• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.11a
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• pp.159-163
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• 2002

So far, many kinds of researches on the chip components and MCM-C RF module especially on the 3-dimensional ceramic module using embedded passives have been performed. LTCC system has many kinds of advantages, like low loss, low cost of process, stability of process etc..The electrical behaviors of components are affected by that of the material systems including dielectrics and conductors. In this study, many kinds of conductor pastes in the variation with metal content and grain size are fabricated and their effect on the characteristics of stripline resonator are examined upto 6 ㎓.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1502-1504
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• 2003

최근 전자기기의 경박단소화 추세는 전자기기의 크기와 가격의 감소를 이끌었으며 이러한 추세는 앞으로 지속될 것이다. 이와 같은 현상으로 전자기기를 구성하는 요소의 절반이상을 차지하는 단위수동소자의 경우 소형화를 넘어 박막화 및 집적화가 절실히 요구되는 실정이다. 따라서 본 연구에서는 현재 GHz 대역의 휴대용 무선통신 송 수신부 등에 사용되고 있는 기판이 $Al_2O_3$ 기판인 점을 고려하여 기판의 공통화를 위해 $Al_2O_3$ 기판 위에 Ta/$Ta_2O_5$/Ta 구조를 갖는 MIM 박막커패시터를 제작하여 그 특성을 고찰하였다. 모든 박막의 증착은 RF-magnetron reactive sputtering법에 의해 이루어졌으며, 유전체 열처리는 $700^{\circ}C$ 진공상태에서 60 sec 동안 수행하였다. XRD 분석결과, as-deposited $Ta_2O_5$ 박막은 열처리 후에 비정질상에서 결정질상으로 변환되었다. Ta/$Ta_2O_5$/Ta/Ti/$Al_2O_3$ 커패시터의 전기적 특성으로는 C-F, C-V, I-V 를 측정하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.2043-2047
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• 2010

This study is to solve problems of depletion of RF bandwidth frequency, confusion possibility, security that current wireless communications system have and is to confirm possibility of applying next generation network. To solve problems of current wireless communications system, visible light communications system for power line communications using ATmega16 Microcontroller is was realized and receiver property was analyzed. PLC exclusive chip APLC-485MA, Microcontroller ATmega16, 5pi bulb type LED and high flux LED, visible light receiving sensor LLS08-A1 were used for transmitter and receiver. Performance was analyzed by designed program and an oscilloscope. It was showed average 20% improved receiver rate rather than bulb type LED in the case of high flux LED through voltage change rate on communication distance and LED type of distance between 10 to 50 cm. The blue LED showed the best performance among measured LED types with above 10% of voltage decreasing rate. But As it gradually becomes more distant, the precise date was difficult to obtain due to weak light. To overcome these sort of problems, specific values such as changing conditions and efficiency value relevant to light emitting parts and visible light receiving sensor should be calculated and continuous study and improvements should also be accomplished for the better communications condition.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07a
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• pp.559-562
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• 2004

The $high-T_c$ Superconducting(HTS) antenna which consists of "H" type resonator has the benefits for the miniaturization of antenna in comparison with the microstrip antenna of the similar dimension. To fabricate the "H" type antenna HTS $YBa_2Cu_3O_{7-x}$(YBCO) thin films were deposited on MgO substrates using rf-magnetron sputtering. Standard etching processes were performed for the patterning of the "H" type antenna. For comparison between normal conducting antennas and superconducting antennas, the gold antennas with the same dimension were also fabricated. An aperture coupling was used for impedance matching between $50\Omega$ feed line and HTS radiating patch. The diverse experimental results were reported in terms of the resonant frequency, the return loss and the characteristics impedance. The "H" type superconducting antenna showed the performance of 1.36 in SWR, 24 % in efficiency, and 14.6 dB in the return loss superior to the normal conducting counterpart.

• Journal of Advanced Navigation Technology
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• v.8 no.2
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• pp.91-97
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• 2004

This paper presents the development of InGaAsP multiple quantum well asymmetric Fabry-Perot modulators(AFPM), which have a vertical structure and high performance and describes measurements of devices operating at 10GHz for next generation broadband wireless communication applications such as picocell systems. Advantages of the AFPM include low drive voltage, which is less than -2V, and -3dB coupling loss, good flatness of the frequency response and simple fiber alignment. A simple link demonstration has been introduced, resulting in 92dB/Hz spurious free dynamic range and 40dB inter-modulation distortion. This modulator could be use for broadband radio over fiber systems such as picocell and multiple RF links.

