• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.9
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• pp.480-485
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• 2017

The main reason for the heat induced accidents occurring at the after stern tube journal bearing is the excessive local pressure caused by the deflection of the propulsion shaft due to the propeller loads. It is expected that the contact area could beenlarged and the local pressure reduced accordingly by using a lining material having alow Young's modulus instead of the existing white metal. The purpose of this work is to investigate the characteristics of the pressure distribution and determine the allowable pressure value in the case where bearing products made of materials having a low Young's modulus are used. In this study, the propeller loads, heat effect, and hull deflection are considered in the evaluation of the local pressure of the ship propulsion shaft. Also, the Hertzian contact condition was applied. From the analysis results in the case where a lining material with a low Young's modulus was used, it was found that a robust design could be achieved and the local pressure could be reduced effectively independent of the load conditions. It will be possible to producenew products made of materials having a low Young's modulus if the manufacturer confirms the performance specifications drawn by this study.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.76-76
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• 2017

4륜 승용관리기는 보통 후방이나 전방에 작업기를 장착하여 작업하나 3륜 승용관리기는 작업기를 복부에 장착함으로 작업의 정밀도, 편이성, 관측의 용이성 향상과 함께 지상고 제고, 차폭 조절, 조향 등의 성능 개선을 기할 수 있다. 국내에서는 3륜 승용관리기용 복부 장착 부속작업기가 거의 개발되어 있지 않으며, 특히 두류 재배에 있어서 일관기계화 작업을 위한 관리작업기의 개발이 매우 필요한 실정이다. 승용관리기의 중경배토기에 의한 작업은 기존 인력에 의한 작업보다 약 87%의 노력을 절감할 수 있으며, 잡초방제 효과도 인력에 비하여 크게 떨어지지 않고, 수량도 증가하는 것으로 보고되고 있다. 따라서 본 연구는 3륜 승용관리기에 적합한 복부장착형의 중경배토기를 설계 제작하였다. 3륜 승용관리기용 중경배토기는 승용관리기의 복부 PTO에서의 구동력 전달을 위한 연결 조인트, 중간축, 기어 및 체인 전동기구, 구동축으로 구성된 동력전달부, 4개의 로타리 날과 후방 1개의 배토날로 구성된 3조의 작업날, 로타리 날과 배토날의 경심 조절을 위한 3조의 바퀴, 흙의 비산 방지를 위한 로타리날 커버 및 케이스, 다양한 조간거리에 적응을 위한 조간조정 나사부, 3륜 승용관리기에의 부착을 위한 프레임 및 부착보조 작업기 이동용 바퀴장치 등으로 구성 설계 제작하였다. 로타리 날과 배토날은 기존 시판 관리기용 날을 사용하였다. 로타리 날은 진행방향으로 회전하도록 하였으며, 날의 회전반경은 약 330 mm, 조당 경운 폭은 약 230 mm 설계하였다. 최대 경심은 100 mm이며, 조간거리의 조절범위는 수동 나사에 의하여 620~900 mm 범위로 무단조절 할 수 있도록 하였다. 중경제초기는 3륜 승용 관리기 복부의 평행링크에 부착되므로 작업기의 이동 및 부착 편이를 위하여 이동용 바퀴를 설치하였다. 제작된 중경배토기의 크기는 길이${\times}$폭${\times}$높이가 $660{\times}2072{\times}880mm$, 중량은 약 200 kg으로 제작되었다.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.4
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• pp.323-329
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• 2018

Traditional options for posterior edentulous treatment include removable partial dentures and implant fixed prostheses. Recently, the concept of implant assisted removable partial denture, in which two treatments are fused, has been introduced in consideration of systemic health and patient's needs, costs, residual alveolar bone status and so on. Implant assisted removable partial denture has the advantage of increasing the retention and stability of the denture and improving its esthetics in cases of large bone defects or biomechanical disadvantages. In addition, it is possible to strategically place the implants in a site where the alveolar bone is relatively sufficient, thereby overcome the limit of the conventional removable partial denture design as well as reducing the burden on a wide range of implant surgery. Cost reduction is also expected. In this case, the patient was treated by placing the implant in both premolar sites of the mandible and fabricating the distal extension removable partial denture with the implant fixed prosthesis as an abutment. After delivering the definitive prosthesis, the patient showed satisfaction with the masticatory function and esthetics. and has been regularly followed-up for more than one year. The following 20-months follow-up case report describes the design of an implant-assisted-removable partial denture (IARPD) in which two cementretained implant crowns used to provide support and stability.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.55-55
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• 2011

