13 results on '"D.M. Wei"'
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2. Design and Testing of the Front-End Electronics of WCDA in LHAASO
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F. Aharonian, Q. An, null Axikegu, L.X. Bai, Y.X. Bai, Y.W. Bao, D. Bastieri, X.J. Bi, Y.J. Bi, H. Cai, J.T. Cai, Z. Cao, J. Chang, J.F. Chang, X.C. Chang, B.M. Chen, J. Chen, L. Chen, M.J. Chen, M.L. Chen, Q.H. Chen, S.H. Chen, S.Z. Chen, T.L. Chen, X.L. Chen, Y. Chen, N. Cheng, Y.D. Cheng, S.W. Cui, X.H. Cui, Y.D. Cui, B.Z. Dai, H.L. Dai, Z.G. Dai, null Danzengluobu, R.S. Dong, X.J. Dong, J.H. Fan, Y.Z. Fan, Z.X. Fan, J. Fang, K. Fang, C.F. Feng, L. Feng, S.H. Feng, Y.L. Feng, B. Gao, C.D. Gao, Q. Gao, W. Gao, M.M. Ge, L.S. Geng, G.H. Gong, Q.B. Gou, J.L. Gu, M.H. Gu, J.G. Guo, X.L. Guo, Y.Q. Guo, Y.Y. Guo, Y.A. Han, H.H. He, H.N. He, J.C. He, S.L. He, X.B. He, Y. He, Z.Q. He, M. Heller, Y.K. Hor, C. Hou, X. Hou, H.B. Hu, S. Hu, S.C. Hu, X.J. Hu, D.H. Huang, Q.L. Huang, W.H. Huang, X.T. Huang, Z.C. Huang, F. Ji, X.L. Ji, H.Y. Jia, K. Jiang, Z.J. Jiang, C. Jin, D. Kuleshov, K. Levochkin, B.B. Li, C. Li, F. Li, H.B. Li, H.C. Li, H.Y. Li, J. Li, K. Li, W.L. Li, X. Li, X.R. Li, Y. Li, Y.Z. Li, Z. Li, E.W. Liang, Y.F. Liang, S.J. Lin, B. Liu, C. Liu, D. Liu, H. Liu, H.D. Liu, J. Liu, J.L. Liu, J.S. Liu, J.Y. Liu, M.Y. Liu, R.Y. Liu, S.M. Liu, W. Liu, Y.N. Liu, Z.X. Liu, W.J. Long, R. Lu, H.K. Lv, B.Q. Ma, L.L. Ma, X.H. Ma, J.R. Mao, A. Masood, W. Mitthumsiri, T. Montaruli, Y.C. Nan, B.Y. Pang, P. Pattarakijwanich, Z.Y. Pei, B.D. Piazzoli, M.Y. Qi, J.J. Qin, D. Ruffolo, V. Rulev, A. Saiz, L. Shao, O. Shchegolev, X.D. Sheng, J.R. Shi, C.X. Song, H.C. Song, Yu. V. Stenkin, V. Stepanov, Q.N. Sun, X.N. Sun, Z.B. Sun, P.H.T. Tam, Z.B. Tang, W.W. Tian, D. della Volpe, B.D. Wang, C. Wang, H. Wang, H.G. Wang, J.C. Wang, J.S. Wang, L.P. Wang, L.Y. Wang, R.N. Wang, W. Wang, X.G. Wang, X.J. Wang, X.Y. Wang, Y.D. Wang, Y.J. Wang, Y.P. Wang, Z. Wang, Z.H. Wang, Z.X. Wang, D.M. Wei, J.J. Wei, Y.J. Wei, T. Wen, C.Y. Wu, H.R. Wu, S. Wu, W.X. Wu, X.F. Wu, S.Q. Xi, J. Xia, J.J. Xia, G.M. Xiang, G. Xiao, H.B. Xiao, G.G. Xin, Y.L. Xin, Y. Xing, D.L. Xu, R.X. Xu, L. Xue, D.H. Yan, X.B. Yan, C.W. Yang, F.F. Yang, J.Y. Yang, L.L. Yang, M.J. Yang, R.Z. Yang, S.B. Yang, Y.H. Yao, Z.G. Yao, Y.M. Ye, L.Q. Yin, N. Yin, X.H. You, Z.Y. You, Y.H. Yu, Q. Yuan, H.D. Zeng, T.X. Zeng, W. Zeng, Z.K. Zeng, M. Zha, X.X. Zhai, B.B. Zhang, H.M. Zhang, H.Y. Zhang, J.L. Zhang, J.W. Zhang, L. Zhang, L.X. Zhang, P.F. Zhang, P.P. Zhang, R. Zhang, S.R. Zhang, S.S. Zhang, X. Zhang, X.P. Zhang, Y. Zhang, Y.F. Zhang, Y.L. Zhang, B. Zhao, J. Zhao, L. Zhao, L.Z. Zhao, S.P. Zhao, F. Zheng, Y. Zheng, B. Zhou, H. Zhou, J.N. Zhou, P. Zhou, R. Zhou, S.Z. Zhou, X.X. Zhou, C.G. Zhu, F.R. Zhu, H. Zhu, K.J. Zhu, and X. Zuo
