期刊文献+
共找到9篇文章
< 1 >
每页显示 20 50 100
A new method of calculating crown projection area and its comparative accuracy with conventional calculations for asymmetric tree crowns
1
作者 Mingrui Zhang Huiquan Bi +1 位作者 Xingji Jin Michael McLean 《Journal of Forestry Research》 SCIE EI CAS CSCD 2024年第4期171-188,共18页
This paper introduces a new method of calculating crown projection area(CPA),the area of level ground covered by a vertical projection of a tree crown from measured crown radii through numerical interpolation and inte... This paper introduces a new method of calculating crown projection area(CPA),the area of level ground covered by a vertical projection of a tree crown from measured crown radii through numerical interpolation and integration.This novel method and other four existing methods of calculating CPA were compared using detailed crown radius measurements from 30 tall trees of Eucalyptus pilularis variable in crown size,shape,and asymmetry.The four existing methods included the polygonal approach and three ways of calculating CPA as the area of a circle using the arithmetic,geometric and quadratic mean radius.Comparisons were made across a sequence of eight non-consecutive numbers(from 2 to 16)of measured crown radii for each tree over the range of crown asymmetry of the 30 trees through generalized linear models and multiple comparisons of means.The sequence covered the range of the number of crown radii measured for calculating the CPA of a tree in the literature.A crown asymmetry index within the unit interval was calculated for each tree to serve as a normative measure.With a slight overestimation of 2.2%on average and an overall mean error size of 7.9%across the numbers of crown radii that were compared,our new method was the least biased and most accurate.Calculating CPA as a circle using the quadratic mean crown radius was the second best,which had an average overestimation of 4.5%and overall mean error size of 8.8%.These two methods remained by and large unbiased as crown asymmetry increased,while the other three methods showed larger bias of underestimation.For the conventional method of using the arithmetic mean crown radius to calculate CPA as a circle,bias correction factors were developed as a function of crown asymmetry index to delineate the increasing magnitude of bias associated with greater degrees of crown asymmetry.This study reveals and demonstrates such relationships between the accuracy of CPA calculations and crown asymmetry and will help increase awareness among researchers and practitioners on the existence of bias in their CPA calculations and for the need to use an unbiased method in the future.Our new method is recommended for calculating CPA where at least four crown radius measurements per tree are available because that is the minimum number required for its use. 展开更多
关键词 Crown radius measurements Interpolated crown contour projected crown area Multiple comparisons of means
下载PDF
Control Measures of Soil Erosion in a Typical Construction Project Area ( Dina 2 Gas Field)
2
作者 Huiming Lv 《Meteorological and Environmental Research》 CAS 2013年第2期53-58,共6页
To treat the relationship between project construction and ecological environment and effectively prevent new soil erosion during the construction, according to the project layout, soil erosion distribution as well as... To treat the relationship between project construction and ecological environment and effectively prevent new soil erosion during the construction, according to the project layout, soil erosion distribution as well as natural and socio-economic conditions, the control measures of newly increased soil erosion along the project were carried out based on site survey and analysis of relevant information. In addition, adhering to the prin- ciple of partition prevention and treatment, some guiding prevention and control measures of the natural zone passed by the project and soil erosion control district were determined, which provided scientific references and technical support for the rational layout of water and soil conservation and ecological restoration measures in Dina 2 gas field. 展开更多
关键词 Typical construction project area Dina 2 gas field Ecological environment Soil erosion Control measures China
下载PDF
Kuche Depression in Tarim is Main Gas Supply Area for Gas Transmission Project 被引量:1
3
《China Oil & Gas》 CAS 2000年第2期12-14,共3页
关键词 Kuche Depression in Tarim is Main Gas Supply Area for Gas Transmission project
下载PDF
Stem Respiration of a Larch (Larix gmelini) Plantation in Northeast China 被引量:11
4
作者 王文杰 杨逢建 +4 位作者 祖元刚 王慧梅 TAKAGI Kentaro SASA Kaichiro KOIKE Takayoshi 《Acta Botanica Sinica》 CSCD 2003年第12期1387-1397,共11页
