In this paper, we propose an algorithm of classification by feature partitioning (CFP) which learns concepts in the batch mode. The proposed algorithm achieved almost the same predictive accuracies as the best results of a CFP algorithm presented by Guvenir and Sirin. However, our algorithm is not affected by parameters and the order of examples.

This paper describes an efficient and simple coding algorithm of universally optimal codes for stationary (ergodic) sources and noiseless channel with unequal symbol costs. The symbol cost indicates the required time (or space) for the transmission (or storage) of that symbol, and the cost of any code symbol depends only on that symbol. The proposed coding algorithm mainly consists of two parts. The first part is based on the well-known Ziv-Lempel coding algorighm proposed in 1978 (sometimes called LZ78), and the second part is based on the Varn coding algorithm. The coding algorithm asymptotically achieves an optimal average cost of codes for stationary sources, and also achieves an optimal cost of codes for stationary ergodic sources with probability one. Furthermore, the computational complexity of the proposed coding algorithm is linear with respect to the length of source sequence and coded sequence.

This paper presents a 4-valued content-addressable memory (CAM) for fully parallel template-matching operations in real-time cellular logic image processing with fixed templates. A universal literal is essential to perform a multiple-valued template-matching operation. It is decomposed of a pair of a threshold operation in a CAM cell and a logic-value conversion shared by CAM cells in the same column of a CAM cellular array, which makes a CAM cell function simple. Since a threshold operation together with a 4-valued storage element can be designed by using a single floating-gate MOS transistor, a high-density 4-valued universal-literal CAM with a single-transistor cell can be implemented by using a multi-layer interconnection technology. It is demonstrated that the performance of the proposed CAM is much superior to that of conventional CAMs under the same function.

The temperature dependence of the central wavelength of narrow-band filters is a serious problem for the dense WDM systems. In this study, we realized a temperature independent narrow-band filter at 1.3 µm wavelength. First, we designed an athermal waveguide in which optical path length is independent of temperature by using a finite element method. Using this athermal waveguide, we designed and fabricated a ring resonator. As a result, we successfully decreased the temperature coefficient of central wavelength to 710-4 nm/K, which is 7% of conventional SiO2 waveguide filters and 0.7% of conventional semiconductor waveguide filters.

The problem of non-preemptive scheduling of real-time periodic tasks with specified release times on a uniprocessor system is known as NP-hard problem. In this paper we propose a new non-preemptive scheduling algorithm and a new static scheduling strategy which use the repetitiveness and the predictability of periodic tasks in order to improve schedulabilities of real-time periodic tasks with specified release times. The proposed scheduling algorithm schedules periodic tasks by using the heuristic that precalculates if the scheduling of the selected task leads to the case that a task misses a deadline when tasks are scheduled by the non-preemptive EDF algorithm. If so, it defers the scheduling of the selected task to avoid the precalculated deadline-missing. Otherwise, it schedules the selected task in the same way as the non-preemptive EDF algorithm. Our scheduling algorithm can always find a feasible schedule for the set of periodic tasks with specified release times which is schedulable by the non-preemptive EDF algorithm. Our static sheduling strategy transforms the problem of non-preemptive scheduling for periodic tasks with specified release times into one with same release times for all tasks. It suggests dividing the given problem into two subproblems, making a non-preemptive scheduling algorithm to find two feasible subschedules for the two subproblems in the forward or backward scheduling within specific time intervals, and then combining the two feasible subschedules into a complete feasible schedule for the given problem. We present the release times as a function of periods for the efficient problem division. Finally, we show improvements of schedulabilities of our scheduling algorithm and scheduling strategy by simulation results.

This paper proposes a new method for recovering the original signals from their linear mixtures observed by the same number of sensors. It is performed by identifying the linear transform from the sources to the sensors, only using the sensor signals. The only assumption of the source signals is basically the fact that they are statistically mutually independent. In order to perform the 'blind' identification, some time-correlational information in the observed signals are utilized. The most important feature of the method is that the full information of available time-correlation data (second-order statistics) is evaluated, as opposed to the conventional methods. To this end, an information-theoretic cost function is introduced, and the unknown linear transform is found by minimizing it. The propsed method gives a more stable solution than the conventional methods.

This paper describes an analytic method, experimental results and simulation results for self-heating in a SOI (Silicon On Insulator) high voltage MOS transistor. The new analytic method enabled the temperature-rise caused by self-heating to be measured precisely. The temperature-rise in an operating transistor was evaluated by measuring the change of the source current against the source current without the self-heating. In advance, the relation between the temperature-rise and the current change had been prepared by measuring the current decrease when the hot-chuck temperature had been changed in iso-thermal condition. By using this method, the dependence of the temperature-rise or the current decrease on the operating condition or the thermal resistance were clarified. Furthermore, these measurement results and the thermal resistance which is calculated by a FEM analysis enabled a fully coupled electrothermal device simulation to be analyzed more precisely. The dependence of the current decrease on the buried oxide thickness were also calculated.

