TY - JOUR A1 - Langer, Christoph A1 - Prommesberger, Christian A1 - Ławrowski, Robert Damian A1 - Schreiner, Rupert A1 - Serbun, Pavel A1 - Müller, Günter A1 - Düsberg, Felix A1 - Hofmann, Martin A1 - Bachmann, Michael A1 - Pahlke, Andreas T1 - Field emission properties of p-type black silicon on pillar structures JF - Journal of Vacuum Science & Technology B N2 - Arrays of black silicon field emission pillar structures were fabricated on p-type silicon substrates. Two types of samples with the same number of pillars (arrays of 10 × 10) but different pillar heights (8 and 20 μm) were prepared as well as a black silicon reference sample without pillars. The field emission properties of these cathodes were investigated both by means of integral current-voltage measurements and by field emission scanning microscopy. Samples with a pillar height of 20 μm revealed onset fields as low as 6.4 V/μm, field enhancement factors up to 800, and emission currents up to 8 μA at an applied field of 20 V/μm. Due to the p-type material, a saturation of the emission current for fields above 11 V/μm was observed. This saturation leads to a stable operation with a current fluctuation of less than ±8%. It was found that samples with a pillar height of 20 μm showed improved emission characteristics compared to samples with a pillar height of 8 μm or without pillars. The voltage maps revealed an increased emission homogeneity after a “burn-in” sequence of the sample. The current map showed that a few of the pillars dominate the emission. Integral current stability measurements were performed under different vacuum pressures, in order to investigate altered emission behavior and a potential degradation of the emitters. At pressures above 10−6 mbar, the sample starts to degrade irreversibly. Nevertheless, even after a harsh treatment over 30 min at 5 × 10−5 mbar and at an applied field of 23 V/μm, the cathode was still operating, and did not fail during further operation over 20 h at 5 × 10−8 mbar and at an applied field of 28 V/μm. Y1 - 2016 U6 - https://doi.org/10.1116/1.4943919 VL - 34 IS - 2 ER - TY - JOUR A1 - Mingels, Stephan A1 - Porshyn, Vitali A1 - Prommesberger, Christian A1 - Langer, Christoph A1 - Schreiner, Rupert A1 - Lützenkirchen-Hecht, Dirk A1 - Müller, Günter T1 - Photosensitivity of p-type black Si field emitter arrays JF - Journal of Applied Physics N2 - We have investigated the properties of black Si field emitter arrays under strong electric fields and laser illumination. A low onset field of 1.8 MV/m for an emission current of 1 nA was obtained. A pronounced saturation region of the dark and photo-enhanced current was observed, which provided a short-term stability of 0.1% at 0.4 μA and 0.7% at 1.0 μA, respectively. As maximum value for the photosensitivity, an on-off current switching ratio of 43 reaching about 13 μA was achieved at a laser power of 15 mW. Electron spectra in the dark and under laser illumination are presented, showing a current and light-sensitive voltage drop across the emitters as well as hints for hot electron emission. Y1 - 2016 U6 - https://doi.org/10.1063/1.4948328 VL - 119 IS - 16 ER - TY - JOUR A1 - Bachmann, Michael A1 - Dams, Florian A1 - Düsberg, Felix A1 - Hofmann, Martin A1 - Pahlke, Andreas A1 - Langer, Christoph A1 - Ławrowski, Robert Damian A1 - Prommesberger, Christian A1 - Schreiner, Rupert A1 - Serbun, Pavel A1 - Lützenkirchen-Hecht, Dirk A1 - Müller, Günter T1 - Extraction of the characteristics of current-limiting elements from field emission measurement data JF - Journal of Vacuum Science & Technology B N2 - In this contribution, the authors will present an algorithm to extract the characteristics of nonideal field emission circuit elements from saturation-limited field emission measurement data. The method for calculating the voltage drop on current-limiting circuit elements is based on circuit theory as well as Newton's method. Since the only assumption the authors make on the current-limiting circuit is a connection in series, this method is applicable to most field emission data showing saturation. To be able to determine the significance of any parameter output, the uncertainties of data and extracted parameters