受迫内流吸收过程传热性能的实验研究

国家自然科学基金;广东省自然科学基金

TDR和FDR测定黄绵土土壤含水量的标定

时域反射仪(TDR)与频率反射仪(FDR)是目前最为先进,并且最具有发展前途的土壤含水量测量仪器。有便利、快捷、准确的优点。介绍了6种基于TDR或FDR原理的仪器对黄绵土含水量进行试验标定的方法与结果。标定结果表明:仪器的测量值与烘干法的测量值之间有一定的差异,CS616和Trime-T3烘干法测定结果接近,但是其余的4种仪器测定值均高于烘干法测定值,在应用这些仪器测定土壤含水量时需要进行标定。

施肥水平对长武旱塬地冬小麦产量影响的模拟

为了在实时气象条件下确定旱塬区适宜的肥力水平和产量水平,在模拟精度验证基础上,应用WinEPIC模型模拟研究了黄土高原长武旱塬地1957～2001年期间不同肥力水平下连作冬小麦田产量效应。模型验证结果表明CK、N、NP处理产量模拟值与观测值之间的相关系数分别为0.740、0.764和0.740,均达到显著水平,WinEPIC模型对不同肥力处理下冬小麦籽粒产量模拟较为准确。模拟结果表明,无肥、低肥、中肥和高肥处理下连作冬小麦的产量均呈现波动性降低趋势,其平均值分别为1.055、1.422、2.405和3.170t/hm2,不同肥力处理间差异显著,以中肥和高肥处理增产效果最好。为黄土高原南部沟壑区旱地小麦生产的可持续发展提供了科学依据。

黄土丘陵区植被次生演替灌木种群的土壤养分效应

研究黄土丘陵区植被次生演替灌木群落形成过程中土壤养分的变化情况。【方法】以白羊草群落为对照,选取杠柳、狼牙刺、丁香、虎榛子和柠条5种乡土树种为研究对象,测定其土壤养分含量,计算灌木群落形成变化过程中的土壤养分指数(Soil Nutrient Index,SNI),分析了各养分因子间的线性相关关系。【结果】不同灌木初期对土壤养分的适应能力大小顺序为:柠条(0.072)>狼牙刺(0.114)>杠柳(0.163)>丁香(0.172)>虎榛子(0.292)。不同植被物种群落土壤SNI值大小顺序为:虎榛子群落(0.979)>狼牙刺群落(0.535)>柠条群落(0.457)>丁香群落(0.341)>杠柳群落(0.333)>白羊草群落(0.145)。从不同灌木群落形成过程所产生的土壤养分改善效应来看,各参试群落相对于白羊草群落土壤养分的增幅分别为:虎榛子(4.740倍)、狼牙刺(2.909倍)、柠条(2.661倍)、杠柳(1.169倍)和丁香(1.168倍)。各土壤养分因子间除土壤全磷与有效磷和有效钾的相关性不显著外,其余各土壤养分因子间均表现出极显著的线性相关关系(P<0.01)。【结论】不同灌木种群所需的适宜土...

