让男人玩尿道的女人,丁香婷婷欧美

2022

Record 229 of

Title:Precision manufacturing of metal mirrors based on additive manufacturing

Author(s):Chen, Wencong(1,2); Sun, Lijun(1,3); Li, Siyuan(1,2); Wu, Junqiang(1); Zhang, Zhaohui(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12169 Issue: DOI: 10.1117/12.2625102 Published: 2022
Abstract:In order to solve the problems of long manufacturing cycle and high processing cost of mirrors in reflective optical systems of space cameras, a method for manufacturing metal mirrors based on additive manufacturing process is proposed.This paper designs an open honeycomb structure on the mirror backplane,mirror blank is prepared by additive manufacturing technology.Preliminary improvement of surface quality with rough machining and diamond turning.Then, a high-precision mirror surface is obtained through surface modification and secondary diamond turning.The diameter of the prepared mirror is 110mm, mass reduction rate of 70% and surface shape accuracy is better than ?/15 RMS(? =632.8nm).The results show that the metal mirror prepared by this process can meet the requirements of high-precision reflective optical systems.The research work in this article can provide technical reference for the application of additive manufacturing technology in the field of optics.It has important reference and guiding significance for the research and application of related fields. ? 2022 SPIE
Accession Number: 20221611967374
Record 230 of

Title:Research on optimal control strategy for velocity stability of space two-dimensional tracking turntable

Author(s):Xie, Meilin(1,3); DIng, Lu(1,3); Cao, Yu(1,2,3); Lian, Xuezheng(1,3); Liu, Peng(1,2,3); Hao, Wei(1,3); Huang, Wei(1,3); Liu, Kai(1,3)
Source: IEEE 6th Information Technology and Mechatronics Engineering Conference, ITOEC 2022 Volume: Issue: DOI: 10.1109/ITOEC53115.2022.9734523 Published: 2022
Abstract:Focusing on the high-definition dynamic imaging requirements of space targets, based on the space two-dimensional turntable equipped with optical equipment, aiming at the image blur caused by speed fluctuation in a single exposure time, this paper focuses on the action mechanism of cable winding torque nonlinearity, torque fluctuation in brushless DC motor control, precision loss caused by speed measurement feedback error, so as to break through the optimal control strategy of turntable speed stationarity under large rotation range and strong coupling torque disturbance [1-3]. The problems are solved by the systematic strategies, such as cable bundle management, precision machining and assembly, high-precision speed feedback, torque compensation in commutation section of Brushless DC motor, target motion trajectory fitting and prediction method. Finally, the simulation realizes azimuth axis speed stability as 0.002°/s(σ) and pitch axis speed stability as 0.0016°/s(σ)[4]. The technology can be applied to the control field with high speed stability of optoelectric turntable or other moving mechanisms[5]. ? 2022 IEEE.
Accession Number: 20221511946633
Record 231 of

Title:A UAV Detection and Tracking Algorithm Based on Image Feature Super-Resolution

Author(s):Li, Bin(1); Qiu, Shi(2); Jiang, Wei(1); Zhang, Wei(1); Le, Mingnan(1)
Source: Wireless Communications and Mobile Computing Volume: 2022 Issue: DOI: 10.1155/2022/6526684 Published: 2022
Abstract:UAV is difficult to detect by visual methods at a long distance, so a UAV detection and tracking algorithm is proposed based on image super-resolution. Firstly, a saliency transformation algorithm is built to focus on the suspected area. Then, a generative adversarial network is established on the basis of ROI to realize the super-resolution of weak targets and restore the high-resolution details of target features. Finally, the cooperative attention module is built to recognize and track UAV. Our experiments show that the proposed algorithm has strong robustness. ? 2022 Bin Li et al.
Accession Number: 20220911708465
Record 232 of

Title:Modeling the modulation transfer function measurement system of large aperture space cameras

