Umströmte Rohr- bzw. Stabbündel sind als Übertrager von Wärmeenergie in einem breiten Spektrum von Anwendungsgebieten zu finden. Beispiele sind Heizkörper, Kühlaggregate, Heizpatronen, industrielle Wärmetauscher und Brennelemente in Kernreaktoren. Für jede dieser Anwendungen besteht die Anforderung, die Wärmeübertragung an den Wärmeübertragerflächen zu optimieren. Dabei besteht eine enge Kopplung zwischen Wärmetransport und Strömungsstruktur. Eine besonders effiziente Form der Wärmeübertragung ist die Verdampfung. Diese wird unter anderem bei Brennelementen in Druckwasserreaktoren genutzt. Hier siedet das Kühlwasser an der Brennstaboberfläche. Durch Kondensation der Dampfblasen in der unterkühlten Kernströmung wird die Wärme dann effizient in die Flüssigphase übertragen. Durch die hohe Verdampfungsenthalpie des Wassers wird beim Strömungssieden ein viel höherer Wärmestrom in das Kühlwasser übertragen, als bei rein einphasig-konvektivem Wärmetransport. Sicherheitstechnisch relevant für Brennelemente in Leichtwasserreaktoren ist der Übergang vom Blasensieden zum Filmsieden (kritischer Wärmestrom). Dieser muss unter allen Umständen vermieden werden, um die Integrität der Brennstabhüllen zu gewährleisten, die bei Überschreiten der kritischen Heizflächenbelastung aufschmelzen bzw. reißen können. Aus diesem Grund werden im Rahmen eines vom Bundesministerium für Bildung und Forschung geförderten Projektes (Förderkennzeichen 02NUK010A) numerische Strömungsberechnungsmodelle entwickelt, die bei der Beschreibung und numerischen Behandlung der Siedephänomene helfen sollen. Zur Validierung dieser Modelle anhand von Experimenten wurde ein Strömungskanal konstruiert, in dem ein vertikales Stabbündel von einem Kältemittel (RC318) aufwärtig durchströmt wird. Der Versuchsstand ist so konzipiert, dass ein optischer und messtechnischer Zugang zu den umströmten Einbauten gegeben ist. Damit sind Messungen in Zweiphasenströmungen ebenso möglich, wie Untersuchungen zur einphasigen Durchströmung. Für später erfolgende Zweiphasen-Experimente mit Stabbeheizung wurden zunächst Voruntersuchungen zur einphasigen Durchströmungen durchgeführt, welche insbesondere Aufschluss über die Homogenität der Strömung in den Unterkanälen sowie die Existenz von Querströmungen geben sollten. Als Messverfahren dafür wurde die Particle Image Velocimetry (PIV) ausgewählt, welche es ermöglicht, zweidimensionale Strömungsfelder aufzuzeichnen. Die experimentellen Studien erfolgten am Optical Multi-Phase Flow Research Laboratory des Nuclear Engineering Department der Texas A&M University in College Station, USA. Die Untersuchungen wurden für drei Volumenstromraten durchgeführt. Der vorliegende Bericht umfasst die Beschreibung des Versuchsstandes und der Messmethodik, eine Vorstellung des Auswerteverfahrens und relevanter Ergebnisse sowie eine Fehlerbetrachtung.

Today, 3D models of cities are created from aerial images using a camera rig. Images, together with sensor data from the flights, are stored for further processing when building 3D models. However, there is a market demand for a more mobile solution of satisfactory quality. If the camera position can be calculated for each image, there is an existing algorithm available for the creation of 3D models. This master thesis project aims to investigate whether the iPhone 4 offers good enough image and sensor data quality from which 3D models can be created. Calculations on movements and rotations from sensor data forms the foundation of the image processing, and should refine the camera position estimations. The 3D models are built only from image processing since sensor data cannot be used due to poor data accuracy. Because of that, the scaling of the 3D models are unknown and a measurement is needed on the real objects to make scaling possible. Compared to a test algorithm that calculates 3D models from only images, already available at the SBD’s system, the quality of the 3D model in this master thesis project is almost the same or, in some respects, even better when compared with the human eye.

