Energy dissipation and heat exchange in magnetorheological suspensions in a rotating magnetic field

We present the results of experiments on the effect of the rheological properties of magnetic suspensions and the regime parameters on energy dissipation and heat transport in a rotating magnetic field.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 1, pp. 57–61, January, 1987.     

Effects of strain on the workability of a high strength low alloy steel in hot compression

Based on the experimental results from the hot compression tests of 42CrMo steel, the efficiencies of power dissipation and instability parameter were evaluated. The effects of strain on the efficiency of power dissipation and instability parameter of 42CrMo steel have been discussed in detail. Processing maps were constructed by superimposition of the instability map over the power dissipation map. The dynamic recrystallization domains and instable zones were identified in the processing map. The effects of strain on microstructural evolutions were correlated with the processing maps. According to the 3D processing maps, the optimum domain of hot deformation is in the temperature range of 1050–1150 °C and strain rate range of 0.01–3 s⁻¹, with its peak efficiency of 32% at about 1140 °C and 0.23 s⁻¹, which are the optimum hot working parameters.     

Effects of viscous dissipation and Joule heat on heat transfer near a rotating disk in the presence of intensive suction

Heat transfer in the bounday layer of an electrically conducting incompressible liquid near a disk rotating in an axial magnetic field is investigated for the case of intensive, uniform suction. The thermal flux intensity near the disk surface is determined in relation to the magnetic field strength and the rotation speed of the disk with an allowance for the viscous and the Joule dissipation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 5, pp. 740–743, November, 1988.     

Influence of collisional dissipation on internal pulsations in a fluidized bed

It is shown that the presence of energy dissipation in particle collisions results in degeneration of their ramdom pulsations and a decrease in pulsation-induced stressed and favours instability of the system.Ural State University, Ekaterinburg, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 3–4, pp. 250–254, September–October, 1994.     

Influence of polymer admixtures on the turbulence structure of flow behind a grating

Experimental investigations of the action of small (20–80 ppm) polymer admixtures on the turbulence structure in the wake behind a grating are performed in a water channel of closed type. The velocity fluctuations are measured by using a single-component Doppler laser velocimeter (DLV). A signal from the DLV was recorded on magnetic disc from three channel sections and the onedimensional energy and dissipation spectra were computed therefrom. It is shown that polymer insertion resulted in reduction of the turbulence level at short ranges from the grating and its increase far from the grating. Influence of the polymer in the spectral distribution appeared in an energy increase in the low-frequency domain and its fast degeneration in the high-frequency band, accompanied by contraction of the spectrum width.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 58, No. 4, pp. 550–556, April, 1990.     

Collective modes and sound propagation in a magnetic field in superfluid3He-B

A high-resolution, ultrasonic (12–89 MHz) acoustic impedance technique has been used to investigate the order parameter collective modes in superfluid³He-B over a pressure range of 0–15 bar and in magnetic fields up to 180 mT. In agreement with earlier experiments, theJ=2 real squashing mode has been observed to split into five components in small magnetic fields. However, contrary to earlier theoretical estimates, the Zeeman shifts have been found to become extremely nonlinear as the magnetic field is increased. The extent of this nonlinearity is largest at low pressures and at temperatures close toT _c. In comparison with recent theoretical work, the nonlinear Zeeman shifts may be explained as a result of two effects. First, there is a significant distortion of the B-phase energy gap in large magnetic fields. Second, there is an important coupling between the sameJ _zsubstates of the differentJ modes. In this sense the nonlinear evolution of the real squashing mode constitutes the observation of the Paschen-Back effect in³He-B. A comparison of the observed Zeeman shifts with theoretical expressions has yielded information about particle-particle and particle-hole interaction effects in the superfluid. In the limitT 0 and above a threshold field, the real squashing mode has been found to possess additional structure. TheJ _z=0 substate has been observed to split into a doublet. The separation between the two components of the doublet is of the order of 100–200 kHz and remains independent of the magnetic field. The origin of the doublet may be understood in terms of a recent theory which postulates a texture-dependent collective mode frequency. Further, at extremely small fields the effects due to dispersion of the real squashing modes have been found to be important. The magnitude of the dispersion-induced mode splitting in zero field is found to be consistent with theoretical predictions. TheJ=2 squashing mode has also been studied in the presence of a magnetic field. TheJ _z=0 state of the squashing mode is observed to shift to lower temperatures in a magnetic field. An additional field dependence of the observed acoustic impedance is interpreted as the evolution of theJ _z=–1, –2 states, but appears to be inconsistent with theoretical predictions.     

Hydrogen maser as a quantum frequency standard

Conclusions The main factors limiting the frequency stability of a hydrogen maser over long periods are magnetic field drift, error in the compensation setting, and inconstancy in bulb temperature. Future researches will be directed to raising the long term stability with continuous operation. We have developed a hydrogen maser with automatic magnetic field stabilization, with an improved frequency modulator that introduces very little Q change, and with a thermostatic cavity. In six months of preliminary tests the systematic frequency drift has been zero from day to day within 10^–13. Atomic clocks of this type may be recommended as working time reference standards.Translated from Izmeritel'naya Tekhnika, No. 11, pp. 29–32, November, 1972.     

