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Steganalysis of stochastic modulation steganography

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Science in china(Series F) 2006年第3期49卷 273-285页

作者： HE Junhui1,2 & HUANG Jiwu1,2 1. School of Information Science and Technology, Sun Yat-sen University, Guangzhou 510275, china 2. Guangdong province key laboratory of Information Security, Guangzhou 510275, china 1. School of Information Science and Technology Sun Yat-sen University Guangzhou 510275 China 2. Guangdong province key laboratory of Information Security Guangzhou 510275 China

Stochastic modulation steganography embeds secret message within the cover image by adding stego-noise with a specific probabilistic distribution. No method is known to be applicable to the estimation of stochastic modulation steganography. By analyzing the distributions of the horizontal pixel difference of images before and after stochastic modulation embedding, we present a new steganalytic approach to accurately estimate the length of secret message in stochastic modulation steganography. The pro- posed method first establishes a model describing the statistical relationship among the differences of the cover image, stego-image and stego-noise. In the case of stegoimage-only steganalysis, rough estimate of the distributional parameters of the cover image＇s pixel difference is obtained with the use of the provided stego-image. And grid search and Chi-square goodness of fit test are exploited to estimate the length of the secret message embedded with stochastic modulation steganography. The experimental results demonstrate that our new approach is effective for steganalyzing stochastic modulation steganography and accurately estimating the length of the secret message.

关键词： information hiding steganography steganalysis stochastic modulation statistical distribution models of difference.

Revisit of Sheppard corrections in linear regression

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Science china mathematics 2010年第6期53卷 1435-1451页

作者： LIU TianQing1,ZHANG BaoXue1,HU GuoRong1 & BAI ZhiDong1,2,1key laboratory for applied Statistics of MOE and School of mathematics and Statistics,Northeast Normal University,Changchun 130024,china 2Department of Statistics and applied Probability,National University of Singapore,Singapore 117543,Singapore 1. key laboratory for applied Statistics of MOE and School of mathematics and Statistics Northeast Normal University Changchun 130024 China2. Department of Statistics and Applied Probability National University of Singapore Singapore 117543 Singapore

Dempster and Rubin(D&R) in their JRSSB paper considered the statistical error caused by data rounding in a linear regression model and compared the Sheppard correction,BRB correction and the ordinary LSE by *** asymptotic results when the rounding scale tends to 0 were also *** a previous research,we found that the ordinary sample variance of rounded data from normal populations is always inconsistent while the sample mean of rounded data is consistent if and only if the true mean is a multiple of the half rounding *** the light of these results,in this paper we further investigate the rounding errors in linear *** notice that these results form the basic reasons that the Sheppard corrections perform better than other methods in D&R examples and their conclusion in general cases is *** in which the Sheppard correction works worse than the BRB correction are also ***,we propose a new approach to estimate the parameters,called "two-stage estimator",and establish the consistency and asymptotic normality of the new estimators.

关键词： asymptotic normality consistency linear regression model rounded data two-stage estimates

Immortal solution of the Ricci flow

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Science china mathematics 2005年第z1期48卷 217-224页

作者： RUAN Qihua & CHEN Zhihua Department of applied mathematics, Tongji University, Shanghai 200092, china Department of mathematics, Putian College, Putian 351100, china Tongji Univ Dept Appl Math Shanghai 200092 Peoples R China Putian Coll Dept Math Putian 351100 Peoples R China

For any complete noncompact Kahler manifold with nonnegative and bounded holomorphic bisectional curvature, we provide the necessary and sufficient condition for the immortal solution to the Ricci flow.

关键词： Ricci flow, immortal solution, holomorphic bisectional curvature.

