• Polymer(Korea)
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• v.25 no.6
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• pp.833-839
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• 2001

The crystallization characteristics of metallocene linear low density polyethylene was investigated by small angle light scattering and comparison was made with Ziegler-Natta linear low density polyethylene. The special efforts were made to find out the effects of branching number, length of branching and co-monomer content of m-LLDPE on the crystallization behavior of m-LLDPE. It was found that m-LLDPE has longer induction time to start crystallization from the amorphous state than that of conventional LLDPE with similar branching number, but the rate of crystallization seems not change much in both LLDPEs. Lowering of branching number in m-LLDPE resulted in both increasing of rate of crystallization and reducing induction time to crystallize. In general, the maximum size of spherulites of m-LLDPE is bigger than that of conventional LLDPE.

• Journal of the Korean Society of Propulsion Engineers
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• v.15 no.1
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• pp.1-10
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• 2011

Combustion and extinction limits in heat-recirculating excess enthalpy reactors employing both gas-phase and catalytic reaction have been examined with an emphasis Reynolds number (Re) effects and possible application to microscale combustion devices. In this paper, geometrically similar reactors of different physical sizes and different numbers of turns were tested with the aim of estimating for combustor characteristics. Combustion efficiency is estimated by measuring exhausted gases through the gas chromatograph. From these results the effect of scale and number of turns are demonstrated and optimal operating conditions for Swiss roll combustors are identified.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.34-42
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• 1999

In late 1997, the portion of registered light-duty diesel vehicle was 25.3% and its emission rate was 17.1% in Korea. Especially, diesel particulate matters(DPM) and NOx are hazardous air pollutants to human health and environment in urban area. The reduction technologies of exhaust emissions from diesel engines are improvement of engine combustion, fuel quality and development of diesel exhaust after treatment , In this study , a light-duty diesel oxidation catalyst(DOC) that is one of the diesel exhaust after treatment was made for performance evaluation and the emission characteristics were tested on CVS-75 mode. And the analysis of the particle size distribution with scanning mobility particle 100, 67.6% and 66.7, 10.0% for Pt and Pt-V catalyst .And for Pt catalyst, the PM increased 7.8% because of increasing sulfate but Pt-V catalyst reduced the PM to 23.0% . Test results of particle size distribution showed that peak values of number and mass densities are respectively 100∼200nm their distribution trend independent of vehicle speed.

• Transactions of the Korean Society of Automotive Engineers
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• v.16 no.6
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• pp.19-25
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• 2008

Selective Catalytic Reduction is effective in the reduction of NOx emission. This research focused to evaluate the performance of a urea-SCR system and was conducted in two procedures. One is SCR reactor test using model gas in order to provide an optimal injection condition itself. In this step, some parametric study on emission temperature, space velocity, aspect ratio and the formation of urea spray were made by using flow visualization and Computation Fluid Dynamics techniques. The basic simulation results contributed in determining the layout for an actual engine test. The other is an engine performance and emission test. The urea injector was placed at the opposite direction of exhaust gases emitted into an exhaust duct and an optimal amount of a reducing agent is estimated accurately under different engine loads and speeds. Furthermore, the variation of NOx emission and applied amount of urea was investigated in terms of modes under the condition of with and without SCR, and other emissions such as PM, CO and NMHC were evaluated quantitatively as well. This research may provide fundamental data for the practical use of urea-SCR in future.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.567-578
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• 2013

A microbial fuel cell (MFC) is a bio-electrochemical device that converts chemical energy in the chemical bonds in organic compounds to electrical energy through catalytic reactions of microorganisms under anaerobic conditions. Power density and Coulombic efficiency are significantly affected by the types of microbe in the anodic chamber of an MFC, configurations of the system and operating conditions. The achievable power output from MFC increased remarkably by modifying their designs such as the optimization of MFC configurations, the physical and chemical operating conditions, and the choice of biocatalysts. This article presents a critical review on the recent advances made in MFC research with the emphasis on MFC configurations, optimization of important operating parameters, performances and future applications of MFC.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.04a
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• pp.31-31
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• 1998

