• 한국습지학회지
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• 제23권1호
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• pp.7-13
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• 2021

급속한 산업발전과 인구증가, 생활 수준의 향상으로 영양염류를 포함한 하·폐수 발생량이 매년 증가하고 있다. 증가하는 하·폐수 발생량과 더불어 미처리 연계처리수(분뇨, 가축분뇨, 산업폐수, 침출수, 음폐수)또한 발생량이 증가하고 있고, 연계처리수 상당 수가 인근 하수처리장으로 연계하여 연계처리되고 있다. 연계처리수는 기존 유입하수와 비교했을 때 저유량 고농도의 특징을 가지고 있기때문에 하수처리장에서는 방류수 수질 악화, 처리량 증가, 오염부하 증가, 충격부하 또는 중금속 유입 등과 같은 많은 문제점을 가지게 된다. 이와같은 문제를 해결하기 위해서 하수처리장에 연계 유입되는 연계처리수의 양 및 수질 등의 조사가 필요하고, 하수처리에 미치는 영향등에 관한 연구가 필요하다. 따라서 본 논문은 연계처리수의 영향을 살펴보기 위해 4계절에 따른 수온조건을 고려했을 때 연계처리수의 영향 및 연계처리수 유입 유량 분배 등 영향인자를 고려하여 시나리오를 만들고 최적의 효율을 나타내는 조건을 분석하고자 한다.

• Korean Chemical Engineering Research
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• 제60권4호
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• pp.525-534
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• 2022

본 연구에서는 물과 전기의 동시 생산이 가능한 pressure retarded membrane distillation (PRMD)의 폐루프식 구성 디자인을 기수담수화에 적용해 최적 운전 조건과 성능 평가를 수행하였다. 시뮬레이션 결과 80 ℃ 이상의 폐열이 공급될 때 순 에너지 생산량이 양수 값을 보이며 90 ℃ 이상일 때 안정적인 전력 생산이 가능한 것을 확인할 수 있었고 최적 유입수 유량은 0.6 kg/s를 나타냈다. 이 조건에서 3 g/L의 기수가 유입될 때 순 에너지 생산량은 2.56 W/m², 물 플럭스는 8.04 kg/m²/hr의 값을 나타냈다. 기수의 농도가 1-3 g/L로 변화할 때 물 플럭스나 에너지 생산량은 큰 변화가 나타나지 않았고, 해수가 유입수로 사용될 때와 비교하면 더 높은 물 플럭스와 순 에너지 생산량을 보였다. 이를 통해 에너지 생산이라는 측면에 집중한다면 기수를 사용해서 PRMD를 운전하는 것이 더 효율적이라는 것을 확인할 수 있었다.

• Computers and Concrete
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• 제29권1호
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• pp.15-29
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• 2022

Concrete-filled steel tubes (CFSTs) are increasingly used as composite sections in structures owing to their excellent load bearing capacity. Therefore, predicting the mechanical behavior of CFST sections under axial compression loading is vital for design purposes. This paper presents the first study on the nonlinear analysis of heated CFSTs with high-strength concrete core containing steel fiber and waste tire rubber under axial compression loading. CFSTs had steel fibers with 0, 1, and 1.5% volume fractions and 0, 5, and 10% rubber particles as sand alternative material. They were subjected to 20, 250, 500, and 750℃ temperatures. Using flow rule and analytical analysis, a model is developed to predict the load bearing capacity of steel tube, and hoop strain-axial strain relationship, and axial stress-volumetric strain relationship of CFSTs. An elastic-plastic analysis method is applied to determine the axial and hoop stresses of the steel tube, considering elastic, yield, and strain hardening stages of steel in its stress-strain curve. The axial stress in the concrete core is determined as the difference between the total experimental axial stress and the axial stress of steel tube obtained from modeling. The results show that steel tube in CFSTs under 750℃ exhibits a higher load bearing contribution compared to those under 20, 250, and 500℃. It is also found that the ratio of load bearing capacity of steel tube at peak point to the load bearing capacity of CFST at peak load is noticeable such that this ratio is in the ranges of 0.21-0.33 and 0.31-0.38 for the CFST specimens with a steel tube thickness of 2 and 3.5 mm, respectively. In addition, after the steel tube yielding, the load bearing capacity of the tube decreases due to the reduction of its axial stiffness and the increase of hoop strain rate, which is in the range of about 20 to 40%.