熔盐电解法制备Al-Li合金的应用基础研究及其工艺初探

Al-Li合金是近年发展起来的新型航空材料，具有低密度、高强度的特点。目前世界上正就如何进一步提高其断裂韧性，使Al-Li合金尽早走出实验室，获得实际用进行广泛，深入的研究。熔盐电解法就是在这种情况下发展起来的。虽然此法现在尚处于研究的初级阶段，但已以其能够在较简单的设备上制备低Na高纯Al-Li合金的特点受到广泛的重视，是一种很有前途的发展方向。针对我国的技术、设备现状，在参考国外研究结果的基础上，采用熔盐电解法制备Al-Li母合金 → 应用合金的制备方法是可以尽快赶上世界发步伐的有效途径。因此，本文作为整个熔盐电解制备Al-Li合金系统研究的一部分，针对目前在此领域中很多应用基础问题，诸如：作为新的电解体系正在探索中的LiCl-KCl-LiF三元相图，Li在液体Al阴极中的扩散系数，利用熔盐电解法制备低Na高纯Al-Li合金的热力学基础及如何克服LiCl强烈的吸水性给电解工艺带来的种种不便等均未得到系统研究的现状，设计完成了一系列有关熔盐电化学和热力学实验，填补了本领域的一些研究空白，并为进一步系统研究工艺条件提供了重要的参考数据。1．用NH_4Cl氯化Li_2CO_3的研究 根据热力学从理论上论证了在200 ℃左右下述氯化反应：Li_2CO_3 + 2NN_4Cl = 2LiCl + 2NH_3~↑ + H_2O~↑ + CO_2~↑可以进行完全。利用DSC方法测定反应产物LiCl的纯度，并用离子色谱法分析反应产物中CO_3~=的含量，结果均证明：在Li_2CO_3:NH_4Cl = 1:4 (mol)时，Li_2CO_3可以定量转化为LiCl，剩余的NH_4Cl完全分解。根据热重分析结果推测NH_4Cl氯化Li_2CO_3的反应历程为：Li_2CO_3 + 2NH_4Cl = 2LiCl + 2NH_3~↑ + H_2O~↑ + CO_2~↑ NH_4Cl = HCl~↑ + NH_3~↑ 而并非是想像中的：NH_4Cl = HCl~↑ + NH_3~↑ 2HCl + Li_2CO_3 = 2LiCl + H2O~↑ + CO_2~↑利用X－射线衍射方法分析产物，结果亦说明氯化可以成功。将1:4（mol）= Li_2CO_3:NH_4Cl混合样品在差热分析反应炉中直接加热测定反应产物LiCl的溶点，并与纯LiCl样品熔点的测定结果相比较，二者完全一致。以上结果说明：不仅可用此氯化反应产物代替LiCl应用于熔盐电解制备Al-Li合金中，而且还可将其应用于LiCl体系的相图测定中。因Li_2CO_3，NH_4Cl均不吸水，极易处理，因此以上研究结果无论对于Al-Li合金的工艺研究还是其他有关LiCl体系的基础研究都是很有价值的。2．直接氯化法制备LiCl-KCl-LiF三元相图的研究。LiCl-KCl-LiF三元相图是研究此体系电解机制的重要基础。为将以上直接氯化法应用于差热分析中制作此三元体系相图，首先用直接氯化法测定了三个已知二元LiCl体系相图：LiCl－KCl；LiCl-LiF；LiCl-NaCl。与文献结果吻合很好。说明将此法应用于差热分析中制作LiCl体系相图结果是可靠的。在LiCl-KCl-LiF三元相图的测定中共做出七个垂直截面，在各截面上读出等温条件下的相界点投影到浓度三角形中，得到等温投影图。结果说明LiCl-KCl-LiF是固态完全不互溶的三元共晶体系，共有三个液－固两相区；三个液－固－固三相区；一个液－固－固－固四相区，（三元共晶平面）和一个固－固－固三相区。四相点温度为348 ℃，其组成在三相平衡线的交点处，在实验上测出近似等于：41.4KCl + 57.3LiCl + 1.3LiF (mol)。3．氯化物体系中Li~+, Na~+析出电位的比较及其去极化作用的研究。在正常电化序中，Li~+应先于Na~+析出。但在以Al作阴极电解LiCl体系时，则由于Li~+在Al上有较强的去极化作用而提前析出。这是熔盐电解法可以制备低Na，高纯Al-Li合金的基础。本文在理论上对此问题进行了较深入的研究。具体内容包括（1）。测定Li~+, Na~+在二元氯化物体系中的析出电位。通过在Al阴极，Mo阴极上二离子析出电位的比较，确认了Li~+在Al阴极上产生很强的去极化作用是能利用电解法制备低Na高纯Al-Li合金的根本原因。并为在工艺研究中选择合适的电流密度提供了参考依据。（2）．根据热力学理论推导出合金化反应产生的自由焓变化与去极化作用的关系：ΔG_x + ΔG_m = -nFΔE。揭示了产生去极化作用的原因。并根据ΔG_x（偏摩尔过剩自由焓）与合金结构的关系提出可以利用二元合金相图推测极化类型及极化大小。并根据动力学原理对温度对极化的影响提出了自己的看法。（3）．求出合金化反应的热效应，认为在一定条件下亦可利用此值作为判断去极化作用大小的标准。（4）．测定Li~+, Na~+在Al-Cu, -Al-RE合金上的析出电位。结果表明Cu，RE的存在均可加强Li~+在阴极上的去极化作用，进一步加大了Li~+, Na~+析出电位之间的差别，有利于制备更纯的Al-Li 使金。为直接生产Al-Cu-Li, Al-RE-Li三元母合金奠定了基础。（5）测定Li~+在不同组成配比的LiCl-KCl熔体中，在Al阴极上的析出电位，并求出LiCl的离子平均活度系数γ＝0.71 (T = 740 ℃), 熔体对理想状态产生负偏离。4．利用阳极计时电位法测定T＝720 ℃时Li在液体Al中的扩散系数D_(Li/Al) = 4.94 * 10~(-5)cm~2·s~(-1)，与利用Stocks-Einstan公式计算出的理论值D_(Li/Al) = 4.85 * 10~(-5)cm~2·s~(-1)吻合较好。5．在上述理论研究的基础之上进行了工艺初探，所得初步结论有：（1）．加入LiF可以提高电效。（2）．采用电流密度为1 A/cm~2时，不加搅拌亦可制备出成份均匀，含Li量为10％（w.f）的Al-Li合金。（3）．根据实验结果提出 Li在熔体中的熔解可能是影响电流效果的主要原因。