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Nuclear and High Energy Physics ,Photomultiplier ,Dynamic range ,Cherenkov detector ,Detector ,law.invention ,Root mean square ,Air shower ,Nuclear Energy and Engineering ,Observatory ,law ,Environmental science ,Electronics ,Electrical and Electronic Engineering ,Remote sensing - Abstract
Water Cherenkov detector array (WCDA) is one of the key parts of the Large High Altitude Air Shower Observatory (LHAASO), the construction of which was completed by the end of 2020. The WCDA covers a 78 000-m2 area and there exist 3120 large size photomultiplier tubes (PMTs) in three ponds: 8-in PMTs are used in WCDA pond No. 1 and 20-in PMTs are used in ponds No. 2 and No. 3. The front-end electronics (FEE) system based on multigain measurement technique is designed to achieve both high-precision time and charge measurements over a large dynamic range from single photon electron (S.P.E.) to 4000 P.E. (for water pond No. 1)/1800 P.E. (for water ponds No. 2 and No. 3). To achieve a high-quality clock distribution and phase alignment as well as mixed transmission of data, clock, and commands in one fiber over a long distance, an enhanced white rabbit (WR) technique is used. Testing of all the 350 FEE modules for the WCDA is presented in this article. Test results indicate that the charge resolution is better than 20% at S.P.E. and 1% at 1800/4000 P.E. and the time resolution is better than 300 ps root mean square (rms), which successfully meets the application requirement. All the FEE modules have been fabricated and installed for the LHAASO WCDA from 2018 to 2020, and the initial commissioning operation indicates that the FEEs function well.
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- 2021
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3. Corrigendum to 'Performance test of the electromagnetic particle detectors for the LHAASO experiment' [Nucl. Instrum. Methods Phys. Res. A 1001 (2021) 165193]
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F. Aharonian, Q. An, null Axikegu, L.X. Bai, Y.X. Bai, Y.W. Bao, D. Bastieri, X.J. Bi, Y.J. Bi, H. Cai, J.T. Cai, Z. Cao, J. Chang, J.F. Chang, X.C. Chang, B.M. Chen, J. Chen, L. Chen, M.J. Chen, M.L. Chen, Q.H. Chen, S.H. Chen, S.Z. Chen, T.L. Chen, X.L. Chen, Y. Chen, N. Cheng, Y.D. Cheng, S.W. Cui, X.H. Cui, Y.D. Cui, B.Z. Dai, H.L. Dai, Z.G. Dai, null Danzengluobu, D. della Volpe, B. D’Ettorre