• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2002.04a
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• pp.70-71
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• 2002

연소실의 세장비(aspect ratio)가 작으면서 추진제의 고 충전을 이용한 단시간 연소 모타는 유도탄의 사출 모타 용으로 사용될 수 있다. 사출 모타는 일반적으로 모타 무게에 대한 제약 조건이 까다롭지 않기 때문에 무게 경량화에 대한 부담은 줄어들지만, 모타의 부피가 커지면 유도탄 발사 장치의 부피가 커지기 때문에 공간적인 측면에서 가능한 작게 하는 것이 시스템 전체의 효율을 증대시킬 수 있다. 또한 사출 모타의 연소 시간이 짧기 때문에(1초 이내) 추진제의 웹 두께가 작으므로 연소실의 주어진 공간에서 추진제를 많이 채우기 위한 방법으로 원통 튜브형 그레인을 여러 개의 다발로 사용하는 방법이 효과적이다. 이러한 관점에서 사출 모타용으로 다발 원통 튜브형 그레인을 설계/제작/연소시험을 하였더니 작은 저주파(약 10Hz)의 연소 불안정 현상이 발생하였다. (그림1). 이러한 주파수 대역은 일반적으로 잘 알려진 연소 불안정 모드 (longitudinal, tangential, and radial mode)와는 다른 아주 특이한 현상이다. 이러한 현상의 주 원인은 연소실 내 압력의 비평형에 의한 현상이라 판단되어 다음과 같은 연구를 수행하였다. 1) 그레인 튜브간의 압력 평형을 원활하게 하기 위하여 그레인에 구멍(홀)을 뚫어서 연소 안정화에 미치는 영향에 대한 연구(그림2), 2) 그레인에 홀을 뚫지 않고 격자와 격자간의 공간을 이용하여 그레인 간에 발생된 저주파의 압력 진동을 산란/소멸 시키는 연소 안정화 연구(그림3).

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1996.05a
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• pp.59-73
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• 1996

체계적 관점에서 추진기관에 요구되는 설계 제한조건의 합리적 조정에 의한 최적화 달성을 위하여 주 체계(Main System)와의 신속한 자료을 제시/교환가 요구된다. 이를 위하여 비록 많은 가정사항들이 내재해 있더라도 성능과 형상, 그리고 무게에 대한 자료을 제시할 수 있는 추진기관 설계 자동화 도구를 개발한다. 본 연구에서는 일차적으로 추진제 조성과 특성의 상관관계를 추진기관 체계와 그레인 내탄도/구조성능의 설계 관점에서 관계식화하여 제시하였다.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.11b
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• pp.609-612
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• 2002

본 논문은 다양한 멀티미디어 응용을 위한 재구성가능(reconfigurable) 구조의 프로세서 설계에 대해서 연구하였다. 설계된 프로세서는 RISC 코어 프로세서와 코스-그레인(coarse-grain) 구조의 재구성가능 셀들의 배열로 이루어진 처리 유닛으로 구성되었다. 여기서 사용된 RISC 코어 프로세서는 하드웨어 구조를 간단히 하기 위하여 MIPS 명령어들 중에서 사용빈도가 높은 것들만 고려하였으며, 재구성가능 처리를 위한 별도의 명령어를 추가하였다. 본 논문에서 제시한 재구성가능 프로세서는 VHDL로 모델링하여 실행을 검증하였으며, 하드웨어의 유연성을 증가하여 다양한 멀티미디어 응용에 적용함과 아울러 속도향상에 기여함을 볼 수 있었다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.349-352
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• 2008

This work is to observe combustion characteristics depending on variation of the solid propellent grain configuration. The LRE (Liquid Rocket Engine) enables adjusting the thrust by controling the required fuel mass glow, but the SRM(Solid Rocket Motor)is not easy to adjust th thrust due to the difficulty of th fuel flow control by its combustion behavior even its configuration is simple. This difficulty can be partly solved by changing th size or the configuration of the propellant grain. In this study a proper grain configuration of a small solid rocket is selected through both the theoretical design and the experimental tests.

