• Tribology and Lubricants
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• 제14권2호
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• pp.42-48
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• 1998

Electro-Rheological (ER) fluid is a class of functional fluid whose apparent viscosity can be varied by the applied electric field strength. The ER fluid is classified into two types; one is a dispersive fluid and the other is a homogeneous. Dispersive ER fluid is a colloidal suspension of fine semiconducting particles in a dielectric liquid and liquid crystal (LC) is classed as homogeneous type ER fluid. LC has been originally developed for some electronic display devices. Various mechanical components applying ER fluid have been developed, and the their performance typically depends on the characteristics of ER fluid which have generally been evaluated by a rotational viscometer. However, the ER fluid introduced into various mechanical components undergoes not only simple shear flow but press flow or oscillating flow. For the evaluation of ER fluid, the authors developed an reciprocating type viscometer. The amplitude is controlled on 5 mm at the frequency from 50 to 1000 Hz. In the present paper, the performance of several types of ER fluid is evaluated by the reciprocating type viscometer and compared with those evaluated by a rotational viscometer.

• The Journal of the Acoustical Society of Korea
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• 제23권4E호
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• pp.140-145
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• 2004

A laboratory study was carried out to investigate the change of ultrasonic velocity as a function of temperature for fluid mud (i.e., suspension). Pulse transmission technique with ultrasonic wave was used for ultrasonic velocity measurement. The five samples for fluid mud were prepared for concentration range of $30.6{\%}\;(1.24\;g/cm^{3}\;in\;density),\;23.3{\%}\;(1.19\;g/cm^{3}),\;11.5{\%}(1.10\;g/cm^{3}),\;7.8{\%}\;(1.08\;g/cm^{3}),\;and\;3.8{\%}\;(1.05\;g/cm^{3})$ by weight. The ultrasonic velocity in fluid mud was investigated to increase $(approximately\;2.83\;to\;4.95\;m/s/^{\circ}C)$ with increasing temperature, due to the effect of viscosity and compressibility of water with changing temperature. But the increasing rate tends to decrease at temperature higher than $30^{\circ}C,$ caused by the effect of viscosity. The concentration of fluid mud more affect to the ultrasonic velocity at higher temperature range than that at lower temperature. Overall the temperature effect on the ultrasonic velocity in fluid mud was a similar rate as for distilled water and seawater, suggesting fluid mud significantly depends on the behavior of water.

• 한국정밀공학회지
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• 제25권10호
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• pp.48-57
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• 2008

MR Fluid, one of functional fluids, is developed for the application to automobile products. MR CDC damper using MR fluid has following principles. When ar electric current is applied to the solenoid, apparent viscosity of MR fluid passing through the annular gap which acts as magnetic circuits varies directly as the intensity of the current. These devices have a simple structure and excellent lime response characteristics, emerging as the alternatives of the conventional semi-active suspension systems. In this study, a design procedure of the magnetic circuit through the solenoid fore and the flux ring functioning as a magnetic path is investigated so as to optimize the design and performance of MR CDC dampers for the vehicles. In addition, an operating point on the B-H curve, the magnetization according to the variation in the annular gap, the pole piece width and the density of MR fluid are studied to design the optimal piston head within the restrained dimension range.

• 한국식품영양과학회지
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• 제22권1호
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• pp.40-47
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• 1993

동부 앙금의 호화성질을 조사한 결과 물결합능력은 52$^{\circ}C$이후 급격히 증가하였고, 현탁액의 광투과도는 $65^{\circ}C$ 이후 직선적으로 증가하였으며 호화 온도는 63.4~76.$0^{\circ}C$이었다. 동부 앙금은 일단계의 팽윤과 용해도가 낮은 특징을 보였고, 호화에 필요한 수분 함량은 37%이었다. 아밀로그래프의 최고점도는 농도가 증가 할 수록 높아졌으나 일정한 농도에서 가열 온도에 따른 영향은 없었다. 각 가열 온도에서 20분 후의 점도와 3$0^{\circ}C$에서의 점도는 일정한 농도에서 가열 온도와 부의 상관관계 (p< 0.05)를, 냉각 점도는 20분 후의 점도와 농도에 관계없이 정의 상관관계 (p<0.05)를 보였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.1682-1686
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• 2004

