Technische Hochschule Köln
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In this work, the symmetry method was first applied to the study of the problem of free convection of van der Waals gas with physical properties that differ from an ideal gas under steady-state conditions. Using the previously obtained simplified form of the equation of state for a van der Waals gas, the nature of the influence of its parameters on the process of convective heat transfer is studied in comparison with the case of using the equation of state for an ideal gas. While solving the problem, it was revealed that nonlinear parameters in the equation of state for van der Waals gas can intensify or worsen the heat transfer process. This feature is associated with the influence of the parameters of the van der Waals gas equation of state on the flow in the boundary layer. The data obtained based on the transport equations in a self-similar form are compared with the results of the previously obtained analytical solution. It is shown that the trends of the influence of the parameters of the simplified equation of state for a van der Waals gas on the Nusselt number agree well with the analytical studies.
Renewable energy (RE) penetration assessment and the development typical meteorological year (TMY) for five cities are considered together in this study. Thus, an integrated method is utilised encompassing RE status assessment and the Sandia method to generate the typical meteorological months of TMY. TMY and long-term data (LT) are then compared as well as a PV system of 3kWc output using TMY and LT under statistical errors. Until 2020 only 11.27% out of 360.02 MW capacity in power demand was RE (hydro and solar). LT and TMY are close for all the towns with a better closeness for Sokode. The latter predicts PV system performance within 2% of the LT in all the sites. More investment has to be put in RE sector because of its potential: 5.27 kWh/m2/day of mean solar radiation, 1238.21 mm of average annual precipitation and 7 m/s of mean wind speed at 50 m above the ground. ARTICLE HISTORY
The penetration of renewable energy resources (RERs) in modern power systems has a significant impact on system frequency. Battery energy storage systems (BESSs) can play a key role to regulate the frequency and improve the system stability considering the low inertia nature of inverter-based DGs. This paper proposes an optimal control strategy based on fuzzy logic control (FLC) to support the microgrid (MG) frequency. In addition to frequency regulation, this strategy includes supplementary control units to protect the battery and manage the battery state of charge (SoC). The first unit protects the battery against high C-rate permanent current which increases battery state of health (SoH) and lifetime. The second unit manages the SoC to increase the BESS availability in transient events and to avoid the negative impact of battery sudden interruption. Moreover, a dynamic objective function in time-domain simulation has been established using DIgSILENT Power Factory which ensures frequency stability improvement and smooth response simultaneously, and particle swarm optimization (PSO) algorithm is used to obtain the optimal parameters of the proposed FLC. To evaluate the stability of the system, the eigenvalue analysis has been employed and the permissible ranges of FLC parameters have been obtained, which were used as acceptable ranges in the optimization process. Finally, the simulation results verified the effectiveness of the proposed controller to regulate the frequency and to enhance the dynamic performance of the MG.
Evolutionary robotics is concerned with optimizing autonomous robots for one or more specific tasks. Remarkably, the energy needed to operate autonomously is hardly ever considered. This is quite striking because energy consumption is a crucial factor in real-world applications and ignoring this aspect can increase the reality gap. In this paper, we aim to mitigate this problem by extending our robot simulator framework with a model of a battery module and studying its effect on robot evolution. The key idea is to include energy efficiency in the definition of fitness. The robots will need to evolve to achieve high gait speed and low energy consumption. Since our system evolves the robots’ morphologies as well as their controllers, we investigate the effect of the energy extension on the morphologies and on the behavior of the evolved robots. The results show that by including the energy consumption, the evolution is not only able to achieve higher task performance (robot speed), but it reaches good performance faster. Inspecting the evolved robots and their behaviors discloses that these improvements are not only caused by better morphologies, but also by better settings of the robots’ controller parameters.
Participatory Design means recognizing that those who will be affected by a future technology should have an active say in its creation. Yet, despite continuous interest in involving people as future users and consumers into designing novel and innovative future technology, participatory approaches in technology design remain relatively underdeveloped in the German HCI community. This article brings together the diversity of voices, domains, perspectives, approaches, and methods that collectively shape Participatory Design in Germany. In the following, we (1) outline our understanding of participatory practice and how it is different from mere user involvement; (2) reflect current issues of participatory and fair technology design within the German Participatory Design community; and (3) discuss tensions relevant to the field, that we expect to arise in the future, and which we derived from our 2021 workshop through a speculative method. We contribute an introduction and an overview of current themes and a speculative outlook on future issues of Participatory Design in Germany. It is meant to inform, provoke, inspire and, ultimately, invite participation within the wider Computer Science community.
Rechte Diskursverschiebungen lassen sich seit der Jahrhundertwende europaweit auf gesellschaftspolitischer Ebene verstärkt wahrnehmen. Durch rassifizierende und menschenfeindliche Narrative wird die gesellschaftliche Spaltung durch Ausschlussmechanismen begünstigt, denen Differenzierungsmechanismen und Normalisierungsvorstellungen zugrunde liegen.
