6,824 research outputs found
A study of the blistering of metal surfaces by solar system ions First quarterly progress report, period ending 14 Jul. 1965
Pure aluminum single crystals irradiated in vacuum to define optimum parameters for oxide film removal with no residual blistering of surfac
Role of internal gases and creep of Ag in controlling the critical current density of Ag-sheathed Bi2Sr2CaCu2Ox wires
High engineering critical current density JE of >500 A/mm2 at 20 T and 4.2 K
can be regularly achieved in Ag-sheathed multifilamentary Bi2Sr2CaCu2Ox
(Bi-2212) round wire when the sample length is several centimeters. However,
JE(20 T) in Bi-2212 wires of several meters length, as well as longer pieces
wound in coils, rarely exceeds 200 A/mm2. Moreover, long-length wires often
exhibit signs of Bi-2212 leakage after melt processing that are rarely found in
short, open-end samples. We studied the length dependence of JE of
state-of-the-art powder-in-tube (PIT) Bi-2212 wires and gases released by them
during melt processing using mass spectroscopy, confirming that JE degradation
with length is due to wire swelling produced by high internal gas pressures at
elevated temperatures [1,2]. We further modeled the gas transport in Bi-2212
wires and examined the wire expansion at critical stages of the melt processing
of as-drawn PIT wires and the wires that received a degassing treatment or a
cold-densification treatment before melt processing. These investigations
showed that internal gas pressure in long-length wires drives creep of the Ag
sheath during the heat treatment, causing wire to expand, lowering the density
of Bi-2212 filaments, and therefore degrading the wire JE; the creep rupture of
silver sheath naturally leads to the leakage of Bi-2212 liquid. Our work shows
that proper control of such creep is the key to preventing Bi-2212 leakage and
achieving high JE in long-length Bi-2212 conductors and coils
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Manas Hysteria
Manas air base, located near Bishkek, has been an important hub supporting the war effort in Afghanistan since the U.S. military opened it in December 2001. Since then, Manas's operations have been threatened by political instability more than once. The root of these recurring basing headaches lies in the fact that the United States simply lacks the authority to establish a military presence in Central Asia. But paying off the Kyrgyz is a short-term solution that will backfire in the long term. Instead, to protect Manas further down the road, the United States must convince the Kyrgyz people that it is interested in more than a transactional relationship
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The Afghanization of Central Asia
President Barack Obama's decision to escalate the US military presence in Afghanistan has generated heated debate. Largely lost in the swirl of discussion is the surge's hidden cost on neighboring Central Asian states
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America and Empire: Thoughts on a Debate
In a recent issue of Foreign Affairs, Alex Motyl posed the question, "Do past empires hold lessons for U.S. foreign policy today?" In a review of two new books (an edited volume by Craig Calhoun and a study by Charles Maier), he concluded that "efforts [to show that they do] yield little payoff." To be sure, the use of the term "empire" has become commonplace in descriptions of contemporary U.S. foreign policy. Yet, save for a small group of exceptions, American political scientists until now have mostly neglected the theoretical investigation of empires and the dynamics of imperial relations. Filling a massive gap in the literature, political scientists Dan Nexon and Thomas Wright's new article "What's at Stake in the American Empire Debate" published in the May 2007 American Political Science Review is one of the most thought-provoking and policy relevant scholarly articles to appear in recent years in the field. The article builds on much of Nexon's previous work on the network properties of early-modern empires, but applies these insights to some of the central problems confronting today's U.S. foreign policy community
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Kyrgyzstan: The Five Lessons of the Great American Air Base Debate
As the Kyrgyz government continues to balance intricate negotiations with both Washington and Moscow over the future of the American military base at Manas, US policymakers would do well to reflect on their recent experience in the Kyrgyz Republic. Though it is tempting to blame the cash-strapped regime of President Kurmanbek Bakiyev and a meddlesome Russia for the difficulties currently faced by the United States in Kyrgyzstan, US planners and officials made their own fair share of faulty assumptions and missteps in dealing with the Manas issue
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Georgia: Examining Possible Sovereign Futures and the Internationalization Option
At a recent special panel on the Georgian crisis convened at the Bled Strategic Forum, European foreign ministers and representatives of international organizations lamented that they had failed to adequately engage Georgia's unresolved or "frozen conflicts." Since the early 1990s, the international community effectively ignored the disputes between Tbilisi and Abkhazia and South Ossetia, allowing tensions to fester until in early August the disputes escalated into a six-day war between Georgia and Russia. Russia's subsequent recognition of Abkhazia and South Ossetia independence has legally challenged Georgia's very territorial integrity and sovereign boundaries. While much of the West struggles to enforce a precarious ceasefire and formulate a common response to Russia's actions, it is worth considering the exact sovereign forms that might govern Georgia in the near future. Three options - indefinite occupation, formal partition or international administration - are possible; though all three pose risks, the internationalization option, the least discussed thus far, may offer the best blueprint for stabilizing the region and eventually resolving status issues
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How the Democratic Tide Rolled Back
Twenty-five years ago the world entered a new era. The Soviet Union had just collapsed, the United States had assumed the leadership of a proclaimed new world order, and liberal democratic capitalism no longer had a viable global challenger. The expectations these changes heralded now appear unfulfilled. Illiberalism is surging around the world, and the post-Cold War era is rapidly giving way to a post-liberal order. Moreover, the very post-Communist states that seemingly were at the epicenter of a liberal transformation have pioneered the counter-norms and tactics that now spread to the West itself
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