In many applications, information retrieval is a very important research field. In several key strategies, the binary trie is famous as a fast access method able to retrieve keys in order. Especially, a Patricia trie gives the shallowest trie by eliminating all nodes which have only one arc, and it requires the smallest storage among the other trie structures. If trie structures are implemented, however, the greater the number of the registered keys, the larger storage is required. In order to solve this problem, Jonge et al. proposed a method to change the normal binary trie into a compact bit stream. This paper proposes the improved trie representation for the Patricia trie, as well as the methods for searching and inserting the key on it. The theoretical and experimental results, using 50,000 Japanese nouns and 50,000 English words, show that this method generates 25-39 percent shorter bit streams than the traditional method. This method, thus, enables us to provide more compact storage and faster access than the traditional method.

Segmenting the images obtained from magnetic resonance imaging (MRI) is an important process for visualization of the human soft tissues. For the application of MR, we often have to introduce a reasonable segmentation technique. Neural networks may provide us with superior solutions for the pattern classification of medical images than the conventional methods. For image segmentation with the aid of neural networks of a reasonable size, it is important to select the most effective combination of secondary indices to be used for the classification. In this paper, we introduce a vector quantized class entropy (VQCCE) criterion to evaluate which indices are effective for pattern classification, without testing on the actual classifiers. We have exploited a newly developed neural tree classifier for accomplishing the segmentation task. This network effectively partitions the feature space into subregions and each final subregion is assigned a class label according to the data routed to it. As the tree grows on, the number of training data for each node decreases, which results in less weight update epochs and decreases the time consumption. The partitioning of the feature space at each node is done by a simple neural network; the appropriateness of which is measured by newly proposed estimation criterion, i. e. the measure for assessment of neuron (MAN). It facilitates the obtaining of a neuron with maximum correlation between a unit's value and the residual error at a given output. The application of this criterion guarantees adopting the best-fit neuron to split the feature space. The proposed neural classifier has achieved 95% correct classification rate on average for the white/gray matter segmentation problem. The performance of the proposed method is compared to that of a multilayered perceptron (MLP), the latter being widely exploited network in the field of image processing and pattern recognition. The experiments show the superiority of the introduced method in terms of less iterations and weight up dates necessary to train the neural network, i. e. lower computational complexity; as well as higher correct classification rate.

We have applied hot-carrier circuit-level simulation to memory peripheral circuits of a few thousand to over 12K transistors using a simple but accurate degradation model for reliability verification of actual memory products. By applying simulation to entire circuits, it was found that the location of maximum degradation depended greatly upon circuit configuration and device technology. A design curve has been developed to quickly relate device-level DC lifetime to circuit-level performance lifetime. Using these results in conjunction with a methodology that has been developed to predict hot-carrier degradation early in the design cycle before TEG fabrication, accurate total-circuit simulation is applied early in the design process, making reliability simulation a crucial design tool rather than a verification tool as technology advances into the deep sub-micron high clock rate regime.

An improved numerical computation model is presented to calculate the metal-ferroelectric-semiconductor field effect transistor (MFSFET) characteristics with a sufficiently large gate area which can be applied for large drain voltages. In the presented model, the polarization of the ferroelectric gate insulator is inhomogeneous and treated as a variable along the channel. We have calculated electrical properties of SrBi2Ta2O9/Si MFSFETs and demonstrate that the conventional model, in which the polarization of the ferroelectric gate insulator (Pd) is treated as a constant, overestimate the drain current when the drain voltage is large. In addition, effects of the ratio of remanent polarization to spontaneous polarization (Pr/Ps ratio) of the ferroelectric film on the transistor characteristics are discussed.

The crystallization process of Sr0. 7Bi2. 3Ta2O9 (SBT) ferroelectric thin films with different crystal orientations formed by chemical liquid deposition using an alkoxide precursor was investigated. One film showed strong c-axis orientation (a-type film), while another shows scarcely any c-axis orientation (b-type film). We report that the crystallization process was the same even when crystal orientation differed. Thin films first change from amorphous to fluorite fine grains; the fluorite grains then change to bismuth layer-structure grains. The different orientation of the SBT films is not caused by different crystallization process. Both SBT films with different crystal orientations consist of fine fluorite grains after 650 heat-treatment. Their leakage current density characteristics differ, however. The leakage current density of the a-type film was independent of the electric field, and showed a low value of 10-8 A/cm2. The leakage current density of the b-type film, however, was dependent on the electric field, and increased continuously with the increasing electric field. After 700 heat-treatment, both films consist of large grains with bismuth layer-structure and fine fluorite grains. The matrix of both films contains large grains with bismuth layer-structure that determines the leakage current density characteristics. Since the fluorite grain size after a 700 heat-treatment is the same as that after 650 heat-treatment, nucleation is predominant at the structural phase boundary from amorphous to fluorite. The bismuth layer-structure grains are large and single-crystal grains after both a 700 and 800 heat-treatment. Increased grain size predominates at the structural phase boundary from fluorite to bismuth layer-structure grains. Clearly, ferroelectric SBT films with bismuth layer-structure are crystallized in two steps, each having a different predominant crystal growth mechanism.

