Diffraction of transmission light through triangular apertures in array of retro-reflective micro-prisms

The array of micro-prisms was described by model of multi-period blazed gratings consisting of triangular apertures. The origins of hexagram-shaped diffraction patterns were interpreted based on multiple-beam interference and diffraction array theorem. The relation between zonal /line ghost fringes and imperfectly fabricated array structures was analyzed. Geometrical performances (e.g., the dihedral angle of micro-prism) were tested by measuring the features of diffraction patterns of samples from three retro-reflective sheeting manufacturers.Comment: Applied Optics(in press), 17 pages, 9 figure

Re-evaluation of Apollo 17 Lunar Seismic Profiling Experiment data

We re-analyzed Apollo 17 Lunar Seismic Profiling Experiment (LSPE) data to improve our knowledge of the subsurface structure of this landing site. We use new geometrically accurate 3-D positions of the seismic equipment deployed by the astronauts, which were previously derived using high-resolution images by Lunar Reconnaissance Orbiter (LRO) in combination with Apollo astronaut photography. These include coordinates of six Explosive Packages (EPs) and four geophone stations. Re-identified P-wave arrival times are used to calculate two- and three-layer seismic velocity models. A strong increase of seismic velocity with depth can be confirmed, in particular, we suggest a more drastic increase than previously thought. For the three-layer model the P-wave velocities were calculated to 285, 580, and 1825 m/s for the uppermost, second, and third layer, respectively, with the boundaries between the layers being at 96 and 773 m depth. When compared with results obtained with previously published coordinates, we find (1) a slightly higher velocity (+4%) for the uppermost layer, and (2) lower P-wave velocities for the second and third layers, representing a decrease of 34% and 12% for second and third layer, respectively. Using P-wave arrival time readings of previous studies, we confirm that velocities increase when changing over from old to new coordinates. In the three-layer case, this means using new coordinates alone leads to thinned layers, velocities rise slightly for the uppermost layer and decrease significantly for the layers below

Kraftwerks- und Speicherbedarf bei hohen Anteilen erneuerbarer Energien

In dieser Dissertation werden der gesamtwirtschaftlich optimale Bedarf und der Einsatz von Kraftwerken, Batterie- und Pumpspeichern sowie Power-to-Gas-Anlagen bei hohen Anteilen erneuerbarer Energien untersucht. Um sowohl einen langen Betrachtungshorizont als auch eine hohe zeitliche Auflösung abzubilden, wird unter Berücksichtigung des Übertragungsnetzes ein Modellkonzept entworfen, welches auf Basis einer Dekomposition eine regionalisierte Analyse erlaubt

Development of an active seismic experiment for lunar exploration

The subject of this thesis was the evaluation of historical Apollo 17 Lunar Seismic Profiling data in combination with the design and operation of a new active seismic experiment for planetary applications. During the Apollo program, running between 1961 and 1972, there were a total of six manned landings. Astronauts deployed a number of scientific instruments on the Lunar surface, some of which continued operation long after the Apollo missions. Among these was the Lunar Seismic Profiling Experiment (LSPE) set up by astronauts on Apollo 17, which consisted of four geophones in a Y-shaped array and eight explosive packages. The setup was used to register the signals of the eight remotely detonated explosions as well as to passively listen for natural seismic signals. To date, this setup represents the largest seismic experiment conducted outside of the Earth. In 2009, the Lunar Reconnaissance Orbiter (LRO) was launched with the task of mapping the lunar surface in high resolution. Special attention was paid to a precision mapping of the Apollo landing sites. It turned out that the positions of the Apollo instruments differed substantially from the previously determined positions, thus requiring updates of the previously determined seismic velocity-depth profiles. The first part of this work was to go back to the original bitstreams of the Apollo data to carry out new arrival time readings for the seismic P-waves. Using the new positional data of the seismic sources and receivers, these were inverted to derive a new velocity-depth profiles. The comparison with historical results showed that the use of the corrected distance data led to a significant reduction in layer thicknesses and a stronger increase in P-wave velocity with depth. Overall, this resulted in a stronger compaction of the subsurface material than previously assumed being indicated. In the second part of this thesis, an active seismic experiment was developed and operated, which was largely based on the idea of the Apollo 17's LSPE. The experiment scenario was now to be set up and carried out by autonomous robotic systems. DLR Bremen developed two autonomous measurement systems, what we called “Remote Units” (RU), for this scenario. The Mascot design of the Japanese Hayabusa2 probe proved to be a suitable basis for this development. Following a number of laboratory tests, the RUs were brought to application in the context of the demo mission “Space” of the Helmholtz Alliance "ROBEX", for which a terrain on Mount Etna in Italy was chosen as the experiment site. Seismic data were successfully obtained, and the evaluation of the data confirmed earlier results on the geology and subsurface structure of the test area determined with standard methods. Thus, the evaluation of the seismic data could not only show that the developed experimental scenario and equipment were suitable to explore near-surface stratifications by means of refraction seismic experiments, but also that the selected test area on Mount Etna, featuring strata of lava flows in the subsurface, actually qualified as a lunar analogue terrain

