• Journal of Advanced Marine Engineering and Technology
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• v.40 no.7
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• pp.663-670
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• 2016

This paper introduces the concept of the computer-aided engineering(CAE) design method for a bypass valve in a system that is used for the safe lifting of mineral resources in deep-seabed mining. Although the bypass valve has a simple mechanism, its design is very difficult because of various influencing factors. This equipment, which has a complex design process, should be developed by CAE-based design method. The method can perform the design, design verification, and virtual experiment at the same time. In this study, the CAE-based method for the design of the bypass valve has been developed using fluid dynamics, multi-body dynamics, and optimization method.

• Journal of the korean Society of Automotive Engineers
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• v.18 no.5
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• pp.53-68
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• 1996

마그네슘이 자동차 경량화에 관심이 되는 이유는 근본적으로 CAFE 규제와 같이 경량화를 통한 화석연료의 소모를 크게 억제해야 한다는 사회적인 규제이나, 지난 10여년간의 기술발전으로 내식성이 나쁘다거나 취급이 위험한 금속이라는 인식이 크게 개선된 데에도 있다. 다른 경량금속에 대한 Mg 지금 가격의 비교조건이 호전되었고 향후 원소 재공급의 다변화가 추진되고 있는 것도 환경을 변화시킨 중요한 요인이다. 그간 중요한 경량화 대체 재료로 연구투자가 많았던 유기고분자 재료 및 FRP 등과 같은 복합재료는 폐기부품의 재활용이 어려움 때문에 호나경친화적인 단점이 부각되어, 이 소재의 증가가 주춤해 있다. 마그네슘의 경우에는 재활용이 가능하고, 진동흡수효과가 매우 커서 소음발생을 크게 줄일 뿐만 아니라, 주행 및 내구성시험에서 치수안정성이 좋고 많은 종류의 전자기기 사용에 의한 전자파 차폐효과도 큰 장점을 가지고 있다. 본 고에서는 Mg 다이캐스팅으로 자동차부품의 경량화 현황과 선진국에서 보는 전망을 미국을 중심으로 정리하고, 이와 관련한 Mg 다이캐스팅으로 자동차부품의 경량화 현황과 선진국에서 보는 전망을 미국을 중심으로 정리하고, 이와 관련한 Mg 기술적인 이슈와 시장전망도 서술하였다. 그리고 현재 우리나라의 연구계와 부품업계에서 추진하고 있는 연구개발 동향을 자동차 업계에 소개하는 의미도 있다. 이처럼 우리나라의 현황을 정리해 보는 것은 국내 자동차 산업이 국제적인 경쟁을 하고 있고 Mg기술과 원료확보에서 일본의 견제를 받고 있는 우리의 현실에서도 필요한 작업으로 생각된다.값들로 구성되는 형상을 내구 성능, 성형성등을 고려하여 최종 형상으로 결정한다. 내구성능의 예측은 금속부품의 내구수명 예측에 널리 이용되고 있는 방법이 방진 고무부품의 경우에도 적용 가능한지를 검토하고, 방진 고무부품에도 일반적으로 적용될수 있는 내구수명 예측방안의 개발 가능성을 타진해 보았다. 본 연구의 목표는 시제품을 제작하기 이전에 설계된 부품에 대한 스프링 상수 및 내구특성을 체계적으로 규명하여 제품 시험의 횟수를 줄이고, 보다 정밀한 제품을 제작할 수 있도록 하기 위한 것이다.세포수는 초기 배반포기배에서 팽윤 배반포기배로 진행됨에 따라 두배에서 세배 정도 증가되었음을 알 수 있었다. 또한, differential labelling과 bisbenzimide기법에서 얻어진 각각의 총세포수를 비교하였을 때 총세포수는 발달의 진행 정도에 따라 증가되며 그와 동시에 동일한 군 간의 세포수도 거의 유사함을 알 수 있었다. 따라서, ICM과 TE를 differential labelling하는 기법은 수정란의 quality를 평가하는데 매우 유용한 기법으로서 착상전 embryo 발달을 연구하는데 효과적으로 이용될 수 있다는 것을 시사한다. 고도의 유의차를 나타낸 반면 비수구, 초생수로구 및 Bromegrass 목초구 간에는 아무런 유의차가 인정되지 않았다. 7. 농지보전 처리구인 배수구와 초생수로구는 비처리구에 비해 낮은 침두 유출량과 낮은 토양유실량을 나타내었다.구보다 14% 절감되는 것으로 나타났다.작용하는 것으로 사료된다.된다.정량 분석한 결과이다. 시편의 조성은 33.6 at%

• Journal of Navigation and Port Research
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• v.29 no.5 s.101
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• pp.389-394
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• 2005

