Effects of vortex pairing on particle dispersion in turbulent shear flows

Particle dispersion in large-scale dominated turbulent shear flow is investigated numerically with special emphasis on the effects of the vortex-pairing phenomenon. The particle dispersion is visualized numerically by following the particle trajectories in a flow consisting of large vortices which are undergoing pairing interaction. The flow field is generated by a discrete vortex method. Important global and local fiow quantities from the numerical simulation compare reasonably well with experimental measurements.

For both cases of point sources with continuous particle release and an initially distributed line source, the particle dispersion results demonstrate that the extent of particle dispersion depends strongly on the Stokes number, the ratio of the particle aerodynamic response time to the characteristic time of the vortex-pairing flow field. Particles with relatively small Stokes numbers disperse laterally at approximately the saine rate as that of the fluid particles and particles with large Stokes numbers disperse much less than the fluid particles. Particles with intermediate Stokes numbers (0.5-5) may be dispersed laterally farther than the fiuid particles and may actually be flung out of the vortex structures. Due to the strong particie entrainment power, the flow during the vortex-pairing process seems to produce higher particle lateral dispersion than the pre-pairing and post-pairing flows.     

免受温度影响的光纤光栅位移传感器

将一定长度、均匀周期的光纤光栅沿轴向刚性粘贴于厚度呈阶跃分布的等腰三角状悬臂梁界线附近的表面上 ,通过观测该光栅反射谱中两个峰值的间距来监测梁自由端在垂直于表面方向上的位移。实验表明该无源温漂位移线性传感装置的传感灵敏度达 9.2 4× 10 -2 nm/ mm,与理论值 9.4× 10 -2 nm/ mm非常接近。     

Cavity Ring Down Laser Absorption Spectroscopy of NiI

用激光蒸发/反应、超声射流和光腔衰荡吸收光谱方法研究NiI在445～510 nm的吸收光谱. 发现两个新的跃迁体系[21.3]²?_5/2～X²?_5/2和[21.9]²Π_3/2～X²?_5/2,并且观察到了同位素分子⁵⁸NiI和⁶⁰NiI光谱. 同时计算得到了电子态[21.3]^{2相似文献}   

Application of magnetic poly(styrene-glycidyl methacrylate) microspheres for immunomagnetic separation of bone marrow cells

Surface-functionalized magnetic poly(styrene-glycidyl methacrylate) (PS-GMA) microspheres were prepared and coupled with Sca-1 antibody for cell selection from murine bone marrow mononuclear cells (MNCs). Biotinylated Sca-1 antibody could be directly coupled to avidin-bound magnetic microspheres. Alternatively, oxidized goat anti-mouse antibody was covalently bound onto the amino group-containing magnetic microspheres in a site-directed manner, and the resultant conjugate was coupled with non-modified Sca-1 antibody. Using the indirect antibody-bound magnetic microspheres, the purity of isolated Sca-1⁺ cells increased with bead-to-cell ratio. Using a bead-to-cell ratio of 10 beads/cell, a purity of 85% Sca-1⁺ cells corresponding to a 17-fold enrichment was achieved.     

Comparison of elemental contents of Korean space foods using instrumental neutron activation analysis

The analysis of mineral contents in space foods is needed to obtain an information on a comprehensive elemental composition as well as the investigation on the effects of human nutrition and health based on the dietary intake of mineral elements. Recently, six items of new Korean space foods (KSFs) such as kimchi, bibimbap, bulgogi, a ramen, a mulberry beverage and a fruit punch which was developed by the KAERI, and the contents of more than 15 elements in the samples were examined by using instrumental neutron activation analysis (INAA). Five biological certified reference materials, NIST SRM were used for analytical quality control. The results were compared with those of common Korean foods reported, and these results will be applied toward the identification of irradiated foods.     

Kinetic Study on the Pretreatment and Enzymatic Saccharification of Rice Hull for the Production of Fermentable Sugars

The production of fermentable sugars from rice hull was studied by dilute acid pretreatment and enzymatic saccharification. Rice hull (15%, w/v) was pretreated by 1% (v/v) sulfuric acid at high temperature (120∼160 °C) for 15, 30, 45, and 60 min, respectively. The maximum sugar concentration from rice hull in the prehydrolysate was obtained at 140 °C for 30 min, but the enzymatic saccharification yield from the corresponding pretreated rice hull is not high. To another aspect, the maximum enzymatic saccharification yield was achieved at 160 °C for 60 min, while the recovery of fermentable sugars was the poorest. To take account of fermentable sugars from pretreatment and enzymatic saccharification, the maximum yield of sugars was obtained only when rice hull was treated at 140 °C for 30 min. Under this condition, 72.5% (w/w) of all sugars generated from the raw material can be recovered. The kinetic study on the enzymatic saccharification of dilute acid pretreated rice hull was also performed in this work by a modified Michaelis–Menten model and a diffusion-limited model. After calculation by a linear and a non-linear regression analysis, both models showed good relation with the experimental results.