• 한국응용과학기술학회지
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• 제27권3호
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• pp.378-384
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• 2010

Regenerated cellulose was prepared from Buckeye wood pulp V60 via dissolution in N-methylmorpholin N-oxide (NMMO) solvent system. The effect of antioxidants such as, n-propylgallate (PG), tris(nonylphenyl) phosphite (TRIS), ethylenediamine tetraacetic acid disodium salt (EDTA), and magnesium sulfate on the properties of regenerated cellulose was studied using X-ray diffraction, copper index calculation, and viscometry. Only addition of more than 0.01% of PG into NMMO solvent was effective to avoid the reduction of the degree of polymerization(DP) of regenerated cellulose during dissolution at $110^{\circ}C$. However, the early stage(within 0.5h of dissolution process) degradation of cellulose was not prevented eventhough up to 0.5% PG was appled to hot NMMO system. In addition, to recover the expensive NMMO after cellulose regenerating process, the washing filtrate was studied using simple techniques, such as refractive index, pH, and conductivity measurements. Through conductivity measurement result, 4-time of washing was enough to remove the NMMO completely from regenerated cellulose.

• 지질공학
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• 제16권1호
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• pp.15-21
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• 2006

야외에서 관찰되는 화강암 기원의 사질 토양시료들에 대한 광물학적 관찰과 입도 분석이 실시되었으며 변수두법에 의해 그들 토양시료들의 투수계수를 측정하였다. 측정된 수리 전도도 값과 토양시료들이 가지는 입도분포 특성과의 관계에 대한 상호 연관성을 정의하였다. 화강암으로부터 풍화된 토양의 입도분포에 의하면 토양은 sand와 loamy sand에 해당되며 변수두 실내 투수시험에 의해 측정된 투수계수는 $1.15X10^{-5}\sim7.31X10^{-4}cm/sec$의 범위로 이는 sand와 silt의 영역에 해당된다. 시험에 사용된 사질토양의 투수계수는 토양의 평균입도 보다는 입도분산과 더 강한 상관관계를 가지고 있음이 뚜렷하게 관찰되며 입도분산도가 증가할수록 투수계수가 감소하는 경향이 뚜렷하다. 연구결과 평균입도가 $0.38\sim1.97mm$인 화강암 기원의 사질토양은 투수계수와 입도분산의 상호관계에 있어서 $y=6.0E-5x^{-1.4}$의 추세선과 잘 일치하고 있음이 밝혀졌다. 이는 실제로 야외에서 관찰되는 토양시료의 입도분산에 대한고려 없이 평균입도만을 이용한 투수계수 예측은 큰 오류를 범 할 수 있음을 지시해 주는 것이다.

• 제어로봇시스템학회논문지
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• 제19권10호
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• pp.891-895
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• 2013

This paper proposes the development of a new method for online analysis which measured acid concentration in a pickling line. Pickling is the most important step to remove surface scale layers and is strongly depending on the exactly controlled pickling liquor composition. Today, there is no feasible system available for the online control of pickling lines. Within this paper, new methods for online analysis of pickling liquors have been tested and implemented into an overall pickling process control tool. This method measured simultaneously the hydrochloric acid and iron ion concentration in a solution of hydrochloric acid by measuring the ultrasonic speed, the solution temperature, and the electrical conductivity. Experimental results showed excellent precision and the measurement error was ${\pm}2g/l$ compared with the neutralization titration measurement.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.123.2-123.2
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• 2010

본 논문에서는 2008년 4월 이후 지열원 열펌프가 설치되어지는 현장에 시험공의 지중열전도도를 현장열응답법을 이용하여 측정하였으며, 그간에 측정된 지중열전도도를 이용하여 전국의 지중온도 및 지중열전도도의 산포도를 정리하였다. 지중열교환기의 심도가 150m일 때 지중온도 분포는 약 $12.0{\sim}19^{\circ}C$의 넓은 분포를 보였으나 대부분의 지중온도가 $15.0{\sim}17.0^{\circ}C$의 범위에 분포하였으며, 지중열전도도의 경우도 마찬가지로 1.50 ~ 9.00 W/mk 값으로 아주 넓은 분포를 보였으나 2.30 ~ 2.90W/mk 값이 가장 많이 나타냈다.

