Double Slab Research Articles

Simultaneously Large and Opposite Lateral Beam Shifts for TEand TM Modes on a Double Metal-Cladding Slab

We report simultaneously large and oppositeGoos–Hänchen shifts for TE and TM beams on a double metal-claddingslab. Theoretical examination shows that both positive and negativelateral shifts are in two orders of the wavelength. It is also foundthat the magnitude of the lateral beam shift strongly depends on thethickness of the upper metal layer. The optimal thickness of the uppermetal layer for zero reflection is found to be the critical thicknessabove which a negative beam shift occurs. Numerical calculations are ingood agreement with the theoretical results.

Synthesis, Crystal Structure and Electronic Structure of Modulated Pd7‐δSnTe2

AbstractPd7‐δSnTe2 was synthesized starting from the elements either by direct reaction at 970 K or by reaction in a tin flux at 1170 K. Depending on the reaction route and starting composition, single crystals of Pd7‐δSnTe2 with slightly different compositions were found: 0.3 ≤ δ ≤ 0.8. The average structure of Pd7‐δSnTe2 (space group I4/mmm, No. 139, a = 4.001(2) Å, c = 20.929(3) Å, Z = 2) is isotypic to those of the respective nickel compounds Ni7‐δSnQ2 (Q = S, Se, Te) and consists of Cu3Au‐like Sn/Pd blocks and NaCl‐like Pd/Te slabs. Additional satellite reflections that occur in the diffraction image of Pd7‐δSnTe2 can be assigned to the modulation vectors q1 = (0, ‐0.4, 0) and q2 = (0.4, 0, 0). The modulated structure was refined in the (3+2) dimensional superspace group I4/mmm(0‐β0, α00)0.ss.mm to an agreement factor of wR2 = 0.070 for 49 parameters and 483 reflections. The origin of the modulation can mainly be attributed to a variation of the occupancy of the Pd sites in the Pn/Te double slabs. Band structure calculations on the stoichiometric phase Pd7SnTe2 suggest metallic behavior for this compound.

Pulsed Gaussian beam interactions with double negative metamaterial slabs: errata

The numerical results, Figs. 16 and 18, for the double negative (DNG) metatmaterial Goos-Hänchen examples were incorrect. Corrected numerical results show closer agreement to predictions.

Pulsed and CW Gaussian beam interactions with double negative metamaterial slabs

The interactions of pulsed and continuous wave (CW) Gaussian beams with double negative (DNG) metatmaterials are considered. Subwavelength focusing of a diverging, normally incident pulsed Gaussian beam with a planar DNG slab is demonstrated. The negative angle of refraction behavior associated with the negative index of refraction exhibited by DNG metamaterials is demonstrated. The transmitted beam resulting from both 3- cycle and CW Gaussian beams that are obliquely incident on a DNG slab are shown to have this property. Gaussian beams that undergo total internal reflection from a DNG metamaterial slab are also shown to experience a negative Goos-Hänchen (lateral) shift. Several potential applications for these effects in the microwave and optical regimes are discussed.

Ｘ線透過法による小型固体モータにおける侵食燃焼効果の精密測定

The erosive burning effects in a small test motor loaded with practical composite propellants have been investigated in detail by using an X-ray absorption diagnostics to measure the propellant local regression. The motor was specially designed to have two propellant slabs and was called as DSM (Double Slab Motor). Significant erosive burning was forced to occur in the motor by varying combustion pressure and mass flux in the port. A new simple correlative equation is derived, which predicts accurately not only pressure history but also local regression of burning surface. The equation is characteristic in the non-dimensionalized threshold mass flux and includes the terms to consider both effects of pressure and of motor scale.

Complex aluminates RE 2SrAl 2O 7 (RE = La, Nd, Sm–Ho): Cation ordering and stability of the double perovskite slab–rocksalt layer P 2/RS intergrowth

The series of complex aluminates RE 2SrAl 2O 7 (RE = La, Nd, Sm, Eu, Gd, Tb, Dy, Ho) was prepared at 1450 °C. Their structure is the double perovskite slab–rocksalt layer P 2/RS intergrowth of the n=2 Ruddelsden–Popper phases. X-ray Rietveld refinement calculations point to a progressive RE-Sr ordering between the ninefold sites in the RS layers and the twelvefold one in the P 2 slabs, respectively. This ordering proves both to improve the ease to prepare these aluminates and stabilize their intergrowth structure. The limit observed for RE=Ho corresponds to a nearly fully ordered distribution of the Ho 3+ and Sr 2+ cations – 91%. Due to an excess structure-bonding anisotropy in the ninefold sites, a further extent to smaller RE 3+ cations is unsuccessful. These results well compare with those regarding the magnetoresistant manganites RE 1+ x Sr 2− x Mn 2O 7: increasing RE-Sr ordering and limit found for Er. The big size A element long range ordering phenomena which are unlikely to depend on redox phenomena of the B element in the P 2 slabs, have to be considered as specific trends of the P 2/RS intergrowth type complex oxides.

