• 상하수도학회지
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• 제32권1호
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• pp.27-35
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• 2018

The stability of liquid ferrate(VI) produced by an innovative method was confirmed and the degradation characteristics of cyclic compounds(Benzene, Aniline, Toluene, 1,4-Dioxane) by liquid ferrate(VI) were investigated under the same reaction conditions. When it was compared with the ferrate manufactured by the wet oxidation method, the liquid ferrate was more stable. And the stability of liquid ferrate was tested at the storage temperature. As a result, only 17.7% of liquid ferrate(VI) has decomposed at the storage temperature($4^{\circ}C$) for 28 days. Among the cyclic compounds, the aniline was rapidly degraded compare to other cyclic compounds, which seems to be due to the electron-donating ability of the substituent, $-NH_2$ group. Especially, when 1,4-dioxane was compared with benzene, the decomposition rate of 1,4-dioxane was lower than that of benzene, suggesting that oxygen atoms hinder the electrophilic reaction. Among 4 cyclic compounds, it was observed that aniline has the highest rate constant than those of other cyclic compounds.

• Tribology and Lubricants
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• 제27권2호
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• pp.88-94
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• 2011

The tribological characteristics of the swash plate surface of a compressor which is for automobile were investigated. For surface treatments, PTFE and $MoS_2$ are used as a solid lubricant, together with copper alloy. Test condition is set considering actual driving condition. Wear testing is conducted using pin on disk type tester, and the coefficient of friction and the temperature on friction surface are measured. Also, to determine the wear patterns, cross-section of friction surface is analyzed by SEM(scanning electrode microscope). The $MoS_2$, both at dry and lubricated conditions, friction surface and the coefficient of friction maintained rather stable results. But, the PTFE, at oil less condition, sample resulted in rather unstable condition. In case of copper alloy, quite higher friction coefficients(higher than 0.1) were obtained at dry condition. At the temperature of $125^{\circ}C$, seizure has occurred.

• 소성∙가공
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• 제15권4호
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• pp.333-339
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• 2006

Hot deformation behavior of a carbon steel (A350 LF2) was characterized by compression tests in the temperature range of $800-1250^{\circ}C$ and the strain rate range of $0.001-10s^{-1}$, The microstructural evolution during hot compression was investigated and deformation mechanisms were analyzed by constructing a deformation processing map. Processing maps were generated using the combination of dynamic material model (DMM) and flow instability theories based on the flow stability criteria and Ziegler's instability criterion. In order to evaluate the reliability of the map, the mirostructural characteristics of the hot compressed specimens were correlated with test conditions in the stable and unstable regime. The combined microstructural and processing map of A350 LF2 was applied to predict an optimum condition and unstable regions for hot forming.

• 전력전자학회논문지
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• 제8권3호
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• pp.239-246
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• 2003

BLDC 전동기는 높은 효율과 출력밀도로 인하여, 현재 산업응용 분야에 널리 적용되고 있으며, 특히 고성능 제어 특성과 저소음 운전특성으로 인하여 가정용 전자제품의 활용도가 높아지고 있다. 본 논문에서는 제한적인 설계조건에서 요구성능을 만족하는 트레드 밀 구동용 BLDC 전동기를 설계하고, 이에 적합한 제어기를 제작하였다. 전동기설계에서 제한된 고정자 구조에 대하여, 제작의 용이성과 경제성을 고려하여 CAD와 FEM 해석을 통하여 영구자석의 형상을 설계하였다. 설계된 제어기는 트레드 밀의 안정된 구동과 성능을 위하여 운전자의 무게와 회전속도에 따라 학습된 제어기의 이득이 사용되도록 제작되었다. 제시된 트레드 밀 구동용 BLDCM과 제어기는 실험을 통하여 성능을 확인하였다.

• Korean Chemical Engineering Research
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• 제52권2호
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• pp.199-204
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• 2014

2성분 응고계에서 다공성 mush 층에서의 조성 대류는 생성되는 제품의 질에 영향을 준다. 본 연구에서는 일정한 속도로 응고되는 mush 층을 고려하였다. 선형 안정성 이론을 사용하여 mush 층에 대한 교란방정식을 유도하였고, 기본상태 온도장과 mush 층에서 기공률의 분포를 수치해법으로 조사하였다. 과열량이 클 때 mush 층의 두께는 열경계층의 두께에 비해 상대적으로 작았다. 과열량이 감소함에 따라 mush 층의 두께를 기준으로 한 Rayleigh 수는 증가하였고, mush 층은 조성 대류에 대해 안정해졌다. mush 층의 윗면에 등온조건을 적용한 경우보다 온도 및 열속의 연속조건을 액체-mush 계면에 적용한 경우에 임계 Rayleigh 수가 더 작게 얻어졌다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2010년도 하계학술대회 논문집
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• pp.91-91
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• 2010