A study on compressive shock wave propagation in metallic foams

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Science china(Physics,Mechanics & Astronomy) 2010年第2期53卷 279-287页

作者： WANG ZhiHua1,2,ZHANG YiFen2,REN HuiLan1 & ZHAO LongMao2 1 State key laboratory of Explosion Science and Technology,Beijing Institute of Technology,Beijing 100081,china 2 Institute of applied Mechanics and Biomedical Engineering,Taiyuan University of Technology,Taiyuan 030024,china 1. State key laboratory of Explosion Science and Technology Beijing Institute of Technology Beijing 100081 China2. Institute of Applied Mechanics and Biomedical Engineering Taiyuan University of Technology Taiyuan 030024 China

Metallic foam can dissipate a large amount of energy due to its relatively long stress plateau,which makes it widely applicable in the design of structural crashworthiness. However,in some experimental studies,stress enhancement has been observed when the specimens are subjected to intense impact loads,leading to severe damage to the objects being protected. This paper studies this phenomenon on a 2D mass-spring-bar model. With the model,a constitutive relationship of metal foam and corresponding loading and unloading criteria are presented; a nonlinear kinematics equilibrium equation is derived,where an explicit integra-tion algorithm is used to calculate the characteristic of the compressive shock wave propagation within the metallic foam; the effect of heterogeneous distribution of foam microstructures on the shock wave features is also included. The results reveal that under low impact pulses,considerable energy is dissipated during the progressive collapse of foam cells,which then reduces the crush of objects. When the pulse is sufficiently high,on the other hand,stress enhancement may take place,especially in the heterogeneous foams,where high peak stresses usually occur. The characteristics of compressive shock wave propagation in the foam and the magnitude and location of the peak stress produced are strongly dependent on the mechanical properties of the foam material,amplitude and period of the pulse,as well as the homogeneity of the microstructures. This research provides valuable insight into the reliability of the metallic foams used as a protective structure.

关键词： aluminum foam heterogeneous intensive pulse loading stress enhancement

Experimental study of gas-water elongated bubble flow during production logging

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Petroleum Science 2011年第2期8卷 157-162页

作者： Lu Jing Wu Xiling key laboratory of Earth Prospecting and Information Technology China University of Petroleum Beijing 102249 China State key laboratory of Petroleum Resource and Prospecting China University of Petroleum Beijing 102249 China

In order to improve the interpretation of production log data on gas-water elongated bubble （EB） flow in horizontal wells, a multi-phase flow simulation device was set up to conduct a series of measurement experiments using air and tap water as test media, which were measured using a real production logging tool （PLT） string at different deviations and in different mixed flow states. By understanding the characteristics and mechanisms of gas-water EB flow in transparent experimental boreholes during production logging, combined with an analysis of the production log response characteristics and experimental production logging flow pattern maps, a method for flow pattern identification relying on log responses and a drift-flux model were proposed for gas-water EB flow. This model, built upon experimental data of EB flow, reveals physical mechanisms of gas-water EB flow during measurement processing. The coefficients it contains are the specific values under experimental conditions and with the PLT string used in our experiments. These coefficients also reveal the interference with original downhole flow patterns by the PLT string. Due to the representativeness that our simulated flow experiments and PLT string possess, the model coefficients can be applied as empirical values of logging interpretation model parameters directly to real production logging data interpretation, when the measurement circumstances and PLT strings are similar.

关键词： Horizontal wells elongated bubble flow flow patterns identification drift-flux model,logging interpretation model

Hemoglobin-biocatalyzed Synthesis of Conducting Molecular Complex of Polyaniline and Lignosulfonate

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Journal of wuhan University of Technology(Materials Science) 2008年第6期23卷 809-815页

作者：胡兴邹国林 Department of Bioengineering Huaihua University State key laboratory of Virology College of Life SciencesWuhan University

A new biocatalyst route for the synthesis of a conducting polyaniline （PANI）/ lignosulfonate （LGS） complex was *** different catalysts such as hemoglobin （Hb）,5,10,15,20-tetrakis （meso-hydroxyphenyl） porphyrin,iron （II） tetrasulfophthalocyanine and ferric chloride were used to polymerize aniline in the presence of a natural polyelectrolytes template *** experimental results show that Hb is an effective catalyst in this case and the synthesis is simple,and the conditions are mild in that the polymerization may be carried out in lower pH （1.0-4.0） buffered solution and optimal pH of *** concentrations of aniline,LGS and H2O2 in feed the favorable conditions for the production of PANI were ***-vis absorption,FTIR,elemental analysis,conductivity,cyclic voltammetry and thermogravimetric analyses confirm the formation of thermally stable and electroactive PANI.

