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Quantum noise in X-ray image intensifiers.

T Porubszky
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Abstract

Explicit expressions are given for the relative variance of the output screen of X-ray image intensifiers, and for detection quantum efficiency as a function of the technical features of the intensifier. The analysis takes into account all conversion stages and physical processes inside the image intensifier and includes a special treatment of scintillation. The results are analysed numerically both for previously reported approximations and for applying this more recent method of detailed visibility calculations.

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Biomedical EngineeringModels, TheoreticalQuantum TheoryRadiographic Image EnhancementX-Ray Intensifying ScreensJournal Article

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T Porubszky. 1987. Quantum noise in X-ray image intensifiers.. https://doi.org/10.1016/0141-5425(87)90011-2

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Optimal design of non-Newtonian, micro-scale viscous pumps for biomedical devices.

The present paper addresses the numerical optimization of geometrical parameters of non-Newtonian micro-scale viscous pumps for biomedical devices. The objective is to maximize the mass flow rate per unit of shaft power consumed by the rotor when an external pressure load is applied along the channel that houses the rotor. Two geometric parameters are considered in the optimization process: (i) the height of the channel that houses the rotor (H) and (ii), the eccentricity (epsilon) of the rotor. Three different micro-scale viscous pump configurations were tested: a straight-housed pump (I-shaped housing) and two curved housed pumps (L- and U-shaped housings). The stress-strain constitutive law is modeled by a power-law relation. The results show that the geometric optimization of micro-scale viscous pumps is critical since the mass flow rate propelled by the rotor is highly dependent on epsilon and H. Numerical simulations indicate that mass flow rate is maximized when epsilon approximately 0, namely when the rotor is placed at a distance of 0.05 radii from the lower wall. The results also show that micro-scale viscous pumps with curved housing provide higher mass flow rate per unit of shaft power consumed when compared with straight-housed pumps. The results are presented in terms optimized dimensions of all three configurations (i.e., H(opt) and epsilon(opt)) and for values of the power-law index varying between 0.5 (shear thinning fluids) and 1.5 (shear-thickening fluids).

Biomedical Engineering↗