• Journal of the Korean Society for Precision Engineering
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• v.33 no.8
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• pp.661-668
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• 2016

Oil deflector prevents oil leakage that occurs in thermoelectric power plant at operating lubricant facilities. Vibration of rotating rotor-induced wear of aluminum tooth in existing oil deflector leads to oil leakage as well as life shortening of the tooth. In this study, an advanced oil deflector was developed for shock absorption and prevention of wear by decreasing clearance (from 0.5 mm to 0.2 mm) between rotor and tooth to minimize oil leakage, and by replacing 2 aluminum teeth in outmost of the oil deflector with hi-performance seal made of engineering plastic. The CFD results were compared between advanced vs. existing oil deflector to determine the amount of oil loss. Structural safety was verified through impact analyses according to the three kinds of engineering plastics, considering cost efficiency, and optimal material of hi-performance seal was chosen.

• Journal of radiological science and technology
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• v.43 no.4
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• pp.289-295
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• 2020

This study investigated the feasibility of establishing a college of medicine in the western region of Chungnam to fill the gap in the medical doctor in charge of essential medical care in the region. Currently, the level of medical services in Chungnam is low compared to provinces across the country and in particular, 7 cities and towns, which account for 760,000 people, one-third of Chungnam's population, are located in the western regions of Chungnam. Because of this, in the event of an emergency patients, it is necessary to travel to Cheonan, Daejeon, Seoul, etc. where the regional emergency medical center is located for more than 1 hour and 30 minutes. In the case of critically ill and emergency patients transfer, it is a situation that misses the golden time and causes valuable loss of life. In order to improve the medical environment in the western region of Chungnam and improve the lives of residents in vulnerable areas of medical services, it is believed that establishing a college of medicine in the western region of Chungnam is essential.

• Korean Chemical Engineering Research
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• v.56 no.2
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• pp.212-221
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• 2018

Process safety incidents and loss events can be prevented if we identify and adequately take measures on process safety incident precursors in a timely manner. If we look into and take action against the process safety hazard factors causing the incident in the refinery and petrochemical plant, major process safety incidents can be prevented through eliminating or decreasing hazardous factors. We conducted a survey for the major process safety incident precursor to look specifically into the potential process safety hazardous factors of refineries and petrochemical plants in the Yeosu chemical complex. A self-assessment checklist, which was published by Center for Chemical Process Safety "Recognizing catastrophic incident warning signs in the process industry" on major incidents warning sign, was used for the survey. Through this survey, the major process safety incident leading indicators in the process industry were found by process safety management elements, and each site and/or facility can use these leading indicators for activities for process safety incident prevention. In addition, we proposed action items required to eliminate the root cause of those process safety incident leading indicators.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.8
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• pp.509-516
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• 2004

The concerns of distributed generations including photovoltaic(PV) system have been increased around the world since PV system is becoming widespread as a clean and gentle energy source for earth. In the future high density grid-connected PV systems will be interconnected with distribution network. As a result, the stability and long-term reliability of PV systems have become more important issues in this area. Grid-connected PV systems have been installed and monitored at field demonstration test center(FDTC) and also data acquisition system(DAS) has been constructed for measuring and analyzing performance of PV system to observe the overall effect of environmental conditions on their operation characteristics. The performance of PV system has been evaluated and analyzed for component perspective (PV array and power conditioning system) and global perspective (system efficiency, capacity factor, and electrical power energy) by field test and loss factors of PV system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.827-833
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• 2002

In this paper, a microstrip array antenna for LMDS(Local Multipoint Distribution Service) receiver with corporate feeding network using Chebyshev polynomials is proposed to get the high gain and low side lobe level. The Chebyshev array method is proposed to design the corporate feeding network. LMDS uses 24~27 GHz microwave frequency band to send and receive broadband signals. Measured antenna shows 23.4 dBi gain, 24.96 GHz center frequency, -29.15 dB return loss and 1.2 GHz bandwidth.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.8
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• pp.1313-1321
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• 2000

