• The Bulletin of The Korean Astronomical Society
• /
• v.34 no.1
• /
• pp.51-51
• /
• 2009

• Journal of Astronomy and Space Sciences
• /
• v.33 no.2
• /
• pp.105-108
• /
• 2016

In this work, based on our previous calculations of spectral energy distributions for a sample of Fermi blazars (Fan et al. 2015a), we calculated the radio loudness and performed correlation analyses. Our analysis results show that radio loudness is closely anti-correlated with synchrotron peak frequency and positively correlated with gamma-ray luminosity, suggesting that the gamma-ray emissions are strongly beamed.

• Journal of Astronomy and Space Sciences
• /
• v.33 no.2
• /
• pp.93-99
• /
• 2016

A redback system is a binary system composed of a pulsar and a main sequence star. The inverse Compton (IC) scattering between the stellar soft photons and the relativistic pulsar wind will generate orbital-modulating GeV photons. We look for these IC emissions from redback systems. A multi-wavelength observation of an unassociated gamma-ray source, 3FGL J2039.6-5618, by Salvetti et al. (2015) detected an orbital modulation with a period of 0.2 days in both X-ray and optical cases. They suggested 3FGL J2039.6-5618 to be a new redback candidate. We analyzed the gamma-ray emission of 3FGL J2039.6-5618 using the data from the Fermi large area telescope (Fermi-LAT) and obtained the spectrum in different orbital phases. We propose that the spectrum has orbital dependency and estimate the characteristic energy of the IC emission from the stellar-pulsar wind interaction.

• Bulletin of the Korean Chemical Society
• /
• v.34 no.3
• /
• pp.912-916
• /
• 2013

The electronic structure of LaFeAsO was analyzed by tight-binding band calculation based upon the normal and shrunk lattices. A strong Fermi surface nesting was found in the normal LaFeAsO, while most of the nesting area was disappeared in the shrunk LaFeAsO. It was found, therefore, high pressure atmosphere is required to become a superconductor for LaFeAsO by suppressing the SDW (spin density wave) state through the disappearance of the Fermi surface nesting.

• Journal of applied mathematics & informatics
• /
• v.27 no.5_6
• /
• pp.1265-1277
• /
• 2009

In this paper, we apply a new decomposition method for solving initial and boundary value problems, which is due to Noor and Noor [18]. The analytical results are calculated in terms of convergent series with easily computable components. The diagonal Pade approximants are applied to make the work more concise and for the better understanding of the solution behavior. The proposed technique is tested on boundary layer problem; Thomas-Fermi, Blasius and sixth-order singularly perturbed Boussinesq equations. Numerical results reveal the complete reliability of the suggested scheme. This new decomposition method can be viewed as an alternative of Adomian decomposition method and homotopy perturbation methods.

• Journal of Astronomy and Space Sciences
• /
• v.33 no.3
• /
• pp.147-166
• /
• 2016

A radio-quiet γ-ray pulsar is a neutron star that has significant γ-ray pulsation but without observed radio emission or only limited emission detected by high sensitivity radio surveys. The launch of the Fermi spacecraft in 2008 opened a new epoch to study the population of these pulsars. In the 2^nd Fermi Large Area Telescope catalog of γ-ray pulsars, there are 35 (30 % of the 117 pulsars in the catalog) known samples classified as radio-quiet γ-ray pulsars with radio flux density (S₁₄₀₀) of less than 30 μJy. Accompanying the observations obtained in various wavelengths, astronomers not only have the opportunity to study the emitting nature of radio-quiet γ-ray pulsars but also have proposed different models to explain their radiation mechanism. This article will review the history of the discovery, the emission properties, and the previous efforts to study pulsars in this population. Some particular cases known as Geminga-like pulsars (e.g., PSR J0633+1746, PSR J0007+7303, PSR J2021+4026, and so on) are also specified to discuss their common and specific features.

• Journal of the Korean Vacuum Society
• /
• v.1 no.1
• /
• pp.83-87
• /
• 1992

Rencently, angle-resolved ultraviolet photoemission measurements of the Fermi surface contours for Mo(011) and W(011) are reported. The electron contour of W(011) is expanded upon hydrogen adsorption, which implies that the surface states consisting of electron pockets are shifted to higher binding energy. This phenomena can be explained by the band flattening. We explained here the reconstruction of W(011) surface induced by adsorption of hydrogen in terms of band flattening of surface states with a combination of S. E. Trullinger long range dipole-dipole interaction force and Kohn anomaly.

• Laser Solutions
• /
• v.11 no.4
• /
• pp.13-20
• /
• 2008

The damage threshold measurement of gold films is carried out with ultrashort-pulse laser. An enhanced two temperature model is developed to encounter the limitation of linear modeling during ultrashort pulse laser ablation. In which the electron heat capacity is calculated using a quantum mechanical approach based on a Fermi-Dirac distribution, temperature-dependent electron thermal conductivity valid beyond the Fermi temperature is adopted, and reflectivity and absorption coefficient are estimated by applying a temperature-dependent electron relaxation time. The predicted damage threshold using the proposed enhanced modelclosely agreed with experimental results, demonstrating the importance of considering transient thermal and optical properties in the modeling of ultrashort pulse laser ablation.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2000.01a
• /
• pp.235-238
• /
• 2000

We have performed ab initio pseudopotential electronic structure calculations for various edge geometries of the (n,n) singlewall nanotube with on without applied fields. Among the systems studied, the one with the zigzag edge exposed by a slant out is found to be the most favorable for the emission due to the existence of unpaired dangling bond states around the Fermi level. The next favorable geometry is the capped nanotube where ${\pi}-bonding$ states localized at the cap and pointing to We tube axis direction occur at the Fermi level. A scaling rule of the induced field linean in the aspect ratio of the tube is also obtained.

• Journal of Magnetics
• /
• v.1 no.1
• /
• pp.4-8
• /
• 1996

Employing the LMTO band method, we have studied electronic and magnetic properties of Fe/Si/Fe trilayer in which the z-direction is chosen to be (111) direction of FeSi with B2 phase, We have also determined electronic structure of bulk FeSi, as a reference material. The ground state of FeSi is paramagnetic insulator with a band gap of 0.05 eV. Band structures of Fe/Si/Fe with varying the thickness of the spacer layer reveal that the spacer layer is metallic, and the states along the growth direction do not disperse much reflecting a two-dimensional nature. Magnetic moment of Fe atom in the interfacial layer of Fe/Si/Fe is reduced a lot as compared to the bulk value, suggesting a strong hybridization between Fe and Si states. The geometry of the Fermi surface indicates that the magnetic coupling period of ~8ML (monolayers) in Fe/Si/Fe is explained with a short Fermi wave vector of bcc Si.