Development of an ecohydrological model at the catchment scale and application in the humid tropics

Ziel der Dissertation war die Entwicklung eines prozessorientierten, ökohydrologischen Modellsystems, das nicht nur den Anforderungen in gemäßigten, sondern auch in tropischen Klimaten gerecht wird. Dieses war auf das in den sommerfeuchten Tropen in Südvietnam gelegene Thi Vai Einzugsgebiet anzuwenden, zu testen sowie für Prognosen zu verwenden. Als besondere Herausforderung für die ökohydrologische Modellierung in den sommerfeuchten Tropen sind die extremen meteorologischen Randbedingungen, die intensive Nutzung des Einzugsgebietes und die geringe Datenlage anzusehen. Hierzu wurde das bestehende hydrologische Modellsystem PANTA RHEI unter anderem um die Module terrestrischer, biogeochemischer Stoffkreislauf (CNP-Modul), Pflanzenwachstum und Wasserqualität erweitert. Das entwickelte ökohydrologische Modellsystem umfasst Wasserqualitätsroutinen, die eine Interaktion zwischen der aquatischen Biomasse, Sauerstoff, Nährstoffen, Detritus und Sediment berücksichtigen. Darüber hinaus werden differenzierte Stoffformen betrachtet und ein Rechenzeitschritt unter einem Tag ermöglicht. Das implementierte Wasserqualitätsmodell schließt Defizite, die bei gängigen ökohydrologischen Modellen auftreten. Daher kann über eine rein frachtbezogene Betrachtung hinausgegangen werden. Da zu Beginn der Studie nahezu keine Daten zur Wasserquantität und -qualität des Einzugsgebietes vorlagen, wurde ein Monitoringprogramm initialisiert. Unter anderem wurden die Wasserqualitätsparameter DO, NH4, NO2, NO3, PO4 sowie TSS erhoben. Die Ergebnisse der Modellkalibrierung zeigen, dass das entwickelte Modellsystem in der Lage ist, die Hydrologie und Wasserqualität der untersuchten Teileinzugsgebiete abzubilden. Eine Sensitivitätsanalyse hat gezeigt, dass die Wasserqualitätsprozesse von Stickstoff besonders durch die Prozesse auf der Landphase geprägt werden. Mittels des entwickelten CNP-Modules konnte die charakteristische Dynamik der Mineralisierung in den sommerfeuchten Tropen plausibel nachgebildet werden. Neben dem verwendeten Verfügbarkeits-Bedarfs-Ansatz, der die Zwischenspeicherung von Nährstoffen in der mikrobiellen Biomasse berücksichtigt, sind die verwendeten Bodenfeuchte-Funktionen von Bedeutung. Weitere Schlüsselkomponenten sind die Prozessgleichungen des Periphytons und die Berücksichtigung von Sedimentkompartimenten. Des Weiteren wurden weitere Anwendungsmöglichkeiten sowie die Prognosefähigkeit des Modellsystems mit veränderten Randbedingungen aufgezeigt.The objective of the dissertation was the development of a process-based, ecohydrological model that meets the requirements of temperate and tropic climates. The developed model was applied to the catchment of the Thi Vai Estuary, which is located in the humid tropics in South Vietnam. It was the aim to test and investigate the predictive power of the developed model. Ecohydrological modeling in the humid tropics is challenging because of extreme meteorological conditions, the high anthropogenic pressure in the investigated catchment and poor data availability. For this purpose, the existing hydrological model PANTA RHEI was, among others, extended with additional modules to simulate terrestrial biochemical cycles (CNP-Module), plant growth and management as well as water quality. The developed ecohydrological model includes water quality procedures, accounting for the interaction of aquatic biomass, dissolved oxygen, nutrients, detritus and sediment. Therefore, the implemented water quality model overcomes deficits found in common ecohydrological models. Additionally differentiated substances are considered and a sub-daily calculation time step is possible. Therefore not only loads but also concentrations can be investigated. At the beginning of the study nearly no data on water quantity and quality was available for the catchment. Hence, a monitoring program was initialized. Among others, the water quality parameters DO, NH4, NO2, NO3, PO4 and TSS, were measured. The simulation results show that the developed model is capable to simulate the hydrology and water quality of the investigated catchment. A sensitivity analysis demonstrated that the water quality of nitrogen is dominated by terrestrial transformation processes. The developed CNP-module is able to simulate the characteristic dynamics of mineralization typically observed in the humid tropics. Beside the implemented Availability and Demand Approach, which is accounting for a temporary storage of nutrients in the microbial biomass, the implemented moisture functions are of particular importance. The consideration of sediment compartments and processes related to periphyton activity were key components in the water quality modeling of the catchment. Furthermore, possible applications and the predictive power of the model under altered boundary conditions were demonstrated by the application on the Thi Vai catchment

Social comparison effects on academic self-concepts-Which peers matter most?

