基于DS证据理论和压缩感知的WSN数据融合策略设计

为了降低WSN数据量和延长网络生命周期,设计了一种基于DS证据理论和压缩感知的WSN混合数据融合策略;首先,在分簇协议的基础上引入了基于DS证据理论和压缩感知的混合模型,然后,采用改进的DS对所有簇成员节点的基本信度分配函数进行加权处理,在簇头处采用加权和归一化的信度分配函数计算证据对各命题的支持程度,将支持程度较大的若干命题作为DS融合结果,在此基础上采用压缩感知方法通过构造测量矩阵对融合结果进行稀疏化表示,并在基站处对稀疏信号进行重构;仿真实验表明,文中方法能有效地实现数据融合,且和其他方法相比,具有重构误差较小和网络生命周期较长的优点,具有较大的优越性。     

Fiber in-line Mach-Zehnder interferometer constructed by selective infiltration of two air holes in photonic crystal fiber

A fiber in-line Mach-Zehnder interferometer is fabricated through selective infiltrating of two adjacent air holes of the innermost layer in the solid core photonic crystal fiber, assisted by femtosecond laser micromachining. The liquid infiltrated has higher refractive index than that of the background silica, and, hence, the two rods created can support a guide mode with lower effective refractive index than that of silica. The interference is produced by the fiber fundamental mode and the guide mode. The free spectral range (FSR) of the interferometer is found to be dependent on the photonic crystal fiber length, and a large FSR corresponds to a short photonic crystal fiber length. Such an interferometer device is robust and exhibits extremely high temperature sensitivity (～7.3?nm/°C for the photonic crystal fiber length of 3.4?cm) and flexible operation capability.     

Microstructure and high-temperature corrosion behaviors of aluminide coatings by low-temperature pack aluminizing process

Aluminide coatings were produced on carbon steel and Fe-5Cr-Mo alloy at a relatively lower temperature below 600 °C in shorter treatment time by a combination of surface refinement process and pack aluminizing process. Repetitive ball impact, generated by mechanical vibration, caused the top-layer refinement of substrates in a conventional pack aluminizing process. The effects of temperature and treatment time on the formation of aluminide coatings were analyzed. The microstructure of the coatings was investigated by SEM, AFM and XRD. The aluminide coatings were one-layer, compacted structure with ultrafine grains and uniform elemental distribution. High-temperature oxidation and sulphidation tests were carried out at 600 °C in air for 200 h and 10% SO₂ + Ar gas mixture atmosphere for 50 h, respectively. The mass gains and spallation indicated that the aluminide coatings significantly improved the high-temperature oxidation and sulphidation resistance.     

Millimeter-wave scattering from neutral and charged water droplets

We investigated 94 GHz millimeter-wave (MMW) scattering from neutral and charged water mist produced in the laboratory with an ultrasonic atomizer. Diffusion charging of the mist was accomplished with a negative ion generator (NIG). We observed increased forward- and backscattering of MMW from charged mist, as compared to MMW scattering from an uncharged mist. In order to interpret the experimental results, we developed a model based on classical electrodynamics theory of scattering from a dielectric sphere with diffusion-deposited mobile surface charge. In this approach, scattering and extinction cross-sections are calculated for a charged Rayleigh particle with effective dielectric constant consisting of the volume dielectric function of the neutral sphere and surface dielectric function due to the oscillation of the surface charge in the presence of applied electric field. For small droplets with radius smaller than 100 nm, this model predicts increased MMW scattering from charged mist, which is qualitatively consistent with the experimental observations. The objective of this work is to develop indirect remote sensing of radioactive gases via their charging action on atmospheric humid air.     

两种基于空间与光谱相结合的TM影像端元提取算法

针对TM影像波段少,光谱信息相对不丰富的情况,提出了两种结合空间与光谱信息的端元提取算法.首先,提出了基于空间分块的端元提取算法,该算法先对影像进行快速浏览,根据地物分布的复杂程度,确定分块的方案,在分块的基础上通过沙漏算法迅速地提取端元;其次,提出了一种基于空间连续性的端元提取算法,此算法也在分块思路指导下,通过光谱...     

