混合柱形二维光子晶体禁带特性研究

研究了正方形和圆形介质柱混合排列的二维光子晶体的能带特性.运用平面波展开法在正方形和正三角形晶格下将混合柱形与统一柱形光子晶体的禁带特性进行计算比较.仿真结果表明:对于正方形晶格,混合柱形使光子晶体的TM模高阶能带向低频方向移动,禁带的宽度和位置介于正方形柱体和圆形柱体之间.在正三角形晶格中,混合柱形光子晶体出现了明显...     

Frame distortion estimation for unequal error protection methods in scalable video coding (SVC)

In many multimedia applications, coded video is transmitted over error prone heterogeneous networks. Because of the predictive mechanism used in video coding, transmission error would propagate temporally and spatially and would result in significant quality losses. In order to address this problem, different error resilience methods have been proposed. One of the techniques, which is commonly used in video streaming, is unequal error protection (UEP) of scalable video coding (SVC). In this technique, different independent layers of an SVC stream are protected differently and based on their importance by using forward error correction (FEC) codes. Accurately analyzing the importance or utility of each video part is a critical component and would lead to a better protection and higher quality of the received video. Calculation of the utility is usually based on multiple decoding of sub-bitstreams and is highly computationally complex. In this work, we propose an accurate low complexity utility estimation technique that can be used in different applications. This technique estimates the utility of each network abstraction layer (NAL) by considering the error propagation to future frames. We utilize this method in an UEP framework with the scalable extension of H.264/AVC codec and it achieves almost the same performance as highly complex estimation techniques (an average loss of 0.05 dB). Furthermore, we propose a low delay version of this technique that can be used in delay constrained application. The estimation accuracy and performance of our proposed technique are studied extensively.     

Texture aided depth frame interpolation

Recent development of depth acquiring technique has accelerated the progress of 3D video in the market. Utilizing the acquired depth, arbitrary view frames can be generated based on depth image based rendering (DIBR) technique in free viewpoint video system. Different from texture video, depth sequence is mainly utilized for virtual view generation rather than viewing. Inspired by this, a depth frame interpolation scheme using texture information is proposed in this paper. The proposed scheme consists of a texture aided motion estimation (TAME) and texture aided motion compensation (TAMC) to fully explore the correlation between depth and the accompanying textures. The optimal motion vectors in TAME and the best interpolation weights in TAMC are respectively selected taking the geometric mapping relationship between depth and the accompanying texture frames into consideration. The proposed scheme is able to not only maintain the temporal consistency among interpolated depth sequence but also improve the quality of virtual frames generated by interpolated depth. Besides, it can be easily applied to arbitrary motion compensation based frame interpolation scheme. Experimental results demonstrate that the proposed depth frame interpolation scheme is able to improve the quality of virtual view texture frames in both subjective and objective criterions compared with existing schemes.     

Towards Fault-Tolerant Fine-Grained Data Access Control for Smart Grid

Data access control within smart grids is a challenging issue because of the environmental noise and interferences. On one hand side, fine-grained data access control is essential because illegal access to the sensitive data may cause disastrous implications and/or be prohibited by the law. On the other hand, fault tolerance of the access control is very important, because of the potential impacts (implied by the errors) which could be significantly more serious than the ones regarding general data. In particular, control bits corruption could invalidate the security operation. To address the above challenges, this paper proposes a dedicated data access control scheme that is able to enforce fine-grained access control and resist against the corruptions implied by the noisy channels and the environmental interferences. The proposed scheme exploits a state-of-the-art cryptographic primitive called Fuzzy identity-based encryption with the lattice based access control and dedicated error-correction coding. We evaluate our proposed scheme by extensive simulations in terms of error correcting capability and energy consumption and results show the efficiency and feasibility of the proposed scheme. To our best knowledge, this paper is the first which addresses fault tolerant fine-grained data access control for smart grid.     

快速解密的自适应安全KP-ABE方案

已有的自适应安全ABE(attribute-based encryption)方案的解密开销随着解密时用到的属性数量呈线性增长。针对该问题,提出了一种快速解密的自适应安全key-policy ABE(FKP-ABE)方案,在合数阶群上构造,支持任意可以表达为线性秘密分享体制(LSSS, linear secret sharing schemes)的单调访问策略,将解密开销降为常数级,并在标准模型下证明该方案是自适应安全的。     

Content based image indexing and retrieval using directional local extrema and magnitude patterns

In this paper, we integrate the concept of directional local extremas and their magnitude based patterns for content based image indexing and retrieval. The standard ditectional local extrama pattern (DLEP) extracts the directional edge information based on local extrema in 0°, 45°, 90°, and 135° directions in an image. However, they are not considering the magnitudes of local extremas. The proposed method integrates these two concepts for better retrieval performance. The sign DLEP (SDLEP) operator is a generalized DLEP operator and magnitude DLEP (MDLEP) operator is calculated using magnitudes of local extremas. The performance of the proposed method is compared with DLEP, local binary patterns (LBPs), block-based LBP (BLK_LBP), center-symmetric local binary pattern (CS-LBP), local edge patterns for segmentation (LEPSEG) and local edge patterns for image retrieval (LEPINV) methods by conducting two experiments on benchmark databases, viz. Corel-5K and Corel-10K databases. The results after being investigated show a significant improvement in terms of their evaluation measures as compared to other existing methods on respective databases.     

Intra-layer network coding for lossy communication of progressive codes

In this paper we discuss layered multicast (LM) of progressive source codes using network coding. LM is absolutely optimal if different sinks in the network are satisfied up to their max-flow. Since absolutely optimal intra-layer network strategies might not exist for general networks, we present conditions under which an absolutely optimal, intra-layer multicast strategy exists for a given network and how that strategy may be efficiently constructed. We also discuss the problem of designing optimal intra-layer multicast strategies for general directed networks.     

电力物联网可信树形批量认证机制

电力物联网设备需要进行可信度量,然而现有数据处理架构存在云端压力过大的问题,现有可信度量架构也存在效率低下、消耗过大等问题.提出一种适用于云边协同电力物联网环境的基于树形结构的可信批量认证机制.该机制采用云边端协同的边缘计算架构缓解云平台压力,设备采用一种轻量级可信架构进行可信度量,获取度量信息;非平衡哈希树存储结构在...