Abstract: X-ray imaging based on variable energy can expand the dynamic range of the imaging system and perfectly show the structure information of the detection objects, by acquiring and fusing the image sequences. However, the fusion method is ordinarily based on image quality optimization, and neglects the gray mapping accuracy of the actual high dynamic imaging. It cannot guarantee the physical matching between the image information and actual structure information. Therefore, in this paper we propose an X-ray image gray characterization algorithm of high dynamic fusion based on variable energy. First, take a standard wedge block as test object, and use the fusion image of low dynamic image sequences as input data. The output data are the actual high dynamic image. Then establish the X-ray imaging gray characterization model by neural network training. At the same time, because the attenuation coefficients of different heterogeneous materials are different, a modified model of physical characterization is established to achieve a correct characterization of real object. Finally, experiments by 12 bit and 16 bit imaging systems acquire the variable voltage image sequences using 12 bit detector. After image fusion, image mapping and gray level correction, the output image not only achieves the same effect of 16 bit detector, but also satisfies the gray relation. Also this method can effectively expand the dynamic range of the imaging system.

Abstract: In this paper, internal waves in three-layer stratified fluid are investigated by using a perturbation method, and the second-order asymptotic solutions of the velocity potentials and the second-order Stokes solutions of the associated elevations of the interfacial waves are presented based on the small amplitude wave theory. As expected, the first-order solutions are consistent with ordinary linear theoretical results, and the second-order solutions describe the second-order modification on the linear theory and the interactions between the two interfacial waves. Both the first-order and second-order solutions derived depend on the depths and densities of the three-layer fluid. It is also noted that the solutions obtained from the present work include the theoretical results derived by Umeyama as special cases.

Abstract: The movement and radiation of fast electrons emitting along the surface of a target irradiated by intense laser pulses has been investigated theoretically and numerically by use of the classical theory of Thomson scattering by free electrons in static field. The results indicate that the surface electrons are oscillating in the quasistatic field and the laser field at the beginning. The electrons will be accelerated when their oscillation frequency comes close to the laser frequency, and the attosecond pulse trains and high harmonic are emitted along the surface by surface electrons. The temporal and spatial characteristics of the acceleration and radiation of electrons in different initial states has been compared. The frequency characteristic of the coherent radiation of electron beams are also investigated.

Abstract: Diamond coating has many excellent properties as the same as those of the natural diamond, such as extreme hardness, high thermal conductivity, low thermal expansion coefficient, high chemical stability, and good abrasive resistance, which is considered as the best tool coating material applied to the high-silicon aluminum alloy cutting. We can use the hot filament chemical vapor deposition method (HFCVD) to deposit a 2–20 μm diamond coating on the cemented carbide tool to improve the cutting performance and increase the tool life significantly. Many experiments have proved that the existence of cobalt phase can weaken the adhesive strength of diamond coating. However, we still lack a perfect theory to explain why the Co element can reduce the adhesive strength of diamond coating is still lacking. What we can do now is only to improve the adhesive strength of diamond coating by doing testing many times in experiments. Compared with these traditional experiments, the first principles simulation based on quantum mechanics can describe the microstructure property and electron density of materials. It is successfully used to investigate the surface, interface, electron component, and so on etc. We can also use this method to study the interface problem at an atomic level. So the first principles based upon density functional theory (DFT) is used to investigate the influence of cobalt binding phase in cemented carbide substrate on adhesive strength of diamond coating. In this article, we uses Material Studios software to build WC/diamond and WC-Co/diamond interface models to evaluate the influence of cobalt phase on the adhesive strength of diamond coating with CASTEP program which can calculate the most stablest structure of film-substrate interface. We use PBE functional form to obtain the exchange potential and relevant potential, and to solve the self-consistent Kohn-Sham equations. We calculate the interfacial bonding energy, analyse the electron density of diamond coating and the bond Mulliken population of diamond film-substrate interface. The results show that the interfacial bonding energy of WC/diamond is 6.74 J/m2 and that of WC-Co/diamond is 5.94 J/m2, which implies that the adhesive strength of WC/diamond is better than that of WC-Co/diamond. We also find that Co element can transfer the charges near the interface of WC/diamond model when the magnetic Co element exists at the WC/diamond interface. As a result, the polarity of tungsten element in tungsten carbide and the polarity of carbon element in diamond coating near the interface turn to be identical polarity, and then the charge density of tungsten in cemented carbide changes from 0.430 e/A3 to 0.201 e/A3 and the charge density of Carbon in diamond changes from-0.045 e/A3 to 0.037 e/A3, and they exclude to each other, so the distance of interface becomes larger than that from the WC/diamond model, which changes from 2.069 Å to 3.649 Å. This can explain why the existence of Co element can weaken the adhesive strength of diamond coating. Meanwhile, Mulliken population analyses show that the bond strength of WC-Co /diamond at the interface is smaller than that of WC/diamond. So this can prove that the cobalt binding phase in cemented carbide substrate can weaken the adhesive strength of diamond coating, and then we need to do some pretreatments in order to reduce the cobalt binding phase in the cemented carbide substrate before depositing diamond coating.

