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Impact of Climate Change and Grazing on Temperate Steppe

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Journal of Integrative Agriculture 2014年第6期13卷 1155-1156页

作者： HOU xiang-yang Member of JIA Editorial Board Key Laboratory of Grassland Resources and Ecology Ministry of Agriculture/Grassland Research Institute/Research Center of the Eurasian Temperate Grasslands Chinese Academy of Agricultural Sciences

Ecosystem of eastern Eurasian steppe is facing more and more challenges of global issues such as climate change, food and ecological security and human excessive utilization since the 21st century. Facing on the increasingly prominent international issues, it is very essential for relevant countries, international organizations and domestic counterparts to enhance systematic and mutual cooperation and exchanges to carry out scientific research and develop protection practice on the Eurasian steppe.

关键词： Impact of Climate Change and Grazing on Temperate Steppe

Adjoining Batch Markov Arrival Processes of a Markov Chain

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Acta Mathematicae Applicatae Sinica 2018年第1期34卷 1-10页

作者： Xiao-yun MO Xu-yan xiang xiang-qun yang College of Mathematics and Statistics Hunan University of Finance and Economics Changsha 410205 China College of Mathematics and Computational Science Hunan University of Arts and Science Changde 415000 China Key Laboratory of High performance Computing and Stochastic Information Processing Ministry of Education of China College of Mathematics and Computer Science Hunan Normal University Changsha 410081 China Hunan Province Cooperative Innovation Center for the Construction and Development of Dongting Lake Ecological Economic Zone Changde 415000 China

A batch Markov arrival process（BMAP） X^＊=（N, J） is a 2-dimensional Markov process with two components, one is the counting process N and the other one is the phase process J. It is proved that the phase process is a time-homogeneous Markov chain with a finite state-space, or for short, Markov chain. In this paper,a new and inverse problem is proposed firstly： given a Markov chain J, can we deploy a process N such that the 2-dimensional process X^＊=（N, J） is a BMAP？ The process X^＊=（N, J） is said to be an adjoining BMAP for the Markov chain J. For a given Markov chain the adjoining processes exist and they are not unique. Two kinds of adjoining BMAPs have been constructed. One is the BMAPs with fixed constant batches, the other one is the BMAPs with independent and identically distributed（i.i.d） random batches. The method we used in this paper is not the usual matrix-analytic method of studying BMAP, it is a path-analytic method. We constructed directly sample paths of adjoining BMAPs. The expressions of characteristic（D_k, k = 0, 1, 2· · ·）and transition probabilities of the adjoining BMAP are obtained by the density matrix Q of the given Markov chain J. Moreover, we obtained two frontal Theorems. We present these expressions in the first time.

关键词： Markov chain batch Markov arrival process (BMAP) adjoining BMAP fixed constant batch independent identically distributed (i.i.d) random batch

Option Pricing by Mean Correcting Method for Non-Gaussian Lvy Processes

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Acta Mathematica Sinica,English Series 2013年第10期29卷 1927-1938页

作者： Luo Gen YAO Gang yang xiang Qun yang School of Mathematics and Statistics Hu'nan Business College College of Mathematics and Computer Science Hu'nan Normal University

For a non-Gaussian Levy model, it is shown that if the model exists a trivial arbitrage-free interval, option pricing by mean correcting method is always arbitrage-free, and if the arbitrage-free interval is non-trivial, this pricing method may lead to arbitrage in some cases. In the latter case, some necessary and sufficient conditions under which option price is arbitrage-free are obtained.

关键词： Non-Gaussian Levy processes mean correcting method option pricing

Application of Moore-Penrose Inverse in Deciding the Minimal Martingale Measure

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Acta Mathematicae Applicatae Sinica 2010年第4期26卷 653-660页

作者： Luo-gen Yao Gang yang xiang-qun yang Information Department of Hunan Business College Changsha 410205China College of Mathematics and Computer Science Hunan Normal UniversityChangsha 410081China

The Moore-Penrose inverse is an important tool in *** paper shows that the MoorePenrose inverse is also an effcient technique in determining the minimal martingale measure if a security price follows a semi-martingale which satisfies some structure *** extend a result of Dzhaparidze and Spreij concerning the Moore-Penrose inverse to the case that the Moore-Penrose inverse of any matrix-valued predictable process is still ***,we obtain an explicit formula of the minimal martingale measure by employing the Moore-Penrose ***,the minimal martingale measure in a generalized Black-Scholes model is found.

关键词： Moore-Penrose inverse minimal martingale measure semi-martingales structure condition

Computationally efficient 2-D DOA estimation for non-uniform two-L-shaped array

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The Journal of China Universities of Posts and Telecommunications 2018年第6期25卷 81-89页

作者： yang Jinsheng xiang yang Chen Weigang Dong yangyang School of Microelectronics Tianjin UniversityTianjin 300072China Joint Laboratory for Ocean Observation and Detection National Laboratory for Marine Science and TechnologyQingdao 266237China School of Electronics Engineering Xidian UniversityXi'an 710071China

A two-dimensional direction-of-arrival(DOA) estimation method for non-uniform two-L-shaped array is presented in which the element spacing is larger than half-wavelength. To extract automatically paired low-variance cyclically ambiguous direction cosines and high-variance unambiguous direction cosines from the sub-blocks, the proposed method constructs and partitions the cross-correlation matrices. Then, the low-variance unambiguous direction cosines are obtained using the ambiguity resolved technique. Simulation results demonstrate that the proposed method has lower computation complexity and higher resolution than the existing methods especially when the elevation angles are between 70 and 90 degrees.

