Full scan design of sequential circuits results in greatly reducing the cost of their test generation. However, it introduces the extra expense of many test clocks to control and observe the values of flip-flops because of the need to shift values for the flip-flops into the scan panh. In this paper we propose a new method of generating compact test sequences for scan-based sequential circuits on the assumption that the number of shift clocks is allowed to vary for each test vector. The method is based on Boolean function manipulation using a shared binary decision diagram (SBDD). Although the test generation algorithm is basically for general sequential circuits, the computational cost is much lower for scan-based sequential circuits than for non-scanbased sequential circuits because the length of a test sequence for each fault is limited. Experimental results show that, for all the tested circuits, test sequences generated by the method require much smaller number of test clocks than compact or minimum test sets for combinational logic part of scan-based sequential circuits. The reduction rate was 48% on the average in the experiments.

The discrete time analysis of logic circuits is usually more efficient than the continuous time analysis, but the preciseness of the discrete time analysis is not guaranteed. The paper shows a method to decide a unit time for a logic circuit under which the analysis result is the same as the result based on the continuous time. The delay time of an element is specified with an interval between the minimum and maximum delay times, and we assume an analysis method which enumerates all possible delay cases under the deisrete time. Our main theorem is as follows: refine the unit time by a factor of 1/2, and if the analysis result with a unit time u and that with a unit time u/2 are the same, then u is the expected unit time.

We discuss delay times derived from the current gain cutoff frequency of a heterostructure field effect transistor and describe three types of novel channel structures for millimeter-wave InP-based HFETs. The first structure discussed is a lattice-matched InGaAs HEMT with high state-of-the art performance. The second structure is an InAs-inserted InGaAs HEMT which harnesses the superior transport properties of InAs. Fabricated devices show high electron mobility of 12,800 cm2/Vs and high transconductance over 1.4 S/mm for a 0.6-µm-gate length. The effective saturation velocity in the device derived from the current gain cutoff frequency in 3.0107 cm/s. The third one is an InGaAs/InP double-channel HFET that utilizes the superior transport properties of InP at a high electric field. Fabricated double-channel devices show kink-free characteristics, high carrier density of 4.51012 cm-2 and high transconductance of 1.3 S/mm for a 0.6-µm-gate length. The estimated effective saturation velocity in these devices is 4.2107 cm/s. Also included is a discussion of the current gain cutoff frequency of ultra-short channel devices.

Most of actual environmental systems show a complicated fluctuation pattern of non-Gaussian type, owing to various kinds of factors. In the actual measurement, the fluctuation of random signal is usually contaminated by an external noise. Furthermore, it is very often that the reliable observation value can be obtained only within a definite fluctuating amplitude domain, because many of measuring equipments have their proper dynamic range and original random wave form is unreliable at the end of amplitude fluctuation. It becomes very important to establish a new signal detection method applicable to such an actual situation. This paper newly describes a dynamical state estimation algorithm for a successive observation contaminated by the external noise of an arbitrary distribution type, when the observation value is measured through a finite dynamic range of measurement. On the basis of the Bayes' theorem, this method is derived in the form of a wide sense digital filter, which is applicable to the non-Gaussian properties of the fluctuations, the actual observation in a finite amplitude domain and the existence of external noise. Differing from the well-known Kalman's filter and its improvement, the proposed state estimation method is newly derived especially by paying our attention to the statistical information on the observation value behind the saturation function instead of that on the resultant noisy observation. Finally, the proposed method is experimentally confirmed too by applying it to the actual problem for a reverberation time measurement from saturated noisy observations in room acoustics.

This paper describes a neural network scheduler for scheduling independent and nonpreemptable tasks with deadlines and resource requirements in critical real-time applications, in which a schedule is to be obtained within a short time span. The proposed neural network scheduler is an integrate model of two Hopfield-Tank neural network medels. To cope with deadlines, a heuristic policy which is modified from the earliest deadling policy is embodied into the proposed model. Computer simulations show that the proposed neural network scheduler has a promising performance, with regard to the probability of generating a feasible schedule, compared with a scheduler that executes a conventional algorithm performing the earliest deadline policy.

A new method of multipath diversity combination is proposed for Direct Sequence Spread Spectrum (DS-SS) mobile communications. In this method, the transmitted signal from the base staion is the sum of a number of the same spread signal, each one delayed and scaled according to the delay and the strength of the multipaths of the transmission channel. As a result the received signal at the mobile unit will already be a Rake combination of the multipath signals. This new method is called Pre-Rake diversity combination because the Rake diversity combination process is performed before transmission By this method the size and complexity of the mobile unit can be minimized, and the unit is made as simple as a non-combining single path receiver. A theoretical examination of the Signal to Noise Ratio (SNR) and the Bit Error Rate (BER) results for the traditional Rake and the Pre-Rake combiners as well as computer simulations show that the performance of the Pre-Rake combiner is equivalent to that of the Rake combiner.

