In situ calibrated angle between the quantization axis and the propagating direction of the light field for trapping neutral atoms

The recently developed magic-intensity trapping technique of neutral atoms efficiently mitigates the detrimental effect of light shifts on atomic qubits and substantially enhances the coherence time. This technique relies on applying a bias magnetic field precisely parallel to the wave vector of a circularly polarized trapping laser field. However, due to the presence of the vector light shift experienced by the trapped atoms, it is challenging to precisely define a parallel magnetic field, especially at a low bias magnetic field strength, for the magic-intensity trapping of85Rb qubits. In this work, we present a method to calibrate the angle between the bias magnetic field and the trapping laser field with the compensating magnetic fields in the other two directions orthogonal to the bias magnetic field direction. Experimentally, with a constantdepth trap and a fixed bias magnetic field, we measure the respective resonant frequencies of the atomic qubits in a linearly polarized trap and a circularly polarized one via the conventional microwave Rabi spectra with different compensating magnetic fields and obtain the corresponding total magnetic fields via the respective resonant frequencies using the Breit–Rabi formula. With known total magnetic fields, the angle is a function of the other two compensating magnetic fields.Finally, the projection value of the angle on either of the directions orthogonal to the bias magnetic field direction can be reduced to 0(4)° by applying specific compensating magnetic fields. The measurement error is mainly attributed to the fluctuation of atomic temperature. Moreover, it also demonstrates that, even for a small angle, the effect is strong enough to cause large decoherence of Rabi oscillation in a magic-intensity trap. Although the compensation method demonstrated here is explored for the magic-intensity trapping technique, it can be applied to a variety of similar precision measurements with trapped neutral atoms.

Integral imaging-based tabletop light field 3D display with large viewing angle

Light field 3D display technology is considered a revolutionary technology to address the critical visual fatigue issues in the existing 3D displays.Tabletop light field 3D display provides a brand-new display form that satisfies multi-user shared viewing and collaborative works,and it is poised to become a potential alternative to the traditional wall and portable display forms.However,a large radial viewing angle and correct radial perspective and parallax are still out of reach for most current tabletop light field 3D displays due to the limited amount of spatial information.To address the viewing angle and perspective issues,a novel integral imaging-based tabletop light field 3D display with a simple flat-panel structure is proposed and developed by applying a compound lens array,two spliced 8K liquid crystal display panels,and a light shaping diffuser screen.The compound lens array is designed to be composed of multiple three-piece compound lens units by employing a reverse design scheme,which greatly extends the radial viewing angle in the case of a limited amount of spatial information and balances other important 3D display parameters.The proposed display has a radial viewing angle of 68.7°in a large display size of 43.5 inches,which is larger than the conventional tabletop light field 3D displays.The radial perspective and parallax are correct,and high-resolution 3D images can be reproduced in large radial viewing positions.We envision that this proposed display opens up possibility for redefining the display forms of consumer electronics.

Scanning transmission electron microscopy: A review of high angle annular dark field and annular bright field imaging and applications in lithium-ion batteries

Scanning transmission electron microscopy（STEM） has been shown as powerful tools for material characterization,especially after the appearance of aberration-corrector which greatly enhances the resolution of STEM. High angle annular dark field（HAADF） and annular bright field（ABF） imaging of the aberration-corrected STEM are widely used due to their high-resolution capabilities and easily interpretable image contrasts. However, HAADF mode of the STEM is still limited in detecting light elements due to the weak electron-scattering power. ABF mode of the STEM could detect light and heavy elements simultaneously, providing unprecedented opportunities for probing unknown structures of materials. Atomiclevel structure investigation of materials has been achieved by means of these imaging modes, which is invaluable in many fields for either improving properties of materials or developing new materials. This paper aims to provide a introduction of HAADF and ABF imaging techniques and reviews their applications in characterization of cathode materials, study of electrochemical reaction mechanisms, and exploring the effective design of lithium-ion batteries（LIBs）. The future prospects of the STEM are also discussed.

