激光雷达监测北京城区夏季边界层气溶胶

运用一种新型边界层气溶胶监测激光雷达,在北京丰台区进行了外场实验,探讨了大气边界层(PBL)内气溶胶消光系数与湿度、风速等气象条件的关系,并给出了消光系数的时空分布。实验结果表明,水平大气气溶胶消光系数与黑碳质量浓度、地面风速等近地气象因子均有较好的相关性;边界层气象因子直接影响气溶胶的时空扩散和分布;在近地面风速较小等条件下,北京城区气溶胶污染在凌晨和上午较下午和前半夜严重。     

基于背景差分的一种运动目标检测方法

针对运动目标检测中,传统背景差分法在运动目标和背景颜色相近时不易检测的缺点,提出了一种检测完整运动目标的方法。该方法对YUV彩色空间下的3个通道分别选取独立的阈值进行初次检测,最大化地利用了视频中图像的色彩信息。在包含初次检测所获运动目标的最小矩形区域内进行二次检测,有效地提高了检测精度。实验证明,相比于常规方法,该方法的检测结果更加清晰完整。     

Self‐Assembly of Atomically Thin Chiral Copper Heterostructures Templated by Black Phosphorus

The fabrication of 2D systems for electronic devices is not straightforward, with top‐down low‐yield methods often employed leading to irregular nanostructures and lower quality devices. Here, a simple and reproducible method to trigger self‐assembly of arrays of high aspect‐ratio chiral copper heterostructures templated by the structural anisotropy in black phosphorus (BP) nanosheets is presented. Using quantitative atomic resolution aberration‐corrected scanning transmission electron microscopy imaging, in situ heating transmission electron microscopy and electron energy‐loss spectroscopy arrays of heterostructures forming at speeds exceeding 100 nm s^?1 and displaying long‐range order over micrometers are observed. The controlled instigation of the self‐assembly of the Cu heterostructures embedded in BP is achieved using conventional electron beam lithography combined with site specific placement of Cu nanoparticles. Density functional theory calculations are used to investigate the atomic structure and suggest a metallic nature of the Cu heterostructures grown in BP. The findings of this new hybrid material with unique dimensionality, chirality, and metallic nature and its triggered self‐assembly open new and exciting opportunities for next generation, self‐assembling devices.     

Feature Selection with Data Field

A new feature selection method is proposed for high-dimensional data clustering on the basis of data field. With the potential entropy to evaluate the importance of feature subsets, features are filtered by removing unimportant features or noises from the original datasets. Experiments show that the proposed method can sharply reduce the number of dimensions and effectively improve the clustering performance on WDBC dataset.     

Bimetal-Incorporated Black Phosphorene with Surface Electron Deficiency for Efficient Anti-Reconstruction Water Electrolysis

Surface reconstruction (SRC) is a common phenomenon and a promotion manner for Ni/Co-based precatalysts during the water splitting process. However, the catalytic surface reconstruction will in turn complicate the streamlined prediction and modeling on the catalytic activity. Hence, the rational design of anti-SRC catalysts is highly desirable, but challengeable. In this article, a series of affordable bimetal-incorporated black phosphorene (BP) catalysts are constructed by an in situ electro-exfoliation/insertion method for anti-SRC water electrolysis. It is found that the bimetals (e.g., NiFe, NiPd) are of cationic and covalent incorporation with electron-deficient state in few-layer BP. The optimized bimetal-BP structures present excellent and stable catalytic performances with low overpotentials in hydrogen evolution (HER, 53 mV, NiPd-BP) and oxygen evolution (OER, 268 mV, NiFe-BP) reactions at 10 mA cm⁻² in 1 m KOH. The anti-SRC behaviors are elucidated by in situ Raman studies during HER/OER, probably due to the balanced electron transfer pathway on Ni sites. This research opens interesting possibilities for designing the anti-SRC catalysts for efficient hydrogen production and authentic structure-activity understandings.     

An optimal linear and elliptical antenna array design using black widow optimisation for 5G communication

This research illustrates a precise linear and elliptical antenna array design for synthesising the optimal far-field radiation pattern in the fifth-generation (5G) communication spectrum using a meta-heuristic optimisation technique known as black widow optimisation (BWO). 5G communication is an emerging technology with revolutionary changes in the wireless communication system with ultra-high data rate, enhanced capacity, low latency and good quality of service. An accurate antenna array design for an ideal far-field radiation pattern synthesis with a suppressed side lobe level (SLL) value and half power beam width (HPBW) is the most crucial aspect of 5G communications. A suppressed SLL is necessary to reduce interference in the entire side lobe region, whereas a low HPBW is required for long-distance communication. Here, the BWO is employed to find the optimal feeding current to each array element to lower the SLL and the HPBW value. The BWO algorithm sustains impeccable equity between the exploration and exploitation stages to impact different potential regions of the search space and generate new solutions to attain the global optima by evading the trap of local optima. The design examples of the linear antenna array (LAA) and elliptical antenna array (EAA) are illustrated in this article by applying the optimal feeding currents to each array element. Compared to the uniform antenna array and methodologies described in the recently published literature, the results obtained utilising the BWO algorithm for designing the LAAs and EAAs demonstrate a substantial development in the reduction of SLL and HPBW.     

一种改进的混合高斯模型运动目标检测算法

针对传统混合高斯模型使用固定学习速率所带来的问题,提出了一种改进的运动目标检测算法。该算法采用自适应的学习速率调整策略,在背景建模初期,采用较大的学习速率加快初始背景的建模,使得模型能更快地适应背景的变化;背景形成以后,根据目标运动的快慢动态调整学习速率,从而能够及时更新背景,消除运动目标的残留和拖影;最后利用基于HSV颜色空间的阴影检测算法消除运动阴影。实验结果表明,改进算法优于传统混合高斯模型,可以更准确地检测出运动目标,更好地消除阴影,并具有较好的自适应性和稳健性。     

基于C8051F040的CAN总线通讯系统设计

作为一种很有前途的现场总线,CAN总线通信相对于一般的串行通信总线,他的实时性、可靠性和灵活性的特点更加突出。介绍了C8051F040内部集成的CAN控制器的使用方法,给出了以此芯片为核心的CAN总线智能节点通讯接口的硬件和软件设计,实际的运行验证了设计的正确性。其设计通用性好、可靠性高、性价比高,具有广泛的应用前景。     

Q开关Nd:YAG激光治疗黑色文身的临床研究

目的：探讨Q开关Nd：YAG激光治疗黑色文身的临床效果。方法：采用Q开关Nd：YAG激光治疗黑色文身200例,能量密度4～8J/cm~2,脉冲宽度5～6ns,重复频率5Hz,光斑直径2～3mm。根据文身的性质需1～7个疗程,疗程间隔6～8周。结果：200例文身中190业余性文身经1～5次治疗,治愈率100%,10例专业性文身经4～7次治疗,治愈率90%。随访3～12个月,无一例发生继发性疤痕和永久性色素改变。结论：Q开关Nd：YAG激光能安全有效去除黑色文身,达到极佳的美容效果。     

流星余迹极低信噪比通信技术

根据流星余迹信道特性,在频域信号处理的基础上提出利用迭代的信号处理方法对极低信噪比条件下的流星余迹通信系统进行信号检测,讨论了实现步骤,并在SPW环境下进行仿真、比较,仿真结果验证了此算法的可行性.