• Journal of the Korean Geotechnical Society
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• v.24 no.12
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• pp.85-92
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• 2008

It is necessary to develop a rational design method for surface reinforcement of very soft ground because most current design works rely on merely crude empirical correlations. In this paper, the mechanical behavior of very soft ground that is surficially reinforced was investigated with the aid of a series of numerical analyses. Several material properties of each dredged soft ground, reinforcement and backfill sand mat have been exercised in the numerical analysis. The result of numerical analysis was compared with those of the laboratory model test. Through the matching process between the numerical and experimental result, it is possible to determine representative material properties of the dredged soft ground, reinforcements and backfill sand mat. These verified material properties permit to evaluate the effect of the stiffness of reinforcement and the thickness of sand mat on the overall deformation of the reinforced soft ground.

• Journal of the Korean Geotechnical Society
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• v.23 no.8
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• pp.69-76
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• 2007

Axial behavior of tapered piles is affected by taper angle, stress state of soils, soil frictional angle and pile-soil interface friction angle. In this paper, a series of model pile load tests were performed using a calibration chamber in order to investigate the effect of taper angle on the axial response of cast-in-place tapered piles in sand. According to results of the tests, as taper angle of piles increased, the shaft load capacity of piles increased but its base load capacity decreased. The unit base load capacity of piles increased with increasing taper angle for medium sand but decreased for dense sand. The ratio of shaft to total load capacity increased with increasing taper angle and with decreasing relative density of soils. The test results also showed that total load capacity per unit pile volume increased with increasing taper angle for medium sand, but it decreased for dense sand. Therefore, it can be stated that tapered piles are economically more beneficial for medium sand than for dense sand.

• Composites Research
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• v.21 no.3
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• pp.9-17
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• 2008

In this paper, the low velocity impact characteristics of filament winding CFRP pressure vessel was investigated using numerical and experimental methods. The cylinder part of CFRP vessel was impacted using triangular shape impactor which simulated the sharp edge of dropping tools and impact response behavior of CFRP was reviewed. The mechanical behavior, such as deformation and stress distribution, were also predicted by explicit finite element method and the validity of the model was investigated. For the quantitative evaluation of the residual strength of the pressure vessel after impact, a series of the ring specimens was cut from the impacted vessel and its burst pressure was measured by hydraulic pressure hoop tension test. As the results, the relationship between the residual strength degradation and the impact energy was successively obtained and a useful methodology to evaluate quantitatively the impact damage tolerance of CFRP pressure vessel was established.

• The Journal of the Acoustical Society of Korea
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• v.41 no.6
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• pp.601-609
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• 2022

In August 2007, coastal upwelling occurred off the east coast of Korea, and vertical water temperature and salinity data were obtained from a real-time surface ocean buoy. Based on the time series observation data, a vertical sound velocity structure was calculated before, during, and after the occurrence of the coastal upwelling, and how the coastal upwelling affects the sound propagation and detection environment through acoustic modeling considering the horizontal scale and actual seabed topography. As a result of comparing and analyzing the low-frequency (500 Hz) sound transmission loss and the target detection range by depth using the parabolic equation model, it was analyzed that if coastal upwelling occurs, a detection gain of up to about 10 dB can be expected. In addition, through this study, it was confirmed that the characteristics of sound propagation can be greatly changed even in a short period of about 2 to 3 days before and after coastal upwelling.

• Asia Pacific Journal of Business Review
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• v.7 no.1
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• pp.1-21
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• 2022

This research aimed to clarify the impacts casted by inwards FDI on New venture creation, industrialization, and the economic growth of Russia. For all of these variables, data was taken about Russia from the site of The World Bank, and the selected duration was from 1995 to 2019. The total duration of the data taken was from 24 years. The time duration was well enough for applying the A.R.D.L. approach to the time series data of the study. This research used the unit root test to know the presence of the unit root for each variable, the lag order selection was made for the data, the bounds cointegration test was also applied, and ARDL Model was used to know about the different effects. With the help of the results derived, it was observed that the impact of private sector investment on new venture creation is significant. In contrast, foreign direct investment and research and development (R&D) effects on new venture creation are insignificant. It was also observed from the results that the impact of R&D on industrialization in Russia is significant, while the effects of FDI and the impact of private sector investment on industrialization in Russia is insignificant. We have fund that the effect of FDI and the impact of private sector investment on the economic growth of Russia is significant. In contrast, the impact of R&D is insignificant to the economic growth of Russia. The study is of great significance as it has raised the importance of R&D for industrialization, FDI, and PSI for economic growth and new venture creation for developing countries.

• Journal of Environmental Health Sciences
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• v.49 no.3
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• pp.149-158
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• 2023

Background: Injury is one of the major health problems in South Korea. Few studies have evaluated both intentional and unintentional injury when investigating the association between exposure to air pollutants and injury. Objectives: We aimed to explore the association between short-term exposure to ambient air pollution and years of life lost (YLLs) due to injury. Methods: Data on daily YLLs for 2002~2019 were obtained from the the Death Statistics Database of the Korean National Statistical Office. This study estimated short-term exposure to particulate matter with an aerodynamic diameter of <10 ㎛ (PM₁₀), particulate matter with an aerodynamic diameter of <2.5 ㎛ (PM_2.5), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), carbon monoxide (CO), and ozone (O₃). This time series study was conducted using a generalized additive model (GAM) assuming a Gaussian distribution. We also evaluated a delayed effect of ambient air pollution by constructing a lag structure up to seven days. The best-fitting lag was selected based on smallest generalized cross validation (GCV) value. To explore effect modification by intentionality of injury (i.e., intentional injury [self-harm, assault] and unintentional injury), we conducted stratified subgroup analyses. Additionally, we stratified unintentional injury by mechanism (traffic accident, fall, etc.). Results: During the study period, the average daily YLLs due to injury was 307.5 years. In the intentional injury, YLLs due to self-harm and assault showed positive association with air pollutants. In the unintentional injury, YLLs due to fall, electric current, fire and poisoning showed positive association with air pollutants, whereas YLLs due to traffic accident, mechanical force and drowning/submersion showed negative associations with air pollutants. Conclusions: Injury is recognized as preventable, and effective strategies to create a safe society are important. Therefore, we need to establish strategies to prevent injury and consider air pollutants in this regard.

