A method for the recognition of Arabic printed scripts entered from an image scanner is presented. The method uses the Hough transformation (HT) to extract features, Dynamic programming (DP) matching technique, and a topological classifier to recognize the characters. A process of characters recognition is further divided into four parts: preprocessing, segmentation of a word into characters, features extraction, and characters identification. The preprocessing consists of the following steps: smoothing to remove noise, baseline drift correction by using HT, and lines separation by making an horizontal projection profile. After preprocessing, Arabic printed words are segmented into characters by analysing the vertical and the horizontal projection profiles using a threshold. The character or stroke obtained from the segmentation process is normalized in size, then thinned to provide it skeleton from which features are extracted. As in the procedure of straight lines detection, a threshold is applied to every cell and those cells whose count is greater than the threshold are selected. The coordinates (R, θ) of the selected cells are the extracted features. Next, characters are classified in two steps: In the first one, the character main body is classified using DP matching technique, and features selected in the HT space. In the second one, simple topological features extracted from the geometry of the stress marks are used by the topological classifier to completely recognize the characters. The topological features used to classify each type of the stress mark are the width, the height, and the number of black pixels of the stress marks. Knowing both the main group of the character body and the type of the stress mark (if any), the character is completely identified.

High Tc superconducting (SC) active antennas made from thin films were produced by the magnetron sputtering method. The SC active antennas are found to be good for detecting 50GHz electromagnetic waves. Furthermore, the improvement of the sensitivity of the SC active antennas is demonstrated with the use of a corner reflector.

This paper describes design considerations for high frequency active BPFs up to 100 MHz. The major design issues for high frequency active filters are the excess phase shift in the integrators and high power consumption of the integrators. Typical bipolar transistor based transconductors such as the Gilbert gain cell and the linearized transconductor with two asymmetric emitter-coupled pairs have been analyzed and compared. It has been clarified that the power consumption of the linearized transconductor can be much smaller than that of the Gilbert gain cell because of its high transconductance to working current ratio while maintaining a signal to noise ratio of the same order. A simple high-speed fully differential linearized transconductor cell is proposed with emitter follower buffers and resistive loads for excess phase compensation. A novel gyrator based transformation for the LC ladder BPF has been introduced. This transformation has resulted in a structure with simple capacitor-coupled active resonators which exactly preserves the original transfer function. A fourth order 10.7 MHz BPF IC was designed using the proposed transconductors. It was fabricated and has demonstrated the usefulness of the proposed approach. In addition, an experimental 100 MHz second order BPF IC with Q=14 has been successfully implemented indicating the potential of the proposed approach.

In this paper, we investigate the discrepancy between a serial version and a parallel version of zero-knowledge protocols, and clarify the information "leaked" in the parallel version, which is not zero-knowledge unlike the case of the serial version. We consider two sides: one negative and the other positive in the parallel version of zero-knowledge protocols, especially of the Fiat-Shamir scheme.

This paper describes the linguistic procedure of our speech dialogue system. The procedure is composed of two processes, syntactic analysis using a finite state network, and discourse analysis using a plan recognition model. The finite state network is compiled from regular grammar. The regular grammar is described in order to accept sentences with various styles, for example ellipsis and inversion. The regular grammar is automatically generated from the skeleton of the grammar. The discourse analysis module understands the utterance, generates the next question for users and also predicts words which will be in the next utterance. For an extension number guidance task, we obtained correct recognition results for 93% of input sentences without word prediction and for 98% if prediction results include proper words.

The diffraction of a plane electromagnetic wave by a parallel-plate waveguide cavity with a thick planar termination is rigorously analyzed for both the E and the H polarization using the Wiener-Hopf technique. Introducing the Fourier transform for the unknown scattered field and applying boundary conditions in the transform domain, the problem is formulated in terms of the simultaneous Wiener-Hopf equations, which are solved exactly in a formal sense via the factorization and decomposition procedure. Since the formal solution involves an infinite number of unknowns and branch-cut integrals with unknown integrands, approximation procedures based on rigorous asymptotics are further presented to yield the approximate solution convenient for numerical computations. The scattered field inside and outside the cavity is evaluated by taking the inverse Fourier transform and applying the saddle point method. Representative numerical examples of the monostatic and bistatic radar cross sections are presented for various physical parameters, and the scattering characteristics of the cavity are discussed in detail.

Fabrication of 0.2 to 0.3 µm features is vital for future ultralarge scale integration devices. An area of particular concern is whether optical lithography can delineate such feature sizes, i.e., less than the exposure wavelength. The use of a phase shift mask is one of the most effective means of improving resolution in optical lithography. This technology basically makes use of the interference between light transmitting through adjacent apertures of the mask. Various types of phase shift masks and their imaging characteristics are discussed and compared with conventional normal transmission masks. To apply these masks effectively to practical patterns, a phase shifter pattern design tool and mask repair method must be established. The phase shifting technology offers a potential to fabricate 0.3 µm features by using the current i-line stepper, and 0.2 µm features by using excimer laser stepper.

