Technische Universität Dresden: Qucosa
Not a member yet
16344 research outputs found
Sort by
Gestaltung von lernförderlichen Umgebungen in der Berufsschule
Get PDFUntersuchungen zeigen, dass die Gestaltung einer lernförderlichen Umgebung bei der Förderung des Lernens und der Entwicklung der Lernenden eine wichtige Rolle spielt. Dies zeigt die Relevanz für Lehrpersonen auf, sich mit diesem Thema auseinanderzusetzen, um eine Lernumgebung für Schüler*innen zu schaffen, die ein Gefühl des Wohlbefindens vermittelt und ihren Lernprozess unterstützt. In der vorliegenden wissenschaftlichen Arbeit wird sich dabei speziell auf die didaktischen Medien fokussiert, wegen ihres signifikanten Einflusses auf die Lernumgebung und den Lernprozess. Den Fragen nach dem Beitrag didaktischer Medien zur Gestaltung einer lernförderlichen Umgebung und den möglichen Gestaltungshinweisen zur Entwicklung einer medialen Lernumgebung in Berufsschulen wird in der vorliegenden Arbeit nachgegangen. Dies geschieht auf Basis einer qualitativen Untersuchung durch Experteninterviews mit Lehrer*innen an Berufsschulen sowie einer vorausgehenden Literaturrecherche. Die zentralen Ergebnisse verdeutlichen, dass eine wichtige Komponente zur Schaffung einer lernförderlichen Umgebung in Berufsschulen das Vorhandensein didaktischer Medien ist. Damit diese zu einer lernförderlichen Umgebung beitragen, sollten sie in der Lernumgebung auf die individuellen Bedürfnisse der Schüler*innen abgestimmt sein, was insbesondere in Berufsschulen von großer Bedeutung ist. Darüber hinaus wurden auf Basis der Interviewergebnisse und aufgrund begrenzter vorhandener Literatur zu der vorliegenden Thematik Gestaltungshinweise zur Einbindung didaktischer Medien in eine lernförderliche Umgebung speziell für Berufsschulen entworfen. Insgesamt verdeutlicht die Entwicklung dieser Gestaltungshinweise den Mehrwert dieser wissenschaftlichen Arbeit für die Praxis und soll dazu beitragen, die mediale Lernumgebung in Berufsschulen zu optimieren
On functional observers for polynomial systems with nonlinear oscillations
No full textIn this contribution we discuss the design of functional observers for polynomial systems. Our approach is based on a high gain design employing an embedded observer. The functional to be estimated is generated from the high gain observer's state. The restriction to polynomial systems allows the representation of the system's and the observer's dynamics as polynomial ideals. For the calculations we utilize methods from algebraic geometry. Our approach is illustrated on a chaotic system
Hair Cortisol and Perceived Stress - Predictors for the Onset of Tics? A European Longitudinal Study on High-Risk Children
No full textSome retrospective studies suggest that psychosocial stressors trigger the onset of tics. This study examined prospective hypothalamic–pituitary–adrenal (HPA) axis activity and perceived stress prior to tic onset. In the present study, 259 children at high risk for developing tics were assessed for hair cortisol concentration (HCC) and parent-on-child-reported perceived stress four-monthly over a three-year period. We used (i) generalised additive modelling (GAM) to investigate the time effects on HCC (hair samples n = 765) and perceived stress (questionnaires n = 1019) prior to tic onset and (ii) binary logistic regression to predict tic onset in a smaller subsample with at least three consecutive assessments (six to nine months before, two to five months before, and at tic onset). GAM results indicated a non-linear increasing course of HCC in children who developed tics, and a steady HCC course in those without tics, as well as a linear-increasing course of perceived stress in both groups. Logistic regression showed that with a higher HCC in hair samples collected in a range of two to five months before tic onset (which refers to cortisol exposure in a range of four to eight months), the relative likelihood of tic onset rose. Our study suggests increased stress prior to tic onset, as evidenced by higher HCC several months before tic onset
Key to High Performance Ion Hybrid Capacitor
