• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2003년도 유체기계 연구개발 발표회 논문집
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• pp.514-519
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• 2003

The objective of this study is to document the secondary flow and the total pressure loss distribution in the contoured endwall installed linear turbine nozzle guide vane cascade passage and to propose an appropriate contraction ratio of the contoured endwall which shows the best loss reduction among the simulated cases. In this study, three different contraction ratio of contoured endwalls have been tested. This study was performed by experimental method and when the contoured endwall has the contraction ratio of 0.17 on exit height the results showed the best loss reduction.

• 신재생에너지
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• 제2권1호
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• pp.46-55
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• 2006

The performance enhancement of heat exchanger in the drying system using solar collector with evacuated tubes is analyzed. First, for this analysis, the heat loss from a reversed trapezoidal fin attached at the pipe is calculated as a function of convection characteristic number ratio, fin base length and fin tip length. Also, the optimum heat loss and fin tip length of the fin under certain conditions are presented. The overall surface effectiveness of the cylinder with reversed trapezoidal fins in the heat exchanger are shown as a function of half fin base height, fin lateral slope and fin tip length.

• 수산해양기술연구
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• 제53권4호
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• pp.309-316
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• 2017

In this paper, numerical modeling is conducted to analyze the tension of an anchor line by varying the size and drag coefficient of a buoy when the trapnet is influenced by the wave and the current simultaneously. A mass-spring model was used to analyze the behavior of trapnet underwater under the influence of waves and current. In the simulation of numerical model, wave height of 3, 4, 5 and 6 m, a period of 4.4 s, and the flow speed of 0.7 m/s were used for the wave and current condition. The drag coefficients of buoy were 0.8, 0.4 and 0.2, respectively. The size of buoy was 100, 50 and 25% based on the cylindrical buoy ($0.0311m^3$) used for swimming crab trap. The drag coefficient of the trapnet, the main model for numerical analysis, was obtained by a circular water channel experiment using a 6-component load cell. As a result of the simulation, the tension of the anchor line decreased proportional to buoy's drag coefficient and size; the higher the wave height, the greater the decrease rate of the tension. When the buoy drag coefficient and size decreased to one fourth, the tension of the anchor line decreased to a half and the tension of the anchor line was lower than the holding power of the anchor even at 6 m of wave height. Therefore, reducing the buoy drag coefficient and size appropriately reduces the trapnet load from the wave, which also reduces the possibility of trapnet loss.

• Journal of Periodontal and Implant Science
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• 제52권1호
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• pp.3-27
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• 2022

Purpose: This study was conducted to evaluate and compare the effects of different graft materials used in alveolar ridge preservation on dimensional hard tissue changes of the alveolar ridge, assessed using cone-beam computed tomography (CBCT) scans. Methods: A systematic electronic search of MEDLINE and the Cochrane Central Register of Controlled Trials and a manual search were conducted from November 2019 until January 2020. Randomized controlled trials were included if they assessed at least 1 variable related to vertical or horizontal hard tissue changes measured using CBCT scans. After a qualitative analysis of the included studies, subgroups were formed according to the graft material used, and a quantitative analysis was performed for 5 outcome variables: changes in vertical alveolar bone height at 2 points (midbuccal and midpalatal/midlingual) and changes in horizontal (buccolingual) alveolar bone width at 3 different levels from the initial crest height (1, 3, and 5 mm). Results: The search resulted in 1,582 studies, and after an independent 3-stage screening, 16 studies were selected for qualitative analysis and 9 for quantitative analysis. The metaanalysis showed a significantly (P<0.05) lower reduction of alveolar ridge dimensions for the xenogenic subgroup than in the allogenic subgroup, both vertically at the midbuccal aspect (weighted mean difference [WMD]=-0.20; standard error [SE]=0.26 vs. WMD=-0.90; SE=0.22) as well as horizontally at 1 mm (WMD=-1.32; SE=0.07 vs. WMD=-2.99; SE=0.96) and 3 mm (WMD=-0.78; SE=0.11 vs. WMD=-1.63; SE=0.40) from the initial crest height. No statistical analysis could be performed for the autogenic subgroup because it was not reported in sufficient numbers. Conclusions: Less vertical and horizontal bone reduction was observed when xenogenic graft materials were used than when allogenic graft materials were used; however, the loss of alveolar ridge dimensions could not be completely prevented by any graft material.

