基于耦合机制的水产养殖和捕捞的协调发展          下载免费PDF全文

苗利明  杨正勇  张迪 《海洋开发与管理》2019,36(8):59-62

为促进我国水产养殖和捕捞的协调发展,进而促进水产业的整体发展,文章基于水产养殖和捕捞的耦合机制,通过建立耦合协调度模型和评价指标体系,定量分析二者的发展水平和协同效应。研究结果表明:从经济、生态和社会角度,水产养殖和捕捞具有相互作用和共同发展的联动机制;根据综合评价指数和耦合协调度的计算,2007-2016年水产养殖和捕捞的发展水平总体向好,协调等级从极度失调向初级协调转变,二者协同效应增强;水产养殖和捕捞的关系是动态的,须把握"度",促进二者协调发展。  相似文献   

徐州市水土流失时空变化研究     

陈报章  渠俊峰  葛梦玉  沈艳文  王安妮  王国斌 《地球信息科学学报》2018,20(11):1622-1630

本文以3S技术为支撑,在修正水土流失方程（RUSLE）的基础上,针对徐州黄泛平原-丘陵地带的特殊地形地貌、对2000年以来徐州市水土流失时空变化特征进行了分析。结果表明：2000-2014年徐州市土壤侵蚀等级以微度为主,微度侵蚀面积占总侵蚀面积多年平均达到76.34%;中度侵蚀次之,所占比例在10%~17%间;剧烈侵蚀所占比例最少。轻度及以上土壤侵蚀等级主要发生在中部微山湖下游、京杭大运河一带的丘陵岗地地区、主城区与故黄河北岸的黄泛平原地区,以及丰县、新沂、邳州的局部区域;土壤侵蚀存在一定程度年际变化特征,睢宁、丰县、邳州的部分地区侵蚀面积年际变化较为明显,土壤侵蚀总面积整体上呈现下降趋势。  相似文献   

Quantifying the impacts of climate change and land use on hydrological processes: A comparison between mountain and lowland agricultural watersheds     

Zhen Cui  Jiacong Huang  Feng Tian  Junfeng Gao  Xuesong Wang  Jun Li 《水文研究》2020,34(26):5370-5383

Mountain and lowland watersheds are two distinct geographical units with considerably different hydrological processes. Understanding their hydrological processes in the context of future climate change and land use scenarios is important for water resource management. This study investigated hydrological processes and their driving factors and eco-hydrological impacts for these two geographical units in the Xitiaoxi watershed, East China, and quantified their differences through hydrological modelling. Hydrological processes in 24 mountain watersheds and 143 lowland watersheds were simulated based on a raster-based Xin'anjiang model and a Nitrogen Dynamic Polder (NDP) model, respectively. These two models were calibrated and validated with an acceptable performance (Nash-Sutcliffe efficiency coefficients of 0.81 and 0.50, respectively) for simulating discharge for mountain watersheds and water level for lowland watersheds. Then, an Indicators of Hydrological Alteration (IHA) model was used to help quantify the alterations to the hydrological process and their resulting eco-hydrological impacts. Based on the validated models, scenario analysis was conducted to evaluate the impacts of climate and land use changes on the hydrological processes. The simulation results revealed that (a) climate change would cause a larger increase in annual runoff than that under land use scenario in the mountain watersheds, with variations of 19.9 and 10.5% for the 2050s, respectively. (b) Land use change was more responsible for the streamflow increment than climate change in the lowland watersheds, causing an annual runoff to increase by 27.4 and 16.2% for the 2050s, respectively. (c) Land use can enhance the response of streamflow to the climatic variation. (d) The above-mentioned hydrological variations were notable in flood and dry season in the mountain watersheds, and they were significant in rice season in the lowland watersheds. (e) Their resulting degradation of ecological diversity was more susceptible to future climate change in the two watersheds. This study demonstrated that mountain and lowland watersheds showed distinct differences in hydrological processes and their responses to climate and land use changes.  相似文献   

