IBVS based on adaptive sliding mode control for a quadrotor target tracking under perturbations

This paper presents the design of a visual control formulated on an adaptive sliding mode controller for a quadrotor executing a target tracking task subject to disturbances. An image projection of the target from a virtual camera approach, and an image-based visual servoing technique are considered to obtain a singularity-free set of image features to control the position and yaw of the rotorcraft. While, an adaptive sliding mode strategy improves the robustness against bounded external perturbations and uncertainties and provides adaptivity to the visual servoing scheme. Furthermore, an analysis based on Lyapunov theory provides sufficient conditions that guarantee the stability of the closed-loop system. A comparison of the proposed adaptive visual servoing against two recent visual servoing strategies is provided, showing superiority in simulation results. Finally, experimental tests of a Parrot AR.Drone 2.0 tracking a static and moving target further demonstrates the advantages and performance.     

Learning region sparse constraint correlation filter for tracking

Correlation filters (CF) have sparked a lot of interest in visual tracking owing to their impressive performance. Most of previous correlation filter methods learn a filter from all features of the sample region. However, some features may be distractive, like those from occlusions and deformations, leading to tracking drift in the next frame. To mitigate this problem, we propose a novel region sparse constraint correlation filter (RSCF) to adaptively ignore those distractive features. The proposed method is formulated based on the elastic net model, and a binary mask is used to directly limit the sparsity of the filter values corresponding to the target region instead of the whole sample region. Besides, a context-aware term is integrated to enhance the discriminant ability of the filter. Last, an ADMM optimization algorithm is proposed to solve the model. Qualitative evaluations have been conducted on well-known benchmark, such as OTB-2013, OTB-2015, Temple-Color 128 and VOT2016. Experiment results demonstrate that the proposed tracker performs favorably against several state-of-the-art methods.     

(t,k, n) XOR-based visual cryptography scheme with essential shadows

Visual cryptography scheme (VCS) shares a binary secret image into multiple shadows, only qualified set of shadows can reveal the secret image by stacking operation. However, VCS suffers the problems of low visual quality of the revealed image and large shadow size. A (t, k, n) XOR-based visual cryptography scheme (XVCS) shares the secret image into n shadows including t essentials and n-t non-essentials. A qualified set of shadows contains any k shadows including t essentials. The revealing process is implemented by XOR operation on the involved shadows. In this paper, we propose a construction method for (t, k, n)-XVCS with essential shadows. The secret image can be revealed perfectly, and the shadow size is small compared with VCS. Theoretical analysis and experimental results show the security and effectiveness of the proposed scheme.     

Windows XP环境下网络地址转换(NAT)的设计与实现

网络地址转换是很重要的一项安全技术.文章介绍了地址转换原理及其在网络防火墙中的应用,同时提出了在Windows XP下实现一个网络地址转换(NAT)的方法.该方法通过将装有Windows XP的PC机作为路由器,在Visual C 6.0开发环境下编程实现对流经网卡的报文,进行截取并修改然后转发到外部网络.     

Oracle存储过程应用实例

Oracle允许将PL／SQL语言编写的存储过程作为数据库对象存储在教据库中，存储过程通过语法分析，将第一次执行编译的SQL语句存储在高速缓冲存储器中．下次使用只需从高速缓冲区中调用已编译的代码，加速了SOL语句的执行。提高了应用系统性能。以某GPS车辆监拉系统为例。给出了Visual C＋＋开发平台下利用ADO链接数据库并调用数据库存储过程的具体过程。     

Bilayer representation for three dimensional visual communication

This paper proposes a bilayer representation of scene consisting of foreground and background. It uses two layers to represent foreground and background, respectively. Unlike previous layer-based approaches, both layers cover the whole region instead of interested regions. Based on the bilayer representation, bilayer stereo matching, view synthesis approach and foreground/background separation algorithm are developed for three dimensional visual communication. They all consist of two steps: recovery of disparity fields of both layers and composition of these disparity fields; synthesis of images of both layers and composition of these images; computation of two layer costs and separation of foreground and background. Experimental results demonstrate that both high quality and high efficiency are achieved by above approaches. They meet the requirements of desktop-based three dimensional visual communication.     

用Access实现仪器设备的信息管理

介绍了用Access实现仪器设备信息管理的具体方法，详细说明了宏和VBA语言的应用。     

POTDR分布式光纤传感及其在安防监测中的应用

提出了一种基于偏振光时域反射计分布式光纤传感技术的新型安防监测系统.该系统使用偏振分束器获取到具有正交偏振态的两路偏振光时域反射计信号,对比验证以确认是否出现了造成偏振态变化的扰动,提高了系统对扰动远程定位检测的准确度,大幅度减小了误判率和漏报率.同时在偏振光时域反射计系统的扰动探测中创造性的采用差值法和相对坐标相结合的方法,首次可以明显并且直观地检测和定位偏振光时域反射计系统中的扰动.最后采用Visual C++开发了一套实时的数据采集与处理软件.实验结果表明该系统具有较高的灵敏度,并在2 km和14 km处获取到具有较高信噪比的扰动信号.     

角膜手术后眼模型的构建和人工晶状体设计

根据角膜屈光手术前的角膜地形图、眼内各组分的轴向间距和波前像差,运用ZEMAX光学设计软件,构建了术前的个性化眼模型.结合角膜屈光手术后实际测量的波前像差,建立了术后个性化眼模型.运用该模型,为角膜屈光手术眼设计了双球面人工晶状体.研究表明:对于角膜屈光手术后人眼,用术后个性化眼模型计算的人工晶状体度数可靠.该模型还能够为术后眼设计矫正像散和其他高阶像差的人工晶状体,同时可以用来评估角膜手术联合白内障术后人眼的光学性能,以及手术中各类偏差对视觉质量的影响.     

Simultaneous perimeter measurement for multiple planar objects

A novel scheme to measure the true boundary perimeters of multiple planar objects is proposed. This scheme is suitable for the simultaneous and accurate measurement of multiple objects’ boundary perimeters with different shape. A geodesic active contour is applied and this scheme consists of three steps. First, the active contour converges to the object's contour edge from an initial position via the iteration of the level set functional . Second, for the convergent active contour, the sub-pixel edge detection and the centroid measurement are applied to obtain every object's edge and centroid coordinate simultaneously. Finally, a centroid-self-calibration technology is applied, which measures the pixel's size equivalence with the computed centroid and a dual-frequency laser to measure every object's true boundary perimeter. Experiments indicate that this scheme's measurement repetition error decreases to ±0.4% and that its single measurement error decreases to ±0.2%. Compared to conventional perimeter measurement schemes, this scheme is highly efficient (i.e., simultaneous measurement of multiple objects’ boundary perimeters) and highly accurate.