The Experts below are selected from a list of 17484 Experts worldwide ranked by ideXlab platform
James Bridges - One of the best experts on this subject based on the ideXlab platform.
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an mdoe assessment of nozzle vanes for high bypass ratio jet noise reduction
AIAA CEAS Aeroacoustics Conference, 2006Co-Authors: Brenda S Henderson, Thomas Norum, James BridgesAbstract:The effect of airfoil-shaped vanes placed in the fan stream of a BPR 8 coannular nozzle model system on the resulting jet noise was investigated. The experiments used a Modern Design of Experiments approach to investigate the impact of a range of vane parameters on the noise reduction achieved at representative takeoff conditions. The experimental results showed that the installation of the vanes decreased low frequency noise radiation in the downstream peak-noise Direction and increased high frequency noise in the Upstream Direction. Results also showed that improper selection of the vane configuration resulted in increased low frequency noise radiation in the Upstream Direction. Large angles of attack are shown to reduce noise near the peak jet noise angle and increase noise in the Upstream Direction. The MDOE analysis yields an optimum design that minimizes perceived noise levels. Limited data taken with a BPR 5 nozzle system showed that the vanes result in better effective perceived noise reduction for lower bypass ratio nozzles than for the BPR 8 model.
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an mdoe assessment of nozzle vanes for high bypass ratio jet noise reduction
AIAA CEAS Aeroacoustics Conference, 2006Co-Authors: Brenda S Henderson, Thomas Norum, James BridgesAbstract:The effect of airfoil-shaped vanes placed in the fan stream of a BPR 8 coannular nozzle model system on the resulting jet noise was investigated. The experiments used a Modern Design of Experiments approach to investigate the impact of a range of vane parameters on the noise reduction achieved at representative takeoff conditions. The experimental results showed that the installation of the vanes decreased low frequency noise radiation in the downstream peak-noise Direction and increased high frequency noise in the Upstream Direction. Results also showed that improper selection of the vane configuration resulted in increased low frequency noise radiation in the Upstream Direction. Large angles of attack are shown to reduce noise near the peak jet noise angle and increase noise in the Upstream Direction. The MDOE analysis yields an optimum design that minimizes perceived noise levels. Limited data taken with a BPR 5 nozzle system showed that the vanes result in better effective perceived noise reduction for lower bypass ratio nozzles than for the BPR 8 model.
Hiroshi Takatori - One of the best experts on this subject based on the ideXlab platform.
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Theoretical and Practical Limits of Next-Generation High-Speed Digital Subscriber Loops
2015Co-Authors: A.f. Shalash, Hiroshi TakatoriAbstract:Abstract—For the single-pair HDSL (HDSL2), the concept of having different Upstream and downstream power spectral densi-ties is highlighted. The signal-to-noise ratio (SNR) at the input of the central office HDSL terminal unit (HTU-C) can be enhanced by boosting the power output of the remote user HDSL terminal unit (HTU-R). Further improvement in performance can be achieved by reducing the HTU-C NEXT interference. Two techniques are proposed to reach this goal. The first approach is to reduce the HTU-C transmitter power in the downstream Direction for shorter reach cables. The second approach is borrowed from the analog frequency-modulation preemphasis/deemphasis frequency tilting in the Upstream Direction. Combining the three techniques leads to at least 6-dB SNR margin improvement for the full reach car-rier serving area loops. Index Terms—Digital subscriber loops, HDSL/HDSL2, preem-phasis/deemphasis, spectrum modification. I
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Theoretical and practical limits of next-generation high-speed digital subscriber loops
IEEE Transactions on Communications, 2000Co-Authors: A.f. Shalash, Hiroshi TakatoriAbstract:For the single-pair HDSL (HDSL2), the concept of having different Upstream and downstream power spectral densities is highlighted. The signal-to-noise ratio (SNR) at the input of the central office HDSL terminal unit (HTU-C) can be enhanced by boosting the power output of the remote user HDSL terminal unit (HTU-R). Further improvement in performance can be achieved by reducing the HTU-C NEXT interference. Two techniques are proposed to reach this goal. The first approach is to reduce the HTU-C transmitter power in the downstream Direction for shorter reach cables. The second approach is borrowed from the analog frequency-modulation preemphasis/deemphasis frequency tilting in the Upstream Direction. Combining the three techniques leads to at least 6-dB SNR margin improvement for the full reach carrier serving area loops.
