低能实验核物理及其应用

简要地介绍了北京大学技术物理系和重离子物理研究所近年来在低能实验核物理及其应用方面的部分研究工作.Some recent studies on the low energy experimental nuclear physics and its applications at the Department of Technicsal Physics and the Institute of Heavy Ion Physics of Peking University are beiefly introduced in this paper.     

质子辐照后的KNbO3晶体的光折变响应特性

实验研究了质子辐照的KNbO₃晶体随光强变化的光折变响应特性,并测量了其光折变时间常数。实验结果揭示出在质子辐照后的KNbO₃晶体中存在着2种不同的光栅,其一是慢成分,是由晶体本身的光折变效应所产生;另一个则是快成分,是由于质子辐照后所产生的辐照效应。实验结果还反映出这2种光栅是由2种不同种类的载流子产生的。     

分析化学课程思政建设的举措

为全面推进课程思政建设,实施教学改革势在必行。本文基于分析化学学科特点以及课程培养目标,从提高教师思政教育能力、构建课程思政体系、深挖分析化学课程思政元素、优化教学评价四个方面出发,提出了全面推进分析化学课程思政建设的一些举措,以促进课程思政有效融入课堂。将思政教育与专业知识进行融合,有利于学生在掌握分析化学理论知识和操作技能的同时,培养以爱国主义为核心的民族精神和以改革创新为核心的时代精神,树立唯物主义的辩证思维、严谨认真和求真务实的科学态度、科学发展观等,形成广泛的课程思政理念共识并深入人心,从而实现教书与育人、立德与树人的有机统一。     

Dependence of the cross sections for Ir isotopes on the values of Qgg in the heavy ion collision

¹⁹⁷Au were irradiated with 47 MeV/u ¹²C ions. Iridium was produced via the multinucleon transfer reactions in bombardments of ¹⁹⁷Au with ¹²C. and was separated radiochemically from Au and the mixture of the reaction products. The γ radioactivities of Ir isotopes were measured by using a HPGe detector. The production cross sections of Ir isotopes were determined from activities of Ir isotopes at the end of bombardment and the other relative data. It has been found that the cross sections for neutron-rich isotopes of iridium show an exponential dependence on the values of Q_gg. Our experimental results also demonstrate lack of correlation between the cross sections and Q_gg in the case of neutron-deficient isotopes of iridium. The fact can be explained from that neutron-rich isotopes of iridium were produced in the deep inelastic transfer reactions.     

Modulation of absorption manner in helicon discharges by changing profile of low axial magnetic field

The modulation of absorption manner in helicon discharge by changing the profile of low axial magnetic field is explored experimentally in this work. The experiments are carried out in Boswell-type antenna driven by 13.56-MHz power source in 0.35-Pa argon environment. The peak of the external non-uniform magnetic field(B_(ex)) along the axis is observed in a range from 0 Gs to 250 Gs(1 Gs = 10~(-4) T), where the electron density varies from 0.5×10~(16) m~(-3) to 9×10~(16) m~(-3).When Bex is located near the tube upper end sealed by a dielectric plate, or near the tube bottom end connected with a diffusion chamber, the plasmas are centralized in the tube in the former case while the strong luminance appears between the edge of the tube and the axial line in the latter case. When Bex is located in the middle of the antenna, moreover, an effective resistance(R_(eff)) peak appears apparently with increasing magnetic field. The glow moves toward first the edge of the tube and then the two antenna legs as the magnetic field increases. The discharge in this case is caused by the absorption of Trivelpiece–Gould(TG) wave. It is suggested that B_(ex) is located in the middle of the antenna to obtain a higher efficiency of power transfer.     

