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Lee-Thedieck C.,Karlsruhe Institute of Technology | Lee-Thedieck C.,Max Planck Institute for Intelligent Systems (Stuttgart) | Lee-Thedieck C.,University of Heidelberg | Rauch N.,South Westphalia University of Applied Sciences | And 5 more authors.
Journal of Cell Science | Year: 2012

In the bone marrow, hematopoietic stem cells (HSCs) reside in endosteal and vascular niches. The interactions with the niches are essential for the maintenance of HSC number and properties. Although the molecular nature of these interactions is well understood, little is known about the role of physical parameters such as matrix elasticity. Osteoblasts, the major cellular component of the endosteal HSC niche, flatten during HSC mobilization. We show that this process is accompanied by osteoblast stiffening, demonstrating that not only biochemical signals but also mechanical properties of the niche are modulated. HSCs react to stiffer substrates with increased cell adhesion and migration, which could facilitate the exit of HSCs from the niche. These results indicate that matrix elasticity is an important factor in regulating the retention of HSCs in the endosteal niche and should be considered in attempts to propagate HSCs in vitro for clinical applications. © 2012. Published by The Company of Biologists Ltd.

Sinsukthavorn W.,South Westphalia University of Applied Sciences | Ortjohann E.,South Westphalia University of Applied Sciences | Mohd A.,Enecsys Micro Inverter | Hamsic N.,South Westphalia University of Applied Sciences | Morton D.,University of Bolton
IEEE Transactions on Industrial Electronics | Year: 2012

Future power distribution requires advanced expandability and flexibility in the integration of distributed energy resources which normally require interfacing units to provide the necessary crossing point to the grid. The core of these interfacing units is power-electronics grid front end, namely, inverters. The inverter is the primary interface that provides not only their principal interfacing control function but also various utility functions. This paper presents the flexible control methodology of inverters as grid front end using an isochronous control function which is used by synchronous generators in conventional power systems to provide load sharing and control. © 2012 IEEE.

Mohd A.,South Westphalia University of Applied Sciences | Ortjohann E.,South Westphalia University of Applied Sciences | Morton D.,University of Bolton | Omari O.,Arab American University - Jenin
Electric Power Systems Research | Year: 2010

This paper presents state-of-the-art review of control methods applied currently to parallel power electronic inverters. Different system architectures, their modes of operation, management and control strategies will be analyzed; advantages and disadvantages will be discussed. Though, it is not easy to give a general view at the state of the art for the research area since it is rapid and going in different directions, this paper will focus on the main streams. This paper will start by briefly reviewing the current trends in power supply systems and the increasing importance for including power electronic devices. Next, the different techniques to parallel inverters suggested in the literature will be checked. These can be categorized to the following main approaches: master/slave control techniques, current/power sharing control techniques, and frequency/voltage droop control techniques. Finally, based on the reviewed state of the art, the study concludes by comparing the different approaches reported. In addition, their weaknesses and strengths are strained. © 2010 Elsevier B.V. All rights reserved.

Platte F.,IANUS Simulation GmbH | Heise H.M.,South Westphalia University of Applied Sciences
Journal of Molecular Structure | Year: 2014

Over recent years terahertz spectroscopy has become a new tool for the characterization of solid materials, in particular for investigating polymorphism and crystallinity in pharmaceutics. Search strategies have been tested for THz spectra of various organic compounds with their spectra taken from the Riken database (http://www.riken.jp), using the GRAMS spectroscopy software. A subset of the entire database was used, which had been processed by removal of atmospheric water vapour lines and smoothing applied based on Savitzky-Golay convolution or time domain filtering. The spectral range available for all library substances was restricted to an interval from 0.9 to 4.5 THz (30-150 cm-1). The number of vibrational bands within this spectral range is much reduced compared with mid-infrared or Raman spectra. The appropriateness of spectral pre-treatment is demonstrated with regard to reliability and robustness of the search methods. In particular, time-domain filters for smoothing and pre-treatment by the removal of water lines and etalon effects have been successfully tested in combination with least squares and correlation methods. With these insights, applications for substance identification, especially for the pharmaceutical industry, may be enlarged. © 2013 Elsevier B.V. All rights reserved.

