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Vývoj MAC protokolu pro bezdrátové senzorové sítě / MAC Protocol for Wireless Sensor NetworksMichálek, Tomáš January 2016 (has links)
The work focuses on introduction to the topic of wireless sensor networks and brings readers the various aspects of problem solving in these networks. Work is closely focused on the energy performance when communicating between devices on a network and discusses the causes of excessive energy consumption. It also addresses the mechanisms for saving energy and is also engaged today protocols that its contribution to proposing solutions to problems. The author had also proposes an adapted protocol, based on lessons learned from previous theoretical sources.
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Automatiserad gatubelysning baserad på omgivningens ljusstyrka : Hur ljussensorteknik kan minska energianvändningen för utomhusbelysning / Automated street lighting based on the ambient lighting of the surroundings : How light sensor technology could reduce the energy usage for outdoor lightingMcCarthy, Tom January 2021 (has links)
Målet med arbetet var att undersöka hur enskilda gatlyktor skulle kunna utrustas med ljussensorteknik för att implementera automatisk dimring med syftet att sänka energianvändningen. Rapporter visar att väg- och gatubelysningen i Sverige stod för 626 GWh år 2016 samt att en stor del av ljuspunkterna fortfarande består av energikrävande högtrycksnatrium. Uppgifter visar även att energisnåla LED-armaturer blir alltmer förekommande som alternativ till högtryckslampor. Målet var att utveckla en prototyp för LED där funktionen bygger på att lysdioderna ska vara släckta när omgivningens ljusstyrka är hög och dynamisk dimras upp när omgivningens ljusstyrka minskar. Arbetet resulterade i en prototyp som fungerar tillfredsställande och efter uppsatta mål. Varje ljussensor läser in ett analogt mätvärde som tolkas av en mikrokontroller som sedan skickar en pulsbreddsmodulerad signal för styrning av lysdiodens belysningsnivå. Generellt visade arbetet att omfattande fortsatta studier behöver göras innan prototypen skulle kunna implementeras i verkligheten. Prototypen behöver även testas och kalibreras i utomhusmiljö med dagsljus. / The goal of this thesis was to investigate how individual streetlights could be equipped with light sensor technology to apply an automatic dimmer function with the purpose of reducing energy usage. Studies show that road and streetlights in Sweden accounted for 626 GWh during the year 2016 and that a large portion of the lights still consists of energy demanding high pressure sodium lamps. Reports also show that energy efficient LED is becoming more and more common as an alternative to high pressure lamps. The goal was to develop a prototype for LED lighting with the function to control the LED’s to be off when the surrounding light levels are high and to dynamically increase the output power when the surroundings light level go down. Each light sensor reads an analog value which is interpreted by a micro controller that sends a pulse width modulated signal to control the LED power output. The finished prototype worked satisfactory and according to the set goals of the thesis. Generally, the thesis showed that extensive research is needed before the prototype could be implemented in real life. The prototype also needs to be tested and calibrated in an outdoor environment with day light.
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High speed comprehensive two-dimenstional gas chromatography/mass spectrometrySamiveloo, Silverraji, Chemistry, Faculty of Science, UNSW January 2005 (has links)
The use of short columns, higher carrier gas velocity and fast temperature programs in Comprehensive Two-Dimensional Gas Chromatography coupled to Time-of- Flight Mass Spectrometry (GC x GC/TOFMS) technique is expected to increase the speed of analysis up to several orders of magnitude when compared to conventional gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS). A systematic evaluation of the GC x GC/TOFMS configuration for high-speed applications has received little attention in the literature. The feasibility of High Speed Comprehensive Two-Dimensional Gas Chromatography coupled to Mass Spectrometry (High speed GC x GC/MS) for complex mixtures has been investigated in this thesis. A particular focus was placed on comparing conventional scanning quadrupole mass spectrometry (qMS) with a newly available non-scanning time-of-flight instruments (TOFMS). Experiments were carried out using GC/qMS, GC x GC/qMS, GC/TOFMS and GC x GC/TOFMS both in normal (slow) and fast temperature rates coupled with high frequency modulation in GC x GC. Initially a complex mixture consists of 24 semivolatile compounds was used as the analyte for the above purpose. In the initial experiments parameters like acquisition rate and duty cycle for qMS were determined to evaluate the effectiveness of the instrument for fast analysis. The practical duty cycle value obtained for the qMS was only about 18 % for single ion and one compound at a dwell time of 10 ms in SIM mode. In both high-speed