In Heterogeneous Wireless Sensor Networks, the mobility of the sensor nodes becomes essential in various applications. During node mobility, there are possibilities for the malicious node to become the cluster head or...In Heterogeneous Wireless Sensor Networks, the mobility of the sensor nodes becomes essential in various applications. During node mobility, there are possibilities for the malicious node to become the cluster head or cluster member. This causes the cluster or the whole network to be controlled by the malicious nodes. To offer high level of security, the mobile sensor nodes need to be authenticated. Further, clustering of nodes improves scalability, energy efficient routing and data delivery. In this paper, we propose a cluster based secure dynamic keying technique to authenticate the nodes during mobility. The nodes with high configuration are chosen as cluster heads based on the weight value which is estimated using parameters such as the node degree, average distance, node's average speed, and virtual battery power. The keys are dynamically generated and used for providing security. Even the keys are compromised by the attackers, they are not able to use the previous keys to cheat or disuse the authenticated nodes. In addition, a bidirectional malicious node detection technique is employed which eliminates the malicious node from the network. By simulation, it is proved that the proposed technique provides efficient security with reduced energy consumption during node mobility.展开更多
Strain growth is a phenomenon observed in containment vessels subjected to internal blast loading. The elastic response of the vessel may become larger in a later stage compared to its response during the initial stag...Strain growth is a phenomenon observed in containment vessels subjected to internal blast loading. The elastic response of the vessel may become larger in a later stage compared to its response during the initial stage. The dynamic responses of infinitely long cylindrical containment vessels subjected to uniformly-distributed internal blast loading are studied using LS-DYNA. The development of bending modes and the interaction between the breathing mode and bending modes are observed. The methodology developed for dynamic elastic buckling analysis is employed to study the strain growth phenomenon in explosion containment vessels. It is shown that the dynamic instable vibration of a containment vessel is the basic mechanism of strain growth.展开更多
The present article examines the livelihood benefits associated with agrobiodiversity in Veracruz, Mexico. Citrus-based agriculture is the principal economic activity in the agricultural sector of the state of Veracru...The present article examines the livelihood benefits associated with agrobiodiversity in Veracruz, Mexico. Citrus-based agriculture is the principal economic activity in the agricultural sector of the state of Veracruz. It is practiced in mono-crop plantations by the majority of farmers, who are rendered vulnerable to price depreciation resulting from simultaneous harvest and over-supply of a single commodity. Some farmers have associated multiple crops in citrus farms （agroforestry techniques） as a strategy to improve their livelihoods. Farmers who increased agrobiodiversity in their farms have significantly improved their livelihoods compared to mono-crop plantation owners. The research shows that increased agro-biodiversity can be a strategy to improve the livelihoods of citrus producers in the state of Veracruz, with significant economic benefits depending on the crop combination： maize-citrus is the least economically profitable combination （providing 21% in terms of internal rate of return）, while pineapple-citrus, banana-citrus and vanilla-citrus give higher returns （41%, 44% and 221% respectively）. The citrus-vanilla crop combination also has the highest benefit-cost ratio, relative to citrus monocrop （1.91） as well as the highest net present value （MX$579,635.73）. The choice of crop ultimately depends on the farmer＇s priorities. The associated benefits can be classified in three ways which correspond to the tripartite goal of sustainable development： （i） ecological sustainability （through increased ecosystem resilience）, （ii） economic stability （through diversified, less risk-prone sources of income）, and （iii） social well-being （through lower）.展开更多
Loess tunnels are widely used in transportation engineering and are irreplaceable parts of transportation infrastructure. In this paper, a dynamic finite element method is used to analyze the coupled effects of a trai...Loess tunnels are widely used in transportation engineering and are irreplaceable parts of transportation infrastructure. In this paper, a dynamic finite element method is used to analyze the coupled effects of a train vibration load and rainfall seepage. By calculating the variation in the safety factor of a loess tunnel because of the effects of various factors, such as different rainfall intensities and soil thicknesses, the dynamic stability of the loess tunnel is studied under the condition of a near-field pulse-like earthquake. The results show that the security and stability of the tunnel decrease gradually with decreasing burial depth. In addition, the plastic strain of the tunnel is mainly distributed on both sides of the vault and the feet, and the maximum value of the critical strain occurs on both sides of the arch feet. Because of the effects of the train vibration load and rainfall seepage, the safety factor of the loess tunnel structure decreases to a certain degree. Moreover, the range and maximum value of the plastic strain increase to various degrees.展开更多
文摘In Heterogeneous Wireless Sensor Networks, the mobility of the sensor nodes becomes essential in various applications. During node mobility, there are possibilities for the malicious node to become the cluster head or cluster member. This causes the cluster or the whole network to be controlled by the malicious nodes. To offer high level of security, the mobile sensor nodes need to be authenticated. Further, clustering of nodes improves scalability, energy efficient routing and data delivery. In this paper, we propose a cluster based secure dynamic keying technique to authenticate the nodes during mobility. The nodes with high configuration are chosen as cluster heads based on the weight value which is estimated using parameters such as the node degree, average distance, node's average speed, and virtual battery power. The keys are dynamically generated and used for providing security. Even the keys are compromised by the attackers, they are not able to use the previous keys to cheat or disuse the authenticated nodes. In addition, a bidirectional malicious node detection technique is employed which eliminates the malicious node from the network. By simulation, it is proved that the proposed technique provides efficient security with reduced energy consumption during node mobility.
