Modelling temperature and concentration dependent solid/liquid interfacial energies

Models for the prediction of the solid/liquid interfacial energy in pure substances and binary alloys, respectively, are reviewed and extended regarding the temperature and concentration dependence of the required thermodynamic entities. A CALPHAD-type thermodynamic database is used to introduce temperature and concentration dependent melting enthalpies and entropies for multicomponent alloys in the temperature range between liquidus and solidus. Several suitable models are extended and employed to calculate the temperature and concentration dependent interfacial energy for Al–FCC with their respective liquids and compared with experimental data.     

Structure of the Ba-induced Si(111)- (3 x 2) reconstruction

The Ba/Si(111) surface, previously known as a 3 x 1 phase, is found to have a 3 x 2 periodicity and a semiconducting band gap. The substrate reconstructs into the honeycomb chain-channel (HCC) structure with Ba atoms in the channel, as in the alkali-metal-induced Si(111)-(3 x 1). However, the metal coverage is determined to be 1/6 monolayers, half the alkali-metal coverage. We propose that the structure and the metal coverage determined for the Ba adsorbate is universal for other alkaline-earth-metal adsorbates. With the alkali-metal-induced 3 x 1 case, our results lead to a rule that one donated electron per 3 x 1 surface unit is necessary to stabilize the HCC reconstruction of Si.     

Spliced-fiber mode filter for 1060-nm single-mode transmission

We present a novel mode filter operating for the 1060-nm band, which selectively removes the power of the high-order mode (HOM) from a conventional single-mode fiber (C-SMF) that supports two modes at the short-wavelength band. Our mode filter is fabricated very easily by fusion-splicing a short section of short-wavelength single-mode fiber in the middle of the C-SMF link. By using our spliced-fiber mode filter (SF-MF), a high HOM suppression performance of > 18 dB has been achieved with a low insertion loss of < 0.3 dB over the full band of optical communications from 1050 nm to 1650 nm. We have also developed a new mode power measurement scheme that takes advantage of the bending sensitivity of the HOM guidance. This measurement scheme enabled us to evaluate accurately the performance factors of the fabricated mode filter.     

Strongly enhanced mode selection in a thin dielectric-coated layered microcavity laser

Strong mode selection through an enhanced interferential coupling effect was observed in a thin dielectric-coated layered cylindrical microcavity laser. The strong coupling effect was induced owing to an enhanced reflectivity of around 50% at the dielectric-coated inner boundary of a fused silica capillary filled with a dye-doped liquid. At an optimized coating thickness of about 0.4 microm, the lasing peaks appeared only at the wavelengths corresponding to the constructive interference condition, whereas those from a bare capillary were weakly modulated.     

Quantum MIMO Communication Scheme Based on Quantum Teleportation with Triplet States

A novel quantum MIMO communication scheme is proposed by generalizing the wireless communication technique to the quantum field. The MIMO quantum teleportation can be implemented with triplet states in order to enhance the capacity and fidelity of the quantum channel, in which an n-qubit sequence of quantum signals can be transmitted through the MIMO quantum channel by applying the diversity technique. The quantum noise filtering is involved before the quantum signals are outputted. The analysis and discussions demonstrate that the quantum MIMO teleportation can be performed securely with high capacity and fidelity.     

Synthesis and optical properties of 10 mol% Ce, 5 mol% Tb co-doped KGdF4 and GdF3 submicro/nanocrystals

By controlling the pH values of prepared solutions, the 10 mol% Ce³⁺, 5 mol% Tb³⁺ co-doped KGdF₄ (synthesized with pH = 3) and the 10 mol% Ce³⁺, 5 mol% Tb³⁺ co-doped GdF₃ (synthesized with pH = 1) submicro/nanocrystals have been synthesized based on a citric acid assisted hydrothermal method. For comparison, the samples synthesized by co-precipitation method (without hydrothermal treatment) with pH = 3 and 1 were also collected. The X-ray diffraction data illustrate that the hydrothermal treated KGdF₄ sample crystallizes in the cubic phase and the GdF₃ sample crystallizes in the orthorhombic phase. However, the samples synthesized by co-precipitation method with pH = 3 and 1 are both cubic phase KGdF₄. The field emission scanning electron microscopy images suggest that the hydrothermal treated KGdF₄ submicro/nanocrystals present spherical morphology and the GdF₃ submicrocrystals are rhombic-shaped. And the photoluminescence excitation and emission spectra as well as the luminescent dynamic curves demonstrate the difference in optical properties of the two hydrothermal treated samples.     

Design of an ultrasonic sensor for measuring distance and detecting obstacles

This paper introduces a novel method for designing the transducer of a highly directional ultrasonic range sensor for detecting obstacles in mobile robot applications. The transducer consists of wave generation, amplification, and radiation sections, and a countermass. The operating principle of this design is based on the parametric array method where the frequency difference between two ultrasonic waves is used to generate a highly directional low-frequency wave with a small aperture. The aim of this study was to design an optimal transducer to generate the two simultaneous longitudinal modes efficiently. We first derived an appropriate mathematical model by combining the continuum model of a bar and countermass with the compatibility condition between a piezoelectric actuator and a linear horn. Then we determined the optimal length of the aluminum horn and the piezoelectric actuator using a finite element method. The proposed sensor exhibited a half-power bandwidth of less than ±1.3° at 44.8 kHz, a much higher directivity than existing conventional ultrasonic range sensors.     

η and η' mesons from lattice QCD

The large mass of the ninth pseudoscalar meson, the η', is believed to arise from the combined effects of the axial anomaly and the gauge field topology present in QCD. We report a realistic, 2+1-flavor, lattice QCD calculation of the η and η' masses and mixing which confirms this picture. The physical eigenstates show small octet-singlet mixing with a mixing angle of θ=-14.1(2.8)°. Extrapolation to the physical light quark mass gives, with statistical errors only, mη=573(6) MeV and mη'=947(142) MeV, consistent with the experimental values of 548 and 958 MeV.     

Ultra-smooth platinum surfaces for nanoscale devices fabricated using chemical mechanical polishing

A technique involving two steps of chemical mechanical polishing (CMP) has been developed to produce ultra-smooth metal surfaces with an RMS roughness better than 0.1 nm. A figure of merit termed degree of smoothness (DOS) is proposed for the purpose of quantifying the extent of smoothness of a polished metal surface. A post CMP metal slurry cleaning solution was used for cleaning Pt slurry for the first time and by applying special techniques, a very high quality clean surface was attained. Applications of the polished Pt electrodes in interfacing molecular switching devices with self-assembled monolayers of molecules have been found to dramatically improve the packing and orientation of the molecular monolayer with a huge improvement in the molecular electronics device yields. These smooth metal surfaces may open doors for new opportunities in future nanoscale devices. PACS 81.05.Bx; 81.16.Rf; 81.65.Ps