多功能平抛运动动量守恒实验演示仪

利用旋转折叠滑轨制作可自由平移旋转平台,配合平抛倾斜轨道,可进行平抛运动竖直水平运动规律的探究,也可进行竖直倾斜平面动量守恒实验的探究,功能多样,资源利用率高,制作简单,取材方便,满足学生及课堂教学需求,提升学生科学思维能力.     

机械能守恒定律及动量守恒定律演示仪器的制作

制作一种可以同时验证机械能守恒和动量守恒的实验装置,并通过这两个实验现象的对比更显著地体现了两个实验的物理现象与原理,有利于学生对机械能守恒与动量守恒原理的理解与认知。     

动量守恒问题中运动的瞬时性

运用动量守恒定律列方程式，方程式同侧的速度必须是同一时刻的瞬时速度，很多人忽视这一问题，甚至在有些教科书、参考书中也有处理欠妥之处．文中以火箭推进问题，三只小船鱼贯而行问题，论述动量守恒问题中运动的瞬时性．     

高能碰撞中动力学起伏的横动量守恒约束

详细研究了高能碰撞末态粒子动量守恒约束条件对归一化阶乘矩的标度行为的影响,进而成功地解释了当前实验中普遍存在的阶乘矩在相角方向上的下弯现象.提出了两种关于阶乘矩的新的统计方法试图部分地消除动量守恒约束的影响,恢复分形系统本身的标度性.     

动量守恒问题中运动的瞬时性

运用动量守恒定律列方程式，方程式同侧的速度必须要同一时刻的瞬时速度，很多人忽视这一问题，甚至在有些教科书、参考书中也有处理欠妥之处，文中以火箭推进问题，三只小船鱼贯而行问题，论述动量守问题中运动的瞬时性。     

关于GLR方程动量守恒的讨论

动力学演化(GLR)方程是小x物理学的一个基本的动力学方程，特别是对于分析HERA的轻子和强子的非弹性散射实验结果以及核内的EMC效应是非常重要的.但是，GLR方程一个严重缺陷就是违背动量守恒.讨论了动量守恒对GLR方程修正的意义，并且指出对实验结果做分析时须注意影响. 关键词：     

模拟碰撞过程实验的有关结果

采用小铅块沿光滑水平面入射光滑斜面滑块模拟碰撞过程,形象地模拟了压缩过程及恢复过程,同时还描述了恢复系数e的物理本质特征.     

动量及能量转换和守恒的互动式教学

本文通过子弹与木块的碰撞过程中作用力和反作用力做功不相等的例子,详细分析了该力学系统在整个过程中动量及能量的转换和守恒.同时,针对这个问题课堂上采用互动式的讨论,使学生更加深入理解动量及能量转换和守恒的本质,收到了良好的教学效果.     

动量守恒定律演示实验的改进

动量守恒定律是力学部分的重点和难点，教材中设计的演示实验(如图1)在实际教学中存在3个问题：     

悬线式二维碰撞实验

提出用长摆线单摆实现在准水平面内的无摩擦运动,用摄像头记录二维碰撞过程,设计了检验二维碰撞中动量守恒和机械能守恒的教学实验.     

La5/8-xPr xCa3/8MnO3体系电输运特性的研究

对La5/8-xPrxCa3/8MnO3(x＝0,0.13,0.20,0.25)体系的电输运特性进行了系统研究.结果表明随着Pr含量的增大金属-绝缘转变温度(TMI)减小,在高于TMI的温度区域,该体系的电输运行为具有绝缘体特性,符合可变程跳跃模型;而在较低温度(50 K以下),其电阻率存在极小值现象,且随磁场的增大而逐渐受到抑制.对这种电阻率极小值现象从强电子-电子相互作用角度进行了分析讨论.     

Electromagnetic momentum conservation in media

That static electric and magnetic fields can store momentum may be perplexing, but is necessary to ensure total conservation of momentum. Simple situations in which such field momentum is transferred to nearby bodies and point charges have often been considered for pedagogical purposes, normally assuming vacuum surroundings. If dielectric media are involved, however, the analysis becomes more delicate, not least since one encounters the electromagnetic energy–momentum problem in matter, the ‘Abraham–Minkowski enigma’, of what the momentum is of a photon in matter. We analyze the momentum balance in three nontrivial examples obeying azimuthal symmetry, showing how the momentum conservation is satisfied as the magnetic field decays and momentum is transferred to bodies present. In the last of the examples, that of point charge outside a dielectric sphere in an infinite magnetic field, we find that not all of the field momentum is transferred to the nearby bodies; a part of the momentum appears to vanish as momentum flux towards infinity. We discuss this and other surprising observations which can be attributed to the assumption of magnetic fields of infinite extent. We emphasize how formal arguments of conserved quantities cannot determine which energy–momentum tensor is more “correct”, and each of our conservation checks may be performed equally well in the Minkowski or Abraham framework.     

