Three-line fluorescence thermometry of optically thick shock-tunnel flow

Two-line fluorescence thermometry measurements based on excitation of the A-X (0, 0) band of nitric oxide were performed in the free-stream flow of a large-scale shock tunnel, the Arnold Engineering Development Center Impulse Facility. Because the flow is optically thick, effects of laser absorption must be taken into account. This can be accomplished by extending the two-line thermometry concept to three lines. We illustrate the three-line technique by combining two-line planar laser-induced fluorescence measurements from separate facility runs. The resulting free-stream temperature T(0) = 468 K ? 65 K is insensitive to assumptions regarding the laser propagation distance through the flow, the vibrational temperature of the flow, and the precise nature of the absorption line shape.     

HB—1耐火粘结剂的研制和应用

HB-1耐火粘结剂是一种性能优良的粘结剂,粘结强度大、砌筑性能好、耐火度高.它能广泛应用于工业锅炉上的砌筑、修补、浇注和涂层。实践证明它优于普通耐火泥浆。同时.HB-1耐火粘结剂还具有施工后不需烘炉即可点火、生产工艺简单。无“三废”排放等优点,因而有良好的经济效益和社会效益。     

Three-dimensional heterostructure of metallic nanoparticles and carbon nanotubes as potential nanofiller

ABSTRACT: The effect of the dimensionality of metallic nanoparticle-and carbon nanotube-based fillers on the mechanical properties of an acrylonitrile butadiene styrene (ABS) polymer matrix was examined. ABS composite films, reinforced with low dimensional metallic nanoparticles (MNPs, 0-D) and carbon nanotubes (CNTs, 1-D) as nanofillers, were fabricated by a combination of wet phase inversion and hot pressing. The tensile strength and elongation of the ABS composite were increased by 39% and 6%, respectively, by adding a mixture of MNPs and CNTs with a total concentration of 2 wt%. However, the tensile strength and elongation of the ABS composite were found to be significantly increased by 62% and 55%, respectively, upon addition of 3-D heterostructures with a total concentration of 2 wt%. The 3-D heterostructures were composed of multiple CNTs grown radially on the surface of MNP cores, resembling a sea urchin. The mechanical properties of the ABS/3-D heterostructured nanofiller composite films were much improved compared to those of an ABS/mixture of 0-D and 1-D nanofillers composite films at various filler concentrations. This suggests that the 3-D heterostructure of the MNPs and CNTs plays a key role as a strong reinforcing agent in supporting the polymer matrix and simultaneously serves as a discrete force-transfer medium to transfer the loaded tension throughout the polymer matrix.     

In situ burning of oil in coastal marshes. 1. Vegetation recovery and soil temperature as a function of water depth, oil type, and marsh type

In-situ burning of oiled wetlands potentially provides a cleanup technique that is generally consistent with present wetland management procedures. The effects of water depth (+10, +2, and -2 cm), oil type (crude and diesel), and oil penetration of sediment before the burn on the relationship between vegetation recovery and soil temperature for three coastal marsh types were investigated. The water depth over the soil surface during in-situ burning was a key factor controlling marsh plant recovery. Both the 10- and 2-cm water depths were sufficient to protect marsh vegetation from burning impacts, with surface soil temperatures of <35 and 48 degrees C, respectively. Plant survival rate and growth responses at these water depth burns were not significantly different from the unburned control. In contrast, a water table 2 cm below the soil surface during the burn resulted in high soil temperatures, with 90-200 degrees C at 0-0.5 cm soil depth and 55-75 degrees C at 1-2 cm soil depth. The 2-cm soil exposure to fire significantly impeded the post-burn recovery of Spartina alterniflora and Sagittaria lancifolia but did not detrimentally affect the recovery of Spartina patens and Distichlis spicata. Oil type (crude vs diesel) and oil applied to the marsh soil surface (0.5 L x m(-2)) before the burn did not significantly affect plant recovery. Thus, recovery is species-specific when no surface water exists. Even water at the soil surface will most likely protect wetland plants from burning impact.     

Effects of wind and air trajectory directions on atmospheric concentrations of persistent organic pollutants near the Great Lakes

Three different regression models involving air temperature, time, and either wind direction or parametric or nonparametric air trajectory direction were used with concentrations of four representative persistent organic pollutants to quantitate the atmospheric transport of these compounds to the Great Lakes. The local wind and parametric trajectory models predicted an optimal source direction for each compound, whereas the nonparametric trajectory model was based on a hypothesized source region. All three regressions were used to calculate the factor by which the partial pressures of each compound measured at five sampling sites increased when the air came from a particular source direction. Dieldrin, chlordane, polychlorinated biphenyl, and polycyclic aromatic hydrocarbon partial pressures were used with each of these regressions, and the correlation coefficients (r2) were evaluated for each model, for each compound, and for each regression term. In general, with the exception of polycyclic aromatic hydrocarbons at some sites, the explanatory powers of the regressions were not improved by the inclusion of any of these directional terms.     

Neutron shielding calculations in a proton therapy facility based on Monte Carlo simulations and analytical models: criterion for selecting the method of choice

Proton therapy facilities are shielded to limit the amount of secondary radiation to which patients, occupational workers and members of the general public are exposed. The most commonly applied shielding design methods for proton therapy facilities comprise semi-empirical and analytical methods to estimate the neutron dose equivalent. This study compares the results of these methods with a detailed simulation of a proton therapy facility by using the Monte Carlo technique. A comparison of neutron dose equivalent values predicted by the various methods reveals the superior accuracy of the Monte Carlo predictions in locations where the calculations converge. However, the reliability of the overall shielding design increases if simulation results, for which solutions have not converged, e.g. owing to too few particle histories, can be excluded, and deterministic models are being used at these locations. Criteria to accept or reject Monte Carlo calculations in such complex structures are not well understood. An optimum rejection criterion would allow all converging solutions of Monte Carlo simulation to be taken into account, and reject all solutions with uncertainties larger than the design safety margins. In this study, the optimum rejection criterion of 10% was found. The mean ratio was 26, 62% of all receptor locations showed a ratio between 0.9 and 10, and 92% were between 1 and 100.     

Bose-Einstein condensates and precision measurements

An ongoing challenge in physics is to make increasingly accurate measurements of physical quantities. Bose-Einstein condensates in atomic gases are ideal candidates for use in precision measurement schemes since they are extremely cold and have laser-like coherence properties. In this paper, we review these two attributes and discuss how they could be exploited to improve the resolution in a range of different measurements.