There are various difficulties in processing spoken dialogs because of acoustic, phonetic, and grammatical ill-formedness, and because of interactions among participants. This paper describes temporal characteristics of utterances in human-human task-oriented dialogs and interactions between the participants, analyzed in relation to the topic structure of the dialog. We analyzed 12 task-oriented simulated dialogs of ASJ continuous speech corpus conducted by 13 different participants whose total length being 66 minutes. Speech data was segmented into utterance units each of which is a speech interval segmented by pauses. There were 3876 utterance units, and 38.9% of them were interjections, fillers, false starts and chiming utterances. Each dialog consisted of 6 to 15 topic segments in each of which participants exchange specific information of the task. Eighty-six out of 119 new topic segments started with interjectory utterances and filled pauses. It was found that the durations of turn-taking interjections and fillers including the preceding silent pause were significantly longer in topic boundaries than the other positions. The results indicate that the duration of interjection words and filled pauses is a sign of a topic shift in spoken dialogs. In natural conversations, participants' speaking modes change dynamically as the conversation develops. Response time of both client and agent role speakers became shorter as the dialog proceeded. This indicates that interactions between the participants become active as the dialog proceeds. Speech rate was also affected by the dialog structure. It was generally fast in the initiating and terminating parts where most utterances are of fixed expressions, and slow in topic segments of the body part of the dialog where both client and agent participants stalled to speak in order to retrieve task knowledge. The results can be utilized in man-machine dialog systems, e.g., in order to detect topic shifts of a dialog, and to make the speech interface of dialog systems more natural to a human participant.

Self-aligned InP/InGaAs heterojunction bipolar transistors (HBTs) were fabricated with emitter electrodes of 12, 22, 25, and 220 µm2 on the same wafer to investigate the influence of lateral scaling on device performance. DC characterization of these devices showed that InP/InGaAs HBTs are less subject to the emitter-size effect than GaAs-based HBTs. Common-emitter current gain β of the smallest 12-µm2 transistor was approximately 60 which is high enough for practical use. High-frequency characteristics of the transistors were almost the same in spite of the large difference in device size. Unity current-gain cutoff frequency fT of the smallest 12-µm2 transistor was as high as 163 GHz at a collector current of 2.3 mA, which ranks with the fT176 GHz achieved by the largest 220-µm2 transistor at a collector current of 45 mA. The smallest device also showed an excellent high-speed performance of fT100 GHz at submilliampere collector currents of Ic0.6 mA. The results indicate that small-lateral-dimension InP/InGaAs HBTs are applicable to high-speed ICs with low power dissipation.

A 3-dimensional specific thickness profile was fabricated on a thin glass diaphragm lens to reduce aberration at short focal distances for greater dynamic focusing. The deformation of the diaphragm was calculated by stress analysis utilizing the Finite Element Method (FEM). Geometric non linearity is considered in the FEM analysis. The glass diaphragm is 10 mm in diameter and the average thickness is 11 µm. To obtain both a curved shape and an optical surface on the glass diaphragm, the 3-dimensional precision grinding technique was utilized. The processed shape matches the designed one with less than 0.3 µm deviation, and the average surface roughness is 0.005 µm. Optical characteristics of the dynamic focusing lens having a specific thickness profile, were measured by Modulation Transfer Function (MTF) measurement equipment. At a focal distance of 250 mm, the specific thickness diaphragm lens resolution is 10 cycles/mm, whereas, the uniform thickness diaphragm is 4 cycles/mm. Even at other focal distances, the specific thickness diaphragm shows superior optical characteristics in comparison with those of the uniform thickness diaphragm. The 3-dimensional profile diaphragm resolution is 2.5 times finer at a focal distance of 250 mm, thus, being capable of displacement control for variable optic devices. This was achieved by employing semiconductor processing methods in conjunction with precision grinding techniques which are necessary for fabricating micro structures.

