• Nuclear Engineering and Technology
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• v.21 no.4
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• pp.308-320
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• 1989

The objective of this work is to investigate the effects of diminished primary coolant inventory and the presence of noncondensible gas during single- and two-phase natural circulation in a PWR loop model. The test model was composed of two loops with a U-tube heat exchanger in each loop. Through a series of tests, it has been confirmed that the two-phase natural circulation flow rates were greatly dependent on primary coolant inventory as previous investigators observed. The primary coolant inventory limit to maintain two-phase natural circulation was found to be the amount of the coolant necessary to keep the waterline of the coolant nozzle hole center in this model. The presence of noncondensible gas impede the single-phase natural circulation, but it did not affect the two-phase natural circulation significantly.

• Natural Product Sciences
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• v.9 no.4
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• pp.235-240
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• 2003

Tectorigenin has an apoptosis-inducing ability and immunosuppressive activity. We investigated the effect of tectorigenin on Phase I and II enzyme activities to elucidate the pharmacological action of the immunosuppressive tectorigenin in the diabetic rat. This compound was obtained from the hydrolysis of tetoridin isolated from the flower of Pueraria thumbergiana (Leguminosae). This crude drug (Puerariae Flos) has been used as a therapeutic for diabetes mellitus in traditional Korean medicine. Tecotrigenin inhibited the formation of malondialdehyde (MDA) and hydroxy radicals in serum and liver but promoted superoxide dismutase (SOD) activity. Low MDA contents and low xanthine oxidase and aldehyde oxidase activities were observed in the tectorigenin-treated rats, suggesting that such Phase I enzyme activities are the major source of lipid peroxidation. However, tectorigenin increased Phase II enzyme activities such as SOD, glutathione peroxidase and catalase, suggesting the activation of free radical-scavenging enzymes. The activities of tectorigenin were comparable to those of glibenclamide, which was employed as a positive control. These results suggest that tectorigenin may share some biological properties with glibenclamide in insulin-dependent-diabetes mellitus (IDDM).

• Korean Journal of Adult Nursing
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• v.21 no.2
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• pp.212-224
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• 2009

Purpose: The purpose of this study was to examine the effects of the cardiac rehabilitation program(Phase III) on cardiovascular and cardiorespiratory function in the elderly (age, ${\geq}$ 60) who experienced acute myocardial infarction. Methods: The design of research was nonequivalent control group pretest-posttest design. Subjects were 10 people in the experimental group and 10 in the control group. The intervention program was the cardiac rehabilitation program(Phase III), and was performed for 50 ~ 60 minutes, twice a week for 8 weeks. The dependent variables were the cardiovascular and cardiorespiratory function. Results: Significant differences were shown in RHR, RSBP, SRPP, SBS, BMI, PT of the experimental group after the intervention. As for the differences in the amount of changes, there were differences among groups in RHR, RSBP, SRPP, SBS, PMET, and PT of the experimental group. Conclusion: The cardiac rehabilitation program(Phase III) may be effective in improving cardiovascular function and enhancing cardiorespiratory function in elderly patients with acute myocardial infarction.

• Environmental Engineering Research
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• v.25 no.3
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• pp.281-289
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• 2020

Environmental fate of ionizable organic pollutants such as perfluoroalkyl acids (PFAAs) are of increasing interest but has not been well understood because of uncertain values for parameters related with atmospheric interphase partitioning behavior. In the present study, not only the values for air-water partition coefficient (K_AW) and dissociation constant (pKa) of PFAAs were induced by adjusting to in situ measurements of air-water distribution coefficient between vapor phase and rainwater but also gas-particle partition coefficients were also estimated using three-phase partitioning model of ionizable organic pollutants, in situ measurements of PFAAs in aerosol and air vapor phase, and obtained parameter values. The pKa values of PFAAs we obtained were close to the minimum values suggested in literature except for perfluorooctane sulfonic acids, and COSMOtherm-modeled K_AW values were assessed to more appropriate among suggested values. When applying parameter values we obtained, it was predicted that air particle-associated fate and transport of PFAAs could be negligible and PFAAs could distribute ubiquitously along the transection from urban to rural region by pH-dependent phase transfer in air. Our study is expected to have some implications in prediction of the environmental redistribution of other ionizable organic compounds.

