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What Determines China's Grain Imports and Self-sufficiency? The Role of Rising Domestic Costs and Varying World Market Prices

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China & World Economy 2019年第5期27卷 1-24页

作者： wusheng yu Tianxiang Li Jing Zhu Department of Food and Resource Economics University of CopenhagenDenmark College of Economics & Management Nanjing Agricultural UniversityChina China Center for Food Security Studies Nanjing Agricultural UniversityChina

China s grain sectors have faced unprecedented challenges in recent years as the ever-increasing and historically high level of grain output has failed to reduce grain imports. On the contrary, high grain imports and high domestic stock have accompanied historically high domestic output, a situation dubbed the "triple high" phenomenon in current policy discussion. This paper explores the role of widening domestic-world market price gaps in determining the triple high phenomenon.Unlike earlier studies that relied on production capacities, this paper argues that domestic production and demand (hence imports) are functions of domestic and world market prices and proposes an analytical framework to explicitly capture such price gaps under restricted trade linkages in general equilibrium. Following this approach, a set of price scenarios for the 2011-2020 period are constructed and simulated in a computable general equilibrium model. Results from the core scenarios, in which recent domestic and world market price trends are assumed to continue, suggest that further widening price gaps would substantially increase grain imports and reduce domestic output (by 60 million tons) and self-sufficiency ratios from base levels. In the alternative scenarios with larger (smaller) price gaps, we find higher (lower) imports and larger (smaller) decreases in domestic output and self-sufficiency ratios. Such results provide important policy implications as China's agricultural policy undergoes significant adjustment.

关键词： computable general equilibrium model domestic-world market price gaps food security grain imports self-sufficiency ratio triple high

Stable isotopic compositions of precipitation events from Kathmandu, southern slope of the Himalayas

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Chinese Science Bulletin 2014年第34期59卷 4838-4846页

作者： Tek Bahadur Chhetri Tandong Yao wusheng yu Li Ding Daniel Joswiak Lide Tian Lochan Prasad Devkota Dongmei Qu Key Laboratory of Tibetan Environment Changes and Land Surface Processes Institute of Tibetan Plateau ResearchChinese Academy of Sciences University of Chinese Academy of Sciences Central Department of Hydrology and Meteorology Tribhuvan University Kathmandu Nepal Yinchuan Meteorological Administration

Investigation of temporal variations in the stable d18 O and d D isotopes from Kathmandu's precipitation events shows that the relatively enriched d18 O and d D values in the winter(the dry season, dominated by the westerlies) were positively correlated with temperature,indicating a temperature effect controlling the changes of d18 O and d D. However, the d18 O and d D values were depleted in the summer(the wet season, dominated by the Indian monsoon), which were negatively correlated with precipitation amount, indicating an amount effect. In addition, the comparison of stable isotopes in precipitation from Kathmandu and Mawlong(near the Bay of Bengal)shows that the overall trends of d18 O and d D values at Kathmandu generally approximate those at Mawlong.However, there remain many differences between the details of the isotopic changes at Kathmandu versus those at Mawlong. Compared with those at Mawlong, the further rainout effect and the more intense lift effect of the oceanic moisture by the high mountains resulted in the moredepleted d18 O and d D values in summer precipitation at Kathmandu. A deuterium excess and the local meteoric water lines reveal that evaporation at Kathmandu exceeds that at Mawlong. The data also show that the Indian monsoon activities at Mawlong are more intense than those at Kathmandu.

关键词：同位素组成稳定同位素降水事件喜马拉雅山南坡温度效应印度季风夏季降水

Isotopic composition of atmospheric water vapor before and after the monsoon＇s end in the Nagqu River Basin

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Chinese Science Bulletin 2005年第23期50卷 2755-2760页

作者： yu wusheng YAO Tandong TIAN Lide WANG yu YIN Changliang Key Laboratory of Cryosphere and Environment Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 China Key Laboratory of Cryosphere and Environment Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China

Atmospheric water vapor samples were col-lected in the Nagqu River Basin in the middle of Tibetan Plateau between August and October in 2004. Results show that there exist some fluctuations of the δ 18O of atmospheric water vapor, especially before and after the monsoon’s end. Moreover, the variety trend of the δ 18O of atmospheric water vapor inverse correlates with that of dew point. Precipitation events make an important effect upon the variation of δ 18O of atmospheric water vapor. During the whole sampling pe-riod, the δ 18O values of atmospheric water vapor are low while precipitation events occurred. The moisture origins also contribute to the variation of δ 18O of atmospheric water vapor. The oceanic moisture transported by the southwest monsoon results in lower δ18O of atmospheric water vapor in the Nagqu River Basin. Compared with the influence of the oceanic moisture, the δ 18O values, however, appear high re-sulting from the effect of the continental air mass in this re-gion.

