Publikationen


5833 Publikationen gefunden
    MobilAngewandte Naturwissenschaften und Wirtschaftsingenieurwesen

    Zeitschriftenartikel

    Michael Drexl, C. Tilk, S. Irnich

    Nested Branch-and-Price-and-Cut for Vehicle Routing Problems with Multiple Resource Interdependencies

    European Journal of Operational Research, vol. 276, no. 2, pp. 549-565

    2019

    DOI: 10.1016/j.ejor.2019.01.041

    Abstract anzeigen

    This paper considers vehicle routing problems (VRPs) with multiple resource interdependencies and addresses the development and computational evaluation of an exact branch-and-price-and-cut algorithm for their solution. An interdependency between two resources means that the two resource consumptions influence one another in such a way that a tradeoff exists between them. This impacts the feasibility and/or the cost of a solution. The subproblem in branch-and-price-and-cut procedures for VRPs is very often a variant of the shortest-path problem with resource constraints (SPPRC). For the exact solution of many SPPRC variants, dynamic-programming based labeling algorithms are predominant. The tradeoffs in problems with multiple resource interdependencies, however, render the application of labeling algorithms unpromising. This is because complex data structures for managing the tradeoff curves are necessary and only weak dominance criteria are possible, so that the labeling algorithm becomes almost a pure enumeration. Therefore, we propose to solve also the SPPRC subproblem with branch-and-price-and-cut. This results in a two-level, nested branch-and-price-and-cut algorithm. We analyze different variants of the algorithm to enable the exchange of columns and also rows between the different levels. To demonstrate the computational viability of our approach, we perform computational experiments on a prototypical VRP with time windows, minimal and maximal delivery quantities for each customer, a customer-dependent profit paid for each demand unit delivered, and temporal synchronization constraints between some pairs of customers. In this problem, tradeoffs exist between cost and load and between cost and time.

    MobilElektrotechnik und MedientechnikTC Freyung

    Zeitschriftenartikel

    Raphaela Pagany, Wolfgang Dorner

    Do Crash Barriers and Fences Have an Impact on Wildlife-Vehicle Collisions? An Artificial Intelligence and GIS-Based Analysis

    ISPRS Internation Journal of Geo-Information, vol. 8, no. 2

    2019

    DOI: 10.3390/ijgi8020066

    Abstract anzeigen

    Wildlife–vehicle collisions (WVCs) cause significant road mortality of wildlife and have led to the installation of protective measures along streets. Until now, it has been difficult to determine the impact of roadside infrastructure that might act as a barrier for animals. The main deficits are the lack of geodata for roadside infrastructure and georeferenced accidents recorded for a larger area. We analyzed 113 km of road network of the district Freyung-Grafenau, Germany, and 1571 WVCs, examining correlations between the appearance of WVCs, the presence or absence of roadside infrastructure, particularly crash barriers and fences, and the relevance of the blocking effect for individual species. To receive infrastructure data on a larger scale, we analyzed 5596 road inspection images with a neural network for barrier recognition and a GIS for a complete spatial inventory. This data was combined with the data of WVCs in GIS to evaluate the infrastructure’s impact on accidents. The results show that crash barriers have an effect on WVCs, as collisions are lower on roads with crash barriers. In particular, smaller animals have a lower collision share. The risk reduction at fenced sections could not be proven as fenced sections are only available at 3% of the analyzed roads. Thus, especially the fence dataset must be validated by a larger sample number. However, these preliminary results indicate that the combination of artificial intelligence and GIS may be used to analyze and better allocate protective barriers or to apply it in alternative measures, such as dynamic WVC risk-warning.

