• 한국결정성장학회지
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• 제13권6호
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• pp.304-308
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• 2003

분리기 내 압력 조절을 통하여 압력 변화가 세라믹 입자 $Al_2O_3$, $Fe_2O_3$ 분급에 미치는 영향을 수치 해석적으로 분석하였다. 입자 분급 해석을 위해 3차원 Lagrangian approach를 이용하였으며, 이를 통해 입자의 분리기 내 거동 경로를 추적하여 각 압력에 따른 분리 가능한 최소 입자 크기(cut-diameter)와 분리율(separation rate)를 계산하였다. 압력 감소는 입자를 운반하는 아르곤 가스의 밀도를 감소시키면서, 분리기 내부 압력 손실을 줄이는 원인이 되었다. 이로 인해 상압에서 분리기 압력이 저압 상태로 변함에 따라, 더 미세한(수 $\mu\textrm{m}$) 입자가 분리 가능함이 예측되었다. 특히 50 torr의 저압 하에서 계산된 세라믹 입자의 분급 양상을 분석하면,$Al_2O_3$ 입자는 4 $\mu\textrm{m}$, $Fe_2O_3$경우는 3$\mu\textrm{m}$ 크기의 입자 분리가 가능하였다.

• 한국연소학회:학술대회논문집
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• 한국연소학회 1997년도 제15회 KOSCO SYMPOSIUM 논문집
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• pp.103-112
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• 1997

In the combustion of the pulverized coal compared with that of liquid fuel or gaseous fuel, serious pollutants such as ash, $NO_x$ and $SO_x$ are released to surroundings. The objective of this study is the reduction of such pollutants in the combustion process. The modeling of cyclone combustor which uses the method of two stage combustion was carried out. The main burner length, scattering angle and air/fuel ratio were considered as parameters. The results show that the shorter the main burner length is, the less the amounts of coals which exit the combustor directly are, but the scattered input of coal is required anyway in order to collect all ashes. It is recommended that the shorter the main burner length is, the less the scattering angle is. And in the case of the scattered input compared with no scattering, the temperature in the combustor is more uniform and the amount of volatile is more reduced.

• 해양환경안전학회지
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• 제26권7호
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• pp.892-903
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• 2020

태풍 내습 시 신속하고 정확한 해일고 예측은, 연안재해 대응에 필수적인 요소이다. 이러한 해일고의 예측을 위해서 기존에는 태풍예측정보를 수치모델에 적용하여 예측자료를 생산하는 것이 대부분 이였다. 이러한 방법은 대용량의 컴퓨팅 자원과 시간이 소요된다는 단점이 있다. 최근에는 인공지능 기반으로 신속하게 예측자료를 생산하는 연구가 다양한 분야에서 진행되고 있으며, 본 연구에서는 인공지능 기반 해일고 예측을 수행하였다. 인공지능 적용을 위해서는 많은 수의 학습자료가 필요하게 되며, 기왕 발생태풍은 개수가 한정되어 있어 본 연구에서는 TCRM(Tropical Cyclone Risk Model)을 통하여 합성태풍을 생성하고, 이를 폭풍해일 모델에 적용하여 해일고 자료를 생성한 후, 학습자료로 활용하였다. 인공지능으로 예측한 해일고와 실제 발생 태풍에 대한 비교 결과, RMSE(Root Mean Square Error)는 0.09 ~ 0.30 m, CC(Correlation Coefficient)는 0.65 ~ 0.94, 최대 해일고의 ARE(Absolute Relative Error)는 1.0 ~ 52.5 %로 분석되었다. 특정 태풍/지점에서는 다소 오차가 크게 나타나고 있으나, 향후 학습자료의 최적화 등을 통하여 정확도를 개선할 수 있을 것으로 기대된다.

• Wind and Structures
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• 제23권5호
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• pp.449-464
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• 2016

Catastrophe models appraise the natural risk of the built-infrastructure simulating the interaction of its exposure and vulnerability with a hazard. Because of unique configurations and reduced number, mid/high-rise buildings present singular challenges to the assessment of their damage vulnerability. This paper presents a novel approach to estimate the vulnerability of mid/high-rise buildings (MHB) which is used in the Florida Public Hurricane Loss Model, a catastrophe model developed for the state of Florida. The MHB vulnerability approach considers the wind pressure hazard exerted over the building's height as well as accompanying rain. The approach assesses separately the damages caused by wind, debris impact, and water intrusion on building models discretized into typical apartment units. Hurricane-induced water intrusion is predicted combining the estimates of impinging rain with breach and pre-existing building defect size estimates. Damage is aggregated apartment-by-apartment and story-by-story, and accounts for vertical water propagation. The approach enables the vulnerability modeling of regular and complex building geometries in the Florida exposure and elsewhere.

