• Publications of The Korean Astronomical Society
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• v.27 no.4
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• pp.259-260
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• 2012

Polycyclic aromatic hydrocarbons (PAHs) in Galactic planetary nebulae (PNe) are investigated by means of the unidentified infrared (UIR) bands. Continuous near- to mid-infrared spectra of PNe are obtained with the AKARI/IRC and the Spitzer/IRS. All 19 PNe in the present study show prominent dust emissions and we investigate the variation in the intensity ratios among the UIR bands. The ionization fraction and the size distribution of PAHs in PNe are derived using the UIR band ratios. We find that the ionization fraction of PAHs in PNe is around 0.0-0.6 and that small PAHs are scarce. The present result indicates a systematic trend of the $3.4{\mu}m$ aliphatic feature to become weak as the PAH ionization fraction increases.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.4
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• pp.312-319
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• 2016

Zero-sequence Circulating Current (ZSCC) flows inevitably in parallel converters that share common DC and AC sources. The ZSCC commonly flowing in all converters increases loss and decreases the overall capacity of parallel converters. This paper proposes a simple and effective ZSCC suppression method based on the Space Vector PWM (SVPWM) with the ZSCC controller. The zero-sequence voltage for the proposed SVPWM is calculated on the basis of the grid voltage and not on the phase voltage references. The limit of the linear modulation region of the converters with the proposed method is analyzed and compared with other methods, thereby proving that the limit of the region can be extended with the proposed method. The effectiveness of the proposed method has been verified through the experimental setup comprising four parallel three-level converters. The ZSCC is confirmed to be well suppressed, and the linear modulation region is extended simultaneously with the proposed method. Moreover, the proposed control method does not require any communication between the converters to suppress the ZSCC unlike other conventional methods.

• Journal of Digital Contents Society
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• v.9 no.2
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• pp.317-323
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• 2008

The purpose of this study is to show typology of virtual world and to look out how virtual world develops especially in Korea. As paradigm changes, the scientific virtual reality and world wide web are absorbed into 3-D virtual world in Metaverse. The metaverse is the convergence of virtually enhanced physical reality and physically persistent virtual space. There are two categories of virtual world, the Ludic Virtual World which is oriented from games like MMORPGs and the Social Virtual World which is oriented from network communication system. Compared to North America and Europe, the Ludic Virtual World and game society grow and develop quickly in Korea. It's because Korean users prefer the online environment where millions of people live out a collective fantasy existence.

• Journal of the Korean Institute of Landscape Architecture
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• v.23 no.4
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• pp.81-96
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• 1996

The idea I set my thesis upon was to develop a methodology for the visually impaired to perceive an environment through their other senses. Since the Blind perceive spatial relationships by combined association of their other senses, it was essential to create a setting where their senses can be amplified. Thus this garden was designed to accommodate two or more of blind person's senses at once to provide more of '3-D' spatial relationship. The main goals of this thesis are, first, to create a place where the Blind can enjoy and nurture their own specific interests. Second, to reveal the nature in its allowing individual analysis and interpretation of a garden. Third, to move away from the prejudice of gardens for the Blind being made of only touching and smelling. To achieve these goals, the most important task was to establish a sense of space. In order to do so, five principles were used; Perspective, Enclosure, Light/Shade, Form, and Environment. After all, the garden for the Blind does not proclaim its purpose in loud terms nor in obvious manner. It should attempt to provide joy, serenity, and activity; a freedom to choose, recognize and analyze nuances of garden, the rhythm of enclosure and openness to experience variety, also to delight in subtle changes and to just imagine.

• Journal of ILASS-Korea
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• v.1 no.2
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• pp.16-23
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• 1996

In case of a high-speed D.I. diesel engine. the injected fuel spray is unavoidable that the impinging on the wall of piston cavity and in this case the geometry of piston cavity has a great influence on the atomization structure and air flow fields. In the field of combustion and in many other spray applications, there are clear evidence of correlation between spray structure and emission of pollutants. Ordinary, the combustion chamber of driving engine have unsteady turbulent flow be attendant on such as the change of temperature, velocity and pressure. So the analysis of spray behavior is difficult. In this study, a single spray was impinged on each cavity wall at indicated angle in a quiescent atmosphere at room temperature and pressure, as being the simplest case, and 3 types of piston cavity such as Dish, Toroidal and Re-entrant type was tested for analyzing the influence of cavity geometry. And hot wire probe was used for analyze non-steady flow characteristics of impinging spray, and to investigate the behavior of spray, the aspects of concentration c(t), standard deviation $\sigma(t)$ and variation factor (v.f.) was measured with the lapse of time.

