A comparative study to investigate two configurations of a two-stage evaporator in a CO2 heat pump chiller

This study is carried out to investigate the performance of a CO2 heat pump chiller that provides heating and cooling simultaneously. For heating applications, hot water is produced at 90°C; while for cooling applications, chilled water is produced at 4°C. The evaporator utilized for chilled water production is a novel two-stage evaporator. Two configurations have been proposed to implement this two-stage evaporator in the CO2 system. One configuration is termed GFES: the first stage is fed by gravity; the second stage is fed by ejector suction. The other configuration is termed EDES: the first stage is fed by the ejector discharge; the second stage is fed by ejector suction. The primary goal of this study is to compare the performances of these two evaporator configurations and their effects on the system’s overall performance. To fulfill this objective simulation models are developed in Modelica. Results show that the COPs are nearly the same for both configurations. In addition, it is observed that the integration of the two-stage evaporator enhances the overall performance as the cooling capacity is shared between the two stages and the suction pressure of the compressor is elevated by utilizing the ejector.acceptedVersio

Comparison of electromagnetic field solvers for the 3D analysis of plasmonic nano antennas

Plasmonic nano antennas are highly attractive at optical frequencies due to their strong resonances - even when their size is smaller than the wavelength - and because of their potential of extreme field enhancement. Such antennas may be applied for sensing of biological nano particles as well as for single molecule detection. Because of considerable material losses and strong dispersion of metals at optical frequencies, the numerical analysis of plasmonic antennas is very demanding. An additional difficulty is caused when very narrow gaps between nano particles are utilized for increasing the field enhancement. In this paper we discuss the main difficulties of time domain solvers, namely FDTD and FVTD and we compare various frequency domain solvers, namely the commercial FEM packages JCMsuite, Comsol, HFSS,and Microwave Studio with the semi-analytic MMP code that may be used as a reference due to its fast convergence and high accuracy.Comment: 12 pages, SPIE conference, Errata added on last pag

Continuously variable W-band phase shifters based on MEMS-actuated conductive fingers

This paper presents four continuously variable W-band phase shifters in terms of design, fabrication, and radiofrequency (RF) characterization. They are based on low-loss ridge waveguide resonators tuned by electrostatically actuated highly conductive rigid fingers with measured variable deflection between 0.3° and 8.25° (at a control voltage of 0-27.5 V). A transmission-type phase shifter based on a tunable highly coupled resonator has been manufactured and measured. It shows a maximum figure of merit (FOM) of 19.5°/dB and a transmission phase variation of 70° at 98.4GHz. The FOM and the transmission phase shift are increased to 55°/dB and 134°, respectively, by the effective coupling of two tunable resonances at the same device with a single tuning element. The FOM can be further improved for a tunable reflective-type phase shifter, consisting of a transmission-type phase shifter in series with a passive resonator and a waveguide short. Such a reflective-type phase shifter has been built and tested. It shows a maximum FOM of 101°/dB at 107.4GHz. Here, the maximum phase shift varied between 0° and 377° for fingers deflections between 0.3° and 8.25

Cocaine/Levamisole-Induced, Skin-Limited ANCA-Associated Vasculitis with Pyoderma Gangrenosum-like Presentation

The use of levamisole as the most frequent adulterant of cocaine has merged in previously unknown toxicities, notably a disease entity called cocaine/levamisole-associated autoimmune syndrome (CLAAS). Clinically, CLAAS can manifest with diverse cutaneous and extracutaneous features sharing common laboratory findings (neutropenia, autoantibody patterns). We report the case of a cocaine-abusing female patient with relapsing episodes of painful ulcers, worsening and expanding over a three-year period. The case exhibited all features of a drug-induced, skin-limited, ANCA-associated vasculitis, evolving over time to PG-like findings. In both disease stages, the patient responded well to the cessation of cocaine exposure and systemic glucocorticosteroids. This case demonstrates the continuous nature of cutaneous CLAAS manifestations in a single patient. CLAAS has become a major public health issue in the at-risk group of cocaine users, and clinicians should be alert of this condition when treating cocaine users presenting with single or multiple skin ulcerations