新型高效偏振光分束器的设计

研究及分析了光波在分束结构中的传播行为和特性,发现当增大波导邻近两侧空气孔半径时,能形成完全光子禁带范围内某一频率光波单一偏振态的传播,基于此原理提出了一种全新结构的偏振光分束器,计算与模拟结构表明,该结构可以实现TE模与TM模高效大角度分离. 器件尺寸不超过17.6 μm×9.8 μm,在集成光回路中无疑有着很大的应用潜力. 关键词： 光子晶体 偏振光分束器 时域有限差分法 平面波展开法     

Comparison of CALIPSO and ground-based lidar profiles over Chung-Li, Taiwan

We report the first inter-comparison of vertical profiles of aerosols and clouds derived from space (CALIPSO) and ground based lidar over Chung-Li, Taiwan. Results show that inter-comparison is closer in case of aerosols than clouds. The strength/shortcoming of the comparison has been also discussed. An iterative calculation to retrieve extinction-to-backscatter ratio (lidar ratio) by using sun-photometer and CALIPSO data is also documented. By using the mentioned method, a mean lidar ratio of 23.5±8.2 sr was found. The derived lidar ratios are lower than former studies. The possible reasons for the difference have been discussed in this paper. The discussed methodology will be helpful to reduce the uncertainty of optical parameters derived from lidar data especially near the surface where the atmosphere is inhomogeneous.     

常规速调管空间功率合成微波源

基于常规速调管,研制了用于开展空间功率合成实验的微波源系统。介绍了50 MW超大功率速调管发射机的系统组成、大功率速调管、相位控制及高功率测试系统等。重点阐述了超大功率速调管发射机的关键技术,并针对超大功率发射机的设计难点提出了具体的解决方案。为提高超大功率发射机的可靠性,设计了基于绝缘栅双极晶体管（IGBT）的感应叠加型全固态调制器。给出了超大功率发射机的测试结果,并探讨了超大功率速调管发射机的改进方法。最后对基于常规速调管,研制用于空间功率合成微波源系统的发展进行了展望。     

Differential FBG sensor for temperature-compensated high-pressure (or displacement) measurement

A differential fiber Bragg grating (FBG) sensor with a free active element bulk-modulus for high-pressure (or displacement) measurement is presented. Based on the differential measurement method and an isosceles triangle cantilever structure, problems of cross-sensitivity and chirped signal in FBG sensor are improved both theoretically and experimentally. Preliminary experiments indicate that temperature-compensated measurement results agree well with the theoretical analysis. Displacement measurement sensitivity is 1.75 pm/μm, and the estimated pressure measurement resolution can reach 0.27 MPa in case the wavelength shift measurement resolution is 0.01 nm.     

Exposure assessment of process by-product nanoparticles released during the preventive maintenance of semiconductor fabrication facilities

This study characterized the process by-product particles (mostly nanoparticles) released during the preventive maintenance of semiconductor fabrication facilities, such as chemical mechanical planarization (CMP), plasma-enhanced chemical vapor deposition (PECVD), and ion implantation. Manual sampling and real-time measurements with direct reading instruments were conducted to assess the exposure levels of nanoparticles and their physical and chemical properties. Significant amount of nanoparticles were observed in the breathing zone of the workers during the maintenance of the PECVD and ion implanters with the peak number concentrations as high as 6,470,000 and 65,444 #/cm³, respectively, indicating that the deposited residual chemicals in the reaction chambers were released as airborne nanoparticles by the maintenance activities. In contrast, nanoparticles released during the maintenance of the local scrubber, CMP, and replacing CMP slurry drums were insignificant. Causes of the particle release were discussed and suggestions were made to mitigate the nanoparticle release and reduce the exposure levels.