Piazzoli, X.J. Dong, J.H. Fan, Y.Z. Fan, Z.X. Fan, J. Fang, K. Fang, C.F. Feng, L. Feng, S.H. Feng, Y.L. Feng, B. Gao, C.D. Gao, Q. Gao, W. Gao, M.M. Ge, L.S. Geng, G.H. Gong, Q.B. Gou, M.H. Gu, J.G. Guo, X.L. Guo, Y.Q. Guo, Y.Y. Guo, Y.A. Han, H.H. He, H.N. He, J.C. He, S.L. He, X.B. He, Y. He, M. Heller, Y.K. Hor, C. Hou, X. Hou, H.B. Hu, S. Hu, S.C. Hu, X.J. Hu, D.H. Huang, Q.L. Huang, W.H. Huang, X.T. Huang, Z.C. Huang, F. Ji, X.L. Ji, H.Y. Jia, K. Jia, K. Jiang, Z.J. Jiang, C. Jin, D. Kuleshov, K. Levochkin, B. Li, B.B. Li, C. Li, F. Li, H. Li, H.B. Li, H.C. Li, H.Y. Li, J. Li, K. Li, W.L. Li, X. Li, X.R. Li, Y. Li, Y.Z. Li, Z. Li, E.W. Liang, Y.F. Liang, S.J. Lin, B. Liu, C. Liu, D. Liu, H. Liu, H.D. Liu, J. Liu, J.L. Liu, J.S. Liu, J.Y. Liu, M.Y. Liu, R.Y. Liu, S.M. Liu, W. Liu, Y.N. Liu, Z.X. Liu, W.J. Long, R. Lu, H.K. Lv, B.Q. Ma, L.L. Ma, X.H. Ma, J.R. Mao, A. Masood, W. Mitthumsiri, T. Montaruli, Y.C. Nan, B.Y. Pang, P. Pattarakijwanich, Z.Y. Pei, M.Y. Qi, D. Ruffolo, V. Rulev, A. Sáiz, L. Shao, O. Shchegolev, X.D. Sheng, J.R. Shi, H.C. Song, Yu.V. Stenkin, V. Stepanov, Q.N. Sun, X.N. Sun, Z.B. Sun, P.H. T. Tam, Z.B. Tang, W.W. Tian, B.D. Wang, C. Wang, H. Wang, H.G. Wang, J.C. Wang, J.S. Wang, L.P. Wang, L.Y. Wang, R.N. Wang, W. Wang, X.G. Wang, X.J. Wang, X.Y. Wang, Y.D. Wang, Y.J. Wang, Y.P. Wang, Z. Wang, Z.H. Wang, Z.X. Wang, D.M. Wei, J.J. Wei, Y.J. Wei, T. Wen, C.Y. Wu, H.R. Wu, S. Wu, W.X. Wu, X.F. Wu, S.Q. Xi, J. Xia, J.J. Xia, G.M. Xiang, G. Xiao, H.B. Xiao, G.G. Xin, Y.L. Xin, Y. Xing, D.L. Xu, R.X. Xu, L. Xue, D.H. Yan, C.W. Yang, F.F. Yang, J.Y. Yang, L.L. Yang, M.J. Yang, R.Z. Yang, S.B. Yang, Y.H. Yao, Z.G. Yao, Y.M. Ye, L.Q. Yin, N. Yin, X.H. You, Z.Y. You, Y.H. Yu, Q. Yuan, H.D. Zeng, T.X. Zeng, W. Zeng, Z.K. Zeng, M. Zha, X.X. Zhai, B.B. Zhang, H.M. Zhang, H.Y. Zhang, J.L. Zhang, J.W. Zhang, L. Zhang, L.X. Zhang, P.F. Zhang, P.P. Zhang, R. Zhang, S.R. Zhang, S.S. Zhang, X. Zhang, X.P. Zhang, Y. Zhang, Y.F. Zhang, Y.L. Zhang, B. Zhao, J. Zhao, L. Zhao, L.Z. Zhao, S.P. Zhao, X. Zhao, F. Zheng, Y. Zheng, B. Zhou, H. Zhou, J.N. Zhou, P. Zhou, R. Zhou, X.X. Zhou, C.G. Zhu, F.R. Zhu, H. Zhu, K.J. Zhu, and X. Zuo
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Physics ,Nuclear physics ,Nuclear and High Energy Physics ,Detector ,Particle ,Instrumentation - Published
- 2022
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4. Workshop on the design and use of clinical trials with multiple endpoints, with a focus on prevention of RSV
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O. Prunas, J. Willemsen, J.L. Warren, L. Bont, J.L. Schwartz, J. Atwell, E. Begier, N. Dean, I. Hirsch, R. Karron, K. Klugman, R. Kramer, E. Leidman, R. Link-Gelles, H. Nair, CA. Panozzo, E. Pelfrene, E.A.F. Simões, P.G. Smith, P. Srikantiah, M.E. Sundaram, D. Thindwa, D.W. Vaughn, E. Wilson, H.J. Zar, V.E. Pitzer, and D.M. Weinberger
