A recognition method of printed Thai characters by the structural analysis of their contours is described. Digital contours of characters are encoded according to directional differences of contour tracing, then, simple arithmetic operations are applied to eliminating noises and extracting concavities and convexities of the contours. Several geometric features of concave and convex arcs are used to calculate similarities of the arcs, then, a pair of the most similar arcs between a model and an input character is determined from the similarities. Finally, for recognizing characters, the similarity between each arc pair of the character portion and the similarity between characters are calculated. By applying the method to 67 categories (670 data) of Thai characters, a very high recognition rate has been obtained.

When paramecia are exposed to a.c. electric field of appropriate strength, the cells show following characteristic behavior in hay infusion with increasing the frequency; (1) the cells repeat going and returning parallel to the lines of the electric field until the frequency reaches about 1 Hz. (2) the cells perform circular movement with their peristome to direct toward the outside of the circle between 1 Hz to 5 Hz and then (3) do rotational movement between about 5 Hz to 500 Hz. As the frequency of the supplied electric field is increased, (4) the cells become swimming perpendicular to the lines of electric field. Beyond the frequency of 2 kHz, (5) the cells swim freely as if the electric field was not supplied. Cell motility of paramecia under d.c. electric field is also examined. On the base of the results obtained, excitability of the cells exposed to the electric field is discussed.

In this paper presented is a theorem: a planar digraph which is embedded in a plane and which has a single source and a single sink both lying on the outer face of the digraph, is acyclic, if and only if all the inner faces are acyclic. Hence the number of tiesets necessary and sufficient for guaranteeing the acyclicity of the digraph is equal to the nullity of the digraph.

We present an Isometric Context-Free Array Grammar (ICFAG) that generates the set of all solid upright rectangles. This is performed by using the property that blank symbols in the rewriting rules enable ICFAGs to sense the local shapes of the host array. Thus ICFAGs are context-sensitive in some sense.

Diversity reception of binary NCFSK through Nakagami fading channels and additive white Gaussian noise using ideal switched diversity is considered. Identical as well as different branch parameters are assumed. The effect of correlation among the branch fadings is also considered.

A Sheffer function is a Boolean function such that one can produce all Boolean functions by using it as a sole basic logic element, and a typical example is the NAND operation. Here we investigate two variations of this concept, that is, Sheffer with constants" and Sheffer with constants under uniform composition". These are considered as more suitable assumptions complying with real electronic circuitry. Our new results in this paper are two explicit formulas, one for the number of n-variable functions Sheffer with constants, and the other for that of those uniformly Sheffer with constants. In particular, it is shown that almost all functions are Sheffer with constants when n is large. Some numerical values of these numbers are calculated in the range of 1n6.

The deconvolution of DLTS signals for multiple deep traps has been automated to reduce the data processing time of DLTS signals analysis and to improve the accuracy of the measurement. A linear non-recursive optimum filter is used for the deconvolution and peak-chaining algorithm has been developed to automate the Arrhenius plotting procedure. The design of the filter, the peak-chaining algorithm and an example of the deconvoluted DLTS signal are described as well as a performance evaluation of the method.

The designs and experiments for the carousel SQUID logic gate are pursued. The novel rf-magnetoron cathode is employed for the formation of tunnel barriers to obtain stable Josephson junctions for heat-cycles with small leak current. The sharp changes of a gate current by the applied control current are observed in the fabricated carousel SQUID gate.

Some properties of periodically correlated stochastic processes such as the mean ergodicity and asymptotic befavior of the periodgram of the processes are studied in this paper. A periodically correlated process (PC-process) is also called periodic nonstationary process, cyclo stationary process and even periodic stationary process although the process may not be stationary, and these are mainly studied as models of signals especially as pulse trains in the communication theory. Although many of interesting results obtained so far are important from the theoretical point of view, they are rather intuitively derived. Therefore we reformulate the process in a rigorous manner, introduce the spectral representation of it when the process is harmonizable in Loève's sense and study mainly about the mean ergodic properties and the limiting behavior of the mean periodgram of the process. Furthermore we study some pulse train processes as particular examples and we show simple examples of nonharmonizable PC-processes which had been thought of as unusual. We point out that by such a theoretical treatment, the position of PC-processes in the theory of nonstatonary processes will be better recognizable and the results obtained here will be useful as the foundation of practical time series and signal analysis in the communication and information theories.

Low-loss and long-length single-mode fibres have been fabricated by the VAD (Vapour phase axial deposition) method. The most important technique was a new torch development in order to form a thick low-loss cladding region in the thin porous preform. The best loss values for the VAD single-mode fibres were 0.35 dB/km at 1.3 µm and 0.2 dB/km at 1.55 µm. The OH absorption loss at 1.39 µm in the fibre was reduced to less than 0.1 dB/km. Moreover it turned out that VAD fibres had less tendency of the loss increase with increasing Δn than MCVD fibres.

In this paper we have represented a model structure of modal lower (first-order) predicate logic (S5) (abbr. MLPC in our paper) in two-sorted extensional language (abbr. EL2), and tried to translate a formula of MLPC into a formula of two-sorted logic (abbr. ELPC) in such a way as preserving provability. (i.e.P in MLPC iff P* in ELPC, where P* is the translation of P). Roughly speaking, modal symbol (necessity) is translated into the universal quantifier k of the domain which expresses the set of possible worlds, and n-ary predicates are n1 -ary predicates. For instance, xP (x) is translated into kx*P* (x*, k), where * denotes the translation. Therefore it is possible to replace a theorem proving of MLPC with that of two-sorted logic ELPC, so we have shown it possible to prove a theorem of MLPC by using the resolution principle in ELPC. Then the completeness of the resolution in two-sorted logic is proved, and a normal form of MLPC is introduced. It is shown that for any formula of MLPC there exists an algorithm to transform the formula into its normal form. This normal form is obtained by decreasing the number of modal symbol in a formula as possible. For instance, xP (x) yQ (y) is transformed into xy (P (x) Q (y)).

