共查询到19条相似文献，搜索用时 296 毫秒
1.
STEPHEN E.BIALKOWSKI 《地理学报(英文版)》1990,(4)
Digital filter smoothing methods for shot-noise-limited data are addressed in this study.The preferredmethod is based on a Gaussian filter in which the width of the Gaussian filter function is varied dependingon the estimate of the second derivative of the raw data.This filter is developed from the standpoint ofmaximum likelihood parameter estimation of the probability density function which describes shot-noise-limited data.The smoothing filter is tested and compared with the conventional sequential regressionfilter.This adaptive Gaussian smoothing filter works better than both the sequential regression and theadaptive Gaussian filter derived for normal noise.For data containing both high-and low-frequencycomponents,the limiting step in the adaptive filter is an estimation of the smoothing interval.Methodsfor determining an optimum smoothing interval are discussed.With the optimized smoothing interval,the adaptive Gaussian filter works well for data sets with a wide range of varying frequency components.In particular,synthetic data typical of atomic emission spectra are used to test this smoothing filter. 相似文献
2.
信息技术时代的企业区位研究(英文) 总被引：3，自引：1，他引：2
The wide application of information and communication technologies(ICTs) has been argued to be critical to spatial transformation of firms.Recent advances in the studies along this line have challenged traditional location theory.The existing literature,however,focuses mainly on the impacts of ICTs on locational conditions and industrial spatial distribution.The dynamics behind such changes have not yet been given sufficient attention by geographers.Given this background,this paper investigates the impact of new ICTs on traditional location theory and the dynamics of industrial re-location that are enabled by new ICTs,based on data collected from an investigation of 178 firms.The paper argues that the application of new ICTs has been a key location factor in the information age,and that the time-cost is becoming critical to the spatial organization of firms,particularly as a result of a shorter product life and mass customization,among other dynamics. 相似文献
3.
长沙城市土地扩张特征及影响因素 总被引：3，自引：2，他引：1
This research systematically analyses land-use map of Changsha city in different periods of time. The spatial form and structural evolution was analysed by studying indices such as city land-use structure proportion, expansion intensity, economic flexibility, population flexibility, changing compactness index and so on. The dynamic mechanism of urban land expansion has been discussed by integrating the regional social economy development situation and many aspects such as the physiographical surrounding, population and economic development, traffic infrastructure, planning and regional development tactic and system innovation. The research indicates that the urban land expansion speed and intensity have steadily increased in Changsha from 1949 to 2004. The expansion form has been from a single external expansion to a combination form of external and internal expansion, from a circular or linear continuous form to a blocky or agglomeration shape. Overall, the urban land expansion of Changsha city is a phasic, diversified and complex process. And no matter what the stage is, it is an organic system containing multiple speed, pattern and shape, which are driven by multiple impetuses. The dominant feature at different stages was highlighted be- cause of the balance and fluctuation between different forces, and the existing urban land border and shape have resulted from the joint efforts of these phasic forces. 相似文献
4.
LI Wenhua 《资源与生态学报(英文版)》2022,13(1):1-1
Humanity turns to a new chapter in 2022. As proud as we are of rapid developments in economics, science, and technology, we are equally concerned about such global issues as biodiversity conservation and the global pandemic of Covid-19. The unprecedented impact human activities have exerted on the global climate system is clearly underscored by the data from the World Meteorological Organization: The previous fifty years since 1970 have been the warmest of the past 2000 years. 相似文献
5.
