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We study, in time domain, the exchange of momentum between an electromagnetic pulse and a threedimensional, discrete, spherical invisibility cloak.We find that a discrete cloak, initially at rest, would experience an electromagnet...
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We study, in time domain, the exchange of momentum between an electromagnetic pulse and a threedimensional, discrete, spherical invisibility cloak.We find that a discrete cloak, initially at rest, would experience an electromagnetic force due to the pulse but would acquire zero net momentum and net displacement. On the other hand, we find that while the cloak may manage to conceal an object and shroud it from the electromagnetic forces associated with the pulse, the cloak itself can experience optomechanical stress on a scale much larger than the object would in the absence of the cloak. We also consider the effects of material dispersion and losses on the electromagnetic forces experienced by the cloak and show that they lead to a transfer of momentum from the pulse to the cloak.
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We consider a setting where a bounded set with a piecewise smooth boundary in Euclidean space is identified with a body with a mirror surface, and the billiard in the complement of the set is identified with the dynamics of light ...
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We consider a setting where a bounded set with a piecewise smooth boundary in Euclidean space is identified with a body with a mirror surface, and the billiard in the complement of the set is identified with the dynamics of light rays outside the body in the framework of geometric optics. We show that in this setting it is possible to construct a body invisible from two points.
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This autoethnographic piece traces how two researchers continually negotiate their privileges, successes, insecurities, challenges, and (non)disabled identities in the neoliberal academy. We interrogate the co-constitution of iden...
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This autoethnographic piece traces how two researchers continually negotiate their privileges, successes, insecurities, challenges, and (non)disabled identities in the neoliberal academy. We interrogate the co-constitution of identity of (1) a mentally disabled researcher and graduate student who researches madness in the midst of dealing with his own struggles maintaining a professional identity and repairing a fractured self; (2) a non-disabled doctoral student who has found academic success, but has had his life stalled multiple times by significant mental health challenges. We propose the concept of the privileged (non)disabled self to capture how researchers become entangled in permanent or temporal disabilities while simultaneously negotiating their accomplishments. We encourage researchers not to sideline their reflections on privilege and disability as irrelevant, but continually examine their identities in order to reveal potential avenues for emancipation.
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Invisible or concealed hinge, having three fixed axes and two slide-able rotational axes, is widely used in the different closures like home doors, laundry machines, cockpit hatches of the boats and even in the notebook computers....
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Invisible or concealed hinge, having three fixed axes and two slide-able rotational axes, is widely used in the different closures like home doors, laundry machines, cockpit hatches of the boats and even in the notebook computers. The employ of this type of hinge is more advantageous with respect to the traditional surface-mounted hinges in terms of security and aesthetic design.Unfortunately, due to the lack of knowledge of kinematics of the hinge, the trajectory of the hinge movement is defined empirically in the known designs, and, as a consequence, all these solutions are not optimal. In this paper, we have analyzed the kinematics of five axes hinge, we have obtained the principal analytical relationships between constructive elements and, as a result, we can control the trajectory of hinge by means of following parameters: starting angle between hinge brackets, ratio of the brackets length, and shape of sliding guides. Therefore, this analytical approach can be used as a tool for the design of the concealed hinge which allows having a desirable trajectory of the door movement.
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In this paper, a new kind of cloak named petal-shaped cloak is proposed, by which multiple objects can be hidden at one time, and they could not perceive each other. The cloaked region which looks like petal is expanded from one s...
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In this paper, a new kind of cloak named petal-shaped cloak is proposed, by which multiple objects can be hidden at one time, and they could not perceive each other. The cloaked region which looks like petal is expanded from one single point. According to coordinate transformation theory, the general constitutive parameters of the N-petals cloak are derived. Full-wave simulations in two dimensions are given to validate the cloaking effect. The simulation results show that the cloak with the proposed parameters performs well.
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The electromagnetic behaviour of a prolate spheroidal cloak is investigated based on a full-wave scattering theory. We find that different physical behaviours related to surface displacement current will be induced at the inner bo...
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The electromagnetic behaviour of a prolate spheroidal cloak is investigated based on a full-wave scattering theory. We find that different physical behaviours related to surface displacement current will be induced at the inner boundary of the perfect spheroidal cloak, depending on the orientation of the cloak with respect to the direction of the incident wave. Such interesting phenomena can also be found in other cloaks, whose inner surface is transformed from a line in the initial coordinate system. A hyperbolidal cloak has also been proposed to further illustrate this point.
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In our study we analyze information restrictions determined by researchers when creating ideal objects of the real world and we classify types of researchers and describe methods of protection against system research.
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In this article, we draw on Michael Lipsky's work on street-level bureaucrats and discretion to analyse a real case setting comprising an interview study of 30 Swedish doctors regarding their experiences of changes in clinical wor...
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In this article, we draw on Michael Lipsky's work on street-level bureaucrats and discretion to analyse a real case setting comprising an interview study of 30 Swedish doctors regarding their experiences of changes in clinical work following patients being given access to medical records information online. We introduce the notion of invisibility work to capture how doctors exercise discretion to preserve the invisibility of their work, in contrast to the well-established notion of invisible work, which denotes work made invisible by parties other than those performing it. We discuss three main forms of invisibility work in relation to records: omitting information, cryptic writing and parallel note writing. We argue that invisibility work is a way for doctors to resolve professional tensions arising from the political decision to provide patients with online access to record information. Although invisibility work is understood by doctors as a solution to government-initiated visibility, we highlight how it can create difficulties for doctors concerning accountability towards patients, peers and authorities.
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To enhance employee performance, many organizations are increasingly using electronic performance monitoring (EPM). The relationship between the frequency of EPMuse and employee performance is examined in 2 field studies. In Study...
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To enhance employee performance, many organizations are increasingly using electronic performance monitoring (EPM). The relationship between the frequency of EPMuse and employee performance is examined in 2 field studies. In Study 1, which uses a unique longitudinal data set, results reveal that shorter time lags between 2 consecutive employee performance assessments are related to better task performance as indicated by call quality metrics. A second field study using matched supervisor- employee and EPM system data is conducted in 2 call centers to extend these results and to focus more directly on the supervisors' use of EPM and its relationship with additional performance criteria:counterproductive work behaviors (CWBs) and organizational citizenship behaviors (OCBs). Results indicate that more frequent supervisory use of EPM is associated with better task performance andOCB. However, supervisory use of EPM was not significantly related to CWB.
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Metamaterials have significantly extended the range of electromagnetic properties available to device designers. An interesting application of these new materials is to the problem of cloaking, where the goal is to render an objec...
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Metamaterials have significantly extended the range of electromagnetic properties available to device designers. An interesting application of these new materials is to the problem of cloaking, where the goal is to render an object invisible to electromagnetic radiation within a certain frequency range. Here, I review the concepts behind recently-proposed invisibility cloaks, and the way in which metamaterials can allow these designs to be realized. To cite this article: B. Wood, C. R. Physique 10 (2009).
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