A high-performance multichannel dual-gate poly-Si TFT fabricated by excimer laser irradiation on a floating a-Si thin film

A new excimer laser annealing (ELA) process that uses a floating amorphous-Silicon (a-Si) thin film with a multichannel structure is proposed for high-performance poly-Si thin-film transistors (TFTs). The proposed ELA method produces two-dimensional (2-D) grain growth, which can result in a high-quality grain structure. The dual-gate structure was employed to eliminate the grain boundaries perpendicular to the current flow in the channel. A multichannel structure was adapted in order to arrange the grain boundary to be parallel to the current flow. The proposed poly-Si TFT exhibits high-performance electrical characteristics, which are a high mobility of 504 cm/sup 2//Vsec and a low subthreshold slope of 0.337 V/dec.     

Natural quality two-band LPC coding of speech at 880 bit/s withframe interpolation

A novel frame interpolation technique for two-band linear predictive coding (LPC) vocoders is proposed for maintaining natural speech quality at bit rates below 1 kbit/s. Experimental results show that the speech quality of the proposed vocoder is quite natural at bit rates 880 bit/s and comparable to that of 4.8 kbit/s CELP     

Influence of ionic liquids on the growth ofEscherichia coli

Ionic liquids are compounds that composed only of ions and are liquid at room temperature. Thus, it is normally named room temperature ionic liquid (RTIL). In this study, the application of RTILs to the extractive fermentation of biomaterials was investigated as a substitute of organic solvents. The relative toxicity of the RTILs on the growth ofE. coli was tested. The inhibition of cell growth in the presence of various ionic liquids was measured using solid and liquid culture, and EC₅₀ of each RTILs was calculated. The number of viable and total cells was measured by the number of colonies and optical density, respectively. Effective concentrations of toxicity (EC₅₀) in these tested systems were similar with conventional solvents, such as acetone, acetonitrile, and ethanol. The viability ofE. coli was affected by the polarity and ionic properties of ionic liquids. The resistance of the microorganisms against ionic liquids was different with the cations and anions composing ionic liquids. No general influence of the anionic compound of the ionic liquids was found on toxicity comparing with distinctive influence of cationic moiety.     

Superplasticity of fine-grained 7475 Al alloy and a proposed new deformation mechanism

A study has been made to investigate the superplastic deformation mechanisms of 7475 Al alloy in relation to the variation of grain size ranging between 5.5 μm and 13 μm. The strain-rate sensitivity (m) was increased with decreasing grain size in the superplastic deformation regime. Microstructural investigation after tension tests revealed that the dispersoid free zones were produced mostly at the grain boundaries normal to the tensile direction. A new model for describing the deformation behavior of the 7475 Al alloy has been proposed based on the assumption that the grain boundary sliding was accommodated by both diffusional flow and slip. This new model well predicts many aspects of experimental results.     

Analysis of issues in gate recess etching in the InAlAs/InGaAs HEMT manufacturing process

We have developed an InAlAs/InGaAs metamorphic high electron mobility transistor device fabrication process where the gate length can be tuned within the range of 0.13 μm–0.16 μm to suit the intended application. The core processes are a two-step electron-beam lithography process using a three-layer resist and gate recess etching process using citric acid. An electron-beam lithography process was developed to fabricate a T-shaped gate electrode with a fine gate foot and a relatively large gate head. This was realized through the use of three-layered resist and two-step electron beam exposure and development. Citric acid-based gate recess etching is a wet etching, so it is very important to secure etching uniformity and process reproducibility. The device layout was designed by considering the electrochemical reaction involved in recess etching, and a reproducible gate recess etching process was developed by finding optimized etching conditions. Using the developed gate electrode process technology, we were able to successfully manufacture various monolithic microwave integrated circuits, including low noise amplifiers that can be used in the 28 GHz to 94 GHz frequency range.     

