• Journal of The Korean Astronomical Society
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• v.37 no.5
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• pp.349-353
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• 2004

Magnetic fields are an important ingredient of galaxy clusters and are indirectly observed on cluster scales as radio haloes and radio relics. One promising method to shed light on the properties of cluster wide magnetic fields is the analysis of Faraday rotation maps of extended extragalactic radio sources. We developed a Fourier analysis for such Faraday rotation maps in order to determine the magnetic power spectra of cluster fields. In an advanced step, here we apply a Bayesian maximum likelihood method to the RM map of the north lobe of Hydra A on the basis of our Fourier analysis and derive the power spectrum of the cluster magnetic field. For Hydra A, we measure a spectral index of -5/3 over at least one order of magnitude implying Kolmogorov type turbulence. We find a dominant scale of about 3 kpc on which the magnetic power is concentrated, since the magnetic autocorrelation length is ${\lambda}_B = 3 {\pm} 0.5\;kpc$. Furthermore, we investigate the influences of the assumption about the sampling volume (described by a window function) on the magnetic power spectrum. The central magnetic field strength was determined to be ${\~}7{\pm}2{\mu}G$ for the most likely geometries.

• 한국전산유체공학회:학술대회논문집
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• 2009.11a
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• pp.97-102
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• 2009

Translocation of biopolymers such as DNA and RNA through a nano-pore is an important process in biotechnology applications. The translocation process of a biopolymer through an artificial nano-pore in the presence of a fluid solvent is simulated. The polymer motion is simulated by Langevin molecular dynamics (MD) techniques while the solvent dynamics are taken into account by lattice-Boltzmann method (LBM). The hydrodynamic interactions are considered explicitly by coupling the polymer and solvent through the frictional and the random forces. From simulation results we found that the hydrodynamic interactions between polymer and solvent speed-up the translocation process. The translocation time ${\tao}_T$ scales with the chain length N as ${{\tau}_T}^{\propto}N^{\alpha}$. The value of scaling exponents($\alpha$) obtained from our simulations are $1.29{\pm}0.03$ and $1.41{\pm}0.03$, with and without hydrodynamic interactions, respectively. Our simulation results are in good agreement with the experimentally observed value of $\alpha$, which is equal to $1.27{\pm}0.03$, particularly when hydrodynamic interaction effects are taken into account.

• Journal of computational fluids engineering
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• v.8 no.2
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• pp.33-41
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• 2003

A simplified simulation model is designed to investigate the vacuum-driven bonding of glass panels in the cell process for LCD manufacturing. The bonding process is modelled by the transient flow of a weakly-compressible fluid in a very thin channel between two horizontal glass panels. An order of magnitude scaling analysis is conducted based on the characteristic feature of the channel of which height is much smaller than the horizontal length scales. It is revealed that the flow in the channel is represented by a Poiseuille flow of a compressible fluid. A finite volume model has been constructed to acquire the numerical solution to the derived simplified equations. For a simple test problem of pressure-driven microchannel flow, an assessment is made of the accuracy and validity of the proposed model. The basic aspects of vacuum-driven bonding are examined numerically, and the applicability of the present simulation model is illustrated.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.56.4-57
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• 2015

We present the optical design and a sensitivity analysis for a wide field of view (FOV) instrument operating at UV and IR wavelengths. The ongoing investigation is performed in collaboration with Omnisys Instruments (Sweden) and focuses on a telluric-limb-viewing instrument that will fly in a low Earth orbit to study mesospheric wave structures over a wide range of horizontal scales in the altitude range 80 - 100 km. The instrument has six wavelength channels which consist of 4 channels of IR and 2 of UV. We are proposing an optical design based on three mirror aplanatic off-axis reflective system. The entrance pupil diameter and effective focal length are 45 mm and 270 mm, respectively. The FOV is $5.5^{\circ}{\times}1^{\circ}$ and the secondary mirror is set for stop. The optical specification is required to have an encircled energy of at least 80 % within a diameter of 21 um. We performed sensitivity analysis for the longest wavelength of 772 nm in consideration of the diffraction limit of system. The results show that tolerance limits for positions and angles of the mirrors are not very sensitive compared with typical error budgets of manufacturing and assembling process. The secondary mirror has the most sensitive tolerance for surface figure of 250 nm in root-mean-square.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.5
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• pp.685-697
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• 1998

Series of recent k-.epsilon. model modification have been carried out with the aid of DNS data to include the effect of near wall. Though these methods opened new way of turbulence modelings, newly developed turbulence models of its kind had yet shortcomings in prediction for the turbulent flows with various Reynolds numbers and various geometric conditions. As a remedy for these shortcomings, a new k-.epsilon. model proposed here by improving the dissipation rate equation and the damping function for eddy viscosity model. The new dissipation rate equation was modeled based on the energy spectrum and magnitude analysis. The damping function for eddy viscosity was also formulated on the ground of distribution of dissipation rate length scales near a wall and the DNS data. The new k-.epsilon. model was applied to the fully developed turbulent flows in a channel and a pipe with a wide range of Reynolds numbers. Prediction results showed that the present model represents properly the turbulence properties in all turbulent regions over a wide range of Reynolds numbers.