Heavy-ion-induced soft errors (single event upset) in submicron silicon-on-insulator (SOI) MOSFETs under space environmental conditions are studied over the temperature range of 100-400 K using three-dimensional device simulator with full-temperature models. The temperature dependence of the drain collected charge is examined in detail when a heavy-ion strikes the gate center perpendicularly. At very low temperatures, SOI MOSFETs have very high immunity to the heavy-ion-induced soft errors. In particular, alpha-particle-induced soft errors hardly occur at temperatures below 200 K. As the temperature increases, the collected charge shows a marked rate of increase. The problem of single event upset in SOI MOSFETs becomes more serious with increasing working temperature. This is because the induced bipolar mechanism is a main factor to cause charge collection in SOI MOSFETs and the bipolar current increases exponentially with increasing temperature. At room and high temperatures, the drain collected charge is strongly dependent on channel length and SOI film thickness.

The convergence characteristics of the adaptive beamformer with the RLS algorithm are analyzed in this paper. In case of the RLS adaptive beamformer, the convergence characteristics are significantly affected by the spatial characteristics of the signals/noises in the environment. The purpose of this paper is to show how these physical parameters affect the convergence characteristics. In this paper, a typical environment where a few directional noises are accompanied by background noise is assumed, and the influence of each component of the environment is analyzed separately using rank analysis of the correlation matrix. For directional components, the convergence speed is faster for a smaller number of noise sources since the effective rank of the input correlation matrix is reduced. In the presence of background noise, the convergence speed is slowed down due to the increase of the effective rank. However, the convergence speed can be improved by controlling the initial matrix of the RLS algorithm. The latter section of this paper focuses on the physical interpretation of this initial matrix, in an attempt to elucidate the mechanism of the convergence characterisitics.

This paper proposes a novel VLSI architecture capable of processing the Lempel-Ziv-based data compression algorithm very fast. The architecture is composed of five main blocks, i.e., a PE-based Match Block, a Consecutive Hit Checker, a Pointer Generator, a Length Generator, and a Code Packer. Flexibility of the PE-based structure makes it possible to adapt to various buffer sizes without any loss of speed or additional control overhead. Since it is designed as a VLSI-oriented architecture, it has simple control logic circuitry. It processes exactly one character per clock cycle and the update of a dictionary buffer is automatically done, therefore it does not require additional accumulated shift operations to prepare for the dictionary buffer. The shift operations have been major problems commonly found in most other architectures. When implemented with the currently available 0.5µm CMOS technology, it is proven by critical path analysis that the architecture can achieve over 100 mega samples (characters) per second with a clock frequency of 100 MHz. This is fast enough for real time data compression for many applications.

A current controlled CMOS output driver was designed by using a temperature-insensitive reference current generator. It eliminates the need for overdesign of the driver transistor size to meet the delay specification at high temperature. Comparison with the conventional CMOS output driver with the same transistor size showed that the ground bounce noise was reduced by 2.5 times and the delay time was increased by 1.4 times, at 25 for 50pF load. The temperature variations of the DC pull-up and pull-down currents of the new output driver were 4% within the temperature range from -15 to 125 compared to the variations of 40 and 60% for pull-up and pull-down respectively for the conventional output driver. The temperature insensitivity of the reference current generator was achieved by multiplying two current components. one which is proportional to mobility and the other which is inversely proportional to mobility, by using a CMOS square root circuit. The temperature variation of the DC output current of the reference current generator alone was 0.77% within the entire temperature range from -15 to 125.

The paper discusses the possibility of building semiconductor lasers whose wavelength stays nearly constant with ambient temperature variation. Several factors affecting the lasing wavelength change with temperature variation in both distributed feedback lasers and Fabry-Perot lasers are addressed and the optimum design of bandgap temperature dependence for the active layer material is discussed. It is pointed out that the most important challenge we face in building temperature-insensitive wavelength lasers is the development of a temperature-insensitive bandgap material for the active layer. Based on published data, it is speculated that such a laser could be developed using a Hg1-xCdxTe/CdTe double heterostructure. Although no data is available yet, we expect a Ga1-xInxAs1-yBiy III-V alloy semiconductor can be used for this purpose. Recently reported T1xIn1-x-yGayP III-V alloy semiconductor might be another promising candidate. Such lasers will greatly advance applications of WDM (Wavelength-Division-Multiplexing) technology to optical fiber communication systems and contribute to network innovations.

