Low-distortion audio-frequency AC reference standard with AC-DCoutput switching capability

A digital AC voltage standard with well-known AC-to-DC output voltage difference is described. The proposed feedback configuration can effectively measure and correct for loading effects, caused by a measuring device. Because the AC standard can generate AC and DC voltages at the same output terminals, the automatic measuring setup for thermal voltage converters (TVC) is considerably simplified. The state-of-the-art stability of output voltage enables it to be used for intercomparison purposes     

Is it time for a moratorium on metadata?

This work discusses the author suggestion for locating content in mixed-media for context-sensitive queries. Also provides examples of nontextual approach, a system for organizing digital photographs in which all of the instances of a particular person can be found based on face recognition rather than keyword matching, and compared with a conventional metadata effort that uses predictive labelling of objects in the base data set.     

Quadratic solitons: recent developments

Multicolor optical solitons mediated by quadratic nonlinearities have been observed experimentally during the last few years in a variety of materials and geometries in a number of laboratories around the world. Today, many of the basic properties of the corresponding soliton families are theoretically well established. Nevertheless, experiments continuously reveal new surprises, and the topic is entering new theoretical and experimental territories. In this paper, we briefly outline the key features of the quadratic solitons and overview the latest developments.     

Photoelectrocatalytic humic acid degradation kinetics and effect of pH,applied potential and inorganic ions

This study addresses the removal of humic acid (HA) dissolved in an aqueous medium by a photoelectrocatalytic process. UV₂₅₄ removal and the degradation of color (Vis₄₀₀) followed pseudo‐first order kinetics. Rate constants were 1.1 × 10^?1 min^?1, 8.3 × 10^?2 min^?1 and 2.49 × 10^?2 min^?1 (R² > 0.97) for UV₂₅₄ degradation and 1.7 × 10^?1 min^?1, 6.5 × 10^?2 min^?1 and 2.0 × 10^?2 min^?1 for color removal from 5 mg dm^?3, 10 mg dm^?3 and 25 mg dm^?3 HA respectively. Following a 2 h irradiation time, 96% of the color, 98% of the humic acid and 85% of the total organic carbon (TOC) was removed from an initial 25 mg dm^?3 HA solution in the photoanode cell. Photocatalytic removal on the same photoanode was also studied in order to compare the two methods of degradation. Results showed that the photoelectrocatalytic method was much more effective than the photocatalytic method especially at high pH values and with respect to UV₂₅₄ removal. The effect of other important reaction variables, eg pH, external potential and electrolyte concentration, on the photoelectrocatalytic HA degradation was also studied. Copyright © 2003 Society of Chemical Industry     

Irradiation systems which adapt to the shape of the heated object

The concept of technical systems designed for adaptive thermal irradiation of objects whose shape and position in space are variable is presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 61, No. 6, pp. 993–997, December, 1991.     

The effect of multipath on the detection of symbol-rate spectrallines by delay and multiply receivers

The effect of a secondary path signal on the detectability of the symbol rate spectral line of a binary phase-shift keyed (BPSK) signal by a delay and multiply receiver is investigated. The measure of detectability used is the rate line signal-to-noise ratio. The parameters that define the secondary path signal are initially modeled as deterministic quantities; the phase of the secondary path signal is then taken to be a random variable independent and uniform on (0, 2π). It is found that, with deterministic path parameters, the presence of a secondary path can seriously affect the detectability of BPSK rate lines. When the phase is taken to be uniform on (0, 2π) over the receiver observation time, then the delay and multiply receiver performs as if no multipath is present. In this case, a noncoherent power addition of the primary and secondary path signals occurs