• International Journal of Naval Architecture and Ocean Engineering
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• 제9권2호
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• pp.160-176
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• 2017

The interaction of focused wave groups with a vertical wall is investigated based on the second order potential theory. The NewWave theory, which represents the most probable surface elevation under a large crest, is adopted. The analytical solutions of the surface elevation, velocity potential and wave force exerted on the vertical wall are derived, up to the second order. Then, a parametric study is made on the interaction between nonlinear focused wave groups and a vertical wall by considering the effects of angles of incidence, wave steepness, focal positions, water depth, frequency bandwidth and the peak lifting factor. Results show that the wave force on the vertical wall for obliquely-incident wave groups is larger than that for normally-incident waves. The normalized peak crest of wave forces reduces with the increase of wave steepness. With the increase of the distance of focal positions from the vertical wall, the peak crest of surface elevation, although fluctuates, decreases gradually. Both the normalized peak crest and adjacent crest and trough of wave forces become larger for shallower water depth. For focused wave groups reflected by a vertical wall, the frequency bandwidth has little effects on the peak crest of wave elevation or forces, but the adjacent crest and trough become smaller for larger frequency bandwidth. There is no significant change of the peak crest and adjacent trough of surface elevation and wave forces for variation of the peak lifting factor. However, the adjacent crest increases with the increase of the peak lifting factor.

• 대한토목학회논문집
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• 제29권4B호
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• pp.365-376
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• 2009

조위발생빈도분포가 상이한 우리나라 해역에 위치한 해안구조물의 마루높이를 설정하는 문제에 있어서 조위의 합리적인 취급이 중요하다. 권혁민 등(2005, 2006)은 해역별 기대월파확률 계산결과로서 조위발생빈도분포의 편차가 크면 클수록 작아지는 경향이 명백함을 보였다. 이는 년 단위 조위의 발생빈도분포가 년 최대파고 급의 파 발생빈도분포와 년 중 언제든 조우 할 수 있다는 가정을 내포하고 있다. 본 연구에서는 파와 조위의 조우 가능성을 년 최대 파급의 파가 발생할 수 있는 여름철 또는 겨울철을 대상으로 계절별 일 최대 조위발생빈도분포를 불확정요소로 취급하여 계산했다. 계산결과, 우리나라 전해역의 기대월파확률이 1%미만으로 수렴됨이 확인되어 이를 시나리오로 제안하고자 한다. 본 시나리오에 의하면 기대월파확률이 동일하도록 마루높이의 설정이 우리나라 전 해역을 대상으로 가능함을 확인하였다. 본 연구에서 마루높이는 전 해역에 대하여 계절별 일 최대조위의 평균값으로부터 설정이 가능한 것으로 추정된다.

• 한국농공학회지
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• 제45권6호
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• pp.109-118
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• 2003

As a fundamental research to establish a safety operation plan for irrigation dams, this study presents hydrologic analysis conducted in Sungju Dam watershed based on various rainfall data. Especially those reservoirs without flood control feature are widely exposed to the risk of flooding, a safe and optimized operation program need to be improved against arbitrary flooding. In this study, reservoir routing program was developed and simulated for reservoir runoff estimation using WMS hydrology model. The model simulated the variations of reservoir elevation under the condition of open or closed emergency gate. In case of closed emergency gate, water surface elevation was given as 193.15 m, and this value exceeds the dam crest height by 1.65 m. When the emergency gate is open, the increment of water surface elevation is given as 192.01 m, and this value exceeds dam crest height by 0.57 m. As an alternative plan, dam height increase can be considered for flood control under the PMP (Probable Maximum Precipitation) condition. Since the dam size is relatively small compare to the watershed area, sound protection can be expected from the latter option rather than emergency gate installation.