GC/qMS and high-speed GC x GC/qMS techniques only about 40 % of the components in the complex mixture were found to be well separated. The acquisition rate of scanning instruments like qMS is incompatible for fast eluting peaks in high speed GC. TOFMS that has an acquisition rate of several hundred spectra per second offer the potential to define the fast GC peaks accurately. The high quality spectra from TOFMS also enable deconvolution of coeluting peaks in the complex mixtures. The advantage of the automated spectral deconvolution is demonstrated for the identification of the coeluting peaks in the complex mixtures. Coelution of peaks is also observed with highspeed GC/TOFMS technique. The high-speed GC x GC/TOFMS was also tested with two different analyte system ??? A pesticide mixture and platformate (an aromatic mixture) to evaluate the suitability for high-speed analysis of complex mixtures. A poor resolution was observed for the pesticide mixture in the two-dimensional plane and it appeared, as there was nearly no orthogonal separation in the second dimension. The platformate mixture displayed a better two-dimensional separation. Chromatographic peak resolution is not really a primary requirement for locating and identifying the coeluting compounds in high-speed GC x GC/TOFMS technique. However, it was observed that the high-speed GC x GC/TOFMS too faced problem to unscramble the mass spectra of those compounds with similar structure and sharing the same unique masses.
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Evaluering av en Klockkorrigerare av klockpulsbreddBreisel, Jonas January 2008 (has links)
<p>Det här examensarbetet presenterar en evaluering av en <em>Klockkorrigerare av klockpulsbredd</em>. Den består främst av en korrigerare av klockpulsbredd (<em>Duty Cycle Corrector DCC</em>) och även en fördröjningslåst loop (<em>Delayed Locked Loop </em><em>DLL</em>). Det finns många olika korrigerare av klockpulsbredden designade förut, de två populäraste arkitekturerna då har varit enkel eller dubbel återkopplings loop. Den huvudsakliga skillnaden mellan dem är att enkel återkopplings loop använder sig av en öppen loop medan den dubbla varianten istället har en stängd loop. I det här projektet kommer en ny arkitektur att presenteras. Konceptet i den nya designen är att dela upp korrigeraren av klockpulsbredden i två delar, en korrigerare och en detektor. Detektorn får utsignalen från den fördröjningslåsta loopen som insignal och talar om för korrigeraren via två utsignaler ifall signalen behöver justeras. Detektorn är uppdelad i två likadana fördröjningselement, som båda är klockade av utsignalen och dess invers från den fördröjningslåsande loopen, fast i omvänd ordning. Det här gör det möjligt att avgöra om klockpulsbredden av signalen är över eller under 50 %. Om så är fallet kommer den att justeras av korrigeraren för att sedan skickas som insignal till den fördröjningslåsande loopen.</p><p>Abstraktionsnivån för det här projektet har varit systemnivå, detta för att kunna vara riktigt säker på att arkitekturen verkligen fungerar innan ett riktigt chip tillverkas. Tips på framtida projekt är att gå vidare till schemanivå för att slutligen göra en implementering och mätningar på ett riktigt chip av den här <em>Klockkorrigeraren av klockpulsbredd </em>när det är känt att idén fungerar.</p><p> </p>
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Evaluering av en Klockkorrigerare av klockpulsbreddBreisel, Jonas January 2008 (has links)
Det här examensarbetet presenterar en evaluering av en Klockkorrigerare av klockpulsbredd. Den består främst av en korrigerare av klockpulsbredd (Duty Cycle Corrector DCC) och även en fördröjningslåst loop (Delayed Locked Loop DLL). Det finns många olika korrigerare av klockpulsbredden designade förut, de två populäraste arkitekturerna då har varit enkel eller dubbel återkopplings loop. Den huvudsakliga skillnaden mellan dem är att enkel återkopplings loop använder sig av en öppen loop medan den dubbla varianten istället har en stängd loop. I det här projektet kommer en ny arkitektur att presenteras. Konceptet i den nya designen är att dela upp korrigeraren av klockpulsbredden i två delar, en korrigerare och en detektor. Detektorn får utsignalen från den fördröjningslåsta loopen som insignal och talar om för korrigeraren via två utsignaler ifall signalen behöver justeras. Detektorn är uppdelad i två likadana fördröjningselement, som båda är klockade av utsignalen och dess invers från den fördröjningslåsande loopen, fast i omvänd ordning. Det här gör det möjligt att avgöra om klockpulsbredden av signalen är över eller under 50 %. Om så är fallet kommer den att justeras av korrigeraren för att sedan skickas som insignal till den fördröjningslåsande loopen. Abstraktionsnivån för det här projektet har varit systemnivå, detta för att kunna vara riktigt säker på att arkitekturen verkligen fungerar innan ett riktigt chip tillverkas. Tips på framtida projekt är att gå vidare till schemanivå för att slutligen göra en implementering och mätningar på ett riktigt chip av den här Klockkorrigeraren av klockpulsbredd när det är känt att idén fungerar.