Methodologies are proposed for combining carrier-phase differential GPS (CDGPS), visual simultaneous localization and mapping (SLAM), and inertial measurements to obtain precise and globally-referenced position and attitude estimates of a rigid structure connecting a GPS receiver, a camera, and an inertial measurement unit (IMU). As part of developing these methodologies, observability of globally-referenced attitude based solely on GPS-based position estimates and visual feature measurements is proven. Determination of attitude in this manner eliminates the need for attitude estimates based on magnetometer and accelerometer measurements, which are notoriously susceptible to magnetic disturbances. This combination of navigation techniques, if coupled properly, is capable of attaining centimeter-level or better absolute positioning and degree-level or better absolute attitude accuracies in any space, both indoors and out. Such a navigation system is ideally suited for application to augmented reality (AR), which often employs a GPS receiver, a camera, and an IMU, and would result in tight registration of virtual elements to the real world. A prototype AR system is presented that represents a first step towards coupling CDGPS, visual SLAM, and inertial navigation. While this prototype AR system does not couple CDGPS and visual SLAM tightly enough to obtain some of the benefit of the proposed methodologies, the system is capable of demonstrating an upper bound on the precision that such a combination of navigation techniques could attain. Test results for the prototype AR system are presented for a dynamic scenario that demonstrate sub-centimeter-level positioning precision and sub-degree-level attitude precision. This level of precision would enable convincing augmented visuals. / text

Intensive care delirium prevention is currently a practice improvement goal of the Society of Critical Care Medicine. Delirium increases morbidity, mortality, time mechanically ventilated, length of stay, and health care spending. The Clinical Practice Guidelines for the Management of Pain, Agitation, and Delirium in Adult Patients in the Intensive Care Unit (PAD guidelines) were revised and published in 2013. The ICU Delirium and Cognitive Impairment Study Group at Vanderbilt University have developed the ABCDEF Bundle protocol as a way of operationalizing the 2013 PAD guidelines. Implementation of the ABCDEF Bundle protocol has been shown to decrease occurrence and duration of delirium while improving morbidity and mortality therefore decreasing length of stay. The purpose of this project is to develop an implementation and evaluation plan of the ABCDEF Bundle for a community hospital's TSICU in Arizona. The Squire guidelines for quality improvement reporting are followed for this project. Implementation and evaluation of the ABCDEF bundle are explained in detail.

Ultrathin fiberscopes typically have an imaging channel and an illumination channeland are available in diameters ranging from 0.5 mm to 2.5 mm. The minimum diam-eter can be reduced by combining the illumination and imaging paths into a singlefiberoptic channel. Constructing a single channel fiberscope requires a technique ofilluminating the tissue, while minimizing the Fresnel reflections and scatter withinthe common illumination and detection channel.A single channel fiberscope should image diffusely reflected light from tissue illu-minated with light filtered for the visible wavelength range (450 - 650 nm). Simplycombining the illumination and collection paths via a beamsplitter results in a lowobject to background signal ratio. The low contrast image is due to a low collectionefficiency of light from the ob ject as well as a high background signal from the Fresnelreflection at the proximal surface of the fiber bundle, where the illumination enters thefiber bundle. The focus of the dissertation is the investigation of methods to reducethe background signal from the proximal surface of the fiber bundle. Three systemswere tested. The first system uses a coherent fiber bundle with an AR-coating on theproximal face. The second system incorporates crossed polarizers into the light path.In addition, a technique was developed, whereby a portion of the image numericalaperture is devoted to illumination and a portion to image signal detection. Thistechnique is called numerical aperture sharing (NA sharing).This dissertation presents the design, construction, testing, and comparison ofthe three single channel fiberscopes. In addition, preliminary results of a study aimedat the usefulness of broadband diffuse reflectance imaging for the identification andtracking of disease progression in mouse esophagus are presented.

In response to public concern over fairness in testing, conducting a differential item functioning (DIF) analysis is now standard practice for many large-scale testing programs (e.g., Scholastic Aptitude Test, intelligence tests, licensing exams). As highlighted by the Standards for Educational and Psychological Testing manual, the legal and ethical need to avoid bias when measuring examinee abilities is essential to fair testing practices (AERA-APA-NCME, 1999). Likewise, the development of statistical and substantive methods of investigating DIF is crucial to the goal of designing fair and valid educational and psychological tests. Douglas, Roussos and Stout (1996) introduced the concept of item bundle DIF and the implications of differential bundle functioning (DBF) for identifying the underlying causes of DIF. Since then, several studies have demonstrated DIF/DBF analyses within the framework of “unintended” multidimensionality (Oshima & Miller, 1992; Russell, 2005). Russell (2005), in particular, examined the effect of secondary traits on DBF/DTF detection. Like Russell, this study created item bundles by including multidimensional items on a simulated test designed in theory to be unidimensional. Simulating reference group members to have a higher mean ability than the focal group on the nuisance secondary dimension, resulted in DIF for each of the multidimensional items, that when examined together produced differential bundle functioning. The purpose of this Monte Carlo simulation study was to assess the Type I error and power performance of SIBTEST (Simultaneous Item Bias Test; Shealy & Stout, 1993a) for DBF analysis under various conditions with simulated data. The variables of interest included sample size and ratios of reference to focal group sample sizes, correlation between primary and secondary dimensions, magnitude of DIF/DBF, and angular item direction. Results showed SIBTEST to be quite powerful in detecting DBF and controlling Type I error for almost all of the simulated conditions. Specifically, power rates were .80 or above for 84% of all conditions and the average Type I error rate was approximately .05. Furthermore, the combined effect of the studied variables on SIBTEST power and Type I error rates provided much needed information to guide further use of SIBTEST for identifying potential sources of differential item/bundle functioning.