Spatial-temporal characteristics and decoupling effects of China’s carbon footprint based on multi-source data 总被引：1，自引：1，他引：0
In 2007, China surpassed the USA to become the largest carbon emitter in the world. China has promised a 60%–65% reduction in carbon emissions per unit GDP by 2030, compared to the baseline of 2005. Therefore, it is important to obtain accurate dynamic information on the spatial and temporal patterns of carbon emissions and carbon footprints to support formulating effective national carbon emission reduction policies. This study attempts to build a carbon emission panel data model that simulates carbon emissions in China from 2000–2013 using nighttime lighting data and carbon emission statistics data. By applying the Exploratory Spatial-Temporal Data Analysis(ESTDA) framework, this study conducted an analysis on the spatial patterns and dynamic spatial-temporal interactions of carbon footprints from 2001–2013. The improved Tapio decoupling model was adopted to investigate the levels of coupling or decoupling between the carbon emission load and economic growth in 336 prefecture-level units. The results show that, firstly, high accuracy was achieved by the model in simulating carbon emissions. Secondly, the total carbon footprints and carbon deficits across China increased with average annual growth rates of 4.82% and 5.72%, respectively. The overall carbon footprints and carbon deficits were larger in the North than that in the South. There were extremely significant spatial autocorrelation features in the carbon footprints of prefecture-level units. Thirdly, the relative lengths of the Local Indicators of Spatial Association(LISA) time paths were longer in the North than that in the South, and they increased from the coastal to the central and western regions. Lastly, the overall decoupling index was mainly a weak decoupling type, but the number of cities with this weak decoupling continued to decrease. The unsustainable development trend of China's economic growth and carbon emission load will continue for some time. 相似文献
6.
Isotopic composition of precipitation over Arid Northwestern China and its implications for the water vapor origin 总被引：1，自引：0，他引：1
In order to reveal the characteristics and climatic controls on the stable isotopic composition of precipitation over Arid Northwestern China, eight stations have been selected from Chinese Network of Isotopes in Precipitation (CHNIP). During the year 2005 and 2006, monthly precipitation samples have been collected and analyzed for the composition of δD and δ18O. The established local meteoric water line δD=7.42δ18O+1.38, based on the 95 obtained monthly composite samples, could be treated as isotopic input function across the region. The deviations of slope and intercept from the Global Meteoric Water Line indicated the specific regional meteorological conditions. The monthly δ18O values were characterized by a positive correlation with surface air temperature (δ18O (‰) =0.33 T (℃)–13.12). The amount effect visualized during summer period (δ18O (‰) = –0.04P (mm)–3.44) though not appeared at a whole yearly-scale. Spatial distributions of δ18O have properly portrayed the atmospheric circulation background in each month over Arid Northwestern China. The quantitative simulation of δ18O, which involved a Rayleigh fractionation and a kinetic fractionation, demonstrated that the latter one was the dominating function of condensation of raindrops. Furthermore, the raindrop suffered a re-evaporation during falling processes, and the precipitation vapor might have been mixed with a quantity of local recycled water vapor. Multiple linear regression equations and a δ18O–T relation have been gained by using meteorological parameters and δ18O data to evaluate physical controls on the long-term data. The established δ18O–T relation, which has been based on the present-day precipitation, could be considered as a first step of quantitatively reconstructing the historical environmental climate. 相似文献
7.
Carey et al.utilized principal components analysis (PCA) to analyze frequency shift data obtained frompiezoelectric sensors formed by coating quartz crystals with 27 different GC stationary phases and testedusing 14 analytes.The objective of the analysis was to determine an optimal reduced set of coatings fordetection of the analytes.The results were correlated with those obtained from cluster analysis.In thispaper the data are re-analyzed using correspondence analysis (CA).The advantage of using CA includea symmetric treatment of sensor coatings and analytes and better identification of the representation ofthe analytes in terms of the detection components.The results obtained by the conjunctive use of PCA,a varimax rotation and cluster analysis were obtained by CA. 相似文献
8.
JOHN MANDEL 《地理学报(英文版)》1992,(5)
The computer has made it possible to scrutinize data rapidly by means of graphics. This should be doneprior to the application of any model to the data, since the model must be validated before using it asa means of analyzing the data. The procedure is illustrated in terms of two examples of real experimentaldata. 相似文献
9.
