Variable-length segmental transmission line and its design guidelines

Waveform distortion is a serious problem in higher-frequency signals on printed circuit boards (PCBs). To overcome this problem, we have already proposed the segmental transmission line (STL) method, which divides transmission lines into several segments with different line widths. Each line width is adjusted to make the reflection noises cancel each other out in order to minimize the signal distortion. In this research, we first analyze the waveform reshaping mechanism of STL. Next, we apply STL to a dual in-line memory module (DIMM) clock-line for high-speed computers. The results give helpful guidelines for STL designs, which shows the efficiency of STL. This work was presented in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007     

Simulations of construction learning for neuron-computer resources

It is well known that information processing in the brain depends on neuron systems. Simple neuron systems are neural networks, and their learning methods have been studied. However, we believe that research on large-scale neural network systems is still incomplete. Here, we propose a learning method for millions of neurons as resources for a neuron computer. The method is a type of recurrent path-selection, so the neural network objective must have nesting structures. This method is executed at high speed. When information processing is executed by analogue signals, the accumulation of errors is a grave problem. We equipped a neural network with a digitizer and AD/DA (Analogue Digital) converters constructed of neurons. They retain all information signals and guarantee precision in complex operations. By using these techniques, we generated an image shifter constructed of 8.6 million neurons. We believe that there is the potential to design a neuron computer using this scheme. This work was presented in part at the Fifth International Symposium on Artificial Life and Robotics, Oita, Japan, January 26–28, 2000     

Behavior emergence of a virtual creature living in complex environments

This study aimed at establishing a new computer-aided animation method using agent-based and physics modeling-based animation. The specific problem we addressed was to install adaptive behavior in a virtual creature placed in a complex environment, and to create its animated behavior automatically. The virtual creature is regarded as an autonomous agent who has sensors, actuators, and controllers. An artificial neural netword (ANN) and a central pattern generator (CPG) were adopted as the controllers. An optimization algorithm was introduced to train the controllers. Numerical experiments proved that the virtual creature acquires effective motions (walking, swimming) to move toward its destination, and to avoid obstacles and other creatures.     

Signal-integrity improvement method and its robustness evaluation for VLSI and VLSI-packaging

Nowadays, a GHz frequency signal needs to be propagated on a printed circuit board (PCB) with low distortions. In addition, a higher-frequency signal of 10 GHz or more will also need to be propagated with low distortion in very-large-scale integration (VLSI) in the future. However, signal propagation with low distortion is getting more and more difficult as the frequency increases. In order to solve this problem and to ensure signal integrity, we have proposed a novel transmission line called a “segmental transmission line” (STL). In the STL, a transmission line is divided into multiple segments of individual characteristic impedance. The multiple segments are designed to fix the waveform distortion on the transmission line by solving a combinatorial explosion problem using a genetic algorithm. In a previous article, we have shown the effectiveness of an STL designed for a GHz clock signal in computer simulations. We have also fabricated two scaled-up STL prototypes for a clock signal using real printed circuit boards (PCBs). In this article, we input a random signal by changing its frequency to the scaled-up STL prototype designed for a 150-MHz clock signal. We show that the STL has high robustness to the random signals and the frequency fluctuations, which indicates the generality of the STL technique.     

Solid‐state characterization and the thermal properties of stereoregular poly(vinyl chloride) prepared by urea clathrate polymerization

The solid‐state characterization of highly stereoregular poly(vinyl chloride) (PVC) prepared by urea clathrate polymerization was carried out by using various instrumental analyses. The structural differences of PVC appeared most remarkably in solubility to organic solvents, IR, WAXD, and solid‐state ¹³C‐NMR spectra. The value of the glass transition temperature (T_g) was about 90°C, not as high as expected, although its detection was quite difficult. The thermal stability was poor, as evidenced by the easy discoloration of this polymer by heat treatment, which was related to the absence of a termination reaction. Dynamic ESR spectra in the solid state clearly indicate that the radical formation occurs at such a low temperature as 160°C in the initial degradation stage. The degradation characteristics of urea clathrate PVC were critically discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2820–2825, 1999     

Development of drift–flux correlation for predicting void fraction in downcomer regions

