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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
91

Natural analogues for geological carbon storage

Shu, Yutong January 2018 (has links)
In CO2 storage sites, seal has a vital role in inhibiting migration of the supercritical CO2 to other geological strata. The major difficulties in studying seals include two aspects: lack of available samples (especially for saline aquifers), and the difficulty to study over geological time and spatial scales. The analysis of natural analogue has been chosen to overcome these difficulties. Hydrocarbon fields are used to investigate the pore throat radii, which is the major factor for capillary sealing of caprocks, using newly established statistics model. Natural CO2 springs at Green River, Utah are used to study how the long-term CO2 charge triggers chemical reactions and migration in shales. One of the major sealing mechanism of caprocks is capillary sealing. Pore throat radius, as the main factor to decide the capillary sealing, has been investigated in this study. As an alternative to the traditional method of mercury injection porosimetry, a statistical model for effective pore throat radii determination has been established. The cumulative percentage and the probability distribution of the effective pore throat radii of the shale caprocks in the UK North Sea oil fields are obtained, which would be used as a reference for the saline aquifers in CO2 storage siting in the future work. Monte Carlo simulation is utilised to get the distribution of the effective pore throat radii. The cumulative distribution from this study has been compared with the distribution by Yang and Aplin (1998). The distribution by the statistical model enables to narrow down the range of effective pore throat radii to 37nm~1700nm, and help to make a better prediction on the pore throat radii. The correlation between the controlling factors of faulting, burial depth, caprock thickness and the pore throat radii have been examined. Good correlation between the depth less than 3000m and the effective pore throat radii indicates clay diagenesis should be the major factor for shallowly buried caprocks. Faulting and caprock thickness present no significant correlation with the effective pore throat radii. Crystal Geyser is used as an ideal natural analogue to study the Mancos Shale alteration. The interacted fluid that deposited travertine is important for the study. Hence, carbonate veins and reduction zones that associated with the activity of the main fault are used as records of the geochemistry of the paleo-fluid, the features of which are compared to the present spring water. The result shows the paleo-fluid was much more saline than the present fluid, with greater flow-rate. The decreased flow-rate might be owing to the self-healing of the fault during the time. Mancos shales outcropped in the hanging wall of the Little Grand Wash fault were sampled to investigate on the alterations triggered by the CO2-charged fluid from the fault and fractures. The result shows the alteration radius of the Mancos has limited within the distance of 20m away from the fault. CO2-rich fluid could interact with deformed shale (both dissolution and precipitation might happen), but no evidence shows the intact Mancos has been altered. The calcite cements in Mancos derived from CO2 sequestration could reach up to 27% (%weight of the whole rock) at 15m away from the fault. The conclusion facilitates the carbon storage siting criteria by Chadwick et al., (2009), who proposed the cautionary thickness of the caprock to be 20m.
92

Rodas compactadoras e aterradoras na qualidade de acabamento de semeadura direta

Soares, Tatiane Aparecida [UNESP] 18 December 2009 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:31:02Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-12-18Bitstream added on 2014-06-13T19:19:56Z : No. of bitstreams: 1 soares_ta_dr_jabo.pdf: 1734974 bytes, checksum: 8d54e9e4e3cc5af52880f71df0be7d31 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O plantio direto consiste em um sistema de manejo conservacionista da produção agrícola, que promove a melhoria das condições físicas, químicas e biológicas do solo. Desta forma, o objetivo do presente trabalho foi a avaliação de sistemas de acabamento de semeadura existentes no mercado nacional, utilizados em semeadoras de precisão para plantio direto, assim como novas propostas, levando em conta fatores que afetam a germinação das sementes e a emergência das plântulas no campo. O experimento foi conduzido na Fazenda Experimental do Instituto Agronômico do Paraná – IAPAR, em Londrina, utilizando-se o delineamento experimental em blocos ao acaso, com oito tratamentos e quatro repetições para a cultura do feijão e três repetições para a cultura da soja. Os tratamentos foram constituídos de oito sistemas de acabamento de semeadura, dotados de componentes com e sem aterramento, sistemas de controle de profundidade de sementes e rodas compactadoras. Foram avaliadas variáveis do solo, das sementes e parâmetros de desempenho das unidades semeadoras. Conclui-se que os discos aterradores melhoram os resultados das unidades de semeadura, beneficiando a operação em diferentes aspectos e aumentando a emergência. As rodas controladoras de profundidade paralelas melhoram os resultados dos discos aterradores, inclusive os de emergência. As rodas compactadoras lisas não são indicadas, pois promovem problemas de selamento superficial. As rodas compactadoras em “V” apresentaram bons resultados, mas as rodas compactadoras com garras e sulcos internos tendem a ser melhores / No-till is a system of conservation management of agricultural production, which promotes the improvement of the physical, chemical and biological soil conditions. Thus, the purpose of this study was to evaluate the systems finish seeding on the market in Brazil, used in precision seeders for no-till planters, as well as new proposals, considering factors that affect seed germination and emergence seedlings in the field. The experiment was conducted at the Experimental Farm of the Agronomic Institute of Paraná – IAPAR, in Londrina, using the randomized block planning with eight treatments and four repetitions for the cultivation of beans and three repetitions for soybean. Treatments consist of eight systems of finish seeding that having components with and without ground finish systems, depth of seed and compactor wheels. Was evaluated soil variables, seeds variables and performance parameters of seeding units. It was concluded that soil cover disks improve the seeding units performance, benefit the operation in different aspects and increasing the emergency. Parallel depth controller wheels improve results of soil cover discs, including the emergency. The flat compactor wheels are not recommended, because they promote soil surface sealing problems. The wheels in V had good results, but the wheels with grip and internal ridges tend to be better
93

