This paper presents a zero-knowledge interactive protocol that demonstrates two factors a and b of a composite number n (=ab) are really known by the prover, without revealing the factors themselves. Here the factors a and b need not be primes. The security of the protocol is based on the difficulty of computing discrete logarithms modulo a large prime.

Via electromigration (EM) performance of aluminum based metallization (AL) systems has been investigated for vias chains of 1500-4000 vias of 1.0 micron diameter. The results show that via EM lifetime can not be enhanced by a simple increase of M2 step coverage in AL/AL vias because the EM induced voids are formed at AL/AL via interface where electrons flow from Ml to M2 even in the case of very poor M2 step coverage. The voids are induced by the boundary layer in AL/AL vias, where a temperature gradient causes discontinuity of aluminum atoms flux. The failure location is not moved though via EM lifetime can be improved by controlling stress in passivation, sputter etch removal thickness and grain size of the first metal. Next, the effect of the boundary layer are eliminated by depositing titanium under the second aluminum or depositing WSi on the first aluminum. In the both cases, via EM lifetime are improved and the failure locations are changed. Especially WSi layer suppresses the voids formation rather than titanium. Models for the failure mechanism in each metallization system are further discussed.

This paper describes the use of optical interconnections in switching systems and discusses our recent achievements in this area. Switching system interconnections are classified based on their application layers. The evolution of optical interconnections in switching systems in discussed in terms of such system requirements as cost, size, and throughput. Recent achievements are discussed: an optical inter-module connector, a free-space digital switch, and a large-capacity optically intra-connected ATM switch.

Checkpointing is one of the most powerful tools to operate a computer system with high reliability. We should execute the optimal checkpointing in some sense. This note shows the optimal checkpoint sequence minimizing the expected loss, Numerical examples are shown for illustration.

Beam-steering devices are attractive for spatial optical interconnections. Those devices are essential not only for fixed connecting routed optical interconnections, but for flexible connecting routed optical interconnections. The flexible connecting routed optical interconections are more powerful than the conventional fixed connecting routed ones. Structures and characteristics of beam-steering devices, a beam-scanning laser diode and a fringe-shifting laser diode, are reported for those interconnections. Using these lasers, the configurations of several optical interconnections, such as optical buses and optical data switching links as examples of fixed and flexible connecting routed optical interconnections are discussed.

It is recognized in Japan that reformation of the national research institutions is urgently necessary. Present situation and constraints are shown and the action items are discussed.

This paper presents two approaches for computing the reliability of complex networks subject to two kinds of failure, open failure and shorted failure. The reliabilities of some series-parallel networks are considered by many analysts. However a practical system is more complex. The methods given in this paper can be applied not only to a series-parallel network but also to a non-series-parallel network which is composed of non-identical and independent components subject to two kinds of failure. This paper also deals with a network subject to flow quantity constraint such as the one which is required to control j or more separate paths. For such a system it is difficult to obtain system reliability because the number of states to be considered in this system is extremely large compared to a conventional 2-state device system. In this paper we obtain the reliabilities for such systems by a combinatorial approach and by a simulation approach.

A new pattern synthesis method for multibeam reflector antennas is described. The Directional Constrained Minimum Power (DCMP) method, which was developed as an adaptive array algorithm, has been applied to reflector antennas with cluster feeds. The main objective of this pattern synthesis is to optimize the excitation distribution of the cluster primary feed in order to reduce the sidelobe level and to attain a high main beam gain. A desired contour beam pattern has also been attained by modifying this method. Furthermore, this paper describes other applications of this method, such as pattern optimization taking account of the frequency characteristics and the change in the radiation pattern due to an antenna pointing system, cross-polarization reduction, and monopulse pattern synthesis for an RF sensor.

For systems in which the probability that an incorrect output is observed differs with input values, we adopt the redundant usage of n copies of identical systems which we call the n-redundant system. This paper presents a method to find the optimal redundancy of systems for minimizing the probability of dangerous errors. First, it is proved that a k-out-of-n redundancy or a mixture of two kinds of k-out-of-n redundancies minimizes the probability of D-errors under the condition that the probability of output errors including both dangerous errors and safe errors is below a specified value. Next, an algorithm is given to find the optimal series-parallel redundancy of systems by using the properties of the distance between two structure functions.

Optical waveguides are one of the key devices for photonic integrated circuits considered to be one of the candidates for optical interconnects. In particular lossless bend type waveguides are necessary to integrate different optical devices monolithically. In this paper, we report on the bending loss characteristics of the multi-quantum well bend waveguide with respect to the bend radius and lateral optical mode confinement. We show that to decrease the bending loss to less than 0.5 dB, it is necessary to increase either the confinement or the bend radius. For an example, when the confinement is around 85%, the bend radius should be more than 2 mm. We also show the application of the S-bend waveguides to directional coupler type optical switch.

