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A new method of calculating the orbital angular momentum spectra of Laguerre-Gaussian beams in channels with atmospheric turbulence

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Chinese Physics B 2017年第11期26卷 232-238页

作者：崔小舟尹霄丽常欢张志超王拥军吴国华 School of Electronic Engineering Beijing University of Posts and Telecommunications beijing Key Laboratory of Space-Ground Interconnection and Convergence Beijing University of Posts and Telecommunications State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications

Studying orbital angular momentum（OAM） spectra is important for analyzing crosstalk in free-space optical（FSO）communication systems. This work offers a new method of simplifying the expressions for the OAM spectra of Laguerre-Gaussian（LG） beams under both weak/medium and strong atmospheric turbulences. We propose fixing the radius to the extreme point of the intensity distribution, review the expression for the OAM spectrum under weak/medium turbulence,derive the OAM spectrum expression for an LG beam under strong turbulence, and simplify both of them to concise ***, we investigate the accuracy of the simplified expressions through simulations. We find that the simplified expressions permit accurate calculation of the OAM spectrum for large transmitted OAM numbers under any type of turbulence. Finally,we use the simplified expressions to analytically address the broadening of the OAM spectrum caused by atmospheric turbulence. This work should contribute to the concise theoretical derivation of analytical expressions for OAM channel matrices for FSO-OAM communications and the analytical study of the laws governing OAM spectra.

关键词： orbital angular momentum(OAM) spectrum atmospheric turbulence free-space optical(FSO) communications

Efficient nonlocal two-step entanglement concentration protocol for three-level atoms in an arbitrary less-entangled W state using cavity input-output process

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Science China(Physics,Mechanics & Astronomy) 2014年第8期57卷 1511-1518页

作者： ZHANG Ru ZHOU SuHua CAO Cong department of Communications & Information Engineering Century College Beijing University of Posts and Telecommunications School of Science Beijing University of Posts and Telecommunications State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications

We present an efficient two-step entanglement concentration protocol(ECP)for three-level atoms trapped in one-sided optical micro-cavities in an arbitrary three-particle less-entangled W state,using the coherent state input-output process in low-Q cavity quantum electrodynamics *** each step of the new proposed protocol,one of the three remote users prepares the auxiliary coherent optical pulses to perform cavity input-output process and then utilizes the standard homodyne measurement to discriminate the final outgoing coherent *** both of the two steps are successful,remote parties can deterministically concentrate the less-entangled W state atoms to a standard maximally entangled W *** with previous ECPs for W state,this protocol has some advantages and can be widely used in current quantum repeater and some quantum information processing tasks.

关键词： entanglement concentration protocol W state cavity input-output process

A Cluster-Based Opportunistic Multicast in Multi-hop Wireless Networks

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Chinese Journal of Electronics 2015年第1期24卷 170-175页

作者： ZHANG Haiyang beijing Key Laboratory of Intelligent telecommunications Software and Multimedia Beijing University of Posts and Telecommunications

Multicast has become increasingly important in multi-hop wireless networks for such applications which deliver shared media and data to multiple ***, the existing multicast protocols for wireless network have large control overhead, and cannot adequately take the advantage of broadcast communication mode in multicast structure for sharing the forwarding path. This paper proposes a Cluster-based opportunistic multicast(COM) algorithm, which constructs multicast tree structure based on clusters by utilizing a stability greedy algorithm to achieve the minimum total Cluster-based expected transmission count(CETX). In this multicast tree structure, the edge is created between the kernel sets respectively belonging to two clusters for improving the forwarding efficiency and the stability of this structure. In the process of data distribution, our multi-layer solution combines multicast and opportunistic routing to improve the efficiency of transmission. Simulation results show that COM scheme can achieve the less total number of sending packets, and higher stability than other topology-based solutions and opportunistic multicast.

关键词： Multi-hop wireless network Multicast Opportunistic routing Cluster.

Improved Prefix Based Format-Preserving Encryption for Chinese Names

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China Communications 2018年第3期15卷 78-90页

作者： Junwei Zou Peng Wang Hong Luo School of Electronic Engineering Beijing University of Posts and Telecommunications beijing Key Laboratory of Intelligent telecommunications Software and Multimedia Beijing University of Posts and Telecommunications

In the era of big data, government, business and personal digital information will be possible for data mining. Data mining requires massive data as a support. However, the direct release of the original mass data, which usually contain some sensitive information of personal or analysis, will result in leakage of user privacy. Therefore, it is becoming increasingly important to protect privacy information in data publishing. In this paper, we focus on the multi-type self-identified format-preserving encryption. First, we introduce a multi-type self-identified format-preserving encryption system and discuss the encryption of various types of data in this system. Then, for the format preserving encryption(FPE) about Chinese name, we study from the encryption model construction and basic encryption scheme. The format-preserving encryption model about Chinese name is constructed and the concept of the name library is presented. Based on this, it is used to not only limit the message space to reduce complexity, but also ensure the cipher in accordance with the Chinese naming habits. In addition, according to the encryption and decryption model, format-preserving encryption process of Chinese name is designed. In order to add new names, the algorithm of name space expansion is proposed. Based on the Prefix, this paper put forward an algorithm named Cycle-Prefix, which enhances the security and dynamics of FPE by using two adjustment factors and the circular encryption. Compared with the traditional Prefix algorithm, experiments show that Cycle-Prefix can not only complete the task of FPE for Chinese name, but also encrypt same plain text into different ciphers under the premise of similar efficiency with Prefix.

