Capturing Regular Human Activity through a Learning Context Memory

A learning context memory consisting of two main parts is presented. The first part performs lossy data compression, keeping the amount of stored data at a minimum by combining similar context attributes — the compression rate for the presented GPS data is 150:1 on average. The resulting data is stored in an appropriate data structure highlighting the level of compression. Elements with a high level of compression are used in the second part to form the start and end points of episodes capturing common activity consisting of consecutive events. The context memory is used to investigate how little context data can be stored containing still enough information to capture regular human activity

Optimization of fuel cell bipolar plates for automotive application

In dieser Arbeit wird das Potential der Bipolarplatten von Polymer-Elektrolyt-Membran (PEM)- Brennstoffzellen zur Steigerung der Leistung und Lebensdauer untersucht. Für die medienführenden Bereiche der Bipolarplatte werden Designrichtlinien entwickelt, die die Auslegung dieser Bereiche auf hohe Stromdichten und homogene Medienverteilung vereinfachen. Im zweiten Abschnitt wird eine Validierungsmethode für automobile Brennstoffzellen mittels kleinen Laborzellen entwickelt, um die Kosten für die Validierung der Bipolarplattendesigns zu reduzieren. Abschließend wird mit den entwickelten Designrichtlinen eine automobile Brennstoffzellenbipolarplatte neu ausgelegt und simulativ und experimentell validiert. Für die Kanalauslegung im aktiven Bereich wird ein empirisches Rechenmodell entwickelt, das die Wechselwirkungen der mechanischen Eigenschaften der Gasdiffusionslage und der Kanalgeometrie bestimmt. Für die Quantifizierung der Ergebnisse des Modells auf die Spannungsverluste der Brennstoffzelle wird ein neues Messverfahren zur Bestimmung des Kontaktwiderstands zwischen mikroporöser Schicht und Katalysatorschicht vorgestellt. Damit ist die schnelle Bewertung verschiedener Kombinationen aus Kanalgeometrien und Gasdiffusionslagen möglich, um die bestmögliche Kombination für hohe Leistungsdichten zu finden. Als Zielvorgabe des Kontaktdrucks zwischen mikroporöser Schicht und Katalysatorschicht wird ein Minimalwert von über 0,19MPa empfohlen. Der Einfluss der Stegbreite im aktiven Bereich wird mit Hilfe von Simulationen bestimmt mit dem Ergebnis, dass vor allem bei hohen Stromdichten die Diffusion des Sauerstoffs durch schmale Stege begünstigt werden muss. Für die Betriebsstabilität der Brennstoffzelle durch die Gasgeschwindigkeiten in den Kanälen des aktiven Bereichs spielt die Stegbreite nur eine untergeordnete Rolle im Vergleich zur Permeabilität der Gasdiffusionslage, die bei unter 0,9 * 10E-15 m² liegen sollte. Die Bipolarplatte kann einen negativen Einfluss auf die Lebensdauer der PEM-Brennstoffzelle haben. Zur Minimierung des Einflusses und damit Steigerung der Lebensdauer werden für die Verteilstruktur und die Hauptkanäle der Bipolarplatte Designrichtlinien entwickelt, die in Abhängigkeit der Betriebsbedingungen und des Bipolarplattendesigns die Verteilung der Medien im aktiven Bereich optimieren. Die Auslegung der Verteilstrukturen sollte über die Druckverlustanteile der Verteilstrukturen am Gesamtdruckverlust der Bipolarplatte erfolgen, da dieser Einfluss deutlich größer als der der Betriebsbedingungen ist. Für die Hauptkanäle des Brennstoffzellenstapels gibt es je nach Zellanzahl im Stapel und dem Druckverlust der Einzelzellen ein optimales Verhältnis für Wasserstoff-, Luft- und Kühlmittelhauptkanäle, um das der jeweilige Auslasshauptkanal größer als der Einlasshauptkanal sein sollte. Zur experimentellen Validierung der Bipolarplattendesigns und derer Wechselwirkungen mit der Gasdiffusionslage sind üblicherweise teure Prototypen nötig. In dieser Arbeit wird gezeigt, dass das Verhalten von automobilen Bipolarplatten auch mittels kostengünstigen kleinen Laborzellen in Abschnitten nachgestellt werden kann, so dass Herstellkosten und -zeit in der Designvalidierung gespart werden. Als Abschluss der Arbeit werden die Kanäle der Verteilstruktur und des aktiven Bereichs eines bestehenden automobilen Bipolarplattendesigns nach den Designrichtlinien neu ausgelegt, um die elektrische Stromdichte und die Verteilung der Medien zu erhöhen. Mit dem experimentell und simulativ validierten Design wird eine Stromdichte von 2,13 A/cm² bei 0,618V (1,32 W/cm²) erzielt.This thesis focuses on the polymer electrolyte membrane (PEM) fuel cell’s bipolar plates potential to increase the power density and durability of the fuel cell stack. Design guidelines are developed for the fluid containing areas of the PEM fuel cell to simplify the design process for high current densities and homogenous fluid distribution in these areas. Secondly, a method to validate the design for automotive fuel cell bipolar plates with laboratory sized plates is proposed and with the design guidelines the active area of an automotive fuel cell is redesigned and validated by simulation and experiment. An empirical model for the interdependencies between the channel width and the mechanical properties of the gas diffusion layer (GDL) is developed. This is combined with the experimental results from a newly developed test method for the contact resistance between the GDL’s micro porous layer and the catalyst layer. This new model allows for quick iterations in the design process without time consuming simulations for each individual design. A target of 0,19MPa is proposed for the minimum contact pressure to reduce electrical losses. For high current density applications the landing width in the active area has to be as small as possible to reduce diffusion losses. In combination with the small landing width the GDL’s permeability should be lower than 0,9 * 10E-15 m² to ensure a stable operation of the fuel cell. The fluid distribution should be as homogenous as possible to reduce the bipolar plate’s effect on the fuel cell durability. For the cross flow region this is achieved by a minimum pressure drop proportion of the total bipolar plate’s pressure drop. The fuel cell’s header design is dependent on the cell count of the fuel cell stack and the pressure drop across the single cell. For all three fluids - hydrogen, air and coolant - an optimum header size relation exists, of which the outlet header should be larger than the inlet header, in order to improve flow distribution across the cells. The experimental validation of automotive bipolar plates, and their interdependencies with the gas diffusion layer, typically requires a complex and expensive prototype. In this thesis it is shown that the behavior of automotive fuel cells can be recreated by small fuel cells in laboratory dimensions, which saves time and production cost in the design phase of a new bipolar plate. Finally, the developed design guidelines are applied to an existing automotive bipolar plate to redesign the cross flow region and active area to increase current density and fluid distribution. This design is validated by simulation and experiment and achieves a current density of 2,13 A/cm² at 0,618V (1,32 W/cm²

