipless RFID sensor tags could be made flexible and lightweight at a very low cost, lending themselves to the realization of ubiquitous intelligence in the IoT era. This thesis investigated three construction methods of printable chipless RFID humidity sensor tags, with focus on the incorporation of the sensing function. In the first method, wireless sensing based on backscatter modulation was separately realized by loading an antenna with a humidity-sensing resistor. An RFID sensor tag could then be constructed by combining the wireless sensor with a chipless RFID tag. In the second method, a chipless RFID sensor tag was built up by introducing a delay line between the antenna and the resistor. Based on time-domain reflectometry (TDR), the tag encoded ID in the delay time between its structural-mode and antenna-mode scattering pulse, and performed the sensing function by modulating the amplitude of the antenna-mode pulse. In both of the above methods, a resistive-type humidity-sensing material was required. Multi-walled carbon nanotubes (MWCNTs) presented themselves as promising candidate due to their outstanding electrical, structural and mechanical properties. MWCNTs functionalized (f-MWCNTs) by acid treatment demonstrated high sensitivity and fast response to relative humidity (RH), owing to the presence of carboxylic acid groups. The f-MWCNTs also exhibited superior mechanical flexibility, as their resistance and sensitivity remained almost stable under either tensile or compressive stress. Moreover, an inkjet printing process was developed for the f-MWCNTs starting from ink formulation to device fabrication. By applying the f-MWCNTs, a flexible humidity sensor based on backscatter modulation was thereby presented. The operating frequency range of the sensor was significantly enhanced by adjusting the parasitic capacitance in the f-MWCNTs resistor. A fully-printed time-coded chipless RFID humidity sensor tag was also demonstrated. In addition, a multi-parameter sensor based on TDR was proposed.The sensor concept was verified by theoretical analysis and circuit simulation. In the third method, frequency-spectrum signature was utilized considering its advantages such as coding capacity, miniaturization, and immunity to noise. As signal collision problem is inherently challenging in chipless RFID sensor systems, short-range identification and sensing applications are believed to embody the core values of the chipless RFID sensor technology. Therefore a chipless RFID humidity sensor tag based on near-field inductive coupling was proposed. The tag was composed of two planar inductor-capacitor (LC) resonators, one for identification, and the other one for sensing. Moreover, paper was proposed to serve as humidity-sensing substrate for the sensor resonator on accounts of its porous and absorptive features. Both inkjet paper and ordinary packaging paper were studied. A commercial UV-coated packaging paper was proven to be a viable and more robust alternative to expensive inkjet paper as substrate for inkjet-printed metal conductors. The LC resonators printed on paper substrates showed excellent sensitivity and reasonable response time to humidity in terms of resonant frequency. Particularly, the resonator printed on the UV-coated packaging paper exhibited the largest sensitivity from 20% to 70% RH, demonstrating the possibilities of directly printing the sensor tag on traditional packages to realize intelligent packaging at an ultra-low cost.QC 20150326
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Amissah, Patrick Ken. "Indoor air quality : combining air humidity with construction moisture". Thesis, University of Strathclyde, 2005. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=21574.
