The present paper deals with the frequency-dependent finite difference time domain ((FD)2TD) method analysis of the light-beam diffraction from a land/groove recording phase-change (PC) disk model with a metal (Al or Au) reflective layer in order to improve the conventional analysis for PC optical disk models with a perfectly conducting reflective layer. The diffracted fields are numerically calculated for both recorded and non-recorded states of the recording layer, and the comparison of the detected signal characteristics between two states is discussed. The crosstalk between the recording marks on lands and grooves are evaluated and the optimum groove depth is examined for Al,Au and perfectly conducting layer models.

In this paper, we propose a delayed feedback guaranteed cost controller design method for uncertain linear systems with delays in states. Based on the Lyapunov method, an LMI optimization problem is formulated to design a delayed feedback controller which minimizes the upper bound of a given quadratic cost function. Numerical examples show the effectiveness of the proposed method.

Multicasting is an efficient communication tool for use in multi-point applications such as conferencing and information distribution. In ad hoc networks, node mobility causes frequent changes of network topology, and re-construction of the multicast tree in an efficient and effective manner becomes a critical issues. In case of link breakage, most of the multicast tree construction protocols available presently require either a total re-build of the tree or to reconnect a disjoined node back to the multicast tree via the shortest path which may disrupt the optimising factors, such as energy consumption, delay or cost, used in the building of the original tree. In this paper, we introduce a computationally efficient recovery algorithm which will also minimise the power consumption on the tree.

A method for a genuinely multivariate analysis of statistical phase synchronization phenomena in empirical data is presented. It is applied to EEG data from a psychological experiment, obtaining results which indicate a possible relevance of this method in the context of cognitive science as well as in other fields.

A microstrip array antenna with 45-degree inclined linear polarization is proposed for automotive radars. The proposed antenna has the advantages of high aperture efficiency, low profile and ease of manufacture. The rectangular radiating elements inclined at 45 degrees to the straight microstrip line are directly connected to it at their corners in the proposed array antenna. The radiating element has a feature that radiation conductance for co-polarization is controlled widely enough to set desired amplitude distribution keeping excited mode for cross-polarization negligibly small. The feed line loss of the linear array antenna having 15 wavelengths is estimated 0.9 dB in the design taking the loss of the microstrip line into account. The performance of two types of developed antennas, for electrical and mechanical scanning radars, is presented. The fan beam subarray antenna for electrical scanning radars has an aperture efficiency of 53% with gain of 22.5 dBi at 76.5 GHz. For mechanical scanning radars, the two-stage series feeding circuit is also proposed for lower feed line loss and setting desired amplitude distribution. The pencil beam array antenna has an aperture efficiency of 39% with gain of 32.2 dBi at 76.5 GHz.

Affine arithmetic is a kind of interval arithmetic defined by Stolfi et al. In affine arithmetic, it is difficult to realize the efficient nonlinear binomial operations. The purpose of this letter is to propose a new dividing method which is able to supply more suitable evaluation than the old dividing method. And this letter also shows the efficiency of the new dividing method by numerical examples.

We consider the problem of constructing nonlinear dynamical systems that realize an arbitrary prescribed tree sources. We give a construction of dynamical systems by using piecewise-linear maps. Furthermore, we examine the obtained dynamical system to show that the structure of the memory of tree sources is characterized with some geometrical property of the constructed dynamical systems. Using a similar method, we also construct a dynamical system generating an arbitrary prescribed reverse tree source and show that the obtained dynamical system has some interesting geometrical property explicitly reflecting the tree structure of the memory of the reverse tree source.

The objective of this study was to explore suitable spatial filters for inverse estimation of cortical potentials from the scalp electroencephalogram. The effect of incorporating noise covariance into inverse procedures was examined by computer simulations. The parametric projection filter, which allows inverse estimation with the presence of information on the noise covariance, was applied to an inhomogeneous three-concentric-sphere model under various noise conditions in order to estimate the cortical potentials from the scalp potentials. The present simulation results suggest that incorporation of information on the noise covariance allows better estimation of cortical potentials, than inverse solutions without knowledge about the noise covariance, when the correlation between the signal and noise is low. The method for determining the optimum regularization parameter, which can be applied for parametric inverse techniques, is also discussed.

