Influence of the Source to Substrate Distance on the Growth,Tribological Properties and Optical Properties of Be Films

The Be films were prepared by thermal evaporation at different sources to substrate distances（SSD） on glass substrates. The decrease of SSD from 90 mm to 50 mm caused the increase of substrate temperature and the rising density of incident Be atoms, thus the properties of Be films greatly changed accordingly. The experimental results showed that the grain diameter in the Be films transited from below 100 nm to 300 nm, the film growth rate increased from 2.35 nm/min to 4.73 nm/min and the roughness increased from 7 nm to 49 nm. The performance study suggested that the friction coefficient of Be films increased from 0.13 to 0.27 and was related to the surface roughness and inner structure, the near-infrared reflectance of Be films increased from 40% to 85% with the increase of wavelength and concurrently decreased with the decrease of SSD, respectively. The performance study indicated that the Be film had the potential application in specific near-infrared reflectance optical system.

Microdroplet targeting induced by substrate curvature

Fundamental understanding of the wettability of curved substrates is crucial for the applications of microdroplets in colloidal science, microfluidics, and heat exchanger technologies. Here we report via lattice Boltzmann simulations and energetic analysis that microdroplets show an ability of transporting selectively to appropriate substrates solely according to substrate shape（curvature）, which is called the substrate-curvature-dependent droplet targeting because of its similarity to protein targeting by which proteins are transported to the appropriate destinations in the cell. Two dynamic pathways of droplet targeting are identified： one is the Ostwald ripening-like liquid transport between separated droplets via evaporating droplets on more curved convex（or less curved concave） surfaces and growing droplets on less curved convex（or more curved concave） surfaces, and the other is the directional motion of a droplet through contacting simultaneously substrates of different curvatures. Then we demonstrate analytically that droplet targeting is a thermodynamically driven process. The driving force for directional motion of droplets is the surface-curvature-induced modulation of the work of adhesion, while the Ostwald ripening-like transport is ascribed to the substrate-curvature-induced change of droplet curvature radius. Our findings of droplet targeting are potentially useful for a tremendous range of applications, such as microfluidics, thermal control, and microfabrication.

Single Radar Measurement Method for Antiaircraft Projectile Miss Distance

To measure miss distance for antiaircraft projectile,a radial velocity identification and positioning method with a single radar is proposed. By analyzing the spatial resolution of multi-frequency ranging radar,the discrimination and testing model of this radar for multi-targets（ projectile and target） is established to analyze the systematic error of antiaircraft miss distance. Then through the aerial target flight test and contrast test with optical test equipment,the validity of the measurement method is verified. This newmethod has the potential to be used in the measurement of antiaircraft projectile miss distance.

Effect of lens focusing distance on laser-induced silicon plasmas at different sample temperatures

We investigated the dependence of laser-induced breakdown spectral intensity on the focusing position of a lens at different sample temperatures(room temperature to 300 ℃) in atmosphere.A Q-switched Nd:YAG nanosecond pulsed laser with 1064 nm wavelength and 10 ns pulse width was used to ablate silicon to produce plasma. It was confirmed that the increase in the sample's initial temperature could improve spectral line intensity. In addition, when the distance from the target surface to the focal point increased, the intensity firstly rose, and then dropped.The trend of change with distance was more obvious at higher sample temperatures. By observing the distribution of the normalized ratio of Si atomic spectral line intensity and Si ionic spectral line intensity as functions of distance and temperature, the maximum value of normalized ratio appeared at the longer distance as the initial temperature was higher, while the maximum ratio appeared at the shorter distance as the sample temperature was lower.

RADAR HRRP RECOGNITION BASED ON THE MINIMUM KULLBACK-LEIBLER DISTANCE CRITERION

To relax the target aspect sensitivity and use more statistical information of the High Range Resolution Profiles (HRRPs), in this paper, the average range profile and the variance range profile are extracted together as the feature vectors for both training data and test data representa-tion. And a decision rule is established for Automatic Target Recognition (ATR) based on the mini-mum Kullback-Leibler Distance (KLD) criterion. The recognition performance of the proposed method is comparable with that of Adaptive Gaussian Classifier (AGC) with multiple test HRRPs, but the proposed method is much more computational efficient. Experimental results based on the measured data show that the minimum KLD classifier is effective.

