F同位素的反应总截面测量和17F可能的质子皮结构

应用透射法对中能区F同位素与C靶的反应总截面进行了测量。发现^17F的反应总截面比其邻近同位素的反应总截面稍有增强。用Glauber模型和BUU模型对F同位素进行了差异因子d的分析。^17F的差异因子d比共附近同位素稍有增强。分析结果表明^17F可能存在质子皮结构。     

弱束缚核17F弹性散射角分散

在兰州放射性束流线(RIBLL)上完成了¹⁷O/¹⁷F+²⁰⁸Pb的弹性散射微分截面角分布测量. 分析了¹⁷O/¹⁷F弹性散射产物的角分散, 即微分截面的对数ln(dσdθ)随散射角平方θ²的依赖关系. 结果表明, 在所测量的角度范围内(6°—20°), ¹⁷O的这一依赖关系可以用一条直线很好地拟合, 而¹⁷F的这一依赖关系需要两条不同斜率的直线才能拟合. ¹⁷F数据拟合中的这种斜率改变可能 起因于¹⁷F的奇异结构. 对其他实验组数据的分析支持以上的结论, 即在一定的角度范围内, 弱束缚核与稳定核相比, 弹性散射产物的微分截面与散射角平方的依赖关系有明显的差异, 这可以作为深入研究"晕/皮核"的一个新探针.     

小角度范围内弱束缚核17F弹性散射微分截面的奇异行为

在兰州放射性束流线(RIBLL)上完成了¹⁷F/¹⁷O+²⁰⁸Pb的弹性散射微分截面角分布测量. 分析了¹⁷F/¹⁷O弹性散射产物微分截面的对数(ln(dσ/dθ))随散射角平方(θ²)的依赖关系. 结果表明, 在所测量的角度范围内(6°—20°), ¹⁷O的这一依赖关系可以用一条直线很好地拟合, 而¹⁷F的这一依赖关系需要两条不同斜率的直线才能拟合. ¹⁷F数据拟合中的这种斜率改变可能起因于¹⁷F的奇异结构. 对其他实验组数据的分析支持以上的结论, 即在一定的角度范围内, 弱束缚核与稳定核相比, 弹性散射产物微分截面的对数与散射角平方的依赖关系有明显的差异, 这可以作为深入研究“晕核”和“皮核”的一个新探针.     

中子与116,118,120,122,124Sn反应非弹性散射的理论计算和分析

应用现有的中子与原子核Sn及其同位素反应的总截面,去弹性散射截面,弹性散射截面和弹性散射角分布的实验数据,获得一组普适的中子与Sn及其同位素反应的光学模型势参数.利用这组光学模型势参数,扭曲波玻恩近似理论,核反应Hauser-Feshbach理论和预平衡反应的激子模型,计算和分析了中子与^{116,118,120,122,124}Sn反应分离能级的非弹性散射截面和角分布.理论计算与实验数据进行了分析比较.     

17C反应截面和去中子截面

利用日本理化学研究所的放射性束流线RIPS, 测量了能量为79A MeV的¹⁷C在¹²C反应靶上的反应截面, 并同时得到了¹⁷C的移去1个、2个及3个中子的截面; 分别利用有限力程Glauber模型和少体Glauber模型结合壳模型的谱因子分析了反应截面和移去1个中子截面, 研究了¹⁷C的密度分布、结构和价中子布居. 反应截面和中子移去截面是两个相互独立的量, 通过对两者的分析, 都可以得出¹⁷C由芯核¹⁶C和价中子组成, 并且价中子主要处于d_5/2轨道的结论. 总结了现有的碳同位素的反应截面和相互作用截面的工作.     

中能中子与208Pb反应的理论计算和分析

在中子与原子核Pb及其同位素反应的总截面,去弹性散射截面,弹性散射截面和弹性散射角分布的实验数据基础上,获得了入射中子能量从1—300MeV的一组普适中子与Pb及其同位素反应的光学模型势参数.应用光学模型,扭曲波玻恩近似理论,宽度涨落修正的Hauser-Feshbach理论,预平衡反应的激子模型和核内级联模型,计算和分析了中子与²⁴⁸Pb反应的所有截面、角分布和能谱.理论计算与实验数据进行了分析比较     

中子与52Cr反应截面的理论分析

根据中子与天然核Cr及其同位素反应的总截面,去弹性散射截面和弹性散射角分布的实验数据,获得了入射中子能量从1MeV—250MeV的一组普适中子与Cr及其同位素反应的光学模型势参数.应用光学模型,扭曲波玻恩近似理论,宽度涨落修正的Hauser-Feshbach理论,和预平衡反应的激子模型,计算和分析了中子与⁵²Cr反应的所有截面、角分布、能谱和双微分截面.理论计算与实验数据进行了分析比较.     

