In this paper, a novel description method of the contour of a shape using extended fractal interpolation functions (EFIFs) is presented. Although the scope of application of traditional FIFs has been limited to cases in which a given signal is represented by a single-valued function, the EFIFs derived by the introduction of a new parameter can describe a multiple-valued signal such as the contour of a shape with a high level of accuracy. Furthermore, the proposed description method possesses the useful property that once a given contour has been modeled by the proposed description method, the shape can be easily expanded at an arbitrary expansion rate. Experimental results show the effectiveness and usefulness of the proposed description method for representing contours.

In-plane-aligned a-axis-oriented YBa2Cu3O7-δ (YBCO) thin films are attractive for the formation of planar intrinsic Josephson devices. In this study, these films were deposited by dc sputtering on LaSrGaO4 (LSGO) (100) substrates and the dependence of the characteristics on the deposition conditions was investigated. In-plane-aligned a-axis-oriented YBCO thin films were successfully grown in the substrate temperature range of 555-615. With the temperature gradient method, it was seen that the critical temperature of the film increased to 81 K. The current-voltage characteristic along the c-axis exhibited clear multibranch structures. These results indicate that ion-cleaning of the substrate surface broadens the growth temperature range of these films and planar intrinsic Josephson devices can be fabricated from these films.

Electrical properties of contacts between head-tail coupled poly(3-hexylthiophene), PHT and Al (and Au) in planer type and sandwich type diodes of Al/PHT/Au have been studied. The contact resistances are directly evaluated by probing the potential profile of PHT between the metal electrodes using micromanipulators installed in scanning electron microscope. In the potential profile of planer type diode, a large potential cliff is observed at Al/PHT interface and some appreciable potential step is also found at PHT/Au interface. The contact resistance at the Al/PHT interface deduced from the potential profile shows the bias and its polarity dependence, indicating the existing of the Schottky like junction. At forward bias, it is found that the residual resistance at Al/PHT interface limits the diode performance. The residual resistance is supposed to be insulating layer of Al oxide. At larger reversed bias, the contact resistance at Al/PHT decreased abruptly due to the Zener breakdown. The potential profile of sandwich type diode is similar to that of planer type diode. It is found that even the PHT/Au contact shows the ohmic behavior, the contact resistance is significant as to limit the maximum current of the cells.

A cache replacement policy which takes the transcoding time into account in making replacement decisions, for the emerging transcoding proxy servers is proposed. Simulation results show the proposed policy outperforms the conventional LRU in both the cache hit rate and the average object transcoding time.

Extensive studies have been made of the public key cryptosystems based on multivariate polynomials. However most of the proposed public key cryptosystems of rate 1.0 based on multivariate polynomials, are proved not secure. In this paper, we propose several types of new constructions of public key cryptosystems based on two classes of randomly generated simultaneous equations, namely, a class based on bijective transformation and another class based on random transformation. One of the features of the proposed cryptosystems is that the sets of random simultaneous equations significantly improve the utilization factor of the transformation. We show an example of the proposed cryptosystem whose size of the ciphertext is only 100 bits.

This paper presents practical modeling procedure of feed patterns, bond wires, and interconnects for microwave bare-chip devices. Dedicated test structures have been designed for the process. Modeling accuracy of BJTs and diodes has been unprecedentedly improved up to 30 GHz with this procedure despite popular SPICE models were used.

The processing of noise-corrupted signals is a common problem in signal processing applications. In most of the cases, it is assumed that the additive noise is white Gaussian and that the constant noise variance is either available or can be easily measured. However, this may not be the case in practical situations. We present a new approach to additive white Gaussian noise variance estimation. The observations are assumed to be from an autoregressive process. The method presented here is iterative, and uses low-order Yule-Walker equations (LOYWEs). The noise variance is obtained by minimizing the difference in the second norms of the noisy Yule-Walker solution and the estimated noise-free Yule-Walker solution. The noise-free solution is constrained to match the observed autocorrelation sequence. In the iterative noise variance estimation method, a variable step-size update scheme for the noise variance parameter is utilized. Simulation results are given to confirm the effectiveness of the proposed method.

