Generalizations of the classical ngram indexing techique provide a powerful tool for the fast retrieval of tree structures. We investigate the special case of binary trees, which are heavily used, for example, in computer linguistics: Given a database T{t1,...,tn} of labeled binary trees and a query tree q, find efficiently all trees t T that contain q as subtree. For supporting queries of this type, we propose an indexing technique that covers the database trees t T with smaller trees of a fixed calss. Thus, each index record represents a subtree that is contained in at least one database tree. To answer a given query q, the database trees of T that contain all of q's cover trees are preselected as candidates, which in turn are tested rigorously for containment of q. We present results from two test suites: one with databases of 10,000 randomly generated binary trees each and one with the 29,394 most extensive phrase structure trees found in the morphosyntactical analysis of the Old Testament's Hebrew texts Genesis, Exodus,and Leviticus.

In this paper, we analyze the convergence behavior of the CMA (Constant Modulus Algorithm) adaptive array working under the steepest decent method, and investigate how to achieve the highest possible output SINR (Signal to Interference plus Noise Ratio). In multipath radio environments, CMA sometimes suppresses the desired signal (stronger one) and selects to receive the interference (the weaker one) resulting in the low output SINR. This is one of the problems met in an optimization system under a nonlinear control equation where there are two or more local minima of the cost function and the final state depends on the initial condition. The study can be done only numerically by starting from various initial values. In our analysis of the CMA adaptive array in multipath radio environments, we will assume that there are two waves which are radiated from the same source and try to find out what conditions may affect the convergence behavior. In this process, we discover the effect of the neglected factor by the previous papers and revise the initial condition to guarantee the reception of the desirable wave. In conclusion, we propose the prescription of the initial weights of the array elements as well as the choice of preferable arrays.

This paper describes a new intelligent computer assisted instruction (ICAI) system for Japanese beginners to learn Korean composition. This system is supported by speech synthesis which is generated by a new method for arbitrary sentences of Japanese and Korean using the natural speech data-base.

In general, multimedia files are much larger than ordinary text files because they consist of multiple monomedia. In order to process large multimedia files in real time, the file system must be able to store and access files efficiently. In th UNIX s5 file system, a multimedia file may be scattered into many disk blocks over the entire disk space, and accessing a multimedia file requires a considerable amount of time for random disk head movement. This paper proposes the internal structure of a multimedia file and its inode which is modified from UNIX s5 file system's. Also, we propose a mechanism for allocating and deallocating contiguous disk blocks for large multimedia files using the bitmap tree and compares its performance with that of the UNIX s5 file system. Our results show that the proposed mechanism reduces considerably the number of disk I/Os required to allocate and deallocate contiguous disk blocks. It also reduces the total access time for large multimedia files by approximately 95% due to the contiguous allocation of disk spaces.

In this paper, electromagnetic scattering by infinite double two-dimensional periodic array of resistive upper and lower elements is considered. The electric field equations are solved by using the moment method in the spectral domain. Some numerical results are shown and frequency selective properties are discussed.

A fully-differential switched-current (SI) circuit provided with clock-feedthrough (CFT) and common mode rejection and offset compensation schemes is described. Different from a conventional SI memory cell, it takes the difference between two differential inputs to deliver the balanced differential currents. Transistor level simulations and error analyses are given to demonstrate its performance.

The disturbance-rejection problem is to find a feedback control law for linear control systems such that the influence of disturbances is completely rejected from the output. In 1970 Wonham and Morse first studied this problem in the framework of the so-called geometric approach. On the other hand, in 1985 Ghosh studied parameter insensitive disturbance-rejection problems with state feedback and with dynamic compensator. In this paper we study the parameter insensitive disturbance-rejection problem with static incomplete-state feedback for linear multivariable systems in the framework of the geometric approach from the mathematical point of view. Necessary conditions and/or sufficient conditions for this problem to be solvable are presented. Finally an illustrative example is presented.

I have examined factors for implementing a high-speed, low-power-consumption thermal head. In conventional thermal heads, a heat insulation layer is provided between the heating resistor and the radiator. I found it desirable to implement fast operation and low power consumption to lower the thermal conductivity of the heat insulation layer and to thin the heat insulation layer. I also found there is an optimum heat characteristic to the thickness of one heat insulation layer. I assumed polyimide as a material for the heat insulation layer which could materialize the hypothesis, and studied necessary items based on the thermal calculation. I manufactured a trial thermal head on the basis of this result and confirmed that our assumptions were correct. In addition, to confirm that the assumption is also ultimately correct, I fabricated a trial thermal head only consisting of a heating resistor and without a protective coat and a heat insulation layer. I confirmed that the structure with only the heating resistor exhibited excellent heat response and consumed less power necessary for heating.