In 1990, Menezes, Okamoto and Vanstone proposed a method that reduces EDLP to DLP, which gave an impact on the security of cryptosystems based on EDLP. But this reducing is valid only when Weil pairing can be defined over the m-torsion group which includes the base point of EDLP. If an elliptic curve is ordinary, there exists EDLP to which we cannot apply the reducing. In this paper, we investigate the condition for which this reducing is invalid.

For the connection request procedure in mobile communication systems, a previous study had shown that the 3-channel systems provide the haighest maximum of stable per channel throughput. In this paper, we propose and study a new algorithm, called the Parallel Collision Resolution Algorithm, which can be implemented in a Q-channel connection request environment, where Q3. For the implementation, the channels are arranged in R groups, where R is a positive integer. The collision resolution scheme distributes the collided messages over all the groups so that throughput and delay measures can be improved. At any point in time, there can be a maximum of R collision resolution schemes operational irrespective of the channel or the group number over which collisions occurred. The performance measures are estimated by computer simulation. Under the new algorithm, almost the same level of the perchannel stable throughput measure of a 3-channel network can be achieved in networks for which Q3. This feature allows freedom to the network designer to employ a higher number of connection request channels without forfeiting high channel utilization rates. When Q is an integral multiple of 3, the maximum stable per channel throughput level achieved can be the same as that achieved by the 3 channel system, if the grouping of channels is such that each group consists of 3 channels. When Q is not an integral multiple of 3, the intuitive strategy of organizing the channels in such a way that Q/3 groups consist of 3 channels each and one group consists of (Q mod 3) channels, may result in much degraded performance. It is found that, if the channels are so organised that no group is composed of (Q mod 3) channels, the performance levels can be substantially enhanced. Also, under the new algorithm, the delay measure is significantly improved, particularly in schemes like the mobile satellite systems with high propagation delays. We conclude that the new scheme presents a promising collision resolution methodology for connection request procedures.

This letter describes an MOS operational transconductance amplifier and an MOS four-quadrant analog multiplier using the quadritail cell, which provides an output current proportional to the square of a differential input voltage. As a result, a linear transconductance amplifier and a quarter-squarer multiplier can be obtained in theoretical circuit analysis.

The static characteristics of GaInAs(P)/GaInAsP quantum well laser diodes (QW LDs), with graded-index separate-confinement-heterostructure (GRIN-SCH) grown by metalorganic chemical vapor deposition (MOCVD), have been investigated experimentally in terms of threshold current density, internal waveguide loss, differential quantum efficiency and light output power. Very low threshold current density of 410 A/cm2, high characteristic temperature of 113 K, low internal waveguide loss of 5 cm-1, high differential quantum efficiency of 82% and high light output power of 100 mW were obtained in 1.3 µm GRIN-SCH multiple quantum well (MQW) LDs by optimizing the quantum well structure including confinement layer and cavity design. Excellent uniformity for the threshold current, quantum efficiency and emission wavelength was obtained in all MOCVD grown buried heterostructure GRIN-SCH MQW LDs. Lasing characteristics of 1.5 µm GRIN-SCH MQW LDs are also described.

In this paper, scattering waves by a strip grating with an anisotropic substrate for the incidence of inclined polarization are analyzed, and polarization characteristics of scatterd waves are calculated. For simplicity, the analysis is limitted to the case of normal incidence and a perfectly conducting strip grating is assumed.

Dynamic performance of ultra-thin SIMOX (Separation by IMplanted OXgen) CMOS circuits has been studied using ring oscillators. A novel concept of current-delay product, along with an equivalent linear resistance of MOSFETs, is applied for deriving effective load capacitance of near 0.1 µm gate CMOS circuits. Calculation results showed quatitative agreement with measurement data. It was found that the gate-fringing capacitance limits the delay time is the case of under 0.2 µm gate-length. The lower bound of power-delay product of SIMOX/SOI is expected as low as 0.2 fJ for the gate length of 0.15 µm at the supply voltage of 1.5 V.

Frequency Selective Screens (FSS) with conductor or complementary aperture array are investigated. The electric current distribution on conductor or the magnetic current distribution on aperture is determined by the moment method in the spectral domain. In addition, the power reflection coefficients are calculated and the scattering properties are considered.

Modeling and performance analysis have played an important role in the economical design and efficient operation of switching systems, and is currently becoming more important because the switching systems should handle a wide range of traffic characteristics, meeting the grade of service requirements of each traffic type. Without these techniques we could no longer achieve economy and efficiency of the switching systems in complex traffic characteristic environments. From the beginning of research on electronic switching systems offering circuit-switched applications, Stored Program Control (SPC) technology has posed challenges in the area of modeling and performance analysis as well as queueing structure, efficient scheduling, and overload control strategy design. Not only teletraffic engineers and performance analysts, but also queueing theorists have been attracted to this new field, and intensive research activities, both in theory and in practice, have continued over the past two decades, now evolving to even a broader technical field including traditional performance analysis. This article reviews a number of important issues that have been raised and solved, and whose solutions have been reflected in the design of SPC switching systems. It first discusses traffic problems for centralized control systems. It next discusses traffic problems inherent in distributed switching systems.

