• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.907-915
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• 2002

In this paper, a compact digital phase shifter to be used an active phased array antenna system for satellite communications was proposed. The even and odd mode analysis for a given reflection-type phase shifter, which uses a folded hybrid coupler as a base element, was performed and the design parameters were derived. Also, to verify experimentally the electrical performances of the proposed structure, X-band 4-bit digital phase shifter was designed and fabricated using Teflon soft substrate $({\varepsilon}_r; =\;2.17)$. Its circuit size was less than 3.5 cm $\times$ 3.0 cm, and it exhibited at least 50 % size reduction as compared with the conventional unfolded configuration. The experimental results of the fabricated phase shifter showed that the average insertion loss and insertion loss variation were less than 3.5 dB, $\pm$ 0.6 dB within the operating band, 7.9 ~ 8.4 GHz, respectively. And, input and output return loss were more than 10 dB, respectively. Also, the phase response of the phase shifter showed 4-bit operation with $\pm$3$^{\circ}$ rms phase error.

• Journal of Korean Society of Disaster and Security
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• v.6 no.2
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• pp.15-22
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• 2013

Recently, 'Government 3.0' has become the topic since the inauguration of the new government. According to Government 3.0 Promotion Master Plan, this means providing bilateral customized administrative service based on the values of opening-up, sharing, and cooperation for the individuals of the people. Currently, if disaster victims, who have private property damaged by natural disasters such as typhoon and torrential rain, want to receive disaster relief service supports such as financial support, tax cut, reduction in electric and communication charges, they have to visit each of applicable organizations and apply for the relief service supports. The application forms and procedures are so diverse and complex that disaster victims undergo many discomforts. So this thesis established the solution of residents' discomforts and the providing of practical benefits through disaster victims' one stop application for service as the research objective. Accordingly, the solution plan was concretely presented through preparing the relief service promotion strategies comprising the establishment of administrative service supporting system and the preparation of legal and institutional device, the establishment of computing system for one stop service and the reinforcement of general publicity for successful promotion of cooperation projects.

• The Journal of the Korea Contents Association
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• v.14 no.9
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• pp.589-597
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• 2014

The increasing demand for various mobile telecommunication services calls for more spectrum resource. Considering the scarcity of spectrum resource and the difficulties of development of higher frequency band, the unique way to meet the increasing demand is to maximize the utilization efficiency of the current spectrum resource. Under the circumstances, various spectrum sharing plans have been in recent studies to dissolve the excess spectrum demand. In addition, spectrum efficiency measurement methods become more important to verify the effectiveness of spectrum sharing and estimate the performance of various wireless systems. Our research addresses measurement methods to estimate spectrum utilization efficiency in a rational manner. Based on ITU-R recommendations, various measuring methods for spectrum utilization efficiency are reviewed. Then a queueing based approach is newly presented as alternatives to the current models. By using the proposed model, the spectrum efficiency increment with the adoption of spectrum sharing plans can be estimated more properly.

• KIPS Transactions on Computer and Communication Systems
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• v.3 no.9
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• pp.273-278
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• 2014

Recent use of electricity during peak hours electricity supply-demand imbalance is inevitable that limit power use force. Therefore, in this paper, a circuit of parallel power operation equipment for peak power reduction which saves the power to electricity storage device during the non-peak power time and supply from the storage power during the expected power shortages time is designed Through this circuitry, the peak power of the commercial power supply with the parallel operation and connection of the commercial power supply and the power supply of the inverter from electricity storage that is a key feature of PRS(Peak power Reduction System) can be controlled. In addition, in order to increase the efficiency, a Transless Power Circuit DC-AC inverter is developed. Moreover, a variable impedance control is applied to the storage of electric power of an Uninterruptible Power Supply associated with a commercial power source.

• Journal of the Microelectronics and Packaging Society
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• v.6 no.4
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• pp.61-71
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• 1999

The recent trend toward higher frequencies, miniaturization and lower-cost in wireless communication equipment is demanding high density packaging technologies such flip chip interconnection and multichip module(MCM) as a substitute of conventional plastic package. With analyzing the recently reported research results of the RF flip chip, this paper presents the technical issues and advantages of RF flip chip and suggest the flip chip technologies suitable for the development stage. At first, most of RF flip chips are designed in a coplanar waveguide line instead of microstrip in order to achieve better electrical performance and to avoid the interaction with a substrate. Secondly, eliminating wafer back-side grinding, via formation, and back-side metallization enables the manufacturing cost to be reduced. Finally, the electrical performance of flip chip bonding is much better than that of plastic package and the flip chip interconnection is more suitable for Transmit/Receiver modules at higher frequency. However, the characterization of CPW designed RF flip chip must be thoroughly studied and the Au stud bump bonding shall be suggested at the earlier stage of RF flip chip development.

