• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.1
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• pp.58-65
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• 2010

For the improvement of fuel consumption, the study on the use of lightweight material or thinner sheet have been carried out in automotive industry. With the need for the use of thinner sheet, the dent resistance became one of the major concern in th design of exterior panels in automotive industry. Many studies have been carried out for the dent resistance by experiment or quasi-static numerical simulation. In this study, the dent formation behavior is investigated by dynamic finite element analysis using ABAQUS. Dent formation may be affected by many factors such as sheet thickness, material properties, pre-strain, and sheet curvature. The effect of these factors on dent resistance is investigated. From the analysis following three conclusions are derived. First, dent resistance become hard as the sheet curvature radius increases. Second, dynamic dent resistance is mainly affected by bending stress rather than tensile stress. Third, the pre-strain itself do not give any guidance for dynamic dent resistance and dynamic dent resistance have to be decided considering the strain hardening and thickness reduction together. The results are considered to be reliable and useful to improve the dent damage of automotive panels.

• Journal of Information Technology Services
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• v.13 no.4
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• pp.275-287
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• 2014

Recently, the volume of unstructured text data generated by various social media has been increasing rapidly; consequently, the use of text mining to support decision-making has also been growing. In particular, academia and industry are paying significant attention to topic analysis in order to discover the main issues from a large volume of text documents. Topic analysis can be regarded as static analysis because it analyzes a snapshot of the distribution of various issues. In contrast, some recent studies have attempted to perform dynamic issue tracking, which analyzes and traces issue trends during a predefined period. However, most traditional issue tracking methods have a common limitation : when a new period is included, topic analysis must be repeated for all the documents of the entire period, rather than being conducted only on the new documents of the added period. Additionally, traditional issue tracking methods do not concentrate on the transition of individuals' interests from certain issues to others, although the methods can illustrate macro-level issue trends. In this paper, we propose an individual interests tracking methodology to overcome the two limitations of traditional issue tracking methods. Our main goal is not to track macro-level issue trends but to analyze trends of individual interests flow. Further, our methodology has extensible characteristics because it analyzes only newly added documents when the period of analysis is extended. In this paper, we also analyze the results of applying our methodology to news articles and their access logs.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.12 no.2
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• pp.121-125
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• 2001

Singing requires exquisite coordination between the respiratory and phonatory system to efficiently control glottal airflow. Respiratory function and vocal aerodynamics were investigated in six female professional sopranos and in six female subjects without vocal training. All sopranos had more than 15 years of formal classic vocal training. Pulmonary function test data on simple pulmonary function, flow volume curve, static lung volumes, maximum inspiratory pressure(MIP), and maximum expiratory pressure(MEP) were obtained from all subjects. Vocal aerodynamic studies of maximum phonation time(MPT), phonation quotient, and mean glottal flow rates (MFR) were also measured in all subjects. Simple pulmonary function in professional sopranos was generally the same as that of other female subjects without vocal training. However, MIP and MEP showing respiratory muscle forces were significantly elevated in professional sopranos, compared to those of other female subjects without vocal training. Maximum phonation times and phonation quotient in sopranos are longer than those of other female subjects even though there were no differences in simple pulmonary function. High-pitched tones were made with significantly higher mean glottal flow rates(GFR) in normal subjects than low-pitched tones, whereas no changes in GFR were found in sopranos. The result indicated that sopranos demonstrated significant improvements in aerodynamic measures of GFR, maximum phonation time, suggesting an increase in glottal efficiency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.89-90
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• 2008

This paper studies the effect of pad at initial stage and wear during braking on the dynamic contact pressure distribution. Wear is influenced by variable factor (contact pressure, sliding speed, radius, temperature) during dynamic braking and variation in contact pressure distribution. Many researchers have conducted complex eigenvalue analysis considering wear characteristic with Lim and Ashby wear map. The conventional analysis method is assumed the pad has smooth and flat surfaces. The purpose of this paper is to validate that wear rate induced by braking is considered for the precise squeal prediction. After obtaining pad wear from experiment, it is incorporated with FE model of brake system. Finally, the comparisons in fugitive nature of squeal will be carried out between the complex eigenvalue analysis and noise dynamometer experiment.

• Korean Journal of Applied Biomechanics
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• v.13 no.3
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• pp.341-354
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• 2003

The purpose of this study was to develop the uniaxial force plate system which is measured by the vertical force. The VGRF(vertical ground reaction force) 1.0 was composed of 2 bath digital scales, 2 indicaters, and analyzing software. This system was newly renovated to VGRF 2,0 which are 2 industrial digital scales, 2 adjustable indicators, and enforced analyzing software. Changes of the new system were as follows. First, the height of the plate was 75% lower than before. Second, sensing ability of the load cell was changed from 90 - 0.05kg to 300 - 0.1kg. Third, the speed of data processing was changed from 17 per second to 60 per second. Fourth, analyzing software was enforced to develop and calculate the data. For the test of the system, two different types(bare foot, high-heeled shoes) gait was adopted. highly skilled female walker(23yrs, height 165cm, body mass 46.8kg) participated for the experimental study. During the dynamic performance(gait analysis), the data of each load cell were very similar to the previous studies. Specifically, bare foot walking had less vertical force than high-heeled shoes. Consequently, VGRF 2.0 can sense the general dynamic movements as well as static load conditions.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.683-690
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• 2002