Disertacijoje aprašomas gretinamasis leksinių samplaikų tyrimas lietuvių gimtosios kalbos vartotojų ir gimtakalbių anglų kalbos vartotojų rašytinėje anglų kalboje. Tyrime naudoti trys skirtingų kalbos mokėjimo lygių vartotojų anglų kalbos tekstynai: pirmakursių studentų ir vyresniųjų kursų studentų, kurių gimtoji kalba – lietuvių, rašiniai, bei anglų gimtosios kalbos vartotojų, t. y. įvairių Didžiosios Britanijos ir JAV universitetų studentų rašiniai. Leksinių samplaikų struktūrinė analizė parodė, jog žemesnio mokėjimo lygio mokinių kalboje dažniau pasitaiko veiksmažodinių samplaikų, o aukštesnio lygio mokinių kalboje – vardažodinių. Tai rodo, jog žemesnio mokėjimo lygio mokinių kalba artimesnė sakytinei anglų kalbai, kuriai būdingos veiksmažodinės leksinės samplaikos. Kylant kalbos mokėjimo lygiui, mokinių rašytinėje kalboje randasi daugiau vardažodinių leksinių samplaikų, kurios dažnesnės rašytiniame diskurse. Funkcinė leksinių samplaikų analizė atskleidė, jog kylant mokinių kalbos mokėjimo lygiui nuosekliai kinta ir tam tikrų kalbos funkcijų raiška: žemesnio lygio mokiniai daugiau dėmesio skiria diskurso organizavimo ir autoriaus pozicijos raiškai, o aukštesnio lygio mokinių kalboje dažnesni referentiniai pasakymai, perteikiantys teksto propozicinį turinį. Leksinių samplaikų analizė pagal jose realizuojamus frazinius junginius atskleidė lietuvių gimtosios kalbos vartotojams būdingų frazinių junginių vartojimo ypatumų. Tyrimo išvados ir taikomoji vertė siejamos su anglų... [toliau žr. visą tekstą] / The study presents a contrastive analysis of learner language which is represented by written English of the Lithuanian EFL learners and native speakers of English. The material for the study comes from three corpora of learner language: two Lithuanian corpora consist of student essays written by first-year students and third-/fourth-year students of English Philology while the native speaker corpus is a selection of argumentative essays from the LOCNESS corpus. The study involves structural and functional analyses of lexical bundles retrieved from the three corpora. The findings of the study show that written English produced by the learners of the lower proficiency levels bears more features typical of spoken English. As the level of proficiency increases, the number of verbal bundles gives way to bundles incorporating noun and prepositional phrases which are more characteristic of the written variety of the language. As regards the distribution of lexical bundles across the functional types, the study proves that the Lithuanian learners pay more attention to discourse organization and expression of stance while in the native speaker material the proportion of referential lexical bundles, used to express propositions, is much more prominent. The study also involves an analysis of phrasal expressions recurring in the lexical bundles. The conclusions and implications of the research may be particularly useful to the practice of ELT/EFL in Lithuania while certain insights of... [to full text]

Šis darbas pratęsia 2010 m. autorės atlikto bakalauro darbo „Elipsinio tipo B-erdvių beveik kontaktiniai metriniai hiperpaviršiai“ tyrinėjimus, apibendrina šio darbo rezultatus kitų tipų ir rūšių -struktūroms ir pritaiko juos liečiamųjų sluoksniuočių paviršių teorijoje. / In the work, the generalized (φ, ξ, η, g)-structures in normalized hypersurfaces M2n-1 T(En) are found and its properties are investigated. Geometric meaning in basis En of some interesting hypersurfaces (hypersphere, hyperplane, hypercone,…) is explained.

