@article{40594, author = {{Bager, F. and Lopez Salas, Nieves and Ernst, S.}}, journal = {{Oil Gas European Magazine}}, number = {{2}}, pages = {{107--111}}, title = {{{Improved propene yields from catalytic cracking: The potential of medium-pore zeolites as additives}}}, volume = {{38}}, year = {{2012}}, } @article{40811, abstract = {{Deadwood moisture affects multiple functions of downed logs in forest ecosystems. They include provision of habitats for xylobionts, additional water stores and organic carbon stocks. In contrast to Northern American forests, little is known about moisture variability in downed logs of important tree species within the Temperate Zone of Europe. Therefore, our study aimed at elucidating this variability according to species, site and decay class (DC). Measurements were taken by TDR during two vegetation periods in eight Carpathian natural forests representing distinct site conditions, ranging from xerothermophilous to subalpine. Downed logs of \emphQuercus spp., \emph{Abies alba} Mill., \emph{Fagus sylvatica} L., and \emph{Picea abies} L., belonging to various DCs, were selected and instrumented with TDR probes. Species and DC-specific TDR calibration showed the importance of intrinsic wood porosity. The course of deadwood moisture consisted of drying during the early decay stage, except for \emph{A. alba} and \emph{F. sylvatica}, and an intense water reabsorption at later decay stages. Average moisture for all species and sites displayed seasonal trends, reflecting the occurrence of precipitation clusters and dry periods, as well as short-term fluctuations. Cross-spectral analysis revealed that both sapwood and heartwood participated in wetting and drying processes, but only after reaching an advanced stage of decay. New findings can be applied in interpreting, modelling and predicting deadwood water stores, habitat properties and respiration.}}, author = {{Pichler, V. and Homolák, M. and Skierucha, W. and Pichlerová, M. and Ramírez, D. and Gregor, J. and Jaloviar, P.}}, journal = {{Ecohydrology}}, number = {{4}}, pages = {{424–434}}, title = {{{Variability of moisture in coarse woody debris from several ecologically important tree species of the Temperate Zone of Europe}}}, doi = {{10.1002/eco.235}}, volume = {{5}}, year = {{2012}}, } @inproceedings{40812, abstract = {{Spectrum sensing has become one of the main components of a cognitive transmitter. Conventional detectors suffer from noise power uncertainties and multiantenna detectors have been proposed to overcome this difficulty, and to improve the detection performance. However, most of the proposed multiantenna detectors are based on non-optimal techniques, such as the generalized likelihood ratio test (GLRT), or even heuristic approaches that are not based on first principles. In this work, we derive the locally most powerful invariant test (LMPIT), that is, the optimal invariant detector for close hypotheses, or equivalently, for a low signal-to-noise ratio (SNR). The traditional approach, based on the distributions of the maximal invariant statistic, is avoided thanks to Wijsman’s theorem, which does not need these distributions. Our findings show that, in the low SNR regime, and in contrast to the GLRT, the additional spatial structure imposed by the signal model is irrelevant for optimal detection. Finally, we use Monte Carlo simulations to illustrate the good performance of the LMPIT.}}, author = {{Ramírez, D. and Iscar, J. and Vía, J. and Santamaría, I. and Scharf, L. L.}}, booktitle = {{Proc.\ IEEE Sensor Array and Multichannel Signal Process. Work.}}, title = {{{The Locally Most Powerful Invariant Test for Detecting a rank-$P$ Gaussian Signal in White Noise}}}, doi = {{10.1109/SAM.2012.6250547}}, year = {{2012}}, } @inproceedings{40820, abstract = {{An alternating optimization algorithm was recently proposed for the K-user multiple-input multiple-output (MIMO) interference channel. For flat-fading channels and feasible problems, this algorithm successfully aligns the interfering signals exploiting the spatial dimensions. In this paper, we consider the case in which all pairwise MIMO channels are frequency-selective (convolutive), and the users transmit broadband signals using a single-carrier scheme. Unlike the flat-fading case, for frequency-selective channels it is necessary to add a spectral mask in the frequency response of the precoders and decoders to avoid trivial solutions. We show in the paper that each step of the alternating minimization algorithm can be reformulated as a convex optimization problem in which the autocorrelation function of the precoders or decoders is obtained. Upon convergence, a final spectral factorization stage must be applied to obtain the precoders and decoders from their autocorrelation functions. Simulation results are provided to illustrate the performance of the proposed algorithm.