• Smart Structures and Systems
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• 제22권2호
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• pp.201-207
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• 2018

This paper proposes a line laser thermography scanning (LLTS) system for multiple crack evaluation on a concrete structure, as the core technology for unmanned aerial vehicle-mounted crack inspection. The LLTS system consists of a line shape continuous-wave laser source, an infrared (IR) camera, a control computer and a scanning jig. The line laser generates thermal waves on a target concrete structure, and the IR camera simultaneously measures the corresponding thermal responses. By spatially scanning the LLTS system along a target concrete structure, multiple cracks even in a large scale concrete structure can be effectively visualized and evaluated. Since raw IR data obtained by scanning the LLTS system, however, includes timely- and spatially-varying IR images due to the limited field of view (FOV) of the LLTS system, a novel time-spatial-integrated (TSI) coordinate transform algorithm is developed for precise crack evaluation in a static condition. The proposed system has the following technical advantages: (1) the thermal wave propagation is effectively induced on a concrete structure with low thermal conductivity of approximately 0.8 W/m K; (2) the limited FOV issues can be solved by the TSI coordinate transform; and (3) multiple cracks are able to be visualized and evaluated by normalizing the responses based on phase mapping and spatial derivative processes. The proposed LLTS system is experimentally validated using a concrete specimen with various cracks. The experimental results reveal that the LLTS system successfully visualizes and evaluates multiple cracks without false alarms.

• 전기학회논문지
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• 제57권7호
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• pp.1150-1156
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• 2008

This paper introduces the PC clustering of the SIMD structure for a distributed processing of on-line contingency to assess a static security of a power system. To execute on-line contingency analysis of a large-scale power system, we need to use high-speed execution device. Therefore, we constructed PC-cluster system using PC clustering method of the SIMD structure and applied to a power system, which relatively shows high quality on the high-speed execution and has a low price. SIMD(single instruction stream, multiple data stream) is a structure that processes are controlled by one signal. The PC cluster system is consisting of 8 PCs. Each PC employs the 2 GHz Pentium 4 CPU and is connected with the others through ethernet switch based fast ethernet. Also, we consider N-1 line contingency that have high potentiality of occurrence realistically. We propose the distributed process algorithm of the SIMD structure for reducing too much execution time on the on-line N-1 line contingency analysis in the large-scale power system. And we have verified a usefulness of the proposed algorithm and the constructed PC cluster system through IEEE 39 and 118 bus system.

• 한국지진공학회논문집
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• 제18권3호
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• pp.125-132
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• 2014

In this study, a series of dynamic centrifuge tests were performed for a soil-foundation-structural interaction system in dry sand with various embedded depths and superstructure conditions. Sinusoidal wave, sweep wave and real earthquake were used as input motion with various input acceleration and frequencies. Based on the results, a natural period and an earthquake load for soil-structure interaction system were evaluated by comparing the free-field and foundation accelerations. The natural period of free field is longer than that of the soil-foundation-structure system. In addition, it is confirmed that the earthquake load for soil-foundation-structure system is smaller than that of free-field in short period region. In contrast, the earthquake load for soil-foundation-structure interaction system is larger than that of free-field in long period region. Therefore, the current seismic design method, applying seismic loading of free-field to foundation, could overly underestimate seismic load and cause unsafe design for long period structures, such as high-rise buildings.

• 한국지진공학회논문집
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• 제17권6호
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• pp.245-255
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• 2013

According to natural frequency of soil, characteristics of earthquake responses of an isolated containment building in nuclear power plants are examined. For this, earthquake response analysis of seismically isolated containment buildings in nuclear power plants is carried out by strictly considering soil-structure interactions. The structure and near-field soil are modeled by the finite element method while far-field soil by consistent transmitting boundary. The equation of motion of a soil-structure interaction system under incident seismic wave is derived. The derived equations of motion are solved to carry out earthquake analysis of a seismically isolated soil-structure system. Generally, the results of this analysis show that seismic isolation significantly reduces the responses of the soil-structure system. However, if the natural frequency of the soil is similar to that of the soil-structure system, the responses of the containment buildings in nuclear power plants rather increases due to interactions in the system.

• 대한기계학회논문집A
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• 제20권7호
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• pp.2108-2117
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• 1996

The purpose of this paper is to investigate the influence of the exciter attached for the measurement of natural frequencies when extracting the frequency response functions of the test structure in experimental modal analysis. The procedure is first to model the attached exciter as an additional degree of freedom system and next to verify the suggested model by experimentally extracting the natural frequencies of the test structure with various values of exciter mass, stinger stiffness and attachment position of the exciter on the test structure. It is concluded that as additional degree of freedom system which includes the natural frequency of the exciter itself and axial stiffness of stinger should be considered to quantatively define the coupling effects of structure-exciter interaction on the measured natural frequencies. It is not the mass of the exciter itself but the coupling effect of the additional degree of freedom mass-spring system consisting of exciter body and armature coil that characterizes the natural frequency deviation. Therefore, when the natural frequency of this additional mass-spring system is outside of the test frequency range, the coupling effect of structure-exciter interaction can be minimized.

