• Journal of the Korean Statistical Society
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• 제3권1호
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• pp.3-12
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• 1974

The two-stage sequential test, suggested by Baker [2] for testing hypotheses $H_0:\mu=\mu_0$ and $H_1:\mu=\mu_1$ of $N(\mu,\sigma^2)$ with the unknown $\sigma^2$ would not be amenable for applications unles some cluses on the choice of the first-stage sample size are available. The study in this paper is intended to shed some light on the size of the first-stage sample. An approximate method is used to estimate an optimal initial sample size that minimizes the average sample number. In brief, the optimal size is a strictly monotone decreasing function of the quantity $(\mu_1-\mu_0)/\sigma$. Empirical and simulation results are used to ascertain the negligible effect of possible errors due to approximations and assumptions used.

• 응용통계연구
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• 제20권3호
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• pp.605-618
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• 2007

모집단 단위들이 희박하게 존재하고 접근하기 어려운 경우에 적용하는 적응추출설계에서의 추출과정은 관심변수의 관측값에 의존한다. 동일한 표본크기에서 적응집락추출의 추정량은 단순임의추출의 추정량에 비해 효율이 더 좋다 적응추출에서 Rao-blackwell의 정리를 적용하여 Murthy의 추정량의 형태로 수정한 한센-휴비_(HH) 추정량과 호르비_-톰슨 (HT) 추정량은 기존의 추정량에 비해 작은 분산을 가진다. 본 연구는 초기표본을 바꿔가면서 기대표본크기와 적응추출의 표본크기 하의 단순임의추출의 추정량과 적응추출의 추정량의 효율을 비교하였다.

• Biotechnology and Bioprocess Engineering:BBE
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• 제7권1호
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• pp.21-25
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• 2002

To maximize and sustain the productivity of Monascus pigments, various environmental and nutritional parameters, such as the initial moisture content, pH, inoculum size, sample size, and nutrient supplement, that influence pigment production were evaluated in solid-state cultures as follows: initial moisture content, $50\%;$ pH, 6.0; inoculum size $1\;\times\;10^4$ spore cells $(grams\;of\;dry\;solid\;substrate)^{-1};$ sample size, 300 g. All supplementary nutrients (carbon, nitrogen, and mineral sources) added has inhibitory effects on the cell growth and red pigment production. In open tray culture the maximum biomass yield and specific productivity of red pigments were 223 mg DCW $(grams\;of\;initial\;dry\;substrate)^{-1}$ and, $47.6\;OD_{500}\;(DCW\;grams)^{-1}h^h{-1}$ respectively.

• Composites Research
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• 제37권3호
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• pp.179-185
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• 2024

본 연구는 Representative Volume Element(RVE) 모델을 사용하여 초기 공극 결함이 있는 단방향 섬유강화 복합재의 횡방향 인장 강도 변화에 대해 정량적 평가 및 조사되었다. 초기 공극 결함을 표본오차와 신뢰 수준을 기준으로 적정 표본의 수가 계산된 후, 총 5000개의 초기 공극 결함이 있는 RVE 모델이 표본 집단으로 생성되었다. 표본 집단은 차원 축소법과 밀도 기반 군집 분석을 통해 유사도 분석이 진행되었으며 편향되지 않은 표본 집단임이 확인 및 검증되었다. 검증된 표본 분석 결과는 복합재 구조의 신뢰성 해석에 적용될 수 있게 Weibull 분포로 표현되었다.

• Journal of Mechanical Science and Technology
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• 제18권5호
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• pp.838-846
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• 2004

Minimum ignition energies of hydrogen/air and methane/air mixtures have been investigated numerically by solving unsteady one-dimensional conservation equations with detailed chemical kinetic mechanisms. Initial kernel size needed for numerical calculation is a sensitive function of initial pressure of a mixture and should be estimated properly to obtain quantitative agreement with experimental results. A simple macroscopic model to determine minimum ignition energy has been proposed, where the initial kernel size is correlated with the quenching distance of a mixture and evaluated from the quenching distance determined from experiment. The simulation predicts minimum ignition energies of two sample mixtures successfully which are in a good agreement with the experimental data for the ranges of pressure and equivalence ratio.