Solar thermochemical water splitting via a two-stage redox cycle has been subjected to numerous theoretical and experimental studies since a couple of decades. It has been considered as a promising technology to generate green hydrogen as it is feasible to directly convert concentrated solar radiation into storable chemical energy. The present article describes the results of an experimental campaign, which has been carried out to further demonstrate the feasibility of this technology. Based on the prior experience from solar gas turbine projects, a combined receiver/reactor has been designed and built up operating at temperatures between 1400 °C and 1000 °C using radiative power of up to 150 kW generated by a large-scale solar simulator (Synlight). The reactor has a total volume of 90 litres with open porous ceramic foam structure. Additionally, high-performance heat exchangers have been used to recover the heat content of the product gases. Typical necessary durations for the sub-cycles, reduction and oxidation as well as durations for the corresponding necessary heating and cooling phases have been determined. By producing up to 8,8g of hydrogen per cycle it could be shown that the production of hydrogen in a medium scale structured reactor is possible.
Potential analyses identify possible locations for renewable energy installations, such as wind turbines and photovoltaic arrays. The results of previous potential studies for Germany, however, are not consistent due to different assumptions, methods, and datasets being used. For example, different land-use datasets are applied in the literature to identify suitable areas for technologies requiring open land. For the first time, commonly used datasets are compared regarding the area and position of identified features to analyze their impact on potential analyses. It is shown that the use of Corine Land Cover is not recommended as it leads to potential area overestimation in a typical wind potential analyses by a factor of 4.7 and 5.2 in comparison to Basis-DLM and Open Street Map, respectively. Furthermore, we develop scenarios for onshore wind, offshore wind, and open-field photovoltaic potential estimations based on land-eligibility analyses using the land-use datasets that were proven to be best by our pre-analysis. Moreover, we calculate the rooftop photovoltaic potential using 3D building data nationwide for the first time. The potentials have a high sensitivity towards exclusion conditions, which are also currently discussed in public. For example, if restrictive exclusions are chosen for the onshore wind analysis the necessary potential for climate neutrality cannot be met. The potential capacities and possible locations are published for all administrative levels in Germany in the freely accessible database (Tool for Renewable Energy Potentials—Database), for example, to be incorporated into energy system models.
Background: Occupational stress, dissatisfaction, higher risk for chronical and psychological disorders impairs the well-being of care nurses staff and maintaining the quality of elderly and disabled care. However, few studies have compared the psychological and physical stress in nurses working in inpatient and outpatient care settings. Aim: The aim of the present study was to compare perceived stress, workload and psychosomatic complaints in nurses working in inpatient and outpatient care settings. Methods: 158 care nurses working in geriatric and disabled care participated in the quantitative cross-sectional survey study. Comparisons of stress, workload and psychosomatic complaints were made between the inpatient and outpatient care group. Results: Nurses working in the outpatient care reported more subjective experience of stress and more workload compared to nurses working in inpatient care. Additionally, nurses working in outpatient care reported more psychosomatic complaints compared to nurses in inpatient care. Conclusions: Our results suggest that inpatient and outpatient nurses experience their nursing activities differently stressful. In future research the differential stress factors need to be explored to provide adequate job training and develop stress prevention programs.
The mapping of sugarcane plantations and their changes is relevant to the economy and the environment, notably due to sugarcane’s interface in the biofuel industry through ethanol. The necessary mapping of sugarcane crop changes is especially challenging when plantation occurs under smallholders’ land ownership structures used for heterogeneous crop management. We evaluated two approaches to address this challenge with the example of sugarcane abandonment in the Norte Fluminense Region, Northeastern Rio de Janeiro state, Brazil. The region is characterized by a large share of smallholders. We trained a random forest classifier for sugarcane for 2018 based on all available Landsat imagery. Based on the concept of temporal generalization, we applied the classifier trained in 2018 for the period from 1986 until 2020. The resulting annual sugarcane probability maps were used as input for two abandonment mapping methods: LandtrendR and muti-temporal cropland abandonment mapping. The performance of both approaches was evaluated based on a stratified sampling approach. We detected three distinct trajectories for sugarcane farmland: i) permanently abandoned sugarcane, ii) fallow sugarcane, and iii) and stable sugarcane. The multi-temporal cropland abandonment mapping performed better for the sugarcane abandonment class (F1 = 0.84) than the LandtrendR approach (F1 = 0.21). The LandtrendR results revealed a higher omission (PA = 0.12) in mapping the sugarcane abandonment class. For the multitemporal cropland abandonment mapping, we found that 66% (67,353 ha) of the stable sugarcane areas were abandoned between 1990 and 2016. The highest abandonment rates occurred between 1990 and 1994 and between 2010 and 2016. The spatial distribution of abandonment was heterogeneous. The earliest abandonment was concentrated in the northern part of the study area. The most recent abandonment was more extensive in the southern part of the study site. Our results highlight the advantages and challenges of using Landsat time series to map sugarcane abandonment in a heterogeneous management system. Our results also highlight the spatially and temporal heterogeneous pattern of sugarcane abandonment in the region and provide the necessary database for subsequent studies to identify underlying and proximate causes for the abandonment.
