• Journal of the Korea Concrete Institute
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• v.20 no.2
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• pp.147-156
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• 2008

In an uniaxial compressive test of a concrete standard specimen (150$\times$300 mm) the crack initiation and extension with the stress increase are the major reason of the failure, which is similar to the breakage of the particle bonding in the simulation by using particle bonded model, especially particle flow code in 3 dimensions (PFC3D) developed by Itasca Consulting Group Inc. That is the main motive to study the possibility of an uniaxial compressive strength test simulation. It is important to investigate the relationship between the micro-parameters and the macro-properties because the 3-dimensional particle bonded model uses the spherical particles to analyze the physical phenomena. Contact bonded model used herein has eight micro-parameters and there are five macro-properties; Young's modulus, Poisson's ratio, uniaxial compressive strength and the crack initiation stress and the ratio concerning the crack propagation with the stress. To simulate the compressive test we made quantitative relationships between the micro-parameters and the macro-properties by using the fractional factorial design and various sensitivity analyses including regression analysis, which result in the good agreement with the previous studies. Also, the stress-stain curve and the crack distribution over the specimen given by PFC3D showed the mechanical behavior of the concrete standard specimen under the uniaxial compression. It is concluded that the particle bonded model can be a good tool for the analyzing the mechanical behavior of concrete under the uniaxial compressive load.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.2
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• pp.106-121
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• 2020

In order to make harbor outskirt facilities robust using the reliability-based design, probabilistic models of wave heights at varying stage of shoaling process optimized for Korean sea waves are prerequisite. In this rationale, we numerically simulate the nonlinear shoaling process of random waves over the beach with a sandbar at its foreshore. In doing so, comprehensive numerical models made of spatially filtered Navier-Stokes Eq., LES [Large Eddy Simulation], dynamic Smagorinsky turbulence closure were used. Considering the characteristics of swells observed at the east coast of Korean Peninsula, random waves were simulated using JONSWAP wave spectrum of various peak enhancement coefficients and random phase method. The coefficients of probabilistic models proposed in this study are estimated from the results of frequency analysis of wave crests and its associated trough detected by Wave by Wave Analysis of the time series of numerically simulated free surface displacements based on the threshold crossing method. Numerical results show that Modified Glukhovskiy wave height distribution, the most referred probabilistic models at finite water depth in the literature, over-predicts the occurring probability of relatively large and small wave heights, and under predicts the occurrence rate of waves of moderate heights. On the other hand, probabilistic models developed in this study show vary encouraging agreements. In addition, the discrepancy of the Modified Glukhovskiy distribution from the measured one are most visible over the surf zone, and as a result, the Modified Glukhovskiy distribution should be applied with caution for the reliability-based design of harbor outskirt facilities deployed near the surf-zone.

• Journal of Korea Water Resources Association
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• v.43 no.8
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• pp.695-707
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• 2010

The frequency and size of typhoon and local severe rainfall are increasing due to the climate change and the damage also increasing from typhoon and severe rainfall. The flood forecasting and warning system to reduce the damage from typhoon and severe rainfall needs forecasted rainfall using radar data and short-term rainfall forecasting model. For this reason, this study examined the applicability of short-term rainfall forecast using translation model with weather radar data to point out that the utilization of flood forecasting in Korea. This study estimated the radar rainfall using Least-square fitting method and estimated rainfall was used as initial field of translation model. The translation model have verified accuracy of forecasted radar rainfall through the comparison of forecasted radar rainfall and observed rainfall quantitatively and qualitatively. Almost case studies showed that accuracy is over 0.6 within 4 hours leading time and mean of correlation coefficient is over 0.5 within 1 hours leading time in Kwanak and Jindo radar site. And, as the increasing the leading time, the forecast accuracy of precipitation decreased. The results of the calculated Mean Area Precipitation (MAP) showed forecast rainfall tend to be underestimated than observed rainfall but the correlation coefficient more than 0.5. Therefore it showed that translation model could be accurately predicted the rainfall relatively. The present results indicate that possibility of translation model application of Korea just within 2 hours leading forecasted rainfall.

