Publikationen

For two-phase geothermal sources, Organic Rankine Cycle (ORC) based binary plant is often applied for power production. In this work, a network topology is designed with the open-source Thermal Engineering Systems in Python (TESPy) software to simulate the stationary operation of the ORC plant. With this topology, the performance of six different working fluids are compared. From the thermodynamic perspective, the gross and net power output are optimized respectively. Results show that R600 has the highest gross power output of 17.55 MW, while R245fa has the highest net power output of 12.93 MW. However, the turbine inlet temperatures for these two working fluids need to be designed at the upper theoretical limit. R245ca and R601a require the heat exchange rates of internal heat exchanger to be larger than 1.51 MW and 0.99 MW to satisfy the re-injection temperature limit, which are smaller than the R600 (6.7 MW) and R245fa (6.0 MW) cases. Besides, the working fluid with lower critical state is preferred for a geothermal source with smaller steam fraction to establish a stable ORC plant. The workflow for the ORC design and optimization in this work is generic, and can be further applied to thermo-economic investigation.

Psychoeducation is generally recommended in the treatment of adult Attention-Deficit/Hyperactivity Disorder (ADHD), but only few studies have systematically assessed the effects of structured clinical psychoeducation. Moreover, although a considerable number of psychoeducational mobile applications exist, none have provided scientific evidence for their effectiveness or safety. Therefore, the present randomized controlled trial investigated a newly developed, free-to-use psychoeducation app for adults with ADHD as a support to a clinical psychoeducation group. 236 adults with ADHD were contacted for study participation, of whom 60 were finally randomized to a psychoeducation group supported either by our developed smartphone app (n = 30) or by traditional pen-and-paper brochures (n = 30). Psychoeducation treatments were conducted in groups of 10, with 8 weekly one-hour sessions between March 2019 and November 2020. Observer-rated ADHD symptom severity (IDA-R interview) was examined as the primary outcome parameter before and after treatment. Across both interventions, ADHD core symptoms were significantly reduced. Notably, the smartphone-assisted psychoeducation was significantly more effective in improving inattention and impulsivity and led to higher homework compliance than the brochure-assisted psychoeducation. No adverse events were reported.

The Measurement Lab (MLab) provides a large and open collection of Internet performance measurements. We make use of it to look at the state of the German Internet by a structured analysis, in which we carve out expressive results from the dataset to identify busy hours and days, the impact of server locations and congestion control protocols, and compare Internet service providers. Moreover, we examine the impact of the COVID-19 lockdown in Germany. We observe that only parts of the Internet show a performance degradation at the beginning of the lockdown and that a large impact in performance depends on the network the servers are located in. Furthermore, the evolution of congestion control algorithms is reflected by performance improvements. For our analysis, we focus on the busy hours. From the end-user perspective, this time is of most interest to identify if the network can support challenging services such as video streaming or cloud gaming at these intervals.

Exergy-based methods support the identification of thermodynamic inefficiencies and the discovery of optimization potentials in thermal engineering applications. Although a large variety of simulation software is available in this field, most do not offer an integrated solution for exergy analysis. While there are commercial products on the market with such capabilities, their access for research and educational purposes is limited. The presented open-source software offers an integrated and fully automated exergy analysis tool for thermal conversion processes. In a first step, physical exergy is implemented, and the tool is then applied to three different example plants to highlight its capabilities and validate the implementation: A solar thermal power plant, a supercritical CO2 power cycle, and an air refrigeration cycle. The respective models and the results of the analyses are presented briefly. By providing the results in modern data structures, they are easily accessible and postprocessible. Future work will include chemical exergy to enable analyses of applications with conversion of matter. Additionally, the implementation of the exergoeconomic analysis and optimization is envisaged.

Although Einstein’s general theory of relativity precisely describes the properties of gravity, it is not clear why gravity is so much weaker than the other fundamental forces of nature. The weakness of gravity could be explained, however, by speculative theories that predict spatial dimensions in addition to the three dimensions we experience in our everyday live. One spectacular way of revealing these extra dimensions would be through the formation of microscopic black holes, which, if there are extra dimensions, might be produced at the Large Hadron Collider. Microscopic black holes would be harmless, but their discovery would revolutionize our physical world picture.