• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2006.03a
• /
• pp.432-439
• /
• 2006

Long span, high-rise bridges are rapidly increasing nowadays. Because of high flexibility, such bridges are easily excited by winds, vehicles, and pedestrians. The vibration of bridge induces a vibration of lamp post and pillar. Wind loads can also excite lamp posts and traffic signal structures directly. Because of low damping, such vibrations of lamp post are frequently amplified and come to collapse or lamp failure. In addition, such vibration makes the maintenance cycle shorter and increases social cost. We conducted vibration tests and identified the dynamic characteristics of two types lamp posts, and proposed tuned mass dampers to control the vibrations. Established models of the lamp posts present the dynamic characteristics of the structures very well and they are used to design TMDs. In this study, we suggested a new-type TMD model that is small, simple, economic and effective to suppress the vibration of lamp posts. The efficiency of TMD was examined by numerically and is to be examined experimentally.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2003.11a
• /
• pp.252-256
• /
• 2003

Tuned Mass Damper(TMD) has been applied in various fields in order to mitigate these vibrations. The shape or configuration of TMDs being unrestricted, a large panel of designs is possible to improve their effectiveness and economical-efficiency, where ingenuity plays an essential role and is required. This study presents an application of a new-type TMD on lamp posts to reduce vibrations induced by loads with large frequency domains such as wind loads. It is shown that the proposed TMD absorbs efficiently the energy without being restricted by frequency contents of the vibration.

• Journal of the Optical Society of Korea
• /
• v.18 no.6
• /
• pp.663-671
• /
• 2014

LED lamp arrangement is a critical issue in indoor visible light communication (VLC) system. In this paper, we analyze the illumination distribution under the arrangement of $2{\times}3$ and propose a method to find the optimal lamp arrangement. The method, based on the MIMO (Multiple Input/Multiple Output) system model and taking the first order reflection into consideration, enables accurate analysis of the arrangement of the LED lamps for any room. The studies show that under the optimal arrangement the uniformity of illumination is improved from 0.55 to 0.86, which guarantees that users can get almost equal lighting effects, no matter where they locate themselves. At the same time, the RMS delay spread distribution which is used to evaluate the inter-signal-interference (ISI) is analyzed, and the simulation results indicate that the optimal arrangement also can improve the communication quality by reducing the fluctuation of the RMS delay spread.

• Journal of the Korea Society of Computer and Information
• /
• v.24 no.1
• /
• pp.129-135
• /
• 2019

This paper is part of research and development for stand-alone solar system without commercial power supply. It implements firmware of controller for operation of stand-alone solar system by applying IoT technology and also develops communication modules that allow multiple solar lamps to send and receive data through wireless network. The controller of the developed stand-alone solar system can effectively charge the power generated by the solar module, taking into account the battery's charge and discharge characteristics. It also has the advantage of attaching wireless communication modules to solar lamp posts to establish wireless communication networks without incurring communication costs. In addition, by establishing IoT gateway middleware platform for each installation site, it forms a foundation to operate multiple solar lamp posts into multiple clusters. And, it is expected that the data collected in each cluster will be used to enable configuration and control of operational information, thereby inducing convenience and efficiency of remote operation and management.

• Journal of the Optical Society of Korea
• /
• v.19 no.4
• /
• pp.351-356
• /
• 2015

Visible light communication (VLC) is considered to be an attractive scheme to realize the broadband wireless communication for an indoor environment. We present a room division multiplexing (RDM) mechanism for an indoor multi-room VLC network, which utilizes the spatial position of the LED lamp in different rooms as a novel dimension of network resource for multiplexing, and thus the network capacity is increased. In such a network, the service interruption caused by user cross-room movement is an important problem, and we propose a double-area-positioning based cross-room switch solution. An experimental platform demonstrates the RDM-deployed VLC network, and validates the performance of the presented switch mechanism.

• Wind and Structures
• /
• v.4 no.2
• /
• pp.163-176
• /
• 2001

Two 12 m high tubular steel lighting columns have been instrumented to determine the wind-induced fatigue loading experienced by such columns. Each column supported a single luminaire mounted on a 0.5 m long bracket. One column was planted in soil, and the other bolted through a welded baseplate to a substantial concrete base. The columns were strain gauged just above the shoulder weld which connected the main shaft to the larger base tube. Forced vibration tests were undertaken to determine the natural frequencies and damping of the columns. Extensive recordings were made of response to winds with speeds from 4 m/s to 17 m/s. Selected records were analysed to obtain stress cycle counts and fatigue lives. Mean drag coefficients were also derived from the strain data to investigate experimentally the effect of Reynolds Number.