新型厘米波双层球形微粒电磁特性研究

在厘米波段,当微粒尺寸小于入射波波长时,利用双层球形颗粒的Mie散射理论,研究了双层球形结构的电磁波散射和吸收特性,结果显示内核为磁性材料的双层球微粒,其吸波能力和隐身性能都优于内核为非磁性材料的双层球微粒。在此基础上,数值计算了内层是碳或铁介质,外层为非磁性等离子体的包覆体新型结构,结果表明该结构具有很好的电磁波衰减和吸收特性。     

沙尘暴多重散射对毫米波衰减影响研究

根据随机介质中电波传播理论,应用等效介电常数法和Mie理论,研究毫米波在沙尘暴中传播的衰减;并应用Monte Carlo方法,研究沙尘暴大气中毫米波多重散射对衰减的影响.分别得到了单次散射和多重散射时沙尘暴引起的毫米波段几个大气窗口频率的特征衰减,及随沙尘大气能见度和沙尘粒子水含量的变化关系.结果表明,当能见度小于1 km时,随着能见度的减小,特征衰减增大很快,多重散射的影响也愈来愈大.衰减随含水量的增加而增加,尤其当沙尘粒子水含量大于1%时增加较为显著.因此,对于预测自然沙尘暴大气对毫米波的衰减,当能见度小于1 km时,必须考虑粒子的多重散射效应.当沙尘粒子的水含量超过1%时,需要考虑水含量的影响.这些研究对民用和军用通信、遥感等系统的开发和应用均具有重要的实际意义.     

Ka及毫米波段大气传输衰减特性研究

由于Ka及毫米波频段电磁波频率极高,大气传播特性不同于低频,受大气气体、降雨等大气环境的影响非常大。本文重点考虑大气中的氧气和水蒸气对电磁波的吸收衰减作用,分别从电磁波频率、大气含水量和温度三个方面具体分析大气对Ka及毫米波频段电磁波的衰减特性,并得出相关结论。     

沙尘环境下太赫兹波衰减特性

对沙尘环境下太赫兹波衰减特性进行研究,在国际电信联盟(ITU)大气衰减模型的基础上,增加了不同类型沙尘的影响。基于大气毫米波传播模型(MPM)预测了1 THz内大气衰减特性;根据Mie散射理论计算了太赫兹波在沙尘环境下因沙尘颗粒产生的衰减;结合以上两种因素得出沙尘环境下太赫兹的衰减特性。本文的研究结果对太赫兹在沙尘环境下传输应用具有重要的参考意义,也为其他颗粒环境太赫兹波传输特性的计算提供了参考。     

水包冰球包层粒子散射特性的研究

基于Mie散射和Aden-Kerker散射理论,利用Matlab仿真模拟工具,分析了水包冰球包层粒子在红外波段、太赫兹波段及毫米波段的散射特性。研究表明,水包冰球包层粒子在这三个波段的散射能力与包层粒子的内外径比有很大关系,水包冰球粒子的复折射率在三个波段随着频率的增大呈线性变化,但在毫米波段的实部变化不大;随着包层粒子的内外径比的不断增大,其散射强度、散射参数在红外波段和太赫兹波段不断增大,在毫米波段则减小。研究结论可对红外波、太赫兹和毫米波的气象应用以及相关检测技术提供参考。     

灰霾中主要污染物粒子散射特性的研究

分析了灰霾污染天气条件下气溶胶的物理光学特性,研究了PM2.5污染物粒子主要成分,包含硫酸铵、硫酸、硝酸铵和碳质气溶胶等粒子。运用Mie散射理论对此类灰霾粒子的光散射特性进行了研究,分析计算了上述几种粒子组分的散射、吸收、消光效率因子以及散射相函数。结果表明硫酸铵、硫酸和硝酸铵粒子主要以散射作用为主,吸收效应很弱几乎为零,且散射效率因子随尺度参数振荡衰减最终趋于常数2,而碳质气溶胶粒子则表现出较强的吸收效应。最后通过对比不同半径不同粒子的散射相函数,结果表明粒子相函数对粒子大小和复折射率较为敏感,且前后向散射具有一定的对称性。该研究结果可用于大气污染光学遥感监测。     

