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.

A technique for pulse code modulation (PCM) encoding using a T-Model neural network is described. Performance evaluation on both the T-Model and the Hopfield model neural-based PCM encoders is carried out with PSpice simulations. The PSpice simulations also show that the T-Model neural-based PCM encoder computes to a global minimum much more effectively and more quickly than the Hopfield one.

A radial line slot antenna (RLSA) is a slotted waveguide planar array for the direct broadcast from satellite (DBS) subscriber antennas. A single-layered RLSA (SL-RLSA) is excited by a radially outward traveling wave. The antenna efficiency of more than 85% has already been realized. These antennas are designed on the assumption of perfectly rotationally symmetrical traveling wave excitation; the slot design is based upon the analysis of a slot pair on the rectangular waveguide model with periodic boundary walls. However, the slots perturb the inner field and the actual antenna operation is not perfectly symmetrical. This causes the efficiency reduction especially for very small size antenna. This paper presents a fundamental analysis of the inner field of the radial waveguide. It is impossible to analyze all the slot pairs in the aperture as it is and only the slots in the inner few turns are considered since these provide dominant perturbation. The calculated results are verified by the experiments and reasonable agreement is demonstrated. Some design policies are suggested for enhancing the rotational symmetry.

A W-graph is a partially known graph which contains wild-components. A wild-component is an incompletely defined connected subgraph having p vertices and p-1 unspecified edges. The informations we know on a wild-component are which has a vertex set and between any two vertices there is one and only one path. In this paper, we discuss the properties of circuits in a W-graph (called W-circuits). Although a W-graph has unspecified edges, we can obtain some important properties of W-circuits. We show that the W-ring sum of W-circuits is also a W-circuit in the same W-graph. The following (1) and (2) are proved: (1) A W-circuit Ci of a W-graph can be transformed into either a circuit or an edge disjoint union of circuits, denoted by Ci*, of a graph derived from the W-graph, (2) if W-circuits C1, C2, , Cn are linearly independent, then C1*, C2*, , Cn* obtained in (1) are also linearly independent.

An unsupervised segmentation technique is presented that is based on a layered statistical model for both region shapes and the region internal texture signals. While the image partition is modelled as a sample of a Gibbs/Markov random field, the texture inside each image segment is described using functional approximation. The segmentation and the unknown parameters are estimated through iterative optimization of an MAP objective function. The obtained tesults are subjectively agreeable and well suited for the requirements of region-oriented transform image coding.

In this paper, we proposes a novel fuzzy control for parameter scheduling of the Hopfield neural network. When a combinatorial optimization problem, such as the traveling salesman problem, is solved by Hopfield neural network, it is efficient to adaptively change the parameters of the energy function and sigmoid function. By changing the parameters on purpose, this network can avoid being trapped at a local minima. Since there exists complex relations among these parameters, it is difficult to analytically determine the ideal scheduling. First, we investigate a bad scheduling to change parameters by simple experiments and find several rules that may lead to a good scheduling. The rules extracted from the experimental results are then realized by fuzzy control. By using fuzzy control, we can judge bad scheduling from vague network stages, and then correct the relations among the parameters. Computer simulation results of the Traveling Salesman Problem (TSP) is considered as an example to demonstrate its validity.

Recent achievements in low-voltage and low-power circuit techniques are reported in this paper. DC current in low-voltage CMOS circuits stemming from the subthreshold current in MOS transistors, is effectively reduced by applying switched-power-line schemes. The AC current charging the capacitance in DRAM memory arrays is reduced by a partial activation of array blocks during the active mode and by a charge recycle during the refresh mode. A very-low-power reference-voltage generator is also reported to control the internal chip voltage precisely. These techniques will open the way to using giga-scale LSIs in battery-operated portable equipment.

Ultrafast MR imaging (e.g., echo-planar imaging) acquires all the data within only several tens of milliseconds. This method, however, is affected by static magnetic field inhomogeneities and chemical shift; therefore, a high degree of field homogeneity and water and fat signal separation are required. However, it is practically impossible to obtain an homogeneous field within a subject even if in vivo shimming has been performed. In this paper, we describe a new ultrafast MR imaging method called Ultrafast Single-shot water and fat Separated Imaging (USSI) and a correction method for field inhomogeneities and chemical shift. The magnetic field distribution whthin the subject is measured before thd scan and used to obtain images without field inhomogeneity distortions. Computer simulation results have shown that USSI and the correction method can obtain water and fat separated images as real and imaginary parts, respectively, of a complex Fourier transform with a single-shot scan. Image quality is maintained in the presence of field inhomogeneities of several ppm similar to those occurring under practical imaging conditions. Limitations of the correction method are also discussed.