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High speed comprehensive two-dimenstional gas chromatography/mass spectrometrySamiveloo, Silverraji, Chemistry, Faculty of Science, UNSW January 2005 (has links)
The use of short columns, higher carrier gas velocity and fast temperature programs in Comprehensive Two-Dimensional Gas Chromatography coupled to Time-of- Flight Mass Spectrometry (GC x GC/TOFMS) technique is expected to increase the speed of analysis up to several orders of magnitude when compared to conventional gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS). A systematic evaluation of the GC x GC/TOFMS configuration for high-speed applications has received little attention in the literature. The feasibility of High Speed Comprehensive Two-Dimensional Gas Chromatography coupled to Mass Spectrometry (High speed GC x GC/MS) for complex mixtures has been investigated in this thesis. A particular focus was placed on comparing conventional scanning quadrupole mass spectrometry (qMS) with a newly available non-scanning time-of-flight instruments (TOFMS). Experiments were carried out using GC/qMS, GC x GC/qMS, GC/TOFMS and GC x GC/TOFMS both in normal (slow) and fast temperature rates coupled with high frequency modulation in GC x GC. Initially a complex mixture consists of 24 semivolatile compounds was used as the analyte for the above purpose. In the initial experiments parameters like acquisition rate and duty cycle for qMS were determined to evaluate the effectiveness of the instrument for fast analysis. The practical duty cycle value obtained for the qMS was only about 18 % for single ion and one compound at a dwell time of 10 ms in SIM mode. In both high-speed GC/qMS and high-speed GC x GC/qMS techniques only about 40 % of the components in the complex mixture were found to be well separated. The acquisition rate of scanning instruments like qMS is incompatible for fast eluting peaks in high speed GC. TOFMS that has an acquisition rate of several hundred spectra per second offer the potential to define the fast GC peaks accurately. The high quality spectra from TOFMS also enable deconvolution of coeluting peaks in the complex mixtures. The advantage of the automated spectral deconvolution is demonstrated for the identification of the coeluting peaks in the complex mixtures. Coelution of peaks is also observed with highspeed GC/TOFMS technique. The high-speed GC x GC/TOFMS was also tested with two different analyte system ??? A pesticide mixture and platformate (an aromatic mixture) to evaluate the suitability for high-speed analysis of complex mixtures. A poor resolution was observed for the pesticide mixture in the two-dimensional plane and it appeared, as there was nearly no orthogonal separation in the second dimension. The platformate mixture displayed a better two-dimensional separation. Chromatographic peak resolution is not really a primary requirement for locating and identifying the coeluting compounds in high-speed GC x GC/TOFMS technique. However, it was observed that the high-speed GC x GC/TOFMS too faced problem to unscramble the mass spectra of those compounds with similar structure and sharing the same unique masses.
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Customer focused development of a variable bent-axis pump/motor for open circuit hydrostatic transmissions, e.g. in hydraulic hybrid drivesHugosson, Conny, Kayani, Omer, Krieg, Mark 02 May 2016 (has links) (PDF)
The paper presents the development methodology of a hydrostatic pump/motor for use in Parker Hannifin’s advanced series hydraulic hybrid transmissions for medium and heavy duty commercial vehicles. With Parker’s established bent-axis pump/motor technology for heavy duty mobile applications as a basis, it describes the main stages of further development and qualification for demanding automotive main drive transmissions. Parker’s APQP based, customer focused product development model was employed for this development which resulted in the variable bent-axis pump/motor C24 for open circuit hydrostatic transmissions. Positive customer results from a large fleet of in-service refuse collection trucks and parcel delivery vans with Parker advanced hydraulic hybrid drive systems using C24 pumps/motors serve as evidence of Parker’s product development model effectiveness.
