检索结果-内蒙古大学图书馆

arXiv 2019年

作者： Zhao, Yuan-Yuan Zhang, Chao Cheng, Shuming Li, Xinhui Guo, Yu Liu, Bi-Heng Ku, Huan-Yu Chen, Shin-Liang Wen, Qiaoyan Huang, Yun-Feng Xiang, Guo-Yong Li, Chuan-Feng Guo, Guang-Can College of the Science China University of Petroleum Qingdao266580 China National Laboratory of Solid State Microstructures School of Physics Collaborative Innovation Center of Advanced Microstructure Nanjing University Nanjing210093 China Peng Cheng Laboratory Shenzhen518055 China Synergetic Innovation Center of Quantum Information and Quantum Physics University of Science and Technology of China Hefei230026 China Department of Control Science and Engineering Tongji University Shanghai201804 China Institute for Advanced Study Tongji University Shanghai200092 China Institute for Quantum Computing Baidu Research Beijing100193 China State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications Beijing100876 China National Laboratory of Solid State Microstructures School of Physics Nanjing University Nanjing210093 China Faculty of Physics University of Vienna Boltzmanngasse 5 Vienna1090 Austria Austrian Academy of Sciences Boltzmanngasse 3 Vienna1090 Austria Department of Physics National Chung Hsing University Taichung40227 Taiwan

Entanglement lies at the heart of quantum mechanics, and has been identified an essential resource for diverse applications in quantum information. If entanglement could be verified without any trust in the devices of observers, i.e., in a device-independent (DI) way, then the high security can be guaranteed for various quantum information processing tasks. In this work, we propose and experimentally demonstrate a DI protocol to certify the presence of entanglement based on Einstein-Podolsky-Rosen (EPR) steering. We first establish the DI verification framework by taking the advantages of measurement-device-independent technique and self-testing, which is able to verify all bipartite EPR-steerable states. In the scenario of three-measurement settings for per party, the protocol is robust in tolerance of inefficient measurements and imperfect self-testing. Moreover, a four-photon experiment is implemented for verification beyond Bell nonlocal states. Our work presents the new insight into quantum physics and paves the way for realistic implementations of secure quantum information processing tasks. Copyright © 2019, The Authors. All rights reserved.

关键词： Quantum optics

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Bidirectional spin-wave-driven domain wall motion in antiferromagnetically coupled ferrimagnets

arXiv

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arXiv 2019年

作者： Oh, Se-Hyeok Kim, Se Kwon Xiao, Jiang Lee, Kyung-Jin Department of Nano-Semiconductor and Engineering Korea University Seoul02841 Korea Republic of Department of Physics and Astronomy University of Missouri ColumbiaMO65211 United States Department of Physics State Key Laboratory of Surface Physics Fudan University Shanghai200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing210093 China Institute for Nanoelectronics Devices and Quantum Computing Fudan University Shanghai200433 China Department of Materials Science and Engineering Korea University Seoul02841 Korea Republic of KU-KIST Graduate School of Converging Science and Technology Korea University Seoul02841 Korea Republic of

We investigate ferrimagnetic domain wall dynamics induced by circularly polarized spin waves theoretically and numerically. We find that the direction of domain wall motion depends on both the circular polarization of spin waves and the sign of net spin density of ferrimagnet. Below the angular momentum compensation point, left- (right-) circularly polarized spin waves push a domain wall towards (away from) the spin-wave source. Above the angular momentum compensation point, on the other hand, the direction of domain wall motion is reversed. This bidirectional motion originates from the fact that the sign of spin-wave-induced magnonic torque depends on the circular polarization and the subsequent response of the domain wall to the magnonic torque is governed by the net spin density. Our finding provides a way to utilize a spin wave as a versatile driving force for bidirectional domain wall motion. Copyright © 2019, The Authors. All rights reserved.

