On a transmission line lowpass filter fabricated on a printed circuit board using open-circuited microstrip straight-line stubs, the frequency at the edge of a passband or stopband tends to be higher than the frequency determined by the filter synthesis theory. One of the reasons for this is thought to be the interconnection of a low-impedance straight-line stub and transmission lines. The length of a constituent transmission line cannot be determined precisely because of the finite width. Therefore, as a means of avoiding the frequency shift between a trial circuit and a theoretical one, we first introduce a radial-line stub, and then show the equivalency of a radial-line stub to a straight-line stub in a range of zero to the first resonant frequency from the view point of their input impedances. Dimensional data of radial-line stubs corresponding to low-impedance straight-line stubs are investigated with respect to examples of three-, five- and seven-element Butterworth and Chebyshev filters. It was found that frequency characteristics of trial lowpass filters using radial-line stubs agree well with theoretical characteristics known as the Butterworth or Chebyshev.

A pilot needs operational information about wind over sea as well as wave height to provide safety of hydroplane landing on water. Near-surface wind speed and direction can be obtained with an airborne microwave scatterometer, a radar designed for measuring the scatter characteristics of a surface. Mostly narrow-beam antennas are applied for such wind measurement. Unfortunately, a microwave narrow-beam antenna has considerable size that hampers its placement on flying apparatus. In this connection, a possibility to apply a conventional airborne radar altimeter as a scatterometer with a nadir-looking wide-beam antenna in conjunction with simultaneous range Doppler discrimination techniques for recovering the wind vector over sea at low speed of flight is discussed, and measuring algorithms of sea surface wind speed and direction are proposed. The principle considered and algorithms proposed in the paper can be used for creation an airborne radar system for operational measurement of the sea roughness characteristics and for safe landing of a hydroplane on water.

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.

This paper studies the local Poisson property of aggregated IP traffic. First, it describes the scenario where IP traffic presents a Poisson-like characteristic within some limited range of time scales when packets from independent traffic streams are aggregated. Each of the independent traffic streams corresponds to a series of correlated IP packets such as those of a transport connection. Since the Poisson-like characteristic is observed only within some limited range of time scales, we call this characteristic the local Poisson property. The limited range of time scales of the local Poisson property can be estimated from a network configuration and characteristics of transport connections. Second, based on these observations, we seek the possibility to apply an ordinary Poisson process to evaluation of the packet loss probability in IP networks. The analytical investigation, where IP traffic is modeled by a superposition of independent branching Poisson processes that presents the local Poisson property, suggests that the packet loss probability can be estimated by a finite-buffer queue with a Poisson process when the buffer size is within a certain range. The investigation is verified by simulations. These findings expand the applicability of conventional Poisson-based approaches to IP network design issues.

In this paper, we first address the current state of broadband services in Korea. Here, we introduce relevant statistics, current access network architectures, and activities of some major carriers. We also briefly introduce Korean government's policies on research and development projects and plans for promoting the country toward an advanced information society. We then introduce a large-scale, collaborative project named "Photonic Access To the Home (PATH)" with five-year period of performance, started in year 2002. The project is under leadership of the government and ETRI in collaboration with universities and industry. We finally provide a rather detailed description of the FTTH (Fiber To The Home) technology based on the wavelength division multiplexing technology, which has been under research in our laboratory as a part of the PATH project. We show some of our achievement including new architectures and networking principles for the FTTH network, analysis of the dynamic allocation of user bandwidth, and the experiment for a low-cost WDM optical source.

This letter outlines a scheme to produce a wider robust bandwidth, with better approximations to the perfect reproduction of pre-recorded acoustic signals. Multi-parameter inverse filtering method is proposed in the virtual sound imaging system for improving the robustness performance. The superiority of this new type of inverse filter is demonstrated on a 3-speaker system.

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.

In this paper, we present a technique to obtain an accurate closed-form spatial Green's function for a coplanar waveguide. The integration of the Sommerfeld integrals is performed on the real axis, and the path deformation is avoided in the sampling data. The results are in good agreement with the numerical integration over wide ranges of the signal frequency and the observation distance.

