Denna avhandling behandlar analog-digitalomvandling. I synnerhet behandlas postkorrektion av analog-digitalomvandlare (A/D-omvandlare). A/D-omvandlare är i praktiken behäftade med vissa fel som i sin tur ger upphov till distorsion i omvandlarens utsignal. Om felen har ett systematiskt samband med utsignalen kan de avhjälpas genom att korrigera utsignalen i efterhand. Detta verk behandlar den form av postkorrektion som implementeras med hjälp av en tabell ur vilken korrektionsvärden hämtas. Innan en A/D-omvandlare kan korrigeras måste felen i den mätas upp. Detta görs genom att estimera omvandlarens överföringsfunktion. I detta arbete behandlas speciellt problemet att skatta kvantiseringsintervallens mittpunkter. Det antas härvid att en referenssignal finns tillgänglig som grund för skattningen. En skattare som baseras på sorterade data visas vara bättre än den vanligtvis använda skattaren baserad på sampelmedelvärde. Nästa huvudbidrag visar hur resultatet efter korrigering av en A/D-omvandlare kan predikteras. Omvandlaren antas här ha en viss differentiell olinjäritet och insignalen antas påverkad av ett slumpmässigt brus. Ett postkorrektionssystem, implementerat med begränsad precision, korrigerar utsignalen från A/D-omvandlaren. Ett utryck härleds som beskriver signal-brusförhållandet efter postkorrektion. Förhållandet visar sig bero på den differentiella olinjäritetens varians, det slumpmässiga brusets varians, omvandlarens upplösning samt precisionen med vilken korrektionstermerna beskrivs. Till sist behandlas indexering av korrektionstabeller. Valet av metod för att indexera en korrektionstabell påverkar såväl tabellens storlek som förmågan att beskriva och korrigera dynamiska fel. I avhandlingen behandlas i synnerhet tillståndsmodellbaserade metoder, det vill säga metoder där tabellindex bildas som en funktion utav flera på varandra följande sampel. Allmänt gäller att ju fler sampel som används för att bilda ett tabellindex, desto större blir tabellen, samtidigt som förmågan att beskriva dynamiska fel ökar. En indexeringsmetod som endast använder en delmängd av bitarna i varje sampel föreslås här. Vidare så påvisas hur valet av indexeringsbitar kan göras optimalt, och experimentella utvärderingar åskådliggör att tabellstorleken kan reduceras avsevärt utan att fördenskull minska prestanda mer än marginellt. De teorier och resultat som framförs här har utvärderats med experimentella A/D-omvandlardata eller genom datorsimuleringar. / Analog-to-digital conversion and quantization constitute the topic of this thesis. Post-correction of analog-to-digital converters (ADCs) is considered in particular. ADCs usually exhibit non-ideal behavior in practice. These non-idealities spawn distortions in the converters output. Whenever the errors are systematic, it is possible to mitigate them by mapping the output into a corrected value. The work herein is focused on problems associated with post-correction using look-up tables. All results presented are supported by experiments or simulations. The first problem considered is characterization of the ADC. This is in fact an estimation problem, where the transfer function of the converter should be determined. This thesis deals with estimation of quantization region midpoints, aided by a reference signal. A novel estimator based on order statistics is proposed, and is shown to have superior performance compared with the sample mean traditionally used. The second major area deals with predicting the performance of an ADC after post-correction. A converter with static differential nonlinearities and random input noise is considered. A post-correction is applied, but with limited (fixed-point) resolution in the corrected values. An expression for the signal-to-noise and distortion ratio after post-correction is provided. It is shown that the performance is dependent on the variance of the differential nonlinearity, the variance of the random noise, the resolution of the converter and the precision of the correction values. Finally, the problem of addressing, or indexing, the correction look-up table is dealt with. The indexing method determines both the memory requirements of the table and the ability to describe and correct dynamically dependent error effects. The work here is devoted to state-space--type indexing schemes, which determine the index from a number of consecutive samples. There is a tradeoff between table size and dynamics: more samples used for indexing gives a higher dependence on dynamic, but also a larger table. An indexing scheme that uses only a subset of the bits in each sample is proposed. It is shown how the selection of bits can be optimized, and the exemplary results show that a substantial reduction in memory size is possible with only marginal reduction of performance. / QC 20101019

