• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2479-2482
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• 2010

Using a pinhole-type glass nozzle equipped for a corona-excited supersonic expansion (CESE), precursor 2,6-dichlorotoluene seeded in a large amount of inert carrier gas helium was discharged to produce jet-cooled but electronically excited benzyl-type radicals. The visible vibronic emission spectrum was recorded with a long-path monochromator to observe vibronic bands in the $D_1{\rightarrow}D_0$ electronic transition of benzyl-type radicals. The spectral analysis revealed the generation of not only the 2,6-dichlorobenzyl radical as a typical product, but also the o-chlorobenzyl radical as an unexpected species, which indicates the possible molecular rearrangement in eliminating a chlorine atom from the benzene ring. A possible mechanism is proposed for the formation of the o-chlorobenzyl radical from the precurs or in the gas phase.

• International Journal of Computer Science & Network Security
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• 제21권12호
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• pp.93-100
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• 2021

Satellite communication for high altitude platform stations (HAPS) and geostationary orbit (GEO) systems suffers from sand and dust (SANDU) storms in desert and arid regions. The focus of this paper is to propose common relations between HAPS and GEO for the atmospheric impairments affecting the satellite communication networks operating above Ku-band crossing the propagation path. A double phase three-dimensional relationship for HAPS and GEO systems is then presented. The comparison model present the analysis of atmospheric attenuation with specific focus on sand and dust based on particular size, visibility, adding gas effects for different frequency, and propagation angle to provide systems' operations with a predicted vision of satellite parameters' values. Thus, the proposed system provides wide range of selecting applicable parameters, under different weather conditions, in order to achieve better SNR for satellite communication.

• 한국추진공학회지
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• 제25권5호
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• pp.18-26
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• 2021

본 연구에서는 실험실 규모의 산업용 가스터빈 싱글노즐 연소기에서의 공진주파수 해석을 위한 고유값 도출을 목적으로 하는 1D 네트워크 모델을 개발하였다. 현대의 산업용 가스터빈은 다양한 요구 조건을 동시에 만족시키기 위하여 일반적으로 매우 복잡한 구조와 유동의 형태를 가지고 있다. 이러한 복잡한 연소기 특징 중 하나인 동일한 축 방향 위치에서 서로 반대 방향의 유동 흐름을 갖는 시스템에서의 네트워크 모델 구현을 목적으로 하였다. 네트워크 모델을 통해 음향장을 해석한 결과를 실제 형상을 그대로 해석한 헬름홀츠 기반의 모델링 결과와 비교하였을 때, 공진주파수와 모드 분포로부터 해석의 타당성을 검증하였다.

• 한국산업융합학회 논문집
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• 제25권4_2호
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• pp.699-706
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• 2022

In this study, Directed energy deposition (DED) among additive manufacturing is applied to repair damaged spindle key parts of planner miller. The material of the spindle key is SCM415, and the P21 Powder is used. In order to find the optimal deposition conditions for DED equipment, a single-line deposition experiment is conducted to analysis five parameters. The laser power affects the width, and the height is a parameter affected by coaxial gas and powder gas. In addition, laser power, powder feed rate, coaxial gas, and powder gas are parameters that affect dilution. Otimal deposition is that 400 W of laser power, 4.0 g/min of powder feed rate, 6.5 L/min of coaxial gas, 3.0 L/min of powder gas and 4.5 L/min of shield gas. By setting the optimum conditions, a uniform deposition cross section in the form of an ellipse can be obtained. Damage recovery process of spindle key consists of 3D shape design of the base and deposition parts, deposition path creation and deposition process, and post-processing. The hardness of deposited area with P21 powder on the SCM415 spindle key is 336 HV for the surface of the deposition, 260 HV for the boundary area, and 165 HV for the base material.

• 대한가정학회지
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• 제36권3호
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• pp.1-14
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• 1998

This research focuses the safety problems for consumers with the viewpoint of behaviorism. Specially three issues are addressed: 1) Variables influencing the consumer's safety consciousness 2) The comparision of consumer's safety seeking behavior according to the product type 3) The relation of variables influencing the consumer's safety-seeking behaviors. In this paper, I deal with mainly the gas products and agricultural products and then observe the consumers' reaction for those two products concerning to the consumer's safety problem. For this purpose, I distributed the questionnaire to the residents I Seoul and suburban area of age between 20 and 60 years old. As a result, consumers put high values and concerns on general safety, but have quite negative concepts on society's safety problems generally. It was found that the consciousness on this problem was higher among those people who were reading journals for consumers, who have high education or high incomes, or who were unemployed house wives. In gas products, the level of consumer's safety seeking behavior and subareas were higher than in agricultural products. In the matter of the variables which affect the consumer's safety seeking behavior directly, those were safety consciousness variables and experience of reading journal for consumer in gas products, and safety consciousness vatiabls, consumer education experience, experience of injury, being employed and being married in agricultural products. Also as the result of path analysis, experience of reading journal for consumer, being employed, education and income level influenced indirectly the consumer safety seeking behavior.

• International Journal of Aeronautical and Space Sciences
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• 제9권1호
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• pp.100-110
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• 2008

It is not easy to monitor and identify all engine faults and conditions using conventional fault detection approaches like the GPA (Gas Path Analysis) method due to the nature and complexity of the faults. This study therefore focuses on a model based diagnostic method using Neural Network algorithms proposed for fault detection on a turbo shaft engine (PW 206C) selected as the power plant for a tilt rotor type unmanned aerial vehicle (Smart UAV). The model based diagnosis should be performed by a precise performance model. However component maps for the performance model were not provided by the engine manufacturer. Therefore they were generated by a new component map generation method, namely hybrid method using system identification and genetic algorithms that identifies inversely component characteristics from limited performance deck data provided by the engine manufacturer. Performance simulations at different operating conditions were performed on the PW206C turbo shaft engine using SIMULINK. In order to train the proposed BPNN (Back Propagation Neural Network), performance data sets obtained from performance analysis results using various implanted component degradations were used. The trained NN system could reasonably detect the faulted components including the fault pattern and quantity of the study engine at various operating conditions.

