• Journal of the Korean Society for Precision Engineering
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• v.12 no.5
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• pp.98-107
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• 1995

The in-process detection of drill wear and breakage is one of the most importnat technical problems in unmaned machining system. In this paper, the monitoring system is developed to monitor abnormal drilling states such as drill breakage, drill wear and unstable cutting using motor current. Drill breakage is detected by level monitoring. Tool wear is classified by fuzzy pattern recognition. The key feature for classification of tool wear is the estimated flank wear which is calculated by the proposed flank wear model. The characteristic of the model is not sensitive to the variation of cutting conditions but is sensitive to drill wear state. Unstable cutting states due to the unsmooth chip disposal and the overload are monitored by the variance/mean ratio of spindle motor current. Variance/mean ratio also includes the information about the prediction of drill wear and drill breakage. The evaluation experiments have shown that the developed system works very well.

• Journal of Communications and Networks
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• v.16 no.6
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• pp.583-591
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• 2014

In wireless communications, knowledge of the signal-to-noise ratio is required in diverse communication applications. In this paper, we derive the variance of the maximum likelihood estimator in the data-aided and non-data-aided schemes for determining the optimal shrinkage factor. The shrinkage factor is usually the constant that is multiplied by the unbiased estimate and it increases the bias slightly while considerably decreasing the variance so that the overall mean squared error decreases. The closed-form biased estimators for binary-phase-shift-keying and quadrature phase-shift-keying systems are then obtained. Simulation results show that the mean squared error of the proposed method is lower than that of the maximum likelihood method for low and moderate signal-to-noise ratio conditions.

• Fashion & Textile Research Journal
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• v.12 no.2
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• pp.214-218
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• 2010

This research was to judge on the gathered skirt's shape by visual images that was from the different gathered skirts according to different sewing conditions; fabrics(cotton, mixed-wool, polyester), ratio of gathers(1.5T, 2.0T, 2.5T). Questionnaire consists of 33 semantic differential scale expressing gathered skirt's image, and 10 items of the shape were measured by 3D measurements method. The data were analyzes by factor analysis, correlation analysis, ANOVA. The image of gathered skirts was composed of the five factors of activities, attraction, grace, softness, and ordinary and it was showed that these five factors occupied 68.4% of the total variance. The shape of gathered skirts was composed of the two factors of the side and the front, and it was showed that these two factors occupied 93.6% of the total variance. According to correlation analysis of visual shape, the front was significant in activities, attraction and ordinary, and the side was significant in activities, grace and ordinary. As a result of ANOVA, the visual images were significant in ratio of gathers. 2.5 ratio of gathered skirts were perceived to be more active and attractive, and 1.5 ratio of gathered skirts were more ordinary and graceful.

• Journal of Korean Society for Quality Management
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• v.41 no.1
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• pp.119-134
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• 2013

Purpose: The purpose of this paper is to show whether the results are changed with respect to the variance of the data, by analysis of data obtained from the Taguchi experimental techniques and general experiment. Because which cannot be prove by mathematical Formula, through experimental examples will show. Methods: Taguchi experiments were carried out with paper Helicopter experiment. Experimental Data are obtained by special designed Drop Test Equipment. While Experimental value arbitrarily changed, we looked at how Significant control Factor of Taguchi Methods and Factor experiments are changed. This process cannot be expressed as a Mathematical formula, but showed as a numerical example. Results: Saw significant changes in the factors when data is outside a certain range of the experimental data. By Test of Equivalence Variance, Experiment data is verified reliability. To find the Control Factor, Taguchi Method is better than the general experiment. Conclusion: We know that a Significant Factor is changed with the range of Variance of Experiment Data. The value of this paper is verified change process with Numerical Data obtained Experiment.

• Journal of the Korean Data and Information Science Society
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• v.18 no.4
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• pp.1171-1177
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• 2007

We consider estimation of the right-tail probability in a log-Laplace random variable, As we derive the density of ratio of two independent log-Laplace random variables, the k-th moment of the ratio is represented by a special mathematical function. and hence variance of the ratio can be represented by a psi-function.

• Communications for Statistical Applications and Methods
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• v.6 no.1
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• pp.11-24
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• 1999

In this paper we propose a method to test $\textit{H}$:$\rho_i$=$\gamma_i$ for 1$\leq$$\textit{i}$$\leq$$\ell$ against $\textit{K}$:$\rho_i$$\neq$$\gamma_i$ for some ｉin k-variance component random or mixed linear model where $\rho$i denotes the ratio of the i-th variance component to the error variance and $\ell$$\leq$K. The test which we call Rao-Wald test is exact and does not depend upon nuisance parameters. From a numerical study of the power performance of the test of the interaction effect for the case of a two-way random model Rao-Wald test was seen to be quite comparable to the locally best invariant (LBI) test when the nuisance parameters of the LBI test are assumed known. When the nuisance parameters of the LBI test are replaced by maximum likelihood estimators Rao-Wald test outperformed the LBI test.

• Journal of KSNVE
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• v.10 no.4
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• pp.642-647
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• 2000

Conventional cepstrum has been widely used to detect echo and fault signals embedded in noise. One of the problems of finding impulse signals using the conventional cepstrum in that it is normally very sensitive to signal to noise ratio (SNR). This paper proposes a signal processing method to detect impulse signal in noisy environment. Because the proposed method minimizes the variance of signal power at a cepstrum domain, it is suggested to be called as minimum variance cepstrum (MV cepstrum). Computer simulations have been performed to understand the characteristics of the MV cepstrum. Both mathematical approach and computer simulations confirmed that the MV cepstrum is a useful technique to detect impulse in noisy environment.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.23 no.56
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• pp.83-92
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• 2000

This paper presents a study on control schemes for gradual increases (drifts) in a process variance. A new control chart, the Drifting Variance Control Chart (DVCC) is designed using Likelihood Ratio Test (LRT), and the ARL performance of the chart is evaluated for different subgroup sizes. The performance of this chart is then compared to some of the popular control schemes for the process dispersion, like the Shewhart S$^2$chart, the CUSUM chart and the EWMA chart. Results are presented and discussed. Also included is a sensitivity analysis that investigates how the DVCC performs when applied to a stepped change in process variance.

• Journal of the Korean Society of Food Science and Nutrition
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• v.24 no.6
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• pp.892-900
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• 1995

Dietary data of 538 middle school students have been analysed to identify the contribution of specific foods to absolute intake and between-person-variance in nutrient consumption. The 24-hour-dietary-recall method had been used to collect the data required. Contribution of specific foods, in terms of ranking order for both absolute intake and between-person-variance have been observed. Ranking order of food for absolute intake was given based on the percen of contribution whereas the ranking order of foods for between-person-variance was given based on the percent of contribution whereas the ranking order of foods for between-person-variance was given based on a coefficient fo variation. As a result, for most of the nutrients(except cholesterol), the ranking order of foods for the between-person-variance was quite different from that of absolute intake. The results indicate that to identify between-person-variance of nutrient intake in an epidemiology study, foods with a high ranking in between-person-variance should be included in developing the food frequency questionnaires rather than foods which showed a high ranking in absolute intake.

• East Asian mathematical journal
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• v.9 no.2
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• pp.333-345
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• 1993