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Journal of Iron and Steel Research International 2011年第11期18卷 46-52页

作者： faNG Xiu-hui YANG ping LU fa-yun MENG Li School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

Mechanical properties, microstructure and texture evolution were studied in two tensile-deformed high manganese TWIP steels at different temperatures. Special attention was paid to the effects of deformation tempera- ture and grain orientation on twinning behavior. The results showed that, at --70 ℃ and at room temperature, both twins and hexagonal martensite were found in a lower manganese steel of 26Mn. With deformation temperature ris- ing, twins became less and they disappeared at 500 ℃. Strong 〈111〉 texture appeared at 300 ℃, while it weakened at 500 ℃ due to the low strain rate and higher stacking fault energy. EBSD measurement revealed the dependence of deformation twinning on grain orientation at all test temperatures.

关键词： high manganese steel warm deformation TWIP effect texture

Detection of nitrogen-overfertilized rice plants with leaf positional difference in hyperspectral vegetation index

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Journal of Zhejiang University-Science B(Biomedicine & Biotechnology) 2010年第6期11卷 465-470页

作者： Qi-fa ZHOU Zhan-yu LIU Jing-feng HUANG College of Life Sciences Zhejiang University Hangzhou 310058 China College of Environmental and Resource Sciences Zhejiang University Hangzhou 310029 China

The main objective of this work was to compare the applicability of the single leaf(the uppermost leaf L1 and the third uppermost leaf L3) modified simple ratio(mSR705 index) and the leaf positional difference in the vegetation index between L1 and L3(mSR705L1-mSR705L3) in detecting nitrogen(N)-overfertilized rice plants.A field experiment consisting of three rice genotypes and five N fertilization levels(0,75,180,285,and 390 kg N/ha) was conducted at Xiaoshan,Hangzhou,Zhejiang Province,China in *** hyperspectral reflectance(350-2500 nm) and the chlorophyll concentration(ChlC) of L1 and L3 were measured at different *** mSR705L1 and mSR705L3 indices appeared not to be highly sensitive to the N rates,especially when the N rate was high(above 180 kg N/ha).The mean mSR705L1-mSR705L3 across the genotypes increased significantly(P<0.05) or considerably from 180 to 285 kg N/ha treatment and from 285 to 390 kg N/ha treatment at all the ***,use of the difference(mSR705L1-mSR705L3) greatly reduced the influence of the stages and genotypes in assessing the N status with re-flectance *** results of this study show that the N-overfertilized rice plants can be effectively detected with the leaf positional difference in the mSR705 index.

关键词： Rice Nitrogen (N) Overfertilization Leaf position Hyperspectral reflectance

Metal hydride work pair development and its application on automobile air conditioning systems

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第2期8卷 197-204页

作者： QIN feng CHEN Jiang-ping ZHANG Wen-feng CHEN Zhi-jiu Institute of Refrigeration and Cryogenic Engineering Shanghai Jiao Tong University Shanghai 200030 China Research Center Zhejiang Yinlun Machinery Co. Ltd. Tiantai 317200 China

Aiming at developing exhaust gas driving automobile air conditioning systems, a hydride pair LaNi4.61Mn0.26A10.13/ La0.6Y0.4Ni4.8Mn0.2 was developed working at 393-473 K/293-323 K/263-273 K. Property tests showed that both alloys have flat plateau slopes and small hystereses; system theoretical coefficient of performance （COP） is 0.711. Based on this work pair, a function proving automobile metal hydride refrigeration system was constructed. The equivalent thermal conductivities of the activated reaction beds were merely 1.1-1.6 W/（m-K）, which had not met practical requirement. Intermittent refrigeration cycles were achieved and the average cooling power was 84.6 W at 423 K/303 K/273 K with COP being 0.26. By altering cycling parameters, experiment data showed that cooling power and system COP increase with the growth of heat source temperature as well as pre-heating and regeneration time while decrease with heat sink temperature increment. This study confirms the feasibility of automobile metal hydride refrigeration systems, while heat transfer properties of reaction beds still need to be improved for better performance.

关键词： Metal hydride Air conditioning Reaction bed Automobile Coefficient of performance (COP)

Large scale synthesis of FeS coated Fe nanoparticles as reusable magnetic photocatalysts

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Frontiers of Materials Science 2013年第3期7卷 308-311页

作者： He feng ping-Zhan SI Xiao-Fei XIAO Chen-Hao JIN Sen-Jiang YU Zheng-fa LI Hong-Liang GE Zhejiang Key Lab of Magnetic Materials China Jiliang University Hangzhou 310018 China

The FeS coated Fe nanoparticles were prepared by using high temperature reactions between the commercial Fe nanoparticles and the S powders in a sealed quartz tube. The simple method developed in this work is effective for large scale synthesis of FeS/Fe nanoparticles with tunable shell/core structures, which can be obtained by controlling the atomic ratio of Fe to S. The structural, magnetic and photocatalytic properties of the nanoparticles were investigated systematically. The good photocatalytic performance originating from the FeS shell in degradation of methylene blue under visible light and the high saturation magnetization originating from the ferromagnetic Fe core make the FeS/Fe nanoparticles a good photocatalyst that can be collected and recycled easily with a magnet. An exchange bias up to tl mT induced in Fe by FeS was observed in the Fe/FeS nanoparticles with ferro/antiferromagnetic interfaces. The enhanced coercivi- ty up to 32 mT was ascribed to the size effect of Fe core.

关键词： magnetic photocatalyst exchange bias FeS coated Fe nanoparticle

L^q Interior Estimates of the Gradient for Weak Solutions of Quasilinear Elliptic Equations

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Acta Mathematica Sinica,English Series 2007年第12期23卷 2225-2234页

作者： feng ping YAO Yong Yong CAI LMAM School of Mathematical Sciences Peking University Bering 100871 P. R. China

The authors present a new proof of L^q interior estimates of the gradient for weak solutions of a quasilinear elliptic equation of p-Laplacian type.