• Journal of Korea Water Resources Association
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• v.55 no.9
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• pp.679-686
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• 2022

As the occurrences of flash floods have increased due to climate change, faster and more accurate precipitation observation using X-band radar has become important. Therefore, the Ministry of Environment installed two dual-pol X-band radars at Samcheok and Uljin. The radar data used in this study were obtained from two different elevation angles and composed to reduce the shielding effect. To obtain quantitative rainfall, quality control (QC), K_DP retrieval, and Hybrid Surface Rainfall (HSR) methods were sequentially applied. To improve the accuracy of the quantitative precipitation estimation (QPE) of the X-band radar, we retrieved parameters for the relationship between rainfall rate and specific differential phase, which is commonly called the R-K_DP relationship; hence, an empirical approach was developed using multiple rain gauges for those two radars. The newly suggested relationship, R = 27.4K^0.81_DP, slightly increased the correlation coefficient by 1% more than the relationship suggested by the previous study. The root mean square error significantly decreased from 3.88 mm/hr to 3.68 mm/hr, and the bias of the estimated precipitation also decreased from -1.72 mm/hr to -0.92 mm/hr for overall cases, showing the improvement of the new method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.235-245
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• 2021

Recently, the frequency of torrential rain is increasing due to climate change, which causes a large amount of debris flows. The purpose of this study was to understand the flow characteristics of debris flow according to the change in channel slope and volumetric sediment concentration and to analyze the effects of a berm on the flow characteristics of debris flow. The flow characteristics of debris flow, such as flow velocity, flow depth, Froude number, and flow resistance coefficients, were calculated using laboratory tests. The effect of a berm was analyzed by comparing the experimental results of a linear channel with those of a one-stepped channel. The results showed that the channel slope affected the flow velocity and flow depth, and the volumetric sediment concentration affected the flow velocity and flow depth, Froude number, and flow resistance coefficient. Moreover, as a berm was installed, the flow velocity and flow depth decreased by up to 26.1% and 71.2%, respectively. This means that installing a berm reduces the flow velocity, thereby reducing the mobility and kinetic energy. These results provide useful information to understand better the flow characteristics of debris flow and the effectiveness of a berm.

• Journal of Korea Entertainment Industry Association
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• v.15 no.8
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• pp.305-313
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• 2021

This study aimed to discover the satisfaction of physical therapy students' major education and the perception of the occupational value of physical therapists and provided basic data to be used for career guidance of college students majoring in physical therapy. A questionnaire survey was conducted online to collect data on participants' general characteristics, motivation for joining the Department of Physical Therapy, satisfaction with their academic majors, and perception of occupational and social value of physical therapy. Using SPSS version 28, frequency and correlation analyses were undertaken and a Chi-square test performed for 174 respondents. As a result of the study, there was no significant difference in major education satisfaction according to gender and grade with as each p-value .368, .685. There was a significant difference in perception of job value according to gender as a p-value .032, and there was no significant difference in the p-value according to gender of .463. There was no significance difference in social job perception according to gender and grade with as each p-value .483, .077. There was positive correlation with the correlation coefficient of .483 that analyzed the level of perception of occupational value of physical therapists according to satisfaction of major education. In conclusion, students's high satisfaction with their academic majors exhibited considerable correlation with their perceived high occupational value of physical therapy. It is believed that these results can be used in career guidance for college students majoring in physical therapy.

