1 西南科技大学信息工程学院，四川 绵阳 621000
2 中国船舶航海保障技术实验室，天津 300131
3 天津航海仪器研究所，天津 300131
4 特殊环境机器人技术四川省重点实验室，四川 绵阳 621000
轮式里程计在复杂不平的地形和光滑的地面上性能较差，传统的激光扫描匹配方法并不总是正确地建立点云之间的对应关系，容易出现点与点之间的异常关联，导致定位精度较差。针对这一问题，提出一种基于方向端点的激光扫描匹配方法。首先，从环境中提取直线端点作为特征点，通过端点间的特征匹配得到相邻时刻移动机器人的相对位姿关系。基于端点的匹配方法在特征点较少时有可能会产生误匹配，为进一步提高匹配精度，利用端点的方向剔除误匹配的特征点。在此基础之上，利用迭代最近邻法进一步优化方向端点的匹配结果，得到更加精准的移动机器人位姿。实验结果表明，所提方法在7 m×7 m的室内光滑地面环境中，能够达到0.12 m的平均定位误差以及1.18°的平均角度误差，与传统的激光扫描匹配方法相比精度更高。
移动机器人定位 激光扫描匹配 特征匹配 激光里程计 激光与光电子学进展
2024, 61(4): 0428010
Author Affiliations
Abstract
College of Communication Engineering, Jilin University, Changchun 130012, China
The nonlinear distortion caused by the Mach-Zehnder modulator (MZM) is one of the main limiting factors for the improvement of the transmission performance of the intensity modulation and direct detection (IM/DD) optical communication system. In order to solve the problem, an improved Volterra nonlinear equalization (VNLE) method is proposed. Compared with the traditional VNLE that uses the least mean square (LMS) to calculate the tap coefficients, the improved VNLE uses the least square (LS) method to obtain more stable convergence. The simulation results show that the VNLE based on LS has better performance when solving complex nonlinear damage. For 25 Gbaud 4-level pulse amplitude modulation (PAM4) signals, the improved VNLE can reduce the bit error rate (BER) to below 10-4 in a 7-km-long single-mode optical fiber transmission system. In addition, in order to make the BER below 10-3, the transmission distance that the improved VNLE can withstand is about 1.5 km longer than that of the traditional VNLE.
光电子快报（英文版）
2022, 18(4): 238
1 太原理工大学信息与计算机学院, 山西 晋中 030600
2 北德克萨斯州大学计算机系, 美国 德克萨斯州 丹顿市 76201
当前主流的眼底视网膜血管分割方法存在细微血管细粒度特征很难采集和细节容易丢失的问题。为解决这一问题,设计了一种改进U-Net模型算法,该算法将U-Net上下采样中的原始卷积层改为二次循环残差卷积层,提升了特征的使用效率;在解码部分引入多通道注意力模型,改善了低对比度下细小血管的分割效果。该算法在DRIVE (Digital Retinal Images for Vessel Extraction)和STARE (Structured Analysis of the Retina)两个数据库的准确率分别为96.89%和97.96%,敏感度分别为80.28%和82.27%,AUC(Area Under Curve)性能分别为98.41%和98.65%,较现有的先进算法有一定的提升。本文所提算法能有效提高眼底图像细微血管分割准确率。
图像处理 视网膜血管 U-Net 循环残差网络 注意力机制 光学学报
2020, 40(12): 1210001
Author Affiliations
Abstract
1 Institute for Electric Light Sources, School of Information Science and Technology, Engineering Research Center of Advanced Lighting Technology, and Academy of Engineering and Technology, Fudan University, Shanghai 200433, China
2 Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6, Canada
In this work, a blue gallium nitride (GaN) micro-light-emitting-diode (micro-LED)-based underwater wireless optical communication (UWOC) system was built, and UWOCs with varied Maalox, chlorophyll, and sea salt concentrations were studied. Data transmission performance of the UWOC and the influence of light attenuation were investigated systematically. Maximum data transmission rates at the distance of 2.3 m were 933, 800, 910, and 790 Mbps for experimental conditions with no impurity, 200.48 mg/m3 Maalox, 12.07 mg/m3 chlorophyll, and 5 kg/m3 sea salt, respectively, much higher than previously reported systems with commercial LEDs. It was found that increasing chlorophyll, Maalox, and sea salt concentrations in water resulted in an increase of light attenuation, which led to the performance degradation of the UWOC. Further analysis suggests two light attenuation mechanisms, e.g., absorption by chlorophyll and scattering by Maalox, are responsible for the decrease of maximum data rates and the increase of bit error rates. Based on the absorption and scattering models, excellent fitting to the experimental attenuation coefficient can be achieved, and light attenuation by absorption and scattering at different wavelengths was also investigated. We believe this work is instructive apply UWOC for practical applications.