No full textZinc ion hybrid capacitors suffer from lack of reversibility and dendrite formation. An electrolyte, based on a solution of a zinc salt in acetonitrile and tetramethylene sulfone, allows smooth zinc deposition with high coulombic efficiency in a Zn||stainless steel cell (99.6% for 2880 cycles at 1.0 mA cm−2, 1.0 mAh cm−2). A Zn||Zn cell operates stably for at least 7940 h at 1.0 mA cm−2 with an area capacity of 10 mAh cm−2, or 648 h at 90% depth of discharge and 1 mA cm−2, 9.0 mAh cm−2. Molecular dynamics simulations reveal the reason for the excellent reversibility: The zinc cation is only weakly solvated than in pure tetramethylene sulfone with the closest atoms at 3.3 to 3.8 Å. With this electrolyte, a zinc||activated-carbon hybrid capacitor exhibits an operating voltage of 2.0 to 2.5 V, an energy-density of 135 Wh kg−1 and a power-density of 613 W kg−1 at 0.5 A g−1. At the very high current-density of 15 A g−1, 29.3 Wh kg−1 and 14 250 W kg−1 are achieved with 81.2% capacity retention over 9000 cycles
Modeling nonlinear optical interactions of focused beams in bulk crystals and thin films: a phenomenological approach
No full textCoherent nonlinear optical μ-spectroscopy is a frequently used tool in modern material science as it is sensitive to many different local observables, which comprise, among others, crystal symmetry and vibrational properties. The richness in information, however, may come with challenges in data interpretation, as one has to disentangle the many different effects like multiple reflections, phase jumps at interfaces, or the influence of the Guoy-phase. In order to facilitate interpretation, the work presented here proposes an easy-to-use semi-analytical modeling Ansatz, which bases upon known analytical solutions using Gaussian beams. Specifically, we apply this Ansatz to compute nonlinear optical responses of (thin film) optical materials. We try to conserve the meaning of intuitive parameters like the Gouy-phase and the nonlinear coherent interaction length. In particular, the concept of coherence length is extended, which is a must when using focal beams. The model is subsequently applied to exemplary cases of second- and third-harmonic generation. We observe a very good agreement with experimental data, and furthermore, despite the constraints and limits of the analytical Ansatz, our model performs similarly well as when using more rigorous simulations. However, it outperforms the latter in terms of computational power, requiring more than three orders less computational time and less performant computer systems
Experimental and numerical investigation of dowel strips for longitudinal and transverse loading
No full textA new field of application for dowel strips are orthotropic composite roadway slabs. In contrast to conventional composite steel bridge construction, the dowel strips create a two-dimensional bond. As a result, they are not only exposed to longitudinal but also to transverse shear forces. Up to now, neither the load-bearing capacity nor the load-deformation behavior under transverse shear forces have been investigated. Furthermore, there are design related deviations from the current approval in form of a lower dowel distance. This paper presents two different types of push-out tests, which provide new insights into small composite dowel strips under longitudinal and transverse loads. Based on these tests and numerical investigations, the effects of smaller dowel strips are analyzed and special features of the load transfer mechanism under transverse shear forces are highlighted. The investigations presented here were carried out as part of the AiF-FOSTA research project P 1265 [1]
Modulation of the hippo-YAP pathway by cyclic stretch in rat type 2 alveolar epithelial cells: a proof-of-concept study
No full textBackground:
Mechanical ventilation (MV) is a life supporting therapy but may also cause lung damage. This phenomenon is known as ventilator-induced lung injury (VILI). A potential pathomechanisms of ventilator-induced lung injury may be the stretch-induced production and release of cytokines and pro-inflammatory molecules from the alveolar epithelium. Yes-associated protein (YAP) might be regulated by mechanical forces and involved in the inflammation cascade. However, its role in stretch-induced damage of alveolar cells remains poorly understood. In this study, we explored the role of YAP in the response of alveolar epithelial type II cells (AEC II) to elevated cyclic stretch in vitro. We hypothesize that Yes-associated protein activates its downstream targets and regulates the interleukin-6 (IL-6) expression in response to 30% cyclic stretch in AEC II.
