We proposed a novel structure that improved the linear characteristics of electroabsorption modulator (EAM) with composite quantum-wells as an absorption core layer. We fabricated three types of EAM's whose active cores were 8 nm thick, 12 nm thick and a composite core with 8 nm thick and 12 nm thick quantum-well (QW), respectively. The transfer functions of EAM's were investigated and their third-order inter-modulation distortion (IMD3) was obtained by calculation. The spurious free dynamic range (SFDR) was measured and compared with three types of QW. The linearity of the device with composite quantum-well showed a large enhancement in SFDR by 9.3 dBHz2/3 in TE mode and 7.0 dBHz2/3 in TM mode compared with the conventional EAM.

We formally define the mobile agent allocation problem from a system-wide viewpoint and then prove that it is strongly NP-complete even if each agent communicates only with two agents. This is the first formal definition for scheduling mobile agents from the viewpoint of load balancing, which enables us to discuss its properties on a rigorous basis. The problem is recognized as preemptive scheduling with independent tasks that require mutual communication. The result implies that almost all subproblems of mobile agent allocation, which require mutual communication of agents, are strongly NP-complete.

We have developed an experimental approach that allows us to estimate the performance of a large-scale enterprise network to update routing information. This approach was applied to the integration of the UFJ Bank network system on January 15, 2002. The main characteristic of this approach is the application of a formula that represents the delays in updating routing information that accompany reductions in CPU resources. This procedure consists of two steps: one is to estimate the reduction in the availability of CPU resources caused by forwarding of data packets at a router, and the other is to estimate the levels of CPU resources required for replying to a query about a new route and subsequently updating the routing information. These steps were applied to estimate the performance of the network in terms of routing information convergence. The results of our experiments on the network showed that updating the routing information was possible as long as the average level of CPU utilization during any five-minute period at the routers was less than 40%. We were able to apply this guideline and thus confirm the stability of the UFJ Bank network.

Press-induced long-period fiber gratings exhibiting strong core-to-cladding mode coupling were formed in photonic crystal fiber. Only one resonance peak was observed over a 600 nm spectral range and the resonant wavelength was tuned over the whole range by tilting a groove plate before pressing the fiber. The resonant wavelength decreased with increasing periodicity of the grating, which was opposite to the trend of the step-index conventional optical fiber. Meanwhile, the resonant wavelength increased with increasing the ambient refractive index, which was also opposite to that of the conventional optical fiber.

In this letter, we propose "Torus Ring", which is a modified version of 2-level hierarchical ring. The Torus Ring has the same complexity as the hierarchical rings, since the only difference is the way it connects the local rings. It has an advantage over the hierarchical ring when the destination of a packet is the adjacent local ring, especially to the backward direction. Although we assume that the destination of a network packet is uniformly distributed across the processing nodes, the average number of hops in Torus Ring is equal to that of the hierarchical ring. However, the performance gain of the Torus Ring is expected to increase, due to the spatial locality of the application programs in the real parallel programming environment. In the simulation results, latencies of the interconnection network are reduced by up to 19%, with moderate ring utilization ratios.

We investigate the error exponent in the lossy source coding with a fidelity criterion. Marton (1974) established a formula of the reliability function for the stationary memoryless source with finite alphabet. In this paper, we consider a stationary memoryless source assuming that the alphabet space is a metric space and not necessarily finite nor discrete. Our aim is to prove that Marton's formula for the reliability function remains true even if the alphabet is general.

In this paper, a modified adaptive fuzzy sliding mode controller for a certain class of uncertain nonlinear systems is presented. We incorporate the fuzzy sliding mode control technique with a modified adaptive fuzzy control technique to design a modified adaptive fuzzy sliding mode controller so that the proposed controller is robust against the unmodeled dynamics and the approximation errors. Firstly, we establish a fuzzy model to describe the dynamic characteristics of the given uncertain nonlinear system. Then, based on the fuzzy model, a fuzzy sliding mode controller is designed. By considering both the information of tracking error and modeling error, the modified adaptive laws for tuning the adjustable parameters of the fuzzy model are derived based on the Lyapunov synthesis approach. Since the modified adaptive laws contain both the tracking error and the modeling error, it implies that the fuzzy model parameters would continuously converge until both the tracking error and modeling error converges to zero. An inverted pendulum control system is simulated to demonstrate the control performance by using the proposed method.

