• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.11
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• pp.2401-2408
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• 1997

The measured pulse shapes provided in the given data package demonstrated pulse distortions due to laser speckle. the distorted pulse shapes were carefully analyzed, modeled, and then applied to the DTTL(Digital-data Transition Tracking Loop)[1] bit synchronizer simulator to measure the mean time delay and its delay variation performance. The result showed that the maximum mean time delay variation with the modeled data was 12.5% when window size equals 1. All the data given were located within this modeled boundary and the maximum eman time delay variation was 7% in this case. The mean time delay variation was known to be smaller by reducing the window size [2][5][6]. The mitigated delay variation was 2.5% in the modeled case and 1.4% in the data set given when the windown size equals 0.1. With the digital DTTL insteal of analog DTTL, similar results was obtained.

• International Journal of Quality Innovation
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• v.2 no.2
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• pp.24-33
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• 2001

As we know, the quality of processes is technically depicted by variation, a product or process with the best quality must naturally require the variation as less as possible. The variation is usually reduced with many ways, say, by adjusting parameters settings under robust design with many turns expensive experiments. So ones are trying to reach the robustness by detecting cheap and simple methods. In this paper, a both practical and simple technique for quality improvement, namely reducing the variation, by data classification is studied. First, all possible system factors are included, which may dominate the variation law. And then we make use of the past observations and their classification as well as boxplot charts to find out the internal rule between the variation and the system factor. Next, adjust the location of the system factor according to the rule so that the variation could, to some extent, be lessened. Finally, two typical quality improvement cases based on data classification are presented.

• Journal of the Korean Data and Information Science Society
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• v.14 no.4
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• pp.1023-1030
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• 2003

When X and Y have independent normal distributions, we develop a Bayesian testing procedure for the equality of two coefficients of variation. Under the reference prior of the coefficient of variation, we propose a Bayesian test procedure for the equality of two coefficients of variation using fractional Bayes factor. A real data example is provided.

• Journal of the Korean Data and Information Science Society
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• v.21 no.1
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• pp.163-172
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• 2010

In this paper, we deal with the problem for testing homogeneity of coecients of variation in several normal distributions. We propose Bayesian hypothesis testing procedures based on the Bayes factor under noninformative prior. The noninformative prior is usually improper which yields a calibration problem that makes the Bayes factor to be dened up to a multiplicative constant. So we propose the objective Bayesian hypothesis testing procedures based on the fractional Bayes factor and the intrinsic Bayes factor under the reference prior. Simulation study and a real data example are provided.

• Bulletin of the Korean Space Science Society
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• 2011.04a
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• pp.27.1-27.1
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• 2011

This study is about the ionospheric variation on the Korean Peninsula using GPS TEC data from Daejeon IGS GPS site. It has accumulated the 11 years GPS data from 2000. In this work, the hourly and daily averaged TEC data are used. Data period covers a full solar cycle from 2000 to 2010 (11 years) which the total observed days are 98%. The mean TEC data shows the annual/semiannual variation, solar cycle and 27 days. GPS TEC has a good correlation with solar F10.7 index. We also compare with planetary Kp and AE indices. The maximum of the daily mean GPS TEC is around 50 TECU at 2000 and that value of 2009 is near 10 TECU. we confirms that the GPS TEC is a good indicator for ionospheric variation for the mid-latitudinal region to understand the ionospheric climatology over Korea Peninsula.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.2
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• pp.184-193
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• 2015

This paper proposes a cost-efficient and automatic method for large data acquisition from a test chip without expensive equipment to characterize random process variation in an integrated circuit. Our method requires only a test chip, a personal computer, a cheap digital-to-analog converter, a controller and multimeters, and thus large volume measurement can be performed on an office desk at low cost. To demonstrate the proposed method, we designed a test chip with a current model logic driver and an array of 128 current mirrors that mimic the random process variation of the driver's tail current mirror. Using our method, we characterized the random process variation of the driver's voltage due to the random process variation on the driver's tail current mirror from large volume measurement data. The statistical characteristics of the driver's output voltage calculated from the measured data are compared with Monte Carlo simulation. The difference between the measured and the simulated averages and standard deviations are less than 20% showing that we can easily characterize the random process variation at low cost by using our cost-efficient automatic large data acquisition method.

