Subluminal and Superluminal Phenomena in a Four-Level Atom

In a four-level atomic system, we investigate the light pulse propagation properties interacting with only one laser field. It is shown that in the steady state, the group velocity of the light pulse can be changed from subluminal to superluminal by varying the field detuning. Meanwhile, the effects of the field intensity on the group velocity are also shown. At last, with special parameters, the analytical solution for the group index is also obtained.     

用XRD法研究MCM-22分子筛的逐级放大合成

在100,250和1 000 mL高压釜静态成功合成MCM-22分子筛的基础上,在2,5和200 L高压釜中进行了MCM-22分子筛的动态合成试验,对合成的样品用XRD等技术进行了表征。结果表明,在静态和动态条件下合成的样品,全部为纯相MCM-22分子筛,且结晶度较高,从100 mL到200 L的放大试验是成功的。     

飞秒时间分辨光抽运探测技术及进展

文章简要介绍了飞秒时间分辨光抽运探测技术以及作者所在实验室的最新研究进展．灵敏度和信噪比是实验中的重要参数，文章着重介绍了作者在这两方面的改进，从而可检测到更微弱信号，并降低了使用的激光功率．配合具有光学窗口的液氦低温系统，还可对更多领域的材料进行研究，其中包括高温超导、生物化学样品和纳米材料等，并可给出物质内部结构等方面的重要信息．     

质子轰击条形结构InGaAsP/InP内调Q DH双稳态激光器

本文报道一种质子轰击条形结构内调Q InGaAsP/InP DH双稳态激光器(简称BSDH)。该激光器具有典型的光输出双稳态特性,实验测得两个典型样品的双稳态工作区电流跨度△I分别为50mA,200mA,它随器件结构参数的选取而异,值得指出的是在不同注入电流下观察到高态激光输出呈单纵模稳频特性,峰值波长λ₀=1.2596μm,频率(波长)稳定度优于10^-5,本文对上述现象从物理上进行了定性的讨论。 关键词：     

产生多个大横动量成份的超高能核作用事例

对甘巴拉山乳胶室得到的一个∑E_r≈1300TeV的r线簇进行了分析,这个事例是发生在乳胶室上方的核作用,产生的高度低于150m,事例的中心部分由5个集团组成,对此事例的特性进行了讨论。 关键词：     

正电子湮没寿命谱的傅里叶变换分析法

本文提出了一种通过傅里叶变换在频域内进行正电子湮没寿命谱分析的方法。文中对正电子湮没寿命谱的傅里叶变换谱的基本特性和该方法的潜在优点进行了若干讨论。 关键词：     

Multi-objective optimization of inverse planning for accurate radiotherapy

The multi-objective optimization of inverse planning based on the Pareto solution set, according to the multi-objective character of inverse planning in accurate radiotherapy, was studied in this paper. Firstly,the clinical requirements of a treatment plan were transformed into a multi-objective optimization problem with multiple constraints. Then, the fast and elitist multi-objective Non-dominated Sorting Genetic Algorithm (NSGA-Ⅱ)was introduced to optimize the problem. A clinical example was tested using this method. The results show that an obtained set of non-dominated solutions were uniformly distributed and the corresponding dose distribution of each solution not only approached the expected dose distribution, but also met the dosevolume constraints. It was indicated that the clinical requirements were better satisfied using the method and the planner could select the optimal treatment plan from the non-dominated solution set.     

空间相机电控机箱的热设计及仿真分析

为了保证空间相机电控机箱在轨运行期间的工作温度满足使用要求,根据电控机箱的结构特点和导热路径,对电控机箱内部大功耗电子元器件进行了详细热控设计,解决了某些电子元器件发热量大、导热路径较长的问题。以某个典型元器件为例,进行了散热效果估算。最后应用有限元分析软件IDEAS-TMG建立了详细的电控机箱热分析有限元模型,根据电控机箱所处温度边界条件进行了稳态仿真分析,给出了电控机箱整体的热响应性能、印制线路板（PCB）及板上大功耗电子元器件的稳态温度分布云图,结果显示,PCB的温度为40.6～51.1℃,板上大功耗电子元器件的结温为46.3～62.5℃,均满足热控设计的指标要求。热分析结果表明电控机箱热设计合理可行,能够满足使用要求。     

同位镀铋膜电极测定爆米花中的痕量铅

采用同位镀铋膜法修饰铂电极,用差分脉冲溶出伏安法对爆米花中痕置铅进行了测定,并优化了实验条件.在优化的实验条件下,分别对2.0×10<'8>-6.0×10<'-7>mol/L和6.0×10<'-7>-1.0×10<'-4>mol/L的pb<'2+>进行了测定,Pb<'2+>溶出峰电流与Pb<'2+>浓度呈良好的线性关系...     

Orbit determination and time synchronization for a GEO/IGSO satellite navigation constellation with regional tracking network

Aiming at regional services,the space segment of COMPASS (Phase I) satellite navigation system is a constellation of Geostationary Earth Orbit (GEO),Inclined Geostationary Earth Orbit (IGSO) and Medium Earth Orbit (MEO) satellites.Precise orbit determination (POD) for the satellites is limited by the geographic distribution of regional tracking stations.Independent time synchronization (TS) system is developed to supplement the regional tracking network,and satellite clock errors and orbit data may be obtai...