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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.
211

. Nanostructuration de la muscovite : Une étude par diffraction d'électrons lents en mode oscillant.

DOREL, Sébastien 17 July 2000 (has links) (PDF)
Nous avons étudié la structure de la surface de mica muscovite clivée à l?air par diffraction d?électrons lents en mode oscillant. Cette nouvelle méthode d?analyse structurale, que nous avons développée à partir d?un système optique standard de résolution conventionnelle, possède une grande sensibilité. En outre, elle permet de former des images de diffraction entières sans procéder, comme le font les autres diffractomètres à haute résolution, à une reconstitution ligne par ligne. Cette caractéristique permet aussi de réaliser des acquisitions d?image qui sont corrélées temporellement avec une excitation extérieure, ce qui rend possible toute une gamme d?expériences nouvelles, notamment dans le cadre de la réponse thermodynamique d?une surface au voisinage d?une transition de phase. Notre étude de la surface du mica muscovite par diffraction d?électrons lents en mode oscillant a permis pour la première fois de mettre en évidence la nanostructuration de sa couche superficielle. Notre interprétation est que lors du clivage, la surface du mica s?auto-organise pour former un arrangement d?îlots à l?intérieur desquels les atomes de potassium occupent les sites réguliers du cristal. Les îlots sont soit de taille définie soit séparés par une distance définie. Dans les zones interstitielles qui les séparent, les ions potassium, en concentration beaucoup plus faible, formeraient une couche amorphe.
212

Establishing low-energy x-ray fields and determining operational dose equivalent conversion coefficients

Larsson, Ylva January 2008 (has links)
<p>Reference radiation fields for x-ray qualities are described by the International Organization of Standards (ISO). This study describes the procedure to establish nine different low energy X-ray qualities at the national metrology laboratory, Swedish Radiation Protection Authority, following the document ISO 4037. Measurements of tube voltage, half-value layer, mean energy and spectral resolution have been performed for qualities N-15, N-20, N-25, N-30, N-40, L-20, L-30, L-35 and L-55. Furthermore, dose equivalent conversion coefficients for operational quantities ambient dose equivalent, personal dose equivalent and directional dose equivalent have been calculated by folding the mono-energetic conversion factors with measured spectral distributions of the x-ray qualities. The spectral distributions were unfolded from pulse-height distributions to photon distributions using simulated data of the semi-conductor detector used for measurements, generated with the Monte Carlo code PENELOPE.</p>
213

Lågenergihus : Att bygga energisnålt

Karlsson, Camilla January 2010 (has links)
<p>A large proportion of the energy consumption is in the building industry and a large part goes to heating our homes and premises. In the developing countries' development now threatens the large consumption of energy in our earth's climate. It is in the West world that we must be good role models in terms of energy efficiency. One solution to reduce energy consumption for heating of buildings may be to continue to build low energy houses and passive houses, but it is also about rebuilding the buildings that currently have high energy consumption such as the old Million program Houses. These buildings will be standing many years and their energy consumption will not diminish over time by itself and energy prices will certainly not diminish in the future. This report will touch on the subject mainly new construction, how to build an energy efficient building, but a smaller portion will touch on the subject rebuilding, particularly the solutions that can fit into economic terms.</p><p><strong> </strong></p><p>Calculations have been done to link the concepts of U<sub>mean</sub> of a building and its energy consumption. This was done by calculations using an Excel document created in connection with this thesis.</p><p> </p><p>The buildings and architectural solutions addressed in this report will focus on apartment buildings where the partner of this thesis is Eskilstuna Municipal Building. Eskilstuna Municipality Property manages buildings and premises to Eskilstuna Municipality, but also owns their own house with rental apartments.<strong></strong></p>
214

Establishing low-energy x-ray fields and determining operational dose equivalent conversion coefficients

Larsson, Ylva January 2008 (has links)
Reference radiation fields for x-ray qualities are described by the International Organization of Standards (ISO). This study describes the procedure to establish nine different low energy X-ray qualities at the national metrology laboratory, Swedish Radiation Protection Authority, following the document ISO 4037. Measurements of tube voltage, half-value layer, mean energy and spectral resolution have been performed for qualities N-15, N-20, N-25, N-30, N-40, L-20, L-30, L-35 and L-55. Furthermore, dose equivalent conversion coefficients for operational quantities ambient dose equivalent, personal dose equivalent and directional dose equivalent have been calculated by folding the mono-energetic conversion factors with measured spectral distributions of the x-ray qualities. The spectral distributions were unfolded from pulse-height distributions to photon distributions using simulated data of the semi-conductor detector used for measurements, generated with the Monte Carlo code PENELOPE.
215

