We propose and analyze a new type of intersectional optical switch using positive refractive index variation in quantum well structure. The switch structure has a built-in refractive index difference in the waveguide, due to which the incident light is reflected to cross port at the OFF state. When the electric field applied to the electrode (ON state), the built-in refractive index difference vanishes by the positive refractive index variation in the quantum well, and the light transmits to straight port. Low insertion loss of lesser than 1 dB and high extinction ratio of more than 20 dB can be obtained at both cross and straight port.

This paper describes state-of-the-art process and device technologies for 3-D ICs and the prospect of its possible applications. 3-dimensional monolithic multilayer structures are expected to be appropriate for high density CMOS and image processing devices. Memory cell and fundamental gate structures have been fabricated with stacked PMOS and NMOS layers. A functional model chip which integrates photosensors, A/D converterss and arithmetic logic units demonstrated a real time image processing capability based on the parallel signal processing. The 3-D structure essentially offers a lot of advantages over conventional ULSI structures, but innovative technology improvement in SOI (Silicon-on-Insulator) and refractive metal interconnection is necessary for realizing practically available 3-D chips.

Cylindrical dielectric waveguide with a periodically varying radius are investigated numerically. The mode-matching method that matches the boundary conditions in the sense of least squares in applied to this problem, using the hybrid-modal representation. The accurate numerical results of the dispersion relations and field distribution are presented for the HE11 mode. It is shown that the attenuation rate in the stopband is significantly smaller than that of TE01 mode, whereas the HE11 mode suffers an additional power leakage due to the coupling with EH11 and HE12 modes of radiation region.

The application of 3D-LSIs for character recognition image sensing processors in described. Three-dimensional LSIs will achieve very high performance by exploiting the structural parallelism by way of the inherence parallelism of an algorithm. As the first step, the three-story structured image sensing processor was implemented integrating 210 pixel photodiodes and 10.4 thousand transistors on a 5.04 mm 11.20 mm die. It is able to sense 6 characters of image at the same time and recognize 64 kind of characters, those are alphabet in capital and lower case, Arabic numerals and some symbols, each consists of 5 7 bit matrix. A four-story structured image sensing processor, which is the second step for realizing the advanced image sensor, integrating 5040 pixel photodiodes and 0.22 million transistors on a 14.3 mm square single die is currently under implementation. The present chip allows 20 times larger degree of data parallelism and several 10 times higher speed of data matching than the previous chip. And some other advantages have been achieved in its functions. Before the implementation of the present chip, its test element circuits were fabricated successively and the functions of the circuit blocks were confirmed. Each floor of 0.6 µm thick SOI film was recrystallized with Ar laser irradiation by the M-shaped beam method with parallel groove structure. The grain boundaries and defects are confined within each ridge region and the defect free single crystal Si film, whose crystal orientation is aligned to the (100) silicon on the lower floor, is grown on each groove region. The maximum temperature of atmosphere during fabrication process was 900. Both chips are made of a number of simple processing elements working in parallel to speed up a computation. So far only several floors can be fabricated as a single die. However the technology has been steadily progressing. The real "intelligent" image sensing processor will be implemented in the near future with 3D integration technology.

A trimming technique for the active RC filter is proposed. This method requires only once of the measurement of initial filter response to find the trimming resistance values. The features of this method are that the roughly selected initial element values are acceptable and the resulting trimming resistance values always increase, which is convenient for the usual laser trimming system.

Logarithmic arithmetic (LA) is a very fast computational method for real numbers. And its precision is better than a floating point arithmetic of equivalent word length and range. This paper shows a method to use LA in computer graphics--picture generation of almost any kind. Various experiments are done--from curve drawing to 3D image generation. The results are all excellent for quality and speed.

Even though coding theory applications in fault tolerant computing started with Hamming code invention, their developments were made almost independently from those in information and communication theories after this initiation. This paper gives a brief overview on coding theory applications in fault tolerant computing. A more detailed survey was made on the most important recent developments. Since there are many items of mutual interest to engineers in both fields, mutual stimulations and cooperations between them would be highly appreciated for future mutual developments in coding theory applications.

