• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.227-236
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• 2020

This paper derives the insertion loss for the bubble layer of an air bubble curtain and an air masker which are used to reduce ocean anthropogenic noise such as the piling noise and the ship noise. The air bubble curtain is considered as a 'fluid-air bubble layer-fluid' model and the environment for the air masker is simplified as an 'vacuum-thin plate-fluid-air bubble layer-fluid' model. The air bubble layer in each model is assumed as the effective medium which has the complex wavenumber and the complex impedance corresponding to the bubble population distribution. The numerical simulations are performed to examine the insertion loss depending on the bubble population, the void fraction, and the thickness of the layer.

• Journal of Korean Society of Transportation
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• v.33 no.2
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• pp.145-158
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• 2015

A network connectivity has been regarded as a key element to strengthen a business competitive power in the aviation industry, so many airport authorities try to attract the new airlines and scheme out new air routes. With this trend, a study for an induced travel demand estimation methodology is needed. This study introduces a demand estimation method, especially for a new air route to a promising destination. With the results of previous studies, the derived demand is classified into four types - Local, Beyond, Behind and Bridge. The explanatory variables are established for each type of demand and the main independent variables are composed of distance, ratio of detour, and relative capacity compared with other airports. The equations using such variables and statistically significant coefficients are suggested as the model to make an estimation of derived demand for a new route. Therefore this study will be expected to take an initial step for all related parties to be involved more deeply into developing new air routes to enhance network connectivity.

• Journal of the Korea Society for Simulation
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• v.32 no.4
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• pp.1-10
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• 2023

This study examines the response when the shock by underwater explosion is transmitted to a vertical launch air-vehicle mounted on a ship using modeling and simulation, and is about a plan to increase method shock resistance to protect the air vehicle. In order to obtain an accurate mathematical model, a dynamic characteristic test was performed on similar equipment, and through this, the mathematical model could be supplemented. And, using the supplemented mathematical model, the air vehicle simulated the shock response by the underwater explosion specified in the BV043 standard. As a result of the first simulation, it was confirmed that air vehicle could not withstand shock, and air vehicle protection method using a ring spring type shock absorber was studied. In addition to the basic shape of abosber, it was confirmed that the ring spring absober can be used to increase the impact resistance of a shipborn vertical launch vehicle by performing simulations for each case by changing deseign varables.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.30 no.6
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• pp.242-252
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• 2018

It is well known that an Oscillating Water Column Wave Energy Converter (OWC-WEC) is one of the most efficient wave absorber equipment. This device transforms the vertical motion of water column in the air chamber into the air flow velocity and produces electricity from the driving force of turbine as represented by the Wells turbine. Therefore, in order to obtain high electric energy, it is necessary to amplify the water surface vibration by inducing resonance of the piston mode in the water surface fluctuation in the air chamber. In this study, a new type of OWC-WEC with a seawater channel is used, and the wave deformation by the structure, water surface fluctuation in the air chamber, air outflow velocity from the nozzle and seawater flow velocity in the seawater channel are evaluated by numerical analysis in detail. The numerical analysis model uses open CFD code OLAFLOW model based on multi-phase analysis technique of Navier-Stokes solver. To validate model, numerical results and existing experimental results are compared and discussed. It is revealed within the scope of this study that the air flow velocity at nozzle increases as the Ursell number becomes larger, and the air velocity that flows out from the inside of the air chamber is larger than the velocity of incoming air into the air chamber.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.04a
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• pp.57-58
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• 1999

• Proceedings of the Korea Air Pollution Research Association Conference
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• 1999.10a
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• pp.415-417
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• 1999

환경연구자들은 대기환경의 개선과 환경기준의 목표달성과 최적 제어기술을 개발하기 위해 각종 모델을 이용하고 있다. 초기 단계에서는 각종 오염인의 배출자료와 기상자료를 이용하여 대기 중 분진의 농도를 추정하는 분산모델 (dispersion model)이 오랜 기간동안 활발하게 이용되어 왔다. 그러나 분산모델은 배출자료의 오차, 수직ㆍ수평적 분산변수의 불확실도, 복잡한 모델 개발에 따른 시간과 비용 등의 문제점을 가지고 있으며, 모델에 포함된 변수에 의해 특성화된 오염원에 대해서만 농도의 추정이 가능하다는 제약점이 있다.(중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.11a
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• pp.504-505
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• 2003

