• 한국해양공학회지
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• 제15권2호
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• pp.11-21
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• 2001

The focus of this paper is on the numerical investigation of obliquely incident wav interactions with a system composed of fully submerged and floating dual buoy/vertical-flexible-membrane breakwaters placed in parallel with spacing between two systems. The fully submerged two systems allow surface and bottom gaps to enable wave transmission over and under the system. The problem is formulated based on the two-dimensional multi-domain hydro-elastic linear wave-body interaction theory. The hydrodynamic interaction of oblique incident waves with the combination of the rigid and flexible bodies was solved by the distribution of the simple sources (modified Bessel function of the second kind) that satisfy the Helmholz governing equation in fluid domains. A boundary element program for three fluid domains based on a discrete membrane dynamic model and simple source distribution method is developed. Using this developed computer program, the performance of various dual systems varying buoy radiuses and drafts, membrane lengths, gaps, spacing, mooring-lines stiffness, mooring types, water depth, and wave characteristics is thoroughly examined. It is found that the fully submerged and floating dual buoy/membrane breakwaters can, if it is properly tuned to the coming waves, have good performances in reflecting the obliquely incident waves over a wide range of wave frequency and headings.

• 대한한의학회지
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• 제27권4호
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• pp.142-149
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• 2006

Objectives : The aim of this study was to investigate the relationship between stress type and Ryodoraku score (RS) in patients with functional dyspepsia. Methods : 92 (30 male, 62 female) patients with functional dyspepsia were included in this study. Degree of stress was evaluated by GARS and BEPSI scale which can assess acute and chronic stress, respectively. RS of the patients was measured, and mean, sum of gaps and standard deviation (SD) in their RS were taken. First, patients were divided into two groups by sex, and by mean RS $40{\mu}A$ (above and below). GARS and BEPSI scale of each group was compared. Second, correlation between stress scales (GARS and BEPSI) and variation indexes of RS (sum of gaps and SD) was examined. Result : 1. The mean RS is higher in male patients than in female ones. 2. No significant difference was noted in GARS and BEPSI scale associated with above end below the mean $40{\mu}A$ RS. 3. The sum of gaps and SD of RS has significant correlation with GARS scale but not with BEPSI scale. Conclusions : These results suggest that the sum of gaps and SD of RS are associated with acute stress in patients with functional dyspepsia. Thus, it is thought that RS can be useful in assessing acute stress in patients with functional dyspepsia.

• 한국인구학
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• 제24권2호
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• pp.235-253
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• 2001

정보격차현상은 정보화 혹은 정보사회로의 진입과 더불어 심각한 사회문제로 부상하리라 예측되고 있으며, 이를 해소하기 위한 사회적 관심들이 적지 않다. 그러나 정보 격차 현황과 추이를 파악하려는 대부분의 연구들은 기술적 분석에 머무르고 있는 실정이다. 본 연구는 기존연구들에서 정보격차 배경변인으로 알려진 거주지역, 성, 연령, 교육수준 및 가구소득 등의 상대적 영향력과 이들 변인에 따른 정보격차가 지난 몇 년간 심화, 지속 혹은 완화되었는지를 파악한다. 이를 위해 본 연구는 한국정보문화센터가 실시한 <1998년도 국민정보화인식 및 정보생화실태조사>와 <2000년도 정보생활 실태 및 정보화인식조사> 자료를 활용하여, 컴퓨터와 인터넷 이용여부에 대한 다중로짓 모형분석을 실시하였다. 그 결과, 1998-2000년이라는 짧은 기간 동안에 컴퓨터와 인터넷 사용에서의 남녀간 격차는 다소 줄어들었으나, 대부분의 사회집단간 격차는 지속되거나 증가하고 있음이 발견되었다. 점차 가속되는 정보화과정에서 이러한 사회경제적 인구학적 배경변인에 따른 정보격차는 사회통합과 발전에 중요한 걸림돌로 등장하며, 그에 따른 사회적 정책적 대응이 요구된다.

• Journal of Yeungnam Medical Science
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• 제41권2호
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• pp.80-85
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• 2024

Background: This study aimed to compare and evaluate the marginal fit of nanocomposite computer-aided design/computer-aided manufacturing (CAD/CAM) inlays. Three types of nanocomposite CAD/CAM blocks (HASEM, VITA Enamic, and Lava Ultimate) were used as materials. Methods: Class II disto-occlusal inlay restorations were prepared on a typodont mandibular right first molar using diamond rotary instruments. The inlays were fabricated using CAD/CAM technology and evaluated using the silicone replica technique to measure marginal gaps at five locations on each inlay. The data were analyzed by two-way analysis of variance and Tukey post hoc tests (α=0.05). Results: There were no significant differences in the marginal gaps based on the type of nanocomposite CAD/CAM inlay used (p=0.209). However, there was a significant difference in the marginal gaps between the measurement regions. The gingival region consistently exhibited a larger marginal gap than the axial and occlusal regions (p<0.001). Conclusion: Within the limitations of this in vitro study, the measurement location significantly influenced the marginal fit of class II disto-occlusal inlay restorations. However, there were no significant differences in the marginal gaps among the different types of CAD/CAM blocks. Furthermore, the overall mean marginal fits of the class II disto-occlusal inlay restorations made with the three types of nanocomposite CAD/CAM blocks were within the clinically acceptable range.

