一种基于空间对称变换的三维模型形状描述方法

 针对基于内容三维模型检索中形状特征提取的关键问题,提出一种基于空间对称变换的三维模型形状特征描述符构造方法,此方法主要依据三维模型内部无处不在的对称特性。首先计算三维模型中点对之间的对称变换,其中点对来源于球面均匀分区采样后顶点集;然后利用点对的对称变换构造三维模型顶点对称空间,并结合空间聚类获得三维模型内部对称关系,从而给出对称区域描述;最后将对称区域描述符集合中数据按照对称区域大小排序后作为整个三维模型形状特征描述符,此特征受三维模型简化、细化、以及几何操作影响较小,且利用特征库后三维模型检索速度比较满意。文章最后分别从特征相似性比较、检索效率以及检索实验结果三个方面验证了方法的有效性。     

基于Reeb图的三维网格模型骨架提取算法

针对目前骨架提取算法存在计算复杂度高、骨架结构不够精确等问题,本文基于Reeb思想提出一种改进的三角网格模型骨架提取算法。首先对三角网格模型进行有效简化,计算简化后的模型特征点,以特征点为聚合点,测地距离函数为映射函数,根据不同顶点的函数值进行特征区域划分,然后利用不同分支的顶点信息进行拓扑分析,连接拓扑构造出的骨架点,并对多余骨架点做删除操作。实验结果表明,可得到较好的骨架提取结果。     

一种SVM学习框架下的Web3D轻量级模型检索算法

随着Web3D技术的发展,对于互联网检索三维模型的需求越来越迫切,特别是基于草图的模型检索.本文对基于草图的三维模型检索相关技术进行了研究,提出了三维模型轻量化处理算法、基于支持向量机三维模型最佳视点选择算法.本文首先对模型进行简化处理,投影三维模型为多个视点图像.其次,使用支持向量机在草图数据集上学习规则,并根据规则进行相应的视点图像分类,获得最佳视点图像.再次,对视点图像提取梯度直方图特征并进行K-means聚类和索引,减少特征空间,获得三维模型的特征字典.最后,在开源数据集上进行相关的实验并对结果进行分析,相关结果表明方法具有很强鲁棒性、准确性.     

基于机载激光雷达数据的复杂建筑物三维自动重建方法

为了解决复杂建筑物三维模型重建存在的边缘像素清晰度低和重建效率低的不足，提出基于机载激光雷达数据的复杂建筑物三维自动重建方法。首先通过机载激光雷达快速采集复杂建筑的三维点云数据，并剔出异常点云数据；其次采用SIFT算法提取点云数据特征点，通过梯度特征提取匹配特征点，根据特征点进行平移与旋转，完成复杂建筑点云数据配准；然后对建筑边缘三维阈值提取，获得高精度重建阈值；最后通过三维轮廓交边拼接优化，复杂建筑物三维自动重建。通过对比测试证明了本方法重建建筑物三维模型的边缘像素的灰度值为25～215,灰度值跨度较大，边缘像素清晰度较高，三维模型的重组时间为60 min～145 min,耗时较少，重建效率较高，说明了本方法对复杂建筑物三维自动重建的应用效果较好。     

基于单样本的大场景地形高度图合成系统设计与实现

随着数字化地形的发展,合成自定义地形的需求变得越来越广泛。文章研究了前人基于样本合成地形的方法并进行改进,设计并实现了基于单样本的大场景地形高度图合成系统。该系统分为图像显示、地形骨架特征提取、用户示意图骨架构建、地形高度图合成以及地形高度图三维可视化五个模块,可实现提取地形图的山脊骨架特征、提取用户图骨架特征以及基于样本地形图合成地形高度图,并可渲染地形高度图生成三维模型。最后通过实验表明,本文设计的基于单样本的大场景地形高度图可有效的合成基于真实地形样本且符合用户特征期望的地形高度图,且系统运行效果良好。     