Brenda S Henderson - One of the best experts on this subject based on the ideXlab platform.
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an mdoe assessment of nozzle vanes for high bypass ratio jet noise reduction
AIAA CEAS Aeroacoustics Conference, 2006Co-Authors: Brenda S Henderson, Thomas Norum, James BridgesAbstract:The effect of airfoil-shaped vanes placed in the fan stream of a BPR 8 coannular nozzle model system on the resulting jet noise was investigated. The experiments used a Modern Design of Experiments approach to investigate the impact of a range of vane parameters on the noise reduction achieved at representative takeoff conditions. The experimental results showed that the installation of the vanes decreased low frequency noise radiation in the downstream peak-noise Direction and increased high frequency noise in the Upstream Direction. Results also showed that improper selection of the vane configuration resulted in increased low frequency noise radiation in the Upstream Direction. Large angles of attack are shown to reduce noise near the peak jet noise angle and increase noise in the Upstream Direction. The MDOE analysis yields an optimum design that minimizes perceived noise levels. Limited data taken with a BPR 5 nozzle system showed that the vanes result in better effective perceived noise reduction for lower bypass ratio nozzles than for the BPR 8 model.
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an mdoe assessment of nozzle vanes for high bypass ratio jet noise reduction
AIAA CEAS Aeroacoustics Conference, 2006Co-Authors: Brenda S Henderson, Thomas Norum, James BridgesAbstract:The effect of airfoil-shaped vanes placed in the fan stream of a BPR 8 coannular nozzle model system on the resulting jet noise was investigated. The experiments used a Modern Design of Experiments approach to investigate the impact of a range of vane parameters on the noise reduction achieved at representative takeoff conditions. The experimental results showed that the installation of the vanes decreased low frequency noise radiation in the downstream peak-noise Direction and increased high frequency noise in the Upstream Direction. Results also showed that improper selection of the vane configuration resulted in increased low frequency noise radiation in the Upstream Direction. Large angles of attack are shown to reduce noise near the peak jet noise angle and increase noise in the Upstream Direction. The MDOE analysis yields an optimum design that minimizes perceived noise levels. Limited data taken with a BPR 5 nozzle system showed that the vanes result in better effective perceived noise reduction for lower bypass ratio nozzles than for the BPR 8 model.
K S Jacobsen - One of the best experts on this subject based on the ideXlab platform.
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methods of Upstream power backoff on very high speed digital subscriber lines
IEEE Communications Magazine, 2001Co-Authors: K S JacobsenAbstract:This article describes the near-far problem in the Upstream Direction of VDSL, which results when the lengths of VDSL loops in a binder vary significantly. Methods of Upstream power backoff to mitigate the near-far problem are then described. Simulation results are presented, and the performances of the methods are discussed.
H Takatani - One of the best experts on this subject based on the ideXlab platform.
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ebsd characterisation and modelling of columnar dendritic grains growing in the presence of fluid flow
Acta Materialia, 2000Co-Authors: H Takatani, Charlesandre Gandin, M RappazAbstract:Columnar dendritic grains of steel grown in the presence of fluid flow (e.g. solidified on turning rolls) have been characterised by Electron Backscattered Diffraction (EBSD) technique. It is shown that grains have a random crystallographic orientation at the surfaces of the sheet in contact with the mould. In the middle of the sheet, the grains which have survived the growth selection mechanisms exhibit a 〈100〉 texture in which the average dendrite trunk Direction is not exactly aligned with the thermal gradient (i.e. the normal to the surfaces of the sheet). It is tilted by about 15° toward the Upstream Direction. This deviation is examined by simulations of grain structure formation based on a three-dimensional Cellular Automaton (CA)–Finite Element (FE) (3D CAFE) model, which has been modified in order to account for fluid flow effects. The modified CA algorithm includes a growth kinetics of the dendrites which is a function of both the undercooling and fluid flow Direction. It is validated by comparing the predicted shape of an individual grain growing under given thermal and fluid flow conditions with an analytical solution. The 3D CAFE predictions of the columnar grains grown in the presence of fluid flow are in good agreement with the experimental EBSD results.
