• Solar Energy
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• v.13 no.2_3
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• pp.91-106
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• 1993

The purpose of this study was to investigate the enhancement of heat transfer coefficient in double pipe fluidized bed heat exchangers. The inner tube used a smooth tube and a finned tube equipped with longitudinal fins. The heat transfer coefficients between the heated tube and fluidized bed of alumina beads were calculated as a function of fluidized velocity in various particle sizes($d_p$=0.41, 0.54, 0.65, 0.77mm) and static bed heights($H_o$=50, 100, 150, 200, 250mm). The coefficient for finned tube is higher than for smooth tube. And the maximum increasing rate is 7.8 times in smooth tube and 12.9 times in finned tube.

• Journal of the Korean Vacuum Society
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• v.15 no.5
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• pp.527-533
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• 2006

Spinel $LiNi_xMn_{2-x}O_4$ thin films were synthesized up to x = 0.9 by a sol-gel method employing spin-coating. The Ni-substituted films were found to maintain cubic structure at low x but to exhibit tetragonal structure for $x{\geq}0.6$. Such cubic-tetragonal phase transition indicates that $Ni^{3+}(d7)$ ions with low-spin $(t_{2g}^6,e_g^1)$ state occupy the octahedral sites of the compound, thus being subject to the Jahn-Teller distortion. By x-ray photoelectron spectroscopy both $Ni^{2+}$ and $Ni^{3+}$ ions were detected. Optical properties of the $LiNi_xMn_{2-x}O_4$ films were investigated by spectroscopic ellipsometry (SE) in the visible?ultraviolet range. The measured dielectric function spectra by SE mainly consist of broad absorption structures attributed to charge-transfer (CT) transitions, $O^{2-}(2p){\rightarrow}Mn^{4+}(3d)$ for 1.9 $(t_{2g})$ and $2.8{\sim}3.0$ eV $(e_g)$ structures and $O^{2-}(2p){\rightarrow}Mn^{3+}(3d)$ for 2.3 $(t_{2g})$ and $3.4{\sim}3.6$ eV $(e_g)$ structures. Also, sharp absorption structures were observed at about 1.6, 1.7, and 1.9 eV, interpreted as due to d-d crystal-field transitions within the octahedral $Mn^{3+}$ ion. The strengths of these absorption structures are reduced by the Ni substitution. Rapid reduction of the CT transition strength involving the eg states for x = 0.6 is attributed to the reduced wavefunction overlap between the $e_g$ and the $O^{2-}(2p)$ states due to the tetragonal extension of the lattice constant by the Jahn-Teller effect.

• Journal of Veterinary Clinics
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• v.32 no.4
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• pp.301-307
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• 2015

The purpose of this study was to compare echocardiographic parameters of cloned beagle dogs with the previously reported reference range. Seven cloned dogs were assessed for anatomical features and cardiac function through left- and right-sided heart and right ventricle outflow tract from M-mode, 2D-mode, pulsed wave Doppler and tissue Doppler imaging. In all the cloned dogs, there were no abnormalities in anatomical structure and measurements were within the normal reference range. In addition, left- and right-sided myocardial function was within the normal reference range. Especially, pulmonary hypertension and right-sided heart failure frequently encountered in cloned animals were not recognized in cloned dogs. In conclusion, no evidence of cardiovascular dysfunction in mature cloned dogs could be identified either at birth or the growing stage in this study. Therefore, serious adverse effects of somatic cell nuclear transfer technology including transgenesis on cardiac morphology and function were not found in cloned dogs.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.263-263
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• 2013

This work examines the dynamic properties of ice surfaces in vacuum for the temperature range of 140~180 K, which extends over the onset temperatures for ice sublimation and the phase transition from amorphous to crystallization ice. In particular, the study focuses on the transport processes of excess protons and chloride ions in ice and their segregative behavior to the ice surface. These phenomena were studied by conducting experiments with a relatively thick (~100 BL) ice film constructed with a bottom $H_2O$ layer and an upper $D_2O$ layer, with excess hydronium and chloride ions trapped at the $H_2O$/$D_2O$ interface as they were generated by the ionization of hydrogen chloride. The migration of protons, chloride ions, and water molecules to the ice film surface and their H/D exchange reactions were measured as a function of temperature using the methods of low energy sputtering (LES) and Cs+ reactive ion scattering (RIS). Temperature programmed desorption (TPD) experiments monitored the desorption of water and hydrogen chloride from the surface. Our observations indicated that both hydronium and chloride ions migrated from the interfacial layer to segregate to the surface at high temperature. Hydrogen chloride gas desorbs via recombination reaction of hydronium and chloride ions floating on the surface. Surface segregation of these species is driven by thermodynamic potential gradient present near the ice surface, whereas in the bulk, their transport is facilitated by thermal diffusion process. The finding suggests that chlorine activation reactions of hydrogen chloride for polar stratospheric ice particles occur at the surface of ice within a depth of at most a few molecular layers, rather than in the bulk phase.

