• 펄프종이기술
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• 제33권5호
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• pp.1-11
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• 2001

In the past, abundant and clean water was available for paper mills'use. However, the growth of population and industry made water less available nowadays. Also, environmental regulation limits wastewater discharge, which affects mill operation cost. Therefore, paper mills are under pressure to use more recycled water and mill system closure. As a result, chemical and physical parameters of water are changing and new environment if being created for microorganisms in paper mill system as well. The more soluble or suspended organic materials are increased as more water is recycled and less or scarce dissolved oxygen is available, depending on the degree of recycled water usage. Microorganism flora ill paper mill system will be a1so shifted according to the environmental change of mill system. Anaerobic bacteria, including sulfate reducing bacteria (SRB), will be dominant in the system as very low or almost no oxygen available in the system. Nevertheless, it is common in domestic paper mills that employ the same and old biocides as a means of microbial control, and microbiological control is often less recognized or even neglected. The right biocide selection for increased reductive environment of mills is critical for operation and estimated loss from paper quality defects such as sheet break, holes due to microbiological cause is tremendous compared to the microbiological control cost. It is imperative to investigate and diagnosis the environmental change of mills for right control of cumbersome microorganisms. Several useful diagnosis tools, including new technology employing OFM(Optical Fouling Monitor) in situ, are illustrated.

• Tribology and Lubricants
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• 제31권6호
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• pp.258-263
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• 2015

Biodiesel is an environmentally-friendly fuel with low smoke emission because it contains about 10% oxygen. Biodiesel fuel prepared by transesterification of vegetable oil or animal fats is susceptible to auto-oxidation. The rate of auto-oxidation depends on the number of methylene double bonds contained within the fatty acid methyl or ethyl ester groups. Biodiesel may be easily oxidized under several conditions, i.e., upon exposure to sunlight, temperature, oxygen environment. Maintenance of the fuel quality of biodiesel requires the development of technologies to increase the resistance of biodiesel to oxidation. Treatment with antioxidants is a promising approach for extending the shelf-life or storage time of biodiesel. The chemical properties of various amine-based antioxidants were evaluated after synthesis of the antioxidants by condensation of phenylenediamine with alkylamines at room temperature. In general, the oxidative stability can be assessed based on various experimental parameters. Such parameters may include temperature, pressure, and the flow rate of air through the samples. The Rancimat method (EN14112) was selected because it is a rapid technique that requires very little sample and provides good precision for oxidative degradation analysis. Specifically, the EN 14112 technique provides enhanced efficiency for oxidative stability evaluation when a larger ester head group is utilized. Therefore, this technique was employed for evaluation of the oxidation stability of biodiesel by the Rancimat method (EN14112).

• 한국표면공학회지
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• 제51권4호
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• pp.231-236
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• 2018

We report p-type electrical characteristics of the amorphous $La_2NiO_{4+{\delta}}$ thin films which were sputtered on the glass substrates using an RF sputtering system. As-deposited thin films at room temperature and $300^{\circ}C$ were amorphous in nature. Post-annealing of the thin film samples over $400^{\circ}C$ resulted in the nano-crystallization of the $La_2NiO_{4+{\delta}}$. The electrical properties of the films were much dependent on the oxygen partial pressure, temperature of the post-annealing and sputtering ambient. The as-deposited samples at room temperature show a hole concentration of $7.82{\times}10^{13}cm^{-3}$, and it could be increased as high as $3.51{\times}10^{22}cm^{-3}$ when the films were post-annealed in an oxygen atmosphere at $500^{\circ}C$. Such p-type conductivity behavior of the $La_2NiO_{4+{\delta}}$ films suggests that the amorphous and nano-crystallized $La_2NiO_{4+{\delta}}$ films have potential for the application as p-type semiconductive or conductive materials at low temperatures where material diffusion is limited.

• 대한임상검사과학회지
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• 제50권2호
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• pp.136-143
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• 2018

심근부담률은 심근산소소비량을 간접적으로 측정하는 지표로 심박수와 수축기 혈압의 곱으로 나타내며, 심근이 받는 부담을 나타낸다. 본 연구는 한국성인을 대상으로 트레드밀 운동부하 검사시 대사증후군에 따른 심근부담률의 적정 수준을 제시함으로써 대사증후군 유병률을 낮추기 위한 심근부담률의 목표치를 설정하여 그 기준을 제시하고자 하였다. 대사증후군 진단은 National Cholesterol Education Program (NCEP)의 Adult Treatment Panel (ATP) III에서 제시한 5가지 진단기준 중 3개 이상 충족하는 경우 대사증후군 진단군(MetS, N=25), 1~2개의 기준에 해당하는 경우를 대사증후군 전단계군(Pre-MetS, N=106), 5개의 진단기준에 해당하지 않는 경우는 대사증후군 위험요인이 없는군(Non-MetS, N=65)으로 분류하였다. 운동부하검사는 Bruce 프로토콜에 따라 시행하였다. 심근부담률은(심박수${\times}$수축기 혈압)${\div}1,000$으로 구하였다. 본 연구결과 대사증후군 진단군에서 도달한 일량이 낮음에도 불구하고 최대 수축기 혈압이 높은 것으로 나타났다. 또한 대사증후군에 따른 운동부하 검사시 심근부담률의 최적 임계점은 운동부하검사 1단계에서는 $12.56mmHg{\times}beats/min{\times}10^{-3}$, 운동부하검사 2단계는 $16.94mmHg{\times}beats/min{\times}10^{-3}$, 운동부하검사 3단계에서는 $21.11mmHg{\times}beats/min{\times}10^{-3}$로 나타났다.