• The Journal of Advanced Prosthodontics
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• 제15권3호
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• pp.101-113
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• 2023

PURPOSE. This randomized controlled trial aimed to evaluate the effect of implants' two different diameters and cantilever lengths on the marginal bone loss and stability of mplants supporting maxillary prostheses. MATERIALS AND METHODS. Ninety-six implants were placed in sixteen completely edentulous maxillary ridges. Patients were randomly divided into two groups: Group A, implants were placed with a cantilever to anterior-posterior AP spread length (CL:AP) at a ratio of 1:3; Group B, implants were placed with a CL:AP at a ratio of 1:2. Patients were further divided into four sub-groups: Groups A1, A2, B1, and B2. Groups A1 and B1 received small diameter implants while Groups A2 and B2 received standard diameter implants. Bone height and stability measurements around each implant were performed at 0, 4, 8 and 24 months after definitive prostheses delivery. RESULTS. Statistical analysis of the mean implant stability and height values revealed an insignificant difference between Group A1 and Group A2 at all the different time intervals while significantly higher values in Group B1 in comparison with Group B2. Results also showed significantly higher values in Group A1 in comparison with Group B1 and an insignificant difference between Group A2 and Group B2 at all the different time intervals. CONCLUSION. It can be concluded that the use of small diameter implants placed with a CL:AP at a ratio of 1:3 provided predictable results and that the 1:2 CL:AP significantly induced more critical bone loss in the small diameter implants group, which can significantly reduce long term success and survival of implants

• 대한물리의학회지
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• 제19권1호
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• pp.31-41
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• 2024

PURPOSE: This study examined the distribution dynamics and proposed determinants, including morphological measurements, clinical laboratory tests, and lifestyle factors among young Korean men aged 20 to 29 years with the coexistence of age-related loss of skeletal muscle mass and obesity (CALSMO). METHODS: Six hundred and sixty-six participants were divided into two groups based on their skeletal muscle mass index, with 12 individuals categorized in the CALSMO group and the remaining 654 in the normal group. The proposed determinants variables consisted of three main components: morphological measurements, clinical laboratory tests, and lifestyle factors. The morphological measurement variables were height, weight, body mass index, waist circumference, and skeletal muscle mass index. The clinical laboratory tests were fasting glucose, triglyceride, total cholesterol levels, and systolic and diastolic blood pressure. The lifestyle factors considered were alcohol consumption and tobacco use. Complex sampling analysis was performed for the evaluation. RESULTS: The distribution dynamics were determined to be 1.81(1.02-3.18) %. Morphological factors, such as height, weight, body mass index, waist circumference, and skeletal muscle mass index, showed significant differences (p < .05). The clinical laboratory test variables, specifically the fasting glucose, triglyceride, and total cholesterol levels, also exhibited significant differences (p < .05). The lifestyle factor, alcohol consumption, also showed a significance (p < .05). CONCLUSION: This study provides insights into the distribution dynamics. The proposed determinants in young Korean individuals with CALSMO are height, weight, body mass index, waist circumference, skeletal muscle mass index, fasting glucose, triglyceride, total cholesterol levels, and alcohol consumption.

• 한국전자파학회논문지
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• 제24권12호
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• pp.1140-1147
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• 2013

본 논문에서는 인천공항 화물터미널 지역에서에서 항공정보통신 무선 채널의 패스 로스 모델에 관해 연구하였다. 인천공항는 송신소 사이트가 신불 및 왕산에 위치하였다. 신불 및 왕산에서 발사된 전파 상태를 분석하기 위해 각 사이트에서 동일한 송신기 및 파워를 이용해 전파를 방사하고 화물터미널에서 측정을 수행하였다. 송신사이트에서 방사된 파워는 측정의 정확성을 위해 변조 신호를 제거한 캐리어 파워를 송신하였다. 측정 환경은 송신소와 안테나를 직결된 상태에서 전파를 방사한다. 수신은 전파 측정을 위해 수신기를 장착한 이동 차량을 이용하여 화물터미널 지역에서 전파 측정을 수행하였다. 화물터미널에서 측정된 데이터를 가지고 패스 로스 계수 및 실험적인 패스 로스 식은 기본적인 패스 로스 모델 및 하타 모델 등을 이용하여 추출하였다. 화물터미널 지역에서 추출된 패스 로스 계수는 신불에서 방사된 패스 로스는 3.67 이고 왕산에서 방사된 패스로스 3.39이었다. 예측 에러의 편차는 각각 14.42 및 10.38이었다. 실험 결과에서는 추출된 패스 로스 계수와 다른 전파 패스모델과 비교하였다. 이러한 결과는 항공정보통신 사이트 최적 위치 선정 및 항공정보통신 서비스 평가에 도움이 될 것이다.

