• Title, Summary, Keyword: WLF

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Identification of Cross-WLF Viscosity Model Parameters Using Optimization Technique (최적화기법을 이용한 Cross-WLF점도 모델 계수 추정)

  • Kim, Sun-Yong;Park, Si-Hwan
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.4
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    • pp.623-632
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    • 2018
  • Predicting the behavior of rheological polymers is highly shear rate- and temperature-dependent. The Cross-WLF viscosity model has become a powerful solution that describes the shear rate- and temperature-dependent characteristics. To estimate the behavior of polymers in computational simulations, the coefficients of the Cross-WLF model should be well identified. An identification technique was proposed to determine the Cross-WLF viscosity model coefficient. The assumption is that the Cross-WLF viscosity model well describes the real characteristics of polymers when the calculated viscosity with the parameters is identical to the reference data. In this study, Auto-desk Moldflow data were used as a reference. The numerical examples showed that the proposed method accurately identifies the Cross-WLF viscosity model coefficients.

Prediction of the Rhelolgical of Soybean Curd during Storage by using WLF equation (저장중의 두부에 WLF식을 이용한 물성 변화 예측에 관하여)

  • Jang, Won-Young;Kim, Byung-Yong;Kim, Myoung-Hwan
    • Korean Journal of Food Science and Technology
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    • v.27 no.2
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    • pp.193-198
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    • 1995
  • The changes in the rheological properties of soybean curd upon the various storage temperatures ($5{\sim}25^{\circ}C$) were measured by the stress-relaxation test and analysed by time-temperature superposition theory. As the storage temperature was lower, higher initial and equilibrium stress of soybean curd were observed. When the stress-relaxation curves were moved horizontally by using the shift-factor on the basis of reference temperature, the master curve was obtained. By applying master curve and shift-factor to the WLF (Williams-Landel-Ferry) equation, activation energy (30kcal/mol) was calculated and storage time at the specific temperature could be predicted, suggesting the equivalent shelf-life of soybean curd texture.

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Quantitative estimation of the energy ux during an explosive chromospheric evaporation in a white light are kernel observed by Hinode, IRIS, SDO, and RHESSI

  • Lee, Kyoung-Sun;Imada, Shinsuke;Watanabe, Kyoko;Bamba, Yumi;Brooks, David H.
    • The Bulletin of The Korean Astronomical Society
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    • v.41 no.2
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    • pp.67.3-68
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    • 2016
  • An X1.6 flare occurred in AR 12192 on 2014 October 22 around 14:06 UT and was observed by Hinode, IRIS, SDO and RHESSI. We analyze a bright kernel which produces a white light flare (WLF) with continuum enhancement and a hard X-ray (HXR) peak. Taking advantage of the spectroscopic observations of IRIS and EIS, we measure the temporal variation of the plasma properties in the bright kernel in the chromosphere and corona. We found that explosive evaporation was observed when the WLF occurred, even though the intensity enhancement in hotter lines is quite weak. The temporal correlation of the WLF, HXR peak, and evaporation flows indicates that the WLF was produced by accelerated electrons. To understand the white light emission processes, we calculated the deposited energy flux from the non-thermal electrons observed by RHESSI and compared it to the dissipated energy estimated from the chromospheric lines (Mg II triplet) observed by IRIS. The deposited energy flux from the non-thermal electrons is about $3.1{\times}10^{10}erg\;cm^{-2}s^{-1}$ when we assume a cut-off energy of 20 keV. The estimated energy flux from the temperature changes in the chromosphere measured from the Mg II subordinate line is about $4.6-6.7{\times}10^9erg\;cm^{-2}s^{-1}$, 15 - 22 % of the deposited energy. By comparison of these estimated energy fluxes we conclude that the continuum enhancement was directly produced by the non-thermal electrons.

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Effect of Aminosiloxane Modifier on Chemorheological Properties of Ortho-cresol Novolac Epoxy (Ortho-cresol Novolac형 에폭시의 화학레올로지 특성에 미치는 아민 개질제의 영향)

  • 김윤진;안병길;김우년;서광석;김환건;윤초규
    • Polymer(Korea)
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    • v.26 no.1
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    • pp.88-97
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    • 2002
  • The effect of aminosiloxane modifier on the chemorheological properties of ortho-cresol novolac epoxy/phenol novelac/triphnylphosphine resin system was investigated aat different isothermal curing temperatures. By adding the aminosiloxane to the resin system, not only conversion rate and conversion were increased but also glass transition temperature was promoted. Critical conversion and gelation time obtained at the crossover point between storage and loss moduli were reduced and thus the viscosity was increased by the aminosiloxane. $C_1$ and $C_2$ in the WLF equation calculated from the glass transition temperature as a function of conversion and measured viscosity were found to vary with the curing temperature. By applying the change of glass transition temperature with conversion, $C_1$ and $C_2$ to WLF equation, it was possible to predict accurately the viscosity change with isothermal curing reaction.