中国城市扩展对气温观测的影响及其高估程度(英文) 总被引：3，自引：1，他引：2
Since the implementation of the reform and opening up policy in China in the late 1970s, some meteorological stations ’entered’ cities passively due to urban expansion. Changes in the surface and built environment around the stations have influenced observations of air temperature. When the observational data from urban stations are applied in the interpolation of national or regional scale air temperature dataset, they could lead to overestimation of regional air temperature and inaccurate assessment of warming. In this study, the underlying surface surrounding 756 meteorological stations across China was identified based on remote sensing images over a number of time intervals to distinguish the rural stations that ’entered’ into cities. Then, after removing the observational data from these stations which have been influenced by urban expansion, a dataset of background air temperatures was generated by interpolating the observational data from the remaining rural stations. The mean urban heat island effect intensity since 1970 was estimated by comparing the original observational records from urban stations with the background air temperature interpolated. The result shows that urban heat island effect does occur due to urban expansion, with a higher intensity in winter than in other seasons. Then the overestimation of regional air temperature is evaluated by comparing the two kinds of grid datasets of air temperature which are respectively interpolated by all stations’ and rural stations’ observational data. Spatially, the overestimation is relatively higher in eastern China than in the central part of China; however, both areas exhibit a much higher effect than is observed in western China. We concluded that in the last 40 years the mean temperature in China increased by about 1.58℃, of which about 0.01℃ was attributed to urban expansion, with a contribution of up to 0.09℃ in the core areas from the overestimation of air temperature. 相似文献
10.
PHILIP K.HOPKE 《地理学报(英文版)》1992,(2)
In many cases,monitoring data for ambient airborne particles can be organized in the form of a three-way data table with one way for chemical species,one for sampling periods and one for sites.A directtrilinear decomposition followed by a matrix reconstruction(DTDMR)is developed to analyze such adata table as a whole.The three-way data set is composed into three two-way matrices by a direct trilineardecomposition(DTD).The column vectors of each of the matrices are called‘source profiles’,‘emissionpatterns’and‘site coefficients’respectively.Particulate sources are identified by examining both theirsource profiles and emission patterns.After the sources have been identified,emission patterns and sitecoefficients are used to produce a three-way matrix that gives estimates of mass contributions of sourcesto the samples collected at every site in every period.By simulation study,not only has the method beenverified,but a good indicator has been found that shows the number of factors(i.e.sources)in thesystem.Unlike other receptor models,DTDMR does not require source profile data and does not involvetrial-and-error procedures.Since DTDMR identifies sources based on variations in two dimensions,it hasa higher potential to distinguish two sources that have similar chemical compositions.The DTDMRmodel has provided excellent results with simulated data and has been applied in a real world three-waydata set. 相似文献
11.
Two general approaches have been applied to understanding the fractal structure of fluvial topography: (1) deterministic, process-based models, and (2) stochastic partial differential equations (PDE). Deterministic models reproduce the fractal behavior of fluvial topography but have two limitations: they often underestimate the amount of lateral valley and ridge migration that occurs in nature, and the complexity has made it difficult to identify the precise origin of fractal behavior in fluvial landscapes. The simplicity of stochastic PDE models has made them useful for investigating fractal behavior, but they incorrectly suggest that fractal behavior is only possible with stochastic forcing. In this paper I investigate whether simplified, deterministic PDE models of landform evolution also exhibit fractal behavior and other features of complexity (i.e. deterministic chaos). These models are based on the KPZ equation, well known in the physics literature. This equation combines diffusion (i.e. hillslope processes) and nonlinear advection (i.e. bedrock or alluvial channel incision). Two models are considered: (1) a deterministic model with uniform erodibility and random initial topography, and (2) a deterministic model with random erodibility and uniform initial topography. Results illustrate that both of these deterministic models exhibit fractal behavior and deterministic chaos. In this context, chaotic behavior means that valley and ridge migration and nonlinear amplification of small perturbations in these models prevent an ideal steady state landscape from ever developing in the large-system limit. These results suggest that fractal structure and deterministic chaos are intrinsic features of the evolution of fluvial landforms, and that these features result from an inverse cascade of energy from small to large wavelengths in drainage basins. This inverse cascade differs from the direct cascade of three-dimensional turbulence in which energy flows from large to small wavelengths. 相似文献
12.
