小口径单壁碳纳米管的最低光学声子模

扶手型及锯齿形单壁碳纳米管的最低光学声子模并不一定是E_2g或E₂模.对于轴向晶格常数比横截面周长大的单壁碳纳米管来说,其最低光学声子模是垂直于其轴向方向振动的一种驻波.通过基于经验势函数的模拟计算,确定这种光学声子模的能量是正比于碳纳米半径的.     

Biotic Resources Abundance and the Corresponding Causes in Panxi Area

0IntroductionThere are luxuriant biotic resources in PanxiArea,where mineral resources,hydraulic re-source and biotic resources are preponderant.Thedevelopment of Panxi Area began withthe exploita-tion of mineral resources,which has established asolidfoundationfor the development of Panxi Area.Withthe consumption of the mineral resources,be-ing a kind of nonrenewable resource,the mineral in-dustry contributes less and less to the developmentof Panxi Area and does more and more harmto en-vir…     

Hilbert空间连续K－框架的冗余与扰动性

基于连续K-框架的定义,给出了Hilbert空间连续K-框架的两个等价刻画.在连续K-框架中挖去部分元素还构成连续K-框架的两个充分条件和不构成连续K-框架的一个充分条件,利用合成算子和两个连续Bessel映射的有界线性算子SF,G去刻画连续K-框架.最后讨论Hilbert空间连续K-框架的扰动.     

A Bayesian based quasi-analytical algorithm for retrieval of inherent optical properties from ocean color

The recently developed quasi-analytical algorithm （QAA） is a promising algorithm for deriving inherent optical properties from ocean color. Unlike the conventional semi-analytical algorithm, QAA does not need a priori knowledge of the spectral shape of chlorophyll absorption. However, several empirical relations, which may not be universally applicable and can result in low noise tolerance, are involved in QAA. In this study, the Bayesian inversion theory is introduced to improve the performance of QAA. In the estimation of total absorption coefficient at the reference wavelength, instead of empirical algorithms used in the QAA, the Bayesian approach is employed in combination with an optical model that uses separate parameters to account explicitly for the contribution of molecular and particle scatterings to remote sensing reflectance, a priori knowledge produced by the QAA, the Akaike＇s Bayesian information criterion （ABIC） for choosing the optimal regularization parameter, and genetic algorithms for global optimization. Coefficients at other wavelengths are then derived using an empirical estimate of particle backscattering spectral shape. When applied to a simulated dataset synthesized by IOCCG, the Bayesian algorithm outperforms QAA algorithm, especially in higher chlorophyll concentration waters. The root mean square errors （RMSEs） between the true and the derived α（440） and bb（440） are reduced from 0.918 and 0.039 m^-1 for QAA-555 to 0.367 and 0.023 m^-1 for Bayes-555, 0.205 and 0.007 m^-1 for QAA-640 to 0.092 and 0.005 m^-1 for Bayes-640, and 0.207 and 0.007 m^-1 for QAA-blending to 0.096 and 0.005 m^-1 for Bayes-blending. Results of noise sensitivity analysis show that the Bayesian algorithm is more robust than QAA.     

全光纤电流互感器的建模与仿真技术研究

在全光纤电流互感器物理模型的基础上,推导出了非线性动态模型,经过等效近似,建立了全光纤电流互感器的线性离散模型,并根据该模型对互感器的动态特性进行了仿真分析.同时,根据全光纤电流互感器的噪声特征建立了随机噪声模型,然后用不同的随机过程来模拟发生各种随机噪声.仿真结果表明:所建模型是合理的,模拟产生的随机噪声能够反映光纤...     

Preparation of Ln3-xEuxS4 （Ln=Ce,Pr, and Nd） ceramics by pressureless sintering

The preparation of ternary rare earth sulfides of Ln3-xEuxS4 （Ln = Ce, Pr, and Nd） ceramics was investigated, and the effect of Eu substitution on Ln3-xEuxS4 ceramics was also studied. Ln3-xEuxS4 powders were synthesized by the sulfurization of their oxide powders using carbon disulfide gas. Ln3-xEuxS4 ceramics were sintered by pressure-less sintering method. All pressureless sintered Ln3-xEuxS4 ceramics crystallized in y-phase. It was found that Eu substitution could improve the density of Ln3-xEuxS4 ceramics. Furthermore, Eu substitution might narrow the optical band gaps of Ln3-xEuxS4 ceramics.     

