• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.172-179
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• 1999

As the martensite structure cause fracture failure during drawing from 5.5mm rod to 3.05mm dia. wire without additional heat treatment, the optium cooling condition to inhibit the occurrence of martensite was investigated. In order to get SAE9254+V quality, the effects of alloying element, vanadium on the mechanical properties were investigated. Based upon CCT and TTT curves and the results form cooling test in mill, optimun cooling was found in the condition of the laying head temp of 780$^{\circ}C$ and of the conveyor speed at 0.15m/sec with the whole cover closed. The wire rods produced under the condition showed the best mechanical properties of 120kg/$\textrm{mm}^2$ in TS and 50% in RA, having an excellent drawability. In vanadium added steels, tensile strength was improved without degrading elongation and charpy impact value. That means the strengthening by vanadium is mainly due to the grain refinement by the fine precipitates during tempering process.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1657-1659
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• 1996

The objective of this study is to provide a life prediction of isothermal fatigue using strain partitioning of high temp. steel for power plants. The experimental system was composed of Instron 8501, induction heating system, extensometer and pyrometer with hydraulic power system

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1988년도 춘계학술대회 논문집
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• pp.7-9
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• 1988

This paper considers problems which must be overcome to produce long lengths of superconductor wire from the 90K Tc superconducting ceramic material, $Y_1Ba_2Cu_3Ox$. Attention is focused on the powder-in-tube process where the superconducting powder is placed in a tube which is then formed into wire. Two major problems are considered, control of the oxygen level and improvement of Jc in the final wire. The results show that Jc of the wire were $400A/cm^2$ at liquid nitrogen temp.

• 상하수도학회지
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• 제21권1호
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• pp.83-89
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• 2007

A biological anoxic-aerobic reactor filled with porous media was operated in lab scale for the advanced wastewater treatment. The experiments were conducted for 6 months with three HRTs (4, 6, 8hr) and temperature of $23{\sim}25^{\circ}C$. Some other experimental conditions were as follows; nitrification reactor (MLSS 4,500mg/L, DO 3.3mg/L, $23{\sim}28^{\circ}C$), denitrification reactor(MLSS 8,000mg/L, ORP -100mV, Temp.$19{\sim}23^{\circ}C$). Average removal efficiencies of SS, $BOD_5$, $COD_{Cr}$, T-N, and T-P were 97.8%, 95.5%, 94.5%, 80.2%, and 60.6%, respectively. The reactor filled with porosity media showed stable removal capacity for organics and nutrients. Fast and complete nitrification and denitrification were accomplished. Maintaining high MLSS with porous media in the nitrification and denitrification reactor appears to enhance the nitrogen removal process. For the higher T-P removal, some coagulant addition process will be needed.

• 대한설비공학회지:설비저널
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• 제5권4호
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• pp.272-280
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• 1976

A natural ventilating type store was designed for the economic and effective storage of citrus fruits in Jejudo. The material used for the wall is scoria, widely distributed in Jejudo and known for high strength and insulation. Design condition was chosen for the period till March of a year and the dry bulb temperature was taken from TAC $5\%$ base. The temperature of the store can be maintained below the limiting temperature of $8^{\circ}C$ for the time length of $7\frac{1}{2}$ hours under the condition of the atmospheric temp, $15.3^{\circ}C$ and the solar insolation. The limiting temperature can he recovered to the initial temperature $(7^{\circ}C)$ by the natural ventilation for 8 hours in the night.

• 펄프종이기술
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• 제33권2호
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• pp.32-40
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• 2001

It is desirable to reduce the amounts of fresh water and reuse the recycled water in papermaking process. In an attempt to improve the efficiency of recycling water refining treatment and to enhance the productivity of OCC recycling mill, up flow anaerobic sludge blanket(UASB) reactor was developed and introduced to Korea recently. In order to maximize the operating efficiency and minimize the adverse side effects it is imperative to estimate and evaluate the total effects of new system, UASB on the whole OCC recycling process. This study was carried out with a view to investigate the effects of the high temperature and alkalinity of process water on the quality ad productivity of testliner of OCC recycling mill which is equipped with UASB reactor and almost closed. Another object of this study was searching for the best available use of UASB treated process water. The results were as follows; Reuse of UASB treated water characterized with high temp and alkalinity was useful to improve the strength and drainage properties of recycled OCC owing to its good points of promoting OCC disintegration and reducing the calcium hardness of process water. However, it might not be avoidable to induce the increase of dissolved solids in process water in accordance with direct introducing of UASB treated water into the former stage of OCC stock preparation. So it would be advisable to adopt the UASB treated water in the stage of clean, screened OCC stock.

• Bulletin of the Korean Chemical Society
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• 제9권5호
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• pp.289-291
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• 1988

The ratio of trivalent to divalent copper has been determined by the redox titration for two superconducting phases of $YBa_2Cu^{3+}_{2x}Cu^{2+}_{3-2x}O_{6.5+x}$ with the onset temp. of 60K (x = 0.23 ${\pm}$ 0.01) and 90K (x = 0.35 ${\pm}$ 0.02), and for the insulating one (x ${\cong}$ 0) which was kept in an ambient atmosphere for 72 hrs. It is found that $T_c$, and the ratio of $Cu^{3+}/Cu^{2+}$ depend strongly on the annealing temperature and time. A typical orthorhombic phase can easily be obtained by a slow cooling or stepwise cooling at $PO_2$ = 1 atm, and shows a high Tc (ca. 90K) superconductivity.

