Bayessches Transferlernen für die Semantische Segmentierung von Luftbildern

Diese Arbeit beschäftigt sich mit dem Problem der semantischen Segmentierung von Luftbildern in Landbedeckungsklassen. Maschinelle Lernverfahren bieten dabei sehr robuste Methoden zur Erzeugung von hochgenauen Klassifikatoren, welche die Basisbausteine von Verfahren zur Erzeugung solcher Segmentierungen darstellen. Moderne und praktikable Lernverfahren sind jedoch nahezu ausschließlich den überwachten Methoden zuzuschreiben. Ihr Wissen über das zu lösende Klassifikationsproblem wird aus gelabelten Stichproben extrahiert, welche zuerst in mühevoller manueller Arbeit von qualifizierten Fachkräften aus den Eingangsbildern erzeugt werden müssen. Die Reduktion dieses manuellen Aufwands wurde daher in vielen Arbeiten als Kernproblem in Angriff genommen, woraus sich sehr unterschiedliche und heutzutage essentielle Teilgebiete des maschinellen Lernens entwickelt haben, wie u. a. dem Transferlernen. Im Transferlernen wird das Anlernen des Klassifikators durch andere, bereits vorhandene Datenquellen augmentiert. Insbesondere gilt für die Domänenadaption, dass das Eingangsbild ungelabelt ist und Klasseninformation lediglich aus diesen Datenquellen abgeleitet werden kann. Dieses Vorgehen kann jedoch nur funktionieren, falls das Eingangsbild und die Datenquellen große Ähnlichkeiten aufweisen und in einer modellierbaren Relation zueinander stehen. Die ansonsten resultierende Verschlechterung der Klassifikation heißt dann negativer Transfer. In dieser Arbeit wird ein bestehendes theoretisches Modell zur Prädiktion von negativen Transfer für die Domänenadaption in ein Bayessches Entscheidungsmodell umformuliert. Dessen Implementierung durch ein Markov-Chain-Monte-Carlo Verfahren ist mit einer hohen Wahrscheinlichkeit dazu in der Lage, aus einer Vielzahl von potentiellen Quellenkandidaten die beste Quelle für ein gegebenes Eingangsbild auszuwählen. Eine anschließend hergeleitete Approximation dieser Methode besitzt eine lineare Laufzeitkomplexität bezüglich der Stichprobengröße und der Anzahl der Quellenkandidaten und erlaubt somit die Verarbeitung von sehr großen Datensätzen mit mehr als 15.000 Lernbeispielen pro Quelle und mehreren Dutzend Quellenkandidaten in weniger als 10 Sekunden. Weiterhin konnte der Speicherverbrauch ohne messbare Einbußen auf wenige Kilobyte pro Quelle reduziert werden. Auf 7 untersuchten Datensätzen reduzierte die Bayessche Quellenselektion den Medianverlust der Klassifikationsgenauigkeit im Vergleich mit konventionellen Ansätzen im Mittel von 5% auf 3%. Das entwickelte Verfahren besitzt keine kritischen Parameter. Eine aufwändige Parametersuche entfällt somit im direkten Vergleich zu Konkurrenzmethoden. In einem weiteren Experiment wurden zunächst ungelabelte Quellenkandidaten verwendet. Durch einen neuartigen Clustering Ansatz, basierend auf dem zuvor entwickelten Quellenselektionsmodell, konnten aus diesen die relevanten Quellen zuverlässig ermittelt werden. Ein manuelles labeln von redundanten Quellen entfällt somit. Auf den untersuchten Datensätzen konnte bei gleichbleibender Klassifikationsgenauigkeit eine Reduktion des Arbeitsaufwandes um bis zu 90% erreicht werden

Cascaded Random Forest for Fast Object Detection ∗

Abstract. A Random Forest consists of several independent decision trees arranged in a forest. A majority vote over all trees leads to the final decision. In this paper we propose a Random Forest framework which incorporates a cascade structure consisting of several stages together with a bootstrap approach. By introducing the cascade, 99 % of the test images can be rejected by the first and second stage with minimal computational effort leading to a massively speeded-up detection framework. Three different cascade voting strategies are implemented and evaluated. Additionally, the training and classification speed-up is analyzed. Several experiments on public available datasets for pedestrian detection, lateral car detection and unconstrained face detection demonstrate the benefit of our contribution.

