• 한국가정과교육학회지
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• 제29권2호
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• pp.41-52
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• 2017

본 연구는 질병관리본부에서 실시한 제10차 청소년건강행태온라인조사 자료를 기반으로 다문화 가정 청소년의 건강행태에 따른 알레르기 질환 관련 요인을 파악하여 천식, 알레르기 비염, 아토피 피부염을 예방하고, 학교에서 알레르기 환자의 효과적인 관리와 증상 완화를 위한 기초자료로 제공하고자 하였다. 이를 위해 다문화 가정 청소년 712명의 자료를 본 연구에 활용하여 조사 대상자의 건강행태 특성, 알레르기 질환 특성은 빈도, 백분율을 산출하였고, 건강행태와 알레르기 질환과의 관계는 교차분석을 실시하였다. 본 연구의 주요 결과를 요약하면 다음과 같다. 첫째, 다문화 가정 청소년의 건강행태 특성은 음주 경험이 있는 학생이 267명(37.5%), 흡연 경험이 있는 학생은 164명(23.0%), 약물 경험이 있는 학생은 35명(4.9%), 우울감이 있는 학생은 198명(27.8%)로 나타났다. 스트레스를 많이 느끼는 학생이 259명(36.3), 피로 회복이 충분하지 않다고 느끼는 학생이 286명(40.2%)으로 나타나 피로감을 많이 느끼고 있었다. 건강하다고 생각하는 학생이 497명(69.8%), 행복하다고 생각하는 학생은 449명(63.1%) 이었으며, 살찐 편이라고 생각하는 학생은 251명(35.3%) 이었다. 둘째, 다문화 가정 청소년의 알레르기 질환 중 천식은 중학생이 46명(6.5%), 고등학생이 35명(4.9%), 알레르기 비염은 중학생이 95명(13.3%), 고등학생은 87명(12.2%), 아토피 피부염은 중학생이 67명(9.4%), 고등학생이 53명(7.4%) 이었다. 천식이 있는 남학생은 47명(6.6%), 여학생은 34명(4.8%), 알레르기 비염이 있는 남학생은 81명(11.4%), 여학생은 101명(14.1%), 아토피 피부염이 있는 남학생은 53명(7.4%), 여학생은 67명(9.4%) 이었다. 다문화 가정 청소년은 천식이 있는 학생이 81명(11.4%), 알레르기 비염이 있는 학생이 182명(25.5%), 아토피 피부염이 있는 학생이 120명(16.8%)으로 알레르기 질환은 알레르기 비염, 아토피 피부염, 천식 순의 발병률을 나타냈다. 셋째, 다문화 가정 청소년의 건강행태 특성에 따른 알레르기 질환은 우울감(p<0.001), 음주 경험(p<0.05), 약물 경험(p<0.05), 건강 인지(p<0.05), 행복 인지(p<0.05), 체형 인지(p<0.05)에서 천식과 유의한 차이가 나타났고, 피로 회복 인지(p<0.001), 건강 인지(p<0.001), 스트레스 인지(p<0.05)에서 알레르기 비염과 유의한 차이가 나타났으며, 체형 인지(p<0.01), 우울감(p<0.05), 피로 회복 인지(p<0.05), 건강 인지(p<0.05), 행복 인지(p<0.05)에서 아토피 피부염과 유의한 차이가 나타났다. 이와 같은 결과를 바탕으로 다문화 가정 청소년의 알레르기 질환에 관련이 높은 변인인 건강 인지, 행복 인지, 체형 인지를 올바르게 정립할 수 있도록 학교와 사회의 적극적인 개입이 필요하며, 우울감, 스트레스 인지, 피로 회복 인지를 올바르게 할 수 있도록 체계적이고 지속적인 지도와 교육이 필요하다.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.61-61
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• 2010

The purpose of this study is to prevent the unstable fracture at the FCA butt weldment of hatch coaming deck in the ultra large containership during service life. In order to do it, the behavior of the embedded crack at the weldment under design loading conditions was evaluated in accordance with BS7910. Here, the level of primary stress induced by ship motion was evaluated by the design code of classification society and FEA. The level of residual stress as secondary stress was calculated in consideration of the restraint degree of weldment and welding heat input by using the predictive equation proposed by authors in the previous study. The fatigue crack growth rate at the weldment was evaluated using CT specimen in accordance with ASTM E647. According to the results, although the allowable defect for embedded crack specified in the classification society exists at the weldment, the occurrence possibility of unstable fracture at the weldment could not be negligible, regardless of CTOD value given in this study. So, in this study, the effect of initial defect size, welding heat input, restraint degree and CTOD on the fracture mechanical characteristics of embedded crack at the weldment was evaluated by the comprehensive fracture assessment. Based on the results, the design criteria including allowable defect, residual stress level and CTOD value was established to prevent the unstable fracture at the FCA butt weldment of hatch coaming deck in an ultra large containership during service life of 20years.

