Non-destructive evaluation of concrete using a capacitive imaging technique : preliminary modelling and experiments

This paper describes the application of capacitive imaging to the inspection of concrete. A two-dimensional finite-element method was employed to model the electric field distribution from capacitive imaging probe, and how it interacts with concrete samples. Physical experiments with prototype capacitive imaging probes were also carried out. The proof-of-concept results indicated that the capacitive imaging technique could be used to detect cracks on the surface of concrete samples, as well as sub-surface air voids and steel reinforcement bars

Production And Studies Of Photocathodes For High Intensity Electron Beams

For short, high-intensity electron bunches, alkali-tellurides have proved to be a reliable photo-cathode material. Measurements of lifetimes in an RF gun of the CLIC Test Facility II at field strengths greater than 100 MV/m are presented. Before and after using them in this gun, the spectral response of the Cs-Te and Rb-Te cathodes were determined with the help of an optical parametric oscillator. The behaviour of both materials can be described by Spicer's 3-step model. Whereas during the use the threshold for photo-emission in Cs-Te was shifted to higher photon energies, that of Rb-Te did not change. Our latest investigations on the stoichiometric ratio of the components are shown. The preparation of the photo-cathodes was monitored with 320 nm wavelength light, with the aim of improving the measurement sensitivity. The latest results on the protection of Cs-Te cathode surfaces with CsBr against pollution are summarized. New investigations on high mean current production are presented.Comment: Submission to LINAC2000 conference, Paper number MOB08, 3 pages, 6 figure

Acute pulmonary pathology and sudden death in rats following the intravenous administration of the plasticizer, DI (2-ethylhexyl) phthalate, solubilized with Tween surfactants

Intravenous administration of 200-300 mg/kg of di(2-ethylhexyl)phthalate (DEHP) solubilized in aqueous solutions of several Tween surfactants caused respiratory distress in rats. There was a dose-dependent lethality with death generally occurring within 90 minutes after injection. The lungs from DEHP:Tween treated animals were enlarged, generally darkened, and in some cases showed hemorrhagic congestion. Neither the overt symptoms nor the morphologic alterations resulting from DEHP:Tween administration could be reproduced by intravenous administration of aqueous Tween solutions alone. The absence of pulmonary abnormalities following the intravenous administration of DEHP as an aqueous emulsion given either alone or even as soon as 2 minutes after pretreatment with Tween 80, suggests that the specific in vivo interaction between DEHP and Tween surfactants depends on the prior formation of water-soluble micelles of DEHP

Modularised process-based modelling of phosphorus loss at farm and catchment scale

In recent years, a co-ordinated programme of data collection has resulted in the collation of sub-hourly time-series of hydrological, sediment and phosphorus loss data, together with soil analysis, cropping and management information for two small (< 200 ha) headwater agricultural catchments in the UK Midlands (Rosemaund, Herefordshire and Cliftonthorpe, Leicestershire). These data sets have allowed the dynamics of phosphorus loss to be characterised and the importance of both storm runoff and drainflow to be identified, together with incidental losses following manure and fertiliser additions in contributing to total annual loss. A modularised process-based model has been developed to represent current understanding of the dynamics of phosphorus loss. Modules describing runoff and sediment generation and associated phosphorus adsorption/desorption dynamics are described and tested. In the model, the effect of a growing crop on sediment detachment processes is represented and the stability of topsoil is considered so that, overall, the model is responsive to farm management factors. Importantly, using data sets available from national-scale survey programmes to estimate model parameters, a transferable approach is presented, requiring only sub-hourly rainfall data and field-specific landcover information for application of the model to new sites. Results from application of the model to the hydrological year 1998–99 are presented. Assessment of performance, which suggests that the timing of simulated responses is acceptable, has focused attention on quantifying landscape and in-stream retention and remobilisation processes.</b></p> <p style='line-height: 20px;'><b>Keywords: </b>phosphorus, erosion, process-based modelling, agricultur

Evaluation and extensions of the probabilistic multi-hypothesis tracking algorithm to cluttered environments

