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101.
Summary An analysis of the overshoot phenomenon which is produced by quartz oscillators during the warm-up time is proposed. A particular
application to oscillators equipped with ?electrodeless? resonators is described.
Résumé Une analyse complète du phénomène de dépassement de fréquence présenté par les oscillateurs à quartz pendant leur période de démarrage est présentée. Une application particulière est faite pour les oscillateurs équipés de résonateurs à électrodes non adhérentes.
Riassunto Si propone un'analisi del fenomeno di overshoot che è prodotto da oscillatori del quarzo durante il tempo di riscaldamento. Si descrive una particolare applicazione ad oscillatori equipaggiati con risonatori ?senza elettrodi?.
Резюме Предлагается анализ явления перерегулировки, которое происходит в кварцевом осцилляторе во время разогрева. Обсуждается применение к осцилляторам, связанным с ?беээлектродными? резонаторами.相似文献
102.
K. Totsuka 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):705-717
Novel massive quantum states appearing in spin chains under a strong magnetic field are discussed. These states lead to plateaus in magnetization
curves. When the systems are axially symmetric and the field is applied parallel to the symmetry-axis, the phenomena are analogous
to metal-insulator transitions. Striking features of the plateau phenomena - exactness and rationality - are explained as
consequences the commensurability condition to the underlying lattice. The effects of the planar anisotropy are also discussed
in detail.
Received: 16 February 1998 / Revised: 20 April 1998 / Accepted: 30 April 1998 相似文献
103.
Volatile flavoring substances in foodstuffs 总被引:1,自引:0,他引:1
H G Maier 《Angewandte Chemie (International ed. in English)》1970,9(12):917-926
The odor of most foods is produced by mixtures of many volatile flavoring substances. Over the past century, numerous food flavors have been analyzed in sufficient detail to allow a survey of the classes of substances responsible, the formation of individual flavoring substances, and their fixation in the foods. In addition to special biosynthetic pathways, the breakdown of fats and the Maillard reaction have been found to be particularly important to the formation of flavoring substances. 相似文献
104.
Summary We consider the case of a plurality of polariton modes due to the valence band structure, and give a one-dimensional model
to compute the optical functions in the exciton frequency range. Interference effects of each mode with itself and with the
other modes are identified by a fine structure in the reflectivity spectrum.
In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching. 相似文献
105.
味觉电化学传感器的研究:甜味物质对模拟生物膜电位振荡的影响 总被引:2,自引:0,他引:2
本文以十六基三甲基溴化铵+乙醇/含苦味酸的硝基苯/蔗糖溶液为研究体系,对影响该体电位振荡的各因进行了探讨,观察到各种甜味物质均能影该体系的振动波形和频率,并发现振荡频率的对数与各甜味物质浓度在一定范围内呈线性关系,初步建立了利用该体系测定甜味物的定笥,定量,工对该味觉电化学传感器的响应机理进行了。 相似文献
106.
107.
A mild phase-transfer catalytic reaction has been conducted to O-alkylate the acidic functions of a lignite humic acid (HA), using tetrabutylammonium hydroxide as the phase-transfer catalyst.
The HA acidic functional groups were made to react, in tetrahydrofuran, by nucleophilic substitution with several alkyl halides—methyl
iodide, and ethyl, propyl, and butyl, and benzyl bromide. The occurrence of the O-alkylation reaction was assessed by elemental analysis and 1H NMR, CPMAS 13C NMR, and FTIR spectroscopy. Bonding of alkyl groups increased the carbon and hydrogen content and the H/C ratios of all
the humic reaction products. Increased nitrogen in the reaction products suggested incomplete removal of the phase-transfer
catalyst after purification of the alkylated HA. 1H NMR and CPMAS 13C NMR spectra of alkylated products provided evidence of the successful occurrence of the alkylation reactions. Infrared spectra
confirmed the NMR results, revealing the characteristic absorption of newly formed alkyl and aryl ethers and esters in the
alkylated products and C–H stretching in the aromatic ring of the benzylated derivative. These findings indicate that humic
matter can be successfully alkylated with several different alkylating groups by catalysed phase-transfer reaction. This O-alkylation reaction has the advantage of being mild, versatile, and high-yielding compared with traditional methylation reactions
applied to HA. The possibility of introducing different alkyl groups into the HA by a mild phase-transfer reaction may become
useful by enabling improved fractionation of humic supramolecular associations and further understanding of the molecular
nature of humic substances. 相似文献
108.