Distribution of Miss Distance in Discrete-Time Controlled System with Noise-Corrupted State Information

Miss distance is an important parameter of assessing highly maneuvering targets interception. Due to the noise-corrupted measurement and the fact that not all the state variables can be directly measured, the miss distance becomes a random variable with a priori unknown distribution. Currently, such a distribution is mainly evaluated by the method of Monte Carlo simulation. In this paper, an analytic approach is obtained in discrete-time controlled system with noise-corrupted state information. The system is subject to a bang-bang control strategy. The analytic distribution is validated through the comparison with Monte Carlo simulation.

CORRECTION OF INFLUENCE OF SUBSTRATE ON MEASUREMENT OF INNER SHELL IONIZATION CROSS SECTIONS

The energy spectra of reflected electrons from the substrates of targets have been calculated by the bipartition model of electron transport, the contributions of the inner shen ionization events produced by the reflected electrons from the substrates in the targets to the x-ray counting in a St(Li) detector have been estimated. It has been confirmed that, by such correction to the measured data, the experimental results of inner shell ionization cross sections by electron impact with fine precision may be obtained under the condition of thick substrate.

远距离和遮挡下三维目标检测算法研究

针对现有三维目标检测算法对存在遮挡及距离较远目标检测效果差的问题,以基于点云的三维目标检测算法(3D object proposal generation and detection from point cloud,PointRCNN)为基础,对网络进行改进,提高三维目标检测精度。对区域生成网络(region proposal network,RPN)获取的提议区域(region of interest,ROI)体素化处理,同时构建不同尺度的区域金字塔来捕获更加广泛的兴趣点;加入点云Transformer模块来增强对网格中心点局部特征的学习;在网络中加入球查询半径预测模块,使得模型可以根据点云密度自适应调整球查询的范围。最后,对所提算法的有效性进行了试验验证,在KITTI数据集下对模型的性能进行评估测试,同时设计相应的消融试验验证模型中各模块的有效性。

基于Transformer复杂运动辨识的机动星凸形扩展目标跟踪方法

针对复杂的机动扩展目标跟踪问题,利用Transformer网络设计了一种有效的星凸不规则形状机动扩展目标跟踪方法。首先,该文研究利用alpha-shape算法建立了星凸形状的变化模型,实现了静态场景下的星凸形扩展目标的形状估计。然后,通过对目标状态转移矩阵进行重新设计,结合Transformer网络对机动扩展目标运动状态转移矩阵进行实时估计,实现了对复杂机动目标运动过程的精准跟踪。进一步地,将估计得到的形状轮廓与运动状态进行融合,最终实现了对星凸形机动扩展目标的实时跟踪。最后,通过构造复杂的机动扩展目标跟踪场景,利用多重性能指标测试算法对形状和运动状态的综合估计性能,验证了算法的有效性。

CoFe/NiFe复合自由层对自旋阀磁电阻变化率的影响

研究CoFe/NiFe复合自由层对自旋阀磁电阻变化率的影响。在实验中通过固定溅射功率、时间和气流,调节靶基距(TSD)得到不同厚度及均匀性的复合自由层CoFe/NiFe薄膜,进而达到优化自旋阀结构提高其磁电阻率的目的。实验结果表明:在TSD分别为8.382 cm、8.890 cm时,制备的CoFe和NiFe单层膜性能最优,电阻标准偏差分别为1.33%、0.98%。通过磁性能综合测试平台对优化后的CoFe/NiFe复合自由层的自旋阀结构进行了测试,磁电阻变化率(MR)较优化前提高了约0.84%。该研究可为高性能自旋阀结构的制备提供参考。

Influence of the distance between target and substrate on the properties of transparent conducting Al-Zr co-doped zinc oxide thin films

Highly transparent and conducting Al-Zr co-doped zinc oxide （ZAZO） thin films were successfully prepared on glass substrate by direct current （DC） magnetron sputtering at room temperature. The distance between target and substrate was varied from 45 to 70 mm. All the deposited films are polycrystalline with a hexagonal structure and have a preferred orientation along the c-axis perpendicular to the substrate. The crystallinity increases obviously and the electrical resistivity decreases when the distance between target and substrate decreases from 70 to 50 mm. However, as the distance decreases further, the crystallinity decreases and the electrical resistivity increases. When the distance between target and substrate is 50 ram, it is found that the lowest resistivity is 6.9 × 10^-4Ω cm. All the deposited films show a high average transmittance of above 92% in the visible range.

