We report in this paper, the performance of AlGaN/GaN HFETs in the context of high power, low noise and high temperature operations, along with a comparison of their characteristics with other conventional technologies. Finally, a single stage modulator driver for long haul optical communications is presented as an example of application of the GaN-based devices high power handling capabilities.

The high-resolution frequency estimators most commonly used, such as Least Square (LS) method based on AR model, MVSE, MUSIC and ESPRIT, determine estimates of the sinusoidal frequencies from the sample noise-corrupted data. In this paper, a new frequency estimation method named Pole-Placement Least Square (PPLS) is presented, which is a modified LS method with a certain number of model poles restricted to the unit circle. The statistical performance of PPLS is studied numerically, and compared with the Cramer-Rao bound as well as the statistical performance corresponding to the LS methods. PPLS is shown to have higher resolution than the conventional LS method. The relationship between poles location and its resolution is also discussed in detail.

We report the investigation of major dispersion mechanisms such as self-heating, trapping, current collapse, and floating-body effects present in AlGaN/GaN HFETs. These effects are analyzed using DC/Pulsed IV, load-pull, low-frequency noise systems, and a cryogenic probe station. This study leads to a better understanding of the device physics, which is critical for accurate large-signal modeling and device optimization.

This paper proposes a disjoint path selection scheme for Generalized Multi-Protocol Label Switching (GMPLS) networks with Shared Risk Link Group (SRLG) constraints. It is called the weighted-SRLG (WSRLG) scheme. It treats the total number of SRLG members related to a link as part of the link cost when the k-shortest path algorithm is executed. In WSRLG, a link that has many SRLG members is rarely selected as the shortest path. Simulation results show that WSRLG finds more disjoint paths than the conventional k-shortest path algorithm. In addition, since WSRLG searches for the weight of the SRLG factor by using a modified binary search algorithm while satisfying the required number of disjoint paths between source and destination nodes, it can find cost-effective disjoint paths.

A new approach to correcting the array amplitude failure by a combination of B-spline techniques and genetic algorithms is proposed. Some array elements indicate the control knots for a B-spline curve by their nominal positions and amplitudes; others distribute the excitation amplitudes according to the sampling points on the curve. The inherent smoothness of the B-spline curves reduce the effect of excessive coupling between adjacent elements. Genetic algorithms are used to search for a quasi-optimized B-spline curve to produce the ultimate amplitude distribution for correcting the array failure. To demonstrate the method's effectiveness, simulation results for correcting failures with three- and four-element failures are presented.

Adaptive arrays with signal blocking have the advantages of fast convergence and robustness to pointing errors as well as of rejecting a coherent interference in addition to incoherent ones. In this paper, we propose a novel method for performance improvement in such arrays with no increase in complexity. The proposed method utilizes all of the array elements to obtain the adaptive output so that its performance is superior to that of the conventional method which does not utilize one of the elements. Their performances are compared analytically and by computer simulation.

This paper presents the design consideration of a polarization-transformation transmission filter, which is composed of a multilayered chiral slab. The optimal material parameters and thickness of each layer of the slab can be determined by using a genetic algorithm (GA). Substituting the constitutive relations for a chiral medium into Maxwell's equations, the electromagnetic field in the medium is obtained. A chain-matrix formulation is used to derive the relationship between the components of the incident, the reflected, and the transmitted electric fields. The cross- and co-polarized powers carried by the transmitted and reflected waves are represented in terms of their electric field components. The procedure proposed for the design of a polarization-transformation filter is divided into two stages. An ordinary filter without polarization-transformation and a polarization-transformation filter for the transmitted wave are designed with a multilayered non-chiral slab and a multilayered chiral slab at the first and the second stages, respectively. According to the specifications of the filters, two functionals are defined with the transmitted and reflected powers. Thus the optimal design of a polarization-transformation filter with the multilayered chiral slab is reduced to an optimization problem where the material parameters and thickness of each chiral layer are found by maximizing the functionals. Applying the GA to the maximization of the functionals, one can obtain the optimal material parameters and thicknesses of the multilayered chiral slab. Numerical results are presented to confirm the effectiveness of the two-stage design procedure. For three types of multilayered chiral slabs, optimal values of refractive indices, thicknesses, and chiral admittances are obtained. It is seen from the numerical results that the proposed procedure is very effective in the optimal design of polarization-transformation filters for the transmitted wave.

