• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.9
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• pp.2164-2170
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• 2010

Digital Radio Frequency Memory, ( as DRFM ), is a device with the ability to restore output to the input RF signal in the required time after storing the incoming RF signals. Therefore DRFM is widely used in Jammer, EW Simulator, Target Echo Generator, and so on. This paper proposes its hardware implementation composed with the high frequency part and the digital processing part consisting of RF input/output module and local oscillator module. It is also proposed the replicated signal generation method which is consisted of the Analog-Digital conversion in the form of pulsed RF signal quantization, and FPGA to save and produce the playback signal, and RF signals to produce a Digital-Analog Conversion in the digital processing unit. This proposed scheme applied to test board and confirmed the validity of the proposed scheme through the test results obtained by the simulated input signals.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.3
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• pp.530-536
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• 2017

The accident of the small vessel is increasing due to the growth of the sea and service industry. According to data from National Statistical Office, for 100 ton less than small ship accident, the most of the shipping incident generated in the small ship by 84% of the total shipping incident in 2015. The radar obligatory mounting is enforced to the small vessel in order to conclude this problem. However, the problems including the maintenance cost and transmission power etc. happens high if the existing pulse radar is mounted in the small vessel. In this development, the development is for small ship fixed type radar the object. And in this paper, by using the phase array antenna revolving electronically around the beam, the antenna which it is applicable to the marine fixed type radar which can solve above problem was made and it tested.

• Korean Chemical Engineering Research
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• v.44 no.1
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• pp.35-39
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• 2006

This study was performed to understand temperature effect on retention behavior of fructose and glucose as sugars and lactic acid and acetic acid as organic acids on poly (4-vinylpyridine) resin. The pulse tests were performed to understand temperature effect on retention time of sugars and the results were not shown large change. As it was able to predict with PVP resin not to be used for sugar separation generally, the results were shown poor resolution for separation of sugars and temperature effect on the resolution change of sugars also was not large. On the other hand, in the case of organic acids on PVP resin, the pulse tests were shown temperature effect on the retention behavior was very large. So, the frontal analyses were performed to understand quantitative adsorption behavior of organic acids at 35 and $65^{\circ}C$. These adsorption characteristics of organic acids with PVP resin system can be used to preparative chromatographic process such as SMB (simulated moving bed).

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.3
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• pp.266-273
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• 2016

In this paper, we propose the signal processing techniques for the command link receiver mounted to aircrafts flying at a high speed. In order to acquire the various information transmitted from ground through radio frequency links, the wide received signal range must be guaranteed as well as the carrier synchronization and symbol synchronization be performed correctly within short pulse sections. After the synchronization step, we should be able to achieve theoretical performance of the modulation and demodulation scheme applied as deciding bit and symbol at the time appointed. By test results, we make sure that the proposed signal processing techniques can be effectively applied command link receiver mounted to aircrafts.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.6
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• pp.559-565
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• 2004

Two different methods were used for the scattering analysis of side-drilled holes(SDH). The scattering models include an explicit model based on the Kirchhoff approximation and the solution of the exact separation of variables. The far-field scattering amplitude was calculated and their time-domain results were compared for the case of shear vertical wave. The exact solution predicts the existence of the creeping wave. The Kirchhoff approximation agreed to the exact solution, except the case of the creeping wave. Two measurement models were introduced to predict the response from the SDHs for the case of immersion, pulse-echo testing. The received voltage was calculated for the case of the shear vertical waves with the incident angle of $45^{\circ}$ to the SDH with the diameter of 1mm, and compared with the experimental results.

• Journal of the Korean Society for Nondestructive Testing
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• v.13 no.3
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• pp.7-13
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• 1993

Fracture behavior of pre-cracked compact tension specimens made of AISI 4130 steel was investigated using acoustic emission (AE) and ultrasonic C-scan measurements. While each specimen was loaded up to a certain level, various acoustic emission parameters were recorded together with the crack opening displacement (COD). An elastic-plastic finite element analysis was performed to calculate COD and the damage (plastic) zone size ahead of crack tip. Ultrasonic C-scans, in a pulse-echo, immersion mode, were done for mapping the damage zone size. The agreement between the finite element results and the measured COD was satisfactory. Based on AE results, the test specimens were found to show ductile behavior. The slope of the total ringdown counts vs. COD curve was useful to determine the crack initiation. The preliminary C-scan images showed evidence of changes in the amplitude of ultrasonic signal in the damaged region, and the shape and size of the damage zone matched qualitatively with the finite element results. A further work on the damage zone sizing was also pointed out.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.338-344
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• 2010

