• Title/Summary/Keyword: ICE 방법

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Icing Characteristics in Liquid-Phase Injection of LPG Fuel (액상분사식 LPG 인젝터의 아이싱 생성 특성 및 억제 방법)

  • Lee, Sun-Youp;Kim, Chang-Up;Choi, Kyo-Nam;Kang, Kern-Yong
    • Journal of ILASS-Korea
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    • v.14 no.4
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    • pp.147-152
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    • 2009
  • Since a liquid-phase LPG injection system allows accurate control of fuel injection and increase in volumetric efficiency, it has advantages in achieving higher engine power and lower emissions compared to the mixer type LPG supplying system. However, this system also leads to an unexpected event called icing phenomenon which occurs when moisture in the air near the injector freezes and becomes frost around the nozzle hole due to extraction of heat from surrounding caused by instant fuel vaporization. As a result, it becomes difficult to control air/fuel ratio in engine operation, inducing exacerbation of engine performance and HC emission. One effort to mitigate icing phenomenon is to attach anti-icing injection tip in the end of nozzle. Therefore, in this study, the effect of engine operation parameters as well as surrounding conditions on icing phenomenon was investigated in a bench test rig with commercially-used anti-icing injection tips. The test results show that considerable ice was deposited on the surface near the nozzle hole of the anti-icing tip in low rpm and low load operating conditions in ambient air condition. This is because acceleration of detachment of deposited ice from the tip surface was induced in high load, high rpm conditions, resulting in decrease in frost accumulation. The results of the bench testing also demonstrate that little or no ice was formed at surrounding temperature below a freezing point since the absolute amount of moisture contained in the intake air is too small in such a low temperature.

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A Basic Study on the Development of Automatic Line Stripe Removal Using Dry Ice Blaster (드라이아이스 블래스터를 이용한 자동화 차선제거 장비 개발을 위한 기초연구)

  • Koo, Ja-Kyung;Moon, Deuk-Soo;Bernold, Leonhard E.;Lee, Tai-Sik
    • Proceedings of the Korean Institute Of Construction Engineering and Management
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    • 2008.11a
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    • pp.800-803
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    • 2008
  • Road is one of the infrastructure facilities, on which lines include various information for guiding a smooth traffic flow. This line marking work is continually removed and re-marked during maintenance. However, some problems exist when the line marking work is conducted. Traditional methods of using grinders and torches have risk of repetitive skill, and workers are exposed directly to the hazardous situations. Moreover, even though the equipment has developed, the line removing work induces environmental contamination and pollution line on the road. Therefore, this study can become one of the eco-friendly cleaning technologies using dry ice blaster equipment, and the new development of equipment will improve method of pavement marking removal. Also, it can introduce innovative automation in construction.

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Field application assessment of observation methods and gauging instruments for improvement of the accuracy of discharge measurement at ice cover (Review of small mountainous catchment) (하천결빙시 유량측정 정확도 제고를 위한 관측방법 및 기기 현장적용평가(산지 소하천 유역을 중심으로))

  • Kim, Dong Phil;Hwang, Seok Hwan;Jung, Sung Won
    • Proceedings of the Korea Water Resources Association Conference
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    • 2004.05b
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    • pp.1082-1085
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    • 2004
  • 산지 소하천 유역에서 하천결빙이 발생하는 시기의 유량측정은 평상시의 유량측정 방법으로는 정확한 유량측정성과를 기대하기는 어렵다. 하천결빙시의 유량측정 자료의 정확도를 높이기 위해서는 관측방법의 개발과 다양한 관측기기의 현장적용평가가 필요하다. 본 논문에서는 관측방법의 새로운 기준 적용과 다양한 관측 기기를 이용하여 유량측정을 수행하고 측정성과를 비교 검토함으로써 현장적용평가를 실시하였으며, 현장평가의 적용을 통해 산지 소하천 유역특성에 적합한 유량측정기술 및 기기의 개발을 이루고자 하였다.

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A Study on the Effect of Cold Application Using a Sponge Bath in Healthy Adults (냉요법 적용방법에 따른 냉요법 효과에 관한 연구-건강한 성인 여성에서 스폰지 목욕방법을 중심으로)