High strain-rate superplasticity in a fine-grained PM 7475 Al Alloy

Superplastic behavior of powder-metallurgy (PM) processed 7475 +0.7Zr Al alloy having a fine grain size of 2 um was investigated. Strain-rate-change tests were conducted at elevated temperatures to examine the strain rate-stress relations. The deformation behavior was analyzed by assuming the presence of threshold stress for grain boundary sliding. After the threshold-stress compensation, the plastic flow was found to correlated well with lattice self-diffusion in pure aluminum. A maximum tensile elongation of up to 1000% was observed at a very high strain rate near l0^-1s^-1 and 515°C. A deformation map was constructed to identify the dominant deformation mechanism for the PM alloy. It was the grain boundary sliding controlled by lattice diffusion in aluminum. Evidence of short fiber or whisker-like formation were observed on the fractured samples over a wide range of temperature.     

A dead reckoning localization system for mobile robots using inertial sensors and wheel revolution encoding

Inertial navigation systems (INS) are composed of inertial sensors, such as accelerometers and gyroscopes. An INS updates its orientation and position automatically; it has an acceptable stability over the short term, however this stability deteriorates over time. Odometry, used to estimate the position of a mobile robot, employs encoders attached to the robot’s wheels. However, errors occur caused by the integrative nature of the rotating speed and the slippage between the wheel and the ground. In this paper, we discuss mobile robot position estimation without using external signals in indoor environments. In order to achieve optimal solutions, a Kalman filter that estimates the orientation and velocity of mobile robots has been designed. The proposed system combines INS and odometry and delivers more accurate position information than standalone odometry.     

Distributed beamforming with one-bit feedback and clustering for multi-node wireless energy transfer

To resolve energy depletion issues in massive Internet of Things sensor networks, we developed a set of distributed energy beamforming methods with one-bit feedback and clustering for multi-node wireless energy transfer, where multiple single-antenna distributed energy transmitters (Txs) transfer their energy to multiple nodes wirelessly. Unlike previous works focusing on distributed information beamforming using a single energy receiver (Rx) node, we developed a distributed energy beamforming method for multiple Rx nodes. Additionally, we propose two clustering methods in which each Tx node chooses a suitable Rx node. Furthermore, we propose a fast distributed beamforming method based on Tx sub-clustering. Through computer simulations, we demonstrate that the proposed distributed beamforming method makes it possible to transfer wireless energy to massive numbers of sensors effectively and rapidly with small implementation complexity. We also analyze the energy harvesting outage probability of the proposed beamforming method, which provides insights into the design of wireless energy transfer networks with distributed beamforming.     

Effects of applied potential and solution temperature on the pitting corrosion of pure aluminium in sulphate ion-containing chloride solution

Effects of applied potential and solution temperatureT _s on the pitting corrosion of pure aluminium (Al) were investigated in 0.01 M NaCl solutions containing various sulphate (SO₄ ^2-) ion concentrations using a potentiodynamic polarisation experiment, the potentiostatic current transient technique, ac impedance spectroscopy and atomic force microscopy (AFM). The potentiodynamic polarisation curves showed a rise in the pitting potentialE _pir values and a simultaneous increase in anodic current density at potentials much higher than theE _pit value as the SO42~ ion concentration increases. This implies that (SO₄ ^2-) ions impede pit initiation at potentials belowE _pit but enhance pit growth aboveE _pit. This was confirmed from the larger pit growth rate parameterb values of pure Al exposed to (SO₄ ^2-) ion-containing chloride solutions during the abrading action than those exposed to (SO₄ ^2-) ion-free chloride solution. Furthermore, at 7_s=25°C, the charge densityQ values for the Al metal dissolution in the presence of (SO₄ ^2-) ions were smaller than the value in its absence. By contrast, as validated by the capacitance values and the AFM images of the re-anodized specimens, an enhanced metal dissolution was observed in (SO₄ ^2-) ion-containing chloride solutions at 7_s=60° and 80°C. From the experimental findings, it is suggested that (SO₄ ^2-) ions act as inhibitors of pitting corrosion on pure Al belowE _pit and at 7_s=25°C, whereas they act as promoters at 7_s=60 ° and 80°C. This originates from the accelerated dissolution of the bare metal extensively exposed to the temperature-sensitive Cl ion attack, which occurs at potentials aboveE _pit