• Nuclear Engineering and Technology
• /
• 제37권4호
• /
• pp.375-384
• /
• 2005

To investigate the flow-accelerated corrosion (FAC) dependency of carbon steel (A106 Gr. B) and low-alloy steels (1Cr-1/2Mo, 21/4Cr-1Mo) on pH, orifice distance, and material, experiments were carried out. These experiments were performed using a flow velocity of 4 m/sec (partly 9 m/sec) at pH $8.0\~10.0$ in an oxygen-free aqueous solution re-circulated in an Erosion-Corrosion Test Loop at $130^{\circ}\;{\ldots}$ for 500 hours. The weight loss of the carbon steel specimens appeared to be positively dependent on the flow velocity. That of the carbon and low-alloy steel specimens also showed to be distinguishably dependent on the pH. At pH levels of $8.0\~9.5$ it decreased, but increased from 9.5 to 10.0. Utility water chemistry personnel should carefully consider this kind of pH dependency to control the water system pH to mitigate FAC of the piping system material. The weight loss of the specimens located further from the orifice in the distance range of $6.8\~27.2$ mm was shown to be greater, except for 21/4Cr-1Mo, which showed no orifice distance dependency. Low alloy steel specimens exhibited a factor of two times better resistance to FAC than that of the carbon steel. Based on this kind of FAC dependency of the carbon and low-alloy steels on the orifice distance and material, we conclude that it is necessary to alternate the composition of the secondary piping system material of NPPs, using low-alloy steels, such as 21/4Cr-1Mo, particularly when the system piping has to be replaced.

• 대한용접접합학회:학술대회논문집
• /
• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
• /
• pp.255-259
• /
• 2002

VIRGO 104 is a low carbon martensitic stainless steel that is applied to the famous Three Gorges Project. By using VOD melting process VIRGO 104 has low carbon and [H] [O] contents, and shows excellent mechanical properties and weldability. The best solution to guarantee welding quality is PWHT by 600 Cx8h.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2008년도 추계학술대회 논문집
• /
• pp.207-210
• /
• 2008

The effects of boron additions in steels have long been recognized as very important, mainly with respect to hardnability of heat treatable steels. we investigated the effect of the microstructure and mechanical properties with cooling condition after heat treatment of the boron-treated(${\fallingdotseq}8{\sim}18ppm$) low carbon(${\fallingdotseq}0.2%C$) low alloy steel. The specimens were austenitised for 10 min at $910^{\circ}C$, cooled for the various periods of time from 10 sec to 30 sec or with water after forming for 15 sec. After cooling, mechanical properties were measured by tensile test and hardness test. For analysis of microstructure, Optical were carried out.

• Carbon letters
• /
• 제6권3호
• /
• pp.148-157
• /
• 2005

Carbon/Carbon Composites due to their far superior thermo-mechanical properties are used in a number of demanding applications. However, the material still is used only in specific high tech applications with few exceptions in general industrial applications. The material is extremely expensive and the major challenge is to reduce its cost. Various innovative processing routes are outlined to reduce the cost of processing.

• 한국자동차공학회논문집
• /
• 제20권3호
• /
• pp.141-147
• /
• 2012

A direct injection diesel engine with large amount of exhaust gas recirculation was used to investigate low temperature diesel combustion. Pilot injection strategy was adopted in low temperature diesel combustion to reduce high carbon monoxide and hydrocarbon emissions. Combustion characteristics and exhaust emissions of low temperature diesel combustion under different pilot injection timings, pilot injection quantities and injection pressures were analyzed. Retarding pilot injection timing, increasing pilot injection quantity and higher injection pressure advanced main combustion timing and increased peak heat release rate of main combustion. As a result of these strategies, carbon monoxide and hydrocarbon emissions were reduced. Soot emission was slightly increased with retarded pilot injection timing while the effect of pilot injection on nitrogen oxides emission was negligible under low combustion temperature condition. Spatial distribution of fuel from the spray targeting visualization was also investigated to provide more insight into the reason for the reduction in carbon monoxide and hydrocarbon emissions.

• 한국세라믹학회지
• /
• 제45권1호
• /
• pp.36-42
• /
• 2008

Carbon/$TiO_2$ composite photocatalysts were thermally synthesized with different mixing ratios of anatase to phenol resin through an ethanol solvent dissolving method. The XRD patterns revealed that only anatase phase can be identified for Carbon/$TiO_2$ composites. The diffraction peaks of carbon were not observed, however, due to the low carbon content on the $TiO_2$ surfaces and the low crystallinity of amorphous carbon. The results of chemical elemental analyses of the Carbon/$TiO_2$ composites showed that most of the spectra for these samples gave stronger peaks for carbon and Ti metal than that of any other elements. The BET surface area increases to the maximum value of $488\;m^2/g$ with the area depending on the amount of phenol resin. From the SEM images, small $TiO_2$ particles were homogeneously distributed to a composite cluster with the porosity of phenol resin-based carbon. From the photocatalytic results, the MB degradation should be attributed to the three kinds of synergetic effects, such as photocatalysis, adsorptivity, and electron transfer by light absorption between supporter $TiO_2$ and carbon.

