Liquefaction and Displacement of Saturated Sand Under Vertical Vibration Loading

In order to investigate the influence of the vertical vibration loading on the liquefaction of saturated sand, one dimensional model for the saturated sand with a vertical vibration is presented based on the two phase continuous media theory. The development of the liquefaction and the liquefaction region are analyzed. It is shown that the vertical vibration loading could induce liquefaction. The rate of the liquefaction increases with the increase of the initial limit strain or initial porosity or amplitude and frequency of loading, and increases with the decrease of the permeability or initial modulus. It is shown also that there is a phase lag in the sand column. When the sand permeability distribution is non-uniform, the pore pressure and the strain will rise sharply where the permeability is the smallest, and fracture might be induced. With the development of liquefaction, the strength of the soil foundation becomes smaller and smaller. In the limiting case, landslides or debris flows could occur.

岩土介质中局部化变形研究的一些新进展

岩土中的剪切带产牛通常是断裂和失稳的前兆，常引起滑坡等地质火害，对油气或水合物等矿藏的开采容易导致压实带形成．压实带的产生使岩上孔隙减小，颗粒破碎，从而导致沉陷、对油气的挤压等．本文重点对剪切带的宽度和压实带的研究现状作综述，阐述在该问题的研究上从微观观测到宏观表述的重要性．通过分析，认为还有如下问题值得研究：怎样准确得出局部化变形带的宽度和方向？局部化变形带形成后孔隙水和油气的渗流会发生什么变化？颗粒层次的微结构特性是通过什么方式影响宏观表现的等等．

用赝势方法计算五种简单金属的Hugoniot曲线

基于本文作者在文献[1]中所导出的冷压P_x,利用德拜固体模型并考虑电子的热压,得到了金属的高温高压状态方程。在与Hugoniot方程联立后,就能算出Hugoniot曲线。本文计算了五种简单金属的Hugoniot曲线。结果表明,在现有实验数据所能达到的范围内,理论计算与实验符合都比较好。

Influence of buoyancy on floating-zone convection of small bond number

Gravity may influence the velocity and temperature distributions, bouyancy may induce Rayleigh instability and the instability may be excited due to the change of free surface shape associating with gravity in the thermocapillary convection. These effects have been studied in the present paper. The results show that gravity may have an important effect in thermocapillary oscillatory convection even for the cases of small Bond number experiments either on the ground or in space.

Efficient two-step digit-set-restricted modified signed-digit algorithm based on optoelectronic shared content-addressable memory

A two-step digit-set-restricted modified signed-digit (MSD) adder based on symbolic substitution is presented. In the proposed addition algorithm, carry propagation is avoided by using reference digits to restrict the intermediate MSD carry and sum digits into {(1) over bar ,0} and {0, 1}, respectively. The algorithm requires only 12 minterms to generate the final results, and no complementarity operations for nonzero outputs are involved, which simplifies the system complexity significantly. An optoelectronic shared content-addressable memory based on an incoherent correlator is used for experimental demonstration. (c) 2005 Society of Photo-Optical Instrumentation Engineers.

大模场面积光纤激光器拉锥法模式选择

大模场面积(LMA)光纤激光器的光束质量通常比单模光纤激光器的光束质量差。采用光纤拉锥的方法进行模式选择,从而提高大模场直径光纤激光器的光束质量。拉锥区距光纤激光器的输出端约5 mm,纤芯最小为9 μm,约为未拉锥部分纤芯直径26 μm的1/3。实验研究表明,在拉锥后,光纤激光器的光束质量因子M2由3.50减小为1.81,相应的斜率效率由63.6%减小为51.1%。虽然拉锥后最大输出功率减少了约19.8%,但其亮度增大为拉锥前的3倍。

Near infrared broadband emission of bismuth-doped aluminophosphate glass

Near infrared broadband emission characteristics of bismuth-doped aluminophosphate glass have been investigated. Broad infrared emissions peaking at 1210nm, 1173nm and 1300nm were observed when the glass was pumped by 405nm laser diode (LD), 514nm Ar+ laser and 808nm LD, respectively. The full widths at half maximum (FWHMs) are 235nm, 207nm and 300nm for the emissions at 1210nm, 1173nm and 1300nm, respectively. Based on the energy matching conditions, it is suggested that the infrared emission may be ascribed to P-3(1) --> P-3(0) transition of Bi+. The broadband infrared luminescent characteristics of the glasses indicate that they are promising for broadband optical fiber amplifiers and tunable lasers. (C) 2005 Optical Society of America.