• Applied Microscopy
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• v.47 no.1
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• pp.43-49
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• 2017

A new method was introduced to distinguish the ferrite, bainite and martensite in transformation induced plasticity (TRIP) steel by using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). EBSD is a very powerful microstructure analysis technique at the length scales ranging from tens of nanometers to millimeters. However, iron BCC phases such as ferrite, bainite and martensite cannot be easily distinguished by EBSD due to their similar surface morphology and crystallographic structure. Among the various EBSD-based methodology, image quality (IQ) values, which present the perfection of a crystal lattice, was used to distinguish the iron BCC phases. IQ values are very useful tools to discern the iron BCC phases because of their different density of crystal defect and lattice distortion. However, there are still remaining problems that make the separation of bainite and martensite difficult. For instance, these phases have very similar IQ values in many cases, especially in deformed region; therefore, even though the IQ value was used, it has been difficult to distinguish the bainite and martensite. For more precise separation of bainite and martensite, IQ threshold values were determined by a correlative TEM analysis. By determining the threshold values, iron BCC phases were successfully separated.

• Journal of Fashion Business
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• v.14 no.3
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• pp.1-19
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• 2010

The Assyrians usually wore two types - the tunic and the shawl. These two types were worn alone, or in combination and changes were introduced by varying the proportions of the tunic or shawl. The tunic appeared to be of the sleeves are short and reaching to the ankles or shortened to knee length according to the rank. Assyrian shawl pattern can be divided into five distinct styless. Many of the styles were suitable for costumes to wear in religious plays and pageants. Fringed shawls were the trademark of forma1 Assyrian costume. The usual badge of rank was a long fringed shawl. Intermediate rank wore shawl with short fringes and lower grade wore no shawl at all. The military costume was comparative uniformity : conical helmets was regarded as Scythic in character, short, fringed tunics, wide belts or helmet, round caps and long tunics covered in metal scales, belted at the waist. Assyrian woman costume was the long tunic with fringed hem and a long fringed shawl or was a plaid tunic and wide belt over it. They wore gold crown and horned Cap and tiara, ugal (head-dress) and the most ordinary earrings were the drop and the cross shape and necklace was made of the coloured stones and bracelets ended with heads of animal was regarded as Scythy style or adorned with a rosette at the centre.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.10
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• pp.820-826
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• 2009

The anisotropic phonon conductions with varying Joule heating rate of the silicon film in Silicon-on-Insulator devices are examined using the electron-phonon interaction model. It is found that the phonon heat transfer rate at each boundary of Si-layer has a strong dependence on the heating power rate. And the phonon flow decreases when the temperature gradient has a sharp change within extremely short length scales such as phonon mean free path. Thus the heat generated in the hot spot region is removed primarily by heat conduction through Si-layer at the higher Joule heating level and the phonon nonlocality is mainly attributed to lower group velocity phonons as remarkably dissimilar to the case of electrons in laser heated plasmas. To validate these observations the modified phonon nonlocal model considering complete phonon dispersion relations is introduced as a correct form of the conventional theory. We also reveal that the relation between the phonon heat deposition time from the hot spot region and the relaxation time in Si-layer can be used to estimate the intrinsic thermal resistance in the parallel heat flow direction as Joule heating level varies.

• Journal of the Korean Society of Combustion
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• v.10 no.3
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• pp.25-33
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• 2005

Fast-time instability is investigated for diffusion flames with Lewis numbers greater than unity by employing the numerical technique called the Evans function method. Since the time and length scales are those of the inner reactive-diffusive layer, the problem is equivalent to the instability problem for the $Li\tilde{n}\acute{a}n#s$ diffusion flame regime. The instability is primarily oscillatory, as seen from complex solution branches and can emerge prior to reaching the upper turning point of the S-curve, known as the $Li\tilde{n}\acute{a}n#s$ extinction condition. Depending on the Lewis number, the instability characteristics is found to be somewhat different. Below the critical Lewis number, $L_C$, the instability possesses primarily a pulsating nature in that the two real solution branches, existing for small wave numbers, merges at a finite wave number, at which a pair of complex conjugate solution branches bifurcate. For Lewis numbers greater than $L_C$, the solution branch for small reactant leakage is found to be purely complex with the maximum growth rate found at a finite wave number, thereby exhibiting a traveling nature. As the reactant leakage parameter is further increased, the instability characteristics turns into a pulsating type, similar to that for L < $L_C$.

• Fisheries and Aquatic Sciences
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• v.15 no.4
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• pp.313-316
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• 2012

Two unrecorded species of the snapper, Lutjanus malabaricus (296.0 mm standard length [SL]) and L. stellatus (350.0 mm SL) belonging to the family Lutjanidae, were first collected from the western coastal waters of Jeju Island, Korea. L. malabaricus is characterized by having a dark marking on the upper half of the caudal peduncle, a band of vomerine teeth that does not protrude posteriorly at the middle, and nine anal soft rays. Compared to its Korean relative, L. malabaricus is distinguishable by having rows of scales that run obliquely in the dorsal-posterior direction above the lateral line (vs. parallel to the lateral line in L. argentimaculatus). L. stellatus can be identified by the absence of wavy blue lines on the head (vs. many blue lines in L. rivulatus) and presence of a white spot above the lateral line (vs. a black blotch on the lateral line in L. rivulatus). We propose new Korean names, "Jin-hong-tung-dom" and "Huin-jeom-tung-dom," for L. malabaricus and L. stellatus, respectively.