Integration of gravity-fed evaporators in CO2 based heat-pump chillers

This study is carried out to model a gravity-fed evaporator for CO2 based heat-pump chillers. The gravity-fed evaporator loop consists of a separator, a downcomer, a heat exchanger, and a riser. The working principle is that the evaporation of fluid in the heat exchanger gives rise to a density gradient in the loop. This density gradient generates the buoyancy force which drives the fluid by overcoming all the pressure drops in the loop. Appropriate equations are derived to estimate these pressure resistances. Finally, the balance between the buoyancy forces and pressure resistances dictates the flowrate in the loop. This procedure is implemented in Modelica to develop the simulation model for the gravity-fed evaporator. The loop dimensions are critical to the performance of the system. Hence it is essential to estimate the loop dimensions accurately. In this study, the simulations are carried out to predict the optimum dimensions to achieve the optimum circulation rate in the loop. It is expected that this study will be helpful in designing optimized gravity-fed evaporators for CO2 based heat-pump chillers.acceptedVersio

Automated avalanche mapping from SPOT 6/7 satellite imagery with deep learning: results, evaluation, potential and limitations

Spatially dense and continuous information on avalanche occurrences is crucial for numerous safety-related applications such as avalanche warning, hazard zoning, hazard mitigation measures, forestry, risk management and numerical simulations. This information is today still collected in a non-systematic way by observers in the field. Current research has explored the application of remote sensing technology to fill this information gap by providing spatially continuous information on avalanche occurrences over large regions. Previous investigations have confirmed the high potential of avalanche mapping from remotely sensed imagery to complement existing databases. Currently, the bottleneck for fast data provision from optical data is the time-consuming manual mapping. In our study we deploy a slightly adapted DeepLabV3+, a state-of-the-art deep learning model, to automatically identify and map avalanches in SPOT 6/7 imagery from 24 January 2018 and 16 January 2019. We relied on 24 778 manually annotated avalanche polygons split into geographically disjointed regions for training, validating and testing. Additionally, we investigate generalization ability by testing our best model configuration on SPOT 6/7 data from 6 January 2018 and comparing it to avalanches we manually annotated for that purpose. To assess the quality of the model results, we investigate the probability of detection (POD), the positive predictive value (PPV) and the F1 score. Additionally, we assessed the reproducibility of manually annotated avalanches in a small subset of our data. We achieved an average POD of 0.610, PPV of 0.668 and an F1 score of 0.625 in our test areas and found an F1 score in the same range for avalanche outlines annotated by different experts. Our model and approach are an important step towards a fast and comprehensive documentation of avalanche periods from optical satellite imagery in the future, complementing existing avalanche databases. This will have a large impact on safety-related applications, making mountain regions safer

Avalanche size estimation and avalanche outline determination by experts: reliability and implications for practice

Consistent estimates of avalanche size are crucial for communicating not only among avalanche practitioners but also between avalanche forecasters and the public, for instance in public avalanche forecasts. Moreover, applications such as risk management and numerical avalanche simulations rely on accurately mapped outlines of past avalanche events. Since there is not a widely applicable and objective way to measure avalanche size or to determine the outlines of an avalanche, we need to rely on human estimations. Therefore, knowing about the reliability of avalanche size estimates and avalanche outlines is essential as errors will impact applications relying on this kind of data. In the first of three user studies, we investigate the reliability in avalanche size estimates by comparing estimates for 10 avalanches made by 170 avalanche professionals working in Europe or North America. In the other two studies, both completed as pilot studies, we explore reliability in the mappings of six avalanches from oblique photographs from 10 participants and the mappings of avalanches visible on 2.9 km2 of remotely sensed imagery in four different spatial resolutions from 5 participants. We observed an average agreement of 66 % in the most frequently given avalanche size, while agreement with the avalanche size considered “correct” was 74 %. Moreover, European avalanche practitioners rated avalanches significantly larger for 8 out of 10 avalanches, compared to North Americans. Assuming that participants are equally competent in the estimation of avalanche size, we calculated a score describing the factor required to obtain the observed agreement rate between any two size estimates. This factor was 0.72 in our dataset. It can be regarded as the certainty related to a size estimate by an individual and thus provides an indication of the reliability of a label. For the outlines mapped from oblique photographs, we noted a mean overlapping proportion of 52 % for any two avalanche mappings and 60 % compared to a reference mapping. The outlines mapped from remotely sensed imagery had a mean overlapping proportion of 46 % (image resolution of 2 m) to 68 % (25 cm) between any two mappings and 64 % (2 m) to 80 % (25 cm) when compared to the reference. The presented findings demonstrate that the reliability of size estimates and of mapped avalanche outlines is limited. As these data are often used as reference data or even ground truth to validate further applications, the identified limitations and uncertainties may influence results and should be considered