Many immersive displays developed in previous researches are strongly influenced by the design concept of the CAVE, which is the origin of the immersive displays. In the view of human-scale interactive system for virtual environment (VE), the existing immersive systems are not enough to use the potential of a human sense further extent. The displays require more complicated structure for flexible extension, and are more restrictive to user's movement. Therefore we propose a novel multi-projector display for immersive VE with haptic interface for more flexible and dynamic interaction. The display part of our system named "D-vision" has a hybrid curved screen which consist of compound prototype with flat and curve screen. This renders images seamlessly in real time, and generates high-quality stereovision by PC cluster and two-pass technology. Furthermore a human-scale string-based haptic device will integrate with the D-vision for more interactive and immersive VE. In this paper, we show an overview of the D-vision and technologies used for the human-scale haptic interface.

We present a simple decoding algorithm that modifies soft bit-flipping algorithm for decoding LDPC codes. In our method, a new parameter is explored to distinguish the variables (symbols) belonging to the same number of unsatisfied constraints. A token is also assigned in the method to avoid repeated flipping of the same variable, rather than using a constant taboo length. Our scheme shows a similar computational load as the taboo-based algorithm, while having a similar decoding performance as the belief propagation algorithm.

An efficient computational Zero-Knowledge Proof of Knowledge whose security relies on the NP-completeness of the Independent Set Problem is presented here. The proposed algorithm is constructed from a bit commitment scheme based on the hardness of the Discrete Logarithm Problem, which guarantees the fulfillment of soundness, completeness and computational zero-knowledge properties, and allows avoiding the use of the Graph Isomorphism Problem, which is present in every known Zero-Knowledge Proofs for the Independent Set Problem.

Japanese terrestrial digital broadcasting (ISDB-T) began in 2003. To spread its signals throughout the country, optical fibers will be used to complement radio-wave networks. This paper describes recent applications of optical transmission of ISDB-T. It also describes our research on re-transmission with 40-GHz Radio On Fiber technology.

As a blind linear-interference-canceller for DS-CDMA mobile communications, the orthogonal matched filter (OMF) minimizes the power of the output while maintaining constant power of the desired signal in the output. This paper studies the extension of OMF to an RAKE receiver (OMF-RAKE), which adaptively controls the steering vectors that determine the constraint. It also applies the QR-RLS algorithm to estimate the OMF-RAKE parameters and investigates a hardware implementation that employs a systolic array. Computer simulations show that OMF-RAKE with the QR-RLS algorithm and the systolic array structure can reduce the computational complexity to about a half that of the conventional RLS-type algorithm without degrading the BER.

Fundamentals of parametric processing in highly nonlinear optical fiber are reviewed. Experimental procedures necessary for construction of one- and two-pump parametric amplifier architectures are described. Pump phase broadening, dispersion fluctuation and birefringence form basic impairment mechanisms in fiber parametric devices and are analyzed in two-pump parametric devices. Parametric signal processing is introduced with specific applications in all-optical regeneration, band conjugation, multicasting, packet switching and signal distortion reversal.

In the Reconfigurable System-On-a-Chip (RSOC), an FPGA core is embedded to improve the design flexibility of SOC. In this paper, we demonstrate that the embedded FPGA core is also feasible for use in implementing the proposed hybrid pattern Built-In Self-Test (BIST) in order to reduce the test cost of SOC. The hybrid pattern BIST, which combines Linear Feedback Shift Register (LFSR) with the proposed on-chip Deterministic Test Pattern Generator (DTPG), can achieve not only complete Fault Coverage (FC) but also minimum test sequence by applying a selective number of pseudorandom patterns. Furthermore, the hybrid pattern BIST is designed under the resource constraint of target FPGA core so that it can be implemented on any size of FPGA core and take full advantage of the target FPGA resource to reduce test cost. Moreover, the reconfigurable core-based approach has minimum hardware overhead since the FPGA core can be reconfigured as normal mission logic after testing such that it eliminates the hardware overhead of BIST logic. Experimental results for ISCAS 89 benchmarks and a platform FPGA chip have proven the efficiency of the proposed approach.

