1 西北农林科技大学， 黄土高原土壤侵蚀与旱地农业国家重点实验室， 陕西 杨凌 712100
2 贵州大学生命科学学院， 贵州 贵阳 550025
3 西北农林科技大学草业与草原学院， 陕西 杨凌 712100
4 绍妍
5 西北农林科技大学， 黄土高原土壤侵蚀与旱地农业国家重点实验室， 陕西 杨凌 712100中国科学院水利部水土保持研究所, 陕西 杨凌 712100
探讨草地群落光谱特征与养分含量的关系， 可为采用高光谱技术诊断草地群落营养状况， 对推进快速无损检测技术应用于草地施肥管理具有重要意义。 以黄土丘陵区典型草地群落， 白羊草（Bothriochloa ischaemum）群落为研究对象， 设置4个氮添加（0、 25、 50和100 kg N·ha-1·yr-1）和4个磷添加(0、 20、 40和80 kg P2O5·ha-1·yr-1)处理。 基于群落冠层光谱和群落氮磷养分含量测定， 结合红边区域内一阶导数处理， 在植被指数、 特征波段和红边参数组成的18个光谱特征参数中， 采用逐步回归方法（SWR）筛选出对白羊草群落氮磷含量及氮磷比敏感的光谱特征参数， 并建立反演模型对草地群落地上部分全氮含量和地上部分全磷含量及其比值进行估测。 结果表明: 白羊草群落氮磷含量随施氮量增加而增加， 氮磷比随施磷量增加而减少; 氮磷添加下光谱反射率在可见光波段与施肥量成反比， 近红外波段与施肥量成正比， 红边区域内一阶导数的“双峰现象”受氮磷添加影响显著; 一些对草地群落氮磷含量较敏感的光谱特征对氮磷含量及氮磷比估测起重要作用， 其中三波段光谱指数(TBSI), R910和红边幅值(AMP)对氮含量的估测模型有极大贡献（R2=0.87, F=18.8***）， 而磷含量估测中差值植被指数(DVI), 修正红边简比率指数(mSR705), R430, R660和AMP对模型贡献明显（R2=0.91, F=20.51***）， Slope725对氮磷比的估测模型贡献最大（R2=0.54, F=5.14***）。 该研究运用高光谱技术实现对白羊草群落养分含量的快速精准估测， 在氮磷含量及其比值与光谱特征参数存在显著相关性的基础上， 成功筛选出建立模型精度最高的参数组合， 为大面积监测氮磷添加后草地养分含量方法和参数选择奠定了基础。
一阶导数 红边参数 植被指数 逐步回归 氮磷添加 First derivative Red edge parameters Vegetation index Stepwise regression N and P addition 光谱学与光谱分析
2023, 43(5): 1612
微波信号的光域产生是目前一个热门的研究课题, 在通信系统、信号处理、雷达等领域有着广泛应用。分别介绍了在微波光子学领域中基于连续射频调制和基于频率-时间映射技术生成特定光脉冲信号的频域合成法和时域合成法, 并对两种方法的几种具体方案进行详细介绍和对比, 从脉冲重复频率的调谐能力、脉冲占空比、脉冲类型、系统结构稳定性等方面分析其优缺点。
微波光子 光学函数波形产生 时域合成法 频域合成法 microwave photonics optical function waveform generation time domain synthesis frequency domain synthesis
Author Affiliations
Abstract
State Key Laboratory of Media Convergence and Communication, Communication University of China, Beijing 100044, China
A photonic approach that can generate triangular and rectangular waveforms is proposed. A dual-electrode Mach-Zehnder modulator (De-MZM) is used to fulfill the external optical carrier suppression (OCS) modulation of a continuous wave (CW). The follow-up four-wave mixing (FWM) in a semiconductor optical amplifier (SOA) makes four primary sidebands exist in the spectrum. Then filtering and optical carrier recovery techniques are used to construct the spectrum aligning with that of a triangular/rectangular waveform. In this work, we also elaborate the influence of errors of key device parameters, by which the feasibility and stability of the system have been verified. Based on this photonic approach, a 10 GHz full-duty-cycle triangular waveform and a 50%-duty-cycle rectangular waveform are successfully obtained. This approach provides a feasible method to generate multiple waveforms.
