由58Fe 和209Bi 熔合后的相关衰变过程得到的109号元素的证据

本文报导了合成109号元素的实验。用能量为4.95,5.05和5.15MeV/u 的~(58)Fe 束轰击~(209)Bi 靶,研究了全熔合产物衰变模式的特性。总辐照剂量为7×10~(17)粒子。所用的实验方法是:用静电场速度过滤器在飞行过程中分离向前方向成峰的反应产物,经过飞行时间装置后注入到位置灵敏固态探测器中,测量其动能,估算出质量、入射的时间和位置。以所有的出射粒子的能量和时间来记录很有限的反应产物发生级联α粒子和(或)自发裂变的继发衰变。在5.15 MeV/u 时的一个特别的衰变过程是:在5ms 和22ms 先分别发射两个α粒子,最后,在13s 后发生自发裂变。第一个α粒子的动能为11.10±0.04MeV。对各种可能的解释进行了详细的分析,例如纯属偶然的信号相关,转移反应产物的衰变和从能量上看允许的余核蒸发等。最后表明质量数为266的109号元素的同位素、即全熔合后的单中子蒸发道、从统计的观点看是最好的指定。本文同时也讨论了合成新元素的前景。     

现代物理教学和多媒体技术

物理教学中,怎样把物理概念、规律传授给学生,并通过生动、活泼的课内外教学使学生领略物理世界的奇景异致,激起学习物理学的兴趣,是物理教师反复思考的问题．以往的教学手段主要是老师通过演示实验、模型,配合简单的作图进行讲授．近年来随着计算机技术的飞速发展,教师利用多媒体信息显示的多样性、过程的交互性、信息的存储性、网络化、智能化等进行教学,取得更佳的教学效果．     

多重表征——建构主义物理教学的新思路

编者按:本文引用了心理学界长期使用的"结构良好领域的知识和结构不良领域的知识"的知识分类观点,实际上就科学知识而言,心理学的那种分类和解释并不很恰当,可以"通过复制与同化而获取"的知识,不能说是结构良好的,只能说是简单的确定的,"概念比较复杂,理解一个概念要涉及灵活性和变化性"的知识是多元的,开放的知识,不应该冠以"不良结构"的帽子,这一点也许正是心理学与自然科学,中、西方文化存在的差异的反映;但是我们认为对上述概念作科学的理解后,本文关于物理教学所讨论的问题仍然是有价值的.     

9-cell TESLA超导加速腔研制中Dumb-Bells的测量与调整

为了保证9-cell超导加速腔在场的平滑度、TM010的频率以及加速器的总长度达到TESLA国际标准,必须确保每个Dumb-Bell在以上各方面达到标准要求.由于冲压、机加工以及电子束焊接等过程会引起形变,因此,必须在完成iris和加强筋的电子束焊接之后对Dumb-Bells进行微波和机械测量,并根据测量的结果对其腔形和长度等作必要的调整.北京大学已经建立了一套完整的测量和调整Dumb-Bells的装置,本文深入研究了Dumb-Bells的测量与调整的方法.     

家用空调风冷冷凝器的数值分析

对单排管的家用空调风冷冷凝器进行了CFD的数值模拟,并搭建了冷凝器的实验系统对3D模型的CFD模拟进行验证.比较结果表明;两者存在一个小偏差(<9%),但是两者的趋势完全一致.CFD计算可以得到一些实验无法得到的内部流动信息,有助于我们更好地理解冷凝器的机理.本文在实验的范围以外进行了"数值实验",冷凝器的其它结构不变,翅片的间距存在一个最优值,同样管间距也存在一个最优值,为设计新的冷凝器提供了合理、可靠的方向.     

光存储技术的原理、应用和发展方向

造纸术的发明使人们可以方便的记录信息,同时也使我国数千年的历史和众多优秀的传统文化得到了较为完整的保存.随着社会的不断进步、科技的高速发展,尤其是计算机和网络技术日新月异的发展,各种信息以不可阻挡的力量涌入人们的生活,人们几乎每天都要处理和存储大量的信息,用纸张来记录信息已远不能满足人们的需求,这就需要一种更为有效的信息存储技术来存储信息,而光存储技术是信存储技术中最有效的方法.本文对光存储技术的原理、应用和发展前景做一简要介绍.     