Author(s):Liu, Shangkuo(1,2); Wang, Zhengfeng(1); Cao, Kun(1); Wang, Tao(1); Zhou, Yan(1); Zhao, Jianke(1); Yao, Baoli(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12166 Issue: DOI: 10.1117/12.2616315 Published: 2022
Abstract:Large aperture space cameras are widely used in high-resolution remote sensing, ultra-weak space targets detection, high-precision astronomical observation, etc. Modulation transfer function (MTF) can directly reflect the information transmission ability of a space camera. Usually, the image quality of a camera is evaluated by measuring its MTF. The MTF of a space camera needs to be measured during alignment of the optical system and electronic system, preset of the vacuum focus position, mechanical experiment, thermal experiment, etc. This paper suggests a method to model the imaging chain of large aperture space camera MTF measurement systems. The model comprehensively considers the factors of the aberration of the collimator, air turbulence, temperature variation, gravity, and environmental vibration. We calibrate the aberration of the collimator, air turbulence, temperature variation, and gravity induced error by measuring the corresponding wavefront error with a 4D laser interferometer. A star point target is placed in the focus position of the collimator to calibrate the environmental vibration through extracting the centroids of the point target images captured by the space camera. The impacts of the previous factors on the MTF measurement results of the space camera are obtained with the proposed model and the corresponding calibration data. The proposed method can evaluate the impacts of different factors on the MTF measurement results and can guide the measurement of large aperture space camera MTF. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.
Accession Number: 20220911734758
Record 233 of

Title:Study on the transit time spread characteristic of 20-in. hybrid photomultiplier tube used for high-energy particle detection

Author(s):Xin, Liwei(1,2); Shen, Tao(1); Tian, Jinshou(2); Guo, Lehui(2); Liu, Hulin(2); Chen, Ping(2); Xue, Yanhua(2); Ji, Chao(2); Wang, Xing(2); Gao, Guilong(2); He, Kai(2)
Source: AIP Advances Volume: 12 Issue: 4 DOI: 10.1063/5.0087552 Published: April 1, 2022
Abstract:According to the requirements of high-energy particle detection for a large photocathode detection surface, low transit time spread (TTS), and low-cost photomultiplier tube (PMT), a kind of 20-in. hybrid large-area PMT based on the silicon (Si) electron multiplier array was designed and optimized. This study tracked the trajectories of photoelectrons from the photocathode to the silicon electron multiplier array based on the Monte Carlo and finite-integral method. The critical effects on the TTS characteristic of the large-area PMT, including the focusing electrode structure, glass shell structure, different potential differences, and relative distance from the photocathode vertex to the silicon electron multiplier array, were studied in detail. After optimizing the structure of the glass shell, the 20-in. hybrid PMT based on the ultra-small Si electron multiplier array with 40 mm collection diameter can achieve an excellent TTS of about 1.87 ns from the photocathode to the Si electron multiplier array at a collection potential difference of 2000 V. ? 2022 Author(s).
Accession Number: 20221511962826
Record 234 of

Title:Research on Precise Synchronous High Voltage Pulse Gating System of Framing Camera

Author(s):Yang, ZhiKun(1); Gou, YongSheng(1); Tian, JinShou(1); Zhao, Wei(1); Yang, Yang(1); Feng, PengHui(1); Wang, Xv(1); Wei, ShiDuo(1,2); Xv, HanTao(1,2); Liu, BaiYu(1); Chen, Zhen(1)
Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 12244 Issue: DOI: 10.1117/12.2635206 Published: 2022
Abstract:In this paper, a special high-voltage pulse synchronization system is designed for the framing camera used in the Z-pinch experiment.The system adopts a system architecture that combines a programmable delay module and a high-voltage pulse generation module. The delay module uses a digital delay chip to achieve picosecond delay. The high-voltage pulse generation module uses a Marx pulse circuit combined in series and parallel to generate high-voltage narrow pulse.Technical parameters: pulse amplitude 2.5kv, pulse width 4.03ns, delay range 2s, delay accuracy 500Ps, pulse jitter less than 150ps. It avoids the line loss and waveform distortion caused by the long transmission line of the traditional delay line method, improves the system integration, reduces the volume and weight of the equipment, and is more convenient to deploy and use. ? 2022 SPIE
Accession Number: 20222612284588
Record 235 of

