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Atmospheric aerosols affect the power production of solar energy systems. Their impact depends on both the atmospheric conditions and the solar technology employed. By being a region with a lack in power production and prone to high solar insolation, West Africa shows high potential for the application of solar power systems. However, dust outbreaks, containing high aerosol loads, occur especially in the Sahel, located between the Saharan desert in the north and the Sudanian Savanna in the south. They might affect the whole region for several days with significant effects on power generation. This study investigates the impact of atmospheric aerosols on solar energy production for the example year 2006 making use of six well instrumented sites in West Africa. Two different solar power technologies, a photovoltaic (PV) and a parabolic through (PT) power plant, are considered. The daily reduction of solar power due to aerosols is determined over mostly clear-sky days in 2006 with a model chain combining radiative transfer and technology specific power generation. For mostly clear days the local daily reduction of PV power (at alternating current) (PVAC) and PT power (PTP) due to the presence of aerosols lies between 13 % and 22 % and between 22 % and 37 %, respectively. In March 2006 a major dust outbreak occurred, which serves as an example to investigate the impact of an aerosol extreme event on solar power. During the dust outbreak, daily reduction of PVAC and PTP of up to 79 % and 100 % occur with a mean reduction of 20 % to 40 % for PVAC and of 32 % to 71 % for PTP during the 12 days of the event.
Pseudopotential (PP)-basierte Lattice-Boltzmann-Methoden werden zunehmend für die Simulation von Mehrphasenströmungen eingesetzt. Da sie auf einem phänomenologischen Ansatz basieren, ist ihr Einsatz mit einem hohen Modellierungsaufwand verbunden. Zudem entstehen an den Phasengrenzen sogenannte Scheingeschwindigkeiten, welche Genauigkeit und numerische Stabilität beeinträchtigen. Daher werden PP-Modelle in dieser Arbeit um drei neue Aspekte erweitert. Erstens wird gezeigt, dass bei der Modellierung unterschiedlicher Kontaktwinkel mit gängigen Methoden in Kombination mit verbesserten Kräfteschemata Scheintröpfchen entstehen. Diese werden durch einen neuartigen Ansatz eliminiert, der auf zusätzlichen Randbedingungen für alle Wechselwirkungskräfte basiert. Diese Technik verhindert nicht nur das Auftreten der Scheintröpfchen, sondern erhöht auch die Stabilität in wandgebundenen Strömungen. Zweitens wird ein neuartiges Verfahren zur Reduktion von Scheingeschwindigkeiten eingeführt. Dabei wird die Diskretisierung der Interaktionskräfte erweitert und die zusätzlichen, freien Koeffizienten in Simulationen statischer Tropfen numerisch optimiert. Die resultierende Diskretisierung wurde in Simulationen stationärer und dynamischer Testfälle validiert, wobei Scheingeschwindigkeiten deutlich reduziert werden konnten. Drittens und letztens wurden die Diffusionseigenschaften in Mehrstoffsystemen detailliert untersucht, wobei eine kritische Abhängigkeit zwischen den makroskopischen Diffusionskoeffizienten und dem Kräfteschema aufgezeigt wird. Diese Analyse bildet die Grundlage für den Vergleich und die zukünftige Entwicklung neuer Potentialfunktionen (für Mehrstoffsysteme) und reduziert den Modellierungsaufwand.
This paper proposes a new artificial neural network-based position controller for a full-electric injection moulding machine. Such a controller improves the dynamic characteristics of the positioning for hot runners, pin valve and the injection motors for varying moulding parameters. Practical experimental data and Matlab’s System Identification Toolbox have been used to identify the transfer functions of the motors. The structure of the artificial neural network, which used positioning error and speed of error, was obtained by numerical modelling in Matlab/Simulink. The artificial neural network was trained using back-propagation algorithms to provide control of the motor current thus ensuring the required position and velocity. The efficiency of the proposed ANN-based controller has been estimated and verified in Simulink using real velocity data and the position of the injection moulding machine and pin valve motors.
Herein we report an update to ACPYPE, a Python3 tool that now properly converts AMBER to GROMACS topologies for force fields that utilize nondefault and nonuniform 1–4 electrostatic and nonbonded scaling factors or negative dihedral force constants. Prior to this work, ACPYPE only converted AMBER topologies that used uniform, default 1–4 scaling factors and positive dihedral force constants. We demonstrate that the updated ACPYPE accurately transfers the GLYCAM06 force field from AMBER to GROMACS topology files, which employs non-uniform 1–4 scaling factors as well as negative dihedral force constants. Validation was performed using β-d-GlcNAc through gas-phase analysis of dihedral energy curves and probability density functions. The updated ACPYPE retains all of its original functionality, but now allows the simulation of complex glycomolecular systems in GROMACS using AMBER-originated force fields. ACPYPE is available for download at https://github.com/alanwilter/acpype.