}}, author = {{Lameiro, Christian and Vía, Javier and Santamaría, Ignacio and Heath Jr., Robert W.}}, booktitle = {{Proc.\ IEEE Int.\ Conf.\ Acoustics, Speech and Signal Process.}}, title = {{{Interference Leakage Minimization for Convolutive MIMO Interference Channels}}}, doi = {{10.1109/ICASSP.2012.6288506}}, year = {{2012}}, } @article{40817, abstract = {{This paper studies large multiple-input multiple-output (MIMO) communication systems with linear precoding and reduced-rank Krylov subspace receivers. We design precoders and analyze their performance by exploiting large-dimensional random matrix theory. We first devise low-complexity precoding schemes that can improve performance of low-rank Krylov subspace receivers in the regime of high signal-to-noise ratio (SNR). We then introduce a potential theory-based method for analyzing the convergence behavior of the mean-squared error (MSE) for various transmission schemes. This method can be applied to a broader range of problems compared to previous analytical tools. The analysis reveals that the MSE decreases super exponentially with the rank of the receiver. Numerical examples show that the proposed precoders can outperform conventional precoders when low-rank Krylov subspace receivers are used, and that the performance of such receivers can be accurately predicted.}}, author = {{Tong, Jun and Schreier, Peter J. and Weller, Steven R.}}, journal = {{{IEEE} {T}rans.\ {S}ignal\ {P}rocess.}}, number = {{5}}, pages = {{2482–2493}}, title = {{{Design and analysis of large MIMO systems with Krylov subspace receivers}}}, doi = {{10.1109/TSP.2012.2187287}}, volume = {{60}}, year = {{2012}}, } @inproceedings{40819, abstract = {{Spectrum sensing is a key component of the cognitive radio (CR) paradigm. Among CR detectors, multiantenna detectors are gaining popularity since they improve the detection performance and are robust to noise uncertainties. Traditional approaches to multiantenna spectrum sensing are based on the generalized likelihood ratio test (GLRT) or other heuristic detectors, which are not optimal in the Neyman-Pearson sense. In this work, we derive the locally most powerful invariant test (LMPIT), which is the optimal detector, among those preserving the problem invariances, in the low SNR regime. In particular, we apply Wijsman’s theorem, which provides us an alternative way to derive the ratio of the distributions of the maximal invariant statistic. Finally, numerical simulations illustrate the performance of the proposed detector.}}, author = {{Ramírez, D. and Vía, J. and Santamaría, I.}}, booktitle = {{Proc.\ IEEE Int.\ Conf.\ Acoustics, Speech and Signal Process.}}, title = {{{The Locally Most Powerful Test For Multiantenna Spectrum Sensing With Uncalibrated Receivers}}}, doi = {{10.1109/ICASSP.2012.6288655}}, year = {{2012}}, } @inproceedings{40821, abstract = {{This paper deals with different techniques for linear equalization (LE) of multipath channels with imperfect channel estimation (CE). We develop a unified framework based on Krylov subspace expansion, which allows us to compare the performance of the conjugate gradient (CG) method, diagonal loading (DL), and a hybrid scheme. Our analysis shows that the DL method generally outperforms its alternatives, but at the cost of higher complexity. However, we also demonstrate that a proper implementation of the low-complexity CG method can also approach the performance of DL. Finally, we show that preconditioning degrades performance when the CE is poor.}}, author = {{Tong, Jun and Schreier, Peter J.}}, booktitle = {{Proc.\ IEEE Int.\ Conf.\ Acoustics, Speech and Signal Process.}}, pages = {{3009–3012}}, title = {{{Regularized linear equalization for multipath channels with imperfect channel estimation}}}, doi = {{10.1109/ICASSP.2012.6288548}}, year = {{2012}}, } @inproceedings{40823, author = {{Eguizabal, Alma and Laughney, Ashley M. and Garcia-Allende, P. Beatriz and Krishnaswamy, Venkataramanan and Wells, Wendy A. and Paulsen, Keith D. and Pogue, Brian W. and Lopez-Higuera, Jose and Conde, Olga M.