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31.
基于马氏距离的荔枝图像分割设计方法 总被引:4,自引:0,他引:4
在基于颜色特征和聚类的马氏距离算法基础上,利用MATLAB软件设计了人机交互式可视化计算机图像分割程序。运用该程序,对荔枝照片进行了图像分割,分离出复杂背景下的荔枝果实图像。结果表明:该程序能较好地解决复杂彩图中目标图像的分割问题,可以消除因不慎而修改源代码的风险;通过数据分析器和滤波器能准确的对采样数据进行判断以及对含噪声的目标图像作进一步处理。 相似文献
32.
本文是研究透视仿射对应在正投影中,如何求直线和平面的交点,点到直线的距离,两平面的交线,平面与立体的截交线等问题。以解决在画法几何中作图繁、误差大的问题,达到提高解题速度,解决工程实际问题。 相似文献
33.
Robert McDonald Meghan McKnight Elizabeth Selig Christy Violin 《Biological conservation》2005,126(1):24-40
The concept of an ecoregion, a discrete spatial area where species composition is presumed to be relatively homogeneous compared to that between areas, has become an increasingly common conservation tool. We test the effectiveness of one ecoregion delineation (World Wildlife Fund) in capturing patterns of change in species composition of birds, mammals, and trees across the United States (excluding Hawaii) and Canada, and describe the extent to which each ecoregion boundary is concurrent with relatively large changes in species composition. Digitized range maps were used to record presence/absence in 50 × 50 km equal-area grid cells covering the study area. Jaccard’s index of similarity was calculated for all pairs of cells in the same or adjacent ecoregions. The average rate at which similarity declined with geographic distance was calculated using pairs of cells within the same ecoregion (intra-ecoregion turnover) or using pairs of cells in adjacent ecoregions (inter-ecoregion turnover). The intra-ecoregion rate varies widely among ecoregions and between taxa, with trees having a faster rate of similarity decline than mammals or birds. For all three species groups, most ecoregion boundaries have similar rates across them (inter-ecoregion) than that within each adjacent ecoregion (intra-ecoregion), with the exception of zones of transition between biomes and major geographical features. Although the ecoregion concept is useful for many other conservation applications, the lack of systematic, high turnover rates along ecoregion boundaries suggests that ecoregions should not be used as a quantitative basis for delineating geographic areas of a particular taxonomic group. 相似文献
34.
中国自实施退耕还林生态补偿政策以来,执行分长江南北两种不同的补偿政策,生态补偿并未考虑退耕还林微观地理区位及造林质量的差异。"一刀切"虽具有统一简化的优点,却忽视了实际存在的造林质量及林地地形、土壤、气候等诸多因素,补偿标准不尽合理。该文为了探讨退耕还林补偿金的合理标准,以张家口地区为研究区,应用遥感(RS)、地理信息系统(GIS)等数据,建立了退耕还林生态补偿体系。结果表明:张家口地区各区县中,单位面积退耕还林补偿系数最高的是尚义县(0.082),退耕还林补偿系数最低是怀来县(0.036),各县单位面积退耕还林补偿系数的差距较大。该文结果为生态补偿金的科学、合理分配提供参考。 相似文献
35.
The biodegradability of chars derived from pyrolysis and
hydrothermal carbonisation (HTC) was studied in short-term
dynamic incubation experiments under controlled conditions.
Carbon dioxide C (CO$_{2}$) emissions from soil-char mixtures in combination
with solid digestate or mineral nitrogen (N) fertiliser were measured
in dynamic chambers for 10 d.~Compared to the original
material (maize straw), pyrolysis and HTC chars showed
significantly lower CO$_{2}$ emissions and slower decay
dynamics; and compared to the soil control, HTC char
increased soil respiration to a significant extent, while
pyrolysis char did not. The addition of mineral N resulted
in a delayed respiration dynamics for HTC char, while the
addition of digestate resulted in an increase in the
respired CO$_{2}$ for pyrolysis char and a decrease for HTC
char. For the first time, a peculiar two-stage decay
kinetics was observed for HTC char, indicating a highly
inhomogeneous substrate consisting at least of two C pools. 相似文献
36.
37.
LIU Zhi CAO Jinzhen.College of Material Science Technology Beijing Forestry UniversityBeijing P. R. China.Department of Wood Science Engineering Hebei Agriculture UniversityBaoding P. R. China 《中国林业科技(英文版)》2006,5(1):14-20
INTRODUCTIONWood-based composites are widely used as woodindustry is developing rapidly. It is quite necessary toimprove the decay resistance of wood-basedcomposites with preservatives or protect them in othermethods to meet the durability requirements. Therefore,many investigations are conducted in this field. Thispaper summarizes the previous and presentinvestigations on the methods of preservative treatmentand the decay resistance of different categories oftreated wood-based composites… 相似文献
38.
宝交早生草莓在0℃下自然降氧贮藏10 d,好果率84%,商品率达98%。用10%CO_2处理可将草莓在0℃的贮藏时间延长到20 d,好果率和商品率均为94%,CO_2浓度超过20%会使草莓产生酒精味。SO_2慢性释放剂处理也有较好的防腐效果。 相似文献
39.
Solke H. De Boer 《European journal of plant pathology / European Foundation for Plant Pathology》2003,109(9):893-899
Erwinia carotovora and Erwinia chrysanthemi are the two most important soft rotting bacteria of commercially-grown plants. They are genetically diverse as is evident from polymorphisms in the pel and recA genes as well as in rrn, the ribsomal gene cluster. Subpopulations grouped into biovars, pathovars, or subspecies associated with various hosts and in different geographic regions suggest specialization in host preference and/or survival in diverse environments. Previous characterization of the pectolytic erwinias as opportunistic pathogens is being replaced by a realization that this group of bacteria exhibits a sophisticated repertoire of pathogenicity and virulence genes and regulators. The presence of an entire hrp gene cluster and associated type III secretion system, and global regulators which regulate virulence determinants such as exoenzyme production and motility, attest to a highly specialized pathogen. The fact that production of extracellular plant cell wall-degrading enzymes are coordinately activated by the diffusible signal molecule N-acyl-homoserine lactone in a population density-dependent manner may explain the occurrence of pectolytic erwinia in asymptomatic plant tissues. Transgenic plants expressing bacterial quorum-sensing signal molecules modulate this sensory system and exhibit resistance to soft rot infection. The pectolytic erwinias, being significant plant pathogens that are neither of quarantine concern nor a human health hazard while readily isolated from field sources, make an ideal model for investigating the genetic basis of plant pathogenesis and environmental fitness. 相似文献
40.
该试验结果表明,地膜覆盖栽培番茄的后期早衰和施肥有关。施肥量多,土壤有效养分和植株的营养状况较好,植株生长发育也较好,小区平均产量最高,达75.2kg,每公倾合4.512万kg,比对照增产16.89%。施肥量低的处理,比对照减产3.76%。 相似文献