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Search Results: 1 - 10 of 7446 matches for " 庄文化 "
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聚丙烯酸钠对3种土壤质地入渗特征的影响
董勤各,冯浩,文化
中国水土保持科学 , 2010,
Abstract: ?采用一维垂直积水入渗法,分析聚丙烯酸钠在4种质量分数(0、0.08%、0.20%与0.50%)处理下对砂土、壤土和黏土水分入渗性能以及kostiakov入渗模型参数的影响。结果表明:聚丙烯酸钠与土壤质量比在0.08%0.50%范围内时,3种土壤质地入渗速率都随时间推移呈下降趋势,土壤入渗能力随聚丙烯酸钠质量分数的增大明显降低;聚丙烯酸钠显著抑制土壤入渗能力;入渗系数k随聚丙烯酸钠用量的增加而下降;入渗指数a值随聚丙烯酸钠用量的增加基本呈上升趋势;k/a值对聚丙烯酸钠的响应随聚丙烯酸钠质量分数的增加逐渐增强。
黏粒质量分数对土壤水分蓄持能力影响的模拟试验
李卓,吴普特,冯浩,赵西宁,文化
中国水土保持科学 , 2009,
Abstract: ?通过人工配制不同质地土壤,测定土壤水分特征参数,研究土壤中黏粒质量分数对其水分蓄持能力的定量影响。结果表明:1)黏粒质量分数对土壤水分蓄持能力有较大影响,土壤持水能力随黏粒质量分数增加而递增。2个水分特征曲线模型——gardner模型及vangenuchten模型中,表征土壤持水能力的参数均随黏粒质量分数增加而增大。2)黏粒质量分数对土壤比水容量有较大影响,试验土壤在任一水吸力水平下的比水容量值均随其黏粒质量分数增大而增大。3)试验土壤饱和含水量、田间持水量分别与黏粒质量分数呈指数、对数正相关,凋萎系数与黏粒质量分数呈指数正相关。4)试验土壤有效水、迟效水含量随黏粒质量分数增加呈先升高后降低趋势,二者与黏粒质量分数均呈抛物线关系,最高点分别出现在黏粒质量分数为35.9%和35.8%处,易效水含量与黏粒质量分数相关性不显著。研究结果可为黄土区土壤水分蓄持机制进一步研究提供一定理论依据。
水垫塘冲击射流附壁区的水力特性
李乃稳,李龙国,文化,刘超
- , 2015, DOI: 10.15961/j.jsuese.2015.03.003
Abstract: 中文摘要: 采用粒子成像测速技术(PIV)获得了水垫塘冲击射流全域瞬时精细流场,并在此基础上,对附壁射流区的流速分布规律和水流紊动特征等水力特性进行了系统研究。结果表明:在附壁射流区,射流横向断面的流速、紊动强度分布呈自相似分布规律,具有自由射流的特征;在射流纵向,流速随着流程增加而线性减小,射流半扩展厚度和紊动强度随流程增加而线性增大;并提出了描述附壁射流区射流横向断面流速、紊动强度分布规律的方程,同时得到了附壁射流区射流纵向上流速、半扩展厚度和紊动强度沿流程变化的计算公式。
Abstract:The particle image velocimetry (PIV) was used to characterize the fine structure of flow fields in a pool with an oblique submerged jet,and on this basis, the jet velocity distribution and turbulence characteristics in the wall-jet region were studied systemically.The results showed that in the wall-jet region,the velocity and turbulence intensity distribution in each of the jet flow cross-sections are the self-similarity,which is the same as that of a free jet. In the wall-jet region,the jet velocity decreases linearly along the jet path,whereas the turbulence intensity,the jet half-width increases linearly as the jet travels.The equations of jet velocity and turbulent intensity distributions were proposed,and the formulas to calculate the jet velocity,the turbulence intensity,the jet half-width changing along the jet path were also obtained.