Zusammenfassung Der deutsche Sozialstaat organisiert soziale Sicherung traditionell auf zwei höchst unterschiedliche Weisen: Zum einen über die erwerbsarbeitszentrierten staatlichen Sozialversicherungen, die typische Risiken im Lebenslauf für alle Erwerbstätigen und ihre Familien absichern, zum anderen über eine bedarfsgeprüfte Existenzsicherung und individualisierte Hilfen im Einzelfall. Diese wohlfahrtsstaatliche Komplementärkonstruktion ist durch sozioökonomische Veränderungsprozesse unter Druck geraten: Ein verringertes Wirtschaftswachstum, steigende Arbeitslosigkeit und die Alterung der Gesellschaft führten zu steigenden Ausgaben in der Sozialpolitik, die nicht durch ein entsprechendes Einnahmenwachstum kompensiert werden konnten. Sowohl das Sozialversicherungs- als auch das Grundsicherungssystem wurde entsprechend angepasst, wobei es nicht nur um die Kürzung von Sozialleistungen ging, sondern auch die normativen Sicherungsziele neu ausgerichtet wurden. Der reformierte Sozialstaat setzt auf Aktivierung, Eigenverantwortung und Selbstbestimmung – und zwar in allen Bereichen. Damit stellt sich auch grundsätzlich die Frage, inwiefern der deutsche Wohlfahrtsstaat in seiner Gesamtheit noch in der Lage ist, soziale Problemlagen aufzufangen. Aus einer ganzheitlichen Perspektive wird dafür plädiert, die Fragmentierung des sozialen Sicherungssystems zu überwinden und auf Basis von konkreten Problemkonstellationen die Organisation des Sozialen neu zu denken.
Zusammenfassung Hintergrund Seit 2015 empfehlen die internationalen Reanimationsleitlinien die Implementierung von spezialisierten Krankenhäusern (sog. Cardiac Arrest Center, CAC) für die Versorgung von Patienten mit außerklinischem Herz-Kreislauf-Stillstand. Ziel Ziel der Studie war es, den potenziellen Einfluss der Zertifizierung von Kliniken als CAC auf das Einweisungsverhalten von Notärzten und Rettungsfachpersonal bei prähospital reanimierten Patienten zu untersuchen. Methoden Eine webbasierte anonyme Befragung mit 20 Items wurde vom 15.05. bis zum 15.06.2018 in Deutschland durchgeführt. Zielgruppen waren im Rettungsdienst tätige Notärzte sowie Rettungsfachpersonal. Wesentliche Ergebnisse Von 437 Teilnehmern wurden die Ergebnisse von 378 Befragten ( n = 292 Notärzte, n = 86 Rettungsfachpersonen) in die statistische Analyse eingeschlossen. 75,1 % ( n = 284) gaben an, dass die CAC-Zertifizierung von Krankenhäusern bei ihrem künftigen Einweisungsverhalten von Patienten mit präklinischem Herz-Kreislauf-Stillstand eine Rolle spielen würde. 78,3 % ( n = 296) erwarteten, dass die CAC-Zertifizierung zu einer Verbesserung der Patientenversorgung führen wird. 78,8 % ( n = 298) befürworteten die Einführung der CAC-Zertifizierung. Die Befragten würden eine zusätzliche Transportzeit von 16,3 min (95 %-KI: 15,2–17,3) akzeptierten, um ein CAC zu erreichen. Fazit Die Zertifizierung von Kliniken als CAC hat das Potenzial, die Entscheidung des Rettungsdienstpersonals bei der Zuweisung von Patienten mit einem präklinischen Herz-Kreislauf-Stillstand zu beeinflussen. Aufgrund der limitierten zusätzlich akzeptablen Transportzeit zur Erreichung eines CAC bedarf es eines bundesweiten, engen Netzes zertifizierter Kliniken.