Methods:
The rat lung L2 cell line was exposed to 30% cyclic equibiaxial stretch for 1 or 4 h. Non-stretched conditions served as controls. The cytoskeleton remodeling and cell junction integrity were evaluated by F-actin and Pan-cadherin immunofluorescence, respectively. The gene expression and protein levels of IL-6, Yes-associated protein, Cysteine-rich angiogenic inducer 61 (Cyr61/CCN1), and connective tissue growth factor (CTGF/CCN2) were studied by real-time polymerase chain reaction (RT-qPCR) and Western blot, respectively. Verteporfin (VP) was used to inhibit Yes-associated protein activation. The effects of 30% cyclic stretch were assessed by two-way ANOVA. Statistical significance as accepted at p < 0.05.
Results: Cyclic stretch of 30% induced YAP nuclear accumulation, activated the transcription of Yes-associated protein downstream targets Cyr61/CCN1 and CTGF/CCN2 and elevated IL-6 expression in AEC II after 1 hour, compared to static control. VP (2 µM) inhibited Yes-associated protein activation in response to 30% cyclic stretch and reduced IL-6 protein levels.
Conclusion: In rat lung L2 AEC II, 30% cyclic stretch activated YAP, and its downstream targets Cyr61/CCN1 and CTGF/CCN2 and proinflammatory IL-6 expression. Target activation was blocked by a Yes-associated protein inhibitor. This novel YAP-dependent pathway could be involved in stretch-induced damage of alveolar cells
Multi-trait point pattern reconstruction of plant ecosystems
No full text1. Plants interact locally in many ways and the processes involved (e.g. competition for resources, natural regeneration, mortality or subsequent succession) are complex. These processes give rise to characteristic spatial patterns that vary over time. The corresponding spatial data, that is the locations of individuals and their specific characteristics (e.g. trees of a certain species and their diameters), are known as point patterns, and their statistical analysis can be used to study the underlying processes and their changes due to environmental scenarios. A special application of point pattern analysis is their numerical reconstruction, which is classically used (a) to generate null models that can be contrasted with observed patterns and (b) to evaluate the information contained in observed data using various summary statistics. Sometimes, the reconstructed datasets are also used to initialise individual-based or agent-based plant models with realistic but artificially generated data in order to analyse or forecast the development of plant systems.
2. Previous reconstruction methods of point patterns consider only one mark, or they consider several marks but neglect their correlations. We introduce a method that considers individual locations and two marks simultaneously (in our example information on tree species, and diameter at breast height). The method uses different summary statistics of the second-order point pattern analysis, such as the pair correlation function and the mark correlation function. By successively modifying the reconstructed spatial pattern, the distance (also called energy), measured in terms of differences in the summary statistics between the generated pattern and the observed pattern, is minimised and a high statistical similarity is achieved.
3. After testing the method on different datasets, the suitability of our method for reconstructing complex spatial forest stands, including the spatial relationships of all considered marks, is shown.
