• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.217-225
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• 2015

Local heating system providing hot air locally to growing parts including shoot apex and flower cluster which were temperature-sensitive organs of cherry tomato was developed to reduce energy consumption for greenhouse heating without decline of crop growth. Growing part following local heating system was composed of double duct distributer which connected inner and outer ducts with hot air heater and winder which moved ducts up and down following growing parts with plant growth. Growing part local heating system was compared with conventional bottom duct heating system with respect to distributions of air and leaf surface temperatures according to height, growth characteristics and energy consumption. By growing part local heating, air temperature around growing part was maintained $0.9{\sim}2.0^{\circ}C$ higher than that of lower part of crop and leaf surface temperature was also stratified according to height. Investigations on crop growth characteristics and crop yield showed no statistically significant difference except for plant height between bottom duct heating and growing part local heating. As a result, the growing part local heating system consumed 23.7% less heating energy than the bottom duct heating system without decrease of crop yield.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.10
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• pp.100-106
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• 2009

In this study, methods of overheat detection at the coupling or wire in electrical facility are investigated, operating characteristic about the optic temperature sensor for continuous on-line temperature monitoring in diagnostics system of electrical facility is analyzed. Heating sources in the experiment for operating characteristics of optic temperature sensor use black body and hot plate, output voltage of optic temperature sensor in accordance with temperature variation is analyzed. Overheat generation due to poor contact at the circuit breaker in panel board detects using a thermocouple, infrared thermal camera and optic temperature sensor, and experiment results are analyzed. The effect of optic temperature sensor is the same that of other methods. These results expect to use basic research material for adjusting field of electrical diagnostics system using RFID type optic temperature sensor in the near future.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.2A
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• pp.157-165
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• 2004

The synchronization algorithm of IEEE 802.11a WLAN(Wireless Local Area Network) has three consecutive processes, which use a short code training symbol, a long code training symbol and a pilot symbol respectively. But in using this synchronization processes, the actual embodiment has two problems. First, the synchronization process has the complex structure using a long code training symbol and a pilot symbol. Second, since the long training symbol is only compensated with the offset correction coefficient, it can not be trusted perfectly. If the equalizer coefficient is obtained in this unstable period, the system performance is degraded. In particular, the system performance becomes worst in case of the 54 Mbps transmission system using the maximum length of data. In this paper, the new algorithm is proposed which can resolve the embodiment complexity of synchronization processes and structural defect, and also it is confirmed by simulation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.6 s.360
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• pp.31-39
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• 2007

In this paper, a system for real-time or periodic measurement and analysis of RF parameters such as forward transmit power and pilot power in CDMA base station systems is proposed. Such RF characteristic parameter measurement can be prevented from system fault and used to achieve optimal service quality and maximum investment return through cell coverage expansion, subscriber capacity increase and so on. For forward power measurement, the local oscillator frequency for the detector is varied so that the transmit power for all channels can be measured. The channel power measurement can be used to analyze the variation in transmit power for changes in voice traffic. By comparing to forward $E_c/I_o$, the pilot channel power can be deducted, which can be used to determine uy degradation in transmit section modules such as the high dover amplifier. Since an accurate analysis of carefully measured data using the CDMA level detector must be made, the system is designed so that measurement errors due to changes in crest factor with modulation method can be overcome.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.38-44
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• 2023

This study aims to determine how agricultural drones are operated for flight tests using a 5G communication in order to carry out a mission such as sensing agricultural crop healthy status with special cameras. Drones were installed with a multi-spectral and IR camera to capture images of crop status in separate altitudes with different speeds. A multi-spectral camera can capture crop image data using five different particular wavelengths with a built-in GPS so that captured images with synchronized time could provide better accuracy of position and altitude during the flight time. Captured thermal videos are then sent to a ground server to be analyzed via 5G communication. Thus, combining two cameras can result in better visualization of vegetation areas. The flight test verified how agricultural drones equipped with special cameras could collect image data in vegetation areas.

• Journal of IKEEE
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• v.27 no.4
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• pp.477-485
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• 2023

In this paper, the effect of AC ripple on the lifetime of lithium-ion batteries is experimentally analyzed. Bidirectional power conversion system(PCS) is used to increase the efficiency of energy storage systems (ESS). When connected to the grid, a current ripple with a frequency twice the grid frequency is applied to the battery due to its structure. Therefore, to analyze the effect of AC ripple on Li-ion battery aging, cycle life test are performed by applying charge/discharge profiles of DC current and DC+AC current ripple specifications. Based on the experimental results, direct current internal resistance (DCIR), incremental capacitance (IC), and surface temperature were analyzed. As a result, it is confirmed that AC ripple does not directly affect degradation and that battery degradation slows down after a certain cycle. These results can serve as a guideline for optimizing filters to reduce ripple on the battery side in applications where AC ripple occurs.

