• Magazine of the Korean Society of Agricultural Engineers
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• v.19 no.3
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• pp.4483-4491
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• 1977

The results obtained are as follows; 1. The variation of the temperature in a vinyl house without heating system is similar to that of air temperature in a day. The difference of maximum temperature and minimum one in a day is 27$^{\circ}C$ which is two times greater than the daily difference of air temperature. 2. When the length of the duct is increased, the high temperature zone is built up in the direction of warm air discharge from the duct, and the low temperature zone is built up in the opposite direction of warm air discharge. But, in case of the duct length is short (0.05 L), the temperature distrubution in a vinyl house become uniform. It is concluded that the shorter length of the duct, the better the distribution of the temperature in a vinyl house is. 3. When the duct is installed at high position, the high temperature zone is built up in the upper zone of the vinyl house and the low temperature zone is built up in the lower zone. And when the position of the duct is low, the rate of temperature variation along the vertical direction become high, and the direct contact of warm air with the plant in the house is occured. It is concluded that the duct should be installed at the position of slightly higher than the plant height. 4. When the fuel consumption rate is fixed at the 101/hr, the lowest temperature warming rate in the vinyl house is 5$^{\circ}C$ without regard to the air temperature.

• Journal of Advanced Navigation Technology
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• v.19 no.3
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• pp.244-249
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• 2015

High-altitude electromagnetic pulse (HEMP) is generated from a nuclear burst at high altitudes above the Earth, the electromagnetic fields reach the ground nearly simultaneously with regard to the operation time of systems. The aim of this analysis is to inquire about HEMP characteristics and to analyze about effect in orthogonal frequency division multiplexing (OFDM) system. Specifically, HEMP characteristics are classified field sources, spatial coverage, time domain behavior, frequency spectrum and field intensities in this study. Bits error rate (BER) of the receiver with the software simulation is confirmed for the HEMP effect. Q-factor made a difference about interference duration by transfer characteristics of system. When Q factor is smaller, the recovery time from HEMP interference is short. To the contrary, if the Q factor is larger, the recovery duration is lasted longer by 300-600%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.710-716
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• 2003

OFDM is a very attractive technique for achieving high-bit-rate data transmission and high spectrum efficiency. However one of disadvantages of OFDM signal is the high PAPR characteristic when multicarriers are added up coherently. In this paper, we propose an adaptive PTS scheme using two threshold levels for PAPR reduction and reducing the amount of PAPR calculations with clipping scheme. Simulation results show that it is almost same between average bit error rate performance of the proposed scheme and that of a conventional scheme. Also, we obtain a great performance gain in the amount of calculations compared to the conventional scheme. Therefore, proposed system has a good performance in data processing time in OFDM wireless communication systems.

• Progress in Superconductivity
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• v.6 no.1
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• pp.13-18
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• 2004

High-.ate in-situ$ YBa_2$Cu$Cu_3$$O_{7-x}$ (YBCO) film growth was demonstrated by means of the electron beam co-evaporation. Even though our oxygen pressure is low, ∼$5 ${\times}$10^{-5}$ Torr, we can synthesize as-grown superconducting YBCO films at a deposition rate of around 10 nm/s. Relatively high temperatures of around 90$0^{\circ}C$ was necessary in this process so far, and it suggests that this temperature at a given oxygen activity allows a Ba-Cu-O liquid formation along with an YBCO epitaxy. Local critical current density shows a clear correlation with local resistivity. Homogeneous transport properties with a large critical current density ($4 ∼ 5 MA/\textrm{cm}^2$ at 77K, 0T) are observed in top faulted region while it is found that the bottom part carries little supercurrent with a large local resistivity. Therefore, it is possible that thickness dependence of critical current density is closely related with a topological variation of good superconducting paths and/or grains in the film bodies. The information derived from it may be useful in the characterization and optimization of superconducting films for electrical power and other applications.

• Journal of Welding and Joining
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• v.21 no.2
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• pp.57-63
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• 2003

Since new types of vehicles or structures made from thin aluminum alloy are under rapid development and some products are already on the market, welding of aluminium sheet is increasing. MIG(Metal Inert Gas), MIG-Pulse, TIG(Tungsten Inert Gas) welding are the typical Ai welding. MIG welding has the advantage of high speed, but it is difficult to apply to the thin plate, because of bum-through by the high heat input and spatter. MIG-Pulse welding can weld without spatter and burn-through, but when the gap exists at the welding joint, there is quite a possibility of bum-through. TIG welding is difficult to weld at a high speed. AC Pulse welding alternates between DCEP(Direct Current Electrode Positive) and DCEN(Direct Current Electrode Negative). DCEN is higher wire melting rate than DCEP, while lower temperature of droplet than DCEP. In AC Pulse welding, far fixed welding current, wire melting rate increases as the EN ratio increases. For fixed wire feed rate, welding current decreases as the EN ratio increases. Because of these features, the temperature of droplet, the depth of penetration, the width of bead decrease and the reinforcement height increases as EN ratio increases, and these are able to weld at a high speed, lower heat input. It is the purpose of this study that design of AC pulse current waveform for MIG welding of Al sheet and estimation of output characteristic.

