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Gharari, S. (author), Hrachowitz, M. (author), Fenecia, F. (author), Gao, H. (author), Savenije, H.H.G. (author)Conceptual environmental systems models, such as rainfall runoff models, generally rely on calibration for parameter identification. Increasing complexity of this type of model for better representation of hydrological process heterogeneity typically makes parameter identification more difficult. Although various, potentially valuable,...journal article 2013
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Gao, Q. (author)Microblogging has become a popular mechanism for people to publish, share, and propagate information on the Web. The massive amount of digital traces that people have left in the microblogging sphere, creates new possibilities and poses challenges for user modeling and personalization. How can microblogging activities be exploited to infer...doctoral thesis 2013
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- Gao, H. (author), Hrachowitz, M. (author), Fenicia, F.F. (author), Gharari, S. (author), Savenije, H.H.G. (author) journal article 2013
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Gao, Y. (author), Suchand Sandeep, C.S. (author), Schins, J.M. (author), Houtepen, A.J. (author), Siebbeles, L.D.A. (author)Auger recombination (AR) can be an important loss mechanism for optoelectronic devices, but it is typically not very efficient at low excitation densities. Here we show that in conductive quantum-dot solids, AR is the dominant charge carrier decay path even at excitation densities as low as 10?3 per quantum dot, and that AR becomes faster as the...journal article 2013
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Chai, L. (author), Al-Sawai, W. (author), Gao, Y. (author), Houtepen, A.J. (author), Mijnarends, P.E. (author), Barbiellini, B. (author), Schut, H. (author), Van Schaarenburg, L.C. (author), Van Huis, M.A. (author), Ravelli, L. (author), Egger, W. (author), Kaprzyk, S. (author), Bansil, A. (author), Eijt, S.W.H. (author)Positron annihilation lifetime spectroscopy and positron-electron momentum density (PEMD) studies on multilayers of PbSe nanocrystals (NCs), supported by transmission electron microscopy, show that positrons are strongly trapped at NC surfaces, where they provide insight into the surface composition and electronic structure of PbSe NCs. Our...journal article 2013
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Rudneva, M. (author), Gao, B. (author), Prins, F. (author), Xu, Q. (author), Van der Zant, H.S.J. (author), Zandbergen, H.W. (author)In situ transmission electron microscopy was performed on the electromigration in platinum (Pt) nanowires (14 nm thick, 200 nm wide, and 300 nm long) with and without feedback control. Using the feedback control mode, symmetric electrodes are obtained and the gap usually forms at the center of the Pt nanowire. Without feedback control,...journal article 2013
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Hayton, D.J. (author), Khudchenko, A. (author), Pavelyev, D.G. (author), Hovenier, J.N. (author), Baryshev, A. (author), Gao, J.R. (author), Kao, T.Y. (author), Hu, Q. (author), Reno, J.L. (author), Vaks, V. (author)We report on the phase locking of a 3.4 THz third-order distributed feedback quantum cascade laser (QCL) using a room temperature GaAs/AlAs superlattice diode as both a frequency multiplier and an internal harmonic mixer. A signal-to-noise level of 60?dB is observed in the intermediate frequency signal between the 18th harmonic of a 190.7?GHz...journal article 2013
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Bozdag, V.E. (author), Gao, Q. (author), Warnier, M.E. (author), Houben, G.J.P.M. (author)Information diversity has a long tradition in human history. Recently there have been claims that diversity is diminishing in information available in social networks. On the other hand, some studies suggest that diversity is actually quite high in social networks such as Twitter. However these studies only focus on the concept of source...conference paper 2013
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Cui, M. (author), Hovenier, J.N. (author), Ren, Y. (author), Vercruyssen, N. (author), Gao, J.R. (author), Kao, T.Y. (author), Hu, Q. (author), Reno, J.L. (author)We report on both measurements and simulations of the beam profile and wavefront of a single-mode, 3.5?THz quantum cascade wire laser, incorporating a lateral corrugated metal-metal waveguide, 3rd-order distributed feedback grating. The intrinsic wavefront was measured by using a Hartmann wavefront sensor (HWS) without any optical components...journal article 2013
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Kloosterman, J.L. (author), Hayton, D.J. (author), Ren, Y. (author), Kao, T.Y. (author), Hovenier, J.N. (author), Gao, J.R. (author), Klapwijk, T.M. (author), Hu, Q. (author), Walker, C.K. (author), Reno, J.L. (author)We report on a heterodyne receiver designed to observe the astrophysically important neutral atomic oxygen [OI] line at 4.7448?THz. The local oscillator is a third-order distributed feedback quantum cascade laser operating in continuous wave mode at 4.741?THz. A quasi-optical, superconducting NbN hot electron bolometer is used as the mixer. We...journal article 2013
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Gao, Y. (author)Semiconductor nanocrystals (NCs), which can have a variety of sizes, shapes and chemical compositions, will be a large and important family of future advanced materials.This thesis focuses on colloidal semiconductor NC solids, also called quantum-dot (QD) solids, which are promising materials for many applications, such as photo-detectors, field...doctoral thesis 2012