This research examines the probabilistic multi-hypothesis tracker (PHMT), a batch mode, empirical, Bayesian data association and tracking algorithm. Like a traditional multi-hypothesis tracker (MHT), track estimation is deferred until more conclusive data is gathered. However, unlike a traditional algorithm, PMHT does not attempt to enumerate all possible combinations of feasible data association links, but uses a probabilistic structure derived using expectation maximization. This study focuses on two issues: the behavior of the PMHT algorithm in clutter and algorithm initialization in clutter. We also compare performance between this algorithm and other algorithms, including a nearest neighbor tracker, a probabilistic data association filter (PDAF), and a traditional measurement oriented MHT algorithm.Naval Undersea Warfare CenterApproved for public release; distribution is unlimited

The Role of Relapse Prevention and Goal Setting in Training Transfer Enhancement

This article reviews the effect of two post-training transfer interventions (relapse prevention [RP] and goal setting [GS]) on trainees’ ability to apply skills gained in a training context to the workplace. Through a review of post-training transfer interventions literature, the article identifies a number of key issues that remain unresolved or underexplored, for example, the inconsistent results on the impact of RP on transfer of training, the lack of agreement on which GS types are more efficient to improve transfer performance, the lack of clarity about the distinction between RP and GS, and the underlying process through which these two post-training transfer interventions influence transfer of training. We offer some recommendations to overcome these problems and also provide guidance for future research on transfer of training

Ensuring effective information flow through the JTB Enterprise in support of combat operations

The goal for this research is to develop recommendations to improve the Joint Improvised Device Defeat Organization (JIEDDO) Test Board (JTB) enterprise test process through enhanced information sharing. Due to the complexity of the environment, structure of the organization, socio-cultural factors, and lack of incentive to share knowledge among test conductors, the JTB is currently not accomplishing its mission as efficiently as possible. We report on the results of a knowledge engineering effort that was conducted on the critical tasks performed by users and the associated critical information that will contribute to increasing the efficiency of information flow between personnel in the JTB, working groups, test ranges, research facilities, and JIEDDO itself. The focus for this effort was on the following questions: What types of information are they seeking when using the JTB portal?; What types of questions are they trying to answer during their daily tasks, and how is this information obatined?; What types of products are produced?; and What procedural improvements can be implemented to ehance knowledge sharing? Improvements are needed to facilitate sharing results resported in capabilities and limitations documents in terms of how well the testing process supports the operational environment

Principles For Aiding Complex Military Decision Making

Paper presented to the Second International Command and Control Research and Technology Symposium, Monterey, Ca.The Tactical Decision Making Under Stress (TADMUS) program is being conducted to apply recent developments in decision theory and human-system interaction technology to the design of a decision support system for enhancing tactical decision making under the highly complex conditions involved in anti-air warfare scenarios in littoral environments. Our goal is to present decision support information in a format that minimizes any mismatches between the cognitive characteristics of the human decision maker and the design and response characteristics of the decision support system. Decision makers are presented with decision support tools which parallel the cognitive strategies they already employ, thus reducing the number of decision making errors. Hence, prototype display development has been based on decision making models postulated by naturalistic decision-making theory. Incorporating current human-system interaction design principles is expected to reduce cognitive processing demands and thereby mitigate decision errors caused by cognitive overload, which have been documented through research and experimentation. Topics include a discussion of: (1) the theoretical background for the TADMUS program; (2) a description of the cognitive tasks performed; (3) the decision support and human- system interaction design principles incorporated to reduce the cognitive processing load on the decision maker; and (4) a brief description of the types of errors made by decision makers and interpretations of the cause of these errors based on the cognitive psychology literature.Funding for the research cited in this paper was received from the Cognitive and Neural Science and Technology Division of the Office of Naval Research

Reception of laser generated ultrasound from a CFRP plate by an air matched piezoelectric composite transducer

Laser generated ultrasound is being investigated [1,2] for testing structures made of both conventional metals and carbon fibre reinforced polymer (CFRP). Laser interferometers are widely used in such work to detect the normal surface motion caused by ultrasonic pulses. Interferometers offer non-contact, remote and high-fidelity detection, together with a potential to cover large areas rapidly by optical scanning. However their cost is high and only in testing large and/or expensive structures may the cost be justified. A lower cost alternative, but with some compromise on the virtues of an interferometer, would be to use an air transducer as a receiver