In this paper, we present for the first time two three-dimensional analytical electrostatic Green's functions for shielded and open arbitrarily multilayered medium structures. The analytical formulas for the Green's functions are simply expressed in the form of Fourier series and integrals, and are applicable to the arbitrary number of dielectric layers. In combination with the complex image charge method, we demonstrate an efficient application to analyze microstrip discontinuities in a three-layered dielectric structure. Numerical results for the capacitance associated with on open-end discontinuity show good agreement with those from a previous paper and the effectiveness of using the analytical Green's functions to analyze three-dimensional electrostatic problems.

This paper proposes a masked data transferring method for the write-back controlled disk cache system employing a fixed-length recording disk drive, enabling data transfer of discontinuous sectors on the same track between the cache and the disk. This paper also evaluates the method. In write-back controlled disk cache sytems, random write requests cause dirty data (write-pending data on a cache) on discontinuous areas on the cache. It is likely that several sectors on the same track become dirty. These dirty sectors must be written onto the disk according to the cache management scheme. In conventional data transferring methods between a disk cache and a disk drive, plural sectors can be transferred in one single operation when the sectors are adjacent, but discrete sectors must be transferred by individual operations. In the methods, an address of the head sector and number of sectors to be transferred are given to the transfer unit. For example, when two sectors on the same track are located closely but not adjacently, and data transfer is requested for those two sectors, the transfer operation for the second sector must be prepared after the first transfer had completed and before the second sector arrives under the disk head. Although the time for the head to pass by the uninterested sector is often too short for the software overhead for the first transfer to be completed and the second transfer to be prepared, which leads to an unwanted extra rotation of the disk. With the masked transferring method proposed in this paper, the micro program creates a bit-map specifying the target sectors to be transferred and passes it to the data transfer unit, enabling to transfer the discontinuous sectors without latency. The method was evaluated using OLTP warkloads. Results show an improvement in random I/O throughput of between 8% and 27%. The masked transferring method is adopted in Hitachi's A-6521 disk subsytems, shipped since December 1993.

A new algorithm for multiple-precision modular multiplication is proposed. It is fast and uses a small amount of main memory, and hence, is useful for application of a public-key cryptosystem to small computers, such as card computers.

Theoretically, corresponding pairs of feature points between two stereo images can determine their 3-D locations uniquely by triangulation. In the presence of noise, however, corresponding feature points may not satisfy the epipolar equation exactly, so we must first correct the corresponding pairs so as to satisfy the epipolar equation. In this paper, we present an optimal correction method based on a statistical model of image noise. Our method allows us to evaluate the magnitude of image noise a posteriori and compute the covariance matrix of each of the reconstructed 3-D points. We demonstrate the effectiveness of our method by doing numerical simulation and real-image experiments.

The classification of remotely sensed multispectral data using classical statistical methods has been worked on for several decades. Recently there have been many new developments in neural network (NN) research, and many new applications have been studied. It is well known that NN approaches have the ability to classify without assuming a distribution. We have proposed an NN model to combine the spectral and spacial information of a LANDSAT TM image. In this paper, we apply the NN approach with a normalization method to classify multi-temporal LANDSAT TM images in order to investigate the robustness of our approach. From our experiments, we have confirmed that our approach is more effective for the classification of multi-temporal data than the original NN approach and maximum likelihood approach.

We present that event-transition diagrams are useful to analyze event concurrent response visually. Event-transition diagrams are dual for state-transition diagrams in graph theory. As an example of an usage of an event-transition diagram, a simple model of a railroad crossing is presented.

