In this paper, a weighted fractional Fourier transform(WFRFT) based cooperative overlay system, aiming to guarantee physical layer(PHY) security, is proposed. The paper elaborates how WFRFT and physical layer properti...In this paper, a weighted fractional Fourier transform(WFRFT) based cooperative overlay system, aiming to guarantee physical layer(PHY) security, is proposed. The paper elaborates how WFRFT and physical layer properties of the wireless medium are collaborated to guarantee the secrecy of wireless transmissions. In the proposed system, WFRFT is first preform on the secret data, such that the transmitted signal is distorted and can only be neutralized by inverse-WFRFT with the same parameter. And then two streams of the transformed sequences that bearing different messages are cooperatively and simultaneously transmitted to two legitimate receivers via a beamforming-liked method, respectively. In general, both the rapid spatial decorrelation property and the inherent security features of WFRFT are leveraged, such that only the eavesdropper's is degraded, and hence, the wireless communication secrecy is reliably guaranteed. Numerical simulations are conducted to evaluate the performance of the proposed system in terms of the average bit error rate and the secrecy capacity.展开更多
Consider the Teichmuller mapping f associated with in the unit disc D and the class of all quasiconformal mappings in D with the boundary values of f. For a special holomorphic function, the present paper gives the ne...Consider the Teichmuller mapping f associated with in the unit disc D and the class of all quasiconformal mappings in D with the boundary values of f. For a special holomorphic function, the present paper gives the necessary and sufficient condition on, such that f is uniquely extremal among the class. Further, for a general holomorphic function, the anthors suggest the models of the best possible growth conditions on, such that f is extremal or uniquely extremal among the class respectively.展开更多
As well known, all higher dimensional Kerr-NUT-Ads metrics with arbitrary rotation and NUT parameters in an asymptotically Ad S spacetime have a new hidden symmetry. In this paper, we show that in the near horizon,the...As well known, all higher dimensional Kerr-NUT-Ads metrics with arbitrary rotation and NUT parameters in an asymptotically Ad S spacetime have a new hidden symmetry. In this paper, we show that in the near horizon,the isometry group is enhanced to include the dilatation and special conformal transformation, and find the conformal transformation contains the cosmological constant. It is demonstrated that for near horizon extremal Kerr-NUT-Ads(NHEK-N-Ad S) only one rank-2 Killing tensor decomposes into a quadratic combination of the Killing vectors in terms of conformal group, while the others are functionally independent.展开更多
The acoustic cloak can manipulate sound waves in surprising ways and enable us to guide the trajectories of waves at will.In contrast to the existing approaches for designing such devices that need exotic material par...The acoustic cloak can manipulate sound waves in surprising ways and enable us to guide the trajectories of waves at will.In contrast to the existing approaches for designing such devices that need exotic material parameters,here we demonstrate how to design a layered and isotropic acoustic cloak based on conformal transformation acoustics.A petal-shaped layered acoustic cloak is designed from the reduction of material parameters of an approximate rectangular cloak.The resultant material parameters span a narrow range,thus strongly facilitating the implementation.The invisibility performance of the cloak for different shapes of acoustic wavefront is verified using a full-wave finite-element analysis.展开更多
A series of symmetrical peptidomimetics （3-8） based on cysteine-modified cyclo（L-Lys-L-Lys）s were synthesized, and their gelation capability in organic solvents was dominated by fluorenylmethyloxycarbonyl （Fmoc）...A series of symmetrical peptidomimetics （3-8） based on cysteine-modified cyclo（L-Lys-L-Lys）s were synthesized, and their gelation capability in organic solvents was dominated by fluorenylmethyloxycarbonyl （Fmoc） and triphenylmethyl （Trt） protecting groups and the exchange of thiol-to-disulfide as well. The peptidomimetics holding Trt （3 and 4） showed no gel performance, while the Fmoc groups promoted 5 and 6 to give rise to thermo-reversible organogels in a number of organic solvents. The self-assembled fibrillar networks were distinctly evidenced in the organogels by transmission electron micros- copy （TEM） and scanning electron microscopy （SEM） observations. Fourier transform infrared spectroscopy （FT-IR） and fluorescence analyses revealed that the hydrogen bonding and ^-rt stacking play as major driving forces for the self-assembly of these organogelators. A 13-turn secondary structure was deduced for the organogel of 6 by virtue of X-ray diffraction, FT-IR and circular dichroism （CD） measurements, and an interdigitated bilayer structure was also presented.展开更多