An excitation signal for a synthesis filter plays an important role in producing high quality speech at a low bit rate. This paper presents a new efficient excitation model, Adaptive Density Pulse (ADP) , for low bit-rate speech coding. This ADP is a pulse train whose density (spacing interval) is constant within a subframe but can be varied subframe by subframe. First, the ADP excitation signal is defined. A procedure for finding the optimal ADP excitation is presented. Some results on investigating the effects of the ADP parameters on the synthesized speech quality are discussed. ADP excitation is introduced to the CELP (Code Excited Linear Prediction) coding method to improve speech quality at bit rates around 4 kbps. A CELP coder with an ADP (ADP-CELP) is described. ADP excitation makes it possible for the CELP coder to follow transient portions of speech signals. Also ADP excitation can reduce computational complexity in selecting the best excitation from a codebook, which has been the primary drawback of CELP. The number of multiplications can be reduced to the order of 1/D2 by utilizing the sparseness of ADP excitation, where D is the pulse interval. The authors evaluated the speech quality of a 4 kbps ADP-CELP coder by computer simulation. ADP excitation improved the performance of conventional CELP in segmental SNR.

This paper presents improvement of data error rate against burst noise by using both chip interleaving and hard limiter in direct sequence spread spectrum (DS/SS) communication systems. Chip interleaving, which is a unique method of DS/SS systems, is effective when burst noise power is small. However, when the burst noise power is large, date error rate is degraded. While, though hard limiter suppresses burst noise power, it gives little effectiveness when the burst noise length is long. Using chip interleaving and hard limiter together, as they work complementary, stable and considerable improvement of data error rate is achieved.

Laser diodes for optical interconnections are ideally high speed, work over a wide temperature range, and are simple to bias. This paper reports high bit-rate modulation with nearly zero bias with very low threshold 1.3µm-wavelength laser diodes over a wide temperature range. At the high temperature of 80, lasing delay was 165 ps with nearly zero bias. We demonstrated 2.5 Gbit/s modulation over a wide temperature range. Eye opening was over 34% of one time slot.

Graph unification is doubtlessly the most expensive process in unification-based grammar parsing since it takes the vast majority of the total parsing time of natural language sentences. A parsing time overload in unification consists in that, in general, no less than 60% of the graph unifications performed actually fail. Thus one way to achieve unification time speed-up is focusing on an efficient, fast way to deal with such unification failures. In this paper, a process, prior to unification itself, capable of filtering or stopping a considerably high percentage of graphs that would fail unification is proposed. This unification-filtering process consists of comparison of signatures that correspond to each one of the graphs to be unified. Unification-filter (hereafter UF) is capable of stopping around 87% of the non-unifiable graphs before unification itself takes place. UF takes significantly less time to detect graphs that do not unify and discard them than it would take to unification to fail the attempt to unify the same graphs. As a result of using UF, unification is performed in an around 71% of the time for the fastest known unification algorithm.

Managed Objects (MOs) can be specified by the combination of a static information model and a dynamic process model. First, this paper presents a mapping of attributes from a process model diagram to an information model diagram. Then, it introduces a concept of topology into these two models and proposes a hypothesis about the relationship of topology in these two models. To explicitly explain the hypothesis, it can be stated that all attributes of incoming or outgoing data related to a process in a process model are mapped to an information model where these attributes are interconnected by an explicit relationship which corresponds to a specific meaning, such as physical containment or logical connection. From an intuitive perspective, it can be said that if two attributes have a close topological relationship in a process model, the mapped attributes also have a close topological relationship in an information model. This hypothesis provides clues for determining whether there is an error in an attribute either in the process model or in the information model. By examining the way attributes of incoming or outgoing data related to a process are mapped to an information model, we can detect whether there is an error with respect to the process. The error correction is performed with the assistance of probability analysis. The method of error detection and correction can be implemented in a computer aided tool. Then, error detection on the attribute level becomes automatic, and error correction on the attribute level becomes interactive through the computer aided tool. Finally, the validity of the hypothesis is confirmed by analyzing ITU-T Recommendation M.3100. The specification of the fabric object class defined in M.3 100 is transformed into these two models and the hypothesis is validated for the analysis of the mapping between these two models.

In formal specification languages for parallel processes, such as CSP and LOTOS, algebraic laws for basic operators are provided that can be used to transform process expressions, and in particular, composition of processes can be calculated using these laws. Process composition can be used to simplify and improve the specification, and also to prove properties of the specification such as deadlock absence. We here test the practicality of process composition using CSP and suggest useful techniques, working in an example with nontrivial size and complexity. We emphasize that the size explosion of composed processes, caused by interleaving of the events of component processes, is a serious problem. Then we propose a technique, which we name two-way pipe, that can be used to reduce the size of the composed process, regarded as a program optimization at specification level.