• Korea Journal of Hospital Management
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• v.12 no.3
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• pp.1-19
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• 2007

This study focused on finding the variation of medical service utilization and medical payments of the patients died by three, cancers, stomach, breast, and colon cancer. For this study, data of the one-year episodes of the health insurance subscribers died in 2004 were selected. The frequency of medical visits, the lengths of slays, the days of outpatient visits, the total period of medical services and the total medical payments were compared by the characteristics of the suppliers and utilizers. The data of the patients died by cerebrovascular diseases and cancer in 2004 were selected. To select the dead by cerebrovascular diseases and cancer in 2004, were matched the 2004 reimbursement data of all medical institutions to the data of funeral fee payment by the National Health Insurance Corporation from January 2004 to May 2005 for the death in 2004. The results of the analysis were as follow. The variation of medical service utilization of the dead by cancers were not small in Korea. The current study found that the variation of medical care utilization was influenced by the factors of suppliers, such as types and locations of medical institutions and the factors of users, such as sex and age. It was suspected that the reimbursement by fee-for-service contributed to the variation quite a lot, but we could not compare the variation between the different reimbursement systems in Korea. The results of the study suggested that tile factors of suppliers and utilizers should he reviewed to reduce the under use and over use expressed by variations of medical service utilization. The processes of care, effective communication and management system should be investigated for the equity of medical service utilization. Additionally, prospective payment could he recommended to reduce the high variation of medical service Use. To find the variation caused by under use and over use, further study need to control the severity of diseases, socio-economic status of the users and the system factors.

• 한국데이터정보과학회:학술대회논문집
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• 2003.10a
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• pp.49-56
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• 2003

When X and Y have independent normal distributions, we develop a Bayesian testing procedure for the equality of two coefficients of variation. Under the reference prior of the coefficient of variation, we propose a Bayesian test procedure for the equality of two coefficients of variation using fractional Bayes factor. A real data example is provided.

• Spatial Information Research
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• v.10 no.2
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• pp.185-199
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• 2002

The objective of this study is to investigate the suitable spatio-temporal analysis method considering the zoning effect of spatial analysis termed the modifiable areal unit problem(MAUP). In former studies of spatio-temporal analysis, there were disagreement between attribute data with spatial data, because of variation of administrative district aggregating attribute data. It is need to consider how the analysis zone effects spatial characteristics and spatio-temporal variation of urban region through land price variation analysis. This study considers MAUP through basic mesh system, which is composed of micro grid. Mesh system can solve disagreement of resolution between spatial data and attribute data.

• Proceedings of the KSRS Conference
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• 2000.04a
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• pp.13-18
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• 2000

We observed sea level variation of the long time at Kerguelen island in the South Indian Ocean with ARGOS data and meteorological data during about 1 year(May 1993~March 1994) through using filter, spectral analysis, coherency and phase, and found characteristics for the two oceanic signal levels(detided oceanic signal level, h$_{detided}$ and seasonal oceanic level, h$_{corr.ib}$). The forms of variations are very well agreed to between ARGOS data and meteorological data for atmospheric pressure in the observed periods. The seasonal difference of sea level between Summer and Winter is about 1.6cm. Both the detided oceanic signal level(h$_{detided}$) variation and the inverted barometer level(h$_{ib}$) variation have a strong correlation for T>1day period bands. Characteristics of h$_{detided}$ variation are decided not by the influence of any meteorological distributions (pressure, winds, etc), but the influence of another factors(temperature, salinity, etc.) for T>2days periods bands. h$_{corr.ib}$ plays an very important role of sea level variation of the long time term(especially T>about 180days period bands).