• Journal of the Korean Chemical Society
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• v.59 no.5
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• pp.413-422
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• 2015

Proton exchange membrane (PEM), which transfers proton from the anode to the cathode, is the key component of the proton exchange membrane fuel cell (PEMFC). Nafion is widely used as PEM due to its high proton conductivity as well as excellent chemical and physical stabilities. However, its high cost and the environmental hazards limit the commercial application in PEMFCs. To overcome these disadvantages, various alternative polymer electrolytes have been investigated for fuel cell applications. We used densely sulfonated polymers to maximize the ion conductivity of the corresponding membrane. To overcome high swelling, dipole-dipole interaction was used by introducing nitrile groups into the polymer backbone. As a result, physically-crosslinked membranes showed improved swelling ratio despite of high water uptake. All the membranes with different hydrophilic-hydrophobic compositions showed higher conductivity, despite their lower IEC, than that of Nafion-117.

• Current Research on Agriculture and Life Sciences
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• v.20
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• pp.77-82
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• 2002

This study was carried out in order to produce useful material for the forest multiple use and forest protection by physico-chemical soil analysis of studied area in Sokwang-ri Forest Genetic Resource Protection Forest which was divided into in standard plots include Tricholoma matsutake and Sarcodon aspratus production forest. The result of physico-chemical soil analysis represented as following. The soil type of T. matsutake production forest was Dry brown forest soil(B1), while on the other hand the soil type of S. aspratus production forest was Moderately moist brown forest soil(B3). Between T. matsutake and S. aspratus production forest did not result in significant changes in soil pH(5.22-5.60) and soil depth(47cm), but available phosphorus, carbon, and nitrogen contents were different results. CN ratio of the fairy ring of T. matsutake was quite lower than that in S. aspratus production forests, which indicated that T. matsutake production forest was built up in the relatively immature soils which contain little organic matter. Generally, it was predicted that Pinus densiflora for. erecta forest succeeded to deciduous tree forest in stable soil environments. To conserve these T. matsutake and S. aspratus production forest, the contents of available phosphorous and exchangeable cation should be increased by continuous soil environment management and it should be established the secondary growth forests of old aged Pinus densiflora for. erecta trees as soon as possible.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.149-149
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• 2019

Gross Primary production (GPP) and evapotranspiration (ET) are the two critical components of carbon and water cycle respectively, linking the terrestrial surface and ecosystem with the atmosphere. The ratio between GPP to ET is called ecosystem water use efficiency (EWUE) and its quantification at the forest site helps to understand the impact of climate change due to large scale anthropogenic activities such as deforestation and irrigation. This study was conducted at the FLUXNET forest site CN-Qia (2003-2005) using Community land model (CLM 5.0). We simulated carbon and water fluxes including GPP, ecosystem respiration (ER), and ET using climatic variables as forcing dataset for 30 years (1981-2010). Model results were validated with the FLUXNET tower observations. The correlation showed better performance with values of 0.65, 0.77, and 0.63 for GPP, ER, and ET, respectively. The model underestimated the results with minimum bias of -0.04, -1.67, and -0.40 for GPP, ER, and ET, respectively. Effect of climate 'CLIM' and '$CO_2$' were analyzed based on EWUE and its trend was evaluated in the study period. The positive trend of EWUE was observed in the whole period from 1981-2010, and the trend showed further increase when simulated with rising $CO_2$. The time period were divided into two parts, from 1981-2000 and from 2001 to 2010, to identify the warming effect on EWUE. The first period showed the similar increasing trend of EWUE, but the second period showed slightly decreasing trend. This might be associated with the increase in ET in the wet temperate forest site due to increase in climate warming. Water use efficiency defined by transpiration (TR) (TWUE), and inherent-TR based WUE (IT-WUE) were also discussed. This research provides the evidence to climate warming and emphasized the importance of long term planning for management of water resources and evaporative demand in irrigation, deforestation and other anthropogenic activities.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.37.2-37.2
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• 2019

Recent investigations of the double red clump in the color-magnitude diagram of the Milky Way bulge cast serious doubts on the structure and formation origin of the outer bulge. Unlike previous interpretation based on an X-shaped bulge, stellar evolution models and CN-band observations have suggested that this feature is another manifestation of the multiple stellar population phenomenon observed in globular clusters (GCs). This new scenario requires a significant fraction of the outer bulge stars with chemical patterns uniquely observed in GCs. Here we show from homogeneous high-quality spectroscopic data that the red giant branch stars in the outer bulge ($>5.5^{\circ}$ from the Galactic center) are clearly divided into two groups according to Na abundance in the [Na/Fe] - [Fe/H] plane. The Na-rich stars are also enhanced in Al, while the differences in O and Mg are not observed between the two Na groups. The population ratio and the Na and Al differences between the two groups are also comparable with those observed in metal-rich GCs. Since these chemical patterns and characteristics are only explained by stars originated in GCs, this is compelling evidence that the outer bulge was mostly assembled from disrupted proto-GCs in the early history of the Milky Way. We will also discuss the implications of this result on the formation of the early-type galaxies in general.