Selektive Kristallisation von Kationen mit Kronenethern

Ziel dieser Arbeit war die Untersuchung der Selektivität bzw. der Bevorzugung des Einbaus unterschiedlich großer Kationen in die Kavität verschiedener Kronenether sowie die Charakterisierung der entstehenden Verbindungen. Grundsätzlich sind die Koordinationspräferenzen der Kronenether mit unterschiedlichen Hohlräumen seit langem bekannt, wobei zunehmend die Auswirkungen weiterer Effekte für die Strukturbildung in den Fokus der Aufmerksamkeit getreten sind. In dieser Arbeit wurde ein erster vergleichender Überblick über die Koordinationspräferenzen in Abhängigkeit verschiedener Faktoren unternommen. Der Fokus lag dabei vor allem auf der Variation des Durchmessers des Kronenetherhohlraums bei Anwesenheit unterschiedlich großer Kationen, auf der Untersuchung der Auswirkungen des Lösungsmittels und den Auswirkungen unterschiedlich stark koordinierender Anionen. Im Rahmen dieser Arbeit konnten bei Seltenerdnitraten grundlegende Koordinationspräferenzen festgestellt werden, die besonders von der Wahl des Lösungsmittels beeinflusst werden. Durch die Variation der Bedingungen konnte die Bildung unterschiedlicher Strukturtypen gesteuert und so die Inkorporation der Kationen in die Kavität der Kronenether beeinflusst werden, wobei die Bildung eines bestimmten Strukturtyps zum Teil über die Wahl des Lösungsmittels beeinflusst werden kann. Dabei waren bei den Seltenerd-Kationen keine direkten Präferenzen für die Inkorporation in die Kavität des Kronenethers in Bezug zur Kationengröße feststellbar. Die Koordination durch den Kronenether führt aber zu – für Lanthanoide – recht hohe Koordinationszahlen. Insgesamt konnten fünf neue Seltenerdmetall-Komplexe und zwei Strukturvarianten mit Kronenethern dargestellt werden. Bei der Untersuchung der Selektivität des Einbaus in die Kavität wurden zudem bekannte Strukturen reproduziert und weitere noch nicht kristallographisch gelöste Strukturen grundlegend charakterisiert. Bei der Verwendung einwertiger Kationen wie Kalium, Lithium oder Silber konnten insgesamt neun neue Verbindungen synthetisiert, aber keine klaren Präferenzen für den Einbau bestimmter Kationen festgestellt werden. Die Strukturen lassen sich den bereits von Pedersen gefundenen allgemeinen Strukturtypen zuordnen. Zwei Silberverbindungen gehören dabei dem eher seltenen 2:3-Strukturtyp (Club-Sandwich) an

Reducing computing time of energy system models by a myopic approach

In this paper, the performance of the existing energy system model PERSEUS-NET is improved in terms of computing time. Therefore, the possibility of switching from a perfect foresight to a myopic approach has been implemented. PERSEUS-NET is a linear optimization model generating scenarios of the future German electricity generation system until 2030, whilst considering exogenous regional characteristics such as electricity demand and existing power plants as well as electricity transmission network restrictions. Up to now, the model has been based on a perfect foresight approach, optimizing all variables over the whole time frame in a single run, thus determining the global optimum. However, this approach results in long computing times due to the high complexity of the problem. The new myopic approach splits the optimization intomultiple, individually smaller, optimization problems each representing a 5 year period. The change within the generation system in each period is determined by optimizing the subproblem, whilst taking into account only the restrictions of that particular period. It was found that the optimization over the whole time frame with the myopic approach takes less than one tenth of the computing time of the perfect foresight approach. Therefore, we analyse in this paper the advantages and draw-backs of a change in the foresight as a way of reducing the complexity of energy system models. For PERSEUS-NET it is found that the myopic approach with stable input parameters is as suitable as the perfect foresight approach to generate consistent scenarios, with the advantage of significantly less computing time

Reducing computing time of energy system models by a myopic approach

In this paper, the performance of the existing energy system model PERSEUS-NET is improved in terms of computing time. Therefore, the possibility of switching from a perfect foresight to a myopic approach has been implemented. PERSEUS-NET is a linear optimization model generating scenarios of the future German electricity generation system until 2030, whilst considering exogenous regional characteristics such as electricity demand and existing power plants as well as electricity transmission network restrictions. Up to now, the model has been based on a perfect foresight approach, optimizing all variables over the whole time frame in a single run, thus determining the global optimum. However, this approach results in long computing times due to the high complexity of the problem. The new myopic approach splits the optimization intomultiple, individually smaller, optimization problems each representing a 5 year period. The change within the generation system in each period is determined by optimizing the subproblem, whilst taking into account only the restrictions of that particular period. It was found that the optimization over the whole time frame with the myopic approach takes less than one tenth of the computing time of the perfect foresight approach. Therefore, we analyse in this paper the advantages and draw-backs of a change in the foresight as a way of reducing the complexity of energy system models. For PERSEUS-NET it is found that the myopic approach with stable input parameters is as suitable as the perfect foresight approach to generate consistent scenarios, with the advantage of significantly less computing time

COVID-19 in a Dutch Nursing Home: A Longitudinal Retrospective Care-Home-Level Case Study on Infection Rate, Survival Rate, and Daily Functioning.

During the pandemic, nursing homes in the Netherlands were heavily affected by COVID-19. This study assesses the impact of COVID-19 on infection rate, survival rate, and daily functioning over the course of two years among residents of a nursing home in the Netherlands that was amongst the first nursing homes to be affected by the pandemic. This retrospective study followed 70 residents during a two-year period, starting in March 2020. Data were collected on baseline characteristics of participants and the onset, duration, and sequelae of COVID-19 infections. Primary outcomes were mortality and infection rate. The secondary outcome was daily functioning using the Barthel Index at intervals of six months. Within two years, 44 (62.9%) residents were diagnosed with COVID-19. During this study, 72.7% (n = 32) of the COVID-positive residents died, of which 22 deaths were related to the COVID-19 infection. Overall mortality was 60% (n = 42), while COVID-related mortality was 31.4% (n = 22). COVID-19 and multimorbidity (>3 morbidities) were independent risk factors for mortality. Barthel Index scores showed no significant difference in daily functioning. Overall, a high COVID-19 infection rate was seen and was the most common cause of death. COVID-19 did not affect functional status over time