The integration of both real-time systems and fault-tolerant systems has been emerged as one of the greatest challenges of this decade. It is called a responsive system, which has the objective to optimeze both timeliness and reliability. The performance measure in responsive systems is responsiveness that tells how probable a system executes correctly on time with faults occurred. While there have been some achievements in communication protocols and specification, we believe that scheduling problems in responsive systems are not understood deeply and sufficiently, yet. In this paper, we discuss the scheduling problem in responsive systems. At first, we investigate the issues in the scheduling and propose the precise definition of the responsiveness. We also suggest a scheduling algorithm called Responsive Earliest Deadline First (REDF) for preemptive aperiodic tasks in a uniprocessor system. We show that REDF is optimal to obtain the maximum responsiveness, and the time complexity is analyzed to be (N 2N). By illustrating a contradictory example, it is shown that REDF can be enhanced if a constraint on tasks is released.

In this work, a statistical analysis is performed for a simple constrained high-order Yule-Walker (YW) tone frequency estimator obtained from the first equation of the constrained high-order YW equations. Explicit expressions for its estimation bias and variance are efficiently derived by virtue of a Taylor series expansion technique. Especially, being explicit in terms of frequency, data length and Signal-to-Noise Ratio (SNR) value, the resulting bias expression can not be obtained by using the asymptotic analyses used for the parameter estimation methods. The obtained expressions are compared with their counterparts of the Pisarenko tone frequency estimator. Simulations are performed to support the theoretical results.

We believe that virtual world communication will subsume BBS and visual communication. Accordingly, we proposed the networked virtual world "Interspace" for visual communication. If we are to achieve education and training in this world, techniques to receive and transmit information without any special training are necessary. The traditional "easy" ways of transmitting information are talking and drawing. In Interspace, users can already talk each other. In this paper we focus on drawing. In daily life we communicate through drawings in various situations. At this time it is important to recognize who is drawing and where the participants are watching. It is difficult to realize these functions using conventional media, but it is possible to realize them in virtual space. In virtual space, the system can clearly represent who is drawing and where participants are watching; expressing topics in virtual space frees us from many physical restrictions. In this paper we discuss the process of drawing when many participants share topics in virtual space; the necessary conditions for our system are considered. We design a system that offers functions to make drawing sheets, to display the view fields of participants, and to share visual fields. Furthermore, we propose the mode of InterSheet called "InterMirror" which shows mirror images of partners and their drawings. We make a prototype and evaluate it. The results indicate the synergistic effect of drawing with voice and the usefulness of drawing for communication in virtual space.

The radiation and scattering characteristics of a metal-strip grating of finite extent printed on the surface of a dielectric waveguide are analyzed within a two-dimensional model. The diffraction properties are obtained from a solution to the problem of surface mode scattering by a finite number of metal strips, taking into account their mutual couplings. The analysis is based on the electromotive force technique which does not require a grating to be periodic. Obtained results concern the antenna applications of radiating gratings excited by the dominant TE or TM surface mode of the wavegude. The proposed approach can be applied not only to the design of radiators but also filters based on periodic strip gratings.

This paper is concerned with synthesizing VLSI array processors from iterative algorithms. Our primary objective is to obtain the highest processor efficiency but not the shortest completion time. Unlike most of the previous work that assumes the index space of the given iterative algorithm to be boundless, the proposed method takes into account the effects of the boundaries of the index space. Due to this consideration, the pseudo-dependence relations are excluded, and most of the independent computations can therefore be uniformly grouped. With the method described in this paper, the index space is partitioned into equal-size blocks and the corresponding computations are systematically and uniformly mapped into processing elements. The synthesized VLSI array processors possess the attractive feature of very high processor efficiency, which, in general, is superior to what is derived from the conventional linear transformation methods.

