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With the introduction of cold electron sources such as nanotubes, X-ray sources became small in size so that many sources are installed in array to form stationary CT, which brings benefits of simplicity in mechanism and fast response. However, the nanotube-based X-ray source is still singly packaged and hence density of X-ray sources is limited, which introduces severe sparse-view artifacts and could not be used in practice. With the invention of X-ray sources device based on ZnO nanowires as cold electron emitters, a large amount of X-ray sources is first integrated in a flat panel device. In this study, we design a stationary CT architecture using high-density sources devices, called HD-SCT, and develop corresponding reconstruction algorithm. Specifically, several flat panel detectors and X-ray sources devices are spliced together to form a source-detector plate. Multiple source-detector plates are organized as a polygon that encloses object to complete CT scanning. In HD-SCT, X-ray sources are close to object which can significantly decrease CT device volume. The X-ray beam emitted by each source just cover part of object and the spot sources alternately light to completely scan object. Simultaneously, we propose a reconstruction method for the specific configuration which adopts an iterative algorithm to resolve the reconstruction based on alterative part projections, as well as a novel correction process of projection completion for the shadowed area of placing X-ray source devices. To validate the design of the proposed HD-SCT, we execute a series of simulation experiments, which show that the proposed HD-SCT and corresponding reconstruction method effectively remove the artifacts caused by the embed X-ray source device. The results also disclose that with the increase of density of X-ray sources, the resolution of reconstruction has been dramatically improved, which demonstrates the practical value of introducing high-density X-ray sources device into stationary CT design.

Compton scatter tomography can reconstruct the electron density distribution using the first-order Compton scattered photons, and has the potential of identifying different materials. However, in Compton scatter tomography, the detected photons may come from all voxels illuminated by the x-ray beam and the information is blended. Although the mixing could be reduced using mechanical collimation, the detected photon number will decrease seriously, which tampers the reconstructed image quality greatly. This paper proposes a Compton scatter tomography scheme based on the scatter physics and photon-counting detector. The Compton scatter photons could be detected without mechanical collimation while fan-beam CT scanning, and scattered signal can be separated into signals emitted from subsets of the entire volume due to geometry constraints associated with energy selection of the photon-counting detector. An analytical model of first-order Compton scatter projection procedure is constructed, and a compressed sensing based method is utilized to reconstruct the electron density distribution. Experiment results demonstrate the accuracy of the signal acquisition model, and the proposed imaging scheme can represent the anatomical structure of the object in electron density.

The occurrence of an interactive effect between warp and weft of woven fabrics under practical working conditions is an important concern for researchers. A novel 3D loading device has therefore been developed to elucidate information on materials subjected to loadings in multiple dimensions. This paper investigated the interactive effects between warp and weft in biaxial tension. Strain fields were characterized by digital speckle correlation method and Poisson’s ratio was calculated at 0° in the warp direction. The effects of different cutting angles and loading threshold values at 0° on the interactive effect were also evaluated. An interactive effect between warp and weft existed, and the influence of load at weft to warp was larger than warp to weft. Weft produced larger strain fields in both directions. As the load in the warp direction linearly increased, force values nonlinearly increased while load ratio decreased. Poisson’s ratio, however, was practically unchanged. Loading mean value curves at ...

Mechanical properties of woven ramie fabric under 3D loadings are fundamental to optimizing the design of woven composites that are frequently subjected to complex stress states. This work proposes a novel 3D test analysis system for evaluating woven natural-fiber fabrics under multidimensional loads. The effects of different loading directions, uniaxial (X direction), biaxial (X and Y), bursting (Z direction), and 3D loading (X, Y, and Z) on the breaking strength of the woven ramie (Boehmeria nivea) fabric were compared. Weft breaking strength was lower than that of warp under uniaxial tension. Variability in warp and weft increased in biaxial tension. Bursting strength was significantly affected by the type of loading head used, with an R20 spherical head producing the highest strength values. Warp and weft were positively correlated under biaxial tension, r = 0.58. The synergistic effect of bursting strength accounted for 12.5% of the total correlation under 3D loadings.