• The Korean Journal of Applied Statistics
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• v.16 no.2
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• pp.321-333
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• 2003

Self-organizing map (SOM), a unsupervised learning neural network, has been developed by T. Kohonen since 1980's. Main application areas were pattern recognition and text retrieval. Because of that, it has not been spread to statisticians until late. Recently, SOM's are frequently drawn in data mining fields. Kohonen's SOM, however, needs improvements to become a statistician's standard tool. First, there should be a good guideline as for the size of map. Second, an enhanced visualization mode is wanted. In this study, principal components self-organizing map (PC-SOM), a modification of Kohonen's SOM, is proposed to meet such needs. PC-SOM performs one-dimensional SOM during the first stage to decompose input units into node weights and residuals. At the second stage, another one-dimensional SOM is applied to the residuals of the first stage. Finally, by putting together two stages, one obtains two-dimensional SOM. Such procedure can be easily expanded to construct three or more dimensional maps. The number of grid lines along the second axis is determined automatically, once that of the first axis is given by the data analyst. Furthermore, PC-SOM provides easily interpretable map axes. Such merits of PC-SOM are demonstrated with well-known Fisher's iris data and a simulated data set.

• The Korean Journal of Applied Statistics
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• v.26 no.1
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• pp.37-47
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• 2013

A Q-Q plot is an effective and convenient graphical method to assess a distributional assumption of data. The primary step in the construction of a Q-Q plot is to obtain a closed-form expression to represent the relation between observed quantiles and theoretical quantiles to be plotted in order that the points fall near the line y = a + bx. In this paper, we introduce a Q-Q plot to assess goodness-of-fit for inverse Gaussian distribution. The procedure is based on the distributional result that a transformed random variable $Y={\mid}\sqrt{\lambda}(X-{\mu})/{\mu}\sqrt{X}{\mid}$ follows a half-normal distribution with mean 0 and variance 1 when a random variable X has an inverse Gaussian distribution with location parameter ${\mu}$ and scale parameter ${\lambda}$. Simulations are performed to provide a guideline to interpret the pattern of points on the proposed inverse Gaussian Q-Q plot. An illustrative example is provided to show the usefulness of the inverse Gaussian Q-Q plot.

• Proceedings of the Technology Innovation Conference
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• 2004.02a
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• pp.288-315
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• 2004

This paper has examined the leapfrogging thesis with the case of catch-up in digital TV by the Korean firms. Despite the disadvantages implied by the technological regime of digital TV and the risks facing early entrants in trajectory choice and initial market formation, the Korean firms had achieved a 'path-creating catch-up' in the sense they chose a different path from the Japanese forerunning firms. As they have been closely watching the technological trends and the standard setting process, there was less risk of choosing the right or wrong technological trajectory. Also, despite the lack of sufficient capability and core knowledge base, the Korean firms had some complementary asset, such as the experience of producing analogue TV, and were able to develop the prototype digital TV and the ASIC chips, given the accesses to the foreign knowledge via overseas R&D posts and acquisition of a foreign company. To secure the initial market size, the Korean targeted the US market from the beginning, and their sources for competitive advantages were the speedy setting up the production system for mass production of products at the initial stage. The initial failure of the Japanese firms and the success of the Korean firms do suggest that the period of paradigm shift, like this toward digital technology, can serve as a window of opportunity for late-comers while penalizing the forerunner.

• Journal of Korean Society on Water Environment
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• v.20 no.6
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• pp.625-630
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• 2004

Granular media filtration is used almost universally as the last particle removal process in conventional water treatment plants. Therefore, superb particle removal efficiency is needed during this process to ensure a high quality of drinking water. However, every particle can not be removed during granular media filtration. Besides the pattern of particle attachment is different depending on physicochemical aspects of particles and suspension. Filtration experiments were performed in a laboratory-scale filter using spherical glass beads with a diameter of 0.55 mm as collectors. A single type of particle suspension (Min-U-Sil 5) and alum coagulation was used to destabilize particles. The operating conditions were similar to those of standard media filtration practice: a filtration velocity of 5 m/h. More favorable particles, i.e., particles with smaller surface charge, were well attached to the collectors especially during the early stage of filtration when zeta potential of particles and collectors are both negative. This selective attachment of the lower charged particles caused the zeta potential distribution (ZPD) of the effluent to move to a more negative range. On the other hand, the ZPDs of the effluent moved from more positive to less positive when the surface charge of particles was positive and this result was thought to be caused by ion transfer between particles and collectors.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.11
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• pp.1035-1045
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• 2017

Classification of age and gender has been carried out through different approaches such as facial-based and audio-based classifications. One of the limitations of facial-based methods is the reduced recognition rate over large distances, while another is the prerequisite of the faces to be located in front of the camera. Similarly, in audio-based methods, the recognition rate is reduced in a noisy environment. In contrast, gait-based methods are only required that a target person is in the camera. In previous works, the view point of a camera is only available as a side view and gait data sets consist of a standard gait, which is different from an ordinary gait in a real environment. We propose a feature extraction method using skeleton models from an RGB-D sensor by considering characteristics of age and gender using ordinary gait. Experimental results show that the proposed method could efficiently classify age and gender within a target group of individuals in real-life environments.

