• Journal of Navigation and Port Research
• /
• v.32 no.3
• /
• pp.215-221
• /
• 2008

Dynamic characteristics of a structure, i.e., natural frequency and mode shape, have been widely using as an input data in the area of structural integrity or health monitoring which combined with the damage evaluation and structural system identification techniques. It is very difficult, however, to get those information by the conventional modal analysis method from large structures, such as the offshore structure or the long-span bridge, since the source of vibration is not available. In this paper, a method to obtain the frequencies and the mode shapes of a large span truss structure using only acceleration responses is studied. The calculation procedures to obtain acceleration responses and frequency response functions are provided utilizing a numerical model of the truss, and the process to extract natural frequencies and mode shapes from the modal analysis is cleary explained. The extracted mode shapes by proposed method are compared with those from eigenvalue analysis for the estimation of accuracy. The validity of the mode shapes is also demonstrated using an existing damage detection technique for the truss structure by simulated damage cases.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.7 no.2
• /
• pp.105-113
• /
• 2003

Because structural systems are becoming lighter and more flexible and have lower natural frequencies and dampings than before, coordinated rhythmic activities such as dancing, audience participation in arenas or concert halls, and aerobics result in undesirable levels of vibration. For rhythmic activities, it is resonant or near resonant behavior that result in significant dynamic amplification and hence human discomfort. The most rational design strategy is to provide enough of a gap between the natural frequency of a floor system and the dominant frequencies excited by planned human activities to assure reasonably that resonance will not occur. For the case study the vibration measurements were performed at the floor of a long-span multi-purpose hall during the rock concert of popular singer.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.4
• /
• pp.160-168
• /
• 2010

Recently, there are a lot of researches related to the high-fluidity concrete (HFC) with field applications. However, most applications and studies are with concretes with high strength level so there are little studies about durability evaluations such as chloride ion penetration properties with normal strength concrete. Therefore, to evaluate the durability of HFC with normal strength level, this study performed the chloride ion penetration test and observed the micro pore distribution with normal strength HFC which contains limestone powder. Experimental results showed that most micro-pores have diameters between 0.005 to 0.05 ${\mu}m$ with HFCs using limestone powder and the average diameter becomes larger with the increase of limestone powder content. Also, it was shown that, with the increase of the limestone powder content, penetration depth and diffusion coefficient of chloride ion increased and diffusion coefficient had good relationships with compressive strength and average pore diameter with the coefficient of determination over 0.90.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.21 no.1
• /
• pp.73-82
• /
• 2008

In this paper, a new regularization method by parameter subset selection method is proposed based on the residual force vector for damage localization. Although subset selection using the fundamental modal characteristics as a residual function has been successful in detecting a single damage location, this method seems to have limited capabilities in the detection of multiple damage locations and typically requires cumbersome weighting values. The method is presented herein and considers cases in which damage detection must be achieved using incomplete measurements of the structural responses. Model expansion is incorporated to deal with this challenge. The unique advantage of employing the new regularization method is that it can reliably identify multiple damage locations. Through an illustrative example, the proposed damage detection method is demonstrated to be a reliable tool for identifying multiple damage locations for a planar truss structure.

• Nuclear industry
• /
• v.7 no.9 s.55
• /
• pp.48-56
• /
• 1987

이 FEMO기술은 지금까지의 재처리기술과 비교하여 약간 새로운 개념을 포함하고 있기 때문에 그 안전성에 대해 인허가 단계에서 충분한 검토를 행한 결과 FEMO기술 고유의 안전성이 인정되어 1985년 11월에 최초의 부분적인 건설허가가 나왔다.

• Computational Structural Engineering
• /
• v.8 no.3
• /
• pp.135-141
• /
• 1995

Any arbitrarily shaped laminated composite shells of revolution can be sum of the conical shell elements. Therefore, finite element model of conical shell element will be developed in this study. To verify consistency and validity of this model, natural vibrations of this model is compared with the analytical solution of cylindrical shell. Herein, an extensive parametric study is presented to assess the modeling capability of this model in class of laminated composite cylinders. It is seen that the proposed model provides highly accurate results with analytical solution. Once development of this conical shell element is done, any arbitrarily shaped composite shells of revolution can be easily analyzed.

