共查询到20条相似文献，搜索用时 31 毫秒
1.
T. S. Chinembiri M. C. Bronsveld D. G. Rossiter T. Dube 《Natural Resources Research》2013,22(4):297-309
In this study, two sampling protocols using a model-based and a design-based framework were juxtaposed to evaluate their precision in the estimation of C stock in the Ludikhola watershed, Nepal. The model-based approach exploits the spatial dependencies in the sampled variable and may therefore be attractive over the design-based approach as it reduces the substantial costs of survey and effort required in the latter. Scales of spatial variability for C stock which resulted in a grid resolution of 10,000 m2 were determined using a reconnaissance variogram. Akaike information criterion was used for the selection of the best linear model of feature space for use in kriging with external drift (KED). Among the five tested covariates, distance, elevation, and aspect were statistically significant, with the best model of feature space accounting for 87.7% variability of C stock. An ANOVA established significance differences in mean C stocks (P = 0.00017). KED using the best model of feature space was found to be more precise, (9.89 ± 0.17) sqrt mg C/ha, than a pure-based approach of ordinary kriging and the design-based approach, (9.91 ± 0.8) sqrt mg C/ha. The confidence bounds of the two estimators showed that their confidence intervals will overlap 99.7% of the time, with both confidence intervals falling within the 95% confidence bounds of each other. There is less uncertainty around the mean C stock estimated using the model-based approach than the mean C stock estimated using the design-based approach. The model-based approach is a prospective option for the REDD framework. 相似文献
2.
Antonio Páez Steven Farber Ruben Mercado Matthew Roorda Catherine Morency 《Urban geography》2013,34(6):815-842
Abstract In this article, we undertake an analysis of accessibility to jobs from the perspective of single-parent household members. Individuals in this demographic segment are of interest due to the fact they often face the double burden of household and employment responsibilities. A case study of the city of Toronto in Canada, an urban area that has seen an increase in absolute and relative numbers of single-parent households in recent years, is presented. Analysis is based on the application of relative accessibility deprivation indicators (RADI), which are calculated using model-based estimates of distance traveled for various population segments, as well as employment data for the city and its surroundings. The results of the analysis indicate that there are substantial differences in the levels of accessibility to jobs between members of single-parent households, in particular females, and members of other types of households. 相似文献
3.
Sytze de Bruin Arnold Bregt Marc van de Ven 《International journal of geographical information science》2013,27(5):457-471
This paper proposes and illustrates a decision analytical approach to compare the value of alternative spatial data sets. In contrast to other work addressing value of information, its focus is on value of control. This is a useful concept when choosing the best data set for decision making under uncertainty due to error in the reported data. Application of the concept requires probabilistic accuracy measures and a loss function representing the cost of incorrect judgement about some target property. This is illustrated by an assessment of the suitability of two digital elevation models (DEMs) for determining the volume of sand required for building a container port. To demonstrate flexibility of the approach, accuracy assessment was based on both a random and a systematic sample of error data, using design-based estimation and model-based prediction, that is geostatistics. Analysis results included the expected loss for each combination of DEM and sampling strategy. These indicated that both DEMs were equally suitable for the intended use. Operational practicability of the method is highly dependent on the willingness of database producers to give access to sample information similar to the quick looks provided to potential users of remote sensing imagery. 相似文献
4.
The variations of breast cancer mortality rates from place to place reflect both underlying differences in breast cancer prevalence and differences in diagnosis and treatment that affect the risk of death. This article examines the role of access to health care in explaining the variation of late-stage diagnosis of breast cancer. We use cancer registry data for the state of Illinois by zip code to investigate spatial variation in late diagnosis. Geographic information systems and spatial analysis methods are used to create detailed measures of spatial access to health care such as convenience of visiting primary care physicians and travel time from the nearest mammography facility. The effects of spatial access, in combination with the influences of socioeconomic factors, on late-stage breast cancer diagnosis are assessed using statistical methods. The results suggest that for breast cancer, poor geographical access to primary health care significantly increases the risk of late diagnosis for persons living outside the city of Chicago. Disadvantaged population groups including those with low income and racial and ethnic minorities tend to experience high rates of late diagnosis. In Illinois, poor spatial access to primary health care is more strongly associated with late diagnosis than is spatial access to mammography. This suggests the importance of primary care physicians as gatekeepers in early breast cancer detection. 相似文献
5.
