• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.6
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• pp.444-451
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• 2017

In this paper, we have evaluated and analyzed OTFS(Orthogonal Time Frequency Space) modulation and OTFS-MIMO(Multiple Input Multiple Output) system. OTFS modulation can concisely compensate delay-Doppler spreading effect by using 2D(2-Dimension) iDFT (inverse Discrete Fourier Transform) and DFT(Discrete Fourier Transform) operation. It enables OTFS system to transmit high-speed data. Especially, OTFS-MIMO system can transmit all data streams without performance degradation on high Doppler frequency channel. As simulation results, we have confirmed that $1{\times}1$ OTFS system's achievable rate is a similar to each stream of $2{\times}2$ OTFS-MIMO system. That is, we have also confirmed that $2{\times}2$ MIMO system can completely achieve double achievable rate in comparison with OTFS system on high Doppler frequency channel.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.11
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• pp.23-31
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• 2008

This paper addresses relationships between diversity techniques and channel coding rates for OFDM and SC-FDE systems. In OFDM systems it is important to select proper channel coding rates according to multi-path channel profiles and low channel coding rates are required with cyclic delay diversity compared to the case of space time coding. On the other hand, it is not necessary to use low channel coding rates for SC-FDE systems where DFT spreading is applied to OFDM and relatively high channel coding rates can be used regardless of diversity techniques.

• Fire Science and Engineering
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• v.31 no.3
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• pp.79-87
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• 2017

Sandwich panels which are having the both sides are bonded with a heat insulating material with an iron plate are used as factories, warehouse structures as advantages of convenience in construction at economic efficiency of material cost. However, in a panel structure constructed by continuous joining of sandwich panels, a joint portion where a panel and a panel are connected is generated. The joint part is a part which is easily vulnerable to fire because flames easily flow into the melting and deformation of the iron plate during fire. The flames flowing into the panel induce diffusion of fire by rapid burning, causing damage of human life and property. In this research, we developed a flame spread prevention plate to prevent spreading of sandwich panel. This is an improvement of the workability by the anti-spreading construction method of the existing previous research, it can be applied independently to the connecting part where the panel and the panel are coupled, designed to prevent inflow and spreading of flame did. The actual fire test of the test method of KS F ISO 13784-1 of the sandwich panel specimen was conducted and the burning behavior corresponding to the presence or absence of application of the flame spread prevention plate was grasped at the panel connection part and its effect was measured. Inserting a fire spreading plate into the test result panel connecting part is measured by delaying the flashover, prevention of collapse of the specimen, and temperature rise of the opening, effectively improving the fire safety of the panel structure It was confirmed as a method that can be secured. It is judged that panel structure will contribute to ensuring fire safety by applying the fire spread prevention construction method of various methods ensuring the workability and economy of panel connection vulnerable to fire.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.5
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• pp.131-138
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• 2008

The channel parameters such as RMS delay spread and Doppler frequency have an effect on performance of system. This paper investigates the effect between the Inter-Code Interference (ICI) and the frequency diversity gain in the multi-rate MC-CDMA system. The multi-rate MC-CDMA system has achieved the more variable data rate than the MC-CDMA and moreover it has the better performance than the OFDMA system, because it has achieved the frquency diversity gain. However, the frequency diversity gain and ICI have a trade-off relationship by using the spreading code. Therefore, we have improved the system performance by efficient choice of system parameters. In order to evaluate the effectiveness of the frequency diversify gain and the ICI effect, we perform simulations by altering the Doppler frequency and RMS delay spread.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.19-22
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• 2009

This thesis offers forecast & warning algorithm about the accessing networks though statistical sampling methods to prevent computer terrors. These networks are occurred among U-city network groups. The main characteristic of current computer attacks is avoiding well-known detection patterns by successive changes in spreading speeds and attacking codes. The improvement of attacking stills leads to a problem causing the defense-time delay and creates vicious cycle that tries to fix networks after damage. Proposed algorithm notices and warns the potential attacking areas through defecting previous attacking signs, analysing attaching results ed tracing attaching sources at the beginning of the attack.

