域名系统(domain name system,DNS)作为互联网资源的名字标识服务,提供了从域名到IP地址的查询转换功能,是用户访问互联网应用的入口,也是用户侧安全威胁感知与防御的关键点。用户侧常见的DNS滥用及相关安全威胁有:网络钓鱼、域名不良...域名系统(domain name system,DNS)作为互联网资源的名字标识服务,提供了从域名到IP地址的查询转换功能,是用户访问互联网应用的入口,也是用户侧安全威胁感知与防御的关键点。用户侧常见的DNS滥用及相关安全威胁有:网络钓鱼、域名不良应用、恶意软件以及利用DNS进行攻击等。防护性DNS(protective DNS,PDNS)服务是一种利用DNS协议和架构的网络安全防护技术,通过对DNS查询进行威胁检测与处置,能够从源头上阻止用户对网络钓鱼网站、不良网站、恶意软件的访问。目前学界对PDNS服务还缺少系统的介绍与研究。对PDNS已有研究工作、应用现状及架构与功能进行系统梳理,对PDNS所涉及的关键技术进行系统综述,主要包括域名威胁处置技术、DNS异常检测技术、威胁情报管理技术和数据存储管理技术,分析PDNS目前面临的问题与挑战,并对PDNS未来发展趋势与研究方向提出了展望。展开更多
高校多校区一体化管理中,校区间人员流动频繁,如何保证学校师生在不同校区获得一致的上网体验成为一个难题。除了加快建设多活数据中心,实现重要信息系统的容灾备份体系之外,网络基础设施服务域名系统(Domain Name System,DNS)的一体化...高校多校区一体化管理中,校区间人员流动频繁,如何保证学校师生在不同校区获得一致的上网体验成为一个难题。除了加快建设多活数据中心,实现重要信息系统的容灾备份体系之外,网络基础设施服务域名系统(Domain Name System,DNS)的一体化部署也面临新挑战。以河海大学南京校区和常州校区为例,通过多活容灾网络架构等技术手段部署一体化智能DNS服务,有效解决网络拥塞和信息系统访问瓶颈的问题,同时提升DNS管理的便捷性和服务的安全可靠性,对相关应用场景具有一定参考价值。展开更多
The parabolic Radon transform has been widely used in multiple attenuation. To further improve the accuracy and efficiency of the Radon transform, we developed the 2- fdomain high-resolution Radon transform based on t...The parabolic Radon transform has been widely used in multiple attenuation. To further improve the accuracy and efficiency of the Radon transform, we developed the 2- fdomain high-resolution Radon transform based on the fast and modified parabolic Radon transform presented by Abbad. The introduction of a new variable 2 makes the transform operator frequency-independent. Thus, we need to calculate the transform operator and its inverse operator only once, which greatly improves the computational efficiency. Besides, because the primaries and multiples are distributed on straight lines with different slopes in the 2-fdomain, we can easily choose the filtering operator to suppress the multiples. At the same time, the proposed method offers the advantage of high-resolution Radon transform, which can greatly improve the precision of attenuating the multiples. Numerical experiments suggest that the multiples are well suppressed and the amplitude versus offset characteristics of the primaries are well maintained. Real data processing results further verify the effectiveness and feasibility of the method.展开更多
A conformal multi-resolution time-domain( CMRTD) method is presented for modeling curved objects. The effective dielectric constant and area weighting are used to derive the update equations of CMRTD. The backward sca...A conformal multi-resolution time-domain( CMRTD) method is presented for modeling curved objects. The effective dielectric constant and area weighting are used to derive the update equations of CMRTD. The backward scattering bistatic radar cross sections( RCS) of the dielectric cylinder and ellipsoid are used to validate the proposed method. The results show that the proposed conformal method is more accurate to deal with the complex curved objects in electromagnetic simulations.展开更多
Rainfall extremes have strong connotations to socio-economic activities and human well-being in Uganda’s Lake Victoria Basin (LVB). Reliable prediction and dissemination of extreme rainfall events are therefore of pa...Rainfall extremes have strong connotations to socio-economic activities and human well-being in Uganda’s Lake Victoria Basin (LVB). Reliable prediction and dissemination of extreme rainfall events are therefore of paramount importance to the region’s development agenda. The main objective of this study was to contribute to the prediction of rainfall extremes over this region using a numerical modelling approach. The Weather Research and Forecasting (WRF) model was used to simulate a 20-day period of extremely heavy rainfall that was observed in the March to May season of 2008. The underlying interest was to investigate the performance of different combinations of cumulus and microphysical parameterization along with the model grid resolution and domain size. The model output was validated against rainfall observations from the Tropical Rainfall Measuring Mission (TRMM) using 5 metrics;the rainfall distribution, root mean square error, mean error, probability of detection and false alarm ratio. The results showed that the model was able to simulate extreme rainfall and the most satisfactory skill was obtained with a model setup using the Grell 3D cumulus scheme combined with the SBU_YLin microphysical scheme. This study concludes that the WRF model can be used for simulating extreme rainfall over western LVB. In the other 2 regions, central and eastern LVB, its performance is limited by failure to simulate nocturnal rainfall. Furthermore, increasing the model grid resolution showed good potential for improving the model simulation especially when a large domain is used.展开更多
