301 research outputs found
Experimental study on the energy deposition of an ns-DBD plasma actuator and its effect on a laminar boundary layer
No full textAn experimental study aimed at the influence of different barrier materials on the energy deposition of nanosecond pulsed dielectric barrier discharge (ns-DBD) plasma actuator was carried out. Additionally, the direct effect of the discharge of an ns-DBD plasma actuator on a low velocity laminar boundary layer was investigated. Three barrier materials were selected for this study. These were Kapton polyimide tape, silicone-rubber and fine polyamide PA2200. Schlieren imagery in quiescent conditions were conducted to visualize the effect of the thermal energy deposition. Particle Image Velocimitry (PIV) was used to obtain the induced velocity fields by a flush mounted ns-DBD plasma actuator with a two layer Kapton barrier in a laminar boundary layer. A backward-time backward-space finite difference discretization of the compressible continuity equation was proposed to quantify the density field disturbance by ns-DBD plasma actuator. Results of the barrier characterization study indicated that a thinner barrier of the same material will allow more thermal energy to be deposited to the air per discharge pulse. A comparison between disturbed density field area and electrical energy usage per pulse, showed that an ns-DBD plasma actuator with a Kapton barrier is the most efficient tested barrier for coupling electrical energy as thermal energy to the near wall volume of air. Additionally, both the structure of the density disturbance in the quiescent air and the plasma discharge structure itself (Figure 1) are strongly dependent on the barrier material. Results of the PIV tests on the effect of discharge by ns-DBD plasma actuator in a laminar boundary layer indicated the presence of small body force. This body force was directed from the grounded exposed electrode to the high voltage covered electrode. Moreover, this body force induced a vortex like disturbance in the boundary layer. Additionally, independent of the streamwise orientation of the ns-DBD plasma actuator electrodes, an increase in energy input results in a local decrease in density. A larger area of density field disturbance was observed for the results were the body force was directed opposite to the freestream flow. It can be concluded that a barrier used in an ns-DBD plasma actuator should have a low thickness, high electrical volume resistivity, low thermal capacitance and low heat capacity in order to efficiently deposit heat to the nearby air. Additionally, based on the density field disturbances in laminar boundary layer flow, the orientation of the ns-DBD plasma actuator (thus the direction of the body force) is able to enhance the impact of the thermal energy deposition through better distribution through the boundary layer.AerodynamicsAerodynamics and Wind energyAerospace Engineerin
Colloquium: Water's controversial glass transitions
No full textWater is the most common and, judged from its numerous anomalous properties, the weirdest of all known liquids and the complexity of its pressure-temperature map is unsurpassed. A major obstacle on the way to a full understanding of water's structure and dynamics is the hard-to-explore territory within this map, colloquially named the no man's land. Many experiments suggest that just before stepping across its low-temperature border, amorphous ices undergo glass-to-liquid transitions while other interpretations emphasize the importance of underlying disordered (nano) crystalline states. Prospects for reconciling the conflicting views regarding the nature of water's glass transitions are discussed
Ultra-slow dynamics in low density amorphous ice revealed by deuteron NMR: indication of a glass transition
No full textThe postulated glass-liquid transition of low density amorphous ice (LDA) is investigated with deuteron NMR stimulated echo experiments. Such experiments give access to ultra-slow reorientations of water molecules on time scales expected for structural relaxation of glass formers close to the glass-liquid transition temperature. An involved data analysis is necessary to account for signal contributions originating from a gradual crystallization to cubic ice. Even if some ambiguities remain, our findings support the view that pressure amorphized LDA ices are of glassy nature and undergo a glass-liquid transition before crystallization
Limits of metastability in amorphous ices: <sup>2</sup>H-NMR relaxation
No full textThe high-frequency reorientation dynamics of O-H-2 bonds is investigated in various amorphous ices including eHDA (expanded high density amorphous ice), LDA-II (low density amorphous ice II) and HGW (hyperquenched glassy water) using H-2-NMR spin-lattice relaxation as a local probe. Both low density forms, HGW and LDA-II, show similar spin-lattice relaxation but differ in the thermal stability with respect to the transition into crystalline cubic ice I-c. HGW already transforms slightly above 135 K whereas LDA-II crystallizes at 150 K. eHDA is distinguishable from other high density amorphous ices in its thermal stability and spin-lattice relaxation. Its relaxation times are much larger compared to those of VHDA (very high density amorphous ice) and uHDA (unrelaxed high density amorphous ice). eHDA does not show annealing effects, transforms sharply into LDA-II above 123 K and provides higher thermal stability as compared to other high density forms.Austrian Science Fund [T463, Y391]; European Research Counci
The timing of mediation: commitment problems in civil wars
No full textThe peaceful settlement of civil wars represents a key challenge for the international community and its policymakers. Even though mediation has become the most common tool of conflict management to settle these conflicts, so far we know relatively little about how to best manage them. This thesis examines mediation in civil wars and by building on the bargaining model of war the author argues that mediators have to concentrate primarily on the resolution of commitments problems in order to establish robust peace agreements. This paper uses an edited version of the Civil War Mediation (CWM) dataset, which comprises 366 mediation events in the time period of 1946 to 2004. By employing logistic regression analyses, the author finds that the later the intermediary enters a conflict, the lower the development and democracy level of the respective state, and the more intense a conflict is, the higher is the probability of a successful mediation outcome. The results also suggest that international and regional organizations are better equipped than other mediators to resolve commitment problems.M.A.Includes bibliographical referencesby Christian Winke
Changes in self-reported and parent-reported health-related quality of life in overweight children and adolescents participating in an outpatient training: findings from a 12-month follow-up study
No full textFinne E, Reinehr T, Schaefer A, Winkel K, Kolip P. Changes in self-reported and parent-reported health-related quality of life in overweight children and adolescents participating in an outpatient training: findings from a 12-month follow-up study. Health and Quality of Life Outcomes. 2013;11(1): 1.Background
Health-related quality of life (HRQoL) was found to improve in participants of weight management interventions. However, information on moderately overweight youth as well as on maintaining HRQoL improvements following treatment is sparse. We studied the HRQoL of 74 overweight, but not obese participants (32.4% male, mean age = 11.61 ± 1.70 SD) of a comprehensive and effective six-month outpatient training at four time-points up to 12 months after end of treatment.