Social comparisons with peers are important sources of self-development during adolescence. Many previous studies showed that students' academic self-concepts (ASC) form by contrasting one's own achievement with the average of one's class or school (the Big-Fish-Little-Pond Effect [BFLPE]). Based on social comparison theory, however, we would expect some peers to be more likely social comparison targets than other peers, for example, because they are more visible or students perceive them as similar to themselves. In this study, we used sociometric data to analyze which peers play the most important role for social comparison effects on ASC. We examined how the average achievement of friends, study partners, peers perceived as popular by the student, as well as same-gender and same-ethnic peers affect the general ASC and how these effects compare to the effect of the classroom's average achievement. The study was based on a German longitudinal sample of 2,438 students (44% no recent immigrant background, 19% Turkish immigrant background, 10% Eastern European immigrant background, 27% other immigrant background) from 117 school classes that were followed from grade 9 to 10. Results from longitudinal social network analysis do not confirm substantial incremental effects of specific types of peers, while class average achievement showed a stable negative effect (confirming the BFLPE). In addition, we could provide evidence for social selection effects based on ASC. We conclude that classrooms provide a specific setting that imposes social comparisons with the "generalized peer" rather than with specific subgroups of peers. (PsycInfo Database Record (c) 2022 APA, all rights reserved)

Multivariate statistical assessment of a polluted river under nitrification inhibition in the tropics.

A large complex water quality data set of a polluted river, the Tay Ninh River, was evaluated to identify its water quality problems, to assess spatial variation, to determine the main pollution sources, and to detect relationships between parameters. This river is highly polluted with organic substances, nutrients, and total iron. An important problem of the river is the inhibition of the nitrification. For the evaluation, different statistical techniques including cluster analysis (CA), discriminant analysis (DA), and principal component analysis (PCA) were applied. CA clustered 10 water quality stations into three groups corresponding to extreme, high, and moderate pollution. DA used only seven parameters to differentiate the defined clusters. The PCA resulted in four principal components. The first PC is related to conductivity, NH4-N, PO4-P, and TP and determines nutrient pollution. The second PC represents the organic pollution. The iron pollution is illustrated in the third PC having strong positive loadings for TSS and total Fe. The fourth PC explains the dependence of DO on the nitrate production. The nitrification inhibition was further investigated by PCA. The results showed a clear negative correlation between DO and NH4-N and a positive correlation between DO and NO3-N. The influence of pH on the NH4-N oxidation could not be detected by PCA because of the very low nitrification rate due to the constantly low pH of the river and because of the effect of wastewater discharge with very high NH4-N concentrations. The results are deepening the understanding of the governing water quality processes and hence to manage the river basins sustainably

The Link between Social and Structural Integration: Co- and Interethnic Friendship Selection and Social Influence within Adolescent Social Networks

Assimilation theories argue that social ties with majority-group members enhance the structural integration of ethnic minority members, whereas under certain conditions, coethnic social ties can also benefit minority members’ socioeconomic outcomes. We examine these propositions through a social network perspective, focusing on friendship networks and educational expectations in adolescence, during which peer socialization is crucial. Longitudinal data from 1,992 adolescents in 91 classrooms allow us to investigate co- and interethnic social selection and social influence processes as well as their aggregated outcomes. In terms of friendship selection, we find that Turkishorigin minority adolescents in Germany have distinct preferences for friends with high educational expectations, among both co- and interethnic peers. In contrast, social influence on Turkish-minority adolescents’ educational expectations is not uniform: only majority-group friends exert a significant (positive) influence. Our results emphasize that bridging social capital gained from social ties with majority-group members enhances ethnic minority adolescents’ educational integration

Discovering Water Quality Changes and Patterns of the Endangered Thi Vai Estuary in Southern Vietnam through Trend and Multivariate Analysis

Temporal and spatial water quality data are essential to evaluate human health risks. Understanding the interlinking variations between water quality and socio-economic development is the key for integrated pollution management. In this study, we applied several multivariate approaches, including trend analysis, cluster analysis, and principal component analysis, to a 15-year dataset of water quality monitoring (1999 to 2013) in the Thi Vai estuary, Southern Vietnam. We discovered a rapid improvement for most of the considered water quality parameters (e.g., DO, NH4, and BOD) by step trend analysis, after the pollution abatement in 2008. Nevertheless, the nitrate concentration increased significantly at the upper and middle parts and decreased at the lower part of the estuary. Principal component (PC) analysis indicates that nowadays the water quality of the Thi Vai is influenced by point and diffuse pollution. The first PC represents soil erosion and stormwater loads in the catchment (TSS, PO4, and Fetotal); the second PC (DO, NO2, and NO3) determines the influence of DO on nitrification and denitrification; and the third PC (pH and NH4) determines point source pollution and dilution by seawater. Therefore, this study demonstrated the need for stricter pollution abatement strategies to restore and to manage the water quality of the Thi Vai Estuary

Simulation assisted process chain design for the manufacturing of bulk hybrid shafts with tailored properties

