New high-resolution positive and negative photoresist method for ?/4-shifted DFB lasers

High-resolution positive and negative photoresists were used to fabricate ?/4-phase-shifted corrugations by holographic exposure. To avoid mixing these photoresists, cyclised polyisoprene was used as a midlayer. The shape and depth of the corrugations on the positive and negative photoresist regions were almost the same. Single-mode operation at the Bragg wavelength was confirmed in lasers with the corrugation.     

Room-temperature lasing operation of GaInNAs-GaAssingle-quantum-well laser diodes

We have succeeded in demonstrating continuous-wave (CW) operation of GaInNAs-GaAs single-quantum-well (SQW) laser diodes at room temperature (RT). The threshold current density was about 1.4 kA/cm², and the operating wavelength was approximately 1.18 μm for a broad-stripe geometry. Evenly spaced multiple longitudinal modes were clearly observed in the lasing spectrum. The full-angle-half-power far-field beam divergence measured parallel and perpendicular to the junction plane was 4.5° and 45°, respectively. A high characteristic temperature (T₀) of 126 K under CW operation and a small wavelength shift per ambient temperature change of 0.48 nm/°C under pulsed operation were obtained. These experimental results indicate the applicability of GaInNAs to long-wavelength laser diodes with excellent high-temperature performance     

Production of d-glucose from pseudo paper sludge with hydrothermal treatment

To convert cellulosic organics contained in industrial paper sludge into glucose, reaction of pseudo paper sludge composed of cellulose and inorganic compounds (calcium carbonate (CaCO₃), talc (Mg₃(Si₄O₁₀)(OH)₂), kaolin (Al₂(Si₂O₅)(OH)₄)) under hydrothermal conditions was studied. Significant amounts of glucose (ca. 23%) could be produced from cellulose in the absence of CaCO₃ for reaction in water at 523 K and 12 min reaction time. On the other hand, in the presence of CaCO3, most glucose decomposed over all conditions, whereas the addition of talc and kaolin to the mixtures increased the glucose yield to about 30%. For the case of chemical recycle of paper sludge with hydrothermal treatment to obtain d-glucose, it can be concluded that it is preferable to separate the calcium carbonate from the paper sludge before hydrothermal treatment.     

Complex-coupled λ/4-shifted DFB lasers with a flat FMresponse from 10 kHz to 17 GHz

Semiconductor lasers with a flat FM response are required for coherent FSK transmission systems. A complex-coupled λ/4-shifted DFB laser is described that gives a flat FM response from 10 kHz to I7 GHz at 15 mW, achieved by using the self-suppressing mechanism of the spatial hole-burning effect     

Optimisation techniques for minimising saw teeth deflection and lumber thickness variation

Lumber size control is an essential element in maximising yield and productivity because a small reduction in rough green target size could lead to substantial savings in wood fibre. One of the key components of rough green target size is sawing variation. In this study, the optimum side clearance of band saw teeth leading to a minimum saw teeth deflection and minimum lumber thickness variation of stellite-tipped and swage-set saws when processing Triplochiton scleroxylon a tropical hardwood were examined. It was observed that the accuracy of kerf width was best with stellite-tipped saws. However, Analysis of variance (ANOVA) at 5% level of significance indicates that there was no significant difference between the accuracy of kerf width of stellite-tipped saws and swage-set saws. It also was observed that at 5% level of significance, the mean kerf width of stellite-tipped saws, which was 4.2 mm, was significantly greater than the mean kerf width of 3.06 mm of the swage-set saws. Sawing variation as indicated by standard deviation of lumber thickness was best for the swage-set saws. A quadratic relationship between sawing variation and side clearance of stellite-tipped saws was established. As the side clearance of the saw increases, the sawing variation decreases until it reaches a minimum value and thereafter, further increase in side clearance of the saw teeth results in an increase in sawing variation. It was observed that an optimum side clearance of 0.69 mm under a saw blade thickness of 1.3 mm was required to produce on the average, a minimum value of 0.42 mm for within-board standard deviation, and 0.59 mm for the total standard deviation. An error margin of less than 1% was achieved when the experimental results for the optimum side clearance was compared with a theoretical assertion.     

Potent antioxidative activity of non‐polyphenolic fraction of green tea (Camellia sinensis) – association with pheophytins a and b

The antioxidative activity of green tea‐derived polyphenols known as catechins has been extensively studied. However, the antioxidative activity of the non‐polyphenolic fraction of green tea has been poorly elucidated and is the subject of the present study. The non‐polyphenolic fraction of green tea showed a significant dose‐dependent suppressive effect against the autooxidation of linoleic acid. The chlorophyll‐related compounds pheophytins a and b showed similar antioxidative activities in the same assay, much higher than those of α‐tocopherol and the green tea catechin (−)‐epigallocatechin‐3‐gallate (EGCG). The non‐polyphenolic fraction of green tea and pheophytins a and b exhibited suppressive activities against superoxide anion (${\bf O}_{2}ˆ{‐}$ ) generation in mouse macrophages induced by 12‐O‐tetradecanoylphorbol‐13‐acetate, showing higher activities than that of EGCG. These results suggest that the non‐polyphenolic fraction of green tea leaves has potent antioxidative activity and that this activity is associated with pheophytins a and b. © 2000 Society of Chemical Industry     

Influence of mechanical properties and mineral salts in wood species on tool wear of high-speed steels and stellite-tipped tools – Consideration of tool wear of the newly developed tip-inserted band saw

This paper is the third in a series of work done on a novel technique for bandsawing, which uses a tip-inserted saw, and is gaining increasing popularity in Japan. It builds up on previous reports on the novel technique for bandsawing, which considered cutting tool hardness, tool wear, accuracy of kerf width, washboarding, and surface profiles of the workpiece. In this paper, ash content analysis and three-point static bending tests were conducted to clarify the influence of mineral salts and mechanical properties of wood samples of Elais guineensis (Oil palm), Strombosia glaucescens (Afina), and Cryptomeria japonica (Sugi) on cutting tool wear. The cutting tools were made from Stellite and High Speed Steels (HSS) of designations SUS420J2 and TiN coated SKH 51 according to the Japan Industrial Standards (JIS). Among the tested wood samples, the highest cutting tool edge recession when machining with SUS420J2 and TiN coated SKH 51 tools were recorded in Oil palm in spite of Afina possessing the highest mechanical strength properties. On the contrary, Stellite in spite of possessing the smallest hardness (HV580) among all the tested cutting tools recorded the lowest cutting tool edge recession when machining wood samples of Oil palm. However, Stellite recorded the highest edge recession when machining Afina, a high density species. Ash content analysis and a scanning electron micrograph of wood samples of the tested wood species show the presence of high proportions of mineral salts in the transverse, radial and tangential sections of Oil palm. This could perhaps account for the high cutting tool edge recessions recorded in wood samples of the Oil palm. The studies have demonstrated that silica accumulation species could have significant effect on tool wear of high speed steels.