A dynamical symmetry breaking model in Weyl space

The dynamical process following the breaking of Weyl geometry to Riemannian geometry is considered by studying the motion of de Sitter bubbles in a Weyl vacuum. The bubbles are given in terms of an exact, spherically symmetric thin shell solution to the Einstein equations in a Weyl-Dirac theory with a time-dependent scalar field of the form beta = f(t)/r. The dynamical solutions obtained lead to a number of possible applications. An important feature of the thin shell model is the manner in which beta provides a connection between the interior and exterior geometries since information about the exterior geometry is contained in the boundary conditions for beta.Comment: 18 pages, RevTex, to be published in J. Math. Phy

Nondestructive test of regenerative chambers

Flat panels simulating internally cooled regenerative thrust chamber walls were fabricated by electroforming, brazing and diffusion bonding to evaluate the feasibility of nondestructive evaluation techniques to detect bonds of various strength integrities. Ultrasonics, holography, and acoustic emission were investigated and found to yield useful and informative data regarding the presence of bond defects in these structures

A Blockchain-based Approach for Data Accountability and Provenance Tracking

The recent approval of the General Data Protection Regulation (GDPR) imposes new data protection requirements on data controllers and processors with respect to the processing of European Union (EU) residents' data. These requirements consist of a single set of rules that have binding legal status and should be enforced in all EU member states. In light of these requirements, we propose in this paper the use of a blockchain-based approach to support data accountability and provenance tracking. Our approach relies on the use of publicly auditable contracts deployed in a blockchain that increase the transparency with respect to the access and usage of data. We identify and discuss three different models for our approach with different granularity and scalability requirements where contracts can be used to encode data usage policies and provenance tracking information in a privacy-friendly way. From these three models we designed, implemented, and evaluated a model where contracts are deployed by data subjects for each data controller, and a model where subjects join contracts deployed by data controllers in case they accept the data handling conditions. Our implementations show in practice the feasibility and limitations of contracts for the purposes identified in this paper

Union renewal in historical perspective

This article revisits contemporary union renewal/revival debates through comparison with the late 1930s resurgence of trade unionism in the UK’s engineering industry. It is argued that the 1930s union renewal arose from more favourable contextual conditions than those currently obtaining. It was led by political activists, with better-articulated organisation and greater resonance in the working class than their contemporary counterparts, and who were assisted by state policy and pro-worker forces. Conclusions are drawn in relation to current debates

Tripartism in comparative and historical perspective

This special issue explores changes in the nature of tripartite arrangements between firms, governments and organized labour across the last century, focusing on their post-1945 heyday. Although tripartism has its origins at the turn of the Twentieth Century, the post-1945 long boom represented an historical high-water mark that may now be seen as quite distinct from our own long period of volatility and crisis. Historical concerns are frequently stimulated by those of the present and this is especially the case in contemporary history. Anglo-Saxon historians may feel that the age of tripartism is at an end, but the contributions within this issue show that although this may accurately reflect current perceptions, tripartism continues , albeit often in weak forms, in other national and transnational contexts; its history therefore retains contemporary resonance. In our present age, it is commonly assumed that the relative power of employers has increased at the expense of government – the central co-ordinating actor in tripartism – and organized labour. Within the firm, not only workers, but also traditional managers have been displaced by assertive investors and allied to them, a new managerial class that has little emotional capital sunk in the firm other than as a vehicle for shareholder value maximization or release, and personal enrichment. From the business historian’s viewpoint, these assumptions raise a number of issues surrounding long term trends and diversity in the nature of the capitalist ecosystem within which tripartism is located. In this connection, there are four alternative points of view on broad approaches to labour management. The first, rooted in the then apparent solidity of the British postwar tripartite settlement, was that the incorporation of labour’s institutions was structurally essential to the state’s role in avoiding or genuinely resolving crises. The second sees tripartism as very much an historical exception, representing to a large extent a product of a very specific set of historic circumstances around the Great Depression and the post-World War Two long boom. The third, a variant of the second, would see historic compromises between state, the firm, and workers as a reflection of the thirty year period of relative global prosperity and growth which had deeper historic roots stretching back at least into the Nineteenth Century. The fourth highlights national diversity in global capitalism and views the labour management options adopted according not only to temporal trends but also to such dimensions as space, scale, and global centre-periphery relations. The latter view implies that elements of post-war compromises may persist, even if, within many of the advanced societies, they do so in dilute form

Nondestructive tests of regenerative chambers

The capabilities and limitations of nondestructive evaluation methods were studied to detect and locate bond deficiencies in regeneratively cooled thrust chambers for rocket engines. Flat test panels and a cylinder were produced to simulate regeneratively cooled thrust chamber walls. Planned defects with various bond integrities were produced in the panels to evaluate the sensitivity, accuracy, and limitations of nondestructive methods to define and locate bond anomalies. Holography, acoustic emission, and ultrasonic scan were found to yield sufficient data to discern bond quality when used in combination and in selected sequences. Bonding techniques included electroforming and brazing. Materials of construction included electroformed nickel bonded to Nickel 200 and OFHC copper, electroformed copper bonded to OFHC copper, and 300 series stainless steel brazed to OFHC copper. Variations in outer wall strength, wall thickness, and defect size were evaluated for nondestructive test response

Nondestructive tests of regenerative chambers, appendix

For abstract, see N75-12058

The minimum free-stream wind speed for initiating motion of surface material on Mars

Estimates of the minimum free-stream wind speed that is required for initiating the motion of surficial material on Mars have ranged from 30 to about 200 meters per second. Thus the best value for this quantity is not well established. Graphical comparison of much of the pertinent data taken in the laboratory and in the field on Earth provides a minimum value for the Bagnold coefficient of 0.08 and this in turn provides a minimum value for the threshold friction velocity of 1.3 meters per second for initiating motion of particulate matter on Mars at low elevations where the pressure is 7 millibars. The most appropriate value of the ratio of friction velocity to free-stream velocity for putative unstable condition appears to be 0.026. Thus the minimum free-stream wind speed for initiating motion is obtained as 50 meters per second. If the surface material on Mars, however, is less cohesive than that on earth, the minimum value may be smaller