Crystal Sheet Research Articles

Magnetostriction and Domain Structure of Grain Oriented Silicon Steel Sheets

The deformations by magnetostriction were measured on 3%Si–Fe (110) single crystal sheets with various deviation angles between the longitudinal direction and [001] axis. In the samples with small deviation angle contract in small field and expand in larger field. This result indicates 4th harmonic vibration will occur in the corner of transformer cores. The deformation is larger than that considering displacement of 180 degree wall followed by rotation magnetization. The deformation was explained by a domain structure composed by 90 degree domain walls.

Heat transfer and fluid flow of natural convection along a vertical flat plate in the transition region: experimental analysis of the wall temperature field

Heat transfer and fluid flow of natural convection along a vertical flat plate were experimentally investigated in the transition region. Local heat transfer coefficients along a vertical flat plate were measured to distinguish the first transition region. The wall temperature and fluid flow were then visualized using a liquid crystal sheet and water-soluble fluorescent paint. Also discussed are the characteristic statistical quantities with the aid of visualizations for the velocity and temperature fields. It was revealed from a series of experiments that horseshoe-shaped low-temperature patterns appear on the wall and that they play a significant role in heat transfer. When the data was ensemble-averaged it was found that the characteristic time-and-space scales of the patterns are statistically independent of not only heat flux but also the position in which they occur. Moreover, W-shaped flow patterns, which possess three-dimensional and unstable structures, appear in the near-wall region. They play a significant role in the laminar to turbulent transition.

Phase contrast using photorefractive LiNbO_3:Fe crystals

We theoretically and experimentally study phase contrast using a photorefractive LiNbO(3):Fe crystal sheet and realize the high-performance phase contrast operation using C-cut LiNbO(3):Fe crystal sheets in which the photovoltaic effect plays an important role. We estimate the maximum photovoltaic field in LiNbO(3):Fe using the phase contrast method.

Formation of slip traces during recrystallization of thin metal sheets

Abstract During a study of the mechanical properties of polycrystalline Ni3Al produced by recrystallizing B-free Ni3Al single crystals, it was discovered that {111{ slip traces formed during grain growth of cold–rolled single crystal thin sheets annealed at 1200°C for 10 hours. Grain growth stops when the slip starts. The slip traces are revealed by the formation of thermal grooves at 1200°C. The formation of slip traces seems to be a general phenomenon during the recrystallization of thin sheets of metals, as slip traces also formed on cold–rolled polycrystalline Cu thin sheets annealed at 922°C for 10 hours. It is proposed that the residual strains/stresses in the thin recrystallized sheets are responsible for the slip processes and also provide a primary driving force for grain growth. Slip begins when the grain size has increased to the point where the yield stress, as determined by the Hall‐Petch relation, equals the residual stress. As the residual stresses and strains are relieved by the slip, grain growth stops, and the traces seen in this study are produced. The resulting grain size can be controlled by changing the level of the yield stress or the residual stresses thereby changing the critical grain size at which the two stresses are equal. Thus thinner specimens will have a smaller grain size because the yield stress decreases with decreasing sample thickness in sheet specimens. Other factors, such as annealing temperature or amount of cold–work also directly influence the final grain size.

Heat Transfer and Flow Characteristics of an Oblique Turbulent Impinging Jet Within Confined Walls

Experiments were conducted to determine the turbulent heat transfer and flow characteristics of an oblique impinging circular jet within closely confined walls using air as a working fluid. The local temperature distribution on the impingement surface was obtained in detail by a thermocamera using a liquid crystal sheet. A correction to the heat flux was evaluated by using the detailed temperature distribution and solving numerically the three-dimensional equation of heat conduction in the heated section. Two-dimensional profiles of the local Nusselt numbers and temperatures changed with jet angle and Reynolds number. These showed a peak shift toward the minor flow region and a plateau of the local heat transfer coefficients in the major flow region. The local velocity and turbulent intensity in the gap between the confined insulated wall and impingement surface were also obtained in detail by a thermal anemometer.

135 ディジタルカラー画像解析による低温壁面上の温度分布の測定

A color image processing technique has been applid to measure the temperature on a wall cooled by a cold air jet. Temperature distribution on the wall was visualized by a thereto-sensitive liquid crystal sheet. To achieve the color image analysis, the optical characteristics affecting to the temperature measure-ments, e.g, intensity of refractive light, relative angle between camera, crys-tal sheet and illumination, media configurations between camera and the crystal sheet, were quantitatively evaluated. The reflected colors from the liquid crys-tal-sheet were captured through a 3-tips color TV camera and the temperature distribution was obtained through a neural network color-temperature calibration scheme. This color image analysis is capable of measuring the spatial distribu-tion of mean temperature on the wall.

