The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
J M Kohler - One of the best experts on this subject based on the ideXlab platform.
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characterisation of residence time and residence time distribution in chip reactors with modular arrangements by integrated optical detection
Chemical Engineering Journal, 2004Co-Authors: M Gunther, Roger Gorges, T Henkel, Mark Kielpinski, Rosina Bierbaum, J. Albert, Steffen Schneider, J. Wagner, J M KohlerAbstract:An experimental setup was built for the characterisation of residence time distribution (RTD) in microreactors. In order to determine the residence time distribution of those devices, the method of pulse marking with a dye tracer was used. For this method of marking, a specially constructed microstructured Injection Unit came to use. Detection of the tracer concentration was made by analysing the transmittance with a self-developed transmittance detection Unit. The obtained residence time distributions were compared with common RTD models by means of fitting methods. The examined static micromixer showed laminar flow behaviour.
Mikael Ostling - One of the best experts on this subject based on the ideXlab platform.
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ESSDERC - Step tunneling-enhanced hot-electron Injection in vertical graphene base transistors
2015 45th European Solid State Device Research Conference (ESSDERC), 2015Co-Authors: Siavash Vaziri, M. Belete, G. Lupina, Max C Lemme, A. D. Smith, E. Dentoni Litta, Mikael OstlingAbstract:This paper presents promising current-voltage characteristics of semiconductor-insulator-graphene tunnel diodes as the hot-electron Injection Unit in graphene base transistors (GBTs). We propose that by using a bilayer tunnel barrier one can effectively suppress the defect mediated carrier transport while enhancing the hot-electron emission through Fowler-Nordheim tunneling (FNT) and step tunneling (ST). A stack of TmSiO/TiO 2 (1 nm/ 5.5 nm) is sandwiched between a highly doped Si substrate and a single layer graphene (SLG) as the electrodes. This tunnel diode exhibits high current with large nonlinearity suitable for the application in GBTs.
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Step tunneling-enhanced hot-electron Injection in vertical graphene base transistors
2015 45th European Solid State Device Research Conference (ESSDERC), 2015Co-Authors: Siavash Vaziri, M. Belete, Dentoni E. Litta, G. Lupina, Max C Lemme, A. D. Smith, Mikael OstlingAbstract:This paper presents promising current-voltage characteristics of semiconductor-insulator-graphene tunnel diodes as the hot-electron Injection Unit in graphene base transistors (GBTs). We propose that by using a bilayer tunnel barrier one can effectively suppress the defect mediated carrier transport while enhancing the hot-electron emission through Fowler-Nordheim tunneling (FNT) and step tunneling (ST). A stack of TmSiO/TiO2 (1 nm/ 5.5 nm) is sandwiched between a highly doped Si substrate and a single layer graphene (SLG) as the electrodes. This tunnel diode exhibits high current with large nonlinearity suitable for the application in GBTs.
Dimitri Mawet - One of the best experts on this subject based on the ideXlab platform.
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Novel implementation of a Kalman filter for speckle nulling with a fiber Injection Unit
Techniques and Instrumentation for Detection of Exoplanets IX, 2019Co-Authors: Manxuan Zhang, Nemanja Jovanovic, Jorge Llop Sayson, Dimitri MawetAbstract:High dispersion coronagraphy (HDC) is a technique that combines high contrast imaging techniques with high spectral resolution spectroscopy to directly characterize exoplanets and provide key information such as chemical composition, temperature, and rotational velocity. A consequence of adaptive optics systems used in direct imaging is the formation of residual bright spots of star lights, called speckles, in the final image. Due to the large difference in brightness between host stars and their planets, these speckles can easily obscure potential exoplanets. In a previous demonstration, it was shown that using monochromatic light and a fiber Injection Unit (FIU), simulated exoplanet light can be directed to a high-resolution spectrograph. The method had speckle suppression that exceeding conventional image-based speckle nulling. With a previous Kalman filter estimator implementation, we found that with the implementation of the algorithm, speckle suppression was even more stable and outperformed traditional speckle nulling. In this update to the estimator, progress has been made in terms of a new filter design, and better estimates of the physical parameters in the laboratory, resulting in a higher speckle nulling performance.