施肥和降水增加对半干旱草地生产力和温室气体排放的影响

人类活动能显著地改变生态系统的属性和功能。这些变化不仅发生在容易观察的局部层面上，如土壤沙化、植被退化等;还能更深刻地影响到微生物控制的温室气体释放，进而影响大尺度上气候的变化。本论文根据2 年田间试验结果报告了人类干扰（草地退耕和施肥）和降水增加30%对中国北部农牧交错区（内蒙古多伦县）半干旱草地生态系统生产力和温室气体排放的影响。 本研究发现氮是影响该区草地和弃耕地生产力的最重要因子，即使低量的氮肥应用(5 g N y-1)也能使该区草地地上净初级生产力（ANPP）增加36-46%。然而氮对草地生产力影响主要集中在地上部分，对地下净初级生产力（BNPP） 影响比较微弱。单独使用磷肥对ANPP 和BNPP 均无显著影响，氮磷混施对ANPP 有显著正交互作用。增加的降水对草地和弃耕地ANPP 和BNPP 有弱的正效应，增加30%降水使草地对照ANPP 增加9-25%，BNPP 增加12%-17%，弃耕地对照ANPP 增加7%-37%，BNPP 增加36%-37% 。草地和弃耕地对照ANPP 并无显著差别，由于高于弃耕地1-3 倍的BNPP，总体上草地比弃耕地有更高的固碳能力。这个结果也说明草地能更有效地把植物地上部分固定的碳转移到地下，这与草地长期发育积累的丰富地下根系和高根冠比物种组成有关。 水肥处理及土地利用方式也深刻改变了温室气体排放。温带草地和弃耕地CO2 排放（系统呼吸：Re）存在显著季节变化，温度、水分和地上生物量是控制这些变化的主要因子。在气候温暖的6-9 月份，生物量和土壤水分是决定系统呼吸季节变化主要因子，而与温度无明显相关。随着氮肥使用，草地和弃耕地呼吸速率加大，其温度敏感系数Q10 也明显升高，这主要与氮肥使用后增加的地上生物量有关。由于水分促进作用和生物量的弱增长，增加的降水也加大了草地和弃耕地CO2 排放。低的地下生物量和有机碳氮并没有导致弃耕地低的CO2 排放，显示了农垦后土壤结构破坏导致的有机碳分解增加不会在农业弃耕后短期内（5-6 年）停止。 除了对生物量的不敏感性外，中国北部半干旱生态系统N2O 排放表现出与CO2 排放类似的变化规律：水分和温度是N2O 季节变化的主导因子;氮肥使用和降水增加都增加了N2O 排放;N2O 排放在草地对照和弃耕地对照之间没有显著差别。更少的根系对无机氮的竞争导致了弃耕地比草地有更高的N2O 释放因子（单位氮添加所引起N2O 释放）。低的土壤水分（<70% WFPS ）和无机氮都是限制反硝化发生的重要条件，因此硝化可能是草地和弃耕地N2O 的最主要来源。半干旱草地生态系统N2O 排放与CO2 排放之间存在着显著线性关系。 中国北部半干旱草地和弃耕地都起着CH4 汇的生态功能。水分是控制CH4 吸收季节变异的主导变量，土壤空隙水含量（WFPS）与CH4 指数递减方程能解释其变异的64%-83% 。增加的降水导致了土壤水分增加，从而引起甲烷氧化菌所需基质（CH4 和O2）扩散受阻，减小了土壤CH4 吸收功能。施肥并没有抑制CH4 吸收，相反由于施肥后植物速生对土壤水的抽干作用，施肥增加了植物速生期时的CH4 吸收。CH4 吸收对农垦引起的土壤微生物生境结构破坏非常敏感，在农业措施停止5-6 年后的弃耕地，CH4 吸收仍比草地低24%。 本研究初步分析了影响中国北部农牧交错区草地生态系统生产力及温室气体排放的自然环境因子和人为因子，给出了它们之间的定性、定量关系，为科学地管理中国北部草地，充分发挥其生态和经济效益功能提供了有效信息。

