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55. Room-temperature nanoseconds spin relaxation in WTe2 and MoTe2 thin films

Author

Wang, Qisheng, Li, Jie, Besbas, Jean, Hsu, Chuang-Han, Cai, Kaiming, Yang, Li, Cheng, Shuai, Wu, Yang, Zhang, Wenfeng, Wang, Kaiyou, Chang, Tay-Rong, Lin, Hsin, Chang, Haixin, and Yang, Hyunsoo

Subjects
Condensed Matter - Materials Science
Abstract

The Weyl semimetal WTe2 and MoTe2 show great potential in generating large spin currents since they possess topologically-protected spin-polarized states and can carry a very large current density. In addition, the intrinsic noncentrosymmetry of WTe2 and MoTe2 endows with a unique property of crystal symmetry-controlled spin-orbit torques. An important question to be answered for developing spintronic devices is how spins relax in WTe2 and MoTe2. Here, we report a room-temperature spin relaxation time of 1.2 ns (0.4 ns) in WTe2 (MoTe2) thin film using the time-resolved Kerr rotation (TRKR). Based on ab initio calculation, we identify a mechanism of long-lived spin polarization resulting from a large spin splitting around the bottom of the conduction band, low electron-hole recombination rate and suppression of backscattering required by time-reversal and lattice symmetry operation. In addition, we find the spin polarization is firmly pinned along the strong internal out-of-plane magnetic field induced by large spin splitting. Our work provides an insight into the physical origin of long-lived spin polarization in Weyl semimetals which could be useful to manipulate spins for a long time at room temperature.

Published
2018

71. Representation Learning Based on Vision Transformer.

Author

Ran, Ruisheng, Gao, Tianyu, Hu, Qianwei, Zhang, Wenfeng, Peng, Shunshun, and Fang, Bin

Subjects
TRANSFORMER models, INFORMATION technology, IMAGE reconstruction, CHANNEL coding, DATA visualization
Abstract

In recent years, with the rapid development of information technology, the volume of image data has grown exponentially. However, these datasets typically contain a large amount of redundant information. To extract effective features and reduce redundancy from images, a representation learning method based on the Vision Transformer (ViT) has been proposed, and to our best knowledge, Transformer was first applied to zero-shot learning (ZSL). The method adopts a symmetric encoder–decoder structure, where the encoder incorporates Multi-Head Self-Attention (MSA) mechanism of ViT to reduce the dimensionality of image features, eliminate redundant information, and decrease computational burden. Consequently, it effectively extracts features, and the decoder is utilized for reconstructing image data. We evaluated the representation learning capability of the proposed method in various tasks, including data visualization, image reconstruction, face recognition, and ZSL. By comparing with state-of-the-art representation learning methods, the outstanding results obtained validate the effectiveness of this method in the field of representation learning. [ABSTRACT FROM AUTHOR]

Published
2024
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72. Application and analysis of superconducting magnetic eddy current heater used in wind thermal power generation system.

Author

Zhang, Wenfeng, Chen, Chen, Liu, Zeyuan, Wang, Youhua, and Liu, Chengcheng

Subjects
*WIND power, *HEAT storage devices, *SUPERCONDUCTORS, *SUPERCONDUCTING coils, *HEATING, *WIND forecasting
Abstract

In order to cope with the grid fluctuation caused by large‐scale wind power connected to the grid, the wind thermal power generation system has been proposed and extensively studied. The wind thermal power generation system uses a wind turbine to drive a heat generation device to heat the heat storage medium, which is further exchanged to drive a turbine to generate electricity. A superconducting magnetic eddy current heater (SMH) is proposed for the characteristics of wind thermal power generation system, which uses non‐resistive, large current‐carrying superconducting coils for excitation, and has high output efficiency and power density. The working principle of magnetic eddy current heating is analysed, and the structure of SMH with no ferromagnetic material and two heating screens inside and outside is proposed according to the characteristics of SMH. An analytical model of the SMH is established, and the influence of the structure and materials of the SMH on the magnetic field distribution is analysed. Based on this, a 22‐pole SMH was designed and analysed for output power at 10–20 rpm. A three‐dimensional magnetism‐stress combined analysis model of SMH is established, and the strain and stress characteristics of SMH are simulated under the condition of maximum output power, which verifies the feasibility of the mechanical properties of existing superconducting materials for application in SMH. [ABSTRACT FROM AUTHOR]

Published
2024
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94. One‐year status of hepatic venous pressure gradient measurement from 85 hospitals in China

