Design and preliminary test results of Daya Bay RPC modules

Resistive Plate Chamber (RPC) modules will be used as one part of the cosmic muon veto system in the Daya Bay reactor neutrino experiment. A total of 189 RPC modules will cover the three water pools in the experiment. To achieve track reconstruction and high efficiency, each module consists of 4 layers, each of which contains two sizes of bare chambers. The placement of bare chambers is reversed in different layers to reduce the overlapping dead areas. The module efficiency and patch efficiency were studied both in simulation and test of the data analysis. 143 modules have been constructed and tested. The preliminary study shows that the module and patch 3 out of 4 layers efficiency reaches about 98%.     

采用响应面回归的汽车多属性声品质预测方法*

单一主观评价分数无法准确描述人耳对声品质的多属性偏好特征。该文在多属性声品质试验数据的基础上,以愉悦度、平顺度和驾驶乐趣的主观评价分数为因变量,通过相关分析筛选出响度、尖锐度和A计权声压级3个主要自变量,引入响应面回归方法,分别建立因变量与自变量之间的预测模型,通过与多元线性模型和BP神经网络模型对比验证了精度。最后,建立多属性主观评价分数之间的量化映射模型。该研究可为多属性汽车声品质的优化控制提供参考。     

酸处理对碳纳米管电子自旋共振谱的研究

采用浓硫酸与硝酸混酸对碳纳米管的进行了酸氧化处理,并采用TEM,FTIR和ESR对处理后的碳纳米管的形貌,官能团类型和电子自旋状态进行了表征。结果表明:酸处理能够切断碳纳米管,并且使其管径变小,同时可以使碳纳米管的C-C键发生断裂,产生-COOH。ESR图谱显示电子自旋谱的峰高比随酸处理时间增加而增加,意味着增加碳纳米管中未成对电子和导带电子数量有所增加。同时酸处理后的碳纳米管的g因子和线宽都随着酸处理时间增加而增加,g因子从2.012增加到2.018,线宽从19×10-4增加到26×10-4,意味着缺陷能够影响电子自旋状态。     

基于材料特性的支片力劲性能表现研究

将纱织支数为40的Conex4070、Conex4055、NPC4055、Cotton基材含浸酚醛树脂后热压成型,采用Klippel SPM模块测试定心支片的力-位移曲线及刚性曲线,结合理论公式及支片基材的材料特性对试验结果进行分析.研究表明,波美度相同时,支片材质对刚性的影响较大,CX4070支片线性好且具有较大的有效刚度Keff,表现出较好的粘弹性特性.随着波美度的增加,CX4070和Cotton支片的Keff降低,且刚性曲线也整体下降;降低Cotton支片的波美度对强度增强的作用有限,对非线性力的增幅低于Conex支片.支片位移相同时,不同基材的支片对应的刚性曲线及波美度差异较大,Cotton材质支片的非线性特征最为明显,其位移在6 mm时的刚性较位移零点增加了82.3％,CX4055支片和CX4070支片的Keff与曲线最低点的刚性值差异较小,CX4055与NPC4055的支片具有较低的共振频率.     

6H-SiC硅面S钝化工艺研究

采用(NH4)2S溶液钝化SiC的Si面,借助反向I-V特性间接表征钝化效果,得到了SiC表面最佳的钝化参数:钝化温度60 ℃、钝化时间30 min、NH3·H2O浓度为2.4 mol/L、(NH4)2S浓度为0.22 mol/L.XPS测试结果表明钝化后的6H-SiC表面形成了Si-S键,反向饱和I-V特性表明S钝化降低了表面的态密度.实验结果与第一性原理计算结果相吻合.     

制备乙酰胆碱酯酶脂质体用于甲基对硫磷的电化学检测

随着农业发展,农产品生产越来越依赖于农药的使用,农药的不合理使用使得水体、土壤和农产品污染严重超标,农药残留引起的中毒事故频繁发生.我国农产品往往因农药残留超标难以跨越国外"绿色壁垒",给企业带来巨大的经济损失.为了保障人民的身体健康,满足进出口贸易的需要,研究农药残留速测技术具有重要的意义~([1]).     

聚乙烯吡咯烷酮分子量对LiFePO4/C形貌及电化学性能的影响

以价廉、低毒的无机盐为原料、去离子水为溶剂,通过简易可行的络合溶胶-凝胶法合成了LiFePO4/C复合正极材料.利用XRD、SEM、EIS及恒流充放电测试考察了聚乙烯吡咯烷酮(PVP)分子量对试样的形貌及电化学性能的影响.结果表明,以PVP-k30为表面活性剂所合成的试样颗粒均匀细小、形貌较规则且单分散性良好;该试样具有优良的电化学性能,0.1C的放电比容量为155.7 mAh/g,3C倍率下放电比容量依然能保持112.4 mAh/g,明显优于其它分子量PVP所制备的试样.     

透过三个植物园探索中国植物园科普发展历程

为了探讨植物园科普发展历程,本文通过调查收集国内三个典型植物园科普演变历史的相关资料,归纳出中国植物园科普发展的三个主要阶段。     

Enhanced thermoelectric performance in p-type Mg_3Sb_2 via lithium doping

The Zintl compound Mg_3Sb_2 has been recently identified as promising thermoelectric material owing to its high thermoelectric performance and cost-effective,nontoxicity and environment friendly characteristics.However,the intrinsically p-type Mg_3Sb_2 shows low figure of merit(z T = 0.23 at 723 K) for its poor electrical conductivity.In this study,a series of Mg_(3-x)Li_xSb2 bulk materials have been prepared by high-energy ball milling and spark plasma sintering(SPS) process.Electrical transport measurements on these materials revealed significant improvement on the power factor with respect to the undoped sample,which can be essentially attributed to the increased carrier concentration,leading to a maximum z T of0.59 at 723 K with the optimum doping level x = 0.01.Additionally,the engineering z T and energy conversion efficiency are calculated to be 0.235 and 4.89%,respectively.To our best knowledge,those are the highest values of all reported p-type Mg_3Sb_2-based compounds with single element doping.