In generating Frequency-Hopping (FH) sequences for Frequency Hopping Spread Spectrum Multiple Access (FH-SSMA) applications, binary maximal-length sequences (m-sequences) over GF(2m) have been preferred because of their characteristics of good Hamming correlation property, long period capability and high speed generation in association with simple hardware implementation based on Feedback Shift Registers (FSR). In practice, however, one difficulty of applying such sequences into the FH-SSMA communication systems with a wide bandwidth such as Military Satellite Communication (MilSatCom) is that the number of hopping frequency slots available may be far from a power of 2 in proportion to the spreading bandwidth. In that case, we can not make good use of the spreading bandwidth. In this paper, we propose a construction of some favorable FH sequences which deals effectively with the above difficulty using FSR and some nonlinear logic by introducing a re-mapping method. We show that the resulting sequences satisfy the (almost) uniform symbol distribution in one period and preserve a reasonably good Hamming correlation property so that they are appropriate for FH-SSMA applications.

In this paper, we present our investigation of Latent Semantic Indexing (LSI) on the local query regions for solving the computation restrictions of the LSI on the global information space. Through the experiments with different SVD dimensionality on the local query regions, the results show that low-dimensional LSI can achieve much better precision than VSM and similar precision to global LSI. Such small SVD factors indicate that there is an almost linear surface in the local query regions. The largest or the two largest singular vectors have the ability to capture such a linear surface and benefit the particular query. In spite of the fact that Local LSI analysis needs to perform the Singular Value Decomposition (SVD) computation for each query, the surprisingly small requirements of the SVD dimension resolve the computation restrictions of LSI for large scale IR tasks. Moreover, on the condition that several relevant sample documents are available, application of low dimensional LSI for these documents can obtain comparable precision with the Local RF in a different manner.

In this letter, we propose a robust IFDD scheme employing an interference canceller, which is used for mitigating interferences from the transmitting signal instead of complex filter bank to reduce the complexity, for the OFDM system using feedback information. According to simulation results, the proposed IFDD OFDM system does not show significant performance degradation but maintains the robustness against the fast time-varying multipath channel, while the TDD OFDM system estimating feedback information from receiving block makes serious performance degradation.

A reduced complexity multiple-input multiple-output (MIMO) equalizer with ordered successive interference cancellation (OSIC) is proposed for combating intersymbol interference (ISI) and cochannel interference (CCI) over frequency-selective multipath channels. It is developed as a reduced-rank realization of the conventional MMSE decision feedback equalizer (DFE). In particular, the MMSE weight vectors at each stage of OSIC are computed based on the generalized sidelobe canceller (GSC) technique and reduced-rank processing is incorporated by using the conjugate gradient (CG) algorithm for reduced complexity implementation. The CG algorithm leads to a best low-rank representation of the GSC blocking matrix via an iterative procedure, which in turn gives a reduced-rank equalizer weight vector achieving the best compromise between ISI and CCI suppression. With the dominating interference successfully cancelled at each stage of OSIC, the number of iterations required for the convergence of the CG algorithm decreases accordingly for the desired signal. Computer simulations demonstrate that the proposed reduced-rank MIMO DFE can achieve nearly the same performance as the full-rank MIMO MMSE DFE with an effective rank much lower than the dimension of the signal-plus-interference subspace.