苹果绵蚜与苹果绵蚜蚜小蜂种间关系的模拟研究——Ⅰ.两种群生物学的数量特征比较

本研究通过对苹果绵蚜(Eriosoma lanigerum Haus.)和苹果绵蚜蚜小蜂(Aphelinus mali Hald.)的生物学和生态学特性的比较分析,得到如下结论:(1)苹果绵蚜完成一世代的积温要求和发育起点温度均低于苹果绵蚜蚜小蜂,二者的有效积温分别为352.19日度和375.51日度,发育起点温度分别为7.62度和7.95度。因此,苹果绵蚜较其寄生蜂更适合于昆明地区的气候条件;(2)苹果绵蚜种群的增长能力大于苹果绵蚜蚜小蜂,二者的内禀增长率在20℃下分别为0.1390和0.1146,在25℃下分别为0.2647和0.1628。这可能是昆明地区苹果绵蚜蚜小蜂不能控制苹果绵蚜为害的主要原因。

银鲫ZP3的表达特征和卵壳ZP3蛋白的分离

克隆得到银鲫(Carassius auratus gibelio)ZP3基因全长cDNA,在体外表达出银鲫的ZP3融合蛋白,并制备出多抗血清;通过免疫印迹和RT-PCR分析,研究了银鲫ZP3在卵子发生过程中的表达特征和在早期发育胚胎中的状态变化。研究结果表明,银鲫ZP3的转录发生在卵黄发生以前,而ZP3蛋白的翻译起始于卵黄形成阶段,且随着卵母细胞进一步成熟,其含量不断增加。ZP3蛋白的存在状态在受精后和早期胚胎发育过程中发生了明显变化。在受精后5—30min期间,抽提液中原始的ZP3蛋白带迅速消失,取而代

Effects of dietary ascorbic acid supplementation on the growth performance, immune and stress response in juvenile Leiocassis longirostris Gunther exposed to ammonia

This experiment was designed to investigate the effect of dietary supplemental ascorbic acid (AA) on the feed intake, growth, serum lysozyme, hepatic superoxide dismutase (SOD) and handling stress response in Chinese longsnout catfish (Leiocassis longirostris Gunther) exposed to three levels of unionized ammonia nitrogen (UIA-N). Juvenile Chinese longsnout catfish were reared in 54 fibreglass tanks with a 3 x 3 factorial design treatment consisting of three supplemental AA levels in ascorbyl 2-monophosphate (38, 364 and 630 mg AA equivalent kg(-1) diet) and three UIA-N concentrations [0.004 (the control), 0.037 and 0.292 mg L-1]. The fish were sampled on the 11th, 32nd and 60th day. On the 62nd day, the remaining fish were subjected to an acute stress by being held in a dipnet out of water for 60 s, and sampled at 30 min post handling. The results showed that the specific growth rate (SGR) in 32 days significantly decreased with increased water UIA-N (P=0.0476) but was not affected by dietary supplemental AA (P > 0.05). After 60 days, SGR, feeding rate (FR) and feed conversion efficiency (FCE) significantly increased with increased dietary supplemental AA (P < 0.001) while remaining unaffected by water UIA-N (P > 0.05). There was no significant interaction between dietary AA and UIA-N for growth responses (P > 0.05). The serum lysozyme activity on the 11th day and the hepatic SOD activity on the 32nd day were significantly affected at high (0.292 mg L-1) water UIA-N. On the 62nd day, the increase in cortisol resulting from acute stress significantly decreased by higher UIA-N (P=0.038). It is suggested that Chinese longsnout catfish displayed an adaptive response after long-term UIA-N exposure, and AA had beneficial effects on the growth and feed intake of catfish and alleviated the negative effects of chronic ammonia stress. A chronically higher ammonia level shows a tendency to inhibit the cortisol response to another acute stressor.

Quantitative structure-property relationship study on reductive dehalogenation of selected halogenated aliphatic hydrocarbons in sediment slurries

In this study, by the use of partial least squares (PLS) method and 26 quantum chemical descriptors computed by PM3 Hamiltonian, a quantitative structure-property relationship (QSPR) model was developed for reductive dehalogenation rate constants of 13 halogenated aliphatic compounds in sediment slurry under anaerobic conditions. The model can be used to explain the dehalogenation mechanism. Halogenated aliphatic compounds with great energy of the lowest unoccupied molecular orbital (E-lumo), total energy (TE), electronic energy (EE), the smallest bond order of the carbon-halogen bonds (BO) and the most positive net atomic charges on an atom of the molecule (q(+)) values tend to be reductively dehalogenated slow, whereas halogenated aliphatic compounds with high values of molecular weight (Mw), average molecular polarizability (a) and core-core repulsion energy (CCR) values tend to be reductively dehalogenated fastest. (C) 2001 Published by Elsevier Science Ltd.