A slit-flow apparatus with laser diffraction method has been developed with significant advances in ektacytometry design, operation and data analysis. In the slit-flow ektacytometry (or laser-diffractometry), the deformation of red blood cells subjected to continuously decreasing shear stress in slit flow is measured. A laser beam traverses a diluted blood suspension flowing through a slit and is diffracted by RBCs in the volume. The diffraction patterns are captured by a CCD-video camera, linked to a frame grabber integrated with a computer, while the differential pressure variation is measured by a pressure transducer. Both measurements of laser-diffraction image and pressure with respect to time enable to determine deformation index and the shear stress. The range of shear stress of 0 ${\sim}$ 35 Pa and measuring time is less than 2 min. When deforming under decreasing shear stress, RBCs change gradually from the prolate ellipsoid towards a circular biconcave morphology. The Deformation Index (DI) as a measure of RBC deformability is determined from an isointensity curve in the diffraction pattern using an ellipse-fitting program. The advantages of this design are simplicity, i.e., ease of operation and no moving parts, low cost, short operating time, and the disposable kit which is contacted with blood sample.

• 약학회지
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• 제29권5호
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• pp.234-245
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• 1985

To clarify the diffusional behavior of p-aminbenzoic acid esters in the presence of polyethylene glycol 400, cellulose membrane permeation rate, solubility and viscosity of p-aminobenzoic acid methyl ester, benzocaine and butamben were determined with PEG solutions of various concentrations. With an increase in PEG concentrations permeation rates from solutions; decreased due to an increase in viscosity of the solution. From suspensions, however, permeation rates increased due to an increase in solubility and when the initial drug concentration was constant, permeation rates were found to be greatest from the PEG-water system with the PEG concentration which transported from the solution to the suspension. Permeation rate of 4.0mg/ml p-aminobenzoic acid methyl ester was $26.51\mu$g/ml$\cdot$hr from 5g/100ml PEG solution, and that of 4.0mg/ml benzocaine was $13.17{\mu}g/ml{\cdot}hr$ from 15g/100ml PEG, solution, and that of 2.0mg/ml butamben was $3.8{\mu}g/ml{\cdot}hr$ from 10g/100ml PEG solution. Permeation rate was 7.0 fold in p-aminobenzoic acid methyl, ester and 3.5 fold in benzocaine compared to butamben.

• 한국세라믹학회지
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• 제37권8호
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• pp.751-759
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• 2000

Effects of the dosage change, from 0 to 2.0 wt% based on cement weight, of naphthalenic (NSF) and polycarboxylic(NT-2) superplasticizers, on the fluidity of cement paste substituted by 10 wt% II-anhydrite and fly ash respectively as well as II-anhydrite and fly ash itself were investigated. Dispersion properties between particles in suspension were investigated by zeta potential test. Initial fluidity and slump loss in the paste system were observed through mini-slump and apparent viscosity changes with elapsed time. Zeta potential on the particle surface was a tendency to increase according to increasing of NSF dosage. Especially, zeta potential of fly ash has the highest value among all particles equivalent to NSF dosage. In the fluidity of cement paste substituted by inorganic particles, the specimen with substitution of 10 wt% II-anhydrite and fly ash for cement was more effective than cement itself to improve initial fluidity and retain stable fluidity of cement paste. In addition, effect of NT-2 and NSF to improve the fluidity of cement paste, addition of 1.0 wt% NT-2 was more effective than 1.5wt% NSF.

• 한국식품과학회지
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• 제17권2호
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• pp.107-112
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• 1985

