共查询到20条相似文献,搜索用时 171 毫秒
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AES分析表明,PECVD SiON-Si界面处存在一个很薄的富Si区域。本研究表明,它与介质膜的界面特性密切相关,对不同组分、不同工艺的介质膜,其界面富Si区域情况不同,从而使界面特性不同。本文给出了PECVD介质膜界面贫H的机理。实验中采用了俄歇能谱、红外光谱,C—V测试等分析手段,研究了膜内部结构。 相似文献
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研究了区域分解法在求解金属散射体的积分方程时的应用。积分算法可以精确地求解各种电磁场问题,但因为受限于格林函数,需要求解较为复杂的矩阵。区域分解法是一种迭代算法,把原来较大的求解区域划分成若干个相对独立的子区域,将原问题的求解转化为在各子区域上分别进行求解,并利用某种数据交换条件在子区域之间传递信息,最后得到原电大区域上的解。由于每个子区域相互独立并且单独划分网格,区域分解法更加适合解决多尺度的电磁散射问题。最后通过与商业软件的对比验证了算法的正确性。 相似文献
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本文首先探讨了用手征Ω介质作为微带天线基片的可能性。应用广义谱域指数矩阵方法,分析了单层和双层手征Ω介质中所有Ω单元的三种不同取向对偶极子天线辐射特性的影响,以及偶极子方向图随手征Ω介质损耗正切的变化情况。 相似文献
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电磁场同物质相互作用问题可以归结为电磁场同不同折射率形成的"势场"相互作用问题。当电磁场(光子)在周期"势场"中传播时,能量将分裂成带。文章从麦克斯韦方程出发,讨论了电磁场与周期介质的相互作用,并用转移矩阵方法导出了系统的色散关系,描述了周期介质中布洛赫波的传播及系统的稳定性。 相似文献
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This paper deals with electromagnetic scattering by nonlinear dielectric objects. In particular, a numerical approach is developed that is aimed at determining the distributions of the electromagnetic field vector inside a three-dimensional nonlinear, inhomogeneous, isotropic scatterer illuminated by a time-periodic incident electric field vector. An integral-equation formulation for the full-vector scattering problem is considered, and the nonlinear effect is taken into account by introducing equivalent sources and a Fourier-series representation. A system of integral equations (for each harmonic vector component and for the static term) is obtained that includes the internal electric field distribution as the unknown. After discretization, the solution is reduced to solving an algebraic system of nonlinear equations. Some preliminary numerical results are reported concerning scatterers that exhibit a specific (quadratic) dependence of the dielectric permittivity on the total electric field. The harmonic components of the scattered electric field outside the objects are also computed 相似文献
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The one-dimensional electromagnetic inverse problem for a stratified dispersive and dissipative slab is considered in the time domain. An optimization approach is used to reconstruct the parameters using the measured reflected field and/or transmitted field. Wave-splitting is used, and an explicit expression for the gradient is derived by introducing dual functions. The reconstruction algorithm is tested with both synthetic and experimental data 相似文献
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Sowinski M.J. Van Putten M.H.P.M. Van Den Berg P.M. Van Rhoon G.C. 《IEEE transactions on bio-medical engineering》1989,36(10):995-1003
The electromagnetic heat dissipation in a radially layered biological tissue inside a ring capacitor (RC) applicator has been investigated. A quasi-static model is introduced to compute the relevant electromagnetic field quantities. The method of computation employs the spatial Fourier transform of all field quantities with respect to the axial coordinate. After an iterative solution of a dual boundary value problem for the electric potential and the current density at the electrodes, an inverse Fourier transform is carried out to compute the quantities that are of interest to the deep-body system at hand. Comparison of numerical results with phantom measurements shows excellent agreement. 相似文献
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Abdul-Kadir Hamid Francis R. Cooray 《AEUE-International Journal of Electronics and Communications》2014,68(11):1106-1111
An exact analytic solution to the problem of scattering of a plane electromagnetic wave from a chirally coated elliptic cylinder defined by a DB boundary has been obtained, by expanding the different electromagnetic fields associated with the problem in terms of suitable elliptic vector wave functions and a set of expansion coefficients. The incident field expansion coefficients are known, but the expansion coefficients associated with the fields scattered outside the coated cylinder and the fields transmitted inside the coating are unknown. These unknown coefficients are obtained by imposing appropriate boundary conditions at the two boundaries. Results have been presented as normalized bistatic and backscattering widths for a variety of admittances, permeabilities, and permittivities of the chiral materials used for the coating, to show their effects on scattering from the chirally coated cylinder. 相似文献
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The two-dimensional problem of radiation of TE and TM waves from a waveguide array with protruding smooth dielectric elements of arbitrary shape is considered, and solution algorithms are suggested. The algorithms are based on applying the method of auxiliary sources for the representation of electromagnetic fields outside and inside the protrusions in combination with the method of integral equations for the electric field at the waveguide aperture. The point matching of the field tangential components on the protrusion-to-free-space boundary and at the waveguide aperture is used to reduce the problem to a system of linear algebraic equations for the amplitudes of the auxiliary filamentary currents and of the waveguide aperture electric field, which is assumed to be piecewise constant. The amplitudes obtained from the solution of the system are used for computing the array reflection coefficient and element pattern, which are shown in some cases to be significantly dependent on the protrusion shape. Examples of arrays with flat-topped element patterns resulting from array geometry numerical optimization are also presented 相似文献