The performance of decision-feedback equalization combined with maximum-likelihood detection (DFE/ML) using the fixed-delay-tree-search/decision feedback (FDTS/DF) algorithm was estimated analytically in terms of the length of the feedback-filter and the depth of the ML-detector. Performance degradation due to error propagation in the feedback-loop and in the ML-detector was taken into account by using a Markov process analysis. It was quantitatively shown that signal-to-noise-ratio (SNR) performance in high-density magnetic recording channels can be improved by combining an ML-detector with a feedback-filter and that the error propagation in the DFE channel can be reduced by using an ML-detector. Finally, it was found that near-optimum performance with regard to channel SNR and error propagation can be achieved, over the channel density range from 2 to 3, by increasing the sum of the feedback-filter length and the ML-detector depth to six bits.

Recently, some speech recognition methods using fusion of visual and auditory information have been researched. In this paper, a study on the mouth shape image suitable for fusion of visual and auditory information has been described. Features of mouth shape which are extracted from gray level image and binary image are adopted, and speech recognition using linear combination method has been performed. From results of speech recognition, the studies on the mouth shape features which are effective in fusion of visual and auditory information have been performed. And the effectiveness of using two kinds of mouth shape features also has been confirmed.

This paper addresses approaches to enhancement of performance of the CMA (Constant Modulus Algorithm) adaptive array antenna in multipath environments that characterize the mobile radio communications. The cost function of the CMA reveals that it has an AGC (Automatic Gain Control) procedure of holding the array output voltage at a constant value. Therefore, if the output voltage by the initial weights is different from the object value, then the CMA may suffer from slow convergence because suppression of the multipath waves is delayed by the AGC behavior. Our objective is to improve the convergence characteristics by adopting the differential CMA for the adaptive array algorithm. First, the basic performance of the differential CMA is clarified via computer simulation. Next, the differential CMA is incorporated into the eigen-beamspace system in which the eigenvectors of the correlation matrix of array inputs are used in the BFN (Beam Forming Network). This BFN creates the optimum orthogonal multibeams for radio environments and works helpfully as a preprocessor of the differential CMA. The computer simulation results have demonstrated that the differential CMA with the eigen-beamspace system has much better convergence characteristics than the conventional CMA with the element space system. Furthermore, a modified algorithm is introduced which gives the stable array output voltages after convergence, and it is confirmed that the algorithm can carry out more successful adaptation even if the radio environments are changed abruptly.

In the program development process, it is ofren necessary for programmers to know the differences between two programs, or two different versions of a program. Since programs have structures such as iteration statement and selection statement, applying text-based tools such as UNIX diff to identify the differences may produce unsatisfactory results. In this paper, we exploit a tree as the internal representation of a program, obtain the mapping between two trees and display the program differences visually based on the mapping and pretty-printing technique so that the structural differences can be identified immediately.

We believe that virtual world communication will subsume BBS and visual communication. Accordingly, we proposed the networked virtual world "Interspace" for visual communication. If we are to achieve education and training in this world, techniques to receive and transmit information without any special training are necessary. The traditional "easy" ways of transmitting information are talking and drawing. In Interspace, users can already talk each other. In this paper we focus on drawing. In daily life we communicate through drawings in various situations. At this time it is important to recognize who is drawing and where the participants are watching. It is difficult to realize these functions using conventional media, but it is possible to realize them in virtual space. In virtual space, the system can clearly represent who is drawing and where participants are watching; expressing topics in virtual space frees us from many physical restrictions. In this paper we discuss the process of drawing when many participants share topics in virtual space; the necessary conditions for our system are considered. We design a system that offers functions to make drawing sheets, to display the view fields of participants, and to share visual fields. Furthermore, we propose the mode of InterSheet called "InterMirror" which shows mirror images of partners and their drawings. We make a prototype and evaluate it. The results indicate the synergistic effect of drawing with voice and the usefulness of drawing for communication in virtual space.

A numerical scheme to analyze a three-dimensional perfectly conducting body that has edges and corners is presented. The geometry of the body can be arbitrary. A new formulation using boundary element method has been developed. This formulation allows that a scatterer has edges and corners, where the behavior of the electromagnetic fields become singular.