High reliability, good fuel economy, increased productivity and long brake life of the vehicles can directly be traced back to the streamlined, front-loaded and iterative development model.
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Modeling and Simulation Tools for Aging Effects in Scaled CMOS DesignJanuary 2014 (has links)
abstract: The aging process due to Bias Temperature Instability (both NBTI and PBTI) and Channel Hot Carrier (CHC) is a key limiting factor of circuit lifetime in CMOS design. Threshold voltage shift due to BTI is a strong function of stress voltage and temperature complicating stress and recovery prediction. This poses a unique challenge for long-term aging prediction for wide range of stress patterns. Traditional approaches usually resort to an average stress waveform to simplify the lifetime prediction. They are efficient, but fail to capture circuit operation, especially under dynamic voltage scaling (DVS) or in analog/mixed signal designs where the stress waveform is much more random. This work presents a suite of modelling solutions for BTI that enable aging simulation under all possible stress conditions. Key features of this work are compact models to predict BTI aging based on Reaction-Diffusion theory when the stress voltage is varying. The results to both reaction-diffusion (RD) and trapping-detrapping (TD) mechanisms are presented to cover underlying physics. Silicon validation of these models is performed at 28nm, 45nm and 65nm technology nodes, at both device and circuit levels. Efficient simulation leveraging the BTI models under DVS and random input waveform is applied to both digital and analog representative circuits such as ring oscillators and LNA. Both physical mechanisms are combined into a unified model which improves prediction accuracy at 45nm and 65nm nodes. Critical failure condition is also illustrated based on NBTI and PBTI at 28nm. A comprehensive picture for duty cycle shift is shown. DC stress under clock gating schemes results in monotonic shift in duty cycle which an AC stress causes duty cycle to converge close to 50% value. Proposed work provides a general and comprehensive solution to aging analysis under random stress patterns under BTI.
Channel hot carrier (CHC) is another dominant degradation mechanism which affects analog and mixed signal circuits (AMS) as transistor operates continuously in saturation condition. New model is proposed to account for e-e scattering in advanced technology nodes due to high gate electric field. The model is validated with 28nm and 65nm thick oxide data for different stress voltages. It demonstrates shift in worst case CHC condition to Vgs=Vds from Vgs=0.5Vds. A novel iteration based aging simulation framework for AMS designs is proposed which eliminates limitation for conventional reliability tools. This approach helps us identify a unique positive feedback mechanism termed as Bias Runaway. Bias runaway, is rapid increase of the bias voltage in AMS circuits which occurs when the feedback between the bias current and the effect of channel hot carrier turns into positive. The degradation of CHC is a gradual process but under specific circumstances, the degradation rate can be dramatically accelerated. Such a catastrophic phenomenon is highly sensitive to the initial operation condition, as well as transistor gate length. Based on 65nm silicon data, our work investigates the critical condition that triggers bias runaway, and the impact of gate length tuning. We develop new compact models as well as the simulation methodology for circuit diagnosis, and propose design solutions and the trade-offs to avoid bias runaway, which is vitally important to reliable AMS designs. / Dissertation/Thesis / Doctoral Dissertation Electrical Engineering 2014
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Abordagem inovadora com plasma de baixa temperatura para a deposição de filmes a partir do acetilacetonato de alumínio / Innovative low temperature plasma approach for deposition of films from aluminum acetylacetonateBattaglin, Felipe Augusto Darriba [UNESP] 06 July 2016 (has links)
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Previous issue date: 2016-07-06 / Filmes de alumina foram depositados a partir de uma nova metodologia de deposição a plasma, utilizando o pó de acetilacetonato de alumínio (AAA) como precursor. Em trabalho prévio do grupo, foi demonstrada a viabilidade do sputtering do AAA em plasmas de argônio para deposição de filmes finos. Os bons resultados obtidos estimularam o desenvolvimento do presente trabalho, visando o aperfeiçoamento da metodologia de deposição. Para isso, primeiramente foram investigados os efeitos da alteração da composição química da atmosfera do plasma, por meio da incorporação de diferentes proporções de oxigênio (O2%) ao argônio, tornando o processo um sputtering reativo. As deposições foram realizadas espalhando-se o pó do AAA no eletrodo inferior de um sistema de plasma acoplado capacitivamente. Argônio, oxigênio ou a mistura de ambos foram admitidos até a pressão de 