Development of heat-and impact-resistant coatings for main pipelines

We have developed composite layered temperature-resistant silicon-organic sandwich-type coatings with thin polyurethane silicon-organic interlayers. We used the following materials as binding components: KO 921 silicon-organic lacquer with addition of éD-20 epoxy resin for prime coat, the same lacquer with addition of PZ 1040 S polyurethane elastomer for thin soft interlayers, and only KO 921 lacquer for thick hard layers. The mineral filler represented a mixture of coal ash and omiacarb in proportion 70 / 30 mass %. We have manufactured and tested laboratory specimens with two hard layers and two interlayers as well as with three hard layers and two thin interlayers. We have established that the developed composite layered coatings exceed, in their basic characteristics, the requirements of the State Standard Committee of Ukraine and foreign normative documents for the rust protection of steel main pipelines. Our coatings possess high impact strength, heightened elasticity and adhesion strength and, as to their electrical insulating characteristics, exceed these requirements by an order of magnitude. We note the complexity of the technology of applying layered composite coatings and the necessity of its improvement. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 42, No. 4, pp. 59–65, July–August, 2006.     

Effect of water inlet velocity on thermal stratification in a mantled hot water storage tank

Thermal stratification in a mantled hot water storage tank is analysed numerically for different water inlet velocities. The aim is to obtain higher thermal stratification and supply hot water for usage as long as possible. Twelve different water inlet velocities to the hot water storage tank are considered. The numerical method is validated by comparing its results against experimental and numerical results from the literature. It turned out that the results obtained from the numerical analysis have shown very good agreements with the results from previous works. As a result, the water temperature in the tank increases with the increase of the water inlet velocities to the mantle but this increment is not proportional. After a period of operation of 7.2 h, which corresponds to the average sunshine duration in Turkey, temperature increments of 6.5 and 35 K have been estimated for the hot water inlet velocities of 0.01 and 0.3 m s^?1, respectively, at a radial distance of 0.1 m and a height of 1 m inside the storage tank. Copyright © 2005 John Wiley & Sons, Ltd.     

Effect of the structure of weld metal on the pitting susceptibility of welded joints of ferritic-austenitic steel

The structure of welded joints of tubes from ferritic-austenitic steel 02Kh22N5AM3 is studied by methods of metallographic, x-ray diffraction, and electron microscopic analyses. Corrosion properties of welded joints are determined in pitting tests. The results of the study are used for developing a mode of welding and heat treatment that increases substantially the corrosion resistance of the weld metal. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 7, pp. 32–35, July, 2006.     

Formation of glass synthesized by sol-gel technology

The process of glass synthesis by the sol-gel method is studied using analysis of EPR spectra. The gelation process and formation of xerogels are considered depending on the temperature-time parameters and the type of initial components. It is established that the glass phase starts to be formed at 800°C. __________ Translated from Steklo i Keramika, No. 8, pp. 9–13, August, 2006.     

Adaptive two-loop Voltage-mode control of DC-DC switching converters

A new two-loop control scheme for voltage-mode control (VMC) of dc-dc switching converters is presented. The proposed method adds a high-gain robust loop with two controllers to the conventional VMC loop, achieving an analog "adaptive" loop in which the "equivalent voltage regulator" varies with the changing power stage parameters given as follows: 1) input voltage; 2) load; and 3) component tolerances. The loop significantly improves the disturbance rejection of the control system, i.e., closed-loop output impedance and audiosusceptibility while preserving the stability and the loop gain crossover frequency to a significant extent. Both the small-signal analysis and the experimental results carried out on a buck converter demonstrate the superiority of the proposed scheme with respect to the conventional single loop.     

Perceptual analysis of handwritten signatures for biometric authentication

The Internet has stimulated increased activity to address key problems relating to the implementation of reliable and robust biometric identity checking. Although not always the biometric modality most readily adopted in such an environment, the handwritten signature continues to offer many advantages over some other more commonly considered biometrics. The authors address some key issues relating to the nature of the handwritten signature and, especially, the strategies used by humans in analysing signature data. Through experimental studies and an analytical investigation, the paper identifies characteristics of the signature which influence its resilience to fraudulent penetration, pointing to some important principles on which to build procedures for both automated and non-automated identity authentication.     

Thermodynamic Analysis of the Wilson Model Using Partial Excess Functions

An approach to thermodynamic analysis of models of liquid solutions is developed. The approach is based on studying local characteristics of the concentration dependences of the partial excess molar functions. The applicability region is established, and constraints on the parameters of the Wilson equation are found.     

Effect of irradiation with low-energy Ar ions on the characteristics of the working and rear sides of single-crystal GaAs substrate

Contactless methods were used to study the characteristics of the front and rear sides of single-crystal GaAs wafers whose rear side was irradiated with low-energy Ar ions. Variations in the optical and photoelectric properties of irradiated and unirradiated sides were detected. A solitonic mechanism for the penetration of defects into the crystal bulk is suggested.     

Evaluating the stabilisation degree of digested sewage sludge: investigations at four municipal wastewater treatment plants.

Further reduction of volatile suspended solids (VSS) during a post-stabilisation step was applied to evaluate the stabilisation degree of digested sewage sludge. For this purpose digested sludge was collected at four municipal wastewater treatment plants (WWTPs) and further stabilised in lab-scale chemostat reactors either under anaerobic or aerobic conditions. Experimental results showed that even in adequately digested sludge a consistent amount of VSS was degraded during aerobic post-stabilisation. It seems that aerobic conditions play a significant role during degradation of residual VSS. Additionally, specific VSS production (gVSS/peCOD110.d) as well as specific oxygen uptake rate were shown to be suitable parameters to assess the degree of sludge stabilisation at WWTPs. Fourier transform infrared spectroscopy was used to reveal changes in the sludge composition. Spectra of treated and untreated sludge samples indicated that the major component of residual VSS in stabilised sludge for instance consisted of biomass, while cellulose was absent.