Accurate prediction of interfacial drag in the downcomer annulus is crucial for the assessment of downcomer void fraction for the loss of coolant accident analysis. The downcomer annulus is the gap between reactor pressure vessel (RPV) exterior and the inner wall of pressure containment vessel (PCV). Based on the previous research, occurrence of the nonuniform two-phase flow in downcomer section is reported, which is partly due to the large wall temperature difference between RPV exterior and the inner wall of PCV. In RELAP5, interfacial drag term in downcomer section is calculated using Kataoka–Ishii and churn-turbulent drift–flux correlations. It has been pointed out that this traditional calculation approach for calculating downcomer void fraction needs modification. The purpose of the current study is to assess the behaviors of drift–flux parameters in downcomer section and to propose an improved distribution parameter model that is suitable for donwcomer boiling analysis.     

A kinetic study of methanol decomposition catalyzed over plate-type palladium catalyst

A kinetic study of the catalytic methanol decomposition to carbon monoxide and hydrogen has been carried out in the pressure range of methanol up to 8 atm at 200 and 250°C over a palladium catalyst supported on an oxidized aluminum plate. The reaction pathway can be proposed as (i) dissociative adsorption of methanol to methoxyl groups and hydrogen adsorbed on palladium sites, (ii) decomposition of the methoxyl groups to carbon monoxide and hydrogen adsorbed, and (iii) desorption of the surface carbon monoxide and hydrogen species. It is suggested that the second step is rate-determining and the surface hydrogen species enhance the decomposition of the methoxyl groups. This revised version was published online in July 2006 with corrections to the Cover Date.     

Development of high-rate anaerobic ammonium-oxidizing (anammox) biofilm reactors

To promptly establish anaerobic ammonium oxidation (anammox) reactors, appropriate seeding sludge with high abundance and activity of anammox bacteria was selected by quantifying 16S rRNA gene copy numbers of anammox bacteria by real-time quantitative PCR (RTQ-PCR) and batch culture experiments. The selected sludge was then inoculated into up-flow fixed-bed biofilm column reactors with nonwoven fabric sheets as biomass carrier and the reactor performances were monitored over 1 year. The anammox reaction was observed within 50 days and a total nitrogen removal rate of 26.0 kg-Nm(-3)day(-1) was obtained after 247 days. To our knowledge, such a high rate has never been reported before. Hydraulic retention time (HRT) and influent NH(4)(+) to NO(2)(-) molar ratio could be important determinant factors for efficient nitrogen removal in this study. The higher nitrogen removal rate was obtained at the shorter HRT and higher influent NH(4)(+)/NO(2)(-) molar ratio. After anammox reactors were fully developed, the community structure, spatial organization and in situ activity of the anammox biofilms were analyzed by the combined use of a full-cycle of 16S rRNA approach and microelectrodes. In situ hybridization results revealed that the probe Amx820-hybridized anaerobic anammox bacteria were distributed throughout the biofilm (accounting for more than 70% of total bacteria). They were associated with Nitrosomonas-like aerobic ammonia-oxidizing bacteria (AAOB) in the surface biofilm. The anammox bacteria present in this study were distantly related to the Candidatus Brocadia anammoxidans with the sequence similarity of 95%. Microelectrode measurements showed that a high in situ anammox activity (i.e., simultaneous consumption of NH(4)(+) and NO(2)(-)) of 4.45 g-N of (NH(4)(+)+NO(2)(-))m(-2)day(-1) was detected in the upper 800 microm of the biofilm, which was consistent with the spatial distribution of anammox bacteria.     

Construction of a dictionary of sequence motifs that characterize groups of related proteins

An automatic procedure is proposed to identify, from the proteinsequence database, conserved amino acid patterns (or sequencemotifs) that are exclusive to a group of functionally relatedproteins. This procedure is applied to the PIR database anda dictionary of sequence motifs that relate to specific superfamiliesconstructed. The motifs have a practical relevance in identifyingthe membership of specific superfamilies without the need toperform sequence database searches in 20% of newly determinedsequences. The sequence motifs identified represent functionallyimportant sites on protein molecules. When multiple blocks existin a single motif they are often close together in the 3-D structure.Furthermore, occasionally these motif blocks were found to besplit by introns when the correlation with exon structures wasexamined.