In this paper, we propose a plausible software reliability growth model by applying a mathematical technique of stochastic differential equations. First, we extend a basic differential equation describing the average behavior of software fault-detection processes during the testing phase to a stochastic differential equation of ItÔ type, and derive a probability distribution of its solution processes. Second, we obtain several software reliability measures from the probability distribution. Finally, applying a method of maximum-likelihood we estimate unknown parameters in our model by using available data in the actual software testing procedures, and numerically show the stochastic behavior of the number of faults remaining in the software system. Further, the model is compared among the existing software reliability growth models in terms of goodness-of-fit.

New focused ion beam (FIB) methods for microscopic cross-sectioning and observation, microscopic crosssectioning and elemental analysis, and aluminum film microstructure observation are presented. The new methods are compared to the conventional methods and the conventional FIB methods, from the four viewpoints such as easiness of analysis, analysis time, spatial resolution, and pinpointing precision. The new FIB methods, as a result, are shown to be the best ones totally judging from the viewpoints shown above.

Leakage enhancement after an ESD event has been analyzed for output buffer LDD MOSFETs. The HBM ESD failure threshold for the LDD MOSFETs is only 200-300 V and the failure is the leakage enhancement of the off-state MOSFETs called as "soft breakdown" leakage. This leakage enhancement is supposed to be caused by trapped electrons in the gate oxide and/or creation of interface states at the gate overlapped drain region due to snap-back stress during the ESD event. The mechanism of the lekage can be explained by band-to-band and/or interface state-to-band tunneling of electrons. The improvement of the HBM ESD threshold has been also evaluated by using two types of drain engineering which are additional arsenic implantation for the output LDD MOSFETs and "offset" gate MOSFET as a protection circuit for the output pins. By using these drain engineering, the threshold can be improved to more than 2000 V.

Mean Time Between Failures (MTBF) is an important measure of practical repairable systems, but it has not been obtained for a repairable linear consecutive-k-out-of-n: F system. We first present a general formula for the (steady-state) availability of a repairable linear consecutive-k-out-of-n: F system with nonidentical components by employing the cut set approach or a topological availability method. Second, we present a general formula for frequency of system failures of a repairable linear consecutive-k-out-of-n: F system with nonidentical components. Then the MTBF for the repairable linear consecutive-k-out-of-n: F system is shown by using the frequency of system failure and availability. Lastly, we derive some figures which show the relationship between the MTBF and repair rate µorρ(=λ/µ) in the repairable linear consecutive-k-out-of-n: F system. The figures can be easily used and are useful for reliability design.

For improving the RSA cryptosystem, more desirable conditions on key structures have been intensively studied. Recently, M.J.Wiener presented a cryptanalytic attack on the use of small RSA secret exponents. To be secure against the Wiener's attack, the size of a secret exponent d should be chosen more than one-quarter of the size of the modulus n = pq (in bits). Besides, it is more desirable, in frequent cases, to make the public exponent e as small as possible. However if small d is chosen first, in such case as the digital signature system with smart card, the size of e is inevitably increased to that of n when we use the conventional key generation algorithm. This paper presents a new algorithm, Algorithm I, for generating of the secure RSA keys against Wiener's attack. With Algorithm I, it is possible to choose the smaller sizes of the RSA exponents under certain conditions on key parameters. For example, with Algorithm I, we can construct the RSA keys with the public exponent e of two-thirds and secret exponent d of one-third of the size of modulus n (in bits). Furthermore we present a modified version of Algorithm I, Algorithm II, for generating of the strong RSA keys having the difficulty of factoring n. Finally we analyze the performances of Algorithm I and Algorithm II.

This paper proposes a new combined fast algorithm for transversal adaptive filters. The fast transversal filter (FTF) algorithm and the normalized LMS (NLMS) are combined in the following way. In the initialization period, the FTF is used to obtain fast convergence. After converging, the algorithm is switched to the NLMS algorithm because the FTF cannot be used for a long time due to its numerical instability. Nonstationary environment, that is, time varying unknown system for instance, is classified into three categories: slow time varying, fast time varying and sudden time varying systems. The NLMS algorithm is applied to the first situation. In the latter two cases, however, the NLMS algorithm cannot provide a good performance. So, the FTF algorithm is selected. Switching between the two algorithms is automatically controlled by using the difference of the MSE sequence. If the difference exceeds a threshold, then the FTF is selected. Other wise, the NLMS is selected. Compared with the RLS algorithm, the proposed combined algorithm needs less computation, while maintaining the same performance. Furthermore, compared with the FTF algorithm, it provides numerically stable operation.

