This paper presents a novel and successful optimization algorithm for optimizing Multiple-valued Logic (MVL) functions based on Petri net theory. Mathematical properties and Petri net modeling tools to implement MVL systems are introduced. On the basis of these properties and modeling tools, the optimization algorithm can synthesize, analyze and minimize an arbitrary quaternary logic function of n-input variables. The analysis technique of optimization algorithm is a well-established concept from both theories of MVL and Petri nets, and this can be applied to specify and optimize any MVL Petri net system. In this paper, Petri nets of Galois field have been proposed in order to form a complete system, which can be used to realize and construct VLSI circuit of any MVL function. Based on the Petri nets of Galois field and the proposed algorithm, the quaternary minimum and maximum functions have been analyzed, minimized, and designed. These applications have demonstrated the usefulness of optimization algorithm. Based on Petri net theory, the analysis revealed important information about MVL Petri net modeled systems, where this information has been used to evaluate the modeled system and suggest improvements or changes. For evaluation, advantages of the proposed method over a conventional logic minimization method are presented. Also, we have observed that the MVL Petri nets have the following advantages: Designers can exhibit clearly, simply and systematically any complex MVL Petri net nodel, number of concurrent operations is increased, number of places and transitions that are needed to realize a MVL model is very small, and the interconnection problems can be greatly reduced.

This paper describes a simple system of measuring the spatial distributions of spectral intensities with AgI-421 nm and AgI-546 nm among many optical spectrums emitted from an arc discharge between separating Ag contacts. In order to detect the intensities of two optical spectrums, the prototype equipment has two sets assembled with a CCD color linear image sensor, a lens and optical filters, which are arranged on rectangularity. The intensities of two spectrums can be recorded with 2 ms time-resolution within a long arc duration on a digital memory. The recorded digital signals are processed by using a personal computer in order to reconstruct two spatial distributions of spectral intensities in a cross section of arc column with the Algebraic Reconstruction Technique.

Recognizable series is a model of a sequential machine. A recognizable series S is represented by a triple (λ,µ,γ), called a linear representation of S, where λ is a row vector of dimension n specifying the initial state, γ is a column vector of dimension n specifying the output at a state, and µ is a morphism from input words to nn matrices specifying the state transition. The output for an input word w is defined as λ(µw) γ, called the coefficient of w in S, and written as (S,w). We present an algorithm which constructs a reduced linear representation of an unknown recognizable series S, with coefficients in a commutative field, using coefficient queries and equivalence queries. The answer to a coefficient query, with a word w, is the coefficient (S, w) of w in S. When one asks an equivalence query with a linear representation (λ,µ,γ), if (λ,µ,γ) is a linear representation of S, yes is returned, and otherwise a word c such that λ (µc) γ(S, c) and the coefficient (S, c) are returned: Such a word c is called a counterexample for the query. For each execution step of the algorithm, the execution time consumed from the initial step to the current step is O(mN 4M), where N is the dimension of a reduced linear representation of S, M is the maximum time consumed by a single fundamental operation (addition, subtraction, multiplication or division), and m is the maximum length of counterexamples as answers to equivalence queries returned until that step.

In communication protocols, the behaviour of a protocol entity is related to the behaviour of another protocol entity as they communicate under sets of communication rules (protocols). Thus, it is desirable to concentrate on the design of one protocol entity and generate the corresponding protocol entity automatically. Furthermore, it is desirable that the protocol is formal, precise and unambiguous that is, it is described using FDTs (Formal Description Techniques). In this paper, we propose a protocol synthesis algorithm in which, from a LOTOS specification of a single given entity, LOTOS specification of the corresponding peer entity is generated automatically. Unlike previous works, where FSMs (Finite State Machines) were used to synthesize protocols, we use LOTOS, which is one of FDTs developed by ISO, in our proposed synthesis algorithm. We prove that the generated protocol is logical errors free, collectively represented as deadlock free, if the given entity is in certain forms which are natural in the context of connunication protocols.

As to the method of multi-layer testing, up to now, the testing system (called PROVES) which testes effectively each N-layer protocol implement of SUT (System Under Test) using the functions of derail-points located between N-layer and (N+1)-layer protocol implements in a test system has been proposed. The test logic programs, which are embedded in the derail-points of the test system, play an important role to realize the protocol error test sequences in the test system. Namely, they modify, add, or delete the correct protocol commands/responses output from the protocol implement part of the lest system, sends these erroneous commands/responses to SUT and observes the output from SUT. This paper proposes the method of validating the correctness of test logic program using the structural properties of Petri nets without coding the test logic programs, where correctness means that the desired output can be obtained by sending or receiving the commands/responses within a constant time under the initial conditions determined uniquely by the test system and SUT. According to our experiment, it is seen that almost all of the logical errors included in the test logic programs used for the experiment can be detected by this method.

