• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.195-195
• /
• 2010

In recent years, Anodic aluminum oxide(AAO) has become popular and attractive materials. It can be easily fabricated and self-organized pore structures. It has been widely used as a biosensor membrane, photonic crystal for optical circuit and template for nanotube growth etc. In previous papers, the theory was developed that AAO shows anisotropic optical properties, since it has anisotropic structure with numerous cylindrical pores. It gives rise to the anisotropy of the refractive index called as birefringence. It can be used as conventional polarizing elements with high efficiency and low cost. Therefore, we would like to compare the theory and experimental results in this study. One method which can measure effective refractive index of thin film is the prism coupling technique. It can give accurate results fast and simply. Furthermore, we can also measure separately the refractive index with different polarization using polarization of the laser (TE mode and TM mode). We calculated the effective refractive index with effective medium approximations (EMAs) by pore size in the SEM image. EMAs are physical models that describe the macroscopic system as the homogeneous and typical method of all mean field theories.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2009.05a
• /
• pp.336-339
• /
• 2009

In this paper, such as battery power or solar energy and fuel cells generated from Renewable energy sources, high voltage to low voltage DC-DC Converter for converting the design of the study. System consists of low voltage ($24{\sim}28$ [VDC]) and Boosts the voltage (270 [VDC]) for a 3 [kW] DC-DC converter and control circuit is configured as, Power switch the ST Tomson's Automotive low voltage high current MOSFET switches STE250NS10S (temperature 250A) was applied to the two parallel. Also, Controller's processor used ATMEGA128, and Gate Drive applies and composed Photo Coupler TLP250. development. Input voltage (24V) and output voltage (270V) for Conversion in the H-bridge converter topology of the circuit output side power and voltage to control the implementation of the Phase shift angle control applied. And, 3kW of power to pass appropriate specification of the secondary side as interpreted by the high frequency transformer, and the experimental production and analysis of the experiment

• Korean Journal of Optics and Photonics
• /
• v.14 no.6
• /
• pp.578-582
• /
• 2003

We propose a novel structure of wavelength selective optical add/drop module comprising two tap couplers and a fiber Bragg grating. The device has unique features including a simpler structure and a lower cost of implementation as compared with existing devices for the same operation. The module performance has been measured and analyzed experimentally. The implemented prototype module shows good performance with no-crosstalk power penalty in a 155 Mbps per channel wavelength-division-multiplexing transmission system but suffers from a relatively high loss of 3.5 ㏈ and 21 ㏈ for transmitted and dropped channels, respectively. While the dropped channel extinction ratio was more than 25 ㏈, the transmitted channel extinction ratio was more than 35 ㏈.

• Journal of Information Technology Services
• /
• v.19 no.6
• /
• pp.31-53
• /
• 2020

The traditional media ecosystem is facing major changes with the expansion of over-the-top (OTT) services. While the percentage of people cutting the cord has already exceeded the percentage of people subscribing to pay TV services in the United States, due to the unique characteristics of the Korean market, it is uncertain whether the cord-cutting trend will have an impact on the Korean media industry despite of the advantages of OTT services. Accordingly, this study has directly determined the beneficial and sacrificial factors of switching to OTT services, as well as the personal and external influences behind the Korean OTT service users' intention to switch. To achieve this, the Value-based Adoption Model (VAM) was used to measure the benefits of OTT services with regards to their content and systems, as well as measure the financial and procedural switching costs of cord-cutting; further, personal innovativeness and consumers' social image were added as external variables. The results of this study showed that consumers take the content and system quality of OTT services and procedural switching costs and into consideration, and that their intention to switch was based on social image. These results could serve as data for consumer analysis regarding the expansion of OTT services into the Korean media industry, and also provide the strategic basis for preparing for sudden changes that may occur in the media ecosystem due to cord-cutting.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.6
• /
• pp.1092-1098
• /
• 2007

Since one decade, the detection of HFPD (High frequency Partial Discharge) has been proposed as one of the effective method for the diagnosis of the power component under service in power grids. As a tool for HFPD detection, Metal Foil sensor based on the embedded technology has been commercialized for mainly power cable due to its advantages. Recently, for the on-site noise discrimination, several PA (Pulse analysis) methods have been reported and the related software, such as Neural Network and Fuzzy, have been proposed to separate the PD (Partial Discharge) signals from the noises since their wave shapes are completely different from each other. On the other hand, the relevant fundamental investigation has not yet clearly made while it is reported that the effectiveness of the current methods based on PA is dependant on the types of sensors. Moreover, regarding the identification of the vital defects introducible into the Power Cable, the direct identification of the nature of defects from the PD signals through Metal Foil coupler has not yet been realized. As a trial for solving above shortcomings, different types of software have been proposed and employed without any convincing probability of identification. In this regards, our novel algorithm 'PA Map' based on the pulse analysis is suggested to identify directly the defects inside the power cable from the HFPD signals which is output of the HFCT and metal foil sensors. This method enables to discriminate the noise and then to make the data analysis related to the PD signals. For the purpose, the HFPD detection and PA (Pulse Analysis) system have been developed and then the effect of noise discrimination has been investigated by use of the artificial defects using real scale mockup. Throughout these works, our system is proved to be capable of separating the small void discharges among the very large noises such as big air corona and ground floating discharges at the on-site as well as of identifying the concerned defects.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.2 no.3
• /
• pp.132-138
• /
• 2010

