Fabrication and characteristics of high-speed implant-confined index-guided lateral-current 850-nm vertical cavity surface-emitting lasers

Process technology of high-speed implant-apertured index-guide lateral-current-injection top dielectric-mirror quantum-well 850-nm vertical cavity surface-emitting lasers (VCSELs) has been developed. Oxygen and helium implantation for aperture definition and extrinsic capacitance reduction, dielectric mirror formation, p- and n-ohmic contact formation, VCSEL resistance, and thermal analysis were investigated. Employing this technology, GaAs/AlGaAs-based 850-nm VCSELs with small signal modulation bandwidths up to 11.5 Gb/s and an eye diagram generated at 12 Gb/s by a pseudorandom bit sequence of 2/sup 31/-1 were achieved. The bit-error rates were below 10/sup -13/. The threshold current is as low as 0.8 mA for 7-/spl mu/m-diameter current apertures and typical slope efficiencies of 0.45-0.5 mA/mW were obtained.     

Estimating block selectivities for physical database design

Access path deployment is a critical issue in physical database design. Access paths typically include a clustered index as the primary access path and a set of secondary indexes as auxiliary access paths. To deploy the right access paths requires an effective algorithm and accurate estimation of the parameters used by the algorithm. One parameter central to any index-selection algorithm is the block selectivity of a query. Existing methods for estimating block selectivities are limited by restrictive assumptions. Furthermore, most existing methods produce estimates useful for aiding the selection of secondary indexes only. Little research has been done in the area of estimating block selectivities for supporting the selection of the clustered index. The paper presents a set of methods that do not depend on any specific assumption, produce accurate estimates, and can be used to aid in selecting the clustered index as well as secondary indexes     

Very high-order microring resonator filters for WDM applications

High-order microring resonators having from 1 to 11 coupled cavities are demonstrated. These filters exhibit low loss, flat tops, and out-of-band rejection ratios that can exceed 80 dB. They achieve performance that is suitable for commercial applications.     

Long-term progression in chronic manganism: ten years of follow-up

We studied the long-term clinical course of five patients with chronic manganese intoxication. The mean scores of the King's College Hospital Rating Scale for Parkinson's disease increased from 15.0 +/- 4.2 in 1987 to 28.3 +/- 6.70 in 1991 and then to 38.1 +/- 12.9 in 1995. The deterioration was most prominent in gait, rigidity, speed of foot tapping, and writing. Tissue concentrations of manganese in blood, urine, scalp hair, and pubic hair returned to normal. Follow-up MRIs did not show paramagnetic high-signal intensity on T1-weighted images. The data indicate that clinical progression in patients with manganese parkinsonism continues even 10 years after cessation of exposure.     

大型离心复合球墨铸铁轧辊的生产

简述了我公司为舞阳铜厂试制４２００ｍｍ厚板轧机离心复合球墨铸铁轧辊的性能要求、内外层双重金属铸造工艺参数的选择及整个铸造生产工艺过程。