• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.3
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• pp.230-234
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• 2009

As concrete ages, the surrounding environment is expected to have growing influences on the concrete. As all the impacts of the environment cannot be considered in the strength-estimating model of a nondestructive concrete test, the increase in concrete age leads to growing uncertainty in the strength-estimating model. Therefore, the variation of the model error increases. It is necessary to include those impacts in the probability model of concrete strength attained from the nondestructive tests so as to build a more accurate reliability model for structural performance evaluation. This paper reviews and categorizes the existing strength-estimating statistical models of nondestructive concrete test, and suggests a new form of the strength-estimating statistical models to properly reflect the model uncertainty due to aging of the concrete. This new form of the statistical models will lay foundation for more accurate structural performance evaluation.

• Geomechanics and Engineering
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• v.4 no.1
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• pp.39-53
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• 2012

Due to strong ground motion of earthquake, the material in the landslide can travel a significant distance from the source. A new landslide model called Multiplex Acceleration Model (MAM) has been proposed to interpret the mechanism of long run-out movement of this type of landslide, considering earthquake behaviors on slope and landslide materials. In previous study, this model was verified by a shaking table test. However, there is a scale limitation of shaking table test to investigate MAM in detail. Thus, numerical simulation was carried out in this study to validate MAM under full scale. A huge rock ejected and A truck threw upwards by seismic force during Wenchuan Earthquake (Ms. 8.0) was discussed based on the simulation results. The results indicate that collisions in P-phase of earthquake and trampoline effect are important behaviors to interpret the mechanism of long run-out and high velocity. The results show that MAM is acceptable and applicable.

• The Journal of Fisheries Business Administration
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• v.45 no.2
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• pp.29-38
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• 2014

This study is to analyse the timing of the structural change of price volatility and the asymmetry of price volatility during the period before and after the timing of the structural change of price volatility using Jeju Farming Olive Flounder's production area market price data from January 1, 2007 to June 30, 2013. The analysis methods of Quandt-Andrews break point test and Threshold GARCH model are employed. The empirical results of this study are summarized as follows: First, the result of Quandt-Andrews break point test shows that a single structural change in price volatility occurred on May 4, 2010 over the sample period. Second, during the period before structural change, daily price change rate has averagely positive value which means price increase, but during the period after structural change daily price change rate has averagely negative value which means price decrease. Also, daily volatility of price change rate during the period before structural change is higher than during the period after structural change. This indicates that price volatility decreases after structural change. Third, the estimation results of Threshold GARCH Model show that the volatility response against price increase is larger during the period after structural change than during the period before structural change. Also the result shows the volatility response against price decrease is larger during the period after structural change than during the period before structural change. And, irrespective of the timing of structural change, price increase has an larger effect on volatility than price decrease. This means volatility is asymmetric at price increase.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.156-159
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• 2008

This paper introduces a remained tensile force estimation method using SI technique based on evolutionary algorithm for externally prestressed tendon. This paper applies the differential evolutionary scheme to SI technique. A virtual model test using ABAQUS 3 dimensional frame model has been made for this work The virtual model is added to the tensile force(28.5kN). Two set of frequencies are extracted respectively from the virtual test and the self-coding FEM 2 dimension model. The estimating tendon tension for the FEM model is 28.31kN. It is that the error in the tendon tension is 1% through the differential evolutionary algorithm. The errors between virtual model and the self-coding FEM model are assumed as the model error.

• Journal of Korean Society for Quality Management
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• v.33 no.3
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• pp.59-70
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• 2005

The purpose of this research is to identify the impact of trust on user acceptance of mobile banking and to identify if causalities among these factors are different between Internet and mobile banking. To test this model, this research applies the technology acceptance model(TAM) that incorporates trust. Additionally, this research use structural equation modeling to test the model and examine cross-group differences using a multi-group comparison method. The empirical results indicate that all path is significant expect the path from trust to intention to use. The results of a multi-group comparison test indicated that the path from trust to attitude, from trust to intention to use, from perceived usefulness to attitude and from perceived to intention to use are different between Internet and mobile banking.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.243-249
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• 2001

In this study, the progressive inelastic deformation, so called, thermal ratchet phenomenon which can occur in high temperature liquid metal reactor was simulated with thermal ratchet structural test facility and 316L stainless steel test cylinder. The inelastic deformation of the reactor baffle cylinder can occur due to the moving temperature distribution along the axial direction as the hot free surface moves up and down under the cyclic heat-up and cool-down of reactor operations. The ratchet deformations were measured with the laser displacement sensor and LVDTs after cooling the structural specimen which experiences thermal load up to $550^{\circ}$ and the temperature differences of about $500^{\circ}C$. During structural thermal ratchet test, the temperature distribution of the test cylinder along the axial direction was measured from 28 channels of thermocouples and the temperatures were used for the ratchet analysis. The thermal ratchet deformation analysis was performed with the NONSTA code whose constitutive model is nonlinear combined kinematic and isotropic hardening model and the test results were compared with those of the analysis. Thermal ratchet test was carried out with respect to 9 cycles of thermal loading and the maximum residual displacements were measured to be 1.8mm. It was shown that thermal ratchet load can cause a progressive deformation to the reactor structure. The analysis results with the combined hardening model were in reasonable agreement with those of the tests.

