• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.14 no.6
• /
• pp.486-494
• /
• 2004

This paper addresses the dynamic modeling and closed-loop eigenvibration analysis of composite rotating pretwisted fan blade modeled as non-uniform thin-walled beam with bi-convex cross-section fixed at the certain presetting angle and incorporating piezoelectric induced damping capabilities. The blade model incorporates non-classical features such as transverse shear, rotary inertia and includes the centrifugal and Coriolis force field. A velocity feedback control law relating the piezoelectiriccally induced transversal bending moment at the beam tip with the appropriately selected kinematical response quantity is used and the beneficial effects upon the closed loop eigenvibration of the blade are highlighted.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.944-949
• /
• 2003

This paper addresses the control of free and dynamic response of composite rotating pretwisted blade modeled as non-uniform thin-walled beam fixed at the certain presetting and pretwisted angle and incorporating piezoelectric induced damping capabilities. A distributed piezoelectric actuator pair is used to suppress the vibrations caused by external disturbances. The blade model incorporates non-uniform features such as transverse shear, secondary warping and includes the centrifugal and Coriolis force field. A velocity feedback control law relating the piezoelectiriccally induced transversal bending moment at the beam tip with the appropriately selected kinematical response quantity is used and the beneficial effects upon the closed loop eigenvibration and dynamic characteristics of the blade are highlighted.

• Magazine of the Korea Concrete Institute
• /
• v.6 no.5
• /
• pp.171-182
• /
• 1994

Recently, several prestressed concrete box girder bridges have experienced severe cracking along the tendon path when prestress force has been transferred to the anchorage zone. The purpose of the present study is therefore to explore characteristics of the local stress distribution, to study the effects of section geometry of anchorage zones, i.e., tendon inclination, tendon eccentricity and concrett. cover thickness anti to develop recornrncnd;itions for specific design criteria for post~tensioned a:lchorage zones. 7'0 accomplish these objectives, a cc~mprehen sive nonlinar finite element study has been conducted. From this study, realistic forrnulas for crackinq and ultimate load capacities are proposed. 'These equations reasonably well predict the crackinq and ultimate loads of prestressed concrete anchorage zones.

• Proceedings of the Safety Management and Science Conference
• /
• 2002.05a
• /
• pp.23-30
• /
• 2002

최근 우리나라의 건설산업은 Project의 규모가 대형화됨에 따라 기계화 시공 신공법 도입등 공정작업이 다양해지고 새로운 방법들이 많이 시도되고 있으며 건설산업도 기획, 설계, 발주, 시공, 유지관리라는 연속적 단계를 통하여 각 단계가 상호 유기적 연관성을 가지므로 건설현장의 근원적 안전성 확보를 위해서 건설 시설물의 Life cycle 전 단계를 걸쳐 안전관리 개념과 기법이 도입되어야 한다. 따라서 본 연구에서는 CM에 의한 단계로 안전성 확보에 주력하고 미국 CMAA의 단계별 기능별(phase, 6Function) 업무내용에서와 같이 Safety Management를 한다. 또한 CM제도 정착에 따른 초기단계를 규정하는 안전관리 법령 재정을 하여 단계적으로 자율적 안전 관리를 유도하여 재해예방을 하도록 해야한다.

• Proceedings of the Korean Society of Fisheries Technology Conference
• /
• 2000.05a
• /
• pp.472-473
• /
• 2000

수산동물의 생식기구에 관한 연구는 우선 자연상태에서 각 종의 정확한 생식주기와 이를 지배하는 요인이 밝혀져야 하는데, 이는 자원증식을 위한 기본적인 연구과제이기도 하다. 참서대는 가자미 목, 참서대과에 속하는 경골어류이며, 한국 남서해안의 수심 70 m 이내의 연안이나 내만에 주로 서식하는 경제성이 높은 저서 정착성 어류이다. Genus Cynoglossus의 생식과 관련된 연구는 매우 적어서 용서대, Cynoglossus abbreviatus의 난소성숙의 유도 및 초기생활사 (Fujita et al., 1986)와 참서대, C. joyneri의 성장과 성숙에 관한 보고 (Choi et al., 1995)가 있을 뿐이다. 따라서 본 연구의 목적은 참서대 암컷 GSI의 월 변화, 포란수, 생식주기 및 생식주기에 따른 난소구조의 변화 등 생식생태를 조사하여 이들 어류의 자원증식을 위한 기초자료를 제공하기 위함이다. (중략)