as well as the parameter correlations are fully taken into account throughout the algorithm. N-type silicon samples with varying external serial resistors are analyzed. All results show a good agreement to the nominal resistor values. Additionally, several p-type samples are analyzed, showing a diodelike behavior. The extracted current-limiting characteristics of the p-type samples are in good agreement with a pn-junction model. The stability of the emission current of the p-type samples is measured by constant voltage measurements and compared to the extracted current-limiting characteristics. The application of the algorithm to measurement data shows that the given algorithm is a valuable tool to analyze field emission measurement data influenced by nonemissive processes. Y1 - 2017 U6 - https://doi.org/10.1116/1.4971768 VL - 35 IS - 2 ER - TY - JOUR A1 - Prommesberger, Christian A1 - Bachmann, Michael A1 - Düsberg, Felix A1 - Langer, Christoph A1 - Ławrowski, Robert Damian A1 - Hofmann, Martin A1 - Pahlke, Andreas A1 - Schreiner, Rupert T1 - Regulation of the Transmitted Electron Flux in a Field-Emission Electron Source Demonstrated on Si Nanowhisker Cathodes JF - IEEE Transactions on Electron Devices N2 - We report on a method to stabilize the transmitted electron flux in a field-emission electron source using an external regulation circuit. The electron source was realized with an array of silicon (Si) nanowhiskers on the top of elongated pillar structures, a mica spacer, and an extraction grid made of Si. As for most applications, the emitted electron current from the cathode is not as crucial as the transmitted electron flux through the extraction grid toward the anode. We investigated a method which allows the regulation directly by the emitted electron flux and not merely on the cathode current. By using this method, we were able to stabilize the emitted electron flux of our electron source down to values below 1%. Simultaneously, it was shown that there is the possibility to stabilize the influencing value in the real application as well. The effectiveness of this method was demonstrated successfully with an X-ray source setup. The measured X-ray photon count rate was stabilized to a standard deviation of 0.30% at a pressure of 1 × 10 -7 mbar. Even in harsh environment of 2 × 10 -5 mbar, a stabilization of the X-ray photon count rate down to a value of 0.63% was achieved. KW - Cathodes KW - Nanostructured devices KW - Current measurement KW - Photonics KW - Electron sources KW - Emissions KW - Voltage measurement Y1 - 2017 U6 - https://doi.org/10.1109/TED.2017.2763239 SN - 5128-5133 VL - 64 IS - 12 PB - IEEE ER - TY - CHAP A1 - Lindner, Matthias A1 - Berndt, Dominik A1 - Jungbauer, Bastian A1 - Ehrlich, Ingo A1 - Schreiner, Rupert A1 - Pipa, Andrei V. A1 - Hink, Rüdiger A1 - Foest, Rüdiger A1 - Brandenburg, Ronny A1 - Max, Alexander A1 - Caspari, Ralf T1 - Fabrication, surface integration and testing of miniaturized dielectric barrier discharge plasma actuators for active flow control applications T2 - AIAA Aviation 2019 Forum, 17-21 June 2019, Dallas, Texas Y1 - 2019 U6 - https://doi.org/10.2514/6.2019-2998 ER - TY - CHAP A1 - Lindner, Matthias A1 - Berndt, Dominik A1 - Tschurtschenthal, Karl A1 - Ehrlich, Ingo A1 - Jungbauer, Bastian A1 - Schreiner, Rupert A1 - Pipa, Andrei V. A1 - Hink, Rüdiger A1 - Foest, Rüdiger A1 - Brandenburg, Ronny A1 - Neuwirth, Daniel A1 - Karpen, Norbert A1 - Bonaccurso, Elmar A1 - Weichwald, Robert A1 - Max, Alexander A1 - Caspari, Ralf T1 - Aircraft Icing Mitigation by DBD-based Micro Plasma Actuators T2 - AIAA AVIATION 2020 FORUM: June 15-19, 2020 N2 - We present the application of plasma actuators as a technology for ice prevention at airfoils. The miniaturized dielectric barrier discharge (DBD) plasma actuators (PA) were fabricated by means of microelectromechanical systems (MEMS). We elucidate how to make the actuator samples scalable and applicable to any desired shape by the use of flexible inorganic zirconia substrates. For this purpose, we applied our developed embedding method to integrate the micro actuators in modern carbon/glass fiber reinforced polymer (CFRP/GFRP) materials. Next, the embedded