Author

Wang, Jitao, Cui, Ting, Zhang, Linpeng, Yan, Zhiping, Li, Lei, Chen, Jinjun, Sun, Junhui, Xiang, Hua, Zhu, He, Wu, Hao, Gengzang, Jiancuo, Zhang, Feng, Wu, Wei, Cao, Guohong, Guo, Wuhua, Shi, Haibin, Xue, Hui, Huang, Guangjun, Yu, Qiang, Niu, Meng, Xiang, Huiling, Kong, Derun, Gou, Wei, Luo, Xuefeng, He, Fuliang, Yuan, Min, Liu, Wei, Wang, Yong, Hu, Hongjie, Zhu, Xiaoli, Yu, Tao, Sun, Qinxue, Qu, Wei, Lu, Ting, Ma, Deqiang, Zhang, Li, Ma, Jun, Yang, Jun, Mu, Ketao, Zhu, Xiaoliang, Xiong, Kai, Ding, Huiguo, Yao, Shengjuan, Huang, Mingsheng, Wang, Fang, Wang, Zexin, Huang, Yong, Li, Jianan, Yi, Hongfeng, Huang, Birun, Zhao, Zhongwei, Feng, Duiping, Lei, Yanming, Hou, Changlong, Guo, Wenbo, Liu, Shirong, Teng, Gaojun, Zhu, Kangshun, Wu, Fan, Hu, Xiaogang, Zhang, Wenfeng, Yang, Shaoqi, Hu, Zhouchao, Pang, Pengfei, Zhuang, Shaowu, Wang, Weidong, Zhu, Qingliang, Zhang, Kunpeng, Liu, Chengyu, Li, Dongliang, Ma, Chao, Jiang, Hong, Zhao, Xingong, Ren, Weixin, Wang, Zhiwei, Yu, Lei, Lin, Fuhuang, Yan, Chaoguang, Wang, Feng, Yu, Lei, Huan, Hui, Shen, Wenyong, He, Shaofei, Zhang, Chengda, Bao, Jinlun, Liu, Jiangtao, Wu, Jun, Zhao, Jianbo, Zhang, Jian, and Qi, Xiaolong

Abstract

Surveys and research on the applications of the hepatic venous pressure gradient (HVPG) are important for understanding the current status and future development of this technology in China. This article aimed to investigate the status of hepatic venous pressure gradient measurement in China in 2022. We investigated the overall status of HVPG technology in China—including hospital distribution, hospital level, annual number of cases, catheters used, average cost, indications, and current challenges by using online questionnaire. By counting the number and percentages of cases of these results, we hope to clarify the current status of HVPG measurements in China. According to the survey, 85 hospitals in China used HVPG technology in 2022 distributed across 29 provinces. A total of 4989 HVPG measurements were performed in all of the surveyed hospitals in 2022, of which 2813 cases (56.4%) were measured alone. The average cost of HVPG measurement was 5646.8 ± 2327.9 CNY. Of the clinical teams who performed the measurements (sometimes multiple per hospital), 94.3% (82/87) used the balloon method, and the majority of the teams (72.4%, 63/87) used embolectomy catheters. This survey clarified the clinical application status of HVPG in China and confirmed that some medical institutions in China have established a foundation for this technology. It is still necessary to continue promoting and popularizing this technology in the future. A survey analysis of hepatic venous pressure gradient for portal hypertension in China. Significant findings of the study Some medical institutions in China have already mastered the technique and applied it in their clinical practices. However, promoting and popularizing hepatic venous pressure gradient (HVPG) is still necessary. What this study adds We analyzed the overall status of HVPG measurement technology in China.

Published
2024
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95. Fast self-powered n-InGaN layer/p-Cu2O microcrystal visible-light photoelectrochemical photodetector with high photocurrent and responsivity.

Author

Zhang, Wenfeng, Deng, Rongli, Luo, Mingrui, Hong, Hao, Pan, Xingchen, and Nötzel, Richard

Subjects
*PHOTODETECTORS, *ELECTRIC fields, *TRIBOELECTRICITY, *INDIUM gallium nitride, *PHOTOCATHODES, *NANOWIRES
Abstract

An efficient visible-light photoelectrochemical photodetector based on a compact In-rich n-InGaN layer activated by p-Cu2O microcrystals operating as photoanode in the self-powered mode is demonstrated. The photocurrent density of 80 µA/cm2 under one-sun illumination is more than 10 times larger than that of a bare InGaN layer. Moreover, the photocurrent density, responsivity of 0.8 mA/W, specific detectivity of 4 × 109 Jones, and response times of 5–8 ms are more than five times better compared to those of our previously reported nanowire counterpart. The excellent performance is attributed to maximized photocarrier separation in the built-in electric field of the internal p–n junction for fully depleted Cu2O microcrystals with maximized height and the planar geometry, guaranteeing unhindered diffusion of the electrolyte to and from the photoanode surface. [ABSTRACT FROM AUTHOR]

Published
2024
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