Title:Thermal Analysis and Verification Test of the Entrance Window Assembly for Space Solar Observatory

Author(s):Wang, Chenjie(1,2); Tao, Wenquan(1); Yang, Wengang(2); Ma, Yixin(2); Qin, Dejin(2); Li, Fu(2)
Source: Guangzi Xuebao/Acta Photonica Sinica Volume: 51 Issue: 4 DOI: 10.3788/gzxb20225104.0412001 Published: April 25, 2022
Abstract:This paper describes the design of the entrance window assembly for the Full-disk Magnetograph (FMG) which is one of the three main payloads of the Advanced Space_based Sloar Observatory mission (ASO-S). The entrance window plays the role to reduce the effect of external space environment on the After Optical System(AOS), to transmit the visible light, and to prevent the infrared radiation and pollution, hence, it is one of the most important components in the design of space solar observatory payloads, as the entrance window is facing the sun all the time on orbit, both its design and verification test are very challenging task.A heat-rejecting entrance window assembly of FMG is designed to ensure that the imaging quality of the whole system is not affected by the drastic change of space environment and the temperature distributions can meet the thermal requirements, then the mechanical, optical and thermal design processes are briefly described. FMG is sun-oriented on orbit with long-term operation, and its optical system is transmissive. Thus, its mirror temperature will be more sensitive to the given solar radiation parameters than the other space optical payloads, and it is necessary to correct solar radiation parameters to improve the accuracy of simulation. Thermal analysis method with equivalent solar radiation parameters is studied to evaluate the heat-rejecting ability of the HEWA, and three analysis cases are selected based on the heat flux of the HEWA and the operational mode of FMG on orbit, while, Case1 and Case 2 are normal operational modes, and Case 3 is a calibration mode.Only 5 nm wide transmission pass-band around the science wavelength (532 nm) is able to reach the AOS of FMG because of the spectral selectivity of the window glasses. The thermal balance test of the HEWA not only needs to simulate the solar radiation intensity, but also needs to simulate solar collimation and spectral characteristics accurately. The solar simulator can simulate the solar radiation intensity, collimation and spectral characteristics adequately, it has higher heat flux simulation accuracy than other methods. Thus thermal balance test with solar simulator is carried out to verify the design and the analysis of the HEWA. Three test cases which are consistent with the analysis cases are carried out during the thermal balance test, quantitatively speaking the analysis results coincide with the test results, however, some main differences exist between them: 1) Temperatures of the baffle during the test are always lower than that of the analysis; 2) The test temperature of the window glasses in normal operational modes are always higher than that of analysis; 3) The temperature difference of Mirror1 in Case 3 is larger than that of the analysis.Some modifications made on the analysis model make the numerical analysis results being quantitatively consistent with the test results. Then the modified analysis model is used to predict the actual on-orbit temperature distribution of the HEWA. From the numerical results, it is found that only about 0.134 W solar radiation is able to pass through the HEWA and be absorbed by the primary mirror of the AOS, the maximum temperature of the window frame on-orbit is 28.2℃, and that of the window glasses is 26.3℃, while the primary mirror of the AOS is able to maintain at 22±2℃. Thus the designed HEWA of FMG is able to withstand each typical condition on orbit and meet the requirements of the mission. It avoids that the optical performance of the space solar observatory payload will decrease or the optical system will be polluted because of the overhigh temperature of the entrance window assembly and the AOS on orbit, which is able to guide the design of transmission optical system and other optical payloads for solar observation. ? 2022, Science Press. All right reserved.
Accession Number: 20221912096701
Record 236 of

Title:Battery screen print defect detection based on stationary velocity fields neural network matching and optical flow rectification