actuator samples were mounted on a mechanical air profile-like fixture and placed in the icing wind tunnel iCORE. The samples were tested in rime ice conditions at temperatures of -15 to -20° C and air speeds up to 30 m/s. Unlike other groups we used a thin film zirconia substrate as dielectric for the plasma actuator. Due to the low substrate thickness of just 150 µm, an operating voltage of 2 kVRMS is already sufficient enough for a stable plasma formation. The experiments show that the operated actuator was able to prevent the ice formation and first indications of a De-icing function were also found. Hence, we show that it is feasible to realize an anti-icing system with zirconia-based plasma actuators operated at lower voltages compared to conventional ones. Y1 - 2020 U6 - https://doi.org/10.2514/6.2020-3243 ER - TY - JOUR A1 - Herrmann, Frank A1 - Büttner, Simon T1 - Automatische Qualitätskontrolle mittels Maschinellem Lernen und SAP Leonardo JF - Anwendungen und Konzepte der Wirtschaftsinformatik N2 - In vielen Unternehmen werden von Menschen durch Ansehen von Produkten Produktionsfehler identifiziert. Die übersehenen Produktionsfehler führen zunehmend häufiger zu teuren Kundenreklamationen. Für die Produktion von Fußbällen wird in dieser Arbeit diese manuelle Qualitätssicherung analysiert. Als Alternative werden die Fußbälle durch einen Roboter fotografiert u nd durch maschinelles Lernen werden Produktionsfehler auf diesen digitalen Fotos identifiziert. Dieser Prüfprozess wird in SAP Leonardo implementiert und damit wird der bereits in einem SAP System implementierte Produktionsprozess (bzw. Unternehmensprozess) erweitert, wodurch ein durchgängig digitalisierter Gesamtprozess implementiert wird. Dadurch werden signifikant bessere Prüfergebnisse erreichtb und die Durchlaufzeit des Prüfprozesses wird substantiell reduziert. KW - Industrie 4.0 KW - SAP Leonardo KW - SAP S/4HANA KW - ERP - System KW - Machine Learning KW - durchgängig digitalisierter Produktionsprozess Y1 - 2019 UR - https://akwi.hswlu.ch/issue/view/376/431 SN - 2296-4592 IS - 10 SP - 46 EP - 53 PB - AKWI ER - TY - JOUR A1 - Prommesberger, Christian A1 - Langer, Christoph A1 - Ławrowski, Robert Damian A1 - Schreiner, Rupert T1 - Investigations on the long-term performance of gated p-type silicon tip arrays with reproducible and stable field emission behavior JF - Journal of Vacuum Science & Technology B N2 - The authors report on the fabrication and characterization of p-type Si tip arrays with an integrated gate electrode for applications as field emission electron sources. After the reactive ion etching of the emitters, the combined thermal dry and wet oxidation was used for both the sharpening of the emitters and for the realization of an enhanced insulation layer. Au was evaporated in a self-aligned process as gate electrode. Arrays of 16 Si tips were fabricated with tip heights of about 3 μm and tip radii of about 20 nm with integrated gate electrode concentrically positioned ≈2 μm below the tip apex. Integral measurements with an additional anode showed improved field emission properties with a reproducible and stable emission behavior. A fast activation of the tips, low onset voltages of about 30 V, and moderate field emission currents up to 0.55 μA were noticed. The field emission parameters were calculated using the Fowler–Nordheim characteristics. A pronounced saturation regime was observed, and current fluctuations of less than ±1% were investigated for 30 min. Long-term measurements were carried out for a period of more than 8 h. In the first 6 h of operation, the authors observed a drift of the emission current from 0.35 to 0.55 μA caused by an increased emission surface. Y1 - 2017 U6 - https://doi.org/10.1116/1.4972519 VL - 35 IS - 1 ER - TY - JOUR A1 - Breuer, Janis A1 - Bachmann, Michael A1 - Düsberg, Felix A1 - Pahlke, Andreas A1 - Edler, Simon A1 - Langer, Christoph A1 - Prommesberger, Christian A1 - Ławrowski, Robert Damian A1 - Schreiner, Rupert A1 - Serbun, Pavel A1 - Lützenkirchen-Hecht, Dirk T1 - Extraction of the current distribution out of saturated integral measurement data of p-type silicon field emitter arrays JF - Journal of Vacuum Science and