• Korean Journal of Construction Engineering and Management
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• v.15 no.5
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• pp.103-114
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• 2014

Data envelopment analysis (DEA) measures the relative efficiency of decision making units (DMUs) with multiple performance factors that are grouped into outputs and inputs. DEA has proven to be superior to simple aggregation of performance measures, and is also useful for evaluating the performance of construction companies for comparison with competitor performance. The purpose of this study was to survey literatures on the application of DEA methodology and to propose a methodological scheme to measure the performance of construction organizations. Articles on previous studies were surveyed and examined as part of a comprehensive review. The survey revealed that the application of DEA in the construction industry was li mited. Further, the survey indicated that there is a need for the development of a methodological framework on the special goals and subjects of performance measurement, methods of data structure and collection, selection of appropriate DEA models, analysis of results, and post-test. Based on the survey, this study identified and discussed the types of major issues and topics for future studies from a methodological perspective, which could be helpful to researchers interested in using DEA to study performance issues in construction organizations.

• Polymer(Korea)
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• v.39 no.3
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• pp.506-513
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• 2015

Ethylidene norbornene (ENB) and its blends with endo-dicyclopentadiene (endo-DCPD) were prepared and reacted via the ring-opening metathesis polymerization (ROMP) reaction with the $1^{st}$ and $2^{nd}$ generation Grubbs' catalysts. Dynamic exothermic behaviors during ROMP and tensile properties after ROMP were evaluated using a differential scanning calorimeter (DSC) and a universal testing machine (UTM) for the samples, respectively. It revealed that the ROMP rate was accelerated with the less contents of endo-DCPD and under the $2^{nd}$ generation catalyst. Also, the addition of endo-DCPD and the $1^{st}$ generation catalyst resulted in higher tensile modulus and strength but lower toughness. Gel fraction measurement and fracture surface observation were made to understand the tensile properties.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.187-195
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• 2015

The gas explosions in offshore installations are known to be very severe according to its geometry and environmental conditions such as leak locations and wind directions, and a dynamic response of structures due to blast loads depends on the load profile. Therefore, a parametric study has to be conducted to investigate the effects of the dynamic response of structural members subjected to various types of load shapes. To do so, a series of CFD analyses was performed using a full-scale FPSO topside model including detail parts of pipes and equipments, and the time history data of the blast loads at monitor points and panels were obtained by the analyses. In this paper, we focus on a structural dynamic response subjected to blast loads changing the magnitude of positive/negative phase pressure and time duration. From the results of linear/nonlinear transient analyses using single degree of freedom(SDOF) and multi-degree-of freedom(MDOF) systems, it was observed that dynamic responses of structures were significantly influenced by the magnitude of positive and negative phase pressures and negative time duration.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.675-682
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• 2015

Current design codes such as AASHTO LRFD or Korean Highway Bridge Design Code recommend of using static force for designing bridge column against vehicle collisions. However, there was an accident that the bridge was collapsed shortly after vehicle impact on bridge pier in Nebraska(near Big Spring, 2003). It was found that the second largest cause of bridge collapse is collision after hydraulic causes. It can be thought that the possibility of truck-bridge collision are getting increasing as the size of truck increases and traffic condition are becoming improved. However, dynamic behavior under the impact loading seldom considered in bridge design procedure due to computational cost and time. In this study, in order to reduce the computational cost for dynamic impact analysis, model reduction method was developed. Obtained results of residual displacement were compared with the results of direct impact simulations.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.6
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• pp.715-722
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• 2011

In this paper, the behavior of nuclear-power plant subjected to an aircraft impact is performed using the parallel analysis. In the erstwhile study of an aircraft impact to the nuclear-power plant, it has been used that the impact load is applied at the local area by using the impact load-time history function of Riera, and the target structures have been restricted to the simple RC(Reinforced Concrete) walls or RC buildings. However, in this paper, the analysis of an aircraft impact is performed by using a real aircraft model similar to the Boeing 767 and a fictitious nuclear-power plant similar to the real structure, and an aircraft model is verified by comparing the generated history of the aircraft crash against the rigid target with another history by using the Riera's function which is allowable in the impact evaluation guide, NEI07-13(2009). Also, in general, it is required too much time for the hypervelocity impact analysis due to the contact problems between two or more adjacent physical bodies and the high nonlinearity causing dynamic large deformation, so there is a limitation with a single CPU alone to deal with these problems effectively. Therefore, in this paper, Message-Passing MIMD type of parallel analysis is performed by using self-constructed Linux-Cluster system to improve the computational efficiency, and in order to evaluate the parallel performance, the four cases of analysis, i.e. plain concrete, reinforced concrete, reinforced concrete with bonded containment liner plate, steel-plate concrete structure, are performed and discussed.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.11 no.1
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• pp.53-62
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• 2017

