This paper presents a novel model of optical associative memory using an optoelectronic neurochips, which detects and processes a two-dimensional input image at the same time. The original point of this model is that the optoelectronic neurochips allow direct image processing in terms of parallel input/output interface and parallel neural processing. The operation principle is based on the nonlinear transformation of the input image to the corresponding the point attractor of a fully connected neural network. The learning algorithm is the simulated annealing and the energy of the network state is used as its cost function. The computer simulations show its usefulness and that the maximum number of stored images is 150 in the network with 64 neurons. Moreover, we experimentally demonstrate an optical implementation of the model using the optoelectronic neurochip. The chip consists of two-dimensional array of variable sensitivity photodetectors with 8 16 elements. The experimental results shows that 3 images of size 8 8 were successfully stored in the system. In the case of the input image of size 64 64, the estimated processing speed is 100 times higher than that of the conventional optoelectronic neurochips.

The student model component of intelligent tutoring systems (ITSs) used to be considered central: it was the means by which the ITS could individually adapt the learning experience to suit the learner's perceived needs. However, the practical difficulty of building reliable student models, the evolution away from the knowledge communication style of ITSs towards a more constructivist philosophy, and the development of new media to support learning interactions have all combined to question the role (if any) for student models in current interactive learning environments (ILEs). In this paper we will explore the new role of student models by considering the lessons learned from five Lancaster projects (SAFE, EPIC, PEOPLEPOWER, CLORIS and SMILE). The main issues revolve (as usual) around the questions of control and learning objectives.

The connection admission control is one of preventive traffic control in ATM networks. The one objective of connection admission control is to keep the network load moderate so as to achieve a performance objective associated with quality of services (QOS). Because the cell loss rate is more sensitive to offered load than the average queuing delay in ATM networks, QOS requirement associated with cell loss rate is considered. The connection admission control acts as one of the major roles in traffic control. The job of connection admission control is to make an acceptance decision for connection set-up request to control the network load. This paper proposed and evaluated a connection admission control method. The proposed method is suitable for real time operation even in large diversity of connection types, because the amount of calculation for connection admission control is reduced remarkably compared to conventional algorithms. Moreover, the amount of calculation for the algorithm does not increase even when the number of connection types increases. The proposed method uses probability function for the number of cells transferred from multiplexed connections and uses recursive equations in estimating cell loss rate.

In this paper, we study the knowledge tightness of zero-knowledge proofs. To this end, we present a new measure for the knowledge tightness of zero-knowledge proofs and show that if a language L has a bounded round zero-knowledge proof with knowledge tightness t(|x|) 2 - |x|-c for some c 0, then L BPP and that any language L AM has a bounded round zero-knowledge proof with knowledge tightness t(|x|) 2-2-O(|x|) under the assumption that collision intractable hash functions exist. This implies that in the case of a bounded round zero-knowledge proof for a language L BPP, the optimal knowledge tightness is "2" unless AM = BPP. In addition, we show that any language L IP has an unbounded round zero-knowledge proof with knowledge tightness t(|x|) 1.5 under the assumption that nonuniformly secure probabilistic encryptions exist.

It is often desired to change the cutoff frequencies of digital filters in some applications like digital electronic instruments. This paper proposes a design of variable lowpass digital filters with wider ranges of cutoff frequencies than conventional designs. Wave digital filters are used for the prototypes of variable filters. The proposed design is based on the frequency scaling in the s-domain, while the conventional ones are based on the z-domain lowpass-to-lowpass transformations. The first-order approximation by the Taylor series expansion is used to make multiplier coefficients in a wave digital filters obtained from a frequency-scaled LC filter become linear functions of the scaling parameter, which is similar to the conventional design. Furthermore this paper discusses the reduction of the approximation error. The curvature is introduced as the figure of the quality of the first-order approximation. The use of the second-order approximation to large-curvature multiplier coefficients instead of the first-order one is proposed.

The structural necessary and sufficient condition for "the transition-liveness means the place-liveness and vice-versa" of a subclass NII of general Petri nets is given as "the place and transition live Petri net, or PTL net, ÑII". Furthermore, "the one-token-condition Petri net, or OTC net, II" which means that every MSDL (minimal structural deadlock) is "transition and place live" under at least one initial token, i.e., II is "transition and place live" under the above initial marking. These subclasses NII, ÑII( NII), and II(ÑII) are almost the general Petri nets except at least one MSTR(minimal structural trap) and at least one pair of "a virtual MSTR or a virtual STR" and "a virtual MSDL" of an MBTR (minimal behavioral trap) in connection with making an MSDL transition-live.

