• Tribology and Lubricants
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• 제38권5호
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• pp.185-190
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• 2022

Among the operating limits of a heat pipe, the capillary limit is significantly affected by the characteristics of the wick, which is determined by the capillary performance. The major parameters for determining capillary performance are the maximum capillary pressure and the spreading characteristics that can be expected through the wick. A well-designed wick structure improves capillary performance and helps improve the stability of the heat pipe by enhancing the capillary limit. The capillary performance can be improved by forming a porous microstructure on the surface of the wick structure through surface modification techniques. In this study, a microstructure is formed on the surface of the wick by using a surface modification method (i.e., an electrochemical etching process). In the experiment, specimens are prepared using stainless-steel screen mesh wicks with various fabrication conditions. In addition, the spreading and capillary rise performances are observed with low-surface-tension fluid to quantify the capillary performance. In the experiments, the capillary performance, such as spreading characteristics, maximum capillary pressure, and capillary rise rate, improves in the specimens with microstructures formed through surface modification compared with the specimens without microstructures on the surface. The improved capillary performance can have a positive effect on the capillary limit of the heat pipe. It is believed that the surface microstructures can enhance the operational stability of heat pipes.

• FOCUS: LIFE SCIENCE
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• 제1호
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• pp.2.1-2.6
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• 2024

This article provides detailed instructions for the correct installation, maintenance, and troubleshooting of capillary gas chromatography (GC) columns. It emphasizes the importance of proper installation to ensure optimal performance and longevity of the column. The document covers various aspects such as column trimming, installation, conditioning, testing, storage, and ferrule selection. The installation process involves ensuring that the heated zones of the GC are cool before placing the column cage in the column oven. It is essential to avoid sharp bends or stress on the capillary column during installation and to connect the front end of the column into the GC inlet at the recommended insertion distance. The document also provides guidance on trimming the column, including the use of a ceramic wafer or capillary column cutter to achieve a clean, burr-free cut. For previously used columns, it recommends removing any capillary caps, positioning the nut and ferrule, and trimming 1-2 cm from the column. After installation, the column should be purged with carrier gas to remove any oxygen and avoid oxidizing the column. Conditioning the column involves ramping to the upper isothermal temperature limit and maintaining this temperature for a specified duration. It is crucial to maintain carrier gas flow during conditioning and not exceed the upper temperature limit of the column to avoid phase damage. The document also discusses testing column performance using a suitable method and performing a test injection to assess performance. It provides recommendations for column storage, including flame-sealing the capillary ends or using retention gaps for long-term storage. Additionally, it emphasizes the importance of routine maintenance and replacement of GC consumables to extend the column's lifetime. Ferrule selection is another important aspect covered in the article, with a variety of ferrule materials available for different applications. The characteristics of common ferrule options are presented in a table, including temperature limits, reusability, and suitability for specific detector types.

• Bulletin of the Korean Chemical Society
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• 제15권11호
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• pp.945-949
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• 1994

Mixtures of cyano complexes of palladium(II) and platinum(II) were separated by capillary electrophoresis using a fused silica capillary as a separation column and 30 mM phosphate buffer (pH 7) containing 15 wt. % acetonitrile as a running buffer. By virtue of the high ionic mobilities of the negatively charged cyano complexes of Pd(II) and Pt(II), they were separated using a cathodic injection and anodic detection scheme. The metal complexes eluted through the capillary were detected by direct UV absorption at 214 nm. A linear relationship between peak area and concentration was obtained for both ions and the detection limit was lower than $10^{-14}$ mole. The proposed method was applied to real sample, e.g., anode slime obtained from an electrolytic copper refinary, as a method for the simultaneous determination of palladium and platinum.

• 한국분말재료학회지
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• 제27권6호
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• pp.468-476
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• 2020

The bone cement used for vertebroplasty must be sufficiently injectable. The introduction of granules reduces the amount of liquid required for liquefaction, implying that higher fluidity is achieved with the same amount of liquid. By employing β-tricalcium phosphate granules with an average diameter of 50 ㎛, changes in injectability are observed based on the paste preparation route and granular fraction. To obtain acceptable injectability, phase separation must be suppressed during injection, and sufficient capillary pressure to combine powder and liquid must work evenly throughout the paste. To achieve this, the granules should be evenly distributed. Reduced injection rates are observed for dry mixing and excessive granular content, owing to phase separation. All these correspond to conditions under which the clustered granules weakened the capillary pressure. The injected ratio of the paste formed by wet mixing displayed an inverted U-type shift with the granular fraction. The mixture of granules and powder resulted in an increase in the solid volume fraction, and a decrease in the liquid limit. This resulted in the enhancement of the liquidity, owing to the added liquid. It is inferred that the addition of granules improves the injectability, provided that the capillary pressure in the paste is maintained.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1487-1492
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• 2004

For the present study, three heat pipes with different thickness of sintered metal wick were manufactured, and their operational performances, such as capillary limit and thermal resistance were tested and compared with theoretical predictions. Experimental results showed good agreement with those by the theoretical model, and that seemed to present that the sintering process we had developed in the present study was valid.

