23Al的β+延发质子测量

利用ＴＯＦ－ Ｅ和０°注入探测器的方法,鉴别并测量了２３Ａｌβ＋延发质子衰变能谱,通过精密脉冲发生器和计数器测得２３Ａｌ的半衰期 Ｔ１／２＝（４７６±４５）ｍｓ．实验中重现了能量为０．２１６,０．２７８,０．４３８,０．４７９ＭｅＶ的低能衰变质子．另外,还观察到了一个新的β＋延发衰变能级 Ｅｘ＝ ８．９１６ＭｅＶ,并给出了它们的相对强度．     

CORRECTIONS TO THE COLLISION TERM IN THE BGK BOLTZMANN EQUATION

With the discrete method of the hexagonal cell and three different velocities of particle population in each cell, a two-dimensional lattice Boltzmann model is developed in this paper.^[1,2] The collision operator in the Boltzmann equation is expanded to fourth order using the Taylor expansion.^[3,4] With this model, good results have been obtained from the numerical simulation of the reflection phenomenon of the shock wave on the surface of an obstacle, and the numerical stability is also good. Thus the applicability of the D2Q 19 model is verified.     

35MeV/u 40Ar+197Au反应中复合核的激发能与温度

利用大面积位置灵敏气体探测器对35MeV/u ⁴⁰Ar+¹⁹⁷Au反应中形成的裂片进行了符合测量,由此得到了裂变复合核的速度分布.在大质量转移假设下扣除前平衡发射粒子的影响,得到复合核的激发能.另外利用望远镜探测器对反应中出射的轻带电粒子也进行了符合测量,并由后角α,p,d,t的能谱提取了复合核的温度.温度与激发能的关系没有表现出理论预言的相变特征.     

Ultrasound wave propagation in glass-bead packing under isotropic compression and uniaxial shear

The axial-stress dependence of sound wave velocity in granular packing is experimentally investigated with tri-axial and uni-axial devices. Preparing samples by repetitive loadings and unloadings in a range of 20 kPa–1000 kPa, we find that the axial-stress dependence of sound wave velocity approaches the Hertz scaling with an exponent of 1/6 for large axial stresses( 400 kPa). Weak deviation from the Hertz scaling is seen at low stresses. Repetitive axial loadings slightly reduce this deviation, and sound velocities increase nonlinearly approaching some saturated values. Velocities for uni-axial case are found slightly to be bigger than those for tri-axial isotropic compression case. These effects are discussed in the frameworks of granular solid hydrodynamics(GSH) and effective medium theory(EMT), which indicate that they cannot be explained with density nor Janssen ratio only. Dissipation occurring during wave propagation may be a non-negligible factor.     

有机磷农药甲基对硫磷的太赫兹(THz)光谱研究

运用太赫兹时域光谱技术(THz-TDS)与理论模拟相结合的方法研究了有机磷农药甲基对硫磷在THz波段的光谱特性。在室温氮气环境中得到了样品在0.2～2.0 THz波段的吸收谱和折射率谱。表明其特征吸收峰分别位于0.65,1.33,1.81和1.91 THz处,其平均折射率为1.39。同时运用密度泛函理论(DFT)计算了甲基对硫磷分子的结构及其在太赫兹波段的振动频率,计算结果与实验数据吻合较好。研究结果表明,实验光谱的特征吸收峰是由分子的集体振动及扭转形成,不同的吸收峰位对应分子不同的振转模式。     

三聚氰胺结石与疑似三聚氰胺结石的红外光谱分析

本文通过对三聚氰胺、尿酸、三聚氰胺结石和疑似三聚氰胺结石的红外光谱分析, 根据它们的特征峰位、峰形的特点和三聚氰胺、尿酸、草酸钙的标准红外光谱比较, 推出三聚氰胺结石由尿酸、尿酸胺、草酸钙和三聚氰胺形成的混合性结石。疑似三聚氰胺结石是草酸钙结石。因此, 红外光谱法可作为一种辅助手段, 为医学诊断提供理论依据。     

Charge Densities of Unstable Nuclei with Electron Scattering

Relativistic mean-field theory and phase-shift analysis are combined together to investigate the elastic Coulomb scattering between electrons and unstable nuclei. Electron scattering at several different energies is studied and compared, in order to see the energy dependence of electron-nucleus scattering. It is shown that electron scattering at 200 MeV or 300 MeV can be used to reveal electron-nucleus scattering information around the first diffraction minimum. Shifts in opposite directions are obtained for the first diffraction minima of the electron scattering off the ground and first excited states of ^17F with ^16O as reference, and similar effects are obtained for ^18Ne. Besides, some neutron-rich N = 8 isotones are also studied. Results show that electron scattering will be very useful and important in studying both proton- and neutron-rich nuclei in the future.     

Bipartite Entanglement Dynamics in Three Qubits System with Dzyaloshinskii-Moriya Interaction

We investigate the bipartite entanglement dynamics of the system composed by three qubits A, B, and C. There is no interaction between A and B, and that of C and B is Dzyaloshinskii-Moriya （DM） spin-orbit interaction. We find that the purity of qubits A and B and the initial state of the qubit C are the two effective parameters to control the entanglement dynamics of the bipartite subsystems. This study sheds some lights on the control of quantum entanglement, which would be helpful for quantum information processing.     

三级自动复叠制冷中制冷剂配比计算方法研究

自动复叠制冷循环有其特殊的优点,但是混合制冷剂的配比选取仍需进一步研究。通过搭建一个三级自动复叠制冷循环实验台,并采用常规复叠制冷循环的方法,粗定制冷剂配比,再使用CSD方程微调,实验数据证明该方法的结果比较合理。     

丰中子奇异核17B的实验研究

在兰州重离子加速器国家实验室(HIRFL)放射性次级束流线(RIBLL)上,用束流透射法测量了丰中子奇异核¹⁷B与C靶反应的总截面.假定¹⁷B具有¹⁵B(核芯)＋2n结构,采用Gauss＋HO形式的密度分布和零力程Glauber模型进行计算的结果可以很好地拟合实验数据,并得出¹⁷B的密度分布有一个很大的弥散,表明¹⁷B是双中子晕核. 关键词： 丰中子奇异核 反应总截面 Glauber模型 密度分布