考虑地形特征的无人机影像分区域加权平差拼接方法
鲁恒,李龙国,贺一楠,文化,蔡诗响,何敬
农业机械学报 , 2015, DOI: 10.6041/j.issn.1000-1298.2015.09.043
Abstract: 无人机遥感手段以其方便、快捷、成本低、可云下飞行的优势正越来越多地应用于农情信息的获取。为了解决无人机影像的数量多、畸变大、影像拼接过程中产生大量累积误差等问题,对拼接过程中如何减少误差累积进行了研究。首先,根据记录影像匹配过程中心点位置计算大致的匹配区域。然后,进行区域网概略计算,列出误差方程。对不同地形特征区域影像赋予权值,进行分区域加权平差。最后,利用3条航带的无人机影像分别对所提方法和直接拼接法进行了实验对比。实验结果表明:所提方法拼接后错位和鬼影现象减少了12%,拼接效率提高了15%,拼接后获得的面积扩大了8%。
基于迁移学习的无人机影像耕地信息提取方法
鲁恒,付萧,贺一楠,李龙国,文化,刘铁刚
农业机械学报 , 2015, DOI: 10.6041/j.issn.1000-1298.2015.12.037
Abstract: 随着精准农业技术的发展,对农作物用地信息快速、准确提取的需求越来越高。同时,无人机技术以其方便、高效、具有低空云下飞行能力等优势被广泛应用于自然资源的调查中。但无人机影像普遍光谱信息较为匮乏,因此很难准确、快速地提取出耕地信息。基于此,提出了一种利用迁移学习机制的耕地提取方法(TLCLE)。首先,利用深度卷积神经网络(DCNN)剔除线状地物(道路、田埂等),然后,通过引入迁移学习机制将DCNN特征训练过程中得到的特征提取方法迁移到耕地提取中,最后,将所提方法与利用易康(eCognition)软件进行耕地提取(ECLE)结果进行对比。研究结果表明:对于实验影像1、2,TLCLE方法耕地提取总体精度分别为91.9%、88.1%,ECLE方法总体精度分别为90.3%、88.3%,2种方法提取精度相当,在保证耕地地块完整、连续性上TLCLE方法优于ECLE方法。
明流泄水道突扩突跌掺气设施空腔长度研究
刘超,李龙国,文化,李乃稳,刘慧芬
- , 2015, DOI: 10.15961/j.jsuese.2015.03.001
Abstract: 中文摘要: 为了查明短有压进口泄洪洞下游明流泄水道上突扩突跌掺气设施底、侧空腔长度随掺气坎尺寸和水流弗劳德数的变化规律,采用模型试验,测试了不同掺气坎尺寸在不同水流条件下的底、侧空腔长度,分析了量纲底、侧空腔长度与掺气坎尺寸和水流弗劳德数的相互关系。结果表明:底空腔长度随着挑坎高度的增加、挑坎坡度的增大、侧扩宽度的增加和水流弗劳德数的增大而增大;侧空腔长度与挑坎高度、挑坎坡度关系不大,随着侧扩宽度的增加而增大,随水流弗劳德数的变化规律为:当侧扩宽度较大时,侧空腔长度随水流弗劳德数的增大而线性增大;当侧扩宽度较小时,侧空腔长度随水流弗劳德数的增大而略微减小。
Abstract:For an aerator with sudden lateral enlargement and vertical drop in free flow chute,the cavity length is governed by a number of independent parameters, including the Froude number,the ramp height of vertical drop, the ramp angle of vertical drop,and the lateral enlargement width of sidewalls,etc.Based on model experiments,the effects of above-mentioned parameters were observed on the bottom cavity length and the lateral cavity length.The results showed that the bottom cavity length is closely related to the ramp height,the ramp angle,the lateral enlargement width and the Froude number,and with higher ramp height,bigger ramp angle,wider lateral enlargement width,and higher Froude number,the bottom cavity length is longer.Yet the lateral cavity length is mainly connected with the lateral enlargement width and the Froude number,which has little relation to the ramp height and the ramp angle.For the lateral cavity length,it increases with the lateral enlargement width.At the condition of larger size of lateral enlargement,the lateral cavity length increases linearly with the Froude number,while a little decreases when the size of lateral enlargement is smaller.