A conformal Runge-Kutta multi-resolution time-domain(C-RKMRTD)method is present and applied to model and analyze curved objects.Compared with the non-conformal method,the proposed method is more accurate.The scatterin...A conformal Runge-Kutta multi-resolution time-domain(C-RKMRTD)method is present and applied to model and analyze curved objects.Compared with the non-conformal method,the proposed method is more accurate.The scattering analyses of the cylinder and ellipsoid are presented to validate the proposed method.The numerical results demonstrate that the proposed scheme perform better than the MRTD method and other higher order methods with a higher accuracy.展开更多
面对ISP主干网,为了检测威胁其管理域内用户安全的僵尸网络、钓鱼网站以及垃圾邮件等恶意活动,实时监测流经主干网边界的DNS交互报文,并从域名的依赖性和使用位置两个方面刻画DNS活动行为模式,而后,基于有监督的多分类器模型,提出面向IS...面对ISP主干网,为了检测威胁其管理域内用户安全的僵尸网络、钓鱼网站以及垃圾邮件等恶意活动,实时监测流经主干网边界的DNS交互报文,并从域名的依赖性和使用位置两个方面刻画DNS活动行为模式,而后,基于有监督的多分类器模型,提出面向ISP主干网的上层DNS活动监测算法DAOS(binary classifier for DNS activity observation system).其中,依赖性从用户角度观察域名的外在使用情况,而使用位置则关注区域文件中记录的域名内部资源配置.实验结果表明:该算法在不依赖先验知识的前提下,经过两小时的DNS活动观测,可以达到90.5%的检测准确率,以及2.9%的假阳性和6.6%的假阴性.若持续观察1周,准确率可以上升到93.9%,假阳性和假阴性也可以下降到1.3%和4.8%.展开更多
We develop a high resolution ground penetrating radar system （LANRCS-GPR） based on the E5071B Vector Network Analyzer （VNA）. This system takes advantage of a wideband and adjustable frequency domain ground penetra...We develop a high resolution ground penetrating radar system （LANRCS-GPR） based on the E5071B Vector Network Analyzer （VNA）. This system takes advantage of a wideband and adjustable frequency domain ground penetrating radar system and adds the characteristics of a network analyzer with ultra-wideband and high precision measurement. It adopts the LAN mode to concatenate system control that reduces construction cost and makes the system easy to expand. The high resolution ground penetrating radar system carries out real time imaging using F-K migration with high calculation efficiency. The experiment results of the system indicate that the LANRCS-GPR system provides high resolution and precision, high signal-to-noise ratio, and great dynamic range. Furthermore, the LANRCS-GPR system is flexible and reliable to operate with easy to expand system functions. The research and development of the LANRCS-GPR provide the theoretical and experimental foundation for future frequency domain ground penetrating radar production and also can serve as an experimental platform with high data gathering precision, enormous information capability, wide application, and convenient operation for electromagnetic wave research and electromagnetic exploration.展开更多
文摘域名系统(domain name system,DNS)作为互联网资源的名字标识服务,提供了从域名到IP地址的查询转换功能,是用户访问互联网应用的入口,也是用户侧安全威胁感知与防御的关键点。用户侧常见的DNS滥用及相关安全威胁有:网络钓鱼、域名不良应用、恶意软件以及利用DNS进行攻击等。防护性DNS(protective DNS,PDNS)服务是一种利用DNS协议和架构的网络安全防护技术,通过对DNS查询进行威胁检测与处置,能够从源头上阻止用户对网络钓鱼网站、不良网站、恶意软件的访问。目前学界对PDNS服务还缺少系统的介绍与研究。对PDNS已有研究工作、应用现状及架构与功能进行系统梳理,对PDNS所涉及的关键技术进行系统综述,主要包括域名威胁处置技术、DNS异常检测技术、威胁情报管理技术和数据存储管理技术,分析PDNS目前面临的问题与挑战,并对PDNS未来发展趋势与研究方向提出了展望。
文摘高校多校区一体化管理中,校区间人员流动频繁,如何保证学校师生在不同校区获得一致的上网体验成为一个难题。除了加快建设多活数据中心,实现重要信息系统的容灾备份体系之外,网络基础设施服务域名系统(Domain Name System,DNS)的一体化部署也面临新挑战。以河海大学南京校区和常州校区为例,通过多活容灾网络架构等技术手段部署一体化智能DNS服务,有效解决网络拥塞和信息系统访问瓶颈的问题,同时提升DNS管理的便捷性和服务的安全可靠性,对相关应用场景具有一定参考价值。
基金sponsored by the National 973 Program(No.2011CB202402)the National Natural Science Foundation of China(No.41104069)the Fundamental Research Funds for the Central Universities(No.14CX06017A)
文摘The parabolic Radon transform has been widely used in multiple attenuation. To further improve the accuracy and efficiency of the Radon transform, we developed the 2- fdomain high-resolution Radon transform based on the fast and modified parabolic Radon transform presented by Abbad. The introduction of a new variable 2 makes the transform operator frequency-independent. Thus, we need to calculate the transform operator and its inverse operator only once, which greatly improves the computational efficiency. Besides, because the primaries and multiples are distributed on straight lines with different slopes in the 2-fdomain, we can easily choose the filtering operator to suppress the multiples. At the same time, the proposed method offers the advantage of high-resolution Radon transform, which can greatly improve the precision of attenuating the multiples. Numerical experiments suggest that the multiples are well suppressed and the amplitude versus offset characteristics of the primaries are well maintained. Real data processing results further verify the effectiveness and feasibility of the method.