Análise da eficácia dos dispositivos de vedação e drenagem utilizados em fundações permeáveis de barragens de terra / Analysis of effectiveness of devices for sealing and drainage used on pervious foundations of earth dams

Antonio Gilberto Simões de Oliveira 07 November 2008 (has links)
A construção de barragens de terra sobre formações geológicas permeáveis constitui um dos mais sérios desafios da engenharia de barragens. Neste tipo de projeto, as principais variáveis que devem ser analisadas são a vazão, o gradiente de saída e a subpressão, todas decorrentes da percolação de água pela fundação. Este trabalho apresenta um estudo acerca da eficácia dos dispositivos de controle da percolação a partir de análises paramétricas realizadas em uma barragem típica utilizando o método dos elementos finitos através do programa SEEP/W. Nestas análises foram variadas as características dos dispositivos e a anisotropia hidráulica do maciço de fundação. Verificou-se que a trincheira de vedação parcial é extremamente ineficaz, que o tapete impermeável à montante apresenta cerca de 60% de eficácia para relações entre o comprimento do tapete e a largura da base da barragem da ordem de 1,70 e que a trincheira de vedação total associada aos dispositivos de drenagem constitui a solução mais eficaz no controle das variáveis vazão, gradiente de saída e subpressão. / The construction of earth dams on pervious geologic formations constitutes one of the most serious problems of the engineering of dams. In this type of project, the main variables that must be analyzed are the discharge, the exit gradient and the uplift pressure, all decurrent ones of the water seepage for the foundation. This work presents a study on the effectiveness of devices of control of the seepage from parametric analyses carried through in a typical dam using the method of the finite elements through program SEEP/W. In these analyses the characteristics of the devices and the hydraulic anisotropy of the foundation mass had been varied. It was verified that the cut-off trench of partial is extremely inefficacious, that the impermeable blanket to the sum presents about 60% of effectiveness for relations between the blanket length and the width of the base of the dam of the order of 1.70 and that the cut-off trench of associated to the drainage devices constitues the solution most effective in the control of the variables discharge, exit gradient and the uplift pressure.
94

INVESTIGATION OF AN AXIAL FLOW ROTARY VALVE SEAL

Stieha, Joseph K. 01 January 2017 (has links)
This thesis investigates potential materials to be used in the rotary sealing industry that provide low power loss and minimize cost. The studied rotary valve utilizes slots that act as timing valves to allow for flow axially, through the seal face, at particular times within a heat pump cycle. This investigation examines various combinations of multiple PTFE materials, plastics, and soft metals that have been proven to provide low friction coefficients. Leakage and wear requirements are stated for the future use of the rotary valve and are used to determine the effectiveness of sealing the fluid while examining the power loss. In conclusion, the study finds the combination of a modified PTFE stationary ring and Aluminum Bronze rotating face to provide the lowest power loss. Numerical analysis was completed to verify the lubrication regime to be partial lubrication and was also used to investigate geometry changes and impact on the power loss.
95