Assuming application to the mobile multiple-access communication, chip-asynchronous mobile-to-base performances of FH/FTH (Frequency-Time-Hopped)-MFTSK (Multi-level Frequency-Time Shift Keying) systems are investigated. Analytical expressions are obtained for the probabilities of false detection and missed detection of signal elements, assuming independent and asynchronous arrival of each of the signal elements with Rayleigh fading and optional AWG noise. Using the result or by simulation and employing dual-k coding, parameter optimization was carried out to obtain the maximum spectrum efficiency. The results of the noisy case analysis and simulation show high noise-robustness of the FTH systems. For a given value of information transmission rate the optimized FTH-MFTSK gives an effectively constant spectrum efficiency for a wide range of the number Kf of frequency chips. As a result, FTH-MFTSK well outperforms FTH-MFSK at any, especially small value of Kf. Relative to the overall optimum FH-MFSK, FTH-MFSK systems show typically around 20% of degradation in spectrum efficiency even with one-eighth of Kf. Compared with FH-MFSK, accordingly, FTH-MFTSK systems allow the designer to reduce, without any degradation in multiple-access performances, the number of frequency chips to the minimum value tolerated by the frequency selective fading characteristics and the time chip duration requirement imposed by the signal-to-noise ratio margin and the transmitter peak power rating.

In order to explain the temperature and frequency characteristics of high-Tc superconductors, a new model is proposed, which will be called the improved three-fluid model, where the momentum relaxation time τ is assumed to depend on temperature in the superconducting and normal states, respectively, although τ has been assumed to be independent of temperature for the conventional three-fluid model. According to this model, the complex conductivity σ1jσ2 and the surface impedance ZsRsjXs, where Rs is the surface resistance and Xs is the surface reactance, are expressed as a function of temperature. The temperature dependences of Zs and for a YBCO bulk estimated using this model agree very well with ones measured by the dielectric-loaded cavity method in room to cryogenic temperature. In particular, a peak of σ1 observed just below the critical temperature Tc in experiments, appeared in the calculated results based on this model. This phenomenon has been already known in the BCS theory. Thus, it is verified that this model is useful to explain the microwave characteristics of high-Tc superconductors in room to cryogenic temperature. On the other hand, the residual normal electron density nres4.2541023 m-3 and the total electron density nt7.3081024 m-3 are obtained by calculation. The ratio nres/nt0.058 can be used as figure of merit to evaluate material quality of high-Tc superconductors; thus it means that there is 5.8% nonpairing electron in this YBCO bulk.

A time division duplex (TDD) direct sequence spread spectrum communication (DS-SS) system is proposed for operation in channels with Rayleigh fading characteristics. It is shown that using the TDD method is advantageous because the devices can be designed more simply, the method is more frequency efficient and as a result the systems will be less costly and less power consuming. It is also shown that an efficient power control method can be implemented for the TDD systems. In contrast to the traditional access techniques such as frequency division multiple access (FDMA) and time division multiple access (TDMA) that are mainly frequency limited, the code division multiple access (CDMA) method which uses the DS-SS technique is interference limited. This means that an efficient power control method can increase the capacity of the DS-SS communications system. Computer simulations are used to evaluate the performance of the TDD power control method. Performance improvement of order of 12 to 17dB at bit error rate (BER) of 10-3 can be obtained for different methods of power control. The advantages of the TDD technique for the future DS-SS systems operating in the Industrial, Scientific and Medical (ISM) band are explained in an appendix to this paper.

In our recent work, a forward test generation method for sequential circuits by using a single time frame was proposed. In order to improve the effectiveness of the method, we introduced an extended mode which can handle the two time frames for a hard-to-test fault and a state escaping phase which can detect a sequence of unsuitable states for test generation. The experimental results show that the improved method is effective in generating higher coverage tests with a small number of tests.

A laser system which has a mirror outside of it to feedback a delayed output has been described by the Maxwell-Bloch equations with time delay. It is shown that a chaotic behavior in the equations can be controlled by using a OPF control algorithm. Our numerical simulation indicates that the chaotic behavior is stabilized on 1, 2 periodic unstable orbits.

Scaling-down of MOSFETs (metal-oxide-semiconductor field effect transistors can be divided to semi-classical and quantum mechanical one. In the regime of semi-classical scaling-down the behavior of electrons and holes can be well described with the effective mass approximation and in the regime of quantum mechanical scaling-down the characteristics of electrons and holes as wave becomes markedly. The minimum size limit of MOSFETs scaled down in semi-classical regime is mainly determined by the subthreshold characteristics and the short channel effect on the threshold voltage and 0.1 µm will be the minimum channel length from practical viewpoints. Scaling down of MOSFETs enhances their operational speed, but the substrates with high resistivity which are often used in SOI (silicon on insulator) substrates result longer dielectric relaxation time. While the dielectric relaxation time becomes longer than the reciprocal of signal frequency, the semiconductors work as lossy dielectrics and may lead to new types of dynamic circuits. Modification of material properties utilizing the wave nature of electrons is an illustration of quantum mechanical way to improve characteristics of MOSFETs. Suppression of optical phonon scattering of two dimensional electrons by introducing two dimensional array of quantum dots into substrates is expected to improve high field characteristics of material. Brillouin zone folding is another way to control the band structure of materials, especially to make the indirect transition band structure to the direct transition band structure. Heat transfer from a chip severely limits the number of devices which can be integrated on the chip. Reduction of signal charge to electronic elementary charge, that is quantum limit, is expected to be useful for realization of nano-power electronics.

