Aspects of CO2 laser engraving of printing cylinders

Results of the experimental and theoretical investigations of CO(2) laser-engraved cylinders are presented. The processed surfaces of test samples are examined by a phase-stepping laser interferometer, digital microscope, and computer-controlled profilometer. Fourier analysis is made on the patterns parallel to the axis of the laser-scribed test ceramic cylinders. The problem of the visually observed banding is discussed.     

Measurement of space charge distribution in epoxy resin

Internal space charge behavior of insulating materials has recently attracted attention of many researchers, and a large number of experimental studies were carried out by using the materials for dc cables, such as XLPE, LDPE, and HDPE. Epoxy resins are used for insulation under strong electric fields in power apparatus and in electronic devices, and we investigated the behavior of internal space charge using the pulsed electroacoustic method. Two types of epoxy resins were studied: insulation-grade and craft-grade. When dc electric fields were applied to the craft resins treated by immersing them into room-temperature water for 8 and 24 h, positive and negative charges accumulated near the anode and the cathode, respectively, and the charge distribution changed with the immersion time. On the other hand, no charge was observed in the insulation-grade epoxy resin. Next, we treated the samples by immersing them into 100 °C water for 8 h. When the sample was treated for 8 h, hetero charge distribution, which means positive charges near the cathode and negative charges near the anode, was observed. This result is consistent with a previous paper reporting that by chemical analysis, secondary decomposition had occurred. These results show that water and temperature influence the internal space charge behavior of epoxy resins. © 1999 Scripta Technica, Electr Eng Jpn, 129(3): 9–16, 1999     

A novel memory cell for multiport RAM on 0.5 μm CMOSSea-of-Gates

A novel memory cell circuit for multiport RAM on CMOS Sea-of-Gates (SOG) has been proposed. It contributes to the operation both at high speed and at low voltage. In addition, a fourfold read bit line technique is also proposed to reduce the access time. A multiport RAM generator with the novel memory cell has been developed. 2-port or 3-port RAM's with flexible bit-word configurations are available. Test chips containing seven generated RAM's were designed and fabricated on 0.5 μm CMOS SOG. The experimental results of the chip show that each RAM operates at over 1.4 V and that the address access time of the 3-port RAM (16b×256w) is 4.8 ns at 3.3 V     

Fluorine passivation of metal surface for self-cleaningsemiconductor equipment

Fluorine passivation of metal surfaces for ULSI process equipment is investigated and passivated film quality is evaluated. Well-polished and pretreated bare surfaces of stainless steel and nickel are passivated with oxygen-free, high-purity fluorine (O₂ and HF less than 1 p.p.m.), and a uniform and stable passivated surface is obtained by introducing two-step fluoridation, i.e. direct fluoridation and the succeeding thermal modification (heat treatment in nitrogen). The fundamental mechanism of the surface fluoridation is investigated by differential thermal analysis. The chemical structure of the passivated films is examined by X-ray diffraction and X-ray photoelectron spectroscopy. Passivated films of stainless steel exhibit a double-layer structure, such as FeF₂ covered by CrF₂, which has a lower vapor pressure than divalent metal fluorides such as FeF₂ , NiF₂, and MnF₂. It has been confirmed that the first fluoridation step produces a nonstoichiometric fluoride which is converted to the stoichiometric structure by the heat treatment in nitrogen. Good passivation performance is achieved as a result of this thermal modification     

A 6-ns 1-Mb CMOS SRAM with latched sense amplifier

A 1-Mb (256 K×4) CMOS SRAM with 6-ns access time is described. The SRAM, having a cell size of 3.8 μm×7.2 μm and a die size of 6.09 mm×12.94 mm, is fabricated by using 0.5-μm triple-polysilicon and double-metal process technology. The fast access time and low power dissipation of 52 mA at 100-MHz operation are achieved by using a new NMOS source-controlled latched sense amplifier and a data-output prereset circuit. In addition, an equalizing technique at the end of the write operation is used to avoid lengthening of access time in a read cycle following a write cycle     

Normal-state and superconducting properties of Sr2RuO4

We discuss some of the current issues on the copper-free layered perovskite superconductor Sr₂RuO₄, for which a sharp transition at T_c = 1.2 K has been reproducibly obtained. The normal state is characterized as an essentially twodimensional Fermi liquid, and the coherent interlayer transport is established only at low temperatures. The cylindrical Fermi surface observed by de Haas-van Alphen experiments is consistent with other thermodynamic and transport properties. Although the specific heat jump across T_cconfirms the bulk superconductivity, the large residual T-linear term which correlates with the variation in T_cis unusual and suggestive of unconventional pairing.On leave from Hiroshima University.     

Reduction of heat flux on divertor plates by remote radiative cooling in doublet III

Using a single null divertor configuration, heat flux intensity and its profile on the divertor plates as a function of plasma current and density were measured with an infrared camera and thermocouples. The vertical width of the heat flux on the divertor plates 2λ is ≈ 10 cm at the lower separatrix and is ≈ 5.5 cm at the upper separatrix. A diffusion coefficient D which is obtained from the measurement of the diffusion length across the scrape-off field lines is roughly proportional to and its magnitude is on the order of Bohm diffusion. The heat flux on the plates decreases by more than a factor of 5 with increasing electron density in the main plasma and is much smaller than that on the limiters in non-diverted plasmas. Only 3% of ohmic input power goes into the divertor plates at high density of the main plasma, while ≈ 20% goes in at low density. The decrease of heat flux is in good agreement with the increase of radiation loss in the divertor region. The heat flux on the divertor plates can be reduced by remote radiative cooling in high density discharges.     

Experimental Evidence for Spin-Triplet Superconductivity in Sr2RuO4

We review the experimental evidence for spin-triplet superconductivity in Sr₂RuO₄. The Knight shift experiments decisively demonstrated that the Cooper-pair symmetry is spin triplet. We discuss the most probable wave function of the Cooper pairs on the basis of the results of a number of key experiments. We point out that a simple picture of the unitary state with the isotropic gap is not compatible with the observed behavior of the specific heat, and that a profound modification of the pairing wave function is needed. We also present the in-plane angular dependence of the upper critical field, with the field applied exactly parallel to the quasi-two-dimensional plane. We discuss the possible implication of the observed fourfold anisotropy in connection with the proposed second superconducting state with a line-node gap.     

Superconducting Properties of the 3-K Phase of Sr2RuO4 near Hc2

The superconducting transition temperature, T _c , of the impurity-free, intrinsic Sr₂RuO₄ is as high as 1.50 K. However, we recently showed that T _c is remarkably increased up to 3 K in the Sr₂RuO₄–Ru eutectic system, in which plate-like microdomains of Ru metal are embedded in the primary-phase Sr₂RuO₄. The phase diagram of the anisotropic upper critical field of the 3-K phase indicates that H _c2 for the field parallel to the RuO₂ plane is strongly suppressed at low temperatures. We argue that the reorientation of the Cooper-pair spin direction near the Sr₂RuO₄–Ru interface may be responsible for this suppression. In addition, we observed unusual hysteresis in the out-of-plane resistivity, ρ _c , at low temperatures and near H _c2, only when the field was applied parallel to the RuO₂ plane.     

Cell culture in a closed nano-space

The minimum size of a closed nano-space in which cells can survive was determined using 4-nl nanowells. One or two cells could divide in the nanowell. Our results suggest that the cell division activity in the nano-space is determined by the conflict between intercellular effects and consumption of substrates.