关键词：那曲河流域西藏氧同位素大气水蒸气季风

Temporal and spatial variations of δ^18O in precipitation of the Yarlung Zangbo River Basin

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Journal of Geographical Sciences 2007年第3期17卷 317-326页

作者： LIU Zhongfang TIAN Lide YAO Tandong GONG Tongliang YIN Changliang yu wusheng Institute of Tibetan Plateau Research CAS Beijing 100085 China Key Laboratory of Cryosphere and Environment Cold and Arid Regions Environmental and Engineering Research Institute CAS Lanzhou 730000 China Institute of Tibetan Water Resource Reconnaissance and Designing Lhasa 850000 China

This paper reveals the temporal and spatial variations of stable isotope in precipitation of the Yarlung Zangbo River Basin based on the variations of δ^18O in precipitation at four stations （Lhaze, Nugesha, Yangcun and Nuxia） in 2005. The results show that δ^18O of precipitation has distinct seasonal changes in the Yarlung Zangbo River Basin. The higher value of δ^18O occurs in spring prior to monsoon precipitation, and the lower value occurs during monsoon precipitation. From the spatial variations, with the altitude-effect and rainout process during moisture transport along the Yarlung Zangbo River Valley, δ^18O of precipitation is gradually depleted. Thus, δ^18O of precipitation decreases gradually from the downstream to the upstream, and the lapse rate of δ^18O in precipitation is approximately 0.34‰/100m and 0.7%J‰/100km for the two reasons. During monsoon precipitation, spatial variation of δ^18O in precipitation is dominated by the amount effect in the large scale synoptic condition.

关键词： Yarlung Zangbo River Basin δ^18O precipitation temporal and spatial variations

Seasonal variations of stable isotope in precipitation and moisture transport at yushu,eastern Tibetan Plateau

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Science China Earth Sciences 2008年第8期51卷 1121-1128页

作者： TIAN LiDe MA LingLong yu wusheng LIU ZhongFang YIN ChangLiang ZHAO ZhongPing TANG Wei WANG yu Laboratory of Tibetan Environment Changes and Land Surface Processes Institute of Tibetan Plateau ResearchChinese Academy of SciencesBeijing 100085China State Key Laboratory of Cryosphere Sciences Chinese Academy of SciencesLanzhou 730000China

Precipitation δ 18O at yushu, eastern Tibetan Plateau, shows strong fluctuation and lack of clear seasonality. The seasonal pattern of precipitation stable isotope at yushu is apparently different from either that of the southwest monsoon region to the south or that of the inland region to the north. This different seasonal pattern probably reflects the shift of different moisture sources. In this paper, we present the spatial comparison of the seasonal patterns of precipitation δ 18O, and calculate the moisture transport flux by using the NCAR/NCEP reanalysis data. This allows us to discuss the relation between moisture transport flux and precipitation δ 18O. This study shows that both the southwest monsoon from south and inland air mass transport from north affected the seasonal precipitation δ 18O at yushu, eastern Tibetan Plateau. Southwest monsoon brings the main part of the moisture, but southwest transport flux is weaker than in the southern part of the Tibetan Plateau. However, contribution of the inland moisture from north or local evaporation moisture is enhanced. The combined effect is the strong fluctuation of summer precipitation δ 18O at yushu and comparatively poor seasonality.

关键词： Tibetan Plateau yushu precipitation stable isotope moisture transport

Study on ChemFET NO_2 Gas Sensor Array

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稀有金属材料与工程 2006年第A3期35卷 104-105页

作者： Guangzhong Xie Junsheng yu Huilin Tai wusheng Suo Yadong Jiang Bangchao Yang School of Optoelectronic Information University of Electronic Science ＆ Technology of China Chengdu 610054 China School of Microelectronics and Solid-State Electronics University of Electronic Science ＆ Technology of China Chengdu 610054 China

Based on conventional metal-oxide-semiconductor field-effect transistor (MOSFET),a novel kind of chemical field-effect transistor (ChemFET) gas sensor array has been designed and fabricated.The obtained sensor consists of self-assembly polyaniline (PAN) composite film containing poly(acrylic acid) (PAA) which was used as gate material of MOSFET instead of conventional metallic gate.The UV-Vis absorption spectra of PAN/PAA films were characterized.The NO_2 gas sensitive property of the ChemFET sensor array was also investigated.Results show that the drain current of devices increases with increasing of back-side voltage,and decreases with the increase of NO_2 concentration when the NO_2 concentration is below 20μg/g.The temperature dependence of ChemFET sensor array shows that the drain current of ChemFET sensor decreases with increasing of temperature.