Dissociating memory networks in early Alzheimer's disease and frontotemporal lobar degeneration - a combined study of hypometabolism and atrophy

Introduction: We aimed at dissociating the neural correlates of memory disorders in Alzheimer’s disease (AD) and frontotemporal lobar degeneration (FTLD). Methods: We included patients with AD (n = 19, 11 female, mean age 61 years) and FTLD (n = 11, 5 female, mean age 61 years) in early stages of their diseases. Memory performance was assessed by means of verbal and visual memory subtests from the Wechsler Memory Scale (WMS-R), including forgetting rates. Brain glucose utilization was measured by [18F]fluorodeoxyglucose positron emission tomography (FDG-PET) and brain atrophy by voxel-based morphometry (VBM) of T1-weighted magnetic resonance imaging (MRI) scans. Using a whole brain approach, correlations between test performance and imaging data were computed separately in each dementia group, including a group of control subjects (n = 13, 6 female, mean age 54 years) in both analyses. The three groups did not differ with respect to education and gender. Results: Patients in both dementia groups generally performed worse than controls, but AD and FTLD patients did not differ from each other in any of the test parameters. However, memory performance was associated with different brain regions in the patient groups, with respect to both hypometabolism and atrophy: Whereas in AD patients test performance was mainly correlated with changes in the parieto-mesial cortex, performance in FTLD patients was correlated with changes in frontal cortical as well as subcortical regions. There were practically no overlapping regions associated with memory disorders in AD and FTLD as revealed by a conjunction analysis. Conclusion: Memory test performance may not distinguish between both dementia syndromes. In clinical practice, this may lead to misdiagnosis of FTLD patients with poor memory performance. Nevertheless, memory problems are associated with almost completely different neural correlates in both dementia syndromes. Obviously, memory functions are carried out by distributed networks which break down in brain degeneration

Achilles tendon suture deteriorates tendon capillary blood flow with sustained tissue oxygen saturation – an animal study

<p>Abstract</p> <p>Background</p> <p>Treatment of ruptured Achilles tendons currently constitutes of conservative early functional treatment or surgical treatment either by open or minimal invasive techniques. We hypothesize that an experimental Achilles tendon suture in an animal model significantly deteriorates Achilles tendon microcirculation immediately following suturing.</p> <p>Methods</p> <p>Fifteen Achilles tendons of eight male Wistar rats (275–325 g) were included. After preparation of the Achilles tendon with a medial paratendinous approach, Achilles tendon microcirculation was assessed using combined Laser-Doppler and spectrophotometry (Oxygen-to-see) regarding:</p> <p indent="1">- tendinous capillary blood flow [arbitrary units AU]</p> <p indent="1">- tendinous tissue oxygen saturation [%]</p> <p indent="1">- tendinous venous filling pressure [rAU]</p> <p>The main body of the Achilles tendon was measured in the center of the suture with 50 Hz. 10 minutes after Achilles tendon suture (6-0 Prolene), a second assessment of microcirculatory parameters was performed.</p> <p>Results</p> <p>Achilles tendon capillary blood flow decreased by 57% following the suture (70 ± 30 AU vs. 31 ± 16 AU; p < 0.001). Tendinous tissue oxygen saturation remained at the same level before and after suture (78 ± 17% vs. 77 ± 22%; p = 0.904). Tendinous venous filling pressure increased by 33% (54 ± 16 AU vs. 72 ± 20 AU; p = 0.019) after suture.</p> <p>Conclusion</p> <p>Achilles tendon suture in anaesthetised rats causes an acute loss of capillary perfusion and increases postcapillary venous filling pressures indicating venous stasis. The primary hypothesis of this study was confirmed. In contrast, tendinous tissue oxygen saturation remains unchanged excluding acute intratendinous hypoxia within the first 10 minutes after suture. Further changes of oxygen saturation remain unclear. Furthermore, it remains to be determined to what extent reduced capillary blood flow as well as increased postcapillary stasis might influence tendon healing from a microcirculatory point of view in this animal setting.</p

Unrecognized hand ischemia after intraarterial drug injection: successful management of a "near miss" event

<p>Abstract</p> <p>Background</p> <p>Complications arising from accidental intraarterial drug injections have been described in the past. However, given the multitude of injected substances and complex pathophysiology, guidelines regarding diagnosis and management of patients with intraarterial injections remain vague. As such it remains unclear, when to expect limb ischemia and whether and for how long to monitor patients after intraarterial injections.</p> <p>Case report</p> <p>We present the case of a "near miss event" in an i.v. drug abuser presenting to the emergency department 3 hours after injection of water dissolved zolpidem (Ambien™) tablets into the right ulnar artery. Chief complaint was forearm pain. Clinical examination at the time revealed no concern for limb ischemia and patient was discharged. The patient returned unplanned 18 hours after injection with an ischemic right hand. Angiography revealed no flow in the distal ulnar artery and minimal flow in the palmar arch. Emergent intraarterial thrombolysis with Urokinase was performed and restored hand perfusion. Clinical follow-up 3 months after injury showed full recovery with regular recapillarisation and normal Allen test.</p> <p>Conclusion</p> <p>This case report highlights the need to rigorously monitor patients with suspected intraarterial injections for potential delayed onset of limb ischemia. This is to our knowledge the first described case report of a successful revascularization after prolonged ischemia with delayed onset after zolpidem injection. We recommend close monitoring of these patients for at least 24 hours in addition to starting prophylactic anticoagulation.</p

Application of a new ray tracing framework to the analysis of extended regions in Si solar cell modules

