• 한국추진공학회지
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• 제27권1호
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• pp.9-16
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• 2023

본 연구에서는 고체추진기관 내 연소관단열재의 열분해와 삭마를 고려하여 단열재의 열응답을 예측할 수 있는 일차원 해석기법을 개발하였다. 모델링에는 연소관단열재 내부에서 발생하는 열분해로 인한 물성변화, 숯층의 팽창 및 분해가스 이동을 고려하였다. 또한 연소가스로부터의 복사/대류 열유속을 경계조건으로 적용하였으며 단열재 표면에서 발생하는 화학적 삭마속도를 대수식으로 모델링하였다. 해석기법 검증을 위해 열전대가 설치된 시험모터에 대한 해석을 수행하였다. 해석으로 도출된 온도분포는 시험과 유사한 값을 나타냈으며 시험과 예측 열파괴두께의 오차는 0.1 mm 내외였다.

• 기술혁신연구
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• 제3권1호
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• pp.1-34
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• 1995

Since 1982, the government of Korea has actively promoted vertical cooperative R&D programs between government-sponsored research institutes (GRIs) and private firms. A number of firms participated in the programs because cooperative R&D could lower the risk and could contribute to rapid commercialization of many technologies. This paper examines the effectiveness of vertical cooperative R&D projects by the modes of cooperation between GRIs and industrial firms, and analyzes the performance of participating firms' technology sourcing strategies for commercial utilization of cooperative R&D results at the project performed from 1982 to 1989 under the Government-Industry Cooperative R&D Program sponsored by the Ministry of Science and Technology(MOST) in Korea. The cooperative R&D projects are classified into 4 groups by two criteria, i.e., the level of participation of firms, and the breadth of cooperation. The findings suggest that firms should actively participate in cooperative R&D projects. In addition, in order to enhance commercial success, cooperation between GRIs and industrial firms should not be limited to R&D stage only. The breadth of cooperation should be extended to commercialization stage. Small- and medium-sized firms participating in vertical cooperative R&D projects in Korea usually lack internal technological capabilities that are needed to commercialize the results of cooperative R&D. Three different technology sourcing strategies - exclusive cooperative R&D strategy, in-house development augmented cooperative R&D strategy, and licensing-in supplemented cooperative R&D strategy - are empirically derived through cluster analysis of the relative usage rates cooperative R&D and of other supplementary technology acquisition methods. The findings suggest that the firms participating in vertical cooperative R&D projects should try to utilize other supplementary technology acquisition methods in order to achieve commercial utilization of the vertical cooperative R&D results.

• 한국수소및신에너지학회논문집
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• 제31권5호
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• pp.480-488
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• 2020

This study was conducted to improve the flow uniformity inside the chip tester through changing the flow path formation according to the inlet and outlet position of chamber. The internal flow and velocity distributions of the modified chamber models (Cases 1-3) were compared with the reference chamber model through three-dimensional Reynolds-averaged Navier-Stokes equations with k-ε turbulence model. The modified chamber models showed the superior flow uniformity characteristics compared to the reference chamber model. To investigate the flow uniformity in the chip tester, the standard deviation of the velocity was defined and compared. Through the internal flow analysis and assesment of the standard deviation, Case 2 among the test cases including the reference model showed the best flow uniformity generally.

• 대한화장품학회지
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• 제24권3호
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• pp.129-133
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• 1998

We have studied a relationship between the pattern of complex modulus change versus internal phase volume ratio and the rheological consistency of concentrated W/O emulsions with Magnesium Sulfate in the range 0.0 to 0.5 wt% and with different oil polarities, respectively. The rheological consistency with time of concentrated W/O emulsion was checked using Fudoh Rheometer and the coalescence of deformed water droplets was examined using polarized light microscope(LEICA DMRP). To find the pattern of complex modulus change of the concentrated emulsions versus internal phase volume ratio, the effect of varying water phase volume fraction from 0.78 up to 0.85 on viscoelastic measurements was investigated using rotational rheometer (HAAKE Rheostress RS 50). The rheological consistency was mainly destroyed by the coalescence of the deformed water droplets. The greater the increase of complex modulus was, the less coalescence occurred and the more consistent the concentrated emulsions were. And the pattern of complex modulus increase versus volume ratio has been explained with the resistance to coalescence of the deformed interfacial film of water droplets in concentrated W/O emulsion.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.1251-1258
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• 2008

The purpose of this research is to introduce the new temporary earth retaining wall system using landslide stabilizing piles. This system is a self-supported retaining wall(SSR) without installing supports such as tiebacks, struts and rakers. The SSR is a kind of gravity structures consisting of twin parallel lines of piles driven below dredge level, tied together at head of soldier piles and landslide stabilizing piles by beams. There are three types of excavation wall structures: standard method for medium retained heights(<8.0m), internal excavation method and slope excavation method for deep-excavation applications(>8.0m). In the present study, the measured data from seven different sites which the SSR was used for excavation were collected and analyzed to investigate the characteristic behavior lateral wall movements associated with urban excavations in Korea.

