Search

The article discusses the synthesis and the properties of the chiral metal surfaces, which are commonly employed in enantioselective catalysis.

The robustness of the hole target against laser parameter changes in a laser spot size and in a laser pulse length against a contaminated proton source layer and against a laser alignment error are described. The multiple-hole target is robust against a laser alignment error and a target positioning error and it has served as a robust target for practical uses to produce a collimated proton beam.

Hemming is a manufacturing process of folding a panel onto itself or another sheet. Quality of hemming is characterized by geometry and formability. This paper presents a response surface study of three-dimensional (3D) curved-surface-curved-edge hemming of an aluminum alloy, AA6111-T4, using finite-element ( FE) analysis. Solid elements and explicit FE solver are used for simulations of flanging, pre- and final hemming, and shell elements with implicit solver are deployed for springback prediction. A novel procedure called 'solid-to-shell mapping' is developed to bridge the solid elements with the shell elements. Verified to be accurate and efficient, the model is utilized in a central composite design to quantitatively explore the relationships between certain key process variables and the hem dimensional quality and formability. The most significant variables are identified as: (i) prehemming angle on roll-in/roll-out; (ii) nominal surface curvature on sheet springback; and (iii) initial sheet strain and flanging die radius on the maximum hemline surface strain of the produced hem. These results provide insights for process parameter selections in designing and optimizing 3D hems under material formability constraints. [DOI: 10.1115/1.2515430] Keywords: aluminum hemming, dimensional quality, formability, solid-to-shell mapping, central composite design

A new conformal finite-difference time-domain (CFDTD) updating scheme for metallic surfaces nonaligned in the grid is presented in this paper. In contrast to existing conformal models, the new model can be formulated with the original Yee FDTD update equation. Therefore, the proposed scheme can be easily added in standard FDTD codes even if the codes are already parallelized or hardware-accelerated. In addition, based on the commonly used conventional stability criterion, a derivation of the stability is presented and based on the conformal geometric information, a time step reduction formula is presented. The time step reduction is used as a user-defined parameter to tradeoff speed versus accuracy. The achievable geometric precision is optimized to a given time step. Therefore, even with the conventional time step (no reduction) the presented scheme profits from the conformal discretization. To show the performance and the robustness of the proposed scheme canonical validations and two real world applications were investigated. A broadband low profile (circular) antenna was successfully simulated showing the benefit of the conformal FDTD method compared to the conventional scheme. Furthermore, a CAD based mobile phone was conformally discretized and successfully simulated showing that the proposed scheme is highly suited for the simulation of advanced engineering problems. Index Terms--Conformal finite-difference time-domain (CFDTD) method, finite-difference time-domain (FDTD) method, subcell.

Recently, there has been an increased interest in the problem of wave transmission through sub-wavelength apertures, following successful experimental demonstration by several groups for enhancing optical power transmission through nano-scale holes in metallic screens due to properly designed periodic corrugation. Oliner, Jackson, and their co-workers explained and justified this phenomenon as the result of the excitation of the leaky waves supported by the corrugated screen. Here we discuss in detail the mechanism and analysis for another setup we have recently proposed, in which metamaterial layers with special parameters may be utilized as covers over a single sub-wavelength aperture in a perfectly electric conducting (PEC) flat screen in order to increase the wave transmission through this aperture, and we provide a detailed physical insights and analytical explanation for this aperture setup that may lead to similar, potentially even more pronounced effects when the proper metamaterial layers are used in the entrance and the exit face of the hole in the flat PEC screen with no corrugation. Some numerical results confirming this theory are presented and discussed. We also investigate the sensitivity of the transmission enhancement to the geometrical and electromagnetic parameters of this structure. Index Terms--Aperture coupling, aperture enhancement, leaky wave, metamaterials, polariton, sub-wavelength aperture.