Experimental evidence of a two-step enhancement in electromigration lifetime is presented through pulsed testing that extends over a wide frequency range from 7 mHz to 50 MHz. It is also found, through an accompanying failure analysis, that the failure mechanism is not affected by current pulsing. Test samples were the lowew metal lines and the through-holes in double-level interconnects. The same results were obtained for both samples. The testing temperature of the test conductor was determined considering the Joule heating to eliminate errors in lifetime estimation due to temperature errors. A two-step enhancement in lifetime is extracted by normalizing the pulsed electromigration lifetime by the continuous one. The first step occurs in the frequency range from 0.1 to 10 kHz where the lifetime increases with (duty ratio)-2 and the second step occurs above 100 kHz with (duty ratio)-3. The transition frequency in the first-step enhancement shifts to the higher frequency region with a decrease in stress temperature or an increase in current density, whereas the transition frequency in the second step is not affected by these stress conditions. The lifetime enhancement is analyzed in relation to the relaxation process during the current pulsing. According to the two-step behavior, two distinct relaxation times are assumed as opposed to the single relaxation time in other proposed models. The results of the analysis agree with the experimental results for the dependence on the frequency and duty ratio of pulses. The two experimentally derived relaxation times are about 5 s and 1 µs.

An efficient algorithm is presented for finding all solutions of piecewise-linear resistive circuits. In this algorithm, a simple sign test is performed to eliminate many linear regions that do not contain a solution. This makes the number of simultaneous linear equations to be solved much smaller. This test, in its original form, is applied to each linear region; but this is time-consuming because the number of linear regions is generally very large. In this paper, it is shown that the sign test can be applied to super-regions consisting of adjacent linear regions. Therefore, many linear regions are discarded at the same time, and the computational efficiency of the algorithm is substantially improved. The branch-and-bound method is used in applying the sign test to super-regions. Some numerical examples are given, and it is shown that all solutions are computed very rapidly. The proposed algorithm is simple, efficient, and can be easily programmed.

This paper describes mixed gas systems of SO2 and NO2 which are the essential corrosive gases in an ordinary atmospheric environment of electronic parts. It describes the corrosion product compositions and the behavior of copper in mixed and separate gases. Results of our tests show the following: (1) The weight of corrosion products with the SO2-NO2 mixed gas approximate the sum of those with the individual gases, however, the corrosion products of SO2 are affected by NO2. (2) Tests of the SO2-NO2 mixed gas closely simulates tests of electronic parts in the ordinary atmospheric environment.

It is important for LSI system designers to estimate computational errors when designing LSI's for numeric computations. Both for the prediction of the errors at an early stage of designing and for the choice of a proper hardware configuration to achieve a target performance, it is desirable that the errors can be estimated in terms of a minimum of parameters. This paper presents a theoretical error analysis of multiply-accumulation implemented by distributed arithmetic(DA) and proposes a new method for estimating the mean-squared error. DA is a method of implementing the multiply-accumulation that is defined as an inner product of an input vector and a fixed coefficient vector. Using a ROM which stores partial products. DA calculates the output by accumulating the partial products bitserially. As DA uses no parallel multipliers, it needs a smaller chip area than methods using parallel multipliers. Thus DA is effectively utilitzed for the LSI implementation of a digital signal processing system which requires the multiply-accumulation. It has been known that, if the input data are uniformly distributed, the mean-squared error of the multiply-accumulation implemented by DA is a function of only the word lengths of the input, the output, and the ROM. The proposed method for the error estimation can calculate the mean-squared error by using the same parameters even when the input data are not uniformly distributed. The basic idea of the method is to regard the input data as a combination of uniformly distributed partial data with a different word length. Then the mean-squared error can be predicted as a weighted sum of the contribution of each partial data, where the weight is the ratio of the partial data to the total input data. Finally, the method is applied to a two-dimensional inverse discrete cosine transform (IDCT) and the practicability of the method is confirmed by computer simulations of the IDCT implemented by DA.

