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A. K. Ghosh A. D. Williams J. M. Zucker J. L. Mathews N. Spinhirne 《Experimental Mechanics》2008,48(2):139-152
In nature, shape and structure evolve from the struggle for better performance. Often, biological structures combine multiple
beneficial properties, making research into mimicking them very complex. Presented here is a summary of observations from
a series of experiments performed on a material that closely resembles the human skull bone’s cancellous structure under acoustic
loads. Transmission loss through flat and curved open-cell polyurethane foam samples is observed using air and water as the
two interstitial fluids. Reduction in strength and stiffness caused by porosity can be recovered partially by filling the
interstitial pores with a fluid. The test findings demonstrate the influence of the interstitial fluid on the mechanical characteristics
of a porous structure in a quantitative manner. It is also demonstrated that the transmission loss does not depend only on
the mass per unit area of the structure as predicted by acoustic mass law. Current tests also demonstrate that the transmission
loss is more sensitive to the interstitial fluid than the shape and support conditions of the structures. Test observations
thus support the concepts of “moisture-sensitivity of biological design” and the “law of hierarchy in natural design”. 相似文献
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The structural and electronic transport properties of La1−x
Ce
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MnO3 (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with
Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration
up to 50% doping. The system La0.5Ce0.5MnO3 also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition. 相似文献
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Jérôme JP. Leon 《Letters in Mathematical Physics》1981,5(1):75-80
We establish a transformation which connects the potentials of the one-dimensional Dirac and Klein-Gordon operators. This transformation links the solutions of the nonlinear evolution equations solvable by means of the two inverse spectral transforms which use the Dirac and Klein-Gordon direct and inverse spectral problems. 相似文献
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A relatively noninvasive method consisting of a face mask sampling device, solid-phase microextraction (SPME) fibers, and a gas chromatography-mass spectrometry (GC-MS) for the identification of volatile organic compounds (VOCs) in bovine breath was developed. Breath of three morbid steers with respiratory tract infections and three healthy steers were sampled seven times in 19 days for 15 min at each sampling. The breath VOCs adsorbed on the divinylbenzene (DVB)-Carboxen-polydimethyl siloxane (PDMS) 50/30 microm SPME fibers were transported to a laboratory GC-MS system for separation and identification with an in-house spectral library of standard chemicals. A total of 21 VOCs were detected, many of them for the first time in cattle breath. Statistical analyses using Chi-square test on the frequency of detection of each VOC in each group was performed. The presence of acetaldehyde (P < or = 0.05) and decanal (P < or = 0.10) were associated more with clinically morbid steers while methyl acetate, heptane, octanal, 2,3-butadione, hexanoic acid, and phenol were associated with healthy steers at P < or = 0.10. The results suggest that noninvasive heath screening using breath analyses could become a useful diagnostic tool for animals and humans. 相似文献
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