Size distribution of magnetite nanoparticles in disperse systems

The histogram for the size distribution of magnetite nanoparticles in a disperse system has been shown to be close to the frequency polygon. The parameters of the histogram have been optimized by least squares. The optimized histogram more accurately represents the size distribution of the nanoparticles and can be used to adequately evaluate the moments and parameters of the distribution and the magnetization of the system. Original Russian Text ? R.A. Ali-zade, 2008, published in Neorganicheskie Materialy, 2008, Vol. 44, No. 2, pp. 210–215.     

Magnetostatic analog for the calculation of phase contours inelectron holography of magnetic films

A method is presented for predicting the electron holographic interference pattern from a given magnetization distribution, and it is explained how phase contours can be sketched using magnetostatic intuition. The presented method is derived from the classical Lorentz force and the de Broglie relation between momentum and wavelength. The calculation of the electron phase to a two-dimensional magnetostatics problem is also mapped to which engineering experience and familiar mathematical methods can be applied. The result is considered simple to state and to remember     

Stretching and distortion of a photosensitive polymer film by surface plasmon generated near fields in the vicinity of a nanometer sized metal pin hole

Here we demonstrate how a surface plasmon (SP) generated near field pattern in the vicinity of a nano-scale pin hole can be used to generate reversible topography changes in a photosensitive polymer film above the opening. This can be achieved by simply changing the polarization state of the plasmon generating incoming light. In the case of linear polarization, the near field intensity pattern causes the film to laterally expand/contract according to the direction of the polarization. For circular polarization, two pronounced rims corresponding to maxima in the topography are observed. In all cases, the topographical variation is in close agreement with the SP intensity distribution computed from finite difference time domain simulation. Our results demonstrate the versatility of using SP near fields to imprint a variety of structures into photosensitive polymer films using only a single metallic mask.     

Spectral and polarization characteristics of the nonspherically decaying radiation generated by polarization currents with superluminally rotating distribution patterns

We present a theoretical study of the emission from a superluminal polarization current whose distribution pattern rotates (with an angular frequency omega) and oscillates (with a frequency Omega) at the same time and that comprises both poloidal and toroidal components. This type of polarization current is found in recent practical machines designed to investigate superluminal emission. We find that the superluminal motion of the distribution pattern of the emitting current generates localized electromagnetic waves that do not decay spherically, i.e., that do not have an intensity diminishing as RP(-2) with the distance RP from their source. The nonspherical decay of the focused wave packets that are emitted by the polarization currents does not contravene conservation of energy: The constructive interference of the constituent waves of such propagating caustics takes place within different solid angles on spheres of different radii (RP) centered on the source. For a polarization current whose longitudinal distribution (over an azimuthal interval of length 2pi) consists of m cycles of a sinusoidal wave train, the nonspherically decaying part of the emitted radiation contains the frequencies Omega +/- momega; i.e., it contains only the frequencies involved in the creation and implementation of the source. This is in contrast to recent studies of the spherically decaying emission, which was shown to contain much higher frequencies. The polarization of the emitted radiation is found to be linear for most configurations of the source.     

Polarization imaging by use of digital holography

We present what we believe to be a new digital holographic imaging method that is able to determine simultaneously the distributions of intensity, phase, and polarization state at the surface of a specimen on the basis of a single image acquisition. Two reference waves with orthogonal polarization states interfere with the object wave to create a hologram that is recorded on a CCD camera. Two wave fronts, one for each perpendicular polarization state, are numerically reconstructed in intensity and phase. Combining the intensity and the phase distributions of these two wave fronts permits the determination of all the components of the Jones vector of the object-wave front. We show that this method can be used to image and measure the distribution of the polarization state at the surface of a specimen, and the obtained results indicate that precise quantitative measurements of the polarization state can be achieved. An application of the method to image the birefringence of a stressed polymethyl methacrylate sample is presented.     

Large-area hard magnetic L10-FePt nanopatterns by nanoimprint lithography

Large-area hard magnetic L1(0)-FePt nanopatterns with out-of-plane texture were fabricated by using a top-down approach. For the fabrication process, ultraviolet nanoimprint lithography (UV-NIL) in combination with inductively coupled plasma reactive Ar-ion etching was used. By this technique a continuous L1(0)-Fe(51)Pt(49) film was nanostructured into a regular arrangement of nanodots over an area of 4 mm(2). The dot dimension and distribution was specified by the stamp, resulting in a dot size of 60 nm and a periodicity of 150 nm. For the large-scale L1(0)-FePt nanopatterns, huge coercivities up to 4.31 T could be achieved. By means of magnetic force microscopy it could be verified that the nanodots were magnetically decoupled from each other and occurred in the single-domain state with perpendicular magnetization.     

