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Fractional Smoothness of Some Stochastic Integrals

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Acta Mathematica Sinica,English Series 2007年第6期23卷 1053-1058页

作者： peng XIE Xi cheng zhang Department of Mathematics Huazhong University of Science and Technology Wuhan 430074 P. R. China

We study the fractional smoothness in the sense of Malliavin calculus of stochastic integrals of the form ∫0^1Ф（Xs）dXs, where Xs is a semimartingale and Ф belongs to some fractional Sobolev space over R.

关键词： fractional Sobolev space stochastic integral interpolation

Aperture shape optimization in intensity-modulated radiation therapy planning

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Nuclear Science and Techniques 2023年第9期34卷 106-117页

作者： Li-Yuan zhang Zhi-Guo Gui peng-cheng zhang Jie Yang Shanxi Provincial Key Laboratory for Biomedical Imaging and Big Data North University of ChinaTaiyuan 030051China School of Medicine Management Shanxi University of Chinese MedicineTaiyuan 030619China

The gradient element of the aperture gradient map is utilized directly to generate the aperture shape without *** process can be likened to choosing the direction of negative gradient descent for the generic aperture shape *** negative gradient descent direction is more suitable under local conditions and has a slow convergence *** overcome these limitations,this study introduced conjugate gradients into aperture shape optimization based on gradient ***,the aperture gradient map of the current beam was obtained for the proposed aperture shape optimiza-tion method,and the gradients of the aperture gradient map were modulated using conjugate gradients to form a modulated gradient *** aperture shape was generated based on the modulated gradient *** proposed optimization method does not change the optimal solution of the original optimization problem,but changes the iterative search direction when generating the aperture *** performance of the proposed method was verified using cases of head and neck cancer,and prostate *** optimization results indicate that the proposed optimization method better protects the organs at risk and rapidly reduces the objective function value by ensuring a similar dose distribution to the planning target *** to the contrasting methods,the normal tissue complication probability obtained by the proposed optimization method decreased by up to 4.61%,and the optimization time of the proposed method decreased by 5.26%on average for ten cancer *** effectiveness and acceleration of the proposed method were verified through comparative *** to the comparative experiments,the results indicate that the proposed optimization method is more suitable for clinical *** is feasible for the aperture shape optimization involving the proposed method.

关键词： Aperture shape Column generation Conjugate gradient Gradient modulation Direct aperture optimization

Asymptotic Theory for Relative-Risk Models with Missing Time-Dependent Covariates

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Acta Mathematicae Applicatae Sinica 2018年第4期34卷 669-692页

作者： Zai-ying ZHOU peng-cheng zhang Ying YANG Department of Mathematical Sciences Tsinghua University Beijing 100084 China Center for Statistical Science of Tsinghua University Beijing 100084 China

Relative-risk models are often used to characterize the relationship between survival time and time-dependent covariates. When the covariates are observed, the estimation and asymptotic theory for parameters of interest are available; challenges remain when missingness occurs. A popular approach at hand is to jointly model survival data and longitudinal data. This seems efficient, in making use of more information, but the rigorous theoretical studies have long been ignored. For both additive risk models and relative-risk models, we consider the missing data nonignorable. Under general regularity conditions, we prove asymptotic normality for the nonparametric maximum likelihood estimators.

关键词： relative-risk model missing time-dependent covariate nonparametric maximum likelihood esti-mation asymptotic normality

Preparation and characterization of Bi2O3/XNBR flexible films for attenuating gamma rays

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Nuclear Science and Techniques 2018年第7期29卷 152-163页

作者： Yi-Chuan Liao Dui-Gong Xu peng-cheng zhang Institute of Materials China Academy of Engineering PhysicsJiangyou 621907China Science and Technology on Surface Physics and ChemistryLaboratory Jiangyou 621908China

