频谱感知技术在认知无线电中的应用

频谱感知是认知无线电的关键技术,能量检测广泛应用于频谱感知。针对认知无线电频谱感知技术较少运用于实践的不足,提出了基于0FDM传输系统的频谱感知。在0FDM系统中利用能量检测的判决结果控制子载波的开关,实现感知结果对数据传输的控制,最后利用认知无线电平台进行实时数据的传输。实验结果表明,系统能够在认知无线电平台上成功进行无线通信的数据发送与接收,频谱感知结果能够有效控制数据传输,为认知无线电由理论研究步向实际应用奠定了基础,具有一定的实用价值。     

弹丸初速对磁阻型线圈发射器发射性能的影响分析

通过设置弹丸初速并研究其对单级磁阻型线圈发射器发射性能的影响,模拟分析前一级线圈弹丸出口速度对后一级线圈发射性能影响的规律;利用Ansoft有限元仿真软件进行了动态仿真,得到弹丸初速对单级磁阻型线圈发射器驱动电流、驱动线圈感应电压、电磁力、弹丸出VI速度、弹丸位移及能量转换效率等影响的规律．研究表明：弹丸初速越大,经过单级线圈加速后弹丸出口速度也越大,但弹丸出口速度增量减小;随着弹丸初速增大,能量转换效率呈现先增大后减小的趋势．     

How the End Begins: The Road to a Nuclear World War III

Ron Rosenbaum, How the End Begins: The Road to a Nuclear World War III. Simon & Schuster, 2011. 305 pages, $28.     

KICKING THE HORNETS’ NEST

This article applies the concept of nuclear ambivalence to the case of the Islamic Republic of Iran. Nuclear ambivalence differs from other approaches to understanding nuclear proliferation in that it focuses on the deeply misunderstood relationship between the two potential uses of nuclear power: energy and weapons. According to this theory, the civilian applications of nuclear technology cannot be separated from the potential military applications and vice versa. Ambivalence, therefore, extends into the realm of states’ nuclear intentions, making it impossible to know with certainty what a potential proliferator's “true” intentions are. This article will demonstrate that the concept of nuclear ambivalence applies in the case of Iran, suggesting that current international nonproliferation efforts run the risk of encouraging rather than discouraging Iranian weaponization. The final section outlines recommendations for policy makers to reverse this counterproductive nonproliferation approach.     

OF HAWKS AND DOVES

The policies toward countries aspiring to acquire nuclear weapons continue to be heavily contested, differing even among countries that consider nuclear proliferation as one of the main threats to international security. This article maps the actual policies of liberal democracies toward Iran and North Korea along a continuum from confrontation to accommodation. Using data from an expert survey, the authors outline four main findings. First, policies toward both Iran and North Korea have become increasingly confrontational over time. Second, no policy convergence was observed among the states studied; that is, notwithstanding the adoption of joint sanctions, differences remained between states preferring confrontation and those opting for accommodation. Third, states maintained remarkably stable policy profiles over time. Finally, despite obvious differences between the norm violations of North Korea and Iran, states generally followed remarkably similar policies toward both countries. The authors’ findings indicate that states exhibit stable preferences for either confrontation or accommodation toward nuclear aspirants. Although a comprehensive examination of the causes of these policy differences is beyond the scope of this article, the authors present evidence that a major cleavage exists between members and non-members of the Non-Aligned Movement, indicating that the degree to which nuclear aspirants’ sovereignty should be respected is a main issue of contention.     

MIDDLE EAST NONPROLIFERATION

The Middle East is a crucial region for the global nonproliferation regime. In 2010, the state parties to the Treaty on the Non-Proliferation of Nuclear Weapons proposed a conference on a Middle East Weapons of Mass Destruction-Free Zone. The nuclear weapon-free zone model, on which this idea builds, has achieved important results in other regions, but faces especially stark challenges in the Middle East. However, the attempt to apply the boldly imaginative zone approach to the Middle East holds promise for building a more inclusive dialogue on nonproliferation and regional security.     

ESCAPE FROM NUCLEAR DETERRENCE

Since the post-World War II genesis of nuclear deterrence, two presidential initiatives have been presented to deliver humanity from the threat of its failure. The first was the Strategic Defense Initiative (SDI), a constellation of space- and ground-based systems that President Ronald Reagan envisioned would render nuclear weapons “impotent and obsolete.” The second is President Barack Obama's roadmap to “a world without nuclear weapons,” commonly referred to as “Global Zero.” While these proposals appear to have little in common, deeper investigation reveals a number of provocative similarities in motivation and presentation. Moreover, both generated fierce debate, often with ideological overtones, about their strategic desirability and technical feasibility. We use these parallels, as well as prominent dissimilarities, to draw lessons from the SDI experience that can be applied to the debate over Global Zero.     

DIVERGING NUCLEAR PATHWAYS IN SOUTH ASIA

Eating Grass: The Making of the Pakistani Bomb, by Feroz Hassan Khan. Stanford University Press, 2012. 544 pages, $29.95.

Managing India's Nuclear Forces, by Verghese Koithara. Brookings Institution Press, 2012. 304 pages, $59.95.     

The Importance of Safeguards Culture

International safeguards is the system of measures put in place by the International Atomic Energy Agency and states to ensure nuclear programs remain dedicated to peaceful purposes. This international safeguards system consists of agreements, inspections, and evaluations that have never considered the safeguards culture of a state or facility. Neither a common definition nor an understanding of safeguards culture is internationally recognized. This article provides an analysis of the concept of safeguards culture and gauges its value to the international safeguards community. The authors explore distinctions among safeguards culture, safeguards compliance, and safeguards performance, and suggest possible indicators of safeguards culture and methods to promote a strong, positive safeguards culture.     

Exploiting the Challenges to Bioweapons Development

ABSTRACT

Widespread and often exaggerated generalizations about the global spread weapons of mass destruction (WMDs) have proven to be not only misleading and technologically naïve, but also unhelpful in formulating effective policies to counter their threat. The new book by George Mason University's Sonia Ben Ouagrham-Gormley dispels the popular narrative that governments and terror groups can easily—and inevitably will—develop WMDs, particularly biological weapons, by exploring the complex external and internal conditions that such programs require, as demonstrated by the Cold War-era biological weapon programs of the superpowers. This empirically grounded and realistic assessment of how states try—and often fail—to develop such programs offers a more reliable basis to craft realistic counterproliferation policies that can elicit international support.