• 통합자연과학논문집
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• 제12권3호
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• pp.78-84
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• 2019

In many cases, the quality of a product is determined by several correlated quality variables. Control charts have been used for a long time widely to control the production process and to quickly detect the assignable causes that may produce any deterioration in the quality of a product. Numerical switching performances of multivariate cumulative sum control chart for simultaneous monitoring all components in the dispersion matrix ${\Sigma}$ under multivariate normal process $N_p({\underline{\mu}},{\Sigma})$ are considered. Numerical performances were evaluated for various shifts of the values of variances and/or correlation coefficients in ${\Sigma}$. Our computational results show that if one wants to quick detect the small shifts in a process, CUSUM control chart with small reference value k is more efficient than large k in terms of average run length (ARL), average time to signal (ATS), average number of switches (ANSW).

• Journal of Positioning, Navigation, and Timing
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• 제6권2호
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• pp.71-78
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• 2017

The sidereal day of a Global Positioning System (GPS) satellite was intended to equal one half of a sidereal day of the Earth. However, the sidereal day of GPS satellites has become unequal to one half of a sidereal day of the Earth. This is fundamentally caused by the non-sphericity of the Earth and the gravity of the Moon. The difference between sidereal days of GPS satellites and the Earth is known as a sidereal shift. The details surrounding sidereal shifts and their origins have yet to be fully understood. We calculated the periodicity of sidereal shifts for GPS satellites using broadcast ephemeris data. To conduct a periodic analysis of the sidereal shift, we employ the Lomb-Scargle periodogram method. It shows that the orbit periods of GPS satellites have small-amplitude perturbations with a 13.6-day period. In addition, we compare the GPS satellite orbit periods with the periodicity of geomagnetic indices and the solar wind parameters to identify the cause of the perturbations. Our results suggest that the solar wind stream might also affect the 13.6-day period of the sidereal shifts.

• 응용통계연구
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• 제22권6호
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• pp.1191-1201
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• 2009

공정관리에서 작은 평균변화를 탐지하기 위하여 누적합 관리도를 사용하는 것이 일반적이다. 자기상관이 존재하는 공정의 경우 시계열 모형에 적합하여 구한 잔차를 관리도에 적용하는 모형기반 관리방법이 활용되고 있다. 그러나 공정에 일정한 크기의 지속적인 수준 변화가 발생하면 잔차에는 동적 평균변화의 패턴이 나타나게 되어 누적합 관리도의 탐지능력은 저하될 수 있다. 본 논문에서는 잔차에 등락을 반복하는 진동(oscillation) 특성의 동적 평균변화가 발생하는 ARMA(1,1) 모형을 대상으로, 그러한 변화를 효율적으로 탐지할 수 있는 새로운 OCUSUM 관리도를 제안하고 모의실험을 통해 최근에 소개된 기존의 CUSUM 관리도와 탐지능력을 비교하였다.

• Journal of Biosystems Engineering
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• 제43권4호
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• pp.311-319
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• 2018

Purpose: The aim of this study is to develop a small combine for harvesting miscellaneous cereal crops. Methods: A prototype small combine was designed and constructed. Its specifications and basic performance were investigated. Results: The prototype small combine for harvesting miscellaneous cereal crops was designed and constructed to reflect similar specifications as those of the conventional combine. The prototype small combine comprises a diesel engine with the rated power/speed of 22.0 kW/2,600 rpm, three-stage primary and two-stage speed range transmission shifts, and a double acting threshing part. The maximum travel speeds of the prototype combine are approximately 0.72 m/s, 2.50 m/s, 0.30 m/s at the low, high speed range shifts in the forward direction, and while traversing in the reverse direction, respectively. The minimum radius of turning was approximately 1.50 m. In a static lateral overturning test, the prototype combine overturned neither to the right nor to left on a $30^{\circ}$ slope. The results of an oilseed rape harvesting test included the maximum operating speed of 0.32 m/s, the grain loss ratio of approximately 9.0%, and the effective field capacity of approximately 10.3 a/h. Additionally, among the outputs in grain outlet, the whole grains, damage grains, and materials other than grain (MOG) ratios accounted for 97.4%, 0.0%, and 2.6%, respectively. Conclusions: The prototype small combine for harvesting miscellaneous cereal crops indicates good driving ability and stability. The results of the oilseed rape harvesting test reveal that the harvesting performance must be enhanced such that the separating and cleaning parts are more suitable for each type of crop, thus reducing grain loss and foreign substances among the outputs in grain outlet. An improved small prototype combine could be used effectively to mechanize the harvesting of miscellaneous cereal crops in small family farms or semi-mountainous areas.

