Pulsed laser deposition of pure fluoroapatite film without OH groups

The relation between O₂ pressure and composition in the pulsed‐laser deposition of fluoroapatite was investigated using both on‐axis and off‐axis methods to determine the optimal conditions for obtaining a pure fluoroapatite film without OH groups. Through this, it was found that an O₂ pressure of 10 Pa, combined with an off‐axis method, results in P/Ca and F/Ca values (0.6 and 0.2, respectively) that match closely with a stoichiometric composition of Ca₁₀(PO₄)₆F₂. Fourier transform infrared spectroscopy analysis confirmed that this optimized film was almost pure fluoroapatite, with no evidence of any OH groups originating from hydroxyapatite. X‐ray diffraction also revealed that this fluoroapatite film crystallizes with a c‐axis orientation perpendicular to its surface.     

Influence of metal electrodes on c‐axis orientation of AlN thin films deposited by DC magnetron sputtering

Nanocrystalline aluminum nitride (AlN) thin films were deposited on two types of metallic seed layers on silicon substrates, (111) textured Pt and (110) Mo, by reactive DC magnetron sputtering at low temperature (200 °C). Both textured films of Pt and Mo promote nucleation, thereby improving the crystallinity and epitaxial growth condition for AlN thin films. The deposited films were examined by X‐ray diffraction, scanning electron microscopy and atomic force microscopy techniques. The results indicated that the preferred orientation of crystallites greatly depends upon the kinetic energy of the sputtered species (target power) and seed layers used. Furthermore, AlN thin films with c‐axis perpendicular to the substrate grew on both types of metal electrodes at all power levels larger than 100 W. By comparing the structural properties and compressive stresses at perfect c‐axis orientation conditions, it is evident that AlN films deposited on (110) oriented Mo substrates exhibited superior properties as compared with Pt/Ti seed layers. Furthermore, less values of compressive stresses (?3 GPa) as compared with Pt/Ti substrates (?7.08 GPa) make Mo preferentially better candidate to be employed in the field of suspended Micro/Nano ‐ electromechanical systems (MEMS/NEMS) for piezoelectric devices. Copyright © 2017 John Wiley & Sons, Ltd.     

五轴联动刀具路径NURBS插补技术

针对复杂曲面五轴加工直线圆弧插补的不足,对五轴加工NURBS插补算法进行相关研究,同时对NURBS插补过程中插补点的曲率分析计算,推导出插补误差与进给速度的关系,实现用进给速度对插补误差自适应地调整。最后,针对双转台五轴数控机床,基于IMSPOST开发了具有NURBS插补的专用后置处理器,实现了NC 程序的输出。实验结果表明：该技术方法提高了刀具运动平稳性和加工精度,优化了加工精度与加工效率,为五轴NURBS插补加工提供了理论指导。     

视线追踪系统中注视点估计算法研究

针对非接触式视线跟踪系统中注视点估计算法鲁棒性差的问题,提出一种基于角度映射的注视点估计算法。首先,根据人眼特性及视觉成像原理,瞳孔中心相对于角膜反射光斑的位置与注视点相对于红外光源的位置之间具有一定的角度映射关系,据此估计出注视点近似位置。然后,在眼球模型结构的基础上分析了眼球角膜曲面对注视点造成的偏差,通过弧长对误差进行补偿。最后,利用非线性多项式模型对眼球视轴和光轴之间的偏差进行拟合,得到最终的视线落点。实验证明,该系统具有较高的精度和自由度,在水平和垂直方向上最大误差均小于1 cm。     

基于测试线法的风轮近尾迹辐射噪声研究

在风洞开口实验段,针对不同尖速比应用BSWA VS302USB振动噪声采集分析系统对水平轴风力机叶尖下游4个角度的测试线进行噪声测试.叶尖辐射声中的主要成分是叶片的旋转谐波声,其向风轮下游传播的过程中迅速衰减.在各测试线上,随着测点向风轮下游移动,叶轮辐射声迅速衰减,并在一定距离之后低于背景声,尖速比越高,风轮下游辐射...     

The fekete-szegö problem for close-to-convex functions with respect to the koebe function

An analytic function f   in the unit disk D :={z ∈ ? : |z| < 1}$\mathbb{D}\hspace{0.17em}:=\left\{z\hspace{0.17em}\in \hspace{0.17em}?\hspace{0.17em}:\hspace{0.17em}\left|z\right|\hspace{0.17em}<\hspace{0.17em}1\right\}$, standardly normalized, is called close-to-convex with respect to the Koebe function k(z) := z/(1−z)², z ∈ D$k\left(z\right)\hspace{0.17em}:=\hspace{0.17em}z/{\left(1-z\right)}^2,\hspace{0.17em}z\hspace{0.17em}\in \hspace{0.17em}\mathbb{D}$ if there exists δ∈(-π/2,π/2) such that Re{eiδ(1−z)²f^′(z)} > 0, ∈ D$\text{Re}\left\{{\text{e}}^{\text{i}\delta }{\left(1-z\right)}^2{f}^{\prime }\left(z\right)\right\}\hspace{0.17em}>\hspace{0.17em}0,\hspace{0.17em}\in \hspace{0.17em}\mathbb{D}$. For the class C(k) of all close-to-convex functions with respect to k, related to the class of functions convex in the positive direction of the imaginary axis, the Fekete-Szegö problem is studied.     

M/G/1重试排队系统的渐近稳定性

用算子半群理论研究了带有重试排队的M/G/1系统.通过解算子方程和预解方程,证明了0是系统算子的本征值,且为虚轴上唯一的谱点.从而得出了当时间趋于无穷时系统时间依赖解收敛于稳态解的结论.     

考虑辊系倾角的轴移式轧机辊系弹性变形计算

采用分段离散法 ,求解轴移式轧机辊系弹性变形 ,其方法主要特点是计算过程中考虑了轴移式轧机由于工作辊的窜动而引起的辊系倾角对辊系变形挠度的影响 ,为藕合计算板凸度时提供更为合理的辊系弹性变形模型。     

Kinematic equations to grind a helical drill point on a virtual axis drill sharpener

The basic structure of a virtual axis drill grinder is presented in terms of the spatial vectors and thegrinding parameters calculated according to the geometry of a helical drill point. The kinematic equations for sharpening the drills on the virtual axis grinder are deduced using the grinding parameters via vector-matrix txansformation.     

Surface instability of orthotropic laminated materials under compression

The piecewise-homogeneous material model and the three-dimensional linearized theory of stability with the assumption of small subcritical strains are used to study the surface buckling of orthotropic and transtropic laminates. A plane problem is formulated, and characteristic equations are derived. A solution is found for a specific transtropic material with different orientations of the isotropy axis __________ Translated from Prikladnaya Mekhanika, Vol. 42, No. 7, pp. 64–72, July 2006.