The additional moment occurs because the superstructures of VLFS are influenced by wave loads instead of earthquake loads. In order to reduce the additional moment, this study used the semi-rigid connections which lie between fully rigid and pinned. If the semi-rigid connections are used for superstructures of VLFS, the moment of beams can be reduced and more economical construction will be possible. This study aims to show the effect of wave loads on structure and the efficiency of the semi-rigid connections due to wave loads by analyzing the time history responses. The dynamic behaviors of the rigid frame are compared with those of the semi-rigid frame considering of static loads, wave loads and combination loads for a four-bay, three-story frames. The semi-rigid connection type is a steel tubular column with square external-diaphragm connections and the time history analysis is used for the dynamic responses. The additional moment responses due to wave loads increase $33\%$ in the rigid frame, $26\%$ in the semi-rigid frame with the spring model.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.12-18
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• 2021

The purpose of this study is to effectively mitigate the bending displacement that occurs in the bridge due to forced vibration. We developed CTMD (Combine Tuned Mass Damper) that combines the relationship between spring and mass to control the bending behavior of simple beams. The experiment was conducted to confirm the control effect according to the change in the mass ratio of the developed CTMD. The developed CTMD is designed and manufactured so that the mass ratio can be adjusted according to the characteristics of the bridge. The maximum load of the spring applied to CTMD was fixed at 33.15 N. In order to evaluate the performance of the developed CTMD, a simple beam composed of hinges and rollers as boundary conditions was fabricated. In the experimental method, a CTMD was installed in the center of a simple beam and the deflection displacement according to the mass ratio was measured. The shaking condition was shaken at 3 Hz to induce the maximum bending behavior of the simple beam. As a result of the experiment, it was confirmed that when the optimal mass ratio was 2.1, the damping rate of the bending behavior displacement was about 71.2 %, indicating the best control effect.

• Composites Research
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• v.36 no.1
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• pp.16-24
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• 2023

This paper presents a multi-scale progressive fatigue damage model incorporating the model for interfacial debonding between fibers and matrix. The micromechanics model for the progressive interface debonding was adopted, which defined the four different interface phases: (1) perfectly bonded fibers; (2) mild imperfect interface; (3) severe imperfect interface; and (4) completely debonded fibers. As the number of cycles increases, the progressive transition from the perfectly bonded state to the completely debonded fiber state occurs. Eshelby's tensor for each imperfect state is calculated by the linear spring model for a damaged interface, and effective elastic properties are obtained using the multi-phase homogenization method. The fatigue damage evolution formulas for fiber, matrix and interface were proposed to demonstrate the fatigue behavior of CFRP laminates under cyclic loading. The material parameters for the fiber/matrix fatigue damage were characterized using the chaotic firefly algorithm. The model was implemented into the UMAT subroutine of ABAQUS, and successfully validated with flat-bar UD laminate specimens ([0]₈,[90]₈, [30]₁₆) of AS4/3501-6 graphite/epoxy composite.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.6
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• pp.423-446
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• 2023

Shield TBM tunnel linings are segmented into segments and rings. This study investigates the response characteristics of the stress and displacement of the segment lining under seismic waves through modeling that considers the interface behavior between segments by applying a shell interface element to the contact surface between segments and rings. And there is no management criteria for ovaling deformation of segment linings in Korea. So, this study the ovality criteria and meaning of segment lining. The results of study showed that the distribution patterns of stress and displacement under seismic waves were similar between continuous linings and segment linings. However, the maximum values of stress and displacement showed differences from segment linings. The stress distribution of the continuous lining modeled as a shell type has a stress distribution that has continuity in the 3D cylindrical shape, but the segment lining is concentrated outside the segment, and the largest stress occurs at the location where the contact surface between the segment and the ring is concentrated. This intermittent and localized stress distribution shows an increasing as the ovality of the lining increases at seismic waves. The ovality at which the increase in stress distribution begins to show irregularity and localization is about 150‰. Ovality of 150‰ is an unrealistic value that cannot represent actual lining deformation. Therefore, the ovality of the segment lining increase with depth, but it does not have a significant impact on the stability caused by seismic load.

