The paper describes the design considerations, fabrication process and performance of the newly developed 1-K ECL gate array implemented with fully self-aligned AlGaAs/GaAs hoterojunction bipolar transistors (HBTs). This gate array consists of 960 three-input OR/NOR ECL basic gates. It contains about 7,600 transistors in a chip area 8.15-mm8.45-mm. The basic (FI=FO=1, wiring length L=0-mm) and loaded (FI=FO=3, L=1-mm) gates exhibit delay times of 33-ps and 82-ps, respectively, with 8.5-mW/gate power dissipation. From the measured values, fan-in, fan-out and wiring delay times of 9-ps/FI, 7-ps/FO and 17-ps/mm are estimated, respectively. These results are in good agreement with the designed results obtained using "SPICE" simulation.

This paper describes a programming system, K-NET for the development of control software for flexible manufacturing systems composed of robots, numerically-controlled machines, transfer machines and automatic storage/retrieval systems. K-NET is based on a high-level Petri net which makes it simple to express operational functions such as synchronization, interlock and concurrence in sequence control. Petri net in K-NET is colored one in which tokens have attributes, and timed one which can provide a notion of stochastic time. K-NET provides many kinds of boxes having specific functions, and gates specified the firing condition and the token flow control with IF-THEN rules. On the other hand, procedural language can be also used for information processing. K-NET can support all development stages including general design, detailed design, programming and testing. K-NET has an editor to input control specifications expressed with Petri net; a simulator to verify edited specifications; a generator to convert the net to C source programs for a computer or to ladder diagrams for a programmable controller; a reporter to print control specifications; and a monitor to display controller status in real-time. K-NET has been used in the development of control software for an automated guided vehicle system, and results show a 2/3rds cost-saving over development with conventional methods in which only procedural language is used.

Thin Si films grown on anodized porous silicon have been characterized using a high-energy ion scattering technique with related simulations of MeV ions in solids. It turned out that the simulations are necessary and very usuful for quantitative and nondestractive analysis of thin films with thicknesses less than 100 nm. In the case of the epitaxial Si films examined, it is often insufficient for the characterization of crystalline quality to measure only the channeling minimum yield, and therefore, it is emphasized that angular scans over the critical angle in the vicinity of a channeling direction must be performed for the analysis of possible imperfections in thin films. The possible imperfections observed in the epitaxial specimen are treated quantitatively.

A specification formalism for business application software is presented. Our approach is to investigate specification documents which are actually used in development projects of business applications in banking, insurance, and government systems. Since the specification documents are prepared mainly for users' review for the developing software, the representation of the documents is designed to be easy to understand for users, only in business terminology without losing a certain level of formality. Also, to avoid redundancy of the specification, there are some implicit assumptions in the specification. We have analyzed some commonality of these assumptions hidden in specification documents and are trying to construct a language by formalizing the underlying system model.

This letter proposes an improvement of the equivalent source method in order to give an accurate solution for the scattering of an electromagnetic plane wave by a conducting cylinder with edges.

An accurate numerical solution is presented for the electromagnetic scattering from infinite strip gratings attached to both sides of a dielectric slab. This structure is a model of polarization discriminating devices. The period of the strips is common to both planes, but the widths and the axes may be different. The direction of propagation and the polarization of an incident plane wave are arbitray. We derive a set of singular integral equations and solve it by the moment method, where the Chebyshev polynomials are successfully used as the basis and the testing functions. This method is accurate and effective owing to the incorporation of the edge condition and the decomposition of the kernel functions into the singular and the regular parts. Numerical calculations are carried out for the purpose of designing polarization discriminators, and it is shown that the band width is widened by decreasing the permittivity of the slab. The cross-polarization characteristics at skew incidence are also discussed.

This paper proposes a model for learning non-parametric densities using finite-dimensional parametric densities by applying Yamanishi's stochastic analogue of Valiant's probably approximately correct learning model to density estimation. The goal of our learning model is to find, with high probability, a good parametric approximation of the non-parametric target density with sample size and computation time polynomial in parameters of interest. We use a learning algorithm based on the minimum description length (MDL) principle and derive a new general upper bound on the rate of convergence of the MDL estimator to a true non-parametric density. On the basis of this result, we demonstrate polynomial-sample-size learnability of classes of non-parametric densities (defined under some smoothness conditions) in terms of exponential families with polynomial bases, and we prove that under some appropriate conditions, the sample complexity of learning them is bounded as O((1/ε)(2r1)/2r1n(2r1)/2r(1/ε)(1/ε)1n(1/δ) for a smoothness parameter r (a positive integer), where ε and δ are respectively accuracy and confidence parameters. Futher, we demonstrate polynomial-time learnability of classes of non-parametric densities (defined under some smoothness conditions) in terms of histogram densities with equal-length cells, and we prove that under some appropriate condition, the sample complexity of learning them is bounded as O((1/ε)3/21n3/2(1/ε)(1/ε)1n(1/δ)).