Radioactive waste has been accumulated at CERN as unavoidable consequence of the use of particle accelerators. The elimination of this waste towards the final repositories in France and Switzerland requires the determination of the radionuclide inventory. In order to calculate the residual induced radioactivity in the waste, it is necessary to determine the spectra of secondary particles which are responsible for the material activation. In complex irradiation environments like in an accelerator tunnel it is expected that the secondary particle spectra vary with the characteristics of the machine components in a given section of tunnel. In order to obtain the production rates of the radionuclides of interest the spectra of secondary particles are to be folded with the appropriate cross sections. Though technically feasible, it would be impractical to calculate the particle spectra in every area of any machine and for all possible beam loss mechanisms. Moreover, a fraction of the waste has unknown radiological history, which makes it impossible to associate an item of waste to a precise area of the machine. Therefore it is useful to try to calculate “representative spectra”, which shall apply to a relatively large part of the accelerator complex at CERN. This thesis is dedicated to the calculation of representative spectra in the arcs of the 450 GeV proton synchrotron, SPS, at CERN. The calculations have been performed using the Monte Carlo code FLUKA. Extensive simulations have been done to assess the dependence of proton, neutron and pion spectra on beam energy, size of the nearby machine component and position with respect to the beam-loss point. The results obtained suggest that it is possible to define one single set of representative spectra for all the arcs of the SPS accelerator, with a minor error associated with the use of these.

Computational science demands extreme performance because the running time of an application often determines the size of the experiment that a scientist can reasonably compute. Unfortunately, traditional compiler technology is ill-equipped to harness the full potential of today's computing platforms, forcing scientists to spend time manually tuning their application's performance. Although improving compiler technology should alleviate this problem, two challenges obstruct this goal: hardware platforms are rapidly changing and application software is difficult to statically model and predict. To address these problems, this thesis presents two techniques that aim to improve a compiler's adaptability: automatic resource characterization and selective, dynamic optimization. Resource characterization empirically measures a system's performance-critical characteristics, which can be provided to a parameterized compiler that specializes programs accordingly. Measuring these characteristics is important, because a system's physical characteristics do not always match its observed characteristics. Consequently, resource characterization provides an empirical performance model of a system's actual behavior, which is better suited for guiding compiler optimizations than a purely theoretical model. This thesis presents techniques for determining a system's data cache and TLB capacity, line size, and associativity, as well as instruction-cache capacity. Even with a perfect architectural-model, compilers will still often generate suboptimal code because of the difficulty in statically analyzing and predicting a program's behavior. This thesis presents two techniques that enable selective, dynamic-optimization for cases in which static compilation fails to deliver adequate performance. First, intermediate-representation (IR) annotation generates a fully-optimized native binary tagged with a higher-level compiler representation of itself. The native binary benefits from static optimization and code generation, but the IR annotation allows targeted and aggressive dynamic-optimization. Second, adaptive code-selection allows a program to empirically tune its performance throughout execution by automatically identifying and favoring the best performing variant of a routine. This technique can be used for dynamically choosing between different static-compilation strategies; or, it can be used with IR annotation for performing dynamic, feedback-directed optimization.

In digital control system, interference, which is mixed in the input signal, has a great influence on the performance of the system. Therefore, processing of input signal has to be done to get useful signal. Finite impulse response (FIR) filter plays an important role in the processing of digital signal. Designing the FIR filter by Matlab can simplify the complicated computation in simulation and improve the performance. By using the methods of window function, frequency sampling and convex optimization techniques, the design of FIR filter has been processed by Matlab. In the view of the designed program of Matlab and I can get the amplitude-frequency characterization. By using the FIR digital filters which have been designed to process the input signal based on the Matlab function, the filtering effect of different digital filters is analyzed by comparing the signal’s amplitude-frequency diagrams which have been generated. The experimental results show that the FIR filters designed in this paper are effective.