In this paper, nano composites material is produced by adding MgO with particle size of 5 [nm] into epoxy resign using as insulating material of power transformer apparatus and molding part to study the volume resistivity of nano composites used epoxy. We measured the volume resistivity using the High Resistance Meter(4329A) depending on changing the amount of addition and temperature in this experience. In result, we have confirmed that 1.0, 3.0, 5.0 and 10.0 [wt%] as about 2.9, 7.6, 7.5 and 6.1 times increased than virgin. Therefore, the characteristic of volume resistivity was relatively stable as specimen by added 3.0 [wt%] than the others.

• 한국전산유체공학회지
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• 제21권1호
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• pp.43-49
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• 2016

Thermal cracking is commonly modeled as plug flow reaction, neglecting the lateral gradients present. In this paper, 2-dimensional computational fluid dynamics including turbulence model and molecular reaction scheme are carried out. This simulation is solved by means of coupled implicit scheme for stable convergence of solution. The reactor is modeled as an isothermal tube, whose length is 1.2 m and radius is 0.01 m, respectively. At first, The radial profile of velocity and temperature at each point are predicted in its condition. Then the bulk temperature and conversion curve along the axial direction are compared with other published data to identify the reason why discussed variations of properties are important to product yield. Finally, defining a new non-dimensional number, Effect of interaction with turbulence, heat transfer and chemical reaction are discussed for design of thermal cracking furnace.

• 대한화학회지
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• 제15권5호
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• pp.256-265
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• 1971

An ESR study has been made on free radicals produced in frozen aqueous solutions (ices) of glycine, DL-${\alpha}$-alanine, DL-serine, L-cysteine, DL-leucine and DL-isoleucine by gamma-irradiation at dry ice temperature. All free radicals induced were decayed concomitant to the successive annealing but the radical species which is believed to be dominant seems to be stable even near the melting point of the ice. These dominant species were found to be identical to those resulted from direct action of radiation in the solid at room temperature. Small but significant changes in the spectra of glycine and DL-${\alpha}$-alanine were observed by varying the microwave power. These results seem to support the view that the spectra obtained were composite consisting of more than two different resonances having different power saturation characteristics. The relative contribution of unidentified resonances to the composite spectra was greater for solutions of low concentration. These resonances are assumed to be induced by indirect effects, mainly hydrogen abstraction by radiation produced hydroxyl radicals and also C-N bond cleavage by hydrated electrons.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.238-243
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• 2003

The solar cells should be operated at the maximum power point because its output characteristics are greatly fluctuated on the variation of insolation, temperature and load. The output power of solar cell is DC, therefore it is necessary to install an inverter among electric power converts. The inverter have to supply a sinusoidal current and voltage to the load and the interactive utility line. In the paper, the proposes a photovoltaic system designed with a step up chopper and single phase PWM voltage source inverter. Synchronous signal and control signal was processed by microprocessor for stable modulation. The step up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power point of solar cell without any influence on the variation of insolation and temperature because solar cell has typical dropping character. The single phase PWM voltage source inverter consists of complex type of electric power converter to compensate for the defect, that is, solar cell cannot be developed continuously by connecting with the source of electric power, from 10 to $20\%$. The single phase PWM voltage source inverter operates in situation that its output voltage is in same phase with the utility voltage. The inverter supplies an ac power with high factor and low level of harmonics to the load and the utility power system.

• 전력전자학회논문지
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• 제5권6호
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• pp.610-619
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• 2000

본 논문에서는 현재 전력저장시스템으로써 가장 많이 사용하고 있는 배터리를 대체할 목적의 5MB (Superconductive Magnetic Bearing)를 이용한 off-line UPS에 관해 연구하였다 영구자석의 덩어리형 고온 초전도 체위에서의 부상득성을 이용하여 베어링 문제의 해결방안에 접근함으로써 고효율의 FES찰 구성하여 단상 off-line UPS에 적용하였으며 제어회로에는 80C 1 96KC 마이크로프로세서를 사용하였고 빠픈 응답윤 요구하는 부분 은 아날로그회로를 사용하여 구성하였다. 에너지 저장모드에서 컨버터 입력천류는 전원전압과 동상의 정현파로 제어하였으며 에너지 회생모드에서는 출력잔압윤 정현파로 제어하기위해 필터커패시터전류릎 직접 제어하였다. 시작 품제작을 통해 시스템의 안장된 동작특성을 확인함으로써 제안된 FES가 Off-line UPS 에서의 에너지 저장매체로써 우수함을 입증하였다.