A double rotation C-scanning system and a software program Under-Sodium MultiVIEW have been developed for the under-sodium viewing of a reactor core and in-vessel structures of a sodium-cooled fast reactor KALIMER-600. Double rotation C-scanning system has been designed and manufactured by the reproduction of double rotation plug of a reactor head in KALIMER-600. Hardware system which consists of a double rotating scanner, ultrasonic waveguide sensors, a high power ultrasonic pulser-receiver, a scanner driving module and a multi channel A/D board have been constructed. The functions of scanner control, image mapping and signal processing of Under-Sodium MultiVIEW program have been implemented by using a LabVIEW graphical programming language. The performance of Under-Sodium MultiVIEW program was verified by a double rotation C-scanning test in water.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.34 no.2
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• pp.135-138
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• 1998

This paper describes the construction and experimetal results of prototype digital telesounder developed to monitor remotely the fish school entered in setnet. The telesounder consists of the sea station and land station. The former consists of an ultrasonic transceiving part of 50 KHz, a hand made 16 bits single board computer (SBC), and a RF MODEM of 9600 bps for data link. The SBC controls the trigger signal to transmit the ultrasonic pulse, maximum detection range, sampling rate in analog to digital converter and data link. The sampling rate of echo data was 80 ${\mu}$s. The later consists of a RF MODEM same as the former one and 486 notebook computer which displays the echogram and saves its raw data. The authors carried out some experiments to confirm the practical use of the telesounder. At results the echogram obtained on the land station is sufficiently good and clear to monitor the behavior of fish school in setnet.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.12B
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• pp.1236-1243
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• 2010

The perimeter defense system was created and its characteristics were evaluated. It was designed to utilize the fiber sensing device, namely OTDR(Optical Time Domain Reflectometer) which has been used for the maintenance of the optical communication network. An OTDR was constituted by a pulse laser with the nature of 1310nm, +15dBm for the observation of 400 meter optical fence. The high-speed 32-bit processor(S3C2440) has applied to MPU(Main Processor Unit) which helps to improve the performance of OTDR algorithms. Consequently, the maximum error was 0.84 meter on the performance test of the 10km monitoring and the pass criteria of ${\pm}1m$ satisfied in all the sections. The alarm delay time was under 3 sec after detecting the disorder. For the case of secondary trespassing after primary trespassing, the optical switch was installed in OTDR to monitor the secondary trespassing and to measure the multi-point detection. Therefore, this paper shows that the detections of secondary trespassing and multi-point is possible by means of optical switch.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.144-144
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• 2016

플라즈마 전해 산화법(Plasma electrolytic oxidation)에 의해 형성된 코팅층은 특유의 기공구조로 인해 부식 환경에 노출 시 부식액의 침투가 급속히 이루어지는 단점이 있다. 이를 극복하기 위한 방법으로 유기코팅, sol-gel법, 폴리머 코팅 등에 의해 기공을 봉공(sealing)하는 방법이 제안되고 있다. 본 연구에서는 Al 합금의 플라즈마 전해 산화 처리 후 질산 세륨 수용액(Cerium nitrate solution)에 의한 봉공 효과를 확인하고자 하였다. PEO 코팅을 위한 전해액은 2g/L의 KOH와 $2g/L\;Na_2SiO_3$를 증류수에 용해시켜 준비하였다. PEO 코팅층은 Al 시편을 전해액 내에 위치시켜 양극으로 하고 STS를 음극으로 하여 $0.1A/cm^2$의 펄스 정전류밀도(주파수: 100Hz, 듀티비: 20%)를 15분 동안 인가하여 형성시켰다. 봉공을 위한 실링액은 증류수에 $0.3g/L\;H_2O_2$와 $1g/L\;H_3BO_3$를 첨가하고, $Ce(NO_3)_3$를 농도 변수로 첨가하여 준비하였으며, PEO 코팅 처리된 시편을 실링액에 침지하여 실링액의 농도와 침지시간을 달리하여 봉공을 실시하였다. 제작된 PEO 코팅층에 대해 SEM, EDS, XRD를 이용한 표면분석을 실시하였으며, 내식성을 확인하고자 동전위분극시험을 실시하였다. 연구 결과, 세륨 실링 처리된 PEO 코팅 층에서 미량의 세륨 성분이 검출되었으나, 세륨계 화합물 생성에 의한 마이크로 크기의 기공의 폐쇄는 관찰되지 않았다. 또한, 전기화학적 특성 평가 결과 실링 처리된 PEO 코팅층의 경우 Al 모재에 비해 2차수 정도 감소된 부식전류밀도를 나타내었다. 이 같은 내식성의 향상은 세륨 성분에 의한 부식 억제 효과 때문으로 판단된다.