Friendly progressive random-grid-based visual secret sharing with adaptive contrast

Visual secret sharing (VSS) schemes providing secret communication services are classified into two categories depending on the method of encoding the secret: visual cryptography (VC)-based and random grid (RG)-based schemes. A friendly progressive version of the VC-based VSS scheme was presented in 2008; however, it is marred by pixel expansion, which is the innate deficiency of conventional VC-based VSS schemes. This paper proposes a suitable user-friendly RG-based VSS scheme with progressive secret reconstruction and without pixel expansion. The experimental results of the developed scheme validated its feasibility, and a theoretical analysis demonstrated its visual quality and security.     

From local to global analysis of defect detectability in infrared non-destructive testing

Several image processing techniques are employed in Infrared Non-Destructive Testing (IRNDT) to enhance defect detectability. To date, there is no adequate global measurement that objectively assesses defect visibility in processed frames. In this work, a Global Signal to Noise Ratio (GSNR) that comprehensively evaluates defect detectability in processed infrared (IR) images is proposed, as well as a defect visibility measure named Infrared Image Quality Index (IRIQI) that compares the structural information of defective and sound areas. In addition, GSNR and IRIQI are validated by using the area under ROC curve (AUC). AUC quantitatively assesses defect visibility by comparing the outcomes of processing techniques to human judgements. The remarkable benefit of this global approach is that it allows one to determine the frame at which processing techniques reveals the majority of the defects by evaluating the times at which AUC curves reach their maxima. The test pieces were a Carbon-Fiber Reinforced Plastic (CFRP) sample containing delaminations and a honeycomb specimen with delaminations, skin unbonds, excessive adhesive, and crushed core.     

Cloud Computing in Mobile Communication Networks

Cloud computing makes computing power universally available and provides flexibility in resource acquisition.It allows for scalable provision of services and more reasonable use of resources.This article considers cloud service deployment and virtualization from the perspective of mobile operators.A solution is proposed that allows mobile operators to maximize profits with minimal investment.     

Information hiding in the sharing domain

Secret image sharing (SIS) can divide a secret image into several shadow images for protection. Information hiding in the sharing domain (IHSD) fuses SIS and information hiding (IH) to simultaneously share any secret image and hide any information, and this technique can be applied in cloud computing, law enforcement and medical diagnoses. IHSD not only marks shadow images with information to prevent malicious tampering and for convenient management, search and identification but also enhances the robustness of IH. In this paper, we first introduce a formal definition of IHSD. Then, we describe a general IHSD model and algorithms with a concrete example in detail. In IHSD, we design the random element utilization model to control the random pixels generated from SIS. Then, we obtain shadow images with hidden information to realize SIS and IH simultaneously. The inputs of SIS with secret images, steganography and extra information in algorithms are without any limitations. Theoretical analyses, experiments and comparisons are presented to prove the effectiveness and feasibility of IHSD.     

频率分辨率概念的教学探讨

频率分辨率是“数字信号处理”课程中的一个重要知识点,该概念紧贴雷达探测等领域的工程应用。但是在传统教学中,往往直接给出频率分辨率的定义和公式,缺乏对概念背后物理意义和工程应用的理解。本文从区分两个单频信号的实际需求出发,给出频率分辨率概念的起因和定义,并且从工程应用的角度对频率分辨率的概念进行了再认识。     

Adaptive Free-Knot Splines

This article proposes a function estimation procedure using free-knot splines as well as an associated algorithm for implementation in nonparametric regression. In contrast to conventional splines with knots confined to distinct design points, the splines allow selection of knot numbers and replacement of knots at any location and repeated knots at the same location. This exibility leads to an adaptive spline estimator that adapts any function with inhomogeneous smoothness, including discontinuity, which substantially improves the representation power of splines. Due to uses of a large class of spline functions, knot selection becomes extremely important. The existing knot selection schemes—such as stepwise selection—suffer the difficulty of knot confounding and are unsuitable for our purpose. A new knot selection scheme is proposed using an evolutionary Monte Carlo algorithm and an adaptive model selection criterion. The evolutionary algorithm locates the optimal knots accurately, whereas the adaptive model selection strategy guards against the selection error in searching through a large candidate knot space. The performance of the procedure is examined and illustrated via simulations. The procedure provides a significant improvement in performance over the other competing adaptive methods proposed in the literature. Finally, usefulness of the procedure is illustrated by an application to actual dataset.     

Multi‐criteria Evaluation of Mobile Network Sharing Policies in Korea

Mobile operators in saturated markets increasingly favor mobile network sharing (MNS) over facility‐based competition. Previous research examining MNS primarily focused on its positive effects, while the negative effects were largely overlooked. This study proposes a decision‐making model using an analytic hierarchy process technique to evaluate decision‐making criteria among various types of MNS policies. The decision‐making model was applied to Wireless Broadband services in Korea to determine the relative importance of both positive and negative evaluation criteria and preference among multiple types of MNS policies. Positive evaluation criteria (that is, efficiency) were far greater in importance than negative evaluation criteria (that is, competition harm). The preference for adopting MNS among five alternative approaches was also revealed. The study findings offer immediate policy insights in Korea and provide a decision‐making framework for policy makers in other countries to utilize.     

The influence of a weak signal seed-wave on picosecond supercontinuum generation in photonic crystal fiber

We present a numerical study of the properties of picosecond supercontinuum (SC) generation when pumping in the normal dispersion region of photonic crystal fibers. Simulation results demonstrate that rogue wave generation can be reduced by adding a weak signal continuous-wave (CW) seed on the main pump pulse. Besides, the red-shifted part of SC exhibits higher degree of coherence and pulse-to-pulse intensity stability.     

Power control based on the Stackelberg game in two-tier femtocell networks

In this paper, the resource allocation strategy is investigated for a spectrum sharing two-tier femtocell networks, in which a central macrocell is underlaid with distributed femtocells. The spectral radius is introduced to address the conditions that any feasible set of users’ signal-to-interference-plus-noise ratio requirements should satisfy in femtocell networks. To develop power allocation scheme with the derived conditions, a Stackelberg game is formulated, which aims at the utility maximization both of the macrocell user and femtocell users. The distributed power control algorithm is given to reduce the cross-tier interference between the macrocell and femtocell with same channel. At last, admission control algorithm is proposed, aiming to exploit the network resource effectively. Numerical results show that the proposed resource allocation schemes are effective in reducing power consumption and more suitable in the densely deployed scenario of the femtocell networks. Meanwhile, it also presents that the distributed power allocation scheme combined with admission control can protect the performance of all active femtocell users in a robust manner.     

基站共建共享的技术要求及解决方案

随着国内移动通信业的迅速发展,不同运营商的网络重复建设造成社会资源严重浪费的现象日益严峻.有效地实现电信基础设施的共建共享,建设资源节约型社会成为当前的一项重要任务.文章针对基站在共建共享中存在的问题和要求进行了讨论和分析,并给出了相应的解决方案和建议,以求能对后续共建共享工作起到一定的帮助和参考作用.