• Korea-Australia Rheology Journal
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• v.20 no.4
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• pp.213-220
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• 2008

The effects of temperature on the rheological properties of the solutions of poly(vinylidene fluoride-co-hexafluopropylene) (PVDF-HFP) in dimethyl acetamide (DMAc) were investigated in terms of frequency and concentration. The effects of temperature on the intrinsic viscosity of the solutions were discussed. In dynamic rheological measurement, the concentrated solutions showed a little unexpected rheological response; as temperature was increased dynamic viscosity was increased and the solutions exhibited more noticeable Bingham body character over the temperature range, 30 to $70^{\circ}C$. In addition, the solution gave longer relaxation time, lower value of loss tangent and higher value of yield stress at higher temperature and at higher concentration. On the other hand, the dilute solutions revealed that intrinsic viscosity was decreased and its Huggins constant was increased with increasing temperature. These physical parameters suggested that the increase of viscosity with increasing temperature resulted from the localized gelation of PVDF-HFP due to reduced solubility to the solvent.

• Elastomers and Composites
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• v.33 no.1
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• pp.44-51
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• 1998

The purpose of this experiments were investigated on the physical properties of rubber com-pounds containing two types carbon black. Bound rubber and interaction coefficient for com-pounds with pure carbon black were higher than those for the compounds with dual phase carbon black. Slightly higher values in 300% modulus and tensile strength indicated that the ratio of rubber-filler bound to rubber-rubber bound of pure carbon black were higher than those of com-pounds with dual phase carbon black. It was founded that dynamic properties, that is rebound, heat build-up, 0 & $60^{\circ}C$ tan $\delta$, and cut and chip loss of compounds with dual phase carbon black were better than those of compounds with pure carbon black, but abrasion property of dual phase carbon black was lower than those of pure carbon black because of low reinforcing ability.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.2
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• pp.70.2-70.2
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• 2019

Recent observational works have reported spiral wave patterns (SWPs) in sunspots, but there is a lack of samples to derive the physical properties. In this presentation, we suggest the automatic method to detect the SWPs in observational data and present their statistical properties. From our method, we find more than 1000 SWPs observed by the Atmospheric Imaging Assembly onboard in the Solar Dynamic Observatory from 2013 to 2018. From our samples, more than half of the SWPs has the one spiral arm. The predominant oscillation period is 2 to 3 minutes. The rotating direction of the spiral arms does not depend on the latitude and the polarity of the sunspots. Our statistical results support the physical model suggested by Kang et al. (2019) that explain the generation of SWPs as the depth of the wave driving source and azimuthal modes in the straight vertical magnetic flux tube.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2006.06b
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• pp.209-213
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• 2006

Relationship between printability and rheological properties of UV flexographic (flexo) inks were investigated. UV flexo suspensions of carbon black in liquid medium having various binding materials such as acylate pre-polymer, di/multi-functional monomer, and diluents, were used as sample inks. Inks were characterized on a rheometer in terms of steady and dynamic behaviors. To understand the rheological properties of UV flexo inks, we must determine the specific rheological properties of chemical and/or physical interactions of their components (pigments, functional monomers, and pre-polymers). In particular, we discussed the influence of multi-functional monomers and the relationship between the rheological properties and transient networks formed by carbon black. In this study, we investigated the interrelationships between rheological properties of UV flexo inks and chemical and/or physical interactions of their components. To investigate correlations between the printability and the rheological behaviors induced by interfacial interactions between ink compositions, we carried out rheological tests of UV ink suspensions. The results were compared with printing tests so as to find out the relationship between printability and rheological properties of ink.

• Journal of Pharmaceutical Investigation
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• v.29 no.4
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• pp.295-307
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• 1999

Using a Rheometries Fluids Spectrometer (RFS II), the dynamic viscoelastic properties of aqueous poly(ethylene oxide) (PEO) solutions in small amplitude oscillatory shear flow fields have been measured over a wide range of angular frequencies. The angular frequency dependence of the storage and loss moduli at various molecular weights and concentrations was reported in detail, and the result was interpreted using the concept of a Deborah number De. In addition, the experimentally determined critical angular frequency at which the storage and loss moduli become equivalent was compared with the calculated characteristic time (or its inverse value), and their physical significance in analyzing the dynamic viscoelastic behavior was discussed. Finally, the relationship between steady shear flow and dynamic viscoelstic properties was examined by evaluating the applicability of some proposed models that describe the correlations between steady flow viscosity and dynamic viscosity, dynamic fluidity, and complex viscosity. Main results obtained from this study can be summarized as follows: (1) At lower angular frequencies where De<1, the loss modulus is larger than the storage modulus. However, such a relation between the two moduli is reversed at higher angular frequencies where De>l, indicating that the elastic behavior becomes dominant to the viscous behavior at frequency range higher than a critical angular frequency. (2) A critical angular frequency is decreased as an increase in concentration and/or molecular weight. Both the viscous and elastic properties show a stronger dependence on the molecular weight than on the concentration. (3) A characteristic time is increased with increasing concentration and/or molecular weight. The power-law relationship holds between the inverse value of a characteristic time and a critical angular frequency. (4) Among the previously proposed models, the Cox-Merz rule implying the equivalence between the steady flow viscosity and the magnitude of the complex viscosity has the best validity. The Osaki relation can be regarded to some extent as a suitable model. However, the DeWitt, Pao and HusebyBlyler models are not applicable to describe the correlations between steady shear flow and dynamic viscoelastic properties.

