Temporal Variations and Driving Factors of Cultivated Land Use Intensity in Shandong Province from 1980 to 2015     

LI Zijun  YU Yuanhe  JIANG Aixia 《资源与生态学报(英文版)》2019,10(3):265-274

Based on the cost-income data of agricultural products and relevant statistical data, taking major grain crops and economic crops in the process of cultivated land use as study cases, we studied characteristics of the temporal variation of cultivated land use intensity and its composition in Shandong Province from 1980 to 2015, and then analyzed its main driving factors. The results showed that: (1) The total intensity of major crops in Shandong Province showed a rising trend from 919.73 Yuan ha^-1 in 1980 to 3285.06 Yuan ha^-1 in 2015, and the average annual intensity of economic crops was higher than that of grain crops. The labor cost and material cost of major crops both showed an increasing trend, but the material input was much higher than labor input for grain crops, while the labor input was much higher than material input for economic crops. (2) The labor intensity of major crops in Shandong Province showed a decreasing trend from 501.75 man-day ha^-1 in 1980 to 161.93 man-day ha^-1 in 2015. The labor intensity of grain crops was lower than that of economic crops and its decline rate was fast. On the contrary, the capital intensity showed an increasing trend from 518.33 Yuan ha^-1 in 1980 to 1159.95 Yuan ha^-1 in 2015. In the internal composition of capital intensity, the proportion of yield-increasing inputs such as seed, farmyard manure, fertilizer, pesticide and drainage and irrigation decreased gradually, while the proportion of labor-saving inputs such as agricultural machinery increased significantly. (3) The cultivated land use intensity in Shandong Province had significant negative correlations with the amount of agricultural labor and cultivated land area per capita. The primary direct driving factor was the net income per unit cost of major crops, but the time response lagged by 1-3 years. The main indirect driving factor was the reform of agricultural policy.  相似文献   

Estimating the maximum impact force of dry granular flow based on pileup characteristics     

XIAO Si-you  SU Li-jun  JIANG Yuan-jun  MEHTAB Alam  LI Cheng  LIU Dao-chuan 《山地科学学报》2019,(10)

The maximum normal impact resultant force(NIRF)is usually regarded as the sum of the static earth pressure of the dead zone and the dynamic impact pressure of the flowing layer.The influence of the interaction between the flowing layer and dead zone on the impact force is ignored.In this study,we classified two impact models with respect to the pileup characteristics of the dead zone.Then,we employed the discrete element method to investigate the influences of the pileup characteristics on the impact force of dry granular flow on a tilted rigid wall.If the final pileup height is equal to the critical value,the maximum NIRF can be estimated using a hydrostatic model,because the main contribution to the maximum NIRF is the static earth pressure of the dead zone.If the final pileup height is less than the critical value,however,the particles in the dead zone are squeezed along the slope surface by the impact ofthe flowing layer on the dead zone,and because of shear effects,the flowing layer causes an entrainment in the dead zone.This results in a decrease in the volume of the dead zone at the moment of maximum NIRF with increases in the slope angle.As such,the maximum NIRF mainly comprises the instant impact force of the flowing layer,so hydro-dynamic models are effective for estimating the maximum NIRF.Impact models will benefit from further study of the components and distribution of the impact force of dry granular flow.  相似文献   

Three Decades of Sea-Ice Variability in Jiaozhou Bay Revealed by Landsat Observations     

HUANG Jue  GUO Lianjie  JIANG Tao  ZHU Hongchun 《中国海洋大学学报(英文版)》2019,(2)

In this study, we used Landsat images and meteorological data to examine the spatiotemporal distribution and variability of sea ice in Jiaozhou Bay(JZB) between 1986 and 2016. The results show that JZB is not always covered by sea ice in winter, but in some extreme cases, sea ice has covered more than one-third of the sea area of the bay. Sea ice in JZB has generally formed between January 1 and February 5, primarily along the coast, and gradually expanding to the central area of the bay. Both meteorological and artificial factors have played important roles in modulating the sea ice distribution. We found sea ice coverage to have been strongly correlated with the accumulated freezing-degree days nine days before the occurrence of sea ice(R2 = 0.767). North-northwest surface winds have dominated the freezing period of sea water in the JZB, and wind speed has exerted a more significant influence on the formation of sea ice when the sea ice coverage has been generally small. Additionally, artificial factors began to affect the expansion of sea ice in JZB since 2007. The construction of the Jiao-Zhou-Bay Bridge(JZBB) is believed to have retarded water flow and reduced the tidal prism, thereby leading to the formation of an ice bridge along the JZBB, which effectively prevents the southward expansion of sea ice.  相似文献   

