Recognition of dynamic patterns in DC-DC switching converters

Techniques for analyzing the dynamic patterns of power flow in high-frequency DC-DC switching power converters are developed. Emphasis is placed on exploring methods for developing reduced-order instantaneous and averaged models. of power electronic circuits for simulation, analysis, and control design. Tools from selective modal analysis are used to develop the dynamic pattern recognition algorithm that facilitates the classification of circuit modules     

一种可认证的动态秘密共享方案

该文基于椭圆曲线加密的安全性提出了一种改进的秘密共享方案。该方案可防欺骗、防参与者数据误发,参与者和管理者相互之间能相互进行身份认证,并且较好地解决了秘密共享的更新和复用问题,该方案在现在网络通信中有较高的应用价值。     

Anti-phishing technique based on dynamic image captcha using multi secret sharing scheme

With the cutting-edge improvement of web, online abuses have been increasing rapidly. Phishing is the most widely recognized abuses performed by digital crooks nowadays. It is an activity to steal private data (for example, client names, passwords and Visa data) in an electronic correspondence. It is a sort of fraud with the end goal of monetary benefit and other fake exercises. It utilizes phony websites that resemble genuine ones. Phishing messages might contain links to sites that are contaminated with malware. In this paper, “an anti-phishing approach using multi secret sharing scheme” is implemented as an answer to this problem. Here, Dynamic Image CAPTCHA based verification using multi secret sharing is performed. Image CAPTCHA is divided into two pieces called shares. Multiple secret pictures are revealed by overlapping the same set of shares at different angles. In the proposed approach, shares are of different modes i.e., user’s share is imprinted on a physical transparency while server’s share is in digital mode. By using the proposed approach, websites and end clients can cross confirm their identity.     

Quasi-linear modeling and control of DC-DC converters

A quasi-linear approach is proposed for modeling and control of DC-DC power converters. The method presented is derived by perturbing an approximate large signal equation around a varying operating point in a reduced variable space. This differs from the usual practice of applying the perturbation technique around a fixed operating condition. In the proposed algorithm, the control equation and the control parameter are constantly adjusted according to environmental changes to meet the specified dynamical requirement     

Implementation of a fuzzy controller for DC-DC converters using aninexpensive 8-b microcontroller

This paper presents an implementation of a fuzzy controller for DC-DC power converters using an inexpensive 8-bit microcontroller. An “on-chip” analog-to-digital (A/D) converter and PWM generator eliminate the external components needed to perform these functions. Implementation issues include limited on-chip program memory of 2 kB, unsigned integer arithmetic and computational delay. The duty cycle for the DC-DC power converter can only be updated every eight switching cycles because of the time required for the A/D conversion and the control calculations. However, it is demonstrated here that stable responses can be obtained for both buck and boost power converters under these conditions. Another important result is that the same microcontroller code, without any modifications, can control both power converters because their behavior can be described by the same set of linguistic rules. The contribution shows that a nonlinear controller such as fuzzy logic can be inexpensively implemented with microcontroller technology     

Numerical state-space average-value modeling of PWM DC-DC converters operating in DCM and CCM

State-space average-value modeling of pulsewidth modulation converters in continuous and discontinuous modes has received significant attention in the literature, and various models have been developed. This paper presents a new approach for generating the state-space average-value model. In the proposed methodology, the so-called duty-ratio constraint and the correction term are extracted numerically using the detailed simulation and are expressed as nonlinear functions of the duty cycle and average-value of the fast state variable. The parasitic effects of circuit elements are readily included. The resulting average-value model is compared to a hardware prototype, a detailed simulation, and several previously published models. The proposed model is shown to be very accurate in predicting the large-signal time-domain transients as well as the small-signal frequency-domain characteristics.     

Reversible data hiding scheme using reference pixel and multi-layer embedding

This paper presents a lossless data hiding scheme. The proposed scheme is based on the pixel difference histogram shifting to spare space for data hiding. Pixel differences are generated between a reference pixel and its neighbors in a pre-assigned block. After the difference histogram shifting, a large number of data can be embedded into the cover image, and multi-layer embedding is used to improve the hiding capacity. Different from previous works based on histogram shifting the proposed scheme can extract the hidden data and recover the exact original cover image with no extra information except the length of hidden data and the stego-image itself. Experimental results show that the average pure payload among eight commonly used grayscale images is up to 1.08 bits per pixel (bpp) while keeping low distortion.     

