• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.3
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• pp.95-106
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• 1983

The probability of failure is used to analyze the reliability of three dimensional slope failure, instead of conventional factor of safety. The strength parameters are assumed to be normal variated and beta variated. These are interval estimated under the specified confidence level and maximum likelihood estimation. The pseudonormal and beta random variables are generated using the uniform probability transformation method according to central limit theorem and rejection method. By means of a Monte-Carlo Simulation, the probability of failure is defined as; $$P_f$$=M/N N: Total number of trials M: Total number of failures some of the conclusions derived from the case study include; 1. If the strength parameters are assumed to be normal variated, the relationship between safety factor and the probability of failure is fairly consistent, regardless of the procedures of analysis and dimensions of assumed rupture surfaces. 2. However if the strength parameters are beta variated, general relationship between $F_s$ and $P_f$ is hardly found.

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.385-388
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• 2002

The researches of a two-phase atomizers have been carried out in the field of automotive and aerospace industries in order to improve the atomization performance of the liquid droplets ejecting from these nozzles. The smaller droplets have the advantages of the reduction of environmental pollution matter and effective use of energy through the improvement of heat and mass transfer efficiency. Thus, to propose the basic information of two-phase flow, an internal mixing atomizer was designed, its shape factor was 0.6 and the liquid feeding hole was positioned at the center of the mixing tube which was used to mix the air and liquid. The experimental work was performed in the field after the nozzle exit orifice. The measurement of the liquid droplets was made by PDPA system. This system can measure the velocity and size of the droplets simultaneously. The number of the droplets used in this calculation was set to 10,000. The flow patterns were regulated by ALR (Air to Liquid mass Ratio). ALR was varied from 0.1024 to 0.3238 depending on the mass flow rate of the air. The analysis of sampling data was mainly focused on the spray characteristics such as flow characteristics distributions, half-width of spray, RMS, and turbulent kinetic energy with ALR.

• Journal of Information Technology Application
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• v.3 no.2
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• pp.83-102
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• 2001

Internet-based shopping business spread rapidly in Korea. Companies are trying to develop and use various strategic competences. The strategies employed by those companies include activities related to the design of shopping site, market positioning, assistance of purchasing process, payment mechanism, and provision of various consumer services. However, the success of these strategies depends on various environmental factors and internal capability of the companies. In this study, I examined four successful Internet shopping mall companies and compared them to draw useful guidelines for Internet-based intermediary business. These four companies were selected because they are all considered successful by now, but brought different background. We found follows. First, each company tried to economize their own historical and developmental background. All of the selected companies were alike in their focus on the whole Internet user group. Customer needs analysis was performed more systematically. The Importance of customer information and the use of it are not sufficient. Second, Each companies consistently emphasized the importance of market-related activities. Despite the differences in initial states, all companies used similar strategies and had similar focus in target market and products. Conclusively, implications from this research for Internet shopping business can be summarized as follows. First, One of the important future directions for Internet shopping mall business is to broaden target market. Second, the provisions of carefully designed customized services are one success factor. Third, As customer traffic increased, the provision of differential customer service becomes a key success factor.

• Journal of the Korean Geotechnical Society
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• v.31 no.10
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• pp.61-76
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• 2015

Recently, geotechnical engineering researches have been conducted on the Limit State Design (LSD) for deep and shallow foundations; however, there are very few studies on the retaining wall. As a basic study for the introduction of the LSD of a railway retaining wall, this study evaluates whether the reliability index satisfies the target reliability index for each failure mode in the standard drawing of the retaining wall. It also analyzes the feasibility of the LSD method by using the Load and Resistance Factor Design (LRFD) for the standard drawing of a retaining wall. In a portion of the standard drawing of the railway retaining wall, the reliability indices of the sliding and bearing capacity failure modes did not satisfy the target reliability index, and could not satisfy the limit state by the LRFD. Hence, the standard drawing of the railway retaining wall will need to be revised if the LSD is to be applied.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.2
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• pp.237-247
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• 2018

The basin characteristics reflect the attributes of geomorphological pattern of basin and stream networks affect the rainfall-runoff. In order to analyze the relationship between the basin runoff and stream morphometric characteristics, the morphometric characteristics were investigated for 27 water-level observation stations on 19 rivers in the Han River basin using Arc-map. The morphometric characteristics were divided into linear, areal and relief aspects for calculation while the annual mean runoff ratio as a basin response by rainfall was estimated using the measured precipitation and discharge to analyze the rainfall-runoff characteristics. The correlation among the morphometric parameters were schematized to analyze the correlations among them. The multiple regression equation for rainfall-runoff ratio was provided with morphometric parameters of stream length ratio, form factor ratio, shape factor, stream area ratio, and relief ratio and the coefficient of determination was 0.691. The RMSE and MAPE between the measured and the estimated annual runoff rates were found as 0.09, 11.61% respectively, the suggested regression equation showed good estimation.

