Hot-carrier degradation of voltage controlled oscillator (VCO) was investigated by a reliability simulator known as BERT. The appropriate monitor of VCO frequency degradation shifts from the saturated drain current of an N MOSFET to linear drain current with an increase in VCO input voltage. The degradation of the VCO drastically increases with a small reduction in initial oscillation frequency. These results imply the need for an appropriate reliability margin around the standard operating point as well as a performance margin, which cannot be achieved by using conventional drain current monitors.

The robust statistics has recently been adopted by the computer vision community. Various robust approaches in the computer vision research have been proposed in the last decade for analyzing the image motion from the image sequence. Because of the frequent violation of the Gaussian assumption of the noise and the motion discontinuities due to multiple motions, the motion estimates based on the straightforward approaches such as the least squares estimator and the regularization often produces unsatisfactory result. Robust estimation is a promising approach to deal with these problems because it recovers the intrinsic characteristics of the original data with the reduced sensitivity to the contamination. Several previous works exist and report some isolated results, but there has been no comprehensive analysis. In this paper robust approaches to the optical flow estimation based on the maximum likelihood estimators are proposed. To evaluate the performance of the M-estimators for estimating the optical flow, comparative studies are conducted for every possible combinations of the parameters of three types of M-estimators, two types of residuals, two methods of scale estimate, and two types of starting values. Comparative studies on synthetic data show the superiority of the M-estimator of redescending ψ-function using the starting value of least absolute residuals estimator using Huber scale iteration, in comparison with the other M-estimators and least squares estimator. Experimental results from the real image experiments also confirm that the proposed combinations of the M-estimators handle the contaminated data effectively and produce the better estimates than the least squares estimator or the least absolute residuals estimator.

Introducing a mathematical model of image noise, we formalize the problem of fitting a line to point data as statistical estimation. It is shown that the reliability of the fitted line can be evaluated quantitatively in the form of the covariance matrix of the parameters. We present a numerical scheme called renormalization for computing an optimal fit and at the same time evaluating its reliability. We also present a scheme for visualizing the reliability of the fit by means of the primary deviation pair and derive an analytical expression for the reliability of a line fitted to an edge segment by using an asymptotic approximation. Our method is illustrated by showing simulations and real-image examples.

The independence number of one-order graph associated with a linear code is formulated. The formulation is represented by the parameters of the generator matrix.

An antenna and multi-carrier combined diversity system using Time Division Duplex (TDD) is proposed to combat with multi-path channel problem which produces frequency-selective fading and degrades the quality of signal transimission. So far multi-carrier modulation technique has been studied to solve this problem. On the other hand, TDD method has been studied to use a transmitter antenna diversity as pre-diversity against flat fading (non-selective fading). Our proposed system merges these two methods in a micro-cellular system as follows. On the reverse link, the base station can select the best combination between the carriers and antennas after receiving the multi-carrier signal from the mobile station. On the forward link, the same combination selected on the reverse link can be used to send the signal from the base station with multi-antenna to the mobile station with a single antenna and produces pre-diversity (transmitter diversity) effect which can reduce the complexity at the mobile station. The pre-diversity must be based on TDD function because the channel has to be observed before the signal transimission. By computer simulations we find that our proposed system can achieve far better performance than conventional systems.

An individual identification system is developed. In this system, we unify profile curve identification and full face image identification to obtain more successful recognition rate. In profile cruve identification process, the P-type Fourier descriptor is made use of. In full face image identification process, mosaic density values are made use of. A combination of the two processes shows higher recognition rates than those obtained by each single process.

This paper presents an O(mn log n) time algorithm for an approximate string matching problem, in which a pattern string may contain variable length don't care characters. This problem is important for searching DNA sequences or amino acid sequences.

