• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2009년도 제33회 추계학술대회논문집
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• pp.101-104
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• 2009

한국항공우주연구원에서는 2004년부터 전남대 및 (주)한화와 공동으로 하이드라진 분해촉매의 국내 개발을 위한 연구에 착수하였으며 약 5년간의 개발 기간을 거쳐 2009년에는 위성에서 요구하는 성능 및 수명 요구조건을 충분히 만족하는 촉매의 개발에 성공하였으며 우주 환경에서의 장기 연소시험을 통해 최종적인 품질 보증을 완료하였다. 본 논문에서는 촉매 개발과 관련된 연구과정과 물성치 측정 및 품질 보증시험 결과에 대해서 서술하였다.

• 한국재료학회지
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• 제29권6호
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• pp.343-348
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• 2019

Structural and mechanical effects of the dynamical precipitation in two copper-base alloys have been investigated over a wide range of deformation temperatures. Basing upon the information gained during the experiment, also some general conclusion may be formulated. A one concerns the nature of dynamic precipitation(DP). Under this term it is commonly understood decomposition of a supersaturated solid solution during plastic straining. The process may, however, proceed in two different ways. It may be a homogeneous one from the point of view of distribution and morphological aspect of particles or it may lead to substantial difference in shape, size and particles distribution. The effect is controlled by the mode of deformation. Hence it seems to be reasonable to distinguish DP during homogeneous deformation from that which takes place in heterogeneously deformed alloy. In the first case the process can be analyzed solely in terms of particle-dislocation-particle interrelation. Much more complex problem we are facing in heterogeneously deforming alloy. Deformation bands and specific arrangement of dislocations in form of pile-ups at grain boundaries generate additional driving force and additional nucleation sites for precipitation. Along with heterogeneous precipitation, there is a homogeneous precipitation in areas between bands of coarse slip which also deform but at much smaller rate. This form of decomposition is responsible for a specially high hardening rate during high temperature straining and for thermally stable product of the decomposition of alloy.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2023년도 학술발표회
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• pp.394-394
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• 2023

The world's sustainable growth is being severely hampered by the inefficient use of water resources. Despite the widely acknowledged importance of trade in global and regional water and food security, societal reliance on local production as well as international trade remains inadequately assessed. Therefore, using South Korea as a case study, this study fills in this research gap by applying the virtual water concept, the logarithmic mean divisia index (LMDI) method, and the Tapio decoupling model. The virtual water concept was used to estimate South Korea's net virtual water trade for major grain crops from 1992 to 2017. Then, the LMDI method was utilized to assess the driving factors causing changes in net virtual water trade. Lastly, the Tapio decoupling model was used to investigate the decoupling relationships between economic growth and the driving factors of net virtual water trade. Results showed that South Korea remains a net importer of virtual water flows with respect to grain crops, with an average import of 16,559.24 million m³ over the study period. In addition, the change in net virtual water trade could be attributed to water intensity effect, product structure effect, economic effect, and population effect. However, water intensity and economic effects were the major decisive factors for decrease and increase in net virtual water trade respectively, while the population and product structure effects had minor positive influences on the net virtual water trade. Furthermore, water intensity and economic growth showed a strong decoupling in most periods, while the decoupling state between product structure and economic growth was observed as expansive negative decoupling. Likewise, population size and economic growth showed a weak decoupling in most periods. The results reveal South Korea's status as it concerns the virtual water trade of grain crops, thus providing valuable insights into the sustainability of trade activities for the management of local water resources.

• 한국정보과학회논문지:데이타베이스
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• 제27권1호
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• pp.79-89
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• 2000

요약화일을 병렬로 처리하기 위해서는 효과적인 요약화일 분산 기법이 요구된다. Hamming Filter에서 분산 기법으로 이용되는 선형코드분산기법(LCDM)은 대부분의 경우 우수한 분산 성능을 갖지만 정적 특성 때문에 요약이 편중될 경우 요약화일을 균등하게 분산하기 어렵다. 또한 제한된 확장성과 비결정성(non-determinism)과 같은 문제점을 가지고 있다. 본 논문에서는 LCDM의 문제점을 해결하는 새로운 요약화일 분산 기법인 내적 기법(inner- product method)을 제안한다. 내적 기법은 요약의 내적에 의해 계산되는 요약 차이(signature difference)를 기반으로 하여 요약화일을 동적으로 분산한다. 다양한 데이타 작업부하에서 모의 실험을 통해 내적 기법이 LCDM보다 우수함을 보인다.

