A method for determining a uniaxial magnetic anisotropy constant of monodomain particles of powdered permanent magnets

A method for determining the uniaxial magnetic anisotropy constant of monodomain particles of powdered permanent magnets is based on the M?ssbauer spectroscopy. The method is experimentally verified on a powdered permanent magnet made of barium ferrite BaFe₁₂O₁₉.     

A method for determining the fibrillar angle in wood tracheids

The predominant direction of fibrils in isolated walls of wood tracheids can be determined from observation of the extinction position in the polarizing microscope. This method cannot be used directly to obtain the fibrillar direction for separate intact cells, because the light path must traverse the opposite walls of the cell, the fibrillar angles of which are similar but of opposite sense. This difficulty may be overcome by impregnating the cell lumens with mercury and using incident (epi-) illumination with crossed polars. The incident light now passes through the upper wall of each cell, suffers reflection at the mercury surface and returns through the same wall. The extinction position gives the predominant fibrillar direction of the upper wall. The method is rapid, has been found suitable for tracheids in wood, wood pulp and paper, and should be of value for the study of other plant cells such as cotton.     

A simple method for determining the extinction ratio of strongly scattering media

In order to determine the extinction ratio k of strongly scattering media, a simple technique for instrumental elimination of the initial curvilinear part of the dependence of optical density D on medium thickness h, D(h) = D ₁ + kh, where D ₁ is the apparent optical density of the surface layers of depth h _c = 1/k (1/k is the depth of radiation penetration into the substance), is proposed. To this end, two-beam recording is used, with the sample of thickness h placed in the working cell and with the shield of thickness h ₀, made of the same material, placed in the comparison cell, provided that h _c < h ₀ < h. The extinction ratio is found from the relation k = dD/dh, where dD = D(h)-D(h ₀) is the difference of the optical densities in the working cell and in the comparison cell and dh = h-h ₀ is the difference of the thicknesses. For samples with h < h _c, two shields of thickness h ₀ are placed in each cell (in the working cell, in front of the sample and behind it) provided that h ₀ > h _c. In this case, k = dD/h, where dD = D(h + 2h ₀)-D(2h ₀).     

Evaluation of the relative quantity of residually compressed grains in steels after their plastic extension on the basis of remanent magnetization

The percentage of residually compressed grains was evaluated on the basis of previously obtained experimental data on the change in the remanent magnetization of steel upon unloading after a plastic extension. In this case, only grains in which the residual compressing stresses exceeded the initial (before plastic deformation) average internal deformations of the first type, which resulted in changing their domain structure to the easy-plane type of state, were considered.     

A polyvalent harmonic coil testing method for small-aperture magnets

A method to characterize permanent and fast-pulsed iron-dominated magnets with small apertures is presented. The harmonic coil measurement technique is enhanced specifically for small-aperture magnets by (1) in situ calibration, for facing search-coil production inaccuracy, (2) rotating the magnet around its axis, for correcting systematic effects, and (3) measuring magnetic fluxes by stationary coils at different angular positions for measuring fast pulsed magnets. This method allows a quadrupole magnet for particle accelerators to be characterized completely, by assessing multipole field components, magnetic axis position, and field direction. In this paper, initially the metrological problems arising from testing small-aperture magnets are highlighted. Then, the basic ideas of the proposed method and the architecture of the corresponding measurement system are illustrated. Finally, experimental validation results are shown for small-aperture permanent and fast-ramped quadrupole magnets for the new linear accelerator Linac4 at CERN (European Organization for Nuclear Research).     

A small-size system on permanent magnets with a field of 1.1 T

A small-size cylindrical magnetic system on Nd-Fe-B-alloy permanent magnets is described. The system has a 55-mm outer diameter, 33-mm height, and 570-g mass. It creates a 1.1-T magnetic induction in a 10-mm-long working gap. The system is made on request of the Russian Academy of Sciences’ Institute of Spectroscopy for measuring Faraday rotation. Original Russian Text ? K.L. Sergeev, 2009, published in Pribory i Tekhnika Eksperimenta, 2009, No. 2, pp. 151–152.     

The influence of biaxial elastic deformation on the coercive force and local remanent magnetization of construction steels

The influence of biaxial elastic tension-compression and tension-tension deformation on the coercive force and remanent magnetization of Cτ3 steel and 09Γ2C pipe steel cross-shaped specimens is studied. It is shown that coercive force grows monotonically with increasing load in the direction of compression under elastic tension-compression deformation and almost does not change under elastic tension-tension deformation. The local remanent magnetization decreases for all the considered types of biaxial elastic deformation. The possibility of using these methods for the evaluation of the stressed state of complexly deformed carbon steel products is discussed.     