Personal communication systems (PCS) have more signalling traffic than conventional fixed networks and require large-scale databases to manage users' profiles, which are sets of data items, such as the location the user is currently visiting and the user's authentication key, necessary for a PCS user to be provided with PCS services. This paper focuses on inter-network roaming in PCS environments. In designing a PCS supporting roaming service, it is essential to avoid increased signalling traffic and data searching time in the database. We first identify the appropriate domains for three routing schemes-Direction Routing, Redirection Routing, and Look-ahead Routing-from the viewpoints of the number of signals for inter-network roaming and roaming probability. We do this for two kinds of PCS database network architecture, Home Location Register (HLR) and Visitor Location Register (VLR), and show that Look-ahead Routing is the best scheme for the HLR network architecture (considering the number of signals for intra-network and inter-network database access) and that in the VLR network architecture, the decreasing of the roaming probability expands domains for which Redirection Routing is appropriate. We also propose a generic PCS data model that inter-network roaming interfaces can use to search effectively for a user's profile. The data model clarifies the contents of a set of data items which share certain characteristics, data items that the contents compose, and the relationships (data structures) between sets of data items. The model is based on the X. 500 series recommendations, which are applied for an Intelligent Network. We also propose a data structure between sets of data items using the directory information tree and show the ASN. 1 notations of the data model.

We show a relationship between the number of negations in circuits and the size of circuits. More precisely, we construct a Boolean function Hn, and show that there exists an integer t, which can range over only two different values, such that the removal of one NEGATION gate causes an exponential growth of the optimal circuit size for Hn.

The problem of test generation for VLSI circuits computationally requires prohibitive costs. Parallel processing on a multiprocessor system is one of available methods in order to speedup the process for such time-consuming problems. In this paper, we analyze the performance of parallel test generation for combinational circuits. We present two types of parallel test generation systems in which the communication methods are different; vector broadcasting (VB) and fault broadcasting (FB) systems, and analyze the number of generated test vectors, the costs of test vector generation, fault simulation and communication, and the speedup of these parallel test generation systems, where the two types of communication factors; the communication cut-off factor and the communication period, are applied. We also present experimental results on the VB and FB systems implemented on a network of workstations using ISCAS'85 and ISCAS'89 benchmark circuits. The analytical and experimental results show that the total number of test vectors generated in the VB system is the same as that in the FB system, the speedup of the FB system is larger than that of the VB, and it is effective in reducing the communication cost to switch broadcasted data from vectors to faults.

Introducing a mathematical model of image noise, we formalize the problem of fitting a conic to point data as statistical estimation. It is shown that the reliability of the fitted conic can be evaluated quantitatively in the form of the covariance tensor. We present a numerical scheme called renormalization for computing an optimal fit and at the same time evaluating its reliability. We also present a scheme for visualizing the reliability of the fit by means of the primary deviation pair. Our method is illustrated by showing simulations and real-image examples.

We propose in this paper a systematic way for analyzing discrete event dynamic systems to classify faults and failures quantitatively and to find tolerable fault event sequences embedded in the system. An automated failure diagnosis scheme with respect to the nominal normal operating event sequences and the supervisory control for tolerable fault event sequences are presented. Moreover the supervisor failure diagnosis with respect to the tolerable fault event sequences is considered. Finally, a case study of plasma etching system is described.

When an image of a 3D object is transmitted or recorded, its range image as well its grey-scale image are required. In this paper, we propose a method of coding for efficient compression of a pair of a pair of range and grey-scale images of 3D objects. We use Lambertian reflection optical model to model the relationship between a 3D object shape and it's brightness. Good illuminant direction estimation leads to good grey-scale image generation and furthermore effects compression results. A method for estimating the illuminant derection and composite albedo from grey-scale image statistics is presented. We propose an approach for estimating the slant angle of illumination based on an optical model from a pair of range and grey-scale images. Estimation result shows that our approach is better. Using the estimated parameters of illuminant direction and composite albedo a synthetic grey-scale image is generated. For comparison, a comparison coding method is used, in which we assume that the range and grey-scale images are compressed separately. We propose an efficient compression coding method for a pair of range and grey-scale images in which we use the correlation between range and grey-scale images, and compress them together. We also evaluate the coding method on a workstation and show numerical results.

We study Lempel-Ziv-Yokoo algorithm [1, Algorithm 4] for universal data compression. In this paper, we give a simpler implementation of Lempel-Ziv-Yokoo algorithm than the original one [1, Algorithm 4] and show its asymptotic optimality for a stationary ergodic source.