• Journal of Agricultural Extension & Community Development
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• v.17 no.4
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• pp.919-931
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• 2010

Forage barley was developed for decreasing the import of forages, and increasing the farmer' income about ten years ago. Nevertheless of higher of farmer' income, the forage barley' area is slowly increased because of lacking of barely seeds. In order to suggest the plan of the urgent spreading on forage barley, the seed-gathering of forage barley was cultivated on 14-provinces and 291ha on 2009. The cultivation area of kyeungnam, kyeungbuk and chunnam province was more than other provence. The youngyang cultivar was cultivated more than orher cultivar. Seed-gathering amount of Youngyang, Uhoo and Yooyun cultiva was 364,213 and 303MT respectively. There were several problems for seed-gathering of forage barley which were the delay of seeding time and the more seeding amount, and the higher seed drying temperature than that of standard manual.

• Journal of the Korean Mathematical Society
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• v.51 no.4
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• pp.703-719
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• 2014

This paper is concerned with the traveling wave solutions of nonlocal dispersal models with nonlocal delays. The existence of traveling wave solutions is investigated by the upper and lower solutions, and the asymptotic behavior of traveling wave solutions is studied by the idea of contracting rectangles. To illustrate these results, a delayed competition model is considered by presenting the existence and nonexistence of traveling wave solutions, which completes and improves some known results. In particular, our conclusions can deal with the traveling wave solutions of evolutionary systems which admit large time delays reflecting intraspecific competition in population dynamics and leading to the failure of comparison principle in literature.

• Proceedings of the IEEK Conference
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• 2002.07c
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• pp.1948-1951
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• 2002

In this paper, we propose a chip timing recovery algorithm that is robust to frequency offset and time variant fading environments for DS/CDMA. The proposed structure is a modified non-coherent Delay Locked Loop (DLL) that employs a decimator. Analytical expression for the proposed non-coherent DLL S-curve and steady-state timing jitter is derived and confirmed by computer simulation. The results show that the proposed structure can reduce a steady-state timing jitter of the regenerated spreading code replica to frequency offset and time-variant fading in mobile radio channel, especially in very low SNR.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.403-405
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• 1999

Power transformers have a tendency of ultra-high voltage and huge capacity as power demand increases day after day. Therefore, the fault by insulation destruction gives rise to large area of power failure in huge capacity transformers. On-line predictive diagnostics is very important In power transformers because of economic loss and its spreading effect. Hence, this study presents experiments of partial discharge method using ultrasonic sensor in order to confirm the possibility of ultrasonic sensor in power transformers. It carries out the experiments of measuring delay time between ultrasonic sensor and transducer, sensitiities by temperature change of oil and by barriers inside transformers. It is also Included wave analysis by ultrasonic sensor for needle-plate electrode powered on through high-voltage equipments.

• Fire Science and Engineering
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• v.24 no.3
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• pp.52-57
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• 2010

Fire protection countermeasure were considered on the straw thatched roof and wooden structure. For the fire resistant treatment, rice straw was soaked in the fire resistant liquid with different soaking time. After treatment, some rice straw sample was washed with water then the rice straws were tested to check the fire resistance performance. And the wood was soaked in the fire resistant liquid at an atmospheric pressure, vacuum-pressure condition and painted with brush on the surface. To analyse the fire resistant performance of rice straw, ignition delay time was measured under the radiant heat flux of cone heater. And the fire resistant performance of wood samples were tested with 45 degree fire resistant test apparatus and cone heater. Based on the cone heater test, the rice straw which most easily ignitable material shows the longer ignition delay time than not treated ones and even in the water washed straw show a longer ignition delay time than not treated ones. And fire resistant treated woods of vacuum-pressure treated sample showed the most excellent performance on fire resistance. And the fire resistant treated by brush and soaking showed a longer ignition delay time than not treated ones. From this experiment, it was found that a fire resistant treatment of rice straw and wood of the house can be protected from the fire spread.