A Study on Compressive Creep Behavior of ACM Rubber using TMA Thermal Analysis (TMA 열분석을 이용한 ACM 고무의 압축크립거동 연구)

  • Ahn, WonSool;Lee, Hyung Seok
    • Elastomers and Composites
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    • v.48 no.2
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    • pp.156-160
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    • 2013
  • A study on compressive creep behavior of ACM rubber for automotive engine gasket was performed using TMA thermal analysis. From the results of isothermal measurements with constant load of 1 N at several different temperatures of 160, 180, 200, and $220^{\circ}C$, compressive creep data at the given temperatures were obtained, and therefrom, shift factor ($a_T$) and master curve at reference temperature of $160^{\circ}C$ were obtained using time-temperature superposition principle (TTSP). $C_1$ and $C_2$ of WLF (Williams-Landel-Ferry) equation were calculated through the WLF plot as -1.107 and 11.571, respectively. From this, life time of ACM rubber at $120^{\circ}C$ was predicted as about 24,000 hrs.

지하수 유동 모텔을 이용한 지하수위 변동법의 적용성 분석

  • 구민호;이대하
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • pp.28-31
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    • 2002
  • The water level fluctuation (WLF) method is a conventional method for quantifying groundwater recharge by multiplying the specific yield to the water level rise. A 2-D unconfined flow model with a time series of the recharge rate is developed. It is used for elucidating the errors of the WLF method which is implicitly based on the tank model where the horizontal flow in the saturated zone is ignored. Simulations show that the recharge estimated by the WLF method is underestimated for the observation well near the discharge boundary. This is due to the fact that the hydraulic stress resulting from the recharge is rapidly dissipating by the horizontal flow near the discharge boundary Simulations also reveal that the recharge was significantly underestimated with increase in the hydraulic conductivity and the recharge duration, and decrease in the specific yield.

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Analysis of Relationship between Temperature and Relaxation Time of Polymer Solution depending on Polymer Concentration and Salinity for Enhanced Oil Recovery (석유회수증진용 폴리머 용액의 농도와 염도에 따른 완화시간과 온도 관계 분석)

  • Kim, Yeong-Gyu;Kang, Pan-Sang;Lim, Jong-Se
    • Journal of the Korean Society of Mineral and Energy Resources Engineers
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    • v.54 no.5
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    • pp.512-520
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    • 2017
  • Polymer flood which is one of enhanced oil recovery technology has been used for mobility control by injecting viscous polymer solution into the reservoir. Viscoelasticity of polymer solution contributes to increase in displacement efficiency of remaining oil. Since viscoelastic properties are affected by temperature, it is necessary to consider relationship between temperature and viscoelasticity for designing the polymer flood. Relaxation time is used as a major parameter to quantify the viscoelasticity of the polymer solution. In this paper, dynamic moduluses were measured using rheometer and relaxation time was determined using cross-over point method. Relaxation time showed positive correlation with polymer concentration and negative correlations with salinity (NaCl) and temperature. In addition, a correlation for estimation of relaxation time depending on temperature was suggested using WLF (William-Landel-Ferry) model.

A Foundamental Study on the Solvent Dyeing Part 1. Change of PET Substrate Treated with Water, TCE and Water/TCE Emulsion. (용제염색에 관한 기초적 연구 제일보 물, TCE 및 물/TCE 처리에 의한 PET 기질의 변화)

  • Chung Doo Jin
    • Journal of the Korean Society of Clothing and Textiles
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    • v.2 no.2
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    • pp.245-252
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    • 1978
  • In order to obtain some information for solvent dyeing, polyethylene terephthalate (PET) was treated with water, tetrachloroethylene yarn (TCE), and water/TCE emulsion for three hours at the temperatures from $40^{\circ}$ to $140^{\circ}C$. The change of fine structure of substratum by measuring the shrinkage, the degree of crystallinity, the stress relacxation modulus and Young's modulus. The P.E.T. film was also treated in water (at $140^{\circ}C$) for 4 hours to stabilize the substratum. By means of film roll cyliderical method, the Disperse Blue 27 was diffused. Then, calculated the diffusion coefficient and examined the application of WLF equation. However, the temperature dependence of the shrinkage could be explain with WLF equation, the diffusion coefficient couldn't be applied the WLF equation when the substratum was stabilized. From the result, the effects on shrinkage were in the order of water

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