Spectrophotometric study of holmium complexation in KOH solutions at 25°C

The complexation of Ho³⁺ in HoCl₃ and KOH solutions at 25°C and saturated vapor pressure was studied by an indicator spectrophotometric technique, and the pH values of the investigated solutions were determined. The stability constants of the hydroxo complexes of Ho³⁺ were measured over a range of pH 9.25–10.10 and at μ≤ 4 × 10^?4 and extrapolated to zero ionic strength.     

8-Gbit/s transmission experiment over 68 km of optical fiber using a Ti:LiNbO3external modulator

We describe the performance of an experimental 1.5-μm lightwave transmission system operating at 8 Gbit/s over 68.3 km of single-mode fiber. The dispersion penalty is limited to 1 dB through the use of external modulation and is attributable to the intrinsic information bandwidth.     

The limit distribution of the maximal deviation of a spline estimate of a probability density

One finds the limit distribution of the maximum absolute value of the normalized deviation of a spline estimate from an unknown probability density.Translated from Veroyatnostnye Raspredeleniya i Matematicheskaya Statistika, pp. 447–467, 1986.     

Electroluminescence spectroscopy for reliability investigations of 1.55 μm bulk semiconductor optical amplifier

This paper demonstrates the complementary relation between functional parameters and electroluminescence spectroscopy for reliability investigations of 1550 nm Semiconductor Optical Amplifiers of 700 μm length active region. Ageing tests have been set to 270 mA-100 °C-1500 h and realized on two different wafers showing more impact on wafer 1 than on wafer 2. Our investigations are particularly focused on interpretation of electroluminescence spectra, from reference and aged SOAs of wafer 1, leading to an improvement of degradation mechanisms understanding. The shift rate to lower energies of the recombination energy peak at 1550 nm, as reported by electroluminescence spectra between reference and aged SOAs in relation with the decrease of optical power measured at 200 mA for the degraded SOA and completed by I(V) characterizations, suggest occurrence of non radiative deep centers near the buried ridge structure in relation with the cleaning process uniformity of interfaces before epitaxial overgrowth. These defects mainly trap majority injected carriers instead of minority carriers reducing the luminescence in the active zone. By monitoring the most sensitive failure indicator (pseudo-threshold current), lifetime distributions are also calculated to determine failure rate, between 150 and 200 FITs over 15 years for operating conditions (25 °C-200 mA) using experimental degradation laws and statistic computations, demonstrating the overall robustness of this technology.     

Fabrication of sharp silicon tips employing anisotropic wet etching and reactive ion etching

We developed a process to obtain sharper silicon tips by employing anisotropic etching in a KOH solution followed by SF₆ plasma etch. The tips were further sharpened using the established thermal oxidation technique to decrease the cone angle and, therefore, obtain smaller curvature radii. We have analyzed the impact of such changes in geometry on a figure of merit associated with the field emission characteristics. An increase in the figure of merit by a factor of three was found in relation to the tips before sharpening.     

Satellite-to-Satellite Range-Rate Measurement

The measurement of range rate between two low-orbiting spacecraft with a precision of better than 1 ?m/s provides a means for sensing global gravity variability. An analysis is given to show the conditions under which this precision can be realized, with emphasis on the requirements of NASA's Geopotential Research Mission. Experimental results obtained with a millimeter-wave demonstration system are presented along with a proposed design for a spaceborne instrument.     

Time-series detection of perspiration as a liveness test in fingerprint devices

Fingerprint scanners may be susceptible to spoofing using artificial materials, or in the worst case, dismembered fingers. An anti-spoofing method based on liveness detection has been developed for use in fingerprint scanners. This method quantifies a specific temporal perspiration pattern present in fingerprints acquired from live claimants. The enhanced perspiration detection algorithm presented here improves our previous work by including other fingerprint scanner technologies; using a larger, more diverse data set; and a shorter time window. Several classification methods were tested in order to separate live and spoof fingerprint images. The dataset included fingerprint images from 33 live subjects, 33 spoofs created with dental material and Play-Doh, and fourteen cadaver fingers. Each method had a different performance with respect to each scanner and time window. However, all the classifiers achieved approximately 90% classification rate for all scanners, using the reduced time window and the more comprehensive training and test sets.     

Dynamic systems inJ m× En

Expanded text of paper read by the author to a meeting of the Kiev Mathematical Society, February 26, 1991.