青海歧穗大黄根部重金属元素特征

为对比青海高原境内不同生境歧穗大黄中七种重金属元素特征,用原子吸收仪进行了分析测试.结果表明,青海歧穗大黄根部Pb元素含量具有随着海拔高度增加而降低的变化特征.     

Neutron powder diffraction experiments on the layered triangular-lattice antiferromagnets RbFe(MoO4)2 and CsFe(SO4)2

Powder specimens of the layered triangular-lattice antiferromagnets RbFe(MoO₄)₂ and CsFe(SO₄)₂ were prepared and neutron powder diffraction experiments were carried out in order to determine the magnetic structure. The magnetic structure of both compounds is the so-called 120^° structure in the triangular plane and is incommensurate between the planes. The ordered moments are confined in the basal ab-plane. It is also found that RbFe(MoO₄)₂ exhibits structural phase transition at around 190 K from to .     

青藏铁路冻土路基温度场随机有限元分析

从一阶Taylor展开式入手,结合冻土温度场计算有限元法,推导了冻土路基温度场随机有限元方程及有关计算公式,并对青藏铁路北麓河试验段冻土路基温度场进行了随机有限元分析,结果表明温度标准差与温度场的分布趋势大致相同,在垂直方向上,最大值都出现在路基上部,向下逐渐减小,但两者分布范围略有不同,路基内部标准差的分布范围明显较大,在一定深度处达到均化。     

温度对Cr^4＋：YAG被动调Q激光器坪区影响

根据激光介质Nd：YAG的发射截面随温度的变化规律，采用被动调Q速率方程进行计算，讨论了激光介质随温度上升单脉冲坪区和坪区重叠空间的改变。结果表明：在-40℃到＋60℃温度内，随激光介质的温度升高，单脉冲坪区逐渐增大，单脉冲坪区重叠空间成逐渐减少趋势，但理论上有足够的坪区重叠空间。     

Improving understanding,learning, and performances of novices in dynamic managerial simulation games

Simulations are increasingly used in training and education because of their success and their advantages as a learning method. However, it has also been observed that the dynamic complexity of simulations creates learning difficulties, and that performance tends to plateau quickly at a level well below benchmark performance. To overcome this difficulty, a gradual‐increase‐in‐complexity approach is proposed, which suggests developing simpler versions of a simulation game that can be used as part of the training. Accordingly, the authors developed a series of inventory‐management simulations and conducted an experiment. The results indicate an improvement in the success of the inventory‐management simulation as a training tool. © 2009 Wiley Periodicals, Inc. Complexity, 2010     

黄土高原半干旱区露水形成的大气物理特征研究

运用2009年在黄土高原典型半干旱区定西的观测资料,分析了半干旱区露水变化特征及其大气影响因子.研究结果表明:在黄土高原半干旱区秋季,日最大凝结量可以达到0.33 mm,最小日凝结量0.09 mm,日平均凝结量为0.23 mm,这对半干旱区而言是可观的水分输入;露水凝结持续时间可以长达14 h.露水的出现频率与风速、大气相对湿度、气温、地-气温差等大气影响因子有显著关系.露水的形成机理十分复杂,是湿度因子、热力因子和动力因子综合作用的结果.在露水形成过程中,大气湿度是内因,为露水形成提供所需水汽;温度则是露水形成的关键,为露水形成提供"源动力",而风速则是重要的外部影响因素,既可以促进露水形成,也可以阻碍露水形成,是露水形成过程中不确定因子.从露水发生频率的分布特征来看,在风速0.5—2 m/s、相对湿度>80%及温度-露点差-3—6℃时、地-气温差<±2℃条件下更易形成露水. 关键词： 黄土高原半干旱区 露水形成 大气影响因子 发生频率     

高效液相色谱-质谱法测定青藏高原植物和土壤样品中氨基酸

提出了高效液相色谱-质谱法测定青藏高原植物和土壤样品中氨基酸的含量。样品中氨基酸经6mol·L~(-1)盐酸溶液提取,加入衍生试剂1,2-苯并-3,4-二氢咔唑-9-乙基氯甲酸酯(BCEOC)进行衍生化反应,衍生化产物经Hypersil BDS C_(18)(4.6mm×200mm,5μm)色谱柱分离,于激发波长(λ_(ex))333 nm和发射波长(λ_(em))390nm进行荧光检测定量,用质谱法定性。色谱分离中采用不同体积比的乙腈与水的混合溶液梯度洗脱,在质谱检测中采用电喷雾离子源正离子模式。方法的检出限(3S/N)为6.3×10~(-15)～1.8×10~(-13)mol之间。以土壤样品为基体,加入20种氨基酸标准作回收试验,测得回收率在89.0%～107.0%之间。     

Influence of shearing on impact polypropylene copolymer: Phase morphology,thermal and rheological behavior

The influences of shearing conducted by a Brabender rheometer on phase morphology,thermal and rheological behavior of a commercial impact polypropylene copolymer(IPC) were studied.The crystallization and melting traces show that short-time annealing at 210°C is unable to completely erase the influence of shearing on the samples.When the samples which were treated at a rotation speed of 80 r/min crystallize at a cooling rate of 10 K/min,their 7_cs and corresponding T_ms obviously rise with the increase of shearing time.Furthermore,the POM results reveal that the shearing can lead to the formation of shish-kebab and the shish-kebab amount is proportional to shearing time.The rheological measurement results show that the treated samples exhibit different G’~ωdependences.The ’second plateau’ appears when the sample is treated at a rotation speed of 60 r/min or 80 r/min for 10 min,and linear G’~ωdependence is observed at other rotation speeds.In addition,it is found that the appearance of the ’second plateau’ depends on the shearing time when the rotation speed is fixed. According to SEM observations,it is proposed that the ’second plateau’ of IPC samples should be ascribed to the aggregation of dispersion particles.     

一种基于图像局部信息的红外图像动态范围压缩算法

红外焦平面探测器输出的信号通常为14bit数字图像,要在常用的显示器上显示必须将14bit的图像压缩到8bit,压缩算法直接影响到了图像的细节和对比度。提出了一种基于图像局部信息的红外图像动态范围压缩算法,通过高斯滤波器将原始红外图像分解为基图像和细节图像,并统计原始图像每个像素的局部方差,然后根据每个像素的局部方差计算细节图像的自动增益函数,最后,将基图像进行平台直方图均衡化后与细节图像合成得到压缩后的图像。通过对多种场景的红外图像进行仿真验证,表明该算法能较好地增强图像的细节。