20,139 research outputs found
A review of computer aided interpretation technology for the evaluation of radiographs of aluminum welds
Industrial radiography is a well established, reliable means of providing nondestructive structural integrity information. The majority of industrial radiographs are interpreted by trained human eyes using transmitted light and various visual aids. Hundreds of miles of radiographic information are evaluated, documented and archived annually. In many instances, there are serious considerations in terms of interpreter fatigue, subjectivity and limited archival space. Quite often it is difficult to quickly retrieve radiographic information for further analysis or investigation. Methods of improving the quality and efficiency of the radiographic process are being explored, developed and incorporated whenever feasible. High resolution cameras, digital image processing, and mass digital data storage offer interesting possibilities for improving the industrial radiographic process. A review is presented of computer aided radiographic interpretation technology in terms of how it could be used to enhance the radiographic interpretation process in evaluating radiographs of aluminum welds
Three-dimensional carrier-dynamics simulation of terahertz emission from photoconductive switches
A semi-classical Monte Carlo model for studying three-dimensional carrier
dynamics in photoconductive switches is presented. The model was used to
simulate the process of photoexcitation in GaAs-based photoconductive antennas
illuminated with pulses typical of mode-locked Ti:Sapphire lasers. We analyzed
the power and frequency bandwidth of THz radiation emitted from these devices
as a function of bias voltage, pump pulse duration and pump pulse location. We
show that the mechanisms limiting the THz power emitted from photoconductive
switches fall into two regimes: when illuminated with short duration (<40 fs)
laser pulses the energy distribution of the Gaussian pulses constrains the
emitted power, while for long (>40 fs) pulses, screening is the primary
power-limiting mechanism. A discussion of the dynamics of bias field screening
in the gap region is presented. The emitted terahertz power was found to be
enhanced when the exciting laser pulse was in close proximity to the anode of
the photoconductive emitter, in agreement with experimental results. We show
that this enhancement arises from the electric field distribution within the
emitter combined with a difference in the mobilities of electrons and holes.Comment: 7 pages, 7 figure
Towards Intelligent Databases
This article is a presentation of the objectives and techniques
of deductive databases. The deductive approach to databases aims at extending
with intensional definitions other database paradigms that describe
applications extensionaUy. We first show how constructive specifications can
be expressed with deduction rules, and how normative conditions can be defined
using integrity constraints. We outline the principles of bottom-up and
top-down query answering procedures and present the techniques used for
integrity checking. We then argue that it is often desirable to manage with
a database system not only database applications, but also specifications of
system components. We present such meta-level specifications and discuss
their advantages over conventional approaches
An Entailment Relation for Reasoning on the Web
Reasoning on the Web is receiving an increasing attention because of emerging fields such as Web adaption and Semantic Web. Indeed, the advanced functionalities striven for in these fields call for reasoning capabilities. Reasoning on the Web, however, is usually done using existing techniques rarely fitting the Web. As a consequence, additional data processing like data conversion from Web formats (e.g. XML or HTML) into some other formats (e.g. classical logic terms and formulas) is often needed and aspects of the Web (e.g. its inherent inconsistency) are neglected. This article first gives requirements for an entailment tuned to reasoning on the Web. Then, it describes how classical logic’s entailment can be modified so as to enforce these requirements. Finally, it discusses how the proposed entailment can be used in applying logic programming to reasoning on the Web
The value of psychological flexibility: Examining psychological mechanisms underpinning a cognitive behavioural therapy intervention for burnout
Little is known of the mechanisms by which interventions for burnout work. Employees of a UK government department were randomly assigned to either a worksite group-based CBT intervention called Acceptance and Commitment Therapy (ACT; n=43), which aimed to increase participants' psychological flexibility, or a waiting list control group (n=57). The ACT group received three half-day sessions of training spread over two and a half months. Data were collected at baseline (T1), at the beginning of the second (T2) and third (T3) workshops, and at six months' follow up (T4). Consistent with ACT theory, analyses revealed that, in comparison to the control group, a significant increase in psychological flexibility from T2 to T3 in the ACT group mediated the subsequent T2 to T4 decrease in emotional exhaustion in that group. Consistent with a theory of emotional burnout development, this significant decrease in emotional exhaustion from T2 to T4 in the ACT group appeared to prevent the significant T3 to T4 increase in depersonalization seen in the control group. Strain also decreased from T2 to T3 in the ACT group only, but no mediator of that improvement was identified. Implications for theory and practice in the fields of ACT and emotional burnout are discussed