• The Journal of the Convergence on Culture Technology
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• v.9 no.2
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• pp.349-355
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• 2023

This study attempted to investigate the effect of competitive anxiety on injury psychology according to the athletic career of tennis athletes at Chinese universities. To study the method, 208 athletes enrolled in a four-year university (0 university, 0 university) located in A City, Hanam Province, were surveyed for a total of three weeks from the end of January to the beginning of February 2023. To verify the research model, frequency analysis, exploratory factor analysis, reliability analysis, and correlation analysis were conducted using SPSS Statistics 25. And independent sample t-test and one-way ANOVA were conducted to find out the differences in variables according to general characteristics, and multiple regression analysis was conducted to verify hypotheses through the concept of measurement. As a result of the study, first, it was found that there was a significant difference in the athletic career of tennis athletes at West China University. Second, the non-standardized coefficient of competition anxiety was found to have a positive (+) effect on exercise weaponry. Third, the non-standardized coefficient of competition anxiety was found to have a positive (+) effect on anxiety and anxiety. Therefore, it was found that other competitive anxiety in the exercise career had an effect on injury psychology. Since competition anxiety according to the athletic career of tennis athletes at Chinese universities affects injury psychology, it suggests that a psychological program that can control competition anxiety and injury psychology of athletes should be developed and introduced to athletes.

• Journal of Navigation and Port Research
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• v.48 no.3
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• pp.192-199
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• 2024

Wave overtopping is a significant natural hazard that occurs in coastal areas, primarily driven by high waves, particularly those generated during typhoons, which can cause coastal flooding. The development of residential and commercial areas along the coast, driven by increasing social and economic demands, has led to a concentration of people and assets in these vulnerable areas. This, coupled with long-term sea level rise and an increase in typhoon frequency, has heightened the risk of coastal hazards. Traditionally, the evaluation of wave overtopping volumes has relied on directly measuring the collected volume of water that exceeds the crest height of structures through hydraulic model experiments. These experiments are averaged over a specific measurement period. However, in this study, we propose a new method for estimating individual wave overtopping volumes. We utilize the temporal variation of wave overtopping heights to develop an observation system that can quantitatively assess wave overtopping volumes in actual coastal areas. To test our method, we conducted hydraulic model experiments on rubble mound breakwaters, which are commonly installed along the Korean coast. We introduce wave overtopping discharge coefficients, assuming that the inundation velocity from the structure's crest is the long-wave velocity. We then predict overtopping volumes based on wave overtopping heights and compare and review the results with experimental data. The findings of our study confirm the feasibility of estimating wave overtopping volumes by applying the overtopping discharge coefficients derived in this study to wave overtopping heights.

• Journal of the Korean Society for information Management
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• v.19 no.1
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• pp.163-187
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• 2002

The objective of this study was not only to evaluate different academic library homepages but to hit upon and suggest a reformation plan for their future improvement. For this purpose. academic library web pages of Korea were divided into three major groups -- those of national universities, private ones, and junior colleges. Their web pages were evaluated using a number of criteria. Also, their circumstances and problems were tried to grasp and the methods to be corrected were suggested in this thesis. Literature review were performed for this study and suggestions and advices from professional groups that is called Delphi method were used as a tool to achieve the objective of this study. For a basic analysis, frequency analysis and descriptive statistics were used for analysing data. Also, t-test, ANOVA, and chi-square analysis were used to examine whether there are any significant differences in each groups or not. and Pearson product-moment correlation coefficients were used to find out the correlation among several variables.

• Korean Journal of Childcare and Education
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• v.8 no.3
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• pp.229-247
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• 2012

The purpose of this study is to investigate the level of mothers' parenting stress according to the knowledge and behaviors that mothers have on infant development. The subjects of this study are 145 mothers whose infants range in age from 18 to 36 months. The instruments used are: 1) Knowledge of Child Development Inventory (KCDI) (Larsen & Juhasz, 1986), 2) Q-sort modified by Ahn (2001), 3) Parenting Stress Scale (PSS) (Kim & Kang, 1997), and a demographic questionnaire. The data analyses used SPSS 12.0 which employs basic statistics, a reliability test, ANOVA and Pearson's correlation. The results of this study indicate a correlation (r= -.20*) between behaviors of child-rearing and parenting stress of mothers. Specifically, mothers behaviors of child-rearing related to cognition development could predict parenting stress.