• Ocean Systems Engineering
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• v.7 no.3
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• pp.299-318
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• 2017

The paper aims at illustrating several key issues and ongoing efforts for development of a reliable fully-Lagrangian particle-based solver for simulation of hydroelastic slamming. Fluid model is founded on the solution of Navier-Stokes along with continuity equations via an enhanced version of a projection-based particle method, namely, Moving Particle Semi-implicit (MPS) method. The fluid model is carefully coupled with a structure model on the basis of conservation of linear and angular momenta for an elastic solid. The developed coupled FSI (Fluid-Structure Interaction) solver is applied to simulations of high velocity impact of an elastic aluminum wedge and hydroelastic slammings of marine panels. Validations are made both qualitatively and quantitatively in terms of reproduced pressure as well as structure deformation. Several remaining challenges as well as important key issues are highlighted. At last, a recently developed multi-scale MPS method is incorporated in the developed FSI solver towards enhancement of its adaptivity.

• Journal of the Korean Wood Science and Technology
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• v.27 no.1
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• pp.56-63
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• 1999

Machinability of three Korean domestic bamboo species, Phyllostachys pubescens Mazel, Phyllostachys nigra var. henonis Stapf. and Phyllostachys bambusoides S. et Z., was studied to investigate the possibility of utilization of Korean domestic bamboo species as raw material for industry. Splitting force reached a maximum within the first inch of knife travel and diminished thereafter. Parallel-sided wedge-type knife with sharpness angle of 15 degree required the lowest maximum splitting force. Roughnesses of surfaces developed during planing and sawing of bamboo were lower than those of Pinus radiata D. Don and quality of ripped surface was better than that of cross-cut surface on bamboo. 62.5 hours were required to dry 12mm-thick Phyllostachys pubescens Mazel from moisture content of 60% to moisture content of 10% at $70^{\circ}C$.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1531-1534
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• 2002

Shape description and its corresponding matching algorithm is one of the main concerns in MPEG-7. In this paper, a new method is proposed for shape registration of 2D objects for MPEG-7 Shapes are recognized using the Hu statistical moments in frequency domain. The Hu moments are moment-based descriptors of planar shapes, which are invariant under general translation, rotational, scaling, and reflection transformation. The image is transformed into frequency domain using Fourier Transform. Annular and radial wedge distributions fur the power spectra are extracted. Different statistical features (Hu moments) are found f3r the power spectrum of each selected transformed individual feature. The Euclidean distance of the extracted moment descriptors of the features are found with respect to the shapes in the database. The minimum Euclidean distance is the candidate for the matched shape. The simulation results are performed on the test shapes of MPEG-7.

• The Journal of the Korean dental association
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• v.48 no.4
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• pp.297-307
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• 2010

Noncarious cervical lesions(NCCLs) are characterized as structural defects found on the tooth surface of the cement-enamel junction. Loss of tooth structure through noncarious mechanisms may vary in etiology and clinical presentation for each individual but presently many clinician now classify this as tooth failure of abfraction due to the stress applied in the cervical area of the tooth under oral physiological and pathological loads. In the current study, we investigated the stress distribution of maxillary premolar with NCCL using simulated 3D finite element analysis. The results were as follows: 1. In the sound maxillary premolar, the stresses were highly concentrated at cervical enamel surface of the mesiobuccal line angle, asymmetrically. 2. Once the lesion has been formed, the highest stress concentration was observed around the apex of the wedge shaped lesion. 3. In four types of NCCL, the patterns of stress distribution were similar and the peak stress was observed at mesial corner and also stresses concentrated at lesion apex. 4. Lesion cavity modification of rounding apex, reduced stress of lesion apex. 5. When restoring the notch-shaped lesion, material with high elastic modulus worked well at the lesion apex and material with low elastic modulus worked well at the cervical cavosurface margin.

• Journal of the Korean Geotechnical Society
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• v.34 no.10
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• pp.61-74
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• 2018

In this study, the pull-out behavior of tunnel type anchorage of suspension bridges was analyzed based on results from laboratory size model tests and numerical analysis. Tunnel type anchorage has found its applications occasionally in both domestic and oversea projects, therefore design method including failure mode and safety factor is yet to be clearly established. In an attempt to improve the design method, scaled model tests were conducted by employing simplified shapes and structure of the Ulsan grand bridge's anchorage which was the first case history of its like in Korea. In the model tests, the anchorage body and the surrounding rocks were made by using gypsum mixture. The pull-out behavior was investigated under plane strain conditions. The results of the model tests showed that the tunnel type anchorage underwent wedge shape failure. For the verification of the model tests, numerical analysis was carried out using ABAQUS, a finite element analysis program. The failure behavior predicted by numerical analysis was consistent with that by the model tests. The result of numerical analysis also showed that the effect of Poisson's ratio was negligible, and that a plugging type failure mode could occur only when the strength of the surrounding rocks was 10 times larger than that of anchorage body.