• 대한토목학회논문집
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• 제35권4호
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• pp.845-852
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• 2015

파랑의 처오름높이는 항만 및 호안구조물의 마루높이 산정에 있어 주요한 설계요소이다. 본 연구에서는 TTP로 피복된 경사식구조물을 대상으로 2차원 수리실험을 수행하였으며, 실험에 적용된 실험파는 불규칙파로서 구조물 toe 위치에서 비쇄파, 쇄파 및 쇄파된 파의 조건을 포함한다. 본 실험결과를 이용하여 사면경사 1:1.5인 경사식구조물의 처오름높이를 산정할 수 있는 경험식을 쇄파 유사성 매개변수를 이용하여 제안하였다. 그리고 본 실험결과는 기존 연구결과인 van der Meer and Stam(1992)의 결과와 비교하였다.

• 대한토목학회논문집
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• 제26권4B호
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• pp.399-404
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• 2006

권혁민 등(2004)은 우리나라 동해안의 실해역 극치파고 및 조위발생빈도분포를 고려한 기대월파확률 산정기법을 제안했다. 권 등의 연구는 동해안의 묵호와 부산지역을 비교하여 조위발생빈도분포가 기대월파확률에 크게 영향을 준다는 것을 예시했으며 그 분포의 표준편차가 크면 클수록 기대월파확률이 작아짐을 보였다. 본 연구는 권혁민 등이 제안한 기대월파확률 계산방법을 준용하여 우리나라 동 남 서 해역의 기대월파확률 특성에 대하여 현행 설계방법에 의해 결정된 마루높이에 대한 평가를 시도하였다. 본 연구결과, 개략적으로 동 남 서 해역으로 갈수록 기대월파확률이 작아짐을 알 수 있다.

• 수산해양기술연구
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• 제22권2호
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• pp.31-35
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• 1986

A bore is a transition between different uniform flows of water. If a long wave of elevation travels in shallow water it steepens and forms a bore. The bore is undular if the change in surface elevation of the wave is less than 0.28 of the original depth of water. This paper describes the growth of an undular bore from a long wave which forms a gentle transition between a uniform flow and still water. A physical account of its development is followed by the results of numerical calculations. Finite-difference approximations are used in the partial differential equations of motion. For undular bores, numerical calculations show that (i) the relationship between relative elevation and relative velocity given by long wave theory is approached for an undular bore, (ii) the amplitude of first crest of an undular bore approaches a finite limit approximately at an exponential rate, and (iii) the distance between the first two crests increases without bound, approximately logarithmically.

• Journal of Periodontal and Implant Science
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• 제31권3호
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• pp.625-631
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• 2001

The anatomic structure around interproximal area plays an important role not only in the natural teeth, but also in the implant. The loss of papilla can lead to cosmetic deformity, phonetic problem, food impaction on the anterior dentition, and masticatory problem, food impaction and proximal caries on the posterior dentition. The purpose of this study was to evaluate the relationship between interdental papilla existence and distance from contact point to alveolar crest in Korean posteior dentition. 45 Korean adult patients(31males, 14 females) participated in this study. Measurements were carreid out total 126 interproximal areas, 18 first premolar, 31 second premolar, 40 first molar, and 37 second molar areas. Papilla index was recorded as suggested by Jemt. Distance between contact point and alveolar crest measrued by Florida $probe^{R}$, after flap elevation. Each distance was measured 10 times by every 0.1mm unit. The results showed that the mean Papilla index 1.37 and mean distance between contact point and alveolar crest was 7.44mm. The correlation between the Papilla index and distance was high negative correlation(Pearson correlation=-0.47), and it was statistically significant(P=0.000) When the distance between contact point and alveolar crest was 5mm, the loss of papilla was appeared almost in half cases. When the distance was 6mm, the papilla loss was present 95%, when 7mm, the papilla loss was 100%.

