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81.
82.
A number of subjective experiments designed not only to assess the tonal and playing qualities of trombones but also to aid the interpretation of objective data is described. Quantifying multi-dimensional quantities such as timbre or quality is usually attempted either by multi-dimensional scaling (MDS) or by semantic differential scaling (SDS) and the advantages and disadvantages of each for the present purpose are briefly reviewed. For both methods additional information is needed either (for SDS) to aid the selection of scales, or (for MDS) to interpret the final results of the computer analysis; in this study such information is available from the investigations of Edwards [1]. A preliminary experiment testing the ability of subjects to rate trombone timbre using SDS showed that the intersubject variance was very large but that the order of factors governing timbre is (i) instrument, (ii) player and (iii) mouthpiece. A second experiment shows that pitch and loudness have a much greater influence on listener's ratings than do player, mouthpiece of instrument. Players' attitudes tested in further experiments show that the task of discriminating instruments when extraneous cues are removed is very hard indeed for most players, but a very few can be of quite remarkable discriminatory ability using either SDS or MDS. Results from one such player indicate clearly that timbre is the predominant acoustic factor deciding discrimination. 相似文献
83.
William W. Pratt 《Nuclear Physics A》1971,160(3):626-629
The γ-rays following the decay of 88Rb have been studied with a 40 cm3 Ge(Li) detector with the aim of resolving discrepancies in some recent determinations of the decay scheme of this isotope. The existence of a 1799 keV γ-ray has been confirmed and three new γ-rays with energies of 1218, 1295 and 1368 keV have been found. All of these results are in good agreement with a decay scheme recently proposed by Ragaini and Knight. 相似文献
84.
Lohmeijer BG Dubois G Leibfarth F Pratt RC Nederberg F Nelson A Waymouth RM Wade C Hedrick JL 《Organic letters》2006,8(21):4683-4686
[reaction: see text] An organocatalytic route to narrowly dispersed poly(carbosiloxanes) of predictable molecular weight and end group fidelity is described. N-Heterocyclic carbenes (NHC) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) catalyze the ring opening of cyclic carbosiloxanes. The pK(b) of the catalyst is important in preventing adverse transetherification reactions and obtaining well-defined polymers. Mechanistic studies indicate that hydrogen bonding to TBD or the NHC activates alcohols or silanols for ring-opening reactions. 相似文献
85.
I. W. Ellms S. I. Hauser L. W. Winkler H. Pecker V. Froboese A. T. Stuart F. Malméjac J. Tillmans O. Heublein H. Noll J. M. Kolthoff H. Klut Dietl L. Dede E. Hauser E. M. Chamot D. S. Pratt A. E. Johnson H. Silvester W. Vaubel G. Denigès E. H. Miller S. Rothenfusser M. Bornand L. Rosenthaler V. Jahn A. Dané L. v. Liebermann D. Acel E. B. Phelps H. L. Shoub Escaich H. Berger G. D. Elsdon N. Evers H. W. Brubaker F. W. Bruckmiller 《Analytical and bioanalytical chemistry》1922,61(4-5):196-205
86.
D. S. Pratt Ch. R. Sanger E. R. Riege A. Stoc E. Schwinge P. Rassfeld E. Havas G. K. Burgess H. Siedentopf W. Biltz J. Shukow W. Kurbatow Holborn Wien R. Loebe W. Dickmann R. Wegscheider Tammann W. Plato Ruffs W. P. White R. Nacken Ernst Jänecke John Johnston L. H. Adams 《Analytical and bioanalytical chemistry》1918,57(3):138-144
87.
Efthymia Paparistodemou Richard Noss Dave Pratt 《International Journal of Computers for Mathematical Learning》2008,13(2):89-110
This article describes how children use an expressive microworld to articulate ideas about how to make a game seem fair with
the use of randomness. Our aim in this study is to disentangle different flavours of fairness and to find out how children
used each flavour to make sense of potentially complex behaviour. In order to achieve this, a spatial computer game was designed
to enable children to examine the consequences of their attempts to make the game fair. The study investigates how 23 children,
aged between 5.5 and 8 years, engaged in constructing a crucial part of a mechanism for a fair spatial lottery machine (microworld).
In particular, the children tried to construct a fair game given a situation in which the key elements happened randomly.
The children could select objects, determine their properties, and arrange their spatial layout in the machine. The study
is based on task-based interviewing of children who were interacting with the computer game. The study shows that children
have various cognitive resources for constructing a random fair environment. The spatial arrangement, the visualisation and
the manipulations in the lottery machine allow us gain a view into the children’s thinking of the two central concepts, fairness
and randomness. The paper reports on two main strategies by which the children attempted to achieve a balance in the lottery
machine. One involves arranging the balls symmetrically and the other randomly. We characterize the nature of the thinking
in these two strategies: the first we see as deterministic and the latter as stochastic, exploiting the random collisions
of the ball. In this article we trace how the children’s thinking moved between these two perspectives.
相似文献
Dave PrattEmail: |
88.
Julian R. Osman Joe A. Crayston Allin Pratt David T. Richens 《Journal of Sol-Gel Science and Technology》2008,46(2):126-132
Mixed IrO2–TiO2 oxides were prepared by the sol–gel method by adding an aqueous solution of an iridium(III) acetate precursor [Ir3O(OAc)6 (HOAc)3]OAc, to titanium tetraethoxide in ethanol. By using an acetylacetonate modifier to stabilize the hydrolysed titanium alkoxide
and by omitting a catalyst, gels were produced in all cases. Transmission electron microscopy and EDX analysis confirmed the
high dispersion of iridium in the dried gel material on the nanometre scale. The images also show spherical cage features
up to 20 nm in diameter. High mass losses of the gels in the TGA scans suggested low degrees of hydrolysis of the acetate
precursor, but calcination gave a crystalline, mixed oxide (TixIr1–xO2) solid solution. The precursor is also soluble in ethanol, which provides a slightly modified route to similar materials. 相似文献
89.
Irradiation of substituted 2-benzylidenecyclopentanone O-alkyl and O-acetyloximes in methanol provides a convenient synthesis of alkyl, alkoxy, hydroxy, acetoxy, amino, dimethylamino and benzo substituted annulated quinolines. para-Substituents yield 6-substituted-2,3-dihydro-1H-cyclopenta[b]quinolines with 8-substituted products being obtained from ortho-substituted starting materials. Reactions of meta-substituted precursors are highly regioselective, with alkyl substituents leading to 5-substituted 2,3-dihydro-1H-cyclopenta[b]quinolines and more strongly electron-donating substituents generally resulting in 7-substituted products. 2-Furylmethylene and 2-thienylmethylene analogues yield annulated furo- and thieno-[2,3e]pyridines respectively. Sequential E- to Z-benzylidene group isomerisation and six pi-electron cyclisation steps result in formation of a short-lived dihydroquinoline intermediate which spontaneously aromatises by elimination of an alcohol or acetic acid. For 2-benzylidenecyclopentanone O-allyloxime, singlet excited states are involved in both steps. 相似文献
90.