Practical Certificateless Aggregate Signatures From Bilinear Maps

Aggregate signature is a digital signature with a striking property that anyone can aggregate n individual signatures on n different messages which are signed by n distinct signers, into a single compact signature to reduce computational and storage costs. In this work, two practical certificateless aggregate signature schemes are proposed from bilinear maps. The first scheme CAS-1 reduces the costs of communication and signer-side computation but trades off the storage, while CAS-2 minimizes the storage but sacrifices the communication costs. One can choose either of the schemes by consideration of the application requirement. Compare with ID-based schemes, our schemes do not entail public key certificates as well and achieve the trust level 3, which imply the frauds of the authority are detectable. Both of the schemes are proven secure in the random oracle model by assuming the intractability of the computational Diffie-Hellman problem over the groups with bilinear maps, where the forking lemma technique is avoided

Solution of Contact Problem for an Arc Crack using Hypersingular intergral Equation

This paper investigates the contact problem for an arc crack, for example, under a remote compression. A hypersingular integral equation (HSIE) for curved cracks in plane elasticity is suggested. It is found that the direct usage of HSIE cannot solve the mentioned contact problem. For the contact problem, one must take necessary modifications for solving the HSIE. The main modified points are as follows. First, one should assume some portion along the crack under contact. The margin or the end of the contacted portion is determined by the vanishing normal contact stress at the margin point. In addition, it is found that a suggested quadrature rule in conjunction with the curve length method provides a very effective way to solve the HSIE. Finally, several numerical examples are given

Elliptic flow of ϕ\phi meson and strange quark collectivity at RHIC

Based on A Multi-Phase Transport (AMPT) model, we have studied the elliptic flow $v_{2}$ of $\phi$ mesons from reconstructed $K^{+}K^{-}$ decay channel at the top Relativistic Heavy Ion Collider energy at Brookhaven National Laboratory. The dependences of $v_{2}$ on transverse momentum $p_T$ and collision centrality are presented and the rescattering effect of $\phi$ mesons in the hadronic phase is also investigated. The results show that experimental measurement of $v_{2}$ for $\phi$ mesons can retain the early collision information before $\phi$ decays and that the $\phi$ $v_2$ value obeys the constituent quark number scaling which has been observed for other mesons and baryons. Our study indicates that the $\phi$ $v_2$ mostly reflects partonic level collectivity developed during the early stage of the nucleus-nucleus collision and the strange and light up/down quarks have developed similar angular anistropy properties at the hadronization.Comment: 5 pages and 5 figures; accepted by Physical Review

Time-varying systems identification using continuous wavelet analysis of free decay response signals

This paper proposes a time-varying approach used for identification of time-varying systems and presents a simulation example of a simple vibration system with time-varying mass, stiffness and damping characteristics, which is a five-storey shear-beam building model. Free decay acceleration response signals are analyzed to reveal time-varying nature of the system. Wavelet analysis is used for system identification. The method is based on a recently developed direct identification algorithm. Numerical results confirm that the proposed method is accurate and effective in identification of the time-varying system

Instantaneous frequency identification of a time varying structure using wavelet-based state-space method

This paper presents a method to identify the instantaneous frequency of the time varying structures based on wavelet and state space methods by using free and forced vibration response data. Firstly, the second-order vibration differential equations are rewritten as the first-order state equations using state space theory. Secondly, both excitation and response signals are projected by the Daubechies wavelet scaling functions. Thus, the first-order state equations are transformed into linear algebraic equations using the orthogonality of the scaling functions. Lastly, the equivalent time varying state space system matrices of time varying structure are extracted directly by solving the linear equations. The instantaneous frequencies are determined via eigenvalue decomposition of the state space system matrices. The proposed identification algorithm is investigated with a four degrees-of-freedom spring-mass-damper model. Numerical simulations demonstrate that the proposed method is robust and effective for identification of the abruptly, smoothly and periodically changing instantaneous frequencies of time varying structures

Does afforestation deteriorate haze pollution in Beijing-Tianjin-Hebei (BTH), China?

Although aggressive emission control strategies have been implemented recently in the Beijing-Tianjin-Hebei area (BTH), China, pervasive and persistent haze still frequently engulfs the region during wintertime. Afforestation in BTH, primarily concentrated in the Taihang and Yan Mountains, has constituted one of the controversial factors exacerbating the haze pollution due to its slowdown of the surface wind speed. We report here an increasing trend of forest cover in BTH during 2001-2013 based on long-term satellite measurements and the impact of the afforestation on the fine-particle (PM2.5) level. Simulations using the Weather Research and Forecast model with chemistry reveal that afforestation in BTH since 2001 has generally been deteriorating the haze pollution in BTH to some degree, enhancing PM2.5 concentrations by up to 6% on average. Complete afforestation or deforestation in the Taihang and Yan Mountains would increase or decrease the PM2.5 level within 15% in BTH. Our model results also suggest that implementing a large ventilation corridor system would not be effective or beneficial to mitigate the haze pollution in Beijing

A Chaotic IP Watermarking in Physical Layout Level Based on FPGA

A new chaotic map based IP (Intellectual Property) watermarking scheme at physical design level is presented. An encrypted watermark is embedded into the physical layout of a circuit by configuring LUT (Lookup Table) as specific functions when it is placed and routed onto the FPGA (Field-Programmable Gate Array). The main contribution is the use of multiple chaotic maps in the processes of watermark design and embedding, which efficiently improves the security of watermark. A hashed chaotic sequence is used to scramble the watermark. Secondly, two pseudo-random sequences are generated by using chaotic maps. One is used to determine unused LUT locations, and the other divides the watermark into groups. The watermark identifies original owner and is difficult to detect. This scheme was tested on a Xilinx Virtex XCV600-6bg432 FPGA. The experimental results show that our method has low impact on functionality, short path delay and high robustness in comparison with other methods