• 한국농공학회:학술대회논문집
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• 한국농공학회 2003년도 학술발표논문집
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• pp.195-198
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• 2003

A small amount of cement can be added to the soil with high water content to improve its engineering properties. It is difficult to point out the exact time when liquified state of soil is transformed into semi-plastic or plastic states when high water content soil is hydrated by cement. In this study fall cone penetration are used to explain the phase change and compactable status of soil cement. And engineering properties of soil cement compacted in plastic state are investigated. Results reveal that fall cone penetration depth of 1mm or less is judged to a compactable state of soil-cement. Permeability and CBR values of soil cement increased with mixing ratio increased.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.245-249
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• 2003

Vapor-liquid equilibrium data were obtained for system of propane + R227ea (Heptafluoropropane) over the temperature range from 253.15 K to 323.15 K at 10 K intervals. Experiments were performed in a circulation type apparatus by injecting vapor through liquid pool using a magnetic pump. This system forms azeotrope in the temperature range of this study. The experimental results were correlated with the Peng-Robinson (PR) equation of state and Redlich-Kwong-Soave (RKS) equation of state using the van der Walls one-fluid mixing rule and were compared with each other.

• 대한기계학회논문집B
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• 제30권9호
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• pp.898-904
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• 2006

A new method measuring thermal conductivity of fluids is proposed in this research. It is based on the steady state heat transfer from a hot central cylinder to a cold outer cylinder located concentrically. This method guarantees more stable measurement than conventional THM(transient hot-wire method) due to its simplicity of theoretical principle. Measurements was made for the three nanofluid samples with different particle concentration of pure, 2% and 4%. Nanofluids are made by mixing the pure transformer oil with AlN nano particles. Design of the sensor module and experimental procedures are explained and comparison of the measuring data between present method and THM was made in detail.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.137-140
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• 2005

The objective of this experimental study is to grasp an influence of moisture state of aggregate on the characteristics of the recycled aggregate concrete. The moisture states of the aggregates were controlled at prewetted, oven-dried and saturated surface-dried states prior to use. To maintain the designed mix proportioning unchanged, the amounts of water and aggregates used in mixing were adjusted according to the actual moisture contents of the aggregates. Test results showed that the saturated surface-dried state aggregate concretes exhibited the highest compressive strength.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2545-2552
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• 2018

$SF_6$ has been widely used in high voltage power equipment, such as gas insulated switchgear (GIS) and gas insulated transmission line (GIL), because of its excellent insulation and arc extinguishing performance. However, $SF_6$ faces two environmental problems: greenhouse effect and high liquefaction temperature. Therefore, to find the $SF_6$ substitute gases has become a research hotspot in recent years. In this paper, the liquefaction characteristics of $SF_6$ substitute gases were studied. Peng-Robinson equation of state with the van der Waals mixing rule (PR-vdW model) was used to calculate the dew point temperature of the binary gas mixtures, with $SF_6$, $C_3F_8$, $c-C_4F_8$, $CF_3I$ or $C_4F_7N$ as the insulating gas and $N_2$ or $CO_2$ as the buffer gas. The sequence of the dew point temperatures of the binary gas mixtures under the same pressure and composition ratio was obtained. $SF_6/N_2$ < $SF_6/CO_2$ < $C_3F_8/N_2$ < $C_3F_8/CO_2$ < $CF_3I/N_2$ < $CF_3I/CO_2$ < $c-C_4F_8/N_2$ < $C_4F_7N/N_2$ < $c-C_4F_8/CO_2$ < $C_4F_7N/CO_2$. $SF_6/N_2$ gas mixture showed the best temperature adaptability and $C_4F_7N/CO_2$ gas mixture showed the worst temperature adaptability. Furthermore, the dew point temperatures of the $SF_6$ substitute gases at different pressures and the upper limits of the insulating gas mole fraction at $-30^{\circ}C$, $-20^{\circ}C$ and $-10^{\circ}C$ were obtained. The results would supply sufficient data support for GIS/GIL operators and researchers.

