• The Journal of Engineering Geology
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• v.23 no.4
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• pp.435-445
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• 2013

Since design response spectrum does not reflect local soil characteristics, site specific response spectrum of observed ground motions appears relatively higher than design response spectrum at high frequency range. These problems have been pointed out from the domestic seismic design industry. Among various estimation methods, this study used the method H/V ratio of ground motion for estimating site amplification. This method has been extended to background noise, Coda waves and S waves recently for estimating site amplification. This study applied this method to the background noise and Coda wave energy. This study analysed more than 267 background noises from 15 macro earthquakes including main Fukuoka earthquake (2005/03/20, M=6.5) and then compared to results from S waves, at 8 main domestic seismic stations. The results showed that most of the domestic seismic stations gave similar results to those from S waves. Each station showed its own characteristics of site amplification property in low, high and specific resonance frequency ranges. Comparison of this study to other studies using different method can give us much information about dynamic amplification of domestic sites characteristics and site classification.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.1
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• pp.114-121
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• 2003

In this paper, low voltage and two stage CMOS Class E RF power amplifier for ISM(Industrial/Scientific/Medical) Open Band is presented. The power amplifier operates at 2.4GHz frequency, and is designed and simulated with a 0.35um CMOS technology and HSPICE simulator. The power amplifier is simple structure of two stage Class E power amplifier. The design procedure determing matching network was presented. The power amplifier is composed of input stage matching network, preamplifier, interstage matching network, power amplifier, and output stage matching network. The matching networks of input stage and interstage were constituted by pi($\pi$) type and L type respectively. At 2.4GHz operating frequency, and with a 2.5V supply voltage, the power amplifier delivers 23dBm output power to a 50${\Omega}$ load with 39% power added efficiency(PAE).

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.5
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• pp.429-437
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• 2015

DDoS attacks have been used for paralyzing popular Internet services. Especially, amplification attacks have grown dramatically in recent years. Defending against amplification attacks is challenging since the attacks usually generate extremely hugh amount of traffic and attack traffic is coming from legitimate servers, which is hard to differentiate from normal traffic. Moreover, some of protocols used by amplification attacks are widely adopted in IoT devices so that the number of servers susceptible to amplification attacks will continue to increase. This paper studies on the analysis of amplification attack mechanisms in detail and proposes defense methodologies for scenarios where attackers, abused servers or victims are in a monitoring network.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.569-577
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• 1999

A wideband RF receiver for satellite mobile communications system was fabricated and evaluated of performance in low noise amplifier and high gain amplifier. The low noise amplifier used to the resistive decoupling and self-bias circuits. The low noise amplifier is fabricated with both the RF circuits and the self-bias circuits. Using a INA-03184, the high gain amplifier consists of matched amplifier type. The active bias circuitry can be used to provide temperature stability without requiring the large voltage drop or relatively high-dissipated power needed with a bias stabilized resistor. The bandpass filter was used to reduce a spurious level. As a result, the characteristics of the receiver implemented here show more than 55 dB in gain, 50.83 dBc in a spurious level and less than 1.8 : 1 in input and output voltage standing wave ratio(VSWR), especially the carrier to noise ratio is a 43.15 dB/Hz at a 1 KHz from 1537.5 MHz.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.3
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• pp.135-142
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• 2017

DDoS (Distributed Denial of Service) exhausts the target server's resources using the large number of zombie pc, As a result normal users don't access to server. DDoS Attacks steadly increase by many attacker, and almost target of the attack is critical system such as IT Service Provider, Government Agency, Financial Institution. In this paper, We will introduce the CNN (Convolutional Neural Network) of deep learning based real-time detection system for DNS amplification Attack (DNS DDoS Attack). We use the dataset which is mixed with collected data in the real environment in order to overcome existing research limits that use only the data collected in the experiment environment. Also, we build a deep learning model based on Convolutional Neural Network (CNN) that is used in pattern recognition.

• The KIPS Transactions:PartB
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• v.16B no.1
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• pp.1-6
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• 2009

It is very difficult to restore the images degraded by motion blur and additive noise. In conventional methods, regularization usually applies to all the images without considering local characteristics of the images. As a result, ringing artifacts appear in the edge regions and noise amplification is in the flat regions, as well. To solve these problems, we propose an adaptive iterative regularization method, using the way of regularization operator considering edge directions. In addition, we suggest an adaptive regularization parameter and an relaxation parameter. In conclusion, We have verified that the new method shows the suppression of the noise amplification in the flat regions, also does less ringing artifacts in the edge regions. Furthermore, it offers better images and improves the quality of ISNR, comparing with those of conventional methods.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.11
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• pp.1608-1614
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• 2022

As competition between universities intensifies due to the recent decrease in the number of students, it is recognized as an essential task of universities to predict students who are underperforming at an early stage and to make various efforts to prevent dropouts. For this, a high-performance model that accurately predicts student performance is essential. This paper proposes a method to improve prediction performance by removing or amplifying abnormal data in a classification prediction model for identifying underperforming students. Existing anomaly data processing methods have mainly focused on deleting or ignoring data, but this paper presents a criterion to distinguish noise from change indicators, and contributes to improving the performance of predictive models by deleting or amplifying data. In an experiment using open learning performance data for verification of the proposed method, we found a number of cases in which the proposed method can improve classification performance compared to the existing method.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2018.06a
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• pp.209-210
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• 2018

본 논문에서는 머신 러닝 분야 중 하나인 딥 러닝에서 DCGAN모델을 이용하여 홀로그램을 생성하는 방법을 제안하였다. 제안한 방법은 홀로그램을 모델링 하는 식에서 객체의 깊이 정보에 따른 코사인 항을 DCGAN을 이용하여 하나의 객체정보에 대한 중간 홀로그램을 생성하였고, 나머지 객체 정보를 이용하여 홀로그램을 이동 및 증폭한 뒤 누적하여 최종 홀로그램을 획득한다.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.181-182
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• 2011

수중에서는 대기와는 달리 매질의 차이로 인하여 통신의 제약이 따르므로 초음파를 이용하여 정보를 송 수신한다. 수중통신을 하기 위해서는 신호를 증폭시키는 전력증폭기와 초음파를 발생시키는 트랜스듀서가 필요하다. 전력증폭기는 수중에서의 발열과 연료문제로 인하여 높은 효율로 동작하여야한다. 하지만 전력증폭기에 인가되는 고정전압과 출력전압의 차이로 인해 손실이 발생하여 효율이 저하된다. 그러므로 본 논문에서는 전력증폭기의 효율 향상을 위해 출력전압에 따라 인가전압을 가변하는 ET(Envelope Tracking) 기술을 적용하기 위한 4[kW]급, 20[kHz]의 대역폭을 갖는 가변 DC-DC 컨버터를 설계하고 시뮬레이션을 통해 특성을 확인하였다.

• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.369-373
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• 2003

As most of the powerline modems use spread spectrum modulation method which has strong immunity against the narrowband fading, or psk modulation method, the amplitude of the signal contains no useful informations. In this paper, we used class D amplifier to implement the drive circuit of the analog front end, and showed that it has great superiority over other existing drive circuits in rapidly impedance changing powerline channel.