• Survey Research
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• v.10 no.1
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• pp.33-56
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• 2009

Landline telephone surveys of the population of households or individuals in Korea often use telephone directories as sampling frames. Recently, the frequency of unlisted numbers in the directories has been increased and the number of households without landline phones has become larger with a spread of mobile phones. Landline telephone coverage has currently reached to a level that raises concerns about the currently due to a coverage bias on the statistics in question. In this paper, we first present the distribution of telephone ownership in Korea and make a comparison with some selected countries. Second, we describe the characteristics of telephone directories. Next, we directly or indirectly estimate the telephone coverage rates of the frames, and show that it may nationally be lower than 65.6% based on additional information. We conclude with remarks about future studies to reduce coverage bias, including the developments of efficient random digit dialing sampling methods.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.159-159
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• 2023

The Amazon River basin is one of the largest basins in the world, and its ecosystem is vital for biodiversity, hydrology, and climate regulation. Thus, understanding the hydrometeorological process is essential to the maintenance of the Amazon River basin. However, it is still tricky to monitor the Amazon River basin because of its size and the low density of the monitoring gauge network. To solve those issues, remote sensing products have been largely used. Yet, those products have some limitations. Therefore, this study aims to do bias corrections to improve the accuracy of Satellite Precipitation Products (SPPs) in the Amazon River basin. We use 331 rainfall stations for the observed data and two daily satellite precipitation gridded datasets (CHIRPS, TRMM). Due to the limitation of the observed data, the period of analysis was set from 1st January 1990 to 31st December 2010. The observed data were interpolated to have the same resolution as the SPPs data using the IDW method. For bias correction, we use convolution neural networks (CNN) combined with an autoencoder architecture (ConvAE). To evaluate the bias correction performance, we used some statistical indicators such as NSE, RMSE, and MAD. Hence, those results can increase the quality of precipitation data in the Amazon River basin, improving its monitoring and management.

• Survey Research
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• v.5 no.1
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• pp.27-49
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• 2004

Recently, in several countries including South Korea, the percentage of households having fixed telephones, which is often called the fixed telephone coverage rates, has decreased due to a rapid spread of mobile phones. It is generally assumed that the lower the rates of coverage, resulting in a major frame undercoverage problem, the greater the possibility of the bias. In this paper, we first take a look at the changes of coverage rates in both fixed telephones and mobile phones in South Korea and examine the coverage rates by sociodemographic characteristics of households. Also, we refer to a change in the level of fixed telephone noncoverage and the resulting problems in the situation. Second, we provide a comparison of the coverage rates for households for some European countries, the United States, Canada etc. Finally, we suggest further research to rise to our research environments increasingly troublesome, owing to the wide spread of mobile phones.

• Journal of the Korean institute of surface engineering
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• v.37 no.1
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• pp.5-12
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• 2004

The enhancement of adhesion for Cu film on polycarbonate (PC) surface with the $Ar/O_2$ gas plasma treatment and dc-bias sputtering was studied. The plasma treatment with this reactive mixture changes the chemical property of PC surface into hydrophllic one, which is shown by the variation of contact angle with surface modification. The micro surface roughness that also gives the high adhesive environment is increased by the $Ar/O_2$ gas plasma treatment. These results were observed distinctly from the atomic force microscopy (AFM). The negative substrate dc-bias effect for the Cu adhesion on PC was also investifated. Accelerated $Ar^{+}$ lons in sheath area of anode bombard the bare surface of PC during initial stage of dc bias sputtering. PC substrate. therefore, has severe roughen and hydrophilic surface due to the physical etching process with more activated functional group. As dc-bias sputtering process proceeds, morphology of Cu film shows better step coverage and dense layer. The results of peel test show the evidence of superiority of bias sputtering for the adhesion between metal Cu and PC.C.

• Journal of Korean Institute of Industrial Engineers
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• v.22 no.1
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• pp.65-82
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• 1996

This paper proposes a sequential procedure which can be used to determine a truncation point and run length to reduce or remove bias owing to artificial startup conditions in simulations aimed at estimating steady-state behavior. It is based on the idea of Lyapunov exponent in chaos theory. The performance measures considered are relative bias, coverage, estimated relative half-width of the confidence interval, and mean amount of deleted data.

• Journal of the Korea Society for Simulation
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• v.7 no.1
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• pp.27-37
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• 1998

Simulation output is generally stochastic and autocorrelated, and includes the initial condition bias. To exclude the bias, the determination of truncation point has been one of important issues for the steady-state simulation output analysis. In this paper, two methods are presented for detection of truncation point in order to estimate efficiently the steady-state measure of simulation output. They are based on the Euclidean distance equation, and the backpropagation algorithm in Neural Networks. The experimental results obtained by M/M/1 and M/M/2 show that the proposed methods are very promising with respect to coverage and relative bias. The methods could be used for the on-line analysis of simulation outputs.