PAMELA合作组的测量数据挑战宇宙射线理论

欧洲PAMELA合作组的科学家声称,PAMELA合作组所获得的测量数据对宇宙射线在宇宙中如何加速的理论提出了挑战.根据他们的说法,通过宇宙的质子和氦核的能谱不仅彼此不同,而且不符合宇宙射线理论中用于描述这些粒子的能谱(通量与能量之间的关系)的简单幂律.这种不一致可能意味着物理学家不得不寻找对宇宙射线加速的新的解释.     

降低了对称程度的狭义相对论

作为爱因斯坦狭义相对论基础的两个假设是:相对性原理和光速不变原理.相对性原理说的是不论对于一个固定不动的观测者,还是对于一个匀速运动的观测者,各种物理现象的规律应该是相同的 光速不变原理认为不论光源如何运动,光速总是恒定的.欲使这两个假设成立,时-空必须具有一定的对称性.将以上这些合并考虑便形成了与旋转及速度之变化有关的所谓Lorentz对称群(以下简称"L对称"):如果在你进行一项物理实验时,实验室上下倒置了或开始以不同的速度移动,但由于L对称,自然界的基本规律是不会改变的.     

高能粒子辐照二氧化硅玻璃E''色心形成机理研究

考虑高能粒子辐照二氧化硅玻璃形成E'色心的情况.建立了E'色心形成的动力学模型,得到了E'色心浓度与辐照剂量的关系式.结果表明,在高能粒子辐照情况下,E'色心的形成包括两个过程,即色心的创造过程和色心的激活过程.色心的创造过程主要由二氧化硅网格中疲劳键的断裂形成或网格中氧移位形成,E'色心浓度随剂量的变化呈线性增长.色心的激活过程主要由二氧化硅玻璃中固有点缺陷形成,E'色心浓度随剂量的变化呈饱和趋势.理论结果和实验结果符合很好,说明建立的模型是有效的.     

欢迎作者将被他刊拒绝的佳作再投本刊

在物理学的科技成就中,激光可算是仅次于核能的1项重大发明创造。第1台激光器是1960年由美国物理学家梅曼(见本刊《邮票上的科学家——佼佼者之路》一书中之M4)发明的。然而《物理评论快报》却拒绝刊登梅曼的论文,理由是:这是微波激射物理方面的文章,对快速出版物不再有价值。这真是令人啼笑皆非!     

Spectroscopic evaluation of the global hardness of the atoms

This study explored a new route for calculating the global hardness of atoms using spectroscopy. Working on a new definition of global hardness and relying on the Bohr model of the hydrogenic atom, a new formula for the global hardness of atoms was derived in terms of the wave number, reflecting the electron transition from the ground state to infinity. Since the spectral lines emitted from an atom bear the signature of all complex and complicated energetic effects, including relativity, in the internal constitution of the atom, it is expected that all such effects are automatically subsumed in the hardness data computed in terms of spectral lines. The hardness of the atoms of the 103 elements of the periodic table have been computed using spectral data and in terms of the new formula suggested in this work. The effect of relativity in pre- and post-lanthanoid elements is distinctly manifest. The express periodic behaviour and correlation of the most important physico-chemical properties of elements suggest that the present approach is an alternative scientifically meaningful method for evaluating the global hardness of atoms.     

超弹性碰撞实验最佳工作条件分析

超弹性碰撞演示实验是灵活运用大学物理知识的典型实验,本文对其最佳工作条件进行了分析,研究表明,当大球和小球的质量比为3时可以达到最佳的实验效果．     

Investigation of the Dynamic Properties of the Lipid Layer of Intraplastid Membranes by Lipophilic Fluorescent Probes

