一种用于机载LiDAR波形数据高斯分解的高斯拐点匹配法

针对小光斑全波形机载激光雷达(LiDAR)波形数据高斯分解法的核心问题——高斯分量个数估计,提出一种高斯拐点匹配法。该算法用平面曲线离散点集拐点的快速查找算法检测波形数据中的拐点,计算过检测出的拐点及其右边第一个点的直线的斜率,根据斜率将所有检测出的拐点分为左、右拐点,一个左拐点与其邻近的一个右拐点组成一个高斯分量,据此可以确定波形数据中高斯分量个数。采用高斯拐点匹配法对模拟和实测波形数据进行分解,并与传统的脉冲检测方法(重心法和高斯脉冲拟合法)相比。结果表明,高斯拐点匹配法方法能极大地减小伪拐点的影响,快速、准确地检测并分解出波形数据中高斯分量,提高波形数据分解速度。同时其能分解出更多的高斯分量,从而提高点云密度。     

基于可变分量的参数随机抽样的激光雷达脉冲波形分解

激光雷达脉冲回波的波形分解方法是提取其波形参数的重要手段，也为反演目标高度、倾斜度和粗糙度、反射率提供直接的参数来源。针对部分信噪比较差且具有一定混叠程度的脉冲回波，提出一种基于可变分量的参数随机抽样方法的波形分解算法（WDVCM）。该算法以高斯混合函数为优化模型，通过随机产生高斯分量的特征参数以及删减或生成高斯分量等操作，并分别基于能量函数和拟合标准差作为参数优化的判据，从而实现波形的分解及其参数提取。利用该算法对美国国家航空航天局（NASA）的对地观测星载激光雷达（GLAS）一个条带中的4584个原始波形进行了处理分析。结果发现，约99%的WDVCM和97%的NASA拟合波形结果的相关系数均超过0.95，其中两者相关系数差异不超过0.05占98%。同时，WDVCM和NASA拟合波形的标准差系数均值分别为2.21和3.28，约89%的WDVCM拟合波形的标准差系数均小于NASA拟合波形的标准差系数。所得结果表明，WDVCM对混叠高斯波形的拟合效果更好，适用性更强。     

基于改进差分进化算法的机载激光雷达波形分解

全波形机载激光雷达数据记录了完整的回波波形,包含了目标的立面细节和后向散射系数等信息,但是这些信息无法在未经处理的情况下直接获取,波形分解是处理波形数据以提取有效信息的重要方法。针对波形分解中常用的参数优化算法对初值敏感,易陷于局部最优的缺点,提出一种基于改进差分(Modified Differential Evolution,MDE)算法的波形分解方法:以广义高斯函数为模型,在预估初值后,将全局优化的MDE算法用于参数优化,最终生成点云。实验结果表明,与基于其他优化算法的波形分解方法相比,该方法在分解精度以及点位精度等方面都有提高。     

星载激光测高仪多模式回波参数提取方法（特邀）

全波形星载激光测高仪的接收波形特征参数可以用于反演目标的形貌信息,传统的波形处理算法不能用于混叠严重以及偏离高斯形态的多模式波形特征参数提取。针对混叠严重的多模式回波,提出一种基于偏正态拟合模型,使用激励Richardson-Lucy反卷积算法、逐层分解算法、梯度下降法和非线性最小二乘拟合算法相组合的波形特征参数提取方法。采用已知参数的波形数据集、机载仿真波形数据集和全球生态系统动态调查（GEDI）激光雷达波形数据,基于波形相关系数与均方根误差（RMSE）、波形特征参数相对误差、波形分量个数提取正确率等评价指标开展波形处理试验,并将处理结果与传统的高斯分解结果进行比较分析。已知参数波形数据集处理结果的平均波形相关系数提升了约2%,RMSE降低了约47%,波形特征参数相对误差平均降低了约5%,分量个数提取正确率提升了约34%;机载仿真数据和GEDI波形数据处理结果的平均波形相关系数分别提升了约1%和2%,RMSE分别降低了约56%和54%。同时,开展了陡坡区域植被高度解算的仿真试验,得到的植被高度准确程度明显高于传统方法。所有处理结果均表明该方法更有利于多模式回波特征参数的提取以及目标参数的反演。     

遮蔽目标的激光雷达回波信息处理

为了探索利用激光雷达探测遮蔽目标,研究了遮蔽目标对激光雷达回波波形的影响,取得了遮蔽目标激光雷达回波波形的仿真数据.采用Levenberg-Marguardt算法对回波非线性拟合,实现了对回波波形的高斯分解,获取了高斯回波分量的个数、位置、半宽和幅度等参数.通过对各个通道分离子波的时间匹配,得到了各个子目标在不同通道的...     