• 대한공간정보학회지
• /
• 제18권3호
• /
• pp.75-81
• /
• 2010

기존의 자전거 도로에 대한 연구는 대부분 자전거 도로의 신설을 통하여 활성화하기 위한 연구가 대부분이었다. 그러나 점차 자전거 도로의 이용자가 증대됨에 따라 녹색 교통수단으로서의 자전거 이용을 활성화하기 위해서는 저탄소 녹색성장 기반의 서비스가 필요한 실정이 되었다. 기존의 자전거 이용정보의 분석은 주로 운동량에 기반하고 있어 사용자의 다양한 요구사항을 수용하고 있지 못하고 있다. 따라서 본 연구에서는 자전거를 이용함으로서 절감할 수 있는 이산화탄소, 유류비, 지구온난화 처리비용 등을 계산할 수 있는 방법을 제안하였다. 이를 위해 GPX(GPS eXchange Format) 파일형태로 제공되는 자전거 이용정보를 구글어스 기반의 3차원 환경에서 디스플레이하고 저탄소 녹색성장 기반의 서비스를 할 수 있는 프로그램을 구현하였다. 개발된 응용프로그램은 기존의 상업용 소프트웨어와 비교하였다. 본 연구를 통해서 자전거 이용자 측면에서 저탄소 녹색성장을 실천할 수 있는 서비스를 개발하였으며 스마트폰과 같은 단말기에도 적용할 수 있을 것으로 사료된다.

• 한국식품영양과학회지
• /
• 제22권2호
• /
• pp.127-131
• /
• 1993

단백식이조건을 달리하여 성장시킨 동물에 $CCl_4$를 투여하였을 때 혈청중 lipoprotein 분획비의 변동 및 이의 원인을 검토할 목적으로 흰쥐를 저단백식이(7% casein : LP) 및 고단백식이 (20% casein : HP)로 성장시킨 후, 50% $CCl_4$(v/v in olive oil)를 복강내 주사한 다음 간 중량 및 혈청 ALT 활성도 측정으로 간손상을 확인함과 동시에, 혈청지질과 혈청 lipoprotein 분획비를 측정하였다. $CCl_4$투여시 체중 당 간무게 및 혈청중 ALT의 활성도는 대조군에 비해 증가하였으며 그 증가율은 HP군이 LP군보다 더 높게 나타났다. 혈청중 총지질, 총 cholesterol 및 triglyceride의 함량은 대조군간에 별다른 차이를 관찰할 수 없었으나, $CCl_4$투여로 인해 이들 지질은 대조군에 비해 감소하였으며, 그 감소율은 HP군이 LP군보다 높게 나타났다. $CCl_4$투여로 인한 lipoprotein분획비의 변동은 대조군에 비하여 양군 공히 pre $\beta$-lipoprotein비율 및 $\alpha$-lipoprotein 비율은 감소되었고, 그 감소율은 HP군이 LP군에 비해 더 크게 나타났다. 한편 $\beta$-lipoprotein비율은 $CCl_4$투여로 인하여 두군 공히 증가하였으며 그 증가율은 HP군에서 높게 나타났다. 이상의 실험결과와 문헌상의 지견을 종합해 볼때 $CCl_4$투여시 LP군에 비하여 HP군에서 간손상이 보다 더 심하게 나타나며, 이로 인하여 apoprotein의 합성억제현상이 초래됨으로써 혈청중 lipoprotein분획비의 변동이 높게 나타날 것으로 생각된다.

• Nuclear Engineering and Technology
• /
• 제43권1호
• /
• pp.1-6
• /
• 2011

The behavior of the non-equilibrium grain boundary segregation of boron in low carbon steel was studied through a particle tracking autoradiography. The behavior of the non-equilibrium grain boundary segregation of boron during continuous cooling was compared with the isothermal kinetics of the non-equilibrium grain boundary segregation of boron at the holding temperature using an effective time method. On the basis of the experiments, the cooling rate dependence of the non-equilibrium segregation of boron was explained using the time dependence of the non-equilibrium segregation of boron in low carbon steel. The experimental observations for the cooling rate dependence of the grain boundary segregation of boron are in good agreement with the time dependence of the grain boundary segregation of boron. The mechanisms of the non-equilibrium segregation of boron during cooling in low carbon steel are also discussed.

• 소성∙가공
• /
• 제9권1호
• /
• pp.66-71
• /
• 2000

The present study tackles the metallurgical subjects involving the thin slab-direct hot rolling process, i.e. mini-mill process. In order to clarify the effect of chemical composition of steel and MnS precipitation behaviors on the development of edge cracking during hot rolling, the content of manganese and sulfur in low carbon steel was varied and the isothermal treatment prior to roughing was applied. Edge cracking during roughing in the hot-rolling process of mini-mill was effectively prevented by means of the isothermal treatment at 115$0^{\circ}C$ for 5 minutes in the 0.4% manganese steel containing sulfur lower than 0.013%. With the increase in manganese content in low carbon steel, coarser MnS developed. The edge cracking index which denotes the total length of edge crack per unit edge-length of rolled specimens was proposed in this paper. It was found that the edge cracking index linearly decreased with the increase in the ratio of MnS.