Transition flow of a fibrous suspension in a pipe as the flow of an anisotropic fluid

The transition flow is considered of a fibrous suspension in a pipe. The flow region consists of two subregions: at the center of the flow a plug formed by interwoven fibers and fluid moves as a rigid body; between the solid wall and the plug is a boundary layer in which the suspension is a mixture of the liquid phase and fibers separated from the plug [1–3]. In the boundary region the suspension is simulated as an anisotropic Ericksen—Leslie fluid [4, 5] which satisfies certain additional conditions. Equations are obtained for the velocity profile and drag coefficient of the pipe, which are both qualitatively and quantitatively in good agreement with the experimental results [6–8]. Within the framework of the model, a mechanism is found for reducing the drag in the flow of a fibrous suspension as compared to the drag of its liquid phase.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 5, pp. 91–98, September–October, 1985.     

Electrohydraulic effect in water-plant heterodisperse systems I. Compositions of the solid residue and the aqueous phase

The electrohydraulic (EH) treatment of water-plant heterodisperse systems leads to the partial degradation of the main components of the plant materials: lignin, cellulose, and carbohydrates. The presence of p-hydroxyphenyl and guaiacyl structures has been established on the basis of the results of the GLC analysis of the ether-extracted phenolic products of plant materials subjected to EH treatment. It has been shown that part of the carbohydrates passes into the aqueous phase in the form of free monosaccharides: pentoses and hexoses. Institute of Chemistry of Plant Substances of Uzbekistan Academy of Sciences, Tashkent. Institute of Organic Chemistry, Siberian Branch, Russian Academy of Sciences, Irkutsk. Siberian Institute of Terrestrial Magnetism, the Ionosphere, and the Propagation of Radio Waves, Siberian Branch, Russian Academy of Sciences, Irkutsk. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 707–711, November–December, 1992.     

Status of the front-end-electronics for the time-of-flight measurements at the MPD experiment

The preamplifier based on the ASIC NINO for the Time of Flight system (TOF) of MPD/NICA was developed and tested. The signal is read from both sides of the strip of the multi gap Resistive Plate Chamber (MRPC). In total there are around 14000 channels of electronics. To measure time of flight of secondary particles from collision of heavy ions on the collider NICA the Time over Threshold (ToT) method is used. According to the bench tests the preamplifier board showed stable work and good time resolution <10 ps for one channel. It was also tested at the test beam facility of the Nuclotron. The time resolution of the TOF detector which used the described preamplifier was reached ～42 ps.     

Wasseruntersuchung

Ohne Zusammenfassung     

High-Dimensional Multivariate Time Series With Additional Structure

High-dimensional multivariate time series are challenging due to the dependent and high-dimensional nature of the data, but in many applications there is additional structure that can be exploited to reduce computing time along with statistical error. We consider high-dimensional vector autoregressive processes with spatial structure, a simple and common form of additional structure. We propose novel high-dimensional methods that take advantage of such structure without making model assumptions about how distance affects dependence. We provide nonasymptotic bounds on the statistical error of parameter estimators in high-dimensional settings and show that the proposed approach reduces the statistical error. An application to air pollution in the USA demonstrates that the estimation approach reduces both computing time and prediction error and gives rise to results that are meaningful from a scientific point of view, in contrast to high-dimensional methods that ignore spatial structure. In practice, these high-dimensional methods can be used to decompose high-dimensional multivariate time series into lower-dimensional multivariate time series that can be studied by other methods in more depth. Supplementary materials for this article are available online.     

Roughening (faceting) transitions on the helium crystal-superfluid interface

The concept of roughening transitions (RT) was first introduced into theory by Burton and Cabrera (1949). RT, which manifests itself in disappearance of smooth facets in equilibrium shape of the crystal (faceting transition), has been under intensive theoretical study in the last few years (Andreev 1981; Rottman and Wortis 1984). Current interest in this field is connected mainly with the problems of “quantum roughening’ and critical behaviour of the surface stiffness. Experimental studies of RT in usual classical crystals meet with serious difficulties due to very long crystal shape relaxation times. In this respect, helium crystals seem to be the best candidates because of their extremely fast growth kinetics which ensures sufficiently short shape relaxation times (Keshishevet al 1982). We have recently investigated the equilibrium shape of large⁴He crystals in the vicinities of the two different RT (T _R=1.2 K and 0.9 K) by a simple optical technique which provides the temperature and angular dependences of the surface stiffness (Babkinet al 1958, 1984, 1985). The data obtained by this method show, in accord with theory, that both studied RT being continuous phase transitions. However, the measured critical behaviour of the surface stiffness cannot be explained satisfactorily by current theories, either by the phenomenological “mean field” theory (Andreev 1981) or by the lattice model calculation (Rottman and Wortis 1984).