Research on machine recognition of handprinted characters

Machine recognition of handprinted Chinese characters has recently become very active in Japan. Both from the practical and the academic point of view, very encouraging results are reported. The work is described systematically and analyzed in terms of so-called feature matching, which is likely to be the mainstream of the research and development of machine recognition of handprinted Chinese characters. A database, ETL8 (881 Kanji, 71 hirakana, and 160 variations for each category), is explained, on which many experiments were performed. Recognition rates reported using this database can be compared, and so somewhat qualitative evaluation of these methods is described. Based on the comparative study, the merits and demerits of both feature and structural matching are discussed and some future directions are mentioned.     

Biplane computed cerebral angiotomography of moyamoya disease (author's transl)

In this paper, the authors report biplane computed cerebral angiotomographic findings in 5 cases of Moyamoya disease. The specific features of Moyamoya disease on the CT image were as follows: On the axial plane, the linear structures of the anterior half of the circle of Willis and the proximal portion of the middle cerebral arteries disappeared, and instead of these normal structures, irregular, tortuous or patchy high-density areas just like a "caterpillar" were shown in the basal cistern and medial Sylvian fissures. On the modified coronal plane, the supraclinoid internal carotid arteries and the carotid fork could be identified only with a difficulty, and abnormal, "nebular" high-density areas consisting of irregular, tortuous or patchy high-density vascular components became visible in the basal cistern extending to the basal ganglia. A modified coronal plane and intravenous minimum dose bolus injection method seemed to be more useful for the visualization of these specific features on the CT image. Even before carotid angiography, we can suspect Moyamoya disease for finding these specific features on the CT image. Carotid angiography has been the only method of diagnosing Moyamoya disease. Instead of this invasive examination, computed cerebral angiotomography is useful in detecting Moyamoya disease conveniently and non-invasively. Therefore, we may conclude that computed cerebral angiotomography is very useful method for screening and follow up study of Moyamoya disease.     

Role of disorder-order transformation in consolidation of ceramics

The ordering of stacking-disordered silicon carbide prepared from the elements by high energy ball milling was investigated during sintering. A sharp increase in density in the temperature region 1700–1800°C was associated with a decrease in the disorder. Samples which had low disorder density showed a more continuous sintering behavior with temperature. Highly dense (up to 99% relative density) SiC can be obtained at 1900°C under a pressure of 70 MPa with no hold time. Similar results were observed for structurally disordered carbon with 10 at% of boron. The sintering behavior exhibited an abrupt density increase in the narrow temperature region of 1450–1600°C and was associated with disorder-order transformation.     

Encapsulation of radioactive metals inside multilayered polyhedral shells of carbon as a barrier to radionuclide release

A carbon nanoencapsulate has a polyhedral outer shell of nested, concentric layers of carbon. The shell defines an internal cavity where a metal is encapsulated. Although the rare-earth carbides readily hydrolyze in moist air, the carbides in these carbon shells did not degrade after exposure to air for considerable lengths of time. This means that the carbide particle is physically enclosed within the carbon cavity completely, and the cavity protects it perfectly against attack of water molecules. Considering intrinsic chemical stability of carbon under oxygen free condition, this structure may be a perfect barrier to extremely long-term release of radionuclides. Because encapsulation of LaC₂ within carbon nanoparticles increased drastically from by-product to major product, it would be possible to find the optimized condition that complete encapsulation is achieved. Intrinsic stability of carbon and carbon coated waste nanoparticles may provide an improved barrier to radionuclide release by groundwater.     

Improving withstand voltage by roughening the surface of an insulating spacer used in vacuum

This paper describes a simple and reliable method of improving the surface insulation strength of a spacer used in vacuum. The method is to roughen the spacer surface to an average roughness R/sub a/ higher than 1 or 2 /spl mu/m. The material of the spacer examined is SiO/sub 2/, PMMA, PTFE or Al/sub 2/O/sub 3/ and their shape is a right cylinder with 10 mm in height and 54 mm in diameter. The spacer is subjected to a ramped DC voltage and its surface charging is observed by using an electrostatic probe embedded in the cathode. It has been found that R/sub a/ decisively affects the charging, which decreases as R/sub a/ increases. Increasing R/sub a/ larger than about 2 /spl mu/m suppresses the charging until a higher applied voltage is reached, thus improving the insulation property.     

High-efficiency photon-number detection for quantum information processing

The visible light photon counter (VLPC) features high quantum efficiency (QE) and low pulse height dispersion. These properties make it ideal for efficient photon-number state detection. The ability to perform efficient photon-number state detection is important in many quantum information processing applications, including recent proposals for performing quantum computation with linear optical elements. In this paper, we investigate the unique capabilities of the VLPC. The efficiency of the detector and cryogenic system is measured at 543 nm wavelengths to be 85%. A picosecond pulsed laser is then used to excite the detector with pulses having average photon numbers ranging from 3-5. The output of the VLPC is used to discriminate photon numbers in a pulse. The error probability for number state discrimination is an increasing function of the number of photons, due to buildup of multiplication noise. This puts an ultimate limit on the ability of the VLPC to do number state detection. For many applications, it is sufficient to discriminate between 1 and more than one detected photon. The VLPC can do this with 99% accuracy.     

Frequency range extension of actively mode-locked lasers integratedwith electroabsorption modulators using chirped gratings

We have fabricated actively mode-locked lasers integrated with electroabsorption modulators and chirped gratings. A chirped grating with a large chirp rate of 1.45 Å/μm can be realized by using multiphase-shifted patterns. Short pulses of 4-6 ps were generated over a wide frequency range from 18.9-19.8 GHz. We observed jumps in the wavelength during detuning. These jumps arise from multiple lobes in the reflectivity spectrum. It is found that the wavelength jumps cause increases in the intensity noise. We showed that by reducing the grating length from 150 to 100 μm the sidelobes were suppressed and the detuning frequency range of over 1% could be realized. A smaller pulsewidth was obtained for the negatively-chirped gratings when compared to the positively chirped gratings