To strike a tradeoff between the security and the consumption of energy,computing and communication resources in the nodes,this paper presents an efficient authentication scheme based on one-way key chain for sensor n...To strike a tradeoff between the security and the consumption of energy,computing and communication resources in the nodes,this paper presents an efficient authentication scheme based on one-way key chain for sensor network. The scheme can provide immediate authentication to fulfill the latency and the storage requirements and defends against various attacks such as replay,impersonation and denial of service. Meanwhile,our scheme possesses low overhead and scalability to large networks. Furthermore,the simple related protocols or algorithms in the scheme and inexpensive public-key operation required in view of resource-starved sensor nodes minimize the storage,computation and communication overhead,and improve the efficiency of our scheme. In addition,the proposed scheme also supports source authentication without precluding in-network processing and passive participation.展开更多
Neutron radiography uses the unique interaction probabilities of neutrons to create images of materials. This imaging technique is non-destructive. MCNP Monte Carlo Code has been used to design an optimized neutron ra...Neutron radiography uses the unique interaction probabilities of neutrons to create images of materials. This imaging technique is non-destructive. MCNP Monte Carlo Code has been used to design an optimized neutron radiography system that utilizes 241Am-Be neutron source. Many different arrangements have been simulated to obtain a neutron flux with higher amplitude and more uniform distribution in the collimator outlet, next to image plane. In the final arrangement the specifications of neutron filter, Gamma-ray shield and beam collimator has been determined. Simulations has been carried out for a 5Ci 241Am-Be neutron source. In this case 43.8 n/cm2s thermal neutron flux has been achieved at a distance of 35 cm from neutron source.展开更多
基金the National Natural Science Foundation of China (Grant No. 60202005).
文摘To strike a tradeoff between the security and the consumption of energy,computing and communication resources in the nodes,this paper presents an efficient authentication scheme based on one-way key chain for sensor network. The scheme can provide immediate authentication to fulfill the latency and the storage requirements and defends against various attacks such as replay,impersonation and denial of service. Meanwhile,our scheme possesses low overhead and scalability to large networks. Furthermore,the simple related protocols or algorithms in the scheme and inexpensive public-key operation required in view of resource-starved sensor nodes minimize the storage,computation and communication overhead,and improve the efficiency of our scheme. In addition,the proposed scheme also supports source authentication without precluding in-network processing and passive participation.
文摘Neutron radiography uses the unique interaction probabilities of neutrons to create images of materials. This imaging technique is non-destructive. MCNP Monte Carlo Code has been used to design an optimized neutron radiography system that utilizes 241Am-Be neutron source. Many different arrangements have been simulated to obtain a neutron flux with higher amplitude and more uniform distribution in the collimator outlet, next to image plane. In the final arrangement the specifications of neutron filter, Gamma-ray shield and beam collimator has been determined. Simulations has been carried out for a 5Ci 241Am-Be neutron source. In this case 43.8 n/cm2s thermal neutron flux has been achieved at a distance of 35 cm from neutron source.
