• 문화기술의 융합
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• 제8권4호
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• pp.407-413
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• 2022

본 연구에서는 약 3년간의 장기계측을 바탕으로 공용중인 복층 교량인 상부 도로교의 신축이음 신축량과 하부 철도교의 케이블 장력 간의 상관관계를 입증함으로서 온도변화에 따른 케이블 장력 평가 경험식을 제안하였다. 본 연구에서 제안한 케이블별 장력 평가 경험식을 이용한 장력 예측결과는 진동법을 이용한 장력과 3% 이내로 잘 일치하는 것으로 나타나 공용중인 케이블의 장력 예측 및 평가에 실험적인 기법인 진동법과 함께 적용이 가능할 것으로 판단되었다. 본 연구에서 제안한 신축량 경험식으로 산출한 추정온도를 케이블 경험식에 적용한 결과, 현장시험 진동법 측정결과와 비교시 높은 신뢰수준을 확보할 수 있을 것으로 분석되었다. 따라서 본 연구에서 제안한 추정온도를 반영한 장력 평가 경험식은 향후 기후변화에 따른 케이블의 장력 예측 및 유지관리방안 수립에 활용될 수 있을 것으로 판단된다.

• 대한토목학회논문집
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• 제31권2D호
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• pp.237-245
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• 2011

Asphalt Plug Joint(APJ)는 미국을 비롯한 유럽의 여러 국가에서 적용사례가 늘어가고 있는 새로운 형태의 신축이음장치이다. APJ는 시공 및 유지보수 비용이 저렴하고 시공이 간단하며, 우수한 평탄성을 확보한다는 장점을 가지고 있으나 조기파손되는 문제점이 드러나 사용성을 방해하고 있다. 이러한 문제를 해결하기 위한 연구가 진행되어 왔고, 기존 연구 중 FEM 해석을 수행하였으나 FEM 해석시 재료를 너무 단순화하여 해석함으로써 해석의 신뢰성이 많이 떨어져 신축이음장치의 거동을 분석하는데 미흡하였다. 따라서 본 논문에서는 이러한 FEM 해석의 신뢰성을 높이기 위해 새로운 재료모델을 제안하고 실제 거동과 비교하여 유효성을 확인하였다. 본 연구에서 FEM 해석은 ABAQUS 전산 프로그램를 사용하였으며 재료모델은 Bramel et al.이 APJ 재료 시험한 결과를 근거로 탄소성모델과 점탄성모델을 제안하였다. 탄소성모델은 시간에 따른 변형속도를 반영하지 못하므로 시간독립해석으로 정의하였으며, 점소성 모델은 변형속도를 반영하므로 시간의존해석으로 정의하였다. 해석을 통해 APJ의 거동에 영향을 미치는 다양한 요소의 영향을 검토하였으며, 시간의존해석이 실제 실험결과와 비슷한 거동을 나타냄을 확인하였다.

• 한국강구조학회 논문집
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• 제25권1호
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• pp.1-13
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• 2013

기존 라멘형 가설교량은 주거더의 온도신축에 따라 벤트부에 과도한 수평력이 유발되는 것을 방지하기 위하여, 연장을 짧게 분할하여 가설되고 있다. 이 때 분할되는 구간에서 중복 설치되는 벤트부가 생기게 되어, 교량의 통수단면 감소와 형하공간 감소에 따른 문제와 중복 설치된 벤트부에 의한 경제성 감소 문제가 발생한다. 따라서 본 연구에서는 라멘형 가설교량 벤트부의 수평력 문제를 해결하고, 중복 설치되는 벤트부를 절감시키기 위한 단부 수평가동-수직구속 부재를 이용한 라멘화 공법을 제안하고, 이에 대한 거동특성분석을 수행하였다.