Portable terminals have the potential of providing information and communication services not only to computer experts at their offices but also to many users being in a variety of daily life situations. The current user interfaces (UIs) of portable terminals are not suitable for a novice user of computers; they require some knowledge on computers from a user. To overcome this problem, the authors tried to implement their knowledge on the daily life in the design of a UI for novice users. As a result, two UI mechanisms, called Novice Interface and Graphical Metaphor Interface, which provide operations, expressions, and data structures in a way similar to those usually used in daily life are proposed. Novice Interface is to provide easy to use environment. It adopts a direct manipulation device with three buttons and a model of data structures, called Small World Model, that limits the number of functions and the depth of hierarchical menu. Graphical Metaphor Interface, being an extension of Novice Interface, is to provide services with a display screen that makes them well-understandable for any user. The proposed UI mechanisms were implemented in a prototype terminal and its software platform. The former offers several applications of the information services (like teleshopping, home banking, or database retrieval) and the communication services (like pen-based image mail, software fax, or telewriting); the latter enables those application programs to provide a consistent UI.

In the paper a problem of wave scattering from a local penetrable inhomogeneity inside a planar dielectric waveguide is studied. The surface potentials method is applied for the problem and the set of systems of BIE is obtained and analyzed from the view-point of their numerical solution. The effective numerical algorithm based on the Nyström method is proposed. The equations for a scattering diagram and mode conversion coefficients are derived.

Optical switching networks to transport vast amounts of information are important for B-ISDN services. Wavelength division multiplexing (WDM) is emerging as the dominant technology for future optical networks. A large capacity photonic ATM switch architecture using WDM technology is proposed in this paper. The proposed switch is suitable for WDM optical ATM networks, that is, an input and an output of the switch are wavelength division multiplexed. The basic switch module of the proposed switch has a simple architecture, and reduces the amount of a buffer hardware by introducing the WDM concept.

This paper investigates the error correcting capabilities of concatenated codes employing algebraic geometry codes as outer codes and time-varying randomly selected inner codes, used on discrete memoryless channels with maximum likelihood decoding. It is proved that Gallager's random coding error exponent can be obtained for all rates by such codes. Further, it is clarified that the error exponent arbitrarily close to Gallager's can be obtained for almost all random selections of inner codes with a properly chosen code length, provided that the length of the outer code is sufficiently large. For a class of regular channels, the result is also valid for linear concatenated codes, and Gallager's expurgated error exponent can be asymptotically obtained for all rates.

The use of existing metallic local line facilities is being studied for providing "video on demand (VOD)" services to residential subscribers across asymmetric digital subscriber lines (ADSL). ADSL carries a high-rate channel in the downstream direction from a central office (CO) to the subscriber, and a low-rate channel in both directions on an existing 2-wire pair. Audio and video signals are compressed by the moving picture experts group's standardized algorithms (MPEG 1 and MPEG 2), and delivered to the subscriber in the high-rate channel. Control (demand and response) signals are transceived in the low-rate channel. This paper presents the line length coverage of ADSL systems given the environment of NTT's local networks. The bit rates in the downstream and upstream directions are assumed to be 1.6-9.2Mbit/s and 24kbit/s, respectively. Two types of ADSL systems are considered: transceiving ADSL signals using the plain old telephone service (POTS) line or the basic rate access (BRA; 320 kbaud ping-pong transmission system) line on the same 2-wire pair. 16-QAM, 32-QAM and 64-QAM are compared as transmission schemes. Intra-system crosstalk interference (interference between identical transmission systems) and inter-system crosstalk interference (interference between different transmission systems) with the existing digital subscriber lines (DSL) are estimated. It is shown that the inter-system crosstalk interference with BRA is most stringent, and ADSL with 16-QAM yields the best performance in NTT's local networks. This paper concludes that realizing ADSL with 16-QAM can achieve channel capacities of up to 9.2Mbit/s for fiber-in-the-feeder (FITF) access systems, but the possibility of applying ADSL to direct access systems is remote except for a restricted short haul use. Some comparisons regarding American local networks are also described.

