Marked extension of diagnosis length in optical time domain reflectometry using 1.32 ?m YAG laser

An optical time domain reflectometer was newly constructed by using a high power Nd:YAG laser operating at a wavelength of 1.32 ?m and a TeO2 acousto-optical light deflector. As a result, the maximum detectable fault location length of 34 km for single-mode fibre and that of 60 km for multimode graded-index fibre were successfully attained.     

The role of microstructural instability on creep behavior of a martensitic 9Cr-2W steel

The microstructural instability during creep and its effect on creep behavior were investigated for a martensitic 9Cr-2W steel. The steel was developed as a low radioactive steel suitable for fusion reactor structure. Creep testing was carried out at 873 K for up to 15,100 ks (4200 hours). The creep curve consisted of transition creep, where creep rate decreased with time, and acceleration creep, where creep rate increased with time. During creep, microstructural instability, such as the recovery of dislocations, the agglomeration of carbides, and the growth of martensite lath subgrains, was observed to occur, which resulted in softening but no hardening. The transition creep was a consequence of the movement and annihilation of excess dislocations, resulting in the decrease in dislocation density and the increase in martensite lath size with time. The acceleration creep was a consequence of a gradual loss of creep strength due to the microstructural instability which occurred from the initial stage of creep.     

The effect of tungsten on creep

The effect of tungsten on creep behavior and microstructural evolution was investigated for tempered martensitic 9Cr steels with various W concentrations from 0 to 4 wt pct. The creep rupture testing was carried out at 823, 873, and 923 K for up to 54 Ms (15,000 hours). The creep and creep rupture strength increased linearly with W concentration up to about 3 wt pct, where the steels consisted of the single constituent of the tempered martensite. It increased only slightly above 3 wt pct, where the matrix consisted of the tempered martensite and δ-ferrite. The minimum creep rate was described by a power law. The apparent activation energy for the minimum creep rate showed a tendency similar to the W concentration dependence of the creep-rupture strength and was larger than the activation energy for self-diffusion at high W concentrations above 1 wt pct. The martensite lath microstructure with fine carbides along lath boundaries was responsible for a high resistance to creep deformation. With increasing W con- centration, the martensite lath microstructure became stabilized, which decreased the minimum creep rate and increased the apparent activation energy for the minimum creep rate.     

Optical soliton communication in a positively and negativelydispersion-allocated optical fibre transmission line

A bright optical soliton described by a nonlinear Schrodinger equation can survive even in a positive dispersion region as long as the average dispersion has a negative value. This allows us to combine fibres with large positive and large negative dispersion, which in turn will enable us to introduce solitons in a commercial system     

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.     

CAE system in mechanical engineering

Two interactive CAE systems in mechanical engineering were developed. One is a general purpose system for structural design. All stages of design from the beninning of structural analysis to the last stage of strength evaluation can be treated so that optimal structures can be obtained by using this system with changing shapes and dimensions of the structures.

The other one is limited for turbomachinery design. But this includes not only analysis and simulation programs but also design programs and accumulated data for the products, etc.

This paper explains these systems and some element programs which support the system.     

Reconstruction of a large abdominal wall defect using combined free tensor fasciae latae musculocutaneous flap and anterolateral thigh flap

A large abdominal wall defect was reconstructed with the use of a flap combining the tensor fasciae latae musculocutaneous flap and the anterolateral thigh flap in four individuals who had undergone extensive abdominal wall resection because of cancer. The flap was harvested as a single combined composite flap and was transferred to the recipient site by means of microvascular surgery. Morbidity was minimal and the outcome was satisfactory in all instances.     

Fabrication of high-quality long-fiber Bragg grating by monitoring 3.1-eV radiation (400 nm) from GeO defects

3.1-eV (400-nm) luminescence is generated by UV radiation at 244 nm and guided in a germanium-doped silica fiber. In this letter, we propose a new technique for fabricating a fiber Bragg grating by monitoring the power of this visible light. The UV beam is scanned so as to maximize the visible light caused by the UV radiation. This enables us to fabricate successfully a chirp-free and high quality fiber Bragg grating.     

Development of a 275-kV liquid cooling-type gas-insulated transformer

Construction of 275-kV and 500-kV substations in densely populated areas is thought to be necessary in the future to maintain a stable supply of electricity. The use of gas-insulated transformers is now considered for substations because such transformers are non-flammable and nonexplosive. Since the completion of the 77-kV gas-insulated transformer in 1979, we have continued research to develop gas-insulated transformers applicable to a higher voltage level up to 500 kV. As the results of the research, 275-kV, 300-MVA a liquid cooling-type gas-insulated transformer has been developed.     

Protective activity of Borrelia duttonii-specific immunoglobulin subclasses in mice

To analyse the immune response of mice to Borrelia duttonii infection, BALB/c mice were inoculated intraperitoneally with B. duttonii strain 406K, and the titres of B. duttonii-specific immunoglobulins - IgM, IgG1, IgG2a, IgG2b and IgG3 - were determined by ELISA. IgM antibodies appeared first, followed by IgG2a and IgG3, and then IgG1 and IgG2b. The protective activity of individual classes and subclasses of B. duttonii-specific immunoglobulins was then determined by passive immunisation of BALB/c mice with immunoglobulin preparations purified by affinity chromatography. The mice were then challenged by intraperitoneal inoculation of B. duttonii. The study demonstrated that B. duttonii-specific IgM and IgG3 protected against the development of spirochaetaemia and death after borrelial infection, whereas B. duttonii-specific IgG1, IgG2a and IgG2b had low protective activities.