• Membrane Journal
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• v.8 no.2
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• pp.86-93
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• 1998

A permeation apparatus has been devdoped which could make the on-line measurements of both flux and permeate composition. Pervaporative experiment of a single component, i.e. water was performed by using poly(vinyl alcohol) membrane crosslinked with glutaraldehyde to confirm the validity of the apparatus. In the experiment, steady-state permeation was obtained in 15 minutes and the measurement could be completed within 20 minutes. A comparison of the on-line measurement was made with the fluxes measured simultaneously by the conventional method in which the permeates were collected by liquid nitrogen. The on-line measurement by the apparatus showed an excellent agreement with the conventional measurement within a difference of $\pm$2%. From the flux data with operating time, 3 kinds of diffusion coefficients of water $D_{slope}, D_{1/2}$, and $D_t$ were determined, which were also coincident with values in a literature. It was confirmed that accurate measurements of fluxes could be obtained from the apparatus.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.15 no.3
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• pp.277-281
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• 2005

Air-line mask is an important personal protective equipment for workers working under hazardous surroundings in which a fixed ventilation system is difficult to be installed. If the air-line mask make loud noise, works wearing the mask may be faced with health problems such as noise induced hearing loss(NIHL). The purpose of this study is to introduce a low noisy technology for workers using air-line mask. A traditional type air-line has been improved to an advanced air-line mask with lesser noise. In the mask, air suppling conduits consists of multi tubes are placed inside of the front of the safety helmet. The noise level reduced from 80dB(A) to less than 80dB(A) when measured by KS A 0701 method at Center for Safety Inspection, Testing and Certification for KOSHA. It is suitable for related regulation[Article 35 of the Industrial Safety and Health Act(Test of Personal Protective Equipment)]. While workers working in noise level of over 90dB(A), they may expose to 82dB(A) or less when they wear the advanced masks. This type masks can be an alternative for works suffering from loud noise generated by traditional air-line masks.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.3
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• pp.37-42
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• 2022

A high-performance wideband transition from microstrip to waveguide is proposed. This transition is designed by consideration of gradual field transformation and optimal impedance matching between microstrip line and fin-line. Clear design guidelines of proposed transition using fin-line taper with offset DSPSL (double-sided parallel stripline) are provided to determine the transition shape and the transition length. The fabricated transition exhibits less than 0.67 dB insertion loss per transition for frequencies from 85 to 108 GHz, and less than 1 dB insertion loss from 83 to over 110 GHz. Proposed transition is expected compact radar and various applications.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.9
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• pp.55-59
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• 2008

In this paper, the linearity of Doherty amplifier has been improved by applying a compact slow-wave microstrip branch-line coupler on the output of Doherty amplifier. The proposed branch coupler has four microstrip high-low impedance resonant cells periodically placed inside the branch-line coupler to result in high slow-wave effect. The new coupler not only effectively reduces the occupied area to 30% of the conventional branch-line coupler at 1.8GHz, but also has high second harmonic suppression performance. We obtained the 3rd-order intermodulation distortion ($IMD_3$) of -31.16 dBc for CDMA applications with that of maintaining the constant power added efficiency (PAE). The IMD3 performance is improved as much as -7 dBc compared with a Doherty amplifier.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.11
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• pp.577-582
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• 2004

In this paper, lumped equivalent circuits for a conventional parallel directional coupler are proposed. This equivalent circuits only have self inductance and self capacitance, so we can design exact lumped equivalent circuit. The equivalent circuit and design formula for the presented lumped element coupler is derived based on the even- and odd-mode properties of parallel-coupled line. By using the derived design formula, we have designed the 3dB and 4.7dB MMIC couplers at the center frequency of 3.4GHz and 5.6GHz respectively. Measurements for the designed MMIC directional couplers show at 4dB and 5.2dB-coupling value at the center frequency of 3.4GHz and 5.6GHz. Excellent agreements between simulation results and measurement results on the designed directional couplers show the validity of this paper

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.86-92
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• 2013

The present paper defines diversity gain for stationary users. This deals in particular with gathering the received signal statistics over possible user positions and orientations in space rather than over time, and to define a meaningful diversity gain related to the cumulative improvement of the performances of the 1% users with the worst receiving conditions. The definition is used to evaluate diversity gain for some typical small antennas in an extreme environment with only line-of-sight (LOS). The LOS environment is regarded as user-distributed 3D-random LOS caused by the statistics of an ensemble of stationary users with arbitrary orientations in the horizontal plane (2D), and with arbitrary orientations of their wireless devices in the vertical plane. Thus, an overall 3D-random distribution of user orientation is assumed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.45 no.4
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• pp.131-136
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• 2008

Two Ka-band 3-stage power amplifiers were designed and fabricated using $0.18-{\mu}m$ CMOS technology. For low loss matching networks for the amplifiers, two substrate-shielded transmission line structures, having good modeling accuracy up to 40 GHz were used. The measured insertion loss of substrate-shielded microstrip-line (MSL) was 0.5 dB/mm at 27 GHz. A 3-stage CMOS amplifier using substrate-shielded MSL achieved a 14.7-dB small-signal gain and a 14.5-dBm output power at 27 GHz in a compact chip area of 0.83$mm^2$. The measured insertion loss of substrate-shielded coplanar waveguide (CPW) was 1.0 dB/mm at 27 GHz. A 3-stage amplifier using substrate-shielded CPW achieved a 12-dB small-signal gai and a 12.5-dBm output power at 26.5 GHz. This results shows a potential of CMOS technology for low cost short-range wireless communication components and system.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1999.12a
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• pp.759-768
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• 1999

In this paper, we developed a simulation model of a car parts assembly line to improve the system performance such as worker's utilization balancing, productivity. This simulation model has been developed using QUEST, a true 3D discrete event simulation pakcage that is designed for modeling and analysis of manufacturing systems. We have suggested the results obtained to improve the system performances of an existing production line.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1998.03a
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• pp.65-70
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• 1998

In this paper, we developed a Windows 95 version off-line programming system which can simulate a track vehicle model in 30 graphics space. The track vehicle was adopted as an objective model. The interface between users and the off-line program system in the Windows 95's graphic user interface environment was also studied. The developing language is Microsoft Visual C++. Graphic libraries, OpenGL, by Silicon Graphics, Inc were utilized for 3D Graphics.

• Transactions on Electrical and Electronic Materials
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• v.16 no.3
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• pp.139-141
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• 2015

Contact resistance of interface between the channel layers and various S/D electrodes was investigated by transmission line method. Different electrodes such as Ti/Au, a-IZO, and multilayer of a-IGZO/Ag/a-IGZO were compared in terms of contact resistance, using the transmission line model. The a-IGZO TFTs with a-IGZO/Ag/a-IGZO of S/D electrodes showed good performance and low contact resistance due to the homo-junction with channel layer.