沙尘暴对低层大气红外辐射的吸收和衰减

根据Mie散射理论用数值法研究了沙尘粒子对大气红外辐射的散射,消光和吸收效率,揭示了不同粒径的沙尘粒子在不同红外辐射波段消光和吸收的特点。考察了三种典型的沙尘天气-浮尘、扬沙和沙尘暴时沙尘对红外辐射的吸收系数和消光系数,得出了沙尘暴天气对红外辐射具有显著的吸收和衰减特别是对于λ=2-2.6υm和λ=3-5υm这两个红外大气窗口的衰减最严重的结论。     

两栖装甲车辆对抗红外／毫米波复合制导方法研究

在分析两栖装甲车辆的毫米波、红外暴露特征和常见的干扰技术,以及人工水雾干扰红外/毫米波复合制导原理的基础上,运用Mie散射理论和热力学理论,对人工水雾干扰红外/毫米波复合制导技术进行了理论分析,给出了单位喷水量条件下,水雾滴径的最佳尺寸,最后模拟计算了人工水雾对红外/毫米波复合制导的干扰性能.     

粒子跟踪法求毫米波雨衰减

根据多重散射的解析理论,利用粒子跟踪法研究了毫米波在离散随机介质中的传播与散射。在考虑多重散射效应的情况下,数值模拟了毫米波段的降雨衰减。理论计算与实验结果相一致。     

太赫兹波段信号在雾中的传输特性研究

太赫兹（THz）波提供的通信带宽和容量远大于毫米波。与可见光和红外光相比,THz脉冲的波长较长,在随机介质中传播时,不但会发生时域和空域的形变,介质中的粒子还会对入射波发生散射,这些都会使得脉冲信号发生衰减。根据Mie理论与随机离散分布粒子的波传播与散射理论,计算了THz波信号入射下雾滴粒子的消光系数,分析了不同THz波波长下,雾滴粒子消光系数随粒子尺寸的变化。结合雾滴粒子谱分布,考虑粒子群的平均体系散射特性,得到了不同波长下的平均反照率与相函数。最后分析了THz波段信号在不同能见度雾中的传输特性。结果表明:大气环境中,雾对THz波产生的吸收和衰减不容忽视,不同THz信号的水的折射率虚部的变化严重影响了THz信号在雾中的传输。     

Curved crystal spectrometer for the measurement of X-ray lines from laser-produced plasmas

In order to diagnose the laser-produced plasmas, a focusing curved crystal spectrometer has been developed for measuring the X-ray lines radiated from a laser-produced plasmas. The design is based on the fact that the ray emitted from a source located at one focus of an ellipse will converge on the other focus by the reflection of the elliptical surface. The focal length and the eccentricity of the ellipse are 1350 mm and 0.9586, respectively. The spectrometer can be used to measure the X- ray lines in the wavelength range of 0.2-0.37 nm, and a LiF crystal （200） （2d = 0.4027 nm） is used as dispersive element covering Bragg angle from 30° to 67.5°. The spectrometer was tested on Shengnang- Ⅱ which can deliver laser energy of 60-80 J/pulse and the laser wavelength is 0.35 μm. Photographs of spectra including the 1 s2p ^1P1-1s^2 ^1S0 resonance line（w）, the 1s2p ^3P2-1s^2 1S0 magnetic quadrupole line（x）, the 1s2p ^3P1-1 s^2 ^1S0 intercombination lines（y）, the 1 s2p ^3S~1-1 s^2 ^1S0 forbidden line（z） in helium-like Ti Ⅹ Ⅺ and the 1 s2s2p ^2P3/2-1 s622s ^2S1/2 line（q） in lithium-like Ti Ⅹ Ⅹhave been recorded with a X-ray CCD camera. The experimental result shows that the wavelength resolution（λ/△ 2） is above 1000 and the elliptical crystal spectrometer is suitable for X-ray spectroscopy.     

Preparation and Characterization of TaN ALD Precursors

High purity organic-tantalum precursors for thin film ALD TaN were synthesized and characterized.Vapor pressure and thermal stability of these precursors were studied.From the vapor pressure analysis,it was found that TBTEMT has a higher vapor pressure than any other published liquid TaN precursor,including TBTDET,TAITMATA,and IPTDET.Thermal stability of the alkyl groups on the precursors was investigated using a 1H NMR technique.The results indicated that the tertbutylimino group is the most stable group on TBTDET and TBTEMT as compared to the dialkylamido groups.Thermal stability of TaN precursors decreased in the following order:TBTDET ＞ PDMAT ＞ TBTEMT.In conclusion,precursor vapor pressure and thermal stability were tuned by making slight variations in the ligand sphere around the metal center.     