Pb(ZrxTi1-x)O3 (PZT) thin films were prepared on various electrodes. When Ir system materials were used as electrodes, fatigue properties of PZT thin films were improved. Moreover, in the case of the PZT thin film on an Ir/IrO2 electrode, not only fatigue but imprint properties were clearly improved. We could find these improvements were caused by good barrier effect of IrO2 from secondary ion mass spectroscopy (SIMS) analysis. By applying these Ir system electrodes, we fabricated stacked capacitors on polycrystalline silicon (poly-Si) plugs. In spite of high temperature thermal processing, we found poly-Si plugs were ohmically connected with the bottom electrodes of the capacitors from hysteresis measurements and I-V characteristics, and could greatly expect them for practical use.

To investigate the possibility of their application to both high density dynamic and nonvolatile ferroelectric random access memories, heteroepitaxial BaxSr1-xTiO3 (BSTO) thin films with various Ba content from x=0 to 1. 0 were prepared on conductive SrRuO3 electrode films, and the crystallographic, dielectric and ferroelectric properties were investigated. The compositional phase boundary between paraelectric and ferroelectric phase at room temperature was located at about x = 0. 12 in the heteroepitaxial films, indicating a quite different composition to that of the bulk (x = 0. 70). At this composition of x = 0. 12, the dielectric constant attained the maximum value of 740 for the BSTO film with a thickness of 77 nm. The composition with a lager Ba content (x 0. 32) showed ferroelectricity at room temperature. The maximum value of remanent polarization of 2Pr = 0. 38 C/m2 was obtained at the composition of x = 0. 70 in this study.

In this paper we derive the expressions of the spectra of waveform relaxation operators for linear differential-algebraic equations which stem from circuit simulation. These expressions suggest ways to split the matrices of the circuit equations such that waveform relaxation will converge. Numerical experimental results are given.

In this paper, we discuss ferroelectric materials suitable for a metal ferroelectric metal insulator semiconductor FET (MFMIS FET). It is important for a ferroelectric material to have a low dielectric constant to enable the application of sufficient electric field to a ferroelectric layer. Films of Sr2Nb2O7 (SNO) and Sr2(Ta1-xNbx)2O7 (STNO) were prepared by the sol-gel method on Pt/IrO2 electrodes for an MFMIS FET. The ferroelectricities of STNO films were confirmed in the range of x=0. 1-0. 3. In case of x=0. 3, the largest remanent polarization was obtained in the hysteresis loop. The remanent polarization and the coercive field are 0. 5 µ C/cm2 and 44 kV/cm, respectively. The film had a low dielectric constant (ε=53). It is considered that the characteristics of STNO thin films are suitable for MFMIS FET.

In this paper, we propose a transformation technique for the multiplications of one variable with multiple constants, which are frequently seen in the various applications of signal processing, image processing, and so forth. The method is based on the exploration of common subexpressions among constants and reduces the number of shifts, additions, and subtractions to implement linear computations with hardware. Our method searches for regularity among elements of a linear transform using matrix decomposition and generates a reduced data-flow graph which preserves the full regularity. We show experimental results obtained using Discrete Cosine Transform (DCT) and Fast Fourier Transform (FFT) and illustrate the effectiveness of the method.

This paper studies a congestion control scheme in integrated variable bit-rate video, audio and data (e. g. , image or text) communications, where each video stream is synchronized with the corresponding audio stream. When the audio and video streams are output, media synchronization control is performed. To avoid congestion, we employ a dynamic video resolution control scheme which dynamically changes the video encoding rate according to the network loads. By simulation, the paper evaluates the performance of the scheme in terms of throughput, loss rate, average delay, and mean square error of synchronization. Numerical results show the effectiveness of the scheme.

We discussed on relationship between the width of slit ray and the accuracy of the measurement system for surface profile of electric contact. To obtain resolution of 10 [µm], we designed the mechanism which keeps constant the focal length between the object and the lens. As a result, the width of slit ray was clear in the whole surface. A section image could measured exactly and enhanced the resolution.

