International Journal of Microgravity Science and Application
Online ISSN : 2188-9783
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Showing 1-5 articles out of 5 articles from the selected issue
  • Suguru SHIRATORI, Takuro USUI, Shiho KOYAMA, Shumpei OZAWA, Hideaki NA ...
    Type: Original Paper
    2021 Volume 38 Issue 3 Pages 380301-
    Published: July 31, 2021
    Released: July 31, 2021
    JOURNALS OPEN ACCESS
    This paper provides a practical implementation of a twophase flow solver for Newtonian fluids with an immiscible interface. The solution procedure is composed of the tangent of hyperbola for interface capturing (THINC), the simple coupled level-set and volumeof- fluid (S-CLSVOF) algorithm, and the density-scaled balanced continuum surface force (DSB-CSF) model. The newly introduced methods in the present study are 1) THINC with slope weighting (THINC/SW) extended to unstructured meshes and an 2) efficient initialization of the level-set function, which enables fewer iterations of the re-initialization. The validity and effectiveness of the present method are confirmed through three benchmark problems with comparison to other solvers. Regarding the accuracy of the interface advection, the present solver showed a sufficiently small error, which is comparable to the other established solvers. Regarding the re-initialization procedure of the level-set function, the number of iterations required by the proposed method is approximately half that required by a conventional method. For the benchmark problem on the thermocapillary flow in a rectangular cavity, it is confirmed that the present solver provides a solution sufficiently close to the asymptotic solution to this problem.
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  • Yoshihiro KOBAYASHI, Masato SHIINOKI, Reina YAMATAKE, Tadahiko MASAKI, ...
    Type: Original Paper
    2021 Volume 38 Issue 3 Pages 380302-
    Published: July 31, 2021
    Released: July 31, 2021
    JOURNALS OPEN ACCESS
    This study establishs a method to determine the diffusion time required for diffusion measurement by using the long capillary technique and through in-situ X-ray fluorescence analysis. A diffusion couple of pure Sn (60 mm height) and Sn90Bi10 (3 mm height) was set to provide stable density layering and maintained at 573 K. The X-ray source was positioned 10 mm above the bottom of the sample. The detected intensity of Lβ emission line of Bi (Bi Lβ) changed mainly because of the diffusion of Bi in liquid Sn. The apparent diffusion coefficients (𝐷𝑎𝑝𝑝) were calculated by fitting the analytical solution for the diffusion to the temporal distribution of Bi Lβ intensity by varying the fitting time range from 0 to 𝑡𝐷 (diffusion time). The change in 𝐷𝑎𝑝𝑝 was large at short 𝑡𝐷, but decreased with increasing 𝑡𝐷. The deviation of 𝐷𝑎𝑝𝑝 from the value corresponding to the longest 𝑡𝐷 and the maximum range scale of the confidence interval of 𝐷𝑎𝑝𝑝 were determined. The largest calculated value is considered to be the systematic error in the diffusion measurement (𝛥𝐷). For the required value of 𝑡𝐷, 𝛥𝐷 becomes less than the acceptable systematic error in the diffusion measurement. The convergent 𝐷𝑎𝑝𝑝 [(2.16±0.09)×10-9 m2/s] agreed with the microgravity reference data in the error range.
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  • Reina YAMATAKE, Masato SHIINOKI, Yoshihiro KOBAYASHI, Tadahiko MASAKI, ...
    Type: Original Paper
    2021 Volume 38 Issue 3 Pages 380303-
    Published: July 31, 2021
    Released: July 31, 2021
    JOURNALS OPEN ACCESS
    This paper proposes a method to process the X-ray fluorescence spectra and evaluate the X-ray fluorescence intensity ratio of liquid alloys using X-ray fluorescence analysis. Pure Sn, Bi, and Sn-Bi alloys (Sn-20, 40, 60, and 80 atomic percentages of Bi) heated at 548 K in a crucible were irradiated using X-rays to obtain spectra at an optimal detection angle and optimal distance between the X-ray source and the sample. Aluminum foil was placed above the sample and used as the thermal protection material for the X-ray source. The obtained spectra were processed using function fitting to subtract the background, and the peak areas of Lα and Lβ emission line of Bi (Bi Lα and Lβ) were calculated as the Bi Lα and Lβ intensity, respectively. The quartic and Gaussian functions were determined to be optimum for calculating the background and the peak areas, respectively. The values for the fitted peaks of the spectra agreed with the energy values of the peak and reliable determination values. Further, the experimental Bi Lα/Lβ intensity ratios were calculated from the measured intensities. The ratios increased with Bi concentration. This increase could be explained using the predicted value, which was obtained using a formula considering X-ray absorption, X-ray fluorescence generation, and the distance dependence of the intensity.
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  • Manami MURATA, Koji HASEGAWA
    Type: Original Paper
    2021 Volume 38 Issue 3 Pages 380304-
    Published: July 31, 2021
    Released: July 31, 2021
    JOURNALS OPEN ACCESS
    This study presents a numerical evaluation of the levitation stabilities of samples in resonant acoustic fields with various reflector geometries and levitated sample radii. Contactless sample manipulation by sound is of great importance in the fields of analytical chemistry, biology, material engineering, and food science. The establishment of the levitation stability plays a critical role in the achievement of reliable acoustic sample manipulation in midair. To enhance the levitation stability in acoustic levitator, we focused on the effect of the reflector curvature radius and sample radius. We characterize the length scale of the reflector and sample radius by the wavelength of sound λ. The radii of curvature of the reflector were varied as 1λ, 1.5λ, 2λ, and ∞. The simulation results revealed that the reflector with the radius of curvature of 1.5λ yielded the best levitation stability to levitate the sample along the vertical direction and hold it along the horizontal direction. With the reflector of the curvature radius of 1.5λ, interactions between the sound fields for four different samples were simulated, and it was demonstrated that all cases were levitated in a stable manner. Our findings can provide deeper insights into contactless sample manipulations for increased sample manipulation stability.
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  • Shohreh GHASEMI, Mahmood Dashti, Fargol Mashhadi Akbarboojar
    Type: Review Paper
    2021 Volume 38 Issue 3 Pages 380305-
    Published: July 31, 2021
    Released: July 31, 2021
    JOURNALS OPEN ACCESS
    1) Background: Space exploration impacts astronauts to a variety of gravitational stresses. Exposure to a reduced gravity environment affects human anatomy and physiology. Countermeasures to restore homeostatic states within the human body have begun. 2) Methods: Six data bases searches (1970–present) were performed for randomized controlled clinical studies, systematic review, comparing the salivary biomarkers in earth to The Space station, search was complimented by an additional hand search of the selected papers and reviews published between 1973 and 2020. Eligible studies were selected based on the inclusion criteria, and quality assessments were conducted. After further searching 12 articles were finally selected 3) Results: We found 459 articles with first search within main databases and 9 articles among gray literature and later using Endnote X9 software we eliminated the duplicate papers and left with 308 and we deleted the 151 duplicated articles and 308 articles and implicating the inclusion and exclusion criteria. After deliberate search through abstracts 12 articles were chosen for full text. 4) Conclusions: Blood volume that gravity forces to the lower extremities of the body is free to uniformly distribute to organs and limbs. While the negative adaptations to spaceflight propose that many of these changes are influenced by an underlying physiological stress process of allostatic load and this can be measured via a common stress hormone: cortisol. Some shuttle missions showed urinary cortisol to be elevated inflight and postflight, Other studies recorded plasma, serum, and salivary cortisol levels to not change from preflight to flight. Thus, this issue remains one of the important issues for future human explorations.
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