We investigate the relationship between two different notions of reducibility among prediction (learning) problems within the distribution-free learning model of Valiant (PAC learning model). The notions of reducibility we consider are the analogues for prediction problems of the many-one reducibility and of the Turing reducibility. The former is the notion of prediction preserving reducibility developed by Pitt and Warmuth, and its generalization. Concerning these two notions of reducibility, we show that there exist a pair of prediction problems A and B, whose membership problems are polynomial time solvable, such that A is reducible to B with respect to the Turing reducibility, but not with respect to the prediction preserving reducibility. We show this result by making use of the notion of a class of polynomially sparse variants of a concept representation class. We first show that any class A of polynomially sparse variants of another class B is reducible to B with respect to the Turing reducibility'. We then prove the existence of a prediction problem R and a class R of polynomially sparse variants of R, such that R does not reduce to R with respect to the prediction preserving reducibility.

The mechanism of UV-excited dry cleaning using photoexcited chlorine radicals has been investigated for removing iron and aluminum contamination on a silicon surface. The iron and aluminum contaminants with a surface concentration of 1013 atoms/cm2 were intentionally introduced via an ammonium-hydrogenperoxide solution. The silicon etching rates from the Uv-excited dry cleaning differ depending on the contaminants. Fe and Al can be removed in the same manner. The removal of Fe and Al is highly temperature dependent, and is little affected by the silicon etching depth. Both Fe and Al on the silicon surface were completely removed by UV-excited dry cleaning at a cleaning temperature of 170, and were decreased by two orders of magnitude from the initial level when the surface was etched only 2 nm deep.

Plasmaless etching using ClF3 gas has been investigated on nitride films with different composition. For the sputter deposited and thermally grown silicon nitride films containing no hydrogen, the etch rate increases and the activation energy decreases with increase of the composition ratio of silicon to nitrogen between 0.75 and 1.3. This fact indicates that the etching is likely to proceed through the reaction between Si and ClF3. The native oxide on the silicon-nitride films can also be removed with ClF3 gas. Ultra-violet light irradiation from a low pressure mercury lamp remarkably accelerates the removal of the native oxide and the etch rate of the thermally grown silicon-nitride films. For the plasma deposited films, the etch rate is strongly accelerate with increasing hydrogen content in the films, but the activation energy hardly depends on the bounded hydrogen in the films, consistent with the results for Si etching.

The introduction of Integrated Services Digital Networks (ISDNs) poses a variety of new questions on telecommunications network design and planning. Furthermore, the formulation of traditional network design and planning problems need to be revisited in the ISDN context. This paper presents an overview of the recent progress and new challenges in developing ISDN design and planning methodologies that exploit revolutionary new telecommunications technologies. It will cover some important issues for ISDN design and planning, and will concentrate on three issues that are of particular importance: Design of networks with digital information transfer capabilities, design of networks with advanced network/traffic control techniques, and use of reliability objectives for network design and planning.

Location theory on networks is concerned with the problem of selecting the best location in a specified network for facilities. Many studies for the theory have been done. However, few studies treat location problems on networks from the standpoint of measuring the closeness between two vertices by the capacity (maximum flow value) between two vertices. This paper concerns location problems, called covering problems on flow networks. We define two types of covering problems on flow networks. We show that covering problems on undirected flow networks and a covering problem on directed flow networks are solved in polynomial times.

A new set of self-consistent linear equations is presented for the analysis of the startup characteristics of gyrotron oscillators with an open cavity consisting of weakly irregular waveguides. Numerical results on frequency detuning and oscillation starting current for a whispering-gallery-mode gyrotron are described in which these equations were utilized. Experiments for making a check on the effectiveness of the derived equations showed that they well express the operation of gyrotrons in comparison with the linear theory using an empty cavity field as the wave field.

Binary Decision Diagrams (BDDs) and Shared Binary Decision Diagrams (SBDDs), which are improved BDDs, are useful for implementing VLSI logic design systems. Recently, these representations, which are graph representations of Boolean functions, have become popular because of their efficiency in terms of time and space. The forms of the BDD vary with the order of the input variables though they represent the same function. The size of the graphs greatly depends on the order. The variable ordering algorithm is one of the most important issues in the application of BDDs. In this paper, we consider methods which reduce the graph size by reordering input variables on a given BDD with a certain variable order. We propose the Minimum-Width Method which gives a considerably good order in a practicable time and space. In the method, the order is determined by width of BDDs as a cost function. In addition, we show the effect of combining our method with the local search method, and also describe the improvement using the threshold. Experimental results show that our method can reduce the size of BDDs remarkably for most examples. The method needs no additional information, such as the topological information of the circuit. The results can be a measure for evaluation of other ordering methods.

