Transvese momentum dependent parton distributions of pion at leading twist

We calculate the leading twist pion unpolarized transverse momentum distribution $f_1(x,k_T^2)$ and the Boer-Mulders function $h_1^\perp(x,k_T^2)$, using leading Fock-state light front wave functions (LF-LFWFs) based on Dyson-Schwinger and Bethe-Salpeter equations. These DS-BSEs based LF-LFWFs provide dynamically generated s- and p-wave components, which are indispensable in producing chirally odd Boer-Mulders function that has one parton spin flipped. Employing a non-perturbative SU(3) gluon rescattering kernel to treat the gauge link of the Boer-Mulders function, we thus obtain both TMDs at hadronic scale and then evolve them to the scale of $\mu^2=4.0$ GeV$^2$. We finally calculate the generalized Boer-Mulders shift and find it to be in agreement with the lattice prediction.Comment: 20 pages, 5 figure

Nonperturbative photon qqˉq\bar{q} light front wave functions from a contact interaction model

We propose a method to calculate the $q\bar{q}$ light front wave functions (LFWFs) of photon at low-virtuality, i.e., the light front amplitude of $\gamma^*\rightarrow q\bar{q}$ at low $Q^2$, based on a light front projection approach. We exemplify this method using a contact interaction model within Dyson-Schwinger equations formalism and obtain the nonperturbative photon $q\bar{q}$ LFWFs. In this case, we find the nonperturbative effects are encoded in the enhanced quark mass and a dressing function of covariant quark-photon vertex, as compared to the leading order quantum electrodynamics photon $q\bar{q}$ LFWFs. We then use nonperturbative-effect modified photon $q\bar{q}$ LFWFs to study the inclusive deep inelastic scattering HERA data in the framework of the color dipole model. The results demonstrate that the theoretical description of data at low $Q^2$ can be significantly improved once the nonperturbative corrections are included in the photon LFWFs.Comment: 11 pages, 4 figure

Additive Manufacturing of Complexly Shaped SiC with High Density Via Extrusion-Based Technique – Effects of Slurry Thixotropic Behavior and 3D Printing Parameters

Additive manufacturing of dense SiC parts was achieved via an extrusion-based process followed by electrical-field assisted pressure-less sintering. The aim of this research was to study the effect of the rheological behavior of SiC slurry on the printing process and quality, as well as the influence of 3D printing parameters on the dimensions of the extruded filament, which are directly related to the printing precision and quality. Different solid contents and dispersant- Darvan 821A concentrations were studied to optimize the viscosity, thixotropy and sedimentation rate of the slurry. The optimal slurry was composed of 77.5 wt% SiC, Y2O3 and Al2O3 powders, 0.25 wt% dispersant and 0.01 wt% defoamer. The printing parameters studied included extrusion pressure, nozzle size, layer height and printing speed; the one that had the most prominent effect on filament width and height was indicated as layer height. The nozzle inner diameter of 1.04 mm, speed of 350 mm/min, layer height of 0.7 mm and extrusion air pressure of 0.31 MPa were the optimal printing parameters. Furthermore, the relationship between the printing parameters and the filament dimensions was successfully predicted by using machine learning and grey system theory. Finally, the relative density of the printed SiC parts sintered at 1900 oC reached 94.7±1.5%

Two-Step Fabrication of BPO₄ Ceramics with Acid Corrosion Resistance and Neutron Shielding Performance

There has been an urgent demand for novel neutron shielding materials (NSMs) with high mechanical strength and low acid corrosion rate to be used in compact shielding design. In this contribution, BPO4 ceramics (BPCs), one of the candidates for such materials, was successfully fabricated by a two-step method using H3BO3 and H3PO4 as raw materials. The evolution of the microstructures was then investigated, followed by testing of mechanical/thermal properties, acid corrosion resistance, and neutron shielding performance. The experimental results indicated that the calcination temperature as well as H3BO3 content in raw materials intuitively affected the densification process of the BPCs. The as-pared BPCs showed reliable mechanical properties with maximum CMOR, compressive strength and elastic modulus of 26.99 MPa, 86.89 MPa and 28.42 GPa, respectively, which also showed a high neutron shielding rate and low acid corrosion rate of 65.11% and 0.016%. The obtained results imply that the BPCs was a promising NSM for use in compact shielding design