• Corrosion Science and Technology
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• 제21권1호
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• pp.53-61
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• 2022

Alloys of Fe-(5.3-29.8)%Mn-(1.1-1.9)%Al-(0.4-0.5)%C were oxidized at 550 ℃ to 650 ℃ for 20 h to understand effects of alloying elements on oxidation. Their oxidation resistance increased with increasing Mn level to a small extent. Their oxidation kinetics changed from parabolic to linear when Mn content was decreased and temperature was increasing. Oxide scales primarily consisted of Fe₂O₃, Mn₂O₃, and MnFe₂O₄ without any protective Al-bearing oxides. During oxidation, Fe, Mn, and a lesser amount of Al diffused outward, while oxygen diffused inward to form internal oxides. Both oxide scales and internal oxides consisted of Fe, Mn, and a small amount of Al. The oxidation of Mn and carbon transformed γ-matrix to α-matrix in the subscale. The oxidation led to the formation of relatively thick oxide scales due to inherently inferior oxidation resistance of alloys and the formation of voids and cracks due to evaporation of manganese, decarburization, and outward diffusion of cations across oxides.

• 한국군사과학기술학회지
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• 제25권1호
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• pp.1-8
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• 2022

Electronic equipment mounted on military vehicles is exposed to external shocks and vibrations. This causes problems in tactical operation and also causes cost loss in equipment maintenance. Therefore, to optimize the test standards for military vehicles with vibration, dynamic characteristics should be analyzed and standardized through actual driving tests. In this paper, the internal structure of 2.5tons military vehicle is designed in the form of a drawer and lathe, and the dynamic characteristics are identified by experiment, and the design is proposed.

• 기술혁신연구
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• 제23권1호
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• pp.61-86
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• 2015

본 연구는 2012년 과학기술정책연구원(STEPI)의 기술혁신조사(KIS)를 이용하여, R&D협력과 내부R&D투자와의 양방향성 관계를 규명하고, 내부R&D투자와 R&D협력이 기술혁신성과에 주는 효과를 분석하였다. 우선 기업의 내부R&D투자와 R&D협력 간의 상호 작용에 관해서는 두 개의 방정식을 설정하고 SUR 모형으로 동시에 추정하였고 내부R&D투자와 R&D협력이 기업의 기술혁신성과에 미치는 효과는 Probit 모형으로 추정하였다. 국내 R&D 활동에 관한 기존 문헌들과는 달리 본 연구는 R&D협력, 내부R&D투자 및 기술혁신과정의 구조적 체계를 감안하여 종합적인 분석을 제시하고자 하였다. 분석결과, R&D협력과 내부R&D투자의 관계는 서로 양방향의 긍정적인 효과가 있음을 확인하였고 내부R&D투자는 기술혁신 실현 가능성을 높인다는 점을 발견하였다. 결론적으로 내부R&D투자와 R&D협력 간의 양방향성과 보완성이 존재하므로 이러한 기능을 높이는 것이 R&D시스템의 효율성 제고에 도움이 된다는 정책적 시사점을 도출하고 있다.

• 한국자동차공학회논문집
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• 제4권3호
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• pp.199-210
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• 1996

The measurements of velocities of internal flow in a scaled-up nozzle were made by laser Doppler velocimetry in order to clarify the effect of internal flow on the characteristics of fuel spray. The investigated length to diameter ratio(L/d) of the orifice were 1, 3, 4, 5 and 8, and inlet radius to diameter ratio(r0/d) were 0 and 0.5. Mean and fluctuating velocities and discharge coefficients were obtained at various Reynolds number ranging between 15,000 and 28,000, and L/d ranging between 1 and 8 in sharp and round inlet nozzle. The turbulent intensity and turbulent kinetic energy at exit in a sharp inlet nozzle were higher than that in a round inlet nozzle. For sharp inlet nozzle, fluctuating velocities near exit were decreased with increasing L/d.

• 한국항행학회논문지
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• 제6권2호
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• pp.113-118
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• 2002

본 논문에서는 휴대단말기 내장형 GPS(Global Positioning System) 안테나를 설계 제작하였다. 안테나를 소형화하는 방법으로 비유전율이 높은 유전체 기판(${\varepsilon}_r$=90)과 작은 접지면($13{\times}13$ mm)을 사용하였다. 또한 안테나의 수신이득 증대를 위하여 증폭회로가 포함된 능동형으로 구성했다. 제작된 안테나의 특성을 측정한 결과, 안테나의 최대이득은 약 12 dBi, 축비는 3 dB 이하이며 증폭회로의 소비전류는 4 mA 이하이다.