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A distribution space for Hilbert transform and its applications

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science china mathematics 2008年第12期51卷 2217-2230页

作者： YANG LiHua school of mathematics and Computing science, sun yat-sen university, guangzhou 510275, china school of mathematics and Computing science Sun Yat-Sen University Guangzhou China

In this paper, a new distribution space is constructed and the definition of the classical Hilbert transform is extended to it. It is shown that is the biggest subspace of on which the extended Hilbert transform is a homeomorphism and both the classical Hilbert transform for L p functions and the circular Hilbert transform for periodic functions are special cases of the extension. Some characterizations of the space are given and a class of useful nonlinear phase signals is shown to be in . Finally, the applications of the extended Hilbert transform are discussed.

关键词： Hilbert transform distribution time-frequency analysis 44A15 46F12

A provable secure fuzzy identity based signature scheme

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science china(Information sciences) 2012年第9期55卷 2139-2148页

作者： WANG ChangJi 1,2 1 school of Information science and Technology,sun yat-sen university,guangzhou 510275,china 2 Guangdong Province Information Security Key Laboratory,sun yat-sen university,guangzhou 510275,china school of Information science and Technology Sun Yat-sen University Guangzhou China Guangdong Province Information Security Key Laboratory Sun Yat-sen University Guangzhou China

To use biometrics identities in an identity based encryption system,Sahai and Waters first introduced the notion of fuzzy identity based encryption(FIBE) in *** et *** it to digital signature and introduced the concept of fuzzy identity based signature(FIBS) in 2008,and constructed an FIBS scheme based on Sahai and Waters's FIBE *** this paper,we further formalize the notion and security model of FIBS scheme and propose a new construction of FIBS scheme based on bilinear *** proposed scheme not only provides shorter public parameters,private key and signature,but also have useful structures which result in more efficient verification than that of Yang et al.'s FIBS *** proposed FIBS scheme is proved to be existentially unforgeable under a chosen message attack and selective fuzzy identity attack in the random oracle model under the discrete logarithm assumption.

关键词： identity based cryptosystem fuzzy identity based encryption fuzzy identity based signature

TOTAL REWARD CRITERIA FOR UNCONSTRAINED/CONSTRAINED CONTINUOUS-TIME MARKOV DECISION PROCESSES

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Journal of Systems science & Complexity 2011年第3期24卷 491-505页

作者： Xianping GUO Lanlan ZHANG school of mathematics and computational science Sun Yat-sen University Guangzhou 510275 China school of Public Health and Tropical Medicine Southern Medical University Guangzhou 510515 China

This paper studies denumerable continuous-time Markov decision processes with expected total reward criteria. The authors first study the unconstrained model with possible unbounded transition rates, and give suitable conditions on the controlled system＇s primitive data under which the authors show the existence of a solution to the total reward optimality equation and also the existence of an optimal stationary policy. Then, the authors impose a constraint on an expected total cost, and consider the associated constrained model. Basing on the results about the unconstrained model and using the Lagrange multipliers approach, the authors prove the existence of constrained-optimal policies under some additional conditions. Finally, the authors apply the results to controlled queueing systems.

关键词： Constrained-optimal policy continuous-time Markov decision process optimal policy total reward criterion unbounded reward/cost and transition rates.

Chemical weathering and chemical runoffs in the seashore granite hills in South china

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science china Earth sciences 2010年第8期53卷 1195-1204页

作者： GAO QuanZhou & TAO Zhen school of Geography and Planning, sun yat-sen university, guangzhou 510275, china school of Geography and Planning Sun Yat-sen University Guangzhou China

Surface runoffs and the contents of major ions and dissolved silicon were surveyed and analyzed based on weekly sampling for one year in a granite watershed of Zhuhai City, Guangdong Province. The results demonstrated that the slope runoff played an essential role in feeding the rivulet during precipitation, whereas the groundwater was more important for the rivulet in the non-raining stages. Dissolved silicon, Na+, HCO3-, and Clions constituted the major chemical components of the rivulet water. Atmospheric CO2 and H2SO4 sourced from the oxidation of pyrite were the main erosive mediums in the natural chemical weathering. Natural chemical weathering, the wet and dry deposition of sea-salt, and acids precipitation contributed approximately equal shares of anions to the rivulet water. The ratio of NO3- to SO42- was more than 1.0 in the runoff of the studied seashore watershed, whereas it is less than 1.0 in the Xijiang River that is adjacent to the study area. This implied that the chemical composition of runoff is controlled mainly by the differences in atmospheric acid precipitation caused by human activities and lithology within the catchments under the same bio-climate zone. The CO2 flux consumed by the rock chemical weathering processes within the seashore granite watershed in South china was (0.35-1.37)×105 mol km-2 a-1.

关键词： chemical weathering granite ion sea-salt acid deposition CO2

Spontaneous chiral-symmetry breaking of lattice QCD with massless dynamical quarks

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science china(Physics,Mechanics & Astronomy) 2007年第1期50卷 6-14页

作者： LUO XiangQian Department of Physics,school of Physics and Engineering,sun yat-sen university,guangzhou 510275,china Department of Physics School of Physics and Engineering Sun Yat-Sen University Guangzhou China

One of the most challenging issues in QCD is the investigation of spontaneous chiral-symmetry breaking, which is characterized by the non-vanishing chiral condensate when the bare fermion mass is zero. In standard methods of the lattice gauge theory, one has to perform expensive simulations at multiple bare quark masses, and employ some modeled functions to extrapolate the data to the chiral limit. This paper applies the probability distribution function method to computing the chiral condensate in lattice QCD with massless dynamical quarks, without any ambiguous mass extrapolation. The results for staggered quarks indicate that this might be a promising and efficient method for investigating the spontaneous chiral-symmetry breaking in lattice QCD, which deserves further investigation.