太原理工大学, 物理与光电工程学院 山西 太原 030024
本文基于Peregrine孤子, 数值研究掺铒光纤环形腔中呼吸脉冲的产生及其演化特性。Peregrine孤子是一个具有时空局域性的高峰值单脉冲。由于背景波与孤子的相互作用, Peregrine 孤子在单模光纤中传输发生分裂。为了产生长距离传输的高峰值脉冲, 就需要消除背景波。本文采用掺铒光纤环形腔的方案来消除背景波的影响。掺铒光纤环形腔由单模光纤, 掺铒光纤和光纤耦合器组成。通过控制环内单模光纤和掺铒光纤长度, 使腔内色散达到近零色散, 实现色散管理。研究表明, 由于呼吸脉冲的峰值强度与Peregrine孤子的初始输入有关。为了获得高峰值的呼吸脉冲, 选取Peregrine 孤子在最大激发位置处的脉冲作为光纤环的初始输入。在光纤环的作用下, Peregrine孤子在近零色散环形腔中可以产生长距离传输的高峰值呼吸脉冲, 而背景波逐渐演化成小的旁瓣脉冲。另外, 高峰值呼吸脉冲的传输特性与色散、非线性和小信号增益有关。净腔色散在［-0.001?0,0.003?7］ ps2范围之内, 可以产生长距离传输的高峰值呼吸脉冲。随着非线性系数的增加, 呼吸脉冲的峰值强度增加, 峰值振荡频率加快, 振荡幅度也增加。当非线性系数增加到一定程度, 局域呼吸脉冲逐渐形成。而小信号增益越大, 呼吸脉冲的峰值强度越高, 但振荡幅度和振荡频率影响较小。
呼吸脉冲 光纤环形腔 Peregrine孤子 非线性薛定谔方程 breathing pulse fiber ring cavity Peregrine soliton nonlinear Schrdinger equation
Author Affiliations
Abstract
1 School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510006, China
2 National Innovation Center for Advanced Medical Devices, Shenzhen 518131, China
3 GBA Branch of Aerospace Information Research Institute, Chinese Academy of Sciences, Guangzhou 510530, China
4 School of Biomedical Engineering, Sun Yat-sen University, Guangzhou 510006, China
5 State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-sen University, Guangzhou 510275, China
6 State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510060, China
7 School of Artificial Intelligence, Guilin University of Electronic Technology, Guilin 541004, China
In this paper, we propose and demonstrate a dual-beam delay-encoded Doppler spectral domain optical coherence tomography (OCT) system for in vivo measurement of absolute retinal blood velocity and flow with arbitrary orientation. The incident beam is split by a beam displacer into two probe beams of the single-spectrometer spectral domain OCT system with orthogonal polarization states and an optical path length delay. We validate our approach with a phantom and in vivo experiments of human retinal blood flow, respectively.
optical coherence tomography ocular perfusion optic nerve head ophthalmology Chinese Optics Letters
2022, 20(1): 011701
1 赤峰工业职业技术学院, 内蒙古 赤峰 024000
2 山东省科学院激光研究所, 山东 济南 250000
通过送粉式激光熔化3D打印装置在6063铝合金作基板上打印粒径尺寸50～100 μm的Al-12%Si合金粉末, 研究有/无横向稳恒磁场下3D打印Al-12%Si合金组织演变规律。研究结果表明, 激光熔化得到的沉积试样表现出明显层状堆积特征, 组织中包含亮白色的α-Al相与Al-Si共晶相以及部分颜色较暗的α-Al相共同叠加组成, 试样致密度达到94%。在磁场强度为0.5 T下, 试样的底部区域形成了珠界面以及边缘生成了众多的等轴状α-Al相, 磁场具有能够使柱状晶转变为等轴晶的作用且能够使α-Al相从柱状晶转变为等轴晶, 并形成高次枝晶臂。
激光熔化 横向稳恒磁场 Al-12%Si合金 组织演变 laser melting transverse steady magnetic field Al-12%Si alloy microstructure evolution
Author Affiliations
Abstract
1 Key Lab of All Optical Network and Advanced Telecommunication Network of EMC, Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044, China
2 College of Physics and Engineering, Qufu Normal University, Qufu 273165, China
This Letter demonstrates a filterless v-band signals and pulses generator scheme with a tunable optical carrier to sideband ratio (OCSR). Through complete theoretical analysis, the mathematical expression of the OCSR that contains the extinction ratio, phase modulation index, and bias angle is obtained. It is found that the OCSR has a wide tuning range, from 50 to 70 dB. By careful adjustment, a 60 GHz millimeter-wave signal with the OCSR at 50.72 dB and the electrical spurious suppression ratio at 36.6 dB can be achieved. Moreover, the discussions of using optimum OCSR to generate a Nyquist pulse or triangular-shaped pulse are also presented in this Letter.