Active optical clock based on four-level quantum system

Active optical clock,a new conception of atomic clock,has been proposed recently.In this work,we propose a scheme of active optical clock based on four-level quantum system.The final accuracy and stability of two-level quantum system are limited by second-order Doppler shift of thermal atomic beam.To three-level quantum system,they are mainly limited by light shift of pumping laser field.These limitations can be avoided effectively by applying the scheme proposed here.Rubidium atom four-level quantum system,as a typical example,is discussed.The population inversion between 6S 1/2 and 5P 3/2 states can be built up at a time scale of 10-6 s.With the mechanism of active optical clock,in which the cavity mode linewidth is much wider than that of the laser gain profile,it can output a laser with quantum-limited linewidth narrower than 1 Hz in theory.An experimental configuration is designed to realize this active optical clock.     

An Improved Genetic Algorithm for Problem of Genome Rearrangement

In view of the fact that the problem of sorting unsigned permutation by reversal is NP-hard, while the problem of sorting signed permutation by reversal can be solved easily, in this paper, we first transform an unsigned permutation of length n,π （π1 ,… ,πn）, into a set S（π） containing 2^n signed permutations, so that the reversal distance of π is equal to the reversal distance of the optimal signed permutation in S（π）. Then analyze the structural features of S（π） by creating a directed graph and induce a new computing model of this question. Finally, an improved genetic algorithm for solving the new model is proposed. Experimental results show that the proposed model and algorithm is very efficient in practice.     

具有二阶扰动和疫苗接种的随机霍乱传染病模型的平稳分布

针对一类具有二阶扰动和疫苗接种的随机霍乱传染病模型,得到了一个关键条件R0S.然后利用随机Lyapunov分析法以及It?公式,证明了当R0S>1时,随机霍乱传染病模型存在遍历平稳分布.因为模型具有二阶扰动,在证明中构造了新颖的随机Lyapunov函数.证明方法可以应用到类似的模型中.     

Measurement of Magnetization Curve and Magnetic Relaxation for 2H-NbSe2 Crystals

The characteristics of electronic transport properties: behaviors of magnetization curve and magnetic relaxation of a typical normal superconductor 2H-NbSe2 are investigated. The results show that Tc and △Tc of the samples are 7. 2,0. 18 K, indicating that superconducting energy gap at zero temperature is 1. 1 meV. No fish tail shape is found in the magnetization curves at several temperatures. The relationship between remnant magnetic moment and time reveals that the magnetic flux creep of the sample agrees with the Kim-Anderson thermal activation model with the relaxation rate S=0.000 36 at T=6 K.     

防止重掺砷CZ单晶硅组分过冷的探讨

在探讨组分过冷数学模型的基础上,针对重掺砷CZ单晶硅的生长,理论计算了防止组分过冷时固液界面处晶体温度梯度G_S的临界值为51.32~33.10 K/cm.以此为依据,设计了具有较大温度梯度的18寸(60 cm)晶体生长热场,以数值模拟的方法,给出了固液界面处晶体的温度梯度G_S的模拟值为54.68~38.14 K/cm.在晶体等径生长的各个阶段,固液界面处晶体的温度梯度G_S的模拟值均在防止组分过冷的临界值之上,可以有效避免晶体生长过程中组分过冷的发生,并利用实际晶体生长试验的结果验证了以上分析的有效性.     

3级储氢系统快速加氢过程的建模及参数优化

在氢气快速加注过程中,由于氢气的快速压缩及焦耳-汤普逊效应会导致气瓶内部温度急剧上升导致气瓶失效,从而产生安全隐患。针对3级储氢系统,建立了高压氢气快速加注过程的数学模型,用于分析车载氢气瓶在不同工作环境中的温升效应。结果显示加氢站储氢系统的控制压力切换点和预冷系统的控制温度对氢气最终状态影响较大。据此,以压力切换点和预冷温度为优化参数,预冷能耗、加注时间及氢气瓶最终氢气状态S_OC为优化目标建立了多目标优化模型,结果表明该方法可以在尽可能减小预冷能耗和提高S_OC的基础上完成高压氢气的快速加注。     

Effects of three coupling coefficients on the spectrum characteristics of superstructure fiber grating

For the superstructure fiber grating (SFG) consisting of fiber Bragg grating (FBG) and long-period fiber grating (LPFG), there exist three kinds of coupling: the contra-directional coupling between forward propagating core mode and backward propagating core mode, the contra-directional coupling between core mode and cladding mode, and the co-directional coupling between core mode and cladding mode. By using the similarity transformation method for the coupled mode equations, the effects of three coupling coefficients κ _co L, κ _cl L, and κ _S L on the transmission and reflection spectra of SFG have been investigated. The simulations show that the overall intensity of the transmission spectrum of SFG is decided by LPFG, that the main lobes of the transmission and reflectivity spectra of SFG are decided by coupling coefficients κ _co L an κ _S L, and that the side lobes of the transmission and reflectivity spectra are decided by coupling coefficients κ _cl L and κ _S L. Biography: YUAN Yinquan (1964–), male, Professor, Ph.D., research direction: fiber optical sensors.     