The commercially available solar cells suffer from low conversion efficiency due to the thermalization and transmission losses arising from the mismatch between the band gap of the semiconductor materials and the solar spectrum. Advanced device architectures based on nanomaterial have been proposed and being successfully used to enhance the efficiency of the solar cells. Quantum dots (QDs) and nanowires (NWs) are the nanosclae structures that have been exploited for the development of the third generation solar cell devices and nanowire based solar cells, respectively. The optical and electrical properties of these materials can be tuned by their size and geometry; hence they have great potential for the production of highly efficient solar cell. Application of QDs and NWs with enhanced optoelectronic properties and development of low-cost fabrication processes render a new generation of economic highly efficient PV devices. The most significant contribution of this PhD study is the development of simple and cost effective methods for fabrication of nanowires and quantum dots for advanced solar cell architectures. In advanced silicon nanowires (SiNWs) array cell, SiNWs have been widely synthesised by the well-known vapor-liquid-solid method. Electron beam lithography and deep reactive ion etching have also been employed for fabrication of SiNWs. Due to the high price and complexity of these methods, simple and cost effective approaches are needed for the fabrication of SiNWs. In another approach, to enhance the cell efficiency, organic dyes and polymers have been widely used as luminescent centers and host mediums in the luminescent down shifting (LDS) layers. However, due to the narrow absorption band of the dyes and degradation of the polymers by moisture and heat, these materials are not promising candidates to use as LDS. Highly efficient luminescent materials and transparent host materials with stable mechanical properties are demanded for luminescent down shifting applications. In this project, simple fabrication processes were developed to produce SiNWs and QDs for application in advanced cell architectures. The SiNWs array were successfully fabricated, characterized and deployed in new cell architectures with radial p-n junction geometry. The luminescence down shifting of layers containing QDs in oxide and glass mediums was verified. The silica coated quantum dots which are suitable for luminescence down shifting, were also fabricated and characterized for deployment in new design architectures. Silicon nanowires were fabricated using two simplified methods. In the first approach, a maskless reactive ion etching process was developed to form upright ordered arrays of the SiNWs without relying on the complicated nano-scale lithography or masking methods. The fabricated structures were comprehensively characterized. Light trapping and photoluminescence properties of the medium were verified. In the second approach, combination of the nanosphere lithography and etching techniques were utilized for wire formation. This method provides a better control on the wire diameters and geometries in a very simple and cost effective way. The fabricated silicon nanowires were used for formation of the radial p-n junction array cells. The functionality of the new cell structures were confirmed through experimental and simulation results. Quantum dots are promising candidates as luminescent centers due to their tunable optical properties. Oxide/glass matrices are also preferred as the host medium for QDs because of their robust mechanical properties and their compatibility with standard silicon processing technology. Besides, the oxide layers are transparent mediums with good passivation and anti-reflection coating properties. They can also be used to encapsulate the cell. In this work, ordered arrays of QDs were incorporated in an oxide layer to form a luminescent down shifting layer. This design benefits from the enhanced absorption of a periodic QD structure in a transparent oxide. The down shifting properties of the layer after deployment on a crystalline silicon solar cell were examined. For this purpose, crystalline silicon solar cells were fabricated to use as test platform for down shifting. In order to examine the down-shifting effect, different approaches for formation of a luminescence down shifting layer were developed. The LDS layer consist of cadmium selenide- zinc sulfide (CdSe/ZnS) quantum dots in oxide and glass layers to act as luminescent centers and transparent host medium, respectively. The structural and optical properties of the fabricated layers were studied. The concept of spectral engineering was proved by the deployment of the layer on the solar cell. To further benefit from the LDS technique, quantum efficiency of the QDs and optical properties of the layer must be improved. Demand for the high quantum efficiency material with desired geometry leaded us to synthesis quantum dots coated with a layer of grown oxide. As the luminescence quantum efficiency of the QDs is correlated to the surface defects, one advantage of having oxide on the outer shell of the QDs, is to passivate the surface non-radiative recombination centers and produce QDs with high luminescent quantum yield. In addition, nanoparticles with desired size can be obtained only by changing the thickness of the oxide shell. This method also simplifies the fabrication of QD arrays for luminescence down shifting application, since it is easier to form ordered arrays from larger particles. QD superlattices in an oxide medium can be fabricated on a large area by a simple spin-coating or dip coating methods. The photonic crystal properties of the proposed structure can greatly increase the absorption in the QDs layer and enhance the effect of down shifting.

The Lithium-ion (Li-ion) battery is one of the major topics currently studied as a potential way to help in reducing greenhouse gas emissions. Major car manufacturers are interested in adapting the Li-ion battery in the power trains of Plug-in Hybrid Electric Vehicles (PHEV) to improve fuel efficiency. Materials currently used for Li-ion batteries are LiCoO2 (LCO) and graphite—the first materials successfully integrated by Sony into Li-ion batteries. However, due to the high cost and polluting effect of cobalt (Co), and the low volumetric capacity of graphite, new materials are being sought out. LiFePO4 (LFP) and SnO2 are both good alternatives for the cathode and anode materials in Li-ion batteries. But, to create high-performance batteries, nano-sized carbon-coated particles of LFP and SnO2 are required. The present work attempts to develop a new synthesis method for these materials: organic template-assisted synthesis for three-dimensionally ordered macroporous (3DOM) LFP and porous SnO2. With the newly developed synthesis, highly pure materials were successfully synthesized and tested in Li-ion batteries. The obtained capacity for LFP was 158m Ah/g, which is equivalent to 93% of the theoretical capacity. The obtained capacity for SnO2 was 700 mAh/g, which is equivalent to 90% of the theoretical capacity. Moreover, Hybrid Pulse Power Characterization (HPPC) was used to test LFP and LCO for comparison and feasibility in PHEVs. HPPC is generally used to test the feasibility and capacity fade for PHEVs. It simulates battery use in various driving conditions of PHEVs to study pulse energy consumption and regeneration. In this case, HPPC was conducted on a half-cell battery for the first time to study the phenomena on a single active material, LFP or LCO. Based on the HPPC results, LFP proved to be more practical for use in PHEVs.

