Numerical Investigation of a Parallel-Plate Atmospheric-Pressure Nitrogen/Ammonia Dielectric Barrier Discharge

In this paper, a planar atmospheric-pressure dielectric barrier discharge (AP-DBD) of nitrogen mixed with ammonia (0?C2?%) is simulated using one-dimensional self-consistent fluid modeling with cell-centered finite-volume method. This AP-DBD is driven by a 30?kHz power source with distorted sinusoidal voltages. The simulated discharge current densities are found to be in good agreement with the experiment data in both phase and magnitude. The simulated results show that the discharges of N₂ mixed with NH₃ (0?C2?%) are all typical Townsend-like discharges because the ions always outnumber the electrons very much which leads to no quasi-neutral region in the gap throughout the cycle. N₂ ⁺ and N₄ ⁺ are found to be the most abundant charged species during and after the breakdown process, respectively, like a pure nitrogen DBD. NH₄ ⁺ increases rapidly initially with increasing addition of NH₃ and levels off eventually. In addition, N is the most dominant neutral species, except the background species, N₂ and NH₃, and NH₂ and H are the second dominant species, which increase with increasing added NH₃. The existence of abundant NH₂ plays an important role in those applications which require functional group incorporation.     

Nanotribological behavior of thermal treatment of zinc titanate thin films

We present a study of the nanotribological behavior of ZnTiO₃ films; the surface morphology, stoichiometry, and friction (μ) were analyzed using atomic force microscopy, X‐ray photoelectron spectroscopy, and nanoscratch system. It is confirmed that the measured values of H and μ of the ZnTiO₃ films were in the range from 8.5 ± 0.4 to 5.6 ± 0.4 GPa and from 0.164 to 0.226, respectively. It is suggested that the hexagonal ZnTiO₃ decomposes into cubic Zn₂TiO₄ and rutile TiO₂ based on the thermal treatment; the H, μ, and R_MS were changed owing to the grain growth and recovery that results in a relax crystallinity of ZnTiO₃ films. From X‐ray photoelectron spectroscopy measured, core levels of O 1 can attribute the weaker bonds as well as lower resistance after thermal treatment. The XRD patterns showed that as‐deposited films are mainly amorphous; however, the hexagonal ZnTiO₃ phase was observed with the ZnTiO₃ (104), (110), (116), and (214) peaks from 620 to 820 °C, indicating that there is highly (104)‐oriented ZnTiO₃ on the silicon substrate. Copyright © 2012 John Wiley & Sons, Ltd.     

Some Inverse Problems in Periodic Homogenization of Hamilton-Jacobi Equations

We look at the effective Hamiltonian \({\overline{H}}\) associated with the Hamiltonian \({H(p,x)=H(p)+V(x)}\) in the periodic homogenization theory. Our central goal is to understand the relation between \({V}\) and \({\overline{H}}\). We formulate some inverse problems concerning this relation. Such types of inverse problems are, in general, very challenging. In this paper, we discuss several special cases in both convex and nonconvex settings.     

Rotating laser scan method to measure the transient free-surface topography of small-scale debris flows

We present an imaging method aimed at measuring the transient three-dimensional topography of rapidly deforming opaque surfaces. The imaging setup features a laser stripe scanned repeatedly across the surface using a spinning wheel with mirror facets. Acquisition rates of 20 scans per second are attained by spinning the wheel rapidly and imaging the resulting stripes using a fast camera. The algorithms adopted to capture the stripes, reconstruct the surface topography for each scan, and calibrate the camera and laser configuration are described. Error estimates for successive steps are evaluated and compared to results from repeat and independent measurements of the final deposit shape. The method is then used to acquire time-resolved measurements of small-scale debris flows. Specifically, we measure the free-surface topography of debris surges as they flow across an idealized canyon–fan transition. In addition to profiling the final deposit shape, the method successfully resolves the transient evolution of the free surface. Applied to textured surfaces, the method can also be combined with particle tracking velocimetry.     

