• 한국전산유체공학회:학술대회논문집
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• 2006.10a
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• pp.101-105
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• 2006

The computational fluid dynamic analysis has been conducted for the thermo-chemical flow field in an arcjet thruster with mono-propellant Hydrazine (N2H4) as a working fluid. The Reynolds Averaged Navier-Stokes (RANS) equations are modified to analyze compressible flows with the thermal radiation and electric field. The Maxwell equation, which is loosely coupled with the fluid dynamic equations through the Ohm heating and Lorentz forces, is adopted to analyze the electric field induced by the electric arc. The chemical reactions of Hydrazine were assumed to be infinitely fast due to the high temperature field inside the arcjet thruster. The chemical and the thermal radiation models for the nitrogen-hydrogen mixture and optically thick media respectively, were incorporated with the fluid dynamic equations. The results show that performance indices of the arcjet thruster with 1kW arc heating are improved by amount of 180% in thrust and 200% in specific impulse more than frozen flow. In addition to thermo-physical process inside the arcjet thruster is understood from the flow field results.

• Current Optics and Photonics
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• v.6 no.4
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• pp.375-380
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• 2022

We demonstrate two types of light field displays based on waveguide grating coupler arrays: a line beam type and a point source type. Ultra violet imprinting of an array of diffractive nanograting cells on the top surface of a 50-㎛-thin slab waveguide can deliver a line beam or a point beam to a multidirectional light field out of the waveguide slab. By controlling the grating vectors of the nanograting cells, the waveguide modes are externally coupled to specific viewing angles to create a multidirectional light field display. Nanograting cells with periods of 300 nm-518 nm and slanted angles of -8.5°~+8.5° are fabricated by two-beam interference lithography on a 40 mm × 40 mm slab waveguide for seven different viewpoints. It is expected that it will be possible to realize a very thin and flexible panel that shows multidirectional light field images through the waveguide-type diffraction display.

• Magazine of the Korean Society of Agricultural Engineers
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• v.12 no.3
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• pp.2035-2042
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• 1970

Korean Janggi and Western plow to have developed for a long time in the east and west were tested and compared in their draft resistance. The charaderistic of Korean Janggi and plow to be able to make deep plowing, on of the most important factors influeneed the increased yield, were ofserved. The study was undertaken to obtain these basic factors' to device and construct the deep plowing Janggi. The results were as follow; 1. The draft resistance of Korean Janggi far less than that of plow and on the dry field, the influence of soil moisture contant to the draft resistance was larger in the Korean Janggi than in the western plow, but on the rice paddy, there was not differences between them. 2. The plow was more stable than that of Janggi in their operation. 3. The relation ship between the specific draft resistance and plowing depth was shown bygthe carved equation. $$K=Ax+\frac{B}{x}+C$$(K ; specific draft restance, x; plowing depth) A, B, C; Constant controled by soil and instrument factor) 4. Minimam values of the specific draft resistance were as follow; a. On the dry field; Korean Janggi; x = $8{\sim}14cm$ $4K=280{\sim}330gr/cm^2$$ Westean plow; x=$10{\sim}12cm$ $$K=480{\sim}490gr/cm^2$$ 6. On the rice paddy; Korean Janggi; x=$8{\sim}12cm$ $$K=255{\sim}280gr/cm^2$ Western plow; x=$7{\sim}10cm$ $$K=415{\sim}420grc/m^2$$

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.1
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• pp.104-117
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• 1999

The Composite materials has been used in the field of high technology industry because of high specific stiffness and high specific strength. Specially, the composite materials has been widely applied to the field of the aircraft and the transportation by the effectiveness of light weight due to low specific weight and reduction of the parts due to bonding, molding and so on. These advantages about the composite have led to study and apply in the transmission shaft for the aircraft and the drive shaft for the automobile. The composite material propeller shaft with the high vibrational stability was designed and analyzed. In order to verify the analysis, two types of experimental test which are the FFT analyzer with impact hammer and the rotational equipment were applied.

• Journal of the Korean Applied Science and Technology
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• v.31 no.2
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• pp.329-336
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• 2014

The conductive polymer composites have attracted considerable attention in the field of industry due to their electrical properties. To understand electrical properties of the composites, their volume specific resistance was measured. Electrical conductivity results showed percolation phenomena. Percolation theories are frequently applied to describe the insulator-to-conductor transitions in the composites composed of conductive filler and insulating matrix. It was found that the percolation threshold strongly depends on the aspect ratio of filler particles. The critical concentration of percolation formed is defined as the percolation threshold. The purpose of this study was to examine electrical properties of the epoxy resins filled with nickel. The sample was prepared using vehicle such as epoxy resin replenished with nickel powder, and the evaluation on their practical use was performed in order to apply them to electric and electronic industry as well as general field. The volume specific resistance of epoxy resin composites was 4.666~13.074 when using nickel powder. Weight loss of the conductive composites took place at $350^{\circ}C{\sim}470^{\circ}C$.

