Injection-locked 1.5 ?m InGaAsP/InP lasers capable of 450 Mbit/s transmission over 106 km

The fluctuation of longitudinal modes of a high-bit-rate modulated 1.5 ?m InGaAsP/InP laser is greatly improved by injection-locking technology. A 106 km transmission at 300 Mbit/s and 450 Mbit/s was achieved with tolerable transmission losses of 37.2 dB and 36.2 dB, respectively, which implies a potential transmission distance of over 145 km.     

Liner thickness measurement for zirconium lined zircaloy cladding tube using dual frequency eddy current method

This paper describes an automatic system for measuring the liner thickness of zirconium lined zircaloy cladding tubes (liner tubes) using a dual frequency eddy current method. The system consists of four components: probe coil, eddy current instrument, scanning mechanism, and mini-computer.Eddy current signals contain thickness information mixed with undesirable information resulting from variations in electrical conductivity of zirconium and zircaloy, and coil to conductor spacing. In order to calculate the liner thickness without a disturbance by such undesirable signals, an optimal equation is formed using signals obtained from a dual frequency eddy current method.It is revealed that the system is able to measure the liner thickness of liner tubes ranging from approximately 40 to 130 μm with an accuracy of a few micro-meters.     

Thermogravimetry of wood treated with water-insoluble retardants and a proposal for development of fire-retardant wood materials

The combustion of wood and methods for the fire retardacy of wood are reviewed briefly first, and then a study on thermogravimetry (TG) and derivative thermogravimetry (DTG) of water-insoluble retardants and wood treated with retardants is presented. In the review of the flaming combustion of wood supported by cellulose, three categories of fire-retardant methods, namely (1) chemical modification of the wood pyrolysis, (2) inhibition of the flaming combustion in the gas phase, and (3) thermal effects to restrain the increase in the temperature of wood and assumed temperature profiles in the heated wood are described. The results of TG and DTG, discussed in terms of kinetics, indicate three kinds of action of the retardant tested: (1) acceleration of dehydration and carbonization, (2) thermal stabilization of the chemical structure of cellulose, and (3) inhibition of the flaming combustion by halogen products. In conclusion, models of fire-retardant wood materials for interior and exterior use are proposed, which contain retardants for the dehydration and the stabilization in the outer layer and those for the inhibition in the inner layer, respectively.     

New method analyzing eye patterns and its application to high-speedoptical transmission system

An advanced method of analyzing eye patterns is proposed which plots the eye pattern as a function of the error rate. The method is applied to high-speed optical-transmission systems and its usefulness is confirmed. Degradation of eye opening due to noise and intersymbol interference is investigated quantitatively using the 10^-10 BER eye. An automatic gain-control system is evaluated from a viewpoint of eye margin, and a gain control system having an improved eye margin performance is proposed. Low-probability abnormal phenomena, such as turn-on fluctuations and mode partitioning in directly modulated distributed feedback (DFB) lasers, are observed using this method     

Modification of the zhang and haykin radar clutter suppression schemes

A modification of the Zhang and Haykin (Z-H) schemes is presented. The modified schemes are based on the assumption that the clutter data of the same range ring of successive scans are highly correlated. Experimental results using real ground clutter have proved that the modified schemes are superior to the Z-H ones.     

Molecular cloning, sequencing and characterization of the genes for adenosylcobalamin-dependent diol dehydratase of Klebsiella pneumoniae

Klebsiella pneumoniae and some of the other Enterobacteriaceae form both diol dehydratase and glycerol dehydratase in response to growth substrates. To compare these enzymes produced by the same bacterium, the pdd genes of K. pneumoniae encoding adenosylcobalamin-dependent diol dehydratase were cloned and sequenced. The sequential three open reading frames (pddA, pddB, and pddC genes) encoded polypeptides of 554, 228, and 174 amino acid residues with predicted molecular weights of 60,379(alpha), 24,401(beta), and 19,489(gamma), respectively. The deduced amino acid sequences of the subunits were 84-100% and 54-71% identical with those reported for diol dehydratases and glycerol dehydratases, respectively.     

Evaluation of 4-Gbit/s optical fiber transmission distance with direct and external modulation

Transmission characteristics for a recently modulated measured distributed-feedbacked (DFB) laser and an externally modulated DFB laser using a Ti:LiNbO/sub 3/, Mach-Zehnder modulator at 4 Gb/s are discussed. The transmission characteristics are estimated by an advanced eye-pattern analysis method. The maximum measured fiber dispersion with a directly modulated laser is 100 to 140 ps/nm when the chirp power penalty is 1 dB. However, for external modulation, there is no power penalty after transmission over a 2220-ps/nm dispersive fiber. This confirms that external modulation has superior transmission characteristics. The modulation scheme for 4-Gb/s systems in terms of these results is discussed.<>