Stem respiration is an important part of the activity of a tree and is an important source of CO2 evolution from a forest ecosystem. Presently, no standard methods are available for the accurate estimation of total st... Stem respiration is an important part of the activity of a tree and is an important source of CO2 evolution from a forest ecosystem. Presently, no standard methods are available for the accurate estimation of total stem CO2 efflux from a forest. In the current study, a 33-year-old (by the year 2001) larch (Larix gmelini Rupr.) plantation was measured throughout 2001-2002 to analyze its monthly and seasonal patterns of stem respiration. Stem respiration rate was also measured at different heights, at different daily intervals and any variation in the larch plantation was recorded. The relationship between stem temperature, growth status and respiration rate was analyzed. Higher respiration rates were recorded in upper reaches of the larch tree throughout the season and these were affected partially by temperature difference. Midday depression was found in the diurnal changes in stem respiration. In the morning, but not in the afternoon, stem respiration was positively correlated with stem temperature. The reason for this variation may be attributed to water deficit, which was stronger in the afternoon. In the larch plantation, a maximum 7-fold variation in stem respiration was found. The growth status (such as mean growth rate of stem and canopy projection area) instead of stem temperature difference was positively correlated with this large variation. An S-model (sigmoid curve) or Power model shows the greatest regression of the field data. In the courses of seasonal and annual changes of stem respiration, peak values were observed in July of both years, but substantial interannual differences in magnitude were observed. An exponential model can clearly show this regression of the temperature-respiration relationship. In our results, Q(10) values ranged from 2.22 in 2001 to 3.53 in 2002. Therefore, estimation of total stem CO2 efflux only by a constant Q(10) value may give biased results. More parameters of growth status and water status should be considered for more accurate estimation. 展开更多
关键词 Larix gmelini stem respiration growth status growth rate canopy projection area Q(10)
下载PDF
HOLDITCH THEOREM FOR THE CLOSED SPACE CURVES IN LORENTZIAN 3-SPACE
5
作者 Handan Yιldιrιm Salim Yce Nuri Kuruoglu 《Acta Mathematica Scientia》 SCIE CSCD 2011年第1期172-180,共9页
In this article, we give the area formula of the closed projection curve of a closed space curve in Lorentzian 3-space L3. For the 1-parameter closed Lorentzian space motion in L3, we obtain a Holditch Theorem taking ... In this article, we give the area formula of the closed projection curve of a closed space curve in Lorentzian 3-space L3. For the 1-parameter closed Lorentzian space motion in L3, we obtain a Holditch Theorem taking into account the Lorentzian matrix multiplication for the closed space curves by using their othogonal projections onto the Euclidean plane in the fixed Lorentzian space. Moreover, we generalize this Holditch Theorem for noncollinear three fixed points of the moving Lorentzian space and any other fixed point on the plane which is determined by these three fixed points. 展开更多
关键词 Lorentzian matrix multiplication Lorentzian motion Holditch Theorem orthogonal projection area
下载PDF
Structure and Flow Characteristics of Flat Fan Nozzles with a Single Orifice Formed by a Rectangular Cut
6
作者 张晓东 董志国 牛志刚 《Journal of Donghua University(English Edition)》 EI CAS 2014年第4期423-428,共6页
The flat fan nozzle with a single orifice formed by a rectangular cut at the nozzle exit through a semi-ellipsoid blind end was developed. The flow rate characteristic of the nozzle was analyzed. Theoretical analysis ... The flat fan nozzle with a single orifice formed by a rectangular cut at the nozzle exit through a semi-ellipsoid blind end was developed. The flow rate characteristic of the nozzle was analyzed. Theoretical analysis shows that the discharge coefficient of the nozzle is a function of the ratio of the projected exit flow area to the cross sectional area of the nozzle input section. Water spraying experiment results show that the discharge coefficient increases with the increase of the ratio of the projected exit flow area to the cross sectional area of the nozzle input section when the rectangular cut depth doesn't exceed the distance from the center of the hemisphere to the nozzle end; conversely,the discharge coefficient decreases with the increase of the ratio; for a given nozzle,the discharge coefficient varies with Reynolds number. 展开更多
关键词 flat fan nozzle flow rate single orifice projected exit flow area discharge coefficient
下载PDF
The Drivers of Land Use Change in the Migration Area, Three Gorges Project, China: Advances and Prospects 被引量:9
7
作者 倪九派 邵景安 《Journal of Earth Science》 SCIE CAS CSCD 2013年第1期136-144,共9页
