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Liu, R. (author), Lühr, H. (author), Doornbos, E. (author), Ma, S.Y. (author)With the help of four years (2002–2005) of CHAMP accelerometer data we have investigated the dependence of low and mid latitude thermospheric density on the merging electric field, Em, during major magnetic storms. Altogether 30 intensive storm events (Dstmin <?100 nT) are chosen for a statistical study. In order to achieve a good correlation Em...journal article 2010
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- Liu, X.L. (author), Ditmar, P.G. (author), Siemes, C. (author), Slobbe, D.C. (author), Revtova, E. (author), Klees, R. (author), Riva, R. (author), Zhao, Q. (author) journal article 2010
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- Van Mieghem, P.F.A. (author), Stevanovic, D (author), Kuipers, F.A. (author), Li, C. (author), van de Bovenkamp, R. (author), Liu, D. (author), Wang, H. (author) journal article 2011
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- Liu, M. (author), Millan, M.G. (author), Aravind, P.V. (author), Brandon, N. (author) journal article 2011
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Liu, H. (author), Doornbos, E.N. (author), Yamamoto, M. (author), Ram, S.T. (author)Thermospheric density simultaneously observed by the CHAMP and GRACE satellites in both the pre?dawn and afternoon local time sectors undergoes significant decrease across both hemispheres during the major stratospheric sudden warming (SSW) in January 2009. This decrease is largest in the equatorial region near the subsolar latitude, reaching ...journal article 2011
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Van Mieghem, P. (author), Stevanovi?, D. (author), Kuipers, F. (author), Li, C. (author), Van de Bovenkamp, R. (author), Liu, D. (author), Wang, H. (author)The decrease of the spectral radius, an important characterizer of network dynamics, by removing links is investigated. The minimization of the spectral radius by removing m links is shown to be an NP-complete problem, which suggests considering heuristic strategies. Several greedy strategies are compared, and several bounds on the decrease of...journal article 2011
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Liu, H. (author), Yamamoto, M. (author), Tulasi Ram, S. (author), Tsugawa, T. (author), Otsuka, Y. (author), Stolle, C. (author), Doornbos, E. (author), Yumoto, K. (author), Nagatsuma, T. (author)Using ground observations of total electron content (TEC) and equatorial electrojet (EEJ) in the Asian sector, along with plasma and neutral densities obtained from the CHAMP satellite, we investigate the ionospheric electrodynamics and neutral background in this longitude sector during the major stratospheric sudden warming (SSW) in January...journal article 2011
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Redi, J.A. (author), Liu, H. (author), Zunino, R. (author), Heynderickx, I.E.J.R. (author)Several attempts to integrate visual saliency information in quality metrics are described in literature, albeit with contradictory results. The way saliency is integrated in quality metrics should reflect the mechanisms underlying the interaction between image quality assessment and visual attention. This interaction is actually two-fold: (1)...journal article 2011
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Liu, H. (author), Redi, J.A. (author), Alers, H. (author), Zunino, R. (author), Heynderickx, I.E.J.R. (author)Reliably assessing overall quality of JPEG/JPEG2000 coded images without having the original image as a reference is still challenging, mainly due to our limited understanding of how humans combine the various perceived artifacts to an overall quality judgment. A known approach to avoid the explicit simulation of human assessment of overall...journal article 2011
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Liu, M. (author), Millan-Agorio, M.G. (author), Aravind, P.V. (author), Brandon, N.P. (author)This paper presents the influence of operation conditions including steam levels, current density and operating time on the performance of Solid Oxide Fuel Cells (SOFCs) fuelled by tar- containing biosyngas. The performance of SOFCs was evaluated by means of recording impedance spectra and polarization curves of the cells before and after tar...journal article 2011
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Liu, H. (author), Heynderickx, I. (author)Developing an objective metric, which automatically quantifies perceived image quality degradation induced by blur, is highly beneficial for current digital imaging systems. In many applications, these objective metrics need to be of the noreference (NR) type, which implies that quality prediction is based on the distorted image only. Recent...journal article 2011