• Journal of the Korea Society of Computer and Information
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• v.12 no.4
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• pp.33-42
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• 2007

Accurate predictions of software release times, and estimation of the reliability and availability of a software product require quantification of a critical element of the software testing process : test coverage. This model called Enhanced non-homogeneous poission process(ENHPP). In this paper, exponential coverage and S-shaped model was reviewed, proposes the Kappa coverage model, which maked out efficiency application for software reliability. Algorithm to estimate the parameters used to maximum likelihood estimator and bisection method, model selection based on SSE statistics and Kolmogorov distance, for the sake of efficient model, was employed. From the analysis of mission time, the result of this comparative study shows the excellent performance of Burr coverage model rather than exponential coverage and S-shaped model using NTDS data. This analysis of failure data compared with the Kappa coverage model and the existing model(using arithmetic and Laplace trend tests, bias tests) is presented.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.12
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• pp.2311-2318
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• 2007

Finite failure NHPP models presented in the literature exhibit either constant, monotonic increasing or monotonic decreasing failure occurrence rates per fault. Accurate predictions of software release times, and estimation of the reliability and availability of a software product require Release times of a critical element of the software testing process : test coverage. This model called Enhanced non-homogeneous Poission process(ENHPP). In this paper, exponential coverage and S-shaped model was reviewed, proposes the Kappa coverage model, which make out efficiency application for software reliability. Algorithm to estimate the parameters used to maximum likelihood estimator and bisection method, model selection based on SSE statistics and Kolmogorov distance, for the sake of efficient model, was employed. Numerical examples using real data set for the sake of proposing Kappa coverage model was employed. This analysis of failure data compared with the Kappaa coverage model and the existing model(using arithmetic and Laplace trend tests, bias tests) is presented.

• Journal of Korea Trade
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• v.25 no.5
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• pp.39-57
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• 2021

Purpose - This research uses ocean marine insurance (OMI) statistics, international emails, focus-group interviews, and surveys to fill the gap between the theory of behavioral insurance, particularly status quo bias (SQB), and the practice of OMI in Korea. The contractual forms of OMI, the oldest and most globalized form of commercial insurance, were developed in the UK as the Institute Cargo Clauses in 1906 and revised in 1963, 1982, and 2009. SQB has been academically explored, mostly in health insurance and the financial services sector, but never in OMI. Thanks to the availability of OMI statistics in Korea, we can conduct SQB research here for the first time in this field. Design/methodology - We show the existence of SQB in the OMI of Korea through Korean statistics between 2009 and 2018, email correspondence with experts in the UK, Germany, and Japan, focus-group interviews with Korean OMI underwriters, an in-depth interview with one underwriter, and a survey of 15 OMI insureds (company representatives). Findings - We find that Korean foreign traders rely on the old-type OMI contracts developed in 1963, whereas other industrialized countries use the newest type of OMI contract developed in 2009. With a simple loss ratio analysis during 2009-2018, we show that the behavior of insurers has little to do with rational profit maximization and is instead driven by irrational bias, as they forgo the more profitable contracts provided by the new clauses by keeping the old clauses. The consistent addiction to old types of contracts in the OMI market suggests strong SQB among Korean exporters, importers, bankers, or insurers, which we confirmed in our interviews and survey. Originality/value - This research has significant originality and academic value because it reports new findings with crucial implications for the development of efficient trade practices and policy. First, this research is based on actual statistics that have not been used in previous Korean research on OMI. Second, this research shows that all-risk OMI policies provide more value to insureds, in terms of coverage given premium, than partial coverage policies, which differs from arguments previously made in Korea. Third, this research reveals strong SQB in Korea, where foreign trade plays a pivotal role in economic growth. That bias could be attributable to uninformed traders, informed but idle insurers, or conservative bankers. Fourth, to further develop foreign trade, policy initiatives are needed to review the current practices of OMI contracts and move forward with the new contract forms. All of these findings and arguments are both new and important.

• Journal of Contemporary Eastern Asia
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• v.14 no.2
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• pp.57-68
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• 2015

This paper examines the New York Times' reaction to the 2010 Brazil-Turkey-Iran (BTI) nuclear deal, the very last diplomatic effort before the imposition of international sanctions track over the following years. The New York Times' (NYT) coverage of the deal is examined using the Critical Discourse Analytic (CDA) approach formulated by Teun van Dijk. The results show a strong bias against the BTI deal throughout the NYT's news coverage. The overarching theme in cover-age of the deal is the imputation of malignant intentions on the part of both Iran ("to kill time to further its nuclear weapons program") and Brazil and Turkey ("to advance their own business dealings with Iran and gaining international recognition"). Also, non-relevant information is used to imply a threat of Iranian development of nuclear weapons. Moreover, the NYT leaves almost totally "unsaid" that president Obama had asked Brazilian and Turkish leaders to go to Tehran and get this deal. Therefore, the NYT basically echoed, and legitimized, discursive practices of the U.S. government on the deal.