• 대한기계학회논문집A
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• 제28권2호
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• pp.174-180
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• 2004

If Fiber Reinforced Metal Laminates(FRMLs) were delaminated, the decrease of stiffness and fiber bridging effect would result in the sudden aggravation of fatigue characteristics. It was reported that the delamination of FRMLs resulted from the crack of metal layers and that it depended on the crack growth. While cracks were made in FRMLs containing a saw-cuts under fatigue loading, cracks could be produced or not in FRMLs with circular holes under the same condition. When the FRMLs with the circular holes produce not the crack but the delamination, it is not possible to analyze it by the conventional fracture parameters expressed as the function of the crack. And so, this research suggests a new analytical model of the delamination to make the comparison of the delamination behavior possible whenever the cracks occur or not. Therefore, a new analytical model called Pseudo Crack Model(PCM) was suggested to compare the delaminations whether cracks were made or not. The relationship between the crack energy consumption rate( $E_{crack}$) and the delamination energy consumption rate( $E_{del}$) was discussed and it was also known that the effect of $E_{del}$ was larger than that of $E_{crack}$.

• 국제초고층학회논문집
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• 제1권1호
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• pp.37-51
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• 2012

New generation of tall and complex buildings systems are now introduced that are reflective of the latest development in materials, design, sustainability, construction, and IT technologies. While the complexity in design is being overcome by the availability and advances in structural analysis tools and readily advanced software, the design of these buildings are still reliant on minimum code requirements that yet to be validated in full scale. The involvement of the author in the design and construction planning of Burj Khalifa since its inception until its completion prompted the author to conceptually develop an extensive survey and real-time structural health monitoring program to validate all the fundamental assumptions mad for the design and construction planning of the tower. The Burj Khalifa Project is the tallest structure ever built by man; the tower is 828 meters tall and comprises of 162 floors above grade and 3 basement levels. Early integration of aerodynamic shaping and wind engineering played a major role in the architectural massing and design of this multi-use tower, where mitigating and taming the dynamic wind effects was one of the most important design criteria established at the onset of the project design. Understanding the structural and foundation system behaviors of the tower are the key fundamental drivers for the development and execution of a state-of-the-art survey and structural health monitoring (SHM) programs. Therefore, the focus of this paper is to discuss the execution of the survey and real-time structural health monitoring programs to confirm the structural behavioral response of the tower during construction stage and during its service life; the monitoring programs included 1) monitoring the tower's foundation system, 2) monitoring the foundation settlement, 3) measuring the strains of the tower vertical elements, 4) measuring the wall and column vertical shortening due to elastic, shrinkage and creep effects, 5) measuring the lateral displacement of the tower under its own gravity loads (including asymmetrical effects) resulting from immediate elastic and long term creep effects, 6) measuring the building lateral movements and dynamic characteristic in real time during construction, 7) measuring the building displacements, accelerations, dynamic characteristics, and structural behavior in real time under building permanent conditions, 8) and monitoring the Pinnacle dynamic behavior and fatigue characteristics. This extensive SHM program has resulted in extensive insight into the structural response of the tower, allowed control the construction process, allowed for the evaluation of the structural response in effective and immediate manner and it allowed for immediate correlation between the measured and the predicted behavior. The survey and SHM programs developed for Burj Khalifa will with no doubt pioneer the use of new survey techniques and the execution of new SHM program concepts as part of the fundamental design of building structures. Moreover, this survey and SHM programs will be benchmarked as a model for the development of future generation of SHM programs for all critical and essential facilities, however, but with much improved devices and technologies, which are now being considered by the author for another tall and complex building development, that is presently under construction.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권3호
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• pp.326-338
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• 2017

The Vortex-induced Motions (VIM) phenomenon of semi-submersibles is relevant for the fatigue life of moorings and risers. Model tests regarding the VIM behavior of a semi-submersible with four square columns were conducted in order to investigate the effects of the current incidence and the aspect ratio of the immerged column. The experimental results show that the largest transverse amplitudes are around 70% of the column width at $30^{\circ}$ and $45^{\circ}$ incidences in a range of reduced velocities from 5 to 8 when the aspect ratio of the immerged column is 1.90. The largest yaw motion occurs at $0^{\circ}$ incidence with the peak value around $4.5^{\circ}$. Similar characteristics of the VIM response are observed for the semi-submersible with aspect ratios of 1.90 and 1.73. When the aspect ratio decreases 50% to 0.87, 30% decrease in the peak transverse amplitudes can be seen.

