大规格高强等边角钢轴压构件承载力研究

对L220X20的Q420角钢进行了轴心受压试验研究,在此基础上进行了理论分析.结合有限元,对大规格角钢进行了参数分析,并与现行《钢结构设计规范》中给出的柱子曲线进行了比较.结果表明:大规格高强等边角钢柱子曲线高于现有《钢结构设计规范》中b类截面柱子曲线,总体介于a类与b类截面柱子曲线之间,现有规范b类柱子曲线适用于大规格高强等边角钢.

Evaluation and Analysis of Provincial Differences in Resources and Environment Carrying Capacity in China

Resources and environment carrying capacity is central to not only regional sustainable development but also major function-oriented zoning. This paper presents an evaluation index system for resources and environment carrying capacity based on four aspects of carrying capacity(i.e., water resources, land resources, the environment, and ecosystems) by using a square deviation decision-making method, and on the basis of above effort evaluates the resources and environment carrying capacity across 31 provincial regions in China(not including Hong Kong, Macao and Taiwan regions of China). In addition, this paper evaluates the current state of socio-economic development, and analyzes the spatial distribution of resources and environment pressure. The results showed that distinct spatial differences in resources and environment carrying capacity and pressure across provincial regions. Resources and environment pressure is affected by both comprehensive resources and environment carrying capacity and socio-economic development. Regions subjected to lower degrees of resources and environment pressure will be restricted by resources and environmental problems through future courses of development owing to excessively low carrying capacities. By contrast, regions with higher comprehensive resources and environment carrying capacity will be subjected to excessively high levels of resources and environment pressure because of rapid socio-economic development. Both of resources and environment carrying capacity and pressure must therefore be considered in the allocation of country-binding targets to provincial regions.

Comprehensive Measurement for Carrying Capacity of Resources and Environment of City Clusters in Central China

Studying the carrying capacity of resources and environment of city clusters in the central China has important practical guidance significance for promoting the healthy, sustainable and stable development of this region. According to their influencing factors and reciprocity mechanism, using system dynamics approaches, this paper built a SD model for measuring the carrying capacity of resources and environment of the city clusters in the central China, and through setting different development models, the comprehensive measurement analysis on the carrying capacity was carried out. The results show that the model of promoting socio-economic development under the protection of resources and environment is the optimal model for promoting the harmony development of resources, environment, society and economy in the city clusters. According to this model, the optimum population scale of the city clusters in 2020 is 42.80×106 persons, and the moderate economic development scale is 22.055×1012 yuan (RMB). In 1996-2020, the carrying capacity of resources and environment in the city clusters took on obvious phase-change characteristics. During the studied period, it is basically at the initial development stage, and will come through the development process from slow development to speedup development.

The Population Carrying Capacity of Waters Ecosystem in China

The study of waters ecosystem and their population carrying capacity demonstrates the role of these ecosystems in economic and social development and provides a theoretical basis for the management and allocation of aquatic ecosystems. In this study, the concept of waters ecosystem population carrying capacity was defined and developmental trends in the population carrying capacity of waters ecosystem in China were evaluated. Results show that waters ecosystem population carrying capacity in China increased from 0.176×109 person year-1 in 2000 to 0.255 × 109 person year-1 in 2010; the population carrying capacity of the standard sea remained at 0.2-0.3 person ha 1; and the standard inland waters population carrying capacity increased from 1.8 to 3.2 person ha-1. This analysis indicates notable regional difference in waters population carrying capacity. In southeastern coastal China and Yangtze River drainage areas where inland waters are widely distributed and aquaculture is developed, the population carrying capacity is higher; however, in northwest China where water resource are deficient and the distribution is relatively small, the waters population carrying capacity is low. The waters ecosystem population carrying capacity of China in 2030 was predicted and results indicate strong potential for increasing waters population carrying capacity.