植物水分来源季节性变化对区域蒸散发模拟的影响
苟思,刘超,贺宇欣,刘挺,李丹利,文化,刘铁刚
- , 2018, DOI: 10.15961/j.jsuese.201700957
Abstract: 中文摘要: 植物水分来源会随季节变化。在旱季表层土壤水分不充裕时,植物会逐步使用深层土壤水或地下水,而当雨季表层土壤水分充足时,植物主要使用表层土壤水。然而当前的水文模型、陆面模式和气象模型很少考虑这一现象。本文对分布式陆面-水文模型ParFlow.CLM进行改进,引入以能量差为驱动的根系吸水计算方法,分析植物水分来源季节性变化对区域蒸散发模拟的影响。改进后的模型能够较好地模拟区域蒸散量和土壤水动态,并能较好地再现植物对地下水的使用情况。改进模型结果显示,植物使用地下水的时间主要集中在旱季,植物对地下水的使用是植物应对干旱的重要策略之一。对比美国加利福利亚州Tonzi实验站干旱年2008和平水年2009的结果,2008年植物使用地下水时间比2009年长53 d,用量高36%。改进模型和原模型结果对比显示:当蒸散发主要受到能量限制时,两个模型的模拟结果较为一致;但当蒸散发主要受到水量限制时,两个模型在蒸散发和深层土壤水的模拟结果上有显著差异。改进模型考虑了植物水分来源季节性变化对区域蒸散发模拟的影响,并能模拟地下水位降低对植物用水的影响。结果表明:改进模型中植物腾发量比原模型结果高71 mm/a,占全年总腾发量的43%。若忽略植物水分来源的季节性变化,会对区域蒸散量和深层土壤水的模拟产生巨大影响,且这种影响在旱季或干旱半干旱地区更为明显。
Abstract:The shift of plant water sources occurs seasonally. During the dry seasons, plants would progressively use deep soil water or groundwater when shallow soil water was depleted. During the wet seasons, when shallow soil water was adequate, plants would mainly use shallow soil water. Few hydrological, land surface and atmospheric models have addressed this phenomenon. This paper aimed to improve the performance of the distributed, land surface-hydrological model ParFlow.CLM. A new simulation method of plant root water uptake based on potential difference was coupled into ParFlow.CLM to analyze the impact of the shift of plant water sources on the regional ET simulation. The improved model was able to simulate the changes of regional ET and soil moisture, and was capable to capture the dynamics of plant groundwater use. The results from the modified model showed that the plants mainly relied on groundwater during the dry seasons. Plant groundwater use was one of the most important plant water-use strategies to mitigate the impacts of droughts. Comparing the results in dry year 2008 with those in normal year 2009, the duration and the amount of plant groundwater use were 53 days longer, 36 % higher in 2008, respectively. The comparison between the modified and original model performances showed that, when ET was energy-limited, the results of two models coincided with each other. However, when ET was water-limited, the two models had significant difference in the simulations of plant transpiration and deep soil moisture dynamics.The impacts of the shift of plant water sources on the regional ET and the influences of groundwater level changes on the plant water use were considered in the modified model. As a result, the plant transpiration result from the modified model was 71 mm/a (43 % of annual transpiration) higher than the results ofthe original model. If the shift of plant water sources was ignored in the numerical models, it would lead to considerable bias in
突扩突跌掺气坎底空腔长度计算
刘超,李龙国,李乃稳,文化,刘慧芬
- , 2015, DOI: 10.15961/j.jsuese.2015.04.001
Abstract: 中文摘要: 突扩突跌掺气坎的底空腔长度既与水力条件和底部掺气坎结构参数有关,也与侧墙掺气坎结构参数有关。以往的底空腔长度计算方法,均针对仅采用底部掺气坎,未设置侧墙掺气坎这类掺气设施,不能反映出侧墙掺气坎结构参数对底空腔长度的影响。基于射流微元体受力平衡法,提出了一种求解明流泄水道突扩突跌掺气坎底空腔长度的计算方法,该方法能够全面反映突扩突跌掺气坎底空腔长度受底部掺气坎、侧墙掺气坎结构参数和水力学参数的影响。通过与30组试验资料和已有研究成果的对比,表明所提出的计算方法具有较高的精度
Abstract:For an aerator with sudden lateral enlargement and vertical drop in free flow chute,the bottom cavity length is governed not only by hydraulic parameters,but also by structural parameters of the bottom aerator and lateral aerator.The previous calculation method for the bottom cavity length failed to consider the effect of lateral aerator’s structural parameters.Based on the hydrodynamic analysis of micro water unit of jet flow from aerator,a new calculation method for the bottom cavity length of jet flow from chute aerators with sudden lateral enlargement and vertical drop was obtained,which considers overall effects of the above mentioned parameters.The comparison with 30 groups of experimental data and existing research results showed that the calculating method proposed in this paper has higher accuracy.
2种高分子保水材料对土壤持水能力的影响
文化,<,sup>,冯浩,<,sup>,吴普特,<,sup>,宁荣昌,史竹叶,<,sup>
中国水土保持科学 , 2008,
Abstract: ?采用离心机法,研究聚丙烯酸钠与聚丙烯酰胺2种高分子化合物在5种使用浓度(占干土质量0、0.01%、0.08%、0.2%与1%)的条件下对3种土壤(砂土、壤土、黏土)持水能力的影响。结果表明:3种土壤在0.011.5mpa水吸力时,持水能力随着2种高分子材料用量的增加而增加,砂土的作用效果较壤土、黏土更显著;2种高分子材料与土壤质量比控制在8/10000~2/1000范围内其作用效果较好,该用量条件下高分子吸持水分平均可释放83.7%供植物吸收利用。2种高分子材料对土壤持水能力的作用效果基本相同。
图书馆自动化集成系统(ILAS)的进展
文化
中国图书馆学报 , 1993,
Abstract:
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