In-Situ Defect Detection in Laser Powder Bed Fusion by Using Thermography and Optical Tomography—Comparison to Computed Tomography

Among additive manufacturing (AM) technologies, the laser powder bed fusion (L-PBF) is one of the most important technologies to produce metallic components. The layer-wise build-up of components and the complex process conditions increase the probability of the occurrence of defects. However, due to the iterative nature of its manufacturing process and in contrast to conventional manufacturing technologies such as casting, L-PBF offers unique opportunities for in-situ monitoring. In this study, two cameras were successfully tested simultaneously as a machine manufacturer independent process monitoring setup: a high-frequency infrared camera and a camera for long time exposure, working in the visible and infrared spectrum and equipped with a near infrared filter. An AISI 316L stainless steel specimen with integrated artificial defects has been monitored during the build. The acquired camera data was compared to data obtained by computed tomography. A promising and easy to use examination method for data analysis was developed and correlations between measured signals and defects were identified. Moreover, sources of possible data misinterpretation were specified. Lastly, attempts for automatic data analysis by data integration are presented

Comprehensive machine data acquisition through intelligent parameter identification and assignment

In today’s highly competitive manufacturing environment, process data monitoring continues to be of high priority, but often relies on modern communication interfaces being provided by PLC manufacturers. This paper proposes an alternative approach in which data is acquired automatically from various PLC models through available interfaces. Multiple Machine Learning algorithms are incorporated to identify machine parameters, which are then assigned to appropriate machine information models. All functionalities can be provided by a dedicated hardware module or as software modules on IPCs. The proposed approach can be integrated into existing Industry 4.0 efforts to accelerate digitalization in challenging environments

Image Reconstruction Analysis for Positron Emission Tomography with Heterostructured Scintillators

