Coating of MgO nanorods with protective layers: Sputtering with a Si target, structure, and photoluminescence properties

We have synthesized MgO/SiO_x core-shell nanorods by employing a sputtering technique with a Si target, for sheathing the MgO nanorods. The samples were characterized by X-ray diffraction, scanning electron microscope, transmission electron microscope and photoluminescence (PL) spectroscopy. The SiO_x shell was close to amorphous, whereas the MgO core was crystalline with a cubic structure. The shape and peak positions of the PL spectrum were not changed by the coating.     

Proposal of novel gain-levered MQW DFB laser with high andred-shifted FM response

A gain-levered multiple quantum well (MQW) distributed feedback (DFB) laser with high FM efficiency is discussed. The device consists of three sections with different bandgap energy. It can be fabricated by a selective area metalorganic vapor phase epitaxy (MOVPE) growth technique. Numerical analysis shows that a flat, red-shifted, and high FM efficiency of above 1 GHz/mA at 20-mW output power can be realized using the gain levering scheme     

Percutaneous mitral balloon valvuloplasty in patients with restenosis after surgical commissurotomy: a comparative study

The inhibition of acetylcholinesterase secretion by male and female Heligmosomoides polygyrus was tested on worms taken from experimentally infected mice and maintained for 3 days in vitro in levamisole. The dose inhibiting 50% of enzyme secretion (ID 50) of male worms was twice the ID 50 for female worms. A similar difference was observed in vivo between the dose of levamisole removing 50% (LD50) of male and female worms from the mouse. Acetylcholinesterase secretion by worms and ID 50 were tested in vitro at 3-weekly intervals from 3 to 21 weeks post infection (WPI). Acetylcholinesterase secretion was always significantly higher for male than for female worms. A decrease of ID 50, correlated with the age of the worms was observed: from 1.5 to 0.5 micrograms/ml for males and from 0.7 to 0.1 micrograms/ml for females. These results were confirmed in vivo by a higher efficacy of the anthelminthic at 21 than at 4 WPI.     

Comparative study of flame structures and NOx emission characteristics in fuel injection recirculation and fuel gas recirculation combustion system

A numerical study with momentum‐balanced boundary conditions has been conducted to grasp the chemical effects of added CO₂ to fuel‐ and oxidizer‐sides on flame structure and NO emission behaviour in H₂–O₂ diffusion flames with varying flame location. A reaction mechanism is proposed to show better agreements with experimental results in CO₂‐added hydrogen flames. Oxidizer‐side dilution results in significantly higher flame temperatures and NO emission. Flame location is dramatically changed due to high diffusivity of hydrogen according to variation of the composition of fuel‐ and oxidizer‐sides. This affects flame structure and NO emission considerably especially the chemical effects of added CO₂. The present work also displays separately thermal contribution and prompt NO emission due to the chemical effects caused by thermal dissociation of added CO₂ in NO emission behaviour. It is found that flame temperature and the flame location affect the contribution of thermal and prompt NO due to chemical effects considerably in NO emission behaviour. Copyright © 2004 John Wiley & Sons, Ltd.     

Bit-error-rate analysis of optically preamplified receivers usingan eigenfunction expansion method in optical frequency domain

An accurate method of analysis is presented for optically preamplified receivers using an eigenfunction expansion technique in the optical frequency domain. Excluding three conventional simplifying assumptions on optical filters, electrical circuits, and amplified spontaneous emission, our method can give accurate predictions to the bit-error probabilities in real systems where the amplified spontaneous emission is the dominant noise     

Solution to the positive real control problem for lineartime-invariant systems

In this paper we study the problem of synthesizing an internally stabilizing linear time-invariant controller for a linear time-invariant plant such that a given closed-loop transfer function is extended strictly positive real. Necessary and sufficient conditions for the existence of a controller are obtained. State-space formulas for the controller design are given in terms of solutions to algebraic Riccati equations (or inequalities). The order of the constructed controller does not exceed that of the plant     

Low temperature epitaxial growth of Si0.5Ge0.5 alloy layer on Si (100) by ion beam assisted deposition

The first results were reported on low temperature epitaxial growth of Si_0.5Ge_0.5 alloy layer on Si (100) by ion beam assisted deposition. Nucleation and the growth of Si_0.5Ge_0.5 alloy layer had been investigated by atomic force microscopy and reflection high energy electron diffraction analysis. The Si_0.5Ge_0.5 alloy layer nucleated on Si (100) via Stranski-Krastanov (SK) mode. The Ar ion bombard-ment improved crystallinity and prolonged layer-by-layer stage of the SK mode. The epitaxial temperature was 200°C lower than 550-600°C in molecular beam epitaxy. In order to explain the mechanism of low temperature epitaxial growth E_Ar (energy transferred to growing film by bombarding Ar ion, eV/atom) value was experimentally calculated. In conclusion, the ion bombardment induced dissociation of three-dimensional islands and enhanced the surface diffusion. The variation of tetragonal strain and its effect on electron mobility were taken into consideration. Electron mobility increased with tetragonal strain as a result of band split.     

1.5 μm GaInAsP/InP distributed reflector (DR) lasers with SCHstructure

The large differential quantum efficiency η_df with one-directional output operation obtained in 1.5-μm distributed reflector (DR) lasers using a thin active layer of 50 nm and the separate-confinement heterostructure (SCH) structure is discussed. η _df of the DR laser was experimentally determined to be twice that of distributed-feedback (DFB) lasers cleaved from the same wafer, which indicates high efficiency and high power characteristics of DR lasers     

Elastic wave and energy propagation in angled beams

This investigation comprises an experimental and numerical study of elastic wave propagation in angled beams. Axial impact by two strikers of different lengths was applied to three steel beams, each bent to incorporate a “V” section of different angle in the middle. Finite element simulation using ABAQUS was employed to examine details of the elastic waves generated in the impact tests. The numerical results correlated well with experimental data, and computational simulation was utilized to analyse the propagation of energy associated with the elastic waves. This demonstrated that after several reflections from and transmission across the bends energy is progressively smeared throughout the entire beam and does not concentrate at any particular segment; the bulk of the energy is conveyed via flexural waves. Numerical simulation of wave propagation in a beam with a single angle was also undertaken to study the energy associated with waves reflected from and transmitted across the bend, and how these are affected by the bend angle. The effects of input pulse duration, beam thickness and beam material properties on energy reflection and transmission at a bend are also discussed; this leads to the conclusion that when a longitudinal pulse of a particular frequency impinges on a bend, the ratio between its wavelength and the beam thickness governs the energy reflected from and transmitted across the bend. Moreover, the bend junction geometry (curvature) is found to have a significant influence on the energy reflected and transmitted, especially for obtuse bend angles.     

The effects of permittivity and thickness of dielectric layers on micro dielectric barrier discharges

The discharge characteristics of a plasma display panel (PDP) cell are investigated by two-dimensional fluid simulation and experiment in order to analyze the effects of permittivity and thickness of dielectric layers. Four-inch test panels having the same cell size as a 50-inch FHD (full high definition) resolution were fabricated to measure static margin, luminance, power consumption, and luminous efficacy. As the dielectric permittivity decreases and the dielectric thickness increases, firing voltage increases, but luminous efficacy increases due to the decreases of power consumption. It was observed that the luminous efficacy increases by 30% in the case of relative permittivity ε_r = 7 and dielectric thickness d = 25 µm compared with the case of ε_r = 12 and d = 35 µm.