共查询到19条相似文献，搜索用时 281 毫秒
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在不相容信息系统中,代数观点与信息论观点下的属性约简是不等价的。阐述了分布约简与信息论观点下约简的等价性,分析了代数观点下区分矩阵的缺陷,提出了基于分布约简的区分矩阵方法。该方法充分考虑了决策系统的不相容情形,得到信息系统在分布约简概念下的约简,理论分析与仿真实例表明了该算法的可行性和有效性。 相似文献
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图像分割是把图像分成各具特性的区域并提取出感兴趣目标的技术和过程,图像分割新算法一直在更新,但都有局限性。本文介绍几种基于图论的图像分割算法,并对各自算法特点进行分析,通过将Normalized Cut归一化割集准则与图像的阈值分割联合起来区分目标和背景,提出了改进权值公式的算法。通过实验比较分析,改进的归一化图像分割算法有效消除了噪声,取得良好的实验效果,更接近人眼视觉的分割效果,并减少了算法的运算量。 相似文献
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给出了一种求一类带弱奇异核Volterra积分微分方程的数值新方法,即基于Laplace变换的数值逆方法,并给出了数值例子. 相似文献
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熵是度量集合不确定程度的一个非常重要的度量，对于直觉模糊集合也是如此。提出一类新的距离测度，并在此基础上发展直觉模糊多属性决策方法。首先构造一类新的直觉模糊熵测度，然后借助其确定多属性问题中的属性权重，进而提出基于新的熵测度的直觉模糊多属性决策法，最后通过饲料供应商选择算例考察算法的有效性和可行性。 相似文献
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利用粗糙集理论((Rough Set))中的知识表达系统和约简算法,在研究区内选取与立地因子关系最密切的树高因子为决策属性,以海拔、母岩、坡度、坡位、土类和土层厚度作为条件属性;决策属性动态聚类和各条件属性值域离散化后,建立立地类型分类决策表,计算决策属性的依赖度及其相对约简,得到马尾松林分立地类型的分类因子为土层厚度、坡位和母岩,并且其重要性分别为0.692 3、0.538 5和0.307 7. 相似文献
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针对木材缺陷图像,采用基于小生境和交叉算子的粒子群算法（NCSPSO）优化支持向量机（SVM）进行图像分割,提取木材缺陷分割图。主要对NCSPSO算法进行改进,寻找最优惩罚系数C和高斯核函数中的参数,然后采用SVM方法对训练样本进行综合训练,以建立最佳分类模型,并对木材缺陷图像分割测试。与模拟退火法（SA）及原NCSPSO算法进行对比实验,从而验证改进NCSPSO算法的优越性。 相似文献
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针对现有光顺算法在去除噪声的同时不能很好地保护好边缘拐角等细节信息的不足,提出了基于灰度图轮廓提取的磨光光顺算法,其采用改进的Laplace算子并经过预处理后对灰度图边缘进行提取,通过轮廓追踪获得图像边缘信息,然后只对非轮廓非细节部分进行光顺.试验结果表明,该方法降低了光顺算法的盲目性,有效地保留了原有数据的细节信息. 相似文献
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基于高频变异免疫进化算法的多峰值函数优化 总被引：1，自引：0，他引：1
多峰值函数优化问题一直是数值优化领域中研究的难点。本文提出一种基于高频变异的改进免疫进化算法,通过克隆选择高频变异抗体来增加群体多样性,又赋予抗体生命期抑制群体暴增,此外引入变异因子提高抗体识别抗原的速度。该算法即克服克隆选择算法的收敛速度慢,又克服遗传算法易陷入局部最优解的不足。对三个多峰值函数优化仿真,并和标准遗传算法、改进遗传算法和佳点遗传算法的计算结果进行比较,证明该方法可以快速收敛到全局最优解。 相似文献
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基于粗糙集的林分经营决策因子分类研究 总被引：3，自引：0，他引：3
以湖南涟源龙山森林公园次生林林分为研究对象,以森林生态系统近自然经营为目标,以林分空间结构理论为指导,选取影响林分经营决策的多个主要因子作为条件属性,以主要经营措施择伐作为决策属性,应用粗糙集理论(Rough Set)进行属性约简,获得各因子的决策优先度和指标权重,精简和优化林分经营决策的指标体系。结果表明:应用优化的经营决策指标体系指导林分经营,有利于林分空间结构的优化和生态系统的稳定,且实际使用简单,操作性强。 相似文献
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《Southern Forests》2013,75(3):207-214
This study presents an application of a stand table projection method for varying stand densities of Eucalyptus grandis in South Africa. The projections of diameter at breast height (dbh) class frequencies are compatible with future values of basal area and stem number per hectare. The application requires an individual tree dbh growth function, a current stand table, and estimates of future basal area, and tree survival. The resulting stand table is adjusted by an algorithm that guarantees that the future stand table is compatible either with observed or predicted values of basal area and stem number per hectare. The results, based on a relatively small experimental dataset, are satisfactory. However, further work based on a larger dataset is required to evaluate the general suitability of the method for stand table projection of Eucalyptus grandis in South Africa, especially regarding variable site conditions. The particular contribution of this study is the fact that we were able to demonstrate the suitability of the Nepal and Somers stand table projection method for a unique dataset from a very densitysensitive Correlated Curve Trend spacing trial. We also made an attempt to present a comprehensive example of a projection to facilitate practical application of this method in the KwaZulu-Natal coastal plain of South Africa. 相似文献
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A regional study of consumer satisfaction and preferences for various chestnut attributes was conducted in 2009. Surveys were distributed to five chestnut growers/sellers in Missouri, Iowa, Kansas, Ohio and Illinois to accompany chestnut sales to their individual customers. Returned surveys represented consumers from 18 states, mainly the U.S. Midwest but also from the East and West coasts. The survey measured consumer satisfaction with the chestnuts purchased (by using affective, cognitive and behavioral constructs), assessed consumer’s general knowledge about chestnuts, frequency of consumption and familiarity with cooking. The survey also included a choice-based conjoint analysis to evaluate the effects of origin, production process and price on consumer preferences for chestnuts. Results show that high satisfaction with chestnuts purchased increases the likelihood of future purchase. Most consumers who buy chestnuts know that chestnuts need to be refrigerated but more educational effort is needed regarding the low fat content of chestnuts as compared to other nuts and the gluten-free attribute of chestnut flour. Conjoint analysis of chestnut attributes (origin, production process and price) confirmed results of past studies. Holding other attributes constant, chestnut origin is the most important attribute influencing purchases, consumers strongly preferring locally grown chestnuts over U.S. grown or imported. Chestnuts grown organically or pesticide free were preferred over conventional production. Price also has a significant influence on the purchase decision but its relative effect was lowered when bundled with the other product attributes. 相似文献