• Phonetics and Speech Sciences
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• v.1 no.4
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• pp.3-9
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• 2009

Acoustically English vowels are defined primarily by formant values. The measurements of the values have been usually made at a few time points of the vowel segment despite the fact that the majority of English vowel formants vary dynamically throughout the segment. This study attempts to collect acoustic data of the nine English vowels published by Hillenbrand et al. (1995) online and to examine the acoustic features of the English vowels for phoneticians and English teachers. The author used Praat to obtain the data systematically at six equidistant timepoints over the vowel segment. Obvious errors were corrected based on the spectrographic display of each vowel. Results show that the first two formant trajectories are important to separate the nine vowels within the front- or back-vowel groups. The third formant trajectories appear comparable except those of the high vowels. Second, the back vowels leave longer traces on the vowel space toward the locus of the following consonant /d/. Third, each vowel has inherent duration, pitch, and intensity patterns. The results match the findings of Yang (2009). From the results, the author concludes that dynamic spectral changes are important in specifying acoustic characteristics of English vowels. Further studies on the application of the vowel trajectories to English pronunciation lessons or on perceptual experiment of synthesized vowels are desirable.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1753-1756
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• 2005

The sheet parts are formed with dies conventionally. But this conventional forming process is not suited to small volume and varied production for the reason of high cost. For the solution of this problem, a new forming process, which is called CNC incremental sheet forming, is being introduced. This process can form sheet parts without die, and is very well suited to small volume and varied production in space flight and automobile. In this paper, dieless CNC forming system based on a machining center is developed. A special device to grasp and pull the blank sheet built in the machining center and tool path generation S/W from STL file of 3-D model are developed. Several sheet parts are incrementally formed to verify the effectiveness of the developed system.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1615-1617
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• 1997

절연재료로서 널리 쓰이는 XLPE(Crosslinked Polyethylene)의 경우, 내부에 발생하는 수트리에 의해 절연체로서의 성능 및 내구성이 많은 영향을 받게 된다. 이에 대한 연구가 진행되어 왔지만 수트리 발생과 진행에 관한 메커니즘은 아직까지 정확하게 알려지지 않은 상태이다. 이 논문에서는 몇 가지의 수트리 억제 컴파운드를 선정하여 시간과 온도에 따른 수트리 발생을 관찰하고, 컴파운드 내의 공간전하 및 전도전류가 수트리 억제에 미치는 영향을 조사하였다. 수트리가속을 위하여 주파수가속열화 방법을 사용하고 온도와 시간에 따른 발생 및 진전을 관찰하였다. 실험에서는 압축성형된 평판형 시편을 사용하였으며 상부전극으로는 $AgNO_3$ 수용액을, 하부전극으로는 금속전극을 사용하였다. 그리고 컴파운드 내부의 공간전하 분포 및 전도전류 측정을 하기위해 PEA(Pulsed Electro Acoustic) 방법을 이용하였다.

• Korean Institute of Interior Design Journal
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• v.15 no.5 s.58
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• pp.183-192
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• 2006

This study analyzes the characteristics of special configuration for wayfinding in general hospitals. To that end, the study categorizes four different hospitals, according to the type of their wayfinding systems. It aims at utilizing the result of the analysis for wayfinding system in general hospitals by applying three elements of analysis methods', perpetual access, depth, and intelligibility. The study result shows as follows: First, there is no difference in special hierarchy when hospitals are analyzed and divided by halls and streets. It means that outpatient departments are located by spatial function and characteristics rather than form of spatial configuration. Second, we found that fewer direction changes are conducive to easier circulation in terms of wayfinding, when we analyzed spatial depth from the main entrances to the outpatient departments. Third, regarding intelligibility, intelligibility of Chungang University Hospital ranked highest. Kunkook University Hospital, Dongkook University Hospital and Seoul National University Hospital ranked 2nd, 3rd, and 4th respectively. It means that difficulty level of wayfinding is not decided by the characteristics of special configuration such as hospital hall and hospital streets but depends on location planning. The difficulty level of wayfinding mainly relies on location planning.

• Journal of the Korean Institute of Gas
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• v.3 no.2 s.7
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• pp.24-33
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• 1999

The minimum safe separation distances from LPG filling station was discussed in this work based on the accident data from 1987 to 1998 in south korea, the initial damage of accident, and standards of countries. The safety distances are adequate to reduce ignition probability by released gas and provide space for implementation of emergency response after ignition. Therefore, the distances are related to the distance to LFL(Lower Flammable Limit) and the length of jet fire to prevent accident escalation. The range of the distance was suggested in this work to make standard with considering economic, culture, and safe guards.