Design and calibration of a depth-of-interaction detector for neutrons and gamma rays

BackgroundRecently, global concerns regarding the illicit transportation and trafficking of nuclear materials and other radioactive sources have increased, leading to increased demands for efficient and rapid security and non-proliferation technologies. The International Atomic Energy Agency's Incident and Trafficking Database has reported 3 235 confirmed incidents involving nuclear and other radioactive materials out of regulatory control from 1993 to 2017. Of these incidents, 278 are associated with trafficking or malicious use of materials such as highly enriched uranium, plutonium, and plutonium-beryllium neutron sources. Therefore, developing depth-of-interaction detector for neutrons and gamma rays is important for effective control of nuclear and radiation materials at national and international cross points such as borders, ports, and airports.PurposeThis study aims to design a depth-of-interaction detector for neutrons and gamma rays and characterize its performance.MethodsHereby, an EJ276 plastic scintillator (Φ3 cm× 15 cm) coupled with two silicon photomultipliers (SiPMs) in both sides was designed as a depth-of-interaction detector for neutrons and gamma rays. The short gate time was optimized to achieve better neutron/gamma-ray discrimination, and the reaction position was determined based on the amplitude ratio and time of flight (TOF) difference between signals from two sides. Finally, Am-Be neutron source and 137Cs γ source were applied to detector parameter optimization and resolution calibration for performance characterization.ResultsExperimental results demonstrate that good consistency in the detection efficiency of the detector at different incident positions, where the resolution of the one-dimensional reaction position is approximately 4.4 cm.ConclusionsThe designed depth-of-interaction detector can be used toreplace detector arrays in neutron scatter cameras and coded-aperture imagers to reduce costs and system complexity

Third Wave of Influenza A(H7N9) Virus from Poultry, Guangdong Province, China, 2014–2015

Fourteen influenza A(H7N9) viruses were isolated from poultry or the environment in live poultry markets in Guangdong Province, China during 2014−2015. Phylogenetic analysis showed that all viruses were descended from viruses of the second wave of influenza A(H7N9) virus infections during 2013. These viruses can be divided into 2 branches

Additive Manufacturing of Complexly Shaped SiC with High Density Via Extrusion-Based Technique - Effects of Slurry Thixotropic Behavior and 3D Printing Parameters

Additive manufacturing of dense SiC parts was achieved via an extrusion-based process followed by electrical-field assisted pressure-less sintering. The aim of this research was to study the effect of the rheological behavior of SiC slurry on the printing process and quality, as well as the influence of 3D printing parameters on the dimensions of the extruded filament, which are directly related to the printing precision and quality. Different solid contents and dispersant- Darvan 821A concentrations were studied to optimize the viscosity, thixotropy and sedimentation rate of the slurry. The optimal slurry was composed of 77.5 wt% SiC, Y2O3 and Al2O3 powders, 0.25 wt% dispersant and 0.01 wt% defoamer. The printing parameters studied included extrusion pressure, nozzle size, layer height and printing speed; the one that had the most prominent effect on filament width and height was indicated as layer height. The nozzle inner diameter of 1.04 mm, speed of 350 mm/min, layer height of 0.7 mm and extrusion air pressure of 0.31 MPa were the optimal printing parameters. Furthermore, the relationship between the printing parameters and the filament dimensions was successfully predicted by using machine learning and grey system theory. Finally, the relative density of the printed SiC parts sintered at 1900 °C reached 94.7±1.5%