• The Journal of the Petrological Society of Korea
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• v.19 no.1
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• pp.51-65
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• 2010

The Dongmakgol Tuff is a stratigraphic unit which is composed of voluminous ignimbrites in the Cheolwon basin. The ignimbrites belong to pumice-rich vitric tuffs that show eutaxitic to parataxitic fabrics from fiamme or pumice clasts. They are almost densely welded and strongly flattened, but often parallel aligned and stretched. Also they exhibit flow indicators such as flow lineations, imbrications, tensional cracks and boudins from their alignment and/or elongation, and lithic and pumice clasts show lateral grading in their average maximum diameter. Flow direction map from the lineations, asymmetric structures and lateral grading diagram indicate that the Dongmakgol Tuff has a source from its southwestern part near a boundary between southern Dongmakri and northern Gomunri, and is considered that the ignimbrites took emplacement processes of laminar flows during the final stage of flowage and the flow lineations are from the result of shear stress during that times.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.7
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• pp.18-23
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• 2000

An active phased away antenna consists of many channels including radiator and active circuitary that contains low noise amplifiers and phase shifters. Each channel has different initial phase shift and gain because of inequality in active circuitary itself, interface between radiator and active circuitary, beam forming network and other antenna configurations. This is an inherent problem in active phased away antenna, therefore each channels' initial phase shifts and gains should be calibrated for obtaining the designed radiation pattern and antenna gain. In this paper, an efficient calibration method for the active phased array antenna is presented. By performing the above method, thhe antenna gain is increased more than 2.0 dB after calibrating considerably unequal 12 channels' initial phase shifts and gains.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.371-379
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• 2011

Active phased array antenna structure is used for modern multi-function radars. To search targets in high clutter environment, the radar receiver needs high dynamic range performance. Though active phased array antenna structure lead to increase of SNR, the SFDR is not increased. In this paper, high SFDR receiver of X-band active phased array radar was designed and manufactured. One channel digital receiver is connected to 32 T/R modules and one PCB assembly is composed to 2 channel digital receivers with RF part, ADC part, LO distribution part and digital down conversion part. A commercial FIFO board was used for digital receiver measurement about major performance in digital output signal condition. The measured digital receiver gain and SFDR is 33 dB and more than 81 dBc each.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.5
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• pp.845-852
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• 2019

The main goal of Signal Intelligence (SIGNT) based on a satellite is to collect valid and accurate data without the topographical constraints, but, due to the characteristics of the satellite communication, the collected signals are greatly vulnerable to the influence of interference and jamming signals because their power are very low. Therefore, the high performance techniques of estimating the angle of arrivals (AOAs) of the collected signals and suppressing interference signals are required for collecting various signals on the ground employing the satellite. In addition, the high quality of the transmission beam-forming technique is required for accurately transmitting the collected information to a ground control center. In this paper, we present a beam-forming satellite system based on a circular array antenna, considering the above techniques, and evaluate and analysis the performance of the presented beam-forming system through the computer simulation. The circular array antenna structure is expected to effectively employ for the SIGINT system based on a satellite, because it is suitable to be installed in the satellite.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.9
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• pp.1-12
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• 1998

We have implemented receiver for a 3 Dimensional Phased-Array Radar detecting the azimuth angle, the altitude, the range of a target on real time. This system consists of high frequency module, which protects receiver and controls sensitivity, intermediate frequency module, monopulse detector, IQ phase detector, AGC controller. A two-channel receiver with same function is implemented for increasing accuracy of target altitude data by amplitude comparison monopulse method. The TSS sensitivity of the receiver is -98dBm. The bandwidth of the receiver is 500 MHz. We can control the system gain manually by 100 dB when be AGC off. The gain and phase unbalance of two channels is 5 dB and 30 degree, respectively. The image rejection rate of the IQ detector is 30 dB. We used duroid substrate and package- type device.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.7
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• pp.166-175
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• 1989

In this paper, we present a method which is based on the concept of the rotation of subspaces. This method is highly related to the angle (or distance) between subspaces arising in many applications. An effective procedures is first derived for finding the optimal transformation matrix which rotates one subspace into another as closely as possible in the least squares sense , and then this algorithm is applied to the solution to general direction-of-arrival estimation problem of multiple broadband plane waves which may be a mixture of incoherent, partially coherent or coherent. In this typical application, the rotation of signal subspaces (ROSS) algorithm is effectively developed to achieve the high performance in the active systems for the case in which the noise field remains invariant with the measurement of the array spectral density matrix (or data matrix). It is not uncommon to observe this situation in sonar systems. The advantage of this techniques is not to require the preliminary processing and spatial prefiltering which is used in Wang-Kaveh's CSS focusing method. Furthermore, the array's geometry is not restricted. Simulation results are presented to illustrate the high performance achieved with this new approach relative to that obtained with Wang-Kaveh's CSS focusing method for incoherent sources and forward-backward spatial smoothed MUSIC for coherent sources including the signal eigenvector method (SEM).