• Journal of Korean Society for Atmospheric Environment
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• 제20권E1호
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• pp.1-14
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• 2004

Meteorological mechanisms in association with long-range transport of Asian dust in April 2001 have been investigated using weather maps, satellite images, TOMS and surface $PM_{10}$ data, backward trajectories, plus modeling output results (geopotential heights, horizontal wind vectors, potential temperatures, and streamlines). The results indicated that long -range transport of Asian dust to the west coast of North America was associated with strong westerlies between the Aleutian low and the Pacific high acting as a conveyor belt. Accelerating westerly flows due to cyclogenesis at the source regions over East Asia transported pollution from the continent to the central Pacific. When the system reached the Aleutian Islands, the intensity of troughs and the westerlies were amplified in the North Pacific. Thereafter the winds between the Aleutian Islands and the Pacific Ocean were more intensified from the air flow transport of the conveyor belt. Consequently, the strong wind in the conveyor belt enhanced the dust transport from the Pacific Ocean to the west coast of North America. This was evidenced by $PM_{10}$ concentration (maximum of about $100{\mu}g\;m^{-3}$) observed In California. Further evidence of the dust transport was found through the observation of satellite images, the distribution of TOMS aerosol index, and the analyses of streamlines and backward trajectories.

• 한국연소학회지
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• 제6권2호
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• pp.36-42
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• 2001

Usually, we use the flame thickness and turbulence scale to classify the flame structure on a phase diagram of turbulent combustion. The flame structure in turbulence is still in debate, and many studies have been done. Since the flame motion is rapid and its reaction zone thickness is very thin, it is difficult to estimate the flame thickness. Here, we propose a new approach to determine the reaction zone thickness based on ion current signals obtained by an electrostatic probe, which has enough time and space resolution to detect flame fluctuation. Since the signal depends on the flow condition and flame curvature, it may be difficult to analyze directly these signals and examine the flame characteristics. However, ion concentration is high only in the region where hydrocarbon-oxygen reactions occur, and we can specify the reaction zone. Based on the reaction zone existing, we estimate the reaction zone thickness. We obtain the thickness of flames both in the cyclone-jet combustor and on a Bunsen burner, compared with theoretically predicted value, the Zeldovich thickness. Results show that the experimentally obtained thickness is almost the same as the Zeldovich thickness. It is concluded that this approach can be used to obtain the local flame structure for modeling turbulent combustion.

• 한국대기환경학회지
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• 제31권6호
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• pp.508-519
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• 2015

The objective of this study was to quantitatively estimate $PM_{2.5}$ source contribution in Gyeongsan. Ambient $PM_{2.5}$ samples have been collected on zefluor, quartz and nylasorb filter by $PM_{2.5}$ samplers of cyclone method from September 2010 to December 2012. Collected samples were analyzed for determining 17 inorganic elements, 8 ions, and 8 carbon components after pretreatment. Based on these chemical information, the PMF model was applied to estimate the quantitative contribution of air pollution sources. The results of the PMF modeling showed that the sources were apportioned by biomass burning source (15.5%), secondary sulfate source (16.0%), industry source (10.4%), soil source (7.0%), gasoline source (9.1%), incinerator source (10.4%), diesel emission source (11.0%), and secondary nitrate source (20.6%), respectively. To analyze local source impacts from various wind directions, the CPF analysis were performed using source contribution results with the wind direction values measured at the site.