Operation and control of a dynamic voltage restorer using transformer coupled H-bridge converters

The dynamic voltage restorer (DVR) as a means of series compensation for mitigating the effect of voltage sags has become established as a preferred approach for improving power quality at sensitive load locations. Meanwhile, the cascaded multilevel type of power converter topology has also become a workhorse topology in high power applications. This paper presents the detailed design of a closed loop regulator to maintain the load voltage within acceptable levels in a DVR using transformer coupled H-bridge converters. The paper presents system operation and controller design approaches, verified using computer simulations, and a laboratory scale experimental prototype.     

Robust control of parallel DC-DC buck converters by combiningintegral-variable-structure and multiple-sliding-surface control schemes

We develop a robust controller for parallel DC-DC buck converters by combining the concepts of integral-variable-structure and multiple-sliding-surface control. The advantages of the scheme are its simplicity in design, good dynamic response, robustness, ability to nullify the bus-voltage error and the error between the load currents of the converter modules under steady-state conditions, and ability to reduce the impact of very high-frequency dynamics due to parasitics on the closed-loop system. We describe a method for determining the region of existence and stability of the sliding manifolds for such parallel converters. The results show good steady-state and dynamic responses     

Modeling of spectrum sharing using ITLinQ scheme in device-to-device networks with full-duplex relays

Telecommunication Systems - This paper considers simultaneous wireless information and power transfer enabled full-duplex multi-user multiple-input multiple-output cognitive networks. By taking...     

NEW PERTURBATION TECHNIQUE FOR TRANSIENT ANALYSIS AND ITS APPLICATIONS IN DC-DC PWM SWITCHING POWER CONVERTERS

An improved perturbation technique proposed in a recent paper (Int. J. Electronics, vol. 63, pp.403-414) has been successfully applied to steady-state analysis of PWM switching converters. This paper extends the algorithm to transient analysis of a broader class of non-linear systems. As an example, the transient response of a Boost PWM switching converter is analyzed to demonstrate its simplicity and accuracy.     

云环境下的数据多副本安全共享与关联删除方案

针对共享在公共云环境的用户数据因所有权与管理权分离而导致的用户隐私泄露问题,结合对称加密算法、属性加密算法和副本定位技术,提出一种云环境下的数据多副本安全共享与关联删除方案,对用户数据进行加密等处理封装成副本关联对象(RAO, replication associated object),随后将RAO共享到云服务商,建立副本关联模型对RAO所产生副本进行管理并实现关联删除。分析表明方案是安全与有效的,能够对用户共享的数据及其副本进行安全共享与关联删除,有效保障了数据多副本的隐私安全。     

基于拍卖理论和补偿激励的频谱共享新算法

针对认知无线电系统中主次用户频谱共享问题,提出了一种基于拍卖理论和补偿激励的频谱共享新算法,该算法基于简化的VCG(vickrey-clarke-groves)拍卖模型,引入次用户间的合作关系,并运用货币补偿激励原则,建立了相应的合作型竞争的频谱博弈模型。该博弈模型不仅具有非合作博弈模型可自动实施的决策模式特点,还兼有寡头联合模型的公平性的特点。理论分析和仿真结果证明了所提出算法的正确性和公平性。     

A distributed authentication and authorization scheme for in-network big data sharing