A framework is described for a peer-to-peer information exchange system, and a collaborative information retrieval (IR) scheme for the system is proposed. The aims of the system include smooth knowledge and information management to activate organizations or communities. Conventional server-centric systems are weak because they create information-providing bottlenecks. Accordingly, the proposed framework targets the collaborative inter-working of personal repositories that accumulate per-user information, and accept and service requests. Issues concerning the framework are addressed. One issue is the retrieval of information from another's personal repository; the retrieval criteria of a system are tightly personalized for its user. The system is assumed to employ a vector space model with a concept-base as its IR mechanism. The vector space on one system is very different from that on another system. Another issue is the automated control of the information-providing criteria. This paper presents solutions to the first problem. To achieve IR that provides satisfactory results to a user requiring information from another's personal repository, we need vector space equalization to compensate for the differences in the vector spaces of the personal repositories. The paper presents a vector space equalization scheme, the automated relevance feedback scheme, that compensates the differences in the vector spaces of the personal repositories. We implement the scheme as a system and evaluate its performance using documents on the Internet.

A minimum feedback node set in a graph is a minimum node subset whose deletion makes the graph acyclic. Its detection in a dependency graph is important to recover from a deadlock configuration. A livelock configuration is also avoidable if a check point is set in each node in the minimum feedback node set. Hence, its detection is very important to establish dependable network systems. In this letter, we give a minimum feedback node set in a trivalent Cayley graph. Assuming that each word has n bits, for any node, we can judge if it is included in the set or not in constant time.

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.

Recently, diverse multimedia applications with stringent multiple Quality of Service (QoS) requirements have been increasing. In particular, multicast communication has become more popular because of its availability and for efficient use of network resources. Most multicasts are point-to-multipoint, in which a source delivers data to multiple designated recipients, such as for video or audio distribution. In the near future, multipoint-to-multipoint communication services, including multimedia collaborations such as video conferencing and distant-learning, will be developed. However, when a conventional multicast routing algorithm is applied to a multipoint-to-multipoint communication service, it might result in excessive traffic concentration on some links. Therefore, we propose a new multipoint-to-multipoint routing method. It utilizes the Fallback+ algorithm to perform multicast routing for the purpose of satisfying multiple QoS requirements and alleviating traffic concentrations. Simulation experiments show that our method improves traffic load balance and achieves efficient use of network resources.

A constant voltage/constant current (CV/CC) parallel operation heterojunction bipolar transistor (HBT) power amplifier (PA) configuration is presented, and its design method is described. A resistor base feed (CC mode) HBT is connected to an inductor base feed (CV mode) HBT in parallel, and compensates the gain expansion of the CV mode HBT due to near class-B operation. By adding CC mode HBT, the total quiescent current can be decreased from 32 mA to 23 mA with adjacent channel leakage power ratio (ACPR) < -40.0 dBc. At the maximum output power region, the fabricated PA achieves output power (Pout) of 26.8 dBm and power added efficiency (PAE) of 42.0% with ACPR of -40.0 dBc, and shows the comparable performances with a conventional PA using CV mode HBT.

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.

In this paper a digital frequency domain RFI (Radio Frequency Interference) cancellation scheme for DMT (Discrete Multitone) based VDSL (Very high speed Digital Subscriber Line) systems is presented. The proposed algorithm has been optimized and characterized in terms of complexity and performance. Optimizations were also performed from an implementation point of view by deducing key dependencies among our RFI model coefficients that let us drastically reduce the size of the memories involved. System simulations showed the effectiveness of the canceller: in terms of VDSL performance parameters such as bit rate, the optimized cancellation scheme recovers almost totally the performance degradation due to RFI.

Weight divided adaptive control method for a microwave FeedForward Power Amplifier (FFPA) is presented. In this adaptive controller, an output signal of a power amplifier is used as reference signal. Additionally, reference signal is divided by the weight of adaptive filter, so that characteristics of the power amplifier, such as temperature dependence, do not have influence on the convergence performances. The proposed adaptive algorithm and the convergence condition are derived analytically and we clarify that the proposed weight divided adaptive algorithm is more stable than the conventional Normalized Least Mean Square (NLMS) algorithm. Then, the convergence condition considering phase calibration error is discussed. The effectiveness of the proposed algorithm are also verified by the nonlinear simulations of the FFPA having AM-AM and AM-PM nonlinearity of GaAsFET.