• Journal of Korean society of Dental Hygiene
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• v.11 no.3
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• pp.313-323
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• 2011

Objectives : The purpose of this study was to examine effect of attribution disposition and self-efficacy on test anxiety in selected college students who major in dental hygiene. This study provides basic data to develop a program for dental hygiene students to reduce test anxiety. Methods : 328 students from A college in Kyungnam, B college in Chunnam and C university in Chungnam who majored in dental hygiene were asked to answer the self-efficacy scale, attribution disposition and test anxiety scale in November and December. 2008. Total of 311 copies were analyzed. Using SPSS 15.0, correlation analysis was conducted and structural model was verified using AMOS 7.0. Evaluation of mediated effect of attribution disposition in suggested structural model was assessed using Sobel verification. Results : 1. Looking at the correlation among self-efficacy, attribution disposition and test anxiety. Self-efficacy had negative relation with external attribution disposition and test anxiety. External attribution disposition had positive relation with test anxiety. 2. Path coefficient from self-efficacy to internal attribution disposition was significant positively and path coefficient from self-efficacy to external attribution disposition was significant negatively. However, the path coefficient from self-efficacy to test anxiety was insignificant. 3. Path coefficient from external attribution disposition to self-efficacy was positively significant. However, the path coefficient from internal attribution disposition to self-efficacy was not significant statistically. 4. In structural model among attribution disposition, test anxiety and self-efficacy, indirect effect of external attribution dispositions was significant statistically. The students with higher self-efficacy showed lower external attribution disposition, the students with lower external attribution disposition showed lower test anxiety. Conclusions : To reduce test anxiety, educators should find a strategy that can improve students' self-efficacy and change their attribution disposition.

• Structural Engineering and Mechanics
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• v.50 no.4
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• pp.471-486
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• 2014

The number of explosive attacks on civilian structures has recently increased. Protection of structure subjected to blast load remains quite sophisticated to predict. The use of the pyramid cover system (PCS) to strengthen sandwich structures against a blast terror has great interests from engineering experts in structural retrofitting. The sandwich steel structure performance under the impact of blast wave effect is highlighted. A 3-D numerical model is proposed to study the PCS layer to strengthen sandwich steel structures using finite element analysis (FEA). Hexagonal core sandwich (XCS) steel panels are used to study structural retrofitting using the PCS layer. Field blast test is conducted. The study presents a comparison between the results obtained by both the field blast test and the FEA to validate the accuracy of the 3-D finite element model. The effects are expressed in terms of displacement-time history of the sandwich steel panels and pressure-time history effect on the sandwich steel panels as the explosive wave propagates. The results obtained by the field blast test have a good agreement with those obtained by the numerical model. The PCS layer improves the sandwich steel panel performance under impact of detonating different TNT explosive charges.

• Geomechanics and Engineering
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• v.32 no.6
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• pp.601-613
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• 2023

Low liquid limit silt, widely distributed in the middle and down reaches of Yellow River, has the disadvantages of poor grading, less clay content and poor colloidal activity. It is very easy to cause vehicle jumping at the bridge-embankment transition section when the low liquid limit silt used as the backfill at the abutment back. In this paper, a series of laboratory tests were carried out to study the physical and mechanical properties of the low liquid limit silt used as back filling. Ground granulated blast furnace slag (GGBFS) was excited by active MgO and hydrated lime to solidify silt as abutment backfill. The optimum ratio of firming agent and the compaction and mechanical properties of reinforced soil were revealed through compaction test and unconfined compressive strength (UCS) test. Scanning electron microscope (SEM) test was used to study the pore characteristics and hydration products of reinforced soil. 6% hydrated lime and alkali activated slag were used to solidify silt and fill the model of subgrade respectively. The pavement settlement regulation and soil internal stress-strain regulation of subgrade with different materials under uniformly distributed load were studied by model experiment. The effect of alkali activated slag curing agent on curing silt was verified. The research results can provide technical support for highway construction in silt area of the Yellow River alluvial plain.

• Structural Engineering and Mechanics
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• v.86 no.6
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• pp.705-714
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• 2023

In order to establish a dynamic model test method of bridge pylons subjected to ocean waves, the similarity method of hydroelastic model test for bridge pylons were analyzed systematically, and a model design and production method was proposed. Using this method, a dynamic test model of a bridge pylon was made, and then a free vibration test on the model structure and a dynamic response test of the model structure under wave actions were conducted in a wave flume. The results of the free vibration test show that the primary natural frequencies of the structure by the model test are close to the design frequencies of the prototype structure, indicating that the dynamic characteristics of the bridge pylon are well simulated by the model structure. The results of the dynamic response test show that wave induced base shear forces and motion responses on the model structure are consistent with the numerical results of the prototype structure. The model test results confirm that the proposed model test design method is feasible and applicable. It has application and reference significances for model testing studies of such marine bridge structures.