• 대한수학회지
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• 제61권2호
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• pp.293-307
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• 2024

In this paper, we give a general method to compute the linear independence measure of 1, log(1 - 1/r), log(1 + 1/s) for infinitely many integers r and s. We also give improvements for the special cases when r = s, for example, ν(1, log 3/4, log 5/4) ≤ 9.197.

• Journal of the Korean Data and Information Science Society
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• 제26권4호
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• pp.1017-1025
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• 2015

In mathematical statistics education, we can use mutual information as a tool for evaluating the degree of dependency between two random variables. The ordinary correlation coefficient provides information only on linear dependency, not on nonlinear relationship between two random variables if any. In this paper as a measure of the degree of dependency between random variables, we suggest the use of symmetric uncertainty and ${\lambda}$ which are defined in terms of mutual information. They can be also considered as generalized correlation coefficients for both linear and non-linear dependence of random variables.

• Communications for Statistical Applications and Methods
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• 제13권2호
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• pp.297-307
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• 2006

Most methods for describing the relationship among random variables require specific probability distributions and some assumptions of random variables. The mutual information based on the entropy to measure the dependency among random variables does not need any specific assumptions. And the redundancy which is a analogous version of the mutual information was also proposed. In this paper, the redundancy and mutual information are explored to multi-dimensional categorical data. It is found that the redundancy for categorical data could be expressed as the function of the generalized likelihood ratio statistic under several kinds of independent log-linear models, so that the redundancy could also be used to analyze contingency tables. Whereas the generalized likelihood ratio statistic to test the goodness-of-fit of the log-linear models is sensitive to the sample size, the redundancy for categorical data does not depend on sample size but its cell probabilities itself.

• The Journal of Korean Physical Therapy
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• 제21권2호
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• pp.39-45
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• 2009

Purpose: The purpose of this study was to determine correlations between the Berg Balance Scale (BBS), Functional Reach Test (FRT), Timed Up & Go (TUG), Motor-Free Visual Perception Reach Test Vertical format (MVPT-V), Functional Independence Measure (FIM). Methods: The subjects used in this study were 35 stroke patients from Cheongju ST. Mary's hospital. Balance was measured by BBS, FRT. Functional mobility was measured by TUG. Visual perception was measured by MVPT-V. FIM was used to evaluate the activities of daily living. Data was analyzed using pearson product correlation. The TUG and MVPT-V index were analyzed by linear regression. Results: There was a statistically significant difference between FRT and BBS (r=0.89, p<0.01), FIM (r=0.74, p<0.05), MVPT-V (r=0.40, p<0.05), and TUG (r=-0.36, p<0.05). There was significant statistical differences between TUG and MVPT-V (r=-0.64, p<.01). However, statistically significant differences were observed between BBS and FIM (r=0.79, p<0.01). The visual close item of the MVPT-V showed the strongest variance in predicting TUG. Conclusion: The use of both quantitative and qualitive scales was shown to be a good measuring instrument for the classification of general clinical performances of stroke patients. In particular, the results suggest that the visual perception test may be able to predict functional locomotion in stroke patients.

• 한국전문물리치료학회지
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• 제14권1호
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• pp.21-27
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• 2007

The purpose of this study was to evaluate isometric trunk extension strength in hemiplegic patients, and to compare that with normal subjects to find a correlation between trunk extension strength and the functional independent degree in hemiplegic patients. Fifteen hemiplegic male patients (mean age $55.2{\pm}10.2$ years) and twenty-five healthy male subjects (mean age $54.6{\pm}10.3$ years) completed isometric trunk extension. Strength was measured at 0, 12, 24, 36, 48, 60, and 72 degrees of trunk flexion. The functional independent degree was assessed by Functional Independence Measure (FIM). Mean isometric trunk extension strength was 91.2 ft-lbs, 120.7 ft-lbs, 142.3 ft-lbs, 156.4 ft-lbs, 173.5 ft-lbs, 184.1 ft-lbs, and 195.3 ft-lbs in the hemiplegic patients group, and 135.6 ft-lbs, 175.6 ft-lbs, 204.4 ft-lbs, 221.9 ft-lbs, 231.2 ft-lbs, 246.8 ft-lbs, and 259.7 ft-lbs in the normal subjects group. The values of isometric trunk extension strength had a descending linear correlation pattern from trunk flexion angle to extension angle. Trunk extension strength in hemiplegic patients was significantly lower than that of normal subjects (p<.05) but did not correlate with the FIM total score (p>.05). Therefore, the isometric trunk extension strength in hemiplegic patients was lower than that of normal subjects and did not correlate with the functional independent degree.