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A Tale of two Cities: A study of access and attitudes to food in the Deepdale and Ingol areas of Preston
Mindfulness and meditation in the workplace: An acceptance and commitment therapy approach
There is a wide-range and growing body of evidence that mental health and behavioural effectiveness are influenced more by how people interact with their thoughts and feelings than by their form (e.g., how negative they are) or frequency. Research has demonstrated this key finding in a wide-range of areas. For example, in chronic pain, psychosocial disability is predicted more by the experiential avoidance of pain than by the degree of pain (McCracken, 1998). A number of therapeutic approaches have been developed that share this key insight: distress tolerance (e.g., Brown, Lejuez, Kahler, & Strong, 2002; Schmidt, Richey, Cromer, & Buckner, 2007), thought suppression (e.g., Wenzlaff & Wegner, 2000), and mindfulness (Baer, 2003). It is also central to a number of the newer contextual cognitive behaviour therapy (CBT) approaches to treatment, such as mindfulness based cognitive therapy (MBCT; Segal, Williams, & Teasdale, 2001), dialectical behaviour therapy (DBT; Linehan, 1993), metacognitive therapy (Wells, 2000), and acceptance and commitment therapy (ACT; Hayes, Strosahl, & Wilson, 1999).
The purpose of this chapter is to describe how ACT conceptualises mindfulness and tries to enhance it in the pursuit of promoting mental health and behavioural effectiveness (e.g., productivity at work). To this end, we discuss ACT’s key construct of psychological flexibility, which involves mindfulness, and how it has led to a somewhat different approach not only to conceptualising mindfulness, but also how we try to enhance it in the workplace. In so doing, we hope to show that whilst formal meditation practice is valued in ACT, it is only one strategy that is used to promote mindfulness, as well as psychological flexibility more generally
First-passage dynamics of obstructed tracer particle diffusion in one-dimensional systems
The standard setup for single-file diffusion is diffusing particles in one
dimension which cannot overtake each other, where the dynamics of a tracer
(tagged) particle is of main interest. In this article we generalise this
system and investigate first-passage properties of a tracer particle when
flanked by crowder particles which may, besides diffuse, unbind (rebind) from
(to) the one-dimensional lattice with rates (). The
tracer particle is restricted to diffuse with rate on the lattice. Such a
model is relevant for the understanding of gene regulation where regulatory
proteins are searching for specific binding sites ona crowded DNA. We quantify
the first-passage time distribution, ( is time), numerically using
the Gillespie algorithm, and estimate it analytically. In terms of our key
parameter, the unbinding rate , we study the bridging of two known
regimes: (i) when unbinding is frequent the particles may effectively pass each
other and we recover the standard single particle result
with a renormalized diffusion constant, (ii) when unbinding is rare we recover
well-known single-file diffusion result . The intermediate
cases display rich dynamics, with the characteristic -peak and the
long-time power-law slope both being sensitive to
High resolution Cherenkov detectors for cosmic ray isotope experiment
Cerenkov detectors are used to measure the velocity of particles in configurations designed to study the isotopic composition of galactic cosmic rays. The geometrical properties of the detector are outlined. Monte-Carlo simulations of photon propagation in a diffusive detector were undertaken. The scattering properties of diffusively reflecting white paint and of surface treatments for the radiator material were measured. It is found that the absorption of light in the radiator is an important light loss mechanism. The simulations are used to find optimal mapping techniques and data reduction strategies. The application of these techniques are discussed with respect to the large area isotopic composition experiment (ALICE) Cerenkov detector
Loss of Spin Entanglement For Accelerated Electrons in Electric and Magnetic Fields
Using an open quantum system we calculate the time dependence of the
concurrence between two maximally entangled electron spins with one accelerated
uniformly in the presence of a constant magnetic field and the other at rest
and isolated from fields. We find at high Rindler temperature the proper time
for the entanglement to be extinguished is proportional to the inverse of the
acceleration cubed.Comment: 10 pages, 4 figures, appendix and other discussion added, fixed some
typographical errors and some references were correcte
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