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1.
Fundamentals of the direct measurement of sound intensity and practical applications 总被引:1,自引:0,他引:1
Sound intensity is a measure of the magnitude and direction of the flow of sound energy. Developments in sound intensity measurement capabilities in the last quarter century have occurred because of several reasons. The main ones include the derivation of the cross-spectral formulation for sound intensity and developments in digital signal processing. This paper begins with a brief historical introduction of sound intensity measurements. Then elementary theory for sound intensity is presented. A section on sound intensity measurements is then included. The next section of the paper discusses sources of measurement error; the major sources of error are described in some detail. The paper continues with a discussion of the main applications of sound intensity measurements: sound power determination, noise source identification, and transmission loss measurements. The paper concludes with a discussion of ISO and ANSI intensity related standards and relevant references. 相似文献
2.
We investigate the connection between the dynamics of
synchronization and the modularity on complex networks. Simulating
the Kuramoto's model in complex networks we determine patterns of
meta-stability and calculate the modularity of the partition these
patterns provide. The results indicate that the more stable the
patterns are, the larger tends to be the modularity of the partition
defined by them. This correlation works pretty well in homogeneous
networks (all nodes have similar connectivity) but fails when
networks contain hubs, mainly because the modularity is never
improved where isolated nodes appear, whereas in the synchronization
process the characteristic of hubs is to have a large stability when
forming its own community. 相似文献
3.
The asymptotic null distribution of the likelihood ratio test for two cases of ordered hypotheses in a particular genetic model is considered. A simple iterative process is proposed in order to get the restricted estimates. It is shown that both tests have asymptotically a chi-bar squared distribution and the same size. A simulation study is also conducted in order to compare the usual unrestricted test with the corresponding one of ordered hypotheses. Finally, the results are extended to some special cases. 相似文献
4.
Gilberto Dini Angela Selvaggi Primicerio 《Rendiconti del Circolo Matematico di Palermo》1989,38(1):60-64
LetR be a Reinhardt domain andD a bounded simply connected strictly pseudoconvex domain withC ∞ boundary. We prove that any proper holomorphic mapF:R →D is, up to biholomorphism ofD, of the form \((z_1^{d_1 } , z_2^{d_2 } , \ldots , z_n^{d_n } )\) withd 1,d 2,…,d n ∈ IN. 相似文献
5.
Cesarino Balsamini Gilberto Spadoni Annalida Bedini Giorgio Tarzia Maurizio Lanfranchi Maria Angela Pellinghelli 《Journal of heterocyclic chemistry》1992,29(6):1593-1598
The alkyl N-(diphenylmethylene)-α,β-dehydroamino acids 1 have been submitted to 1,3-dipolar cycloadditions with nitrile oxides. The reactivity of these compounds depends on the type and on the stereochemistry of the β-substituents. With the unsubstituted terms 1a,b the reaction occurs on the C,C double bond, providing a good method for the synthesis of the 4,5-dihydroisoxazole derivatives 3a,b,c and for the gem-functionalized 4,5-dihydroisoxazoles amino carboxylic ester 5. The β-substituted compounds 1c,d,e , inert to 1,1-dimethylethylnitrile oxide, undergo the reaction to the N,C double bond, thus giving with 2a,b the 4,5-dihydro-1,2,4-oxadiazole derivatives 4. All the reactions occur with high site- and regioselectivity. 相似文献
6.
7.
The design and construction of a simple device for measuring ionic concentrations (or pH) with ion-selective electrodes are described. The automated system includes a special electronic circuit with an operational amplifier, a signal conditioner and a personalcomputer. A digital multimeter can be used if automation is not required. The results obtained in tests with iodide-, chloride- and nitrate-selective electrodes and glass electrodes show very good agreement with those obtained with sophisticated commercial apparatus. 相似文献
8.
Gilberto Schiavon Gianni Zotti Gino Bontempelli 《Journal of Electroanalytical Chemistry》1984,161(2):323-335
The electrochemical reduction of [Ni(PPh3)2(p-C6H4Br)Br] in acetonitrile results in a polymeric coating of a nickel-containing poly-p-phenylene, formulated as [-Ni(p-C6H4)n-] (n=6?7) on the basis of elemental analysis, IR, UV, MS and ESCA measurements. This coating is found to undergo a two-electron reversible reduction and a one-electron reversible oxidation with a large potential window (3.6 V), without the polymeric film being destroyed. Moreover, the polymer obtained is shown to be electroactive towards dissolved reactants via permeation or mediated electron transfer, depending on the molecular size of the electroactive species employed. 相似文献
9.
Gino Bontempelli Franco Magno Benedetto Corain Gilberto Schiavon 《Transition Metal Chemistry》1985,10(1):8-11
Summary The reduction of nickel perchlorate in the presence of carbon monoxide and substituted phosphines or diphosphines has been studied in acetonitrile by cyclic voltammetry. The results show that only mono- and bis-carbonylphosphinenickel(O) complexes are formed, while no evidence for the formation of carbonyl-nickel(I) and -nickel(II) species was obtained. Although the oxidation processes are not reversible, a good correlation between the anodic peak potentials relative to nickel(O) complexes and the -donor--acceptor abilities of the phosphines employed was observed. 相似文献
10.
Rosanna Toniolo Alan Valentino G. Bontempelli Gilberto Schiavon 《Fresenius' Journal of Analytical Chemistry》1998,360(2):260-262
A simple method for the analysis of nanoliter droplets is proposed, which is profitable when larger samples cannot be collected
as, for instance, in the case of several biological fluids and particularly in clinical chemistry. A glass capillary associated
to a micromanipulator is used to collect submicroliter volumes which are partially transferred into transparent polymeric
tubings with known internal diameters (120–178 μm), where the volumes sampled are measured by meniscus collimations with a
collimator microscope at suitable magnification. Both ends of these tubings are preliminarily equipped with ferrules and fittings,
so as to make them suitable for connection as the loop to a conventional high-pressure injection valve. The reliability of
this procedure has been tested for the analysis of Na+, K+ and Ca2+ present in minute synthetic standard samples (10–200 nL) by a conventional ion-chromatographic instrumentation. Relative
standard deviations in peak area measurements (5–6%) are discussed in terms of the whole approximation affecting volume measurements,
which depends on both the inconstancy of the inner diameter of the polymeric tubings employed and the uncertainty characterizing
meniscus collimations. The proposed procedure can be easily extended to the determination of any organic or inorganic species
present in very small samples, provided that their detection can be achieved by any chromatographic approach or, more generally,
by flow injection analysis.
Received: 16 June 1997 / Revised: 12 August 1997 / Accepted: 14 August 1997 相似文献