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Suyama T. Yokoo M. Sawada H. Nagoya A. 《Very Large Scale Integration (VLSI) Systems, IEEE Transactions on》2001,9(1):109-116
This paper reports on an innovative approach for solving satisfiability problems for propositional formulas in conjunctive normal form (SAT) by creating a logic circuit that is specialized to solve each problem instance on field programmable gate arrays (FPGAs). This approach has become feasible due to recent advances in reconfigurable computing and has opened up an exciting new research field in algorithm design. SAT is an important subclass of constraint satisfaction problems, which can formalize a wide range of application problems. We have developed a series of algorithms that are suitable for a logic circuit implementation, including an algorithm whose performance is equivalent to the Davis-Putnam procedure with powerful dynamic variable ordering. Simulation results show that this method can solve a hard random 3-SAT problem with 400 variables within 1.6 min at a clock rate of 10 MHz. Faster speeds can be obtained by increasing the clock rate. Furthermore, we have actually implemented a 128-variable 256-clause problem instance on FPGAs 相似文献
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Tkatchenko S. Rachidi F. Ianoz M. 《Electromagnetic Compatibility, IEEE Transactions on》2001,43(2):117-129
We present a theory for the EMC problem of electromagnetic field coupling to a long line with arbitrary terminations. The theory is applicable for the high-frequency plane wave electromagnetic field excitations, when the transmission line approximation is no longer valid. Analytical expressions are derived for the induced current along the line, and at the two-line terminals. The coefficients of these expressions are determined using a procedure based on the exact solutions of the integral equation for two similar line configurations, but having a significantly shorter length. The method is, therefore, particularly efficient when considering the electromagnetic field coupling to very long lines. The advantage of the proposed approach is that, in contrast with transmission line approximation, it takes into account high-frequency radiation effects. Furthermore, it allows a considerable reduction in computation time and storage requirements with respect to conventional numerical solutions based on the thin-wire approximation 相似文献
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Zhenhua Zhang Xiaodi Zhao Jian Zhang Guohua Bai Hua Guo Weiwei Liu Bin Zhang Jin Wang Lianze Ji Fu-rong Chen Lizhong Zhao Xuefeng Zhang 《Advanced functional materials》2023,33(5):2210325
Electromagnetic field-responsive mechanical deformation enables remote control of dynamic devices including micro-robotic machines and smart surfaces. Metal–insulator transition (MIT) of vanadium dioxide (VO2) is developed for micro devices that are electrically or optically activated, but none of these is electromagnetic field-responsive. Herein, a micro-pillar array composed of epitaxial VO2 nanobeams that are asymmetrically coated with Cr, Au, and silicon oxide layers is demonstrated. Localized Joule heat, induced by the eddy current effect within the Cr or Au metal layer under an electromagnetic field, provides a high-sensitive thermal response that triggers MIT of VO2, thus activates bending and relaxing of the micro-pillars. For accurate and site-specific control of the bending, layers of amorphous silicon oxide are added to the structure to endow tunable stiffness through electron beams-matter interaction. These micro-pillars are optimized to be a 2D, tractable surface on which directional transportation by remote control of the electromagnetic field in a liquid medium is realized. This discovery provides novel ideas for the design of electromagnetic field-responsive structures. 相似文献
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Bucci O.M. D'Elia G. Migliore M.D. 《Antennas and Propagation, IEEE Transactions on》1999,47(9):1377-1385
A general approach to the near-field far-field transformation from amplitude only near-field data is presented. The estimation of the far field is stated as an intersection finding problem and is solved by the minimization of a suitable functional. The difficulties related to the possible trapping of the algorithm by a false solution (common to any nonlinear inverse problem) are mitigated by setting the problem in the space of the squared field amplitudes (as already done in a number of existing papers) and by incorporating all the a priori knowledge concerning the system under test in the formulation of the problem. Accordingly, the a priori information concerning the far field, the near field outside the measurement region and the accuracy of the measurement setup and its dynamic range are properly taken into account in the objective functional. The intrinsic ill conditioning of the problem is managed by adopting a general, flexible, and nonredundant sampling representation of the field, which takes into account the geometrical characteristics of the source. As a consequence, the number of unknowns is minimized and a technique is obtained, which easily matches the available knowledge concerning the behavior of the field. The effectiveness of the approach is shown by reporting the main results of an extensive numerical analysis, as well as an experimental validation performed by using a very low cost near field facility available at the Electronic Engineering Department, University of Napoli, Italy 相似文献