060.0060 Fiber optics and optical communications 060.5625 Radio frequency photonics 320.5550 Pulses Chinese Optics Letters
2017, 15(6): 060605
Author Affiliations
Abstract
Key Lab of All Optical Network & Advanced Telecommunication Network of EMC, Beijing Jiaotong University, Beijing 100044, China
A scheme of triangular-shaped pulses with full duty cycle generation is proposed and analyzed. Benefiting from the feature of orthogonal polarization, two approximate sinusoidal signals on different polarization states can be combined without inducing coherent interference. By tuning the time mismatching between the two signals, an approximately triangular-shaped profile can be obtained in the optical intensity. It is found that the modulation index β is no longer a fixed one, but it can be aligned within a proper range of 0.92 to 1.57. To evaluate the proposal, impacts of radio frequency voltage fluctuation, bias voltage drift, and time mismatching are discussed. Within the defined fitting error (η≤3%), the tolerable range of the modulation index, time mismatching, and voltage have been found, which insures a simple operation in practice.
060.1155 All-optical networks 060.5625 Radio frequency photonics Chinese Optics Letters
2017, 15(11): 110601
郭淑军 1,2,3,4,5,*刘伟 1,2,3,4,5金媛 1,2,3,4,5王强 1,2,3,4,5[ ... ]陈小佳 1,2,3,4,5
1 暨南大学生物医药研究院, 广东 广州 510632
2 暨南大学细胞生物学系, 广东 广州 510632
3 基因工程药物国家工程研究中心, 广东 广州 510632
4 广东省生物工程药物重点实验室, 广东 广州 510632
5 广东省生物技术药物工程技术研究中心, 广东 广州 510632
目的: 以小鼠为模型, 建立一种基于流式细胞仪为检测手段的快速分离脂肪来源干细胞的方法, 解决间充质干细胞进入实际应用过程中遇到的难题。方法: 取BALB/c小鼠腹股沟内侧的皮下脂肪组织, 采用Ⅰ型胶原酶消化等系列措施, 获取脂肪干细胞(adipose-derived stem cells, ADSCs)。所得细胞分离培养4代后, 流式细胞仪分选出CD73+CD45- ADSCs后成骨诱导分化。碱性磷酸酶染色和实时荧光定量PCR检测其分化情况。结果: 刚分离培养的ADSCs细胞普遍呈圆形或椭圆形, 传至第三代的细胞, 非MSCs细胞逐渐被淘汰, 剩余的细胞形态逐渐变得一致, 细胞形态呈梭形。流式细胞仪检测发现ADSCs细胞表面抗原标记CD73+CD45- 为20.7%。所得的ADSCs成骨诱导分化后碱性磷酸酶(alkaline phosphatase, ALP)染色呈阳性, 实时荧光定量PCR检测成骨标志基因发现它们表达上调, 其中ALP的表达高达22倍。结论: 本方法可以获得纯度较高的ADSCs, 且耗时少成本低; 且提示可采用该方法来获得大量的人源ADSCs用于组织工程修复。
脂肪 间充质干细胞 分离 adipose mesenchymal stem cells isolation
Author Affiliations
Abstract
Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044, China
A quasi-optical single-sideband (quasi-OSSB) modulation approach with a tunable carrier-to-sideband ratio (CSR) is proposed and demonstrated. By simply tuning the polarizing angle, a continuously tunable CSR can be obtained. Since the upper sideband is highly suppressed during the CSR’s tuning, quasi-OSSB modulation signals with extremely small interference are generated. An experiment is undertaken for verification. It is found that the target CSR can be continuously tuned over a wide range, which can be used to improve the receiver sensitivity of the fiber links.
060.0060 Fiber optics and optical communications 060.2360 Fiber optics links and subsystems 060.5625 Radio frequency photonics Chinese Optics Letters
2015, 13(8): 080606