• The Journal of the Acoustical Society of Korea
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• v.28 no.6
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• pp.557-565
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• 2009

To perceive the direction and the distance of a sound, we always use a couple of information. Head Related Transfer Function (HRTF) contains the information that sound arrives from a sound source to the ears of the listener, like differences of level, phase and frequency spectrum. For a reproduction system using 2 channels, we apply HRTF to many algorithms which make 3d sound. But it causes a problem to localize a sound source around a certain places which is called the cone-of-confusion. In this paper, we proposed the new algorithm to reduce the confusion of sound image localization. The difference of frequency spectrum and psychoacoustics theory are used to boost the spectral cue among each directions. To confirm the performance of the algorithm, informal listening tests are carried out. As a result, we can make the improved 3d sound in 2 channel system based on a headphone. Also sound quality of improved 3d sound is much better than conventional methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.5
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• pp.1005-1015
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• 2000

In this paper, the performance of Hybrid CDU MFSK system has been analyzed in the environment that narrowband Class-A impulsive noise include Gaussian noise in wireless communication channel and Nakagami fading. The performance of system improved to adopting both of technique MRC diversity and BCH channel coding. The results show that there is substantial degraded in Hybrid CDMA system performance by impulse index is stronger and the fading index is smaller. But also improvement can be obtained when BCH coding techniques are adopted. Additional MRC diversity techniques is more improvement than BCH coding techniques when degraded environment with the low fading index. But BCH coding techniques is more improvement than MRC diversity techniques when fading index has been increased. The Hybrid CDMA MFSK system is incomplete to voice communication standard BER$(10^{-3})$ in Rayleigh fading by independent each adopting techniques BCH coding and MRC diversity. But it's satisfy(improvement can be obtained) to voice communication standard BER in strong impulse noise(24dB over) by adopting techniques BCH coding and MRC diversity at a time. Additional it's a substantial enhancement $(10^{-3})$satisfaction) in fading index (m=3, 22dB) in addition to strong impulse noise and 24dB over with data service standard $(10^{-5})$ BER satisfaction. This result show that there is error performance improved by diversity branch and coding advantage.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• autumn
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• pp.180-185
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• 2003

The increase of traffic over a bridge has been emerged as one of the most severe problems in view of bridge maintenance, since the load effect caused by the vehicle passage over the bridge has brought out a long-term damage to bridge structure, and it is nearly impossible to maintain operational serviceability of bridge to user's satisfactory level without any concern on bridge maintenance at the phase of completion. Moreover, bridge maintenance operation should be performed by regular inspection over the bridge to prevent structural malfunction or unexpected accidents front breaking out by monitoring on cracks or deformations during service. Therefore, technical breakthrough related to this uninterested field of bridge maintenance leading the public to the turning point of recognition is desperately needed. This study has the aim of development on automated inspection system to lower surface of bridge superstructures to replace the conventional system of bridge inspection with the naked eye, where the monitoring staff is directly on board to refractive or other type of maintenance .vehicles, with which it is expected that we can solve the problems essentially where the results of inspection are varied to change with subjective manlier from monitoring staff, increase stabilities in safety during the inspection, and make contribution to construct data base by providing objective and quantitative data and materials through image processing method over data captured by cameras. By this system it is also expected that objective estimation over the right time of maintenance and reinforcement work will lead enormous decrease in maintenance cost.

• Journal of the Korean Wood Science and Technology
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• v.43 no.6
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• pp.884-889
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• 2015

Appropriate evaluation of thermal insulation property of structural member and valid control of cooling/heating energy are important for improving building's energy efficiency. The typical heating system of house in Korea is the floor heating one. The radiation heating system is not only appropriate to climate and geographic conditions of Korea, but also advantageous to provide emotional comfort by the warm feeling of floor. Based on living conditions in Korea, scaled models of the wooden house and concrete house were designed. The ceiling was made of styrofoam insulation and the four sided walls and bottom were made of plywood and concrete, respectively. The floor was heated by heating film. Indoor vertical temperature distributions by floor heating system were measured by thermocouple, and surface temperatures on walls were measured by infrared thermography. Also, thermal insulation property of wooden wall was evaluated to build database for improving energy efficiency of wooden building. It is expected that collected data during tests of various types of floor and wall composition could be referenced for evaluating thermal environment of actual conditions of houses.