冷原子系综中偏振关联光子对的产生和测量

我们在~(87)Rb冷原子系综中进行了关联光子对的产生和测量。通过自发拉曼散射过程,产生了一个Stokes光子和一个原子自旋波激发。利用电磁感应透明效应将存储在原子系综中的自旋波转化为一个anti-Stokes光子。在两相互正交的偏振基下,测量了Stokes光子和anti-Stokes光子之间的交叉关联函数。实验结果表明,交叉关联函数g~(2)达到~75,表现了强的非经典关联。基于现场可编程门阵列(FPGA)的自编程的多通道符合器被用于光子脉冲信号的采集和逻辑处理,大大提高了偏振关联光子对的产生和测量速度,为以后量子中继技术中的高效信息处理提供了重要基础。     

拓扑空间(组)的同伦等价变换及有序介质状态的拓扑分类

凝聚态和相变物理的一个重要部分是研究有序相的状态和缺陷,近二十年来,应用代数拓扑学方法对有序介质的状态和缺陷进行分类,增进了人们对相变等过程的认识,从而引起广泛的注意,虽然从本质上说,缺陷拓扑分类也可纳入状态拓扑分类的框架,国际上迄今的有关研究却主要针对缺陷;除织构(孤子)态外,对一般状态甚少涉及,本文试图     

INTERLAYER EXCHANGE COUPLING IN COMPLEX MAGNETIC MULTILAYERS

We extend the hole confinement model of Edwards et al. to the problem of two kinds of complex magnetic sandwich structures. One is the magnetic sandwich covered on both sides by nonmagnetic films(case 1) and the other is that covered by magnetic films(case 2). The interlayer exchange coupling and the angular dependence of coupling energy in the two cases are investigated systematically. For case 1, our results show that the magnetic and outer nonmagnetic films influence significantly the oscillation behavior of exchange coupling and the appearance of noncollinear exchange coupling is very sensitive to the thickness of magnetic and outer nonmagnetic layers. Our results also show that the nonoscillatory component of the coupling generally varies with the thickness of magnetic(outer nonmagnetic) films and the results in the case where the thickness of both magnetic(outer nonmagnetic) films vary simultaneously are significantly different from that in the case where the thickness of one of the two magnetic(outer nonmagnetic) films is fixed while the other is varied, which is qualitatively in agreement with the experimental measurements. For case 2, the exponential dependence of exchange coupling on the thickness of the intermagnetic layer has been obtained, similar to the Parkin's experimental results for giant magnetoresistance.     

反磁化形核行为的微磁学研究

本文指出,在对称情况下,微磁学中的反磁化形核问题是一个典型的分歧问题。利用对分歧问题的研究结果,在详细分析Brown方程分歧解的稳定性之后,得到的结论是:形核场是Brown方程的最大分歧点,Brown,Frei,Aharoni和Shtrikman等人用线性化方法获得的结果,包含在本文的笫一级微扰近似的结果中。不局限于线性化近似,文中还得到了形核场近旁的反磁化行为,它们或者连续地沿分歧解进行,或者是一个不连续跃变;同时,还给出了连续和不连续形核的判据。     

气垫船稳态船波势及波阻的边界元法

本文给出了气垫船在静水中航行时稳态船波势问题的边界元数值分析方法，根据本文的数值计算方法，可以得到气垫船行时所兴起的波浪形状以及气垫附近流场情况，由此可计算气垫所受到的兴波阻力，本文的方法适用于任意已知气压分布情况。     

Tunneling magnetoresistance of the double spin-filter junctions at nonzero bias

A recent theoretical estimation indicated that the NM/FI/FI/NM double spin-filter junction (DSFJ, here the NM and FI represent the nonmagnetic electrode and the ferromagnetic insulator (semiconductor) spacer, respectively) could have very high tunneling magnetoresistance (TMR) at zero bias. To meet the requirement in research and application of the magnetoresistance devices, we have calculated the dependences of tunneling magnetoresistance of DSFJ on the bias (voltage), the thicknesses of ferromagnetic insulators (semiconductors) and the average barrier height. Our results show that except its very high value, the TMR of DSFJ does not decrease monotonously and rapidly with rising bias, but increase slowly at first and decrease then after having reached a maximum value. This feature is in distinct contrast to the ordinary magnetic tunnel junction FM/NI/FM (FM and NI denote the ferromagnetic electrode and the nonmagnetic insulator (semiconductor) spacer, respectively), and is of benefit to the use of DSFJ as a magnetoresistance device.     

