Standardmäßig erfolgt die Datenaufbereitung der Neutronenwirkungsquerschnitte für Reaktorkernrechnungen mit 2D-Zellcodes. Ziel dieser Arbeit war es, einen 3D-Zellcode zu entwickeln, mit diesem Code 3D-Effekte zu untersuchen und die Notwendigkeit einer 3D-Datenaufbereitung der Neutronenwirkungsquerschnitte zu bewerten. Zur Berechnung des Neutronentransports wurde die Methode der Erststoßwahrscheinlichkeiten, die mit der Ray-Tracing-Methode berechnet werden, gewählt. Die mathematischen Algorithmen wurden in den 2D/3D-Zellcode TransRay umgesetzt. Für den Geometrieteil des Programms wurde das Geometriemodul eines Monte-Carlo-Codes genutzt. Das Ray-Tracing in 3D wurde auf Grund der hohen Rechenzeiten parallelisiert. Das Programm TransRay wurde an 2D-Testaufgaben verifiziert. Für einen Druckwasser-Referenzreaktor wurden folgende 3D-Probleme untersucht: Ein teilweise eingetauchter Regelstab und Void (Vakuum oder Dampf) um einen Brennstab als Modell einer Dampfblase. Alle Probleme wurden zum Vergleich auch mit den Programmen HELIOS (2D) und MCNP (3D) nachgerechnet. Die Abhängigkeit des Multiplikationsfaktors und der gemittelten Zweigruppenquerschnitte von der Eintauchtiefe des Regelstabes bzw. von der Höhe der Dampfblase wurden untersucht. Die 3D berechneten Zweigruppenquerschnitte wurden mit drei üblichen Näherungen verglichen: Lineare Interpolation, Interpolation mit Flusswichtung und Homogenisierung. Am 3D-Problem des Regelstabes zeigte sich, dass die Interpolation mit Flusswichtung eine gute Näherung ist. Demnach ist hier eine 3D-Datenaufbereitung nicht notwendig. Beim Testfall des einzelnen Brennstabs, der von Void umgeben ist, erwiesen sich die drei Näherungen für die Zweigruppenquerschnitte als unzureichend. Demnach ist eine 3D-Datenaufbereitung notwendig. Die einzelne Brennstabzelle mit Void kann als der Grenzfall eines Reaktors angesehen werden, in dem sich eine Phasengrenzfläche herausgebildet hat.

Standardmäßig erfolgt die Datenaufbereitung der Neutronenwirkungsquerschnitte für Reaktorkernrechnungen mit 2D-Zellcodes. Ziel dieser Arbeit war es, einen 3D-Zellcode zu entwickeln, mit diesem Code 3D-Effekte zu untersuchen und die Notwendigkeit einer 3D-Datenaufbereitung der Neutronenwirkungsquerschnitte zu bewerten. Zur Berechnung des Neutronentransports wurde die Methode der Erststoßwahrscheinlichkeiten, die mit der Ray-Tracing-Methode berechnet werden, gewählt. Die mathematischen Algorithmen wurden in den 2D/3D-Zellcode TransRay umgesetzt. Für den Geometrieteil des Programms wurde das Geometriemodul eines Monte-Carlo-Codes genutzt. Das Ray-Tracing wurde auf Grund der hohen Rechenzeiten parallelisiert. Das Programm TransRay wurde an 2D-Testaufgaben verifiziert. Für einen Druckwasser-Referenzreaktor wurden folgende 3D-Probleme untersucht: Ein teilweise eingetauchter Regelstab und Void (bzw. Moderator mit geringerer Dichte) um einen Brennstab als Modell einer Dampfblase. Alle Probleme wurden zum Vergleich auch mit den Programmen HELIOS (2D) und MCNP (3D) nachgerechnet. Die Abhängigkeit des Multiplikationsfaktors und der gemittelten Zweigruppenquerschnitte von der Eintauchtiefe des Regelstabes bzw. von der Höhe der Dampfblase wurden untersucht. Die 3D berechneten Zweigruppenquerschnitte wurden mit drei üblichen Näherungen verglichen: linearer Interpolation, Interpolation mit Flusswichtung und Homogenisierung. Am 3D-Problem des Regelstabes zeigte sich, dass die Interpolation mit Flusswichtung eine gute Näherung ist. Demnach ist hier eine 3D-Datenaufbereitung nicht notwendig. Beim Testfall des einzelnen Brennstabs, der von Void (bzw. Moderator geringerer Dichte) umgeben ist, erwiesen sich die drei Näherungen für die Zweigruppenquerschnitte als unzureichend. Demnach ist eine 3D-Datenaufbereitung notwendig. Die einzelne Brennstabzelle mit Void kann als der Grenzfall eines Reaktors angesehen werden, in dem sich eine Phasengrenzfläche herausgebildet hat.

