• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.11
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• pp.2021-2026
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• 2007

In the parer, we design a non-coherent UWB system by adopting the architecture of a simplified asynchronous transmission and the edge-triggered pulse transmission, which makes e system performance independent of the share of the transmitted waveform, robust to multipath channels. The designed non-coherent UWB transceiver architecture has an advantage of the simple realization since any mixer, high-speed correlator, and high-sampling A/D converter are not necessary at the cost of performance degradation of about 3dB. Further, the designed non-coherent UWB transceiver is actually implemented with the wireless CANVAS prototype testbed in short range indoor application environments such as a lecture room. The implemented prototype testbed is proven to offer the data rate of 115kbps on the conditions of Peer-to-Peer(P-to-P) in the indoor channel within the range of about 10m.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2B
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• pp.167-173
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• 2004

This paper reports on the development of a 60㎓ wide bandwidth wireless transceiver using NRD waveguide. We fabricated a wireless transceiver using NRD waveguide, which consists of a 3 dB directional coupler, a bandpass filter, a Gunn oscillator, an ASK modulator, and a Balanced Mixer. The new transceiver is capable of transmitting an output power of 10mW to a distance of more than 1 Km, operating in 60㎓ frequency and bandwidth of 2㎓. The value of BER reached approximately 10 when the transceiver was tested at the 155.52Mbps ATM(OC 3) at the communication distance of 1 km. It demonstrated an impressively stable transmission feature of BER l0$^{6}$ even in the heavy rainfall.

• Journal of ILASS-Korea
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• v.14 no.1
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• pp.28-33
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• 2009

This paper presents the performance and emissions characteristics of a small spark-ignited 2-stroke gasoline and LPG engine. The engine used in this paper is a single cylinder, two-stroke, air-cooled SI engine for brush cutter. We measured the rpm, torque, fuel consumption and HC, CO, NOx emissions in associated with the dynamometer load at WOT. The results showed that as engine revolution speed decreased, the excess air ratio of gasoline engine kept going about 0.9 and that of LPG engine increased 0.83 to 1.05. Torque and power of gasoline engine was higher than LPG engine. In exhaust emissions, HC emissions of gasoline engine was lower than LPG engine. In low speed area, CO emissions of LPG engine was lower than gasoline engine. Both gasoline engine and LPG engine emitted little NOx emissions.

• Electronics and Telecommunications Trends
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• v.34 no.6
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• pp.61-70
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• 2019

Recently, research and development for next-generation mobile communication and short-range wireless communication has begun worldwide along with the provision of commercial services of 5G mobile communication technology. In response to this trend, the THz band has attracted considerable attention as a frequency band for transmitting 100 Gbps of large-capacity wireless data. For communication in the THz band, research and development of approaches based on photonics and electronics is being actively performed; the configurations, characteristics, and performances of these two methods for THz transmission have been seriously examined. Among them, we reviewed the technical issues in implementing THz wireless transmission technology using photonics technology. We also introduced the Electronic and Telecommunications Research Institute's (ETRI) development of photonics-based THz short-range transmission technology starting from 2019 and including some initial results. In the near future, 100 Gbps high-capacity wireless data transmission technology utilizing photonics technology is expected to be commercially available and applied to various applications, such as 3D hologram transmission, uncompressed large capacity medical data transmission, and multiple augmented reality/virtual reality (AR/VR).

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.1
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• pp.11-21
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• 2013

The Geyoungju Ca-bentonite with dry density of 1.6 g/$cm^3$ has been considered as a standard buffer material for the disposal of high level waste in KAERI disposal system design. But it had relatively lower thermal conductivity compared with other surrounding materials, that was one of key parameters to limit the increase of the disposal density in the disposal system. In this study, various additives were selected and mixed with the Ca-bentonite in different mixing methods in order to increase the thermal conductivity from 0.8 W/mK to 1.0 W/mK. As an additive, CNT (Cabon Nano Tube), graphite, alumina, CuO, and $Fe_2O_3$ were selected, which are chemically stable and have good thermal conductivity. As mixing methods, dry hand-mixer mixing, wet milling and dry ball mill mixing were applied for the mixing. Above all, the ball mill mixing was proved to be most effective since the produced mixture was most homogeneous and showed higher increase in the thermal conductivity. From this study, it was confirmed that the thermal conductivity for the Geyoungju Ca-bentonite could be improved by adding small amount of highly thermal conductive material to 1.0 W/mk. In conclusion, it was believed that the experimental results will be valuable in the disposal system design if the additive effects on the swelling and permeability on the compact bentonite are also approved in further studies.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.4 s.48
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• pp.543-548
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• 2004

For pearl pigments used for splendor or gloss effect of make-up products, especiallv point make-up products like eye-shadow and blusher, we studied the variation of particle size distribution by the grinding time and by the binder used as a binding agent. In this study. high speed mixer was used and the particle sire distribution was measured by using the light scattering method. In case of pearl pigments, its median diameter of $5{\;}{\mu}m$, the particle size was reduced to 4.6 um when it was ground for 120 s. When it was applied for the pearl pigment of $45{\;}{\mu}m$, the particle size was reduced to $27{\;}{\mu}m$. We confirmed that the latter was reduced more largely and the original gloss was reduced too. For the binder, we studied the correlation between particle size of raw material and grinding time. We also investigated the effects of the binder contents on the variation of particle size distribution of products by aggregation of particles.

