Wireless Mesh Networks is vulnerable to attacks due to the open medium, dynamically changing network topology, cooperative algorithms, Lack of centralized monitoring and management point. The traditional way of protec...Wireless Mesh Networks is vulnerable to attacks due to the open medium, dynamically changing network topology, cooperative algorithms, Lack of centralized monitoring and management point. The traditional way of protecting networks with firewalls and encryption software is no longer suffi- cient and effective for those features. In this paper, we propose a distributed intrusion detection ap- proach based on timed automata. A cluster-based detection scheme is presented, where periodically a node is elected as the monitor node for a cluster. These monitor nodes can not only make local intrusion detection decisions, but also cooperatively take part in global intrusion detection. And then we con- struct the Finite State Machine （FSM） by the way of manually abstracting the correct behaviors of the node according to the routing protocol of Dynamic Source Routing （DSR）. The monitor nodes can verify every node＇s behavior by the Finite State Ma- chine （FSM）, and validly detect real-time attacks without signatures of intrusion or trained data.Compared with the architecture where each node is its own IDS agent, our approach is much more efficient while maintaining the same level of effectiveness. Finally, we evaluate the intrusion detection method through simulation experiments.展开更多
SMEs are in a rapid growth, it has become a new economic growth point. It is critical for SMEs to healthy and sustainable growth, and the capital structure is an important factor in its development. Therefore, the pap...SMEs are in a rapid growth, it has become a new economic growth point. It is critical for SMEs to healthy and sustainable growth, and the capital structure is an important factor in its development. Therefore, the paper has a research on the current situation of SMEs capital structure is important.展开更多
Under strong shocks,long-span spatial-latticed structures may collapse due to dynamic instability or strength failure.The elasto-plastic dynamic behaviors of three spatiallatticed structures,including two double-layer...Under strong shocks,long-span spatial-latticed structures may collapse due to dynamic instability or strength failure.The elasto-plastic dynamic behaviors of three spatiallatticed structures,including two double-layer cylindrical shells and a spheri-cal shell used for the 2008 Olympic Games in Beijing,were quantitatively examined under multi-support excitation(MSE) and uniform support excitation(USE).Numerical analyses described several important parameters such as the peak acceleration and displacement responses at key joints,the number and distribution of plastic elements,and the deformation of the shell at the moment of collapse.Results of the analysis revealed the features and the failure mechanism of the spatial-latticed structures under MSE and USE.In both scenarios,the double-layer reticulated shell collapsed in the "overflow" mode,collapse was govrned by the number of invalid plastic elements rather than the total number of plastic elements,and the collapse of the structure began with damage to certain local regions near the supports.By comparing the numbers and distributions of the plastic members under MSE to those under USE,it was observed that the plastic members spread more sufficiently and the internal forces were more uniform under MSE,especially for lower apparent velocities in soils.Due to the effects of pseudo-static displacement,the stresses in members near supports under MSE were higher than those under USE.These regions are prone to failure during earthquakes and deserve special attention in the seismic design of reticulated structures.展开更多
We investigate the low-energy electronic structure ofa Weyl semimetal quantum dot （QD） with a simple model Hamiltonian with only two Weyl points. Distinguished from the semiconductor and topological insulator QDs, t...We investigate the low-energy electronic structure ofa Weyl semimetal quantum dot （QD） with a simple model Hamiltonian with only two Weyl points. Distinguished from the semiconductor and topological insulator QDs, there exist both surface and bulk states near the Fermi level in Weyl semimetal QDs. The surface state, distributed near the side surface of the QD, contributes a circular persistent current, an orbital magnetic moment, and a chiral spin polarization with spin-current locking. There are always surface states even for a strong magnetic field, even though a given surface state gradually evolves into a Landau level with increasing magnetic field. It indicates that these unique properties can be tuned via the QD size. In addition, we show the correspondence to the electronic structures of a three-dimensional Weyl semimetal, such as Wey[ point and Fermi arc. Because a QD has the largest surface-to-volume ratio, it provides a new platform to verify Weyl semimetal by separating and detecting the signals of surface states. Besides, the study of Weyl QDs is also necessary for potential applications in nanoelectronics.展开更多
基金Acknowledgements Project supported by the National Natural Science Foundation of China （Grant No.60932003）, the National High Technology Development 863 Program of China （Grant No.2007AA01Z452, No. 2009AA01 Z118 ）, Project supported by Shanghai Municipal Natural Science Foundation （Grant No.09ZRI414900）, National Undergraduate Innovative Test Program （091024812）.
