AutoRL Hyperparameter Landscapes

Although Reinforcement Learning (RL) has shown to be capable of producing impressive results, its use is limited by the impact of its hyperparameters on performance. This often makes it difficult to achieve good results in practice. Automated RL (AutoRL) addresses this difficulty, yet little is known about the dynamics of the hyperparameter landscapes that hyperparameter optimization (HPO) methods traverse in search of optimal configurations. In view of existing AutoRL approaches dynamically adjusting hyperparameter configurations, we propose an approach to build and analyze these hyperparameter landscapes not just for one point in time but at multiple points in time throughout training. Addressing an important open question on the legitimacy of such dynamic AutoRL approaches, we provide thorough empirical evidence that the hyperparameter landscapes strongly vary over time across representative algorithms from RL literature (DQN and SAC) in different kinds of environments (Cartpole and Hopper). This supports the theory that hyperparameters should be dynamically adjusted during training and shows the potential for more insights on AutoRL problems that can be gained through landscape analyses

Residents’ Democratic engagement in public housing and urban areas – structures, formalities and technologies

The workshop gathers people from various sectors inside and outside academia to discuss the current state of, and the prospects for IT in the support of residents’ democratic engagement in, and around, public housing.

Alternative Antriebe für Rangierlokomotiven

Überblick über die Ergebnisse zweier Studien zur Thematik alternativer Antriebe in Rangierlokomotiven. In der Studie "Machbarkeitsanalyse alternativer Antriebe im Einsatzgebiet von Rangierloks in Deutschland" im Auftrag der NOW wurden Anforderungen an alternative Antriebe auf Basis für verschiedene Einsatzfelder von Rangierlokomotiven ermittelt. Für fünf lokal emissionsfreie Antriebe wurden für eine dreiachsige und eine Drehgestelllokomotive Leistungstrajektorien für generische Profile simuliert, die erforderlichen Wandler- und Speicherkomponenten in Hinblick auf die zur Verfügung stehenden Bauräume dimensioniert. Schließlich wurden die Marktpotentiale alternativer Antriebe in Deutschland ermittelt. In der durch das MWIDE (Ministerium für Wirtschaft, Innovation, Digitalisierung und Energie Nordrhein-Westfalen) geförderten Vorstudie Wasserstoffrangierlokomotive (Projektpartner Duisport und ZBT) wurde die Machbarkeit von Brennstoffzellenhybrid-Rangierlokomotiven im Einsatzfeld von Duisport Rail ermittelt. Auf Basis einer Messdatenauswertung wurden typische Einsatzprofilkategorien abgeleitet und die dafür erforderlichen Energiewandler und Energiespeicher ausgelegt und hinsichtlich der Fahrzeugintegrierbarkeit bewertet

Kernergebnisse der Machbarkeitsanalyse alternativer Antriebe im Einsatzgebiet von Rangierloks in Deutschland

Das DLR-Institut für Fahrzeugkonzepte hat im Auftrag der NOW GmbH die Machbarkeit und die Potenziale alternativer Antriebe im Einsatzfeld von Rangierlokomotiven in Deutschland untersucht. Die untersuchten alternativen Antriebskonzepte umfassen: Akkuantrieb (ohne Oberleitungsanbindung), Brennstoffzellenhybrid, Wasserstoff-Verbrennungsmotor, BiMode-Akku-Oberleitungs-Hybrid sowie BiMode-Brennstoffzellen-Oberleitungs-Hybrid. Als repräsentative Fahrzeuge wurden eine dreiachsige und eine Drehgestell-Rangierlokomotive herangezogen. Diese Broschüre fasst die wesentlichen Ergebnisse der Studie zusammen

Alternative Antriebe für Rangierlokomotiven - Machbarkeitsanalyse

In diesem Vortrag wird die Eignung verschiedener alternativer Antriebe für Rangierlokomotiven dargestellt. Zudem werden Potentiale und Limitationen batterie- und wasserstoffbasierter Antriebe aufgezeigt sowie das zukünftige Marktpotential von Rangierlokomotiven mit alternativen Antrieben in Deutschland abgeschätzt

Einsatzpotenziale alternativer Antriebe in Rangierlokomotiven

In diesem Beitrag wird die grundsätzliche Eignung verschiedener alternativer Antriebe für Rangierlokomotiven untersucht, basierend auf betrieblich-technischen Anforderungen. Zudem werden Potentiale und Limitationen batterie- und wasserstoffbasierter Antriebe aufgezeigt sowie das zu-künftige Marktpotential von Rangierlokomotiven mit alternativen Antrieben in Deutschland abgeschätzt

Groundwater N2O emission factors of nitrate-contaminated aquifers as derived from denitrification progress and N2O accumulation

