Let B（G） denote the bipartite double cover of a non-bipartite graph G with v ≥ 2 vertices and s edges. We prove that G is a perfect 2-matching covered graph if and only if B（G） is a 1-extendable graph. Furthermor...Let B（G） denote the bipartite double cover of a non-bipartite graph G with v ≥ 2 vertices and s edges. We prove that G is a perfect 2-matching covered graph if and only if B（G） is a 1-extendable graph. Furthermore, we prove that B（G） is a minimally l-extendable graph if and only if G is a minimally perfect 2-matching covered graph and for each e = xy ∈ E（G）, there is an independent set S in G such that ｜ГG（S）｜ = ｜S｜ ＋ 1, x ∈ S and ｜ГG-xy（S）｜ = ｜S｜ Then, we construct a digraph D from B（G） or G and show that D is a strongly connected digraph if and only if G is a perfect 2-matching covered graph. So we design an algorithm in O（x√vε） time that determines whether G is a perfect 2-matching covered graph or not.展开更多
As a two-dimensional(2D)material,monolayer MoS2which limits its optical applications has a low absorption efficiency.In this paper,we propose a three-band perfect metamaterial absorber in the visible light range based...As a two-dimensional(2D)material,monolayer MoS2which limits its optical applications has a low absorption efficiency.In this paper,we propose a three-band perfect metamaterial absorber in the visible light range based on monolayer MoS_(2).The peak absorptivity of the structure at each resonance wavelength is nearly perfect,moreover,the light absorption of monolayer MoS2is obviously enhanced at the three resonant wavelengths.The dielectric–dielectric–metal structure we designed produces the coupling of Fabry–Perot resonance and high-order diffraction guided-mode resonance at different absorption peaks,which has been proved by the slab waveguide theory.In addition,the multi-modal absorption phenomenon is explained by extracting the equivalent impedance.The results show that we can adjust the absorption peak wavelength by regulating the parameters of the structure.This structure not only provides an idea for enhancing the interaction between light and two-dimensional materials but also has potential applications for optical detection devices.展开更多
The healthcare IoT system is considered to be a significant and modern medical system.There is broad consensus that these systems will play a vital role in the achievement of economic growth in numerous growth countri...The healthcare IoT system is considered to be a significant and modern medical system.There is broad consensus that these systems will play a vital role in the achievement of economic growth in numerous growth countries.Among the major challenges preventing the fast and widespread adoption of such systems is the failure to maintain the data privacy of patients and the integrity of remote clinical diagnostics.Recently,the author proposed an end-to-end authentication scheme for healthcare IoT systems(E2EA),to provide a mutual authentication with a high data rate between the communication nodes of the healthcare IoT systems.Although the E2EA authentication scheme supports numerous attractive security services to resist various types of attack,there is an ambiguous view of the impact of the desynchronization attack on the E2EA authentication scheme.In general,the performance of the authentication scheme is considered a critical issue when evaluating the applicability of such schemes,along with the security services that can be achieved.Therefore,this paper discusses how the E2EA authentication scheme can resist the desynchronization attack through all possible attack scenarios.Additionally,the effect of the desynchronization attack on the E2EA scheme performance is analyzed in terms of its computation and communication costs,based on a comparison with the recently related authentication schemes that can prevent such attack.Moreover,this research paper finds that the E2EA authentication scheme can not only prevent the desynchronization attack,but also offers a low cost in terms of computations and communications,and can maintain consistency and synchronization between the communication nodes of the healthcare IoT systems during the next authentication sessions.展开更多
基金Acknowledgements The authors would like to thank the referees very much for their careful reading and their very instructive suggestions which improve this paper greatly. This work was supported in part by the National Natural Science Foundation of China （Grant No. 11201158）.
文摘Let B（G） denote the bipartite double cover of a non-bipartite graph G with v ≥ 2 vertices and s edges. We prove that G is a perfect 2-matching covered graph if and only if B（G） is a 1-extendable graph. Furthermore, we prove that B（G） is a minimally l-extendable graph if and only if G is a minimally perfect 2-matching covered graph and for each e = xy ∈ E（G）, there is an independent set S in G such that ｜ГG（S）｜ = ｜S｜ ＋ 1, x ∈ S and ｜ГG-xy（S）｜ = ｜S｜ Then, we construct a digraph D from B（G） or G and show that D is a strongly connected digraph if and only if G is a perfect 2-matching covered graph. So we design an algorithm in O（x√vε） time that determines whether G is a perfect 2-matching covered graph or not.
基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB43010000)the National Natural Science Foundation of China(Grant Nos.61835011 and 12075244)+1 种基金Key Research Projects of the Frontier Science of the Chinese Academy of Sciences(Grant No.QYZDY-SSW-JSC004)the National Key Research and Development Program of China(Grant No.2020YFB2206103).
文摘As a two-dimensional(2D)material,monolayer MoS2which limits its optical applications has a low absorption efficiency.In this paper,we propose a three-band perfect metamaterial absorber in the visible light range based on monolayer MoS_(2).The peak absorptivity of the structure at each resonance wavelength is nearly perfect,moreover,the light absorption of monolayer MoS2is obviously enhanced at the three resonant wavelengths.The dielectric–dielectric–metal structure we designed produces the coupling of Fabry–Perot resonance and high-order diffraction guided-mode resonance at different absorption peaks,which has been proved by the slab waveguide theory.In addition,the multi-modal absorption phenomenon is explained by extracting the equivalent impedance.The results show that we can adjust the absorption peak wavelength by regulating the parameters of the structure.This structure not only provides an idea for enhancing the interaction between light and two-dimensional materials but also has potential applications for optical detection devices.
文摘The healthcare IoT system is considered to be a significant and modern medical system.There is broad consensus that these systems will play a vital role in the achievement of economic growth in numerous growth countries.Among the major challenges preventing the fast and widespread adoption of such systems is the failure to maintain the data privacy of patients and the integrity of remote clinical diagnostics.Recently,the author proposed an end-to-end authentication scheme for healthcare IoT systems(E2EA),to provide a mutual authentication with a high data rate between the communication nodes of the healthcare IoT systems.Although the E2EA authentication scheme supports numerous attractive security services to resist various types of attack,there is an ambiguous view of the impact of the desynchronization attack on the E2EA authentication scheme.In general,the performance of the authentication scheme is considered a critical issue when evaluating the applicability of such schemes,along with the security services that can be achieved.Therefore,this paper discusses how the E2EA authentication scheme can resist the desynchronization attack through all possible attack scenarios.Additionally,the effect of the desynchronization attack on the E2EA scheme performance is analyzed in terms of its computation and communication costs,based on a comparison with the recently related authentication schemes that can prevent such attack.Moreover,this research paper finds that the E2EA authentication scheme can not only prevent the desynchronization attack,but also offers a low cost in terms of computations and communications,and can maintain consistency and synchronization between the communication nodes of the healthcare IoT systems during the next authentication sessions.
