• 한국재료학회지
• /
• 제3권3호
• /
• pp.292-299
• /
• 1993

본 연구에서는 탄소/탄소복합재료의 마모특성에 대한 탄소섬유 길이의 영향을 고찰하였다. 매트릭스 precursor로 레졸형의 페놀수지와 강화재로 표면처리를 하지않은 PAN계 단섬유형 탄소섬유를 사용하여 액상함침법으로 1회의 고온열처리 공정과 4회의 탄화공정을 통하여 탄소/탄소복합재료를 제조하였다. Disk-on-disk형의 마모시험기를 통하여 상대 마찰재로 AISI 304 stainliss steel을 사용하여 0.6MPa(61 ${\times}{10^3}$Kg/$m^2$)의 압력과 0.71m/sec의 미끄러짐 속도하에서 측정된 탄소/탄소복합재료의 마찰계수는 0.2-0.3이었다. 마찰계수에 대한 섬유의 길이의 영향은 크게 나타나지 않았지만, 마모 속도는 섬유의 길이가 증가함에 따라 증가하는 경향이 나타났다. 본 실헙 결과를 섬유 강화 플라스틱의 마모 모델을 적용하여 고찰하여 본 결과, 섬유의 길이가 증가함에 따라 탄소/탄소복합재료의 마모 속도가 증가되는 경향은 생성된느 마모조각의 크기가 커기기 때문에 나타난 현상으로 판단되었다.

• 터널과지하공간
• /
• 제18권4호
• /
• pp.289-299
• /
• 2008

화강풍화암 및 풍화토층 깍기 비탈면의 붕괴 원인 분석을 위해 수행한 안정성 검토 사례를 통해 화강암을 모암으로 하는 지역에 폭넓게 분포하는 화강풍화암 및 풍화토 깍기 비탈면 설계 시 유념해야 할 사항들을 살펴보았다. 지질 및 지반 조사를 통한 지반특성 파악하였으며 한계평형해석 및 수치해석을 통한 안전율 검토, 강우 및 파괴 이력 비교 분석 등 일련의과정을 비탈면 안정성 검토를 위해 수행하였다. 대상 지역 깍기 비탈면의 안정성 검토 결과로서 비탈면의 붕괴 원인은 주로 집중 강우 시 지반조건상 연약한 상부 지반에서의 전단강도 감소에 기인함을 알 수 있었다. 또한, 지하수 유입 경로와도 밀접한 관련이 있는 것으로 분석되었으며, 이를 기초로 비탈면의 안정화를 위한 대책공을 제시하였다.

• Korean Journal of Acupuncture
• /
• 제27권1호
• /
• pp.159-168
• /
• 2010

Objective: ZhangJinYoPian(藏珍要編, ZJYP) is a book witten by Song-WooGe in the late 19th century. While Korea has lost this book to tell us Korea traditional acupuncture treatment in the late 19th century, This book appeared as a manuscript in Japan. There is no reaserch or study carried out for this book. Furthermore, a few people know existence of this book. So I analyzed acupuncture treatment of the ZJYP and sort out the distinctive feature of it. Method: For that, I studied bibliographic information of this book and classified contents of it into three parts - medical thought, needle manipulation and acupoint selection to consider it's caracteristics. Results and Conclusions: 1. The author of ZJYP thought that weakness of good power in the body and strongness of evil power out of the body cause a disease. so Doctor should examine quality of both to care patient's pain. 2. The author of ZJYP thought that needle manipulation is one of the most important thing. Doctors can use needle manipulation to control patient condition. Especially, he suggested cooling and heating manipulation except reinforcement and reduction. 3. He stressed viscera and bowels. he located viscera and bowels theory in front of the book to explain relationship of these. It shows us that ZJYP maintained academic characteristics of acupuncture in Chosun-Korea. 4. While He minimized the number of acupoints used in treatment, he multiplied its combination. He selected one or two acupoints from each meridian pathway. It include Eight Confluent points(八脈交會穴). But these points were used in different ways to control the viscera and bowels, not to care the eight extra meridians.