Experimental Study of High-Temperature Range Latent Heat Thermal Energy Storage

Wickramaratne, Chatura 14 November 2017 (has links)
Among all thermal energy storage (TES) systems, latent heat thermal energy storage (LHTES) attracts high interest due to its high energy density and high exergetic efficiency. Due to the high enthalpy of fusion and low cost, inorganic salts are becoming popular as phase change materials and are used as the storage media in LHTES systems. The main drawbacks for the inorganic salts are their low thermal conductivity and high reactivity above 500°C. Therefore, designing a cost-effective containment at these conditions with longevity is a challenge. Macro-encapsulation of the PCM is one way to solve both the PCM containment issue as well as the low thermal conductivity problem. However, finding a practically viable encapsulation technique is a challenge especially for temperatures above 500°C. In the present study, encapsulation techniques were investigated for two temperature ranges; 500°C – 600°C and 600°C above. Metallic encapsulation was adopted for the 500°C – 600°C temperature. Commercially available, low-cost carbon-steel tubes were used, and the encapsulation shape was cylindrical. A 200µm coating of Ni was applied to strengthen the corrosion resistance. For temperatures above 600°C, a novel approach involving the use of ceramic materials was investigated for encapsulating chloride based PCMs. Low-cost ceramics with excellent thermal and chemical stability under molten-salt conditions were identified as the encapsulants. The influence of sintering temperature on the reactivity of feldspar, ball clay, kaolin and the mixture thereof with molten sodium chloride was investigated. The results were used to develop an optimum ceramic capsule fabrication procedure, using a green ceramic body followed by sintering at 1190°C. An innovative sealing process of in-situ layered eutectic formation was introduced. Sealing was performed at a temperature above the eutectic melting point of the salt mixture but below the individual melting points of each salt. The fabricated capsule survived more than 500 thermal cycles without showing degradation in its thermo-physical properties. Alumina (99%) based capsule containing NaCl-KCl was tested successfully for 1000 thermal cycles with a PCM weight loss of less than 5%. A lab-scale setup was designed and constructed to test an industry scalable LHTES system suitable for supplementing heat to a steam-powered cycle. Metallic cylindrical capsules were used with a eutectic of sodium sulfate (Na2SO4) and potassium chloride (KCl), which melts at 515°C, as the PCM for energy storage. This system was modeled and validated with experimental measurements. The calculated ratio of exergy to energy efficiency was around 89% (for 380-535°C). Flow irregularities were found due to a bend in the flow channel. Therefore, flow conditioners were investigated. A modified system with the flow conditioners and radiation shields showed 98% exergy to energy efficiency ratio (for 495-535°C). The overall efficiency of the system, however, was found to be low due to the heat losses from the storage tank. Finally, a novel design of a TES system using spherical capsules is proposed with additional enhancement gained from the experimental work on the lab-scale LHTES system. The innovation of this design lies in the manufacturing process to forms multiple spherical capsules using sheet metals. The adoptability of this technique for higher or lower temperature LHTES applications depends on the properties of the selected sheet metal. Any formable sheet metal can be used depending on the compatibility with PCM and HTF.
96

Sellado dentinario inmediato y resin coating como técnicas de protección dentinaria

Maestri Fernández-Concha, Renato Stefano 14 December 2018 (has links)
El objetivo de esta revisión fue recopilar información sobre las técnicas de Sellado Dentinario Inmediato (SDI) y Resin Coating (RC) como incremento de las fuerzas de adhesión. Asimismo, el siguiente trabajo describe las principales características de cada técnica, así como sus ventajas y desventajas. / The aim of this review was to collect information about the Immediate Dental Sealing (IDS) and Resin Coating (RC) techniques to achieve an increase in bond strengths. Also, this article describes its main characteristics as well as advantages and disadvantages. / Tesis
97

Optimal Enclosure Doors - Design and Evaluation / Optimala tätningslösningar för utomhusskåp - konstruktion och utvärdering