• 한국공간구조학회논문집
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• 제18권1호
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• pp.55-65
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• 2018

In order to reduce the seismic response of the spatial structure, a seismic isolation system with sufficient flexibility is used. The natural period of structure with seismic isolation system got be long to avoid prominent period. In this study, The seismic response of the truss-arch structure, which is modeled in three types according to the rise-span ratio is analyzed on El-centro, Northridge and Artificial Earthquake and compared with the seismic response of the truss-arch structure with lead rubber bearing(LRB). When seismic load is applied to the truss arch with isolation system, the horizontal acceleration response of the truss arch is reduced and vertical seismic response is also reduced. The application of the seismic isolation system is effective in controlling the seismic response.

• 간호행정학회지
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• 제20권4호
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• pp.414-425
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• 2014

Purpose: The purpose of this study was to identify hospital nurses' recognition of the team system and the effectiveness of the team system as an organizational structure. Methods: A self-report questionnaire was used to collect data from 247 general hospital nurses during 4 months in 2013. Analysis was done using descriptive statistics, t-test, ANOVA, Pearson correlation coefficients and factor analysis with SPSS 18.0. program Results: There was no significant difference in nurses' recognition of team structure (t=2.06, p=.153) or effect of team structure (t=0.36, p=.549) according to use of team system. In hospitals with a team system, there were positive correlations between recognition of the effect of the team system and age (r=.25, p=.033), and total clinical career (r=.26, p=.012). In hospitals not using a team system, nurses' recognition of team structure as an organizational system (r=.31, p<.001), nurses' recognition of team structure, total (r=.30 p<.001) correlated significantly with the effects of team system. Conclusion: Results of this study provide a retrospection view of the team system in nursing organizational systems. The nursing team system's ultimate goal needs to be confirmed for complementary nursing care. Also, more studies on nurses' perceptions of, and effectiveness of the team system are necessary.

• 가정과삶의질연구
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• 제4권2호
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• pp.9-24
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• 1986

This study aims at providing the data in order to understand home management and to mange home efficiently through attempting systems approach to home management focused on purchase decision making and marital role structure. For the purpose of this study, regarding housing purchase decision making process as a system, environmental characteristics as inputs, marital role structure and the satisfaction of purchase management as outputs, relation between inputs and outputs; the understanding about these components was established as research problem. And then the framework of analysis being based on theoretical references was suggested, and questionnaires were administrated to housewives. The result of this study is as follows: 1) Marital role structure was differently shown according to the phases of decision making process. 2) Marital role structure was differently shown according to the level of environmental characteristics. 3) The statisfaction of purchase manag ment was influenced by environmental characteristics. According to these results, home management can be understood in the view of system. That is, the morphostatic characteristics of family system can be grasped in environmental supra system in conideration of the structure of managerial sub system; the morphogenic characteristics of family system can be grasped centering on the relationship to environment.

• 한국공간구조학회논문집
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• 제10권3호
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• pp.49-56
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• 2010

본 연구에서는 스마트 최상층 면진시스템을 적용한 고층건물의 풍응답 제어성능을 검토해보았다. 이를 위하여 77층 초고층 건물을 예제구조물로 선택하였고 풍동실험을 통해서 얻은 풍하중을 사용하여 수치해석을 수행하였다. 예제구조물의 최상층은 FPS 및 MR 감쇠기로 구성된 스마트 면진시스템을 이용하여 주구조물과 분리된다. 주구조물의 동적응답을 저감시키는 것이 스마트 최상층 면진시스템의 가장 중요한 목표이지만 면진된 최상층의 과도한 응답은 구조물을 불안정하게 만들 수 있다. 따라서, 본 연구에서는 면진된 최상층과 주구조물을 효과적으로 제어하기 위하여 스카이훅제어기를 제어알고리즘으로 사용하였다. 제안된 스마트 최상층 면진시스템의 제어성능을 검토하기 위하여 일반적인 수동 최상층 면진시스템의 제어성능과 비교하였다. 수치해석결과 제안된 스마트 최상층 면진시스템을 이용하면 일반적인 수동 최상층 면진시스템에 비해서 면진층의 변위를 효과적으로 줄이면서도 구조물의 응답을 저감시킬 수 있음을 확인할 수 있었다.

• 토지주택연구
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• 제8권3호
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• pp.181-187
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• 2017

To proactively respond to internal and external changes such as the recent demographic change and rising demand for diversified housing types, this study investigated the framed-structure free plan public house model proposed by the LH to look at the seismic performance of framed-structure apartment according to damper system use through non-linear analysis. The effectiveness thereof was also examined in terms of performance and economy. As a result, the proposed damper system application method to framed-structure free plan public house model was found to meet the performance requirements of the present earthquake-resistant design (KBC2016) and effective to apply to designs. The max response displacement and max response acceleration were compared based on the nonlinear analysis. As a result, the building with damper system showed better earthquake resistance performance than earthquake-resistant structure thanks to the damper system, although the base shear of earthquake-resistant system was reduced by 20% in design. The damper system is expected to help reduce building damage while ensuring excellent earthquake resistance performance. In addition, the framework quantities of earthquake-resistant structure and structure with damping system were compared. As a result, columns were found to reduce concrete amount by about 3.9% and rebar, by about 7.3%. Walls showed about 12.6% reduction in concrete and about 10.7% in rebar. In terms of cost, framework construction cost including formwork and foundation expenses was expected to drop by about 5~6%.