We present a standardized procedure to measure the amount of speckle in laser based projection systems. The parameters of the measurement procedure are chosen such that the measured speckle contrast values are in correspondence with the subjective speckle perception of a human observer, independent of the particularities of the laser projector's illumination configuration. The resulting measurement configuration consists of a single digital image sensor in combination with a camera lens of which the settings are related to the human eye. In addition, a standardized measurement procedure and speckle pattern analysis method are suggested. Finally, the speckle measurement set-up is applied to a laser projection system and corresponding subjective speckle perception results of a large test public are discussed.
Early detection of residual tumour and local tumour progression (LTP) after radiofrequency (RF) ablation is crucial in the decision whether or not to re-ablate. In general, standard contrast-enhanced computed tomography (CT) is used to evaluate the technique effectiveness; however, it is difficult to differentiate post-treatment changes from residual tumour. Dual-energy CT (DECT) is a relatively new technique that enables more specific tissue characterisation of iodine-enhanced structures because of the isolation of iodine in the imaging data. Necrotic post-ablation zones can be depicted as avascular regions by DECT on greyscale- and colour-coded iodine images. Synthesised monochromatic images from dual-energy CT with spectral analysis can be used to select the optimal keV to achieve the highest contrast-to-noise ratio between tissues. This facilitates outlining the interface between the ablation zone and surrounding tissue. Post-processing of DECT data can lead to an improved characterisation and delineation of benign post-ablation changes from LTP. Radiologists need to be familiar with typical post-ablation image interpretations when using DECT techniques. Here, we review the spectrum of changes after RF ablation of liver, kidney, and lung lesions using single-source DECT imaging, with the emphasis on the additional information obtained and pitfalls encountered with this relatively new technique.Teaching Points•Technical success of RF ablation means complete destruction of the tumour.•Assessment of residual tumour on contrast-enhanced CT is hindered by post-ablative changes.•DECT improves material differentiation and may improve focal lesion characterisation.•Iodine maps delineate the treated area from the surrounding parenchyma well.
This paper reports on an investigation into the fatigue strength of thick-walled cylinders that contain a small transverse hole or cross bore in the cylinder wull having either a chamfer or a blending radius at its intersection with the main cylinder bore. Fatigue tests surprisingly show that plain cross-bore cylinders having thickness ratios K = 1.4 and 2.0 have a fatigue life that is marginally greater than comparable cylinders with blending features. A finite element inuestigation shows that local high stresses are produced on the surface of blending features and these stresses are considerably greater in magnitude than those found in plain cross-bore cylinders. These stress findings are used to explain the experimental fatigue life results obtained. NOTATION K K , stress concentration factor q, hoop stress uL local maximum principal stress z shear stress zB shear stress at bore of cylinder thickness ratio (outer diameter to inner diameter) COO391 Q IMechE 1992
The introduction of a small transverse opening or cross-bore into the wall of a cylindrical pressure vessel is sometimes necessary. Under static conditions such a cross-bore may have little effect on the bursting pressure of a plain cylinder, but under cyclic stress conditions, the fatigue life of the vessel is severely reduced. If the cross-bore axis is offset from the radial centre-line of the cylinder, then the fatigue life of such a vessel is shown to be substantially greater than that of a similar vessel containing a radial cross-bore.
An analysis is presented of the process of die drawing isotropic polymers, in the form of circular rods, to produce highly oriented materials with enhanced mechanical properties. The stresses in a small element of material undergoing the drawing process have been analyzed using a force‐equilibrium approach and the initial yield and flow stresses in the material have been predicted from the von‐Mises yield criterion. The stress‐strain‐strain rate characteristics of the polymer used in the analysis were deduced from uniaxial tensile test data obtained at the same temperature at which the die drawing occurred. Experimental results are presented of the stress in polypropylene GSE‐108 rods when die drawn at 90°C in a purpose‐built die drawing facility. Novel techniques were used to determine the stress and strain distributions along the die. A comparison of the experimental results and the analytical predictions shows good agreement.
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