Karlsson, Tobias January 2008 (has links)
<p>Within the telecommunication business there are a lot of different hardware designs made for outside locations. Many of these outdoor products contain sensitive electronic equipment and all of these designs must be able to function in extreme environments. They might be mounted on the ground, on a wall or on masts at varying altitudes. They need to be enclosed and protected against blizzards, moisture, sandstorms, earthquakes, dust and similar contaminations or nature phenomena in order to assure a reliable and proper function of the device.</p><p>To delimit this thesis the focus is completely set on outdoor enclosures with hinged doors. The sealing solution for the enclosure door is crucial because it is the weakest link in the environmental protection. The aim with this thesis is to find a robust yet versatile sealing solution for Ericsson outdoor cabinets.</p><p>The sealing solution does not only concern the gasket design, it is in fact the entire principle when it comes to seal the door. Interesting features are choice of locking system, the positions of the hinges and other details which might affect the sealing of the enclosure door.</p><p>The project includes the whole product development process from pre-study to concept development and evaluation of proposal design. The pre-study contain extensive literature research, benchmark and a state of the art investigation. A number of concepts are generated, screened, compared and ranked with systematic concept development methods. At last, one final concept is selected for further development. The chosen sealing solution is refined and a functional model is made. A simple prototype of the sealing solution is designed, manufactured and tested to validate the functionality of the concept.</p><p>An economical analysis is performed in order to approximate the manufacturing cost of the gasket proposed in the sealing solution and to compare the unit price for different batch sizes. The water intrusion test indicates that the solution seems promising and that the result is a simple and robust sealing solution that easily can be implemented on various enclosure types.</p> / <p>Inom telecom-industrin finns det många typer av hårdvara som är konstruerad för att placeras utomhus. Många av dessa utomhusprodukter innehåller känslig elektronisk utrustning och alla dessa konstruktioner måste fungera i extrema miljöer. De kan monteras på marken, på väggar eller på master på olika höjder. De måste vara täta och skyddade mot snöstormar, fukt, sandstormar, jordbävningar, damm och liknande föroreningar eller naturfenomen för att säkerställa en tillförlitlig och korrekt funktion hos anordningen.</p><p>För att begränsa detta examensarbete är fokus helt inställt på utomhusskåp med gångjärnsupphända dörrar. Tätningslösningen för skåpdörren är kritisk eftersom den utgör den svagaste länken i väderskyddet. Målet med detta examensarbete är att hitta en robust men samtidigt mångsidig lösning för Ericssons utomhuskabinet.</p><p>Tätningslösningen handlar inte enbart om packningsutformningen utan den täcker faktiskt hela principen för hur dörren tätas. Intressanta delar är val av lås-lösning, placeringen av gångjärnen och andra detaljer som kan påverka tätningen av skåpsdörren.</p><p>Projektet behandlar hela produktutvecklingsprocessen från förstudie till konceptutveckling och utvärdering av föreslagen konstruktion. Förstudien innehöll en utförlig litteraturstudie, en ”benchmark” och en ”state of the art” undersökning. Ett antal koncept genererades, kontrollerades, jämfördes och rankades med hjälp av systematiska konceptutvecklingsmetoder. Till sist valdes ett slutgiltigt koncept ut för vidare utveckling. Den valda tätningslösningen förfinades och en funktionsmodell byggdes. En enkel prototyp av tätningslösningen konstruerades, tillverkades och testades för att validera funktionen hos konceptet.</p><p>En ekonomisk analys utfördes för att uppskatta tillverkningskostnaden för den föreslagna packningen i tätningslösningen och för att jämföra enhetspriset för olika seriestorlekar. Ett vattentäthetstest visar att lösningen verkar lovande och att resultatet är en enkel och robust tätningslösning som på ett enkelt sätt kan implementeras på olika skåpstyper.</p>
98

Prediction of grout spread and sealing effect

Eriksson, Magnus January 2002 (has links)
No description available.
99

Förseglingsegenskaper hos pappersförpackningar med konventionell plast och bioplast / Sealability of paper packaging containing conventional plastics and bioplastics

Karlsson, Sandra January 2012 (has links)
Pappersbaserade förpackningar är ett område som växer snabbt. För att hålla ihop en förpackning och skydda dess innehåll är det nödvändigt mednågon form av förslutningsystem. I projektet har förslutningar i form av varmförseglingar studerats för olika sorters förpackningsmaterial. Vidvarmförsegling pressar två varma metallbackar ihop materialen vilket gör att en försegling bildas mellan dem. Hur stark en försegling blir beror påmaterialegenskaper och på de parameterinställningar som används vid försegling. Vilken analysmetod och vilka inställningar proverna analyseratsmed påverkar de resultat som erhålls. Studien inkluderade flexibla material för applikationer inom medicin och livsmedel samt styva material vilkavar svåra att analysera med de analysmetoder som fanns tillgängliga. Förseglingar gjordes i laboratoriemiljö och i kommersiellatillverkningsmaskiner för att undersöka om dessa kan jämföras. Experimenten visar bland annat att förseglingsegenskaperna varierar beroende påtyp av plast och papper, materialets tjocklek och ytvikt. Förseglingsstyrkan är också olika beroende på om den testas längs eller tvärs materialetstillverkningsriktning. Genom en stor mängd analyser har en strategi för hur olika material bör utvärderas arbetats fram. / Paperboard and paper based solutions are of rapidly increasing interest to the packaging industry. Packaging needs a sealing system to keep theproduct inside safe. One common type of sealing is heat sealing, i.e. the materials are placed between two hot sealing bars which are closedtogether to form a seal. The strength of such seals depend on the properties of the material and the settings during sealing. The test method and thesettings used when analysing samples do also influence the results. This study of sealing properties includes flexible material for medicalapplications and materials used in food applications, as well as stiff and thick materials used in food applications which are harder to analyse usingcurrent methods. Sealing properties are for some materials compared between seals made in commercial packaging machines and seals made in thelaboratory. The results from this study show that sealability is dependent on 1) what kind of paper and what kind of plastic are used; 2) thicknessand weight of the material; and 3) whether the test is performed in or cross machine direction. Finally, a method is proposed on how to evaluatedifferent kinds of materials based on data generated by this study.
100

