Strong mechanically-induced effects in DC current-biased suspended Josephson junctions

Superconductivity is a result of quantum coherence at macroscopic scales. Two superconductors separated by a metallic or insulating weak link exhibit the AC Josephson effect - the conversion of a DC voltage bias into an AC supercurrent. This current may be used to activate mechanical oscillations in a suspended weak link. As the DC voltage bias condition is remarkably difficult to achieve in experiments, here we analyse theoretically how the Josephson effect can be exploited to activate and detect mechanical oscillations in the experimentally relevant condition with purely DC current bias. We unveil for the first time how changing the strength of the electromechanical coupling results in two qualitatively different regimes showing dramatic effects of the oscillations on the DC current-voltage characteristic of the device. These include the apperance of Shapiro-like plateaux for weak coupling and a sudden mechanically-induced retrapping for strong coupling. Our predictions, measurable in state of the art experimental setups, allow the determination of the frequency and quality factor of the resonator using DC only techniques.Comment: 10 pages, 6 figure

The government's place in the housing industry

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Barriers to women in the UK construction industry

Purpose – This paper aims to identify the main barriers that lead to the under-representation of women in the UK construction industry. The study, funded by ConstructionSkills, seeks to explore the issues that women face and investigate the potential positive impact that continuous professional development (CPD) may have upon improving the retention and career progression of women. Design/methodology/approach – The study uses an open-ended grounded theory (GT) approach, including 231 semi-structured questionnaires and nine focus groups with women from a range of professional occupations. All the findings were analysed using keyword analysis to identify the top two barriers that women face, alongside a series of cross-cutting key themes and issues. Findings – The findings reveal that male-dominated organisational cultures and inflexible working practices are the main barriers to women in the UK construction industry, irrespective of job role or profession. This paper concludes by arguing for a sea-change in the expansion of CPD opportunities for women in managerial, confidence and communication based skills, with accompanying networking and support systems to facilitate the retention and advancement of women in the industry sector. Research limitations/implications – Due to the research approach, the data are not generalisable. Therefore, researchers are advised to research and test the findings with a larger group. Researchers are also recommended to investigate the impact of expanded CPD opportunities for both men and women. Originality/value – The paper puts forward a business case for the advancement of specific CPD training for women, to facilitate the expansion of equality and diversity in the workforce in the UK construction industry

The effectiveness of investigation in the settlement of labor disputes.

Thesis (Ph.D.)--Boston University.The dissertation titled "The Effectiveness of Investigation in the Settlement of Labor Disputes" represents a comprehensive analysis of the experience of the Federal government with the use of investigation(more popularly designated as fact-finding) boards in the settlement of critical labor disputes. Investigation refers to that types of governmental intervention wherein the parties to a labor dispute appear as witnesses before a governmentally appointed board that investigates and publicizes all pertinent data relating to the dispute. The report of the board may or may not contain recommendations on how the issues should be resolved. If the recommendations are made, they are not binding upon the parties, because the decision to accept rests with the two disputants. Investigation may be voluntary or compulsory. It is voluntary when both sides agree to present their case to the investigation panel. It is compulsory when both parties required to submit their sides of the case to the panel. The dissertation seeks to determine whether the Federal government experience with the investigation has been effective in resolving critical labor disputes without at the same time seriously interfering with the carrying on of free collective bargaining between the disputants. [TRUNCATED

Model confirmation in climate economics

Benefit–cost integrated assessment models (BC-IAMs) inform climate policy debates by quantifying the trade-offs between alternative greenhouse gas abatement options. They achieve this by coupling simplified models of the climate system to models of the global economy and the costs and benefits of climate policy. Although these models have provided valuable qualitative insights into the sensitivity of policy trade-offs to different ethical and empirical assumptions, they are increasingly being used to inform the selection of policies in the real world. To the extent that BC-IAMs are used as inputs to policy selection, our confidence in their quantitative outputs must depend on the empirical validity of their modeling assumptions. We have a degree of confidence in climate models both because they have been tested on historical data in hindcasting experiments and because the physical principles they are based on have been empirically confirmed in closely related applications. By contrast, the economic components of BC-IAMs often rely on untestable scenarios, or on structural models that are comparatively untested on relevant time scales. Where possible, an approach to model confirmation similar to that used in climate science could help to build confidence in the economic components of BC-IAMs, or focus attention on which components might need refinement for policy applications. We illustrate the potential benefits of model confirmation exercises by performing a long-run hindcasting experiment with one of the leading BC-IAMs. We show that its model of long-run economic growth—one of its most important economic components—had questionable predictive power over the 20th century

Robustifying Language Models with Test-Time Adaptation

Large-scale language models achieved state-of-the-art performance over a number of language tasks. However, they fail on adversarial language examples, which are sentences optimized to fool the language models but with similar semantic meanings for humans. While prior work focuses on making the language model robust at training time, retraining for robustness is often unrealistic for large-scale foundation models. Instead, we propose to make the language models robust at test time. By dynamically adapting the input sentence with predictions from masked words, we show that we can reverse many language adversarial attacks. Since our approach does not require any training, it works for novel tasks at test time and can adapt to novel adversarial corruptions. Visualizations and empirical results on two popular sentence classification datasets demonstrate that our method can repair adversarial language attacks over 65% oComment: 8 Pages 2 Figures Submitted to ICLR Worksho

Tunable mechanically-induced hysteresis in suspended Josephson junctions

The coupling of superconducting systems to mechanical resonators is an emerging field, with wide reaching implications including high precision sensing and metrology. Experimental signatures of this coupling have so far been small, seldom and often reliant on high frequency AC electronics. To overcome this limitation, in this work we consider a mechanical resonator suspended between two superconducting contacts to form a suspended Josephson junction in which the electronic normal- and super-currents can be coupled to mechanical motion via the Lorentz force due to an external magnetic field. We show both analytically and numerically that this electro-mechanical coupling produces unprecedented mechanically-induced hysteresis loops in the junction's DC I-V characteristic. Firstly, we unveil how this new hysteresis may be exploited to access a huge mechanically-induced Shapiro-like voltage plateau, extending over a current range comparable with the junction's critical current. We then investigate a sudden mechanically-induced retrapping that occurs at strong coupling. Our analytical treatment provides a clear explanation for the effects above and allows us to derive simple relationships between the features in the DC I-V characteristic and the resonance frequency and quality factor of the mechanical resonator. We stress that our setup requires only DC current bias and voltage measurements, allowing the activation and detection of high-frequency mechanical oscillations in state of the art devices and without the need of any AC equipment