• Journal of the Korean Chemical Society
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• v.55 no.6
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• pp.952-959
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• 2011

Novel phosphorylated derivatives of ribavirin 5-16 were synthesized by the reaction of 4-nitrophenyl phosphorodichloridate with various amino acid esters in the presence of triethylamine in dry tetrahydrofuran through the intermediates 3. On further reaction of 3 with ribavirin in THF and pyridine in the presence of TEA afforded the title compounds 5-16. Their structures were characterized by IR, $^1H$, $^{13}C$, $^{31}P$ NMR and mass spectral analyses. All the title compounds were found to exhibit potent in vitro anticancer activity against MCF-7 breast cancer cell lines.

• Bulletin of the Society of Naval Architects of Korea
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• v.21 no.2
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• pp.29-34
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• 1984

The degree of deviation from the orthogonality relations of the actual ship's natural modes and its effects on the vibration responses are numerically investigated. The results show that, for the practical application of the modal analysis, it is not an essential requirement in utilization of the expansion theorem to assume the added mass being constant regardless of the mode shapes, or to take the dry hull's natural modes. That is, it is more reasonable to take the actual ships natural modes as the set of the normal modes and to get the solution of the normal coordinates equation by neglecting both the inertia coupling and the stiffeness coupling.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.3
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• pp.220-229
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• 2003

An experimental study on the air-side pressure drop and heat transfer coefficient of slit fin-tube heat exchanger has been carried out. The data reduction methodology for air-side heat transfer coefficients in the literature is not based on a consistent approach. This paper focuses on new method of data reduction to obtain the air-side performance of fin-tube heat exchanger using R22 and recommends standard procedures for dry surface heat transfer estimation in fin-tube heat exchanger having refrigerant on the tube-side. Results are presented as plots of friction f-factor and Colburn j -factor against Reynolds number based on the fin collar outside diameter and compared with previous studies. The data covers a range of refrigerant mass fluxes of 150~250 kg/$m^2$s with air flows at velocity ranges from 0.6 m/s to 1.6 m/s.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1177-1184
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• 2005

A numerical analysis was carried out on the heat and mass transfer, and pressure drop characteristics of the modular tube bundle heat exchanger. The finite volume method with a $k-\varepsilon$ turbulence model was used for the analysis. Due to condensation, the total heat transfer rate is observed about $4\~8\%$ higher than that on dry surfaces. Total heat transfer rate increases with increase in the velocity, temperature and relative humidity of incoming air. It also increases with decreasing the aspect ratio of heat exchanger tube. The inlet velocity of cooling water has little effect on the total heat transfer when the other conditions are fixed.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.3
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• pp.230-240
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• 2004

An experimental investigation was conducted to study two-phase flow distribution in a T-type distributor of slit fin-and-tube heat exchanger using R22. A comparison was made between the predictions by previously proposed tube-by-tube method and experimental data for the heat transfer rate of evaporator. Experiments were carried out under the conditions of saturation temperature of 5$^{\circ}C$ and mass flow rate varying from 0.6 to 1.2kg/min. The inlet air has dry bulb temperature of 27$^{\circ}C$, relative humidity of 50% and air velocity varying from 0.63 to 1.71㎧. Experiment show that air velocity increased by 85.2% is need for T-type distributor with four outlet branches than that of two outlet branches under the superheat of 5$^{\circ}C$, which resulted in air-side pressure drop increase of 130% for T-type distributor with four outlet branches as compared to two outlet branches.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.76.2-76.2
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• 2019

Shells in early-type galaxies are low surface brightness tidal debris, which are wide concentric arcs of overdense stellar regions with large opening angles. The most widely accepted mechanism today for shell formation is the merger scenario, but the dominant merger type producing shells is not clearly understood yet: major/minor and wet/dry mergers. Since shells are regarded as smoking-gun evidence of merging events, detailed understanding of shell galaxies is very useful to constrain the formation process of early-type galaxies. In this study, we investigate the metallicity gradients of eight early-type shell galaxies using CALIFA IFU data to better understand the nature and origins of galaxy shells. We estimate simple stellar population properties out to three effective radius from the measurement of Lick/IDS absorption line indices. We compare the metallicity gradients of shell galaxies with those of normal early-type galaxies in the same mass range. In this presentation, we discuss how much the gradients of shell galaxies are different from those of normal early-type galaxies and what the existence of galaxy shells implies about galaxy formation.