We have proposed a connection-based optical wavelength division multiplexing network architecture. For the networks such as inter-office LANs, the guarantee of the bandwidths of connection-oriented calls is necessary. Notable features of the network are that multicast can be executed without copying the same data, and that time slots are rearrangeable to increase the throughput. The topology is passive star and a network controller (NWC) is connected to manage the time slot assignment. Each station's transmitting wavelength is fixed and is different from that of other stations. Each receiver changes the receiving wavelength slot by slot. Stations reserve time slots with permission of the NWC. Once a time slot is reserved the station can use the slot in every frame until the reservation is cancelled. This feature guarantees the bandwidths of connection-oriented calls. Upon receiving a time slot request, the NWC searches for a not-in-use slot common to the source station's transmitter (Tx) and the destination station's receiver (Rx). If there is no common empty slot and both the Tx and the Rx have empty slots, the NWC rearranges the already allocated time slots to create a new common empty slot. Simulations were performed to estimate the blocking rates for various cases of call bandwidth including multi-bitrate (the case in which various bandwidth calls are generated in a network) and multicast call, the calculation load of the NWC when it assigns a time slot including rearrangement, and the success rate of rearrangement. It was found that the blocking rate with the rearrangement is greatly reduced (1/10) compared with the case without rearrangement of the same throughput when the number of slots in a frame is more than 120, the number of stations in the network is 60 and the blocking rate without the rearrangement is less than 10-2. Over 100 Gbps throughput can be achieved when the number of slots in a frame is 120-240, the number of stations is 60, the bitrate of a transmitter is 2.5Gbps and the blocking rate is about 10-2. The rearrangement is especially effective in the case of multi-bitrate in which the blocking rate can be reduced to 1/100 that of the case without rearrangement at some point. It is also shown that a slot assignment including rearrangement can be executed sufficiently quickly (5s). These results indicate that practical realization of this access control architecture is possible.

This paper investigates the effect of crosstalk in multichannel coherent optical ASK systems. A closed-form signal-to-noise ratio (SNR) expression as a function of number of channels, channel separation, laser phase noise, intermediate frequency (IF) filter bandwidth expansion factor (α), system bit rate (Rb=1/T), and additive shot noise is presented. When the desired channel is between two channels in the electrical domain, the minimum permissible electrical domain channel spacing for a 1dB sensitivity penalty due to crosstalk is found to be 4.85Rb when α is optimum; and 8Rb when α=5 for νT=0.30 at BER=10-9. A fairly good agreement is found between the results of this work and those of a previous study.

This paper proposes a technique for estimating the harmonic frequencies based on instantaneous frequency (IF) of speech signals. The main problem is how to decompose the speech signal into the harmonic components. For this purpose, we use a set of bandpass-filters, each of whose center frequencies changes with time in order to track the instantaneous freuency of its output. As a result, the outputs of the band-pass filters become the harmonic components, and the instantaneous frequencies of the harmonics are accurately estimated. To evaluate the effectiveness of the approach, we apply it to pitch determination of speech. Pitch determination is simply accomplished by selecting the correct fundamental frequency out of the harmonic components. It is confirmed that the pitch extraction using the proposed pitch determination algorithm (PDA) is stable and accurate. The most significant feature of the PDA is that the extracted pitch contour is smooth and it requires no post-processing such as nonlinear filtering or any smoothing processes. Several examples are presented to demonstrate the capability of the harmonics estimation technique and the PDA.

This paper discusses crystal-growth and device-design issues associated with the development of high-performance InP/InGaAs heretostructure bipolar transistors (HBTs). It is shown that a highly Si-doped n+-subcollector in the HBT structure causes anomalous Zn redistribution during metalorganic vapor phase epitaxial (MOVPE) growth. A thermodynamical model of and a useful solution to this big problem are presented. A novel hybrid structure consisting of an abrupt emitter-base heterojunction and a compositionally-graded base is shown to enhance nonequilibrium base transport and thereby increase current gain and cutoff frequency fT. A double-heterostructure bipolar transistor (DHBT) with a step-graded InGaAsP collector can improve collector breakdown behavior without any speed penalty. We also elucidate the effect of emitter size shrinkage on high-frequency performance. Maximum oscillation frequency fmax in excess of 250 GHz is reported.