Shock-Induced Near-Wall Two-Phase Flow Structure Over a Micron-Sized Particles Bed

The present paper studies numerical modelling of near-wall two-phase flows induced by a normal shock wave moving at a constant speed, over a micronsized particles bed. In this two-fluid model, the possibility of particle trajectory intersection is considered and a full Lagrangian formulation of the dispersed phase is introduced. The finiteness of the Reynolds and Mach numbers of the flow around a particle as well as the fineness of the particle sizes are taken into account in describing the interactions between the carrier- and dispersed- phases. For the small mass-loading ratio case, the numerical simulation of flow structure of the two phases is implemented and the profiles of the particle number density are obtained under the constant-flux condition on the wall. The effects of the shock Mach number and the particle size and material density on particle entrainment motion are discussed in detail.The obtained results indicate that interphase non-equilibrium in the velocity and temperature is a common feature for this type of flows and a local particle accumulation zone may form near the envelope of the particle trajectory family.

Domain structure of a Nd60Al10Fe20Co10 bulk metallic glass

Magnetic domain structure of Nd60Al10Fe20Co10 bulk metallic glass (BMG) has been studied by using magnetic-force microscopy. In the magnetic-force images it is shown that the exchange-interaction-type magnetic domains with a period of about 360 nm do exist in the BMG, which is believed to be associated with the appearance of hard-magnetic properties in this system. The existence of the large-scale domains demonstrates that the magnetic moments of a great deal of short-scale ordered atomic clusters in the BMG have been aligned by exchange coupling. Annealing at 715 K leads to partial crystallization of the BMG. However, the exchange coupling is stronger in the annealed sample, which is considered to arise from the increase of transition-metal concentration in the amorphous phase due to the precipitation of Nd crystalline phase.

Investigation of Mn-Implanted n-Type Ge

Mn+ irons were implanted to n-type Ge(1 1 1) single crystal at room temperature with an energy of 100 keV and a dose of 3 x 10(16) cm(-2). Subsequently annealing was performed at 400degreesC for 1 h under flowing nitrogen gas. X-ray diffraction measurements show that as-implanted sample is amorphous and the structure of crystal is restored after annealing. Polycrystalline germanium is formed in annealed sample. There are no new phases found except germanium. The samples surface morphologies indicate that annealed sample has island-like feature while there is no such kind of characteristic in as-implanted sample. The elemental composition of annealed sample was analyzed by Auger electron spectroscopy. It shows that manganese ions are deeply implanted into germanium substrate and the highest manganese atomic concentration is 8% at the depth of 120 nm. The magnetic properties of samples were investigated by an alternating gradient magnetometer. The annealed sample shows ferromagnetic behavior at room temperature.

Characterization Of Crystal Structure In Binary Mixtures Of Latex Globules

Colloidal crystals formed by two types of polystyrene particles of different sizes (94 and 141 nm) at various number ratios (94:141 nm) are studied. Experiments showed that the formation time of crystals lengthens as the number ratio of the two components approaches 1:1. The dependence of the mean interparticle distance (D-0), crystal structure and alloy structure on the number ratio of the two types of particles was Studied by means of Kossel diffraction technique and reflection spectra. The results showed that as the number ratio decreased, the mean interparticle distance (D-0) became larger. And the colloidal crystal in binary mixtures is more preferably to form the bcc structure. This study found that binary systems form the substitutional solid solution (sss)-type alloy structure in all cases except when the number ratio of two types of particles is 5:1, which results instead in the superlattice structure. (C) 2008 Elsevier Inc. All rights reserved.

A simple method to simulate shrinkage-induced cracking in cement-based composites by lattice-type modeling

A new numerical procedure is proposed to investigate cracking behaviors induced by mismatch between the matrix phase and aggregates due to matrix shrinkage in cement-based composites. This kind of failure processes is simplified in this investigation as a purely spontaneous mechanical problem, therefore, one main difficulty during simulating the phenomenon lies that no explicit external load serves as the drive to propel development of this physical process. As a result, it is different from classical mechanical problems and seems hard to be solved by using directly the classical finite element method (FEM), a typical kind of "load -> medium -> response" procedures. As a solution, the actual mismatch deformation field is decomposed into two virtual fields, both of which can be obtained by the classical FEM. Then the actual response is obtained by adding together the two virtual displacement fields based on the principle of superposition. Then, critical elements are detected successively by the event-by-event technique. The micro-structure of composites is implemented by employing the generalized beam (GB) lattice model. Numerical examples are given to show the effectiveness of the method, and detailed discussions are conducted on influences of material properties.