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The project aims to improve the modelling of moisture transfers at internal surfaces by linking the finite volumes representing the Heat, Air and Moisture (HAM) and Computational Fluid Dynamics (CFD) domains. Conflation of both models facilitates the detailed study of moisture flow as it impacts on indoor air quality and occupant health. The thesis lays down the conceptual framework for the subsequent development of an indoor air quality analytical tool. The work thus improves the modelling of construction feature risk assessment, for example, moisture absorption and desorption at the internal fabric surfaces in as much as it relates to indoor air quality. Through such an improvement, an indoor air quality analytical tool for the prediction of time-varying temperature/humidity conditions at specific locations within the building is enabled and subsequently these conditions may be related to the likely occurrence of mould. Humidity in indoor spaces is one of the most important factors in the determination of indoor air quality. High indoor humidity is a major contributor to the accumulation of moisture in the building envelope. This often results in dampness within the building envelope and subsequent health-related problems for the occcupants. Moderation of the indoor relative humidity, temperature and moisture content of the indoor air amongst others is a pre-requisite for a healthy building because it affects the perception of indoor air quality, thermal comfort, occupant health (asthma, respiratory illness, etc), building durability, material emission and energy consumption. Excessively high relative humidity promotes the growth of moulds and mildew on building surfaces. The basis for the envisaged conflation evolves around the boundary layer theory as it pertains to the velocity, thermal and concentration profiles associated with flow parallel to a flat surface, a phenomenon which is recognised as being similar in nature to buoyancy-driven convective heat transfer within building enclosures (White 1988). Within the framework of modelling of indoor air flows, the conflated modelling approach is very much dependent upon the treatment of the internal surface convection, for example, in the conflation of HAM and CFO models. This is referred to as the pivot point for the handshaking between HAM and CFO modelling domains. Within the framework of this project, the pivot point refers to the treatment of surface convection mass transfer at the internal surface to facilitate the hand shaking between HAM and CFO modelling domains. The two-time step coupling approach based on the loose coupling algorithm is adapted for the conflation. The technique involves a process whereby the HAM and CFO models are processed independently but exchange information at the interface at every time-step. The numerical method for the solution of the Navier-Stokes equations is based on the co-located grid arrangement, whereby all flow variables are defined in the centre of the grid cells. The transport equations are integrated for each grid cell and the Gauss Theorem applied to yield an integral over the cell face. These cell face integrals are then approximated using interpolation of the cell centred data. For the resolution of flow in the near-wall regime, the Low-Reynolds number k-ε turbulence model is used. A configuration mechanism with a rules-based moisture control algorithm to facilitate the handshaking of the HAM and CFO domains is presented. Methods for the solution of problems due to moisture migration across the interface, which are effected through variation of the convective mass transfer coefficient, hm, through variation of the standard k-ε turbulence model, namely the lowReynolds number model with its embedded wall damping functions and through adjustment of the source terms of governing transport equations of the CFO and HAM models are also discussed.
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Hewison, Tim J. "Profiling temperature and humidity by ground-based microwave radiometers". Thesis, University of Reading, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.654501.
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Glen, Thomas. "The degradation of organic solar cells in high humidity". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709206.
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Weir, Edward A. "The impact of humidity and moisture on electronic equipment". Thesis, University of Sussex, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413314.
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Elvin, Malin. "The effect of humidity and temperature on paper properties". Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-54905.
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The study was performed at Billerudkorsnäs at the section Box Lab which offers knowledge and solutions for packaging. Paper that can be used to create packaging interacts with the surrounding environment, but has only been tested for a few climates. This thesis aims to investigate more climates and see how paper is affected by humidity and temperature and try to determine the cause of the results. The methods used to measure this was primary tensile test and moisture content analysis but also a test to evaluate creep was performed in climates with high humidity. From this, the mechanical properties of the paper were calculated. The test was performed in a climate chamber and the choice of methods was limited by what could be performed in the climate chamber. The materials tested were chosen to give a good representation of what is commonly used in the containerboard business. The climates for testing were selected from the ability of the climate chamber as well as interesting climates for the company. The results show that the papers are weakest at high RH, but the results indicate that the temperature solely impacts the properties of the paper. The highest moisture content does not necessarily mean the lowest value for a chosen property. The causes for the results are not clear since the patterns found are not bound to a certain quality but rather to paper in general. Therefore, more research on the area is suggested to try to determine what causes the material to react to temperature.
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Khan, Arshad Y. "Analysis of open sorption and refrigeration humidity control systems". access full-text online access from Digital Dissertation Consortium, 1988. http://libweb.cityu.edu.hk/cgi-bin/er/db/ddcdiss.pl?8819235.
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Sandgren, Elin. "Leaching of Glass Waste – Structure and Humidity Cell Tests". Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388059.