다수계(한강, 수원 317호) 및 일반계(올찰) 찹쌀 전분의 이화학적 성질과 정도의 특성을 비교 검토한 결과는 다음과 같다. 한강, 수원 317호 및 올찰 찹쌀 전분의 광투과도는 각각 $50^{\circ}C$, $55^{\circ}C$ 및 $60^{\circ}C$이후 증가하기 시작하였으며, 세가지 시료 모두 $75^{\circ}C$이후 일정값을 보였다. 팽화력 및 용해도는 한강이 $50^{\circ}C$에서, 수원 317 및 올찰은 $55^{\circ}C$에서 증가하기 시작하였고 한강이 가장 높은 팽화력을, 울찰이 가장 낮은 값을 보였다. 아밀로그람에 의한 초기호화온도는 한강이 $63^{\circ}C$, 수원 317이 $65.5^{\circ}C$, 울찰이 $67^{\circ}C$이었으며, 한강이 모든 지표에서 가장 높은 값을 보였다. 5% 전분현탁액의 가열온도 및 시간의 영향에서 점도는 전단속도의 증가에 따라 감소하였으며, 동일 전단속도에서 가열시간의 증가에 따라 정도는 증가하였다. 찹쌀 전분의 호화완료온도는 다수계가 $65^{\circ}C$, 30분이었고, 일반계는 $70^{\circ}C$, 30분이었다. 농도의 증가에 따라 다수계 및 일반계 찹쌀 전분의 점도는 지수 함수적으로 증가하였으며, 4.5% 근처에서 기울기가 서로 다른 두 개의 직선을 보였다. 호화액의 겉보기 점도는 전단속도의 증가에 따라 직선적으로 감소하였으며 가압 호화액은 상압 호화액보다 다소 높았고, 점도는 한강, 수원 317, 올찰의 순서이었다. 찹쌀 전분의 알카리 호화는 한강 및 올찰은 0.19N NaOH에서 각각 20 및 24분 후에, 수원 317은 0.20N NaOH에서 18분 후에 일정한 점도를 보였다. 찹쌀 전분의 호화에 필요한 알카리의 임계농도는 한강, 수원 317 및 올찰에서 각각 3.8, 4.0, 3.8 meq NaOH/g이었다.

• Composites Research
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• 제35권4호
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• pp.277-282
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• 2022

본 연구에서는 저가 재료인 전분과 물 기반의 현탁액을 이용하여 과속방지턱에 응용 가능한 스마트 소재를 개발하고 물성을 평가하였다. 유변물성측정기를 이용하여 전단율에 따른 점도 및 전단력을 측정하여 전분 농도별 전단농화 발생 현상을 확인하였다. 물체의 낙하 시험과 5-25 km/h의 주행 속도로 충격 후 진동을 측정한 자전거 주행 시험을 통해 거시적인 전단농화현상을 확인하였고, 과속방지턱의 적용 가능성을 확인하였다. 점도 측정 결과, 초기에 전단담화 구간에 이어 전단농화가 발생하였고, 전단농화 현상을 유발하는 임계 변형률은 농도가 증가함에 따라 감소하였다. 또한 전분 농도 증가에 따라 점도와 전단력이 크게 증가하였다. 낙하시험과 자전거 주행시험 결과 현탁액이 단시간에 고체 상태로 바뀌었고 충격 에너지가 유체에 흡수되었다. 유체의 농도와 가하는 충격(속도)이 증가할수록 전단농화현상이 쉽게 발생하였다. 최종적으로 물과 전분 기반의 비뉴턴 유체로 5-25 km/h 범위에서 구동하는 스마트 과속방지턱 재료의 개발을 제안하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1155-1158
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• 2005

Micro-stereolithography is a newly proposed technology as a means that can fabricate a 3D micro structure of free form. It makes a 3D micro-structure by dividing the shape into many slices of relevant thickness along horizontal surfaces, hardening each layer of slice with a focused laser beam, and stacking them up to a desired shape. However, we do not anticipate the electric conductivity of the final product at the existing micro-stereolithography. The reason is that this technology uses polymer to make the product. Thus the new suspension which was mixed conventional photopolymer with metal powder was developed in this study. The developed suspensions were based on SL5180 which is commercialized resin and IMS03 that is made in our laboratory. And Triton X-100 was added at the suspension for getting the scattering effect and stabilizing effect. The layer recoating device was developed to be flat the mixed high viscosity suspension. A 3D micro structure was manufactured by using recoating system and micro-stereolithography system. The fabricated product was sintered to get the electric conductivity. After sintering, a pure copper product was made. In this study, new process was developed by making metal micro structure having an electric conductivity. This technology broadened the realm of the micro-stereolithography technology. And it will be applied to make the 3D micro structure of free form which has a high hardness and an electric conductivity in the near future.