Big data has a strong demand for a network infrastructure with the capability to support data sharing and retrieval efficiently. Information-centric networking (ICN) is an emerging approach to satisfy this demand, where big data is cached ubiquitously in the network and retrieved using data names. However, existing authentication and authorization schemes rely mostly on centralized servers to provide certification and mediation services for data retrieval. This causes considerable traffic overhead for the secure distributed sharing of data. To solve this problem, we employ identity-based cryptography (IBC) to propose a Distributed Authentication and Authorization Scheme (DAAS), where an identity-based signature (IBS) is used to achieve distributed verifications of the identities of publishers and users. Moreover, Ciphertext-Policy Attribute-based encryption (CP-ABE) is used to enable the distributed and fine-grained authorization. DAAS consists of three phases: initialization, secure data publication, and secure data retrieval, which seamlessly integrate authentication and authorization with the interest/data communication paradigm in ICN. In particular, we propose trustworthy registration and Network Operator and Authority Manifest (NOAM) dissemination to provide initial secure registration and enable efficient authentication for global data retrieval. Meanwhile, Attribute Manifest (AM) distribution coupled with automatic attribute update is proposed to reduce the cost of attribute retrieval. We examine the performance of the proposed DAAS, which shows that it can achieve a lower bandwidth cost than existing schemes.     

Evaluation of mismatch and non‐uniform illumination losses in monolithically series‐connected GaAs photovoltaic converters

This work evaluates the influence of mismatch illumination on the performance of GaAs monolithically series‐connected photovoltaic converters under laser illumination. A theoretical model which takes into account nonuniform illumination, light spillage and mismatch losses is presented. The influence of laser spot size on the converter efficiency is also addressed. The laser spot size must be chosen in order to make a trade‐off between mismatch and nonuniform illumination losses, which predominate in a laser spot diameter smaller than the diameter of the device, and spillage losses, which predominate in a laser spot diameter larger than that of the device. For single photovoltaic converters, it is advisable to reduce the laser spot diameter to values to less than that of the converter. For multiple photovoltaic converters, especially if there is a considerable misalignment between the light source and the device, a spot diameter slightly larger than that of the device is recommended. Otherwise, mismatch losses could severely limit MPC performance. When the laser beam diameter equals the device diameter, and for a 5% misalignment, efficiencies of 55.0, 53.6 and 50.1% are envisaged, for two‐, three‐ and six‐sector multiple photovoltaic converters, respectively. Copyright © 2002 John Wiley & Sons, Ltd.     

Channel state-aware joint dynamic cell coordination scheme using adaptive modulation and variable reuse factor in OFDMA downlink

This paper proposes three different dynamic cell coordination schemes using adaptive link adaptation and variable frequency reuse for OFDMA downlink cellular networks, which are composed of greedy cell coordination for flat fading channel, dynamic maximum C/I cell coordination (DMCC), and dynamic proportional fairness cell coordination (DPFCC) for frequency selective fading channel. The performances of the proposed dynamic cell coordination schemes are compared to those with no cell coordination schemes and static reuse coordination schemes using conventional proportional fair (PF) scheduling in terms of system throughput and fairness. Simulation results demonstrate that the proposed schemes allow the radio network controller (RNC) and base stations (BSs) to apply different reuse factors on each subchannel in consideration of different interference conditions of individual users so as to increase the system throughput and guarantee QoS requirement of each user on the multicell environment, where the performance of conventional OFDMA downlinks might have become degraded due to persistent interference from other cells. In frequency flat fading, the proposed dynamic schemes achieve, on average, a 1.2 times greater system throughput than no cell coordination, a 1.4 times greater static cell coordination and a 3 times greater simplified subchannel allocation scheme (SSAS) (Kim et al. in Proceedings of IEEE VTC spring’04, vol. 3, pp. 1821–1825, 2004). In frequency selective fading, the proposed scheme, DMCC, showed a 2.6 times greater throughput than that of a single reuse factor of one for all subcarriers, and DPFCC demonstrated a single reuse factor as good as one.     

动态频谱共享研究现状及展望

动态频谱共享作为解决频谱供需矛盾的有效方式之一,在国际上受到了广泛关注.首先,对动态频谱共享的发展情况进行了概述.然后,对国际上动态频谱共享的政策制定、标准化及应用情况等进行了梳理.最后,结合无线电管理现状,分析了实施动态频谱共享在频率管理、台站管理及无线电监测等方面的影响及挑战.     

EPON动态带宽分配算法研究

文章针对EPON上行多路访问机制,提出了一种新的动态带宽分配算法:动态最大访问窗口(DMTW)算法.给出了模型和仿真结果,证明了这种算法的正确性和优势.