A robust adaptive filtering algorithm was established recently (I. Yamada, K. Slavakis, K. Yamada 2002) based on the interactive use of statistical noise information and the ideas developed originally for efficient algorithmic solutions to the convex feasibility problems. The algorithm is computationally efficient and robust to noise because it requires only an iterative parallel projection onto a series of closed half spaces highly expected to contain the unknown system to be identified and is free from the computational load of solving a system of linear equations. In this letter, we show the potential applicability of the adaptive algorithm to the identification problem for the second order Volterra systems. The numerical examples demonstrate that a straightforward application of the algorithm to the problem soundly realizes fast and stable convergence for highly colored excited speech like input signals in possibly noisy environments.

It is still an open question whether software agents should be personified in the interface. In order to study the effects of faces and facial expressions in the interface, a series of experiments was conducted to compare subjects' responses to and evaluation of different faces and facial expressions. The experimental results obtained demonstrate that: 1) personified interfaces help users engage in a task, and are well suited for an entertainment domain; 2) people's impressions of a face in a task are different from ones of the face in isolation. Perceived intelligence of a face is determined not by the agent's appearance but by its competence; 3) there is a dichotomy between user groups which have opposite opinions about personification. Thus, agent-based interfaces should be flexible to support the diversity of users' preferences and the nature of tasks.

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.

The millimeter wave bandpass filter using the Whispering-Gallery mode (WG mode) dielectric disk resonators is presented in this paper. A 4 stage maximally flat bandpass filter is constructed with the PTFE disk resonators. For the filter design, the coupling coefficients of this mode in the coupled disk resonators are calculated by an approximated separation of variables method. Furthermore, the external Q values of the disk resonator excited by a dielectric waveguide are investigated experimentally. Designed center frequency is 60 GHz and 3 dB band width is 150 MHz. Furthermore, as an attempt to improve the spurious characteristics, another filter structure which consists of some kinds of dielectric disk is tested. As a result, some spurious responses are reduced considerably.

Mobile location can be achieved by using the time-of-arrival (TOA) and angle-of-arrival (AOA) measurements. In this Letter, we analyze the location accuracy of an TOA-AOA hybrid algorithm with a single base station in the line-of-sight scenario. The performance of the algorithm is contrasted with the Cramer-Rao lower bound and Federal Communications Commission Emergency 911 requirements.

A problem of estimating biopotential sources in the brain based on EEG signals observed on the scalp is known as an important inverse problem of electrophysiology. Usually there is no closed-form solution for this problem and it requires iterative techniques such as the Levenberg-Marquardt algorithm. Considering the nonlinear properties of inverse problem, and signal to noise ratio inherent in EEG signals, a back propagation neural network has been recently proposed as a solution. In this paper, we investigated the properties of neural networks and its localization accuracy for single dipole source localization. Based on the results of extensive studies, we concluded the neural networks are highly feasible in single-source localization with a small number of electrodes (18 electrodes), also examined the usefulness of this method for clinical application with a case of epilepsy.

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, 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.

In this paper, we propose a fast full-search block matching algorithm for motion estimation, based on binary edge information. The binary edge information allows a faster search by reducing the computational complexity. It also reduces error, which is generated by the block located on the boundary of moving objects. After we transform the input image into an edge-based image using Sobel masks, we convert the result into a binary edge image using median-cut quantization. We then perform block matching using the binary edge image. If there exists blocks such that the error of the binary block matching exceeds threshold, we only perform edge intensity-based block matching within those blocks. We improve computational efficiency by eliminating an unnecessary searching process in no-motion regions. Simulation results have shown that the proposed method reduces the computational complexity and provides similar PSNR performance to the Full Search Block Matching Algorithm (FS-BMA)

We present a method for recognition of two-hand gestures. Two-hand gestures include fine-grain descriptions of hands under a complicated background, and have complex dynamic behaviors. Hence, assuming that two-hand gestures are an interacting process of two hands whose shapes and motions are described by switching linear dynamics, we propose a coupled switching linear dynamic model to capture interactions between both hands. The parameters of the model are learned via EM algorithm using approximate computations. Recognition is performed by selection of the model with maximum likelihood out of a few learned models during tracking. We confirmed the effectiveness of the proposed model in tracking and recognition of two-hand gestures through some experiments.

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.

We evaluate resolution models for resource allocation in a GMPLS distributed control plane for heterogeneous all-optical networks. In a practical regional-to-backbone network environment, the local resolution model is advantageous in resource utilization, protocol compatibility and scalability. We demonstrate a lookup procedure, which inter-works with OSPF-TE and RSVP-TE protocols and allocates resources in the local resolution model.