• Journal of Korean Society on Water Environment
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• v.24 no.3
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• pp.340-344
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• 2008

Electro-flotation (EF) was applied to a sequencing batch reactor process (SBR) in order to enhance solids-liquid separation. Solids-liquid separation was good enough in the SBR coupled with EF (EF-SBR) and it was possible to maintain the concentration of mixed liquor suspended solids (MLSS) high in the EF-SBR. Under moderate organic loading condition (COD loading rate: 6 g/day), control SBR (C-SBR) showed similar treatment efficiencies with the EF-SBR. Under high organic loading condition (COD loading rate: 9.6 g/day), the solids-liquid separation in the C-SBR was deteriorated due to proliferation of filamentous bulking organisms at high F/M ratio. However, the EF-SBR was operated stably and with the high MLSS concentration (above 4,000 mg/L) regardless of the organic loading conditions during overall operating period leading to the satisfactory effluent quality. Gas production rate of the electrodes was gradually decreased because of anodic corrosion and scale build-up at the surface of cathode. However it could be partially overcome by use of corrosion-proof electrode material (SUS-316 L) and by periodic current switching between the electrodes.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.7
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• pp.43-51
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• 2013

This paper describes the development of the telemetry link system for the high data rate transmission in high speed rocket application. In consideration of bandwidth efficiency, frequency selective fading and doppler frequency offset, we used DQPSK instead of PCM/FM which has been the primary modulation format in aeronautical telemetry. Also we used the spatial diversity with multiple receiving antennas to mitigate multipath interference which is the dominant channel impairment and the Turbo Product Code for Forward Error Correction to improve bit error rate performance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.111-113
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• 2011

This study investigated about how much the limestone's volume was changed as time passed while maintaining a certain level of moisture condition in the limestone material for concrete under high temperature. The result is summarized as follows: It was appeared that the limestone material under high temperature emitted some CO₂ resulting from the decarboxylation, so that as the heating temperature was increased, the limestone's length change rate was decreased. In the leave time change after heating the stone, the both conditions of 50% and 100% made the limestone create Ca(OH)₂ using some H₂O. So it was appeared that as time passed, the limestone's length change rate first increased because of its volume expansion, but the rate was reduced after the limestone material was crumbled.

• Proceedings of the IEEK Conference
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• 2003.07b
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• pp.791-794
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• 2003

The increasing computational capability of processors is driving the need for high bandwidth links to communicate and store the information that is processed. Such links are often an important part of multi processor interconnection, processor-to-memory interfaces and Serial-network interfaces. This paper describes a 0.11-${\mu}{\textrm}{m}$ CMOS 4 Gbp s/pin 3-Level transceiver using RSL/(Rambus Signaling Logic) for high bandwidth. This system which uses a high-gain windowed integrating receiver with wide common-mode range which was designed in order to improve SNR when operating with the smaller input overdrive of 3-Level. For multi-gigabit/second application, the data rate is limited by Inter-Symbol Interference (ISI) caused by low pass effects of channel, process-limited on-chip clock frequency, and serial link distance. In order to detect the transmited 4Gbps/pin with 3-Level data sucessfully ,the receiver is designed using 3-stage sense amplifier. The proposed transceiver employes multi-level signaling (3-Level Pulse Amplitude Modulation) using clock multi phase, double data rate and Prbs patten generator. The transceiver shows data rate of 3.2 ~ 4.0 Gbps/pin with a 1GHz internal clock.

• Journal of Power System Engineering
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• v.21 no.2
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• pp.20-26
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• 2017

This study was carried out to investigate the effect of precipitate on the high temperature deformation stability of incoloy 825 alloy. $Cr_{23}C_6$ carbide was precipitated under $950^{\circ}C$, but was not detected over $1,000^{\circ}C$. Most of the precipitation consist of $Cr_{23}C_6$ carbide. Strain-rate sensitivity was the highest in 0.01/s and the lowest in 10/s. Strain-rate sensitivity was decreased sharply below $950^{\circ}C$. In the temperature between $850^{\circ}C{\sim}1,150^{\circ}C$, plastic instable area did not exist. It showed the lowest Ziegler Parameter value of 0.06 Ziegler Parameter was the lowest as 0.06 at $850^{\circ}C$ with 10s-1 of strain. The highest Ziegler Parameter value(0.43) was found in plastic deformation at $1,050^{\circ}C$ with 0.01s-1 of strain. It tends to have an higher resistance to the high temperature deformation under $950^{\circ}C$, due to the precipitation.