국지규모의 기상해석을 위한 기존의 방법은 중규모 모델로부터 down-nesting에 의한 방법으로 모델의 해상도를 향상시켜 기상장을 해석하는 것이 일반적이다(Clark and Farley, 1984). 그러나, 이 방법은 단지 물리적인 격자구조만을 향상시킨 것으로 근본적인 모델 내부 구조의 향상을 가져온 것은 아니다. 따라서, 다양한 토지 피복이 혼재해 있는 도심지를 대상으로 하는 고해상도의 국지기상 모델에 대하여 계산시간과 정확성을 고려한 효율적인 지표면 열수지 모델의 구축이 요구되고 있다. (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.183-184
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• 2000

종합적인 오존대책을 구축하기 위해서는 광화학 옥시단트의 생성물리ㆍ화학과정 및 생물기원(자연발생원) 탄화수소의 영향을 고려한 3차원 광화학반응 모델의 구축이 가장 절실하다. 특히, 광화학 옥시단트는 국지적인 순환(해륙풍)및 혼합층에 의해 지배되기 때문에 지형을 고려한 3차원 기상장 수치모델(도시규모)과 광화학을 포함한 농도장(광화학반응 모델) 모델에 의한 대상지역의 시간적, 공간적인 오존농도 분포를 재현할 수 있는 모델 개발이 필요하다. (중략)

• Korean Journal of Remote Sensing
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• v.39 no.2
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• pp.207-221
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• 2023

This study suggests deep neural network models for estimating air temperature with Level 1B (L1B) datasets of GEO-KOMPSAT-2A (GK-2A). The temperature at 1.5 m above the ground impact not only daily life but also weather warnings such as cold and heat waves. There are many studies to assume the air temperature from the land surface temperature (LST) retrieved from satellites because the air temperature has a strong relationship with the LST. However, an algorithm of the LST, Level 2 output of GK-2A, works only clear sky pixels. To overcome the cloud effects, we apply a deep neural network (DNN) model to assume the air temperature with L1B calibrated for radiometric and geometrics from raw satellite data and compare the model with a linear regression model between LST and air temperature. The root mean square errors (RMSE) of the air temperature for model outputs are used to evaluate the model. The number of 95 in-situ air temperature data was 2,496,634 and the ratio of datasets paired with LST and L1B show 42.1% and 98.4%. The training years are 2020 and 2021 and 2022 is used to validate. The DNN model is designed with an input layer taking 16 channels and four hidden fully connected layers to assume an air temperature. As a result of the model using 16 bands of L1B, the DNN with RMSE 2.22℃ showed great performance than the baseline model with RMSE 3.55℃ on clear sky conditions and the total RMSE including overcast samples was 3.33℃. It is suggested that the DNN is able to overcome cloud effects. However, it showed different characteristics in seasonal and hourly analysis and needed to append solar information as inputs to make a general DNN model because the summer and winter seasons showed a low coefficient of determinations with high standard deviations.

• Journal of the Korean Solar Energy Society
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• v.30 no.3
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• pp.16-24
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• 2010

Recently environmental regulations like the Kyoto Protocol, adopted in 1997, required the 5.2% reduction of the greenhouse gas emission in 1990. And 13th General Assembly in 2007, held in Bali of India, have agreed to duty reduction even in developing countries in 2013. Korean government needs the researches on climate change and the strategic programs for greenhouse gas reduction. In this paper Colorado State University Mesoscale Model(CSU-MM) was applied to simulate the relationship between surface albedo and air temperature. Meteorological model simulation in region of Ansan-City, Shiheung-City showed that mean air temperature became lower with the increase of albedo value. Simulated air temperature became lower $-0.16^{\circ}C$ and $-0.66^{\circ}C$ by 5% and 20% increase of albedo values respectively. And cooling energy saving amount in air conditioning process was calculated according to lowered air temperature. The reduction of air temperature resulted the reduction of air conditioning energy in personal house and commercial buildings. The increase of albedo from 5% to 20% resulted the reduction of air conditioning energy from 44,493 MWh/yr to 183,796 MWh/yr. Additionally the reduction of greenhouse gas emission through the energy saving was calculated after IPCC guideline. In terms of greenhouse gas emission $CO_2$ was reduced form -30,414 ton-$CO_2$/yr to -125,638 ton-$CO_2$/yr according to the reduction of electric energy.