Shape recovery effects in deformed NaCl whiskers

Processes of shape recovery by NaCl whiskers, previously deformed by bending, are studied. The studies reveal that there are two successive stages in the recovery, developing at different temperatures. A relation is established between recovery effect and the internal friction in whiskers.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 76–80, December, 1978.     

Localization of electromagnetic waves in three-dimensional fractal cavities

Three-dimensional fractals called the Menger sponge, with a fractal dimension D=log(20/log(3, were fabricated from epoxy resin by stereolithography. Clear attenuation of both reflection and transmission intensity was observed at 12.8 GHz for a cubic specimen with an edge size of 27 mm that was constructed up to the third stage of the self-similar patterns. The electromagnetic field was found to be confined in the central part of the specimen at this frequency. The localization is not caused by the presence of a photonic band gap as in photonic crystals but should be attributed to a singular photon density of states realized in the fractal structure. This is the first report on such localization of electromagnetic waves in three-dimensional fractal cavities.     

Two transparent boundary conditions for the electromagnetic scattering from two-dimensional overfilled cavities

We consider electromagnetic scattering from two-dimensional (2D) overfilled cavities embedded in an infinite ground plane. The unbounded computational domain is truncated to a bounded one by using a transparent boundary condition (TBC) proposed on a semi-ellipse. For overfilled rectangular cavities with homogeneous media, another TBC is introduced on the cavity apertures, which produces a smaller computational domain. The existence and uniqueness of the solutions of the variational formulations for the transverse magnetic and transverse electric polarizations are established. In the exterior domain, the 2D scattering problem is solved in the elliptic coordinate system using the Mathieu functions. In the interior domain, the problem is solved by a finite element method. Numerical experiments show the efficiency and accuracy of the new boundary conditions.     

An approximate projection technique for the calculation of electromagnetic properties of deformed nuclei

A three-dimensional angular momentum projection is carried out for cranking model wave functions. The projected matrix elements of electromagnetic operators are evaluated using a method originally developed by Kamlah for the case of projected energy, which is valid for large deformations and weakly triaxial nuclei. The calculated spectroscopic quadrupole moments deviate substantially from the predictions of a rigid rotor model with axial symmetry. For E2 transitions the deviations are small. Projected values of the magnetic moments are almost identical with those of a semiclassical calculation. Cranking model wave functions are decomposed into its components having good angular momentum.     

基于随机拓扑的复杂腔体电磁辐射统计特性

针对电磁波经孔缝耦合进入多端口微波混沌腔体的电磁辐射问题,推导了孔缝随机耦合模型,以预测单腔体各孔缝处耦合电压的统计特性;并将该模型与电磁拓扑理论结合,提出了一种复合计算方法孔缝随机拓扑模型,用于分析级联腔体的孔缝耦合电压和传输系数等电磁量的统计特性,将该算法的计算结果与网络级联理论的计算结果进行对比,验证了算法的正确性。该模型可成为分析复杂不规则混沌腔体的孔缝耦合问题以及混响室研究的有利工具。     

基于随机拓扑的复杂腔体电磁辐射统计特性

针对电磁波经孔缝耦合进入多端口微波混沌腔体的电磁辐射问题,推导了孔缝随机耦合模型,以预测单腔体各孔缝处耦合电压的统计特性;并将该模型与电磁拓扑理论结合,提出了一种复合计算方法孔缝随机拓扑模型,用于分析级联腔体的孔缝耦合电压和传输系数等电磁量的统计特性,将该算法的计算结果与网络级联理论的计算结果进行对比,验证了算法的正确性。该模型可成为分析复杂不规则混沌腔体的孔缝耦合问题以及混响室研究的有利工具。     

Energies and electromagnetic moments of deformed nuclei in the rare-earth region

Strutinsky-type cranking calculations with inclusion of pairing correlations have been performed for the rare-earth nuclei ^{156, 158, 164}Dy and ¹⁶⁴Er. The pairing effects contribute significantly and with their inclusion the calculated yrast spectra agree very well with experiments. Using Hartree-Fock-Bogouliubov cranking wave functions we have calculated the magnetic moments and quadrupole moments for states up to spin $\text{I = 20}\text{h}\text{?}$. The quadrupole moments are found to be constant over the whole spin range. The gyromagnetic factors g(I) show a strong I-dependence for ^{156, l58}Dy, a weaker one for ¹⁶⁴Er and none for ¹⁶⁴Dy. The sensitivity of this spin dependence on the single-particle occupation and the pairing degrees of freedom is studied. It is found that the spin variation of the gyrofactors is a rotational alignment effect.     

任意形状金属腔体内电磁脉冲的三维计算

提出了模拟任意形状腔体中的内电磁脉冲的三维直角坐标系时域有限差分(FDTD)算法。该算法采用FDTD共形网格技术模拟任意形状腔体的边界,可以解决腔体内非对称的边界问题。推导了射线斜入射的差分方程,进行了三维数值计算,并采用直角坐标系FDTD算法和柱坐标系FDTD算法计算了射线斜入射圆柱腔体产生的内电磁脉冲,二者吻合很好,验证了直角坐标系FDTD算法正确性。     

Rigorous computation of time-dependent electromagnetic fields ingyrotron cavities excited by internal sources

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     

任意形状金属腔体内电磁脉冲的三维计算

提出了模拟任意形状腔体中的内电磁脉冲的三维直角坐标系时域有限差分(FDTD)算法。该算法采用FDTD共形网格技术模拟任意形状腔体的边界,可以解决腔体内非对称的边界问题。推导了射线斜入射的差分方程,进行了三维数值计算,并采用直角坐标系FDTD算法和柱坐标系FDTD算法计算了射线斜入射圆柱腔体产生的内电磁脉冲,二者吻合很好,验证了直角坐标系FDTD算法正确性。     

Modeling of the scattering of electromagnetic waves by cavities of elliptic cross section

Based on the mode method, we develop a technique for calculation of the effective scattering area (ESA) of a perfectly conducting cavity of elliptic cross section with the rear wall covered by a radio-absorbing coating (RAC) of constant thickness. In the case where the incident electromagnetic wave is E-polarized, we numerically calculate the angular dependences of the monostatic ESA of an elliptic cavity with and without the RAC. The results of calculations are compared with the obtained experimental data. Voronezh State University, Voronezh, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 43, No. 5, pp. 426–432, May, 2000.     

