2020
2020
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Record 193 of
Title:Performance analysis and experiment study on multi-sectional cylindrical magnetic shield device used for atom interferometric measurement
Author(s):Wang, Xianhua(1); Jia, Sen(1); Hao, Anqing(1,2); Zhao, Xiaodong(1); Song, Wei(1,2)Source: Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument Volume: 41 Issue: 5 DOI: 10.19650/j.cnki.cjsi.J2006224 Published: May 1, 2020Abstract:The gravitational and environmental stray magnetic fields will introduce measurement noises and system errors during atom interferometric measurement process. Usually, the magnetic shield material sheets are rolled and welded to become the cylindrical segments, which are spliced to form the cylindrical magnetic shield device with enough length. To clarify the influence of this fabrication method on the magnetic shielding performance, the variations of residual magnetic field distribution in shielding area caused by the number of shield layers, the axial and transverse weld seams and adding caps on both ends of the shield device are analyzed in detail in this paper. The results show that the existence of the axial weld seam with the width of 4 mm has little influence on magnetic shielding, however the presence of the transverse weld seam with the width of 4 mm on the shield with lower relative magnetic permeability will introduce obvious magnetic flus leakage, adding caps on both ends of the shield device may reduce the residual magnetic field intensity, but it can hardly enlarge the region of uniform magnetic field. Based on the analysis results, a dual-layered cylindrical magnetic shield device used for the interference area of the upward-projectile cold atom-interferometry gravimeter was fabricated, and the actual measurement results reveal that a uniform magnetic field region with length of 700 mm and unevenness of 4 nT is obtained after demagnetization, which satisfies the requirements of atom interferometric measurement, and has good consistency with the simulation results. ? 2020, Science Press. All right reserved.Accession Number: 20203609131203 -
Record 194 of
Title:Design and test of flexible support structure for large aperture lightweight mirror
Author(s):Jun, Sun Li(1,2); Zhen, Liu(3); Bo, Zhang Zhao(1); Hui, Li(1); Yuan, Li Si(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11570 Issue: DOI: 10.1117/12.2580427 Published: 2020Abstract:To ensure the high surface accuracy and high thermal stability of space mirror, a lightweight design for the Φ514mm ULE primary mirror of a space remote sensor and flexible support structure with three-point was carried out. By further optimizing the parameters of the flexible supporting structure, the requirements of the optical index were met. The finite element model of the mirror assembly was established, and the static and dynamic characteristics of the assembly were analyzed. The results showed that the surface shape accuracy (RMS) of the mirror assembly is better than 8 nm under a load case of 1g gravity when the optical axis is level, and the first-order natural frequency of the component is 254 Hz. Finally, a mechanical test was carried out on the mirror assembly. The test results showed that the first-order frequencies of the three directions of the mirror assembly are all greater than 100 Hz , the error between the test data and the finite element analysis results does not exceed 10%. Analysis and test results showed that, the reasonable support structure design can effectively lower the change of the mirror surface shape caused by assembly stress and thermal stress, and has good dynamic performance. It is verified that the mirror and its supporting structure designed in this paper are reasonable, which provides reference and ideas for the design of flexible supporting structure of similar space mirror. ? 2020 SPIE. All rights reserved.Accession Number: 20204909580490 -
Record 195 of
Title:Study of size variations in the focal spot of a Wolter-1 mirror under point-source condition