Author(s):Zhao, Zhuo(1); Li, Bing(1); Zhang, Shaojie(1); Liu, Tongkun(1); Cao, Jie(2)
Source: Review of Scientific Instruments Volume: 93 Issue: 11 DOI: 10.1063/5.0095555 Published: November 1, 2022
Abstract:In this study, an automatic defect detection method is proposed for screen printing in battery manufacturing. It is based on stationary velocity field (SVF) neural network template matching and the Lucas-Kanade (L-K) optical flow algorithm. The new method can recognize and classify different defects, such as lacking, skew, and blur, under the condition of irregular shape distortion. Three critical processing stages are performed during detection: (1) Image preprocessing was performed to acquire the printed region of interest and then image blocking was carried out for template creation. (2) The SVF network for image registration was constructed and the corresponding dataset was built based on oriented fast and rotated brief feature matching. (3) Irregular print distortion was rectified and defects were extracted using L-K optical flow and image subtraction. Software and hardware systems have been developed to support this method in industrial applications. To improve environment adaptation, we proposed a dynamic template updating mechanism to optimize the detection template. From the experiments, it can be concluded that the method has desirable performance in terms of accuracy (97%), time efficiency (485 ms), and resolution (0.039 mm). The proposed method possesses the advantages of image registration, defect extraction, and industrial efficiency compared to conventional methods. Although they suffer from irregular print distortions in batteries, the proposed method still ensures a higher detection accuracy. ? 2022 Author(s).
Accession Number: 20225113283599
Record 237 of

Title:Stable continuous-wave mode-locked laser from a 1645 nm Er:YAG ceramic oscillator

Author(s):Liu, Yangyu(1); Cao, Xue(1); Xian, Anhua(1); Liu, Guangmiao(1); Zhou, Wei(1); Wang, Haotian(1); Wang, Yishan(2); Jia, Baohua(3); Tang, Dingyuan(1); Shen, Deyuan(1,4)
Source: Applied Physics Express Volume: 15 Issue: 2 DOI: 10.35848/1882-0786/ac481c Published: February 2022
Abstract:We demonstrate stable continuous-wave mode-locking (CWML) pulses around 1645 nm by employing a homemade Er:YAG ceramic. By using a fiber laser and semiconductor saturable absorber mirror (SESAM) with a modulation depth of 1.2%, we get ML pulses with an output average power up to 815 mW, a pulse width shortened as ～4 ps, and a peak power of ～1.8 kW. With the SESAM of the modulation depth of 2.4%, second-order harmonic ML pulses were also obtained. As far as we know, this is the first report of CWML from Er3+-doped ceramics and also the shortest pulse duration in Er3+-doped solid-state oscillators. ? 2022 The Japan Society of Applied Physics.
Accession Number: 20220611611933
Record 238 of

Title:Thermal imaging drift monitoring of Doppler asymmetric spatial heterodyne spectroscopy for wind measurement based on segmented edge fitting

