Nihon Reoroji Gakkaishi
Online ISSN : 2186-4586
Print ISSN : 0387-1533
ISSN-L : 0387-1533
Volume 39 , Issue 3
Showing 1-7 articles out of 7 articles from the selected issue
ORIGINAL ARTICLES
  • Tomoko Takahashi, Mitsuyo Tsuge, Hiro Ogoshi
    2011 Volume 39 Issue 3 Pages 93-98
    Published: July 15, 2011
    Released: July 06, 2011
    JOURNALS FREE ACCESS
    The present study used semi-liquid foods, prepared in three different levels of hardness with the use of commercial thickening agents (containing xanthan gum, guar gum, or processed starch as the main substance for thickening), as samples to examine the relation between the physical properties of those food samples and the electromyography (EMG) of human beings during swallowing. The EMG during swallowing was obtained through measurement of EMG from supra-hyoid musculatures during swallowing. The flow behavior and the frequency dependence of dynamic viscosity, obtained through measurements of physical properties, demonstrated that the xanthan gum sample and processed starch sample have weak gel structures, and that the gel structure was particularly strong for xanthan gum sample. In contrast, the guar gum sample was found to have a sol-like structure. For the xanthan gum sample which has a gel structure in the solution, the harder the sample, the larger the EMG during swallowing tended to be. In the case of samples with hardness level of 8×102N/m2, which is the hardest sample used in the present study, the EMG during swallowing for xanthan gum sample was found to be significantly larger compared with that of the sol-structured guar gum sample. These findings suggest that, for xanthan gum sample, the harder the sample, the more swallowing efforts are being made by human beings when conveying the sample bolus from the oral cavity to the pharynx. It can also be assumed that, among samples at a hardness level of 8×102N/m2, which requires more swallowing efforts compared with samples of other hardness levels used in the present study, the EMG during swallowing for guar gum sample that demonstrates sol-like structure when the sample bolus is being conveyed from the oral cavity to the pharynx, was significantly smaller compared with that of the xanthan gum sample. The outcome of the present study suggest that, for semi-liquid foods prepared with the use of commercial thickening substances as swallow-support agents, the hardness level of the semi-liquid food can exert different influences on the EMG during swallowing, depending on the main ingredient used as thickening substance.
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  • Masaaki Motozawa, Takahiro Watanabe, Yasuo Kawaguchi
    2011 Volume 39 Issue 3 Pages 99-104
    Published: July 15, 2011
    Released: July 06, 2011
    JOURNALS FREE ACCESS
    Particle image velocimetry (PIV) measurements were performed on drag-reducing channel flow with surfactant additives. In order to clarify the large-scale structures, the measurement field was set to a relatively large size (130 mm in the streamwise direction × 40 mm in the wall-normal direction). The surfactant used in this experiment was a cationic surfactant CTAC, and NaSal was added to the solution with the same weight concentration as counter ions. We examined the effects of Reynolds number ranging from 15000 to 30000 and concentration of CTAC which was set to 25 ppm or 40 ppm in the flow. Based on these measurements, two-dimensional two-point correlations were calculated to illustrate the characteristic structures. In drag-reducing flow, there were large-scale fluid lumps in the near-wall region. These structures extended toward the streamwise direction and were inclined at approximately 10 degrees to the channel wall. These characteristic structures were only observed in the case of high drag reduction rate and the tendency of these structures did not change with varying Reynolds number. It is thus considered that turbulent coherent structures change, and sweep and ejection which produce skin frictional drag are suppressed.
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  • Takehiro Yamamoto, Kazuhiro Sawa
    2011 Volume 39 Issue 3 Pages 105-111
    Published: July 15, 2011
    Released: July 06, 2011
    JOURNALS FREE ACCESS
    Shear banding emerges in shear flows of wormlike micelle solutions and is observed as band velocity profiles in velocity measurement experiments. In our previous experiments, multi-band velocity profiles were captured in shear flows of a CTAB/NaSal solution between parallel plates. The relationship between the band velocity profile and the micellar network structure is an interesting issue. In the present study, the orientation behavior of the micelle network was numerically analyzed using a network scission model. Brownian dynamics simulations were carried out for a two-species model of micelle networks derived in the Vasquez-Cook-McKinley model. The numerical results indicate that the effect of the orientation of short micelles on the behavior of the entire system is small, whereas long micelles tend to align well in the flow direction, their degree of orientation is relatively high, and their orientation behavior strongly affects the orientation of the entire system. Numerical analysis using the BD simulation provides useful information on the flow-induced structures of the micelle network, and hence the present approach is effective for the analysis of the mechanism of shear banding.
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  • Ali Ahmadpour, Hossein Amini-Kafiabad, Jila Samadi, Kayvan Sadeghy
    2011 Volume 39 Issue 3 Pages 113-117
    Published: July 15, 2011
    Released: July 06, 2011
    JOURNALS FREE ACCESS
    In the present work, nonlinear acoustic oscillation of a single spherical gas bubble immersed in an unbounded thixotropic fluid is studied numerically. Using Moore's structural model as the constitutive equation of the liquid surrounding the bubble, the general Rayleigh-Plesset integro-differential equation, which governs bubble dynamics, is solved numerically using the Gauss-Laguerre Quadrature (GLQ) method. It is shown that at sufficiently high pressure amplitudes, typical of medical ultrasound applications, a second harmonics may be observed in the bubble's response.
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  • Toshiyuki Shikata, Yuichi Kuruma, Kenji Hanabusa
    2011 Volume 39 Issue 3 Pages 119-125
    Published: July 15, 2011
    Released: July 06, 2011
    JOURNALS FREE ACCESS
    Dynamic viscoelastic measurements, viscosity growth function measurements at the onset of steady shear flows and dielectric measurements were carried out in a highly viscoelastic system (SEH2B/C10), solutions of 1-stearoylamino-3,5-bis(2-ethylhexylaminocarbonyl)benzene (SEH2B) in n-decane (C10), to investigate structure and dynamics of a supramolecular polymer formed in the system via intermolecular hydrogen bonding. The SEH2B/C10 system showed almost the same viscoelastic and dielectric features: a single Maxwell element type viscoelasticity and single Debye-type dielectric response, over a wide concentration range as that observed in another, previously examined, supramolecular polymeric system (DO3B/C10) formed by N,N',N”-tris(3,7-dimethyloctyl)benzene-1,3,5- tricarboxamide in C10 irrespective of distinctive difference in chemical structure between SEH2B and DO3B. These reveal that structure including macro-dipole moments and dynamics of the supramolecular polymer of SEH2B is similar to that of the suprapolymer of DO3B beyond the difference in their chemical structures.
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NOTE
  • Yohji Kawasaki, Hiroshi Watanabe, Takashi Uneyama
    2011 Volume 39 Issue 3 Pages 127-131
    Published: July 15, 2011
    Released: July 06, 2011
    JOURNALS FREE ACCESS
    The Kohlrausch-Williams-Watts (KWW) relaxation function, FKWW(t) = exp{-(t/τKWW)β} with 0 < β ≤ 1 has been often utilized to describe relaxation processes in systems governed by cooperativity/coupling of molecules therein. Nevertheless, this function has not been well addressed in the general, phenomenological framework of linear relaxation phenomena, for which the relaxation function is expressed as F(t) = Σp gpexp{-t/τp} with gp and τp being the normalized intensity and characteristic time of pth (exponential) relaxation mode. In this study, the KWW function is analyzed to address this function in this general framework and derive analytical expressions of average relaxation times.
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