A wireless powered small volume light source composed of light emitting diode (LED) array is developed for implantation. According to the volt-ampere characteristics of LED and the load characteristics of coil coupling power supply, the light power and work distance of implant LED-array are optimized by changing the number and series-parallel connection mode of LEDs in receiver. The wireless powered implant can provide 5.4 mW light. The entire implant is seamlessly packaged within parylene, a biocompatible material, coating by chemical vapor depositing. The volume of the implant is 9 mm×4 mm×3 mm, the weight of which is only 0.25 g. The device can work continuously for more than three weeks in 0.9% saline and the prime prototype of the device has been validated by animal implantation.

高光谱图像分类是利用高光谱数据图谱合一且光谱信息丰富的特点, 对图像中的每个像素进行分门别类, 以达到对地物目标进行高精度分类和自动化识别的目的, 是对地观测的重要组成部分。在分析高光谱图像特点的基础上, 本文从普通机器学习和深度学习这两方面对高光谱图像像素级分类的研究进展及效果进行总结、评述和比较, 通过具体实验的结果对比, 直观地展现各种算法的优劣。针对高光谱分类问题, 本文从两个方面对今后的研究方向及发展前景进行了分析和展望。一方面, 在算法研究上, 高光谱图像分类算法可在保证分类精度的前提下降低算法的复杂度, 利用多源遥感数据、多特征综合、多尺度复合, 提升小样本、少参数分类模型的分类精度, 适应智能化、快速化高光谱遥感对地观测的发展要求; 另一方面要紧密结合市场应用需求, 重视高光谱图像在实际中的应用, 研究具有市场竞争力的高效分类算法, 提升高光谱图像分类在遥感技术应用领域的竞争力。

An implantable optrode composed of fiber and multi-channel flexible thin-film electrode is developed. The flexible recording electrode is made from polyimide and is wrapped around the optical fiber. The front end of the fiber is ta-pered by wet etching. With the tapered shape, the light can leak from the sidewall of the fiber, and the tapered tip makes it easy to be implanted. The flexible electrode is attached with its recording sites aligning to the tapered part on the fiber. With this method, the fiber acts as an optical waveguide, as well as a support probe for flexible thin-film electrode. This novel device simplifies the fabrication process and decreases the size of the optrode. The device works well in vivo and the optical caused spike can be recorded with signal-to-noise ratio of 6:1.

In order to ensure stable, correct and real-time high-speed transmission of indoor visible light communication (VLC), the key modulation and demodulation technologies of orthogonal frequency division multiplexing (OFDM) are studied in this paper. The time-domain synchronization, frequency synchronization and channel equalization of receiver are analyzed and optimized by utilizing short and long training preamble. Moreover, field programmable gate array (FPGA) development board (Xilinx Kintex-7) and Verilog hardware description language are used to realize the design of proposed OFDM-VLC system. Simulation and experiment both verify the feasibility of the hardware designs of this system. The proposed OFDM-based VLC system can process signal in real-time, which can be used in actual VLC application systems.

分别在直流偏置和交流偏置下, 对大功率GaN基LED的电学和光学特性进行了研究。结果显示, 通过改变靠近p型层的量子垒(也就是最后一个量子垒)中的In组分可以调控有源区中的载流子分布。有源区内积累的电子会引起负电容效应。而通过降低有源区量子垒的势垒高度, 可以改善LED中载流子传输特性, 并实现载流子复合速率及通信调制带宽20%的提高。这个工作将有助于理解GaN基LED中载流子分布对频率特性的影响, 并为设计适用于可见光通信的大功率高速LED奠定基础。

In this paper, we present the design, simulation, fabrication and characterization of a terahertz (THz) filter based on metamaterial consisting of the periodical double symmetric splits ring resonator (DS-SRR) array. We can observe that the metamaterial-based filter possesses a band-pass transmission when the electrical field is along y direction, and it possesses a low-pass transmission when the electrical field is along x direction. Our results demonstrate that the proposed filter can realize the switching between band-pass effect and low-pass effect by only changing the polarization direction of the incident electromagnetic wave. Moreover, the calculated surface current distributions are also used to analyze the switchable mechanism of the THz metamatrial filter. Therefore, the proposed THz wave filter has a potential application in THz wave communication systems.

基于交叉簧片柔性铰链(简称‘交叉铰链’) 设计了一种用于光束跟踪、精密指向和瞄准的同轴八铰微位移放大机构。该机构使用菱形构型, 用交叉铰链作集中柔性元件, 节点处交叉铰链两两同轴配合使用, 以便保证运动的平稳输出。研究了机构的运动学以及力学性能, 计算了微位移机构的行程放大比和灵敏度; 根据交叉铰链的刚度模型, 推导出微位移机构的理论刚度; 最后, 应用有限元软件对机构进行建模并对运动学、静力学以及动力学性能进行仿真。完成了样机的加工和测试, 测试结果显示, 机构放大比为1.905, 理论与测试误差低于2.2%, 结构刚度为18.21 N/mm, 误差低于0.32%, 一阶频率为8.8 Hz, 误差低于5%。分析结果验证了本设计的可行性和有效性。该机构适用于空间高精度微位移领域。

提出两种基于图像欧氏距离的非线性降维方法.该方法利用高光谱图像物理特性, 将图像欧氏距离引入到传统的流形降维算法中.与其它应用于高光谱图像的降维算法相比, 该算法具有诸多优点.图像欧氏距离的引入, 在考虑高光谱图像本身的空间关系的同时, 很好地保持了数据点之间的局部特性, 可以实现有效地去除原始数据集光谱维和空间维的冗余信息.实际高光谱数据的实验结果表明, 该算法应用于高光谱图像分类时, 与其它常见的方法相比具有更高的分类精度.

空间高分辨率遥感仪器的发射过程和在轨复杂的温度环境条件会使其光学焦平面发生偏离, 从而影响相机的成像质量。为补偿相机焦平面位置的变化, 本文根据高分辨红外相机的在轨应用环境以及光学设计要求, 对相机的调焦机构进行了方案设计和误差分析。计算了结构误差对系统精度的影响, 对不同类型结构的精度进行了归类, 并利用齐次坐标变换矩阵建立了误差分析模型。同时, 详细分析了误差源的特性、概率分布和变换矩阵参量间的关系。利用Monte Carlo法进行了仿真, 结果表明该机构设计合理, 满足仪器的使用要求。样机测试表明, 该机构行程内轴向位置误差为(-0.01±0.003 6) mm, 透镜最大倾斜角为25″, 最大离轴量为0.005 mm。目前, 该机构已成功在轨使用。

片上集成光源是未来光电子系统中光源发展的主要趋势, LED光源作为片上集成光源的主要缺点是其出光效率低, 二维光子晶体是提高LED出光效率的有效手段。 本工作设计了C波段LED的基本结构及参数, 并采用时域有限差分法计算了不同阵列不同占空比的二维光子晶体能带结构, 利用禁带理论选取提高C波段LED出光效率的最优二维光子晶体结构参数, 结果表明三角排列空气孔二维光子晶体晶格常数a=500 nm且占空比Rp=0.44的光子晶体结构最优。