Predicting Surface Roughness and Moisture of Bare Soils Using Multi- band Spectral Reflectance Under Field Conditions

Soil surface roughness, denoted by the root mean square height(RMSH), and soil moisture(SM) are critical factors that affect the accuracy of quantitative remote sensing research due to their combined influence on spectral reflectance(SR). In regards to this issue, three SM levels and four RMSH levels were artificially designed in this study; a total of 12 plots was used, each plot had a size of 3 m × 3 m. Eight spectral observations were conducted from 14 to 30 October 2017 to investigate the correlation between RMSH, SM, and SR. On this basis, 6 commonly used bands of optical satellite sensors were selected in this study, which are red(675 nm), green(555 nm), blue(485 nm), near infrared(845 nm), shortwave infrared 1(1600 nm), and shortwave infrared 2(2200 nm). A negative correlation was found between SR and RMSH, and between SR and SM. The bands with higher coefficient of determination R^2 values were selected for stepwise multiple nonlinear regression analysis. Four characterized bands(i.e., blue, green, near infrared, and shortwave infrared 2) were chosen as the independent variables to estimate SM with R^2 and root mean square error(RMSE) values equal to 0.62 and 2.6%, respectively. Similarly, the four bands(green, red, near infrared, and shortwave infrared 1) were used to estimate RMSH with R^2 and RMSE values equal to 0.48 and 0.69 cm, respectively. These results indicate that the method used is not only suitable for estimating SM but can also be extended to the prediction of RMSH. Finally, the evaluation approach presented in this paper highly restores the real situation of the natural farmland surface on the one hand, and obtains high precision values of SM and RMSH on the other. The method can be further applied to the prediction of farmland SM and RMSH based on satellite and unmanned aerial vehicle(UAV) optical imagery.

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。

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.

红外光谱辐射计镜头视场角测量研究

红外光谱辐射计作为经典的航空发动机红外辐射强度测试仪器,具有光谱分辨率高、测量精度高、响应快、光谱范围广等优点。在使用过程中,红外光谱辐射计需要根据被测目标尺寸及测量距离选择合适的镜头,利用测量的光谱辐射亮度乘以镜头视场的面积,才能得到发动机红外辐射强度。由于加工及装配误差,红外光谱辐射计配套镜头的视场角会偏离其出厂默认值,导致测试偏差。设计了一种红外光谱辐射计镜头视场角测量方法,制作了测量装置,并测量了VSR-3型红外光谱辐射计的标准镜头的视场角。测量结果表明:镜头有效视场角与出厂默认角度存在4%的偏差。通过修正该偏差,能够提高航空发动机红外辐射强度测量精度。

二维浅海波导中声场边界处理的谱无限元方法

针对传统无限元法在截断声场边界上计算精度低的问题,提出了一种基于GR (Gauss-Radau)插值的谱无限元法,以高精度处理无限远边界对声场计算的影响。首先,采用映射函数构建从自然坐标系到笛卡尔坐标系的节点转换函数,获得两种坐标系之间的映射雅克比矩阵;然后,利用基于GR插值的形函数,模拟单元节点的声压,结合映射雅克比矩阵,对二维声场波动方程进行变分处理,推导了无限单元对应的积分表达式,用于模拟实际浅海波导环境下无限远处的声传播。与基于镜像法的解析解和传统无限元法结果的对比表明:所提方法结果与解析解一致性高,相对误差约为1%,验证了该方法的有效性和准确性。

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 b2line 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 polarization 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 In SAR 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 M_S7.0 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 constructed 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.

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 Ms8.0Wenchuan earthquake in 2008 and Ms7.1 Yushu earthquake in 2010.A large number of strong motion recordings were accumulated by the National Strong Motion Observation 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.

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.

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.

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.

Trace amounts of impurities in electrolytic manganese metal by sector field inductively coupled plasma mass spectrometry

An analytical method, using sector field inductively coupled plasma mass spectrometry(SF-ICP-MS) for rapid simultaneous determination of Be, Na, Mg, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, As, Sn, Sb, Pb and Bi in electrolytic manganese metal, was described. At the beginning, the samples were decomposed by HNO3 and H2 SO4, and then analyzed by SF-ICP-MS. Most of the spectral interferences could be avoided by measuring in different mass resolution modes. The matrix effects due to the excess of sulfuric acid and Mn were evaluated. Correction of matrix effects was conducted by using the internal standard elements. The optimum condition for the determination was investigated and discussed. The detection limit is in the range of 0.001 0.169 μg/L. The current method is applied to the determination of trace impurities in electrolytic manganese metal. And experiments show that good results can be obtained much faster, more accurately and conveniently by current method.

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.

