Flensburg University of Applied Sciences

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Jauch C.,Flensburg University of Applied Sciences
Wind Engineering | Year: 2016

In this article, the control strategy for a previously proposed flywheel system that is integrated in a wind turbine rotor is presented. This control strategy allows the flywheel system to serve two purposes: support of the frequency in the grid and mechanical load mitigation in the wind turbine. For the first purpose, extra energy is fed into the grid whenever there is a contingency; alternatively, the varying power output from the wind turbine can be stabilized. For the latter purpose, the flywheel is applied to detune the eigenfrequency of the most vibratory components in a wind turbine, that is, the rotor blades. Simulations are shown to illustrate the principle and the performance of the proposed system. It is concluded that the controls of the flywheel system manage to support the grid frequency and also mitigate mechanical vibrations in different operating points of the wind turbine. © The Author(s) 2016.

Jauch C.,Flensburg University of Applied Sciences
Wind Engineering | Year: 2014

In this article a wind model is presented that allows simulation of realistic wind speeds over the area of a wind farm. The primary propose of this model is power system simulations, where fast simulation speed is crucial, and where it is undesirable to use different tools to run a simulation. The proposed wind model combines the too simple wind models commonly used in power system simulations of wind turbines and a sophisticated wind model that represents the different wind speeds that occur across a wind turbine rotor. The result is a farm wind model for simulating the power system behaviour of a wind farm.

Zachow M.,Flensburg University of Applied Sciences
CEUR Workshop Proceedings | Year: 2016

Mobile applications (apps) are increasingly popular and run on a wide range of different operating systems and devices. Fragmentation is one of the differences between mobile apps and web-or desktop based applications and presents a challenge in delivering high quality apps. Automated testing can help to overcome it. This paper presents a case study on designing a continuous delivery pipeline for an Android app focused on simple setup. © Copyright 2016 for the individual papers by the papers' authors.

Mercorelli P.,Lüneburg University | Werner N.,Flensburg University of Applied Sciences
IEEE Transactions on Industrial Electronics | Year: 2016

The paper deals with an adaptive control strategy based on the resonance concept to minimize the regulation energy of a new generation of actuators for intake valves of camless engines. The new actuator contains different parts, but basically it consists of a piezo part and a hydraulic one. Even though this work considers a particular application, the solutions proposed in the paper are quite general. The regulator consists of a cascade structure which combines feedforward actions with an external resonance controller strategy. These controllers guarantee that each single part of the actuator works at the frequency given by the velocity of the revolution of the engine. The parameters of the valve controller and of its feedforward action change adaptively in accordance with any change in the velocity of the revolution of the engine. Real measurements on an intake valve of a camless engine are shown. © 2016 IEEE.

Enning B.,Flensburg University of Applied Sciences
Frequenz | Year: 2011

Two new configurations for the realization of two-tap transversal filters in 50 ω. delay line technique with cosine and sine frequency responses are proposed. Examples are given for the conversion of nonreturn-to-zero signals into partial response signals with duobinary, bipolar, and modified duobinary shape which can be applied in electrical and optical transmission systems. Calculated and measured results for Gbit/s signal processing are compared. Copyright © 2011 De Gruyter.

Wolff M.,Helmholtz Center Geesthacht | Ebel T.,Helmholtz Center Geesthacht | Dahms M.,Flensburg University of Applied Sciences
Advanced Engineering Materials | Year: 2010

Sintering of magnesium powder is strongly inhibited by a stable oxide layer that is formed immediately after exposure to air. In contrast to e.g. titanium, no solubility of oxygen in solid magnesium is reported; therefore, the oxide layer is not dissolved during sintering. In this study, different methods are investigated in order to overcome this problem. It is shown that magnesium can be sintered if the sintered parts are surrounded by magnesium getter material. Calcium additions improve sinterability. The optimum calcium content lies in the range of 0.6wt%. For a long time the sintering of Mg was known as infeasible (1), but now the current research, shown in this paper, highlights ways and means to accomplish the sintering of Mg and its alloys (2). Through the use of getter material and a labyrinth like crucible configuration, the sintering to open porous as well as closed dense parts could be accomplished. This work constitute a cornerstone for the prospective MIM of Mg and the future production of biodegradable Mg-bone implants. © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Verano-Braga T.,University of Southern Denmark | Miethling-Graff R.,Flensburg University of Applied Sciences | Wojdyla K.,University of Southern Denmark | Rogowska-Wrzesinska A.,University of Southern Denmark | And 3 more authors.
ACS Nano | Year: 2014

