Structural changes of glass-ceramics of the Cu2O-Al2O3-SiO2 system on heating in air

The behaviour of copper ions in low thermal expansion glass-ceramics prepared from Cu₂O · Al₂O₃ ·_nSiO₂ glasses, or in-spodumene type Cu₂O · Ae₂O₃ ·nSiO₂ crystals included in the glass-ceramics on heating in air was investigated. On hewing at 300 to 500° C, the copper ions behaved as in the corresponding glasses. Cuprous ions in the glass-ceramics or-spondumene type crystals were oxidized into the cupric state, and at the same time an equal amount of cuprous ions to those oxidized were expelled out of the specimen for the requirement of electrical charge neutrality and then reacted with oxygen to form CuO on the surface. The oxidation of cuprous ions and the decrease of the copper content of the-spondumene type crystals brought about a considerable decrease in the lattice spooings.     

Normal Spectral Emissivity Measurement of Molten Cu–Co Alloy Using an Electromagnetic Levitator Superimposed with a Static Magnetic Field

The normal spectral emissivity of molten Cu–Co alloy with different compositions was measured in the wavelength range of 780 nm to 920 nm and in the temperature range of 1430 K to 1770 K including the undercooled condition by an electromagnetic levitator superimposed with a static magnetic field. The emissivity was determined as the ratio of the radiance from a levitated molten Cu–Co droplet measured by a spectrometer to the radiance from a blackbody calculated by Planck’s law at a given temperature, where a static magnetic field of 2.5 T to 4.5 T was applied to the levitated droplet to suppress the surface oscillation and translational motion of the sample. We found little temperature dependence of the normal spectral emissivity of molten Cu–Co alloy. Concerning the composition dependence, the emissivity decreased markedly above 80 at%Cu and reached that of pure Cu, although its dependence was low between 20 at%Cu and 80 at%Cu. In addition, this composition dependence of the emissivity of molten Cu–Co alloy can be explained well by the Drude free-electron model.     

A Microcomputer System for Spatiotemporal Visual Receptive Field Analysis

A microcomputer system was developed to measure visual spatiotemporal receptive fields. The system performs three functions: 1) generation of a binary spatiotemporal white-noise stimulus, 2) acquisition of spike discharges from retinal ganglion cells, and 3) extraction of the linear part of the spatiotemporal receptive flelds by cross correlating the input against the output. We have applied this system to the measurement of the spatiotemporal receptive fields of cat and catfish retinal ganglion cells.     

Recovery of population inversion in an erbium-doped fiber amplifier observed by temporally resolving amplified spontaneous emissions

We report on the recovery of population inversion in a CW-pumped erbium-doped fiber amplifier. Spontaneous emissions after the input of signal pulses were temporally resolved. The recovery time for population inversion was estimated to be a few hundred microseconds. The pump power and signal width dependences of the recovery were measured. We discuss the dependences by applying an analytical formula derived for the temporal evolution of population inversion.     

Reversible and Precisely Controllable p/n‐Type Doping of MoTe2 Transistors through Electrothermal Doping

Precisely controllable and reversible p/n‐type electronic doping of molybdenum ditelluride (MoTe₂) transistors is achieved by electrothermal doping (E‐doping) processes. E‐doping includes electrothermal annealing induced by an electric field in a vacuum chamber, which results in electron (n‐type) doping and exposure to air, which induces hole (p‐type) doping. The doping arises from the interaction between oxygen molecules or water vapor and defects of tellurium at the MoTe₂ surface, and allows the accurate manipulation of p/n‐type electrical doping of MoTe₂ transistors. Because no dopant or special gas is used in the E‐doping processes of MoTe₂, E‐doping is a simple and efficient method. Moreover, through exact manipulation of p/n‐type doping of MoTe₂ transistors, quasi‐complementary metal oxide semiconductor adaptive logic circuits, such as an inverter, not or gate, and not and gate, are successfully fabricated. The simple method, E‐doping, adopted in obtaining p/n‐type doping of MoTe₂ transistors undoubtedly has provided an approach to create the electronic devices with desired performance.     

Surface modification of poly(3,4-ethylene dioxthiophene):poly(styrene sulfonic acid) (PEDOT:PSS) films by atmospheric-pressure argon plasma for organic thin-film solar cells

Highly-conductive poly(3,4-ethylene dioxythiophene):poly(styrene sulfonic acid) (PEDOT:PSS) films obtained by the addition of dimethylsulfoxide (DMSO) and the argon plasma exposure were used as a transparent conductive anode (TCA) for copper-phthalocyanine (CuPc)/C60 organic thin-film solar cells (OSCs). The CuPc/C60 OSCs on as-grown DMSO added PEDOT:PSS layer showed a power efficiency of 0.6%, whereas it was improved markedly to 1.34% after the atmospheric-pressure argon plasma exposure, which was comparable to that formed on indium-tin-oxide layer. Effects of the DMSO addition and the argon plasma exposure in the spin-coated PEDOT:PSS films is demonstrated in terms of the in-depth characterization of optical and electrical properties.     

An on-chip active decoupling circuit to suppress crosstalk in deep-submicron CMOS mixed-signal SoCs

A decoupling circuit using an operational amplifier is proposed to suppress substrate crosstalk in mixed-signal system-on-chip (SoC) devices. It overcomes the parasitic inductance problem of on-chip capacitor decoupling. The effect of the proposed decoupling circuit is not limited by parasitic fine impedance. A 0.13-/spl mu/m CMOS test chip showed that substrate noise at frequencies from 40 MHz to 1 GHz was incrementally suppressed by sequentially activating three of the proposed circuits in parallel. The power dissipation of each circuit was 3.3 mW at a 1.0-V power supply. The test chip measurement showed that the proposed decoupling reduced crosstalk by 31% at 200 MHz, whereas it was reduced by 4.4% with capacitor decoupling. This 7:1 ratio, or 17 dB, corresponds to the gain of the opamp. Design of the opamp and its feedback loop for active decoupling is simple, making the opamp useful for SoC applications.     

A genetic algorithm for the optimal sequential partitioning problem

The optimal sequential problem is defined as the problem of finding the minimum cost partition of the nodes of a directed acyclic graph into subsets of a given size, subject to the constraint that the precedence relationships among the elements are satisfied. A heuristic algorithm based on tabu search has been proposed for this problem [2]. However, there is a tendency for the solutions obtained by tabu search to become trapped in bad local optima in parallel graphs with random edge costs. In this paper we present a genetic algorithm for the optimal sequential partitioning problem. We develop an effective two‐point partial order crossover satisfying sequential conditions, which preserve better blocks that have a larger sum of edge costs. In this crossover we introduce the roulette selection method to escape local optima. We also assess the effectiveness of the algorithm. The results show that this proposed algorithm outperforms any other algorithm using tabu search in terms of solution quality. © 2001 Scripta Technica, Electr Eng Jpn, 135(4): 43–51, 2001     

Motion coordination algorithm for distributed agents in the cellular warehouse problem

A distributed approach is shown to coordinate the motions of transport tables for the cellular warehouse problem. In this approach, the tables are considered to be autonomous agents, and a built-in behavior function given by artificial neural networks (ANNs) and the evolved problem-oriented connection weights navigate the agents to their specified goals. To determine the agent to be moved, a measure of the priority to move is introduced. We show that distributed agents with the learned behavior function and the negotiation value perform a similar strategy to a “serializable” solution forN-puzzle problems, which provides a good heuristic strategy for large-scale problems. This work was presented, in part, at the Sixth International Symposium on Artificial Life and Robotics, Tokyo, Japan, January 15–17, 2001