2-Harmonic Maps Between Riemannian Manifolds and Conservation Laws( Ⅰ )

As a generalization of harmonic maps,J. Eells and L.Lemaire present asuggestion of polyharmonic map of order κ,f: M→N,between Riemannianmanifolds which is the critical point critical point of the generalized k-energy functional, ifM is compact,     

Precise integration method for solving singular perturbation problems

This paper presents a precise method for solving singularly perturbed boundary-value problems with the boundary layer at one end. The method divides the interval evenly and gives a set of algebraic equations in a matrix form by the precise integration relationship of each segment. Substituting the boundary conditions into the algebraic equations, the coefficient matrix can be transformed to the block tridiagonal matrix. Considering the nature of the problem, an efficient reduction method is given for solving singular perturbation problems. Since the precise integration relationship introduces no discrete error in the discrete process, the present method has high precision. Numerical examples show the validity of the present method.     

离子交换微柱在线富集-电感耦合等离子体原子发射光谱法测定黄芪中稀土元素

以阳离子交换树脂微柱为柱填充材料,采用电感耦合等离子体原子发射光谱法(ICP-AES)进行检测,研究了三种阳离子树脂在动态条件下对16种稀土离子的交换性能。并确定了最佳交换及洗脱条件。结果表明:005×7树脂的富集效果最好,在4 mL.min-1的进样速度下稀土元素均被定量富集,用4 mol.L-1HCl溶液能迅速地将微柱上稀土离子完全洗脱。富集倍数可达32~42倍,稀土元素的检出限为0.09~2.49μg.L-1,相对标准偏差为1.2%~4.7%(n=6)。方法应用于茶叶标准样品中稀土元素的测定,其测定值与标准值吻合。并对内蒙古产区的黄芪中的稀土元素进行了测定,加标回收率在91%~110%之间。     

Realization of semiconducting Cu2Se by direct selenization of Cu(111)

Bulk group IB transition-metal chalcogenides have been widely explored due to their applications in thermoelectrics. However, a layered two-dimensional form of these materials has been rarely reported. Here, we realize semiconducting Cu₂Se by direct selenization of Cu(111). Scanning tunneling microcopy measurements combined with first-principles calculations allow us to determine the structural and electronic properties of the obtained structure. X-ray photoelectron spectroscopy data reveal chemical composition of the sample, which is Cu₂Se. The observed moiré pattern indicates a lattice mismatch between Cu₂Se and the underlying Cu(111)-$\sqrt{3}$×$\sqrt{3}$ surface. Differential conductivity obtained by scanning tunneling spectroscopy demonstrates that the synthesized Cu₂Se exhibits a band gap of 0.78 eV. Furthermore, the calculated density of states and band structure demonstrate that the isolated Cu₂Se is a semiconductor with an indirect band gap of ～ 0.8 eV, which agrees quite well with the experimental results. Our study provides a simple pathway varying toward the synthesis of novel layered 2D transition chalcogenides materials.     

掺Mn基区InGaAsP/InP双集电区异质光敏晶体管

为了用液相外延法制出高速、高增益异质光敏晶体管,采用了新型的双集电区结构,并且采用Mn作为p型掺杂剂,以代替常用的Zn或Cd制作p~+-n~-集电结.制出的台面型HPT的典型光增益为144;在 80 ps Gaussian光脉冲作用下,其输出脉冲上升时间为 400ps.半峰宽为1.2ns.     

对称双势垒量子阱中自旋极化输运的时间特性

电子的隧穿时间是描述量子器件动态工作范围的重要指标. 本文考虑k³ Dresselhaus 自旋轨道耦合效应对系统哈密顿量的修正, 结合转移矩阵方法和龙格-库塔法来解含时薛定谔方程, 进而讨论了电子在非磁半导体对称双势垒结构中的透射系数及隧穿寿命等问题. 研究结果发现:由于k³ Dresselhaus 自旋轨道耦合效应使自旋简并消除, 并在时间域内得到了表达, 导致自旋向上和自旋向下电子的透射峰发生了自旋劈裂; 不同自旋取向的电子构建时间和隧穿寿命不同, 这是导致自旋极化的原因之一; 电子的自旋极化在时间上趋于稳定. 关键词： 自旋极化输运 透射系数 隧穿寿命 自旋极化率     

低聚苯乙烯基膦酸-磷酸氢锆固载salen Mn(Ⅲ)的合成及其催化苯乙烯环氧化反应

Salen Mn(Ⅲ)配合物是目前己知的高活性烯烃环氧化用催化剂[1,2],虽然在均相条件下选择性好、转化率高、反应条件温和,但难于从反应体系中分离回收和重复使用而大大限制了它的应用;且随着时间的推移,典型配合物的二聚形成含氧或超氧配合物从而导致催化活性下降.因此选择合适的方法将活性组分固载到有机或无机载体上,是均相催化剂多相化的一种重要方法[3].     

富氧条件下Co/MOR 催化剂上甲烷选择催化还原NO

采用浸渍法制备了一系列用于甲烷选择催化还原(CH₄-SCR)氮氧化物的Co/MOR催化剂。采用XRD、BET、TG-MS、H₂-TPR、NH₃-TPD和NO-TPD等手段对催化剂进行表征,并对其在甲烷选择催化还原氮氧化物反应中的活性进行评价。结果表明,钴物种以Co₃O₄尖晶石形态存在于Co/MOR催化剂中;与MOR载体相比,引入钴物种后,催化剂的酸性、氧化还原能力和对NO的吸脱附能力均发生了变化。在甲烷选择催化还原氮氧化物反应中,Co/MOR的催化活性与其氧化还原性能和对NO的吸脱附性能直接相关;其中,Co负载量为10%的Co(10)/MOR催化剂的CH₄-SCR脱硝活性最好,在330℃下NO的转化率达54.2%。     

表面解吸化学电离质谱法快速检测蔬菜中痕量氨基甲酸酯

采用自行研制的表面解吸常压化学电离源（SDAPCI）,首次在无需样品预处理的前提下用质谱法直接测定了多种蔬菜表面残留的痕量氨基甲酸酯,并用串联质谱对所获得的不同氨基甲酸酯农药的离子进行了结构鉴定,排除了检测结果的假阳性。该方法对待测样品无污染,方法检测限低于10－14g/cm2,单个样品的测定时间平均少于1 s,特别适合于对批量样品进行快速检测。