    NachhaltigTC Freyung

    Zeitschriftenartikel

    Javier Valdés, Luis Ramirez Camargo, Y. Masip Macia, A. Poque González

    Cogeneración en Chile: Capacidades, desarrollo y perspectivas

    [Status: In Press]

    Avances en Energías Renovables y Medio Ambiente (AVERMA)

    2019

    Abstract anzeigen

    RESUMEN: En Chile, el proyecto de cogeneración más antiguo data de 1930 y operó hasta el año 1997. Sin embargo, pese a que la tecnología lleva introducida largo tiempo, pocos son los estudios que han analizado el potencial de CHP y su evolución. Un primer paso para el estudio del potencial del país es la creación de un catastro que incluya la capacidad instalada. El interés de este ejercicio radica en el potencial de integración de mayores cantidades de CHP en el sistema eléctrico con el objetivo de hacer frente a la intermitencia de fuentes de energía no convencionales. Además, las plantas CHP pueden ayudar a alcanzar los objetivos de eficiencia energética gracias a la posibilidad de los generadores de volcar a la red tanto la electricidad como calor no consumido en los procesos productivos. Sin embargo, para que esto ocurra es necesario el desarrollo de un marco regulatorio acorde a las capacidades y características de las plantas de CHP. El objetivo de este artículo es precisamente identificar las características de las instalaciones en industrias específicas, así como su evolución, con el objetivo de extrapolar los datos al resto de la economía y obtener un potencial de CHP para el país. Para ello, se han hecho consultas de catastros anteriores, así como entrevistas con empresas para conocer el estado actual del parque de plantas de CHP en el país. Palabras clave: cogeneración, eficiencia energética, flexibilidad del sistema eléctrico 1.

    DigitalAngewandte WirtschaftswissenschaftenTC Grafenau

    Zeitschriftenartikel

    Ali Fallah Tehrani, M. Aggarwal

    Modelling Human Decision Behaviour with Preference Learning

    INFORMS Journal on Computing, vol. 31, no. 2

    2019

    DOI: 10.1287/ijoc.2018.0823

    Abstract anzeigen

    Preferences provide a means for specifying the desires of a decision maker (DM) in a declarative way. In this paper, based on a DM’s pairwise preferences, we infer the DM’s unique decision model. We capture (a) the attitudinal character, (b) relative criteria importance, and (c) the criteria interaction, all of which are specific to the DM. We make use of the preference-learning (PL) technique to induce predictive preference models from empirical data. Because PL is emerging as a new subfield of machine learning, we could use standard machine-learning methods to accomplish our learning objective. We consider the DM’s exemplary preference information in the form of pairwise comparisons between alternatives as the training information. The DM’s decision model is captured in terms of (a), (b), and (c), through the parameters of an attitudinal Choquet integral operator. The proposed learning approach is validated through an experimental study on 16 standard data sets. The superiority of the proposed method in terms of predictive accuracy and easier interpretability is shown both theoretically as well as empirically.

    IQW

    Zeitschriftenartikel

    Andreas Gegenfurtner, M. Gebhardt, G. Casale, J.-T. Kuhn, J. DeVries, J. Jungjohann

    Measurement invariance of a direct behavior rating multi-item scale

    Social Sciences, vol. 8, no. 46, pp. 1-23

    2019

    DOI: 10.3390/socsci8020046

    Abstract anzeigen

    Direct Behavior Rating (DBR) as a behavioral progress monitoring tool can be designed as longitudinal assessment with only short intervals between measurement points. The reliability of these instruments has been evaluated mostly in observational studies with small samples based on generalizability theory. However, for standardized use in the pedagogical field, a larger and broader sample is required in order to assess measurement invariance between different participant groups and over time. Therefore, we constructed a DBR with multiple items to measure the occurrence of specific externalizing and internalizing student classroom behaviors on a Likert scale (1 = never to 7 = always). In a pilot study, two trained raters observed 16 primary school students and rated the student behavior over all items with a satisfactory reliability. In the main study, 108 regular primary school students, 97 regular secondary school students and 14 students in a clinical setting were rated daily over one week (five measurement points). IRT analyses confirmed the instrument’s technical adequacy, and latent growth models demonstrated the instrument’s stability over time. Further development of the instrument and study designs to implement DBRs are discussed.