• 한국농공학회논문집
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• 제64권5호
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• pp.9-16
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• 2022

Syngas, also known as synthesis gas, synthetic gas, or producer gas, is a combustible gas mixture generated when organic material (biomass) is heated in a gasifier with a limited airflow at a high temperature and elevated pressure. The present research was aimed at modifying the existing LPG engine generator for fully operated syngas. During this study, the designed gasifier-powered woodchip biomass was used for syngas production to generate power. A 6.0 kW LPG engine generator was modified and tested for operation on syngas. In the experiments, syngas and LPG fuels were tested as test fuels. For syngas production, 3 kg of dry woodchips were fed and burnt into the designed downdraft gasifier. The gasifier was connected to a blower coupled with a slider to help the air supply and control the ignition. The convection cooling system was connected to the syngas flow pipe for cooling the hot produce gas and filtering the impurities. For engine modification, a customized T-shaped flexible air/fuel mixture control device was designed for adjusting the correct stoichiometric air-fuel ratio ranging between 1:1.1 and 1.3 to match the combustion needs of the engine. The composition of produced syngas was analyzed using a gas analyzer and its composition was; 13~15 %, 10.2~13 %, 4.1~4.5 %, and 11.9~14.6 % for CO, H₂, CH₄, and CO₂ respectively with a heating value range of 4.12~5.01 MJ/Nm³. The maximum peak power output generated from syngas and LPG was recorded using a clamp-on power meter and found to be 3,689 watts and 5,001 watts, respectively. The results found from the experiment show that the LPG engine generator operated on syngas can be adopted with a de-ration rate of 73.78 % compared to its regular operating fuel.

• Natural Product Sciences
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• 제28권4호
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• pp.187-193
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• 2022

Lysimachia christinae Hance was commonly used in Oriental medicine for treating the hepatitis virus, cholecystitis and cholagogic efficiency. According to the previous study, it possesses high antioxidant and anti-inflammatory activity. Simultaneous determination analytical method of isolated eight compounds, cynaroside (1), 2-(3,4-dimethoxyphenyl) ethyl O-α-L-arabinopyranosyl-(1→2)-O-[6-deoxy-α-L-mannopyranosyl-(1→3)] β-D-glucopyranoside (2), stearylester ricinoleic acid (3), (E)-4-(3,4-dimethoxyphenyl) but-3-en-1-yl palmitate (4), 2-hydroxy-24-methoxy-4-tetracosenoic acid (5), 2-hydroxy-24-propoxy-4-tetracosenoic acid (6), β-sitosterol (7), and androst-16-ene-3,6-diol (8) were established by using HPLC-DAD. This HPLC analysis was detected on a Dionex C18 column (5 ㎛, 120 Å, 4.6 mm × 150 mm) at 25℃. The mobile phase consisted of 0.1% trifluoroacetic acid and acetonitrile at a flow rate of 1 mL/min. Validation of the method was assessed by linearity, precision and accuracy test. Calibration curve was good at r² > 0.9998. Limits of detection (LOD) ranged from 0.19 to 8.18 g/ml and Limits of quantification (LOQ) ranged from 0.19 to 24.80 g/ml. The relative standard deviations (RSD) values of precision test, intra- and inter- day, were less than 0.99% and 1.0%. The accuracy test results ranged from 98.81% to 106.49% and RSD values were less than 0.95%. These results showed that the HPLC-DAD method was very reliable and accurate for the quantity analysis of eight compounds in L. christinae extract for quality control.

• 한국응용과학기술학회지
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• 제40권1호
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• pp.71-80
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• 2023

실버 페이스트는 상대적으로 낮은 열처리로 공정이 가능하기 때문에 전자 소자 응용분야에서 유용한 전극 재료이다. 본 연구에서는 은 페이스트 전극에 대기압 플라즈마 제트를 이용하여 전극 표면을 처리 했다. 이 플라즈마 제트는 11.5 kHz 작동 주파수에서 5.5 ~ 6.5 kV의 고전압을 사용하여 아르곤 분위기에서 생성되었다. 플라즈마 제트는 대기압에서 수행함으로써 인쇄 공정에 더 유용할 수 있다. 플라즈마 처리시간, 인가된 전압, 가스유량에 따라 전극의 표면은 빠르게 친수성화 되었으며 접촉각의 변화가 관찰되었다. 또한, 대면적 샘플에서 플라즈마 처리 후 접촉각의 편차가 없었는데, 이는 기판의 크기에 관계없이 균일한 결과를 얻을 수 있었다는 것을 의미한다. 본 연구의 결과는 대면적 전자소자의 제조 및 향후 응용 분야에서 적층 구조를 형성하는데 매우 유용할 것으로 기대된다.

• International Journal of Oral Biology
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• 제48권1호
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• pp.1-7
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• 2023

