模型图法在数学教学中的应用

新加坡学生在TIMSS中屡次表现突出.引起了不同国家教育工作者对新加坡数学教育的极大关注.问题解决一直是新加坡数学课程的核心,考虑到问题解决的重要作用,新加坡数学大纲建议,为中小学学生列出问题解决策略来帮助他们解决问题.在所有的策略中,模型图法是最为突出的策略.且看小学里的一个运用模型图法解应用题的例子.如图1,一把尺子和两支铅笔共需1.40元,一把尺子花费要比一支铅笔多20分,那么一把尺子花费     

Analysis of ultra-broadband high-energy optical parametric chirped pulse amplifier based on YCOB crystal

A new type of optical parametric chirped pulse amplifier is designed and analyzed for the amplification of pulse centered at 808 nm.A novel crystal,yttrium calcium oxyborate YCa4O(BO3)3(YCOB),is utilized in the power amplification stage of optical parametric amplification(OPA).Noncollinear phase matching parameters in the xoz principle plane of YCOB,compared with those in BBO and DKDP,are analyzed by numerical simulation.The results show that YCOB rather than DKDP can be used in the power amplification stage of OPA to realize the amplification of chirped pulse to several joules with a gain bandwidth exceeding 100 nm.This can be used to gain a high intensity pulse of ～10 fs after the compressor.     

聚氨酯橡胶超弹性本构模型拟合效果评估

对聚氨酯橡胶进行了单轴拉伸、单轴压缩和平面拉伸试验,采用常用的超弹性本构模型拟合试验数据,并基于拟合优度、拟合曲线与试验曲线相似性、相对偏差三方面,对拟合效果进行评估．结果表明：采用拟合优度评估,能从总体上反映超弹性本构模型对试验数据的拟合效果,采用拟合曲线与试验数据相似性的对比进行评估,能直观反映超弹性本构模型对试验数据的拟合效果,若同时考虑相对偏差,则可以反映超弹性本构模型与试验数据之间的相对偏差量,更为准确地对超弹性本构模型的拟合效果进行评估．     

一种基于新型插值单元的稳态传热边界元法

为了提高边界元法在求解稳态热问题时的计算精度,通过使用一种新型单元插值方法(称为扩展单元插值法),实现对稳态传热问题的求解。扩展单元是在传统不连续单元的边界配置虚拟节点,把原非连续单元变成高阶的连续单元,并将其作为新型的插值单元。利用虚拟节点和内部源节点构造出的插值函数,可以精确插值边界上的连续和不连续物理场,插值精度要比原始不连续单元高两阶。另外,边界积分方程只在传统的不连续单元的内部节点处建立,只包含内部源节点的自由度,而虚拟节点的自由度可通过与内部源节点之间的关系消除掉,因此最终系统方程的求解规模不会增加。这种新型的插值单元继承了传统连续和不连续单元的优点,克服了它们的缺点。数值结果表明,此种单元插值方法用于求解稳态传热问题时可获得较高的计算精度和收敛性。     

成也萧何,败也萧何？——高管金融经历与公司债券融资

基于印记理论和高层梯队理论,本文以2008至2018年发行公司债券的上市公司为研究对象,考察高管金融经历对公司债券融资的影响机理。结果表明:首先,高管金融经历在提高公司债券发行成功率的同时也会增加债券融资成本和违约风险,而对发债规模与期限并不会产生显著影响,在控制可能的内生性问题后结论依然成立;其次,具有金融经历的高管所任职公司会通过盈余管理来提高债券发行成功率,但也会增加债券的融资成本和违约风险;最后,具有证券公司或商业银行工作经历的高管对公司债券融资的影响更为显著。本文有助于实务界和理论界理解高管异质性特征对公司债券融资的影响机制,为监管部门制定防范金融风险的政策提供可靠的理论依据。     

A Novel Method for PIT Effects Based on Plasmonic Decoupling

A tunable dual-band stop-band THz spectrum can be realized in a hybrid structure, which consists of metal nanoribbon arrays clad by graphene nanoribbons. Dual-band spectra can be controlled separately by the nanoribbon width ω and graphene chemical potential μ_c. We explain that two local plasmonic modes excited at graphene ribbons belong to different gratings, which uncouple with each other by electro-magnetic shielding of the metal ribbons. Furthermore, plasmonic induced transparent(PIT) effects can also be realized by making the two transmission notches close to each other, with better performance than the PIT system based on plasmonic coupling,such as with a larger extinction radio and a tunable transparency window.     

