实数遗传算法的改进及性能研究

提出一种粒子群优化方法(PSO)与实数编码遗传算法(GA)相结合的混合改进遗传算法(HIGAPSO).该方法采用混沌序列产生初始种群、非线性排序选择、多个交叉后代竞争择优和变异尺度自适应变化等改进遗传操作;并通过精英个体保留、粒子群优化及改进遗传算法(IGA)三种策略共同作用产生种群新个体,来克服常规算法中收敛速度慢、早熟及局部收敛等缺陷.通过四个高维典型函数测试结果表明该方法不但显著提高了算法的全局搜索能力,加快了收敛速度;而且也改善了求解的质量及其优化结果的可靠性,是求解优化问题的一种有潜力的算法.     

自适应变异的粒子群优化算法

本文提出了一种新的基于群体适应度方差自适应变异的粒子群优化算法(AMPSO).该算法在运行过程中根据群体适应度方差以及当前最优解的大小来确定当前最佳粒子的变异概率,变异操作增强了粒子群优化算法跳出局部最优解的能力.对几种典型函数的测试结果表明:新算法的全局收搜索能力有了显著提高,并且能够有效避免早熟收敛问题.     

基于遗传算法的改进智能优化蚁群算法

针对蚁群算法加速收敛和早熟停滞现象的矛盾,根据遗传算法的交叉算子、变异算子和粒子群算法的粒子极值,采用一种优化蚁群算法,以在加速收敛和防止早熟停滞现象之间取得更好的平衡.在利用该算法解决TSP问题中,当前解与个体极值和全局极值分别进行交叉操作,产生的解为新的位置信息.通过对50个城市问题进行实验,结果表明,该方法比一般蚁群算法具有更好的收敛速度和稳定性,适合于求解大规模的问题.     

引入模式搜索算子的粒子群优化算法

针对粒子群优化算法(PSO)在解决复杂的高维优化问题时容易陷入局部最优和收敛速度慢的问题,结合模式搜索算法较强的局部搜索能力,提出一种引入模式搜索算子的粒子群优化算法(HJPSO).为避免最优粒子陷入局部最优而导致整个种群出现搜索停滞,在PSO算法的迭代过程中加入判断粒子陷入局部最优的机制,当检测到早熟停滞迹象时,使用模式搜索算子对整个粒子群当前搜索到的历史最优位置进行模式搜索以帮助算法跳出局部最优点.标准测试函数的运行结果表明,该算法具有较强的跳出局部最优的能力,收敛速度较快,稳定性好.     

基于VB和Access的温度采集系统的设计与实现

针对函数优化问题,提出了一种基于离差平方和法的粒子群优化算法。该算法用混沌序列初始化粒子的位置和速度,选择好于粒子群优化算法产生的粒子位置。通过离差平方和法进行聚类,利用分类方式来更新粒子的速度。最后将算法应用到3个典型的函数优化问题中,数值结果比较表明,提高了算法搜索能力,全局最优解的精度和收敛速度。     

两阶段动态多粒子群协作优化

为了解决粒子群优化（Particle Swarm Optimization,PSO）容易陷入到局部最优的问题,提出一种两阶段动态多粒子群协作优化算法.算法中包含一个主粒子群和多个从粒子群,每个从粒子群都搜索部分问题域,主粒子群协调各从粒子群向最优解收敛并获得搜索到的最优解.在第一阶段,在粒子少的问题域产生新的从粒子群,从而确保粒子比较好地覆盖问题域.在第二阶段,删除同一子区域中位置重叠的从粒子群,减少搜索时间.用五个测试函数与两层粒子群优化（Two-layer Particle Swarm Optimization,TLPSO）进行了比较,结果表明此算法能在高维多峰函数优化时获得更好的解.     

基于克隆粒子群算法的图像分割方法

最大熵阈值法是目前图像分割中应用最广泛的方法之一。为了快速准确地自动确定图像分割阈值,把克隆选择算法和粒子群算法相结合,提出克隆粒子群优化算法。利用这种改进方法对最大熵图像分割函数进行全局寻优。克隆选择算法和粒子群算法的结合克服了各自的缺点,克隆选择的多样性补偿了粒子群的多样性差的缺点,粒子群的快速性补偿了克隆选择的收敛速度慢的缺点。克隆粒子群方法克服了传统遗传算法易出现早熟、陷入局部最优等的问题,加快了图像分割函数收敛速度,最后能够快速准确地得到图像分割的最佳阈值。实验表明,改进后的算法分割速度较快,易于收敛到最优解,并且得到的分割阈值更加稳定。     

基于群体早熟程度和非线性周期振荡策略的改进粒子群算法简

提出了一种新的粒子群优化算法——基于群体早熟收敛程度和非线性周期振荡策略的自适应混沌粒子群优化算法。利用混沌的遍历特性初始化粒子的速度和位置,根据种群的早熟收敛程度和粒子的适应度值自适应地调整惯性权重;学习因子则采用非线性周期振荡策略,模拟鸟类觅食过程中交替出现的分散和重组现象。基准测试函数的仿真结果表明,所提出的算法不仅收敛速度快、寻优质量高,而且具有良好的稳定性。     

改进的粒子群优化算法用于方向图阵列综合

为了克服粒子群优化算法早熟收敛,本文提出了一种改进的小波变异粒子群优化算法,由于该算法每次迭代时以一定的概率选中粒子进行小波变异扰动,能够克服算法后期易发生早熟收敛和陷入局部最优的缺点。同时将改进的算法应用于天线阵列方向图综合问题中,综合效果好于现有文献。     

改进粒子群算法的多峰值优化研究

粒子群优化算法对于多维函数的最优解搜索存在前期易陷入局部最优,后期收敛速度缓慢的问题.将改进的k-中心点聚类分析与PSO相结合提出了一种混合粒子群算法KM-PSO,用于多峰值问题的优化.在算法中,利用k-中心点聚类分析方法将粒子群划分成若干个子群,结合PSO的隐含并行搜索的优势增强了寻优性能.不仅增加了粒子间的信息交换,抑制了早熟收敛,还提高了全局寻优速度和计算精度.仿真实验结果表明,KM-PS0性能优于基本粒子群优化算法.     

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.     

Call for Papers

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