基于鲁棒鉴别特征学习的图像特征提取算法

为了增强图像特征鉴别力和鲁棒性,获取图像紧致特征表达是关键.现有的图像特征学习方法大多采用最大化L2范数的方式定义,导致其对噪声和异常值十分敏感.针对这个问题,提出了一种基于L2,1范数的鲁棒鉴别特征学习算法.该算法在数据预处理中加入了类内聚拢操作,使得同类样本尽可能靠近,减小了类内异常样本以及强噪声样本的影响;此外,...     

碱土金属卤化物理化性质QSPR的研究

根据无机物成键原子的结构特征,提出用新的方法：δi^S=（mizi＋ziEi）/2ninj来计算无机分子中原子特征值δi^S,构建新的拓扑指数^mS.用^0S、^1S作为分子结构特征描述符,通过Statistica5.0软件进行多元线性回归,按照标准偏差取最小,相关系数取最大的原则,建立碱土金属卤化物的物理化学性质Pi与分子结构描述符（^0S、^1S）之间的定量相关方程,并对相关关系进行显著性检验.结果表明,新的拓扑指数对分子结构选择区分性高,具有比较高的相关性和精度,并且计算简便,物理意义明确,建立的各种方程得出的各种物理化学性质预测值与实验值之间能很好地吻合,比其他文献方法更具有广泛性.     

Generation of broadly tunable mid-infrared femtosecond pulses by a LiNbO3 optical parametric amplifier

Combining the configurations of collinear and small-angle noncollinear phase-matching, a mid-infrared （MIR） femtosecond optical parametric amplifier （OPA） with extended tunability is proposed and demonstrated. A tuning range from 2.0 μm to 4.7 μm is demonstrated by a two-stage LiNbO3-based femtosecond OPA, which well exceeds the typical tuning range reported so far. MIR femtosecond pulses with energy up to 30 μJ are obtained.     

Influence of growth conditions on the electrochemical synthesis of SnS thin films and their optical properties

Tin sulfide (SnS) thin films were prepared by electrodeposition onto fluorine-doped tin oxide (FTO) glass substrates using an aqueous solution containing SnCl₂ and Na₂S₂O₃ at various deposition potentials (E) and bath concentrations. The pH value and temperature of the solution were kept constant. The deposited films were characterized using X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), photoluminescence (PL), and ultraviolet–visible (UV–Vis) spectroscopy. The FESEM images demonstrated that changes in the deposition potential (E) and solution concentration led to marked changes in the morphology of the deposited SnS films. Energy-dispersive X-ray analysis (EDXA) results showed that the Sn/S atomic ratio strongly depended on both the solution concentration and the deposition potential. To obtain an Sn/S atomic ratio approximately equal to 1, the optimal Sn2+/S₂O₃2- molar ratio and E parameter were 1/8 and -1.0 V, respectively. The XRD patterns showed that the synthesized SnS was obviously polycrystalline, with an orthorhombic structure. The effects of the variations of bath concentration and deposition potential on the band-gap energy (E_g) were studied using PL and UV–Vis experiments. The PL spectra of all the SnS films contained two peaks in the visible region and one peak in the infrared (IR) region. The UV–Vis spectra showed that the optical band-gap energy varies from 1.21 to 1.44 eV.     

Measurement of the absorption spectrum of H2O+ in the visible region

Together with the 74 lines belonging to (0,9,0)- (0,0,0) band, the high-resolution absorption spectrum of H₂O⁺ A²A₁-X²B₁ system was observed in the visible region of 16680 — 17300 cm^-1 using optical heterodyne magnetic rotation enhanced velocity modulation spectroscopy for the first time, which verifies the high sensitivity and high signal to noise ratio (S/N) of this technique.     

光接收机调谐前端的分析

为了设计高性能的谐振式光接收机,应用场效应管模型和多种调谐网络的拓扑形式,提出了一个统一的光接收机调谐前端分析方法。推导出了对多种调谐网络通用的计算公式,用以计算谐振频率、传输函数和等效输入噪声电流密度,便于应用计算机优化光接收机的电路拓扑形式。使用该方法,编制计算机辅助程序模拟了各种不同型式的电感谐振式光接收机的特性,对于光接收机前端设计具有指导作用。     

Thermodynamic determination of fragility in La-based glass-forming liquid

Differences in the thermodynamic functions between the liquid and crystalline states of La-based bulk metallic glasses alloys were calculated with the specific heat capacity Cp and the fusion heat ΔHf,which we measured. Fragility indexes having different thermodynamic definitions were calculated from the temperature dependence of excess entropy ΔSliq-cry. It is ambiguous for La-based glass-forming liquid to evaluate fragility from the intercepts of ΔSliq-cry-temperature curves. We found that the thermodynam...