• 한국축산식품학회지
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• 제18권1호
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• pp.50-56
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• 1998

Scanning electron microscopic appearance of infant milk formula indicated that mostly agglomerate with few or more diverse number of particles and also apple like as well as typical feature of drying in raw milk. Small particle of infant milk formula become agglomerate progressively. Some sample represent crystalline rectangular among the globular agglomerates which seem to be a different composites or those of solubility. Some sample showed the irregular porosity at central sec-scanning electron microscopic study between Korea and European products.

• Journal of Magnetics
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• 제3권3호
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• pp.86-88
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• 1998

A portable RF HTS SQUID-based susceptometer was used for small size magnetized sample testing in weak DC (up to 200A/m) and AC (up to 4 A/m) magnetic fields. The system resolution for the magnetic moment is of the order of $1.6{\times}10^{-10} A.m^2$. The measured DC susceptibility of a tested sample agrees well with the value obtained by using a commercial liquid helium susceptometer.

• 한국콘텐츠학회논문지
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• 제15권7호
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• pp.428-435
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• 2015

우리 기업의 타인자본조달에 관한 통계지표를 살펴보면 대기업은 은행의 기업대출과 회사채 등의 직접금융을 함께 사용하여 자본을 조달하고 있는 반면, 중소기업은 은행대출에 계속 의지하고 있음을 확인할 수 있다. 이러한 현실을 감안하여 본 연구에서는 기업의 타인자본조달을 실증분석하는데 있어 표본선택편의가 존재하고 이를 감안한 연구모형을 사용해야 한다고 주장한다. 이러한 주장을 뒷받침하기 위해 1990년부터 2013년까지의 상장기업 자료를 통해 부채구조를 설명하는 실증분석을 수행한 결과 선행연구에서와 마찬가지로 기업의 회사채사용에 있어 기업규모, 1대주주 지분율, 유형자산 구성비, 수익성, 배당성향 등이 영향을 미치고 있음을 확인할 수 있었으며, 패널표본선택모형에 투입된 Inverse Mills Ratio 변수가 유의하게 나타나 패널표본선택모형을 사용하는 것이 타당함을 확인하였다. 이러한 결과는 기업의 타인자본조달에 있어 표본선택편의가 존재하며 이에 관한 연구에서 이를 반드시 감안해야 함을 의미한다.

• 환경위생공학
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• 제21권1호
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• pp.1-11
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• 2006

This study was to investigate concentration characteristics of atmospheric PCBs in soil sample and pine needle at rural area. Profiles of PCB congener detected in pine needle and soil sample have a difference that low molecular PCBs mainly existed in pine needle, whereas high molecular PCBs were mainly existed in soil sample because of their different vapor pressure and octanol-air partitioning coefficient($K_{OA}$) of each congeners. Correlation coefficients(r) of PCB congeners simultaneously detected in soil and pine needle were significant (r>0.71, p<0.01), which showed that PCB congeners patterns of atmosphere could be estimated in using pine needle and soil sample indirectly. The contributions(%) of higher molecular PCBs(>penta-CB) to total PCBs in soil sample were higher than those of pine needle and the contribution of lower molecular PCBs(

• 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.

• Transactions on Electrical and Electronic Materials
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• 제11권1호
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• pp.37-41
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• 2010

The authors investigated the photoluminescence (PL) and the electron paramagnetic resonance (EPR) from an magnesium (Mg)-doped GaN thin film with a delta-doped layer. The regularly doped sample shows a PL peak at 2.776 eV for the as-grown sample, and the peak shifts to 2.904 eV and increases in intensity for the annealed sample. The delta-doped sample also shows the same PL peak as does the regularly doped sample. However, only the annealed delta-doped layer shows a sharp EPR with a small isotropic Lande g-factor, $g_{II}$, of 2.029. This resonance is attributed to the delta-doped layer, which forms a hole-bound Mg-N atomic structure instead of the $Mg_{Ga}-V_N$ defect complex, indicating that the delta-doped sample was not optically activated to form PL centers but was instead electrically activated to form a hole-bound state.

• ALGAE
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• 제24권2호
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• pp.111-120
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• 2009

Choosing an appropriate sample unit is a fundamental decision in the design of ecological studies. While numer-ous methods have been developed to estimate organism abundance, they differ in cost, accuracy and precision.Using both field data and computer simulation modeling, we evaluated the costs and benefits associated with twomethods commonly used to sample benthic organisms in temperatc kelp forests. One of these methods, theTargeted Sampling method, relies on different sample units, each "targeted" for a specific species or group ofspecies while the other method relies on coefficients that represent ranges of bottom cover obtained from visual esti-mates within standardized sample units. Both the field data and the computer simulations suggest that both meth-ods yield remarkably similar estimates of organisnm abundance and among-site variability, although the Coefficientmethod slightly underestimates variability armong sample units when abundances are low. In contrast, the twomethods differ considerably in the effort needed to sample these communities; the Targeted Sampling requiresmore time and twice the persormel to complete. We conclude that the Coeffident Sampling metliod may be bettcrfor environmental monitoring programs where changes in mean abundance are of central conccm and resources arelimiting, but that the Targeted sampling methods may be better for ecological studies where quantitative reIation-ships among species and small-scale variability in abundance are of central concern.