• The Plant Pathology Journal
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• v.38 no.6
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• pp.616-628
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• 2022

Resistance to pyraclostrobin due to a single nucleotide polymorphism at 143rd amino acid position on the cytochrome b gene has been a major source of concern in red pepper field infected by anthracnose in Korea. Therefore, this study investigated the response of 24 isolates of C. acutatum and C. gloeosporioides isolated from anthracnose infected red pepper fruits using agar dilution method and other molecular techniques such as cytochrome b gene sequencing, polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and allele-specific polymerase chain reaction (PCR). The result showed that four isolates were resistant to pyraclostrobin on agar dilution method and possessed GCT (alanine) codon at 143rd amino acid position, whereas the sensitive isolates possessed GGT (glycine). Furthermore, this study illustrated the difference in the cytochrome b gene structure of C. acutatum and C. gloeosporioides. The use of cDNA in this study suggested that the primer Cacytb-P2 can amplify the cytochrome b gene of both C. acutatum and C. gloeosporioides despite the presence of various introns in the cytochrome b gene structure of C. gloeosporioides. The use of allele-specific PCR and PCR-RFLP provided clear difference between the resistant and sensitive isolates. The application of molecular technique in the evaluation of the resistance status of anthracnose pathogen in red pepper provided rapid, reliable, and accurate results that can be helpful in the early adoption of fungicide-resistant management strategies for the strobilurins in the field.

• Journal of Korea Technology Innovation Society
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• v.6 no.3
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• pp.373-390
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• 2003

With limited resources, proper allocation of the national R&D budget is very crucial matter for reinforcing the national competence, and the importance of selecting strategic R&D fields have been increasingly emphasized by technology policy-makers and CTOs. This paper deals with technology relevance/cluster analysis, which measures technological dependency and relevancy among technologies, and how it can be used for selecting the strategic R&D fields especially satisfying SMEs(small and medium enterprises)' specific needs. As a result of this study, technology-product tree composed of 7 major technology fields, 22 clusters, 41 groups, 335 core-need technologies and hundreds of related business items are produced that can be used for designing SMEs' R&D/business portfolio as well as R&D investment decision-making of the Ministry of Small and Medium Business Administration.

• ETRI Journal
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• v.34 no.1
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• pp.134-137
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• 2012

Power metal-oxide semiconductor field-effect transistor (MOSFET) devices are widely used in power electronics applications, such as brushless direct current motors and power modules. For a conventional power MOSFET device such as trench double-diffused MOSFET (TDMOS), there is a tradeoff relationship between specific on-state resistance and breakdown voltage. To overcome the tradeoff relationship, a super-junction (SJ) trench MOSFET (TMOSFET) structure is studied and designed in this letter. The processing conditions are proposed, and studies on the unit cell are performed for optimal design. The structure modeling and the characteristic analyses for doping density, potential distribution, electric field, width, and depth of trench in an SJ TMOSFET are performed and simulated by using of the SILVACO TCAD 2D device simulator, Atlas. As a result, the specific on-state resistance of 1.2 $m{\Omega}-cm^2$ at the class of 100 V and 100 A is successfully optimized in the SJ TMOSFET, which has the better performance than TDMOS in design parameters.

• Journal of Radiopharmaceuticals and Molecular Probes
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• v.6 no.1
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• pp.46-52
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• 2020

Radiopharmaceuticals that can be consumed in specific disease site play a key role In order to diagnose and treat the diseases. In addition, radiopharmaceuticals can be used for diagnostic or therapeutic purposes depending on the type of the labeled radioactive isotope. Recently, theragnostic radiopharmaceuticals that can simultaneously diagnose and treat are developed. Therefore, the development of target-specific radiopharmaceuticals is a very important research topic in the field of molecular imaging and therapy. This review paper summarizes the basic considerations for the development of radiopharmaceuticals. For new researchers or students who are now beginning in the field of radiopharmaceuticals, we intend to assist in the development of radiopharmaceuticals by describing the definition of radiopharmaceuticals, the ideal radiopharmaceutical conditions, the considerations for developing new radiopharmaceuticals, the factors affecting the design of radiopharmaceuticals, the requirements of radioisotope labeling reactions, and finally the definition and importance of molar activity in radiopharmaceuticals.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.4
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• pp.833-838
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• 2005

In this paper, we propose SAR(Specific absorption rate) reduction methods based on surface electric field distribution relation for mobile handsets. Proposed the new method that is able to consider improvement of the SAR from the very beginning step of developing the mobile handsets. Analysis of mobile handset with human body(head) using finite element method(FEM). Results of this method, SAR reduced about $50\;\%$.