• 한국농공학회지
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• 제18권1호
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• pp.4079-4086
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• 1976

In many reservoir projects, economic considerations will necessitate a design utilizing surcharge. Determination of the most economical combination of surcharge and spillway capacity for a given spillway crest level will require flood routing studies and economic studies of the dam-reservoir-spillway combinations. Many methods of actual flood routing have been devised, each of them with its advantages and disadvantages. Some of these methods are listed below: (1) Arithmetical trial-and-error method. (2) Modified Puls' method (3) Cheng's graphical method (4) Horton's arithmetical method (5) Ekadahl's arithmetical method (6) Digital computer programming. For the purpose of preliminary design and cost estimating of dams and spillways, it is often required to estimate, for a given design flood and spillway crest level. the approximate values of two among the three characteristics of the spillway spillway length, maximum discharge and surcharge depth at maximum discharge, when one of these quantities is given. As is well known, the outflow hydrograph for an ungated overflow spillway assumes the form of a wave-shaped curve with a minimum point for Q=o At zero time and a maximum point for Q=Qmax at its intersection with the falling leg of the inflow hydrograph (see Fig. 4) The shaded area between the inflow and outflow hydrographs represents at the approximate scale the temporary retention Vt. In line with the remarks, draw by free hand the assumed outflow hydrograph with its maximum point for the given Qmax (see Fig. 4) and by planimetration find Vt. From the reservoir capacity curve (Fig. 3) find Vs for the given spillway crest level and make V=Vs+Vt. From the above curve find surcharge water elevation for V and surcharge depth Hmax over spillway crest. From the discharge formula compute {{{{L= { Q} over { { CH}^{3/2 } } }}}} The methed provides a means for a quick and fairly accurate estimation of spillway capacity.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제34권4호
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• pp.475-479
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• 2008

Aim: The aim of this study was to investigate the arterial arcade of maxillary sinus by determining the distance between the alveolar crest and the inferior border of the vessels in Korean population. Materials and methods: 76 patients and 87 available sinuses were determined by CT scan (Implagraphy, Vatech, Seoul, Korea). The distance between alveolar crest and inferior border of the vessel was determined considering the tooth area of posterior maxilla. Results: The lowest distance was observed on first molar area and the average distance is 16.9 mm. Discussions: it is important in sinus lift surgery that the vessels not to be damaged and that the anastomosis is situated in the lateral wall of maxillary sinus, which has to be exposed to gain access to the maxillary sinus. The knowledge of arterial arcade of maxillary sinus is important to perform the sinus floor elevation procedure effectively.

• 대한토목학회논문집
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• 제28권1B호
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• pp.11-20
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• 2008

본 연구에서는 국내 중소규모 댐의 대부분을 차지하는 자연 월류형 여수로의 홍수배제능력 증대를 위해 여수로의 월류부 형상 개선에 따른 배제유량을 분석하였다. 대표적인 댐으로서 대수호지를 선정하였으며 여수로 배제유량 분석을 위해 3차원 수리해석 프로그램인 FLOW-3D를 적용하였다. 여수로 개축모형으로서 직선형 래버린스위어 및 곡선형 래버린스위어를 적용하여 각 모형별 월류양상 및 방류량을 현 상태인 선형 측수로식 여수로와 비교하였다. 수치해석 결과의 검증을 위해 Froude 상사법칙에 의해 1/40로 축소된 수리모형 실험 자료와 비교해 본 결과 측수로 내 흐름 및 월류양상이 서로 잘 일치하였으며 측벽 옹벽에서의 수위도 근사하였다. 설계홍수위 시 위어형상 별 측수로 내 월류양상을 비교해 보면 선형 측수로 여수로의 경우 위어를 통과한 측수로 내 흐름이 원활하였으나 직선형 및 곡선형 래버린스위어의 경우 방류량이 현 상태에 비해 40 cms 증가하여 위어를 월류한 흐름이 수면 위를 타고 반시계 방향으로 돌게 되며 잠류가 발생되는 것으로 나타났다. 저수지 수위-방류량 모의 결과 직선형 및 곡선형 래버린스위어 모두 현 상태인 선형 측수로식 위어에 비해 유효길이를 더 확보할 수 있어서 저수위에서는 최대 71%의 방류량 증가 효과를 보였지만 수위가 증가함에 따라 측수로 내 잠류가 발생하고 수맥간섭이 심해져 방류곡선의 경사가 점차 완만해졌다.