The book describes the main physical processes and phenomena in pulsed electric breakdown. The knowledge and the control of the electric breakdown of liquids is important not only for the insulation ...inside power systems but it is also used for the creation and information of high voltage and high current pulses. Such high-voltage micro- and nanosecond pulses find wide application in experimental physics, electro discharge technology, physics of dielectrics, radar detection and ranging, high-speed photography. The nature of charge carriers, mechanism of formation and evolution of the gas phase, and their role in charge ignition (initiation) and development are considered. In particular, the spatiotemporal laws of propagation and parameters of charge channels are described in detail and the boundery conditions of the breakdown initiation are formulated. The monograph is useful for experts in high-voltage pulsed technology, physics of dielectrics, and electrical insulation as well as to students of the corresponding fields.
•The mechanical losses Q–1 of gypsum stone in the range 25–120 °C were studied.•There were two maxima losses Q–1 from 0.02 to 0.2 at 90 °C and 110 °C.•The minimum loss Q–1 about 0.01 was in the range ...from 95 to 105 °C.•Two loss maxima corresponded to two resonance frequency minima of the specimens.•The phase transitions from dihydrate to α– and β–hemihydrates caused maxima of Q–1.
Experimental studies of the temperature dependence of internal mechanical losses in terms of Q−1 in the range from 25 to 120 °C used gypsum stone specimens from the Novomoskovskoye deposit (Tula region, Russia). This investigation is important to determine optimal modes of heat treatment of gypsum stone to obtain construction gypsum. The specimens were cylinders 40 mm in diameter and 75 mm in length with piezoelectric transducers at the ends. They included three types of rocks: gypsum, flint, and thin coal interlayers. The groups included specimens consisting of gypsum without flint layers, two layers consisting of a gypsum layer at one end and a flint layer at the other, and three layers with a flint layer in the middle part of the specimen. Losses Q–1 were determined as f0/(fmax – fmin), where fmax and fmin were frequencies at the level of 1/√2 of the maximum amplitude of sample longitudinal oscillations at the resonance frequency f0. In the temperature range up to 80 °C, the loss Q–1 increased monotonically, while the resonance frequency f0 decreased. There were two maxima of Q–1 and f0 at 85 and 110 °C. The phase transitions of gypsum from dihydrate to hemihydrates (α- and β-hemihydrates) and then to the anhydrous state (dehydrate) caused these maxima.
Unique bridgehead nitrones, 8-oxa-6-azabicyclo3.2.1oct-6-ene 6-oxides, have been assembled diastereoselectively via acetyldihydropyrans, products of one-pot self-organization of two molecules of ...ketones and two molecules of acetylene, which after oximation undergo acid-catalyzed ring closure. The proposed mechanism includes the enol double-bond protonation, followed by intramolecular cyclization involving the interaction of the carbocation formed with a nitrogen atom. A broad range of substrates tolerate this facile transformation, in which the bridgehead nitrones were isolated in high yields.
A convenient synthesis of pyrrolo2,1-aisoquinolinium salts from 1-pyrrolines and alkynes through rhodium-catalyzed C–H functionalization/N-annulation tandem reaction is described. The protocol ...features a good substrate tolerance, mild reaction conditions, and high yields of target products. Exploration of the alkyne scope unexpectedly revealed a novel labile functional group-promoted rhodium-catalyzed C–H functionalization/C-annulation/elimination cascade reaction of 1-pyrrolines with electron-deficient alkynes.
The three-component reaction of ketones, arylacetylenes, and guanidine catalyzed by the KOBu t /DMSO system leads to 2-aminopyrimidines in up to 80% yield. Depending on structure of the starting ...ketones, the aromatization of intermediate dihydropyrimidines occurs either with loss of hydrogen molecules or methylbenzenes. The latter process takes place in the ketones, in which one of the substituents is not a methyl group. The reaction conditions are tolerable for dialkyl-, aryl(hetaryl) alkyl-, and cycloalkyl ketones.
A nonlinear control system depending on a parameter is considered in a finite-dimensional Euclidean space and on a finite time interval. We study the dependence on the parameter of the reachable sets ...and integral funnels of the differential inclusion corresponding to the system. Under certain conditions on the control system, the degree of this parameter dependence is estimated.
We consider a nonlinear control system in a finite-dimensional Euclidean space and on a finite time interval. The system varies over some less time interval, and the differential equation describing ...the system is replaced with some other differential equation. As a result, a new control system appears on the initial time interval. We study how much the integral funnel of the system is changed under such a replacement. We obtain the upper estimate for the Hausdorff distance between the integral funnels of differential inclusions related to the initial and varied systems.