Optimal Enclosure Doors - Design and Evaluation / Optimala tätningslösningar för utomhusskåp - konstruktion och utvärdering

Karlsson, Tobias January 2008 (has links)
Within the telecommunication business there are a lot of different hardware designs made for outside locations. Many of these outdoor products contain sensitive electronic equipment and all of these designs must be able to function in extreme environments. They might be mounted on the ground, on a wall or on masts at varying altitudes. They need to be enclosed and protected against blizzards, moisture, sandstorms, earthquakes, dust and similar contaminations or nature phenomena in order to assure a reliable and proper function of the device. To delimit this thesis the focus is completely set on outdoor enclosures with hinged doors. The sealing solution for the enclosure door is crucial because it is the weakest link in the environmental protection. The aim with this thesis is to find a robust yet versatile sealing solution for Ericsson outdoor cabinets. The sealing solution does not only concern the gasket design, it is in fact the entire principle when it comes to seal the door. Interesting features are choice of locking system, the positions of the hinges and other details which might affect the sealing of the enclosure door. The project includes the whole product development process from pre-study to concept development and evaluation of proposal design. The pre-study contain extensive literature research, benchmark and a state of the art investigation. A number of concepts are generated, screened, compared and ranked with systematic concept development methods. At last, one final concept is selected for further development. The chosen sealing solution is refined and a functional model is made. A simple prototype of the sealing solution is designed, manufactured and tested to validate the functionality of the concept. An economical analysis is performed in order to approximate the manufacturing cost of the gasket proposed in the sealing solution and to compare the unit price for different batch sizes. The water intrusion test indicates that the solution seems promising and that the result is a simple and robust sealing solution that easily can be implemented on various enclosure types. / Inom telecom-industrin finns det många typer av hårdvara som är konstruerad för att placeras utomhus. Många av dessa utomhusprodukter innehåller känslig elektronisk utrustning och alla dessa konstruktioner måste fungera i extrema miljöer. De kan monteras på marken, på väggar eller på master på olika höjder. De måste vara täta och skyddade mot snöstormar, fukt, sandstormar, jordbävningar, damm och liknande föroreningar eller naturfenomen för att säkerställa en tillförlitlig och korrekt funktion hos anordningen. För att begränsa detta examensarbete är fokus helt inställt på utomhusskåp med gångjärnsupphända dörrar. Tätningslösningen för skåpdörren är kritisk eftersom den utgör den svagaste länken i väderskyddet. Målet med detta examensarbete är att hitta en robust men samtidigt mångsidig lösning för Ericssons utomhuskabinet. Tätningslösningen handlar inte enbart om packningsutformningen utan den täcker faktiskt hela principen för hur dörren tätas. Intressanta delar är val av lås-lösning, placeringen av gångjärnen och andra detaljer som kan påverka tätningen av skåpsdörren. Projektet behandlar hela produktutvecklingsprocessen från förstudie till konceptutveckling och utvärdering av föreslagen konstruktion. Förstudien innehöll en utförlig litteraturstudie, en ”benchmark” och en ”state of the art” undersökning. Ett antal koncept genererades, kontrollerades, jämfördes och rankades med hjälp av systematiska konceptutvecklingsmetoder. Till sist valdes ett slutgiltigt koncept ut för vidare utveckling. Den valda tätningslösningen förfinades och en funktionsmodell byggdes. En enkel prototyp av tätningslösningen konstruerades, tillverkades och testades för att validera funktionen hos konceptet. En ekonomisk analys utfördes för att uppskatta tillverkningskostnaden för den föreslagna packningen i tätningslösningen och för att jämföra enhetspriset för olika seriestorlekar. Ett vattentäthetstest visar att lösningen verkar lovande och att resultatet är en enkel och robust tätningslösning som på ett enkelt sätt kan implementeras på olika skåpstyper.

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