Unsteady flow generator for gases using an isothermal chamber

We propose a chamber called an ‘isothermal chamber’ that can produce almost isothermal conditions due to its large heat transfer area obtained by filling it with steel wool. Using this chamber, a simple method to measure flow rates of ideal gases has been developed. In this paper, we propose an unsteady flow generator for gases using the isothermal chamber that can be useful for measuring the dynamic characteristics of gaseous flow meters. The mass flow rate is generated by controlling the pressure change during air discharge in the isothermal chamber using a servo valve. Steady and unsteady oscillatory flow is generated with the generator, and the effectiveness of the generator is demonstrated.     

Prediction of brittle fracture initiating at ends of CJP groove welded joints with defects: study into applicability of failure assessment diagram approach

A series of tests, which reproduced brittle fracture starting from the region around the terminations of complete joint penetration groove welded joints, was conducted. The joint models under study represented a portion of welded beam flange-to-through diaphragm joints in beam-to-column connections. Various artificial weld defects were installed in the welded joints prior to testing. Test results were evaluated based on the failure assessment diagram approach specified in BS 7910. The conventional failure assessment diagrams predicted occurrences of brittle fracture erring on the very conservative side as expected, especially when applied to surface defects. The failure assessment diagram approach was modified by considering the effect of enhanced apparent toughness of material due to the loss of crack tip constraint. The modified failure assessment approach was found to predict the test results well.     

Anisotropic elasticity of magnetically ordered agarose gel

The physical properties of agarose gel prepared under strong magnetic fields were investigated. The storage modulus was measured by the reflection method with an ultrasonic pulse. The measurement results of the gel''s elasticity indicate that agarose gel has anisotropic properties. The elasticity and its anisotropy depend on the concentration of the gel and the magnetic field to which it is exposed. The experimental results indicate that the anisotropic network structure of the gel is induced by the exposure to the magnetic field during gelation. The gelation mechanism under a magnetic field is discussed.     

Roles of rare earth oxide additives in millimeter-wave sintering of AlN

Roles of rare earth oxide (RE2O3) additives in millimeter-wave(MM) sintering of AlN were investigated from the standpoints of phase diagram, heating characteristics of rare earth oxides, and morphology of intergranular oxide phase. In the millimeter-wave sintering of AlN, densification temperature decreased with the decrease of the ionic radius of rare earth ion and was closely related with the eutectic temperature in the RE2O3-Al2O3 binary system. The lowest densification temperature in the millimeter-wave sintering of AlN with Yb2O3 additive was attributed to the largest heating rate of Yb2O3·Al2O3 binary oxide under millimeter-wave radiation. Furthermore, the lowest densification temperature could be attained while selecting the Yb2O3 content so as to form the intergranular phase with the eutectic composition in the Yb2O3-Al2O3 binary system. The result showed good agreement with the above mentioned during the sintering of Si3N4 with Yb2O3-Al2O3 additive. From TEM observation, it was verified that film-like intergranular oxide phase formed under millimeter-wave radiation was favorable for attaining high thermal conductivity in the Yb2O3 added AlNs.     

New Methods for High-Dimensional Verified Quadrature

Conventional verified methods for integration often rely on the verified bounding of analytically derived remainder formulas for popular integration rules. We show that using the approach of Taylor models, it is possible to devise new methods for verified integration of high order and in many variables. Different from conventional schemes, they do not require an a-priori derivation of analytical error bounds, but the rigorous bounds are calculated automatically in parallel to the computation of the integral.The performance of various schemes are compared for examples of up to order ten in up to eight variables. Computational expenses and tightness of the resulting bounds are compared with conventional methods.     

Global and local effects in gain-coupled multiple-quantum-well DFBlasers

Global and local effects in gain-coupled multiple-quantum-well distributed feedback lasers are analyzed using a new approach that combines a submicrometer two-dimensional analysis together with a longitudinal transfer-matrix calculation. Issues such as complex coupling, the standing wave effect, hole burning, and barrier effects are examined in some detail. It is also shown that, due to the local interactions, the grating contrast is nonuniform along the cavity, leading to the new phenomenon of differential longitudinal spatial hole burning     

Uncooled InAs0.09Sb0.91 photoconductors with cutoff wave- length extended to 11.5 μm

Uncooled InAsSb photoconductors were fabricated. The photoconductors were based on InAs0.05Sb0.95 and InAs0.09Sb0.91 thick epilayers grown on InAs substrates by melt epitaxy (ME). Ge immersion lenses were set on the photoconductors. The cutoff wavelength of InAs0.09Sb0.91 detectors is obviously extended to 11.5 mm, and that of InAs0.05Sb0.95 detectors is 8.3 mm. At room temperature, the peak detectivity of Dλp at wavelength of 6.8 mm and modulation frequency of 1 200 Hz is 1.08×109 cm.Hz1/2.W-1 for InAs0.09Sb0.91 photoconductors, the detectivity D at wavelength of 9 mm is 7.56×108 cm.Hz1/2.W-1, and that at 11 mm is 3.92×108 cm.Hz1/2.W-1. The detectivity of InAs0.09Sb0.91 detectors at the wavelengths longer than 9 mm is about one order of magnitude higher than that of InAs0.05Sb0.95 detectors, which rises from the increase of arsenic (As) composition in InAs0.09Sb0.91 materials.