The optical design of a LED illuminator and camera imaging system were studied for potential use in a small medical "robotic type" probe to be used for minimally invasive abdominal surgery. Beam shaping optical reflectors were studied to increase the intensity distribution of the LED beam directed toward a close-by target surface. A CMOS/CCD camera and lens was used to image the targeted area. In addition, extensive optical ray tracing simulations were made to predict the intensity patterns. The experimental measurements and ray tracing simulations were in good agreement, and indicated that 20 degree cone reflectors for the LED sources and appropriate micro-lens/CCD chip imaging optics should provide a useful image at a working distance of about 5 cm.

Computational stereo estimates 3D structure by analyzing visual changes between two or more passive images of a scene that are captured from different viewpoints. It is a key enabler for ubiquitous autonomous systems, large-scale surveying, virtual reality, and improved techniques for compression, tracking, and object recognition. The fact that computational stereo is an under-constrained inverse problem causes many challenges. Its computational and memory requirements are high. Typical heuristics and assumptions, used to constrain solutions or reduce computation, prevent treatment of key realities such as reflection, translucency, ambient lighting changes, or moving objects in the scene. As a result, a general solution is lacking. Stochastic models are common in computational stereo, but stochastic algorithms are severely under-represented. In this dissertation I present two stochastic algorithms and demonstrate their advantages over deterministic approaches. I first present the Quality-Efficient Stochastic Sampling (QUESS) approach. QUESS reduces the number of match quality function evaluations needed to estimate dense stereo correspondences. This facilitates the use of complex quality metrics or metrics that take unique values at non-integer disparities. QUESS is shown to outperform two competing approaches, and to have more attractive memory and scaling properties than approaches based on exhaustive sampling. I then present a second novel approach based on the Hough transform and extend it with distributed ray tracing (DRT). DRT is a stochastic anti-aliasing technique common to computer rendering but which has not been used in computational stereo. I demonstrate that the DRT-enhanced approach outperforms the unenhanced approach, a competing variation that uses re-accumulation in the Hough domain, and another baseline approach. DRT’s advantages are particularly strong for reduced image resolution and/or reduced accumulator matrix resolution. In support of this second approach, I develop two novel variations of the Hough transform that use DRT, and demonstrate that they outperform competing variations on a traditional line segment detection problem. I generalize these two examples to draw broader conclusions, suggest future work, and call for a deeper exploration by the community. Both practical and academic gaps in the state of the art can be reduced by a renewed exploration of stochastic computational stereo techniques. / text

The Scheimpflug principle was recommended as allowing distortion-free imaging; however, a detailed analysis reveals geometrical errors as well as distortions arising from absorption of light along the optical pathway. Correction formulas and factors will be presented and applied to the biometry of the eye. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Basal cell carcinoma is a form of a non-melanoma skin tumour, that commonly forms over the sun exposed regions of the head and neck. Investigation of the rate of occurrence at different sites on face and neck shows considerable variation from site to site. The inner canthus has a disproportionate number when compared to more exposed sites. The eye brow ridge, cheek bone and nose limit the field of view of the inner canthus, thus it is expected to receive less radiation than other more exposed regions. To explain the disproportionate rate, it is hypothesised that a portion of radiation incident onto the eye is reflected to the inner canthus. The aim of this thesis is to investigate the contribution that the radiation reflected off the surface of the eye makes to the overall dose on the inner canthus. The inter reflections between the eye and inner canthus were studied through the use of the ray tracing program Zemax. Zemax was used to trace rays in a non