同轴送粉激光熔覆粉束质量分布密度模型与实验测量

为实现四粉针同轴送粉模式下粉束空间质量分布密度的全参数化准确预测,本文建立了粉束空间质量分布密度的全参数化理论计算数学模型,并提出了一种简易的实验检测方法。理论计算与实验检测结果表明:计算结果与实验结果的变化趋势完全一致,在离焦量为0时,计算结果与实验结果高度吻合(接近100%),验证了所建模型的准确性和有效性。

基于视觉感知模型的指纹图像质量评价算法

指纹在刑事侦查和法庭科学领域被称为物证之首,在打击犯罪、维护社会稳定中发挥着十分重要的作用。指纹鉴定的结论是有效证据形成和刑事案件侦破的关键,而指纹图像质量直接影响指纹鉴定结论的准确性和可靠性,因此精准客观的指纹图像质量评价算法是辅助指纹专家进行指纹鉴定必不可少的工具。目前,美国国家标准与技术研究院研发的NFIQ2.0指纹图像质量评价算法得到国内外专家学者的广泛关注,但该算法质量评价结果与指纹专家的质量评价结果存在较大偏差,且缺乏对指纹图像局部区域的质量评价,所以无法满足刑事侦查和法庭科学领域指纹鉴定任务的需要。基于此,将指纹图像质量评价问题拓展到质量空间上,学习指纹专家对纹线局部区域的质量感知策略,提出基于专家感知的质量评价算法。实验结果表明本文算法对指纹图像整体质量评价的结果能够与指纹专家的质量评价结果保持一致,并且符合刑事侦查和法庭科学的应用场景。此外,进一步在国际公开指纹数据集上与NFIQ2.0算法进行对比实验,结果表明本文算法的质量评价分数更为合理,能够有效降低指纹匹配算法的拒识率。

不同生育期水分亏缺和施氮量对茄子根系生长、产量及水分利用效率的影响

【目的】研究3个不同生育期水分亏缺和施氮量对茄子根系生长、空间分布及产量和水分利用效率的影响。【方法】利用盆栽试验,设置低氮(N1,0.1g/kg)、中氮(N2,0.3g/kg)、高氮(N3,0.5g/kg)3个施氮水平,分别在茄子开花坐果期、初果期、盛果期3个不同生育期进行水分亏缺处理,以不亏水处理为对照(CK),共12个处理,对不同生育期水、氮处理茄子的总根长、总根干质量和鲜质量、产量及水分利用效率进行测定,并建立相应的水分生产函数。【结果】在施氮量相同的情况下,与不亏水处理相比,盛果期水分亏缺N1、N2和N3处理对总根长和总根干质量影响显著,其中茄子总根长较对照分别降低了12.39%,18.82%和15.29%,总根干质量分别下降了42.31%,33.46%和25.42%。与对照相比,开花坐果期、初果期、盛果期水分亏缺处理茄子的总根鲜质量在N1处理下分别较对照降低了21.86%,9.35%和39.03%;N2处理下,分别降低了2.7%,14.99%和48.23%;N3处理下,分别降低了41.1%,3.7%和35.07%。与对照相比,开花坐果期、初果期、盛果期水分亏缺处理茄子的产量在N1处理下,分别较对照降低了6.13%,10.84%和14.64%;N2处理下,分别降低了3.94%,5.62%和11.6%;N3处理下,分别降低了11.35%,4.23%和16.14%。随着施氮量的增加,所有处理总根长、总根干质量、鲜质量和产量均呈现先上升后下降的趋势。在低氮和中氮条件下,开花坐果期水分亏缺处理既获得了较高的产量,也实现了较高的水分利用效率。茄子根系干质量在垂直方向上呈对数递减趋势;盛果期水分亏缺对各层根系分布的影响最大;随着施氮量的增加,根系分布呈现高氮浅根化趋势。在N1和N2处理下,水分敏感指数在盛果期最大,其次是初果期和开花坐果期;在N3处理下,各水分敏感指数的大小顺序依次为盛果期>开花坐果期>初果期。【结论】茄子对盛果期的水分亏缺最为敏感,该时期亏水不仅限制了根系的生长和空间分布,而且降低了茄子的产量;在低氮和中氮条件下,开花坐果期的水分亏缺对茄子根系生长发育、产量的影响较小,而且获得了较高的水分利用效率。与低氮和高氮相比,中等施氮水平有利于茄子根系的生长及产量和水分利用效率的提高。