• 대한치과보철학회지
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• 제38권2호
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• pp.200-213
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• 2000

Lasers have given dentistry a new rapid, economic, and accurate technique for metal joining. Although laser welding has been recommended as an accurate technique, there are some limitations with this technique. For example, the two joining surfaces must have a tight-fitting contact, which may be difficult to achieve in some situations. The tensile samples used for this study were made from a custom-made pure titanium and type III gold alloy plates. 27 of 33 specimens were sectioned perpendicular to their long axis with a carborundum disk and water coolant. Six specimens remained and served as the control group. A group of 6 specimens was posed as butt joints in custom parallel positioning device with a feeler gauge at each of three gaps : 0.00, 0.25. and 0.50mm. All specimens were then machined to produce a uniform cross-sectional dimension, none of the specimens was subjected to any subsequent form of heat treatment. Scanning electron microscopy was performed on representative tested specimens at fractured surfaces in both the parent metal and the weld. Vickers hardness was measured at the center of the welds with a micropenetrometer using a force of 300gm for 15 seconds. Measurement was made at approximately $200{\mu}m\;and\;500{\mu}m$ deep from each surface. One-way analysis of variance (ANOVA) and Scheffe's test was calculated to detect differences between groups. The purpose of this study is to compare the strength and properties of the joint achieved at various butt Joint gaps by the laser welding of type III gold alloy and pure titanium tensile specimens in an argon atmosphere. The results of this study were as follows : 1. When indexing and welding pure titanium, there was no decrease in ultimate tensile strength as compared with the unsectioned alloys for indexing gaps of 0.00 to 0.50mm, although with increasing gap size may come increased distortion (p>0.05). 2. When indexing and welding type III gold alloy, there were significant differences in ultimate tensile strength among groups with weld gaps of 0.00mm, 0.25 and 0.50mm, and the control group. Group with butt contact without weld gap demonstrated a significant higher ultimate tensile strength than groups with weld gaps of 0.25 and 0.50mm (p<0.05). 3. When indexing and welding the different metal combination of type III gold alloy and pure titanium, there were significant differences in ultimate tensile strength between groups with weld gaps of 0.00, 0.25, and 0.50mm. However, the mechanical properties of the welded joint would become too brittle to be acceptable clinically (p<0.05). 4. The presence of large pores in the laser welded joint appears to be the most important factor in controlling the tensile strength of the weld in both pure titanium and type III gold alloy.

• 한국산림과학회지
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• 제89권4호
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• pp.502-512
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• 2000

컴퓨터 시뮬레이션을 통하여 미국 북부 이차 활엽수림지역의 2개 임분을 대상으로 노숙림 발달과정을 평가하였다. 한 임분(phelps)은 77년생 임목들이 대부분 차지하고 있는 동령임분이고, 다른 임분(Wildcat Creek)은 노숙림의 구조적 특정을 다소 갖고 있는 연령이 많은 임목들이 있는 이령임분이다. 각 임분은 노숙림 자연발달 과정을 평가하기 위하여 임분구조, 직경분포, 고사목의 크기분포, 임분의 숨틈(Gap)크기, 3차원 임분공간도 및 수관투영도와 같은 구조적 특정을 이용하여 실시하였다. 본 시뮬레이션에 의하면, Phelps 임분은 현재를 기준으로 74년 후에, Wildcat Creek 임분은 13년 후에 노숙림 초기단계에 각각 도달하였다. 45년 시뮬레이션 동안 두 임분의 흉고직경분포는 직경크기가 커짐에 따라 모두 넓고, 평평한 형태를 나타냈으며, 고사목 크기분포에서는 두 임분 모두 직경크기가 커짐에 따라 고사목 수가 감소하는 경향을 나타냈다. Phelps의 숲틈 크기는 시뮬레이션 초기 연도보다 45년 후에 작게 나타난 반면, Wildcat Creek의 숲틈은 시뮬레이션 동안 일정한 패턴을 보였고, 큰 나무들의 고사로 인하여 큰 숲틈이 형성되었다.