sequential mode incident onto a model eye and periorbital region. To obtain the models of the eye and periorbital region, both magnetic resonance imaging and a casting process was investigated, with the later being superior for our uses. With the model obtained, it was used in a series of three dimensional ray tracing programs. On a macroscopic scale there is a small increase in the irradiance on the inner canthus (2 % over a 1 cm2 area). Peaks of high irradiance (19 % increase in irradiance above direct irradiance) were discovered over the surface when the detector was divided into 200 mm elements. It was concluded that these increases above the direct irradiance in these small regions, increases the possibility of the occurrence of a Basal cell carcinoma. Individual facial geometry, will greatly effect the location and size of these peaks and as a result an experimental method to measure the dose distribution across the inner canthus was proposed. Initially it was planned to use polysulphone film to measure the erythemal dose on the inner canthus. Results from the modelling indicated that any measurements made had to be at a high spatial resolution. Polysulphone film was found to be inadequate for this, due to its large uncertainties. An alternative method was investigated so that a population study could be performed in future studies using visible radiation and high dynamic range images gave a simple and effective clinical assessment tool. The high dynamic range images showed hot spots in the irradiance across the inner canthus agreeing with the model. The small spots of high relative irradiance may not be the only reason for the increased rate in this region. Greater skin sensitivity and absence of sun screen use at this site are other possibilities. It is believed however that the irradiance distribution across the inner canthus on a microscopic scale goes a long way to increasing the risk for certain people.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: We design and implement a prototype digital watermarking scheme that uses spread-transform dither modulation to embed hidden binary message signals into uncompressed digital video signals. The hidden messages are intended to identify the original recipient of a particular copy of a digital video, so that in the event that a pirate copy of that video is found, the recipient can be incriminated as a pirate. We test the ability of the watermark signal to survive various modifications to the watermarked video, including lossy compression, frame deletion, and amplitude scaling. We find that the scheme performs well when watermarked videos remain uncompressed, but the scheme is not sufficiently robust against lossy compression. We also implement a dynamic traitor tracing scheme based on the scheme of Fiat and Tassa, which is designed to identify a group of pirates who combine their watermarked videos in an attempt to defeat the watermarking scheme. We test the traitor tracing scheme in a simulated digitally watermarked video broadcast system where a pirate rebroadcast is monitored. We find that when the pirate rebroadcast is delayed, our traitor tracing scheme identifies and disconnects the pirates more quickly than the scheme of Fiat and Tassa. / AFRIKAANSE OPSOMMING: Ons ontwerp en implementeer ’n digitale watermerkskema-prototipe wat strektransform-bibbermodulasie gebruik om binêre boodskapseine in digitale videoseine te verskuil. Die doel van die versteekte boodskappe is om die oorspronklike ontvanger van ’n bepaalde digitale video-afskrif te identifiseer. Indien ’n onwettige afskrif van die video ontdek word, kan die oorspronklike ontvanger daarvoor verantwoordelik gehou word. Ons toets die vermoë van die watermerksein om verskeie veranderinge aan die gewatermerkte video te oorleef, byvoorbeeld kompressie, die verwydering van videorame, en amplitudeskalering. Die skema vaar goed in die afwesigheid van videokompressie, maar is nie robuus wanneer die video beduidend saamgepers word nie. Ons implementeer ook ’n dinamiese skema vir verraaier-opsporing, gebaseer op ’n tegniek deur Fiat en Tassa. Die doel van hierdie skema is om groepe gebruikers te identifiseer wat saamwerk om ’n watermerkskema te kul deur gewatermerkte videos te kombineer. Ons toets die verraaier-opsporingskema in ’n simulasie van ’n gewatermerkte video-uitsendingstelsel wat ’n roofuitsending monitor. Wanneer die roofuitsending vertraag is, vind ons dat die voorgestelde verraaier-opsporingskema die skuldige gebruikers vinniger uitwys as die skema van Fiat en Tassa.

