• 한국해양학회지
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• 제20권1호
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• pp.43-49
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• 1985

서해안 장구만에 발달하는 조간대에서 24개의 표층시료 및 18개의 코아를 채 취하여 퇴적물의 조직 및 퇴적구조를 조사하였다. 이 조간대 지역은 대체로 silt flat, sandy-silt flat, silty-sand flat 으로 구분되며 해안선에서 바다쪽으로 갈수 록 입도가 조립화되는 경향을 보여준다. 코아의 X-ray촬영에 의해 나타나는 퇴적구 조는 bioturbation, current ripple laminae, parallel laminae등이며 지역에 따라 현저 한 차이를 보이고 있다. Bioturbation구조는 1차적으로 형성된 물리적 퇴적구조를 파괴하고 있으며, 만조선 쪽으로 갈수록 그 정도가 증가하고 있다. current ripple laminae 는 bioturbation정도가 비교적 적은 silty-sand, sandy-silt지역에 잘 나타나 며, 몇번의 창조류와 낙조류에 의해 형성된 미세한 사층리를 잘 보여주고 있다. 내 만쪽에 나타나는 parallel laminae는 silt/clay호층의 두께 1mm이하의 층리로이루어 져 있는 반면, 외만쪽에 나타나는 parallel laminae는 sand/silt/호층의 두께 1~5mm 의 층리로 구성되어 있는 것이 특징이다.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.499-512
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• 2004

The effects of swirl intensity on non-reacting and reacting flow characteristics in a flat flame burner (FFB) with four types of swirlers were investigated. Experiments using the PIV method were conducted for several flow conditions with four swirl numbers of 0, 0.26, 0.6 and 1.24 in non-reacting flow. The results show that the strong swirling flow causes a recirculation, which has the toroidal structures, and spreads above the burner exit plane. Reacting flow characteristics such as temperature and the NO concentrations were also investigated in comparison with non-reacting flow characteristics. The mean flame temperature was measured as the function of radial distance, and the results show that the strong swirl intensity causes the mean temperature distributions to be uniform. However the mean temperature distributions at the swirl number of 0 show the typical distribution of long flames. NO concentration measurements show that the central toroidal recirculation zone caused by the strong swirl intensity results in much greater reduction in NO emissions, compared to the non-swirl condition. For classification into the flame structure interiorly, the turbulence Reynolds number and the Damkohler number have been examined at each condition. The interrelation between reacting and non-reacting flows shows that flame structures with swirl intensity belong to a wrinkled laminar-flame regime.

• 대한기계학회논문집B
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• 제20권10호
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• pp.3322-3333
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• 1996

A numerical analysis has been conducted to investigate a modified floating-zone crystal growth process in which most of the melt surface is covered with a heated ring. The crystal rod is not only pulled downward but rotated around its axisymmetric line during crystal growth process in order to produce the flat interface of crystal growth and the single crystal growth of NaNO3 is considered in 6mm diameter. The present study is made from a full-equation-based analysis considering a pulling velocity in all of solid and liquid domains and both of solid-liquid interfaces are tracked simultaneously with a governing equation in each domain. Numerical results are mainly presented for the comparison of the surface shape of rotational crystal rod with that of no-rotational crystal rod and the effects of revolution speeds of the crystal rod. Results show that the rotation of crystal rod produces more its flat surface. In addition, the shape of crystal growth near the centerline is more concaved with the increase in the revolution speed of crystal rod. The flow pattern and temperature distribution is analyzed and presented in each case. As the pulling velocity of crystal rod is increasing, the free surface of the melt below the heated ring is enlarged due to the crystal interface migrating downward.

• 한국정밀공학회지
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• 제22권11호
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• pp.125-134
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• 2005

Recently, there have been reported on the results that the material life is reduced by fretting conditions and the initial crack made by low stress under fretting. The purpose of this paper is to show that the results of finite element analysis for the fretting contact problems of a flat rounded punch are nearly consistent with the theoretical solutions and to research that the results about effects of the contact zone according to geometries and mechanical properties of pad.

• 한국환경복원기술학회지
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• 제12권5호
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• pp.59-76
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• 2009

This study was conducted to supply basic data for restoration and management of forests in Civilian Control Zone, with surveying naturalized plants around abandoned military camps. The total study sites are 72 abandoned military camps, from Gosung in east region to Paju in west region of Civilian Control Zone. The naturalized index of total area is 12.6%, and naturalized index of east and middle regions are 12.1% and 8.4%. But its index of west region is 15.9%. These results are due to geographical characteristics. The east and middle regions are in steep mountainous districts, and so but west region is flat district, and so naturalized plants was imported by only army. But west region is in flat districts, and so imported method of naturalized plants is very various. The main naturalized plants are Ambrosia trifida and Ambrosia artemisiifolia var. elatior in Civilian Control Zone. The main dispersion pattern of naturalized plants are gravity dispersion pattern ($D_4$) and wind and water dispersion pattern ($D_1$). The all naturalized plants are photophilic plants in survey sites. And so, if abandoned military camps are recovered to forests, the naturalized plants are disappeared because of the change of sunlight condition. So it is necessary to manage and recover forests, even if that area is Civilian Control Zone.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.454-459
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• 2001