In this paper, we present the score classification accuracy of BBS(Berg Balance Scale) which is the most commonly used balance evaluation tool using machine learning. Data acquisition was performed using the Noraxon system and an inertial sensor of Noraxon system was attached to the body in 8 locations (left and right ankle, left and right upper buttocks, left and right wrists, back, forehead). Based on the 3-axis accelerometer of the inertial sensor, the feature vector STFT(Short Time Fourier Transform) and SAM(Signal Area Magnitude) were extracted. Then, the items of the BBS were divided into static movement and dynamic movement depending on the operation characteristics, and the feature vectors were selected according to the sensor attachment positions which affect the score for each item of the BBS. Feature vectors selected for each item of BBS were classified using GMM(Gaussian Mixture Model). As a result of the accuracy calculation for 40 subjects, 55.5%, 72.2%, 87.5%, 50%, 35.1%, 62.5%, 43.3%, 58.6%, 60.7%, 33.3%, 44.8%, 89.2%, 51.8%, 85.1%, respectively.

• Journal of the Korean Solar Energy Society
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• v.36 no.6
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• pp.25-35
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• 2016

In this study, the evaluation of the dynamic behavior and thermal performance of the "Façade integrated Natural circulation Solar Water Heating System" installed in the residential house was carried out. Experimental tests were performed during the all year around in the rural houses of $166m^2$ in size. Facade integrated solar collector of $5m^2$ were installed on the south-facing. Electrical heater of 1 kW capacity as an auxiliary heater was installed at the upper part of the heat storage tank. The analyzing results are as follows. (1) Monthly average solar fraction was 51 to 87% and yearly average value is 64%. (2) Hot water supply temperature in December which has the lowest solar altitude is 37 to $76^{\circ}C$. The highest working fluid temperature of solar collector in this period was below $84^{\circ}C$. The temperature difference of working fluid between the collector inlet and outlet has been shown to be around 9 to $26^{\circ}C$. (3) Overheating which is one of the biggest problems during summer did not appear at all, but rather had hot water supply temperature is rather low as $30{\sim}47^{\circ}C$ in summer than winter, which is supplied by a small solar load. The solar collecting temperature has been shown to maintain below $55^{\circ}C$. (5) The thermal performance of Facade integrated solar collector can be increase due to the reduction of heat loss to the back of the collector wall integration of the collector is reduced. As a conclusion, Facade integrated natural circulation type Solar Water Heating System is a well-functioning without any pumps or controllers, and it was found that the disadvantages of conventional solar water heaters, hot water or hot water system can be greatly improved.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.85-85
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• 2017

