• Journal of the Korean earth science society
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• v.41 no.6
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• pp.684-694
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• 2020

In this study, we developed a rubric for assessing middle school students' conceptual understanding about dew point. For this purpose, we analyzed 9th grade students' responses collected by using a multi-tiers constructed-response item of National Assessment of Educational Achievement (NAEA) and classified the types of the responses according to their characteristics. In addition, we analyzed the distribution of student response types according to mean achievement scores and developed an assessment rubric of conceptual understanding about dew point. The findings are as follows: First, the analysis of student responses to finding dew point in the saturation curve showed that many students had no or lack understanding of the scientific concept of dew point. Second, as a result of analyzing the student response to the water vapor condensation process at dew point, the proportion of scientific conception types was very low, while the proportion of misconception types was relatively high and the types varied as well. Third, a four- level assessment rubric was developed based on the analysis of the distribution of student response types according to the mean achievement scores. Based on the findings, we suggested the development and utilization of assessment rubric in the field of Earth science education.

• Journal of the Korean earth science society
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• v.39 no.1
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• pp.103-116
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• 2018

The purpose of this study was to explore $6^{th}$ graders learning progression for lunar phase change focusing astronomical systems thinking. By analyzing the results of previous studies, we developed the constructed-response items, set up the hypothetical learning progressions, and developed the item analysis framework based on the hypothetical learning progressions. Before and after the instruction on the lunar phase change, we collected test data using the constructed-response items. The results of the assessment were used to validate the hypothetical learning progression. Through this, we were able to explore the learning progression of the earth-moon system in a bottom-up. As a result of the study, elementary students seemed to have difficulty in the transformation between the earth-based perspective and the space-based perspective. In addition, based on the elementary school students' learning progression on lunar phase change, we concluded that the concept of the lunar phase change was a bit difficult for elementary students to learn in elementary science curriculum.

• Journal of the Korean earth science society
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• v.39 no.3
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• pp.260-274
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• 2018

The purpose of this study was to propose curriculum and teaching sequence for seasonal change by exploring a learning progression. For the purpose, 4 steps of construct modeling approach (specifying construct, item design, outcome space, and measurement model) proposed by Wilson (2005) was applied. In the stage of specifying construct, 'length of shadow according to seasons', 'position of constellation according to seasons', 'seasons of the southern hemisphere and northern hemisphere', 'cause and phenomenon of seasonal change' were selected as the subconstructs of seasonal changes, and constructed a construct map showing the level of development from level 1 to level 4 for each subconstruct based on the results of the previous research. In the item design stage, we developed five assessment items consisting of 3 items in the form of C-E (choose and explain) and two items in the form of CR (constructed response), applied it to 383 elementary, middle and high school students. In the outcome space stage, the students' responses to the assessment items were categorized based on the construct map. The categories were classified into 4 levels according to student ability and scores of 1-4 were given. In the measurement model stage, we applied the partial credit model of the Rasch model and compared whether the learning pathway created from the results of students' response coincides with the construct map. Based on the results of the research, we modified the construct map and finally created hypothetical learning progression on seasonal change. Finally, we proposed an orientation of curriculum amendment and effective teaching sequence for seasonal change.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.114-121
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• 2009

In this study, acceleration responses of caisson structures under various environmental conditions are experimentally examined as a basic study to develop the health assessment technique for harbor structures. To achieve the objective, three approaches are implemented. Firstly, a target caisson structure is selected and its small-scaled caisson is constructed in the laboratory. Secondly, a finite element model of the caisson is generated to identify dynamic responses of the baseline structure. Thirdly, experimental tests are performed on the caisson model to examine dynamic responses under various boundary conditions and impact locations. Four different boundary conditions, 'standing on concrete floor', 'standing on styrofoam block', 'standing on sand-mat' and 'hanging by crane', are considered and correlation coefficients of frequency response functions between four states are analyzed.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.3
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• pp.171-180
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• 2016

Earthquake event keeps increasing every year, and the recent cases of earthquake hazards invoke the necessity of seismic study in Korea, as geotechnical earthquake hazards, such as strong ground motion, liquefaction and landslides, are a significant threat to structures in industrial hub areas including coastal facilities. In this study, systemized framework of integrated assessment of earthquake-induced geotechnical hazard was established using advanced geospatial database. And a visible simulation of the framework was specifically conducted at two coastal facility areas in Incheon. First, the geospatial-grid information in the 3D domain were constructed with geostatistical interpolation method composed of multiple geospatial coverage mapping and 3D integration of geo-layer construction considering spatial outliers and geotechnical uncertainty. Second, the behavior of site-specific seismic responses were assessed by incorporating the depth to bedrock, mean shear wave velocity of the upper 30 m, and characteristic site period based on the geospatial-grid. Third, the normalized correlations between rock-outcrop accelerations and the maximum accelerations of each grid were determined considering the site-specific seismic response characteristics. Fourth, the potential damage due to liquefaction was estimated by combining the geospatial-grid and accelerations correlation grid based on the simplified liquefaction potential index evaluation method.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1077-1092
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• 2007

The structural analysis model for estimate of load carrying capacity of railway bridge on service line is important to determine safety of bridges in service, we need to take response of bridge exactly, applying analysis model similar to the real railway bridge most. Track structure which is to distribute loads and decrease vibrations occurred from running train is constructed on the railway bridges. And it is important factor which should be considered to understand exact dynamic and static responses of bridge. But track structure is currently classified as a none structural members in the structural analysis model for estimating load carrying capacity of railway bridge and not considered in analysis model. That's the reason it is difficult to understand exact behavior of bridges. Therefore, the major objective of this study is to develop an analytical track-bridge model which is similar to real railway bridges considering track structure for safety assessment of railway bridge on service line to be effectively done.