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Glass production has historically occurred at around 50 glassworks in Sweden, in a region known as the Kingdom of Crystals (Glasriket). Today, most of these sites are no longer active and left behind is glass waste of different forms (both as fragments of finished glass as well as unrefined glass melts). Consequently, increased concentrations of different metals, especially arsenic, lead and cadmium, have been found around the sites, both in soil as well as in ground and surface water. Between 2016 and 2019, the Geological Survey of Sweden (SGU) assigned Golder Associates AB (Golder) to evaluate the environmental risks at three different glassworks: Flerohopp, Åryd and Alsterbro. The results, based on humidity cell tests (HCT) conducted on glass samples from each site, showed that glass itself leached to a surprisingly high extent. Based on this, the aim of this master thesis has been to explain trends in glass leaching by a thorough literature review and through the analysis of HCT data of glass samples. Additionally, the speciation of different metals in the leachate was investigated based on geochemical modelling using PHREEQC. Results from the literature review show that one of the possible mechanisms for the leaching of glass in contact with water is ion exchange, which occurs at the surface of the glass, namely between glass components and H+ ions in water. Additionally, the literature also argues that glass with higher silica content form a more resilient structure, in contrast to glass which contains a large amount of modifiers, such as Na and Ca. Researchers speculate that adding such modifiers to the glass mass opens up the structure, making it more vulnerable upon contact with water. Looking at the total concentration of elements from the three glassworks, the results show a variation in silica content in relation to other elements. In line with this hypothesis, the sample from Åryd, which contained a higher proportion of modifiers, showed a high leaching rate of both Na and Si. Furthermore, the result shows that the leaching of Na and As follows the same pattern over the HCT period for all glassworks. This is, to some extent, also the case for Pb although the correlation is not as significant. This could be explained by the result from geochemical modelling, showing that As tends to dissolve into the leachate while Pb is more prone to forming secondary minerals. Hence explaining their differences in leaching behavior. The result from this study showed no clear correlation between Ca and either As or Pb which could potentially be explained by the formation of precipitates. However, another approach to describe the difference in the behavior between Na and Ca is based on the glass structure itself as well as the hypothesis that Na+ participate in ion exchange to a larger extent than Ca2+. Consequently, the leaching of Na+ makes the surface structure more vulnerable, thereby promoting the leaching of other components such as As and Pb.Produktion av glas har historiskt skett på cirka 50 glasbruk i Sverige i ett område som kallas Glasriket. I dag är produktionen vid majoriteten av dessa glasbruk avvecklad och kvar på platserna finns glasavfall i olika former, både som skärvor av färdigt glas och som ej färdigställd glasmassa. Som en konsekvens av detta har förhöjda halter av olika metaller, särskilt arsenik, bly och kadmium, påträffats i jorden såväl som i grund- och ytvattnet kring glasbruken. Mellan åren 2016 och 2019 gav Sveriges geologiska undersökning (SGU) i uppdrag till Golder Associates AB (Golder) att uträtta huvudstudier och bedömma risker vid tre olika glasbruk, Flerohopp, Åryd och Alsterbro. Resultaten, baserade på fuktkammarförsök på glassavfall, påvisade att glas lakade till en överraskande hög utsträckning. Detta resultat lade grunden till detta examensarbete med frågeställningar i syfte att förklara lakning av glas baserat på en genomgående litteraturstudie samt analys av resultat från fuktkammarförsöken. Vidare har även geokemisk modellering med programmet PHREEQC gjorts för att identifiera olika specifieringar av metaller som kan förväntas påträffas i lakvätskan. Resultat från litteraturstudien visar att en möjlig process som kan förklara lakning av glas vid kontakt med vatten är jonbyte mellan glasets beståndsdelar och H+-jonerna i vattnet. Tidigare studier påvisar att ett högre kiselinnehåll i glaset skapar en mer motståndskraftig struktur än glas som innehåller en förhållandevis hög andel modifierare, såom Na och Ca. Forskare spekularar kring huruvida tillsatsen av modifierare till glasmassan bidrar till att öppna upp glasstrukturen och som en konsekvens av detta göra strukturen mer sårbar. Vid analys av prover tagna vid de tre olika glasbruken påvisade resultaten ett varierat kiselinnehåll i förhållande till övriga ämnen. I linje med denna hypotes påvisade provet från Åryd den högsta andelen modifierare och samtidigt även den högsta lakningen av Na såväl som Si. Vidare påvisar resultatet att lakningen av Na och As följer samma mönster över hela fuktkammarförsöket. Detta kan delvis ses för Pb men korrelationen är inte lika signifikant som för As. En förklaring till detta baseras på resultat från geokemisk modellering, där As tenderar att gå i lösning medan Pb kan förväntas forma sekundära mineral vilket därmed kan antas kontrollera lakningen. Resultatet från denna studie visade ingen korrelation mellan varken Ca och As eller Ca och Pb vilket också skulle kunna förklaras av utfällningar i form av Ca-mineral i lakvätskan. En annan utgångspunkt för att beskriva den skillnad som kan ses mellan Na och Ca baseras på själva glasstrukturen och hur Na+ deltar i jonbyte till en högre grad än vad Ca2+ gör. Som en konsekvens av detta bidrar lakningen av Na+ till att ytan på glaset blir mer sårbar och på så sätt gör att ämnen som As och Pb blir mer lättåtkomliga. Detta resulterar i en större möjlighet för dessa att delta i reaktioner på ytan och därmed laka ut från strukturen.