This paper reviewed existing literatures on land use change since the demonstration phase of the Three Gorges Project and found that reservoir inundation, migration resettlement, urban relocation, and post-supporting ... This paper reviewed existing literatures on land use change since the demonstration phase of the Three Gorges Project and found that reservoir inundation, migration resettlement, urban relocation, and post-supporting construction were first paid more attention to, when analyzing the driving forces of land use change in the migration area. However, at the post-migration period (the end of migration resettlement), above-mentioned drivers had not obviously driven land use change, but the evolutions of "migration demands" replacing them increasingly became the major drivers of land use change in the migration area. Therefore, the future priority fields of land use explanations in the mi- gration area, Three Gorges Project were (1) identifying the corresponding relationships between the spatial distributions of land use change and migration resettlement and indigenous inhabitants; (2) un- derstanding the change of "migration demands" and their causing "indigenous inhabitants' demands" being how to drive land use transforms; (3) finding the driving processes of the conflict and exclusion between immigrants and indigenous inhabitants, and the transfer of immigrants and indigenous in- habitants on land use change; and (4) measuring the dynamic feedback of "migration demands" at dif- ferent stages on the processes, directions and their corresponding impacts of land use change in order to building the coupling framework among "migration demands", driver behaviors, and land use. This paper presents a new access for the explanation of land use change and also supplies scientific proofs to obtain adaptive decision-making to optimize land use patterns in the migration area, Three Gorges Project. 展开更多
关键词 land use change migration de-mands driving forces Three Gorges project migration area.
原文传递
Global Trade Center,A New Landmark Project in Anzhen Area
8
《Beijing Review》 2006年第44期46-46,共1页
The overall planning of Beijing Global Trade Center (GTC) is being carried out by the U.S. designing firm EDAW and the first-phase office building has already been put into use, while the second and third phases are u... The overall planning of Beijing Global Trade Center (GTC) is being carried out by the U.S. designing firm EDAW and the first-phase office building has already been put into use, while the second and third phases are under construction. Guided by the modernity, hi-tech design, a human-oriented approach, and the integration of land- 展开更多
关键词 project Global Trade Center A New Landmark project in Anzhen Area LANDMARK
原文传递
Study on integrated calculation of ecological water demand for basin system 被引量:4
9
作者 JIN Xin YAN DengHua +4 位作者 WANG Hao ZHANG Cheng TANG Yun YANG GuiYu WANG LingHe 《Science China(Technological Sciences)》 SCIE EI CAS 2011年第10期2638-2648,共11页
The operation of reservoir(s) has a certain impact on the downstream hydrologic regime,and even endangers the ecological water safety of river corridor and ecosystems which interact with river system.Therefore,ecologi... The operation of reservoir(s) has a certain impact on the downstream hydrologic regime,and even endangers the ecological water safety of river corridor and ecosystems which interact with river system.Therefore,ecological operation needs to be carried out in order to ensure ecological water use of downstream zone.The key technological support is the estimation and integrated calculation of ecological water demand.The connotation of the integrated calculation on ecological water demand lies on that the ecological water demand of different ecosystems is integrated to meet the requirements of water allocation and operation on watershed scale in terms of hydrological cycle.Considering the practical requirement of ecological operation of reservoir(s),this study proposed an integrated calculation approach of ecological water demand according to the ecological water demand in various ecosystems as well as the hydraulic connection among them;it established an integrated calculation model of regional ecological water demand by means of the distributed hydrological model,and studied the integrated calculation in Yalong River basin which is the source area of the west route of South-North Water Transfer Project as an example.The results indicated that the integrated calculation model more effectively combined the ecological water demand and hydraulic connection of ecosystems in time and space,compared with the lumped water balance analysis,since the former conquered the defect of insufficient ecological water source and supplement on multiple spatial and temporal scales,and met the demand of ecological operation of reservoir(s). 展开更多
关键词 ecological operation of reservoir ecological water demand integrated calculation distributed hydrological model west route of South-North Water Transfer project in Yalong River source area
原文传递
上一页 1 下一页 到第
使用帮助 返回顶部