Current states and domains in systems with electron-hole pairing

Nonlinear collective excitations and inhomogeneous states of the excitonic phase are examined with the interband transitions of pairing particles taken into account. We obtain a Ginzburg-Landau-like equation and find the necessary conditions for a second-order phase transition to take place. The nonlinear equation describing the excited (inhomogeneous) state of the system in a simple case appears to be the Sine-Gordon equation. It is shown that domains of magnetization or polarization appear in the excited state of the excitonic antiferromagnetic or antiferroelectric. There are also other excited states, where the charge density coexists with the magnetization density. The collective excitations are manifested as nonlinear magnetization or polarization waves, moving domains of magnetization, etc.     

蒸压加气混凝土孔结构表征的图像分析方法

采用数码相机采集图像.利用Matlab将加气混凝土砌块断面照片转化为灰度照片,并对照片进行去噪、直方图均衡化、二值化处理,采用图像分析法实现了对蒸压加气混凝土的宏观孔孔隙率、孔面积及其分布等孔结构特征的计量.分析结果表明,基于Matlab图像分析法可以对蒸压加气混凝土的孔结构进行初步的量化表征,但限于所采用数码相机的分辨率,该方法只适合表征蒸压加气混凝土中的宏观孔.通过改进程序分辨能力、相片拍摄技巧以及样品准备与处理方法可以大幅减小图像分析法的表征误差,提高方法的准确性.     

Mechanism and symmetry properties of depolarization in weak scattering of light

The mechanism and some symmetry properties of depolarization upon weak scattering of light from a class of random media were studied theoretically. Departing from the angular distribution of the degree of polarization, our derivations showed the mechanism that induces the change of polarization can be split into two parts of different nature. One is the vectorial effect that redistributes the original light components, and the other is the interaction effect of the medium that modulates the correlation properties of the incident field. We also showed that there is dependence of the angular distribution on the incident polarization state; i.e., the angular pattern and its symmetry depend on both the orientation and ellipticity of the incident polarization. Random light was analyzed in the space-frequency domain.     

Investigation of temperature-dependent polarization, dielectric, and magnetization behavior of multiferroic layered nanostructure

The PbZr_0.53Ti_0.47O₃(PZT)/CoFe₂O₄(CFO) layered nanostructures show lowering of dielectric constant and polarization, and an enhanced magnetization with a decrease in temperature from 400 K to 100 K. The temperature dependence of the real part of the dielectric constant illustrates a step-like behavior, whereas the imaginary part gives a relaxation peak near the step maxima temperature. A slow decrease in the polarization was observed from 300 K to 200 K, with an eventual collapse of polarization at ~ 100 K, and a complete polarization recovery with heating, these phenomena is reproducible over cycles of experiment. Remanent magnetization of the layered nanostructure was found to be three times higher at 100 K than that at room temperature. There is a slow enhancement in remanent (internal) magnetization with lowering of temperature, resulting in slow polarization switch and finally the collapse. The temperature-dependent dielectric, polarization and magnetization were different from the parent layer, indicating a kind of dynamic magneto-electric coupling in the layered nanostructures.     

Theory of magnetographic printing

The magnetic force of attraction between a recording surface and magnetic particles (the "developer" or "toner") is analyzed. The recording medium is assumed to be magnetically hard, the toner particles to be magnetically soft. The distribution of recording magnetization is taken to be periodic in the interior of an image area and uniform in an image free area. The toner particles are assumed to be part magnetic, part nonmagnetic material. In most of the calculations it is assumed that the magnetic susceptibility of the toner particles is small compared to unity. In the interior of an image area the force density has primarily a component perpendicular to the recording plane. This component decreases exponentially with distance from the recording plane, if the distribution of magnetization is sinusoidal. Near the edge of an image area the force density also has a tangential component, but this is generally smaller than the normal component. For toner particles with similar internal structure the force per unit mass always decreases with increasing particle size. Considered as a function of recording wavelength (at constant particle size) it shows a maximum at a wavelength comparable to the particle diameter.The force acting on a small particle (simeq 10mum) in the immediate vicinity of the recording surface can be several hundred times the force of gravity. The implications of these results in regard to color printing are discussed.     