Abstract: In this paper we study the rotating electroosmotic flow of a power-law fluid with Navier slip boundary conditions under high zeta potential subjected to the action of a vertical magnetic field in a variable cross-section microchannel. Without using the Debye–Hückel linear approximation, the finite difference method is used to numerically calculate the potential distribution and velocity distribution of the rotating electroosmotic flow subjected to an external magnetic field. When the behavior index 〈inline-formula〉〈tex-math id="M4"〉\begin{document}$n = 1$\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20212327_M4.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20212327_M4.png"/〉〈/alternatives〉〈/inline-formula〉, the fluid obtained is a Newtonian fluid. The analysis results in this paper are compared with the analytical approximate solutions obtained in the Debye–Hückel linear approximation to prove the feasibility of the numerical method in this paper. In addition, the influence of behavior index 〈i〉n〈/i〉, Hartmann number 〈i〉Ha〈/i〉, rotation angular velocity 〈inline-formula〉〈tex-math id="M5"〉\begin{document}$\Omega $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20212327_M5.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20212327_M5.png"/〉〈/alternatives〉〈/inline-formula〉, electric width 〈i〉K〈/i〉 and slip parameters 〈inline-formula〉〈tex-math id="M6"〉\begin{document}$\beta $\end{document}〈/tex-math〉〈alternatives〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20212327_M6.jpg"/〉〈graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20212327_M6.png"/〉〈/alternatives〉〈/inline-formula〉 on the velocity distribution are discussed in detail. It is obtained that when the Hartmann number 〈i〉Ha〈/i〉 〉 1, the velocity decreases with the increase of the Hartmann number 〈i〉Ha〈/i〉; but when the Hartmann number 〈i〉Ha〈/i〉 〈 1, the magnitude of the 〈i〉x〈/i〉-direction velocity 〈i〉u〈/i〉 increases with the augment of 〈i〉Ha〈/i〉.

