• 한국분말재료학회지
• /
• 제10권6호
• /
• pp.422-429
• /
• 2003

The reduction mechanism of the composite powders mixed with $WO_3$ and CuO has been studied by using thermogravimetry (TG), X-ray diffraction, and microstructure analyses. The composite powders were made by simple Turbula mixing, spray drying, and ball-milling in a stainless steel jar with the ball to powder ratio of 32 to 1 at 80 rpm for 1 h without process controlling agents. It is observed that all the oxide composite powders are converted to W-coated Cu composite powder after reducing treatment under hydrogen atmosphere. For the formation mechanism of W-coated Cu composite powder, the sequential reduction steps are proposed as follows: CuO contained in the ball-milled composite powder is initially reduced to Cu at the temperature range from 20$0^{\circ}C$ to 30$0^{\circ}C$. Then, $WO_3$ powder is reduced to W $O_2$ via W $O_{2.9}$ and W $O_{2.72}$ at higher temperature region. Finally, the gaseous phase of $WO_3(OH)_2$ formed by reaction of $WO_2$ with water vapour migrates to previously reduced Cu and deposits on it as W reduced by hydrogen. The proposed mechanism has been proved through the model experiment which was performed by using Cu plate and $WO_3$ powder.

• 한국추진공학회지
• /
• 제23권4호
• /
• pp.61-69
• /
• 2019

세 가지 다른 온도($60^{\circ}C$, $70^{\circ}C$ 그리고 $75^{\circ}C$)에서 1년 동안 복기추진제의 가속 노화 시험을 수행하였다. 추진제의 노화 특성을 평가하기 위해 고성능 액체크로마토그래피(HPLC)와 AKTS-Thermokinetics 소프트웨어를 사용하여 안정제 함량과 속도론적 분석을 수행하였다. 그 결과, 추진제의 안정제 함량은 노화 온도 및 노화 기간에 따라서 점차적으로 감소하였다. $75^{\circ}C$에서의 안정제 감소 속도는 $70^{\circ}C$와 비교하여 약 2배 정도 빠른 것으로 나타났다. 이러한 실험값들을 속도론적 SB 모델과 2단계 모델로 모사하였고, n1=1, n2=0에서 실제데이터를 가장 잘 모사하였다.

• 한국수소및신에너지학회논문집
• /
• 제35권2호
• /
• pp.152-161
• /
• 2024

In this study, a fuel cell system for future defense unmanned vehicles was designed and validated. A Co/Al₂O₃-Ni foam catalyst for NaBH₄ hydrolysis was characterized using several analytical methods. A NaBH₄ hydrogen generation system with the Co/Al₂O₃-Ni foam catalyst continuously generated hydrogen at elevated reaction temperatures. The fuel cell system with the NaBH₄ hydrogen generation system was designed and tested. The performance of the fuel cell system was comparable to that of the fuel cell system using pure hydrogen. Therefore, the fuel cell system with the NaBH₄ hydrogen generation system is a suitable power source for future defense unmanned vehicles owing to its easy refueling and simple system.

• 한국응용과학기술학회지
• /
• 제35권3호
• /
• pp.865-875
• /
• 2018

식물성 오일을 이용한 바이오 항공유의 제조공정에서 탈산소 반응의 적절한 운전조건 선정을 통한 생성물 물성 최적화는 최대의 바이오항공유 수율을 얻기 위해 필수적인 요소이다. 이에 따라 팜유의 탈산소화 반응이 1 wt.% $Pt/Al_2O_3$촉매가 장입된 내경이 1인치인 고정층 반응기에서 수행되었다. 업그레이딩 공정을 통하여 수송 연료로 활용될 수 있는 액체 생성물(organic liquid product)은 가스크로마토그래피 방법으로 그 조성을 분석하였다. 피드 내의 팜유/수소 비율과 수소 압력은 탈카르복실레이션과 수첨탈산소 반응에 영향을 주어 생성물의 조성 변화를 초래하였다. 반응 온도가 증가함에 따라 탈산소 생성물의 연속적 크래킹 반응이 촉진되어 $C_5{\sim}C_{14}$영역의 생성물 조성이 증가하였다. 본 연구의 결과는 팜유의 탈산소화 반응 특성의 이해 뿐 아니라 연속 공정인 수첨 업그레이딩 공정을 통한 바이오 항공유의 제조에 도움을 줄 수 있다.