• 한국군사과학기술학회지
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• 제5권3호
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• pp.105-112
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• 2002

A combined process of non-thermal plasma and catalytic techniques has been investigated to treat toxic gas compounds in air. The treated gas in the present study is $CH_3$CN that has been known to be a simulant of toxic chemical agent. A planar type dielectric barrier discharge(DBD) reactor has been used to generate non-thermal plasma that produces various chemically active species, O, N, OH, $O_3$, ion, electrons, etc. Several different types of adsorbents and catalysts, which are MS 5A, MS 13X, Pt/alumina, are packed into the plasma reactor, and have been tested to save power consumption and to treat by-products. Various aspects of the present techniques, which are decomposition efficiencies along with the power consumption, by-product analysis, reaction pathways modified by the adsorbents and catalysts, have been discussed in the present study.

• 대한화학회지
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• 제12권4호
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• pp.146-149
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• 1968

A new chelate compound, tris(8-bydroxyquinolino)molybdenum(III), [$Mo(C_9H_6ON)_3$], has been prepared by the method of electrolytic reduction of the acidic molybdate solution. Thermal decomposition products of the chelate has been studied by DTA and TGA method. It is concluded that the decomposition product is a yellowish green colored bis(8-hydroxyquinolino)dioxo molybdenum(VI), [$MoO_2(C_9H_6ON)_2$].

• ETRI Journal
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• 제40권5호
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• pp.634-642
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• 2018

Projection spectral analysis is investigated and refined in this paper, in order to unify principal component analysis and independent component analysis. Singular value decomposition and spectral theorems are applied to nonsymmetric correlation or covariance matrices with multiplicities or singularities, where projections and nilpotents are obtained. Therefore, the suggested approach not only utilizes a sum-product of orthogonal projection operators and real distinct eigenvalues for squared singular values, but also reduces the dimension of correlation or covariance if there are multiple zero eigenvalues. Moreover, incremental learning strategies of projection spectral analysis are also suggested to improve the performance.

• Nonlinear Functional Analysis and Applications
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• 제27권1호
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• pp.189-201
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• 2022

The aim of the current work is to investigate the numerical study of a nonlinear Volterra-Fredholm integro-differential equation with initial conditions. Our approximation techniques modified adomian decomposition method (MADM) and variational iteration method (VIM) are based on the product integration methods in conjunction with iterative schemes. The convergence of the proposed methods have been proved. We conclude the paper with numerical examples to illustrate the effectiveness of our methods.

• 한국수소및신에너지학회논문집
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• 제13권2호
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• pp.101-109
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• 2002

This work was focused on the thermal decomposition of methane into hydrogen and carbon black without emitting carbon dioxide. Extensive experimental investigation on the thermal decomposition of methane has been carried out using a continuous flow reaction system with tubular reactor. The experiments were conducted at the atmospheric pressure condition in the wide range of temperature ($950-1150^{\circ}C$) and flow rate (250 - 1500 ml/min) in order to study their dependency on hydrogen yield. During the experiments the carbon black was successfully recovered as an useful product. Undesirable pyrocarbon was also formed as solid film, which was deposited on the inside surface of tubular reactor. The film of pyrocarbon in the reactor wall became thicker and thicker, finally blocking the reactor. The design of an efficient reactor which can effectively suppress the formation of pyrocarbon was thought to be one of the most important subjects in the thermal cracking of methane.

• Journal of Radiation Protection and Research
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• 제42권2호
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• pp.91-97
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• 2017

Background: A gamma energy identifying algorithm using spectral decomposition combined with smoothing method was suggested to confirm the existence of the artificial radio isotopes. The algorithm is composed by original pattern recognition method and smoothing method to enhance the performance to identify gamma energy of radiation sensors that have low energy resolution. Materials and Methods: The gamma energy identifying algorithm for the compact radiation sensor is a three-step of refinement process. Firstly, the magnitude set is calculated by the original spectral decomposition. Secondly, the magnitude of modeling error in the magnitude set is reduced by the smoothing method. Thirdly, the expected gamma energy is finally decided based on the enhanced magnitude set as a result of the spectral decomposition with the smoothing method. The algorithm was optimized for the designed radiation sensor composed of a CsI (Tl) scintillator and a silicon pin diode. Results and Discussion: The two performance parameters used to estimate the algorithm are the accuracy of expected gamma energy and the number of repeated calculations. The original gamma energy was accurately identified with the single energy of gamma radiation by adapting this modeling error reduction method. Also the average error decreased by half with the multi energies of gamma radiation in comparison to the original spectral decomposition. In addition, the number of repeated calculations also decreased by half even in low fluence conditions under $10^4$ ($/0.09cm^2$ of the scintillator surface). Conclusion: Through the development of this algorithm, we have confirmed the possibility of developing a product that can identify artificial radionuclides nearby using inexpensive radiation sensors that are easy to use by the public. Therefore, it can contribute to reduce the anxiety of the public exposure by determining the presence of artificial radionuclides in the vicinity.