Steganography is a technique that conceals the very existence of communication by means of hiding secret messages in innocuous cover objects. We previously developed a steganographic method that uses standard MIDI files (SMFs) as cover objects. Our method could conceal the secret messages in SMFs without changing their sound. We also investigated the effectiveness of our method against steganalysis. This steganalytic research revealed that files embedded using our method are vulnerable to detection, because stego SMFs lose the imprints borne by sequencers. In this study, we describe two improved methods of steganography that enable even stego SMFs to keep the sequencer's imprint. As a result, we improved the resistance of SMFs against steganalysis but there was a slight reduction in the embedding rate.

In this paper, we propose a blind adaptive channel identification and equalization algorithm with phase offset compensation for single-input multiple-output (SIMO) channel. It is based on the one-step forward multichannel linear prediction error method and can be implemented by an RLS algorithm. Phase offset problem is inherent part of any second-order statistics-based blind identification and equalization. To solve this problem, we use a blind adaptive algorithm called the constant modulus derotator (CMD) algorithm based on constant modulus algorithm (CMA). Moreover, unlike many known subspace (SS) methods or cross relation (CR) methods, our proposed algorithms do not require channel order estimation. Therefore, our algorithms are robust to channel order mismatch.

An IP (Internet Protocol) over WDM network is expected to be an infrastructure for the next-generation Internet by directly carrying IP packets on the WDM-based network. Among several architectures for IP over WDM networks, one promising way is to overlay a logical topology consisting of lightpaths over the physical WDM network so that IP packets are carried on the lightpaths. The conventional methods for designing the logical topology have been focusing on maximizing throughput of the traffic. However, when the WDM network is applied to IP, the end-to-end path provided by the logical topology of the WDM network is not suitable to IP since IP has its own metrics for route selection. In this paper, we propose a new heuristic algorithm to design a logical topology by considering the delay between nodes as an objective metric. This algorithm uses a non-bifurcated flow deviation to obtain a set of routes that IP packets are expected to traverse. Our proposal is then compared with conventional methods in terms of the average packet delays and throughput. It is shown that our method becomes effective when the number of wavelengths is a limited resource.

There have been numerous studies on the enhancement of the noisy speech signal. In this paper, we propose a completely new speech enhancement method, that is, a filtering of a dissonant frequency based on improved fundamental frequency estimation which is developed in frequency domain. The subjective test results indicate that the proposed method provides a significant gain in audible improvement especially for speech contaminated by colored noise and a husky voice. Therefore if the filter is employed as a pre-filter for speech enhancement, the output speech quality and intelligibility should be greatly enhanced.

The case postpositions usually have more than one semantic role in Korean. The adverbial postpositions among various postpositions especially make the development of Korean-based machine translation system difficult, because they have more semantic roles than others. In this paper, we describe a new method for resolving semantic ambiguities of adverbial postpositions using decision tree induction. The lack of training examples in decision tree induction is overcome by clustering words into classes using a kind of greedy algorithm. The cross validation results show that the presented method achieves 76.5% of accuracy on the average, which is 20.3% improvement over the baseline method.

It is shown that the glass structure change is a simple and widely applicable method to modify refractive index locally in various glass fibers. A small part of a glass fiber is heated immediately to above its melt temperature by arc discharge, and then the molten fiber undergoes rapid cooling, which freezes the change of the glass structure. Therefore the refractive index of the fiber is decreased partially by the glass structure change induced by rapid solidification. The index reduction in a fiber fabricated from multicomponent glasses is estimated to be more than 0.006. To clarify that rapid solidification works for various glasses including silica glasses, long-period gratings are written in a standard telecommunication fiber with various discharge currents and times. The peak loss of more than 25 dB is obtained within only 6 periods. The index change can be adjusted by the discharge conditions. The gratings are not degraded by heating the whole gratings at 700C for 2 hours, and are highly temperature-stable. It is shown that resonance wavelengths can be tuned by controlling the heating temperature and heating time.

In this paper, our aim is to extract real-time movement-related potentials, especially readiness-potentials, from EEGs with a small number of scalp electrodes. We proposed a method composed of independent component analysis (ICA), dipole tracing (DT) and scalp Laplacian methods. The proposed method shows a good real-time RP extraction capability from a single-trial of movement by means of the selection of EEGs with high reliability based on the DT and the improvement of the spatial resolution of the scalp potentials based on the scalp Laplacian.

Recent years have witnessed a growing interest in employing animated agents for tasks that are typically performed by humans. They serve as communicative partners in a variety of applications, such as tutoring systems, sales, or entertainment. This paper first discusses design principles for animated agents to enhance their effectiveness as tutors, sales persons, or actors, among other roles. It is argued that agents should support their perception as social actors by displaying human-like social cues such as affect and gestures. An architecture for emotion-based agents will be described and a simplified version of the model will be illustrated by two interaction scenarios that feature cartoon-style characters and can be run in a web browser. The second focus of this paper is an empirical evaluation of the effect of an affective agent on users' emotional state which is derived from physiological signals of the user. Our findings suggest that an agent with affective behavior may significantly decrease user frustration.