• International Journal of Computer Science & Network Security
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• v.21 no.9
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• pp.212-222
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• 2021

Multiple waves of COVID-19 highlighted one crucial aspect of this pandemic worldwide that factors affecting the spread of COVID-19 infection are evolving based on various regional and local practices and events. The introduction of vaccines since early 2021 is expected to significantly control and reduce the cases. However, virus mutations and its new variant has challenged these expectations. Several countries, which contained the COVID-19 pandemic successfully in the first wave, failed to repeat the same in the second and third waves. This work focuses on COVID-19 pandemic control and management in Saudi Arabia. This work aims to predict new cases using deep learning using various important factors. The proposed method is called Deep Learning and Dynamic Weighing-based (DLDW) COVID-19 cases prediction method. Special consideration has been given to the evolving factors that are responsible for recent surges in the pandemic. For this purpose, two weights are assigned to data instance which are based on feature importance and dynamic weight-based time. Older data is given fewer weights and vice-versa. Feature selection identifies the factors affecting the rate of new cases evolved over the period. The DLDW method produced 80.39% prediction accuracy, 6.54%, 9.15%, and 7.19% higher than the three other classifiers, Deep learning (DL), Random Forest (RF), and Gradient Boosting Machine (GBM). Further in Saudi Arabia, our study implicitly concluded that lockdowns, vaccination, and self-aware restricted mobility of residents are effective tools in controlling and managing the COVID-19 pandemic.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.18 no.2
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• pp.117-128
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• 2008

Compared with the existing bar code system, RFID system has lots of advantages such as it identifies automatically massive objects. We might anticipate RFID technology will be a substitution for an optical bar code system in the near future. However, their feature that uses radio waves may cause various security problems. Many kinds of solutions have been researched to overcome these security problems. In this paper, we analyze the previous proposed protocols. And then, we categorize RFID authentication into two types according to the synchronization requirement between a Back-end Database and a Tag. In addition, we introduce the previous proposed approaches to tag search problem in RFID authentication. And we propose an efficient method which provides fast tag search by using membership test algorithm, a Bloom filter.

• International Journal of Computer Science & Network Security
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• v.23 no.2
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• pp.13-30
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• 2023

Since the COVID-19 vaccine became available, people have been sharing their opinions on social media about getting vaccinated, causing discussions of the vaccine to trend on Twitter alongside certain events, making the website a rich data source. This paper explores people's perceptions regarding the COVID-19 vaccine during certain events and how these events influenced public opinion about the vaccine. The data consisted of tweets sent during seven important events that were gathered within 14 days of the first announcement of each event. These data represent people's reactions to these events without including irrelevant tweets. The study targeted tweets sent in Arabic from users located in Saudi Arabia. The data were classified as positive, negative, or neutral in tone. Four classifiers were used-support vector machine (SVM), naïve Bayes (NB), logistic regression (LOGR), and random forest (RF)-in addition to a deep learning model using BiLSTM. The results showed that the SVM achieved the highest accuracy, at 91%. Overall perceptions about the COVID-19 vaccine were 54% negative, 36% neutral, and 10% positive.

• ETRI Journal
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• v.45 no.1
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• pp.105-118
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• 2023

We tested the feasibility of automated discrimination of patients with panic disorder (PD) from healthy controls (HCs) based on multimodal physiological responses using machine learning. Electrocardiogram (ECG), electrodermal activity (EDA), respiration (RESP), and peripheral temperature (PT) of the participants were measured during three experimental phases: rest, stress, and recovery. Eleven physiological features were extracted from each phase and used as input data. Logistic regression (LoR), k-nearest neighbor (KNN), support vector machine (SVM), random forest (RF), and multilayer perceptron (MLP) algorithms were implemented with nested cross-validation. Linear regression analysis showed that ECG and PT features obtained in the stress and recovery phases were significant predictors of PD. We achieved the highest accuracy (75.61%) with MLP using all 33 features. With the exception of MLP, applying the significant predictors led to a higher accuracy than using 24 ECG features. These results suggest that combining multimodal physiological signals measured during various states of autonomic arousal has the potential to differentiate patients with PD from HCs.

• Proceedings of the Korea Information Processing Society Conference
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• 2021.11a
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• pp.185-188
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• 2021

본 논문에서는 기술의 빠른 발전에도 불구하고 줄어들지 않는 화재 사고, 그 중에서도 많은 인명피해를 내는 실내 화재 사고에 대하여 기존 실내 화재 알림 시스템의 한계점인 알림의 양치기 소년화로 인한 안전 불감증 증가와 알림의 사각지대 문제를 해결하고자 새로운 대안 시스템을 설계 및 구현하고, 실험 검증을 진행하였다. 위 두 가지 문제점을 해결하기 위해, 본 연구에서는 스마트폰이 매우 대중적으로 보급되어 있다는 점을 기반으로 IoT, 엣지 컴퓨팅, 비콘 등을 응용한다. 비콘 신호를 broadcasting 하는 엣지 노드의 신호 범위 내에 진입하면 사용자 정보를 수집하여 대상 건물에 출입한 대상을 특정한다. 말단 센서 노드와 엣지 노드 간의 무선 RF 통신으로 화재를 모니터링하며 화재가 발생했을 시 특정된 대상들에게만 스마트폰 어플의 푸시 알림으로 화재 발생 상황을 전송하는 시스템을 설계 및 구현하였다. 시스템 성능 평가를 위해 동국대학교 건물 내에서 수평, 수직으로 이동하며 실험을 진행하였고, 그 결과를 통해 대안 시스템의 성능과 한계를 분석하여 이를 실내 공간에 적용하기 위한 적합성을 평가하였다.