Mechanical properties and microstructures of machinable silicon carbide

Mechanical properties and microstructures of machinable silicon carbide, fabricated by pressureless sintering of silicon carbide fine powder with the aid of polysilastyrene, have been examined. Drastic changes in microstrucyure and in mechanical properties between specimens sintered at below 1773 K and at above 1873 K were observed. By sintering at above 1883 K the macinable silicon carbide had a good strength of more than 200 Mpa with high reliability, which was maintained beyond 1773 K. Polysilastyrene was converted in -phase silicon carbide and ribbon carbon in the pores. The (001) plane of carbon is parallel to the (111) planes of -phase silicon carbide.     

Solid-state source of atomic oxygen for low-temperature oxidation processes: application to pulsed laser deposition of TiO2:N films

An atomic oxygen (AO) source has been redesigned to coordinate with a pulsed laser deposition system and used to grow nitrogen-doped TiO(2) films by deposition of TiN and simultaneous irradiation of the substrate with AO. The AO source uses an incandescently heated thin tube of zirconia as an oxygen permeation media to generate pure AO of low kinetic energy. The emission flux is calibrated using a silver-coated quartz crystal microbalance. The thin shape of the probe and transverse emission geometry of this emission device allow the emission area to be positioned close to the substrate surface, enhancing the irradiation flux at the substrate. AO irradiation is crucial for formation of TiO(2) phases via oxidation of the deposited TiN laser plume, and is effective for decrease of the substrate temperature for crystallization of anatase phase to as low as around 200 °C.     

Production technology for amorphous silicon-based flexible solar cells

We have developed a-Si-based solar cells with plastic film substrate and achieved a stabilized efficiency of 9% in a 40 cm×80 cm cell. The structure and fabrication process of flexible solar cells are presented. Then we discuss the merits and demerits of our process from the viewpoint of mass production, and clarify that the SCAF cell has a good adaptability to mass production.     

A digital signal processing type frequency locked loop for frequency shift keying demodulation

In this paper, we propose a digital signal processing type frequency locked loop (DSP-FLL) using a frequency difference detector (FDD). Since the DSP-FLL is controlled by the frequency, the pole of the voltage controlled oscillator vanishes in the baseband equivalent circuit. Therefore, the transfer function becomes first order and a ringing does not occur. Furthermore, it can be understood from the detection property of the FDD that a cycle slip does not occur and the DSP-FLL can pull in the frequency step input up to half of the sampling frequency.     

Protection relaying scheme based on fault reactance operation type

The theories of operation of existing relays are roughly divided into two types: the current differential type based on Kirchhoff's first law and the impedance type based on Kirchhoff's second law. We can use Kirchhoff's laws to rigorously formulate fault phenomena, so the circuit equations are represented as nonlinear simultaneous equations whose variables are the fault point k and the fault resistance R_f. This method has two defects: (1) a heavy computational burden in iterative calculation by the N‐R method and (2) the relay operator cannot easily understand the principle of numerical matrix operation. The new protection relay principles proposed in this paper focus on the fact that the reactance component at the fault point is close to zero. The reactances X_f(S) and X_f(R) at the ends of the branch are calculated by solution of linear equations. If the signs of X_f(S) and X_f(R) are not the same, it can be inferred that the fault point is located in the branch. This reactance X_f corresponds to the difference in branch reactance between the actual fault point and an imaginary fault point. Thus, the relay engineer can understand the fault location in terms of the concept of “distance.” Simulation results using this new method indicate that it can provide much more precise estimation of fault locations than those obtained by inspection of operating transmission lines. © 2009 Wiley Periodicals, Inc. Electr Eng Jpn, 168(1): 29–40, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20720     

Giant Piezoresistive Effects in Single Grain Boundaries of Semiconducting Barium Titanate Ceramics*

Extremely large piezoresistive effects with a gage factor (elastoresistance) of > 1 × 10⁶ in single grain boundaries of thin ceramic bars of semiconducting barium titanate have been observed at room temperature. Thin barium titanate ceramic bars with a diameter in the range of 10 to 20 μm were prepared to consist of single grains joined together in series. Large piezoresistive effects were observed for some of the single grain boundaries in the present samples under compressive stresses, but no distinct piezoresistance was observed in the grain bulk. A giant piezoresistive effect with a gage factor of 3 × 10⁷ was observed for a single grain boundary which exhibited a saw-tooth type PTCR (positive temperature coefficient of resistivity) characteristic with a significantly large bias dependence of it. This demonstrates that the piezoresistive phenomenon may be interpreted in terms of the change of the potential barrier height due to the change of ferroelectric domain morphologies in the vicinity of grain boundaries under mechanical and electric stresses.     

Stratum Corneum Lipid Structure Investigated by EPR Spin-Probe Method: Application of Terpenes

Electron paramagnetic resonance (EPR) in conjunction with a slow-tumbling simulation was utilized for defining stratum corneum (SC) lipid structure. SC from the back of hairless mouse (HOS:HR-1) was stripped consecutively from one to three or four times using a glass plate coated with a cyanoacrylate resin. Aliphatic spin probes, 5-doxylstearic acid (5-DSA) and 3β-doxyl-5α-cholestane (CHL), were used to evaluate the SC ordering. EPR spectrum of 5-DSA incorporated in the SC demonstrated a characteristic peak for the first strip. A slow-tumbling simulation for 5-DSA showed clear differences in EPR intensities as well as ordering values (S ₀) of the SC for control and terpenes treated SC. The α-terpineol enhanced the permeation of the single chain 5-DSA about three times more than that of the control. However, EPR spectra of CHL in the SC did not show a clear difference for each strip, except for the signal intensity. The results imply that CHL permeates into SC lipid differently from 5-DSA. The enhancement of the 5-DSA is more significant than that of CHL. Therefore, the present results can be useful for various drug administrations via the skin.