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排序方式: 共有551条查询结果,搜索用时 15 毫秒
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Vijay?AnandEmail authorView authors OrcID profile Justas?Jodele Ethan?Knight Erik?Prisell Owe?Lyrsell Ephraim?Gutmark 《Flow, Turbulence and Combustion》2018,100(3):829-848
An experimental analysis of valved pulsejets based on the Curtis-Dyna design and the concomitant results are discussed in the current paper. By altering the combustor length, the tail pipe length and by adding a flare at the aft-end, twelve different pulsejet configurations are tested. An axially-distributed array of piezoelectric pressure sensors and ion probes reveal the pressure and combustion dynamics inside these devices. Evidence is attained to support the claim that valved Curtis-Dyna pulsejets of the tested configurations behave like a Helmholtz resonator. Each cycle of a pulsejet is composed of temporally and spatially restrained combustion events. Altering the geometry induces an amplitude modulated low frequency instability inside the pulsejet that is characterized by sinusoidally-varying peak cycle pressures. The operating frequency, peak pressures and combustion activity of the pulsejets are characterized to reveal that reliable pulsejet operation requires proper amount of coupling — defined by low time lags — between the pressure peaks and combustion events. 相似文献
85.
We study the shift of a long period grating’s resonance wavelength with UV induced refractive index changes in an all-solid photonic bandgap fiber. A long period grating is mechanically imprinted in an all-solid photonic bandgap fiber with Germanium doped silica high-index rods in a lower-index silica background. The index of the high-index rods is modified through UV exposure, and we observe that the long period grating’s resonance shifts with the bandgaps. With a sensitivity of 21,000 nanometers per refractive index unit and a 8.8 nm resonance width changes of refractive index of 3 × 10−6 are in principle detectable 相似文献
86.
Using cross-correlation frequency-resolved optical gating, we observe the phase-sensitive resonance in the interaction of a soliton with a continuous wave in a photonic crystal fiber. This interaction strongly depends on the difference in the phase velocities of the orthogonally polarized fiber modes and leads to generation of a new spectral peak. The spectral and temporal structure of this signal is revealed in our measurements, which are supported by analytical theory and numerical simulations. 相似文献
87.
Saad FA Buurma NJ Amoroso AJ Knight JC Kariuki BM 《Dalton transactions (Cambridge, England : 2003)》2012,41(15):4608-4617
The synthesis of a thiourea substituted derivative of tris(pyridyl-2-methyl)amine (TPA) is reported. Two of the three pyridine rings are substituted in the 6-position with benzoylthiourea groups. These thiourea groups undergo intramolecular hydrogen bonding to form six-membered rings which leaves one N-H group available to form hydrogen bonds with other molecules. This reports details how the complexation of this new ligand with transition metal ions yields complexes with differing geometries. Seven co-ordinate Mn(II) and Cd(II), six co-ordinate Ni(II) and five co-ordinate Co(II), Cu(II) and Zn(II) complexes have been isolated. 相似文献
88.
Long V. Dinh Douglas A. Knight Mark Paskevicius Craig E. Buckley Ragaiy Zidan 《Applied Physics A: Materials Science & Processing》2012,107(1):173-181
Many of the current synthesis methods for aluminum hydride (alane—AlH3) involve reacting AlCl3 and LiAlH4 in solvents. The reaction requires the formation of an alane adduct such as AlH3⋅[(C2H5)2O] prior to obtaining crystallized stable α-AlH3. This process requires several hours of pumping in a vacuum system to remove the ether and convert the alane etherate into
stable α-alane. This crystallization process is both costly and hazardous because a large amount of highly flammable material (e.g.
ether) is removed by vacuum pumps over several hours. Conversely, the work presented herein describes novel methods to synthesize
adduct-free alane. It is demonstrated here that AlH3 can form by mixing AlCl3 and LiAlH4 in the solid state and heating to 75∘C; only α-AlH3 was obtained. The α-AlH3 product can be washed with minimal solvents leading to zero formation of alane adducts. In addition, the unwanted LiCl by-product
is also removed during the solvent wash, resulting in halide-free α-alane. Although simply mixing and heating the reactants led to a 40% yield of alane, having the reactants compacted and mechanically
pressed while heating increases the yield to 60% crystalline α-AlH3. 相似文献
89.
Trammell SA Nita R Moore M Zabetakis D Chang E Knight DA 《Chemical communications (Cambridge, England)》2012,48(34):4121-4123
Using a low power green laser, we have demonstrated a rate acceleration of ~2-fold for the hydrolysis of methyl parathion by irradiating the plasmon absorption band of Au nanoparticles capped with a Cu(bpy) catalyst. 相似文献
90.
Keith Knight 《Extremes》2001,4(2):87-103
Smith (1994) proposes estimation in linear regression models with non-negative errors by maximizing the sum of fitted values subject to the constraint that the fitted values can be no larger than the corresponding response value. In this paper, we consider the limiting distribution of these estimators under very general conditions. Some extensions to local polynomial estimation are also considered. 相似文献