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31.
D. R. Snelling K. A. Thomson F. Liu G. J. Smallwood 《Applied physics. B, Lasers and optics》2009,96(4):657-669
Laser-induced incandescence (LII) was used to derive temperatures of pulsed laser heated soot particles from their thermal
emission intensities detected at two wavelengths in a laminar ethylene/air co-annular diffusion flame. The results are compared
to those of a numerical nanoscale heat and mass transfer model. Both aggregate and primary particle soot size distributions
were measured using transmission electron microscopy (TEM). The model predictions were numerically averaged over these experimentally
derived size distributions. The excitation laser wavelength was 532 nm, and the LII signal was detected at 445 nm and 780 nm.
A wide range of laser fluence from very low to moderate (0.13 to 1.56 mJ/mm2) was used in the experiments. A large part of the temporal decay curve, beginning 12–15 nsec after the peak of the laser
excitation pulse, is successfully described by the model, resulting in the determination of accommodation coefficients, which
varies somewhat with soot temperature and is in the range of 0.36 to 0.46. However, in the soot evaporative regime, the model
greatly overpredicts the cooling rate shortly after the laser pulse. At lower fluences, where evaporation is negligible, the
initial experimental cooling rates, immediately following the laser pulse, are anomalously high. Potential physical processes
that could account for these effects are discussed. From the present data the soot absorption function, E(m), of 0.4 at 532 nm is obtained. A procedure for correcting the measured signals for the flame radiation is presented. It
is further shown that accounting for the local gas temperature increase due to heat transfer from soot particles to the gas
significantly improves the agreement in the temperature dependence of soot cooling rates between model and experiments over
a large range of laser fluences. 相似文献
32.
Suriya Ounnunkad 《Solid State Communications》2006,138(9):472-475
La or Pr substituted barium hexaferrites, Ba1−x(La or Pr)xFe12O19, x=0.00-0.20, were successfully prepared by a citrate combustion process. The sintered bodies were structurally and magnetically studied by powder X-ray diffraction (XRD) and vibrating sample magnetometry (VSM). All XRD patterns show the single phase of the magnetoplumbite barium ferrite without other intermediate phases. Magnetization (MS) and coercive field (HC) could be improved by substitutions of La or Pr ions on Ba ion basis sites. The MS reveal magnetic behavior with respect to La or Pr ions content, showing an increase at first and then a decrease. The HC increases remarkably with increasing La or Pr ions content. 相似文献
33.
We consider the thorium distributions that are coincident with the distribution of ejecta after the Mare Imbrium impact occurs on the lunar surface and derive a simple model on the spherical target to predict the thickness of Imbrium ejecta deposits as a function of distance from the centre of the Imbrium basin. Then we use the result of Lunar Prospector's gamma ray experiment to test the hypothesis that the distribution of thorium on the lunar surface has an origin from the Mare Imbrium. 相似文献
34.
In wastewater treatment processes, and particularly in activated sludge systems, efficiency is quite dependent on the operating conditions, and a number of problems may arise due to sludge structure and proliferation of specific microorganisms. In fact, bacterial communities and protozoa identification by microscopy inspection is already routinely employed in a considerable number of cases. Furthermore, quantitative image analysis techniques have been increasingly used throughout the years for the assessment of aggregates and filamentous bacteria properties. These procedures are able to provide an ever growing amount of data for wastewater treatment processes in which chemometric techniques can be a valuable tool. However, the determination of microbial communities’ properties remains a current challenge in spite of the great diversity of microscopy techniques applied. In this review, activated sludge characterization is discussed highlighting the aggregates structure and filamentous bacteria determination by image analysis on bright-field, phase-contrast, and fluorescence microscopy. An in-depth analysis is performed to summarize the many new findings that have been obtained, and future developments for these biological processes are further discussed. 相似文献
35.