• Journal of Energy Engineering
• /
• v.26 no.2
• /
• pp.12-22
• /
• 2017

Korea Hydro & Nuclear Power Co. (KHNP) has implemented engineering programs for operating nuclear power plants. Engineering programs are maintenance rule (MR), functional importance determination (FID), single point vulnerability (SPV) and functional equipment group (FEG). Recently, KHNP has developed engineering programs for APR1400 feedwater supplying system to establish the advanced engineering system and will verify the suitability of engineering programs through implementing in new nuclear power plant. Consequently, it is expected that the reliability of APR1400 feedwater supplying system will be improved by implementing engineering programs.

• Journal of Korean Society of Steel Construction
• /
• v.21 no.2
• /
• pp.135-144
• /
• 2009

This study aims to suggest an appropriate flexural reinforcement technique by evaluating the reinforcement capacity of specimens that underwent flexural reinforcement according to the post-tension method with the anchoring position of an unbonded tension member on the conventional SC composite beam and the applied tension level as variables. For the experiment, up to a predetermined yield load was applied to each type of specimen and then, unbounded post-tensioning was additionally conducted to examine its reinforcement capacity. The analysis of the said experiment showed that the post-reinforced SC composite beam was characterized by significantly improved yield stress and initial stiffness, compared with the pre-reinforced one and the experimental measurements/theoretical values of maximum stress ranged from 0.95 to 1.13 following reinforcement. There was little or no change depending on the maximum stress and tension in the specimen (D160, Class 240) whose neutral axis and upper part had anchoring devices mounted prior to reinforcement. Rather, the ductility decreased with the increasing tension. On the contrary, in the case of the other specimen (Class D120) whose neutral axis had anchoring devices mounted after reinforcement, both the maximum stress and ductility increased with increasing tension, which indicates that the latter tension reinforcement was reasonably appropriate and effective for the neutral axis reinforcement.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.3
• /
• pp.12-20
• /
• 2023

This study presents basic data on how to secure stability by analyzing the change in tensile force of steel rod and the inclination characteristics of PSC BOX in the "Temporary fixation system using internal prestressing tendon", which is mainly applied to construction of superstructures by FCM. To date, it has been difficult to confirm the changes in tension force of the steel rod and the inclination of the PSC BOX because the steel rod was installed vertically inside the pier and the PSC BOX. Therefore, measurement of the change in length of the steel rod and the displacement of PSC BOX were performed using a micro-measured FBG sensor. Comparisons of the calculated tensile force and the residual tensile force of the steel rod revealed that the safety factor decreased in all bridges. The cause was mainly identified to be the loss of tensile force in fixation~1segment, and countermeasures are suggested. The analysis of the inclination characteristics showed that the inclination increased with the segment progresses even in bridges with sufficient safety factor, and the difference before and after the segment was confirmed. In addition, the increase in inclination was related to the loss of tension force in the steel rod, and the stress on the opposite sides of the inclination was further reduced. It is believed that upward tensile force is generated in the steel rod on the opposite side of the inclined side due to the unbalanced moment, causing the difference in stress of the steel rod between the two sides.