褚绍唐先生的学术思想与贡献     

周维国  张佳琦  段玉山  蒋连飞  郭锋涛 《地理学报》2019,74(8):1695-1706

褚绍唐先生是中国著名的地理教育家,历史地理学家,华东师范大学地理系教授。褚先生的地理教育思想构建起了中国中小学地理教育教学与研究的基本框架,先生组织发起的地理教育学术组织和创办的学术期刊仍发挥着巨大作用,先生编写的中小学地理教学大纲和教材惠及数代人。褚先生对上海历史地理的研究颇有建树,对上海的城市发展过程、成陆过程,水系变化等有独特见解。褚先生对《徐霞客游记》的整理和校点工作具有划时代意义,同时,先生也是徐霞客研究领域的大师。此外,褚先生还在城市地理学、地图学、地理文献翻译等领域做出了贡献。  相似文献   

一种旋转塑性势面模型及非关联塑性流动法则     

徐日庆  蒋佳琪  冯苏阳  鞠露莹 《岩土力学》2020,41(5):1474-1482

为了较好地描述软土塑性应变发展规律，提出了一种改进的塑性流动模型。该模型采用了与屈服函数形式相同，但具有一定倾角 的塑性势函数。土体在变形过程中，塑性流动方向会依赖于塑性势面的旋转而变化，直至达到破坏状态。通过对常规三轴试验结果的分析可以发现：在剪切过程中，塑性势面旋转角的初值 与终值 较为稳定，不受围压变化影响。在此试验观察基础上，引入了归一化的旋转角参数 以及描述土体应力状态的参数 ，在采用蛋形势函数的情况下二者具有良好的分段线性关系。利用该关系，建立了改进的塑性流动法则，只需要2个额外的模型参数。对所提出的塑性流动模型进行了验证，计算结果表明该模型能较好地反映塑性应变的变化趋势。  相似文献   

闽中南平—宁化构造带南华纪陆缘弧岩浆活动：对武夷造山带构造演化的新启示     

姜杨  赵希林  李龙明  潘桂棠  徐敏成  黄文成  刘欢 《中国地质》2020,47(4):1010-1024

南平—宁化构造带沿线出露着以万全岩群和楼前组、西溪组等为代表的一系列新元古代火山-沉积岩系。系统的岩石学、年代学和地球化学研究表明,福建明溪和江西瑞金地区的楼前组浅变质英安岩和晶屑凝灰岩分别形成于(729±4)Ma和(735±6.7)Ma(LA-ICP-MS锆石U-Pb法),SiO2含量变化在65.22%～74.54%,相对富Al2O3(11.05%～16.80%)富碱(Na2O+K2O=4.88%～10.19%)而贫CaO、MgO和FeOT,ANK值和A/CNK值分别为1.23～1.78和0.98～1.57,Nb/Ta=12.44～17.28,Nd/Th=2.07～3.51,Ti/Zr=6.08～10.37,Ti/Y=68.51～154.71,属过铝质S型火山岩;明显富集大离子亲石元素(Ba、Rb等)而亏损高场强元素(Nb、Ta、Ti、P等),Zr/Nb=16.65～24.07,Th/Ta=12.94～16.93,δEu呈现明显负异常(0.33～0.62),显示岛弧岩浆岩的地球化学特征。综合区域地质资料及前人研究结果提出,南平—宁化一线在713 Ma前为活动大陆边缘环境,洋壳俯冲引发的岩浆活动形成了沿南平—宁化—瑞金一线展布的陆缘弧中酸性火山岩带,暗示此时南、北武夷之间尚未拼合形成统一的武夷地块,因而华夏地块不存在统一的前南华纪结晶基底。  相似文献   

Effect of Shale Reservoir Characteristics on Shale Oil Movability in the Lower Third Member of the Shahejie Formation,Zhanhua Sag     

NING Chuanxiang  MA Zhongliang  JIANG Zhenxue  SU Siyuan  LI Tingwei  ZHENG Lunju  WANG Guozhen  LI Fengxun 《《地质学报》英文版》2020,94(2):352-363

