• 품질경영학회지
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• 제30권2호
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• pp.99-117
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• 2002

Variable sampling interval(VSI) and variable sample size(VSS) control charts vary the sampling rate for the next sample depending on the current chart statistic. This paper develops EWMA charts with the VSI and VSS features, and investigates the effectiveness of these charts in context of an economic model. The economic properties of these charts are evaluated by using Markov chain methods. The model contains cost parameters which allow the specification of the costs associated with sampling, false alarms, and operating off target. This economic model can be used to quantify the cost saving that can be obtained by using control charts with the VSI and VSS features instead of with the fixed sampling rate(FSR) feature, and can also be used to gain insight into the way that control charts with the VSI and VSS features should be designed to achieve optimal economic performance. The economic performance of X charts with the VSI and VSS features is also considered.

• 품질경영학회지
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• 제32권4호
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• pp.252-264
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• 2004

Variable sampling Interval (VSI) control charts vary the sampling interval according to value of the control statistic while the sample size is fixed. It is known that control charts with 2-state VSI scheme, which uses only two sampling intervals, give good statistical properties. Variable sample size (VSS) control charts vary the sample size according to value of the control statistic while the sampling interval is fixed. In the VSS scheme no optimal results are known for the number of sample sizes. It is also known that the variable sampling rate (VSR) $\bar{X}$ control chart with 2-state VSS and 2-state VSI scheme leads to large improvements In performance over the fixed sampling rate (FSR) $\bar{X}$ chart, but the optimal number of states for sample size Is not known. In this paper, the VSR Χ charts with multi-state VSS and 2-state VSI scheme are designed and compared to 2-state VSS and 2-state VSI scheme. The multi-state VSS scheme is considered to, achieve an additional improvement by switching from the 2-state VSS scheme. On the other hand, the multi-state VSI scheme is not considered because the 2-state scheme is known to be optimal. The 3-state VSS scheme improves substantially the sensitivity of the $\bar{X}$ chart especially for small and moderate mean shifts.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 19-21 Oct. 1992
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• pp.927-930
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• 1992

VSS identification approach is based on following concept, i.e. while in sliding motion, the switching of control inputs refects system uncertainites. Therefore, if there exist some operations that make the information form the switiching control inputs be achievable, then the unknown parameters can be actually identification mechanisms which can fully make use of the available information. Two different types of VSS identifiers are taken into consideration. The first type uses adjustable model whose structure is similar to that of identified systems. From the viewpoint of contro, this type of VSS identifiers may be regraded as direct identifier vecause the identified system is handled as an open loop. On the other hand, if the identified system is controlable in the sense of VSS(sliding mode can be generated through chosing control inputs), the second type of VSS identifier, the indirect VSS identifier, can be constructed according to the linerized system strucutre while staying in sliding mode. Therefroe it can be applied to some nonlinear systems which are not linear in parametric space by general identification algorithms, whereas linear in parametric space when sliding mode is existed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1988년도 한국자동제어학술회의논문집(국내학술편); 한국전력공사연수원, 서울; 21-22 Oct. 1988
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• pp.54-57
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• 1988

In this thesis, after the inverted pendulum being made, its state equation was established with parameters obtained by the state space approach and its position stabilization control was performed with VSS. The switching function of VSS was obtained from pole placement method and as the result of VSS control was compared with that of optimal regulator control, its robustness was clarified in sliding mode. The position and stabilization control of the inverted pendulum Wstem were acomplished with VSS.

• 유기물자원화
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• 제29권4호
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• pp.41-46
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• 2021

초음파/과산화칼슘 처리(US/CaO₂)에 따른 하수슬러지의 가용화 정도를 확인하고자 과산화칼슘의 주입량(0.01, 0.02, 0.03, 0.04 및 0.05 g CaO₂/g VSS)에 따른 처리 효율을 비교하였다. 가용화의 주요 지표인 VSS 감량화율, 가용화율, SCOD/VSS, SCOD 증가속도 및 미생물의 세포벽이 파쇄되었는지 확인하기 위하여 LB-EPS와 TB-EPS를 측정하였다. 실험결과, US/CaO₂(0.05 g CaO₂/g VSS) 조건에서 가용화율은 50.7%로 US 처리(23.4%)보다 높은 효율을 나타내었으며, VSS 감량화율도 US/CaO₂(0.05 g CaO₂/g VSS) 조건에서 17.7%, US 조건에서는 7.1%로 가용화율과 유사한 경향을 나타내었다. 조사시간 10분부터 90분까지 SCOD의 증가속도는 US/CaO₂(0.02 g CaO₂/g VSS) 조건에서 0.0151 min^-1으로 가장 빠른 속도를 나타내었다. TB-EPS는 US/CaO₂(0.05 g CaO₂/g VSS)조건에서 59.0%, US 조건에서 36.4% 감소하였다. TB-EPS는 초기 10분동안 빠르게 감소하였으며, 이후부터 상대적으로 완만하게 줄어드는 것을 확인할 수 있었다. 과산화칼슘의 주입량에 따른 TB-EPS의 감소량은 큰 차이가 없는 것으로 나타났다.