This thesis is about the structure of the boundary of the universe, i.e., points where the geometric structures of spacetime cannot be continued. In partic­ular, we study the structure of the b-boundary by B. Schmidt. It has been known for some time that the b-boundary construction has several drawbacks, perhaps the most severe being that it is often not Hausdorff separated from interior points in spacetime. In other words, the topology makes it impossible to distinguish which points in spacetime are near the singularity and which points are ‘far’ from it. The non-Hausdorffness of the b-completion is closely related to the concept of fibre degeneracy of the fibre in the frame bundle over a b-boundary point, the fibre being smaller than the whole structure group in a specific sense. Fibre degeneracy is to be expected for many realistic spacetimes, as was proved by C. J. S. Clarke. His proofs contain some errors however, and the purpose of paper I is to reestablish the results of Clarke, under somewhat different conditions. It is found that under some conditions on the Riemann curvature tensor, the boundary fibre must be totally degenerate (i.e., a single point). The conditions are essentially that the components of the Riemann tensor and its first derivative, expressed in a parallel frame along a curve ending at the singularity, diverge sufficiently fast. We also demonstrate the applicability of the conditions by verifying them for a number of well known spacetimes. In paper II we take a different view of the b-boundary and the b-length func­tional, and study the Riemannian geometry of the frame bundle. We calculate the curvature Rof the frame bundle, which allows us to draw two conclusions. Firstly, if some component of the curvature of spacetime diverges along a horizontal curve ending at a singularity, R must tend to — oo. Secondly, if the frame bundle is extendible through a totally degenerate boundary fibre, the spacetime must be a conformally flat Einstein space asymptotically at the corresponding b-boundary point. We also obtain some basic results on the isometries and the geodesics of the frame bundle, in relation to the corresponding structures on spacetime. The first part of paper III is concerned with imprisoned curves. In Lorentzian geometry, the situation is qualitatively different from Riemannian geometry in that there may be incomplete endless curves totally or partially imprisoned in a compact subset of spacetime. It was shown by B. Schmidt that a totally imprisoned curve must have a null geodesic cluster curve. We generalise this result to partially im­prisoned incomplete endless curves. We also show that the conditions for the fibre degeneracy theorem in paper I does not apply to imprisoned curves. The second part of paper III is concerned with the properties of the b-length functional. The b-length concept is important in general relativity because the presence of endless curves with finite b-length is usually taken as the definition of a singular spacetime. It is also closely related to the b-boundary definition. We study the structure of b-neighbourhoods, i.e., the set of points reachable from a fixed point in spacetime on (horizontal) curves with b-length less than some fixed number e > 0. This can then be used to understand how the geometry of spacetime is encoded in the frame bundle geometry, and as a tool when studying the structure of the b-boundary. We also give a result linking the b-length of a general curve in the frame bundle with the b-length of the corresponding horizontal curve. / digitalisering@umu

abstract: There is a growing interest in the creation of three-dimensional (3D) images and videos due to the growing demand for 3D visual media in commercial markets. A possible solution to produce 3D media files is to convert existing 2D images and videos to 3D. The 2D to 3D conversion methods that estimate the depth map from 2D scenes for 3D reconstruction present an efficient approach to save on the cost of the coding, transmission and storage of 3D visual media in practical applications. Various 2D to 3D conversion methods based on depth maps have been developed using existing image and video processing techniques. The depth maps can be estimated either from a single 2D view or from multiple 2D views. This thesis presents a MATLAB-based 2D to 3D conversion system from multiple views based on the computation of a sparse depth map. The 2D to 3D conversion system is able to deal with the multiple views obtained from uncalibrated hand-held cameras without knowledge of the prior camera parameters or scene geometry. The implemented system consists of techniques for image feature detection and registration, two-view geometry estimation, projective 3D scene reconstruction and metric upgrade to reconstruct the 3D structures by means of a metric transformation. The implemented 2D to 3D conversion system is tested using different multi-view image sets. The obtained experimental results of reconstructed sparse depth maps of feature points in 3D scenes provide relative depth information of the objects. Sample ground-truth depth data points are used to calculate a scale factor in order to estimate the true depth by scaling the obtained relative depth information using the estimated scale factor. It was found out that the obtained reconstructed depth map is consistent with the ground-truth depth data. / Dissertation/Thesis / M.S. Electrical Engineering 2010