Degradation failure features of chromium-plated gun barrels with a laser-discrete-quenched substrate

The effect of substrate laser-discrete quenching on the degradation failure of chromium-plated gun barrels was metallurgically investigated. The results show that substrate laser-discrete quenching changes the failure patterns of chromium coatings during firing, and some periodic through-thickness cracks in the fired chromium coatings are justly located at original substrate zones between two adjacent laser-quenched tracks. Moreover, chromium coatings and the laser-quenched zones on the substrate are simultaneously degraded in microstructure and property during firing. Furthermore, the periodic structure of the laser-discrete-quenched steel (LDQS) substrate near the breech remains after firing, and the hardness of the fired laser-quenched zones is still higher than that of original substrates. The specific failure features were utilized to illustrate the mechanism of the extended service life of chromium-plated gun barrels with the LDQS substrate. (c) 2007 Elsevier B.V All rights reserved.

A characteristics study on the performance of a 2-stage light gas gun

In order to obtain an overall and systematic understanding of the performance of a two-stage light gas gun (TLGG), a numerical code to simulate the process occurring in a gun shot is advanced based on the quasi-one-dimensional unsteady equations of motion with the real gas effect,;friction and heat transfer taken into account in a characteristic formulation for both driver and propellant gas. Comparisons of projectile velocities and projectile pressures along the barrel with experimental results from JET (Joint European Tons) and with computational data got by the Lagrangian method indicate that this code can provide results with good accuracy over a wide range of gun geometry and loading conditions.

Optimization of 2-stage gas gun for fusion refueling pellet injection with consideration of real effects

Analytic expression of pellet acceleration by constant base pressure with consideration of gas-wall friction, heat transfer and viscous dissipation that important for high speed injection is obtained. The process of compression stage is formulated by a set of governing equations and can be numerically integrated. Excellent confirmation with experiments is obtained and the ways to optimum match the compression stage with the launch stage are suggested.

脉宽压缩光栅用的多层膜设计和性能分析

应用于啁啾脉冲放大技术中的脉宽压缩光栅是基于多层膜作为基底，利用全息干涉技术和离子束技术刻蚀而成。脉宽压缩光栅的衍射效率和抗激光损伤阈值一方面依赖于光栅结构的设计，另一方面很大程度上取决于作为基底的多层膜的设计。给出了以413．1nm作为写入波长，1053nm作为使用波长的多层介质光栅膜的设计．样品在ZZS-800F、型真空镀膜机上采用电子束蒸发方式沉积而成，并给出了膜系结构对光学性能影响因素的详细分析，结果表明膜系H3L(H2L)^9H0．5L2．03H满足光栅膜的指标。给出了样品光学特性测试，其使用波

Optical properties of semiconductor quantum-well material using photonic crystal fabricated by micro-fabrication machine

Two-dimensional photonic crystals in near infrared region were fabricated by using the focused ion beam ( FIB) method and the method of electron-beam lithography (EBL) combined with dry etching. Both methods can fabricate perfect crystals, the method of FIB is simple,the other is more complicated. It is shown that the material with the photonic crystal fabricated by FIB has no fluorescence,on the other hand, the small-lattice photonic crystal made by EBL combined with dry etching can enhance the extraction efficiency two folds, though the photonic crystal has some disorder. The mechanisms of the enhanced-emission and the absence of emission are also discussed.

A Structured Prediction Approach for Statistical Machine Translation

We propose a new formally syntax-based method for statistical machine translation. Transductions between parsing trees are transformed into a problem of sequence tagging, which is then tackled by a search- based structured prediction method. This allows us to automatically acquire transla- tion knowledge from a parallel corpus without the need of complex linguistic parsing. This method can achieve compa- rable results with phrase-based method (like Pharaoh), however, only about ten percent number of translation table is used. Experiments show that the structured pre- diction approach for SMT is promising for its strong ability at combining words.

Foreign gene transfer into Chinese shrimps (Penaeus chinensis) with gene gun

Plasmids pG DNA-RZ1 with a GFP (green fluorescent protein) reporter gene and a ribozyme gene incising penaeid white spot baculovirus (WSBV) were first introduced into the fertilized eggs of Chinese shrimps by gene gun. The treated and control samples of different development stages were observed with a fluorescent microscope. The transient expression of GFP gene was high in nauplius and zoea larvae. Results from RT-PCR and PCR for adults showed that the foreign genes had been transferred into the shrimps and had expressed the corresponding proteins. This work has established a transgenic method for penaeid shrimps, which will set base for the application of genetic engineering breeding into industry.

蒙古北部Gun Nuur湖泊沉积物的地球化学特征及其古环境意义

了解过去是认识现在和预测未来的基础。全新世是距离现今最近的时代，对全新世环境变化的研究是探究人类与环境相互关系的主要内容。蒙古高原位于气候敏感区域，是全球能量传输的重要通道，同时受到3个气候子系统的共同影响（冬季风、夏季风、西风带），决定了此地区高分辨的记录将可为全新世全球气候变化提供重要的区域证据。但是受研究条件所限，目前蒙古高原的研究多限于在其南部的中国境内，很少涉及蒙古国内的古环境研究。 鉴于此，本文选取蒙古北部Gun Nuur湖泊沉积为研究对象，系统探讨了该湖芯沉积物中碳酸盐含量、碳酸盐碳、氧同位素、有机质含量、有机质碳同位素等地球化学指标在高分辨率气候变化重建中的重要应用价值，得出主要结论和认识如下： 1. Gun Nuur湖心沉积物中碳酸盐含量主要受夏季温度的影响，温度升高，碳酸钙和CO2的水中溶解度减小，进而碳酸盐更容易沉淀。 2. Gun Nuur碳酸盐氧同位素与反映湖区降水/蒸发比的湖泊水位有较明确的关系，即降水/蒸发比降低，水位下降，碳酸盐氧同位素值上升。 3. 温度以及由温度引起的蒸发速率的变化，和生物过程共同影响着湖泊碳酸盐碳同位素的组成，使得Gun Nuur湖心碳酸盐δ13C值气候信息不够敏感。 4. Gun Nuur沉积物有机质δ13C含量主要反映湖泊古生产力的变化，湖泊生产力高时，δ13C值偏正，湖泊生产力低时，δ13C偏负。 5. 由于Gun Nuur湖心沉积物有机质含量反映了历史时期该地区冬季的温度和冬季持续时间的长短，所以这可以作为东亚冬季风的一个良好的指标，并据此重建了过去8000年以来东亚冬季风的变化。