• Journal of the Korean Mathematical Society
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• v.61 no.2
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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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• v.26 no.4
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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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• v.13 no.2
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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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• v.21 no.2
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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.

• Physical Therapy Korea
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• v.14 no.1
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.6 s.237
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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.

• Proceedings of the KSME Conference
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• 2003.11a
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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.

• The Korean Journal of Applied Statistics
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• v.16 no.2
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• pp.455-467
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• 2003

There has been a long debate on the applicability of the chi-square approximation to statistics based on small sample size. Extending comparison results among Pearson chi-square Χ$^2$, generalized likelihood .ratio G$^2$, and the power divergence Ι(2/3) statistics suggested by Rudas(1986), recently developed disparity statistics (BWHD(1/9), BWCS(1/3), NED(4/3)) we compared and analyzed in this paper. By Monte Carlo studies about the independence model of two dimension contingency tables, the conditional model and one variable independence model of three dimensional tables, simulated 90 and 95 percentage points and approximate 95% confidence intervals for the true percentage points are obtained. It is found that the Χ$^2$, Ι(2/3), BWHD(1/9) test statistics have very similar behavior and there seem to be applcable for small sample sizes than others.

• Korean Chemical Engineering Research
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• v.52 no.4
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• pp.425-429
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• 2014

Until a recent day, degradation of PEMFC MEA(membrane and electrode assembly) has been studied, separated with membrane degradation and electrode degradation, respectively. But membrane and electrode were degraded coincidentally at real PEMFC operation condition. During simultaneous degradation, there was interaction between membrane degradation and electrode degradation. Hydrogen permeability was used often to measure degradation of electrolyte membrane in PEMFC. In case of hydrogen permeability measured by LSV(Linear Sweep Voltammetry) method, the degradation of electrode decrease the value of hydrogen crossover current due to LSV methode's dependence on electrode active area. In this study hydrogen permeability was measured by gas chromatograph(GC) when membrane and electrode degraded at the same time. It was showed that degradation of electrode did not affect the hydrogen permeability measured by GC because of GC methode's independence on electrode active area.

• 한국전기화학회:학술대회논문집
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• 2001.11a
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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.