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- Kumar, A. Vijaya (author) journal article 2005
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Kumar, A. (author), Kumar, P. (author), Anandan, A. (author), Fernandes, T.F. (author), Ayoko, G.A. (author), Biskos, G. (author)The aim of this study is to identify current knowledge gaps in fate, exposure, and toxicity of engineered nanomaterials (ENMs), highlight research gaps, and suggest future research directions. Humans and other living organisms are exposed to ENMs during production or use of products containing them. To assess the hazards of ENMs, it is important...journal article 2014
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Ren, Y. (author), Hovenier, J.N. (author), Higgins, R. (author), Gao, J.R. (author), Klapwijk, T.M. (author), Shi, S.C. (author), Bell, A. (author), Klein, B. (author), Williams, B.S. (author), Kumar, S. (author), Hu, Q. (author), Reno, J.L. (author)A terahertz (THz) heterodyne spectrometer is demonstrated based on a quantum cascade laser (QCL) as a local oscillator (LO) and an NbN hot electron bolometer as a mixer, and it is used to measure high-resolution molecular spectral lines of methanol (CH3OH) between 2.913–2.918 THz. The spectral lines are taken from a gas cell containing methanol...journal article 2010
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Gharari, S. (author), Shafiei, M. (author), Hrachowitz, M. (author), Kumar, R. (author), Fenicia, F. (author), Gupta, H.V. (author), Savenije, H.H.G. (author)Many environmental systems models, such as conceptual rainfall-runoff models, rely on model calibration for parameter identification. For this, an observed output time series (such as runoff) is needed, but frequently not available (e.g., when making predictions in ungauged basins). In this study, we provide an alternative approach for parameter...journal article 2014
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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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Kumar, A. (author), Blacquière, G. (author)A subsurface image obtained from seismic data is influenced by the acquisition geometry, as it contains an acquisition foot-print which can obscure the true reflection response of the subsurface. Hence, the acquisition geometry should be designed in such a way that it allows high-quality images and fulfils the criteria for reservoir...journal article 2013
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Adam, A.J.L. (author), Kaalynas, I. (author), Hovenier, J.N. (author), Klaassen, T.O. (author), Gao, J.R. (author), Orlova, E.E. (author), Williams, B.S. (author), Kumar, S. (author), Hu, Q. (author), Reno, J.L. (author)The need to reach single-mode lasing and minimize at the same time the electrical dissipation of cryogenically operated terahertz quantum cascade lasers may result in small and subwavelength cavity dimensions. To assess the influence of such dimensions on the shape of the laser emission, we have measured the beam pattern of two metal-metal...journal article 2006
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- Kumar, V.S. (author) journal article 2004
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- Bhaskaran, P.K. (author), Kumar, R.R. (author), Barman, R. (author), Muthalagy, R. (author) journal article 2010
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Harman, C.J. (author), Rao, P.S.C. (author), Basu, N.B. (author), McGrath, G.S. (author), Kumar, P. (author), Sivapalan, M. (author)Temporal patterns of solute transport and transformation through the vadose zone are driven by the stochastic variability of water fluxes. This is determined by the hydrologic filtering of precipitation variability into infiltration, storage, drainage, and evapotranspiration. In this work we develop a framework for examining the role of the...journal article 2011
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- Kumar, R. Prasanth (author) journal article 2005
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- Kumar, V.S. (author) journal article 2003
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El Gawhary, O. (author), Kumar, N. (author), Pereira, S.F. (author), Coene, W.M.J. (author), Urbach, H.P. (author)Scatterometry is a well established technique currently utilized in research, as well as in industrial applications, to retrieve the properties of a given scatterer (the target) by looking at how the light coming from a certain source is diffracted in the far field. Currently the light source is often a discharge lamp that, after wavelength...journal article 2011
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El Gawhary, O. (author), Wiegmann, A. (author), Kumar, N. (author), Pereira, S.F. (author), Urbach, H.P. (author)Through-focus phase retrieval methods aim to retrieve the phase of an optical field from its intensity distribution measured at different planes in the focal region. By using the concept of spatial correlation for propagating fields, for both the complex amplitude and the intensity of a field, we can infer which planes are suitable to retrieve...journal article 2013
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Gao, J.R. (author), Hovenier, J.N. (author), Yang, Z.Q. (author), Baselmans, J.J.A. (author), Baryshev, A. (author), Hajenius, M. (author), Klapwijk, T.M. (author), Adam, A.J.L. (author), Klaassen, T.O. (author), Williams, B.S. (author), Kumar, S. (author), Hu, Q. (author), Reno, J.L. (author)We report the first demonstration of an all solid-state heterodyne receiver that can be used for high-resolution spectroscopy above 2?THz suitable for space-based observatories. The receiver uses a NbN superconducting hot-electron bolometer as mixer and a quantum cascade laser operating at 2.8?THz as local oscillator. We measure a double...journal article 2005
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Kajikawa, K. (author), Nagai, Y. (author), Uchiho, Y. (author), Ramakrishnan, G. (author), Kumar, N. (author), Ramanandan, G.K.P. (author), Planken, P.C.M. (author)Electromagnetic wave emission based on optical rectification at terahertz (THz) wavelengths was observed from surface-immobilized gold nanospheres (SIGNs) above a gold surface. Although the excitation wavelength is off-resonant with the localized surface plasmons, the THz emission field was observed to be approximately 4.8 times greater than...journal article 2012
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Kumar, N. (author), Abdi, F.F. (author), Trzesniewski, B. (author), Smith, W.A. (author), Planken, P.C.M. (author), Adam, A.J.L. (author)We demonstrate emission of terahertz pulses from a BiVO4/Au thin film interface, illuminated with femtosecond laser pulses. Based on the experimental observations, we propose that the most likely cause of the THz emission is the Photo-Dember effect caused by the standing wave intensity distribution formed at the BiVO4/Au interfaces.journal article 2015
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Kumar, N. (author), Strikwerda, A.C. (author), Fan, K. (author), Zhang, X. (author), Averitt, R.D. (author), Planken, P.C.M. (author), Adam, A.J.L. (author)We report on direct measurements of the magnetic near-field of metamaterial split ring resonators at terahertz frequencies using a magnetic field sensitive material. Specifically, planar split ring resonators are fabricated on a single magneto-optically active terbium gallium garnet crystal. Normally incident terahertz radiation couples to the...journal article 2012
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Ramakrishnan, G. (author), Kumar, N. (author), Planken, P.C.M. (author), Tanaka, D. (author), Kajikawa, K. (author)Emission of terahertz radiation is observed when surface plasmons are excited on a thin film of gold, in the Kretschmann geometry. When a hemicyanine-terminated alkanethiol self-assembled monolayer of thickness 1.2 nm is deposited on the gold film, stronger terahertz emission is observed. Our experimental results confirm that enhanced terahertz...journal article 2012
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Ingolfsson, O. (author), Kumar, R. (author), Hagen, C.W. (author), Hari, S. (author)To study the potential role of low energy secondary electrons in focused electron beam induced deposition (FEBID) we have studied FEBID using 1,1-dichloro-1-silacyclohexane, silacyclohexane and 1,3,5-trisilacyclohexane. While the first of these compounds shows appreciable cross sections for dissociative electron attachment (DEA) in the gas phase...journal article 2015