Author(s):Li, Linsen(1,2,3); Zhang, Chunmin(2); Qiang, Pengfei(1,2); Sheng, Lizhi(3); Liu, Zhe(3); Zhou, Xiaohong(3); Zhao, baosheng(3)Source: Optik Volume: 201 Issue: DOI: 10.1016/j.ijleo.2019.163446 Published: January 2020Abstract:In this study, a geometric model of Wolter-I X-ray focusing mirror was established, and a set of equations were derived for determining the parameters of glass substrate focusing mirror. In order to study the focal spot diffusion at the theoretical focal point under the condition of point light source. A formula for calculating the focal spot size of the single-layer focusing mirror at the theoretical focal length under point-source incident light was derived through theoretical analysis. A set of Wolter-I X-ray focusing mirror were fabricated through a slumping process using Schott D263 T glass,which is designed based on the derived equations. Ray tracing software was used to simulate the size variations of focal spot under parallel incident light and point-source incident light. A test system was constructed, and experiments were conducted to verify the validity of the calculation formula and the results of the simulation analysis. The test results showed that the theoretical results are in good agreement with the experimental results. ? 2019Accession Number: 20194207555616 -
Record 196 of
Title:Catalyst-free growth of dense γ-In2Se3 nanosheet arrays and their application in photoelectric detectors
Author(s):Kou, Yumeng(1); Chen, Lida(1); Mu, Jianglong(1); Miao, Hui(1); Wang, Yishan(2); Hu, Xiaoyun(1); Teng, Feng(1)Source: Nanotechnology Volume: 31 Issue: 19 DOI: 10.1088/1361-6528/ab674a Published: February 20, 2020Abstract:In this work, a dense γ-In2Se3 nanosheet array has been fabricated using the chemical vapor deposition method under atmospheric pressure. Compared with crystal silicon, the photodetector based on the γ-In2Se3/p-Si heterojunction exhibits a high responsivity (96.7 mA W-1) at the near-infrared region, a presentable current on/off ratio (～1000) and excellent detectivity (2.03 1012 jones). Simultaneously, the obtained photodetector demonstrated a fast response speed (0.15 ms/0.5 ms) and a broadband sensitive wavelength from ultraviolet (340 nm) to near-infrared (1020 nm). The photoelectric experimental data of the device shows that its high performance is attributed to the high-light absorption capacity of the material, the rational energy band structures of γ-In2Se3 and p-Si, and the effective separation of photo-generated carriers caused by the formed type-II heterojunction. Our work provides the primary experimental basis for the photodetection application of the γ-In2Se3 nanostructure. ? 2020 IOP Publishing Ltd.Accession Number: 20201108296235 -
Record 197 of
Title:Discrete Deep Hashing with Ranking Optimization for Image Retrieval
Author(s):Lu, Xiaoqiang(1); Chen, Yaxiong(1); Li, Xuelong(2)Source: IEEE Transactions on Neural Networks and Learning Systems Volume: 31 Issue: 6 DOI: 10.1109/TNNLS.2019.2927868 Published: June 2020Abstract:For large-scale image retrieval task, a hashing technique has attracted extensive attention due to its efficient computing and applying. By using the hashing technique in image retrieval, it is crucial to generate discrete hash codes and preserve the neighborhood ranking information simultaneously. However, both related steps are treated independently in most of the existing deep hashing methods, which lead to the loss of key category-level information in the discretization process and the decrease in discriminative ranking relationship. In order to generate discrete hash codes with notable discriminative information, we integrate the discretization process and the ranking process into one architecture. Motivated by this idea, a novel ranking optimization discrete hashing (RODH) method is proposed, which directly generates discrete hash codes (e.g., +1/-1) from raw images by balancing the effective category-level information of discretization and the discrimination of ranking information. The proposed method integrates convolutional neural network, discrete hash function learning, and ranking function optimizing into a unified framework. Meanwhile, a novel loss function based on label information and mean average precision (MAP) is proposed to preserve the label consistency and optimize the ranking information of hash codes simultaneously. Experimental results on four benchmark data sets demonstrate that RODH can achieve superior performance over the state-of-the-art hashing methods. ? 2012 IEEE.Accession Number: 20202408810211 -