11,0 Pa. O plasma foi gerado pela aplicação de sinal de radiofrequência (13,56 MHz, 150 W) ao eletrodo contendo o pó, mantendo-se o eletrodo superior, também utilizado como porta-amostras, aterrado. O tempo de deposição foi de 90 minutos. Investigou-se o efeito da O2%, variada de 0 a 100%, nas propriedades dos filmes. Na etapa subsequente, filmes foram depositados por sputtering reativo utilizando-se a condição considerada ótima na última etapa do trabalho (O2% = 25%) e mantendo-se as condições de pressão, potência e tempo de tratamento constantes. Todavia, ao invés de aterrar o porta-amostras, pulsos retangulares negativos (600 V, 2 kHz, 1-100% de ciclo de trabalho) foram aplicados, promovendo bombardeamento iônico durante a deposição por sputtering reativo. O efeito do ciclo de trabalho dos pulsos nas propriedades dos filmes foi avaliado. Na última etapa do trabalho, filmes foram depositados pelo sputtering reativo a partir de atmosferas contendo 25% de O2 e 75% de Ar e em condições mais energéticas que as utilizadas nos ciclos anteriores. Para tal um primeiro conjunto de amostras foi preparado mediante aquecimento resistivo do porta-amostras (410ºC) em plasma de menor pressão (4,0 Pa) que a anteriormente utilizada. O tempo de deposição foi de 28 minutos. Um segundo conjunto de amostras foi preparado associando-se bombardeamento iônico de mais alta energia, pela aplicação de pulsos de 1200 V (20% ciclo de trabalho) ao porta-amostras e também reduzindo a pressão da atmosfera de deposição para 4,0 Pa. Nesta condição, o tempo de deposição foi de 60 minutos. Comparou-se os resultados obtidos nestes experimentos aos equivalentes obtidos anteriormente. A espessura da camada foi obtida por meio de um perfilômetro e a taxa de deposição pela razão entre espessura e tempo de deposição. A composição elementar e a estrutura molecular dos filmes foram investigadas através das técnicas de espectroscopia de retroespalhamento Rutherford e de absorção no infravermelho, respectivamente. Difração de raios X foi utilizada para investigar a microestrutura dos filmes. Inspeções na morfologia e composição química das superfícies foram conduzidas associando microscopia eletrônica de varredura e espectroscopia de energia dispersiva. A rugosidade foi derivada de perfis topográficos adquiridos por perfilometria e microscopia de força atômica, enquanto a molhabilidade da superfície foi determinada através da técnica de gota séssil. De forma geral, os filmes depositados apresentaram contribuições de grupos orgânicos e de inorgânicos relacionados à alumina amorfa. O aumento da O2% afetou a cinética do plasma, proporcionando alterações na taxa de deposição (1 a 25 nm/min), rugosidade (1 a 13 nm) e redução na concentração de carbono proveniente do precursor, de 43% (O2% = 0%) para 6% (O2% = 100%). Com o aumento na O2% também foram encontradas variações na densidade dos filmes, dentro da faixa de 0,7 a 1,9 g/cm³, e tendência de queda no ângulo de contato de 53 para 17°. Por sua vez, quando o bombardeamento iônico é associado ao processo de deposição, altera-se a taxa de crescimento dos filmes (3 a 29 nm/min) e a morfologia da superfície, por meio do alívio de tensões internas e aumento da estabilidade física da estrutura resultante. A composição química não sofreu alterações, devido as condições do sputtering reativo permanecerem inalteradas nas deposições. Já a rugosidade e a molhabilidade da superfície apresentaram comportamentos condizentes com os resultados da morfologia e topografia. Quando condições mais energéticas de deposição foram empregadas, filmes óxidos com contaminações orgânicas foram obtidos para a deposição que empregou aquecimento resistivo do porta-amostras. Nesta condição, devido a redução na pressão total, mesmo com o aquecimento resistivo a taxa de deposição foi maior (~ 6 vezes) que aquela obtida sem aquecimento. Para a situação em que bombardeamento iônico de alta energia foi utilizado, estrutura e composição química similares ao do composto precursor foram obtidas. Os resultados são interpretados em termos dos processos predominantes em cada uma das metodologias empregadas. / Alumina films were deposited by a new plasma deposition method using aluminum acetylacetonate (AAA) powder as precursor. In a previous study by our group, the feasibility of AAA sputtering in argon plasmas for thin films deposition was demonstrated. The good results obtained stimulated the development of this work, aiming at the improvement of the deposition methodology. For this, the effects of modifications in the chemical composition of the plasma atmosphere were first investigated, through the use of different oxygen to argon proportions (O2%), making the process a reactive sputtering. The depositions were performed by spreading the AAA powder on the lower electrode of a capacitively coupled plasma system. Argon, oxygen or a mixture of both were admitted up to a pressure of 11.0 Pa. Application of radiofrequency power (13.56 MHz, 150 W) to the powder covered electrode generated the plasma, keeping the upper electrode, also used as a