Crack detection of steel girders using Brillouin optical time domain analysis

This article presents the results from an experimental program designed to evaluate the performance of a system consisting of a readout unit and a ribbon type Fiber Optic Sensor (FOS) based on Brillouin Optical Time Domain Analysis (BOTDA). The system is intended for the detection of cracks as well as the monitoring of long-term performance for steel bridge girders. The program consisted of introducing a crack at the center of a 3-m-long steel beam and monitoring its progression using static loading tests performed at ambient and sub-zero temperatures. For sensor lengths similar to those used in the field, the resonant frequency shifts per unit increase in crack width were found to decrease from 114 MHz/mm at ambient temperature (~25C) to 65 MHz/mm at -10C. Results also revealed nonlinearity and variability, which can be attributed to an incompatibility between the settings of the laser pump in the readout unit and the sensor length. Significant losses were detected along the bonded segments of the sensor and were attributed to the presence of ripples along the sensor. These undulations worsen with a reduction in temperature and are induced by the bonding procedure as well as the slack provided in the plastic sleeves containing the splices.

Military Service Pensions for Veterans of the Irish Revolution, 1916–1923

In 1924 the Irish Free State government passed legislation to award pensions to veterans of the Irish revolution and Civil War. This article argues that the motivation for the pensions was the need to placate the national army after a failed mutiny in 1924 and that this explains their unusual nature in being based on service alone rather than disability. It will also explore the problems this created for defining service, examine the extension of eligibility to former republican enemies of the state and women revolutionaries in 1934, and describe the application and assessment procedure.

Cold War Politics in Britain and the Contested Legacy of the Spanish Civil War

This article offers a sustained examination of how the vicissitudes of the Cold War shaped changing interpretations of the Spanish Civil War in Britain. Considering the perspectives of participants and historians, it focuses on the diverse strands of the Left that frequently drew on the civil war to attack each other and to make wider arguments about the global Cold War. First, with the aim of criticizing Communist take-overs in Eastern Europe in the late 1940s, the article analyzes retrospective assaults on Communist party tactics and Soviet foreign policy in Spain. Second, in order to argue that the Soviet Union took a counter-revolutionary line after 1956, it investigates the re-emergence of debates over the Spanish revolution. Third, to express disapproval of the United States, it examines the increasing use of the civil war as an analogy in Cold War international affairs from the 1960s. Fourth, in support of non-Soviet Left-of-Centre collaboration, most notably Eurocommunism in the 1970s and opposition to Margaret Thatcher’s Conservative government in the 1980s, it considers the renewed emphasis on the popular front. The trajectories of these debates reveal that, over time, the weight of the Left’s criticism moved from the Soviet Union towards the United States.