Neutron Spectroscopic Factors of ^7Li and Astrophysical ^6Li（n,γ）^7Li Reaction Rates

Angular distributions of the ^7Li（^6Li, ^6Li）^7Li elastic scattering and the ^7Li（^6Li, ^7Lig.s.）^6Li, ^7Li（^6Li, ^7Li0.48）^6Li transfer reactions at Ec.m. = 23.7 MeV are measured with the Q3D magnetic spectrograph. The optical potential of ^6Li ＋ ^7Li is obtained by fitting the elastic scattering differential cross sections. Based on the distorted wave Born approximation （DWBA） analysis, spectroscopic factors of ^7Li =^6Li n are determined to be 0.73 ± 0.05 and 0.90 ± 0.09 for the ground and first exited states in ^7Li, respectively. Using the spectroscopic factors, the cross sections of the ^6 Li（n, γ0,1）^7 Li direct neutron capture reactions and the astrophysical ^6Li（n, γ）^7 Li reaction rates are derived.     

近似逼近l_1精确罚函数的罚函数

本文对可微非线性规划问题提出了一类新的近似渐近算法与一类渐近算法,它们都是基于一类逼近l1精确罚函数的罚函数而提出的.并证明了近似算法所得序列若有聚点则其为原问题的最优解;若所得序列为无界的,则给出了序列值收敛到最优值的一个充分条件.对渐近算法,在弱的假设条件下,证明了算法所得的极小点列有界,且其聚点均为原问题的最优解.并在Mangasarian-Fromovitz约束条件下,证明了有限次迭代之后,所有迭代均为可行的,即迭代所得的极小点为可行点.     

分析化学教学中培养学生学习兴趣的几点探讨

结合以往的教学实践,针对学生学习分析化学课程中存在的一些问题,就如何培养医学检验和卫生检验专业学生的学习分析化学兴趣,进行了几点简要的探讨.     

Microstructure of epitaxial superconductive YBa2Cu3O7 thin films prepared at different deposition rates

A study is reported on the growth mechanism of YBa₂Cu₃O₇ with different growth speeds by high resolution transmission microscopy (HRTEM) and analysis of the interface and thin film microstructure. Two thin films were synthesized by pulse laser deposition on [100], miscut 5°, SrTiO₃ substrate at 820 °C, one with a pulse laser frequency of 1 Hz and one with 6 Hz. Cross-sections were studied by an H-9000 NAR HRTEM along the [010] direction. The growth process of the sample made at 1 Hz was as follows. First, distorted step flow growth occurred on a step-mediated substrate surface of 3–4 cells thickness. Second, about a 15 nm thickness of island shape growth becomes superimposed on the area of the step flow layer. Finally, thin film growth occurred but with growth fluctuation. The sample made at 6 Hz showed the characteristics of island growth; the growth area of island or ball shape was of small size and dense distribution, and seemed to be a confused mosaic stack. The influence of growth speed on YBCO epitaxial film microstructure was studied explicitly by HRTEM.     

泡沫铜基底原位生长的铜基导电金属有机框架作为双功能电催化剂

以泡沫铜为基底生长氢氧化铜纳米线,通过原位转化合成二维导电金属有机框架(MOF)材料Cu_3HITP_2(HITP=2,3,6,7,10,11-六氨基三亚苯)作为双功能催化剂,可直接用作析氧及氧还原反应的工作电极,而无需使用额外的基底或粘合剂,且无需后续热处理。研究发现以氢氧化铜纳米线为模板的Cu_3HITP_2表现出了更大的电化学比表面积,这种新型的电极可在碱性溶液(0.1和1.0 mol·L~(-1) KOH)中可以稳定运行,析氧反应中在电流密度达到10 mA·cm~(-2)时的过电位仅为1.53 V,超越了商业二氧化钌的催化性能。此外,该催化剂在氧还原反应中的半波电位达到0.75 V,优于大多数MOF材料。     

Electronic Curves Crossing in Methyl Iodide by Spin--Orbit Ab Initio Calculation

An ab initio investigation of electronic curve crossing in a methyl iodide molecule is carried out using spin-orbit multiconfigurational quasidegenerate perturbation theory. The one-dimensional rigid potential curves and optimized effective curves of low-lying states, including spin-orbit coupling and relativistic effects, are calculated. The spin-orbit electronic curve crossing between ^3Qo＋ and ^1Q1, and the shadow minimum in potential energy curve of ^3Qo＋ at large internuclear distance are found in both sets of the curves according to the present calcu- lations. The crossing position is in the range of Re-1 = 0.2370 3：0.0001 nm. Comparisons with other reports are presented.     

