• Journal of Institute of Control, Robotics and Systems
• /
• v.13 no.3
• /
• pp.218-223
• /
• 2007

The dissipation of high-power ultrasonic energy at the faces of the defect causes an increase in temperature. It is resulted from localized selective heating in the vicinity of cracks because of the friction effect. In this paper the measurement of size and direction of crack using UET(Ultrasound Excitation Thermography) is described. The ultrasonic pulse energy is injected into the sample in one side. The hot spot, which is a small area around the crack tip and heated up highly, is observed. The hot spot, which is estimated as the starting point of the crack, is seen in the nearest position from the ultrasonic excitation point. Another ultrasonic pulse energy is injected into the sample in the opposite side. The hot spot, the ending point of the crack, is seen in the closest distance from the injection point also. From the calculation of the coordinates of both the first hot spot and the second hot spot observed, the size and slope of the crack is estimated. In the experiment of STS fatigue crack specimen(thickness 14mm), the size and the direction of the crack was measured.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.45 no.5
• /
• pp.499-506
• /
• 2012

We estimated the population size and fishing mortality of Pacific cod Gadus macrocephalus during the spawning season in waters off Woipo, Geoje Island, Korea, using a mark-recapture method. We marked and released 51 cod>50 cm in total length; six were recaptured by local fishermen during the period from December 15 to 31, 2009. The estimated population size was ca. 180,000 and the fishing mortality of the exploitable cod was 26%. Although we could assume a closed population due to the short survey period, we evaluated the uncertainty in the estimates by applying bootstrap resampling because the sample size was small. The estimated 95% confidence interval was 94,000-568,000 for the population size and 8-49% for fishing mortality. Our study demonstrated that the application of mark-recapture methods and bootstrap resampling can be useful in stock assessment for fisheries management in Korea, but requires a larger sample size, spatially extensive coverage, and sophisticated mark-recapture models based on a refined sampling design for reliable stock assessment and biological reference points in sustainable cod management.

• Korean Journal of Exercise Nutrition
• /
• v.23 no.1
• /
• pp.36-47
• /
• 2019

[Purpose] We conducted a meta-analysis to evaluate the effects of Taekwondo training on the physical fitness factors in Korean elementary students comprehensively and quantitatively. [Methods] We classified research studies published until November 2018 according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and selected a total of 17 research items; a meta-analysis of these items was then conducted. We used the Comprehensive Meta-Analysis 3.0 and Review Manager 5.3 to analyze the mean effect size, study quality, and publication bias. [Results] Taekwondo training improved the cardiopulmonary endurance, muscle endurance, and power of the elementary students, but was not practical or less useful on other physical fitness factors. The meta-regression analysis of the cardiopulmonary endurance and power items showed that the effect size was large when the sample size was small. Therefore, it is necessary to consider the sample size in interpreting the effect size for these two items. Further, during correction of the publication bias for the power items, the improvement effect by Taekwondo training was eliminated. [Conclusion] Taekwondo training is helpful for improving the cardiopulmonary endurance and muscle endurance of Korean elementary students but is not useful for other physical fitness factors.

• Journal of the Korean Data and Information Science Society
• /
• v.13 no.2
• /
• pp.329-340
• /
• 2002

Two methods are proposed for constructing a confidence interval on the among group variance component in a unbalanced one-way random effects model. Computer simulation is used to compare these methods with alternative procedures. The results indicate that the method1 and methods2 perform well over small group size and large sample size respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.15 no.3
• /
• pp.238-243
• /
• 2002

The dielectric properties and synthesis of $LaAIO_3$ ceramics from mixtures of $La_2O_3$ and $AI(OH)_3$ via ground(planetary ball mill) and unground(wet ball mill) were investigated. The single phase $LaAIO_3$ of ground powder was formed at $1000^{\circ}C$, while that of unground powder was formed at $1300^{\circ}C$. Density and grains of ground sample showed 98% of theory density and a uniform size of 0.75\mu\textrm{m}$, respectively, However those of unground sample showed 93% and non-uniform sizes of 4-5 $\mu\textrm{m}$. Dielectric constant and temperature coefficient of capacitance ($\tau$c) of both ground and unground samples were 21~22 and +70~74 ppm$/^{\circ}C$, respectively. Dielectric loss of ground sample(0.0004) was 10 times as low as that of unground sample(0.003) due to a uniform and small gram size.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.12 no.3
• /
• pp.1243-1263
• /
• 2018

