• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.3
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• pp.23-28
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• 2021

In recent years, research on smart factory wireless mobile communication technology that wirelessly remotely controls utilities is being actively conducted. The Wi-SUN(Wireless Smart Utility Network) Alliance proposed Wi-SUN protocol structure suitable for building a platform such as a smart factory as a new wireless communication standardization standard based on EEE802.15.4g/e. It analyzes the performance of the IEEE802.15.4e CSL(Coordinated Sampled Listening) Mode MAC(Media Access Control) in terms of latency and looks at considerations for efficient operation.

• Wind and Structures
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• v.33 no.6
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• pp.437-446
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• 2021

As wind turbine rotors increase, the overall loads and dynamic response become an important issue. This problem is augmented by the exposure of wind turbines to severe atmospheric events with unconventional flows such as tornadoes, which need specific designs not included in standards and codes at present. An experimental study was conducted to analyze the loads induced by a tornado-like vortex (TLV) on horizontal-axis wind turbines (HAWT). A large-scale tornado simulation developed in The Wind Engineering, Energy and Environment (WindEEE) Dome at Western University in Canada, the so-called Mode B Tornado, was employed as the TLV flow acting on a rigid wind turbine model under two rotor operational conditions (idling and parked) for five radial distances. It was observed that the overall forces and moments depend on the location and orientation of the wind turbine system with respect to the tornado vortex centre, as TLV are three-dimensional flows with velocity gradients in the radial, vertical, and tangential direction. The mean bending moment at the tower base was the most important in terms of magnitude and variation in relation to the position of the HAWT with respect to the core radius of the tornado, and it was highly dependent on the rotor Tip Speed Ratio (TSR).

• Wind and Structures
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• v.34 no.3
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• pp.303-312
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• 2022

As wind turbine rotors increase, the overall loads and dynamic response become an important issue. This problem is augmented by the exposure of wind turbines to severe atmospheric events with unconventional flows such as tornadoes, which need specific designs not included in standards and codes at present. An experimental study was conducted to analyze the loads induced by a tornado-like vortex (TLV) on horizontal-axis wind turbines (HAWT). A large-scale tornado simulation developed in The Wind Engineering, Energy and Environment (WindEEE) Dome at Western University in Canada, the so-called Mode B Tornado, was employed as the TLV flow acting on a rigid wind turbine model under two rotor operational conditions (idling and parked) for five radial distances. It was observed that the overall forces and moments depend on the location and orientation of the wind turbine system with respect to the tornado vortex centre, as TLV are three-dimensional flows with velocity gradients in the radial, vertical, and tangential direction. The mean bending moment at the tower base was the most important in terms of magnitude and variation in relation to the position of the HAWT with respect to the core radius of the tornado, and it was highly dependent on the rotor Tip Speed Ratio (TSR).

• Product Safety
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• no.2 s.146
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• pp.14-19
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• 2006

올해 7월부터 본격적으로 발효되는 RoHS(유해물질사용에 관한 규제 - Directive on the Restriction of the use of certain Hazardous Substances in EEE)는 관련업체가 부담해야 하는 책임과 준수사항이 까다로워 대응에 큰 어려움이 예상된다. 즉, 전기제품내에 납, 수은, 카드늄 등 6대 물질의 사용을 제한해야 함에 따라 제품생산에 지대한 변화가 뒤따를 것으로 예상된다. 이제는 전세계적으로 '녹색경영'이라는 새로운 트랜드가 대두되고 있으며, 이것은 대기업뿐만 아니라 중소기업들의 새로운 대응이 필요한 현안으로 적절한 이해와 적극적 대응책마련이 시급하다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.7B
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• pp.1034-1042
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• 2010

As many researchers have been interested in Green IT, Energy Efficient Ethernet(EEE) with rate adaptation has recently begun to receive many attention. However, the rate adaptation scheme can have different energy efficiency and delay according to the characteristics of various traffic patterns. Therefore, in this paper, we analyze the impact of different traffic patterns on the energy efficiency and delay in Ethernet with rate adaptation. To do this, firstly we design a rate adaptation simulator which consists of Poisson based traffic generator, Pareto distribution based ON-OFF generator and Ethernet node with rate adaptation by using OPNET Modeler. Using this simulator, we perform the simulation in view of the total number of switching, transmission rate reduction, energy saving ratio and average queueing delay. Simulation results show that IP traffic patterns with high self-similarity affect the number of switching, rate reduction and energy saving ratio. Additionally, the transition overhead is caused due to the high self-similar traffic.