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Immunologic diseases. Allergy ,RC581-607 - Abstract
A meeting held in Lisbon, Portugal, in February 2023 focused on critical aspects of clinical trial design for respiratory syncytial virus (RSV) preventative therapies. The meeting addressed two primary areas: enhancing the efficiency and success of randomized controlled trials (RCTs) for RSV preventative therapies and designing RCTs to better inform post-licensure decision-making. Topics included the selection of primary endpoints, innovative approaches to incorporating multiple endpoints and historical data, and the challenges and benefits of sequential trial designs. The discussion also touched on meta-regression models for obtaining more robust, context-specific estimates of vaccine efficacy. Overall, the meeting underscored the importance of balancing efficiency and robustness in RSV vaccine trial design, while recognizing the need for further discussions involving regulatory and advisory bodies.
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- 2024
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5. Performance of LHAASO-WCDA and observation of the Crab Nebula as a standard candle *
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F. Aharonian, Q. An, 克古 Axikegu, L.X. Bai, Y.X. Bai, Y.W. Bao, D. Bastieri, X.J. Bi, Y.J. Bi, H. Cai, J.T. Cai, Z. Cao, J. Chang, J.F. Chang, X.C. Chang, B.M. Chen, J. Chen, L. Chen, M.J. Chen, M.L. Chen, Q.H. Chen, S.H. Chen, S.Z. Chen, T.L. Chen, X.L. Chen, Y. Chen, N. Cheng, Y.D. Cheng, S.W. Cui, X.H. Cui, Y.D. Cui, B.Z. Dai, H.L. Dai, Z.G. Dai, 罗布 Danzengluobu, D. della Volpe, B. D'Ettorre Piazzoli, X.J. Dong, J.H. Fan, Y.Z. Fan, Z.X. Fan, J. Fang, K. Fang, C.F. Feng, L. Feng, S.H. Feng, Y.L. Feng, B. Gao, C.D. Gao, Q. Gao, W. Gao, M.M. Ge, L.S. Geng, G.H. Gong, Q.B. Gou, M.H. Gu, J.G. Guo, X.L. Guo, Y.Q. Guo, Y.Y. Guo, Y.A. Han, H.H. He, H.N. He, J.C. He, S.L. He, X.B. He, Y. He, M. Heller, Y.K. Hor, C. Hou, X. Hou, H.B. Hu, S. Hu, S.C. Hu, X.J. Hu, D.H. Huang, Q.L. Huang, W.H. Huang, X.T. Huang, Z.C. Huang, F. Ji, X.L. Ji, H.Y. Jia, K. Jiang, Z.J. Jiang, C. Jin, D. Kuleshov, K. Levochkin, B.B. Li, C. Li, F. Li, H.B. Li, H.C. Li, H.Y. Li, J. Li, K. Li, W.L. Li, X. Li, X.R. Li, Y. Li, Y.Z. Li, Z. Li, E.W. Liang, Y.F. Liang, S.J. Lin, B. Liu, C. Liu, D. Liu, H. Liu, H.D. Liu, J. Liu, J.L. Liu, J.S. Liu, J.Y. Liu, M.Y. Liu, R.Y. Liu, S.M. Liu, W. Liu, Y.N. Liu, Z.X. Liu, W.J. Long, R. Lu, H.K. Lv, B.Q. Ma, L.L. Ma, X.H. Ma, J.R. Mao, A. Masood, W. Mitthumsiri, T. Montaruli, Y.C. Nan, B.Y. Pang, P. Pattarakijwanich, Z.Y. Pei, M.Y. Qi, B.Q. Qiao, D. Ruffolo, V. Rulev, A. Sáiz, L. Shao, O. Shchegolev, X.D. Sheng, J.R. Shi, H.C. Song, Yu.V. Stenkin, V. Stepanov, Q.N. Sun, X.N. Sun, Z.B. Sun, P.H.T. Tam, Z.B. Tang, W.W. Tian, B.D. Wang, C. Wang, H. Wang, H.G. Wang, J.C. Wang, J.S. Wang, L.P. Wang, L.Y. Wang, R.N. Wang, W. Wang, X.G. Wang, X.J. Wang, X.Y. Wang, Y.D. Wang, Y.J. Wang, Y.P. Wang, Z. Wang, Z.H. Wang, Z.X. Wang, D.M. Wei, J.J. Wei, Y.J. Wei, T. Wen, C.Y. Wu, H.R. Wu, S. Wu, W.X. Wu, X.F. Wu, S.Q. Xi, J. Xia, J.J. Xia, G.M. Xiang, G. Xiao, H.B. Xiao, G.G. Xin, Y.L. Xin, Y. Xing, D.L. Xu, R.X. Xu, L. Xue, D.H. Yan, C.W. Yang, F.F. Yang, J.Y. Yang, L.L. Yang, M.J. Yang, R.Z. Yang, S.B. Yang, Y.H. Yao, Z.G. Yao, Y.M. Ye, L.Q. Yin, N. Yin, X.H. You, Z.Y. You, Y.H. Yu, Q. Yuan, H.D. Zeng, T.X. Zeng, W. Zeng, Z.K. Zeng, M. Zha, X.X. Zhai, B.B. Zhang, H.M. Zhang, H.Y. Zhang, J.L. Zhang, J.W. Zhang, L. Zhang, L.X. Zhang, P.F. Zhang, P.P. Zhang, R. Zhang, S.R. Zhang, S.S. Zhang, X. Zhang, X.P. Zhang, Y. Zhang, Y.F. Zhang, Y.L. Zhang, B. Zhao, J. Zhao, L. Zhao, L.Z. Zhao, S.P. Zhao, F. Zheng, Y. Zheng, B. Zhou, H. Zhou, J.N. Zhou, P. Zhou, R. Zhou, X.X. Zhou, C.G. Zhu, F.R. Zhu, H. Zhu, K.J. Zhu, X. Zuo, and (The LHAASO Collaboration)
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Physics ,Nuclear and High Energy Physics ,010308 nuclear & particles physics ,Cherenkov detector ,Point source ,Astrophysics::High Energy Astrophysical Phenomena ,Cosmic distance ladder ,Gamma ray ,Astronomy and Astrophysics ,Cosmic ray ,Astrophysics ,01 natural sciences ,law.invention ,Crab Nebula ,law ,0103 physical sciences ,Spectral energy distribution ,Angular resolution ,010306 general physics ,Instrumentation - Abstract
The first Water Cherenkov detector of the LHAASO experiment (WCDA-1) has been operating since April 2019. The data for the first year have been analyzed to test its performance by observing the Crab Nebula as a standard candle. The WCDA-1 achieves a sensitivity of 65 mCU per year, with a statistical threshold of 5 . To accomplish this, a 97.7% cosmic-ray background rejection rate around 1 TeV and 99.8% around 6 TeV with an approximate photon acceptance of 50% is achieved after applying an algorithm to separate gamma-induced showers. The angular resolution is measured using the Crab Nebula as a point source to be approximately 0.45° at 1 TeV and better than 0.2° above 6 TeV, with a pointing accuracy better than 0.05°. These values all match the design specifications. The energy resolution is found to be 33% for gamma rays around 6 TeV. The spectral energy distribution of the Crab Nebula in the range from 500 GeV to 15.8 TeV is measured and found to be in agreement with the results from other TeV gamma ray observatories.
