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3. On the stability of solar chemical particle receivers

Author

Ries, H., Tschudi, H.R., and Spirkl, W.

Subjects
Chemical reactors -- Evaluation, Decomposition (Chemistry) -- Models, Engineering and manufacturing industries, Environmental issues
Abstract

We model the decomposition reaction of a solid powder into a solid plus gas in a mixed homogeneous open solar reactor and derive criteria for stability. Instability may occur via a feedback mechanism whereby gas produced in the decomposition reaction reduces the inflow, which leads to even higher reaction rate. For a variety of reactions proposed for solar application, we list the limits of stable operation as the maximum fraction of solid educt in the input carrier gas both for complete as well as for partial decomposition.

Published
1998

5. Optimal parallel flow in solar collectors for nonuniform irradiance

Author

Spirkl, W., Ries, H., and Kribus, A.

Subjects
Heat -- Radiation and absorption, Solar collectors -- Research, Solar radiation -- Research, Engineering and manufacturing industries, Environmental issues
Abstract

We consider volumetric thermal absorbers exposed to nonuniform irradiance. The fluid flows perpendicular to the absorber surface. The fluid transport from front to rear surface elements is connected in a parallel configuration. We investigate the optimum adjustment of the local mass flux or, equivalently, the local absorber temperature. Three different strategies are compared: (1) strategy of uniform mass flux, (2) strategy of uniform exit temperature, and (3) a strategy with a locally optimized temperature-flow profile. Significant improvement of strategy (2) compared to (1) and of strategy (3) compared to (2) is observed for the case of a black-body absorber which is isothermal in the direction normal to the absorber surface. We find it to be advantageous to include even regions where the stagnation temperature is below the desired exit temperature.

Published
1997

6. Performance of surface and volumetric solar thermal absorbers

Author

Spirkl, W., Ries, H., and Kribus, A.

Subjects
Heat -- Radiation and absorption, Solar thermal energy -- Research, Engineering and manufacturing industries, Environmental issues
Abstract

Thermal surface absorbers convert all incident radiation to heat at a single local temperature. The fluid flows perpendicular to the radiation's propagation direction. In contrast, in volumetric absorbers the fluid flows parallel to the radiation's propagation direction, and the absorber may exhibit temperature stratification along the radiation's direction. This raises the question whether reabsorption of parts of the thermal emission coming from the hotter absorber sections renders the volumetric absorber superior to the surface absorber. For the case of isotropic radiation, we compare the efficiency of the volumetric and the surface absorber with each other and with an isothermal absorber. We find that the nonselective volumetric absorber is less efficient than the nonselective surface absorber for the assumption of perfect heat transfer between absorber and fluid. Thus we conclude that in practical high-flux applications, the superiority of volumetric absorbers stems from the enhanced heat transfer area. If the fluid flows against the direction of radiation propagation the volumetric absorber is slightly more efficient than if it flows with this direction. We also discuss the effect of the two-flux approximation on simulation of isotropic volumetric absorbers.

Published
1997

8. A HIGHLY EFFICIENT LOW-PRESSURE UV-RICH DETECTOR WITH OPTICAL AVALANCHE RECORDING

Author

BRESKIN, A., primary, CHECHIK, R., additional, FRAENKEL, Z., additional, SAUVAGE, D., additional, STEINER, V., additional, TSERRUYA, I., additional, CHARPAK, G., additional, DOMINIK, W., additional, FABRE, J. P., additional, GAUDAEN, J., additional, SAULI, F., additional, SUZUKI, M., additional, FISCHER, P., additional, GLÄSSEL, P., additional, RIES, H., additional, SCHÖN, A., additional, and SPECHT, H. J., additional

Published
1995
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9. Exploring the experiences of siblings of adults with intellectual/developmental disabilities during the COVID‐19 pandemic.

Author

Redquest, B. K., Tint, A., Ries, H., and Lunsky, Y.

