published_or_final_version / abstract / Physics / Doctoral / Doctor of Philosophy

In this thesis, we propose a circuit design technique that reduces the energy utilized by any logic circuit for computation. We achieve this, by reducing the voltage swing on the circuit without greatly compromising the speed of operation and keeping in mind the noise margin constraints. Our technique involves the use of head or tail transistors that provide a Vth drop in the voltage swing. We choose to use head or tail transistors on alternate logic levels providing us with an option of driver stage, based on the noise margin of the subsequent stage. We demonstrate the working of this concept on inverter chains, to prove the correctness as well as the ability of the reduced voltage swing circuits to drive subsequent stages. We also discuss the implementation of this technique on basic gates and simple combinational circuits. We then show detailed experiments on a larger circuit, in this case a Kogge-Stone parallel prefix adder. We will discuss the overheads involved in the design and methods to partially overcome these by the use of selectively skewed gates and application of forward body bias. Finally we implement the same design using a different technology to demonstrate the scalability of the technique. / text

Xu Xiangdong. / "December 2001." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

In rural Scotland there has been a trend over the last 40 years towards mass market housing development which employs standardised housing models and suburban planning layouts. These have little relationship to rural landscape characteristics, regional climatic variations or historic rural communities. While they comply with current building standards, they fall significantly short of proposed improvements for energy performance which require all new homes to be ‘Zero Carbon’ by 2016/17 if practical and the European target of ‘Nearly Zero Energy Homes’ by the end of 2020. It is recognised that changes in legislation to reach these targets are falling behind schedule and energy analysis methods are flawed due to outdated calculation methodologies and imprecise climate data. This research firstly provides an in-depth context for rural housing provision outlining the drivers and legislative requirements. The first section of the literature review investigates planning and current practice in housing, whilst the second section outlines the requirements for improved energy efficiency from the European to Scottish contexts. The research then goes on to quantify the effects of regional climatic variation, in nine areas across Scotland, on space heating energy demand (SSHD). It utilises a best practice ultra-low energy housing prototype to demonstrate the requirement for regional solutions. All of the studies use a customised version of the Passivhaus Planning Package, an industry leading energy quantification methodology for heating energy calculations. A series of studies define the design envelope for achieving regional solutions by quantifying the relationship between the variation of design and form on the SSHD in the extremes of the Scottish regional climates. The variables relate to common metrics: orientation, glazing areas, roof forms and building typology. A separate study also compares the effect of Zero Carbon Homes and Passivhaus performance specification on SSHD. This method is developed further to determine the effect of building design on SSHD and heat load using seven contemporary Scottish Government exemplar housing designs. Improvements to the energy efficiency of these designs are made by considering variations to orientation and glazing design which are then discussed in relation to their impact on design quality. The results of the research demonstrate an increase of 81% in SSHD caused by regional variation across Scotland with up to a 29% increase from the UK average climate used in the UK’s legislative analysis method SAP. This requires significant increases in insulation levels to retain SSHD performance. Alterations to the buildings orientation demonstrate an increase of 165% SSHD when deviating 180° from south, which is significantly higher than guidance suggests. The analysis of existing exemplar designs demonstrate a threefold increase in SSHD due to building form and orientation in some designs. The optimisation of the same designs illustrates a 45% reduction in SSHD through improved orientation and glazing design. This thesis contributes to improving design thinking and assessment methodologies for new rural Scottish housing by highlighting the importance of climatically responsive design along with the consideration of appropriate energy efficient forms. The results of the thesis contribute to the debate surrounding the appropriate response of new housing in rural Scottish environments and highlights the importance of regional approaches and passive solar design for reduced housing energy use. This thesis contributes original knowledge on the effects of Scottish climate and building form on the SSHD of ultra-low energy housing in Scotland. The extent to which a number of principle architectural planning and design parameters can be varied and optimised across different climatic regions will give architects and designers a more quantitative understanding of their design decisions and impact on space heating energy performance across Scotland.

