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To date, the behavior of the pionic leading-twist distribution amplitude (DA) which is a universal physical quantity and is introduced into high-energy processes involving pions based on the factorization theorem is not completely consistent. The form of is usually described by phenomenological models and constrained by the experimental data on exclusive processes containing pions or the moments computed using QCD sum rules and the lattice QCD theory. Evidently, an appropriate model is extremely important to determine the exact behavior of . In this paper, by adopting the least squares method to fit the ξ-moments calculated using QCD sum rules based on the background field theory, we perform an analysis on several commonly used models of the pionic leading-twist DA in the literature; these include the truncation form of the Gegenbauer polynomial series, the light-cone harmonic oscillator model, the form extracted from the Dyson-Schwinger equations, the model from the light-front holographic AdS/QCD, and a simple power-law parametrization form.

In this study, α+β Ti-Al-V-Mo-Nb alloys with the addition of multiple elements that are suitable for laser additive manufacturing (LAM) were designed according to a Ti-6Al-4V cluster formula. This formula can be expressed as 12[Al-Ti12](AlTi2)+5[Al-Ti14]((Mo, V, Nb)2Ti), in which Mo and Nb were added into the alloys partially instead of V to give alloys with nominal compositions of Ti-6.01Al-3.13V-1.43Nb, Ti-5.97Al-2.33V-2.93Mo, and Ti-5.97Al-2.33V-2.20Mo-0.71Nb (wt.%). The microstructures and mechanical properties of the as-deposited and heat-treated samples prepared via LAM were examined. The sizes of the β columnar grains and α laths in the Nb-containing samples are found to be larger than those of the Ti-6Al-4V alloy, whereas Mo- or Mo/Nb-added alloys contain finer grains. It indicates that Nb gives rise to coarsened β columnar grains and α laths, while Mo significantly refines them. Furthermore, the single addition of Nb improves the elongation, whereas the single addition of Mo enhances the strength of the alloys. The simultaneous addition of Mo/Nb significantly improves the comprehensive mechanical properties of the alloys, leading to the best properties with an ultimate tensile strength of 1,070 MPa, a yield strength of 1,004 MPa, an elongation of 9%, and micro-hardness of 355 HV. The fracture modes of all the alloys are ductile-brittle mixed fracture.

The purpose of this study was to clarify the differences in soil bacterial community diversity in different land uses in the coastal zone of the Jialing River and to provide theoretical reference for reasonable land development and resource protection of the Jialing River basin. Based on second generation high-throughput sequencing technology, the diversity, structural composition, functional types, and influencing factors of soil bacterial communities in different land use types were analyzed. The results showed that:① there were some differences in soil physical and chemical properties among different land uses. The nutritional indexes of agricultural land and soil wetland were significantly higher than those of natural forest land and sandy soil wetland (

In this paper, we study the pion leading-twist distribution amplitude $\phi_{2;\pi}(x,\mu)$ by improving the traditional light-cone harmonic oscillator model within the reconstruction of the function $\varphi_{2;\pi}(x)$. In order to constraining the model parameters, we calculate its moments $\langle\xi^n\rangle_{2;\pi}|_\mu$ in the framework of QCD background field theory sum rule (BFTSR) up to $10^{\rm th}$ order. Considering the fact that the sum rule of the $0^{\rm th}$ moment $\langle\xi^0\rangle_{2;\pi}|_\mu$ cannot be normalized, we suggest a more reasonable sum rule formula for $\langle\xi^n\rangle_{2;\pi}|_\mu$. Then, we obtain the values of $\langle\xi^n\rangle_{2;\pi}|_{\mu_0}$ with $n=(2,4,6,8,10)$ at the initial scale $\mu_0 = 1~{\rm GeV}$. The first two moments are: $\langle \xi^2\rangle_{2;\pi}|_{\mu_0} = 0.271 \pm 0.013$, $\langle\xi^4\rangle_{2;\pi}|_{\mu_0} = 0.138 \pm 0.010$; and the corresponding Gegenbauer moments are $a^{2;\pi}_2(\mu_0) = 0.206 \pm 0.038$, $a^{2;\pi}_4(\mu_0) = 0.047 \pm 0.011$, respectively. After fitting the moments $\langle\xi^n\rangle_{2;\pi}|_{\mu}$, we obtained the appropriate model parameters by using the least square method. The resultant behavior for twist-2 pion DA is more closely to the AdS/QCD and lattice result, but is narrower than that by Dyson-Schwinger equation. Furthermore, we calculate the pion-photon transition form factors (TFF) and $B\to\pi$ TFF within light-cone sum rule approach, which are conform with experimental and theoretical results., Comment: 15 pages, 6 figures, matches the version to appear in PRD

