• Proceedings of the IEEK Conference
• /
• 2000.11b
• /
• pp.325-328
• /
• 2000

The control of the data retention time is a main issue for realizing future high density dynamic random access memory. In this paper, we propose the new implantation scheme by gate-related ion beam shadowing effect and buffer-enhanced $\Delta$ Rp increase using buffered N- implantation with tilt and 4X-rotation that is designed on the basis of the local-field-enhancement model of the tail component. We report an excellent tail improvement of the retention time distribution attributed to the reduction of electric field across the cell junction due to the redistribution of N- concentration which is intentionally caused by Ion Beam Shadowing and Buffering Effect using tilt implantation with 4X-rotation.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2023.05a
• /
• pp.585-587
• /
• 2023

Long-tailed datasets have an imbalanced distribution because they consist of a different number of data samples for each class. However, there are problems of the performance degradation in tail-classes and class-accuracy imbalance for all classes. To address these problems, this paper suggests a learning method for training of long-tailed dataset. The proposed method uses and combines two methods; one is a resampling method to generate a uniform mini-batch to prevent the performance degradation in tail-classes, and the other is a reweighting method to address the accuracy imbalance problem. The purpose of our proposed method is to train the learning models to have uniform accuracy for each class in a long-tailed dataset.

• Journal of the Korean Society for information Management
• /
• v.35 no.1
• /
• pp.157-182
• /
• 2018

As data management and processing techniques have been developed rapidly in the era of big data, nowadays a lot of business companies and researchers have been interested in long tail data which were ignored in the past. This study proposes methods for generating and controlling a network of technical terms based on text mining technique to enhance data utilization in the distribution of long tail theory. Especially, an edit distance technique of text mining has given us efficient methods to automatically create an interlinking network of technical terms in the scholarly field. We have also used linked open data system to gather experimental data to improve data utilization and proposed effective methods to use data of LOD systems and algorithm to recognize patterns of terms. Finally, the performance evaluation test of the network of technical terms has shown that the proposed methods were useful to enhance the rate of data utilization.

• Journal of Forest and Environmental Science
• /
• v.8 no.1
• /
• pp.51-66
• /
• 1992

This study was carried out to investigate the micromorphology of vessel wall sculpture such as shape of perforation plate, perforation rim, steepness of perforation plate, occurrence of vestured pit, warty layer and ray-vessel pitting on 13 species of Fagaceae in Korea. The results were summarized as follows ; 1. In the species examined, all sample species except Fagus crenata var. multinervis have simple perforation plate. But Fagus crenata var. multinervis has simple and scalariform perforation plate (it was called to combination perforation plate) in a tree stem. 2. The shapes of perforation rim could be classified into five types; Type A without tail, Type B with small tail on both sides, Type C with long tail on both sides, Type D with tail only one side and Type E with the very short interval between perforations. Among five types, Type Band C have higer frequency of distribution than the others. 3. The steepness of perforation plate measured was about 20 degree on pore zone and 43 degree on outside parts of pore zone. 4. Species with vestured pit were Q. aliena, Q, dentata, Q. variabilis, Fagus crenata var. multinervis, Castanopsis cuspidata var sieboldii, Q. acuta, Q. stenophylla, and Q. glauca. But the extent of vesturing was very slight and vestured pits were observed mainly in ray-vessel pit of some vessel elements. 5. Species with warty layer on the inner surface wall of all vessel elements were Q. acuta, Q. stenophylla, Q. glauca, Fagus crenata var. multinervis and species with warty layer of some vessel elements were Q. aliena, Q, dentata, Q. variabilis, Castanopsis cuspidata var. sieboldii. 6. Species with palisade ray-vessel pit were Q. acuta, Q. stenophylla, Q. glauca, Castanea crenata, Castanea bungeana, Q. aliena, Q. serrata, Q. mongolica, and species with scalariform ray-vessel pit was Fagus crenata var. multinervis and species with oval ray-vessel pit were Q, dentata, Castanopsis cuspidata var sieboldii.

• Journal of the Korea Safety Management & Science
• /
• v.13 no.1
• /
• pp.195-202
• /
• 2011

The study interprets each of three classification models based on Bath-Tub Failure Rate (BTFR), Extreme Value Distribution (EVD) and Conjugate Bayesian Distribution (CBD). The classification model based on BTFR is analyzed by three failure patterns of decreasing, constant, or increasing which utilize systematic management strategies for reliability of time. Distribution model based on BTFR is identified using individual factors for each of three corresponding cases. First, in case of using shape parameter, the distribution based on BTFR is analyzed with a factor of component or part number. In case of using scale parameter, the distribution model based on BTFR is analyzed with a factor of time precision. Meanwhile, in case of using location parameter, the distribution model based on BTFR is analyzed with a factor of guarantee time. The classification model based on EVD is assorted into long-tailed distribution, medium-tailed distribution, and short-tailed distribution by the length of right-tail in distribution, and depended on asymptotic reliability property which signifies skewness and kurtosis of distribution curve. Furthermore, the classification model based on CBD is relied upon conjugate distribution relations between prior function, likelihood function and posterior function for dimension reduction and easy tractability under the occasion of Bayesian posterior updating.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.13 no.2 s.54
• /
• pp.231-242
• /
• 2009

