The Computation of Fields and Signals due to Ferromagnetic Anomalies

In this paper we develop a model for the computation of electromagnetic fields in anomalous regions of ferromagnetic cylinders. The role of electric and magnetic current densities as sources for these fields is explicitly presented. The starting point for the development is the computation of a three-dimensional Green’s function for the cylinder, from which the appropriate integral relations between the field and its sources can be derived. The rigorous calculation of the anomalous current source within the anomalous region requires the solution of an integral equation that has the Green’s function as its kernel. We do not carry out this calculation, but approximate the anomalous current by the applied field due to the exciting coil (which, for our examples is an infinite solenoid that is coaxial to the cylinder). Once the field within the anomalies is determined, the field external to the wall of the tube may be computed, and this provides the signal that is sensed by a coil, or other means

A Computer Model of Eddy-Current Probe-Crack Interaction

A general three-dimensional eddy-current probe model, developed by Sabbagh Associates and reported in [1], [2] and [3], has been adapted for the calculation of probe-flaw interactions. The theoretical model, [4] and [5], uses integral equations with dyadic Green’s function kernels, and is applicable to both probe and flaw calculations at arbitrary skin depths and frequencies. Discrete approximations of the integral equations are solved using a highly efficient algorithm based on recent developments in numerical techniques and their application to the solution of large problems in electromagnetic field-theory

A Model of Eddy-Current Probes with Ferrite Cores

The classical work of Dodd and his coworkers at the Oak Ridge National Laboratory deals with the analysis, design and optimization of eddy-current probe coils wound around an air core. Many applications, however, require that the magnetic field produced by the probe coil be “shaped” or confined to certain regions of space, especially at higher frequencies, and this necessitates the use of highly permeable core materials, such as ferrites

A Network Recovery Strategy Scheme Based on Network Failure Scenarios and Topologies

Network failures happen frequently. There is a need for recovery mechanisms to reduce service interruption. Recovery mechanismsâ advantages and disadvantages are described extensively based on their characteristics and performances. However, it is more desirable that network recovery strategies are chosen based on failure scenarios and topologies. In this paper, we propose a recovery scheme and focus on networks whose paths and resources from source to destination nodes are computed and negotiated primarily at source nodes, Ingress Label Switched Router (LSR), which are the case for Generalized Multiprotocol Label Switching (GMPLS) networks. Choosing proper network recovery mechanisms depends on many parameters such as distance of failure from source node, degree distribution of nodes, availabilities of alternative paths, and maximum allowed-hopcount increase in alternative paths. Three recovery mechanisms: Haskin, Global and Local Protection are compared with the proposed restoration scheme. By changing parameters on appropriate ranges and by using probability of received data packet at the destination node, e.g. probability of error as one of the performance criteria, we can make a fair judgment on choosing a network strategy by considering available network parameters and topology

Continuity in the neural system supporting children's theory of mind development: Longitudinal links between task-independent EEG and task-dependent fMRI.

Children's explicit theory of mind (ToM) understandings change over early childhood. We examined whether there is longitudinal stability in the neurobiological bases of ToM across this time period. A previous study found that source-localized resting EEG alpha attributable to the dorsal medial prefrontal cortex (DMPFC) and right temporoparietal junction (RTPJ) was associated with children's performance on a battery of theory of mind tasks. Here, we investigated a small subset of children (N = 12) in that original study as a preliminary investigation of whether behavioral measures of ToM performance, and/or EEG localized to the DMPFC or RTPJ predicted ToM-specific fMRI responses 3.5 years later. Results showed that preschoolers' behavioral ToM-performance positively predicted later ToM-specific fMRI responses in the DMPFC. Preschoolers' resting EEG attributable to the DMPFC also predicted later ToM-specific fMRI responses in the DMPFC. Given the small sample, results represent a first exploration and require replication. Intriguingly, they suggest that early maturation of the area of the DMPFC related to ToM reasoning is positively linked with its specific recruitment for ToM reasoning later in development, affording implications for characterizing conceptual ToM development, and its underlying neural supports

Developmental differences in the structure of executive function in middle childhood and adolescence

