• Journal of Environmental Science International
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• v.8 no.1
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• pp.135-144
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• 1999

Air quality modeling about coastal urban region such as Pusan shoud be consider shipping source emmited from ships anchoraging and running. It has been proved at our previous studies that the ratios of air pollutants emission amount in coastal area to inland are 12.2% for NO$_2$ and 11.7% for $SO_2$ and the air qualify of coastal urban area consierably counts on ships. Also the dispersion pattern of the all pollutants followed local circulation system in this region. Therefore this study has been developed air quality model which can describe the formation, transport, transformation and deposition processes of air pollutants considering shipping source. Currently, restriction for emission amount of ships does not exist, so our study will be useful to set the omission standard and for devising air quality policy in coastal urban region.

• Journal of Korean Society for Atmospheric Environment
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• v.23 no.4
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• pp.430-439
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• 2007

The objective of this work is the air quality modeling according to the practical roughness length using the building information as surface boundary conditions. As accurate wind and temperature field are required to produce realistic urban air quality modeling, comparative simulations by various roughness length are discussed. The prognostic meteorological fields and air quality field over complex areas of Seoul, Korea are generated by the PSU/NCAR mesoscale model (MM5) and the Third Generation Community Multi-scale Air Quality Modeling System (Models-3/CMAQ), respectively. The simulated $O_3$ concentration on complex terrain and their interactions with the weak synoptic flow had relatively strong effects by the roughness length. A comparison of the three meteorological fields of respective roughness length reveals substantial localized differences in surface temperature and wind folds. Under these conditions, the ascended mixing height and weakened wind speed at night which induced the stable boundary stronger, and the difference of simulated $O_3$ concentration is $2{\sim}6\;ppb$.

• Journal of the Society of Naval Architects of Korea
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• v.42 no.3
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• pp.183-189
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• 2005

A modeling of a hydraulic-gun-aerator is proposed to set up a design procedure for such devices. The aerators are used to destroy any thermal stratification that are responsible for the degradation of water qualify of lakes. The aerator produces ascending flow by using air bubbies released instantly near the bottom of the lake into a cylindrical pipe installed vertically. Differently form the diffuser-aerators, they can pull up the cold, oxygen depleted water directly to the region of the free surface, and they are believed to work effectively especially for relatively deeper lakes. Their design procedure has not been established yet though, and we propose a model focusing on the exit flow velocity at the top of the aerator through the examination of presently operating devices.

• The Journal of the Acoustical Society of Korea
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• v.24 no.7
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• pp.379-386
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• 2005

Among various kinds of hearing aids which have been developed so far. the conventional air conduction hearing aids have some problems such as the acoustic distortion, an howling effect due to acoustic feedback. Another type of hearing aid. the cochlear implant system can be applied to the profound imparied person. However. it shows the disadvantage that there is no possibility of recovery of the acoustic organ such as ossicle. On the other hand. the implantable middle ear heaving device directly vibratos the ossicular chain and has better sound qualify. good cosmetics for appearance. and wide frequency responses so that it can overcome the defects or the conventional hearing aids. In this paper, a mathematical modeling and a momentum equation derivation of the DET has been performed. For the optimization of the structure dimension generating maximal vibrating force of the DET. the computer simulation using a finite element analysis (FEA) software has been performed. Also. the vibrating transducer has been designed to make the frequency characteristics or the transducer be similar to those of the normal middle ear. Through the experimental results, the measured vibration characteristics of the DET has been evaluated to verify the performance for the application to implantable middle ear hearing devices.