We propose an nn optical switch that is suitable for flexible and reliable optical access networks and for reconfigurable optical inter-module connections in large-scale processing systems. The switch consists of an intersecting waveguide matrix, matching oil, and microactuators. Switching is based on the movement of oil due to capillary pressure, which is controlled by the microactuator. The necessary switching conditions were calculated and the results showed that both the oil volume and the microactuator position must be controlled. A trial optical switch was fabricated to test the switching principle, and switching and self-holding were both confirmed. These results show the feasibility of a very small self-holding nn optical switch that uses a waveguide matrix and microactuators made by using microfabrication technologies.

We have proposed a digital beamforming (DBF) self-beam-steering array antenna which features maximal ratio combining enabling it to efficiently use the received power or to rapidly track the desired signal. The DBF self-beam-steering array antenna utilizes digital signal processing with an active array antenna configuration. ASIC implementation of the digital signal processor is inevitable for DBF antenna application in practical mobile communications environments. In this paper, we present a scheme for implementing a digital signal processor in ASICs using ten FPGAs (Field Programmable Gate Arrays) for the DBF self-beam-steering array antenna. Results of some experiments obtained in a large radio anechoic chamber are shown to confirm a basic function of the system.

Banyan networks are used in multiprocessor computer applications for an ATM switching. In this paper, we study the continuous blocking of the first n-stage which makes the performance of the banyan networks decrease. We use the 2-dilated banyan networks into the banyan networks to remove the continuous blocking of the first n-stage. We call the new networks as the hybrid dilated banyan networks. We explain how to analyze the throughput of this networks at each stage. Based on the analysis of input rate and output rate at each stage, we can design the hybrid dilated banyan networks with the desirable output rate. The result of analysis shows the hybrid dilated banyan networks have higher performance and feasibility than the banyan networks.

Checkers, self-testers, and self-correctors for a function f are powerful tools in designing programs that compute f. However, the relationships among them have not been known well. In this paper, we first show that (1) if oneway permutations exist, then there exists a language L that has a checker but does not have a self-corrector. We then introduce a novel notion of "self-improvers" that trans form a faulty program into a less faulty program, and show that (2) if a function f has a self-tester/corrector pair, then f has a self-improver. As the applications of self-improvers, we finally show that (3) if a function f has a self-tester/corrector pair, then f has a flexible self-tester and (4) if a function f has a self-tester/corrector pair, then f has self-improver that transforms a faulty program into an alomost correct program.

A fault in multi-processing system arbitration circuits result in incorrect arbitration or abnormal operation of the system. A highly reliable system requires dependable arbitration in order to operate properly. Previously, we proposed alternate competing arbitration suitable for highly reliable systems. In this paper, we propose a method for improvement of fault detection and location using additional checkers. This method is effective to maintain reliability of the system.

In this paper we propose a method of formal verification of totally self-checking (TSC) properties of combinational circuits using logic function manipulation. We show that the problem of verification of TSC properties can be transformed to a satisfiability problem of decision functions formed from characteristic functions of a circuit's output code words. Then the problem can be solved using binary decision diagrams (BDD). Experimental results show the effectiveness of the proposed method.

Mechanism of the noise generation caused by the optical feedback in semiconductor laser was experimentally determined. Two types of the mode competition phenomena were confirmed to be the generating mechanisms. Applicability of the self-sustained pulsation to be a noise reduction method was also discussed.

This paper presents a new method for the selftuning control of nonminimum phase discrete-time stochastic systems using approximate inverse systems obtained from the leastsquares approximation. Using this approximate inverse system the gain response of the system can be made approximately unit and phase response exactly zero. We show how unstable polezero cancellations can be avoided. This approximate inverse system can be used in the same manner for both minimum and nonminimum phase systems. Moreover, the degrees of the controller polynomials do not depend on the approximate inverse system. We just need an extra FIR filter in the feedforward path.

This paper reports on a high-speed silicon bipolar transistor with an fT and fMAX of over 40 GHz, we call it the Advanced Boro-silicated-glass Self-Aligned (A-BSA) transistor. In basic BSA technology, a CVD-BSG film is used not only as a diffusion source to form the intrinsic base and the link base regions but also as a sidewall spacer between the emitter and the base polysilicon electrodes. An A-BSA transistor offers three advancements to this technology: (1) a graded collector profile underneath the intrinsic base region to suppress the Kirk effect; (2) an optimized design of the link base region to prevent the frade-off effect between fT and base resistance; and (3) a newly developed buried emitter electrode structure, consisting of an N++-polysilicon layer, a platinum silicide layer, and a CVD tungsten plug, to prevent the emitter plug effect. Furthermore, our transistor uses a BPSG filled trench isolation to reduce parasitic capacitance and improve circuit performance. In this paper, we describe device design, process technology and characterization of the A-BSA transistor, with it we have performed several application ICs, operating at 10Gb/s and above. The A-BSA transistor achieved an fT of 41 GHz and an fMAX of 44 GHz under optimized conditions.

