Rapid sensing of trace ionic substances with the novel porous monolith type ion exchanger

Biological and chemical sensor with a rapid response in microlevel test is required for health and environmental monitor. A novel sensing due to porous ion exchanger with three-dimensional acceptor has been first attempted to develop a high-performance sensor. This porous monolith type ion exchanger has an open-cellular monolith structure with 5–50-μm diameter pores. The trace amount of inorganic ions dissolved in aqueous solutions can be quantitatively determined with the impedance given by the monolith, which attracts and adsorbs the ions rapidly. We have succeeded in detecting ions with a concentration as low as 10⁻⁷ mol. The porous ion exchanger has a potentiality as a high-performance device for biological and chemical sensing. POLYM. ENG. SCI., 47:1666–1670, 2007. © 2007 Society of Plastics Engineers     

Recovery of neutron-induced damage of SiC by thermal annealing up to 1400 °C

Recovery of the specimen length of neutron-irradiated SiC was observed using a precision dilatometer. The specimens were heated isothermally and isochronally. The accuracy of length measurement at high temperature using the dilatometer was compared with that of length measurement at room temperature using a micrometer. It was clarified that the dilatometer method showed high accuracy and stability. The dilatometer method was applied to observe length recovery by isothermal annealing at 1200 °C of the neutron-irradiated SiC, and at least two recovery rates were clarified.     

Two-dimensional numerical simulation of side-gating effect in GaAsMESFETs

Two-dimensional device simulations that confirm that the side-gating effect in GaAs MESFETs occurs on semi-insulating substrates containing hole traps are discussed. A negative voltage applied on a side gate, a separate n-type doped region, causes an increase in the thickness of the negatively charged layer at the FET channel interface in the substrate, through hole emission from hole traps. The FET channel current is modulated by the electron depletion of the n-type channel, which results from the compensation for the extension of the negatively charged layer at the n-i interface into the i-substrate containing hole traps. The magnitude of the drain current reduction is determined by the total acceptor concentration in the substrate and the donor concentration of the channel. However, the magnitude is independent of the side-gate distances     

A poly-silicon TFT with a sub-5-nm thick channel for low-power gain cell memory in mobile applications

This work presents a gain-cell solution in which a novel ultrathin polysilicon film transistor provides the basis for dense and low-power embedded random-access memory (RAM). This is made possible by the new transistor's 2-nm-thick channel, which realizes a quantum-confinement effect that produces a low leakage current value of only 10/sup -19/ A at room temperature. The memory has the potential to solve the power and stability problems that static RAM (SRAM) is going to face in the very near future.     

An all DC-powered Josephson logic circuit

A novel DC-powered Josephson circuit is reported. An improved HUFFLE-type DC flip-flop with a parallel resistor, to prevent hang-up, is constructed by combinational circuits as well as sequential circuits. The basic device is a vertical type two-junction interferometer with only three-metal layers. The design rule is 2.5 μm. High junction-current density allows for a wide operating margin even with a low inductance load. Basic circuit function test elements have been completed. The DC flip-flop with excess gate current works as a GHz range VCO (voltage controlled oscillator) for internal clock generation. The speedup junction successfully accelerated the switching speed. The ring-oscillator showed a minimum gate delay of 11.3 ps     

Enhancement of turbulent jet diffusion flame blowout limits by annular counterflow

The effects of a proposed combustion technique, named as annular counterflow, on the enhancement of jet diffusion flame blowout limits were investigated by a series of experiments conducted for the present study. Annular counterflow was formed in a concentric annulus, in which fuel jet was ejected from a nozzle and air was sucked into an outer cylinder encompassing the nozzle. Three fuel nozzles and outer cylinders of different sizes were utilized to perform the experiments. Schlieren technique and normal video filming were employed for the visualization of diverse flame morphologies triggered by the said flow. Gas samplings were taken and scrutinized by the use of a gas chromatograph. Results showed that the blowout limits can be enhanced dramatically by an increase in volume flow rates of air‐suction. Mixing enhancement is achieved with frequent and strong outward ejection of fluids from the cold jet when this technique is applied. The blowout limits are further extended when the diameter of outer cylinders becomes smaller and/or that of the fuel nozzle becomes larger. The base widths of lifted flames were found to be narrower in the interim of annular counterflow application. The rates of increase in flame lift‐off heights and base widths along with an increase in fuel flow velocities become sluggish when the volume flow rates of air are increased. The amount of fuel that was sucked into the outer cylinder was found to be negligible and trivial. A model based on annular and coaxial jet was developed to predict the lifted flame base width and blowout limits. The coincidence between the prediction and experimental results unambiguously validates that the momentum of air‐suction dominates the beneficial effect. Copyright © 2001 John Wiley & Sons, Ltd.     

Microstructure and superconducting properties of rapidly-quenched copper-based alloys containing immiscible lead and bismuth elements

Copper-based superconducting alloys including finely dispersed f c c lead or h c p (Pb- Bi) particles in f c c copper matrix have been obtained by rapid quenching (Cu-M)_100-x Pb_x and (Cu-M)_100-x (Pb_0.6Bi_{0.4 x} (M = aluminium, silicon or tin;x < 10 at%) alloys containing immiscible elements such as lead and bismuth. The particle size and interparticle distance were about 30 to 130 nm and 20 to 200 nm for had particles and about 30 to 60 nm and 30 to 150 nm for (Pb- Bi) particles. The transition temperature,T _c, was in the range of 3.2 to 5.5 K for the Cu-M-Pb alloys and 6.2 to 6.3 K for the Cu-M-Pb-Bi alloys. Critical magnetic field,H _c2, and critical current density,J _c, for the later alloys were 0.47 to 0.93T at 4.2 K and 1.1 × 10⁵ to 2.7 × 10⁵ Am^–2 at zero applied field and 4.21 K. The mechanism of the appearance of such a soft-type superconductivity for the rapidly quenched copper-based alloys was discussed, and inferred to be due to the formation of a percolation path of a superconducting lead or Pb-Bi phase along the grain boundaries, sub-boundaries and/or tangled dislocations where the lead or Pb-Bi phase precipitated preferentially, rather than the proximity effect based on lead or Pb-Bi particles.     

Tensile strained QW structure for low-threshold operation of short-wavelength, AlGaInP LDs emitting in the 630 nm band

The amount of tensile strain introduced into QWs and the optimum QW structure are evaluated for low-threshold operation of AlGaInP LDs in the wavelength range 630-640 nm. Very low threshold current of 32 mA under CW operation at 20 degrees C is achieved in an index-guided SQW LD emitting at 632 nm.<>     

Improvement of polymer/fullerene solar cells by controlling geometry of the ITO substrate surface

We have found that the short-circuit current, J_sc, of polymer/fullerene [RR-P3HT/C₆₀] solar cells has a clear dependence on the surface roughness of the ITO/glass substrate. We prepared an ITO surface with an average roughness, R_a, of 0.7–11 nm by chemical etching. At first J_sc increases with the increase in ITO surface roughness and then gradually decreases. The maximum performance was obtained at R_a≈4 nm. J_sc is also high with a very flat surface of R_a=0.7 nm. This feature can be attributed to the trade-off between the increase in absorption light path length and film-quality deterioration.     

Effects of the doping profile on current characteristics in BSITs

Proposed are two doping profiles of the conducting channel in bipolar-mode static induction transistors (BSITs) that improve the current handling capability. By using the results obtained from two-dimensional device simulations, it is shown that BSITs with the proposed profiles exhibit higher drain current density and DC current gain than conventional BSITs. Also discussed is the tradeoff between the current and voltage capabilities