素域上部分bent函数的谱特征

本文在素域上讨论了部分bent函数的谱特征,得到了素域上部分bent函数的几个新的刻画,揭示了部分bent函数的平衡性、线性结构及非零谱值点之间的相互关系,并对部分bent函数的恒变线性结构进行了分类,指出了它们之间的相互关系。     

Novel pyrene-based donor–acceptor organic dyes for solar cell application

Pyrene is an alternant polycyclic aromatic hydrocarbon consisting of four fused benzene rings with a large, flat aromatic system, showing high thermal stability, extensive electron delocalization and electron accepted nature. In this work, pyrene was firstly employed as π-conjugated bridge to construct electron donor–π–electron acceptor (D–π–A) organic dyes, where diarylamine or indoline was used as donor, and cyanoacrylic acid as electron acceptor. The peryne-based dyes were employed as sensitizers in dye-sensitized solar cells, and give a short circuit photocurrent density (J_sc) of 12.1 mA/cm², an open circuit voltage (V_oc) of 0.71 V, and a fill factor (FF) of 0.71, corresponding to an overall conversion efficiency (η) of 6.1% under AM 1.5 conditions.     

一种基于Arnold置乱和DCT编码的无载体信息隐藏方法北大核心CSCD

近年来十分火热的搜索映射式无载体信息隐藏虽具有一定的鲁棒性,但其隐藏容量较低、传输负载大且算法复杂度高。针对以上问题,该文章提出一种基于Arnold置乱和离散余弦变换(discrete cosine transform,DCT)编码的无载体信息隐藏方法。该算法先对图片进行Arnold置乱,再对DCT后的低频系数进行编码,接着更换置乱参数来构建索引表。选择索引表中与秘密信息相同的编码值所对应的参数构建候选队列,最后筛选出鲁棒性强的参数作为密钥发送给接收方。实验结果表明,该方法与现有方法相比大大提高了嵌入容量,拥有更强的抗JPEG压缩性能。并且减少了传输负载,算法简捷,具有较强的应用价值。     

多路输入大功率LED智能驱动电路系统设计

采用单片机智能控制以实现由风、光、市电多路输入的大功率LED驱动电路设计。其中,风光发电互补系统实现了不同工作情况下的最大功率点跟踪控制策略,并以模拟的风光能源展示发电特性,完善了风光互补措施。蓄电池充电控制方案分段优化充电过程,以智能化操控实现能源的最大利用。从而实现了驱动电路整体最优性能的设计。     

Heterogeneous Cooperative Localization for Social Networks

Location-aware techniques has become a hot research topic with great value in commercial and military applications. Cooperative localization, which utilizes multiple sensors in portable devices to estimate locations of the mobile users in the social networks, is one of the most promising solution for the indoor geo-location. Traditional cooperative localization methods are based on ranging techniques, they are highly dependent on the distance interpreted from the received signal strength (RSS) or time of arrival from anchors. However, a precise ranging procedure demands high performance hardware which would increase the cost to the current mobile platform. In this paper, we describes four ranging-free probabilistic cooperative localization algorithms: centroid scheme, nearest neighbor scheme, kernel scheme and AP density scheme to improve the accuracy for the indoor geo-location using current mobile devices. Since the GPS sensor embedded in the smart phone is able to provide accurate location information in the outdoor area, those mobile nodes can be used as calibrated anchors. The position of the indoor mobile node can be estimated by exchanging locations and RSSs from shared wireless access points information between the target node and anchor nodes. An empirical evaluation of the system is given to demonstrate the feasibility of these cooperative localization algorithms by reporting the results in a real-world environments, e.g. suburban area and city downtown. Moreover, we compared our results with the WiFi positioning system made by Skyhook Wireless to validate the accuracy of the proposed algorithms. Meanwhile, a Monte Carlo simulation is carried out to evaluate the performance of the cooperative algorithms under different scenarios. Results show that given the same scenario setting, the AP density scheme and kernel scheme outperform than other schemes.     

A novel biometrics method to secure wireless body area sensor networks for telemedicine and m-health

The development of the wireless body area sensor network (BASN) is imperative for modern telemedicine and m-health, but security remains a formidable challenge yet to be resolved. As nodes of BASN are expected to be interconnected on or in the human body, the body itself can form an inherently secure communication pathway that is unavailable to all other kinds of wireless networks. This article explores the use of this conduit in the security mechanism of BASN; that is, by a biometrics approach that uses an intrinsic characteristic of the human body as the authentication identity or the means of securing the distribution of a cipher key to secure inter-BASN communications. The method was tested on 99 subjects with 838 segments of simultaneous recordings of electrocardiogram and photoplethysmogram. By using the interpulse interval (IPI) as the biometric trait, the system achieved a minimum half total error rate of 2.58 percent when the IPIs measured from signals, which were sampled at 1000 Hz, were coded into 128-bit binary sequences. The study opens up a few key issues for future investigation, including compensation schemes for the asynchrony of different channels, coding schemes, and other suitable biometric traits.     

血管数字减影图象中的结构特征提取

基于Ｘ线数字减影图象的三维血管结构重建很大程度上依赖于图象中血管的有效检测和结构关系描述。本文给出一个在局部特征检测基础上的结构特征提取和组织方法，涉及结构分析之前的中间视觉处理层次，即将图象中主要结构分离出来供结构分析之用。首先用一个突出结构检测算法独立地组织和选择中轴曲线片断和边缘曲线片断，然后将两者信号相结合以验证突出结构算法获得的结果并滤除噪声结构。     

一种获取摄像机安装高度及倾角的简易标定方法

提出了一种在摄像机内参数已知的情况下,通过地面上已知的4个及以上共面点求解出摄像机安装高度和安装倾角的标定方法.选定地面为X-O-Y面,则Z轴方向的平移因子即为摄像机的安装高度.方法借鉴了利用共面点进行标定的方法,在计算过程中利用投影矩阵元素间的比值关系,巧妙地消除了深度因子的影响,求解出了旋转角度和摄像机的安装高度,进而得到了摄像机的外参数矩阵.将多组实验计算出的安装高度结果和实际测量值相对比,得到的误差非常小,证明了该算法计算简便且具有较高的准确性.     

格的归约理论和它在密码学中的应用

介绍和讨论了格理论在公钥密码体制中的应用.利用格的归约技术可以分析研究计算部分密钥位与整个密钥位的计算复杂性.在均匀模式下,计算基于公钥系统的Okamoto协议的2loglogp密钥位与计算整个密钥的难度是相同的.用格的理论建立了一个公钥密码系统,且该系统是安全的,除非能够在多项式时间内从n维格L中找到最短的非零向量.