A bismuth oxide(Bi_2O_3)-dispersed carboxylated nitrile butadiene rubber(XNBR) flexible film was prepared as a flexible lead-free material for gamma ray(c-ray)***,obtaining a uniform and stable dispersion of Bi_2O_3 in carboxylated nitrile butadiene rubber latex(XNBRL) is a challenge due to sedimentation induced by the remarkable density ***,this challenge was approached by reducing the Bi_2O-3 particle radius,increasing the viscosity of the latex,and adding a *** experimental results confirmed that Bi2 O3 was well dispersed in the XNBRL in the concentration range of 30–70 wt%.The mechanical properties demonstrated that the Bi_2O_3/XNBR flexible films had a good resistance to oil,acid,alkali,and hot *** linear attenuation coefficients of the Bi_2O_3/XNBR flexible films obtained from the experiments were in good agreement with the calculated *** attenuation efficiencies of the Bi_2O_3/XNBR flexible films with different thicknesses and Bi_2O_3 contents were investigated for a few different γ-ray *** results showed that the Bi_2O_3/XNBRflexible films have wide application prospects for low-energy γ-ray attenuation.

关键词： gamma 电影光线 Bi2O3 丁二烯橡胶粒子半径机械性质分散剂

B4C/NRL flexible films for thermal neutron shielding

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Nuclear Science and Techniques 2018年第2期29卷 17-25页

Boron carbide/natural rubber latex(B_4 C/NRL)flexible films were prepared via dip-molding with B_4 C content in the range of 5–55 wt% for thermal neutron(0.0253 e V) shielding. B_4 C was well dispersed in NRL according to microscopic observation. Both the inside and outside surfaces of the film were smooth. For B_4 C/NRL flexible films, the minimum elongation at break was greater than 600%, the minimum tensile strength was greater than 12 MPa, and the hardness was in the range of 35–55 HA,which were suitable for preparing flexible wearable products. The attenuation efficiencies of the B_4 C/NRL flexible films for thermal neutrons were also calculated. The B_4 C/NRL flexible films exhibit good attenuation effect for thermal neutrons.

关键词： B4C Natural rubber latex Thermal neutron Shield Flexible film

Indefinite Linear Quadratic Optimal Control Problem for Singular Linear Discrete-time System: Krein Space Method

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自动化学报 2007年第6期33卷 635-640页

作者： CUI peng zhang cheng-Hui School of Control Science and Engineering Shandong University Jinan 250061 P. R. China

有限时间地平线不定线性二次(LQ ) 为单个线性分离变化时间的系统的最佳的控制问题被讨论。为单个系统的不定的 LQ 最佳的控制问题能在一个合理假设下面为标准州空间的系统被转变到那。不定的 LQ 最佳的控制问题对为向后的随机的系统的... 详细信息

有限时间地平线不定线性二次(LQ ) 为单个线性分离变化时间的系统的最佳的控制问题被讨论。为单个系统的不定的 LQ 最佳的控制问题能在一个合理假设下面为标准州空间的系统被转变到那。不定的 LQ 最佳的控制问题对为向后的随机的系统的设计的双，这被显示出。因此，最佳的 LQ 控制器能被计算 Kalman 过滤器的获得矩阵获得。为不定的 LQ 问题保证一个唯一的答案的必要、足够的条件被给。这个问题的一个明确的解决方案以 Riccati 差别方程的答案被获得。

关键词：模糊线性二次最佳控制单次线性离散时间系统有限时间差异方程 KaLman过滤

Influences of Alloying Elements on Oxidation Behavior of Steels and Microstructure of Oxide Scales

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Journal of Iron and Steel Research International 2016年第3期23卷 231-237页

作者： Hui-bin WU Di WANG peng-cheng zhang Jin-ming LIANG Sheng LIU Di TANG National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing

