• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.77-78
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• 2011

A multi-step quasi-global mechanism is developed for the kerosene/oxygen combustion analysis including dissociation products. Reaction constants of the global reaction are determined to have agreement with experimental data. The mechanism is used for the numerical analysis of the combustion flow field of the kerosene/oxygen shear coaxial injector. The results from high-resolution numerical analysis confirmed qualitatively that the recess enhance the fuel/air mixing and combustion efficiency by the increased flow instabilities.

• Journal of the Daesoon Academy of Sciences
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• v.26
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• pp.77-110
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• 2016

The purpose of this article is to study on the Correlative linkage between the cosmic principle of birth-growth and contraction-recess and the Non action Tao. The split time between birth-growth and contraction-recess is the conflict between the Prior Time and Posterior Time as the Great Renewal. The cycle of this Chaotic Renewals is the cycle of a cosmic circulation as 129,600 years. In relation to the correlative linkage of function, Jeong-san Sangje governs all the beings of the universe by means of the cosmic principle birth-growth and contraction-recess. Also Jeong-san Sangje, using the Non action Tao governing all the beings of the universe and let them exist as the original selves. Thus, the two necessities are mutual interdependent and mutual complementary. In relation to the correlative linkage of substance, Jeong-san Sangje is included in the cosmic life which forms of all the existences. That is personal God of Jeong-san Sangje that is a part of the cosmic life. So that Jeong-san Sangje is included in the cosmic life, the basis of all the cosmic affairs. He is also subordinate to the cosmic principle but he simultaneously governs it. Jeong-san Sangje is trans-versal mediator between the cosmic principle and the cosmic life of Non action Tao, since it is the origin of his mind. To understand the nature of Jeong-san Sangje who becomes one with the cosmic life, the old causal way of thinking which inquires the timely order and seeks for causes and effects should be abandoned. The new way of thinking is thus different from the old one. The core of cosmic life is abstracted as the essence-energy and god-blood. This structure is similar to the cosmic principle of birth-growth and contraction-recess. The death is a kind of event caused by the depletion of the essence, and all beings could altered into the god. It also would be returned to the natural birth place of the cosmos, as it were, that can be called the 'Return to the Origin'. As the cosmos goes to the new epoch, humans have been living together with the cosmic principle. Now we can expect the Posterior Time to open to humans as cosmic life of Non action Tao.

• Proceedings of the IEEK Conference
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• 2002.06b
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• pp.213-216
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• 2002

A double-heterostructure AIGaAs/GaAs PHEMT (Pseudomorphic High Electron Mobility Transistor) using digital recess has been successfully realized. Futhermore, the differences of gm,nax, fT, fmax between two samples are as low as 0.62%, 1.58% and 2.56 % respectively. Experimental results are presented demonstrating the etch rate and Process invariability with respect to hydrogen peroxide and acid exposure times with uniformity among devices on a sample.

• Clinical and Experimental Pediatrics
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• v.51 no.10
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• pp.1123-1126
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• 2008

A lung hernia, defined as the protrusion of pulmonary tissue and pleural membranes through a defect in the thoracic wall, is a rare event. It can be congenital or acquired, and cervical, thoracic, or diaphragmatic in location. We report the rare occurrence of a congenital atraumatic lung herniation through the azygoesophageal recess. An 8-month-old male infant, who was born at 35 weeks gestation, had a chronic cough. Chest radiography showed haziness at the right lower lobe of the lung (RLL). Chest computed tomography (CT) revealed herniation of the RLL through the azygoesophageal recess. If persistent unilateral haziness is observed on chest radiography, the possibility of lung herniation should be considered.

• Journal of the Korean Society of Propulsion Engineers
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• v.24 no.1
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• pp.24-33
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• 2020

In this study, model combustion tests were conducted to investigate the combustion instability characteristics of swirl coaxial injectors for a liquid rocket engine. To examine the effects of the combustion chamber resonant frequency and the injector mixing conditions, pressure fluctuations in the combustion chamber were measured by changing the combustion chamber length, injector recess length, and propellant mixture ratio. From the test results, the variation in the pressure fluctuations for each experimental condition was confirmed and the combustion stability was evaluated by stability mapping. It was found that the longitudinal mode and Kelvin-Helmholtz instabilities occurred due to the change in the combustion chamber and recess lengths.

