4,766 research outputs found

    QualitÀtssicherung von textilen Kohlenstofffaserpreforms mittels prozessintegrierter Wirbelstromsensor-Arrays

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    Um dem Bedarf nach ressourcenschonender individueller MobilitĂ€t gerecht zu werden, muss die ProduktivitĂ€t der Herstellungsprozesse kohlenstofffaserverstĂ€rkter Kunststoffe gesteigert werden. Die vorliegende Arbeit verfolgt dabei den Ansatz der Prozessintegration von Wirbelstromsensoren, um defektbehaftete Bauteile in qualitĂ€tskritischen Prozessschritten zu identifizieren und vor weiteren Bearbeitungsschritten aus dem Prozess auszuschleusen. Die Arbeit fokussiert sich dabei auf das sog. Preforming des Resin Transfer Mouldings (RTM) bei dem Kohlestofffasermatten als textile Halbzeuge verformt werden. Dabei mĂŒssen qualitĂ€tskritische Defekte wie fehlerhafte FaserbĂŒndelorientierungen oder Falten im Textil zuverlĂ€ssig erkannt werden. Das dafĂŒr betrachtete Sensorkonzept, mit dem diese Defekte erkannt werden sollen, basiert auf dem Funktionsprinzip der halbtransformatorischen Spulenanordnungen. Diese werden zu einem sog. Spulen-Array verschaltet und können in die Formwerkzeuge des Preformings integriert werden. Das erlaubt einen hohen Prozessintegrationsgrad und eine 100%-QualitĂ€tssicherung, bei der alle gefertigten Teile geprĂŒft werden können. Der betrachtete Sensor muss allerdings hinsichtlich seiner Gestaltungsmöglichkeiten bewertet werden, denn neben der Wahl der Spulenbauart- und -form mĂŒssen zusĂ€tzlich die möglichen relativen Anordnungen der Spulenelemente bewertet werden. DafĂŒr ist ein experimenteller Ansatz gewĂ€hlt worden, um relevante EinflĂŒsse auf das SignalĂŒbertragungsverhalten zu identifizieren und optimale Designparameter fĂŒr das Sensor-Array ableiten zu können. Es konnte dabei gezeigt werden, dass als printed circuit boards ausgefĂŒhrte Spulen insbesondere fĂŒr die PrĂŒfung flacher Bauteile geeignet sind. Im Gegensatz dazu sind konventionelle zylindrische Spulen fĂŒr die PrĂŒfung schalenförmiger Geometrien zu bevorzugen. Basierend auf diesen Erkenntnissen werden Wirbelstromsensor-Arrays entwickelt, prototypisch aufgebaut und erprobt. Dies beinhaltet die mechanische und elektrische Gestaltung der Komponenten. DarĂŒber hinaus werden Methoden diskutiert, mit denen die Rohdaten des Sensors in eine auswertbare Form gebracht werden können. Die dabei gewonnenen Messdaten erlauben eine quantitative Ermittlung von FaserbĂŒndelorientierungen in Kohlenstofffaser-Preforms. Die Ergebnisse einer Messunsicherheitsermittlung nach VDA Band 5.1 lassen die Schlussfolgerung zu, dass das entwickelte System in seiner dargestellten Form nicht den Anforderungen einer Serienfertigung genĂŒgt. Allerdings können KlassierprĂŒfungen mit einer Klassenbreite von 6,662° durchgefĂŒhrt werden. Um die Anwendungsmöglichkeiten des erforschten Systems darĂŒber hinaus zu erhöhen, werden zudem gezielt defektbehaftete Bauteile gefertigt und derart geprĂŒft, dass eine Methode des maschinellen Lernens genutzt werden kann, um Defekte automatisiert erkennen zu können

    Development and Application of Eddy Current Sensor Arrays for Process Integrated Inspection of Carbon Fibre Preforms

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    This publication presents the realisation of a sensor concept, which is based on eddy current testing, to detect textile defects during preforming of semi-finished carbon fibre parts. The presented system has the potential for 100% control of manufactured carbon fibre based components, allowing the immediate exclusion of defective parts from further process steps. The core innovation of this system is given by the high degree of process integration, which has not been implemented in the state of the art. The publication presents the functional principle of the sensor that is based on half-transmission probes as well as the signals that can be gained by its application. Furthermore, a method to determine the optimum sensor resolution is presented as well as the sensor housing and its integration in the preforming process