Shannon R. M. O'Lear 《The Professional geographer》1996,48(2):209-217
The expansion of the Internet and e-mail access around the globe, especially into less-developed areas, raises the question of how geographers might use this technology for research purposes and the development of appropriate methodologies. This paper identifies three ways in which the use of e-mail surveys for geographic research differs from traditional mail surveys. First, there are substantial differences in selecting an appropriate sample population. Second, electronic medium considerations such as alphabet character translation, survey format, and receiving end conditions pose unique data collection challenges. Third, ascertaining that e-mail addresses to be included in a survey are operative is discussed as a useful means of maximizing the potential of an e-mail survey. Examples from an e-mail survey of environmentalists in Russia illustrate these points. 相似文献
6.
《The Professional geographer》2013,65(2):209-215
The expansion of the Internet and e-mail access around the globe, especially into less-developed areas, raises the question of how geographers might use this technology for research purposes and the development of appropriate methodologies. This paper identifies three ways in which the use of e-mail surveys for geographic research differs from traditional mail surveys. First, there are substantial differences in selecting an appropriate sample population. Second, electronic medium considerations such as alphabet character translation, survey format, and receiving end conditions pose unique data collection challenges. Third, ascertaining that e-mail addresses to be included in a survey are operative is discussed as a useful means of maximizing the potential of an e-mail survey. Examples from an e-mail survey of environmentalists in Russia illustrate these points. 相似文献
7.
Karen D. Johnson&#x;Webb 《The Professional geographer》2002,54(3):406-421
The North Carolina Hispanic population has grown at a rapid pace in recent years. Before 1980, the majority of Hispanics in North Carolina were engaged primarily in migrant agricultural work. Hispanics who are part of the new influx are arriving in urban areas and are working at nonagricultural pursuits. Previous research and anecdotal evidence suggest that Hispanic newcomers come from other U.S. jurisdictions and from abroad. Labor migration occurs in response to demand for labor, and labor demand is meditated by employers’ preferences and hiring practices. However, focusing solely on employer demand for labor ignores the role of past U.S. immigration policy and the large growth in services employment in the Sunbelt that have fueled the Hispanic in–migration. This research project explored the attitudes and recruiting behavior of employers in the Triangle region of North Carolina. A newspaper content analysis was undertaken, and interviews were conducted with selected intermediaries and a group of employers. Qualitative analysis of the data collected revealed that these employers utilize the social networks of their immigrant Hispanic employees to recruit new workers. They also use a variety of other recruiting methods to recruit Hispanics both locally and from abroad. If this practice is widespread, it may be fueling the influx of Hispanic immigrants to North Carolina. Employers interviewed extolled the work ethic of Hispanic workers and often bypassed native–born workers, whom they felt were inferior employees. These findings have ramifications for future immigration policy and for the success of welfare–to–work programs. Employer demand for labor is one factor that must be considered when formulating new immigration policy. 相似文献
8.
Juliana Maantay 《The Professional geographer》2013,65(3):406-408
The North Carolina Hispanic population has grown at a rapid pace in recent years. Before 1980, the majority of Hispanics in North Carolina were engaged primarily in migrant agricultural work. Hispanics who are part of the new influx are arriving in urban areas and are working at nonagricultural pursuits. Previous research and anecdotal evidence suggest that Hispanic newcomers come from other U.S. jurisdictions and from abroad. Labor migration occurs in response to demand for labor, and labor demand is meditated by employers’ preferences and hiring practices. However, focusing solely on employer demand for labor ignores the role of past U.S. immigration policy and the large growth in services employment in the Sunbelt that have fueled the Hispanic in–migration. This research project explored the attitudes and recruiting behavior of employers in the Triangle region of North Carolina. A newspaper content analysis was undertaken, and interviews were conducted with selected intermediaries and a group of employers. Qualitative analysis of the data collected revealed that these employers utilize the social networks of their immigrant Hispanic employees to recruit new workers. They also use a variety of other recruiting methods to recruit Hispanics both locally and from abroad. If this practice is widespread, it may be fueling the influx of Hispanic immigrants to North Carolina. Employers interviewed extolled the work ethic of Hispanic workers and often bypassed native–born workers, whom they felt were inferior employees. These findings have ramifications for future immigration policy and for the success of welfare–to–work programs. Employer demand for labor is one factor that must be considered when formulating new immigration policy. 相似文献
9.
