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De Gersem H.,Wave Group
IEEE Transactions on Magnetics | Year: 2010

The performance of a magnetic brake is calculated by a cross-sectional model where stator and air gap are discretized by finite elements, whereas the nonlinear ferromagnetic rotor is discretized by spectral elements, in order to guarantee a sufficient resolution of the thin eddy-current layers. © 2006 IEEE. Source

Kaseyama T.,Japan National Institute of Materials Science | Kaseyama T.,University of Tsukuba | Furumi S.,Wave Group | Zhang X.,Japan National Institute of Materials Science | And 3 more authors.
Angewandte Chemie - International Edition | Year: 2011

(Figure Presented) High in fiber: 1D fibrous superstructures are formed by an enantiopure phthalhydrazide-functionalized helicene in nonpolar solvents. Trimeric disks are formed by hydrogen-bonding interactions of phthalhydrazide units that are longitudinally interlocked for optimal packing (see picture). The resulting supramolecular assemblies exhibited large circularly polarized luminescence in solution. © 2011 Wiley-VCH Verlag GmbH & Co. KGaA. Source

This article describes a brief review of recent research advances in chiral liquid crystals (CLCs) for laser applications. The CLC molecules have an intrinsic capability to spontaneously organize supramolecular helical assemblages consisting of liquid crystalline layers through their helical twisting power. Such CLC supramolecular helical structures can be regarded as one-dimensional photonic crystals (PhCs). Owing to their supramolecular helical structures, the CLCs show negative birefringence along the helical axis. Selective reflection of circularly polarized light is the most unique and important optical property in order to generate internal distributed feedback effect for optically-excited laser emission. When a fluorescent dye is embedded in the CLC medium, optical excitation gives rise to stimulated laser emission peak(s) at the band edge(s) and/or within the CLC selective reflection. Furthermore, the optically-excited laser emission peaks can be controlled by external stimuli through the self-organization of CLC molecules. This review introduces the research background of CLCs carried out on the PhC realm, and highlights intriguing precedents of various CLC materials for laser applications. It would be greatly advantageous to fabricate active CLC laser devices by controlling the supramolecular helical structures. Taking account of the peculiar features, we can envisage that a wide variety of supramolecular helical structures of CLC materials will play leading roles in next-generation optoelectronic molecular devices. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Published online in Wiley InterScience DOI 10.1002/tcr.201000013Recent developments of chiral liquid crystals (CLCs) that can be used for a wide variety of laser applications are discussed. Liquid crystal compounds with molecular chirality have an intrinsic capability to self-organize the supramolecular helical assemblages, which are 1D periodic structures possessing characteristic optical properties. Tailoring the CLC materials and device structures enables a variety of applications in next-generation molecular optoelectronic devices. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Source

Teppati V.,Polytechnic University of Turin | Bolognesi C.R.,Wave Group
IEEE Transactions on Instrumentation and Measurement | Year: 2012

In this paper, a thorough evaluation of calibration residual uncertainty of on-wafer load-pull systems at millimeterwave frequencies, with actual comparisons between real-time and non-real-time load-pull systems, is reported for the first time. Two figures of merit for uncertainty evaluation are taken into account, showing the differences between the two methodologies. In the case of non-real-time systems, based on a simulation tool developed for the purpose, typical values of uncertainties to be expected at millimeter-wave frequencies are shown. Finally, a methodology to reduce calibration residual uncertainty of nonreal- time load-pull measurements, based on the optimization of a thru load-pull map, is for the first time introduced, and its effects on actual measurements of microwave HBTs at 40 GHz are shown. © 2012 IEEE. Source

Decaestecker E.,Catholic University of Leuven | De Gersem H.,Wave Group | Michalakis Y.,IRD Montpellier | Raeymaekers J.A.M.,Catholic University of Leuven | Raeymaekers J.A.M.,University of Basel
Ecology Letters | Year: 2013

An increase in biological diversity leads to a greater stability of ecosystem properties. For host-parasite interactions, this is illustrated by the 'dilution effect': a negative correlation between host biodiversity and disease risk. We show that a similar mechanism might stabilise host-parasite dynamics at a lower level of diversity, i.e. at the level of genetic diversity within host species. A long-term time shift experiment, based on a historical reconstruction of a Daphnia-parasite coevolution, reveals infectivity cycles with more stable amplitude in experienced than in naive hosts. Coevolutionary models incorporating an increase in host allelic diversity over time explain the detected asymmetry. The accumulation of resistance alleles creates an opportunity for the host to stabilise Red Queen dynamics. It leads to a larger arsenal enhancing the host performance in its coevolution with the parasite in which 'it takes all the running both antagonists can do to keep in the same place'. © 2013 John Wiley & Sons Ltd/CNRS. Source

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