Oral squamous cell carcinoma (OSCC), which accounts for approximately 90% of oral cancers, has a high rate of local recurrence and a poor prognosis despite improvements in treatment. Exosomes released from OSCC cells promote cell proliferation and metastasis. Although it is clear that the biogenesis of exosomes is mediated by the endosomal sorting complex required for transport (ESCRT) machinery, the gene expression pattern of ESCRT, depending on the cell type, remains elusive. The exosomal release from the human OSCC cell lines, HSC-3 and HSC-4, and their corresponding gefitinib-resistant sub-cell lines, HSC-3/GR and HSC-4/GR, was assessed by western blot and flow cytometry. The levels of ESCRT machinery proteins, including Hrs, Tsg101, and Alix, and whole-cell ubiquitination were evaluated by western blot. We observed that the basal level of exosomal release was higher in HSC-3/GR and HSC-4/GR cells than in HSC-3 and HSC-4 cells, respectively. Long-term gefitinib exposure of each cell line and its corresponding gefitinib-resistant sub-cell line differentially induced the expression of the ESCRT machinery. Furthermore, whole-cell ubiquitination and autophagic flux were shown to be increased in gefitinib-treated HSC-3 and HSC-4 cells. Our data indicate that the expression patterns of the ESCRT machinery genes are differentially regulated by the characteristics of cells, such as intracellular energy metabolism. Therefore, the expression patterns of the ESCRT machinery should be considered as a key factor to improve the treatment strategy for OSCC.

• 자원리싸이클링
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• 제32권2호
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• pp.33-42
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• 2023

금속 에멀젼(metal emulsion)은 제강 공정의 효율성을 높이는 방법으로 수십 년 동안 연구되어 왔습니다. 본 연구는 육안으로 관찰하기 어려운 고온 실험의 단점을 보완하기 위해 상온에서 관찰 가능한 수모델을 이용하여 수행하였다. 슬래그 내 금속 에멀젼의 대신하여 증류수를 실리콘 오일에 적하하여 운동량 균형 방정식에 의한 계산 결과와 비교하는 실험을 하였다. 물방울의 하강 속도는 물방울의 직경과 유체(실리콘 오일)의 점도가 증가함에 따라 감소하였다. 교반 조건에서 실리콘 오일에서 물방울의 하강 속도를 시뮬레이션하기 위해 유체(실리콘 오일)의 유속을 입자 이미지 속도계(PIV) 방법으로 측정하였다. 물방울의 하강 속도 계산은 점성 실리콘 오일을 교반하거나 교반하지 않고 측정된 값과 잘 일치하였다.

• Journal of Korea Trade
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• 제27권1호
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• pp.1-18
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• 2023

Purpose - Using a sample of Korean multinational corporations, we examine whether the relationship between tax risk and the implied cost of capital discriminates between the environmental, social, and corporate governance (ESG) of highly rated firms. Design/methodology - Firms with high tax risks have an increased uncertainty of future cash flows. Therefore, as the volatility of future cash flow increases, information asymmetry and the required return increases. Highly rated ESG firms can reduce information asymmetry, thereby weakening the positive relationship between tax risk and cost of capital. We employ the standard deviation of the cash effective tax rate as proxy of tax risk. We utilize the ESG rating data of the Korea Corporate Governance Service (KCGS). We use a PEG model, MPEG model, and GM model to measure the implied cost of capital. Findings - We find a positive association between the implied cost of capital and tax risk. The positive relationship between tax risk and the implied cost of capital weakens in highly rated ESG firms. Highly rated ESG firms prefer a stable tax position to invest after-tax cash flows into sustainable management. Therefore, the negative effects of tax risk on cost of capital can be reduced. Originality/value - This study provides empirical evidence that ESG activities can mitigate the negative impact of tax risk on the cost of capital for Korean multinational corporations. In a business environment where ESG activities are more important, the empirical results that ESG activities can reduce the corporate risk of Korean FDI companies are expected to provide implications for the ESG activities of multinational corporations.

• 분석과학
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• 제36권1호
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• pp.32-43
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• 2023

This study reports for the first time about a stability indicating RP-HPLC method for qualitative and quantitative determination of acalabrutinib in bulk and dosage form and in presence its impurities 1, 2 and 3. The chromatographic separation was carried on Zorbax XDB-C18 (250×4.6 mm; 5 µ id) as stationary phase, Phosphate buffer pH 6.4 and methanol 80:20 (v/v) as mobile phase at a flow rate of 1.0 mL/min, UV detection was carried at wavelength of 238 nm and the analysis was completed with a run time of 15 min. In these conditions the retention time of acalabrutinib and its impurities 1, 2 and 3 was observed to be 3.50, 4.83, 8.40 and 9.93 min respectively. The method was validated for system suitability, range of analysis, precision, specificity, stability and robustness. Spiked recovery at 50 %, 100 % and 150 % was carried for both standard and impurities and the acceptable % recovery of 98-102 was observed for acalabrutinib and both impurities studied and the % RSD in each spiked level was found to be less than 2. Stability tests were done through exposure of the analyte solution to five different stress conditions i.e expose to 1N hydrochloric acid, 1 N sodium hydroxide, 3 % peroxide, 80 ℃ temperature and UV radiation at 254 nm. In all the degradation condition, standard drug acalabrutinib was detected along with both the impurities studied and the degradation products were successfully separated. In the formulation analysis there is no other chromatographic detection of other impurities and formulation excipients. Hence the developed method was found to be suitable for the quantification of acalabrutinib and can separate and analyse impurities 1 and 2.