Performance characteristics of PEM fuel cells under different working conditions in magnetic field applicationsDuan, Linhao; Wu, Maoliang; Zhang, Kun
doi: 10.1117/12.2686777pmid: N/A
In the Proton Exchange Membrane Fuel Cell (PEMFC), oxygen and water are one of the main reactants and products. Through the electrochemical workstation, the effect of the bipolar plate on the performance of the proton exchange membrane fuel cell after magnetization was studied. The results show that the presence of magnetic field improves the performance of proton exchange membrane fuel cells. On this basis, the difference between magnetic field and performance improvement of proton exchange membrane fuel cells at different temperatures is studied, so as to determine the most suitable magnetic field condition. The operating temperature of a proton exchange membrane fuel cell. In this experiment, the influence of magnetic field on the performance of proton exchange membrane fuel cells under different measurement ratios of cathodes was also explored, and it was concluded that the change of oxygen flow had a great impact on concentration polarization, and when the cathode measurement ratio was 1.8 to approximately 2.0, the magnetic field played a role in promoting the performance of proton exchange membrane fuel cells.
Design of bifocal metalens with extended depth of focusMa, Yaqi; Wu, Fei; Xu, Yishen; Ye, Yan
doi: 10.1117/12.2686971pmid: N/A
The extended depth of focus (DOF) of optical systems can improve the longitudinal range of imaging. Although it is possible to achieve a stable extension of the focal depth by using the traditional Inverse Quartic Axicon (IQAX) with the Seidel spherical aberration, its large volume and bulky structure prevent its application in small integrated optical systems. In contrast, a metasurface, with a small volume, thin thickness, and flexible control of light waves, provides a wider range of applications as extended DOF lenses. We have here developed a bifocal metalens with a polarization-dependent extended DOF. By combining the Pancharatnam – Berry phase with the spatial multiplexing method, the incident left circularly polarized light and right circularly polarized light were then focused on different transverse positions. The here-designed bifocal metasurface lens, with its extended DOF, can be applied in areas like multi-channel information encryption, optical imaging and detection.
Adsorption of formaldehyde by biochar prepared by thermal plasmaZhang, Yuqing; Lu, Xianqin; Xin, Qi; Liu, Wei; Xia, Tao
doi: 10.1117/12.2686963pmid: N/A
Wheat straw was treated by thermal plasma technology to prepare biochar. In this study, the effects of different preparation methods (thermal plasma and traditional pyrolysis) and plasma treatment time (3, 4, 5 and 10min) on the characterization of biochar and its adsorption of formaldehyde were studied. Results showed that for plasma treatment method, the treatment time played a leading role in the physicochemical and surface properties of biochar. When the plasma treatment time was 5 min and 10 min, biochar had a relatively high number of functional groups. The specific surface area of biochar treated by plasma for 4 min was increased to 256.17 m2/g. As well as, compared with the traditional pyrolysis method, the biochar prepared by thermal plasma got significantly improved adsorption capacity for formaldehyde, in which the concentration of formaldehyde decreased from 1.654 mg/L to 0.854 mg/L, 0.592 mg/L, 0.555 mg/L and 0.534 mg/L for biochar prepared by thermal plasma with 3 min, 4 min, 5 min and 10 min respectively. This study suggested that compared with pyrolysis method, the plasma treatment was an efficiency method to produce biochar from wheat straw in short time and the plasma treated biochar got high potential as the adsorbent to remove formaldehyde.
Preparation and characterization of nano-TiO2/paraffin-based composite phase change microcapsulesZhang, Yunfeng; Chen, Zewei; Zhang, Lu; Zhang, Jie; Zhong, Wei
doi: 10.1117/12.2686707pmid: N/A
A novel phase change microcapsule with paraffin wax as the core material and nano-TiO2 modified polysulfone resin(PSF)as the shell material was developed based on the solvent volatilization method. The composite microcapsules were characterized by Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Differential Scanning Calorimeter (DSC) and Thermogravimetric Analysis (TGA) to test the comprehensive performance of the composite microcapsules. The results showed that the overall performance of the microcapsules was the best when the nano-TiO2 was added at 3%, with the average particle size of 103.83 μm reaching the minimum, the melting enthalpy of 104.50 J/g, the crystallization enthalpy of 104.00 J/g, and the encapsulation efficiency of 68.54%; The chemical structure of the composite phase change microcapsules was not affected after adding a certain amount of nano-TiO2, and the surface of the microcapsules was smoother, which increased the continuity of the microcapsules. The thermal stability and thermal properties of microcapsules were also significantly improved.
Research on calibration method of one-dimensional marine LDVGao, Na; Zhao, Wenwu; Xu, Yunong; Cheng, Guangxin
doi: 10.1117/12.2687365pmid: N/A
Aiming at the problem that the combined navigation accuracy of marine Strapdown Inertial Navigation System (SINS) and Laser Doppler Velocimetry (LDV) is limited by the calibration accuracy of LDV, a calibration method of LDV for marine was proposed. Firstly, the working principle of LDV in marine integrated navigation system is analyzed, and then the error model of 1D LDV is established. Then, starting from the calibration method of LDV in land integrated navigation system, the calibration method of LDV in marine integrated navigation system is explored. The mean value method is proposed to estimate the velocity of water flow in the frame alignment stage, and then parameters analytical calibration and filtering calibration are carried out for marine LDV. In the filtering calibration stage, a velocity correction filtering calibration method based on DGPS is proposed. The influence of the change of water velocity on the calibration results is avoided. Finally, simulation experiments are carried out to verify the feasibility of the calibration method.
