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Nuclear Science and Techniques 2018年第11期29卷 152-158页

作者： M.Hassanzadeh S.M.Sadat Kiai Reactor and Nuclear Safety School Nuclear Science and Technology Research Institute (NSTRI) Plasma and Nuclear Fusion Research School Nuclear Science and Technology Research Institute (NSTRI)

One of the most important safety features of nuclear facilities is the shielding material used to protect the operating personnel from radiation exposure. The most common materials used in radiation shielding are concretes. In this study, a Monte Carlo N-Particle eXtended code is used to calculate the gamma-ray attenuation coefficients and dose rates for a new concrete material composed of MnFe_2O_4 nanoparticles, which is then compared with the theoretical and experimental results obtained for a SiO_2 nanoparticle concrete material. According to the results, the average relative differences between the simulations and the theoretical and experimental results for the linear attenuation coefficient(l) in the SiO_2 nanoparticle materials are 6.4% and 5.5%, respectively. By increasing the SiO_2 content up to 1.5% and the temperature of MnFe_2O_4 up to 673 K, l is increased for all energies. In addition, the photon dose rate decreases up to 9.2% and3.7% for MnFe_2O_4 and SiO_2 for gamma-ray energies of0.511 and 1.274 MeV, respectively. Therefore, it was concluded that the addition of SiO_2 and MnFe_2O_4 nanoparticles to concrete improves its nuclear properties and could lead to it being more useful in radiation shielding.

关键词： Shielding Radiation Concrete Attenuation coefficient Photon dose MCNPX code SiO2 and MnFe2O4 nanoparticles

Leakage Is Prohibited:Memory Protection Extensions Protected Address Space Randomization

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Tsinghua Science and Technology 2019年第5期24卷 546-556页

作者： Fei Yan Kai Wang the Key Laboratory of Aerospace Information Security and Trusted Computing Ministry of Education School of Cyber Science and Engineering Wuhan University

code reuse attacks pose a severe threat to modern applications. These attacks reuse existing code segments of vulnerable applications as attack payloads and hijack the control flow of a victim application. With high code entropy and a relatively low performance overhead, Address Space Layout Randomization(ASLR) has become the most widely explored defense against code reuse attacks. However, a single memory disclosure vulnerability is able to compromise this defense. In this paper, we present Memory Protection Extensions(MPX)-assisted Address Space Layout Randomization(M-ASLR), a novel code-space randomization scheme. M-ASLR uses several characteristics of Intel MPX to restrict code pointers in memory. We have developed a fully functioning prototype of M-ALSR, and our evaluation results show that M-ASLR:(1) offers no interference with normal operation;(2) protects against buffer overflow attacks, code reuse attacks, and other sophisticated modern attacks;and(3) adds a very low performance overhead(3.3%) to C/C++ applications.

关键词： Address Space Layout Randomization (ASLR) Intel Memory Protection Extensions (MPX) code reuse attack

Junction Point Elimination based Tamil Handwritten Character Recognition:An Experimental Analysis

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Journal of Systems Science and Systems Engineering 2020年第1期29卷 100-123页

作者： M.Antony Robert Raj S.Abirami Department of Information Science and Technology Anna UniversityChennai 600025

Optical Character Recognition is the mechanical or electronic conversion of images of typed,handwritten or printed text into machine-encoded text for online reading and study.In this OCR technique,Tamil handwritten character recognition is one of the most needed and challengeable subjects of research.An encounter between selection and extraction of proper features eliminates the issues faced by the Tamil handwritten recognition.The character and the writers complexities are the major difficulties and challenges faced by this recognition system.Eventually,the character complexity can be overcome by any pre-extraction or selection process,wherein,structured or statistical pre-extraction algorithm can be designed,discovering the essential features,in the case of writer difficulties.The challenges of Tamil handwritten characters are structure over looping;unnecessary character portion;structure discontinuations and so on.The character portions in this research are chosen by implementing a new algorithm called the Junction Point Elimination(JPE)after conscientious analysis done on the existing algorithms like Zoning,Zoning and Junction Point(ZJP)and the Junction Point (JP) based feature pre-extraction process.The novelty behind this work is introducing an algorithm in order to truncate the problem in the existing feature selection and preextraction algorithms.Suitable feature extraction and classification algorithm are chosen and applied on the features extracted by JPE to test whether the same can be reached in successful manner.The final analysis and experiments shows that the JPE is better than the others.

