• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.1
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• pp.11-18
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• 2011

Wave overtopping reef system with guide vanes convert incident wave energy on the reef type structures into electric power. Previous studies decided shape parameters likes slope, height of the sloping arm and shape of guide vane. In this paper, using these shape parameters produce 1/7 scale model and construct integration scale model system combining water pressure head turbine, power generation, power control, operating control and monitoring system. In these systems, we measure the overtopping and power generation with different wave heights and periods and compare the results with the previous studies. This was confirmed designed overtopping and power generation, then we suggest efficient control system.

• Smart Structures and Systems
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• v.2 no.3
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• pp.237-251
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• 2006

Piezoelectric sensors have many applications in geotechnical engineering, especially in characterizing soils through measurement of wave velocities. Since mechanical properties of a material are closely associated with wave velocities, piezoelectric sensors provide a reliable and non-destructive method for the determination of soil properties. This paper presents results of recent research on measuring stiffness of a wide range of soils such as clay, sand, and gravel, characterizing anisotropic properties of soil induced by external loading, measuring stiffness of base and subgrade materials in the pavement, determining soil properties in a centrifuge model during the flight of a centrifuge, and understanding wave propagation in granular materials under micro-gravity environment using this technique.

• Journal of Digital Convergence
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• v.16 no.1
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• pp.147-152
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• 2018

Recently, as the demand for transmission of ultra-high quality media data such as UHD, AR, and VR increases, various technologies for this have been actively developed and IEEE 802.11ad standard have been commercialized. In this paper, a test bed is constructed to analyze the indoor wireless environment using the IEEE 802.11ad standard based on mmWave, and the experimental results of various indoor wireless environments are introduced and analyzed. We compared the data from the module by data transmission, such as signal to noise ratio(SNR) and throughput. And we measured the beam pattern and width of the module and compared the effects on the indoor environment of the corridor and the office. This shows that the signal reflection of the wall shows higher SNR values and is more suitable to use for indoor than outdoor. It is confirmed that the loss when not in line of sight(LoS) is not enough to compensate the wall reflected signal. As a result, it is judged to be suitable for the indoor use of the mmWave LAN and can be usefully used for further experiments.

• Atmosphere
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• v.16 no.2
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• pp.111-124
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• 2006

This study examines seasonal variability of the surface energy balance at the King Sejong Station, Antarctica, using measurements and estimates of the components related to the balance for the period of 1996 to 2004. Annual average of downward shortwave radiation at the surface is 81 $Wm^{-2}$ which is 37% of the extraterrestrial value, with the monthly maximum of 188 $Wm^{-2}$ in December and the minimum of 8 $Wm^{-2}$ in June. These values are relatively smaller than those at other stations in Antarctica, which can be attributed to higher cloudy weather conditions in Antarctic front zone. Surface albedo varies between ~0.3 in the austral summer season and ~0.6 in the winter season. As a result, the net shortwave radiation ranges from 117 $Wm^{-2}$ down to 3 $Wm^{-2}$ with annual averages of 43 $Wm^{-2}$. Annual average of the downward longwave radiation shows 278 $Wm^{-2}$, ranging from 263 $Wm^{-2}$ in August to 298 $Wm^{-2}$ in January. The downward longwave radiation is verified to be dependent strongly on the air temperature and specific humidity, accounting for 74% and 79% of the total variance in the longwave radiation, respectively. The net longwave radiation varies between 25 $Wm^{-2}$ and 40 $Wm^{-2}$ with the annual averages of 30 $Wm^{-2}$. Accordingly, the annual average energy balance is dominated by radiative warming of a positive net all-wave radiation from September to next March and radiative cooling of a negative net all-wave radiation from April to August. The net all-wave radiative energy gain and loss at the surface is mostly balanced by turbulent flux of sensible and latent heat. The soil heat flux is of negligible importance in the surface energy balance.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1023-1030
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• 2021

Korea Maritime Safety Tribunal (KMST) statistics released in of 2019 indicated that most collision accidents involving small-size vessels with less than 20 gross-tonnage occur mainly due to operational carelessness, such as forward-looking negligence and unskilled vessel control. As an effective remedy, training and education for vessel operators are being strengthened to prevent accidents. However, collision accidents are increasing, and technical measures are continuously developed to reduce accidents caused by human factors. In this study, an avoidance algorithm and prototype of terminal-controller against collision between two nearby vessels was developed for implementation on relative navigation control by adopting WAVE telecommunication technology. Moreover, several sea trial tests were performed to verify the collision avoidance algorithm and control system using two fishing vessels for dif erent scenarios.