Low-Power High-Performance Ternary Content Addressable Memory Circuits

Mohan, Nitin January 2006 (has links)
Ternary content addressable memories (TCAMs) are hardware-based parallel lookup tables with bit-level masking capability. They are attractive for applications such as packet forwarding and classification in network routers. Despite the attractive features of TCAMs, high power consumption is one of the most critical challenges faced by TCAM designers. This work proposes circuit techniques for reducing TCAM power consumption. The main contribution of this work is divided in two parts: (i) reduction in match line (ML) sensing energy, and (ii) static-power reduction techniques. The ML sensing energy is reduced by employing (i) positive-feedback ML sense amplifiers (MLSAs), (ii) low-capacitance comparison logic, and (iii) low-power ML-segmentation techniques. The positive-feedback MLSAs include both resistive and active feedback to reduce the ML sensing energy. A body-bias technique can further improve the feedback action at the expense of additional area and ML capacitance. The measurement results of the active-feedback MLSA show 50-56% reduction in ML sensing energy. The measurement results of the proposed low-capacitance comparison logic show 25% and 42% reductions in ML sensing energy and time, respectively, which can further be improved by careful layout. The low-power ML-segmentation techniques include dual ML TCAM and charge-shared ML. Simulation results of the dual ML TCAM that connects two sides of the comparison logic to two ML segments for sequential sensing show 43% power savings for a small (4%) trade-off in the search speed. The charge-shared ML scheme achieves power savings by partial recycling of the charge stored in the first ML segment. Chip measurement results show that the charge-shared ML scheme results in 11% and 9% reductions in ML sensing time and energy, respectively, which can be improved to 19-25% by using a digitally controlled charge sharing time-window and a slightly modified MLSA. The static power reduction is achieved by a dual-VDD technique and low-leakage TCAM cells. The dual-VDD technique trades-off the excess noise margin of MLSA for smaller cell leakage by applying a smaller VDD to TCAM cells and a larger VDD to the peripheral circuits. The low-leakage TCAM cells trade off the speed of READ and WRITE operations for smaller cell area and leakage. Finally, design and testing of a complete TCAM chip are presented, and compared with other published designs.
216

Lågenergihus : Att bygga energisnålt

Karlsson, Camilla January 2010 (has links)
A large proportion of the energy consumption is in the building industry and a large part goes to heating our homes and premises. In the developing countries' development now threatens the large consumption of energy in our earth's climate. It is in the West world that we must be good role models in terms of energy efficiency. One solution to reduce energy consumption for heating of buildings may be to continue to build low energy houses and passive houses, but it is also about rebuilding the buildings that currently have high energy consumption such as the old Million program Houses. These buildings will be standing many years and their energy consumption will not diminish over time by itself and energy prices will certainly not diminish in the future. This report will touch on the subject mainly new construction, how to build an energy efficient building, but a smaller portion will touch on the subject rebuilding, particularly the solutions that can fit into economic terms.   Calculations have been done to link the concepts of Umean of a building and its energy consumption. This was done by calculations using an Excel document created in connection with this thesis.   The buildings and architectural solutions addressed in this report will focus on apartment buildings where the partner of this thesis is Eskilstuna Municipal Building. Eskilstuna Municipality Property manages buildings and premises to Eskilstuna Municipality, but also owns their own house with rental apartments.
217