To reveal the effect of shale reservoir characteristics on the movability of shale oil and its action mechanism in the lower third member of the Shahejie Formation(Es3l), samples with different features were selected and analyzed using N2 adsorption, high-pressure mercury injection capillary pressure(MICP), nuclear magnetic resonance(NMR), high-speed centrifugation, and displacement image techniques. The results show that shale pore structure characteristics control shale oil movability directly. Movable oil saturation has a positive relationship with pore volume for radius > 2 μm, as larger pores often have higher movable oil saturation, indicating that movable oil is present in relatively larger pores. The main reasons for this are as follows. The relatively smaller pores often have oil-wetting properties because of organic matter, which has an unfavorable effect on the flow of oil, while the relatively larger pores are often wetted by water, which is helpful to shale oil movability. The rich surface provided by the relatively smaller pores is beneficial to the adsorption of immovable oil. Meanwhile, the relatively larger pores create significant pore volume for movable oil. Moreover, the larger pores often have good pore connectivity. Pores and fractures are interconnected to form a complex fracture network, which provides a good permeability channel for shale oil flow. The smaller pores are mostly distributed separately;thus, they are not conducive to the flow of shale oil. The mineral composition and fabric macroscopically affect the movability of shale oil. Calcite plays an active role in shale oil movability by increasing the brittleness of shale and is more likely to form micro-cracks under the same stress background. Clay does not utilize shale oil flow because of its large specific surface area and its block effect. The bedding structure increases the large-scale storage space and improves the connectivity of pores at different scales, which is conducive to the movability of shale oil.  相似文献   

利用背景噪声成像研究合肥-金华剖面地壳速度结构及径向各向异性的东西差异   总被引：3，自引：1，他引：2       下载免费PDF全文

吴珊珊  姜明明  何玉梅  赵亮  艾印双 《地球物理学报》2018,61(2):584-592

背景噪声成像能够为地壳内部结构提供地震波速的观测证据，能够增进对地壳结构与物性的认识.本文利用背景噪声成像方法对合肥-金华流动地震台阵55个台站数据进行了分析反演，获得了华北克拉通与华南块体东部构造边界附近区域的地壳S波速度与径向各向异性结构.成像结果表明，以东经118°-118.5°附近为界，西北部表现为地壳低速异常和中下地壳正的径向各向异性，东南部表现为地壳高速异常，下部地壳存在负的径向各向异性.由此，本文推测地震波速结构差异反映了地壳内部物质与温度的差异，这种差异与两个地区自中生代晚期以来经历了截然不同的岩浆活动相关.  相似文献   

饱和土体-地下综合管廊结构地震响应分析          下载免费PDF全文

蒋录珍  李双飞  石文倩  安军海  陈艳华 《地震工程学报》2018,40(6):1224-1230

将土体视为固-液两相介质,基于饱和土体有效应力原理,建立饱和土体-地下综合管廊结构体系相互作用动力模型:在地应力平衡的静力状态下采用Duncan-Chang非线性弹性本构模型,在地震波作用的动力状态下采用Davidenkov非线性黏弹性本构模型;考虑饱和土体黏弹性动力人工边界条件,将地震动作用转化为作用在人工边界节点上的动力荷载。模型考察不同地震波时程、地震波加速度峰值、入射角度、孔隙率以及地应力场的影响,得出如下结论:(1)地震波的卓越周期与场地卓越周期相近时引起结构上的变形最大;随着地震波加速度峰值的增大结构变形增大;随着地震波入射角度的增加结构变形增大,地震波斜入射情况下产生的行波效应使得结构变形最大。(2)土体材料的孔隙水压力是影响地震中结构变形的主要因素之一。(3)将土体材料考虑为单相介质时结构上的变形要比考虑为固-液两相介质时大得多,直接将饱和土体场地中得到的地震波等效荷载施加到单相土介质-结构动力相互作用模型上,能够得到与完全基于有效应力法一致的结果。  相似文献   

基于纹理和空间特征的中分辨率影像滨海水产养殖用地提取研究     

王雪峰  冯雪  苏奋振  张宇  王武霞  蒋会平 《地球信息科学学报》2018,20(5):694-702

近年来,水产养殖用地分布广泛,但由于其在影像上所表现的复杂性和不均匀性,造成该用地类型提取中的困难,尤其针对中分辨率遥感影像。对此,本文提出了一种基于纹理和空间特征的养殖用地提取方法,该方法主要包括3个步骤：首先,利用纹理熵和归一化差异水体指数NDWI实现水产养殖用地的粗提取;然后,依据相邻地物间的关系实现同类型地物合并;最后,本文构建一种相对宽度作为地物的近似宽度,再次利用NDWI实现水产养殖用地的准确识别。本文以越南万丰湾为研究区域,以Landat-8融合影像（融合后的像元大小为15 m）的目视解译结果为标准,对本文方法与最小距离法分类结果进行比较。实验结果表明,该方法的精度可达91.13%,远高于传统的面向对象方法,并且所提方法的错误率和虚假率分别为0.09%和8.87％,表明了该方法可靠性,因而该方法可为基于中分辨率影像的地物类型提取提供一种有效手段。  相似文献