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AFIFY, AHMED SABRY SHEHATA. "Elaboration and characterization of humidity sensors for environmental monitoring". Doctoral thesis, Politecnico di Torino, 2016. http://hdl.handle.net/11583/2639114.
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The water content in surrounding air is an important factor for the well-being of humans and animals, as the level of comfort is determined by a combination of two factors: relative humidity and ambient temperature.
Humidity is also an important factor for operating certain equipment such as high-impedance electronic circuits, electrostatic-sensitive components, high-voltage devices, fine mechanisms, etc. Nonetheless, moisture is the ingredient common to most manufactured goods and processed materials.
Thus, humidity sensors have been receiving wide attentions since decades. Yet, despite the high request, major advances in these sensors in terms of simple structure, lower cost, better selectivity, durability and reliability are always needed. Throughout the years, a large number of materials based on polymers, composite and ceramics have been tested, due to their own features and specific operating conditions. However, great attention has been paid to ceramic materials due to their chemical inertness which allow them to operate in harsh conditions. Amongst the different studied humidity sensors, impedance-based ones are used most commonly. The operation principle of the impedance sensors is based on the dependence of the impedance (or either capacitance or resistance) of the sensor element recognizing the nature and amount of water molecules on the surface or in the bulk. The resistance or impedance of the resistive-type sensor decreases as the relative humidity (RH)increases. Ions or electrons, or both of them, are the conduction carriers for resistive-type humidity sensors. The common construction of the resistive-type ceramic humidity sensors consists of a ceramic substrate with noble metal interdigitated electrodes coated with humidity sensing ceramic materials, both deposited by screen-print technique [1].
Metal oxides and metal oxide based composites are the most popular materials to be used as resistive sensing elements: TiO2, TiO2–SnO2, TiO2–WO3, TiO2–Cu2O–Na2O, KTaO3//TiO2(bilayered), TiO2/KTaO3 (bilayered), TiO2–K2O–LiZnVO4, Al2O3, AlO(OH), SiO2, WO3, Cr2O3–WO3, SnO2, a noble metal doped SnO2, SnO2: ZrO2 (bilayered), single Sb doped SnO2, K+-dopedSnO2–LiZnVO4, MnO2 –Mn3O4, Li+-doped Fe2O3, Au3+ and Li+ co-doped Fe2O3, Li+, Zn2+ and Au3+ co-doped Fe2O3, NiMoO4–MoO3, Li+-doped NiMoO4–MoO3, CuMoO4–MoO3 and PbMoO4–MoO3 [1]. Spinel-type oxides and composites based on spinel-type oxides are also used for humidity resistive sensing elements: MgAl2O4, Sr2+-doped CoAl2O4, Sr2+-doped BaAl2O4, Sr2+-doped ZnAl2O4, MgFe2O4, MgAl2O4–MgFe2O4, Mg0.8Li0.2Fe2O4, Mg0.9Sn0.1Fe2O4, MgFe2O4–CeO2, MgCr2O4–TiO2, Zn2SnO4–LiZnVO4 and ZnCr2O4–K2CrO4 [1]. Finally, Perovskite-type oxides and composites based on perovskites have been used for humidity sensing elements too: NaH2PO4 doped BaTiO3, MnTiO3, Li+ doped Ca0.35Pb0.65TiO3, BaNbO3, LaFeO3, K+-doped nanocrystalline LaCo0.3Fe0.7O3 (La0.93K0.07Co0.3Fe0.7O3) and Sr-doped SmCrO3 (Sm0.90Sr0.10CrO3) [1].