단기하중하의 국내 합성 더블티 슬래브 댑단부 전단거동 평가

단기하중하의 국내 합성 더블티 슬래브 댑단부 전단거동 평가

Design optimization of optically pumped terahertz lasers in stepped quantum wells

Asymmetric stepped quantum wells (QWs) have been used in many optoelectronic devices. This paper proposes a modulation doping position at the edge of the stepped well to minimize the potential distortion caused by the doping. As a result, parasitic potential wells are eliminated, and the sensitivity of the energy levels to dopant concentrations is substantially reduced. We also suggest a stacked design to juxtapose two QW slabs in order to improve the waveguide mode overlap in optically pumped terahertz lasers using the structure. The percentage of overlap between the active QWs layers and the laser mode increases from 9.8% for a thinned substrate single slab scheme to 68.4% for the stacked double slabs, respectively, with two highly doped layers acting as plasma waveguide. A diffraction integral model is established to simulate the laser cavity tolerance to possible misalignment in the stacked design. Our modelling result shows that the diffraction loss due to small (few micrometre) misalignment or difference in slab length is negligible compared to other losses in the laser system.

Prominent part of calcium ordering in the formation and stability of the intergrowth type solid solution La2Sr1−xCaxAl2O7

The partial substitution of Ca2+ for Sr2+ in La2SrAl2O7 was performed. The structure of the solid solution La2Sr1−xCaxAl2O7 (x≤0.5) consists in the regular intergrowth of double perovskite P2 slabs with unit rocksalt RS slabs. As the main result of Rietveld structure calculations, Ca2+ is found to replace Sr2+ in the A2 sites of the RS slabs (nine-fold CN); the random occupancy of the A1 sites (12-fold CN) in the middle of the P2 slabs by La3+ and Sr2+ remains nearly unchanged. The formation of the P2–RS intergrowth of the solid solution is easier than that of La2SrAl2O7 but its stability is progressively weakened when the amount of Ca2+ increases. This is the very likely consequence of the simultaneous presence of La3+ and Ca2+ in the RS slabs. The comparison of these ordering phenomena in the aluminates and the corresponding superconducting cuprates is taken into account.

Scheme for calculating the electronic structure of polar surfaces

A method for calculating the electronic structure at polar surfaces, based on a symmetric slab approach with column IV atoms at the center of the polar double slab, is introduced. Ab initio calculations with this method return very good results. Four different III-V (111) surfaces are compared, with corresponding results obtained by the pseudohydrogen termination method.

High-resolution cardiac imaging using an interleaved 3D double slab technique

A three-dimensional (3D) gradient-echo sequence with interleaved double-slab excitation was developed and optimized for the requirements in pediatric cardiac imaging. For this purpose high contrast between blood and myocardium signal should be obtained without the use of contrast agents. An acceptable measuring time for a large region examined with high spatial resolution should be achieved as well, especially with regard to the small structures of the heart and vessels of infants. The presented approach works with gradient moment nulling and a short echo time of 5.5 ms resulting in generally high signal intensity and only minor signal losses due to turbulent flow. The sequence allows simultaneous ECG-gated recording of two separately excited slabs with small thickness (10 mm) and with a distance of several centimeters between them. Thus, common effects of presaturation in 3D imaging can be avoided, although a relatively short measuring time is achievable. In order to get a 3D data set with good signal homogeneity of blood and of the other structures across a large volume of interest several double-slab measurements with suitable positions must be performed. The latter aspect is especially important for postprocessing techniques as multiple planar reconstruction and maximum intensity projection. Examples of applications of the new technique and appropriately postprocessed images are presented allowing demonstration even of subtle cardiac malformations.