• Journal of Korean Society for Atmospheric Environment
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• v.34 no.1
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• pp.166-176
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• 2018

The n-alkanes which are stable compounds in the atmosphere are emitted by anthropogenic sources and biological sources. The goal of this study is to understand characteristics of n-alkane distributions in $PM_{2.5}$ of the Anmyeon Island which is one of background site in Korea. The concentration of n-alkanes in $PM_{2.5}$ was measured at Anmyeon Island for one year from June 2015 to May 2016. The average concentration of total n-alkanes (${\sum}$ n-alkanes) from C20 to C34 was $14.02{\pm}10.26ng\;m^{-3}$ and ranged from 1.77 to $47.65ng\;m^{-3}$. Various diagnostic parameters were used to identify the source. As a result, it is considered that Anmyeon Island had a large influence of biological sources during non-heating period, while the influence of anthropogenic emission during the heating period was significant. Principle Component Analysis (PCA) was performed and yielded three components that accounted for 93.6% of the total variance in n-alkanes. Factor 1, which accounted for 42.3% of the total variance, indicated anthropogenic source including fossil fuel and biomass combustion, while, Factor 3 was interpreted as the biological sources such as plant wax.

• Food Science and Biotechnology
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• v.16 no.2
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• pp.238-242
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• 2007

Square root models were developed for predicting the kinetics of growth of Listeria monocytogenes in sesame leaves as a function of temperature (4, 10, or $25^{\circ}C$). At these storage temperatures, the primary growth curves fit well ($R^2=0.898$ to 0.980) to a Gompertz equation to obtain lag time (LT) and specific growth rate (SGR). The square root models for natural logarithm transformations of the LT and SGR as a function of temperature were obtained by SAS's regression analysis. As storage temperature ($4-25^{\circ}C$) decreased, LT increased and SGR decreased, respectively. Square root models were identified as appropriate secondary models for LT and SGR on the basis of most statistical indices such as coefficient determination ($R^2=0.961$ for LT, 0.988 for SGR), mean square error (MSE=0.l97 for LT, 0.005 for SGR), and accuracy factor ($A_f=1.356$ for LT, 1.251 for SGR) although the model for LT was partially not appropriate as a secondary model due to the high value of bias factor ($B_f=1.572$). In general, our secondary model supported predictions of the effects of temperature on both LT and SGR for L. monocytogenes in sesame leaves.

• Journal of the Korean Solar Energy Society
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• v.34 no.1
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• pp.81-90
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• 2014

The Jeju-Korea power system is a small-sized network with a system demand ranging from a autumn minimum of 350MW to a summer peak of 716MW. Because Jeju island is well exposed to north-east winds with high speed, applications to connect to Jeju power system are flooded. Considering physical/environmental constraints, Jeju Self-governing Province has also target for the wind power capacity of 1,350MW by 2020. It amounts to two or three times of Jeju average-demand power and wind power limit capacity announced by Korea Power Exchange (KPX) company. Wind farm connection agreements will be signed to maximize utilization of wind resource. In spite of submarine cable HVDC connected to Korea mainland, Jeju power system is independently operated by frequency and reserve control. This study reevaluates wind power limit based on the KPX criteria from 2016 to 2020. First of all wind power generation limit are affected by off-peak demand in Jeju power system. Also the possibility capacity rate of charging wind power output is evaluated by using energy storage system (ESS). As a result, in case of using 110MWh ESS, wind power limit increases 33~55MW(30~50% of ESS), wind power constraint energy decreases from 68,539MWh to 50,301MWh and wind farm capacity factor increases from 25.9 to 26.1% in 2020.

• Atmosphere
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• v.29 no.5
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• pp.537-550
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• 2019

To analyze the observation environment of solar radiation stations operated by the Korea Meteorological Administration (KMA), we analyzed the skyline, Sky View Factor (SVF), and solar radiation due to the surrounding topography and artificial structures using a Digital Elevation Model (DEM), 3D camera, and solar radiation model. Solar energy shielding of 25 km around the station was analyzed using 10 m resolution DEM data and the skyline elevation and SVF were analyzed by the surrounding environment using the image captured by the 3D camera. The solar radiation model was used to assess the contribution of the environment to solar radiation. Because the skyline elevation retrieved from the DEM is different from the actual environment, it is compared with the results obtained from the 3D camera. From the skyline and SVF calculations, it was observed that some stations were shielded by the surrounding environment at sunrise and sunset. The topographic effect of 3D camera is therefore more than 20 times higher than that of DEM throughout the year for monthly accumulated solar radiation. Due to relatively low solar radiation in winter, the solar radiation shielding is large in winter. Also, for the annual accumulated solar radiation, the difference of the global solar radiation calculated using the 3D camera was 176.70 MJ (solar radiation with 7 days; suppose daily accumulated solar radiation 26 MJ) on an average and a maximum of 439.90 MJ (solar radiation with 17.5 days).

• Geophysics and Geophysical Exploration
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• v.12 no.4
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• pp.281-288
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• 2009

Using analytical method, intrinsic absorption and scattering attenuation was lately separated from total quality factor $(Q^{-1}_t)$ on the seismic data of Korean Peninsula. However, we should use numerical method rather than the analytical method to consider depth dependent structure of scattering. The direct simulation Monte Carlo (DSMC) method, as a kind of the numerical method, is good option due to its extended availability from 1 to 3-dimensional model; but there is few study to use it. In this paper, we introduced the analytical method and the DSMC method, and compared the results of the two analysis applied to the isotropic scattering model. While the scattering attenuation coefficients $(\eta_s)$ are identical, the intrinsic absorption coefficients $(\eta_i)$ for the analytical method are larger than those for DSMC method and have large errors. In addition, the $(Q^{-1}_t)$ by the previous studies show closer to DSMC method than analytical method.