In this paper, we present for the first time two three-dimensional analytical electrostatic Green's functions for shielded and open arbitrarily multilayered medium structures. The analytical formulas for the Green's functions are simply expressed in the form of Fourier series and integrals, and are applicable to the arbitrary number of dielectric layers. In combination with the complex image charge method, we demonstrate an efficient application to analyze microstrip discontinuities in a three-layered dielectric structure. Numerical results for the capacitance associated with on open-end discontinuity show good agreement with those from a previous paper and the effectiveness of using the analytical Green's functions to analyze three-dimensional electrostatic problems.

Recent high-speed bipolar technologies based on SICOS (Sidewall Base Contact Structure) transistors are reviewed. Bipolar device structures that include polysilicon are key technologies for improving circuit characteristics. As the characteristics of the upward operated SICOS transistors are close to those of downward transistors, they can easily be applied in memory cells which have near-perfect soft-error-immunity. Newly developed process technologies for making shallow base and emitter junctions to improve circuit performance are also reviewed. Finally, complementary bipolar technology for low-power and high-speed circuits using pnp transistors, and a quasi-drift base transistor structure suitable for below 0.1 µm emitters are discussed.

High speed GaAs ICs (Integrated Circutis) using FETs (Field Effect Transistors) are reported. As the fabricating techniques, ion implantation processes for both 0.5 µm and 0.2 µm gate FETs using W/Al refractory metal and 0.2 µm recessed gate process with MBE grown epitaxial wafers are shown. These fabrication processes are selected depending on the circuit speed and the integration level. The outline of the circuit design and the examples of ICs, which are developed for 10 Gb/s optical communication systems, are also shown with the obtained characteristics.

This letter is concerned with the evaluation of the average computational complexity of the maximum likelihood decoding of a linear block code using its trellis diagram. Each section of the L-section minimal trellis diagram for a linear block code consists of parallel components which are structurally identical subgraphs without cross connection between them. A parallel component is also known to be decomposed into subgraphs, and a decoding algorithm by using the structure of the subgraphs of parallel components was proposed, and an upper bound on the worst case computational complexity was derived. In this letter, the average computational complexity of the decoding algorithm is evaluated by computer simulation. We evaluated the average numbers of additions and comparisons performed in the decoding algorithm for example codes, (64,45) extended and permuted binary primitive BCH code, the third order Reed-Muller (64,42) code and its (64,40) subcode. It is shown that the average numbers are much smaller than those for the worst case, and hence the decoding algorithm is efficient when the number of sections, L, is small, say 4 or 8, for the example codes. Especially, for the (64,45) extended binary primitive BCH code with L4, the average numbers of additions and comparisons in the decoding algorithm for finding the survivor's metric of each state after finding the smallest metric among parallel branches are about 1/50 and 17/100 of those in the conventional exhaustive search, respectively. The number of additions and comparisons by the conventional search for all the example codes is smallest when L is 4. As a result, the decoding algorithm with L4 gives the smallest number of operations among those decoding methods considered here.

We consider the identification of a class of systems which are both time-varying and nonlinear. Time-varying nonlinear systems are often encountered in practice, but tend to be avoided due to the difficulties that arise in modelling and estimation. We study a particular time-varying polynomial model, which is a member of the class of time-varying Wiener models. The model can characterise both time-variation and nonlinearity in a straightforward manner, without requiring an excessively large number of coefficients. We formulate a procedure to find least-squares estimates of the model coefficients. An advantage of the approach is that systems with rapidly changing dynamics can be characterised. In addition, we do not require that the input is stationary or Gaussian. The approach is validated with an application to an automobile modelling problem, where a time-varying nonlinear model is seen to more accurately characterise the system than a time-invariant nonlinear one.

The traceability of data flow diagrams against structure charts is very important for large software development. Specifying if there is a relationship between a data flow diagram and a structure chart is a time consuming task. Existing CASE tools provide a way to maintain traceability. If we can extract the input-output relationship of a system from a structure chart, the corresponding data flow diagram can be automatically generated from the relationship. For example, Benedusi et al. proposed a reverse engineering methodology to reconstruct a data flow diagram from existing code. The methodology develops a hierarchical data flow diagram from dependency relationships between the program variables. The methodology, however, transforms each module in structure charts into a process in data flow diagrams. The reconstructed diagrams may have different processes with the same name. This paper proposes a transformation algorithm that solves these problems. It analyzes the structure charts and extracts the input and ouput relationships, then determines how the set of outputs depends on the set of inputs for the data flow diagram process. After that, it produces a data flow diagram based on the include operation between the sets of output items. The major characteristics of the algorithm are that it is simple, because it only uses the basic operations of sets, it generates data flow diagrams with deterministic steps, and it can generate minimal data flow diagrams. This process will reduce the cost of traceability between data flow diagrams and structure charts.