机械连接预应力实心方桩承台节点抗震性能试验研究          下载免费PDF全文

孙传智  缪长青  李爱群    鲜铖  朱方之 《世界地震工程》2019,35(4):039-49

预应力管桩在高烈度抗震设防地区已禁用，而普通钢筋混凝土方桩成本较高。首先针对卡扣式机械连接预应力混凝土实心方桩、PHC管桩和普通钢筋混凝土方桩与承台处的节点进行拟静力试验，并利用试验数据针对Park-Ang损伤模型进行了修正，进行了损伤指数分析。研究结果表明:预应力方桩比普通钢筋混凝土方桩的抗裂性能明显好，而预应力混凝土实心方桩承台节点耗能能力和延性低于预应力管桩和普通钢筋混凝土方桩；截桩施工导致桩端部损失部分预应力，相比较未截桩试件屈服荷载和极限荷载均减小，节点裂缝开展较早，损伤较未截桩试件严重；增配普通钢筋试件的滞回曲线比较饱满，水平承载能力和位移延性得到提升，节点抗震性能得到提升与改善；预应力混凝土实心方桩损伤前期较小，而一旦发生损伤后，损伤指数发展较快。  相似文献   

应变率效应对600 MPa级高强钢筋混凝土框架结构抗震性能影响研究          下载免费PDF全文

孙传智  李爱群  缪长青  乔燕  左工 《世界地震工程》2019,35(2):165-170

为了更真实地进行钢筋混凝土结构抗震性能评估，应该考虑材料的应变率效应影响。600 MPa级高强钢筋作为新一代建筑钢材，尚无考虑应变率效应影响的600 MPa级高强钢筋混凝土框架结构抗震性能研究。首先进行了不同应变率下600 MPa级高强钢筋拉伸力学性能试验，利用试验数据拟合得到600 MPa级高强钢筋在不同应变率下的强度提高系数表达式，并利用OpenSees软件进行了配置600 MPa级高强钢筋混凝土框架结构抗震性能模拟分析，研究了应变率效应对框架结构抗震性能的影响。研究结果表明:随着应变率的增大，钢筋的屈服强度和极限强度均得到提高，屈服强度最大提高11.5%，极限强度最大提高8.9%；随着所考虑的材料应变率增加，配置600 MPa级高强钢筋框架结构最大顶点位移总体上呈减小趋势，地震波强度越强，应变率效应影响越大，而层间位移角减小幅值相差不大。研究成果可作为600MPa级高强钢筋混凝土框架结构抗震评估的依据。  相似文献   

新疆塔里木盆地温宿凸起新温地1井、2井获高产工业油流     

杨有星  张君峰  高永进  周新桂  张金虎  白忠凯  韩淼 《中国地质》2020,47(1):251-252

正1研究目的(Objective)温宿凸起位于新疆塔里木盆地西北部,面积约4500 km~2。石油企业先后在该地区部署实施二维地震测线约3200 km,探井4口(阿1井、温参1井、温宿1井、阿苏2井),油气勘探历经50余年未取得突破,并退出油气勘查权。重新评价认识该地区的石油地质条件并获得油气突破是本次工作的主要目的(图1)。  相似文献   

集聚空间组织型式对中国地市尺度工业SO2排放的影响     

胡志强  苗长虹  袁丰 《地理学报》2019,74(10):2045-2061

集聚外部性是集聚影响工业污染排放的重要机制,不同的集聚空间组织型式具有不同的污染排放行为和减排效果。以中国285个地市工业SO₂排放为例,依据集聚经济理论,将集聚空间组织型式细分为集聚密度、企业地理临近度、专业化、多样性、相关多样性、非相关多样性等不同类型,在系统分析工业SO₂排放与集聚空间格局的基础上,通过构建计量经济模型,考察了不同集聚空间组织型式对工业SO₂排放强度的影响。结果表明：① 工业SO₂排放强度与工业集聚密度在空间上具有非对称性,污染排放强度西高东低,工业集聚密度、企业地理临近、多样性、相关和非相关多样性为东中高西部低;② 工业集聚对工业SO₂排放强度的影响存在空间溢出效应,相邻地区集聚密度、多样性和相关多样性水平的上升有利于本区域工业污染排放强度的下降,但专业化水平的上升则会提升本区域的工业污染排放强度;③ 提高集聚密度、引导企业集中布局有利于工业SO₂排放强度下降,多样且关联的产业组织结构有利于污染减排,而专业化和非关联产业的集中会提高污染排放强度;④ 集聚型式对工业SO₂排放强度的影响存在区域和城市规模上的异质性,集聚密度、企业地理临近、多样性和相关多样性对中西部污染减排的作用比东部明显,专业化和非相关多样性不利于东中部地区的污染减排;城区人口规模20万以下的小城市提高集聚密度、减少多样性特别是非相关多样性更有利于污染减排;城区人口规模20~50万的小城市和50~100万的中等城市,提高企业的地理接近度和多样性水平特别是相关多样性水平,有利于其降低污染排放强度;城区人口规模在100万以上的大城市,提高集聚密度和产业多样性水平在一定程度上有利于其污染减排,但其减排效果因拥挤效应而明显下降;⑤ 进一步降低工业SO₂排放强度,需要走集聚化道路,坚持提高集聚密度,因地制宜引导企业集中布局,着力提高产业在关联基础上的多样性水平,加强区域间联防联控,重视区域间的产业联系与环保合作。  相似文献   