• Journal of Korea Water Resources Association
• /
• v.37 no.9
• /
• pp.729-736
• /
• 2004

Analysis of reflection of random waves propagating over rectangular submerged non-porous breakwaters was performed by using the eigenfunction expansion method. In this study, random waves were generated by superposition of several monochromatioc waves. Reflection coefficients were calculated by summing each numerical results of regular waves. Predicted results from the eigenfunction expansion method were in a good agreement with the results of laboratory measurements. Reflection coefficients of random waves were also resonated at the Bragg reflection condition.

• Journal of Convergence for Information Technology
• /
• v.10 no.9
• /
• pp.206-214
• /
• 2020

This study analyzed the impact of direct and indirect subsidies on profitability in general hospitals in Korea. The data were collected from medical institution accounting information disclosure system of 270 general hospitals from 2016 to 2018. The analysis index used the ratio of net profit to business revenue for profitability, and Subsidies index the ratio of subsidies to business revenue(state subsidies for facility investment purposes, Fund related to essential business, research revenue and contribution revenue). According to the study, the ratio of state subsidies, which are direct subsidies, was very high at 57.30 percent for public institution hospitals. ratio of Fund related to essential business, which is a tax reduction effect with indirect subsidies, had the highest at 6.69 percent for Private University Hospitals. which are Indirect subsidies for deficit or operational assistance, research revenue ratio had the highest 2.8 percent for National University Hospitals, contribution revenue ratio had the highest 36.4 percent for public institutions. As a result of looking at the impact of subsidies on profitability, Nation University Hospitals had the lower the ratio of Fund related to essential business and the ratio of research revenue, the higher the net profit ratio of Business revenue. Medical Corporation Hospitals and Foundation Hospitals had the higher the ratio of Fund related to essential business to business revenues, the higher the net profit ratio of business revenue. These results mean that profitability may fluctuate depending on the utilization of funds related to essential business.

• Journal of Soil and Groundwater Environment
• /
• v.13 no.6
• /
• pp.1-16
• /
• 2008

There are generally two types of groundwater vulnerability assessments. Intrinsic vulnerability is based on the assessment of natural climatic, geological and hydrogeological attributes and specific vulnerability relates to a specific contaminant, contaminant class, or human activity. Several methods to assess groundwater vulnerability, which are based on hydrogeologic setting and socio-economical environment, have been developed in USA and Europe. A Modified-DRASTIC model including a lineament factor has been developed in South Korea, but it still has some limitations. To develop a solid and applicable method in this country, many data of quality, hydraulic features, GIS data, and pollution source, produced from a Basic Survey based on Article 5 of the Groundwater Act and other research projects, need to be collected, analyzed and verified introducing the previous methods.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1997.05a
• /
• pp.527-533
• /
• 1997

문헌자료 간의 종속성을 고려한 베이지안(Bayesian) 방법을 개발하였으며, 이를 바탕으로 원자력발전소의 일반 기기 신뢰도 데이타 베이스를 구축하였다. 기존에 개발되어 사용되어 온 3단계 베이지안 자료 분석 코드인 MPRDP (Multi-Purpose Reliability Data Process) [1,2,3]는 기존의 신뢰도 데이타 베이스 계산 코드들과는 달리 문헌자료를 2단계에서 처리한 후 3단계에서 발전소 고유 자료를 처리하여 계산하도록 개발되었다. 그러나 이전에는 일반 자료들간의 종속성을 고려하지 못하고 동일한 자료원을 근거로 만들어진 여러 자료원들을 모두 독립적인 것으로 처리하였다. 본 논문에서는 모수적 선험적 베이지안 방법의 일종인 ML-IIl(Type II Maximum Likelihood) 방법을 이용하여 자료들 간의 종속성을 처리[5]하였다. 솔레노이드 구동밸브를 예로 종속성 처리에 따른 분석 결과의 차이를 보여 주었으며, 또한 일부 기기에 대한 국내 고유 자료를 바탕으로 MPRDP를 통한 기기 신뢰도를 추정하였다.