• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.8 no.6
• /
• pp.73-81
• /
• 2009

Wireless media communication has lower robustness and stability than wired communication because of narrow bandwidth and unstable channel state. To make up for the deficient points of wireless communication, we used the diversity effect of cooperation communication and the error correction effect of channel coding schemes. In this paper, the cooperative communication system with RCPC codes and Hybrid ARQ transmission scheme is proposed for improving reliability on wireless communication, and we executed these simulations. From the simulation results, proposed system is showed lower BER performance than legacy system. In addition, we confirm the fact that the channel state of Relay-node and source-node is more important than the channel state of Relay-node and destination-node.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.3C
• /
• pp.243-250
• /
• 2009

In this paper, a closed-form expression of the ergodic channel capacity for a narrow-band time-reversal communication scheme is analytically formulated. In the time-reversal communication scenario, a transmitter sends a signal and a so-called time-reversal array receives the signal. Then, the received signal is reversed in the time do main and resent to the original transmitter. Here, one transmitter and an antenna array for the time-reversal array are assumed. Since the spacing between the array elements is large, the signals received by each antenna element can be considered independent. For simplicity, the communication channel is assumed stationary, whose properties are not changed for the time-reversal process. Based on the obtained formulation, the channel capacities for the time-reversal and the conventional channels are compared.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.02a
• /
• pp.319-319
• /
• 2012

현재 폭넓게 이용되고 있는 STI (Shallow Trench Isolation) 공정에서 active edge 부분에 발생하는 기생 transistor의 subthreshold hump 특성을 제어하는 연구가 활발히 이루어지고 있다. 일반적으로 STI 공정을 이용하는 MOSFET에서 active edge 부분의 얇게 형성된 gate oxide, sharp한 active edge 형성, STI gap-fill 공정 중에 생기는 channel dopant out-diffusion은 subthreshold hump 특성의 주된 요인이다. 이와 같은 문제점을 해결하기 위해 active edge rounding process와 channel dopant compensation의 implantation을 이용하여 subthresold hump 특성 개선을 연구하였다. 본 연구는 STI 공정에 필요한 wafer와 phosphorus를 함유한 wafer를 한 chamber 안에서 auto-doping하는 방법을 이용하여 subthresold hump 특성을 구현하였다. phosphorus를 함유한 wafer에서 빠져나온 phosphorus가 STI 공정중인 wafer로 침투하여, active edge 부분의 channel dopant인 boron 농도를 상대적으로 낮춰 active edge 부분의 가 감소하고 leakage current를 증가시킨다. transistor의 channel length, gate width이고, wafer#No가 클수록 phosphorous를 함유한 wafer까지의 거리는 가까워진다. wafer #01은 hump 특성이 없고, wafer#20은 에서 심한 subthreshold hump 특성을 보였다. channel length 고정, gate width를 ~으로 가변하여 width에 따른 영향을 실험하였다. active 부분에 대한 SCM image로 확인된 phosphorus에 의한 active edge 부분의 boron 농도 감소와 gate width vs curve에서 확인된 phosphorus에 의한 감소가 narrow width로 갈수록 커짐을 확인하였다.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.12 no.2
• /
• pp.309-314
• /
• 2008

Analog-to-digital converters(ADCs) used in instrumentation and measurements often require high absolute accuracy, including excellent linearity and negligible dc offset. Incremental(integrating) data converters(IDCs) provide a solution for such measurement applications, as they retain most of the advantages of conventional $\Delta{\Sigma}$ converters, and yet they are capable of offset-free and accurate conversion. In this paper, a design technique for implementing multiplexed incremental data converters to convert narrow bandwidth AC signals over multi-channel is discussed. It incorporates the operation principle, topology, and digital decimation filter design. The theoretical results are verified by simulation results.

• The Journal of Korea Robotics Society
• /
• v.16 no.4
• /
• pp.291-298
• /
• 2021

In this study, we present a multi-sensor module for snake robot searching survivors in a narrow space. To this end, we integrated five sensor systems by considering the opinions of the first responders: a gas sensor to detect CO₂ gases from the exhalation of survivors, a CMOS camera to provide the image of survivors, an IR camera to see in the dark & smoky environment, two microphones to detect the voice of survivors, and an IMU to recognize the approximate location and direction of the robot and survivors. Furthermore, we integrated a speaker into the sensor module system to provide a communication channel between the first responders and survivors. To integrated all these mechatronics systems in a small, compact snake head, we optimized the positions of the sensors and designed a stacked structure for the whole system. We also developed a user-friendly GUI to show the information from the proposed sensor systems visually. Experimental results verified the searching function of the proposed sensor module system.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.12 no.4
• /
• pp.473-481
• /
• 2012

