Classical solutions of some ℂP 1-like models

We present solutions to the classical equations of motion of a class of P ¹-like models. We calculate their action and study their stability properties.     

Structure and convergence of Poincaré-like normal forms

The general term of the Poincaré normalizing series is explicitly constructed for non-resonant systems of ODEs in a large class of equations. In the resonant case, a non-local transformation is found, which exactly linearizes the ODEs and whose series expansion always converges in a finite domain. Examples are treated.     

Bound-to-extended state absorption in quantum wells confined byδ-like barriers

Within the framework of a simple envelope function and effective mass approximation, by including the spatial variation of effective mass and nonparabolicity effects, we have investigated the energy spectrum and intersubband optical absorption in a quantum well with additional thin and higher (δ -like) cladding barriers on either side of the well. The dependence of the absorption coefficient on the structure parameters, doping level, photon energy and temperature has been investigated. The absorption coefficient and spectrum strongly depend on the cladding barrier tunnel transparency. The peak absorption wavelength is shifted towards the high energies as the barrier transparency decreases. The temperature shift of the absorption peak is very small. The results are compared with experiments of Schneider et al. taking into account the broadening induced by well width fluctuations.     

Classification scheme for adiabatic hyperspherical potential curves fordtμ-like systems

A quantum three-body Coulomb system of two heavy and one light particles (m ₁m ₃,m ₂m ₃) is considered in the framework of the adiabatic hyperspherical approach. Two sets of approximate quantum numbers are found that specify the adiabatic hyperspherical potential curves at small and large hyperradii. A complete classification scheme is obtained for the potential curves of the mesic moleculedt.     

Ultrafast α-like relaxation of a fragile glass-forming liquid measured using two-dimensional infrared spectroscopy

Ultrafast two-dimensional infrared (2D-IR) spectroscopy is used to study the picosecond dynamics of a vibrational probe molecule dissolved in a fragile glass former. The spectral dynamics are observed as the system is cooled to within a few degrees of the glass transition temperature (T(g)). We observe nonexponential relaxation of the frequency-frequency correlation function, similar to what has been reported for other dynamical correlation functions. In addition, we see evidence for α-like relaxation, typically associated with long-time, cooperative molecular motion, on the ultrafast time scale. The data suggests that the spectral dynamics are sensitive to cooperative motion occurring on time scales that are necessarily longer than the observation time.     

Synthesis and characterization of “mulberry”-like Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/multiwalled carbon nanotube nanocomposites

Nanocomposites composed of multi-wall carbon nanotubes (MWNTs) and Fe₃O₄ nanoparticles were fabricated using solvothermal method. Transmission and scanning electron microscopy, energy dispersive spectroscopy, and X-ray powder diffraction measurements confirmed that these mulberry-like Fe₃O₄ microparticles which were combined with the MWNTs in a random pattern are constructed with tiny nanocrystallites (12 nm in average diameter). The magnetic properties of the Fe₃O₄/MWNTs nanocomposites were measured using a vibrating sample magnetometer. Results showed that the Fe₃O₄/MWNTs nanocomposites exhibited superparamagnetism at room temperature and possessed a lower saturation magnetization (around 27.6 emu/g) than that of the pure Fe₃O₄ nanoparticles (around 33.7 emu/g). The Fe₃O₄/MWNTs nanocomposites have potential applications in engineering and medicine.     

以“ 做”促“ 思”

物理解题是有些学生很头痛的问题, 这些学生拿到一道题目有的无从下手, 有的瞎做一气, 有的思路正 确动手做了就错, 有的只能做出一半 …… 怎样才能让这些学生找到正确的思路呢? 如何帮助这些学生更好地解决 问题, 养成良好的解题习惯呢?     