基金supported by the National Basic Research Program of China under Grant 2013CB329003the National Natural Science Founda-tion General Program of China under Grant 61171110
文摘In this paper, a weighted fractional Fourier transform(WFRFT) based cooperative overlay system, aiming to guarantee physical layer(PHY) security, is proposed. The paper elaborates how WFRFT and physical layer properties of the wireless medium are collaborated to guarantee the secrecy of wireless transmissions. In the proposed system, WFRFT is first preform on the secret data, such that the transmitted signal is distorted and can only be neutralized by inverse-WFRFT with the same parameter. And then two streams of the transformed sequences that bearing different messages are cooperatively and simultaneously transmitted to two legitimate receivers via a beamforming-liked method, respectively. In general, both the rapid spatial decorrelation property and the inherent security features of WFRFT are leveraged, such that only the eavesdropper's is degraded, and hence, the wireless communication secrecy is reliably guaranteed. Numerical simulations are conducted to evaluate the performance of the proposed system in terms of the average bit error rate and the secrecy capacity.
文摘Consider the Teichmuller mapping f associated with in the unit disc D and the class of all quasiconformal mappings in D with the boundary values of f. For a special holomorphic function, the present paper gives the necessary and sufficient condition on, such that f is uniquely extremal among the class. Further, for a general holomorphic function, the anthors suggest the models of the best possible growth conditions on, such that f is extremal or uniquely extremal among the class respectively.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11275099 and 11435006
文摘As well known, all higher dimensional Kerr-NUT-Ads metrics with arbitrary rotation and NUT parameters in an asymptotically Ad S spacetime have a new hidden symmetry. In this paper, we show that in the near horizon,the isometry group is enhanced to include the dilatation and special conformal transformation, and find the conformal transformation contains the cosmological constant. It is demonstrated that for near horizon extremal Kerr-NUT-Ads(NHEK-N-Ad S) only one rank-2 Killing tensor decomposes into a quadratic combination of the Killing vectors in terms of conformal group, while the others are functionally independent.
文摘The acoustic cloak can manipulate sound waves in surprising ways and enable us to guide the trajectories of waves at will.In contrast to the existing approaches for designing such devices that need exotic material parameters,here we demonstrate how to design a layered and isotropic acoustic cloak based on conformal transformation acoustics.A petal-shaped layered acoustic cloak is designed from the reduction of material parameters of an approximate rectangular cloak.The resultant material parameters span a narrow range,thus strongly facilitating the implementation.The invisibility performance of the cloak for different shapes of acoustic wavefront is verified using a full-wave finite-element analysis.
基金the National Natural Science Foundation of China (21174018)
文摘A series of symmetrical peptidomimetics （3-8） based on cysteine-modified cyclo（L-Lys-L-Lys）s were synthesized, and their gelation capability in organic solvents was dominated by fluorenylmethyloxycarbonyl （Fmoc） and triphenylmethyl （Trt） protecting groups and the exchange of thiol-to-disulfide as well. The peptidomimetics holding Trt （3 and 4） showed no gel performance, while the Fmoc groups promoted 5 and 6 to give rise to thermo-reversible organogels in a number of organic solvents. The self-assembled fibrillar networks were distinctly evidenced in the organogels by transmission electron micros- copy （TEM） and scanning electron microscopy （SEM） observations. Fourier transform infrared spectroscopy （FT-IR） and fluorescence analyses revealed that the hydrogen bonding and ^-rt stacking play as major driving forces for the self-assembly of these organogelators. A 13-turn secondary structure was deduced for the organogel of 6 by virtue of X-ray diffraction, FT-IR and circular dichroism （CD） measurements, and an interdigitated bilayer structure was also presented.