关键词： Spin waves

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Research on offense and defense technology for iOS kernel security mechanism

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AIP Conference Proceedings 2018年第1期1955卷

作者： Sijun Chu Hao Wu State Key Laboratory of Mathematical Engineering and Advanced Computing Zhengzhou 450000 China

iOS is a strong and widely used mobile device system. It’s annual profits make up about 90% of the total profits of all mobile phone brands. Though it is famous for its security, there have been many attacks on the iOS operating system, such as the Trident apt attack in 2016. So it is important to research the iOS security mechanism and understand its weaknesses and put forward targeted protection and security check framework. By studying these attacks and previous jailbreak tools, we can see that an attacker could only run a ROP code and gain kernel read and write permissions based on the ROP after exploiting kernel and user layer vulnerabilities. However, the iOS operating system is still protected by the code signing mechanism, the sandbox mechanism, and the not-writable mechanism of the system’s disk area. This is far from the steady, long-lasting control that attackers expect. Before iOS 9, breaking these security mechanisms was usually done by modifying the kernel’s important data structures and security mechanism code logic. However, after iOS 9, the kernel integrity protection mechanism was added to the 64-bit operating system and none of the previous methods were adapted to the new versions of iOS [1]. But this does not mean that attackers can not break through. Therefore, based on the analysis of the vulnerability of KPP security mechanism, this paper implements two possible breakthrough methods for kernel security mechanism for iOS9 and iOS10. Meanwhile, we propose a defense method based on kernel integrity detection and sensitive API call detection to defense breakthrough method mentioned above. And we make experiments to prove that this method can prevent and detect attack attempts or invaders effectively and timely.

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A Novel Timing-based Network Covert Channel Detection Method

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Journal of Physics: Conference Series 2019年第1期1325卷

作者： Shoupu Lu Zhifeng Chen Guangxin Fu Qingbao Li State Key laboratory of Mathematical Engineering and Advanced Computing Zhengzhou Henan Province 450001 China Henan University of Economics and Law Zhengzhou Henan Province 450000 China P.O.Box 5111 Beijing China

Network stealth events are endless, and covert timing channel is one of the most difficult means to prevent. In order to further improve the detection rate of covert timing channel, several typical network covert timing channel construction algorithms are analyzed. On the basis of the above analysis, a detection method based on IPDs multidimensional features was proposed in this paper. IPDs of covert timing channels from three dimensions: shape, change rule and data statistics are analyzed. Respectively, polarization feature, autocorrelation feature, clustering feature are proposed, and the three features are unified into a model. The threshold method is used to determine whether the channel to be detected is a normal channel. Experiments show that the method can detect the existing covert timing channel with less time cost and compared with the traditional detection method has a certain rate of improvement.

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Highly Oxygen Non-Stoichiometric BaSc0.25Co0.75O3-δas a High-Performance Cathode for Intermediate-Temperature Solid Oxide Fuel Cells

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ChemElectroChem 2018年第5期5卷 785-792页

作者： Bo Liu Jaka Sunarso Yuan Zhang Guangming Yang Dr. Wei Zhou Zongping Shao Jiangsu National Synergetic Innovation Center for Advanced Materials State Key Laboratory of Materials-Oriented Chemical Engineering Nanjing Tech University Nanjing 210009 China College of Chemical Engineering Nanjing Tech University Nanjing 210009 China Research Centre for Sustainable Technologies Faculty of Engineering Computing and Science Swinburne University of Technology Kuching 93350 Malaysia Department of Chemical Engineering Curtin University Western Australia 6845 Australia

Lowering the operating temperature of solid oxide fuel cells (SOFCs) is highly desirable to reduce the cost and increase the lifetime, which relies upon the development of a cathode component with high oxygen reduction reaction (ORR) activity at a lower temperature. Herein, we report the characterization of high-performance BaSc x Co 1- x O 3- δ ( x =0, 0.125, 0.25, and 0.375) perovskite SOFC cathodes. Unlike BaCoO 3- δ , which adopts 2H-hexagonal perovskite structure, the replacement of 25 mol % of Co with Sc stabilizes the cubic structure, which also leads to the significant reduction in area specific resistances and their activation energies between 650 and 500 °C (for BaSc 0.25 Co 0.75 O 3- δ ) relative to the non-doped BaCoO 3- δ . In this temperature range, BaSc 0.25 Co 0.75 O 3- δ displayed a remarkably high ORR activity compared to Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF), the current cathode benchmark. We attribute such superior ORR performance to the higher oxygen non-stoichiometries of BaSc 0.25 Co 0.75 O 3 -δ relative to BSCF, which also translates to the higher oxygen bulk diffusion and surface exchange coefficients for the former compared to the latter. As a result, a single fuel cell based on an anode-supported 20 μm thick samarium-doped ceria electrolyte and BaSc 0.25 Co 0.75 O 3- δ cathode achieved a very high peak power density of 1723 mW cm −2 at 650 °C. We also demonstrated the possibility to increase the ORR activity of the BaSc 0.25 Co 0.75 O 3-δ cathode by impregnation of a low amount of silver.