sample holder, grounded. Deposition times of 90 minutes were used. The effects of varying the oxygen proportion from 0 to 100%, on the film properties were studied. In the subsequent stage, films were deposited by reactive sputtering using the condition considered best in the last stage of the work (O2% = 25%) and keeping the pressures, power and treatment time constant. Instead of grounding the sample holder, however, negative rectangular pulses (600 V, 2 kHz, 1-100% duty cycle) were applied, promoting ion bombardment during the deposition by reactive sputtering. The influence of the pulse duty cycle on the properties of the films was evaluated. In the last study stage, films were deposited by reactive sputtering from atmospheres containing 25% O2 and 75% Ar and with more energetic conditions than those used in previous cycles. For such, a first samples set was prepared by resistive heating of the sample holder (410ºC) in a lower plasma pressure (4.0 Pa) than that previously used. The deposition time was 28 minutes. A second samples set was carried out associating ion bombardment of the highest energy, by the application of the 1200 V pulses (20% duty cycle) to the sample holder and also reducing the pressure of the deposition atmosphere to 4.0 Pa. In this condition, the deposition time was 60 minutes. The results obtained in these experiments were compared to the equivalent obtained previously. Film thickness was obtained by profilometry and the deposition rate calculated as the ratio between the thickness and deposition time. Elemental composition and molecular structure of the films were investigated using Rutherford backscattering and infrared absorption spectroscopy, respectively. X-ray diffraction was used to investigate the microstructure of the films. Surface morphology and chemical composition were studied using scanning electron microscopy and energy dispersive spectroscopy. Roughness was derived from topographic profiles acquired by profilometry and atomic force microscopy, whereas the surface wettability was determined using the sessile drop technique. In general, the deposited films showed contributions from organic and inorganic groups related to amorphous alumina. Increasing in O2% affected the plasma kinetics, providing changes in deposition rate (1 to 25 nm/min), roughness (1 to 13 nm) and reduction in the carbon concentration coming from the precursor, 43% (O2% = 0%) to 6% (O2% = 100%). With the increase in O2% it was also found variations in the films density, within the range from 0.7 to 1.9 g/cm³, and a downward trend in the contact angle of 53 to 17°. In turn, when the ion bombardment is associated with the deposition process, changes are found in the deposition rate (3 to 29 nm/min) and the surface morphology, through the internal strains relief and increased in the physical stability of resulting structure. The chemical composition did not suffer changes because the conditions of the reactive sputtering remain unchanged in the depositions. The roughness and surface wettability showed behavior consistent with the morphology and topography results. When more energetic conditions were employed, oxide films with organic contaminations were obtained for the deposition which applied the sample holder resistive heating. In this condition, due to the reduction in the total pressure, even with the resistive heating the deposition rate was higher (~ 6 times) than that obtained without heating. For the situation which high-energy ion bombardment was used, the structure and chemical composition similar to the precursor were obtained. The results are interpreted in terms of the prevailing processes in each of the methodologies applied.
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Design and Implementation of Large-Scale Wireless Sensor Networks for Environmental Monitoring ApplicationsYang, Jue 05 1900 (has links)
Environmental monitoring represents a major application domain for wireless sensor networks (WSN). However, despite significant advances in recent years, there are still many challenging issues to be addressed to exploit the full potential of the emerging WSN technology. In this dissertation, we introduce the design and implementation of low-power wireless sensor networks for long-term, autonomous, and near-real-time environmental monitoring applications. We have developed an out-of-box solution consisting of a suite of software, protocols and algorithms to provide reliable data collection with extremely low power consumption. Two wireless sensor networks based on the proposed solution have been deployed in remote field stations to monitor soil moisture along with other environmental parameters. As parts of the ever-growing environmental monitoring cyberinfrastructure, these networks have been integrated into the Texas Environmental Observatory system for long-term operation. Environmental measurement and network performance results are presented to demonstrate the capability, reliability and energy-efficiency of the network.
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