• Journal of the Korean Society of Propulsion Engineers
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• v.27 no.1
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• pp.9-16
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• 2023

This paper investigated the method to predict a thermal response of internal insulation in a solid rocket motor considering both thermal decomposition and ablation. Changes in properties due to the thermal decomposition, swelling of char layer and movement of decomposition gases inside the material were considered during a modeling. And radiative/convective heat flux from the exhaust gas were applied as boundary conditions, while the chemical ablation of the material surface is modeled with algebraic equations. Test SRM with thermocouples was solved for a validation purpose. The results showed that predicted temperatures have identical trends and values compared to the experimental values. And an error of predicted thermal destruction depth was around 0.1 mm.

• Journal of Technology Innovation
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• v.3 no.1
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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.

• Transactions of the Korean hydrogen and new energy society
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• v.31 no.5
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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.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.24 no.3
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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.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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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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• v.21 no.1
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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.

• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.1
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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.

• Journal of Technology Innovation
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• v.23 no.1
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• pp.61-86
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• 2015

This study provides an empirical analysis based on 2012 Korea Innovation Survey (STEPI) to investigate the relation between R&D cooperation and in-house R&D investment. The study further analyzes the effect of the R&D cooperation and in-house R&D investment on technical innovation. First, the relation between company's in-house R&D investment and R&D cooperations is estimated with the two equations using SUR models. Second, the effect of in-house R&D investment and R&D cooperation on the company's technical innovation is estimated using Probit model. This study differs from other existing R&D studies using Korean data in that empirical models are based on structural relationships among in-house R&D, R&D cooperation, and technical innovation. The results can be summarized as follows; the R&D cooperation expands the in-house R&D investment and the in-house R&D strengthen the R&D cooperation. Furthermore, In-house R&D investment increases the chances of success in innovation. As we obtain evidence of complementary relation between R&D cooperation and in-house R&D investment, it is necessary to develop environment conducive to this complementarity in order to have more efficient R&D system.

• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.3
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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.

• Journal of Advanced Navigation Technology
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• v.6 no.2
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• pp.113-118
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• 2002

In this paper, an internal GPS antenna for mobile phones is designed and fabricated. For the miniaturization of the antenna, high permittivity dielectric substrate((${\varepsilon}_r$=90) and small ground plane ($13mm{\times}13mm$) are used. To increase the receive gain, the antenna is composed with LNA(Low Noise Amplifier). Results of the manufactured antenna($13mm{\times}13mm{\times}8mm$) show that the maximum antenna gain is about 12 dBi, the axial ratio is less than 3 dB, and the current consumption of LNA is less than 4 mA.