Electronic Structure of Semiconductor Nanocrystals

This paper reviews our recent development of the use of the large-scale pseudopotential method to calculate the electronic structure of semiconductor nanocrystals, such as quantum dots and wires, which often contain tens of thousands of atoms. The calculated size-dependent exciton energies and absorption spectra of quantum dots and wires are in good agreement with experiments. We show that the electronic structure of a nanocrystal can be tuned not only by its size,but also by its shape. Finally,we show that defect properties in quantum dots can be significantly different from those in bulk semiconductors.     

Critical Stage Rule-Based Real Time Dispatch（RTD）System in Highly-Mixed-Products （HMP） FAB

An improving utilization and efficiency of critical equipments in semiconductor wafer fabrication facilities are concerned. Semiconductor manufacturing FAB is one of the most complicated and cost sensitive environments. A good dispatching tool will make big difference in equipment utilization and FAB output as a whole. The equipment in this paper is In-Line DUV Scanner. There are many factors impacting utilization and output on this equipment group. In HMP environment one of the issues is changing of reticule in this area and idle counts due to load unbalance between equipments. Here we'll introduce a rule-based RTD system which aiming at decreasing the number of recipe change and idle counts among a group of scanner equipment in a high-mixed-products FAB.     

GaAsSb/InAlAs PA DHBTs Grown by Production MBE

The epi material growth of GaAsSb based DHBTs with InAlAs emitters are investigated using a 4 × 100mm multi-wafer production Riber 49 MBE reactor fully equipped with real-time in-situ sensors including an absorption band edge spectroscope and an optical-based flux monitor. The state-of-the-art hole mobilities are obtained from 100nm thick carbon-doped GaAsSb. A Sb composition variation of less than ± 0.1 atomic percent across a 4 × 100mm platen configuration has been achieved. The large area InAlAs/GaAsSb/InP DHBT device demonstrates excellent DC characteristics,such as BVCEO＞6V and a DC current gain of 45 at 1kA/cm2 for an emitter size of 50μm × 50μm. The devices have a 40nm thick GaAsSb base with p-doping of 4. 5 × 1019cm-3 . Devices with an emitter size of 4μm × 30μm have a current gain variation less than 2% across the fully processed 100mm wafer. ft and fmax are over 50GHz,with a power efficiency of 50% ,which are comparable to standard power GaAs HBT results. These results demonstrate the potential application of GaAsSb/InP DHBT for power amplifiers and the feasibility of multi-wafer MBE for mass production of GaAsSb-based HBTs.     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Noise character analysis and the restraint of self-pulsation laser diodes

We calculate the Langevin noise sources of self-pulsation laser diodes, analyze the effects of active region noise and saturable-absorption region noise on the power fluctuation as well as period fluctuation, and propose a novel method to restrain the noise effects. A visible SIMULINK model is established to simulate the system, The results indicate that the effects of noise in absorption region can be ignored; that with the increase of DC injecting current, the noise effects enhance power jitter, and nevertheless, the period jitter is decreased; and that with external sinusoidal current modulating the self-pulsation laser diode, the noise-induced power jitter and period jitter can be suppressed greatly. This work is valuable for clock recovery in all-optical network.     

High-quality single-crystal CdSe nanoribbons and their optical properties

Large-scale synthesis of single-crystal CdSe nanoribbons is achieved by a modified thermal evaporation method, in which two-step-thermal-evaporation is used to control CdSe sources＇ evaporation. The synthesized CdSe nanoribbons are usually several micrometers in width, 50 nm in thickness, and tens to several hundred micrometers in length. Studies have shown that high-quality CdSe nanoribbons with regular shapes can be obtained by this method. Room-temperature photolumines-cence indicates that the lasing emission at 710 nm has been observed under optical pumping （266 nm） at power densities of 25-153 kW/cm^2. The full width half maximum （FWHM） of the lasing mode is 0.67 nm     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

中国建立EB级存储实验室,致力云计算应用(英文)

正With the support of 863 programs,Sugon Information Industry Co.,Ltd.,set up a dawning EB-class storage laboratory to address massive data storage requirements and largescale cloud computing demonstration applications.The Dawning EB-class cloud storage system adopts advanced fault-tolerant architecture,efficient data fault-tolerant algorithms with user authentication and data encryption policies to deal with the"lost""wrong"and"stolen"problems of data for ensuring the reliability and safety of the EB-class storage system in the public network application environments.The Dawning EB-class Storage Laboratory taking advan-