• 한국지반환경공학회 논문집
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• 제9권3호
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• pp.35-43
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• 2008

본 연구는 소규모 하수고도처리시설에 대해 변형 연속회분식공정을 적용하여 그 효용성을 평가하였다. 변형 연속회분식공정은 단일 반응조 내에서 유기물질 및 질소, 인 등이 제거되며 유입수의 유량 및 수질특성에 의해 적합한 운전방식을 선택할 수 있다. 각 공정의 기능 향상을 위해 원수 유입조건의 제어, 간헐 폭기방식에 의한 무산소 및 호기조건의 적절한 분배 그리고 처리수와 잉여슬러지의 고액분리를 위한 처리수 배출장치의 적용으로 설계된 유량 및 수질에 비해 낮은 부하 조건임에도 1일 3Cycle 운전모드로써 안정적인 처리효율을 나타냈다. 평가결과 유기물질 제거효율은 BOD의 경우 평균 120.4mg/L에서 6.8mg/L로 94.4%, CODMn은 95.7mg/L에서 11.0mg/L로 88.5%의 처리효율을 나타냈다. T-N의 제거효율은 평균 32.2mg/L의 유입수 농도에 대해서 약 69.6%, T-P의 경우는 유입수 농도 4.65mg/L에 대해 73.6%의 처리효율을 나타냈다. 동절기 평균 T-N과 T- P의 처리효율은 58.8%, 68.5%로 약간 감소하였지만 안정적인 처리효율을 나타냈다. 1차 무산소 호기조건에서 BOD는 90%, T-N은 67% T-P는 46%정도로 제거되었으며 T-P는 2차 무산소 호기조건에서 약 70%정도 제거되었다. 따라서 유입수의 간헐유입과 무산소 호기조건의 적정한 분배에 의해 질산화, 탈질 및 인의 과잉섭취에 유기물이 적절히 이용된 것으로 평가되어 소규모 고도하수처리시설에 적합한 공정으로 판단된다.

• 환경위생공학
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• 제16권2호
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• pp.47-55
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• 2001

We investigated to find the optimum operation condition of electrolysis which have an influence on removal efficiency of heavy metals. When we experimented the testing wastewaters containing each 250mg/L of Cu and Ni ions, we got the variables like as pH, amount of electrolyte(NaCl), different species of electrode, electrode gap, electric strength, the number of electrodes, after fastening positive electrode plate with Al, Fe, Ti and negative electrode plate with Stainless Steel plate.

• 환경위생공학
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• 제16권3호
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• pp.87-95
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• 2001

We've been investegated to find the optimum operation condition of electrlysis which have an influance on disposal efficiency of heavy metals. When we electrolyzed the testing wastewaters containing each 250mg/L of Cr and Zn ions, we exerimented with using variables like as pH, NaCl, electrode gap, electric current strength, the number of electrodes, after fastening positive electrode plate with Al, Fe, Ti and negative electrode plate with Stainless Steel Plate.

• 환경위생공학
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• 제14권2호
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• pp.25-31
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• 1999

Energy recovery technology from municipal solid waste has been increasingly established in many countries. Anaerobic treatment of municipal sewage sludge has low digestion efficiency because of low organic loading rate of sewage sludge. The purpose of this study was to evaluate anaerobic biodegradability of food waste which was based on organic loading rate and seeding rate. From the results of anaerbic biodegration, the optimum condition for seeding rate was turn out over 40%, which did not inhibition of methane production.

• Journal of Welding and Joining
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• 제22권5호
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• pp.26-31
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• 2004

In order to propose the optimum welding condition for field application, the effects of welding heat input and cooling rate at PWHT on the mechanical properties were investigated. Submerged arc welding of 1.25Cr-0.5Mo steel for pressure vessel was conducted at welding heat inputs of 15.2kJ/cm, 30.9kJ/cm, and 44.8kJ/cm, and cooling rates of 184$^{\circ}C$/hr, 55$^{\circ}C$/hr, and 2$0^{\circ}C$/hr at PWHT. From the test results, as the welding heat input increase up to 30.9kJ/cm, the changes of microstructure and impact toughness were small. At the heat input of 44.8kJ/cm, however, toughness decreased obviously due to the coarsening of coarse-grained HAZ and formation of ferrite at bainite grainboundary of weld metal. On the other hand, cooling rates at PWHT did not effect on the changes in microstructure and mechanical properties. Even though tensile strength and impact toughness at all welding conditions of this study were above the minimum specification requirement, it was confirmed that heat input of 30.9kJ/cm was the optimum welding condition to improve welding performance by higher heat input.