Effect of Incidence Angle of Magnetic Field on the Performance of a Polycrystalline Silicon Solar Cell under Multispectral Illumination

The aim of this work is to investigate, with a three-dimensional steady-state approach, the effect of the incidence angle of a magnetic field on the performance of a polycrystalline silicon solar cell under multispectral illumination. The magneto-transport and continuity equations of excess minority carriers are solved to find the expression of the density of excess minority carriers and the related electrical parameters, such as the photocurrent density, the photovoltage and the electric power, of a grain of the polycrystalline silicon solar cell. The influence of the incidence angle of the magnetic field on the diffusion coefficient, the short-circuit photocurrent density, the open-circuit photovoltage and the electric power-photovoltage is studied. Then, the curves of the electric power-photovoltage is used to find the maximum electric power allowing to calculate, according to the incidence angle of the magnetic field, the fill factor and the conversion efficiency. The study has shown that the increase of the incidence angle of the magnetic field from 0 rad to π/2 rad, can reduce the degradation of the performance of solar cells.

Dynamic measurement of beam divergence angle of different fields of view of scanning lidar

The laser beam divergence angle is one of the important parameters to evaluate the quality of the laser beam.It can not only accurately indicate the nature of the beam divergence when the laser beam is transmitted over a long distance,but also objectively evaluate the performance of the laser system.At present,lidar has received a lot of attention as a core component of environment awareness technology.Micro-electromechanical system(MEMS)micromirror has become the first choice for three-dimensional imaging lidar because of its small size and fast scanning speed.However,due to the small size of the MEMS micromirror,the lidar scanning system has a small field of view(FOV).In order to achieve a wide range of scanning imaging,collimating optical system and wide-angle optical system are generally added to the system.However,due to the inherent properties of the optical lens,it is impossible to perfect the imaging,so the effects of collimating and expanding the beam will be different at different angles.This article aims to propose a measurement system that dynamically measures the divergence angles of MEMS scanning lidar beams in different fields of view to objectively evaluate the performances of scanning lidar systems.

Combination of structure tensor and tilt angle in the edge detection of potential field data

Edge detection is a commonly requested task in the interpretation of potential field data. Different methods have different results for varied depths and shapes of geological bodies. In this paper,we propose using the combination of structure tensor and tilt angle to detect the edges of the sources,which can display the edges of shallow and deep bodies simultaneously. Through tests on synthetic potential field data,it is obvious that the proposed edge detection methods can display the sources edges more clearly and precisely,compared with other commonly used methods. The application on real potential field data shows similar result,obtaining the edges of layers and faults clearly. In addition,another advantage of the new method is its insensitivity to noise.

Three-Dimensional Study of the Effect of the Angle of Incidence of a Magnetic Field on the Electrical Power and Conversion Efficiency of a Polycrystalline Silicon Solar Cell under Multispectral Illumination

A three-dimensional approach to the effect of magnetic field incidence angle on electrical power and conversion efficiency is performed on a front-illuminated polycrystalline silicon bifacial solar cell. A solution of the continuity equation allowed us to present the equations of photocurrent density, photovoltage and electric power. The influence of the angle of incidence of the magnetic field on the photocurrent density, the photovoltage and the electric power has been studied. The curves of electrical power versus dynamic junction velocity were used to extract the values of maximum electrical power and dynamic junction velocity and to calculate those of conversion efficiency. From this study, it is found that the conversion efficiency values increase with the angle of incidence of the magnetic field.