In this paper, we consider the problem of estimating the time-varying directions-of-arrival (DOAs) of coherent narrowband cyclostationary signals impinging on a uniform linear array (ULA). By exploiting the cyclostationarity of most communication signals, we investigate a new computationally efficient subspace-based direction estimation method without eigendecomposition and spatial smoothing (SS) processes. The proposed method uses the inherently temporal property of incident signals and a subarray scheme to decorrelate the signal coherency and to suppress the noise and interfering signals, while the null subspace is obtained from the resulting cyclic correlation matrix through a linear operation. Then an on-line implementation of this method is presented for tracking the DOAs of slowly moving coherent signals. The proposed algorithm is computationally simple and has a good tracking performance. The effectiveness of the proposed method is verified through numerical examples.

This paper examines the descriptive power and the limitations of a simple reinforcement learning model (REL), comparing the simulation results with the results of an economic experiment employing human subjects. Agent-based computational economics and experimental economics are becoming increasingly popular as tools for economists. A new variety of learning model using games with a unique equilibrium is proposed and examined in both of the fields mentioned above. However, little attention is given to games with multiple equilibria. We examine threshold public goods games with two types of equilibria, where each player in a five-person group simultaneously contributes the public goods from her private endowments. In the experiments, we observe two patterns of the subjects' behavior: the cooperative and non-cooperative patterns. Our simulation results show that the REL reproduces the cooperative pattern, but does not reproduce the non-cooperative pattern. However, the results suggest that the REL does reproduce the non-cooperative pattern in terms of the agents' internal states. That implies that deterministic strategies would be required to reproduce the non-cooperative pattern in the games. We show an example of the REL with deterministic strategies.

This paper first presents an active integrated antenna configuration designed for broadband mobile wireless access systems using the 25-GHz band. This active integrated antenna comprises a microstrip antenna array and RF front-end circuits adopting spatial power combining schemes for reduced power consumption of the power amplifiers. Furthermore, the antenna and RF circuits are integrated into each side of a thick copper backing plate and both are connected through microstrip line /slot transitions. The developed active integrated antenna achieves the output power of 14.6 dBm and a noise figure of less than 5 dB. The wireless system using the developed active integrated antenna achieves a 6-dB improvement in the packet error rate compared to that using a passive antenna with the same array design as the active integrated antenna. Furthermore, we obtained the first license of the active integrated antenna for commercial use in high-speed wireless communication systems in Japan.

In 1982, Buckles and Petry proposed fuzzy relational database for incorporating non-ideal or fuzzy information in a relational database. The fuzzy relational database relies on the specification of similarity relation in order to distinguish each scalar domain in the fuzzy database. These relations are reflexive, symmetric, and max-min transitive. In 1989, Shenoi and Melton extended the fuzzy relational database model of Buckles and Petry to deal with proximity relation for scalar domain. Since reflexivity and symmetry are the only constraints placed on proximity relations, proximity relation is considered as a generalization of similarity relation. However, we realized that naturally relation between fuzzy information is not symmetric. Here, we consider using conditional probability relation to represent similarity between two fuzzy data. Related to the properties of conditional probability relation, we introduce an interesting mathematical relation, called weak similarity relation, as generalization of similarity relation as well as proximity relation in which conditional probability relation is regarded as a concrete example of the weak similarity relation. In this paper, we propose design of fuzzy relational database to deal with conditional probability relation for scalar domain. These relations are reflexive and not symmetric. In addition, we define a notion of asymmetric redundant tuple based on two interpretations generalizing the concept of redundancy in classical relational database. In the relation to data querying, we discuss partitioning of domains with the objective of developing similarity class. Finally, we propose a new definition of partial fuzzy functional dependency (PFFD). Fuzzy functional dependency (FFD) as an extension of functional dependency (FD), usually used in design of fuzzy relational database, can be generated by the PFFD. Inference rules that are similar to Armstrong's Axioms for the FFD are both sound and complete.

Passification of a non-square linear system is considered by using a parallel feedforward compensator (PFC) and a squaring gain matrix. In contrast to the previous result, a technical assumption is removed by modifying the structure of the PFC. As a result, the broader class of non-square systems can be made passive by the proposed design method. Using the static output feedback (SOF) algorithms, the input-dimensional PFC and the squaring matrix can be designed systematically. The effectiveness of the proposed method is illustrated by practical system examples in the control literature.