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Academic self-regulation is a key factor for motivation and learning achievement. Yet with the large range of individual factors, this is not a one-size-fits-all proposition. This study of L2 Technical English students at two German universities explored learners’ expectations and motivations, in particular regarding self-regulation and self-efficacy via the individual’s time investment in self-led study. In an initial survey, learners (N=1646) reported on their English skill levels and anticipated learning habits. Complementarily, the retrospective survey investigated learners’ (N=796) actual behavior during the course, their perceptions of language skill improvement, and their satisfaction. The initial survey indicates a clear understanding that time investment in self-regulated study will lead to greater improvement, an outcome confirmed in the retrospective survey. Additionally, students who invested more time in their coursework were more satisfied with their achievement, although most learners acknowledge they should have studied more. The results verify that learners recognize the nexus between self-regulation and language skill improvement, yet university students are not satisfied with their capacity to self-regulate their language learning strategies. While differences in students’ skill levels and academic self-efficacy result in divergent degrees of progress, students of all types report benefits to their language skills when motivated to self-regulated study.
We investigate the influence of the geometry and doping level on the performance of n-type silicon nanowire field emitters on silicon pillar structures. Therefore, multiple cathodes with 50 by 50 pillar arrays (diameter: 5 μm, height: 30 μm, spacing: 50 μm) were fabricated and measured in diode configuration. In the first experiment, we compared two geometry types using the same material. Geometry 1 is black silicon, which is a highly dense surface covering a forest of tightly spaced silicon needles resulting from self-masking during a plasma etching process of single crystal silicon. Geometry 2 are silicon nanowires, which are individual spaced-out nanowires in a crownlike shape resulting from a plasma etching process of single crystal silicon. In the second experiment, we compared two different silicon doping levels [n-type (P), 1–10 and <0.005 Ω cm] for the same geometry. The best performance was achieved with lower doped silicon nanowire samples, emitting 2 mA at an extraction voltage of 1 kV. The geometry/material combination with the best performance was used to assemble an integrated electron source. These electron sources were measured in a triode configuration and reached onset voltages of about 125 V and emission currents of 2.5 mA at extraction voltages of 400 V, while achieving electron transmission rates as high as 85.0%.
Eine Herausforderung performancebasierter Prüfverfahren zur Bewertung der Dauerhaftigkeit ist die Beschleunigung natürlicher Mechanismen. Dies ist notwendig, um innerhalb kurzer Zeit die Langzeit-Leistungsfähigkeit ermitteln zu können. Die Bestimmung der Frost-Tausalzbeständigkeit von Beton kann durch den CDF-Test erfolgen, welcher für Betone mit ausreichendem Frost-Tausalz-Widerstand sehr gut funktioniert. Bei Proben mit einer unzureichenden bzw. unbekannten Performance können erhöhte Randabwitterungen auftreten, welche durch das Ablösen des seitlichen Abdichtbands entstehen. Der zunehmende Randeinfluss führt so zu einer Verfälschung der Ergebnisse und zu einer Unterschätzung der tatsächlichen Performance des Bauteils. In diesem Beitrag werden Mörtel- und Betonprobekörper mit unterschiedlichen Abwitterungsraten in Anlehnung an das CDF-Verfahren untersucht. Zusätzlich wird die Oberflächenschädigung der Proben anhand einer neuartigen Messmethode mittels hochauflösendem 3D-Laserscanning ausgewertet. Die Ergebnisse zeigen, dass die Randeffekte mit der Laserscan-Methode umgangen und vergleichbare Ergebnisse zu den CDF-Untersuchungen erzielt werden können. Somit können Betone ohne Randeinflüsse charakterisiert und eine präzise Prognose der Langzeitbeständigkeit getroffen werden.
A comparative analysis of two different approaches developed to deal with molecular relaxation in photoacoustic spectroscopy is here reported. The first method employs a statistical analysis based on partial least squares regression, while the second method relies on the development of a digital twin of the photoacoustic sensor based on the theoretical modelling of the occurring relaxations. Methane detection within a gas matrix of synthetic air with variable humidity level is selected as case study. An interband cascade laser emitting at 3.345 µm is used to target methane absorption features. Two methane concentration ranges are explored targeting different absorptions, one in the order of part-per-million and one in the order of percent, while water vapor absolute concentration was varied from 0.3 % up to 2 %. The results achieved employing the detection techniques demonstrated the possibility to efficiently retrieve the target gas concentrations with accuracy > 95 % even in the case of strong influence of relaxation effects.
Transition metal dichalcogenide (TMDC) nanotubes complement the field of low-dimensional materials with their quasi-1D morphology and a wide set of intriguing properties. By introducing different transition metals into the crystal structure, their properties can be tailored for specific purpose and applications. Herein, the characterization and a subsequent preparation of single-nanotube field emission devices of MoxWx-1S2 nanotubes prepared via the chemical vapor transport reaction is presented. Energy-dispersive X-ray spectroscopy, Raman spectroscopy, and X-ray diffraction indicate that the molybdenum and tungsten atoms are randomly distributed within the crystal structure and that the material is highly crystalline. High resolution transmission electron microscopy and electron diffraction (ED) patterns further corroborate these findings. A detailed analysis of the ED patterns from an eight-layer nanotube reveal that the nanotubes grow in the 2H structure, with each shell consists of one bilayer. The work function of the nanotubes is comparable to that of pure MoS2 and lower of pure WS2 NTs, making them ideal candidates for field emission applications. Two devices with different geometrical setup are prepared and tested as field emitters, showing promising results for single nanotube field emission applications.