Preparation techniques can considerably affect the physical, chemical and gas sensing properties of the metal oxide sensors. Developments of new preparative routes, as well as compositional variations, are two perspective approaches for the design of highly sensitive and selective gas sensor materials.Reference:
[1] T.A. Blanka, L.P. Eksperiandova, K.N. Belikov, Recent trends of ceramic humidity sensors development: A review. Sensors and Actuators B, 228 (2016) 416–442.
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Wang, Chao-Shen, i 王超聖. "PMMA/CNTs nanocomposite humidity sensing materials and flexible humidity sensors". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/33029471498745797070.
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碩士中國文化大學
應用化學研究所
95
This research discusses second separately the various subjects nanocomposite materials for humidity sensors application and flexible humidity sensor based on copolymer. First section: Nanocomposite materials for humidity sensors application In this study resistance type humidity sensors was fabricated by using nanocomposite materials. The methyl methacrylate(MMA) added with multi-walled carbon nanotubes(MWCNTs), ethanol(EtOH), potassium hydroxide(KOH) and azobisisobutyronitrile(AIBN) were used as the precursor solution of nanocomposite materials for humidity sensors application. The solution of nanocomposite materials were spin-coated on an alumina substrate with a pair of comb-like golden electrodes and then synthesized at 70 ℃ for 6 h in air for copolymerization, the humidity sensors were obtained. The thin films were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and Fourier transform infrared spectroscopy (FT-IR). We discussed the effect of amount of MWCNTs on electrical and humidity properties. Moreover, the KOH was added into PMMA/MWCNTs nanocomposite materials to increase sensitivity and linearity. 0.024 g MWCNTs and 0.01 ml of 10% KOH had better humidity sensing properties. Such as good linearity and sensitivity, fast response and recovery time, low hysteresis and stability. Second section: Flexible humidity sensors based on copolymer A novel flexible resistive-type humidity sensor was fabricated through in situ co-polymerization of methyl methacrylate (MMA) and [3-(methacrylamino)propyl] trimethyl ammonium chloride(MAPTAC) copolymer on a polyester (PET) substrate. The activation energy for conduction and the copolymer/substrate interface were used to explain the differences of humidity sensing characteristics of the sensors fabricated on a PET substrate, in comparison with those fabricated on an alumina substrate. The humidity sensing characteristics of the flexible humidity sensor could be comparable with the sensor fabricated on an alumina substrate. The flexible humidity sensor showed acceptable linearity (Y = -0.0327X + 5.9345; R2 = 0.9351) between logarithmic impedance (log Z) and RH in the range of 10-90%RH, average hysteresis (within 1.85%RH), good response (45 s) and recovery time (150 s), and long-term stability (120 days at least), measured at 1V, 1 kHz and 25 ℃.
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Chung, Hsiu-Ying, i 鍾秀瑩. "PEO humidity sensor". Thesis, 2001. http://ndltd.ncl.edu.tw/handle/80621715348402342100.
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碩士國立成功大學
材料科學及工程學系
89
The measurement and control of humidity is important in many application areas, including agriculture, medicine, food production, electronics etc. So it has generated a vast number of publications. The advantages of polymeric humidity sensor include high sensitivity, less sensitive to contamination and low cost. There are two main types of polymeric sensors: capacitance type and resistance type in which the sensing mechanisms are that the capacitance increases with increasing humidity and the resistance decreases with increasing humidity respectively. The materials of resistance type sensors are hydrophilic polymers that would be soluble in water. The PEO + LiClO4 thin films were coated on Al2O3 substrate with interdigital structure of Pt electrode by dipping method in this thesis. The effects of Li/O mole ratio on sensing property and microstructure were investigated. And one porous protection layer, HMDS film, was coated on the PEO film. The effects of adding protection layer on sensing property were also