Late in the summers of 1997 and 1998 surveys of common eider ( Somateria mollissima ) colonies were conducted throughout Avanersuaq Municipality in north-west Greenland. Although old information from eider colonies was available, these surveys provided the first almost all colonies in the district, thereby improving the baseline data for assessing future population changes. The surveys were based on nest counts, and all but two colonies in the district were counted, In total, 3800 nest were counted and an educated guess for the total population in Avanersuaq Municipality, including the two inaccessible colonies, would be around 5000 pairs. Average clutch size was 3.74 similar to or higher than in other areas of Greenland and high Artic Canada suggesting favourable conditions for eiders in the survey area. Comparison with older data suggests that the breeding population in Avanersuaq is stable. This observation contrasts with the declines ocserved in other parts of Greenland. Further studies into possible population specific mirigation routs and wintering areas as well as the direct and indirect effects of the intensive winter hunting in south-west Greenland are warranted. 相似文献
10.
长江三角洲人口与经济的非均衡格局及其影响因素研究 总被引：3，自引：2，他引：1
人口与经济分布格局是反映区域差异的重要指标。结合不一致指数、重心方法及不均衡指数等对长江三角洲人口与经济的非均衡格局演变进行研究,并基于2000~2015年的面板数据回归对其影响因素进行实证研究。研究发现,长江三角洲人口与经济非均衡格局呈现相对稳定状况,但随着区域发展格局转变带来的人口与经济分布格局的差异化演变,区域人口与经济的整体非均衡性有所弱化。对人口与经济非均衡格局影响因素分析表明,不同时期人口与经济不一致指数影响因素存在差异,在始终受城市发展差异影响的同时也伴随着市场力量的趋强和政府影响的弱化。 相似文献
11.
NILS ARE ØRITSLAND 《Polar research》1998,17(1):101-105
Two censuses made of the population of Svalbard reindeer on Edgeøya in 1983 and 1996 resulted in 1586 and 2434 individuals respectively. Together with data from earlier population surveys (1969-77), this indicates, numerically, a population growth during the period 1969-96. Because of the weaknesses in the different census methods used, we cannot conclude that in reality a population growth has taken place even though the numerical data is correct. Therefore an average population size of 1730 (± 451 SD) individuals for the period 1969-96 is suggested. Earlier estimates of vegetated area indicate that the present data corresponds to reindeer densities averaging 1.05 and ranging from 0.79 to 1.47 individuals/km2 . 相似文献
12.
Weights-of-evidence (WofE) and logistic regression techniques were used in a GIS framework to predict the spatial likelihood
(prospectivity) of crushed-stone aggregate quarry development. The joint conditional probability models, based on geology,
transportation network, and population density variables, were defined using quarry location and time of development data
for the New England States, North Carolina, and South Carolina, USA. The Quarry Operation models describe the distribution of active aggregate quarries, independent of the date of opening. The New Quarry models describe the distribution of aggregate quarries when they open. Because of the small number of new quarries developed
in the study areas during the last decade, independent New Quarry models have low parameter estimate reliability. The performance
of parameter estimates derived for Quarry Operation models, defined by a larger number of active quarries in the study areas,
were tested and evaluated to predict the spatial likelihood of new quarry development. Population density conditions at the
time of new quarry development were used to modify the population density variable in the Quarry Operation models to apply
to new quarry development sites. The Quarry Operation parameters derived for the New England study area, Carolina study area,
and the combined New England and Carolina study areas were all similar in magnitude and relative strength. The Quarry Operation
model parameters, using the modified population density variables, were found to be a good predictor of new quarry locations.
