Nickel/microcapsules composite electrocoatings; the synthesis of water-containing microcapsules and preparation of the coatings

Composite coatings, the product of electrolytic codeposition of solid particles in a metallic matrix have been developed and utilized in industry as wear resistant coatings. The work described in this paper concerns the development of water-containing metallic coatings prepared by the electrolytic codeposition of water-containing microcapsules from nickel Watts plating baths under pulse reversed current conditions. The water-containing polystyrene microcapsules employed in the codeposition experiments were produced by the complex emulsion/solvent evaporation technique. The influence of the use of two types of stabilizers on the size and the surface chemistry of the microcapsules is discussed. The microcapsules prepared in both cases are rigid spheres with compact walls and a smooth surface. The different stabilizers showed a significant influence on the dispersability of the capsules in the plating solution and their codeposition behaviour. The codeposition experiments carried out with the use of a rotating disc electrode revealed the influence of the plating parameters on the incorporation procedure and on the quality of the composite electrodeposits.     

Testing images independently of translations and linear deformations

This article considers the theory of construction of criteria that are independent of the motions of images, as as well rotations and linear deformations. A method is presented for construction of new types of criteria that have the following distinctive features: they make it easy to construct functionals for measurement of the characteristics of motion of standard images; the theory can easily be extended to the case of grey-scale and colored images; the criteria that are obtained are amenable to parallel computation; the proposed theory makes it easy to construct new criteria. Translated from Izmeritel’naya Tekhnika, No. 8, pp. 13–16, August, 1996.     

Adhesion of streptococci to saliva-coated and uncoated composite-based resins

This study was designed to evaluate the bacterial adhesion to five types of experimental composite-based resins and a commercial composite resin used as a control. Physicochemical surface characteristics of composite resins with and without an artificial saliva coating were measured. The relationship between the numbers of adhering cells (Streptococcus sanguis, S. mutans and S. sobrinus) and surface characteristics was analysed. The values of contact angles and the number of adhering cells were small with saliva coating. S. sanguis ATCC 10557 showed a positive correlation (r=0.835, p<0.05) with the contact angles of uncoated resins, whereas no relationship was observed for saliva-coated resins. With S. mutans Ingbritt the cell numbers adhering to resins correlated strongly (p<0.01) with the values of zeta potential of resins for either saliva coated or uncoated. Electrical repulsion forces had a strong contribution to adherence of cells such as S. mutans and S. sobrinus which show a high absolute zeta potential.     

Computer analysis,design and simulation of horizontal ground heat exchangers

This paper presents a new computerized procedure for dealing with the design of horizontal ground heat exchangers (HGHE). The computer program is based on the transient model of coupled nonlinear partial differential equations governing heat and mass flow in soils. The model is two-dimensional and delineates the operation of ground heat storage with the HGHE and such phenomena as freezing/thawing and drying/rewetting of soil moisture. Comprehensive climatological data, such as ambient temperature, solar radiation, wind velocity, rainfall, snowfall, snow characterstics, and water vapour pressure is used to simulate conditions at the ground surface over any required length of time. The package can be applied to any geographical location by changing climatic and soil data input. The designer has the possibility of selecting any of 12 types of soils from sand to clay, 12 commercial heat pumps, nine different configurations of the HGHE, 16 plastic pipes for ground coils, and 13 ground coil fluids. The program, however, does not calculate the length of the HGHE but it evaluates the thermodynamic performance of a ground heat pump system and provides comprehensive data on thermal and hydraulic conditions in ground heat storage. The length of the ground heat exchanger is obtained from a line source theory model or from site dimensions and pipe spacing. Computed results for ground heat exchanger operation correlate fairly well with experimental data. Simulation of temperature and moisture content in the ground for natural conditions (no heat extraction/deposition) showed a fair agreement with field data. The entire computer program is user-friendly, interactive, menu-driven, and written in FORTRAN 77.     

A simple and effective precoding scheme for noise whitening onintersymbol interference channels

A precoding scheme for noise whitening on intersymbol interference (ISI) channels is presented. This scheme is compatible with trellis-coded modulation and, unlike Tomlinson precoding, allows constellation shaping. It can be used with almost any shaping scheme, including the optimal SVQ shaping, as opposed to trellis precoding, which can only be used with trellis shaping. The implementation complexity of this scheme is minimal-only three times that of the noise prediction filter, hence effective noise whitening can be achieved by using a high-order predictor     

Torsion of an elastic space with a crack on the surface of revolution

Numerical methods for solving integral equations of an axisymmetric problem of torsion of an elastic space with cracks on the surface of revolution are suggested for the cases of cracks crossing the axis of symmetry and cracks that have no common points with this axis. We also present relations for calculating the stress intensity factors at crack tips. Numerical results are obtained for a conic or paraboloidal simply connected crack and for a doubly connected crack lying on a surface formed by the revolution of an arbitrarily oriented straight segment or a parabolic arc. The crack faces are either subjected to a constant load or free of any forces; the body is subjected to torsion at infinity.Karpenko Physico-Mechanical Institute, Ukrainian Academy of Sciences, L'viv. Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 29, No. 6, pp. 87–93, November–December, 1993.     

Anomalous photoemission threshold in high-T c oxide superconductor with Cs and K submonolayers

The photoemission threshold and photocurrent spectra were investigated for Bi₂Sr₂CaCu₂O₈ crystals with K or Cs submonolayer films. The different films of K or Cs were deposited on the Bi-O surface in the temperature range 80–250 K. We observed an appreciable (up to 0.3 eV) energy shift of the threshold and a strong modification of the photocurrent spectra for different temperatures and submonolayer coverages. The appropriate model of such a phenomena is based on a quasimetallic K or Cs clusters effect and additional 2D-polaronic effect.