abstract: Mostly, manufacturing tolerance charts are used these days for manufacturing tolerance transfer but these have the limitation of being one dimensional only. Some research has been undertaken for the three dimensional geometric tolerances but it is too theoretical and yet to be ready for operator level usage. In this research, a new three dimensional model for tolerance transfer in manufacturing process planning is presented that is user friendly in the sense that it is built upon the Coordinate Measuring Machine (CMM) readings that are readily available in any decent manufacturing facility. This model can take care of datum reference change between non orthogonal datums (squeezed datums), non-linearly oriented datums (twisted datums) etc. Graph theoretic approach based upon ACIS, C++ and MFC is laid out to facilitate its implementation for automation of the model. A totally new approach to determining dimensions and tolerances for the manufacturing process plan is also presented. Secondly, a new statistical model for the statistical tolerance analysis based upon joint probability distribution of the trivariate normal distributed variables is presented. 4-D probability Maps have been developed in which the probability value of a point in space is represented by the size of the marker and the associated color. Points inside the part map represent the pass percentage for parts manufactured. The effect of refinement with form and orientation tolerance is highlighted by calculating the change in pass percentage with the pass percentage for size tolerance only. Delaunay triangulation and ray tracing algorithms have been used to automate the process of identifying the points inside and outside the part map. Proof of concept software has been implemented to demonstrate this model and to determine pass percentages for various cases. The model is further extended to assemblies by employing convolution algorithms on two trivariate statistical distributions to arrive at the statistical distribution of the assembly. Map generated by using Minkowski Sum techniques on the individual part maps is superimposed on the probability point cloud resulting from convolution. Delaunay triangulation and ray tracing algorithms are employed to determine the assembleability percentages for the assembly. / Dissertation/Thesis / Ph.D. Mechanical Engineering 2011

Alcohol liver disease (ALD) is a major health concern throughout the world. Currently, in the United States, 17 million people suffer from alcoholism, of which 1.4 million people are receiving treatment [1, 2]. The link between ethanol metabolism, reactive oxygen species (ROS) and liver injury in ALD has been well characterized over the last couple decades [3-10]. Ethanol metabolism relies on the availability of the cofactor NAD+ for the oxidation of ethanol into acetate, consequently causing alterations in redox potential. Redox dysfunction within the mitochondria can affect multiple pathways important in maintaining cellular homeostasis. Chapter 1 provides an introduction to the role of ethanol metabolism in oxidative stress and alcohol liver injury (ALI). During ethanol metabolism, both the cytochrome bc1 and NADH dehydrogenase complexes within the mitochondria have been demonstrated to be major contributors to ROS formation and “leak” free radicals [11-13]. As a result, the free radicals superoxide (O2-) and hydrogen peroxide (H2O2) is diffused into the cytoplasm where they can react with other molecules, proteins and DNA and cause tissue injury [4, 14]. Chapter 1 aims to introduce the link between ethanol metabolism and histone post-translational modifications (PTM) such as tyrosine nitration and lysine acetylation using proteomics techniques. Chapter 2 uses a global proteomic study to identify links between gender and ALI. A 10-day chronic-binge mouse model was employed in order to identify gender-specific proteins that may influence the development of ALD. It has previously been established that females are more susceptible to developing ALD, however, the cause is still unknown. This study identifies gender differences in the family of cytochrome P450 proteins using a mouse model for chronic-binge alcohol exposure. The cytochrome P450 family of proteins are important in the metabolism of toxic compounds, such as acetaldehyde, a byproduct of ethanol metabolism. Interestingly, I also identified that female mice expressed naturally higher levels of histone acetylation prior to alcohol exposure when compared to males. Following alcohol exposure, the female mice did not show much change in acetylation, whereas male acetylation levels were raised to similar levels of the female mice. These acetylation changes raised the question, how does alcohol influence epigenetic marks on histone proteins? Recently, new evidence has emerged that supports the role of epigenetics in the pathophysiology of ALD [4, 14-27]. Ethanol metabolism will promote shifts in redox potential and mitochondrial dysfunction, the result is the formation of reactive oxygen and/or nitrogen species (ROS/RNS) [4, 5, 7, 10, 14, 28]. As ethanol is metabolized, the accumulation of ROS/RNS species such as NO- and O2- can induce the post-translational modification nitrotyrosine. Shifts in redox potential will cause the electron transport chain to “leak” the free radical O2-. Another free radical known as nitric oxide (NO-) has been shown to be elevated during times of ethanol consumption [29, 30]. Traditionally, NO has a protective role within the cell at low concentrations, however, in surplus can lead to tissue damage. Ethanol-induced increases in NO- and O2- can instigate to peroxynitrite (ONOO-) formation; a potent oxidant and nitrating agent of tyrosine residues [29, 31-34]. Chapter 3 examines the indirect effect of alcohol metabolism and ROS/RNS formation on histone tyrosine nitration. This