The two-stage linear discrimination analysis (TSLDA) is a feature extraction technique to solve the small size sample problem in the field of image recognition. The TSLDA has retained all subspace information of the between-class scatter and within-class scatter. However, the feature information in the four subspaces may not be entirely beneficial for classification, and the regularization procedure for eliminating singular metrics in TSLDA has higher time complexity. In order to address these drawbacks, this paper proposes an improved two-stage linear discriminant analysis (Improved TSLDA). The Improved TSLDA proposes a selection and compression method to extract superior feature information from the four subspaces to constitute optimal projection space, where it defines a single Fisher criterion to measure the importance of single feature vector. Meanwhile, Improved TSLDA also applies an approximation matrix method to eliminate the singular matrices and reduce its time complexity. This paper presents comparative experiments on five face databases and one handwritten digit database to validate the effectiveness of the Improved TSLDA.

• The Korean Journal of Applied Statistics
• /
• v.24 no.1
• /
• pp.137-143
• /
• 2011

The classification of subjects with unknown distribution in a small sample size often involves order-restricted constraints in multivariate parameter setups. Those problems make the optimality of a conventional likelihood ratio based statistical inferences not feasible. Fortunately, Roy (1953) introduced union-intersection principle(UIP) which provides an alternative avenue. Multivariate linear rank statistics along with that principle, yield a considerably appropriate robust testing procedure. Furthermore, conditionally distribution-free test based upon exact permutation theory is used to generate p-values, even in a small sample. Applications of this method are illustrated in a real microarray data example (Lobenhofer et al., 2002).

• Journal of Astronomy and Space Sciences
• /
• v.11 no.2
• /
• pp.154-164
• /
• 1994

The secular period behavior of 23 field RR Lyrae stars is studied in order to determine if the observed period changes could be attributed, at least in the mean, to stellar evolution. The sample of stars is subdivided into two Oosterhoff groups based on the metallicity and period-shift. Despite the small sample size, we found a distinct bias toward positive period changes in the group II variables. The period changes of the group I variables, however, are small and in the mean near zero. This is consistent with the behavior predicted by the recent evolutionary models, as was the case for the variables in globular clusters. This provides yet another support for the Lee, Demarque, and Zinn (1990) evolutionary models of RR Lyrase stars and their explanation of the Sandage period-shift effect.

• The Korean Journal of Applied Statistics
• /
• v.15 no.1
• /
• pp.187-199
• /
• 2002

When the sample size is small, exact tests are often employed because the asymptotic distribution of the test statistic is in doubt. The advantage of exact tests is that it is guaranteed to bound the type I error probability to the nominal level. In this paper we review the methods of constructing exact tests, the algorithm and commercial software. We also examine the difference between exact p-values obtained from exact tests and true p-values obtained from the true underlying distribution.

• Journal of Magnetics
• /
• v.3 no.4
• /
• pp.127-133
• /
• 1998

I have overviewed the change in GMR on annealing, in conjunction with the change in microstructure. The Co46Al19O35 granular thin films were annealed at 30$0^{\circ}C$ for various annealing time to change the microstructure. The magnitude of GMR decreases considerably with increasing annealing time, although the size of Co granules estimated from TEM observation show a small change. Parameter fits of magnetization curves and magnetoresistance curves to the Langevin function suggest that large clusters consisting of several small Co granules, which are coupled ferromagnetically, are related with the decrease of GMR on annealing. The temperature dependence of electrical resistivity ($\rho$) shows the relationship of log $\rho$ versus $T^{-1/2}$ for the sample annealed for 10 min., 1 hr. and 6 hrs. However, the sample annealed for 38 hrs. shows the relationship of log $\rho$ versus$ T^{-1/4},$ which represents a significant change in the transport mechanism.