The baseline distribution of a structure represents the statistical distribution of dynamic response feature from the healthy state of the structure. Generally, damage-sensitive dynamic response feature of a structure manifest themselves near the tail of a baseline statistical distribution. In this regard, some researchers have paid attention to extreme value distribution for modeling the tail of a baseline distribution. However, few researches have been conducted to theoretically understand the extreme value distribution from a perspective of statistical damage assessment. This study investigates the asymptotic convergence of domain of attraction in extreme value distribution through parameter estimation, which is needed for reliable statistical damage assessment. In particular, the asymptotic convergence of a domain of attraction is quantified with respect to the sample size out of which each extreme value is extracted. The effect of the sample size on false positive alarms in statistical damage assessment is quantitatively investigated as well. The validity of the proposed method is demonstrated through numerically simulated acceleration data on a two span continuous truss bridge.

• The Mathematical Education
• /
• v.39 no.2
• /
• pp.167-177
• /
• 2000

In this thesis we concerned with the degree of similarity in pairs of scores having a common mean and variance could express similarity in terms of the absolute difference between the standardized scores. We particulary discussed the distribution of absolute differences between pairs of T scores among many standardized scores and demonstrated the procedures for calculating the lower limit of Med(│d│) values i. e. the maximum possible similarity with medians and correlation coefficients of the equivalent form tests by using the folded normal distribution, although other researchers expressed the degree of similarity using only the standard normal distribution. We also described many cases how to use those techniques and to apply effectively them in real evaluation fields.

• Communications for Statistical Applications and Methods
• /
• v.21 no.6
• /
• pp.501-512
• /
• 2014

Stylized facts on asset return are fat-tail, asymmetry, volatility clustering and structure changes. This paper simultaneously captures these characteristics by introducing a multi-regime models: Finite mixture distribution and regime switching GARCH model. Analyzing the daily KOSPI return from $4^{th}$ January 2000 to $30^{th}$ June 2014, we find that a two-component mixture of t distribution is a good candidate to describe the shape of the KOSPI return from unconditional and conditional perspectives. Empirical results suggest that the equality assumption on the shape parameter of t distribution yields better discrimination of heterogeneity component in return data. We report the strong regime-dependent characteristics in volatility dynamics with high persistence and asymmetry by employing a regime switching GJR-GARCH model with t innovation model. Compared to two sub-samples, Pre-Crisis (January 2003 ~ December 2007) and Post-Crisis (January 2010 ~ June 2014), we find that the degree of persistence in the Pre-Crisis is higher than in the Post-Crisis along with a strong asymmetry in the low-volatility (high-volatility) regime during the Pre-Crisis (Post-Crisis).

• Journal of the Korean Magnetics Society
• /
• v.7 no.4
• /
• pp.186-190
• /
• 1997

We measured an anisotropy inhomogeniety and dispersion of rf sputterd permalloy thin films by TBP(Transverse Biased Permeability) measurement method. Angular distribution function had a shape similar to the Lorentzian distribution, but magnitude distribution function deviates from the sysmetric Lorentzian distribution because of long tail to the region of a high Hk value. With increasing film thickness, the angular and magnitude anisotropy dispersion increased. The increase of angular dispersion was due to both the increase of grain size and local anisotropy in thicker films.

• Journal of the Korean Data and Information Science Society
• /
• v.28 no.2
• /
• pp.421-433
• /
• 2017

The CTE (conditional tail expectation) is a useful risk management measure for a diversified investment portfolio that can be generally estimated by using a transformed univariate distribution. Hong et al. (2016) proposed a multivariate CTE based on multivariate quantile vectors, and explored its characteristics for multivariate normal distributions. Since most real financial data is not distributed symmetrically, it is problematic to apply the CTE to normal distributions. In order to obtain a multivariate CTE for various kinds of joint distributions, distribution fitting methods using copula functions are proposed in this work. Among the many copula functions, the Clayton, Frank, and Gumbel functions are considered, and the multivariate CTEs are obtained by using their generator functions and parameters. These CTEs are compared with CTEs obtained using other distribution functions. The characteristics of the multivariate CTEs are discussed, as are the properties of the distribution functions and their corresponding accuracy. Finally, conclusions are derived and presented with illustrative examples.