• Tribology and Lubricants
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• 제12권4호
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• pp.52-59
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• 1996

The results of the electrical contact conductivity of multi-contact spots accounting the surface roughness and the non-conductive films of different origins such as air, water, cutting oil, and machining oil are presented. The array of metal spheres compressed between two flat plates has been used for simulation of the contact behavior of multiple contact of solids, under normal loading. Measurement of electrical contact resistance has been made using the equipment providing the adequate accuracy in the range of micro Ohms. The data on electrical contact resistance have been compared with theoretical predictions using the multiple contact model of constriction resistance. The effect of single spot number and array on conductivity of contact has been evaluated. The results of the experiments show that the contact resistance are closely related to the number of loading cycles, form of surface roughness, and presence of non-conductive films that reduce the size of the real electrical contact spots.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제37회 추계학술대회논문집
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• pp.805-806
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• 2011

고온, 고압조건에서 작동하는 연소기 내벽을 보호하기 위해서 적용되는 니켈크롬도금의 열전도도를 측정하였다. 측정된 결과와 현재 재생냉각 해석에서 사용되는 데이터를 비교하면 20~25% 정도의 여유를 가지고 있는 것으로 나타났다.

• 한국세라믹학회지
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• 제44권8호
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• pp.424-429
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• 2007

Novel conductive $CO_2$ membranes composed of dual phases, molten carbonates and electronic conducting ceramics, were investigated. As the microstructure control of electronic conducting ceramic supports is extremely important to keep the molten carbonates stable in the membranes by a capillary force applied by the pore structure of the supports, we have scrutinized the microstructure of the electronic conducting supports utilizing microscopic images and gas permeability measurement. From the evaluation of the electrical conductivities of the molten carbonates and the electronic conducting ceramic supports, we found that the ionic conductivity of the molten carbonates could determine $CO_2$ flux through the dual phase membranes if the surface exchange rate were relatively high enough.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.130-133
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• 2006

In order to study the relationship between the discharge characteristics of an ac PDP and the surface conductivity of MgO thin film, the surface current across a ring shaped MgO film was measured by exposure to monochromatic vacuum ultraviolet from the synchrotron radiation source whose wavelength ranges from 60nm to 240nm $(5.5eV{\sim}25eV)$. The experimental results show that the surface current begins to increase rapidly at the photon energy of about 9 eV which might correspond to the valence band edge of MgO. The difference in the surface current level correlate well with the differences in the preparation method of MgO films and their respective discharge characteristics such as the firing, minimum sustain voltages, address voltage margin and address discharge delay time.

• 대한화학회지
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• 제6권2호
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• pp.130-132
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• 1962

A new method of evaluating the mixing time in the continuous flow stirred tank is herein proposed. Experimental results to test the concept are also presented.The mixing time is defined as the time interval between the injection of a slug of an electrolyte solution into the tank and the moment at which an essentially straight line begins on a plot of the conductivity of effluent versus time.The proposed method of measuring the mixing time is valid even for the low mixing time (5 seconds) and the results obtained agree well with previous work, where the mixing time measurements were carried out by the injection of a dye into the feed stream.

• 한국정밀공학회지
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• 제10권2호
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• pp.138-145
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• 1993

The bath cryostat of cryogenic apparatuses which are generally used to study physical phenomena under low temperature and ultra low temperature has been desigened and constructed. The practical use of the cryostat is verified by the measurement of the storage life of liquid heloum and liquid nitrogen vessels. The cryostat consists of triple structure of high vacuum environment in order to minimize the evaporation rate of liquid helium and liquid nitrogen by thermal conductivity and radiant heat. The minimum thickness which can stand against inner and outer pressures is calculated from considering the strength of the material.