This paper proposes a small 1/4Vcc bit-line swing scheme and a related sense amplifier scheme for low power 1 V operating DRAM. Using the proposed small bit-line swing scheme, the stress bias of memory cell transistor and capacitor is reduced to half that of the conventional DRAM, resulting in improvement of device reliability. The proposed sense amplifier scheme achieves high speed and stable sensing/restoring operation at 250mV bit-line swing, which is much smaller than threshold voltage. The proposed scheme reduces the total power dissipation of bit-line sensing/restoring operation to 40% of the conventional one. This paper also proposes a small 4F2 size memory cell and a new twisted bit-line scheme. The array noise is reduced to 8.6% of the conventional DRAM.

The quality of a modular software system depends on the reliabilities of the software modules and the software operational profile. When the software is designed for multiple customers having different operational profiles, different customers may experience different software quality. It is important to ensure that no customer will suffer from a poor software quality. In this paper, we formulate and solve three reliability allocation problems for modular software system designed for multiple customers. In these reliability allocation problems, we consider the software operational profile of every customer while fulfilling such practical constraints as cost budget and software quality requirement. The numerical results show that when the operational profiles of the customers are more skewed, it is more beneficial to take their operational profiles into account.

We develop a new class of stochastic Petri net: non-regenerative stochastic Petri net (NRSPN), which allows the firing time of its transitions with arbitrary distributions, and can automatically generate a bounded reachability graph that is equivalent to a generalization of the Markov renewal process in which some of the states may not constitute regeneration points. Thus, it can model and analyze behavior of a system whose states include some non-regeneration points. We show how to model a system by the NRSPN, and how to obtain numerical solutions for the NRSPN model. The probabilistic behavior of the modeled system can be clarified with the reliability measures such as the steady-state probability, the expected numbers of visits to each state per unit time, availability, unavailability and mean time between system failure. Finally, to demonstrate the modeling ability and analysis power of the NRSPN model, we present an example for a fault-tolerant system using the NRSPN and give numerical results for specific distributions.

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.

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.

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.

There is a growing demand for high reliability beyond what current RAID can provide and there are various levels of user demand for data reliability. An efficient data placement scheme called RM2 has been proposed in [10], which makes a disk array system resistant to double disk failures. In this paper, we consider how to choose an optimal striping unit for RM2 particularly when no workload information is available except read/write ratio. For experimental purposes, we develop a disk array simulator incorporating RM2 as one of the data placement schemes including other schemes of RAID levels. In the case of disk read operations, it is shown that RM2 has an optimal striping unit of 4/3T for large requests and 8/3T for small requests, where T represents the size of a single track. We have also shown that, if any disk write operations are involved, an optimal striping unit becomes 1/3T for large requests and 8/3T for small requests.

A new, simple test circuit for measuring the threshold voltage distribution of flash EEPROM cell transistors is described. This circuit makes it possible to perform a reliability test for a large number of memory cell transistors with easy static operation because it reduces the measuring time drastically. In addition, this circuit can measure the highest and lowest thresh-old voltages of memory cell transistors easily. This method is suitable for performing the reliability test, such as program/erase endurance test and data retention test, for a large number of flash memory cell transistors. The usefulness of this new test circuit has been confirmed by applying it to 64 Kbit NAND-type flash memory cell array.

ElectroStatic Discharge (ESD) testing of integrated circuits subjects circuit elements to very high currents for short periods of time. A modified Transmission Line Pulse (TLP) measurement system for characterizing transistors and other circuit elements under high currents for ESD performance prediction and understanding is presented which can both stress devices and measure leakage. For the TLP system to yield useful information test structures are needed which vary the important design parameters for the circuit elements. Guidelines for transistor test structure design for use with the system are presented and demonstrated for PMOS transistors.

Based on a simple model for the statistical error characteristics of range sensing, a numerical scheme called renormalization is presented for optimally fitting a planar surface to data points obtained by range sensing. The renormalization method has the advantage that not only an optimal fit is computed but also its reliability is automatically evaluated in the form of the covariance matrix. Its effectiveness is demonstrated by numerical simulation. A scheme for visualizing the reliability of computation by means of the primary deviation pair is also presented.

Theoretically, corresponding pairs of feature points between two stereo images can determine their 3-D locations uniquely by triangulation. In the presence of noise, however, corresponding feature points may not satisfy the epipolar equation exactly, so we must first correct the corresponding pairs so as to satisfy the epipolar equation. In this paper, we present an optimal correction method based on a statistical model of image noise. Our method allows us to evaluate the magnitude of image noise a posteriori and compute the covariance matrix of each of the reconstructed 3-D points. We demonstrate the effectiveness of our method by doing numerical simulation and real-image experiments.

This paper investigates the error correcting capabilities of concatenated codes employing algebraic geometry codes as outer codes and time-varying randomly selected inner codes, used on discrete memoryless channels with maximum likelihood decoding. It is proved that Gallager's random coding error exponent can be obtained for all rates by such codes. Further, it is clarified that the error exponent arbitrarily close to Gallager's can be obtained for almost all random selections of inner codes with a properly chosen code length, provided that the length of the outer code is sufficiently large. For a class of regular channels, the result is also valid for linear concatenated codes, and Gallager's expurgated error exponent can be asymptotically obtained for all rates.