Stacking Structure of Confined 1‐Butanol in SBA‐15 Investigated by Solid‐State NMR Spectroscopy

Understanding the complex thermodynamic behavior of confined amphiphilic molecules in biological or mesoporous hosts requires detailed knowledge of the stacking structures. Here, we present detailed solid‐state NMR spectroscopic investigations on 1‐butanol molecules confined in the hydrophilic mesoporous SBA‐15 host. A range of NMR spectroscopic measurements comprising of ¹H spin–lattice (T₁), spin–spin (T₂) relaxation, ¹³C cross‐polarization (CP), and ¹H,¹H two‐dimensional nuclear Overhauser enhancement spectroscopy (¹H,¹H 2D NOESY) with the magic angle spinning (MAS) technique as well as static wide‐line ²H NMR spectra have been used to investigate the dynamics and to observe the stacking structure of confined 1‐butanol in SBA‐15. The results suggest that not only the molecular reorientation but also the exchange motions of confined molecules of 1‐butanol are extremely restricted in the confined space of the SBA‐15 pores. The dynamics of the confined molecules of 1‐butanol imply that the ¹H,¹H 2D NOESY should be an appropriate technique to observe the stacking structure of confined amphiphilc molecules. This study is the first to observe that a significant part of confined 1‐butanol molecules are orientated as tilted bilayered structures on the surface of the host SBA‐15 pores in a time‐average state by solid‐state NMR spectroscopy with the ¹H,¹H 2D NOESY technique.     

Optimal economic production quantity policy for imperfect process with imperfect repair and maintenance

This study integrates maintenance and production programs with the economic production quantity (EPQ) model for an imperfect process involving a deteriorating production system with increasing hazard rate: imperfect repair and rework upon failure (out of control state). The imperfect repair performs some restorations and restores the system to an operating state (in-control state), but leaves its failure until perfect preventive maintenance (PM) is performed. There are two types of PM, namely imperfect PM and perfect PM. The probability that perfect PM is performed depends on the number of imperfect maintenance operations performed since the last renewal cycle. Mathematical formulas are obtained for deriving the expected total cost. For the EPQ model, the optimum run time, which minimizes the total cost, is discussed. Various special cases are considered, including the maintenance learning effect. Finally, a numerical example is presented to illustrate the effects of PM, setup, breakdown and holding costs.     

Characterization of multilayer nanofiltration membranes using positron annihilation spectroscopy

Positron annihilation spectroscopy (PAS) coupled with a slow positron beam was used to characterize in situ the layer structure and depth profile of the cavity size in thin film composite (TFC) polyamide nanofiltration (NF) membranes prepared by the interfacial polymerization method. Two techniques, using PAS coupled with a slow positron beam of Doppler broadening energy spectra (DBES) and positron annihilation lifetime spectroscopy (PALS) designed to reveal the layer structure and the cavity sizes contained in a multilayer thin film composite NF membrane, were assessed. To the best knowledge of the authors, a characterization of the depth profile of cavities in NF membranes using PAS coupled with a slow positron beam has never been reported. The membranes selected have a composite structure containing three layers: a selective polyamide layer, a transition layer, and a porous support prepared by the phase inversion technique. Furthermore, the cavity size distribution in the selective top layer plays an important role in determining the performance of the NF membranes.     

Single photon sources with single semiconductor quantum dots

In t.his contribution, we briefly recall the basic concepts of quantum optics and properties of semicon- ductor quantum clot. （QD） which a.re necessary to the nnderstanding of the physics of single-photon generation with single QDs. Firstly, we address the theory of quantmn emitter-cavity system, the fluorescence and optical properties of semiconductor QDs, and the photon statistics as well as opti- cal properties of the QDs. We then review the localizatioll of single semiconductor QDs in quantum confined optical microcavity systems to achieve their overall optical properties and perfornances in terms of strong coupling regime, elfieiency, directionality, and polarization control. Furthermore, we will discuss the recenl, progress on the fabrication of single photon sources, and various a.pproaehes for embedding single QDs into mieroca,vities or photonic crystal nanoeavities and show how to ex- tend the wavelength range. We focus in part;icular on new generations of electrically driven QD single photon source leading to high repetition rates, efficiencies at elevated temperature operation. Besides strong eoupling regime, and high collection new development;s of room temperature sin- gle photon emission in the strong coupling regime are reviewed. The generation of indistinguishable photons and remaining challenges for pract ical single-photon sources are also discussed.