江西相山铀矿田CUSD2-2孔成像光谱编录与蚀变分带研究

岩心成像光谱扫描与编录将是数字化时代地质调查和矿产资源勘查的新一代技术,通过相山铀矿田CUSD2-2孔中的应用,改进岩心成像光谱编录中的数据预处理流程及方法,并结合地质分析合理确定端元光谱和蚀变带。在CUSD2-2孔岩心成像光谱编录中,提取了长波云母、短波云母、绿泥石+云母、赤铁矿、方解石和蒙脱石共6种光谱端元,根据矿物学原理和相山铀矿田蚀变特征,认为长波云母为水云母(伊利石)化,短波云母应为绢云母(白云母)化,绿泥石+云母主要为绿泥石化;在已识别的6类热液蚀变中,赤铁矿化主要受岩石破碎带控制,其余5种蚀变受岩性和断裂破碎带双重控制。整个钻孔从上到下可分为浅部(0~980 m)中度碱性蚀变,中部(980~1230 m)原生岩石及深部(1230~2600 m)弱酸-碱耦合蚀变3个蚀变带;由于CUSD2-2孔位于两条NNE向断裂夹持部位,深部弱酸-碱耦合蚀变带的发现表明该区深部存在热液作用,进一步认为其邻区可能存在更强的酸性蚀变和伴生较好铀矿化。

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.

城市轨道交通车内噪声特性及贡献率分析

以某城市轨道交通B型车为研究对象,通过现场实测分析不同速度条件下司机室内和客室内噪声时域变化规律和频谱特性。基于统计能量分析理论建立B型车车内噪声预测模型,通过实测结果对比验证模型的准确性,最后研究车体结构及轮轨噪声源对车内总声压级的贡献率。结果表明:所建立的车内噪声预测模型可以较为准确地预测城市轨道交通车内噪声,且计算效率高。列车速度从75 km/h增大到115 km/h,司机室内噪声增大3.9 dB(A)~5.2 dB(A),客室声压级增大3.6 dB(A)~5.2 dB(A);列车车速每增大10 km/h,司机室内声压级增大约1.36 dB(A),客室内声压级增大约0.9 dB(A)~1.0 dB(A);车内转向架上方测点声压级大于车厢中部噪声,差值为0.3 dB(A)~1.7 dB(A)。车内噪声源主要来自于轮轨噪声和车体底板声辐射,车体侧墙、车门和车窗对车内声压级的贡献整体较小。

医用电子直线加速器射野能谱特性研究

目的 探究医用电子直线加速器射野变化对X射线能量注量、能谱及平均能量的影响,为加速器能谱测量作为射野运行精度的质控手段提供理论依据。方法 以基于蒙特卡罗算法的EGSnrc程序用于电离辐射传输模拟,使用BEAMnrc建立Varian TrueBeam系列加速器机头模型,并分别设置1 cm×1 cm~10 cm×10 cm射野。使用BEAMdp调用BEAMnrc计算生成的相空间文件进行能量注量、能谱及平均能量的结果分析。结果 射野大小对能量注量及能谱结构影响较大,射野越大,相同能量下的注量越高,普峰值越大。在选定射野中能量注量差异最大达98.9%,能谱差异最大达99.0%,有均整过滤器(Flattening Filter,FF)模式下高注量能量区间为0.5~1.2 MeV,峰位约0.33 MeV。与无均整过滤器(Flattening Filter Free,FFF)模式下高注量能量区间为0.3~1.0 MeV,峰位约0.26 MeV。同时射野大小对平均能量影响不明显,FF模式约为1.4MeV,FFF模式约为1.2 MeV。结论 医用电子直线加速器不同射野能量注量及能谱具有一定特异性,可通过对能量注量和能谱的分析作为判断加速器射野运行精度的辅助手段。

外电场下氨分子光谱与激发特性研究

利用筛选的B3PW91密度泛函方法在CC-PVQZ基组下优化出氨分子的基态稳定构型,并考察了不同外电场对NH_(3)分子的特性及红外光谱(IR)的影响,在此基础上利用TD-DFT考察了不同外电场对NH_(3)分子前9个激发态的影响.结果表明:电场由0 a.u.增加至0.04 a.u.时,NH_(3)的构型参数与电场强度有明显的依赖关系;总能量(E_(T))呈下降的趋势;偶极矩(μ)呈增加的趋势;最高占据分子轨道(HOMO)的能级呈降低的趋势,最低空分子轨道(LUMO)的能级呈增加的趋势;能隙(E_(G))呈增加的趋势,即外电场会影响NH_(3)参与化学反应的能力;IR在电场考察范围内的特征峰位置及强度均会受到电场的影响,即可利用电场对分子的IR进行调控,从而便于对相关谱图信息的捕捉;外电场对NH_(3)分子的激发能及振子强度均有影响,因此,可以利用外电场来调控NH_(3)的激发特性.