• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.149-155
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• 2008

To evaluate the formulae for the stability of riprap, the formulae of Isbash, California division of highway, Netherlands, ASCE, Pilarczk, and Maynord are comparatively analysed with the experimental results. The critical velocity which initiates the motion of riprap is increased with the weight and the size in diameter and the riprap size with water depth, Froude number, shear velocity with mean velocity, Shields parameter have great correlation with them. The results by 6 formulae are overestimated in riprap size in diameter and the result by Maynord formula proposed by U.S. Army Corps of Engineers estimates rather correct. The results by Isbash, Netherlands, and Pilarczk are overestimated in riprap weight but the result by California division of highway formula coincides with experimental result. In the experimental results of model riprap artificially made by gypsum with light weight density, the critical velocity is increased with shape factors. The critical velocity appears greater in regular arrangement of model riprap than in random arrangement of it. Therefore the shape factor and the degree of interlocking are an important parameters in riprap stability.

• Journal of Nutrition and Health
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• v.39 no.8
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• pp.841-849
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• 2006

This study compared the nutritional quality of Korean adults's consumption of lunch prepared at home, commercial places, and institutions. The one day food intake data collected via 24-hour recall in the 2001 National Health and Nutrition Survey were analyzed. Individuals with 19-64 years of age were selected (n = 5,756). Sampling weights in the Survey were used to generate nationally representative estimates. Lunch was categorized into three groups according to the place where the lunch was prepared. home, commercial places, and institutions such as schools and work places. Comparison among the three groups was made for 19-39 years old men (n = 1,387) and women (n =1,572) and 40-64 years old men (n = 1,364) and women (1,433), respectively. The lunch prepared away from home contained more calories. The lunch prepared commercially was higher in calories percentages from fat than that prepared either at home or at institutions. Across the age and gender groups, lunch prepared at home contribute a high level of sodium intake. Among individuals with 40-64 years of age, but not those with 19-39 years of age, lunch prepared commercially was as sodium dense as that prepared at home. Among individuals with 19-39 years of age, the sodium density of lunch prepared commercially was about the same as that prepared at institutional food service of which the menus were planned by dieticians. Such differences in nutritional quality among meals prepared at home, commercial places, and institutions should be considered and applied for the content development of nutrition education and policy.

• International Journal of Reliability and Applications
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• v.7 no.1
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• pp.27-39
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• 2006

Many real world cases in material failure analysis do not follow perfectly the normal distribution. Forcing of the normality assumption may lead to inaccurate predictions and poor product quality. We examine the failure process of the internal bond (IB or tensile strength) of medium density fiberboard (MDF). We propose a forced censoring technique that closer fits the lower tails of strength distributions and better estimates extremely smaller percentiles, which may be valuable to continuous quality improvement initiatives. Further analyses are performed to build an accelerated common-shaped Weibull model for different product types using the $JMP^{(R)}$ Survival and Reliability platform. In this paper, a forced censoring technique is implemented for the first time as a software module, using $JMP^{(R)}$ Scripting Language (JSL) to expedite data processing, which is crucial for real-time manufacturing settings. Also, we use JSL to automate the task of fitting an accelerated Weibull model and testing model homogeneity in the shape parameter. Finally, a package script is written to readily provide field engineers customized reporting for model visualization, parameter estimation, and percentile forecasting. Our approach may be more accurate for product conformance evaluation, plus help reduce the cost of destructive testing and data management due to reduced frequency of testing. It may also be valuable for preventing field failure and improved product safety even when destructive testing is not reduced by yielding higher precision intervals at the same confidence level.

• Journal of the Korean Data and Information Science Society
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• v.25 no.4
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• pp.715-725
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• 2014

This study uses a quantile regression analysis to investigate intergenerational economic mobility in Korea. The analysis is based on data from the 1st through 11th waves of the Korean Labor and Income Panel Study (KLIPS) conducted from 1998-2008. The household nature of the data allows us to link parents' incomes to children's incomes at different points in time. Using a quantile regression analysis instead of mean one reveals that the effect of fathers' earnings are different across the conditional distribution of sons' earnings, particularly being larger on the upper quantile than on the lower quantile. After controlling effect of sons' college education by including a dummy variable for the degree, however, the pattern among quantile effects for fathers' earnings is no longer clear. Instead a new pattern emerges that education has a much larger effect on the upper quantiles than on the lower ones. Using nonparametric estimates of conditional density curves based on the quantile regression results, we derive some interesting features in graphical forms, which are not obvious in numerical analysis.

• Journal of Environmental Policy
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• v.9 no.4
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• pp.53-76
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• 2010

This paper attempts to estimate and compare environmental Kuznets curves (EKC) for$CO_2$ emissions of five regions constituting South Korea. For this, panel data of $CO_2$ emission for these regions are constucted for the period 1990 - 2007. Close inter-dependency among these five regions is considered by using a seemingly unrelated regression (SUR) model. In addition to real per-capita income, price index of energy sources and population dens ity are included as control variables. Results of estimates show the robust existence of EKC's in all these regions. EKC turning points of five regions range between 13.7 and 21.6 million Korean Won, showing a large variation. This difference among regions should be conisidered for the effective implementation of policies targeting the reduction of $CO_2$ emmission. In addition, the increase of energy price is found help reduce the $CO_2$ emmision while the rise of population density seems to lead to the increase of $CO_2$ emission.

