Cao Y.,CAEP - China Academy of Engineering Physics
Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams | Year: 2013
The optimized design method based on signal to noise ratio of the image is presented for the object of two-dimensional Gaussian distribution based on the theoretical analysis of the technology of X-ray in-line phase contrast imaging. The imaging systems under the radiation of sub-micrometer focus X-ray source, laser-based micrometer focus X-ray source and synchrotron radiation X-ray source are optimized by means of numerical simulation. The outcome shows that the method based on signal to noise ratio can increase the signal to noise ratio of the image and get more reasonable imaging distance premised by decreasing the contrast slightly when compared with the contrast method.
Peng S.M.,CAEP - China Academy of Engineering Physics
Journal of Nuclear Materials | Year: 2015
Beryllides (Be12Ti) are expected to be used as the advanced neutron multiplier in the DEMO blanket because of their peculiar properties. In this paper the structural, elastic, and electronic properties of Be12Ti under high pressure are studied through first-principle calculations based on pseudopotential plane-wave density functional theory (DFT) within the generalized gradient approximation (GGA). The calculated lattice parameters are in good agreement with experimental data and the calculated elastic constants of Be12Ti increase monotonically with increasing pressure, demonstrating that Be12Ti satisfies the mechanical stability criteria under applied pressure. Related mechanical properties such as bulk modulus (B), shear modulus (G), Young's modulus (E), and Poisson's ratio (ν) are also studied for polycrystalline Be12Ti. The calculated B/G value shows that Be12Ti behaves in a ductile manner, and high pressure can significantly improve the ductility of Be12Ti. Additionally, the electronic properties of Be12Ti under several different pressures are successfully calculated and discussed. © 2015 Published by Elsevier B.V.
Gao Y.,CAEP - China Academy of Engineering Physics
Qiangjiguang Yu Lizishu/High Power Laser and Particle Beams | Year: 2015
The counter-Meshing Gears (CMG) mechanism is a discrimination mechanism which can be used in combination locks for high-consequence system surety. For an arbitrary binary Unlocking Symbol Sequence composed of equal number symbols of A and B, i.e. NA+NB, how to realize the binary discrimination teeth coding of its corresponding CMG mechanism with minimum fixed gear levels C and gear divisions D, is an important practical problem which is firstly well defined as the Optimal Normalizing CMG Coding Problem. With the toolbox comprising previously reported terms and methods, e.g. the CMG classification method, the 2-D Maze Map and the 3-color circular alternant coloring method for Critical Trap Grids (CTGs), optimal normalizing coding theory and methods for CMG Mechanisms are systematically discussed. Two optional coding methods, and their minimum requirement for the coding space (characterized with C×D) and coding algorithm, are all presented. A Figure of Merit (FoM) which characterizes the CMG coding efficiency is defined on the coding space and the symbol length of the Unlocking Symbol Sequence which dedicated for. By the FoM with clear physical meanings, the two optional Optimal Normalizing CMG Coding methods are compared, and it is concluded that the first type CMG mechanism with a coding space of C=3 and D=N+2 is the preferred method. As to the first type CMG mechanism, there is no difference between the Optimal Normalizing Coding, the previously reported Optimized coding with minimum gear levels, thus the minimum coding space of C=3 and D=N+2 are both needed and the 3-color circular alternant CTGs coloring method is a suitable coding method for both two. With application of the 3-color circular alternant CTGs coloring method, a distinct fingerprint feature can be revealed in the 2-D verification maze map that all CTGs are circular regularly allotted to only three color sets, i.e. the predesigned gear-teeth meshing between the two coupled composite gear A and B for error-locking function will alternately happen in only three discrimination gear levels. ©, 2015, Editorial Office of High Power Laser and Particle Beams. All right reserved.
He H.-L.,CAEP - China Academy of Engineering Physics
Gaoya Wuli Xuebao/Chinese Journal of High Pressure Physics | Year: 2013
A physical criterion of dynamic tensile fracture has been introduced, based on the knowledge of the micro-mechanism and the measurement of the damage evolution. The physical criterion has suggested two critical damage parameters, named as the critical void coalescence damage Dl and the critical fracturing damage Df. These two parameters are associated with a damage function model and a percolation-softening function, by which the fracture process is characterized as that the damage slowly increases in a linear manner from the initial state (D=D0) to the void linkage state (D=Dl), then changes to a nonlinear growth and rapidly approaches to the critical fracturing state (D=Df), while a final step catastrophically leads to the complete fracture state (D=1.0). Experimental measurements and numerical simulations for both of the plate impact and the cylindrical tube have verified that these two parameters (Dl and Df) physically constrain the dynamic tensile fracture and may be considered as the intrinsic material constant. Application of this physical criterion for the prediction of dynamic tensile fracture under intricate loading and for complex geometrical system has been discussed.
Zhang X.,CAEP - China Academy of Engineering Physics
Journal of Fluids and Structures | Year: 2013
A numerical study with spectral element method for a dynamic resonant shear stress sensor concept is presented in this paper, in which the numerical model of the sensor consisted of an unsteady three-dimensional boundary layer model for the flow and a simple mechanical model for the sensor itself. Spectral element method was used to explore fluid flow properties around the sensor in the three-dimensional boundary layer model. The three-dimensional unsteady spectral element method code was first verified with Blasius solutions in a flat plate boundary layer flow. The sensor's sensitivity to wall shear stress was then numerically determined in a laminar boundary layer. Finally, the physical mechanism of the dynamic resonant shear stress sensor was analyzed by using the verified model. The results showed that the sensitivity of the dynamic resonant shear stress sensor was due to the energy lost produced by the oscillating interaction between the sensor and fluid flow. © 2013 Elsevier Ltd.