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목탑 상륜부 찰주 구성재료에 따른 진동 모드 특성에 관한 연구
황종국 한국풍공학회 2021 한국풍공학회지 Vol.25 No.1
본 연구에서는 목탑 상륜부 구조물의 진동 특이성을 분석하였다. 목탑 상륜부 구조물은 공예가들에 의해서 만들어지기 때문 에 공학적인 판단을 받지 않고 설치되어 불안정한 상황이 발생될 수 있다. 최초에 설계된 평화의 탑 상륜부는 전체 높이 7,720mm 중 에서 약 2/3높이에 해당하는 5,150mm까지는 스테인레스 스틸을 사용하고 나머지 2,570mm는 황동으로 설계되어 제작 의뢰되었다. 최 초 설계안에 대해 진동해석을 수행하고 모드별 유효질량을 산출한 결과 2차모드의 유효질량이 1차모드의 유효질량보다 크게 산출되 었다. 이런 현상의 개선을 위해 황동 부분을 스테인레스로 변경하여 2차 설계안이 준비되었고 2차 안에 대한 진동해석을 수행한 결과 1차모드가 지배적인 모드로 전환되었다. 본 연구의 결과로, 2차모드의 유효질량이 1차모드의 유효질량보다 큰 것이 전단력 미친 영향 의 정도를 정확하게 판단하기는 어렵다. 이 부분에 대해 추후 연구가 진행되어야 정확한 언급이 가능할 것으로 판단된다. In this study, the vibration characteristic of the Sang-Ryun Structure of a wooden tower was analyzed. Since the Sang- Ryun Structure of the wooden tower is made by craftsmen, it may be installed without engineering judgment, resulting in an unstable situation. The Sang-Ryun Structure of the Tower of Peace, which was initially designed, is made of stainless steel up to 5,150mm, which is about 2/3 of the total height of 7,720mm, and the remaining 2,570mm is designed with brass. As a result of performing vibration analysis on the initial design and calculating the effective mass for each mode, the effective mass of the second mode was calculated larger than the effective mass of the first mode. To improve this phenomenon, a second design proposal was prepared by changing the brass part to stainless steel, and as a result of performing the vibration analysis for the second order, the first order mode was converted to the dominant mode. As a result of this study, it is difficult to accurately determine the effect on shear force when the effective mass of the second mode is larger than that of the first mode. It is believed that further research on this part will be required to make an accurate comment.
A review of synthesis strategies for MOF-derived single atom catalysts
황종국 한국화학공학회 2021 Korean Journal of Chemical Engineering Vol.38 No.6
Single atom catalysts (SACs) have attracted great attention as promising catalysts that integrate the benefits of both heterogeneous and homogeneous catalysts. SACs exhibit unique properties that are otherwise difficult to achieve, such as high atom utilization efficiency, unprecedentedly high catalytic activity and selectivity. However, it still remains a great challenge to prepare stable SACs without particle aggregation and sintering. Among the various fabrication methods for SACs, metal-organic framework (MOF)-derived synthesis routes have shown great potential by taking advantage of MOFs’ high structural/chemical tunability, large surface area and high porosity. In this review, the synthesis strategies for MOF-derived SACs are comprehensively summarized and classified into five classes, metal node modification, ligand modification, guest encapsulation, migration and trapping, and others. The current challenges and future opportunities of MOF-derived SACs are further discussed. This review will be useful for the rational design of MOF-derived SACs for various catalytic reactions.
Resisting capacity of Korean traditional wooden structural systems subjected to static loading
황종국,Samuel Kwak,Ji-Hyun Kwak 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.30 No.3
This paper investigates the structural behavior of Korean traditional wooden structures on the basis of the structural analysis using the commercialized program, SAP 2000. All the structural systems were analyzed, and the rotational stiffness at each joint was inferred from the experimental result for a half scale model of Bongjeong-sa (a temple in South Korea). In addition, the artificial control of analysis parameters was prevented because the structural analysis was focused on the realization of the most exact structural behavior of real structures. The analysis was carried out for the horizontal and vertical static loads, and all the secondary members were excluded in the structural analysis. The obtained results show that the resisting capacity of the primary structural system is greater than that of the expanding structural system.
황종국 한국풍공학회 2008 한국풍공학회지 Vol.12 No.2
The main objective of this paper is to investigate some questions regarding the dynamic characteristic of steeple in Korean stone pagoda. The steeple of Korean stone pagoda is composed usually stone ring and molded steel bar. Recent measurement data for weather have shown that the energy of typhoon are increased gradually. By this reason, the question has been raised as to the stability of stone pagoda. Especially, we must look more carefully into the vibration of steeple on stone pagoda. There has been no study that tried to figure out the vibration characteristic of steeple by wind. An one-sixth scale model is designed to perform wind tunnel test. For this model, we attempted force balance test. From force balance test, we figured out the vibration displacement of the top of steeple, maximum base shear, maximum overturning moment and wind force spectra. From force balance test, we figured out the maximum base shear of 6,800 N, the maximum overturning moment of 19,500 N-m. The analysis of spectra revealed that the magnitude of spectrum energy was not large and the unique phenomenon of spectrum energy was not figure out. So, one conclusion to draw is that the steeple of stone pagoda was safe for wind load. However, the vibration was caused by wind and the continuous vibration of steeple will show the decay of contact part. By this reason, it needs further consideration about the contact of steeple.