• Journal of the Korean earth science society
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• v.45 no.4
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• pp.292-303
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• 2024

We study quasi-spherical, supersonic accretion flows around black holes using high-accuracy numerical simulations. We describe a code, the Lagrangian Total Variation Diminishing (TVD), and a remap routine to address a specific issue in the Advection Dominated Accretion Flow (ADAF) that is, appropriately handling the angular momentum even near the inner boundary. The Lagrangian TVD code is based on an explicit finite difference scheme on mass-volume grids to track fluid particles with time. The consequences are remapped on fixed grids using the explicit Eulerian finite-difference algorithm with a third-order accuracy. Test results show that one can successfully handle flows and resolve shocks within two to three computational cells. Especially, the calculation of a hydrodynamical accretion disk without viscosity around a black hole shows that one can conserve nearly 100% of specific a ngular momentum in one-and two-dimensional cylindrical coordinates. Thus, we apply this code to obtain a numerically similar ADAF solution. We perform simulations, including viscosity terms in one-dimensional spherical geometry on the non-uniform grids, to obtain greater quantitative consequences and to save computational time. The error of specific angular momentum in Newtonian potential is less than 1% between r~10r_s and r~10⁴ r_s, where r_s is sink size. As Narayan et al. (1997) suggested, the ADAFs in pseudo-Newtonian potential become supersonic flows near the black hole, and the sonic point is r_sonic~5.3r_g for flow with α =0.3 and γ=1 .5. Such simulations indicate that even the ADAF with γ=5/3 is differentially rotating, as Ogilvie (1999) indicated. Hence, we conclude that the Lagrangian TVD and remap code treat the role of viscosity more precisely than the other scheme, even near the inner boundary in a rotating accretion flow around a nonrotating black hole.

• ALGAE
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• v.39 no.2
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• pp.75-96
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• 2024

Rhodomonas (Cryptophyceae) and species assigned to this genus have undergone numerous taxonomic revisions. This also applies to R. marina studied here as it was originally assigned as a species of Cryptomonas and later considered a variation of R. baltica, the type species. Despite being described more than 130 years ago, R. marina still lacks a comprehensive characterization. Light and electron microscopy were employed to delineate a strain from western Greenland. The living cells were 18 ㎛ long and 9 ㎛ wide, elliptical in shape with a pointed to rounded posterior and truncated anterior in lateral view. Two sub-equal flagella emerged from a vestibulum, where also a furrow extended. In transmission electron microscopy, the furrow was associated with a tubular gullet and the pyrenoid embedded in a deeply lobed chloroplast. The chloroplast contained DNA in perforations and was surrounded by starch grains. A tubular nucleomorph was enclosed within the pyrenoid matrix. In scanning electron microscopy, the inner periplast consisted of rectangular plates with rounded edges and posteriorly these were replaced by a sheet-like structure. The water-soluble pigment was Crypto-Phycoerythrin type I (Cr-PE 545). A phylogenetic inference based on SSU rDNA confirmed the identity of strain S18 as a species of Rhodomonas as it clustered with congeners but also Rhinomonas, Storeatula, and Pyrenomonas. These genera formed a monophyletic clade separated from a diverse assemblage of other cryptophyte genera. To further explore the phylogeny of R. marina a concatenated phylogenetic analysis based on the SSU rDNA-ITS1-5.8S rDNA-ITS2-LSU rDNA region was performed but included only closely related species. The secondary structure of nuclear internal transcribed spacer 2 was predicted and compared to similar structures in related species. Using morphological and molecular signatures as diagnostic features the description of R. marina was emended.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.7 no.2
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• pp.79-88
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• 1987

This study is intended to propose a system reliability analysis model for R.C. bridge superstructures based on the systems reliability theory. Approximately assuming that the ultimate capacity of the superstructures is reached, when two adjacent girders fail subsequently, a practical system reliability model is proposed, which is based on a point estimate for Level II parallel-series system modelling. The sensitivity analysis of system reliabilities for the variation of the coefficients of correlations between the failure modes is performed by applying the proposed model for R.C. T beam bridges. It is observed that the point estimate method for the proposed model corresponds to the average value of the Ditlevsen's bound, and the system reliability index, ${\beta}_s$, varies quite sensitively according to the variation of the cofficients of correlations. Systems reliabilities of a few existing T beam bridges are analyzed by applying the proposed practical system reliability method of this study, and, in addition, the preferable direction of the development of the reliability-based code calibration using the system target reliability index concept are suggested.

