Passive worms can passively propagate through embedding themselves into some sharing files, which can result in significant damage to unstructured P2P networks. To study the passive worm behaviors, this paper firstly ...Passive worms can passively propagate through embedding themselves into some sharing files, which can result in significant damage to unstructured P2P networks. To study the passive worm behaviors, this paper firstly analyzes and obtains the average delay for all peers in the whole transmitting process due to the limitation of network throughput, and then proposes a mathematical model for the propagation of passive worms over the unstructured P2P networks. The model mainly takes the effect of the network throughput into account, and applies a new healthy files dissemination-based defense strategy according to the file popularity which follows the Zipf distribution. The simulation results show that the propagation of passive worms is mainly governed by the number of hops, initially infected files and uninfected files. The larger the number of hops, the more rapidly the passive worms propagate. If the number of the initially infected files is increased by the attackers, the propagation speed of passive worms increases obviously. A larger size of the uninfected file results in a better attack performance. However, the number of files generated by passive worms is not an important factor governing the propagation of passive worms. The effectiveness of healthy files dissemination strategy is verified. This model can provide a guideline in the control of unstructured P2P networks as well as passive worm defense.展开更多
Studied on multi-component combustible gas,methane mainly,explosion char- acteristics of high gas mine,obtained the rules of gas explosive limit that influenced by environment temperature,pressure,concentration of oxy...Studied on multi-component combustible gas,methane mainly,explosion char- acteristics of high gas mine,obtained the rules of gas explosive limit that influenced by environment temperature,pressure,concentration of oxygen,other combustible gas,coal dust,energy of fire source,and the inert gas,proposed a new method of divide gas explo- sive triangle partition,and gave new partition linear equations.The gas explosive triangle and its new partition has important directive significance in distinguishing if the fire area has a gas explosion when sealing or opening fire area,or fire extinguishing in sealed fire area,and judging if there will be a gas explosion or other trend while fire extinguishing with inert gas.展开更多
Some unsafe languages,like C and C++,let programmers maximize performance but are vulnerable to memory errors which can lead to program crashes and unpredictable behavior.Aiming to solve the problem,traditional memory...Some unsafe languages,like C and C++,let programmers maximize performance but are vulnerable to memory errors which can lead to program crashes and unpredictable behavior.Aiming to solve the problem,traditional memory allocating strategy is improved and a new probabilistic memory allocation technology is presented.By combining random memory allocating algorithm and virtual memory,memory errors are avoided in all probability during software executing.By replacing default memory allocator to manage allocation of heap memory,buffer overflows and dangling pointers are prevented.Experiments show it is better than Diehard of the following aspects:memory errors prevention,performance in memory allocation set and ability of controlling working set.So probabilistic memory allocation is a valid memory errors prevention technology and it can tolerate memory errors and provide probabilistic memory safety effectively.展开更多
基金National Natural Science Foundation of China (No.60633020 and No. 90204012)Natural Science Foundation of Hebei Province (No. F2006000177)
文摘Passive worms can passively propagate through embedding themselves into some sharing files, which can result in significant damage to unstructured P2P networks. To study the passive worm behaviors, this paper firstly analyzes and obtains the average delay for all peers in the whole transmitting process due to the limitation of network throughput, and then proposes a mathematical model for the propagation of passive worms over the unstructured P2P networks. The model mainly takes the effect of the network throughput into account, and applies a new healthy files dissemination-based defense strategy according to the file popularity which follows the Zipf distribution. The simulation results show that the propagation of passive worms is mainly governed by the number of hops, initially infected files and uninfected files. The larger the number of hops, the more rapidly the passive worms propagate. If the number of the initially infected files is increased by the attackers, the propagation speed of passive worms increases obviously. A larger size of the uninfected file results in a better attack performance. However, the number of files generated by passive worms is not an important factor governing the propagation of passive worms. The effectiveness of healthy files dissemination strategy is verified. This model can provide a guideline in the control of unstructured P2P networks as well as passive worm defense.
基金the National Natural Science Fund of China(50474010)the National"Eleventh Five-year Plan"Science and Technology Support Plan of China(2006BAK03B0503)+1 种基金the Fund of Education Department Liaoning Province(05L-174)the Fund of Education Department Liaoning Province(20060389)
文摘Studied on multi-component combustible gas,methane mainly,explosion char- acteristics of high gas mine,obtained the rules of gas explosive limit that influenced by environment temperature,pressure,concentration of oxygen,other combustible gas,coal dust,energy of fire source,and the inert gas,proposed a new method of divide gas explo- sive triangle partition,and gave new partition linear equations.The gas explosive triangle and its new partition has important directive significance in distinguishing if the fire area has a gas explosion when sealing or opening fire area,or fire extinguishing in sealed fire area,and judging if there will be a gas explosion or other trend while fire extinguishing with inert gas.
基金supported by the Natural Science Foundation of China under Grant No.61100205the National High-Tech Research and Development Plan of China under Grant No.2009AA01Z433the Project of the Fundamental Research Funds of Beijing Institute of Technology
文摘Some unsafe languages,like C and C++,let programmers maximize performance but are vulnerable to memory errors which can lead to program crashes and unpredictable behavior.Aiming to solve the problem,traditional memory allocating strategy is improved and a new probabilistic memory allocation technology is presented.By combining random memory allocating algorithm and virtual memory,memory errors are avoided in all probability during software executing.By replacing default memory allocator to manage allocation of heap memory,buffer overflows and dangling pointers are prevented.Experiments show it is better than Diehard of the following aspects:memory errors prevention,performance in memory allocation set and ability of controlling working set.So probabilistic memory allocation is a valid memory errors prevention technology and it can tolerate memory errors and provide probabilistic memory safety effectively.