The use of nanoparticles in foods, materials, and clinical treatments has increased dramatically in the past decade. Because of the possibility of human exposure to nanoparticles, there is an urgent need to investigate the molecular mechanisms underlying the cellular responses that might be triggered. Such information is necessary to assess potential health risks arising from the use of nanoparticles, and for developing new formulations of next generation nanoparticles for clinical treatments. Using mass spectrometry-based proteomic technologies and complementary techniques (e.g., Western blotting and confocal laser scanning microscopy), we present insights into the silver nanoparticle-protein interaction in the human LoVo cell line. Our data indicate that some unique cellular processes are driven by the size. The 100 nm nanoparticles exerted indirect effects via serine/threonine protein kinase (PAK), mitogen-activated protein kinase (MAPK), and phosphatase 2A pathways, and the 20 nm nanoparticles induced direct effects on cellular stress, including generation of reactive oxygen species and protein carbonylation. In addition, we report that proteins involved in SUMOylation were up-regulated after exposure to 20 nm silver nanoparticles. These results were further substantiated by the observation of silver nanoparticles entering the cells; however, data indicate that this was determined by the size of the nanoparticles, since 20 nm particles entered the cells while 100 nm particles did not. © 2014 American Chemical Society.

Jauch C.,Flensburg University of Applied Sciences
Wind Energy | Year: 2015

In this paper, a flywheel energy storage that is an integral part of a wind turbine rotor is proposed. The rotor blades of a wind turbine are equipped with internal weights, which increase the inertia of the rotor. The inertia of this flywheel can be controlled by varying the position of the weights, i.e. by positioning them closer to the center of rotation (closer to the hub) or closer to the tip of the blades. The simulation model used in this study is introduced briefly. The equation system of the flywheel is set up. Finally, simulations of different scenarios show the performance of this controllable flywheel. The conclusion is that the proposed system can mitigate transients in the power output of wind turbines. Hence, it can support the frequency control in a power system by contributing to the power system inertia. Copyright © 2014 John Wiley & Sons, Ltd.

Holm M.,Helmholtz Center Geesthacht | Ebel T.,Helmholtz Center Geesthacht | Dahms M.,Helmholtz Center Geesthacht | Dahms M.,Flensburg University of Applied Sciences
Materials and Design | Year: 2013

This study presents the results of investigations on Ti-6Al-4V alloyed with 1-5. wt.% gadolinium. The Ti-6Al-4V. +. Gd samples are fabricated by metal injection moulding (MIM) using Ti-6Al-4V and elemental gadolinium powder.In previous investigations, it is shown that TiB precipitates in Ti-6Al-4V fabricated by MIM result in a microstructure refinement, while the removal of oxygen improves the ductility. Thus, rare earth elements could possibly combine both effects in one, by reacting with oxygen from the titanium matrix and by forming small oxides leading to grain refinement.Because there are actually no investigations concerning Ti-6Al-4V alloyed with gadolinium, this study mainly gives a first overview to show how the microstructure and mechanical features of Ti-6Al-4V change.In order to provide this overview, this study shows that it is possible to prepare a reasonable homogeneous powder metallurgical Ti-6Al-4V alloy with Gd additions by using the MIM-technique. Adding Gd to Ti-6Al-4V alloy powder and processing the blend by MIM leads to significant grain refinement and a slight change in pore size and shape. However, strength and ductility are reduced by the addition of Gd. © 2013 Elsevier Ltd.

Jauch C.,Flensburg University of Applied Sciences | Hippel S.,Flensburg University of Applied Sciences
IET Renewable Power Generation | Year: 2016

In this study a flywheel (FW) system, which is integrated in the rotor of a wind turbine (WT), is proposed. It is made of hydraulic-pneumatic piston accumulators and its primary purpose is to provide the power system with inertia. Power system inertia is an essential premise for primary frequency control. The equations describing the system are presented. Simulation results show that the performance of such a FW system is superior to the commonly used approach of using WTs to provide the power system with so-called synthetic inertia.

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