中国科学院机构知识库网格系统: 检索

浏览/检索结果: 共4条，第1-4条

帮助

条数/页：排序方式：
	空气中多氯萘和多氯联苯的分布特征研究学位论文 OAI收割北京: 中国科学院大学, 2017 作者: 朱青青 \| 收藏 \| 浏览/下载：31/0 \| 提交时间：2018/07/05 多氯萘多氯联苯 Pcns 空气 Pcbs 颗粒物 Atmosphere 分布特征 Particle Distribution Characteristics.
	Theoretical analysis of emission characteristics of second-order distributed feedback semiconductor lasers (EI CONFERENCE) 会议论文 OAI收割 Semiconductor Lasers and Applications IV, October 18, 2010 - October 19, 2010, Beijing, China 作者: Liu Y.; Liu Y.; Qin L.; Liu Y.; Wang L. 收藏 \| 浏览/下载：24/0 \| 提交时间：2013/03/25 Based on the modified coupled-wave theory the emission characteristics including threshold gain photon density distribution in the cavity and external differential quantum efficiency for second-order DFB lasers are investigated. Numerical simulation results show that for given device structure with wavelength of 1.55 m the feedback coupling coefficient and the surface radiation coupling coefficient of the second-order grating have great influence on the emission characteristics of the device. By choosing different duty cycles of the grating we can change the two coupling coefficients which affect the emission characteristics. For an overall consideration an optimal duty cycle of 0.43 is chosen. The optimized results show that the device works without degeneracy modes and spatial burning hole. Besides the side-mode suppress ratio (SMSR) and external differential quantum efficiency reach as high as 42 dB and 47% respectively. 2010 SPIE.
	Dome design and coupled thermal-mechanical analysis of supersonic missile (EI CONFERENCE) 会议论文 OAI收割 2009 International Conference on Optical Instruments and Technology, OIT 2009, October 19, 2009 - October 22, 2009, Shanghai, China Xing-qiao A.; Qun W.; Hong-guang J. 收藏 \| 浏览/下载：58/0 \| 提交时间：2013/03/25 A review of high-speed flow pressure and aerodynamic heating effect on Supersonic missile's dome is given. The dome should have excellent properties in optical mechanical and chemical characteristics. A design of dome on supersonic mode is described according to tactical guide line of a missile. The dome made of quartz which is about 8mm thick and 141mm in window diameter. To check up the reliability of the dome a reasonable finite element model (FEM) of dome is established and a thermal-mechanical Analysis to the dome by finite element software NASTRAN has carried on through these can obtained the distribution of temperature field and stress field when the speed is 2.3Ma. The results indicated that the stress was concentrated in the joint of the dome end and the Missile Section and the maximum stress was 16.4Mpa. The stress of other nodes was smaller than the allowable stress of quartz glass. Reference to the results of the analysis a lightweight revision to the dome structural dimension and a new method of dome fixing have put forward which can reduce the stress concentration. 2009 SPIE.
	The synthesis and field emission property of carbon nanotubes on carbon fibers substrate (EI CONFERENCE) 会议论文 OAI收割 Technical Digest of the 20th International Vacuum Nanoelectronics Conference, IVNC 07, July 8, 2008 - July 12, 2008, Chicago, IL, United states Leyong Z.; Weibiao W.; Jingqiu L.; Yuxue X.; Da L.; Song C.; Haifeng Z. 收藏 \| 浏览/下载：33/0 \| 提交时间：2013/03/25 Using ferrocene as catalyst precursor C2H2 as carbon source carbon nanotubes (CNTs) with uniform density were synthesized on carbon fibers substrate by floating catalyst method. The morphology and microstructure were characterized by field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscopy (HRTEM). The observation showed that the length of CNTs is about 2 m the average space between adjacent CNTs is about 300 nm and the diameter of CNT is about 45 nm. The less dense "short and stubby" aligned CNTs films should have good electron field emission characteristics. The results of field emission showed that the emission current of CNTs/carbon fibers was 5 A at the field of 2.5 V/m and the emission current can be 280 A with a field of 7 V/m (the specimen area is 0.25 cm2 and the distance between cathode and anode is 200 m). The calculation based on the F-N plot indicated that the field enhancement factor of CNTs tip is 499122. Using the conductivity and chemical stability of carbon fibers and the uniform and sparse density distribution of CNTs on carbon fibers substrate the tip predominance of carbon nanotubes can be exerted and simultaneously the effect of screening effects between adjacent carbon nanotubes on the field emission performance can also be effectively decreased. The CNTs synthesized on carbon fibers substrate has many predominances for the fabrication of cold cathode devices. For example using the removability of carbon fibers the cathode of CNTs/carbon fibers can be arbitrarily moved enlaced or combined to form different patterns and the cathode of CNTs/carbon fibers can be also fabricated in large size. Therefore CNTs/carbon fibers may have potential application in field emission displays.