4. The presented method is a powerful tool for generating point pattern data. With minor changes, it even enables the reconstruction of forest stands and plant systems larger than those used to collect the inventory data, and although we used two marks only to demonstrate the power of the method, it is easy to include more marks
Rethinking LoRa for the IoT: An InformationCentric Approach
No full textIn this article, we present LoRa-ICN, a new long-range communication system that provides a versatile data-oriented integration of battery-driven LoRa nodes into the Internet of Things (IoT). LoRa-ICN builds on two paradigms: information-centric networking (ICN), which enables more direct, data-oriented communication between Internet systems and the low-power wireless domain, and 802.15.4 DSME, which is an IoT MAC layer that facilitates reliable LoRa transmissions. While the combination of LoRa and DSME is generally better suited for bi-directional end-to-end communication, it still incurs considerable long and variable transmission latencies, and challenges the network layer transition between the power-constrained wireless domain and the Internet. Our design and implementation on actual off-the-shelf IoT hardware includes extensions to ICN that enable delay-tolerant data retrieval between LoRa nodes and an application on the Internet. An experimental comparison between default ICN mechanisms and our extensions shows that LoRa-ICN is able to achieve a high data delivery rate, while dealing with the higher latencies explicitly, thus providing a viable option for re-imaging LoRa networks with a data-oriented, Internet-friendly approach
Partial Brackish Water Desalination for Injection in Hydraulic Barriers and for Drinking Water Treatment
No full textGlobal water consumption is increasing continuously, while the quantity and quality of freshwater resources are decreasing simultaneously. Due to the salinization of groundwater resources in coastal and inland regions, caused by high sodium, chloride, and nitrate concentrations, these resources can no longer be used as drinking water or for irrigation without desalination. Rising sea levels and increasing groundwater abstraction cause severe coastal groundwater salinization. This process affects arid, semi-arid, and humid regions. Within the Abstraction-Desalination-Recharge methodology, saline groundwater is extracted near the coast, desalinated, and then used for inland groundwater recharge to remediate the saline aquifer. The extraction of saline groundwater acts thereby as a negative hydraulic barrier and the groundwater recharge as a positive hydraulic barrier.
This thesis analyses the suitability of different desalination processes within the Abstraction-Desalination-Recharge methodology. A multi-criteria decision analysis and cost calculation of different brackish water desalination processes were used to evaluate the application in various local and temporal scenarios for economic, ecological, technical, and social boundary conditions. Since the saline groundwater quality defined the costs and the function of the desalination, this parameter has the highest influence on the suitability of the process. Nanofiltration and brackish water reverse osmosis has the lowest costs of 0.3-0.6 €/m³ desalinating saline groundwater with a total dissolved solids concentration of 1-10 g/L. However, electrochemical desalination processes show a low energy consumption, low need for utilization of chemicals, and high process flexibility for desalination of slightly and moderately saline groundwater. In addition, the desalination performance of electrochemical processes can be optimized by using monovalent ion selective membranes.
Desalination performance, yield, and energy consumption for the partial desalination of saline groundwater were compared in lab-scale tests with nanofiltration, brackish water reverse osmosis, and membrane capacitive deionization. Depending on the process and the saline groundwater concentration, the energy consumption of desalination is 0.2‑2.9 kWh/m³ regarding a yield of 35-70% and equalled previous calculations and simulations. Membrane capacitive deionization shows a low energy consumption for low desalination requirements. However, membrane capacitive deionization is not suitable for desalination of a saline groundwater concentration above 2 g/L.
In total, full demineralization of brackish water is neither necessary nor energy efficient for groundwater recharge or for drinking water treatment and irrigation. Selective removal of monovalent ions is energetically and ecologically more profitable for brackish water desalination. However, there have been only a few studies on the energy efficiency of selective desalination of brackish water so far. In the second part of the thesis, the removal of nitrate in monovalent selective membrane capacitive deionization (mMCDI) was investigated. Nitrate can be selectively removed by using nanofiltration membranes or monovalent selective ion exchange membranes combined with suitable process settings. The specific energy consumption with modified anion exchange membranes in the mMCDI is thereby lower compared to traditional desalination processes for specific conditions. Whether the mMCDI is suitable for practical use in hydraulic barriers for the selective removal of sodium and chloride still needs to be investigated in the future.
Overall, this dissertation provides a detailed overview of the desalination performance, energy consumption, and costs for the partial desalination of brackish water for use in hydraulic barriers as well as for drinking water treatment. Important key figures for the utilization of suitable groundwater desalination techniques and the potential of selective desalination for brackish water desalination are represented. This work provides the first insights for a combined model of the desalination and transport processes in the aquifer to take a holistic view of the Abstraction-Desalination-Recharge methodology. In such a model, the use of selective monovalent ion desalination should be integrated, whereby the influence of materials and process conditions in a mixed ion system requires further research to optimize the trade-off between desalination, energy consumption and water recovery