Femtosecond time-resolved photoelectron spectroscopy (fsTRPES) experiments have been used to study the photoelectron energy spectra of simple molecules since the 1980’s. Analysis of these spectra provides information about the ultrafast internal conversion dynamics of the parent ions. However, ultraviolet pulses must be used for these pump-probe experiments in order to ionize the molecules. Since current solid state lasers, such as the Ti:sapphire laser, typically produce pulses centered at 800nm, it is necessary to generate UV pulses with nonlinear frequency mixing techniques. I therefore constructed an optical setup to generate the 3rd and 4th harmonics, at 266.7nm and 200nm, respectively, of a Ti:sapphire (Ti:sa) chirped-pulse amplified (CPA) laser system that produces 35fs pulses centered at 800nm. Thin Beta-Barium Borate (β-BaB2O4 or BBO) crystals were chosen to achieve a compromise between short pulse durations and reasonable conversion efficiencies, since ultrashort pulses are quite susceptible to broadening from group velocity dispersion (GVD). Output energies of around 11μJ and 230nJ were measured for the 266.7nm and 200nm pulses, respectively. The transform limits of the 3rd and 4th harmonic pulse lengths were calculated from their measured spectral widths. We found that the 266.7nm bandwidth was large enough to support sub-30fs pulses, and due to cutting at the lower-wavelength end of the 200nm spectrum, we calculated an upper limit of 38fs. The pulses were compressed with pairs of CaF2 prisms to compensate for dispersion introduced by transmissive optics. Two-photon absorption (TPA) intensity autocorrelations revealed fully compressed pulse lengths of 36 ± 2 fs and 42 ± 4 fs for the 3rd and 4th harmonics, respectively.

Garden of Eden imagery is ubiquitous in contemporary print advertising in North America, especially in advertisements directed at women. Three telling characteristics emerge in characterizations of Eve in these advertising reconstructions. In the first place, Eve is consistently hypersexualized and over-eroticized. Secondly, such Garden of Eden images often conflate the Eve figure with that of the Serpent. Thirdly, the highly eroticized Eve-Serpent figures also commonly suffer further conflation with the Garden of Eden itself. Like Eve, nature becomes eroticized. In the Eve-Serpent-Eden conflation, woman becomes nature, nature becomes woman, and both perform a single narrative plot function, in tandem with the Serpent. The erotic and tempting Eve-Serpent-Eden character is both protagonist and antagonist, seducer and seduced. In this dissertation, I engage in an ecofeminist narratological analysis of the Genesis/Fall myth, as it is retold in contemporary fashion magazine advertisements. My analysis examines how reconstructions of this myth in advertisements construct the reader, the narrator, and the primary characters of the story (Eve, Adam, the Serpent, and Eden). I then further explore the ways in which these characterizations inform our perceptions of woman, nature, and environmentalism. Using a narratological methodology, and through a poststructuralist ecofeminist lens, I examine which plot and character elements have been kept, which have been discarded, and how certain erasures impact the narrative characterizations of the story. In addition to what is being told, I further analyze how and where it is told. How is the basic plot being storied in these reconstructions, and what are the effects of this version on the archetypal characterizations of Eve and the Garden of Eden? What are the cultural and literary contexts of the reconstructed narrative and the characters within it? How do these contexts inform how we read the characters within the story? Finally, I examine the cultural effects of these narrative reconstructions, exploring their influence on our gendered relationships with each other and with the natural world around us.

No description available.

A concentric pneumatic nebulizer (CPN) and a custom designed flow focusing nebulizer (FFN) are characterized. As will be shown, the classical Nukiyama-Tanasawa and Rizk-Lefebvre models lead to erroneous size prediction for the concentric nebulizer under typical operating conditions due to its specific design, geometry, dimension and different flow regimes. The models are then modified to improve the agreement with the experimental results. The size prediction of the modified models together with the spray velocity characterization are used to determine the overall nebulizer efficiency and also employed as input to a new Maximum Entropy Principle (MEP) based model to predict joint size-velocity distribution analytically. The new MEP model is exploited to study the local variation of size-velocity distribution in contrast to the classical models where MEP is applied globally to the entire spray cross section. As will be demonstrated, the velocity distribution of the classical MEP models shows poor agreement with experiments for the cases under study. Modifications to the original MEP modeling are proposed to overcome this deficiency. In addition, the new joint size-velocity distribution agrees better with our general understanding of the drag law and yields realistic results.