• Water Engineering Research
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• v.2 no.1
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• pp.1-10
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• 2001

The frequency analyses for the precipitation data in Korea were performed. We used daily maximum series, monthly maximum series, and annual series. For nonparametric frequency analyses, variable kernel estimators were used. Nonparametric methods do not require assumptions about the underlying populations from which the data are obtained. Therefore, they are better suited for multimodal distributions with the advantage of not requiring a distributional assumption. In order to compare their performance with parametric distributions, we considered several probability density functions. They are Gamma, Gumbel, Log-normal, Log-Pearson type III, Exponential, Generalized logistic, Generalized Pareto, and Wakeby distributions. The variable kernel estimates are comparable and are in the middle of the range of the parametric estimates. The variable kernel estimates show a very small probability in extrapolation beyond the largest observed data in the sample. However, the log-variable kernel estimates remedied these defects with the log-transformed data.

• Korean Journal of Ecology and Environment
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• v.43 no.1
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• pp.161-167
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• 2010

In this study, we implemented an experimental approach of ecological model development in order to emphasize the importance of input variable selection with respect to time-delayed arrangement between input and output variables. Time-series modeling requires relevant input variable selection for the prediction of a specific output variable (e.g. density of a species). Inadequate variable utility for input often causes increase of model construction time and low efficiency of developed model when applied to real world representation. Therefore, for future prediction, researchers have to decide number of time-delay (e.g. months, weeks or days; t-n) to predict a certain phenomenon at current time t. We prepared a total of 3,900 equation models produced by Time-Series Optimized Genetic Programming (TSOGP) algorithm, for the prediction of monthly averaged density of a potamic phytoplankton species Stephanodiscus hantzschii, considering future prediction from 0- (no future prediction) to 12-months ahead (interval by 1 month; 300 equations per each month-delay). From the investigation of model structure, input variable selectivity was obviously affected by the time-delay arrangement, and the model predictability was related with the type of input variables. From the results, we can conclude that, although Machine Learning (ML) algorithms which have popularly been used in Ecological Informatics (EI) provide high performance in future prediction of ecological entities, the efficiency of models would be lowered unless relevant input variables are selectively used.

• Journal of Korean Institute of Industrial Engineers
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• v.22 no.3
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• pp.413-426
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• 1996

Modern society, as a result of high industrial technology, is characterized by a series of mass production, moss consumption and mass disposal. As the mass disposal is known as the major culprit of destroying ecological system of our environment, human prosperity is in turn threatened by this indiscrete activities. Under current industrial technology which pursuit maximum profit, environmental problems could not be solved. This paper proposes recycle manufacturing systems of assemble products as a measure of current non-recycle manufacturing systems. Products are also composed of a number of ports. All parts are represented by a function of time cost performance variable as reuse level. We develop on information systems which give all the information on reused and recycled parts. We try to implement this result on a real fields. We confide ourselves to the contribution to on effective solution of environmental problems and to give profit to assembly manufacturing and consumers.

• Steel and Composite Structures
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• v.34 no.4
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• pp.511-524
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• 2020

In this research, a simple four-variable trigonometric integral shear deformation model is proposed for the static behavior of advanced functionally graded (AFG) ceramic-metal plates supported by a two-parameter elastic foundation and subjected to a nonlinear hygro-thermo-mechanical load. The elastic properties, including both the thermal expansion and moisture coefficients of the plate, are also supposed to be varied within thickness direction by following a power law distribution in terms of volume fractions of the components of the material. The interest of the current theory is seen in its kinematics that use only four independent unknowns, while first-order plate theory and other higher-order plate theories require at least five unknowns. The "in-plane displacement field" of the proposed theory utilizes cosine functions in terms of thickness coordinates to calculate out-of-plane shear deformations. The vertical displacement includes flexural and shear components. The elastic foundation is introduced in mathematical modeling as a two-parameter Winkler-Pasternak foundation. The virtual displacement principle is applied to obtain the basic equations and a Navier solution technique is used to determine an analytical solution. The numerical results predicted by the proposed formulation are compared with results already published in the literature to demonstrate the accuracy and efficiency of the proposed theory. The influences of "moisture concentration", temperature, stiffness of foundation, shear deformation, geometric ratios and volume fraction variation on the mechanical behavior of AFG plates are examined and discussed in detail.

• Magazine of the Korea Concrete Institute
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• v.8 no.1
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• pp.111-120
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• 1996

Drying shrinkage is a very important properties of concrete, which is affected by environmental conditions. The environmental conditions are temperature, relative humidity, and wind speed, which is quite variable and its effct on drying shrinkage is quite complex, too. In this study, environmental effects on drying shrinkage wrer integrated into one variable-evaporation rate. In several different environmental conditions, evaporation rate was measured with Evaporometer and compared with PCA chart, and also compared with measured drying shirnkage to verify the possibility of being a single parameter. The results are summarized in a prediction chart and prediction equation for drying shrinkage.