• Clinical and Experimental Pediatrics
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• 제59권3호
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• pp.126-131
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• 2016

Purpose: To evaluate the diagnostic value of the Vesikari Scoring System (VSS) as an early predictor of pathogens in children with acute gastroenteritis (AG). Methods: In this retrospective study, the VSS score, absolute neutrophil count (ANC), and C-reactive protein (CRP) levels were analyzed in 107 hospitalized children with AG, aged 6 months to 17 years. Patients were divided into nonspecific, viral, and bacterial groups according to the pathogens detected using a multiplex polymerase chain reaction (PCR) test. Results: Patients in the bacterial group had significantly higher CRP values and VSS scores compared to those in the viral group and significantly higher VSS scores compared to those in the nonspecific group (P<0.05). Patients in the viral group had significantly higher VSS scores than those in the nonspecific group (P<0.05). Logistic regression analysis revealed that VSS was the most effective diagnostic tool for predicting the type of pathogen (P<0.05). The area under the receiver operating characteristics curve of VSS was significantly greater than that for ANC and CRP (P<0.05). At a cutoff point of 10 in the VSS, an acceptable diagnostic accuracy could be achieved for distinguishing between bacterial and viral pathogens in AG. Conclusion: VSS can be considered a useful and reliable infectious marker for pediatric gastroenteritis. VSS may be a good early predictor of the type of pathogen, enabling development of a treatment plan before results from a stool culture or PCR test are available.

• 한국환경보건학회지
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• 제19권3호
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• pp.17-21
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• 1993

Characteristics of a downflow anaerobic packed bed reactor with raschig ring ceramics as a packing were measured and discussed for the basic evaluation of the process. A synthesized glucose substrate wastewater were used as a feed and process characteristics such as pH, biogas production, composition of produced gas, COD removal and VSS were measured with the hydraulic retention time (HRT) changing from 0.25 to 2 days. As a result, this type of reactor was applicable in continuous operation within the given HRT range and the transient period approaching the steady state was about 20 days. The content of methane in produced gas increase with HRT was always high above 50% enough to use as energy source. The COD removal efficiency increased gradually as HRT increased. The axial profile of VSS concentration in the reactor usually showed the maximum at the lower region and the minimum at the middle. The VSS concentration at the upper region and the exit appeared similarly. However, at 0.25 day of HRT, the VSS concentration of effluent became higher than that of the upper region. Therefore the optimum HRT of this reactor occurred about 0.5 day, at which the production of methane began to be just stabilized and loss of VSS and COD removal were resonable.

• 전자공학회논문지
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• 제52권7호
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• pp.127-134
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• 2015

본 연구에서는 다입출력 불확실 선형 플랜트를 위한 포화함수에 의한 연속 슬라이딩 면 변환 가변 구조 시스템이 주어진다. 이론적으로 불연속 슬라이딩 면 변환 가변구조 시스템을 제안한다. 사전에 결정된 슬라이딩 면 위에 슬라이딩 모드의 다입출력 존재 조건과 함께 페루프 지수 안정성에 대해 검토한다. 실제 응용을 위하여 포화 함수에 의하여 불연속 가변구조 시스템의 연속 근사화를 이룬다. 실제적인 관점에서 가변 구조 시스템의 내부 특성인 제어입력의 불연속성을 많이 개선한다, 설계 예와 시뮬레이션 연구를 통하여 제안된 연속 변환 가변구조 시스템 제어기의 유용성을 입증한다.

• 품질경영학회지
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• 제28권3호
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• pp.44-52
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• 2000

In this paper we apply VSS X chart to the case when two assignable causes effect the process mean shift. We compare the case when two compound assignable causes effect the process mean with another one which effects individually. For the practical use of VSS $\bar{X}$ chart we propose the sample size which minimizes the average number of samples until the signal is given in out-of-control state.

• 품질경영학회지
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• 제31권3호
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• pp.126-135
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• 2003

A basic assumption in standard applications of control charts is that the observations are statistically independent. However, this assumption is often violated from processes in many industries. The presence of autocorrelation has a serious impact on the performance of control charts, causing a dramatic increase in the frequency of false alarms. This paper considers a process in which the observations can be modeled as a first order autoregressive(AR(1)) process, and develops (equation omitted) charts with the variable sample size(VSS) scheme for monitoring the mean of this process.