• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38B no.11
• /
• pp.924-933
• /
• 2013

In this paper, we propose a modeling of the broadcasting in the IEEE 802.11p MAC protocol for the VANET(Vehicular Ad hoc Networks). Due to the fact that the beacon message which is needed for the safety services is shared via broadcasting, the analytical modeling of the broadcasting is crucial for the optimum design of the services. Two characteristics specific to the IEEE 802.11p are reflected in the modeling; the time limited CCH interval caused by the channel switching between the CCH and SCH, and no retransmission of the broadcasted messages. In the proposal, we assumed no restriction on the moment of generation of the beacon messages. We allow the messages to be generated and broadcasted within the whole CCH interval. Simulation results prove the accuracy of the proposed modeling. Noticeable improvements are also observed in terms of the performance indices such as the successful delivery ratio, transmission delay, and the variation of the delay.

• The Journal of the Acoustical Society of Korea
• /
• v.34 no.5
• /
• pp.394-402
• /
• 2015

CMA (Constant Modulus Algorithm) is one of the well-known algorithms in blind acoustic channel equalization. Generally, CMA converges slowly and the speed of convergence is dependent on a step-size in the CMA procedure. Many researches have tried to speed up the convergence speed by applying a variable step-size to CMA, e.g. the orthogonal projection CMA and algebraic optimal step-size CMA. In this paper, we summarize these two algorithms, and we propose a new CMA with improved convergence performance. The improvement comes from the switching between the orthogonal projection CMA and algebraic optimal step-size CMA. In simulation results, we show the performance improvement in the time invariant channels as well as in time varying channel.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.18 no.11
• /
• pp.1299-1308
• /
• 2007

In this paper, we propose the calibration method of monopulse slope to minimize the variation of angle estimate in frequency agile noncoherent monopulse system. We analyze the monopulse slope characteristics of antenna and RF receiver including the phase and gain imbalances of each receiving channel and present the calibration method to minimize the phase and gain imbalances of RF receiver channels including antenna. In addition, we present the calibration method using channel switching to minimize the gain imbalance of IF receiver channels. The measured average monopulse slope within the frequency bandwidth is -0.96, the maximum variation of angle estimate is similar to theoretical value, $0.15^{\circ}$ at ${\pm}2^{\circ}$ azimuth and $0.03^{\circ}$ at $0^{\circ}$ azimuth.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08b
• /
• pp.1281-1283
• /
• 2007

In this paper, the properties of n-channel poly-Si TFTs with different channel widths are reported. Poly-Si fabricated using ELA on glass substrates has high quality as a material for applications such as TFT-LCDs. The fabricated n-channel TFTs have a double stack structure of oxide-nitride which acts as an insulator layer. The results show that the small channel TFTs exhibited a lower $V_{TH}$ and the wide channel TFTs had a higher $I_{DSAT}$. The nchannel poly-Si TFTs with an $I_{ON}/I_{OFF}$ value of more than $10^4$ can be reliable switching devices for AMOLED displays.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.29 no.6
• /
• pp.327-331
• /
• 2016

Resistive random access memory (ReRAM) of metallic conduction channel mechanism is based on the electrochemical control of metal in solid electrolyte thin film. Amorphous chalcogenide materials have the solid electrolyte characteristic and optical reactivity at the same time. The optical reactivity has been used to improve the memory switching characteristics of the amorphous $As_2Se_3$-based ReRAM. This study focuses on the formation of holographic lattices patterns in the amorphous $As_2Se_3$ thin film for straight conductive channel. The optical parameters of amorphous $As_2Se_3$ thin film which is a refractive index and extinction coefficient was taken by n&k thin film analyzer. He-Cd laser (wavelength: 325 nm) was selected based on these basic optical parameters. The straighten conduction channel was formed by holographic lithography method using He-Cd laser.$ Ag^+$ ions that photo-diffused periodically by holographic lithography method will be the role of straight channel patterns. The fabricated ReRAM operated more less voltage and indicated better reliability.