全局收敛LM 的激光雷达波形数据分解方法

全波形激光雷达是遥感领域的新兴技术,相比传统激光雷达,它对后向散射回波进行全数字化的记录,通过分解返回波形能够得到更加丰富的地物属性信息,因此波形分解是激光雷达全波形数据处理的核心内容。针对传统LM算法容易陷入局部最优解的问题,提出一种全局收敛LM的激光雷达全波形数据分解方法。该方法引入全局收敛LM算法对波形进行拟合,获得波形分量参数的最优解,利用迭代的波峰检测策略实现复杂重叠波形分量的逐步分解。通过对GLAS、LVIS与Lite Mapper-5600的波形数据分解实验证明:该方法相比传统LM算法能够得到更具鲁棒性的波形分解结果,并且适用于星载波形数据、机载大光斑以及机载小光斑波形数据,具备较高实用价值。     

采样频率和激光脉宽对全波形激光雷达测距精度的影响

全波形激光雷达测距精度,又称测距重复精度或测距标准差,受激光器出光稳定性、激光脉宽、探测器响应时间抖动、电路噪声、波形形态、波形采样频率和波形处理算法等因素影响。理论分析了不同采样频率和不同脉宽对全波形激光雷达测距精度的影响,并采集不同的采样频率(1.25、2.5、5 GHz)和不同脉宽(1、2、3、···、10 ns)条件下的波形数据,经滤波、插值、波形提取等预处理后,利用线性高斯拟合、加权线性高斯拟合、迭代加权线性高斯拟合、期望最大化算法、和Levenberg Marquardt算法共5种算法计算测距值并统计测距精度。实验结果表明,EM算法获得的测距精度相比其他4种算法受到波形畸变的影响最小;加权线性高斯拟合算法获得的测距精度受采样频率变化的影响最小;相同波形幅值条件下,实际脉宽增加2.47倍,利用EM算法获得的测距精度从0.97 mm下降至1.18 mm,因此增加脉宽会降低测距精度;在光脉宽为4 ns的情况下,5 GHz采样频率数据在EM算法获得的测距精度分别为2.5 GHz、1.25 GHz采样频率数据的测距精度的1.71倍和3.07倍,而当2.5 GHz和1.25 GHz采样频率数据分别插值2倍和4倍至5 GHz后,仅为1.17倍和1.29倍,因此提高采样频率能够提高测距精度,而对低采样频率数据进行插值能够获得接近高采样频率数据的测距精度。     

基于小波变换的高光谱激光雷达回波微弱信号处理技术

针对高光谱激光雷达回波信号能量弱导致的波形信息常常淹没在噪声中而难以提取的问题,基于高光谱激光雷达原理验证样机系统采集到的高光谱激光雷达回波信号数据,通过分析小波变换参数选取对信号处理的影响,寻找到一种基于小波变换的高光谱激光雷达回波微弱信号的处理方法,即在sym6小波3层分解下,运用软阈值函数和启发式阈值处理可有效处理高光谱激光雷达回波微弱信号,运用该方法在仅有少量回波样本信号数量情况下,达到高斯拟合在数倍回波样本信号数量情况下的处理效果,降低了提取出波形信息所需要的高光谱激光雷达回波信号探测时间。     

基于小波变换的高斯曲线拟合在峰值定位中的应用

针对低速率解调仪采样获得光纤布喇格光栅反射光谱解调精度低的缺点,采用了一种基于小波变换的高斯(WTG)曲线拟合方法。利用小波变换对反射光谱信号进行分解,对小波细节分量进行阈值量化处理,在此基础上,运用处理后的细节分量和近似分量对信号进行重构;然后对重构后的信号插值并进行高斯曲线拟合,使用Levenberg-Marquardt(LM)算法优化高斯拟合系数。仿真实验结果表明:与直接寻峰算法、高斯拟合算法相比,WTG算法的峰值定位误差最小,解调精度更高。     

基于粒子群算法的3维激光雷达回波分解

为了提高3维激光雷达回波分解的精度和准确度,采用粒子群算法与最小二乘法相结合的方法,分析了激光雷达回波分解原理以及粒子群算法原理,研究了粒子群算法在激光雷达回波信号分解中的应用;进行了理论分析与实际数据验证,取得了实际激光雷达回波数据的分解结果。结果表明,采用粒子群算法与最小二乘法相结合的分解方法,激光雷达回波可以更高精度地分解为一系列单个波形的叠加,并获得了延时、强度及脉宽等参量,拟合度提高至0.989,一定程度上抑制了噪声的干扰。该算法可以有效提高激光雷达回波分解的精度。     

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-