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Antonio Uris Jose Maria Bravo Jaime Llinares Hermelando Estelles 《Applied Acoustics》2004,65(4):421-430
In this paper the influence on sound reduction index of the length and the depth of sound leaks at the perimeter of lightweight partitions was examined. It was shown that the most important decrease on sound reduction index is caused by the first slit between lightweight partition and one of the structural members. When the length of the slit is increased, the decrease on sound reduction index is less significative. Calculated results show the same effects as measured ones. 相似文献
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The Pb-PAN system in the presence of non-ionic surfactants (polyoxyethylene nonylphenols) has been studied spectrophotometrically. The optimum conditions for Pb determination are pH 9 (Na(2)B(4)O(7)-HClO(4)), 5% surfactant and measurement at 555 nm. The system obeys the Lambert Beer law over the Pb concentration range 1.3-4.5 ppm; the molar absorptivity is 2.02 x 10(4) l.mole(-1).cm(-1) at 555 nm. The relative standard deviation is 0.9% and the limit of detection 0.12 ppm. Lead can be determined in acetic acid extracts of ceramic enamels by extraction with sodium diethyldithiocarbamate into carbon tetrachloride and stripping with 4M hydrochloric acid to remove interferent species. The results obtained are in agreement with those obtained by a standard AAS method. 相似文献
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Jose Maria Bravo Jaime SinisterraAntonio Uris Jaime LlinaresHermelando Estelles 《Applied Acoustics》2002,63(10):1051-1059
In this paper the influence on sound reduction index of a thin air layer between gypsum board layers of lightweight partitions has been examined. It has been shown that the air layer between gypsum boards causes a decrease in sound reduction index due to mass-air-mass resonance. When the thin air layer is filled with a damping layer, the sound reduction index is increased for frequencies around the critical frequencies. Predictions show similar effects to those measured. 相似文献
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Antonio Uris Jaime SinisterraJose Maria Bravo Jaime LlinaresHermelando Estelles 《Applied Acoustics》2002,63(7):813-818
In this paper measured sound reduction index data for lightweight partitions with gypsum board layers attached to the frame with two different screw spacings are presented. Data are used to show the effect of screw spacings and to quantify the effect on sound reduction index. The results show that screw spacing had a great effect in double walls where each gypsum board layer was attached to each side of a timber frame. 相似文献
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The Cd-PAN system in the presence of non-ionic surfactants (polyoxyethylene nonylphenols), which dissolve the reagent and complex by formation of micelles, has been studied spectrophotometrically. The optimum conditions for Cd determination are pH 9 (Na2B4O7-HClO4), 2% of surfactant and measurement at 555 nm. The complex is Cd(PAN)2 and its conditional formation constant is 3.5 × 1011. The system obeys the Lambert-Beer law, with an error of 0.9% over the Cd concentration range 0.44–1.74 ppm; the molar absorptivity is 4.94 × 1041·mole−1.cm−1 at 555 nm. The relative standard deviation is 0.7% and the limit of detection 0.009 μg/ml. The selectivity with respect to species important in the ceramic industry is adequate for application of the method to determination of Cd in acetic acid extracts of ceramic enamels. 相似文献
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