Schulze H.,South Westphalia University of Applied Sciences
IEEE Transactions on Communications | Year: 2016

The indoor wireless optical communication channel is characterised by the multiple reflections of the light from the surrounding walls. We present a new frequency-domain simulation method for this channel. In contrast to the known time-domain simulation techniques, our method is not restricted to a finite order of reflections. We show that the contributions of an infinite number of reflections can be summed up analytically to a formula that can be handled by standard numerical methods. We illustrate the method by comparing it to the results of previous time domain simulations, and we apply it to the numerical evaluation of some further model scenarios with more than one transmitter. © 2016 IEEE.

Aufderheide D.,South Westphalia University of Applied Sciences | Krybus W.,South Westphalia University of Applied Sciences
VECIMS 2010 - 2010 IEEE International Conference on Virtual Environments, Human-Computer Interfaces and Measurement Systems, Proceedings | Year: 2010

The estimation of a camera's egomotion is a highly desireable goal in many different application fields such as augmented reality (AR), visual navigation, robotics or entertainment. Especially for real-time modeling the former estimation of the camera trajectory is an elementary step towards the generation of three dimensional scene models. This paper presents a framework for simultaneous recovery of scene structure and camera motion by combining visual and inertial cues. For this purpose two different system designs are proposed: a loosely-coupled system and a monolithic design, which adapts ideas from non-linear state estimation as extended Kalman filtering (EKF) for structure and motion recovery. © 2010 IEEE.

Schwung A.,South Westphalia University of Applied Sciences
IEEE International Conference on Automation Science and Engineering | Year: 2015

This paper presents a novel approach to cyber-physical modeling of compression systems. The proposed model covers both physical as well as virtual, i.e. control components. As the modeling framework we employ hybrid automata due to their ability to conveniently handle both continuous and discrete dynamics. Simulation results comparing the proposed model with a complex real world compression system model underline the effectiveness of the approach. © 2015 IEEE.

Schulze H.,South Westphalia University of Applied Sciences
2010 International ITG Workshop on Smart Antennas, WSA 2010 | Year: 2010

We apply the Monte-Carlo simulation model to a frequency selective fading channel including space-variance. This model is suited to simulate the performance of a multi-antenna system for a moving receiver (or transmitter). It takes into account that the time-variance of the channel due to this motion has its origin in the space-variance. We emphasize that for such a channel, time and frequency correlations cannot be separated. ©2010 IEEE.

Low-cost specialization, differentiation, and diversification are common business models of urban farms in developed countries. Similarities and differences between them as well as detailed insights into specific farm characteristics are widely absent in scientific discourses. This paper compares farm structures, success factors, obstacles, clients' expectations, and policy wishes between specialized, differentiated, and diversified farms as well as diversifiers into agriculture. A standardized questionnaire was used for 21 personal in-depth farm interviews located in metropolitan areas of North Rhine-Westphalia, Germany. Being located in a metropolitan area is the most often named Unique Selling Proposition (USP). This is also mentioned as most important success factor followed by sociability and personal contact to clients, which both underpin the importance of direct producer-consumer linkages in urban settings. Additionally, it is assumed that a single food criterion is not sufficient to be successful, but several have to be merged to meet clients' expectations. In terms of marketing, differentiated and diversified farmers prefer a multi-channel approach, while specialized farmers and diversifiers into agriculture focus mainly on one specific channel. While both specialized farmers and diversifiers into agriculture cultivate smaller areas of farmland, the latter one offers the greatest number of jobs including those outside agricultural production. The findings obtained are expected to support farms and agricultural advisory services in individual decision making of future business development strategies and increase knowledge of urban farming's main business models. © 2016 by the author licensee MDPI, Basel, Switzerland.

Zandian R.,South Westphalia University of Applied Sciences | Witkowski U.,South Westphalia University of Applied Sciences
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2016

In this paper, the localisation capabilities of ultra-wideband (UWB) communication devices are evaluated. A test platform is designed to perform experiments in indoor environments, to record the data for different node set-ups and to evaluate the results in practice. The platform development comprises hardware design of the anchor and tag node, development of the PC software for communication to the nodes, collecting the measured distance data and performing localisation algorithms. At the end, some experiments are performed in both line of sight (LOS) and non-line of sight (NLOS) cases with blocking and non-blocking barriers. The experiment results confirm a distance measurement accuracy of 10 cm in LOS conditions for 85 % of the measured distances in the range of 0.5 m to 30 m. In NLOS cases an additional offset can be observed in the measurement results causing a higher relative error for short distances. © Springer International Publishing Switzerland 2016.

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