Lots of self-tuning control schemes have been proposed for tuning the parameters of control systems. Among them, pole-assignment schemes have been widely used for tuning the parameters of control systems with unknown time delays. They are usually classified into two methods, the implicit and the explicit methods according to how to identify the parameters. The latter has an advantage to design a control scheme by taking account of the stability margin and control performance. However, it involves a considerably computational burden to solve a Diophantine equation. A simple scheme is proposed in this paper, which can construct a multivariable self-tuning pole-assignment control system, while taking account of the stability margin and control performance without solving a Diophantine equation.

We propose a real-time low-rate video compression algorithm using fixed-rate multi-stage hierarchical vector quantization. Vector quantization is suitable for mobile computing, since it demands small computation on decoding. The proposed algorithm enables transmission of 10 QCIF frames per second over a low-rate 29.2 kbps mobile channel. A frame is hierarchically divided by sub-blocks. A frame of images is compressed in a fixed rate at any video activity. For active frames, large sub-blocks for low resolution are mainly transmitted. For inactive frames, smaller sub-blocks for high resolution can be transmitted successively after a motion-compensated frame. We develop a compression system which consists of a host computer and a memory-based processor for the nearest neighbor search on VQ. Our algorithm guarantees real-time decoding on a poor CPU.

Divisor-Skip Wavelength Division Multiplexing (DS-WDM) ring is an optical interconnection network for workstation clusters or parallel machines which can connect various number of nodes easily using wavelength division multiplexing techniques. However, the wavelength-ordered routing algorithm proposed for the DS-WDM ring requires complicated processes in each router. Here, a new routing algorithm called the comparing dimensional number routing algorithm for the DS-WDM ring is proposed and evaluated. Although the diameter and average distance are almost same as traditional wavelength-ordered routing, the cost and latency are much reduced.

By adopting a network architecture in which not only a calling but also a called terminal can select a wavelength, a novel WDM network becomes possible. This we call Wavelength Assignment Photonic Network (WAPN). In this network wavelengths are a kind of network resources and according to requests from terminals, wavelengths are allocated or assigned to calls. In the system a wavelength used for a call is to be used for another call after the call is terminated. By supplying wavelengths to the home, a bitrate-free, protocol free or even transmission method free network can be realized. In this paper, from a viewpoint of S/N or Q factor, WAPN is evaluated with special focus on the node architecture--i. e. , from the viewpoint of node size, number of switching stages, crosstalk level,and losses, because the allowable node size is the crucial issue to decide the whole network capacity. After brief explanations of this proposed system, the model for system evaluations will be established and a node system is to be evaluated for some practical parameter values considering especially traffic characteristics of a node. As a result of this study a node system with capacity more than 100 thousands erl (about 20 Tbps throughput) can be constructed using present available technologies, which will enable us to construct large WAPN network with radius of 2,000 km and subscribers of about 50 millions.

The hybrid electrical/optical multi-chip integration technique for optical modules for optical network system has been developed. Employing the technique, a 44 broadcast-and-select type optical matrix switch module has been realized. The module consists of four sets of silica waveguide 1 : 4 splitters/4 : 1 combiners, four 4-channel arrays of polarization insensitive semiconductor optical amplifiers with spot-size converters as optical gates, printed wiring chips for electrical wiring and single mode fibers for optical signal interface on planar waveguide platform fabricated by atmospheric pressure chemical vapor deposition. All the gates and the wiring chips were mounted precisely onto the platform at once in flip-chip manner by self-align technique using AuSn solder bumps. Coupling loss between the waveguide and the SOA gate was estimated to be 4.5 dB. Averaged fiber-to-fiber signal gain, on-off ratio and polarization dependent loss for each of the signal paths was 7 dB 2 dB, more than 40 dB and 0.5 dB, respectively. High speed 10 Gb/s photonic cell switching as short as 2 nsec has been successfully achieved.

Since the inception of optical networking, a goal has been to create an all-optical network. The rapid breakthrough for WDM in point to point links has brought this prospect considerably closer, however, at the same time, questions regarding the scalability of the all-optical network remain. In this paper, we review our recent research in this area, partly performed within the European Union project METON (METropolitan Optical Network), and discuss the all-optical approach and different optoelectronic alternatives, mainly of the 2R (reamplify and reshape) type.

The pseudo-inverse model for the associative memory has an iterative algorithm converging to its weight matrix. The present letter shows that the same algorithm except for the lack of self couplings can be derived by simple consideration of the energy of the network state.