关键词： Junction point elimination chain code zoning prism tree quad tree support vector machine

Design of Irregular QC-LDPC code Based Multi-Level coded Modulation Scheme for High Speed Optical Communication Systems

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China Communications 2019年第5期16卷 106-120页

作者： Liqian Wang Dongdong Wang Yongjing Ni Xue Chen Midou Cui Fu Yang Beijing University of Posts and Telecommunications Beijing 100876China The 54th Research Institute of China Electronics Technology Group Corporation Shijiazhuang 050081China Science and Technology on Communication Networks Laboratory Shijiazhuang 050081China College of Information Science and Engineering Yanshan UniversityQinhuangdao 066000China College of Information Science and Engineering Hebei University of Science and TechnologyShijiazhuang 050000China The Key Laboratory for Computer Virtual Technology and System Integration of Hebei Province Yanshan University Qinhuangdao 066000China

In this paper, we focus on the design of irregular QC-LDPC code based multi-level coded modulation(MLCM) scheme by jointly optimizing the component code rate and the degree distribution of the irregular QC-LDPC component code. Firstly, the sub-channel capacities of MLCM systems is analyzed and discussed, based on which the optimal component code rate can be obtained. Secondly, an extrinsic information transfer chart based two-stage searching algorithm is proposed to find the good irregular QC-LDPC code ensembles with optimal component code rates for their corresponding sub-channels. Finally, by constructing the irregular QC-LDPC component codes from the designed ensembles with the aim of possibly enlarging the girth and reducing the number of the shortest cycles, the designed irregular QC-LDPC code based 16QAM and 64QAM MLCM systems can achieve 0.4 dB and 1.2 dB net coding gain, respectively, compared with the recently proposed regular QC-LDPC code based 16QAM and 64QAM MLCM systems.

关键词： quasi-cyclic low-density parity check (QC-LDPC) code irregular, extrinsic information transfer(EXIT) chart generalized mutual information(GMI) multi-level coded modulation(MLCM)

Impacts of optimization strategies on performance,power/energy consumption of a GPU based parallel reduction

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Journal of Central South University 2017年第11期24卷 2624-2637页

作者： Phuong Thi Yen Lee Deok-Young Lee Jeong-Gun Smart Computing Lab. Department of Computer EngineeringHallym UniversityChuncheon 24252Korea College of General Education Hallym UniversityChuncheon 24252Korea

In the era of modern high performance computing, GPUs have been considered an excellent accelerator for general purpose data-intensive parallel applications. To achieve application speedup from GPUs, many of performance-oriented optimization techniques have been proposed. However, in order to satisfy the recent trend of power and energy consumptions, power/energy-aware optimization of GPUs needs to be investigated with detailed analysis in addition to the performance-oriented optimization. In this work, in order to explore the impact of various optimization strategies on GPU performance, power and energy consumptions, we evaluate performance and power/energy consumption of a well-known application running on different commercial GPU devices with the different optimization strategies. In particular, in order to see the more generalized performance and power consumption patterns of GPU based accelerations, our evaluations are performed with three different Nvdia GPU generations(Fermi, Kepler and Maxwell architectures), various core clock frequencies and memory clock frequencies. We analyze how a GPU kernel execution is affected by optimization and what GPU architectural factors have much impact on its performance and power/energy consumption. This paper also categorizes which optimization technique primarily improves which metric(i.e., performance, power or energy efficiency). Furthermore, voltage frequency scaling(VFS) is also applied to examine the effect of changing a clock frequency on these metrics. In general, our work shows that effective GPU optimization strategies can improve the application performance significantly without increasing power and energy consumption.

关键词： parallel reduction GPU code optimization power energy voltage frequency scaling

Rock fragmentation under different installation polar angles of TBM disc cutters

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Journal of Central South University 2017年第10期24卷 2306-2313页

作者：程永亮钟掘梅勇兵夏毅敏 State Key Laboratory of High Performance Complex Manufacturing Central South University China Railway Construction Heavy Industry Co. Ltd.

