PCET based copy-move forgery detection in images under geometric transforms

With the advent of the powerful editing software and sophisticated digital cameras, it is now possible to manipulate images. Copy-move is one of the most common methods for image manipulation. Several methods have been proposed to detect and locate the tampered regions, while many methods failed when the copied region undergone some geometric transformations before being pasted, because of the de-synchronization in the searching procedure. This paper presents an efficient technique for detecting the copy-move forgery under geometric transforms. Firstly, the forged image is divided into overlapping circular blocks, and Polar Complex Exponential Transform (PCET) is employed to each block to extract the invariant features, thus, the PCET kernels represent each block. Secondly, the Approximate Nearest Neighbor (ANN) Searching Problem is used for identifying the potential similar blocks by means of locality sensitive hashing (LSH). In order to make the algorithm more robust, morphological operations are applied to remove the wrong similar blocks. Experimental results show that our proposed technique is robust to geometric transformations with low computational complexity.     

Study on the security of the authentication scheme with key recycling in QKD

In quantum key distribution (QKD), the information theoretically secure authentication is necessary to guarantee the integrity and authenticity of the exchanged information over the classical channel. In order to reduce the key consumption, the authentication scheme with key recycling (KR), in which a secret but fixed hash function is used for multiple messages while each tag is encrypted with a one-time pad (OTP), is preferred in QKD. Based on the assumption that the OTP key is perfect, the security of the authentication scheme has be proved. However, the OTP key of authentication in a practical QKD system is not perfect. How the imperfect OTP affects the security of authentication scheme with KR is analyzed thoroughly in this paper. In a practical QKD, the information of the OTP key resulting from QKD is partially leaked to the adversary. Although the information leakage is usually so little to be neglected, it will lead to the increasing degraded security of the authentication scheme as the system runs continuously. Both our theoretical analysis and simulation results demonstrate that the security level of authentication scheme with KR, mainly indicated by its substitution probability, degrades exponentially in the number of rounds and gradually diminishes to zero.     

山西省近50年风速变化及突变特征分析

利用线性拟合、M-K方法对山西省22个气象观测站1960—2010年的逐日风速资料进行了倾向、突变、逐年代变化等特征分析。研究表明,近50年来山西省平均风速存在明显的下降趋势,平均风速由20世纪60年代的2.16 m/s下降到21世纪初的1.86 m/s;不同时间段呈现不同的变化特征,1979—1989年风速出现显著下降,年均递减率达到0.046 m/s,变率远超出其他时段;对近50年山西省平均风速进行M-K检验后发现,在1982年出现明显的突变点。山西省四季平均风速均呈下降趋势,四季风速下降速率最快的为春季,冬季次之,夏季风速下降速率最慢。同样,四季风速均发生突变,突变时间点分布在1980—1985年间。除8月外,山西省各个月份风速也呈下降趋势,且均出现突变现象。     

省级以下现代天气业务集约化发展研究

在梳理中国气象局现代气象业务发展,特别是现代天气业务发展思路和成效的基础上,结合公共气象服务面临的新形势和新需求,分析了省级以下现代天气业务集约化发展面临的新问题,提出了优化省市县三级的重点业务分工、改进预报预警技术和业务流程、完善相关业务标准、创新基层一体化业务服务方式、进而推进核心气象业务集约化发展的建议,包括：①实施“预报核心上移、服务重心下沉”战略,逐步建立适应气象服务体制改革要求的业务布局。强化省级大数据（基础数据、预报服务产品库和综合一体化平台等）环境部署、精准化天气预报技术路线及流程的革新、灾害性天气预警技术把关等业务核心地位,强化市级短期精细化要素预报订正和气象服务社会化的组织与协调,强化县级基层气象防灾减灾的社会化组织和协调、灾害性天气及气象灾害风险预警职能。②创新基层海量数值天气预报（NWP）产品集成应用方式,关注气象要素格点、情景预报技术发展,探索综合业务平台升级以及预报产品无缝隙、网格化、精细化制作技术。③进一步理清灾害性天气预报预警业务的上下级分工,创新管理模式,完善集约化业务平台和流程,整合专业化的信息发布平台和流程。④完善产品格式、标准和方法,推进业务质量检验评估体系建设。⑤强化多方式业务培训,提升业务科技创新能力,推进县级监测、预报和服务业务的一体化,全面提升县级精细化预报、灾害性天气及气象灾害预警服务能力。     

Recover Fault Services via Complex Service-to-Node Mappings in Wireless Sensor Networks

With the motivation of seamlessly extending wireless sensor networks to the external environment, service-oriented architecture comes up as a promising solution. However, as sensor nodes are failure prone, this consequently renders the whole wireless sensor network to seriously faulty. When a particular node is faulty, the service on it should be migrated into those substitute sensor nodes that are in a normal status. Currently, two kinds of approaches exist to identify the substitute sensor nodes: the most common approach is to prepare redundancy nodes, though the involved tasks such as maintaining redundancy nodes, i.e., relocating the new node, lead to an extra burden on the wireless sensor networks. More recently, other approaches without using redundancy nodes are emerging, and they merely select the substitute nodes in a sensor node’s perspective i.e., migrating the service of faulty node to it’s nearest sensor node, though usually neglecting the requirements of the application level. Even a few work consider the need of the application level, they perform at packets granularity and don’t fit well at service granularity. In this paper, we aim to remove these limitations in the wireless sensor network with the service-oriented architecture. Instead of deploying redundancy nodes, the proposed mechanism replaces the faulty sensor node with consideration of the similarity on the application level, as well as on the sensor level. On the application level, we apply the Bloom Filter for its high efficiency and low space costs. While on the sensor level, we design an objective solution via the coefficient of a variation as an evaluation for choosing the substitute on the sensor level.     

基于变周期技术的自适应数据采集算法

在数据采集系统中,按需采集是平衡数据数量、提高数据质量的有效手段。本文所提出的自适应数据采集算法是基于有限采样点的一元线性回归拟合,通过实时地对采集到的数据进行分析,不断修正采样周期,使得采样周期能够快速、准确地适应被测对象的动态变化。MATLAB软件仿真表明,本方法对于被测量加速变化具有较强的动态捕捉能力,能够在降低平均采样频率的前提下减小采样失真度,且与同类方法相比失真度低,稳定性高,是测控系统中实时数据采集的一种较好的代替方案。     

盖下坝水电站坝址区岩溶发育情况初步分析

盖下坝水电站工程为高山峡谷型电站,坝址区及附近岩石为碳酸盐岩,属中等坚硬易溶岩.岩溶发育是影响本工程库水外渗的重大工程地质问题之一.从施工开挖揭示的各种溶蚀现象中分析岩溶发育特征及其规律,为防渗设计提供依据.