    DigitalIQW

    Zeitschriftenartikel

    Andreas Gegenfurtner, D. Dagnone, J.J.G. van Merriënboer, McGraw, Nick C J, A. Hall, D. Howes, A. Szulewski, G. Dashi, R. Egan

    A new way to look at simulation-based assessment: the relationship between gaze-tracking and exam performance

    Canadian Journal of Emergency Medicine (CJEM), vol. 21, no. 1, pp. 129-137

    2019

    DOI: 10.1017/cem.2018.391

    Abstract anzeigen

    CLINICIAN'S CAPSULEWhat is known about this topic?Gathering visual information effectively is an important task of a physician leader when managing a resuscitation case.What did this study ask?Are there particular visual information-gathering patterns associated with performance in simulated resuscitation scenarios?What did this study find?Certain visual patterns (e.g., focusing on case-specific clinically relevant stimuli) are associated with better performance in a simulated resuscitation setting.Why does this study matter to clinicians?The ability to characterize physician visual patterns across a competence continuum has implications for trainee assessment and medical education.

    IQW

    Zeitschriftenartikel

    Andreas Gegenfurtner, R. van Geel, L. Testers, S. Brand-Gruwel

    From monocontextual to multicontextual transfer: Organizational determinants of the intention to transfer generic information literacy competences to multiple contexts

    Frontline Learning Research, vol. 7, no. 1, pp. 23-42

    2019

    DOI: 10.14786/flr.v7i1.359

    Abstract anzeigen

    An important goal of educational designers is to achieve long-term transfer of learning that is the learner's application of newly acquired competencies. Extensive research during more than a century shows that especially in formal educational settings this fundamental aspect of education often occurs poorly or not at all, leading to what is called a Transfer Problem. To address this transfer problem, the present study examines intentions to transfer learning to multiple contexts; this focus on multiple transfer contexts extends previous research focusing on a single transfer context, typically the workplace. The present study aimed to estimate the influence of five organizational variables (peer support, supervisor support, opportunity to use, openness to change, and feedback) on transfer intention in two different transfer contexts: study and work. Participants were 303 students at an open university attending a course in information literacy. The model was tested using structural equation modelling. The results indicated that before starting the course supervisor support and feedback were considered the strongest predictors of intention to transfer new learning in both the study and the work contexts. This research is amongst the first in the training literature to address multi-contextuality and examines intentions to transfer generic competences to the two transfer contexts study and work within one single study.

    NachhaltigElektrotechnik und Medientechnik

    Zeitschriftenartikel

    J. Michalicka, S. Li, Z. Bi, Y. Zhang, Ondrej Man, Y. Hong, Y. Wu, W. Ni, H. Fan, Günther Benstetter, L. Liu, Q. Yang, D. Liu

    The effect of O2 impurity on surface morphology of polycrystalline W during low-energy and high-flux He+ irradiation