  • Chung, Hyun-Sook;Kang, Kyu-Sook;Hwang, Ae-Ran
    • The Korean Nurse
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    • v.28 no.3
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    • pp.68-82
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    • 1989
  • This study was a quasi-experimental research study to test the characteristics of temperature regulation according to sponge bath methods of cold application. Thirteen volunteers were selected from among nursing college students according to an established criteria using a purposive sampling technique. Four different cold application methods were used: $\circled1$ tepid water sponge bath at $28^{\circ}C$, $\circled2$ 20% alcohol sponge bath at $28^{\circ}C$, $\circled3$ 40% alcohol sponge bath at $28^{\circ}C$ and $\circled4$ tepid water sponge bath at 28$^{\circ}$C plus an ice bag to the head. Changes in rectal temperature, mean skin temperature, mean body temperature, heat content change and thermal discomfort during the cold application were measured at 5 minute intervals over a 120 minute period. The data collection period was from Dec. 20, 1988 to Feb. 3, 1989. The data were analyzed using descriptive statistics, simple regression, ANOVA, Duncan's multiple range test and Pearson correlation coefficient using the SPSS-X Program. The results of the study are summarized as follows. Five general hypothesis were tested. Hypothesis 1 that "Change in heat content will be decreased for each cold application method according to the cold application time" was rejected. (tepid water sponge bath: after 10 minutes of cold application, 20% alcohol sponge bath: after 25 minutes of cold application: 40% alcohol sponge bath: after 45 minutes of cold application, tepid water sponge bath plus an ice bag to the head: after 80 minutes of cold application) Hypothesis 2 that "Thermal discomfort will be changed for each cold application method according to the cold application time" was rejected after 5minutes of cold application. Hypothesis 3 that "Change in heat content will differ among the cold application methods" was accepted except 0~5, 0~10, 0~65, 0~105 and 0~120 minute. This difference showed significance only between sponge bath methods and tepid water sponge bath plus an ice bag to the head. Hypothesis 4 that "Thermal discomfort will differ among the cold application methods" was accepted at 15, 20, 35, 45, 75, 80, 90, 95, 100, 105, 110, 115 and 120 minute of cold application time. This difference showed significance only between sponge bath methods and tepid water sponge bath plus an ice bag to the head. Hypothesis 5 that "The higher the change in heat content, the higher the thermal discomfort during the cold application time" was accepted for between 10~60 and 75 minute of cold application. In conclusion, this study showed that in sponge bath at $28^{\circ}C$, 10~80 minute was a effective cold application time in the view of heat loss through the skin. Concerning the effects of evaporation and thermal discomfort, it was found that there was no difference with regard to the solutions; tepid water sponge bath; 20% alcohol sponge bath or 40% alcohol sponge bath at a $28^{\circ}C$ controlled solution temperature. So it was thought that the type of solution itself did not have a big influence on the heat loss through skin. The combined effect of sponge bath with an ice bag to the head showed a significant difference and also showed a slight increase in thermal discomfort. On the basis of this research it can be concluded that cold application, for example, an ice bag to the head during a tepid water sponge bath is a good method as it increase heat loss through conduction, although fit can also cause a slight increase in thermal discomfort. The correlation between changes in heat content and thermal discomfort were not high. So factors other than change in heat content are considered to have an effect on the cognition of thermal discomfort.

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A NEW PRESSURE GRADIENT RECONSTRUCTION METHOD FOR A SEMI-IMPLICIT TWO-PHASE FLOW SCHEME ON UNSTRUCTURED MESHES (비정렬 격자 기반의 물-기체 2상 유동해석기법에서의 압력기울기 재구성 방법)

  • Lee, H.D.;Jeong, J.J.;Cho, H.K.;Kwon, O.J.
    • Journal of computational fluids engineering
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    • v.15 no.2
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    • pp.86-94
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    • 2010
  • A thermal-hydraulic code, named CUPID, has been developed for the analysis of transient two-phase flows in nuclear reactor components. A two-fluid three-field model was used for steam-water two-phase flows. To obtain numerical solutions, the finite volume method was applied over unstructured cell-centered meshes. In steam-water two-phase flows, a phase change, i.e., evaporation or condensation, results in a great change in the flow field because of substantial density difference between liquid and vapor phases. Thus, two-phase flows are very sensitive to the local pressure distribution that determines the phase change. This in turn puts emphasis on the accurate evaluation of local pressure gradient. This paper presents a new reconstruction method to evaluate the pressure gradient at cell centers on unstructured meshes. The results of the new scheme for a simple test function, a gravity-driven cavity, and a wall boiling two-phase flow are compared with those of the previous schemes in the CUPID code.

Numerical Analysis of Melting Process in a Water Tank for Fuel-cell Vehicles (연료전지 자동차의 물탱크 해빙과정에 대한 수치해석적 연구)

  • Kim, Hark-Koo;Jeong, Si-Young;Hur, Nahm-Keon;Lim, Tae-Won;Park, Yong-Sun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.19 no.8
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    • pp.585-592
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    • 2007
  • Good cold start characteristics are essential for satisfactory operation of fuel cell vehicles. In this study, the melting process has been numerically investigated for a water tank used in fuel cell vehicles. The 2-D model of the tank containing ice and plate heaters was assumed and the unsteady melting process of the ice was calculated. The enthalpy method was used for the description of the melting process, and a FVM code was used to solve the problem. The feasibility study compared with other experiment showed that the developed program was able to describe the melting process well. From the numerical analysis carried out for different wall temperatures of the pate heaters, some important design factors could be found such as local overheating and pressurization in the tank.