• Structural Engineering and Mechanics
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• v.84 no.1
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• pp.17-33
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• 2022

An experimental study is carried out to investigate the performance of the cutting tool regarding the insert wear, surface roughness, cutting forces, cutting power and material removal rate of three coated carbides GC2015 (TiCN-Al₂O₃-TiN), GC4215 (Al₂O₃-Ti(C,N)) and GC1015 (TiN) during the dry turning of AISI4140 steel. For this purpose, a Taguchi design (L₉) was adopted for the planning of the experiments, the effects of cutting parameters on the surface roughness (R_a), tangential cutting force (F_z), the cutting power (P_c) and the material removal rate (MRR) were studied using analysis of variance (ANOVA), the response surface methodology (RSM) was used for mathematical modeling, with which linear mathematical models were developed for forecasting of R_a, F_z, P_c and MRR as a function of cutting parameters (V_c, f, and a_p). Then, Multi-Objective Ant Lion Optimizer (MOALO) has been implemented for multi-objective optimization which allows manufacturers to enhance the production performances of the machined parts. Furthermore, in order to characterize and quantify the flank wear of the tested tools, some machining experiments were performed for 5 minutes of turning under a depth of 0.5 mm, a feed rate of 0.08 mm/rev, and a cutting speed of 350 m/min. The wear results led to a ratio (V_B-GC4215/V_B-GC2015) of 2.03 and (V_B-GC1015/V_B-GC2015) of 4.43, thus demonstrating the efficiency of the cutting insert GC2015. Moreover, SEM analysis shows the main wear mechanisms represented by abrasion, adhesion and chipping.

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2449-2453
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• 2007

L-[18F]FMAU ([18F]1b) was prepared from the precursor 2-O-[(trifluoromethyl)-sulfonyl]-1,3,5-tri-Obenzoyl- α-L-ribofuranose, by coupling the radioactive fluoro-sugar with the corresponding silylated thymine in 4 steps. The final products, including the α and β anomers, were purified using reverse phase HPLC with an appropriate solvent (5% CH3CN/H2O) at a flow rate of 3.0 mL/min. The total elapsed time of synthesis was about 180-200 min from EOB. The α/β anomeric ratio of the compounds was about 1:9, and the radiochemical purity of the product (β-form) was >98% with decay-corrected yields of 25-35%. All radioactive samples were confirmed using co-injection with pure non-radioactive analogues in every step. In the cellular uptake in vitro test of herpes simplex virus-thymidine kinase (HSV1-TK) gene expressed cells, the percent uptake of injected dose (%ID) of L- and D-FMAU was 37.28 and 65.86, respectively after 240 min incubation. However, the relative uptake (MCA-TK/MCA cellular uptake ratio) of L-FMAU was higher than that of D-FMAU (%ID of L-FMAU, 0.36 and D-FMAU, 0.93 after 240 min incubation in MCA cells). This means that L-FMAU will show better specific HSV1-TK gene expressed cell uptake for selective HSV1-TK gene imaging.

• Journal of the Korean GEO-environmental Society
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• v.10 no.6
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• pp.27-33
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• 2009

In this study, it was analysed physical characteristics, TS, moisture, C/N ratio, leaching test, and element analysis in landfill wastes of 10 years old without landfill pretreatment. The Organic material content was 7.2%~23.5% and soil was the main inorganic materials which it's rate was 54.1%~71.0%, in landfill wastes. The results of TS, VS, and moisture were represented 51.5%~68.1%, 23.6%~56.1%, 32.0%~48.4%, respectively. The analysis of hazardous materials did not indicate Hg, $Cr^{+6}$, CN, Organic Phosphorus, TCE and PCE, however the Pb of leaching materials showed 0.023~0.092 mg/L, which was the highest. As the result of the element analysis, C was 47.74%~56.72%, N was 4.09%~9.92%, the C/N ratio was 5.76~12.57 and the result of soils around landfill was the highest heavy material, Pb, 2.465 mg/kg~10.251 mg/kg. The objectives of this paper are to investigate states, stabilization of these closed landfills and to gain suitable data for post-closure care using some parameters through analysis of landfill environment.