LiAl_5O_8∶Fe~(3+)发光粉的发光性能(英文)

Fe3+激活的铝酸锂是深红色发射的红色荧光粉,其发射的峰值波长为675nm,呈现出少有的纯正的深红色发光。本文对LiAl5O8:Fe3+荧光粉的基质组成和激活剂浓度进行了研究。结果表明:Fe3+掺杂LiAl5O8的激发光谱,在λem=673nm的波长监测下,有序相的激发光谱在284nm处有强吸收带,为Fe3+-O2-电荷迁移带;激发波长λex=254nm的有序相样品的发射波长峰值为673nm,并伴随一个在长波方向轻微不对称得,发射是属于4T1(4G)-6A1(6S)的跃迁。当原料Li2CO3与Al2O3的量的比为0.21时,样品的发光强度最好;样品的发光强度随激活剂Fe3+的浓度的增加而提高,当浓度达到0.5%时,发光强度达到最大值,超过0.5%时呈现出浓度猝灭效应。     

Graphical analysis of angular momentum for collision products

The complexity of atomic and nuclear structures and their collision processes involves conservation laws, bearing mainly on angular momenta; indeed angular momentum treatments prove most laborious. The analytic treatments, preferably carried out in Racah’s calculus, combine initially independent elements stepwise into structures branching out into resulting products. Graphical procedures that ensure phase and amplitude control of their manifold elements, illustrate these sequential steps and provide their results. The present report should familiarize readers with these procedures through examples of reactions of increasing complexity, bearing of course on structure calculations as well. The report has thus two aims: (i) computing correlation functions for reactions yielding several emitted particles (hence of arbitrary complexity) in terms of a novel method of computation, and (ii), describing the mathematical techniques relevant to solve high-complexity angular momentum problems, including the computation of many-body systems’ bound states. The complexity reflects the symmetries of the reaction products, and, more generally, of many-body system. The basic mathematical tool for such treatments is the Racah calculus which employs recoupling transformations, thus avoiding the many summations required by expansions in terms of vector coupling coefficients. The application of the Racah calculus is greatly aided by appropriate definitions and graphical procedures ensuring phase and amplitude control of their manifold elements, as well as illustrating the physical content. Beginning with photon absorption by discrete states, our examples progress to an Auger process yielding a correlation function with seven direction and polarization parameters.     

Co掺杂La5/8Ca3/8MnO3体系的结构和输运特性研究

系统研究了La5/8Ca3/8Mn1-xCoxO3(0.0≤x≤0.3)体系的结构和输运特性.结果表明,随着Co掺杂浓度的增加,体系的晶胞体积单调减小,并出现正交到四方的结构变化;绝缘体-金属转变(I～M)温度TIM向低温区移动,对应的峰值电阻率ρp急剧升高.在高温区(T>TIM)体系的输运特性满足可变程跃迁模型,对低浓度掺杂(x≤0.1)样品,具有典型的绝缘-金属转变行为,在低温区(T相似文献   

The momentum conservation law in special relativity

The derivation of the functional form of the relativistic momentum of a particle has a history going back to Lewis and Tolman's paper of 1909, yet satisfactory presentations seem to be few in number. Careful examination of the several types of derivation shows that their shortcomings are avoidable and allows the presentation of exact and improved analyses.     

Optical spectroscopy of Ce 3+ ions in BaY 2 F 8 single crystals

In the present work we report on the spectroscopic properties of the Ce 3+ ion in BaY 2 F 8 single crystals. The absorption and excitation spectra of the emission centered at 340 v nm have been measured in the temperature range 15-300 v K. The 340 v nm emission consists of two broad partially overlapping bands, peaking at 324 and 347 v nm (at 15 v K), respectively. The full width at half maximum is about 0.5 v eV at room temperature. The absorption spectrum of the lowest in energy component of the f M d transition of Ce 3+ reveals at low temperature a marked vibronic structure. High resolution (0.02 v cm m 1 ) Fourier transform infrared spectroscopy in the wave number range 500-5000 v cm m 1 and in the temperature range 9-300 v K has been exploited to monitor the f level splitting. The absorption transitions from the three Stark components of the 2 F 5/2 manifold to the four of the 2 F 7/2 one, have been monitored in the wave number range 2000-3400 v cm m 1 . The wave number separation at 9 v K between the lowest level of the ground 2 F 5/2 manifold and lowest one of the 2 F 7/2 manifold is found to be 2197.47 v cm m 1 in good agreement with the splitting detected between the two components of the d M f emission.     

微过氧化物酶-8的聚集程度对其与La3+相互作用的影响

UV-Vis吸收光谱的结果表明,由于La3 与微过氧化物酶-8(MP-8)分子血红素上的两个丙酸基的羧基氧发生强的键合作用,使血红素卟啉环的非平面性增加。NaCl能增加MP-8分子的聚集程度,导致La3 与MP-8相互作用引起的血红素卟啉环的非平面性增加的程度大大降低。甲醇虽然能降低MP-8的聚集程度,但对La3 与MP-8分子相互作用引起血红素卟啉环的非平面性增加程度的影响较小。