• The Journal of the Acoustical Society of Korea
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• v.35 no.4
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• pp.261-271
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• 2016

In the prediction of response of a pile in soil, numerical approaches such as a finite element method are generally applied due to complicate nonlinear behaviors of soils. However, the numerical methods based on the finite elements require heavy efforts in pile and soil modelling and also take long computing time. So their usage is limited especially in the early design stage in which principal dimensions and properties are not specified and tend to vary. On the contrary, theoretical approaches adopting linear approximations for soils are relatively simple and easy to model and take short computing time. Therefore, if they are validated to be reliable, they would be applicable in predicting responses of a pile in soil, particularly in early design stage. In case of wind turbines regarded in this study, it is required to assess their natural frequencies in early stages, and in this simulation the supporting pile inserted in soil could be replaced with a simplified elastic boundary condition at the bottom end of the wind turbine tower. To do this, analysis for a pile in soil is performed in this study to extract the spring constants at the top end of the pile. The pile in soil can be modelled as a beam on elastic spring by assuming that the soils deform within an elastic range. In this study, it is attempted to predict pile deformations and influence factors for lateral loads by means of the beam-on-spring model. As two example supporting structures for wind turbines, mono pile and suction pile models with different diameters are examined by evaluating their influence factors and validated by comparing them with those reported in literature. In addition, the deflection profiles along the depth and spring constants at the top end of the piles are compared to assess their supporting features.

• Korean Journal of Heritage: History & Science
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• v.54 no.1
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• pp.220-237
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• 2021

This study carried out the conservation treatment for the mattress put on the bed, which is one of 4 items in National Folklore Cultural Heritage, the Red-lacquered Furniture with the inlaid mother-of-pearl design used by Empress Sunjeonghyo (presumed), after identifying the characteristics of the manufacturing techniques and the used materials. And the study intends to compare it with the mattress placed in the Daejojeong in the Changdeokgung Palace in order to identify the characteristics of mattresses domestically used during the 1920s and 1930s. From the analysis of the mattress presumably used by Empress Sunjeonghyo, it was identified that the mattress frame was made of pinaceous hemlock spruce while the webbing and twine in the structural parts were made of jute. The findings are as follows: the burlap had a filling material that was made of jute; the straw mat was made from Oryza; and, the rest of the filling material was cotton. Rayon was used for the top cover while cotton was used for the bottom. As a result of research on the materials and the inner structure, it was found that mattress was manufactured in the form of the upholstery style mainly found in chairs and day-beds in Western furniture. Based on analysis results, materials identical to the original were adopted during the conservation treatment. Next, the process of dismantling, cleaning, repair, reinforcement and assembling was conducted. During the dismantling process, the top cover was newly discovered and some letters (Yokohama, Kobe, and Joseon) were found in the burlap filling, but there was no trace which can clarify its maker or production place. dry cleaning was carried out on the structural parts, filling materials, and the cover, and then the repair and reinforcement were done, preserving the existing materials in the upholstery structure and using the same materials for conservation. The webbing in the structural parts was reinforced using materials identical to the original, and the twine was used for arranging and fixing the springs into wooden frames. For the damaged cotton cloth and burlap, reinforcement materials identical to the original were put over it and sown. For the damaged area of the top cover, reinforcement cloth was cut and then added inside and the damaged area was sown. Assembling was carried out in the reverse order of the dismantling. After the burlap identical to the original material was inserted into the areas in contact with the springs and then fastened, a filling pad, reinforcement cloth, a straw mat, cotton cloth, cotton felt, wide cotton cloth for protecting the cover, and the cover were layered and fastened with tacks. The two mattresses used by Empress Sunjeonghyo differed only by the period of production and followed the same Western upholstery style consisting of the frames, filling materials, and covers. During the conservation treatment process, a velvet cover was newly discovered and the traces of repair in the past were found. Furthermore, identifying straw mats, straw bags, and straws for filling material, this study confirmed changes in the materials used according to the production environment. In the future, it is expected to see changes in the conservation materials during the conservation treatment and manufacturing techniques used for chairs and sofas in the upholstery style belonging to the modern cultural artifacts.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.198-203
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• 2012

Leguminous cover crops fix nitrogen from the atmosphere. The objective of this research was carried out to decrease fertilizer amount by cover crops-wheat mixtures cultivation. Field experiment was conducted at upland soil 2008 to 2009. Cover crops were used crimson clover and hairy vetch. Treatments consisted of three wheat-crimson clover (wheat 10 kg + crimson clover 1, 3, $5kg\;10a^{-1}$), wheat-hairy vetch mixture (wheat 10 kg + hairy vetch $2kg\;10a^{-1}$), and wheat - hairy vetch mixture - crimson clover (wheat 10 kg + hairy vetch 2 kg + crimson clover $3kg\;10a^{-1}$). These treatments were divided into no fertilizer and top dressing. The yield of wheat and crimson clover mixtures had no significantly differences compared to wheat only at top dressing plots. Also soil chemical and physical properties were a little bit improved such as OM, $NO_3$-N, and bulk density etc by wheat-crimson clover mixtures. Therefore, we suggested that crimson clover and wheat mixture could be used to reduction of fertilizers amount for environmental friendly wheat production.