Intergranular coesite and coesite inclusions in dolomite from the Dabie Shan: Constraints on the preservation of coesite in UHP rocks          下载免费PDF全文

Penglei Liu  Hans‐Joachim Massonne  Junfeng Zhang  Yao Wu  Zhenmin Jin 《地学学报》2017,29(3):154-161

Intergranular coesite is extremely rare in, and bears crucial information on the formation and preservation of, ultrahigh‐pressure (UHP) rocks. Here, we report the first occurrence of intergranular coesite in a metasedimentary rock, which occurs in the Ganjialing area in the Dabie Shan, east‐central China, and contains abundant coesite inclusions in both garnet and dolomite. We investigated the content of structural water in these minerals with Fourier transform infrared spectroscopy. Our new results undermine the ubiquity of the “pressure‐vessel” model and highlight the role of reaction kinetics in preserving coesite due to the availability of water in UHP rocks.  相似文献   

北京城市下垫面对雾影响的数值模拟研究   总被引：2，自引：0，他引：2       下载免费PDF全文

张亦洲  苗世光  李青春  戴永久 《地球物理学报》2017,60(1):22-36

为了探究北京城市下垫面对雾天气过程的影响,为北京地区雾数值预报水平的提高提供理论基础和科学依据,选取2011年10月29日北京地区雾天个例进行了数值模拟试验,通过对WRF/Noah/UCM模式系统中城市冠层参数的调整,显著改善了模式对此次雾天气过程的模拟效果.使用参数调整后的模式系统通过敏感性试验分析研究了北京城市下垫面对雾发生、发展和消散过程的影响.结果表明:参数调整后的WRF/Noah/UCM模式系统能够与实际观测较相符地模拟此次发生在北京地区的雾天气过程,北京城市下垫面主要通过对温度的改变对雾的形成、发展和消散产生显著影响,使雾不易在城市及其附近形成和发展,延后城市地区雾的形成,但城市的存在也使得城市地区及其附近雾不易消散,相较于没有城市时消散时间延后.  相似文献   

Artificial Martian frozen orbits and Sun-Synchronous orbits using continuous low-thrust control     

Zhigang Wu  Fanghua Jiang  Junfeng Li 《Astrophysics and Space Science》2014,352(2):503-514

This paper analyses three types of artificial orbits around Mars pushed by continuous low-thrust control: artificial frozen orbits, artificial Sun-Synchronous orbits and artificial Sun-Synchronous frozen orbits. These artificial orbits have similar characteristics to natural frozen orbits and Sun-Synchronous orbits, and their orbital parameters can be selected arbitrarily by using continuous low-thrust control. One control strategy to achieve the artificial frozen orbit is using both the transverse and radial continuous low-thrust control, and another to achieve the artificial Sun-Synchronous orbit is using the normal continuous low-thrust control. These continuous low-thrust control strategies consider J ₂, J ₃, and J ₄ perturbations of Mars. It is proved that both control strategies can minimize characteristic velocity. Relevant formulas are derived, and numerical results are presented. Given the same initial orbital parameters, the control acceleration and characteristic velocity taking into account J ₂, J ₃, and J ₄ perturbations are similar to those taking into account J ₂ perturbations for both Mars and the Earth. The control thrust of the orbit around Mars is smaller than that around the Earth. The magnitude of the control acceleration of ASFOM-4 (named as Artificial Sun-Synchronous Frozen Orbit Method 4) is the lowest among these strategies and the characteristic velocity within one orbital period is only 0.5219 m/s for the artificial Sun-Synchronous frozen orbit around Mars. It is evident that the relationship among the control thrusts and the primary orbital parameters of Martian artificial orbits is always similar to that of the Earth. Simulation shows that the control scheme extends the orbital parameters’ selection range of three types of orbits around Mars, compared with the natural frozen orbit and Sun-Synchronous orbit.  相似文献