• 한국연소학회지
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• 제18권2호
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• pp.23-31
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• 2013

Compact steam boiler is a useful heat exchanger in a space-intensive system. There are some constraints in terms of sizing and designing the space confined in the system which is usually used in vessels. In this study, design considerations for heavy duty heat exchangers of compact steam boilers are presented and evaluated. Especially, evaporator tubes of marine boiler which are exposed to a high temperature environment are considered. Also, extended surface designs with a high temperature are examined. In order to determine the criteria with considerations of both heat transfer rate and pressure drop in the heat exchanger, they are evaluated with major variables, such as the tube diameter, the number of tubes, and the tube length. Finally, the design parameters are estimated as the bare tubes are installed instead of the finned tubes.

• 대한치과보철학회지
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• 제31권1호
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• pp.11-18
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• 1993

Autopolymerising and visible light cured resin are used to reline dentures. But relined surface are easily contaminated by water or saliva in the mouth during clinical procedure. This study was to find out the effect of surface contamination on the transverse strength of the relined denture base. To accomplish this, the specimens of $65\times10\times3mm$ were made with heat-cured(Lucitone 199), visible light-cured(Triad), and autopolymerizing resin(Kooliner). Measurements of transverse strength were taken for each specimen. Specimens made of heat-cured resins, sizing $65\times10\times1.5mm$, were relined with heat-cured, light-cured, and autopolymerizing resin, respectively. Specimens relined with autopolymerizing and light-cured resins were further classified into not-contaminated, water-contaminated and saliva-contaminated groups. Again, measurements of the transverse strength were taken for each group. The results were as follows 1. The transverse strength of heat-cured resin was superior to all the other resins. 2. The transverse strength of each specimen decreased after relining in the following order, heat-cured, visible light-cured, and autopolymerizing resin. 3. Surface contamination produced an decrease in transverse strength, especially in the saliva contaminated group. According to these results, water or saliva contamination should be avoided during intraoral relining procedures.

• 펄프종이기술
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• 제42권1호
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• pp.64-73
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• 2010

This study was conducted to modify the surface properties of papers by formation of hydrophobic self-assembled monolayer(SAM) on paper surface with silanes. A base paper I(0.5% AKD) and base paper II(1.0-1.5% AKD) were reacted with silanes(PFDTES, DMDCS, MODDCS) by immersion method and vapor deposition method. Hydrophobic SAMs(contact angle value>$120^{\circ}C$) were obtained on all papers after treatment with $10^{\mu}l$ PFDTES for 15min, with $50^{\mu}l$ DMDCS for 30min, with $50^{\mu}l$ MODDCS for 300min. When applying PFDTES to paper surface, lower silane concentration and shorter reaction time were required, whereas MODDCS with long alkyl chain required the longest reaction time of 300min. The st$\ddot{o}$ckight sizing degree of silane treated papers were increased between 105sec(base paper I) and 130sec(base paper II). The wet tensile strength of PFDTES-treated base papers(I, II) increased by 10-34% after SAM formation. However, the wet tensile strength of the DMDCS-treated base paper(I) was found to decrease from 0.067kN/m to 0.038kN/m; this may due to the cellulose degrading as a result of generated hydrogen chloride when hydroxyl group of cellulose were reacted with DMDCS. No apparent changes of PPS roughness on silane-treated papers are observed. The ATR-IR spectrum showed absorption peak located at 465 and 1200cm-1 which can be assigned to the Si-O-C asymmetric stretching and Si-O-C bonds, respectively.

• 비파괴검사학회지
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• 제34권3호
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• pp.254-259
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• 2014

중수로 원자로는 한 개의 원자로용기로 구성된 경수로와는 달리 약 380여개의 연료채널(fuel channel)로 구성되어 있다. 연료채널을 구성하는 압력유지 기기인 압력관(pressure tube)은 지르코니움 합금(Zr-2.5wt% Nb) 재질로서 치수는 내경이 103.4 mm, 두께가 약 4.19 mm, 길이가 6.36 m인 튜브 형태의 관이다. 압력관은 내부에 핵연료 다발과 냉각재가 내장되며 압력관의 기능은 연료를 지지하고 열수송 유체인 중수($D_2O$)를 이송한다. 압력관의 단순한 기하학적인 형상으로 인하여 자동화 비파괴검사가 가능하고 접근성이 우수하다. 연료채널은 경수로형 원전과 동일하게 설치전과 운전중에 원자력안전위원회 법령 요건에 따라 주기적으로 엄격한 비파괴검사를 수행하여 건전성을 확인한다. 연료채널의 주기적 비파괴검사에는 초음파탐상 및 와전류탐상검사 기법을 적용한 체적 비파괴검사 기술이 적용된다. 이중에서 와전류탐상검사 기법은 초음파탐상검사에서 검출된 결함의 확인을 위한 보충검사기술로 적용되고 있지만 표면결함에 대한 검출능이 초음파탐상검사 기법보다 우수한 장점을 가지고 있다. 본 논문에서는 압력관 내부 표면 비파괴검사에 적용되고 있는 와전류탐상검사 기술의 압력관 내면에 발생할 수 있는 결함의 검출 및 깊이 측정 특성에 대한 연구결과를 기술하였다. 즉, 와전류검사 기술은 압력관 내면에 발생할 수 있는 아주 미세한 결함을 매우 우수한 분해능으로 검출할 수 있으므로 초음파탐상검사 결과 확인을 위한 보충기술로서 매우 유용하지만, 결함의 깊이 측정은 오차가 매우 크게 발생하므로 결함 깊이 측정에는 적합하지 않고 오직 표면결함 검출에만 적용하는 것이 바람직하다.

