Results 1 to 10 of about 3,307 (154)
Nonlinear free vibration analysis of Timoshenko beams with porous functionally graded materials
Xibei Gongye Daxue Xuebao, 2022 基于Timoshenko梁变形理论研究多孔功能梯度材料梁的非线性自由振动问题。针对多孔功能梯度材料梁的孔隙均匀分布和孔隙线性分布2种形式, 根据广义Hamilton原理推导多孔功能梯度材料Timoshenko梁的非线性自由振动的控制微分方程组并对方程组进行无量纲化。采用微分变换法(DTM)对各种边界条件下的控制微分方程组进行变换, 得到等价代数特征方程。计算了多孔功能梯度材料Timoshenko梁在固支-固支(C-C)、固支-简支(C-S)、简支-简支(S-S)和固支-自由(C-F ...
TENG Zhaochun, MA Lingquan, FU Xiaohua
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Matching expert range maps with species distribution model predictions
Conservation Biology, Volume 34, Issue 5, Page 1292-1304, October 2020., 2020 Abstract Species’ range maps based on expert opinion are a critical resource for conservation planning. Expert maps are usually accompanied by species descriptions that specify sources of internal range heterogeneity, such as habitat associations, but these are rarely considered when using expert maps for analyses.
Kumar Mainali +3 more
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Effects of Plant Density Regulation on Soil Physical Properties and Plant Diversity of Plantations in Yellow River Flood Plain of Northern Shandong Province [PDF]
, 2022 [Objective] The effects of plant density regulation on soil physical properties and plant diversity of different plant stands in the Yellow River flood plain were analyzed in order to provide a theoretical basis for optimizing stand growth, improving ...
Chen Ping +3 more
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Drivers of plant traits that allow survival in wetlands
Functional Ecology, Volume 34, Issue 5, Page 956-967, May 2020., 2020 A free Plain Language Summary can be found within the Supporting Information of this article. Abstract Plants have developed a suite of traits to survive the anaerobic and anoxic soil conditions in wetlands. Previous studies on wetland plant adaptive traits have focused mainly on physiological aspects under experimental conditions, or compared the ...
Yingji Pan +8 more
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Shuitu Baochi Xuebao, 2021 采用X-ray computed tomography（CT）技术研究了果树行间不同油菜间作密度（CK：清耕；L：低密度间作；M：中密度间作；H：高密度间作）对土壤大孔隙特征参数的影响。结果表明：油菜间作改善了果树行间（0—60 cm）土壤大孔隙特征，各土层的土壤大孔隙数量、大孔隙面积、大孔隙度等参数分别较清耕显著提高（P 1 mm）在各土层间的数目多、差异小，并且在0—30 cm土壤剖面上的成圆率最高。中、高密度油菜间作的土壤大孔隙特征参数均优于清耕及低密度间作，而中密度间作的土壤大孔隙分布更均匀 ...
何娜娜 +4 more
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Shuitu Baochi Xuebao, 2023 以明确自然界中广泛存在的层状结构土壤孔隙分布特征为目的。选黄土高原典型坝地土壤剖面为研究对象,利用CT扫描技术分析耕作层、犁底层、心土层土壤三维结构,探讨层状土孔隙参数随土层结构变化及界面层孔隙特征。结果表明:(1)瘦长型孔隙(孔隙形状系数≤0.2)是各土层土壤孔隙的主要形态。各土层的孔隙参数具有明显差异。耕作层的总孔隙度最高,大孔隙(≥1 mm)分布较多;犁底层孔隙总数量最高,含有较多孤立的小孔隙(≥0.1~0.5 mm)和微小孔隙(≥0.06~0.1 mm),但连通性最差 ...
张佐源 +5 more
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Shuitu Baochi Xuebao, 2023 为了明确农业生产过程中耕作方式对田间土壤孔隙结构及土壤水分运动特性的影响,以广西农地蔗田为研究对象,基于土壤切片技术分析研究免耕和垄耕2种典型耕作方式蔗田的田间土壤孔隙结构特征,并结合土柱模拟入渗试验,探究土壤孔隙结构对土壤水分运动的影响,进一步揭示孔隙结构与土壤水分运动特性之间的相互作用关系。结果表明:随着土层深度的增加,免耕蔗田孔隙形态以聚集的团块状分布为主,垄耕蔗田孔隙形态以条状分布为主。与免耕蔗田相比,垄耕蔗田的土壤总孔隙度和＞2.5 mm孔径的孔隙度分别增加32.5%和21.9 ...
刘俊杰 +5 more
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Shuitu Baochi Xuebao, 2007 采集了太湖地区3种主要水稻土（白土、黄泥土和乌栅土）的原状土柱为供试土样，利用CT扫描技术，在不破坏土体结构的前提下，准确地得出了不同深度土壤剖面上各种大孔隙的数量、面积以及分布状况。结果表明，3种水稻土均以表层的大孔隙度最大，在30～40cm处达到一个最低点，再往下又呈波浪形变化。土柱各截面上大孔隙面积的变异系数随着深度的变化与大孔隙度相似，大孔隙度大的层次其变异系数也较大。等效直径越大的孔隙（〉5mm）在土壤不同深度下数量的变化也越大。表层上大直径（〉5mm）的大孔隙较多，在土壤剖面30 ...
吴华山, 陈效民, 陈粲
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, 2018 针对我国荒漠化危害严重,不利于植物种植等系列问题,以番茄为试验材料,结合纸膜、保水剂、生物基固沙剂等不同保水固沙措施,分析各处理下基质的理化性质以及番茄的生物学性状,以探明各处理对沙地环境的改善效果及对番茄生长的影响,为沙漠的防治及沙产业的发展提供参考。结果表明:瓦楞纸处理显著提高了番茄果实的有机酸、可溶性糖含量,分别比CK高27. 78%、8. 87%,其pH值比CK高0. 89,速效氮含量是CK的40倍;牛皮纸处理20~40 cm含水量比CK高73.
兰挚谦 +10 more
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Shuitu Baochi Xuebao, 2023 为探明生物结皮如何改善土壤物理性质从而促进水土保持,针对黄土高原风沙土和黄绵土上发育的藓结皮,以无结皮为对照,原状取样后分别使用高分辨率CT扫描仪和高精度土壤贯入仪测定其孔隙性状与穿透阻力,并构建结构方程模型剖析生物结皮对土壤孔隙度和穿透阻力的作用途径。结果表明:藓结皮发育改变土壤孔隙特征参数,并显著提高表层0—2 cm土壤总孔隙度(p＝0.01),在此土层内,风沙土和黄绵土上藓结皮的总孔隙度比无结皮分别增加1.62,2.12倍,且藓结皮的孔隙度随土层深度增加呈指数降低。藓结皮和无结皮的土壤面孔率在0 ...
余星兴 +4 more
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