• KSCE Journal of Civil and Environmental Engineering Research
• /
• 제40권1호
• /
• pp.105-110
• /
• 2020

This study provides a method and data for predicting the flight initiation wind speed of wind-borne debris. From the force equilibrium acting on debris including aerodynamic and inertia forces, the equation for predicting the flight initiation wind speeds are presented. Wind tunnel tests were carried out to provide necessary aerodynamic data in the equation for the debris with various aspect ratios. The proposed equation for flight initiation wind speeds was validated from free flying tests in the wind tunnel. The flights of debris were mostly initiated by slip when width to thickness was less than 10, otherwise overturning were dominant. The actual flight initiation speeds were lower than that of the computed ones. The surface boundary layer flow and the gap between the debris and surface might affect the prediction error.

• Ceramist
• /
• 제1권2호
• /
• pp.63-73
• /
• 1998

현재 원자력발전에 사용되는 핵연료는 산화물 핵연료가 그 주종을 이루고 있다. 특히, 고속증식로용 핵연료로는 최근까지 혼합산화물 핵연료가 개발, 사용되어 왔다. 그러나 이 산화물 핵연료 못지 않게 경제성 및 안전성 관점에서 이를 능가할 수 있는 핵연료 재료로서 탄화물 및 질화물 등의 비산화물 세라믹 핵연료도 그 동안 꾸준히 연구되어 왔으며, 최근 들어서는 새로운 개념의 Pu 혹은 Minor Actinide burning용 핵연료 후보재료로도 각광을 받고 있다. 이들 비산화물 세라믹 핵연료는 산화물 핵연료에 비해 증식능력이 좋아, 특히 8~12년의 증배시간을 갖는 고속증식로 개발의 가능성을 보여준다. 이는 그 특성이 산화물 핵연료의 경우에 비해 더 높은 중금속(Heavy Metal) 밀도와 열전도도를 갖는 장점 때문이며, 이로 인해 높은 선출력(linear power)을 낼 수 있어 소형 노심의 설계가 가능하다. 본 고에서는 고속증식로 뿐만 아니라 다른 형태의 원자로에의 사용에서도 그 응용가치와 개발의 여지가 충분히 있는 비산화물 세라믹 핵연료의 기초특성, 제조기술, 그리고 그 성능에 대하여 비교, 분석함으로써 앞으로의 핵연료 개발연구에 보다 효율적이고 다양한 방향을 제시하고자 하였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• 제36권4호
• /
• pp.373-378
• /
• 2012

The objective of this research is to examine the probabilistic approach to evaluating turbine ejection frequency considering common-cause failure. This paper identifies basic turbine ejection mechanisms under high and low speeds and presents a detailed probabilistic methodology (fault tree) for assessing ejection frequency. The alpha factor methodology is applied to common-cause failure evaluations. The frequencies under different test schemes are compared and the propagation of uncertainty through the fault tree model is evaluated. The following conclusions were reached: (1) the turbine blade ejection frequency due to ductile failure under high speed is around 8.005E-7/yr; (2) if common-cause failure is considered, the frequency will be increased by 11% and 33% depending on the test scheme; and (3) if the parameter uncertainties are considered, the frequency is estimated to be in the range of 9.35E-7 to 1.13E 6, with 90% confidence.

• Journal of the Korea institute for structural maintenance and inspection
• /
• 제26권5호
• /
• pp.103-111
• /
• 2022

Fine dust can cause serious problems to human health, and fugitive dust generated at construction sites is one of the main sources of fine dust in Korea. However, monitoring of the amount of fugitive dust generated at the ready-mixed concrete plant site is not performed, and only passive monitoring methods are partially applied in the field. Since it is impossible to control fugitive dust after it is exposed to the air, it is very important to suppress the occurrence or to remove it immediately at the stage of occurrence. Therefore, after identifying the characteristics through real-time monitoring in the fugitive dust generation stage, systematic management is required for suppressing or removing scattering dust in the field. In this study, the scattering dust generation characteristics were analyzed by measuring the particle mass concentration(PMC) of Fugitive dust generated at the aggregate unloading site of the ready-mixed concrete plant in real-time.

