PCA-Fisher判别模型在煤层底板突水预测中的应用

针对当前煤层底板突水影响因素复杂、预测精度低及难度大等问题,通过结合主成分分析法(PCA)和Fisher判别分析法,构建了PCA-Fisher煤层底板突水判别模型,并将该判别模型应用于贵州省六盘水月亮田煤矿9号煤层对其进行底板突水危险性预测.笔者将含水层水压、隔水层厚度及煤层倾角等6个指标作为影响该煤层底板突水危险性的...     

Constructing refined null models for statistical analysis of signed networks

The establishment of effective null models can provide reference networks to accurately describe statistical properties of real-life signed networks.At present,two classical null models of signed networks(i.e.,sign and full-edge randomized models)shuffle both positive and negative topologies at the same time,so it is difficult to distinguish the effect on network topology of positive edges,negative edges,and the correlation between them.In this study,we construct three re-fined edge-randomized null models by only randomizing link relationships without changing positive and negative degree distributions.The results of nontrivial statistical indicators of signed networks,such as average degree connectivity and clustering coefficient,show that the position of positive edges has a stronger effect on positive-edge topology,while the signs of negative edges have a greater influence on negative-edge topology.For some specific statistics(e.g.,embeddedness),the results indicate that the proposed null models can more accurately describe real-life networks compared with the two existing ones,which can be selected to facilitate a better understanding of complex structures,functions,and dynamical behaviors on signed networks.     

氘含量对DKDP晶体横向受激拉曼散射增益系数的影响

本文测量了不同氘含量K(H_1-xD_x)₂PO₄晶体(DKDP晶体)在Z(XX)Y散射配置下的自发拉曼散射光谱, 并详细分析了氘含量对与横向受激拉曼散射(TSRS)增益系数有关的拉曼频移、半峰宽和散射强度的影响. 然后通过与去离子水拉曼散射对比得出了不同氘含量DKDP晶体的TSRS增益系数. 结果表明随着氘含量的增加DKDP晶体的TSRS增益系数先减小至KDP晶体的40.1%, 后增大至68.9%; 本文认为掺氘后拉曼半峰宽的变化是引起TSRS增益系数随氘含量变化的主要原因.     

KDP晶体受激拉曼散射特性

详细比较了磷酸二氢钾(KDP)晶体的自发拉曼散射和受激拉曼散射光谱,在受激拉曼散射(SRS)中观察到了自发拉曼散射中最强的振动模的三阶Stokes光(559.43,589.74,623.50nm),由于其他振动模的受激拉曼散射增益系数较小,其SRS光谱未观察到。另外,比较了传统生长的未退火和退火后的KDP晶体及快速生长的锥区和柱区KDP晶体的受激拉曼散射增益系数,结果表明生长方法和热退火对KDP晶体的受激拉曼散射增益系数无明显影响。     

铅铈和铅钙锡合金阳极腐蚀膜的性能研究

利用叠加交流伏安法、线性电位扫描法、交流阻抗技术和XPS研究了铅铈合金和铅钙锡合金在阳极1.28 V, 4.5 mol/L的硫酸溶液中所形成的阳极腐蚀膜. 结果表明: 稀土铈能抑制阳极膜中高阻抗的Pb(II)化合物的生长, 降低腐蚀膜的阻抗, 并增加膜的孔隙率. 同时可以提高合金的析氢过电位, 有利于电池免维护性能的提高.     

Characterization, Crystal Structure and Initial DNA Binding Interaction of Two Cu（Ⅱ） Complexes with 4,5-Diazafluoren-9-one

Two new complexes [Cu（dafo）2（en）]（ClO4）2·2H2O （en=NH2CH2CH2NH2） 1 and [Cu（dafo）2（dap）]（ClO4）2·2H2O [dap=NH2CH2CH（CH3）NH2] 2 （dafo=4,5-diazafluoren-9-one） have been synthesized and characterized by elemental analysis, IR and UV spectra. Meanwhile, the complex 1 has been characterized by single crystal X-ray diffraction analysis. The initial DNA binding interactions of the complexes 1 and 2 have been investigated by UV spectra, emission spectra and cyclic voltammogram. Concluding the results of three methods used to measure the interaction of complexes 1 and 2 with DNA, the action mode of the two complexes with DNA is intercalation, and character of ligands and steric effect may affect the interaction of the complexes with DNA.     

磁性固相萃取结合GC－MS检测烟叶中拟除虫菊酯类农药残留

该文基于β-环糊精(β-CD)的磁性复合材料(Fe3O4@SiO2@β-CD)建立了磁固相萃取结合气相色谱－质谱法同时检测烟草中联苯菊酯、甲氰菊酯、氟氯氰菊酯和溴氰菊酯4种拟除虫菊酯类农药残留的分析方法,对比了键合不同环糊精衍生物的复合材料(Fe3O4@SiO2@α-CD、Fe3O4@SiO2@β-CD和Fe3O4@S...     

短时临近预报和预警发布系统设计

政府部门对气象防灾减灾越来越重视,对气象短时临近预报的准确性和时效性要求也越来越高.宁波市气象局开发了气象短时临近预报和预警发布系统.该系统采用了WebGIS软件ArcGIS Srever 和Oracle数据库,结合J2EE平台、Struts架构和Adobe的FLEX技术进行开发,把地理信息与各种气象数据结合起来直观显示,方便预报员在短时间内对灾害性天气进行分析预报,发布预警信号.     

p型GaN/Al0.35Ga0.65N/GaN应变量子阱中二维空穴气的研究

对Ga面p型GaN/Al0.35Ga0.65N/GaN应变异质结构中形成的二维空穴气(2DHG)进行了研究.首先基于半导体-绝缘体-半导体异质结构模型确定了应变异质中的临界厚度,然后自洽求解薛定谔方程和泊松方程,计算了当中间势垒层AlGaN处于完全应变状态和半应变状态两种条件下,顶层GaN及中间层AlGaN厚度的变化对2DHG分布的影响.计算结果表明,势垒层AlGaN和顶层GaN的应变状态和厚度对极化引起的2DHG面密度及分布有重要影响.在此基础上制备了p型GaN/Al0.35 Ga0.65N/GaN应变量子阱结构肖特基器件,并通过器件的C-V测试证实了异质结处2DHG的存在.器件响应光谱的测试结果表明,由于p型GaN/Al0.35Ga0.65N/GaN量子阱中强烈的极化作用和Stark效应使得器件零偏压和反向偏压时的响应光谱都向短波方向移动了10 nm,在零偏压下器件在280 nm处的峰值响应为0.022 A/W,在反向偏压为1 V时,峰值响应达到0.19 A/W,已经接近理论值.     

用电流比较法测电阻

本文介绍了一种用比较法测量电阻的途径