The disc cutters of tunnel boring machine(TBM) are installed with different polar angles. This causes the cutting depth difference between adjacent disc cutters on the tunnel face. A rock-cutting model was established to study the rock fragmentation law between adjacent disc cutters with different polar angles based on particle flow code(PFC). The influence of polar angle of adjacent disc cutters on rock cracks and stresses under different cutter spacing and penetration was studied. Research shows that polar angle difference leads to the discontinuity of rock-fragmentation process by adjacent cutters. The effect of rock-fragmentation is influenced by the cutting depth difference between adjacent cutters. The effect of rock-fragmentation performed best, meanwhile large rock blocks were flaked when the difference of cutting depth is half of the penetration. Too large or small difference of the cutting depth will cause high specific energy consumption of rock fragmentation. The specific energy consumption is relatively small when the difference of cutting depth is half of the penetration.

关键词： tunnel boring machine disc cutter polar angle particle flow code rock fragmentation

Novel virtual user scheme to increase data confidentiality against eavesdropping in OCDMA network

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Chinese Optics Letters 2011年第12期9卷 46-50页

作者： Vishav Jyoti R.S.Kaler Department of Electronics and Communication Thapar University

We propose a novel technique to increase the confidentiality of an optical code division multiple access （OCDMA） system. A virtual user technique is analyzed and implemented to make an OCDMA system secure. Using this technique, an eavesdropper will never find an isolated authorized user＇s signal. When authorized users and virtual users transmit data synchronously and asynehronously, network security increases by 25% and 37.5%, respectively.

关键词： OCDMA code Novel virtual user scheme to increase data confidentiality against eavesdropping in OCDMA network data

Fiber-based optical parametric amplifier for 40-Gb/s NRZ-DPSK signal transmission system employing QC-LDPC codes

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Chinese Optics Letters 2013年第11期11卷 13-16页

作者：郑健别红霞张雪坤类春阳房明李莎康哲 School of Information and Communication Engineering Beijing University of Posts and Telecommunication Department of Medical Information Engineering Zunyi Medical College State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunication

In this letter, we investigate quasi-cyclic low-density parity-check （QC-LDPC） codes in a 40-Gb/s nonreturn-to-zero differential phase-shift keying （NRZ-DPSK） signal transmission system based on a fiber- based optical parametric amplifier （FOPA）. A constructed algorithm of QC-LDPC codes according to the optimizing set of shift vMues on the circulant permutation matrix （CPM） of the basis matrix is proposed. Simulation results prove that the coding gain in the encoded system can be realized at 10.2 dB under QC- LDPC codes with a code rate of 5/6 when the bit error rate （BER） is 10-9. In addition, the error-floor level originating from the uncoded system is suppressed.

关键词： LDPC code NRZ Fiber-based optical parametric amplifier for 40-Gb/s NRZ-DPSK signal transmission system employing QC-LDPC codes DPSK QC

A random linear code based secure transmission scheme for wireless fading channels

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Science China(Information Sciences) 2017年第4期60卷 241-243页

作者： Lukman A.OLAWOYIN Nana ZHANG A.O.OLOYEDE Nasir FARUK Hongwen YANG Wireless Communication Center Beijing University of Posts and Telecommunications Department of Telecommunication Science University of Ilorin

Dear editor,Wireless transmissions are vulnerable to potential security threats such as eavesdropping and wiretapping since unauthorized reception is facilitated through wireless channels[1].Traditional system security is mainly implemented in the higher layers of the communication protocol stack,relying on authentication and cryptography[2].The recent researches explore security in the physical layer[3],which can help to protect the information

关键词： code length A random linear code based secure transmission scheme for wireless fading channels

Determination of optimal period of absolute encoders with single track cyclic gray code

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Journal of Central South University 2008年第S2期15卷 362-366页

作者：张帆朱衡君 School of Mechanical Electronic and Control Engineering Beijing Jiaotong University

Low cost and miniaturized rotary encoders are important in automatic and precise production. Presented here is a code called Single Track Cyclic Gray code (STCGC) that is an image etched on a single circular track of a rotary encoder disk read by a group of even spread reading heads to provide a unique codeword for every angular position and features such that every two adjacent words differ in exactly one component, thus avoiding coarse error. The existing construction or combination methods are helpful but not sufficient in determining the period of the STCGC of large word length and the theoretical approach needs further development to extend the word length. Three principles, such as the seed combination, short code removal and ergodicity examination were put forward that suffice determination of the optimal period for such absolute rotary encoders using STCGC with even spread heads. The optimal periods of STCGC in 3 through 29 bit length were determined and listed.

关键词： rotary encoder absolute encoder single track grey code cyclic reliability