This paper presents a novel HTS microstrip pseudo-lumped element resonator for the compact and simple filter design. A 7-pole bandpass filter with quasi-elliptic response is designed and fabricated using non-adjacent couplings between resonators. A seven-pole quasi-elliptic filter is fabricated using double sided YBCO on a LaAlO$_3$ substrate with thickness of 0.5 mm and dielectric constant of 23.5. The filter has an insertion loss of 0.8 dB at 20K, a bandwidth of 8 MHz at the center frequency of 1774 MHz, and an attenuation of 33 dB for the cut-off-band of 1 MHz.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.109-114
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• 2003

Wireless communication systems are inevitable for efficient underwater activities. Because of the poor propagation characteristics of light and electromagnetic waves, acoustic waves are generally used for the underwater wireless communication. Although there are many kinds of information type, visual images take an essential role especially for search and identification activities. For this reason, we developed an acoustic-based underwater image transmission system under a dual use technology project supported by MOCIE (Ministry of Commerce, Industry and Energy). For the application to complicated and time-varying underwater environments all-digital transmitter and receiver systems are investigated. Array acoustic transducers are used at the receiver, which have the center frequency of 32kHz and the bandwidth of 4kHz. To improve transmission speed and quality, various algorithms and systems are used. The system design techniques will be discussed in detail including image compression/ decompression system, adaptive beam- forming, fast RLS adaptive equalizer, ${\partial}/4$ QPSK (Quadrilateral Phase Shift Keying) modulator/demodulator, and convolution coding/ Viterbi. Decoding.

• Carbon letters
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• v.15 no.4
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• pp.255-261
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• 2014

Multi-walled carbon nanotube reinforced epoxy composites were fabricated using shear mixing and sonication. The mechanical, viscoelastic, thermal, and electrical properties of the fabricated specimens were measured and evaluated. From the images and the results of the measurements of tensile strengths, the specimens having 0.6 wt% nanotube content showed better dispersion and higher strength than those of the other specimens. The Young's moduli of the specimens increased as the nanotube filler content was increased in the matrix. As the concentrations of nanotubes filler were increased in the composite specimens, their storage and loss moduli also tended to increase. The specimen having a nanotube filler content of 0.6 wt% showed higher thermal conductivity than that of the other specimens. On the other hand, in the measurement of thermal expansion, specimens having 0.4 and 0.6 wt% filler contents showed a lower value than that of the other specimens. The electrical conductivities also increased with increasing content of nanotube filler. Based on the measured and evaluated properties of the composites, it is believed that the simple and efficient fabrication process used in this study was sufficient to obtain improved properties in the specimens.

• Journal of The Korean Dental Society of Anesthesiology
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• v.11 no.2
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• pp.164-171
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• 2011

Altered consciousness may be the first clinical sign of a serious medical problem that requires immediate and intensive therapy to maintain life. There are many causes of the loss of consciousness in the dental office setting, such as, vasodepressor syncope, drug administration or ingestion, orthostatic hypotension, epilepsy, hypoglycemic reaction, acute adrenal insufficiency, cerebrovascular accident, hyperglycemic reaction, acute myocardial infarction, acute allergic reaction and hyperventilation. This is a case report of syncope and coma during endodontic treatment of a maxillary third molar under local infiltration anesthesia in multiple medically compromised patient. The main cause was thought to be hypoglycemic reaction. The patient was transferred to the medical emergency room and cared properly by the emergency medical physicians. The prognosis was good.

• Journal of The Institute of Information and Telecommunication Facilities Engineering
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• v.8 no.2
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• pp.90-95
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• 2009

All-optical fiber-type gain flattening filer (GFF) for an EDFA (Erbium doped fiber amplifier) were fabricated by using a FBT (fiber biconical tapered) process and the performance of the GFF was tested and athermal package was proposed. Historically, the chief contributor to gain unevenness has been the EDFA. Due to the inherent gain response of the EDFA's operation, there is always a modest imbalance in the gain applied as a function of wavelength. FBT methods have been used to make fiber type couplers and WDM filter since 1980. Attractivity of this methods was simple, cost effective and thermal stability. Simulation program tool is made to design target GFF profile for this paper. Fiber coupler manufacturing machine is modified for the GFF process. The final GFF is obtained by cascading 4 unit filter that has 6 taper stage. Test result shows 1 dB of wavelength flatness in the C band. Polarization dependent loss is under 0.15dB. The center wavelength variation is below ${\pm}$0.35nm at the temperature range of $20^{\circ}C$ to $70^{\circ}C$.