• Journal of The Korean Astronomical Society
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• v.14 no.2
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• pp.55-71
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• 1981

On the basis of observational constraints, particularly the relationship between metal abundance and cumulative stellar mass, a simple two-zone disk-halo model for the chemical evolution of our Galaxy was investigated, assuming different chemical processes in the disk and halo and the infall rates of the halo gas defined by the halo evolution. The main results of the present model calculations are: (i) The halo formation requires more than 80% of the initial galactic mass and it takes a period of $2{\sim}3{\times}10^9$ yrs. (ii) The halo evolution is divided into two phases, a fast collapse phase ($t=2{\sim}3{\times}10^8$ yrs) during which period most of the halo stars $({\sim}95%)$ are formed and a later slow collapse phase which is characterized by the chemical enrichment due to the inflow of external matter to the halo. (iii) The disk evolution is also divided into two phases, an active disk formation phase with a time-dependent initial mass function (IMF) up to $t{\approx}6{\times}10^9$ yrs and a later steady slow formation phase with a constant IMF. It is found that at the very early time $t{\approx}5{\times}10^8$ yrs, the metal abundance in the disk is rapidly increased to ${\sim}1/3$ of the present value but the total stellar mass only to ${\sim}10%$ of the present value, finally reaching about 80% of the present values toward the end of the active formation phase.

• Korean Journal of Materials Research
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• v.16 no.6
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• pp.394-399
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• 2006

Ferroelectric $HoMnO_3$ thin films were deposited on the Si(100) substrate at $700^{\circ}C$ for 2 hrs by metalorganic chemical vapor deposition (MOCVD) and post-annealed at 850oC by rapid thermal process (RTP). Electrical properties and crystalline phases of $HoMnO_3$ thin films were investigated as a function of postannealing time. Single phase of hexagonal symmetry with c-axis preferred orientation was obtained from $HoMnO_3$ thin films post-annealed at $850^{\circ}C$ for 5 min, while the c-axis preferred orientation was decreased with the increase of post-annealing time, and the thin films post-annealed at $850^{\circ}C$ for 15 min showed the mixture phases of hexagonal and orthorhombic symmetry. P-E (Polarization-Electric field) hysteresis loop of ferroelectric $HoMnO_3$ thin films was observed only for the single phase of hexagonal symmetry, but that was not observed for the mixture phases of the hexagonal and orthorhombic symmetry, which was discussed with the bond valence of Mn ion of crystalline phase. Leakage current density was dependent on the microstructure of thin films as well as the change of valence of Mn ion.

• Journal of Microbiology
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• v.39 no.1
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• pp.74-78
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• 2001

The transcription of the chitin synthase genes (chss) was cell cycle-regulated in Aspergillus nidulans and the expression pattern was classified into two groups. Group one, containing chsA and chsC, showed decreasing transcription level upon entry into the S-phase and no further variation during the remainder of the cell cycle. However, group two, containing chsB, chsD, and csmA showed a sharp decrease of mRNA level upon entry into the G2-phase and an increase during the M-phase. Our results suggested that the chss, belonging to same group with the similar expression pattern during the cell cycle are functionally linked and that chsD may play a role in hyphal growth and development in A. nidulans.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.5
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• pp.96-104
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• 2000

This paper represents to develop a computer software system which is capable to analyze the phase transformation of high strength steel(BV-AH32) and to predict heat transfer and welding residual stress due to phase transformation during Gas Metal Arc(GMA) welding. The developed model was considered temperature dependent properties such as young's modules, coefficient of thermal expansion and yield stress as well as the double ellipsoidal heat distribution by the moving arc. From the results, it was found that the longitudinal and transverse residual stresses calculated by the coupled analysis of heat transfer, residual stress and phase transformation showed good agreement with the experimental data. In addition, the temperature distribution as well as longitudinal and transverse residual stresses of weldment by the 1-pass and 2-pass of welding were also determined.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.24-35
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• 1997

Melting process inside in a vertical cylinder has been investigated numerically to observe heat transfer characteristics in the latent heat storage vessel applied to the thermal storage system. The time-dependent boundary fitted coordinate system was introduced to overcome the difficulty caused by the moving boundary. The present results are in good agreement with the available previous data when the initial subcooling effect of the solid phase is not considered. It is found that the melting is promoted by the natural convection, but is delayed by the initial subcooling effect of the solid phase.

• Proceedings of the KWS Conference
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• 1999.10a
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• pp.310-313
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• 1999

This paper represents to develop a computer software system which is capable to analyze the phase transformation of high strength steel(BV-AH32) and to predict heat transfer, residual stress due to phase transformation during Gas Metal Arc(GMA) welding. The developed model was taken into account temperature dependent of young's modules, coefficient of thermal expansion and yield stress as well as the double ellipsoidal heat distribution by the moving arc. The results showed that the longitudinal and transverse residual stresses calculated by the coupled analysis of heat transfer, residual stress and phase transformation are in good agreement with the experimental data. In addition, the temperature distribution as well as longitudinal and transverse residual stresses of weldment were determined at the 1-pass and 2-pass of welding.