Extreme storm events in coastal zones play significant roles in shaping the morphology of boulder beaches.However,boulder displacement and the geomorphological evolution of boulder beaches driven by different extreme ...Extreme storm events in coastal zones play significant roles in shaping the morphology of boulder beaches.However,boulder displacement and the geomorphological evolution of boulder beaches driven by different extreme storm events,especially typhoon events,remain poorly understood.Thus,boulder displacement and the geomorphic response on a boulder beach in Fujian,southeastern China,were explored before,during and after a cold wave event(Dec.1–7,2020)and before and after Typhoon In-Fa(Jul.19–27,2021),a large tropical storm.This was achieved by tracking 42 tagged boulders distributed in the intertidal and supratidal zones using Radio Frequency Identification(RFID)and topographic surveys using real-time kinematic techniques,respectively.The results showed obvious disparities in boulder displacement in different geomorphic zones due to cold wave and typhoon events that were mainly characterized by migration magnitude,range,direction,and mode of transport.The typhoon event led to rapid and substantial changes in the overall morphology of the boulder beach,while the cold wave event impacted the intertidal morphology of the boulder beach to only a small extent.The surrounding structure of boulders,beach slope and beach elevation had a combined dominant effect on boulder displacement under the same extreme event.Hydrodynamic factors(effective wave energy fluxes,incident wave direction,storm surge and water level)had dominant effects on boulder displacement during different extreme events.In terms of a single event,the magnitude of the boulder displacement driven by the typhoon was much greater than that driven by the cold wave.However,considering the frequency and duration of cold waves in winter,the impact of multiple consecutive cold waves on the geomorphology of the boulder beach cannot be ignored in this study area.Alternating and repeated interactions between these two processes constitute the complete geomorphic evolution of the boulder beach.This study contributes to improved predictions of the morphodynamic response of boulder beaches to future storms,especially large tropical storms,and facilitates better coastal management.展开更多
<b>Background:</b> The novel Coronavirus disease 2019 (COVID-19) has rapidly evolved into a global emergency with far-reaching consequences. Multiple models predict mounting morbidity and mortality in the ...<b>Background:</b> The novel Coronavirus disease 2019 (COVID-19) has rapidly evolved into a global emergency with far-reaching consequences. Multiple models predict mounting morbidity and mortality in the absence of appropriate interventions. Screening of sub-clinical cases through technological tools has the potential to eliminate virus containment in the population. <b>Objective: </b>Our aim was to develop an effective application that detected early COVID-19 infections and resulted in four-dimensional (4-D) data visualization systems to develop safe networks whilst respecting user privacy. <b>Methods: </b>We proposed an algorithm for a novel form of contact tracing and screening that can detect infection before manifestation of clinical symptoms and signs. We developed a simulation model that demonstrated impact on the pandemic through percent change in the “trigger point”. <b>Results: </b>A “trigger point” based on personal risk assessment generated a visual report to the community network. The following outcomes were rendered in the app: live surveillance of metadata, hotspot mapping, targeted live health messaging to a large population, an infection control passport technology, and personal hotspot avoidance warnings. Our model suggested that higher adoption of such strategies can potentially eliminate viral carriage in the population. <b>Conclusions: </b>Our proposed technology-enabled screening, detection, and elimination strategy presents a novel approach to eliminate the viral containment. This app could be applied to the COVID-19 pandemic as well as other outbreaks and epidemics in the future to control the unprecedented disease spread.展开更多
Groundwater is an important source of drinking water.Groundwater pollution severely endangers drinking water safety and sustainable social development.In the case of groundwater pollution,the top priority is to identi...Groundwater is an important source of drinking water.Groundwater pollution severely endangers drinking water safety and sustainable social development.In the case of groundwater pollution,the top priority is to identify pollution sources,and accurate information on pollution sources is the premise of efficient remediation.Then,an appropriate pollution remediation scheme should be developed according to information on pollution sources,site conditions,and economic costs.The methods for identifying pollution sources mainly include geophysical exploration,geochemistry,isotopic tracing,and numerical modeling.Among these identification methods,only the numerical modeling can recognize various information on pollution sources,while other methods