• Journal of Welding and Joining
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• 제32권3호
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• pp.74-80
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• 2014

Due to environmental regulations (RoHS, WEEE and ELV) of the European Union, electronics and automotive electronics have to eliminate toxic substance from their devices and system. Especially, reliability issue of lead-free solder joint is increasing in car electronics due to ELV (End-of-Life Vehicle) banning from 2016. We have prepared engine control unit (ECU) modules soldered with Sn-40Pb and Sn-3.0Ag-0.5Cu (SAC305) solders, respectively. Degradation characteristics of solder joint strength were compared with various conditions of automobile environment such as cabin and engine room. Thermal cycle test (TC, $-40^{\circ}C$ ~ ($85^{\circ}C$ and $125^{\circ}C$), 1500 cycles) were conducted with automotive company standard. To compare shear strength degradation rate with eutectic and Pb-free solder alloy, we measured shear strength of chip components and its size from cabin and engine ECU modules. Based on the TC test results, finally, we have known the difference of degradation level with solder alloys and use environmental conditions. Solder joints degradation rate of engine room ECU is superior to cabin ECU due to large CTE (coefficient of thermal expansion) mismatch in field condition. Degradation rate of engine room ECU is 50~60% larger than cabin room electronics.

• Journal of Welding and Joining
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• 제17권6호
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• pp.53-61
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• 1999

The use of thick plate in increasing in recent years due to the rapid expansion of chemical plants, nuclear plants, ships and other industrial plants. Welding is the most popular joining techniques employed in manufacturing industrial machineries and structures. Normally, Groove shapes are prepared according to appropriate rules and regulations such as KS, JIS, AWS, LR, DNV and etc. for various thicknesses of plate. However those groove angles tend to be too large. As a result of large groove angle, residual stress, deformation of material and strength reduction is obtained. Therefore, the reliability and safety of structures and machinery tend to be decreasing. Therefore, in this paper, theoretical as well as experimental study are carried out to find optimum groove shapes for T-welded joint of mild steel. The test specimen are made in same condition with simulation model. Welding residual stresses measurement by sectional cutting method. ⅰ) The mechanical difference for change the thickness of plate and groove angle are not appeared. ⅱ) In a mechanical point of view minimum preparation angle(40°) is more suitable than maximum groove angle(60℃). ⅲ) The measurement value and distribution of welding residual stresses are not effected largely by groove angle. It is mechanical restraint that mainly affect welding residual stresses distribution. In mechanical point of view minimum groove angle is more suitable than maximum groove angle. Therefore, it is appropriate to minimize the size of groove shape in strength and safety.

• 한국직업건강간호학회지
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• 제7권1호
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• pp.97-114
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• 1998

The occupational health services for the minor enterprises are poor comparing with that of large enterprises in Korea. In 1997, Korean government announced officially the law on joint employment system of occupational health practitioners to solve the problems. This study is to develop the model on the joint employment system of occupational nurse practitioners for minor enterprises in Korea based on the opinions of occupational health nurses (OH Ns). The data were collected by questionnares from October to November in 1997. The number of subjects was 210 occupational health nurses who had participated the mandatory nursing education program provided by the Korean Occupational Health Nurses Association(KOHNA). The response rate was 47.1%. The contents of questionnaires were general characteristics, occupational & job characteristics of OHNs, and the views on the joint employment system. The SAS-PC program was used for the statistical analysis. The results were as followed, (1) The proper number of industies was 3 and the appropriate number of workers was 448 for one joint employed occupational nurse practitioner (J EONP). (2) 44.7% of the OHNs wanted that the Ministry of Labor monitored the way and content of contraction b/w JEONP and minor emterprises, 82.6% of the OHNs wanted that KOHNA managed the employment informations. (3) The OHNs of occupational health agencies showed more positive attitude than the OHNs of private industries on the joint employment system. (4) 88.3% of the OHNs wanted the education training for JEONP. Especially in occupational hygiene and safety control. (5) The OHNs expected the role expansion of Occupational Health Nursing by JEONP system. At the same time they worried the adverse effects. For the successful execution of this system, it is necessary the cooperation among the Ministry of Labor, KOHNA, the minor enterprises, and the OHNs.