To manufacture semi-finished hybrid workpieces with tailored properties, a finite element simulation assisted process chain design was investigated. This includes the process steps of cross wedge rolling, hot geometry inspection, induction hardening, and fatigue testing. The process chain allows the utilisation of material combinations such as high-strength steels with low-cost and easy to process steels. Here, plasma transferred arc welding is applied to supply the process chain with hybrid specimen featuring different steel grades. An overview of the numerical approaches to consider the various physical phenomena in each of the process steps is presented. The properties of the component behaviour were investigated via the finite element method (FEM) and theoretical approaches. At first, the manufacturing of a hybrid workpiece featuring a near net shape geometry with improved mechanical properties due to recrystallising the weld was computed, using the example of a cross wedge rolling process. The rolling process was designed by means of FEM to determine suitable process parameters and to reduce experimental testing. An optical multi-scale geometry inspection of the hot workpiece is meant to be carried out after each manufacturing step to detect potential undesired forming or cooling-induced deformations. Due to the heat transfer from the hot component to the ambient medium, an optical measurement is affected by the developing inhomogeneous refractive index field in air. To gain a basic understanding of the refractive index field and induced light deflection effects, computations were conducted using heat transfer and ray tracing simulations. According to the proposed process route, a subsequent local heat treatment of the hybrid component is required to adapt the mechanical properties by a spray cooling assisted induction hardening. The heat treatment step was computed via a 2D FEM calculation. After finishing by machining, the hybrid material shafts are examined in fatigue tests under load conditions. To predict the component’s lifetime under rolling contact fatigue, a damage accumulation model was combined with an FE simulation. The resulting residual stress state after quenching and the geometry after the finishing process were used as input data for the fatigue life calculations

Interdisziplinäre Studienprojekte gestalten: Aus der Praxis für die Praxis

In dem Praxisband werden Konzepte und praktische Umsetzung von fachbereichsübergreifenden Studienprojekten dokumentiert. Grundlage ist das Know-how aus über 30 interdisziplinären Projekten für 10 000 Studierende an der Technischen Universität Darmstadt. Die Publikation wendet sich an Lehrende, Hochschuldidaktiker sowie Lehr- und Studiengangentwickler. Das Autorenteam führt in das didaktische Konzept ein und erläutert die Gestaltung interdisziplinärer Wochen-, Semester- und Kleingruppenprojekte. Schwerpunkte der weiteren Kapitel sind die Qualifizierung von Studienprojekt-Tutoren sowie der strukturelle Rahmen für die flächendeckende Einführung von interdisziplinären Studienprojekten. Zahlreiche Übersichten, Checklisten, Beispiele und Vorlagen erleichtern die Umsetzung in die Praxis.The practical handbook documents concepts and practical implementation of interdepartmental study projects. It is based on know-how from more than 30 interdisciplinary projects for 10,000 students at Technische Universität Darmstadt. The publication is intended for teaching staff, university educationalists, as well as course developers. The team of authors gives an introduction to the didactic concept and explains the design of interdisciplinary weekly and semesterly projects and projects in small groups. Other chapters focus on qualification of study project tutors, as well as structural frameworks for comprehensive introduction of interdisciplinary study projects. Practical implementation is facilitated by numerous overviews, checklists, examples and models

Common Warming Pattern Emerges Irrespective of Forcing Location

The Earth's climate is changing due to the existence of multiple radiative forcing agents. It is under question whether different forcing agents perturb the global climate in a distinct way. Previous studies have demonstrated the existence of similar climate response patterns in response to aerosol and greenhouse gas (GHG) forcings. In this study, the sensitivity of tropospheric temperature response patterns to surface heating distributions is assessed by forcing an atmospheric general circulation model coupled to an aquaplanet slab ocean with a wide range of possible forcing patterns. We show that a common climate pattern emerges in response to localized forcing at different locations. This pattern, characterized by enhanced warming in the tropical upper troposphere and the polar lower troposphere, resembles the historical trends from observations and models as well as the future projections. Atmospheric dynamics in combination with thermodynamic air-sea coupling are primarily responsible for shaping this pattern. Identifying this common pattern strengthens our confidence in the projected response to GHG and aerosols in complex climate models

From dynamical scaling to local scale-invariance: a tutorial

Dynamical scaling arises naturally in various many-body systems far from equilibrium. After a short historical overview, the elements of possible extensions of dynamical scaling to a local scale-invariance will be introduced. Schr\"odinger-invariance, the most simple example of local scale-invariance, will be introduced as a dynamical symmetry in the Edwards-Wilkinson universality class of interface growth. The Lie algebra construction, its representations and the Bargman superselection rules will be combined with non-equilibrium Janssen-de Dominicis field-theory to produce explicit predictions for responses and correlators, which can be compared to the results of explicit model studies. At the next level, the study of non-stationary states requires to go over, from Schr\"odinger-invariance, to ageing-invariance. The ageing algebra admits new representations, which acts as dynamical symmetries on more general equations, and imply that each non-equilibrium scaling operator is characterised by two distinct, independent scaling dimensions. Tests of ageing-invariance are described, in the Glauber-Ising and spherical models of a phase-ordering ferromagnet and the Arcetri model of interface growth.Comment: 1+ 23 pages, 2 figures, final for