Helicity of harmonic generation and attosecond polarization with bichromatic circularly polarized laser fields

We theoretically investigate the high-order harmonic generation(HHG) of helium atom driven by bichromatic counterrotating circularly polarized laser fields. By changing the intensity ratio of the two driving laser fields, the spectral chirality of the HHG can be controlled. As the intensity ratio increases, the spectral chirality will change from positive-to negativevalue around a large intensity ratio of the two driving fields when the total laser intensity keeps unchanged. However, the sign of the spectral chirality can be changed from positive to negative around a small intensity ratio of the two driving fields when the total laser intensity changes. At this time, we can effectively control the helicity of the harmonic spectrum and the polarization of the resulting attosecond pulses by adjusting the intensity ratio of the two driving laser fields. As the intensity ratio and the total intensity of the driving laser fields increase, the relative intensity of either the left-circularly or right-circularly polarized harmonic can be enhanced. The attosecond pulses can evolve from being elliptical to near linear correspondingly.

Field survey around strong motion stations and its implications on the seismic intensity in the Lushan earthquake on April 20,2013

The Ms7.0 Lushan earthquake on April 20, 2013 is another destructive event in China since the Ms8.0 Wenchuan earthquake in 2008 and Ms7.1 Yushu earth- quake in 2010. A large number of strong motion recordings were accumulated by the National Strong Motion Obser- vation Network System of China. The maximum peak ground acceleration （PGA） at Station 51BXD in Baoxing Country is recorded as -1,005.3 cm/s2, which is even larger than the maximum one in the Wenchuan earthquake. A field survey around three typical strong motion stations confirms that the earthquake damage is consistent with the issued map of macroseismic intensity. For the oscillation period 0.3-1.0 s which is the common natural period range of the Chinese civil building, a comparison shows that the observed response spectrums are considerably smaller than the designed values in the Chinese code and this could be one of the reasons that the macroseismic intensity is lower than what we expected despite the high amplitude of PGAs. The Housner spectral intensities from 16 stations are also basically correlated with their macroseismic intensities, and the empirical distribution of spectral intensities from Lushan and Wenchuan Earthquakes under the Chinese scale is almost identical with those under the European scale.

Some issues in diagnostics of solar chromospheric magnetic fields with the Mg b_2 line

Up to now, exact measurements of chromospheric magnetic fields have not been as successful as those done in the photosphere. We are currently engaging in diagnostics of chromospheric magnetic fields with the Mg b2 line by employing the Multi-Channel Solar Telescope at Huairou Solar Observing Station. Therefore, how to improve accuracy in the measurement is the main issue of our present study. To this end, we first study linear calibration coefficients for longitudinal and transverse components of chromospheric fields, which vary with wavelength, in the case of a weak field assumption. Then the polarization crosstalk introduced by instruments is analyzed in detail with two numerical simulation methods. Comparisons of the po- larization signals between cases with and without correction are presented. The result indicates that polarization accuracy is greatly improved after crosstalk correction.

Coseismic displacement estimate of the 2013 M_S7.0 Lushan, China earthquake based on the simulation of near-fault displacement field

Usually, GPS observation provides direct evidence to estimate coseismic displacement. However, GPS stations are scattered, sparse and cannot provide a detailed distribution of coseismic displacement. Strong ground motion records share the same disadvantages as GPS in estimating coseismic displacement. Estimations from InSAR data can provide displacement distributions; however, the resolution of such methods is limited by the analysis techniques. The paper focuses on estimating the coseismic displacement of the Ms7.0 Lushan earthquake on April 20, 2013 using a simulation of the wave field based on the elastic wave equation instead of a quasi-static equation. First, the media and source models were con- structed by comparing the simulated velocity and the record velocity of the ground motion. Then simulated static displacements were compared with GPS records. Their agreement validates our results. Careful analysis of the distribution of simulated coseismic displacements near the fault reveals more details of the ground motion. For example, an uplift appears on the hanging wall of the fault, rotation is associated with the horizontal displacement, the fault strike and earthquake epicenter provide the main control on motion near the faults, and the motion on the hanging wall is stronger than that on the footwall. These results reveal additional characteristics of the ground motion of the Lushan earthquake.

