• Tribology and Lubricants
• /
• 제34권5호
• /
• pp.175-182
• /
• 2018

Accumulation of coal ash at the boiler wall reduces combustion and fuel efficiency. The design of a wall blower is important to effectively remove coal ash. We present numerical results for the removal of coal ash from boiler walls of domestic coal-fired power plants, associated with the computational fluid dynamics for the flow from spray nozzle to boiler wall. The numerical model simulates an erosion process in which the multiphase fluid comprising saturated vapor and fluid water is sprayed from the nozzle, and the water particles impact the boiler wall. We adopt the Finnie erosion model for water particles. We obtain the erosion rate density as a function of nozzle angle and its injection angle. As excessive coal ash removal usually induces damage to the boiler wall, the removal operation typically focuses on a large area with uniform depth rather than the maximum removal of coal ash at a specific location. In order to estimate the removal performance of the wall blower nozzle considering several functionality and reliability factors, we evaluate the optimal injection and nozzle angles with respect to the biggest cumulative and highest erosion rates, as well as the widest range and lowest standard deviation of the erosion rate distribution.

• 한국주거학회논문집
• /
• 제24권2호
• /
• pp.25-33
• /
• 2013

The purpose of this study was to compare the differences between two types of wall removal projects. One was the case that removed one side wall of the apartment in Daegu, another was the instance that eliminated the walls between two apartments in Gimcheon. For this study, the observation method was performed to know the using pattern on the street space, and survey including resident's opinion and satisfaction about result of the project was conducted to gather data. The total number of objects to analysis was 157. The conclusion of this study is as follows. First, when the space was secure from danger of cars, people could access easily. And when it had interesting elements, the street space after wall removal was used by residents. Second, the effective method to connect places was to make intermediate space after wall removal project. In this sense, the way can help to improve the level of quality the daily life of residents. Finally, in the apartment-oriented wall removal project, it could supplement the flaw of the detached house-oriented project and effective potentiality for vitalization of community.

• 한국지하수토양환경학회:학술대회논문집
• /
• 한국지하수토양환경학회 2003년도 추계학술발표회
• /
• pp.285-288
• /
• 2003

When the soil vapor extraction as a remediation method of contaminated soil and groundwater has been used, the effects of curtain wall, mode of pump operation were examined by numerical simulation. Consequently, it was found that the removal rate was enhanced in case that the curtain wall was established around the extraction well with the extraction pumps operated alternatively. It was because that the removal of high density gas around the extraction well was possible.

• 한국공작기계학회논문집
• /
• 제13권6호
• /
• pp.17-22
• /
• 2004

A study for investigating the effects of the cutting conditions (radial depth of cut feed per tooth) and the number of tooth on the side wall of prismatically milled workpiece is described. This study is available not only for understanding the geometrical characteristics of the end milled side wall but also for finding the optimal cutting conditions. In this work, the side wall geometry was characterized by the straightness and the location of maximum peak point. Through this study, it was revealed that the geometrical characteristics of the end milled side wall are strongly related to the material removal per tooth and the number of tooth.

• 한국수자원학회논문집
• /
• 제32권2호
• /
• pp.121-129
• /
• 1999

본 연구는 토양 및 지하수 오염의 정화방법으로써 토양증기 추출법을 이용할 경우, 이의 효율적 운용을 위하여 추출공 주변에 차단벽을 설치할 경우, 추출펌프유량의 크기 및 펌프가동의 형태 등이 제거효율에 미치는 영향을 평가하기 위하여 수치해석을 이용하여 검토하였다. 그 결과 추출공 주위에 차단벽을 설치할 경우 및 추출펌프의 운용을 단속적으로 실시하였을 경우, 추출공 주변에 고농도의 가스분포를 밀집시킴으로 인해 고농도의 가스를 제거할 수 있게 되어 제거율이 상승하였다. 추출유량의 크기변화가 TCE가스의 제거율에 미치는 영향을 추출유량이 클수록 상승하지만 TCE가스의 정화효율은 추출유량의 크기에는 의존하지 않는다는 것을 알 수 있었다.

• 한국연소학회지
• /
• 제10권2호
• /
• pp.1-8
• /
• 2005

Incomplete combustion due to quenching in a narrow confinement has been a major problem for realization of a reliable micro combustion device. In most micro combustors, effects of flows are absent in the quenching because the flow is laminar and no severe stretch is present. In such circumstance, quenching is caused either by heat loss or by removal of active radicals to the wall surface of the confinement. An experimental investigation was carried out to investigate the relative significance of these two causes of quenching of a premixed flame. A premixed jet burner with a rectangular cross section at the exit was built. At the burner exit, the flame stands between two walls with adjustable distance. The gap between the two walls at which quenching occurs was measured at different wall surface conditions. The results were analyzed to estimate the relative significance of heat loss to the wall and the removal of radicals at the surface. The measurements indicated that the quenching distance was independent of the wall surface characteristics such as oxygen vacancy, grain boundary, or impurities at low temperature. At high temperature, however, the surface characteristics strongly affect the quenching distance, implying that radical removal at the wall plays a significant role in the quenching process.