关键词： solid oxide fuel cells perovskites cathode high oxygen non-stoichiometry

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Observation of a Dynamical Sliding Phase Superfluid with P-Band Bosons

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Physical Review Letters 2018年第26期121卷 265301-265301页

作者： Linxiao Niu Shengjie Jin Xuzong Chen Xiaopeng Li Xiaoji Zhou School of Electronics Engineering and Computer Science Peking University Beijing 100871 China State Key Laboratory of Surface Physics Institute of Nanoelectronics and Quantum Computing and Department of Physics Fudan University Shanghai 200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing 210093 China Collaborative Innovation Center of Extreme Optics Shanxi University Taiyuan Shanxi 030006 China

Sliding phases have been long sought after in the context of coupled XY models, as they are of relevance to various many-body systems such as layered superconductors, freestanding liquid-crystal films, and cationic lipid-DNA complexes. Here we report an observation of a dynamical sliding phase superfluid that emerges in a nonequilibrium setting from the quantum dynamics of a three-dimensional ultracold atomic gas loaded into the P band of a one-dimensional optical lattice. A shortcut loading method is used to transfer atoms into the P band at zero quasimomentum within a very short time duration. The system can be viewed as a series of “pancake”-shaped atomic samples. For this far-out-of-equilibrium system, we find an intermediate time window with a lifetime around tens of milliseconds, where the atomic ensemble exhibits robust superfluid phase coherence in the pancake directions, but no coherence in the lattice direction, which implies a dynamical sliding phase superfluid. The emergence of the sliding phase is attributed to a mechanism of cross-dimensional energy transfer in our proposed phenomenological theory, which is consistent with experimental measurements. This experiment potentially opens up a novel venue to search for exotic dynamical phases by creating high-band excitations in optical lattices.

关键词： Bose-Einstein condensates Cold gases in optical lattices Decoherence in quantum gases Superfluidity

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Correction to: A robust image steganography based on the concatenated error correction encoder and discrete cosine transform coefficients

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Journal of Ambient Intelligence and Humanized computing 2019年第5期11卷 1903-1903页

作者： Bao, Zhenkun Guo, Yanqing Li, Xiaolong Zhang, Yi Xu, Meng Luo, Xiangyang State Key Laboratory of Mathematical Engineering and Advanced Computing Zhengzhou China Zhengzhou Science and Technology Institute Zhengzhou China School of Information and Communication Engineering Dalian University of Technology Dalian China Institute of Information Science Beijing Jiaotong University Beijing China

The article “A robust image steganography based on the concatenated error correction encoder and discrete cosine transform coefficients” written by Zhenkun Bao et al. was originally published electronically on the p...

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Dynamic formation of quasicondensate and spontaneous vortices in a strongly interacting Fermi gas

arXiv

引用

arXiv 2019年

作者： Liu, Xiang-Pei Yao, Xing-Can Deng, Youjin Wang, Yu-Xuan Wang, Xiao-Qiong Li, Xiaopeng Chen, Qijin Chen, Yu-Ao Pan, Jian-Wei Hefei National Laboratory for Physical Sciences at the Microscale Department of Modern Physics University of Science and Technology of China Hefei230026 China Shanghai Branch CAS Center for Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai201315 China Shanghai Research Center for Quantum Sciences Shanghai201315 China State Key Laboratory of Surface Physics Institute of Nanoelectronics and Quantum Computing Department of Physics Fudan University Shanghai200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing210093 China MinJiang Collaborative Center for Theoretical Physics College of Physics and Electronic Information Engineering Minjiang University Fuzhou350108 China