For a mesa-isolated small geometry SOI MOSFET, the potentials in the silicon film, front, back, and side-wall oxide layers can be derived three-dimensionally. Using Taylor's series expansions of the trigonometric functions, the derived potentials are written in terms of the natural length that can be determined by using the derived formula. From the derived 3-D potentials, the minimum values of the front and the back surface potentials are derived and used to obtain the closed-form expressions for the front and back gate threshold voltages as functions of various device parameters and applied bias voltages. Obtained results can be found to explain the drain-induced threshold voltage roll-off and the narrow width effect of a fully depleted small geometry SOI MOSFET in a unified manner.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.2
• /
• pp.297-306
• /
• 2022

AtoN is an acronym for aids to navigation that indicate the position or direction of navigable areas and obstructions. AtoN should be arranged in consideration of unfamiliar navigator's convenience when it is indicated as the limits of navigable areas. Several narrow channels exist on the SW coast of Korea owing to the geographical effect, and the lateral or cardinal marks by the IALA maritime buoyage system are arranged along the narrow channels. This is an actual case study that analyzed the AtoN's role for safety navigation after changes in the maritime traffic environment owing to aquarfarm's development on narrow channels in the Korean SW coast. The analysis results of 5 narrow channels indicated that certain marks did not function properly as lateral or cardinal marks owing to the aquarfarm's location on navigable areas. Therefore, the following were suggested to improve AtoN on narrow channels: changing the position of marks, installing aquafarm's marks, and expressing the aquafarm's position on the nautical chart.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.12 no.2
• /
• pp.91-100
• /
• 2004

Plate heat exchangers (PHE) have been widely used in different industrial applications, because of high heat transfer efficiency per unit volume. Basic study is performed for PHE to the application of intercooler in automobile. In order to understand the flow phenomena in the plate heat exchanger, a channel which was formed by the upper and lower plate in single plate was considered as calculation domains. Because chevrons attached on the upper plate are brazed with chevrons attached on the lower plate, the flow channel has very complex configuration. This complex geometry was analyzed by Fluent. In order to validate this methodology the proper experimental and theoretical data are collected and compared with numerical results. Finally, due to the lack of experimental values for PHE to the application of intercooler, various chevron angles and air velocities at inlet were tested in terms of physical phenomena. From this point of view, results of velocity vector, path lines, static pressure, heat flux, heat transfer coefficient, and Nusselt number are physically reasonable and accepted for the solutions. From these results, the correlations for pressure drop and Nusselt number with respect to chevron angle and Reynolds number in specific PHE are obtained for the design purpose. Thus, the methodology of the flow analysis in the full geometry of the channel was established for the predictions of performance in plate heat exchanger.

• Journal of electromagnetic engineering and science
• /
• v.4 no.4
• /
• pp.183-189
• /
• 2004

In this paper, the Eigen-RAKE receiver in wideband direct sequence code-division multiple access(DS-CDMA) systems with downlink smart antenna is analyzed for different spreading bandwidths(1.25 MHz, 5 MHz, 10 MHz) and different channel environments(macro, micro). The realistic spatio-temporal wideband multipath channel is assumed, one of which is standardized multiple-input single-output(MISO) radio channel model for WCDMA link-level simulations proposed by $3^{rd}$ generation partnership project(3GPP) contributions. We assumed spatial scattering phenomenon in which many unresolvable path signals within a limited range of spatial angle simultaneously contribute to the signals received at the receiver. Several multipaths within one chip are distinguished into each one and the first multipath components are selected as the desired signal and the others are considered self-interference. Downlink DS-CDMA system with eigenbeamformer using wider bandwidth present better performance than that using narrow bandwidth system by employing Eigen-RAKE receiver of many number of branches. It is shown that the downlink eigenbeamformer is more effective in typical urban macro cellular environments when using Eigen-RAKE receiver.

• Journal of Navigation and Port Research
• /
• v.29 no.3 s.99
• /
• pp.181-187
• /
• 2005

In order to reduce the management risks of and secure traffic safety of Aqua-bus which will be operated at the channel of Wolmi do and Yungjong-do for the first time in Korea, we investigate maritime traffic and natural environment around the channel, and analyze the factors of risk involved in her operation. We also propose the countermeasure to secure the safety of navigation in her service including precautionary area, exclusive terminal, operation management, and etc.