Abstract: Peristalsis is an important dynamic phenomenon in the field of biomedical research, and has great application prospects in microscale fluids. In recent years, this biomimetic (peristaltic) phenomenon has gained widespread attention due to its large-scale applications in various medical and industrial fields, such as radiation therapy, peristaltic blood pumps, and drug delivery systems. In this study, the electroosmotic flow and heat transfer characteristics are investigated under high wall Zeta potential and slip boundary conditions for a certain type of biological fluid that satisfies the Newtonian fluid model. Fluid flows under the joint action of external electric field, magnetic field, and Joule heating. Firstly, without using the Debye-Hückel linear approximation, the numerical solutions are given by using the Chebyshev spectral method for the nonlinear Poisson-Boltzmann equation, the fourth-order differential equation satisfied by the stream function, and the thermal energy equation. The results are compared with those obtained by using the Debye-Hückel linear approximation to demonstrate the effectiveness of the numerical method used in this study. Secondly, the effects of wall Zeta potential, Hartmann number 〈 inline-formula 〉 〈 tex-math id="M11" 〉 \begin{document}$H$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M11.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M11.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 , electroosmotic parameter 〈 inline-formula 〉 〈 tex-math id="M12" 〉 \begin{document}$m$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M12.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M12.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 , slip parameter 〈 inline-formula 〉 〈 tex-math id="M13" 〉 \begin{document}$\beta $\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M13.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M13.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 are discussed on the flow characteristics, peristaltic pumping, and trapping phenomena under electromagnetic environments, and the influence of Joule heating parameter 〈 inline-formula 〉 〈 tex-math id="M14" 〉 \begin{document}$\gamma $\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M14.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M14.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 and Brinkman number 〈 inline-formula 〉 〈 tex-math id="M15" 〉 \begin{document}$Br$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M15.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M15.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 is explored on heat transfer characteristics. The results show that 1) wall Zeta potential plays an important role in controlling the velocity of fluid peristaltic flow; 2) the increase of electroosmotic parameter 〈 inline-formula 〉 〈 tex-math id="M16" 〉 \begin{document}$m$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M16.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M16.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 and slip parameter 〈 inline-formula 〉 〈 tex-math id="M17" 〉 \begin{document}$\beta $\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M17.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M17.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 increases the flow velocity in the central region of the channel, while the increase of Hartmann number 〈 inline-formula 〉 〈 tex-math id="M18" 〉 \begin{document}$H$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M18.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M18.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 hinders the flow of fluid; 3) these flow behaviors exhibit opposite trends near the channel walls; 4) the number of streamlines captured by peristaltic transport decreases with Hartmann number 〈 inline-formula 〉 〈 tex-math id="M19" 〉 \begin{document}$H$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M19.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M19.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 and electroosmotic parameter 〈 inline-formula 〉 〈 tex-math id="M20" 〉 \begin{document}$m$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M20.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M20.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 increasing; 5) the increase of Joule heating parameter 〈 inline-formula 〉 〈 tex-math id="M21" 〉 \begin{document}$\gamma $\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M21.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M21.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 and Brinkman number 〈 inline-formula 〉 〈 tex-math id="M22" 〉 \begin{document}$Br$\end{document} 〈 /tex-math 〉 〈 alternatives 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M22.jpg"/ 〉 〈 graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="6-20231685_M22.png"/ 〉 〈 /alternatives 〉 〈 /inline-formula 〉 leads temperature to rise.

Abstract: Based on the small steepness parameter assumption, the three-layer incompressible, inviscid and irrotational fluid system of arbitrary depth is discussed by using the perturbation method, and a unified theory of nonlinear interfacial-internal wave propagation and the approximate nonlinear evolution equations (NEEs) for interfacial-internal elevations are given on the basis of the rigid upper boundary and the flat impermeable bottom. At last we also discuss on NEEs arising from various limiting cases of fluid depth. It is also noted that the theories obtained from the present work include the theoretical results derived by Yoshimasa Matsuno (1993) as special cases.

Abstract: By using the homotopy analysis method (HAM), the electrostatic potential distribution problems of a type of high-order weakly nonlinear composite with a cylindrical inclusion randomly embedded in a host medium, which obeyes a current-field constitutive relation of J = σ E + χ |E|2E + η|E|4E, are investigated under the action of an external direct current electric field. With the mode expansion method, the current-field constitutive relation and their boundary conditions are transformed into a series of boundary value problems of nonlinear ordinary differential equations. Then the HAM is used to solve the boundary value problems of nonlinear ordinary differential equations and the asymptotic analytical solutions of electrostatic potential distribution in the inclusion and the host regions are given.

Abstract: In this paper, interfacial waves in three-layer stratified fluid with background current are investigated using a perturbation method, and the second-order asymptotic solutions of the velocity potentials and the second-order Stokes wave solutions of the associated elevations of the interfacial waves are presented based on the small amplitude wave theory, and the Kelvin-Helmholtz instability of interfacial waves is studied. As expected, for three-layer stratified fluid with background current, the first-order asymptotic solutions (linear wave solutions), dispersion relation and the second-order asymptotic solutions derived depend on not only the depths and densities of the three-layer fluid but also the background current of the fluids, and the second-order Stokes wave solutions of the associated elevations of the interfacial waves describe not only the second-order nonlinear wave-wave interactions between the interfacial waves but also the second-order nonlinear interactions between the interfacial waves and currents. It is also noted that the solutions obtained from the present work include the theoretical results derived by Chen et al (2005) as a special case. It also shows that with the given wave number k　(real number) the interfacial waves may show Kelvin-Helmholtz instability.