Investigating landing gear noise using fly-over data: The case of a Boeing 747-400

Modeling the noise originating from a landing gear has proven to be a challenging task, because of its complicated structure. In full-scale, landing gear noise can only be investigated experimentally by source localization techniques and fly-over measurements with microphone arrays. In the present work, measurements of a Boeing B747-400 were used to determine the contribution of the landing gear to the overall noise emitted during a fly-over and how the broadband noise from the landing gear scales with the flight velocity. A tonal source from the nose landing gear was identified at 380 Hz with a harmonic at 760 Hz and it most likely originates from a cavity. It was also found that the Power Spectral Density (PSD) of the high frequency broadband component varies linearly with frequency and there is some scaling with the ow velocity. Finally, the nose landing gear was shown to be a significant contributor to the overall airframe noise as expected.

Modification of Fe/Cu multilayers under 400 keV Xe20+ irradiation

Two kinds of Fe/Cu multilayers with different modulation wavelength were deposited on cleaved Si(100) substrates and then irradiated at room temperature using 400 keV Xe20+ in a wide range of irradiation fluences. As a comparison, thermal annealing at 300-900 degrees C was also carried out in vacuum. Then the samples were analyzed by XRD and the evolution of crystallite structures induced by irradiation was investigated. The obtained XRD patterns showed that, with increase of the irradiation fluence, the peaks of Fe became weaker, the peaks related to Cu-based fcc solid solution and Fe-based bcc solid solution phase became visible and the former became strong gradually. This implied that the intermixing at the Fe/Cu interface induced by ion irradiation resulted in the formation of the new phases which could not be achieved by thermal annealing. The possible intermixing mechanism of Fe/Cu multilayers induced by energetic ion irradiation was briefly discussed.

Iron XII to XXII spectra measurements between 250 and 400 angstrom

This paper reports laboratory measurements of the spectrum of the most abundant transition Fe ions in the universe. Spectrum of iron of low-lying excited states has been observed in the wavelength range 250-400 angstrom at Chinese Institute of Atomic Energy on the HI-13 tandem accelerator with beams of 130 MeV. A number of spectral lines have been mainly classified as transitions of magnesium-, sodium-, neon-, fluorine-like ions. A total of 54 lines have been measured. Most of them have been mainly ascribed to 3s3p(k)-3p(k+1), 3s(2)3p(k)-3s3p(k+1), 2p(5)3s-2p(5)3p, 3s3d-3p3d and 2p(5)3p-2p(5)3d resonance transitions. These spectral lines have been identified, among which 21 are new and accurately measured. The analysis of the spectra was based on a comparison with other experimental results and calculated values. (c) 2010 Elsevier Ltd. All rights reserved.

UNITY-400超导核磁共振波谱仪锁通道故障维修几例

介绍了美国Varian公司制造的NUITY-400超导核磁共振波谱仪氘锁通道故障几例的检查、分析及排除方法。

UNITY-400超导核磁共振波谱仪SUN工作站电源的代换

本文介绍了用国产微机电源代替UNITY-400超导核磁共振波谱仪工作站电源的方法和步骤。

The Celtic Inscriptions of Britain: Phonology and Chronology, c. 400-1200, Publications of the Philological Society, 37

Sims-Williams, P. (2002). The Celtic Inscriptions of Britain: Phonology and Chronology, c. 400-1200. Publications of the Philological Society, 37. Oxford: Blackwell Publishing. RAE2008