• 응용통계연구
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• 제27권1호
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• pp.1-11
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• 2014

세 개 이상의 집단에 대한 생존분포의 비교를 위해 가중 로그순위 검정법(Weighted Logrank test)과 그의 특별한 경우인 로그순위 검정법(Logrank test)이 널리 쓰인다. 그러나 이 방법은 근사적인 분포를 이용한 방법이므로 표본 크기가 작은 경우에는 유효하지 못할 수 있으며, 각 집단의 중도절단 분포가 동일하다는 가정 또한 충족되어야 하기 때문에 이 가정이 충족되지 못할 경우에도 검정법의 유효성을 장담할 수 없다. 표본 크기가 작은 경우에 대한 대안으로, 분포에 대한 가정이 없이 관찰된 자료만으로 검정통계량의 분포를 추정하고 그 분포를 이용해 검정하는 순열 검정법(Permutation test)이 제안되었으나, 순열 검정법 또한 각 집단의 중도절단 분포가 동일하다는 가정이 충족되어야 한다. 따라서 순열 검정법을 향상시킨 순열-대치 검정법(Permutation-Imputation test)이 대안이 될 수 있는데, 이는 대치 단계(Imputation step)에서 귀무가설 하에서의 생존확률이 집단에 의존하지 않도록 자료를 조정한 후 순열 검정 단계(Permutation step)를 통해 검정하는 방법이다. 본 논문에서는 근사적 방법, 순열 검정법, 순열-대치 검정법을 로그순위 검정법과 가중 로그순위 검정법의 한 형태인 Prentice-Wilcoxon 검정법에 적용해 각 검정법의 유효성과 검정력을 비교하였다.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 1995년도 춘계공동학술대회논문집; 전남대학교; 28-29 Apr. 1995
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• pp.869-879
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• 1995

The new field of learning control develops controllers that learn to improve their performance at executing a given task, based on experience performing this task. The simplest forms of learning control are based on the same concept as integral control, but operating in the domain of the repetitions of the task. In the previous paper, I had studied the use of such controllers in a decentralized system, such as a robot with the controller for each link acting independently. The basic result of the paper is to show that stability of the learning controllers for all subsystems when the coupling between subsystems is turned off, assures stability of the decentralized learning in the coupled system, provided that the sample time in the digital learning controller is sufficiently short. In this paper, we present two examples. The first illustrates the effect of coupling between subsystems in the system dynamics, and the second studies the application of decentralized learning control to robot problems. The latter example illustrates the application of decentralized learning control to nonlinear systems, and also studies the effect of the coupling between subsystems introduced in the input matrix by the discretization of the system equations. The conclusion is that for sufficiently small learning gain, and sufficiently small sample time, the simple learning control law based on integral control applied to each robot axis will produce zero tracking error in spite o the dynamic coupling in the robot equations. Of course, the results of this paper have much more general application than just to the robotics tracking problem. Convergence in decentralized systems is seen to depend only on the input and output matrices, provided the sample time is suffiently small.

• 응용통계연구
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• 제16권2호
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• pp.455-467
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• 2003

소표본 분할표 자료에서 적합도 검정통계량들의 카이제곱 근사 적용 가능에 대하여 많은 연구가 진행되었다. 소표본에서 세 가지 검정 통계량(피어슨 카이제곱 Χ$^2$, 일반화 가능도비 G$^2$, 그리고 역발산 Ι(2/3) 검정통계량)에 관하여 비교한 Rudas(1986)의 연구를 확장하여, 최근에 제안된 차이측도(BWHD(1/9), BWCS(1/3), NED(4/3) 검정통계량)를 포함시켜 비교 분석하였다. 독립모형의 이차원 분할표, 조건부 독립모형과 한 변수 독립 모형을 따르는 삼차원 분할표에 대한 모의실험을 통하여 생성된 90과 95 백분위수와 이에 대응하는 95% 신뢰구간을 살펴보고 실제 백분위수와 비교하였다. 그 결과 Χ$^2$, Ι(2/3), 그리고 BWHD(1/9) 검정통계량이 유사한 결과를 나타내었고 이 통계량들이 기존에 제안된 검정통계량들보다 적은 표본크기에서도 카이제곱 근사방법에 적용 가능함을 발견하였다.