• 한국군사과학기술학회지
• /
• 제23권5호
• /
• pp.444-451
• /
• 2020

This study was conducted to develop the hydraulic brake assembly for MUAV(Medium-altitude Unmanned Aerial Vehicle). The brake assembly has the self-gap adjuster which performs to maintain a constant gap between the piston and the disk, even if the friction pad wore down. The function of adjuster helps to keep the brake-reaction speed constant and prevent the unnecessary abrasion of the wear pad during the life of the brake assembly. The development of the aircraft hydraulic brake assembly with the self-gap-adjuster in this paper is the first ever in South Korea. The concept of the mechanism was defined and the formula which is necessary to calculate the friction force was set up in the paper. The tester was invented for the functional test and the proper operation of the self-gap-adjuster was confirmed through the test. Dynamo tests and flight tests were also carried out to verify the braking performance of the brake assembly.

• 한국재료학회지
• /
• 제4권3호
• /
• pp.339-348
• /
• 1994

탄소/페놀릭 복합재의 삭마 미세구조와 특성에 대하여 설명하였다. 삭마현상은 추진제와 산화제 사이의 반응에 의한 수증기와 탄산가스의 몰분율에 의해 좌우된다. 그러나, 이 연구논문은 삭마현상이 탄소섬유의 직조형태, 직조밀도, tow크기에 의해서도 변화될 수 있음을 주사전자현미경, 밀도, 열전도도. 삭마표면등을 통해 설명했다. 3가지의 직조형태중, 3K8HS 직조구조가 3K twill구조나 12K8HS구조보다 우수한 내삭마성을 보임을 설명했다.

• Korean Chemical Engineering Research
• /
• 제50권2호
• /
• pp.343-347
• /
• 2012

충전형 저온 플라즈마 반응기 내에서의 가스 상 시안화합물의 분해특성을 반응기로 투입되는 방전 전력, 시안화합물의 유입농도, 운반기체인 공기의 습도 및 반응기 내의 충전물질 등을 변수로 연구하였다. 저온플라즈마 방전의 경우 시안화합물들의 분해는 트리클로로에틸렌에 비하여 상대적으로 매우 낮은 효율을 보였다. 그러나 플라즈마 방전 영역에 알루미나 또는 백금/알루미나 구슬을 충전한 경우 분해효율이 크게 높아졌으며 이는 플라즈마 반응과 더불어 백금/알루미나의 촉매작용에 의한 촉매 반응이 동시에 작용함에 기인한 것으로 판단된다.

• 항공우주시스템공학회지
• /
• 제9권3호
• /
• pp.23-30
• /
• 2015

In this study, a transient structural load analysis system was constructed to calculate the applied load on the suspension equipment corresponding to the aircraft flight conditions based on military specifications. Aircraft flight data (altitude, velocity, acceleration, angle of attack and etc. at aircraft center of gravity) were used as input parameters and the calculated load of the suspension equipment at wings on the left and right side was printed out for the structural load analysis. As a calculation procedure, first of all, load analysis was carried out at the center of gravity of the external store, Secondly, a trial reaction force analysis was conducted on hook and swaybrace of suspension equipment. All procedure of calculations was programed to analyze the structural load automatically. To verify the numerical results, structural load analysis using the experimental flight data was performed.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제5권3호
• /
• pp.343-355
• /
• 2005

As the propellants decompose, they release nitrogen oxides which reduce the shelf life of the propellants by accelerating decomposition rate. The activated carbon fiber was used to extend the shelf life of the propellants that was stockpiled by the military. It is found that the activated carbon fiber adsorbs the nitrogen oxides which were produced by spontaneous reaction of the propellants. As a result, the activated carbon fiber extend the shelf life of the propellants by reducing decomposition rate of the propellants. If 20g of propellant store with 2g of activated carbon fiber, the shelf life of the propellants can be lengthened by 1.4 times.

• 한국군사과학기술학회지
• /
• 제8권1호
• /
• pp.14-24
• /
• 2005

A propellant mainly consisting of nitric ester including nitrocellulose, nitroglycerine and nitroguanidine is characteristic of being decomposed naturally. And this phenomenon is known as being affected mostly by its storing temperature. In this research, the effect of storing temperature on self life has been studied by measuring the contained quantity of residual stabilizer of propellant KM30A1, ignition powder and combustible cartridge case, which are parts of 155MM propelling charge K676 and K677; the method for the measurement is acceleration aging test, and decomposition reaction equation and Berthlot Equation were used for the calculation. The result of this research shows that propellant KM30A1, ignition powder, combustible cartridge case in order of decreasing self life, and the self life decreases to 1/3 as the temperature increases by $10^{\circ}C$.