• Pediatric Infection and Vaccine
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• v.11 no.1
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• pp.112-120
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• 2004

Purpose : Methicillin Resistant-Coagulase Negative Staphylococcus(MR-CNS) infection has become an increasingly important cause of morbidity in NICU infants. We investigated the c linical characteristics of MR-CNS sepsis. Methods : This study included 40 neonates with MR-CNS sepsis who were admitted to the neonatal intensive care unit of Kangnam Sacred Heart Hospital, Hallym University from January 1998 to July 2002. MR-CNS sepsis was defined as MR-CNS recovery from blood with clinical symptoms and signs of infection. Retrospective analyses of the medical records of patients with MR-CNS sepsis were performed. The analyses included demographic findings, clinical features, hospital courses, risk factors for infection including invasive procedures and mortality. Results : From 1998 to 2002, there were 40 cases of MR-CNS sepsis, comprising 17.7% of late onset infections in NICU of Kangnam Sacred Heart Hospital. The male/female ratio was 1.5 : 1. The mean gestational age of infected babies was $32.4{\pm}4.3$ weeks at birth. And the first positive MR-CNS culture was done in the day $10.6{\pm}9.3$ after birth. Clinical symptoms such as fever, dyspnea, cyanosis, grunting, bradycardia, vomiting and diarrhea were frequent in MR-CNS. Mechanical ventilation was applied in 12 cases and catheter was inserted in 11 cases. The mortality(12.5%) directly attributable to MR-CNS sepsis was similar to other late onset infections. Conclusion : MR-CNS is a pathogen responsible for most late onset and nosocomial infections. And it will be life-threatening in high-risk neonate. Awareness of increasing infections due to MR-CNS in NICU is important not only for infection control but also placing a great limit in use of antibiotics and invasive procedures, especially in premature infants.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.9
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• pp.708-713
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• 2013

KARI is developing a solar-electric powered HALE UAV(EAV-3). For demonstrating the technology, EAV-2H, a down-scaled version of EAV-3, is developed and after EAV-2H's initial flight test, the directional stability and control need to be improved. Thus, the vertical tail and rudder of EAV-2H are redesigned with Advanced Aircraft Analysis(AAA). Size of the rudder is increased from mean chord ratio of rudder to vertical tail, $C_r/C_v(%)=30$ to $C_r/C_v(%)=60$ and size of the vertical tail is reduced 15%. As a result, the directional control to side wind($v_1$) is improved to sideslip angle, ${\beta}(deg)=25^{\circ}$ and $v_1(m/sec)=3.54$. Also, variation of airplane side force coefficient with sideslip angle ($C_{y_{\beta}}$) and variation of airplane side force coefficient with dimensionless rate of change of yaw rate ($C_{y_r}$) are reduced 15% and 22%, respectively to minimize the effect of side wind. The empennage design of EAV-2H is verified with flight tests and applied to design of KARI's solar-electric-powered EAV-3.

• Journal of Microbiology and Biotechnology
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• v.19 no.9
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• pp.1055-1064
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• 2009

Enteroviruses were identified and characterized from patients with aseptic meningitis and other enterovirus-related diseases in Chungnam, Korea from 2005 to 2006. Enteroviruses were isolated from 79 of 519 cases (15.2%) in 2005, and 37 of 386 cases (9.6%) in 2006. Based on partial VP1 sequencing, a total of 116 enterovirus isolates were resolved into 13 types. Prevalent among the Chungnam isolates were echovirus 18 and coxsackievirus B5 in 2005, and echoviruses 5 and 25 in 2006. This is the first time echoviruses 5 and 18 have been identified in Korea since enterovirus surveillance began there in 1993. The temporal distribution of enterovirus epidemics in Chungnam showed a remarkable seasonal pattern, with cases occurring during most of the three months of the summer from June to August. The highest rate of enterovirus-positive cases occurred in patients less than 1 year of age. The ratio of male to female enterovirus-positive patients was approximately 1.8:1. Comparison of the VP1 amino acid sequences of the 15 coxsackievirus B5 isolates with reference strains revealed that all Chungnam isolates are substituted at positions 23 (V231), 19 (S19G), 75 (Y75F), and 95 (N95S). Upon comparing the nine ECV5 isolates with foreign strains, it was found that only the Chungnam isolates, with the exception of Kor06-ECV5-239cn, have P at position 153 and F at position 146. The three ECV9 isolates from 2006 show alterations at amino acids 36, 148, and 154 outside of the BC-loop and at position 84 in the BC-loop, whereas the seven isolates from 2005 and the other ECV9 strains in the database only show the alteration at position 84 (D, I, N, S). The five ECV25 isolates have an S residue at position 134, whereas most of the foreign strains have an N residue.