By a novel controlled combustion synthesis method, a large number of nanostructured ZnO whiskers with different morphologies, such as tetra-needles, long-leg tetra-needles and multi-needles, are prepared without any additive in open air at high temperature. The morphologies and crystalline structures of the as-prepared ZnO nanostructured whiskers are investigated by SEM and XRD. The possible growth mechanism on the nanostructured ZnO whiskers is proposed. The experimental results indicate that the dielectric constants and losses of the nanostructured ZnO whiskers are very low, demonstrating that the nanostructured ZnO whiskers are low-loss materials for microwave absorption in X-band. However, obvious microwave absorption in nanostructured ZnO whiskers is observed. The quasi-microantenna model may be attributed to the microwave absorption of the ZnO whiskers. 相似文献
36.
B. Borasoy E. Epelbaum H. Krebs D. Lee U. -G. Meißner 《The European Physical Journal A - Hadrons and Nuclei》2008,35(3):357-367
We discuss lattice simulations of the ground state of dilute neutron matter at next-to-leading order in chiral effective field
theory. In a previous paper the coefficients of the next-to-leading-order lattice action were determined by matching nucleon-nucleon
scattering data for momenta up to the pion mass. Here the same lattice action is used to simulate the ground state of up to
12 neutrons in a periodic cube using Monte Carlo simulations. We explore the density range from 2% to 8% of normal nuclear
density and analyze the ground-state energy as an expansion about the unitarity limit with corrections due to finite scattering
length, effective range, and P -wave interactions. 相似文献
37.
A model is derived linking microdroplet emission of a liquid-metal ion source (LMIS) to the actual current–voltage characteristic
and operating temperature. All parameters were experimentally investigated using an indium LMIS, confirming the relationships
found. The model allows for the first time the optimisation of a LMIS for low droplet emission at high emission currents.
This is very important for application as a thruster, which has been developed at ARC Seibersdorf research. It can be also
used to extrapolate droplet emission values along the current–voltage characteristic.
Received: 29 January 2002 / Accepted: 7 October 2002 / Published online: 17 December 2002
RID="*"
ID="*"Corresponding author. Fax: +43-50550/3366, E-mail: martin.tajmar@arcs.ac.at 相似文献
38.
39.
E.?Epelbaum H.?Krebs D.?Lee U.?-G.?Mei?ner 《The European Physical Journal A - Hadrons and Nuclei》2009,40(2):199-213
We present lattice calculations for the ground-state energy of dilute neutron matter at next-to-leading order in chiral effective
field theory. This study follows a series of recent papers on low-energy nuclear physics using chiral effective field theory
on the lattice. In this work we introduce an improved spin- and isospin-projected leading-order action which allows for a
perturbative treatment of corrections at next-to-leading order and smaller estimated errors. Using auxiliary fields and Euclidean-time
projection Monte Carlo, we compute the ground state of 8, 12, and 16 neutrons in a periodic cube, covering a density range
from 2% to 10% of normal nuclear density. 相似文献
40.
Chang-Hong Yang Xiu-Feng Cheng Xiu-Jie Yi Guang-Peng Ma Fu-Yi Jiang Jian-Ru Han 《Solid State Communications》2005,134(7):461-464
K0.5Bi0.5TiO3 thin films were deposited on fused quartz, n-type Si(100) and Pt/TiO2/SiO2/Si substrates by repeated coating/dying cycles. X-ray diffraction analysis shows that the films annealed at 700 °C for 10 min present perovskite phase. Atomic force microscopy reveals that the surface morphology is smooth, the grain sizes of the films on Si(100) are quite larger than on fused quartz. The capacitance-voltage hysteresis loops at various sweeping speed are collected as are polarization types. The films in the ON and OFF states are relatively stable. The films also exhibit a hysteresis loop at an applied voltage of 4 V, with a remanent polarization of 9.3 μC/cm2 and a coercive voltage of 2 V. The insulating property of negative bias voltage is better than that of positive bias voltage. The transmittance of the films is between 74 and 82% in the wavelength range of 200-2000 nm. 相似文献