基于CMIP5模式的干旱内陆河流域未来气候变化预估 总被引：3，自引：1，他引：2
我国西北干旱半干旱地区水资源短缺、生态环境脆弱,未来气候变化预估对水资源管理具有重要的现实意义。以黑河流域为研究区,基于1960-2014年月值NCEP再分析资料与气象要素实测资料,建立逐步回归降尺度模型;针对模型不足,提出一种补充逐步回归降尺度模型;经2006-2014年CMIP5中CNRM-CM5模式的区域适用性评价,选取适宜模型进行2016-2060年CNRM-CM5模式下的流域未来气候变化预估。主要结论为：（1）补充逐步回归模型的模拟效果总体要好于逐步回归模型,两模型对流域气温的模拟效果要好于降水。（2）降尺度模型的CNRMCM5模式适用性评价表明,RCP4.5与RCP8.5路径下,补充回归模型的适用性总体好于逐步回归模型。（3）两种路径下,黑河流域上中游未来年均降水量分别为324.94 mm、330.15 mm,未来流域降水分布的不均匀性增强。（4）两种路径下黑河流域中下游未来年均气温分别为10.25℃、10.77℃。 相似文献
13.
基于分形方法的旅游景区(点)系统等级结构研究--以南京市旅游景区(点)系统为例 总被引：10，自引：0，他引：10
以南京市旅游景区(点)系统为例,提出了对旅游景区(点)系统的等级结构进行了分形研究的基本方法。认为可以把景区(点)系统中各景点的旅游吸引力评分值当作一个离散型集合,通过计算它们的信息分维值来反映系统等级结构分布的变化性,计算出Zipf维数和分维值来反映系统等级结构分布的模式。在旅游景区(点)定量评价的基础上,根据旅游联系性把南京市旅游景区(点)系统分为三个景点体系,测算各景点体系信息维数值、Zipf维数值,对各种分维数值和分维数坐标图进行比较和分析,认为南京市旅游景点体系等级结构具有较好的分形特征,但具体到内部有一定的差异,并对景点体系等级结构的优化的方法和途径进行了分析。 相似文献
14.
海河流域夏季降水关键区季内演变及其环流配置的定量化分析 总被引：1，自引：0，他引：1
海河流域夏季降水的空间分布具有明显的季节内变化特征,利用海河流域148个地面气象台站逐日降水资料以及NCEP/NCAR再分析资料,分析了流域夏季各月降水关键区的分布变化以及与其对应的大气环流系统的季内配置差异,并定量计算了主要环流系统对季内各月关键区降水的影响作用大小。结果表明：海河流域夏季降水关键区稳定表现出一种季节内变化,即以海河流域东北部滦河和北三河下游台站降水贡献率最大值区为轴心,从初夏（6月）至盛夏（7月和8月）,降水关键区在季节内呈顺时针移动,由海河流域东北部移至流域东部和南部再移至流域东部和中部。初夏,东北冷涡活动对流域关键区降水影响最显著,相对贡献率达69.6%;盛夏7月,流域关键区降水异常主要和西太平洋副热带高压（西太副高）脊线位置有关,其相对贡献率在60%以上;8月,西太副高脊线和东亚夏季风指数对流域关键区降水的相对贡献大小相当。海河流域降水关键区在夏季各月的分布变化,与这些环流系统的季内变化路径（南北摆动或向北推进）具有很好的一致性。 相似文献
15.
长沙城市形态与用地类型的时空演化特征 总被引：7，自引：4，他引：3
运用GIS技术与高级编程方法提取了长沙市1979、1996年、2003年的城市用地现状图的数据信息,借助最小二乘技术,通过幂指数拟合,计算出了各年份的城市形态与用地结构的分维数,并探讨了长沙城市分形演化的机理和城市形态演化的信息熵。通过对分维数的时空变化所包括信息的分析,发现长沙城市形态及各职能类用地存在明显的分形特征,且各类职能用地的分维小于城市形态的整体分维,符合理论上推断的城市分维包容原理,整个城市形态朝着混沌向有序渐趋优化演化,但同时也存在绿化用地与对外交通用地发展不够完善的问题。 相似文献
16.
