Since carelessness in driving causes a terrible traffic accident, it is an important subject for a vehicle to avoid collision autonomously. Real-time collision detection between a vehicle and obstacles will be a key target for the next-generation car electronics system. In collision detection, a large storage capacity is usually required to store the 3-D information on the obstacles lacated in a workspace. Moreover, high-computational power is essential not only in coordinate transformation but also in matching operation. In the proposed collision detection VLSI processor, the matching operation is drastically accelerated by using a Content-Addressable Memory (CAM) which evaluates the magnitude relationships between an input word and all the stored words in parallel. A new obstacle representation based on a union of rectangular solids is also used to reduce the obstacle memory capacity, so that the collision detection can be parformed only by parallel magnitude comparison. Parallel architecture using several identical processor elements (PEs) is employed to perform the coordinate transformation at high speed based on the COordinate Rotation DIgital Computation (CORDIC) algorithms. The collision detection time becomes 5.2 ms using 20 PEs and five CAMs with a 42-kbit capacity.

By using measured attenuation time-series data over 2 years at 19.5GHz with an integration time of 1 sec, effects of the integration time on attenuation statistics are presented. It is observed that the effect on cumulative distribution of attenuation and the relation between annual and the worst-month cumulative time percentages are not significant for the practical prediction purposes. The effect is significant in attenuation duration statistics.

This paper describes a bitline control circuit and redundancy technique for high-density dynamic content addressable memories (CAMs). The proposed bitline control circuit can efficiently manage a dynamic CAM cell accompanied by complex operations; that is, a refresh operation, a masked search operation, and partial writing, in addition to normal read/write/search operations. By adding a small supplementary circuit to the bitline control circuit, a circuit scheme with redundancy which prevents disabled column circuits from affecting a match operation can also be obtained. These circuit technologies achieve higher-density dynamic CAMs than conventional static CAMs. These technologies have been successfully applied to a 288-kbit CAM with a typical cycle time of 150 ns.

We studied minority carrier collection in high-density stacked-capacitor DRAM cells using a three-dimensional device simulator. We estimated the collected charge for incident angle, location, and junction size and showed that, compared to the conventional structure by a twin-well process, an n-well-guarded cell array fabricated using a triple-well process effectively reduced the charge injected into cells. The reduction was because the n-well absorbed most of the electrons. A so-called "size-effect" did exist and smaller junctions performed better. We concluded that storage capacitance in a 256 M-bit DRAM cell could be reduced, compared to that in previous devices, which would, in turn, help reduce costs in fabricating high-density DRAM.

A new concept for a positioning satellite system based on a new satellite constellation has been studied. The system needs a minimum of four satellites injected into quasi-geostationary orbit (QGEO) with high inclination. Due to the QGEO characteristic, the satellites are orbiting within continuous visibility range of ground control stations (GCS), from which the satellite time is controlled through the link connections of the feeder and the intersatellite communication (ISC). Consideration is made for the required high accuracy and quality checks against malfunction, wherever the satellites may be positioned. The orbit data processing function, another major function, is performed independently of the time control. The case of global coverage attained by twelve satellites has been studied in this paper. When a constellation of satellites for a global navigation satellite system (GNSS) is designed, conditions to obtain a good geometric dilution of precision (GDOP) at all places and times should be considered. Therefore, the satellites will be spread out in wide directions and are in an asymmetrical arrangement when seen by an observer are considered when setting the parameters of the ephemerides of the constellation. Under the restraints of the designed constellation, the GDOP value distribution for a third of the world map with area time parameters is computed and summarized in histograms for the system evaluation.

A method for constructing a compact non-blocking, large matrix-size, optomechanical switch is proposed. It can be switched arbitrarily by disconnecting and reconnecting ferrules on the matrix board. A 250500, 25-mm-ferrule-pitch, 800W855D945H (mm) switch is fabricated. Although the space above the board is densely packed with many ferrule-terminated-fibers, because of the way in which they are arranged and the control of their length, there is no discernible excess loss due to fiber bending.

