Measuring equipment and test bench to control evolution of acoustic-deformation and heat fields induced in solids under failure by fluids

The authors have developed a procedure and a test bench for studying evolution of various nature physical fields in modeling geomedium fracture by fluids. The test bench performs synchronous recording of macro- and micro-deformation, heat and acoustic emission induced in physical models of geomedium under loading to discontinuity. The experimental procedure has been trialed. The analysis of the synchronized test data allows a conclusion on the existence of time–space relationship between different nature physical fields induced during failure of solids.     

Product composition of the dynamic conversion of brown coal in supercritical water

The product composition of the dynamic conversion of brown coal, which was continuously supplied as a water-coal slurry to a flow reactor at 30 MPa, was studied. The temperature of water and coal particles was increased from room temperature to 400°C (top part of the reactor). The conversion of the organic matter of coal was ～48%, and the products collected at the reactor outlet consisted of solid tar components, substances dissolved and emulsified in water, and volatile substances, whose major constituent was CO₂. The composition of solid tar components and oils was determined.     

Terahertz emission at impurity electrical breakdown in Si(Li)

Terahertz electroluminescence caused by impurity-induced breakdown in lithium-doped silicon crystals is studied. The spectrum of the terahertz emission exhibits lines corresponding to intracenter electronic transitions between excited states of the impurity and sublevels of the ground state of the lithium donor. The spectrum also shows a background signal, which, apparently, is a manifestation of the effects due to heating at electric excitation.     

Control adjustment of an air-gas path based on the localization principle

Control adjustment of the air-gas path of a thermal power boiler using the localization principle is considered. A mathematical model of the object, its constituent equations, conditions of their derivation, and the transition to state equations are described. The synthesis problem is formulated and controllers are calculated for each channel of the system. A block diagram of the automatic control system is designed and is used to model the transient processes to make conclusions on the system. A program for automatic calculation of the coefficients of differential equations is presented.     

Division of supporting-pressure zones

Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 4, pp. 3–11, July–August, 1995.     

Oxidation of a coal particle in flow of a supercritical aqueous fluid

A study was made of the conversion of single spherical coal particles of diameter 1–5 mm in a supercritical H₂O/O₂ fluid with an oxygen mass fraction of 0–6.6% in a semibatch reactor at a pressure of 30 MPa and a temperature of 673–1023 K. A decrease in the particle mass was observed in two parallel processes: gasification of coal with water and oxidation of coal with oxygen. An activation energy 19 ± 7 kJ/mole and a pre-exponential factor 10^−2±0.4 sec⁻¹ were obtained under the assumption of zero order for the concentration H₂O and an Arrhenius dependence for the rate of gasification with water. The oxidation with oxygen at a temperature above 780 K was found to be limited by the rate of O₂ diffusion to the coal organic matter. Below 780 K, the rate of heterogeneous oxidation with oxygen is described by a first-order reaction for the concentration of O₂ and a zero-order reaction for the concentration of H₂O with an activation energy of 150 ± 27 kJ/mole and a pre-exponential factor of 10^7.6±1.9 cm³/(g · sec). __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 23–31, March–April, 2008.     

Inelastic Interaction of an Electron with a C60 Cluster

The method of intersecting beams of C₆₀ fullerene clusters and of electrons is used to investigate the production of C ₆₀ ⁺ and C ₆₀ ^– ions and the radiation in the wavelength range from 300 to 800 nm for the electron energy E _e ranging from zero to 100 eV. The absolute values of the ionization and electron-attachment cross sections [⁺(E _e ) and ^–(E _e ), respectively] are determined. A maximum of ⁺(E _e ) of 0.53 nm²is observed at E _e = 52 eV. For a C₆₀ cluster excited by electron impact, delayed (150 s) ionization initiated by collision with the surface and ionization due to thermionic emission (its characteristic time at E _e = 60 eV is 6 s) is observed. It is found that, for E _e < 0.4 eV, the formation of C ₆₀ ^– is defined by the polarization capture of an s-electron (^– E _e ^–1 ), and a formula is suggested for determining ^–(E _e ). In the region of E _e from 1 to 6 eV, the cross section ^–(E _e ) shows only slight variations about ^–(E _e ) = 0.36 ± 0.03 nm². For E _e > 7.5 eV, C ₆₀ ^– ions proved to be unstable to electron autodetachment. In the region of intersection of C₆₀ and electron beams, radiation of a quasicontinuous spectrum described by a modified Planck formula for the thermal emission of spherical particles of diameter d is recorded. For E _e > 47 eV, the brightness temperature proved to be 3150 ± 50 K. It is found that this radiation is emitted predominantly by hot C ₆₀ ^+* ions produced as a result of thermionic emission from C ₆₀ ^* . The rate of radiation loss of energy by a C ₆₀ ^+* ion and the cross section for the formation of radiating C ₆₀ ^+* ions are found to be, respectively, 5.5 × 10⁵ eV/s at T = 3150 K and 2 × 10^–2 nm² at E _e = 60 eV.