• Fisheries and Aquatic Sciences
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• v.10 no.1
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• pp.43-52
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• 2007

The relationships among long-term climatic change in the southern part of the Korean peninsula, oceanic conditions of the South Sea, Korea, and winter catches of major small pelagic fishes were analyzed using 33 years of time-series data from 1971-2003. In the early 1990s, winter climatic conditions in the southern part of the Korean peninsula shifted to a warmer regime with higher air temperature, weaker wind speed, and lower relative humidity. Also, winter sea surface temperature (SST) became consistently higher in the South Sea. The annual catch of major small pelagic fishes in the South Sea increased dramatically in the mid 1990s, whereas the catch of total fishes decreased in the late 1980s. In particular, the winter catch started to increase markedly in the late 1980s, and has remained over 120,000 M/T since the late 1990s. Correlation analysis of the winter catch of major small pelagic fishes and environmental factors showed that catch was correlated with air temperature (r=0.468, P< 0.01), wind speed (r=-0.732, P< 0.01), relative humidity (r=-0.73l, P< 0.01), and SST (r=0.672, P< 0.01). Multiple regression analysis between the winter catch of major small pelagic fishes (Y) and environmental factors (X) resulted in the equation: $Y=-0.017-0.217\;X_3-0.486\;X_4+0.325\;X_5(R^2=0.754,\;P<0.000)$.

• Korean Journal of Microbiology
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• v.39 no.3
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• pp.192-196
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• 2003

To obtain large pools of lactic acid bacteria, a strain was isolated from Tongchimi. Through its sugar fermentation and analysis of 16S rRNA gene, it was identified to be Lactobacillus plantarum HB1. This strain is Gram-positive and catalase-negative. In the range of 1～88 bp in the HB1 16S rRNA gene, the HB1 strain was homologous with other L. plantarum strains by almost 100%, and in the range of the rest 32 bp, the HB1 strain showed considerable variation, compared to other strains. Nitrate which may exist in radish can be easily converted to nitrite. The nitrite interacts with amine, and becomes nitrosamine which may cause stomach cancer. The culture obtained by HB1 strain could eliminate 400 ${\mu}M$ nitrite within 1.5 hr. It is necessary to isolate specific components which are involved in nitrite elimination in the culture and to study on its mechanism.

• The Journal of the Korean Society for Microbiology
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• v.22 no.3
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• pp.295-300
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• 1987

Salmonella strains isolated from blood in the Dong-san hospital, Taegu during the period from 1971 to 1986 were studied for species distribution, drug resistance, and R plasmids. The number of strains was 2,527 and all of them were classified into S. typhi and S. paratyphi A. Approximately 300 strains were isolated in the period from 1974 to 1976 and 1978, 268 in 1982, and 204 in 1983, but the numbers isolated in the 1980's have a tendency to decrease as compared with those of the 1970's. S. typhi occupied 85% or more of strains isolated until 1976, but the isolation frequency decreased yearly with some variation, and S. paratyphi A increased gradually from 1974. Only 4 strains of S. paratyphi A were resistant to some drugs, and the resistance was not transferred to E. coli by conjugation. S. typhi resistant to drugs were 15 in 1971 through 1973, 24 in 1974, and 13 in 1975, but afterwards only few resistant strains were isolated. These strains were resistant to two or more drugs; chloramphenicol(Cm), tetracycline(Tc), streptomycin(Sm), sulfisomidine(Su), ampicillin(Ap), and kanamycin(Km) and no strain resistant to other drugs tested was found. Strains resistant to 3 or less drugs didn't transfer the resistance to E. coli by conjugation. There were 15 strains resistant to four or more drugs, and were isolated in years from 1972 to 1976. These strains transferred the resistance to E. coli, and the resistance was considered to be mediated by R plasmids. Transfer frequency was higher at $25^{\circ}C$ than at $37^{\circ}C$ and patterns of transferred resistance were Cm, Tc, Sm, Su; Ap, Km; Cm. R plasmids having markers of Cm, Tc, Sm and Su were classified into Inc H1.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.4
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• pp.342-354
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• 2013

The aim of this work is to investigate and study the quantum effects in the modeling of nanoscale symmetric double-gate InAlAs/InGaAs/InP HEMT (High Electron Mobility Transistor). In order to do so, the carrier concentration in InGaAs channel at gate lengths ($L_g$) 100 nm and 50 nm, are modelled by a density gradient model or quantum moments model. The simulated results obtained from the quantum moments model are compared with the available experimental results to show the accuracy and also with a semi-classical model to show the need for quantum modeling. Quantum modeling shows major variation in electron concentration profiles and affects the device characteristics. The two triangular quantum wells predicted by the semi-classical model seem to vanish in the quantum model as bulk inversion takes place. The quantum effects thus become essential to incorporate in nanoscale heterostructure device modeling.

