再谈部分电路的感生电动势

由于中学课程内容的限制, 加上学生自身数学知识有限, 对感生电动势很难有准确深入的把握, 难以 领会其实质. 而现在的教学辅导材料鱼龙混杂, 有些题目实则是误导. 以一道典型题的错解为例, 分析其错误原因, 并给出详细的正确解题过程     

Structural,electronic,and magnetic properties of vanadium atom-adsorbed MoSe_2 monolayer

Using the first-principles calculations, we study the structural, electronic, and magnetic properties of vanadium adsorbed MoSe_2 monolayer, and the magnetic couplings between the V adatoms at different adsorption concentrations. The calculations show that the V atom is chemically adsorbed on the MoSe_2 monolayer and prefers the location on the top of an Mo atom surrounded by three nearest-neighbor Se atoms. The interatomic electron transfer from the V to the nearestneighbor Se results in the polarized covalent bond with weak covalency, associated with the hybridizations of V with Se and Mo. The V adatom induces local impurity states in the middle of the band gap of pristine MoSe_2, and the peak of density of states right below the Fermi energy is associated with the V- dz~2 orbital. A single V adatom induces a magnetic moment of 5 μBthat mainly distributes on the V-3d and Mo-4d orbitals. The V adatom is in high-spin state, and its local magnetic moment is associated with the mid-gap impurity states that are mainly from the V-3d orbitals. In addition,the crystal field squashes a part of the V-4s electrons into the V-3d orbitals, which enhances the local magnetic moment.The magnetic ground states at different adsorption concentrations are calculated by generalized gradient approximations(GGA) and GGA+U with enhanced electron localization. In addition, the exchange integrals between the nearest-neighbor V adatoms at different adsorption concentrations are calculated by fitting the first-principle total energies of ferromagnetic(FM) and antiferromagnetic(AFM) states to the Heisenberg model. The calculations with GGA show that there is a transition from ferromagnetic to antiferromagnetic ground state with increasing the distance between the V adatoms. We propose an exchange mechanism based on the on-site exchange on Mo and the hybridization between Mo and V, to explain the strong ferromagnetic coupling at a short distance between the V adatoms. However, the ferromagnetic exchange mechanism is sensitive to both the increased inter-adatom distance at low concentration and the enhanced electron localization by GGA+U, which leads to antiferromagnetic ground state, where the antiferromagnetic superexchange is dominant.     

由Pb-O螺旋链构筑具有罕见ecl拓扑结构的铅(Ⅱ)配位聚合物

Under hydrothermal condition, a novel coordination polymer [Pb(C₄H₄O₆)]_n has been successfully synthesized by reaction flexible racemic ligand D,L-tartaric acid (C₄H₄O₆) and Pb(Ⅱ)(NO₃)₂. Its structure is determined by single-crystal X-ray diffraction analysis and further characterized by X-ray powder diffraction, IR, CHN and TG analyses. It crystallizes in tetragonal, space group I4₁/acd with a=1.569 0(2) nm, c=1.009 5(2) nm, V=2.485 0(7) nm³, Z=16. Its structure contains left- and right-handed helical chains. Such helical chains with opposite chirality are alternatively arranged and further connected to form a three-dimensional framework. Topology analysis shows that it presents rare ecl topological structure. CCDC: 771026.     

大黄鱼大型座底式围栏养殖的不同形式和管理的效果

为了解大黄鱼大型座底式围栏养殖的不同形式和管理的效果, 在详细介绍围栏结构和饲养管理技术的基础上, 对养殖效果进行了比较. 结果: 在加强饲养管理的条件下, 以钢管柱桩+铜合金网衣围栏养殖效果最佳, 台州大陈岛海域的该种形式围栏2017~2018年平均单位面积产量达到27kg·. 研究结果可为大黄鱼围栏养殖的形式选择提供参考, 同时为大型围栏养殖提供管理经验     

