Tungsten thermal neutron dosimeter

Tungsten-185 activity, which is produced by neutron activation of tungsten-184, determines thermal neutron flux. Radiochemical separation methods and counting techniques for irradiated tungsten provide accurate determination of the radiation exposure

Cross and magnetic helicity in the outer heliosphere from Voyager 2 observations

Plasma velocity and magnetic field measurements from the Voyager 2 mission are used to study solar wind turbulence in the slow solar wind at two different heliocentric distances, 5 and 29 astronomical units, sufficiently far apart to provide information on the radial evolution of this turbulence. The magnetic helicity and the cross-helicity, which express the correlation between the plasma velocity and the magnetic field, are used to characterize the turbulence. Wave number spectra are computed by means of the Taylor hypothesis applied to time resolved single point Voyager 2 measurements. The overall picture we get is complex and difficult to interpret. A substantial decrease of the cross-helicity at smaller scales (over 1-3 hours of observation) with increasing heliocentric distance is observed. At 5 AU the only peak in the probability density of the normalized residual energy is negative, near -0.5. At 29 AU the probability density becomes doubly peaked, with a negative peak at -0.5 and a smaller peak at a positive values of about 0.7. A decrease of the cross-helicity for increasing heliocentric distance is observed, together with a reduction of the unbalance toward the magnetic energy of the energy of the fluctuations. For the smaller scales, we found that at 29 AU the normalized polarization is small and positive on average (about 0.1), it is instead zero at 5 AU. For the larger scales, the polarization is low and positive at 5 AU (average around 0.1) while it is negative (around - 0.15) at 29 AU.Comment: 14 pages 5 figures. Accepted for publication on European Journal of Mechanics B/Fluids (5/8/2015

Turbulence in the solar wind: spectra from Voyager 2 data at 5 AU

Fluctuations in the flow velocity and magnetic fields are ubiquitous in the Solar System. These fluctuations are turbulent, in the sense that they are disordered and span a broad range of scales in both space and time. The study of solar wind turbulence is motivated by a number of factors all keys to the understanding of the Solar Wind origin and thermodynamics. The solar wind spectral properties are far from uniformity and evolve with the increasing distance from the sun. Most of the available spectra of solar wind turbulence were computed at 1 astronomical unit, while accurate spectra on wide frequency ranges at larger distances are still few. In this paper we consider solar wind spectra derived from the data recorded by the Voyager 2 mission during 1979 at about 5 AU from the sun. Voyager 2 data are an incomplete time series with a voids/signal ratio that typically increases as the spacecraft moves away from the sun (45% missing data in 1979), making the analysis challenging. In order to estimate the uncertainty of the spectral slopes, different methods are tested on synthetic turbulence signals with the same gap distribution as V2 data. Spectra of all variables show a power law scaling with exponents between -2.1 and -1.1, depending on frequency subranges. Probability density functions (PDFs) and correlations indicate that the flow has a significant intermittency.Comment: 14 pages, 7 figures. Discussion improved since the previous versio

Integrating testing techniques through process programming

Integration of multiple testing techniques is required to demonstrate high quality of software. Technique integration has three basic goals: incremental testing capabilities, extensive error detection, and cost-effective application. We are experimenting with the use of process programming as a mechanism of integrating testing techniques. Having set out to integrate DATA FLOW testing and RELAY, we proposed synergistic use of these techniques to achieve all three goals. We developed a testing process program much as we would develop a software product from requirements through design to implementation and evaluation. We found process programming to be effective for explicitly integrating the techniques and achieving the desired synergism. Used in this way, process programming also mitigates many of the other problems that plague testing in the software development process

An assessment of the risk arising from electrical effects associated with carbon fibers released from commercial aircraft fires

The risks associated with electrical effects arising from carbon fibers released from commercial aviation aircraft fires were estimated for 1993. The expected annual losses were estimated to be about $470 (1977 dollars) in 1993. The chances of total losses from electrical effects exceeding$100,000 (1977 dollars) in 1993 were established to be about one in ten thousand

Geographies of digital skill

In an era of rapid technological change, especially considering the rise of robotics and AI, there is widespread anxiety about the impacts of digital technologies across a vast range of industries. Policy responses to this changing employment landscape champion the necessity for growing ‘digital skills’. However, we argue that these dominant macropolitical interpretations draw on a restricted understanding of spatiality where digital skills are discretely located in particular bodies and in particular geographical locations. The paper develops a novel geographical response through an exploration of the micropolitics of digital skills. This focuses on the material and practical dimensions of work with digital technologies that produces a more dynamic spatiality and thus a more complex politics of labour. We argue that the dynamic spatiality of digital skills can be evaluated according to: (1) site-specific dimensions, as digital skills are co-minglings of humans and technologies; (2) extensive dimensions, as digital skills are networked across geographically dispersed sites; and (3) intensive dimensions, as digital skills emerge across bodies and environments through repetitive practices. This analysis suggests that policy declarations of digital skills ‘shortages’ are problematic, since they overlook the contested and shifting forms of enablement and constraint that labour practices involving digital technologies give rise to. Unpacking this labour politics therefore requires geographical approaches that are adept at grasping these complex spatialities of labour

Geographies of digital skill.

In an era of rapid technological change, especially considering the rise of robotics and AI, there is widespread anxiety about the impacts of digital technologies across a vast range of industries. Policy responses to this changing employment landscape champion the necessity for growing ‘digital skills’. However, we argue that these dominant macropolitical interpretations draw on a restricted understanding of spatiality where digital skills are discretely located in particular bodies and in particular geographical locations. The paper develops a novel geographical response through an exploration of the micropolitics of digital skills. This focuses on the material and practical dimensions of work with digital technologies that produces a more dynamic spatiality and thus a more complex politics of labour. We argue that the dynamic spatiality of digital skills can be evaluated according to: (1) site-specific dimensions, as digital skills are co-minglings of humans and technologies; (2) extensive dimensions, as digital skills are networked across geographically dispersed sites; and (3) intensive dimensions, as digital skills emerge across bodies and environments through repetitive practices. This analysis suggests that policy declarations of digital skills ‘shortages’ are problematic, since they overlook the contested and shifting forms of enablement and constraint that labour practices involving digital technologies give rise to. Unpacking this labour politics therefore requires geographical approaches that are adept at grasping these complex spatialities of labour

158µJ pulses from a single transverse mode, large mode-area EDFA

We report the amplification of 10pJ-100pJ, semiconductor diode pulses up to an energy of 158µJ and peak powers >100kW in a multi-stage fibre amplifier chain based on a single-mode, large mode-area erbium doped amplifier design. These results represent the highest single-mode pulse energy ever extracted from any doped fibre system