Optical gain in zinc-blende GaN/Ga1-xAlxN strained quantum well laser

Based on the valence subbands of the zinc-blende GaN/Ga0.85Al0.15N strained quantum wells obtained by a 6x6 Hamiltonian (including heavy hole, light hole and spin-orbit splitting band), optical gain and radiative current density are calculated for the strained quantum well laser structures. The compressive strain in the GaN well region strongly depresses the TM mode optical gain and enhances the TE mode optical gain.

Effects of Cu-Wire Surface Fluctuations on Early Failures

Different chemical mechanical polishing （CMP） slurries are used to obtain single-damascene Cu-wires with different surface fluctuations as well as pre-existing surface-defects in wires with rougher surfaces. The presence of such pre-existing defects strongly increases the rate of early failures to almost 100%, reduces electromigration lifetime rapidly to the level of early failures, and changes the multimodal failure distribution into monomodal. The activation energy （0. 74±0.02eV） for the failure mechanism associated with these pre-existing defects confirms a dominant surface diffusion. It shows how a weakest link approximation analysis can he applied to a single wire by dividing the wire into relevant segments and assigning different failure mechanisms to the various segments. The analysis confirms that, although surface-defects are not the fastest early failure mechanism, the ten times higher surface-defectdensity in the rougher wires is responsible for the observed high early-failure rate and unreliable performance.

Application of the characteristic CIP method to a shallow water model on the sphere

Semi-implicit algorithms are popularly used to deal with the gravitational term in numerical models. In this paper, we adopt the method of characteristics to compute the solutions for gravity waves on a sphere directly using a semi-Lagrangian advection scheme instead of the semi-implicit method in a shallow water model, to avoid expensive matrix inversions. Adoption of the semi-Lagrangian scheme renders the numerical model always stable for any Courant number, and which saves CPU time. To illustrate the efficiency of the characteristic constrained interpolation profile (CIP) method, some numerical results are shown for idealized test cases on a sphere in the Yin-Yang grid system.

