• Communications for Statistical Applications and Methods
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• v.17 no.1
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• pp.127-140
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• 2010

In interim analysis, group sequential tests are widely used for the ethical, scientific, and economic reasons. In this paper, we propose the group sequential tests using both type I and type II error spending rate functions when the response variable is discrete, especially binomial distribution, in the interim analysis. In addition, we propose new error spending rate function which covers the formerly proposed. Our method has good property that is flexible, fast and easily applicable. A numerical simulations are carried out to evaluate our method and it shows good performance.

• Journal of the Korean Data and Information Science Society
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• v.20 no.6
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• pp.1009-1014
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• 2009

The Internet has changed the daily lives of human being in Korea and elsewhere in the world. It has changed the paradigms of traditional commercial activities and created immense opportunities for new business models. Recently, there has been much attention to the internet shopping mall as a means of commercial transaction. To make internet shopping mall competitive, effective customer satisfaction service should be provided and it is necessary to dynamic analysis method for customers' purchasing pattern. In this paper we apply the sequential analysis to comparison of two kinds of sales through the analysis of customers' purchasing pattern.

• 대한방사선방어학회:학술대회논문집
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• 2010.04a
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• pp.190-191
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• 2010

• Communications for Statistical Applications and Methods
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• v.3 no.2
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• pp.291-298
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• 1996

통계학분야 그리고 또 다른 많은 분야에서 수치적 계산을 다루는 문제가 자주 발생한다. 적당한 컴퓨터 컴퓨터 시간안에 상당한 정도의 정확성을 줄 수 있고 또한 보다 광범위하게 사용 가능한 유용한 알고리즘의 필요성을 느낀다. 이러한 문제에 가능한 하나의 몬테칼로 알고리즘인 주표본 알고리즘을 소개하였다. 그리고 특히 본 눈문에서는 축차확률비검정의 오차확률을 계산하는 곳에 주표본 알고리즘을 적용하고 결과를 비교분석하였다.

• Journal of the Korean GEO-environmental Society
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• v.19 no.12
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• pp.47-58
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• 2018

Duncan & Chang(1970) proposed the Duncan-Chang model that a linear relation of transformed stress-strain plots was reconstituted from a nonlinear relation of stress-strain curve of triaxial compression test using hyperbolic theory so as to estimate an initial tangent modulus and ultimate deviator stress for the soil specimen. Although the transformed stress-strain plots show a linear relationship theoretically, they actually show a nonlinearity at both low and high values of strain of the test. This phenomenon indicates that the stress-strain curve is not a complete form of a hyperbola. So, if linear regression analyses for the transformed stress-strain plot are performed over a full range of strain of a test, error in the estimation of their linear equations is unavoidable depending on ranges of strain with non-linearity. In order to reduce such an error, a modified regression analysis method is proposed in this study, in which linear regression analyses for transformed stress-strain plots are performed over the entire range of strain except the range the non-linearity is shown around starting and ending of the test, and then the initial tangent modulus and ultimate deviator stresses are calculated. Isotropically consolidated-drained triaxial compression tests were performed on compacted weathered soil with a modified Proctor density to obtain their model parameters. The modified regression analyses for transformed stress-strain plots were performed and analyzed results are compared with results estimated by 2 points method (Duncan et al., 1980). As a result of analyses, initial tangent moduli are about 4.0% higher and ultimate deviator stresses are about 2.9% lower than those values estimated by Duncan's 2 points method.

• Proceedings of the KAIS Fall Conference
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• 2009.12a
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• pp.241-244
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• 2009

많은 저개발 국가들이 경제성장을 하기위한 다양한 요인이 존재할 수 있다. 하지만 본 모델링은 외부 변수로서 자본의 투입에 따른 효과만을 고려하여 모델링을 세워보았다. 경제발전을 이루는 초기조건들이 나중에 지속적인 영향을 미치게 된다는 것을 수식으로 표현하여 보았고, 적기에 투입된 자본의 축차적 투입이 결국 경제의 레벨을 올려서 그것이 경제발전에 기여하게 된다는 직관을 수식적인 모델링으로 확인하게 된다. 3가지의 중요한 가정을 통해서 단순화한 경제모델을 바탕으로 분석이 되었으며, 이러한 단순 모델링을 향후 일반적인 모델링화 할 수 있는 방법은 추가 연구주제가 될 수 있다.

• The Korean Journal of Applied Statistics
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• v.26 no.4
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• pp.581-594
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• 2013

A group sequential design can end a clinical trial early if a confirmed efficacy or a futility of study medication is found during clinical trials. Adaptation can adjust the design of clinical trials based on accumulated data. The key to this methodology is considered to control the overall type 1 error rate while maintaining the integrity of clinical trials. The estimation would be more complex and the sample size calculation will be more difficult if the clinical trials have repeated measurement data. Lee et al. (2002) suggested a repeated observation case by using the independent increments properties of the interim test statistics and investigated the properties of the proposed confidence interval based on the stage-wise ordering. This study extend Lee et al. (2002) to adaptive group sequential design. We suggest test statistics for the adaptation as redesigning the second stage of clinical trials and induce the stage-wise confidence interval of parameter of interests. The simulation will help to confirm the suggested method.

• Journal of Korea Society of Industrial Information Systems
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• v.15 no.3
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• pp.51-57
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• 2010

Steganography techniques can be used to hide data within digital images with little or no visible change in the perceived appearance of the image. I propose a steganalysis to detecting hidden message in sequential steganography. This paper presents adjusted technique for detecting abrupt jumps in the statistics of the stego signal during steganalysis. The repeated statistical test based on CUSUM-SPRT runs constantly until it reaches decision. In this paper, I deal with a new and improved statistic $g_t$ by computing $S^{t^*}_j$.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.248-254
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• 2005

This paper presents a quantitative method of sequential separation of $^{90}Sr,\;^{241}Am$ and Pu nuclides with an anion exchange resin and a Sr-Spec resin. The Pu isotopes were purified with an anion exchange resin. The americium and strontium fractions were separated from the matrix elements with an oxalate co-precipitation method. Americium fraction was separated from the strontium fraction with iron co-precipitation method and purified from lanthanides with anion exchange resin. Strontium-90 was purified from other hindrance elements with the Sr-Spec resin after oxalate co-precipitation. The measurement of Pu and Am isotopes was carried out by an ${\alpha}$-spectrometer. Strontium-90 was measured by a liquid scintillation counter. The radiochemical procedure of $^{90}Sr,\;^{241}Am$ and Pu nuclides investigated in this study has been validated by application to IAEA-Reference soils.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.16 no.6
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• pp.1250-1259
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• 2012

In this paper, a time-domain comparator is proposed for a successive approximation (SA) analog-to-digital converter (ADC) with a low power and high resolution. The proposed time-domain comparator consists of a voltage-controlled delay converter with a clock feed-through compensation circuit, a time amplifier, and binary phase detector. It has a small input capacitance and compensates the clock feed-through noise. To analyze the performance of the proposed time-domain comparator, two 1V 10-bit 200-kS/s SA ADCs with a different time-domain comparator are implemented by using 0.18-${\mu}m$ 1-poly 6-metal CMOS process. The measured SNDR of the implemented SA ADC is 56.27 dB for the analog input signal of 11.1 kHz, and the clock feed-through compensation circuit and time amplifier of the proposed time-domain comparator enhance the SNDR of about 6 dB. The power consumption and area of the implemented SA ADC are 10.39 ${\mu}W$ and 0.126 mm2, respectively.