Simulation of a hollow cone-shaped probe in aberration-corrected STEM for high-resolution tomography

In a simulation study, we found that focal depth extension using a hollow cone-shaped probe with an annular aperture is useful for three-dimension (3D) tomography of aberration-corrected scanning transmission electron microscopy (STEM). Our calculations showed that, for 200 kV STEM, a sub-angstrom sized probe could extend the focal depth from a few to more than several tens nm. We also examined the influence of obstructing bridges, including actual fabricated annular apertures, on focused probe intensity distribution. We found that, to avoid any distortion of probe intensity, the width of the bridges should be narrow. Quantitative evaluation showed that the ratio of obstructing area of the bridges to the area of the annular slit should be less than 0.11.     

Synthesis of Lanthanofullerenes by Laser Ablation Using Pulsed and CW-Nd:YAG Lasers

Endohedral lanthanum fullerenes, La@C₆₀, La@C₈₂ and La₂C₈₀, were synthesized by ablation of graphite and La₂O₃ in flowing Ar buffer gas with a 1064 nm beam from a pulsed-Nd: YAG laser in which the graphite was heated by the CW-Nd:YAG laser up to 2500 °C. The La-fullerenes were also prepared by laser ablation of a lanthanum-graphite composite rod. The extractant fullerenes from the carbon soot were analyzed by laser-desorption time of flight mass spectrometry (LD-TOF MS). The relative yield of La@C₈₂, increased with increasing temperature of the rod in the range of 700-2300 °C.     

Reconstructing clusters for preconditioned short‐term load forecasting

This paper presents a new preconditioned method for short‐term load forecasting that focuses on more accurate predicted value. In recent years, the deregulated and competitive power market increases the degree of uncertainty. As a result, more sophisticated short‐term load forecasting techniques are required to deal with more complicated load behavior. To alleviate the complexity of load behavior, this paper presents a new preconditioned model. In this paper, clustering results are reconstructed to equalize the number of learning data after clustering with the Kohonen‐based neural network. That enhances a short‐term load forecasting model at each reconstructed cluster. The proposed method is successfully applied to real data of one‐step ahead daily maximum load forecasting. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 161(1): 26–33, 2007; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20300     

Design method for a new control system for an autonomous underwater vehicle using linear matrix inequalities

The independent administrative corporation Japan Agency for Marine–Earth Science and Technology (JAMSTEC) has developed a small light autonomous underwater vehicle (AUV) named marine robot experimental 1 (MR-X1).¹ The motion control of MR-X1 is considered in this article. Since the dynamics of MR-X1 mainly depends on its own speed, the motion control is a nonlinear control system. We propose a new controller design method for this system using linear matrix inequalities (LMIs). This algorithm gives a solution as a linear matrix inequality, and can be adapted to solve many LMIs simultaneously. LMIs can be obtained by substituting several speeds into the dynamics of the MR-X1. The proposed controller, which can be derived from the solution of the LMIs, was adapted to MR-X1 and showed good performance in experiments. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

Electrostatic probe measurement in an industrial furnace for high-temperature air conditions

Electrostatic probe measurements are reported that identify flame location, displacement speeds of reaction region, and other flame properties within an industrial furnace that is operated with high-temperature preheated air. The electrostatic probe has advantages over other methods when a furnace is operated with high-temperature air. The probe consisted of a fine detection wire and a supporting tube that played a role of the reference electrode. The reaction regions were found to be widely dispersed and weakened as they moved downstream. However, the ion-current signals still included many sharp peaks, perhaps associated with the thin reaction thickness, contrary to the flame structure expected from the high-temperature air combustion. It was also possible to estimate the displacement speeds of reaction region by using the cross-correlation method between two ion current records detected by parallel detection components. The results demonstrate that the electrostatic probe is useful to detect the structure and state of the reaction mode in industrial furnaces even in the presence of high-temperature air combustion.     