• 대한기계학회논문집A
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• 제29권6호
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• pp.795-803
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• 2005

This paper studies the observability of calibration system with a measurement operator. The calibration system needs a simple digital indicator to measure the mobile table movements with respect to the MC coordinate. However, it yields the concern about the poor parameter observability due to measuring only a part of the movements. We uses the QR-decomposition to find the optimal calibration configurations maximizing the linear independence of rows of an observation matrix. The number of identifiable parameter is examined by the rank of the observation matrix, which represents the parameter observability. The method is applied to a 6-axis MC with parallel tilting table and the calibration results are presented. These results verify that all necessary kinematic parameters are observable and the calibration system has robustness to the noise using optimal calibration configurations.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1512-1517
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• 2003

This paper presents the calibration for the parallel typed tilting table. The calibration system needs only simple sensing device which is a digital indicator to measure the orientation of a table. The calibration algorithm is developed by a measurement operator. It eliminates the concern about the poor parameter observability due to a large number of parameters of parallel-mechanism. This paper uses the QR-decomposition to find the optimal calibration configurations maximizing the linear independence of rows of a observation matrix. The number of identifiable parameters is examined by the rank of the observation matrix, which represents the parameter observability. The method is applied to a Parallel-typed Tilting Table and all the necessary kinematic parameters are identifiable.

• 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.

• Korean Chemical Engineering Research
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• 제52권4호
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• pp.425-429
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• 2014

최근까지 대부분의 PEMFC MEA(Membrnae and Electrode Assembly) 열화 연구는 전극과 전해질 막 각각 분리되어 연구되었다. 그런데 실제 PEMFC 운전조건에서는 전극과 전해질 막은 동시에 열화된다. 동시열화과정에서 전극열화와 전해질 막 열화는 상호 작용한다. 전해질 막의 열화정도를 측정하는데 수소투과도가 많이 사용되고 있다. 그런데 동시 열화가 발생했을 때 선형 쓸음 전기량 측정법(Linear Sweep Voltammetry, LSV)에 의해 수소투과도를 측정하면 전극열화가 수소투과전류를 감소시키는데, LSV 방법이 전극 촉매의 활성 면적에 의존하기 때문이다. 본 연구에서는 전극과 막 동시 열화과정에서 기체 크로마토그래프에 의한 PEMFC 전해질막의 수소투과도를 측정하였다. 기체 크로마토그래프 측정 방법은 전극 상태와 무관하기 때문에 전극과 막 동시 열화 과정에서 수소투과도가 전극 열화 영향을 받지 않음을 확인하였다.

• 한국전기화학회:학술대회논문집
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• 한국전기화학회 2001년도 전지기술심포지움
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• pp.145-161
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• 2001

Novel characterization of thermal properties of a battery has been introduced by defining its frequency-dependent thermal impedance function. Thermal impedance function can be approximated as a thermal impedance spectrum by analyzing experimental temperature transient which is related to the thermal impedance function through Laplace transformation. In order to obtain temperature transient, a process has been devised to generate external heat pulse with heating wire and to measure the response of battery. This process is used to study several commercial Li-ion batteries of cylindrical type. The thermal impedance measurements have been performed using potentionstat/galvanostate controlled digital signal processor, which is more commonly available than flow-meter usually applied for thermal property measurements. Thermal impedance spectra obtained for batteries produced by different manufactures are found to differ considerably. Comparison of spectra at different states of charge indicates independence of thermal impedance on charging state of battery. It is shown that thermal impedance spectrum can be used to obtain simultaneously thermal capacity and thermal conductivity of battery by non-linear complex least-square fit of the spectrum to thermal impedance model. Obtained data is used to simulate a response of the battery to internal heating during discharge. It is found that temperature inside the battery is by one-third larger that on its surface. This observation has to be considered to prevent damage by overheating.