Improvements for building-performance simulations by a comparative finite-element method analysis
(2023)
This paper presents a method to improve building-performance simulations (BPS) by the comparison and analysis of different approaches based on finite-element method (FEM) models. The lumped parameter method (LPM) is used in several BPS programs and tools. It has the advantage of fast computing times and comparably good accuracy for thermal and energy loads. With the help of detailed FEM simulations, it is possible to further improve the degree of detail and accuracy while maintaining the high simulation speed.
In this work, we compare time-dependent results for local temperatures in a generic reference room within a given periode of time. In a second step, the differences between the models with respect to various physical effects are analyzed and used to introduce additional equations into the LPM model in order to improve its accuracy. Thus, we discuss potentials for improvement for BPS and demonstrate a method of a practical implementation.
The results show minor differences of less than 0.1 K for radiation and heat transfer, so their level of detail in BPS is appropriate. In these terms, no improvements were pursued within the work. However, the FEM simulation is capable of calculating the internal convective heat transfer and thermal bridges more accurately due to the use of computational fluid dynamics (CFD) and the geometrically precise representation of the FEM model. Here, deviations of up to 1 K in room temperature (convective heat transfer) and up to 0.5 K in wall temperatures (thermal bridges) were pointed out.
By improving the LPM with equations obtained from the FEM, these deviations can be reduced to less than 0.2 K, which is a considerable improvement in accuracy.
Silicon micro venturi nozzles for cost-efficient spray coating of thin organic P3HT/PCBM layers
(2017)
Improvements on spray coating are of particular interest to different fields of technology as it is a scalable deposition method and processing from solutions offer various application possibilities outside of typical facilities. When it comes to the deposition of expensive and film-forming media such as organic semiconductors, consumption and nozzle cleaning issues are of particular importance. We demonstrate the simple steps to design and fabricate micro venturi nozzles for economical spray coating with a consumption as low as 30-50 mu l.min(-1). For spray coating an active area of 25 cm(2) a 2.45-4.01 fold coating efficiency is observed compared to a conventional airbrush nozzle set. The electrical characterization of first diodes sprayed with an active layer thickness of similar to 750 nm using a single micronozzle at a coating speed of 1.7 cm(2).min(-1) reveals a good external quantum efficiency of 72.9% at 532 nm and a dark current of similar to 7.4.10(-5) mA.cm(-2), both measured at -2 V. Furthermore, the high resistance of the micronozzles against solvents and most acids is provided through realization in a silicon wafer with silicon dioxide encapsulation, therefore allowing easy and effective cleaning.
At risk of reproductive disadvantage? Exploring fertility awareness among migrant women in Germany
(2022)
This study examined awareness about fertility among immigrant women and non-migrants in Germany. The social relevance of infertility and fertility treatment is increasing in Western countries due to continually low overall birth rates, a high rate of childlessness, and a gap between the desired and actual numbers of children. While there is growing interest in infertility and reproductive medicine in general, previous studies have rarely included immigrant or ethnic minorities in Europe. This study investigated whether knowledge on the age-related fertility decline (ARFD) varies between migrant groups and the majority group, and the role of education. Working hypotheses were drawn from theoretical considerations on frameworks of migrant assimilation. The analysis was based on data collected in a social science pilot study on reproductive medicine, representative of the general population (‘NeWiRe’ 2014–2015). The sample included 962 women aged 18–50 years living in Germany. Approximately 81% of the sample were immigrants who originated from Turkey, Poland, the Balkan countries or countries of the (post-Soviet) Commonwealth of Independent States. While rather poor overall, knowledge on ARFD was found to be significantly lower in the migrant groups compared with the majority group. This minority-group disadvantage cannot be explained by sociodemographic or cultural variables. Future research should include minority groups in empirical studies on awareness about fertility in order to better understand the causes of this disadvantage, and the potential reproductive needs of migrants.
We present a sensitive and compact interband cascade laser (ICL) based photoacoustic setup for the detection of gaseous hydrocarbons and discuss its applicability towards trace gas analysis. We investigated the performance of the sensor for trace concentrations of methane, ethane and acetylene diluted in nitrogen. The excitation of methane and ethane was accomplished using one tunable diode laser, covering a range from 3360 to 3372 nm, which was replaced by a separate ICL at 3025 nm for acetylene detection. The influence of ambient parameters such as temperature, flow rate and pressure as well as potential cross-sensitivities towards O2 and H2O have been examined in terms of methane and acetylene detection. A series of simulations proved several of these influences to be attributed to relaxation effects. With a 3σ limit of detection (LoD) of 6.8 parts per billion (ppbV) in case of methane, 2.3 ppbV regarding ethane and 3.6 ppbV in terms of acetylene, the sensor demonstrates a great potential for applications in the field of trace gas analysis.
Academic self-regulation is a key factor for motivation and learning achievement. Yet with the large range of individual factors, this is not a one-size-fits-all proposition. This study of L2 Technical English students at two German universities explored learners’ expectations and motivations, in particular regarding self-regulation and self-efficacy via the individual’s time investment in self-led study. In an initial survey, learners (N=1646) reported on their English skill levels and anticipated learning habits. Complementarily, the retrospective survey investigated learners’ (N=796) actual behavior during the course, their perceptions of language skill improvement, and their satisfaction. The initial survey indicates a clear understanding that time investment in self-regulated study will lead to greater improvement, an outcome confirmed in the retrospective survey. Additionally, students who invested more time in their coursework were more satisfied with their achievement, although most learners acknowledge they should have studied more. The results verify that learners recognize the nexus between self-regulation and language skill improvement, yet university students are not satisfied with their capacity to self-regulate their language learning strategies. While differences in students’ skill levels and academic self-efficacy result in divergent degrees of progress, students of all types report benefits to their language skills when motivated to self-regulated study.