Asynchronous Transfer Mode (ATM) is considered to bo the key technology for realizing B-ISDN. This paper discusses current research on ATM switching nodes for high-speed communication networks. Although some ATM switching nodes have been deployed, much work continues for resolving problems as regards operations and maintainability, such as ATM layer performance evaluation including layered management scheme upon detection of line failure, function test methods regarding channel connectivity for multicasting, and real-time ATM traffic-monitoring mechanism with QoS control. To achieve sufficient ATM node maintainability, the ATM cell transfer quality on the VP and VC levels should be ensured both within the ATM nodes and between adjacent ATM nodes. Since ATM switching nods handle many kinds of virtual paths and virtual channels, each channel's connectivity must be confirmed. This paper proposes ATM layer performance evaluation concept, layered management scheme upon detection of line failure, function test methods for a multicast switch using test cells that periodically pass through pre-determined switching path routes. It also proposes the concept of test cell generation for simulating multiplexed ATM test cells taking ATM truffic characteristics into account. Furthermore, this paper describes a fault diagnosis scheme using test cells that can continually observe the entire ATM connection length in the system. A real-time traffic monitoring hardware configuration and an interface with software control are also discussed and it is clarified that the required functions can be realized by using commercially available DSPs.

We discuss fabrication of InGaAs quantum dot structures using the self-assembling growth technique with the Stranski-Krastanow growth mode in MOCVD, including optical ploperties of the nano-structures. The formation process of the quantum dot islands was clarified by observing the samples grown under various conditions with an atomic force microscope. A trial for self-alignment of the quantum dots was also investigated. On the basis of these results, as the first step toward the ultimate semiconductor lasers in which both electrons and photons are fully quantized, a vertical microcavity InGaAs/GaAs quantum dot laser was demonstrated. Finally a perspective of the quantum dot lasers is discussed, including the bottleneck issues and the impact of the quantum dot structures for reducing threshold current in wide bandgap lasers such as GaN lasers.

We have recently discovered a novel phenomenon for the fabrication of nanostructures. A self-organization phenomenon of a strained InGaAs/AlGaAs system on a GaAs (311)B substrate during metal-organic vapor phase epitaxial growth is described, and nano-scale confinement lasers with self-organized InGaAs quantum disks are mentioned. Low-threshold operation of strained InGaAs quantum disk lasers is achieved under a continuous-wave condition at room temperature. The threshold current is around 20 mA, which is consider-ably lower than that of a reference double-quantum-well laser on a GaAs (100) substrate grown side-by-side. However, the light output versus the driving current exhibits a pronounced tendency towards a saturation compared to that of the (100) quantum well laser. We also discuss new methods using self-organization for nanofabrication to produce high-quality low-dimensional optical devices, considering requirements and the current status for next-generation optical devices.

This paper discusses our newly developed technology for making GaAs/InGaAs/GaAs Tetrahedral-Shaped Recess (TSR) quantum dots. The heterostructures were grown by low-pressure MOVPE in tetrahedral-shaped recesses created on a (111) B oriented GaAs substrate using anisotropic chemical etching. We examined these structures by using cathodoluminescence (CL) measurements, and observed lower energy emissions from the bottoms of, and higher energy emissions from the walls of the TSRs. This suggests carrier confinement at the bottoms with the lowest potential energy. We carried out microanlaysis of the structures by using TEM and EDX, and found an In-rich region that had grown vertically from the bottom of the TSR with a (111)B-like bond configuration. We also measured a smaller diamagnetic shift of the lower energy photoluminecscence (PL) peak in the structure. Based on these results, we have concluded that the quantum dots are formed at the bottoms of TSRs, mainly because of the dependence of InAs composition on the local crystalline structure in this system. We also studied the lateral distribution and vertical alignment of TSR quantum dots by CL and PL measurements respectively. The advantages of TSR quantum dot technology can be summarized as follows: (i) better control in dot positioning in the lateral direction, (ii) realization of dot sizes exceeding limitations posed by lithography, (iii) high uniformity of dot size, and (iv) vertical alignment of quantum dots.

This paper describes an adaptive neural vector quantization algorithm with a deleting approach of weight (reference) vectors. We call the algorithm an adaptive learning and self-deleting algorithm. At the beginning, we introduce an improved topological neighborhood and an adaptive vector quantization algorithm with little depending on initial values of weight vectors. Then we present the adaptive learning and self-deleting algorithm. The algorithm is represented as the following descriptions: At first, many weight vectors are prepared, and the algorithm is processed with Kohonen's self-organizing feature map. Next, weight vectors are deleted sequentially to the fixed number of them, and the algorithm processed with competitive learning. At the end, we discuss algorithms with neighborhood relations compared with the proposed one. The proposed algorithm is also good in the case of a poor initialization of weight vectors. Experimental results are given to show the effectiveness of the proposed algorithm.