Memory type polymer dispersed liquid crystal (PDLC) can be applied to a thermal addressing display device cell. Making use of its easy fabrication of large area display using flexible film substrate, the PDLC film can be used as reusable paper for direct-view mode display. In this study, memory type PDLC cells are prepared with an aluminum reflector deposited onto one side of the substrate and the reflection property in the PDLC cell with the reflector is clarified and compared to that without the reflector in the off-, on- and memory-states. The increase of contrast ratio and the decrease of driving voltage can be concurrently realized by decreasing the cell thickness by attaching the reflector. In addition, the reflected light in the off-state is bright and colorless due to the reflector, as compared with the weak, bluish reflected light in the cell without the reflector. Reflected light in the on-state and the memory-state are tinged with blue.

This paper proposes that a combination of pre-chirping and dispersion compensation is effective in suppressing the waveform distortion due to the self-phase modulation and the group-velocity dispersion in 10 Gb/s repeaterless transmission using 1.3-µm zero-dispersion single-mode fibers (SMF) operating at a wavelength of 1.55µm. The following results were obtained through simulation. 1) Setting the α-parameter of a LiNbO3 optical modulator negative (α1.0) gives a large tolerance of the launched power Pin. 2) For 90-km SMF transmission, the maximum Pin is obtained when the dispersion compensation ratio β is from 50% to 70%. 3) For the allowable β as a function of the transmission distance when a dispersion compensator is located in the receiver (post-compensation scheme), the lower limit of β is determined by the constant residual dispersion value, which agrees well with the dispersion tolerance without dispersion compensation. Our 90-km SMF transmission experiments using a LiNbO3 optical modulator and a dispersion compensating fiber (DCF) confirmed the simulation results regarding the optimum value of β and the large tolerance of the fiber launched power. Based on the above investigations, we achieved a 10-Gb/s repeaterless 140-km SMF transmission with α1.0 and post-compensation.

This paper presents a heuristic floorplanning method that improves the method proposed by Vijayan and Tsay. It is based on tentative insertion of constraints, that intentionally produces redundant constraints to make it possible to search in a wide range of solution space. The proposed method can reduce the total area of blocks with the removal and insertion of constraints on the critical path in both horizontal and vertical constraint graphs. Experimental results for MCNC benchmarks showed that the quality of solutions of the proposed method is better than [7],[8] by about 15% on average, and even for the large number of blocks, the proposed method keeps the high quality of solutions.

This paper proposes a new environment for high-level VLSI design specification validation using "Algorithmic Debugging" and evaluates its benefits on three significant examples (a protocol processor, an 8-bit CPU, and a Prolog processor). A design is specified at a high-level using the structured analysis (SA) method, which is useful for analyzing and understanding the functionality to be realized. The specification written in SA is transformed into a logic programming language and is simulated in it. The errors (which terminate with an incorrect output in the simulation) included in the three large examples are efficiently located by answering junt a few queries from the algorithmic debugger. The number of interactions between the designer and the debugger is reduced by a factor of ten to a hundred compared to conventional simulation based validation methodologies. The correct SA specification can be automatically translated into a Register Transfer Level (RTL) specification suitable for logic synthesis. In this environment, a designer is freed from the tedious task of debugging a RTL specification, and can concentrate on the design itself. This environment promises to be an important step towards efficient high-level VLSI design specification validation.

This paper describes the circuit design and experimental results of a video-rate 10-b analog-to-digital converter (ADC) suitable for consumer video products, such as high-definition TV sets. Triple-stage conversion scheme combined with two new conversion methods, "Dynamic Sliding Reference Method" and "Triangular Interpolation Method," and an internal Bi-CMOS Sample/Hold circuit have been developed. These conversion methods require no adjustment circuit to fit reference voltages between conversion stages and realize small active area. As a result, a maximum conversion frequency of 16 MHz, acceptable SNRs of 56 dB and 48 dB for 10 kHz and 8 MHz input frequency respectively and small DNLE of 0.75 LSB have been achieved. This ADC is fabricated with 1.2 µm Bi-CMOS technology and integrates very small number of bipolar transistors of 2 K on a small active area of 2.52.7 mm2 and consumes 350 mW.

