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91.
92.
Temporal sequences of planar laser-induced fluorescence (PLIF) images of several high-speed, transient flowfields created in a reflection-type shock tunnel facility were acquired. In each case, the test gas contained either nitric oxide or the hydroxyl radical, the fluorescent species. The processes of shock reflection from an endwall with a converging nozzle and of underexpanded free jet formation were examined. A comparison was also made between PLIF imaging and shadow photography. The investigation demonstrated some of the capabilities of PLIF imaging diagnostics in complex, transient, hypersonic flowfields, including those with combustion.Nomenclature
A
spontaneous emission rate
-
A
las
cross sectional area of laser sheet
-
B
laser absorption rate
-
C
opt
constant dependent on optical arrangement, collection efficiency, etc.
-
D
nozzle throat diameter
-
E
p
laser pulse energy
-
f
J
Boltzmann fraction of absorbing state
-
g
spectral convolution of laser and absorption lineshapes
-
k
Boltzmann constant
-
M
s
incident shock Mach number
-
N
noise, root-mean-square signal fluctuation
-
P
static pressure
-
P
1
initial pressure of test gas in shock tube
-
P
a
free jet ambient pressure
-
P
s
stagnation pressure
-
Q
electronic quenching rate of excited state
-
S
PLIF signal
-
t
time between shock reflection and image acquisition
-
T
static temperature
-
T
s
stagnation temperature
-
a
mole fraction of absorbing species 相似文献
93.
Hui Xiong William Frietze Donald W. Andisik Glen E. Ernst William E. Palmer Lindsay Hinkley Jeffrey G. Varnes Jeffrey S. Albert Chris A. Veale 《Tetrahedron letters》2010,51(51):6741-6744
An efficient synthetic route based on generation and subsequent electrophilic reaction of a Boc-protected azabicyclo[2.2.1]heptane anion to prepare a potent GlyT1 uptake inhibitor (1) is described. 相似文献
94.
Lancaster KM Sproules S Palmer JH Richards JH Gray HB 《Journal of the American Chemical Society》2010,132(41):14590-14595
Redox and spectroscopic (electronic absorption, multifrequency electron paramagnetic resonance (EPR), and X-ray absorption) properties together with X-ray crystal structures are reported for the type 2 Cu(II) C112D/M121E variant of Pseudomonas aeruginosa azurin. The results suggest that Cu(II) is constrained from interaction with the proximal glutamate; this structural frustration implies a "rack" mechanism for the 290 mV (vs NHE) reduction potential measured at neutral pH. At high pH (~9), hydrogen bonding in the outer coordination sphere is perturbed to allow axial glutamate ligation to Cu(II), with a decrease in potential to 119 mV. These results highlight the role played by outer-sphere interactions, and the structural constraints they impose, in determining the redox behavior of transition metal protein cofactors. 相似文献
95.
Pogorelsky I. V. Polyanskiy M. N. Babzien M. Yakimenko V. Dover N. P. Palmer C. A. J. Najmudin Z. Schreiber J. Shkolnikov P. Dudnikova G. 《Laser Physics》2011,21(7):1288-1294
A picosecond CO2 laser was used successfully in a number of experiments exploring advanced methods of particle acceleration [1]. Proton acceleration
from gas-jet plasma exemplifies another advantage of employing the increase in laser wavelength from the optical to the mid-IR
region. Recent theoretical- and experimental-studies of ion acceleration from laser-generated plasma point to better ways
to control the ion beam’s energy when plasma approaches the critical density. Studying this regime with solid-state lasers
is problematic due to the dearth of plasma sources at the critical electron density ∼1021 cm−3, corresponding to laser wavelength λ = 1 μm. CO2 laser offers a solution. The CO2 laser’s 10 μm wavelength shifts the critical plasma density to 1019 cm−3, a value attainable with gas jets. Capitalizing on this approach, we focused a circular polarized 1-TW CO2 laser beam onto a hydrogen gas jet and observed a monoenergetic proton beam in the 1–2 MeV range. Simultaneously, we optically
probed the laser/plasma interaction region with visible light, revealing holes bored by radiation pressure, as well as quasi-stationary
soliton-like plasma formations. Our findings from 2D PIC simulations agree with experimental results and aid in their interpretation. 相似文献
96.