It is shown that for a class of interval matrices we can estimate the location of eigenvalues in a very simple way. This class is characterized by the property that eigenvalues of any real linear combination of member matrices are all real and thus includes symmetric interval matrices as a subclass. Upper and lower bounds for each eigenvalue of such a class of interval matrices are provided. This enables us to obtain Hurwitz stability conditions and Schur ones for the class of interval matrices and positive definiteness conditions for symmetric interval matrices.

State space explosion is a serious problem in analyzing discrete event systems that allow concurrent occurring of events. A new method is proposed for generating reduced state spaces of systems. This method is an improvement of Valmari's stubborn set method. The generated state space preserves liveness, livelocks, and terminal states of the ordinary state space. Petri nets are used as a model of systems, and a method is shown for generating a reduced state space from a given Petri net.

Reliability of an electric contact can be defined by two parameters, contact resistance and wear, and the parameters of contacts operated in arcing condition are governed by the arc discharge. Thus the measurement on the relationship between the parameters and arc phenomena is necessary to improve the contact performance. The parameters for arcing electric contacts and problems were reviewed, and new concept for electric contact testing systems was proposed. Measurement with such an advanced system should be concurrent parallel measurement, quantitative measurement of degradation, systematic measurement, and analysis of arc discharge phenomena. Some examples of advanced measurement systems and new data obtained with such systems were described. Systematic results on relationships between condition and performance parameters were obtained by systematic measurement with systematically settled conditions, such as opening speed or material condition. A measurement method for the metallic phase arc duration was developed by the authors, and role of the metallic phase arc on contact performance parameters was found from interpretation of obtained data. The real-time surface profile measurement of an operating contact and the optical transient spectrum analyser for arc light radiated from breaking contact were also described.

The methodology for latchup-free design in bipolar and PMOS merged gates, so-called BiPMOS gates, is considered. Although BiPMOS gates can provide higher switching characteristics than conventional, individually drawn, BiCMOS gates even when the supply voltage is reduced, the general methodology to prevent latchup has been lacking. This paper presents an approximate, but sufficiently correct, mathematical technique to solve the Laplace equation, which gives the distribution of latchup trigger current for the given BiPMOS drawings. It is shown that the resistances of the collector plug and the spreading resistance under the base-collector junction greatly influence latchup, and that the well-emitter overlapping space becomes a problem in the case of a single collector. The distribution of latchup triggering current for the double-emitter double collector NPN transistor indicates the optimum position of the source diffusion area.

The new algorithm for VP bandwidth control described and analyzed in this paper is a revised version of the Successive Modification Method. Its operation is based only on call-level performance (call blocking probabilities) measured in real time, without explicitly taking the cell-level performance into account. This algorithm does not need to predict future traffic demand and to perform network-wide optimization according to the predicted traffic. These features are well suited for a B-ISDN environment, with the variety of ATM bearer services and the uncertainty of their traffic demand and other characteristics. This paper describes the relationship between the proposed control and other traffic controls in ATM networks, such as CAC and VP shaping/policing. It also offers a solution to the problem of the competition that arises when several VPs in the same transmission path need increased bandwidth. Evaluation of the transient behavior of the VP bandwidth occupied by VCs shows that there is a lower limit in the control cycle and that this limit can be estimated as the longest average holding time of VCs among all services. Numerical results obtained using a call-by-call simulator show that proposed control is effective in preventing the performance degradation caused by a large traffic imbalance in communications networks. Comparison of the proposed control with a dynamical alternate routing for VC reveals that the VP bandwidth control is effective in relieving only the areas showing serious performance degradation, but that it is not so effective in improving the overall network performance.

The prediction of a relay contact's life is still very important for support and maintenance of the Crossbar Switching Systems. It was found through surveys and experiments that the protected shower arc is the main reason for switching-relay contact erosion at existing Crossbar Switching Systems, if the contacts were not heavily activated. If the contacts were heavily activated, a long sustained steady arc might occur and severely erode the contacts. This paper proposes an arch energy estimation method for the prediction of contact erosion using object-oriented simulation technology when a steady arc occurs at protected contacts. The arc energy is expressed in a simulation model through analysis, and the model was confirmed through experimentation. The simulation model was used for building block programs of an expert system to predict the life span of switching relays in the existing Crossbar Switching Systems.

