It is very difficult to shield low frequency sound waves. This is mainly because in order to cause wave scattering or reflection, the usual wisdom is that the size of the scatterers must be on the order of the wavelength. Since low frequency sound has long wavelength, it follows that the shielding m.....
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This invention belongs to the area of medicinal and health products. The invention provides a traditional Chinese medicinal formula and its preparation methods for treating and preventing menopausal symptoms and osteoporosis. The formula is prepared by boiling Radix Angelica Sinensis, Radix Astragal.....
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Despite the introduction of new building and construction methods, concrete is still the most versatile and widely produced industrial material in the world. While it is rare for concrete structure to fail due to lack of intrinsic strength, there is increasing number of cases of concrete structures .....
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