• Ocean and Polar Research
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• v.44 no.4
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• pp.287-296
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• 2022

High-frequency (HF) radar measures sea surface currents from the radio waves transmitted and received by antenna on land. Since the data quality of HF radar measurements sensitively depend on the radio wave environment around antenna, Antenna Pattern Measurements (APM) plays an important role in evaluating the accuracy of measured surface currents. In this study, APM was performed by selecting the times when the background noise level around antenna was high and low, and radial data were generated by applying the ideal pattern and measured pattern. The measured antenna pattern for each case was verified with the current velocity data collected by drifters. The radial velocity to which the ideal pattern was applied was not affected by the background noise level around antenna. However, the radial velocity obtained with APM in the period of high background noise was significantly lower in quality than the radial velocity in a low noise environment. It is recomended that APM be carried out in consideration of the radio wave environment around antenna, and that the applied result be compared and verified with the current velocity measurements by drifters. If it is difficult to re-measure APM, we suggest using radial velocity in generating total vector with the ideal pattern through comparative verification, rather than poorly measured patterns, for better data quality.

• Journal of People, Plants, and Environment
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• v.24 no.6
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• pp.639-649
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• 2021

Background and objective: Various images from visual display terminals (VDTs) as well as living lighting are important parts of our daily life; thus, properly controlling the lighting environment - that is, illuminance, color temperature and good images from VDTs - can have a substantial effect on improving the mental health and work efficiency in everyday life. We examined electroencephalography (EEG) and heart rate variability (HRV) responses to various lighting conditions in 25 university students as they viewed images of a green landscape or traffic congestion. Methods: EEG was performed in darkness and when the room was illuminated with 10 different light-emitting diode (LED) color temperatures, while the EEG and HRV responses to green landscape or traffic congestion image stimuli were measured in darkness and during room illumination with three different LED color temperatures. Results: We found a significant difference between darkness and high LED illumination (400 lx) at 7 (CZ, F4, FZ, O1, O2, OZ, and T6) of 30 channels, while the alpha wave activity increased during darkness. In the second experiment, the green landscape image stimuli in the 30 lx-2600 K lighting condition elicited theta wave activity on the EEG, whereas the traffic congestion image stimuli under high LED illumination elicited high beta and gamma wave activities. Moreover, the subjects exhibited better stress coping ability and heart rate stability in response to green landscape image stimuli under illuminated conditions, according to their HRV. Conclusion: These results suggest that lower color temperatures and illumination levels alleviate tension, and that viewing green landscape image stimuli at low illumination, or in darkness, is effective for reducing stress. Conversely, high illumination levels and color temperatures are likely to increase tension and stress in response to traffic congestion image stimuli.

• Proceedings of the Korea Information Processing Society Conference
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• 2017.04a
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• pp.463-465
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• 2017

ICT기술이 빠르게 발전함으로써 헬스케어, 스마트홈, 스마트 씨티, 스마트카, 웨어러블과 같이 다양한 인간중심의 서비스가 개발되고 있다. 이러한 인간중심 서비스를 제공하기 위해 여러 센서들을 이용하여 작은 네트워크를 구현한다. 일반적으로 많은 무선 프로토콜 중 Z-Wave를 많이 사용한다. 센서들의 정보를 AES기반으로 암호화하여 Controller와 Device간 통신하는데 가장 효율적이지만 Z-Wave통신으로 데이터를 보내기위해 암호화 키를 생성할 때 사용되는 값이 평문으로 전송되기 때문에 보안위협이 존재한다. 따라서 이러한 보안 위협을해결하기 위해 Controller와 Device간 암호화 키를 생성할 시 Diffie-Hellman을 이용하여 보다 안전한 프로토콜을 제안한다.

• Weed & Turfgrass Science
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• v.7 no.3
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• pp.283-283
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• 2018

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.579-584
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• 2009

Arrangement of the facilities for improving harbor functions depends on sea and land conditions such as the ship's arrival and departure conditions, waves and tide. And the plan and the size of the facilities depend much on harbor and marine environment condition such as cargo quantity, ship size, ship traffic and seawater circulation. Among these, waves have so much effect on a breakwater design that it is the most important to understand their characteristics and to apply them to breakwater design. Therefore, to analyze the effect of waves characteristics over a rubble mound breakwater, we have calculated wave pressure by using numerical analysis at each tide level and have analyzed the effect of wave pressure on structure stability by conducting the stability analysis with the wave pressure. As a result, it is found that during low and mean tide level time the biggest wave pressure is estimated near calm water level. But during high tide time, the biggest wave pressure is estimated in front of capping. And the stability analysis indicates also that a structure is most unstable when low tide time wave pressure is acting on. After reviewing the stability of a structure by applying vertical and horizon wave forces, it is concluded that safety factor is lower than ordinary time(max. about 15%), is also reviewed when designing a rubble mound breakwater.