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- 2021
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6. Effects of thermal-cold cycling on the dimensional stability of TiC reinforced steel matrix composite
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Z.Y. Cai, D.M. Wei, X.X. Tu, Peng Zhihong, L.R. Xiao, and Xingxing Zhao
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Austenite ,Materials science ,Precipitation (chemistry) ,Mechanical Engineering ,Composite number ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Microstructure ,01 natural sciences ,0104 chemical sciences ,Carbide ,Mechanics of Materials ,Residual stress ,Martensite ,Vickers hardness test ,General Materials Science ,Composite material ,0210 nano-technology - Abstract
Thermal-cold cycling (TCC) treatment was applied to improve the dimensional stability of TiC reinforced steel matrix composite materials in this study. Also, the microstructure, related properties and potential stability mechanisms were investigated. When the TCC cycles were 3, Vickers hardness reached the peak value of 1051.7 HV and relative dimensional change was only 0.012% in a natural service for 30 days. Besides, the retained austenite disappeared and residual stress dramatically decreased from −740 MPa to −357 MPa. It demonstrated that the TiC reinforced steel matrix composite possessed the best dimensional stability after 3 TCC cycles. A variety of stabilizing mechanisms, including martensitic refinement, retained austenite-martensite transformation, carbides precipitation, and residual stress release were observed, hence resulting in a significantly improvement of the dimensional stability of the composite.
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- 2020
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7. Introduction to the High Energy cosmic-Radiation Detection (HERD) Facility onboard China’s Future Space Station
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Shuang-Nan Zhang, Oscar Adriani, Herd Consortium, Sebastiano Albergo, Giovanni Ambrosi, Qi An, Philipp Azzarello, Yonglin Bai, Tianwei Bao, Paolo Bernardini, Bruna Bertucci, Xiaojun Bi, Massimo Bongi, Sergio Bottai, Weiwei Cao, Zhen Cao, Junying Chai, Jin Chang, Guoming Chen, Y Chen, Zhen Chen, X.H. Cui, Z.G. Dai, Raffaello D’Alessandro, Margherita Di Santo, Yongwei Dong, Matteo Duranti, Yizhong Fan, Kun Fang, C.Q. Feng, Hua Feng, Valerio Formato, Piergiorgio Fusco, Jiarui Gao, Fabio Gargano, Nicola Giglietto, Quanbu GOU, Yi Qing Guo, Huihai He, hongbo HU, Peng Hu, G.S. Huang, Jing Huang, Y.F. Huang, H. Li, Ran Li, Yong Li, Z. Li, E.W. Liang, Sujie Lin, H. Liu, Hongbang Liu, J.B. Liu, S.B. Liu, S.M. Liu, Xin Liu, Francesco Loparco, Junguang Lyu, Giovanni Marsella, Mario Nicola Mazziottai, Ivan De Mitri, Nicola Mori, Paolo Papini, Mark Pearce, Wenxi Peng, Martin Pohl, Zheng Quan, Felix Ryde, Dalian Shi, Meng Su, X.L. Sun, Xin Sun, Antonio Surdo, Z.C. Tang, Elena Vannuccini, Roland Walter, Bingbing Wang, Bo Wang, J.C. Wang, J.M. Wang, Junjing Wang, Le Wang, Ruijie Wang, X.L Wang, Xiangyu Wang, Zhigang Wang, D.M. Wei, Bobing Wu, J. Wu, Qiong Wu, Xin Wu, X.F. Wu, Ming Xu, Z.Z. Xu, H.R. Yan, P.F. Yin, Y.W Yu, Qiang Yuan, M. Zha, L. Zhang, Li Zhang, Yi Zhang, Y.L. Zhang, and Z.G. Zhao
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Computer Science::Robotics ,High energy ,business.industry ,Astrophysics::High Energy Astrophysical Phenomena ,Astrophysics::Instrumentation and Methods for Astrophysics ,Environmental science ,Cosmic ray ,Aerospace engineering ,Space astronomy ,business ,Space (mathematics) ,China - Abstract
The High Energy cosmic-Radiation Detection (HERD) facility is one of several space astronomy payloads onboard China's Space Station, which is planned for operation starting around 2025 for about 10 ...