Remote labs for students' design experiments are available in engineering education for several years. To ensure students' acceptance it is important to have an appropriate and stimulating user interface. So the usage and control of a remote lab has to be devised from the students' point of view. The contribution describes the FPGA (Field Programmable Gate Array) remote lab of the Bonn-Rhein-Sieg University and the design of its user interface from students' perspective.
In this contribution we present the concept for creating an “International Chair” position at a German University of Applied Sciences and our experiences in its first implementation. Our primary goal was to increase the diversity of the university’s teaching personalities and enrich student education by including content, methods, examples and experiences from other cultures. This gives students an international and intercultural learning experience that is otherwise only acquired through studying abroad. We conclude that the International Chair is a valuable and powerful university tool for increasing international exposure to the departments, their staff and students.
In this paper we present a new initiative to promote collaborative learning through industry partnered, interdisciplinary, student and user centred projects. This was achieved through the development of rehabilitation devices augmented with gamified software. Today development of software systems often requires people from different specialities who can work in multidisciplinary teams to achieve a common objective. A key challenge, therefore, is producing graduates with an understanding of a number of disparate skills across many discipline boundaries. Undergraduates may be knowledgeable in one specific discipline but will not be aware of the issues brought to bear by other relevant disciplines. In an effort to overcome this limitation, a cross-discipline course “Serious Games and Welfare Technology” was developed that allows students from different disciplines to work together to produce innovative, technology- supported health solutions. The course, an EU funded Erasmus+ initiative, was supported by a MOOC and enabled multi- disciplined and multinational teams to produce solutions for leading Health technology companies in the areas of rehabilitation and aging support. Following the first year of offering the course with a cohort of students from 5 countries, we report on the experiences and outcomes achieved from a number of viewpoints.
A traditional way to teach bachelor students in electrical engineering is organized such that theoretical knowledge is predominant in the first year while applications and practical experiences are reserved for later stages of their education. In this contribution, we want to introduce a reverse approach: In a freshmen course at Bonn-Rhein-Sieg University of Applied Science, students gain hands-on experience with resistances, condensers and other active parts, like transistors or relays from the very first day. We present how the combination of practical experience directly linked with theoretical knowledge enhances students' learning. It promotes deeper understanding of the theory and a better transfer between theory and practice. This teaching approach is adapted to address two main goals: First, to give practical experience to first-semester students as a basis for further laboratory and working situations. Second, to create a deeper and more sustainable understanding of physics by directly observing the effects that are described in formulas. The key to success is to find an efficient solution to carry out this approach with the given spatial and financial resources-which means, to do it in the lecture hall with very few material resources. To show that this innovative teaching concept really enhances the competencies of the students, an innovative evaluation approach was used where the students have to reflect upon their competencies before and after the course.
During the dawn of chemistry1,2 when the temperature of the young Universe had fallen below ~4000 K, the ions of the light elements produced in Big Bang nucleosynthesis recombined in reverse order of their ionization potential. With its higher ionization potentials, He++ (54.5 eV) and He+ (24.6 eV) combined first with free electrons to form the first neutral atom, prior to the recombination of hydrogen (13.6 eV). At that time, in this metal-free and low-density environment, neutral helium atoms formed the Universe’s first molecular bond in the helium hydride ion HeH+, by radiative association with protons (He + H+ → HeH+ + hν). As recombination progressed, the destruction of HeH+ (HeH+ + H → He + H2 +) created a first path to the formation of molecular hydrogen, marking the beginning of the Molecular Age.
