七年级电功及电功率的学习

关于电功及电功率的教材,在与学习苏联电力化的物理原理有关的知识范围中,占有重要的地位。这些概念的理解、关于它们的量度单位的清楚的观念以及进行有关的简单计算的技能应该是综合技术教育的必要组成部分。可惜,在七年级的物理教科书中,这个学习材料的叙述是形式的、干燥的、很简单的,并且从     

超声波及其应用

超声就是普通的弹性介质的机械扳动,这种振动以一定的速度传播并且具有一定的能量。超声波——是介质的互相更替的稠密和稀疏。超声的传播速度与介质的弹性和介质的密度有关。超声波的波长,也和普通的声波一样,决定于两相隣的稠密或稀疏之间的距离。超声频率的下限     

大气的激光监测

在人口稠密的工业区,大气污染已成为严重的问题,研究污染物以及它们和大气组分的反应已成为迫切的需要了.为了预示与日俱增的污染源对环境的影响和采取及时而有效的措施,需要建立大气的数学模型.这些模型的发展、完善和与之相关的连续监测,要求具有广泛的监测功能. 地球上的生命不仅直接或间接地受近地面的大气组分的影响,而且还受到平流层及平流层以上的大气组分的影响.要用合理的成本来恰当地监测这广阔的区域,为此激光监测是唯一可能提供这种功能的技术. 一、大气遥感技术的特点 激光器的发现促进了人们对物质的非线性特性的研究,以及关…     

开放教学资源下新的教学方式的探讨与尝试

网络时代信息是开放的、共享的和丰富的.网络时代的学习有其自身的特点.作为教育者,我们应该从教学的各个环节作出相应的改变,使我们的教学更加适应时代的发展,从而达到"授之以渔"的教育境界.基于这样的认识,我们在双语物理课的教学中有步骤地指导学生借助互联网上公开的、丰富的信息和学习资源进行课程的学习和课题研究.结果表明这种尝试极大地提高了学生的自我学习的能力和学习兴趣,起到了事半功倍的作用,弥补了课堂教学的不足.     

一种基于迈斯纳效应的超导电机的驱动力的计算

超导体的迈斯纳效应是超导体的特有的性质之一,超导驱动的电机正是利用超导体的这个性质而设计的一种新型电机,由于驱动原理与传统的电机有很大的不同,这种电机的驱动力的计算一直是这种超导电机设计中要解决的主要问题,针对一种结构的电机,利用理论分析和数值计算的方法计算了一种基于超导体迈斯纳效应的超导电机驱动力的大小,为这种电机的设计提供了主要依据。     

物理学和天文学

历史上，物理学和天文学的发展是密切联系的。它们在整个现代科学的发展和技术的发达上起到了先锋的作用。物理学的基本规律和天文学提供的广亵的实验室构成了理想的科学发展的基础。20世纪的一系列科学上的重要突破正是这种优良结合的产物。今天，天文学和物理学又共同面对着更新的前测问题，并一道酝酿着新的科学上的重大进展。它们所取得的每一个进展也必然伴随着技术的创新和提高，也不断更新着人类的认识和文明。     

时间,计时标准和原子时钟

一、时间和它的标准问题在这星球土发展、生存和繁衍的人类,他们起始有时间观念恐怕不比有空间的观念来得迟。这种时间观念存在的表现有时是非常自然的。人是生存在三维空间里的,但是人类思维的发展是动的,辩证地开展的,是四维空间的。人类对于时间的感觉,是从因时而异的物质变化而觉察得的。最简单的物质的变化是一种物体的运动。不要以为颐和园门前的铜狮是     

寂静地震与地震预测的物理问题

寂静地震是指发生了缓慢的位错、但几乎不辐射地震波的“地震” .在目前的地震预测的物理学研究中 ,通常是通过计算历史上曾经发生过的地震所引起的应力变化 ,或者通过研究地震活动的统计性质或“图像动力学” ,来推测一个断层带上发生地震的危险性 .寂静地震的信息的缺失 ,形成了地震预测的物理学研究中的一个很大的“盲区” ,而在相当程度上 ,解决地震预测的物理问题的主要困难和可能的突破的希望 ,也许就在于此 .寂静地震的研究目前还很不深入 .关于寂静地震的性质 ,文章作者提出两个猜想 :(1)寂静地震的频度 ,满足类似于GR定律的幂律分布 ;(2 )最大的寂静地震的地震矩 ,与“可见”的最大地震的地震矩相当 .     