经济欠发达地区中心城市空间拓展分析——以南充市为例 总被引：2，自引：2，他引：0
以四川省南充市为例,探讨了西部经济欠发达地区中心城市的空间拓展规律。基于多时相Landsat TM遥感数据和GIS的定量研究方法,以城市分形理论为基础,结合对城市实体地域空间在不同方向上的拓展分析,系统探讨了南充城市空间在不同时期的形态特征。通过人机交互的监督分类方法,提取了1988、1993、1999、2002和2007年5个年份的南充中心城市实体地域数据,在GIS中进行了叠加。采用半径法进行城市分形研究,发现各个时期南充城市总体上存在分形特征,但维数存在两个标度区,而且标度区之间的维数具有跳跃性,以此判断出城市在不同阶段的增长动力存在差异——从自然增长主导的扩张模式向多种增长力量共同作用的综合模式演化。在对南充城市实体地域进行分象限拓展分析后,发现南充城市在演化过程中存在明显的方向性,总体趋势为东北-西南的轴向拓展,并以此为基础建立了城市空间扩展模型。 相似文献
17.
There are only limited surface water resources available in the Heihe River Basin （HRB）, a typical inland river basin in the arid region of northwestern China, where groundwater overexploitation is a serious problem. Groundwater has become one of main resources of fresh water in the HRB. In this paper, temporal and spatial variations of groundwater in the HRB are estimated by the Gravity Recovery and Climate Experiment （GRACE） satellites. Our analysis shows that groundwater storage in the HRB reaches its highest in the summer of 2005, and then begins to decline in the following years and reaches steady status in 2008. Spatially, groundwater shows a decline in the upper HRB in the first two years and a slight increase in the following years, while this phenomenon is reversed in the middle HRB where groundwater slightly increases in 2005 and then declines in the following three years. In the lower HRB, GRACE detects a continual increase in the full six-year period. This approach is proven successful when employed in the HRB and thus offers a new insight into monitoring groundwater variations in a river basin with limited or even without any observed data. 相似文献
18.
As a typical inland river basin in arid Northwest China, having distinct hydrological characteristics and severe and representative
water problems, the Heihe River Basin (HRB) has attracted considerable research interest worldwide and in 2007
became a pilot basin of the G-WADI network of UNESCO/IHP. Many research programs have been conducted in the HRB
since the 1980s, producing rich knowledge and data about the basin, which will be very helpful to further studies. This paper
reviews research efforts related to hydrologic modeling and ongoing model integration studies performed in the HRB in recent
years. Recently, an observation network covering the whole area and a Web-based data-sharing system have been established
which can greatly improve data acquisition. This paper tabulates modeling activities in past years, including model applications,
model modifications and enhancements, and model coupling efforts. Also described is a preliminary modeling integration
tool designed to quickly build new models, which has been developed for hydrologic modeling purposes. Challenges
and issues confronted in current studies are discussed, pointing toward key research directions in the future. 相似文献
19.
土地利用类型结构的多尺度转换特征 总被引：10，自引：4，他引：6
尺度一直是LUCC到GLP研究所关注的重要问题。以不同比例尺的辽宁省土地利用数据为例,以贵州省土地利用数据进行验证,系统探讨了土地利用类型结构在不同尺度间可能存在的转换特征。结论如下:(1)辽宁省土地利用的分形结构跨1 ∶ 10万、1 ∶ 50万、1 ∶ 100万这3个比例尺客观存在;(2)对不同比例尺的同一区域不同土地利用类型而言,各土地利用类型分维在不同比例尺之间存在的响应关系并不一致,某些土地利用类型的分维随着比例尺由1 ∶ 10万向1 ∶ 50万再向1 ∶ 100万的变小,分维呈现变大趋势,而某些土地利用类型的分维随比例尺的变化并不如此,所以,对于不同的土地利用类型而言存在一定的差别,不可一概而论;(3)不同尺度间的土地利用类型结构只能够在两两连续间隔的两种比例尺土地分维之间建立起关系显著的定量关系模型。所得结论对科学认知土地结构空间配置的多尺度特征以及建立相应尺度转换模型具有积极的参考意义。 相似文献