基于光纤双锥滤波的波长可调谐掺铒光纤激光器

针对波长可调谐掺铒光纤激光器系统结构复杂的问题,本文提出并设计了一种基于光纤双锥干涉滤波结构的波长可调谐窄线宽掺铒光纤激光器,实现了激光波长灵活可调谐输出。采用单模光纤与多模光纤拉锥技术制备全光纤SMS(single-multi-single)干涉结构,并将SMS滤波器插入环形腔掺铒光纤激光器谐振腔中作为调制单元。实验中所制备的SMS滤波器干涉周期为0.67 nm,激光器工作阈值为67 mW。泵浦功率为120 mW时,通过调整激光器谐振腔内损耗,在1567.37～1574.69 nm光谱范围内实现了单波长激光可调谐输出,激光边模抑制比高于24.83 dB,3 dB线宽小于0.22 nm,最高功率差值低于2.04 dB;通过调节偏振控制器,所设计激光器能够实现双波长激光可切换输出,输出激光波长间隔小于1.32 nm, 3 dB线宽小于0.23 nm;实验中对1574.07 nm单波长激光输出稳定性进行了测试,在25 min测试时间内,没有出现模式跳变,功率漂移小于0.16 dB。结果表明所设计的光纤激光器具有较好的波长调谐能力及稳定性。     

高精度输出半导体激光器的温度控制系统设计

本文利用高信噪比的运算放大器、半导体制冷器,设计了一种激光器的温控系统,其能为半导体激光器提供高稳定度的恒温控制(ATC),从而提高了半导体激光器的使用寿命和输出波长的单一性。     

包层泵浦光纤激光器

本文在概述双包层光纤结构和包层泵浦技术的基础上,综述了近年来 连续输出高功率光纤激光器、被动调Q光纤激光器和拓宽光纤激光器波长范围技术的最新进展,并展望了包层泵浦光纤激光器的应用前景。     

基于光纤F-P腔的湿度传感器研究

在理论和实验的基础上分析了光纤F-P腔湿度传感器的湿度敏感特性,使用了低精细度的光纤F-P腔分析理论,即只考率在两个反射面上反射功率最强的一次反射光.以陶瓷插芯固定光纤端面,并在此基础上制备高反射率银膜和多孔硅膜构成F-P结构,得到了在低于85%的相对湿度环境下,每0.6nm的波长漂移对应于10%的相对湿度变化,与传统湿度计5%的测量精度相比有了很大的提高,并且实验证明其具有较好的重复性和线性度.因此认为这种结构的湿度传感器具有很好的湿度传感性能.     

光子晶体光纤中均匀Bragg光栅的特性

三角格子的PCF具有C6v对称性,其中写入的均匀光纤Bragg光栅的传输特性与PCF的结构参数关系密切。Bragg波长λB随空气孔数量增加而增大,在空气孔较多时向某个波长渐近。随着空气孔间距∧f的增大,正反向基模在光栅区域的耦合系数近似线性减小,Bragg波长λB增大。λB随空气孔相对大小f增大而减小,但是耦合系数却随f增大而增大。     

光纤激光器阵列动态特性的数值模拟分析

本文主要对光纤激光器阵列的动态特性进行了数值模拟分析.通过选取不同的耦合模式展示了输出光强与增益系数之闯的关系。为进一步讨论阵列输出相干解的稳定陆提供了理论基础。     

光栅温度传感光谱重构LabView实现

光纤光栅是近年来发展迅速的光纤无源器件之一,基于光栅波长对温度敏感特性制成的温度传感器备受关注,该类传感器研究的重点是波长的精确检测。利用虚拟仪器LabView开发平台,提取光谱信息,并对原始信号进行重构运算,进而获得精确的波长信息,反应温度情况。重点介绍了三种光谱重构的算法,高斯拟合、多项式拟合和功率加权拟合方法,并对各种方法进行了理论分析和实验研究,实验验证高斯拟合算法为最佳算法。     

基于DS18820的半导体激光温度控制系统

本文介绍一种基于DS18820的半导体激光温度控制系统,从数字温度传感器和单片机与DS18820的典型接口两个方面详细介绍了激光器温度控制电路,并阐述了整流输出电路即利用PWM技术对温度进行调节控制,使半导体激光器的温度趋于稳定.     

一种双光路输出的反射式光纤位移传感器

将探头处光纤的随机排列和对分排列相结合,设计了一种双光路输出的反射式光纤位移传感器.利用两路信号的比值,既可提高测量范围、叉可减小光源发光强度波动和被测量物表面反射率变化的影响.     