The dependence of mode partition characteristics of 1.3 µm Fabry-Perot laser diodes on the modulation frequency and the modulation code has been investigated. From measurements with the frequency domain method and a simple analysis, it is confirmed that the modulation frequency dependence of k-value is caused by a competition among longitudinal modes which occurs with a time constant of several nano seconds. The mode partition characteristics in NRZ code is more affected by this mode competition than that in RZ code. Nevertheless, the k-value in NRZ code at modulation frequency fb is about the same as that in RZ code at modulation frequency fb/2. A simple formula which gives the k-value as a function of the modulation frequency is derived.

Learning control is a new approach to the problem of skill refinement for robotic systems by repetitive training. A class of simple learning control algorithms with a forgetting factor and without use of the derivative of velocity signals for motion control of robot manipulators is proposed and the convergence property is discussed. The robustness of such a learning control scheme with respect to initialization errors, disturbances, and measurement noise is studied extensively. It is proved that motion trajectories converge to a neighborhood of the desired one and eventually remain in it. In the argument the passivity of robot dynamics and displacement robot dynamics plays a fundamental role. Relations of the size of attraction neighborhoods with the magnitudes of initialization errors and other disturbances are obtained, which suggests a rule for selection of the forgetting factor in the progress of learning. Based on these results, two classes of learning control called "interval training" and "selective learning" are proposed in order to accelerate the speed of convergence.

This paper newly proposes HOMomorphic Transformer (HOMT) in order to formalize relations among strictness-related analyses (SRAs) on first-order functional programs. A HOMT is defined to be a composition of special instances of abstract interpretation, and has enough ability to treat known SRAs including head/tail/total strictness detection on nonflat domains. A set of HOMTs, furthermore, is an algebraic space such that some composition of HOMTs can be reduced to a simpler HOMT. This structure gives a transformational mechanism between various SRAs, and further clarifies the equivalence and the hierarchy among them. First, we show a construction of a HOMT as a composition of Unit-HOMTs (U-HOMTs) which are specified by quadruplet representations. Second, algebraic relations among HOMTs are shown as reduction rules among specific pairs of quadruplet representations. Thus, hierarchy among HOMTs can be clarified by finding some adequate quadruplet representation which bridges a HOMT to the other. Third, various SRAs are formalized as HOMTs in either forward or back-ward manners. They are also shown to be safe under unified discussions. Finally, their equivalence and hierarchy are examined in terms of an algebraic structure of HOMTs.

This paper considers processor utilization in faulty hypercube multiprocessor. The utilization is proportional to the continuity of processor allocation model based on Gray code. Busy and faulty processors make this model fragmented. That prevents assigning of larger tasks onto hypercube and decreases processor utilization. A set of procedures is derived which reassigns active tasks so that a new task configuration along with faulty processors makes as little damage as possible to the continuity of allocation model. First, a hypercube fragmentation measure is defined and a task reassigning technique presented. Then, procedures are given which determine: (1) active tasks to be reassigned, (2) their new optimal locations and (3) the shortest reassigning paths. At last, it is proved that while increasing processor utilization, presented scheme minimizes task reconfiguration overhead.

The electrical properties of thin-film SOI (silicon-on-insulator) MOSFETs, revealed by two-dimensional device simulation and experiments using electron-beam recrystallized SOI films, are reviewed and their technological perspectives are discussed. It is shown that thin-film SOI devices have a number of advantages along with some disadvantages. Carrier confinement by an interlayer SiO2 enhanced the influence of the gate electrode on the channel potential, thereby realized a high punchthrough resistance, making impurity doping into the SOI films unnecessary. The subthreshold slope factor exhibited a nearly ideal behavior, although it was somewhat degraded in the short channel region due to a two-dimensional capacitance coupling between the channel and the source or the drain. A very small capacitive-coupling between the channel and the silicon substrate made the vertical electric field extremely small, bringing about a significant increase in carrier mobility. The kink effect was confirmed to disappear due to an elevated SOI potential, which prevented impact-ionized holes from accumulating in the SOI body. The drain-current overshoot was found to be improved drastically, indicating that excess holes quickly recombine with electrons after gate turn-on, bringing about a stabilized SOI potential. However, the drain breakdown voltage had a tendency to decrease with SOI thinning, which proved to be due to an increase in the electric field at the drain. CMOS ring oscillators made with 2 µm design rule operated approximately three times faster than bulk counterparts at room temperature. It is predicted that thin-film SOI MOSFETs will have a better scalability than bulk MOSFETs not only because of their high punchthrough resistance, but because of a number of additional advantages, such as ease in device isolation as well as shallow junction formation, no impurity-induced problems, and possibility of a different scaling scenario from that in bulk devices, and so on. It is concluded that, despite some technological barries, thin-film SOI MOSFETs can offer quite a viable alternative to bulk MOSFETs as high density ULSIs, while achieving very high speed.