• Bulletin of the Korean Chemical Society
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• v.22 no.2
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• pp.171-178
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• 2001

A Purge and Trap Concentrator has been used to analyze various volatile organic compounds in water, operating several parameters affecting the extraction efficiencies of these compounds. The object of the present study was to observe the purge efficiencies of 40 volatile organic compounds (VOCs) in water, according to the change of parameters (purge time, dry purge time, sample temperature), and to determine the optimum condition of analysis of VOCs. The Purge and Trap Concentrator was interfaced with a narrow capillary connected to a gas chromatography mass spectrometer. At this condition, the detection limits of VOCs were in the range of 0.1-0.5 ㎍/L.

• Elastomers and Composites
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• v.55 no.4
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• pp.249-256
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• 2020

Superabsorbent polymers (SAPs) can absorb and retain ten to thousand times their dry mass of water because of their three-dimensional hydrophilic structures. Conventional SAPs are mainly composed of poly(acrylic acid sodium salt) derived from petrochemicals. The present work is aimed at limiting the use of the petrochemical component by replacing it with a biomass-based material. First, the core-SAP was prepared via the terpolymerization of itaconic acid, vinylsulfonic acid, and cellulose, and the optimum conditions in terms of material input ratio were determined. Following this, the core-SAP was surface-crosslinked by esterification with butane diol to improve its liquid permeability and absorbency under load (AUL). The liquid permeability was measured according to the amount of 0.9 wt.% NaCl solution passing between the swollen SAP particles under a given pressure, and the AUL was estimated from the weight of this solution absorbed under 0.3 psi pressure.

• Journal of Aquaculture
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• v.18 no.2
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• pp.115-121
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• 2005

This study was performed to investigate the formation and mass production of resting eggs by freshwater rotifer, Brachionus calyciflorus as influenced by different aeration supplements and exchange intervals of culture water in 15-L culture vessels and 500 L culture tanks. The maximum densities and mixis rates of the rotifers were not different between experimental group exposed to air or oxygen supplements. However, the fertilization rate and formation of resting eggs of the rotifers in the air-supplemented group were significantly higher than those in the oxygen supplemented group. In the experiment concerning exchange interval of culture water, the maximum density of the rotifers and formation of resting eggs in the batch culture were significantly higher than those in the semi-continuous culture with exchange of water every day. The formation of resting eggs per Chlorella dry weight was highest in the semi-continuous culture with exchange of water every day. The resting eggs of rotifers were produced at a density of $51.8{\sim}57.9{\times}10^6$ eggs in 500-L culture tanks. In this study, the batch culture with air is an effective method for mass production of resting eggs by the freshwater rotifer, B. calyciflorus, and the efficiency of mass production of resting eggs by this rotifer was similar to that of the seawater rotifers, B. plicatilis and B. rotundiformis.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.4 no.2
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• pp.224-239
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• 1994

In this study we examined several subjective symptoms in an exposed group and an unexposed group to perchloroethylene. The exposed group consists to 30 workers employed in 23 dry-cleaning establishments located in Chung Cheung Do, whereas the unexposed group consists of 42 officers employed in a certain university. This study was conducted from October, 1993 to March, 1994. Also we investigated personal exposure levels and area concentration of PCE, and performed hematological and biochemical examination in blood and urine samples from the exposed group. The results are : 1. The exposed group highly complains several subjective symptoms, particularly in neuropsychiatry, eye, respiratory system and digestive system, compared with the unexposed group. But complaint rates in the exposed group are not related with PCE exposure levels. 2. PCE exposure levels for all dry-cleaning establishment varied widely, from 0.18 to 37.58ppm. The mean exposure level for centers of chain was 16.85ppm, and for local laundries was 8.83ppm, while for self-service establishment it was 3.07ppm. Eighty three percent of the workers were exposed less than the half-level(25.0ppm) of the Korea 50.0ppm standard for eight-hour PCE exposure. Seventeen percent of them exceeded the half-level of the Korea TLV. 3. Statistical correlation exists between the work load(number of operation cycles of equipment and the mass of processed textiles) and the personal exposure levels to be observed. 4. In hematological examination the values of WBC, RBC, Hgb, Hct, MCV, MCH, MCHC and PLT in the exposed group were within normal ranges. In biochemical examination(GOT, GPT, ALP, U-A and LDH) most of the items were within normal ranges. From this surveys conducted on 23 dry-cleaning establishments, the complaint rates of the exposed group to PCE in several subjective symptoms were higher than those of the unexposed group, and PCE exposure levels in all dry-cleaning establishment were below the Koera standard 50.0ppm. In hematological and biochemical examination the significant abnormalities by occupational exposure to PCE were not observed. However, the workers employed in dry-cleaning establishments are always faced with risk, becauses they are also exposed to several organic solvents used to remove stains. Therefore, various measures to improve occupational environment in dry-cleaning establishment should be considered.