共查询到19条相似文献,搜索用时 187 毫秒
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束维国 《核电子学与探测技术》2005,25(6):698-701
缓冲区溢出攻击是最为常见的计算机攻击手段之一。通过分析Linux缓冲区溢出的原理,提供了一种可以防范系统缓冲区溢出攻击的方法,并在Linux系统上实现。 相似文献
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针对当前网络入侵检测技术存在的报警信息量太大、误报警多以及缺乏报警语义描述等问题,结合相应事例,采用时序关联方法对网络入侵行为的报警信息进行分析.设计了时序识别语言,实现了对端口扫描的报警精简,对FTP缓冲区溢出的误报警检测,以及对NetBios DCERPC攻击报警的语义改进.实验证明,该方法可有效解决上述问题. 相似文献
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海量存储系统中磁带文件缓存管理 总被引:1,自引:0,他引:1
针对磁带库的数据访问特点,根据高能物理领域的实际需求,提出了分组协同缓存策略.这一策略以缓存模型为基础,结合本地缓存与协同缓存的优点,把缓冲区分成不同的组,不同组的缓冲区之间相互独立;同一组的缓冲区由网络上不同节点上的磁盘组成,这些磁盘之间相互协作.还对该缓存策略的目录管理、更新算法、一致性等问题进行了详细分析.实验说明,该策略能很好的满足高能物理领域的数据处理和海量存储需求. 相似文献
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PSA中不确定性分析实现方法研究 总被引:2,自引:5,他引:2
不确定性分析能够量化PSA模型中的不确定性因素从而为决策者提供决策支持.提出一种基于蒙特卡罗模拟的故障树不确定性分析方法用于求得置信区间的上下确界,该方法将模拟求解过程中的对超越方程的求解问题转化成优化问题,并充分利用了优化问题中目标函数的属性特征,选择黄金分割点法来进行一维搜索求解.在此基础上为加速收敛对黄金分割点算法做了改进.该方法已应用于自主开发的PSA分析软件RiskA中.并将RiskA不确定性分析结果和其他的PSA软件进行了校核,校核结果表明这种方法是正确的. 相似文献
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用综合核方法求解中子输运临界问题的误差分析 总被引:1,自引:0,他引:1
基于中子积分输运方程的综合核近似方法,具有准确、快速的特点,其计算精度和收敛性与求积组的选取密切相关.文章简要介绍了求解中子输运临界问题的综合核方法,采用数值方法分析了综合核近似的计算误差和收敛性,并提出了新的求积组来提高综合核方法的计算精度.应用综合核方法计算了均匀平板介质中各向同性和线性各向异性散射的单群、双群中子临界问题,并与离散纵标法S32结果和文献结果进行了比较.计算结果表明采用合适的求积组,综合核方法在低阶时能够得到较高精度的结果. 相似文献
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液体闪烁体探测器中子解谱方法研究现状及发展 总被引:1,自引:0,他引:1
中子解谱是中子探测的一项关键技术.利用液体闪烁体探测器求解中子能谱本质上是核物理领域的一个反演问题.简要介绍了液体闪烁体探测器结构及工作过程,概述了基于该类探测器的中子能谱求解原理,重点对各种解谱方法进行了数学描述,对其求解过程进行了归纳总结,最后指出了中子能谱求解方法的发展趋势. 相似文献
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GAO Zao-chun CHEN Yong-shou SUN Yang 《中国原子能科学研究院年报》2005,(1):57-58
A possible scheme of realizing shell model calculations for heavy nuclei is based on a deformed basis and the projection technique. Here we present a new development, in which one starts with triaxially-deformed multi-quasi-particle configurations, builds the shell-model space through exact three-dimensional angular-momentum-projection, and diagonalizes a realistic two-body Hamiltonian in this space. The new model enables us to understand the old problem of signature inversion from a different view. 相似文献
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全陶瓷微胶囊封装(FCM)燃料是重要的候选事故容错燃料,与传统燃料相比,FCM燃料的双重非均匀性使得其有效多群截面计算面临较大的挑战。本文提出一种改进的缺陷因子方法来处理FCM燃料在共振能区和非共振能区的自屏效应,实现FCM燃料的等效均匀化。通过颗粒丹可夫因子守恒来构建新的等效模型以克服传统的体积权重等效模型无法考虑燃料棒间自屏的影响;在共振能量段,基于新的等效一维球模型求解超细群慢化方程获得共振能量段的超细群缺陷因子;在非共振能量段,利用新等效模型的特征值计算获得快群和热群的多群缺陷因子;在此基础上实现FCM燃料棒的等效均匀化。本方法已在高保真中子学程序NECP-X上实现,并在一系列工况下进行了测试,与蒙特卡罗程序的比较表明,本方法能处理不同情况下的双重非均匀性,并可获得准确的有效自屏截面。 相似文献
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The nucleon optical model is widely used to calculate the elastic scattering cross-sections and polarizations. The only requirement, in using the optical model for a reliable prediction of the nuclear data is the unique set of optical model parameters (OMP). The uncertainties in the OMP lead to uncertainties in calculated cross-sections and thus the deficiency in the model itself. To our knowledge, there is no technique, to estimate the limits of variation of OMP to establish good fits with consequent reduction of optical model deficiency between these limits. In this paper, we propose D-optimal criterion and the technique of Determinant Inequalities developed by us to simulate OMP with reduced optical model deficiency. Our technique enables one to simulate the limits of variation of the OMP with the existing covariance data. The simulation of these limits would aid to establish good fits among the OMP. Further, the variation in the range of deficiency in the optical model can be ascertained well in advance. We demonstrate the utility of our technique to the OMP of 239Pu. 相似文献
