• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.267-268
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• 2002

Engine testing of new low-sulfur, low-phosphorus anti wear components is expensive and time consuming so bench testing of potential candidates is highly desirable as a first step evaluation. Electrical contact resistance (ECR) has been shown to be a convenient method to assess antiwear film formation in a ball-on-flat bench wear test. Correlation of the bench test to fired engines was demonstrated for lubricants varying only in the type of detergent. Previous papers have examined film formation by one and two component formulations of zinc dialkyldithiophosphate (ZnDTP) and detergents. In this study, the ECR technique is systematically extended to formulations including ZnDTP, detergent, and dispersant. Both type and level of components are considered and the implications for engine performance are discussed.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.12
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• pp.60-69
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• 1997

We present an average method based on the multirate signal processing and dynamic allocation average for the purpose of monitoring event-related potentials(ERP) and continuously and dynamically. In the proposed method, first, latency shifts are detected through the cross correlation between a current response and the reference response. Then, the multirate signal processing which is composed of up-sampler, lowpass filter, and down sampler is performed to compensate the latency shifts of the reference response, therefore we obtain the reference response with a peak latencies compenated by those of a current response. Finally, the single response is obtained by averaging the compensated reference response and a current response. In the simulation, the results of quantitative evaluation by simulation and the results using linical data are presented. From the result, the proposed method reflects dynamic time-varying ERP more exactly than previous methods and is also effective in consecutive monitoring of ERP.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.625-633
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• 2006

Spatial variability of ground motions has significant influence on dynamic response of longitudinal structures such as bridges and tunnels. The coherency function, which quantifies the degree of positive or negative correlation between two ground motions, is often used to describe the spatially variable ground motions. This paper compares two available procedures for developing spatially variable ground time histories from a given coherency function. Hao's method shows serious limitation, resulting in unrealistic decrease in coherency with increase in distance Abrahamason's method, on the other hand, preserves important characteristics of the reference ground motion. Therefore, the Abrahamason's method is recommended to be used in developing spatially varying ground motions.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.10
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• pp.89-97
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• 1997

To extract time-varying evoked potential (EP), segement latency corrected average method is presented. This method is composed of three steps. First, adaptive filtering for reducing the effect of artifacts and removing background noise is performed. Next, validated intervals of individual segments are aligned, and latency components are detected by cross-correlation between the previously obtained and measured EPs within the intervals. Finally, after the detected latency component, responses of segments are groupe and averaged, the shole corrected EP signal is obtained. In the experiments, the resutls of the conventional methods including simple averaging, Woody's method, and peak component latency corrected averaging are obtained, the results compared with the present method for evaluating performance. Therefore, the presented method confirms that it reflects the latency variations of fundamental peaks and gets the improved EP.

• Structural Engineering and Mechanics
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• v.57 no.3
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• pp.529-541
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• 2016

Under the interaction between dam body, dam foundation and external environment, the dam structural behavior presents the time-varying nonlinear characteristics. According to the prototypical observations, the correct identification on above nonlinear characteristics is very important for dam safety control. It is difficult to implement the description, analysis and diagnosis for dam structural behavior by use of any linear method. Based on the rescaled range analysis approach, the algorithm is proposed to identify and extract the fractal feature on observed dam structural behavior. The displacement behavior of one actual dam is taken as an example. The fractal long-range correlation for observed displacement behavior is analyzed and revealed. The feasibility and validity of the proposed method is verified. It is indicated that the mechanism evidence can be provided for the prediction and diagnosis of dam structural behavior by using the fractal identification method. The proposed approach has a high potential for other similar applications.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.3
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• pp.208-217
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• 1990

A rectangular test section is devised by assuming two dimensional melting of a solid phase change material heated from two sides which are maintained at constant temperature and allowing a free expansion due to density difference between solid and liquid. The timewise melting shape is recorded photographically by the shadow graph method for several experimental conditions. The analysis shows that the melting process consists of four regimes. At first, the pure conduction heat transfer is dominant, and as time goes by natural convection grows and plays a role greatly. Experiments are carried out varying not only the wall temperature but height of the wall. Each effect of them on the melting process is obtained in the form of combination of dimensionless parameters, $Ste^{0.8}\;FoRa^{0.2}$. An algebraic correlation is suggested, which predicts the melted fraction well.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.1009-1012
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• 2004

Recently, the concern on sound qualify (SQ) is on the steep increase in the fields of vehicle and home appliance and over the fast few decades a considerable number of studies have been conducted on SQ evaluation. As a result, basic procedure for SQ evaluation has been already suggested. Although most interesting sounds have time-varying features, however, little is known about their SQ evaluation. The purpose of this study is to systematize a method for SQ evaluation of non-stationary sound. For this, various listening tests procedure for non-stationary sound is introduced and it is attempted to find out correlation between various SQ metrics and subjective data obtain from listening test. Booming of car interior noise in acceleration is used as an example and finally, representative value is obtained for the interesting sensation of non-stationary sound.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.197-198
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• 1998

We tested the capability of Pointwise Correlation Dimension(PD2), Approximate Entropy (ApEn) and LZ complexity, as alternative measures of a biological signal. For this purpose, we analyzed standard data and a healthy child's 24-hour heart rate variability. Our conclusion is as follows. First, PD2, ApEn and LZ complexity can be used for discerning chaotic attractor, white noise, and periodic signal. Second, these measures show different characteristics on day and night. Third, these measures can be used for detecting time-varying characteristics of biological signals.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.29 no.11 s.242
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• pp.1277-1284
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• 2005

The combustion characteristics of methane oxygen diffusion flames have been investigated to give basic information for designing industrial oxyfuel combustors. NOx reduction has become one of the most determining factors in the combustor design since the small amount of nitrogen is included from the current low cost oxygen production process. Flame lengths decreased with increasing fuel or oxygen velocity because of the enhancement of mixing effect. Correlation equation between flame length and turbulent kinetic energy was proposed. NOx concentration was reduced with increasing fuel or oxygen velocity because of the enhanced entrainment of the product gas into flame zone as well as the reduction of residence time in combustion zone.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.163-167
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• 2003

Based on the transient finite difference solution of Richards' equation, an infiltration model is developed to analyze temporal variation of precipitation recharge in the region of monsoon climates. Simulation results obtained by using time series data of 20-year daily precipitation and pan evaporation indicate that a linear relationship between the annual precipitation and the annual recharge holds for the soils under the monsoon climates with varying degrees of the correlation coefficient depending on the soil types. A sensitivity analysis reveals that the water table depth has little effects on the recharge for the sandy soil, whereas, for the loamy and silty soils, rise of the water table at shallow depths causes increase of evaporation by approximately 100㎜/yr and a corresponding decrease in recharge. A series of simulations for two-layered soils illustrate that the amount of recharge is dominantly determined by the soil properties of the upper layer, although the temporal variation of recharge is affected by both layers.