연안 및 해안공학의 발달과 더불어 부유식방파제의 기능적 효율성이 중요시 되고 있다. 흔히 사용되어오던 착저식방파제는 설치에 많은 시간과 경비가 소요되고 환경 및 생태계에 많은 변화를 줄 수 있으며, 설치 예정지의 수리학적 특성 등의 여건에 많은 제약을 받는 단점이 있다. 부유식방파제는 일본 등의 선진국을 중심으로 활용이 잦아지고 있는 방파제로서 수면 위에 설치되기 때문에 수중 생태계에 미치는 영향이 적은 친환경방파제이다. 또한 기존에 시공된 중력식방파제와는 달리 수심에 제한을 덜 받고, 공사기간이 짧기 때문에 경제적이다. 실제 시공사례로는 2007년 마산 원전항에 완공된 부유식방파제가 대표적이며, 지금까지도 부유식방파제에 대한 여러 연구자들의 관심이 증가하고 있는 추세이다. 방파제뿐만 아니라 우리나라처럼 국토의 면적이 작은 지역에서 증가하는 해상물동량을 소화하기 위해서 부유식방파제 등을 이용한 항만의 시공이 필요한 실정이다. 이러한 부유식방파제의 분석적인 측면에 있어서 수치해석은 파랑과 구조물의 상호작용을 해석하는 데 한계가 있으며, 부유식방파제 단면형상을 정확하게 재현할 수 없으므로, 수리모형실험을 통한 부유식방파제의 연구가 필요할 것으로 판단된다. 최근 기술의 발달로 인한 유동장 해명이 가능해 졌으며, PIV(Particle image velocimetry) 및 LDV시스템은 다양한 분야에서 응용되고 있다. 특히, LDV시스템은 측정하려는 한 지점에 대하여 레이저 빔을 단면(Cross-section)으로 만들고 입자의 산란광을 후방산란(Back scatter)으로 받아서 도플러 효과를 이용, 속도에 대한 주파수를 획득하며, 유속을 측정하는 장비로 매우 높은 정확도와 비접촉식 이라는 장점을 가지고 있다. 또한, PIV 시스템에 비하여 측정시간이 오래 걸리는 반면 데이터를 가공하지 않고 활용할 만큼 높은 정확성을 가지고 있다. 본 연구에서는 수리모형실험을 통하여 단독형, 2열형 및 3열형 부유식방파제의 형상, 흘수 및 거리를 변화시키며 유동장을 수집하였으며, 방파성능에 따른 와의 생성 및 소멸시점에서의 파랑변형과의 관계를 분석하였다. 방파제의 형상과 흘수를 달리하여 수리모형실험을 수행하였으며, 와류의 상관관계를 분석하였다. 또한, 연직 2차원 Navier-Stokes 방정식 모형을 이용하여 수치모형실험을 수행하였으며, 수치모형실험 결과와 수리모형실험 결과를 비교 분석하였다. 후방방파제에서 발생되는 파랑은 입사파의 주기가 길어질수록 상대적으로 커지는 현상을 보였으며, 흘수심이 깊어질수록 전방방파제 입사 면에서 자유 수면이 높게 관측되는 결과를 보였다. 또한, 비교적 장주기파랑에 해당하는 입사파랑의 경우 전달파고비 산정에 있어서 설계기준인 0.5를 대다수 초과하는 반면, 3열형 구조에서는 대부분이 0.5이하로 상당히 높은 방파성능 결과를 나타내었다.

• The korean journal of orthodontics
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• v.28 no.6 s.71
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• pp.905-914
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• 1998

The goals of this study were to present presurgical naso-alveolar molding (PNAM) appliance in unilateral cleft lip and palate treatment and to evaluate the effects of PNAM appliance on alveolar molding. Samples were consisted of 4 unilateral cleft lip and palate infants (3 males and 1 female, mean age=23.2 days after birth) who were treated with PNAM appliances in Department of Orthodontics, Seoul National University Dental Hospital. Average alveolar cleft gap between the greater and lesser segment was 8.27mm and average duration of alveolar molding treatment was 9.7 weeks. These patients' models were obtained at initial visit (T1) and alter successful alveolar molding (T2). Seven linear and five angular variables were measured by using photometry and digital caliper. All statistical analyses were performed by SPSS win ver. 7.5 program. Paired t-test was used to compare the mean values. 1. The posterior part of alveolar segments are the stable structures during alveolar molding treatment period in infants. 2. Forward growth of the greater segment may be hindered by the action of alveolar molding. 3. The closure of cleft gap during alveolar molding were usually due to inward and backward bending of the anterior part of the greater segment and outward bending of the whole lesser segment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.468-476
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• 2019

This paper presents the means of improving the strength of LTV's FRP structure for resolve and prevent quality problems. LTV secures enough kerb weight by applying FRP materials at hood and rear van assembly. However, because of FRP's inherent limitations, many initial quality problems such as crack at connections have occurred. Moreover, hood assy' is concerned about fall of endurance, because hood assy' have operated in abnormal condition. Therefore, this study executes lamination structure optimizations of FRP structure for improving bending strength. As a results, hood and rear van's bending strength at connections is improved 8.1 times and 1.5 times, respectively. Also hood assy's plate secures endurance life and improve 1.7 times of critical load about abnormal operating conditions through 1.4 times improvement of bending strength.