A detailed numerical solution of the design criteria of in-phase lateral and single-longitudinal-mode operation GaInAsP/InP DFB laser arrays is presented. The analysis, including broad-area pumped and stripe-geometry pumped index-guided arrays, was carried out on the basis of the eigenvalue equation method. It is shown that there exists a cut-off array pitch co, at which all of the higher-order array modes are cut off. For the pitch larger than the cut-off pitch co, the modal discrimination is evaluated by the threshold gain difference between the in-phase lateral and higher-order array modes. As a result, the modal discrimination was found to decrease with the increase of the number of elements and the array pitch which is limited to be smaller than twice the cut-off pitch co to attain a stable in-phase lateral- and single-longitudinal-mode operation.

In high-speed packet networks, protocol processing overhead time becomes remarkable in determining the system performance. In this paper, we present a new Selective-Repeat ARQ scheme (called Block SR-ARQ sheme), in which a packet is transmitted or retransmitted in the same way as basic SR-ARQ scheme, but a single acknowledgement packet is used to acknowledge a block of packets. The maximum number of packets acknowledged by an acknowledgement packet is defined as block size. We analyze the system throughput and the average packet delay over the system, and the accuracy of approximately analyzed results is validated by simulation. Furthermore, we show that there exists an optimal block size which obtains both the maximum throughput and the minimum average packet delay.

A multi-valued addressing scheme is proposed for a high speed, high packing density memory system. This scheme is a level-multiplex addressing scheme instead of standard time-multiplex addressing scheme, and provides all address signals to the DRAM at the same time without increasing the address pin counts. This scheme makes memory matrix strechable and achieves the low power dissipation using the enhanced partial array activation. The 16 Mb stretchable memory matrix DRAM (16MbSTDRAM) is examined using this addressing design. A power dissipation of 121.5 mW, access time of 30 ns, and 20 pin have been estimated for 3.3 v 16MbSTDRAM with X/Y=15/9 adress configuration. The low power battery-drive memory system for such as the note-book or the handheld-type personal computers can be realized by the STDRAMs with the multi-valued addressing scheme.

An efficient reconstruction algorithm for diffraction tomography based on the modified Newton-Kantorovich method is presented and numerically studies. With the Fréchet derivative obtained for the Helmholtz equation, one can derive an iterative formula for getting an object function, which is a function of refractive index of a scatterer. Setting an initial guess of the object function to zero, the pth estimate of the function is obtained by performing the inverse Fourier transform of its spectrum. Since the spectrum is bandlimited within a low-frequency band, the algorithm does not require usual regularization techniques to circumvent ill-posedness of the problem. For numerical calculation of the direct scattering problem, the moment method and the FFT-CG method are utilized. Computer simulations are made for lossless and homogeneous dielectric circular cylinders of various radii and refractive indices. In the iteration process of image reconstruction, the imaginary part of the object function is set to zero with a priori knowledge of the lossless scatterer. Then the convergence behavior of the algorithm remarkably gets improved. From the simulated results, it is seen that the algorithm provides high-quality reconstructed images even for cases where the first-order Born approximation breaks down. Furthermore, the results demonstrate fast convergence properties of the iterative procedure. In particular, we can successfully reconstruct the cylinder of radius 1 wavelength and refractive index that differs by 10% from the surrounding medium. The proposed algorithm is also effective for an object of larger radius.

A new design method is proposed for realizing a hypercube network (HC) structured multicomputer system on a wafer using wafer-scale integration (WSI). The probability that an HC can be constructed on a wafer is higher in this method than in the conventional method; this probavility is called a construction probability. We adopt the FUSS method for the processor (PE) address allocation in our desing because it has a high success probability in the allocation. Even if the design renders the address allocation success probalility hegher, it is of no use if it makes either the maximum wiring length between PEs or the array size (wiring area) larger. A new wiring channel structure capable of connecting PEs on a wafer is proposed in this paper, where a channel, called a basic channel, is used. A one-dimensional-array sub-HC row network (RN) or column networks (CN) can be constructed using the basic channel. The sub-HC construction method, which embeds wirings into the basic channel, is also proposed. It requires almost the same wiring width as conventional method. However, it has an advantage in that maximum wiring length between PEs can be about half that of the conventional method. If PEs must be shifted in the case of PE defects, they can be shifted and connected to the basic channel using other PE shifting channels, and an RN or CN can be constructed. The maximum wiring length between PEs, array size, and construction probability will also be derived, and it will be shown that the proposed design is superior to the conventional one.