Investigation of the properties of a magnetofluidized bed and development of a new gas purification technology based on them for simultaneous removal of solid and gaseous substances from hot waste gases

The results of investigation of the influence of the mechanical, thermal, structural, catalytic, and regenerative characteristics of granular oxide catalysts on the efficiency of decontamination of volatile organic substances in the catalyst unit and of the filtration rate, amount, and concentration of dust, the size of filter particles, the direction and intensity of a magnetic field, and other parameters on the behavior of the particles, the structure, the porosity, the resistance, the optimum fluidization rates, and the efficiency of collection of dust in magnetofluidization of magnetic particles have been given. The diagram and operating principles of a new technology for simultaneous decontamination of volatile organic matter and collection of dust have been presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 77, No. 6, pp. 59–73, November–December, 2004.     

Deformation of copper under the action of strong magnetic fields and cryogenic temperatures

Results are presented for an experimental study of the effect of a strong constant and pulsed magnetic field on the mechanical characteristics and deformation features of copper M1 at 293–4.2 K. Dependences have been obtained for the increase in specimen strain on the intensity of a pulsed magnetic field and flow stress, and possibilities have been studied for increasing the effectiveness of pulsedmagnetic deformation of metals. A calculation relationship is suggested for determining the critical stress level under strong skin-effect conditions of a magnetic field.Institute of Strength Problems, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Problemy Prochnosti, No. 12, pp. 32–36, December, 1989.     

Magnetic properties of porous iron compacts

Magnetic hysteresis measurements, magnetoacoustic emission, and the Barkhausen effect have been used to investigate the magnetic properties of six porous iron compacts with porosities in the range 0.3–6.2% and pore sizes in the range 1.6–13.2 µm. Coercivity and maximum permeability varied with pore size, showing respectively a maximum and a minimum for pore areas in the range 50–100 (µm)², corresponding to pore diameters 8–11 µm. Significant correlations were found between several of the magnetic parameters including a fundamental relationship between coercivity, initial permeability, and maximum differential permeability. There were also indications of a correlation between magnetic properties and the initial molding pressure, although these were not conclusive. However, none of the magnetic properties was found to vary in a progressive manner with percentage porosity, although it is conceivable that if all other variables, such as pore size and grain size, remained constant, that changes in magnetic properties with porosity could be detected from magnetic measurements.     

A high sensitivity gradiometric magnetometer

We have investigated the possibility of raising the sensitivity of a magnetometer by using integrated microelectronic magnetic field sensor and gradiometric magnetic flux transforms, made from high temperature superconductors. A sensitivity of 10^–9 T has been achieved experimentally, on cooling the sensors to liquid nitrogen temperatures.Translated from Izmeritel'naya Tekhnika, No. 12, pp. 11–13, December, 1994.     

Spin Manipulation Using Magnetic II–VI Semiconductors

Recently, efficient spin injection, being the first step towards semiconductor spin electronics, by using BeMnZnSe as a spin filter was accomplished. Such a spin filter made it possible to align the spin orientation of conduction electrons and subsequently inject them into GaAs. However, controlling spin orientation of conduction electrons by an external voltage would be very desirable for semiconductor-based magnetoelectronics. This can be accomplished by using spin switch structures, based on resonant tunneling through magnetic quantum wells, with two separate spin-up and spin-down resonances. Here we summarize both our recent results on spin injection as well as on spin aligner and magnetic resonant tunneling structures. For accomplishing the latter, we have developed magnetic resonant tunneling diodes based on BeTe–ZnMnSe–BeTe structures. Resonant tunneling diode is meant to serve as a spin switch because of the existence of two separate spin-up and spin-down resonances. The tunneling carriers have subsequently been injected into a nonmagnetic GaAs p–i–n light emitting diode. Circular polarization of the emitted light is an indicator of the spin polarization of injected electrons. At constant magnetic field and current, degree of spin polarization could be changed from 81% to 38% by only varying the voltage across the magnetic resonant tunneling device.     

Model of a nonstationary isotropic turbulent flow of a liquid with polymer additives

A closed equation is investigated for a function that describes the evolution in time of the energy distribution of turbulent velocity pulsations over different length scales in an isotropic flow of dilute solutions of linear high-molecular-weight polymers. A program for a numerical solution of this equation is developed. Results are obtained for the time variation of turbulent pulsation energy, dissipation rate, efficiency of polymer additives, and other characteristics for different Reynolds numbers and different concentrations of the polymer additives. The results obtained indicate decreased dissipation of the turbulent flow and are in good qualitative agreement with existing experimental facts.Academic Scientific Complex A. V. Luikov Institute of Heat and Mass Transfer of the Academy of Sciences of Belarus, Minsk. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 67, Nos. 5–6, pp. 362–372, November–December, 1994.     