Finding DC solutions of nonlinear networks is one of the most difficult tasks in circuit simulation, and many circuit designers experience difficulties in finding DC solutions using Newton's method. Piecewise-linear analysis has been studied to overcome this difficulty. However, efficient piecewiselinear algorithms have not been proposed for nonlinear resistive networks containing the Gummel-Poon models or the Shichman-Hodges models. In this paper, a new piecewise-linear algorithm is presented for solving nonlinear resistive networks containing these sophisticated transistor models. The basic idea of the algorithm is to exploit the special structure of the nonlinear network equations, namely, the pairwise-separability. The proposed algorithm is globally convergent and much more efficient than the conventional simplical-type piecewise-linear algorithms.

This paper considers the subliminal channel, hidden in an identification scheme, for transferring signatures. We observe the direct parallelization of the Fiat-Shamir identification scheme has a subliminal channel for the transmission of the digital signature. A positive aspect of this hidden channel supplies us how to transfer signatures without secure channels. As a formulation of such application, we introduce a new notion called privately recordable signature. The privately recordable signature is generated in an interactive protocol between a signer and a verifier, and only the verifier can keep the signatures although no third adversary can record the signatures. ln this scheme, then the disclosure of the verifier's private coin turns the signer's signature into the ordinary digital signature which is verified by anybody with the singer's public key. The basic idea of our construction suggests the novel primitive that a transferring securely signatures without secret channels could be constructed using only one-way function (without trapdoor).

This paper describes the current situations and future directions of intelligent CAI researches/development in Japan. Then necessity of intelligence in CAIs/Educational systems are thought over corresponding to the model of teaching and the cognitive model of human learning like the situated learning, knowledge construction and so on. Originally, the main aims of ITSs/ICAIs are to tealize the high level environment of individual teaching/learning. So it is the most important to incorporate the intellectual function of teaching into the system. Whatever kinds of teaching purposes ITSs have, they have the quite complex structure which consists of the domain knowledge base (Expert system), student model, the tutoring knowledge base, the powerful human interface, and sophisticated inference engine with plural functions by artificial intelligence technology. In this paper, the technological and educational points of view are discussed, surveyed and summarized based on intelligent teaching functions of ITSs/ICAIs. Moreover, the meaning of new paradigm from ITSs to ILE are mentioned under the new technology of networking and multi-media.

As promising copy networks of very large multicast switching networks for Broadband ISDN, multi-stage Recursive Copy Networks (RCN) have been proposed recently. In the multicast switch structure, the RCN precedes a point-to-point switch. At an RCN, all the copies of a master cell are generated recursively, i.e., a few copies of the master cell are made initially, and by considering each of these copies to be master cells, more copies are made which, in turn, are again considered to be master cells to make still more copies, the process thus progressing recursively till all the required copies are made. By this principle of recursive generation of copies, the number of copies that can be generated is independent of the hardware size of the RCN. A limitation of RCNs is that buffer sizes at all stages except the first stage have to be large so as to keep the cell loss due to buffer overflow within desired limits. This paper inspects a flow control scheme by which the probability of buffer overflow can be kept low, even though the buffer sizes at later stages are not large. Under this flow control procedure, a cell is not transmitted from a stage to the succeeding stage, if the occupancy level of the buffer of the succeeding stage exceeds a threshold. We study by simulation the performance aspects of such a flow control scheme in RCNs under cut-through switching scheme and under store-and-forward switching scheme. At high load intensities, the overflow probability can be reduced by an order of magnitude in 2-stage RCNs and by two orders of magnitude in 3-stage RCNs. To restrict the overflow probability within a given limit, the required buffer size is less under flow control than under no flow control. The implementation of the flow control is simple and the control overhead is small, thereby making the scheme attractive for implementation in high speed switching environments. Further, the proposed flow control scheme does not disturb the cell sequence.

This paper describes the effective countermeasures for exfoliation of large-sized ceramic capacitors, deterioration of dummy resistors and developement of a spark sensor with UVtrons at 300-500 kW transmitting stations. Cracks and exfoliation were found at the electrode of large-sized ceramic capacitors in the output circuit of the 500 kW transmitter. The exfoliation was caused by the temperature rise and the thermal fatigues at the electrode with the Nickel plating including Irons. A pure Nickel-plated electrode including no Irons and a new soldering method using disk-typed solder with a large adhesive area are employed in order to reduce the temperature rise. The temperature rise of the improved capacitor was 18 lower than the conventional one. Deterioration of ELEMA resistors of the 300 kW dummy antenna was discovered. The damage of the resistor was caused by the concentration of the electric current followed by the thermal stress cycle which made mechanical exhaustion at the electrode. Therefore, oval-shaped type resistors with much longer electric current path (20% up) to suppress the concentration of current flow and much slower temperature rise are newly developed. In case that sparks occurred at DC or RF high voltage impressed sections of the high power transmitting equipment, the discharged points could be seriously damaged by the transmitter energy itself. In orded to prevent this, a spark detector using UV (Ultra violet) trons is developed and installed at the matchign circuit of the 500 kW transmitter. Conventional UV sensors with only one UVtron could not detect feeble discharges and sparks with a duration time of less than 150 ms because of false outputs by the back ground noise. Since choosing three out of four UV trons system is employed, possibility producing a false output will be just one to 445 years theoretically. This means extremely reliable and sensitive spark detection system are constructed. These countermeasures have improved reliability of the transmitting equipment greatly. No damages have been found in the transmitters ever since.

