Traditional wireless sensor networks(WSNs)are typically deployed in remote and hostile environments for information collection.The wireless communication methods adopted by sensor nodes may make the network highly vul...Traditional wireless sensor networks(WSNs)are typically deployed in remote and hostile environments for information collection.The wireless communication methods adopted by sensor nodes may make the network highly vulnerable to various attacks.Traditional encryption and authentication mechanisms cannot prevent attacks launched by internal malicious nodes.The trust-based security mechanism is usually adopted to solve this problem in WSNs.However,the behavioral evidence used for trust estimation presents some uncertainties due to the open wireless medium and the inexpensive sensor nodes.Moreover,how to efficiently collect behavioral evidences are rarely discussed.To address these issues,in this paper,we present a trust management mechanism based on fuzzy logic and a cloud model.First,a type-II fuzzy logic system is used to preprocess the behavioral evidences and alleviate uncertainty.Then,the cloud model is introduced to estimate the trust values for sensor nodes.Finally,a dynamic behavior monitoring protocol is proposed to provide a balance between energy conservation and safety assurance.Simulation results demonstrate that our trust management mechanism can effectively protect the network from internal malicious attacks while enhancing the energy efficiency of behavior monitoring.展开更多
The applicability of ultrasonic pulse velocity （UPV） method to in-situ monitor setting and hardening process of foamed concrete （FC） was systematically investigated. The UPVs of various FC pastes were automaticall...The applicability of ultrasonic pulse velocity （UPV） method to in-situ monitor setting and hardening process of foamed concrete （FC） was systematically investigated. The UPVs of various FC pastes were automatically and continuously measured by a specially designed ultrasonic monitoring apparatus （UMA）. Ultrasonic tests were performed on FC mixtures with different density （300, 500, 800 and 1 000 kg/m3）, and different fly ash contents （0%, 20%, 40% and 60%）. The influence of curing temperatures （20, 40, 60 and 80~C） was also studied. The experimental results show that three characteristic stages can be clearly identified during the setting process of an arbitrary FC paste： dormant stage, acceleration stage, and deceleration stage. Wet density, fly ash content, and curing temperature have great impact on setting behavior. A stepwise increase of the wet density results in shorter dormant stage and larger final UPV. Hydration reaction rate is obviously promoted with an increase in curing temperature. However, the addition fly ash retards the microstn,lcture formation. To aid in comparing with the ultrasonic results, the consistence spread test and Vicat needle test （VNT） were also conducted. A correlation between ultrasonic and VNT results was also established to evaluate the initial and final setting time of the FC mixtures. Finally, certain ranges of UPV with reasonable widths were suggested for the initial and final setting time, respectively.展开更多
随着国家公园游憩需求不断增加,科学监测与管理国家公园游憩行为已成为平衡游憩需求与保护生态资源的科学途径。文章以我国第一批正式成立的国家公园——武夷山国家公园为研究案例地,基于“两步路户外助手”GNSS轨迹及标注点数据,结合Op...随着国家公园游憩需求不断增加,科学监测与管理国家公园游憩行为已成为平衡游憩需求与保护生态资源的科学途径。文章以我国第一批正式成立的国家公园——武夷山国家公园为研究案例地,基于“两步路户外助手”GNSS轨迹及标注点数据,结合Open Street Map获取的武夷山国家公园交通路网数据、旅游景点POI数据以及“八爪鱼采集器”爬取的携程网、小红书网络评论文本,通过将GNSS轨迹数据栅格化处理,利用ROST CM6、ArcGIS进行内容分析和密度分析,从而探析2016年至2023年武夷山国家公园游憩行为时空特征与旅游热点分布特征。研究表明:(1)游客主要关注于旅游吸引物,且积极情绪比重大;(2)游客游憩活动轨迹高峰月份显著,波动趋势大致相同,受节假日影响较小;(3)游客活动淡旺季差异较小,淡季有非热点区域集中倾向;(4)游客活动轨迹区域高度集中,多集中于武夷山国家级风景名胜区和武夷山自然保护区,轨迹点集中度较标注点更为显著;(5)游客活动轨迹与内部道路、景点POI重合度高,部分游客偏向参与区域内的露营等生态游憩活动。展开更多
