Crystallographic and magnetic properties of hydride R3Fe29-xTxHy (R=Y, Ce, Nd, Sm, Gd, Tb and Dy; T=V and Cr)

The crystallographic and intrinsic magnetic properties of hydride R3Fe29-xTxHy (R=Y, Ce, Nd, Sm, Gd, Tb, and Dy; T=V and Cr) have been investigated. The lattice constants and the unit cell volume of R3Fe29-xTxHy decrease with increasing R atomic number from Nd to Dy, except for Ce, reflecting the lanthanide contraction. Regular anisotropic expansions, mainly along the a- and b-axis rather than along the c-axis, are observed for all the compounds upon hydrogenation. Hydrogenation leads to an increase in Curie temperature. First-order magnetization processes (FOMP) occur in magnetic fields of around 1.5 T and 4.0 T at 4.2 K for Nd3Fe24.5Cr4.5H5.0 and Tb(3)Fc(27.0)Cr(2.0)H(2.8), and around 1.4 T at room temperature for Gd3Fe28.0Cr1.0H4.2 Abnormal crystallographic and magnetic properties of Ce3Fe29-xTxHy suggest that the Ce ion is non-triply ionized.

基于融合模板的均值移动头部跟踪算法

针对被跟踪头部目标特征状态随时间变化而与参考模板不匹配的问题,提出一种基于融合参考模板的均值移动算法,即将被跟踪目标在不同状态下所呈现出的不同特征使用采样的方法进行融合,如将头部跟踪过程中正面的肤色信息和后面的发色信息进行融合,从而形成一个包含不同特征的参考模板.在跟踪过程中,使用该融合模板可以有效地克服由被跟踪目标特征变化导致跟踪失败而不能实现头部连续跟踪的问题.通过头部跟踪实验可以看出,该算法实现了复杂环境下的具有360°旋转的头部跟踪,并且在一定程度上提高了跟踪精度.

人工湿地塘床系统净化污水的机理研究

人工湿地处理污水实验场经过多年的运行已形成了较稳定的具有多 种生物种类的适合污水处理的生态系统，活水公园人工湿地塘床系统运行时间仅一年，初步显示了湿地生态系统的生物多样性特点。筛选出了菖蒲、芦苇、茭白、香蒲、水竹、马蹄莲、凤眼莲、浮萍、睡莲等适合本地人工湿地塘床系统种植的湿地植物。人工湿地塘床系统是由各种湿地单元与各种各样的高、低等生物和所处的开放式的环境共同构成了较为完整的具有净化污水功能的生态系统，因此，与生物滤池相比，把人工湿地塘床系统称为生态滤池显得更为合适。其出水具有生物安全性。实验结果表明，实验场对生活污水中的COD_(Cr)、BOD_5、TP的去除率在80％以上，对TN的去除率为60.60% ～ 86.4%，细菌总数的去除率为86.9% ～ 99.6%，总大肠菌群的去除率为94.6% ～ 99.7%，其出水水质能够满足二级污水处理的要求。活水公园对枯水期府河水中的COD_(Cr)、BOD_5、TN、TP的去除率在85％以上，总大肠菌群的去除率为99.97%，其净化效果能够满足污水深度处理的需要。湿地植物光合作用向水体供氧能力的试验研究结果表明，在几种光照控制条件静态试验和现场试验中，菖蒲、香蒲、茭白、水竹、凤眼莲等植物植株水面以上的茎、叶在光照条件下进行光合作用时并没有引起根层区水体内溶解氧浓度的升高（氧增），反出现下降（氧亏）。说明这些植物水上部分光合作用对水体DO没有贡献。浮萍光合作时引起氧增的作用较弱，仅维持低水平，试验期间9:00 ～ 15:00的氧增幅度在0.11 ～ 1.13mg/L之间，平均为0.44mg/L。芦苇在9:00 ～ 15:00光合作用时根层区水体氧增幅在-0.20 ～ 1.07mg/L之间，平均为0.30mg/L。上述这些植物植株的水面以下的根、根茎、茎、叶如果暴露在光照条件下时，会进行光合作用，产生的氧直接释放到水体并引起氧增的作用非常明显，试验期间9:00 ～ 15:00的氧增幅度在1.91 ～ 16.1mg/L之间。人工湿地处理污水系统植物床基质内各测点的上、下层COD_(Cr)值虽有一定的差别，但经过成对平均数比较分析发现这种差别并未形成明显的趋势。污水在植物床基质中流动时，随着迁移距离的延长，其中的COD_(Cr)的降解速率呈现先快后慢的趋势，根据动态变化规律，建立了COD_(Cr)在植物床基质层内沿程水平迁移降解动态变化模型：C_L = C_o exp(4.629 * 10~(-5)L~2-0.01567L，0 ≤ L ≤ 100。经验证，模型预测值与实际监测值呈非常显著相关（r ≥ 0.9946 > r_(0.0005(4))，r_(0.0005(4)) = 0.9741)。在人工湿地塘床系统运行监测过程中，发现处于光照下的水体中的pH呈周期性变化，与DO的变化规律相似，在试验期间，9:00 ～ 15:00的pH和DO都呈上升趋势，两者呈协同周期性变化。经相关性回归分析，pH的变化规律与DO呈非常显著相正关，植物床表层渍水区pH与DO的回归关系相关系数r = 0.9129 > r_(0.01(70))(r_(0.01(70)) = 0.302)，植物塘内的pH与DO的相关系数r = 0.8584 > r_(0.01(60))(r_(0.01(60)) = 0.325)，植物床基质层内的pH与DO之间的相关性较差。相关分析结果表明，DO变化幅度大的水体中，pH的变化幅度也就越大，两者之间的相关性也就越显著，这可能与水体中氧化还原电位和水生植物光合作用伴随的代谢活动有关。这种相关性和协同周期性变化具有一定的生态学意义，并会给净化污水的效果产生影响。

