Study of laser carving three-dimensional structures on ceramics: Quality controlling and mechanisms

Three-dimensional (3D) laser carving is a new, very flexible process and is very useful for machining the hard and/or brittle materials such as ceramics, carbide and hardened steel with high precision, excellent productivity and surface quality. In this paper, the effects of laser processing parameters on single-layer carving depth and surface quality are analyzed by laser carving on an Al₂O₃ ceramic with different processing parameters. The mechanisms of laser carving are also studied. A mathematical model of the relationship between the laser processing parameters and the laser carving depth is established, which is useful in obtaining the best machining parameters with the shortest time. Finally, a 3D pattern is successfully carved using the optimum parameters.     

Preparation and properties of the single 110 K phase Bi(Pb)-Sr-Ca-Cu-O superconductor

The single 110 K phase Bi(Pb)–Sr–Ca–Cu–O superconductor was made by sintering in air. Its zero-resistance temperature is 106 K, and it is an orthorhombic cell witha=5.403 Å,b=5.412 Å andc=37.062 Å. It formed around the low-T _c phase. The forming period of the 110 K phase can be shortened by multiple sintering and grinding. If PbO is mixed into the samples after the 85 K phase has formed, the forming rate of the 110 K phase can be increased significantly. EDAX analysis of grain composition confirms that the Pb atoms enter the unit cell, and probably Pb cations replace some Ca cations.     

Fast-electron optical spectrum of a two-dimensional electron gas in the presence of the Rashba effect

We examine how the Rashba spin-orbit interaction (SOI) affects the fast-electron optical spectrum of a two-dimensional electron gas (2DEG). It is found that for a spin-split 2DEG, the spectrum of optical absorption is mainly induced by plasmon excitation via inter-SO electronic transition. From the width and position of the spectrum, the Rashba spin-splitting can be identified optically and, therefore, important spintronic properties can be measured though optical experiments.     

Ionic liquid-based headspace single-drop microextraction coupled to gas chromatography for the determination of chlorobenzene derivatives

A novel method, based on the coupling of ionic liquid-based headspace single-drop microextraction (SDME) with gas chromatography (GC), is developed for the determination of chlorobenzene derivatives. For the SDME of five chlorobenzene derivatives, a 1.0 μL 1-octyl-3-methylimidazolium hexafluorophosphate microdrop is exposed for 20 min to the headspace of a 15 ml aqueous sample containing 20% (w/v) NaCl placed in 25 ml vial at 40 °C. Then, the extractant is directly injected into the injector block of the GC instrument. To avoid ionic liquid leaking into the chromatographic column, a small glass tube is placed in the injection block. Under optimized operation conditions, linear relation between peak areas and analyte concentrations up to 1.5 mg L^?1 has been obtained The detection limits range from 0.1 to 0.5 μg L^?1 for the various analytes. The relative standard deviations at 1.0 μg L^?1 range from 7.7 to 12.4%, and the enrichment factors from 41 to 127. The method is simple and sensitive, and does not suffer from the influence of a solvent peak. Its applicability is demonstrated by the determination of chlorobenzenes in wastewater samples.     

FBP Algorithms for Attenuated Fan-Beam Projections

A filtered backprojection (FBP) reconstruction algorithm for attenuated fan-beam projections has been derived based on Novikov's inversion formula. The derivation uses a common transformation between parallel-beam and fan-beam coordinates. The filtering is shift-invariant. Numerical evaluation of the FBP algorithm is presented as well. As a special application, we also present a shift-invariant FBP algorithm for fan-beam SPECT reconstruction with uniform attenuation compensation. Several other fan-beam reconstruction algorithms are also discussed. In the attenuation-free case, our algorithm reduces to the conventional fan-beam FBP reconstruction algorithm.     

Uranium(VI) extraction by Winsor II microemulsion systems using trialkyl phosphine oxide

Summary The parameters affecting the formation of the microemulsion were investigated and the microemulsion region was determined. The extraction of uranium(VI) from HNO₃ solution into a water in oil microemulsion was studied. The effects of the concentration of extractant (TRPO), the volume ratio of oil to water and the acidity of outer water phase on the extraction equilibrium of uranium(VI) are discussed and the appropriate conditions are obtained. The result showed the microemulsion has great efficiency for uranium(VI) extraction.     

Combinatorial interpretations of the q-Faulhaber and q-Salié coefficients

Recently, Guo and Zeng discovered two families of polynomials featuring in a q-analogue of Faulhaber's formula for the sums of powers and a q-analogue of Gessel-Viennot's formula involving Salié's coefficients for the alternating sums of powers. In this paper, we show that these are polynomials with symmetric, nonnegative integral coefficients by refining Gessel-Viennot's combinatorial interpretations.     

Spontaneously generated walking X-shaped light bullets

In quadratic nonlinear media with normal dispersion and nonvanishing group velocity mismatch between fundamental wave and second-harmonic pulses, the wave packets of two harmonics can be locked together in propagation in the form of walking X-shaped light bullets. The output wave packets are developed into X-shaped light bullets with significant group delay time due to mutual dragging and significant shifting in spatiotemporal spectrum due to delayed nonlinear phase shift. We also show that spontaneously generated phase-front tilting can balance the dragging force induced by group velocity mismatch and lead to zero-velocity walking X-shaped light bullets.     

Optimal Control for Multiscale Elliptic Equations with Rough Coefficients

This paper concerns the convex optimal control problem governed by multiscale elliptic equations with arbitrarily rough $L^\infty$ coefficients, which has not only complex coupling between nonseparable scales and nonlinearity, but also important applications in composite materials and geophysics. We use one of the recently developed numerical homogenization techniques, the so-called Rough Polyharmonic Splines (RPS) and its generalization (GRPS) for the efficient resolution of the elliptic operator on the coarse scale. Those methods have optimal convergence rate which do not rely on the regularity of the coefficients nor the concepts of scale-separation or periodicity. As the iterative solution of the nonlinearly coupled OCP-OPT formulation for the optimal control problem requires solving the corresponding (state and co-state) multiscale elliptic equations many times with different right hand sides, numerical homogenization approach only requires one-time pre-computation on the fine scale and the following iterations can be done with computational cost proportional to coarse degrees of freedom. Numerical experiments are presented to validate the theoretical analysis.     

Pressure-tuning domain-wall chirality in noncentrosymmetric magnetic Weyl semimetal CeAlGe

Science China Physics, Mechanics & Astronomy - The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is the largest and most sensitive single-dish radio telescope in the world and...