• 미술이론과 현장
• /
• 제3호
• /
• pp.35-50
• /
• 2005

For us, any regional art exist? Almost all art events today take place mostly in Seoul. Concentrating on the reinforcement of its power, the regional art world remains isolated without any connection with the Seoul art community. It is completely closed off from the central art scene. The regional art world seems to consider that more helpful in consolidating its status. It is in real sense suffering the absence of art criticism and art media, lack of an understanding of art and backwardness of art education. Many regional artists are dreaming of moving out from their domain, aspiring to be a member of the central art world. They make an effort to assimilate into a refined, modern style of the central art circle, rather than striving to create works imbued with regionality and locality. As the artists living in the provinces, the characteristics of their district should be above all else reflected in their art. Although they are less informed about the latest trend of culture and art, their art has to be something passionately and obstinately embodying the intrinsic quality of their regions. They have to find a practical solution more positively, instead of merely complaining about the poor condition of the regional art community. There is the need to bring about a turnabout in our awareness that regional art is confined to any limit and cannot be in the center of the entire art world. What' s most significant is to dissolve factionalism and not to depend on school ties or regional networks. As a reaction against authoritarianism, regional art has to put emphasis on attaining its originality. For this, regional art should respect regional tradition, history and background and break away from an old convention of wielding power.

• 한국구조물진단유지관리공학회 논문집
• /
• 제14권3호
• /
• pp.201-208
• /
• 2010

본 연구에서는 현장타설 철근콘크리트 구조체에 대한 국내외 허용오차 관련기준을 검토하여, 현행 국내 허용오차 기준의 수준을 검토함과 동시에 합리적인 시공오차 측정방법과 측정기기를 제시하였다. 또한 국내 공동주택을 대상으로 철근콘크리트 구조 부재의 시공오차를 조사하여 현재 국내 시공오차 허용범위 만족도를 검토하고, 구조체의 저항능력 평가 시, 부재크기 오차의 불확실성을 고려한 합리적인 안전성 평가를 위한 자료를 제공한다.

• 한국해양공학회지
• /
• 제30권4호
• /
• pp.294-302
• /
• 2016

Because of the importance of steel material saving and rational ship structural design due to the rapid increase in steel prices, a ship structural design system was developed for plate members reinforced by doubler plates subjected to biaxial in-plane compressive loads. This paper mainly emphasizes the design system improvement and upgrade according to the change in the in-plane loading condition of the doubler plate from the single load discussed in a previous paper to the biaxial in-plane compressive load discussed in this paper. A direct design process by a structural designer was added to this developed optimized system to increase the design efficiency and provide a way of directly inserting a designer's decisions into the design system process. As the second stage of preliminary steps of doubler design system development, design formulas subjected to these biaxial loads used in the doubler plate design system were suggested. Based on the introduction of influence coefficients $K_t_c$, $K_t_d$, $K_b_d$ and $K_a_d$ based on the variations in the doubler length, breadth, doubler thickness, and average corrosion thickness of the main plate reinforced by the doubler plate, respectively, the design formulas for the equivalent plate thickness of the main plate reinforced by the doubler plate were also developed, and a hybrid design system using these formulas was suggested for the doubler plate of a ship structure subjected to a biaxial in-plane compressive load. Using this developed design system for a main plate reinforced by a doubler plate was expected to result in a more rational reinforced doubler plate design considering the efficient reinforcement of ship plate members subjected to these biaxial loads. Additionally, a more detail structural analysis through local strength evaluations will be performed to verify the efficiency of the optimum structural design for a plate member reinforced by a doubler plate.

• 한국지리정보학회지
• /
• 제22권2호
• /
• pp.97-106
• /
• 2019

오늘날 수많은 건설 시설물 중에서 항상 시설하여 관리해야하는 다양한 중대형 교량구조물의 안전상황을 점검하기 위하여 여러 가지의 계측장비를 이용하고 있지만 대부분 일정한 주기별로 교량의 변위거동을 측정하고 확인하는 방법을 사용하고 있다. 지속적으로 안전상황을 점검하기 위하여 여러 가지의 계측장비를 이용하고 있지만 대부분 실시간으로는 주요 시설물의 변위와 거동을 측정하고 상시적으로 확인하지 못하고 있는 것이다. 본 연구에서는 대형 교량구조물의 운행에 위험을 사전에 감지할 수 있도록 GNSS 및 환경센서와 드론영상 데이터를 무선 네트워크로 전송하여 사용할 수 있도록 하였다. 그 결과, 실시간으로 교량의 미세변위와 그 상태를 진단함으로서 위험 요소가 예상되는 교량의 구조부에 대한 보강, 수리 및 재해 방지 조치가 가능하도록 하여, 각종 재난과 사고를 사전에 예방하고 방재할 수 있는 새로운 대안을 제시할 수 있었다.

