• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.1
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• pp.125-131
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• 1997

The extinction of premixed flames under the influence of stretch is studied numerically. A wide range of fuel (hydrogen, ethylene, acetylene, methane, propane and methanol) and air mixtures are established in an opposed jet and their flame properties such as flame speed, flame thickness, thermal diffusivity, and stretch rate at extinction are computed. Computations are made using several chemical kinetic mechanism (Smooke, Kee et al. and Peters). The major result is that, in contrast to the various previous claims of extinction Karlovitz number varying over three orders of magnitude, it is found to be constant around two for all of the mixtures tested. That is, premixed flames are extinguished when the physical flow time decreases (due to increased stretch rate) to the point where it approximately equals the chemical reaction time. Here the relevant chemical reaction time is not the one computed using the one-dimensional flame properties as originally suggested in the formulation of Karlovitz number, but rather it is the one obtained using the stretched flame properties which fully reflect the effect of straining on the flame structure.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1756-1757
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• 2011

본 논문에서는 FXLMS 알고리즘을 이용하여 3차원 폐공간(반무향실)에서의 순음(125Hz)을 이용하여 부 음원과 에러센서의 위치 변화에 따른 소음저감 정도를 분석하였으며, 이 결과를 바탕으로 능동형 방음벽의 구현의 기초자료로 활용하고자 하였다. 부음원(제어스피커, 이하 부음원)과 에러센서간 거리차는 0.5m, 1.5m, 2.5m를 대상으로 실험을 실시하였으며 그 중 거리차가 1.5m 지점의 경우, 125Hz부근에서는 최대 18.3dB, Overall(80Hz~200Hz)값은 18.2dB(A)의 소음저감 효과가 있는 것으로 나타나, 가장 효과적인 부음원과 에러센서간의 거리차인 것으로 평가되었다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.125-131
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• 2009

In this paper, we proposed the remote visual monitoring system on mobile robot platform. The proposed system is composed of ARM9 core PXA255 processor, micro CMOS camera and wireless network and the captured visual image is transmitted via 803.11b/g wireless LAN(WLAN) for remote visual monitoring operations. Robot platform maneuvering command is transmitted via WLAN from host and the $640{\times}480$, $320{\times}240$ pixel fixed visual image is transmitted to host at the rate of $3{\sim}10$ frames per second. Experimental system is implemented on Linux OS base and tested for remote visual monitoring operation and verified the proposed objects.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.730-740
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• 1996

Boiling heat transfer coefficients of pure refrigerants (R22, R32, R134a, R125, R290, and R600a) and refrigerant mixtures (R32/Rl34a, R290/ R600a, and R32/R125) are measured experimentally and compared with Chen's correlation. The test section is a seamless stainless steel tube with inner diameter of 7.7mm and uniformly heated by applying electric current directly to the tube. Heat fluxes range from 10 to 30kW$^2$. Mass fluxes are set to 424 ~ 742kg/m$^{2}$s for R22, R32, R134a, R32/R134a, and R32/Rl25 ; 265 ~ 583kg/m$^{2}$s for R290, R600a, and R290/R600a. Heat transfer coefficients depend strongly on heat flux at a low quality region and become independent as quality increases. Convective boiling term in the Chen's correlation predicts experimental data of the pure refrigerants fairly well (relative error of 12.1% for the data of quality over 0.2). The correlation for pure substances overpredicts the heat transfer coefficients for nonazeotropic refrigerant mixtures.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.1
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• pp.125-132
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• 2002

An experimental study on the characteristics of stability of propane turbulent nonpremixed jet flames discharged normal to air free-streams with uniform velocity profile is conducted. Experimental observations are focused on the flame shape, the stability considering two kinds of flame, lift-off distance, and the flame length according to velocity ratio. In order to investigate the mixing structure of the flame base at the lower limit, we employ the RMS technique and measure the species concentration by a gas chromatography. In the results of the stability curve and lifted flame, it is fecund that the dependency of nozzle diameter is closely related to the large-scale vortical structure representing counter-rotating vortices pair. Also, the detailed discussion on the phenomenon of blowout due to this large vortical motion, is provided.

• Journal of Biosystems Engineering
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• v.27 no.2
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• pp.125-132
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• 2002

In order to investigate the optimum moisture content of paddy for milling process, a series of tests were conducted by examining the recovery rate and whiteness of milled rice in relation with the various moisture content. Hwabong-byeo and Dongjin-byeo varieties which were major paddies cultivated in Korea were used for the experiment. The test was performed with small experimental milling machines. In order to minimize the unexpected factors, environment conditions were kept in constant during the experiment. As a result, the recovery rate of milled rice were varied as the changes in milling time and degree of whiteness. However, the recovery rate of milled rice increases as its moisture content increases untill a certain point of moisture content and decreases slowly afterward. This certain point can be called optimum moisture content for rice milling. Also, it has a different value depending on the variety. In this experiment, optimum moisture content of Hwabong-byeo and Dongjin-byeo were considered around 14.8% and 15.3%, respectively. It is not sure that these optimum moisture contents for the two varieties would assume the same values irrespective of harvest year and place. However, it could be concluded that the optimum moisture content for rice milling is around 15%(w.b.) for Hwabong-byeo and 15.5%(w.b.) for Dongjin-byeo, respectively.

