• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.1B
• /
• pp.15-25
• /
• 2006

Using kinematic wave equation, the influence of moving storms to runoff was analysised with a focus on watersheds. Watershed shapes used are the oblong, square and elongated shape, and the distribution types of moving storms used are uniform, advanced and intermediate type. The runoff hydrographs according to the rainfall distribution types were simulated and the characteristics were explored for the storms moving down, up and cross the watershed with various velocity. The shape, peak time and peak runoff of a runoff hydrograph are significantly influenced by spatial and temporal variability in rainfall and watershed shapes. A rain storm moving in the cross direction of channel flow produces a higher peak runoff than in the downstream direction and upstream direction. A peak runoff from a storm moving downstream exceeds that from a storm moving upstream. For storms moving downstream peak time was more delayed than for other storm direction in the case of elongated watershed. The runoff volume and time base of the hydrograph decreased with the increasing storm speed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.1D
• /
• pp.203-209
• /
• 2006

SAR (Synthetic Aperture Radar) technology, which is not influenced by cloud cover because of using electromagnetic wave of long wavelength, has an advantage in mapping the earth. NASA, recognizing these strong points of SAR, launched SRTM (Shuttle Radar Topography Mission), and acquired the topographic information of the earth. SRTM and NED (National Elevation Data) of USGS were used for the research and vegetation height map was produced through differentiating the two data. Correlation between SRTM-NED and planting year was analyzed to see the relationship. Strong correlation was detected and it shows the feasibility of estimating timber age and eventually creating timber age map from SRTM-NED. Additional analyses were conducted to check if the linearity is influenced by regional characteristics and forest uniformity. As results, the correlation between SRTM-NED and timber age is influenced by roughness of the terrain. Overall, this paper shows that timber age estimation using SRTM and NED can be sufficiently practical.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.6A
• /
• pp.809-817
• /
• 2008

Recently, the external prestressing method is being much frequently used in strengthening reinforced concrete structures because of it's excellent load resistance and serviceability increases comparing to other strengthening methods. However, it is true that the research on fatigue performance of concrete structures strengthened by the external prestressing using FRP tendons is rare. Therefore, the purpose of this study is to evaluate the safety and feasibility of the external prestressing method by analyzing the characteristics of the reinforced concrete beam strengthening using FRP tendons under repeated loads. Test variables adopted in this experimental study are the types of external prestressing material (steel or FRP tendon) and the repeated load ranges. The repeated load range have the minimum 50% of yield load of reinforced concrete beam and the maximum 70-85%. The test beams are loaded by 4 point loadings with 3 Hz sine wave. From this experimental study, it is confirmed that the reinforced concrete beams strengthened using FRP tendons have sufficient safety against fatigue, especially in FRP tendon itself, tendon at deviators and tendon at anchorages.

• Earthquakes and Structures
• /
• v.25 no.1
• /
• pp.27-41
• /
• 2023

This study focused on nonlinear effective stress site response analysis using two coupled constitutive models, that is, the DM model (Dafalias and Manzari 2004), which incorporated a simple plasticity sand model accounting for fabric change effects, and the PMDY03 model (Khosravifar et al. 2018), that is, a 3D model for earthquake-induced liquefaction triggering and postliquefaction response. A detailed parametric study was conducted to validate the effectiveness of nonlinear site response analysis and porewater pressure (PWP) generation through a true coupled formulation for assessing the initiation of liquefaction at ground level. The coupled models demonstrated accurate prediction of liquefaction triggering, which was in line with established empirical liquefaction triggering relations in published databases. Several limitations were identified in the evaluation of liquefaction using the cyclic stress method, despite its widespread implementation for calculating liquefaction triggering. Variations in shear stiffness, represented by changes in shear wave velocity (Vs1), exerted the most significant influence on site response. The study further indicated that substantial differences in response spectra between nonlinear total stress and nonlinear effective stress analyses primarily occurred when liquefaction was triggered or on the verge of being triggered, as shown by excess PWP ratios approaching unity. These differences diminished when liquefaction occurred towards the later stages of intense shaking. The soil response was predominantly influenced by the higher stiffness values present prior to liquefaction. A key contribution of this study was to validate the criteria used to assess the triggering of level-ground liquefaction using true coupled effective-stress constitutive models, while also confirming the reliability of numerical approximations including the PDMY03 and DM models. These models effectively captured the principal characteristics of liquefaction observed in field tests and laboratory experiments.

• Computers and Concrete
• /
• v.32 no.1
• /
• pp.15-26
• /
• 2023

In order to study the anti-seismic performance of full light-weight concrete utility tunnel, EL Centro seismic waves were input, and the seismic simulation shaking table test was carried out on the four utility tunnel models. The dynamic characteristics and acceleration response of the system consisting of the utility tunnel structure and the soil, and the interlayer displacement response of the structure were analyzed. The influence law of different construction methods, haunch heights and concrete types on the dynamic response of the utility tunnel structure was studied. And the experimental results were compared with the finite element calculation results. The results indicated that with the increase of seismic wave intensity, the natural frequency of the utility tunnel structure system decreased and the damping ratio increased. The assembling composite construction method could be equivalent to replace the integral cast-in-place construction method. The haunch height of the assembling composite full light-weight concrete utility tunnel was increased from 30 mm to 50 mm to enhance the anti-seismic performance during large earthquakes. The anti-seismic performance of the full light-weight concrete utility tunnel was better than that of the ordinary concrete utility tunnel. The peak acceleration of the structure was reduced by 21.8% and the interlayer displacement was reduced by 45.8% by using full light-weight concrete. The finite element simulation results were in good agreement with the experimental results, which could provide reference for practical engineering design and application.