We present a topological framework of stepwise specification for concurrent systems in this paper. Some of description techniques can make topologies on the system space. Such topologies corresponds to abstract levels of those description techniques. Using a family of such description techniques, one can specify systems stepwisely. This framework allows to bridge various DTs and modularizing, so that global properties and module properties of systems become to be related to each other. Within this framework, we show derivation of a LOTOS cpecification from temporal logic formulae. An extended version of LOTOS with respect to concurrency is used in this paper. A semantics including concurrency is introduced to do this in this method. The method presented in this paper is applied to mobile telecommunication.

We have studied the performances of several types of vortex flow transistors including prototype flux flow transistors (FFTs), nanobridge vortex flow transistors (NBVFTs) based on a parallel array of nanobridges, planar Josephson vortex flow transistors (planar JVFTs) based on a parallel array of grain boundary Josephson junctions, and JVFTs with a stacked structure (stacked JVFTs). The NBVFTs had considerably higher magnetic field sensitivity and shorter response time than the FFTs. A flux-to-voltage transfer function V/φ of 2.6 m V/φo and a modulation depth of 0.5 mV were obtained for the NBVFT composed of 2 nanobridges, while the current gain was small. The temperature dependence of the device parameters (the dynamic resistance and the inductance) suggests that the surface barrier to the Abrikosov vortex entry into the nanobridge strongly contributes to the relatively large V/φ values. The response time of the nanobridge is estimated to be 5 ps. On the other hand, the JVFTs showed large current gains because of the small kinetic inductance of the Josephson junction. The planar JVFT composed of 3 Josephson junctions with an asymmetrical geometry showed a current gain of 2.2 at 4.2 K. Also, the stacked JVFT showed the current gain of 2.0, while the maximum value of V/φ was 210 µV/φo. The mutual inductance between the control line and the superconducting loop within the transistor was enhanced in the stacked JVFT. This enhancement may yield a short response time compared to that of the planar JVFT. When we apply these vortex flow transistors, we should take account of the properties peculiar to each transistor.

We study Lempel-Ziv-Yokoo algorithm [1, Algorithm 4] for universal data compression. In this paper, we give a simpler implementation of Lempel-Ziv-Yokoo algorithm than the original one [1, Algorithm 4] and show its asymptotic optimality for a stationary ergodic source.

A laser power optimizing method for multi-pulse recording is described. Multi-pulse recording uses the recording pulse formed by bias part and comb part. To obtain best readout signal characteristics and reduce the time for optimizing, new mark pattern is recorded and then two parts of the recording pulse are individually adjusted by evaluating the detected signals during pre-write testing. At the optimized laser power by this method, a good qualitative eyepattern was obtained. As a result, this new method proves to be suitable for the multi-pulse recording and adapted to various disks with different recording properties.

This paper describes the effects of operating temperature on delay time in a 1-V multi-threshold CMOS(MTCMOS) circuit, Delay-time analysis including the temperature factor shows that the delay-time variation of the CMOS circuit becomes amall for low-voltage operation and the variation is mainly determined by the threshold voltage and its variation-rate with temperature. As a design method of a MTCMOS circuit with both high-threshold and low-threshold MOSFETs, optimization of the low-threshold voltage at which the delay-time of the circuit is independent of operating temperature is described in detail. The validity of the design method is confirmed by the evaluation of a gate-chain TEG and a 1-V 12 K-gate digital-filter LSI fabricated with o.5-µm MTCMOS technology.

Adapting the principle of parametron oscillation, a small implantable temperature sensor requiring no internal power supply is described. Since this sensor's oscillation frequency is half that of the excitation frequency, the oscillated signal can be measured from the reception side, free of any signal, interference, simply by positioning the sensor and the excitation antenna so that; 1) they are separated up to 95 cm in the air; 2) a 41 cm gap, the phantom equivalent of the thickness of the human abdomen maintain between them. In the temperature-dependent quartz resonator sensor, oscillation occurs only when frequency and temperature correspond. The excitation power is then adjusted so that the frequency bandwidth narrows. As a result, the margin of error in measuring the temperature is minimized; (0.07).

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.

Three dimensional model based coding methods are proposed as next generation image coding methods. These new representations need 3D reconstruction techniques. This paper presents a method that extracts the surfaces of static objects that occlude other objects from a spatiotemporal image captured with straight-line camera motion. We propose the concept of occlusion types and show that the occlusion types are restricted to only eight patterns. Furthermore, we show occlusion type pairs contain information that confirms the existence of surfaces. Occlusion information gives strong cues for segmentation and representation. The method can estimate not only the 3D positions of edge points but also the surfaces bounded by the edge points. We show that combinations of occlusion types contain information that can confirm surface existence. The method was tested successfully on real images by reconstructing flat and curved surfaces. Videos can be hierarchically structured with the method. The method makes various applications possible, such as object selective image communication and object selective video editing.