The dynamic properties of the lipid layer of intraplastid membranes have been studied by analyzing the stationary and kinetic spectral polarization characteristics of the fluorescence of lipophilic probes of pyrene and diphenylhexatriene (DPH). Based on the data of the decay of the fluorescence anisotropy of pyrene, the value of the microviscosity of lipids in the membranes of prolamellar bodies (PLB) and protilakoids of etioplasts has been calculated. The pyrene molecules built into the membranes of etioplasts have a relatively high rotational mobility (stationary anisotropy r _s < 0.1). The DPH molecules rotate with difficulty in etioplast membranes (r _s > 0.3). After photoreduction of protochlorophyllide (Pd) in vivo, the rotation of the pyrene and DPH molecules in the membranes of prolamellar bodies becomes easier and this leads to a decrease in r _s. Illumination raised the degree of excimerization of the pyrene immersed into lipids (_exc = 337 nm), and the microsurrounding of the molecules of the probe in lipids became more hydropholic (the relationship between the vibronic maxima at 373 and 387 nm decrease). The set of data obtained points to a decrease in the microviscosity of the lipid layer of the membranes of prolamellar bodies as a result of illumination of sproutings.     

物理力学公式、定律在"和平号"空间站坠毁过程中的运用

利用物理力学定律对“和平号”空间站坠毁过程作了比较详细的计算和描述，旨在使读者在航天器有关知识有更多了解。     

Accuracy of Determining the Optical Parameters of Thin Films by the Method of the Reflectance-Spectrum Extrema Envelopes

A technique to evaluate the accuracy with which the optical parameters of thin films are determined by the method of reflectance-spectrum extrema envelopes is presented. The general case of s-polarized light impinging obliquely on a weakly absorbing thin film formed on an absorbing substrate is discussed. Rather simple analytical expressions are derived which can easily be used in program realization on computers for calculating errors. On the basis of the error analysis, a procedure for determining the optical constants and thickness of thin films is proposed, which allows one to reach the maximum accuracy in solving the inverse problem of spectrophotometry. The optical constants and the thicknesses of the films of perylenetetracarboxylic acid and 2-[4-(4-aminophenyl)phenyliminomethyl]phenol formed on silicon substrates are found by the developed technique in the spectral range 550–900 nm.     

波导弯曲半径与弯曲损耗的关系

介绍了分析波导弯曲损耗的保形变换法和归一化方法以及由此得到的波导弯曲半径与弯曲损耗的关系式.建立了弯曲损耗经验公式,由该公式得出了四种常用材料的波导弯曲半径与弯曲损耗的曲线,并将已报道的相应材料制作的AWG中的最小弯曲半径及其对应的损耗实验数据与这些曲线上的相应数值进行了比较,结果表明,弯曲损耗经验公式在确定AWG中的最小弯曲半径时,有一定的参考价值.     

澄清对相对论性原理和协变性的误解

近来有些文章断言,在一个惯性参考系里能量守恒的物理系统,在别的参考系看来能量也一定守恒.实际上这些作者混淆了物理方程式的协变性和相对性原理.本文将澄清这一误解.     

测量可溶性物质的密度

常规方法测量可溶性物质（如食盐）的密度遇到了困难,经过分析研究和实验检测,本文给出的3种实验方法的确可行,实验结果误差较小。     

Fluorescence-polarization detection of the scattering of molecular beams by a surface

We investigate analytically the effect of the forces that act both in the plane of a scattering surface and normally to it on the polarized fluorescence of reflected molecules in forward scattering. We show that as the velocity of the beam of incident molecules increases, the polarization degree of the fluorescence of reflected molecules becomes substantially different from that of free and/or desorbed molecules. Therefore, the detection of the scattering of molecular beams by a surface using the polarization degree of fluorescence can serve as a rather reliable means of diagnosing surfaces and determining the modes of scattering. Institute of Molecular and Atomic Physics, National Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 205–212, March–April, 1999.     

Entropies of the various components of the universe

In this study, we investigate the entropies of photons, ideal gas-like dust (baryonic matter), and a special kind of dark energy in the context of cosmology. When these components expand freely with the universe, we calculate the entropy and specific entropy of each component from the perspective of statistics. Under specific assumptions and conditions, the entropies of these components can satisfy the second law of thermodynamics independently. Our calculations show that the specific entropy of matter cannot be a constant during the expansion of the universe, except for photons. When these components interact with the space-time background, particle production (annihilation) can occur. We study the influence of the interaction on the entropies of these components and obtain the conditions guaranteeing that the entropy of each component satisfies the second law of thermodynamics.