黄龙世界自然遗产地岷江冷杉原始林群落结构与植物多样性：生境差异性研究

黄龙世界自然遗产地岷江冷杉林(Abies faxoniana)生境类型多样，群落结构复杂，群落植物种类组成多样性丰富。揭示不同生境的生物多样性及其差异是认识生物多样性格局、形成及维持机制的前提和进行多样性保育的基础。本文采用样方法对黄龙钙化滩生境、阴坡非钙化生境及半阳坡非钙化生境的岷江冷杉原始林植物群落结构及植物多样性进行了研究。结果表明： 黄龙岷江冷杉林具有明显的复层异龄结构，垂直结构明显，乔木、灌木、草本、苔藓层次分明。共发现高等植物386 种，其中维管植物46 科103 属163 种，苔藓植38 科83 属物223 种。各层片结构及物种组成如下: (1)钙化滩生境、阴坡非钙化生境、半阳坡非钙化生境分别发现乔木18 种、13种、8 种。乔木层均可分为两个亚层，第一亚层优势种均为岷江冷杉，第二亚层主要为岷江冷杉异龄树或其它大高位芽物种。钙化滩生境第一亚层除优势种岷江冷杉外混生有巴山冷杉(Abies fargesii)、粗枝云杉(Picea asperata)以及阔叶树种白桦(Betula platyphylla)等，第二亚层主要为岷江冷杉异龄树；阴坡非钙化生境第一亚层除优势种岷江冷杉外间有巴山冷杉和白桦，第二亚层物种主要为川滇长尾槭(Acer caudatum var. prattii)；半阳坡非钙化生境第一亚层除优势种岷江冷杉外混生有巴山冷杉，第二亚层主要为岷江冷杉异龄树。依乔木层优势种的差异，钙化滩生境及半阳坡非钙化生境为岷江冷杉纯林，阴坡非钙化生境为岷江冷杉－川滇长尾槭混交林。不同生境乔木层郁闭度、乔木密度、树高结构、直径结构均存在差异。 (2)钙化滩生境发现灌木41 种，平均盖度为18.49±1.72(％)，平均高度为52.12±4.45(cm)，优势种为直穗小檗(Berberis dasystachya)；阴坡非钙化生境发现灌木30 种，平均盖度为29.33±2.56 (％)，平均高度为119.55±8.01 (cm)，优势种为箭竹 (Fargesia spathacea) 、唐古特忍冬(Lonicera tangutica) 和袋花忍冬(Lonicera saccata)；半阳坡非钙化生境发现灌木29 种，平均盖度为31.35±1.93 (％)，平均高度为107.55±4.24 (cm)，优势种为箭竹(Fargesia spathacea)。不同生境灌木层结构和物种组成多样性差异显著，钙化滩生境的灌木盖度、高度总体上较非钙化的坡地生境低, 钙化滩生境灌木以小型叶的落叶灌木为主，沟两侧非钙化的坡地生境上则发育了丰富箭竹。 (3)钙化滩生境发现草本46 种，平均盖度为7.18±0.79 (％)，平均高度为5.04±0.26(cm)，以山酢浆草(Oxalis griffithii)为优势种；阴坡非钙化生境发现草本物种71 种，平均盖度达29.04±2.31(％)，平均高度为9.08±0.52(cm)，以钝叶楼梯草(Elatostema obtusum)、山酢浆草为优势种；半阳坡非钙化生境草本物种50 种，平均盖度为以8.79±0.82(％)，平均高度为7.67±0.43 (cm)，以扇叶铁线蕨(Adiantum flabellulatum)、双花堇菜(Viola biflora)、华中蛾眉蕨(Lunathyrium shennongense)、山酢浆草为优势种。阴坡非钙化生境草本层片发育良好，多样性最为丰富，盖度和物种丰富度均显著高于钙化滩生境和半阳坡非钙化生境。 (4)钙化滩生境发现苔藓物种140 种，平均盖度达84.25±1.30 (％)，以仰叶星塔藓(Hylocomiastrum umbratum) 等大型藓类为优势种；阴坡非钙化生境发现苔藓物种115 种，平均盖度为79.29±1.64 (％)，以刺叶提灯藓(Mnium spinosum)、大羽藓(Thuidium cymbifolium)、毛尖燕尾藓(Bryhnia trichomitra)等个体较小的物种为优势种；半阳坡非钙化生境发现苔藓物种91 种，平均盖度为60.64±1.93 (％)，也以刺叶提灯藓为优势种。 (5)钙化滩生境、阴坡非钙化生境、半阳坡非钙化生境的物种数分别为234 种、221 种、175 种。乔木层的Shannon-Wiener 指数分别为0.75 ±0.12、1.87±0.12、1.78±0.07（灌木层，0.44±0.08、1.71± 0.15、2.49±0.06；草本层，0.33±0.13、1.31±0.15 、2.15±0.08； 苔藓层1.30±0.11、2.08±0.04、1.73±0.11，）；Pielou 均匀度指数分别为0.45±0.05、0.29±0.06、0.28±0.08（灌木层，0.75±0.03、0.68±0.05、0.52±0.06；草本层，0.68±0.02、0.77±0.02、0.74±0.02；苔藓层，0.40±0.03、0.63±0.02、0.52±0.03）；Simpson's 优势度指数分别为0.63±0.06、0.78±0.04、0.83±0.07（灌木层，0.21±0.03、0.28±0.05、0.45±0.06；草本层，0.25±0.02、0.12±0.01、0.17±0.01；苔藓层，0.45±0.04、0.18±0.01、0.31±0.04）。三种生境间乔木层、草本层的Sorenson 群落相似性系数较低, 灌木层、苔藓层的的Sorenson 群落相似性系数较高。 综上所述，黄龙岷江冷杉林的群落结构、植物多样性在三种生境间存在差异性，这将意味着我们在进行黄龙世界自然遗产地的森林经营管理时要较多地关注岷江冷山林群落在不同生境中的差异性。 There were multiplex habitat types, complicated community structure and abundant species composition in the Huanglong World Natural Heritage Site. Uncovering the differences of biodiversity among different habitats was a precondition to understand the distribution, formation and sustaining mechanism of the biodiversity, and the foundation of biodiversity conservation. In the present study, using plenty of quadrants, we investigated the community structure and the biodiversity of the primitive Abies faxoniana forest in different habitats (travertine bottomland, semi-sunny-slope non-calcified habitat and shady-slope non-calcified