Currently there is considerable world-wide speculation regarding the introduction of optical fiber cable into access networks, because optical fiber has a big potential for providing attractive multimedia services. Since optical fiber cable can provide a variety of grade of services, high-reliability of cable networks would be required compared with the conventional copper cable networks. To develop multimedia telecommunication networks as an infrastructure, it is urgent to clarify the highly reliable optical fiber cable network architecture. Since cable network architecture deeply depends on regional conditions such as demand, area size, duct layer networks (consisting of ducts, manholes, tunnels, feeder points etc.), it is necessary to develop a cable network designing tool with user-friendly interfaces for efficiently evaluating cable network architectures. This paper firstly proposes the heuristic algorithms enhanced by the disjoint-shortest-path and the depth-first-search methods that would be applicable for real access networks. Secondly, the design method of highly reliable optical fiber cable network based on the heuristic algorithms in terms of network cost and unavailability caused by cable breakdown is proposed. It can design the combination of star- and loop-shaped (where two diversified routes exist between a feeder point and central office) cable network. Furthermore, comparison with the conventional design method which simply applies star- or loop-shaped cable network is done in terms of economy and reliability on real access networks in the Tokyo metropolitan area. It is concluded that the proposed method can reduce the network cost further and realize a short unavailability value compared with the conventional method.

This paper studies the problem of reconstructing a planar surface from stereo images of multiple feature points that are known to be coplanar in the scene. We present a direct method by applying maximum likelihood estimation based on a statistical model of image noise. The significant fact about our method is that not only the 3-D position of the surface is reconstructed accurately but its reliability is also computed quantitatively. The effectiveness of our method is demonstrated by doing numerical simulation.

An optimum design scheme for logical network topologies on a Flexible Multi-QoS Logical ATM Network, named Full-Net, is proposed. Full-Net offers high-quality Virtual-Path (VP) networks and controls end-to-end QoS only at the VP-network's access points. To develop the optimum network topology for multimedia traffic in a single ATM network, a logically con figured Virtual Channel Handler (VCH) interconnection network is associated with each QoS class. Many logical networks can be mapped at the same time on the same network, because mapping is independent of the network's physical implementation. To achieve an optimum design scheme for logical networks, the number of disjoint routes is introduced as the parameter used to optimize logical network topology. The number of disjoint routes is chosen so as to maximize total network efficiency. The optimum number of disjoint routes depends on the required QoS, VC-traffic characteristics, and traffic demand. By choosing the relevant cost characteristics, the network operator can easily maximize network efficiency and provide customers with the QoS they request at minimum cost. The proposed optimum multi-QoS network design scheme on a Full-Net architecture is an efficient solution to implementing multi-QoS control in an ATM network.

A new approximation calculation method, named the Recursive Matrix-calculation (RM) method, is proposed. It uses matrix calculation to determine the number of link disjoint paths under a hop link number constraint, i.e. hop limit. The RM method does not overestimate the number of link disjoint paths. When networks are designed by this method, network reliability is perfectly guaranteed. Moreover, the RM method is based on matrix calculation, so CPU time can be reduced by using super-computers equipped with vector processors. Simulation results confirm that the RM method yields rapid approximations that are conservative. Thus the proposed method is very useful for designing reliable multimedia networks.

Thickness dependence of breakdown properties in control and N2O-Oxynitrided oxides was investigated. Nitrogen atoms piled up at the Si/SiO2 interface increase charge-to-breakdown (QBD) under substrate injection conditions for oxide thickness below 10 nm, while no meaningful improvement is observed above 10 nm. This thickness dependence is explained by the fact that N2O-oxynitridation reduces oxide defects near the Si/SiO2 interface. N2O-oxynitridation of the oxides reduces the number of neutral electron traps due to the chemical reaction of oxide defect with nitrogen atoms. Electron trapping of N2O-oxynitrided oxides is significantly suppressed; the reduction of electron trapping events into neutral electron traps increases QBD under substrate injection. On the other hand, under gate injection, N2O-oxynitrided oxides show low rate of hole trapping during the initial stress period. However, in heavily injected condition, electron trapping is not suppressed, resulting in little improvement of QBD. In addition, the control and N2O-oxynitrided oxides show quite similar dependence of QBD on stress current density, which is related primarily to the carrier transport phenomena (tunneling, traveling, impact ionization and hole injection).

We describe a new water sensing system for optical fiber cable networks. This system consists of optical fibers, water sensors and an OTDR (Optical Time Domain Reflectometer). The water sensor contains material which swells on contact with water and bends the optical fiber. The OTDR monitors the optical loss increase caused by this fiber bending and determines its location. In this system it is very important to determine the loss increase caused by the water sensor in terms of the OTDR performance. Therefore, we clarified the relationship between the water sensor structure and the increase in loss. Based on this study, we fabricated a sensor which causes a 5dB loss increase. The measured value is very close to the calculated value.

New detection method of passivation defect was studied. The method was the Cu decoration method without bias (bias-free Cu decoration). As the result of comparison with conventional method, it was found that a bias-free Cu decoration method was effective, sensitive and simple. In this method, the difference of humidity resistance induced by poor passivation coverage could be evaluated.

Plasma damage to gate oxide is studied using the test structures with various length antennas. It is shown that the plasma damage to gate oxide can be monitored quantitatively by measuring charge to breakdown (QBD). From the QBD measurements, it is confirmed that the degradation occurs in the duration of over-etching but not in the duration of main etching. The breakdown spots in gate oxide are detected by a photon emission method. The breakdown are caused by plasma damage at the LOCOS edge. A LOCOS structure plays an important role for the degradation by the plasma damage.