The finite-difference beam-propagation method is applied to the analysis of hollow slab waveguides (HSWs). The attenuation constants for the TE0 and TE1 modes are evaluated and compared with those obtained by the perturbation theory. The propagating field and differential power loss in the transition from a straight HSW to a bent HSW are revealed and discussed.

For analyzing the transient electromagnetic fields caused by electrostatic discharge (ESD), a new ESD model is presented here. Numerical calculation is also given to explain the distinctive phenomenon being well-recognized in the ESD event.

This paper proposes a group-to-group communications algorithm that can extend the range of distributed systems where we can achieve active replication fault-tolerance to partner model distributed systems, in which all processes communicate with each other on an equal footing. Active replication approach, in which all replicated processes are active, can achieve fault-tolerance with low overhead because checkhpoint setting and rollback are not required for recovery from process failure. This algorithm guarantees that each replicated process in a process group has the same execution history and that communications between process groups keeps consistency even in the presence of process failure and message loss. The number of control messages that must be transmitted between processes for a communication between process groups is only a linear order of the number of replicated processes in each process group. Furthemore, this algorithm reduces the overhead for reconfiguration of a process group by keeping process failure and recovery information local to each process group.

An approximate but sufficiently accurate high frequency solution is developed in this paper for analyzing the problem of electromagnetic plane wave scattering by an open-ended, perfectly-conducting, semi-infinite parallel-plate waveguide with a thin layer of lossy or absorbing material on its inner wall, and with a planar termination inside. The high frequency solution combines uniform geometrical theory of diffraction (UTD) and aperture integration (AI) methods. The present method has several advantages in comparison with other methods.

In this paper, we quantitively analyzed speech data in seven different styles to make natural Japanese conversational speech synthesis. Three reading styles were produced at different speeds (slow, normal and fast), and four speaking styles were produced by enacting conversation in different situations (free, hurried, angry and polite). To clarify the differences in prosodic characteristics between conversational speech and read speech, means and standard deviations of vowel duration, vowel amplitude and fundamental frequency (F0) were analyzed. We found large variation in these prosodic parameters. To look more precisely at the segmental duration and segmental amplitude differences between conversational speech and read speech, control rules of prosodic parameters in reading styles were applied to conversational speech. F0 contours of different speaking styles are superposed by normalizing the segmental duration. The differences between estimated values and actual values were analyzed. Large differences were found at sentence final and key (focused) phrases. Sentence final positions showed lengthening of segmental vowel duration and increased segmental vowel amplitude. Key phrase positions featured raising F0.

Prosodic features of the spoken Japanese play an important role in the transmission of linguistic information concerning the lexical word accent, the sentence structure and the discourse structure. In order to construct prosodic rules for synthesizing high-quality speech, therefore, prosodic features of speech should be quantitatively analyzed with respect to the linguistic information. With a special focus on the fundamental frequency contour, we first define four prosodic units for the spoken Japanese, viz., prosodic word, prosodic phrase, prosodic clause and prosodic sentence, based on a decomposition of the fundamental frequency contour using a functional model for the generation process. Syntactic units are also introduced which have rough correspondence to these prosodic units. The relationships between the linguistic information and the characteristics of the components of the fundamental frequency contour are then described on the basis of results obtained by the analysis of two sets of speech material. Analysis of weathercast and newscast sentences showed that prosodic boundaries given by the manner of continuation/termination of phrase components fall into three categories, and are primarily related to the syntactic boundaries. On the other hand, analysis of noun phrases with various combinations of word accent types, syntactic structures, and focal conditions, indicated that the magnitude and the shape of the accent components, which of course reflect the information concerning the lexical accent types of constituent words, are largely influenced by the focal structure. The results also indicated that there are cases where prosody fails to meet all the requirements presented by word accent, syntax and discourse.

