一种层次初始的聚类个数自适应的聚类方法研究

K均值聚类算法是一种常见且有效的基于划分的聚类算法。为解决该聚类算法对初始中心敏感的问题,常用的方法是层次化初始聚类中心。然而,层次初始的聚类算法仍然需要将聚类个数作为输入参数,在高维数据和海量数据中不易应用。基于能够自动确定聚类数目的目的,采用DBI度量,提出一种层次初始的聚类个数自适应的聚类方法（简称DHIKM）。通过UCI数据集和仿真数据上的实验,证明DHIKM可以在采样数据中快速找到合适的聚类个数,实验结果表明该算法在聚类质量与收敛速度上的有效性。     

对K-means算法初始聚类中心选取的优化

针对传统K-means算法对初始聚类中心选取的问题,提出了基于数据样本密度和距离来选取初始聚类中心的改进K-means算法,该算法保证了初始中心点集的第一点为确定的(最大密度点),在基于距离最远的其他中心点搜索过程中,得到的中心点也基本上是确定的,消除了初始中心点选择的随机性,同时保证了获得较高质量的初始中心点。理论分析和实验结果表明:改进的k-means算法是一种有效的入侵检测方法,根据此方法设计的入侵检测系统是有效可行的。     

一种基于高斯分布的自适应 DBSCAN 算法

针对传统的 DBSCAN 算法只能依靠经验来设置阈值(min Pts ,Eps)和无法对多密度数据集进行有效聚类的不足,提出了一种可适用于所有密度分布特征的数据集的基于高斯分布的自适应 DBSCAN 算法.该算法根据数据集的特点寻找最大的聚类效果指数(CEI)来确定 min Pts ,通过 Distk 图的层次数确定 Eps 个数并通过高斯分布中的参数估计来确定每个密度层次 Eps 大小,最后用所求得阈值进行聚类.将该算法与传统的 DBSCAN 算法分别应用于单密度数据集和多密度数据集,结果显示该算法更有效.     

基于量子谐振子模型的聚类中心选取算法

提出了一种基于量子谐振子模型的聚类中心选取算法.该算法以量子谐振子波函数从高能态到基态过程中的概率变化过程为理论模型来描述聚类问题中数据对象向聚类中心点的聚集行为,能够快速查找到最优的聚类个数及较好的聚类中心点所在的网格;数据读入网格结构之后,算法的处理时间与数据集规模无关.实验结果表明:CCSA-QHOM算法较适合于处理每个子类局部区域的网格密度分布呈单峰特性的数据集的聚类中心选择问题.     

一种基于密度的k-means聚类算法

针对k-means算法中对初始聚类中心和孤立点敏感的缺点,提出一种基于密度的改进k-means算法.该算法引入信息熵和加权距离,从近邻密度出发,去除孤立点对算法的影响,同时确定初始聚类中心,使得聚类中心相对稳定.实验表明,该算法在准确性、运行效率上均有10%以上的提升.     

一种基于相关系数的模糊C-均值聚类算法

针对传统模糊C-均值聚类算法同等对待每个属性的局限性和初始聚类中心选择的随机性,提出了一种基于相关系数优化的模糊C-均值聚类算法.首先,该算法通过计算离散系数和信息熵来确定每个属性的权重,从而强化了重要属性对聚类过程的影响,削弱了冗余属性的作用,改善了聚类效果;其次,采用相关系数和密度函数来确定样本点的密度,从而突出了样本点在同一类别中的作用;再次,将归一化后的样本点密度作为每个样本的权值;最后,由相关系数及样本点密度确定初始聚类中心.实验结果表明,该算法比传统的FCM算法具有更好的聚类效果.     

基于数据场的k-means改进算法

针对k-means算法需要人为给出聚类个数k、聚类结果严重依赖初始聚类中心的选等问题,提出一种基于数据场的k-means改进算法。该算法通过计算每个数据点的势值,根据聚类中心的势值比周围邻居的势值大,并与其它聚类中心有相对较大距离的特点,从而确定k个聚类中心;最后将其它数据点按k-means算法聚类。仿真实验表明,改进算法在不需要人为设定参数的情况下能准确找出聚类个数k以及初始聚类中心。     

基于密度的K-means初始聚类中心选取算法

传统K-means算法的初始聚类中心从数据集中随机抽取,聚类结果会随着初始聚类中心的不同而产生波动。针对这一问题,提出一种基于密度的优化初始聚类中心选取算法,通过计算每个数据对象的密度参数和邻域距离,选取k个处于高密度分布的点作为初始聚类中心。在聚类类别数给定的情况下,使用标准的UCI数据库进行对比实验,发现改进后的算法较传统算法有相对较高的准确率和稳定性。     

基于聚类算法人脸识别方法的研究

研究基于聚类算法进行人脸识别的方法.通过学习过程训练RBF神经网络的连接权值、隐含层中心和宽度等参数.通过仿真实验数据对比分析了人脸图像子图像的保留个数、每幅子图像保留奇异值向量的个数以及聚类因数、因数的选取,为聚类算法人脸识别取得良好的应用效果提供了量化的指导.     

一种基于相对密度的快速聚类算法

基于相对密度的聚类算法和快速DBSCAN聚类算法是典型密度聚类算法DBSCAN的两种改进算法,但这两种方法仍存在不足.文中提出一种基于相对密度的快速聚类算法,实验证明了该方法的有效性.     

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-