Reflection type optical switches with intersecting waveguides and curved electrodes are newly proposed. The guided incident mode is expanded into an infinite spectrum of plane wavelets. The effects of light tunneling into the transmission port is taken care of by treating the 3-layer structure and using its reflection and transmission coefficients in estimation of the extinction ratios. It is found that the electrode curved in the form of an exponential spiral provides remarkably improved power reflectivity. This is because it poses a constant angle of incidence (smaller than the critical angle) to all variously oriented impinging wavelets. In this way, all plane wavelets are made to undertake total reflections. These total reflections result in considerably high extinction ratios to be achivable at the transmission port. It is also shown that the electrode length is shorter and the intersection angle is wider than those corresponding to a straight electrode. Therefore, it is concluded that the curvature of the electrode improves the switching characteristics of the device.

Narrow emitter effects in self-aligned bipolar transistors are discussed. Besides the increase of a non-ideal base current, the decrease of an ideal base current is newly observed, and a consequent fluctuation of the current gain becomes wider in the smaller emitter geometry. Both phenomena are attributed to the reduction of an emitter-impurity concentration.

We propose an optical computing architecture called pure optical parall array logic system (P-OPALS) as an instance of sophisticated optical computing system. On the P-OPALS, high density images can be processed in parallel using the optical system with high resolving power. We point out problems on the way to develop the P-OPALS and propose logical foundation of the P-OPALS called single-input optical array logic (S-OAL) as a solution of those problems. Based on the proposed architecture, an experimental system of the P-OPALS is constructed by using three optical techniques: birefringent encoding, selectable discrete correlator, and birefringent decoding. To show processing capability of the P-OPALS, some basic parallel operations are demonstrated. The results obtained indicate that image consisting of 300 100 pixels can be processed in parallel on the experimental P-OPALS. Finally, we estimate potential capability of the P-OPALS.

In this paper, we clarify fundamental properties of conventional back-propagation neural networks to learn chaotic dynamical systems by some numerical experiments. We train three-layers networks using back-propagation algorithm with the data from two examples of two-dimensional discrete dynamical systems. We qualitatively evaluate the trained networks with two methods analysing geometrical mapping structure and reconstruction of an attractor by the recurrent feedback of the networks. We also quantitatively evaluate the trained networks with calculation of the Lyapunov exponents that represent the dynamics of the recurrent networks is chaotic or periodic. In many cases, the trained networks show high ability of extracting mapping structures of original two-dimensional dynamical systems. We confirm that the Lyapunov exponents of the trained networks correspond to whether the reconstructed attractors by the recurrent networks are chaotic or periodic.

This paper describes the development of an environmental ICAI system for English conversation learning, which is equipped with a simulation-based learning environment and an advisor function. Recently there have been various educational applications or tools for adult second language education, where the learning target is the acquisition of formal knowledge of a language. When considering the implementation of a practical CAI system, methods for developing communicative competence in learners are required. Although there are a number of ICAI systems for conversation learning, often the methodologies which they apply are not completely suitable for the acquisition of the required fundamental knowledge. Our system, based on the architecture of environmental CAI, enhances communication skill acquisition. The system has a learning environment with the following features: (1) A simulation of language activities, implemented in the role-playing game style, which helps to promote a learner's motivation. (2) Educational behavior of the system is varied through the modification of the learning environment and changes in the simulation progress and control commands. (3) An induction strategy, which can cause learners to fail to achieve a learning target, is executed by an advisor mechanism. The system is a prototype architecture for application in environmental ICAI systems for simulation based learning. We believe that the architecture of this system is an efficient framework for linguistic education.