@article{4831, abstract = {{Polarization of light is essential for some living organisms and many optical applications. Here, an orientation dependent polarization conversion effect is reported for light reflected from diamond‐structure‐based photonic crystals (D‐structure) inside the scales of a beetle, the weevil Entimus imperialis. When linearly polarized light propagates along its 〈100〉 directions, the D‐structure behaves analogous to a half‐wave plate in reflection but based on a different mechanism. The D‐structure rotates the polarization direction of linearly polarized light, and reflects circularly polarized light of both handednesses without changing it. This polarization effect is different from circular dichroism occurring in chiral biological photonic structures discovered before. The structural origin of this effect is symmetry breaking inside D‐structure's unit cell. This finding demonstrates that natural photonic structures can exploit multiple functionalities inherent to the design principles of their structural organization. Aiming at transferring the inherent polarization effect of the biological D‐structure to technically realizable materials, three simplified biomimetic structural models are derived and it is theoretically demonstrated that they retain the effect. Out of these structures, functioning woodpile structure prototypes are fabricated.}}, author = {{Wu, Xia and Rodríguez-Gallegos, Fernando L. and Heep, Marie-Christin and Schwind, Bertram and Li, Guixin and Fabritius, Helge-Otto and von Freymann, Georg and Förstner, Jens}}, issn = {{2195-1071}}, journal = {{Advanced Optical Materials}}, keywords = {{tet_topic_phc, tet_topic_bio}}, number = {{24}}, pages = {{1800635}}, publisher = {{Wiley}}, title = {{{Polarization Conversion Effect in Biological and Synthetic Photonic Diamond Structures}}}, doi = {{10.1002/adom.201800635}}, volume = {{6}}, year = {{2018}}, } @article{4165, abstract = {{Metal nanoparticles host localized plasmon excitations that allow the manipulation of optical fields at the nanoscale. Despite the availability of several techniques for imaging plasmons, direct access into the symmetries of these excitations remains elusive, thus hindering progress in the development of applications. Here, we present a combination of angle-, polarization-, and space-resolved cathodoluminescence spectroscopy methods to selectively access the symmetry and degeneracy of plasmonic states in lithographically fabricated gold nanoprisms. We experimentally reveal and spatially map degenerate states of multipole plasmon modes with nanometer spatial resolution and further provide recipes for resolving optically dark and out-of-plane modes. Full-wave simulations in conjunction with a simple tight-binding model explain the complex plasmon structure in these particles and reveal intriguing mode-symmetry phenomena. Our approach introduces systematics for a comprehensive symmetry characterization of plasmonic states in high-symmetry nanostructures.}}, author = {{Myroshnychenko, Viktor and Nishio, Natsuki and García de Abajo, F. Javier and Förstner, Jens and Yamamoto, Naoki}}, issn = {{1936-0851}}, journal = {{ACS Nano}}, keywords = {{tet_topic_plasmonics}}, number = {{8}}, pages = {{8436--8446}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Unveiling and Imaging Degenerate States in Plasmonic Nanoparticles with Nanometer Resolution}}}, doi = {{10.1021/acsnano.8b03926}}, volume = {{12}}, year = {{2018}}, } @article{4324, abstract = {{We study the dependence of the intensity and linear polarization of light scattered by isolated particles with the compact irregular shape on their size using the discontinuous Galerkin time domain numerical method. The size parameter of particles varies in the range of X = 10 to 150, and the complex refractive index is m = 1.5 + 0i. Our results show that the backscattering negative polarization branch weakens monotonously, but does not disappear at large sizes, up to the geometrical optics regime, and can be simulated without accounting for wave effects. The intensity backscattering surge becomes narrower with increasing particle size. For X = 150, the surge width is several degrees.}}, author = {{Grynko, Yevgen and Shkuratov, Yuriy and Förstner, Jens}}, issn = {{0146-9592}}, journal = {{Optics Letters}}, keywords = {{tet_topic_scattering}}, number = {{15}}, pages = {{3562}}, publisher = {{The Optical Society}}, title = {{{Intensity surge and negative polarization of light from compact irregular particles}}}, doi = {{10.1364/ol.43.003562}}, volume = {{43}}, year = {{2018}}, } @inproceedings{5469, abstract = {{In diesem Beitrag werden simulatorische und messtechnische EMV-Untersuchungen von Gleichspannungswandlern vorgestellt. Der Fokus liegt auf leitungsgeführten Störspannungen, ihre Abhängigkeit vom Schaltungslayout und ihre Unterdrückung durch Filterung. Der Simulationsprozess besteht aus kombinierten Feld- und Netzwerksimulationen. Zur Bewertung der Simulationsresultate werden zwei Prototypen gezeigt, die gute und schlechte EMV-Eigenschaften aufweisen. Bei der Beurteilung der Resultate wird insbesondere Wert auf die Untersuchung gelegt, inwieweit einfache Schaltungssimulationen ausreichen, um leitungsgeführte Störspannungen korrekt vorherzusagen und wann aufwändigere Feldsimulationen notwendig sind.