Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract： Nd2Fe14B/α-Fe composite magnets were fabricated by mechanically ball milling. The influence of Dy2O3 doping on the coercivity of the nanocomposite magnets was studied in detail. It was found that the coercivity of the composite magnets can be significantly improved by Dy2O3 doping, and the annealing temperature corresponding to the maximum coercivity decreases with the increase of Dy2O3 content. X-ray diffraction analysis shows that the lattice parameters of Nd2Fe14B decreased due to Dy2O3 doping, indicating that (Nd, Dy)2Fe14B hard magnetic phase formed after Dy partial replacement for Nd. Therefore, the enhancement of coercivity of the magnets can be mainly attributed to the increase of the magnetic crystalline anisotropy of the hard magnetic phase. However, with the increase of the magnetic crystalline anisotropy, the effective exchange coupling length was shortened, thereby, the coercivity dropped due to over doping of Dy2O3.
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-11 Cooperative journals: 《干旱区研究》
Abstract：阐明斑块尺度上物种共存格局，对于深入认识荒漠草原破碎化草地生物多样性的维持机理具有重要意义。按斑块的土壤生境退化程度，选取短花针茅荒漠草原3类典型群落斑块为研究对象，对比分析不同斑块的物种构成、多样性及物种间的共存关系格局。结果表明：① 斑块A属单优种短花针茅（Stipa breviflora）群落；斑块B为短花针茅+草木樨状黄耆（Astragalus melilotoides）群落；斑块C为苦豆子（Sophora alopecuroides）+老瓜头（Cynanchum komarovii）+猪毛蒿（Artemisia scoparia）群落。② 群落结构中斑块A和斑块B多样性相近，均高于无短花针茅生长的斑块C。③ 基于零模型的分析结果显示，物种共存格局的复杂性和强度为：斑块A>斑块B>斑块C，且下降趋势明显，斑块A存在的16组显著物种对中有4组为显著竞争关系，而斑块C中的物种对减少到7组，且仅存在猪毛蒿与苦豆子组显著竞争物种对。结论：表明未沙化的土壤生境斑块是荒漠草原破碎化草地生物多样性维持的一个重要前提，土壤生境的退化显著降低了斑块内部群落组织的复杂性和物种间相互作用的强度，不利于群落的自我维持。
Subjects: Geosciences >> Other Disciplines of Geosciences submitted time 2019-09-10 Cooperative journals: 《干旱区研究》
Abstract：以荒漠草原人工中间锦鸡儿(Caragana intermedia)灌丛为对象，研究降雨量及降雨强度对两类形态灌丛（健康组和退化组）穿透雨、树干茎流和冠层截留的影响。结果表明：① 试验期间共观测到有效降雨33次，以中小降雨事件为主，总降雨量为251 mm，次平均降雨量和平均降雨强度分别为7.6 mm和1.14 mm·h-1，其中降雨量＜2 mm，降雨强度＜1 mm·h-1的降雨事件出现次数最多。② 健康组和退化组中间锦鸡儿平均穿透雨率、树干茎流率和冠层截留率分别为66.7%、8.5%、24.8%和75.4%、8.7%、16.0%，两类形态灌丛之间穿透雨和截留存在显著差异（P＜0.05）。③ 两类形态灌丛的穿透雨量、树干茎流量、截留量与降雨量成线性函数、对数函数和幂函数关系，且其穿透雨率、树干茎流率和截留率与降雨量、降雨强度之间成对数函数和幂函数关系。灌丛形态退化显著改变了冠层降雨再分配格局，冠层截留显著降低，穿透雨显著增加，潜在提高了降水对土壤水分的直接补充，一定程度上有利于人工中间锦鸡儿稳定性的维持。
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