Real-time animation of spark discharge

We have developed a CG technique that creates real-time animations of spark discharges. The technique proposed in this paper has factors related to the generation of a discharge, such as electric charge distribution and boundary conditions in a virtual space as the input, and generates spark discharge shape patterns based on the electric field defined by the input information. An electric field is expressed by the Laplace equation. Our method efficiently obtains the numerical solution of the equation using the calculation technique of the conjugate gradient method implemented on GPU, and can cope with dynamic changes in input. It also produces discharge patterns in both two and three dimensions. In addition, an efficient pseudo-dimensional expansion technique is proposed in this paper, which uses multiple two-dimensional electric fields to generate three-dimensional discharge patterns.     

Circuit level prediction of device performance degradation due to negative bias temperature stress

A circuit level methodology for predicting performance degradations due to negative bias temperature stress is developed in this paper. Degradation mechanism is discussed based on experimental observations. Then, models that consist of a threshold voltage shift and a drain current reduction are developed based on the degradation mechanism. The developed models are implemented into a compact MOSFET model so that we can directly link the local degradation of pMOSFETs’ electrical characteristics to the total circuit performances. The validity of the developed models is confirmed by the good agreement in simulated and measured results of I–V characteristics of pMOSFET in all the transistor working region before and after negative bias temperature stress. Then, circuit performance prediction is carried out for the stressed 199-stage ring oscillator on its waveform and oscillation frequency. Excellent agreements between the experimental results and predicted results are obtained.     

Selective pyrolysis of polystyrene to that with a desired low polymeric degree

To obtain low polymeric polystyrene (PS), pyrolysis of high polymeric PS in solution was studied in the temperature range from 290 to 400°C by using additives or acid catalysts. The low polymeric PS targeted here was that with average molecular weight of 10⁴. When the feed PS was pyrolyzed in tetralin by adding sulfur or diphenyl disulfide, the molecular weight of PS decreased greatly, even at lower temperatures, and the desired low polymeric PS was formed in a relatively large amount at the temperatures below 350°C. The degradation behavior was able to be explained in terms of a random polymer chain scission mechanism initiated by sulfur radicals formed from the additives. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 2299–2305, 1998     

Experimental demonstration and analysis of high performance and low 1/f noise Tri-gate MOSFETs by optimizing device structure

In this paper, we experimentally investigate the performance of multi-gate MOSFETs (MUGFETs) using the advanced radical gate oxide and the accumulation-mode (AM) FD-SOI MOSFETs. Firstly, we experimentally demonstrate that the drain current in AM multi-gate MOSFET is improved about 1.3 times compared with conventional inversion-mode (IM) MOSFETs with the same gate oxide. Secondly, we indicate that 1/f noise levels in AM MUGFETs are obviously suppressed compared with the conventional IM MUGFETs. The advantages resulted from the AM device structure for MUGFETs are demonstrated in this experiment.     

Improvement of critical current density in Y---Ba---Cu---F---O compounds by addition of platinum

Platinum added Y---Ba---Cu---F---O compounds with nominal composition YBa₂Cu₃F_0.4O_xPt_y {y=0, 0.3, 0.5} were prepared by a partial melt process performed at lower temperature than the conventional melt process. Optical micrograph observations showed that Y₂BaCuO₅ (211) particles increase in density and are dispersed finely when increasing the doping of Pt up to 0.3 wt%. For the 0.5 wt% Pt sample, however, the size of the 211 particles became larger than in the samples containing less than 0.3 wt% Pt. The magnetization was measured using a SQUID magnetometer in the temperature range 20–77 K under magnetic fields B_e up to 1 T. The magnetization M also increased with increasing quantity of platinum up to 0.3 wt%. The J_c values estimated from the width of the magnetization curves were 9.8×10⁷ A/m² for the 0.3 wt% Pt sample and 5.4×107 A/m² for the undoped sample at 77 K and B_e=0.8 T. In addition, the whereabouts of the platinum in the quenched samples was investigated by using electron spectroscopy for chemical analysis (ESCA).