The Effects of an Inclined Magnetic Field, Brownian Motion, and Thermophoresis on the Flow of Electrically Conducting and Chemically Reacting Casson Nanofluids Using Soret-Dufour Mechanisms

This research explored the effects of an angled magnetic field, Brownian motion, and thermophoresis on the flow of an electrically conducting and chemically reacting Casson nanofluid under the influence of the Soret-Dufour mechanism. A set of partial differential equations is generated by the flow mode. The governing partial differential equations are solved numerically using the spectral collocation method after being transformed to self-similar forms. The effect of various fluid parameters on the velocity profile, temperature profile, and nanoparticle concentration is addressed. A quantitative agreement is observed when previous findings are compared to the current results. The skin friction, local Nusselt number, and local Sherwood number are also examined, and the results are presented in the table. This study discovered that the inclined magnetic field has a significant impact on the flow of the electrically conducting fluid by delaying its mobility within the boundary layer. The plastic dynamic viscosity, which acts as a barrier to fluid flow, is shown to degenerate the fluid velocity when the Casson parameter is increased. As a consequence, the findings may be used to improve thermal science instruments and increase industrial output.

A Study on the Spectral Form of Nearshore Water Waves

The spectral form of wind waves is investigated based on the ocean wave data observed at three nearshore stations of Taiwan. In this study, the generalized forms of Pierson-Moskowitz spectrum and JONSWAP spectrum are used to describe the local wave spectrum by selecting suitable spectral form parameters. It is shown that, at a specific site, the similarity of wave spectral form exists. Thus it is possible to use a representative spectral form for a given nearshore region to describe the wave spectrum at this nearshore. On the other hand, the effects of relative water depth on spectral form are examined. The feasibility of two spectral models in finite water depth is evaluated by using the same field wave data.

Turbulent Wind Field Simulation of Wind Turbines With Rotational Effects

为准确得到风轮旋转效应对风力发电机组湍流风速脉动分量的影响，推导了旋转Fourier自谱和互谱。分析了风轮旋转效应通过相干函数和相位延迟体现的物理本质，提出了引入相位延迟参数的旋转Fourier自谱和互谱。以旋转Fourier自谱和互谱的模构建旋转谱矩阵，对其进行Cholesky分解，将相位延迟引入谱表现方法中实现风力发电机组湍流风场的模拟。最后，结合某1．5Mw三叶片变桨距风电机组进行纵向脉动风速时程的数值模拟，并对计算功率谱与目标谱进行了校核，证明该文算法可以更为准确地模拟作用在风轮旋转叶片上的脉动风速时程。

Exposure of Weak Time-Invariant Electromagnetic Fields to B16-BL6 Cell Cultures Alter Biophoton Emission Profile as a Function of Distance

Biophoton emission is produced by all living systems;this emission pattern has been shown to be altered by the presence of an electromagnetic field (EMF). Cultures of B16-BL6 cells were exposed to a weak EMF produced by a specially constructed EM generator, called the “Resonator”, for one hour. This EM generator incorporates multiple geometric ratios in its design, including the golden ratio (phi), pi, root 2, root 3, and root 5. It has been used previously to purify water of toxins. There was a significant decrease in mean photon counts from B16-BL6 cells exposed at a distance of 1 m compared to those exposed at 0 m. Alterations in the spectral power density variability were also observed in the 8 - 10 Hz range. The EM generator may have an impact on the viability of the exposed cell cultures, but only at specific distances.