• Coupled systems mechanics
• /
• 제8권4호
• /
• pp.315-338
• /
• 2019

The numerical investigations have been carried out on reinforced concrete slab against blast loading to demonstrate the accuracy and effectiveness of the finite element based numerical models using commercial package ABAQUS. The response of reinforced concrete slab have been studied against the influence of weight of TNT, standoff distance, boundary conditions, influence of air blast and surface blast. The results thus obtained from simulations were compared with the experiments available in literature. The inelastic behavior of concrete and steel reinforcement bar has been incorporated through concrete damage plasticity model and Johnson-cook models available in ABAQUS were presented. The predicted results through numerical simulations of the present study were found in close agreement with the experimental results. The damage mechanism and stress response of target were assessed based on the intensity of deformations, impulse velocity, von-Mises stresses and damage index in concrete. The results indicate that the standoff distance has great influence on the survivability of RC slab against blast loading. It is concluded that the velocity of impulse wave was found to be decreased from 17 to 11 m/s when the mass of TNT is reduced from 12 to 6 kg. It is observed that the maximum stress in the concrete was found to be in the range of 15 to $20N/mm^2$ and is almost constant for given charge weight. The slab with two short edge discontinuous end condition was found better and it may be utilised in designing important structures. Also it is observed that the deflection in slab by air blast was found decreased by 60% as compared to surface blast.

• Composites Research
• /
• 제31권6호
• /
• pp.371-378
• /
• 2018

본 연구에서는 폴리유산 나노복합재의 열탄성 거동을 예측하기 위해 분자동역학 전산모사를 수행하고 그 결과를 열탄성 미시역학 모델 예측해와 비교하였다. 폴리유산의 두 이성질체인 D유산(Poly D-lactide)와 L유산(Poly L-lactide)을 혼합한 스테레오 콤플렉스를 모델링하였고 이들을 기지로 사용한 탄소나노튜브 나노복합재를 구성하였다. 유산의 분해 유무에 따른 유리전이온도와 탄성계수 그리고 열팽창계수를 앙상블 전산모사를 통해 예측하였다. 미시역학 모델에서는 계면의 완전 결합을 가정한 이중입자 모델을 적용하여 탄성계수와 열팽창계수를 동일한 조성에서 예측하였다. 그 결과 열적 안정성에 있어 스테레오 콤플렉스에 탄소나노튜브가 첨가될 경우 유산의 뛰어난 계면 흡착과 이에 따른 열적 안정성 향상을 보였다. 순수한 유산과 나노복합재 모두 가수 분해에 따른 열적 특성 변화는 관찰되지 않았다. 또한, 스테레오 콤플렉스와 나노튜브 간 계면은 약한 불완전 결합상태 임을 알 수 있었다.

• Steel and Composite Structures
• /
• 제38권3호
• /
• pp.337-353
• /
• 2021

Micro-electro-mechanical systems (MEMS) are widely employed in sensors, biomedical devices, optic sectors, and micro-accelerometers. New reinforcement materials such as carbon nanotubes as well as graphene platelets provide stiffer structures with controllable mechanical specifications by changing the graphene platelet features. This paper deals with buckling analyses of functionally graded graphene platelets micro plates with two piezoelectric layers subjected to external applied voltage. Governing equations are based on Kirchhoff plate theory assumptions beside the modified couple stress theory to incorporate the micro scale influences. A uniform temperature change and external electric field are regarded along the micro plate thickness. Moreover, an external in-plane mechanical load is uniformly distributed along the micro plate edges. The Hamilton's principle is employed to extract the governing equations. The material properties of each composite layer reinforced with graphene platelets of the considered micro plate are evaluated by the Halpin-Tsai micromechanical model. The governing equations are solved by the Navier's approach for the case of simply-supported boundary condition. The effects of the external applied voltage, the material length scale parameter, the thickness of the piezoelectric layers, the side, the length and the weight fraction of the graphene platelets as well as the graphene platelets distribution pattern on the critical buckling temperature change and on the critical buckling in-plane load are investigated. The outcomes illustrate the reduction of the thermal buckling strength independent of the graphene platelets distribution pattern while meanwhile the mechanical buckling strength is promoted. Furthermore, a negative voltage, -50 Volt, strengthens the micro plate stability against the thermal buckling occurrence about 9% while a positive voltage, 50 Volt, decreases the critical buckling load about 9% independent of the graphene platelet distribution pattern.