• Journal of Environmental Health Sciences
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• v.37 no.5
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• pp.342-347
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• 2011

Healthy worker effect (HWE) refers to the consistent tendency for actively employed individuals to have a more favorable mortality experience than the population at large. Although HWE has been well known since the 1970s, only a few studies in occupational epidemiology have attempted to fully define and evaluate HWE. HWE can be separated into effects on the initial hiring into the workforce (healthy worker hire effect) and those on continuing employment (healthy worker survival effect). In this review, we summarize the methods for minimizingor adjusting for the healthy worker effect available in occupational epidemiology. It is noteworthy that healthy worker survival effect appears complicated, considering that employment status plays simultaneous roles as a counfounding variable and intermediate variable, whereas healthy worker hire effect may be adjusted by incorporating health status at baseline into the statistical model. In addition, two retrospective cohort studies for workers in the semiconductor industry and Vietnam veterans in Korea, respectively, were introduced, and their results were explained in terms of healthy worker effect.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.727-729
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• 2002

In this paper, we proposed quad variable rates ADPCM coding method and its implementation on C6000 DSP, which is modified from the standard ADPCM of ITU G.726 for speech quality improvement considering the environmental noise Four coding rates, 16Kbps, 24Kbps, 32Kbps and 40Kbps are used for speech window samples and the rate decision threshold is decided by the environmental noise level. The object of the proposed method is to reduce the coding rate while retaining the speech quality and the speech quality is considerably close to 40Kbps single rate coder with the coding rate close to 16Kbps single rate coder under the environmental noise. The environmental noise level affects the coding rate and the noise level is calculated per every speech window samples. At high noise level, more samples are coded at higher rates to enhance the quality, but at low noise level, only the big speech signals are coded at higher rates and more speech samples are coded at lower coding rates to reduce the coding rates. The influence of the noise on tile speech signal is considerably high for small signals and the small signal has the higher ZCR (zero crossing rate). The method is simulated in PC and to be implemented on C6000 floating point DSP board in real time operations.

• The Korean Journal of Community Living Science
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• v.28 no.2
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• pp.313-328
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• 2017

The purpose of this study was to analyze the role of perceived market influence, which is an important psychological factor influencing consumer behavior in the market, and explain how consumer beliefs related to the market can affect sustainable consumer behavior. First, this study found that gaps in perceived market influence were statistically significant for age and job. Second, environmental concern, organic food consumption (vegetables and meats), and purchase behavior of organic foods were found to be significantly different by degree of perceived market influence of consumers. The mean values were found to be high for the group having strong perceived market influence. This tendency suggests an association between higher perceived market influence consumers and more environmentally friendly consumer behavior. Lastly, this study used Structural Equation Modeling to analyze the effect of perceived market influence as a moderating variable and mediating variable on the relationship between environmental concerns and consumer behavior toward organic foods. The results show a mediating effect on perceived market influence, but a moderating effect could not be found. This result implies that perceived market influence might indirectly affect consumer behavior when transferring environmental concerns to consumer behavior toward organic foods.

• Korea Journal of Hospital Management
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• v.22 no.3
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• pp.46-60
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• 2017

The purpose of this study is to analyze the difference of productivity according to environmental factors among 25 Regional base public hospitals. Also this study is to propose a method to improve the productivity of Regional base public hospitals in the future by improving the public performance and stable management performance by studying the productivity variables affecting profitability. The survey period was based on the last three years, and 25 Regional base public hospitals were selected for the survey. The dependent variable is the total capital medical marginal profitability and the medical profit marginal profitability which are the indicators of profitability. The independent variable, productivity, is classified into three indicators: capital productivity, labor productivity, and value added productivity. The ANOVA analysis method was used to analyze the productivity difference according to the frequency factor and the environmental factors of the Regional base public hospitals. Finally, we conducted a hierarchical regression analysis to examine the productivity variables affecting profitability. The results of this study showed that there were differences in productivity due to environmental factors such as hospital size, competition in the local medical market, and differences in management performance. The difference in productivity and profitability depending on the environmental factors suggests that it is difficult for Regional base public hospitals in each regional base to perform a balanced public service. In order to overcome this, it is necessary to provide balanced medical services such as government financial support expansion, regional medical demand forecasting and facility infrastructure construction.

• The Bulletin of The Korean Astronomical Society
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• v.27 no.1
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• pp.40-40
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• 2002