共查询到20条相似文献,搜索用时 45 毫秒
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Pawe Karasiski 《Optics Communications》2007,280(2):351-358
The paper presents the influence of refractive profile shape on the distribution of modal attenuation in planar metal-clad optical waveguide structures. A calculation method has been presented in which we applied the Snyder–Love expression on modal attenuation coefficients and matrix method 4 × 4 for the analysis of planar waveguides. The obtained results are almost identical with the exact results for refractive profiles: the parabolic, exponential, Gaussian and linear ones. It has been demonstrated that the applied calculation method can be used in waveguides of any profiles of the refractive index. 相似文献
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George Graham Jon Petzing Margaret Lucas John Tyrer 《Optics and Lasers in Engineering》1999,31(2):147
Existing modal analysis techniques based on pointwise methods such as accelerometers and laser vibrometers, suffer from the compromises required to infer whole field vibration behaviour from a predetermined number of discrete measurement data points. The measurement grid is normally chosen before the most sensitive areas of the test piece have been identified and this can lead to a requirement for further grid refinement, with the consequent spatial and temporal disadvantages. Whole-field modal analysis using electronic speckle pattern interferometry (ESPI) has been developed, and focuses on the manipulation of optical information to provide a grid of data points which is transferred to a modal analysis software package for comparison with traditional point wise modal data sets. The advantages of obtaining the initial whole-field vibration picture in real time and subsequently overlaying a chosen measurement data grid, are demonstrated. Modal analysis of a steel plate is presented, which demonstrates single displacement vector measurements. Data is transferred into modal analysis software allowing ESPI mode shape information to be directly compared with measurements using other pointwise techniques and finite element analysis (FEA), through a modal assurance criterion (MAC) calculation. Further results are presented for multiple displacement vector analysis of high-power ultrasonic components, demonstrating the ability to accurately measure the modal characteristics of complex dynamic components. 相似文献
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We report a first principles calculation to investigate the electron transport properties of defected armchair graphene nanoribbon (AGNR) influenced by Stone-Wales (SW) defect. The SW defect is found to be able to effectively influence the electronic structure of the defected AGNRs, and their electron transport behaviors can exhibit prominent differences depending on the symmetry of the nanostructured morphology. Moreover, our simulations have revealed that the introducing of the SW defect could be favorable for the electron transport of the defective AGNR. Our investigation has confirmed the possibility of tuning the electron transport of graphene nanoribbon by introducing a topological defect, which could be helpful to extending the field of applications for graphene nanoribbon-based nanodevices. 相似文献
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Mamou-Mani A Frelat J Besnainou C 《The Journal of the Acoustical Society of America》2008,123(4):2401-2406
A finite element model of a piano soundboard is used to study the effect of the strings tension (downbearing) on its vibration, considering the ribs, the bridges and the crown. The downbearing is modeled with the prestress theory. Prestress calculation with linear and nonlinear models including geometric rigidity are compared in terms of the modal frequencies. The effects of the downbearing in modal frequencies and mobility are investigated and the importance of the crown on these results is evaluated. A simple phenomenological law is exhibited, which characterizes the evolution of eigenfrequencies with downbearing, including the initial crown. 相似文献
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非线性包层多量子阱波导的TE波 总被引:3,自引:0,他引:3
给出用以分析非线性包层多量子阱波导TE模光学非线性与双稳性的理论公式与计算方法。指出用均方根等效折射率法解本征方程是有效的简化方法。用本文方法分析了模折射率对波导总功率的依赖关系,芯区功率与总功率之间的双稳性以及模场分布与模折射率的关系。讨论了波导参数对光学非线性、双稳性及模场的分布的影响。 相似文献
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现有深海地声参数反演研究通常基于全波场理论,存在计算量大、多值性以及需要准确的水文环境信息等问题。针对这一问题,提出一种基于简正波频散特征的深海低声速沉积层海底参数反演方法。在南海北部大陆坡海域的一次实验中,坐底式水听器(深度约1740 m)接收的沉底弹信号中观察到一种低频成分先到而高频成分后至的到达结构,由被限制在低声速沉积层的简正波组成。通过匹配沉积层简正波60-220 Hz频段内的到达时间差对实验海域的低声速海底参数进行反演,得到沉积层厚度为16.4 m,沉积层声速为1450.5 m/s,与底质采样数据比较吻合,且具有较高的可信度,验证了所提方法的有效性。由于沉积层密度对简正波频散特征的敏感性较差,其反演结果可信度不是很高,需要进一步研究。 相似文献
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Effect of Electron Correlations and Breit Interactions on Ground-State Fine-Structures along the Nitrogen-Like Isoelectronic Sequence 下载免费PDF全文
The accurate atomic data of nitrogen and nitrogen-like ions have an importance role in fusion plasma studies and astrophysics studies. The precise calculation of fine-structures is required to obtain such atomic data. Along the whole nitrogen isoelectronic sequence, the contributions of the electron correlations, the Breit interactions and the quantum electrodynamics corrections oi1 the ground-state fine-structures are elucidated. When Z is low, the electron correlations are important, and the Breit interactions, which cannot be neglected cause interesting anomalous fine-structure splittings. When Z is high, the electron correlations are less important, and the Breit interactions are important in addition to spin-orbit interactions for precise calculations. 相似文献
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Jelonnek J. Grudiev A. Schunemann K. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1999,27(2):374-383
Computation in frequency, as well as in time domain of the electromagnetic field in aperture-coupled cavities which are excited by electron beams, requires an accurate representation of the field. Furthermore, a fast tool for simulation of beam-field interaction in electron tubes is desirable. Application of the modal expansion method, which utilizes both the solenoidal and the irrotational eigenfunctions of the equivalent short-circuited cavity, is generally rigorous but numerically inefficient. In this contribution, three main steps towards a more accurate and simultaneously more efficient analysis are presented. First, it is shown how the irrotational magnetic eigenfunctions can be eliminated from the analysis. Furthermore, some poorly convergent series in the frequency domain analysis as well as in the time-domain analysis are replaced by analytic expressions. Finally, the modal analysis is directly formulated in time domain using rigorous boundary conditions. Numerical results are presented for idealized structures with impressed current density and for self-consistent calculations which are compared to analytical or to numerical results, respectively. Thus, excellent accuracy of the developed method is proved and significant simplifications are justified. For weakly inhomogeneous cavities, the influence of mode conversion on field profile and on numerical aspects is also discussed 相似文献
