• Journal of the Korean Mathematical Society
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• v.51 no.6
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• pp.1291-1304
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• 2014

In 2005 Kadiri proved that the Riemann zeta function ${\zeta}(s)$ does not vanish in the region $$Re(s){\geq}1-\frac{1}{R_0\;{\log}\;{\mid}Im(s){\mid}},\;{\mid}Im(s){\mid}{\geq}2$$ with $R_0=5.69693$. In this paper we will show that $R_0$ can be taken $R_0=5.68371$ using Kadiri's method together with Platt's numerical verification of Riemann Hypothesis.

• Journal of the Chungcheong Mathematical Society
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• v.20 no.3
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• pp.203-210
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• 2007

Let X be a hyperbolic region in the complex plane C such that the hyperbolic metrix ${\lambda}_X(w){\mid}dw{\mid}$ exists. Let $R(X)=sup\{{\delta}_X(w):w{\in}X\}$ where ${\delta}_X(w)$ is the euclidean distance from w to ${\partial}X$. Here ${\partial}X$ is the boundary of X. A hyperbolic region X is called a Bloch region if R(X) < ${\infty}$. In this paper, we obtain lower bounds for the hyperbolic metric on Bloch regions in terms of the distance to the boundary.

• Journal of Sensor Science and Technology
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• v.31 no.4
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• pp.255-259
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• 2022

In this study, we fabricated ZnS substrates with excellent transmittance in the mid-infrared region (3-5 ㎛) using hot pressing instead of conventional chemical vapor deposition (CVD). Diamond-like carbon (DLC) was coated on either one or both sides of the ZnS substrates to improve their mechanical properties and transmittance efficiency. To reduce the reflectance and further improve transmittance in the mid-infrared region, anti-reflection (AR) coating was designed for DLC/ZnS /AR and AR/ ZnS /AR structures. The coating structure, microstructure, and optical properties of the AR-coated ZnS substrates were subsequently investigated by employing energy dispersive X-ray spectroscopy, scanning electron microscopy, and Fourier-transform infrared (FTIR) spectroscopy. The FTIR spectroscopy results demonstrated that, in the mid-infrared region, the average transmittance of the samples with AR coating on one and both sides increased by approximately 18% and 27%, respectively. Thus, AR coating improved the transmittance of the ZnS substrates.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.5 no.1
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• pp.41-46
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• 2011

A sensorineural hearing loss(SNHL) occurs when the cochlea in the inner has functional problem. The region in the cochlea with no(or very few) functioning inner hair cells or neurons called 'dead regions'. Amplification using hearing aid over a frequency range corresponding to a dead region may not a beneficial. In this paper, we compared speech recognition with different location of dead region and gain and searched effective gain for hearing aid with dead region. In order to experiment, eight people who has normal hearing ware tested, and we used white noise and babble noise(SNR=0 dB). we divided by three conditions, low, mid and high frequency dead region. In addition, the gains in dead region ware 14.5 dB, 11.5dB and 6 dB gain. There ware different results by location of dead region. The result of WRS and preference in mid-frequency dead region and high-frequency dead region ware higher than them in low-frequency dead region. When we compared as gains, the score of WRS with lower gain was higher than 14.5 dB gain, and the preference was lower as higher gain.

• Phonetics and Speech Sciences
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• v.9 no.2
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• pp.39-51
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• 2017

The current study aims to investigate the effect of sociolinguistic factors such as region, generation and gender on the acoustic properties of Korean high and mid back vowels. We analyzed the vowel productions of one hundred twenty-eight subjects from the Korean Standard Speech Database, chosen to represent the different possible combinations of region, generation, and gender. The results reveal a chain-like shift in the back vowels. Unlike previous studies that have reported /o/-/u/ becoming closer as a result of a decreasing F1 in /o/, we found that the distance between the two vowels is decided more by the changing F2 in /u/. Also, the F2 of /u/ and /ɯ/, and the F2 of /ʌ/ and F1 of /o/ appear to move in tandem. Lastly, this study suggests that the reason the vowel changes differ across gender and regional dialects could be because they are all converging on to the standard Korean.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.127.1-127.1
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• 2012

