• 정보처리학회논문지:컴퓨터 및 통신 시스템
• /
• 제4권2호
• /
• pp.57-64
• /
• 2015

피크 임계값을 사용하는 걸음 검출 알고리즘에서 충분한 정확도로 걸음을 검출하기 위해서는 3축 가속도 센서가 20Hz 이상의 주파수로 샘플링을 수행하여야 한다. 그러나 $I^2C$나 SPI를 통하여 데이터를 전송받는 상용의 통합 MPU와 연결되는 디지털 센서 장치들의 샘플링 주파수는 아날로그 방식의 샘플링 회로들에 비하여 매우 낮은 경향이 있다. 센서의 샘플링 주파수가 낮게 되면 충분한 데이터를 확보할 수 없기 때문에 측정 결과의 정확도가 떨어지게 된다. 본 연구에서는 피크 임계값 방식의 피크 검출 알고리즘에서 데이터가 20Hz 이하의 낮은 주파수로 샘플링될 경우에 샘플링 주파수와 피크 임계값 사이에 함수관계가 있음을 발견하였으며, 실험을 통하여 임계 함수를 도출하였다. 고정 임계값 대신에 샘플링 주파수에 따른 임계 함수를 적용하고, 테스트 프로토콜에 의하여 실험을 수행한 결과, 각 걸음 유형에 대하여 평균적으로 1.2% 미만의 걸음 검출 오차율을 얻을 수 있었다. 그러므로 걸음 검출 알고리즘이 걸음 모드에 따라서 적절히 결정된 임계 함수로부터 샘플링 주파수에 적합한 임계값을 사용하여 걸음을 검출한다면, 걸음 검출 및 걸음수 측정의 정확도는 매우 높아질 수 있다. 이러한 결과는 걸음수 측정 장치에만 적용되는 것이 아니라, 샘플링 주파수가 낮게 설계될 수밖에 없는 소형, 저가의 유비쿼터스 기기에도 적용해 정확도를 효과적으로 향상시킬 수 있다.

• Journal of the Korean Statistical Society
• /
• 제32권2호
• /
• pp.103-119
• /
• 2003

Properties of stochastic regression imputation are discussed under the uniform within-cell response model. Variance estimator is proposed and its asymptotic properties are discussed. A limited simulation is also presented.

• Communications for Statistical Applications and Methods
• /
• 제4권1호
• /
• pp.185-191
• /
• 1997

Bayesian estimation of multinomial and Poisson parameters under starshped restriction is considered. Most Bayesian estimations in order restricted statistical inference require the high-dimensional integration which is very difficult to evaluate. Monte Carlo integration and Gibbs sampling are among alternative methods. The Bayesian estimation considered in this paper requires only evaluation of incomplete beta functions which are extensively tabulated.

• Journal of the Korean Data and Information Science Society
• /
• 제6권1호
• /
• pp.39-51
• /
• 1995

This paper deals with the problem of obtaining some Bayes estimators of Rayleigh reliability function in a time censored sampling with incomplete information. Using the priors about a reliability function some Bayes estimators are proposed and studied under squared error loss and Harris loss.

• 한국산업보건학회지
• /
• 제6권1호
• /
• pp.125-137
• /
• 1996

This study was designed to investigate effects of relative humidity on the breakthrough of charcoal tubes at a fixed vapor concentration and sampling time during mixed organic vapor sampling. A vapor generator was used to generate three different concentrations of mixed organic vapor and a stainless steel chamber was fabricated and utilized to maintain three different percentages of relative humidity while maintaining a constant temperature. The results were as follows; 1. At high relative humidity, breakthrough of mixed organic vapor occurred quickly at low vapor concentration than at high vapor concentration because of the reduced adsorption volume of charcoal tube due to humidity. 2. Breakthrough by competitive adsorption of vapors onto charcoal tube was observed at first from n-hexane having the lowest boiling point and highest vapor pressure among the three organic vapors investigated, followed by TCE. No breakthrough was observed from toluene under all experimental conditions. 3. For n-hexane, breakthrough was observed after 2 hours of sampling and breakthrough rates were increased as relative humidity increased. For TCE, breakthrough was found after 3 hours of sampling and breakthrough rates by sampling time were increased as vapor concentration increased. 4. The adsorbed amount of mixed organic vapor at breakthrough was shown to have statistically significant correlations with sampling time, relative humidity, and vapor concentration in descending order of correlation. Relative humidity and sampling time for n-hexane and sampling time and concentration for TCE were both statistically significantly correlated. 5. Relative humidity was found to affect the amount of breakthrough of mixed organic vapor and n-hexane. Among three percentages of relative humidity investigated, the amount of breakthrough at 85 % relative humidity was significantly larger than those of at lower percentages of relative humidity. No statistically significant difference was found between 25 % and 55 % relative humidity. 6. The results of multiple regression analysis between breakthrough and relative humidity, vapor concentrations showed that the coefficient of determination of mixed organic vapor was 0.263 and those of n-hexane and TCE were 0.275 and 0.189, respectively. 7. Flow rates of sampling pumps used were found to be affected by relative humidity present. At 25 %, 55 %, and 85 % relative humidity, the relative errors of sampling pump were 1.4 %, 13.4 %, and 18.6 %, respectively. In conclusion, the results of this study showed that high relative humidity could reduce the adsorption volume of charcoal tubes and subsequently increase breakthrough rates. Therefore, to prevent breakthrough when sampling mixed organic vapors, it is suggested that either sampling volume be reduced on the flow rate be lowered so as to minimize breakthrough of the most volatile organic vapor in the mixture. In addition, since the flow rates of a sampling pump can be adversely affected by high relative humidity, it is recommended to use a constant flow mode pump when sampling in the highly humid environment.