Commentary of research situation and innovation frontier in hydro-structure engineering science

In order to utilize water and hydropower resources in China,multitudes of water projects are established or to be constructed as an integral part of the national economy's infrastructure.Under these circumstances,there are two outstanding problems:1) a mass of existing dams are in danger and 2) in the southwest water-conservancy construction plan,dozens of existing or planned dams are high dams or even super high dams with heights between 200 and 300 m.In accordance with demands of "the National Program for Medium-and Long-Term Scientific and Technological Development" on the innovation frontier in hydro-structure engineering science,various key problems in science and technology such like stress analysis,ultimate bearing capacity,nonlinearity etc.for high dams,super high dams and sick dams have been investigated.This paper makes a commentary on the advances and results of the researches,then analyzes the advantages and disadvantages of current theoretics and methodologies,and finally presents corresponding research directions and the frontier of innovation.

Carbon carry capacity and carbon sequestration potential in China based on an integrated analysis of mature forest biomass

Forests play an important role in acting as a carbon sink of terrestrial ecosystem.Although global forests have huge carbon carrying capacity(CCC)and carbon sequestration potential(CSP),there were few quantification reports on Chinese forests.We collected and compiled a forest biomass dataset of China,a total of 5841 sites,based on forest inventory and literature search results.From the dataset we extracted 338 sites with forests aged over 80 years,a threshold for defining mature forest,to establish the mature forest biomass dataset.After analyzing the spatial pattern of the carbon density of Chinese mature forests and its controlling factors,we used carbon density of mature forests as the reference level,and conservatively estimated the CCC of the forests in China by interpolation methods of Regression Kriging,Inverse Distance Weighted and Partial Thin Plate Smoothing Spline.Combining with the sixth National Forest Resources Inventory,we also estimated the forest CSP.The results revealed positive relationships between carbon density of mature forests and temperature,precipitation and stand age,and the horizontal and elevational patterns of carbon density of mature forests can be well predicted by temperature and precipitation.The total CCC and CSP of the existing forests are 19.87 and 13.86 Pg C,respectively.Subtropical forests would have more CCC and CSP than other biomes.Consequently,relying on forests to uptake carbon by decreasing disturbance on forests would be an alternative approach for mitigating greenhouse gas concentration effects besides afforestation and reforestation.

Regional Differentiation and Classification for Carrying Constraints on the Resources and Environment of China

Research on the relationship between national resource constraint-region types and environmental carrying capacity is essential for the continued development of Chinese industrialization and urbanization.Thus,utilizing a series of key indexes including the per-capita potential of available land resources,the per-capita potential of available water resources,the degree of environmental stress,and the degree of ecological restriction,a step-by-step,integrated measuring method is presented here to understand the constrained carrying elements of water and land resources as well as environment and ecology.Spatial differences are analyzed and area types classified at the county level across China.Results reveal that：（1）Almost 90%of China is strongly constrained by both resources and the environment,while nearly 50%of national territory is strongly constrained by two elements,especially in areas of intensive population and industry to the east of the Helan-Longmen Mountain line;（2）Densely populated areas of eastern and central China,as well as on the Tibetan Plateau,are strongly constrained by a shortage of land resources,while North China,the northwest,northeast,the Sichuan basin,and some southern cities are experiencing strong constraints because of water shortages.In contrast,the North China plain,the Yangtze River delta,northern Jiangsu,Sichuan province,Chongqing municipality,Guizhou and Guangxi provinces,the northeast plain,and the northern Loess Plateau are constrained by high levels of environmental stress.Areas of China that are strongly ecologically constrained tend to be concentrated to the southwest of the Tianshan-Dabie Mountain line,as well as in the northeast on the Loess Plateau,in the Alashan of Inner Mongolia,in northeast China,and in the northern Jiangsu coastal area;（3）Constraints on national resources and environmental carrying capacity are diverse and cross-cut China,meanwhile,multi-element spatial distribution does reveal a degree of relative centralization.With the exception of the Tibetan Plateau which is resources-ecological constraint,other areas subject to cross constraints are mainly concentrated to the east of the Helan-Longmen Mountain line.