一维强振荡变系数奇异摄动问题的多尺度有限元计算

针对含小参数的一维强振荡变系数奇异摄动扩散方程,提出了多尺度有限元的有效计算方法.通过求解微分算子的子问题得到多尺度基函数,能刻画出强振荡的微观信息.利用节点基函数映射,形成约化降阶矩阵,仅求解小规模代数方程组,在粗网格即能获得高精度结果,从而得到不依赖于摄动系数大小的、一致收敛的数值模拟.

光强振荡下的光伏电池最大功率点跟踪方法

受共享单车等移动载体运动影响,光伏电池常处于振动状态,从而造成光强振荡。为消除因光强振荡对光伏电池输出功率的影响,提出一种光强振荡下光伏电池最大功率点跟踪(MPPT)方法。首先,基于对光强振荡下MPPT特性的分析,建立了光强电压阈值MPPT算法。最后,仿真及实验验证结果表明该方法可有效消除光强振荡引起的干扰。与扰动观察法相比,该方法可使输出功率提高2.72%。

贝塞尔光束透射多边形二元振幅光阑的理论研究

本文提出一种多边形二元振幅光阑,并将其应用于压制贝塞尔光束在自由空间传输过程中的光强振荡。利用严格的数学推导,得出多边形二元振幅光阑的等效振幅透射系数公式。通过对贝塞尔光束轴上光强的优化设计,得到多边形二元振幅光阑的最佳结构参数。基于完全的瑞利-索莫菲方法的数值模拟结果显示,优化设计的多边形二元振幅光阑,不仅沿光轴方向,而且在垂直于光轴的横截面内,均很好地压制了贝塞尔光束的光强振荡。相比于现有文献中的渐变振幅光阑或心形二元振幅光阑,本文提出的多边形二元振幅光阑具有加工简单、成本低廉的优势,将为贝塞尔光束在实际光学系统中的广泛应用提供重要的指导价值。

分析强非线性高阶系统的一种新方法

作者在文献[1,2]中提出了等效小参量法的原理。这种方法利用等效小参量的概念,将谐波平衡法和扰动法结合起来,其中,扰动法原理用来获得周期解的修正项。本文的贡献在于提出了一种使计算精确度大为提高的算法。这种新方法采用一个逼近非线性函数主要部分的幂级数,提高了近似解的精确度,使计算程序简单化,适用于强非线性系统,因而克服了传统扰动法的缺点。在本文中,这种改进的算法是以等效小参量法的简化程序来叙述的,也可以看作是一种改进的扰动法。

我国股票市场“政策市”现象的理论阐释

我国股票市场"政策市"现象由来已久,但一直缺乏规范的解释。"政策市"实质上是相关制度和政策变动引致的市场系统风险的体现,根本上取决于制度改革和政策制定的方式本身。我们将"摸着石头过河"式的制度改革和政策制定方式,描述为代理变量的随机过程,建立了其马尔可夫过程假说;再根据假说构造了股票定价和市盈率决定的随机Gordon模型,推导出我国股市强振荡性的几个命题。研究表明,"摸着石头过河"的政策方式必然引起"政策市",不利于发挥资本市场的基本功能;应逐步采用连贯和平稳的制度改革和政策制定方式,以消除系统性的政策不确定性造成的预期变动和股市的强烈振荡。

Intraseasonal oscillation intensity over the western North Pacific:Projected changes under global warming

The 30-60-day intraseasonal oscillation(ISO) and 10-20-day ISO are two dominant oscillation modes over the western North Pacific during boreal summer.With daily data derived from eight CMIP5 models,changes of the ISO intensities are projected under the 1.5 and 2.0℃ global warming levels under the Representative Concentration Pathway(RCP) 4.5 and RCP8.5 scenarios.Most of the models agree that the ISO intensities increase along a belt region from the south Indochina Peninsula(ICP) to the east to the Philippines.The variation pattern shows little difference between different warming levels or scenarios.Results indicate that the spatial distribution of ISO anomalies is related with the variation of background fields.Enriched lower-level humidity and moist static energy favor the intensity increases of ISOs,which are projected to be larger over the whole western North Pacific,with the most conspicuous changes located over the east to the Philippines for humidity but over the south of the ICP for moist static energy.In contrast,the ISOs over the west to Indonesia and northeast to the Philippines decrease,which is consistent with the local descending motions.

Bose-Hubbard Model in Checkerboard Superlattices with a Magnetic Field

In this paper we investigate classical and quantum phase transitions of Bose-Hubbard model in checkerboard superlattices with a magnetic field at the mean-field level. By analyzing stability of normal state phase boundaries are obtained analytically for zero and finite temperature in a unified theoretical frame and easily extended to the situation without the magnetic field. All results illustrate that the introduction of the magnetic field enhances the stability of normal state and Mort insulator. In addition we also note that the critical hopping term presents an oscillating behavior inversely following the upper boundary of Hofstadter butterfly.