Author(s):Zhang, Ya-Fei(1,2); Feng, Yu-Tao(1); Fu, Di(1,2); Chang, Chen-Guang(1,2); Li, Juan(1); Bai, Qing-Lan(1); Hu, Bing-Liang(1)
Source: Wuli Xuebao/Acta Physica Sinica Volume: 71 Issue: 8 DOI: 10.7498/aps.71.20212086 Published: April 20, 2022
Abstract:Doppler asymmetric spatial heterodyne spectroscopy is recently developed for spaceborne measurement of middle and upper atmospheric wind field, which relies on the accurate inverse of interferogram phase to calculate the Doppler shift of airglow emission lines. The change of temperature leads the optical and mechanical components to thermally deformed, causing the imaging plane to thermally drift relative to the detector, changing the distribution of interferogram phase on pixels, and directly introducing phase errors to affect the wind speed inversion. In order to reduce the influence of imaging thermal drift on phase inversion, the segmented fitting method is used in this paper to detect the sub-pixel edges of notch patterns and monitor imaging thermal drift accordingly. In the thermal stability test of a near-infrared Doppler asymmetric spatial heterodyne interferometer prototype, the thermal imaging drifts and ambient temperature show a high consistency in the trend of high-frequency oscillation, and the correlation coefficient can reach 0.86 after removing the baseline. After phase correct by using the thermal imaging shift, the high-frequency oscillation of interferogram phase shift is also greatly suppressed. In order to further verify the accuracy of the algorithm, the influence of the data signal-to-noise ratio and the data distribution characteristic parameter errors used in the fitting on the edge detection are simulated. The results show that the edge detection accuracy is restricted mainly by the data signal-to-noise ratio and the accuracy of the fringe frequency parameters. When the error of the fringe frequency parameter used for fitting is less than 0.5%, the error of other data distribution characteristic parameters is less than 5%, and the data signal-to-noise ratio is enhanced more than 35 times, the algorithm in this paper can achieve a detection accuracy higher than 0.05 pixels. Copyright ? 2022 Acta Physica Sinica. All rights reserved.
Accession Number: 20221712041719
Record 239 of

Title:Design and realization of catadioptric long wave infrared multiscale optical system

Author(s):Yang, Shen(1,2); Hu, Wang(1,2); Yaoke, Xue(1,2); Yang, Song(1,2,3); Yongjie, Xie(1,2); Zhe, Bai(1,2); Yue, Pan(1,2); Meiying, Liu(1,2); Wenhui, Fan(1,2)
Source: Infrared Physics and Technology Volume: 123 Issue: DOI: 10.1016/j.infrared.2022.104111 Published: June 2022
Abstract:To realize the global super large field of view (FOV) and medium resolution imaging in satellite ocean remote sensing, we propose a catadioptric multiscale optical system based on the concentric double spherical mirrors with non optical axis. In this paper, according to the non optical axis characteristics of the multiscale optical system objective, the concentric double spherical mirrors with non optical axis characteristics is proposed as the objective to construct the catadioptric multiscale optical system, which can be used in the long wave infrared band (LWIR). Taking the system parameters of MODIS-N as example, the catadioptric multiscale system for LWIR based on concentric double spherical mirror is designed. The system works in the band of 7.5–12.5 μm, the resolution of the sub star point is 325 m, and the imaging FOV is 110°×1.4° (6-channel splicing FOV). The aberration analysis shows that the imaging quality of the system is good. According to the imaging experiment of the single channel prototype, the multiscale design idea based on concentric double spherical mirror is reasonable. ? 2022 Elsevier B.V.
Accession Number: 20221211822517
Record 240 of

Title:The time varying reliability analysis for space focusing mechanism based on probability model

Author(s):Cheng, Penghui(1,2); Wu, Mengyuan(1); Li, Chuang(1)
Source: Journal of Mechanical Science and Technology Volume: 36 Issue: 11 DOI: 10.1007/s12206-022-1022-9 Published: November 2022
Abstract:Compared with the ground focusing mechanism, the working environment of space focusing mechanism is more harsh and complicated. Hence the accurate prediction of its reliability is indispensable. However, it is unrealistic to obtain sample parameters of reliability analysis through repeated entity tests, due to the limitation of project cost and timetable, which lead to many existing model cannot be applied directly. We focus on a screw guide type space focusing mechanism, and propose a new time varying reliability probabilistic model that can characterize the reliability of discontinuous motion mechanisms with discrete multi-load. Its primary uncertainties and failure modes are evaluated quantitatively by failure mode effects analysis. The total damage of intermittent operation is treated as accumulative effect caused by each focusing work. And main parameters of the model are obtained by analytical calculation of mechanism wear reliability model. Finally, an integrated theoretical method are constructed and verified in this article, and the time varying reliability of proposed focusing mechanism are also discussed. ? 2022, The Korean Society of Mechanical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature.
Accession Number: 20224513057107

首頁上一頁 16 17 18 1920下一頁尾頁