关键词： NO2 sensitivity ChemFET sensor self-assembly polyaniline poly (acrylic acid)

Glacial distribution and mass balance in the Yarlung Zangbo River and its influence on lakes

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Chinese Science Bulletin 2010年第20期55卷 2072-2078页

作者： YAO TanDong LI ZhiGuo YANG Wei GUO XueJun ZHU LiPing KANG ShiChang WU YanHong yu wusheng Key Laboratory of Tibetan Environment Changes & Land Surface Processes Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China State Key Laboratory of Cryosphere Chinese Academy of Sciences Lanzhou 730000 China Key Laboratory of Digital Earth Sciences Center for Earth Observation and Digital Earth Chinese Academy of Sciences Beijing 100190 China

Glaciers in the Yarlung Zangbo River witness severe glacial retreat nowadays,which gives important influence on lake processes in the region.We have studied glacial distribution,glacial mass balance and found large deficit in glacial mass and its impact in the region.Our study also integrated the variation in glacial-fed lakes of the Nam Co and Ranwu Lake,and presented an initial assessment of the impact of glacial mass balance on lakes.The study has shown a significant contribution of glacial melting to recent lake expansion and lake level rising.

关键词：冰川物质平衡冰川分布雅鲁藏布江湖泊变化冰川退缩冰川融化纳木错上升

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饱和过程中黏土岩变形和水化膨胀特性研究

岩石力学与工程学报 2022年第S2期41卷 3534-3542页

作者：于洪丹陈卫忠谭贤君雷江赵武胜中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室湖北武汉430071 陕西省交通规划设计研究院有限公司陕西西安710065

在原位状态下,黏土岩呈现饱和状态,而在实际实验室研究中,由于钻孔取芯、运输、储存和加工等因素的影响,黏土岩已经失水并呈现非饱和状态。因此,在试验测试前将黏土岩尽量恢复至原位饱和状态是进一步试验测试的重要前提。本文以黏土岩... 详细信息

在原位状态下,黏土岩呈现饱和状态,而在实际实验室研究中,由于钻孔取芯、运输、储存和加工等因素的影响,黏土岩已经失水并呈现非饱和状态。因此,在试验测试前将黏土岩尽量恢复至原位饱和状态是进一步试验测试的重要前提。本文以黏土岩为研究对象,通过无外力作用的黏土岩饱水试验及原位应力下的饱和试验,重点研究饱和过程中黏土岩的变形规律及水化膨胀特性。试验研究表明:无外力作用下,含中心圆孔黏土岩由于饱水过程中黏土矿物的水化膨胀、崩解、混和堆积逐步充填原有的孔洞;在原位应力作用下,水溶液作用仍使黏土岩内部黏土矿物快速水化膨胀,宏观上表现为试样体积迅速膨胀的同时孔隙度显著增大,且膨胀变形量与试样初始饱和度呈现负相关;在试验研究基础上,基于Comsol Multiphysics多场耦合有限元软件中的流体流动模块,建立黏土岩渗流-应力耦合数学模型,进行原位应力下黏土岩饱和过程的数值仿真,重点分析饱和过程中黏土岩试样内部孔隙水压力及饱和度随时间的演化规律;探讨饱和过程中黏土岩的孔压系数B值,并进一步分析加载步骤对黏土岩饱和过程的影响。研究结果将对黏土岩等岩石物理力学特性的相关研究提供试验指导及理论依据。

关键词：岩石力学黏土岩饱和变形规律水化膨胀

不同麻醉方式对糖尿病手术患者血流动力学的影响

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中外医学研究 2023年第29期21卷 148-152页

作者：苏宇黄武生高州市中医院广东高州525200

目的:分析不同麻醉方式对糖尿病手术患者血流动力学的影响。方法:选择2020年5月—2022年5月高州市中医院收治的70例糖尿病手术患者,以抽签法按序分为研究组和对照组,各35例。为研究组提供全身麻醉联合硬膜外阻滞麻醉,对照组则提供全身... 详细信息

目的:分析不同麻醉方式对糖尿病手术患者血流动力学的影响。方法:选择2020年5月—2022年5月高州市中医院收治的70例糖尿病手术患者,以抽签法按序分为研究组和对照组,各35例。为研究组提供全身麻醉联合硬膜外阻滞麻醉,对照组则提供全身麻醉。对比两组不同时点的空腹血糖和糖化血红蛋白、疼痛评分、血流动力学指标及术后感染发生率。结果:插管后5 min和手术开始时,两组空腹血糖和糖化血红蛋白比较,差异无统计学意义(P>0.05);手术开始后30 min及手术完成时,研究组空腹血糖和糖化血红蛋白均明显低于对照组,差异有统计学意义(P0.05);手术开始后30 min及手术完成时,研究组收缩压和舒张压均明显低于对照组,差异有统计学意义(P<0.05)。研究组术后72 h的感染发生率为14.29%(5/35),明显低于对照组的42.86%(15/35),差异有统计学意义(χ^(2)=7.000,P=0.008)。结论:糖尿病手术患者采用全身麻醉联合硬膜外阻滞麻醉有助于稳定术中血流动力学指标,降低血糖波动幅度。

关键词：全身麻醉硬膜外阻滞麻醉糖尿病血流动力