397 research outputs found

    Heating of Micro-protrusions in Accelerating Structures

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    The thermal and field emission of electrons from protrusions on metal surfaces is a possible limiting factor on the performance and operation of high-gradient room temperature accelerator structures. We present here the results of extensive numerical simulations of electrical and thermal behavior of protrusions. We unify the thermal and field emission in the same numerical framework, describe bounds for the emission current and geometric enhancement, then we calculate the Nottingham and Joule heating terms and solve the heat equation to characterize the thermal evolution of emitters under RF electric field. Our findings suggest that, heating is entirely due to the Nottingham effect, that thermal runaway scenarios are not likely, and that high RF frequency causes smaller swings in temperature and cooler tips. We build a phenomenological model to account for the effect of space charge and show that space charge eliminates the possibility of tip melting, although near melting temperatures reached.Comment: 8 pages, 10 figure

    The ā€œTrumpā€ Effect: Political Elite and Support for Free Trade in America

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    While previous literature has offered two broad categories of explanation for individual trade preferences: economic self-interest and non-economic factors, we contend that during times of intensified elite discourse on trade, individuals may follow elite opinions to form their opinions on trade. Utilizing data from the 2016 American National Election Survey, we examine the effect of Trumpā€™s protectionist views and rhetoric on public trade opinion. We argue that there was a ā€œTrump effectā€ on trade attitudes among the mass public in 2016 and this effect went beyond the party line, meaning that Trump supporters, regardless of their partisanship, were more likely to be influenced by his protectionist views and to adopt anti-free trade positions. Moreover, we suggest a conditional effect of political knowledge on the ā€œTrump effectā€ of trade opinion. Our empirical tests offer strong support for both hypotheses, suggesting a significant ā€œTrump effectā€ on public trade opinion in 2016

    PARTISANSHIP, TRUMP FAVORABILITY, AND CHANGES IN SUPPORT FOR TRADE

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    Why has the relationship between partisan identification and Americansā€™ trade attitudes shifted in recent years? We suggest that recent shifts in trade attitudes among partisans are driven by Donald Trump, who staked out a position on trade that is at odds with the position on trade traditionally held by Republicans. Using panel data from the Voter Study Group (VSG) surveys from 2011, 2016, and 2017, we conduct cross-sectional analyses showing that the relationship between partisanship and trade attitudes has shifted dramatically from 2011 to 2016/2017; in 2011, Republicans were significantly more supportive of expanded trade, but by 2016/2017 the relationship had reversed, with Democrats significantly more supportive of trade. We link changes over time in trade attitudes with how Americans evaluate Trump: individuals with favorable attitudes toward Donald Trump are significantly more likely to shift their attitudes in an anti-trade direction from 2011-2016. Because so many more Republicans have favorable attitudes toward Trump, the aggregate effect of Trump favorability is to shift Republicans as a group to be less favorable toward trade than Democrats. We suggest that Donald Trump has had a transformative effect on Americansā€™ trade attitudes, with previous supporters (opponents) of expanded trade now expressing opposing (supporting) attitudes

    Budget Processes: Theory and Experimental Evidence

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    This paper studies budget processes, both theoretically and experimentally. We compare the outcomes of bottom-up and top-down budget processes. It is often presumed that a top-down budget process leads to a smaller overall budget than a bottom-up budget process. Ferejohn and Krehbiel (1987) showed theoretically that this need not be the case. We test experimentally the theoretical predictions of their work. The evidence from these experiments lends strong support to their theory, both at the aggregate and the individual subject level

    Monitoring and Pay: An Experiment on Employee Performance under Endogenous Supervision

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    We present an experimental test of a shirking model where monitoring intensity is endogenous and effort a continuous variable. Wage level, monitoring intensity and consequently the desired enforceable effort level are jointly determined by the maximization problem of the firm. As a result, monitoring and pay should be complements. In our experiment, between and within treatment variation is qualitatively in line with the normative predictions of the model under standard assumptions. Yet, we also find evidence for reciprocal behavior. Our data analysis shows, however, that it does not pay for the employer to solely rely on the reciprocity of employees

    The UN in the lab

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    We consider two alternatives to inaction for governments combating terrorism, which we term Defense and Prevention. Defense consists of investing in resources that reduce the impact of an attack, and generates a negative externality to other governments, making their countries a more attractive objective for terrorists. In contrast, Prevention, which consists of investing in resources that reduce the ability of the terrorist organization to mount an attack, creates a positive externality by reducing the overall threat of terrorism for all. This interaction is captured using a simple 3Ɨ3 ā€œNested Prisonerā€™s Dilemmaā€ game, with a single Nash equilibrium where both countries choose Defense. Due to the structure of this interaction, countries can benefit from coordination of policy choices, and international institutions (such as the UN) can be utilized to facilitate coordination by implementing agreements to share the burden of Prevention. We introduce an institution that implements a burden-sharing policy for Prevention, and investigate experimentally whether subjects coordinate on a cooperative strategy more frequently under different levels of cost sharing. In all treatments, burden sharing leaves the Prisonerā€™s Dilemma structure and Nash equilibrium of the game unchanged. We compare three levels of burden sharing to a baseline in a between-subjects design, and find that burden sharing generates a non-linear effect on the choice of the efficient Prevention strategy and overall performance. Only an institution supporting a high level of mandatory burden sharing generates a significant improvement in the use of the Prevention strategy

    Incomplete Punishment Networks in Public Goods Games: Experimental Evidence

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    Abundant evidence suggests that high levels of contributions to public goods can be sustained through self-governed monitoring and sanctioning. This experimental study investigates the effectiveness of decentralized sanctioning institutions in alternative punishment networks. Our results show that the structure of punishment network significantly affects allocations to the public good. In addition, we observe that network configurations are more important than punishment capacities for the levels of public good provision, imposed sanctions and economic efficiency. Lastly, we show that targeted revenge is a major driver of anti-social punishment
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