关键词： lattice QCD spontaneous chiral-symmetry breaking dynamical quarks

Twisted Ate pairing on hyperelliptic curves and applications

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science china(Information sciences) 2010年第8期53卷 1528-1538页

作者： ZHANG FangGuo 1,2 1 school of Information science and Technology, sun yat-sen university, guangzhou 510275, china 2 Guangdong Key Laboratory of Information Security Technology, guangzhou 510275, china school of Information science and Technology Sun Yat-Sen University Guangzhou China Guangdong Key Laboratory of Information Security Technology Guangzhou China

In this paper we show that the twisted Ate pairing on elliptic curves can be generalized to hyperelliptic curves, and give a series of variations of the hyperelliptic Ate and twisted Ate pairings. Using the hyperelliptic Ate pairing and twisted Ate pairing, we propose a new approach to speeding up the Weil pairing computation. For some hyperelliptic curves with high degree twist, computing Weil pairing by our approach may be faster than Tate pairing, Ate pairing, and all other known pairings.

关键词： Ate pairing Weil pairing hyperelliptic curves pairing-based cryptosystems twisted curves

Secure multi-party computation protocol for sequencing problem

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science china(Information sciences) 2011年第8期54卷 1654-1662页

作者： TANG ChunMing 1,2,SHI GuiHua 1 & YAO ZhengAn 3 1 school of mathematics and Information science,guangzhou university,guangzhou 510006, china 2State Key Laboratory of Information Security, Institute of Software science,Chinese Academy of sciences,Beijing 100080,china 3 school of mathematics and computational science,sun yat-sen university,guangzhou 510275,china school of mathematics and Information science Guangzhou University Guangzhou China State Key Laboratory of Information Security Institute of Software Science Chinese Academy of Sciences Beijing China school of mathematics and computational science Sun Yat-Sen University Guangzhou China

In the field of multi-party computation,an important problem is how to construct an efficient and secure multi-party computation protocol for certain specific *** the present study,we make use of a secret sharing scheme to construct an efficient and secure multi-party computation protocol for sequencing *** protocols are perfectly secure against both a passive adversary that can corrupt at most t (n-1)/2 participants, and an active adversary that can corrupt at most t < n/3 *** simplest sequencing problem is the Millionaires' problem.

关键词： secure multi-party computation sequencing problem secret sharing

Calibration based universal JPEG steganalysis

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science in china(Series F) 2009年第2期52卷 260-268页

作者： HUANG FangJun1,2 & HUANG JiWu1,2 1 school of Information science and Technology,sun yat-sen university,guangzhou 510275,china 2 Guangdong Key Lab. of Information Security Technology,sun yat-sen university,guangzhou 510275,china school of Information science and Technology Sun Yat-Sen University Guangzhou China Guangdong Key Lab. of Information Security Technology Sun Yat-Sen University Guangzhou China

For steganalysis of JPEG images, features derived in the embedding domain appear to achieve a preferable performance. However, with the existing JPEG steganography, the minor changes due to the hidden secret data are not easy to be explored directly from the quantized block DCT （BDCT） coefficients in that the energy of the carrier image is much larger than that of the hidden signal. In this paper, we present an improved calibration-based universal JPEG steganalysis, where the microscopic and macroscopic calibrations are combined to calibrate the local and global distribution of the quantized BDCT coefficients of the test image. All features in our method are generated from the difference signal be- tween the quantized BDCT coefficients of the test image and its corresponding microscopic calibrated image, or calculated as the difference between the signal extracted from test image and its corresponding macroscopic calibrated image. The extracted features will be more effective for our classification. Moreover, through using the Markov empirical transition matrices, both magnitude and sign dependencies along row scanning and column scanning patterns existed in intra-block and inter-block quantized BDCT coefficients are employed in our method. Experimental results demonstrate that our proposed scheme outperforms the best effective JPEG steganalyzers having been presented.

关键词： JPEG steganography steganalysis microscopic calibration macroscopic calibration

High norbornene incorporation in ethylene-norbornene copolymerization with a bis(α-alkyloxoimine) titanium-MAO catalyst

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science china Chemistry 2010年第8期53卷 1634-1640页

作者： GAO HaiYang1,2,HU Hao1 & WU Qing1,2 1Institute of Polymer science,school of Chemistry and Chemical Engineering,sun yat-sen (Zhongshan) university,guangzhou 510275,china 2Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education sun yat-sen (Zhongshan) university,guangzhou 510275,china Institute of Polymer science School of Chemistry and Chemical Engineering Sun Yat-Sen (Zhongshan) University Guangzhou China Key Laboratory for Polymeric Composite and Functional Materials of Ministry of Education Sun Yat-Sen (Zhongshan) University Guangzhou China

A novel bis(α-alkyloxoimine) titanium(IV) complex was synthesized and used as a catalyst precursor to catalyze homo-and copolymerization of ethylene and *** titanium complex activated with methylalumoxane exhibits good activities for the homopolymerizations of ethylene and norbornene under high temperature to produce high-molecular-weight linear polyethylene and vinyl-type polynorbornene,***-norbornene copolymers with high molecular weight can also be produced by this *** incorporation of norbornene from 0 to 76 mol% in the copolymers can be controlled by varying the charged norbornene.13C NMR analyses show that the microstructures of the ethylene-norbornene copolymers with low norbornene incorporation are predominantly alternated and isolated norbornene units,while those with high norbornene incorporation are random polymers containing long norbornene sequences.

关键词： catalyst ethylene norbornene polymerization copolymerization