This paper proposesd a non-blocking multi-stage ATM switch based on a hierarchical-cell-resequencing (HCR) mechanism and high-speed WDM interconnection and reports on its feasibility study. In a multi-stage ATM switch, cell-based routing is effective to make the switch non-blocking, because all traffic is randomly distributed over intermediate switching stages. But due to the multi-path conditions, cells may arrive out of sequence at the output of the switching fabric. Therefore, resequencing must be performed either at each output of the final switching stage or at the output of each switching stage. The basic HCR switch performs cell resequencing in a hierarchical manner when switching cells from an input-lines to a output-line. As a result, the cell sequence in each output of the basic HCR switch is recovered. A multi-stage HCR switch is constructed by interconnecting the input-lines and output-lines of these basic HCR switches in a hierarchical manner. Therefore, the cell sequence in each final output of the switching fabric is conserved in a hierarchical manner. In this way, cell-based routing becomes possible and a multi-stage ATM switch with the HCR mechanism can achieve 100% throughput without any internal speed-up techniques. Because a large-capacity multi-stage HCR switch needs a huge number of high-speed signal interconnections, a breakthrough in compact optical interconnection technology is required. Therefore, this paper proposes a WDM interconnection system with an optical router arrayed waveguide filter (AWGF) that interconnects high-speed switch elements effectively and reports its feasibility study. In this architecture, each switch element is addressed by a unique wavelength. As a result, a switch in a previous stage can transmit a cell to any switch in the next stage by only selecting its cell transmission wavelength. To make this system feasible, we developed a wide-channel-spacing optical router AWGF and compact 10-Gbit/s optical transmitter and receiver modules with a compact high-power electroabsorption distributed feedback (EA-DFB) laser and a new bit decision circuit. Using these modules, we confirmed stable operation of the WDM interconnection. This switch architecture and WDM interconnection system should enable the development of high-speed ATM switching systems that can achieve throughput of over 1 Tbit/s.

An optical cell buffer (OCB) for use in photonic ATM switch, is needed in order to resolve contention between optical cells. A 320-Gb/s-throughput switch system with 32 wavelength channels requires a buffer size of 13 and a wavelength bandwidth of 25 nm. We developed an optical cell buffer with a four-nested-taps configuration and fabricated it with electroabsorption gates and gain clamped optical amplifiers. The output level variation, which determines the stability of operating condition, is less than 2.4 dB under typical conditions and the insertion loss variation is suppressed to within 5 dB. This OCB can be used in a 320-Gb/s photonic ATM switch.

Spot-size-converter integrated semiconductor optical amplifiers have been developed as gate elements for optical switch matrices. An S-shape waveguide has been introduced to prevent re-coupling of unguided light to the output fiber. An angled-facet structure effectively suppressed light reflection at the end facets. Consequently, a high extinction ratio of 70 dB and a high fiber-to-fiber gain of 20 dB were achieved. Sufficient optical coupling characteristics to a flat-ended single-mode fiber with a coupling loss of 3.5 dB were also demonstrated.

Design and evaluation of a high-performance switch architecture for free-space photonic switching systems is described. The switch is constructed of 22 switching elements and employs special multistage interconnection patterns. The connection setup algorithm and the control procedure at the switching elements are based on a "rerouting algorithm."" Performance analysis shows that the blocking probability of the switch is easily controlled by increasing the number of switching stages. Example implementations of this switch are shown in which birefringent plates, polarization controllers, etc. are used.

State of the arts on guided-wave optical switch arrays are reviewed. In this paper, electro-optic Ti:LiNbO3 devices are mainly described in comparison with crosspoint switch element structures and switch array architectures. Packaging technologies and stability problems are discussed for practical system applications. Recent development on other materials such as semiconductor waveguides, thermo-optic glass/polymer waveguides are also reviewed briefly.

To enhance the extinction ratio (ER) of NRZ-to-inverted-RZ converter based on cross-gain compression of a semiconductor optical amplifier (SOA), a modified terahertz optical asymmetric demultiplexer (TOAD) is cascaded. ER is improved from 1.6-6.7 dB to 5.4-14.5 dB, depending on the intensity of input optical NRZ signal. The proposed NRZ-to-inverted-RZ converter enhances and regulates ER to a high value (14.5 dB) for very wide optical NRZ signal intensity range.

