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We surveyed small-scale farmers in the Kenyan Rift Valley province (Narok and Nakuru districts) to describe constraints to, and changes in, livestock production and to assess the extent to which farmers have adopted new technologies promoted by extension services. In the arid areas of southern Narok, farmers' main constraints were drought and disease. Farmers in Nakuru district, situated in the fertile highlands of the Rift Valley, were also affected by disease but also lacked markets and capital. Although 83% of the farmers had regular contact with extension services that provided advice on new technologies and livestock production innovations, only about half of the respondents implemented the proposed changes. Many of those who did change (38%) improved pasture/nutrition/manure management and relatively few (16%) improved their animal breeding practices. Results of a multinomial logit model revealed that, apart from the significant differences between the two districts, the nature of the advice and the expected outcomes had the strongest influence on the probability of successfully implementing changes to livestock production. The results further suggest that adoption of new technologies is limited by lack of knowledge, inadequate support and a failure to target local needs and conditions and empower livestock keepers. 相似文献
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李晓培 《广东海洋大学学报》1998,(2)
设m、n是正整数a1,a2,…,an是不同的奇数。本文证明了,当m＞1且n是2的方幂时Schur多项式f(x）=（x-a1）2m（x-a2)2m(x-an)2m+1在有理数域Q上是不可约的,该结果部分地解决了Schur猜想问题。 相似文献
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To fully understand forest resources, it is imperative to understand the social context in which the forests exist. A pivotal part of that context is the forest ownership. It is the owners, operating within biophysical and social constraints, who ultimately decide if the land will remain forested, how the resources will be used, and by whom. Forest ownership patterns vary substantially across the United States. These distributions are traditionally represented with tabular statistics that fail to capture the spatial patterns of ownership. Existing spatial products are not sufficient for many strategic-level planning needs because they are not electronically available for large areas (e.g., parcels maps) or do not provide detailed ownership categories (e.g., only depict private versus public ownership). Thiessen polygon, multinomial logit, and classification tree methods were tested for producing a forest ownership spatial dataset across four states with divergent ownership patterns: Alabama, Arizona, Michigan, and Oregon. Over 17,000 sample points with classified forest ownership, collected as part of the USDA Forest Service, Forest Inventory and Analysis (FIA) program, were divided into two datasets, one used as the dependent variable across all of the models and 10 percent of the points were retained for validation across the models. Additional model inputs included a polygon coverage of public lands from the Conservation Biology Institute’s Protected Areas Database (PAD) and data representing human population pressures, road densities, forest characteristics, land cover, and other attributes. The Thiessen polygon approach predicted ownership patterns based on proximity to the sample points in the model dataset and subsequent combining with the PAD ownership data layer. The multinomial logit and classification tree approaches predicted the ownership at the validation points based on the PAD ownership information and data representing human population, road, forest, land cover, and other attributes. The percentage of validation points across the four states correctly predicted ranged from 76.3 to 78.9 among the methods with corresponding weighted kappa values ranging from 0.73 to 0.76. Different methods performed slightly, but statistically significantly, better in different states Overall, the Thiessen polygon method was deemed preferable because: it has a lower bias towards dominant ownership categories; requires fewer inputs; and is simpler to implement. 相似文献
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单桩静载荷试验极限承载力的预测 总被引：5，自引：0，他引：5
桩基承载力对桩基抗震性能有很大影响。介绍了一种单桩静载荷试验极限承载力的预测法——多项式回归法。在静载荷试验中，由于种种原因终止荷载未达到极限荷载时，可用上述方法进行推测。同时通过实例对比说明，这种方法对于静载荷试验具有一定的经济效益。 相似文献
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It is possible to reconstruct the past variation of an environmental variable from measured historical indicators when the
modern values of the variable and the indicators are known. In a Bayesian statistical approach, the selection of a prior probability
distribution for the past values of the environmental variable can then be crucial and the selection therefore should be made
carefully. This is particularly the case when the data are noisy and the statistical model used is complex since the influence
of the prior on the results can then be especially strong. It can be difficult to elicit the prior probability distribution
from the available information, since usually there are no measured data on the past values of the variable one wants to reconstruct
and different reconstructions are typically consistent with each other only at a coarse level. To overcome these difficulties
we propose to use a non-informative smoothing prior, possibly in combination with an informative prior, that simply penalizes
for roughness of the reconstruction as measured by the variability of its values. We believe that it can sometimes be easier