Atomistic biomolecular simulations predominantly utilize additive force fields (FF), where the electrostatic potential is modeled by fixed point charges. Among other consequences, the lack of polarizability in these models undermines the balance of hydrophilic/hydrophobic non-bonded interactions. Simulations of water/alkane systems using the TIP3P water model and CHARMM36 parameters reveal a 1 kcal/mol over-estimate of the experimental transfer free energy of water to hexadecane; more recent optimized water models (SPC/E, TIP4P/2005, TIP4P-Ew, TIP3P-FB, TIP4P-FB, OPC, TIP4P-D) overestimate this transfer free energy by approximately 2 kcal/mol. In contrast, the polarizable SWM4-NDP and SWM6 water models reproduce experimental values to within statistical error. As an alternative to explicitly modeling polarizability, this paper develops an efficient automated workflow to optimize pair-specific Lennard-Jones parameters within an additive FF. Water/hexadecane is used as a prototype and the free energy of water transfer to hexadecane as a target. The optimized model yields quantitative agreement with the experimental transfer free energy and improves the water/hexadecane interfacial tension by 6%. Simulations of five different lipid bilayers show a strong increase of water permeabilities compared to the unmodified CHARMM36 lipid FF which consistently improves match with experiment: the order-of-magnitude underestimate for monounsaturated bilayers is rectified and the factor of 2.8 - 4 underestimate for saturated bilayers is turned into a factor of 1.5 - 3 overestimate. While agreement with experiment is decreased for the diffusion constant of water in hexadecane, alkane transfer free energies, and the bilayers' area per lipid, the method provides a permeant-specific route to achieve a wide range of heterogeneous observables via rapidly optimized pairwise parameters.
During the dawn of chemistry1,2, when the temperature of the young Universe had fallen below some 4,000 kelvin, the ions of the light elements produced in Big Bang nucleosynthesis recombined in reverse order of their ionization potential. With their higher ionization potentials, the helium ions He2+ and He+ were the first to combine with free electrons, forming the first neutral atoms; the recombination of hydrogen followed. In this metal-free and low-density environment, neutral helium atoms formed the Universe’s first molecular bond in the helium hydride ion HeH+ through radiative association with protons. As recombination progressed, the destruction of HeH+ created a path to the formation of molecular hydrogen. Despite its unquestioned importance in the evolution of the early Universe, the HeH+ ion has so far eluded unequivocal detection in interstellar space. In the laboratory the ion was discovered3 as long ago as 1925, but only in the late 1970s was the possibility that HeH+ might exist in local astrophysical plasmas discussed4–7. In particular, the conditions in planetary nebulae were shown to be suitable for producing potentially detectable column densities of HeH+. Here we report observations, based on advances in terahertz spectroscopy8,9 and a high-altitude observatory10, of the rotational ground-state transition of HeH+ at a wavelength of 149.1 micrometres in the planetary nebula NGC 7027. This confirmation of the existence of HeH+ in nearby interstellar space constrains our understanding of the chemical networks that control the formation of this molecular ion, in particular the rates of radiative association and dissociative recombination.
An der Hochschule Bonn‐Rhein‐Sieg setzten sich Chemiestudenten freiwillig parallel zum eigentlichen Fachstudium und fachübergreifend mit dem Begriff Nachhaltigkeit auseinander. Die Lehrveranstaltungen zeigen ihnen die gesellschaftlichen Bezüge naturwissenschaftlicher Inhalte und bringen sie dazu, ihr Selbstverständnis als Chemiker zu überdenken.
This Research to Practice Work in Progress Paper describes an outcome-based evaluation performed over three consecutive courses taught to electrical engineering students. The courses are delivered in the study entry phase: Computer Science 1 and 2 in the first and second semester and Digital Design in the third semester. The outcome-based evaluation was introduced to evaluate the progress made by students during the courses. Covering three semesters taught by two different lecturers, it gives a long-term view of the learning process in the study entry phase. The “outcome-based evaluation” methodology is proposed in literature and was introduced at our university at the end of 2016. Particular attention needs to be paid to formulating the questionnaire. The lecturers therefore cooperate with an evaluation officer from the university.
ICT has traditionally been a hostile territory for women. In information societies, this implies a drastic reduction in opportunities and autonomy for women. In emergent economies, the situation is even worse due to women’s subordinate status in society and little research regarding the intersection between gender and the digital divide. Such is the case in Latin America. In light of this, the purpose of this essay is to introduce a first comprehensive review of the few studies made in Latin America, against the background of the history of women’s digital exclusion. Based on a review of literature, we identify the main causes for women’s digital exclusion in the region and talk about the prospects for development of gender policies in the BRICS countries (Brazil, Russia, India, China and South Africa). We conclude that what this group of countries may achieve in regard to gender equality, will mark the future of the world. The aim of this essay is to make a call for the creation of inter - national research networks and propose the BRICS as host for these efforts, as they combine characteristics that will make them leaders of change in vast regions.