从“教学”到“导学”

1大学生学习方式的现状及不足 中国地质大学刘杰,庞岚所作的有关调查显示：在约1500名被调查学生中,课程经常需要重修的占13．89％,偶尔重修和重修课程没超过两门的学生有28．29％和27．93％,这三项加在一起是70．11％．照此推算,全校大约超过70％的学生都有重修课程的经历．大学生目前学习的状况不容乐观．究其原因,学生们主要把它归结为自身的学习兴趣或对专业的兴趣等方面．但相关的调查结果显示,学生对学习的精力投入不足才是主要原因,包括不上课、不做作业、课余不学习、没有学习计划以及没有养成良好的学习习惯等．     

Comment on “order parameter of <Emphasis Type="Italic">A</Emphasis>-like <Superscript>3</Superscript>He phase in aerogel”

We argue that the inhomogeneous A phase in aerogel is energetically more preferable than the “robust” phase suggested by Fomin [5].     

四、“光学”和“原子结构”

光学一、教材的系统和重点本编内容可分为光度学、几何光学和物理光学三部分。所谓光度学,是指从事光流的测量以及测定光现象中的定量特性的知识。课本中则只阐述了一些简单光度量的概念。在几何光学中,是从观察光在两种媒质界面上的光现象开始,再分开来研究反射现象和折射现象中存在的规律以至光路控制的原理和光学仪器。     

始于“集邮”,终于“思想”

物理学研究虽然要从研究一个个自然现象,进行知识点"集邮"开始,但追求的是"思维经济",追求利用简单的规律来描述复杂的世界。学习物理虽亦始于"集邮"但不能终于"集邮",而要重视思维方式的训练与建构。     

光速的“不变”和“变”

光速不变原理是狭义相对论的重要物理基础,也是整个现代物理学中具有重大影响的基本原理之一.对光速不变原理的深入讨论和进一步的实验验证,无疑将产生广泛而深远的影响.自然科学是相对真理,光速不变原理当然也不例外,即一方面它包含有绝对真理的成份,因而它确能具有广泛的适用范围.但同时它又是相对的、近似的、有条件的.因此,对光速不变原理的正确性的简单否定或绝对化,都是不对的. 一、光速的不变性 光迹不变原理是从孕育狭义相对论的一系列实验──如曹顿-诺布尔电容器实验、瑞利折射介质实验、斐索实验、迈克耳孙-莫霍实验(特别是迈氏…     

从“布基球”到“布基管”和“布基洋葱”

在回顾Ｃ６０等布基球基本概貌的基础上，介绍了这方面的一些最新进展，讲述了布基管的概念及其和布基球的关系。叙述了布基管的一些有趣的物理性质，它可以是良导体，也可以成为近零能隙或有中等大小能隙的半导体。这些物理性质和它的结构有密切的关系。最后介绍了以Ｃ６０等布基球为核心的多层类石墨结构的球－布基洋葱。     

动力学中的“独立”与“叠加”

在动力学中，有两个独立性原理：“力的独立作用原理”和“运动的独立性原理”．将这两条原理结合起来，认识力的分解和运动的分解之间的相关性，对于我们解决那些因物体受外力作用而做较为复杂的曲线运动的问题或因短暂冲击而改变运动方向等方面的难题，是十分必要的．     

“深度撞击”成功“炮轰”彗星

太平洋时间7月3日22时52分(北京时间7月4日13时52分)，美国宇航局“深度撞击”号探测器释放的撞击器“击中”目标——坦普尔1号彗星，地面控制大厅里一片欢呼，“炮轰”彗星大片正式上演．     

此“ 活”非彼“ 活”

新课程标准中提倡学生自主、 合作、 探究的学习方式, 要求“ 让学生乐于探索, 勤于动手, 善于发现” . 随 着新课程改革的深入, 物理课堂要让学生“ 活”起来, 学生的积极主动性要被调动起来, 才能在对问题的积极讨论中 迸发出令人意想不到的智慧火花. 这就需要创建互动的课堂讨论情境, 问题的设置要有针对性, 同时关注学生的个 体差异, 处理好独立思考与小组讨论的关系, 并及时指导, 鼓励总结, 才能为沉闷的课堂注入一股活水, 满目生花     

物理学中的“场”和“理想模型”

一物理学中＂场＂的概念桌子、黑板、房、树木……都是由分子、原子组成的,而分子、原子又是由电子、质子、中子等基本粒子组成的.这些实物都是物质.物质是客观存在的,能作用于我们的感觉器官而引起感觉的东西.在我们周围的物质世界里,