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Improved MPEG-4 High-Efficiency AAC With variable-length Soft-Decision Decoding of the Quantized Spectral Coefficients

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China Communications 2019年第10期16卷 65-82页

作者： Sai Han Hongbing Ma Ping Zhang Tim Fingscheidt China United Network Communications Group Company Limited Beijing 100033China Beijing University of Posts and Telecommunications Beijing 100876China Institute for Communications Technology Technische Universitat BraunschweigBraunschweig 38106Germany

MPEG-4 High-Efficiency Advanced Audio Coding (HE-AAC) is designed for low bit rate applications, such as audio streaming in mobile communications. The HE-AAC audio codec offers a better coding efficiency since variable-length codes (VLCs) are adopted. However, HE-AAC has originally been designed for storage and error-free transmission conditions. For the transmission over bit error-prone channels, error propagation is a serious problem for the VLCs. Therefore, a robust HE-AAC decoder is desired, especially for mobile communications. In contrast to traditional hard-decision decoding, utilizing bit-wise channel reliability information, softdecision (SD) decoding has been known to offer better audio quality. In HE-AAC, the global gain parameter is coded with fixedlength codes (FLCs), while the scale factors and quantized spectral coefficients are coded with VLCs. In this work, we apply FL/SD decoding to the global gain parameter, VL/SD decoding to the parameters scale factors and quantized spectral coefficients. Especially, in order to apply VL/SD decoding to the quantized spectral coefficients, a new modified trellis representation in VL/SD decoding is proposed. An improved HE-AAC performance is clearly observed, with the support of both instrumental measurements and a subjective listening test.

关键词： variable-length soft-decision decoding HE-AAC trellis representation quantization spectral coefficients

variable-length sequential dynamic features-based malware detection

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High Technology Letters 2016年第4期22卷 362-367页

作者：杜冬高 Li Gaochao Ma Yan Network and Information Center Institute of Network TechnologyBeijing University of Posts and Telecommunications National Computer Network Emergency Response Technical Team/Coordination Center of China Institute of Information Engineering Chinese Academy of Sciences Beijing Key Laboratory of Intelligent Telecommunications Software and Multimedia Beijing University of Posts and Telecommunications

In order to solve the problem that traditional signature-based malware detection systems are inefficacious in detecting new malware,a practical malware detection system is constructed to find out new malware. Application programming interface( API) call sequence is introduced to capture activities of a program in this system. After that,based on variable-length n-gram,API call order can be extracted from API call sequence as the malicious behavior feature of a software. Compared with traditional methods,which use fixed-length n-gram,the solution can find more new malware. The experimental results show that the presented approach improves the accuracy of malware detection.

关键词： application programming interface(API) call order variable-length n-gram malware detection

Axially variable-length solid element of absolute nodal coordinate formulation

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Acta Mechanica Sinica 2019年第3期35卷 653-663页

作者： Jialiang Sun Qiang Tian Haiyan Hu Niels L.Pedersen State Key Laboratory of Mechanics and Control of Mechanical Structures College of Aerospace EngineeringNanjing University of Aeronautics and AstronauticsNanjing 210016China MOE Key Laboratory of Dynamics and Control of Flight Vehicle School of Aerospace EngineeringBeijing Institute of TechnologyBeijing 100081China Department of Mechanical Engineering Solid MechanicsTechnical University of Denmark2800 Kongens LyngbyDenmark

An axially variable-length solid element with eight nodes is proposed by integrating the arbitrary Lagrangian-Eulerian (ALE) formulation and the absolute nodal coordinate formulation (ANCF). In addition to the nodal positions and slopes of eight nodes, two material coordinates in the axial direction are used as the generalized coordinates. As a consequence, the nodes in the ALE-ANCF are not associated with any specific material points and the axial length of the solid element can be varied over time. These two material coordinates give rise to a variable mass matrix and an additional inertial force vector. Computationally efficient formulae of the additional inertial forces and elastic forces, as well as their Jacobians, are also derived. The dynamic equation of a flexible multibody system (FMBS) with variable-length bodies is presented. The maximum and minimum lengths of the boundary elements of an FMBS have to be appropriately defined to ensure accuracy and non-singularity when solving the dynamic equation. Three numerical examples of static and dynamic problems are given to validate the variable-length solid elements of ALE-ANCF and show their capability.

关键词： Flexible multibody dynamics Arbitrary Lagrangian-Eulerian formulation Absolute nodal coordinate formulation variable-length solid element

FPGA based multi-channel variable-length FFT implementation

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太赫兹科学与电子信息学报 2017年第3期15卷 469-474页

作者： WANG Jiawei YU Le YANG Haigang FENG Guanglang SUN Jiabin LUO Yang Institute of Electronics Chinese Academy of ScienceBeijing 100190China Computer and Information Engineering Beijing Technology and Business UniversityBeijing 100048China

High-speed real-time digital frequency analysis is one major field of Fast Fourier Transform(FFT)application,such as Synthetic Aperture Radar(SAR)processing and medical imaging.In SAR processing,the image size could be 4 k×4 k in normal and it has become larger over the years.In the view of real-time,extensibility and reusable characteristics,an Field Programmable Gate Array(FPGA)based multi-channel variable-length FFT architecture which adopts radix-2 butterfly algorithm is proposed in this paper.The hardware implementation of FFT is partially reconfigurable architecture.Firstly,the proposed architecture in the paper has flexibility in terms of chip area,speed,resource utilization and power consumption.Secondly,the proposed architecture combines serial and parallel methods in its butterfly computations.Furthermore,on system-level issue,the proposed architecture takes advantage of state processing in serial mode and data processing in parallel mode.In case of sufficient FPGA resources,state processing of serial mode mentioned above is converted to pipeline mode.State processing of pipeline mode achieves high throughput.

关键词： Field Programmable Gate Array Fast Fourier Transform multi-channel parallel mode variable-length reconfigurable architecture