• Structural Engineering and Mechanics
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• 제18권4호
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• pp.429-440
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• 2004

Remotely Operated Vehicle of 6000-meters is a new conceptual equipment made to replace the manned systems for investigating the deep-sea environment, and all of the ROV systems in operational condition strongly depend on the connecting cables. In this point of view dynamics of the ROV cable system is very important for operational and safety aspects as a cable generally encounters great tension. Researches have been executed on this problem, and most of papers have been mainly focused on the operational condition of ROV system in deep sea. This paper presents the dynamic cable response analysis during ROV launching condition rather than the operational one in order to provide the design guide of a ROV cable system in this circumstance, considering the coupling effects between cable and wave-induced ship motion. To obtain the variations of cable tensions during a ROV launching, a pre-stressed harmonic response analysis was carried out. Wave-induced tensions of the cable during ROV launching were obtained in real sea states using FE modeling, and the basic design guide of a ROV cable system was obtained.

• Computers and Concrete
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• 제19권6호
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• pp.659-666
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• 2017

Based on the Arrhenius equations, several hydration exothermic models that precisely calculate the influence of concrete's self-temperature duration on its hydration exothermic rate have been presented. However, the models' convergence is difficult to achieve when applied to engineering projects, especially when the activation energy of the Arrhenius equation is precisely considered. Thus, the models' convergence performance should be improved. To solve this problem and apply the model to engineering projects, the relationship between fast iteration and proper expression forms of the adiabatic temperature rise, the coupling relationship between the pipe-cooling and hydration exothermic models, and the influence of concrete's self-temperature duration on its mechanical properties were studied. Based on these results, the rapid convergence of the hydration exothermic model and its coupling with pipe-cooling models were achieved. The calculation results for a particular engineering project show that the improved concrete hydration exothermic model and the corresponding mechanical model can be suitably applied to engineering projects.

• 한국전자파학회논문지
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• 제25권3호
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• pp.304-310
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• 2014

본 논문에서는 두 루프(공진체)를 이용한 자계 결합 무선 전력 전송 방식의 결합계수(k)와 공진기의 Q 값 그리고 수신부의 최적 부하($R_{L,opt}$)에 대하여 제한되는 전송 효율의 문제점을 극복하기 위해 메타 물질(SRR 또는 RR), 도체, Relay 방법 등을 무선 전력 전송 시스템에 삽입 또는 시스템 주변에 위치시켜 전송 효율 증가하는 방법을 연구하였다. 위 방법을 통해 각 Case 결과에 따라 11~60 % 이상의 효율 증가를 확인할 수 있었다. 각기 다른 물질을 이용하여 전송 효율이 증가되는 최적의 방법을 관찰하였으며, EM 시뮬레이션을 이용하여 검증 및 분석하였다.

• 대한기계학회논문집A
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• 제31권1호
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• pp.77-88
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• 2007

Axiomatic Design has been developed as a general design framework during past two decades and TRIZ has been developed for a design tool over 50 years. Axiomatic design is quite excellent in that design should be decoupled. When a design matrix is established, the characteristics of the design are identified according to the coupling properties. If the design is coupled, a decoupling process should be found. However, axiomatic design does not specifically indicate how to decouple a coupled design. In this research, the coupling manner is classified into six patterns. Each pattern could be solved by an appropriate TRIZ module. A table, which matches the coupling pattern and a TRIZ module, is proposed for effective application of the two design theories. The decoupling ideas are proposed by using TRIZ modules. When the number of decoupled designs is more than one, the engineer should select the final idea. The proposed method is applied to practical cases such as a tape feeder and a beam adjuster of the laser marker.

• Spatial Information Research
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• 제18권1호
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• pp.49-56
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• 2010

시가지 범람 문제를 고려할 경우 침수심의 정량적인 수치계산에 의한 재해 위험을 평가하는 것이 중요하다. 본 연구에서는 2002년 막대한 시가지 침수 피해를 경험한 바 있는 삼척시를 대상으로 범람 모의 계산에 의한 시가지 침수피해 평가를 수행하였다, 입력자료의 변환과정에서 생길 수 있는 에러를 줄이기 위해 시가지 조도계수, 표고, 건물의 점유율 등은 ArcGIS에서 바로 전산화하여 시가지 범람모형을 구축하였으며 계산된 침수심을 토대로 격자별로 피해액을 산정하였다 본 연구를 통하여 강우유출, 침수심 모의 계산, 피해액의 정량적 산정이라는 일연의 과정이 통합적으로 수행되어 향후 시가지 배수계획에 기여할 것으로 기대된다.