    Fusion Engineering and Design, vol. 139, pp. 96-103

    2019

    DOI: 10.1016/j.fusengdes.2019.01.003

    Abstract anzeigen

    The interaction between the impurities (such as carbon, nitrogen, oxygen) and the plasma-facing materials (PFMs) can profoundly influence the performance and service of the PFMs. In this paper, we investigated the influence of oxygen (O2) impurity in the helium radio frequency (RF) plasma on the surface morphology of polycrystalline tungsten (W) irradiated at the surface temperature of 1450 ± 50 K and the ion energy of 100 eV. The pressure ratio of O2 to He (R) in RF source varied from 4.0 × 10−6 to 9.0 × 10-2. The total irradiation flux and fluence were ˜1.2 × 1022 ions·m-2·s-1 and ˜1.0 × 1026 ions·m-2, respectively. After He+ irradiation, the specimen surface morphology was observed by scanning electron microscopy. It was found that with increasing R from 4.0 × 10−6 to 9.0 × 10-2 the thickness of nano-fuzz layer at the W surface was thinner and thinner, accompanied by the formation of rod-like structures. The erosion yield increased from 5.2 × 10-4 to 2.3 × 10-2 W/ion when R varied from 4.0 × 10-6 to 9.0 × 10-2. The X-ray diffraction analysis shows that tungsten oxides were formed at the near surface of specimens when R exceeded 1.8 × 10-2. The erosion yield measurements revealed that in addition to surface physical sputtering process, the chemical erosion process could occur due to the interaction between oxygen-containing species and W at the surface. The results indicated that the presence of O2 impurity in He plasma can obviously affect the surface microstructure of W. The study suggested that O2 impurity can effectively reduce the growth of nano-fuzz structures.

    GesundAngewandte GesundheitswissenschaftenEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    Irmgard Tischner, N. Moller

    Young people’s perceptions of fat counsellors: “How can THAT help me?”

    Qualitative Research in Psychology, vol. 16, no. 1, pp. 34-53

    2019

    DOI: 10.1080/14780887.2018.153638

    Abstract anzeigen

    Being fat is widely recognised as a stigmatised identity which disproportionately impacts women, both personally and professionally. Women are numerically dominant as therapy practitioners, and we use this group to explore the ways a “fat counsellor” is imagined in the context of counselling. A qualitative story completion task, about a woman starting therapy, was presented to 203 British young people ages 15–24. Participants were 75% female, 88% white, 93% heterosexual, and 98% able-bodied. The story stem did not specify the sex of the counsellor, who was identified as fat; the vast majority of stories assumed the counsellor was female. Overall, fatness was perceived as negatively affecting therapy and the counsellor’s professional credibility because fatness was equated with a lack of psychological health, which rendered fat counsellors professionally “unfit.” This finding extends the literature on “weight bias” in professional settings and has implications for counsellors of all body sizes.

    GesundAngewandte GesundheitswissenschaftenEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    Irmgard Tischner

    Tomorrow is the start of the rest of their life – so who cares about health? Exploring constructions of weight-loss motivations and health using story completion

    Qualitative Research in Psychology, vol. 16, no. 1, pp. 54-73

    2019

    DOI: 10.1080/14780887.2018.1536385

    Abstract anzeigen

    In Western societies, health is closely associated with body weight and weight loss, achieved through individual health behaviour. I examined such associations in constructions of weight-loss motivations and health in stories generated using the novel method of story completion. The story stem featured either a female or male protagonist deciding to lose weight; 148 women and 22 men (ages 18–24) provided stories in response. A social constructionist thematic analysis identified five themes: health as clothing size and means to an end; weight-loss activity as good for every woman; tomorrow is going to be the start of the rest of their life; tell me when I’m okay — it’s not about wellbeing; and weight loss as signifier of the “true self.” Considering the adverse social and psychological consequences reflected in the stories and the longstanding elusiveness of successful weight-loss methods, I support calls to review the dominant weight-focused approach to public health.

    NachhaltigElektrotechnik und MedientechnikTC Freyung

    Beitrag (Sammelband oder Tagungsband)

    Javier Valdés, Luis Ramirez Camargo, Y. Masip Macia, A. Poque González

    Cogeneración en Chile: Capacidades, desarrollo y perspectivas

    Memorias de la XLI Reunión de Trabajo de la ASADES (Nov 5-10, 2018; Cordoba, Argentina)

    2019

    ISBN: 978-987-29873-1-2

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenEuropan Campus Rottal-Inn

    Zeitschriftenartikel

    A. Rineiski, S. Gianfelici, W. Maschek, B. Vezzoni, Rui Li, C. Matzerath Boccaccini, F. Gabrielli, M. Flad

    Probabilistic evaluation of the energetics upper bound during the transition phase of an unprotected loss of flow accident for a sodium cooled fast reactor by using a Phenomenological Relationship Diagram