• 한국환경보건학회지
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• 제34권5호
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• pp.374-381
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• 2008

In this study, the factors affecting biological N and P removal using SND (simultaneous nitrification and denitrification) process were investigated and evaluated to examine the possibility of treating N and P through SND with NADH by surveying N and P traces in an aeration tank. Variations of $NH_4^+$-N+$NO_3^-$-N concentration were used to estimate the degree of SND in each point (P2, P3, P4, P5) of the aeration tank and these variations showed that denitrification efficiency in P2 (front zone), nitrification and denitrification efficiencies in P4 (middle zone) were 67%, 86% and 39%, respectively. When $PO_4^{-3}$-P concentration was analyzed in each point of the aeration tank, it was shown that $PO_4^{-3}$-P concentration coming into P2 was 1.25 mg/L, which increased to 2.22 mg/L by P release in P2 zone and then decreased to 0.74 mg/L by P uptake in P4. Consequently, we were able to estimate which high P removal efficiency observed in this study was caused by biological phosphorus removal. To determine the operating factors affecting effluent T-N, we analyzed the correlation among FN/M ratio, C/N ratio, Temp., SRT etc and these results showed that the correlation among FN/M ratio, C/N ratio and Temp was not high. However, the relationship of SRT and other parameters (effluent $NH_4^+$-N and effluent BOD) and the short SRT could have an affect on effluent $NH_4^+$-N and so effluent BOD could be increased. Thus, SRT operation should be controlled over 10 days. The results for analyzing the correlation between SRT and influent $NO_3^-$-N in order to investigate the operating factors affecting effluent T-P showed that T-P or $PO_4^{-3}$-P was not highly correlation with SRT, whereas $PO_4^{-3}$-P concentration increased along with increasing $NO_3^-$-N concentration into P2. Based on these results, we concluded, using regression analysis (R2=0.97), that effluent $PO_4^{-3}$-P concentration depends on $NO_3^-$-N concentration into P2.

• 한국재료학회지
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• 제8권10호
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• pp.879-883
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• 1998

초합금의 진공정밀주조시에 진공하에서 용해한 합금을 $1000~1700^{\circ}C$로 가열한 세라믹 주형에 주입하고 난 후, 용탕이 장시간 주형안에 노출됨으로써, 주형의 고온강도가 높아야 하므로 고품위의 주형재를 사용하여 왔으나, 저품위의 값싼 소재를 사용하여 고품위의 주형과 동등한 효과를 갖게 하고자 주형내의 Silica 함량을 조절하였다. 그 결과 SiO2 첨가량이 7.7wt.%일 때, 다른 시험편에 비해 소성강도와 고온강도가 10-55%가량 증가 하였다. 따라서 일반적으로 정밀주조 주형으로 사용하는 용융알루미나와 colloidal silica의 혼합비를 제어하여 단결절 주조용 주형을 개발하였다.

• 한국잡초학회지
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• 제16권4호
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• pp.309-316
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• 1996

파대가리를 스크리닝 실험재료로 이용하거나 자연조건에서의 방제를 위한 기초자료를 획득하고자 번식기관의 발아특성과 제초제에 대한 반응을 조사하였다. 1. 파대가리 휴면타파(休眠打破)에는 저온습윤과 고온건조가 효과적이었으며 저온습윤 조건에서는 1-2 개월 저장으로, $40^{\circ}C$ 고온에 저장할 경우는 3개월째 이상의 저장이 필요하였다. 근경(根莖)의 경우는 휴면(休眠)이 없거나 매우 낮았다. 파대가리 종자의 발아최적온도는 $30^{\circ}C$ 내외인 반면에 근경(根莖)의 경우는 16-$20^{\circ}C$ 범위로서 두 번식 기관간에 다른 온도반응을 보였으며 종자의 발아에는 광(光)이 요구되었다. 2. 근경(根莖)이 3cm 깊이에 심겨 있으면 번식정도가 50% 정도 감소되었으며 4cm 에서는 80% 이상 감소되었다. 파종당시에 담수처리(湛水處理)된 번식기관은 전혀 발아되지 못하였다. 생육중에 담수처리(湛水處理)를 할 경우 근경(根莖)으로부터 나온 유묘(幼苗)는 잎이 물속에 담겨 있을지라도 어느 정도 생육이 되었지만 종자로부터 나온 유묘(幼苗)는 더 이상 생육하지 못하였다. 근경(根莖)의 생체중 감소가 50% 이상 될 정도로 건조되면 출아력(出芽力)이 상실되는 경향이었다. 3. 처리된 약제들중 토양처리효과가 비교적 뚜렷한 것은 amitrole, DTP, fluridone, bensulfuron 등이었고, 경엽처리효과가 양호한 것은 fluridone, bentazone, benfuresate, bensulfuron 등이었다.