微型同轴脉管制冷机最低制冷温度影响因素的实验研究

本文对微型同轴脉管制冷机最低制冷温度的影响因素进行了实验研究。试验结果表明:在其他运行参数不变的情况下,随着氢浓度的逐渐减少,最低制冷温度也逐渐降低,当氢的摩尔浓度小于20％时,其最低制冷温度和纯氦相差不大。不同的氢氦配比下,该脉管制冷机的最佳运转频率为16.7 Hz。随着系统平均压力的提高,最低制冷温度也随之下降,但变化幅度越来越小。     

谱峰相对强度比法在碳炔含量测定中应用

碳炔材料是一种不溶不熔高聚物 ,红外谱图是最简易的一种分析测试工具。将 C—H键的振动峰面积与 C C键的振动峰面积相关联 ,用谱峰相对强度比法测定不同制备条件下产生的碳炔材料的相对含量。结果表明 ,两者比值对反应物浓度的变化具有相关性 ,可用作碳炔材料制备中实验条件的优选手段。     

STUDY OF OPTICAL PUMPING OF ALKALI ATOMIC BEAM IN STRONG MAGNETIC FIELDS

We have gained a very comprehensive set of results for infrared diffraction (10.6μm wavelength) from fabricated single grooves of reflection with widths in the range of 5μm to 65μm. The experimental results show that the diffraction can still occur when the groove width becomes comparable to or less than the wavelength of the probing light. Variations of the diffraction intensities have a very regular sinusoidal relationship with the polarization angle of the incident light; and the diffraction intensities are the when the incident light is TM polarized. However, the diffraction intensities will be a minimum when the incident light is TE polarized; and the biger the diffraction angle, the higher the rate of change of the diffractive intensity with increasing polarization angle of the incident light.     

镶嵌于基质中的金属超微粒子特性研究(Ⅰ)——超微粒子的量子阱点模型

提出超微粒子(UFP)的量子阱点模型。模型假定UFP的主要特性由其非定域电子(简称电子)决定,电子被束缚在三维有限深势阱内。电子的行为由二部分组成:单电子的和集体化的。电子能谱主要由单电子行为决定。模型反映了UFP的一些重要特性,例如块体材料逸出功,UFP原子半径和第一电离能,而忽略UFP更精细的结构。这种近似被证明是合理的。一系列有用的公式和预言被导出。(1)主要的UFP特性,量子尺寸效应和电子能谱的壳层结构。(2)UFP的逸出功和费密能级公式,这对于其他模型是困难的。导出的UFP逸出功随尺寸变化的公式 关键词：     

阴极荧光光谱有效收集效率的计算与测量（I）

从点光源均匀发光模型出发,重点导出了回转半椭球面镜的阴极荧光(Cathodoluminescence,简称CL)光谱有效收集效率η_λ~(eff)的计算公式,分析讨论了收集效率η_λ~(eff)与椭球参数e、收集角、Δφ出射角Δ(?)以及出射光束方位角θ_N的关系,给出了相应的理论计算和模拟实验结果.研究表明,理论计算与实验结果一致.     

无标样X射线定量分析最小二乘法方程的稳定解

无标样法是X射线定量分析的重要方法。无标样定量联立方程中经常出现的病态方程使定量结果出现很大的误差。最小二乘法方程组在某些组合情况下也会出现严重的病态方程。本文提出可以获得可靠的稳定解的无标样X射线定量最小二乘法。指出不同样品数及组合条件下获得稳定解的计算方法:直接最小二乘法、算术平均法、稳定性因子判别法。 关键词：     

双波长光学低相干干涉术用于血氧饱和度测量的数值分析

提出了采用双波长光学低相干干涉仪（Optical low coherence interferometer，OCI）来测量人体视网膜血管中血氧饱和度（Oxygen Saturation，SO2）的方法．详细阐述了双波长光学低相干干涉术用于血氧饱和度测量的基本原理，并分析了OCI中双波长的选择原则．基于内径为200μm的毛细玻璃管的简易人眼视网膜血管模型，分别模拟了光源中心波长为680nm和820nm时血液血氧饱和度由40％提高到60％时对应干涉信号的变化．数值分析表明，要判别20％的血氧饱和度变化，0CI系统灵敏度至少要达到70dB．     

PGNAA系统中D-T中子管的慢化装置优化设计

为了提高PGNAA系统中D-T中子管的中子慢化效率,获得更高的热中子产额,借助蒙特卡罗模拟,确定了以铅为中子反射层、5个聚乙烯层和铅层相互交替作为中子慢化层、碳化硼含量为3%的含硼聚乙烯作为中子吸收层以及铅作为γ屏蔽层的中子慢化装置模型。针对中子产额为3×107 n/s 的D-T中子管,该慢化装置输出面低于5 eV中子通量可达5.28×106 n/s,占总中子通量的30.8%,有效提高了中子慢化效率。经过验证模拟结果能够满足实验要求。To improve the moderating efficiency of D-T Neutron Generator in PGNAA system, and get higher thermal neutron yield, the Monte Carlo code MCNP was used to optimize the moderation setup. The lead was selected as neutron reflector and gamma absorber, 5 polyethylene layers and 4 lead layers constituted the neutron moderator and 3% boron-doping polyethylene was selected as neutron absorber. For the yield of 3107 n/s D-T Neutron Generator, this moderation setup can provide a yield of lower than 5 eV of 5.28106 n/s, accounting for 30.8% of total neutron yield, dramatically improves the moderating efficiency. It is proved that the simulation results can satisfy the requirement of PGNAA system by preliminary experimental verification.     

Contrast Adaptation Decreases Complexity in Retinal Ganglion Cell Spike Train

The difference in temporal structures of retinal ganglion cell spike trains between spontaneous activity and firing activity after contrast adaptation is investigated. The Lempel-Ziv complexity analysis reveals that the complexity of the neural spike train decreases after contrast adaptation. This implies that the behaviour of the neuron becomes ordered, which may carry relevant information about the external stimulus. Thus, during the neuron activity after contrast adaptation, external information could be encoded in forms of some certain patterns in the temporal structure of spike train that is significantly different, compared to that of the spike train during spontaneous activity, although the firing rates in spontaneous activity and firing activity after contrast adaptation are sometime similar.     

白灵菇多糖的提取及含量的测定

苯酚-硫酸分光光度法测定白灵菇中多糖含量。测定波长485nm,多糖换算因子f=1.59,在5.00—70.00μg/mL范围内吸光度与被测物含量呈良好的线性关系,相关系数r=0.9998,方法的回收率在96.66%—102.33%%之间,相对标准偏差RSD在2.01%—3.10%之间。测定结果表明,白灵菇中含有丰富的多糖。本法简便、准确、重现性好,可作为白灵菇多糖含量的测定方法。