Technology B N2 - At the moment, only complicated techniques are known for the determination of array properties of field emitter arrays such as the number of active tips, the current distribution, or the individual tip radii. In this work, a method for extracting these parameters from integral measurement data is presented. A model describing the characteristics of a single emitter, including the saturation as a function of the applied voltage and the emitter radius, is developed. It is shown that experimental data of field emitter arrays can be represented as the sum of these functions and the characteristic parameters can be fitted to field emission data of an array. Using this method, the values of the radii as well as the parameters of distribution models can be determined directly. Analysis of experimental data from p-type Si emitter arrays shows that only 1–2% of the tips contribute significantly. Y1 - 2018 U6 - https://doi.org/10.1116/1.5035189 VL - 36 IS - 5 PB - AIP Publishing ER - TY - JOUR A1 - Edler, Simon A1 - Bachmann, Michael A1 - Breuer, Janis A1 - Dams, Florian A1 - Düsberg, Felix A1 - Hofmann, Martin A1 - Jakšič, Jasna A1 - Pahlke, Andreas A1 - Langer, Christoph A1 - Ławrowski, Robert Damian A1 - Prommesberger, Christian A1 - Schreiner, Rupert T1 - Influence of adsorbates on the performance of a field emitter array in a high voltage triode setup JF - Journal of Applied Physics N2 - In the present work, black-silicon field emitter arrays (FEAs) are investigated regarding the influence of residual gas pressure on the characteristics and lifetime in the high voltage triode setup. Current-voltage-characteristics at different pressure levels are recorded and show a decreasing emission current with rising pressure. This decrease can be explained by an increase of the work function and charging of the emitter surface caused by adsorbates. The emission current can be restored to its initial value by heating of the FEA up to 110 °C during active emission. With this regeneration procedure, an extended lifetime from about 20 h to 440 h at a residual gas pressure of 10−5 mbar is achieved. Y1 - 2017 U6 - https://doi.org/10.1063/1.4987134 VL - 122 ER - TY - THES A1 - Zrenner, Louis T1 - Modellierung des gekoppelten thermischen und hydraulischen Verhaltens von ZFSV-Bettungen bei erdverlegten Höchstspannungsleitungen BT - Berechnung der thermo-hydraulischen Wechselwirkungen in Plaxis 2D anhand der Messergebnisse des DC CTL DBI Projekts N2 - Durch die dezentrale Energiegewinnung, welche aus dem Fokus auf regenerative Stromerzeugung resultiert, ist ein Ausbau des Übertragungsnetzes alternativlos – auch mit Hinblick auf den steigenden Strombedarf in den kommenden Jahrzehnten. Der Ausbau ist bereits beschlossene Sache, schreitet aber schleppend voran. Die Gründe hierfür sind jedoch nicht etwa Verzögerungen in der Bauausführung, sondern vor allem die Ablehnung innerhalb der Bevölkerung gegenüber dem Neubau von Stromtrassen. Jahrelange Planungs- und Genehmigungsphasen sowie regelmäßige Änderungen der Trassenverläufe sind die Folge. Die Bürgerbewegungen gegen den Netzausbau sind meist mit auf dem Einfluss auf das Landschaftsbild, der Strahlungsbelastung oder Lärmbelästigung begründet. Eine Erdverlegung würde hinsichtlich dieser Probleme (trotz kurzfristiger Mehrbelastung während der Bauphase) eine Alternative darstellen, weist jedoch baubedingte Problematiken wie den Abtransport der Verlustwärme auf. Bei einer klassischen Sandbettung hängt die Wärmeleitfähigkeit maßgeblich vom Wassergehalt des Sandes ab, welcher je nach Witterungslage und geologischen Gegebenheiten sehr stark schwankt. Als Folge muss die Trasse für den ungünstigsten Fall und damit unwirtschaftlich bemessen werden. Im Rahmen des Forschungsprojekts „DC-CTL DBI“ wurde eine gasisolierte HGÜ-Leitung (GIL) erdverlegt und einem Langzeitversuch unterzogen. Anstelle einer Sandbettung wurde jedoch ein zeitweise fließfähiger, selbstverdichtender Verfüllbaustoff (ZFSV) verwendet. Für den Einsatz als thermische Bettung bietet ein ZFSV mehrere Eigenschaften, welche eine klassische Sandbettung nicht bietet. So ist mit Hinblick auf die verschweißte Aluminium-Hülle der GIL kein Verdichtungsaufwand nötig, welcher