The present study is concerned with the flow patterns induced by other impellers in a rectangular tank Impellers are FBT(Flat blade turbine), PBT(Pitched blade turbine), Shroud turbine, Rushton Turbine, and Helical ribbon turbine. The solution of flows in moving reference frames requires the use of 'moving' cell zone. The moving zone approaches are MRF(Multiple reference frame), which is a steady-state approximation and Sliding method, which is a unsteady-state approximation. Numerical results using two moving zone approaches are compared with experiments by Ranade & Joshi, which have done extensive LDA measurements of the flow generated by a standard six-bladed Rushton turbine in a cylindrical baffled vessel. In this paper we simulated the flow patterns with above mentioned moving zone approaches and impellers. Turbulence model is RNG k-$\epsilon$ model.

• Journal of Mechanical Science and Technology
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• 제14권4호
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• pp.401-407
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• 2000

An elastic-plastic finite element analysis is performed to investigate detailed closure behavior of fatigue cracks and the numerical results are compared with experimental results. The finite element analysis performed under plane stress using 4-node isoparametric elements can predict fatigue crack closure behavior. The mesh of constant element size along crack surface can not predict the opening level of fatigue crack. The crack opening level for the constant mesh size increases linearly from initial crack growth. The crack opening level for variable mesh size, is almost flat after crack tip has passed the monotonic plastic zone. The prediction of crack opening level using the variable mesh size proportioning the reversed plastic zone size with the opening stress intensity factors presents a good agreement with the experimental data regardless of stress ratios.

• 한국환경과학회지
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• 제31권12호
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• pp.1027-1038
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• 2022

The intertidal zone has both land and marine characteristics and shows complex weather environments. These characteristics are suited for studying climate change, energy balance and ecosystems, and may play an important role in coastal and marine weather prediction and analysis. This study was conducted at Odo Island, approximately 300m from the mainland in Yeosu. We built a weather observation system capable of real-time monitoring on the mud flat in the intertidal zone and measured actual weather and marine data. Weather observation was conducted from April to June 2022. The results showed changes in air temperature and water temperature with changes in the tide level during spring. Correlation analysis revealed characteristic changes in air temperature and water temperature during the day and night, and with inundation and exposure.

• 대한기계학회논문집B
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• 제27권4호
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• pp.447-457
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• 2003

An experiment in a turbulent non-premixed flat flame was carried out in order to investigate the effect of swirl number on the flow and combustion characteristics. First. stream lines and velocity distribution in the flow field were obtained using PIV method. In contrast with the axial flow without swirl, highly swirled air induced stream lines along the burner tile. and backward flow was caused by recirculation in the center zone of the flow field. In the combustion. the flame with swirled air also became flat and stable along the burner tile with increment of the swirl number. Flame structure by measuring OH and CH radicals intensity and by calculating Damkohler number(Da) and turbulence Reynolds number(Re$_{T}$) was examined. It appeared to be comprised in the wrinkled laminar-flame regime. Backward flow by recirculation of the burned gas decreased the flame temperature and emissions concentrations as NO and CO. Consequently, the stable flat flame with low NO concentration was achieved.d.

• 대한원격탐사학회지
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• 제21권5호
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• pp.405-415
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• 2005

It is difficult to classify tidal flat surface that is composed of a mixture of mud, sand, water and microphytobenthos. We used a Linear Spectral Unmixing (LSU) method for effectively classifying the tidal flat surface characteristics within a pixel. This study aims at 1) detecting algal mat using LSU in the Saemangeum tidal flats, 2) determining a suitable end-member selection method in tidal flats, and 3) find out a habitual characteristics of algal mat. Two types of end-member were built; one is a reference end-member derived from field spectrometer measurements and the other image end-member. A field spectrometer was used to measure spectral reflectance, and a spectral library was accomplished by shape difference of spectra, r.m.s. difference of spectra, continuum removal and Mann-Whitney U-test. Reference end-members were extracted from the spectral library. Image end-members were obtained by applying Principle Component Analysis (PCA) to an image. The LSU method was effective to detect microphytobenthos, and successfully classified the intertidal zone into algal mat, sediment, and water body components. The reference end-member was slightly more effective than the image end-member for the classification. Fine grained upper tidal flat is generally considered as a rich habitat for algal mat. We also identified unusual microphytobenthos that inhabited coarse grained lower tidal flats.