关键词： aperture extension two-dimensional DOA estimation cross-correlation matrix ambiguity resolved

The mean correcting martingale measures for exponential additive processes

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Applied Mathematics(A Journal of Chinese Universities) 2016年第1期31卷 81-88页

作者： YAO Luo-gen yang Gang yang xiang-qun School of Mathematics and Statistics Hunan University of Commerce Changsha 410205 China College of Mathematics and Computer Science Hunan Normal University Changsha 410081 China

The mean correcting martingale measure for the stochastic process defined as the exponential of an additive process is constructed. Necessary and sufficient conditions for the existence of mean correcting martingale are also obtained. The investigation of this paper will establish a unified way that is applicable both to the case of Ldvy processes and that of the sums of independent random variables. As an application, we present the necessary and sufficient conditions that the discounted stock price process is a martingale.

关键词： Mean correcting martingale measure additive processes option pricing.

On skin friction in wall-bounded turbulence

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Acta Mechanica Sinica 2021年第4期37卷 589-598,I0002页

作者： Zhenhua Xia Peng Zhang xiang I.A.yang Department of Engineering Mechanics Zhejiang UniversityHangzhou 310027China Mechanical Engineering Pennsylvania State UniversityState CollegePA 16802USA

In this paper,we derive mathematical formulas for the skin friction coefficient in wall-bounded turbulence based on the Reynolds averaged streamwise momentum equation and the total ***,with a theoretical or empirical relation of the total stress,the skin friction coefficient is expressed in terms of the mean velocity and the Reynolds shear stress in an arbitrary wall-normal region[h〇,h\].The formulas are validated using direct numerical simulation data of turbulent channel and boundary layer flows,and the results show that our formulas estimate the skin friction coefficient very accurately with an error less than 2%.The present integral formula can be used to determine the skin friction in turbulent channel and boundary layer flows at high Reynolds numbers where the near-wall statistics are very difficult to measure accurately.

关键词： Wall-bounded turbulence Skin friction Integral formula

Catalytic Preparation of Methyl Formate from Methanol over Silver

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Chemical Research in Chinese Universities 2005年第5期21卷 573-576页

作者： yang Zhi LI Jing yang xiang-guang WU Yue Changchun Institute of Applied Chemistry Chinese Academy of Sciences Changchun 130022 P. R. China Graduate School Chinese Academy of Sciences Belting 100039 P. R. China

A catalytic reaction over a silver catalyst performed in an unregarded temperature region（473-873 K） with a long catalytic lifetime for the production of methyl formate from methanol was provided as a potential preparing route. The optimal yield of methyl formate（ca. 14. 8% ） with a selectivity 〉90% was obtained at about 573 K. Because α- oxygen species and bulk oxygen species coexist in the unregarded temperature region, a synergistic process concerning α-oxygen species and bulk oxygen species was proved over Oα -rich and Oγ-rich samples.

关键词： Silver Methanol Methyl formate Oxygen species Svnergistic effect

Reynolds-number scaling analysis on lift generation of a flapping and passive rotating wing with an inhomogeneous mass distribution

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Chinese Journal of Aeronautics 2024年第2期37卷 259-269页

作者： Suyang QIN Haotian HANG yang xiang Hong LIU J.C.Wu center for aerodynamics school of aeronautics and astronauticsshanghai jiao tong universityshanghai 200240china

Insects usually fly by passively rotating wings,which has been applied to the design of flapping-wing Micro-Air Vehicles(MAVs)to reduce mechanical *** this paper,a robotic passive rotating-wing model is designed to investigate wing kinematics and lift generation,which are measured by a high-speed camera and a force transducer,*** addition,flow fields are measured using the Particle Image Velocimetry(PIV).Experimental results demonstrate that passive rotating motion has a coordinative relationship with actively stroking *** the stroke amplitude or frequency increases,the rotating amplitude is *** characterize the active stroking motion,a driving Reynolds number Redrivingis defined,which varies from 68 to 366 in this *** the gravity center of the wing towards trailing ed ge induces the increase of additional torque M,which decreases the wing rotating amplitude and promotes the advance of wing *** find that the timing of wing rotation is gradually delayed and the mean lift coefficient C^(-)_(L)monotonously decreases as *** increasing the additional torque M,C^(-)_(L)is slightly improved and approaches to the lift coefficient of a real fruit fly at driving Re approximately equal to *** instantaneous lifts combined with the vortical structures further demonstrate that the lift generation associated with wing rotation is mainly attributed to the growth of the LeadingEdge Vortex(LEV)and the passive wake capture *** wake capture is influenced by LEV,reversal stroke motion and wing additional torque together,which can only maintain the lift at a high level for a considerable *** high-lift generation mechanisms of flapping and passive rotating flight could shed light on the simplified design of MAVs and the improvement of their aerodynamic performance.

关键词： Flapping flight Unsteady lift Passive rotation Vortex flow Leading-edge vortex