• Tuberculosis and Respiratory Diseases
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• v.43 no.2
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• pp.274-279
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• 1996

Pulmonary veno-occlusive disease is a rare cause of pulmonary hypertension in which the primary abnormality is obliterative obstruction of pulmonary veins, especially venules. Clinicaly, we should suspect this disease in the case of congestive cardiac failure with pulmonary hypertension, chronic interstitial pulmonary edema, and normal or elevated wedge pressure on cardiac catheterization. We experience a case of pulmonary hypertension due to pulmonary veno-occlusive disease. A 55-years -old woman developed progressive dry cough and dyspnea for 3 months. Physical examination showed normal heart sounds, diffuse crackles in the whole lung fields. The liver was not palpable and pitting edema was absent. The diagnosis was made by chest HRCT, 2-D echocardiography, normal pulmonary capillary wedge pressure on cardiac catheterization, and confirmed by thoracoscopic lung biopsy. This patient was treated with vasodilator(calcium antagonist) and with mild symptomatic improvement. We reported a case of pulmonary veno-occlusive disease with review of literatures.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2003.09a
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• pp.42-42
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• 2003

목적 : 조사면 크기에 따른 금속쐐기와 가상쐐기에 의한 6 MV 와 15 MV 엑스선의 출력 및 상부와 하부 에 설치하는 금속쐐기의 출력을 비교하고자 한다. 대상 및 방법 : Varian Clinac21EX(미국)는 두부의 상부와 하부에 설치하는 각각의 금속쐐기와 제한기에 의한 가상쐐기 기능을 가지고 있다. 금속쐐기의 쐐기각은 네 가지 (15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$, 60$^{\circ}$)이며 투과력에 무관하게 한 쐐기각에 대한 쐐기는 사하부는 각 1 개이고, 가상쐐기는 일곱 가지 ($10^{\circ}$, 15$^{\circ}$, 20$^{\circ}$, 25$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$, 60$^{\circ}$) 이다. 각 쐐기에 대하여 3$\times$3～20$\times$20 $\textrm{cm}^2$ 의 조사면 크기에서 6 및 15 MV 엑스선의 쐐기출력인수 (wedge field output factor)를 $d_{max}$와 10 $\textrm{cm}^2$ 깊이에서 측정하였다. 조사면크기와 측정깊이에 따른 쐐기출력인수의 변화추이를 관찰하였다. 쐐기출력인수 O $F_{Wdg}$는 다음과 같다. O $F_{Wdg}$(r)= $D_{Wdg}$(r)/ $D_{op}$ ( $r_{0}$) 여기서 $r_{0}$와 r은 각각 민조사면의 기준조사면크기, 쐐기조사면크기이다. 하부쐐기에 대한 상부쐐기의 출력인수의 상대적인 백분율 차이, %ROD=l00$\times$(O $F_{upWdg}$/O $F_{lowWdg}$ lowWdg/ - 1)를 구하였다. 조사면크기와 깊이에 따른 %ROD의 변화추이를 평가하였으며 쐐기 각각에 대하여 출력인수를 측정해야하는지 평가하였다. 결과 : 금속쐐기에 대한 쐐기출력인수는 방사선의 투과력과 깊이에 관계없이 조사면 크기가 커짐에 따라 증가하였으나 가상쐐기의 쐐기출력인수는 쐐기각이 작은 경우에는 조사면크기가 커짐에 따라 증가하다가 감소하였으며 최대값을 보이는 조사면크기는 쐐기각이 커짐에 반하여 감소하였으며 투과력에 관계없이 60。 쐐기에 대해서는 조사면 크기가 4 cm(A/P=1) 이상에서 조사면크기가 커짐에 따라 감소하였다. 6 MV 엑스선 에 대한 10 cm 깊이에서 15。 쐐기와 15 MV 엑스선에 대한 10 cm 깊이에서 45。 쐐기의 A/P 가 1.5보다 작은 조사면을 제외하고는 조사면의 크기가 커짐에 따라 %ROD는 감소하였다. $d_{max}$에서는 15。 쐐기와 30。 쐐기에 대해서는 %ROD가 음수였으며 절대값이 증가하였다. 이는 곧 조사면의 크기가 커짐에 따라 상부쐐기의 쐐기출력계수가 하부쐐기와 접근하고 드디어는 상부쐐기의 출력인수가 하부쐐기의 출력인수보다 작아질 수도 있다는 것을 의미하고 있다. 또한 %ROD 는 쐐기각이 클수록 변화가 컸으며, 조사면 크기가 커짐에 따라 10 cm 깊이에서보다 $d_{max}$에서 더 급하게 감소하였다. %ROD 는 6 MV 엑스선에 대해서는 -0.52～4.18 % 였고, 15 MV 엑스선에 대해서는 -0.44-4.18 % 였다. 결론 : 두 가지 투과력의 엑스선이 방출되는 선형가속기의 상하부 쐐기와 가상쐐기의 출력인수를 측정하여 비교하였다. 결과에서 얻어진 결론은 아래와 같다. 1. 조사면의 크기가 커짐에 따라 금속쐐기의 출력계수 는 증가하였으나 가상쐐기의 경우는 증가하다가 감소하거나 큰 쐐기각에 대해서는 감소만 하였다. 2. 상부쐐 기와 하부쐐기는 쐐기출력인수가 4% 이상 차이가 날 수 있으므로 독립적으로 측정하여 이용하여야 할 것이다.것이다.다.