The concept of structure engineering has been proposed for exploring the next generation of radiation detectors with improved performance. A TOF-PET geometry with heterostructured scintillators with a pixel size of 3.0x3.1x15 mm3 was simulated using Monte Carlo. The heterostructures consisted of alternating layers of BGO as a dense material with high stopping power and plastic (EJ232) as a fast light emitter. The detector time resolution was calculated as a function of the deposited and shared energy in both materials on an event-by-event basis. While sensitivity was reduced to 32% for 100 μm thick plastic layers and 52% for 50 μm, the CTR distribution improved to 204±49 ps and 220±41 ps respectively, compared to 276 ps that we considered for bulk BGO. The complex distribution of timing resolutions was accounted for in the reconstruction. We divided the events into three groups based on their CTR and modeled them with different Gaussian TOF kernels. On a NEMA IQ phantom, the heterostructures had better contrast recovery in early iterations. On the other hand, BGO achieved a better contrast to noise ratio (CNR) after the 15th iteration due to the higher sensitivity. The developed simulation and reconstruction methods constitute new tools for evaluating different detector designs with complex time responses

Phenotypic characterization of skeletal abnormalities of Osteopotentia mutant mice by micro-CT: a descriptive approach with emphasis on reconstruction techniques

PurposeThe novel protein osteopotentia (Opt) has recently been described as an essential regulator of postnatal osteoblast maturation and might possibly be responsible for some of the rarer types of osteogenesis imperfecta. Our aim was the evaluation of micro CT for the qualitative morphological assessment of skeletal abnormalities of Osteopotentia-mutant mice in comparison to radiography and histology.Materials and methodsFour homozygous mice with insertional mutations in the Opt gene and three wild-type controls were examined ex vivo using radiography and micro-CT. Two of the homozygous animals were evaluated histologically (trichrome reagent). For the micro-CT evaluation three-dimensional (3D) surface reconstructions and two-dimensional (2D) multiplanar reformations (MPRs) were applied.ResultsThe Opt-homozygous mice exhibited severe growth. The radiographic examinations showed osteopenia and fractures with hypertrophic callus formation and pseudarthroses of the forelimbs and ribs. Micro-CT confirmed these findings and was able to demonstrate additional fractures especially at smaller bones such as the metacarpals and phalanges. Additional characterization and superior delineation of cortices and fracture fragments was achieved by 2D MPRs. Histological correlation verified several of these imaging findings.ConclusionMicro-CT is able to screen Opt-mutant mice for osseous pathologies and furthermore characterize these anomalies. The modality seems superior to conventional radiography, but is not able to demonstrate cellular pathology. However, histology is destructive and more time- and material-consuming than micro-CT. Additional information may be gathered by 2D MPRs

New instruments of administrative procedure in Germany? : between acceptance and mediation

Disturbance of intestinal wound closure leads to insufficient anastomotic healing and is associated with considerable morbidity following colorectal resections. Matrix metalloproteinases (MMPs) play a crucial role in regulation of wound closure. Here fluorescence endoscopy was evaluated for assessment of MMP-2/-9 expression during failed intestinal anastomotic healing.Distal colonic anastomoses were performed as a model for disturbed healing in 36 Balb/c mice. Healing was evaluated endoscopically, macroscopically, and histologically after 1, 3 and 5 days. For detection of MMP-2/-9 expression fluorescence endoscopy (FE) was used following i.v.-administration of a Cy5.5-labeled MMP-2/-9 specific tracer. FE was complemented by quantification of the fluorescence signal using the MS-FX PRO Optical Imaging System. An overall leakage score was calculated and correlated with the results of FE.With increasing incidence of anastomotic leakage from POD1 (17%) to POD5 (83%) the uptake of the MMP tracer gradually increased (signal-to-noise ratio (SNR), POD1: 17.91 ± 1.251 vs. POD3: 30.56 ± 3.03 vs. POD5: 44.8 ± 4.473, P<0.0001). Mice with defective anastomotic healing showed significantly higher uptake compared to non-defective (SNR: 37.37± 3.63 vs. 26.16± 3.635, P = 0.0369). White light endoscopy and FE allowed evaluation of anastomotic healing and visualization of mucosal MMPs in vivo. Using FE based detection of MMPs in the anastomosis, an overall positive predictive value of 71.4% and negative predictive value of 66.6% was calculated for detection of anastomotic leakage.During disturbed anastomotic healing increased expression of MMP-2/-9 was observed in the anastomotic tissue. Fluorescence endoscopy for detection of MMP-2/-9 during the healing process might be a promising tool for early identification of anastomotic leakage