40,48Ca+90,96Zr融合反应的动力学模型研究

应用改进的量子分子动力学模型,在严格挑选初始核考虑弹靶结构效应的基础上,研究了近垒和垒上融合反应^40,48Ca+^90,96Zr. 研究表明: 4个反应的理论计算截面与实验值很好符合; 丰中子反应⁴⁰Ca+⁹⁶Zr的垒下融合截面比其他3个反应有明显增强的现象.为了理解丰中子反应⁴⁰Ca+⁹⁶Zr与⁴⁰Ca+⁹⁰Zr相比垒下融合截面增强,而Ca+⁹⁶Zr垒下融合截面没有明显增强的原因, 进一步分析了484个反应的融合位垒,中子转移与融合位垒的关系、中子转移与Q值的关系,结果表明: 正反应Q值会引起核子(特别是中子)转移的增强,从而导致动力学融合位垒的下降和垒下融合截面增强.     

80MeV/u 20Ne轰击9Be碎裂产物反应总截面的测量

介绍了用透射法测量中能区²⁰Ne打⁹Be靶碎裂产生的次级束与Si靶作用的核反应总截面的方法,以及实验的探测器布局、实验过程和实验结果.并对理论上预言有奇异结构的核¹²N,¹⁷Ne和¹⁷F的实验结果与其相邻核进行了比较.     

中子与裂变核238U反应双微分截面的理论分析

根据中子与原子核U及其同位素反应的总截面,去弹性散射截面和弹性散射角分布的实验数据,获得了入射中子能量0.1—20MeV的一组普适中子与U及其同位素反应的光学模型势参数.应用光学模型,核裂变理论,耦合道理论,扭曲波玻恩近似理论,宽度涨落修正的Hauser-Feshbach理论和预平衡反应的激子模型,计算和分析了中子与²³⁸U反应的所有截面、角分布、能谱和双微分截面.理论计算与实验数据进行了分析比较     

Requirements for Optical Systems for Virtual Displays

Currently, there are many types of virtual displays and new types arise every year. However, their vast majority appear technically inapplicable because they are inconsistent with a number of key factors related to the eye physiology. In this paper, we present the general requirements for optical systems of virtual displays, taking into account human eye physiology.     

溶剂化的热力学集团展开理论

把二元溶液的过剩内能（ｅｘｃｅｓｓ ｅｎｅｒｇｙ）分成溶剂－溶剂、溶剂－溶质及溶质－溶质相互作用部分。利用集团展开方法给出了二元溶液在正则系综的配分函数的表达式,利用该表达式得到了溶质的偏摩尔内能（ｐａｒｔｉａｌ ｍｏｌａｒ ｅｎｅｒｇｙ）和偏摩尔熵（ｐａｒｔｉａｌ ｍｏｌａｒ ｅｎｔｒｏｐｙ）的表达式。在无限稀溶液情形,过剩偏摩尔内能的溶剂－溶剂部分又称重组织内能（ｒｅｏｒｇａｎｉｚａｔｉｏｎ ｅｎｅｒｇｙ）,它反映了溶质存在时对其周围溶剂分子之间的相互作用能的影响。研究表明,在溶质的粒子数密度相对较大时,溶质分子之间的相互作用将影响过过剩偏摩尔内能的溶剂－溶剂部分,对于稀溶液,过氧偏摩尔内能的溶剂－溶剂部分与溶质的摩尔分数成线性关系。对低蜜度二元溶液,溶质的过剩偏摩尔内能和过剩偏摩尔熵也与溶质的摩尔分数成线     

内窥镜校正中棋盘格标志点自动提取方法

为了解决具有大畸变内窥镜标定的标志点提取困难和人工参与较多等问题,提出了一种简单快速准确的棋盘格标志点提取方法。该方法是采用粗提取和优化来完成棋盘格标志点的提取的:首先利用高斯滤波去除图像噪声,并计算两次图像的梯度特征,利用梯度极值约束得到粗提取的角点;然后利用棋盘格标志点的对称特点消除噪声点的影响,并得到优化的角点位置。实验结果表明,该方法简单易行,计算量小,不需要人工干预即可获得全部标志点,反投影误差小于0.2pixel。     