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- 2017
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8. Feedback minimization of the first-passage failure of a hysteretic system under random excitations
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D.M. Wei, Ronghua Huan, and Xueping Li
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Stochastic control ,Dynamical systems theory ,Mechanical Engineering ,Aerospace Engineering ,Ocean Engineering ,Statistical and Nonlinear Physics ,Condensed Matter Physics ,Optimal control ,Nonlinear system ,Nuclear Energy and Engineering ,Control theory ,Random vibration ,Boundary value problem ,First-hitting-time model ,Random dynamical system ,Civil and Structural Engineering ,Mathematics - Abstract
The stochastic optimal bounded control of a hysteretic system for minimizing its first-passage failure is presented. The hysteretic system subjected to random excitation is firstly replaced by an equivalent nonlinear non-hysteretic system. The controlled non-hysteretic system is reduced to a one-dimensional controlled diffusion process by using the stochastic averaging of the energy envelope method. The dynamical programming equations and their associated boundary and final-time conditions for the problems of maximization of reliability and mean first-passage time are formulated. The optimal control law is derived from the dynamical programming equations and the control constraints. The dynamical programming equations for the maximum reliability problem and the mean first-passage time problem are finalized and solved numerically. Finally, numerical results are worked out to illustrate the application and effectiveness of the proposed method.
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- 2010
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9. Mean first-passage time of general bistable systems driven by white noise excitations
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Z.G. Ying, D.M. Wei, and Xueping Li
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Physics ,Bistability ,Mechanical Engineering ,Monte Carlo method ,White noise ,Condensed Matter Physics ,Pontryagin's minimum principle ,Quantitative Biology::Subcellular Processes ,Mechanics of Materials ,General Materials Science ,Boundary value problem ,Statistical physics ,First-hitting-time model ,Civil and Structural Engineering - Abstract
The mean first-passage time (MFPT) of one-dimensional and multi-dimensional bistable systems with weak damping driven by white noise excitations is studied. The Pontryagin equation governing the MFPT is established based on the stochastic averaging method and the MFPT is obtained through solving the Pontryagin equation together with its boundary conditions. By comparing the theoretical results and the results from a Monte Carlo simulation, it is verified that the MFPT can be predicted quite well using the proposed method. Furthermore, it is shown that the MFPT decreases when the density of the random excitations or the correlative strength of two excitations increases.
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- 2009
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10. Fractal effect and anisotropic constitutive model for concrete
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H. Zhang and D.M. Wei
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Materials science ,business.industry ,Applied Mathematics ,Mechanical Engineering ,Isotropy ,Constitutive equation ,Structural engineering ,Mechanics ,Plasticity ,Condensed Matter Physics ,Fractal dimension ,Stress (mechanics) ,Fractal ,Fracture toughness ,Fracture (geology) ,General Materials Science ,business - Abstract
An elasto-anisotropic damage constitutive model for concrete is developed in this work. Disregarding the coupling between the isotropic and the anisotropic damage, the isotropic damage variables are defined as functions of the microcrack fractal dimension, and the anisotropic parts are expressed by the lengths of cracks in concrete which various in different directions. The Helmholtz free energy is decomposed into the elastic deforming, damage and irreversible deforming components, with the last component used to replace the plastic deformation. Therefore the damage constitutive formulas for concrete are derived based on continuum damage mechanics. Evolution laws for both isotropic and anisotropic damage variables are derived, in which the anisotropic parts are obtained by modifying an empirical model. The critical fracture stress and the fracture toughness are investigated for materials with a single fractal crack based on the fractal geometry and the Griffith fracture criterion. Numerical computation is conducted for concrete under the uniaxial and the biaxial compression. The results indicate that the material stiffness degradation can be well addressed when the anisotropic damage is incorporated; the irreversible deformation is greatly related to the behavior of the descending branch beyond the peak load. The validation of the presented model is proofed by comparing results with the experimental data. This model provides an approach to link the macro properties of a material with its micro-structure change.