Both the aggregate industry and the land management community can use the model approach to target areas for more detailed
site evaluation for quarry location. The models can be revised easily to reflect actual or anticipated changes in transportation
and population features. 相似文献
13.
Evaluations connect ecosystem and human welfare to achieve restoration. There have been an increasing number of studies conducted on various ecosystem service assessments, but little research has focused on inland river basins playing a critical role in development in northwestern China. The distinct differences in natural endowment, socioeconomic characteristics among the upper, middle and downstream inland river basin require heterogeneity during evaluation. The objective of this study was to verify the existence of population preference heterogeneity and examine impact factors using choice experiment surveys in the Shiyang River Basin, China. A mixed logit model using data from 714 households across the entire basin estimated mean willingness to pay and the standard deviation for ecological attributes. Ordinary least squares (OLS) was employed to estimate the effects of exogenous variables on all willingness to pay estimations. The results demonstrate that ecosystem service values are heterogeneous among people. Willingness to pay is affected by personal and regional characteristics. Government involvement will be required to seek differentiated ecosystem services values among populations and facilitate public support. 相似文献
14.
全国农情监测与估产的运行化遥感方法 总被引：105，自引：3，他引：102
农作物遥感估产包括农作物的长势与产量趋势监测及产量的早期预报。在总结１５年来国内遥感估产成果的基础上,提出了以充分利用已有成果为基础的全国范围农作物估产运行化遥感方法。建成了ＮＯＡＡ ＡＶＨＲＲ数据实时预处理系统,并利用每旬的ＡＶＨＲＲ最大ＮＤＶＩ图像与上年同期数据对比实现全国范围的家作物遥感长势监测。在高精度耕地数据库的支持下,通过提取不同作物种植成数估算作物种植面积。种植成数可以用ＴＭ和多时相 相似文献
15.
转型期广州市居住迁移影响因素于户籍之间的比较 总被引：7，自引：3，他引：4
住房制度改革以来,中国城市居住迁移率大规模增加,成为城市重构和社会空间分异的基础动力。利用生命历程理论,通过家庭问卷调查,本文使用事件史模型动态地模拟了居住迁移,并比较外来人口与本地人口居住迁移影响因素的差异。整体来看,1980年以来年均居住迁移率呈上升趋势,外来人口的年均居住迁移率要比本地人口高。住房性质、婚姻变化、工作变动、居住区位和年份等变量都显著影响居住迁移,反映了住房制度改革、住房市场和分配环境、家庭生命周期等因素对居住迁移的影响;但影响程度户籍间的差异明显,工作地区位的变动导致通勤成本的变化是外来人口居住迁移的最显著影响因子,而家庭生命周期和住房特征变量是本地人口居住迁移的最显著影响变量,反映了两者之间的本质差别。居住区位对本地人口的居住迁移影响显著,内圈层居民的迁移率相对较低,而居住区位变量对外来人口的影响相对较弱。 相似文献
16.
《Norsk geografisk tidsskrift. Norwegian journal of geography》2012,66(3):189-198
In Norway, the management of natural and cultural resources is subject to increasing public scrutiny. Conflicts are escalating over many issues concerning the balance between preservation and utilisation. Traditionally conflicts over issues like growth in commercial nature tourism, predator control, forest policies, protected areas management, cultural heritage protection, and rights associated with common access, have been explained in terms of opposing values, attitudes, and goals between urban and rural interests. However, historical differences between the urban and rural in terms of social conditions, employment opportunities, services, cultural norms, and lifestyles are no longer clear-cut or predictable. Nor can differences between urban and rural communities easily explain attitudes or values held in relation to the environment. To examine how a local community and a population of tourists feel about an area we examine data from two separate surveys from the Femundsmarka-Røros region in Southern Norway. This region includes a wilderness-type national park and a historic mining town recognised as a World Heritage Site and including a diverse agricultural landscape. We compare the perspective of the community with that of tourists regarding the strength and nature of attachment to place, and reasons and priorities for resource protection. We also assess how residence and experience of using the area affect attachment to place and attitudes to management priorities. The results have implications both for the management of this particular area, and for how we approach attitude diversity in resource management. 相似文献
17.