For the efficient circuit simulation by the direct method, network tearing and latency techniques have been studied. This letter describes a circuit simulator SPLIT with hierarchical decomposition and latency. The block size of the latent subcircuit can be determined dynamically in SPLIT. We apply SPLIT to the MOS circuit simulation and verify its availability.

Mechanism for radiation phenomenon caused by a finite-length transmission line is discussed. Coupling of an external wave to a transmission line has been studied by using a circuit concept because of a TEM transmission. Since the relationship between coupling and radiation is reciprocal, radiation can be treated by using the circuit concept. It is shown that the equations obtained by using the field theory are quite coincident with those by the circuit theory. From the resultant, it can be concluded that the radiated fields are composed of those by the line current of TEM and the terminal currents. A method for an application of the circuit concept to radiation due to a trace on a printed circuit board is studied by comparing the experimental results.

A new model for a computer simulation of RF capacitive type hyperthermia has been developed by taking account of the following points. Blood flow is usually determined by many physiological parameters, but is regarded as a function of only blood temperature under some conditions. The temperature dependence of blood flow of tumors and normal tissues is assumed by referring the data obtained by Song et al. and Tanaka. The blood temperature which is elevated by externally applied power significantly affects temperatures of the body and the tumors. The transport of heat from the body surface is studied by considering air convection. These points are examined by experiments on a computer with simple phantom models and real patients. The results of simulation on the patient have shown a good agreement with clinical inspection based on CT images and a temperature of the stomach.

The behavior of TM-wave scattering from a dielectric-loaded semicircular trough in a conducting half-space is investigated. The dielectric loading is made of a circular cylinder which lies in a semi-circular trough in the perfectly conducting plane. The formulation is numerically evaluated to investigate the scattered field pattern for various dielectric loading conditions. It is found that the scattering patterns exhibit the resonant behavior due to both of the concave surface contour and the dielectric loading.

Low-field mobilities and velocity versus electric field relations are among the key input parameters for drift-diffusion simulations of field-effect and bipolar transistors. For example, most device simulations that treat scattering from ionized impurities contain mobilities or velocity versus field relations based on the Born approximation (BA). The BA is insensitive to the sign of the charged impurity and is especially poor for ionized impurity scattering because of the relatively strong scattering of long-wavelength carriers, which have low energies, and therefore violate the validity condition for the BA. Such carriers occur at high symmetry points in the Brillouin zone and are critical for device behavior. There has been a tendency in the past to assume that majority and minority mobilities are equal. This assumption can lead to incorrect interpretations of device data and thereby misleading design strategies based on such simulations. We have calculated the majority electron and minority hole mobilities in GaAs at 300 K for donor densities between 51016 and 11019 cm-3 and the majority hole and minority electron mobilities for acceptor densities between 51016 and 11020 cm-3. We have included all the important scattering mechanisms for GaAs: acoustic phonon, polar optic phonon, nonpolar optic phonon (holes only), piezoelectric, ionized impurity, carrier-carrier, and plasmon scattering. The ionized impurity and carrier-carrier scattering processes have been calculated with a quantum mechanical phase-shift analysis to obtain more accurate matrix elements for these two scattering mechanisms. We compare the total scattering rate for majority electrons due to ionized impurities based on exact phase shifts and on the BA used by Brooks-Herring. We also present additional data that show the differences between the exact phase-shift analyses and the BA for majority electron scattering rates as functions of carrier energy and scattering angle. These results show that the calculated low-field mobilities are in good agreement with experiment, but they predict that at high dopant densities minority mobilities should increase with increasing dopant density for a short range of densities. This effect occurs because of the reduction of plasmon scattering and the removal of carriers from carrier-carrier scattering because of the Pauli exclusion principle. Some recent experiments support this finding. These results are important for device modeling because of the need to have reliable values for the minority mobilities and velocity-field relations.

There have been several studies related to a reduction of the amount of computational resources used by Turing machines. As consequences, Linear speed-up theorem", tape compression theorem" and reversal reduction theorem" have been obtained. In this paper, we discuss a leaf reduction theorem on alternating Turing machines. Recently, the result that one can reduce the number of leaves by a constant factor without increasing the space complexity was shown for space- and leaf-bounded alternating Turing machines. We show that for time- and leaf-bounded alternating Turing machines, the number of leaves can be reduced by a constant factor without increasing time used by the machine. Therefore, our result says that a constant factor on the leaf complexity does not affect the power of time- and leaf-bounded alternating Turing machines.