• International Area Studies Review
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• v.20 no.1
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• pp.147-165
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• 2016

We empirically examine the validity of second generation endogenous growth theory suing 21 OECD countries' panel data(1981~2011). Due to non-stationarity in all variables, we test the cointegrated relationships strongly supporting the semi-endogenous growth model. In the estimation of total factor productivity growth function, the growth of domestic and foreign R&D investment levels statistically significantly affect total factor productivity growth. R&D intensity, however, has significant impacts on the total factor productivity growth only in a few models, and international technology gap also has positive impacts on GDP growth. Thus the semi-endogenous growth model is relatively supported while fully endogenous growth model is weakly and occasionally supported in OECD countries. The policy implication of supporting the semi-endogenous growth model is that the sustaining growth requires increasing R&D expenditures.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.210.2-210.2
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• 2012

Using Fresnel reflection and Hapke BRDF model with Apollo 10084 soil sample's scattering properties, we constructed a real scale optical lunar model and used it to simulate lunar apparent albedo and moonshine. For Fresnel reflection, the refractive index of $1.68{\pm}0.5$ was used. For Hapke BRDF parameters from BUGs BRDF measurement, the single scattering with w=0.33, hot spot width h=0.017, average phase angle ${\zeta}$=-0.086 and Legendre polynomial coefficients b=0.308, c=0.425 in wavelength 700nm with two types of Henyey-Greenstein phase function was applied. The computation model includes the Sun as a Lambertian scattering sphere, emitting 1.5078 W/m2 at 700nm in wavelength. The Sun and Moon models were then imported into the IRT based radiative transfer computation. The trial simulation of the irradiance levels of moonshine lights shows that they agree well with the ROLO measurement data. We then estimate the lunar apparent albedo to 0.11. The results are to be compared with the measurement data.

• Korean Journal of Optics and Photonics
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• v.31 no.2
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• pp.59-70
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• 2020

We discuss a modified numerical model based on the Monte Carlo radiative transfer (MCRT) method, i.e., the MCRT matrix method, for the analysis of atmospheric scattering effects in three-dimensional flash LIDAR systems. Based on the MCRT method, the radiative transfer function for a LIDAR signal is constructed in a form of a matrix, which corresponds to the characteristic response. Exploiting the superposition and convolution of the characteristic response matrices under the paraxial approximation, an extended computer simulation model of an overall flash LIDAR system is developed. The MCRT matrix method substantially reduces the number of tracking signals, which may grow excessively in the case of conventional Monte Carlo methods. Consequently, it can readily yield fast acquisition of the signal response under various scattering conditions and LIDAR-system configurations. Using the computational model based on the MCRT matrix method, we carry out numerical simulations of a three-dimensional flash LIDAR system operating under different atmospheric conditions, varying the scattering coefficient in terms of visible distance. We numerically analyze various phenomena caused by scattering effects in this system, such as degradation of the signal-to-noise ratio, glitches, and spatiotemporal spread and time delay of the LIDAR signals. The MCRT matrix method is expected to be very effective in analyzing a variety of LIDAR systems, including flash LIDAR systems for autonomous driving.

• Journal of Navigation and Port Research
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• v.27 no.2
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• pp.193-198
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• 2003

The slew motion of a single point moored ship by the external forces is considered to control itself. The maneuvering equations of motion are derived to express the motion of a ship. The wind forces and the wave forces are considered as the external forces of the single point moored ship in the simulation. The wave forces in the time domain analysis are generated from the frequency transfer function calculated by 3-D source distribution method. The wind forces are used the results from OCIMF(1994). To control the slew motion, the bow thruster and the bridle anchoring with 2nd anchor are used in the numerical simulation.

• Korean Journal of the Atmospheric Sciences
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• v.78 no.9
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• pp.2657-2675
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• 2021

A new k-distribution scheme of longwave radiation without the correlated-k-distribution assumption is developed. Grouping of spectral points is based on the line-by-line (LBL)-calculated absorption coefficient k at a few sets of reference pressure p_r and temperature θ_r, where the cooling rate is substantial in a spectral band. In this new scheme, the range of k(p_r, θ_r) of a band is divided into a number of equal intervals, or g groups, in log₁₀(k_r). A spectral point at the wavenumber ν is identified with one of the g groups according to its k_ν(p_r, θ_r). For each g group, a Planck-weighted k-distribution function H_g and a nonlinearly averaged absorption coefficient ${\bar{k}}_g(p,{\theta})$ are derived. The function H_g and the absorption coefficient ${\bar{k}}_g(p,{\theta})$ constitute the new k-distribution scheme. In this k-distribution scheme, a spectral point can only be identified with a g group regardless of pressure and temperature, which is different from the correlated-k distribution scheme. The k-distribution scheme is applied to the H₂O, CO₂, O₃, N₂O, and CH₄ absorption bands, and results are compared with LBL calculations. To balance between the accuracy and the computational economy, the number of g groups in a band of a given gas is chosen such that 1) the difference in cooling rate is <0.1 K day^-1 in the troposphere and <1.0 K day^-1 in the stratosphere and 2) the difference in fluxes is <0.5 W m^-2 at both the top of the atmosphere and the surface. These differences are attained with 130 g groups, which is the sum of the g groups of all five gases.

• Journal of Energy Engineering
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• v.12 no.2
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• pp.84-92
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• 2003

A one-dimensional thermal-hydraulic analysis computer program is developed for thermal sizing of a copper bonded steam generator. It is assumed that the conduction heat transfer of copper region between the hot side and the cold side tube is one-dimensional and its thermal resistance is derived as a function of a tube pitch. The flow regions of the water/steam side are divided into four regions: subcooled, saturated, film boiling, and super-heated. The number of tube selected ranges from 250 to 3500 and the pitch to tube diameter (P/D) ratios are 1.4, 1.6 and 1.8 for the parametric study calculation. The calculation results showed that when the number of tube was 2500, the length of the heating tube was about 12 m and the outside diameter of the steam generator was about 3 m. If the P/D ratio increases, the thermal resistance of copper component also increases, however the length of the heating tube is not so much increased.