Computational investigation of the temperature and geometric characteristics of VVÉR fuel in the Kozlodui nuclear power plant (Bulgaria) under normal operating conditions

A method of performing stationary thermomechanical calculations of VVéR-440 and-1000 fuel elements, using the TRANSURANUS computer code to obtain the dependence of the temperature and radius of the fuel elements on the lineal power ensity and burnup, is described. These dependences are intended for use in neutron-physical calculations of the VVéR reactor at the Kozlodui nuclear power plant in stationary and transient regimes. The results obtained with this computer program are compared with calculations performed using the certified TOPRA-s code. The comparison shows reasonable agreement between the results of calculations of the fuel temperature. __________ Translated from Atomnaya énergiya, Vol. 101, No. 5, pp. 336–342, November, 2006.     

Symbolic computation with sequences

We present several classes of univariate sequences and sketch some algorithms for computing with sequences from these classes. The text was submitted by the author in English.     

Laser milling of ceramic components

Conventional methods of producing ceramic components are based on sintering technology which requires expensive tooling making it uneconomic for small batch fabrication. Laser milling provides a new method of producing parts in a wide range of materials, including ceramics, directly from CAD data. This paper considers the technical capabilities of laser milling when applied to the machining of microcomponents from alumina and silicon nitride ceramics. The main parameters affecting the material removal characteristics of laser milling are reviewed. A new technique for machining alumina components is proposed emphasising the importance of correct set-up design in achieving a high level of accuracy. Process parameters influencing part quality are analysed and guidelines for machine set-ups are formulated. The paper concludes with an assessment of the accuracy of the laser milling process.     

Boat sampling and inservice inspections of the reactor pressure vessel weld No. 4 at Kozloduy NPP, Unit 1

The paper deals with reactor pressure vessel (RPV) boat sampling performed at Kozloduy Nuclear Power Plant, Unit 1, from August to November 1996. Kozloduy NPP, Unit 1 has no reactor vessel material surveillance program. Changes in the material fracture toughness resulting from the fast neutron irradiation which cannot be monitored without removal of the vessel material. Therefore, the main objective of the project was to cut samples from the RPV wall in order to obtain samples of the RPV material for further structural analyses. The most critical area, i.e. weld No. 4 was determined as a location for boat sampling. Replication technique was applied in order to obtain precise determination of the weld geometry necessary for positioning of the cutting tool prior to boat sampling, and determination of divot depth left after boat sampling and grinding of sample sites. Boat sampling was performed by electrical discharge machining (EDM). Grinding of sample sites was implemented to minimize stress concentration effects on sample sites, to eliminate surface irregularities resulting from EDM process, and to eliminate recast layer on the surface of the EDM cut. Ultrasonic, liquid penetrant, magnetic particles, and visual examinations were performed after grinding to establish baseline data in the boat sampling area. The project preparation activities, apart from EDM process, and the site organization lead was entrusted to INETEC. The activities were funded by the PHARE program of the European Commission.     

Changes in the physicochemical and optical properties of chalcogenide thin films from the systems As—S and As—S—TI

Changes in some physical and optical properties of thermally evaporated thin films from the systems As—S and As—S—Tl over a wide range of concentrations have been investigated. The influence of the conditions of vacuum deposition and light exposure has been demonstrated. The optical transmission and reflection of thin layers deposited on BK-7 optical substrates have been measured in the spectral region of 350–2000 nm and the linear (n) and nonlinear (n ₂) refractive indices and optical band-gap, E _g, as well as the oscillator fitting constants, were calculated. Boling's formula is used to predict n ₂ from the dispersion and the magnitude of n. Data for changes in the glass-transition temperature, T _g, microhardness, and rate of dry etching of thin chalcogenide films before and after exposure to light are presented. The addition of Tl in As₂S₃ leads to an increase in the refractive index and decrease in the optical band-gap. After illumination a photodarkening or photobleaching effect was observed depending on the evaporation conditions. Some of the layers change their etching rate in a plasma which make them suitable for practical applications. Conclusions on the homogeneity of the layers and the origin of photostructural changes in them are drawn.     

Comparison of texture features based on Gabor filters

Texture features that are based on the local power spectrum obtained by a bank of Gabor filters are compared. The features differ in the type of nonlinear post-processing which is applied to the local power spectrum. The following features are considered: Gabor energy, complex moments, and grating cell operator features. The capability of the corresponding operators to produce distinct feature vector clusters for different textures is compared using two methods: the Fisher (1923) criterion and the classification result comparison. Both methods give consistent results. The grating cell operator gives the best discrimination and segmentation results. The texture detection capabilities of the operators and their robustness to nontexture features are also compared. The grating cell operator is the only one that selectively responds only to texture and does not give false response to nontexture features such as object contours.     

Primary non-Hodgkin lymphoma of the anterior abdominal wall

Examining 26 patients with early recurrent venous thrombophilias and ischemic attacks revealed that 6 cases had Va factor resistance to activated C protein. The latter suggests that thrombophilia associated with hereditary C- protein resistance is recorded in the Russian population, among the residents of West Siberia in particular.     

Optimum design of a high-power, high-frequency transformer

A procedure for optimum design of a high-power, high-frequency transformer is presented. The procedure is based on both electrical and thermal processes in the power transformer and identifies: (a) the VA-rating of ferrite cores in relation to the operating frequency; (b) the optimum flux density in the core; and (c) the optimum current densities of the windings providing maximum transformer efficiency. Since the transformer is the major contributor to the volume and weight of the power supply, the results of transformer analysis can be used for entire power supply optimization as well. Two high-power, high-frequency transformers are optimally designed, built, and tested. Practical results show good agreement with the theory     

Ultimate-strength germanium nanowires

Semiconducting nanowires (NWs) are important "building blocks" for potential electrical and electromechanical devices. Here, we report on the mechanical properties of supercritical fluid-grown Ge NWs with radii between 20 and 80 nm. An analysis of the bending and tensile stresses during deformation and failure reveals that while the NWs have a Young's modulus comparable to the bulk value, they have an ultimate strength of 15 GPa, which is the maximum theoretical strength of these materials. This exceptional strength is the highest reported for any conventional semiconductor material and demonstrates that these NWs are without defect or flaws that compromise the mechanical properties.     

A 0.2–2 Gb/s 6x OSR Receiver Using a Digitally Self-Adaptive Equalizer

This paper presents a very robust 6x OSR receiver for 0.2-2 Gb/s binary NRZ signals, introducing an adaptive equalizer that is auto-calibrating on sample data statistics for reliable data recovery in presence of excessive intersymbol interference, noise and crosstalk. The proposed time domain analysis of the data eye obtained with the oversampling architecture is used to tune the equalizer transfer characteristic. The auto-calibration scheme is fully implemented in the digital domain, resulting in a hardware and power efficient architecture with low process-voltage-temperature (PVT) sensitivity. This robust and highly digitized receiver is demonstrated in 0.18 CMOS technology and is able to equalize variable cable losses up to 22 dB @ 1 GHz. The self-adaptive equalizer solution occupies only 0.05 and consumes 9 mW from a 1.8 V supply and can handle up to 20 m 100 Omega STP cable @ 2 Gb/s. The entire receiver consumes 110 mW operating at 2 Gb/s with bit error rates of better than < 10^-12.