中国极化电子离子对撞机探测器设计

核子是构成宇宙可见物质的最主要成分，也是研究强相互作用的最佳实验室。对核子内部结构的研究是当前理论和实验研究的重要前沿。在核子内部结构的实验研究中，电子- 离子对撞机(Electron Ion Collider, EIC)是最理想的装置，能提供核子内部最清晰的图像，是人类认识物质世界深层次结构，特别是核子与原子核结构最理想的工具。中国极化电子离子对撞机EicC项目，设想在已开建的HIAF 高能离子束的基础上进行升级:将离子束流升级成15~20 GeV 的极化束流，建设3~5 GeV 高能极化电子束流，实现质心系能量为10~20 GeV双极化电子- 离子对撞，在海夸克能区对核子内部结构进行精细测量，并对质子质量、奇特强子态等诸多重要物理课题展开研究。在本文中，我们开发了EicC 快模拟软件，对探测器性能进行参数化模拟；通过物理模拟汇集EicC探测需求，利用探测器模拟软件进行优化并提出EicC 探测器谱仪的初步设计方案。该谱仪方案提供了接近全立体角的覆盖范围和大动量范围内的粒子鉴别能力，兼顾EicC项目丰富的物理课题。     

Spatial Characteristics of Thomson Scattering Spectra in Laser and Magnetic Fields

Spatial characteristics of Thomson scattering spectra are studied for an electron moving in the circularly polarized laser field in the presence of a strong uniform magnetic field. The results show that the angular distributions of the spectra with respect to the azimuthal and polar angles exhibit different symmetries, respectively, which depend on the fields and electron parameters sensitively and significantly. Moreover, for relatively large parameters such as high laser intensity, high magnetic resonance parameter as well as large initial momentum of electron, the two lobes in spectra tend to the laser-propagating direction so that the radiation can be collimated in the forward direction. Furthermore, an important finding is that by choosing the appropriate fields and initial momentum of electron, the high frequency part of the Thomson scattering spectra can reach the frequency range of soft x-ray,in which a high radiation power per solid angle as ～10~(11) a.u. can be obtained.     

水凝胶纳米颗粒对溶菌酶的亲和研究

采用沉淀聚合法,将不同配比的温敏性单体N-异丙基丙烯酰胺(NIPAm)、电负性单体丙烯酸(Aac)、疏水性单体N-叔丁基丙烯酰胺(t BAM)和交联剂N,N'-亚甲基双丙烯酰胺(Bis)共聚,得到一系列聚合物水凝胶纳米颗粒(NPs),改变表面活性剂的用量,得到不同粒径的NPs。通过扫描电镜和动态光散射对NPs形貌和粒径进行表征,并对NPs吸附溶菌酶进行动力学研究。实验结果表明,所得到的NPs呈圆球状、粒径均匀且分布窄。当优化单体比例为Aac 20%,t BAM 40%,NIPAm 38%,Bis 2%时,NPs吸附性能最佳;NPs粒径从386.20 nm减小至77.25 nm,其吸附性能逐渐增大。在优化的条件下制备的水凝胶纳米颗粒,对溶菌酶的吸附在5 min内可以达到平衡,吸附率可以达到68.7%,利用NPs温敏性可实现对溶菌酶的脱附,具有良好重复利用性。     

Synthesis and Crystal Structure of 4-(N,N-Diphenylamino)styrene- 4′-N-methylpyridinium Iodine

The title compound 4-(N,N-diphenylamino)styrene-4′-N-methylpyridinium iodine (abbreviated to PASMPI) was synthesized by a facile condensation reaction with a high yield. The red crystal including a molecule of CHCl3 was obtained by recrystallization in chloroform/ethanol. Its crystal structure was determined by a four-circle diffractometer. The crystal data: C26H23N2ICHCl3, Mr = 609.73, orthorhombic, space group Pbca, a = 15.422(5), b = 14.042(5), c = 24.693(5) , V = 5347(3) 3, Z = 8, Dc = 1.515 g/cm3, F(000) = 2432, μ(MoKa) = 0.057 mm-1, the final R = 0.0439 and wR = 0.0772. The results reveal that the molecule is a completely reverse system. The molecular rotation from non-coplanar to coplanar may play an important role in increasing the fluorescence intensity under the condition of staining DNA.