A novel via chain structure for failure analysis at 65 nm-node fixing OPC using inner and outer via chain dummy patterns has been proposed. The inner dummy is necessary to localize failure site in 200 nm pitch via chain using an optical beam induced resistance change method. The outer dummy protects via chain pattern from local flare and optical proximity effects. Using this test structure, we can identify the failure point in the 1.2 k and 15 k via chain fabricated by Cu/low-k single damascene process. This test structure is beneficial in the application to the 65 nm-node technologies and beyond.

This paper investigates a relationship between inkdot and one-pebble for two-dimensional finite automata (2-fa's). Especially we show that (1) alternating inkdot 2-fa's are more powerful than nondeterministic one-pebble 2-fa's, and (2) there is a set accepted by an alternating inkdot 2-fa, but not accepted by any alternating one-pebble 2-fa with only universal states.

We have implemented a distributed sensor system based on an array of fiber Bragg gratings (FBGs), which can measure up to 1000 points with a single piece of fiber. The system consists of FBGs having the same resonant wavelengths and small reflectivities (0.1 dB), and a wavelength tunable optical time-domain reflectometer (OTDR). To interrogate the distributed grating sensors and to address the event locations simultaneously, we have utilized the tunable OTDR. A thermoelectric temperature controller was used to tune the emission wavelength of the OTDR. The operating temperature of the laser diode was changed. By tuning the pulse wavelength of the OTDR, we could identify the FBGs whose resonant wavelengths were under change within the operating wavelength range of the DFB LD. A novel sensor cable with dry core structure and tensile cable was fabricated to realize significant construction savings at an industrial field and in-door and out-door applications. For experiments, a sensor cable having 52 gratings with 10 m separations was fabricated. To prevent confusion with unexpected signals from the front-panel connector zone of the OTDR, a 1 km buffer cable was installed in front of the OTDR. The proposed system could distinguish and locate the gratings that were under temperature variation from 20 to 70.

The finite difference time domain (FDTD) method has been developed in tandem with the progress of computer technology since K. S. Yee applied it to the analysis of an electromagnetic problem in 1966. The FDTD method is widely recognized as a powerful computational tool for analyzing electromagnetic problems involving complex geometries, such as antennas, microwave and optical waveguides and interaction between antennas and the human body. The commercial electromagnetic simulators based on the FDTD are also being developed very actively because users are able to trace temporal electromagnetic behaviors and to easily obtain a practical level of accuracy. However, the user must understand the principle of the method in order to use the simulator efficiently. In this paper, the basic concept and the principle of the FDTD method are reviewed for beginners, including graduate course students, rather than specialists in this discipline. Several recent topics concerning electromagnetic and antenna problems are also introduced.

New decoding algorithms for binary linear codes based on the concave-convex procedure are presented. Numerical experiments show that the proposed decoding algorithms surpass Belief Propagation (BP) decoding in error performance. Average computational complexity of one of the proposed decoding algorithms is only a few times greater than that of the BP decoding.

The problems with the CV characterization on very leaky (thin) nitrided oxide are mainly due to the measurement precision and MOS gate dielectric model accuracy. By doing S-parameter measurement at RF frequency and using simple but reasonably accurate model, we can obtain proper CV curves for very thin nitrided gate dielectrics. Regarding the measurement frequency we propose a systematic method to find a frequency range in which we can select measurement frequencies for all biases to obtain a full CV curve. Moreover, we formulated the first order relationship between the measurement frequency range and the test structure design for CV characterization. With the established formulae, we redesigned the test structures and verified that the formulae can be used as a guideline for the test structure design for RFCV measurements.