220.4830 Systems design 290.5850 Scattering, particles 290.5825 Scattering theory 230.6080 Sources Chinese Optics Letters
2019, 17(10): 100010
中国农业大学食品科学与营养工程学院, 北京 100083
为了提升便携式近红外仪器中单一水果模型应用的广泛性, 创新性的将不同仪器间模型传递的思想应用在不同种类水果间可溶性固形物（soluble solid content, SSC）的模型传递。 基于苹果、 梨、 桃三种水果在SSC含量范围、 果型大小以及果皮厚度等的相近物理化学特性, 提出利用简单的斜率/截距（Slope/Bias）算法对苹果SSC的偏最小二乘(partial least square, PLS)模型进行传递, 仅用少量的梨和桃样品即可将苹果SSC模型应用于其SSC值的预测, 更快捷方便且节约成本。 对于梨样品, 用35个标准样品, 预测集均方根误差（root mean square error of prediction, RMSEP）值由直接预测的1.009 °Brix降为0.565 °Brix; 对于桃样品, 用40个标准样品, RMSEP由直接预测的1.726 °Brix降为0.677 °Brix。 为了验证该模型传递方法的可行性, 通过斜率/截距算法, 采用梨和桃模型对其他两种水果的SSC进行预测, 其中利用建立的梨SSC模型, 经斜率/截距算法模型传递后, 对于苹果样品, 用30个标准样品, RMSEP值达到0.597 °Brix, 对于桃样品, 用40个标准样品, RMSEP值达到0.689 °Brix; 利用建立的桃SSC模型, 经斜率/截距算法模型传递后, 对于苹果样品, 用35个标准样品, RMSEP值达到0.654 °Brix, 对于梨样品, 用30个标准样品, RMSEP值达到0.439 °Brix。 研究结果表明: 斜率/截距（Slope/Bias）方法可用于苹果、 梨、 桃等相近种类水果间的模型传递, 为近红外光谱仪在相似种类物质间的预测提供了新思路。
近红外光谱 模型传递 Slope/Bias算法 苹果 梨 桃 NIR spectroscopy Model transfer Slope/Bias algorithm Apple Pear Peach
Author Affiliations
Abstract
1 College of Food Science and Nutritional Engineering China Agricultural University, Beijing 100083, P. R. China
2 National Engineering Research Center for Vegetables (NERCV) Beijing 100097, P. R. China
Nondestructive evaluation of melon quality is in great need of comprehensive study. Soluble solids content (SSC) and firmness are the two indicators of melon internal quality that mostly affect consumer acceptance. To provide guidance for fruit classification, internal quality standards was preliminarily established through sensory test, as: Melon with SSC over 12° Brix, firmness 4–5.5 kgf · cm-2 were considered as satisfactory class sample; and SSC over 10° Brix, firmness 3.5–6.5 kgf · cm-2 as average class sample. The near infrared (NIR) nondestructive detection program was set as spectra collected from the stylar-end, Brix expressed by the average SSC of inner and outer mesocarp, each cultivar of melon was detected with its own optimum integration time, and the second derivative algorithm was used to equalize them. Using wavelength selected by genetic algorithms (GA), a robust SSC model of mix-cultivar melon was established, the root mean standard error of cross-validation (RMSECV) was 0.99 and the ratio performance deviation (RPD) nearly reached 3.0, which almost could meet the accuracy requirement of 1.5° Brix. Firmness model of mix-cultivar melon was acceptable but inferior.
Melon nondestructive detection near-infrared fruit quality soluble solids content firmness Journal of Innovative Optical Health Sciences
2015, 8(6): 1550032
吉林大学超硬材料国家重点实验室, 长春 130012
利用高压原位拉曼光谱技术研究了非静水条件对CeO2纳米八面体高压结构相变的重压影响。研究表明: 在非静水条件下(无传压介质), 当压力达到26 GPa时, CeO2纳米八面体发生由立方萤石型结构到正交α-PbCl2型结构的可逆结构相变, 相变压力低于相应的体材料(30 GPa)。相反, 在准静水压条件下, CeO2纳米八面体的相变压力为33 GPa, 高于其体材料。研究表明, 实验条件对CeO2纳米八面体结构稳定性具有重要影响。
二氧化铈纳米八面体 高压 实验条件 结构稳定性 CeO2 nano-octahedrons high pressure experimental conditions structural stability
吉林大学超硬材料国家重点实验室, 长春 130012
采用金刚石对顶砧装置对直径分布在1. 3nm左右的单壁碳纳米管进行了高压拉曼光谱研究。实验结果表明随压力的增加碳管的截面形状发生了由圆到椭圆再到扁平的变化, 这和我们之前的研究结果一致。从31 GPa卸压至常压后碳管的结构得到了较好的保持, 这个压力值明显高于传统的SP2键结构的碳材料所能稳定存在的压力范围(20 GPa以下)。通过对碳管G-band半峰宽的详细分析, 我们认为在较高的压力下碳管之间发生了成键, 形成了一种更为稳定的结构。这种结构对高压下的碳管起到了保护作用, 从而使碳管表现出了较好的可逆性。
单壁碳纳米管 拉曼光谱 高压 Single-wall carbon nanotube Raman spectrum high pressure
