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为了提高网络流量预测的准确性,提出一种小波分解和组合模型相融合的网络流量预测预测模型。首先采用小波分析对网络流量进行分解,得到网络流量的趋势序列和波动序列,然后分别采用自回归差分滑动平均模型和极限学习机对它们进行建模和预测,最后采用仿真实验测试组合模型的性能。仿真结果表明,相对于其它网络流量预测模型,组合预测模型提高了网络流量预测精度,降低了预测误差更小。 相似文献
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针对混沌海杂波背景下的微弱信号检测问题,结合互补集成经验模态分解理论,提出了一种优化的核极限学习机微弱信号检测方法。采用互补集成经验模态分解法将混沌信号分解为一系列固有模态函数,通过核极限学习机对经相空间重构后的各模态函数分别建立预测模型,利用人工蜂群算法对核极限学习机的正则化系数和核参数进行优化,重构预测信号,从预测误差中检测出混沌海杂波背景中的微弱信号(瞬态信号与周期信号)。分别以Lorenz 系统和IPIX 雷达海杂波数据为例进行了仿真,并研究了不同强度的噪声对微弱信号检测的影响。结果表明:该方法可以有效地从混沌背景中检测出微弱目标信号,当系统不存在噪声时,Lorenz 系统得到的均方根误差0. 000 000 12 (-118. 959 1 dB)比传统极限学习机方法的均方根误差0. 001 345 08(-80. 154 7 dB)降低了4 个数量级;若SNR逸0 dB,噪声对微弱目标信号检测的影响可以忽略;但当SNR<-7 dB,则无法检测出微弱信号。 相似文献
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为了提高网络流量的预测精度,提出一种组合核函数高斯过程的网络流量预测模型。首先采用混沌理论构建网络流量的学习样本,然后将网络流量的训练样本输入组合函数高斯回归模型进行训练,建立网络流量预测模型,最后采用多个网络流量数据进行单步和多步预测对比测试。结果表明,相对于对比模型,本文模型准确描述了复杂多变的网络流量变化趋势,提高了网络流量的预测精度。 相似文献
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改进粒子群算法优化最小二乘支持向量机的网络流量混沌预测 总被引:1,自引:0,他引:1
为了提高网络流量的预测准确性,针对最小二乘支持向量机参数优化方法的缺陷,提出一种改进粒子群算法优化最小二乘支持向量机的网络流量混沌预测模型。首先将最小二乘支持向量机参数作为粒子初始位置,然后通过粒子群之间信息交流、互相协作找到最优参数,并对惯性权重和学习因子进行改进,最后对网络流量数据进行重构,并采用最优参数的最小二乘支持向量机建立网络流量预测模型。实验结果表明,本文模型提高了网络流量的预测精度,并大幅度减少了训练时间,可以满足网络流量在线预测要求。 相似文献
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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. 相似文献
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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. 相似文献
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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. 相似文献
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YUXiao-hua XIANGYu-qun 《半导体技术》2005,30(2):30-32,37
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. 相似文献
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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. 相似文献
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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. 相似文献
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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 相似文献
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TANG Bin JIANG Xing-fang LIU Zhi-min 《光电子快报》2008,4(1):78-80
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. 相似文献
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Tian-hua Xu Feng Tang Wen-cai Jing Hong-xia Zhang Da-gong Ji Chang-song Yu Ge Zhou Yi-mo Zhang 《光电子快报》2008,4(4):292-294
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. 相似文献
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《中国通信》2014,(9)
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 相似文献