• Korean Journal of Optics and Photonics
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• v.10 no.3
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• pp.259-264
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• 1999

The relationship is derived for color CRT display system between the spectral radian existence emitted and digital inputs. The amount of spectral radiant existence depends on the characteristics of the video board, electric circuits, and CRT as well as digital inputs. Especially, the function of this relationship changes as the amplifier gain and offset voltage of electric circuits. In this study, we set the test display system on the optimum state which satisfies gun independence characteristics by using the contrast and the brightness controls of display. Temporal stability, special uniformity, and color distinction of CRT display system are evaluated at the optimum state. Also contrasts in dark room and illuminated room are compared.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.225-228
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• 2000

Addition effects of metal oxide on the characteristics of infrared radiator of porous cordierite have been investigated. The porosity was increased with adding the graphite for 2MgO $.$ 2A1$_2$O$_3$$.$5SiO$_2$. The microstructure and the spectral emissivity were investigated as a function of metal oxide additives. The prosity and the emissivity were decreased with increasing amounts of CuO additives. The prosity and the emissivity were increased with increasing amounts of CoO, MnO$_2$ additives. The infrared radiator of cordierite system which spectral emissivity was 0.927 and 0.928 at from 5$\mu\textrm{m}$ to 20$\mu\textrm{m}$ wavelength as a 9wt% of CoO and MnO$_2$ additives.

• Proceedings of the KSPS conference
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• 2005.11a
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• pp.67-70
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• 2005

Voice conversion (VC) is a technique for modifying the speech signal of a source speaker so that it sounds as if it is spoken by a target speaker. Most previous VC approaches used a linear transformation function based on GMM to convert the source spectral envelope to the target spectral envelope. In this paper, we propose several nonlinear GMM-based transformation functions in an attempt to deal with the over-smoothing effect of linear transformation. In order to obtain high-quality modifications of speech signals our VC system is implemented using the Harmonic plus Noise Model (HNM)analysis/synthesis framework. Experimental results are reported on the English corpus, MOCHA-TlMlT.

• Journal of the Optical Society of Korea
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• v.14 no.1
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• pp.49-54
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• 2010

In this study, the use of a continuous-wave (CW) supercontinuum (SC) seeded by an erbium-doped fiber's amplified spontaneous emission (ASE) for optical-coherence tomography imaging is experimentally demonstrated. It was shown, by taking an in-depth image of a human tooth sample, that due to the smooth, flat spectrum and long-term stability of the proposed CW SC, it can be readily applied to the spectral-domain optical-coherence tomography system. The relative-intensity noise level and spectral bandwidth of the CW SC are also experimentally analyzed as a function of the ASE beam power.

• Earthquakes and Structures
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• v.16 no.1
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• pp.69-82
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• 2019

As the residual displacement and/or drift demands are commonly used for seismic assessment of buildings, the estimation of these values play a very critical role through earthquake design philosophy. The residual displacement estimation of fixed base structures has been the topic of numerous researches up to now, but the effect of soil flexibility is almost always omitted. In this study, residual displacement demands are investigated for SDOF systems with period range of 0.1-3.0 s for near-field and far-field ground motions for both fixed and interacting cases. The elastoplastic model is used to represent non-degrading structures. Based on time history analyses, a new simple yet effective equation is proposed for residual displacement demand of any system whether fixed base or interacting as a function of structural period, lateral strength ratio and spectral displacement.

• Journal of Astronomy and Space Sciences
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• v.38 no.4
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• pp.193-202
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• 2021

We present analysis results of Korean VLBI Network (KVN) four-band data for the highly variable blazar 3C 279. We measured the 22, 43, 86, and 129 GHz flux densities and spectral indices of the source using contemporaneous data taken over 5.6 years. We used the discrete correlation function to investigate correlations between the radio emission properties and those measured in the optical (2 × 10¹⁴ - 1.5 × 10¹⁵ Hz), X-ray (0.3-10 keV), and gamma-ray (0.1-300 GeV) bands. We found a significant correlation between the radio spectral index and gamma-ray flux without a time delay and interpreted the correlation using an extended jet scenario for blazar emission.

