我国土壤侵蚀状况与主要影响因素分析

我国土壤侵蚀面积达 492万km2 ,占国土总面积的 5 1 .2 % ,已严重影响和制约着国民经济的发展和社会的安定。 1 998年洪灾便是土壤侵蚀对大自然的最大惩罚 ,现已引起社会各界的重视。为了从中吸取经验教训 ,对土壤侵蚀与降雨 ,土壤侵蚀与坡长、坡度 ,土壤侵蚀与植被建设三个大的方面作了系统分析 ,研究土壤侵蚀产生的原因和发展规律 ,从中可以知道这三个方面是影响土壤侵蚀的最为关键因子 ,并找出其对生态环境的危害性 ,提出最佳的综合防治对策 ,将土壤侵蚀的危害降低到最低程度

生物制剂对沙地樟子松苗木成活生长及生理特征的影响

采用Pt菌剂、ABT生根粉、HRC吸水剂和GGR 6植物生长调节剂等生物制剂,研究了不同生物制剂对2年生樟子松苗木田间试验的造林成活率、植株高度、单株生物量、细根量和盆栽试验苗木的叶片光合和水分利用效率等生理特征的影响。结果表明:(1)Pt3(3号菌剂)、ABT(ABT生根粉)和HRC(HRC吸水剂)均显著地提高樟子松苗木的成活率,它们分别比对照处理苗木成活率高29.3%、23.6%和9.4%,而GRR(GGR植物生长调节剂)和Pt1(1号菌剂)处理苗木的造林成活率同对照处理苗木成活率差异不显著;(2)Pt3、ABT处理均显著地促进了苗木细根生长,分别比对照处理多34.72和15.18 cm,而HRC、CGR和Pt1同对照处理没有显著差异;回归分析表明细根量与苗木成活率呈显著正相关,说明生物制剂提高成活率是通过细根量的增加来实现的;(3)Pt3和ABT处理的苗木高度比对照多2.2、1.5cm和1.1cm,单株生物量干重分别大1.73、0.72g和0.33g,针叶长度、单个针叶面积和单株植株针叶数量分别多1.54和0.096cm、0.188cm2和0.116cm2、31和23束;而Pt1和GGR处理对苗木高度和单株生物量影响不显著;(4)Pt3和ABT处理显著地提高了苗木叶片叶绿素含量和光合速率及水分利用效率等生理指标方面,而其它生物制剂对苗木生理指标影响不显著。生物制剂通过提高苗木生长量和增强生理活动提高樟子松沙地造林成活率。

20世纪90年代LUCC过程对中国农田光温生产潜力的影响:基于气候观测与遥感土地利用动态观测数据

在20世纪90年代中国气候观测数据和遥感土地利用动态观测数据的支持下,计算了中国20世纪90年代农田光温生产潜力的变化.结果表明:20世纪90年代的LUCC过程直接导致了中国农田光温生产潜力总量和区域分布的变化,总体趋势是南减北增,总量净增加2622万吨;在各种土地利用类型之间的相互转变和转化过程中,耕地扩张和农田损失是导致全国农田光温生产潜力总量净变化的主要原因,耕地扩张使全国农田光温生产潜力总量净增加8335万吨,占全国农田光温生产潜力总量的3.50%,主要分布在东北、西北和华北等农林、农牧交错区和沙漠绿洲区,主要是由于该地区大面积的农田开垦所导致;农田损失使全国农田光温生产潜力总量净减少5713万吨,占全国农田光温生产潜力总量的2.40%,主要分布在黄淮海平原、长江三角洲、珠江三角洲、陇中、东南沿海、四川盆地东南部以及乌鲁木齐—石河子一带,主要是由于该区域经济发展较快,城市扩张明显,城乡建设用地大量侵占耕地的缘故.

双马来酰亚胺改性氰酸酯树脂及其复合材料

制备了一种新型的双马来酰亚胺改性氰酸酯树脂以提高这类树脂的耐热性,力学性能及成型工艺性。对合成的树脂作了流变分析,对其玻纤复合材料进行了力学性能测试和热失重分析,结果表明,当双马树脂达到改性氰酸酯树脂的质量分数的37.5%时,新型改性氰酸酯树脂的5%热失重温度为432℃。改性氰酸酯基复合材料在常温条件下的拉伸强度为492.4 MPa,弯曲强度为526.3 MPa

Simulation Study of Aggregate Morphologies Formed by ABC Linear Triblock Copolymers in a Selective Solvent Through the Self-Consistent Field Theory

The effect of the hydrophobic properties of blocks B and C on the aggregate morphologies formed by ABC linear triblock copolymers in selective solvent was studied through the self-consistent field theory. Five typical micelles, such as core-shell-corona, hamburger-like, segmented-wormlike, were obtained by changing the hydrophobic properties of blocks B and C. The simulation results indicate that the shape and size of micelle are basically controlled by the hydrophobic degree of the middle block B, whereas the type of micelle is mainly determined by the hydrophobic degree of the end block C.