环形薄壁分布孔的相对角度测量方法

通过对环形薄壁分布孔的原测量方法的弊端分析,提出一种适合该类孔组的测量和数据处理办法-模拟点连线法,即利用配合芯轴找出孔的模拟位置,通过作图与计算得出最终孔组间的角度。通过数据比对分析,可以确定该方法测量结论真实可靠。     

A portable scanning electron microscope column design based on the use of permanent magnets

A portable scanning electron microscope (SEM) column design is presented which makes use of permanent magnets. Simulation results predict that such an SEM column is feasible and that it can be compact. The column height is typically less than 12 cm. The column is designed to be modular, so that it can fit onto a wide range of different specimen chamber types, and can also be readily replaced.     

A method for determining the thermal EMF and thermal conductivity

A method for measuring the thermal emf and thermal conductivity of conducting samples is described. After the temperature and potential differences are measured between the sample’s ends, on which metal contacts are deposited, at a specified direct current, the current is turned off, and instantaneous values of the integral thermal emf are measured directly at the metal contacts. Using the results from measuring the temperature and potential differences during passage of the direct current, the electrical and thermal conductivities of the sample are calculated. A specific feature of this technique is the use of additional thick metal layers being in contact with the surfaces of the metal contacts at the sample’s ends, which are aimed at stabilizing the temperature gradient along the sample when the current source is switched off.     

A procedure for determining components of the specific electrical conductivity tensor of anisotropic semiconductor films

A simple procedure for determining components of the specific electrical conductivity tensor of anisotropic semiconductor films is proposed. Expressions obtained for calculating the specific conductivities are based on the solutions to the corresponding boundary electromagnetic problems; hence, they do not depend on the type of substance and can be applied for studying films of various anisotropic semiconductor materials. The presented procedure is checked by experiments.     

Quadrupole lenses on the basis of permanent magnets for a PRIOR proton microscope prototype

Four quadrupole lenses based on permanent magnets of the NdFeB material (PMQ) were developed for the imaging section for forming images of the ion-optical system of the PRIOR proton microscope prototype: the effective length of two of them is 144 mm, and the other two are 288 mm long. The field induction at the radius of the lens aperture is 1.77 Т, and the aperture is 30 mm in size. The modular design of the PMQ makes it possible to vary the length of the lenses, compensate for the offset of the magnetic axis from the ion optical axis of the microscope channel, and decrease the variation of the angular position of the magnetic medians. The PMQ magnetic field was adjusted, scanned, and its main characteristics were determined. The 3D mathematical models of the magnetic-field distribution that are obtained as a result of PMQ measurements are intended for the use in calculations of the beam dynamics during adjustment of the ion-optical system of the proton microscope and for attaining the highest spatial resolution. The developed lenses were used in the first experiments on the PRIOR facility.     

A speckle-correlation method for determining the dispersion of optical fibers and scattering parameters in optically inhomogeneous media using lasers with frequency deviation

A speckle-correlation method for determining the dispersion of short optical fibers and phase delays in multiply scattering bulk media is described. This method is based on measurements of the deterministic transverse dynamics of speckle structures in the output radiation of fibers or stationary scattering media upon tuning of the laser-radiation frequency. The range of measurements of phase delays is inversely proportional to the laser-radiation deviation and depends linearly on the fiber length or thickness of the scattering medium. Probing with radiation of tunable single-frequency quantum-dimensional laser diodes (λ = 635 nm and Δν = c/2Ln ≈ 130 GHz) and solid-state microlasers (YAG:Nd, λ = 532 nm and Δν = c/2Ln ≈ 84 GHz) allowed the dispersion to be determined in multimode (D = 50 μm and NA = 0.2) fibers with a minimum length <1 m and low-mode (D = 9 μm and NA = 0.17) fibers with a length of ～20m. The use of digital video cameras for recording scattered speckle fields during probing of fluoroplastic phantoms with a thickness of <2 cm allowed measurements of phase delays during laser frequency tuning with a deviation of several tens of gigahertz. This technique can serve as the basis for developing coherent optical tomographs.     

A proximate method for determining the refractive indices of liquids

A simple method for measuring the refractive index of liquids that fill thin-wall cylindrical cells of any diameter is described. The method is based on the light-refraction phenomenon in cylindrical lenses and is implemented using a system of lines that are regularly positioned in a plane and are observed in monochromatic light through a liquid-filled cylinder. Images of lines are turned relative to the initial orientation, and the rotation angle is unambiguously related to the refractive index of the liquid.     