• 한국IT서비스학회지
• /
• 제8권4호
• /
• pp.17-40
• /
• 2009

This study is to guide to estimate service quality on ITSM operation based on ITIL(IT Infrastructure Library). ITIL v2 and v3 provide how to integrate framework of IT service and business process. It is widely used as ITSM operation base. As a latest IT trend, ITSM covers Hardware, Software, SaaS, Network, Call center, Helpdesk, ASP portal and IT operation. Servicedesk is selected as target area where valid sampling is addressable and service change is rapid. Traditional Helpdesk was focusing on technical support to solve internal IT issues passively. But it was evolved into Service Desk which focus in process and provide integrated service from customer's business view point preventively and proactively. Accordingly outsourcing types business are normally performed by group of professional capability. Service quality is measured under the SLA(Service Level Agreement). This study utilized SERVQUAL model as service quality measuring tool developed by Parasuraman, Zeitaml and Berry to find critical factors to satisfy customer. And test was processed regarding effectiveness of IT organization and customer view point thru sampling. Though valid parameters can be changed by ITSM areas under the SERVQUAL models, they naturally can be accepted as a index of service quality measurement after sampling test with acceptable significance. And I recommend to follow this study as a preparation before official SLA.

• 한국조사연구학회:학술대회논문집
• /
• 한국조사연구학회 2001년도 춘계학술대회
• /
• pp.59-71
• /
• 2001

층화 다단계 샘플링에서 모총계 추정을 위하여 동질선형추정량을 고려하고, 이 추정량의 설계기반분산추정법을 고찰하였다. 한 방법은 분산을 일단계 분산과 이단계 분산으로 구분하여 각 층에서 각각을 비편향 추정하는 방법이고, 또 다른 방법은 이단계 표본에서 선정한 부차표본을 이용하여 일단계 분산만을 추정하여 전체분산을 비편향 추정하는 방법이다. 전자는 이단계 분산이 추정 가능할 때 이용하기 좋으며 후자는 이단계 분산을 추정할 수 없을 때 용이하게 쓸 수 있다. 각각의 추정법에 대하여 동질선형추정량에 대한 비음 비편향 분산 추정량의 형태를 제안하였다. 향후 실제 조사에서 본 논문에서 제안한 분산추정법이 효과적으로 사용될 수 있기를 기대한다.

• Journal of the Korean Data and Information Science Society
• /
• 제28권2호
• /
• pp.451-459
• /
• 2017

There are many researches showing that when a process change has occurred, variable sampling intervals (VSI) control chart is better than the fixed sampling interval (FSI) control chart in terms of reducing the required time to signal. When the process engineers use VSI control procedure, frequent switching between different sampling intervals can be a complicating factor. However, average number of samples to signal (ANSS), which is the amount of required samples to signal, and average time to signal (ATS) do not provide any control statistics about switching performances of VSI charts. In this study, we evaluate numerical switching performances of multivariate VSI EWMA chart including average number of switches to signal (ANSW) and average switching rate (ASWR). In addition, numerical study has been carried out to examine how to improve the performance of considered chart with accumulate-combine approach under several different smoothing constant and sample size. In conclusion, process engineers, who want to manage the correlation coefficients of related quality variables, are recommended to make sample size as large and smoothing constant as small as possible under permission of process conditions.

• 한국조사연구학회지:조사연구
• /
• 제2권1호
• /
• pp.59-71
• /
• 2001

층화 다단계 샘플링에서 모총계 추정을 위하여 동질선형추정량을 고려하고. 이 추정량의 설계기반 분산추정법을 고찰하였다. 한 방법은 분산을 일단계 분산과 이단계 분산으로 구분하여 각 층에서 각각을 비편향 추정하는 방법이고, 또 다른 방법은 이단계 표본에서 선정한 부하표본을 이용하여 일단계 분산만을 추정하여 전체분산을 비편향 추정하는 방법이다. 전자는 이단계 분산이 추정 가능할 때 이용하기 좋으며 후자는 이단계 분산을 추정할 수 없을 때 용이하게 쓸 수 있다. 각각의 추정법에 대하여 동질선형추정량에 대한 비음 비편향 분산 추정량의 형태를 제안하였다. 향 후 실제 조사에서 본 논문에서 제안한 분산추정법이 효과적으로 사용될 수 있기를 기대한다.

• 한국음향학회지
• /
• 제20권2호
• /
• pp.52-57
• /
• 2001

수중에서 음원까지의 거리를 추정하는 방법들이 연구되어 왔다. 그 가운데 초점 빔 형성기를 사용한 거리 추정 기법은 낮은 신호대 잡음비를 갖는 환경에서 우수한 성능을 갖는 것으고 알려져 있으나 다중 음원 환경에서는 성능 저하가 초래된다. 이에 본 논문에서는 두 개의 초점 빔 형성기를 사용하여 거리를 추정하는 방법을 제안하였다. 또한 표본화 주파수가 낮으면 초점 빔 형성기를 정확하게 원하는 위치로 지향할 수 없기 때문에 빔 패턴의 왜곡이 발생하게 되고, 그 결과 거리 추정 기법의 성능 저하를 초래한다. 그리고 이 논문에서는 표본화 주파수가 초점 빔 형성기를 이용하는 거리 추정 기법에 미치는 영향에 대해서도 고찰하도록 한다. 시뮬레이션을 통해 연구된 내용들을 검증하였다.