Study on the estimation of Euler angles for Macao Science Satellite-1

The Euler angle estimation is a calibration method for vector data measured by the magnetometer on a satellite.It is used to find the relative rotation between the coordinate system of the magnetometer and the satellite(usually determined by Star Imagers).Before launch of the low-orbit,low-inclination Macao Science Satellite-1(known as MSS-1),we simulated the estimation of Euler angles by using the magnetic measurements of the in-orbit Swarm and China Seismo-Electromagnetic Satellite(noted as CSES),with various data combinations.In this study,11 data sets were designed to analyze the estimation results for the MSS-1 orbit by using a joint estimation method of the geomagnetic field model parameters and Euler angles.For the model results,we found that all the spatial power spectral lines showed behavior consistent with that of the CHAOS-7.8 model at low degrees(corresponding to large-scale magnetic signals).The spectra of models without global data coverage deviated much more(by a maximum of~10^(4) nT^(2))from those of the CHAOS-7.8 model at higher degrees.For models with global data coverage and with various data combinations,the spectral lines were distributed similarly.Moreover,the models with accordant power spectral distributions demonstrated different Euler angle estimations.As more vector data at higher latitudes were included,the estimated Euler angles varied monotonically in all three directions.The models with vector data in the same latitude range showed similar Euler angle results,regardless of whether the poleward scalar data were included.The largest value difference was found between the models using vector data within±40°latitudes and those using vector data within±60°latitudes,which reached to~28″.Therefore,we concluded that the inversion of the spherical harmonic Gauss coefficients in our tests was mainly affected by the spatial coverage range of the data,whereas the estimation of Euler angles largely depended on the latitude range where the vector data could be obtained.These results can be used for future in-flight data testing.We expect the estimation of Euler angles to improve as other methods are adopted.

宽波段大视角液晶偏振转换器研究进展

偏振转换器能够通过对入射光偏振态的动态调控间接实现几何相位型多功能光学器件光学响应特性的动态可调。基于液晶的偏振转换器具有调控效率高、调控面积大、紧凑化程度高等诸多优势,是目前应用较为广泛的偏振转换器。本文围绕偏振转换效率、工作波段、视场角3个核心参量,系统介绍了液晶偏振转换器最新的研究进展,分别给出了典型液晶偏振转换器和大视角宽波段液晶偏振转换器的详细结构和性能表现,同时介绍了液晶偏振转换器工作波段和视角的拓展方法。该项工作能够为液晶偏振转换器结构设计与应用提供必要的参考,同时为基于几何相位或新型相位调控模式的研究提供一些思路。

基于格拉姆角场和PSO-CNN的滚动轴承故障诊断方法

针对卷积神经网络的结构对滚动轴承故障诊断精度有较大影响的问题,提出一种基于格拉姆角场和粒子群优化卷积神经网络结构的故障诊断方法。采用格拉姆角场对一维轴承振动数据重构,保留原始数据信息的同时包含了时间相关性;采用粒子群优化算法对编码后的卷积神经网络结构迭代寻优。利用西储大学的轴承数据集进行试验验证,试验结果表明,该方法可自适应生成网络结构,平均诊断精度为99%,相对于其他主流卷积神经网络结构可以获得更好的故障诊断精度。

2020年7月12日唐山古冶M_(S)5.1地震前延庆地电场变化

采用日均值曲线形态、日均值一阶差分及优势方位角法,对2020年7月12日唐山古冶M_(S)5.1地震前北京延庆地震台地电场异常变化进行分析。该台2套地电场日均值具有较为清晰、稳定的年变,存在季节性变化,自2020年5月开始出现年变畸变或年变幅改变,表明在地震孕育过程中台站所在区域地下构造活动由平稳到逐渐加剧。地电场日均值一阶差分在震前1-3个月呈高频突跳或丛集异常变化,震后逐渐平稳。日均值一阶差分可反映日均值突跳、阶跃和快速明显的趋势变化,对缓慢渐变过程反映弱。方位角背景值中间值约为70°,与延庆台所在区域主压应力轴平均值74.45°相当,代表了该区域的主要裂隙方向。方位角的改变,可以反映地震孕育过程中一定范围内地下应力应变活动。方位角自2020年5月跳变范围收窄,变化幅度约为45°,异常开始至发震约3个月。应用方位角法,可以提取台站周边300 km范围内M_(S)5左右地震地电场短期异常变化。