A new method for determining the mechanical stability of lubricating greases

Mechanical stability is of central importance when dealing with the long-term service-length of grease-lubricated roller bearings. Poor stability will lead to consistency degradation of the grease, because of mechanical forces between the rolling parts of the bearing. The result can be leakage of grease through seals, or at worst a total failure of the bearing. The present investigation was initiated because present-day methods for prediction of mechanical stability show weak correlation with real service-length. The aim of the project was to develop a useful alternative. In order to fulfil this, both field tests and laboratory tests were carried out. In the field tests, nine different commercial greases were examined in the wheel bearings of five ore waggons, used for transporting ore by railroad from the Kiruna Mine in northern Sweden to Narvik in northern Norway for shipping to foreign markets. The test ore waggons travelled a distance of about 300,000 km during a period of 3 years. Small samples of greases were taken, on eight different occasions, for consistency testing. After the end of the test period, the damage on the bearings was also studied. In the laboratory tests, new undestroyed greases of the same brand as in the field tests were examined using conventional methods, such as the V2F, the Roll Stability Test and the Grease Worker. Comparisons between the field tests and these laboratory tests indicate poor correlation. In addition to these conventional methods, the relevance of the shear strength of the greases to the prediction of the mechanical stability was also tested. The shear stress τ_L depends on the applied pressure p, thus τ_L=τ₀+γ·p where τ₀ is the shear stress at atmospheric pressure. γ is a property of the lubricant in the same way as viscosity or density. It was found that γ correlates well with the mechanical stability in service. Increased γ values lead to a decrease in the mechanical stability. One reasonable explanation is that high γ values correspond to high shear stresses in the grease, and thus severe conditions for the thickener.     

Novel torque motor model for performance design and analysis of a servo valve with permanent magnets

Servo valves are widely used for modern hydraulic actuator control. This valve consists of a torque motor with permanent magnets. In present study, a novel torque motor model is derived by considering magnetic flux leakage and demagnetization effect of the permanent magnets involved in the servo valve. The derived model was validated by comparing experimental data with the model calculation represented with physical parameters. Since these two important physical phenomena, missing in the previously well-known model, are considered in the newly derived torque motor model, it can be used for the physical parameter design of a torque motor and the analysis of a servo valve controlling electro-hydraulic servo systems.

     

基于小波变换的纹理特征变化检测方法研究

本文提出和实验了一种基于小波变换的区域纹理特征差值的变化检测方法,该方法通过小波变换提取区域纹理特征,而后采用差值求得其变化部分.实验结果表明,该方法对于高分辨率的遥感影像具有较好的检测效果,同时提高了运算速度,从理论和实践方面证明了该方法的可行性和有效性.     

Calibration of instrument and sample parameters for small angle X-ray scattering

A method for calibrating the parameters of a small angle X-ray scattering instrument using the diffraction ring of a standard sample is presented. A generalized geometric model for small angle X-ray scattering was constructed and detailed mathematical derivations presented to solve for the relevant instrument parameters, which were then used to convert two-dimensional small angle X-ray scattering data to standard curves. The method is valid regardless whether the detector photosensitive plane is perpendicular or tilted with respect to the beam. Small angle X-ray scattering was performed using standard calibration samples to validate the methodology.     

A method for determining void arrangements in inverse opals

The periodic arrangement of voids in ceramic materials templated by colloidal crystal arrays (inverse opals) has been analysed by transmission electron microscopy. Individual particles consisting of an approximately spherical array of at least 100 voids were tilted through 90° along a single axis within the transmission electron microscope. The bright‐field images of these particles at high‐symmetry points, their diffractograms calculated by fast Fourier transforms, and the transmission electron microscope goniometer angles were compared with model face‐centred cubic, body‐centred cubic, hexagonal close‐packed, and simple cubic lattices in real and reciprocal space. The spatial periodicities were calculated for two‐dimensional projections. The systematic absences in these diffractograms differed from those found in diffraction patterns from three‐dimensional objects. The experimental data matched only the model face‐centred cubic lattice, so it was concluded that the packing of the voids (and, thus, the polymer spheres that composed the original colloidal crystals) was face‐centred cubic. In face‐centred cubic structures, the stacking‐fault displacementvector is . No stacking faults were observed when viewingthe inverse opal structure along the orthogonal <110>‐type directions, eliminating the possibility of a random hexagonally close‐packed structure for the particles observed. This technique complements synchrotron X‐ray scattering work on colloidal crystals by allowing both real‐space and reciprocal‐space analysis to be carried out on a smaller cross‐sectional area.     

A method for determining dislocation Burgers' vectors in ice

It is shown that the usual method of Burgers' vector analysis in the Transmission Electron Microscope (TEM) using invisibility criteria is unlikely to succeed for ice. A method is outlined using a novel application of computer-simulated imaging which can be used to perform such an analysis.