Rapid in-process measurement of surface roughness using adaptive optics

We present an in-process measurement of surface roughness by combining an optical probe of laser-scattering phenomena and adaptive optics for aberration correction. Measurement results of five steel samples with a roughness ranging from 0.2 to 3.125 μm demonstrate excellent correlation between the peak power and average roughness with a correlation coefficient (R(2)) of 0.9967. The proposed adaptive-optics-assisted system is in good agreement with the stylus method, and error values of less than 8.7% are obtained for average sample roughness in the range of 0.265 to 1.119 μm. The proposed system can be used as a rapid in-process roughness monitor/estimator to further increase the precision and stability of manufacturing processes in situ.     

A unified formulation of PVD-based finite cylindrical layer methods for functionally graded material sandwich cylinders

A unified formulation of finite cylindrical layer methods (FCLMs) based on the principle of virtual displacements (PVDs) is developed for the quasi-three-dimensional (3D) bending and free vibration analyses of simply-supported, functionally graded material (FGM) sandwich circular hollow cylinders, in which the material properties of the FGM layer are assumed to obey the power-law distributions of the volume fractions of the constituents through the thickness coordinate. In this formulation, the cylinder is divided into a number of cylindrical finite layers, where the trigonometric functions and Lagrange polynomials are used to interpolate the in- and out-of-surface variations of the displacement components of each individual layer, respectively. Because an h-refinement is adopted in this article to yield the convergent solutions, the relative orders used for expansion of the displacement components remain variable, and can be freely chosen as linear, quadratic and cubic ones. The accuracy and convergence rate of a variety of PVD-based FCLMs developed in this article are assessed by comparing their solutions with the available 3D ones.     

Flux-splitting dispersion-relation-preserving dual-compact upwind scheme for solving the Maxwell’s equations on non-staggered grids

This study proposes a flux-splitting Maxwell’s equations solver for modeling electromagnetic waves in two-dimensional non-staggered grids. A fifth-order spatially accurate dual-compact upwind scheme was developed in a three-point grid stencil to approximate the first-order derivative term. The integrity of the proposed finite-difference time-domain method for solving TM-mode Maxwell’s equations verified using two-dimensional test problems. The benchmark Mie-scattering problem was also shown to be in good agreement with the semi-analytic result.     

Gauss-Hermite quadratures for functions from Hilbert spaces with Gaussian reproducing kernels

We study univariate integration with the Gaussian weight for a positive variance α. This is done for the reproducing kernel Hilbert space with the Gaussian kernel for a positive shape parameter γ. We study Gauss-Hermite quadratures, although this choice of quadratures may be questionable since polynomials do not belong to this space of functions. Nevertheless, we provide the explicit formula for the error of the Gauss-Hermite quadrature using n function values. In particular, for 2αγ ²<1 we have an exponential rate of convergence, and for 2αγ ²=1 we have no convergence, whereas for 2αγ ²>1 we have an exponential divergence.     

Stepwise construction of the Cr-Cr quintuple bond and its destruction upon axial coordination

Give me five! Terdentate 2,6-diamidopyridyl ligands were used to stabilize the Cr-Cr quintuple bond and have made it possible to isolate and characterize not only the Cr-Cr quintuple-bonded complex, but also the mixed-valent intermediates (Cr(I) and Cr(II)), which are important species in the formation of type?I quintuple-bonded complexes.     

Lowest enthalpy polymorph of cold-compressed graphite phase

Based on an ab initio evolutionary algorithm, a novel carbon polymorph with an orthorhombic Cmcm symmetry is predicted, named as C carbon, which has the lowest enthalpy among the previously proposed cold-compressed graphite phases.     

Effects of pinhole diameters on beam characteristics for silicon thin film optical inspection

Peak power density stability and beam-wander precision of probe laser are important factors affecting the inspection results in the precision thin film optical measurements. Pinhole is frequently used as a spatial filter in the optical inspection system. In this work, four different diameters of pinhole are investigated experimentally. It is found that pinhole diameter of 0.3 mm is considered to be a promising candidate for mounting in front of probe laser for silicon thin film optical inspection due to better peak power density stability and better beam-wander precision.     

Enantioselectivity of basic analytes in CZE enantioseparation under reversed-polarity mode using sulfated beta-cyclodextrins as chiral selectors: An unusual temperature effect

Temperature effects on the enantioselectivity of basic analytes in CZE enantioseparation were studied under reversed-polarity mode using randomly sulfate-substituted beta-CDs (MI-S-beta-CD) as chiral seletors. Two catecholamines (epinephrine and isoproterenol) and two structurally related compounds (octopamine and norephedrine) were selected as test compounds in an electrophoretic system at low pH. The mobility differences between the (+)-enantiomers and the (-)-enantiomers of the two catecholamines and dopamine at 40 degrees C are greater than those at 25 degrees C with MI-S-beta-CD, even at a concentration as low as 0.3% w/v. Thus the enantioselectivity of these three basic analytes increases with increasing temperature. This phenomenon results from the inequality of the temperature effect on the mobility of the two enantiomers. In contrast, norephedrine behaves differently. The (+)-enantiomers of these basic analytes were found to migrate faster than the (-)-enantiomers. Consequently, the unusual temperature effect on the enantioselectivity can be observed when the mobility difference of the (+)-enantiomer between 40 and 25 degrees C is greater than that of the (-)-enantiomer using MI-S-beta-CD at a concentration greater than about 0.7% w/v for enantioseparation of isoproterenol, 0.4% w/v for epinephrine, and 0.3% w/v for octopamine. This unusual temperature effect offers the advantages to enhance enantioselectivity, to improve enantioseparation, and to reduce migration times.