• Journal of the Korean Institute of Telematics and Electronics
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• v.19 no.2
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• pp.14-22
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• 1982

The design and manufacfure technology of the large aperture cassegrain antenna was first studied in the country, and its performances in a trial manufactured product are measured and compared. In order to design this cassegrain antenna with reference to several literatures, the schemed order was decided. Especially, for the cassegrain antenna of 4.6m diameter which is becoming the television receiving antenna directly from satellite, in advanced countries, the 1/12 sized small section of its parabolic curved surface is made primarily with the precision of less difference than 1/16λ depth. Cares are taken also on the computer program so that the size and position of primary radiator may satisfy the minimum blocking with the given sub-reflector. The preformances of the designed antenna are shown as being 43dB in gain, 1.15 or less in VSWR, 1.1$^{\circ}$ of beam angle etc., and found to be not worse than those of foreign productions with similar type and size.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.9 s.112
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• pp.829-835
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• 2006

In this paper, new structure of the Cassegrain reflector antenna whose spill-over is efficiently reduced by modified reflectors is proposed for high power. It can be achieved by designing the geometry of subreflector in Cassegrain system using two hyperbolic curves in order to be suitable a lager beamwidth of feeding pattern without broadening main reflector. Finally, radiation efficiency and side lobe level of the proposed Cassegrain reflector antenna can be improved respectively 9 %, 10 dB than conventional one.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.10
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• pp.851-868
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• 2015

A radio telescope which has been dominantly used for millimeter and submillimeter wave radio astronomy is a cassegrain antenna. A various receivers with specified observing bandwidths are installed on cassegrain antenna so as to carry out to investigate a diverse radio astronomy. A beam guiding system should be required so that a various receiver can be conducted their own observational frequency bands. The beam guiding system based on Gaussian beam transmission theory consists of quasi-optical circuit used such ellipsoidal mirror, dielectric lens and feed horn. In this paper, not only Gaussian beam transformations based on Gaussian beam theory are presented, but also design techniques for quasi-optical circuit are given. By using proposed design techniques, both Gaussian beam quasi-optical circuits to be used for cassegrain antenna and design results are also described. Properties of key focusing elements such ellipsoidal mirror and dielectric lens and feed horn are also discussed. It is expected that beam guiding system to be applied cassegrain antenna could be easily designed by using proposed design techniques.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.943-953
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• 2007

In this paper, we propose a Cassegrain antenna with a scalar feed horn opt rating in Ka-band. For an effective EM simulation of the Cassegrain antenna, the near-field of the feed hone is used ai the equivalent source of the Cassegrain antenna using the surface equivalent theorem. A corrugated circular horn operating with $HE_{11}$ mode is used as the feed horn. The angle and feed center of the main and sub reflectors are optimized to achieve maximum antenna efficiency. The designed feed horn shows the gain of 19dBi, the side-lobe level of less than -25dB and the half power beam width of $20^{\circ}$ at 33 GHz. The Cassegrain antenna shows the gain of 41dBi, the efficiency of 60%, the side-lobe level of less than -20dB and the half power beam width of $1.2^{\circ}$.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2006.11a
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• pp.419-422
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• 2006

Improvement of performance of sorbitol model rocket was studied. The rocket designed in this work was compared with the rocket manufactured previously with respect to the shape of body, grain of rocket motor, motor case and recovery system. From this comparative work, it is found that mass ratio is required to be increased and the rocket was designed under safety regulation.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.3
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• pp.48-55
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• 2014

In present study, design and hot fire tests of the pryostarter are conducted. To prevent the turbopump RPM overshoot, regressive mass flow rate profile is applied. Sudden decrease of the mass flow rate at the end of the propellant burning is realized as well. Firing test results show good agreements with the design requirements. Through the study with ignition substance variations, combustion products and ignition performances are improved.