Subjects
SIBLINGS, DEVELOPMENTAL disabilities, EXPERIENCE, HEALTH, PEOPLE with intellectual disabilities, PSYCHOSOCIAL factors, SOCIAL support, WELL-being, COVID-19 pandemic
Abstract

Background: The COVID‐19 pandemic has caused many adults with intellectual/developmental disabilities (IDD) to lose their daily routines and social support, and as a result, many adults with IDD are increasingly reliant on their family caregivers. Siblings often play a crucial support role for their brothers and sisters with IDD. As such, this study aimed to describe the experiences of adult siblings of people with IDD during the COVID‐19 pandemic. Methods: The Sibling Collaborative worked with researchers to codesign an online survey, completed by 91 people, exploring sibling supports and concerns during the COVID‐19 pandemic. The survey also aimed to identify helpful resources for siblings during this time. Results: The results showed that the majority of siblings are supporting their brother or sister with IDD during the COVID‐19 pandemic and are concerned about the health and well‐being of their brother/sister. The most common concern related to disruption of their brother's or sister's routine and activities. Although responses of older and younger siblings did not differ from each other, siblings whose brother or sister with IDD lived with family had some unique concerns relative to those whose siblings no longer lived with family. Siblings described how their own self‐care and relationships with others, as well as support for their brother/sister, were particularly helpful during the COVID‐19 pandemic. Conclusions: Siblings are providing key support to their brother or sister with IDD during the COVID‐19 pandemic, and they too must be supported. Siblings should be included in efforts to disseminate resources targeting people with IDD and their feedback and input must be obtained. It is also important to include sibling mental wellness as caregiver supports are created and implemented. More research is needed to further understand how to support sibling caregivers. [ABSTRACT FROM AUTHOR]

Published
2021
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11. Nonisothermal receivers

Author

Ries, H., Kribus, A., and Karni, J.

Subjects
Solar collectors -- Design and construction, Solar energy storage -- Equipment and supplies, Solar heating -- Equipment and supplies, Engineering and manufacturing industries, Environmental issues
Abstract

The reradiation losses, inherent to every thermal receiver, can be significantly reduced by exposing the working fluid to monotonously increasing irradiance and preventing energy exchange between parts of the receiver that are at different temperatures. In this way the highest temperatures are reached only near the end of the working fluid's path. The improvement is much more pronounced for nonuniform as compared to uniform irradiance. For a Gaussian distribution of irradiance we calculate improvements exceeding a factor of two for the efficiency at a given temperature (0.8 of the peak stagnation temperature), and for the temperature at a given efficiency of 0.8. These results are independent of the peak irradiance and of the width of the distribution. Even a coarse partitioning into two mutually isothermal parts can already produce a significant improvement over the totally isothermal receiver.

Published
1995

16. Solar thermophotovoltaics: An assessment.

Author

Spirkl, W. and Ries, H.

Subjects
*PHOTOVOLTAIC cells, *SOLAR cells, *PHOTONS, *RADIATION
Abstract

Discusses a model of a solar thermophotovoltaic (STPV) device both for improving the efficiency of one-band-gap photovoltaic cells by matching the photon energy to the band gap and for concentrating diffuse radiation. Definition of thermophotovoltaic; Investigation of a general SPTV system with ideal components; Characteristics of a one-band-gap photovoltaic cell.

Published
1985
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19. The transverse energy distribution in16O-nucleus collisions at 60 and 200 GeV per nucleon

