Experimental evaluation of a subsonic expansion tube

Subsonic expansion tube evaluation as device for studying particle drag in subsonic compressible slip flo

Wandel im Gesundheitswesen: Analyse der Auswirkungen auf Ärzte und Patienten am Beispiel der Ukraine

Background The health care sector is experiencing a drastic transition all over the world. This has an impact not only on the way hospitals, clinics, special-care homes etc. are organized, but also on patients, personnel and other stakeholders involved. The consequences of changes for both physicians and patients are investigated using a comprehensive health care reform in Ukraine as an example. Methods The analysis is based on empirical data collected from general physicians in 2 Ukrainian cities. Based on the Job Demands-Resources Model, we developed a set of hypotheses and tested them using the structural equation modelling technique. A total of 178 general physicians (81% of the approached population) participated in the study. Results Our investigation reveals a clear relationship between the organizational job demands (additional tasks, structural changes, new processes) and their psychological effects (e. g., burnout). The latter have a negative impact on cooperation of physicians in hospitals leading to lower patient satisfaction. Discussion and Conclusions Change in health care is inevitable. The example of Ukraine shows that openness of hospitals towards change reduces the probability of physicians’ burnout and, eventually, increases patient satisfaction. We strongly suggest applying the process management approach in order to increase openness to change, especially in turbulent times

Flexible transition strategies towards future well-to-wheel chains: an evolutionary modelling approach

Well to wheel (WTW) analyses mainly focus on alternative road fuel/vehicle systems that are very different from the current crude oil based individual transport system. A large share of WTW chains evaluated require changes in the energy source, new fuel production facilities, different fuel distribution systems and also modifications of the vehicles. An immediate transition to such a new system would be an unprecedented technological discontinuity. Historical examples of successful technological changes are characterized by stepwise transitions of subsystems. In this paper, we present a model that identifies likely sequences of stepwise transitions in analogy to the fitness landscape model in evolutionary biology. Applying this methodology allows for a dynamic interpretation of otherwise static WTW information. We show that sequences of transitions are path dependent, so that current decisions predetermine the future WTW system. We, therefore, argue that flexible initial transition steps that allow for different transition paths later on are favorable. Results suggest that improvements of vehicle technologies are most flexible if decision makers focus on decreasing WTW energy requirements. A full transition to diesel, as a first step, is advisable if WTW greenhouse gases should be reduced.Alternative fuels, Hydrogen, Lock-in, Fitness-landscape

A complex systems methodology to transition management

There is a general sense of urgency that major technological transitions are required for sustainable development. Such transitions are best perceived as involving multiple transition steps along a transition path. Due to the path dependent and irreversible nature of innovation in complex technologies, an initial transition step along some preferred path may cut off paths that later may turn out to be more desirable. For these reasons, initial transition steps should allow for future flexibility, where we define flexibility as robustness regarding changing evidence and changing preferences. We propose a technology assessment methodology that identifies the flexibility of initial transition steps in complex technologies. We illustrate our methodology by an empirical application to 2646 possible future car systems.NK-model, complexity, flexibility, irreversibility, path dependence, transition path, transition management, sustainable development, car technology

Equation of motion method for Full Counting Statistics: Steady state superradiance

For the multi-mode Dicke model in a transport setting that exhibits collective boson transmissions, we construct the equation of motion for the cumulant generating function. Approximating the exact system of equations at the level of cumulant generating function and system operators at lowest order, allows us to recover master equation results of the Full Counting Statistics for certain parameter regimes at very low cost of computation. The thermodynamic limit, that is not accessible with the master equation approach, can be derived analytically for different approximations.Comment: 7 pages, 3 figures, revised version, accepted by PR

Bosonic behavior of entangled fermions

Two bound, entangled fermions form a composite boson, which can be treated as an elementary boson as long as the Pauli principle does not affect the behavior of many such composite bosons. The departure of ideal bosonic behavior is quantified by the normalization ratio of multi-composite-boson states. We derive the two-fermion-states that extremize the normalization ratio for a fixed single-fermion purity P, and establish general tight bounds for this indicator. For very small purities, P<1/N^2, the upper and lower bounds converge, which allows to quantify accurately the departure from perfectly bosonic behavior, for any state of many composite bosons.Comment: 9 pages, 5 figures, accepted by PR

Advances in modelling subglacial lakes and their interaction with the Antarctic ice sheet

Subglacial lakes have long been considered hydraulically isolated water bodies underneath ice sheets. This view changed radically with the advent of repeat-pass satellite altimetry and the discovery of multiple lake discharges and water infill, associated with water transfer over distances of more than 200 km. The presence of subglacial lakes also influences ice dynamics, leading to glacier acceleration. Furthermore, subglacial melting under the Antarctic ice sheet is more widespread than previously thought, and subglacial melt rates may explain the availability for water storage in subglacial lakes and water transport. Modelling of subglacial water discharge in subglacial lakes essentially follows hydraulics of subglacial channels on a hard bed, where ice sheet surface slope is a major control on triggering subglacial lake discharge. Recent evidence also points to the development of channels in deformable sediment in West Antarctica, with significant water exchanges between till and ice. Most active lakes drain over short time scales and respond rapidly to upstream variations. Several Antarctic subglacial lakes exhibit complex interactions with the ice sheet due to water circulation. Subglacial lakes can therefore—from a modelling point of view—be seen as confined small oceans underneath an imbedded ice shelf.</jats:p

Bandwidth renormalization due to the intersite Coulomb interaction

The theory of correlated electrons is currently moving beyond the paradigmatic Hubbard $U$, towards the investigation of intersite Coulomb interactions. Recent investigations have revealed that these interactions are relevant for the quantitative description of realistic materials. Physically, intersite interactions are responsible for two rather different effects: screening and bandwidth renormalization. We use a variational principle to disentangle the roles of these two processes and study how appropriate the recently proposed Fock treatment of intersite interactions is in correlated systems. The magnitude of this effect in graphene is calculated based on cRPA values of the intersite interaction. We also observe that the most interesting charge fluctuation phenomena actually occur at elevated temperatures, substantially higher than studied in previous investigations.Comment: New appendix on benzen