• Wind and Structures
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• v.27 no.2
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• pp.71-88
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• 2018

At the University of Western Ontario (UWO), numerical tools represented in semi-closed form solution for the conductors and finite element modeling of the lattice tower were developed and utilized significantly to assess the behavior of transmission lines under downburst wind fields. Although these tools were validated against other finite element analyses, it is essential to validate the findings of those tools using experimental data. This paper reports the first aeroelastic test for a multi-span transmission line under simulated downburst. The test has been conducted at the three-dimensional wind testing facility, the WindEEE dome, located at the UWO. The experiment considers various downburst locations with respect to the transmission line system. Responses obtained from the experiment are analyzed in the current study to identify the critical downburst locations causing maximum internal forces in the structure (i.e., potential failure modes), which are compared with the failure modes obtained from the numerical tools. In addition, a quantitative comparison between the measured critical responses obtained from the experiment with critical responses obtained from the numerical tools is also conducted. The study shows a very good agreement between the critical configurations of the downburst obtained from the experiment compared to those predicted previously by different numerical studies. In addition, the structural responses obtained from the experiment and those obtained from the numerical tools are in a good agreement where a maximum difference of 16% is found for the mean responses and 25% for the peak responses.

• Wind and Structures
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• v.34 no.2
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• pp.199-213
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• 2022

The current study investigates the dynamic effects in the tornado-structure response of an aeroelastic self-supported lattice transmission tower model tested under laboratory simulated tornado-like vortices. The aeroelastic model is designed for a geometric scale of 1:65 and tested under scaled down tornadoes in the Wind Engineering, Energy and Environment (WindEEE) Research Institute. The simulated tornadoes have a similar length scale of 1:65 compared to the full-scale. An extensive experimental parametric study is conducted by offsetting the stationary tornado center with respect to the aeroelastic model. Such aeroelastic testing of a transmission tower under laboratory tornadoes is not reported in the literature. A multiaxial load cell is mounted underneath the base plate to measure the base shear forces and overturning moments applied to the model in three perpendicular directions. A three-axis accelerometer is mounted at the level of the second cross-arm to measure response accelerations to evaluate the natural frequencies through a free-vibration test. Radial, tangential, and axial velocity components of the tornado wind field are measured using cobra probes. Sensitivity analyses are conducted to assess the variation of the structural dynamic response associated with the location of the tornado relative to the lattice transmission tower. Three different layouts representing the change in the orientation of the tower model relative to the components of the tornado-induced loads are considered. The structural responses of the aeroelastic model in terms of base shear forces, overturning moments, and lateral accelerations are measured. The results are utilized to understand the dynamic response of self-supported transmission towers to the tornado-induced loads.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.1
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• pp.59-63
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• 2022

In recent years, research on smart factory wireless mobile communication technology that wirelessly remotely controls utilities is being actively conducted. The Wi-SUN(Wireless Smart Utility Network) Alliance proposed Wi-SUN protocol structure suitable for building a platform such as a smart factory as a new wireless communication standardization standard based on EEE802.15.4g/e. It analyzes the performance of the IEEE802.15.4e CSL(Coordinated Sampled Listening) Mode MAC(Media Access Control) in terms of power consumption and looks at considerations for efficient operation. Although CSL-MAC can dramatically reduce power consumption at the receiving end in an asynchronous manner, it has been found that the transmitting end has a disadvantage in that power consumption occurs due to an excessive wake-up sequence.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.2
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• pp.65-70
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• 2024

In recent years, research on smart factory wireless mobile communication technology that wirelessly remotely controls utilities is being actively conducted. The Wi-SUN (Wireless Smart Utility Network) Alliance proposed a Wi-SUN protocol structure suitable for building a platform such as a smart factory as a new wireless communication standardization standard based on EEE802.15.4g/e. It analyzes the performance of the IEEE802.15.4e Receiver Initiated Transmission(RIT) Mode Media Access Control (MAC) in terms of throughput and latency, and looks at considerations for efficient operation. RIT mode shows that as the check interval becomes longer, delay time and throughput decrease. It was shown that as the traffic load increases, if the RIT check interval is shortened, the delay time can be shortened and throughput can be increased. RIT mode has the advantage of low power consumption and has neutral characteristics between IEEE802.15.4 and CSL mode in terms of delay time and throughput.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.71-78
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• 2005

The purpose of FMECA is to identify parts and design whose damage can effect the mission performance and to improve the spacecraft design using these data. In consequence of this analysis, each failure mode which can be happened during operation and manufacturing period is identified, and their effects on mission performance are reviewed. In this technical report, the FMECA procedures and results for the satellite which is now under development are showed.