A quasi-TEM wave characterization method is proposed for tight couplers which are constructed of coupled microstrip lines with conductor overlay. The characterization is carried out with consideration for strip conductor thickness by applying the rectangular boundary division method and a sequential optimization procedure. Estimated characteristics of a quarter-wavelength tight coupling section are given in the graphical form for the design of structural dimensions. A trial 3-dB hybrid coupler is designed with this method and its measured characteristics are compared with theoretical ones.

This is the first to three expository articles, which aim to survey the chaos theory from an engineering point of view. This paper, in the first place, presents a brief introduction to chaos. Then, it is pointed out that the study of chaos from an engineering point of view is a challenging area in engineering science.

After Diffie and Hellman's paper, there have been published many cryptosystems, where large composite numbers are used as the public keys, and the factorization of them are used as the secret keys. But, on the other hand, there also have been published many integer-factoring algorithms that factor composite numbers rapidly. So methodologies to construct primes that are strong for such algorithms are needed to guarantee the safety of such cryptosystems. Here we propose a randon polynomial time algorithm for constructing strong primes that uses a probabilistic primality testing algorithm.

In order to reconstruct the 3 D geometric model of a real object from multi-view line drawings some restrictions in a symmetric space of the original 3 D space have been set up. Based on these restriction a new algorithm of 3 D geometric model reconstruction is proposed. This method can work effectively under the more natural condition than other methods, and it is suitable for the situation of auxiliary views as well as the situation of perspective projection. Some practical computational results have been made which show that this algorithm is effective.

The resequencing delay for a queueing system with multiple servers under a threshold-type scheduling is analyzed. We first derive the general expressions for the average total delay which is the sum of resequencing delay and queueing delay. The expressions are also applicable to the conventional M/M/n queueing system as the special case of zero-threshold policy. Next, the numerical calculation is carried out for the queueing system with 3 servers under a threshold-type scheduling to consider the impact of the multiple thresholds on the average resequencing delay. It is found that the resequencing delay as well as the queueing delay for a queueing system with multiple servers of different service rates can be recuced under a threshold-type scheduling by selecting the threshold values appropriately. The threshold-type scheduling is more effective to reduce the resequencing delay compared to the queueing delay especially in the region of modest traffic intensity and as the difference of the service rates becomes larger.

In a nonlinear dynamical circuit with sinusoidal external source, we frequently encounter various bifurcation phenomena of steady states such as jump and hysteresis phenomenon, frequency entrainment, etc. The steady state corresponds to a periodic solution of the circuit equations described by nonlinear ordinary differential equations. The generic bifurcations of the periodic solution are known as codimension one bifurcations: tangent bifurcation, period doubling bifurcation and the Hopf bifurcation. At a bifurcation value of parameters, if a periodic solution satisfies two bifurcation conditions, then the bifurcation refers as a codimension two bifurcation. This type of bifurcation may be observed in high dimensional systems with several parameters. In Ref.(1), we have classified codimension two bifurcations and proposed a numerical method for obtaining the bifurcation parameters. To illustrate the occurrences of some types of codimension two bifurcations, we analyzed a circuit described by 3-dimensional differential equation. For 3-dimensional system, however, two types of bifurcations never occur. In this paper, we shall treat 4-dimensional system as an illustrating example. In this example, we shall see all types of codimension two bifurcations defined in this paper. For a global property of bifurcation set of parameters, it is found that a type of codimension two bifurcation occurs successively together with the period doubling cascade and the Hopf bifurcations. This bifurcation sequence may cause a new route to the generation of chaotic oscillations.

The simultaneous measurement of five field components (three magnetic and two electric components) was carried out on board the ionospheric Aureol-3 satellite in a frequency range from 10 Hz to 1.5 kHz, and we have developed a systematic signal processing of direction finding for ionospheric and magnetospheric ELF emissions at eight selected frequencies mainly based on the likelihood concept. So, the purpose of this paper is to present the detailed description of those systematic direction finding measurements at frequencies above and below the proton gyrofrequency, but more emphasis is placed on the latter frequency range where two possible modes of propagation may coexist. This kind of systematic analyses will be of great use in the future wave analysis system on the spacecrafts.

The author shows experimentally how the nonlinear line transforms the noise spectrum and will discuss 1/f fluctuation phenomena which are widespread in nature. The line is a one-dimensional LC ladder type distributed line with loss, where the capacitor C changes with the line voltage. The experimental and computer-simulated results show a tendency that the white noise is transformed into the 1/f type one along the noise propagation.

This article discusses chaotic responses observed from a periodically forced neural-type oscillator introduced by Newcomb et al. Describing the circuit dynamics by an autonomous equation, we can derive a one-dimensional return map explicity and therefore can prove a sufficient condition of chaos generation in Lasota & Yorkes' sense. Also, our mapping procedure is valid for various other systems and seems to contribute for design of them.