赝标Goldstone玻色子的手征拉氏量的 Gasser-Leutwyler系数

基于我们提出的参数化的完全穿衣服的夸克传播子,我们预言了未知的赝标Goldstone玻色子的手征拉氏量的Gasser-Leutwyler系数Li。预言的G-L系的数值与在文献中广泛应用的经验值和其他许多具有QCD特征的理论模型所预言的值一致。说明参数化的夸克传播子的适用性和可靠性。     

基于低维相变薄膜的显示器件光学性质的研究

采用传输矩阵模型研究了基于低维相变薄膜的显示器件的光学特性与器件结构的关系。显示器件的类型有反射型和透射型,器件结构的关键参数包括Ge_2Sb_2Te_5(GST)层的厚度、ITO层的厚度、GST层的晶态与非晶态的变化。结果表明:对于反射型器件,ITO层的厚度对器件的反射光谱影响较大,可以通过改变ITO层的厚度达到改变器件颜色的效果;GST层的厚度为12 nm时,GST的晶态与非晶态的变化使器件有最好的颜色对比度且消耗较低的电功率。对于透射型器件,通过使用超薄的GST薄膜,器件的透明度可以保持很高,器件的透明度在GST的厚度超过几纳米后迅速下降。     

Time domain finite volume method for the transient response and natural characteristics of structural-acoustic coupling in an enclosed cavity

A time domain finite volume method（TDFVM）based on wave theory is developed to analyze the transient response and natural characteristics of structural-acoustic coupling problems in an enclosed cavity.In the present method,the elastic dynamic equations and acoustic equation in heterogeneous medium are solved in solid domains and fluid domains respectively.The structural-acoustic coupling is implemented according to the continuity condition of the particle velocity along the normal direction and the normal traction equilibrium condition on the interface.Several numerical examples are presented to validate the effectiveness and accuracy of the present TDFVM.Then the effects of water depth on the acoustic and vibration characteristics and the natural characteristics of a structural-acoustic coupling system are analyzed.The numerical results show that the increase of water depth leads to a stronger coupling between the water and structure and the decrease of natural frequencies of coupling system,The computational cost and memory of this method are small and it can be applicable to structural-acoustic coupling problems in the heterogeneous fluid.     

Modeling Gain Dynamics in EDFAs: Space-Resolved Versus Lumped Models

We present a detailed comparison of dynamic space- and frequency-resolved and lumped erbium-doped fiber amplifier (EDFA) models. The space- and frequency-resolved models are based on an iterative solution of propagation equations for pump, multiple signals, and spectral components of forward and backward propagating amplified spontaneous powers and rate equations for pump, metastable, and ground energy level population densities of erbium ion. In contrast to space-resolved models, the lumped model solves a single ordinary differential equation for time evolution of the length-averaged metastable level population and is therefore substantially less computer time consuming. Both the space, and frequency-resolved and the lumped models give almost identical results when used for an analysis of surviving channel power excursions in concatenated EDFAs fed by multiwavelength signal and add/drop scenarios. For a statistical analysis of output power and signal-tonoise ratio fluctuations in EDFA cascades fed by burst-mode packet traffic, only lumped models can be used.     

镧和铕与邻菲罗啉谷氨酸配合物的NMR和IR研究

合成了稀土镧和铕与谷氨酸，邻菲罗啉形成的二元及三元配合物，经元素分析确定该配合物的组成为Ｌｎ（ｐｈｅｎ）（Ｇｌｕ）３．７Ｈ２Ｏ（Ｌｎ＝Ｌａ，Ｅｕ）；Ｅｕ（Ｇｌｕ）３；１２Ｈ２Ｏ。用核磁共振和红外光谱研究与配体与稀土离子的配位方式，讨论了稀土离子的顺磁性及屏蔽效应对配合物的ＮＭＲ谱图的影响。     

利用ICP-AES分析大豆体内Mn和Zn分配及收支平衡

长期定位试验和ICP-AES测试相结合,研究了下辽河平原土壤有效Mn和Zn浓度变化以及不同施肥制度下大豆体内Mn和Zn浓度与含量的变化。结果表明：下辽河平原土壤有效Zn浓度已濒临临界值,应加强对其监测;大豆籽实和秸秆体内Zn浓度受施肥影响变化较小;而籽实中Mn浓度受施肥影响变化较大,且NPK和NPKO处理显著高于O和CK处理;养分循环再利用在增加大豆生物量的同时,Mn和Zn携出亦呈增加趋势;土壤-作物系统中,Mn和Zn均出现收支赤字,其赤字大小顺序为NPKO＜O＜CK＜NPK,表明养分循环可以显著减缓这种赤字,使生态系统更可持续。     