We investigated the dynamics of denitrification and nitrous oxide (N2O) accumulation in 4 nitrate (NO3-) contaminated denitrifying sand and gravel aquifers of northern Germany (Fuhrberg, Sulingen, Thulsfelde and Gottingen) to quantify their potential N2O emission and to evaluate existing concepts of N2O emission factors. Excess N-2 - N-2 produced by denitrification - was determined by using the argon (Ar) concentration in groundwater as a natural inert tracer, assuming that this noble gas functions as a stable component and does not change during denitrification. Furthermore, initial NO3- concentrations (NO3- that enters the groundwater) were derived from excess N-2 and actual NO3- concentrations in groundwater in order to determine potential indirect N2O emissions as a function of the N input. Median concentrations of N2O and excess N-2 ranged from 3 to 89 mu g N L-1 and from 3 to 10 mg N L-1, respectively. Reaction progress (RP) of denitrification was determined as the ratio between products (N2O-N + excess N-2) and starting material (initial NO3- concentration) of the process, characterizing the different stages of denitrification. N2O concentrations were lowest at RP close to 0 and RP close to 1 but relatively high at a RP between 0.2 and 0.6. For the first time, we report groundwater N2O emission factors consisting of the ratio between N2O-N and initial NO3--N concentrations (EF1). In addition, we determined a groundwater emission factor (EF2) using a previous concept consisting of the ratio between N2O-N and actual NO3--N concentrations. Depending on RP, EF(1) resulted in smaller values compared to EF(2), demonstrating (i) the relevance of NO3- consumption and consequently (ii) the need to take initial NO3--N concentrations into account. In general, both evaluated emission factors were highly variable within and among the aquifers. The site medians ranged between 0.00043-0.00438 for EF(1) and 0.00092-0.01801 for EF(2), respectively. For the aquifers of Fuhrberg and Sulingen, we found EF(1) median values which are close to the 2006 IPCC default value of 0.0025. In contrast, we determined significant lower EF values for the aquifers of Thulsfelde and Gottingen. Summing the results up, our study supports the substantial downward revision of the IPCC default EF5-g from 0.015 (1997) to 0.0025 (2006).DF

Development and validation of risk-adjusted quality indicators for the long-term outcome of acute sepsis care in German hospitals based on health claims data

Background Methods for assessing long-term outcome quality of acute care for sepsis are lacking. We investigated a method for measuring long-term outcome quality based on health claims data in Germany. Materials and methods Analyses were based on data of the largest German health insurer, covering 32% of the population. Cases (aged 15 years and older) with ICD-10-codes for severe sepsis or septic shock according to sepsis-1-definitions hospitalized in 2014 were included. Short-term outcome was assessed by 90-day mortality; long-term outcome was assessed by a composite endpoint defined by 1-year mortality or increased dependency on chronic care. Risk factors were identified by logistic regressions with backward selection. Hierarchical generalized linear models were used to correct for clustering of cases in hospitals. Predictive validity of the models was assessed by internal validation using bootstrap-sampling. Risk-standardized mortality rates (RSMR) were calculated with and without reliability adjustment and their univariate and bivariate distributions were described. Results Among 35,552 included patients, 53.2% died within 90 days after admission; 39.8% of 90-day survivors died within the first year or had an increased dependency on chronic care. Both risk-models showed a sufficient predictive validity regarding discrimination [ AUC = 0.748 (95% CI: 0.742; 0.752) for 90-day mortality; AUC = 0.675 (95% CI: 0.665; 0.685) for the 1-year composite outcome, respectively], calibration (Brier Score of 0.203 and 0.220; calibration slope of 1.094 and 0.978), and explained variance ( R 2 = 0.242 and R 2 = 0.111). Because of a small case-volume per hospital, applying reliability adjustment to the RSMR led to a great decrease in variability across hospitals [from median (1st quartile, 3rd quartile) 54.2% (44.3%, 65.5%) to 53.2% (50.7%, 55.9%) for 90-day mortality; from 39.2% (27.8%, 51.1%) to 39.9% (39.5%, 40.4%) for the 1-year composite endpoint]. There was no substantial correlation between the two endpoints at hospital level (observed rates: ρ = 0, p = 0.99; RSMR: ρ = 0.017, p = 0.56; reliability-adjusted RSMR: ρ = 0.067; p = 0.026). Conclusion Quality assurance and epidemiological surveillance of sepsis care should include indicators of long-term mortality and morbidity. Claims-based risk-adjustment models for quality indicators of acute sepsis care showed satisfactory predictive validity. To increase reliability of measurement, data sources should cover the full population and hospitals need to improve ICD-10-coding of sepsis

Timely sleep facilitates declarative memory consolidation in infants

Human infants devote the majority of their time to sleeping. However, very little is known about the role of sleep in early memory processing. Here we test 6- and 12-mo-old infants’ declarative memory for novel actions after a 4-h [Experiment (Exp.) 1] and 24-h delay (Exp. 2). Infants in a nap condition took an extended nap (≥30 min) within 4 h after learning, whereas infants in a no-nap condition did not. A comparison with age-matched control groups revealed that after both delays, only infants who had napped after learning remembered the target actions at the test. Additionally, after the 24-h delay, memory performance of infants in the nap condition was significantly higher than that of infants in the no-nap condition. This is the first experimental evidence to our knowledge for an enhancing role of sleep in the consolidation of declarative memories in the first year of life

Alternative powertrains for shunting locomotives - analysis of feasibility and limitations

Zero-emission powertrain technologies for shunting locomotives are becoming increasingly relevant as potential replacement candidates to diesel operated powertrains. We investigate the feasibility of zero-emission technologies in light of generic operational shunter locomotive profiles and available limited space and mass of a widely in use MaK G 1206 four axle center-cab shunting locomotive. Two generic shunting locomotive operational cycle profiles were defined based on a survey among German shunting locomotive operators: a pure shunting profile and a mixed shunting and mainline service profile. Daily energy demand at DC link level in both scenarios is similar (1,469 and 1,368 kWh respectively), but average power is higher in the mixed mainline/shunting profile. Powertrain candidates were fuel cell hybrid, battery electric, overhead wire battery electric, BiMode overhead battery electric and hydrogen internal combustion engine. Key powertrain component dimensioning for both scenarios is done using a hybridization tool incorporating volumetric and efficiency specifications of state-of-the-art railway components. The fuel cell hydrogen and overhead wire battery electric drivetrains can fulfill the energy and power requirements for the defined operational profiles, whereas the hydrogen internal combustion engine powertrain has limitations due to installation space restrictions in terms of hydrogen storage tanks. Advancements in energy storage technologies might influence the applicability of alternative powertrain systems, not only of hydrogen-based but also of battery-based propulsion systems. Further research and demonstration projects on zero-tailpipe emission shunting locomotives are recommended