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941.
942.
A K Náb?lek Z Czyzewski L A Krishnan 《The Journal of the Acoustical Society of America》1992,92(3):1228-1246
Vowel identification was tested in quiet, noise, and reverberation with 20 normal-hearing subjects and 20 hearing-impaired subjects. Stimuli were 15 English vowels spoken in a /b-t/context by six male talkers. Each talker produced five tokens of each vowel. In quiet, all stimuli were identified by two judges as the intended targets. The stimuli were degraded by reverberation or speech-spectrum noise. Vowel identification scores depended upon talker, listening condition, and subject type. The relationship between identification errors and spectral details of the vowels is discussed. 相似文献
943.
944.
Raman spectrum of a single crystal of sodium iodide has been recorded for the first time using λ 2537 excitation. The general features of the spectrum are discussed in the light of the existing theories on the dynamics of the alkali halides. 相似文献
945.
K. N. Ninan K. Krishnan V. N. Krishnamurthy 《Journal of Thermal Analysis and Calorimetry》1991,37(7):1533-1543
Thermogravimetric studies on two varieties of calcium carbonate viz., analytical reagentgrade and insitu generated from calcium oxalate monohydrate, were carried out. The kinetics and mechanism of their solid-state thermal decomposition reaction were evaluated from the TG data using integral methods and the effect of procedural factors such as heating rate, sample mass and method of computation on them were also studied. The procedural variables in the range studied had no marked influence on the results; however the kinetic parameters were marginally higher for the insitu generated calcium carbonate. This trend is explained by the presence of more micropores in the insitu generated calcium carbonate as well as the mechanism of its decomposition following phase boundary reaction with cylindrical symmetry.
Dedicated to Prof. Dr. H. J. Seifert on the occasion of his 60th birthday
We thank Director, VSSC for the kind permission to publish this work. Thanks are due to Mr. A. Natarajan for the support in SEM studies. 相似文献
Zusammenfassung An zwei verschiedenen Arten von Calciumcarbonat (analytisch rein bzw. in situ hergestellt aus Calciumoxalatmonohydrat) wurden thermogravimetrische Untersuchungen durchgeführt. Die Kinetik und der Mechanismus der thermischen Feststoffzersetzungsreaktionen wurde unter Anwendung integrativer Verfahren aus TG-Daten ermittelt. Auch der Einfluß experimenteller Bedingungen, wie z.B. von Aufheizgeschwindigkeit, Probenmasse und Rechenmethode wurden untersucht. Die experimentellen Bedingungen haben im untersuchten Intervall keinen sichtlichen Einfluß auf die Ergebnisse; in jedem Falle hatten die kinetischen Parameter für in situ hergestelltes Calciumcarbonat wesentlich höhere Werte. Dies wird durch die Anwesenheit von wesentlich mehr Mikroporen in dem in situ hergestellten Calciumcarbonat erklärt. Der Reaktionsmechanismus der Zersetzung wird mittels Phasengrenzreaktionen mit zylindrischer Symmetrie erklärt.
Dedicated to Prof. Dr. H. J. Seifert on the occasion of his 60th birthday
We thank Director, VSSC for the kind permission to publish this work. Thanks are due to Mr. A. Natarajan for the support in SEM studies. 相似文献
946.
Abstract— Intramolecular donor-acceptor systems bearing porphyrins covalently linked to phenol-phthalein at various distances and at different orientations have been synthesized. Optical absorption and emission spectra and magnetic resonance studies reveal interaction between the porphyrin unit and lactone/semiquinone forms of phenolphthalein. The charge-transfer quenching of fluoresence in these systems is found to be more pronounced compared to the intermolecular systems. The lifetime studies are interpreted in terms of intramolecular electron transfer. 相似文献
947.
948.
Tong D Farooqi SM Stanojevic J Krishnan S Zhang YP Côté R Eyler EE Gould PL 《Physical review letters》2004,93(6):063001
In the laser excitation of ultracold atoms to Rydberg states, we observe a dramatic suppression caused by van der Waals interactions. This behavior is interpreted as a local excitation blockade: Rydberg atoms strongly inhibit excitation of their neighbors. We measure suppression, relative to isolated atom excitation, by up to a factor of 6.4. The dependences of this suppression on both laser irradiance and atomic density are in good agreement with a mean-field model. These results are an important step towards using ultracold Rydberg atoms in quantum information processing. 相似文献
949.
Krishnan R Voo JK Riordan CG Zahkarov L Rheingold AL 《Journal of the American Chemical Society》2003,125(15):4422-4423
Reaction of the nickel metalloligands [EtN2S2]Ni (EtN2S2, N,N'-diethyl-3,7-diazanonane-1,9-dithiolate) or K2[Ni(phmi)] (phmi, N,N'-1,2-phenylenebis(2-sulfanyl-2-methylpropionamide)) with [Cu(CH3CN)4]BF4 yields polynuclear complexes in which two copper(I) ions are bridged by the nickel metalloligands. Alternatively, reaction with the Cu(I) source, [(PhTttBu)Cu] (PhTttBu, phenyltris((tert-butylthio)methyl)borate), generates discrete binuclear NiCu complexes that may serve as models of the acetyl coenzyme A synthase active site. The binuclear species react reversibly with CO via rupture of the thiolate bridges. 相似文献
950.
Bicontinuous microemulsions arise in a narrow concentration range for ternary blends containing two immiscible homopolymers and the corresponding diblock copolymer. Steady shear reveals four distinct regimes of response as a function of shear rate, corresponding to flow-induced transitions in fluid structure. In situ neutron scattering shows flow-induced anisotropy in the nanometer-scale microemulsion structure at moderate shear rates, while higher rates induce bulk phase separation, with micron-size morphology, which is characterized with in situ light scattering and optical microscopy. 相似文献