基金supported in part by the Chongqing Electronics Engineering Technology Research Center for Interactive Learningin part by the Chongqing key discipline of electronic informationin part by the Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN202201630)。
文摘Traditional wireless sensor networks(WSNs)are typically deployed in remote and hostile environments for information collection.The wireless communication methods adopted by sensor nodes may make the network highly vulnerable to various attacks.Traditional encryption and authentication mechanisms cannot prevent attacks launched by internal malicious nodes.The trust-based security mechanism is usually adopted to solve this problem in WSNs.However,the behavioral evidence used for trust estimation presents some uncertainties due to the open wireless medium and the inexpensive sensor nodes.Moreover,how to efficiently collect behavioral evidences are rarely discussed.To address these issues,in this paper,we present a trust management mechanism based on fuzzy logic and a cloud model.First,a type-II fuzzy logic system is used to preprocess the behavioral evidences and alleviate uncertainty.Then,the cloud model is introduced to estimate the trust values for sensor nodes.Finally,a dynamic behavior monitoring protocol is proposed to provide a balance between energy conservation and safety assurance.Simulation results demonstrate that our trust management mechanism can effectively protect the network from internal malicious attacks while enhancing the energy efficiency of behavior monitoring.
基金Founded by the key laboratory of high performance civil engineering materials(2010CEM002)the National Natural Science Foundation of China(51178106,51138002)+1 种基金the Program for New Century Excellent Talents in University(NCET-08-0116),973 Program(2009CB623200)the Program sponsored for scientific innovation research of college graduate in Jiangsu province(CXLX_0105)
文摘The applicability of ultrasonic pulse velocity （UPV） method to in-situ monitor setting and hardening process of foamed concrete （FC） was systematically investigated. The UPVs of various FC pastes were automatically and continuously measured by a specially designed ultrasonic monitoring apparatus （UMA）. Ultrasonic tests were performed on FC mixtures with different density （300, 500, 800 and 1 000 kg/m3）, and different fly ash contents （0%, 20%, 40% and 60%）. The influence of curing temperatures （20, 40, 60 and 80~C） was also studied. The experimental results show that three characteristic stages can be clearly identified during the setting process of an arbitrary FC paste： dormant stage, acceleration stage, and deceleration stage. Wet density, fly ash content, and curing temperature have great impact on setting behavior. A stepwise increase of the wet density results in shorter dormant stage and larger final UPV. Hydration reaction rate is obviously promoted with an increase in curing temperature. However, the addition fly ash retards the microstn,lcture formation. To aid in comparing with the ultrasonic results, the consistence spread test and Vicat needle test （VNT） were also conducted. A correlation between ultrasonic and VNT results was also established to evaluate the initial and final setting time of the FC mixtures. Finally, certain ranges of UPV with reasonable widths were suggested for the initial and final setting time, respectively.
文摘随着国家公园游憩需求不断增加,科学监测与管理国家公园游憩行为已成为平衡游憩需求与保护生态资源的科学途径。文章以我国第一批正式成立的国家公园——武夷山国家公园为研究案例地,基于“两步路户外助手”GNSS轨迹及标注点数据,结合Open Street Map获取的武夷山国家公园交通路网数据、旅游景点POI数据以及“八爪鱼采集器”爬取的携程网、小红书网络评论文本,通过将GNSS轨迹数据栅格化处理,利用ROST CM6、ArcGIS进行内容分析和密度分析,从而探析2016年至2023年武夷山国家公园游憩行为时空特征与旅游热点分布特征。研究表明:(1)游客主要关注于旅游吸引物,且积极情绪比重大;(2)游客游憩活动轨迹高峰月份显著,波动趋势大致相同,受节假日影响较小;(3)游客活动淡旺季差异较小,淡季有非热点区域集中倾向;(4)游客活动轨迹区域高度集中,多集中于武夷山国家级风景名胜区和武夷山自然保护区,轨迹点集中度较标注点更为显著;(5)游客活动轨迹与内部道路、景点POI重合度高,部分游客偏向参与区域内的露营等生态游憩活动。
