AWGN信道下线性分组码的差错概率下界分析

提出了一种线性分组码的最大似然译码(ML-decoding)差错概率下界的计算方法。差错概率的下界优化实质上是对联合事件概率下界的优化,算法结合改进的Dawson-Sankoff界的优化准则,提出了AWGN信道下线性分组码差错冗余事件的判决准则,得到了误码率下界的计算表达式。该表达式只依赖码字的Hamming重量分布与信噪比,较之类deCaens界与类KAT界,本算法得到的下界更紧,计算量更低。针对LDPC等线性分组码的数值结果证明了算法的优越性能。     

Expeditionary police advising: some causes of failure

ABSTRACT

The practice of dispatching teams of police advisors to other states to build or train foreign security forces began at the end of the nineteenth century, yet there exists no definitive history of the practice, or any definitive theoretical approach underpinning why such missions succeed or fail. Drawing upon their recent edited book on expeditionary police advising, and by examining the donor or sending states, the host nations, and the use of police in counterinsurgency situations, the authors present some key reasons why such missions fail, and lay some groundwork for additional study of this important subject.     

Bedeviled by a Paradox: Nitze,Bundy, and an Incipient Nuclear Norm

ABSTRACT

This article explores how two influential American policy makers—Paul Nitze and McGeorge Bundy—wrestled with the idea of a norm against the use of nuclear weapons. Existing scholarship has overlooked how both Bundy and Nitze came to understand the idea of nuclear non-use, especially related to the credibility of threats to use nuclear weapons. Using documentary evidence from their personal papers, this article illuminates the thinking of Bundy and Nitze, finding that both engaged with the idea of a norm of non-use of nuclear weapons in their strategic writing and thought.     

Comprehensive Prohibition of Nuclear Weapons: An Emerging International Norm?

ABSTRACT

There have been calls for the abolition of nuclear weapons from the day they were invented. Over the last fifteen years, some indications can be found that such calls have been getting louder, among them Barack Obama's famous 2009 speech in Prague. In this article, we investigate if support for a comprehensive norm that would prohibit development, possession, and use of nuclear weapons is really growing. To assess the current status of that norm, we use the model of a “norm life cycle,” developed by Martha Finnemore and Kathryn Sikkink. We then analyze 6,545 diplomatic statements from the review process of the Treaty on the Non-Proliferation of Nuclear Weapons as well as from the UN General Assembly First Committee on Disarmament and International Security, covering the years 2000 to 2013. The evidence shows that a comprehensive prohibition can be considered an emerging international norm that finds growing support among states without nuclear weapons and nuclear weapon states alike. Only a core group of states invoke the norm consistently, however. This leads us to conclude that the “tipping point” of the life cycle, at which adherence to a new norm starts to spread rapidly, has yet to be reached.     

Book review

This paper investigates the economic roots of separatist terrorism in Turkey. The political conventional wisdom is that poverty in highly Kurdish‐populated, south‐eastern Turkey is one of the most important causes of separatist terrorism and Turkish–Kurdish conflict in Turkey. Therefore, many economic policies have been implemented to improve the economic conditions in the south‐eastern part of the country. Using the Global Terrorism Database and Vector Autoregression (VAR) methodology, I find that there is no causal relationship between economic conditions in south‐eastern Turkey and separatist terrorism. Therefore policy‐makers should be cautious in using economic measures to prevent separatist terrorism in Turkey.