Intensity of the Trough over the Bay of Bengal and Its Impact on the Southern China Precipitation in Winter

In this study, the intensity of the trough over the Bay of Bengal (BBT) and its association with the southern China precipitation, the Madden-Julian Oscillation (MJO) and the Rossby wave propagation along the African-Asian subtropical Jet stream (AASJ) are investigated on the intraseasonal time scale. The results show that the intensity of the BBT affects the southern China precipitation more directly and to a greater degree than the MJO. The peak amplitude of the BBT tended to occur in phase-3 of the MJO. The strong BBT was substantially modulated by the Rossby wave propagation along the AASJ, which was triggered by the anomalous upstream circulation similar to the pattern of the North Atlantic Oscillation (NAO). Therefore, from the perspective of medium- and extended-range weather forecasts, the NAO- like pattern may be regarded as a precursory signal for the strong BBT and thus the southern China precipitation.

Long-term changes in wintertime persistent heavy rainfall over southern China contributed by the Madden-Julian Oscillation

During the boreal winter,abundant persistent heavy rainfall(PHR)amount and significant rainfall variability at subseasonal timescale are generally observed over the southern sector of East China,where the large-scale circulation and moisture transport are tightly connected with the equatorial Madden-Julian Oscillation(MJO).As the MJO convections occur over the equatorial Indian Ocean(MJO phases 1-4),the low-level moisture convergence is enhanced over southern China(SC,108°-120°E,21°-26°N)with the divergence to the north.Thus,a positive anomaly of PHR amount appears in SC but a negative anomaly of PHR amount is seen in the Yangtze River valley(YR,113°-122°E,28°-30°N).In contrast,the divergence(convergence)of moisture flux anomalies in the SC(YR)associated with the western equatorial Pacific MJO convections(phases 5-8)limits(benefits)the occurrence of PHR in the SC(YR).The wintertime PHR over southern China is found to undergo a long-term change over the past three decades(1979-2011)with a decreasing(an increasing)trend of PHR amount in the SC(YR).The change in PHR amount occurs consistently with the decadal change in MJO activity.In the earlier decade(1979-1994,E1),the active Indian Ocean(western Pacific)MJO events appeared more frequently while they became less frequent in the recent decade(1995-2011,E2).Accordingly,the Indian Ocean(western Pacific)MJO-related moisture convergence(divergence)anomalies in the SC tend to be weakened(enhanced),contributing to the decrease in PHR amount over the SC in the recent decade.

Quantum Dot Lasers Fabricated by Self-organized Growth

Quantum dot lasers have excellent characteristics such as temperature stability of threshold current and ultra-high material gain. Quantum dot structures fabricated by self-organized growth have high crystalline perfection, high quantum yield of radiative recombination and high size homogeneity. Main advantages and operating properties of quantum dot lasers fabricated by self-organized growth are briefly introduced.

Oscillator Strengths for 2s~2-2p~2P Transitions of the Lithium IsoelectronicSequence from NaIX to CaXVIII

The nonrelativistic dipole-length, -velocity and -acceleration absorptionoscillator strengths for the 1s~22s-1s~22p transitions of the lithium isoelectronic sequence from Z= 11 to 20 are calculated by using the energies and the multiconfiguration interaction wavefunctions obtained from a full core plus correlation (FCPC) method. In most cases, the agreementbetween the oscillator strengths values from the length and velocity formula is up to four or fivedigit. Our results are aiso in good agreement with previous theoretical data available in theliterature.

Effective-Field Theory for Kinetic Ising Model on Honeycomb Lattice

As an analytical method, the effective-field theory （EFT） is used to study the dynamical response of the kinetic Ising model in the presence of a sinusoidal oscillating field. The effective-field equations of motion of the average magnetization are given for the honeycomb lattice （Z = 3）. The Liapunov exponent A is calculated for discussing the stability of the magnetization and it is used to determine the phase boundary. In the field amplitude ho / ZJ-temperature T/ZJ plane, the phase boundary separating the dynamic ordered and the disordered phase has been drawn. In contrast to previous analytical results that predicted a tricritical point separating a dynamic phase boundary line of continuous and discontinuous transitions, we find that the transition is always continuous. There is inconsistency between our results and previous analytical results, because they do not introduce sufficiently strong fluctuations.

Different Interaction Models in Strong Decays of Negative Parity N^＊ ResonancesUnder 2 GeV

In this paper, by using harmonic-oscillator wave functions of different interaction models, i.e. OPE (onepion-exchange model), OPsE (only pseudoscalar meson exchange model), the extended GBE (Goldstone-boson-exchange model including vector and scalar mesons), and OGE (one-gluon-exchange model), we calculate and compare the strong decays of negative parity N* resonances under 2 GeV. We find that the conventional mixing angles are correct, and GBE and OGE are obviously superior to OPE and OPsE.

