Probability-Theoretic and Statistical Analysis of Dictionary Texts

We consider probability-theoretic and statistical models and methods for computing the characteristics of dictionary structures. Results of a statistical analysis of several commonly used dictionaries are presented in order to test the adequacy of the computing methods proposed.     

Neural-Net Analysis of the Plasticity of ÉP-450 Ferrite–Martensite Steel with Different Alloying Element Concentrations

The results of a computational experiment with a neural-net model simulating the effect of the chemical composition on the plastic properties of ÉP-450 steel are presented. It is shown that computer-aided development of reactor steel with prescribed properties is, in principle, possible.     

SVBR-75/100 Multipurpose Modular Low-Power Fast Reactor with Lead–Bismuth Coolant

The results of development work on the SVBR-75/100 modular fast reactor cooled by lead–bismuth coolant are presented. The design is based on the experience gained operating reactors in nuclear-powered submarines. The SVBR-75/100 reactor is inherently safe because of its low power, the chemical inertness and high boiling point of the lead–bismuth coolant, and the integrated basin-type arrangement of the first-loop equipment. This eliminates the conflict between the safety and economic requirements that is characteristic of conventional-type reactors. The lower power makes it possible to build the reactor in a factory and deliver the reactor using any form of transportation to the nuclear power plant site. All safety systems operate passively. Most of these systems are used as normal-operating systems. This creates conditions for multipurpose applications of such reactor modules in developed and developing countries.     

Effect of broaching on high-temperature fatigue behavior in notched specimens of INCONEL 718

Notches were machined in specimens of INCONEL 718 by a broaching process, where differing broaching runs led to differing extents of subsurface deformation and surface roughness. Fatigue tests were carried out at 600 °C with a trapezoidal loading waveform at 0.25 Hz. The broaching process that led to the more severe subsurface deformation (but lower surface roughness) showed the worst fatigue performance. Analysis of total strain amplitude in the notch root with the aid of an elastoplastic finite-element (FE) model showed that the work hardening related to the subsurface deformation caused by the different broaching can account for the difference in fatigue lives. Differences in initiation and growth behavior were seen for the two broached finishes as well as for broached and subsequently polished samples. These differences are discussed in terms of a change in crack growth initiation and growth mechanisms due to the presence of the work-hardened layer.     

Micromechanical approach to damage mechanics of composite materials with fabric tensors

The purpose of this study is to apply continuum damage mechanics – introduced through the concept of fabric tensors – to composite materials within the framework of the theory of elasticity. A directional data model of damage mechanics for composite materials will be developed using fabric tensors. The introduction of fabric tensors into the analysis of damage of composite materials will allow for an enhanced and better understood physical meaning of damage. The micromechanical approach will be used here to relate the damage effect through fabric tensors to the behavior of composite materials. In this approach, damage mechanics is introduced separately to the constituents of the composite material through different constituents’ damage effect tensors. The damaged properties of the composite system as a whole can then be obtained by proper homogenization of the damaged properties of the constituents.

The derivation of a generalized formulation of damage evolution will be shown here in a mathematically consistent manner that is based on sound thermodynamic principles. Numerical examples will be presented to show applicability. In addition, damage evolution for the one-dimensional tension case is also illustrated.     

Electrophoretic deposition of electrolyte materials for solid oxide fuel cells

Electrophoretic deposition of electrolyte materials for solid oxide fuel cells, including La_0.8Sr_0.2Ga_0.875Mg_0.125O_3–x , yttria stabilized zirconia and (Ce_0.8Gd_0.2)O_1.9, was studied under various experimental conditions. The use of phosphate ester as a dispersant and poly (vinyl butyral) as a binder enabled high deposition rate and formation of crack-free, adherent deposits. Electrodeposition rates were quantified in experiments performed at constant current and constant voltage modes from suspensions in ethanol, isopropanol and mixed ethanol—isopropanol solvents. The microstructure of as prepared and sintered deposits was studied by electron microscopy. The bath composition was optimized to enable formation of dense deposits.     

Bipolar electric fatigue behaviour as a function of field strength in antiferroelectric (Pb,Ba,La)(Zr,Sn,Ti)O3 ceramics

The bipolar electric fatigue behaviour of antiferroelectric ceramics with the composition of Pb_0.88Ba_0.10La_0.02(Zr_0.55Sn_0.35Ti_0.10)O₃ was investigated under various cycling fields. The material exhibits a degradation in the maximum field induced strain, a diffuse AFE-FE phase transition and an enhancement in the diffusion character of the FE-AFE phase transition due to electric cycling. Those variations increase with cycle number, indicating a logarithmic fatigue up to 10⁸ cycles. There is no indication for the variations to be recovered, and the symmetry of the negative and positive parts of the strain hysteresis loops still remains. Higher cycling field results in a stronger deterioration of the maximum field induced strain and a larger extent of diffusion in AFE-FE and FE-AFE phase transitions. The normalized maximum strain shows nearly the same scale of degradation when the materials are cycled at various electric fields. After a heat treatment at 500°C for 1 h, the variations in the AFE-FE and FE-AFE phase transition due to cycling disappear, whereas the maximum strain resumes almost to its original value. Electrochemical variations are considered to contribute to the main fatigue mechanism for the material under investigation.     

Effect of gas mixing ratio on gas-phase composition and etch rate in an inductively coupled CF4/Ar plasma

In this work, we carried out investigations aimed at understanding the effect of gas mixing ratio on plasma parameters, gas phase composition and etch rate in CF₄/Ar inductively coupled plasma. For this purpose, a combination of experimental methods and modelling was used. Experiments showed that electron temperature and electron density are not very sensitive to variations of Ar content in CF₄/Ar plasma. From a zero-dimensional plasma model, the densities of both neutral and charged particles change monotonically. The analysis of surface kinetics based on an ion-assisted etching mechanism showed the possibility of non-monotonic etch rate behaviour due to a concurrence of chemical and physical etching pathways.     

A continuum model for pumping performance of turbomolecular pumps in all flow regimes

In the present study a continuum model for one-dimensional plane Couette-Poiseuille flow is implemented to turbomolecular pumps in different flow regimes. Pumping performance of various turbomolecular pumps including 6 single rotors, a rotor-stator row, a rotor-stator-rotor row, and a multi-row with 13 alternative rotor-stator rows is considered here. The obtained results show that the model provides good quantitative values for pumping performance of turbomolecular pumps over the whole regimes ranging from molecular flow to transition to slip flow.