Social data from census and household surveys provide key information for monitoring the status of populations, but the data utility can be limited by temporal gaps between surveys. Recent studies have pointed to the potential for remotely sensed satellite sensor data to be used as proxies for social data. Such an approach could provide valuable information for the monitoring of populations between enumeration periods. Field observations in Assam, north-east India suggested that socioeconomic conditions could be related to patterns in the type and abundance of local land cover dynamics prompting the development of a more formal approach. This research tested if environmental data derived from remotely sensed satellite sensor data could be used to predict a socioeconomic outcome using a generalised autoregressive error (GARerr) model. The proportion of female literacy from the 2001 Indian National Census was used as an indicator of socioeconomic conditions. A significant positive correlation was found with woodland and a significant negative correlation with winter cropland (i.e., additional cropping beyond the normal cropping season). The dependence of female literacy on distance to nearest road was very small. The GARerr model reduced residual spatial autocorrelation and revealed that the logistic regression model over-estimated the significance of the explanatory covariates. The results are promising, while also revealing the complexities of population–environment interactions in rural, developing world contexts. Further research should explore the prediction of socioeconomic conditions using fine spatial resolution satellite sensor data and methods that can account for such complexities. 相似文献
18.
Dr Helen Mounsey 《International journal of geographical information science》2013,27(5):451-454
Abstract This is the second of two papers which elaborates a framework for embedding urban models within GIS. In the first paper (Batty and Xie 1994), we outlined how the display functions of a proprietary GIS could be used to organize a series of external software modules which contained the central elements of the modelling process, namely dataset selection and analysis, and model specification, calibration, and prediction. In that paper, we dwelt on display and data analysis functions whereas here we outline the model-based functions of the system. We begin by reviewing residential location models based on population density theory, stating continuous and discrete model forms, and calibration methods. We then illustrate a pass through the software using data for the Buffalo urban region, showing how observed data and model estimates can be evaluated through graphic display. We present ways in which the system can be used to explore and fit a variety of models to different zoning systems and in so doing, show how subset selection and aggregation can be used to find models with good fit. Finally we draw conclusions and outline an agenda for further research. 相似文献
19.
中国城市群人口老龄化时空格局 总被引：15，自引：2，他引：13
老龄化和城市化是当今世界面临的两大人口问题。城市群是城市发展到成熟阶段的空间组织形态,是老龄化的特殊区域。本文基于2000年和2010年全国人口普查分县数据,综合应用地理探测器和变异系数等方法,清晰地刻画了中国20个城市群人口老龄化的空间格局及其变化特征,审视了人口老龄化变化的影响因素。结果表明：① 2000年中国城市群人口老龄化平均水平为7.32%,其中12个城市群的人口属于成年型,到2010年时人口老龄化平均水平已上升为9.00%,除珠三角与宁夏沿黄城市群外,其余18个城市群均步入了老年型人口,表现出明显的水平升级与类型替变态势。② 老龄化高值、较高值区域不断向内陆城市群跃迁。③ 城市群老龄化的增量和增速存在显著的区域差异,老龄化水平的低值区和高值区增量少、增速慢,而较低值、中值和较高值区增量多、增速快。总体上表现出区域性城市群——国家级城市群——地区性城市群老龄化速度递减的态势。④ 在城市群内部,老龄化分布格局表现出隆升—塌缩并存的现象。国家级城市群内部老龄化分布格局从隆升结构向塌缩结构转变,城市群中心区人口老龄化水平降低;而地区性城市群和区域性城市群内部老龄化分布格局则从均质结构向隆升结构转变,中心区人口老龄化水平上升。⑤ 城市群人口老龄化是内外因素综合影响的结果,基期老龄化程度、人口年龄结构替变和人口流动性是主导性因素。其中人口年龄结构的普遍性抬升是城市群老龄化升级与类型替变的关键,低龄人口迁入到城市群对人口老龄化则起到“稀释作用”,城市群发育阶段不同引致的聚集和扩散效应对老龄化则起到诱导作用。 相似文献