• 한국전자파학회논문지
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• 제18권8호
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• pp.862-865
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• 2007

RFID 시스템에서는 현재 같은 주파수 대역에서 송신 단과 수신 단이 사용되며, 이에 따라 듀플렉서를 사용할 수 없게 되며 커플러를 사용하게 된다. 커플러를 사용함으로써 송신 누설 신호는 수신 단으로 직접적으로 영향을 주며, 이에 따라 태그의 인식 거리가 제한되는 부정적인 영향을 미치게 된다. 본 논문에서는 Rx 단으로 직접 적으로 영 향을 주는 Tx 누설 신호를 감쇄시키는 방법을 소개하고 ADS2006 시뮬레이션으로 이를 검증하였다

• 한국기계가공학회지
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• 제16권1호
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• pp.70-76
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• 2017

The pollution problem of fossil energy sources has caused the development of green energy harvesting systems. Piezoelectric energy harvesting technology has been developed under those external environmental factors. A piezoelectric energy harvester can be defined as a device which transforms mechanical vibration or impact energy into electrical energy. Most researches have focused on bender structures. However, these have a limitation on energy efficiency because of the small effective electromechanical coupling factor, around 10%. Therefore, we should look for a new design for energy harvesting. A cymbal energy harvester can be a good candidate for the high-power energy harvester because it uses a high amplification mechanism using endcaps while keeping a higher electromechanical coupling factor. In this research, we focused on energy efficiency improvements of the cymbal energy harvester by changing the polarization direction, because the electromechanical coupling factor of the k33 mode and the k15 mode is larger than that of the k31 mode. Theoretically, we checked the cymbal harvester with radial polarization and it could obtain 6 times larger energy than that with the k31 direction polarization. Furthermore, we verified the theoretical expectation using the finite element method program. Consequently, we could expect a more efficient cymbal harvester with the radial polarization by comparing two polarization directions.

• Journal of Power Electronics
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• 제16권5호
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• pp.1639-1649
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• 2016

This paper presents a family of soft-switching DC-DC converters with a simple auxiliary circuit consisting of a coupled winding and a pair of auxiliary switch and diode. The auxiliary circuit is activated in a short interval and thus the circulating conduction losses are small. With the auxiliary circuit, zero-voltage-switching (ZVS) and zero-current-switching are achieved for the main and auxiliary switches respectively, over wide input voltage range and load variation. In addition, the reverse-recovery problem of diodes is significantly alleviated because of the leakage inductor. Furthermore, the coupled inductor simultaneously serves as the main and auxiliary inductors, contributing to reduced magnetic component in comparison with the conventional zero-voltage-transition (ZVT) converters. Experimental results based on a 500 W prototype buck circuit validate the advantages and effectiveness of the proposed magnetic coupling ZVS converter.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1177-1182
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• 2006

This paper is concerned with the vibration analysis of a simply-supported rectangular plate with a circular cutout. Even though there have be en many methods developed for the free vibration of the rectangular plate with a rectangular cutout., very few research has been carried out for the rectangular plate with a circular cutout. In this paper, a new methodology called independent coordinate coupling method, which was developed to save the computational effort for the free vibration analysis of rectangular plate with a rectangular cutout, is applied to the case of circular cutout. The independent coordinate coupling method employs the global coordinate system for the plate and the local coordinate system for the cutout. In the case of the rectangular plate with a circular cutout, the global coordinate system is the Cartesian co ordinate system and the local coordinate system is the polar coordinate system. By imposing the compatibility condition, the relationship between the global coordinates and the local coordinates is derived. This equation is then used for the calculation of the mass and stiffness matrices resulting in eigenvalue problem. The numerical results show the efficacy of the proposed method.

• 한국소음진동공학회논문집
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• 제16권6호
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• pp.643-650
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• 2006

This paper is concerned with the vibration analysis of a simply-supported rectangular plate with a circular cutout. Even though there have been many methods developed for the free vibration of the rectangular plate with a rectangular cutout, very few research has been carried out for the rectangular plate with a circular cutout. In this paper, a new methodology called independent coordinate coupling method, which was developed to save the computational effort for the free vibration analysis of rectangular plate with a rectangular cutout, is applied to the case of circular cutout. The independent coordinate coupling method employs the global coordinate system for the plate and the local coordinate system for the cutout. In the case of the rectangular plate with a circular cutout, the global coordinate system is the Cartesian coordinate system and the local coordinate system is the polar coordinate system. By imposing the compatibility condition, the relationship between the global coordinates and the local coordinates is derived. This equation is then used for the calculation of the mass and stiffness matrices resulting in eigenvalue problem. The numerical results show the efficacy of the proposed method.