Spatial distribution of SiCln （n=O-2） in SICl4 plasma measured by mass spectroscopy

For a better understanding of the deposition mechanism of thin films in SiCl4 source gas, we have measured the spatial distributions of SiCln （n=0-2） radicals in SICl4 radio frequency glow discharge plasma utilizing a mass spectrometer equipped with a movable gas sampling apparatus. The experimental results demonstrate that the relative densities of SiCln （n=0-2） radicals have peak values at the position of 10 mm above the powered electrode along the axial direction; the relative densities of the Si and SiCIn （n=1, 2） radicals have peak values at the positions of 27mm and 7 mm away from the axis along the radial direction, respectively. Generally speaking, in the whole SICl4 plasma bulk region, the relative density of Si is one order of magnitude higher than that of SICl, and the relative density of SiCl is several times higher than that of SICl2. This reveals that Si and SiCl may be the primary growth precursors in forming thin films.

Spatial Distribution of Soil Organic Matter Using Geostatistics: A Key Indicator to Assess Soil Degradation Status in Central Italy

Soil organic matter (SOM) content is one of the main factors to be considered in the evaluation of soil health and fertility. As timing, human and monetary resources often limit the amount of available data, geostatistical techniques provide a valid scientific approach to cope with spatial variability, to interpolate existing data and to predict values at unsampled locations for accurate SOM status survey. Using geostatistical and geographic information system (GIS) approaches, the spatial variability of some physical and chemical soil parameters was investigated under Mediterranean climatic condition in the Abruzzo region of central Italy, where soil erosion processes accelerated by human induced factors are the main causes of soil degradation associated with low SOM content. Experimental semivariograms were established to determine the spatial dependence of the soil variables under investigation. The results of 250 soil sampling point data were interpolated by means of ordinary kriging coupled with a GIS to produce contour maps distribution of soil texture, SOM content related to texture, and C/N ratio. The resulting spatial interpolation of the dataset highlighted a low content of SOM in relation with soil texture in most of the surveyed area (87%) and an optimal C/N ratio for only half of the investigated surface area. Spatial location of degraded area and the assessment of its magnitude can provide decision makers with an accurate support to design appropriate soil conservation strategies and then facilitate a regional planning of agri-environmental measures in the framework of the European Common Agricultural Policy.

Soil Quality in Relation to Agricultural Production in the North China Plain

Sustainable agricultural production is of vital importance to food supply security. This study aimed to investigate crop yield response to spatial variability of soil quality at a county scale in the North China Plain （NCP） and subsequently derive key soil quality indicators. Soil samples were geo-referenced and taken in 2008 from both surface （0-20 cm） and subsurface （20-40 cm） layers in 132 fields throughout the Fengqiu County, located in the centre of the NCP, for subsequent soil properties＇ analyses. Annum crop yields were obtained from the same fields where soil samples were collected. Soil quality was evaluated based on a fuzzy set with 13 soil properties, and its spatial distributions were investigated by integrating geostatistical analysis and geographic information system （GIS） techniques. Soil quality indices were classified into five grades, and their spatial distributions were mapped within the county. The surface soil qualities were about one to two grades higher than the subsurface soil. The quality indices for surface and subsurface soils were positively associated with the annual crop yields, suggesting the importance of both. Soil organic matter, total nitrogen, available P, and available K contributed 50% of the combined weight to the soil quality index and were identified as key indicators of soil quality status in the area in terms of sustainability.