87,324 research outputs found
Localization of electric field distribution in graded core-shell metamaterials
The local electric field distribution has been investigated in a core-shell
cylindrical metamaterial structure under the illumination of a uniform incident
optical field. The structure consists of a homogeneous dielectric core, a shell
of graded metal-dielectric metamaterial, embedded in a uniform matrix. In the
quasi-static limit, the permittivity of the metamaterial is given by the graded
Drude model. The local electric potentials and hence the electric fields have
been derived exactly and analytically in terms of hyper-geometric functions.
Our results showed that the peak of the electric field inside the cylindrical
shell can be confined in a desired position by varying the frequency of the
optical field and the parameters of the graded profiles. Thus, by fabricating
graded metamaterials, it is possible to control electric field distribution
spatially. We offer an intuitive explanation for the gradation-controlled
electric field distribution
Corruption and Cross-Border Investment: Firm-Level Evidence
This paper studies the impact of corruption on inward foreign direct investment using a unique firm-level data set. It examines two effects of corruption simultaneously: a reduction in the volume of foreign investment and a shift in the ownership structure. Corruption makes local bureaucracy less transparent and hence acts as a tax on foreign investors. Moreover, corruption affects the decision to take on a local partner. On the one hand, corruption increases the value of using a local partner to cut through the bureaucratic maze. On the other hand, corruption decreases the effective protection of investor’s intangible assets and lowers the probability that disputes between foreign and domestic partners will be adjudicated fairly, which reduces the value of having a local partner. The importance of protecting intangible assets increases with investor’s technological sophistication, which tilts the preference away from joint ventures in a corrupt country. Empirical evidence shows that corruption reduces inward FDI and shifts the ownership structure towards joint ventures. Technologically more advanced firms are found to be less likely to engage in joint ventures.http://deepblue.lib.umich.edu/bitstream/2027.42/39879/3/wp494.pd
Diverse Temporal Properties of GRB Afterglow
The detection of delayed X-ray, optical and radio emission, "afterglow",
associated with -ray bursts (GRBs) is consistent with fireball models,
where the emission are produced by relativistic expanding blast wave, driven by
expanding fireball at cosmogical distances. The emission mechanisms of GRB
afterglow have been discussed by many authors and synchrotron radiation is
believed to be the main mechanism. The observations show that the optical light
curves of two observed gamma-ray bursts, GRB970228 and GRB GRB970508, can be
described by a simple power law, which seems to support the synchrotron
radiation explanation. However, here we shall show that under some
circumstances, the inverse Compton scattering (ICS) may play an important role
in emission spectrum and this may influence the temporal properties of GRB
afterglow. We expect that the light curves of GRB afterglow may consist of
multi-components, which depends on the fireball parameters.Comment: Latex, no figures, minor correctio
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