• Journal of Korea Water Resources Association
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• v.48 no.12
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• pp.1023-1035
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• 2015

This study applies 3-D N-S solver based on PBM (Porous Body Model), LED-WASS-3D ver 2.0 to directly analyze non-linear interaction of seawater-freshwater-coastal aquifer in order to simulate the seawater infiltration into coastal aquifer. This numerical simulation is the first trial in Korea, as well as unusual and new numerical analysis abroad. Firstly, to validate the applied numerical model, the validity and effectiveness was verified for the numerical model by comparing and considering it with the result of laboratory experiment for seawater-freshwater interface in coastal aquifer. And then it simulated the seawater infiltration into coastal aquifer considering the changed levels of seawater and groundwater in order to analyze the distribution characteristics of flow field and seawater-freshwater interface of coastal aquifer as the level difference between seawater and groundwater and rate of seawater level (${\Delta}h/h$) increased. In addition, the characteristics of seawater infiltration were analyzed from the vertical salinity in the coastal aquifer by ${\Delta}h/h$, which cannot be obtained from existing non-diffusion numerical models. Finally, it analyzed the effect of ${\Delta}h/h$ on the seawater infiltration distance in coastal aquifer, which was indexed.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.14 no.2
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• pp.72-78
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• 1981

The purpose of this study is to find directivity characteristics and relative gain of directivity of the wedge horn in conjunction with a projector with varing horn length, horn angle and frequency. The horns are constructed with aluminum plate covered with styrofoam. By using hinges the horn angle could be varied with wide range. Measurements were made over the frequency range of 25 KHz-100 KHz by varing the horn lengths from 5cm to 21cm and the horn angles up to 90 degrees. The followings were the results obtained from the study, 1. As the horn angle increased, the beam width for tile major lobe initially decreased and then increased. At 80 KHz with horn length 21cm the minimum beam widths were obtained with 16 degrees in horizontal plane and 36 degrees in vertical plane. 2. The maximum relative gains of directivity were 4.4 dB in horizontal plane and 3.4 dB in vertical plane when the horn length was 21cm. 3. Beam width was decreased with increasing of frequency. 4. When the mouth apertures were small the major lobes obtained by the experiment agreed with the computed ones, and when the mouth apertures were wide the major lobes by the observed were wide than the computed ones.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.313-320
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• 2000

The purpose of this study was to evaluate on the interfacial morphology between dentin and restorative materials. In this in vitro study, the cavity wall restorated with 3 different kinds of tooth colored restorative materials [resin-modified Glass Ionomer cement (Fuji II LC), composite resin (Z-100), compomer (Dyract)]. The thirty extracted human molar teeth without caries and/or restorations are used. The experimental teeth were randomly divided into three groups of ten teeth each. In each group, Wedge shaped cavities (width: 3mm, length: 2mm, depth: 1.5mm) were prepared at the cementoenamel junction on buccal and lingual surfaces. The adhesive of composite resin were mixed with rhodamine B. Primer of composite resin, Prime & Bond 2.1 of Dyract and liquid of Fuji II LC were mixed with fluorescein. In group 1, the cavity wall was treatment with dentin conditioner, and then restorated with Fuji II LC. In group 2, the cavity wall was treatment with Prime & Bond 2.1 and then restorated with Dyract. In group 3, the cavity wall was etching with 10% maleic acid, applied with primer and bonding agent and then restorated with Z-100. The interface between dentin and restorative materials was observed by fluoresence imaging with a confocal laser scanning microscope. The results were as follows : 1. In Glass ionomer group, adaptation of resin modified Glass-ionomer restoration against cavity wall is tight, but the crack formed inside of restoration were observed. 2. In Dyract group, the penetration of resin tag is shorter and the width of hybrid layer is narrower than composite resin group. 3. In Z-100 group, primer penetrated deeply through dentinal tubule. Also bonding agent was penetrated along the primer, but the penetration length is shorter than primer part, and in 3-D image, the resin tag is conical shape and lateral branch is observed.