文摘Wireless Mesh Networks is vulnerable to attacks due to the open medium, dynamically changing network topology, cooperative algorithms, Lack of centralized monitoring and management point. The traditional way of protecting networks with firewalls and encryption software is no longer suffi- cient and effective for those features. In this paper, we propose a distributed intrusion detection ap- proach based on timed automata. A cluster-based detection scheme is presented, where periodically a node is elected as the monitor node for a cluster. These monitor nodes can not only make local intrusion detection decisions, but also cooperatively take part in global intrusion detection. And then we con- struct the Finite State Machine （FSM） by the way of manually abstracting the correct behaviors of the node according to the routing protocol of Dynamic Source Routing （DSR）. The monitor nodes can verify every node＇s behavior by the Finite State Ma- chine （FSM）, and validly detect real-time attacks without signatures of intrusion or trained data.Compared with the architecture where each node is its own IDS agent, our approach is much more efficient while maintaining the same level of effectiveness. Finally, we evaluate the intrusion detection method through simulation experiments.
文摘SMEs are in a rapid growth, it has become a new economic growth point. It is critical for SMEs to healthy and sustainable growth, and the capital structure is an important factor in its development. Therefore, the paper has a research on the current situation of SMEs capital structure is important.
文摘Under strong shocks,long-span spatial-latticed structures may collapse due to dynamic instability or strength failure.The elasto-plastic dynamic behaviors of three spatiallatticed structures,including two double-layer cylindrical shells and a spheri-cal shell used for the 2008 Olympic Games in Beijing,were quantitatively examined under multi-support excitation(MSE) and uniform support excitation(USE).Numerical analyses described several important parameters such as the peak acceleration and displacement responses at key joints,the number and distribution of plastic elements,and the deformation of the shell at the moment of collapse.Results of the analysis revealed the features and the failure mechanism of the spatial-latticed structures under MSE and USE.In both scenarios,the double-layer reticulated shell collapsed in the "overflow" mode,collapse was govrned by the number of invalid plastic elements rather than the total number of plastic elements,and the collapse of the structure began with damage to certain local regions near the supports.By comparing the numbers and distributions of the plastic members under MSE to those under USE,it was observed that the plastic members spread more sufficiently and the internal forces were more uniform under MSE,especially for lower apparent velocities in soils.Due to the effects of pseudo-static displacement,the stresses in members near supports under MSE were higher than those under USE.These regions are prone to failure during earthquakes and deserve special attention in the seismic design of reticulated structures.
基金supported by the National Natural Science Foundation of China(Grants Nos.11747122,11274364,and 11574007)the National Basic Research Program of China(Grant Nos.2017YFA0303301,and2015CB921102)+1 种基金the Natural Science Foundation of Shandong Province(Grant No.ZR2018PA007)the Doctoral Foundation of University of Jinan(Grant No.160100147)
文摘We investigate the low-energy electronic structure ofa Weyl semimetal quantum dot （QD） with a simple model Hamiltonian with only two Weyl points. Distinguished from the semiconductor and topological insulator QDs, there exist both surface and bulk states near the Fermi level in Weyl semimetal QDs. The surface state, distributed near the side surface of the QD, contributes a circular persistent current, an orbital magnetic moment, and a chiral spin polarization with spin-current locking. There are always surface states even for a strong magnetic field, even though a given surface state gradually evolves into a Landau level with increasing magnetic field. It indicates that these unique properties can be tuned via the QD size. In addition, we show the correspondence to the electronic structures of a three-dimensional Weyl semimetal, such as Wey[ point and Fermi arc. Because a QD has the largest surface-to-volume ratio, it provides a new platform to verify Weyl semimetal by separating and detecting the signals of surface states. Besides, the study of Weyl QDs is also necessary for potential applications in nanoelectronics.
