Reversible Optical Change of Amorphous Red Phosphorus in Reduced Phosphate Glasses

Amorphous red phosphorus formed in reduced phosphate glasses was found to show a photodarkening effect by illuminating the glasses with light approximately equivalent to its absorption edge; the optical transmission edge shifts toward longer wavelengths on illumination, and then a distinct deepening of the reddish color is observable visually. The photo-darkened specimen recovers its original transmission when it is heated at 300° to 350°C. This darkening-restoring process is confirmed to be reversible by repeated illumination and heating. Transmission measurements over a range of elevated temperatures suggest that this optical characteristic of red phosphorus is unique to its amorphous state.     

Photosensitive Mechanism of Dopant-Free, Ultraviolet-Sensitive Calcium Aluminate Glasses

Calcium aluminate glasses show high sensitivity to ultraviolet radiation without the doping of optically active components. A mechanism is proposed to account for their photosensitivity on the basis of the result that the cause of UV-induced coloring is the emergence of two kinds of paramagnetic centers, an aluminum-oxygen hole center (Al-OHC) and an ozonide (O^-₃). In this model, a peroxy linkage connecting tetrahedrally coordinated Al³⁺s and a physically dissolved O₂ molecule are assumed to be present in the glasses as structural defects. On exposure to UV rays, the peroxy linkage homolvtically dissociates into a pair of A1-OHC's by absorbing UV quanta and one of the two resulting A1-OHC's combines with a nearby O₂ to form an ozonide. Experimental evidences substantiating the mechanism are also reported.     

Solution convexity of a system of linear interval equations

A necessary and sufficient condition for a convex solution set to a system of linear interval equations is presented. The relation between the convexity and feasibility of an optimization problem is also discussed. An extended Leontief system is proposed as an application of the results.     

Valency Control of Glow Discharge Produced a-SiC:H and its Application to Heterojunction Solar Cells

A new type of amorphous silicon solar cell having a conversion efficiency of 8% level is introduced. The cell has a wide band gap window layer made of hydrogenated amorphous silicon carbide, (a-SiC:H), with a good valency control. Electrical, optical and optoelectronic properties of a-SiC:H have been investigated, together with their valency controllability. A design concept and some key technologies to improve solar cell performance with this new material are demonstrated. A series of technical data on material preparation and cell performance are presented. Clear improvements in cell performance, not only I_DC but also V_DC, have been obtained. The realistic limit of the conversion efficiency in a-Si solar cells is estimated and discussed.     

Photosensitive Characteristics of Dopant-Free, Ultraviolet-Sensitive Calcium Aluminate Glasses

Calcium aluminate glasses show high sensitivity to ultraviolet radiation without the doping of optically active components. In this paper, photosensitive characteristics and the cause of UV-induced coloring were investigated for these glasses. Ultraviolet rays below 270 nm were effective for inducing the coloring. The most effective wavelength agreed with that of the apparent absorption edge. In the ternary system with SiO₂ or GeO₂, the sensitivity was monotonically reduced with the amount of the third component and almost vanished for the compositions containing 40 mol%. On the basis of the establishment of a close correlation between two optical absorption bands and two electron spin resonance signals induced by UV illumination, the UV-induced coloring was concluded to be due to the emergence of an aluminum-oxygen hole center (Al-OHC) and an ozonide (O₃^-).     

Allergic Skin Reactivity and Chemical Properties of Allergens in Two Grades of Lactose

Skin tests of the nondialyzable fraction of lactose were performed on patients with a clinical diagnosis of cow's milk allergy. The yields of brownish-colored residue, allergens (ALG), were 0.006% from reagent grade lactose (ALG 1) and 0.011% from lactose used in a commercial infant food formula (ALG 2). The ALG was separated into four fractions by chromatography on Sephadex G-75. The highest incidences of positive skin reaction among the four ALG 1 and ALG 2 fractions were 8/9 and 8/12 respectively. The ALG fractions were identified as a sugar protein complex and the protein moiety of ALG contained high amounts of glutamic acid (or glutamine), threonin, asparagic acid (or asparagine) and proline.     