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- 2009
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11. Using volume-time curves with real-time three-dimensional echocardiography to analyze right ventricular function in patients with pneumoconiosis
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Y. Ding, W. He, and D.M. Wei
- Subjects
Adult ,Male ,medicine.medical_specialty ,Time Factors ,Heart Ventricles ,Anterior wall ,Echocardiography, Three-Dimensional ,Blood Pressure ,Right ventricular ejection fraction ,Internal medicine ,Genetics ,medicine ,Humans ,In patient ,cardiovascular diseases ,Prospective Studies ,Molecular Biology ,Stroke ,Aged ,Aged, 80 and over ,Ventricular function ,business.industry ,Pneumoconiosis ,Three dimensional echocardiography ,Heart ,Stroke Volume ,General Medicine ,Middle Aged ,medicine.disease ,Case-Control Studies ,Cardiology ,Ventricular Function, Right ,Female ,business ,Range of motion - Abstract
We evaluated right ventricular function in patients with pneumoconiosis using real-time three-dimensional echocardiography (RT3DE). A total of 80 consecutive patients were prospectively recruited, 44 of whom were diagnosed with pneumoconiosis, and the remaining 36 age- and gender-matched healthy volunteers served as the control group. All patients underwent both 2D and 3DE. The tricuspid regurgitation pressure (TRPG), right ventricular anterior wall thickness and range of motion, right ventricular posterior wall thickness and range of motion, right ventricular end-diastolic volume, right ventricular end-systolic volume, and right ventricular ejection fraction (RVEF) were measured. The RVEF of healthy volunteers ranged from 50 to 78%, while the RVEF of pneumoconiosis patients ranged from 29 to 73%. TRPG influenced RVEF by 77.3% (P = 0.006) and showed a negative correlation (r = -0.643, P < 0.01). Volume-time curves (VTC) of patients with pneumoconiosis showed more troughs (low stroke volumes) than the VTCs of normal subjects. Evaluation of right ventricular function in patients with pneumoconiosis using RT3DE can provide additional clinical information.
- Published
- 2014
12. The emission features of GRB afterglows
- Author
-
D.M. Wei and T. Lu
- Subjects
Physics ,Shock wave ,Astrophysics::High Energy Astrophysical Phenomena ,Compton scattering ,Synchrotron radiation ,Astronomy ,Astrophysics::Cosmology and Extragalactic Astrophysics ,Astrophysics ,Gamma-ray burst ,Light curve ,Ejecta ,Polarization (waves) ,Afterglow - Abstract
Here we talk about the effects of inverse Compton scattering (ICS) and jet on GRB afterglows. In the simplest fireball model, synchrotron radiation is believed to be the main mechanism of GRB emission, however, here we will show that under some circumstances, the inverse Compton scattering may play an important role, and can change the light curves of GRB afterglows. Beaming of relativistic ejecta in GRBs has been postulated by many authors in order to reduce the total GRB energy, thus it is very important to look for the observational evidence of beaming. Here we analyze the dynamical evolution of the jet blast wave, calculate the jet emission analytically, we find that the sharp break predicted by Rhoads will actually not exist, and for most cases the afterglow light curve will almost not be affected by sideways expansion unless the beaming angle is extremely small. We demonstrate that only when θ0
- Published
- 2001
- Full Text
- View/download PDF
13. Prediction on the very early afterglow of X-ray flashes.
- Author
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Y.Z. Fan, D.M. Wei, and C.F. Wang
- Subjects
- *
X-ray astronomy , *X-ray bursts , *GAMMA ray bursts , *INTERSTELLAR medium , *X-ray telescopes , *ARTIFICIAL satellites - Abstract
In the past two years, tremendous progress in understanding X-ray flashes has been made. Now it is widely believed that X-ray flashes and gamma-ray bursts are intrinsically the same, and that their very different peak energy and flux may be merely due to our different viewing angles to them. Here we analytically calculate the very early afterglow of X-ray flashes, i.e. the reverse shock emission powered by the outflows interacting with the interstellar medium. Assuming , we have shown that typically the R-band flux of reverse shock emission can be bright to ∼16–17th magnitude (the actual values are model-dependent and sensitive to the initial Lorentz factor of the viewed ejecta). That emission is bright enough to be detected by the telescope on work today such as Robotic Optical Transient Search Experiment (ROTSE-III) or the upcoming Ultraviolet and Optical Telescope (UVOT) carried by the Swift satellite, planned for launch in late 2004. [ABSTRACT FROM AUTHOR]
- Published
- 2004
- Full Text
- View/download PDF
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