Author

Åkesson, T., Almehed, S., Angelis, A. L. S., Armenise, N., Atherton, H., Aubry, P., Bartels, H. W., Bartley, J. H., Beaudoin, G., Beaulieu, J. M., Beker, H., Benary, O., Bettoni, D., Bisi, V., Blevis, I., Bøggild, H., Breskin, A., Chechik, R., Cleland, W., Clemen, M., Collick, B., Corriveau, F., Dagan, S., Dederichs, K., Dell'Uomo, S., Depommier, P., Devenish, R. C. E., Di Liberto, S., Di Giacomo, N., Dodd, J. R., Dolgoshein, B., Dress, A., En'yo, H., Erlandsson, B., Esten, M. J., Fabjan, C. W., Faessler, M., Fischer, P., Fraenkel, Z., Gaidot, A., Gavrilenko, I., Gibrat-Debu, F., Giubellino, P., Glässel, P., Goerlach, U., Haglund, R., Hamel, L. A., van Hecke, H., Hedberg, V., Heifetz, R., Heymann, F. F., Hölscher, A., Huber, S., Jacak, B., Jarslkog, G., Johansson, S., Kalinovski, A., Kantserov, A., Kraner, H., Kroh, V., Lamarche, F., Leroy, C., Lissauer, D., London, G., Lörstad, B., Lounis, A., Ludlam, T., Marzari-Chiesa, A., Masera, M., Mayburov, S., Mazzoni, M. A., McCubbin, M. L., McCubbin, N. A., McGaughey, P., Meddi, F., Mjörnmark, U., Muciaccia, M. T., Murray, M., Neubert, M., Nevski, P., Nilsson, S., Olsen, L., Oren, Y., Pansart, J. P., Park, Y. M., Pfeiffer, A., Piuz, F., Polychronakos, V., Poulard, G., Price, M., Rahm, D., Ramello, L., Riccati, L., Ries, H., Romano, G., Roosen, R., Rosa, G., Russ, J., Schukraft, J., Sekimoto, M., Sellden, B., Seman, M., Shmeleva, A., Shotton, P., Sidorov, V., Simone, S., Sirois, Y., Sletten, H., Smirnov, S., Soltani, J., Sondheim, W., Specht, H. J., Stumer, I., Sumarokov, A., Sunier, J., Tcherniatin, V., Thodberg, H. H., Thompson, J., Tikhomirov, V., Trent, P. T., Tserruya, I., Wigmans, R., Willis, W., and HELIOS Collaboration

Published
1988
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20. Transverse energy distributions in16O-nucleus collisions

Author

Corriveau, F., Åkesson, T., Almehed, S., Angelis, A. L. S., Armenise, N., Atherton, H., Aubry, P., Bartels, H. W., Bartley, J. H., Beaudoin, G., Beaulieu, J. M., Beker, H., Benary, O., Bettoni, D., Bisi, V., Blevis, I., Bøggild, H., Breskin, A., Chechik, R., Cleland, W., Clemen, M., Collick, B., Dagan, S., Dederichs, K., Dell'Uomo, S., Depommier, P., Devenish, R. C. E., DiLiberto, S., DiGiacomo, N., Dodd, J. R., Dolgoshein, B., Dress, A., En'yo, H., Erlandsson, B., Esten, M. J., Fabjan, C. W., Faessler, M., Fischer, P., Fraenkel, Z., Gaidot, A., Gavrilenko, I., Gibrat-Debu, F., Giubellino, P., Glässel, P., Goerlach, U., Haglund, R., Hamel, L. A., van Hecke, H., Hedberg, V., Heifetz, R., Heymann, F. F., Hölscher, A., Huber, S., Jacak, B., Jarlskog, G., Johansson, S., Kalinovski, A., Kantserov, A., Kramer, H., Kroh, V., Lamarche, F., Leroy, C., Lissauer, D., London, G., Lörstad, B., Lounis, A., Ludlam, T., Marzari-Chiesa, A., Masera, M., Mayburov, S., Mazzoni, M. A., McCubbin, M. L., McCubbin, N. A., McGaughey, P., Meddi, F., Mjörnmark, U., Muciaccia, M. T., Murray, M., Neubert, M., Nevski, P., Nilsson, S., Olsen, L., Oren, Y., Pansart, J. P., Park, Y. M., Pfeiffer, A., Piuz, F., Polychronakos, V., Poulard, G., Price, M., Rahm, D., Ramello, L., Riccati, L., Ries, H., Romano, G., Roosen, R., Rosa, G., Russ, J., Schukraft, J., Sekimoto, M., Sellden, B., Seman, M., Shmeleva, A., Shotton, P., Sidorov, V., Simone, S., Sirois, Y., Sletten, H., Smirnov, S., Soltani, J., Sondheim, W., Specht, H. J., Stumer, I., Sumarokov, A., Sunier, J., Tcherniatin, V., Thodberg, H. H., Thompson, J., Tikhomirov, V., Trent, P. T., Tserruya, I., Wigmans, R., Willis, W., and HELIOS Collaboration