• 자원환경지질
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• 제57권2호
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• pp.177-184
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• 2024

연구는 국내 골재 생산 과정에서 발생하는 케이크의 발생을 줄이는 방안을 찾고자 수행되었다. 8개 습식 골재 생산 업체의 케이크를 수집하여 입도를 분석하였다. A 골재 생산 현장에서 시료를 채취하고 입도 분석을 수행했다. 생산 공정을 모델링하여 모래 회수 장치 전후에서 물질 수지를 계산했다. 8개의 케이크 입도 분석 결과 하나의 시료에서 모래가 50% 포함된 사례도 있었고 나머지는 약 5~25% 포함하고 있었다. 케이크 내 다양한 모래가 포함하고 있다는 결과는 현장의 모래 회수 장치의 회수 효율이 다양함을 의미할 수 있다. A 업체 파쇄 공정에서 모래 입도는 2차 파쇄 때보다 3차 파쇄 때에 2.8배 증가했고 케이크 입자도 더 많이 발생했다. 모래 회수 공정을 모사한 결과 사이클론 및 탈수체의 분극점이 낮아질수록 모래 생산은 증가했고 케이크 발생은 적어지는 추세가 나타났다. 현장에서 케이크의 발생을 줄이기 위해서 골재생산 공정에서 특히 모래 회수 장치의 적정 운전이 필요할 것으로 판단되었다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1996년도 춘계 학술대회논문집
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• pp.58-67
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• 1996

This paper describes some computational results of various energy and environmental systems using Patankar's SIMPLE method. The specific topics handled in this study are jet bubbling reactor for flue gas desulfurization, cyclone-type afterburner for incineration, 200m tall stack for 500 MW electric power generation, double skin and heat storage systems of building energy saving for the utilization of solar heating, finally turbulent combustion systems with liquid droplet or pulverized coal particle. A control-volume based finite-difference method with the power-law scheme is employed for discretization. The pressure-velocity coupling is resolved by the use of the revised version of SIMPLE, that is, SIMPLEC. Reynolds stresses are closed using the standard $k-{\varepsilon}$ and RNG $k-{\varepsilon}$ models. Two-phase turbulent combustion of liquid drop or pulverized coal particle is modeled using locally-homogeneous, gas-phase, eddy breakup model. However simple approximate models are incorporated for the modeling of the second phase slip and retardation of ignition without consideration of any detailed particle behavior. Some important results are presented and discussed in a brief note. Especially, in order to make uniform exit flow for the jet bubbling reactor, a well-designed structure of distributor is needed. Further, the aspect ratio in the double skin system appears to be one of important factors to give rise to the visible change of the induced air flow rate. The computational tool employed in this study, in general, appears as a viable method for the design of various engineering system of interest.

• 대기
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• 제16권1호
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• pp.33-48
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• 2006

A classification of snowfall type based on development mechanism is proposed using previous snowfall studies, operational experiences, etc. Five types are proposed: snowfall caused by 1) airmass transformation (AT type), 2) terrain effects in a situation of expanding Siberian High (TE type), 3) precipitation systems associated with extratropical cyclones (EC type), 4) indirect effects of extratropical cyclones passing over the sea to the south of the Korean peninsula (ECS type), and 5) combined effects of TE and ECS types (COM type). Snowfall events during 1981-2001 are classified according to the 5 types mentioned above. For this, 118 events, with at least one station with daily snowfall depth greater than 20 cm, are selected. For the classification, synoptic weather charts, satellite images, and precipitation data are used. For TE and COM types, local sea-level pressure chart is also used to confirm the presence of condition for TE type (this is done for events in 1990 and thereafter). The classification shows that 109 out of 118 events can be classified as one of the 5 types. In the remaining 8 events, heavy snowfall occurred only in Ullung Island. Its occurrence may be due to one or more of the following mechanism: airmass transformation, mesoscale cyclones and/or mesoscale convergence over the East Sea, etc. Each type shows different characteristics in location of snowfall and composition of precipitation (i.e., dry snow, rain, and mixed precipitation). The AT-type snowfall occurs mostly in the west coast, Jeju and Ullung Islands whereas the TE-type snowfall occurs in the East coast especially over the Young Dong area. The ECS-type snowfall occurs mostly over the southern part of the peninsula and some east cost area (sometimes, whole south Korea depending on the location of cyclones). The EC- and COM-type snowfalls occur in wider area, often whole south Korea. Precipitation composition also varies with the type. The AT-type has a snow ratio (SR) higher than the mean value. The TE- and EC-type have SR similar to the mean. The ECS- and COM-type have SR values smaller than the mean. Generally the SR values at high latitude and mountainous areas are higher than those at the other areas. The SR value informs the characteristics of the precipitation composition. An SR value larger than 10 means that all precipitation is composed of snow whereas a zero SR value means that all precipitation is composed of rain.