The Single Instruction, Multiple Data (SIMD) architecture enables computation in parallel on a single processor. The SIMD operations are implemented on some processors such as Pentium 3/4, Athlon, SPARC, or even on smart cards. This paper proposes efficient algorithms for assembling an elliptic curve addition (ECADD), doubling (ECDBL), and k-iterated ECDBL (k-ECDBL) with SIMD operations. We optimize the number of auxiliary variables and the order of basic field operations used for these addition formulas. If an addition chain has k-bit zero run, we can replace k-time ECDBLs to the proposed faster k-ECDBL and the total efficiency of the scalar multiplication can be improved. Using the singed binary chain, we can compute a scalar multiplication about 10% faster than the previously fastest algorithm proposed by Aoki et al. Combined with the sliding window method or the width-w NAF window method, we also achieve about 10% faster parallelized scalar multiplication algorithms with SIMD operations. For the implementation on smart cards, we establish two fast parallelized scalar multiplication algorithms with SIMD resistant against side channel attacks.

Software reuse has been recognized as important. According to our research, when a software product is reused, products correlated to the reused one may be reusable. This paper proposes a model for software products and a technique to retrieve correlated products. The paper also presents equations to evaluate correlation values, which is guidance for selecting reusable correlated products. Since correlated products can be identified by tracing product relationships, the proposed model manages both products and relationships.

A novel method is presented to compute moments of high-speed VLSI interconnects, which are modeled as coupled RLC trees. Recursive formulae of moments of coupled RC trees are extended to those for coupled RLC trees by considering both self inductances and mutual inductances. Analytical formulae for voltage moments at each node are derived explicitly. The formulae can be efficiently used for estimating delay and crosstalk noise. The inductive crosstalk noise waveform can be accurately and efficiently estimated using the moment computation technique in conjunction with the projection-based order reduction method. Fundamental aspects of the proposed approach are described in details. Experimental results show the increased accuracy of the proposed method over that of the traditional ones.

The discrete nature of data in a functional domain can generally be replaced by the global nature of data in the spectrum domain. In this paper we propose a fast procedure to detect autosymmetric function as an application of the spectrum technique. The autosymmetric function differs from the usual symmetric function and strongly relates with EXOR-based representations. It is known that many practical logical networks are autosymmetric, and this nature allows a useful functional class to realize a compact network with EXOR gates. Our procedure is able to detect autosymmetric functions quickly by using spectral coefficients. In experiments, our technique can detect the autosymmetry of most networks with a small number of checks of the spectrum.

An NRD guide transmitter and a receiver were developed for a wireless multi-channel TV-signal distribution system at 60 GHz. The main emphasis was placed on a band-widening technique of the NRD guide beam-lead diode mount based on an electromagnetic field simulator, where each dimension of the beam lead diode mount was optimized. The agreement between the simulation and measurement is quite satisfactory. The up-converter fabricated by assembling a band-pass filter and a Schottky barrier diode mount has a good linearity as well as a flat output power of 2 dBm on the average over a bandwidth of at least 2 GHz. Moreover, the down-converter has a flat conversion loss performance of less than 7 dB in the same bandwidth. An NRD guide transmitter and a receiver characterized by small size and high performance were fabricated and successfully employed for the wireless distribution of TV signals for more than 100 channels.

The Communications Research Laboratory (CRL) started a new project named the New Generation Mobile Network Project in April 2002. The target of this project is the development of new technologies to enable seamless and secure integration of various wireless access networks such as 3rd and 4th generation cellular, wireless LAN, high-speed mobile wireless, wired communications, and broadcasting networks. This paper presents an overview of CRL's new generation mobile communication system that is called The Multimedia Integrated Network by Radio Access Innovation Plus (MIRAI+), as well as details the role of Software Radio Technology (SDR) in MIRAI+.

The traditional way of approaching device-level placement problems for analog layout is to explore a huge search space of absolute placement representations, where cells are allowed to illegally overlap during their moves. This paper presents a novel exploration technique for analog placement, operating on a subset of tree representations of the layout, where the typical presence of an arbitrary number of symmetry groups of devices is directly taken into account during the search of the solution space. The efficiency of the novel approach is due to the use of red-black interval trees, data structures employed to support operations on dynamic sets of intervals.

