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Large deviation principles for stationary NA sequences

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Chinese Science Bulletin 1998年第7期43卷 536-540页

作者： hu yijun department of mathematics, wuhan university, wuhan 430072. china department of mathematics Wuhan University Wuhan China

Under general conditions, the large deviation principles for partial sums of stationary NA sequences are proved.

关键词： NA sequence stationary sequence partial sums large deviation principle.

Recent progress and prospects of electrolytes for electrocatalytic nitrogen reduction toward ammonia

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Chinese Chemical Letters 2024年第4期35卷 3-16页

作者： Sajid Mahmood Haiyan Wang Fang Chen yijun Zhong Yong hu Key Laboratory of the Ministry of Education for Advanced Catalysis Materials Department of ChemistryZhejiang Normal UniversityJinhua 321004China The Center for Applied mathematics and Bioinformatics(CAMB) Gulf University for Science and TechnologyMishref 32093Kuwait Hangzhou Institute of Advanced Studies Zhejiang Normal UniversityHangzhou 311231China

Electrochemical nitrogen reduction reaction(ENRR) provides a promising strategy to achieve sustainable synthesis of ammonia. However, despite great efforts devoted to this research field, the problems such as low energy efficiency and weak selectivity still impede its practical implementation. Most of the research to date has been concentrated on creating sophisticated electrocatalysts, and adequate knowledge of electrolytes is still lacking. Herein, the recent progress in electrolytes for ENRR, including alkaline, neutral,acidic, water-in-salt, organic, ionic liquid, and mixed water-organic electrolytes, is thoroughly reviewed to obtain an in-depth understanding of their effects on electrocatalytic performance. Recently developed representative electrocatalysts in various types of electrolytes are also introduced, and future research priorities of different electrolytes are proposed to develop new and efficient ENRR systems.

关键词： Electrocatalytic nitrogen reduction Ammonia Electrolytes Production rate Faradaic efficiency

Risk assessment of agricultural green water security in Northeast china under climate change

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Science china Earth Sciences 2024年第7期67卷 2178-2194页

作者： Jingxuan SUN Guangxin ZHANG Yanfeng WU Liwen CHEN Peng QI Boting hu yijun XU Northeast Institute of Geography and Agroecology.Chinese Academy of Sciences Changchun 130102China university of Chinese Academy of Sciences Beijing 100049China State Key Laboratory of Black Soils Conservation and Utilization Northeast Institute of Geography and AgroecologyChinese Academy of SciencesChangchun 130102China School of Renewable Natural Resources Louisiana State University Agricultural Center227 Highland RoadBaton RougeLA 70803USA

Northeast china is an important base for grain production,dominated by rain-fed agriculture that relies on green ***,in the context of global climate change,rising regional temperatures,changing precipitation patterns,and increasing drought frequency pose threats and challenges to agricultural green water *** study provides a detailed assessment of the spatiotemporal characteristics and development trends of green water security risks in the Northeast region under the base period(2001-2020)and the future(2031-2090)climate change scenarios(SSP245 and SSP585)using the green water scarcity(GWS)index based on raster-scale crop spatial distribution data,Delta downscaling bias-corrected ERA5 data,and CMIP6 multimodal *** the base period,the green water risk-free zone for dry crops is mainly distributed in the center and east of the Northeast region(72.4% of the total area),the low-risk zone is primarily located in the center(14.0%),and the medium-risk(8.3%)and high-risk(5.3%)zones are mostly in the *** SSP245 and SSP585 future climate change scenarios,the green water security risk shows an overall expansion from the west to the center and east,with the low-risk zone increasing to 21.6% and 23.8%,the medium-risk zone increasing to 16.0% and 17.9%,and the high-risk zone increasing to 6.9% and 6.8%,*** dry crops with GWS greater than 0.1 as in need of irrigation,the irrigated area increases from 27.6%(base period)to 44.5%(SSP245)and 48.6%(SSP585),with corresponding increases in irrigation water requirement(IWR)of 4.64 and 5.92 billion m~3,respectively,which further exacerbates conflicts between supply and demand of agricultural water *** response to agricultural green water security risks,coping strategies such as evapotranspiration(ET)-based water resource management for dry crops and deficit irrigation are *** results of this study can provide scientific basis and decision support for the development

关键词： Climate change Food security Green water security risk Irrigation water requirement Green water scarcity

Optimal Portfolio Selection Strategies under Some Constraints

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wuhan university Journal of Natural Sciences 2009年第4期14卷 281-286页

作者： LUO Kui,WANG Guangming,hu yijun School of mathematics and Statistics,wuhan university,wuhan 430072.hubei,china School of mathematics and Statistics Wuhan University Wuhan 430072 Hubei China

A portfolio selection problem for any utility function is introduced, where all the market coefficients are random and the wealth process under any admissible trading strategy is not allowed to be below a benchmark wealth process. The problem is completely solved using a decomposition approach. First, the portfolio selection problem is formulated, and its feasibility is characterized. Then, the problem is decomposed to two steps to solve. After a system of equations for a Lagrange multiplier is solved, the portfolio selection problem is derived as the replicating portfolios of contingent claims. Finally, some simulations are demonstrated.