위성체의 보조추진시스템은 임구궤도까지의 궤도진입 및 임무궤도상에서의 속도 또는 자세제어에 필요한 임펄스를 제공한다. 단일하이드라진 추력기는 하이드라진(H$_2$H$_4$)과 자발적 촉매(Shell 405)의 발열 및 흡열 열분해 반응에 의해 발생하는 질소($N_2$), 수소(H$_2$), 암모니아(NH$_3$), 혼합가스를 노즐을 통해 방출하므로써 요구되는 impulse를 얻는다. 단일하이드라진 추력기 설계는 주입기, 촉매대, 노즐과 기타 설계 형태에 따른 다지관, 링, 스크린, 지지판 등의 부수적인 부품으로 구성된다. 추력기 제작 과정은 크게 piece-parts 기계가공, HEA(Head End Assembly)와 TCA(Thrust Chamber Assembly)로 구성되고 각 세부공정마다 전수시험 및 검사를 가진다. 연소시험설비는 최소 모사진 공 수준이 고도 100,000 ft(8.4 torr)를 만족시킬 수 있는 진공설비, 시험제어부, 성능변수 측정 및 처리부, 추진제 가압 공급부, 기타 환경 안전 및 부대 설비로 구성된다. 추력기 연소성능시험 절차는 추진제 충전 및 오염 여부 표본 검사, 가압 및 공급 라인 이상여부 확인, 추력기 장착, 추진제 가압 및 공급, 시험장치 보정, 진공 모사 및 연소성능시험, data 처리 등으로 구성된다.

• Journal of the Korean Institute of Gas
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• v.2 no.1
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• pp.1-6
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• 1998

A low power (below than 300 mW) catalytic bead combusible gas sensor is developed and utilized with a computer controlled sampling system for measuring heat content of natural gas. The heat content of gas is proportional to the change in the energy required to exposure to the sample of combustible gas. The heat content of natural gas samples ranging 36.30 - 39.88 $MJ/m^3$ is measured in the range of approximately $1\%$ error, which is comparable to its nominal heat content. Each gas represents a slightly different curve of sensitivity to sensor temperature. Thus all of the sensitivities are not equal to every temperature. In calibration process the choice of a optimum operating temperature is an important factor that influences the overall performance of the measurement system.

• Journal of the Microelectronics and Packaging Society
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• v.14 no.1
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• pp.49-53
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• 2007

The direct methanol fuel cell (DMFC) is a promising power source for portable applications due to many advantages such as simple construction, compact design, high energy density, and relatively high energy-conversion efficiency. In this work, an electrochemical methanol sensor for monitoring the methanol concentration in direct methanol fuel cells was fabricated using a thin composite nafion membrane as the electrolyte. We have analyzed the I-V characteristic of the fabricated methanol sensor as a function of methanol concentration, catalyst electrode and platinum(Pt) thickness. The fabricated sensor was analyzed by I-V measurement with various methanol concentration. When we measured the sensor characteristics with 10nm Pt and at 1V, the current value was $1.30{\times}10^{-6}A,\;1.96{\times}10^{-6}A\;and\;2.80{\times}10^{-6} A$ for three methanol concentration of 1M, 2M and 3M, respectively. When the methanol concentration was fixed at 2M, the current value of the fabricated device with Pt layers of 5, 10 and 15 nm thickness was $3.06{\times}10^{-6}A,\;1.96{\times}10^{-6}A\;and\;1.00{\times}10^{-6}A$, respectively. These results lead us to the conclusion that when the methanol concentration increases, the output current increases and when the catalyst electrode become thinner, the current increase more. It showed that, the thinner the catalyst electrode, the more electrochemistry become activation.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.479-485
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• 2011

Pt-Bi/C catalysts supported on carbon black with various Pt/Bi ratios were synthesized by a reduction method. Chloroplatinic acid hydrate ($H_2PtCl_6{\cdot}xH_2O$) and bismuth (III) nitrate pentahydrate ($Bi(NO_3)_3{\cdot}5H_2O$) were used as precursors for Pt and Bi, respectively. Before loading metal on carbon, heat treatment and pretreatment of carbon black in an acidic solution was conducted to enhance the degree of dispersion. The physical property of the synthesized catalysts was investigated by X-ray diffraction and X-ray photoelectron spectroscopy. The XRD pattern of untreated Pt-Bi/C catalyst showed BiPt and $Bi_2Pt$ peaks in addition to Pt peaks. These results imply that Bi atoms were incorporated into the Pt crystal lattice by Pt-Bi alloy formation. The catalytic activity for methanol oxidation was measured using cyclic voltammetry in a mixture of 0.5 M $H_2SO_4$ and 0.5 M $CH_3OH$ aqueous solution. The addition of proper amount of Bi was found to significantly improve catalytic activity for methanol oxidation. The catalytic activity for methanol oxidation was closely related to the stability between electrode and electrolyte. In order to investigate the stability of catalysts, chronoamperometry analysis was carried out in the same solution at 0.6 V.

