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Wärme‐ und Kältespeicher von Gebäuden beruhen auf verschiedenen Konzepten der Wärmeübertragung. Bei thermischen Hybridspeichern befindet sich das Phasen-wechselmaterial (PCM) makroverkapselt in PCM‐Objekten, die im Speicherbehälter positioniert sind und vom Wärmeträgerfluid umströmt werden. Die experimentellen Untersuchungen widmen sich den Belade‐ und Entladeeigenschaften des in Kugeln makroverkapselten PCM. Es wird gezeigt, dass die spezifische Wärmeübertragungs-leistung eines Hybridspeichers unmittelbar von der Größe der Kugeln als auch von der spezifischen Wärmeleitfähigkeit des PCM abhängt.
We consider a risk model in discrete time with dividends and capital injections. The goal is to maximise the value of a dividend strategy. We show that the optimal strategy is of barrier type. That is, all capital above a certain threshold is paid as dividend. A second problem adds tax to the dividends but an injection leads to an exemption from tax. We show that the value function fulfils a Bellman equation. As a special case, we consider the case of premia of size one. In this case we show that the optimal strategy is a two barrier strategy. That is, there is a barrier if a next dividend of size one can be paid without tax and a barrier if the next dividend of size one will be taxed. In both models, we illustrate the findings by de Finetti’s example.
Polyimides rank among the most heat-resistant polymers and find application in a variety of fields, including transportation, electronics, and membrane technology. The aim of this work is to study the structural, thermal, mechanical, and gas permeation properties of polyimide based nanocomposite membranes in flat sheet configuration. For this purpose, numerous advanced techniques such as atomic force microscopy (AFM), SEM, TEM, TGA, FT-IR, tensile strength, elongation test, and gas permeability measurements were carried out. In particular, BTDA–TDI/MDI (P84) co-polyimide was used as the matrix of the studied membranes, whereas multi-wall carbon nanotubes were employed as filler material at concentrations of up to 5 wt.% All studied films were prepared by the dry-cast process resulting in non-porous films of about 30–50 μm of thickness. An optimum filler concentration of 2 wt.% was estimated. At this concentration, both thermal and mechanical properties of the prepared membranes were improved, and the highest gas permeability values were also obtained. Finally, gas permeability experiments were carried out at 25, 50, and 100 ◦C with seven different pure gases. The results revealed that the uniform carbon nanotubes dispersion lead to enhanced gas permeation properties.
How Digital Strategy and Management Games Can Facilitate the Practice of Dynamic Decision-Making
(2020)
This paper examines how digital strategy and management games that have been initially designed for entertainment can facilitate the practice of dynamic decision-making. Based on a comparative qualitative analysis of 17 games—organized into categories derived from a conceptual model of decision-making design—this article illustrates two ways in which these games may be useful in supporting the learning of dynamic decision-making in educational practice:
(1) Players must take over the role of a decider and solve situations in which players must pursue different conflicting goals by making a continuous series of decisions on a variety of actions and measures; (2) three of the features of the games are considered to structure players’ practice of decision-making and foster processes of learning through the curation of possible decisions, the offering of lucid feedback and the modification of time. This article also highlights the games’ shortcomings, from an educational perspective, as players’ decisions are restricted by the numbers of choices they can make within the game, and certain choices are rewarded more than others. An educational application of the games must, therefore, entail a critical reflection of players’ limited choices inside a necessarily biased system.
Water security is a major concern for water-scarce cities that face dynamic water challenges due to limited water supply, climate change and increasing water demand. Framing urban water security is challenging due to the complexity and uncertainties of the definitions and assessment frameworks concerning urban water security. Several studies have assessed water security by granting priority indicators equal weight without considering or adapting to the local conditions. This study develops a new urban water security assessment framework with application to the water-scarce city
of Madaba, Jordan. The study applies the new assessment framework on the study area and measures urban water security using the integrated urban water security index (IUWSI) and the analytic hierarchy process (AHP) as a decision management tool to prioritise and distinguish indicators that affect the four dimensions of urban water security: drinking water, ecosystems, climate change and water-related hazards, and socioeconomic aspects (DECS). The integrated urban water security index (IUWSI) highlights the state of water security and intervention strategies in Madaba. The study reveals that urban water security in Madaba is satisfactory to meet basic needs, with shortcomings in some aspects of the DECS. However, Madaba faces poor security in terms of managing climate- and water-related risks. The IUWSI framework assists with a rational and evidence-based decision-making process, which is important for enhancing water resources management in water-scarce cities.