关键词： portfolio selection Lagrange multiplier stochastic differential equation Monte-Carlo simulation

UNIFORM ESTIMATE ON FINITE TIME RUIN PROBABILITIES WITH RANDOM INTEREST RATE

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Acta Mathematica Scientia 2010年第3期30卷 688-700页

作者：明瑞星何晓霞胡亦钧刘娟 School of mathematics and Information Sciences Jiangxi Normal University School of mathematics and Statistics Wuhan University College of Science Wuhan University of Science and Technology College of mathematics and Statistics Hubei Normal University

We consider a discrete time risk model in which the net payout （insurance risk） {Xk, k = 1, 2,...} are assumed to take real values and belong to the heavy-tailed class L∩ D and the discount factors （financial risk） {Yk, k = 1,2,...} concentrate on [θ, L], where 0 〈 0 〈 1, L 〈 ∞, {Xk, k = 1,2,...}, and {Yk, k=1,2,...} are assumed to be mutually independent. We investigate the asymptotic behavior of the ruin probability within a finite time horizon as the initial capital tends to infinity, and figure out that the convergence holds uniformly for all n ≥ 1, which is different from Tang Q H and Tsitsiashvili G （Adv Appl Prob, 2004, 36： 1278-1299）.

关键词： Random interest rate finite time ruin probability uniformity

OPTIMAL PROPORTIONAL REINSURANCE WITH CONSTANT DIVIDEND BARRIER

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Acta Mathematica Scientia 2010年第3期30卷 791-798页

作者：袁海丽胡亦钧 School of mathematics and Statistics Wuhan University

In this article, we consider an optimal proportional reinsurance with constant dividend barrier. First, we derive the Hamilton-Jacobi-Bellman equation satisfied by the expected discounted dividend payment, and then get the optimal stochastic control and the optimal constant barrier. Secondly, under the optimal constant dividend barrier strategy, we consider the moments of the discounted dividend payment and their explicit expressions are given. Finally, we discuss the Laplace transform of the time of ruin and its explicit expression is also given.

关键词： Stochastic control constant barrier time of ruin expected discounted dividend payment moments Laplace transform of the time of ruin

Synthesis and Structural Determination of (2R,4S,SS)-(+)-Threo-5-(2,2-dichloroacetamido)-4-(4-nitrophenyl)-2-aryl-1,3-dioxanes

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Chinese Chemical Letters 1999年第3期10卷 199-200页

作者： Jun LIU Xian Ming hu Han Sheng XU(department of Chemistry, wuhan university, wuhan 430072. department of Chemistry Wuhan University Wuhan 430072 China

(2R,4S,SS)-(+)-threo-5-(2,2-dicloroacetamido)-4-(4-nitrophenyl-2aryl-l,3dioxanes, were synthesized with high diastereoselectivity and good yields. The structuresofacetals were determined and the configurations were co... 详细信息

关键词： Acetals diastereoselective synthesis chloramphenicol 2D-NMR

Assessment of the Respiratory Disease Mortality Risk from Single and Composite Exposures to PM_(2.5)and Ozone—Guangzhou City,Guangdong Province,china,2018-2021

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china CDC weekly 2024年第34期6卷 857-861,I0001-I0006页

作者： Hongwei Tu yijun hu Keqi hu Peipei Dong Yue Wen Jing Jiang Xuedan Xu Jinxu huang Jiemin Zhu Changyun He Qiuxia Chen Yongying Liu Guangdong Provincial Center for Disease Control and Prevention Guangzhou CityGuangdong ProvinceChina Jinan university Guangzhou CityGuangdong ProvinceChina department of Science and Education Guangdong Second Provincial General HospitalGuangzhou CityGuangdong ProvinceChina Sun Yat-sen university Guangzhou CityGuangdong ProvinceChina

Summary What is already known about this topic?Fine particulate matter(PM_(2.5))and ozone(O_(3))are prevalent pollutants in the atmosphere,which threaten human health,especially the respiratory ***,people are exposed to a mixture of various pollutants in the ***,the single and combined effects of both pollutants need to be investigated.

关键词： environment. ozone Guangdong

The　Construction　of　Statisticaly　Self-similar　Measures

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wuhan university Journal of Natural Sciences 1997年第1期2卷 21-26页

作者： $$$$ hu Dihe department of mathematics,wuhan university,wuhan 430072.china

We have studied statistically self similar measures together with statistically self similar sets in this paper.A special kind of statistically self similar measures has been constructed and a class of statisticall... 详细信息

关键词： statistically self similar random set statistically self similar measure Hausdorff measure Hausdorff metric distribution