A new SOI device structure--a fully DEpleted Lean channel TrAnsistor (DELTA)--which has a new vertical gate structure and an ultra-thin film, bulk Si SOI structure, is proposed. Through experiments and simulation, its fabrication processes and device characteristics are discussed. By using such a new device structure, crystal quality problems caused by recrystallization of poly-Si are solved. DELTA provides a 7.5 times larger channel current than that of conventional planar MOSFETs with the same mask layouts. This is due to a vertical channel structure and a thin film effect. Also, DELTA shows an excellent subthreshold swing of 62 mV/decade. Furthermore, by using a two-carrier device simulator, the punchthrough phenomena in thin film SOI MOSFETs are reexamined from the viewpoint of hole behavior in the substrate. As a result, it was found that the punchthrough resistance of thin film SOI MOSFETs is not always stronger than that of conventional ones. Despite disappearance of the so-called substrate floating effects, attention will still have to be paid to hole behavior in realizing sophisticated SOI devices.

Weibull-distributed ground, sea, sea-ice and weather clutter were measured in Japan for various radar resolutions and wavebands. Weibull clutter and its suppression techniques are reviewed. Especially, Weibull CFAR in two-dimensional clutter rejection system is emphasized.

Classification algorithms with hierarchical structure are quite effective for the classification of remotely sensed multi-spectral images because the data are vast in volume and have redundancy in spatial, spectral and/or, in some sense, temporal structure. The algorithms bring us high speed and high accuracy in the classification. A couple of hierarchical algorithms developed by the authors in spectral and spatial meaning are described with experimental results.

A numerical analysis was made of anomalous modal interference patterns of the sunrise VLF signals as observed on transequatorial east-west paths. The Earth-ionosphere waveguide modal propagation parameters were obtained below an anisotropic inhomogeneous ionosphere with the realistic earth's magnetic field and an exponential electron density profile at a frequency of 18.6 kHz. Numerical estimation of the mode conversion coefficients of day modes to night modes was also made for some sunrise terminator model. Dominantly propagating modes which produced modal interference effects in a nighttime waveguide were identified from the efficiency of the generation of nighttime modes by the first day mode in passing through the terminator. Large reduction in the mode conversion ratio of the two dominantly propagating modes at night within the equatorial region was caused by the reduction in the efficiency of the conversion of day mode 1 into dominantly propagating lower night mode on account of a change in mode character along the path. Anomalous increase in the interference spacing near the magnetic equator was obtained numerically using some exponential profiles although its maximum value was two times as large as that obtained experimentally.

This paper describes the advanced underground radar techniques developed by authors using signal processing to noise and clutter rejection, to pulse compression, to antenna beam compression and to target's identification. Underground radars which were developed and are developing in Japan are also introduced.

A nonlinear dynamic circuit model is proposed to represent the differential-algebraic equations arising from the analysis of power system transient stability. By using the circuit-theoretic model, the following results are obtained. (1) Conditions are derived for the existence of Hamiltonian formulation of power systems. (2) A formula for calculating the critical reclosing time is derived using the Hamiltonian. (3) Conditions are obtained for the power system to reach synchronism asymptotically.

A new concept of fuzzy tensions and fuzzy potentials is proposed as a mathematical tool for qualitative analysis of network problems. In this paper we first describe modeling of curriculum networks and fail-safe networks in which the concept of fuzzy tensions appears naturally as a well-balanced curriculum plan or reliability assignment. Algebraic properties of fuzzy tensions and potentials are thoroughly investigated and consistency of specifications is shown to be expressible by a simple condition on circuits of the underlying network.