Design of liquid crystal metalens for achromatic full-color imaging with multiplexed phase codingCao, Wenhui; Sun, Ti; Wang, Chinhua
doi: 10.1117/12.2686988pmid: N/A
Liquid crystals metalens (LC-ML) has attracted much attention due to its powerful functions in shaping light field with planar structure and its great application potentials. However, LC-MLs usually suffer from large chromatic aberration resulting from high phase dispersion. Here, we propose and demonstrate achromatic imaging at red-green-blue (RGB) wavelengths 450 nm, 526 nm, and 630 nm with optimized wavelength multiplexed phase coding in a single liquid crystals metalens. The optimized wavelength multiplexed phase coding, which works on three operating wavelengths simultaneously, is introduced via the complex field of summation of the individual optical fields at selected RGB wavelength and can be achieved via photo-patterning an azo-dye doped LC. The optical efficiency of the fabricated achromatic liquid crystals metalens can be optimized by applying appropriate voltages. The proposed achromatic LC-ML at multi-wavelengths is easy to fabricate and has a potential application in the display field.
Research on board-level thermal dissipation of the mini LED in COB packagingWang, Wenli; Xiang, Yu
doi: 10.1117/12.2687165pmid: N/A
In view of the high Thermal Flux Density encountered with the Mini LED in COB (Chip on Board) packaging, board-level thermal dissipation is becoming more and more important. This paper analyses characteristics and trends of board-level thermal dissipation of the Mini LED. First, board-level materials are developing from the ordinary PCB (Printed Circuit Board) to metallic materials and ceramic materials. Second, the limitation of process technologies and material costs make thermal dissipation of hybrid substrates the future direction for development. In order to meet the requirements of thermal dissipation for different power devices and products, optimization design and simulation analysis of the thermal dissipation structure becomes a real necessity. Therefore, digitalized thermal simulation design and accurate thermal simulation design become a practical necessity. Finally, the reliability and the interface crack of a large number of micro pores caused by Mini LED board-level thermal dissipation are analyzed. To ensure the massive production of the Mini LED, the process level and the quality control of the entire manufacturing process must be improved.
Automated progress tomography using genetic algorithm for quantum key distributionDong, Xiang
doi: 10.1117/12.2686752pmid: N/A
Polarization maintenance of quantum communication links is one of the keys to the stable and long-term operation of optical quantum communication. At present, many solutions are based on link process tomography result for polarization compensation. To automate process tomography for automated polarization compensation when the link is changed, this paper presents an automated optical path process tomography method based on genetic algorithm. This method uses sensors to automatically obtain input and output states and depends on genetic algorithm to optimize the post-processing of process tomography. In this way, the method can automatically solve the transmission process in the optical path. Besides, the experimental verification is completed by using a single-mode fiber simulation optical path black-box. The experimental results demonstrate that the fidelity of polarized light can reach an average of 0.9966. This method can automate the process tomography of the optical path Therefore, the method has the potential to improve the efficiency and reliability of polarization compensation in quantum communication.
Preparation and characterization of photoluminescent silicon nanoparticles and its preliminary results in solar cellsChen, Ren; Hu, Yunfei; Li, Xuegeng; Zhang, Shun; Wan, Sicheng; He, Jinxing
doi: 10.1117/12.2686867pmid: N/A
Silicon nanoparticles were used as down-conversion materials on the solar cell surface to achieve better absorption in the short-wavelength range. Photoluminescent silicon Nanoparticles (NPs) have been successfully produced by electrochemical etching process. The effects of different electrochemical conditions on the properties of silicon NPs were discussed, including current density, process time, and silicon substrate resistivity. After that surface modification of Si NPs was also carried out to achieve a stable suspension, which was then spin-coated directly on the solar cell surface. Preliminary results of those Si particles showed a positive effect, an increase of 0.81% (abs.) for power conversion efficiency has been achieved in silicon heterojunction solar cells.
Analytical model of magnetic torque of rotating permanent magnet mechanical antenna arrayWang, Xiaoyu; Li, Ziyi; Yang, Xijie; Duan, Jiaqi; Sun, Deli; Feng, Qing; Cui, Dongning
doi: 10.1117/12.2686679pmid: N/A
In order to solve the problem of lacking the corresponding magnetic torque resolution model in the design process of permanent magnet type mechanical antenna，this thesis discusses the basic form of antenna array and establishes the magnetic torque model for hetero-axial linear mechanical antenna array, derives the time-varying curve of magnetic torque during rotation, verifies the accuracy of the torque model through simulation, and analyzes the relationship between magnetic torque and permanent magnet spacing and permanent magnet magnetization direction. It is concluded that in order to reduce the torque required to drive the antenna, the inter-magnet torque should be increased, and when selecting the permanent magnets, the permanent magnets with the magnetization direction along the shortest side should be selected for the same volume case. The analytical model provides theoretical support for the design and optimization of the structure of the permanent magnet type mechanical antenna array.