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Siemes, C. (author), Ditmar, P. (author), Riva, E.M. (author), Slobbe, D.C. (author), Liu, X.L. (author), Farahani, H. (author)The Gravity Recovery and Climate Experiment (GRACE) satellite mission measures the Earth’s gravity field since March 2002. We propose a new filtering procedure for post-processing GRACE-based monthly gravity field solutions provided in the form of spherical harmonic coefficients. The procedure is tuned for the optimal estimation of linear trends...journal article 2012
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Liu, K. (author), Xia, K. (author), Bauer, G.E.W. (author)We compute the shot noise in ballistic and disordered Fe|MgO|Fe tunnel junctions by a wave-function-matching method. For tunnel barriers with ?5 atomic layers we find a suppression of the Fano factor as a function of the magnetic configuration. In the antiparallel configuration the shot noise is full up to a threshold bias that indicates the...journal article 2012
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Liu, Y. (author), Salemink, H.W.M. (author)In this paper we demonstrate a sensor based on a two-dimensional photonic crystal cavity structure. Design, theoretical simulations, fabrication and experiments are shown to illustrate the working principle of this device. Sensitivity of our sensor is determined by observing the shift of resonant wavelength of the photonic crystal cavity as a...journal article 2012
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Liu, Y. (author), Weerts, A.H. (author), Clark, M. (author), Hendricks Franssen, H.J. (author), Kumar, S. (author), Moradkhani, H. (author), Seo, D.J. (author), Schwanenberg, D. (author), Smith, P. (author), Van Dijk, A.I.J.M. (author), Van Velzen, N. (author), He, M. (author), Lee, H. (author), Noh, S.J. (author), Rakovec, O. (author), Restrepo, P. (author)Data assimilation (DA) holds considerable potential for improving hydrologic predictions as demonstrated in numerous research studies. However, advances in hydrologic DA research have not been adequately or timely implemented in operational forecast systems to improve the skill of forecasts for better informed real-world decision making. This is...journal article 2012
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Liu, D. (author), Blenn, N. (author), Van Mieghem, P.F.A. (author)ur society contains all types of organizations, such as companies, research groups and hobby clubs. Affliation networks, as a large and important portion of social networks, consist of individuals and their affiation relations: Two individuals are connected by a link if they belong to the same organization(s). Affliation networks naturally...journal article 2012
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Liu, D. (author), Blenn, N. (author), Van Mieghem, P.F.A. (author)Social networks, as well as many other real-world networks, exhibit overlapping community structure. In this paper, we present formulas which facilitate the computation for characterizing the overlapping community structure of networks. A hypergraph representation of networks with overlapping community structure is introduced. Using the...journal article 2012
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Zhou, Y.L. (author), Ma, S.Y. (author), Liu, R.S. (author), Luehr, H. (author), Doornbos, E. (author)The controls of merging electrical field, Em, and IMF (interplanetary magnetic field) magnitude, B, on the storm-time changes in upper thermospheric mass density are statistically investigated using GRACE accelerometer observations and the OMNI data of solar wind and IMF for 35 great storms during 2002–2006. It reveals the following: (1) The...journal article 2013
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Liu, D. (author), Trajanovski, S. (author), Van Mieghem, P. (author)For a fixed number N of nodes, the number of links L in the line graph H(N,L) can only appear in consecutive intervals, called a band of L. We prove that some consecutive integers can never represent the number of links L in H(N,L), and they are called a bandgap of L. We give the exact expressions of bands and bandgaps of L. We propose a model...journal article 2013
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Gemmell, N.R. (author), McCarthy, A. (author), Liu, B. (author), Tanner, M.G. (author), Dorenbos, S.N. (author), Zwiller, V. (author), Patterson, M.S. (author), Buller, G.S. (author), Wilson, B.C. (author), Hadfield, R.H. (author)Direct monitoring of singlet oxygen (1O2) luminescence is a particularly challenging infrared photodetection problem. 1O2, an excited state of the oxygen molecule, is a crucial intermediate in many biological processes. We employ a low noise superconducting nanowire single-photon detector to record 1O2 luminescence at 1270 nm wavelength from a...journal article 2013