• The Journal of the Acoustical Society of Korea
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• v.24 no.7
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• pp.402-409
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• 2005

In this paper. we propose a coding method using a matching pursuit algorithm in a strongly periodic highband signal. Also. we propose an efficient quantizer for the estimated parameters : spectral magnitude and phase. Based on the error concealment principle and sinusoidal model. the MP algorithm requires the high-precision pitch period estimation. To estimate more accurate pitch period. the refined pitch obtained from lowband speech is used. which increases the efficiency of bit allocation. The spectral magnitude parameters are quantized by the method which is combined with MDCT (Modified Discrete Cosine Transform) and multi-stage structure. The spectral phase quantizer uses the $2{\pi}$ modular characteristic of phases and the weighted function by spectral magnitudes. To evaluate the efficiency of the proposed method. we applied it to analysis-by-synthesis system. Furthermore we suggest the possibillity of scalable wideband speech codecs based on band-split structure.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.51 no.1
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• pp.102-110
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• 2015

The characteristics of aquatic light fields are generally reflected in the visual systems of fishes inhabiting them. Therefore, research on light sensitivity of fish is useful to explain the correlation between the visual function and habitat, behavior and distribution of fish. Rockfish is an important species in coastal ecology and also one of the main species for culturing in Korea. To make a contribution on the maintenance of the fish resources and understanding the ecology of the rockfish, the visual spectral sensitivities of the dark-adapted rockfishes were measured in the range of visible light (405~660 nm) using a light source of light-emitting diodes (LEDs). In order to assess electrophysiological response of the fish, the ERGs (electroretinograms) of the dark-adapted rockfishes were recorded on a data logger (12 bits) and a laptop computer. Juvenile (n=5; weight: $20.3{\pm}5.2g$; total length: $10.3{\pm}0.7cm$) and adult (n=5; weight: $87.8{\pm}21.8g$; total length: $18.1{\pm}1.3cm$) rockfishes were used in experiment. The visual threshold of juvenile and adult rockfish were 11.66 (log quanta/$cm^2/s$) and 11.81 (log quanta/$cm^2/s$) in 574 nm, respectively. The peak wavelength of the spectral sensitivity in the dark-adapted juvenile and adult rockfish was commonly 551 nm (series of green color). Collectively, these results demonstrate that the rockfish has suitable visual capabilities for inhabiting coastal water in Korea.

• Journal of the Korean earth science society
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• v.30 no.7
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• pp.810-823
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• 2009

One of the critical factors in accurate determination of earthquake source parameters, and in prediction of seismic hazards is the detailed information related to the site amplification characteristics. The site amplification characteristics of the broad-band seismic stations in Korea were estimated as a function of frequency in the range of 0.2 to 20 Hz. A total of 1275 seismograms recorded from 43 earthquakes observed from 2003 to 2008 in the southern Korean Peninsula were used. It was found that the site amplification ratios for 28 stations estimated from the inversion of the ground motion model were approximately concordant with those obtained from the horizontal-to-vertical (H/V) spectral ratio except for some stations. The spectral site amplification characteristics obtained in this study did not show any considerable spatial distribution. It revealed to be largely correlated with the degree of weathering rather than the basement rock type. Considering the spectral site amplification ratio, 28 broad-band stations were classified into four groups and the characteristics of each group were described in the text.

• Phonetics and Speech Sciences
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• v.8 no.4
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• pp.39-47
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• 2016

While acoustic studies in the past decade documented a raised /o/ by showing their lowered first formants (F1) almost overlapped with those of high back vowel /u/, no consensus has been made in terms of how this /o/-raising affects the vowels as a system in Seoul Korean. The current study aimed to investigate the age- and gender-related differences of the relative distance among the vowels to better understand the influence of this on-going sound change on the vowel system. We measured the static and dynamic spectral characteristics (F1 and F2) of the seven Korean monophthong vowels /e a ʌ o u ɨ i/ in the spontaneous speech of Seoul Corpus, and depicted the patterns of 30 individual speakers (10 speakers in each group of teens, 20s and 40s) as a function of age and gender. The static spectral examination showed low F1 values of /o/ in the spontaneous speech corpus confirming the vowel /o/ raising, and also revealed greater F2 values of /u, ɨ/ suggesting their anterior articulations. The tendencies were stronger when the speakers were younger and female. The spectral trajectories further showed that the F1 and F2 between /o/ and /u/ were differentiated throughout the vowel mid-point although the trajectories gradually merged near the vowel mid point in the older male speakers' productions. The acoustic evidence of contrast among /o, u, ɨ/ supports that the raised /o/ is not indicative of a merger with /u/ but rather implying a chain-like vowel shift in the Seoul Korean.