Preparation and characterization of La2Zr2O7 coating with the addition of Y2O3 by EB-PVD

Thermal barrier coatings (TBCs) of La2Zr2O7 (LZ) with the addition of 3 wt.% Y2O3 (LZ3Y) were deposited by electron beam-physical vapor deposition (EB-PVD). The phase stabilities, thermophysical and mechanical properties, and chemical compositions of these ceramics and coatings were studied in detail. The phase stability and thermal expansion behavior of LZ3Y bulk material are identical to those of LZ bulk material, but the mechanical properties of the former are superior to those of the latter. Elemental analysis and X-ray diffraction indicate that compositional deviation of LZ coating can be optimized after doping by 3 wt.% Y2O3, Y2O3 acts as a dopant as well as a process regulator. The optimal composition of LZ3Y coating could be effectively achieved by the addition of excess Y2O3 into the ingot and by properly controlling the current of electron beam (i.e. similar to 650 mA).

Host-sensitized luminescence of Dy3+, Pr3+, Tb3+ in polycrystalline SrIn2O4 for field emission displays

SrIn2O4:Dy3+/Pr3+/Tb3+ white/red/green phosphors were prepared by the Pechini sol-gel process. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), diffuse reflectance, photoluminescence, cathodoluminescence spectra, and lifetimes were utilized to characterize the samples. XRD reveal that the samples begin to crystallize at 800 degrees C and pure SrIn2O4 phase can be obtained at 900 degrees C. FE-SEM images indicate that the SrIn2O4:Dy3+, SrIn2O4:Pr3+, and SrIn2O4:Tb3+ samples consist of fine and spherical grains with size around 200-400 nm. Under the excitation of ultraviolet light and low-voltage electron beams (1 - 5 kV), the SrIn2O4:Dy3+, SrIn2O4: Pr3+, and SrIn2O4: Tb3+ phosphors show the characteristic emissions of Dy3+ (F-4(9/2) - H-6(15/2) at 492 nm and 4F(9/2) - 6H(13/2) at 581 nm, near white), Pr3+ (P-3(0) - H-3(4) at 493 nm, D-1(2) - H-3(4) at 606 nm, and P-3(0) - H-3(6) at 617 nm, red) and Tb3+ (D-5(4) - F-7(6,5,4,3) transitions dominated by D-5(4) - F-7(5) at 544 nm, green), respectively. All of the luminescence resulted from an efficient energy transfer from the SrIn2O4 host lattice to the doped Dy3+, Pr3+, and Tb3+ ions, and the luminescence mechanisms have been proposed.

Theoretical investigations of La2C2 cluster

Possible structures of La2C2 were studied and proposed by use of density functional theory. All proposed isomers are planar. The results indicate that the structure with the lowest symmetry (C-1) is the most stable. Linear isomers are not favored.

Melt crystallization of poly(ether ether ketone ketone) under strong electric field

In this paper, melt crystallization of poly(ether ether ketone ketone) (PEEKK) under strong electric field was investigated. In the crystal structure of PEEKK, the length of c axis was found to he 1.075 nm, increasing by 7% compared to that of PEEKK crystallized without strong electric field. The molecule chains might take a more extended conformation through the opening of the bridge bond angles by increasing from 124 degrees to 144 degrees under strong electric field in the crystal structure.

PA1010/66共聚物的松弛行为

研究了PA1010/66共聚物在液氮温度与Tm之间的松弛行为与组成的关系发现不同的松弛温度及损耗因子随共聚物组成的改变而变化的趋势不同随66含量增加，Tγ总趋势下降，Tβ总趋势增加，Tα先下降后增加；tanδ(γ)·tan-1δ(α)和tanδtan-1δ(α)先下降后增加，tanδ(α)先增大后减小。66占50％时，Tγ、Tβ极大，Tα最小；tanδ(γ)tanδ(β)、tanδ(β)·tan－1δ(α)最小，tanδ(α)最大.