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demonstration of a speckle nulling algorithm and kalman filter estimator with a fiber Injection Unit for observing exoplanets with high dispersion coronagraphy
Adaptive Optics Systems VI, 2018Co-Authors: Jorge Llop Sayson, Dimitri Mawet, Jacquesrobert Delorme, Garreth Ruane, Nikita Klimovich, Nemanja JovanovicAbstract:High-dispersion coronagraphy (HDC) combines high contrast imaging techniques with high spectral resolution spectroscopy to observe exoplanets and determine characteristics such as chemical composition, temperature, and rotational velocities. It has been demonstrated in lab that with monochromatic light, a fiber Injection Unit (FIU), in which an optical fiber is used to couple to light from the exoplanet, could be used to direct exoplanet light to a high-resolution spectrograph, with robust performance and speckle suppression that exceeds conventional image-based speckle nulling. We now demonstrate in lab a FIU based speckle nulling scheme with a Kalman filter estimator. We currently find that speckle nulling with a Kalman filter is more stable and outperforms traditional speckle nulling by 10% in suppression in the presence of white detector noise.
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Wavefront control for minimization of speckle coupling into a fiber Injection Unit based on the electric field conjugation algorithm
Adaptive Optics Systems VI, 2018Co-Authors: Jorge Llop Sayson, Dimitri Mawet, Jacquesrobert Delorme, Nemanja Jovanovic, Garreth Ruane, Daniel Echeverri, Nikita KlimovichAbstract:A fiber Injection Unit situated in the focal plane behind a coronagraph feeding a high resolution spectrograph can be used to couple light from an exoplanet to obtain high resolution spectra with improved sensitivity. However, the signal-to-noise ratio of the planet signal is limited by the coupling of starlight into the single mode fiber. To minimize this coupling, we need to apply a control loop on the stellar wavefront at the input of the fiber. We present here a wavefront control algorithm based on the formalism of the Electric Field Conjugation (EFC) controller that accounts for the effect of the fiber. The control output is the overlap integral of the electric field with the fundamental mode of a single mode fiber. This overlap integral is estimated by sending probes to a deformable mirror. We present results from simulations, and laboratory results obtained at the Caltech Exoplanet Technology Lab’s transmissive testbed. We show that our approach offers a significant improvement in starlight suppression through the fiber relative to a conventional EFC controller. This new approach improves the contrast of a high contrast instrument and could be used in future missions.
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Keck Planet Imager and Characterizer (KPIC): status update
Adaptive Optics Systems VI, 2018Co-Authors: Dimitri Mawet, Jacquesrobert Delorme, Nemanja Jovanovic, Scott Lilley, Daniel Echeverri, C. Z. Bond, Sylvain Cetre, M. Chun, D. Hall, J K WallaceAbstract:Here we report on the status of the The Keck Planet Imager and Characterizer (KPIC), which is an on-going series of upgrades to the W.M. Keck II adaptive optics system and instrument suite focused on exoplanet imaging and spectroscopic characterization. The KPIC infrared pyramid wavefront sensor and fiber Injection Unit to high-resolution infrared spectrograph NIRSPEC have been assembled, integrated and are under-going tests at the University of Hawaii before installation at the Summit in the Fall of 2018.
