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排序方式: 共有379条查询结果,搜索用时 31 毫秒
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An investigation of the MECA behaviour of sulphate, sulphite, metabisulphite, peroxodisulphate, thiocyanate, thiosulphate and sulphide ions, has shown that ng amounts of these anions may be determined in samples of a few μl. Metal ion interferences in the determination of sulphate and sulphite are removed by addition of phosphoric acid. 相似文献
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Summary The calculation of electronically excited states with the internally contracted multiconfiguration-reference configuration interaction (CMRCI) method is discussed. A straightforward method, in which contracted functions for all states are included in the basis, is shown to be very accurate and stable even in cases of narrow avoided crossings. However, the expense strongly increases with the number of states. A new method is proposed, which employs different contracted basis sets for each state, and in which eigensolutions of the Hamiltonian are found using an approximate projection operator technique. The computational effort for this method scales only linearly with the number of states. The two methods are compared for various applications.Dedicated in honor of Prof. Klaus Ruedenberg 相似文献
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The intramolecular and long-range ferromagnetic coupling between p-phenylenediamine radical cations in head-to-tail coupled oligo(1, 4-phenyleneethynylene)s and oligo(1,4-phenylenvinylene)s between neighbors and next-nearest neighbors is described. UV/vis/near-IR experiments show that the radical cations are localized in the pendant p-phenylenediamine units of the conjugated oligomers. The ESR spectra of these oligo(1,4-phenyleneethynylene) and oligo(1, 4-phenylenvinylene) di(radical cation)s are consistent with those of a triplet state. A linear behavior is observed for the doubly integrated ESR intensity of the DeltaM(s) = +/-1 and DeltaM(s) = +/-2 signals with the inverse temperature (I approximately 1/T), consistent with Curie's law. This behavior indicates a triplet ground-state diradical with a large triplet-singlet energy gap or possibly a degeneracy of singlet and triplet states. 相似文献
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D W Later B E Richter D E Knowles M R Andersen 《Journal of chromatographic science》1986,24(6):249-253
Three classes of drugs were screened for analysis feasibility by capillary column supercritical fluid chromatography. These included steroids, therapeutic antibiotic drugs, and drugs of abuse, such as cannabinoids. Supercritical fluid carbon dioxide was used as the mobile phase in conjunction with a methylpolysiloxane stationary phase capillary column and a flame ionization detector. All compounds considered were analyzed either as single component solutions, simple mixtures, or in actual complex mixtures. 相似文献
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J. K. Knowles 《Archive of Applied Mechanics (Ingenieur Archiv)》1985,55(5):321-332
Summary This paper is concerned with damped linear dynamical systems which fail to satisfy the socalled convenience hypothesis, an assumption that guarantees the existence of classical normal modes. Under suitable conditions, estimates are given for the error committed when such a system is described approximately by a differential equation which does satisfy the convenience hypothesis. One of these estimates is used to derive an upper bound on the frequency response of systems which do not violate the convenience hypothesis too severely.
Ein Beitrag zu den gedämpften, linearen, dynamischen Systemen
Übersicht Die Arbeit befaßt sich mit gedämpften, linearen, dynamischen Systemen, welche die Bequemlichkeitshypothese nicht erfüllen. Dabei wird untersucht, welchen Fehler man macht, wenn man eine allgemeine viskose Dämpfung durch eine zugeordnete modale Dämpfung entsprechend dieser Hypothese ersetzt. Eine der Fehlerabschätzungen wird verwendet zur Herleitung einer oberen Schranke der Antwortamplitude von Systemen, welche die Bequemlichkeitshypothese nicht allzu sehr verletzen.相似文献