半导体激光器恒流驱动电路设计

本文设计了一种半导体激光器驱动电路,用场效应管作电流控制元件,运用负反馈原理稳定输出电流,并且对输出电流进行了稳定度分析。激光器的最大输出电流为500m A,控制电压可以直接调节激光器的输出电流。电路带有限流保护、慢启动保护,保证激光器安全稳定地工作。     

Optofluidic characterization of marine algae using a microflow cytometer

The effects of global warming, pollution in river effluents, and changing ocean currents can be studied by characterizing variations in phytoplankton populations. We demonstrate the design and fabrication of a Microflow Cytometer for characterization of phytoplankton. Guided by chevron-shaped grooves on the top and bottom of a microfluidic channel, two symmetric sheath streams wrap around a central sample stream and hydrodynamically focus it in the center of the channel. The lasers are carefully chosen to provide excitation light close to the maximum absorbance wavelengths for the intrinsic fluorophores chlorophyll and phycoerythrin, and the excitation light is coupled to the flow cytometer through the use of an optical fiber. Fluorescence and light scatter are collected using two multimode optical fibers placed at 90-degree angles with respect to the excitation fiber. Light emerging from these collection fibers is directed through optical bandpass filters into photomultiplier tubes. The cytometer measured the optical and side scatter properties of Karenia b., Synechococcus sp., Pseudo-Nitzchia, and Alexandrium. The effect of the sheath-to-sample flow-rate ratio on the light scatter and fluorescence of these marine microorganisms was investigated. Reducing the sample flow rate from 200 μL/min to 10 μL/min produced a more tightly focused sample stream and less heterogeneous signals.     

粤港澳大湾区都市农业建设分析

定量分析珠三角九市农业发展优势与劣势,其发展优势在于农业现代化水平和农业社会化服务水平相对较高,发展短板在于农业劳动生产效率偏低和财政对农业的支持保护力度不足;综合分析粤港澳三地在科技创新、装备制造、金融、会展等领域对都市农业发展的支撑条件。在此基础上,提出粤港澳大湾区都市农业发展方向为:全球农业种业创新中心、现代农业装备研发和制造中心、养生食品研发中心、国际农业交流交易中心、国家农业全面对外开放先行区和农业金融创新服务试验区;并从顶层设计、人力资本、财政投入、资源保护利用等方面提出加快粤港澳大湾区都市农业建设的措施建议。     

动态性环境中企业连锁董事与绩效关系的实证研究

基于中国的转型经济环境,从连锁董事的中观和微观两个维度出发,考察连锁董事网络位置和连锁董事在董事会中的比例与企业绩效的关系在动态环境中的表现。研究结果显示:连锁董事网络的镶嵌效应对处于连锁董事网络中不同位置企业的绩效的影响是不同的,在经济转型背景下,在高动态性的环境中,处于连锁董事网络中心位置的企业,绩效较低。     

基于夜间灯光数据的1992—2020年老挝经济社会发展时空变化

老挝是中国的重要邻国,也是“一带一路”倡议和澜沧江—湄公河合作机制的重要合作伙伴,经济基础较为薄弱,但发展势头迅猛,经济社会发展深受周边国家的影响。本文以长时间序列夜间灯光数据为主要数据源,构建了一套适用于老挝实际的DMSP和VIIRS夜间灯光数据集成方法,通过对老挝全国夜间灯光的空间分异、灯光重心的时空演变、各行政区灯光高值区变化、主要城市及边境地区的灯光时空特征分析,系统研究了1992—2020年老挝经济社会发展空间格局及变化特征。研究表明：①2020年,老挝灯光高值区面积仅占国土总面积的1.0%,各省（市）发展水平差距明显,未来发展潜力巨大;②1992—2020年,灯光重心的空间变化轨迹呈鲜明的“V”字型特征,2006年后北部地区城市发展速度相对快于南部地区;③按2020年灯光高值区面积进行评价,老挝最大的5个城市依次是万象市、沙湾拿吉市、巴色市、琅勃拉邦市和沙耶武里市;④首都万象的城市首位度虽持续下降,但仍处于绝对优势,万象灯光高值区面积占老挝全国的1/3;⑤老泰边境是老挝边境经济社会活动的主要地区,老中边境地区面积虽小,但2013年以来灯光数据提升最快。精准认知老挝经济社会发展的空间格局及其时间变化,对于开展中老合作具有现实意义。     