Producing more food for a growing population requires sustainable crop intensification and diversification, particularly in high-potential areas such as the seasonal floodplain wetlands of sub-Saharan Africa (SSA). With emerging water shortages and concerns for conserving these multi-functional wetlands, a further expansion of the cropland area must be avoided as it would entail increased use of blue water for irrigation and infringe on valuable protected areas. We advocate an efficient use of the prevailing green water on the existing cropland areas, where small-scale farmers grow a single crop of rainfed lowland rice during the wet season. However, soil moisture at the onset of the rains (pre-rice niche) and residual soil moisture after rice harvest (post-rice niche) may suffice to cultivate short-cycled crops. We developed a methodological approach to analyze the potential for green water cultivation in the pre- and post-rice niches in the Kilombero Valley Floodplain in Tanzania, as a representative case for seasonal floodplain wetlands in SSA. The three-step approach used open-access remote sensing datasets to: (i) extract cropland areas; (ii) analyze soil moisture conditions using evaporative stress indices to identify the pre- and post-rice niches; and (iii) quantify the green water availability in the identified niches through actual evapotranspiration (AET). We identified distinct patterns of green water being available both before and after the rice-growing period. Based on the analyses of evaporative stress indices, the pre-rice niche tends to be longer (~70 days with average AET of 20–40 mm/10-day) but also more variable (inter-annual variability >30%) than the post-rice niche (~65 days with average AET of 10–30 mm/10-day, inter-annual variability <15%). These findings show the large potential for cultivating short-cycled crops beyond the rice-growing period, such as green manure, vegetables, maize, and forage legumes, by shifting a portion of the nonproductive AET flows (i.e., soil evaporation) to productive flows in form of crop transpiration. A cropland area of 1452 to 1637 km² (53–60% of the total cropland area identified of 2730 km²) could be cultivated using available green water in the dry season, which shows the significance of such change for food security, livelihoods, and resilience of the agricultural community in Kilombero. A wider application of the developed approach in this study can help identifying opportunities and guiding interventions and investments towards establishing sustainable intensification and diversification practices in floodplain wetlands in SSA.
Communication styles may play an important part in promoting or discouraging genuine engagement in participatory design, all the more so where design projects involve young people with additional needs receiving social work support. While technology designers may seek to set up a participatory process, the – possibly unconscious – communicative acts and language employed by a facilitator may play a crucial role in supporting or undermining participatory strategies, even where the participatory methods employed are appropriate to the planned process. This study presents findings of a conversation analysis undertaken on the opening minutes of a virtual participatory design workshop, showing how the sequence analyzed sets up a basis for participation that appears contradictory within itself.
Laser powder bed fusion (L-PBF) offers significant potentialities for the design of complex part geometries. Due to the specific combination of properties, tungsten heavy alloys are used for special applications such as X-ray and γ-radiation shielding, balancing weights, collimators and molds. For optimum performance, complex geometries can be required in those applications. L-PBF of tungsten heavy alloys such as W-Ni-Fe is challenging due to the high thermal conductivity, high viscosity of the liquid phase, the high melting point and sensitivity to thermal cracking. The effect of L-PBF processing parameters on the material microstructure is therefore studied for different W-Ni-Fe powders, applying substrate preheating temperatures up to 800 °C. Furthermore, the impact of thermal post-treatment is investigated, leading to a microstructure close to conventionally sintered material. Crack-free samples can be generated from all powders, but residual and heterogeneously distributed pores are still detected. It is shown that evaporation of NiFe binder matrix during L-PBF is significantly lower for pre-alloyed powders than for mixed powders.
The COVID-19 situation shows that a deep understanding of how pandemics spread and how they can be managed is important in a multitude of domains. Various studies have shown that students benefit from game-based learning approaches. Therefore, we introduce the concept of a web-based serious game to teach students important aspects when dealing with pandemic situations.
Managed entry agreements (MEA) represent one of the main topics of discussion between the European National Payers Authorities. Several initiatives on the subject have been organized over the past few years and the scientific literature is full of publications on the subject. There is currently little international sharing of information between payers, mainly as a result of the confidentiality issues. There are potential benefits from the mutual sharing of information, both about the existence of MEAs and on the outcomes and results. The importance of involving all the players in the decision-making process on market access for a medicinal product (MP) is that it may help to make new therapies available to patients in a shorter time. The aim of this project is to propose a new pathway of value-based MEA (VBMEA), based on the analysis of the current Italian pricing and reimbursement framework. This requires elaboration of a transparent appraisal and MEA details with at least a 24-month contract. The price of the MP is therefore valued based on the analysis of the VBMEA registries of the Italian Medicines Agency. Although the proposal focuses on the Italian context, a similar approach could also be adapted in other nations, considering the particularities of the single health technology assessment (HTA)/payer system.
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5,131 members
Thomas Bartz-Beielstein
  • Institute for Data Science, Engineering, and Analytics. Faculty of Computer Science and Engineering Science
Philipp Schaer
  • Institute of Information Science
Christoph Pörschmann
  • Institute of Communications Engineering
Daniel Gaida
  • Faculty of Computer Science and Engineering Science
Wolfgang Konen
  • Institute of Informatics
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