Nonlinearity of a ferroelectric layer described using a planar capacitor model

A method for calculating the capacitance-voltage (C-U) characteristic of a planar ferroelectric film capacitor with allowance for the material nonlinearity is proposed. The nonlinear properties of the ferroelectric material are described in terms of the Ginzburg-Devonshir equation under the conditions of minimum free energy of the planar capacitor. An analysis of the results shows that the capacitance of a planar ferroelectric film capacitor can be calculated using the proposed elementary model with a relative error not exceeding 2%.     

Characterization of a CH planar laser-induced fluorescence imaging system using a kHz-rate multimode-pumped optical parametric oscillator

The performance characteristics of a new CH planar laser-induced fluorescence (PLIF) imaging system composed of a kHz-rate multimode-pumped optical parametric oscillator (OPO) and high-speed intensified CMOS camera are investigated in laminar and turbulent CH4-H2-air flames. A multi-channel Nd:YAG cluster that produces up to 225 mJ at 355 nm with multiple-pulse spacing of 100 μs (corresponding to 10 kHz) is used to pump an OPO to produce up to 6 mJ at 431 nm for direct excitation of the A-X (0, 0) band of the CH radical. Single-shot signal-to-noise ratios of 82:1 and 7.5:1 are recorded in laminar premixed flames relative to noise in the background and within the flame layer, respectively. The spatial resolution and image quality are sufficient to accurately measure the CH layer thickness of ~0.4 mm while imaging the detailed evolution of turbulent flame structures over a 20 mm span. Background interferences due to polycyclic-aromatic hydrocarbons and Rayleigh scattering are minimized and, along with signal linearity, allow semi-quantitative analysis of CH signals on a shot-to-shot basis. The effects of design features, such as cavity finesse and passive injection seeding, on conversion efficiency, stability, and linewidth of the OPO output are also discussed.     

Fiber-optic polarizer using birefringent crystal as a cladding

A new type of fiber-optic polarizer has been developed in which the birefringent material is formed around the core fiber as a cladding. A NaNO(3) single crystal is used as the birefringent material. The extinction ratios for the polarized light are measured for fibers with cores of various radii and claddings of various lengths. The extinction ratios obtained are typically 31.2 dB for a core diameter of 6 μm and a cladding length of 6 mm.     

The write field of a ring head for a double layer perpendicular medium

The write field of a ring head used with the preferred medium for perpendicular recording (CoCr with an underlayer of softmagnetic material) is discussed and compared with the write field of a Thin- -Film Single Pole (TF-SP) head on the basis of two-dimensional calculations. It is found that the saturation of the underlayer plays an important role in the shape as well as the magnitude of the calculated write field.     

Light propagation in a planar dielectric waveguide with a gyrotropic layer

The nature of the magneto-optic Kerr effect in a planar dielectric waveguide geometry has been investigated by calculation of the Jones matrix for a planar waveguide structure with a gyrotropic magnetic material as one wall. The intensity of the component of the field that is in the polarization state orthogonal to the input was calculated as a function of length of the gyrotropic material and input polarization state. The degree of polarization rotation depends on the relative orientation of the magnetization in the magnetic material and the direction of propagation. It is found that there exists an optimal waveguide length and input polarization at which the output signal is maximized and that a significant enhancement in polarization rotation is available with respect to free-space reflection. These results indicate that a magnetic-film-bounded planar waveguide can be used for device applications such as magnetic field sensors or magneto-optic modulators.     

An efficient multi‐layer planar 3D fracture growth algorithm using a fixed mesh approach

We present a planar three‐dimensional (3D) fracture growth simulator, based on a displacement discontinuity (DD) method for multi‐layer elasticity problems. The method uses a fixed mesh approach, with rectangular panel elements to represent the planar fracture surface. Special fracture tip logic is included that allows a tip element to be partially fractured in the tip region. The fracture perimeter is modelled in a piece‐wise linear manner. The algorithm can model any number of interacting fractures that are restricted to lie on a single planar surface, located orthogonal to any number of parallel layers. The multiple layers are treated using a Fourier transform (FT) approach that provides a numerical Green's function for the DD scheme. The layers are assumed to be fully bonded together. Any fracture growth rule can be postulated for the algorithm. We demonstrate this approach on a number of test problems to verify its accuracy and efficiency, before showing some more general results. Copyright © 2001 John Wiley & Sons, Ltd.     

Thermoconvective waves in a layer with free boundaries

We show that in a thin layer of a liquid, for which the influence of its boundaries is substantial, the propagation of weakly attenuating thermoconvective waves is possible close to and beyond the stability threshold. We obtain the characteristics of weakly attenuating harmonics.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 26, No. 1, pp. 104–111, January, 1974.     

