Feature- and Structure-Preserving Network Reduction for Large-Scale Transmission Grids

Many countries are currently challenged with the extensive integration of renewable energy sources, which necessitates vast capacity expansion measures. These measures in turn require comprehensive power flow studies, which are often computationally highly demanding. In this work a reduction strategy for large-scale grid models is introduced which not only reduces the model complexity but also preserves the structure and designated grid features. The objective is to ensure that areas crucial to the behavior and the relation of all elements to their physical counterparts remain unchanged. This is accomplished through a specifically designed reduction method for suitable areas identified through topological, electrical and market-based approaches for which we provide an open-source implementation. We show that the proposed strategy adapts to various models and accomplishes a strong reduction of buses and branches while retaining a low dispatch and branch flow deviation. Furthermore, the accuracy of the reduction generalizes well to other scenarios.Comment: 13th IEEE PowerTech Conference 201

How can consumer trust in organic products be enhanced?

The study presented explores consumer trust in organic food and the effectiveness of enhancing consumer trust by communication strategies on traceability. The research is based on the general finding that trust is one of the most crucial aspects when consumer decide whether to buy or not to buy organic products. However, there are hardly any empirical works which analyse in detail consumer trust in organic food and the ways it can be enhanced. First, based on a quantitative inquiry of 600 persons in Germany the study presented investigates consumer trust in the different actors involved in the organic supply chain (farmers, processors, traders, labels), in distinct attributed qualities such as benefits for health, ecology and animal welfare as well as the customers’ criteria for assessing trustworthiness of the organic products. Empirical data is analysed by multivariate statistics such as cluster analysis to identify distinct consumer segments with respect to their trust characteristics. In a second step there will be a qualitative research method using interviews combined with a visualizing technique. The aim of this method is to understand the consumers’ attitudes towards the supply chain of organic food and the complex construct of trust better. The results shall help to develop communication strategies for enhancing consumer trust in organic food

Ten Things to Watch in Africa in 2023

Russia's war against Ukraine has accelerated international competition for influence in Africa. Structural weaknesses and post-pandemic instabilities continue to threaten achievements in the fields of democratic governance, peace and security, as well as development. We present a select list and analysis of "ten things to watch" in Africa in 2023. Politics: Democratic quality will depend on the nature of polls, as the electoral calendar is heavily packed. Important general elections that could trigger social unrest are scheduled in the Democratic Republic of the Congo, Nigeria, and Zimbabwe. Peace and security: Against the backdrop of continued structural-conflict risks, Jihadism and related ethno-regional tensions pose a major security challenge that may spill over to neighbouring states, especially from the Sahel to West African coastal countries. The recent ceasefire in Ethiopia's Tigray Region could be a first positive step towards peace. International arena: Amid Russia's war against Ukraine, many African governments were reluctant to join the international coalition condemning the Putin regime. Continued Western pressure on African countries to isolate Russia fosters African agency. At the same time, we expect to see an intensifying "new scramble for Africa" that includes both China and Middle Eastern countries. Socio-economic development: African countries will slowly rebound from the COVID-19 pandemic's socio-economic effects, but high poverty, inequality, and government debt hamper economic growth. Progress on joint efforts to counter the climate crisis remains slow. Western support for African countries in their struggle for democracy, peace and security, as well as development requires a "new start" that focuses on prevention rather than ad hoc responses to current crises. The European Union and United States should avoid lapsing into Cold War habits of only assisting African governments if they "break away" from Russia. Germany needs to formulate a sound Africa policy that balances values and national interests with realistic assessments of the policy's potential in light of bigger players like China

From Between-Person Statistics to Within-Person Dynamics

Change is the most prominent aspect of research endeavors in developmental and educational psychology. To date, preferred methods for studying change, especially those that rely on quantitative methodologies, are based on sample-based correlational analyses conducted with longitudinal panel studies. In this article we argue that research designs need to move beyond a between-person research strategy because dynamic processes occur within individual children and adolescents. The aim is to provide developmental and educational researchers with a guide to gathering and analyzing data so as to be able to answer questions about processes of change and development from a within-person perspective. Our discussion of current practices and our guidance on future research is based on a dynamic systems view on development.In entwicklungs- und pädagogisch-psychologischen Studien liegt der Fokus oft auf der Beschreibung und Erklärung von Veränderungsprozessen. Bisher stützen sich quantitative Studien in diesem Bereich typischerweise auf stichprobenbasierte Panel-Designs (Between-Person-Perspektive). Im vorliegenden Beitrag wird argumentiert, dass die Untersuchung dynamischer Veränderungsprozesse anderer Forschungsansätze bedarf, die solche Prozesse auf der Ebene des Individuums abzubilden versuchen (Within-Person-Perspektive). Ziel dieses Beitrags ist es, Forschenden, die sich mit Fragestellungen nach der Entwicklung von Kindern und Jugendlichen befassen, eine Orientierungshilfe für die Planung solcher prozessorientierten Studien zu geben. Die Diskussion bisheriger und zukünftiger Forschungsstrategien erfolgt auf der Basis Dynamischer Systemtheorien der menschlichen Entwicklung

Slow motion of quasi-stationary multi-pulse solutions by semistrong interaction in reaction-diffusion systems

In this paper, we study a class of singularly perturbed reaction-diffusion systems, which exhibit under certain conditions slowly varying multi-pulse solutions. This class contains among others the Gray-Scott and several versions of the Gierer-Meinhardt model. We first use a classical singular perturbation approach for the stationary problem and determine in this way a manifold of quasi-stationary $N$-pulse solutions. Then, in the context of the time-dependent problem, we derive an equation for the leading order approximation of the slow motion along this manifold. We apply this technique to study 1-pulse and 2-pulse solutions for classical and modified Gierer-Meinhardt system. In particular, we are able to treat different types of boundary conditions, calculate folds of the slow manifold, leading to slow-fast motion, and to identify symmetry breaking singularities in the manifold of 2-pulse solutions

Slow motion of quasi-stationary multi-pulse solutions by semistrong interaction in reaction-diffusion systems

In this paper, we study a class of singularly perturbed reaction-diffusion systems, which exhibit under certain conditions slowly varying multi-pulse solutions. This class contains among others the Gray-Scott and several versions of the Gierer-Meinhardt model. We first use a classical singular perturbation approach for the stationary problem and determine in this way a manifold of quasi-stationary $N$-pulse solutions. Then, in the context of the time-dependent problem, we derive an equation for the leading order approximation of the slow motion along this manifold. We apply this technique to study 1-pulse and 2-pulse solutions for classical and modified Gierer-Meinhardt system. In particular, we are able to treat different types of boundary conditions, calculate folds of the slow manifold, leading to slow-fast motion, and to identify symmetry breaking singularities in the manifold of 2-pulse solutions

A short primer on lung stereology

The intention of this short primer is to raise your appetite for proper quantitative assessment of lung micro-structure. The method of choice for obtaining such data is stereology. Rooted in stochastic geometry, stereology provides simple and efficient tools to obtain quantitative three-dimensional information based on measurements on nearly two-dimensional microscopic sections. In this primer, the basic concepts of stereology and its application to the lung are introduced step by step along the workflow of a stereological study. The integration of stereology in your laboratory work will help to improve its quality. In a broader context, stereology may also be seen as a contribution to good scientific practice