• 대한정형외과스포츠의학회지
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• 제8권1호
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• pp.51-55
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• 2009

수지 근위 지관절의 전방 회전 탈구는 매우 드물게 발생한다. 저자들은 여자 유도 선수에서 발생한 수지 근위 지관절의 전방회전 탈구를 경험하였기에 이를 문헌고찰과 함께 보고하고자 한다. 24세 여자 유도 선수로 총 4번의 근위 지관절 전방 탈구가 발생하였다. 수술 시 회전 손상으로 파열된 척측 측부 인대와 파열 없이 늘어져 있는 중앙 건을 확인할 수 있었다. 수술적 치료로 파열된 척측 측부 인대 봉합술과 중앙 건과 측부대 사이를 봉합하여 근위 지관절의 배측부를 강화 시켜주었다. 술 후 운동시에 탈구는 다시 발생하지 않았다. 수지 근위 지관절의 전방 회전 탈구는 매우 드문 손상이지만 다른 탈구처럼 조기 진단과 치료, 그리고 단계적인 재활이 무엇보다 중요하겠다.

• 대한기계학회논문집A
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• 제21권10호
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• pp.1541-1550
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• 1997

Since the ceramic/metal joint material is made at a high temperature, the residual stress develops when it is cooled from bonding temperature to room temperature due to remarkable difference of thermal expansion coefficient between ceramic and metal. As residual stress at ceramic/metal joints influences the strength of joints, it is important to estimate residual stress quantitatively. In this study, it is attempted to estimate joint residual stress of Si$_3$N$_4$STS304 joints quantitatively and to compare the strength of joints. The difference of residual stress is measured when repeated thermal cycl is loaded, under the conditions of the practical use of the ceramic/metal joint. The residual stress increases at 1 cycle of thermal load but decreases in 3 cycles to 10 cycles of thermal load. And 4-point bending test is performed to examine the influence of residual stress on fracture strength. As a result, it is known that the stress of joint decreases as the number of thermal cycle increases.

• 대한치과교정학회지
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• 제45권3호
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• pp.121-129
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• 2015

Objective: This study aimed to assess three-dimensional changes in the temporomandibular joint positions and mandibular dimensions after correction of dental factors restricting mandibular growth in patients with Class II division 1 or division 2 malocclusion in the pubertal growth period. Methods: This prospective clinical study included 14 patients each with Class II division 1 (group I) and Class II division 2 (group II) malocclusions. The quad-helix was used for maxillary expansion, while utility arches were used for intrusion (group I) or protrusion and intrusion (group II) of the maxillary incisors. After approximately 2 months of treatment, an adequate maxillary arch width and acceptable maxillary incisor inclination were obtained. The patients were followed for an average of 6 months. Intraoral and extraoral photographs, plaster models, and cone-beam computed tomography (CBCT) images were obtained before and after treatment. Lateral cephalometric and temporomandibular joint measurements were made from the CBCT images. Results: The mandibular dimensions increased in both groups, although mandibular positional changes were also found in group II. There were no differences in the condylar position within the mandibular fossa or the condylar dimensions. The mandibular fossa depth and condylar positions were symmetrical at treatment initiation and completion. Conclusions: Class II malocclusion can be partially corrected by achieving an ideal maxillary arch form, particularly in patients with Class II division 2 malocclusion. Restrictions of the mandible in the transverse or sagittal plane do not affect the temporomandibular joint positions in these patients because of the high adaptability of this joint.

• Journal of Advanced Marine Engineering and Technology
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• 제37권7호
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• pp.694-700
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• 2013

The design of the exhaust manifold for the pulse converters of a 4 strokes high power medium-speed diesel engine is presented in terms of fatigue analysis. The said system undergoes thermal expansion due to high temperature of exhaust gas and is exposed to intrinsic vibration of the internal combustion engine. Moreover, the exhaust pulse generates pressure pulsating along the runner inside manifold. Under such circumstances, the design and construction of exhaust manifold must be carried out in a way to prevent early failure due to fracture. To validate the design concept, a test rig was developed to simulate the combination of thermal and vibrational movements, simultaneously. Experimental results showed that a certain sense of reliability can be achieved by considering a field factor obtained from the results of engine bench tests.