Graphene oxide (GO)-based wideband optical polarizer using a non-adiabatic microfiber

In this paper, a microfibre polarizer based on graphene oxide (GO) is proposed and demonstrated. A microfibre was coated with GO using the drop-casting technique. The extinction ratio (ER) has been measured at wideband range of 1310, 1460, 1550 and 1600 nm. The highest ER obtained in this experiment was 37.0 dB measured at 1480 nm wavelength. The result has been achieved with a GO coating thickness of 24 μm and coating length of 12 mm. This work demonstrates a polarizing effect of GO-coated microfibre.     

Influence of the layer thickness of a double-layer medium on the reproduced signal in perpendicular recording

The influence of the thickness of the layers in a single-layer or double-layer medium and of the permeability of the backlayer on the reproduced signal in perpendicular recording is investigated theoretically. With the aid of the reciprocity theorem of magnetic recording the harmonic response is calculated. For a highly permeable isotropic backlayer, the influence of its thickness proves to be small.     

Vibration in mode III of an elastic layer containing a crack perpendicular to the boundary edge

A mathematical formulation of the problem of stresses and displacements in an elastic layer which contains a crack perpendicular to the boundary and subjected to a vibrating stress, in mode III, is developed. The boundary conditions for the case of free loading at the edges of the strip are used to obtain a solution to this problem. The problem is reduced to the solution of a Fredholm integral equation. In Part II the problem describing the case of rigid constraint at the edges of an elastic strip containing a vibrating external crack in mode II is reduced to the Fredholm integral equation of the second kind. In Part III the solution of the problem describing the case of a strip containing a vibrational crack in mode III and laying on a rigid boundary is presented.

---

Résumé On développe une formulation mathématique du problème des containtes et déplacements dans une couche élastique comportant une fissure perpendiculaire au bord d'une bande et soumise à une sollicitation vibratoire de mode III. Les conditions aux limites de bord suivantes sont envisagées: (1) sollicitation libre en bordure de bande, (2) bridage sévère des bords de la bande et (3) maintien de la bande dans une fixation rigide. Dans les trois cas, le problème est ramené à la solution d'une intégrale de Fredholm.

     

Analysis of cracks perpendicular to bimaterial interfaces using a novel finite element

Inverse square root, 1/, singularity characterizes the stress field at the crack tip of homogeneous isotropic elastic media. This 1/ singularity does not, however, hold for cracks present in inhomogeneous solids; such as, a crack terminating at a right angle to bimaterial interface, which is the subject of the current paper. A few attempts have been made to treat this problem analytically. However, in view of the complexity of the resulting equations and the numerical difficulties associated with these attempts, only a very limited number of approximate solutions exist. It is therefore the objective of this study to: (i) provide a comprehensive theoretical treatment of the current boundary value problem using the eigenfunction expansion method, and (ii) to utilize the results of the eigenfunction method to develop a novel singular finite element which is capable of treating cracks terminating perpendicularly to interfaces accurately and efficiently. To establish the validity of the method, a number of test cases are examined and compared with existing simplified solutions. Furthermore, numerical examples are provided to show the effect of the elastic mismatch and crack length upon the resulting stress intensity factors and the associated stress fields.     

A cryogenic level indicator using a voltage controlled oscillator

A cryogenic level indicator, which may be used with different types of sensors (viz diodes, carbon germanium resistors etc) and for all kinds of liquid cryogens is described. The indication is given by a 2 W audio alarm. The alarm sounds as soon as the sensor is out of liquid cryogen by about 2 mm.     

Data storage and retrieval using perpendicular media andmagnetoresistive read transducer

We have investigated magnetic recording on multilayer perpendicular media using a conventional peak detect channel and a commercial magnetoresistive recording head. A finite impulse response filter was used to equalize the impulse response from perpendicular media into a unipolar pulse. Equalized pulses had a PW₅₀ of 174 nm and a D₅₀ of 131 kfei. Without write precompensation, a linear density of 204 kbits per inch (kbpi) with a 3.3 ns error window margin and a data transfer rate of 75 Mbit/s was measured with an error rate of 4×10^-7. The signal waveform was stable and had good up-down amplitude symmetry     

Viscosity measurements near a critical point using a novel torsion oscillator

A torsion-oscillator viscometer has been constructed for the measurement of the viscosity of fluids near both liquid-vapor and liquid-liquid critical points. This viscometer has a resolution of ±0.2% and operates at a low frequency (0.6 Hz) and a very low shear rate (0.05 Hz). Thus, it can be used closer to critical points than other viscometers before encountering the non-Newtonian phenomena associated with critical slowing down. This viscometer was used to study the viscosity anomaly near the consolute point of mixtures of methanol and cyclohexane along paths of constant pressure and paths of constant volume at temperatures spanning the range 10^–5 < (T-T _c)/T _c<10^–2. The data are consistent with a simple, power-law divergence of the viscosity with a multiplicative background characterized by an apparent exponent y0.041. Recent theoretical estimates for y are near 0.033. If the data are to be fit with the theoretical value of y, one must simultaneously restrict the range of the data and introduce additional unphysical parameters into the fitting function.Paper presented at the Ninth Symposium on Thermophysical Properties, June 24–27, 1985, Boulder, Colorado, U.S.A.     