• 펄프종이기술
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• 제46권4호
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• pp.1-10
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• 2014

In papermaking industry, inorganic fillers are widely used for the purpose of improving opacity, brightness, printability, uniformity and dimensional stability. They are also useful for production costs and energy savings. In the past, inorganic fillers in papermaking industry only focused on micro-scale but recently, new trials on nano-powdered technology are applying. Even nano-powdered fillers are rapidly utilized for improving the optical and surface properties in coating and surface sizing, there still have some problems in wet-end process due to poor dispersibility and retention. In this study, nano-particled calcium carbonate was produced by milling the PCC and its applicability between micro sized and nano sized calcium carbonated was compared in wet-end process, and finally the sheet properties were evaluated. Nano-PCC was not retained in sheet structure without applying retention system, but with retention system nano-powdered PCC was absorbed on fiber surface with expanding the fiber networks. The application of PAM-bentonite system has resulted in high ash retention and bulky structure for copier paper, and good optical properties in brightness and opacity. However, it required to solve the weakness of low tensile property due to interruption of hydrogen bonding by nano fillers.

• 융합정보논문지
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• 제10권7호
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• pp.138-146
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• 2020

본 논문은 다양한 설계하중조건 상태에서 자동채염기 구조설계의 성능분석과 개선을 위해 실험계획법을 이용한 설계민감도 평가와 대리모델의 특성에 대한 비교연구를 수행하였다. 실험계획법은 수치해석 기반의 직교배열설계 방법을 이용하였다. 설계인자는 주요 구조부재의 두께치수 변수를 고려하였고, 응답치는 중량과 강도성능을 선정하였다. 직교배열실험을 통해 설계인자 별 응답치에 대한 정량적인 영향도를 분석하였다. 또한 최소의 중량증감으로 구조성능을 개선할 수 있는 최적의 설계조건을 탐색하였다. 직교배열실험 결과를 이용하여 반응표면모델, 크리깅모델, 그리고 체비쇼프 직교 다항식과 같은 다양한 대리모델을 생성하였다. 대리모델의 결과를 통해 직교배열실험 결과의 타당성을 검증하였다. 자동채염기 구조설계 공간 탐색에는 반응표면모델이 가장 적합한 대리모델로 평가되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.187-191
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• 2006

Sputter deposition followed by surface treatment was studied using reactive RF plasma as a method for preparing titanium oxide $(TiO_2)$ films on the FTO $(SnO_2: F)$ substrate for dye-sensitized solar cells (DSCs). Anatase structure $TiO_2$ films deposited by reactive RF magnetron sputtering under the conditions of $Ar/O_2(5%)$ mixtures, RF power of 600W and substrate temperature of $400^{\circ}C$ were surface-treated by inductive coupled plasma (ICP) with $Ar/O_2$ mixtures at substrate temperature of $400^{\circ}C$, and thus the films were applied to the DSCs. We have chosen a solar cell width as a variable of a large-scaled DSCs and confirmed electric characteristics of an individual cell. As a result, the higher the internal resistance of DSC becomes, the wider the width gets. Internal resistance makes it difficult to collect photoelectron generated from dye. Ultimately up sizing DSC causes the increase of internal resistance and then has a bad effect on the cell characteristics.

• 비파괴검사학회지
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• 제21권5호
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• pp.526-531
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• 2001

공통축 형태로 배치된 비자성체 이중관에 있어서 유한요소해석 상용 소프트웨어와 실험적인 방법을 각각 이용하여 원격장 와전류 에너지의 전달 경로를 연구하였다. 연구결과 이중관에 있어서 원격장 와전류 에너지는 두 관 사이의 공간을 따라 흐르는 것이 아니라, 단일 튜브의 경우와 마찬가지로 외측 튜브의 외면을 따라 흐름을 확인하였다. 이는 원격장 와전류 효과의 관벽투과 특성이 이중관에 있어서도 유효함을 보여주는 것이다. 따라서, 중수로형 핵연료 채널과 같은 이중관 형태를 대상으로 내관 및 외관의 내 외부 결함 탐상, gap 분포 및 지지대의 위치 확인 등에 원격장 와전류 방법의 관벽투과 특성이 응용될 수 있음을 보였다.

• 한국해양공학회지
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• 제34권4호
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• pp.253-262
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• 2020

This study provides a comparative analysis of experiments-based enhancements and sensitivity evaluations for the structural design of an automatic ocean salt collector under various load conditions. The sizing variables of the structural members were considered as design factors. The strength and weight performances were selected as output responses. The design of experiments used in the comparative study consisted of the orthogonal array design, Box-Behnken design, and central composite design. The response surface model, one of the metamodels, was applied to the approximate model generation. The design enhancement performance metrics, including numerical costs and weight minimization, according to the design of experiments, were compared from the best design case results. The central composite design method showed the most enhanced design results for the structural design of the automatic ocean salt collector.

• 한국펄프종이공학회:학술대회논문집
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• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.2
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• pp.475-478
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• 2006

Environment-friendly shock-absorbing materials were made using a vacuum forming method from waste wood collected from local mountains in Korea. The waste wood was pulped by thermomechanical pulping. The TMP cushions showed superior shock-absorbing properties with lower elastic moduli compared to EPS and pulp mold. Even though the TMP cushions made using different suction times had many free voids in their inner fiber structure, their apparent densities were a little higher than EPS and much lower than pulp mold. The addition of cationic starch improved the elastic modulus of the TMP cushions without increasing the apparent density, which was different from surface sizing with starch. The porosity of the TMP cushions was a little greater than EPS and much less than pulp mold. Finally, the TMP cushions have great potential to endure external impacts occurring during goods distribution.