文摘Strain growth is a phenomenon observed in containment vessels subjected to internal blast loading. The elastic response of the vessel may become larger in a later stage compared to its response during the initial stage. The dynamic responses of infinitely long cylindrical containment vessels subjected to uniformly-distributed internal blast loading are studied using LS-DYNA. The development of bending modes and the interaction between the breathing mode and bending modes are observed. The methodology developed for dynamic elastic buckling analysis is employed to study the strain growth phenomenon in explosion containment vessels. It is shown that the dynamic instable vibration of a containment vessel is the basic mechanism of strain growth.
文摘The present article examines the livelihood benefits associated with agrobiodiversity in Veracruz, Mexico. Citrus-based agriculture is the principal economic activity in the agricultural sector of the state of Veracruz. It is practiced in mono-crop plantations by the majority of farmers, who are rendered vulnerable to price depreciation resulting from simultaneous harvest and over-supply of a single commodity. Some farmers have associated multiple crops in citrus farms （agroforestry techniques） as a strategy to improve their livelihoods. Farmers who increased agrobiodiversity in their farms have significantly improved their livelihoods compared to mono-crop plantation owners. The research shows that increased agro-biodiversity can be a strategy to improve the livelihoods of citrus producers in the state of Veracruz, with significant economic benefits depending on the crop combination： maize-citrus is the least economically profitable combination （providing 21% in terms of internal rate of return）, while pineapple-citrus, banana-citrus and vanilla-citrus give higher returns （41%, 44% and 221% respectively）. The citrus-vanilla crop combination also has the highest benefit-cost ratio, relative to citrus monocrop （1.91） as well as the highest net present value （MX$579,635.73）. The choice of crop ultimately depends on the farmer＇s priorities. The associated benefits can be classified in three ways which correspond to the tripartite goal of sustainable development： （i） ecological sustainability （through increased ecosystem resilience）, （ii） economic stability （through diversified, less risk-prone sources of income）, and （iii） social well-being （through lower）.
基金supported in part by the National Natural Science Foundation of China(Grant No.51478212)the Education Ministry Doctoral Tutor Foundation of China(Grant No.20136201110003)
文摘Loess tunnels are widely used in transportation engineering and are irreplaceable parts of transportation infrastructure. In this paper, a dynamic finite element method is used to analyze the coupled effects of a train vibration load and rainfall seepage. By calculating the variation in the safety factor of a loess tunnel because of the effects of various factors, such as different rainfall intensities and soil thicknesses, the dynamic stability of the loess tunnel is studied under the condition of a near-field pulse-like earthquake. The results show that the security and stability of the tunnel decrease gradually with decreasing burial depth. In addition, the plastic strain of the tunnel is mainly distributed on both sides of the vault and the feet, and the maximum value of the critical strain occurs on both sides of the arch feet. Because of the effects of the train vibration load and rainfall seepage, the safety factor of the loess tunnel structure decreases to a certain degree. Moreover, the range and maximum value of the plastic strain increase to various degrees.
