排序方式: 共有62条查询结果,搜索用时 15 毫秒
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土壤水溶性盐是表征土壤盐碱化程度的重要指标,也是评价耕地地力的重要参数,被纳入第三次全国土壤普查(“三普”)监测指标体系中。重量法是测定土壤水溶性盐总量的最常用方法,其测定过程易受多种因素影响,导致其测定结果不准。鉴于此,本文设计试验分别验证了水溶性盐浸提和浸提液固液分离这两个过程对测定结果的影响,结果表明浸提液固液分离是影响土壤水溶性盐总量测定准确度和精密度的主要因素。基于此进一步探究4种不同固液分离方式(布氏漏斗过滤、滤膜真空抽滤、离心、滤纸组合过滤)对测定结果的影响,结果表明相较于其它方式,滤纸组合过滤测定结果准确度高,适用于土壤水溶性盐总量的测定。对改进后的重量法测定土壤水溶性盐总量进行方法学确认,结果表明其检出限为0.01 g/kg,测定下限为0.04 g/kg;方法的准确度和精密度、适用范围等均符合相关要求。本文推荐的土壤水溶性盐总量测定方法为:土壤样品采用1:5土水比浸提,180 r/min振荡3 min,浸提液采用滤纸组合自然过滤;其测定结果的准确度和精密度符合相关要求。本文旨在为“三普”内业检测提供参考和借鉴,为全面摸清不同区域土壤水溶性盐含量水平及土壤盐渍化程度提供技术支撑。 相似文献
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A new Na(I) coordination polymer, [Na2(Hpimdc)(H2 pimdc)(phen)2]n(1), has been synthesized by the reaction of NaOH with 2-propyl-4,5-imidazoledicarboxylic acid(H3 pimdc)and 1,10-phenanthroline(phen). The Na(I) coordination polymer 1 was characterized by single-crystal X-ray diffraction analysis and elemental analysis. In 1, the bridged ligand H3 pimdc adopts two modes(singly deprotonated and doubly deprotonated) to coordinate with the Na(I) ion.The Na(1) ion is six-coordinated with three N atoms from a phen ligand and a H2 pimdc ligand,three O atoms from a Hpimdc ligand and two other different H2 pimdc ligands. The Na(2) ion is also six-coordinated with three N atoms from a phen ligand and a Hpimdc ligand, three O atoms from a H2 pimdc ligand and other two different Hpimdc ligands. Complex 1 exhibits a 1 D chain structure built up by μ-H2 pimdc-and μ-Hpimdc2-ligands. The antitumor activities of complex 1 against human SGC7901, A549 and H08910 cells have been tested. 相似文献
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时间域振幅比法层析成像利用直达波的振幅变化来反演介质的衰减系数,具有简易快速等优点,在单一地质构造勘察中极具优势,但该方法易受几何扩散、仪器响应、天线耦合以及辐射模式等因素的干扰,导致成像结果失真,难以适应复杂地质构造的高精度成像.为解决该问题,提出质心频率下移法,从频率域分析振幅谱与衰减系数的关系,在此基础上实现衰减层析成像,此外,采用正则化least-squares QR (LSQR)分解算法求解层析成像方程组,提高计算速度和数值稳定性.数值模型算例和实测算例的结果表明,电磁波通过衰减介质时质心频率向主频方向减小,质心频率下移法具有较高成像精度. 相似文献
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在用溶胶-凝胶方法成功制备纳米TiO2、纳米CeO2包覆纳米TiO2材料的基础上,进行了氧敏性能、阻抗谱的测试和对比,并且通过热力学和活化能计算对实验结果进行了分析.实验结果表明:纳米CeO2包覆纳米TiO2材料的氧敏性能优于纯TiO2材料,.当包覆4.9mol?O2时材料的氧敏性能最好.热力学计算证明:CeO2对TiO2起到催化作用,从而改善TiO2的氧敏性能.对材料活化能计算表明:包覆纳米CeO2后材料的晶粒、晶界活化能显著降低,TiO2的活性得到提高:并且随着CeO2包覆量降低活化能降低,说明活化能存在极小值,CeO2包覆量有最优值,从而解释了实验结果中出现极值的现象. 相似文献
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Reduced-temperature ordering of FePt nanoparticle assembled films by Fe30Pt70/Fe3O4 core/shell structure 下载免费PDF全文
In this paper, Fe30Pt70/Fe3O4 core/shell nanoparticles were synthesized by chemical routine and the layered polyethylenimine (PEI)-Fe30Pt70/Fe3O4 structure was constructed by molecule-mediated self-assembly technique. The dimension of core/shell structured nanoparticles was that of 4nm core and 2 nm shell. After annealing under a flow of forming gas (50%Ar2+30%H2) for 1 h at or above 400℃, the iron oxide shell was reduced to Fe and diffused to Pt-rieh core, which leaded to the formation of L1. phase FePt at low temperature. The x-ray diffraction results and magnetic properties measurement showed that the chemical ordering temperature of Fe30Pt70/Fe3O4 core/shell nanoparticles assembly can be reduced to as low as 400℃. The sample annealed at 400℃ showed the eoereivity of 4KOe with the applied field of 1.5T. The core/shell structure was suggested to be an effective way to reduce the ordering temperature obviously.[第一段] 相似文献
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Au/MOF催化剂的制备、表征及其催化三组分偶联反应 总被引:2,自引:0,他引:2
采用后合成共价修饰法和一锅法分别制备了催化剂IRMOF-3-SI-Au(PS)和IRMOF-3-SI-Au(OP),运用X射线衍射、红外光谱、热重-差热分析、透射电镜以及程序升温还原对催化剂进行了表征,探索了这两种催化剂在醛、炔和胺三组分偶联反应中的催化性能,并推测了可能的反应机理.结果表明,两种催化剂对醛、炔和胺三组分偶联反应均具有较高的催化活性,产物炔丙基胺类选择性为100%,且可循环使用;结晶度较低的IRMOF-3-SI-Au(PS)的活性高于结晶度较高的IRMOF-3-SI-Au(OP);催化剂对芳香醛和脂肪醛以及环状胺均具有较高的催化活性,且对带有吸电子基团的芳香醛的活性高于带有供电子基团的. 相似文献
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We introduce elementary and Φ-free Lie triple systems and study the properties of these systems.In particular,structures of subsystems of an elementary Lie triple system and a class of Φ-free Lie triple systems are investigated. 相似文献
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以NaNO_3, KNO_3和Na_2CO_3混合物为熔盐体系,采用熔盐法(MSS)在1500℃成功合成了绿色发光Lu_(3-x)Ce_xAl_5O_(12)(x=0.03~0.15)荧光粉,合成温度比传统的高温固相法低约300℃。利用荧光光谱仪研究了其发光性能,激发光谱中出现了两个激发主峰,分别位于350和453 nm,而发射峰位于543 nm处。Ce~(3+)的最优掺杂浓度为x=0.12,浓度猝灭方式为电偶极-电偶极相互作用。利用扫描电镜,观察了合成的荧光粉的形貌,并分析了其粒径分布。荧光粉的颗粒尺寸为亚微米到微米级,在0.16~1.35μm之间,平均粒径为0.54μm,颗粒近似球形且无聚集。此外,也探究了其热稳定性,发现该荧光粉热稳定性良好,计算的热猝灭活化能ΔE为0.1589 eV。随着Ce~(3+)浓度的增加,荧光粉的色坐标从浅绿色向黄绿色偏移。研究结果表明,熔盐法相比传统的高温固相法在制备的温度、荧光粉形貌等方面具有明显的优势,有望成为荧光粉制备的一种经济可行的方法。 相似文献