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排序方式: 共有206条查询结果,搜索用时 28 毫秒
21.
22.
D. Hooper 《Analytical and bioanalytical chemistry》1907,46(10-11):742-742
23.
An improved version of the four-hole directional pressure probe, or Cobra probe, is described, in which the frequency response has been extended to 1.5 kHz. The probe measures all three orthogonal mean and turbulent velocity components at a point in the flow field. The probe also resolves the local mean and turbulent components of static pressure, allowing moments between the fluctuating velocity components and pressure to be determined. The techniques developed to allow the improved frequency response and the use of the probe in turbulent, developed pipe flow (a calibration flow) are described. Also given are the turbulent pressure-velocity correlations, which show a high degree of anticorrelation for one velocity component. 相似文献
24.
G. M. Schneider J. D. Hooper A. R. Musgrove G. J. Nathan R. E. Luxton 《Experiments in fluids》1997,22(6):489-495
A novel fluid mixing device, described elsewhere, has been shown to have a dramatic effect on the combustion characteristics
of a fuel jet. The main features of the flow are the deflection of the jet between 30° and 60° from the nozzle axis and its
precession about that axis. Many of the factors governing the nozzle instabilities which drive the mixing in the external
field are imprecisely defined. It is the aim of the present paper to examine, in isolation from the nozzle instabilities,
the influence of precession on a deflected jet as it proceeds downstream from the nozzle exit. The fluid dynamically driven
phenomena within the nozzle which cause the precession are in the present investigation replaced by a mechanical rotation
of a nozzle from which is emerging a jet which is orientated at an angle from the nozzle axis. By this means the effect of
precession on the deflected jet can be investigated independently of the phenomena which cause the precession.
The experimental data reported here has been obtained from measurements made using a miniature, rapid response four-hole “Cobra”
pitot probe in the field of the precessing jet. Phase-averaged three dimensional velocity components identify the large scale
motions and overall flow patterns. The measured Reynolds stresses complement the velocity data and are found to be compatible
with the higher entrainment rates of the jet found in earlier investigations.
Received: 8 November 1995 / Accepted: 27 September 1996 相似文献
25.
We present quantum chemistry simulations of aluminum clusters surrounded by a surface layer of cyclopentadiene-type ligands to evaluate the potential of such complexes as novel fuels or energetic materials. Density functional theory simulations are used to examine the aluminum-ligand bonding and its variation as the size of the aluminum cluster increases. The organometallic bond at the surface layer arises mainly from ligand charge donation into the Al p orbitals balanced with repulsive polarization effects. Functionalization of the ligand and changes in Al cluster size are found to alter the relative balance of these effects, but the surface organometallic bond generally remains stronger than Al-Al bonds elsewhere in the cluster. In large clusters, such as the experimentally observed Al(50)Cp(12)*, this suggests that unimolecular thermal decomposition likely proceeds through loss of surface AlCp* units, exposing the strained interior aluminum core. The calculated heats of combustion per unit volume for these systems are high, approaching 60% that of pure aluminum. We discuss the possibility of using organometallic aluminum clusters as a means of achieving rapid combustion in propellants and fuels. 相似文献
26.
27.
H. Bøggild E. Dahl-Jensen K.H. Hansen J.E. Hooper E. Lohse B.N. Mortensen R. Møller J.Harreskov Nielsen 《Nuclear Physics B》1974,72(2):221-227
19 GeV collisions in the CERN 2 meter hydrogen bubble chamber have been investigated for the number of prongs associated with an observed p, Λ, π? or Ks0 with specified cms momentum components. For p and Λ the associated charged particles have been classified according to their longitudinal direction relative to the observed p and Λ 相似文献
28.
M.R. Belmont R.M. Hooper P.A.C. Amechi 《Journal of Physics and Chemistry of Solids》1985,46(5):607-617
Charge transients were measured in high-quality single-crystal octadecane after electron beam irradiation. The signals produced were of significantly greater duration than the ionization pulse but were not interpretable by conventional uniform field time-of-flight analysis. By assuming that the specimens contained a strong inbuilt polarization field, it was possible to predict the properties of the observed charge transients and obtain values for the positive and negative drift mobilities. The results indicated a positive species with a mobility of 0.7 × 10?4 m2 V?1 s?1 and a negative carrier value of 1.6 × 10?4 m2 V?1 s?1. The standard deviations observed in the data were large, being 0.3 × 10?4 m2 V?1 s?1 and 0.8 × 10?4 m2 V?1 s?1, respectively. This scatter was significantly in excess of the estimated experimental error. 相似文献
29.
C.A. Iglesias R.W. Lee C.F. Hooper B.L. Whitten 《Journal of Quantitative Spectroscopy & Radiative Transfer》1984,32(3):241-247
We consider (i) the use of approximate ion microfield distributions as inputs into spectral line shapes and (ii) the effects of individual lines on unresolved transition array (UTA) profiles observed in highly ionized plasmas. Spectral line shapes and line wings have significant effects on mean opacity calculations. 相似文献
30.