Contact recording systems have been studied for future magnetic recording disks with a high recording density. Tribological key technologies for ultra-low spacing and high wear performance are required for the contact systems. Particularly, a liquid lubrication system plays an important roll for reducing a mechanical spacing and improving wear performances. However, a lubrication design concept for contact recording systems is not established. In this study, molecular design of lubricants for contact systems will be discussed from a viewpoint of bouncing and wear behaviors. As a result, a minimum bouncing height of 3 nm and a high wear performance were obtained for ion-etched contact sliders by the optimization of design parameters, i. e. pad design and lubricant material.

A new learning method is proposed to enhance the performances of the fuzzy ARTMAP neural network in the noisy environment. It combines the average learning and slow learning for the weight vectors in the fuzzy ARTMAP. It effectively reduces a category proliferation problem and enhances recognition performance for noisy input patterns.

In the floorplan design problem, soft blocks can take various rectilinear shapes. The conventional floorplanning methods, however, restrict their shapes only to rectangle. As a result, waste area often remains in the layout. Some floorplanning methods have been developed to handle rectilinear hard blocks, however, no floorplanning methods have been developed to optimize rectilinear soft blocks. In this paper, we propose a floorplanning method which places rectilinear soft blocks. The advantages of the method are reducing both waste area and wire length. We present Separate-Rejoin method which efficiently forms rectilinear shapes for soft blocks. The result is obtained quickly because the method is based on the slicing structure in spite of handling rectilinear block. Thus, our method is suitable for practical use in terms of layout area, wire length and processing time. We applied our method to a benchmark example and an industrial data. For the benchmark example, our method reduces waste area by 25% and wire length by 13% in comparison with the conventional rectangular soft block approach.

The structure of bidirectional syndrome decoding for binary rate (n-1)/n convolutional codes is investigated. It is shown that for backward decoding based on the trellis of a syndrome former HT, the syndrome sequence must be generated in time-reversed order using an extra syndrome former H*T, where H* is a generator matrix of the reciprocal dual code of the original code. It is also shown that if the syndrome bits are generated once and only once using HT and H*T, then the corresponding two error sequences have the intersection of n error symbols, where is the memory length of HT.

Penumbral imaging is a technique which uses the facts that spatial information can be recovered from the shadow or penumbra that an unknown source casts through a simple large circular aperture. The technique is based on a linear deconvolution. In this paper, a two-step method is proposed for decoding penumbral images. First a local-statistic filter based on adaptive windowing is applied to smooth the noise; then, followed by the conventional linear deconvolution. The simulation results show that the reconstructed image is dramatically improved in comparison to that without the noise-smoothing filtering, and the proposed method is also applied to real experimental X-ray imaging.

In this paper, we study bifurcations of equilibrium points and periodic solutions observed in a resistively coupled oscillator with voltage ports. We classify equilibrium points and periodic solutions into four and eight different types, respectively, according to their symmetrical properties. By calculating D-type of branching sets (symmetry-breaking bifurcations) of equilibrium points and periodic solutions, we show that all types of equilibrium points and periodic solutions are systematically found. Possible oscillations in two coupled oscillators are presented by calculating Hopf bifurcation sets of equilibrium points. A parameter region in which chaotic oscillations exist is also shown by obtaining a cascade of period-doubling bifurcation sets.

An image recognition system using NEURO4, a programmable parallel processor, is described. Optical flow is the velocity field that an observer detects on a two-dimensional image and gives useful information, such as edges, about moving objects. The processing time for detecting optical flow on the NEURO4 system was analyzed. Owing to the parallel computation scheme, the processing time on the NEURO4 system is proportional to the square root of the size of images, while conventional sequential computers need time in proportion to the size. This analysis was verified by experiments using the NEURO4 system. When the size of an image is 84 84, the NEURO4 system can detect optical flow in less than 10 seconds. In this case the NEURO4 system is 23 times faster than a workstation, Sparc Station 20 (SS20). The larger the size of images becomes, the faster the NEURO4 system can detect optical flow than conventional sequential computers like SS20. Furthermore, the paralleling effect increases in proportion to the number of connected NEURO4 chips by a ring expansion scheme. Therefore, the NEURO4 system is useful for developing moving image recognition algorithms which require a large amount of processing time.

This paper describes the design and performance of a high-speed 6-bit ADC using SiGe HBT for measuring-instrument applications. We show that the Gummel-Poon model suffices for SiGe HBT modeling and then we describe that the folding/interpolation architecture as well as simple, differential circuit design are suitable for ADC design with SiGe HBT. Measured results show that the nonlinearity of the ADC is within 1/2 LSB, and the effective bits are 5. 2 bits at an input frequency of 100 MHz and 4. 2 bits at 200 MHz with 768 MS/s. We also describe some design issues for folding/interpolation ADC.