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.3
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• pp.174-181
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• 2014

Design procedure of LEG(Linear Electric Generator) is introduced by performing the time-domain analysis for the heaving motion of a floating buoy coupled with LEG. A vertical truncated buoy is selected as a point absorber and a double-sided Halbach array mover and cored slotless stator is adopted as a linear electric generator. LEG with a double-sided Halbach array mover and cored slotless stator is designed with the input data such as the heave motion velocity and wave exciting forces in time-domain. The validity of designed LEG is confirmed by performing generating-characteristic-analysis under the sinusoidal motion of a buoy, based on the numerical techniques such as FE(Finite Element) analysis. In particular, an ECM(Equivalent Circuit Method) is employed as the design tool for the prediction of generating characteristics under irregular wave conditions. Finally, we confirm that the ECM gives reasonable and fast results without sacrifice of accuracy.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.109-116
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• 1999

This paper presents an experimental study on the behavior of CFT Column to H-Beam Endplate Connections with penetrated H/T bolts under monotonic loading. The object of this study is to estimate accurately the effect about the thickness of endplate and the arrangement of H/T bolts which was not got a grip on the results reported in the previous paper. Main parameters are the thickness of endplates (12mm, 16mm) and the arrangemement of H/T bolts (EP1, EP2, EP3 Type). The experimental results compared and analysed. 1) The specimens were classified by Bjorhovde's and EC3's method. 2) A formula to predict the ultimate moment of connection was derived based on the T-stub model, and theoretical value $(_tM_u)$ computed by the formula corresponded to the experimental value $(_eM_u)$.

• The Transactions of the Korea Information Processing Society
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• v.4 no.5
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• pp.1172-1181
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• 1997

A militimedia data is a data mixed of formatted data like an audio and video. Multimedia data has characteristics that it need large amount of storage,wide network bandwith andreal time responsibolity. Because of these characteristocs, the VOD server and continous media storage server have a disk stripe structure or disk stripe sructure or disk array structure(RAID).In the parallel disk access system,high-speed play-back of continous media using segment interleavung may not ensure Qos pf other cioents because of the concentrated load within some disks. The load concentration of disks is related to both the number of disks in the system and playback rate of contimous media.In this paper. we describe that high-speed playback scheme,which is independent of the number of disk and plyback rate can be achieved by technique of changing the in-teval of access to segnent location.We show the experimental result of this technique in this pater.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.156-156
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• 2013

대기압 저온 플라즈마는 간단한 구조 및 제작, 쉬운 조작성, 낮은 온도 특성, 높은 화학적 반응성과 같은 많은 장점에도 불구하고, 플라즈마의 에너지가 낮아 다양한 산업적 응용에 제약을 받아왔다. 이러한 단점을 극복하기 위해서 대기압에서 저온 플라즈마의 에너지를 높이는 여러 시도가 있었으며, 그 중 가까이 인접해 있는 둘 이상의 플라즈마 젯들의 결합 현상(plasma jet-to-jet coupling)을 이용하여 플라즈마 강도를 높이려는 시도가 보고되었다. 본 연구에서는 플라즈마를 발생시키는 유리관을 서로 모아 벌집모양의 배열을 갖는 플라즈마 젯 어레이 장치를 만들어 플라즈마 젯 사이에 상호결합을 유도하여 강한 플라즈마 발광을 발생시켰다. 플라즈마 젯 어레이 장치 중 가운데 위치한 플라즈마 젯은 대기압 플라즈마 젯의 형태를 구현하는 역할을 하고, 가운데를 둘러싼 주변의 여러 플라즈마 젯들은 중앙의 플라즈마 젯에 많은 하전입자를 제공하여 플라즈마 젯의 발광강도를 높이는 역할을 하는 것을 확인했다. 헬륨기체를 사용한 이 플라즈마 젯은 $100^{\circ}C$ 이하의 온도임에도 불구하고 ITO 유리의 유리면을 식각할 만큼 높은 에너지를 가졌다. 이러한 대기압 저온플라즈마 장치에서 플라즈마의 강도를 더 높이기 위해서는 플라즈마 젯 간 결합이 더 많이 일어나는 것이 중요하므로, 이를 위해 주변의 플라즈마 젯의 개수를 높이는 시도를 하였다. 플라즈마 젯 어레이 소자의 중심에 위치한 유리관의 크기를 크게 하고, 주변부의 유리관의 크기를 상대적으로 작게 하여 벌집형태의 배열보다 더 많은 유리관을 주변부에 위치시킨 후 플라즈마를 발생시키고 전기 광학적 특성을 측정하였다. 그 결과, 실험조건에 따라 가운데 플라즈마 젯에서 3배에서 5배 이상 높은 플라즈마의 발광강도를 얻었으며, 플라즈마 젯도 더 안정적으로 발생하였다. 주변부의 유리관의 개수가 증가하면 더 많은 양의 하전 입자들이 플라즈마 결합 과정에 참여하게 되고 결과적으로 더 큰 플라즈마의 발광강도를 나타내는 것이다. 본 실험은 하전입자의 상호작용에 의해 발생하는 서로 인접한 플라즈마 젯 간의 결합이 대기압 저온 플라즈마 젯의 플라즈마 발광강도를 높이는 좋은 방법임을 보였다. 이러한 플라즈마 젯 간의 결합은 대기압 저온 플라즈마의 에너지를 높일 수 있는 쉽고 간단한 방법이며, 이 방법을 이용하여 대기압 저온 플라즈마를 표면처리, 표면개질은 물론, 식각 및 증착, 나아가서는 의료/바이오 분석 기술 등 다양한 학문적, 산업적 응용에도 적용할 수 있을 것으로 기대한다.