• Journal of ILASS-Korea
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• v.27 no.4
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• pp.188-194
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• 2022

In this study, the behavior of water droplet impacting on a thin horizontal orifice was investigated. The impact behavior modes, transition velocities and diameters of daughter droplets were analyzed by changing the droplet velocity, orifice diameter and orifice thickness. Four typical modes of impacting droplet on an orifice were observed. The single-droplet and double-droplet transition velocities increased with increasing the orifice thickness and decreased with increasing the orifice diameter. On the other hand, the multi-droplet transition velocity decreased and then increased as the orifice diameter increased. At thin orifice thickness, the single droplet diameter approximated the orifice diameter, and increasing the orifice thickness produced a droplet larger than the orifice diameter. In the case of double droplet mode, the diameter of the first droplet showed a similar tendency like the single droplet mode, but the diameter of the second droplet was smaller than that of the first droplet, and the difference between them was affected more by the orifice thickness.

• Journal of the Korean Society of Radiology
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• v.81 no.3
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• pp.714-718
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• 2020

Herpetic mastitis is extremely rare, and its imaging findings remain unclear. We report a case of herpes simplex mastitis in an adolescent woman and describe the clinical and ultrasound features. The patient showed unilateral nipple and areolar skin thickening and axillary lymphadenopathy on B-mode ultrasonography. Doppler ultrasonography revealed multiple linear and branching blood flows in the areolar area. The lesion was verified as herpes simplex mastitis via a skin biopsy. This report shows that the radiologic features of herpes simplex mastitis may be similar to those of Paget's disease because of localized nipple and areolar skin thickening and increased vascularity.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.57 no.3
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• pp.302-309
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• 2024

This study estimates the target strength of anchovy Engraulis japonicus required for studying their distribution and density using acoustics and evaluates the acoustic scattering characteristics of anchovies by frequency using the Kirchoff ray mode (KRM) model. The experiment was conducted on 30 anchovies with 4.7-21.5 cm total length. The maximum TS_cm (Simming angle, 9.1°; standard deviation, ± 13.1°) according to total length was -66.9, -65.2, -64.4, and -63.4 dB at 38, 70, 120, and 200 kHz, respectively. The average TS_cm (Simming angle: 9.1°, standard deviation: ± 13.1°) according to total length was -68.9, -68.8, -69.6, and -70.0 dB at 38, 70, 120, and 200 kHz, respectively. The results of this study provide an important basis for future studies that use acoustics to estimate the target strength of anchovies.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.13 no.4
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• pp.14-20
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• 2017

Refrigerant having high global warming potentials will be phased out due to environmental protection issues. R410A has been widely used in geothermal heat pump. However, it has a little high GWP by 2088 value. One of the recommended substitute for R410A refrigerant is R452B which having a GWP by 698 value. In this paper, the heating and cooling performance of the water-to-water geothermal heat pump unit with R452B was experimentally investigated. The performance of the heat pump adopting R452B was also compared with the system applying R410A. The heating and cooling capacity of R452B heat pump system showed a slightly lower values within 2% comparing with R410A system. However, the R452B system's coefficient of performance was enhanced by 5.2% and 13.7% at heating and cooling mode, respectively.

• Journal of the Korean Professional Engineers Association
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• v.27 no.2
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• pp.42-54
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• 1994

Nowadays communication network is steadily changing from a main body of telephone to a network which is creating new services such as multimedia etc. Jhis article introduces a bud of new service and new network which are able to sustain the above service. Including Korea, world advanced countries have been digitatizing their network with N-ISDN (narrowband ISDN) by e.g. 64K b/s and 1.5M b/s. New service by N-ISDN are extraordinary, though it can not solve all kinds of services. To solve these problems, a solving platform should be constituted. B-ISDN(broadband ISDN), as a platform has to be built to deal with almost all uinds of services, whatever the communication speed, communication mode or communication quality may be. Korea Telecommunication Authority(KTA) opened the narrowband ISDN(N-ISDN) at the end of 1993. This was one step previous opening of the broadband ISDN(B-ISDN) service scheduled to be rendered in 2001. B-ISDN, receiving and transmitting by far more information with high speed than the N-NSDN does, is one of G-7 Progects which the Korean government is driving foreward to raise the national scientific power to seven advan ced countries. This is also linked with an extremely high speed information network scheduled to be built by the Ministry of Communications in 2015.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.780-788
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• 2011

The lack of QoS (Quality of Service) support functionalities in IEEE 802.11 DCF mode makes it difficult to provide real-time multimedia services in WLANs. In this paper, we propose an effective available bandwidth measurement method in IEEE 802.11b DCF environments. The proposed method measures the total channel idle time and the collision probability during each measurement period. Then, the available bandwidth is calculated by considering those measured information and the transmission overheads at MAC and PRY layers. The performances of the proposed method are evaluated using OPNET simulator. The simulation results show that the proposed method provides more exact results than existing comparable schemes.