Cs^＋-K^＋ Exchange in Z-Cut KTiOPO4 Crystal Covered with Chromium Masking Layer

Cs^＋-K^＋ ion exchanges are performed on z-cut KTiOPO4 crystals with chromium coating covered. The temperature of ion exchange is 430℃, and the time range from 15min to 30min. The dark mode spectra of the samples are measured by the prism coupling method. The channel structures on the samples are observed by a microscope and the near field pattern of the channel waveguides are measured by the end-fire coupling method. The refractive index of the samples increases and the increments at surface are modulated due to the existence of Cr film. In the region covered by Cr film, the refractive index of the samples at the surface increases dramatically in a shallow layer. The results of energy dispersive x-ray spectra indicate that in the region covered with Cr film, Cr ions participate in the ion exchange process, and enhance the refractive index. The results may provide a possibility that achieves index enhancement and Cr doping synchronically.     

Difference of Oxide Hetero-structure Junctions with Semiconductor Electronic Devices

Charge carrier injection is performed in Pr0.7Ca0.3MnO3 （PCMO） hetero-structure junctions, exhibiting the stability without electric fields and dramatic changes in both resistance and interface barriers, which are entirely different from behaviour of semiconductor devices. The disappearance and reversion of interface barriers suggest that the adjustable resistance switching of such hetero-strueture oxide devices should associate with motion of charge carriers across interfaces. The results suggest that injected carriers should be still staying in devices and result in changes of properties, which lead to a carrier self-trapping and releasing picture in a strongly correlated electronic framework. Observations in PCMO and oxygen deficient CeO2-δ devices show that oxides as functional materials could be used in mieroeleetronics with some novel properties, in which the interface is very important.     

Relationship of Polaron Exchange with Ferromagnetic and Insulator--Metal Transitions in Doped Manganites

We report the experiment results and data analyses based on a polaron exchange model for La0.7Ca0.3MnO3 and Pr0.7（Sr1-xCax）0.3MnO3 epitaxial thin films. In the polaron exchange model with an energy balance condition, critical temperature of Tc for stable ferromagnetic （FM） ordering should depend on △E as kBTc = E0 exp（-△E/kBTc）, where A E denotes the potential barrier for the exchange polarons to overcome. Using the small polaron hopping model, the resistivity peak temperature Tp is a function of the hopping energy Ehop. The dependence of Tp on Ehop is similar to the dependence of Tc on AE, which reveals that the polaron exchange relates to FM and insulator-metal transitions. The result indicates that the polaron exchange model is a simple way for describing the FM ordering, and is very helpful for understanding of complex doped manganites.     

二次生长法NaA沸石分子筛膜的合成与表征——推荐一个研究型综合实验

介绍一个研究型综合实验——二次生长法NaA沸石分子筛膜的合成与表征。实验预先利用热浸渍法在α-Al_2O_3多孔载体管外表面引入NaA沸石分子筛晶种,再通过二次生长法合成NaA沸石分子筛膜。用扫描电子显微镜和X射线衍射仪表征载体管和NaA沸石分子筛及膜的形貌和结构,并利用渗透蒸发乙醇脱水膜分离装置测试膜的分离性能。通过本实验使学生了解膜分离技术这一科学前沿领域,激发学生对科学研究的兴趣,培养学生的科研探究能力。本实验涵盖合成、表征及性能测试,知识要点多、学科覆盖面广,有利于提升学生的实践操作能力、创新意识和综合运用知识的能力。