Rubidium Tetrachlorocadmate: X-Ray Diffraction Measurements and an Electronic Structure Study

The structure of Rb2CdCl4single crystal at room temperature has been determined from X-ray diffraction of the MoKαline (λ=0.7107 Å). After refinement through blocked least-squares methods, the reliability factorRin the final cycle is 3.07%. The following results have been obtained: tetragonal system, space groupI4/mmm,a=b=5.195(1) Å,c=16.130(1) Å;F(000)=380;Dm=3.243 g/cm3;Z=2. The structure can be viewed as made of layers of CdCl6octahedra chains (Cd–Cl(1)=2.597(1) Å and Cd–Cl(2)=2.572(1) Å) separated by double slabs of rubidium atoms perpendicular to thecdirection. First-principles density functional theory calculations have been carried out to determine the electronic density distribution. The calculated equilibrium structure is in satisfactory agreement with the experimental data. Electronic density maps have been drawn from ab initio wavefunctions calculated both at the experimental and theoretical equilibrium geometries. Analysis of the calculated atomic populations confirms the highly ionic character of the electronic charge distribution in the crystal.

New Mixed Conductors, Ag x I w Bi2Sr2Can-1CuaOy (0.75 < x < 1.2, n = 1, 2, and 3)

New intercalation compounds, Ag x I w Bi2Sr2Can-1CuaOy (0.75 < x < 1.2, n = 1 2, and 3) have been prepared by the stepwise intercalation of I and Ag into the layered high-Tc superconductor, Bi2Sr2Can-1CunOy. For all three cases (n = 1, 2, and 3), powder XRD analysis indicated that the Ag-I intercalation expanded the [Bi-O]2 double slabs within host block by ∼7.3 Å, with subtle changes in physical properties of the pristine. From the Fourier 1-dimensional electron density mapping and the extended X-ray absorption fine structure (EXAFS) analysis to configure the interlayer structure of Ag x I w , sublattice, it was revealed that the two-dimensional Ag x I w species retained a similar iodine skeleton as found in β-AgI, but with a slightly distorted Ag+ position. The Ag+ ionic conductivity of Ag x I w Bi2Sr2Can-1CuaOy was turned out to be comparable with that of well known superionic conductors.

Hydrothermal synthesis and structural characterization of a three-dimensional organically-templated vanadium phosphate [H 3NCH 2CH 2NH 3][(VO) 3(H 2O) 2(PO 4) 2(HPO 4)

The title compound [(H 3NCH 2CH 2NH 3)][(VO) 3(H 2O) 2(PO 4) 2(HPO 4)] was synthesized from the hydrothermal reaction of V 2O 5:V:H 3PO 4:H 2NCH 2CH 2NH 2:H 2O in the mole ratio of 1:1:10:5:740. The compound crystallizes in the triclinic space group P1¯ with unit cell parameters a = 10.187(1), b = 10.241(1), c = 8.2137(7) Å, α = 90.398(8), β = 95.930(9) and γ = 117.325(7)°, V = 755.7(1) Å 3, Z = 2, D calc = 2.570 g cm −3, R = 0.0032, Rw = 0.035. The data were collected by using ω-2 θ scan technique and the structure was solved by direct method. The structure consists of binuclear units of corner-sharing [VO 6] octahedra and square-pyramidal [VO 5] units linked by phosphate tetrahedra, forming double extended polyhedral slabs in the (101) plane with these slabs connected by corner-sharing [HPO 4] tetrahedra to form a corner-sharing three-dimensional cage structure about the diammonium cations.

Crystal structure and dielectric properties of the mixed Aurivillius phase Bi 7Ti 4NbO 21

The crystal structure of the ferroelectric mixed Aurivillius phase Bi 7Ti 4NbO 21 was determined for the first time by X-ray diffractometry using a single crystal obtained by a flux method in Bi 2O 3 excess. It can be described as a regular stacking of double and triple perovskite-type slabs interleaved by Bi 3O 2 layers along the a axis. Nb is located in the double perovskite-type layers only with a random Nb/Ti distribution whereas the octahedral sites within the triple perovskite-type layers are occupied by Ti only. The thermal evolution of the dielectric constant between room temperature and 900 °C show two phase transitions at 650 and 830 °C. Combined analyses of experimental data support that the highest transition temperature corresponds to the Curie temperature, whereas the lowest one could be assigned to a phase transition within the orthorhombic symmetry by a change of the space group.

Bonding patterns and instabilities in them=2 Ruddlesden–Popper phases: LaSr2Mn2O7 and La2CaCu2O6

We present the results of high level band structure calculations on the important layered compounds LaSr2Mn2O7 and La2CaCu2O6 ; both of which have the structure of the m=2 member of the Ruddlesden–Popper phases and comprise intergrowths of double perovskite slabs with rock-salt slabs. The cuprate additionally has an ordered oxygen defect. For further comparison, the band structure of tetragonal La2CuO4 has also been calculated. The manganite is a material exhibiting giant magnetoresistance (GMR) effects and the cuprates can be doped to give superconductors. The calculations have been performed using the TB-LMTO-ASA programs within the local (spin) density approximation L(S)DA; for the manganite, spin-polarized calculations result in a magnetic ground state; calculations on the ferromagnet and two antiferromagnetic structures are compared. The calculations show up similarities and differences between the bonding patterns of these two structurally related compounds that display widely different ground states when they are doped. The instabilities on or near the Fermi surface possibly implicated in the stabilization of the different ground states are, however, quite similar in character.