• Journal of Environmental Science International
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• v.18 no.4
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• pp.355-367
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• 2009

Comparison study on the land surface temperatures, which are calculated from four different algorithms for MODIS data, was carried out and the characteristics of each algorithm on land surface temperature estimation were also analysed in this study. Algorithms, which are well used for various satellite data analysis, in the comparisons are proposed by Price, Becker and Li, Ulivieri et al., and Wan. Verification of estimated land surface temperature from each algorithm is also performed using observation based regression data. The coefficient of determination ($R^2$) for daytime land surface temperature estimated from Wan's algorithm is higher than that of another algorithms at all seasons and the value of $R^2$ reach on 0.92 at spring. Although $R^2$ for Ulivieri's algorithm is slightly lower than that for Wan's algorithm, the variation pattern of land surface temperature for two algorithms are similar. However, the difference of estimated values among four algorithms become small at the region of high land surface temperature.

• Bulletin of the Korean Chemical Society
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• v.7 no.5
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• pp.367-371
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• 1986

Dynamic and equilibrium properties of n-alkane chains immersed in solvent molecules have been investigated by a molecular dynamics method. The n-alkane chain is assumed to be a chain of elements (CH$_2$) interconnected by bonds having a fixed bond length and bond angle, but each bond of the chain is allowed to execute hindered internal rotation. We studied the effect of the number of the chain elements (N$_c$ = 10, 15 and 20) on the equilibrium properties of the system, e.g., the pair correlation functions between a chain element and solvent molecules, g$_{cs}$(r), and between the chain elements, g$_{cc}$(r), and the configurational properties such as the mean-square end-to-end distance < R$^2$ >, the mean-square radius of gyration < S$^2$ >, and the eigenvalues of the moment-of-inertia tensor < S$_i^2$ > / < S$^2$ > (i = 1, 2 and 3). We also studied the dynamic properties of the system, e.g., the autocorrelation function C(A;t) where A = R$^2$(t), = S$^2$(t), or = ${\vec{V}}(t)({\vec{V}}$ = velocity of the center of mass), and the diffusion coefficient D. The g$_{cs}$(r)'s are almost equal irrespective of the change of Nc while g$_{cc}$(r) becomes larger as N$_c$ increases; The MD computed configurational properties < R$^2$2 > and < S$^2$ > were found to be a little different from the values calculated from the statistical equations of < R$^2$ > and < S$^2$ >, it may be due to the fact that our model for the MD simulations includes a long-range volume effect. From the < S$_i^2$ > / < S$^2$ >, it is found that the chain molecule has a nearly spherical shape irrespective of the variation of N$_c$. For the dynamic properties we found that the C(R$^2$;t) and C(S$^2$;t) of lower N$_c$ decay faster than those of higher N$_c$, while the C($\vec V$;t) of the center of mass in the chain is weakly dependent on the N$_c$. The center of mass diffusion coefficient D$_c$ decreases as N$_c$ increases while the end point diffusion coefficient D$_e$ is nearly equal irrespective of the change of N$_c$.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.183-191
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• 2008

This study evaluated influence of the loading head dimension on characteristics of deformation strength ($S_D$) of asphalt mixtures. Kim test and Wheel tracking (WT) test were conducted to evaluate $S_D$ characteristics with relation to WT results for various mixtures. The $S_D$ values and coefficient of variation of $S_D$ values of r=10mm were smaller than those of r=10.5mm. It was also found that $S_D$ values obtained using r=10mm loading head showed high correlations with rut parameters of WT test. It was indicated that the aggregate size and radius (r) of round cut were statistically significant variables on $S_D$ at = 0.05 level in the analysis of variance. However, in interaction of r and aggregate size showed no significance within $10{\sim}19mm$ aggregate size at the same level. Therefore, it was concluded that the diameter (D) of 40mm and the bottom edge radius (r) of 10mm was suitable dimension of loading head for deformation strength test.