Methods
HRQoL was measured by self-report and proxy-report versions of the generic German KINDL-R, including six sub domains, and an obesity-specific additional module. Changes in original and z-standardized scores were analyzed by (2×4) doubly multivariate analysis of variance. This was done separately for self- and proxy-reported HRQoL, taking into account further socio-demographic background variables and social desirability. Additionally, correlations between changes in HRQoL scores and changes in zBMI were examined.
Results
There were significant multivariate time effects for self-reported and proxy-reported HRQoL and a significant time-gender interaction in self-reports revealed (p < .05). Improvements in weight-specific HRQoL were evident during treatment (partial η2 = 0.14-0.19). Generic HRQoL further increased after end of treatment. The largest effects were found on the dimension self-esteem (partial η2 = 0.08-0.09 for proxy- and self-reported z-scores, respectively). Correlations with changes in weight were gender-specific, and weight reduction was only associated with HRQoL improvements in girls.
Conclusions
Positive effects of outpatient training on generic and weight-specific HRQoL of moderately overweight (not obese) children and adolescents could be demonstrated. Improvements in HRQoL were not consistently bound to weight reduction. While changes in weight-specific HRQoL were more immediate, generic HRQoL further increased after treatment ended. An extended follow-up may therefore be needed to scrutinize HRQoL improvements due to weight management
Monte Carlo simulations for dosimetry and treatment planning in hadron therapy
No full textUm in der Strahlentherapie von der im Vergleich zu Photonen erhöhten Dosiskonformität mit Protonen und Schwerionen profitieren zu können, müssen die Dosimetrie und die Bestrahlungsplanung verbessert werden. Dosisverteilungen werden klinisch mit Näherungsalgorithmen berechnet. Monte Carlo (MC) Methoden ermöglichen jedoch eine viel genauere Berechnung von Dosis und Reichweite. In dieser Arbeit wird das MC Programm SHIELD-HIT verwendet um die Genauigkeit des Näherungsverfahrens zu untersuchen und Skalierungsmethoden zu entwickeln. Weiterhin wird das Ionisierungspotential für Wasser neu bestimmt, was die Berechnung von Reichweiten erheblich verbessert. Es wird erstmalig das Verhältnis der Massenbremsvermögen Wasser/Luft für Ionen mit MC bestimmt, welches Dosismessungen erheblich verbessert. SHIELD-HIT wird an experimentelle Winkel- und Tiefenverteilungen sowie Ladungsmessungen angepasst, was die Berechnung von biologischer und physikalischer Dosis verbessert. Als eine direkt klinisch relevante Anwendung, wurde die Neutronenbelastung, des Patienten bei Kohlenstoffbestrahlung untersucht.von Katrin Henkne
Werk aan de winkel: Case study Delft
No full textDe case studies in het kader van het onderzoek "Werk aan de Winkel" zijn bedoeld als locale illustratie bij mogelijke toekomstscenario's. Het gaat daarbij om de vraag, welke verschillende situaties in een gemeente denkbaar zijn bij de twee groeiscenario's en de verschillende consumententypen, zoals die in het hoofd rapport zijn genoemd. Na een beschrijving van het winkelareaal, zijn op basis van een indeling van het winkelareaal in 1995 , en uitgaande van een totaal benodigd winkelareaal in een gemeente in het jaar 2015, verschillende mogelijke verdelingen van het areaal over typen winkelcentra opgesteld, en vervolgens vergeleken met de thans bekende plannen van de gemeente. Daaruit kunnen enkele voorlopige conclusies worden getrokken. Het case study-rapport bevat ook een aantal algemene opmerkingen over uitbreidingen en aanpassingen van winkelcentra, en (on)mogelijkheden om gewenste veranderingen (zoals uitbreidingen en aanpassingen) in winkelcentra door te voeren, alsmede een korte bespreking van belangen en intenties van partijen.Architectur
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sj-pdf-1-jbr-10.1177_07487304221107833 – Supplemental material for Examining the Efficacy of Bright Light Therapy on Cognitive Function in Hematopoietic Stem Cell Transplant Survivors
No full textSupplemental material, sj-pdf-1-jbr-10.1177_07487304221107833 for Examining the Efficacy of Bright Light Therapy on Cognitive Function in Hematopoietic Stem Cell Transplant Survivors by Lisa M. Wu, Heiddis B. Valdimarsdottir, Ali Amidi, Kathryn J. Reid, Sonia Ancoli-Israel, Katrin Bovbjerg, Rina S. Fox, Lauren Walker, Amreen Matharu, Erin T. Kaseda, John P. Galvin, Kehinde Adekola, Gary Winkel, Frank Penedo and William H. Redd in Journal of Biological Rhythms</p
Moist Rayleigh-Benard Convection
No full textWe report the observations from turbulent thermal Rayleigh-Benard convection experiment with a two-phase liquid-vapor binary mixture. Evaporation/condensation processes in a turbulent convection are accompanied by the formation of cloud like structures above the liquid-vapor interface. We also found that a liquid film condensation on the underside of the top plate results in regular hexagonal patterns of falling droplets
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