• Journal of Environmental Impact Assessment
• /
• v.18 no.3
• /
• pp.171-183
• /
• 2009

This study aims to analyze the sedimentary environment change in mid-channel bar of the lower Geum river basin after the construction of the estuary barrage using multi-temporal satellite data and GIS. The sedimentary environment changes were observed in mid-channel bar areas. The mid-channel bar F was found to have been newly formed for 10 years(1996-2006), whereas the mid-channel bar B located between mid-channel bar A and C has disappeared by erosion during the same periods. When examined by section, the areas of the mid-channel bar in the upper stream section from the Yipo's reference point generally increased due to the prevailing sedimentary environments, and those of the downstream section decreased where corrosive environments are dominant. In ternms of the centroid movement, the mid-channel bars grew up toward the downstream by switching erosion and accumulation, as sedimentation was prevailing in the downstream area of mid-channel bars and corrosion was dominant in the upper stream. Through grain size analysis, the study areas are divided into three sections according to the average grain size. In Section I, the mid-channel bars were formed as a result of sedimentary process of tides in the past. In Section II, the mid-channel bars were formed partly through the sedimentary process of rivers although the sedimentary process of tides is prevailing. In Section III, the mid-channel bars were formed mainly through the sedimentary process of rivers, even if it showed the sedimentary process of tides in the past.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.13 no.5
• /
• pp.239-247
• /
• 2013

In network based on multi-interface, there are needed channel assignment strategy that reduce interference and improve bandwidth efficiency by assigning each interface to available channels in order to utilize effectively multiple wireless interfaces on each node. MCS protocol had been proposed, which improve capacity and throughput of network by using hybrid assignment. MCS uses as the criterion to assign channel the number of node that use the same channel in contention area. but there have an problem that this information exactly does not reflect actually offered channel load. in this paper, we proposes CAMCS protocol to assign channel by that the channel busy degree to indicate the occupancy rate of channel by nodes as well as the number of nodes that use the same channel in inference area is used as criterion for estimation channel load, and conform performance improvement effect by simulation.

• Journal of Biomedical Engineering Research
• /
• v.32 no.3
• /
• pp.207-217
• /
• 2011

Electrode impedances are measured to quantitatively characterize the electrode-electrolyte or cell-electrode interfaces. In the case of high-density microelectrode arrays(MEAs) that have been developed for brainmachine interface applications, the characterization process becomes a repeating and time-consuming task; a system that can perform the measurement and analysis in an automated fashion with accuracy and speed is required. However, due to the large number of channels, parasitic capacitance and off-capacitance components of the switching system become the major factors that decreased the accuracy for the measurement of high impedance microelectrodes. Here we investigated the implementation of automatic impedance measurement system with analyzing the causes of possible measurement-related problems in multichannel switching configuration. Based on our multi-channel measurement circuit model, we suggest solutions to the problems and introduce a novel impedance measurement scheme using electro-mechanical relays. The implemented measurement system could measure |Z| < 700 $k{\Omega}$ of impedance in - 10% errors, which can be widely applicable to high density neural recording MEAs.

• Journal of Fashion Business
• /
• v.26 no.3
• /
• pp.1-18
• /
• 2022

The COVID-19 pandemic has not only increased customer preference for contactless methods but also created digital business opportunities in a variety of industries. Particularly in the fashion industry, contactless distribution and contactless shopping have increased significantly. This study identifies the changed consumers' perception of contactless shopping, which has been expanded due to the COVID-19 pandemic and analyzes specific factors that influence shopping switching intention to derive efficient marketing plans for post COVID-19 era. The study targeted Korean male and female consumers. The perceived value, usefulness, and alternative attractiveness of contactless shopping had a significant effect on shopping switching intention, and a moderating effect of offline fashion stores was confirmed. These results indicate that customers' experience in a fashion store influences their next online and offline shoping. This study, therefore, proposed the direction that the fashion industry should advance from a marketing perspective in the post COVID-19 era.

• Journal of IKEEE
• /
• v.22 no.2
• /
• pp.499-505
• /
• 2018

Since feedback field-effect transistors (FBFETs) have ideal switching characteristics resulting from feedback phenomenon caused by electrons and holes in the channel region, the researches about FBFET devices have been proposed and demonstrated worldwide recently. The device operated with novel principle can operate as a switching electronic device. Besides, because the hysteresis characteristics of the device by accumulated electrons and holes in channel region can be also utilized for memory applications, its application range is wide. In this paper, we cover various device structures of FBFET proposed until now and their operation mechanism, and then look into their applicable fields.