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First version of the fiber Injection Unit for the Keck Planet Imager and Characterizer
Ground-based and Airborne Instrumentation for Astronomy VII, 2018Co-Authors: Jacquesrobert Delorme, Nemanja Jovanovic, J K Wallace, Randy Bartos, Scott Lilley, Daniel Echeverri, C. Z. Bond, Sylvain Cetre, Shane Jacobson, Dimitri MawetAbstract:Coupling a high-contrast imaging instrument to a high-resolution spectrograph has the potential to enable the most detailed characterization of exoplanet atmospheres, including spin measurements and Doppler mapping. The high-contrast imaging system serves as a spatial filter to separate the light from the star and the planet while the high-resolution spectrograph acts as a spectral filter, which differentiates between features in the stellar and planetary spectra. The Keck Planet Imager and Characterizer (KPIC) located downstream from the current W. M. Keck II adaptive optics (AO) system will contain a fiber Injection Unit (FIU) combining a high-contrast imaging system and a fiber feed to Keck’s high resolution infrared spectrograph NIRSPEC. Resolved thermal emission from known young giant exoplanets will be injected into a single-mode fiber linked to NIRSPEC, thereby allowing the spectral characterization of their atmospheres. Moreover, the resolution of NIRSPEC (R = 37,500 after upgrade) is high enough to enable spin measurements and Doppler imaging of atmospheric weather phenomenon. The module was integrated at Caltech and shipped to Hawaii at the beginning of 2018 and is currently undergoing characterization. Its transfer to Keck is planned in September and first on-sky tests sometime in December.
M Gunther - One of the best experts on this subject based on the ideXlab platform.
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characterisation of residence time and residence time distribution in chip reactors with modular arrangements by integrated optical detection
Chemical Engineering Journal, 2004Co-Authors: M Gunther, Roger Gorges, T Henkel, Mark Kielpinski, Rosina Bierbaum, J. Albert, Steffen Schneider, J. Wagner, J M KohlerAbstract:An experimental setup was built for the characterisation of residence time distribution (RTD) in microreactors. In order to determine the residence time distribution of those devices, the method of pulse marking with a dye tracer was used. For this method of marking, a specially constructed microstructured Injection Unit came to use. Detection of the tracer concentration was made by analysing the transmittance with a self-developed transmittance detection Unit. The obtained residence time distributions were compared with common RTD models by means of fitting methods. The examined static micromixer showed laminar flow behaviour.
Siavash Vaziri - One of the best experts on this subject based on the ideXlab platform.
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ESSDERC - Step tunneling-enhanced hot-electron Injection in vertical graphene base transistors
2015 45th European Solid State Device Research Conference (ESSDERC), 2015Co-Authors: Siavash Vaziri, M. Belete, G. Lupina, Max C Lemme, A. D. Smith, E. Dentoni Litta, Mikael OstlingAbstract:This paper presents promising current-voltage characteristics of semiconductor-insulator-graphene tunnel diodes as the hot-electron Injection Unit in graphene base transistors (GBTs). We propose that by using a bilayer tunnel barrier one can effectively suppress the defect mediated carrier transport while enhancing the hot-electron emission through Fowler-Nordheim tunneling (FNT) and step tunneling (ST). A stack of TmSiO/TiO 2 (1 nm/ 5.5 nm) is sandwiched between a highly doped Si substrate and a single layer graphene (SLG) as the electrodes. This tunnel diode exhibits high current with large nonlinearity suitable for the application in GBTs.
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Step tunneling-enhanced hot-electron Injection in vertical graphene base transistors
2015 45th European Solid State Device Research Conference (ESSDERC), 2015Co-Authors: Siavash Vaziri, M. Belete, Dentoni E. Litta, G. Lupina, Max C Lemme, A. D. Smith, Mikael OstlingAbstract:This paper presents promising current-voltage characteristics of semiconductor-insulator-graphene tunnel diodes as the hot-electron Injection Unit in graphene base transistors (GBTs). We propose that by using a bilayer tunnel barrier one can effectively suppress the defect mediated carrier transport while enhancing the hot-electron emission through Fowler-Nordheim tunneling (FNT) and step tunneling (ST). A stack of TmSiO/TiO2 (1 nm/ 5.5 nm) is sandwiched between a highly doped Si substrate and a single layer graphene (SLG) as the electrodes. This tunnel diode exhibits high current with large nonlinearity suitable for the application in GBTs.