• KSTLE International Journal
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• v.1 no.1
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• pp.43-47
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• 2000

Oil seals will experience a small amplitude dynamic excitation due to the shaft eccentricity as well as out-of-roundness of the shaft. The direct integration method is selected to analyze the time domain response of the seal lip-shaft contact. The physical properties of rubber seal materials are experimentally analyzed. Effects of both frequency and temperature on the material stiffness behavior are investigated for the linear viscoelastic materials of the seal. Using the nonlinear transient model, a finite element analysis of the lip-shaft contact behaviors under dynamic conditions is presented as a function of the shaft eccentricity, the shaft interference and the garter spring stiffness. The FEM results based on the experimental data indicate that the increased rotating speed may produce the separation conditions. These results will be very useful in predicting the leakage of oil seals under dynamic conditions.

• The Korean Journal of Food And Nutrition
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• v.14 no.6
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• pp.596-604
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• 2001

Twelve varieties of Korean rice and ten varieties of Japanese rice were selected. After being milled. they were analyzed about various physicochemical properties such as moisture, protein and amylose, a -amylase activity, gelatinization properties. And after being cooked with proper amount of water texture and other physical properties were measured by Texturometer, Tensipresser and Rheolograph-micro. Finally the sensory evaluation test was carried out. The results were as follows. 1. In case of protein contents, amylose contents and $\alpha$-amylase activity, Korean rice had a slightly higher value than Japanese As a consequence. Korean rice showed a little stronger hardness and a little weaker stickiness compared with Japanese rice. 2. Amylose contents showed very high correlation with other physicochemical properties and peak viscosity and gelatinization temperature of RVA, the ratio of stickiness to hardness( -Hl/Hl ) of Texturometer and the tan $\delta$(the ratio of dynamic loss to dynamic viscoelasticity) of Rheolograph-micro showed high correlation with other analyzed properties. 3. The ( -/+)work balance of low compression test(25% ) of Tensipresser analysis(texture analysis on the surface of cooked rice) and tan f of Rheolograph-micro showed very high correlation with sensory evaluation results. By using this parameters as major independent variables, some trials to derive high confidence multiple regression equations were accomplished. By the equations it would be possible to make an approximate pre-estimate of eating quality for unknown japonica rice.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.7
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• pp.562-568
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• 2014

This study aimed to identify changes in the physical properties of artificial mineral-fiber materials used as building insulation that had been installed in the outer walls of buildings for a long time. To achieve this goal, glass fiber and rock wool were collected from outer walls in actual buildings and their acoustic and thermal performances were measured. These were compared with measurements from similar products manufactured recently. The results showed that old, used samples had a lower sound absorption coefficient compared to recently manufactured materials. The old samples also displayed increased compressibility compared to new materials. For example, the compressibility difference for glass wool was 7.32 mm. Old samples had a dynamic stiffness $1.28MN/m^3$ higher than new material samples. The thermal conductivity of both old and new samples increased within creasing temperature. They showed similar results at temperatures between 0 and $20^{\circ}C$.

• 한국지구물리탐사학회:학술대회논문집
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• 1999.08a
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• pp.156-175
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• 1999

Recently the application of geophysical well logging to geotechnical site investigation is increasing, because the merit that geophysical logs provide the high resolution and in-situ physical properties in volumes of rock surrounding the borehole. Geophysical well logs are used to identify lithologic boundaries and fracture, to determine the physical properties of rock(i.e., density, velocity etc.), and to detect permeable fracture zones that could be conduits for ground water movement through the rocks. The principle of heat-pulse meter, the calibration of gamma-gamma logging, and principles and data processing of full waveform sonic logging are briefly reviewed, and the case studies of geophysical logs are discussed. Correlation between velocity by sonic logging and rock mass classification such as RMR(Rock Mass Rating) value is considered.

• Textile Coloration and Finishing
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• v.29 no.2
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• pp.77-85
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• 2017

The interfacial adhesion between fiber and matrix affects the physical properties of fiber reinforced composites. In this study, 3-(Methacryloyloxy)propyltrimethoxy silane(MPS) coupling agent was used to increase the interfacial adhesion between polyketone fiber and epoxy resin. The change of surface chemical composition of polyketone fiber treated with MPS was analyzed using a FTIR-ATR. The interfacial bonding between fiber and resin increased with silane coupling agent largely. Consequently, interfacial shear strength(IFSS) was enhanced with increasing concentration of MPS coupling agent and thus, the physical properties of the composites such as flexural properties and dynamic mechanical properties were changed. Flexural strength and modulus increased when the MPS concentration was higher than 0.5wt%. The dynamic storage modulus of Polyketone/Epoxy composites treated with MPS was higher than that of the untreated one. When the MPS concentration of 3wt%, the highest storage modulus was obtained.