• Journal of Korea Entertainment Industry Association
• /
• v.13 no.7
• /
• pp.219-227
• /
• 2019

In this paper, we proactively looked at the structure and characteristics of each instrument in order to compare and analyze the sound colors of the western violin, chinese erhu and korean haegeum, which are representative bow string instruments. Also, many performers have simply been unable to fully explain how the violin is rich in pitch and the haegeum has a unique tone. Also, many performers thinks that violin sounds rich just because it has many overtones and have been unable to fully explain how haegeum makes unique tone. While previous research data show that most instruments are studied and published by analyzing their own frequencies or related cases of acoustic studies, this study provides a visual look how the harmonics composition, which determines musical instruments' timbres, consists of and suggests data specifically by analyzing each sound pressure of integer multiple overtones so that the structure of instruments' unique timbre can be understood. Based on this, we hope that it will be of considerable help to the development of virtual musical instruments of korean traditional instruments, which are relatively small compared to western virtual instruments, by reproducing instrument sounds through the synthesizers in the future.

• Journal of Korea Entertainment Industry Association
• /
• v.13 no.4
• /
• pp.71-82
• /
• 2019

Today's media environment is becoming very complicated and the trend of media convergence is getting clearer. The convergence of media is the supreme hot issue. In this wave of convergence, there has also been a huge change between movies and electronic games. The remake boom between them showed a tremendous economic effect that can be achieved by exchanging two media of essentially different characteristics. As computer virtual reality technologies evolve, electronic games will provide a virtual world that can satisfy the demands of the visual, auditory, and tactile aspects very real to the public with the Internet. At that time, movies and other media will be thoroughly melted into the virtual world created by electronic games, and they will become an element of the virtual world as those media that exist in the truth world.

• Korean Journal of Social Welfare Studies
• /
• v.43 no.2
• /
• pp.61-85
• /
• 2012

The purpose of this study is to examine whether the national pension affects the life satisfaction of old age, using the first and third-wave data from the Korean Retirement and Income Study. The study analyzes the relationship between the national pension and life satisfaction, using several operational definitions of these two variables. This study utilizes the Difference-in-Difference(2D) models and panel data analysis. The main results are : First, the result of simple 2D shows that there is not significantly difference between the pensioner and that of non-pensioner. Second, the result of 2D regression also shows that pension is not significantly associated with life satisfaction of the old age. Lastly, the result of fixed-effect model confirms that the national pension does not have a statistically meaningful effect on the life satisfaction, controling for the unobserved characteristics of the old age. This study also conducts sensitivity analysis and discusses policy implications.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2022.10a
• /
• pp.194-196
• /
• 2022

When electromagnetic wave transmitted from the radar antenna hits the target, a specific type of electric field is formed according to the electrical characteristics and appearance of the target, which is called an RCS pattern. There are various commercial programs that calculate the RCS of the target and plot the RCS pattern. For the analysis of large targets such as warships or ships, a program with a high frequency analysis method, which has a faster calculation speed than the low frequency analysis method is suitable. XGTD, a high-frequency analysis program, can quickly plot a two-dimensional RCS pattern for 360 degrees of a target, but a three-dimensional RCS pattern cannot be obtained. In this paper, it is proposed that a method of plotting two-dimensional RCS patterns of a target from various angles using XGTD, generating a three-dimensional RCS pattern using this, and converting it into a three-dimensional antenna pattern file.

• Journal of Korean Academy of Dental Administration
• /
• v.11 no.1
• /
• pp.54-61
• /
• 2023

This study was conducted to identify factors related to discomfort while speaking in the elderly and provide fundamental data for establishing oral health care policies for a healthy old age. Using the raw data from the 8th wave of the National Health and Nutrition Examination Survey (2020), we conducted an analysis to examine the relationship between speaking discomfort and mental health, as well as oral health care behavior, among 1,278 elderly individuals in Korea. Differences in speaking discomfort were analyzed based on general characteristics, mental health, and oral health care behavior using complex sample cross-analysis. Additionally, factors associated with speaking discomfort were analyzed using complex sample multiple logistic regression analysis. As a result, individuals with depression experienced higher levels of speaking discomfort (p<0.05), and individuals experiencing high levels of stress also reported higher levels of speaking discomfort (p<0.05). As a factor affecting speaking discomfort, it was found that speaking discomfort was 2.56 times higher (p<0.001) when dental care was not met, and speaking discomfort was 3.05 times higher (p<0.05) when teeth brushing was less frequent. As a result of the aforementioned findings, it is believed that a customized oral health promotion program is necessary to expand dental health insurance coverage for the elderly and improve oral healthcare.