关键词： Chinese name format-preservingencryption name library encryption model

Controlling optical properties of periodic gold nanoparticle arrays by changing the substrate,topologic shapes of nanoparticles,and polarization direction of incident light

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Chinese Physics B 2011年第8期20卷 460-465页

作者：李婷于丽逮志欣宋钢张恺 State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications School of Science Beijing University of Posts and Telecommunications

The effects of various parameters including thickness and dielectric constants of substrates, shapes of nanoparticles, and polarization direction of incident light, on the extinction spectra of periodic gold nanoparticle arrays are investigated by the full-vectorial three-dimensional （3D） finite difference time domain （FDTD） method. The calculated results show that the substrate affects the extinction spectra by coupling the fields co-excited by the substrate and gold nanoparticles. Extinction spectra are influenced by the shapes of the nanoparticles, but there are no obvious changes in extinction spectra for similar shapes. The polarization direction of incident light has a great influence on the extinction spectra. The implications of these results are discussed.

关键词： localized surface plasmon extinction spectra gold nanoparticles

EABDS: Attribute-Based Secure Data Sharing with Efficient Revocation in Cloud Computing

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Chinese Journal of Electronics 2015年第4期24卷 862-868页

作者： HUANG Qinlong MA Zhaofeng YANG Yixian FU Jingyi NIU Xinxin Information Security Center Beijing University of Posts and Telecommunications National Engineering Laboratory for Disaster Backup and Recovery Beijing University of Posts and Telecommunications

Ciphertext-policy attribute-based encryption(CP-ABE) is becoming a promising solution to guarantee data security in cloud computing. In this paper,we present an attribute-based secure data sharing scheme with Efficient revocation(EABDS) in cloud *** scheme first encrypts data with Data encryption key(DEK) using symmetric encryption and then encrypts DEK based on CP-ABE, which guarantees the data confidentiality and achieves fine-grained access control. In order to solve the key escrow problem in current attribute based data sharing schemes, our scheme adopts additively homomorphic encryption to generate attribute secret keys of users by attribute authority in cooperation with key server, which prevents attribute authority from accessing the data by generating attribute secret keys *** scheme presents an immediate attribute revocation method that achieves both forward and backward *** computation overhead of user is also reduced by delegating most of the decryption operations to the key *** security and performance analysis results show that our scheme is more secure and efficient.

关键词： Attribute-based encryption Data sharing Attribute revocation Key escrow Cloud computing

Optomagnonically tunable whispering gallery cavity laser wavelength conversion

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Chinese Physics B 2023年第2期32卷 293-297页

作者：朱奕宁朱子虚裴安邦高永潘 International School Beijing University of Posts and TelecommunicationsBeijing 100876China School of Information and Communication Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China School of Electronic Engineering Beijing University of Posts and TelecommunicationsBeijing 100876China

We achieve laser wavelength conversion in an optomagnonical whispering gallery cavity by adjusting the strength of the applied static magnetic field. Numerical simulations are carried out on a yttrium iron garnet(YIG) sphere under different cavity quality factors or coupling strength. It is found that a high cavity quality factor will not always mean a high cavity excitation field for Gaussian lasers with finite linewidth. On state of the art, the high cavity quality factor will always mean the higher lightwave conversion rate. In addition, we also find that increasing the mode coupling strength is beneficial to the conversion of the laser. Our study provides new insights into generation of highly precise tunable coherent light.

关键词： cavity optomagnonics YIG sphere laser modulation

Study on coexistence between DCS1800 and TDD-LTE systems in multi-mode terminals

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The Journal of China Universities of posts and telecommunications 2014年第6期21卷 24-29页

作者： ZHENG Zhi-hui ZHAO Cheng-lin Li Bin TAO Hong-bo School of Telecommunication Engineering Beijing University of Posts and Telecommunications The State radio Monitoring Center Testing Center

It＇s well known that the mobile stations will comprise a wide range of radio access technologies（RAT）, providing user with flexible and efficient access to multi-media service and high data rate communications. Although much work has been done for coexistence analysis between different systems base stations（BS）, most of them have not addressed the interference within multi-mode terminal. Hence, for filling the gap, The authors in the article present coexistence studyies of digital cellular system at 1 800 MHz（DCS1800） and time division duplex long term evolution（TDD-LTE） network in multi-mode terminal with multi-service provisioning. A new system model for coexistence was introduced and how deterministic analysis can be done within the terminal was explained. The interference evaluation model was given based on relations between reference sensitivity and signal-to-noise ratio（SNR）, which is also deduced. The system simulation methodology was provided and assumption used in simulation was given. Simulation results were shown with different system parameters. Numeric results indicate that multi-mode terminal is mainly affected by local interference. The minimum antenna isolation required for a health system operation was provided.

关键词： TDD-LTE systems coexistence analysis multi-mode terminal deterministic analysis sensitivity degradation

Variational learning for finite Beta-Liouville mixture models

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The Journal of China Universities of posts and telecommunications 2014年第2期21卷 98-103页

作者： LAI Yu-ping ZHOU Ya-jian PING Yuan GUO Yu-cui YANG Yi-xian Information Security Center Beijing University of Posts and Telecommunications department of Computer Science and Technology Xuchang University School of Science Beijing University of Posts and Telecommunications

In the article, an improved variational inference （VI） framework for learning finite Beta-Liouville mixture models （BLM） is proposed for proportional data classification and clustering. Within the VI framework, some non-linear approximation techniques are adopted to obtain the approximated variational object functions. Analytical solutions are obtained for the variational posterior distributions. Compared to the expectation maximization （EM） algorithm which is commonly used for learning mixture models, underfitting and overfitting events can be prevented. Furthermore, parameters and complexity of the mixture model （model order） can be estimated simultaneously. Experiment shows that both synthetic and real-world data sets are to demonstrate the feasibility and advantages of the proposed method.

关键词： variational inference model selection factorized approximation Beta-Liouville distribution mixing modeling