Fast forward modeling of muon transmission tomography based on model voxelization ray energy loss projection

To solve the problems associated with low resolution and high computational effort infinite time,this paper proposes a fast forward modeling method for muon energy loss transmission tomography based on a model voxelization energy loss projection algorithm.First,the energy loss equation for muon transmission tomography is derived from the Bethe–Bloch formula,and the imaging region is then dissected into several units using the model voxelization method.Thereafter,the three-dimensional(3-D)imaging model is discretized into parallel and equally spaced two-dimensional(2-D)slices using the model layering method to realize a dimensional reduction of the 3-D volume data and accelerate the forward calculation speed.Subsequently,the muon energy loss transmission tomography equation is discretized using the ray energy loss projection method to establish a set of energy loss equations for the muon penetration voxel model.Finally,the muon energy loss values at the outgoing point are obtained by solving the projection coefficient matrix of the ray length-weighted model,achieving a significant reduction in the number of muons and improving the computational efficiency.A comparison of our results with the simulation results based on the Monte Carlo method verifies the accuracy and effectiveness of the algorithm proposed in this paper.The metallic mineral identification tests show that the proposed algorithm can quickly identify high-density metallic minerals.The muon energy loss response can accurately identify the boundary of the anomalies and their spatial distribution characteristics.

Ultra High Energy Cosmic Rays： Spectral Signatures and Observations

The observations of Ultra High Energy Cosmic Rays （UHECR） are renewed, focusing on the energy spectra as measured by HiRes, Telescope Array （TA） and Auger detectors （PAO）. It is found that highest energy Auger steepening does not agree with GZK cutoff, which is most probably explained by the nuclei mass composition detected by Auger. At present the difference in mass composition in Auger and HiRes/TA data remains the main unsolved problem of UHECR origin.

The Effect of Spatial Structure Character of Heat Source on the Ray Path and the Evolution of Wave Energy of Meridional Wave Train

This paper studies correlations between the spatial structure character of thermal forcing and deformation and the amplitude of rays of meridional wave train. It is shown that if thermal forcing appears a meridional linear variation the rays of quasi-stationary planetary wave may propagate along oblique lines and if the meridional variability of heat source has second order term the rays show distinct deformation as a great circular route. Additionally, the inhomogeneous distribution may cause lower frequency oscillations in mid- and low-latitudes. The combination of zonal and meridional wave numbers and distributive character of heat source may form an inverse mechanism of variational trend of generized wave energy, reflecting in some degree the physical process of transition between meridional and zonal flow patterns.

Novel correction method for X-ray beam energy fluctuation of high energy DR system with a linear detector

A high energy digital radiography （DR） testing system has generated diverse scientific and technological interest in the field of industrial non-destructive testing. However, due to the limitations of manufac-turing technology for accelerators, an energy fluctuation of the X-ray beam exists and leads to bright and dark streak artifacts in the DR image. Here we report the utilization of a new software-based method to correct the fluctuation artifacts. The correction method is performed using a high pass filtering operation to extract the high frequency information that reflects the X-ray beam energy fluctuation, and then subtracting it from the original image. Our experimental results show that this method is able to rule out the artifacts effectively and is readily implemented on a practical scanning system.

Implications of gamma-ray photon measurements at the LHAASO on Lorentz symmetry

The Large High Altitude Air Shower Observatory(LHAASO)has reported the measurement of photons with high energies of up to 1.42 PeV from twelve gamma-ray sources.We are concerned with the implications of the LHAASO data on the fate of Lorenz symmetry at such high energy levels;thus,we consider the interaction between gamma rays and photons in the cosmic microwave background(CMB)and compute the optical depth,mean free path,and survival probability of photons from these gamma-ray sources.Employing the threshold value predicted by standard special relativity,the lowest survival probability for observed gamma ray photons is found to be approximately 0.60,which is fairly high and implies that abundant photons with energies above the threshold may reach the Earth without Lorentz symmetry violation.We conclude that it is unreasonable to argue that Lorentz symmetry would be violated using current observations at the LHAASO.

Origin of hardening in spectra of cosmic ray nuclei at a few hundred GeV using AMS-02 data

Many experiments have confirmed spectral hardening at a few hundred GeV in the spectra of cosmic ray(CR)nuclei.Three different origins have been proposed:primary source acceleration,propagation,and the superposition of different kinds of sources.In this work,a broken power law has been employed to fit each of the spectra of cosmic ray nuclei from AMS-02 directly,for rigidities greater than 45 GeV.The fitting results of the break rigidity and the spectral index differences less than and greater than the break rigidity show complicated relationships among different nuclear species,which cannot be reproduced naturally by a simple primary source scenario or a propagation scenario.However,with a natural and simple assumption,the superposition of different kinds of sources could have the potential to explain the fitting results successfully.Spectra of CR nuclei from a single future experiment,such as DAMPE,will provide us the opportunity to do cross checks and reveal the properties of the different kinds of sources.

Assessment of serial changes of bone mineral density at lumbar spine and femoral neck before and after liver transplantation

Objective To assess serial changes of bone mass before and after orthotopic liver transplantation (OLT) . Methods Consecutive bone mineral density (BMD) of lumbar spine (L2 L4) and femoral neck in 38 patients with chronic liver failure within 2 months before OLT, 6, 12 and 24 months after OLT was determined using dual energy X ray absorptiometry. Results 29% of 38 patients before OLT had osteoporosis (BMD below 2 standard deviate). BMD levels at L2 L4 and femoral neck decreased and incidence of osteoporosis increased in the first 6 months after OLT. Over beyond 6 months post OLT BMD levels at L2 L4 increased to just slightly above the pretransplant level and incidence of osteoporosis decreased from 36.8% (6 months after OLT) to 7.9% (24 months after OLT). Although BMD levels at femoral neck by 12 and 24 months after OLT gradually increased, BMD levels at femoral neck were still lower than those before OLT. Conclusions There was already a low bone mass in patients with chronic liver disease before OLT and liver transplantation induced a marked and rapid bone loss.