基金Supported by the National Natural Science Foundation of China(61172024)the Funding of Jiangsu Innovation Program for Graduate Education and the Fundamental Research Funds for the Central Universities(CXZZ12-0156)
文摘A conformal multi-resolution time-domain( CMRTD) method is presented for modeling curved objects. The effective dielectric constant and area weighting are used to derive the update equations of CMRTD. The backward scattering bistatic radar cross sections( RCS) of the dielectric cylinder and ellipsoid are used to validate the proposed method. The results show that the proposed conformal method is more accurate to deal with the complex curved objects in electromagnetic simulations.
文摘Rainfall extremes have strong connotations to socio-economic activities and human well-being in Uganda’s Lake Victoria Basin (LVB). Reliable prediction and dissemination of extreme rainfall events are therefore of paramount importance to the region’s development agenda. The main objective of this study was to contribute to the prediction of rainfall extremes over this region using a numerical modelling approach. The Weather Research and Forecasting (WRF) model was used to simulate a 20-day period of extremely heavy rainfall that was observed in the March to May season of 2008. The underlying interest was to investigate the performance of different combinations of cumulus and microphysical parameterization along with the model grid resolution and domain size. The model output was validated against rainfall observations from the Tropical Rainfall Measuring Mission (TRMM) using 5 metrics;the rainfall distribution, root mean square error, mean error, probability of detection and false alarm ratio. The results showed that the model was able to simulate extreme rainfall and the most satisfactory skill was obtained with a model setup using the Grell 3D cumulus scheme combined with the SBU_YLin microphysical scheme. This study concludes that the WRF model can be used for simulating extreme rainfall over western LVB. In the other 2 regions, central and eastern LVB, its performance is limited by failure to simulate nocturnal rainfall. Furthermore, increasing the model grid resolution showed good potential for improving the model simulation especially when a large domain is used.
基金Supported by the National Nature Science Foundation of China(61172024)the Funding of Jiangsu Innovation Program for Graduate Education and the Fundamental Research Funds for the Central Universities(CXZZ120156)the Postdoctoral Science Foundation of China(2013M531350)
文摘A conformal Runge-Kutta multi-resolution time-domain(C-RKMRTD)method is present and applied to model and analyze curved objects.Compared with the non-conformal method,the proposed method is more accurate.The scattering analyses of the cylinder and ellipsoid are presented to validate the proposed method.The numerical results demonstrate that the proposed scheme perform better than the MRTD method and other higher order methods with a higher accuracy.
文摘面对ISP主干网,为了检测威胁其管理域内用户安全的僵尸网络、钓鱼网站以及垃圾邮件等恶意活动,实时监测流经主干网边界的DNS交互报文,并从域名的依赖性和使用位置两个方面刻画DNS活动行为模式,而后,基于有监督的多分类器模型,提出面向ISP主干网的上层DNS活动监测算法DAOS(binary classifier for DNS activity observation system).其中,依赖性从用户角度观察域名的外在使用情况,而使用位置则关注区域文件中记录的域名内部资源配置.实验结果表明:该算法在不依赖先验知识的前提下,经过两小时的DNS活动观测,可以达到90.5%的检测准确率,以及2.9%的假阳性和6.6%的假阴性.若持续观察1周,准确率可以上升到93.9%,假阳性和假阴性也可以下降到1.3%和4.8%.
基金This project was supported by National Natural Science Foundation of china (No.40474042)
文摘We develop a high resolution ground penetrating radar system （LANRCS-GPR） based on the E5071B Vector Network Analyzer （VNA）. This system takes advantage of a wideband and adjustable frequency domain ground penetrating radar system and adds the characteristics of a network analyzer with ultra-wideband and high precision measurement. It adopts the LAN mode to concatenate system control that reduces construction cost and makes the system easy to expand. The high resolution ground penetrating radar system carries out real time imaging using F-K migration with high calculation efficiency. The experiment results of the system indicate that the LANRCS-GPR system provides high resolution and precision, high signal-to-noise ratio, and great dynamic range. Furthermore, the LANRCS-GPR system is flexible and reliable to operate with easy to expand system functions. The research and development of the LANRCS-GPR provide the theoretical and experimental foundation for future frequency domain ground penetrating radar production and also can serve as an experimental platform with high data gathering precision, enormous information capability, wide application, and convenient operation for electromagnetic wave research and electromagnetic exploration.