For the production of high quality synthetic sounds in a text-to-speech system, an excellent synthesizing method of speech signals is indispensable. In this paper, a new speech analysis-synthesis method for the text-to-speech system is proposed. The signals of voiced speech, which have a line spectrum structure at intervals of pitch in the linear frequency domain, can be represented approximately by the superposition of sinusoidal waves. In our system, analysis and synthesis are performed using such a harmonic structure of the signals of voiced speech. In the analysis phase, assuming an exact harmonic structure model at intervals of pitch against the fine structure of the short-time power spectrum, the fundamental frequency f0 is decided so as to minimize the error of the log-power spectrum at each peak position. At the same time, according to the value of the above minimized error, the rate of periodicity of the speech signal is detemined. Then the log-power spectrum envelope is represented by the cosine-series interpolating the data which are sampled at every pitch period. In the synthesis phase, numerical solutions of non-linear differential equations which generate sinusoidal waves are used. For voiced sounds, those equations behave as a group of mutually synchronized oscillators. These sinusoidal waves are superposed so as to reconstruct the line spectrum structure. For voiceless sounds, those non-linear differential equations work as passive filters with input noise sources. Our system has some characteristics as follows. (1) Voiced and voiceless sounds can be treated in a same framowork. (2) Since the phase and the power information of each sinusoidal wave can be easily controlled, if necessary, periodic waveforms in the voiced sounds can be precisely reproduced in the time domain. (3) The fundamental frequency f0 and phoneme duration can be easily changed without much degradation of original sound quality.

The authors developed a portable Japanese text-to-speech system using a pocket-sized formant speech synthesizer. It consists of a linguistic processor and an acoustic processor. The linguistic processor runs on an MS-DOS personal computer and has functions to determine readings and prosodic information for input sentences written in kana-kanji-mixed style. New techniques, such as minimization of a cost function for phrases, rare-compound flag, semantic information, information of reading selection and restriction by associated particles, are used to increase the accuracy of readings and accent positions. The accuracy of determining readings and accent positions is 98.6% for sentences in newspaper articles. It is possible to use the linguistic processor through an interface library which has also been developed by the authors. Consequently, it has become possible not only to convert whole texts stored in text files but also to convert parts of sentences sent by the interface library sequentially, and the readings and prosodic information are optimized for the whole sentence at one time. The acoustic processor is custom-made hardware, and it has adopted new techniques, for the improvement of rules for vowel devoicing, control of phoneme durations, control of the phrase components of voice fundamental frequency and the construction of the acoustic parameter database. Due to the above-mentioned modifications, the naturalness of synthetic speech generated by a Klatt-type formant speech synthesizer was improved. On a naturalness test it was rated 3.61 on a scale of 5 points from 0 to 4.

This paper presents a method for verifying safety property of a communication protocol modeled as two extended communicating finite-state machines with two unbounded FIFO channels connecting them. In this method, four types of atomic formulae specifying a condition on a machine and a condition on a sequence of messages in a channel are introduced. A human verifier describes a logical formula which expresses conditions expected to be satisfied by all reachable global states, and a verification system proves that the formula is indeed satisfied by such states (i.e. the formula is an invariant) by induction. If the invariant is never satisfied in any unsafe state, it can be concluded that the protocol it safe. To show the effectiveness of this method, a sample protocol extracted from the data transfer phase of the OSI session protocol was verified by using the verification system.

To make a fast Bi-CMOS SRAM yield high without speed degradation, three defect-repair methods, the address comparison method, the fuse decoder method and the distributed fuse method, were considered in detail and their advantages and disadvantages were made clear. The distributed fuse method is demonstrated to be further improved by a built-in fuse word driver and a built-in fuse column selector, and fuse analog switches. This enhanced distributed fuse scheme was examined in a fast Bi-CMOS SRAM. A maximun access time of 14 ns and a chip size of 8.8 mm17.4 mm are expected for a 4 Mb Bi-CMOS SRAM in the future.