}}, booktitle = {{SPIE Photonics West 2012-BIOS, VI Biomedical Applications of Light Scattering}}, title = {{{Enhanced tumor contrast during breast lumpectomy provided by independent component analysis of localized reflectance measures}}}, year = {{2012}}, } @inproceedings{40822, author = {{Eguizabal, Alma and Laughney, Ashley M. and Garcia-Allende, P. Beatriz and Krishnaswamy, Venkataramanan and Wells, Wendy A. and Paulsen, Keith D. and Pogue, Brian W. and Lopez-Higuera, Jose and Conde, Olga M.}}, booktitle = {{SPIE Photonics West BIOS, VI Biomedical Applications of Light Scattering}}, title = {{{Blind breast tissue diagnosis using independent component analysis of localized backscattering response}}}, year = {{2012}}, } @inproceedings{40818, author = {{Enneking, Christoph and Stein, Manuel and Castañeda, Mario and Antreich, Felix and Nossek, Josef A.}}, booktitle = {{Proceedings of IEEE/ION PLANS 2012}}, title = {{{Multi-Satellite Time-Delay Estimation for Reliable High-Resolution GNSS Receivers}}}, year = {{2012}}, } @article{40810, abstract = {{This paper considers large multiple-input multiple-output (MIMO) communication systems with linear precoding and linear minimum mean-squared error (LMMSE) equalization based on the iterative conjugate gradient (CG) algorithm. Convergence of the CG algorithm is fast when the eigenvalues of the received signal’s covariance matrix are clustered, suggesting that mean-squared error and receiver complexity can be managed with judicious precoder design. In order to accelerate convergence of an iterative CG receiver, we incorporate constraints on two measures of eigenvalue clustering into the precoder design. Closed-form solutions to the optimal precoders are derived using majorization theory and convex optimization techniques. We show that if there are constraints on receiver complexity, the proposed precoders can improve performance for large MIMO systems operating over slowly time-varying fading channels.}}, author = {{Tong, Jun and Schreier, Peter J. and Weller, Steven R.}}, journal = {{IEEE Trans.\ Wireless Comm.}}, number = {{8}}, pages = {{2828–2837}}, title = {{{Linear precoding for MIMO systems with low-complexity receivers}}}, doi = {{10.1109/TWC.2012.070912.110877}}, volume = {{11}}, year = {{2012}}, } @inproceedings{40807, abstract = {{The Strong Uncorrelating Transform (SUT) allows blind separation of a mixture of complex independent sources if and only if all sources have distinct circularity coefficients. In practice, the circularity coefficients need to be estimated from observed data. We propose a generalized likelihood ratio test (GLRT) for separability of a complex mixture using the SUT, based on estimated circularity coefficients. For distinct circularity coefficients (separable case), the maximum likelihood (ML) estimates, required for the GLRT, are straightforward. However, for circularity coefficients with multiplicity larger than one (non-separable case), the ML estimates are much more difficult to find. Numerical simulations show the good performance of the proposed detector.}}, author = {{Ramírez, D. and Schreier, P. J. and Vía, J. and Santamaría, I.}}, booktitle = {{Proc.\ IEEE Int.\ Work. Machine Learning for Signal Process.}}, title = {{{GLRT For Testing Separability Of A Complex-Valued Mixture Based On The Strong Uncorrelating Transform}}}, doi = {{10.1109/MLSP.2012.6349785}}, year = {{2012}}, } @inproceedings{40804, abstract = {{This paper advocates that the convergent systems property and incremental stability are two intimately related though different properties. Sufficient conditions for the convergent systems property usually rely upon first showing that a system is incrementally stable, as e.g. in the celebrated Demidovich condition. However, in the current paper it is shown that incremental stability itself does not imply the convergence property, or vice versa. Moreover, characterizations of both properties in terms of Lyapunov functions are given. Based on these characterizations, it is established that the convergence property implies incremental stability for systems evolving oncompact sets, and also when a suitable uniformity condition is satisfied.}}, author = {{Rüffer, Björn S. and van de Wouw, Nathan and Mueller, Markus}}, booktitle = {{Proc. 51st IEEE Conf. Decis. Control}}, pages = {{2958–2963}}, title = {{{From convergent dynamics to incremental stability}}}, year = {{2012}}, } @inproceedings{40808, abstract = {{The monogenic signal allows us to decompose a two-dimensional real signal into a local amplitude, a local orientation, and a local phase. In this paper, we introduce the random monogenic signal and study its second-order statistical properties. The monogenic signal may be represented as a quaternion-valued signal. We show that for homogeneous random fields, we need exactly two quaternion-valued covariance functions for a complete second-order description. We also introduce a stochastic model for unidirectional signals and a measure of unidirectionality.