Realization of integrated polarizer and color filters based on subwavelength metallic gratings using a hybrid numerical scheme

This study realizes integrated polarizer and RGB (red, green, and blue) color filters using single- and multiple-layered subwavelength metallic grating structures. A hybrid numerical scheme based on the rigorous coupled-wave analysis method and a genetic algorithm is used to determine the optimal values of the grating period, filling factor, and grating thickness of three different grating structures, namely, a single-layer grating, a double-layer grating, and a double-layer grating with a lateral shift. The optical performance of the various structures is evaluated and compared in terms of the transmission efficiency at the center wavelengths 700.0?nm, 546.1?nm, and 435.8?nm of red, green, and blue light, respectively, and the extinction ratio over the visible wavelength spectrum (380-780?nm). It is shown that the double-layer grating achieves a transmission efficiency of about 50% and an extinction ratio of around 60?dB. Thus, this grating structure provides a convenient and effective means of achieving the polarizing and filtering functions in LCD panels using a single device.     

利用混沌振子系统识别超声导波信号的仿真研究

本文提出了一种基于改进型杜芬混沌振子系统的强噪声下超声导波的识别和定位方法。首先,采用(-x3+x5)作为杜芬方程的非线性恢复力项,提高了系统的敏感性;其次,利用Melnikov方法、并结合待检测信号频率、噪声水平设置了杜芬系统参数;再次,利用驱动力幅值变化使得杜芬系统产生间歇式混沌,并将系统由大周期态向混沌吸引子过度的临界态作为检测系统。为了说明杜芬系统对噪声信号的免疫力,分析了随机噪声对系统扰动的统计特性。最后,利用导波信号对系统相轨图的显著变化识别导波信号,并提出了二分法用于识别导波发生时刻,并对输入信号的长度影响进行了讨论。仿真算例表明,利用杜芬系统相轨图对噪声和导波信号截然不同的响应特点,可以有效地检测弱导波信号,该方法对于延长导波的检测范围、以及提高微缺陷的检测灵敏度具有重要意义。     

Heat-convection waves in a semi-infinite horizontal liquid layer with free boundaries

A solution is found for the complete problem of the propagation of small-amplitude heat-convection waves in a semi-infinite horizontal layer of a thermally compressible liquid. The waves are excited by a periodically varying temperature of a vertical side wall.     

Combined effects of heat treatment and seed layer materials on magnetic properties of CoCrPt perpendicular media

Samples of glass/Ti(20 nm)/CoCrPt (20 nm)/Ti (3.2 nm) and glass/seed (Cr or Cu)/Ti(20 nm)/CoCrPt(20 nm)/Ti (3.2 nm) were deposited by magnetron sputtering at ambient temperature or 200 °C. All samples were post-annealed at 400 °C for 15 min. For either Cu or Cr seed layer, post-annealing can enhance the out-of-plane coercivity. For post-annealed samples with either Cr or Cu seed layers, the ambient temperature growth induce an enhancement in the coercivity but a reduction in the slope of hysteresis loop at the coercivity, in comparison with that of the elevated temperature growth. With identical post-annealing and growth conditions, Cr or Cu seed layers can enhance the out-of-plane coercivity, in comparison with those grown on bare substrates. The nucleation field is negative for Cr seed layer and positive for the Cu seed layer although they have close coercivity. With the same growth and post-annealing conditions, the magnetic properties of CoCrPt layers depend on the seed layer thickness. Evolution of magnetic properties can be explained in terms of changes of structural properties of constituent layers.     

Planar resonator and integrated oscillator using magnetostatic waves

A simple planar resonator using a magnetostatic wave (MSW) excited by aluminum finger electrodes with two bonding pads was realized on YIG/GGG (yttrium-iron-garnet film on a gadolinium-gallium-garnet crystal) substrate with two reflection edges. The tunable MSW resonator chip (2 mm×5 mm) exhibited a sharp notch filter response, as deep as 20-35 dB, and a high loaded Q up to 2000, which was tunable over the microwave frequency range from 2 to 4 GHz. A small tunable oscillator (8 cm³) was experimentally demonstrated using the MSW planar resonator and a silicon bipolar transistor integrated on a ceramic microwave circuit substrate. Microwave oscillation with spectral purity, at the same level as that of YIG sphere technology, was observed at 3 GHz. The experimental results indicate the technical areas where improvement must be made to realize a practical oscillator configuration