On the conformational and packing behaviour of acyclic sugar amphiphiles: The crystal structures of [formula omitted] and [formula omitted] and the supramolecular assembly-forming properties of [formula omitted

The crystal structure of N-(1- octyl)- d-arabinonamide [space group P2 1, a=4.855(3) A ̊ , b=30.45(3) A ̊ , c=10.59(1) A ̊ , β=94.46(6)° ] shows two independent molecules arranged in an antiparallel manner in the asymmetric unit. Their head groups and octyl chains are extended, but the overall shape of the molecules is different. The packing arrangement in the crystal, with interdigitating head groups and oligomethylene tails, has never been observed before with aldonamides, but is identical with that of the glucitol amphiphile MEGA-8. Comparison of the packing of the arabinonamide molecules in the crystal with that of other amphiphiles crystallizing in an antiparallel arrangement reveals a similar behaviour, suggesting a common mechanism of crystallization for these compounds. N-(1- Dodecyl)- d-ribonamide [space group P1, a=4.815(2) A ̊ , b=5.464(2) A ̊ , c=18.084(4) A ̊ , a=81.77(2)°, β=87.78(3)°, γ=83.83(3)° ] displays one molecule in the asymmetric unit. It exhibits two straight-chain segments from C-2 to C-5 and C-2 to C-14, respectively, and shows an unexpected 1,3-syndiaxial interaction between C-1, the carbonyl carbon atom, and O-4. The hydrogen-bond patterns involve a quadrilateral homodromic cycle between between four molecules related by translation along the two 5 Å axes. The molecular packing is head-to-tail as observed in the crystal structures of amphiphilic gluconamides displaying an analogous homodromic cycle. It has been shown earlier that N- octyl- d-gluconamide forms solid micellar fibers in water, whereas the analogous ribose derivative investigated in this paper forms planar bilayer sheets instead of micellar threads, although the molecular interactions in the crystal sheets are similar to those in gluconamide. N- Octyl- d-arabinonamide , on the other hand, forms ill-defined tubular bilayers.

矩形狭流路内膜冷却挙動

Film cooling behavior in thin rectangular channel was studied experimentally by using water. The film thickness and the wall temperature distribution were visualized with an ink and a thermochromic liquid crystal sheet, respectively. The wavy temperature distributions on the wall just after injection slit was observed in spite of the two-dimensional film. The empirical film cooling model by Goldstein et al., which was developed based on gas flow, failed to predict the film cooling effectiveness using water. The k-e low Reynolds number turblent model predicted well the experimental results of the relatively low injection rate but overestimated the film cooling effectiveness at the higher injection rate. The overestimation was considered to be due to the underestimation of fluid mixing near the wall in the model.

Characteristics of Heat Transfer and Fluid Flow in the Rectangular Duct with a Rotating Cylinder.

An experimental investigation was performed to study the effect of a rotating cylinder near the wall of a rectangular duct on heat transfer coefficient and fluid flow of forced convection. Local heat transfer coefficients were first measured by varing the rotational speed and the distance between cylinder and wall. The results showed that the positions of maximum and minimum in the profiles of the heat transfer at a fixed distance from the wall were almost invariable even when the cylinder was rotating. The wall temperature and fluid flow were also visualized using a liquid crystal sheet and fluorescent paint. It was noted that low-temperature streaks appeared on the wall, and that they strongly affected heat transfer characteristics. It was further determined that the position of the reattachment shifted upstream as rotational speed increased.

Distribution of the satellite reflections of the modulation and its thermal stability in single-crystal Bi2Sr2CaCu2Oy

The satellite distribution around the main reflections of the incommensurate modulation in Bi2Sr2CaCu2Oy has been studied by means of x-ray diffraction on a number of single crystals. The presence of the forbidden reflections which are incompatible with a B-centered Bravais lattice is found to be correlated with the spread of the mosaic blocks in the crystal sheet and therefore spurious to the distribution of the satellite reflections in the reciprocal space. Diffraction data collected for a highly oriented crystal annealed in flowing nitrogen at 650 °C for 60 h have shown that the structural modulation is coherent with the Bi2Sr2CaCu2Oy phase and robust to the anneal. Relationships between superconductivity, structural modulation, and oxygen content in the compound are discussed.

Planform structure of turbulent Rayleigh-Bénard convection

The planform structure of turbulent Rayleigh-Bénard convection is obtained from visualising a liquid crystal sheet stuck to the bottom hot surface. The bottom plate of the convection cell is Plexiglas and the top plate is glass. Water is the 3est liquid and the Rayleigh number is 4 × 10 7. The planform pattern reveals randomly moving hot streaks surrounded by cold regions suggesting that turbulent Rayleigh-Bénard convection is dominated by quasi-two-dimensional randomly moving plumes. Simultaneous temperature traces from two vertically separated thermocouples indicate that these plumes may be inclined forward in the direction of horizontal motion. The periodic eruption of thermals observed by Sparrow et al [3] and which forms the basis of Howard's model is not observed.