Published
1988
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24. Luminescence and efficiency of an ideal photovoltaic cell with charge carrier multiplication

Author

Ries H and Spirkl W

Subjects
Multiple exciton generation, Physics, Impact ionization, Work (thermodynamics), Solar cell efficiency, business.industry, Band gap, Thermodynamic efficiency limit, Optoelectronics, Multiplication, Charge carrier, business
Abstract

We discuss the potential of an ideal photovoltaic cell with charge carrier multiplication by impact ionization. Thermodynamics requires that carrier multiplication modifies luminescence as well. Such a cell may be described as a hot-carrier cell where interband equilibrium is inhibited and where thermalization is restricted to the band edges. We show that in the limit of low band-gap energy this cell is equivalent to a thermal absorber coupled to a Carnot engine. In conjunction with a spectral filter, a finite band-gap cell with carrier multiplication can even surpass the work obtainable from a selective thermal absorber. In principle, charge carrier multiplication can be tailored such that a single-gap cell matches a fully selective conversion device. A high-efficiency, thin-film cell with carrier multiplication may be thought of as a single-band-gap cell on the basis of a low-band-gap material, with efficiency close to the value of a fully selective device. Low absorptivity for photons below the threshold for carrier multiplication might be realized with an indirect transition. When the solar irradiance exceeds a certain threshold all photons above gap energy may be used.

Published
1995
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25. Impact of surface parameter uncertainties on the development of a trough in the Fram Strait region

Author

Ries, H., Schluenzen, K., Bruemmer, B., Claussen, M., https://orcid.org/0000-0001-6225-5488, and Mueller, G.

Subjects
Atmospheric Science, Oceanography
Abstract

The impacts of the sea-ice characteristics distribution, roughness, temperature and thermal conductivity on an on-ice moving trough in the Fram Strait on 7 March 2002 are investigated. The situation is simulated with the mesoscale transport and fluid model METRAS and the named characteristics are varied within the range of observational uncertainty. The test cases are evaluated against aircraft measurements performed within the 'Fram Strait Cyclone Experiment 2002'. The model's sensitivity on the changes in sea-ice characteristics is quantified by statistical means. The strongest impacts on the near-ground temperature are found from sea-ice temperature, manifesting as an overall bias, and the positioning of the sea-ice edge, manifesting as a phase error. Only higher than natural homogenization of the sea-ice cover leads to some reduction of the amplitude error. A reduction of the sea-ice surface roughness is performed by applying an unrealistically small roughness length of ! z(0) = 1 mm. This reduces the negative wind speed bias, enhances the advection of contrasting air masses and improves the frontal sharpness. The thermal conductivity has the smallest influence. The lateral forcing taken from 'European Centre for Medium-Range Weather Forecasts' (ECMWF) reanalyses shows the strongest effect on the limited area model performance.

Published
2010

27. Strong-wind events and their influence on the formation of snow dunes: observations from Kohnen station, Dronning Maud Land, Antarctica

Author

Birnbaum, G., Freitag, J., Brauner, R., König-Langlo, G., Schulz, E., kipfstuhl, J., Oerter, H., Reijmer, C.H., Schlosser, E., Faria, S.H., Ries, H., Loose, B., Herber, A., Duda, M. G., Powers, J. G., Manning, K. W., van den Broeke, M.R., Marine and Atmospheric Research, Dep Natuurkunde, and Sub Dynamics Meteorology

Abstract

Analyses of shallow cores obtained at the European Project for Ice Coring in Antarctica (EPICA) drilling site Kohnen station (758000 S, 008040 E; 2892ma.s.l.) on the plateau of Dronning Maud Land reveal the presence of conserved snow dunes in the firn. In situ observations during three dune formation events in the 2005/06 austral summer at Kohnen station show that these periods were characterized by a phase of 2 or 3 days with snowdrift prior to dune formation which only occurred during high wind speeds of >10ms–1 at 2m height caused by the influence of a low-pressure system. The dune surface coverage after a formation event varied between 5% and 15%, with a typical dune size of (4 2)m (8 3) m, a maximum height of 0.2 0.1m and a periodicity length of about 30 m. The mean density within a snow dune varied between 380 and 500 kgm–3, whereas the mean density at the surrounding surface was 330 5kgm–3. The firn cores covering a time-span of 22 2 years reveal that approximately three to eight events per year occurred, during which snow dunes had been formed and were preserved in the firn.