무동력 복합작업기는 치즐쟁기와 디스크의 배열에 따라 작업성능이 좌우된다. 프레임과 디스크, 치즐쟁기에 가해지는 기본적인 힘의 상태를 확인하기 위한 정적 구조해석을 수행하였다. 복합작업기는 디스크는 $18^{\circ}$가 경사진 형태로 전면9개 후면9로 총 18개, 치즐쟁기(Chiselplow)는 4개로, 디스크는 모두 18개이다. 정적인 상태에서 끄는 견인력은 100마력, 150마력, 200마력으로 하였으며 Inventor의 해석 시스템은 힘을 N으로 사용하기 때문에 각 마력에 부가되는 하중을 N으로 치환하여 사용하였다. 구속조건은 frame과, disc, chisel plow에 맞닿는 면을 구속하고, 힘의 방향은 프레임과 트랙터의 연결면, 디스크 날과 땅의 접촉면에 적용했다. front /rear 디스크는 이론상으로는 양 디스크가 쌍으로 마주하고 있어서 스캔데이타를 중심으로 모델링한 결과를 바탕으로, 전후면 디스크해로우의 해석을 수행하였다. 조립 또는 사용상의 문제점이나 자연적인 유격에 의해 어느 정도 대칭이 되지 않을수 있으나 그 정도에 따라 진동과 내구성에 문제가 될 수도 있기에 한쌍에 대해 모델링을 통한 해석을 수행하였다. 해석결과에 따르면 디스크에 작용하는 폰미세스 응력은 극한강도에 미치지 않은 것으로 나타났으며 Frame의 최대 폰 미세스 응력을 제외하면, 대부분의 응력은 항복강도에 현저히 미치지 못하는 수치이고, 프레임의 경우는 150마력, 200마력으로 힘을 가할 때 항복강도는 넘는 수치이지만 극한인장강도에는 미치지 못하는 수치인 것을 알 수 있었다. 100마력에 폰 미세스 응력의 최대값은 0.161918 MPa이고 프레임 강의 항복강도인 207MPa와 디스크의 항복강도인 250MPa에 못 미치는 수치이다. 150마력과 200마력의 힘으로 회전할 때의 폰 미세스 응력의 최대값은 0.286425MPa과 0.381921 MPa로 항복강도인 250MPa에 크게 못 미치는 수치이다. 그 이유는 디스크해로우 방식의 복합작업기는 견인저항력이 작게 설계되고 작업속도를 개선하기 위한 목적으로 사용되기 때문으로 사료된다. 벤치마킹 기대의 Rear 디스크도 마찬가지로 각도는 $18^{\circ}$이며, 동일한 구속조건을 적용하여 시뮬레이션을 수행하였으며 해석결과는 모두 항복강도 이내로 예측 되었다. 디스크에 최대로 응력이 미치는 부분은 디스크와 프레임이 연결되는 허브 부분이다. 각도가 커짐에 따라 응력이 증가하므로 이를 감안한 설계인자 도출이 가능하다. 마력과 각도가 증가함에 따라 디스크 해로우에 작용하는 폰미세스 응력과, 접촉압력이 증가하므로 이에 대한 검토와 동적하중인 로드프로파일을 적용한 해석을 수행하여 내구수명 특성에 대한 연구를 수행할 계획이다.

• Journal of the Korean Wood Science and Technology
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• v.36 no.6
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• pp.1-12
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• 2008

A series of the studies on the applied physical properties of domestic species have been conducted last three years. Liriodendron tulipifera, Betula costata, Paulownia coreana were examined on sorption property, thermal property, electric property, acoustic property. Because the same apparatus and experimental procedures were used for all species, their results can be easily comparable. The experiments for sorption property were conducted with 80 mesh wood powder and resulted in their EMC's and sorption isotherms. The thermal conductivity and diffusivity, and electric resistance and volumetric electric resistivity were measured with a thermal-wire device and a high electric resistance meter. The differences of the thermal and electric properties between quarter-and flat-sawn specimens were observed, which was partially attributed to their anatomical differences. An acoustic measurement system was used to evaluate dynamic MOE and internal friction. This paper provides the useful fundamental data for designing a wood structure, correcting a portable resistance-type moisture meter, and acoustic properties of wood.

• Journal of Korean Society of Transportation
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• v.17 no.4
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• pp.59-69
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• 1999

A Freeway corridor is a network consisting of a few Primary longitudinal roadways (freeway or major arterial) carrying a major traffic movement with interconnecting roads which offer the motorist alternative paths to his/her destination. Control measures introduced to ameliorate traffic performance in freeway corridors typically include ramp metering at the freeway entrances, and signal control at each intersections. During a severe freeway incident, on-ramp metering usually is not adequate to relieve congestion effectively. Diverting some traffic to the Parallel surface street to make full use of available corridor capacity will be necessary. This is the purpose of the traffic management system. So, an integrated traffic control scheme should include three elements. (a)on-ramp metering, (b)off-ramp diversion and (c)signal timing at surface street intersections. The purpose of this study is to develop an integrated optimal control model in a freeway corridor. By approximating the flow-density relation with a two-segment linear function. the nonlinear optimal control problem can be simplified into a set of Piecewise linear programming models. The formulated optimal-control Problem can be solved in real time using common linear program. In this study, program MPL(ver 4.0) is used to solve the formulated optimal-control problem. Simulation results with TSIS(ver 4.01) for a sample network have demonstrated the merits of the Proposed model and a1gorithm.