Papers by Keyword: Spatial Resolution

Abstract: Effects of magnetic material, coating thickness, and tip radius on the magnetic force microscope (MFM) spatial resolution and the switching field have been investigated. MFM tips are prepared by coating soft and hard magnetic materials on non-magnetic Si-base tips. MFM spatial resolutions better than 8 nm are obtained by optimizing the coating layer thickness at around 20 nm on the Si tips with top radius of 3 – 5 nm. The switching field can be increased greater than 1 kOe by coating a high-K_u magnetic material and by increasing the coating thickness. The tips are successfully applied to the observations of magnetic thin films which include magnetization structures less than 20 nm in length.

Abstract: With the rapid development of DOA (direction-of-arrival) estimation methods, the existing beamforming technologies still have the problem of a way to balance high spatial resolution and robust performance. The aperture extension characteristics of fourth-order cumulants is used to raise the spatial resolution of the array in this paper. By using the structure of minimum redundancy array, the calculation of the fourth-order cumulants matrix can be reduced. Simulations of the properties of fourth–order cumulants beamforming method are analyzed in this paper, including the resolution analysis, multi-sources analysis and error analysis. Simulation results show that the fourth-order cumulants beamforming method has a higher spatial resolution than the conventional beamforming method without increasing the number of the array sensors.

Abstract: In recent years, the demand for high spatial resolution in X-ray residual stress analysis has drastically increased. The locations of interest are frequently small foot radii of teeth of gears. Also the inner surface of holes or hollow cylinders in general with small diameter must be investigated after opening the cylindrical cavities. In resolving such measuring problems, significant progress has been made in reproducibly manufacturing and applying glass capillary X-ray optics. With focusing elliptical polycapillaries and conventional laboratory X-ray sources, spot sizes of few 10 μm can be realized at sufficiently intensities for residual stress analyses. However, glass capillary optics require refined alignment strategies which are completely different from those for conventional beam shaping optics. Moreover, the small spot sizes cannot be aligned and positioned on the sample surface by eye. Microscopy fixtures are required. Finally, measurements in small radii result in high precision requirements for the diffractometers as well as for the sample positioning in axes and directions which are significantly less relevant when measuring on plane surfaces. The specific requirements resulting from residual stress analyses with high spatial resolution using glass capillaries and small spot sizes at curved surfaces are described and discussed.

Abstract: Magnetic force microscope (MFM) tips are prepared by coating Si tips of 4 nm radius with [Co (1 nm)/M(1 nm)]₂₀ (M = Pt, Pd, Ni) multilayer films. An MFM tip prepared by coating 40-nm-thick Co film is employed as a reference tip. The influences of M layer material on the spatial resolution and the switching field of MFM tip are investigated. The spatial resolutions of Co/M multilayer coated tips are estimated to be within 9.4 ± 0.3 nm for all the M materials, which is about 6% inferior to that of Co coated tip (8.8 nm). Higher switching fields of 1425 and 825 Oe are respectively observed for the tips coated with Co/Pt and Co/Pd multilayers, whereas the field of tip coated with Co/Ni multilayer is 275 Oe which is similar to that of Co coated tip (325 Oe). The switching field is influenced by the magnetic anisotropy of multilayer film. An MFM tip coated with Co/Pt multilayer film is useful to observe the magnetic domain structure of permanent magnets and magnetic recording media.

Abstract: In the work digital x-ray apparatus on the basis of the gas-discharge linear detector is considered. X-ray images of laboratory rats are presented. Application prospects of gas-discharge detectors as a solution of the up-to-date radiographic problems are deduced.

Abstract: The paper presents the construction of the sensor array and do research on the spatial resolution of EMT system. As it directly determines the detection performance of the system. Rigorous experiment schemes have been designed to test and verify the spatial resolution of EMT system. And then, the application performance of the EMT system is shown.

Abstract: Spatial resolution is an important parameter in distributed optical fiber Raman temperature sensor system (DOFRTS). In this paper, a 10 kilometers long DOFRTS with spatial resolution of about 6 meters is constructed. The spatial resolution is limited by electrical bandwidth of the photodetector circuit and the data acquisition part. The abrupt temperature changes along the fiber axis are treated as temporal pulse signals, and a linear amplitude coefficient modification algorithm is used to improve the spatial resolution. The experimental results show that the temperature amplitudes from 3 meters region to 6 meters can be modified accurately. Therefore, a DOFRTS of high spatial resolution but low system cost could be successfully constructed.

Abstract: Effects of magnetic material, coating thickness, and tip radius on magnetic force microscope (MFM) spatial resolution have been systematically investigated. MFM tips are prepared by using an UHV sputtering system by coating magnetic materials on non-magnetic Si tips employing targets of Ni, Ni-Fe, Co, Fe, Fe-B, and Fe-Pd. MFM spatial resolutions better than 9 nm have been confirmed by employing magnetic tips coated with high magnetic moment materials with optimized thicknesses.

Abstract: Multi beam sonar needs complex data processing lying on human intervention to get accurate depth contour and low accuracy in sonar image which prevent its popular use in surveying seafloor targets. To survey seafloor target in different depth by GeoSwath, this article presents survey parameter setting method such as ping length, ship velocity to increase points over targets, navigation line parallel to heading of target during survey, adopting along track filter to depth data processing and using TVG control over amplitude data to get accurate depth grid and sonar image of seafloor target. Finally, the way is used to measure the artificial object in harbor and two ship wrecks at sea, which improve GeoSwath survey capability with compound detection and is helpful for make precise map for waterway. Also this work is helpful to achieve detecting seafloor objects fast, accurately, effectively in underwater large scale area during salvation and rescue task.

Abstract: Single normal hot-wire measurements of the streamwise component of velocity were taken in boundary layer flows subjected to pressure gradients at matched friction Reynolds numbers Reτ ≈ 3000. To evaluate spatial resolution effects, the sensor lengths are varied in both adverse pressure gradient (APG) and favorable pressure gradient (FPG). A control boundary layer flow in zero pressure gradient ZPG is also presented. It is shown here that, when the sensor length is maintained a constant value, in a contant Reynolds number, the near-wall peak increases with (adverse) pressure gradient. Both increased contributions of the small- and especially large-scale features are attributed to the increased broadband turbulence intensities. The two-mode increase, one centreing in the near-wall region and the other one in the outer region, makes spatial resolution studies in boundary layer flow more complicated. The increased large-scale features in the near-wall region of an APG flow is similar to large-scales increase due to Reynolds number in ZPG flow. Additionally, there is also an increase of the small-scales in the near-wall region when the boundary layer is exposed to adverse pressure gradient (while the Reynolds number is constant). In order to collapse the near-wall peaks for APG, ZPG and FPG flows, the APG flow has to use the longest sensor and conversely, the FPG has to use the shortest sensor. This study recommends that the empirical prediction by Huthins et. al. (2009) to be reevaluated if pressure gradient flows were to be considered such that the magnitude of the near-wall peak is also a function of the adverse pressure gradient parameter.