Salt Penetration and Corrosion in Prestressed Concrete Members

DTFH61-87-C00031A study was made of the condition of prestressed concrete PS/C bridge elements located in adverse, potentially corrosive environments. A total of five bridges were subjected to detailed surveys. Additional structures were surveyed visually and given limited investigation. Bridges were located both in northern climates subjected to application of roadway deicing salts and in southern areas subjected to marine spray. Results indicated that, in northern areas, primary cause of deterioration of PS/C members is due to penetration of solutions containing deicing salts through concrete cover and through anchorage zones. Improperly designed and maintained joints and drainage systems are the primary pathways for the salt ingress. In southern areas primary cause of deterioration is marine salts sprayed directly onto substructural elements by wave action. Recommendations concerning procedures, parameters and threshold values for detection of corrosive environments and assessing the condition of prestressing steel in bridge components are included

Signal Processing for Longitudinal Parameters of the Tevatron Beam”,

Abstract We describe the system known as the Tevatron SBD The oscilloscope provides 8 bits of resolution. To use this range efficiently, a DC offset in the scope sets the baseline to ~30 counts (out of 255). The high gain channel accomodates the antiproton signal and the proton signal is contained in the low gain channel. In practice, we synthesize the proton signal from both channels thus improving the resolution on the proton signal by ~ 8. The signal is sampled at 5GS/s. To reduce the effect of digitizing noise, a set of 32 sweeps is taken and averaged (within the 6200). Each sweep covers 21 usecs, a full Tevatron period, and successive sweeps are taken every ~ 42 usec, triggered by the Low Level RF proton marker. (The 1.2 millisecond of acquisition is small compared to the synchrotron period of the Tevatron.) A second set of sweeps triggered by the antiproton marker is taken to obtain the antiproton RF timing. The data from an acquisition (200 kbytes) are transferred via ethernet to the Macintosh G5 for processing. GENERAL DESCRIPTION A schematic is shown in Signal Processing The (gain dependent) time offset between the channels is determined by a simple convolution and linear interpolation is used to align the high gain channel. We have not found any need to correct the gain ratio from its nominal value. A 200 tap (40 ns) FIR filter is applied to remove the effects of dispersion in the long cable SIGNAL PROCESSING Signal Acquisition The RWCM has broad (>2 GHz) bandwidth with a 1.34 ohm resistance formed by 88 120 ohm resistors across the ceramic gap. We use a Lecroy 6200 oscilloscope as digitizer. The RWCM output is brought to the service building via 280 ft of 7/8" heliax cable and then split to provide two copies of the signal, just upstream of the oscilloscope. The signals are fed to two input channels with a gain ratio of ~8, the present ratio of proton to antiproton intensities. The split is positioned so that any reflections from one channel input will arrive at the other channel with 50 ns (2.5 buckets) delay. The baseline is found by a histogramming technique in 18 separate sections as shown i

Design of an electro-optical sampling experiment at the AWA facility

The free space electro-optical (EO) sampling technique is a powerful tool for analyzing the longitudinal charge density of an ultrashort e-beam. In this paper, we present (1) experimental results for a laser-based mock-up of the EO experiment [1] and (2) a design for a beam-based, single-shot, EO sampling experiment using the e-beam from the Argonne Wakefield Accelerator (AWA) RF photoinjector. For the mock-up, a tabletop terahertz experiment is conducted in the AWA laser room. The mock-up uses an IR beam incident on <110> ZnTe crystal to produce a THz pulse via optical rectification. Detection is based on the cross correlation between the THz field and the probe IR laser field in a second <110> ZnTe crystal

Learning from the UK’s research impact assessment exercise: a case study of a retrospective impact assessment exercise and questions for the future

National governments spend significant amounts of money supporting public research. However, in an era where the international economic climate has led to budget cuts, policymakers increasingly are looking to justify the returns from public investments, including in science and innovation. The so-called ‘impact agenda’ which has emerged in many countries around the world is part of this response; an attempt to understand and articulate for the public what benefits arise from the research that is funded. The United Kingdom is the most progressed in implementing this agenda and in 2014 the national research assessment exercise, the Research Excellence Framework, for the first time included the assessment of research impact as a component. For the first time within a dual funding system, funding would be awarded not only on the basis of the academic quality of research, but also on the wider impacts of that research. In this paper we outline the context and approach taken by the UK government, along with some of the core challenges that exist in implementing such an exercise. We then synthesise, together for the first time, the results of the only two national evaluations of the exercise and offer reflections for future exercises both in the UK and internationally