• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.446-451
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• 2000

In this paper, a new adaptive cross-coupling control (CCC) algorithm with an improved contour error model is proposed to maintain contouring precision in high-speed nonlinear contour machining. The proposed method utilizes variable controller gains based on the instantaneous curvature of a contour and the feedrate command. The proposed method is evaluated and compared with the conventional CCC for nonlinear contouring motion through computer simulations. The simulation results show that the proposed CCC improves the contouring accuracy more effectively than the existing method.

• 한국정밀공학회지
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• 제17권11호
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• pp.108-114
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• 2000

In this paper, a new adaptive cross-coupling control(CCC) method with an improved contour error model is proposed to maintain contouring precision in high-speed nonlinear contour machining. The proposed method utilizes variable controller gains based on the instantaneous curvature of a contour and the feedrate command. The proposed method is evaluated and compared with the conventional CCC for nonlinear contouring motion through computer simulations. The simulation results show that the proposed CCC improves the contouring accuracy more effectively than the existing method.

• Geomechanics and Engineering
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• 제17권5호
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• pp.465-473
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• 2019

Biocementation due to the microbially induced calcium carbonate precipitation (MICP) process is a potential technique that can be used for soil improvement. However, the effect of biocementation may be affected by many factors, including nutrient concentration, bacterial strains, injection strategy, temperature, pH, and soil type. This study investigates mainly the effect of chemical concentration on the formation of calcium carbonate (e.g., quantity, size, and crystalline structure) and unconfined compressive strength (UCS) using different treatment time and chemical concentration in the biotreatment. Two chemical concentrations (0.5 and 1.0 M) and three different treatment times (2, 4, and 8 cycles) were studied. The effect of chemical concentrations on the treatment was also examined by making the total amount of chemicals injected to be the same, but using different times of treatment and chemical concentrations (8 cycles for 0.50 M and 4 cycles for 1.00 M). The UCS and CCC were measured and scanning electron microscopy (SEM) analysis was carried out. The SEM images revealed that the sizes of calcium carbonate crystals increased with an increase in chemical concentrations. The UCS values resulting from the treatments using low concentration were slightly greater than those from the treatments using high concentration, given the CCC to be more or less the same. This trend can be attributed to the size of the precipitated crystals, in which the cementation efficiency increases as the crystal size decreases, for a given CCC. Furthermore, in the high concentration treatment, two mineral types of calcium carbonate were precipitated, namely, calcite and amorphous calcium carbonate (ACC). As the crystal shape and morphology of ACC differ from those of calcite, the bonding provided by ACC can be weaker than that provided by calcite. As a result, the conditions of calcium carbonate were affected by test key factors and eventually, contributed to the UCS values.

• 동아시아식생활학회지
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• 제19권6호
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• pp.950-957
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• 2009

Mustard Leaf Kimchi (MLK) is a traditional fermented Korean vegetable food. This study was conducted to investigate the effects of part vacuum treatment on MLK packed in a glass bottle during fermentation. There have been a few previous studies that examined the chemical and microbial changes during MLK fermentation. However, the major object of this study was to investigate the antioxidative activities of vacuum treated MLK. In this study, the antioxidative activity of vacuum treated mustard leaf Kimchi (VM) and control mustard leaf Kimchi (CM) were examined. VM and CM were fermented at $5^{\circ}C$ for 8 weeks. A model system was designed to evaluate the antioxidative activity of crude chlorophylls and carotenoids (CCC) extracts from Mustard leaf Kimchi. The oxidative reaction of the linoleic acid mixture system at $30^{\circ}C$ in the dark was quantified determining the peroxide value and conjugated dienoic acid content. The effect of the CCC extracts on lipid peroxidation in a rat liver homogenate was examined. Formation of lipid peroxides was estimated by the TBA value, and the CCC extracts were found to inhibit the TBA value. Chlorophyll a and b, and carotenoids, Which are the major components in the CCC extracts of Kimchi were isolated on a DEAE-sepharose CL-6B and Sepharose CL-6B column and TLC. The effects of chlorophyll a and b, caroteins on linoleic acid autoxidation were measured by determining the peroxide value. In addition, their effects on free radical scavenging were investigated by DPPH. In this assay, chlorophyll a showed the greatest antioxidative activity followed by chlorophyll b, and carotenoids. MLK contains a sufficient content of chlorophyll a and b, and carotenoid which have strong antioxidative activities.

• 기술표준
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• 통권14호
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• pp.20-26
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• 2003

• 한국식품영양과학회지
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• 제26권4호
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• pp.563-568
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• 1997

갓김치의 발효과정 중 chlorophylls, chlorophyll de-rivatives 및 carotenoids의 함량 변화와 갓김치에서 얻어진 이의 조획분의 항산화성을 살펴보았다. 갓김치 발효기간에 따른 chlorophylls 및 carotenoids의 함량은 발효 7일 동안 chlorophylls가 pheophytins로 급격히 전환되었으며 chlorophylls와 함께 chlorophyllides는 높은 농도는 아니지 만 15일 까지는 존재하다가 그 이후 모두 pheophytins와 pheophorbides로 변했다. 갓김치 발효기간 동안 total chlorophylls에는 큰 변화없이 거의 일정하게 유지 되었으나 carotenoids는 발효 말기인 25일째에 초기 함량의 43.7%로 감소되었다. 갓김치에서 얻어진 chlorophylls와 carotenoids 조분획이 지방질의 자동산화에 미치는 영향을 조사하였을 때 $\alpha$-tocophe-rol 보다 높은 항산화성을 나타내었으며 발효기간에 따른 갓김치의 항산화성을 비교하였을 때 유의적으로 차 이는 없었다. 갓김치의 chlorophylls와 carotenoids 분획이 지방산의 산화에 대한 저해작용을 나타내는 동안 chlorophylls와 caratenoids의 감소율을 비교했을 때 총 chlorophylls가 총 caratenoids 보다 안정성이 높았다.

