Historical review of OCR research and development

Research and development of OCR systems are considered from a historical point of view. The historical development of commercial systems is included. Both template matching and structure analysis approaches to R&D are considered. It is noted that the two approaches are coming closer and tending to merge. Commercial products are divided into three generations, for each of which some representative OCR systems are chosen and described in some detail. Some comments are made on recent techniques applied to OCR, such as expert systems and neural networks, and some open problems are indicated. The authors' views and hopes regarding future trends are presented     

Highly efficient four-wave mixing in an optical fiber with intensity dependent phase matching

Wavelength conversion via four-wave mixing in an optical fiber is investigated under a pump intensity dependent phase-matching condition. To obtain a high conversion gain, we use a fiber with a small mode-field diameter (4.2 /spl mu/m) and a small dispersion slope (0.0307 ps/km/nm/sup 2/). When the signal wavelength is set so that it is 9.2 nm longer than the zero-dispersion wavelength of the fiber, we obtain a wavelength conversion gain of greater than 5 dB over a pump wavelength region of more than 8 nm.     

EXOS-D (AKEBONO) very low frequency plasma wave instruments (VLF)

The Akebono (EXOS-D) satellite has been successfully observing the Earth's magnetosphere since it was launched on February 21, 1989. The objectives of VLF instruments on board the satellite were to investigate the behavior of plasma waves associated with accelerated auroral particles, wave-particle interaction mechanisms, and propagation characteristics of whistler-mode waves in the magnetosphere. The instruments measured not only the dynamic spectra of VLF waves up to 15 kHz by a wideband receiver, but also their absolute field intensities, wave normal vectors, and Poynting vectors. Two electric and three magnetic components with a bandwidth of about 50 Hz up to 12.5 kHz are sent to measure the wave normal vectors and Poynting vectors. The antenna impedance is measured to determine the correct absolute electric field intensities. The instruments have successfully measured the wave spectra, the wave normal vectors. Poynting vectors, the precise wave intensities, the antenna impedance, etc. The present paper describes the unique features of the instruments, especially the Poynting flux analyzers in more detail. Obtained scientific results are also reviewed     

Rate-distortion theory for the Shannon cipher system

Rate distortion theory is considered for the Shannon cipher system (SCS). The admissible region of cryptogram rate R, key rate R_k, legitimate receiver's distortion D, and wiretapper's uncertainty h is determined for the SCS with a noisy channel. Furthermore, inner and outer bounds of the admissible region of R, R_k, D, and wiretapper's attainable minimum distortion D˜ are derived for the SCS with a finite discrete source and a noiseless channel     

Slot-coupled microstrip antenna with a triplate line feed whereparallel-plate mode is suppressed

In a slot-coupled microstrip antenna with a triplate line feed, the parallel-plate mode is excited by the slot, resulting in a decrease of radiation efficiency. The authors present a technique for suppressing the parallel-plate mode in this type of the antenna. Measured results confirm the effective performance of the proposed method     

Phase and amplitude comparison between experiment and calculation of ultrabroad-band pulses generated in a taper fiber

Using a cross-correlation frequency-resolved optical gating apparatus, the phases and amplitudes of ultrabroad-band optical pulses from a taper fiber have been measured for various input pulse peak powers. The measured waveforms have been compared with calculated waveforms using a finite-difference in the frequency domain method, in which no envelope approximations were used and the variation of the taper shape was taken into account. Excellent agreement between the measured and the calculated waveforms was obtained when the additional dispersion of a normal fiber and an objective was considered.     

Destruction of volatile organic compounds used in a semiconductorindustry by a capillary tube discharge reactor

Nonthermal plasma technologies offer an innovative approach to the problem of decomposing various volatile organic compounds (VOCs). The authors focused on DC capillary tube discharge plasma reactors to study the decomposition/destruction efficiency for toluene, EGM, trichloroethane and trichloroethylene at 50-2300 ppm levels in dry air. The effects of gas flow rate, VOC concentration and reactor operating conditions on decomposition and analysis of reactant conversion for each VOC were investigated. The results show that VOC destruction efficiency as high as 90% can be achieved, even under a short residence time (3.8 ms) with a destruction energy efficiency of up to 95 g (VOC)/kWh. Laboratory-scale plasma technology was successfully demonstrated for its potential application for VOC control in the semiconductor clean-room environment     

S/N and error rate performance in AlGaAs semiconductor laser preamplifier and linear repeater systems

The applications of AlGaAs semiconductor laser preamplifier and linear repeaters in single mode optical fiber transmission systems were studied through the baseband signal-to-noise ratio and bit error rate performance measurement. Experiments were carried out with the Fabry-Perot cavity laser amplifiers whose characteristics are improved by reducing the input mirror reflectivity to 6 percent. The use of a preamplifier improves the minimum detectable power by 7.4 dB over the Si-APD direct detection level when the received signal is amplified by 30 dB before photodetection. The use of two linear repeaters increases the regenerative repeater gain by 37 dB. These experimental results are in good agreement with theoretical predictions based on the photon statistic master equation analysis.     

S/N performance of an AlGaAs laser preamplifier and a linear repeater system

Baseband signal-to-noise-ratio characteristics in an AlGaAs laser preamplifier and a linear repeater system were studied theoretically and experimentally. The AlGaAs laser preamplifier improved the minimum detectable power by 1.6 dB over the level achieved by direct detection with an Si APD. 37 dB regenerative repeater gain was experimentally obtained in the system with two optical repeaters at 100 Mbit/s data rate.     

Contrasting effects of water-soluble and water-insoluble dietary fibers on bile acid conjugation and taurine metabolism in the rat

The effect of the type of dietary fiber on the bile acid and taurine metabolism was examined in rats. Diets containing 10% of various water-soluble fibers (citrus pectin, konjak mannan, guar gum) as compared to a fiber-free diet increased biliary excretion of total bile acids. In contrast, water-insoluble dietary fibers (cellulose, corn bran, chitin; 10% in the diets) as well as cholestyramine (5% in the diet) considerably, decreased bile acid excretion. Water-soluble dietary fibermediated increases in bile acid excretion were totally attributable to increases in glycine-conjugates. Thus, these fibers greatly increased by the bile acid glycine-to-taurine ratio (G/T). Excretio of glycine conjugates decreased more than that of taurine conjugates in rats fed various water-insoluble dietary fibers. As a results, G/T in rats fed water-insoluble fibers was significantly lowered as compared to G/T in animals fed a fiber-free diet. Cholestyramine did not affect the G/T ratio of bile acids. Fecal bile acid excretion and the activities of hepatic cholesterol 7α-hydroxylase (EC 1.14.13.17) in rats fed various water-soluble dietary fibers approximately doubled as compared to the respective values for rats fed a fiber-free diet. Whereas cholestyramine greatly increased these parameters, water-insoluble fibers did not significantly affect them. Various water-soluble fibers decreased hepatic concentration and urinary excretion of taurine as well as the activity of hepatic cysteine dioxygenase (EC 1.13.11.20). In contrast, water-insoluble fibers considerably increased hepatic taurine concentrations and enzyme activities. The parameters for taurine metabolism were unaffected by cholestyramine. It was suggested that the types of dietary fiber affected hepatic taurine synthesis and thus modified bile acid glycine/taurine ratios.