}}, author = {{Baumgarten, Tim and Scholz, Peter and Sievers, Denis and Förstner, Jens}}, booktitle = {{Elektromagnetische Verträglichkeit - Internationale Fachmesse und Kongress 2018}}, editor = {{Garbe, Heyno}}, isbn = {{978-3-95735-077-0}}, location = {{Düsseldorf}}, pages = {{47}}, title = {{{Simulation leitungsgeführter Störspannungen von DC-DC-Wandlern}}}, year = {{2018}}, } @article{6525, author = {{Krauter, Stefan}}, journal = {{Solar Energy}}, pages = {{768–776}}, title = {{{Simple and effective methods to match photovoltaic power generation to the grid load profile for a PV based energy system.}}}, volume = {{159}}, year = {{2018}}, } @article{6562, author = {{Feldmann, Nadine and Jurgelucks, Benjamin and Claes, Leander and Schulze, Veronika and Henning, Bernd and Walther, Andrea}}, journal = {{tm - Technisches Messen}}, number = {{2}}, pages = {{59--65}}, publisher = {{Walter de Gruyter GmbH}}, title = {{{An inverse approach to the characterisation of material parameters of piezoelectric discs with triple-ring-electrodes}}}, doi = {{10.1515/teme-2018-0066}}, volume = {{86}}, year = {{2018}}, } @article{6567, author = {{Johannesmann, Sarah and Düchting, Julia and Webersen, Manuel and Claes, Leander and Henning, Bernd}}, issn = {{0171-8096}}, journal = {{tm - Technisches Messen}}, keywords = {{Continous-fibre reinforced plastics, material parameters, orthotropy, ultrasonics}}, number = {{85}}, pages = {{478--486}}, title = {{{An acoustic waveguide-based approach to the complete characterisation of linear elastic, orthotropic material behaviour}}}, doi = {{10.1515/teme-2017-0132}}, volume = {{2018}}, year = {{2018}}, } @inproceedings{6568, author = {{Johannesmann, Sarah and Brockschmidt, Tobias and Rump, Friedhelm and Webersen, Manuel and Claes, Leander and Henning, Bernd}}, booktitle = {{Sensoren und Messsysteme}}, pages = {{231--234}}, publisher = {{VDE Verlag GmbH}}, title = {{{Acoustic material characterization of prestressed, plate-shaped specimens}}}, year = {{2018}}, } @article{6577, author = {{Webersen, Manuel and Johannesmann, Sarah and Düchting, Julia and Claes, Leander and Henning, Bernd}}, journal = {{Ultrasonics}}, pages = {{53--62}}, title = {{{Guided ultrasonic waves for determining effective orthotropic material parameters of continuous-fiber reinforced thermoplastic plates}}}, doi = {{10.1016/j.ultras.2017.10.005}}, volume = {{84}}, year = {{2018}}, } @inproceedings{6578, author = {{Webersen, Manuel and Johannesmann, Sarah and Düchting, Julia and Claes, Leander and Henning, Bernd}}, booktitle = {{Fortschritte der Akustik - DAGA 2018}}, pages = {{1263--1266}}, title = {{{Akustische Charakterisierung der richtungsabhängigen elastischen Eigenschaften faserverstärkter Kunststoffe}}}, year = {{2018}}, } @inproceedings{6584, author = {{Feldmann, Nadine and Henning, Bernd}}, booktitle = {{Fortschritte der Akustik}}, pages = {{1275--1278}}, title = {{{Efficient optimisation of initial values for characterising piezoelectric material parameters}}}, year = {{2018}}, } @inproceedings{6586, author = {{Thiel, Christian and Feldmann, Nadine and Henning, Bernd}}, booktitle = {{Sensoren und Messsysteme 2018}}, pages = {{536--539}}, publisher = {{VDE Verlag GmbH}}, title = {{{Extraction of Interpretable Features from Temporal Measurements using Approximate Prototypes}}}, year = {{2018}}, } @misc{6593, author = {{Claes, Leander and Feldmann, Nadine and Henning, Bernd}}, title = {{{Materialparameter von bleihaltigen und bleifreien Piezokeramiken und ihre Bedeutung in der Anwendung}}}, year = {{2018}}, } @misc{6594, author = {{Claes, Leander and Zeipert, Henning and Koppa, Peter and Tröster, Thomas and Henning, Bernd}}, title = {{{Additiv gefertigte, akustische Diffusor-Strukturen für Ultraschallanwendungen}}}, year = {{2018}}, } @misc{6595, author = {{Feldmann, Nadine and Jurgelucks, Benjamin and Claes, Leander and Henning, Bernd}}, title = {{{Vollständige Charakterisierung von piezoelektrischen Scheiben mit Ringelektroden}}}, year = {{2018}}, } @misc{6596, author = {{Webersen, Manuel and Johannesmann, Sarah and Brockschmidt, Tobias and Rump, Friedhelm and Claes, Leander and Henning, Bernd}}, title = {{{Einfluss mechanischer Vorspannung auf das mechanische Materialverhalten von Polymeren}}}, year = {{2018}}, } @inproceedings{11760, abstract = {{Acoustic event detection, i.e., the task of assigning a human interpretable label to a segment of audio, has only recently attracted increased interest in the research community. Driven by the DCASE challenges and the availability of large-scale audio datasets, the state-of-the-art has progressed rapidly with deep-learning-based classi- fiers dominating the field. Because several potential use cases favor a realization on distributed sensor nodes, e.g. ambient assisted living applications, habitat monitoring or surveillance, we are concerned with two issues here. Firstly the classification performance of such systems and secondly the computing resources required to achieve a certain performance considering node level feature extraction. In this contribution we look at the balance between the two criteria by employing traditional techniques and different deep learning architectures, including convolutional and recurrent models in the context of real life everyday audio recordings in realistic, however challenging, multisource conditions.