The 40.8-MHz VHF coherent scatter ionospheric radar, located in South Korea (Gyeryong, $36.18^{\circ}N$, $127.14^{\circ}E$), has been operating since December 2009 to investigate ionosphere E- and F-region field-aligned irregularities (FAIs) of mid-latitude. During the observation, we found E- and F-region FAIs appeared frequently: continuous echoes during the post-sunrise period and Quasi-Periodic (QP) echoes at nighttime for E region ; strong post-sunset and pre-sunrise FAIs for F region. The characteristics of E- and F-region FAIs are presented in terms of seasonal and local time variations of occurrence during December 2009 to August 2012. In addition, to investigate the correlation with geomagnetic activity to FAIs occurrence, we compared K-index variations to local time occurrence. It is worth to note our occurrence result since long term observation over several years in the mid-latitude has not yet been carried out.

• Nuclear Engineering and Technology
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• v.54 no.8
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• pp.3166-3175
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• 2022

The most numerical investigations of the thermal-hydraulic phenomena following the loss of the residual heat removal capability during the mid-loop operation of the pressurized water reactor were performed according to simplifications and are not sufficiently accurate. To perform more accurate and more reliable predictions of thermal-hydraulic accidents in a nuclear power plant using computational fluid dynamics codes, a more detailed methodology is needed. Modelling results identified that thermal stratification and natural convection are observed. Temperatures of lower monitoring points remain low, while temperatures of upper monitoring points increase over time. The water in the heated region, in the upper unheated region and the pipe region was well mixed due to natural convection, meanwhile, there is no natural convection in the lower unheated region. Water temperature in the pipe region increased after a certain time delay due to circulation of flow induced by natural convection in the heated and upper unheated regions. The modelling results correspond to the experimental data. The developed computational fluid dynamics methodology could be applied for modelling of two-component single/two-phase natural convection and thermal stratification phenomena during the mid-loop operation of the pressurized water reactor or other nuclear and non-nuclear installations at similar conditions.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.771-775
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• 2006

There has been much effort to find suitable methods for structural analysis in the mid-frequency region where traditional low frequency methods have increasing uncertainties whilst statistical energy analysis is not strictly applicable. Systems consisting of relatively stiff beams coupled to flexible plates have a particularly broad mid-frequency region where the beams support only a few modes whilst the plate has a high modal density and modal overlap. A system of two parallel beams coupled to a plate is investigated based on the wave method, which is an approximate method. The wave model is extended from a single-beam-plate system, to a plate with two identical beams which is modelled using a symmetric-anti symmetric technique. Experimental results such as powers and energy ratios show the validity of the analytical wave models.

• Journal of the Korean Society of Laryngology, Phoniatrics and Logopedics
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• v.7 no.1
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• pp.20-26
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• 1996

The purposes of this study were to analyze the sound of bird's frequency region and pattern and to discuss hearing impaired children's auditory discrimination. The results were ie follows; 1) The sounds of bird's frequency region were divided into Low(below 1, 000Hz), Mid(between 1, 000 and 4, 000Hz) and High(between 2, 000 and 4, 000Hz). 2) The sounds of bird, which were same, long, high pattern, were in Mid ＆ High. Short and high pattern were above High.

• Proceedings of the Optical Society of Korea Conference
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• 1989.02a
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• pp.70-72
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• 1989

The laser magnetic resonance (LMR) which makes use of paramagnetic properties of transient species is a powerful technique for the study of molecular radical ions. A liquid nitrogen cooled cw CO laser is developed for the LMR spectrometer in the mid-infrared region of the spectrum. The laser mid-infrared region of the spectrum. The laser system is designed to allow broad-band operation from 5 to 8${\mu}{\textrm}{m}$. The design details will be presented.