    Microscopic Transport Theory of Nuclear Processes

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    We formulate a microscopic theory of the decay of a compound nucleus through fission which generalizes earlier microscopic approaches of fission dynamics performed in the framework of the adiabatic hypothesis. It is based on the constrained Hartree-Fock-Bogoliubov procedure and the Generator Coordinate Method, and requires an effective nucleon-nucleon interaction as the only input quantity. The basic assumption is that the slow evolution of the nuclear shape must be treated explicitely, whereas the rapidly time-dependent intrinsic excitations can be treated by statistical approximations. More precisely, we introduce a reference density which represents the slow evolution of the nuclear shape by a reduced density matrix and the state of intrinsic excitations by a canonical distribution at each given shape of the nucleus. The shape of the nuclear density distribution is described by parameters ("generator coordinates"), not by "superabundant" degrees of freedom introduced in addition to the complete set of nucleonic degrees of freedom. We first derive a rigorous equation of motion for the reference density and, subsequently, simplify this equation on the basis of the Markov approximation. The temperature which appears in the canonical distribution is determined by the requirement that, at each time t, the reference density should correctly reproduce the mean excitation energy at given values of the shape parameters. The resulting equation for the "local" temperature must be solved together with the equations of motion obtained for the reduced density matrix.Comment: 33 pages, accepted in Nucl. Phys.

    Prophylactic Drain Placement in Childhood Perforated Appendicitis: Does Spillage Matter?

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    Background: Prophylactic abdominal drains for perforated appendicitis in children have generally been regarded as obsolete because several studies showed inferior results for drain placement in the past. Despite these results, prophylactic abdominal drains for perforated appendicitis remain omnipresent in pediatric surgery especially when gross spillage is observed at the time of appendectomy. Here, we hypothesize that even if accounting for gross intra-abdominal spillage, prophylactic drain placement for perforated appendicitis in children is not beneficial. Patients and Methods: The charts of all children (<18 years) who underwent an appendectomy at our institution from July 2013 to March 2020 were analyzed. The data from 65 patients who presented with perforated appendicitis were included. Patients were grouped according to the amount of intraoperative spillage. Demographics, laboratory data, operative findings, and postoperative outcomes were analyzed. Results: Of all patients, 34 were male, and 31 were female, with a mean age of 10.5 ± 3.7 years. There were no statistically significant differences between the groups for age and sex (p = 0.6985 and p = 0.6222, respectively). Prophylactic drains were placed according to the surgeon's preference in 32 children. There were no statistically significant differences between the groups in the rate of intra-abdominal abscess formation, wound infection, and bowel obstruction, regardless of the amount of spillage encountered during an appendectomy. However, independently of the amount of spillage, the length of hospital stay was longer in the children in which a drain had been placed (p = 0.0041). Conclusion: In our cohort, we could not find a benefit from drain placement even in case of gross spillage at the time of appendectomy. Rather, drain placement was associated with an increase in length of hospital stay

    Conception of an Eddy Current In-process Quality Control for the Production of Carbon Fibre Reinforced Components in the RTM Process Chain

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    The integration of quality control processes in immature production systems such as the resin transfer moulding (RTM) process in the production of carbon fibre reinforced plastics (CFRP) faces numerous challenges. Requirements towards the reliability and product design as well as the consideration of economic restrictions lead to challenging requirements for measurement systems. This paper presents the development of a process integrated quality control using eddy current inspection. The concept focuses on an eddy current sensor array that is integrated in a preforming tool and thus enables a 100% quality control of CRFP parts with minor effects on the production environment

    Total Psoas Muscle Area as a Marker for Sarcopenia Is Related to Outcome in Children With Neuroblastoma