• Earthquakes and Structures
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• v.10 no.3
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• pp.645-667
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• 2016

The 750 m long "De Bosset" bridge in the Cephalonia Island of Western Greece, being the area with the highest seismicity in Europe, was constructed in 1830 by successive stone arches and stiff block-type piers. The bridge suffered extensive damages during past earthquakes, such as the strong M7.2 earthquake of 1953, followed by poorly-designed reconstruction schemes with reinforced concrete. In 2005, a multidisciplinary project for the seismic assessment and restoration of the "De Bosset" bridge was undertaken under the auspices of the Greek Ministry of Culture. The proposed retrofitting scheme combining soil improvement, structural strengthening and reconstruction of the deteriorated masonry sections was recently applied on site. Design of the rehabilitation measures and assessment of the pre- and post-interventions seismic response of the bridge were based on detailed in-situ and laboratory tests, providing foundation soil and structural material properties. In-situ inspection of the rehabilitated bridge following the strong M6.1 and M6.0 Cephalonia earthquakes of January 26th and February 3rd 2014, respectively, revealed no damages or visible defects. The efficiency of the bridge retrofitting is also proved by a preliminary performance analysis of the bridge under the recorded ground motion induced by the above earthquakes.

• Computers and Concrete
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• v.11 no.1
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• pp.51-61
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• 2013

This paper describes earthquake response of the Arhavi Highway Tunnel its geometrical properties, 3D finite element model and the linear time history analyses under a huge ground motion considering soil-structure interaction. The Arhavi Highway Tunnel is one of the tallest tunnels constructed in the Black Sea region of Turkey as part of the Coast Road Project. The tunnel has two tubes and each of them is about 1000 m tall. In the study, lineartime history analyses of the tunnel are performed applying north-south, east-west and up accelerations components of 1992 Erzincan, Turkey ground motion. In the time history analyses, Rayleigh damping coefficients are calculated using main natural frequency obtained from modal analysis. Element matrices are computed using the Gauss numerical integration technique. The Newmark method is used in the solution of the equation of motion. Because of needed too much memory for the analyses, the first 10 second of the ground motions, which is the most effective duration, is taken into account in calculations. The results obtained 3D finite element model are presented. In addition, the displacement and stress results are observed to be allowable level of the concrete material during the earthquakes.

• Journal of Institute of Control, Robotics and Systems
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• v.19 no.4
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• pp.299-305
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• 2013

The complexity and severe nonlinearity of multi-machine power systems make it difficult to design a control input for voltage regulation using modern control theory. This paper presents a model-based PID control scheme for the regulation of the bus voltage to a desired value. To this end, a fourth-order linear system is constructed using input and output data obtained using the TSAT (Transient Security Assessment Tool); the input is assumed to be applied to the grid through the STATCOM (STATic synchronous COMpensator) and the output from the grid is a bus voltage. On the basis of the model, it is identified as to which open-loop poles of the system make the response to a step input oscillatory. To reduce this oscillatory response effectively, a model-based PID control is designed in such a way that the oscillatory poles are no longer problematic in the closed loop. Simulation results show that the proposed PID control dampens the response effectively.

• Structural Engineering and Mechanics
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• v.77 no.2
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• pp.231-243
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• 2021

In this paper, a dynamic response mapping model of the wheel-rail system is established by using the support vector regression (SVR) method, and the hierarchical safety thresholds of the subgrade void are proposed based on the reliability theory. Firstly, the vehicle-track coupling dynamic model considering the subgrade void is constructed. Secondly, the subgrade void area, the subgrade compaction index K30 and the fastener stiffness are selected as random variables, and the mapping model between these three random parameters and the dynamic response of the wheel-rail system is built by using the orthogonal test and the SVR. The sensitivity analysis is carried out by the range analysis method. Finally, the hierarchical safety thresholds for the subgrade void are proposed. The results show that the subgrade void has the most significant influence on the carbody vertical acceleration, the rail vertical displacement, the vertical displacement and the slab tensile stress. From the range analysis, the subgrade void area has the largest effect on the dynamic response of the wheel-rail system, followed by the fastener stiffness and the subgrade compaction index K30. The recommended safety thresholds for the subgrade void of level I, II and III are 4.01㎡, 6.81㎡ and 9.79㎡, respectively.