Published
2010

28. Irradiation programme HFR phase IIb - SPICE. Impact testing on up to 16.3 dpa irradiated RAFM steels. Final report for task TW2-TTMS 001b-D05

Author

Gaganidze, E., Dafferner, B., Ries, H., Rolli, R., Schneider, H. C., and Aktaa, J.

Subjects
ddc:620, Engineering & allied operations
Abstract

Bestrahlungsprogramm HFR Phase IIb – SPICE: Kerbschlagbiegeuntersuchungen an bis 16.3 dpa bestrahlten RAFM Stählen Die Untersuchung des bestrahlungsinduzierten Versprödungsverhaltens von niedrigaktivierbaren ferritisch-martensitischen (RAFM) Stählen bildet das Ziel der vorliegenden Arbeit. Die Neutronenbestrahlung bei verschiedenen Bestrahlungstemperaturen (250-450 °C) bis zu einer Schädigung von 16,3 dpa (nominell) wurde im Hoch Fluss Reaktor („High Flux Reactor“) Petten im Rahmen des HFR Phase IIb (SPICE) Bestrahlungsprogramms durchgeführt. Die Kerbschlageigenschaften wurden an miniaturisierten Charpy-V Proben (des KLST Typs) mittels der instrumentierten Kerbschlagbiegeversuche ermittelt. Der Hauptschwerpunkt des Bestrahlungsprogramms liegt in der Untersuchung des Einflusses der Neutronenbestrahlung auf die mechanischen Eigenschaften von einem europäischen RAFM Referenzstahl für die Erste Wand des Demonstrationsreaktors (DEMO), EUROFER97, bei zwei verschiedenen Wärmebehandlungen. Die mechanischen Eigenschaften von EUROFER97 wurden mit denen von internationalen Referenzmaterialien (F82H-mod, OPTIFER-Ia, GA3X und MANET-I), welche im SPICE Projekt untersucht wurden, verglichen. Die Bestrahlungsresistenz von bis 16,3 dpa bei 250-450 °C bestrahltem EUROFER97 ist vergleichbar mit der von besten Referenz-Strukturmaterialien. Es wurde für alle untersuchten RAFM Stähle eine erhebliche Tieftemperaturversprödung (Tirr ≤ 300 °C) beobachtet. Die Wärmebehandlung von EUROFER97 bei höherer Austenisierungstemperatur führt zur wesentlichen Verbesserung des Versprödungsverhaltens bei niedrigen Bestrahlungstemperaturen (Tirr ≤ 350 °C). Bei Tirr ≥ 350 °C liegen die Sprödbruchübergangstemperaturen (DBTT) von untersuchten niedrigaktivierbaren Stählen unterhalb von -20 °C und damit weit unterhalb der Anwendungstemperatur. Die Analyse des Verfestigungs- vs. Versprödungs- Verhaltens deutet auf die verfestigungsdominierte Versprödung unterhalb von Tirr ≤ 350 °C mit 0,17≤ C100 ≤ 0,53 °C/MPa. Oxiddispersionsgehärteter ODS EUROFER Stahl mit 0,5 wt.% Y2O3 wurde bei ausgewählten Temperaturen bestrahlt. Bereits im unbestrahlten Zustand zeigte ODS EUROFER keine be- friedigende Kerbschlagbiegeeigenschaften, gekennzeichnet durch eine niedrige USE = 2,54 J und durch eine große DBTT = 135 °C. Die Zunahme von USE für Bestrahlungstemperaturen unterhalb von Tirr ≤ 350°C deutet außerdem auf ein nicht optimiertes Herstellungsverfahren. Bei Tirr = 250 °C ist die bestrahlungsinduzierte Verschiebung der Übergangstemperatur vergleichbar mit der vom EUROFER97. Bei höheren Bestrahlungstemperaturen zeigt hingegen ODS EUROFER größere Versprödung im Vergleich zum Referenzmetall. Die Rolle des Heliums in der Materialversprödung wurde an EUROFER97 basierten Stählen untersucht, welche mit verschiedenem Bor Gehalt (0,008-0,112 wt.%) dotiert wurden. Bor dotierte Proben zeigen zunehmende Versprödung und Abnahme der Zähigkeit mit der Zunahme des generierten Helium Gehalts. Bis zu einem Helium Gehalt von 84 appm ist bei Tirr = 250 °C Helium induzierte Versprödung auf Helium induzierte Verfestigung zurückzuführen. Höhere Helium Konzentrationen führten zu weiteren Versprödungsmechanismen zusätzlich zur Helium induzierten Verfestigung.