To increase the accuracy of a near field antenna measurement system, it is necessary to know radiation characteristics of a probe to detect near field data. Open ended waveguide used as a near field probe in our system was analyzed using Transmission Line Matrix (TLM) method which is a time domain electromagnetic solver. Validity of this analysis has been confirmed by comparison with experimental data and existing theoretical approximation. Frequency dependence of a complex reflection coefficient at the waveguide aperture has been derived and is shown to agree with measured values. The radiation pattern of the open ended waveguide with mounting structure is also calculated. Ripples on both the amplitude and phase patterns are correctly predicted by our simulation. This method can be applied to accurately model the effect of probe antennas to enhance the accuracy of near field antenna range.

A novel isolation structure which has a buried insulator between polysilicon electrodes (BIPS) has been developed. The BIPS isolation employs the refilling CVD-oxides in openings between polysilicon electrodes by photoresist etchback process. Device characteristics and parasitic effects of BIPS isolation have been compared with that of LOCOS isolation. Using BIPS isolation, we can almost suppress the narrow-channel effects and achieve the deep submicron isolation. No degradation on the subthreshold decay of devices with BIPS isolation can be obtained. The use of BIPS isolation technology yields a DRAM cell of small area. The successful fabrication of deep submicron devices with BIPS isolation clearly demonstrates that this technology has superior ability to overcome the LOCOS isolation.

This paper gives field experimental results on 16-ary quadrature amplitude modulation/time division multiple access (16QAM/TDMA) and trellis coded 16QAM/TDMA systems for land mobile communications in order to evaluate its capability of achieving large capacity and high quality data transmission. Pilot symbol aided space diversity and symbol timing synchronization based on maximum likelihood (ML) estimation are applied to both 16QAM/TDMA and trellis coded 16QAM/TDMA to improve transmission quality. For the trellis coded 16QAM/TDMA, trellis coding with Viterbi decoding and 2-frame symbol interleaving are further employed. The field experiments were conducted in the Tokyo metropolitan area of Japan. The results show that 16QAM/TDMA and trellis coded 16QAM/TDMA are practical modulation/access schemes for land mobile communication systems.

The frequency characteristics of whole-body averaged specific absorption rates (SARs) in a human model exposed to a near field of an electric dipole or a magnetic dipole are calculated, using a finite-difference time-domain method. The dependences of the characteristics on the orientation of the dipole and on the distance from the source to the model are investigated. It is shown that the resonant peak of the SAR that appears in the E-polarized far-field exposure is observed only when the source is E-polarized and is located at 80cm, while the peak vanishes or is not noted when the source is located at 40cm and 20cm nor when it is H-polarized. The relationships between the whole-body averaged SARs and the incident electromagnetic field strengths are also investigated. It is suggested that the spatially-averaged value of the dominating component between the electric field and the magnetic field over the space where a human body would occupy provides a relevant measure to estimate the whole-body averaged SAR of a body in the vicinity of a small radiation source.

For the study of the biological effects of ELF (Extremely Low Frequency) electric fields, the perception mechanism of ELF electric fields was analyzed. When a human body is exposed to an electric field, the hair on the body surface moves due to the electric force exerted on the hair. In theoretical analysis, it was shown that the force is approximately proportional to the dielectric constant of hair and the spatial gradient of the square of the electric field at the hair. The dielectric constant of hair was measured with different temperatures and humidities of the surrounding air. A technique was developed to estimate the electric force exerted on a hair during the field exposure. After experiments with model hair, the technique was applied to a body hair of a living human being. It was found that the force increased with field strength and relative humidity. The variations of the force agreed well with those expected from the theoretical analysis and the measurement of hair dielectric constants. These results explain the cause of the reported variation in the threshold of biological effects of an electric field. The results will help to establish a practical safety standard for the held exposure.

An estimation method for efficiently calculating the field intensity in the Fresnel region of broadside colinear array antennas is developed, and its performance is experimentally verified. The calculation utilizes only the antenna design data, and is readily applicable to arbitrary array antennas. This method can provide a safety protection zone in the proximity of array antennas, in order to protect radio communication personnel and general public from the potentially hazardous radiofrequency exposure.

This paper describes a novel technique to realize high performance digital sequential circuits by using Hopfield neural networks. For an example of applications of neural networks to digital circuits, a novel gate circuit, full adder circuit and latch circuit using neural networks, which have the global convergence property, are proposed. Here, global convergence means that the energy function is monotonically decreasing and each circulit always operates correctly independently of the initial values. Finally the several digital sequential circuits such as shift register and asynchronous binary counter are designed.