等效零折射率材料微腔中均匀化腔场作用下的简正模劈裂现象

研究了零折射率材料微腔中人造原子与腔模的相干耦合现象.首先通过数值模拟的方法研究了在二维光子晶体微腔中填充阻抗匹配的零折射率材料后腔模的场分布.结果表明零折射率材料的引入使得原本以驻波场形式存在的腔模分布在整个微腔中变得近似均匀且值最大.其次,将人造原子放入腔中的不同位置并与腔模耦合,结果从频谱上观察到腔模的劈裂与人造原子在腔中的位置无关.最后,利用微波实验,通过开口谐振环等效的人造原子与一维复合左右手传输线等效的零折射率材料微腔之间的耦合验证了仿真结果的准确性.该结果为腔量子电动力学中量子点对位难的问题提供了新的方案,同时零折射率材料微腔也为今后研究原子与光子之间的相互作用提供了一个新的平台.     

Effective theory for deformed nuclei

Techniques from effective field theory are applied to nuclear rotation. This approach exploits the spontaneous breaking of rotational symmetry and the separation of scale between low-energy Nambu–Goldstone rotational modes and high-energy vibrational and nucleonic degrees of freedom. A power counting is established and the Hamiltonian is constructed at next-to-leading order.     

Low-Q cavities for high-power gyrotrons

The parameters of free oscillations in gyrotron resonators with a lowered reflection from the diffractive energy output for the purpose of reducing ohmic heating by rf power loss have been calculated. A gyrotron with such a cavity has been studied experimentally. The gyrotron had an efficiency of more than 45% with an output of 350 to 700 kW when operating in the 3.6-mm H_11,3 mode.Institute of Applied Physics, Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 37, No. 3, pp. 381–386, March, 1994.     

Residual stress determination in aluminium using electromagnetic acoustic transducers

The residual stresses in a shrink-fit specimen were measured ultrasonically, using shear-horizonal (SH) waves transmitted and received by noncontacting electromagnetic acoustic transducers. The presence of stress induces a small change in the velocity of the SH-waves. The difference in velocities of orthogonally polarized SH-waves (acoustic birefringence) was measured with a simple time-interval averaging system; this velocity difference can be related to the difference of principal stresses. The presence of material anisotropy (texture) in the specimen also causes relative velocity changes comparable to stress-induced changes. A simple method was used to remove the anisotropy-dependent component of the total relative velocity change, thereby allowing a determination of residual stress. This method consisted of measuring the birefringence in unstressed reference specimens and subtracting it from the birefringence measured at stressed locations. For the specimen used here, good agreement between theoretical and experimental values of stress was obtained.     

OPE formulae for deformed super-Virasoro algebras

We show the OPE formulae for three types of deformed super-Virasoro algebras: the Chaichian-Presnajder deformation, the Belov-Chaltikhian deformation and its modified version. Fundamental (anti-) commutation relations toward a ghost realization of deformed super-Virasoro algebra are also discussed.     

Vertex operators for deformed Virasoro algebra

Vertex operators for the deformed Virasoro algebra are defined, their bosonic representation is constructed, and a difference equation for the simplest vertex operators is described. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 11, 876–881 (10 June 1996) Published in English in the original Russian journal. Edited by Steve Torstveit.     

Shell structure for deformed nuclear shapes

Eigenvalues for the harmonic oscillator without l·s or l² terms suggest a deformed shell structure for nuclei with axes ratios 2 : 1 and deformation ? = 0.6 with corresponding nucleon “magic numbers” 2, 4, 10, 16, 28, 40, 60, 80 110 and 140, subject to small modifications due to spin-orbit and other correction terms. Experimental evidence of reasonably stable highly deformed structures corresponding to nucleon numbers 16, 20, 28, 40 and 60 (64) is presented. Attempts to calculate the corresponding potential energy surfaces using the Strutinsky shell correction method are described.     

Shell model calculations for heavy deformed nuclei

The pseudo SU(3) model is shown to be a powerful scheme for describing the excitation spectra as well asB(E2) andB(M1) transition strengths in heavy deformed nuclei. It is also useful for describing double beta decay amplitudes for transitions from the ground state of an even-even nucleus to the ground and excited states of the daughter nucleus, both for the two and zero neutrino emitting modes. The existence of selection rules which strongly restricts the decays is discussed. Anti-correlations between the quadrupole deformation and the Gamow-Teller (GT⁺) strength are found in an extension of the pseudo SU(3) model which explicitly includes pairing, which is also able to describe the fragmentation of the scissors mode. The projected shell model is introduced and proposed as an alternate means for studying single and double beta decay processes. Presented by J.G. Hirsch at the Workshop on calculation of double-beta-decay matrix elements (MEDEX’97), Prague, May 27–31, 1997. This work was supported in part by CONACyT (México), CONICET (Argentina), NSF and DOE (U.S.A.).