    Nuclear Engineering and Design, vol. 341, no. 146-154

    2019

    DOI: 10.1016/j.nucengdes.2018.11.004

    Abstract anzeigen

    One of the main research goals of the GEN-IV systems is enhancing their safety compared with the former Sodium-Cooled Fast Reactor (SFR) designs. A key issue is the capability of accidents prevention as well as of demonstrating that their consequences do not violate the safety criteria. In order to fulfill such requirements, risk analyses of severe core disruptive accidents are performed. Since the beginning of the SFR development, Hypothetical Core Disruptive Accidents (HCDAs) have played an outstanding role. Numerous safety analyses have been performed for developing and licensing past SFR designs and nowadays a large database of results is available. In particular, a large amount of results of the mechanistic SIMMER-II and SIMMER-III/IV analyses for various core designs and different power classes is available at the Karlsruhe Institute of Technology (KIT). The current paper describes the probabilistic approach based on the Phenomenological Relationship Diagram (PRD), which is used to evaluate the Probability Distribution Function (PDF) of the thermal energy release during the transition phase of an unprotected loss of flow accident scenario for a SFR. The technique allows taking into account the mechanistic nature of the accident scenario. In fact, the available results of the mechanistic analyses of HCDAs in SFRs are used to assess the PDFs of the dominant phenomena affecting the thermal energy release, which are propagated in the PRD by employing a Monte Carlo method.

    NachhaltigTC Freyung

    Beitrag (Sammelband oder Tagungsband)

    Javier Valdés, Luis Ramirez Camargo, Y. Masip Macia, Wolfgang Dorner

    Assessment of on-site steady electricity generation from renewable energy sources in Chile

    Energy Procedia (Contributions to the 10th International Conference on Applied Energy ICAE 2018), vol. 158

    2019

    DOI: 10.1016/j.egypro.2019.01.266

    Abstract anzeigen

    Chile has an immense renewable energy potential but their integration in the energy system constitutes a major challenge. The complex topography of the country, the isolation of the different electric grids and the variability of renewable energy sources, makes energy transmission from locations with high variable renewable power generation potential to the demand centres not an easy task. The present study aims at assessing the potential of combining solar power, wind power and storage systems to provide steady loads already from the source. Such a combination should take advantage of complementarity between variable renewable sources and serves to simplify their integration in the energy system. The analysis relies on an optimization model to size hybrid renewable energy systems and 10 years of weather data from the brand new ERA-5 reanalysis. Necessary system sizes to constantly generate 1 MWh of electricity for every hour during the period 2008-2017 are calculated for all possible locations across the country. The results show that the necessary generation and storage capacities to provide a steady energy output are very high even for areas with exceptionally high renewable energy potential.

    NachhaltigTC Freyung

    Beitrag (Sammelband oder Tagungsband)

    Luis Ramirez Camargo, Wolfgang Dorner, K. Gruber, F. Nitsch

    Hybrid renewable energy systems to supply electricity to self-sufficient residential buildings in Central Europe

    Energy Procedia (Contributions to the 10th International Conference on Applied Energy ICAE 2018), vol. 158

    2019

    DOI: 10.1016/j.egypro.2019.01.096

    Abstract anzeigen

    This work evaluates potentials of photovoltaic and battery systems with additional micro-generation wind turbines (10.5 kW) to cover electricity demand of residential users in two countries in Central Europe. It relies on high-resolution regional reanalysis data and a techno-economical optimization model. Maps showing the number of wind turbines, photovoltaic and battery systems sizes necessary to supply electricity for clusters of electricity self-sufficient single-family houses across Germany and the Czech Republic are generated. No general trends that apply for the two countries concerning the relation between the sizes of the different technologies were identified. However, it was possible to determine several large areas where the inclusion of small wind turbines decreases the total system costs and considerably reduces the required storage capacities. Results are discussed and compared to previous work on self-sufficient single-family houses.