• Korean Journal of Plant Resources
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• v.26 no.1
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• pp.52-59
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• 2013

This study was carried out to develop the proper cultivation methods of Brachythecium rivulare and Myuroclada maximowiczii which showed high-value for the interior landscaping and potting. Growth of two moss species cultivated in the compost covered with cloth was vigorous compared to that grown in containers only using cloth or compost, and their harvesting processes were easier. The growth and harvest easiness of mosses cultivated in compost were great rather than in bark or peatmoss. Compared to division, the spray of crushed mosses using mixer was effective for both gametophyte generation and their harvesting processes. In addition, the optimum inoculum for each container ($27{\times}17{\times}3cm$) was 2.0 g in B. rivulare and 4.0 g in M. maximowiczii. Overall growth of B. rivulare treated with nutrient solution (N:P:K=20:20:20) was inhibited compared to control, fresh-weight gain was reduced toward the higher concentration. But fresh-weight gain of M. maximowiczii was the highest with $0.25g{\cdot}L^{-1}$ treatment. Therefore, adequate moisture supply, after spraying crushed mosses (2.0 and 4.0 g each) in the compost covered with cloth, were the appropriate cultivation methods for B. rivulare and M. maximowiczii. Nutrient solution treatment with low concentration, during the cultivation period, would be the proper way only for M. maximowiczii.

• Journal of the Korean Institute of Gas
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• v.26 no.6
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• pp.24-29
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• 2022

This paper is a purpose to Analyze and study the failure examples for a engine oil leakage of camshaft bearing seal, poor contact by computer connector fin damage and vaporizer inferiority on LPG automotive. The first example, when the researcher disassembled the cylinder head of engine to establish the cause for oil leakage, he confirmed the engine oil leakage by damaged between the engine intake camshaft bearing and seal part. The second example, the connector fin of power source line that control the starting of a car supplied with engine computer. As a result, it found the fact that the engine operation stopped because of cutting of the power source by connector fin damage. The third example, it verified the engine incongruity phe cutting of the power source by connector fin damage. The third example, it verified the engine incongruity phenomenon as thd gas didn't flow the vaporizer by foreign substance deposit. Finally, it supplied a small quantity gas from vaporizer to mix. As the computer controlling mix opening condition supplied a air as opening signal, the air and fuel became rarefied state. it knew that the engine didn't produce prpper power. Therefore, a car have to throughtly inspect not in order to arise the failure symptoms.

• Journal of the East Asian Society of Dietary Life
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• v.21 no.4
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• pp.577-586
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• 2011

This study was carried out to investigate food service management practices in various operation types of child care center in Gyeonggi area of Korea, and to provide basic information for improving food service management policies at child care centers. Self-administrated questionnaires were collected from 102 child care center directors. The statistical analysis was completed using SPSS ver. 18.0 program. Approximately 97.1% of the directors were women. The number of total children were difference in public, private and home care centers respectively (p<0.001), and time of operation was significantly (p<0.01). Only 8.9% of the centers employed a dietitian, whereas 92.5% of the centers employed cook or assistant cook, thus food service was not managed by professionals in most centers. All of the centers had been self-operated and meals were prepared in a conventional manner. In approximately 89.2% of the centers servings snacks twice a day. Menu planner of the centers which have no dietitian was the child care information center (47.5%) or the director (34.7%). In most centers, the directors was also purchasing manager and 36.0% of the center purchased food every day. These results indicated that food service management guidelines need to be established by the child care center type with the government control and financial support. We recommended that they furnish the efficient food service program for food service management.

• Journal of Advanced Navigation Technology
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• v.1 no.1
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• pp.23-34
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• 1997

A multi-channel digital GPS receiver has been developed including a RF-to-IF engine (engine 1), a digital signal processing engine (engine 2) with a microprocessor interfacing, and a navigation software. A high speed SiGe heterojunction bipolar transistor (HBT) as a active device has been mounted on chip-on-board (COB) type hybrid ICs such as LNA, mixer, and VCO in RF front-end of the engine 1 board. A 6-channel digital correlator together with a real-time clock and a microprocessor interface has been realized using an Altera Flex 10K FPGA as well as ASIC technology. Navigation software controlling the correlator for GPS signal tracking, retrieval and storing a message retrieval, and position calculation has been implemented. The GPS receiver was tested using a single channel STR2770 simulator. Successful navigation message retrieval and position determination was confirmed.