• Journal of the Korean Society of Propulsion Engineers
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• v.20 no.4
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• pp.68-76
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• 2016

This research is carried out for the performance evaluation of the injector that is one of the critical components of bipropellant-rocket-engine. Spray characteristics are investigated in detail according to the recess length and injection pressure on the swirl-coaxial-injector using gaseous methane and liquid oxygen as propellants. A visualization is conducted by the Schlieren photography that is composed of a light source, concave mirrors, knife, and high-speed-camera. A hollow-cone-shape is identified in the liquid spray that is spread only by inner injector and the spray angle is decreased due to the diminution of swirl strength in accordance with the increase of the length of injector orifice. When the injector sprays the liquid through the inner injector with the aid of gas through the outer injector, the spray angle in external mixing region tends to increase with rise of the recess length, while in internal mixing region, it is decreased. It is also confirmed that the same tendency of the spray angle with recess length appears irrespective of the injection pressure of liquid spray.

• Journal of ILASS-Korea
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• v.10 no.3
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• pp.29-37
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• 2005

The spray and acoustic characteristics of a gas/liquid swirl coaxial injector are studied experimentally. The self-pulsation is defined as a pressure and flow rate oscillations by a time-delayed feedback between liquid and gas phase. Self-pulsation has strong influences on atomization and mixing processes and accompanies painful screams. So. the spray and acoustic characteristics are investigated. Spray patterns are observed by shadow photography technique in order to determine the onset of self-pulsation. And self-pulsation boundary with Injection conditions and recess length is get. To measure the frequency of the spray oscillation. oscillation of the laser intensity which passes through spray is analyzed by Fast Fourier Transform. For acoustic tests, a PULSE System was used. Acoustic characteristics of a swirl coaxial injector are investigated according to the injection conditions. such as the pressure drop or the liquid and gas phase. and injector geometries. such as recess length and gap size between the inner and outer injector. Front the experimental results. the increase of recess length leads to the rapid increase of the sound pressure level. And as the pressure drop of the liquid phase increases. the frequency of the self?pulsation shifts to the higher frequency. The frequency of spray oscillations is the same as that of the acoustic fields by self-pulsation.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.125-130
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• 2004

Experimental study on combustion characteristics of double swirl coaxial injectors has been conducted for the assessment of critical injector design parameters. A reusable, unielement thrust chamber has been fabricated with a water-cooled copper nozzle. Two principle design parameters, a swirl angle and a recess length, have been investigated through hot firing tests for the understanding of their effects on high pressure combustion. Clearly, both parameters considerably affect the combustion efficiency, dynamics and hydraulic characteristics of an injector. Internal mixing of propellants in a recess region increases combustion efficiency along with the increase of a pressure drop required for flowing the same amount of mass flow rates. It is concluded that pressure buildup due to flame can be released by the increase of LOx flow axial momentum or the reduction of a recess length. Dynamic pressure measurements of the thrust chamber show varied dynamic behaviors depending on injector configurations.

• Journal of the Semiconductor & Display Technology
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• v.12 no.3
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• pp.23-27
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• 2013

This paper is for enhancing the breakdown voltage of MHEMTs with an InP-etchstop layer. Gate-recess structures has been simulated and analyzed for the breakdown of the devices with the InP-etchstop layer. The fully removed recess structure in the drain side of MHEMT shows that the breakdown voltage enhances from 2V to almost 4V and that the saturation current at gate voltage of 0V is reduced from 90mA to 60mA at drain voltage of 2V. This is because the electron-captured negatively fixed charges at the drain-side interface between the InAlAs barrier layer and the $Si_3N_4$ passivation layer deplete the InGaAs channel layer more and thus decreases the electron current passing the channel layer. In the paper, the fully-recessed asymmetric gate-recess structure at the drain side shows the on-breakdown voltage enhancement from 2V to 4V in the MHEMTs.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.04a
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• pp.20-23
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• 2011

The spray and atomization characteristics of swirl coaxial injectors which use gas methane and LOx as propellants are investigated experimentally with a recess length variation. Mass distribution and spray angle are measured by a patternator and droplet size to find atomization characteristics are measured by GSV(Global Size and Velocity) system. As a result, when the liquid sprayed, the spray angle decreased and the atomization characteristic was improved with the recess length increase. When the gas and liquid injected simultaneously, the spray angle was decreased and the atomization characteristic was improved comparing to only the liquid injection.