• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.4
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• pp.67-73
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• 2007

In recent years hydrogen peroxide has become considerably more attractive as a green rocket propellant so a laboratory model of hydrogen peroxide thruster adopted silver catalyst and a test facility has been developed to research a hydrogen peroxide propulsion. The design scheme of thruster and the test data are presented including ignition delay, efficiency of characteristic exhaust velocity. As a result, 95% of efficiency of characteristic exhaust velocity was obtained at steady state operation condition.

• The Korean Journal of Quaternary Research
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• v.11 no.1
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• pp.1-24
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• 1997

한반도의 석기문화는 전기구석기부터 시작되는데 동아시아지역에 퍼져 살던 고인류 집단의 일파가 한반도로 확산하여 온 것으로 판단된다. 이들의 석기문화는 아슐리안주먹도 끼를 공반한 정형화되지 않은 구석기공작이었다, 중기구석기는 르발르와기법의 유무에 대한 논란이 남아있으며 전기적인특성이 그대로 지속되는 시기이다. 그러나 약 3만년전의 후기구 석기시대가 되면 석인석기공작이 나타나고 석기도 대단히 정교해 지는데 이 석기 공작은 동 아시아로 확산되어 오던 현생인류의 도구이었다. 바이칼호부근에서 기원한 세석인문화는 한 반도의 전역으로 퍼져나갔다,. 이 석기공작은 중석기를 거쳐 신석기에 이를 때 까지 눌러 떼 기기법과 함께 존속하였다, 신석기시대에는 마제기법이 나타나게 되고 어로용도구들이 새로 이 추가되기 시작한다 그리고 간단한 가공으로 만든 농경구들이 추가되기 시작하는데 중후 기에 가서는 마제농경수확구가 증가하게 된다, 청동기시대에는 금속기의 영향을 받은 마제 석검등의 대단히 정교한 석기들이 훌현하고 또한 석기의 기능에 의례적인 기능이 추가되면 서 양식이 분화하기 시작한다, 그러면서 생산구들도 효율성이 높게 발달해 나가게 된다.

• Water for future
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• v.27 no.4
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• pp.19-22
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• 1994

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.4
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• pp.341-347
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• 2011

This work studies the performance of an injector for a monopropellant thruster, comparing a conventional and new injector types. The conventional injector consists of 8 nozzles on a convex surface allowing the jet to be diverged. The new injector, we suggested, is an impinging type with nozzle holes on a concave surface. The fuel streams through the nozzle holes are collide at a point on an axial direction, which allow to atomize the liquid streams and to spray more uniformly along circular direction. The performance of the injectors is investigated by using computational fluid dynamics, particle image velocimetry and high speed camera visualization.

• Journal of the Korean Society of Propulsion Engineers
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• v.8 no.4
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• pp.84-90
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• 2004

A performance evaluation is made in terms of thrust, impulse bit. and specific impulses for a set of mono-propellant hydrazine thrusters producing 0.95 lbf of nominal thrust at an inlet pressure of 350 psia. With a brief description on the hot-firing test configuration and procedures. a typical data obtained from steady-state firing mode is given directly showing the variational behavior of propellant supply pressure, mass flow rate, vacuum condition, and thrust. The performance features are successfully compared to the reference criteria of 1-lbf standard mono-propellant rocket engine. Additionally. a statistical inter-thruster treatment is concisely depicted for the justification of selected thrusters as a grouped member of flight model for spacecraft propulsion system.

• Plant Disease and Agriculture
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• v.4 no.2
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• pp.45-46
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• 1998

• Water for future
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• v.30 no.4
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• pp.127-130
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• 1997

• 건강소식
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• v.4 no.12 s.38
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• pp.12-14
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• 1976

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.89-95
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• 2017

The improvement of a flow coefficient for the recirculation chill-down flow in a main oxidizer shut-off valve has been presented. The flow coefficient, which is mainly affected by the recirculation outlet port size and the configuration inside the valve, has been predicted with measured flow coefficient values. The comparison of experimentally measured flow coefficient with the predicted value shows the effect of valve inside configuration on the flow coefficient. Consequently, the flow coefficient is twice the previous value and about 75% of the pressure loss assigned to the main oxidizer shut-off valve can be used for additional pressure losses for other components in the recirculation chill-down system of a launch vehicle.

• Applied Microscopy
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• v.37 no.2
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• pp.73-82
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• 2007

The antennae of millipedes have a prominent function in detecting various types of environmental stimuli. The structural modification of the antennae is closely associated with the degree of sense recognition. Here we study functional morphology of the antennae of the millipede Cawjeekelia pyongana using field emission scanning electron microscope (FESEM). The antennae generally include eight segments, called articles. On the surface of the antennae, there are a variety of sensory receptors which include olfactory and mechanical receptors. We could identify four different types of antennal sensory organs in C. pyongana as follows: apical cone (Ac), trichoid sensilla (Ts), chaetiform sensilla (Cs) and basiconic sensilla (Bs). The most prominent of which is four APs at the 8th article. Both of the Is and the Cs are abundantly observed almost all of the antennal segments. They are long and strong bristles with longitudinal grooves acuminating toward the tip. The Bs is further divided into three subtypes: large basiconic sensilla $(Bs_1)$, small basiconic sensilla $(Bs_2)$ and spiniform basiconic sensilla $(Bs_3)$. The $Bs_1$ is located at the 5th and 6th articles, while the $Bs_2$ and $Bs_3$ can be seen at the 5th and at the 7th article, respectively.