正则强码的分解与伯努利分布

本文得到正则强码的伯努利分布定理。还研究强码的分解,给出正则强码可分解为两个正则强码复合的充要条件。     

光学多目标识别的新方案

介绍一种数学形态学的击中与否（Ｈｉｔ－ｏｒ－Ｍｉｓｓ）算法，能快速准确实现光学多目标识别的新方案，避免了普通光学相关目标识别方法中经常出现的错误信号，因此，其目标识别结果更为有效可靠。     

假蜜环菌的研究 Ⅰ.菌种的分离与鉴定

应用发光柳树朽木煎剂治疗胆囊炎,取得初步效果,这在医疗上还是首次,本文主要介绍菌种的分离和鉴定工作。 首先我们从发光柳树朽木上分离到一株发光真菌,菌丝体能发出浅蓝色的荧光,在人工培养基上生长时,此菌具有十分发达的不发光的根状菌索;形成的子实体丛生,不发光,菌盖浅蜜黄色,边缘薄,菌褶延生,菌柄杏仁黄色,略为扭曲,纤维质,无菌环,孢子印白色,孢子广椭圆形,光滑。经鉴定,这株发光真菌为假蜜环菌[Armillariella tabescens(Scop,ex Fr.)Sing]。     

时空混沌序列的局域支持向量机预测

结合局域预测法计算速度快的优点和支持向量机的泛化性能好、全局最优、稀疏解等特性，用局域支持向量机预测研究了时空混沌序列的局域预测性能，并用局域支持向量机预测模型讨论了嵌入维数、邻近个数选择以及时空混沌的耦合方式和格子间的耦合强度变化对时空混沌局域预测性能的影响.研究结果表明：局域支持向量机不仅比全局支持向量机、局域零阶预测、局域线性预测等方法具有更好的预测性能，且具有对嵌入维数和邻近个数不敏感的优点；时空混沌的耦合方式和格子间的耦合强度对时空混沌序列的预测性能有明显影响.     

Elimination of Crystallographic Wing Tilt of Canti-Bridged Epitaxial Laterally Overgrown GaN Films by Optimizing Growth Procedure

Canti-bridged epitaxial lateral overgrowth （CBELO） of GaN is performed by metalorganic chemical vapour deposition （MOCVD） on maskless V-grooved sapphire substrates prepared by wet chemical etching with different mesa widths. The wing tilt usually observed in ELO is not found in the CBELO GaN with wide mesa widths, while it can be detected obviously in the GaN with narrow mesa widths. The wing tilt of CBELO GaN grown on a grooved sapphire substrate with narrow mesa can be controlled by adjusting the thickness of the nucleation layer. The dependence of the wing tilt on the nucleation layer thickness is studied. Cross-sectional scanning electron microscopy is used to characterize the geometry of the wing regions, and double crystal x-ray diffraction is used to analyse the structural characteristics and to measure the magnitude of the crystalline wing tilt. It is found that the crystalline wing tilt can be eliminated completely by first growth of a thin nucleation GaN layer then the CBELO GaN. Possible reason and the origin of the wing tilt in CBELO GaN films are also discussed.     

固定边界条件下Fermi-Pasta-Ulam-Tsingou短链能量均分性质研究

采用固定边界条件,数值研究了Fermi-Pasta-Ulam-Tsingou (FPUT)短链的能量均分性质.研究发现,在较强的非线性强度区间内,能量均分时间t_eq与能量密度ε满足t_eq～ε^-4.0的标度关系.在该非线性强度区间内,能量通过相邻本征模之间的共振不停的传输,并最终达到能量均分状态.这说明,即使不存在非平庸的六波共振,只要相邻本征模间的共振可以发生,t_eq～ε^-4.0的标度关系就能出现.随着非线性强度的减小,该标度关系不再成立.此时,能量是通过高频本征模的共振逐渐向低频本征模传输的.