集成LCC-S拓扑的二维全向无线电能传输系统无盲区能量捕获方法研究

针对二维全向无线电能传输技术存在空间磁场完整度与电流控制策略复杂度的竞争问题,该文提出一种集成LCC-S拓扑的二维全向无线电能传输系统无盲区能量捕获方法。该系统以二维正交线圈为电磁耦合机构,并将其集成于LCC-S型补偿拓扑。同时提出一种自调整参数设计方法,实现系统在二维空间内产生时均旋转磁场以及系统的零相角输入。通过场-路耦合有限元模型分析系统在二维空间内磁场分布情况,随时间峰值磁场强度矢量轨迹为圆形。搭建集成型二维全向无线电能传输的实验样机,实验结果表明,该系统实现单一电源驱动下无盲区的二维全向电磁能量捕获。

有限视场下的攻击时间和角度多约束制导律

针对精确打击任务存在导引头视场受限这一过程约束的制导问题,提出了一种考虑视场限制以及攻击角度和时间多种约束的制导律.首先,在以比例导引项实现精确命中的基础上,利用最优控制理论,采用弹目距离加权控制能耗形式的指标函数,设计了攻击角度控制项,并推导了相应的剩余飞行时间解析预测表达式.其次,基于最优误差动力学方法,设计了攻击时间相关的控制项,保证了攻击时间误差的有限时间收敛.同时,针对导引头视场有限的问题,分析了各控制项对前置角收敛性的影响,利用特定的限制函数确保前置角在整个制导过程中始终处于有效视场内,并给出了前置角的有界性及收敛性证明.数学仿真结果验证了所提出制导律对多约束制导问题的有效性.

基于GADF融合RDSAN的跨工况轴承故障诊断

针对在不同工况下获取到的滚动轴承振动数据特征分布存在差异,以及由于存在噪声而导致故障特征不明显的问题,提出了一种融合格拉姆角差场(GADF)与残差深度子领域自适应(RDSAN)模型的跨工况轴承故障诊断方法。首先,为充分利用GADF在故障特征差异化显示上的优势,利用GADF来生成滚动轴承一维振动时域信号对应的图像数据集;其次,将数据集输入RDSAN模型,其中使用由改进图像集预训练的ResNet-18网络结构进行源域与目标域通用特征的进一步提取,并引入局部最大均值差异(LMMD)计算匹配条件分布距离进行子领域自适应;最后,在添加0.5 dB高斯白噪声的CWRU滚动轴承数据集上进行跨工况试验验证,结果表明所提方法的平均诊断精度达到96.8%;将所提出的方法与不同的诊断方法进行比较分析,结果验证了该方法的有效性和优越性。

基于含避障角人工势场法的机器人路径规划

针对基于距离的人工势场法(Artificial potential field, APF)存在的局部极小值问题,提出了一种含避障角的人工势场法的避障路径规划方法。在平面环境中,采用斜率判定路径规划过程中的位置关系,通过机器人当前点到障碍物的距离与障碍物的影响半径二者之差得出人工势场法中的排斥力,并对排斥力的偏转角进行调整;另外,在空间环境中利用圆弧插补理论将机器人平面避障问题转换为空间避障问题;基于机器人构型配置对改进人工势场法进一步完善以满足实际避障要求。仿真和实验研究结果表明,含避障角的人工势场法,在单个或多个障碍物环境中进行避障路径规划时解决了局部极小值的问题,同时实现了6自由度机器人末端在避障时的轨迹曲线平滑无振荡,验证了所提出避障路径规划方法的可行性。

基于格拉姆角场和多尺度残差神经网络的地震事件分类方法

以江苏地震台网中心搜集并标注的天然地震、人工爆破和塌陷事件为试验数据样本,提出了一种基于格拉姆角场和多尺度残差神经网络的新的地震事件分类方法。首先对波形数据进行滤波、归一化等预处理,然后应用格拉姆角场对地震波形数据进行二维编码得到二维图像,再将此经过编码后的图像作为多尺度残差神经网络的输入进行分类模型的训练和测试,从而得出分类结果。采用上述方法对1078个天然地震台站记录、981个爆破台站记录和830个塌陷台站记录进行试验,结果显示:最终以单条波形为单位的地震事件分类准确率为92.55%,以单个台站为单位的分类准确率为96.36%,这表明基于格拉姆角场和多尺度残差神经网络的地震分类方法具有良好的效果。