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Weißenburg

    Beitrag (Sammelband oder Tagungsband)

    Gerhard, R., Dmitry Rychkov, Wang, J.

    Influence of Charge Density on Charge Decay in Chemically Modified Polypropylene Films

    Proceedings of the IEEE 2nd International Conference on Dielectrics, Budapest, Hungary

    2018

    ISBN: 978-1-5386-6389-9

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Weißenburg

    Beitrag (Sammelband oder Tagungsband)

    F. He, Gerhard, R., Schulze, M., Wirges, W., Dmitry Rychkov, Wang, J.

    Senskin deformable silicone-elastomer sensors for structural health monitoring: assessment of strain sensitivity and correction for thermal expansion

    Proceedings of the 8th International Conference on Electromechanically Active Polymer (EAP) Transducers & Artificial Muscles , Valpré Ecully - Lyon, France

    2018

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Weißenburg

    Beitrag (Sammelband oder Tagungsband)

    F. He, G. Gidion, Gerhard, R., Schulze, M., Wirges, W., Dmitry Rychkov, Wang, J.

    Soft Stretchable All-Silicone Sensor for Transport-Infrastructure Monitoring

    Sensoren und Messsysteme 2018 19. ITG-/GMA-Fachtagung

    2018

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Weißenburg

    Beitrag (Sammelband oder Tagungsband)

    Kuznetsov, A., Dmitry Rychkov, V. Stojharov, Rychkov, A. A.

    The Influence of Recrystallization Regimes on Electret Charge Stability in Low-Density Polyethylene Films

    Proceedings of the IEEE 2nd International Conference on Dielectrics, Budapest, Hungary

    2018

    ISBN: 978-1-5386-6389-9

    NachhaltigAngewandte Naturwissenschaften und WirtschaftsingenieurwesenTC Weißenburg

    Zeitschriftenartikel

    Damigos, Y., Kourousis, D., Frankenstein, B., Gerhard, R., Amditis, A., Cheilakou, E., Dmitry Rychkov, Bouklas, C., Tsopelas, N., Anastasopoulos, A.

    Strain monitoring system for steel and concrete structures

    Procedia Structural Integrity, vol. 10, pp. 25-32

    2018

    DOI: 10.1016/j.prostr.2018.09.005

    Abstract anzeigen

    The present work is part of a collaborative H2020 European funded research project called SENSKIN, that aims to improve Structural Health Monitoring (SHM) for transport infrastructure through the development of an innovative monitoring and management system for bridges based on a novel, inexpensive, skin-like sensor. The integrated SENSKIN technology will be implemented in the case of steel and concrete bridges, and tested, field-evaluated and benchmarked on actual bridge environment against a conventional health monitoring solution developed by Mistras Group Hellas. The main objective of the present work is to implement the autonomous, fully functional strain monitoring system based on commercially available off-the-shelf components, that will be used to accomplish direct comparison between the performance of the innovative SENSKIN sensors and the conventional strain sensors commonly used for structural monitoring of bridges. For this purpose, the mini Structural Monitoring System (mini SMS) of Physical Acoustics Corporation, a comprehensive data acquisition unit designed specifically for long-term unattended operation in outdoor environments, was selected. For the completion of the conventional system, appropriate foil-type strain sensors were selected, driven by special conditioners manufactured by Mistras Group. A comprehensive description of the strain monitoring system and its peripheral components is provided in this paper. For the evaluation of the integrated system’s performance and the effect of various parameters on the long-term behavior of sensors, several test steel pieces instrumented with different strain sensors configurations were prepared and tested in both laboratory and field ambient conditions. Furthermore, loading tests were performed aiming to validate the response of the system in monitoring the strains developed in steel beam elements subject to bending regimes. Representative results obtained from the above experimental tests have been included in this paper as well.