Dynamic analysis of V-folded cavity for TEM00 operation of end-pumped solid-state laser

Based on graphic analysis design method of optical resonator, a simple design expression of V-folded cavity of end-pumped solid-state lasers with TEM00 operation is described, which satisfies two criterias of the resonator design. We give numerical simulation of spot size as a function of thermal focal length using this design approach whose advantages are validated experimentally.

V^3＋：YAG晶体的生长、色心与光谱性能研究

采用石墨电阻加热的温梯法生长了V：YAG晶体，晶体的不同部位呈现两种不同的颜色：浅绿色和黄褐色．通过对比分析不同颜色V：YAG晶体的室温吸收光谱，推断出石墨发热体高温下扩散出来的C可以起到还原作用，提高晶体中V^3＋tetra离子的浓度，同时诱导了F心的形成．在1300℃下，对不同颜色的V：YAG晶体进行真空退火处理，发现处于八面体格位中的V^3＋离子在热激发作用下与近邻的四面体格位Al^3＋离子存在置换反应，由此产生一定浓度的四面体格位V^3＋离子．同时，F心在退火过程中被完全消除，释放出来的自由电子被

Characteristics and optical spectra of V : YAG crystal grown in reducing atmosphere

A V:YAG single crystal was grown by the temperature gradient technique (TGT) with graphite-heating elements. The as-grown crystal has different colorations of light green and yellow brown in different parts. Distribution of vanadium in three samples with different colorations was determined by inductively coupled plasma-mass spectrometry. From the absorption spectrum of the yellow-brown part with peaks at 370, 820 and 1320nm, we can deduce that the reducing atmosphere of carbon diffused from the heating elements can increase the concentration of tetrahedral V3+ ions and induce F color centers. All three samples exhibited light-green color after annealing in vacuum or H-2 atmospheres. In the vacuum annealing process, the V3+ ions in tetrahedral positions were enhanced through two methods: one method is the exchanging of octahedral V3+ and tetrahedral Al3+ ions in neighboring sites under thermal excitation, the other is that F color centers were thoroughly eliminated and the escaped free electrons could be captured by V ions with higher valance states to further improve the concentration of tetrahedral V3+ ions. Besides the two mechanisms, the H-2 annealing process greatly improved the V-tetra(3+) ions through the reduction effect of H-2. (c) 2006 Elsevier B.V. All rights reserved.

Frequency of the mtDNA 9-bp deletion in Chinese ethnic groups

The 9-bp deletion in the COII/tRNA(Lys) intergenic region (region V) of human mitochondrial DNA was screened in 1521 Chinese from 16 ethnic groups and 9 Hen geographic groups. The highest frequency was found in populations of Miao (32.4%) and Bouyei (30.8

上海曹扬环浜污染水体的生态修复

曹扬环浜是一条环形封闭水道,水质低于地表水V类标准,水体处于严重超富营养化水平,全浜暴发蓝藻水华现象。在采用截污、造流、生态恢复等生态工程措施综合治理后,随着健康水生态系统的建立,河浜水质逐步变好(由劣V类改善为接近Ⅲ类标准),水体透明见底,沉水植物覆盖率达70%~90%,水体一直维持“清水草型稳态”。重点介绍了河道治理中采用的生态修复措施及其作用,并从截污、营养盐、水生生物等方面分析了各项工程措施对抑制藻类生长、水质改善的影响,对我国城市小型河道的综合治理有很好的借鉴作用。

保安湖麦穗鱼种群生物学V.生产力

在 1 995年 1 0月至 1 996年 1 1月 ,依据有关种群参数估算了保安湖 1 # 试验围拦中麦穗鱼的生产力。月平均瞬时生长率的变化与年龄和季节有关 ,随着年龄增加生长率降低 ,在生活史的早期阶段生长最快 ,生长率一般在春、夏季较高。在研究期间 ,种群平均生物量为1 8 2 7kg·hm- 2 ,周年生产力为 36 53kg·hm- 2 ·a- 1 ,P/B系数为 2 0。 1 996世代对总生产力的贡献为 67 9%。种群月平均生物量及生产力均表现出了较明显的季节变化 ,生物量在秋季(9月 )