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Ren, Y. (author), Hayton, D.J. (author), Hovenier, J.N. (author), Cui, M. (author), Gao, J.R. (author), Klapwijk, T.M. (author), Shi, S.C. (author), Kao, T.Y. (author), Hu, Q. (author), Reno, J.L. (author)We demonstrate an experimental scheme to simultaneously stabilize the frequency and amplitude of a 3.5 THz third-order distributed feedback quantum cascade laser as a local oscillator. The frequency stabilization has been realized using a methanol absorption line, a power detector, and a proportional-integral-derivative (PID) loop. The amplitude...journal article 2012
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Cui, M. (author), Hovenier, J.N. (author), Ren, Y. (author), Polo, A. (author), Gao, J.R. (author)We demonstrate for the first time that the Hartmann wavefront sensor (HWS) principle can be applied for characterizing the wavefronts of terahertz (THz) electromagnetic radiation. The THz Hartmann wavefront sensor consists of a metallic plate with an array of holes and a twodimensional scanable pyro-electric detector. The THz radiation with...journal article 2012
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Van der Kuur, J. (author), Beyer, J. (author), Bruijn, M. (author), Gao, J.R. (author)SAFARI is an imaging Fourier Transform Spectrometer for 35–200 ?m under development for flight on the Japanese IR-satellite SPICA (2018). The 3.25 m diameter actively cooled telescope (<6K) will provide a sky background limited signal, which implies that detectors will need to have an NEP of 3.5?10 ?19 W/Hz ? ? ? in order not to be limiting the...journal article 2012
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Hayton, D.J. (author), Gao, J.R. (author), Kooi, J.W. (author), Ren, Y. (author), Zhang, W. (author), De Lange, G. (author)We report on a method to stabilize a hot electron bolometer (HEB) mixer at 2.5 THz. The technique utilizes feedback control of the local oscillator (LO) laser power by means of a swing-arm actuator placed in the optical beam path. We demonstrate that this technique yields a factor of 50 improvement in the spectroscopic Allan variance time which...journal article 2012
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Lindeman, M.A. (author), Khosropanah, P. (author), Hijmering, R.A. (author), Ridder, M. (author), Gottardi, L. (author), Bruijn, M. (author), Van der Kuur, J. (author), De Korte, P.A.J. (author), Gao, J.R. (author), Hoevers, H. (author)Transition-edge-sensor (TES) bolometers are the chosen detector technology for the SAFARI Imaging Spectrometer on the SPICA telescope. For this mission, SRON is developing bolometers, each consisting of a TiAu TES that is weakly coupled to the thermal bath through thin legs of silicon nitride. In order to understand and optimize the bolometer...journal article 2012
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Hijmering, R.A. (author), Khosropanah, P. (author), Ridder, M. (author), Lindeman, M. (author), Gottardi, L. (author), Bruijn, M. (author), Van der Kuur, J. (author), De Korte, P. (author), Gao, J.R. (author), Hoervers, H. (author), Jackson, B. (author)At the Netherlands Institute for Space Research (SRON) we are developing Transition Edge Sensors (TES) bolometers for the SAFARI Imaging Spectrometer on the SPICA telescope. With the current design of the SPICA telescope a background magnetic field of about a Gauss with fluctuations of a couple percent is expected. The effect of this external...journal article 2012
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Gottardi, L. (author), Bruijn, M. (author), Gao, J.R. (author), Den Hartog, R. (author), Hijmering, R. (author), Hoevers, H. (author), Khosropanah, P. (author), De Korte, P. (author), Van der Kuur, J. (author), Lindeman, M. (author), Ridder, M. (author)SRON is developing the Frequency Domain Multiplexing (FDM) read-out and the ultra low NEP TES bolometers array for the infra-red spectrometer SAFARI on board of the Japanese space mission SPICA. The FDM prototype of the instrument requires critical and complex optimizations. For single pixel characterization under AC bias we are developing a...journal article 2012
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Khosropanah, P. (author), Hijmering, R.A. (author), Ridder, M. (author), Lindeman, M.A. (author), Gottardi, L. (author), Bruijn, M. (author), Van der Kuur, J. (author), de Korte, P.A.J. (author), Gao, J.R. (author), Hoevers, H. (author)Transition edge sensors (TES) are the chosen detector technology for the SAFARI imaging spectrometer on the SPICA telescope. The TES are required to have an NEP of 2–3 × 10?19 W/? Hz to take full advantage of the cooled mirror. SRON has developed TiAu TES bolometers for the short wavelength band (30–60 ?m). The TES are on SiN membranes, in which...journal article 2012
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Ren, Y. (author), Hovenier, J.N. (author), Cui, M. (author), Hayton, D.J. (author), Gao, J.R. (author), Klapwijk, T.M. (author), Shi, S.C. (author), Kao, T.Y. (author), Hu, Q. (author), Reno, J.L. (author)We report frequency locking of two 3.5-THz third-order distributed feedback (DFB) quantum cascade lasers (QCLs) by using methanol molecular absorption lines, a proportional-integral-derivative controller, and a NbN bolometer. We show that the free-running linewidths of the QCLs are dependent on the electrical and temperature tuning coefficients....journal article 2012