• The Korean Journal of Nuclear Medicine
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• v.32 no.1
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• pp.99-108
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• 1998

Intraperitoneal administration of radioisotopes is suggested to treat the metastatic ovarian cancer in the peritoneal cavity. Administering beta-emitting radioisotopes into the peritoneal cavity allows the maximum energy delivery to the cancerous cells of the peritoneal wall surface while sparing the normal cells located in deep site of the peritoneal wall. In this study, dose estimates of the peritoneal wall are provided to be used for prescribing the amount of $^{166}Ho$-chitosan complex administered. The $^{166}Ho$-chitosan complex diffused in the peritoneal fluid may attach to the peritoneal wall surface. The attachment fraction of $^{166}Ho$-chitosan complex to the peritoneal wall surface is obtained by simulating the ascites with Fischer rats. Both volume source in the peritoneal fluid and the surface source over the peritoneal wall surface are counted for the contribution to the peritoneal wall dose. The Monte Carlo code EGS4 is used to simulate the energy transfer of the beta particles emitted from $^{166}Ho$. A plane geometrical model of semi-infinite volume describes the peritoneal cavity and the peritoneal wall. A semi-infinite plane of $10{\mu}m$ in thickness at every 1 mm of depth in the peritoneal wall is taken as the target in dose estimation. Greater than 98 percents of attachment fraction has been observed from the experiments with Fischer rats. Given $1.3{\mu}Ci/cm^2$ and $2.4{\mu}Ci/ml$ of uniform activity density, absorbed dose is 123 Gy, 8.59 Gy, 3.00 Gy, 1.03 Gy, and .327 Gy at 0 mm, 1 mm, 2 mm, 3 mm, and 4 mm in depth to the peritoneal wall, respectively.

• Geomechanics and Engineering
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• v.6 no.4
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• pp.359-376
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• 2014

Thermal conductivity of ground has a great influence on the performance of Ground Heat Exchangers (GHEs). In general, the ground thermal conductivity significantly depends on the density (or porosity) and the moisture content since they are decisive factors that determine the interface area between soil particles which is available for heat transfer. In this study, a large number of thermal conductivity experiments were conducted for soils of varying porosity and moisture content, and a database of thermal properties for the weathered granite soils was set up. Based on the database, a 3D Curved Surface Model and an Artificial Neural Network Model (ANNM) were proposed for estimating the thermal conductivity. The new models were validated by comparing predictions by the models with new thermal conductivity data, which had not been used in developing the models. As for the 3D CSM, the normalized average values of training and test data were 1.079 and 1.061 with variations of 0.158 and 0.148, respectively. The predictions became somewhat unreliable in a low range of thermal conductivity values in considering the distribution pattern. As for the ANNM, the 'Logsig-Tansig' transfer function combination with nine neurons gave the most accurate estimates. The normalized average values of training data and test data were 1.006 and 0.954 with variations of 0.026 and 0.098, respectively. It can be concluded that the ANNM gives much better results than the 3D CSM.

• The Journal of the Acoustical Society of Korea
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• v.18 no.8
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• pp.94-99
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• 1999

It is the hybrid structure of HMM and neural network(NN) that shows high recognition rate in speech recognition algorithms. And it is a method which has majorities of statistical model and neural network model respectively. In this study, we propose a new style of the hybrid structure of semi-continuous HMM(SCHMM) and radial basis function(RBF), which re-estimates weighting coefficients probability affecting observation probability after Baum-Welch estimation. The proposed method takes account of the similarity of basis Auction of RBF's hidden layer and SCHMM's probability density functions so as to discriminate speech signals sensibly through the learned and estimated weighting coefficients of RBF. As simulation results show that the recognition rates of the hybrid structure SCHMM/RBF are higher than those of SCHMM in unlearned speakers' recognition experiment, the proposed method has been proved to be one which has more sensible property in recognition than SCHMM.

• Journal of IKEEE
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• v.22 no.3
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• pp.651-657
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• 2018

IEEE 802.11 wireless LANs support 20, 40, 80 and 160MHz bandwidth transmission. In general, the data rate increases as the transmission bandwidth increases. However, the transmission power spectral density decreases, which may lead to increasing packet errors and retransmissions. In this paper, we derive a mathematical model of energy consumption with consideration of various factors such as transmission bandwidth, packet error rate and data size. Based on the model, we design a scheme to adapt a transmission bandwidth for each frame transmission. The scheme estimates packet error rates for different bandwidth cases, updates the table of energy consumption and selects the best bandwidth for the next transmission. The simulation study with VoIP traffic shows the energy consumption of the scheme under various environments.

• Journal of Advanced Navigation Technology
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• v.18 no.6
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• pp.533-540
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• 2014

We propose an age estimation-based smart digital signage for the next-generation airport service. The proposed system can recognize the face of the customer so that it can display the selective information. Using a webcam, the system captures the face of the customer and estimates the age of the customer by calculating the wrinkle density of the face and applying bayesian classifier. The developed age estimation method is tested with a face database for the performance evaluation. We expect the new digital signage may improve the satisfaction of customers of the airport business.