中国城市价值链功能分工及其影响因素     

盛科荣  王丽萍  孙威 《地理研究》2020,39(12):2763-2778

价值链的空间重组正在深刻的改变着城市体系的经济景观,建立在价值链分工基础上的城市功能结构的研究已经成为经济地理学的重要课题。将中国上市公司500强企业网络划分为公司总部、商务服务、研究开发、传统制造、现代制造、物流仓储和批发零售七种类型功能区块,研究了中国城市价值链功能分工及其影响因素。结果发现：沿着价值链的功能分工已经成为中国城市体系经济景观的显著特征,功能多样化城市和功能专业化城市并存于中国城市体系,东部地区和城市密集地区的城市在价值链分工中占据了更好的地位;中国城市按照价值链中的优势功能可以划分为九种类型,少数城市转变为承载公司总部、研究开发、商务服务等多样化功能的高等级中心城市,而大量中小城市则转变为传统制造专业化基地;市场潜力、关键资源、区位条件、营商环境等城市属性特征是城市功能分工的重要影响因素,城市资源、区位可达性等属性特征的增强将提高城市成为总部基地、商务中心和研究基地的概率,而降低城市成为传统制造基地的概率。  相似文献   

基于ROMS和4DVAR的沿轨与网格化SSH数据同化效果评价   总被引：1，自引：1，他引：0  

周超杰  丁效华  张杰  杨俊刚  马强 《海洋学报(英文版)》2018,37(9):50-58

Remote sensing products are significant in the data assimilation of an ocean model. Considering the resolution and space coverage of different remote sensing data, two types of sea surface height(SSH) product are employed in the assimilation, including the gridded products from AVISO and the original along-track observations used in the generation. To explore their impact on the assimilation results, an experiment focus on the South China Sea(SCS) is conducted based on the Regional Ocean Modeling System(ROMS) and the four-dimensional variational data assimilation(4 DVAR) technology. The comparison with EN4 data set and Argo profile indicates that, the along-track SSH assimilation result presents to be more accurate than the gridded SSH assimilation, because some noises may have been introduced in the merging process. Moreover, the mesoscale eddy detection capability of the assimilation results is analyzed by a vector geometry–based algorithm. It is verified that, the assimilation of the gridded SSH shows superiority in describing the eddy's characteristics, since the complete structure of the ocean surface has been reconstructed by the original data merging.  相似文献   

Exploring future changes in smallholder farming systems by linking socio-economic scenarios with regional and household models     

《Global Environmental Change》2014

We explore how smallholder agricultural systems in the Kenyan highlands might intensify and/or diversify in the future under a range of socio-economic scenarios. Data from approximately 3000 households were analyzed and farming systems characterized. Plausible socio-economic scenarios of how Kenya might evolve, and their potential impacts on the agricultural sector, were developed with a range of stakeholders. We study how different types of farming systems might increase or diminish in importance under different scenarios using a land-use model sensitive to prices, opportunity cost of land and labour, and other variables. We then use a household model to determine the types of enterprises in which different types of households might engage under different socio-economic conditions. Trajectories of intensification, diversification, and stagnation for different farming systems are identified. Diversification with cash crops is found to be a key intensification strategy as farm size decreases and labour costs increase. Dairy expansion, while important for some trajectories, is mostly viable when land available is not a constraint, mainly due to the need for planting fodders at the expense of cropland areas. We discuss the results in relation to induced innovation theories of intensification. We outline how the methodology employed could be used for integrating global and regional change assessments with local-level studies on farming options, adaptation to global change, and upscaling of social, environmental and economic impacts of agricultural development investments and interventions.  相似文献   

池塘养殖刺参安全度夏技术研究          下载免费PDF全文

刘锡胤  周文江  贺加贝  张晓明  陈伟  黄华  张岚 《海洋开发与管理》2018,35(2):103-108

文章概述夏季池塘养殖刺参死亡症状和灾情特点,分析刺参死亡原因主要包括池水盐度骤降、池水温度升高、池水pH值下降、池水分层、有机污染和刺参自身原因。在此基础上,提出池塘养殖刺参安全度夏的技术措施,主要包括科学合理选择养殖地址、规范池塘建设、做好度夏前准备工作、水质管理、及时清除水草和大型藻类、采取降温措施以及补充营养等,涉及大量具体操作方法,具有科学性和实用性。  相似文献   

Exploring river nitrogen and phosphorus loading and export to global coastal waters in the Shared Socio-economic pathways     

《Global Environmental Change》2022

This global spatially explicit (0.5 by 0.5 degree) analysis presents the nitrogen (N) and phosphorus (P) inputs, processing and biogeochemical retention and delivery to surface waters and river export to coastal seas according to the five shared socioeconomic pathways (SSP). Four systems are considered: (i) human system; (ii) agriculture; (iii) aquaculture; (iv) nature. Exploring the changes during 1980–2015 and 2015–2050 according to the SSPs shows that the natural nutrient sources have been declining in the past decades and will continue to decline in all SSPs in future decades due to massive land transformations, while agriculture, human sewage and aquaculture are becoming increasingly dominant (globally up to 80% of nutrient delivery). More efforts than those employed in any of the SSPs are needed to slow down the global nutrient cycles. One of the drivers of the proliferation of harmful algal blooms is the tendency towards increasing N:P ratios in global freshwaters and export to the global coastal seas; this is the result of increasing N:P in inputs in food production, more efficient biogeochemical retention of P than of N in river basins, and groundwater N legacies, which seems to be most pronounced in a united world that strives after sustainability. The diverging strategies to achieve UN Sustainable Development Goals 14 (life below water), 2 (zero hunger) and 6 (clean water and sanitation) therefore require a balanced management system for both N and P in all systems, that accounts for future nutrient legacies.  相似文献   