In order to figure out the oxidation behavior of steels during heating,five micro-alloyed steels were subjected to continuous and isothermal oxidation using the thermo gravimetric analyzer and the Gleeble-3500thermo-mechanical *** microstructure of oxide scales,especially the thickness fractions of Fe2O3,Fe3O4 and FeO layers,was analyzed using the scanning electron microscope（SEM）,electron probe microanalyzer（EPMA）and electron backscattered diffraction（EBSD）*** micro-alloyed steels containing alloying elements（Si,Cr,Ni and Cu）show a higher oxidation resistance compared with the low carbon *** is found that alloying elements accumulated at scale/substrate interface during high temperature *** elements function in two ways in the oxidation of steels：one is enhancing the scale/substrate interface and consequently suppressing the blister of scales;and the other is impeding the outward diffusion of iron cations from substrate to scales,resulting in the decrease of oxidation *** the diffusion of iron cations is impeded,the thickness fractions of Fe2O3 and Fe3O4of micro-alloyed steels are more than those of low carbon steels.

关键词： micro-alloyed steel high temperature oxidation oxidation kinetics microstructure oxide scale

Tensile deformation behavior of nickel-free high-manganese austenitic cryogenic-temperature steel

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Journal of Iron and Steel Research International 2022年第5期29卷 793-801页

作者： Xin-tian Wang Hui-bin Wu Yang Gu Li-xiong Xu peng-cheng zhang Qi-bo Tang National Center for Materials Service Safety University of Science and Technology BeijingBeijing100083China Collaborative Innovation Center of Steel Technology University of Science and Technology BeijingBeijing100083China

Nickel-free high-manganese austenitic Fe–24.4Mn–4.04Al–0.057C steel was produced by smelting,and the homogenized forged billet was *** plastic deformation mechanism was investigated through tensile testing of the hot-rolled *** characterization techniques such as scanning electron microscopy,transmission electron microscopy,electron backscattered diffraction,and X-ray diffraction were used to analyze the microstructural evolution of steel under different strain *** steel had a single austenite phase,which was stable during *** hot rolling,annealing twins were observed in the microstructure of the *** steel showed an excellent combination of mechanical properties,like a tensile strength of 527 MPa,impact energy of 203 J at−196℃,and an elongation of 67%till *** the initial deformation stage,the dislocations were generated within the austenite grains,entangled and accumulated at the grain boundaries and annealing twin *** twins participated in plastic deformation and hindered the dislocation *** the deformation progressed,the dislocation slip was hindered and produced stress concentration,and the stacking faults evolved into mechanical twins,which released the stress concentration and delayed the necking.

关键词： High-manganese steel Austenite grain Tensile deformation Mechanical twin Annealing twin

Influence of Inclusion on Corrosion Behavior of E36 Grade Low-alloy Steel in Cargo Oil Tank Bottom Plate Environment

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Journal of Iron and Steel Research International 2014年第11期21卷 1016-1021页

作者： Hui-bin WU Jin-ming LIANG Di TANG Xiao-tong LIU peng-cheng zhang Yuan-jie YUE National Engineering Research Center of Advanced Rolling Technology University of Science and Technology Beijing

Corrosion behavior of low-alloy steel was investigated in simulated cargo oil tank （COT） bottom plate service environment （10% NaCl solution, pH = 0.85）. The corrosion behavior of inclusion was studied by in-situ scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS）. It was found that pitting corrosion was inclined to occur around the place where inclusions exist. After initial corrosion, an area of 10-20μm in diameter was formed as a cireinate cathode around the edge of inclusion. MnS inclusion dissolved in the simulated COT corrosion solution before low-alloy steel matrix, and pitting was formed at the place where MnS dissolved. TiO2 inclusion dissolved in the simulated COT corrosion solution after low alloy steel matrix, and pitting was formed at the place where steel matrix dissolved. The corrosion tended to occur at the area where the curvature radius of inclusion is smaller. The size of round TiO2 inclusions had little influence on corrosion behavior in this certain environment.

关键词： cargo oil tank corrosion behavior low alloy steel pitting mechanism inclusion