Microstructure and corrosion resistance of vanadium films deposited at different target-substrate distance by HPPMS

High power pulsed magnetron sputtering（HPPMS）, a novel physical vapor deposition technology, was applied to prepare vanadium films on aluminum alloy substrate in this paper. The influence of target–substrate distance（Dt–s）（ranging from 8 to 20 cm） on phase structure, surface morphology, deposition rate, and corrosion resistance of vanadium films was investigated. The results show that the vanadium films are textured with a preferential orientation in the（111） direction except for that fabricated at 20 cm. With Dt–sincreasing, the intensity of（111） diffraction peak of the films decreases and there exists a proper distance leading to the minimum surface roughness of 0.65 nm. The deposition rate decreases with Dt–sincreasing. All the V-coated aluminum samples possess better corrosion resistance than the control sample. The sample fabricated at Dt–sof 12 cm demonstrates the best corrosion resistance with the corrosion potential increasing by 0.19 V and the corrosion current decreasing by an order of magnitude compared with that of the substrate. The samples gain further improvement in corrosion resistance after annealing, and if compared with that of annealed aluminum alloy, then the corrosion potential of the sample fabricated at 20 cm increases by 0.415 V and the corrosion current decreases by two orders of magnitude after annealed at 200 °C. If the annealing temperature further rises to 300 °C, then the corrosion resistance of samples increases less obviously than that of the control sample.

改进自适应加权的海面目标距离测量和跟踪

海上目标距离探测和跟踪是海洋安全和军事应用中的关键任务之一,针对复杂海面环境在海杂波等影响因素下目标距离测量精度低的问题,提出了一种改进的多传感器数据融合算法。该算法利用海面舰船雷达及陆地雷达联合探测结果,先对多个数据源数据进行坐标系转换,利用Robust Z-score方法进行纵向数据预处理剔除异常数据,再通过重新定义置信距离度量,将置信度较高的传感器结果代替被踢除数据后,对结果进行自适应加权融合。同时,为了进一步提高数据精度,引入了一种分段融合机制,将改进的传感器数据融合算法与阶梯式自适应加权融合算法进行级联,通过度量各分段融合结果的相似度,设定一个置信阈值,通过该置信阈值确定最终的融合结果。仿真实验结果证实了算法的有效性和准确性。

基于改进人工势场法的通用航空路径规划

通用航空飞机在飞行过程除了要面对障碍物和天气系统的威胁,同时也受到飞行空域的限制,往往飞机只能在一块固定的空域或狭小的飞行走廊内飞行,一旦飞出限制空域,则有可能引发飞行冲突,甚至发生严重的安全事故。针对这些问题,在人工势场法斥力势场函数中添加航空器和目标点之间的相对距离函数,首先解决传统人工势场法存在的目标不可达问题和局部极小点问题,然后在算法中加入航路边界斥力影响因子,使飞机避障后在边界斥力的作用下重回航路中心。经过MATLAB仿真验证,试验结果表明,改进后的人工势场法能够实现主动避障和飞机航迹的规划。

MNTH-YOLOv8:一种用于食品包装中蚊虫高效检测的深度学习方法

食品安全一直是社会关注的焦点,而在食品包装印刷生产过程中,蚊虫的夹杂会对食品安全构成威胁。针对食品包装质检过程中蚊虫检测仍是人工筛查的现状,以及蚊虫目标尺寸小、所处背景复杂的特点,提出了一种基于深度学习的全自动MNTH-YOLOv8检测方法。该方法是在YOLOv8强大的目标检测功能基础上,结合通道特征部分卷积模块、SimAM注意力机制和改进的特征融合模块,并以CIoU与归一化Wasserstein距离作为定位回归损失函数的优化模型。对真实数据集的检测结果表明,MNTH-YOLOv8表现出显著优势,不仅有效提高了小目标蚊虫的检测精度,还在保持检测速度的前提下减少了参数量。MNTH-YOLOv8在食品包装中蚊虫的实时检测应用上拥有广阔前景。

射频能量收集印刷天线仿真模型中长丝机织物结构简化方法及有效性

获得仿真精确度高且计算成本低的仿真模型是高效设计织物基丝网印刷射频能量收集天线的基础。本文构建了长丝机织物天线基底的几种不同简化结构特征的仿真模型,采用HFSS仿真软件模拟了织物仿真模型与电磁波的相互作用,且以孔隙率和粗糙度为变量参数化分析了具有不同仿真结构基底的天线性能差异,并实际制备了几种不同简化结构基底的天线。结果表明:通过对比反射率和透射率发现,细观交织结构可以等效为具有孔洞和/或凹凸结构模型,均匀结构模型基底的天线辐射性能、增益及效率都显著偏高。进一步以射频能量收集为场景的模型有效性及验证结果表明,仿真模拟结果与实际测试结果吻合良好,且不同简化结构基底的天线性能也无显著性差异。在超高频范围内,不同简化结构基底的天线最大传输距离达220 cm,在1 m处的单位面积接收信号强度在8.442 mW/cm^(2)以上,天线输出电压和能量转换效率可分别达135 mV、60%。因此,为节约计算成本,就孔隙率不超过30%且粗糙度在5.39μm以下的长丝平纹机织物基底,在丝网印刷超高频射频能量收集天线仿真模拟中可将其等效为均匀介质模型。