Variance related premium principle is one of the most important principles not only in practice applications but also in research field of actuarial science. In this paper, the Bayesian models are established under variance related premium principle. The Bayesian estimate and credibility estimate of risk premium are derived. Furthermore, some statistical properties of estimators are discussed. In the models with multitude contract data, the unbiased consistent estimates of the structure parameters are proposed. Finally, the empirical Bayes estimator are proved to be asymptotically optimal. 相似文献
109.
The isotopic compositions of carbon compounds in landfill leachate provide insights into the biodegradation pathways that dominate the different stages of waste decomposition. In this study, the carbon geochemistry of different carbon pools, environmental stable isotopes and compound-specific isotope analysis (CSIA) of leachate dissolved organic carbon (DOC) fractions and gases show distinctions in leachate biogeochemistry and methane production between the young area of active waste emplacement and the old area of historical emplacement at the Trail Road Landfill (TRL). The active area leachate has low DOC concentrations (<200 mg l?1) dominated by fulvic acid (FA=160 mg l?1), and produces CH4 dominantly by CO2 reduction (D? excess=20.6‰). Leachate generated in the area of older waste has high DOC (>4770 mg l?1) dominated by FA (4482 mg l?1) and simple fatty acids (acetic=1008 mg l?1 and propionic=608 mg l?1), and produces CH4 by the acetate fermentation pathway (D? excess=9.8‰). CSIA shows an advanced degradation and a progressive accumulation of 13C of fatty acids in leachate from the older area. The enriched 13C value of FA (?20 and?26‰ for the older and active parts, respectively,) and of low molecular weight DOC (?8 and?27‰) as well as of the bulk DOC (?21 and?25‰) shows more advanced degradation in the older part of the landfill, which is consistent with the shift in the humic/FA ratios (0.05 and 0.18). The 13C enrichment of acetate (?12‰) above the 13C of DOC (?21‰) and of propionic acid (?19‰), in older leachate, suggests that this acetate has not evolved from the simple degradation of larger organic molecules, but by homoacetogenesis from the enriched dissolved inorganic carbon (DIC) pool (8‰) and H2, which produce a more enriched 13C of acetate. In contrast, the 13C of the minor acetate in the active area (?17‰) indicates that CO2-reducing bacteria must be the primary consumers of H2, which has resulted in enriched 13CDIC (10‰) and depleted 13CCH4 (?58‰). 相似文献
110.
Ever since the discovery of carbon nanotubes (CNTs) by Iijima in 1991, there have been extensive research efforts on their synthesis, physics, electronics, chemistry, and applications due to the fact that CNTs were predicted to have extraordinary physical, mechanical, chemical, optical, and electronic properties. Among the various forms of CNTs, single-walled and multi-walled, random and aligned, semiconducting and metallic, aligned CNTs are especially important since fundamental physics studies and many important applications will not be possible without alignment. Even though there have been significant endeavors on growing CNTs in an aligned configuration since their discovery, little success had been realized before our first report on growing individually aligned CNTs on various substrates by plasma-enhanced chemical vapor deposition (PECVD) [Science 282 (1998) 1105–1108]. Our report spearheaded a new field on growth, characterization, physics, and applications of aligned CNTs. Up to now, there have been thousands of scientific publications on synthesizing, studying, and utilizing aligned CNTs in various aspects. In this communication, we review the current status of aligned CNTs, the physics for their alignment, their applications in field emission, optical antennas, subwavelength light transmission in CNT-based nanocoax structures, nanocoax arrays for novel solar cell structures, etc. The focus of this review is to examine various aligned CNT systems, either as an individual or as an array, either the orientation is vertical, parallel, or at other angles to the substrate horizon, either the CNT core structures are mostly hollow channels or are composed of complex compartments. Major fabrication methods are illustrated in detail, particularly the most widely used PECVD growth technique on which various device integration schemes are based, followed by applications whereas current limitations and challenges will also be discussed to lay down the foundation for future developments. 相似文献