Current Issue : July - September Volume : 2015 Issue Number : 3 Articles : 5 Articles
This paper describes a study where a new X-ray machine for security screening featuring\nmotion imaging (i.e., 5 views of a bag are shown as an image sequence) was evaluated\nand compared to single view imaging available on conventional X-ray screening systems.\nMore specifically, it was investigated whether with this new technology X-ray screening\nof passenger bags could be enhanced to such an extent that laptops could be left inside\npassenger bags, without causing a significant impairment in threat detection performance.\nAn X-ray image interpretation test was created in four different versions, manipulating the\nfactors packing condition (laptop and bag separate vs. laptop in bag) and display condition\n(single vs. motion imaging). There was a highly significant and large main effect of packing\ncondition. When laptops and bags were screened separately, threat item detection was\nsubstantially higher. For display condition, a medium effect was observed. Detection could\nbe slightly enhanced through the application of motion imaging. There was no interaction\nbetween display and packing condition, implying that the high negative effect of leaving\nlaptops in passenger bags could not be fully compensated by motion imaging. Additional\nanalyses were carried out to examine effects depending on different threat categories\n(guns, improvised explosive devices, knives, others), the placement of the threat items\n(in bag vs. in laptop) and viewpoint (easy vs. difficult view). In summary, although motion\nimaging provides an enhancement, it is not strong enough to allow leaving laptops in bags\nfor security screening....
Forced oilââ?¬â??water displacement is the crucial\nmechanisms of secondary oil recovery. The knowledge of\nrelative permeability is required in the simulation of multiphase\nflow in porous media. Obvious dynamic effect of\ncapillary pressure occurs in that the formation of ultra-low\npermeability reservoir (the permeability is <1 X\n10-3 lm2) is tight and the pores and throats are very small.\nIn addition, the significant capillary end effect causes\nserious errors when calculating relative permeabilities. For\nthese reasons, the JBN method (neglecting capillary pressure)\ndoes not apply. Therefore, the dynamic capillary\npressure and capillary end effects should be taken into\naccount. This work focuses on calculating two-phase relative\npermeability of ultra-low permeability reservoir\nthrough considering the dynamic capillary pressure and\neliminating the influence of capillary end effects. Firstly,\nlaboratory core scale measurements of in situ water phase\nsaturation history based on X-ray CT scanning technique\nwere used to estimate relative permeability. Secondly, a\nmathematical model of two-phase relative permeability\nconsidering the dynamic capillary pressure was established.\nThe basic problem formulations, as well as the more\nspecific equations, were given, and the results of\ncomparison using experimental data are presented and\ndiscussed. Results indicate that the dynamic capillary\npressure measured at laboratory core scale in ultra-low\npermeability rocks has a significant influence on the estimation\nof unsteady-state relative permeability. The mathematical\ncalculating method was compared with the history\nmatching method and the results were close, suggesting\nreliability for ultra-low permeability reservoirs. Importantly,\nthe proposed methods allow measurement of relative\npermeability from a single experiment. Potentially this\nrepresents a great time savings....
Although magnetic imaging with polarized x-rays is a rather young scientific discipline,\nthe various types of established x-ray microscopes have already taken an important role in\nstate-of-the-art characterization of the properties and behavior of spin textures in advanced\nmaterials. The opportunities ahead will be to obtain in a unique way indispensable\nmultidimensional information of the structure, dynamics and composition of scientifically\ninteresting and technologically relevant magnetic materials....
Introduction: X-ray imaging is an important part of medicine and plays a crucial role\nin radiotherapy. Education in this field is mostly limited to textbook teaching due to\nequipment restrictions. A novel simulation tool, ImaSim, for teaching the fundamentals\nof the x-ray imaging process based on ray-tracing is presented in this work. ImaSim is\nused interactively via a graphical user interface (GUI).\nMaterials and methods: The software package covers the main x-ray based medical\nmodalities: planar kilovoltage (kV), planar (portal) megavoltage (MV), fan beam computed\ntomography (CT), and cone beam CT (CBCT) imaging. The user can modify the photon\nsource, object to be imaged and imaging setup with three-dimensional editors. Objects\nare currently obtained by combining blocks with variable shapes. The imaging of\nthree-dimensional voxelized geometries is currently not implemented, but can be added\nin a later release. The program follows a ray-tracing approach, ignoring photon scatter in\nits current implementation. Simulations of a phantom CT scan were generated in ImaSim\nand were compared to measured data in terms of CT number accuracy. Spatial variations\nin the photon fluence and mean energy from an x-ray tube caused by the heel effect were\nestimated from ImaSim and Monte Carlo simulations and compared.\nResults: In this paper we describe ImaSim and provide two examples of its capabilities.\nCT numbers were found to agree within 36 Hounsfield Units (HU) for bone, which\ncorresponds to a 2%attenuation coefficient difference. ImaSim reproduced the heel effect\nreasonably well when compared to Monte Carlo simulations.\nDiscussion: An x-ray imaging simulation tool is made available for teaching and research\npurposes. ImaSim provides a means to facilitate the teaching of medical x-ray imaging....
The popularity of composite materials is continuously\ngrowing with new varieties being developed and\ntested with different machining processes to establish their\nsuitability. Destructive as well as non-destructive methods,\nsuch as ultrasonics, X-ray radiography and eddy-current,\nhave previously been used to ensure that the combination\nof particular machining methods and composites provide\nthe required quality that can allow the required lifespan\nof the final product. X-ray computed tomography (CT) is\napplied as a novel method in this paper to obtain quantitative\ndata about the inner and outer structures of carbon fibre\nreinforced polymer (CFRP) drilled holes providing more\ninformation than any other non-contact and non-destructive\nevaluation. This is combined with precise measurements\nfrom optical CMM and image processing for a full analysis\nfor the entire part. This method can provide accurate\nmeasurements for all the layers of the CFRP and very little\ninteraction from the operator minimising the human error.\nThe method complies with VDI/VDE 2630 standard and\nthe quality of the acquired measurements is assured. The\nresults can assist in establishing the best machining process,\nprovide accurate measurements of diameter, circularity and\npositioning of the hole and information about delaminated\nareas....
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