• 한국통신학회논문지
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• 제38A권9호
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• pp.765-772
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• 2013

본 논문에서는 인천공항 Concourse 지역에서 항공정보통신 무선 채널의 경로 손실 모델에 관해 연구하였다. 항공정보통신 주파수 밴드인 VHF/UHF 채널 중에 두 개의 주파수에 대해 전파 측정을 수행하였다. 현재 운영 중인 송신 사이트에서 변조 신호를 제거한 캐리어 파워를 송신하였으며, 전파 측정을 위해 수신기를 장착한 이동 차량을 이용하여 Concourse 지역에서 전파 측정을 수행하였다. 송신 파워, 주파수, 안테나 위치 등은 현재 운용 조건과 같다. 경로 손실 계수 및 실험적인 경로 손실 식은 기본적인 경로 손실 모델 및 하타 모델 등을 이용하여 추출하였다. Concourse 지역에서 추출된 LOS/NLOS 경로 손실 계수는 128.2MHz 및 269.1MHz에서 각각 3.1/3.13 및 3.01/3.38이었고 예측 에러의 편차는 각각 2.77/3.17 및 4.01/3.66이었다. 추출된 경로 손실 계수를 이용하여 Concourse 지역에서 전파 경로 손실식과 실험적인 경로 손실 계수를 도출하였으며 또한 다른 전파 패스 모델과 비교하였다. 이러한 결과는 항공정보통신 사이트 최적 위치 선정 및 항공정보통신 서비스 평가에 도움이 될 것이다.

• Journal of Periodontal and Implant Science
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• 제44권2호
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• pp.50-56
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• 2014

Purpose: The aims of this study were to measure the distance of the intraosseous vascular anastomosis in the anterolateral wall of the maxillary sinus from different reference points, and to correlate the location of the intraosseous vascular anastomosis with the tooth position and the residual bone height of the maxilla. Methods: Computed tomography (CT) images were taken from 283 patients undergoing dental implants placement in the posterior maxilla. Three horizontal lines were drawn at the ridge crest, maxillary sinus floor, and the position of the anastomosis. A vertical second line at the center of each tooth was drawn perpendicular to the horizontal lines. The distance from the ridge crest to the maxillary sinus floor and the distance from the maxillary sinus floor to the bony canal were measured from the intersections of the horizontal and vertical lines. The residual alveolar bone height was used to categorize three groups: group 1,<4 mm; group 2, between 4 and 8 mm; and group 3, >8 mm. Results: The residual bone height values of different tooth positions were significantly different (P=0.0002). The distance from the maxillary sinus floor to the intraosseous vascular anastomosis was significantly different between groups 1 and 3 (P=0.0039). At the molar sites, a moderate negative correlation was found between the residual bone height and the distance from the maxillary sinus floor to the intraosseous anastomosis. The distances of the alveolar ridge crest and the maxillary sinus from the intraosseous vascular anastomosis were not significantly different between sexes. Conclusions: Within the limitations of this study, sites with a higher residual bone height in the molar regions were at a relatively high risk of artery damage during window osteotomy preparation; therefore, we recommend taking more precautions when using a lateral approach for sinus elevation.

• 한국환경복원기술학회지
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• 제20권3호
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• pp.19-31
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• 2017

Plants are the basis for sustainable green growth, and the value of existence and importance of trees including landscape Plants can't be emphasized enough. Therefore, they are precious living things thriving in all sorts of public services, and continuous civil complaints for justifiable compensation of landscape Plants are filed. First, the standard formula of planting intervals according to production target specifications is calculated using root-collar caliper and diameter at breast height, and apply (1) standard medium sized trees which have not yet reached commercialization [deciduous tree production goal (R(B) less than 6cm]= (target standard)= [target standard $R(cm){\times}15{\times}0.7$]. (2) In case of commercialization(R6~R10)= [target standard $R(cm){\times}15{\pm}5%$], (3) In case of more than R12= [target standard $R(cm){\times}15{\times}130%$] shall be applied. In case of using diameter at breast height (4) In case of commercialization(B6~B10)= [target standard $B(cm){\times}20{\times}15{\pm}5%$], (5) In case of more than B12= [target standard $B(cm){\times}20{\times}130%$] shall be applied. Second, appraisal methods based on tree classification of compensation for loss are classified according to planted locations. (1) landscape trees within a house=[price of arrival at the site+planting cost], (2) landscape trees in places such as arboretum=[management technology of tress + relocation expenses considering scarcity of the trees (3) landscape trees in a place of loads= [landscape tree production cost + work out added price. In case of producted landscape threes (4) landscape trees ready to be commercialized as sales loss.