Construction of Earth's gravitational field model from CHAMP,GRACE and GOCE data

The basic principle of spectral combination method is discussed,and the general expressions of the spectral weight and spectral combination of the united-processing of various types of gravimetric data are shown.What＇s more,based on degree error RMS of potential coefficients,the detailed expressions of spectral combination formulae and the corresponding spectral weights in the Earth＇s gravitational field model（EGM） determination using GOCE ＋ GRACE and CHAMP ＋ GRACE ＋ GOCE are derived.The fundamental situation that ulux-champ2013 s,tongji-GRACE01,go-cons-gcf-2-tim-r5 constructed respectively by CHAMP,GRACE,GOCE data and go-cons-gcf-2-dir-r5 constructed by syncretic processing of GRACE,GOCE and LAGEOS data are explained briefly,the degree error RMS,cumulative geoid height error and cumulative gravity anomaly error of these models are calculated.A syncretic model constructed from CHAMP,GRACE and GOCE data,which is expressed by champ ＋ grace ＋ goce,is obtained based on spectral combination method.Experimentation results show that the precision of CHAMP data model is the lowest in satellite-only models,so it is not needed in the determination of syncretic models.The GRACE data model can improve the GOCE data model in medium-long wavelength,so the overall precision of syncretic model can be improved.Consequently,as many types of gravimetric data as possible should be combined together in the data processing in order to strengthen the quality and reliability with widening scope and improve the precision and spatial resolution of the computational results.

二值振幅型远场超分辨消色差聚焦器件研究

具有远场超分辨聚焦特性、消色差、小尺寸和易加工的光学聚焦器件在光学成像、光学显微和光刻等领域具有巨大应用潜力.本文提出了一种基于光学超振荡基本原理,结合角谱衍射理论和二进制粒子群算法的二值振幅型远场超分辨消色差聚焦器件设计方法.为了验证所提出设计方法,首先针对波长λ_(1)=405 nm,λ_(2)=532 nm和λ_(3)=632.8 nm的径向偏振光对二值振幅型远场超分辨聚焦器件振幅进行优化设计,再对三者振幅分布进行逻辑“与”操作,使其同时含有3个工作波长远场超分辨聚焦的振幅分布信息.仿真结果表明:在3个波长入射条件下相应的峰值半高全宽分别为0.441λ_(1) (0.179μm),0.469λ_(2 )(0.249μm)和0.427λ_(3) (0.270μm),低于阿贝衍射极限,实现了远场超分辨消色差聚焦,且同时聚焦较小的旁瓣比率(<15%).此类器件具有易加工、消色差和超分辨等优点,适用于光学系统微型化、集成化.所提出的设计方法可拓展至其他光学波段,并为相关光学研究领域提供核心聚焦器件.

Calibration and data restoration of light field modulated imaging spectrometer

A light field modulated imaging spectrometer （LFMIS） can acquire the spatial-spectral datacube of targets of interest or a scene in a single shot. The spectral information of a point target is imaged on the pixels covered by a microlens. The pixels receive spectral information from different spectral filters to the diffraction and misalignments of the optical components. In this paper, we present a linear spectral multiplexing model of the acquired target spectrum. A calibration method is proposed for calibrating the center wavelengths and bandwidths of channels of an LFMIS system based on the liner-variable filter （LVF） and for determining the spectral multiplexing matrix. In order to improve the accuracy of the restored spectral data, we introduce a reconstruction algorithm based on the total least square （TLS） approach. Simulation and experimental results confirm the performance of the spectrum reconstruction algorithm and validate the feasibility of the proposed calibrating scheme.

Magnetic Field Configurations Corresponding to Electric Field Patterns That Evoke Long-Term Potentiation Shift Power Spectra of Light Emissions from Microtubules from Non-Neural Cells

