梯度轴棱锥产生周期性局域空心光束的几何光学分析

利用几何光学的光学追迹法,对梯度轴棱锥系统产生周期性局域空心光束（bottle beam）的演变过程进行描述。利用光学仿真软件的光照度分析功能,对光束传播中不同传播距离的截面光强分布进行了模拟。结果表明,通过改变两个轴棱锥底角大小,可以对周期性局域空心区域的长度进行控制。这种梯度轴棱锥系统可以很容易地产生尺寸非常小的周...     

轴棱锥透镜系统产生局域空心光束的几何光学解释

利用几何光学的光线追迹法形象地描述了轴棱锥透镜系统产生局域空心光束过程.分析了局域空心光束传输过程中的光强分布;同时利用光线追迹法分析了透镜焦距对局域空心光束尺寸大小的影响.结果表明,局域空心光束的尺寸随着透镜焦距的增大而增大.实验中利用轴棱锥透镜系统产生局域空心光束,并对不同位置的光斑进行了拍摄,分析了局域空心光束的演变过程及其横向光强分布.实验与理论模拟的结果相吻合.因而容易选择不同尺寸的局域空心光束对不同微粒进行囚禁.     

Propagation of hermite-cosh-gaussian beams passing through ABCD optical system with an annular aperture

By using the expansion of the aperture function into a finte sum of complex Gaussian functions, the corresponding analytical expressions of Hermite-cosh-Gaussian beams passing through annular apertured paraxially and symmetrically optical systems written in terms of ABCD matrix were derived, and they could reduce to the cases with squared aperture. In a similar way, the corresponding analytical expressions of cosh-Gaussian beams through annular apertured ABCD matrix were also given. The method could save more calculation time than that by using the diffraction integral formula directly.     

空心高斯光束通过光阑透镜系统的传输特性

为了研究空心光束通过硬边光阑透镜傍轴ABCD光学系统后的传输特性,利用柯林斯衍射积分公式,推导出了空心高斯光束通过受圆孔硬边光阑限制的傍轴ABCD光学系统的传输公式,所得公式可用来描述空心高斯光束通过任意傍轴ABCD光学系统的传输.研究了光阑、透镜以及光阑透镜系统对空心高斯光束传输特性的影响,并用数值例做了详细说明.结果表明,光阑和透镜均会使光束的光场分布向源平面前移,光阑会破坏空心高斯光束的空心性,而单纯的透镜只改变光场分布,不会破坏光束的空心性.这一结果对于空心光束的产生和应用有理论指导意义.     

Effects of Sb,Zn doping on structural,electrical and optical properties of SnO2 thin films

Highly transparent, low resistive pure and Sb, Zn doped nanostructured SnO₂ thin films have been successfully prepared on glass substrates at 400° C by spray pyrolysis method. Structural, electrical and optical properties of pure and Sb, Zn doped SnO₂ thin films are studied in detail. Powder X-ray diffraction confirms the phase purity, increase in crystallinity, size of the grains (90–45 nm), polycrystalline nature and tetragonal rutile structure of thin films. The scanning electron microscopy reveals the continuous change in surface morphology of thin films and size of the grains decrease due to Sb, Zn doping in to SnO₂. The optical transmission spectra of SnO₂ films as a function of wavelength confirm that the optical transmission increases with Sb, Zn doping remarkably. The optical band gap of undoped film is found to be 4.27 eV and decreases with Sb, Zn doping to 4.19 eV, 4.07 eV respectively. The results of electrical measurements indicate that the sheet resistance of the deposited films improves with Sb, Zn doping. The Hall measurements confirm that the films are degenerate n-type semiconductors.     