• Journal of Korean Society for Quality Management
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• v.51 no.2
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• pp.315-327
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• 2023

Purpose: Recently, research has continued to predict the time of failure of the facility through measurement data obtained by attaching a sensor to the facility. However, depending on the facility, it may be difficult to attach a sensor. The purpose of this study is to propose a power generation maintenance plan system based on failure record data obtained from Continuous Ship Unloader, one of the facilities that is difficult to attach sensors. Methods: This study uses data collected from 2012 to 2022 from the 'CSU-1B' model among Continuous Ship Unloader operated by Korea Midland Power Co., LTD. By fitting fault record data to the Weibull distribution, appropriate maintenance cycles and ranges for each target facility subsystem are derived. In addition, maintenance group between subsystems is selected through Euclidean distance, a metric often used for time series data similarity. Through this, a system for establishing an maintenance plan for power generation facilities is proposed. Results: The results of this study are as follows. For the 17 subsystems of the Continuous Ship Unloader, proper maintenance cycles and ranges were determined, and a total of four maintenance groups were chosen. This resulted in the creation of an power generation maintenance plan system and the establishment of an maintenance plan. Conclusion: This study is a case study of power generation facilities. We proposed a maintenance plan system for Continuous Ship Unloader among power generation facilities.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6B
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• pp.561-569
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• 2010

In this study, the impact of climate change on extreme drought events is investigated by comparing drought severity-area-duration curves under present and future climate. The depth-area-duration analysis for characterizing an extreme precipitation event provides a basis for analysing drought events when storm depth is replaced by an appropriate measure of drought severity. In our climate-change impact experiments, the future monthly precipitation time series is based on a KMA regional climate model which has a $27km{\times}27km$ spatial resolution, and the drought severity is computed using the standardized precipitation index. As a result, agricultural drought risk is likely to increase especially in short duration, while hydrologic drought risk will greatly increase in all durations. Such results indicate that a climate change vulnerability assessment for present water resources supply system is urgent.

• Computers and Concrete
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• v.32 no.1
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• pp.99-117
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• 2023

The crack under the influence of the higher intensities of the stresses grows and the structure gets collapsed with the time when the crack length reaches to critical value. Therefore, the fracture behavior of a structure in terms of stress intensity factors (SIF) becomes important to determine the remaining fracture strength and capacity of material and structure for avoiding catastrophic failure, increasing safety and further improvement in the design. The robustness of the method has been demonstrated by comparing the numerical results with analytical and experimental results of some problems. XFEM is used to model cracks and holes in structures and predict their strength and reliability under service conditions. Further, XFEM is extended with a stochastic method for predicting the sensitivity in terms of output COVs and fracture strength in terms of mean values of stress intensity factors (SIFs) of a structure with discontinuities (cracks and holes) under tensile loading condition with input individual and combined randomness in different system parameters. In stochastic technique, the second order perturbation technique (SOPT) has been used for the predicting the fracture behavior of the structures. The stochastic/perturbation technique is also known as Taylor series expansion method and it provides the reliable results if the input randomness is less than twenty percentage. From the present numerical analysis it is observed that, the crack tip near to the hole is under the influence of the stress concentration and the variational effect of the input random parameters on the crack tip in terms of the SIFs are lesser so the COVs are the less sensitive. The COVs of mixed mode SIFs are the most sensitive for the crack angles (α=45° to 90°) for all the values of c₁ and d₁. The plate with the shorter distance between hole and crack is the most sensitive with all the crack angles but the crack tip which is much nearer to the hole has the highest sensitivity.

• Journal of People, Plants, and Environment
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• v.22 no.1
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• pp.75-89
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• 2019

This study aimed to examine the current status of mobile applications for garden design and extract valuable contents for the development of garden design programs for future reference. Mobile applications released in Korean or English on Google Play App Market as of July, 2018 were analyzed in this study (1 application in Korea and 14 applications overseas). The purposes of this study are to analyze the components of the programs for those who actually intend to create a garden and to use it as a resource for developing mobile applications for garden design. Thus, program components and contents were analyzed for garden design applications based on real space (1 application in Korea and 3 applications overseas) that could actually help users. The analysis of mobile applications for garden design shows that while overseas garden programs are rapidly developing in various fields, the number of garden design mobile applications developed in Korea and the amount of information platforms are significantly insufficient. This study suggested flowchart for garden design mobile applications based on the analysis results of existing garden design application. This flowchart includes a series of processes from planning/designing gardens to purchasing plants and facilities to constructing/maintaining gardens for users who intend to design and create a real garden. Furthermore, this study proposed a freemium business model based on 4R(Reflex, Reality, Real place, Real communication) marketing strategies for mobile applications. Realistic experiences can be increased through graphics and information about gardens and plants provided in this study, and location-based information services as well as the creation of systems connected with vendors and suppliers of products related to gardens can induce consumers' purchasing behaviors. Additionally PR activities through various garden-related cultural events are expected to attract more users.