This paper describes an adaptively weighted code division multiplexing (AW-CDM) system, in other words, power controlled spread-spectrum multiplexing system and describes its application to hierarchical digital broadcasting of television signals. The AW-CDM, being combined with multi-resolutional video encoder, can provide such a hierarchical transmission that allows both high quality services for fixed receivers and reduced quality services for mobile/portable receivers. The carrier and the clock are robustly regenerated by using a spread-spectrum multiplexed pseudorandom noise (PN) sounder as a reference in the receiver. The PN reference is also used for Rake combining with signals via different paths, and for adaptive equalization (EQ). In a prototype AW-CDM modem, three layers of hierarchical video signals (highs: 5.91Mbps, middles: 1.50Mbps, and lows: 0.46 Mbps) are divided into a pair of 64 orthogonal spread-spectrum subchannels, each of which can be given a different priority and therefore a different threshold. In this case, three different thresholds are given. The modem's transmission rate is 9.7Mbps in the 6MHz band. Indoor transmission tests confirm that lows (weighted power layer I), middles (averaged power layer II), and highs (lightened power layer III) are retrievable under conditions in which the desired to undesired signal ratios (DURs) are respectively 0dB, 8.5dB, and 13.5dB. If the undesired signals are multipaths, these performances are dramatically improved by Rake combining and EQ. The AW-CDM system can be used for 20-30 Mbps advanced television (ATV) transmission in the 6-MHz bandwidth simply by changing the binary inputs into quaternary or octonary inputs.

A stepwise refinement method of communications service specifications is proposed to generate communications software that can conform to any network architecture. This method uses a two-layered language; one layer is a service specification description language (STR), and the other layer is a supplementary specification description language for implementing STR description on a communications system (STR/D). STR specifies terminal behaviors that can be recognized from a perspective outside of the communications systems. With STR, a communications service is defined by a set of rules that can be described without detailed knowledge of communications systems or communications network architectures. Each STR rule describes a global state transition of terminals. Supplementary specifications, such as terminal control and network control, are needed to implement communications services specified by STR rules. These supplementary specifications are described by STR/D rules. Communications services, such as UPT (Universal Personal Telecommunication), are standardized so that they can be provided on a given functional model consisting of functional entities. Specifications for each functional entity in a network are obtained from the two kinds of initially described specifications mentioned above. The obtained specifications are described by STR(L) and STR/D(L) rules, which specify local specifications of a functional entity. These specifications for functional entities are then transformed into software specifications, and finally communications software is generated from these software specifications. This stepwise refinement method makes it possible to generate communications software that can conform to any functional model from service specifications.

A three-dimensional analysis of Whispering-Gallery modes (W. G. modes) in a coaxial dielectric resonator is proposed and presented. The coaxial dielectric resonator is constructed from a lossy dielectric disk and ring which have diameters of several tens times as large as wavelength. Eigenvalue equations of the W. G. modes are derived rigorously from field expressions and boundary conditions. The resonant frequencies, unloaded Q values and field distributions are calculated numerically from the eigenvalue equations. These calculated results are in good agreement with experimental ones for an X band model. As a result, it is shown that a considerable quantity of modal energy can be confined in a loss-less gap between the disk and ring, and then the unloaded Q value is higher than that of a conventional dielectric disk and ring resonator.

This paper discusses the characteristics of the nonlinearly amplified spread–spectrum (SS) signals. We evaluate the symbol error–rate performance with the conventional receiver, changing the length of the spreading sequence. In addition, we also propose the receiver with MLSE. The configuration of the MLSE for the nonlinearly amplified signals is generally complicated; however we show that the complexity of the MLSE receiver can be reduced, as the number of required reference sequences in the receiver for an SS signal is small. As the result, it is shown that the error rate performance of the nonlinearly amplified SS signal can be improved by this proposed receiver and that the degradation caused by the nonlinear amplification can be made negligibly small with a sufficiently long spreading sequence.

An efficient full–wave spectral domain moment method is developed to compute the current distribution and the radiation associated with microstrip discontinuities. Two techniques are used to increase the efficiency of the method of moments algorithm so that a transmission line of moderate electrical size can be analyzed in reasonable time.

Synchronization has been one of the problems in M–ary spread spectrum communication systems. In this letter, we propose the frame synchronization method using the Hadamard matrix and a frame synchronization method of PCM communication systems. Moreover, we analyze the probabilities of keeping synchronous state and frame renewal rates, and we evaluate the relationship between these probabilities and the number of stages of counters.