基于形状分解的书法字骨架提取新方法

针对传统骨架提取算法产生的骨架毛刺较多、交叉处易产生畸变的问题,文章提出一种书法字骨架提取新方法。在基于形状分解思想的基础上,将书法字骨架提取转化成一个分步的问题:由于点云模型能够充分利用现有汉字的底层信息,因此文章采用K-均值聚类算法分割书法字图像;并提出一种适用于书法字特征的以四邻域像素点距离为聚类中心的增量聚类算法提取书法字的部件骨架;最后基于字的拓扑结构连接部件骨架形成完整的骨架。实验结果表明,该方法在骨架提取中表现出了极大的优势,获得了质量较好的骨架,为骨架提取提供了新的思路。     

基于向量内积的新型骨架提取方法

为了提高骨架提取的准确性和连通性,提出了一种基于向量内积的新型骨架提取方法。对二值图像进行欧氏距离变换,获得了由内部像素点指向边界点的边界向量,通过比较内部像素点8-邻域范围内对应边界向量内积值符号在4个方向上的变化情况确定了边界向量方向发生重大变化的次数,并据此选取候选骨架点;采用基于回归分析的方法确定延伸方向,并完成连接操作生成完整的骨架线。实验结果表明,该算法能够保证骨架的连通性和完整性,且骨架定位准确,平均正确率达到92.27%,同时可以克服边界扰动,是一种有效的骨架提取算法。     

基于多视图SIFT特征的三维模型检索

研究了一种基于多视图SIFT特征的三维模型检索算法。首先对三维模型进行多视图投影,得到其余方位的三维投影深度图,并在各投影深度图上提取SIFT特征。分别利用按模型特征数比例分次建立码本及建立模型库整体码本这两种方式建立了模型库的码本,继而将模型的SIFT特征聚类量化,并用一个多维向量将其表示出来。通过计算三维模型特征向...     

基于卷积神经网络的高效三维模型检索方法

目前基于视图的三维模型检索已经成为一个研究热点.该方法首先将三维模型表示为二维视图的集合,然后采用深度学习技术进行分类和检索.但是现有的方法在精度和效率方面都有待提升.本文提出了一种新的三维模型检索方法,该方法包括索引建立和模型检索.在索引建立阶段,选择代表性视图输入到训练好的卷积神经网络(Convolutional Neural Network,CNN)中以提取特征和分类,进而根据特征类别对特征进行组织以建立索引在检索阶段,使用CNN和投票算法将输入模型的代表性视图分类为一个类别,然后仅选择这个类别的特征而不是所有类别的特征进行相似度匹配,因此减少了搜索空间.此外,随着用于检索的视图数量的逐渐增加,一旦可以确定三维模型,检索过程将提前终止.实验的数据选用刚性三维模型数据集ModelNet10,ModelNet40和非刚性三维模型数据集McGill10.结果表明,该方法在提升检索效率的同时,确保检索准确率分别高达94％、92％和100％.     

利用弹头目标微动信息的两种三维散射中心提取方法

雷达目标三维散射中心提取技术广泛应用于散射特性分析、建模以及目标跟踪。结合空间机动目标的微动信息,可以间接得到雷达视角信息。本文在分析了此转化关系的基础上,提出两种三维散射中心提取方法,分别是投影方程求解法和球面拟合法。原理上,分别从代数和几何两个方向体现一维投影距离到三维空间位置的映射原理;算法上,解方程法是基于映射原理,进而求解矩阵方程来实现的;球面拟合法根据一维投影数据的球形分布规律从映射图中提取球面,过原点的直径与球面的交点即为强散射中心。GTD散射模型回波数据和暗室测量数据分别验证了这两种方法的有效性。最后,对两种方法的特点和性能进行了比较,同信噪比下,球面拟合法优于解方程法约15dB。      

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.     

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.     

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.     

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.     

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.     

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正Communications—VLSI Researches and industries of telecommunications have been growing rapidly in the last 20 years and will keep their high growing pace in the next decade.The involved researches and developments cover mobile communications,highway and last-mile broadband communication,domain specific communications,and emerging D2D M2M communications.Radio communication steps into its