<p>Miljö och energianvändning blir ett mer aktuellt ämne. 40 % av landets totala energianvändning går idag till bostäder.[1] Om elpriserna stiger under den närmsta tiden kommer det med stor säkerhet leda till att människor blir mer kostnadsmedvetna och gärna hittar sätt för att minska sina energikostnader. Som ett led i detta har hustillverkare tagit fram ett energisnålt alternativ till det vanliga huset. Det benämns lågenergihus och använder mindre energi än de hus som är vanliga på marknaden idag. Det här är möjligt genom att lågenergihus byggs på ett annorlunda vis jämfört med ett ordinärt hus. Bland annat används mer isolering och bättre fönster och dörrar. Dessutom är täthet ett viktigt begrepp för att minska värmeförlusterna. Rapporten syftar till att redogöra för vad som karaktäriserar lågenergihus och ge vägledning vid byggande av dessa. Vidare ska rapporten ge svar på frågorna, vilka är problemen och vilka är fördelarna med lågenergihus? Hur ser byggprocessen ut och vad är viktigt att tänka på i de olika skedena i processen? samt, är det ekonomiskt rimligt att bygga lågenergihus? För att få svar på dessa frågor har jag använt mig av litteratur, intervjuer samt informationssökning på nätet, dessutom har jag använt mig av de kunskaper som införskaffats under studietiden. I rapporten har jag valt att endast behandla energianvändning då miljöfrågan är alltför omfattande. Vidare ger rapporten en introduktion till vad som är utmärkande för lågenergihus rent byggnadstekniskt och lotsar läsaren genom byggprocessens olika skeden samt vilka aktörer som är inblandade och vilka deras respektive ansvarsområden är. Dessutom pekar rapporten ut vad som är viktigt för dig som byggherre att tänka på under de olika skedena i byggprocessen i form av planering, utformning, konstruktion, installationer, utgifter, försäkringar, kontroller och avtal, vare sig du väljer att uppföra byggnaden i egen regi eller anlita en entreprenör.</p><p>Rapporten ger exempel på lösningar gällande konstruktion, installationer och värmesystem som är lämpliga i ett lågenergihus. Dessutom görs en energiberäkning på ett lågenergihus ritat av författaren till rapporten. Beräkningen ger huset en energianvändning på 56 kWh/m², år, vilket är ca hälften av vad lagar och föreskrifter anger som maximalt värde ett hus får ha. Idéer och tankar som legat till grund för huset beskrivs. Då detta hus ritats har även andra idéer implementerats som inte är specifika för lågenergihus, utan syftar till att huset ska ha en beredskap vid tillexempel elavbrott. I slutet av rapporten ges även tips på hur du som husägare ytterligare kan spara energi och bidra till en hållbar utveckling.</p><p>[1]Gross, Holger (2008). <em>Energismarta småhus: vägledning och råd till byggherrar, arkitekter och ingenjörer</em>. Stockholm: Gross produktion i samarbete med Villaägarnas riksförbund</p><p> </p> / <p>The environment and the use of energy is becoming a more present subject. Today the real estate industry accounts for more than 40% of Sweden’s total energy consumption.[1]As energy prices rise, energy-saving in buildings is becoming increasingly important to homeowners. As result of this, house manufacturers have created a new type of energy-saving house called low-energy house. This house has a different construction in comparison to an ordinary house. The theses aims to give guidance when building a low-energy house and answer the following questions, what are the problems and what are the benefits, which are the different phases of the building process, what issues are important to consider in these phases and is it economically realistic to build a low-energy house. To be able to answer these questions I have collected material from litterateur, interviews, and web searching. In addition I also have used the knowledge I have obtained during my period of studies. The thesis only concern the energy consumption as the environmental part of it is too substantial. In addition the thesis gives a presentation of the building process, who are involved and what are their field of responsibility. Furthermore it points out what you as a future owner of a house/building proprietor should be attentive to during the building process so that no mistakes are made that causes the end results not turning out as expected. Different laws, rules, contracts, norms and authorities that occurs in the building process,  are accounted for and explained in the thesis in such a way that is easy to grasp for those not familiar to the subject.</p><p> </p><p>The report gives advice and example of solutions in terms of construction and installations e.g. heating distribution system that are appropriate in a low-energy house.</p><p>The thesis includes a calculation of the energy use of a low-energy house, which shows that the house uses about 56 kWh/m², year. In comparison, this is about half the maximum limit decided by the Swedish constitution BBR.</p><p> </p><p> A suggestion for a low-energy house is displayed in the paper, it is the same housed used for the calculation of energy use. Ideas and thoughts regarding the house are described. This suggestion also implements a few ideas’ that perhaps contributes additionally to energy-savings and a sustainable environment.</p><h2><em> </em></h2><p>[1] Gross, Holger (2008). <em>Energismarta småhus: vägledning och råd till byggherrar, arkitekter och ingenjörer</em>. Stockholm: Gross produktion i samarbete med Villaägarnas riksförbund</p>

The interactions of a model synthetic liquid fuel reactant (furan) with a model hydrodeoxygenation catalyst (clean and sulfided single crystal molybdenum) were investigated using the following UHV tools: Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and temperature programed reaction spectroscopy (TPRS). In addition to furan, the reactions of hydrogen, carbon monoxide, ethylene, and propene on clean and sulfided Mo(110) were also examined. All adsorbates exposed to the extremely reactive clean or sulfided Mo(110) surface decomposed, yielding gaseous H��� and surface C. In addition, furan TPRS caused the production of gaseous CO. The presence of background hydrogen caused no major changes in the TPRS of furan or the other adsorbates. Sulfur pre-adsorption caused the chemical shifting of H��� TPRS peaks. Both sulfur and carbon pre-adsorption resulted in the Van der Waal's radius blocking of adsorption sites for all adsorbates studied. / Graduation date: 1997

Graduation date: 1997

Tritium is a radioactive hydrogen isotope that is typically produced via neutron interaction with heavy water (D2O), producing tritiated water (DTO). As a result of this, tritium accounts for roughly a third of all occupational exposures at a CANDU type nuclear power plant. This identifies a need to study the biological effects associated with tritium (and low energy electrons in general). However, there are complications regarding the dosimetry of tritium, as well as difficulties in handling and using tritium for the purposes of biophysics experiments. To avoid these difficulties, an experiment has been proposed using photons to mimic the beta decay energy spectrum of tritium. This would allow simulation of the radiation properties of tritium, so that a surrogate photon source can be used for biophysics experiments. Through experimental and computational means, this work has explored the use of characteristic x-rays of various materials to modify the output spectrum of an x-ray source, such that it mimics the tritium beta decay spectrum. Additionally, the resultant primary electron spectrum generated in water from an x-ray source was simulated. The results from this research have indicated that the use of characteristic x-rays is not a viable method for simulating a tritium source. Also, the primary electron spectrum generated in water shows some promise for simulating tritium exposure, however further work must be done to investigate the slowing down electron spectrum. / UOIT

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