can only identify a certain aspect of pollution sources.The remediation technologies of groundwater can be divided into in-situ and ex-situ remediation technologies according to the remediation location.The in-situ remediation technologies enjoy low costs and a wide remediation range,but their remediation performance is prone to be affected by environmental conditions and cause secondary pollution.The ex-situ remediation technologies boast high remediation efficiency,high processing capacity,and high treatment concentration but suffer high costs.Different methods for pollution source identification and remediation technologies are applicable to different conditions.To achieve the expected identification and remediation results,it is feasible to combine several methods and technologies according to the actual hydrogeological conditions of contaminated sites and the nature of pollutants.Additionally,detailed knowledge about the hydrogeological conditions and stratigraphic structure of the contaminated site is the basis of all work regardless of the adopted identification methods or remediation technologies.展开更多
This paper presented a new-type CNC curve grinding machine, in order to conquer the disadvantages of conventional NC curve grinding machine and improve surface quality, dimensional accuracy and machining efficiency. T...This paper presented a new-type CNC curve grinding machine, in order to conquer the disadvantages of conventional NC curve grinding machine and improve surface quality, dimensional accuracy and machining efficiency. The new-type grinder adopts some high and new technologies: ① the normal tracing device could make grinding wheel coincide with the normal direction of the machining points in work piece, and improve surface quality and dimensional accuracy; ② the digital image on-line recognition system could monitor machining process and compensate wheel wear in real time; ③ linear motor drive mechanism could realize the exact adjustment of the grinding head digitally and increase the machining efficiency. The math models of normal tracing and circular tolerance zone were presented. The experimental results show that the new-type CNC curve grinding machine equipped with the three devices mentioned above is easy to realize the precision grinding of any complex curve, and improve surface quality, dimensional accuracy and machining efficiency.展开更多
目前,国内外很多厂商推出了Linux系统中的终端检测响应(Endpoint Detection and Response,EDR)系统,为云平台、物联网、大数据计算等基础设施提供全面的安全检测和防护服务。但是,针对EDR文件防护功能的绕过攻击能够帮助恶意行为规避监...目前,国内外很多厂商推出了Linux系统中的终端检测响应(Endpoint Detection and Response,EDR)系统,为云平台、物联网、大数据计算等基础设施提供全面的安全检测和防护服务。但是,针对EDR文件防护功能的绕过攻击能够帮助恶意行为规避监控,造成严重的系统和数据安全风险。针对开源和商业闭源的Linux EDR系统,首先,阐述了文件防护功能的底层实现机制,对其核心技术原理进行了分析;其次,重点梳理了4种现有公开的文件防护绕过技术,提出了3种尚未公开的绕过技术,并且总结提炼为3种攻击类型;再次,基于上述绕过技术编写了验证工具,通过测试证明了这些技术方法对于部分Linux EDR系统的文件防护绕过能力;最后,给出了相应的安全防护建议。展开更多
基金The National Natural Science Foundation of China under contract No.41930538the Scientific Research Foundation of the Third Institute of Oceanography,Ministry of Natural Resources under contract No.2019029.
文摘Extreme storm events in coastal zones play significant roles in shaping the morphology of boulder beaches.However,boulder displacement and the geomorphological evolution of boulder beaches driven by different extreme storm events,especially typhoon events,remain poorly understood.Thus,boulder displacement and the geomorphic response on a boulder beach in Fujian,southeastern China,were explored before,during and after a cold wave event(Dec.1–7,2020)and before and after Typhoon In-Fa(Jul.19–27,2021),a large tropical storm.This was achieved by tracking 42 tagged boulders distributed in the intertidal and supratidal zones using Radio Frequency Identification(RFID)and topographic surveys using real-time kinematic techniques,respectively.The results showed obvious disparities in boulder displacement in different geomorphic zones due to cold wave and typhoon events that were mainly characterized by migration magnitude,range,direction,and mode of transport.The typhoon event led to rapid and substantial changes in the overall morphology of the boulder beach,while the cold wave event impacted the intertidal morphology of the boulder beach to only a small extent.The surrounding structure of boulders,beach slope and beach elevation had a combined dominant effect on boulder displacement under the same extreme event.Hydrodynamic factors(effective wave energy fluxes,incident wave direction,storm surge and water level)had dominant effects on boulder displacement during different extreme events.In terms of a single event,the magnitude of the boulder displacement driven by the typhoon was much greater than that driven by the cold wave.However,considering the frequency and duration of cold waves in winter,the impact of multiple consecutive cold waves on the geomorphology of the boulder beach cannot be ignored in this study area.Alternating and repeated interactions between these two processes constitute the complete geomorphic evolution of the boulder beach.This study contributes to improved predictions of the morphodynamic response of boulder beaches to future storms,especially large tropical storms,and facilitates better coastal management.
