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1.
The standardized mutual active and reactive sound power of a clamped plate, representing the energy aspect of the reciprocal interactions of two different in vacuo modes, has been computed. It was assumed that the vibrations are axisymmetric, elastic and time harmonic, the plate's transverse deflection is small as compared with the plate's size, and that the vibration velocity is small as compared with the acoustic wavenumber generated. The Kirchhoff-Love theory of a perfectly elastic plate was used. The integral formulae for the mutual sound power were transformed into their Hankel representations which made possible their subsequent computation. A closed path integral was used to express the integral in its Hankel representation to compute the mutual active sound power. The asymptotic stationary phase method was used to compute the two magnitudes, i.e., the mutual active and reactive sound power. The results obtained are the asymptotic formulae valid for the acoustically fast waves. The oscillating as well as the non-oscillating terms have been identified in the formulae to make possible their further separate analysis. The availability of the asymptotic formulae makes possible some fast numerical computations of the mutual sound power. Moreover, the formulae presented herein, together with those for the individual modes known from the literature, make a complete basis for further computations of the total sound power of the plate's damped and forced vibrations in fluid.  相似文献   
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As part of a project funded by the European Commission (EC) for the development and evaluation of multiresidue methods for analysis of drinking and related waters, 15 European laboratories evaluated a method using styrene-divinylbenzene co-polymer solid-phase extraction followed by gas chromatography/mass spectrometry. The main aim of the study was to evaluate whether the method meets the requirements of EC Directive 98/83 in terms of accuracy, precision, and detection limit for 22 pesticides according to the following requirements: limit of detection, < or = 0.025 microg/L; accuracy, expressed as recovery between 75 and 125%; and precision, expressed as repeatability relative standard deviation of the method of < 12.5% and as reproducibility relative standard deviation of the method of < 25%. Analyses for unknown concentrations were performed with fortified commercial bottled and tap waters. All laboratories were able to achieve detection limits of 0.01 microg/L for all pesticides except dimethoate and desisopropylatrazine (0.02 microg/L). The criteria for repeatability were met for all compounds except trifluralin, dimethoate, and lindane in bottled water and chlorpyrifos, dimethoate, and lindane in tap water. The criteria for reproducibility were met for all compounds except trifluralin, dimethoate, and lindane in bottled water and pendimethalin, chlorpyrifos, dimethoate, terbutryn, and lindane in tap water. In terms of accuracy, the method meets the requirements for all pesticides in both matrixes, except for lindane in bottled water and lindane and chlorpyrifos in tap water.  相似文献   
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The main components of organic micro pollution regularly found in the river Elbe, belong to the wide spectrum of pesticides, nitro and chloro benzenes and the chelating agents, especially ethylenediaminetetraacetic acid (EDTA). The level of organic micro pollution with pesticides and the other organic micro pollutants in the upper and middle reaches of the river Elbe between Schmilka and Wittenberge was determined over a period of nearly three years. Four sample preparation methods (SPE: solidphase extraction and LLE: liquid-liquid extraction both with and without derivatization) have been used to analyze a wide spectrum of pesticides with different polarities by GC/ECD, NPD and MS. The pesticide pollution caused by the triazines decreases significantly from 0.35 g/l (mean value) in 1992 up to 0.15 g/l (mean value) in 1994. The correlation with the river water flow shows the diffuse character of the triazine input. In the last year of the pesticide screening a change to the more polar substances such as phenoxyalkanoic acid and nitrophenol pesticides as well as chloralkanoic acid pesticides have been noticed. The origin of trichloroacetic acid (TCA) can be explained by the waste influence, supported by the good correlation of the TCA course with the chloroform concentrations determined.  相似文献   
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This paper presents a simple, self‐contained account of Gårding's theory of hyperbolic polynomials, together with a recent convexity result of Bauschke‐Güler‐Lewis‐Sendov and an inequality of Gurvits. This account begins by establishing some new results. The first concerns the existence of a pointwise arrangement of the eigenvalues so that they become global real analytic functions. The second asserts that the associated “branches” are independent of the choice of hyperbolic direction. © 2013 Wiley Periodicals, Inc.  相似文献   
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This review emphasizes the breadth of metallic and metallic-like polymers evaluated as to thermal properties. Techniques usefully applied to particular systems are noted with the aim of suggesting their application to other systems.  相似文献   
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There have been several previous studies of the dc conductivity of poly(ethylene terephthalate). Disagreement among the various authors indicates the difficulties inherent in this measurement: several authors [1,2] found evidence for ionic conduction through a hopping process; others [3,4] proposed conduction by electrons injected through a barrier.  相似文献   
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