• Journal of Rhinology
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• v.25 no.2
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• pp.75-79
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• 2018

Background and Objectives: To investigate the common site of recurrent epistaxis after initial intervention such as packing and cauterization had failed and to evaluate the efficacy of surgical endoscopic electrocautery. Subjects and Method: Retrospective review of 47 patients with recurrent and uncontrolled idiopathic epistaxis between October 1995 and March 2016. All patients underwent endoscopic examination in the operating room after hospitalization. We performed electrocautery when a bleeding site was found. Results: The most common sites of bleeding were the inferior meatus (28%), sphenoethmoid recess (23%), superior septum around the olfactory cleft (13%), and the posterior end of the middle turbinate (15%). There was no serious complication during the one week after surgery. In 46 (98%) patients, refractory epistaxis was successfully controlled. One patient had recurrent epistaxis after electrocautery and underwent endoscopic sphenopalatine artery ligation. Conclusion: In patients with refractory idiopathic epistaxis after failure of first-line treatment, endoscopic examination through a surgical approach and electrocautery for suspected bleeding are effective.

• Journal of Navigation and Port Research
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• v.47 no.1
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• pp.1-9
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• 2023

Many studies have analyzed marine accidents, and since marine accident information is updated every year, it is necessary to periodically analyze and identify the causes. The purpose of this study was to prevent accidents by identifying and analyzing the causes of marine accidents using previous and new data. In marine accident data, 1,921 decisions by the Korea Maritime Safety Tribunal on marine accidents on fishing ships over 16 years were collected in consideration of the specificity of fishing ships, and 1,917 cases of accident notification text history by the Ministry of Maritime Affairs and Fisheries over 3 years were collected. The decision data and text data were classified according to variables and quantified. Prior probability was calculated using a Bayesian network using the quantified data, and fishing ship marine accidents were predicted using backward propagation. Among the two collected datasets, the decision data did not provide the types of fishing ships and fishing areas, and because not all fishing ship accidents were included in the decision data, the text data were selected. The probability of a fishing ship marine accident in which engine damage would occur in the West Sea was 0.0000031%, as calculated by backward propagation. The expected effect of this study is that it is possible to analyze marine accidents suitable for the characteristics of actual fishing ships using new accident notification text data to analyze fishing ship marine accidents. In the future, we plan to conduct research on the causal relationship between variables that affect fishing ship marine accidents.

• The korean journal of orthodontics
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• v.37 no.1 s.120
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• pp.44-55
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• 2007

Objective: Previous studies have reported that morphological features of the first cervical vertebra (atlas) have been associated with mandibular growth direction. The purpose of this study was to show the possible positional and morphological changes of the Atlas from activator treatment in Class II malocclusion patients. Methods: Lateral cephalometric radiograph tracings were made at initial, middle and final stages of treatment. Angular and linear measurements of skeletal and morphological features were measured on the anatomical landmarks and reference planes. Results: The skeletal effects of activator treatment on Class II malocclusion patients were evident on ramal height, body length, effective body length, ANB, and overjet. Clockwise rotation of the long axis of the Atlas was found in Group 1, but there was no inclination change of the Atlas in groups 2 and 3. There was no significant correlation between anterior and posterior positions of the atlas or morphological change in all groups. - except for posterior movements of the Atlas found in group 1. Conclusion: Clockwise rotation of the atlas axis resulted from activator treatment in Cl II malocclusion patients. Change in atlas axis can be thought of as an indicator for success of activator treatment.

• The korean journal of orthodontics
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• v.26 no.2 s.55
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• pp.219-232
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• 1996

The purpose of this study was to evaluate treatment effects of bionator in Class II division 1 malocclusion by FEM(Finite Element Method). The 73 subjects were classified into good result group and poor result group in reference to posttreatment molar relation, posttreatment overbite and overjet, posttreatment profile, and relapse. Pretreatment and posttreatment lateral cephalograms were taken and FEM was performed. The results were as follow; 1. There was no statistical significance in treatment changes between the sexes, and between the treatment result groups. 2. Treatment changes were not significantly different among the age groups. 3. The effect of treatment period groups on skeletal and dentoalveolar changes were analyzed using ANOVA. Body of maxilla, upper incisor, anterior face, ramus, upper anterior face, lower anterior face and treatment effect were correlated with the treatment period, but correlation coefficients were low. 4. The results of present investigation confirm that Class II bionator can assist in the correction of Class II division 1 malocclusion, mainly due to dentoalveolar changes. 5. There is significant difference in skeletal and dentoalveolar pattern between good result group and poor result group. In poor result group, maxilla was relatively downward and backward rotated, mandible was relatively backward rotated, upper incisor was in relatively lingual position, lower incisor was in relatively labial position.