• 한국콘텐츠학회논문지
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• 제7권3호
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• pp.17-24
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• 2007

중앙에 컨퍼런스 서버가 위치하여 컨퍼런스 전체를 제어하고 관리하는 SIP(Session Initiation Protocol) 기반의 밀결합 형태의 컨퍼런스 방식은 포커스(focus)와 믹서의 위치에 따라 중앙 집중형, 단말서버형, 미디어 서버 분리형, 믹서 분산형 등 여러 모델로 분류할 수 있는데 모두 각각의 장단점을 가지고 있다. 본 논문에서는 서버와 참가자 사이에 오가는 SIP 시그널링 메시지 양을 줄일 수 있고 서버의 미디어 믹서 부하를 경감시킬 수 있으며 또한, 대규모 컨퍼런스로의 확장이 용이한 SIP 기반의 효율적인 혼성 형태의 컨퍼런스 모델을 제안하고 이를 설계 및 구현하였다. 이 모델에서는 참가자 수가 미리 정해진 일정한도를 넘으면 서버는 특정 기능을 가진 참가자들을 선택하여 이들로 하여금 컨퍼런스 상태 이벤트 패키지의 통지 기능 및 미디어 믹서 기능을 서버와 분담하도록 한다. 각 참가자는 서버에 컨퍼런스 상태 이벤트 패키지를 등록할 때 특정 헤더 메시지로 이와 같은 기능의 보유 여부를 알릴 수 있고 서버는 컨퍼런스 정보 데이터베이스에 이를 표시하여 나중에 기능을 분담할 참가자들을 선정할 수 있게 된다. 제안된 방식은 실험을 통하여 성능을 측정하였다.

• Tribology and Lubricants
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• 제6권1호
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• pp.36-51
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• 1990

A parametric study of the thermal effects of a half-circumferential grooved journal bearings under aligned and misaligned conditions has been carried out by solving numerically the coupled Reynolds and energy equation system. Five different sets of boundary conditions for the energy equation have been used which include mixing between recirculating oil and inlet oil and a contraction ratio for the cavitation region. The effects of changes of the inlet oil temperature and pressure, the wall temperature and the L/D ratio have also been examined. For the range of parameters found in internal combustion engines, the mixing effectiveness at the groove and the resulting final mixture temperature have been found to be as important as the wall temperature and the heat transfer rate. The variability of the temperature, though, has been shown to smooth out the peaks of both pressure and friction during misaligned condition Distributions of friction and pressure in the oil are also examined which may be useful in attempts to reduce friction without reducing load. Results for an axial grooved bearing are also presentsed for comparision purpose.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2015년도 추계 학술논문 발표대회
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• pp.109-110
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• 2015

In this study, fresh state properties and mechanical properties of low slump concrete which is applied to road pavement have been evaluated by mixing modified sulfur. As results, influence of mixing modified sulfur on the workability was low. Also, compressive strength, and flexural strength tend to decrese with increasing addition rate of modified sulfur. However compressive strength, and flexural strength of modified sulfur concrete were equivalent with that of plain concrete.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2014년도 제49회 KOSCO SYMPOSIUM 초록집
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• pp.339-342
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• 2014

Rotary kiln produces lime from limestone through thermal decomposition. Ring formation in kiln internal wall is known issue that decreases productivity. The cause of ring formation is temperature imbalance as flame leans toward upper wall. Therefore, burner nozzle geometry was changed to improve air-fuel mixing state which leads to prevention of ring formation. CFD simulation and experimental test were performed in this study to investigate the effect of air-fuel mixing on flame structure, temperature and $NO_X$ concentration. It is shown that combustion efficiency has been enhanced and $NO_X$ concentration has been decreased by using swirl flow for secondary combustion air. It's also shown that flame has been straightened by using straight flow for secondary combustion air.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1991년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 22-24 Oct. 1991
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• pp.1693-1698
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• 1991

An axial dispersion model is developed for the slim reactor employed in the LDPE autoclave process so that imperfect mixing caused by large L/D ratio (10-20) may be quantified by Peclet number. The model is then used to investigate the effect of mixing on the reactor performance represented by the monomer conversion, the reactor temperature, the molecular weight, and the polydispersity. In addition, the existence of steady state multiplicity is identified with the initiator feed concentration or the feed temperature as the bifurcation parameter. The effects of the initiator feed concentration and the feed temperature are also examined.