Changfoged1685

This study examines the thermal behavior of a laser ignited thermite composed of aluminum and bismuth trioxide. Temperature data were collected during the reaction using a four-color pyrometer and a high-speed color camera modified for thermography. The two diagnostics were arranged to collect data simultaneously, with similar fields of view and with similar data acquisition rates, so that the two techniques could be directly compared. Results show that at initial and final stages of the reaction, a lower signal-to-noise ratio affects the accuracy of the measured temperatures. Both diagnostics captured the same trends in transient thermal behavior, but the average temperatures measured with thermography were about 750 K higher than those from the pyrometer. This difference was attributed to the lower dynamic range of the thermography camera's image sensor, which was unable to resolve cooler temperatures in the field of view as well as the photomultiplier tube sensors in the pyrometer. Overall, while the camera could not accurately capture the average temperature of a scene, its ability to capture peak temperatures and spatial data make it the preferred method for tracking thermal behavior in thermite reactions.The wavelength demultiplexer (deWMUX) is an indispensable component for the wavelength diversity system. In this paper, we propose a subwavelength-grating-assisted $1 \times 2$ deWMUX based on the principle of multimode interference, which aims to output 1.55 and 2 µm wavelengths from two different channels. The simulation results show that the contrast of the designed deWMUX at both wavelengths is greater than 24 dB, the insertion loss is less than 0.5 dB, and the 1 dB bandwidth is wider than 100 nm. In addition, the manufacturing tolerances of the device are also studied.A spectroscopic Mueller matrix ellipsometer based on two rotating Fresnel rhomb compensators with a nearly achromatic response and optimal retardance is described. In this instrument, the compensators rotate in a discrete manner instead of continuously rotating, and this allows for a well-conditioned measurement even for low intensity samples. Moreover, in this configuration, the exposure time of the CCD detector can be varied within orders of magnitude without interfering with the dynamics of the compensator rotation. VX-11e in vivo An optimization algorithm determines the optimal set of discrete angles that allows the determination of the Mueller matrix in the presence of noise. The calibration of the instrument is discussed, and examples of experimentally determined Mueller matrices are provided.Free-space optical communication brings large-capacity communication with excellent confidentiality, though fatal obstacles are set by atmospheric turbulence that causes phase shifting in laser links. Therefore, we derived a novel, to the best of our knowledge, iterative wavefront correction algorithm based on a complete second-order deformable mirror (DM) Shack-Hartmann wavefront sensor model as a solution to it. For correcting static wavefront aberration, the proposed algorithm possesses a converging speed faster than the traditional one. In terms of correcting dynamic atmospheric turbulence, it can achieve convergence within two iterations with a residual wavefront root mean square value of less than 1/8 wavelength. The input wavefront under 1.5 wavelength can be corrected on our testbed due to the deformability of the micromachined membrane DM. The research result offers a solution for atmospheric turbulence in the adaptive optics field and may contribute to the development of free-space optical communication.Here we report our study on methods proposed for the design and fabrication of a metallic irregular Fabry-Perot (F-P) filter array for a miniature spectrometer to improve its performance and convenience in implementation. The method in designing suggests including both types of unit-cell filters that have broader single passband peaks of lower-order resonance modes and narrower multiple passband peaks of higher-order resonance modes in the F-P filter array for improved performance in reconstructive measurement of a spectrum with both finer and broader features in a wide spectral range. The fabrication method suggests using fewer film-deposition steps to form a larger number of different film thicknesses for the interspacing dielectric layers in the arrayed F-P filters. The processes involve inexpensive facilities and low-resolution patterning techniques in defining the unit cells of the filter array and can be conveniently fabricated using standard planar processing technologies. Resonant transmission spectrum profiles and passband peak positions of unit-cell filters are irregularly distributed in as-designed and -fabricated filter arrays. Based on the route of acquiring spectrum via computational reconstruction, such irregularities can facilitate designing and fabrication of F-P-type filter arrays for miniature spectrometers to achieve both high performance and low cost.A dual-interface period-mismatched rotating rectangular grating structure was designed for crystalline silicon thin film solar cells. The relevant parameters of the grating structures were optimized, and the absorption enhancement mechanisms were also explained by optoelectronic simulation analysis. The numerical results show that the rotating rectangular structure can improve the light-trapping performance by coupling light into the c-Si film to excite the waveguide mode and localized surface plasmon resonances. Moreover, it is found that the light-trapping effect of the rear grating rotating structure is better than that of the front grating rotating structure, because the rear interface can better excite localized surface plasmon resonances. The photocurrent density of the dual-interface period-mismatched rotating rectangular grating structure is increased to $18.01\; \rm