Numerical Analysis of the Melting Process of Ice Using Plate Heaters with Constant Heat Flux (일정 열유속 조건의 판형 히터에 의한 해빙과정의 수치해석)

  • Kim, Hark-Koo;Jeong, Si-Young;Hur, Nahm-Keon;Lim, Tae-Won;Park, Yong-Sun
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.19 no.6
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    • pp.434-440
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    • 2007
  • One of the cold start problems of a FCV is the freezing of the water in the water tank when a FCV is not in operation and the surrounding temperature drops below $0^{\circ}C$. The ice in the tank should be melted as quickly as possible for a satisfactory operation of fuel cell vehicles. In this study, the melting process for the constant heat fluxes of the plate heaters was numerically calculated in the 2-D model of the tank and plate heaters. The enthalpy method and FVM code was used for this analysis. The changes of the temperature with heat fluxes and the heat transfer area could be investigated. The energy balance error was found to increase with the heat flux. From this numerical analysis, the proper heat flux value and some important design factors relating local overheating and pressurization of the water tank could be examined.

Reliability-Based Wind-Resistant Design Criteria of Transmission Towers (신뢰성에 기초한 송전철탑의 내풍설계기준)

  • Cho, Hyo Nam;Shin, Jae Chul;Lee, Seung Jae
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.14 no.5
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    • pp.1043-1053
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    • 1994
  • This study suggests a practical but rational approach for the development of reliability-based LRFD criteria for transmission towers under wind and ice loadings in Korea. Based on available statistical data on wind speed and icing on transmission lines in Korea, the design wind and ice loads are obtained by Monte Carlo Simulations. In the study, the AFOSM reliability method and an Importance Sampling Technique are used for the element and system reliability evaluation of actual transmission towers. Based on the selected target reliabilities, a set of load and resistance factors for the LRFD criteria are calibrated using the AFOSM and the code optimization technique.

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Prevention Technologies of environmental contamination and IMO action in Arctic Ice-covered Waters (극지해역에서의 환경오염 방지 기술 및 IMO 동향)

  • Kang, Jae-Sung;Kim, Ki-Pyoung;Kang, Ho-Keun;Kim, Dae-Heon
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2011.06a
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    • pp.237-239
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    • 2011
  • 최근 국제해사기구(International Maritime Organization, IMO)는 "극지를 운항하는 선박에 대한 안전기준(Polar Code)"를 제정하여 결정하기로 하였으며, 2012년까지 완료하여 법제화하기로 하였다. 이는 최근의 극해 지역의 연속적인 사고의 심각성에 대한 대비책의 일환이다. 2004년도에 알라스카 앞바다에 침몰한 Selendang Ayu 는 6600만 톤의 콩, 170만 리터의 연료유와 55,564 리터의 MDO 및 다른 오염물질을 바다에 유출하였다. 이는 주변의 동물들에게 심각한 영향을 끼쳤고, 아직까지도 유출되어진 오염물질들을 완전히 처리하지 못한 상태이다(Arctic marine shipping assessment, Arctic council 2009.). 즉, 기름이 유출을 하면 방재시설이 다른 육상에서 오기 전까지는 상당히 오랜 시간 동안, 사고 지역 주변을 오염시키게 되며, 유빙이나 극한의 온도는 방재 작업을 더욱 힘들게 한다. 본 연구에서는 극해와 같은 해역에서 기름이 유출 하였을 때에 대응하는 방법, 즉 현존하는 기계적인 복구 방식, 점화식 처리 방식 과 유처리제 방식을 소개하고, 그에 대한 국제규정 및 기술 발전 동향에 대해서도 설명한다.

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A Study of Player Changed-pattern Model for Game Bots Detection in MMORPG (MMORPG에서 게임 봇 프로그램 탐지를 위한 플레이어 패턴 변화 모델에 관한 연구)

  • Yoon, Tae-Bok;Lee, Jee-Hyong
    • Journal of Korea Game Society
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    • v.11 no.1
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    • pp.121-129
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    • 2011
  • In an online-game, the various game service victimized cases are generated by the bots program or auto program. Particularly, the abnormal collection of the game money and item loses the inherent fun of a game. It reaches ultimately the definite bad effect to the game life cycle. This paper collects and analyzes the pattern of game behavior change for the bots detection method. By using the game activity changing information of the human and game activity changing information of the bots, the degree of resemblance was measured. It utilized in the bots detection method. In an experiment, by using the served online-game, the model of a user and bots were generated and similarity was distinguished. And the reasonable result was confirmed.