Propagation of MHD body and surface waves in magnetically structured regions of the solar atmosphere

The fact that magnetically structured regions exist in the solar atmosphere has been known for a number of years. It has been suggested that different kinds of magnetohydrodynamic (MHD) waves can be efficiently damped in these regions and that the dissipated wave energy may be responsible for the observed enhancement in radiative losses. From a theoretical point of view, an important task would be to investigate the propagation and dissipation of MHD waves in these highly structured regions of the solar atmosphere. In this paper, we study the behavior of MHD body and surface waves in a medium with either a single or double (slab) magnetic interface by use of a nonlinear, two-dimensional, time-dependent, ideal MHD numerical model constructed on the basis of a Lagrangean grid and semi-implicit scheme. The processes of wave confinement and wave energy leakage are discussed in detail. It is shown that the obtained results depend strongly on the type of perturbations imposed on the interface or slab and on the plasma parameter, β. The relevance of the obtained results to the heating problem of the upper parts of the solar atmosphere is also discussed.

Electronic Structure of Layered Oxides Containing M(2)O(7) (M = V, Nb) Double Octahedral Slabs.

The electronic structure of M(2)O(7) double octahedral slabs with low d electron counts has been studied. It is shown that the nature of the low d-block bands is strongly dependent on the d electron count and the distortions of the layer. All d(1) systems are expected to be similar and to exhibit Fermi surfaces which result from the superposition of both one-dimensional (1D) and two-dimensional (2D) contributions. For lower d electron counts the electronic structure is quite sensitive to the existence of M-O bond alternations perpendicular to the layer and off-plane distortions of the equatorial O atoms. The Fermi surface of these systems can either be purely 2D or have 1D and 2D portions like those of the d(1) systems. It is suggested that the recently reported phase Rb(2)LaNb(2)O(7) could be a 2D metal. It is also proposed that chemical reduction of the A'[A(n)()(-)(1)Nb(n)()O(3)(n)()(+1)] Dion-Jacobson phases with n = 3 could lead to metallic conductivity, in contrast with the results for the n = 2 phases.

Cantor network, control algorithm, two-dimensional compact structure and its optical implementation

A compact integrating module technique for packaging a optical multistage Cantor network with a polarization multiplex technique is suggested. The modules have a unique configuration, which is the solid-state combination of a polarization rotator, double birefringent slabs, and a 2 × 2 switch array. The design and the fabrication of an eight-channel optical nonblocking Cantor network are demonstrated, and a fast-setup control algorithm is developed. The network systems are easy to assemble and insensitive to environment disturbance.

3-D Magnetic Model Inversion for Structure Mapping

A series of three-dimensional magnetic models has been designed to represent a wide range of geological structures. The models have been incorporated into automatic inversion routines, so that their parameters may be derived quickly from magnetic anomalies. The objective in developing this modelling scheme was to devise tools for applying to aeromagnetic data that would yield quantitative structural information, complementing the qualitative interpretations usually carried out. The models are based on simple slab components, and include single and double slabs, horizontal and plunging fold structures. The number of critical parameters for each model has been minimised to facilitate stable and rapid inversion. The inversion modelling scheme has been tested in the area of the Kurrawang Syncline near Kalgoorlie, WA. Here a magnetic conglomerate marker horizon has been folded and subsequently faulted. The results from the inversions of aeromagnetic data show excellent agreement with the known geology. It has been found that orientations tend to be determined more reliably than do thicknesses and depths. Other structures that have been modelled are the Mount Edwards folded ultramafic belt, near Widgiemooltha, WA, which is complicated by cross-cutting dykes; and a series of banded ironstones that host copper-gold mineralisation at Osborne, Queensland. The modelling technique is useful for testing an initial qualitative interpretation by trying the appropriate model and finding out if it can be made to fit. If a model fits well, then valuable structural information (strikes, dips, plunge etc) can be obtained. Although the modelling procedures were developed for use in reconnaissance mapping with airborne data, they are equally applicable to prospect exploration and ground survey measurements.