This paper presents an analysis of the dose rate in tissue irradiated by an electromagnetic near field of a circular loop antenna. An analytical model comprised of a circular loop antenna located in the vicinity of the semi-infinite plane of a homogeneous biological medium was formulated. A quasi-static hypothesis was not introduced. The theoretical formulation was rigorously developed based on Maxwell equations which used an electric vector potential, cylindrical coordinates and a Hankel transform. The internal electric field E and the specific absorption rate (SAR) were adopted as indices for the dose in the tissue. This formulation was applied to the dosimetry of a high-frequency therapeutic device (HFTD) and experiment of irradiation to a frog web. The frequency of the applied electro-magnetic fields (EMF) was 9-10MHz. The distance between the antenna and tissue was 2.0-3.2mm. The dose of HFTD were 0.75V/m and 0.35mW/kg, respectively. The dose of experiment of the irradiation to a frog web were 0.42-2.08V/m and 0.11-2.69mW/kg, respectively. The SAR values obtained by this analysis were small enough to conclude that the effects were non-thermal. The calculated SARs of these experiments were compared with estimated SARs in experiments on calcium efflux change due to a weak modulated RF field. All were found to be of the same order of magnitude.

To study the biological effects of the ion-current commonly found under ultra-high voltage DC transmission lines, a technique was developed to evaluate the human exposure to the ion-current field. This technique is based on numerical analysis using the boundary element method. The difficulty of handling the space charge in the calculation was overcome by assuming a lumped source ion-current. This technique is applicable to a three-dimensionally complex object such as a human body. In comparison with theoretical values, the accuracy of this technique was evaluated to be satisfactory for our purposes. It was then applied to a human body in an ion-current field. The distribution of the electric field along the body surface was obtained. The general characteristics of the field distribution were essentially the same as in those without space charges. However, it was found that the strength of the field concentration was significantly enhanced by the space charges. Further, the field exposure when a human body was charged by an ion-current was evaluated. As the charged voltage increases, the position of the field concentration moves from a human's head toward his legs. But the shock of micro spark increases. This technique provides a useful tool for the study of biological effects and safety standards of ion-current fields.

The studies on the biological effects of ELF electric fields conducted in Japan are reviewed. Among international studies, they are characterized as the studies from the viewpoint of bioengineering. In early studies, the safety standard of high voltage transmission lines was determined by a distinct biological effect, i.e., the sensation of the spark discharge caused by electrostatic induction. In numerical analysis, the field coupling to both animal and human bodies became well understood. Some new measurement techniques were developed which enabled us to evaluate the field exposure on a human body. A system was developed to realize the chronic exposure of an electric field on mice and cats. An optical telemetry technique was developed to measure the physiological response of an animal when it was exposed to an electric field. An ion-current shuttle box was developed to investigate the behavioral change of a rat when it was exposed to an ion-current as well as an electric field. In animal experiments, a mechanism of sensing the field was investigated. The cause of the seasonal change of field sensitivity was found. In cases of chronic exposure, suppression of growth was suspected. In shuttle box studies, an avoidance behavior from an ion-current was quantified. To find whether there are any adverse or beneficial effects of the field exposure on human beings, further study is required to clarify the mechanisms of the biological effects.

This paper surveys the researches on biological and electeromagnetic environments in RF (radio frequency) and microwave regions in Japan. Publicized research reports on biological objectives, evaluation of exposure rate, electromagnetic environments and guideline for the protection from radio wave nuisances are briefly introduced. Some researches on the evaluation of the exposure rate caused by the near field effect of portable radio transceiver are reviewed. Radio frequency exposer protection guidelines in Japan are also described.

The biological effects of power frequency electric and magnetic fields have been a source of concern for the past many years, especially since 1979 when an epidemiological study report suggested a positive relationship between childhood cancer and exposure to power frequency electromagnetic fields from residential overhead power lines. The extensive studies of dosimetry and biological effects have since been carried out. It is believed that power frequency electromagnetic fields does induce biological effects (no serious threat to human health). The clear explanations for the possible interaction mechanisms remain to be identified. The problem with the study on dosimetry has been lack of theory that applies to the physical interaction of power frequency electric and magnetic fields with humans. At present, it seems to be widely accepted that the density of induced currents in the human body can be used as the decisive parameter in evaluating human exposure to these fields. In order to predict the distribution of induced current density inside a human body exposed to electric fields, magnetic fields, or electric and magnetic fields that coexist, the precise measurements of electromagnetic environments are necessary. According to necessity, the fields have to be characterized in terms of strength, orientation and phase angle. This paper presents: (1) Measurements of power frequency electromagnetic environments in 187kV substation yard and in the vicinity of the ground under 187 kV line using laboratory-made instruments; (2) Development of magnetic field exposure monitor; and (3) Review of state of the art of theoretical dosimetry for electric fields, magnetic fields and combined electric and magnetic fields, and evaluation method of human exposure for the future research.