单光子卫星量子通信噪声和干扰分析

卫星量子通信是建立全球量子通信网络的最佳选择之一。针对采用偏振编码的卫星量子通信中的偏振保持问题,研究了大气散射和卫星与地面站间相对运动等因素对量子偏振态相位和对准的影响以及相位延迟和对准误差对系统量子误码率的影响,分析了背景噪声和系统硬件噪声对通信产生的影响以及单光子通信过程中可能受到的光子分离攻击干扰,为量子信号认知设计提供借鉴意义。     

A Rich Vein for “Reality Mining”北大核心CSSCISSCI

Arik Hesseldahl In the aftermath of the September 11 attacks, U.S. officials quickly turned their attention to other potential targets, including California's Golden Gate Bridge. What would happen if terrorists took down the bridge between San Francisco and Marin County? How much of the region would be affected and for how long?     

Post-audits for managing cyber security investments: Bayesian post-audit using Markov Chain Monte Carlo (MCMC) simulation

With increasing security spending in organizations, evaluation of the quality and effectiveness of IT security investments has become an important component in managing these projects. The academic literature, however, is largely silent on post-audit of such investments, which is a formal evaluation of IT resource allocation decisions. IT post-audits are considered a useful risk management tool for organizations and are often emphasized in security certifications and standards. To fill this research gap and contribute to practice, we suggest post-auditing of IT security investments using the generic Markov Chain Monte Carlo (MCMC) simulation approach. This approach does not place stringent conjugate assumptions and can handle high-dimensional Bayesian post-audit inference problems often associated with information security resource allocation decisions. We develop two Bayesian post-audit models using the MCMC method: (1) measuring the effectiveness of an IT security investment using posterior mean score ratios (MSR), and posterior crossover error rates (CER); and (2) measuring the effectiveness through detection of a denial of service (DOS) attack using Bayesian estimation to statistically compare the degree of divergence using the concept of entropy. We demonstrate the utility of the proposed methodology using an email intrusion detection system application.     

The impact of 11/13 Paris terrorist attacks on stock prices: evidence from the international defence industry

This study explores the effect of the Paris terrorist attacks on the stock returns and the volatility for the most important companies in the global defence industry. To this end, it employs the General Autoregressive Conditional Heteroscedasticity methodology. The findings clearly indicate that this terrorist event has a positive impact on both the returns and the volatility of these stocks.     

通过试飞测量大型直升机超短波天线的方向图

超短波天线方向图的精确测量对摸清机载通信系统性能底数，指导部队战术应用具有重要意义。针对传统试飞方法均不适用于大型直升机天线方向图测量的问题,通过分析大型直升机的飞行性能特点，提出了一种新的适用于大型直升机的超短波天线方向图试飞方法。通过分析计算给出了试飞中载机高度、速度、姿态等参数的限制数据，制定了详细的试飞流程，提出了逐架次、逐频点采集校准数据并完成校准曲线拟合的方法，得到了较高的测量精度。该方法已在某大型直升机定型试飞中进行了应用，试飞结果表明该方法的测量结果与传统测量方法之间的标准差在1.6 dB内，试飞效率提高了66%.     

EMPIRICAL ANALYSIS OF SPECULATIVE ATTACKS WITH CONTRACTIONARY REAL EFFECTS

The effects of a currency crisis on a country's economy depend on nonlinear relations among several variables that characterize the economic, financial, legal and socio‐political structure of the country at the onset of the crisis. Those effects can be associated with contractions or expansions in output. Historically, contractionary speculative attacks are more frequent. This paper uses a parametric censored heteroscedastic TOBIT model to empirically analyse how different economic and financial variables determine the real effects of a contractionary speculative attack. Variables describing the banking sector, the international trade, the severity of the crisis and foreign interest rates are found to be significant in explaining the size of currency crises' contractionary real effects. The TOBIT's results are compared with alternative modelling strategies. Copyright © 2012 John Wiley & Sons, Ltd.     

医院计算机网络建设的设计与研究

本文以银川市中医医院为背景,探讨了由于IP地址规划不合理而造成的网络维护工作繁琐,以及由于广播域较大引起的ARP频繁攻击等问题,提出了一套合理的计算机IP地址规划及VLAN划分方案,不仅为网络维护工作带来了极大的便利,同时也有效解决了ARP攻击频繁发生的问题。     

浅谈ARP原理及ARP攻击、判断、防范技术

ARP攻击不是病毒,但是它的危害却不亚于病毒,它轻可造成计算机网络通信变慢、甚至瘫痪,重则造成用户信息的泄漏,许多用户都深受其害;然而,使用众多杀毒软件对之却都毫无办法。本文从介绍ARP的工作原理入手,分析网络上是如何利用ARP进行伪装欺骗实施攻击的,如何判断是否遭遇了ARP攻击,以及如何防范和处理ARP攻击。     

A Delphi-based risk analysis — Identifying and assessing future challenges for supply chain security in a multi-stakeholder environment

Identifying and assessing the potential impact and likelihood of future events, which might evolve into risks, are a prerequisite to identify future security challenges. In particular, risks associated with global supply chains are special since they involve a multitude of international stakeholders with different perspectives on security needs and measures. Therefore, it is essential to determine which techniques and instruments are best suited for risk assessment in complex and multi-organizational environments. The Delphi expert survey technique has proven to be a valuable instrument for long-term decision making support as well as foresight, and has a potential value for risk assessment. We contribute to this research strand and conduct a Delphi-based risk analysis. Our research concentrates on man-made risks in global supply chains which are particularly uncertain in terms of type, location, and affected supply chain partners and can therefore be classified as inherently “wicked” issues, i.e. issues that are multidimensional with often unpleasant outcomes. We illustrate that Delphi research makes a fivefold contribution to risk analysis by: (1) identifying and quantifying risks; (2) analyzing stakeholder perceptions and worldviews; (3) stimulating a global communication process; (4) identifying weak signals, outlier opinions, and wildcards; (5) and facilitating risk scenario development.     

浅析ARP的攻击原理及解决办法

ARP(Address Resolution Protocol)是地址解析协议,是-种将IP地址转化成物理地址的协议.从IP地址到物理地址的映射有两种方式:表格方式和非表格方式.ARP具体说来就是将网络层(IP层,也就是相当于OSI的第三层)地址解析为数据连接层(MAC层,也就是相当于OSI的第二层)的MAC地址.