Nonmonotonic reasoning is a logical inference system which attempts to approximate human commonsense reasoning and is characterized as defeasible: having reasonably drawn a conclusion from some premises we may be forced to retract that conclusion upon learning new facts. This paper introduces a Petri net model for nonmonotonic reasoning with nonmonotonic rules generated by annotated logic programs and the unless operator. In the Petri net model, a fixpoint of a nonmonotonic theory can be represented as a maximal and consistent support of a firing sequence. We propose a structural method for finding extensions (coherent consequences) for a given set of nonmonotonic logic rules. It is based on the T-invariant technique for testing fireability of a goal transition in the Petri net model of Horn clause logic programs.

In clad contacts of bonded dissimilar metals used in relays and switches, the bonding state affects the switching performance of those devices. Examining the bonding state and analyzing the relationship between the bonding state and the causes of malfunction, such as welding of the contact, leads to improvement in reliability of electromechanical devices. In this experiment we examined, with an ultrasonic microscope, the bonding state in riveted clad contacts which had been subjected to load-breaks of in-rush current, and were able to demonstrate the causal relation of the bonding state with malfunctions of the contacts. The use of the ultrasonic microscope made it possible to perform a hitherto difficult detailed analysis of the bonding state of clad contacts. It was also confirmed that this was an extremely effective method for studying the relationship with switching performance.

Composite materials of solid lubricants, such as graphite, MoS2, WS2, etc., and metals are being used as the sliding electrical contacts. However, few reports have so far been presented on the detailed characteristics of such composite materials. It is shown in this report that contact resistance and coefficient of friction of the sliding contact of the composite material of Cu-Nb system against Cu were higher than those of the sliding contact of the composite material of Cu-Sn system against Cu. It was, further, found that composite materials of Cu-Sn system were superior to those of Cu-Nb system being both contact resistances and coefficients of friction lowered. At the same time, it was found that performances of composite materials of Cu-Sn alloy base containing exclusively WS2 were superior to those containing both WS2 and MoS2. It was, therefore, suggested that proper samples suitable for the service conditions should be selected from the composite materials of Cu-Sn system which contain exclusively WS2 for the practical applications.

In the design of 3-D filter detecting Linear Trajectory Signal (LTS), there may be paid little attention to the noise rejective characteristics. In this paper, we treat the noise rejection ability of the filter detecting LTS having margins both in its velocity and direction.

Arc discharge between electrodes of relays and switches often causes contact surface damage through material transfer and arc erosion. Especially, material transfer sometimes occurs and brings serious failure even under lower load that is quite smaller than the minimum arc current value of contact material. In this paper, contact surface configuration, material transfer, and arc erosion characteristics of Ag and AgPd 60 contacts were experimentally studied after 0.5 or 1 million switching operations at various load levels. The followings can be made clear. Firstly, it was confirmed that the arcs and material transfer occurred even under such current that was lower than the minimum arc current. Therefore, the definition of the arc occurrence boundary current was newly determined. Secondly, the relation between load conditions (current and power supply voltage) and contact surface configuration (craters and pips) caused by material transfer was studied. The arc erosion behaviors of tested samples could be classified into two types: material transfer type and wear-out type. As one of the primary factors of transition from the former type to the latter one, contact activation was considered. The influences of load conditions and organic gas emitted from relay structure on arc characteristics was experimentally examined. The results indicated that load current greatly influenced the amount of material transfer and that power supply voltage affected the occurrence of the wear-out type significantly. The activation behavior of the contact surface could be found through observing the bridge voltage waveform.

Measuring mechanical characteristics of optical disks is significant not only for designing drives but also for assuring disk interchangeability. This paper shows that the lens-movement detection method has the greatest overall potential and thus fits to a practical system for measuring mechanical characteristics. A system based on this method was constructed by developing simple and accurate capacitive sensors that can be built into an optical head to detect lens movement. The system configuration includes a precision turntable and a high-duarability reference disk to fully extract the potential. Test results show that this measuring system has adequate measuring range, accuracy, and stability. Some applications of this system are described in this paper. They show that the system is useful for evaluating and improving optical disk mechanical characteristics.

Optical WDM (Wavelength Division Multiplexing) technology is a method of exploiting the huge bandwidth of optical fibers. Local lightwave networks which use fixed wavelength transmitters and receivers can be built in a multihop fashion. In multihop local lightwave networks, packets arrive at their destination by hopping a number of intermediate nodes. The channel sharing schemes for multihop lightwave networks have been proposed for efficient channel utilization, but those schemes result in the degradation of network capacity and the user throughput. In this paper, we propose an improved WDM channel sharing scheme using the logically bidirectional perfect shuffle interconnection pattern, achieving smaller number of average hops for transmission and better channel utilization efficiency. Better channel utilization efficiency is obtained without much deteriorating the network capacity and the user throughput. TDMA (Time Division Multiple Access) protocol can be used to control the sharing of channels, and time delay and lost packet probability analysis based on TDMA is performed.