Digital image analysis of X-ray and neutron radiography for the inspection and the monitoring of nuclear materials

The article shows the digital image analysis of X-ray and neutron radiography (NR) ad hoc developed for the inspection and monitoring of nuclear samples, used in several experiments at the High Flux Reactor of the Institute for Energy (JRC-Petten). This application is valuable not only in the characterization of the sample and of the experimental assembly, but also in acquiring information on the sample behaviour during and after the irradiation.The inspection foresees the X-ray radiography of the sample in order to detect the eventual presence of fabrication defects. During and/or after the irradiation, NR helps to understand the sample behaviour under irradiation (such as swelling, disintegration). NR can also be performed before the irradiation for comparison with NR during the irradiation and with the X-ray.The image analysis is used for acquiring qualitative and quantitative information from these inspection techniques at a high level of accuracy.     

The microstructure and mechanical properties of Bi(Pb)-Sr-Ca-Cu-Ag metallic precursor ribbons produced by the melt-spinning process

Metallic precursor ribbons of Bi-Pb-Sr-Ca-Cu with nominal compositions of 1.4-0.6-2-3-4, respectively, were made by vacuum induction melting followed by melt-spinning. Silver at the level of 12–81 vol% was added to produce precursor-Ag alloy ribbons. These ribbons were subjected to a controlled atmosphere oxidation and annealing to produce superconducting oxide/Ag microcomposites. All of the alloys with up to 73 vol% Ag can be processed into superconducting ribbons with zero resistance atT=104–110 K and a critical current density of 200–600 A cm⁻² at 77 K in zero field. The relationship of the Ag content, melt-spinning processes, microstructure and mechanical properties of the metallic precursor ribbons were studied by microhardness tests, bending tests, scanning electron microscopy and electron probe microanalysis. The maximum bending strain of the metallic precursor ribbons was found to increase from 0.3–1.7% as the silver content increased from 12–81 vol%, while the ribbon hardness was found first to increase with silver content increasing from 12–62 vol%, then to decrease with further increases in silver content. The mechanical properties were also strongly affected by the melt-spinning processes,i.e. by the ejection pressure applied to the melt and wheel surface speed. The best bending strain for the metallic precursors with 52 vol% Ag achieved so far is ∼0.85%, which was obtained by using an ejection pressure of 69 kPa and a wheel speed of 9.5 m s⁻¹. The mechanical properties of the precursor ribbons is critically important for producing superconducting coils and long wires, which were made by first winding the metallic ribbons on MgO spools, followed by suitable oxidation and annealing.     

Jet break-up and air entrainment by low velocity turbulent water jets

Correlating equations are developed for air entrainment by plunging water jets with velocities in the range between 2 and 5 m/sec. Energy considerations are shown to be a good basis for predictive equations. Two different situations are distinguished depending on whether or not the jet is near its break-up length; for jets produced by nozzles within which turbulence is fully developed the break length is correlated by

Beyond 90% of the total break length the air entrainment produced by vertical jets from 2·85 to 10 mm diameter is given by

For shorter jets which are vertical or inclined, there is a length dependence which leads to the relationship, accurate within 15%, of

     

Robust control of an electromagnetic active suspension system: Simulations and measurements

This paper considers the control of a novel high bandwidth electromagnetic active suspension system for a quarter car model in both simulations and experiments. The nature of the control problem with multiple objectives that have to be optimized as well as the uncertain parameters of the plant call for an H_∞-controller. By changing weighting filters different controllers can be designed, emphasizing either comfort or handling. Using the high bandwidth of the actuator comfort can be improved by 40% over the passive BMW whilst keeping suspension travel within the same limits. Using a different controller, handling can be improved up to 30%, limited by RMS actuator force.     

Antiangiogenic factors and maternal hemodynamics during intensive hemodialysis in pregnancy

We report on a 21‐year‐old pregnant patient with IgA nephropathy who was initiated on intensive hemodialysis (8 hours of hemodialysis 3 times a week) at a gestational age of 26 weeks on the basis of worsening kidney function resulting in rapidly progressive fatigue and difficulties in metabolic control. Throughout the pregnancy, and while on intensive hemodialysis, 24‐hour ambulatory blood pressure control was within the target, and results of weekly 24‐hour measurement of central hemodynamics and pulse wave velocity, and of serial levels of circulating (anti‐)angiogenic factors were comparable to normal pregnancies. Estimated fetal growth evolved along the 50th percentile, and no polyhydramnios was detected. After induction for a sudden, unexplained increase in blood pressure, she delivered a healthy boy of 2480 g at a gestational age of 36 weeks. This case adds to the expanding literature that supports the use of intensive hemodialysis in pregnant patients with end‐stage renal disease and illustrates, for the first time, the potential use of serial (anti‐) angiogenic factors and 24‐hour measurements of blood pressure and hemodynamic indices in order to facilitate monitoring of these complicated patients.     

Antiparallel DNA duplex formation between alternating alpha d(GA)n and beta d(GA)n sequences

In the Adult Intensive Care Unit of The Prince of Wales Hospital, Sydney, Australia, inspiratory gas is humidified to saturation at 37 degrees C. This stops the buildup of dried sputum within the endotracheal tubes and thus prevents blocked tubes and the increased resistance caused by partial obstruction. Inspiratory and expiratory hose heater wires are used to produce a completely dry circuit, allowing the elimination of water traps and circuit support arms without the resistance of a heat and moisture exchanger.     

The rubber particle size dependence of crazing in polypropylene

The tensile crazing and Charpy impact behavior of polypropylene modified with styrene-butadiene copolymer (SBR) and ethylene-propylene-diene monomer (EPDM) was studied. Various rubber particle size distributions were obtained by varying the relative viscosities between rubbery phase and PP matrix. Transmission electron microscopy and computer-aided image analysis were used to provide particle size information. In general, PP blends with smaller rubber particles are tougher and more ductile than those with larger particles, probably because the former represents a more efficient use of rubbery phase in promoting crazing and/or shear yielding. Samples with average particle diameter D? ≥ 0.5 μm were found to exhibit pronounced crazing. Within a given sample, no crazes appeared to develop around individual rubber particles with D < 0.5 μm. The higher the D, the greater the propensity to form crazes. The behavior of samples with D? ? 0.5 μm appeared to be dominated by shear yielding; very few crazes could be found. That there exists a critical rubber particle size is explained by the requirement that sufficient stress concentration be maintained to a finite radial distance to permit the initiation and growth of a craze, which requires a finite volume. Small particles, inducing smaller stress-enhanced zones, are therefore not effective in initiating crazes.     

Space Charge Segregation at Grain Boundaries in Titanium Dioxide: II, Model Experiments

A quantitative study of space charge solute segregation at grain boundaries in TiO₂ is conducted, using a new STEM method for the measurement of aliovalent solute accumulation. It is shown that the electrostatic potential at grain boundaries can be varied in sign and magnitude with doping, oxygen pressure, and temperature, and that the isoelectric point lies in slightly donor-doped compositions for samples annealed in air. The experimental results closely fit the space charge model in Part I. Space charge solute segregation is found even in defect regimes of high electron concentration. Approximately one in ten grain boundaries are "special" in exhibiting no detectable segregation; in one such instance a twin boundary is identified. Among boundaries with significant amounts of segregation, clear differences in potential also exist. From the potential determined in acceptor- and donor-doped compositions, the Frenkel energy (assumed to be lower than the Schottky energy in TiO₂) can be separated into its individual terms. An average value for the titanium vacancy formation energy of g_vTi = 2.4 eV and an upper limit to the titanium interstitial formation energy of g_Tii = 2.6 eV are obtained.