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In order to evaluate a fiber amplifier’s output beam quality, we have explored the beam quality factor calculation. A theoretical beam quality factor calculation method is presented in this paper. The method bases on modal power decomposition, laser rate equations and Fourier diffraction theory. Through the rate equations, each modal power weight factor at the fiber output facet is obtained. By the modal power decomposition, the optical field at the fiber output facet is established. Finally, running Fourier transformation, the beam diverging state in free space and corresponding M 2 parameter are obtained. The calculation process is verified with applying it to working out the beam M 2 parameters of large-mode-area (LMA) fiber amplifier system under different conditions. The numerical results help us well know and predict the out beam property. Some obtained results are also accord with other reporting outcomes. 相似文献
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V. P. Afanas’ev B. M. Smirnov D. A. Zhilyaev 《Journal of Experimental and Theoretical Physics》2014,119(1):138-145
General principles are discussed for a gas discharge plasma involving excited atoms where electron-atom collision processes dominate. It is shown that an optimal kinetic model of this plasma at not large electric field strengths can be based on the rate constants of quenching excited atom states by electron impact. The self-consistent character of atom excitation in gas discharge plasma is important and results in the tail of the energy distribution function of electrons being affected by the excitation process, which in turn influences the excitation rate. These principles are applied to an argon gas discharge plasma where excitation and ionization processes have a stepwise character and proceed via formation of argon atom states with the electron shell 3p 54s. 相似文献
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Solitary dopants in semiconductors and dielectrics that possess stable electron structures and interesting physical properties may be used as building blocks of quantum computers and sensor systems that operate based on new physical principles. This study proposes a phenomenological method of parameterization for a single-particle energy spectrum of dopant valence electrons in crystalline semiconductors and dielectrics that takes electron–electron interactions into account. It is proposed to take electron–electron interactions in the framework of the outer electron shell model into account. The proposed method is applied to construct the procedure for the determination of the effective dopant outer shell capacity and the method for calculation of the tunneling current in a single-electron device with one or several active dopants–charge centers. 相似文献
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P. Gnielka 《Journal of sound and vibration》1983,90(2):157-172
In all methods of balancing flexible rotors currently in use (modal balancing and influence coefficient techniques) test masses and test runs are required for the calculation of correction masses. In the modal balancing procedure suggested by Gasch and Drechsler [1] a simple identification method is used to find the generalized unbalances without test runs. In this paper the Gasch and Drechsler balancing procedure is reported and extended to multibearing rotors with initial shaft bow. Systematic experiments done on two test rotors are described. The results show that flexible shafts mounted in ball bearings can be balanced with very good results. Even rotors in fluid film bearings, exceeding the scope of modal theory, were balanced with good results. 相似文献
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MO Xiao-Hu FU Cheng-Dong ZHANG Jian-Yong QIN Qing QU Hua-Min WANG Yi-Fang XU Jin-Qiang ZHANG Tian-Bao 《中国物理C(英文版)》2008,32(12)
The proposed beam energy measurement system at BEPCⅡ is composed of three parts:the laser source and optics system,the laser-electron interaction system and the HPGe detector system.The working principles of each system are expounded together with the calculation for preliminary design.The normalizations of laser and electron beams are put forth and used for the evaluation of intensity of the backscattering photon.The simulation of HPGe detector is also performed for understanding the working properties. 相似文献
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采用基于密度泛函理论的第一性原理计算, 对(6,0)单壁氧化锌纳米管、铝掺杂、氮掺杂和铝氮共掺杂纳米管的能带结构、态密度和差分电荷密度进行了研究. 结果表明, 氮掺杂可以在纳米管禁带中引入受主能级, 实现纳米管的p型掺杂, 但是受主能级局域性较强, 导致氮溶解度低. 引入铝元素可以有效降低氮形成受主能级局域性, 激活氮元素, 铝氮共掺杂有望成为氧化锌纳米管一种更为有效的p型掺杂方法.
关键词:
氧化锌纳米管
电子结构
共掺杂
第一性原理计算 相似文献
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This paper discusses an analytical technique for calculating the relaxation in time of the electron distribution function f in an environment in which no perturbing forces act on the electrons. For t = 0, f may have any arbitrary form presumed to be caused by perturbing forces which were not zero during t < 0. The technique then allows calculation of the relaxation of f in time for the following types of electron collisions: a) elastic collisions with cold neutrons, b) excitation collisions in which the threshold energy for an elastic excitation collision is small compared to the electron energy, c) ionizing collisions when the energy lost by the electron is small compared to its energy, and d) any combination of the above. In this paper the method is described and simple examples are presented to illustrate the physics of relaxation for the collisional categories listed above. It is pointed out that a number of important problems can be solved by this technique primarily in the area of nuclear EMP: the forrnative lag time problem and the calculation of thermalization time. In addition, the details of the afterglow of extinguished discharges in the monotomic gases can be determined. 相似文献