甲基对硫磷水解酶结构和功能的研究

本研究以本实验室分离的有机磷农药高效降解菌Pseudomonas sp．WBC-3为材料，通过X-射线晶体学研究确定了甲基对硫磷水解酶（MPH）的三维结构，并在结构基础上探讨了甲基对硫磷水解酶的结构与功能的关系。利用生物信息学手段对Pseudomonas sP.WBC-3中的甲基对硫磷水解酶基因进行分析，推测论H的结构基因的编码序列为398-1393 bp，蛋白大小为331个氨基酸，且具有一个由35个氨基酸组成的信号肤。同时发现，MPH是一个不同于具有相似生物学功能的有机磷水解酶（OPH）的蛋白质，而且在PDB库中尚无与MPH同源性较高的蛋白结构。晶体的生长依赖于高纯度的蛋白质的获得。在本研究中，我们采用阳离子交换树脂和凝胶过滤两步纯化获得了纯度达95％以上的MPH溶液，并采用等离子体质谱仪测定MPH为含锌的金属酶。采用悬滴蒸汽扩散法获得了PI和P43212两种晶型的晶体以及硒标记的MPH晶体。在获得单晶以后，最终利用尸43212晶型的晶体通过多波长反常散射法（MAD）解析了MPH的三维结构。MPH的晶体结构为同源二聚体，具有与OPH类似的二价金属离子组成的活性中心：其中一个单体含有两个锌离子，另一个单体含有一个锌离子和一个锅离子；每个单体的两个金属离子通过AsP 151、His 152、His 302、His 147、His 149、His 234和A印255与蛋白质相连，一个H2O分子桥连于两个金属离子，还有一个H2O分子只与一个金属离子配位。在MPH三维结构知识的基础上，利用分子生物学手段对MPH活性中心附近可能的底物结合氨基酸位点进行了研究。通过定点突变获得了针对Trp179，Phe 196和Phe 119三个位点的六个突变体W179F、W179A、F196W、F196A、FllgW和Fll9A，系统比较了突变体与野生酶的催化动力学特点。结果表明Trp 179，Phel％是MPH活性中心的底物结合部位的关键氨基酸。而Phe 119在与底物结合中的作用不明显。

Initiation and development of water film by seepage

When water seeps upwards through a saturated soil layer, the soil layer may become instability and water films occur and develop. Water film serves as a natural sliding surface because of its very small friction. Accordingly, debris flow may happen. To investigate this phenomenon, a pseudo-three-phase media is presented first. Then discontinuity method is used to analyze the expansion velocity of water film. Finally, perturbation method is used to analyze the case that a water flow is forced to seep upwards through the soil layer while the movement of the skeleton may be neglected relative to that of water. The theoretical evolutions of pore pressure gradient, effective stress, water velocity, the porosity and the eroded fine grains are obtained. It can be seen clearly that with the erosion and re-deposited of fine grains, permeability at some positions in the soil layer becomes smaller and smaller and, the pore pressure gradient becomes bigger and bigger, while the effective stress becomes smaller and smaller. When the effective stress equals zero, e.f. liquefaction, the water film occurs. It is shown also that once a water film occurs, it will be expanded in a speed of (U)(t)/(1 - E >).

A study on water film in saturated sand

Water film can serve as a sliding surface and cause landslides on gentle slopes. The development of "water film" in saturated sand is analyzed numerically and theoretically based on a quasi-three-phase model. It is shown that stable water films initiate and grow if the choking state (where the fluid velocity decreases to near zero) remains steady in a liquefied sand column. Discontinuity can occur in pore water velocity, grain velocity and pore pressure after the initiation of a water film. However, the discontinuity and water film can disappear once the choking state is changed. The key to the formation of water film is the choking in the sand column caused by eroded fine grains.

Characteristic rainfall for warning of debris flows

A characteristic rainfall is introduced to overcome the difficulties encountered in determining a critical rainfall value for triggering debris flow. The characteristic value is defined as the rainfall at which debris-flow occurrence probability shows a rapid increase, and can be used as a warning rainfall threshold for debris flows. Investigation of recorded debris flows and 24-hour rainfall data at Jiangjia basin, Yunnan Province, in southwestern China, demonstrates the existence of such a characteristic rainfall. It was found that the characteristic rainfall corresponds to the daily rainfall of 90% cumulative probability by analyzing the basin's daily rainfall histogram. The result provides a simple and useful method for estimating a debris-flow warning rainfall threshold from the daily rainfall distribution. It was applied to estimate the debris-flow warning rainfall threshold for the Subaohe basin, a watershed in the 2008 Wenchuan earthquake zone with many physical characteristics similar to those of the Jiangjia basin.

降雨作用下滑坡转化泥石流分析研究

对降雨入渗条件下诱发北川县魏家沟泥石流起动的影响因素进行研究。在室内人工降雨试验模拟泥石流起动的基础上,得到魏家沟泥石流起动的临界雨强,并利用FLAC软件建立降雨在坡体中入渗分析的数值模拟模型,分析坡度、雨强、土性参数以及土体饱和度对坡体失稳的影响,坡体在降雨情况下塑性区的出现与延展及坡面拉应力区的发展情况。研究结果表明:降雨入渗后孔隙水压力的升高主要在坡脚附近,即距坡脚1/5的坡高范围内。坡脚处孔隙水压力最大,沿着坡面往上逐渐减小,且坡面较大水平位移也主要集中在1/5坡高范围内。因此,降雨入渗诱发泥石流的起动最先可能出现在坡脚附近,并随着坡度增加、雨强增大、土体饱和度增大,坡体稳定性降低至失稳,促进泥石流的起动。