Low-Frequency Relaxation Spectrum of La 2 CuO 4 Oxide Compound

La_2CuO_4, the parent compound of the La system high-temperaturesuperconductors, can be rendered superconducting at～40 K by substituting A~(2+)(A=Ca, Sr, Ba) at La~(3+) sites or introducing excess oxygen to compound by annealingunder high oxygen pressures as well as other treatments. It is a hard Moot insulatorof which crystal cells contain Cu-O sheet, and 3D antiferromagnetic property has

Noise suppression for photorefractive image amplification in the LiNbO3:Fe crystal sheet

The dependence of competition between the forward scattering light and climbing light in the LiNbO3:Fe crystal sheet on the incident angle of the pump light beam is discussed. On the basis of the light climbing and beam size effects, a new method for a low-noise, high-gain image amplification in thin crystal is described.

FDTD simulation of microwave sintering of ceramics in multimode cavities

Microwave sintering of ceramics in multimode cavities, particularly the use of picket-fence arrangements, has recently received considerable attention. Various types of ceramics have been successfully sintered and, in some cases, a desirable and unique effect has been observed. At present, various aspects of the sintering profess such as preparation of sample sizes and shapes, types of insulations, and the desirability of including a process stimulus such as SiC rods are considered forms of art and highly dependent on human expertise. The simulation of realistic sintering experiments in a multimode cavity may provide an improved understanding of critical parameters involved and allow for the development of guidelines towards the optimization of the sintering process. In this paper, we utilize the FDTD technique to model various geometrical arrangements and material compatibility aspects in multimode microwave cavities and to simulate realistic sintering experiments. The FDTD procedure starts with the simulation of a field distribution in multimode microwave cavities that resembles a set of measured data using liquid crystal sheets. Also included in the simulation is the waveguide feed as well as a ceramic loading plate placed at the base of the cavity. >

Light-climbing effect in LiNbO_3:Fe crystal

The light-climbing effect in a LiNbO(3):Fe crystal sheet was experimentally studied, and the mechanism for light climbing proposed was proved to be correct. The relevant optical properties were investigated.

A dipole-type intracavitary hyperthermic applicator with a metallic reflector: experiments and theoretical analysis.

A water-cooled electromagnetic (EM) dipole, for intracavitary hyperthermia, embodying a metallic reflector to give directional characteristics to the SAR and then to the heating pattern in the biological tissue, is considered. The influence of the reflector on the SAR deposition has been theoretically modelled with an EM analysis which uses the method of moments (MOM). A thermal model, based on the heat transfer equation, is used to predict temperature distribution, which exhibits a directivity related to the angular extension of the reflector. Experiments have been carried out in a polyacrylamide phantom. The temperature distribution detected with a liquid crystal sheet shows fairly good agreement with theoretical predictions.

ANISOTROPIC LIGHT-INDUCED SCATTERING BY PHOTOREFRACTIVE FOUR-WAVE MIXING IN c-CUT LiNbO3:Fe CRYSTAL SHEET

A new kind of anisotropic photorefractive light-induced diffracted ring pattern——ovallike pattern in c-cut LiNbO 3 :Fe crystal sheet is observed and a mechanism of four-wave mixing induced by the incident light and its strong backward scattered light is proposed to explain the experimental results.

Observation of the modulated structure in Bi 2Sr 2CaCu 2O y single crystals by using an X-ray rotating-anode diffractometer

With a conventional X-ray rotating-anode diffractometer, structure characterization of a pure and highly oriented Bi 2Sr 2CaCu 2O y single crystal sheet with large dimensions of 5×1.8×0.03 mm 3 has been conducted. Incommensurate satellites corresponding to a modulation 0.21 b ∗+ c ∗ have been observed up to second order. Apart from the asymmetry in intensities of the symmetrically located satellites, we revealed one more characteristic of the modulated structure, that the satellites are stretched along the c ∗ direction to form poles in reciprocal space. The technique used is suggested to be convenient and practical for studies concerning especially the modulations for large crystals.

Natural convection of a magnetic fluid in a cubic enclosure

Laminar natural convection heat transfer of a magnetic fluid in a cubic enclosure is examined experimentally. Wall-temperature distributions are visualized by thermosensitive liquid crystal sheets. The effect of the magnetic field on the transient temperature distributions, and the local and averaged Nusselt numbers are discussed.

The visualization of RF probe electric fields

An assembly of resistive paper and liquid crystal sheet, conveniently and cheaply constructed for visual detection of the electric fields associated with an rf probe, is presented. Electrical asymmetries, and "hot-spots" usually associated with conservative electric fields, are easily visualized by the color patterns displayed. The device is of considerable assistance in probe design and the minimization of dielectric loss.