Far field imaging of a dielectric inclusion

A non-iterative topological sensitivity framework for guaranteed far field detection of a dielectric inclusion is presented. The cases of single and multiple measurements of the electric far field scattering amplitude at a fixed frequency are taken into account. The performance of the algorithm is analyzed theoretically in terms of resolution, stability, and signal-to-noise ratio.Comment: 6 pages, 5th International Workshop on New Computational Methods for Inverse Problems, ENS Cachan, Franc

Detection of Electromagnetic Inclusions using Topological Sensitivity

In this article a topological sensitivity framework for far field detection of a diametrically small electromagnetic inclusion is established. The cases of single and multiple measurements of the electric far field scattering amplitude at a fixed frequency are taken into account. The performance of the algorithm is analyzed theoretically in terms of its resolution and sensitivity for locating an inclusion. The stability of the framework with respect to measurement and medium noises is discussed. Moreover, the quantitative results for signal-to-noise ratio are presented. A few numerical results are presented to illustrate the detection capabilities of the proposed framework with single and multiple measurements.Comment: 31 pages, 5 figure

Topological Sensitivity Based Far-Field Detection of Elastic Inclusions

The aim of this article is to present and rigorously analyze topological sensitivity based algorithms for detection of diametrically small inclusions in an isotropic homogeneous elastic formation using single and multiple measurements of the far-field scattering amplitudes. A $L^2-$cost functional is considered and a location indicator is constructed from its topological derivative. The performance of the indicator is analyzed in terms of the topological sensitivity for location detection and stability with respect to measurement and medium noises. It is established that the location indicator does not guarantee inclusion detection and achieves only a low resolution when there is mode-conversion in an elastic formation. Accordingly, a weighted location indicator is designed to tackle the mode-conversion phenomenon. It is substantiated that the weighted function renders the location of an inclusion stably with resolution as per Rayleigh criterion.Comment: 31 pages, 1 figur

Elastic scattering coefficients and enhancement of nearly elastic cloaking

The concept of scattering coefficients has played a pivotal role in a broad range of inverse scattering and imaging problems in acoustic and electromagnetic media. In view of their promising applications, we introduce the notion of scattering coefficients of an elastic inclusion in this article. First, we define elastic scattering coefficients and substantiate that they naturally appear in the expansions of elastic scattered field and far field scattering amplitudes corresponding to a plane wave incidence. Then an algorithm is developed and analyzed for extracting the elastic scattering coefficients from multi-static response measurements of the scattered field. Moreover, the estimate of the maximal resolving order is provided in terms of the signal-to-noise ratio. The decay rate and symmetry of the elastic scattering coefficients are also discussed. Finally, we design scattering-coefficients-vanishing structures and elucidate their utility for enhancement of nearly elastic cloaking

Elastic scattering coefficients and enhancement of nearly elastic cloaking

The concept of scattering coefficients has played a pivotal role in a broad range of inverse scattering and imaging problems in acoustic and electromagnetic media. In view of their promising applications, we introduce the notion of scattering coefficients of an elastic inclusion in this article. First, we define elastic scattering coefficients and substantiate that they naturally appear in the expansions of elastic scattered field and far field scattering amplitudes corresponding to a plane wave incidence. Then an algorithm is developed and analyzed for extracting the elastic scattering coefficients from multi-static response measurements of the scattered field. Moreover, the estimate of the maximal resolving order is provided in terms of the signal-to-noise ratio. The decay rate and symmetry of the elastic scattering coefficients are also discussed. Finally, we design scattering-coefficients-vanishing structures and elucidate their utility for enhancement of nearly elastic cloaking

An empirical review of television as potentially beneficial medium for children; exploring some realities

The purpose of this literature review is to identify and review research which supports the view that children’s television is a potentially beneficial medium; that in certain circumstances it can be a powerful educational tool; that it can inform and inspire; and that it is culturally relevant to today’s children.Many discussions of television’s impact on children focus only on its negative influence in relation to violence and advertising, for example, but it is also important to recognise that television can also have a positive impact.As two noted commentators point out: Television can be of general benefit to children.It can bring them into contact with aspects of life they would not otherwise become aware of.It can provide a valuable tool in the home and at school not simply to keep children occupied but also, if used appropriately, as a constructive way to use their time….Television is not a ‘one-eyed monster’ lurking impishly in the corner of the living room, kitchen or bedroom waiting to exert an evil influence over young members of the household.It is a channel through which a range of entertainment, drama and learning can be obtained and experienced and increasingly these days it is under the control of the viewer (Gunter and McAleer, 1997: xii-xiii)

A Critical Review on Universal Grammar of Chomsky in Learning a Second language

As many scholars have their own viewpoints and perspectives on Chomsky's universal grammar theory, this article shows recent developments in L2 learning by Chomsky. A significant turning point at the moment is Chomsky's UG approach to language education, particularly its values and parameters. Many researchers argue that with SLA, UG has problems like Fries and Palmer. They say that there are linguistic variations that make it difficult to differentiate between the SLA and the first language acquisition. It is possible to further clarify what would be specifically based on in future linguistic studies by assessing the challenges, so that development will be advanced towards language learning and SLA