In the present communication we propose the application of unsupervised Artificial Neural Networks (ANN) to solve general ill-posed problems and particularly we apply them to the the estimation of the direction of arrival (DOA) of VLF/ELF radio waves. We use the wave distribution method which consists in the reconstruction of the energy distribution of magnetospheric VLF/ELF waves at the ionospheric base from observations of the wave's electromagnetic field on the ground. The present application is similar to a number of computerized tomography and image enhancement problems and the proposed algorithm can be straightforwardly extended to other applications in which observations are linearly related to unknowns. Then, we have proven the applicability and also we indicate the superiority of the ANN to the conventional methods to handle this kind of problems.

Superconductive LSIs with Josephson junctions have features such as low power dissipation and high switching speed. In this paper, we review our developed 4-Kbit RAM with vortex transitional memory cells as an illustration of superconductive LSIs with Josephson junctions. We have developed a fabrication process technology for the 4-Kbit RAM. In the 4-Kbit RAM, 380ps access time and 9.8 mW power dissipation have been experimentally obtained. And also, we have estimated a suitable moat structure to reduce the influence of trapped magnetic structure. The 4-Kbit RAM has been successfully operated with a bit yield of 99.8%. Furthermore, we discuss GHz testing which is one of the most significant issues concerning superconductive digital LSIs.

A 33-cm-Diagonal High-Resolution(1280 1024RGB, which stands for red, green, and blue) TFT-LCD with low, uniform parasitic capacitance between gate electrodes and source/drain electrodes has been developed using Fully Self-Aligned a-Si TFTs. The fabricated TFT-LCD shows no visible seams between block shot exposure regions, even in the display of gray images. In this paper, we describe(1) our full self-alignment technology for the TFTs, including the fabrication process and the technology for reducing OFF current in the TFTs under illumination, (2) SPICE simulation for estimating pixel voltage shift in the fabricated TFT-LCD, and (3) performance results for the fabricated TFT-LCD.

This paper provides an architectural study of optical ring trunk-transmission networks using either Time Division Multiplexing (TDM) or Wavelength Division Multiplexing (WDM). A timeslot arrangement algorithm for distributed controlled TDM rings is proposed that minimizes the number of slots (wavelengths) required in bi-directional ring networks. This algorithm is applied in a straightforward manner to wavelength arrangement in WDM ring networks. The technique, characterized by timeslot (or wavelength) conversion, realizes common add/drop procedures in all Add/Drop Multiplexers (ADMs) when they are connected logically in a mesh topology. A self-healing algorithm is also proposed for network restoration. It offers good performance in terms of protection line-capacity, restoration delay, and survivability against multiple failures.

Various reconfiguration schemes against faults of mesh-connected processor arrays have been proposed. As one of them, the mesh-connected processor arrays model based on single-track switches was proposed in [1]. The model has an advantage of its inherent simplicity of the routing hardware. Furthermore, the 2 track switch model [2] and the multiple track switch model [3] were proposed to enhance yields and reliabilities of arrays. However, in these models, Simplicity of the routing hardware is somewhat lost because multiple tracks are used for each row and column. In this paper, we present a builtin self-reconstruction approach for mesh-connected processor arrays which are partitioned into sub-arrays each using single-track switches. Spare PEs which are located on the boundaries of the sub-arrays compensate faulty PEs in these sub-arrays. First, we formulate a reconfigulation algorithm for partitioned mesh-arrays using a Hopfield-type neural network, and then its performance for reconfigulation in terms of survival rates and reliabilities of arrays and processing time are investigated by computer simulations. From the results, we can see that high reliabilites are achieved while processing time is a little and hardware overhead (links and switches) required for reconstruction is as same as that for the track switch model. Next, we present a hardware implementation of the neural algorithm so that a built-in self-reconfigurable scheme may be realized.

A self-organizing neural network model of spatio-temporal visual receptive fields is proposed. It consists of a one-layer linear learning network with multiple temporal input channels, and each temporal channel has different impulse response. Every weight of the learning network is modified according to a Hebb-type learning algorithm proposed by Sanger. It is shown by simulation studies that various types of spatio-temporal receptive fields are self-organized by the network with random noise inputs. Some of them have similar response characteristics to X- and Y-type cells found in mammalian retina. The properties of receptive fields obtained by the network are analyzed theoretically. It is shown that only circularly symmetric receptive fields change their spatio-temporal characteristics depending on the bias of inputs. In particular, when the inputs are non-zero mean, the temporal properties of center-surround type receptive fields become heterogeneous and alter depending on the positions in the receptive fields.