反复上呼吸道感染患儿发样微量元素锌,铜,铁检测结果分析

采用示波极谱法对１８３名反复上呼吸道感染患儿及１１８名健康体检儿同时进行发样锌，铁，铜测定，结果表明，反复上呼吸道感染儿发锌，铁均低于健康体检儿，有高度显著性差异，铜只在婴儿组反复感儿高于健康体检儿，其它各年龄组反复上感儿低于健康栓检儿或无显著性差异，说明以２儿童进行常规发样微量元素普查，发现低锌，低铁者及时给予补充，可减少感染性疾病的发生率。铜与免疫功能的关系尚待研究。     

微米晶单斜氧化锆高压相变制备亚微米四方多晶氧化锆

高压相变已逐渐发展成为一种制备纳米/亚微米多晶陶瓷块体材料的有效方法。高压可以抑制原子的长程扩散进而抑制晶粒长大,高压下截获的新相不受初始材料晶粒尺寸的制约,通过热力学调控可以得到晶粒尺寸更小的多晶块体材料。陶瓷材料在特定热力学条件下通常会发生相变,新相的形成要经历形核、生长的过程。采用晶粒尺寸为2μm的单斜ZrO2与晶粒尺寸为50 nm的Y2O3以97:3的摩尔比混合,在5.5 GPa、800～1700℃温压区间内对初始材料进行烧结,采用X射线衍射、扫描电镜、透射电镜对所得样品进行表征。研究结果表明:高压下截获了单斜相和亚微米四方相复合的多晶ZrO2块体材料,1200、1400、1600和1700℃温度下获得的四方相的平均晶粒尺寸为(145±62) nm、(246±165) nm、(183±62) nm和(245±107) nm。利用高压相变以微米晶制备细晶粒多晶块体材料,可以避免常规方法中以纳米粉末为初始材料制备细晶粒多晶块体材料存在的团聚、吸附及晶粒长大的问题,进而发展一种以微米晶为初始材料通过高压相变制备高性能细晶粒多晶块体材料的方法。     

硅探测器的数字化脉冲形状甄别

介绍了利用硅探测器的脉冲形状甄别进行粒子鉴别的原理。详细叙述了基于数字化方法的脉冲形状甄别的实现。采样频率和位数是数字化方法的两个重要参数。对于硅探测器信号,采用100 MS/s,12 bit的Digitizer可以满足脉冲形状甄别法对时间分辨的要求。同时对该方法粒子鉴别的特征和能量阈值做了简要的分析和对比。粒子背面入射硅探测器的所得的阈值低于正面入射的情况。例如对于氖周围的同位素,背面入射情况的阈值约为100 MeV,为正面入射情况下鉴别阈值的二分之一,相当与ΔE-E方法中ΔE探测器厚度约为60 μm情况下的阈值。最后定性讨论了硅探测器的电阻率不均匀性和沟道效应对粒子鉴别性能的影响。In this paper Pulse Shape Discrimination(PSD) for silicon detector has been briefly introduced. The emerging digital method successfully applied to detector signal processing makes digital PSD method one of the most promising particle identification methods. Sampling frequency and the number of bits are two key parameters of digital method. For silicon detector signal, adopting 100 Ms/s, 12 bit Digitizer can satisfy the time resolution requirement of PSD method. The identification characteristic and energy threshold of this method have been discussed and compared with both front injection and rear injection cases. Energy threshold with rear injection usually is much lower than that with front injection. For example, around for Neon isotope energy threshold with rear injection is about 100 MeV which is only half of the threshold with front injection, also equivalent to thickness of about 60 μm silicon detector threshold in ΔE-E method. At the end the impact of silicon detector's resistivity nonuniformity and channel effect on the identification capacity of PSD method has been discussed in detail.     

20Mgβ衰变谱学与15O(α,γ)19Ne反应(英文)

15O（α,γ）19Ne（p,γ）20Na反应链是高温CNO循环向快速质子俘获过程突破的一条关键路径,相关的反应率输入量可通过20Mg的β衰变可布居19Ne共振态并测量其衰变性质来获得。通过高效率高精度地测量20Mg β衰变中产生的质子与γ射线得到了20Mg衰变的详细信息,并构建了完整的衰变纲图,还进行了19Ne 4 033 keV共振态衰变性质的探索,获得了该态在20Mg β衰变中被布居的分支比上限。通过比20Mg和20O镜像能级跃迁的结果确认了同位旋非对称性,为检验相关理论模型提供了精确的实验数据。对于突破路径中有重要影响的19Ne 4 033 keV共振态的性质,有待更高统计的实验进一步研究。The breakout from the hot CNO cycle to the rapid proton capture process can occur via the 15O(α,γ)19Ne(p,γ)20Na reaction sequence, and the β decay of 20Mg can be used as an alternative method to characterize some specific resonances, which will provide detailed nuclear structure input for reaction rate calculations. The reliable information on the decay properties and structure of 20Mg was obtained by measuring the emitted particles and γ-rays in the β decay with high efficiency and high resolution. Attempt was also made to search for the decay channels associated with the 4 033 keV resonance in 19Ne. To test fundamental symmetries, the transitions in the mirror decays of 20Mg and 20O were compared. The precise experimental data presented here would be important to constrain the theoretical calculations. It is desirable to clarify the astrophysically relevant problem by further experiments with improved statistics on the basis of the present work.