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《Scandinavian Journal of Forest Research》2012,27(4):405-409
Spore germination, growth and appresssoria formation for Melampsora willow rust were studied for compatible and incompatible hosts to elucidate penetration specificity and prehaustorial events in the infection process. Rust originating from Salix dasyclados was inoculated on a compatible (S. dasyclados) and an incompatible (Salix daphnoides) clone and, for comparison, on the non-host plants tomato, tobacco and poplar. The same experimental procedure was also carried out for rust originating from poplar. Rust development was followed for 5 days at 20 h intervals using a microscope with fluorescent equipment. The study showed that the Melampsora rust can develop on, and penetrate, the leaf regardless of whether the rust was inoculated on compatible or incompatible willow plants. However, the fungus was able to infect and reproduce itself only in compatible interactions. For willow rust in the prehaustorial stage, the study indicated that specific recognition mechanisms were unnecessary to start the infection process. 相似文献
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Peach (Prunus persica L. Batsch) shoots grafted onto compatible or incompatible clones of rootstocks of myrobolan plum (Prunus cerasifera L. Ehrh. cv. myrobolan) were observed in a greenhouse for 100 days after grafting. The incompatible grafts showed foliar symptoms of incompatibility and reduced shoot growth about 60 days after grafting. Light microscopic studies revealed that cambial activity stopped earlier in the rootstocks, than in the scions, of incompatible grafts. Structural modifications were also observed in the phloem of incompatible grafts. Compared with the compatible graft rootstock, the number of sieve elements differentiated from the cambial zone was reduced in the incompatible graft rootstock, whereas the production of parenchyma cells was not affected. No important ultrastructural alteration was observed in the sieve tubes of the incompatible grafts. However, osmiophilic granulations near the plasma membrane of sieve plates were observed more frequently in the rootstocks of incompatible grafts than in ungrafted myrobolan controls. It is concluded that the external symptoms of incompatibility are not related to massive structural modifications or degeneration of the conducting tissues. 相似文献
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To characterize the structural events associated with incompatibility of graft development, we conducted a histological study of compatible and incompatible pear/pear and pear/quince grafts that had been grown for five months in a greenhouse. Multivariate analysis of histological data describing the structure of the graft union allowed us to discriminate between compatible and incompatible combinations before either macroscopic examination or qualitative microscopic examination differences between graft combinations became evident. The histological variables responsible for the discrimination between incompatible and compatible unions were related to three typical symptoms of graft incompatibility: bark discontinuity, which was the main feature; cambial dysfunction; and accumulation of starch in the scion. Little cell necrosis was observed at the interface of incompatible grafts at the 5-month stage of graft development. Multivariate analysis of histological data provides a new tool for studying early structural events resulting from the graft incompatibility response and for diagnosing early graft incompatibility. 相似文献
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《Forest Policy and Economics》2008,10(4):205-219
With changes in land management planning and a new federal fire policy, increased emphasis has been placed on protecting a broader set of resource values such as those associated with sensitive species habitat or cultural resources. Fire managers have long needed a system for assessing values at risk across the landscape that can be implemented in accordance with the budgeting and appropriation process and that can be updated annually or every several years. A viable system has to be operational at a reasonable cost and it must support strategic planning and budgeting. Currently available valuation methods, in their entirety, can be costly and time consuming making them problematic for these purposes. Consequently, managers have become accustomed to assessing values at risk without the direct support of structured economic analysis. This paper discusses an approach (Marginal Attribute Rate of Substitution) to assessing values at risk for initial attack planning and budgeting. MARS is an attribute based method for estimating rates of substitution among fire protection attributes in a spatial context. It consists of and builds upon specific elements from well known and peer-reviewed valuation methods for resource valuation. As such, MARS relies upon stated preference, expert opinion, the hedonic price equation and other familiar procedures. The paper concludes with an empirical example of the application of MARS to a forested area in California. As the first construction of this approach it has the potential for further modification and refinement for those that may find it of interest. 相似文献