Signcryption, which was introduced by ZHEN~ is a cryptographic primitive that fulfils the functions of both digital signature and encryption and guarantees confidentiality, integrity and non-repudiation in a more effi...Signcryption, which was introduced by ZHEN~ is a cryptographic primitive that fulfils the functions of both digital signature and encryption and guarantees confidentiality, integrity and non-repudiation in a more effi- cient way. Certificateless signcryption and pro- xy signcryption in identity-based cryptography were proposed for different applications. Most of these schemes are constructed by bilinear pairings from elliptic curves. However, some schemes were recently presented without pai- rings. In this paper, we present a certificateless proxy identity-based signcryption scheme with- out bilinear pairings, which is efficient and secure.展开更多
An exergy analysis was performed considering the combustion of methane and agro-industrial residues produced in Portugal (forest residues and vines pruning). Regarding that the irreversibilities of a thermodynamic pro...An exergy analysis was performed considering the combustion of methane and agro-industrial residues produced in Portugal (forest residues and vines pruning). Regarding that the irreversibilities of a thermodynamic process are path dependent, the combustion process was considering as resulting from different hypothetical paths each one characterized by four main sub-processes: reactant mixing, fuel oxidation, internal thermal energy exchange (heat transfer), and product mixing. The exergetic efficiency was computed using a zero dimensional model developed by using a Visual Basic home code. It was concluded that the exergy losses were mainly due to the internal thermal energy exchange sub-process. The exergy losses from this sub-process are higher when the reactants are preheated up to the ignition temperature without previous fuel oxidation. On the other hand, the global exergy destruction can be minored increasing the pressure, the reactants temperature and the oxygen content on the oxidant stream. This methodology allows the identification of the phenomena and processes that have larger exergy losses, the understanding of why these losses occur and how the exergy changes with the parameters associated to each system which is crucial to implement the syngas combustion from biomass products as a competitive technology.展开更多
基金supported by the National Natural Science Foundation of China under Grants No.61272499,No.10990011
文摘Signcryption, which was introduced by ZHEN~ is a cryptographic primitive that fulfils the functions of both digital signature and encryption and guarantees confidentiality, integrity and non-repudiation in a more effi- cient way. Certificateless signcryption and pro- xy signcryption in identity-based cryptography were proposed for different applications. Most of these schemes are constructed by bilinear pairings from elliptic curves. However, some schemes were recently presented without pai- rings. In this paper, we present a certificateless proxy identity-based signcryption scheme with- out bilinear pairings, which is efficient and secure.
基金the Portuguese Foundation for Science and Technology (FCT) for the given support to the grant SFRH/BPD/71686the project PTDC/AAC-AMB/103119/2008
文摘An exergy analysis was performed considering the combustion of methane and agro-industrial residues produced in Portugal (forest residues and vines pruning). Regarding that the irreversibilities of a thermodynamic process are path dependent, the combustion process was considering as resulting from different hypothetical paths each one characterized by four main sub-processes: reactant mixing, fuel oxidation, internal thermal energy exchange (heat transfer), and product mixing. The exergetic efficiency was computed using a zero dimensional model developed by using a Visual Basic home code. It was concluded that the exergy losses were mainly due to the internal thermal energy exchange sub-process. The exergy losses from this sub-process are higher when the reactants are preheated up to the ignition temperature without previous fuel oxidation. On the other hand, the global exergy destruction can be minored increasing the pressure, the reactants temperature and the oxygen content on the oxidant stream. This methodology allows the identification of the phenomena and processes that have larger exergy losses, the understanding of why these losses occur and how the exergy changes with the parameters associated to each system which is crucial to implement the syngas combustion from biomass products as a competitive technology.