We report an experimental study of quench dynamics across the superfluid transition temperature Tc in a strongly interacting Fermi gas by ramping down the trapping potential. The nonzero quasi-condensate number N0 at temperature significantly above Tc in the unitary and the BEC regimes reveals the pseudogap physics. Below Tc, a rapid growth of N0 is accompanied by spontaneous generation of tens of vortices. We observe a power law scaling of the vortex density versus the quasi-condensate formation time, consistent with the Kibble-Zurek theory. Our work provides an example of studying emerged many-body physics by quench dynamics and paves the way for studying the quantum turbulence in a strongly interacting Fermi gas. Copyright © 2019, The Authors. All rights reserved.

关键词： Electron gas

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Observation of a dynamical sliding phase superfluid with P-band bosons

arXiv

引用

arXiv 2018年

作者： Niu, Linxiao Jin, Shengjie Chen, Xuzong Li, Xiaopeng Zhou, Xiaoji School of Electronics Engineering and Computer Science Peking University Beijing100871 China State Key Laboratory of Surface Physics Institute of Nanoelectronics and Quantum Computing Department of Physics Fudan University Shanghai200433 China Collaborative Innovation Center of Advanced Microstructures Nanjing210093 China

Sliding phases have been long sought-after in the context of coupled XY-models, of relevance to various many-body systems such as layered superconductors, free-standing liquid-crystal films, and cationic lipid-DNA complexes. Here we report an observation of a dynamical sliding-phase superfluid that emerges in a nonequilibrium setting from the quantum dynamics of a three-dimensional ultracold atomic gas loaded into the P-band of a one-dimensional optical lattice. A shortcut loading method is used to transfer atoms into the P-band at zero quasi-momentum within a very short time duration. The system can be viewed as a series of "pancake"-shaped atomic samples. For this far-out-of-equilibrium system, we find an intermediate time window with lifetime around tens of milliseconds, where the atomic ensemble exhibits robust superfluid phase coherence in the pancake directions, but no coherence in the lattice direction, which implies a dynamical sliding-phase superfluid. The emergence of the sliding phase is attributed to a mechanism of cross-dimensional energy transfer in our proposed phenomenological theory, which is consistent with experimental measurements. This experiment potentially opens up a novel venue to search for exotic dynamical phases by creating high-band excitations in optical lattices. Copyright © 2018, The Authors. All rights reserved.

关键词： Liquid films

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Constraints on Heavy Decaying Dark Matter from 570 Days of LHAASO Observations