Propagation of a few-cycle laser pulse in a V-type three-level system

Propagation of a few-cycle laser pulse in a V-type three-level system (fine structure levels of rubidium) is investigated numerically. The full three-level Maxwell-Bloch equations without the rotating wave approximation and the standing slowly varying envelope approximation are solved by using a finite-difference time-domain method. It is shown that, when the usual unequal oscillator strengths are considered, self-induced transparency cannot be recovered and higher spectral components can be produced even for small-area pulses. (c) 2005 Pleiades Publishing, Inc.

Analysis on a new type magneto-optical disk for blue lasers

The conventional TbFeCo magneto-optical (MO) medium has a relatively smaller Kerr rotation angle in the blue region than in the red. With the recording wavelength gradually moving to the short wavelength, if TbFeCo is still used as recording medium, the conventional MO disk structure must be optimized to get a larger carrier to noise ratio (CNR). Sabi et al. have found that adding a metal layer attached to the TbFeCo film as thermal control layer is a useful way to get a high CNR. In this paper, we proved this through calculation, and carried out optimization of the new type of disk. Calculation results showed that the new structure is useful in preventing an excessive temperature increase, and has a better thermal response. (c) 2005 Elsevier B.V. All rights reserved.

Numerical analysis and comparison of three metal-oxide-type super-resolution near field structures

Based on the Fresnel-Kirchkoff diffraction theory, we build up a Gaussian diffraction model of metal-oxide-type super-resolution near field structure (super-RENS), which can describe far field optical properties. The spectral contrast induced by refractive index and the structural changes in AgOx, PtOx and PdOx thin films, which are the key functional layers in super-RENS, are studied by using this model. Comparison results indicate that the spectral contrast intensively on laser-induced distribution and change of the refractive index in the metal-oxide films. The readout mechanism of the metal-oxide-type super-RENS optical disc is further clarified. This Gaussian diffraction model can be used as a simple and effective method for choosing proper active materials in super-RENS.

Structure-change-dependent transmittance of PtOx thin film in super-resolution near-field structure: Diffraction effect analysis

To study working mechanism of super-resolution near-field structure (super-RENS) optical disk from a far-field optics view is very necessary because of the actual far-field writing/readout process in the optical disk system. A Gaussian diffraction model based on Fresnel-Kirchhoff diffraction theory of PtOx-type super-RENS has been set up in this Letter. The relationship between micro-structural deformation (change of bubble structure and refractive index profile) with far-field optical response of PtOx thin film has been studied with it in detail. The simulation results are in good agreement with the experimental results reported in literatures with a designed configuration. These results may provide more quantitative information for better understanding of the working mechanism of metal-oxide-type super-RENS. (c) 2007 Elsevier B.V. All rights reserved.

Band structure of photonic crystal fibers with silica rings in triangular lattice

The characteristics of the cladding band structure of air-core photonic crystal fibers with silica rings in triangular lattice are investigated by using a standard plane wave method. The numerical results show that light can be localized in the air core by the photonic band gaps of the fiber. By increasing the air-filling fraction, the band gap edges of the low frequency photonic band gaps shift to shorter wavelength.. whereas the band gap width decreases linearly. In order to make a specified light fall in the low frequency band gaps of the fiber, the interplay of the silica ring spacing and the air-filling fraction is also analyzed. It shows that the silica ring spacing increases monotonously when the air-filling fraction is increased, and the spacing range increases exponentially. This type fiber might have potential in infrared light transmission. (c) 2006 Elsevier B.V. All rights reserved.

A new protein structure of P-II class snake venom metalloproteinases: it comprises metalloproteinase and disintegrin domains

A new metalloproteinase-disintegrin, named Jerdonitin, was purified from Trimeresurus jerdonii venom with a molecular weight of 36 kDa on SDS-PAGE. It dose-dependently inhibited ADP-induced human platelet aggregation with IC50 of 120 nM. cDNA cloning and sequencing revealed that Jerdonitin belonged to the class II of snake venom metalloproteinases (SVMPs) (P-II class). Different from other P-II class SVMPs, metalloproteinase and disintegrin domains of its natural protein were not separated, confirmed by internal peptide sequencing. Compared to other P-II class SVMPs, Jerdonitin has two additional cysteines (Cys219 and Cys238) located in the spacer domain and disintegrin domain, respectively. They probably form a disulfide bond and therefore the metalloproteinase and disintegrin domains cannot be separated by posttranslationally processing. In summary, comparison of the amino acid sequences of Jerdonitin with those of other P-II class SVMPs by sequence alignment and phylogenetic analysis, in conjunction with natural protein structure data, suggested that it was a new type of P-II class SVMPs. (C) 2003 Elsevier Inc. All rights reserved.