A stored channel simulator for digital mobile radio enviroments is proposed, which enables the field tests in the laboratory under identical conditions, since it can reproduce the actual multipath radio channels by using the channel impulse responses (CIR's) measured in the field. Linear interpolation of CIR is introduced to simplify the structure of the proposed simulator. The performance of the proposed simulator is confirmed by the laboratory tests.

A two-dimensional photoemission analysis of hot-carrier effects in LOCOS- and trench-isolated CMOS devices with channel width ranging from 160 µm to 0.2 µm is described. Photoemission-intensity profiles can be measured in spatial resolution of 0.1 µm. Different photoemission characteristics are observed in n-MOSFETs depending on isolation technology; M-shaped photoemission-intensity profiles are observed as gate voltage becomes higher in trench-isolated ones, but scarcely measured in LOCOS-isolated ones. As for p-MOSFETs, similar characteristics are observed independent on isolation technology and slightly M-shaped profiles are observed at higher gate voltages. The recession of 0.1-0.2 µm in photoemission area from the gate electrode edge due to gate bias dependence of the pinch-off points of n--LDD drain is observed when gate voltage increases from 1 V to 6 V. Meanwhile the recession of the pinch-off points in p-MOSFETs is less than 0.1 µm even when gate voltage increases from 2 V to 8 V. A qualitative explanation for the experimental results is given for four kinds of MOSFETs in comparing each device structure near the isolation edge.

Statistically improved results of power line radiation (PLR) over Eastern Asia observed at 50 and 60Hz are described in this paper. A total number of 150 orbits, which had been observed from June 1984 to January 1986, by the Japanese scientific satellite OHZORA, are used to detect PLR over Eastern Asia around the Japanese Islands. Depending on the increase in the number of data points, the statistical characteristics of the background noise can be precisely determined by using the improved technique compared with the initial analysis. Statistically reasonable data points are detected as PLR based on the +3 criterion, where is the standard deviation of the background noise. Therefore, the statistical reliability for rejecting the background noise is 99.85%. Then, these detected data are applied to the cause-and-effect test. When the statistically detected data points are placed on the map of Eastern Asia, the points cover Eastern Japan and the east coast of China for 50Hz, and they cover Western Japan for 60 Hz. The maps of the detection ratios and those of the average field strengths indicate the positive correlation with the ground maps of the electric power generation at 50 and 60 Hz. The positive correlation is more clearly seen at 50Hz since the background noise is somewhat weaker than that at 60Hz. This close relationship between the satellite observation and the electric power generation suggests that the detection of PLR is not caused by chance, and that PLR penetrates into the ionosphere and propagates approximately just upward. The decrease of field strength with altitude can be interpreted as the gradual decrease of the refractive index from 400 to 700km. Therefore, the detection ratio and the average field strength with respect to the satellite altitude suggest PLR propagating from the bottom of the ionosphere. According to these observational results, it is concluded that PLR in Eastern Asia is high above the high electric power generating regions over Japan and China, and that the satellite observation is capable of estimating PLR field below the ionosphere. These results are the first direct indication that the PLR field is enhanced over the high electric power generation region, and is penetrating into the ionosphere.

The performance of various ARQ protocols has recently been analyzed for multidestination environments. In all previous work, the round-trip delays between the transmitter and each of the receivers are assumed (or forced) to be equal to the maximum one, to simplify the analysis and/or the operation. This assumption obviously will sacrifice the system performance. In this paper, we evaluate the throughput efficiencies of three multidestination GBN ARQ protocols under unequal round-trip delays. In the investigated protocols, multiple copies of each data block are (re)transmitted contiguously to the receivers. Tight lower bounds are obtained for the throughput efficiencies of the schemes in which each data block is transmitted with the optimum number of copies. Results show that assuming all the round-trip delays to be equal to the maximum one may sacrifice the performance significantly. We also compare the performances of the three investigated protocols. In general, the performance becomes better as the transmitter utilizes more of the outcomes of previous transmission attempts.