• 대한기계학회논문집A
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• 제21권12호
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• pp.2019-2028
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• 1997

It has been well established that resistant force and wear that occur during rolling motion depend on several factors such as material type, hardness, subsurface microstructure, applied load, and speed. The purpose of this work is to investigate the effect of microstructure and the state of deformed layer on the rolling contact characteristics in dry and lubricated rolling contacts. The results of this work show that the rolling resistance behavior depends on the state of the deformed layer. Also, lubrication can reduce the plastic flow at the surface but may still have an effect on the subsurface strain. The cross-sectional view of the microstructure shows that surface traction has a difinite effect on the morphology of the surface region. That is, significant slip seems to have taken place between the ball than those of the dry rolling case. The surface generation effects were significantly less compared to the case of dry rolling contact.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 추계학술대회 논문집 학회본부 C
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• pp.1010-1013
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• 1998

In micromechanical system (MEMS) such as microactuators. thin film has been widely used as structural material. MEMS materials have difference with bulk in terms of mechanical properties. So, we design the advanced test structure for micromechanical properties of MEMS. The designed structure includes the newly developed pre-crack and it is driven by electrostatic force. To measure the fracture toughness, the pre-crack formation in the test structure is developed with conventional etching process. The advanced test structure is fabricated by application of semiconductor technology. After this, we propose analytical methodology to evaluate the fracture toughness and fatigue properties through a prediction of crack behavior from the variations of stiffness and frequency. Additionally, life time of a mirror plane used in DVD(Digital Video Disk) is measured as a function of capacitance and applied voltage under the accelerated conditions. Ultimately, we propose the method to evaluate the micromechanical reliabilities of the MEMS materials using the advanced test structure.

• International Journal of Concrete Structures and Materials
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• 제10권3호
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• pp.271-295
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• 2016

In this study, an extensive literature review has been conducted on the material characterization of UHPC and its potential for large-scale field applicability. The successful production of ultra-high performance concrete (UHPC) depends on its material ingredients and mixture proportioning, which leads to denser and relatively more homogenous particle packing. A database was compiled from various research and field studies around the world on the mechanical and durability performance of UHPC. It is shown that UHPC provides a viable and long-term solution for improved sustainable construction owing to its ultrahigh strength properties, improved fatigue behavior and very low porosity, leading to excellent resistance against aggressive environments. The literature review revealed that the curing regimes and fiber dosage are the main factors that control the mechanical and durability properties of UHPC. Currently, the applications of UHPC in construction are very limited due to its higher initial cost, lack of contractor experience and the absence of widely accepted design provisions. However, sustained research progress in producing UHPC using locally available materials under normal curing conditions should reduce its material cost. Current challenges regarding the implementation of UHPC in full-scale structures are highlighted. This study strives to assist engineers, consultants, contractors and other construction industry stakeholders to better understand the unique characteristics and capabilities of UHPC, which should demystify this resilient and sustainable construction material.

• 한국정밀공학회지
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• 제27권2호
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• pp.102-108
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• 2010

Recently, carbon fiber reinforced plastic(CFRP) composite materials have been widely used in various fields of engineering because of its advanced properties. Also, CFRP composite materials offer new design flexibilities, corrosion and wear resistance, low thermal conductivity and increased fatigue life. However CFRP composite materials are susceptible to impact damage due to their lack of through-thickness reinforcement and it causes large drops in the load-carrying capacity of a structure. Therefore, the impact damage behavior and subsequently load-carrying capacity of impacted composite materials deserve careful investigation. In this study, the residual strength and impact characteristics of plain-woven CFRP composites with impact damage are investigated under axial tensile test. By using obtained residual strength and Tan-Cheng failure criterion, residual strength of CFRP laminate with arbitrary fiber angle were evaluated.

• 한국지반신소재학회논문집
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• 제2권3호
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• pp.39-46
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• 2003

국내 도로포장의 주요 파손형태는 주변환경 및 반복교통하중 조건에 의한 소성변형, 피로균열, 반사균열, 온도균열 등이 있는데, 포장이 설계수명에 도달하기 이전에 주로 발생하며 이로 인한 도로포장의 유리관리에 막대한 국가예산이 낭비되고 있는 실정이다. 본 연구는 토목섬유를 보강한 아스팔트 포장 시스템을 평가하는 것으로 이를 위해 아스팔트 포장 소성변형에 대한 토목섬유의 보강효과를 분석하고자 휠트래킹 시험을 수행하였으며, 토목섬유 보강에 따른 토목섬유와 아스팔트 혼합물의 거동특성을 고찰하였다.