Record 198 of
Title:All-fiber phase shifter based on hollow fiber interferometer integrated with Au nanorods
Author(s):Luo, Meng(1); Yang, Xinghua(1); Teng, Pingping(1); Liu, Zhihai(1); Kong, Depeng(2); Zhang, Jianzhong(1); Yang, Jun(1); Tian, Fengjun(1); Gao, Danheng(1); Li, Zhanao(1); Yuan, Libo(1,3); Li, Kang(4); Copner, Nigel(4)Source: Sensors and Actuators, A: Physical Volume: 301 Issue: DOI: 10.1016/j.sna.2019.111750 Published: 1 January 2020Abstract:We propose and demonstrate a novel all-fiber phase shifter by integrating a microstructured hollow fiber (MHF) and gold nanorods (GNRs) with photothermal effect. There are two cores and a central hole in the MHF. One core is suspended on the inner surface of the central hole, which serves as the sensing arm. The other one located in the cladding is as the reference arm. A Mach-Zehnder interferometer (MZI) can be fabricated simply through splicing multimode fiber-single mode fiber structures at both ends of the MHF. In this device, the center hole of MHF is filled with the solution of GNRs. The GNRs around the sensing arm is excited by near infrared light in the core via the evanescent interaction and the released heat because of the photothermal effect. Then, the refractive index around the sensing arm is modulated and the interference dips can be reversibly shifted. Experimental results show that spectral shift efficiency about -37.5 pm/mW near 1560 nm can be obtained under an excitation laser at the wavelength of 805 nm. This all-optical device based on MHF and GNRs has great potentials in integrated all-fiber signal controlling. ? 2019 Elsevier B.V.Accession Number: 20194907776071 -
Record 199 of
Title:Improved two-step optimization procedure used for designing an apodizer and Lyot stop in the Lyot coronagraph
Author(s):Ge, Rui(1,2); Zhao, Hui(1); Wei, Jing-Xuan(3); Duan, Yong-Qiang(1); Bai, Zhe(1); Li, Chuang(1); Wang, Yuan-Bo(1); Fan, Xue-Wu(1)Source: Applied Optics Volume: 59 Issue: 16 DOI: 10.1364/AO.391959 Published: June 1, 2020Abstract:The Lyot coronagraph is a widely known astronomical instrument used to realize direct imaging of exoplanets, and designing transmittance of an apodizer and Lyot stop is the key to obtaining high-contrast imaging. In this paper a new (to the best of our knowledge) optimization procedure used to design the apodizer and Lyot stop in the Lyot coronagraph is proposed. A two-step optimization program is established to obtain the optimum transmittance of an apodizer and Lyot stop in a sequential way. By using the optimized apodizer and Lyot stop obtained through the proposed optimization procedure, both the stellar light and its diffraction light could be strongly suppressed. Numerical results indicate that such an optimized Lyot coronagraph can produce a 1e-10 extinction of the stellar light near the diffraction limit (1.59 λ=D), and a high contrast imaging of 1e-07 could still be obtained even with the influence of light intensity of planets themselves. In addition, the two-step optimization procedure brings in two benefits. First, the two-step optimization is approximately 1000 times faster than the joint optimization method [J. Astron. Telesc. Instrum. Syst. 2, 011012 (2016)]. Second, the optimum transmittance of the Lyot stop is binary, and therefore, the requirements of the production process are reduced, resulting in a greatly reduced cost. At the same time, the performance of the optimized Lyot coronagraph is also analyzed in the case of a monochromatic light incident and bandwidth light incident, and the effect of the diameter of the Lyot stop on the results is also discussed in this paper, which makes sense when designing a coronagraph. ? 2020 Optical Society of America.Accession Number: 20202308791880 -
Record 200 of
Title:Non-iterative complex wave-field reconstruction based on Kramers-Kronig relations