• 전기의세계
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• v.24 no.4
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• pp.3-5
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• 1975

우리 인간은 그들이 개발한 과학과 기술에 의하여 자연 중에 존재하는 많은 자원을 그들의 생활에 도움이 되는 물체로 바꾸어 왔고 각종 에너지를 그들이 필요로 하는 형태로 바꾸었으며 또 그들이 사는 환경을 더욱 안락하도록 개조하여 왔다. 인간에 계속해서 현재와 같이 생활상태를 향상시키며 번영을 시도한다면 과학기술개발은 영원히 계속될 것이다. 이 과학기술개발에 관한 노력은 과거에는 가치관의 차이로 국가간의 노력의 차이가 있었으나 현재는 선후진국을 막론하고 과학기술에 의한 공업진흥이 국가사회의 경제개발의 원동력이며 그 생활향상의 열쇠가 된다는 것을 다 깨닫고 있다. 이와 같은 과학기술과 인간생활과의 숙명적인 관계중에서도 전기학술과 인간관계는 타과학과의 관계보다 훨씬 깊은 바가 있다. 우리는 호수에 물의 위치 에너지, 석탄이 가지고 있는 열에너지, 바람이 가지고 있는 운동에너지 등을 비롯하여 최근에 발견된 원자에너지까지도 이를 전기에너지로 변환시켜서 이용하고 있다. 장래 어떠한 에너지가 새로 개발되더라도 전기에너지로 변환되어 현재와 같이 우리 생활에 기여할 것은 틀림없다. 이는 전기에너지의 사용편리성으로 볼 때 이의를 제기할 사람은 없을 것이다. 따라서 각종에너지를 전기에너지로 바꾸는 발전기술과 이 장치의 제조공업, 이를 수요지까지 수송하는 송변전기술과 이 장치의 제조공업, 공장에서 사용되는 전기기기들의 운전사용기술과 가정에서 소요되는 전기기기의 제조공업 이상 전기공업의 여러 방치에 소요되는 원자재의 제조공업 등 소위 전기기술은 인간생활과 절대 불가분의 기술이며 앞으로도 인류의 존재와 더불어 영원한 발전을 계속할 것이다. 전기기술발전없이 인간사회와 국가의 산업발전을 기대한다는 것은 어리석은 일이라 아니할 수 없다. 가까운 장래 우리나라 계통이 당면하여야 할 계통제어에 관한 몇가지 문제를 고찰하고저 한다. 단 개개의 문제에 관한 구체적인 해석 또는 검토에 관하여는 다음 기회에 미루기로하고, 우선 여기서는 당면문제로서 대처하지 않으면 안될 자동주파수제어문제및 계통의 경제운용문제만에 한정하여, 이것을 우리나라의 현상과 관련시켜 개설하고, 이들의 자동화에 관한 기본적인 문제를 간단히 적어 보겠다. 가능하다. 제작완료된 ASIC은 기능시험을 완료했으며 실제 line-of-sight(LOS) 시스템 구현에 적용중이다. 시대를 살아 갈 회원들이다. '컨텐츠의 시대'가 개막되는 것이며, 신세기통신과 SK텔레콤은 선의의 경쟁 과 협력을 통해 이동인터넷 서비스의 컨텐츠를 개발해 나가게 될 것이다. 3배가 높았다. 효소 활성에 필수적인 물의 양에 따른 DIAION WA30의 라세미화 효율에 관하여 실험한 결과, 물의 양이 증가할수록 그 효율은 감소하였다. DIAION WA30을 라세미화 촉매로 사용하여 아이소옥탄 내에서 라세믹 나프록센 2,2,2-트리플로로에틸 씨오에스터의 효소적 DKR 반응을 수행해 보았다. 그 결과 DIAION WA30을 사용하지 않은 경우에 비해 반응 전환율과 생성물의 광학 순도는 급격히 향상되었다. 전통적 광학분할 반응의 최대 50%라는 전환율의 제한이 본 연구에서 찾은 DIAION WA30을 첨가함으로써 성공적으로 극복되었다. 또한 고체 염기촉매인 DIAION WA30의 사용은 라세미화 촉매의 회수 및 재사용이 가능하게 해준다.해준다.다. TN5 세포주를 0.2 L 규모 (1 L spinner flask)oJl에서 세포간의 응집현상 없이 부유배양에 적응,배양시킨 후 세포성장 시기에 따른 발현을 조사한 결과 1 MOI의