A closing electromagnetic mechanism for rail transit direct-current circuit breaker is designed. But it is found that the temperature is too high when the mechanism kept closing for a long time because of the coils high power. Based on the theory of electromagnetic field and electromagnet design, the distribution of magnetic field and the electromagnetic force of electromagnetic mechanism are simulated by finite element analysis software ANSYS. An improved mechanism is manufactured according to the simulation results. The experiments show that the improved scheme can effectively reduce the electromagnetic mechanisms closing maintenance power, and the accuracy of simulation results is validated.

Laser-induced breakdown spectroscopy (LIBS) has attracted much attention in terms of both scientific research and industrial application. An important branch of LIBS research in Asia, the development of data processing methods for LIBS, is reviewed. First, the basic principle of LIBS and the characteristics of spectral data are briefly introduced. Next, two aspects of research on and problems with data processing methods are described: i) the basic principles of data preprocessing methods are elaborated in detail on the basis of the characteristics of spectral data; ii) the performance of data analysis methods in qualitative and quantitative analysis of LIBS is described. Finally, a direction for future development of data processing methods for LIBS is also proposed.

In the 5-axis machining, when the tool orientation approaches the one of the rotation axis, the sharp changing of the rotation angles obtained by the transforming of tool orientations causes a large over cutting or under cutting for the limit of the machine’s dynamic characteristic, which is called singular problem. After analyzing the causing of the singular problem, the position of singular point, the singular value and the nonlinear error, etc, an improved plane interpolation algorithm based on plane interpolation of tool orientation algorithm is given out in the paper following with the simulation and test of the circumference milling of the tilt plane (tilt angle: 1°) separately with the plane interpolation and improved plane interpolation based on a 5-axis machining center with two swiveling heads (rotation axes: C/A). The results prove that the new interpolation is valid and correct.

By circumference milling with 5-axis machine or machining center has quite the machining efficiency and the surface quality of the products been improved. But when inclined inside surface of cavity is circumference milled with the default linear interpolation of rotation angle algorithm, it results in a serious non-linear error, which takes on over cutting or under cutting, e.g. the inclined plane will be over milled by the machine with dual swivel-head machining center. In order to resolve this problem, the direct interpolation algorithm of tool orientation is developed after analyzing the algorithm of linear interpolation of rotation angles and its non-linear error is. The algorithm is reported and tested with the object of a machine with AB-axis swivel head. The testing results proved that it can resolve the problem of non-linear error.

In this paper, a robust adaptive fuzzy dynamic surface control for a class of uncertain nonlinear systems is proposed. A novel adaptive fuzzy dynamic surface model is built to approximate the uncertain nonlinear functions by only one fuzzy logic system. The approximation capability of this model is proved and the model is implemented to solve the problem that too many approximators are used in the controller design of uncertain nonlinear systems. The shortage of “explosion of complexity” in backstepping design procedure is overcome by using the proposed dynamic surface control method. It is proved by constructing appropriate Lyapunov candidates that all signals of closed-loop systems are semi-globally uniformly ultimate bounded. Also, this novel controller stabilizes the states of uncertain nonlinear systems faster than the adaptive sliding mode controller (SMC). Two simulation examples are provided to illustrate the effectiveness of the control approach proposed in this paper.