First-principle calculation of the recombination cross-section assisted by acoustic phonons at shallow impurities in semiconductors

Summary An original Monte Carlo study of the equilibrium microscopic and macroscopic recombination cross-sections at shallow impurity centres is presented. Both cross-sections are investigated in lightly dopedp-Si as functions of the temperature and ionized acceptor concentration. In order to treat generation-recombination processes we extend the semi-classical Boltzmann equation through a simulation of the carrier motion in the energy-configuration space of an impurity centre. The analysis of the scattering rates as a function of the total carrier energy enables a microscopic interpretation of the capture process to be carried out. The role of excited levels is naturally included and found to be of main importance at increasing lattice temperatures. Numerical results are then compared with available experiments and existing analytical calculations.     

机载电子设备机柜布线工艺设计

时电子机柜传统的走线方式进行了分析、解剖，提出了新的走线方案模式，从工艺角度时机柜走线结构进行了改进设计，使之更适合于机栽机柜的布线要求。     

电子设计自动化的人工进化实现途径

电路进化设计仿照生物进化原理,通过进化计算配置电路或系统的内部结构来获得预期的电路功能。本文简述了电路进化设计的基本原理和发展概况,通过实例说明其实现步骤和关键技术,并且讨论现存的主要问题及相关的研究方向。     

电子线路综合性、设计性实验教学方法探讨

作者结合在指导电子线路综合性、设计性实验的过程中的体会，讨论了电子线路综合性、设计性实验的层次化、模块化和菜单化的教学方法和部分开放式的教学模式，并对实验报告模式改革进行了探讨。     

电子稳像技术中的坐标变换及像偏移函数分析

为了进行图像偏移的数字补偿 ,需要分析图像的偏移函数 ,要对定坐标系O0 X0 Y0 Z0 ,CCD摄像机载体坐标系O1X1Y1Z1和像空间坐标系O2 X2 Y2 Z2 进行坐标变换 ,从而得出图像偏移与载体运动速度的关系 ,为数字电子稳像奠定基础。     

Spectral and Acid–Base Properties of Arylidene Derivatives of Dicyclopentano[b,e]pyridines Serving as Fluorescent pH-Indicators

The bathochromic shifts of absorption and emission bands upon the protonation of dicyclopentano[b,e]pyridines fall in the range of 3500-5500 cm^–1. Both the neutral and protonated forms show high fluorescence quantum yields. The spectral and acid–base properties of these compounds may be varied within a broad range by introducing electron-donor substituents into the aromatic side rings. The protonation constants in the ground and excited states of each of these compounds have similar values as a result of steric hindrance arising upon protonation of the pyridine nitrogen atom.     

Theoretical study on structures of Ga3N, GaN3, Ga3N2 and Ga2N3 clusters

The structures of Ga_3N, GaN_3, Ga_3N_2 and Ga_2N_3 clusters are studied using the full-potential linear-muffin-tin-orbital molecular dynamics (FP-LMTO MD) method. Four structures for Ga_3 N, five structures for GaN_3, nine structures for Ga_3N_2 and nine structures for Ga_2N_3 have been obtained. The most stable structures of these clusters are planar ones. A strong dominance of the N－-N bond over the Ga－-N and Ga－-Ga bonds appears to control the structural skeletons, supporting the previous result obtained by Kandalam and co-workers. The most stable structures of these small GaN clusters displayed semiconductor-like properties through the calculation of the HOMO－LUMO gaps.     

Studies on the process of Bi12MO20 (M=Ti,Ge, Si) formation from oxides

Using DSC technique, the chemical interaction in Bi₂O₃+MO₂ mixtures resulting the Bi₁₂MO₂₀ phase, (M=Ti, Ge and Si) was monitored. Kinetic parameters for the primary stage of interaction were yielded by the non-isothermal method of kinetic evaluation of experimental heat flux DSC curves. The model of three-dimensional diffusion according to Jander was fitted as the best in a statistical sense.

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Zusammenfassung Mittels DSC wurde die Bildung von Bi₁₂MO₂₀-Phasen aus Bi₂O₃+ MO₂-Gemischen (mitM= Ti, Ge uns Si) untersucht. Die kinetischen Parameter für den ersten Schritt der Reaktion erhielt man mittels einer nichtisothermen Methode der kinetischen Auswertung der experimentellen Wärmefluß-DSC-Diagramme. Als bestes Modell zur Beschreibung des Vorganges ergab sich das dreidimensionale Diffusions modell von Jander.

     

稀土钻酸盐的电子和红外光谱研究

本文考察了具有钙钛矿型晶体结构的稀土钴酸盐LnCoO_3(Ln=La～Er)的电子和红外光谱,用晶体学和Ln-O,Co-O键的共价性讨论了实验结果,发现中心离子Co~(3+)的电子跃迁受到稀土离子Ln~(3+)的有规律的影响。LnCoO_3有其特定的CoO_6基团振动光谱,Ln-O的共价性随着稀土元素原子序数的增大而加强:重稀土的红外光谱比轻稀土更丰富,有的还出现分裂现象。用IR技术考察了制备等过程中晶体结构的变化。     

Charge states of transition metal in “Cr, Co and Ni” doped Ln0.5Ca0.5MnO3 CMR manganites

The XAS study at Cr, Co, Ni and Mn K-edges was performed for the doped CMR manganites Ln_0.5Ca_0.5Mn_1-xB_xO₃ with Ln=La, Nd, Sm and B= Cr, Co, Ni (), on the samples that were studied previously for their ferromagnetic-metallic to antiferromagnetic-insulator transition. We observed that the formal charges of the doping elements are Ni²⁺, Co²⁺ and Cr³⁺. It is also evidenced that the average formal charge of the manganese is increased after doping, in agreement with the charge compensation keeping “O₃” stoichiometry. These results suggest that the doping elements participate directly to the band structure. Received: 9 January 1998 / Received in final form: 6 April 1998 / Accepted: 7 April 1998