}}, author = {{Ebbers, Janek and Nelus, Alexandru and Martin, Rainer and Haeb-Umbach, Reinhold}}, booktitle = {{DAGA 2018, München}}, title = {{{Evaluation of Modulation-MFCC Features and DNN Classification for Acoustic Event Detection}}}, year = {{2018}}, } @inproceedings{11835, abstract = {{Signal dereverberation using the weighted prediction error (WPE) method has been proven to be an effective means to raise the accuracy of far-field speech recognition. But in its original formulation, WPE requires multiple iterations over a sufficiently long utterance, rendering it unsuitable for online low-latency applications. Recently, two methods have been proposed to overcome this limitation. One utilizes a neural network to estimate the power spectral density (PSD) of the target signal and works in a block-online fashion. The other method relies on a rather simple PSD estimation which smoothes the observed PSD and utilizes a recursive formulation which enables it to work on a frame-by-frame basis. In this paper, we integrate a deep neural network (DNN) based estimator into the recursive frame-online formulation. We evaluate the performance of the recursive system with different PSD estimators in comparison to the block-online and offline variant on two distinct corpora. The REVERB challenge data, where the signal is mainly deteriorated by reverberation, and a database which combines WSJ and VoiceHome to also consider (directed) noise sources. The results show that although smoothing works surprisingly well, the more sophisticated DNN based estimator shows promising improvements and shortens the performance gap between online and offline processing.}}, author = {{Heymann, Jahn and Drude, Lukas and Haeb-Umbach, Reinhold and Kinoshita, Keisuke and Nakatani, Tomohiro}}, booktitle = {{IWAENC 2018, Tokio, Japan}}, title = {{{Frame-Online DNN-WPE Dereverberation}}}, year = {{2018}}, } @inproceedings{11837, abstract = {{We present a block-online multi-channel front end for automatic speech recognition in noisy and reverberated environments. It is an online version of our earlier proposed neural network supported acoustic beamformer, whose coefficients are calculated from noise and speech spatial covariance matrices which are estimated utilizing a neural mask estimator. However, the sparsity of speech in the STFT domain causes problems for the initial beamformer coefficients estimation in some frequency bins due to lack of speech observations. We propose two methods to mitigate this issue. The first is to lower the frequency resolution of the STFT, which comes with the additional advantage of a reduced time window, thus lowering the latency introduced by block processing. The second approach is to smooth beamforming coefficients along the frequency axis, thus exploiting their high interfrequency correlation. With both approaches the gap between offline and block-online beamformer performance, as measured by the word error rate achieved by a downstream speech recognizer, is significantly reduced. Experiments are carried out on two copora, representing noisy (CHiME-4) and noisy reverberant (voiceHome) environments.}}, author = {{Heitkaemper, Jens and Heymann, Jahn and Haeb-Umbach, Reinhold}}, booktitle = {{ITG 2018, Oldenburg, Germany}}, title = {{{Smoothing along Frequency in Online Neural Network Supported Acoustic Beamforming}}}, year = {{2018}}, } @inproceedings{11872, abstract = {{The weighted prediction error (WPE) algorithm has proven to be a very successful dereverberation method for the REVERB challenge. Likewise, neural network based mask estimation for beamforming demonstrated very good noise suppression in the CHiME 3 and CHiME 4 challenges. Recently, it has been shown that this estimator can also be trained to perform dereverberation and denoising jointly. However, up to now a comparison of a neural beamformer and WPE is still missing, so is an investigation into a combination of the two. Therefore, we here provide an extensive evaluation of both and consequently propose variants to integrate deep neural network based beamforming with WPE. For these integrated variants we identify a consistent word error rate (WER) reduction on two distinct databases. In particular, our study shows that deep learning based beamforming benefits from a model-based dereverberation technique (i.e. WPE) and vice versa. Our key findings are: (a) Neural beamforming yields the lower WERs in comparison to WPE the more channels and noise are present. (b) Integration of WPE and a neural beamformer consistently outperforms all stand-alone systems.}}, author = {{Drude, Lukas and Boeddeker, Christoph and Heymann, Jahn and Kinoshita, Keisuke and Delcroix, Marc and Nakatani, Tomohiro and Haeb-Umbach, Reinhold}}, booktitle = {{INTERSPEECH 2018, Hyderabad, India}}, title = {{{Integration neural network based beamforming and weighted prediction error dereverberation}}}, year = {{2018}}, }