mA/cm^2$, which is 76.05% higher than that of the planar 300 nm thick c-Si structure. The research results provide general guidance for the design of grating structures for thin-film solar cells.Solar steam generation has widespread application in wastewater treatment, seawater desalination, liquid-liquid separation, and other fields, providing potential opportunities for producing fresh water. Up until now, most researchers in this field focused on enhancing the evaporation rate of the solar steam generation device. However, problems in terms of its portability and flexibility still exist when it comes to real application scenarios. Herein, we propose a novel, to the best of our knowledge, integrated multi-layer textile composed of reduced graphene oxide/cotton (RGO/cotton) fabric, cotton yarn, and polypropylene (PP) fabric for solar-driven steam generation. The evaporation rate obtained by the integrated multi-layer textile as prepared is $0.83\;\rm kg\cdot m^- 2\cdot\rm h^- 1$ under one sun solar radiation, which is 3.16 times higher than that of blank experiment and is superior to many previously reported works. Its remarkable evaporation performance is mainly attributed to the inherent multi-layer structures, where porous RGO/cotton fabric exhibits ultra-water vapor permeability, hydrophilic cotton yarn supplies water continuously, and low-density hydrophobic PP fabric hinders heat sustainably. Based on the results of application performance evaluation, the integrated multi-layer textile with scalable manufacturability, portability, durability, and flexibility is expected to boost the development of solar-driven steam generation.Infrared image denoising is an essential inverse problem that has been widely applied in many fields. However, when suppressing impulse noise, existing methods lead to blurred object details and loss of image information. Moreover, computational efficiency is another challenge for existing methods when processing infrared images with large resolution. An infrared image impulse-noise-suppression method is introduced based on tensor robust principal component analysis. Specifically, we propose a randomized tensor singular-value thresholding algorithm to solve the tensor kernel norm based on the matrix stochastic singular-value decomposition and tensor singular-value threshold. Combined with the image blocking, it can not only ensure the denoising performance but also greatly improve the algorithm's efficiency. Finally, truncated total variation is applied to improve the smoothness of the denoised image. Experimental results indicate that the proposed algorithm outperforms the state-of-the-art methods in computational efficiency, denoising effect, and detail feature preservation.A 3D spatially resolved coupled mode and perturbation analysis for the transverse mode instability (TMI) threshold powers in Yb-doped fiber amplifiers is presented in this paper. Threshold powers are computed in the quantum and thermal Rayleigh scattering limits and are compared with those calculated by other coupled mode analyses. Quantum-limited threshold powers are found to be more than three times greater than those calculated with coupled-mode analyses that use uniform and/or average gain approximations. link2 The analysis presented here includes pump depletion, gain saturation, and transverse hole burning. Simulations are applied to co-, cnt-, and bidirectionally pump amplifier configurations. The appearance of TMI is attributed to the formation of a dynamic thermal grating, which enables the exchange of optical power between the fundamental mode (FM) and higher-order mode (HOM). The sole approximation made is that the power in the HOM is much less than that in the FM. link3 A distributed thermal Rayleigh scattering model is introduced that includes a ray-optic representation of the fiber mode structure that relates the Rayleigh power captured by the HOM to the waveguide structure. The location and strength of the thermal gratings are identified to assist in the application of mitigation techniques.As an essential component in applications such as video coding, autonomous navigation, and surveillance cameras, efficient and robust motion estimation is always required. This paper proposes a robust block-matching algorithm consisting of a rough matching step and a fine matching step for motion estimation. In the coarse matching step, an improved adaptive rood pattern search strategy combined with an anti-interference similarity criterion is developed to improve the computational efficiency and robustness. In the fine matching step, after performing a subpixel estimation procedure, a bilateral verification scheme is demonstrated to decrease the motion estimation errors caused by environmental disturbances. Experiments are carried out over popular video and image sequences, and several measurement indexes are used to quantify the performance of the proposed method and other motion estimation methods. Comparative analysis and quantitative evaluation demonstrate that the proposed method exhibits strong robustness and can achieve a good balance between computational efficiency and complexity.In this paper, we investigate depolarization properties of a quartz double-wedge Cornu depolarizer with respect to the generation of spatially unpolarized light in terms of on-average randomly occupied states on the Poincaré sphere. Spatially resolved Stokes parameter measurements yield transformed polarization states and polarization-dispersed characteristic fringes for the Stokes parameters. Their spatial symmetry, the degree of polarization, and spatially integrated Stokes parameters as a function of the aperture-determined input diameter together with a Mueller matrix calculus model confirm the successful generation of equator states incorporating the ensemble of all purely linearly polarized states, thus on spatial average representing unpolarized light.