关键词： hemoglobin polyaniline biocatalyst conductivity lignosulfonate

MELTING CRYSTALLIZATION BEHAVIOR OF NYLON 66

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Chinese Journal of Polymer Science 2001年第3期19卷 237-246页

作者： Qing-xin Zhang Zhi-shen Mo State key laboratory of Polymer Physics & Chemistry Changchun Institute of applied Chemistry Chinese Academy of Sciences, Changchun 130022, china Chinese Acad Sci Changchun Inst Appl Chem State Key Lab Polymer Phys & Chem Changchun 130022 Peoples R China

Analysis of isothermal and nonisothermal crystallization kinetics of nylon 66 was carried out using differential scanning calorimetry (DSC). The commonly used Avrami equation and that modified by Jeziorny were used, respectively, to fit the primary stage of isothermal and nonisothermal crystallizations of nylon 66. In the isothermal crystallization process, mechanisms of spherulitic nucleation and growth were discussed. The lateral and folding surface free energies determined from the Lauritzen-Hoffman treatment are sigma = 9.77 erg/cm(2) and sigma (e) = 155.48 erg/cm(2), respectively; and the work of chain folding is q = 33.14 kJ/mol. The nonisothermal crystallization kinetics of nylon 66 was analyzed by using the Mo method combined with the Avrami and Ozawa equations. The average Avrami exponent (n) over bar was determined to be 3.45. The activation energies (DeltaE) were determined to be -485.45 kJ/mol and -331.27 kJ/mol, respectively, for the isothermal and nonisothermal crystallization processes by the Arrhenius and the Kissinger methods.

关键词： nylon 66 crystallization kinetics activation energy

A NUMERICAL METHOD FOR DETERMINING THE OPTIMAL EXERCISE PRICE TO AMERICAN OPTIONS

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Journal of Computational mathematics 2003年第3期21卷 305-310页

作者： Xiong-hua Wu Xiu-juan Feng (Department of applied mathematics, Tongji University, Shanghai 200092, china ) Department of applied mathematics Tongji University 上海 800092

American options can be exercised prior to the date of expiration, the valuation of American options then constitutes a free boundary value problem. How to determine the free boundary, i.e. the optimal exercise price, is a key problem. In this paper, a nonlinear equation is given. The free boundary can be obtained by solving the nonlinear equation and the numerical results are better.

关键词： American options Free boundary Optimal exercise price Nonlinear equation.

Lie Point Symmetries of Differential-Difference Equations

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Communications in Theoretical Physics 2004年第5期41卷 645-648页

作者： DING Wei~1 TANG Xiao-Yan~(2,3) 1 Department of applied mathematics,Shanghai Jiao Tong University,Shanghai 200030,china2 Department of Physics,Shanghai Jiao Tong University,Shanghai 200030,china3 State key laboratory of Scientific and Engineering Computing,Institute of Computational mathematics and Scientific Engineering Computing,Academy of mathematics and System Sciences,the Chinese Academy of Sciences,P.O.Box 2719,Beijing 100080,china State key laboratory of Scientific and Engineering Computing Institute of Computational Mathematics and Scientific Engineering Computing Academy of Mathematics and System Sciences the Chinese Academy of Sciences P.O. Box 2719 Beijing 100080 China

In this paper,the classical Lie group approach is extended to find some Lie point symmetries of differential-difference *** reveals that the obtained Lie point symmetries can constitute a Kac-Moody-Virasoro algebra.

关键词： Lie point symmetry differential-difference equation Kac Moody-Virasoro algebra