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Heui-Joo Choi Author Vitae Minsoo Lee Jong Youl Lee 《Nuclear Engineering and Design》2010,240(10):2714-2720
A new method was proposed for the manufacture of a copper-cast iron canister for the spent fuel disposal based on the cold spray coating technique. The thickness of a copper shell could be fabricated to be as thin as 10 mm with the new method. Around 6 tons of copper could be saved with a 10 mm thick canister compared with a 50 mm thick canister. The electrochemical properties of the cold sprayed copper layer and forged copper were measured through a polarization test. The two copper layers showed very similar electrochemical properties. The lifetime of a 10 mm copper canister was estimated with a mathematical model based on the mass transport of sulfide ions through the buffer. The results showed that the canister lifetime was more than 140,000 years under the Korean granite groundwater condition. The thermal analysis with a current pre-conceptual design of a CANDU spent fuel canister showed that the maximum temperature between the canister and the saturated buffer was below the thermal criteria, 100 °C. Finally, the mechanical stability of the copper canister was confirmed with a computer program, ABAQUS, under the rock movement scenario. 相似文献
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本文介绍一种基于VME总线的高速A/D缓冲系统的原理和结构。着重阐述了高速数据采集技术,高速FIFO缓冲技术,存储器总线切换技术,VME及PC/ISA总线接口技术在本系统中的成功应用。 相似文献
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全陶瓷微密封(FCM)燃料是一种弥散颗粒燃料。由于弥散颗粒燃料存在双重非均匀性,传统的确定论方法及蒙特卡罗方法皆难以处理这种双重非均匀效应以获得有效多群截面。本文基于超细群方法建立FCM燃料的有效多群截面计算方法。为描述燃料棒内TRISO颗粒的非均匀性,在共振能量段,通过采用超细群方法求解包含TRISO颗粒的一维球模型得到超细群缺陷因子,通过超细群缺陷因子修正所有核素的超细群截面即可将颗粒和基质均匀化。由于TRISO颗粒在热能区也存在较强的自屏效应,在热能区,利用穿透概率及碰撞概率等价得到多群缺陷因子,通过多群缺陷因子修正所有核素的多群截面将燃料和基质均匀化。均匀化后的FCM燃料组件即可视为普通压水堆燃料组件进行共振计算。利用丹可夫修正因子等价得到FCM燃料组件各燃料棒的等效一维棒模型,对一维棒模型求解超细群慢化方程从而得到共振能量段的有效自屏截面。数值结果表明,该方法能有效处理FCM燃料的双重非均匀性,得到精确的有效自屏截面。 相似文献
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The analysis of an unintended main safety valve opening at Ignalina NPP was performed with COCOSYS code in order to assess its capability in simulation of the transient processes that occur inside Accident Localisation System of Ignalina NPP. COCOSYS has several user-selected options, e.g. zone model (EQUIL._MOD, NONEQUILIB), water flow model (BAL_DRAIN, DRAIN_BOT), etc for nodalisation development. The influence of a zone model selection, a water overflow model selection and efficiency of heat exchanger in Condenser Tray Cooling System was investigated and presented in the paper. The performed analysis supported introduction of new water overflow model in COCOSYS code and showed that COCOSYS code can be applied for the analysis of Accident Localisation System of Ignalina NPP. 相似文献
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为了减轻由于稳压器波动管热分层引起的热疲劳效应及降低安装难度,提出了在M310型压水堆稳压器中加大波动管与主回路夹角的布置改进方案.波动管的布置改进将引起反应堆厂房内部结构布置的改变,对地震响应产生影响.根据设计改进重建结构计算模型,进行抗震分析,并与旧模型的相应结果进行对比,探讨设计改进对反应堆厂房地震响应的影响,为改进方案的论证提供参考. 相似文献