Photon counts were measured every 15 ms for 75 s from microtubule-enriched preparations (and nuclei) from mouse melanoma cells during baseline and after 2 min exposures to 1 μT magnetic fields. The magnetic fields were generated from a circular array of solenoids and presented with accelerating or decelerating rotation velocities. The range of photon radiant flux density was in the order of 10-12 W·m-2. Microtubules preparations that had been exposed for only 2 min to a magnetic field configuration corresponding to the electric field pattern that induced long-term potentiation in neural tissue when applied as electric current displayed peaks of spectral power densities within 7 - 8 Hz, 9.5 Hz, 14 - 15 Hz, and 22 Hz bands. The major peak (9.4 Hz) bandwidth was approximately 0.1 Hz. While microtubule preparations exposed for 2 min to a 7 Hz sine-wave or in the absence of a field emitted an overall similar level of spectral power density, the peaks in power density were not present. Treatment with the LTP patterned fields, compared to the baseline or sine-wave fields primarily altered the frequency band in which the amplitude of the photon field was expressed. These results suggest that the photon emissions from microtubule preparations have the capacity to respond to specifically-patterned or geometric shapes of magnetic fields by altering spectral configurations rather than the absolute numbers of photons.

基于无人机多光谱植被指数的生菜全氮含量预测

我国露地蔬菜种植规模庞大,生产方式高度集约化,但过量施肥等导致的水氮利用效率低下的问题较为严重。为实现露地蔬菜规模化种植中精准施肥、高效生产的目标,以露地生菜为研究对象,设无氮(N0)、低氮(N1)、高氮(N2)三个处理,通过无人机搭载多光谱相机,建立3种多光谱植被指数(NDVI、RVI和SAVI)与生菜叶绿素、生物量、吸氮量、全氮含量数据集,并构建单生育期和多生育期氮素诊断模型。结果表明:(1)在莲座期和结球期,生菜各处理NDVI、RVI和SAVI值表现出随施氮量的增加而增大,但在收获期,N1处理达到最大值。(2)在生菜结球期,NDVI与生菜的产量、吸氮量、叶绿素均存在显著相关性,其中生菜全氮含量与叶绿素在p≤0.01水平下显著相关,相关系数(R)为0.51;综合生菜多生育期,NDVI值与生菜的产量、叶绿素、吸氮量和全氮含量均在p≤0.001水平下达到极显著相关,相关系数分别为0.85、0.82、0.81和0.71。(3)通过相应数据集拟合出指数、线性、对数和幂函数4种模型关系,建立生菜多生育期植株全氮最佳预测模型:全氮=16.52ln(NDVI)+73.514;应用生菜全氮估层模型反演基地生产田块,其平均相对误差为3.22%、RMSE=0.5566、NRMSE=0.0108,说明模型估算效果均较好,通过无人机多光谱遥感对蔬菜氮素诊断具有一定的可行性。

基于密集台阵的近场与远场地震动迟滞相干函数模型分析

迟滞相干性是表征地震动空间变化特性的一个重要指标,为研究近场与远场地震动的迟滞相干性的空间变化特性及其差异,基于美国UPSAR台阵记录的2004年Parkfield M_(w)6.0地震的近场记录,以及中国自贡台阵记录的2008年汶川M_(s)8.0地震的远场记录,分别分析了两个密集台阵近场和远场地震动的水平向和竖向相干函数随距离、频率的变化规律,对比了近场和远场地震动迟滞相干性的差异;将基于实际数据的迟滞相干性值与常用的三种相干模型进行拟合分析,揭示了不同相干模型的优势和局限性。结果表明:近场与远场地震动的相干性衰减速度有明显差异,在低频和近距离时,远场记录的相干性要明显大于近场记录;相干性随着距离和频率的衰减速度不同,相干函数模型需要对频率和距离项使用不同的参数描述;现有模型对近场和远场地震动的拟合效果差异较大,对远场记录的拟合效果要优于近场记录;三种模型对同一事件的拟合效果不同,多参数模型效果最好,双参数模型其次,单参数模型适用性较差。研究结果可为近场和远场区相干性模型的选用提供依据。

