Improved coupling efficiency of a strained InGaAs-AlGaAs quantum-well laser into a fiber Bragg grating

We describe a highly efficient coupling of up to 78% into a single mode fiber (SMF) by utilizing a low-divergence-angle InGaAs-AlGaAs laser and a new high-NA aspheric lens, resulting in the coupled optical output of over 300 mW with a kink-free performance. The kink-free 300 mW of fiber-coupled power is the largest power reported from a diode laser wavelength stabilized using a fiber Bragg grating. A 3% fiber Bragg grating makes the optical output stabilize at a wavelength of 1.016 /spl mu/m for an optical output power up to 310 mW and without any distinct decrease of the optical output. The coupling tolerance for lateral offsets is improved by utilizing a thermal-diffused expanded-core technique even in the case of using a high-NA coupling aspheric lens. We have also achieved a 300-mW fiber-coupled wavelength-stabilized InGaAs-AlGaAs semiconductor laser butterfly module using a fiber Bragg grating.     

Suppression effects of active power filter on harmonics of distribution system including capacitors

Voltage distortion of 6.6-kV distribution systems has been increasing recently especially in commercial areas. Harmonic currents of certain orders are amplified and voltage distortions are generated by the resonance between system impedance and static capacitor under the leading power factor condition. This paper describes the results of a test on suppression effects on model systems and an actual system. The effect of the use of an active power filter on the resonant harmonics of the system including capacitor was verified.     

Stoichiometry-dependent deep levels in undoped p-type Al0.38Ga0.62As grown by liquid phase epitaxy

Photocapacitance (PHCAP) and photoluminescence (PL) measurements were applied to unintentionally doped p-type Al_0.38Ga_0.62As grown by liquid phase epitaxy using the temperature difference method under controlled vapor pressure. PHCAP spectra revealed three dominant deep levels at E_v+0.9, E_v + 1.45, and E_v+1.96 eV, and a deep level at E_v+0.9−1.5 eV which was not neutralized by forward bias injection. These level densities increase with increasing arsenic vapor pressure and net shallow acceptor density. Furthermore, PL spectra reveal a deep level at 1.6–1.7 eV. The PL intensity of this deep level increases with increasing arsenic vapor pressure. These deep levels are thought to be associated with excess As.     

The geometrical evaluation of effective diffusion coefficient in the liquid phase for porous bodies consisting of spherical elementary particles

To evaluate the intraparticle diffusion coefficient, De, of a component in a liquid, it was assumed that the pore structure of a porous catalyst was a space between an assembly of fine particles. This structure has been found for the metal oxide catalysts. The diffusivity ratio, δ (= De/D), was geometrically estimated in the direction normal to the representative plane (100), (110) or (111) of cubic closed, body centered cubic, simple cubic, or diamond packing of spherical elementary particles. The value δ was found to approximate the porosity ?. Larger pore constrictions gave smaller δ/? values. Reaction rates were measured for the hydrogenation of nitrobenzene in ethanol. The efficiency of this evaluation of De was supported by the agreement of the experimental effectiveness factor with the theoretical factor.     

PERFORMANCE OF A PRESSURIZED TWO-STAGE FLUIDIZED GASIFICATION PROCESS FOR PRODUCTION OF LOW-BTU GAS FROM COAL CHAR

A two-stage pressurized fluidized-bed gasification process has been developed to produce low-heating value gases from coal char. The reactor was 0.075 m id. and 1.4 m long, and gasification experiments were conducted under pressures up to 790 kPa and at temperatures up to 1323 K. A partition disc was used to divide the fluidized bed into two stages, using the first stage as a partial combuster and gasifier and the second stage as a gasifier. The disc was designed to control compositions of coal char particles in both stages so that the heat required for the endothermic gasification reaction in the second stage can be provided by the heat of combustion in the first

For conditions examined here, the disc with an opening ratio of 40° was found to give optimum distribution of the char particles in both stages without ash agglomeration. It was also shown that all oxygen gas was completely consumed within the first stage

The heating value of the product gas increased with the char feed rale. However, there may be an oplimum Teed ratio of char and sand-particles since the higher char feed rate causes more frequent ash agglomeration as well as less carbon conversion     

Hot Isostatic Processing of Shocked Si3N4 Powder

To enhance the sinter ability of Si₃N₄, powders mixed with 0, 2, and 5 wt% Y₂O₃ were explosively shock-treated. Compacts of these powders were encapsulated in 96% silica glass containers and isostatically hot-pressed. The shocked Si₃N₄ with 5 wt% Y₂O₃ was pressed to a density of 3.09 g/cm³ (95.4% of theoretical) at 1400°C under 430 MPa for 3 h, whereas the unshocked material attained only 82.4% of theoretical density under the same hot isostatic pressing conditions.     

Weighted Homo-Lumo Energy Separations for the Polyene References of Fullerenes with Up to 100 Carbon Atoms

Abstract

The T value represents the HOMO-LUMO energy separation of a ?-electronic system weighted with the number of conjugated atoms. We found that this value is kept almost constant for the polyene references defined graph-theoretically for isolated-pentagon isomers of fullerenes with up to 100 carbon atoms. on this numerical basis, the T value can safely be considered as a realistic index of kinetic stability or chemical inertness for all fullerenes without abutting pentagons.     

Polyethyleneimine/chitosan hexamer-mediated gene transfection into intestinal epithelial cell cultured in serum-containing medium

In search of an efficient nonviral vector, polyethyleneimine (PEI)-based vectors were examined. In general, the transfection efficiency of nonviral vectors is suppressed by serum. Here we show that PEI based vectors, particularly, the chitosan hexamer-PEI vector, could perform efficient gene transfection into intestinal epithelial cells (IEC-6) in the presence of serum. The conjugation order of the two polymers with a plasmid (first, chitosan hexamer; second, PEI) was found to be an important factor in enhancing transfection efficiency.     

Quantitative perceptual representation of prepositional semantics

In this paper we concentrate on spatial prepositions, more specifically we are interested here in projective prepositions (eg. in front of, to the left of) which have in the past been treated as semantically uninteresting. We demonstrate that projective prepositions are in fact problematic and demand more attention than they have so far been afforded; after summarising the important components of their meaning, we review the deficiencies of past and current approaches to the decoding problem; that is, predicting what a locative expression used in a particular situation conveys. Finally we present our own approach. Motivated by the shortcomings of contemporary work, we integrate elements of Lang's conceptual representation of objects' perceptual and dimensional characteristics, and the potential field model of object proximity that originated in manipulator and mobile robot path-finding.     

Bulge forming of braided thermoplastic composite tubes under axial compression and internal pressure

In this study, the bulge forming of fiber reinforced thermoplastic (FRTP) composite braided tubes was studied as a new forming technique utilizing fiber orientation rearrangement (the trellis effect) at temperatures near the matrix melting point. It is shown that free bulge forming with the trellis effect can easily result in high expansion without buckling only by axial compression. This is when the stress of the matrix is small enough to rearrange the fiber orientation of the braid. To improve the surface quality and dimensional accuracy, bulge forming with closed dies and internal pressure was also examined experimentally. The appropriate conditions for axial penetration and internal pressure are established. The kinematics of braid is also considered, and calculations from the model are evaluated from experiments. In addition, the kinematic state of braid after deformation is simulated by calculation from the geometric braid model. It is found that the “normalized profile” of the bulged tube does not change during the process and the thickness of the matrix depends on changing fiber orientation.