• Asian Pacific Journal of Cancer Prevention
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• 제16권9호
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• pp.3945-3949
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• 2015

Background: For brachytherapy of cervical cancer, applicator shifts can not be avoided. The present investigation concerned Utrecht interstitial applicator shifts and their effects on organ movement and DVH parameters during 3D CT-based HDR brachytherapy of cervical cancer. Materials and Methods: After the applicator being implanted, CT imaging was achieved for oncologist contouring CTVhr, CTVir, and OAR, including bladder, rectum, sigmoid colon and small intestines. After the treatment, CT imaging was repeated to determine applicator shifts and OARs movements. Two CT images were matched by pelvic structures. In both imaging results, we defined the tandem by the tip and the base as the marker point, and evaluated applicator shift, including X, Y and Z. Based on the repeated CT imaging, oncologist contoured the target volume and OARs again. We combined the treatment plan with the repeated CT imaging and evaluated the change range for the doses of CTVhr D90, D2cc of OARs. Results: The average applicator shift was -0.16 mm to 0.10 mm for X, 1.49 mm to 2.14 mm for Y, and 1.9 mm to 2.3 mm for Z. The change of average physical doses and EQD2 values in Gy${\alpha}/{\beta}$ range for CTVhr D90 decreased by 2.55 % and 3.5 %, bladder D2cc decreased by 5.94 % and 8.77 %, rectum D2cc decreased by 2.94 % and 4 %, sigmoid colon D2cc decreased by 3.38 % and 3.72 %, and small intestines D2cc increased by 3.72 % and 10.94 %. Conclusions: Applicator shifts and DVH parameter changes induced the total dose inaccurately and could not be ignored. The doses of target volume and OARs varied inevitably.

• 한국데이터정보과학회:학술대회논문집
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• 한국데이터정보과학회 2003년도 춘계학술대회
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• pp.89-95
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• 2003

Cumulative sum(CUSUM) control charts for monitoring dispersion matrix under multivariate normal process are proposed. Performances of the proposed CUSUM charts are measured in terms of average run length(ARL) by simulation. Numerical results show that small reference values of the proposed CUSUM chart is more efficient for small shifts in the production process.

• Communications for Statistical Applications and Methods
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• 제12권2호
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• pp.265-273
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• 2005

In this paper, we proposed multivariate EWMA control charts for both combine-accumulate and accumulate-combine approaches to monitor dispersion matrix of multiple quality variables. Numerical performance of the proposed charts are evaluated in terms of average run length(ARL). The performances show that small smoothing constants with accumulate-combine approach is preferred for detecting small shifts of the production process.

• 품질경영학회지
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• 제40권4호
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• pp.467-480
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• 2012

Purpose: This paper introduces new 2-of-3 main and supplementary runs rules to increase the performance of the classical $\bar{X}$ control chart for detecting small process shifts. Methods: The proposed runs rules are compared with other competitive runs rules by numerical experiments. Nonlinear optimization problem to minimize the out-of-control ARL at a specified shift of process mean for determining action and warning limits at a time is formulated and a procedure to find two limits is illustrated with a numerical example. Results: The proposed 2-of-3 main and supplementary runs rules demonstrate an improved performance over other runs rules in detecting a sudden shift of process mean by simultaneous changes of mean and standard deviation. Conclusion: To increase the performance in the detection of small to moderate shifts, the proposed runs rules will be used with $\bar{X}$ control charts.

• Interdisciplinary Bio Central
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• 제6권1호
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• pp.1.1-1.6
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• 2014

A growing body of evidence shows that most psychological traits are polygenic, that is they involve the action of many genes with small effects. However, the study of selection has disproportionately been on one or a few genes and their associated sweep signals (rapid and large changes in frequency). If our goal is to study the evolution of psychological variables, such as intelligence, we need a model that explains the evolution of phenotypes governed by many common genetic variants. This study illustrates simple statistical tools to detect signals of recent polygenic selection: a) ANOVA can be used to reveal significant deviation from random distribution of allele frequencies across racial groups. b) Principal component analysis can be used as a tool for finding a factor that represents the strength of recent selection on a phenotype and the underlying genetic variation. c) Method of correlated vectors: the correlation between genetic frequencies and the average phenotypes of different populations is computed; then, the resulting correlation coefficients are correlated with the corresponding alleles' genome-wide significance. This provides a measure of how selection acted on genes with higher signal to noise ratio. Another related test is that alleles with large frequency differences between populations should have a higher genome-wide significance value than alleles with small frequency differences. This paper fruitfully employs these tools and shows that common genetic variants exhibit subtle frequency shifts and that these shifts predict phenotypic differences across populations.

• 지구물리와물리탐사
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• 제27권2호
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• pp.129-143
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• 2024

자기지전류(magnetotelluric, MT) 탐사 시, 지표면 부근의 작은 불균질체가 존재할 경우 겉보기비저항이 주파수와 무관하게 이동하는 정적효과(static shift)가 발생한다고 알려져 있다. 이러한 정적효과가 자료에 포함되어 있으면 지하 구조 해석에 오류가 발생하기 때문에 정적효과에 의한 왜곡을 해결하기 위한 연구가 지난 수십년 동안 수행되어 왔다. 가장 대표적인 방법으로는 역산 전에 MT 자료에서 정적효과를 제거하기 위해 보정하는 방법이 있다. 이와 달리, 역산 과정에서 정적효과를 역산의 변수로 포함시켜 그 크기를 추정하거나 따로 정적효과를 추정하지 않고 역산 과정에서 보정을 수행하기도 한다. 이외에도 다른 물리탐사 기법을 통해 얻은 자료를 사용하여 MT 탐사 정적효과를 제거할 수 있다. 하지만 지금까지 연구된 보정법들은 1차원적인 정적인 반응에만 국한되어 있어 2차원이나 3차원의 자료를 역산하고 해석하는 데에는 여전히 한계가 있다. 이 논문에서는 지금까지 MT 자료에서 정적효과를 처리하는 여러 방법들에 대해 분석하여 향후 정적효과 관련 연구를 위한 기초를 제공하고자 한다.