Leaching of uranium and 226ra from low-level radioactive waste from port hope,ontario

Uranium and radium were leached from a low-level radioactive soil sample neutralized with limestone from Port Hope, ON, in single stage and multistage leaching tests. The leachants used were alkaline EDTA, sodium citrate, sodium potassium tartrate, acidic ferric chloride, hydrochloric acid, nitric acid and hydrochloric or nitric acid plus boric acid mixtures. All leaching tests except the two-stage acid leachings proved ineffective in yielding leach residues with low residual ²²⁶Ra concentrations of < 100 pCi/g. Leaching with 4 mol/L HNO₃ in the first stage followed by treatment with 4 mol/L HNO₃ plus 0.05 mol/L boric acid in the second stage proved effective and gave a leach residue with 85 pCi/g ²²⁶Ra and 16 ppm uranium.     

Energy, economics and environmental impacts of renewable energy systems

The renewable based electricity generation technologies were assessed against a range of sustainability indicators using data obtained from the literature. These indicators are cost of electricity generation, greenhouse gas emissions and energy pay-back time. All the three parameters were found to have a very wide range for each technology. For grading different renewable energy sources a new figure of merit has been proposed, linking greenhouse gas emissions, energy pay-back time and cost of electricity generated by these renewable energy sources. It has been found out that wind and small hydro are the most sustainable source for the electricity generation.     

Mass transfer study of the electropolishing of vertical cylinders with active ends under natural convection conditions

Rates of electropolishing of vertical copper cylinders with active ends in H₃PO₄ were studied by measuring the limiting current under natural convection. Variables studied were H₃PO₄ concentration, cylinder diameter and aspect ratio. The rate of polishing of the whole cylinder was represented by the mass transfer equation $$Sh = 0.33(Sc Gr)^{0.32}$$ for the range 1.17 × 10¹⁰ < Sc Gr < 5.11 × 10¹¹. Rates of mass transfer were measured also at vertical cylinder with insulated ends, and the upward facing surface (disc). Data for the vertical cylindrical surface were represented for the range 8.75 × 10⁹ < Sc Gr < 1.1 × 10¹² by the equation $$Sh = 1.206(Sc Gr)^{0.255}$$ while data at the upward facing disc were correlated for the range 0.11 × 10¹⁰ < Sc Gr < 46 × 10¹⁰ by the equation $$Sh = 0.17Sc^{0.396} (Sc Gr)^{0.146}$$ A comparison between the measured rate of mass transfer at the whole cylinder and the value calculated by adding the rates of mass transfer at the separate surfaces of the cylinder shows that the measured value deviates from the calculated value, the degree of deviation increases with increasing Sc × Gr. Deviation was attributed to flow interaction at the different cylinder surfaces.     

3D激光三角测量技术为机器视觉提供深度

0前言 技术的进步和成本的降低使3D视觉成为一种可以用于半导体和电子、电动车电池制造、汽车制造、食品生产和药品包装等多种应用和行业的技术.如今,在生产制造自动化、机器人引导和质量控制领域中3D传感器和轮廓仪越来越多地被应用.     

Low loss multilayer microstrip line for monolithic microwave integrated circuits applications

This paper describes the multilayer microstrip structure using low dielectric constant polyimide as a buffer layer between the microstrip conductor and the GaAs substrate to reduce dissipation loss, especially for very high impedance microstrip lines. The new structure provides about half the dissipation loss and about 40% higher characteristic impedance in comparison to the conventional microstrip line on GaAs substrate having the same conductor widths. An empirical formula for the equivalent dielectric constant compatible with commercial computer-aided design tools was developed to design monolithic microwave integrated circuits (MMICs) using this medium. The multilayer microstrip structure is compatible with ITT's 4′ MSAG^® process which uses polyimide for crossovers and scratch protection. The present structure has great potential in realizing low loss and wideband matching networks including low noise, high power, and high efficiency amplifiers, and passive components on GaAs substrate with improved insertion loss and bandwidth performance, and three-dimensional MMICs. © 1998 John Wiley & Sons, Inc. Int J RF and Microwave CAE 8: 441–454, 1998     

Automatic testing of MMIC wafers

Microwave probes are used extensively for linear and nonlinear characterization of microwave devices on wafer and are commercially available for use at frequencies up to 65 GHz. An on-wafer noise measurement test system, for discrete devices, is now commercially available and on-wafer power measurement techniques are emerging slowly. These probes are also getting more recognition for the testing of packaged chips, packages, and modules. More accurate calibration techniques and their on-wafer validation are being developed. Automatic testing of MMIC wafers, using an integrated test system, is a key requirement for the development of low-cost IC production.     

Mass Transfer Study of the Electropolishing of Horizontal and Vertical Rectangular Ducts under Free Convection Conditions

Rates of electropolishing of the outer surface of horizontal and vertical rectangular copper ducts were studied by measuring the limiting current of the anodic dissolution of these ducts in phosphoric acid under natural convection conditions. Phosphoric acid concentration and duct dimensions were varied to provide Sc Gr range of 1.46 × 10⁹–1.42 × 10¹¹. Under these conditions rates of polishing of vertical ducts were found to fit the equation Sh = 1.05 (Sc Gr)^0.27 while rates of polishing of horizontal ducts were found to fit the equation Sh = 0.7 (Sc Gr)^0.233 Sc^0.1. The present study recommends the use of the vertical position in practice owing to the uniformity of the hydrodynamic conditions at the four vertical planes which give rise to a uniform degree of polishing all over the duct.     

Structural, absorption and fluorescence spectral analysis of Pr ions doped zinc bismuth borate glasses

Glasses having composition 20ZnO·xBi₂O₃·(79.5 − x)B₂O₃·0.5Pr₆O₁₁ were prepared by melt quench technique. The amorphous nature of the prepared glass samples was confirmed by X-ray diffraction. The spectroscopic properties of these glasses were investigated by recording optical absorption and fluorescence spectra. The structural investigations of the glasses were carried out by recording the IR spectra. The optical properties of Pr³⁺ ions doped zinc borate glasses with varying concentration of bismuth oxide have been studied. The Judd-Ofelt intensity parameters Ω_λ (λ = 2, 4, 6) and other radiative properties like radiative transition probability, radiative life time, branching ratio and stimulated emission cross-section of the prepared glasses have been calculated. The variation of Ω₂ with Bi₂O₃ content has been attributed to changes in the asymmetry of the ligand field at the rare earth ion site and to the changes in their rare earth oxygen (RE-O) covalency. The branching ratio for ³P₀ → ³F₂ transition is 42% and the predicted spontaneous radiative transition probability rates are fairly high (14,347-14,607 s⁻¹). This is beneficial for lasing emission. The stimulated emission cross-section for all the emission bands has been calculated.     

Effect of Superimposed Pulsating Flow on Liquid‐Solid Mass Transfer in Fixed Beds

The liquid‐solid mass transfer behaviour of a fixed bed of cylinders has been studied using the dissolution of copper in acidified dichromate solution under pulsating flow conditions. The bed diameter was 100 mm. The depth of the working section was 95 mm and the length and diameter of the cylinders were 19.1 mm. Variables studied were steady flow superficial liquid velocity, and oscillation amplitude and frequency. Data have been correlated as the Sherwood number in terms of Schmidt number and the cylinder Reynolds numbers for steady and oscillatory flow. The form of the correlation permits comparison with literature data for the limiting cases where either of these Reynolds numbers is zero.