While ray tracing of solar cells was established decades ago, ray tracing of entire modules has met obstacles, mainly because module optics are affected by geometric structures varying over a large scale of dimensions. In this paper, we introduce a ray tracing framework that is based on a modular structure made up of separate plugins. While existing plugins can be used for common effects such as light sources, absorption in materials, etc., specialized plug-ins can be written by users to handle problem-specific properties. We demonstrate the functionality of our approach by ray tracing a test module containing 9 crystalline Si solar cells. Good agreement between light-beam induced current (LBIC) measurements and ray tracing is achieved

Optimizing the Solar Cell Front Side Metallization and the Cell Interconnection for High Module Power Output

Improving the light trapping in a module results in an increase in the generated current. Consequently, an optimization of the front grid metallization of the cell is required for the best trade-off between series resistance, shading, and recombination losses. For this purpose, we combine ray tracing and electrical solar cell and module calculations that explicitly account for cell and module interactions. Our model bases on experimentally verified input parameters: We determine the electrical and optical properties of the front metal fingers of passivated emitter and rear cells (PERC). We show that the effective optical width of the front metal fingers in the module is significantly reduced by 54%. The optimized simulated module has 120 half-size PERC with 20.2% cell efficiency and has an output power of 295.2 W. This is achieved with an increased number of 120 front metal fingers per cell, four white-colored cell interconnection ribbons (CIR), and an increased cell spacing. Applying these optimized design changes to an experimental module we measure a module power output of 294.8 W and a cell-to-module (CTM) factor of 1.02. Measured and simulated power agree and the deviations in Voc, Isc and FF are less than 0.91%rel. We perform a module power gain analysis for the fabricated module and simulate a potential maximum module power of 374.1 W when including further improvements.German Federal Ministry for Economic Affairs and Energy/032564

Increased Light Harvesting by Structured Cell Interconnection Ribbons: An Optical Ray Tracing Study Using a Realistic Daylight Model

A key for increasing the module efficiency is improved light harvesting. The structuring of solar cell interconnection ribbons (CIR) is a promising option for improved light harvesting as it can easily be integrated into current module production. We perform ray tracing simulations of complete PV modules in 3D exhibiting geometric features such as profiled CIR and surface textured cells. We evaluate the increase in module performance by a light harvesting string (LHS) under realistic irradiation conditions with respect to angular and spectral distribution. Using the realistic irradiation for a location in Germany, a location at the polar circle and a location at the equator we simulate the enhancement of short-circuit current density Jsc resulting from the use of LHS. Our results show Jsc gains between 1.00% and 1.86% depending on the location and module orientation. We demonstrate the applicability of our model by comparing measurements and simulations for a one-cell module that we measure and simulate under various angles of the light incidence

Semiautomatic quality control of topographic reference datasets

The usefulness and acceptance of spatial information systems are mainly dependent on the quality of the underlying geodata. This paper describes a system for semiautomatic quality control of existing geospatial data via automatic image analysis using aerial images, high-resolution satellite imagery (IKONOS and RapidEye) and low-resolution satellite imagery (Disaster Monitoring Constellation, DMC) with mono- and multi-temporal approaches focusing on objects which cover most of the area of the topographic dataset. The goal of the developed system is to reduce the manual efforts to a minimum. We shortly review the system design and then we focus on the automatic components and their integration in a semiautomatic workflow for verification and update. A prototype of the system has been in use for several years. From the experience gained during this time we give a detailed report on the system performance in its application as well as an evaluation of the results

PV module current gains due to structured backsheets

We evaluate the optical performance of PV modules with respect to an increase in short circuit current density. Our evaluation is based on the combination of ray tracing simulations and measurements on test modules with four types of backsheets: Two of them are structured, the third is white and diffusively reflecting and the fourth reflects no light. Under normal incidence, structured backsheets reflect incoming light at an angle that causes total internal reflection at the glass/air interface, which guides the light to the solar cell surface. Three different irradiance conditions are studied: a) standard testing conditions (STC) with light incident perpendicular to the module surface, b) variation in the angle of incidence and c) light source with mean annual distribution of angles of incidence. Using the measured refractive index data in ray tracing simulations we find a short circuit current density (Jsc) gain of up to 0.9 mA/cm2 (2.3%) for monofacial cells and a structured backsheet, when compared to a white backsheet with diffuse reflection. For bifacial cells we calculate an even larger Jsc increase of 1.4 mA/cm2 (3.6%). The Jsc increase is larger for bifacial cells, since some light is transmitted through the cells and thus more light interacts with the backsheet. Our optical loss analysis reveals the best performance in STC for edge-aligned Ag grooves. This structure reduces absorption losses from 1.8 mA/cm2 to 0.3 mA/cm and reflection losses from 0.7 mA/cm to 0 mA/cm. This trend also holds under various angles of incidence as confirmed consistently by Jsc measurements and ray racing simulations. Simulations using an annual light source emitting a mean annual distribution of angles of incidence reveal grooves in both orientations edge alignment and east-west alignment achieve similar current gains of up to 1.5% for mono- and of 2.5% for bifacial cells compared to modules with white back sheets. This indicates that for modules with light guiding structures such as these backsheets optimization for STC differs from optimization for annul yield