Dynamics of Front Driven by Convection Field in Bistable Media

The front dynamics driven by a convection field in a model of FitzHugh-Nagumo type is studied both analytieMly and numerically. Saddle-node bifurcation induced by the convection field is found by using a singular perturbation analysis of front solutions. Convection field accelerates the B1och front propagating opposite the direction of convection field, but inhibits the Bloch front propagating along the direction of convection field. In addition convection field drives Ising front to travel opposite the direction of convection field.     

Dynamic Crossover in Metallic Glass Nanoparticles

We report the dynamic crossover behavior in metallic glass nanoparticles(MGNs)with the size reduction based on the extensive molecular dynamics(MD)simulations combined with the activation-relaxation technique(ART).The fragile-to-strong transition of dynamics can be achieved by just modulating the characteristic size of MGNs.It can be attributed to the abnormal fast surface dynamics enhanced by the surface curvature.By determining the potential energy surface,we reveal the hierarchy-to-flat transition of potential energy landscape(PEL)in MGNs,and demonstrate the intrinsic flat potential landscape feature of the MGN with size smaller than a critical size.Our results provide an important piece of the puzzle about the size-modulated potential energy landscape and shed some lights on the unique properties of MGs in nanoscale.     

基于荧光光谱—模拟退火法年份白酒中乙酸浓度预测研究

近年来年份白酒市场中行业规范有所缺失,因此年份白酒的研究具有深远意义和市场价值.白酒中单体物质的浓度会随着白酒的年份改变,检测白酒中单体浓度可用来鉴定白酒质量及其年份.基于国内某品牌年份原桨白酒的三维荧光光谱,对其中乙酸浓度进行了建模研究.对原始光谱进行了小波分解和求导预处理.研究发现小波分解第一层和第二层呈噪声特征,...     

Radiography of a K_α X-ray source generated through ultrahigh picosecond laser–nanostructure target interaction

Laser-driven ultrafast X-ray sources are widely used for diagnostic radiography. However, there is a large divergence of fast electrons when they are generated by an intense short-pulse laser interacting with a foil target.We design a nanowire array target to achieve a more compact point X-ray source. Fast electrons are confined and guided by the nanowire array structure in order to generate a Kαsource with a small spot size. In our work, the smallest measured source size is comparable to the laser spot size, while the conversion efficiency can reach2.4 × 10-4.     

NaYF_4∶Yb~(3+),Tm~(3+)/CdSe纳米异质结构的近红外上转换发光性能

采用两步高温热分解法合成了纳米异质结构的Na YF4∶Yb3+,Tm3+/Cd Se。X射线衍射测试结果表明样品由纯六角相的Na YF4(β-Na YF4)和纤锌矿型Cd Se组成。980 nm激发的上转换光谱表明Na YF4∶Yb3+,Tm3+和Cd Se之间存在能量传递,Tm3+将Yb3+传递给它的能量部分地传递给Cd Se,被激发的Cd Se又将能量回传给Tm3+的相应能级,最终使得Na YF4∶Yb3+,Tm3+的紫外和蓝光发射完全消失,而797 nm的近红外发射大幅增强。Na YF4∶Yb3+,Tm3+/Cd Se纳米异质结构的激发光和发射光均处于生物组织的光学透过窗口(700~1 100 nm),对生物组织的光损伤小,在生物医学领域有很大的应用潜力。     

Fe20Al80非晶态粉末的晶化特征和穆斯堡尔效应

Fe₂₀Al₈₀非晶态粉末是通过180球磨而制备的。X射线衍射和透射电子显微镜实验不但证实它的非晶性,而且给出它的平均颗粒度大小和晶化产物。穆斯堡尔谱测量确定了该非晶态粉末的顺磁性和晶化度。 关键词：     

Can the Fullerene Cso Encage the Tetrahedral Td-N4？ A Density Functional Study

The generalized gradient approximation based on density functional theory is used to study the structural, electronic and magnetic properties of the endohedral complex of Cso with tetrahedral Td N4. The most unstable Ih Cso can most effectively stabilize the N4 molecule, similar to the ease of Ih N4 C60 [Structural Chemistry 16 （2005）567]. It is worth noting that the cage becomes nonmagnetic due to the encaging of N4.     

二价钌有机螯合物Ru(dpphen)2+3与花生酸混合LB膜的结构及光谱特性

对不同组分的Ru(dpphen)