Composite polyurethane(PU)-SiO_2 hollow fiber membranes were successfully prepared via optimizing thetechnique of dry-jet wet spinning,and their pressure-responsibilities were confirmed by the relationships of pure wa...Composite polyurethane(PU)-SiO_2 hollow fiber membranes were successfully prepared via optimizing thetechnique of dry-jet wet spinning,and their pressure-responsibilities were confirmed by the relationships of pure water flux-transmembrane pressure(PWF-TP)for the first time.The origin for this phenomenon was analyzed on the basis of membranestructure and material characteristics.The effects of SiO_2 content on the structure and properties of membrane wereinvestigated.The experimental results indicated that SiO_2 in membrane created a great many interfacial micro-voids andplayed an important role in pressure-responsibility,PWF and rejection of membrane:with the increase of SiO_2 content,theability of membrane recovery weakened,PWF increased,and rejection decreased slightly.展开更多
Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state ...Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state of dynamic load and factor of dynamic load of thegearing, the changing situation of dynamic load and dynamic load factor vs some affecting factorssuch as gear width, helix angle and accuracy grade etc are investigated. A series of conclusions areobtained: ①With the increasing in the values of gear width, the dynamic load factor appears slowdecreasing tendency in most region of gear width. ②When the accuracy grades of the gearing areimproved, the values of dynamic load factor decrease. ③The value of dynamic load factor appears adecreasing tendency with the increasing of value of helix angle at the same ratio of criticalrotational speed.展开更多
The mechanical properties of the steel pipe rolled with continuously casting round billet after determining the chemical composition in steel were studied.The results show that the total reduction ratio should be high...The mechanical properties of the steel pipe rolled with continuously casting round billet after determining the chemical composition in steel were studied.The results show that the total reduction ratio should be higher than 5.2 when the line pipes of grade B,grade 20 and other general seamless pipe were rolled with continuously casting round billet.And the total reduction ratio should be higher than 10.2 and the grain size should be controlled more than grade 7 for casing of oil countryside tubular goods(OCTG).展开更多
Most existing secret sharing schemes are constructed to realize generalaccess structure, which is defined in terms of authorized groups of participants, and is unable tobe applied directly to the design of intrusion t...Most existing secret sharing schemes are constructed to realize generalaccess structure, which is defined in terms of authorized groups of participants, and is unable tobe applied directly to the design of intrusion tolerant system, which often concerns corruptiblegroups of participants instead of authorized ones. Instead, the generalized adversary structure,which specifies the corruptible subsets of participants, can be determined directly by exploit ofthe system setting and the attributes of all participants. In this paper an efficient secret sharingscheme realizing generalized adversary structure is proposed, and it is proved that the schemesatisfies both properties of the secret sharing scheme, i.e., the reconstruction property and theperfect property. The main features of this scheme are that it performs modular additions andsubtractions only, and each share appears in multiple share sets and is thus replicated. The formeris an advantage in terms of computational complexity, and the latter is an advantage when recoveryof some corrupted participants is necessary. So our scheme can achieve lower computation cost andhigher availability. Some reduction on the scheme is also done finally, based on an equivalencerelation defined over adversary structure. Analysis shows that reduced scheme still preserves theproperties of the original one.展开更多
The Canetti-Krawczyk (CK) model is a formalism for the analysis of key-exchange protocols, which can guarantee many security properties for the protocols proved secure by this model. But we find this model lacks the a...The Canetti-Krawczyk (CK) model is a formalism for the analysis of key-exchange protocols, which can guarantee many security properties for the protocols proved secure by this model. But we find this model lacks the ability to guarantee key generation center (KGC) forward secrecy, which is an important security property for key-agreement protocols based on Identity. The essential reason leading to this weakness is that it does not fully consider the attacker's capabilities. In this paper, the CK model is accordingly extended with a new additional attacker's capability of the KGC corruption in Identity-based systems, which enables it to support KGC forward secrecy.展开更多
文摘Composite polyurethane(PU)-SiO_2 hollow fiber membranes were successfully prepared via optimizing thetechnique of dry-jet wet spinning,and their pressure-responsibilities were confirmed by the relationships of pure water flux-transmembrane pressure(PWF-TP)for the first time.The origin for this phenomenon was analyzed on the basis of membranestructure and material characteristics.The effects of SiO_2 content on the structure and properties of membrane wereinvestigated.The experimental results indicated that SiO_2 in membrane created a great many interfacial micro-voids andplayed an important role in pressure-responsibility,PWF and rejection of membrane:with the increase of SiO_2 content,theability of membrane recovery weakened,PWF increased,and rejection decreased slightly.
基金This project is supported by Science and Technology Developing Foundation of Tianjin Higher Education (No.20030703).
文摘Based on theory of mechanical dynamics, meshing characteristic as well as thedynamic model of double circular arc helical gearing, an analysis approach and a computer programhave been developed for studying the state of dynamic load and factor of dynamic load of thegearing, the changing situation of dynamic load and dynamic load factor vs some affecting factorssuch as gear width, helix angle and accuracy grade etc are investigated. A series of conclusions areobtained: ①With the increasing in the values of gear width, the dynamic load factor appears slowdecreasing tendency in most region of gear width. ②When the accuracy grades of the gearing areimproved, the values of dynamic load factor decrease. ③The value of dynamic load factor appears adecreasing tendency with the increasing of value of helix angle at the same ratio of criticalrotational speed.
文摘The mechanical properties of the steel pipe rolled with continuously casting round billet after determining the chemical composition in steel were studied.The results show that the total reduction ratio should be higher than 5.2 when the line pipes of grade B,grade 20 and other general seamless pipe were rolled with continuously casting round billet.And the total reduction ratio should be higher than 10.2 and the grain size should be controlled more than grade 7 for casing of oil countryside tubular goods(OCTG).
文摘Most existing secret sharing schemes are constructed to realize generalaccess structure, which is defined in terms of authorized groups of participants, and is unable tobe applied directly to the design of intrusion tolerant system, which often concerns corruptiblegroups of participants instead of authorized ones. Instead, the generalized adversary structure,which specifies the corruptible subsets of participants, can be determined directly by exploit ofthe system setting and the attributes of all participants. In this paper an efficient secret sharingscheme realizing generalized adversary structure is proposed, and it is proved that the schemesatisfies both properties of the secret sharing scheme, i.e., the reconstruction property and theperfect property. The main features of this scheme are that it performs modular additions andsubtractions only, and each share appears in multiple share sets and is thus replicated. The formeris an advantage in terms of computational complexity, and the latter is an advantage when recoveryof some corrupted participants is necessary. So our scheme can achieve lower computation cost andhigher availability. Some reduction on the scheme is also done finally, based on an equivalencerelation defined over adversary structure. Analysis shows that reduced scheme still preserves theproperties of the original one.
基金supported by the National Natural Science Foundation of China(Grant No.90204012)the National“863”High-tech Project of China(Grant No.2002AA143021)the Excellent Young Teachers Program of MOE,China and the Key Project of Chinese Ministry of Education
文摘The Canetti-Krawczyk (CK) model is a formalism for the analysis of key-exchange protocols, which can guarantee many security properties for the protocols proved secure by this model. But we find this model lacks the ability to guarantee key generation center (KGC) forward secrecy, which is an important security property for key-agreement protocols based on Identity. The essential reason leading to this weakness is that it does not fully consider the attacker's capabilities. In this paper, the CK model is accordingly extended with a new additional attacker's capability of the KGC corruption in Identity-based systems, which enables it to support KGC forward secrecy.