Kim Z Suri B Zaretskey V Novikov S Osborn KD Mizel A Wellstood FC Palmer BS 《Physical review letters》2011,106(12):120501
We present results on a circuit QED experiment in which a separate transmission line is used to address a quasilumped element superconducting microwave resonator which is in turn coupled to an Al/AlO(x)/Al Cooper-pair box charge qubit. With our device, we find a strong correlation between the lifetime of the qubit and the inverse of the coupling between the qubit and the transmission line. At the smallest coupling we measured, the lifetime of the Cooper-pair box was T?=200 μs, which represents more than a twentyfold improvement in the lifetime of the Cooper-pair box compared with previous results. These results imply that the loss tangent in the AlO(x) junction barrier must be less than about 4×10?? at 4.5 GHz, about 4 orders of magnitude less than reported in larger area Al/AlO(x)/Al tunnel junctions. 相似文献
97.
Optimization of magnetic field sweep and field modulation amplitude for continuous-wave EPR oximetry
Palmer J Potter LC Ahmad R 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,209(2):337-340
For continuous-wave electron paramagnetic resonance spectroscopy, what settings of magnetic field sweep width and field modulation amplitude yield the best accuracy in estimated linewidth? Statistical bounds on estimation error presented in this work provide practical guidance: set the sweep width and modulation amplitude to 8 and 4 times the half-width half-maximum linewidth, Γ, respectively. For unknown linewidths in the range [Γ(min),Γ(max)] the worst-case estimation error is minimized by using settings designed for Γ(max). The analysis assumes a Lorentzian lineshape and a constant modulation amplitude across the extent of the irradiated paramagnetic probe. The analytical guidelines are validated using L-band spectroscopy with a particulate LiNc-BuO probe. 相似文献
98.
S.D. Gopal Ram G. Ravi MR. Manikandan T. Mahalingam M. Anbu Kulandainathan 《Superlattices and Microstructures》2011,50(4):296-302
In the present work, a controlled growth of ZnO nanostructures by manipulating Zn metal ion concentration by the chelating action of ethylene diaminetetra acetic acid in hydrothermal method is studied. EDTA produces metal–chelate complex by the formation of bidentate ligand with Zn2+ in the solution and diminishes the reactivity of Zn metal cations. Concentration of EDTA in the mother solution was varied in different ranges like 3, 5 and 10 mM while retaining the zinc metal salt and the NaOH concentration the same. Three different morphologies of wurtzite structured ZnO nanostructures such as nanorods-bunch, separate/discrete uniformly sized hexagonal nanorods and tapered flower petals like shapes are achieved by 3, 5 and 10 mM strengths of EDTA, respectively. The medium concentration 5 mM of EDTA is found to have moderate control over producing ZnO nanostructures of uniform diameter and a high aspect (length to diameter) ratio. An array of vertically aligned free standing ZnO nanorods with uniform spacing is successfully achieved by the addition of 5 mM of EDTA in the mother solution and the same is studied for its fluorescence property at an excitation of 325 nm and it has exhibited a characteristic UV emission of ZnO around 383 nm. 相似文献
99.
Based on real traffic data measured on American, UK and German freeways, we study common features of traffic congestion. We have found that traffic features [J] and [S] defining traffic phases “wide moving jam” (J) and “synchronized flow” (S) in Kerner’s three-phase theory are indeed common spatiotemporal traffic features observed in the UK, the USA and Germany. For the testing of Kerner’s “line J”, representing the propagation of the wide moving jam’s downstream front, four different methods for a study of moving jam propagation in empirical data are studied and compared for each congested traffic situation occurring in the three countries. A statistical study of velocities of wide moving jam fronts is presented, which has been performed through the analysis of database containing more than 280.000 min of observed wide moving jams measured on about 1200 km long freeway network in Hessen (Germany) during more than two years. 相似文献
100.
Andrew P. Mendham John Spencer Babur Z. Chowdhry Trevor J. Dines Muhammad Mujahid Rex A. Palmer Graham J. Tizzard Simon J. Coles 《Journal of chemical crystallography》2011,41(9):1323-1327