Author(s):Shen, Cheng(1); Pan, An(2); Liang, Mingshu(1); Yang, Changhuei(1)Source: arXiv Volume: Issue: DOI: null Published: May 11, 2020Abstract:A new computational imaging method to reconstruct the complex wave-field is reported. Due to the existence of zero frequency component, the measured signal by amplitude modulation of pupil has a spectrum similar to the one of off-axis hologram. The mathematical analogy between them is established in this paper. Based on this observation and analyticity of band-limited signal under any diffraction-limited system, an algorithm from Kramers-Kronig (KK) relations is utilized to recover the phase information only from the intensity patterns. From the sensing side, only two measurements are required at least. From the reconstruction algorithm side, our method is iteration-free and parameter-free, also without any assumption on sample characteristics. It owns several advantages over existing phase imaging methods and could provide a unique perspective to understand current computational imaging methods. Copyright ? 2020, The Authors. All rights reserved.Accession Number: 20200545650 -
Record 201 of
Title:In-situ oxidation fabrication of 0D/2D SnO2/SnS2 novel Step-scheme heterojunctions with enhanced photoelectrochemical activity for water splitting
Author(s):Mu, Jianglong(1); Teng, Feng(1); Miao, Hui(1); Wang, Yishan(2); Hu, Xiaoyun(1)Source: Applied Surface Science Volume: 501 Issue: DOI: 10.1016/j.apsusc.2019.143974 Published: 31 January 2020Abstract:The transfer/separation of interfacial charge carriers relies heavily on the appropriate interfacial contact of heterojunction. In-situ heterojunction will be an effective way for enhancing charge transfer rate since the tight interface, which is conductive to promote the photoelectrochemical or photochemical activity. Herein, 0D/2D SnO2/SnS2 novel Step-scheme (S-scheme) heterojunctions have been successfully constructed by solvothermal method and in-situ oxidation technique through controlling the annealed temperature in N2/H2 atmosphere. The SnS2 nanosheets annealed at 400 °C (SS-400) reveals the highest photocurrent density (0.33 mA cm?2) at 1.23 V vs. RHE under AM 1.5G, that is approximately of 1.9 and 1.2 times than SS-300 (0.17 mA cm?2) and SS-500 (0.27 mA cm?2), respectively. The SS-400 shows the hydrogen and oxygen evolution of 5.5 and 2.7 μmol cm?2h?1, and the corresponding faradaic efficiencies are about 89.4% and 87.7%, respectively. The mainly enhanced reason of SS-400 is that appropriate amount of 0D SnO2 nanoparticles generated on the surfaces and edges of 2D SnS2 nanosheets fabricate the in-situ of S-scheme heterojunctions, which are accelerating the recombination of carriers with relatively weaker redox capacity and promoting the separation of carriers with relatively stronger redox capacity. Meantime, the barrier factor, internal electric field, coulomb interaction, and applied bias factors can also promote the recombination of carriers with weak redox capacity (electrons of SnO2 and holes of SnS2). This work will provide a novel thought for designing and constructing the mechanism of S-scheme heterojunctions for photoelectrochemical water splitting. ? 2019 Elsevier B.V.Accession Number: 20194307566178 -
Record 202 of
Title:Hierarchical Feature Fusion Network for Salient Object Detection
Author(s):Li, Xuelong(1); Song, Dawei(2); Dong, Yongsheng(1)Source: IEEE Transactions on Image Processing Volume: 29 Issue: DOI: 10.1109/TIP.2020.3023774 Published: 2020Abstract:Convolutional Neural Network (CNN) has shown their advantages in salient object detection. CNN can generate great saliency maps because it can obtain high-level semantic information. And the semantic information is usually achieved by stacking multiple convolutional layers and pooling layers. However, multiple pooling operations will reduce the size of the feature map and easily blur the boundary of the salient object. Therefore, such operations are not beneficial to generate great saliency results. To alleviate this issue, we propose a novel edge information-guided hierarchical feature fusion network (HFFNet). Our network fuses features hierarchically and retains accurate semantic information and clear edge information effectively. Specifically, we extract image features from different levels of VGG. Then, we