• Journal of Korean Society of Environmental Engineers
• /
• 제35권8호
• /
• pp.547-553
• /
• 2013

This paper investigates the effect of coal-fired fly ash on dry $CO_2$ sorbents as the supports and additives. For this purpose, various kinds of dry sorbent were manufactured by mixing fly-ash, the primary $CO_2$ absorption components (NaOH and CaO) and water with their different combination. Thereafter, their $CO_2$ absorption performance and the property were analyzed. As a result, variation of absorption efficiency and temperature as well as $CO_2$ desorption of the sorbents are confirmed, which may be primarily ascribed to fly-ash addition to the sorbents. Particularly, fly-ash effect is strongly measured in the sorbent manufactured by mixing all four components (named WNCF sorbents). Absorption efficiency of WNCF sorbents at $550^{\circ}C$ is 35.6% higher than that of flyash free sorbent and desorption is solely observed in WNCF sorbents. Fly-ash in WNCF sorbents leads to increase the dispersity of $CO_2$ absorption components and decrease their particle size in the sorbents. In addition, fly-ash is used as the supports and pozzolanic reaction is hindered by NaOH in WNCF sorbent. Furthermore, $CO_2$ desorption from the sorbents may be due to fly-ash. The interaction between fly-ash and $CO_2$ absorption components substantially attenuate the strength between captured $CO_2$ in CaO and NaOH.

• Fire Science and Engineering
• /
• 제26권3호
• /
• pp.60-66
• /
• 2012

In this study, it was evaluated the fire risk during welding cutting tasks. Welding-cutting machines are representatively used at construction sites. Inverter AC/DC TIG welding macnine and inverter air plasma cutting machine were used in experiments. Temperature of spreaded cinders was measured using a thermal camera. Cinder sizes and spread range were measured according to the height and input current. It was also evaluated the fire risk during welding-cutting process, when flammable materials were located around the working area. There were used hay, dust fence, urethane foam, vinyl, paper and oil as flammable materials. Temperature of spreaded cinders was reached at about $450^{\circ}C$. Cinders were spread approximately 4.7 m, when a worker carried out cutting process at 2.5 m height. The possibility of a fire is very high, when flammable materials were located around the working area.

• Journal of the Korea institute for structural maintenance and inspection
• /
• 제27권4호
• /
• pp.70-77
• /
• 2023

Fine dust is a cause of serious ecological problems, and fugitive dust generated from construction sites is a major source of fine dust in Korea. However, at construction sites, including concrete manufacturing industry sites, measurements are rarely made at the fugitive dust generation stage, and passive removal methods are the majority. Therefore, in this study, a fugitive dust measurement method suitable for managing fugitive dust generated during aggregate unloading in the concrete manufacturing industry sites was selected. In addition, the purpose was to analyze the amount of fugitive dust reduction according to the operation of the reduction system by applying the automatic fugitive dust reduction system to the aggregate unloading site. As a result, the reliability of the light scattering method was secured through the comparative measurement of the beta-ray absorption method and the light scattering method, and the light scattering method correction coefficient was calculated and applied to the measured value of the fugitive dust particle mass concentration at the concrete manufacturing industry sites. In addition, the fugitive dust reduction rate according to the operation of the automatic fugitive dust reduction system was derived.

• Proceedings of the Korean Institute of Industrial Safety Conference
• /
• 한국안전학회 2000년도 춘계 학술논문발표회 논문집
• /
• pp.37-41
• /
• 2000

폐기물 소각시 발생되는 각종 유해가스 및 비산회재(fly ash)는 후처리 설비에 의해 배출허용기준치 이하로 처리된 후 대기 중으로 방출되도록 환경 규제되고 있다. 그러나 포집된 비산회재(fly ash) 및 노하부 배출재(bottom ash) 내에는 미 연소된 상태로 배출된 유해성 유기물질(다이옥신, 퓨란류 등)과 중금속 성분이 함유되어 있어 이들 소각잔류물(incineration residues)을 안정화나 무해화 처리 없이 단순 매립할 경우 강우에 의해 소각잔류물 내의 유해성분이 침출됨에 따라 토양이나 지하수 등에 2차 환경오염을 일으키게 된다. (중략)

• Elastomers and Composites
• /
• 제31권4호
• /
• pp.247-255
• /
• 1996

금속이나 고분자 재료에 비하여 세라믹스는 우수한 내열성과 고온 물성을 가지고 있음에도 불구하고, 잘 깨지는 특성과 제조시 많은 열량을 필요로 하는 단점 때문에 그 동안 고온 구조용 부품으로서 광범위하게 사용되지 못하였다. 본 연구에서는 polycarbosilane을 이용하여 C/C 복합체를 포함한 산화물 및 비산화물 세라믹 복합체의 저온 치밀화 제조 공정을 확립하였다. polympr precursor를 열처리하여 얻은 $Al_2O_3$와 SiC 장섬유를 대표적인 산화물, 비산화물 세라믹스인 알루미나와 탄화규소에 각각 보강하여 파괴에너지가 기존의 단체 세라믹스에 비하여 10배 이상 향상된 세라믹 복합체를 제조하였다. 복합체 제조시 polycarbosilane을 결합제로 첨가하였으며 polycarbosilane이 SiC로 전이되는 $1150^{\circ}C$에서 열처리하여 이론 밀도의 73% 이상을 얻었다.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 한국방사성폐기물학회 2010년도 추계 학술논문요약집
• /
• pp.389-390
• /
• 2010