In the present study, the real-time monitoring system is developed based on the wireless sensor network (WSN) and power line communication (PLC) employed in the 3,000-ton-class training ship. The WSN consists of sensor nodes, router, gateway and middleware. The PLC is composed of power lines, modems, Ethernet gateway and phase-coupler. The basic tests show that the ship has rather good environments for the wired and wireless communications. The developed real-time monitoring system is applied to recognize the thermal environments of main-engine room and one cabin in the ship. The main-engine room has lots of heat sources and needs careful monitoring to satisfy safe operation condition or detect any human errors beforehand. The monitoring is performed in two regions near the turbocharger and cascade tank, considered as heat sources. The cabin on the second deck is selected to monitor the thermal environments because it is close to the heat source of main engine. The monitoring results of the cabin show the thermal environment is varied by the human activity. The real-time monitoring for the thermal environment would be useful for the planning of the ventilation strategy based on the traces of the human activity against inconvenient thermal environments as well as the recognizing the temperature itself in each cabin.

• Korean Journal of Optics and Photonics
• /
• v.8 no.2
• /
• pp.169-173
• /
• 1997

Most conventional lithography systems have been oriented to fabricate electronic devices. Therefore, it is not so easy to fabricate large aspect ratios of waveguide patterns with those systems. When considering costs and efficiencies, a laser lithography system provides number of benefit in realizing waveguide patterns. However, because the conventional laser lithography system could make only positive tone masks, it is inconvenient in determining the direction of the waveguide. A simple and reliable technique to produce negative tone masks was developed by using the laser beam writing. This technique was not sensitive to environmental situations such as dust, vibration, intensity variation. Making use of the technique a variety of device patterns such as Y-branch, directional coupler, and highly smooth S-shape bend could be successfully fabricated with a good contrast.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2004.05b
• /
• pp.804-806
• /
• 2004

As a noninvasive imaging meathod, optical coherence tomography system has been extensively studied because it has some advantage such as imaging of high resolution, low cost, and compace size configuration. The optical power of the sample signal reflected from an object is usually very small in optical coherence tomography(OCT) due to absorption and scattering in a sample material. Furthermore, there happens a serious loss of sample signal power in a fiber coupler because it does not transfer to a photodetector but return to the optical source. In order to improve the SNR of OCT system, basic Michelson and Mach-Zehnder interferometer types were configured then, we compared simulation with measurement of reference sample Therefore, an On in configuration of Math-Zehnder interferometer was demonstrated in order to improve the signal to noise ratio

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.9A
• /
• pp.867-875
• /
• 2005

In this paper, we fabricated along distance wireless communication transmitter and receiver over the 100 which used NRD technology. To make the transmitter and receiver of 400Hz band using the non radiative dielectric wave guide, transmitter was composed of gm oscillator, m modulator and antenna, receiver was composed of local gum oscillator, balanced mixer, 3dB direction coupler and antenna. Also we executed a wireless communication image transmission examination to the transmitter and receiver. We receive the image information in real-time data transmission from receiver after we send the image signal in the wireless distance of the 10km. Therefore, the 400Hz band U transmitter and receiver to be developed will be used widely for the transmission system CATV or broadband transmission system. This will be utilized also to the link device of a long distance high speed wireless communication network.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.26 no.11C
• /
• pp.64-74
• /
• 2001

In this paper, a dynamic minislot reservation protocol(DMRP) is proposed and analyzed to improve the performance of the multicast traffic processing in wavelength division multiplexing(WDM) networks. For the proposed protocol analysis, the WDM network architecture with a passive star coupler is used. One pair of transceiver is used for a control channel and the ocher pair of transceiver with one fixed transmitter and one tunable receiver are used for data transmission. In this protocol. the packets which fail to have successful transmission in the present time slot due to data channel and destination collisions, have priority to have successful reservation in the contention-less minislots of the next time slot. Therefore, protocols have improved the throughput and the system delay performance caused by the reduced probabilities of control channel contentions and destination collisions probability. Today, the efficient protocol that can handle the various types of data traffic is needed. As results, the DMRP is useful to improve the performance of throughput and system delay characteristics regardless of the kinds of traffic.