Although it has been argued that the structure of executive function (EF) may change developmentally, there is little empirical research to examine this view in middle childhood and adolescence. The main objective of this study was to examine developmental changes in the component structure of EF in a large sample (N = 457) of 7–15 year olds. Participants completed batteries of tasks that measured three components of EF: updating working memory (UWM), inhibition, and shifting. Confirmatory factor analysis (CFA) was used to test five alternative models in 7–9 year olds, 10–12 year olds, and 13–15 year olds. The results of CFA showed that a single-factor EF model best explained EF performance in 7–9-year-old and 10–12-year-old groups, namely unitary EF, though this single factor explained different amounts of variance at these two ages. In contrast, a three-factor model that included UWM, inhibition, and shifting best accounted for the data from 13–15 year olds, namely diverse EF. In sum, during middle childhood, putative measures of UWM, inhibition, and shifting may rely on similar underlying cognitive processes. Importantly, our findings suggest that developmental dissociations in these three EF components do not emerge until children transition into adolescence. These findings provided empirical evidence for the development of EF structure which progressed from unity to diversity during middle childhood and adolescence

Light effective hole mass in undoped Ge/SiGe quantum wells

We report density-dependent effective hole mass measurements in undoped germanium quantum wells. We are able to span a large range of densities ($2.0-11\times10^{11}$ cm$^{-2}$) in top-gated field effect transistors by positioning the strained buried Ge channel at different depths of 12 and 44 nm from the surface. From the thermal damping of the amplitude of Shubnikov-de Haas oscillations, we measure a light mass of $0.061m_e$ at a density of $2.2\times10^{11}$ cm$^{-2}$. We confirm the theoretically predicted dependence of increasing mass with density and by extrapolation we find an effective mass of $\sim0.05m_e$ at zero density, the lightest effective mass for a planar platform that demonstrated spin qubits in quantum dots

Effect of cavities on the behaviour of model pile under axial loading in sand

Presence of cavities in soils is an important area of interest within the field of geotechnical engineering. A better understanding of the behaviour of such soils, particularly in locations where the presence of gypsum deposits is apparent, will have a large impact on the stability of foundations and allows designers and engineers to have a convincing explanation of this phenomenon on the stability of foundations in general. The research offers an experimental investigation to study the performance of axially loaded piles embedded in sandy soils with cavities. The experimental study comprised a full laboratory testing programme carried out on small scale piles embedded in predetermined cavities within a soil mass. The experimental model has the capability to investigate the effect of different cavity locations on the ultimate pile resistances. Thirteen cavity locations were chosen to study their influence on the ultimate carrying load of single pile. It was concluded that the maximum ultimate carrying load of the pile is reduced by the presence of the cavity within the soil mass. This reduction varies according to the cavity location. The effect of cavity’s presence on the ultimate bearing capacity of pile ranged from 0% to 30.82% for side cavities, while the range of reduction factor for cavities under the pile tip is from 31.58% to 43.4%. The reduction in pile capacity increases when the cavity is closer to the pile. Also, pile settlement value without cavity is less than the settlement of the same pile with cavity

Advanced Model of Eddy-Current NDE Inverse Problem with Sparse Grid Algorithm

In model-based inverse problem, some unknown parameters need to be estimated. These parameters are used not only to characterize the physical properties of cracks, but also to describe the position of the probes (such as lift off and angles) in the calibration. After considering the effect of the position of the probes in the inverse problem, the accuracy of the inverse result will be improved.With increasing the number of the parameters in the inverse problems, the burden of calculations will increase exponentially in the traditional full grid method. The sparse grid algorithm which introduced by Sergey A. Smolyak was used in our work. With this algorithm, we obtain a powerful interpolation method that requires significantly fewer support nodes than conventional interpolation on a full grid. In this work,we combined sparse grid toolbox TASMANIAN which is produced by Oak Ridge National Laboratory and professional eddy-current NDE software VIC-3D®to solve a specific inverse problem. An advanced model based on our previous one is used to estimate depth and width of the crack, lift off and two angles of the position of probes. Considering the calibration process, pseudorandom noise is considered in the model and statistics behavior is discussed

Sylvia Plath's The Bell Jar: a Mirror of American Fifties

With its portrayal of a talented yet frustrated young American woman in the 1950s, Sylvia Plath's The Bell Jar (1963) depicts the experiences of a nineteen-year-old girl before her mental breakdown. Benefitting from a Friedanian second wave feminism, this paper aims to trace the root of disappointment and identity crisis in Plath's heroine, Esther Greenwood. It is understood that besides being a personal issue, her frustration is the outcome of sociocultural factors. The lack of role models and the contradictory messages sent by the media lead to her anxiety, disillusionment, and uncertainty. The Bell Jar proposes a solution: it is indeed possible for a woman to hold a fulfilling career and at the same time be a caring wife and a loving mother. And this is the answer Esther tries to figure out at a time when the boundaries between the domestic sphere and the outside world are clearly defined for women