气象业务系统融入“天擎”“天镜”的技术要点分析     

杨远恒  李进讷  廖婷婷  莫仕灯  李波 《中低纬山地气象》2022,46(6):111-114

随着气象业务系统的集约化程度越来越高,“云”+“端”的业务构建模式将成为主流,省级气象部门新的业务系统构建直接基于“天擎”作为数据和算力支撑,“天镜”提供统一实时业务监控的模式开展。而原来研发的气象业务系统则要通过“云化”改造融入“天擎”“天镜”。本文通过分析融入“天擎”“天镜”技术要点,总结贵州前期系统融入过程中的经验,为今后各单位业务系统顺利融入提供借鉴和指导。  相似文献   

Comparative Study of Hydrogen and Carbon Isotopic Composition of Gases Generated from the Pyrolysis of a Peat under Saltwater and Freshwater Conditions     

WU Yingzhong  DUAN Yi  ZHAO Yang  CAO Xixi  MA Lanhu  QIAN Yaorong  LI Zhongping  XING Lantian 《《地质学报》英文版》2018,92(5):1879-1887

To understand the influence of the diagenetic water medium on the isotopic compositions of thermogenic coalbed gas, both hydrous and anhydrous closed-system pyrolyses were performed at temperatures of 250°C to 650°C on an herbaceous marsh peat. Compared to the results of anhydrous pyrolysis, the hydrocarbon gases generated from hydrous pyrolyses have very different hydrogen isotopic compositions. However, the carbon isotopic compositions of the hydrocarbon gases became only slightly heavier in hydrous pyrolysis, compared to that from anhydrous pyrolysis. With the progress of thermal evolution from peat to a more advanced thermal maturity of vitrinite reflectance values (Ro) of 5.5% during the pyrolysis, the difference in the average δD value increased from 52‰ to 64‰ between the hydrous pyrolysis with saltwater and anhydrous pyrolysis and increased from 18‰ to 29‰ between the hydrous pyrolysis with freshwater and anhydrous pyrolysis, respectively. The difference in the average δ13C value was only 1‰–2‰ between the hydrous and anhydrous pyrolysis. The relationships between the δD values of the generated hydrocarbon gases and Ro values as well as among δD values of the hydrocarbon gas species are established. The close relationships among these parameters suggest that the water medium had a significant effect on the hydrogen isotopic composition and a minimal effect on the carbon isotopic composition of the hydrocarbon gases. The results of these pyrolyses may provide information for the understanding of the genesis of coalbed gas from herbaceous marsh material with the participation of different diagenetic water media.  相似文献   

基于模糊故障树的GIS产品的可靠性分析   总被引：1，自引：1，他引：0  

胡圣武  袁占良  王新洲  陶本藻 《测绘科学》2006,31(1):49-50

本文首次把模糊故障树方法引入到GIS产品的可靠性分析,并就模糊故障树的基本理论作了简单的介绍,阐述了模糊故障树的建造和基于三角模糊数和梯形模糊数运算规则,结合GIS产品的特性论述了模糊故障树用于GIS产品可靠性分析的步骤,然后用实例进行了分析,最后就全文进行总结并指出了需要解决的问题。  相似文献   

俄罗斯油气钻采废弃物处理及其利用研究          下载免费PDF全文

汤凤林  赵荣欣  周欣  段隆臣  Третьяк А.А. 《探矿工程》2022,49(5):202-207

生态安全和环境保护是世界各国都非常关心的问题。地质钻探和石油天然气钻采工作中产生大量废弃物,直接影响生态安全和环境保护,给经济建设和人民生活带来很大的负面影响。俄罗斯钻探工作者对此进行了研究,取得了一定效果。他们主要采用综合处理方法和磁化处理方法。利用这2种方法,废弃物不仅可以再生,而且还可以二次使用,有一定的创新和实际意义,值得引起我们的重视,建议对此进行研究与讨论。  相似文献   

Situating corporate framings of child labor: Toward grounded geographies of working children in globalized agriculture     

《Geoforum》2015

The expansion of multinational corporations into agricultural production around the world is resulting in new forms of engagement in specific places. In the context of neoliberal restructuring, these engagements are tied to shifting landscapes of societal, governmental and industry-based perceptions on the role of corporations in labor regimes. But how are these engagements developed and how do they connect to the everyday lives of workers? In India, when Monsanto expanded into hybrid cotton seed production in the early 2000s, the corporation came under pressure to address concerns over the widespread employment of children and young workers for seed pollination. In response, the corporation developed an approach to child labor that, I argue, works to reinforce generalized and problematic notions of childhood and work. Corporate engagements in global agriculture need to be situated in time and space, and alongside the experiences of workers. Children experience attempts to shape their patterns of work and mobility as a series of surmountable obstacles, disconnected from the process of deciding whether or not they will engage in this work. Drawing on qualitative fieldwork in Gujarat and Rajasthan, and documentary analysis of public documents, I outline the development of a corporate response to child labor and place it within the context of the rise of corporate social responsibility, global ideas of child labor, and in the specific case of cotton seed production in western India. I demonstrate that contextualized geographies of working children in globalized agriculture reveal the nature of multinational corporations’ engagements in specific places.  相似文献