• KSBB Journal
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• 제25권3호
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• pp.205-214
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• 2010

역류크로마토그래피 (counter-current chromatography, CCC)는 일련의 분배과정을 한 개의 튜브 내에서 연속적으로 일어나도록 고안된 시스템으로서 컬럼으로는 polytetrafluoroethylene(PTFE) 튜브가 다층으로 감겨있는 원통형의 홀더 3개가 서로 기어를 통해 물려있으며, 홀더가 회전과 공전을 통해 튜브의 꼬임을 방지하는 rotary seal-free flow centrifuge 시스템으로 되어있다. 역상 HPLC (reverse phase HPLC)에서는 고정상이 실리카에 결합된 유기물단 (organic moiety)이 수용성 이동상 물질에 의해서 용매화 (solvated)되는 반면 CCC는 실리카 대신에 강한 중력장에 의해 분리되는 자유로운 용매가 고정상이 되며 이 고정상의 부피비율은 20-30%에 이른다. 즉 고체담체에 결합된 유기관능기 대신에 물과 섞이지 않는 hexane 같은 유기용제가 고정상으로 사용되는 것이다. 고속역류크로마토그래피 (high-performance countercurrent chromatography, HPCCC)는 CCC의 기능을 향상시킨 분리시스템으로서 높은 중력장하에서 높은 이동상 속도와 높은 분리효율과 짧은 분리시간을 특징으로 하고 있다. 특히 mg 단위에서 kg 단위로의 스케일업이 선형적으로 가능하다는 큰 장점을 지니고 있다. 이 총설에서는 현재까지 개발된 CCC의 일반적인 이론을 간략히 정리하고 최신 HPCCC 장비의 적용 예를 살펴보고 그 응용분야로서 생리활성물질의 분리 및 정제와 관련된 연구동향을 정리하였다.

• 한국식품영양과학회지
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• 제12권3호
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• pp.236-239
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• 1983

녹두(綠豆) 발아과정(發芽過程) 중(中) 당함량(糖含量)을 측정(測定)하기 위하여 자엽(子葉)과 배축(胚軸)으로 구분(區分)하여 총당(總糖)과 환원당(還元糖)의 변화(變化)를 분석(分析)하여 얻어진 결과(結果)는 다음과 같다. 1. 녹두(綠豆)는 발아(發芽)함에 따라 총당(總糖)은 감소(減少)하고 환원당(還元糖)은 증가(增加)하는 경향(傾向)을 보인다. 2. 발아기간(發芽期間) 중(中) 총당(總糖) 함량(含量)은 ash구(區)가 가장 높고 ccc구(區), 무처리구(無處理區) 및 gibb구(區)의 순(順)이었다. 3. 발아기간(發芽期間) 중(中) 환원당(還元糖) 함량(含量)은 ash구(區), 무처리구(無處理區), gibb구(區) 및 ccc구(區) 순(順)으로 ccc는 억제효과(抑制效果)를 나타냈다. 4. 96시간(時間) 이후(以後) 자엽(子葉)과 배축부(胚軸部)의 총당(總糖) 함량(含量)이 비슷하게 나타냈다.

• The Journal of Asian Finance, Economics and Business
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• 제7권3호
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• pp.115-125
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• 2020

This paper investigates the impact of working capital management on the firm's profitability. The research sample includes 119 non-financial listed companies on Vietnam stock market over a period of 9 years from 2010 to 2018. Two statistical approaches include Ordinary least squares (OLS) and fixed effects model (FEM) are employed to address econometric issues and to improve the accuracy of the regression coefficients. The empirical results show the negative and significant impacts of the working capital management, which measured by cash conversion cycle (CCC) and three components of the CCC including accounts receivable turnover in days (ARD), inventory turnover in days (INVD), and accounts payable turnover in days (APD) on the firm's profitability measured by return on assets (ROA) and Tobin's Q. It implies that firms can increase profitability by keeping the optimization of the working capital management measured by the CCC, which includes shortening the time to collect money from clients, accelerating inventory flow and hold the low payment time to creditors. Besides, the profitability of firms was impacted by the sale growth rate, firm size, leverage, and age. Therefore, this paper provides a new insight to managers on how to improve the firm's profitability with working capital management.

• Toxicological Research
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• 제17권
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• pp.79-82
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• 2001

The infection of liver flukes, Clonorchis sinensis (CS) and Opisthorchis viverrini (OV), has been known as a risk factor to induce cholangiocellular carcinoma (CCC) in human living in the endemic area, providing promoting effect on the liver initiated by chemical carcinogens. The present study evaluated the relationship between the dosage level of dimethylnitrosamine (DMN) and the infection load of CS in the neoplastic development by histopathological examination of the treated hamsters. To evaluate the effects of DMN, different doses of DMN ranging from 0 to 25 ppm were administered to hamsters with 20 CS metacercariea. For the risk assessment of the infection load, 0, 5, 15, 50 CS metacercariae were respectively infected with 12 ppm DMN. The mortality was closely related to the infection load rather than the concentration of DMN. The infection of CS clearly promoted the induction of CCC even at dose level of 6 ppm DMN. Only five metacercariae were enough to promote CCC induction at the concentration of 12 ppm DMN.