• Bulletin of the Korean Chemical Society
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• 제26권2호
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• pp.297-302
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• 2005

The determination of total phenols was accomplished by capillary-high performance liquid chromatography (capillary-HPLC) after nitrosation of the U.S.E.P.A. classified 11 priority pollutant phenols, using the nitrosated parent phenol (POHNO) as a reference for calibration. The optimum mobile phase composition for this analysis was found by examining the effect of changing the percentage of acetonitrile (MeCN) in the mobile phase on retention factors (k values) and peak intensities. As MeCN percentage was increased, k values were reduced and peak intensities were generally increased. From the results obtained, it was found that the optimum mobile phase was 90%(v/v) MeCN solution at pH 8.0, the detection wavelength of 400 nm, and a detection limit (D.L., concentration at signal to noise ratio (S/N) of 3.0) of 4.5 ${\times}$ $10^{-7}$ M. In addition, 10 of the 11 phenols present in mineral or waste water were separated after the nitrosation by capillary-HPLC. The optimum mobile phase for separation was a 40%(v/v) MeCN solution at pH 5.0.

• 대한기계학회논문집B
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• 제39권7호
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• pp.599-607
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• 2015

본 연구에서는 나노유체의 유동학 특성을 반영한 히트파이프 열적특성을 연구하였다. $Al_2O_3$와 CuO 나노입자를 적용한 나노유체를 작동유체로 하여 나노입자 부피비와 응집도에 대한 히트파이프 성능을 확인하였다. 나노입자의 부피비와 응집도가 증가할수록 점성과 열전도도는 증가하는 것으로 나타났으며 두 인자는 히트파이프 성능에 영향을 주었다. 나노입자응집이 없는 경우에는 나노입자의 부피비 증가가 모세관압력한계 성능을 향상시켰지만 응집도가 증가하면 입자부피비가 증가해도 모세관압력한계가 감소했다. 그리고 나노입자의 열전도도, 부피비, 응집도에 대한 히트파이프 열저항을 분석하였다. 히트파이프의 투과율이 높을수록 최대열수송량은 입자부피비에 미치는 영향이 컸으며 3차원 그래프를 통해 윅 특성에 대한 최적화된 나노입자부피비를 확인하였다.

• 대한화학회지
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• 제39권8호
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• pp.635-642
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• 1995

Purge & Trap-GC/MS 전처리 방법과 capillary column gas chromatography/ mass spectrometry 분석법을 이용한 휘발성유기물 분석에 있어서, 보다 효울적으로 시료를 주입하는 방법에 대하여 연구하였다. 미국환경청에서 제시한 물 중의 휘발성 유기물 분석방법에서 이용하는 moisture control nodule 과 cryorefocusing에 따르는 여러가지 문제점을 관찰하였다. 이러한 무제점을 해결하기 위해 개선된 시료 주입방식을 제시하고, 여러가지 트랩과 컬럼의 특성을 조사하여 최적 실험조건을 구하였다. 이때 사용한 Purge & Trap 장치의 트랩은 carbopack B/carboxen 1000과 1001이었으며, 기체 크로마토그라프의 컬럼은 주문 제작한 dimethyldiphenylpolysiloxane crosslingking moiety capillary 컬럼을 사용하였다. 본 연구에서 제시한 방법으로 물 중에 포함된 54종의 휘발성유기물을 대상으로 동시분석할 때의 정확도와 정밀도에 대해 조사하였으며, 각 화합물에 대한 method detection limit를 구하였다.

• 분석과학
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• 제8권4호
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• pp.835-841
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• 1995

The quantitation of inorganic anions in various drinking waters were investigated using capillary electrophoresis(CE) and the results were compared with ion chromatography(IC). With CE, in contrast to IC, was demonstrated rapid analysis, good efficiency, a low detection limit and the low comsumption of a solvent and samples. CE analysis was used 5 mM sodium chromate(pH 8.0) containing 20 mM tetraalkylammoniumbromide at -25kV applied voltage with indirect UV detection at 254 nm. This results in exceedingly short analysis time within 3 min. with efficiencies approaching 200,000 theoretical plates. The coefficients of variants of migration time are less than 0.8% and those of peak area are less than 2.3%. Detection limits for quantitative determination were 300 ppb-50 ppm level. These optimum conditions are applicable to various samples without pretreatment.

• 설비공학논문집
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• 제13권10호
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• pp.1025-1033
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• 2001

A scaling analysis is provided which predicts the sliding velocity of a liquid drop down an inclined surface. The analysis is based on the balance of the gravitational work rate that drives the drop sliding and the resistances by capillary and viscous forces. The capillary resistance is accounted for via the contact angle hysteresis, which is quantified by measuring the critical inclination causing the drop to start sliding. The sliding of the drop is governed by the rate of the viscous dissipation of the Stokes flow. The analysis result in its limit form for small contact angles is consistent with previous results. In the experiments to verify the analysis results, the measured sliding velocity of various liquid drops are shown to obey the predictions made in this study.