POINTWISE SPACE-TIME BEHAVIOR OF A COMPRESSIBLE NAVIER-STOKES-KORTEWEG SYSTEM IN DIMENSION THREE

The Cauchy problem of compressible Navier-Stokes-Korteweg system in R^(3) is considered here.Due to capillarity effect of material,we obtain the pointwise estimates of the solution in an H^(4)-framework,which is different from the previous results for the compressible Navier-Stokes system in an H^(6)-framework[24,25].Our result mainly relies on two different descriptions of the singularity in the short wave of Green’s function for dealing initial propagation and nonlinear coupling respectively.Our pointwise results demonstrate the generalized Huygens’principle as the compressible Navier-Stokes system.As a corollary,we have an L^(p) estimate of the solution with p>1,which is a generalization for p≥2 in[33].

YSO coded aperture camera based on depth of interaction for location correction

Purpose Coded aperture imaging was a widely used imaging method for radiation sources.However,the traditional gamma camera based on two-dimensional projection information for coded aperture imaging ignored the influence of the interaction depth of particles and detectors on the projection information,which reduced the imaging quality of the camera to some extent.Therefore,a method of correcting the coded gamma camera based on the interaction depth of particles and detectors is proposed to improve the location accuracy of detectors.Methods The camera developed in this work uses a 7×7 YSO crystal array coupled with two 7×7 Si-PM arrays.The crystal is evenly divided into 11 parts in the depth direction,with a voxel size of 3×3×3 mm3.The coded mask is a 13×13 array,which is a mosaic of two cycles of 7×7 modified uniformly redundant array mask.The depth resolution of the detector is obtained via the subsurface laser engraving dual-end readout method.After obtaining the three-dimensional position information of the interaction point the projection information obtained by the detector is layered,and the image is reconstructed.According to the spatial position information of the detector and the coded mask,the corresponding field of view of each layer of the detector is calculated,and the reconstructed image of each layer is amplified and superimposed according to the ratio of the field of view to obtain the reconstructed image combined with the depth information.Results and conclusion According to Monte Carlo simulation and radiation source imaging experiment results,this method can effectively improve the positioning ability of the detector.For the experimental scenario mentioned in the paper,the location accuracy can be improved by up to 1.54°.

Alpha particle detection with a planar CdZnTe detector and relative simulations

Purpose The performance of CZT inγ-ray and X-ray detection is growing rapidly in these years.However,there are only a few reports on its utilization inαparticle detection.Therefore,to study the properties of CZT for detection ofαparticle,a detection system has been manufactured,and a series of simulations have been done.Methods A 22×22×0.7mm^(3) planar CZT detector is deployed to detect theαparticles from a radiation source containing Am-241 and Pu-239,while COMSOL MultiPhysics and GEANT4 are employed in the simulation of charge collection and interaction betweenαparticles and CZT.Results An energy resolution of 1.47%FWHM at 5.486MeV and 1.32%at 5.157MeV has been achieved.A simulated spectrum has been created,and it is analogous to the one from experiment.Conclusion The experiment results show the potential of CZT inαdetection.The simulations are confirmed effective and will guide a better design of the detecting system.

Experiment validation of the high stability of long-term transmitted gamma photon counting of a new CdZnTe semiconductor detector and its preliminary applications

Purpose To develop a detector system with high stability in counting the detection of transmitted gamma photons,which can be applied in the area of non-destructive testing.Method We used the cadmium zinc telluride(CZT)detector with single-polarity electrodes to substitute the traditional scintillator detector and front-end read-out electronics based on our self-designed low-noise charge-sensitive amplifier.Results and conclusion The energy resolution of 662 keV from 137Cs radioactive source was improved to 1.9%,and the relative standard deviation of different total counts of transmitted photons detected decreased to 0.05%when the counts were more than 5×107,which means the impact from the statisticalfluctuation of long-term gamma photons counting will not be a main obstacle to achieving high precision in the area of non-destructive testing.The preliminary experiment of inspecting the inner gaps in the metal rodsfilled with samples also proved to have good prospects for the CZT detector in non-destructive testing.