The performance of processing elements can be improved by the progress of VLSI circuit technology, while the communication overhead can not be negligible in parallel processing system. This paper presents a unified scheduling that allocates tasks having different task processing times in multiple processing elements. The objective function is formulated to measure communication time between processing elements. By employing constraint conditions, the scheduling efficiently generates an optimal solution using an integer programming so that minimum communication time can be achieved. We also propose a VLSI processor for robotics whose latency is very small. In the VLSI processor, the data transfer between two processing elements can be done very quickly, so that the communication cycle time is greatly reduced.

This paper presents a new Hypermedia communication platform supported by the new digital image medium of super high definition (SHD) images. This new image communication platform will encourage the integration of all existing media to realize rich and realistic visual communication over B-ISDN. SHD images have a resolution of more than 20482048 pixels and the frame rate is more than 60 frames/sec. To achieve an real-time compression of SHD moving images, parallel signal processing systems with peak performance of 0.5 Tera Flops will be necessary. The specification requirements, signal processing and communication technologies needed to achieve SHD image communication are discussed. The relationship of hypermedia to SHD images is also examined.

A least squares approximation method of recursive digital filters for finite interval response with zero value outside the interval is presented. According to the characteristic of the method, the modified Gauss Method is utilized in iteratively determining design parameters. Convergence, together with the stability of the resulting filter, are guaranteed.

By a measure we mean a function µ from {0, 1}* (the set of all binary sequences) to real numbers such that µ(x)0 and µ({0, 1}*). A malign measure is a measure such that if an input x in {0, 1}n (the set of all binary sequences of length n) is selected with the probability µ(x)/µ ({0, 1}n) then the worst-case computation time tWOA (n) and the average-case computation time tav,µA(n) of an algorithm A for inputs of length n are functions of n of the same order for any algorithm A. Li and Vitányi found that measures that are known as a priori measures are malign. We prove that a priori" -ness and malignness are different in one strong sense.

The mechanism of environment-dependent self-organization of "positional information" in a coupled nonlinear oscillator system is proposed as a new principle of realtime coordinative control in biological distributed system. By modeling the pattern formation in tactic response of Physarum plasmodium, it is shown that a global phase gradient pattern self-organized by mutual entrainment encodes not only the positional relationship between subsystems and the total system but also the relative relationship between internal state of the system and the environment.

In this paper, a new time series analysis method is proposed. The proposed method uses the exponential (EXP) model. The residual signal is assumed to be identically and independently distributed (IID). To achieve accurate and efficient estimates, the parameter of the system model is calculated by maximizing the logarithm of the likelihood of the residual signal which is assumed to be IID t-distribution. The EXP model theoretically assures the stability of the system. This model is appropriate for analyzing signals which have not only poles, but also poles and zeroes. The asymptotic efficiency of the EXP model is addressed. The optimal solution is calculated by the Newton-Raphson iteration method. Simulation results show that only a small number of iterations are necessary to reach stationary points which are always local minimum points. When the method is used to estimate the spectrum of synthetic signals, by using small α we can achieve a more accurate and efficient estimate than that with large α. To reduce the calculation burden an alternative algorithm is also proposed. In this algorithm, the estimated parameter is updated in every sampling instant using an imperfect, short-term, gradient method which is similar to the LMS algorithm.

A new redundancy technique especially suitable for ultra-high-speed static RAMs (SRAMs) has been developed. This technique is based on a decoding-method that uses two kinds of fuses without introducing any additional delay time. One fuse is initially ON and can be turned OFF afterwards, if necessary, by a cutting process using a focused ion beam (FIB). The other is initially OFF and can be turned ON afterwards by a connecting process using laser chemical vapor deposition (L-CVD). This technique is applied to a 64 kbit SRAM having a 1.5-ns access time. The experimental results obtained through an SRAM chip repaired using this redundancy technique show that this technique does not introduce any increase in the access time and does not reduce the operational margin of the SRAM.

In this paper, we propose an algorithm of O(|V|min{k,|V|,|A|}|A|) time complexity for finding all k-edge-connected components of a given digraph D=(V,A) and a positive integer k. When D is symmetric, incorporating a preprocessing reduces this time complexity to O(|A|+|V|2+|V|min{k,|V|}min{k|V|,|A|}), which is at most O(|A|+k2|V|2).