• Proceedings of the Safety Management and Science Conference
• /
• 2002.05a
• /
• pp.199-205
• /
• 2002

최근 산업안전/보건분야에서 누적외상성질환(Cumulative Trauma Disorders： CTDs)과 직업성요통(Low Back Injury)과 같은 근골격계질환은 산업현장에서 어렵지 않게 발견할 수 있는 신종 산업재해의 일종이다. 특히 미국의 경우, 발생건수와 그로 인한 인적/물적 손실이 급격하게 증가되고 있는 것으로 나타나고 있다. 그러나 미국과 같이 근골격계질환의 폐해를 일찌감치 인식하고 그 해결방안을 연구해온 나라들에서는 현재 환자관리 및 인간공학적인 기준 등을 포함하는 예방지침들이 잘 정착되어 있는 실정이다. 우리나라의 경우에는 작업환경 등의 조건과 상황이 미국과 같은 구미 선전국과 비숫하고, 특히 제조업의 생산체계가 그런 나라들과 매우 유사하여 근골격계질환의 발생과 그로 인한 인적/물적 손실이 적지 않을 것이라고 예상할 수 있지만 아직까지 CTDs에 대한 전반적인 이해가 부족하고, 정확한 실태가 파악되지 못하였으며, 따라서 체계적인 관리 대책 또한 마련되어있지 않은 실정이다. 본 조사에서는 서울 근교의 수송기계관련 사업장의 작업들에 대한 작업자세에 중심을 둔 인간공학평가를 통하여 조사 작업의 근골격계질환에 대한 상대적인 위험도, 위험요인 등을 파악하고, 그에 따른 개선 대책의 방향을 제시하고자 하였다. 특히, 각 부위별 위험점수와 부위별 증상호소율의 상환분석결과, 작업자 개인적 수준에서는 통계적으로 유의한 차는 없는 것으로 분석되었으나, 부서별로 분석한 결과, 작업시 주로 사용하는 오른쪽 상지의 경우, 오른쪽 어깨, 팔꿈치, 손목 순으로 통계적으로 유의하게 관련이 있는 것으로 나타났다. 즉 증상호소율과 해당 신체부위의 위험도 점수는 서로 정적(positive)한 관계에 있는 것으로 나타났고, 상지 중 주로 사용하는 오른쪽 부담의 위험도 자세 점수와 증상호소는 비교적 높은 상관관계에 있는 것으로 나타났다. 따라서 이와 같은 인간공학적 분석결과는 향후 인간공학적인 개선대책의 개발 뿐만 아니라 의학쪽에서 근골격계질환을 접근하는 초기단계에서 매우 유용한 역할을 할 수 있으리라 생각된다.

• Journal of the Korean Institute of Traditional Landscape Architecture
• /
• v.32 no.4
• /
• pp.132-142
• /
• 2014

This study is the first stage to identify distinctive characteristics of American Romantic Garden compared to English Romantic Garden. The purpose of the study is to identify characteristics of transitional garden in the early period of America by analyzing of Paca garden, Mount Vernon and Monticello when English Naturalistic Garden was firstly imported. The analysis studied historical background, people who designed garden, formal garden and characteristics of natural garden through reference. Also based on data through reference and field research, spatial configuration and garden factors of each site were analyzed. In spatial configuration, straight line and curve line, formal terrace and natural slope, visible axis and invisible axis, symetric and asymmetric, and perspective and oblique perspectives were used as analyzing factors. As a result of analysis, each garden showed different type from that of formal gardens from colony period, which is natural garden of asymmetric garden(English natural garden) coexisted. Paca garden which planned formal garden and natural garden in each space showed characteristics of each space, but in formal garden residential axis and garden axis does not coincide which shows it is out of formal garden type. Such phenomena and the fact that naturalistic garden coexist in the same garden shows that the formal garden type from early days in US is starting to change in different types. Mount Vernon garden, similar to Paca garden, was designed to have two different types of gardens in harmony rather than divide the space into different space and design it. It adapted serpent walkway but shows symmetric by central axis and considered formalistic plan through same materials. However through terrace in hills and spatial plan of oblique perspective, one could observe that naturalistic type was beginning to settle in US gardens. Through Monticello analysis, space was designed with major characteristics of naturalistic garden which is serpent walkway, ornamental farm, winding flower bed grove and bush and oblique perspective, and it completely duplicates characteristics of naturalistic garden which could not be found in gardens imported from UK.