En Route to European Journals of Inorganic and Organic Chemistry

In 1997 a new journal structure for the chemical literature in Europe will begin to evolve. Recueil des Travaux Chimiques des Pays-Bas will unite with Liebigs Annalen and Chemische Berichte; furthermore, Chemistry - A European Journal will become independent of Angewandte Chemie, its “carrier journal”. Recueil was founded in 1882 and is the journal of the Royal Netherlands Chemical Society (KNCV); Chemische Berichte (1865) and Liebigs Annalen (1832) are German Chemical Society (GDCh) journals. With these heritages in mind, we will apply the image of a “European House”, often used by politicians, to scientific publishing in Europe

Ableitung von bodenphysikalischen Parametern für Waldstandorte in Schleswig-Holstein

Die steigende Nachfrage nach großmaßstäblichen Standorts- und Bodeninformationen im Bereich der forstlichen Planungs- und Entscheidungs­unterstützung stellt immer höhere Anforderungen an die Qualität von bodenphysikalischen Basisinformationen (Sand-, Schluff- und Tongehalt, Skelett- und Humusgehalt und Trockenrohdichte). Diese gehen direkt in statistische und prozessorientierte Modelle zur flächenhaften Bewertung des Wasser- und Stoffhaushaltes ein. Abhängig von der Maßstabsebene, in der die flächenhaften Bodeninformationen vorliegen, ergeben sich unterschiedliche Unsicherheiten für die auf diesen Daten basierenden Auswertungen. In Schleswig-Holstein liegen flächenhafte bodenphysikalische Angaben in Form der Waldbodenübersichtskarte im Maßstab 1 : 1.000.000 (BÜK1000), der Bodenübersichts­karte im Maßstab 1 : 200.000 (BÜK 200, BGR©2015) und – bisher noch nicht vollständig - der Bodenkarte im Maßstab 1 : 25.000 (BK25) vor. Die forstliche Standortskarte für Waldflächen in Schleswig-Holstein (1 : 25.000) deckt zwar viele Gebiete ab, die von der BK25 nicht erfasst werden, sie enthält jedoch nur eingeschränkt bodenphysikalische Informationen. Da der forstliche Standortstyp Standorte mit ähnlichen Umwelt­bedingungen und waldbaulichen Möglichkeiten zusammenfasst, wurden die Standortstypen als übergeordnete Einheit zur Herleitung von Bodenleitprofilen verwendet. Vorhandene Bodenprofile (4759) wurden anhand des zugewiesenen forstlichen Standorttyps gruppiert. Für forstliche Standortstypen zu denen mindestens fünf Bodenprofile vorhandenen waren, wurden die Parameter mit verschiedenen Methoden (horizont-, tiefenstufenbezogen) aggregiert. Zur Evaluierung, der nach unterschiedlichen Methoden abgeleiteten bodenphysikalischen Parameter eines Bodenleitprofils dienten die Bodenprofile der zweiten Bodenzustands­erhebung im Wald (BZE II). Die Ergänzung von Bodeninformationen für nichtkartierte Flächen im Maßstab 1 : 25.000 anhand der erstellten Bodenleitprofile für forstliche Standorttypen lieferte hinreichend genaue und verzerrungsfreie Schätzungen der bodenphysikalischen Parameter im Vergleich mit den BZE II-Profilen. Die Qualität der flächenhaften Information basierend auf den erstellten Bodenleitprofilen ist vergleichbar mit den bodenphysikalischen Informationen der BK25