Published
2008
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30. Active Terahertz Imaging for Security

Author

Hübers, Heinz-Wilhelm, Ewert, Uwe, Hansen, K.P., Ritchie, D., Merkel, H., Nuscheler, F., Döngi, F., Ries, H., Tredicucci, A., Koch, M., Bradshaw, J., Tropper, A., Langer, M., and Sieber, A.

Subjects
THz rays, security research, security at airports, terahertz imaging, detecting threats, chemicals, pathogens, explosives
Published
2006

32. Off-axis extra lines in powder pattern electron paramagnetic resonance of Cr3+ in YAlO3.

Author

Rakhimov, R.R., Wilkerson, A.L., Loutts, G. B., and Ries, H. R.

Subjects
ELECTRON paramagnetic resonance, CHROMIUM ions
Abstract

Focuses on off-axis extra lines contained in powder sample electron paramagnetic resonance (EPR) spectrum of Cr3+ ions in YAlO3 crystals. Orientation dependence of the EPR spectrum; Transition between the central Kramers doublet in the powder system; Angular variations of the EPR spectra.

Published
1997
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35. Strong-wind events and their influence on the formation of snow dunes: observations from Kohnen station, Dronning Maud Land, Antarctica

Author

Marine and Atmospheric Research, Dep Natuurkunde, Sub Dynamics Meteorology, Birnbaum, G., Freitag, J., Brauner, R., König-Langlo, G., Schulz, E., kipfstuhl, J., Oerter, H., Reijmer, C.H., Schlosser, E., Faria, S.H., Ries, H., Loose, B., Herber, A., Duda, M. G., Powers, J. G., Manning, K. W., van den Broeke, M.R., Marine and Atmospheric Research, Dep Natuurkunde, Sub Dynamics Meteorology, Birnbaum, G., Freitag, J., Brauner, R., König-Langlo, G., Schulz, E., kipfstuhl, J., Oerter, H., Reijmer, C.H., Schlosser, E., Faria, S.H., Ries, H., Loose, B., Herber, A., Duda, M. G., Powers, J. G., Manning, K. W., and van den Broeke, M.R.

Published
2010

36. Strong-wind events and their influence on the formation of snow dunes: Observations from Kohnen Station, Dronning Maud Land, Antarctica

Author

Birnbaum, Gerit, Freitag, Johannes, Brauner, Ralf, König-Langlo, Gert, Schulz, E., Kipfstuhl, Sepp, Oerter, Hans, Reijmer, C. H., Schlosser, E., Faria, S. H., Ries, H., Loose, Bernd, Herber, Andreas, Duda, M. G., Powers, J. G., Manning, K. W., Van den Broeke, M. R., Birnbaum, Gerit, Freitag, Johannes, Brauner, Ralf, König-Langlo, Gert, Schulz, E., Kipfstuhl, Sepp, Oerter, Hans, Reijmer, C. H., Schlosser, E., Faria, S. H., Ries, H., Loose, Bernd, Herber, Andreas, Duda, M. G., Powers, J. G., Manning, K. W., and Van den Broeke, M. R.

Published
2010

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