Monte Carlo Simulation for Polychromatic X-ray Fluorescence Computed Tomography with Sheet-Beam Geometry

X-ray fluorescence computed tomography based on sheet-beam can save a huge amount of time to obtain a whole set of projections using synchrotron. However, it is clearly unpractical for most biomedical research laboratories. In this paper, polychromatic X-ray fluorescence computed tomography with sheet-beam geometry is tested by Monte Carlo simulation. First, two phantoms (A and B) filled with PMMA are used to simulate imaging process through GEANT 4. Phantom A contains several GNP-loaded regions with the same size (10 mm) in height and diameter but different Au weight concentration ranging from 0.3% to 1.8%. Phantom B contains twelve GNP-loaded regions with the same Au weight concentration (1.6%) but different diameter ranging from 1mm to 9mm. Second, discretized presentation of imaging model is established to reconstruct more accurate XFCT images. Third, XFCT images of phantom A and B are reconstructed by fliter backprojection (FBP) and maximum likelihood expectation maximization (MLEM) with and without correction, respectively. Contrast to noise ratio (CNR) is calculated to evaluate all the reconstructed images. Our results show that it is feasible for sheet-beam XFCT system based on polychromatic X-ray source and the discretized imaging model can be used to reconstruct more accurate images

Resolving "dirty" effects around black holes by decoupling the Teukolsky equation

Detecting the environment around the supermassive black holes and tests of general relativity are important applications of extreme-mass-ratio inspirals (EMRIs). There is still a challenge to efficiently describe various "dirty" impacts on the inspirals like dark matter, gas, dipole radiation, electromagnetic interaction, and so on. In this Letter, we find the inherent linearity of the asymptotic solution of the inhomogeneous Teukolsky equation. Based on this property, we completely decouple the factors of the perturber and the background spacetime in the energy fluxes and waveforms. With the new decoupling form, the waveforms of EMRIs with non-geodesic motion in Kerr spacetime can be calculated conveniently. This will help to resolve the environment (including gas, field, dark matter, electromagnetic interaction, etc.) around the supermassive black holes and test general relativity.Comment: 6 pages + supplementary materials, 4 figure

Numerical Study Of Inlet Gas Velocity Effects On Droplet Behaviors In Microchannel

In this study, the numerical simulation of liquid water behaviors inside a single straight microchannel is conducted using Volume of fluid (VOF) method and dynamic contact angle (DCA) model. Two different gas inlet velocities are considered in the simulation to investigate the gas velocity effects on the droplet behaviors. The general process of the liquid water evolvement inside the channel are presented and discussed. The results indicate that the water droplet will form into long slug flow under lower gas inlet velocity and thin film flow under higher gas inlet velocity

catena-Poly[[bis­(2-amino­ethane­sulfon­ato-κ2 N,O)nickel(II)]-μ-1,4-bis­(1H-imid­azol-1-yl)benzene-κ2 N 3:N 3′]

In the hydro­thermally prepared title coordination polymer, [Ni(C2H6NO3S)2(C12H10N4)]n, the NiII ion and the 1,4-bis­(1H-imidazol-1-yl)benzene ligand occupy special positions on inversion centers. The metal ion shows a slightly distorted octa­hedral coordination geometry, being linked to two N atoms of two 1,4-bis­(imidazol-1-yl)benzene ligands and to two O and two N atoms of two chelating 2-amino­ethane­sulfonate ligands. The 1,4-bis­(imidazol-1-yl)benzene ligands bridge symmetry-related NiII ions forming polymeric chains along the [110] direction

Influence of friction variability on isolation performance of a rolling-damper isolation system

Previously, many isolation systems with friction action are designed ignoring the variability of friction coefficient. By taking a rolling-damper isolation system as the study object, this paper analyzed the effects of non-uniform distribution of rolling friction coefficient on its isolation performance through a compiled computer program. The results show that the errors associated with the maximum structural relative displacement, acceleration and residual displacement due to ignoring the friction variability are sequentially growing, and this rule is weakened by the damper. Under the condition of large friction variability and little damper action, the calculation of the maximum structural relative displacement and acceleration should consider the friction variability. When the structural residual displacement is concerned, the variability of rolling friction coefficient should be fully considered regardless of friction variability degree