This paper presents an algorithm for viewpoint-based similarity discernment of linguistic concepts on Semantic Network Array Processor (SNAP). The viewpoint-based similarity discernment plays a key role in retrieving similar propositions. This is useful for advanced knowledge processing areas such as analogical reasoning and case-based reasoning. The algorithm assumes that a knowledge base is constructed for SNAP, based on information acquired from the WordNet linguistic database. The algorithm identifies paths on the knowledge base between each given concept and a given viewpoint concept, then computes a similarity degree between the two concepts based on the number of nodes shared by the paths. A small scale knowledge base was constructed and an experiment was conducted on a SNAP simulator that demonstrated the feasibility of this algorithm. Because of SNAP's scalability, the algorithm is expected to work similarly on a large scale knowledge base.

This paper proposes a method to transform a CORDIC ARMA lattice filter, which is originally realized for signal analysis, into a signal synthesis lattice filter (CORDIC ARMA lattice synthesis filter). In order to perform such a transformation and then obtain the CORDIC ARMA lattice synthesis filter, we must implement the followings with CORDIC: (1) the structure of the altered lattice filter; and (2) an angle calculation module. However, we cannot achieve such an implementation as an extension of the CORDIC ARMA lattice filter algorithm. Therefore, this paper proposes CORDIC implementation schemes for both the structure and module, and then we realize the CORDIC ARMA lattice synthesis filter. By using CORDIC processors, the elementary sections of the CORDIC ARMA lattice synthesis filter are efficiently implemented without any multipliers. Since the obtained signal synthesis lattice filter consists of dedicated CORDIC processors, it keeps the advantage of the CORDIC ARMA lattice filter, that is a simple structure.

Based on a previous work on handwritten Japanese kanji character recognition, a postprocessing system for handwritten Japanese address recognition is proposed. Basically, the recognition system is composed of CombNET-II, a general-purpose large-scale character recognizer and MMVA, a modified majority voting system. Beginning with a set of character candidates, produced by a character recognizer for each character that composes the input word and a lexicon, an interpretation to the input word is generated. MMVA is used in the postprocessing stage to select the interpretation that accumulates the highest score. In the case of more than one possible interpretation, the Conflict Analyzing System calls the character recognizer again to generate scores for each character that composes each interpretation to determine the final output word. The proposed word recognition system was tested with 2 sets of handwritten Japanese city names, and recognition rates higher than 99% were achieved, demonstrating the effectiveness of the method.

Design and evaluation of a high-performance switch architecture for free-space photonic switching systems is described. The switch is constructed of 22 switching elements and employs special multistage interconnection patterns. The connection setup algorithm and the control procedure at the switching elements are based on a "rerouting algorithm." Performance analysis shows that the blocking probability of the switch is easily controlled by increasing the number of switching stages. Example implementations of this switch are shown in which birefringent plates, polarization controllers, etc. are used.

In this paper, the computational issue in the problem of learning Bayesian belief networks (BBNs) based on the minimum description length (MDL) principle is addressed. Based on an asymptotic formula of description length, we apply the branch and bound technique to finding true network structures. The resulting algorithm searches considerably saves the computation yet successfully searches the network structure with the minimum value of the formula. Thus far, there has been no search algorithm that finds the optimal solution for examples of practical size and a set of network structures in the sense of the maximum posterior probability, and heuristic searches such as K2 and K3 trap in local optima due to the greedy nature even when the sample size is large. The proposed algorithm, since it minimizes the description length, eventually selects the true network structure as the sample size goes to infinity.

Predicate Circumscription is a fundamental formalization of common sense reasoning. In this paper, we study a new approximation formula of it. In our previous works, we investigated Lifschitz's pointwise circumscription and its generalization, which functions as a finite approximation to predicate circumscription in the first-order framework. In this paper, at first, we study the ability of the generalized pointwise circumscription more closely, and give a simple example which shows that it cannot be complete even when a minimized predicate has only finite extension on the minimal models. Next, we introduce a new approximation formula, called finite constructive circumscription, in order to overcome that limitation. Finally, we compare expressive power of the two approximation methods with of predicate circumscription schema, and propose a open problem that should be solved to clarify that the completeness of predicate circumscription schema with respect to minimal model semantics.

State of the arts on guided-wave optical switch arrays are reviewed. In this paper, electro-optic Ti:LiNbO3 devices are mainly described in comparison with crosspoint switch element structures and switch array architectures. Packaging technologies and stability problems are discussed for practical system applications. Recent development on other materials such as semiconductor waveguides, thermo-optic glass/polymer waveguides are also reviewed briefly.