habitat) in the Huanglong World Natural Heritage Site. The main results are as follows: All the primitive Abies faxoniana forests in the three habitats were uneven-aged with obvious vertical structure including tree layer, shrub layer, herb layer and bryophyte layer. A total of 386 higher plants including 163 vascular plant species (103 generic, 46 families) and 223 bryophyte species (83 generic, 38 families) were investigated. The structure and species composition of each layer are as follows: (1) There were 18, 13 and 8 tree species in travertine bottomland, shady-slope non-calcified habitat and semi-sunny-slope non-calcified habitat, respectively. The tree layers in all habitats can be divided into two clear sub-layers. The upper tree layers were dominated by Abies faxoniana, and the lower tree layers were dominated by uneven-aged Abies faxoniana or other phanerophytes species. There were Abies fargesii , Picea asperata and Betula platyphylla besides the dominated species (Abies faxoniana) in the upper tree layer in travertine bottomland, and the lower tree layers were dominated by uneven-aged Abies faxoniana; There were Abies fargesii and Betula platyphylla besides the dominated species (Abies faxoniana) in the upper tree layer in shady-slope non-calcified habitat, and the lower tree layers were dominated by Acer caudatum var. prattii; There was Abies fargesii besides the dominated species (Abies faxoniana) in the upper tree layer semi-sunny-slope non-calcified habitat, and the lower tree layers were dominated by uneven-aged Abies faxoniana. According to composition percentage of dominate species in tree layer, both the forest in travertine bottomland and in semi-sunny-slope non-calcified habitat could be ranked as pure forest, and the forest in shady-slope non-calcified habitat could be ranked as mingled forest. There were significant differences in crown density, plant density, height structure and diameter structure among the three habitats. (2) A total of 41 shrub species (average coverage 18.49±1.72％; average height 52.12±4.45 ㎝)were found in travertine bottomland, and the dominate species was Berberis dasystachya; A total of 30 shrub species (average coverage 29.33±2.56 ％;average height 119.55±8.01 ㎝)were found in shady-slope non-calcified habitat, and the dominate species was Fargesia spathacea, Lonicera tangutica and Lonicera saccata. A total of 29 shrub species (average coverage 31.35±1.93％; average height 107.55±4.24 ㎝) were found in semi-sunny-slope non-calcified habitat, and the dominate species was Fargesia spathacea. There were significant differences in structure and species diversity of the shrub layers among the three habitats. The coverage and height of shrub had lower value in travertine bottomland than in two non-calcified habitats. Moreover, travertine bottomland was dominated by deciduous shrub species with microphyll and non-calcified habitats developed abundant Fargesia spathacea species. (3) A total of 46 herb species (average coverage 7.18±0.79％;average height 5.04±0.26 ㎝)were found in travertine bottomland, and the dominate species was Oxalis griffithii; A total of 71 herb species (average coverage 29.04±2.31％;average height 9.08±0.52 ㎝)were found in shady-slope non-calcified habitat, and the dominate species was Elatostema obtusum and Oxalis griffithii. A total of 50 herb species (average coverage 8.79±0.82％;average height 7.67±0.43 ㎝) were found in semi-sunny-slope non-calcified habitat, and the dominate species was Adiantum flabellulatum, Viola biflora, Lunathyrium shennongense and Oxalis griffithii. Herb layers developed well in shady-slope non-calcified habitat and had the higher species richness and coverage than travertine bottomland and semi-sunny-slope non-calcified habitat. (4) A total of 140 bryophyte species (average coverage 84.25±1.30％)were found in travertine bottomland, and the dominate species was big bryophyte species such as Hylocomiastrum umbratum and so on; A total of 115 bryophyte species (average coverage 79.29±1.64％)were found in shady-slope non-calcified habitat, and the dominate species was small bryophyte species such as Mnium spinosum, Thuidium cymbifolium, Bryhnia trichomitra and so on. A total of 91 bryophyte species (average coverage 60.64±1.93％) were found in semi-sunny-slope non-calcified habitat, and the dominate species was Mnium spinosum. (5) There were 234, 221 and 175 plant species in travertine bottomland, shady-slope non-calcified habitat and semi-sunny-slope non-calcified habitat, respectively. Shannon-Wiener index of the tree layer was 0.75 ±0.12, 1.87±0.12 and 1.78±0.07 (the shrub layer, 0.44±0.08, 1.71± 0.15 and 2.49±0.06; the herb layer, 0.33±0.13, 1.31±0.15 and 2.15±0.08; the bryophyte layer, 1.30±0.11, 2.08±0.04 and 1.73±0.11.) for the three habitats, respectively; Pielou index of the tree layer was 0.45±0.05, 0.29±0.06 and 0.28±0.08 (the shrub layer, 0.75±0.03, 0.68±0.05 and 0.52±0.06; the herb layer, 0.68±0.02, 0.77±0.02 and 0.74±0.02; the bryophyte layer, 0.40±0.03, 0.63±0.02 and 0.52±0.03.) for the three habitats, respectively. Simpson's index of the tree layer was 0.63±0.06, 0.78±0.04 and 0.83±0.07 (the shrub layer, 0.21±0.03、0.28±0.05、0.45±0.06; the herb layer, 0.25±0.02, 0.12±0.01 and 0.17±0.01; the bryophyte layer, 0.45±0.04, 0.18±0.01 and 0.31±0.04.) for the three habitats, respectively. There were low Sorenson index both in the tree layer and in the herb layer among the three habitats, whereas, high Sorenson index occurred both in the shrub layer and in the bryophyte layer. To sum up, there were differences both in community structure and plant diversity among the three different habitats, which means that we should pay more attention to habitats heterogeneities of the primitive Abies faxoniana forest when we take action to manage the forest in the Huanglong World Natural Heritage Site.

深层治癌重离子束的配送

利用重离子束流治疗深层肿瘤的临床实验将在中国科学院近代物理研究所(IMP)进行。束流配送系统是重离子治癌临床实验的关键系统,输送束流均匀辐照照射野。重离子束流经过回旋加速器初步加速,注入重离子冷却储存环(CSR)的主环(CSRm),累积、加速后通过共振引出,经深层治癌束运线输送到照射野。针对重离子治癌要求和现场可利用空间,优化设计了束运线,得到了灵活调节束斑尺寸的透镜参数。通过模拟束流扫描过程,验证了扫描系统的可行性。