• Journal of Korea Society of Digital Industry and Information Management
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• v.14 no.3
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• pp.87-101
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• 2018

Minors' law evasion is getting serious. Some of them make a fake ID card or use a stolen ID card illegally. They are illegally used for buying alcohol, cigarette, bond or going to club, pub, motel and so on. On the latest News, there was a case that teens rented a car with a driver licence without checking and had severe car accident. Like this case, car rental service was fined and suspended from business because they did not figure out ID card's counterfeit or modification. Thus, this study investigates the detecting method about the ID card(including a driver license) counterfeit, modification or illegal use. The server has a database of 17~19's minors one fingerprint and services whether the visitor is adult true or not. The method will be usable and economical for business. Then, it was compared and analyzed with methods already in use in business.

• Journal of Digital Contents Society
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• v.5 no.3
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• pp.187-191
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• 2004

Rapid time variations of the mobile communication channel have a dramatic effect on the performance of multi-carrier modulation. This paper analyzed the bit error rate (BER) performance for multi-carrier code division multiple access (MC-CDMA) network, and derived the equivalent signal-to-total noise plus interference(SNIR) of MC-CDMA system in the reverse link, the performance of MC-CDMA/BPSK signal is evaluated taking into account the fraction of partial-band interference and interference power. and the effect of partial-band interference is comprehensively studied in order to further improve the Qos of multi-carrier multimedia system.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.515-515
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• 2013

RF는 사이클로트론에서 빔을 원하는 에너지로 가속하기위해 쓰인다. MC50 사이클로트론에는 두 개의 DEE가 있고 각각 독립된 LLRF모듈과 증폭기를 통해 제어된다. 주요 제어변수는 DEE1,2의 Voltage와 양단간의 Phase인데 이는 RF Generator에서 특정 주파수로 발생된 RF 시그널의 Amplitude와 Phase를 RF Modulator에서 변조하므로 제어되어진다. 지금 현재의 Modulator는 오래되어 DEE Voltage의 컨트롤이 잘 이루어지지 않고 있고 가끔 연결부위에서 문제를 보여 새 Modulator를 제작하게 되었다. 기존의 LLRF는 아날로그 방식인데 아날로그 방식은 외부제어가 어렵고 확장이 쉽지 않아 디지털 제어방식으로 설계하였다. 새 LLRF는 저속처리부와 고속처리부로 두 부분으로 구성하였다. Final amplifier와 cavity의 상태를 체크하는 저속처리부는 PLC로 RF 시그널의 Amplitude와 Phase를 제어하는 고속처리부는 FPGA로 제어할 계획이다.

• The Journal of the Acoustical Society of Korea
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• v.34 no.2
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• pp.91-97
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• 2015

In this paper, wireless communication from a smart phone to a hearing aid using audible frequency band sound was considered. 1kHz single channel carrier frequency was applied for amplitude shift keying (ASK) binary data modulation, and the result of the transmission and reception was tested. The overall system process was precisely explained and experimentally evaluated. The result will be applied for realizing a digital hearing aid with remote control feature by a smart phone.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.4
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• pp.467-473
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• 1999

We have realized the two kinds of power line communication systems by the FSK MODEM. The first approach is the DS-SS (Direct suquence-spread spectrum) technique using 8 bits pseudo noise, the other is Convolutional coding method by the new algorithm. Their characteristics are comparied with each other by experimenting their Bit Error Rates (BER) in high level of Noise. The results have showed that two systems are useful to the application of HA (Home Automation) systems.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.11
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• pp.1934-1939
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• 2006

Current digital communication system is selecting very various digital Modulation way. Need linear power amplifier necessarily to reduce interference for contiguity channel maximum in this communication system and at the same time, power amplifier of high efficiency is required. In this paper Compare with result of equilibrium power amplifier that design Doherty power amplifier of way that linearity and efficiency are improved at the same time through simulation optimization techniques and at the same time design through simulation, efficiency 20% linearity showed 10dB that is improved.

• Journal of Digital Convergence
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• v.10 no.2
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• pp.153-159
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• 2012

Now a days, U-healthcare comes into the spotlight as a new business model which combines RFID technology with medical service in the well-being era and IT popularization. U-healthcare service needs a method that can deals with hand-writing, overlap data, forgery and falsification of data, difference between information version that happen in medical process because of graft between RFID technology and u-healthcare. This paper proposes RFID based user certification protocol to protect user's privacy who gets medical service through U-healthcare. In the protocol, secret information of patient does the XOR with the secret key that is created in the hospital to reconsider the stability of security system of U-healthcare and user's data forgery and falsification and privacy and then saves it in the secret key field of patient in DB table. Also, it informs the case of illegal access to certification server and make it approved the access of u-healthcare service by differentiating whether u-healthcare is illegal or not.

• Journal of Digital Convergence
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• v.13 no.10
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• pp.343-351
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• 2015

With the diverse services of the current M2M environment being expanded to the organizations, the corporations, and the daily lives, the possibility of the occurrence of the vulnerabilities of the security of the related technologies have become an issue. In order to solve such a problem of the vulnerability of the security, this thesis proposes the technique for applying the cryptography algorithm for the protection of the device key of the M2M environment. The proposed technique was based on the elliptic curve cryptography Through the key exchange and the signature exchange in the beginning, the security session was created. And the white box cipher was applied to the encryption that creates the white box table using the security session key. Application results cipher algorithm, Elliptic Curve Cryptography provides a lightweight mutual authentication, a session key for protecting the communication session and a conventional white-box cipher algorithm and was guaranteed the session key used to encrypt protected in different ways. The proposed protocol has secure advantages against Data modulation and exposure, MITM(Man-in-the-middle attack), Data forgery and Manipulation attack.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.462-473
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• 1999

This paper addresses the current measurement issue of all digital field oriented control of ac motors. The p paper focuses on the effect of low-pass filter and also on the sampling of the fundamental component of the m motor current. The low-pass filter, which suppresses the switching noise of the motor current, introduces v variable phase delay according to the current ripple frequency. It is shown that the current sampling error c consists of the fundamental component and high frL'quency ripple components. In this paper, the dependency of t this current sampling e$\pi$or on the reference voltage vector is investigated analytically and a sampling technique i is proposed to minimize the error. The work is based on the three phase symmetry pulse width modulation l inverter driving an induction machine. With this technique, the bandwidth of current regulator can be extended t to the limit given by the switching frequency of the inverter and more precise torque regulation is possible.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.6 s.97
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• pp.603-614
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• 2005

In this paper, digital ultra-narrowband Walky-Talky using direct conversion method for CQPSK modulation scheme is implemented with satisfying the requirements of APCO P25. RF transceiver design and implementation scheme that minimize the influence of DC-offset and AC-coupling at ultra-narrowband is proposed. This scheme also minimizes the influence of nonlinear characteristic at power amplifier fir CQPSK modulation method. Test results of full system including DSP module and direct conversion RF transceiver show that FCC emission mask at 36.8 dBm PEP meets the standard requirements. The characteristic of receiver AGC by PWM control signal is linear at 40 dB dynamic range and voice communication at input power level of -116 dBm is successful. Also it is verified that the performance of BER versus frequency offset and versus SNR meets the standard requirements.