We present a procedure that compensates for phase aberrations in digital holographic microscopy by computing a polynomial phase mask directly from the hologram. The phase-mask parameters are computed automatically without knowledge of physical values such as wave vectors, focal lengths, or distances. This method enables one to reconstruct correct and accurate phase distributions, even in the presence of strong and high-order aberrations. Examples of applications are shown for microlens imaging and for compensating for the deformations associated with a tilted thick plate. Finally we show that this method allows compensation for the curvature of the specimen, revealing its surface defects and roughness. Examples of applications are shown for microlenses and metallic sphere imaging. OCIS codes: 090.1760, 090.1000, 180.0180, 120.5050, 120.3620.

Anomalous field enhancement occurs between two-plasmon-resonant surfaces. This model is expected to be useful for metal surfaces having roughness.

The possibility of quantum control of surface photochemical reaction was demonstrated for the system of Cs/Cu(III). The report stated that the phase dependence of two-photon photoemission spectra demonstrated the control of desorptive motion of Cs atoms.

A study was conducted to assess the validity of a simple sharp-kink approximation which relates the contact angle of a liquid on a surface to its density, its surface tension, and the effective molecule-surface potential. The equation might be applied to study the temperature-dependence of the contact angle for helium or alkali metal surfaces.

The article presents surface-enhanced Raman scattering process by a spectroscopic method to boost 14-order-of-magnitude that changes the weak inelastic-scattering effect into a single-molecule level.

Byline: Pimo He The focus of this paper is to review our recent achievements in understanding the growth mechanism of organic semiconductors on metal surfaces and the electronic structures at the organic semiconductor/metal interface with scanning tunnelling microscopy (STM) and photoemission spectroscopy (PES) measurements. By choosing model systems of high-symmetrical organic molecules growth on metal surfaces, especially at the initial growth stage, the driving forces for the formation of organic ordered layers are addressed, for example, perylene growth on Ru(0001) in monolayer regime is mainly controlled by the laterally repulsive molecule-molecule interaction. Concerning whether band bending occurs within organic semiconductor layer on metal surfaces, growth of N,N'-bis-(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4,4'-diamine (NPB) overlayer on the well-defined Ag(111) surface and PES measurements are performed. The results showed band bending occurring within the organic overlayer, and the decrease of the work function with NPB thickness results from contributions from both the band bending and the dipole layer formed due to surface polarisation at the NPB/Ag(111) interface.

The location of the reducible sites of the [2Fe-2S] clusters can be determined by studying quantitatively the interactions between the magnetic moments carried by all the metal sites of the system. The results provide a detailed description of the electron-transfer system of Desulfovibrio gigas AOR when combined with the electron-transfer pathways proposed on the basis of the X-ray crystal structure.

A systematic density functional theory (DFT) of hydrogen adsorption on Fe(111) at various coverages is presented. The coverage effects on the adsorption configrations and adsorption energies are addressed.

A study carried out has developed a new electronic composition-property relationship between the adsorption energy of molecules binding unequally to multiple atoms on metal surfaces and the electronic properties of the surface. Details of the consequences of our electronic composition-property relationship for catalyst design are discussed.

The research group has focused on self assembled w-functionalized alkanethiol monolayers on freshly deposited metal surfaces. The monolayers are characterized by grazing angle reflectance FTIR spectroscopy, scan tunneling microscopy and cyclic voltammetry.

The basic characteristics of the near-field intensities of the proposed I -shaped aperture in the pyramidal structure is investigated which would provide high emission intensity and small spot size simultaneously. It was found that the I-shaped aperture in the pyramidal structure had a higher near field intensity and much smaller spot size than those of conventional simple square aperture.

Scanning tunneling microscopy is used to investigate adsorbate interactions and reactions on metal surfaces. The manners in which adsorbates perturb the surface electronic structure in their vicinity are discussed.

The molecular dynamics simulations are used to investigate the ion beam induced smoothening of crystalline and amorphous substrates. Low energy recoil events in an amorphous substrate lead to the sinking of a nanoparticle indicating that thermal spikes are not required for radiation-induced viscous flow.

Investigation was carried out on the molecular orientation dependence of the o-p conversion of H(sub 2) interacting with a metal surface and the conversion yield for a perpendicular orientation is larger than that for a parallel orientation. The results not only show a strong dependence on the orientation of the H-H bond with respect to the surface, but also on the H(sub 2) c.m. distance from the surface.