半导体激光器结构设计与波导层的优化

针对1.31μm半导体激光器工作时,远场发散角过大以及AlGaInAs/GaAs材料体系中Al组分的氧化导致器件性能下降问题。提出了在InGaAsP/InP结构基础上,上下波导层采用GaAsP材料,与由InGaAsP材料构成的有源区形成异质结结构。相比同质结构制作的波导层,异质结波导层结构依据不同材料的折射率不同,实现有源层和波导层之间较大的折射率差,从而达到更好的波导限制。对1.31μm激光器中的In_(1-x)Ga_(x)As_(y)P_(1-y)材料组分进行理论计算,并根据该材料的折射率和晶格常数,对GaAs_(y)P_(1-y)材料组分、厚度进行理论计算。使用ALDS仿真软件,对同质结波导层和异质结波导层两种结构进行模拟分析。最后确定使用100 nm厚度的GaAs_(0.145)P_(0.855)材料分别作为波导层和限制层,有效减小远场垂直发散角,提高了激光器发射的光束在空间分布的圆对称形态。

印刷电路板换热器内翅片布置方式的场协同分析与讨论

为了研究超临界CO_(2)的传热性能并提高其换热性能,通过采用超临界CO_(2)作为传热流体,以翼型翅片为例,使用数值模拟的方法探究印刷电路板换热器内的不连续翅片通道,分析几种翅片布置方式的传热和阻力性能,得出翅片的最佳布置方式。同时通过场协同理论,即通过分析温度场、压力场和速度场之间的协同性对模拟结果进行分析与讨论。结果表明,当交错距离为4 mm时,其传热性能与阻力性能均为最优,拥有最小的温度场与速度场协同角和最大的压力场与速度场协同角,表明这种布置方式可以使温度场与速度场的协同性和压力场与速度场的协同性均为最优,且它们之间的协同性均随着入口质量流量的增大而变差。

小型风洞实验设计与布局方法的优化

考虑到小型风洞实验在航空航天、汽车制造等领域中的应用,结合理论及实际应用,指出小型风洞在设计和布局中存在的问题,包括设备尺寸及空间利用率、流场均匀性、桨叶设计及整流罩布局等,通过一系列的优化方法,如调整风洞尺寸、采用高效率风扇、改进导流片设计提高实验的准确性及效率,为风洞实验提供稳定准确的环境,促进风洞技术的发展。

三杯风速传感器非水平风场测量性能

为解决三杯风速传感器在计量检定条件下与观测场景中环境差异所导致的测量数据误差,致力于研究空气流速计量标准在量值传递过程中的真实性、准确性和一致性,为新一代三杯风速传感器作为计量器具的新产品型式评价提供思路和参考指标,依据杯式测风仪测量方法与自动气象站风速风向传感器检定规程,并在实验中加入了主体由角度编码器构成的自动化转盘系统,设计了三杯风速传感器在非水平风场内测量性能水平实验。通过调整三杯风速传感器在风洞试验段内的倾斜角度,模拟其在自然界非水平风场中的测量状态,同步采集风洞的标准指示风速、三杯风速传感器的实测风速以及其相应的倾斜角度,计算示值误差,利用方差分析、趋势分析、相关性分析和线性回归分析等统计方法,对不同倾斜角度下三杯风速传感器示值误差进行研究,得出了三杯风速传感器在风洞试验段内的示值误差与实测风速和倾斜角度之间的相关关系,提出了三杯风速传感器在非水平风场下的测量性能指标。研究了三杯风速传感器在非水平风场中实测风速与标准风速和倾斜角度的回归关系,提出了三杯风速传感器在计量环境下非水平风场中数据的量值传递修正算法。