基于Zigbee和LabVIEW的新型城市照明监控系统

基于CC2530模块、Zigbee协议栈和LabVIEW编程设计了一种新型城市照明监控系统。该系统由自组织网络支撑,根据能量均衡的原则设计系统的基本架构;基于Zigbee协议栈进行功能定制,从而采集光照强度和链路质量强度,并为各节点设置自定义标签和睡眠周期;利用LabVIEW编程开发监控中心客户端。该系统首先由各监控节点采集信息,然后将这些信息发送给路由器或基站,最后上传给监控中心客户端,从而实现了城市照明系统精准、快速地监控与维护,此外,客户端还能在节点出现异常时报警。     

A robust unscented transformation for uncertain moments

This paper proposes a robust version of the unscented transform (UT) for one-dimensional random variables. It is assumed that the moments are not exactly known, but are known to lie in intervals. In this scenario, the moment matching equations are reformulated as a system of polynomial equations and inequalities, and it is proposed to use the Chebychev center of the solution set as a robust UT. This method yields a parametrized polynomial optimization problem, which in spite of being NP-Hard, can be relaxed by some algorithms that are proposed in this paper.     

Vibration suppression and output constraint of a variable length drilling riser system

In this paper, we mainly concentrate on the control issue of a variable length drilling riser under condition of unknown disturbances and output constraint. The studied flexible drilling riser system with variable length, variable tension, variable speed and restricted boundary output is essentially a nonlinear distributed parameter system. For achieving the vibration suppression and ensuring the boundary output within the constrained range, an appropriate control scheme with output signal barrier is put forward by integrating boundary control method, barrier Lyapunov function with finite-dimensional backstepping technique, where disturbance observer is employed for coping with the boundary disturbance. Moreover, the Lyapunov’s synthetic method is applied for the steadiness research of the studied flexible drilling riser system, and the simulations are presented to display the usefulness of proposed control scheme.     

Efficient sequential harvesting of solar light by heterogeneous hollow shells with hierarchical pores

In nature, sequential harvesting of light widely exists in the old life entity, i.e. cyanobacteria, to maximize the light absorption and enhance the photosynthesis efficiency. Inspired by nature, we propose a brand new concept of temporally-spatially sequential harvesting of light in one single particle, which has purpose-designed heterogeneous hollow multi-shelled structures (HoMSs) with porous shells composed of nanoparticle subunits. Structurally, HoMSs consist of different band-gap materials outside-in, thus realizing the efficient harvesting of light with different wavelengths. Moreover, introducing oxygen vacancies into each nanoparticle subunit can also enhance the light absorption. With the benefit of sequential harvesting of light in HoMSs, the quantum efficiency at wavelength of 400 nm is enhanced by six times compared with the corresponding nanoparticles. Impressively, using these aforementioned materials as photocatalysts, highly efficient photocatalytic water splitting is realized, which cannot be achieved by using the nanoparticle counterparts. This new concept of temporally-spatially sequential harvesting of solar light paves the way for solving the ever-growing energy demand.     

Tube-based output feedback model predictive control of polytopic uncertain system with bounded disturbances

This paper addresses the output feedback model predictive control (OFMPC) of the constrained polytopic uncertain system in the presence of bounded state and output disturbances. The controller is designed in such a way that the unmeasurable state of the real system is bounded by the tube whose center is the estimated state of the disturbance-free (reference) model. The infinite-horizon reference control sequence is parameterized as a free control move followed by an output feedback law based on the reference state observer. By applying the OFMPC approach, the reference model is asymptotically stable so that robust stability of the real disturbed system is guaranteed. A numerical example is provided to illustrate the effectiveness of the proposed technique.     

科研项目学术价值评价及影响因素研究

以科研项目的成果评价为出发点,本研究综合考虑项目产出论文的数量和质量,构造国家自然基金项目h指数,对项目的学术价值进行评价。结果显示,自然科学基金信息学部2013年实施、2016年结题的502个面上项目平均产出7篇被引次数不小于7的论文。从项目申请人特征、项目本身特征和项目申请单位特征三方面研究基金项目学术价值产出的影响因素,结果表明项目承担人的特征对基金项目科研价值产出影响十分明显,特别是项目承担人的学术研究基础对基金项目学术价值产出有明显的促进作用。不同学科的基金项目学术价值产出存在显著差异,项目承担单位的情况对项目学术价值产出影响并不显著。