• Bulletin of the Korean Chemical Society
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• v.2 no.4
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• pp.125-129
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• 1981

The addition reactions of cysteine without blocking amino and carboxyl groups to substituted and unsubstituted ${\beta}$-nitro-styrene derivatives were investigated. ${\beta}$-Nitrostyrene(1a), p-methyl-${\beta}$-nitrostyrene(1b), 3,4,5-trimethoxy-$[\beta}$ -nitrostyrene(1c), $[\varpi}$-3,4-methylenedioxy-${\beta}$ -nitrostyrene(1d), o-, m- and p-chloro-${\beta}$ -nitrostyrene (1e, 1f, 1g) and o-, m- and p-methoxy-${\beta}$-nitrostyrene (1h, 1i, 1j) easily undergo addition reactions with cysteine to form S-(2-nitro-1-phenylethyl)-L-cysteine(3a), S-[2-nitro-1-(p-methyl)phenyl-ethyl]-L-cysteine(3b), S-[2-nitro-1-(3',4',5'-trimethoxy) phenylethyl]-L-cysteine(3c), S-[2-nitro-1-($[\vatpi}$ -3',4'-methylenedioxy)phenylethyl]-L-cysteine(3d), S-[2-nitro-1-(o-chloro)phenylethyl]-L-cysteine(3e), S-[2-nitro-1-(m-chloro)-phenylethyl]-L-cysteine(3f), S-[2-nitro-1-(p-chloro)phenylethyl]-L-cysteine(3g), S-[2-nitro-1-(o-methoxy)phenylethyl]-L-cysteine(3h), S-[2-nitro-1-(m-methoxy)phenylethyl]-L-cysteine(3i) and S-[2-nitro-1-(p-methoxy)phenylethyl]-L-cysteine(3j), respectively. The structure of adducts were confirmed by means of UV-spectrum, IR-spectrum, molecular weight measurement and elemental analysis. The various factors effecting the yield of cysteine adducts to ${\beta}$-nitrostyrene derivatives were also studied.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.44 no.3
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• pp.125-132
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• 2021

In this study, the improvement of the IP system, which is the core infrastructure of the MRO project, and its effect were analyzed. Systematic problems and problems that are not competitive in the actual operating environment were systematically derived, and based on this, the most suitable method for target system development was found and improved. And the data of the improved system was analyzed and the effect was verified through empirical analysis of the system improvement effect through the user questionnaire. As a result of the study, the item with the highest improvement effect was convenience, which increased by 12.43 points. Then it increased by 10.25 points in terms of features. In particular, you will notice a significant improvement in speed by 30-50%. This is because the empirical analysis results are more objective and realistic than other conceptual models. Also, from the practical point of view, based on the results of the empirical analysis, corporate management can more effectively promote the intellectual property system, which is expected to contribute to the enhancement of corporate competitiveness.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.26-31
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• 2015

This paper deals with a size-reduced Ku-band waveguide limiter. Basically, it passes the signal from 16.125 GHz through 16.375 GHz, but when excessively high power is injected to the input port, it should change to a bandstop filter. Furthermore, it is required to change to bring attenuation by more than 20 dB and 50 dB over a narrow band and the entire passband, respectively. Therefore, in order to meet this requirement, a limiting device is implemented with multiple PIN-diode posts that enable the limiter to be the bandpass filter and stopband one at the off and on states of the PIN-diode switch, respectively. So, the design goes through the equivalent circuit modelling and the geometry is realized in the accurate electromagnetic analysis CAD tool. Finally, the result is discussed to shed light on whether it complies with the aforementioned requirement.

• The Korea Journal of Herbology
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• v.26 no.4
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• pp.125-132
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• 2011

Objectives : An aim of study is to investigate effects of curculiginis rhizoma in vitro (factor Xa (FXa) inhibitor assay, prothrombinase assay, prothrombin time (PT) assay, activated partial thromboplastin time (aPTT) assay) and in vivo experiment (blood clotting time, thromboxane B2 content assay in serum and weight of thrombus by AV-shunt rat model). Methods : We gained a human serum and used serum in vitro study such as factor X activity (FXa) inhibition, prothrombinase inhibition, prothrombin time (PT) and activated partial thromboplastin time. Fifteen SD rats were divided into three groups (intact control group and two experimental group treated with extract of Curculiginis Rhizoma(ECR)). Rats were orally administrated DW (intact control group), 600 mg/kg concertration of ECR and 200 mg/kg concertration of ECR. After one hour, we anesthetized rats and made arteriovenous (AV) shunt rat models to study weights of thrombus, took a hole blood to study content of thromboxane B2 and blood clotting time. Results : In vitro, ECR increased a inhibitory activity of FXa, prothrombinase and aPTT compared than intact control group. Especially ECR made significant increase of FXa and prothrombinase inhibitory activity (p<0.05, p<0.01). And PT were increased in ECR control group compared with intact control group. In vivo, a blood clotting time of experiment group treated with ECR 600 mg/kg were significantly increased compared with that of intact control group (p<0.05) and content of thromboxane B2 was significantly decreased in group treated with ECR 600 mg/kg in seum. The weight of thrombus were significantly reduced in group treated with ECR 600 mg/kg compared with intact control group (p<0.05). But in vivo experiment study, those of group treated with ECR 200 mg/kg were reduced compared with those of intact control group without statistical significance. Conclusions : ECR has a antithromboic activity in internal course with inhibitory activity of FXa and prothrombinase in vitro, it required to research more study for effective compounds.