• 대한전자공학회논문지
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• 제26권7호
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• pp.73-82
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• 1989

실리콘계 절연박막 형성을 위한 저온공정을 개발하기 위하여 photo-CVD장치를 제작하여 $SiO_2$ 박막을 $50{\sim}250^{\circ}C$ 범위에서 증착시켰다. 이때 $SiH_4/N_2O$ 혼합가스는 수은증감반응법을 사용하지 않고 저압수은램프의 직접 광여기에 의해 분해시켰다. AES와 ESCA 분석결과 Si와 O의 화학량론적 구성이 거의 모든 공정조건에서 1:2로 나타났고, Si와 O원자의 결합상태가 $SiO_2$의 형태로 이루어져 있음을 보여주었다. 그리고 박막의 굴절율은 $1.39{\sim}1.44$의 범위로 나타나, 저온증착에 의해 밀도가 비교적 낮은 박막이 형성됨을 보였다.

• 자원리싸이클링
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• 제18권5호
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• pp.19-25
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• 2009

몰리브덴 산업에서 가장 중요한 광물인 휘수연석($MoS_2$) 정광은 일련의 산화배소정제 공정을 통하여 공업용 산화몰리브덴(technical grade $MoO_3$)으로 제조되어 각종 몰리브덴 화합물의 중요한 원료로서 사용된다. 본 연구에서는 저품위 휘수연석 정광의 산화배소 특성을 조사하였다. 실험은 0.08 atm~0.21 atm의 산소분압과 793~823 K의 배소은도 범위에서 TGA 장비를 사용하여 수행하였으며, 사용한 휘수연석 정광의 입자크기는 평균 $67\;{\mu}m$ 이다. 실험 결과 산화배소 온도 823 K, 시간 60분에서 95% 이상의 휘수연석이 산화몰리브덴으로 전환되는 것으로 나타났다. 또한 Jander 식이 저품위 몽골산 휘수연석 정광의 산화배소 속도 데이터를 분석하는데 유용한 것으로 분석되었으며, 산소 분압에 대해서는 0.11 차인 것으로 조사되었다.

• 한국세라믹학회지
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• 제49권4호
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• pp.369-374
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• 2012

Based on the structure feature of a tree, a cylindrical $Ti_2AlC$/graphite layered composite has been fabricated through heat treating a graphite column and six close-matched thin wall $Ti_2AlC$ cylinders bonded with the $Ti_2AlC$ powders at $1300^{\circ}C$ and low oxygen partial pressure. SEM examination reveals that the bond interlayers between cylinders or that between cylinder and column are not fully dense without any crack formation. During the compressive test, the strain of the $Ti_2AlC$/graphite layered composite is about twice higher than that of the monolithic $Ti_2AlC$ ceramic, and the compressive strength of the layered composite is 348 MPa. The layered composite show the noncatastrophic fracture behaviors due to the debonding and shelling off of the layers, which are different from the monolithic $Ti_2AlC$ ceramic. The mechanism of the improved deformation capacity and noncatastrophic failure modes are attributed to the presence of the central soft graphite column and cracks deflection by the bond interlayers.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.205-205
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• 2009

As a p-type semiconductor NiO is potential material which can be used in many application including QD-LED. NiO films were deposited on glass substrates using rf-sputtering method. The properties of resistivity, surface roughness, etc in the NiO films were investigated at different sputtering parameters. The resistivity of $l.88{\times}10^{-2}{\sim}3.71{\times}10^{-2}{\Omega}cm$ with sputtering power(80~200 watts) and change was very low. The sputtering pressure at 3~60 mTorr resulted in rather broad change ofresistivity of $0.58{\times}10^{-2}{\sim}4.67{\Omega}cm$. The oxygen content in sputtering gas was found to be very effective to control the resistivity from $2.01{\times}10^{-2}$ to $1.22{\times}10^2{\Omega}cm$ with 100~2.5% $O_2$ in Ar gas. In addition, the surface roughness showed the RMS values of 0.6~1.1 nm and the dependence on sputtering parameters was weak.

• 한국결정성장학회지
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• 제14권3호
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• pp.90-94
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• 2004

The variation of electrical properties of (Ba,Sr)$TiO_3$ [BST] thin films for Metal-Insulator-Semiconductor (MIS) capacitors was investigated. BST thin films were deposited on p-Si(100) substrates by the RF magnetron sputtering with temperature range of 500~$600^{\circ}C$. The dielectric properties of MIS capacitors consisting of AUBST/$SiO_2$/Si sandwich structure were measured for various conditions. We examined the characteristics of MIS capacitor with various oxygen pressure, substrate temperature and (Ba+Sr)/Ti ratio. It was found that the leakage current was reduced in MIS capacitor with high quality $SiO_2$ layer was grown on bare p-Si substrate by thermal oxidation. The BST MIS structure showed relatively high capacitance even though it is the combination of high-dielectric BST thin films and $SiO_2$ layer. The charge state densities of the MIS capacitors and Current-voltage characteristics of the MIS capacitor were investigated. By applying $SiO_2$ layer between BST thin films and Si substrate, low leakage current of $10^{-10}$ order was observed.

• 융복합기술연구소 논문집
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• 제3권1호
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• pp.15-18
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• 2013

The next generation alternative fuel of diesel, DME (Dimethyl Ether) discharges particulate matter hardly due to chemical structural as oxygen-fuel so it has the eco-friendly property. Despite these advantages, the DME has the technical difficulties to apply to the diesel engine because of a low calorific value, viscosity and compressibility effects. From this point of view, we performed experimental studies on improved reliability of DME common-rail vehicle and lubricity enhancement of DME fuel for empirical distribution of eco-friendly DME fuel. Also we analyzed solubility of lubrication enhancer according to a drop in temperature, try to secure reliability about core parts of DME vehicle by applying lubrication enhancer in the DME common-rail vehicle.