Possibilities and limits of chemical weed control in potato cultivation

Die Pflanzenschutzdienste von Bayern, Baden-Württemberg, Rheinland-Pfalz und Hessen führten von 2012 bis 2018 ein Ringversuchsprogramm zur Prüfung neuer Herbizide im Kartoffelbau durch. An 26 Versuchsstandorten wurden 13 verschiedene Herbizidbehandlungen hinsichtlich Unkrautbekämpfungsleistung und Kulturverträglichkeit geprüft. An den Versuchsstandorten traten regelmäßig vier unterschiedliche Leitunkräuter auf. Die häufigsten Unkräuter waren Gänsefuß-Arten (CHESS), Winden-Knöterich (POLCO), Einjähriges Bingelkraut (MERAN) und Schwarzer Nachtschatten (SOLNI). Im Mittel über alle Standorte und Behandlungsvarianten wurde mit 94 % eine ausreichende Gesamt-Unkrautwirkung erzielt. Wichtige Leitunkräuter wie Gänsefuß-Arten (CHESS), Behaartes Franzosenkraut (GASCI), Hühnerhirse (ECHCG) und Kletten-Labkraut (GALAP) konnten mit mittleren Wirkungsgraden von ³ 97 % sicher kontrolliert werden. In Abhängigkeit von einzelnen Behandlungsvarianten und Standorten konnten die Unkräuter Einjähriges Bingelkraut (MERAN) und Winden-Knöterich (POLCO) dagegen nicht mehr sicher bekämpft werden. Schwarzer Nachtschatten (SOLNI) kann als generelles Problemunkraut im Kartoffelbau bezeichnet werden. Die Kulturverträglichkeit der geprüften Herbizid-Kombinationen kann als gut bis sehr gut bezeichnet werden. Einzelne beobachtete, kurzfristige Kulturbeeinträchtigungen waren auf Standorteffekte zurückzuführen.From 2012 to 2018, the plant protection services of Bavaria, Baden-Württemberg, Rhineland-Palatinate and Hesse carried out an interlaboratory test programme for the testing of new herbicides in potato cultivation. At 26 experimental sites, 13 different herbicide treatments were tested for weed control performance and crop compatibility. Four different common weeds regularly appeared at each experimental site. The most common weeds were goosefoot (CHESS), wild buckwheat (POLCO), annual mercury (MERAN) and black nightshade (SOLNI). On average across all locations and treatment options, 94% of the total weed control efficacy was sufficient. Important common weeds such as goosefoot, hairy galinsoga (GASCI), barnyardgrass (ECHCG) and cleavers (GALAP) could be safely controlled with average efficiencies of ³ 97%. Depending on the individual treatment options and locations, however, annual mercury and wild buckwheat could no longer be controlled safely. Black nightshade (SOLNI) can be described as a general problem weed in potato cultivation. The culture tolerance of the tested herbicide combinations can be described as good to very good. Individual short-term cultural impairments observed were attributable to location effects

Combined analysis of gut microbiota, diet and PNPLA3 polymorphism in biopsy‐proven non‐alcoholic fatty liver disease

Background and aims: Non-alcoholic fatty liver disease (NAFLD) is a global health burden. Risk factors for disease severity include older age, increased body mass index (BMI), diabetes, genetic variants, dietary factors and gut microbiota alterations. However, the interdependence of these factors and their individual impact on disease severity remain unknown. Methods: In this cross-sectional study, we performed 16S gene sequencing using fecal samples, collected dietary intake, PNPLA3 gene variants and clinical and liver histology parameters in a well-described cohort of 180 NAFLD patients. Principal component analyses were used for dimensionality reduction of dietary and microbiota data. Simple and multiple stepwise ordinal regression analyses were performed. Results: Complete data were available for 57 NAFLD patients. In the simple regression analysis, features associated with the metabolic syndrome had the highest importance regarding liver disease severity. In the multiple regression analysis, BMI was the most important factor associated with the fibrosis stage (OR per kg/m2 : 1.23, 95% CI 1.10-1.37, P < .001). The PNPLA3 risk allele had the strongest association with the histological grade of steatosis (OR 5.32, 95% CI 1.56-18.11, P = .007), followed by specific dietary patterns. Low abundances of Faecalibacterium, Bacteroides and Prevotella and high abundances of Gemmiger were associated with the degree of inflammation, ballooning and stages of fibrosis, even after taking other cofactors into account. Conclusions: BMI had the strongest association with histological fibrosis, but PNPLA3 gene variants, gut bacterial features and dietary factors were all associated with different histology features, which underscore the multifactorial pathogenesis of NAFLD