| 1. |
- Faccio, Ricardo, et al.
(författare)
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Electronic and Structural Distortions in Graphene Induced by Carbon Vacancies and Boron Doping
- 2010
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Ingår i: JOURNAL OF PHYSICAL CHEMISTRY C. - : American Chemical Society. - 1932-7447 .- 1932-7455. ; 114:44, s. 18961-18971
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Tidskriftsartikel (refereegranskat)abstract
- We present an ab initio-DFT/GGA-study on the structural and electronic distortions of modified graphene by the creation of vacancies, the inclusion of boron atoms, and the coexistence of both, by means of total energy and band structure calculations. In the case of coexistence of boron atoms and vacancy, the modified grapheme presents spin polarization only when B atoms locate far from vacancy. Thus, when a boron atom fills single and divacancies, it suppresses the spin polarization of the charge density. In particular, when B atoms fill a divacancy, a new type of rearrangement occurs, where a stable BC4 unit is formed inducing important out-of-plane distortions to graphene. All these findings suggest that new chemical modifications to grapheme and new types of vacancies can be used to modify its electronic properties.
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| 2. |
- Patil, Ajinkya H., et al.
(författare)
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Constraining the epoch of reionization with the variance statistic : simulations of the LOFAR case
- 2014
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 443:2, s. 1113-1124
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Tidskriftsartikel (refereegranskat)abstract
- Several experiments are underway to detect the cosmic-redshifted 21-cm signal from neutral hydrogen from the Epoch of Reionization (EoR). Due to their very low signal-to-noise ratio, these observations aim for a statistical detection of the signal by measuring its power spectrum. We investigate the extraction of the variance of the signal as a first step towards detecting and constraining the global history of the EoR. Signal variance is the integral of the signal's power spectrum, and it is expected to be measured with a high significance. We demonstrate this through results from a simulation and parameter estimation pipeline developed for the Low-Frequency Array (LOFAR)-EoR experiment. We show that LOFAR should be able to detect the EoR in 600 h of integration using the variance statistic. Additionally, the redshift (z(r)) and duration (Delta z) of reionization can be constrained assuming a parametrization. We use an EoR simulation of z(r) = 7.68 and Delta(z) = 0.43 to test the pipeline. We are able to detect the simulated signal with a significance of four standard deviations and extract the EoR parameters as z(r) = 7.72(-0.18)(+0.37) and Delta z = 0.53(-0.23)(+0.12) in 600 h, assuming that systematic errors can be adequately controlled. We further show that the significance of detection and constraints on EoR parameters can be improved by measuring the cross-variance of the signal by cross-correlating consecutive redshift bins.
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| 3. |
- Sanchez-Fernandez, C. J., et al.
(författare)
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Dual-band microstrip patch antenna based on short-circuited ring and spiral resonators for implantable medical devices
- 2010
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Ingår i: IET Microwaves, Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1751-8725 .- 1751-8733. ; 4:8, s. 1048-1055
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Tidskriftsartikel (refereegranskat)abstract
- Along this document, an innovative dual band microstrip patch antenna is proposed for implantable medical devices. Particularly, the covered bands are MICS (402-405 MHz) and ISM (2.4-2.48 GHz). The antenna has a multilayer configuration where the feeding line and the radiating elements are located at different levels. The radiating elements of the antenna are a split ring resonator (SRR) coupled to a Spiral. Both elements are short-circuited to the ground plane to achieve size reduction. In addition, the effects of human body geometry and dielectric properties on the characteristics of the proposed design are studied. Three models of the human body are investigated: one-layer, three-layer and a realistic human body based on the Voxel Man dataset. Finally, simulated results have been validated by measuring return losses of the antenna embedded in mimicking gels, radiation patterns (in anechoic chamber) and radiation efficiency (in reverberation chamber).
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