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971.
While all-optical networks become more and more popular as the basis of the next generation Internet(NGI)infrastructure,such networks raise many critical security issues.High power inter-channel crosstalk attack is one of the security issues which have negative effect on information security in optical networks.Optical fiber in optical networks has some nonlinear characteristics,such as self phase modulation(SPM),cross phase modulation(XPM),four-wave mixing(FWM)and stimulated Raman scattering(SRS).They can be used to implement high power inter-channel crosstalk attack by malicious attackers.The mechanism of high power inter-channel crosstalk attack is analyzed.When an attack occurs,attack signal power and fiber nonlinear refractive index are the main factors which affect quality of legitimate signals.The effect of high power inter-channel crosstalk attack on quality of legitimate signals is investigated by building simulation system in VPI software.The results show that interchannel crosstalk caused by high power attack signal leads to quality deterioration of legitimate signals propagated in the same fiber.The higher the power of attack signal is,the greater the fiber nonlinear refractive index is.The closer the channel spacing away from the attack signal is,the more seriously the legitimate signals are affected by attack.We also find that when attack position and power of attack signal are constant,attack signal cannot infinitely spread,while its attack ability shows a fading trend with the extension of propagation distance. 相似文献
972.
The paper aims to research on online mind map as interface of learning resource integration and sharing.We developed a web application that provides a interface to allow users to create a knowledge mind map.With the online mind mapping tool,the electronic learning resource will be discovered and shared in the form of subject-oriented package,it is more flexibly than the other E-Learning systems,and the interaction and cooperation of the users are strengthened to some extent. 相似文献
973.
Reliability Prediction Method Based on State Space Model for Rolling Element Bearing 总被引:1,自引:0,他引:1
Reliability analysis based on equipment’s performance degradation characteristics is one of the significant research areas in reliability research. Nowadays, many researches are carried on multi-sample analysis. But it is limited for a single equipment reliability prediction. Therefore, the method of reliability prediction based on state space model(SSM) is proposed in this research. Feature energy of the monitored signals is extracted with the wavelet packet analysis and the associated frequency band energy with online monitored data. Then,degradation feature is improved by moving average filtering processing taken as input pair model parameter of SSM to be estimated. In the end, state space predicting model of degradation index is established. The probability density distribution of the degradation index is predicted, and the degree of reliability is calculated. A real testing example of bearing is used to demonstrate the rationality and effectiveness of this method. It is a useful method for single sample reliability prediction. 相似文献
974.
975.
沈阳地铁一、二号线自运营以来均采用单一大交路模式组织行车,受各项条件限制,现有行车组织模式很难满足未来客流增长的需要。本文从客流情况、折返能力、车辆数量等运营现状进行分析,研究在保证一、二线运力相互匹配情况下如何进一步提升运力,并且深入分析单一大交路模式过渡到大小交路模式后应急情况下的运营调整措施,最终确定沈阳地铁更加合理的行车间隔及运营交路模式。 相似文献
976.
文章通过问卷调查以及个案访谈等形式考察南通市失独家庭现状,分析了失独家庭面临的主要问题,并提出了社工介入方案,以期为地方政府解决失独家庭问题提供一些参考意见。 相似文献
977.
目的探讨射线诱导后DNA损伤修复相关基因在放射敏感性不同鼻咽癌细胞系CNE-2、CNE-2R的差异表达。方法中性彗星分析法检测细胞DNA的双链断链(DSB);免疫荧光技术检测磷酸化组蛋白γH2AX焦点形成、射线照射后细胞放射性损伤的时间剂量效应及放射敏感性的变化;基因芯片(OHS-029)技术检测CNE-2及CNE-2R细胞2Gy照射前后的基因差异表达;Western blot方法验证二者的差异表达蛋白质。结果 4Gy的9MeV-β射线照射后2h,CNE-2R细胞与CNE-2细胞相比,细胞DNA损伤程度加重,且随时间的延长更为明显。荧光显微镜显示,2Gy的9MeV-β射线照射后6h,CNE-2各时间段细胞γH2AX阳性细胞率明显高于CNE-2R组。DNA损伤相关基因表达谱分析发现,CNE-2和CNE-2R细胞相比,差异表达的DNA损伤修复相关基因共37个,其中上调基因24个,下调13个,其中6个位点差异6倍以上,3个位点低于0.1的差异表达;Western blot结果显示,与CNE-2细胞相比,GADD45a、RRAD1在CNE-2R中的表达水平明显下调,而ERCC1及PRKDC蛋白质明显上调,与基因芯片的研究结果一致。结论 9MeV-β射线照射后CNE-2细胞DNA的损伤程度较CNE-2R细胞明显,CNE-2R细胞放射抗拒性与DNA损伤修复能力的基因差异表达相关。通过对筛选出的靶基因进行调控,有可能改变细胞的放射敏感性。 相似文献
978.
979.
980.
国外非声探潜与隐身技术发展趋势 总被引:1,自引:0,他引:1
潜艇的非声特征包括潜艇自身的磁场特征、光学特征、雷达特征和红外特征,以及潜艇运动在周围水体中留下的"痕迹"——尾迹特征。论文从直接探测潜艇自身物理场特征和间接探测潜艇尾迹特征两个方面,对潜艇的非声特征和非声探测技术的发展进行了回顾,并分析了非声探测技术的对潜艇的威胁,展望了非声隐身技术措施及发展方向。 相似文献