bei aktueller Bauform zweifelsfrei in Schäden resultieren würde. Darüber hinaus weisen Flüssigböden durch den Bentonit-Gehalt eine höhere adsorbierende Oberfläche auf, wodurch der Anteil des Haftwassers im Boden zunimmt und die Wärmeleitfähigkeit der Bettung in ihrer Konstanz positiv beeinflusst wird. Im Zuge dieser Arbeit wurden die thermischen und hydraulischen Transportprozesse um die GIL mittels FEM in Plaxis2D untersucht und transient über den gesamten Messzeitraum (18 Monate) berechnet. Hierfür wurden die Materialparameter durch labortechnische Versuche ermittelt und die Messergebnisse einer verbauten Wetterstation als Randbedingungen (Niederschlag, Temperatur, Evapotranspiration) aufgebracht. Die Ergebnisse aus Plaxis2D wurden abschließend mit der im Feldversuch verbauten Sensorik verglichen. Es zeigte sich, dass sowohl die Boden- als auch die Leitertemperaturen nur um wenige Grad von den Messwerten der Sensorik abweichen. Anders als bei den etablierten analytischen Bemessungsrechnungen, welche stets auf Vereinfachungen basieren, können auch Effekte wie konvektiver Wärmetransport oder Austrocknung bei gleichzeitig höherer Genauigkeit der Ergebnisse untersucht werden. Um den Rechenaufwand gering zu halten, wurden lediglich die thermischen und hydraulischen Entwicklungen und Einflüsse des Bodens berücksichtigt. Es ist aber durchaus möglich, Verformungen und Kräfte in die Berechnung zu integrieren und so ein ganzheitliches Berechnungsmodell zu erstellen. KW - Geotechnik KW - ZFSV KW - Erdkabel KW - FEM KW - underground cables Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-17905 ER - TY - JOUR A1 - Lauer, Norina A1 - Giordano, Katharina A1 - Kreiter, Daniel A1 - Leusch, Vera A1 - Corsten, Sabine T1 - "Mach mal ’ne App" BT - Qualitätssicherung digitaler Entwicklungen am Beispiel der App BaSeTaLK JF - Forum Logopädie N2 - Die Entwicklung qualitativ hochwertiger Apps zur Gesundheitsversorgung erfordert einen aufwendigen Entwicklungsprozess, an den sich eine Evaluation der App-gestützten Maßnahme anschließen sollte, um Aussagen zur Wirksamkeit treffen und somit den App-Einsatz begründen zu können. In diesem Beitrag wird die nutzerzentrierte Entwicklung der App BaSeTaLK vorgestellt, mit der eine Tablet-gestützte Stimulation biographisch orientierter Gespräche bei älteren Menschen zur Verbesserung des psychischen Wohlbefindens ermöglicht werden soll. Nach erfolgreicher Evaluation könnten LogopädInnen als MultiplikatorInnen den Einsatz der App vermitteln. KW - App KW - Biografieforschung KW - Qualitätskontrolle KW - Senioren KW - Design Thinking Y1 - 2021 U6 - https://doi.org/10.2443/skv-s-2021-53020210304 VL - 35 IS - 3 SP - 20 EP - 27 PB - Schulz-Kirchner ER - TY - GEN ED - Rudolph, Clarissa ED - Reber, Anne ED - Dollsack, Sophia T1 - Geschlechtergerechtigkeit und MINT BT - Irritationen, Ambivalenzen und Widersprüche in Geschlechterdiskursen an Hochschulen KW - Hochschule KW - MINT-Fächer KW - Gleichstellung KW - Frauenförderung Y1 - 2022 SN - 978-3-8474-1674-6 U6 - https://doi.org/10.3224/84742519 PB - Verlag Barbara Budrich CY - Opladen ; Berlin ; Toronto ER - TY - JOUR A1 - Lührmann, Melanie A1 - Weiss, Matthias T1 - The Effect of Working Time and Labor Force Participation on Unemployment BT - A New Argument in an Old Debate JF - Economic Modelling N2 - This paper introduces a new argument into the theoretical literature on labor market effects of changes in working hours and labor force participation. We advance a general equilibrium model in which increased labor supply reduces unskilled unemployment via consumer demand: longer work hours and higher labor force participation imply higher incomes and less (leisure) time. In consequence, home production is reduced in favor of outsourcing domestic tasks to the market, shifting consumer demand toward unskill-intensive goods. Relative demand for unskilled labor rises and unemployment falls. Finally, we provide empirical support for the basic mechanisms of our model for Germany. KW - Working time reduction KW - Labor force participation KW - Low skill unemployment KW - Home production KW - Time use Y1 - 2010 U6 - https://doi.org/10.1016/j.econmod.2009.07.024 VL - 27 IS - 1 SP - 67 EP - 82 ER -