fuse the features hierarchically to generate high-level semantic information and low-level edge information. In order to retain better information at different levels, we adopt a one-to-one hierarchical supervision strategy to supervise the generation of low-level information and high-level information respectively. Finally, we use low-level edge information to guide the saliency map generation, and the edge guidance fusion is able to identify saliency regions effectively. The proposed HFFNet has been extensively evaluated on five traditional benchmark datasets. The experimental results demonstrate that the proposed model is fairly effective in salient object detection compared with 10 state-of-the-art models under different evaluation indicators, and it is superior to most of the comparison models. ? 1992-2012 IEEE.Accession Number: 20204209362567 -
Record 203 of
Title:A sequential optimization procedure designed for Lyot coronagraph aiming to realize high contrast direct imaging for exoplanets
Author(s):Ge, Rui(1,2); Wang, Pengfei(1,2); Wang, Yuanbo(1); Zhao, Hui(1); Wei, Jingxuan(3); Duan, Yongqiang(1); Fan, Xuewu(1)Source: Proceedings of SPIE - The International Society for Optical Engineering Volume: 11443 Issue: DOI: 10.1117/12.2561263 Published: 2020Abstract:Coronagraph is a powerful instrumentation that can be used to realize direct exoplanet imaging. Because the stars are far brighter than the exoplanets, a very high requirement for extinction is raised to obtain a high contrast imaging. By optimizing the transmittance of the entrance pupil and the Lyot stop in Lyot Coronagraph, a sequential optimization procedure is proposed to obtain even higher contrast imaging. In this manuscript, the usually adopted joint optimization in the existing literatures is divided into two steps, which we call the sequential optimization procedure. First, the entrance pupil is optimized for maximum transmission while the contrast constraint is imposed on the focal plane of the lens behind it. Second, the Lyot stop is optimized for maximum transmission with the contrast constraint imposed on the imaging plane. Compared with the joint optimization procedure, the sequential one can provide additional advantages. In terms of performance, under the same conditions, an IWA(Inner working angle) of 1.53λ/D can be obtained while the IWA for joint one is 2.01λ/D. Moreover, the sequential optimization is much faster. Referring to practical applications, the optimum transmittance of Lyot stop in sequential case becomes binary and therefore easy to fabricate. However sequential optimization reduces the throughput approximately 36.81%, which is a drawback that should be compensated. ? COPYRIGHT SPIE. Downloading of the abstract is permitted for personal use only.Accession Number: 20210509847561 -
Record 204 of
Title:The phase transitions and magnetocaloric effects in Ga-doped Heusler Ni50Mn36Sn14 alloys
Author(s):Cao, Kaiyan(1); Wang, Dingchen(1); Tian, Fanghua(1); Zhao, Qizhong(1); Chang, Tieyan(1); Zhang, Haosu(2); Zhou, Chao(1); Zuo, Wenliang(1); Yang, Sen(1); Song, Xiaoping(1); Zhang, Yin(1)Source: Japanese Journal of Applied Physics Volume: 59 Issue: 1 DOI: 10.7567/1347-4065/ab5c59 Published: January 1, 2020Abstract:Recent investigations in the magnetocaloric effect mainly focus on the discovery of new materials exhibiting large refrigeration capacity, tuneable working temperature and negligible hysteresis. In this context, different magnetic phase transitions of Ni50Mn36Ga x Sn14-x (0 ≤ x ≤ 14) ferromagnetic shape memory alloys have been systematically investigated and the phase diagram with morphotropic phase boundary (MPB) was drawn accordingly. In particular, magnetocaloric effects were calculated and compared in the vicinity of Curie transition, martensitic transition and MPB, respectively. As a result, the magnetocaloric effect of the Ni50Mn36Ga5Sn9 alloy has a wide working temperature range and zero thermal hysteresis at the MPB compared to the effect occurring at other transitions, and the effective refrigeration capacity could reach a compared value 96 J kg-1 in this case. ? 2019 The Japan Society of Applied Physics.Accession Number: 20200908224099