• Journal of Biomedical Engineering Research
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• v.21 no.4
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• pp.339-344
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• 2000

The mucociliary system is one of the most important airway defense mechanisms in human body and impairment of ciliary movement results in various diseases in respiratory tract. In this study, we have developed a system that can measure ciliary movement in vivo and quantified ciliary beat frequency (CBF) through autoregressive (AR) power spectrum. To measure the frequency in vivo, we applied a photoelectric method that was composed of a laser light and a fiber optic probe. Scattered signals are transferred to a PC in which they are displayed on the monitor and its CBF is determined by the AR method in were acquired. For 8 normal subjects, the analyzed CBFs ranged from 5 to 10Hz and its mean was 7.3${\pm}$1.1Hz. This result showed similar aspects to the reported results of CBFs to data. We expect that this result will be applied in various clinical studies such as analysis of CBF changes by drugs or by diseaes.

• Journal of Practical Engineering Education
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• v.9 no.1
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• pp.7-13
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• 2017

This study will provide a practical plan of engineering education through the study of major activities connected with the production of works to accomplish the graduation conditions by completing the comprehensive design subject and the result of the performance. The designed subject is to measure the minimum safety distance during driving using the obstacle detection function of the ultrasonic sensor and to perform the avoidance algorithm based on the measurement value of the acceleration gyro sensor. It is proposed an access surveillance system that minimizes the damage of drones, surrounding objects, and people, and improves air mobility. Experimental results show that the obstacles around the drone are detected by five ultrasonic sensors and the difference of output value is applied to each motor of the drone and obstacle avoidance is confirmed. In addition, the content and level of the data for measuring the achievement of learning achievement in the engineering education certification program were used and the results were confirmed to be consistent with the description of the engineering problem level required for the graduates of 4-year engineering college.

• Journal of Advanced Navigation Technology
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• v.26 no.2
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• pp.85-90
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• 2022

In this study, in order to test the performance of the aircraft system, a threat signal simulator that can transmit a signal similar to the actual threat to the aircraft under test with high power was designed. The high-power threat signal simulator should be able to transmit broadband (UHF band, L band, S band, X band) communication signals and radar signals, and control to transmit signals accurately directed to the aircraft through interfacing tracking radar. The signal strength of the developed equipment is 63 dBm to 93 dBm or more depending on type of signal, and the tracking precision is less than 0.1 degree, which satisfies the required performance. And it was confirmed that the antenna of the high-power threat signal simulator can accurately direct the signal to the aircraft position through the tracking radar interfacing.

• Journal of the Institute of Convergence Signal Processing
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• v.23 no.1
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• pp.44-49
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• 2022

Abstract Recently, with the development of IoT technology and communication media, various video equipment is being used in industrial fields. Image data acquired from cameras and sensors are easily affected by noise during transmission and reception, and noise removal is essential as it greatly affects system reliability. In this paper, we propose a weight filter algorithm based on the pixel value distribution pattern to preserve details in the process of restoring images damaged in AWGN. The proposed algorithm calculates weights according to the pixel value distribution pattern of the image and restores the image by applying a filtering mask. In order to analyze the noise removal performance of the proposed algorithm, it was simulated using enlarged image and PSNR compared to the existing method. The proposed algorithm preserves important characteristics of the image and shows the performance of efficiently removing noise compared to the existing method.

• Journal of Advanced Navigation Technology
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• v.27 no.3
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• pp.300-305
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• 2023

In this paper, we confirmed that an efficient sensor network can be established at a low cost by applying Geofencing technology to a LoRa-based sensor network and verified its effectiveness in disaster management such as forest fires. We detected changes through GPS, gyro sensors, and combustion detection sensors, and defined the validity size of the Geofencing cell accurately. We proposed a LoRa Payload Frame Structure that has a flexible size according to the size of the sensor information.