空化水射流在渐进成形与冲蚀领域的对比分析

目的将高压水射流渐进成形技术与空化现象相结合,探索一种新的加工形式——空化水射流渐进成形技术,研究不同空化喷嘴内部结构、工作靶距对成形和冲蚀的影响。方法设计了5种不同内部结构的空化喷嘴,在相同工艺参数和不同靶距的条件下,对厚度为0.5 mm、尺寸为200 mm×200 mm的5052铝合金板以及厚度为10 mm、尺寸为50 mm×50 mm的1060铝合金块进行成形和冲蚀实验,测量样品成形高度和冲蚀损失质量,观察电子显微镜下样品的冲蚀外貌形态。结果喷嘴内部结构对空化效果有很大影响,有锥形扩散段的喷嘴空化效果更好,作用半径更大。喷嘴的作用区域呈3层圆环状,由许多涡旋组合而成。产生的空泡沿流动方向运动,在靶体附近溃灭,释放冲击力。在成形和冲蚀2种工况下,均存在最佳靶距,且随着靶距的增大,空化水射流的表面形态也发生变化,圆环的第1层直径保持不变,第2层、第3层直径显著增大。结论空化喷嘴的内部结构和靶距对空化水射流成形和冲蚀的影响较大,在实际生产应用中应根据使用场景、工作范围选择合适的工艺参数,以提高效率。

基于MDk-DPC的空中目标自动分群方法

空中目标分群本质上是一个类数未知的聚类问题,也是战场态势估计领域中的研究热点。针对未知的空战场环境,从聚类角度提出一种基于流形距离和k近邻采样密度的MDk-DPC算法。引入流形距离代替欧氏距离,以增加同一流形中目标的相似性;利用k近邻计算目标的局部密度,使其能更真实地反映目标周围分布;通过自适应选取聚类中心方法确定聚类中心,并运用密度峰值算法指定剩余点类别完成分群。仿真实验表明,所提方法在人工合成数据集和UCI真实数据集上均有更好的聚类性能,同时通过对空战场仿真数据进行分群验证了所提方法的可行性和有效性。

行进间地面机动目标射击诸元解算方法

针对地面机动目标运动模式未知、无源跟踪缺乏距离量测信息导致传统射击诸元解算方法解命中精度下降的问题,提出一种基于纯角度测量的行进间地面机动目标射击诸元解算方法。在传统固定参数的当前统计(CS)模型基础上,利用模糊推理动态调整机动频率,并根据加速度历史估计信息设置机动加速度方差,提高目标方位角的估计精度;在一次测距的基础上,基于简化刚体弹道模型,利用割弦迭代法计算出命中点坐标,并在每次迭代中利用虚拟脱靶量对射击诸元进行修正,减少对弹道方程的计算次数,提高射击诸元解算的实时性和精度。仿真结果表明,该方法有效可行,基于模型参数自适应的CS模型提高了目标角度跟踪的精度,基于虚拟脱靶量的迭代修正算法提高了诸元解算的实时性,解命中精度相对于传统射击诸元解算方法得到了显著改善。

基于锚框的远距离多尺度红外目标跟踪技术

在红外目标跟踪过程中,由于目标距离和视角的变化,红外目标的成像面积通常很小,使得红外图像中缺乏足够的像素信息,无法准确提取目标的特征,增加了目标跟踪的难度。因此,提出基于锚框的远距离多尺度红外目标跟踪技术。利用编码的方式对应追踪框图与真实框图,得到目标框中心坐标值。为保证计算的精准度,通过设定特征融合阈值判定提取信息与真实信息较高的重叠度,并按照锚框的边缘、中心以及顶点坐标对应划分像素网格,根据特征值输出分类输出向量,完成红外目标特征提取。由此采用损失函数给出锚框、目标框、实际框的类别损失以及候选框等不同类别损失函数,按照不同点在网格中的体素值,以编码形式逐一对比候选框和真实框数据,通过迭代实现远距离多尺度红外目标跟踪。实验结果表明,所提方法对远距离多尺度红外目标的识别效果较好,查全率曲线基本保持在0.9以上。说明所提方法具有良好的远距离多尺度红外目标跟踪效果。