• Journal of Fashion Business
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• v.24 no.2
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• pp.1-16
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• 2020

Hijab as a symbol of women's oppression due to the opening and reform of Islamic State group, is becoming more diverse as younger generation begins to dress more freely than ever before, spreading the perception that it is a fashion item. In response, this research conducted a theoretical review about the history of hijab, various forms of hijab, and characteristics of hijab using relevant literature, media reports, and fashion media articles. As an empirical study, image-oriented photo data shared by Tehran Street Fashion from 2015 to November 2019 were analyzed separately by fashion majors into color, pattern, and hijab-making forms. According to the analysis, six different fashion images were categorized as romantic feminine, modern chic, natural elegant, classic formal, sporty casual and gorgeous ethnic. For Muslim women in the past, hijab was worn as a repressive and closed sense by the religious system. However, in modern times, it is a way to express one's style and ideas as a fashion item. It is also and a means to express one's thoughts and beliefs. Through aesthetic consideration of Hijab as a fashion item, it was found that it was a medium for freedom of expression and a medium for beauty and individuality.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.2
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• pp.87-96
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• 2012

With a view to determine a safe speed the limit of a manipulator arm, several experiments was performed with a multi-jointed manipulator in maintenance and decommissioning tasks of nuclear facilities. Under the simulated emergency conditions, which were generated with random combinations of manipulator arm speed, failure probability and failure type, response characteristics of human operators to various malfunctions of a manipulator arm were measured in terms of reaction time, number of false alarm, and number of misses. This paper demonstrated that failure type, manipulator axes and manipulator arm speed has significant effects on human reaction time. As a whole the reaction time was slightly increased with manipulator arm speed, which is showed somewhat different pattern due to failure type. The reaction time to an axis acting on a workpiece directly, which could flex and extend, was fastest and much more its standard deviation was small. Various factors which may affect safe speed were also described.

• Fashion & Textile Research Journal
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• v.19 no.1
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• pp.49-60
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• 2017

In this study, change trends and specific times for change in body size were sought to be identified by using manual measurements for Korean adult women at 20 to 89 of age, along with examinations of change trends and specific times of change in body shape based on body index values. The examinations of means, deviations, and variation coefficients revealed that there was a tendency of most height related measures to decrease. In addition, combined with decrease in height, growth in weight led to increased BMI, thus resulting in increase in measures of circumference, thickness, and breadth in the torso area. The BMI trends showed that with increasing age, BMI increased, reaching the peak between the ages of 55 and 59 and then decreasing from 64 of age, with the steepest increase in BMI at ages from 50 to 54. The examination of differences in the body flatness ratio for different parts of body found that with increasing age the ratio decreased, indicating a tendency for gradual change to round body shapes. The analysis of 3D body shape found that there were more back-bends and lowered shoulder levels with age, accompanied with a tendency for more bended legs and more inclined-forward necks. The key trends in changes in body measurements by age and detailed estimates of 3D standard body shape drawn out from this study are expected to significantly contribute to establishing a basic database for generating patterns reflecting age features of Korean adult females.

• Journal of the Korean Society of Clothing and Textiles
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• v.17 no.3
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• pp.459-469
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• 1993

The purpose of this study is to investigate the relationship between body-types and skirt-patterns by analyzing various fitting conditions of the skirt patterns in relation to the body-types. To achieve this, fitting tests were done on six types of skirt-patterns. The tests included four body-types selected according to the existing classification of the types of under part of the body. Sensory tests were performed on the existing patterns and new drafting method based on the results of the fitting tests. The results of the fitting tests and sensory test are as follows. 1. The existing skirt-patterns were relatively well-fitted except for certain parts in standard somatotype (body-type A). 2. The new drafting method, designed on the basis of the fitting test on the existing patterns, scored high on all of the eighteen items included in the test This signifies the excellence of the new drafting method. 3. In the case of the allocation between the front and the back, which is the difference between the educational patterns and industrial patterns, the best silhouette was achieved when the hip-line and the waist-line were same sized both in the back and in the front. However, in the case of body-type D it was better when there was a 1cm difference between the back and the front. 4. The number of darts that best fits young persons were found to be eight, to keep their side hip-curve smooth. Further, it is desirable to set the center line of the dart as the vertical waist-line. 5. The best length of the darts were determined to be 12.5cm, 11ch in the back, and 11cm, 9.5cm in the front. Adjustments would be made according to the differing body-types in the range of 0.5cm. 6. The lowerness of the back waist-line for the normal was determined at 1.5cm, with some variations in other body-types. 7. The front waist-line was needed to be 1cm lowered in the case of body-type B, whereas, in the case of body-type D, it was needed to be 1cm raised.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.410-413
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• 2005

The results of an experimental and analytical study of composite pressure hull on buckling pressure are presented for LRN 300. Composite tensile test was done to know the composite material properties applied FE analysis for URN composite. We predicted the buckling and post buckling analysis of composite laminated cylindrical panels under external compression by using ABAQUS /Standard[Ver 6.4]. To obtain nonlinear static equilibrium solutions for unstable problems, where the load-displacement response can exhibit the type of nonlinear buckling behavior, during periods of the response, the load and/or the displacement may decrease as the solution evolves, used the modified Riks method. The modified Riks method is an algorithm that allows effective solution of such cases [7]. Experiments were conducted to verify the validation of present analysis for cross-ply laminated shells. The shells considered in the study have two different lamination patterns, $[{\pm}45/0/90]_{18s\;and}\;[/0/90]_{18s}$. Cylindrical panel of experiment and analysis have the radius of 200mm, length of 210mm and 60 degree of cutting angle. The critical load from experiment is $69\%$ of that of numerical analysis, because the fracture of matrix was generated before buckling. So URN 300 is not proper to use at the condition under high external pressue.