考虑线损电量优化分布的配电网线路最优组合模型

为了解决高耗能、低功率因数等负荷情况下传统降损措施难以满足线损率要求的问题,实现基于网络的线损管理方法,提出了一种配电网线路最优组合模型。阐述了线损电量优化分布方法在线损管理工作中的应用场景及解决的问题,并根据场景及应用需求,构建了线路最优组合模型。针对核心模块提出线路最优组合算法,以组合后线损率满足考核要求的线路数量最大化为目标,以线损率考核标准为约束条件,利用建模工具进行求解。算例结果表明:该模型能够有效确定配电网高损负荷的转移方向,为后续的网络重构、网络规划等工作提供可靠的依据。     

狭缝型微空心阴极维持放电等离子体

为在高气压条件下获得稳定、大体积的放电等离子体,实验研究了氩气中的狭缝型微空心阴极放电(SMHCD)特性. 设计了包括SMHCD的三电极放电系统,并利用SMHCD作为预电离源(等离子体阴极),在不同放电条件下测试了该系统的放电特性并讨论了其放电模式. 结果表明,SMHCD具有微空心阴极放电的特性,在适当条件下可以形成稳定的辉光放电. 利用SMHCD离子源可以获得大体积、高气压的狭缝型微空心阴极维持放电(SMSD)等离子体. SMSD具有普通直流辉光放电的特性,且SMHCD本身的放电电流以及第三电极处所加的电压对SMSD的形成有十分重要的作用. 该系统可以产生大面积均匀等离子体.     

水热法合成硼酸钙的场发射扫描电镜分析

以工业硼酸、硼砂和氧化钙为原料,通过改变反应温度和原料配比,用水热法合成了系列硼钙化合物.根据化学分析和XRD分析数据确定了各种合成产物的化学组成、物相名称,用场发射扫描电镜(FE-SEM)对六种硼酸钙的显微形貌、颗粒大小进行了表征,发现它们的显微形貌、颗粒大小有很大的不同.CaO·3B2O3·5H2O呈条板状,厚度在100～300 nm之间;2CaO·5B2O3·5H2O呈大纳米薄片,厚度在50～100 am的居多;2CaO·3B2O3·H2O则是纳米细线,直径在100 nm左右;4CaO·5B2O3·7H2O呈小纳米薄片状,厚度在100 nm左右;2CaO·B2O3·H2O呈球粒状,大小在500 am～1μm;CaO·B2O3呈粗针状,粗、细端直径在150～300 nm之间.     

长效抗剪切聚合物驱油剂的合成及性能

为了提升驱油用聚合物在苛刻油藏环境中的耐温与抗盐性,设计合成了一种以多元胺-丙烯酸甲酯为聚合前体,具有超支化结构的聚酰胺-胺类单体,并在此基础上合成了一种长效抗剪切聚合物(LSRP)。考查了聚合单体浓度、引发温度、聚合时间、引发剂组成和加量及水解度等因素对LSRP溶液黏度的影响,采用FTIR和1HNMR表征了单体及聚合物结构,对聚合物增黏、抗剪切、抗盐、注入性及驱油性能进行了评价。结果表明:聚合物LSRP具有较好的增黏能力、抗剪切性和稳定性,当原油黏度70～300 m Pa·s时,室内驱油实验采收率较水驱增加20%以上,矿场试验注入后期压力平稳上升。     

西安地区湿地资源研究

目的为了解西安湿地资源现状和湿地环境的变迁,保护和开发利用湿地资源及湿地在西安生态环境与经济社会发展中的地位和作用.方法经过对遥感资料的分析,并结合现场测量和人工调绘,系统分析研究西安湿地资源的类型、分布、面积、功能等基本状况.结果首次对西安湿地进行了分类,查明西安地区湿地面积为900.96 km2,占全市总面积的8.9%,其中天然湿地面积为822.05 km2,占湿地总面积的91.24%,人工湿地面积为78.91 km2,占湿地总面积的8.76%.结论天然湿地面积每年以0.83%速度减少,天然湿地面积呈下降趋势,人工湿地面积变化呈上升趋势,湿地资源在逐年减少.湿地的生态功能正在衰退,湿地生态环境的恶化,影响到地区环境变化.