关键词： L^q interior estimates weak solutions quasilinear elliptic maximal function

A New Algorithm for Decomposition of Graphical Models

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Acta Mathematicae Applicatae Sinica 2012年第3期28卷 571-582页

作者： ping-feng XU Jian-hua GUO School of Mathematics and Statistics Northeast Normal UniversityChangchun 130024China School of Basic Science Changchun University of TechnologyChangchun 130012China

In this paper, we combine Leimer＇s algorithm with MCS-M algorithm to decompose graphical models into marginal models on prime blocks. It is shown by experiments that our method has an easier and faster implementation... 详细信息

关键词： decomposition graphical models MCS-M algorithm Leimer's algorithm prime blocks

Solar sail time-optimal interplanetary transfer trajectory design

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Research in Astronomy and Astrophysics 2011年第8期11卷 981-996页

作者： Sheng-ping Gong Yun-feng Gao Jun-feng Li School of Aerospace Tsinghua University Beijing 100084 China

The fuel consumption associated with some interplanetary transfer trajectories using chemical propulsion is not affordable. A solar sail is a method of propulsion that does not consume fuel. Transfer time is one of the most pressing problems of solar sail transfer trajectory design. This paper investigates the time-optimal interplanetary transfer trajectories to a circular orbit of given inclination and radius. The optimal control law is derived from the principle of maximization. An indirect method is used to solve the optimal control problem by selecting values for the initial adjoint vari- ables, which are normalized within a unit sphere. The conditions for the existence of the time-optimal transfer are dependent on the lightness number of the sail and the inclination and radius of the target orbit. A numerical method is used to obtain the boundary values for the time-optimal transfer trajectories. For the cases where no time-optimal transfer trajectories exist, first-order necessary conditions of the optimal control are proposed to obtain feasible solutions. The results show that the transfer time decreases as the minimum distance from the Sun decreases during the transfer duration. For a solar sail with a small lightness number, the transfer time may be evaluated analytically for a three-phase transfer trajectory. The analytical results are compared with previous results and the associated numerical results. The transfer time of the numerical result here is smaller than the transfer time from previous results and is larger than the analytical result.

关键词： techniques: miscellaneous -- solar sail -- solar polar orbit

A sharp gradient estimate for the weighted p-Laplacian

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Applied Mathematics(A Journal of Chinese Universities) 2012年第4期27卷 462-474页

作者： WANG Lin-feng ZHU Yue-ping School of Science Nantong UniversityNantong 226007China

Let M be an n-dimensional complete noncompact Riemannian manifold with sectional curvature bounded from below, dμ = e^h（x） dV（x） the weighted measure and △μ,p the weighted p-Laplacian. In this paper we consider the non-linear elliptic equation △μ,pu=-λμ,p｜u｜^p-2ufor p ∈ （1, 2）. We derive a sharp gradient estimate for positive smooth solutions of this equation. As applications, we get a Harnack inequality and a Liouville type theorem..

关键词： weighted p-Laplacian gradient estimate Harnack inequality Liouville theorem.

High-dimensional *** Problem over Short Intervals

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Acta Mathematica Sinica,English Series 2014年第2期30卷 213-228页

作者： Zhe feng XU Tian ping ZHANG Department of Mathematics Northwest University College of Mathematics and Information Science Shaanxi Normal University

Letk be a positive integer and n a nonnegative integer,0 〈 λ1,...,λk＋1 ≤ 1 be real numbers and w =（λ1,λ2,...,λk＋1）.Let q ≥ max{[1/λi ]：1 ≤ i ≤ k ＋ 1} be a positive integer,and a an integer coprime to *** by N（a,k,w,q,n） the 2n-th moment of（b1··· bk c） with b1··· bk c ≡ a（mod q）,1 ≤ bi≤λiq（i = 1,...,k）,1 ≤ c ≤λk＋1 q and 2（b1＋ ··· ＋ bk ＋ c）.We first use the properties of trigonometric sum and the estimates of n-dimensional Kloosterman sum to give an interesting asymptotic formula for N（a,k,w,q,n）,which generalized the result of *** we use the properties of character sum and the estimates of Dirichlet L-function to sharpen the result of N（a,k,w,q,n） in the case ofw =（1/2,1/2,...,1/2） and n = *** order to show our result is close to the best possible,the mean-square value of N（a,k,q） φk（q）/2k＋2and the mean value weighted by the high-dimensional Cochrane sum are studied too.

关键词： D. H. Lehmer problem short intervals trigonometric sum character sum Cochrane sum

Interest rate swap pricing with default risk under variance gamma process

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Applied Mathematics(A Journal of Chinese Universities) 2017年第1期32卷 93-107页

作者： YANG Xiao-feng YU Jin-ping College of Economics and Management Hangzhou Normal University Hangzhou 311121 China. Zhejiang Yongan Technology Limited Corporation Hangzhou 310014 China.

Under the assumption that the dynamic assets price follows the variance gamma process, we establish a new bilateral pricing model of interest rate swap by integrating the reduced form model for swap pricing and the structural model for default risk *** pricing model preserves the simplicity of the reduced form model and also considers the dynamic evolution of the counterparty assets price by incorporating with the structural model for default risk measurement. We divide the swap pricing framework into two parts, simplifying the pricing model relatively. Simulation results show that, for a one year interest rate swap, a bond spread of one hundred basis points implies a swap credit spread about 0.1054 basis point.

关键词： swap pricing default gamma variance bilateral Brownian assets assumption implies