• 동력기계공학회지
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• 제13권6호
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• pp.95-101
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• 2009

The generator for gas turbine power generation consists of the rotor which generates magnetic field, the winding coil which is the path for the field current and the wedge and retaining ring which prevents the radial movement of the coil. Relatively severe deformation was observed at the coil end section during the inspection of the generator for peaking-load operation, and the thermal-electricity and the centrifugal force were evaluated by the simple modeling of the windings to find the cause. But the simulation stress was not sufficient to induce the coil plastic deformation. The analysis result seems to be applicable to the base-load generators which runs continuously without shut down up to a year, but there had been more deformation than simulated for the generator which is started up and shut down frequently. The cause of the coil deformation was the restriction of the expansion and shrinkage. The restriction occurs when the winding coil shrinks, and the stress overwhelms the yield stress and cause the plastic deformation. The deformation is accumulated during the start-ups and shut-downs and the thermal growth occurs. The factors which induce the coil restriction during the expansion and shrinkage should be reduced to prevent the unallowable deformation. The resolutions are cutting off the field current earlier during the generator shut-down, modifying the coil end section to remove the stress concentration and making the insulation plate inserted between the coil end section and the retaining ring have the constant thickness.

• 한국전기전자재료학회논문지
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• 제26권5호
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• pp.401-409
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• 2013

Numerical analysis on RF (Radio-Frequency) thermal plasma treatment of micro-sized Ni metal was carried out to understand the synthesis mechanism of nano-sized Ni powder by RF thermal plasma. For this purpose, the behaviors of Ni metal particles injected into RF plasma torch were investigated according to their diameters ($1{\sim}100{\mu}m$), RF input power (6 ~ 12 kW) and the flow rates of carrier gases (2 and 5 slpm). From the numerical results, it is predicted firstly that the velocities of carrier gases need to be minimized because the strong injection of carrier gas can cool down the central column of RF thermal plasma significantly, which is used as a main path for RF thermal plasma treatment of micro-sized Ni metal. In addition, the residence time of the injected particles in the high temperature region of RF thermal plasma is found to be also reduced in proportion to the flow rate of the carrier gas In spite of these effects of carrier gas velocities, however, calculation results show that a Ni metal particle even with the diameter of $100{\mu}m$ can be completely evaporated at relatively low power level of 10 kW during its flight of RF thermal plasma torch (< 10 ms) due to the relatively low melting point and high thermal conductivity. Based on these observations, nano-sized Ni metal powders are expected to be produced efficiently by a simple treatment of micro-sized Ni metal using RF thermal plasmas.

• KEPCO Journal on Electric Power and Energy
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• 제5권2호
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• pp.93-101
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• 2019

$1,100^{\circ}C$급 가스터빈 1단 버켓 사용품 및 주조품 분석을 위하여 기계적 특성과 미세 구조를 분석하여 최종적으로 상기고온부품의 품질을 평가 하였다. 가스터빈 1단 버켓은 고온부품들 중 1단 노즐을 제외하고 가장 고온 및 고압의 환경에서 노출되어 운전되고 있으며, 또한 1단 버켓은 회전체이므로 손상 시 후단의 버켓 및 노즐에 대해 추가적인 설비 파손을 야기하여 막대한 경제적 손실을 초래할 수 있다. 따라서, 버켓의 국산화를 위한 주조품의 경우 발전소현장에 적용하여 사용하기 이전에 신뢰성이 선 검증되어야만 한다. 본 연구에서는 국내 주조품의 미세조직분석 및 기계적 특성평가를 수행하여 주조품질을 평가하고 전력연구원에서 설계한 품질조건을 만족함을 확인하였으며, 품질 비교를 위해 수명의 46% (11,067EOH)를 운전한 사용품에 대해서도 미세조직분석 및 기계적 특성 평가를 수행하였다.

• 한국추진공학회지
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• 제4권1호
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• pp.93-101
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• 2000

엔진 운용 중에 유로(flow Path)에 놓여 있는 팬 블레이드(blade)들은 많은 외부하중에 노출되어 있어서 고주기 피로(high cycle fatigue)에 의한 피로 파괴의 위험성이 크다. 그 중 가장 중요하게 평가되는 것이 주기적인 가진력에 의한 공진 현상과 그에 따른 피로파괴 가능성이다. 본 논문에서는 유동장 (flow field)이 지주(struts)에 의해 영향을 받게 되고, 이러한 유동장의 분포가 지주 후방에서 주기함수 형태로 팬 블레이드를 가진 할 때, 팬 블레이드에서의 진동 응답 특성과 구조적인 안정성을 평가하였다. 팬 블레이드의 피로강도를 시험적으로 평가하고, 팬 블레이드 전방 지주에 의한 공기 가진력을 가정하여 유한 요소 해석을 통한 구조적 안정성을 평가하였다. 그리고 엔진 시험에서 측정된 서지 압력 하중을 팬 블레이드의 유한요소 모델에 적용하여 구조적 영향을 평가함으로써 팬 블레이드의 구조적인 안정성을 확인하였다.