Thermal degradation of PVC in various solvents at 180° has been observed to be in the following order: benzonitrite > nitrobenzene > cyclohexanone > dioctyl phthalate > α-bromonaphthalane > decahydronaphthalene. The effect has been explained on the basis of β-eliminations of E1-type favoured by polar solvents. An inhibition in PVC degradation has been observed in nitrobenzene containing stationary hydrogen chloride gas. The deceleration in degradation by predissolved HCl has been accounted for as a Mass Law effect. 相似文献
A new phthalic acid ester 1,2-benzenedicarboxylic acid bis(2S-methyl heptyl) ester (1) was isolated from the hexane extract of the whole plant of Ajuga bracteosa. In addition, chloroform and methanol extracts yielded neo-clerodane diterpene ajugarin-I and two iridoid glycosides, reptoside and 8-O-acetyl harpagide. The structures of all the compounds were confirmed by extensive spectroscopic analysis. From the two oily fractions nine and six volatile constituents respectively were identified by GCMS. Linalyl acetate was found to be common in both the oil fractions. This plant is a new source of linalyl acetate, a valuable perfumery compound. 相似文献
In this paper, the influence of an exponential volume fraction law on the vibration frequencies of thin functionally graded cylindrical shells is studied. Material properties in the shell thickness direction are graded in accordance with the exponential law. Expressions for the strain-displacement and curvature-displacement relationships are taken from Love＇s thin shell theory. The Rayleigh-Ritz approach is used to derive the shell eigenfrequency equation. Axial modal dependence is assumed in the characteristic beam functions. Natural frequencies of the shells are observed to be dependent on the constituent volume fractions. The results are compared with those available in the literature for the validity of the present methodology. 相似文献
The measurement of a distributed property is frequently encountered in engineering applications. The impact of a possible measurement error on the measured distribution is described and two methods to account for such an error are detailed: A Fourier transform based deconvolution procedure and a moment based deconvolution approach via kernel estimators are presented. The deconvolution methods can be used in many particle characterization and process applications where particle features or properties are commonly presented in a distributed form. In the current instance, these methods are carefully explored by using artificially generated data and applied to experimental data obtained from filter cake thickness measurements. 相似文献
We investigate the decays D(0)-->pi(-)l(+)nu and D(0)-->K(-)l(+)nu, where l is e or mu, using approximately 7 fb(-1) of data collected with the CLEO III detector. We find R(0) identical with B(D(0)-->pi(-)e(+)nu)/B(D(0)-->K(-)e(+)nu)=0.082+/-0.006+/-0.005. Fits to the kinematic distributions of the data provide parameters describing the form factor of each mode. Combining the form factor results and R(0) gives |f(pi)(+)(0)|(2)|V(cd)|(2)/|f(K)(+)(0)|(2)|V(cs)|(2)=0.038(+0.006+0.005)(-0.007-0.003). 相似文献
Summary: Denim jeans have consistently been fashionable around the world. This fabric inspired strong opinions from historians, teenagers, and movie stars, and has acquired different styles throughout the years. Most jeans today are stonewashed; this technique first become popular in 1970. Now, in addition to pumice stones, enzymes are used on the cotton fabrics to create the stonewashed look. Nowadays, plasma treatment is a cost‐effective and environment‐friendly process which is able to modify the properties of the fabric surface in order to achieve this effect. Plasma surface treatment changes the properties of the fabric up to a limited depth (several molecular layers), leaving the bulk properties of even the most delicate materials unchanged. In this study, we have investigated the effect of low‐temperature Argon plasmas on the decolorizing of denim surfaces. The denim fabrics were placed on a copper cathode and were exposed to the plasmas for different periods of time, varying from 2.5 to 15 min. The homogeneity of the plasma was secured by means of a magnetic field. The results, which were very good decolorized, varnished surfaces of the fabrics will be discussed.
Photographs of denim samples before (top) and after (bottom) a treatment with a low‐temperature Ar plasma. 相似文献
The \"hot potato voice\" is widely recognized as a symptom of peritonsillar cellulitis or abscess; yet there have been no studies assessing the resonance characteristics of the vocal tract in peritonsillitis. Analysis was undertaken of formant frequencies in the articulation of the vowels /i:/. /a:/ and /u:/ in six subjects with peritonsillitis and compared with articulation once the peritonsillitis had settled. Significant variation was found in F1 when articulating /i:/ and in F2 when articulating /a:/, which are explainable by dyskinesis of the peritonsillar musculature. These findings were compared with six subjects articulating the same vowels with and without a hot potato in their mouth. Variation was found in both F1 and F2 when articulating /i:/, which can be related to interference of the potato with movement of the anterior tongue. The changes in the vocal tract differ in these two cases and the title \"hot potato voice\" in peritonsillitis is a misnomer. 相似文献