文摘<b>Background:</b> The novel Coronavirus disease 2019 (COVID-19) has rapidly evolved into a global emergency with far-reaching consequences. Multiple models predict mounting morbidity and mortality in the absence of appropriate interventions. Screening of sub-clinical cases through technological tools has the potential to eliminate virus containment in the population. <b>Objective: </b>Our aim was to develop an effective application that detected early COVID-19 infections and resulted in four-dimensional (4-D) data visualization systems to develop safe networks whilst respecting user privacy. <b>Methods: </b>We proposed an algorithm for a novel form of contact tracing and screening that can detect infection before manifestation of clinical symptoms and signs. We developed a simulation model that demonstrated impact on the pandemic through percent change in the “trigger point”. <b>Results: </b>A “trigger point” based on personal risk assessment generated a visual report to the community network. The following outcomes were rendered in the app: live surveillance of metadata, hotspot mapping, targeted live health messaging to a large population, an infection control passport technology, and personal hotspot avoidance warnings. Our model suggested that higher adoption of such strategies can potentially eliminate viral carriage in the population. <b>Conclusions: </b>Our proposed technology-enabled screening, detection, and elimination strategy presents a novel approach to eliminate the viral containment. This app could be applied to the COVID-19 pandemic as well as other outbreaks and epidemics in the future to control the unprecedented disease spread.
基金funded by the National Natural Science Foundation of China(41907175)the Open Fund of Key Laboratory(WSRCR-2023-01)the project of the China Geological Survey(DD20230459).
文摘Groundwater is an important source of drinking water.Groundwater pollution severely endangers drinking water safety and sustainable social development.In the case of groundwater pollution,the top priority is to identify pollution sources,and accurate information on pollution sources is the premise of efficient remediation.Then,an appropriate pollution remediation scheme should be developed according to information on pollution sources,site conditions,and economic costs.The methods for identifying pollution sources mainly include geophysical exploration,geochemistry,isotopic tracing,and numerical modeling.Among these identification methods,only the numerical modeling can recognize various information on pollution sources,while other methods can only identify a certain aspect of pollution sources.The remediation technologies of groundwater can be divided into in-situ and ex-situ remediation technologies according to the remediation location.The in-situ remediation technologies enjoy low costs and a wide remediation range,but their remediation performance is prone to be affected by environmental conditions and cause secondary pollution.The ex-situ remediation technologies boast high remediation efficiency,high processing capacity,and high treatment concentration but suffer high costs.Different methods for pollution source identification and remediation technologies are applicable to different conditions.To achieve the expected identification and remediation results,it is feasible to combine several methods and technologies according to the actual hydrogeological conditions of contaminated sites and the nature of pollutants.Additionally,detailed knowledge about the hydrogeological conditions and stratigraphic structure of the contaminated site is the basis of all work regardless of the adopted identification methods or remediation technologies.
基金Shanghai Science and Technology Foundation of China (No.021111125)
文摘This paper presented a new-type CNC curve grinding machine, in order to conquer the disadvantages of conventional NC curve grinding machine and improve surface quality, dimensional accuracy and machining efficiency. The new-type grinder adopts some high and new technologies: ① the normal tracing device could make grinding wheel coincide with the normal direction of the machining points in work piece, and improve surface quality and dimensional accuracy; ② the digital image on-line recognition system could monitor machining process and compensate wheel wear in real time; ③ linear motor drive mechanism could realize the exact adjustment of the grinding head digitally and increase the machining efficiency. The math models of normal tracing and circular tolerance zone were presented. The experimental results show that the new-type CNC curve grinding machine equipped with the three devices mentioned above is easy to realize the precision grinding of any complex curve, and improve surface quality, dimensional accuracy and machining efficiency.