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    Background: Sarcopenia describes a generalized loss of skeletal muscle mass, strength, or function. Determined by measuring the total psoas muscle area (tPMA) on cross-sectional imaging, sarcopenia is an independent marker for poor post-surgical outcomes in adults and children. Children with cancer are at high risk for sarcopenia due to immobility, chemotherapy, and cachexia. We hypothesize that sarcopenic children with neuroblastoma are at higher risk for poor post-operative outcomes. Patients and Methods: Retrospective analysis of children with neuroblastoma ages 1–15 years who were treated at our hospital from 2008 to 2016 with follow-up through March 2021. Psoas muscle area (PMA) was measured from cross-sectional images, using computed tomography (CT) and magnetic resonance imaging (MRI) scans at lumbar disc levels L3-4 and L4-5. tPMA is the sum of the left and right PMA. Z-scores were calculated using age- and gender-specific reference values. Sarcopenia was defined as a tPMA z-score below −2. A correlation of tPMA z-scores and sarcopenia with clinical variables and outcome was performed. Results: One hundred and sixty-four children with workup for neuroblastoma were identified, and 101 children fulfilled inclusion criteria for further analysis, with a mean age of 3.92 years (SD 2.71 years). Mean tPMA z-score at L4-5 was −2.37 (SD 1.02). Correlation of tPMA z-score at L4-5 with weight-for-age z-score was moderate (r = 0.54; 95% CI, 0.38, 0.66). No association between sarcopenia and short-term outcome was observed. Sarcopenia had a sensitivity of 0.82 (95% CI, 0.62–0.93) and a specificity of 0.48 (95% CI 0.36–0.61) in predicting 5-year survival. In a multiple regression analysis, pre-operative sarcopenia, pre-operative chemotherapy in the NB2004 high-risk group, unfavorable tumor histology, and age at diagnosis were associated with 5-year survival after surgery, with hazard ratios of 4.18 (95% CI 1.01–17.26), 2.46 (95% CI 1.02–5.92), 2.39 (95% CI 1.03–5.54), and 1.01 (95% CI 1.00–1.03), respectively. Conclusion: In this study, the majority of children had low tPMA z-scores and sarcopenia was a risk factor for decreased 5-year survival in children with neuroblastoma. Therefore, we suggest measuring the tPMA from pre-surgical cross-sectional imaging as a biomarker for additional risk stratification in children with neuroblastoma

    Particle number projection with effective forces

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    The particle number projection method is formulated for density dependent forces and in particular for the finite range Gogny force. Detailed formula for the projected energy and its gradient are provided. The problems arising from the neglection of any exchange term, which may lead to divergences, are throughly discussed and the possible inaccuracies estimated. Numericala results for the projection after variation method are shown for the nucleus 164Er and for the projection before variation approach for the nuclei 48-50Cr. We also confirm the Coulomb antipairing effect found in mean field theories.Comment: 33 pages, 8 figures. Submit to Nuc. Phys.

    Determinants of bank profitability in transition countries: What matters most?

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    The aim of this paper is to investigate the determinants of bank profitability in the early transition countries of Central and Eastern Europe (CEE), and in the late transition countries of the former USSR. We apply a GMM technique for the period covering 2000–2013. The results show that profitability persists and the determinants of bank profitability vary across transition countries. Particularly, the banking sector of early transition countries is more competitive. However, the impact of credit risk on bank profitability is positive in early transition countries, but negative in late transition countries. Government spending and monetary freedom negatively influence bank profitability only in late transition countries. Moreover, better capitalised banks are more profitable in early transition countries implying that these banking sectors are more robust. A range of possible approaches that governments can take to further develop banking sectors are discussed

    The Early Asymmetries of Supernova 2008D / XRF 080109

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    Spectropolarimetry of the Type Ib SN 2008D, associated with the XRF 080109, at two separate epochs, are presented. The epochs of these observations correspond to V-band light curve maximum and 15 days after light curve maximum (or 21 and 36 days after the XRF). We find SN 2008D to be significantly polarized, although the largest contribution is due to the interstellar polarization component of Q_ISP=0+/-0.1% and U_ISP=-1.2+/-0.1%. At the two epochs, the spectropolarimetry of SN 2008D is classified as being D1+L(HeI)+L(Ca II). The intrinsic polarization of continuum wavelength regions is <0.4%, at both epochs, implying an asymmetry of the photosphere of <10%. Similar to other Type Ibc SNe, such as 2005bf, 2006aj and 2007gr, we observed significant polarization corresponding to the spectral features of Ca II, He I, Mg I, Fe II and, possibly, O I 7774, about a close-to-spherically-symmetric photosphere. We introduce a new plot showing the chemically distinct line forming regions in the ejecta and comment on the apparent ubiquity of highly polarized high-velocity Ca II features in Type Ibc SNe. The polarization angle of Ca II IR triplet was significantly different, at both epochs, to those of the other species, suggesting high-velocity Ca II forms in a separate part of the ejecta. The apparent structure in the outer layers of SN 2008D has implications for the interpretation of the early-time X-ray emission associated with shock break-out. (abridged)Comment: ApJ Subm., 45 pages, 13 figure
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