• The Science & Technology
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• v.32 no.9 s.364
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• pp.22-23
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• 1999

과학과 종교는 대화가 가능한가? 지난 4월 미국에서는 노벨물리학 수상자인 와인버그와 성공회 목사인 폴킹혼이 '과학과 종교간의 건설적인 대화'라는 제목으로 토론을 벌였다. 이들 두사람은 신의 존재와 사람의 선악행위 등을 토론대상으로 올려 놓았지만 신학의 권위는 계시에 있고 과학의 권위는 실험에 있기 때문에 중요한 형이상학적인 문제는 해결되지 않은 채 토론은 끝났다.

• 한국ITS학회:학술대회논문집
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• 2002.11a
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• pp.138-140
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• 2002

• Proceedings of the Korean Society of Grassland Science Conference
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• 2003.06a
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• pp.159-160
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• 2003

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.609-610
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• 2010

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.3
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• pp.1-8
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• 2011

In this paper, data transmission corrugated horn antenna for RF sensor satellite system and its radiation characteristic are presented. The proposed antenna is designed, fabricated and measured to obtain the maximum gain at ${\pm}60^{\circ}$ of its radiation patterns. The result of the proposed antenna is that the return loss is less than -15 dB and the gain is over 5 dBi at ${\pm}60^{\circ}$ of its radiation patterns. From these results, it is confirmed that the proposed can be used as data transmission corrugated horn antenna for RF sensor satellite system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.18 no.3
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• pp.43-48
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• 2018

Offset parabolic antenna have been widely used for satellite communication system. To locate feedhorn on antenna system, it requires arbitrary structure which forces to fix on system. However, arbitrary scatterer increases sidelobe level of elevation axis. To solve this problem, we need to predict which angle level is increased by arbitrary scatterer simply. Because conventional simulation method takes a long time to simulate parabolic antenna system and needs exclusive software. In this paper we can calculate sidelobe angle simply by using raytracing method, check coincidence between calculated and simulated result and show how arbitrary scatterer affects sidelobe lavel of elevation axis of offset parabolic antenna depending on angle and location of arbitrary structure.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.5 s.149
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• pp.578-585
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• 2006

Cavitation related erosion damages on semi-spade rudder generally occur at around leading edge of lower-face and behind gap of lower pintle. To get the idea of gap entrance profile for the latter case, a series of tests with large models has been carried out at MOERI. In the tests, the flow pattern around lower pintle have been investigated and visualized by high speed camera. Additionally, cavitation inception tests and pressure measurements have also been conducted for better comparison. As a result a new model (F rudder) has been developed. The new model turned out to have stable pressure distribution along the surface and so the cavitation inception speeds within ${\pm}5^{\circ}$ of rudder angle were delayed approx. 4 knots in average.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.2
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• pp.168-177
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• 2003

The performance sensitivity analysis due to manufacturing/alignment errors is performed for the Ku-band offset parabola antenna of the domestic Communications and Broadcasting Satellite. The performance variations due to reflector random surface error, which inevitably happens during reflector manufacturing, are statistically analyzed using RMS error and correlation interval. The impact on the antenna performance of the fred hem's position and angular errors is investigated, and the sensitive directions are identified. When the target tolerances are applied, the performance degradations are found to be within the loss budget or corresponding performance margins.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.7
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• pp.1247-1257
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• 2000

Offset-fed dish antennas are considered. Offset-fed dish antennas are widely used for DBS reception, the problem of offset-fed dish antenna has, however, received little attention because of its complicated and asymmetric geometry. A Fourier-transform technique and Physical Optics are employed to express the fields radiated from offset-fed reflector and feed horn aperture. The simultaneous equations are solved to obtain a solution in a fast convergent series, thus facilitating the numerical computation. For given parameters such as diameter of reflector, focal length, offset height of reflector center, exact solutions are derived. Since offset-fed dish antenna has an application as multi-beam antenna using multiple feed, a brief feasablity of dual beam antenna for Korea-SAT (116$^{\circ}$E, EIRP 59 dBW) and Orion-SAT (139$^{\circ}$E, EIRP 54 dBW) is given in Conclusion.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.13 no.3
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• pp.53-60
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• 2004

We have developed and manufactured an experimental ultrasonic polishing machine with frequency of 20kHz at the power of vibration 1.7㎾ for effective ultrasonic polishing in processing of high hardness material. Design of the horn is performed by the FEM analysis. The following conclusions were empirically deduced through experimental results to clarify the major elements which affect the surface roughness during the ultrasonic process by following the experimental plans. The ultrasonic polishing machine has been developed in parts of structure part, ultrasonic generator, vibrator. We were able to process the high hardness material without difficulty as a result of ultrasonic polishing by utilizing the groove added step-type horn. Through analyzing by applying the experimental plans, the rotating speed of the horn was determined to be the major factor in influencing the surface roughness. In the case of ceramic, wafer, we were able to obtain good surface roughness when the feed rate and the ultrasonic output were higher. Because the load on slurry particle increases when the ultrasonic output is higher, the processed surface becomes worse in the case of optical glass.