Figure of merit for spectrometers for EDXRF

How should one select the best detector for a particular measurement in energy dispersive X‐ray fluorescence (EDXRF)? How should one select the optimum system configuration, i.e. the best shaping time and beam current? Manufacturers provide a variety of specifications, such as energy resolution and maximum count rate, but these are indirectly related to the end use of an EDXRF instrument, the measurement and detection limit of the measured elemental concentrations. We suggest in this paper using the time required to achieve a given statistical uncertainty as a figure of merit. We derive scaling rules for this figure of merit based on conventional specifications, including energy resolution, peaking time, maximum count rate, detector area, and intrinsic efficiency. These scaling rules also include the peak to background ratio of a photopeak and the number of overlapping peaks. We then show how this figure of merit can be used to select the optimum detector and spectrometer configuration for specific applications and compare the results to data obtained with typical systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Memory for pitch versus memory for loudness

The decays of pitch traces and loudness traces in short-term auditory memory were compared in forced-choice discrimination experiments. The two stimuli presented on each trial were separated by a variable delay (D); they consisted of pure tones, series of resolved harmonics, or series of unresolved harmonics mixed with lowpass noise. A roving procedure was employed in order to minimize the influence of context coding. During an initial phase of each experiment, frequency and intensity discrimination thresholds [P(C) = 0.80] were measured with an adaptive staircase method while D was fixed at 0.5 s. The corresponding physical differences (in cents or dB) were then constantly presented at four values of D: 0.5, 2, 5, and 10 s. In the case of intensity discrimination, performance (d') markedly decreased when D increased from 0.5 to 2 s, but was not further reduced when D was longer. In the case of frequency discrimination, the decline of performance as a function of D was significantly less abrupt. This divergence suggests that pitch and loudness are processed in separate modules of auditory memory.     

Convolution identities for quasiprobabilities for Bose functions

We present identities relating the equations of motion of various quasiprobabilities for quantum oscillators. These identities turn out useful for checking the consistency of approximations made in constructing the equations of motion with the basic Bose commutator. Moreover, our identities allow to identify the quasiprobability distributions which have the easiest-to-solve equations of motion.     

Microscopic basis for Fick's law for self-diffusion

We investigate self-diffusion in a classical fluid composed of two species which are distinguished through the color of their particles, either black or white, but are identical as regards their mechanical properties. Disregarding color the fluid is in thermal equilibrium. We show that if a single test particle in the one-component fluid moves asymptotically as Brownian motion, then the color density and current in certain classes of nonequilibrium states are related, on the appropriate macroscopic scale, through Fick's law, and the former is governed by the diffusion equation. If in addition several test particles move asymptotically as independent Brownian motions, then the colored fluid is, on a macroscopic scale, in local equilibrium with parameters governed by the solution of the diffusion equation.Part of this work was done while both authors were at IHES, Bures-sur-Yvette, France.Supported in part by NSF Grant No. PHY 78-15920-02.Supported by a Heisenberg fellowship of the Deutsche Forschungsgemeinschaft.     

Formula for the absorption coefficient for multi-wall nanotubes

We present a formalism for calculating the absorption coefficient of a pair of coaxial tubules. A spatially nonlocal, dynamical self-consistent field theory is obtained by calculating the electrostatic potential produced by the charge density fluctuations as well as the external electric field. There are peaks in the absorption spectrum arising from plasma excitations corresponding either to plasmon or particle-hole modes. In this Letter, we numerically calculate the plasmon contribution to the absorption spectrum when an external electric field is applied. The number of peaks depends on the radius of the inner as well as outer tubule. The height of each peak is determined by the plasmon wavelength and energy. For a chosen wave number, the most energetic plasmon has the highest peak corresponding to the largest oscillator strength of the excited modes. Some of the low-frequency plasmon modes have such weak coupling to an external electric field that they are not seen on the same scale as the modes with larger energy of excitation. We plot the peak positions of the plasmon excitations for a pair of coaxial tubules. The coupled modes on the two tubules are split by the Coulomb interaction. The energies of the two highest plasmon branches increase with the radius of the outer tubule. On the contrary, the lowest modes decrease in energy as this radius is increased. No effects due to inter-tubule hopping are included in these calculations.