This paper presents an experimental environment of an intelligent tutoring system called EXPITS. In this environment, users learn functions and the structure of the intelligent tutoring system and characteristics of knowledge processing. EXPITS provides facilities for investigating internal processes and internal states of the intelligent tutoring system. These facilities include visualization tools and controllers of internal processes. Because the internal states and behavior of ITS depend on student's understanding states, one cannot get total understanding of ITS without information about student's knowledge states. To solve this problem, we introduce a pseudo student which simulates a human student in order to visualize explicitly all information which affects ITS behavior. Target users of EXPITS are school teachers, who are users of intelligent tutoring systems, university students who are studying artificial intelligence and postgraduate students who are specially studying intelligent tutoring systems. We have designed EXPITS to achieve different learning objectives for these three kinds of users. The learning objective for school teachers is to understand the differnce between intelligent tutoring systems and traditional CAI systems. University students are expected to understand characteristics of knowledge processing and rule based systems. Lastly, EXPITS provides postgraduate students who are studying intelligent tutoring systems with a test bed for examining ability and efficiency of the system in different configurations by changing parameters and by replacing constituents of the system. To achieve these purposes, EXPITS has experimental facilities for the following four themes; relationship between the domain knowledge representation method and teaching activities, the selection method of teaching paradigms, relationship between problem solving processes and teaching activities, and student modeling.

The crosstalk characteristics of a long-wavelength monolithically integrated photoreceiver array are analyzed. The device consists of an array of transimpedance photoreceivers fabricated on a semi-insulating InP substrate. The distance between the photodetectors is large enough to suppress the photonic crosstalk. Therefore, the crosstalk of the device is mainly due to signal propagation from the channels through the power line shared by each channel on the chip. This crosstalk is inevitable to the photoreceiver arrays which employ common power lines. The magnitude of the crosstalk largely depends on the impedance of the power-supply circuit outside the chip. The crosstalk spectrum often has a peak and recess structure. The crosstalk peak at the edge of the operating band-width is due to the resonance characteristic of the transimpedance amplifier. The other peak and recess structures on the spectrum are due to the resonance phenomena of on-chip and off-chip capacitors and inductance on the power-supply line outside the chip. This crosstalk can be reduced by using on-chip bypass capacitance and dumping resistance. However, the resonance due to the capacitance and inductance on the power-supply circuit outside the chip can't be controlled by the on-chip components. Therefore, an optimized design for the power supply circuit outside the chip is also indispensable for suppressing crosstalk.

A Si metal insulator semiconductor tunnel emitter transistor (Si MIS TET) which is a new type of bipolar transistor was fabricated and its electrical properties for the temperature range of 100 K - 300 K were investigated. The common emitter mode current gain obtained was 75 at 300 K and 74 at 100 K. It was confirmed by measuring the temperature dependence of the base current that the inversion base layer indeed functioned as a base of the Si MIS TET. The current gain of the Si MIS TET did not decrease at low temperature of 100 K, though the current gain of the conventional Si bipolar transistor decreases at low temperature due to the emitter bandgap narrowing in heavily doped emitter. This origin was that the carrier injection mechanism between the emitter and the base was tunneling.

The paper proposes and reports on pototyping a work bench system for novice Prolog programmers which consists of a visually-structured interactive tracer and a prototype-based programming support. The tracer actually is a simulated interpreter in Prolog. It is interpreted by a Prolog interpreter being embedded with facilities interfacing programs in Prolog and the objects programmed in C. It displays, by way of these objects, the past, current and future goals, highlights variable sharing and value substitution, and marks the current goals and backtrack choice points. It is at user's will to let the tracer show and hide subgoals as well as to let it backtrack when it failed, step back for redoing or terminate tracing. The programming support module first provides the programmer with structural prototype patterns and the roles of the constituent functions. We developed a support system for the 2 types of recursive definitions. After having selected the prototype, the user is requested to specify the data types and the names of variables to be put in the arguments, which propagate through the structure. The support module then offers a menu of primitive or user-registered constituent functions as may be useful in processing and/or obtaining user-specified types of data. Thirdly the system lets the user express his/her intention by sample input-output data instances in his/her task goals. It makes the values propagate through the structures thus motivating the user to design the constituent functions. At the goal recursion point, the user is allowed to creep into examining the definitions of the reduced versions of the instances, helping the user find the condition with which the recursion terminates. Finally the module assists the user to convert the structural descriptions into Prolog programs.