Spectral Studies of Oscillations Observed by the High-Latitude Radar and Magnetometers

A comparative spectral analysis of high-latitude magnetic and Doppler radar measurements is presented. The analysis takes into account the Doppler effect that is inherent in magnetic observations. The frequency shifts between the magnetic and radar data are estimated （removed） indirectly by formulating the spectral analysis of magnetic data as the Schuster problem of hidden periodicities. There is a satisfactory agreement between the basic frequencies of equidistant spectra found in the magnetic data and frequencies found in the corresponding Doppler radar data. Some conclusions relevant to these findings are discussed.

Numerical Calculation of 3－D Turbulent Flow in Curvilinear Coordinate Systems with Nonstaggered Grids

The nonstaggered grids are adopted in this paper for solving the governing equations of flows in the curvilinear coordinate systems. The present paper demonstrates the basic reason and corresponding eliminating method for the pressure oscillation, and deduces the corrected expressions for the curvilinear velocity components in which an additional term representing the difference between the 1-e and 2- difference values for the pressure gradient appears. Thus if an oscillatory pressure field were arisen, the magnitude of this term would be large and would act to remove the oscillation; whereas for nonoscillatory field the magnitude of this term remains small. As examination for the numerical method,3-D turbulent flow in a square duct with 90° bend and 3-D turbulent mixing flow in a lobed-mixer were calculated respectively. The numerical results are satisfactory.

Theoretical Analysis of the Pressure OscillationPhenomena in Capillary Pumped Loop

Based on the physical model of capillary pumped loop (CPL) system, the phenomena of pressure oscillation are simplilied and analyzed. From a set of non-linear differential equations, the influence ofsystem parameters on the performance of the CPL is discussed, including the working temperature(the Set point), loop resistance, vapor volume etc. From the analysis, some measures were taken tohoprove the performance of the loop. Meanwhile, the reason why the deprive of the CPL occurs duringthe operation is given by analyzing the theoretical calculation results.

Direct prejudgement of hot images with detected diffraction rings in high power laser system

A direct prejudgement strategy that takes the diffraction ring as the analysis target is put forward to predict hot images induced by defects of tens of microns in the main amplifier section of high power laser systems. Analysis of hot-image formation process shows that the hot image can be precisely calculated with the extracted intensity oscillation of the diffraction ring on the front surface of the nonlinear plate. The gradient direction matching （GDM） method is adopted to detect diffraction tings. Recognition of simulated diffraction rings shows that it is feasible to directly prejudge hot images induced by those closely spaced defects and the defects that are far apart from each other. Image compression and cluster analysis are utilized to optimize the performance of the GDM method in recognizing actually collected diffraction images. Results show that hot images induced by defects of tens of microns can be directly prejudged without redundant information.

A Four-Element Sensor Array Consisting of Asymmetric Distributed-Feedback Fiber Lasers

A sensor array system formed by arranging four asymmetric distributed-feedback fiber lasers （DFB-FL） in ascending order according to their slope efficiencies was proposed. The output flatness could be effectively improved with the application of asymmetric DFB-FLs. The last element had almost the same output with the others although it obtained the smallest pump power. The relative intensity noise （RIN） and relaxation oscillation frequency of the sensor array were also analyzed. It is found that the relaxation oscillation frequency of a certain DFB-FL was relevant to its relative position in the array. And the RIN of a certain DFB-FL was always affected by the other elements in the array, which was not dependent on the order of their arrangement.

Dynamic Analysis of Vibrating Systems with Nonlinearities

The max-min approach is applied to mathematical models of some nonlinear oscillations.The models are regarding to three different forms that are governed by nonlinear ordinary differential equations.In this context,the strongly nonlinear Duffing oscillator with third,fifth,and seventh powers of the amplitude,the pendulum attached to a rotating rigid frame and the cubic Duffing oscillator with discontinuity are taken into consideration.The obtained results via the approach are compared with ones achieved utilizing other techniques.The results indicate that the approach has a good agreement with other well-known methods.He's max-min approach is a promising technique and can be successfully exerted to a lot of practical engineering and physical problems.

Energy of a solid sphere under nonstationary oscillations

Analytical solution for spherically symmetric nonstationary oscillations of acoustic and elastic solid sphere is given.Time dependence of potential,kinetic and internal energy of a solid sphere is analyzed.The received results are of practical importance for a wide range of problems connected to testing of material dynamic strength parameters and to the problems of optimizing(minimizing)energy needed for fracture of solids.