考虑钟差修正的脉冲星与多普勒差分组合导航

为了提高导航系统长时间航行的导航精度和钟差修正能力, 提出了一种钟差修正的X射线脉冲星与多普勒差分组合导航方法.X射线脉冲星导航(X-ray pulsar navigation, XPNAV)使用脉冲到达时间作为导航量测量, 多普勒差分导航测量两个时刻航天器相对于太阳的多普勒速度, 并将两个多普勒速度的差值作为导航的量测量, 这里采用两个多普勒速度的差值可避免多普勒速度偏差; 在此基础上, 将星载时钟钟差增广为新的状态变量, 建立组合导航系统, 使用联邦无迹卡尔曼滤波器(unscented Kalman filter, UKF)融合导航信息.仿真结果表明, 该方法可以抑制多普勒速度偏差对导航的影响, 控制星载时钟钟差, 并提供更高的导航估计精度.     

Vapor specific extents of uptake by nanometer scale charged particles

The uptake of vapor molecules by nanometer scale aerosol particles (clusters) is of fundamental importance in aerosol science; uptake is the first step of condensational growth in both the ambient as well as in condensation based particle detectors. However, uptake is not well understood at the nanometer scale. We examined the uptake of organic vapor molecules by nanometer scale sodium chloride cluster ions ((NaCl)_x(Na⁺)_z and (NaCl)_x(Cl^?)_z) using a differential mobility analyzer coupled with a time-of-flight mass spectrometer. Through monitoring cluster ion inverse mobilities as functions of solvent vapor pressure in the mobility analyzer, the extent of uptake was monitored for 1-butanol, ethanol, methyl ethyl ketone (MEK), and toluene. With butanol vapor pressures in the <300 Pa range, shifts in inverse mobility in excess of a factor of 2 were observed for nearly all examined clusters. Ethanol and MEK uptake led to shifts for positively charged cluster ions upwards of a factor of 1.5. Ethanol exposure led to similar sized shifts for negatively charged clusters ions, while MEK exposure led to negative ion inverse mobility shifts less than a factor of 1.3. Toluene was sorbed much less efficiently than the other solvents; toluene exposure led to shifts in inverse mobility below a factor of 1.2. In total, relative inverse mobility shifts, which are direct functions of the extent of vapor uptake, were found to be only weakly dependent on cluster ion size when compared to the influence of vapor molecular structure and cluster ion charge polarity. Classical (Kelvin-based) models are found inadequate to explain the observed mobility shifts, and we instead used a site-specific, Langmuir type model to describe the vapor uptake behavior by the cluster ions.

© 2017 American Association for Aerosol Research     

水坠砂地基处理在沙漠地区工程中的试验及应用

本文对靖边化工园区砂土地区砂土的工程性质和砂土的水理性质进行了试验性研究，对水坠砂地基处理技术在工程中应该如何应用的问题进行了试验和分析，以便为水坠沙技术的广泛应用提供一些科学的试验性基础数据。     

Contribution of morphological awareness to Chinese-English biliteracy acquisition.

This study is an investigation of the contribution of morphological awareness in Chinese-English biliteracy acquisition. Comparable tasks in Chinese and English were administered to test children's skills in morphological awareness, phonological awareness, oral vocabulary, word reading, and reading comprehension. The results showed that after the effect of Chinese-based predictors had been accounted for, English morphological awareness of compound structure still contributed to variance in both character reading and reading comprehension in Chinese. This finding indicates a cross-language morphological transfer in acquisition of two distinct writing systems. The transfer from English L2 to Chinese L1 is due to the bilingual children's rapidly increasing English L2 skills in their primary school years. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

从WAP业务发展规律看移动增值业务的一般特性

从2000年开始,WAP业务在我国经历了一波三折的发展历程,从最开始遭遇市场冷遇到如今的迅速增长,甚至成为移动增值业务的主要增长潜力业务之一,其发展规律与特点都很值得探究.作为典型的移动增值业务之一,WAP业务的发展规律也反映了移动增值业务的一般特性.     

Defect Bragg Fiber With Low Loss for Broadband and Zero Dispersion Slow Light

Narrow bandwidth and large group velocity (v_g) dispersion are two fatal limitations of slow light in Bragg fibers. In this paper, by introducing a well-designed defect layer into the cladding of the Bragg fiber, the modal characteristics are modified by the coupling between the core mode and the defect mode. The defect location mainly determines the coupling strength and, thus, exerts a strong influence on v_g and dispersion. The defect thickness mainly determines the resonant wavelength of the defect waveguide and, thus, the wavelength where the modal coupling takes place. Consequently, the two limitations of the slow-light propagation in the Bragg fiber are overcome through proper optimization of the defect parameters. Around 1550 nm, a slow-light bandwidth up to 90 nm is achieved at an average v_g of c/5 (c is the light velocity in a vacuum) under N = 2, whereas an average v_g of c/10 is achieved with a bandwidth of 20 nm under N = 5. On the other hand, the slow-light propagation of v_g = 0.074c with both zero dispersion and zero dispersion slope is achieved, which is able to support applications requiring a subterahertz bandwidth of optical pulse. All of the fiber designs ensure sufficient low losses and good optical field distribution. The results are helpful in developing various Bragg-fiber-based slow-light devices.     

剪影——重庆龙头寺公园生态厕所设计

生态厕所是通过一定的现代科技手段的应用,能够有利于改变或减少传统公厕所排放物对周围环境的污染;能够有利于改变或减少传统公厕对清理、消除排放物而必须付出的对自然生态物质的消耗;能够对排放物进行回收利用处理的生态化;能够使设计具有人性化,在外型设计上注重与周围景观的谐调,成为景观中有机的组成部分。[1]     

关于通信设备的直流电缆截面的选择

目前正在运行的通信设备的直流电缆截面太大,安装和维护时施工困难,浪费投资,而且实际的负载电流偏小,压降很低.希望设计单位和设备厂家能够对通信设备的电压降重新进行整定和计算,将电缆截面降低到最小程度.在不影响设备正常运行的条件下,降低施工难度、节省投资.     

Effect of DBR Geometry on Reflectivity and Spectral Linewidth of DBR Lasers

对DBR几何参量不同的InGaAs-GaAs-AlGaAs DBR半导体激光器样品的输出线宽进行了测量和分析.样品激光器DBR光栅取不同的长度和蚀刻深度以考察其几何特性对耦合系数、反射率以及输出线宽的影响.线宽通过自差频测量系统测量得到.对实验结果与理论计算结果进行了对比.对测得的光学特性参数与几何特性参数之间的联系进行了分析.在此基础上讨论了DBR几何特性对激光器输出线宽的影响.研究结果为该类型DBR半导体激光器的制造提供了有用的信息.