• 상하수도학회지
• /
• 제23권5호
• /
• pp.655-667
• /
• 2009

An experimental study is performed on reducing the pollutants supplied by storm water through enhancing efficiency of SS from the detention storage tank where CSOs are kept temporarily before discharge to the receiving water system. SS removal efficiency is investigated in accordance with various conditions of the detention pond-such as its length, the existence of training wall, and the use of gravel filling. The removal efficiency is strongly affected by the detention pond's length until the critical falling distance of the suspended solids is reached. For cases where the tank has a length longer than this critical condition, the removal rate shows less sensitivity. To enhance the SS removal efficiency of tanks of shorter than the critical length, we studied alternative types of tank in which inside training walls are installed. The results showed improvement of 14 to 37% in removal efficiency in 2hours detention(2 training walls). The important factor in achieving a high SS removal rate is ensuring the critical length of the detention pond, but for the cases where the basin length cannot be guaranteed, baffles or a gravel filling scheme may be introduced to attain considerable efficiency. The results of studying and comparing different storage tank conditions show that, in terms of elimination efficiency, a storage tank with gravel filling and training walls > a storage tank with gravel filling > a storage tank with training walls > an empty tank. The experimental results should contribute to development of related further research, by empirically verifying the already assumed importance of critical falling distance, training walls, and gravel filling schemes.

• 한국태양에너지학회 논문집
• /
• 제24권2호
• /
• pp.33-38
• /
• 2004

Outside wall systems we lost much energy from the dew of thermal bridge and unsuitable adiabatic construction. The air vent wall system can make reduce cooling loads from the outside wall in summer. The basic concept is connected with buoyant force by the difference of density. An external surface of a wall absorbs solar radiation, and transfers it to the air in the cavity. The warmed air gets buoyant force. So the warmed air is released through the top opening and cooler outside air replaces the space in the cavity. So because of the cavity and the openings, the cooling load reduction by natural ventilation is believed to be considerable. The purpose of this study is finding optimal length of air cavity by numerical analyses.

• Journal of Microbiology and Biotechnology
• /
• 제18권7호
• /
• pp.1335-1341
• /
• 2008

The cell wall material from fruiting bodies of Laetporus sulphureus has been suggested as a new alternative to mutan for the mutanase induction in Trichoderma harzianum. Structural analyses revealed that the cell wall fraction from this polypore fungus contained 56.3% of (1$\rightarrow$3)-linked $\alpha$-glucans. When the strain T. harzianum F-340 was grown on a cell wall preparation from L. sulphureus, the maximal enzyme productivity obtained after 3 days of cultivation was 0.71 U/ml. This yield was about 1.8-fold higher than that achieved on mutan, known so far as the best, but expensive and inaccessible, inducer of mutanase production. Cell-wall-induced mutanase showed a high hydrolytic potential in reaction with a dextranase-pretreated mutan, where maximal degrees of saccharification and solubilization of this biopolymer (80% and 100%, respectively) were reached in 3 h at 45$^{\circ}C$. The mutanase preparation was also effective in degradation of streptococcal mutan and its removal from oral biofilms, especially in a mixture with dextranase.

• Restorative Dentistry and Endodontics
• /
• 제17권2호
• /
• pp.413-420
• /
• 1992

The purpose of this study was to compare the effectiveness of hand instrumentation with K - file and ultrasonic instrumentation and irrigation system in removing pulpal debris and canal wall planing. 20 mandibular molar teeth were instrumented to size 30 K - file and 20 teeth were instrumented with ultrasonic Suprasson. And Normal Saline and 2.5% NaOCl were used as irrigation solution. All specimens were viewed at the coronal, middle, and apical third of the root canals for the evaluation of the cleaning effect under the multiview microscope. The result were as follows : 1. All of the technique and irrigation solution was effecient in the debris removal and canal wall planing at the cervical and middle thirds of the root canal. 2. All of the techniques and irrigation solutions was less efficient in the debris removal and canal planing at the apical third of the root canal. 3. The debris removal and canal wall planing was depended more on the anatomical variations of the root canal than on the techniques and irrigation solutions.