光正交频分复用通信的原理、关键技术及其应用

光正交频分复用技术是一种将电域正交频分复用与光纤通信技术相结合的新型光通信技术,具有高频谱利用率、有效抵抗光纤链路中的色度色散、偏振模色散和非线性效应等优点,在大容量、长距离光纤通信系统和光接入网中有着广阔的应用前景。介绍了光正交频分复用(O-OFDM)系统的工作原理、结构及其关键技术的国内外研究现状,讨论了O-OFDM应用有待深入研究的技术和问题,展望了O-OFDM技术的发展趋势和应用前景。     

非线性衍射像件输入输出系统

分析了体积光栅成像关系后，推导了物像关系计算公式，采用此公式具有较高的精确计算值。在此基础上得出体积光栅与体积全息的横向放大率、轴向放大率及角伸缩放大率公式，证明了成像伸缩特性与物像坐标值、波长比例系数μ之间的关系。     

光孤子通信原理与进展

当光纤中的色散与非线性效应平衡相消时,其中传输的光脉冲便可形成光孤子。利用光孤子传输长久不变形的原理,构成一种超高速、超长距离的光纤通信系统——光孤子通信系统。本文较为详细地阐明了这种新颖通信模式的基本原理与组成,以及有关设计上的一些考虑。在叙述中还对光孤子通信的近期发展情况作了若干评述。     

RS232型多串行通道单纤光端机的设计与实现

为有效延长数据的传输距离,解决电缆传输数据时电磁辐射、防电磁干扰、点对点设备间不共地、抗雷击以及信道资源共享等难题,采用多协议串行通信控制器Intel 82530和单纤双向TTL光收发一体模块设计了多串行通道单纤光端机。设计中,谋求了硬、软件规模最佳平衡点。对产生通信误差的原因进行分析,通过计算,选取合适的晶体振荡器,控制了多串行通道单纤光端机的通信误差,对常用的通信速率可获得准确的波特率。多串行通道单纤光端机可广泛应用于将串行数据远传至异地的单芯光纤的点到点连接,它克服了电缆传输数据的弊端,提高了数据的可靠性,同时也减少了有色金属和信道资源的消耗。     

Preparation and degradation of the optical properties of nano-, meso-, and macroporous silicon

In the work some peculiarities in formation of the porous silicon, its morphology and composition were investigated, as well as some optical properties of this material. Porous silicon was obtained on the substrates of single-crystalline Si as well as on the silicon structures with p–n junctions. In order to obtain nano-, meso- and macroporous silicon as well as multi-layered porous structures several technological parameters (were controlled) varied—orientation of the substrates, conductivity type and composition of the etchant. Correlation between photoluminescence intensity of the obtained samples and intensity of the absorption band in their IR spectra (the band at 616 cm⁻¹) that is due to the presence of Si–Si bonds in porous layer was observed. The influence of the porous silicon storage in the air on the degradation of its photoluminescence parameters was also estimated.     

A review on evolving domains of Internet of Things: Architecture,applications, and technical challenges

The Internet of Things (IoT) is a system that includes smart items with different sensors, advanced technologies, analytics, cloud servers, and other wireless devices that integrate and work together to create an intelligent environment that benefits end users. With its wide spectrum of applications, IoT is revolutionizing both the current and future generations of the Internet. IoT systems can be employed for broad-ranging real applications, such as agriculture, the environment, cities, healthcare, and the industrial sector. In this paper, we briefly discuss the three-tier architectural view of IoT, its different communication technologies, and the smart sensors. Moreover, we study various application areas of IoT such as the environmental domain, healthcare, agriculture, smart cities, and industrial, commercial, and general aspects. A critical analysis is shown for the existing schemes and techniques related to this work. Further, this paper addresses the basic context, tools and evaluation approaches, future scope, and the advantages and disadvantages of the aforestated IoT applications. A comprehensive analysis is provided for each domain along with its fundamental parameters like the quality of service (QoS), network longevity, scalability, energy efficiency, accuracy, and cost. Finally, this study highlights the technical challenges and open research problems existing in different IoT applications.     

产学研结合教育的理论问题及其在生物医学工程高等教育的实践

从产学研结合教育的基本原则、实施途径、教学形式、目标任务等方面对生物医学工程高等教育产学研结合人才培养模式进行探讨,阐述了我国生物医学工程高等教育产学研结合教育的基本内涵。实施缘由、适应范围、与常规教育模式的差异、基本状况,以及取得的教育教学效果和社会效果。