For mobile/personal satellite systems, an ARQ protocol with low transmitter/receiver complexity as well as high throughput performance in a long Round-Trip-Delay (RTD) and even in a bad channel condition is required. In this paper, a new Selective-Repeat (SR) ARQ with multicopy retransmission is proposed and a performance on an AWGN channel is analyzed. The proposed scheme can be viewed as a modified version for SR + Stutter (ST) Scheme 2 [6]. The basic idea of the strategy is to repeat only erroneous blocks stored in the vN block transmitter buffer multiple times, when v consecutive retransmissions in SR mode are received in error, where N denotes RTD in blocks. Numerical analysis and simuration results in the case of N block transmitter/receiver buffer show that the proposed scheme presents better performance than SR + ST scheme 2 of 2N block buffer, especially that the robustness in the high BER region is remarkable.

This paper presents a model for a wide-band fading channel for terrestrial mobile applications. The model is based on the results of measurements made in a heavily built-up urban environment using a 25 MHz signal centred at approximately 2.6 GHz. This paper presents measured impulse responses and details the parameter extraction process used to determine the characteristics of the channel. These parameters are used in the channel simulation package and the output of these simulations are compared to the original data.

A close correlation between the YBa2Cu3Oy film morphology and location of the (100) MgO substrate during growth by excimer laser ablation was obtained. When the susbtrate was placed inside the fringe portion of the laser plume, the spiral shape was most clearly seen on the entire film surface for both the conventional and eclipse ablation methods. When the substrate was placed outside the plume, the spiral growth was less pronounced. On the other hand, when the substrate was placed inside the plume core, marked deformation of the morphology occurred, and the superconducting critical temperature was lowered. This correlation was explained to some extent by the spatial variation of kinetic energy of the flying growth species.

To evaluate the coding performance of a multilevel coding scheme for Rayleigh fading channel, a virtual automatic gain control and interleaving are applied to the scheme. The automatic gain control is assumed only for the theoretical evaluation of the performance. It is noted that the bit error-rate performance of the scheme for phase shift keying does not change whether the control is assumed or not. By the effect of the virtual automatic gain control and the interleaving, a fading channel with Gaussian noise is theoretically converted into an equivalent time-invariant channel with non-Gaussian noise. The probability density function of the converted non-Gaussian noise is derived. Then, the function is applied to a formula of the bit error-rate of the scheme for non-Gaussian noise. The formula is derived for phase shift keying by modifying that for pulse amplitude modulation. The coding performance for the non-Gaussian noise channel is evaluated by the formula, and the suitable coding with ideal interleaving is searched. As a result, the coding gain of 28 dB is obtained at the bit error-rate of 10-6 by using BCH code of length 31. This result is confirmed by a simulation for the fading channel. Then, the effectiveness of the formula for finite interleaving is evaluated. Finally, the usefulness of the formula, where the noise power is doubled, is shown for a case of a differential detection.

In 1989, Ahlswede and Dueck introduced a new formulation of Shannon theory called identification via channels. This paper presents a simple construction of codes for identification via channels when the probability of false identification is measured by its average. The proposed code achieves the identification capacity, and its construction does not require any knowledge of coding theory.

Many numerical simulation problems of natural phenomena are formulated by large tridiagonal and block tridiagonal linear systems. In this paper, an efficient parallel algorithm to solve a tridiagonal linear system is proposed. The algorithm named bi-recurrence algorithm has an inherent parallelism which is suitable for parallel processing. Its time complexity is 8N - 4 for a tridiagonal linear system of order N. The complexity is little more than the Gaussian elimination algorithm. For parallel implementation with two processors, the time complexity is 4N - 1. Based on the bi-recurrence algorithm, a VLSI oriented tridiagonal solver is designed, which has an architecture of 1-D linear systolic array with three processing cells. The systolic tridiagonal solver completes finding the solution of a tridiagonal linear system in 3N + 6 units of time. A highly parallel systolic tridiagonal solver is also presented. The solver is characterized by highly parallel computability which originates in the divide-and-conquer strategy and high cost performance which originates in the systolic architecture. This solver completes finding the solution in 10(N/p) + 6p + 23 time units, where p is the number of partitions of the system.