A 400 Mb/s optical fiber fransmission system was designed for field trial using single-mode fibers. The system is targeted to 20 km repeater spacing using InGaAsP/InP DH laser diode (LD) and Ge-APD as an optical device. This paper describes the design philosophy for the single-mode fiber transmission system and the field trial results. The error rate performance is expressed by signal to noise ratio (SNR) for practical high-speed digital optical repeater, putting emphasis on LD mode partition noise. Based on the SNR analysis and results obtained from several preliminary experiments, the design procedures for the 400 Mb/s transmission system were clarified. Through the field trial, it has become clear that the 400 Mb/s optical transmission system is practically applicable to long-haul transmission systems.

The problem of specifying the optimum receiver in quantum detection theory is considered for application to optical communications. The quantum minimax rule is formulated and a necessary and sufficient condition for it is given. This rule provides a powerful calculation method in obtaining the quantum optimum solution. Several examples are worked out to prove superiority of the minimax strategy in practical problems. For the case of ternary coherent signals, in particular, is obtained an explicit equation of error probability. Furthermore the minimax rule gives a good penetrating calculation method to obtain suboptimum receivers in case accompanied by an additive external noise.

Three efficient designs of Self-Checking (SC) checkers for various 2-rail codes (Self-Checking Two-rail code Checker: SCTC) are described. In the designs, only one type of modules with 2 pairs of inputs and a pair of outputs is used. The module is realized by a 2-level AND-OR circuit, and denoted by N2. Every N2 in a checker needs a set of 4 test patterns (the set is denoted by T) to detect any fault in N2. Firstly, it is shown that any tree (fanout-free) circuit consisting of only N2's is an SCTC if the number of code words is (32n-21) or more. Secondarily, a design which is called a checking design is proposed. For a given 2-rail code and a properly constructed checker, the checking design checks whether T is applied or not to every N2 in the checker. If T is applied, the checker becomes an SCTC. Whether the checking design can construct an SCTC or not is a probability phenomenon mainly due to the number of code words in the given 2-rail code. Therefore, the probability is derived from practical experiments. The probability shows that SCTC's can be constructed by the checking design for most codes. Thirdly, an algorithmic design is proposed for codes consisting of a very few code words. A necessary and sufficient condition for which an SCTC can be constructed for a given code is presented, and the algorithmic design is described. The experimental results show that the algorithmic design can construct SCTC's successfully.

Analytical expressions of lateral resolution of synthetic focus acoustic imaging systems are simply obtained by schematic consideration. A proper choice of a transducer array setup and a compressed pulse waveform yields good performance.

We proposed a description and coding method of Chinese characters using their structural features. In this paper, we propose a pattern generation method of Chinese characters as an application of the description and coding method. In the method, the generation process of a character can be regarded as a derivation process of sentence which expresses the character, then a Chinese character can be generated iteratively not depending on the numbers of its components and also generated in various shapes by changing some parameters needed for the generation. We can get natural shapes of characters by choosing adequate values of parameters. Many applications using this pattern generation method are considered.

Operation modes in the system of two mutually synchronized oscillators with both single-ended and double-ended control systems are investigated. The necessary and sufficient conditions for settling common frequency in the system are obtained. It is shown that system in the steady state can be operated in one of several modes. Number of possible modes in the double-ended control system cannot exceed two while in the single-ended control system this number depends on the magnitude of total delay. The necessary and sufficient conditions of existence of separate modes are obtained. The differences between single-ended and double-ended control schemes are pointed out.

This paper studies the experimental application of our new formative evaluation method, Unified Evaluation Method", which combines the pupil's self-evaluation and the teacher's objective evaluation of a pupil's answer to each problem in an achievement test. At first, we give an outline of the unified evaluation method and its data processing system. In spite of easiness of a test practice based on the method, the unified evaluation informations through the test are so new and more detail than ever that they can serve to improve both pupil's self-evaluation and learning process as feedback informations. Next, two examination projects related to our new information of pupil's self-evaluation state are investigated based on practial data: One is the influence due to the differences of both pupil's grade (or age) and sex. Another is the relation between pupil's self-evaluation state and learning activity. By these analyses, we have obtained useful guidance knowledge for the teacher who will make use of the unified evaluation method to know and guide pupils better. Finally, we verify availability of our method (mainly the feedback effect of unified evaluation information) through case studies. Freedback information based on the unified evaluation has proved to be effective for improvement of both pupil's self-evaluation and learning processes.

Twisted single-mode fibers show a high degree of polarization for any incident polarization state, when phase compensation is performed at the fiber output. The performance is demonstrated in a 1.14 km long fiber with a twist rate of 2 turns/m. Polarization degree, output polarization ellipticity, and output polarization major axis angle were studied experimentally and theoretically in terms of the fiber twist rate. Preservation of circular polarization without phase compensation, in particular, is also verified in the twisted fiber. Polarization characteristics are stable against external perturbations. It was also confirmed that proper orthogonal elliptical polarization states exist, in genaral, which are maintained over a 5 km long fiber.

This paper presents a topological switch cell reduction method by introducing a new concept, called near full switch" (NFS) and evaluates throughput characteristics of NFS structures, when applied to communications networks.