A simple analysis of the Einstein relation in quantum confined non-parabolic semiconductors in the presence of a parallel magnetic field

An attempt is made to study the Einstein relation for the diffusivity-mobility ratio of the carriers in quantum confined non-parabolic semiconductors in the presence of a parallel magnetic field at low temperatures on the basis of new electron dispersion laws of quantum wells (QWs) and quantum wells wires (QWWs) of such materials. It is found, taking QW and QWWs of Hg_1–xCd_xTe and In_1–xGa_xAs_yP_1–y lattice-matched to InP as examples, that the diffusivity-mobility ratio increases with increasing electron concentration, decreasing alloy composition and decreasing film thickness in various oscillatory manners in both the cases. The magnetic field and the quantum wire structure enhance the numerical values of the same ratio. We have suggested an experimental method of determining the Einstein relation in degenerate materials having arbitrary dispersion laws. In addition, the corresponding well-known results of relatively wide-gap quantum confined materials in the absence of the magnetic field have been obtained as special cases of our generalized formulations, under certain limiting conditions.     

Simplified System for Creating a Bose–Einstein Condensate

We designed and constructed a simplified experimental system to create a Bose–Einstein condensate in ⁸⁷Rb. Our system has several novel features including a mechanical atom transfer mechanism and a hybrid Ioffe–Pritchard magnetic trap. The apparatus has been designed to consistently produce a stable condensate even when it is not well optimized.     

Optimization of hot workability of an Al-Mg-Si alloy using processing maps

The hot workability of an Al-Mg-Si alloy has been studied by conducting constant strain-rate compression tests. The temperature range and strain-rate regime selected for the present study were 300–550 °C and 0.001–1 s^–1, respectively. On the basis of true stress data, the strain-rate sensitivity values were calculated and used for establishing processing maps following the dynamic materials model. These maps delineate characteristic domains of different dissipative mechanisms. Two domains of dynamic recrystallization (DRX) have been identified which are associated with the peak efficiency of power dissipation (34%) and complete reconstitution of as-cast microstructure. As a result, optimum hot ductility is achieved in the DRX domains. The strain rates at which DRX domains occur are determined by the second-phase particles such as Mg₂Si precipitates and intermetallic compounds. The alloy also exhibits microstructural instability in the form of localized plastic deformation in the temperature range 300–350 °C and at strain rate 1 s^–1.     

Magnetic properties of hydrothermally synthesized strontium hexaferrite as a function of synthesis conditions

Fine particles of strontium hexaferrite, SrFe₁₂O₁₉, with a narrow size distribution have been synthesized hydrothermally from mixed aqueous solutions of iron and strontium nitrates under different synthesis conditions. The relationship between the synthesis variables (temperature, time and alkali molar ratio) and the magnetic properties has been investigated. The results have shown that, as the synthesis temperature increases, the saturation magnetization of the particles increases up to a plateau and the coercivity decreases. As the alkali molar ratio R(=OH^–/NO ₃ ^– ) increases, the coercivity decreases and goes through a local minimum, while the saturation magnetization increases and goes through a local maximum. Increasing the synthesis time from 2 h to 5 h has no significant effect on the saturation magnetization, but decreases the coercivity. An anisotropic sintered magnet with a high saturation magnetization value of 67.26 e.m.u g^–1 (4320 G) has been fabricated from the hydrothermally synthesized powders.Relationship between the c.g.s and S.I.units which are used in this paper are as follows: 1 erg = 10^–7 J, 1 e.m.u. cm^–3 = 12.57×10^–7 Wom^–2 (tesla), 1 oersted (Oe) = 79.6 A m^–1, 1 G = 10^–4 tesla (T).     

Heat transfer during laminar flow of a viscoelastoplastic medium in a circular tube

An approximate analytical solution is obtained for the problem of heat transfer during the laminar flow of a viscoelastoplastic medium in a circular tube disregarding the energy dissipation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 34, No. 6, pp. 1066–1069, June, 1978.     

Convective heat transfer for a nonlinear viscoplastic medium in a circular pipe

Heat transfer is considered for a viscoplastic material of nonlinear type flowing with dissipation in a circular tube with developed laminar flow and boundary conditions of the first kind.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 19, No. 5, pp. 850–860, November, 1970.     

Spectrum of the electron-phonon interactions of zinc single crystals induced by a basal-dislocation network

A dislocation spectrum of the electron-phonon interactions (EPI) of zinc single crystals is obtained for the first time. It is shown that dislocations are a source of hypersonic waves. Possible mechanisms of energy dissipation in vibrations of the network of basal dislocations in the point-contact zone are considered. It is noted that a change in the effective transport function of EPI results from the inertial properties of dislocations.Physicotechnical Institute of Low Temperatures, Khar'kov. Translated from Inzhenerno-Fizisheskii Zhurnal, Vol. 67, Nos. 1–2, pp. 81–85, July–August, 1994.