• Bulletin of the Korean Chemical Society
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• v.20 no.3
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• pp.301-306
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• 1999

Hepatitis C virus (HCV) has been known to be an enveloped virus with a positive strand RNA genome and the major agent of the vast majority of transfusion associated cases of hepatitis. For viral replication, HCV structural proteins are first processed by host cell signal peptidases and NS2/NS3 site of the nonstructural protein is cleaved by a zinc-dependent protease NS2 with N-terminal NS3. The four remaining junctions are cleaved by a separate NS3 protease. The solution conformations of NS4B/5A, NS5A/5B substrates and NS5A/5B inhibitor have been determined by two-dimensional nuclear magnetic resonance (NMR) spectroscopy. NMR data suggested that the both NS5A/5B substrate and inhibitor appeared to have a folded tum-like conformation not only between P1 and P6 position but also C-terminal region, whereas the NS4B/5A substrate exhibited mostly extended conformation. In addition, we have found that the conformation of the NS5A/5B inhibitor slightly differs from that of NS5A/5B substrate peptide, suggesting different binding mode for NS3 protease. These findings will be of importance for designing efficient inhibitor to suppress HCV processing.

• Journal of Korean Society on Water Environment
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• v.25 no.2
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• pp.322-328
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• 2009

The advantage of simultaneous nitrification and denitrification (SND) is to reduce requirement of oxygen as well as tank volume. The fludized media was used in the oxic (aerobic) tank of Membrane-BNR to enhance the efficiency of SND. Nowadays, the interest of applying membrane to the wastewater treatment plant has been increased, which is proved by a lot of research published about the MBR. The Membrane-BNR, consisted of total 5 reactors might be called the compact process by using the fludized media and having short HRT of 6.5 hr. It could attain the further removal of not only the organics but also nutrients such as T-N and T-P. The mode A and B were identified with or without the step feed of influent. The mode A was classified with 3 modes according to the different DO concentration in the fludized media aerobic reactor, and the mode B with step feed was operated with the optimum DO condition. The step-feed was capable of improving TN removal efficiency under the domestic wastewater with the low ratio C/N. On the other hand, the efficiency of SND with the 1.0~1.5 mg/L DO in the oxic media tank was better than the one with below 1.0 mg/L, on which the nitrification did not happen enough, and with above 3.5 mg/L, on which the reduction of anoxic area in the tank happened. It means that the profitable nitrification should be performed prior to the denitrification step. The removal efficiency of nitrogen by SND was about 20% among of total denitrified nitrogen. And some organic carbon consumed could be reduced by the endogeneous denitrification.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.5
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• pp.489-494
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• 2013

This study aims to understand the mode characteristics of a droplet under a periodic forced vibration. To predict the resonance frequency of a droplet, theoretical and experimental approaches were employed. A high-speed camera was used to capture the various deformation characteristics of a droplet-mode shape, detachment, separated secondary droplet, and skewed deformation. The comparison between the theoretical and the experimental approaches shows a ~10% discrepancy in the prediction of the resonance frequency, which appears to be caused by the effect of contact line friction, nonlinear wall adhesion, and experimental uncertainty. Owing to contact-line pinning and smaller amplitude, the droplet shape becomes symmetric and the size of each lobe at the resonance frequency exceeds that at the neighbor, which is out of resonance.

• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2070-2078
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• 2014

In this work, the frequency response of gate-all-around (GAA) Ge/GaAs heterojunction tunneling field-effect transistor (TFET) with hetero-gate-dielectric (HGD) and pnpn channel doping profile has been analysed by technology computer-aided design (TCAD) device-circuit mixed-mode simulations, with comparison studies among ppn, pnpn, and HGD pnpn TFET devices. By recursive tracing of voltage transfer curves (VTCs) of a common-source (CS) amplifier based on the HGD pnpn TFET, the operation point (Q-point) was obtained at $V_{DS}=1V$, where the maximum available output swing was acquired without waveform distortion. The slope of VTC of the amplifier was 9.21 V/V (19.4 dB), which mainly resulted from the ponderable direct-current (DC) characteristics of HGD pnpn TFET. Along with the DC performances, frequency response with a small-signal voltage of 10 mV has been closely investigated in terms of voltage gain ($A_v$), unit-gain frequency ($f_{unity}$), and cut-off frequency ($f_T$). The Ge/GaAs HGD pnpn TFET demonstrated $A_v=19.4dB$, $f_{unity}=10THz$, $f_T=0.487$ THz and $f_{max}=18THz$.