• 한국세라믹학회지
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• 제15권3호
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• pp.157-167
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• 1978

The batch compositions and physical properties of slag-ceramics were studied with respect to their formability from the molten state and conditions of nucleation and crystal growth treatment. The selected batch compositions for nucleation and growth studies were slag, 56%; silica sand, 28%; $Na_2O＋MgO$, 8% and $TiO_2＋$chromite, 8%. The optimum nucleation condition was the temperature of 75$0^{\circ}C$ with 6 hrs. holding time and the optimum growth condition was the temperature 975$^{\circ}C$ with zero holding time. The slag-ceramics prepared under the above conditions showed the best developed microtexture. The grown crystals were identified as diopside with the average grain size of 5.7$\mu\textrm{m}$, and the amount of crystal grown were about 53% by weight. The prepared specimens of slag-ceramics showed the microhardness, 793kg/$\textrm{mm}^2$; MOR, 1,050 kg/$\textrm{cm}^2$ and thermal expansion coefficient, $85{\div}10^{-7}$cm/cm/$^{\circ}C$($25^{\circ}C$~$700^{\circ}C$).

• 동력기계공학회지
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• 제12권3호
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• pp.55-59
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• 2008

In this paper, we have investigated on collection efficiency of fine particle of glass fiber-filter bag according to the surface treatment. The solution consisted of polytetrafluoroethylene(teflon), graphite powder, silicon resin and water was used as a basic surface treatment agent. Tensile strength of glass filter-bag increased with up to 3hrs and then decreased with surface treatment time. Tensile strength and initial modulus of the glass fiber-filter bag treated by iodine after basic surface treatment for 3hrs were lower than those of basic surface treatment for 3hrs, however collection efficiency and fracture strain were higher than those of basic surface treatment for 3hrs. Glass fiber-filter bag with lower initial modulus and more strain will be extend the durable period and the one treated by iodine after basic surface treatment 3or 3hrs is expected high collection efficiency of fine particle. This method makes it possible to manufacture glass fiber-filter bag of the optimum condition.

• 열처리공학회지
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• 제26권4호
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• pp.165-172
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• 2013

In the present study, the microstructure and solution treatment response of Al-Zn-Mg alloys bars by thixo-extrusion was investigated. The alloy bars were solution treated at 400, 430, 460 and $490^{\circ}C$ for various times. In order to examine the microstructures and phase analysis of the samples after solution treatment, it was performed by optical and scanning electron microscopy. And, Vickers hardness and electrical conductivity was measured on the solution treated samples for each condition to investigate the solution treatment response of extruded bars during solution treatment. The results show that the optimum solution heat treatment conditions of thixo-extruded Al-Zn-Mg alloy for minimization of the grain growth and degradation promotion of the second phase is a temperature of $460^{\circ}C$ and holding time of 0.5 to 2 h.

• 대한환경공학회지
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• 제22권5호
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• pp.811-817
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• 2000

본 연구에서는 생물학적으로 질산화/탈질 처리한 침출수와 기존 라군 처리한 침출수를 대상으로 응집과 펜톤산화시 최적 처리조건을 탐색하고, 펜톤산화시 알카리도가 COD 처리효율에 미치는 영향을 조사하였다. Jar-Tester를 이용한 응집처리시 염화제이철($FeCl_3$)의 적정 투입농도는 약 $1500mgFe^{3+}/L$로 조사되었으며, 이때 $COD_{Cr}$은 약 55%, $COD_{Mn}$은 약 64%의 처리효율을 나타냈다. 응집처리후($1,500mgFe^{3+}/L$) 펜톤처리시 약품투입비는 $Fe^{2+}/H_2O_2$의 비 1.5에서 COD 처리효율은 약 80%로 최대 처리효율을 나타냈으며, 이때 최적 약품투입농도는 철염 $600mgFe^{2+}/L$, 과산화수소수 $400mgH_2O_2/L$이었다. 펜톤 산화시 유입수의 알카리도가 증가됨에 따라 COD 처리효율이 저하되었다.

• 상하수도학회지
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• 제21권4호
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• pp.467-475
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• 2007

This study was conducted to examine temperature effects on hydrogen production in anaerobic fermentation. 18 batch reactors were operated at mesophilic ($35^{\circ}C$) and thermophilic conditions ($55^{\circ}C$) to achieve maximum hydrogen production in anaerobic fermentation. Optimum hydrogen production conditions were also investigated at each temperature. Different trends were observed regarding pH effects on hydrogen production. This effect was not significant for mesophilic fermentation ($35^{\circ}C$). In this case, pH may not drop to interfere hydrogen production during the test. However, hydrogen production decreased without pH control for thermophilic condition ($55^{\circ}C$). Effects of heat treatment were observed for both fermentation process. Hydrogen production with heat treatment was higher than hydrogen production without heat treatment for both fermentation processes. The amount of produced hydrogen for each substrate concentration with temperature changes showed that more hydrogen was produced at $35^{\circ}C$ than at $55^{\circ}C$.