We show examples of accurate computer-aided design of power coupling between two dielectric slab waveguides of finite length by using the boundary-element method (BEM) based on guided-mode extracted integral equations (GMEIE's). The integral equations derived in this paper can be solved by the conventional BEM. Various properties in numerical calculations of GMEIE's are examined. The reflection and coupling coefficients of the guided wave as well as the scattering power are calculated numerically for the case of incidence TM guided-mode. The presented results are checked by the energy conservation law and reciprocity theorem. The results show that it is possible to design an optimum coupling between two dielectric slab waveguides by using the BEM based on GMEIE's.

With no doubt the Internet will achieve advantages in exploiting software agents for applications, thanks to their autonomy in carrying out tasks. In such a scenario, appropriated methodologies are needed to manage the interactions among agents. The BRAIN framework proposes an interaction model based on roles, each one composed by a set of capabilities and an expected behavior. The achieved advantages are agent-oriented features, separation of concerns and reuse of solutions and experiences. In this paper we present two interaction infrastructures, Rolesystem and RoleX, which rely on the above mentioned role-based interaction model. These infrastructures allow agents to assume roles and to interact. An application example and the comparison with other approaches show the effectiveness of our approach.

The performance enhancement technology for indoor-to-outdoor wireless communication systems is discussed in this study. In outdoor communication systems, transmitted signals may be severely degraded mainly by multipath fading effect of the channel and this problem can be overcome using conventional multiple antenna technology and array signal processing algorithms. But, since channel characteristics depend on both multipath fading and angle spread in indoor-to-outdoor communication systems, conventional algorithms which do not consider the effect caused by angle spread cannot give good results. In this letter, characteristics of indoor-to-outdoor channels are analyzed and a channel model suitable for this situation is proposed. And a new array antenna processing algorithm exploiting the concept of the mean steering vector is presented and the system performance is analyzed. It can be shown that the proposed algorithm outperforms conventional methods through computer simulations for the case in which signals sent from indoor transmitters arrive at outdoor receivers.

In this paper, a high-performance pipelining architecture for 2-D inverse discrete wavelet transform (IDWT) is proposed. We use a tree-block pipeline-scheduling scheme to increase computation performance and reduce temporary buffers. The scheme divides the input subbands into several wavelet blocks and processes these blocks one by one, so the size of buffers for storing temporal subbands is greatly reduced. After scheduling the data flow, we fold the computations of all wavelet blocks into the same low-pass and high-pass filters to achieve higher hardware utilization and minimize hardware cost, and pipeline these two filters efficiently to reach higher throughput rate. For the computations of N N-sample 2-D IDWT with filter length of size K, our architecture takes at most (2/3)N2 cycles and requires 2N(K-2) registers. In addition, each filter is designed regularly and modularly, so it is easily scalable for different filter lengths and different levels. Because of its small storage, regularity, and high performance, the architecture can be applied to time-critical image decompression.

The architecture and implementation of a novel processor suitable wireless terminal applications, is introduced. The wireless terminal is based on the novel dual-mode baseband processor for DECT and GSM, which supports both heterodyne and direct conversion terminal architectures and is capable to undertake all baseband signal processing, and an innovative direct conversion low power modulator/demodulator for DECT and GSM. The state of the art design methodologies for embedded applications and innovative low-power design steps followed for a single chip solution. The performance of the implemented dual mode direct conversion wireless terminal was tested and measured for compliance to the standards. The developed innovative terminal fulfils all the requirements and specifications imposed by the DECT and GSM standards.

We propose an analysis method for Franz-Keldysh (FK) oscillations appearing in photoreflectance (PR) spectra of heterojunction device structures, which enables precise and simultaneous evaluation of the built-in electric field strength and band-gap energy. Samples for PR measurements were n+-GaAs/n-Al0.3 Ga0.7 As/i-GaAs heterostructures with different Al0.3Ga0.7As-layer thickness. We have found that the phase of the FK oscillations originating from the i-GaAs buffer layer depends on the Al0.3 Ga0.7 As-layer thickness. We have derived a calculation model for FK oscillations that includes the interference of probe light. From the comparison of the calculated spectra with the measured spectra, we conclude that mixing of the real and imaginary parts of a modulated dielectric function, which is caused by the probe-light interference, gives rise to the phase shift of the FK oscillations. Our FK-oscillation analysis method reduces ambiguity in the estimation of band-gap energy that is considerable in a conventional analysis.