Static and fatigue tests were performed to evaluate fatigue strength in scallop at field bolted joints of longitudinal rib and deck plate in orthotropic steel decks. Numerical parametric studies using finite elemtn analysis were also conducted to show the influence of parameters such as length and radius of scallop, and thickness of deckplate on the stress concentration at the scallop. In the low stress level, fatigue tests yielded cracks at the scallop while in the high stress level, catastrophic failure of longitudinal rib occurred following the failure of handhole cover plate. Fatigue strength was compared with JSSC specification and the predicted S-N curves using Shigley and Juvinall methods, and a satisfactory result was obtatined.

• Journal of the Ergonomics Society of Korea
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• v.23 no.3
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• pp.39-52
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• 2004

Icons are the main element of the graphic user interface (GUI). They can help users perform effectively on the computer, especially when the icons reflect user`s mental model. However, few studies in Korea represented Korean users` mental models in icon design. The purpose of this study, therefore, was to ascertain whether existing icons agreement with Korean twentieth mental model, and to deduce properties of Korean twentieth mental model. To do that, 10 icons from two commercially available toolbar-icons of word processing programs were compared with the newly developed icons, which were developed to represent Korean user`s mental modelthrough interviews, surveys, and mental model sketches. The results show that five new metaphors were found: a dog-eared part on the bottom right corner new for new document, a magnifying glass for search, a red pencil for spell-check, `＋` and `` signs in the magnifying glass for zoom, and a yellow post-it for paste. These new icons were preferred to the existing. Korean twentieth users preferred rather complex and dynamic icons than simple and static ones even though icon development guideline said simple icons are better.

• Journal of Electrical Engineering and Technology
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• v.7 no.5
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• pp.653-658
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• 2012

Load modeling has a significant influence on power system analysis and control. In recent years, measurement-based load modeling has been widely practiced. In the load modeling algorithm, the model structure is determined and the parameters of the established model are estimated. For parameter estimation, least-squares optimization method is applied. The model parameters are estimated so that the error between the measured values and the predicted values is to be minimized. By introducing sliding window concept, on-line load modeling method can be performed which reflects the dynamic behaviors of loads in real-time. For the purpose of data acquisition, the measurement system including PMU is implemented in university level. In this paper, case studies are performed using real PMU data from Korea Univ. and Seoul National University of Science and Technology. The performances of modeling real and reactive power behaviors using exponential and ZIP load model are evaluated.

• Journal of the Korean Society of Safety
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• v.27 no.4
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• pp.43-49
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• 2012

In the design of high speed railway bridges is important a impact factor as a tool of assessing the dynamic capacitys of bridges. However, the impact factor(or dynamic amplification factor, DAF) of high speed railway bridges may essentially be changeable because the dynamic response is affected by the long train length(380 m), number of axles and high speed velocity(300 km/h)(Korea Train eXpress: KTX). Therefore, on this study will be examined the dynamic capacity and stability of the typical PSC Box Girder of high speed railway bridge. At first, the static/dynamic analysis is performed considering the axle load line of KTX based upon existing references. Additionally, the KTX moving load is transformed into the dynamic time series load for conducting various parameter studies like axle length, analytical time increment, velocity of KTX. The time history analysis is repeatedly performed to get maximum dynamic responce by varying axle load length, analytical time increment, velocity of KTX. The study shows that dynamic analysis has resonable results with optimal axle load length(0.6 m) and time increment(0.01 sec.) and maximum DAF and dynamic resonance happens at 270 km/h velocity of KTX.

• Journal of Electrical Engineering and Technology
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• v.4 no.4
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• pp.467-475
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• 2009

Congestion management is one of the technical challenges in power system deregulation. This paper presents single objective and multi-objective optimization approaches for optimal choice, location and size of Static Var Compensators (SVC) and Thyristor Controlled Series Capacitors (TCSC) in deregulated power system to improve branch loading (minimize congestion), improve voltage stability and reduce line losses. Though FACTS controllers offer many advantages, their installation cost is very high. Hence Independent System Operator (ISO) has to locate them optimally to satisfy a desired objective. This paper presents optimal location of FACTS controllers considering branch loading (BL), voltage stability (VS) and loss minimization (LM) as objectives at once using GA. It is observed that the locations that are most favorable with respect to one objective are not suitable locations with respect to other two objectives. Later these competing objectives are optimized simultaneously considering two and three objectives at a time using multi-objective Strength Pareto Evolutionary Algorithms (SPEA). The developed algorithms are tested on IEEE 30 bus system. Various cases like i) uniform line loading ii) line outage iii) bilateral and multilateral transactions between source and sink nodes have been considered to create congestion in the system. The developed algorithms show effective locations for all the cases considered for both single and multiobjective optimization studies.