The Enhancement of standard dense phase carbon dioxide (DPCD) pasteurization by additional mechanical effects wasassessed in this work. These effects were induced during pasteurization by the sudden depressurization in a narrow mini-tube. The high flow velocities, moderate pressures (40–80 bar) and low temperatures (25–45°C) lead to intense degasifica-tion and shear stress. The inactivation of the test microorganismEscherichia coliDH5a(E. coliDH5a) was determinedbefore and after depressurization in the minitube, representing entirely chemical DPCD via dissolved CO2and total inacti-vation comprising the effects of dissolved CO2and mechanical effects, respectively. Compared to conventional DPCDpasteurization, which is mostly attributed to chemical effects, the additional mechanical effects increased the inactivationefficiency considerably.
This article explores the relationship between digital transformation and disaster risk.Vulnerability studies aim at differentiating impacts and losses by using fine-grained information fromdemographic, social, and personal characteristics of humans. With ongoing digital development,these characteristics will transform and result in new traits, which need to be identified andintegrated. Digital transformations will produce new social groups, partly human, semi-human,or non-human—some of which already exist, and some which can be foreseen by extrapolating fromrecent developments in the field of brain wearables, robotics, and software engineering. Thoughinvolved in the process of digital transformation, many researchers and practitioners in the field ofDisaster Risk Reduction or Climate Change Adaptation are not yet aware of the repercussions fordisaster and vulnerability assessments. Emerging vulnerabilities are due to a growing dependency ondigital services and tools in the case of a severe emergency or crisis. This article depicts the differentimplications for future theoretical frameworks when identifying novel semi-human groups and theirvulnerabilities to disaster risks. Findings include assumed changes within common indicators of socialvulnerability, new indicators, a typology of humans, and human interrelations with digital extensionsand two different perspectives on these groups and their dependencies with critical infrastructure.
Against the background of a worldwide decrease in the number of gauging stations,the estimation of river discharge using spaceborne data is crucial for hydrological research, rivermonitoring, and water resource management. Based on the at-many-stations hydraulic geometry(AMHG) concept, a novel approach is introduced for estimating river discharge using Sentinel-1time series within an automated workflow. By using a novel decile thresholding method, no a prioriknowledge of the AMHG function or proxy is used, as proposed in previous literature. With arelative root mean square error (RRMSE) of 19.5% for the whole period and a RRMSE of 15.8%considering only dry seasons, our method is a significant improvement relative to the optimizedAMHG method, achieving 38.5% and 34.5%, respectively. As the novel approach is embedded intoan automated workflow, it enables a global application for river discharge estimation using solelyremote sensing data. Starting with the mapping of river reaches, which have large differences inriver width overthe year, continuous river width time series are created using high-resolution andweather-independent SAR imaging. It is applied on a 28 km long section of the Mekong River nearVientiane, Laos, for the period from 2015 to 2018.
This paper presents a life cycle assessment (LCA) of photovoltaic (PV) solar modules whichhave been integrated into electric vehicle applications, also called vehicle integrated photovoltaics(VIPV). The LCA was executed by means of GaBi LCA software with Ecoinvent v2.2 as a backgrounddatabase, with a focus on the global warming potential (GWP). A light utility electric vehicle (LUV)named StreetScooter Work L, with a PV array of 930 Wp, was analyzed for the location of Cologne,Germany. An operation time of 8 years and an average shadowing factor of 30% were assumed.The functional unit of this LCA is 1 kWh of generated PV electricity on-board, for which an emissionfactor of 0.357 kg CO2-eq/kWh was calculated, whereas the average grid emissions would be 0.435 kgCO2-eq/kWh. Hence, charging by PV power hence causes lower emissions than charging an EV bythe grid. The study further shows how changes in the shadowing factor, operation time, and otheraspects affect vehicle’s emissions. The ecological benefit of charging by PV modules as compared togrid charging is negated when the shadowing factor exceeds 40% and hence exceeds emissions of0.435 kg CO2-eq/kWh. However, if the operation time of a vehicle with integrated PV is prolonged to12 years, emissions of the functional unit go down to 0.221 kg CO2-eq/kWh. It is relevant to point outthat the outcomes of the LCA study strongly depend on the location of use of the vehicle, the annualirradiation, and the carbon footprint of the grid on that location.