Distortion of inductive read head signal due to side-writtenmagnetization

We apply a Fourier series model to calculate distortion in an inductive read head signal due to side-written magnetization patterns in thin-film magnetic recording media. This model predicts that a magnetization pattern consisting of in-track longitudinal and transverse track edge magnetizations will produce a signal distorted by the flux from the side magnetization. By using parameters obtained from a direct magnetic image of the patterns, this analysis predicts the morphology and magnitude of signal distortion as a function of pattern dimensions. The implication of this distortion for higher bit densities suggested for the future was found to be significant. The proposed method will offer reliable means to quantitatively assess the effect of side writing at such densities     

Image analysis measurements of duplex grain structures

Several types of duplex grain size distributions in five different alloys were evaluated using image analysis. Most of the grain structures contained annealing twins. Those with straight interfaces could be recognized and deleted from the image, leaving only grain boundaries. One specimen exhibited curved twin boundaries, caused by deformation, and they could not be discriminated by the system as currently programmed. Grain areas were measured and grouped according to their relationship to the ASTM grain size scale. An area-weighted histogram was shown to be excellent for revealing the nature of the distribution, while a numerical-frequency histogram was insensitive. The intersection of these two curves separated only one of the four bimodal distributions. A deconvolution approach, using the area-weighted curve only, should be evaluated. An arithmetic grain area classification approach using 25 classes based on the data range, to split the two grain area populations based upon the intersection of the number percent and area percent curves, worked well for two of the four specimens. Image analysis detection of grains results in a small portion of the image (about 6–12%) assigned to the grain boundaries. In manual measurement methods, the area occupied by the grain boundaries is not considered, and it does not influence measurements. Thus, compared to manual methods, image analysis undersizes grains slightly producing a relatively small positive bias in the grain size number, which could be ignored, but can be eliminated or reduced.     

基于背景代表色提取的迷彩伪装颜色选取算法

为了达到好的伪装效果,迷彩颜色应与背景色调相融合,以使人眼及光学仪器难以探测和分辨.因此,背景主色的准确提取是确定迷彩颜色的前提.利用灰度直方图可以确定背景图像中的主要灰度,但无法区分不同色调.而基于颜色直方图的背景主色提取方法的运算量太大.本文提出了一种基于HSI模型和量化颜色直方图的迷彩颜色选取算法.利用HSI颜色模型描述背景颜色特性,通过特殊量化方式对背景的颜色直方图进行量化,接着借助阈值方法选取背景主色作为迷彩颜色.结合迷彩伪装图案设计方法对上述迷彩颜色选取算法进行了实验分析,并通过边缘检测和相关跟踪方法对不同背景下的目标迷彩伪装效果进行了验证.     

Quantitative Error Assessment in Pattern Matching: Effects of Intensity Pattern Noise, Interpolation, Strain and Image Contrast on Motion Measurements

Abstract: Basic concepts in probability are employed to develop analytic formulae for both the expectation (bias) and variance for image motions obtained during subset‐based pattern matching. Specifically, the expectation and variance in image motions in the presence of uncorrelated Gaussian intensity noise for each pixel location are obtained by optimising a least squares intensity matching metric. Results for both 1D and 2D image analyses clearly quantify both the bias and the covariance matrix for image motion estimates as a function of: (a) interpolation method, (b) sub‐pixel motion, (c) intensity noise, (d) contrast, (e) level of uniaxial normal strain and (f) subset size. For 1D translations, excellent agreement is demonstrated between simulations, theoretical predictions and experimental measurements. The level of agreement confirms that the analytical formulae can be used to provide a priori estimates for the ‘quality’ of local, subset‐based measurements achievable with a given pattern. For 1D strain with linear interpolation, theoretical predictions are provided for the expectation and co‐variance matrix for the local displacement and strain parameters. For 2D translations with bi‐linear interpolation, theoretical predictions are provided for both the expectation and the co‐variance matrix for both displacement components. Theoretical results in both cases show that the expectations for the local parameters are biased and a function of: (a) the interpolation difference between the translated and reference images, (b) magnitude of white noise, (c) decimal part of the motion and (d) intensity pattern gradients. For 1D strain, the biases and the covariance matrix for both parameters are directly affected by the strain parameter p₁ as the deformed image is stretched by (1 + p₁). For 2D rigid body motion case, the covariance matrix for measured motions is shown to have coupling between the motions, demonstrating that the directions of maximum and minimum variability do not generally coincide with the x and y directions.     

