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91.
Tree health is a critical parameter for evaluating urban ecosystem health and sustainability. Traditionally, this parameter has been derived from field surveys. We used multispectral remote sensing data and GIS techniques to determine tree health at the University of California, Davis. The study area (363 ha) contained 8,962 trees of 215 species. Tree health conditions were mapped for each physiognomic type at two scales: pixel and whole tree. At the pixel scale, each tree pixel within the tree crown was classified as either healthy or unhealthy based on vegetation index values. At the whole tree scale, raster based statistical analysis was used to calculate tree health index which is the ratio of healthy pixels to entire tree pixels within the tree crown. The tree was classified as healthy if the index was greater than 70%. Accuracy was checked against a random sample of 1,186 trees. At the whole tree level, 86% of campus trees were classified as healthy with 88% mapping accuracy. At the pixel level, 86% of the campus tree cover was classified as healthy. This tree health evaluation approach allows managers to identify the location of unhealthy trees for further diagnosis and treatment. It can be used to track the spread of disease and monitor seasonal or annual changes in tree health. Also, it provides tree health information that is fundamental to modeling and analysis of the environmental, social, and economic services produced by urban forests.  相似文献   
92.
93.
近年来,在刑事司法中时常遇到这样的问题1997年才全面修订的、有400多个罪名的刑法典对一些犯罪案件却难以适用.通过对中、日两国刑事立法的比较分析,探讨了刑法罪名简略与繁缛的利弊得失.认为罪名的简繁各有利弊,但简略利大于弊;法的特性决定罪名的高度概括性;刑法的适用需要法官的判断和推理;关键是尽快改革司法体制,大力提高法官的整体素质.  相似文献   
94.
Increasingly around the industrialized world, labour markets rely upon the paid work of women, many of whom have dependents. Such changing patterns of paid work by women — and by men — are located within work/care regimes that are more or less hostile to the needs of paid workers who care for others. This article sets out a model of work/care regimes and locates the Australian case within international and historical contexts. In Australia, the unchanging normative male worker archetype dominates institutions of work and care, while the cultures of motherhood and fatherhood remain stoically resistant to renovation. In the meantime, the behaviour of working women runs ahead of these unchanging cultures and institutions, creating a policy interest in ‘reconciling’ work and care, but a failure to provide it. The reasons for this failure are outlined.  相似文献   
95.
What do we mean by progress and cumulation in the social and human sciences? Recent thinking in the philosophy and history of science has led to an abandonment of some versions of logical positivism and of verificationism that had a strong deductive and theory testing orientation. What is to replace them is less clear. This paper argues that progress and cumulation can be seen as a process of evaluation and retention within an epistemic community. Scholarly disciplines differ in their social structure and in their epistemic and normative commitments. Since sociology is a fragmented discipline, progress and cumulation differ within its multiple subdisciplines, which to varying extents represent epistemic communities. Brief sketches of progress (advance) and cumulation in several subdisciplines are offered.  相似文献   
96.
作者运用理论分析和实证分析相结合的方法对佛山市经济发展的实践予以深刻剖视后指出:佛山市经济建设处在从物质投入主导型向科技进步主导塑转变的转折点上,在跨世纪的经济发展与经济竞争中,佛山市必须实行科技兴市的新发展战略,作者对佛山市科技兴市战略的涵义,目标,条件作了深入分析,并进而设计了科技兴市战略的运行机制和政策落点。  相似文献   
97.
When a researcher enters an interview, she has already construed it as being a standard type of communicative event. This article considers how a researcher's construal of a communicative event as either an ethnographic or survey interview shapes the production of information. Interview standards entail epistemological assumptions that directly inform the type of information sought and produced. I consider this process through a comparison of the elicitation techniques I employed in survey and ethnographic interviews conducted during research in Mexico. I draw on theory in linguistic anthropology on the nature of meaning in language, examining how dialogicality and interaction are essential to understanding the construal of communicative events.  相似文献   
98.
Abstract.  The likelihood ratio statistic for testing pointwise hypotheses about the survival time distribution in the current status model can be inverted to yield confidence intervals (CIs). One advantage of this procedure is that CIs can be formed without estimating the unknown parameters that figure in the asymptotic distribution of the maximum likelihood estimator (MLE) of the distribution function. We discuss the likelihood ratio-based CIs for the distribution function and the quantile function and compare these intervals to several different intervals based on the MLE. The quantiles of the limiting distribution of the MLE are estimated using various methods including parametric fitting, kernel smoothing and subsampling techniques. Comparisons are carried out both for simulated data and on a data set involving time to immunization against rubella. The comparisons indicate that the likelihood ratio-based intervals are preferable from several perspectives.  相似文献   
99.
1917年京直水灾与赈济情况略述   总被引:1,自引:0,他引:1  
1917年,京直地区出现了数十年未遇的大水灾,一百多个县被淹,几百万人口受灾,灾情十分严重。水灾发生后,北洋政府和社会各界予以高度重视,施行了一系列赈灾措施,使灾民的困苦得到一定程度的缓解。但是,在赈灾过程中也存在着不少的弊端,使赈灾效果大打折扣,这是由当时的社会政治环境所造成的。  相似文献   
100.
Summary.  The paper performs an evaluation of the data that were collected in the sixth wave of the British Household Panel Survey (BHPS) on childhood family structure. After comparing such data with a large number of studies by using external sources, we find that the BHPS data overestimate the proportion of people who report an experience of life in a non-intact family during childhood by about 10%. Although an explanation based on recall error that deteriorates with the age of the BHPS respondents is possible, the overestimation is likely to be accounted for by non-ignorable attrition that may affect most of the comparison studies based on longitudinal data. Conversely, comparisons with other independent measurements from the BHPS itself reveal that the wave 6 data underestimate the proportion of young people who have lived at least part of their childhood in a non-intact family by about 8%. The probability of disagreement between these two sets of measures is strongly associated with poor interview characteristics, which may affect the comparison measure more than the wave 6 measure. Despite such differences, there is therefore a substantial degree of similarity between the family structure information that was collected in the sixth wave of the BHPS and the host of highly diverse records against which it has been compared.  相似文献   
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