• 터널과지하공간
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• 제2권2호
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• pp.251-264
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• 1992

In this study, the size effect in measuring the fracture toughness of rock was investigated using the ISRM Suggested Method for Fracture toughness using Chevron Bend Specimens. Total 58 specimens were prepared with 4 different diameters, 29, 42, 54, 68mm and center cut-chevron notch. In addition to this, to evaluated the effect of anisotropy of Jecheon granite, which is the sample for this study, core drilling direction was adjusted perpendicular(short transverse) and parallel(arrester) to the rift plane in the sample and the measured fracture toughness for each direction were compared. Important results obtained from this study are as follows. Level ll test condition is more adequate than l, because of low data scattering and precision and corrected fracture toughness of Jechoen granite measured and 2.2MPa{{{{ SQRT { m} }}}} for arrester direction with minimum initial crack length 0.7cm. From the relationship between core diameter and initial crack length presented in the ISRM testing method, the specimen diameter should be bigger than 47mm. The fracture toughnesses measured for arrester and short transverse directon show 10% difference. This is to the anisotropy of Jecheon granite possessing rift plane.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.901-905
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• 2005

Monte Carlo localization is known to be one of the most reliable methods for pose estimation of a mobile robot. Much research has been done to improve performance of MCL so far. Although MCL is capable of estimating the robot pose even for a completely unknown initial pose in the known environment, it takes considerable time to give an initial estimate because the number of random samples is usually very large especially for a large-scale environment. For practical implementation of the MCL, therefore, a reduction in sample size is desirable. This paper presents a novel approach to reducing the number of samples used in the particle filter for efficient implementation of MCL. To this end, the topological information generated off- line using a thinning method, which is commonly used in image processing, is employed. The topological map is first created from the given grid map for the environment. The robot scans the local environment using a laser rangefinder and generates a local topological map. The robot then navigates only on this local topological edge, which is likely to be the same as the one obtained off- line from the given grid map. Random samples are drawn near the off-line topological edge instead of being taken with uniform distribution, since the robot traverses along the edge. In this way, the sample size required for MCL can be drastically reduced, thus leading to reduced initial operation time. Experimental results using the proposed method show that the number of samples can be reduced considerably, and the time required for robot pose estimation can also be substantially decreased.

• 한국산업융합학회 논문집
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• 제2권2호
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• pp.61-68
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• 1999

The variety of crystalline structure and mechanical properties of PP filament treated with dry heat treatment at different draw ratio has been studied. Crystalline structure and mechanical properties of annealed PP filament at different draw ratio has been examined by XRD, UTM, and density method. Heat treatment has been carried out $100^{\circ}C$, $120^{\circ}C$ $140^{\circ}C$ for 30min. in dry oven. From the results of this study, it found the following facts. It was found that the crystallinity and crystallite size of (110) plane of sample were increased with increasing of annealed temperature and draw ratio. The crystalline form of annealed sample which was undrawn showed ${\alpha}$, ${\beta}$ mixing form below $120^{\circ}C$ and showed ${\alpha}$ form at $140^{\circ}C$. But the crystalline form of annealed sample which was drawn showed ${\alpha}$ form at $120^{\circ}C$. Initial modulus and tensile strength were increased with increasing of annealing temperature, and the degree of orientation was decreased with decreasing of annealing temperature.

• 품질경영학회지
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• 제42권3호
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• pp.445-458
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• 2014

Purpose: Present study was designed to examine the casual relationships among web service quality, customer satisfaction, initial trust and off-line visit intention in hospital website. Research object was limited to web service quality of general hospital. We applied path analysis model in order to test the hypotheses and research model. Methods: Survey tool, that is, Questionnaire had obtained validity through literature survey, exploratory survey and pretest and sample 320 was selected. For statistical treatment of pretest and main analysis, SPSS18.0 and AMOS18.0 were employed and Structural equation model was employed as analysis method. Results: Result of this study shows as follows. Factors of web service quality have an effect on customer satisfaction and initial trust, both of customer satisfaction and initial trust have an effect on off-line visit intention. Also customer satisfaction affects initial trust. Especially, customer satisfaction and initial trust were empirically confirmed as the important factors preceding off-line vis it intention. Conclusion: Therefore, present study shows that customer satisfaction and initial trust are important factors that medium and small size hospitals have to emphasize to raise performance. However, present study has some limitations to additionally research in the future.

• Korea-Australia Rheology Journal
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• 제15권4호
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• pp.197-208
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• 2003

Two measures of distributive mixing are examined: the standard deviation $\sigma$ and the maximum error E, among average concentrations of finite-sized samples. Curves of E versus sample size L are easily interpreted in terms of the size and intensity of the worst flaw in the mixture. E(L) is sensitive to the size of this flaw, regardless of the overall size of the mixture. The measures are used to study distributive mixing for time-periodic flows in a rectangular cavity, using the mapping method. Globally chaotic flows display a well-defined asymptotic behavior: E and $\sigma$ decrease exponentially with time, and the curves of E(L) and $\sigma$ (L) achieve a self-similar shape. This behavior is independent of the initial configuration of the fluids. Flows with large islands do not show self-similarity, and the final mixing result is strongly dependent on the initial fluid configuration.