Smidtyates4005

Tomographic approaches in confined space require advanced imaging algorithms that can properly consider the refractive distortion as the imaging rays pass through the optical wall. Our previous work established an algorithm (cross-interfaces computed tomography, CICT) and practically solved tomographic problems in confined space. However, critical restriction was found in CICT, which is that images simulated at small azimuth angles are contaminated with noticeable signal loss and become unusable. Based on this recognition, this work has developed an improved tomography approach, namely, full-field cross-interfaces computed tomography (FCICT), to extend the available view angles to all perspectives. The key to this approach involves the 3D domain discretization using voxel parallelepipeds instead of traditional voxel layers to establish the ray-tracing relationship between imaging planes and the measurement domain. The imaging process of FCICT is first validated by quantitatively comparing the grid imaging locations in measured and simulated projections of a calibration plate. By evenly distributing the view angles in the whole azimuth angle range, the FCICT reconstruction is then numerically validated by reconstructing a simulated double-cone flame phantom. The reconstruction presents a high correlation coefficient of $\sim98\%$ with the original phantom. Finally, the FCICT is employed to reconstruct an ethylene-air premixed flame. Comparisons show that re-projections generated by the FCICT reconstruction are in accordance with measured flame images, with the mean correlation coefficients of more than 95%.Underwater polarization differential imaging requires the estimation of different parameters, and the parameters can be accurately obtained by using optical correlation. However, optical correlation as a criterion function to estimate parameters takes a lot of time. To expedite the parameters' estimation process, we propose two operations to process underwater polarization images. One operation is to update the analyzer angle range to reduce the number of processed images. The other is image downsampling, which reduces the amount of calculation for the corresponding images. U18666A supplier In experiments, we confirmed the feasibility of our method. We have obtained an average of 42 times the calculation speed increase under the conditions of updating the analyzer angle range 3 times and reducing the image scale by 16 times. The results of our method are consistent with those of traditional methods. This established method is conducive to the practical application of underwater polarization differential imaging.In this paper, a novel photonic crystal fiber (PCF) based on tellurite glass with high birefringence and high nonlinearity is designed. Six small air holes arranged nearly rectangularly are added in the fiber core to form the near-elliptic core. By using the finite-element method with the help of COMSOL Multiphysics software, we investigate and simulate the birefringence, effective mode area, nonlinear coefficient, and the dispersion characteristics. Simulation results show that by optimizing the structure parameters of the core, at the wavelength of 1.55 µm, the birefringence is up to $5.05 \times 10^- 2$; the nonlinear coefficient can reach a maximum of $1896\;\rmW^- 1\;\rmk\rmm^- 1$; moreover, the zero dispersion points can be obtained around the wavelength 1.55 µm. The proposed structure is easy to fabricate. The advantage of the proposed PCF has potential applications in polarization control, communication systems, and supercontinuum generation.Light can be absorbed and scattered when traveling through water, which results in underwater optical images suffering from blurring and color distortion. To improve the visual quality of underwater optical images, we propose a novel, to the best of our knowledge, image sharpening method. We utilize the relative total variation model to decompose images into structure and texture layers in a novel manner. On those two layers, the red-blue dark channel prior (RBDCP) and detail lifting algorithms are proposed, respectively. The RBDCP model calculates background light based on brightness, gradient discrimination, and hue judgment, which then generates transmission maps using red-blue channel attenuation characteristics. The linear combination of the Gaussian kernel and binary mask is employed in the proposed detail lifting algorithm. Furthermore, we combine the layers of restoration structure and enhancement texture for image sharpening, inspired by the concept of fusion. Our methodology has rich texture information and is effective in color correction and atomization removal through RBDCP. Extensive experimental results indicate that the proposed method effectively balances image hue, saturation, and clarity.The life of ceramic tools restricts the development of the manufacturing industry and can be increased through the enhancement of surface performance. Laser surface texturing is a feasible technology to improve ceramic tool life based on the relationship between surface properties and the laser-texturing process. In this study, $\rm Al_2\rm O_3$ substrates have been textured by an ytterbium fiber laser system with a wavelength of 1064 nm and a pulse duration of 50 ns. First, the damage threshold of $\rm Al_2\rm O_3$ was measured to provide a basis for selecting laser-texturing parameters. The surface morphology was characterized using a white confocal scanning microscope and a scanning electron microscope to investigate the characteristics of laser processing. Water contact angles were measured to investigate the relationship between laser parameters and changes in wettability. The surface energy of the superhydrophobic ceramic was calculated based on the contact angle. Combined X-ray photoelectron spectroscopy (XPS) measurement was used to explore the mechanism of wettability changes from the chemical component and microstructure perspectives. The friction coefficient of $\rm Al_2\rm O_3$ was determined by a ball-on-disc wear test. The results showed that laser texturing can significantly improve the surface hydrophobicity and friction stability.