The method of constructing a graph G with the maximum cardinality of minimum cut-sets, which is 2e/n, has been obtained by Harary in 1962, where n is the number of nodes and e is the number of edges. Afterward, the problem of finding a simple graph G which minimizes the number of minimum cut-sets with cardinality 2e/n subject to λ(G)2e/n was solved by Bauer, Boesch, Suffel and Tindell in 1985. Generalizing this, a necessary and sufficient condition for a simple graph with n nodes and e edges to minimize the number of cut-sets with cardinality z has been recently presented by Sun, Nagamochi and Kusunoki in 1989, where z is chosen such that 2e/nz22e/n3 for2e/n3, or z2, 3, for2e/n2. In this paper, we generalize the above results to multiple graphs, and give a necessary and sufficient condition for a multiple graph G with n nodes and e edges to minimize the number of minimum cut-sets whose cardinality is2e/n.

The relationship between a multirate quadrature mirror filters (QMF) system and an output sampling polyphase model of a periodically time varying digital filter is examined. It is proved that a polyphase model of a periodically time varying digital filter is equivalent to a specified multirate QMF system. Using the derived relationship, another type of polyphase model of a periodically time varying digital filter which is called an input sampling polyphase model is proposed and analyzed. Furthermore, the equivalence of two types of polyphase models, i.e., the conventional output sampling polyphase model and the proposed input sampling polyphase model, is discussed and conditions for their equivalence are obtained.

It was unknown whether there exists a language accepted by a two-way nondeterministic one counter automaton, but not accepted by any nondeterministic rebound automaton. This paper solves this problem, and shows that there exists such a language.

The basic selective-repeat ARQ scheme can achieve very high throughput. However, it encounters a resequencing problem. We analyze the average resequencing delay approximately under the assumption that the arrivals of NAK's are totally independent of the past history of the system. And, we examine its characteristics from numerical examples.

Theoretical description with a potential is made for inhomogeneous structures of high field domain and current filament in semiconductors with a negative differential conductivity (NDC) appearing under voltage- and current-controlled conditions, respectively. The potential proposed here can describe systematically a route from homogeneous state to the patterned state through the instability of homogeneous state, whereas previously proposed potentials can describe only the patterned state. The potential is constructed from two internal variables: one is the variable dependent on the spatial coordinate which exhibits the spatial pattern in the NDC region, while another remains constant spatially but changes discontinuously its value when the patterned state bifurcates from a thermodynamic branch of the homogeneous state. The bifurcation to spatial pattern is examined in a similar way to the first-order phase transition in equilibrium systems. At the same time, the property of the resulting pattern is discussed from analogy with the phase separation.

This letter demonstrates an experimental result on chaos observed in a very practical electronic circuits called the phase-locked loops. Namely, we report that chaos can in fact occur in a practical FM demodulator circuit made of a phase-locked loop IC module (MC14046B) operating under widely employed high-damping case as well as very low-damping case.

This paper proposes a new technique for designing 2-D diamond-shaped half-band FIR filters with maximally flat amplitude property. First, a 2-D half-band FIR filter is defined and several interesting properties of this filter are explained. Then a design method using these properties is explained and some design examples are shown. Finally, we discuss the advantages of our method by comparing with the previously proposed method.

The phase-locked loop (PLL) is a versatile functional device widely used in many electronic system. We found previously that the PLL can become chaotic under some operating conditions for wide range of system parameter values. The reason why the PLL can cause chaos is closely related to the homoclinic orbits of which existence are proved by Melnikov method. In this paper, we review the motivation and significance of chaos occurring in the PLL circuits. Then we confirm various chaotic characteristics of the phase-locked loop equation having the homoclinic orbits such as the fractal basin boundaries and sensitive dependence on initial conditions of a solution. At last, we investigate the route to chaos of the periodic solution of first type (PS1) by calculating the bifurcation diagram, and presents a new results that the PS1 can be chaotic via the period-doubling cascade.

Contact contamination is verified by the measurement of static contact resistance so far. However, in case of the contamination of organic thin film, new evaluation method is needed in stead of static contact resistance. Then, quantitative analysis of the contact cleaning effect was conducted using contact activation characteristics, dynamic contact resistance pattern and so on when the ultrasonic cleaning, immersion cleaning, vapor cleaning and jet blow cleaning were performed for relay contacts. As a result ,it was clarified that characteristics of the dynamic contact resistance depends upon the nature of the organic film on the contact surface and the effect of each contact cleaning method was quantitatively compared.

Canard is a new phenomenon of slow-fast systems, which was found by the numerical computations. Our primary purpose of this paper is to study the canard from the experimental viewpoint. The following results are obtained by the experimental observation of a nonlinear circuit: (1) Canard really appears in the actual circuit. But canard's life in the circuit is extremely short. (2) When a canard vanished, an irregular oscillations or a cycle with period two is still there, which usually does not occur in the two dimensional autonomous systems.