to set an overall prior distribution on the roughness than to agree on a prior for the actual values of the reconstructed
variable. Note that by using a smoothing prior one incorporates into the model itself the smoothing step usually done before
or after the actual numerical reconstruction. Another idea proposed in this paper is to integrate the reconstruction model
with a multiscale feature analysis technique known as SiZer. Multiscale analysis of the posterior distribution of the reconstructed
variable makes it possible to infer its statistically significant features such as trends, maxima and minima at several different
time scales. While only temperature is considered in this paper, the technique can be applied to other environmental variables. 相似文献
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This paper utilizes the 2009/2010/2011 American Community Survey to examine spatial patterns of later-life relocation from the state of New York into Florida. Given that the first-wave of the Baby Boom generation reached the retirement age of 65 years in January 2011 and many more will continue to do so, examining the mobility/subsequent residential choices of this group is a worthwhile undertaking. This research paper is also a noteworthy contribution because it offers an interdisciplinary study of spatial statistics and population geography. Exploratory spatial analysis and multinomial regressions suggest older adults from New York leave select origins, such as Capital District, Mid-Hudson, and Lower Hudson. In addition, these older adults select preferred destinations in Florida, such as Fort Myers, Fort Pierce–Stuart, and West Palm Beach. This finding can inform planners, policy analysts, and social workers about how to best address issues related to health and community services since not all older adult migrants seeking coastal and recreational areas in Florida maintain greater wealth and better health. 相似文献
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Marcus Adolphson 《Journal of Geographical Systems》2008,10(4):345-367
The changes of land use patterns and urban structures could be seen as the dynamic result of the trade off between public
and private interests. Thereby the land use change is to some extent unpredictable. The focus in the current study is to measure
the importance of spatial location factors regarding new residential and commercial buildings in relation to existing urban
amenities and political guidelines. The relative importance of the location factors was studied by multinomial regression
analysis. Results from this study reveal that the location profiles of new urban object types attained here indicate strong
correspondence with local political land use guidelines and to clustering. The spatial distribution of new urban settlements
does not in general correspond to the monocentric urban scheme where firms and residents locate in spatial proximity to urban
centres.
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Armed-conflicts often occur in tropical areas considered to be of high ‘conservation-value’, termed as such for their biodiversity or carbon-storage functions. Despite this important overlap, few studies have assessed how forest-biomass is affected by armed-conflicts. Thus, in this paper we develop a multinomial logit model to examine how outcomes of the interactions between carbon-storage, armed-conflict and deforestation rates are linked to social, institutional and economic factors. We use Colombia as a case study because of its protracted armed-conflict, high forest-cover, sustained deforestation rates and on-going peace processes. Our empirical results show that the impacts of armed-conflicts on forest-cover are connected to specific socio-economical processes, such as unequal land distribution and land-grabbing, which typically occurs as part of ‘agricultural colonization’. Findings address a research gap by providing statistically sound evidence for associations between armed-conflicts and land-related grievances, which has rarely been demonstrated empirically. Our results also suggest that forest commons are associated with reduced armed-conflict, and simultaneously provide contributions to carbon storage and to meeting basic needs. Moreover, our forest-conflict transition models provide useful visual means to capture and relay to policymakers-the causes of forest cover-changes in a conflict-affected country. Finally, our findings imply that in dedicating their efforts to resolving land-ownership disputes, the Colombian government might uphold their international climate change commitments via reducing deforestation and hence forest based carbon emissions, while pursuing their national security objective via undermining opportunities for guerrilla groups to operate. 相似文献
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This study employed data from the 2005/06 Uganda national household survey to identify adaptation strategies and factors governing their choice in Uganda's agricultural production. Factors that mediate or hinder adaptation across different shocks and strategies include age of the household head, access to credit and extension facilities and security of land tenure. There are also differences in choice of adaptation strategies by agro-climatic zone. The appropriate policy level responses should complement the autonomous adaptation strategies by facilitating technology adoption and availing information to farmers not only with regard to climate related forecasts but available weather and pest resistant varieties. 相似文献
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