Passivhusen på Oxtorget

Brandt, Fredrik, Jonsson, Mathilda January 2008 (has links)
Syftet med vårt examensarbete är att undersöka hur passivhus eller så kallade nollenergihus skiljer sig i funktion samt uppbyggnad från konventionella hus. I vår undersökning tar vi upp hur utformning, orientering, material samt ett väl fungerande klimatskal påverkar energiförbrukningen. Vi har tittat närmare på faktorer som sparar energi samt hur ett typiskt passivhus är uppbyggt. För att se hur teorin fungerar i praktiken har vi tittat närmare på befintliga passivhus, nämligen de på Oxtorget i Värnamo. Vi har kommit fram till att passivhus fungerar och vi anser det som väldigt viktigt att man fortsätter driva fram arbetet och informera om dess betydelse för miljön. Passivhus blir mer och mer uppmärksammat. De är något dyrare att bygga, men man tjänar in det i längden. Lönsamheten är dock inte det viktigaste utan känslan av att man gör något bra för miljön. / The main purpose with our diploma work is to examine how passive houses or so called zero energy houses differ in function and construction compared to conventional houses. In our research we present different things such design, orientation, materials and how a fully functional climate shell affects the energy consumption. We’ve looked closer at some factors that save energy and how a typical passive house is constructed. To see how theory works in practice we have looked at existing passive houses, and that is the passive houses on Oxtorget in Värnamo. We have come to the conclusion that the passive houses works and we believe that it is very important that we continues to carry on the work and inform people about its importance to the environment. Passive houses are becoming more and more noticed. They are somewhat more expensive to build but in time you will earn the money spent back. The profit is not the most important but the feeling that you do something good for the environment.
218

Fjärrvärmeanslutna passivhus : Fallstudie av värmelaster och innetemperaturer i fyra flerbostadshus

Nilsson, Daniel January 2012 (has links)
Intresset kring lågenergibyggnader blir allt större och så kallade passivhus, med god isolering, hög lufttäthet och värmeåtervinning, byggs i allt större utsträckning i Sverige och andra europeiska länder. Vissa frågetecken har dock uppkommit kring inomhusklimatet i husen och risken för både under- och övertemperaturer. En annan viktig aspekt är hur husens egenskaper påverkar värmelasterna och hur detta i sin tur påverkar energiförsörjningssystemet. I detta examensarbete undersöks dessa båda aspekter – värmelastegenskaper och innetemperaturer – i fyra likadana nybyggda flerbostadshus i Falkenberg. Mätvärden från husens tekniska system, inklusive lufttemperaturmätningar i samtliga lägenheter, analyseras. Husen består av totalt 108 lägenheter, värms med fjärrvärme och använder ca 50 kWh/m2 Atemp årligen. Värmelastegenskaperna kännetecknas framförallt av låga effektbehov för både uppvärmning och varmvatten samt relativt stora svängningar över dygnet. Husen tycks vara känsligare för variationer i interntillskott än konventionella hus, vilket leder till regelbundna svängningar i effektbehovet för uppvärmning, med en topp under natten och morgonen. Detta leder till förstärkta svängningar i fjärrvärmenätet, vilket skulle kunna undvikas med hjälp av effektstyrning. Passivhusens stora termiska tröghet talar för en sådan möjlighet. Även innetemperaturen uppvisar regelbundna dygnsvariationer, som kan vara något större än i vanliga hus. Låga temperaturer förekommer tidvis under vintern, men resultaten pekar inte på några brister i de tekniska systemen. Temperaturen på sommaren är inte högre än i andra hus, och övertemperaturer tycks inte vara något stort problem i dessa hus. Det kan dock finnas en möjlighet att minska risken för övertemperaturer ytterligare genom användning av nattkyla under varma perioder. Denna möjlighet kan vara ett sätt att utnyttja passivhusens speciella egenskaper för att ytterligare förbättra konceptet. / There is today an increasing interest in low-energy buildings, and the so-called “passive houses” are becoming increasingly popular in Sweden and other European countries. There are however some concerns regarding the indoor climate in these houses, notably the risk of too low indoor temperatures in the winter and too high temperatures in the summer. Another issue is the heat load characteristics of this type of buildings, and how these affect the energy systems. In this thesis, these two aspects – heat load characteristics and indoor temperatures – are analysed in four identical multi-family buildings in Falkenberg, Sweden, using measured values from the buildings’ technical systems and measured indoor air temperatures in all dwellings. The buildings are heated with district heating, comprise 108 dwellings in total and use approximately 50 kWh/m2 annually (space heating, hot water and electricity for building services). The heat loads are mainly characterised by low but varying heat demands for space heating and hot water. The buildings appear to have a higher than usual sensitivity for variations in heat from internal sources and solar gains, leading to regular variations in the heat demand for space heating and fluctuations in the total heat demand. These fluctuations, which may negatively affect the energy system, could be avoided by actively controlling the heat demand for space heating. There are also daily fluctuations in the indoor temperatures, but the buildings perform well in this aspect, with temperatures that stay within the acceptable range most of the time. The summer indoor temperatures do not get higher than in other buildings. A possibility for further improvement within this area could be the use of forced ventilation during the night in hot periods, and hence utilising the buildings’ well insulated and airtight building envelope to keep heat out during the day. This possibility might further improve the passive house concept.
219