“阿利•伯克”级驱逐舰红外目标特性研究

在海战对抗中,红外导弹是打击驱逐舰目标的重要武器。为了能有效论证红外导弹对驱逐舰目标的探测能力,首先需要获取典型驱逐舰红外目标特性,为此本文开展“阿利·伯克”级驱逐舰红外目标特性研究工作。建立了“阿利·伯克”级驱逐舰三维物理模型,通过数值仿真分别计算了模型在巡航状态下的流场特性与中、长波红外辐射特性。研究结果表明,军事舰船目标烟囱排放羽流温度最高达688.5 K,舰体温度较低且均匀。舰船目标中波光谱辐射主要由高温羽流贡献,长波光谱辐射主要由常温舰体贡献。且中、长波光谱辐射特征受观测角度影响较大,中波光谱辐射强度最高值在正侧方探测角,达65000 W/(sr·μm),长波光谱辐射强度最高值在正上方探测角,达18200 W/(sr·μm)。

基于时均流场的湍流边界层内壁面压力脉动功率谱计算方法研究

针对湍流边界层内壁面压力脉动功率谱的计算问题,该文结合Grasso修订的TNO-Blake解析模型、RANS(Reynolds average Navier-Stokes)时均流场解,发展一种脉动压力计算方法,近壁面附近采用RANS数值解,对于壁面附近湍流各向异性特性,流向和横向异性模型参数采用Stalnov推荐数值,法向异性模型参数采用试验参数,对某平板上一点处的压力脉动功率谱进行了计算,分析了湍流能谱模型、迁移速度等影响,并与Goody模型结果进行对比。研究表明,该文计算方法合理可行,能快速获取壁面压力脉动功率谱,可为工程装备设计的振动噪声分析提供输入。

滑坡面瑞雷波波场模拟及H/V谱比探测

滑坡是一种分布广泛、数量众多、危害巨大的地质灾害,准确确定滑坡滑动面对滑坡防治具有重大意义。传统的勘探手段,如钻探和地球物理方法在起伏较大的滑坡地形中具有诸多限制。本文以四川省屏山县东池庄滑坡为参考,建立了起伏地形软弱性土质滑坡模型,进行了瑞雷波波场模拟并经过模式分离后计算求得水平/垂直(H/V)谱比曲线。对比分析了波场传播及H/V谱比曲线的特征,发现在110道检波器排列中,中心部位检波器的峰值频率可作为计算土石分界面的卓越频率。设计了土层厚度分别为25、31、35 m的滑坡模型,发现土层厚度与峰值频率呈负相关关系。给出了地层为黏性土与泥岩时的频率-深度经验公式,得到了连续滑动面信息,经验公式计算结果与实际模型吻合较好。

基于危险斥力场的车间AGV挂接路径规划算法研究

自动导航车辆(AGV)要实现物料的运输,需要通过车钩等装置挂接料车。在对车间AGV物流车的导航算法研究中,避障路径规划一直都是研究的重点。借鉴人工势场法和万有引力定律,使用危险斥力场对车间自动导航小车挂接工况中的道路和障碍物建立模型,考虑到AGV慢速行驶的特点,选择线性二自由度动力学模型对车辆建模,进一步分析AGV挂接过程中的约束条件,采用危险斥力场积分最小的“最安全”及兼顾快速的性能指标作为优化目标,建立最优控制问题数学模型,使用高斯伪谱法进行求解。求解结果和仿真分析验证算法的有效性,基于危险斥力场的车间AGV挂接路径规划算法能够规划出一条安全无碰撞的路径。

基于概率密度演化的输电塔-线体系抗风可靠性分析

以三线两塔直线段输电塔-线体系为工程对象,应用有限元数值模拟,建立了基于概率密度演化的输电塔-线体系抗风可靠性分析方法。首先,应用谱表示-降维方法模拟结构脉动风场,生成风荷载的代表性样本集合。然后,结合概率密度演化理论,分析了输电塔-线体系考虑气弹效应的随机动力反应。最后,应用等价极值思想构建了风荷载作用下输电塔-线体系失效准则,进而对输电塔-线体系的抗风可靠性进行精细化分析。本文结合谱表示-降维方法与概率密度演化理论,实现了仅用较少数量的代表性样本来精细地分析结构的抗风可靠性,为工程实践提供参考。