Technical University of Dortmund

About: Technical University of Dortmund is a education organization based out in Dortmund, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Large Hadron Collider & Neutrino. The organization has 13028 authors who have published 27666 publications receiving 615557 citations. The organization is also known as: Dortmund University & University of Dortmund.

Recommendations with a Purpose

Abstract: The purpose of recommenders is often summarized as "help the users find relevant items", and the predominant operationalization of this goal has been to focus on the ability to numerically estimate the users' preferences for unseen items or to provide users with item lists ranked in accordance to the estimated preferences. This dominant, albeit narrow, view of the recommendation problem has been tremendously helpful in advancing research in different ways, e.g., through the establishment of standardized evaluation procedures and metrics. In reality, recommender systems can serve a variety of purposes from the point of view of both consumers and providers. Most of the purposes, however, are significantly underexplored, even though many of them are arguably more aligned with the real-world expectations for recommenders than our current predominant paradigm. Therefore, it is important to revisit our conceptualizations of the potential goals of recommenders and their operationalization as research problems. In this paper, we discuss a framework of recommendation goals and purposes and highlight possible future directions and challenges related to the operationalization of such alternative problem formulations.

A Virtual Synchronous Generator Control Strategy for VSC-MTDC Systems

Abstract: With the rapid increase of renewable energy sources and power electronic converters in the power system, the inertia of the power system is declined and the stability problem is more serious than ever before. In this paper, a virtual synchronous generator (VSG) control strategy is proposed to enable the voltage-source converter-based multiterminal high-voltage direct current (VSC-MTDC) system to damp the low-frequency oscillation modes. Both rotational inertia part and governor part are modeled in the VSG controller. The $V^2-P-\omega$ characteristic is developed based on the $V^2-P$ droop control to emulate the action of the speed governor when the frequency of ac grid deviates from the nominal value. The virtual inertia part is used to emulate the inertia response of the synchronous generator. The communication between VSC stations is unnecessary with the autonomous power allocation ability of the $V^2-P-\omega$ characteristic. Modal analysis is utilized to test the system stability and optimize the controller parameters. Two test systems which include offshore wind farms, VSC-MTDC systems, and onshore power grids are built in the DIgSIENT/PowerFactory. The simulation results verify the effectiveness of the proposed VSG strategy.

Endocrine Disruptors : Update on Xenoestrogens

Abstract: Endocrine disruptors and their possible impact on human and animal health have become a topic of discussion and an area of active research in toxicology. A focus has been on xenoestrogens, i.e., environmental chemicals with estrogenic activity. In principle, there is agreement that such compounds, in high doses, may cause developmental, reproductive and tumorigenic effects (“hazard”). A matter of controversy is the question of risks associated with xenoestrogens under realistic (low) exposure scenarios; this is due to uncertainty on how to assess the interactions of exogenous compounds with the endocrine system and its complex regulation. Our overview will address topics including: consequences from previous clinical use of the potent estrogen diethyl- stilbestrol with particular emphasis on dose-response relationships, other observations in humans exposed to estrogenic chemicals in an occupational context, and available information on exposure levels of synthetic and naturally occurring estrogens in the diet. Together with a critical appraisal of methods to detect and quantitate the estrogenic activity of synthetic and naturally occurring chemicals, novel aspects in the risk assessment for endocrine active compounds are discussed.