Mechanism of Ni-Zn Ferrite Formation in the Presence of Molten Li2SO4-Na2SO4

Nickel-zinc ferrite powder was prepared from the constituent oxides in the presence of molten Li₂SO₄-Na₂SO₄. The effect of ZnO on the reactivity of NiO was studied. The process of Ni-Zn ferrite formation was followed by X-ray diffraction and thermomagnetic analyses. Particle size and shape of the product were determined by scanning electron microscopy. In the presence of molten salt, ZnO enhances the reactivity of NiO, and Ni-Zn-ferrite formation is completed at lower temperature than Ni ferrite formation. In the reaction for the formation of Ni-Zn ferrite, Zn ferrite forms before NiO is incorporated into the ferrite phase. The reaction between the initially formed Zn ferrite and NiO leads to a rate of Ni-Zn ferrite formation higher than that of Ni ferrite formation from NiO and Fe₂O₃.     

Calibration of Modified Spalart-Allmaras Model Parameters for Linear Compressor Cascade Corner Flow

In this study,Bayesian parameter calibration is applied to Saplart-Allmaras (SA) turbulence model,and the prediction improvement by the calibrated model is demonstrated.The quantity of interest (QOI) is the pitch-wise distribution of Mach number in the corner separation flow region.The 10 model parameters included in the SA model with Rotation-Curvature correction are considered as random variables obeying uniform prior probability distributions.The order of generalized Polynomial Chaos (gPC) used for sensitivity analysis and surrogate model in calibration is incrementally increased during the calibration process.Posterior convergence is obtained at the 3rd order expansion level in this study.At this final level,sensitivity analysis indicates 3 model parameters,cb1,κ and Cr3 are the most influential random variables,and 3-parameter Bayesian calibration is conducted.The likelihood function in the Bayesian theorem is specified in the form of Gaussian distribution,including experimental uncertainty.The combination of prior and likelihood brings the posterior distribution of model parameters,and Maximum A Posterior (MAP) value is selected as a calibrated parameter set.The flow simulation with calibrated parameters shows a significant increase in the accuracy of the Mach number profile in the corner separation region.The increase in accuracy is attributed to enlarged turbulent viscosity due to the parameter modification of the turbulent viscosity source term.The calibrated parameter is also tested in the off-design flow field,not included in the calibration process.The calibrated CFD again shows improved accuracy for corner separation prediction,and the effectiveness of the parameter set outside of the calibration field is demonstrated.     

Terahertz Active Metamaterials Based on Stacked Closed‐Ring Resonator Arrays

Metamaterials, which can show novel optical functionalities beyond conventional optics, have been actively studied in recent years. As one of approaches to add tunability on resonant characteristics of metamaterials, slightly shifting relative position of stacked metamaterials or metasurfaces has been reported. In this study, based on numerical simulation we have designed stacked closed‐ring resonator (CRR) arrays that show relatively large spectral shift with a small lateral shift of the stacked layers in terahertz (THz) range. We also show that changing dielectric constant of the dielectric media between CRR arrays is also effective to obtain large spectral shift of the resonant responses. Our findings may be utilized to develop novel type of THz active devices and also sensing devices.     

Novel guidelines for the development of pM-selective glass electrodes from oxide glasses

There have been no guidelines for developing pM-selective (M = alkali metal ions) glass membrane electrodes. One of the key points for developing pM-selective glasses is to make glasses not responsive to changes in pH, since pM-measurements can be disturbed by the pH of the solution. As hydrogen-bonded protons in glasses are mobile and their mobility is thought to be responsible for pH-sensitivity, glasses for pM-selective electrodes should contain no hydrogen-bonded protons and no non-bridging oxygen. In this paper, guidelines for developing pH-selective glasses are proposed by using pNa-selective glasses in the Na₂O–Al₂O₃–SiO₂ system as examples. This revised version was published online in November 2006 with corrections to the Cover Date.