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71.
Remington PJ Knight JS Hanna D Rowley C 《The Journal of the Acoustical Society of America》2005,117(1):68-78
A prototype hybrid system consisting of active and passive components for controlling far-field locomotive exhaust noise has been designed, assembled, and tested on a locomotive. The system consisted of a resistive passive silencer for controlling high-frequency broadband noise and a feedforward multiple-input, multiple-output active control system for suppressing low-frequency tonal noise. The active system used ten roof-mounted bandpass speaker enclosures with 2-12-in. speakers per enclosure as actuators, eight roof-mounted electret microphones as residual sensors, and an optical tachometer that sensed locomotive engine speed as a reference sensor. The system was installed on a passenger locomotive and tested in an operating rail yard. Details of the system are described and the near-field and far-field noise reductions are compared against the design goal. 相似文献
72.
Hanna TA Ghosh AK Ibarra C Zakharov LN Rheingold AL Watson WH 《Inorganic chemistry》2004,43(24):7567-7569
Molybdenum monooxo compoundsMoO(OAr)4-nCln (n=0-2, Ar=2,6-Me2C6H3 or 2,6-i-Pr2C6H3) have been synthesized starting from the dioxo precursor MoO2Cl2. The complexes are characterized spectroscopically and by X-ray diffraction. The formation mechanism likely involves phenol precoordination followed by addition across the Mo=O bond. 相似文献
73.
Südmeyer T Aus der Au J Paschotta R Keller U Smith PG Ross GW Hanna DC 《Optics letters》2001,26(5):304-306
We demonstrate what is to our knowledge the first synchronously pumped high-gain optical parametric oscillator (OPO) with feedback through a single-mode fiber. This device generates 2.3-2.7 W of signal power in 700-900-fs pulses tunable in a wavelength range from 1429 to 1473 nm. The necessary high gain was obtained from a periodically poled LiTaO(3) crystal pumped with as much as 8.2 W of power at 1030 nm from a passively mode-locked Yb:YAG laser with 600-fs pulse duration and a 35-MHz repetition rate. The fiber-feedback OPO setup is compact because most of the resonator feedback path consists of a standard telecom fiber. Because of the high parametric gain, the fiber-feedback OPO is highly insensitive to intracavity losses. For the same reason, the synchronization of the cavity with the pump laser is not critical, so active stabilization of the cavity length is not required. 相似文献
74.
[formula: see text] Oxidation of 2,3-disubstituted 1,4-dioxenes 3 with m-chloroperbenzoic acid in methanol followed by nucleophilic addition of allyltrimethylsilane in the presence of TiCl4 afforded dienes 5, which have been converted to oxabicyclo[4.2.1] nonenes 8 in excellent yield by olefin ring-closing metathesis reaction. 相似文献
75.
Broderick NG Ross GW Offerhaus HL Richardson DJ Hanna DC 《Physical review letters》2000,84(19):4345-4348
We report on the fabrication of what we believe is the first example of a two-dimensional (2D) nonlinear photonic crystal [Berger, Phys. Rev. Lett. 81, 4136 (1998)], where the refractive index is constant but where the 2nd order nonlinear susceptibility is spatially periodic. Such crystals allow for efficient quasi-phase-matched 2nd harmonic generation using multiple reciprocal lattice vectors. External 2nd harmonic conversion efficiencies >60% were measured with picosecond pulses. The fabrication technique is extremely versatile and should allow for the fabrication of a broad range of 2D crystals including quasicrystals. 相似文献
76.
77.
JPC – Journal of Planar Chromatography – Modern TLC - A new, simple, accurate, and rapid high-performance thin-layer chromatographic method has been developed for the determination of... 相似文献
78.
79.
Conductance data are reported for NaI, KI, RbI, CsI, NH4I, NaClO4, and KClO4 in propylene carbonate at 25°C in the concentration range 1×10–4 –8.3×10–3M. Analysis of the data with the current conductance theories indicates negligible ion-association, strong cation-solvent and weak anion-solvent interactions. 相似文献
80.
Normal modes of s-triazine and cyanuric acid were calculated at the DFT(B3LYP)/6-311++G(d,p) level. These modes were analyzed in terms of potential energy distribution (PED), computed using a specially designed set of symmetry coordinates. The normal-mode analysis was described in detail and the PED matrix definition used in the calculations was provided. Particular attention has been devoted to the degenerate vibrations. The experimental infrared spectra of s-triazine and cyanuric acid isolated in low-temperature Ar matrices have been recorded and interpreted by comparison with the theoretically predicted normal modes. In the spectrum of matrix-isolated s-triazine, the IR bands originating from 13C and 15N isotopologues with one of the ring atoms substituted by a rare isotope were detected. These bands were identified thanks to the excellent agreement between the experimentally observed and theoretically predicted isotope shifts. 相似文献