Identification and characterization of a new class of human immunodeficiency virus type 1 recombinants comprised of two circulating recombinant forms, CRF07_BC and CRF08_BC, in China

We identified a new class of human immunodeficiency virus type 1 (HIV-1) recombinants (00CN-HH069 and 00CN-HH086) in which further recombination occurred between two established circulating recombinant forms (CRFs). These two isolates were found among 57 HIV-1 samples from a cohort of injecting drug users in eastern Yunnan Province of China. Informative-site analysis in conjunction with bootscanning plots and exploratory tree analysis revealed that these two strains were closely related mosaics comprised of CRF07_BC and CRF08_BC, which are found in China. The genotype screening based on gag-reverse transcriptase sequences if 57 samples from eastern Yunnan identified 47 CRF08_BC specimens (82.5%), 5 CRF07_BC specimens (8.8%), and 3 additional specimens with the novel recombinant structure. These new "second-generation" recombinants thus constitute a substantial proportion (5 of 57; 8.8%) of HIV-1 strains in this population and may belong to a new but yet-undefined class of CRF. This might be the first example of CRFs recombining with each other, leading to the evolution of second-generation inter-CRF recombinants.

Macroinvertebrate community structure in Three-Gorges Reservoir, China

We investigated the macroinvertebrate community structure in Three-Gorges Reservoir during a three-year period after the reservoir became operational. Comparison with data of previous authors obtained before the damming showed that the benthic community changed drastically in the reservoir. Oligochaetes and chironomids dominate the present community. An apparent annual cycle in the benthic community (expressed as richness, density and community type) was found in the second year, lagging one year behind the annual cycle of transparency. After the second year, a Nais-Polypedilum community type, occurring in winter and spring with low inflow discharge and high transparency, was followed by a Limnodrilus community type that occurred in autumn and summer under contrasting conditions. Despite river regulation and damming, it appeared that macroinvertebrates in subtropical canyon-shaped reservoirs remained influenced by floods.

HYDROGRAPHIC VARIATIONS IN SIZE STRUCTURE OF PLANKTON BIOMASS IN A CHANGJIANG FLOODPLAIN LAKE

The size structure of the planktonic community in a Changjiang floodplain lake (Lake Chenhu, Hubei, P. R. China) was described for the inundation period of May through September 1983. The modality of the Sheldon-type size distributions changed hydrographically with the spectral profiles being bimodal during low, rising, mid-high and falling water phases, and trimodal soon after filling and shortly before falling. The modal peaks corresponded respectively to the dominant organisms of chlorophytes and nauplii, while the troughs centered on the bacteria and macrocrustacean size classes in the lake. The slope of the normalized biomass spectrum (an index of plankton size distribution) was less than -1.0 for the filling and falling phases or close to -1.0 for the high water period, indicating that the planktonic biomass tended to decrease or evenly distributes across logarithmically ordered size classes, respectively. This observed variation in the size distribution of the plankton community mainly resulted from changes in water levels and contents of particulate inorganic matter (PIM) in the lake.

Fabrication and Characterization of High Power InGaN Blue-Violet Lasers with an Array Structure

InGaN/GaN multi-quantum-well-structure laser diodes with an array structure are successfully fabricated on sapphire substrates. The laser diode consists of four emitter stripes which share common electrodes on one laser chip. An 800-mu m-long cavity is formed by cleaving the substrate along the < 1 (1) over bar 00 >. orientation using laser scriber. The threshold current and voltage of the laser array diode are 2A and 10.5 V, respectively. A light output peak power of 12W under pulsed current injection at room temperature is achieved. We simulate the electric properties of GaN based laser diode in a co-planar structure and the results show that minimizing the difference of distances between the different ridges and the n-electrode and increasing the electrical conductivity of the n-type GaN are two effective ways to improve the uniformity of carrier distribution in emitter stripes. Two pairs of emitters on a chip are arranged to be located near the two n-electrode pads on the left and right sides, and the four stripe emitters can laser together. The laser diode shows two sharp peaks of light output at 408 and 409 nm above the threshold current. The full widths at half maximum for the parallel and perpendicular far field patterns are 8 degrees and 32 degrees, respectively.