project used mass-spectrometry to identify novel targets of histone tyrosine nitration using a mouse-model of chronic-binge alcohol exposure. Interestingly, histone H3 was found to be nitrated on the hinge-region of the N-terminal tail at tyrosine 41. Molecular dynamics of the nitrated and unmodified proteoforms revealed that the DNA prefers a change in conformation upon H3Y41 nitration. Further studies using an antibody synthesized against the nitrated H3y41 region of the protein revealed potential targets within the genome important in fatty acid synthesis and metabolism. Chapter 4 looks at the direct influence of alcohol metabolism and its contribution to histone acetylation via acetate production and acetyl-CoA. Alcohol metabolism has traditionally been thought influence acetylation through the sirtuin family of deacetylase proteins. Sirtuin deacetylases are NAD+-dependent and have been shown to be a regulate protein acetylation within the mitochondria, cytoplasm, and nucleus during times of ethanol exposure [35-37]. Shifts in redox potential attributed to ethanol metabolism can inhibit sirtuin deacetylase activity by out-competing the enzymes for available NAD+, ultimately leading to mitochondrial and nuclear hyperacetylation [17, 28, 38-42]. Currently, there is evidence that ethanol increases acetylation of histone 3 lysine 9, which then targets activation of the alcohol dehydrogenase gene (ADH) [17, 18, 43]. Moreover, Shukla et.al. (2008) support the idea that ethanol can alter epigenetic transcriptional activation based on which modification is selected for a site during times of stress when it can be occupied by more than one modification [22]. Chapter 4 demonstrates the use of mass-spectrometry to metabolically trace 13C2-labeled ethanol in vivo. These new data show clear evidence of 13C2 heavy-labeled ethanol being incorporated into known sites of acetylation on the N-terminal tails of histone H3 and H4. Incorporation of heavy-label was calculated using extracted ion chromatograms (XIC) for the double and singly acetylated and unmodified peptides belonging to H3K9-R17 and H3K18-R23. Total change in acetylation was also assessed for each peptide using the ratio of ratios of total acetylation to unmodified peptide over the fold change in ethanol- to control-fed groups. An interesting observation was observed in that the incorporation of heavy-label suggests site-selectivity of lysine residues over time. Histone 4 contains multiple sites of acetylation on the peptide H4K5-R17, making it hard to quantify manually. MaxQuant evidence files in conjunction with R were used to calculate the 13C2 incorporation on the multiple H4 acetyl-sites over 24-hours. Ethanol-heavy label incorporation at multiple acetyl-sites occurred as a mixture suggesting a role in transcriptional regulation. These new data establish a link between alcohol metabolism and known epigenetic marks on histone proteins. These studies have now established that alcohol metabolism is indirectly linked to histone tyrosine nitration through increased ROS/RNS and directly through acetate production. Understanding how these epigenetic marks fluctuate as ALD progresses will provide potential targets for the development of new drug therapies. The epigenetic marks identified in these studies have previously been established to be important activators in transcription. These data provide novel techniques using proteomics-based metabolic tracing in vivo. Future studies will assess how these marks change after chronic ethanol exposure and whether the changes in epigenetics are heritable. Understanding hereditary of alcoholism will provide insight to those predisposed to the disease.

Submitted by Pedro Accorsi Amaral (pedroaccorsi10@hotmail.com) on 2017-07-05T20:10:04Z No. of bitstreams: 1 Master Thesis.pdf: 2092692 bytes, checksum: cf0bf23ba85b5e1297c36503f1a0d52a (MD5) / Approved for entry into archive by ÁUREA CORRÊA DA FONSECA CORRÊA DA FONSECA (aurea.fonseca@fgv.br) on 2017-07-06T20:51:03Z (GMT) No. of bitstreams: 1 Master Thesis.pdf: 2092692 bytes, checksum: cf0bf23ba85b5e1297c36503f1a0d52a (MD5) / Made available in DSpace on 2017-07-20T18:01:11Z (GMT). No. of bitstreams: 1 Master Thesis.pdf: 2092692 bytes, checksum: cf0bf23ba85b5e1297c36503f1a0d52a (MD5) Previous issue date: 2017-05-16 / This work addresses the determinants of the decisions made by small powers to fight alongside great powers in major conflicts. When faced with the request from a great power to participate in wars, some peripheral countries abide and others remain uninvolved. To explain this variation, the case study of the Colombian participation in the Korean War is used, comparing the country to other Latin American cases. Building on rational choice models of leaders’ behavior, I expect that leaders decide to go to war when the rewards for this action increase their likelihood of remaining in power. I use explicit process tracing to investigate the causes for the Colombian decision and organize them into necessary and sufficient conditions. Evidence suggests that the causes for the Colombian participation in Korea were an attempt from the president to improve his relationship with the United States in order to obtain more foreign aid, the Colombian authoritarian regime, and an attempt from the president to please the armed forces, which had the power to keep him in office. I also use synthetic control method to test whether the Colombian decision increased the foreign aid received by the country from the United States. Results show a significant increase in received aid. These findings corroborate the expectation that leaders of small powers will go to war in order to receive more aid and to make policy concessions for those who hold the power to keep them in office, and that they are rewarded from the great power for this decision under certain conditions.