Utvärdering av befintliga passivhus : En byggnadsfysikalisk bedömning och mätningar om temperatur, och fukt analys på ytterväggarna

Husseini, Hazhar January 2012 (has links)
Energy price are on the way up to a high level that will not diminish in the future make us to focus more on the sustainable development for a better solution of residential houses. Passive house or low energy housing are one of the solution to make residential more environment friendly, in same time it´s a financial security using less energy, and saving money. The last 10 years in Germany and all around Europe the concept of passive house been developed, and people aim to know more about these concept that leading the market more attractive for passive houses. A passive house is a well designed building highly insulated and air tight with mechanical ventilated system for the whole building envelope that minimizes the use of energy for heating [1]. The housing company Mimer has chosen to invest in low energy consumption in every new housing project.  These future plan projects are decided to use less than 75 kwh per square meter annually in purchased energy [2]. This thesis is about new constructed passive houses, and focuses on the evaluations of the temperature, and moisture condition for attic, external walls and joist. Reason for doing this investigation is to see if passive houses fulfill the building codes regarding moisture, and temperature changes, and to find in early stage suspicious changes that could affect badly on the building envelop. The aim of this study is -         Moisture risk analyses of the attic, external walls and joist -         Studying temperature analysis   With highly insulated walls the risk for moistures extra sensitive than normal building construction.  Also during summer time the comfort inside may be surprised by high indoor temperature and one solution for that could be using sun shading.
220

Low-Power High-Performance Ternary Content Addressable Memory Circuits

Mohan, Nitin January 2006 (has links)
Ternary content addressable memories (TCAMs) are hardware-based parallel lookup tables with bit-level masking capability. They are attractive for applications such as packet forwarding and classification in network routers. Despite the attractive features of TCAMs, high power consumption is one of the most critical challenges faced by TCAM designers. This work proposes circuit techniques for reducing TCAM power consumption. The main contribution of this work is divided in two parts: (i) reduction in match line (ML) sensing energy, and (ii) static-power reduction techniques. The ML sensing energy is reduced by employing (i) positive-feedback ML sense amplifiers (MLSAs), (ii) low-capacitance comparison logic, and (iii) low-power ML-segmentation techniques. The positive-feedback MLSAs include both resistive and active feedback to reduce the ML sensing energy. A body-bias technique can further improve the feedback action at the expense of additional area and ML capacitance. The measurement results of the active-feedback MLSA show 50-56% reduction in ML sensing energy. The measurement results of the proposed low-capacitance comparison logic show 25% and 42% reductions in ML sensing energy and time, respectively, which can further be improved by careful layout. The low-power ML-segmentation techniques include dual ML TCAM and charge-shared ML. Simulation results of the dual ML TCAM that connects two sides of the comparison logic to two ML segments for sequential sensing show 43% power savings for a small (4%) trade-off in the search speed. The charge-shared ML scheme achieves power savings by partial recycling of the charge stored in the first ML segment. Chip measurement results show that the charge-shared ML scheme results in 11% and 9% reductions in ML sensing time and energy, respectively, which can be improved to 19-25% by using a digitally controlled charge sharing time-window and a slightly modified MLSA. The static power reduction is achieved by a dual-VDD technique and low-leakage TCAM cells. The dual-VDD technique trades-off the excess noise margin of MLSA for smaller cell leakage by applying a smaller VDD to TCAM cells and a larger VDD to the peripheral circuits. The low-leakage TCAM cells trade off the speed of READ and WRITE operations for smaller cell area and leakage. Finally, design and testing of a complete TCAM chip are presented, and compared with other published designs.

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