discussed. The results show that the relationship between resistance and humidity was linear for the Li/O=1/15, 1/10, 1/5 and 1/4 thin films measured with an impedance meter at the range between 10k and 200k Hz. In the same humidity environment, the resistance of PEO film with more added LiClO4 was lower. The response times were 13, 14, 15 and 17 secs for the Li/O=1/15, 1/10, 1/5 and 1/4 thin films respectively, as the humidity was raised from 20 to 55%RH. They were 75, 90, 200 and 210 secs for the Li/O=1/15, 1/10, 1/5 and 1/4 thin films as humidity was reduced from 100 to 65%RH. The Li/O=1/4 thin film had the best humidity sensitivity since part of LiClO4 was not dissociated in a low humidity and the LiClO4 was gradually dissociated to increase the number of Li ion as humidity was increased. Coating one porous HMDS protection on PEO thin film would increase the life double in high humidity environment and without affecting the sensing property. The response time of PEO film with porous protection layer would be extended. As the humidity was increased from 20 to 55%RH, the response time was 32 secs. In the desorption process, the response time increased from 210 to 3970 secs as humidity was decreased from 100 to 65%RH,. The thicknesses of one-layer, three-layer and five-layer thin films were 1∼3μm, 9μm and 18μm, respectively. The roughness decreased as film thickness increased. The thickness of film did not affect the sensing property and sensitivity, but the response time would be longer with the increased film thickness. The response times were 9 secs for one-layer and three-layer films, and 11 secs for five-layer film as humidity was raised from 20 to 55%RH, and 93, 104 and 161 secs for one-layer, three-layer and five-layer films, respectively, as humidity was reduced from 100 to 65%RH. 英文摘要………………………………………………………………..Ⅲ目錄……………………………………………………………………..Ⅴ 圖目錄………………………………………………………………...VIII 表目錄……………………………………………………………..…...XII 第一章 前言……………………………………………………………1 1-1 濕度感測簡介……………………………………………………1 1-2 濕度之表示方法…………………………………………………2 1-3 濕度感測器之要件………………………………………………3 1-4 濕度感測器之種類………………………………………………6 1-4-1 陶瓷濕度感測器……………………………………………6 1-4-2 電解質濕度感測器…………………………………………8 1-4-3 高分子濕度感測器…………………………………………8 1-4-3-1 電容式高分子濕度感測器……………………………9 1-4-3-2 電阻式高分子濕度感測器…………………………..10 第二章 理論基礎………………………………………………………19 2-1 聚氧化乙烯簡介………………………………………………...19 2-2 HMDS簡介…………………………………………………….19 2-3 高分子電解質…………………………………………………...20 2-4 PEO濕度感測器……………………………………………….20 第三章 實驗步驟………………………………………………………26 3-1 實驗流程……………………………………………………….26 3-2 實驗步驟……………………………………………………….27 3-2-1 試片的清洗………………………………………………...27 3-2-2 鍍液的配製………………………………………………..27 3-2-3 薄膜的製備………………………………………………..27 3-2-4 電性量測…………………………………………………..28 3-2-5 DSC分析………………………………………………….28 3-2-6 X光繞射分析……………………………………………..28 3-2-7 偏光顯微觀察……………………………………………..28 3-2-8 掃描式電子顯微鏡 ( SEM ) 觀察……………………….29 3-2-9 紅外線光譜 ( FTIR ) 分析………………………………29 3-2-10 拉曼光譜分析………………………………………….….29 第四章 結果與討論……………………………………………………32 4-1 Li/O莫耳數對感測性質與微結構之影響…………………….32 4-2 保護膜(HMDS)對濕度感測性質的影響…………………...…57 4-3 膜厚之影響…………………………………………………….70 第五章 結論……………………………………………………………77 參考文獻…………………..……………………………………………79
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LIN, YI-SHENG, i 林益生. "Ceramic humidity sensor:theory and fabrication". Thesis, 1986. http://ndltd.ncl.edu.tw/handle/15993112270494864498.
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Yu-Feng, Tsai, i 蔡裕豐. "Development of Automated Humidity Sensing". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/13720135305625654915.
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碩士聖約翰科技大學
電機工程系碩士班
102
With the accelerated pace of life, even the favorite watering plants cannot take into account, occasional business trip, traveling, visiting relatives also normal thing, ,and who is going home flowers tube? The flower and more than 80% growth problems are problems caused by the plants watered; finally Plants months, because water is not timely, long bad for almost withered flowers to beautify their homes. we will use Development of automated humidity sensing , which is a controller based on Arduino Mini Pro, using soil moisture sensors for monitoring soil moisture, temperature and humidity sensors by measuring the humidity control watering pumps, then the numerical results on the temperature and humidity display LCD, so as to achieve the purpose of automatic humidity sensing. Keywords: Arduino Mini Pro, soil moisture, LCD