• The Journal of Advanced Prosthodontics
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• 제7권4호
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• pp.294-302
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• 2015

PURPOSE. The purpose of this study was to verify the clinical-feasibility of additive manufacturing by comparing the accuracy of four different manufacturing methods for metal coping: the conventional lost wax technique (CLWT); subtractive methods with wax blank milling (WBM); and two additive methods, multi jet modeling (MJM), and micro-stereolithography (Micro-SLA). MATERIALS AND METHODS. Thirty study models were created using an acrylic model with the maxillary upper right canine, first premolar, and first molar teeth. Based on the scan files from a non-contact blue light scanner (Identica; Medit Co. Ltd., Seoul, Korea), thirty cores were produced using the WBM, MJM, and Micro-SLA methods, respectively, and another thirty frameworks were produced using the CLWT method. To measure the marginal and internal gap, the silicone replica method was adopted, and the silicone images obtained were evaluated using a digital microscope (KH-7700; Hirox, Tokyo, Japan) at 140X magnification. Analyses were performed using two-way analysis of variance (ANOVA) and Tukey post hoc test (${\alpha}=.05$). RESULTS. The mean marginal gaps and internal gaps showed significant differences according to tooth type (P<.001 and P<.001, respectively) and manufacturing method (P<.037 and P<.001, respectively). Micro-SLA did not show any significant difference from CLWT regarding mean marginal gap compared to the WBM and MJM methods. CONCLUSION. The mean values of gaps resulting from the four different manufacturing methods were within a clinically allowable range, and, thus, the clinical use of additive manufacturing methods is acceptable as an alternative to the traditional lost wax-technique and subtractive manufacturing.

• 한국측량학회지
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• 제32권2호
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• pp.87-93
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• 2014

지적 필지를 구성하고 있는 폴리곤 집합은 현실세계의 국토를 반영하는 가장 기반이 되는 데이터 집합이다. 따라서 지적 필지는 서로 간에 겹쳐있거나 공백을 가지지 않는 위상적 무결성이 보장되어야하는 데이터이다. 하지만, 여러 가지 이유로 필지들 간의 겹침과 공백의 문제가 발생하고 있고, 이러한 경우 폴리곤의 경계들은 주변의 폴리곤과 정확하게 인접하고 있지 못하기 때문에 의도하지 않은 겹침 영역과 공백 영역이 생산되고 있다. 이와 같이 정확하게 인접되어 있지 않은 경계가 불확실한 모서리를 하나 이상 포함하고 있는 경우, 이 폴리곤을 불확실한 영역이라고 부른다. 본 논문에서는 이러한 영역을 탐색하기 위한 TTA 기법을 제안하고자 한다. TTA 처리 순서는 우선 폴리곤 데이터 집합으로부터 포인트와 폴리라인을 추출하여 제한된 델로네 삼각분할을 수행한다. 다음으로 각 삼각형마다 데이터 집합과 중첩되는 면의 수를 세어 삼각형에 태깅을 수행한다. 태깅 값이 0 또는 1 이상인 삼각형을 추출한 후 연결성을 가지고 있는 삼각형끼리 병합을 수행하여 위상적 모순이 있는 영역들을 발견한다. 본 실험에서는 제안하는 알고리즘을 자동화하여 실세계에서 경계가 교차하는 지적 데이터에 적용하여 실험을 하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.447-452
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• 2001

Quenching phenomena of hemispherical downward facing convex surfaces with narrow gaps have been investigated experimentally. Experiments employed test sections having 1 and 2 mm in gap thickness and 1 atm in system pressure. From interpretations of the temperature and the heat flux history, it was found that the flooding inside the gap was restricted by CCFL phenomena and quenching process was propagated from lower to upper region of the internal copper shell. The ratio of the maximum heat fluxes at 1 mm to 2mm in gap thickness was the almost same that obtained by steady state experiments. The quenching scenario of the hemispherical downward facing surface with narrow gap has been suggested.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 1999년도 춘계종합학술대회
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• pp.47-49
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• 1999

균일물질의 내부결함으로 발생되는 공기층이나 불순물층은 균일물질과 다른 굴절률을 가지고 있으므로 전자기파가 투과할 때 다굴절이 발생된다. 발생된 다굴절은 공기층이나 불순물층의 두께가 아주 작을 때 시간영역에서의 전자기파분석으로는 그 유무를 판단하는데 한계가 있다. 하지만 주파수영역에서는 다중반사에 의한 총투과율과 위상변화에 의해 그 존재유무를 판단할 수 있으며, 또한 Febry-Perot 이론에 의해 그 두께와 굴절률을 정확히 측정할 수 있다.