基于卷积神经网络的印刷品颜色缺陷检测

目的 提取样本图像颜色直方图特征对卷积神经网络进行训练,达到快速、高准确率检测图像颜色缺陷的目的.方法 将标准图像从RGB颜色空间转换至HSV颜色空间,通过改变图像H,S,V三分量值获取训练样本和测试样本;在HSV颜色空间中非均匀量化图像的颜色直方图,得到所有训练样本和测试样本的颜色直方图特征;利用样本图像颜色直方图特征训练卷积神经网络,然后对测试样本进行检测,研究检测的速度、准确率,并将该检测方法与逐像素、超像素、BP神经网络和支持向量机方法进行对比.结果 对于图片尺寸为512×512的彩色图像,卷积神经网络检测单幅图片的平均检测时间约为57.66 ms,训练样本图像为50000张时,卷积神经网络方法对10000张测试样本进行检测的准确率为99.77％.结论 卷积神经网络方法在保证高准确率的前提下大幅提高检测精度,对于印刷品色差缺陷在线检测具有良好的应用价值.     

Image indexing by Color Plane Moment

Among the features of content‐based image retrieval, color features provide important clues to search similar image contents. In addition to color, there exists more information in the image. In this article, we propose a new method for content‐based image retrieval: Color Plane Moment (CPM). This method combines colors' content and their spatial distribution to improve image query results. It integrates the ideas of color histogram, backprojection, and moments. The CPM uses backprojection as one of the image preprocessing methods and computes the invariant moments with those dominant color plane images after preprocessing. There are several dominant colors chosen by color histogram in an image, and each can be expressed by seven invariant moment values that represent spatial distribution of those dominant color planes, respectively. Simulation results demonstrate that the proposed technique outperforms the other techniques. © 2002 Wiley Periodicals, Inc. Int J Imaging Syst Technol 12, 139–148, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10022     

Scaling of the equilibrium magnetization in the mixed state of type-II superconductors

We discuss the analysis of mixed-state magnetization data of type-II superconductors using a recently developed scaling procedure. It is based on the fact that, if the Ginzburg-Landau parameter κ does not depend on temperature, the magnetic susceptibility χ(H,T) is a universal function of H/H_c2(T), leading to a simple relation between magnetizations at different temperatures. Although this scaling procedure does not provide absolute values of the upper critical field H_c2(T), its temperature variation can be established rather accurately. This provides an opportunity to validate theoretical models that are usually employed for the evaluation of H_c2(T) from equilibrium magnetization data. In the second part of the paper we apply this scaling procedure for a discussion of the notorious first order phase transition in the mixed state of high-T_c superconductors. Our analysis, based on experimental magnetization data available in the literature, shows that the shift of the magnetization accross the transition may adopt either sign, depending on the particular chosen sample. We argue that this observation is inconsistent with the interpretation that this transition always represents the melting transition of the vortex lattice.     

One-dimensional-based automatic defect inspection of multiple patterned TFT-LCD panels using Fourier image reconstruction

Thin film transistor-liquid crystal display (TFT-LCD) has been used in a wide range of electronic devices. For large-sized and high-density TFT-LCD panel inspection, a high-resolution line scan is demanded. A TFT-LCD panel image at a fine resolution presents very complicated patterns with less regularity. The paper proposes a non-referential defect detection scheme that directly works on the one-dimensional (1D) line images using the Fourier image reconstruction. The 1D grey-level line image is first divided into small segments, each of the length of the repeated period for a given TFT-LCD panel. The divided segments are then combined as a two-dimensional (2D) image. The frequency components corresponding to the 1D background pattern can be easily identified in the 2D Fourier spectrum. By eliminating the frequency components in the 2D Fourier spectrum that represent the periodic structural pattern of the combined 2D image and then back-transforming the image using the inverse Fourier transform, the 2D Fourier reconstruction process can effectively remove the complicated background pattern and well preserve local anomalies. Experimental results on a number of micro-defects embedded in different patterned regions of TFT-LCD panels show that the proposed method can reliably detect various ill-defined defects.     

Ferroelectric and magnetic properties of multiferroic BiFeO(3)-based composite films

BiFeO(3)-based composite films were fabricated onto the Pt/Ti/SiO(2)/Si(100) substrates by a chemical solution deposition (CSD) method using the precursor solutions with various excess iron composition followed by annealing at 923 K for 30 minutes under oxygen gas flow. Coexistence of spontaneous magnetization and remanent polarization could be obtained in the BiFeO(3)-based composite films with high excess iron composition. The remanent magnetization of almost 20 emu/cm(3) and the magnetic coercive field of 1.5 kOe were obtained at the iron composition ratio of Fe/Bi = 1.25. In this specimen, the remanent polarization at 90 K was approximately 10 microC/cm(2) at the electric field of 1500 kV/cm. Structural analysis suggested that the remanent polarization has a possibility to increase by suppressing the formation of the secondary phases of Bi(2)Fe(4)O(9) and alpha-Fe(2)O(3), these are the nonferroelectric material as well as antiferromagnetic phase.