}}, author = {{Olhede, S. C. and Ramírez, D. and Schreier, P. J.}}, booktitle = {{Proc.\ IEEE Int.\ Conf.\ Image Process.}}, title = {{{The Random Monogenic Signal}}}, doi = {{10.1109/ICIP.2012.6467404}}, year = {{2012}}, } @article{40805, abstract = {{We study the instantaneous frequency (IF) of continuous-time, complex-valued, zero-mean, proper, mean-square differentiable, nonstationary Gaussian stochastic processes. We compute the probability density function for the IF for fixed time, which generalizes a result known for wide-sense stationary processes to nonstationary processes. For a fixed point in time, the IF has either zero or infinite variance. For harmonizable processes, we obtain as a consequence the result that the mean of the IF, for fixed time, is the normalized first-order frequency moment of the Wigner spectrum.}}, author = {{Wahlberg, Patrik and Schreier, Peter J.}}, journal = {{Probab.\ Math.\ Statist.}}, pages = {{69–92}}, title = {{{On the instantaneous frequency of Gaussian stochastic processes}}}, volume = {{32}}, year = {{2012}}, } @article{40173, abstract = {{Here, There, Everywhere Random walks are a powerful mathematical method that can be used to simulate certain processes in biology, chemistry, or even the stock market. They present a statistical method for mapping the possible routes that processes can take. Quantum walks are expected to be able to probe multiple paths simultaneously. Quantum walks have been demonstrated for one-dimensional, or straight-line, walks. Now, Schreiber et al. (p. 55 , published online 8 March) demonstrate an optical system that can simulate quantum walks over a two-dimensional system, thereby providing the capability of describing much more complex processes. }}, author = {{Schreiber, Andreas and Gábris, Aurél and Rohde, Peter P. and Laiho, Kaisa and Štefaňák, Martin and Potoček, Václav and Hamilton, Craig and Jex, Igor and Silberhorn, Christine}}, issn = {{0036-8075}}, journal = {{Science}}, keywords = {{Multidisciplinary}}, number = {{6077}}, pages = {{55--58}}, publisher = {{American Association for the Advancement of Science (AAAS)}}, title = {{{A 2D Quantum Walk Simulation of Two-Particle Dynamics}}}, doi = {{10.1126/science.1218448}}, volume = {{336}}, year = {{2012}}, } @article{40175, author = {{Christ, Andreas and Silberhorn, Christine}}, issn = {{1050-2947}}, journal = {{Physical Review A}}, keywords = {{Atomic and Molecular Physics, and Optics}}, number = {{2}}, publisher = {{American Physical Society (APS)}}, title = {{{Limits on the deterministic creation of pure single-photon states using parametric down-conversion}}}, doi = {{10.1103/physreva.85.023829}}, volume = {{85}}, year = {{2012}}, } @article{40264, author = {{Haller, Melanie}}, journal = {{In: SDHS 2012 Proceedings, https://sdhs.org/proceedings-2012#sessiondetails (Digitale Tagungspublikation)}}, title = {{{Buenos Aires is everywhere – subjectivities and territories in Tango Argentino}}}, year = {{2012}}, } @article{41236, author = {{Jensen, Christopher and Buck, Doris and Dilger, Herbert and Bauer, Matthias and Phillipp, Fritz and Roduner, Emil}}, issn = {{1359-7345}}, journal = {{Chem. Commun.}}, keywords = {{Materials Chemistry, Metals and Alloys, Surfaces, Coatings and Films, General Chemistry, Ceramics and Composites, Electronic, Optical and Magnetic Materials, Catalysis}}, number = {{6}}, pages = {{588--590}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Maximum hydrogen chemisorption on KL zeolite supported Pt clusters}}}, doi = {{10.1039/c2cc37933c}}, volume = {{49}}, year = {{2012}}, } @article{41253, author = {{Conrad, Franziska and Bauer, Matthias and Sheptyakov, Denis and Weyeneth, Stephen and Jaeger, Dominik and Hametner, Kathrin and Car, Pierre-Emmanuel and Patscheider, Jörg and Günther, Detlef and Patzke, Greta R.}}, issn = {{2046-2069}}, journal = {{RSC Advances}}, keywords = {{General Chemical Engineering, General Chemistry}}, number = {{7}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{New spinel oxide catalysts for visible-light-driven water oxidation}}}, doi = {{10.1039/c2ra20169k}}, volume = {{2}}, year = {{2012}}, }