Comparison between formulas of rotational band for axially symmetric deformed nuclei

The experimental rotational spectra of the deformed nuclei available in even-even and odd-A nuclei in the rare-earth and actinide regions are systematically analyzed with several rotational spectra formulas,including Bohr-Mottelson's I(I+l)-expansion,Harris'w2-expansion,ab and abc formulas.It is shown that the simple 2-parameter ab formula is much better than the widely used 2-parameter Bohr-Mottelson's AB formula and Harris'αβ formula.The available data of the rotational spectra of both ground-state band in even-even nuclei and one-quaasiparticle band in odd-A nuclei can be conveniently and rather accurately reproduced by ab formula and abc formula.The moment of inertia and the variation with rotational frequency of angular momentum can be satisfactorily reproduced by ab and abc formulas.     

Temperature Sensitivity Control and Mechanical Stress Effect of Boron-Doped Long-Period Fiber Gratings

We will present in this work the quantitative analysis of the relationship between the doping concentrations of GeO 2 and B 2 O 3 in the core and cladding regions and the temperature sensitivity of the resonance wavelength shift in long-period fiber gratings (LPFGs). Based on this analysis, the temperature sensitivity was suppressed and enhanced to 0.002 nm/°C and 0.28 nm/°C, respectively. We will also discuss the effect of the residual mechanical stress on the optical and mechanical properties of LPFGs. In particular, we will present the measurement results of the dependence of the refractive index change and mechanical strength on the residual mechanical stress in the boron-doped fibers with depressed clad and matched clad.     

Astrophysical combustion

There are three main astrophysical combustion systems: the evolution of stars, formation of interstellar dust and particulates, and the transition to hadrons in the early universe. These are described in terms of general combustion concepts, such as ignition, laminar and turbulent flames, detonations, multiphase flows, and particle and soot formation. Viewed in this way, the universe and many of its most important astronomical components are combustion systems, and we should use these as naturally occurring laboratories for exploring new and familiar combustion regimes. A more detailed discussion focuses on one type of combustion system, the ignition and development of turbulent flames in Type Ia supernovae, and the importance of the transition to a detonation.     

Design and simulation of the wire scanner for the injector linac of BEPC Ⅱ

BEPC Ⅱ,the upgrade project of Beijing Electron Positron Collider (BEPC),is an accelerator with large beam current and high luminosity,so an efficient and stable injector is required.Several beam diagnostic and monitoring instruments are used.A new diagnostic instrument--wire scanner,has been designed and will be used to nleasure the profile of the linac beam of BEPC Ⅱ.This paper describes the prototype of this system and the cause of heat generating of the wire.Some simulation results of the heat and force by using finite element method software-ANSYS(R),2) are presented and discussed.     

桂皮和小茴香中砷、铅、镉和汞的测定

用电感耦合等离子体-原子发射光谱法(ICP-AES)对桂皮和小茴香中的有害元素砷、铅、镉和汞进行了定量测定.结果表明,该方法简便可靠,具有良好的精密度和准确度.本文为桂皮、小茴香的种植及入药等方面提供了一些有用的信息.     

Synthesis of Pd and Rh metal nanoparticles in the interlayer space of organically modified montmorillonite

This study reports the synthesis of palladium and rhodium metal nanoparticles supported on montmorillonite (MMT) and partially organically modified MMT (POMM) using tetraamine palladium and hexaamine rhodium complex as precursor for palladium and rhodium respectively. The synthesized nanoparticles were characterized by powder X-ray diffraction PXRD and TEM. The PXRD study shows characteristic crystallographic planes for Pd and Rh metal and confirm the formation of metal nanoparticles in MMT and POMM. The TEM images reveal the effect of organic modification of MMT on decreasing particle size of Pd and Rh metal. The Pd and Rh metal nanoparticles are agglomerated in pristine MMT while nanoparticles are well dispersed in POMM. ICP-AES analysis was carried out to estimate quantitative amount of Pd and Rh metal in MMT and POMM.