arXiv

引用

arXiv 2022年

作者： Cao, Zhen Aharonian, F. An, Q. Axikegu Bai, L.X. Bai, Y.X. Bao, Y.W. Bastieri, D. Bi, X.J. Bi, Y.J. Cai, J.T. Cao, Zhe Chang, J. Chang, J.F. Chen, E.S. Chen, Liang Chen, Long Chen, M.J. Chen, M.L. Chen, Q.H. Chen, S.H. Chen, S.Z. Chen, T.L. Chen, Y. Cheng, H.L. Cheng, N. Cheng, Y.D. Cui, S.W. Cui, X.H. Cui, Y.D. D'Ettorre Piazzoli, B. Dai, B.Z. Dai, H.L. Dai, Z.G. Danzengluobu Della Volpe, D. Duan, K.K. Fan, J.H. Fan, Y.Z. Fan, Z.X. Fang, J. Fang, K. Feng, C.F. Feng, L. Feng, S.H. Feng, X.T. Feng, Y.L. Gao, B. Gao, C.D. Gao, L.Q. Gao, Q. Gao, W. Gao, W.K. Ge, M.M. Geng, L.S. Gong, G.H. Gou, Q.B. Gu, M.H. Guo, F.L. Guo, J.G. Guo, X.L. Guo, Y.Q. Guo, Y.Y. Han, Y.A. He, H.H. He, H.N. He, S.L. He, X.B. He, Y. Heller, M. Hor, Y.K. Hou, C. Hou, X. Hu, H.B. Hu, Q. Hu, S. Hu, S.C. Hu, X.J. Huang, D.H. Huang, W.H. Huang, X.T. Huang, X.Y. Huang, Y. Huang, Z.C. Ji, X.L. Jia, H.Y. Jia, K. Jiang, K. Jiang, Z.J. Jin, M. Kang, M.M. Ke, T. Kuleshov, D. Levochkin, K. Li, B.B. Li, Cheng Li, Cong Li, F. Li, H.B. Li, H.C. Li, H.Y. Li, J. Li, Jian Li, Jie Li, K. Li, W.L. Li, X.R. Li, Xin Li, Y.Z. Li, Zhe Li, Zhuo Liang, E.W. Liang, Y.F. Lin, S.J. Liu, 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. Liu, Y.N. Long, W.J. Lu, R. Luo, Q. Lv, H.K. Ma, B.Q. Ma, L.L. Ma, X.H. Mao, J.R. Masood, A. Min, Z. Mitthumsiri, W. Nan, Y.C. Ou, Z.W. Pang, B.Y. Pattarakijwanich, P. Pei, Z.Y. Qi, M.Y. Qi, Y.Q. Qiao, B.Q. Qin, J.J. Ruffolo, D. Sáiz, A. Shao, C.Y. Shao, L. Shchegolev, O. Sheng, X.D. Shi, J.Y. Song, H.C. Stenkin, Yu.V. Stepanov, V. Su, Y. Sun, Q.N. Sun, X.N. Sun, Z.B. Tam, P.H.T. Tang, Z.B. Tian, W.W. Wang, B.D. Wang, C. Wang, H. Wang, H.G. Wang, J.C. Wang, J.S. Key Laboratory of Particle Astrophyics Experimental Physics Division Computing Center Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China University of Chinese Academy of Sciences Beijing100049 China Tianfu Cosmic Ray Research Center Sichuan Chengdu China Dublin Institute for Advanced Studies 31 Fitzwilliam Place 2 Dublin Ireland Max-Planck-Institut for Nuclear Physics P.O. Box 103980 Heidelberg69029 Germany State Key Laboratory of Particle Detection and Electronics China University of Science and Technology of China Anhui Hefei230026 China School of Physical Science and Technology School of Information Science and Technology Southwest Jiaotong University Sichuan Chengdu610031 China College of Physics Sichuan University Sichuan Chengdu610065 China School of Astronomy and Space Science Nanjing University Jiangsu Nanjing210023 China Center for Astrophysics Guangzhou University Guangdong Guangzhou510006 China Key Laboratory of Dark Matter and Space Astronomy Purple Mountain Observatory Chinese Academy of Sciences Jiangsu Nanjing210023 China Key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai200030 China Ministry of Education Tibet Lhasa850000 China National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China Hebei Normal University Hebei Shijiazhuang050024 China Zhuhai519000 China Dipartimento di Fisica Dell'Università di Napoli 'Federico II' Complesso Universitario di Monte Sant'Angelo via Cinthia Napoli80126 Italy School of Physics and Astronomy Yunnan University Yunnan Kunming650091 China Département de Physique Nucléaire et Corpusculaire Faculté de Sciences Université de Genève 24 Quai Ernest Ansermet Geneva1211 Switzerland Institute of Frontier and Interdisciplinary Science Shandong University Shandong Qingdao266237 China Department of Engineering Physics Tsinghua University Beijing100084

The kilometer squarearray (KM2A) of the large high altitude air shower observatory (LHAASO) aims at surveying the northern γ-ray sky at energies above 10 TeV with unprecedented sensitivity. γ-ray observations have long been one of the most powerful tools for dark matter searches, as, e.g., high-energy γrays could be produced by the decays of heavy dark matter particles. In this Letter, we present the first dark matter analysis with LHAASO-KM2A, using the first 340 days of data from 1/2-KM2A and 230 days of data from 3/4-KM2A. Several regions of interest are used to search for a signal and account for the residual cosmic-ray background after γ/hadron separation. We find no excess of dark matter signals, and thus place some of the strongest γ-ray constraints on the lifetime of heavy dark matter particles with mass between 105and 109GeV. Our results with LHAASO are robust, and have important implications for dark matter interpretations of the diffuse astrophysical high-energy neutrino emission. © 2022, CC BY.

关键词： Gamma rays

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