This paper discusses an object-oriented approach to temporal multimedia data modeling in OMEGA; a multimedia database management under development at the University of Library and Information Science. An object-orientated approach is necessary to integrate various types of heterogeneous multimedia data, but it has become clear that current object-oriented data models are not sufficient to represent multimedia data, particularly when they are temporal. For instance, the current object-oriented data models cannot describe objects whose attribute values change time-dependently. Also, they cannot represent temporal relationships among temporal multimedia objects. We characterize temporal objects as instances of a subclass of class TimeInterval with the temporal attributes and the temporal relationships. This temporal multimedia data model is designed upward compatible with the ODMG-93 standard object model. To organize a temporal multimedia database, a five temporal axes model for representing temporal multimedia objects is also introduced. The five temporal axes--an absolute, an internal, a quasi-, a physical, and a presentation time axis--are necessary to describe time-dependent properties of multimedia objects in modeling, implementing and use. A concrete example of this organization method is also illustrated.

This paper deals with the improvement of performance in the transform and subband image coding systems with negatively-correlated input signal. Using a more general source model than the AR(1) model as an input, the coding performance for the transform and subband coding schemes is evaluated in terms of the coding gain over PCM. The source model used here has such resonant band characteristics that its power spectrum has a peak at some frequency between 0 and π/2 for positive autocorrelation and between π/2 and π for negative autocorrelation. It is shown that coding schemes are classified into two classes; one has the pairwise mirror-image property in their filter banks and performs symmetrically regardless of the sign of the autocorrelation, and the other has no that property and performs asymmetrically with inferior performance for negative autocorrelation. Among the well-known transform and subband coding schemes, the DHT and QMF coding systems belong to the former class and the DCT and SSKF coding systems to the latter. In order to remedy the inferior performance, we propose the method in which one modulates the negatively-correlated signal sequences by the alternating sign signal with unity magnitude (-1)n to convert them into positively-correlated sequences. The algorithms are presented for the DCT and SSKF image coding systems with the adaptive signal modulation. In the DCT coding systems, we are particularly concerned with the DCT-based hierarchical progressive coding mode of operation, since the signal modulation works well for that coding mode. The SSKF image coding system has the regular quad-tree structure with three stages. The simulation results for test images show that our method can successfully be applied to the images with a considerable amount of energy in the frequency range higher than π/2 in horizontal or vertical direction, such as fingerprints and textile patterns sampled at a rate close to the Nyquist rate. The paper closes with a brief introduction to the modification of our DCT-based method.

The tandem structure of a matched filter (MF) and a maximum likelihood sequence estimator (MLSE) using the Viterbi algorithm (VA) has been considered to be an optimal receiver for digital pulse-amplitude sequences in the presence of intersymbol interference (ISI) and additive white Gaussian noise (AWGN). An adaptive array antenna has the capability of filtering received signals in the spatial domain as well as in the temporal one. In this paper, we propose a receiver structure using an adaptive array antenna, a digital filter and the VA that is spatially and temporally optimal for multi-user detection in a direct sequence code division multiple access (DS/CDMA) environment. This receiver uses a tapped delay line (TDL) array antenna and the VA, which provides a maximum likelihood sequence estimate from the spatially and temporally whitened matched filter (ST-WMF) output. Performance of the proposed receiver is evaluated by theoretical analysis and computer simulations.

This paper proposes and investigates a tap selectable Viterbi equalizer for mobile radio communications. When the multipath channel is modeled by a tapped delay line only, the taps which may seriously affect the data sequence estimation are selected and used to calculate the trellis metric in the Viterbi algorithm. The proposed equalization algorithm can reduce the number of path metric calculations and the number of path selections in the Viterbi algorithm. Moreover, we propose an extended equalizer which has antenna diversity. This equalizer calculates the path metric using the antenna outputs and results of channel estimators. Computer simulation is used to evaluate the BER performance of the proposed equalizer in a multipath radio channel.

A new high-performance fault-tolerant ATM switching network is proposed. This network contains the baseline network and has many redundant switching elements to enhance the fault tolerance and throughput of the conventional multistage interconnection networks. The presented routing algorithm is very simple and can support a very huge number of paths between each input-output pair. The paths can be used to route cells when internal cell contentions occur in switching elements. The redundant switching elements at the last stage offer two access points to the output ports to resolve the output conflict. Performance analysis and simulation results show that this network has better maximum throughput even for faulty conditions. Among various networks, it has the largest number of redundant paths, and the greatest unit node contribution and unit edge contribution.

Signal processing antennas have been studied not only for interference suppression but also for high-resolution estimation of radio environment such as directions-of-arrival of incident signals. These two applications are based on the common technique, that is, null steering. This tutorial paper reviews the MUSIC algorithm which is one of the typical high-resolution techniques. Examining the eigenvector beam patterns, we demonstrate that the high-resolution capability is realized by steering nulls. The considerations will be useful for understanding the high-resolution techniques in the signal processing antennas. We then describe a modified version of MUSIC (Root MUSIC). We show the performance and robustness of the method. Furthermore, we introduce radar target identification and two-dimensional radar target imaging. These study fields are new applications of the signal processing antennas, to which a great deal of attention has been devoted recently.

This paper addresses approaches to enhancement of performance of the CMA (Constant Modulus Algorithm) adaptive array antenna in multipath environments that characterize the mobile radio communications. The cost function of the CMA reveals that it has an AGC (Automatic Gain Control) procedure of holding the array output voltage at a constant value. Therefore, if the output voltage by the initial weights is different from the object value, then the CMA may suffer from slow convergence because suppression of the multipath waves is delayed by the AGC behavior. Our objective is to improve the convergence characteristics by adopting the differential CMA for the adaptive array algorithm. First, the basic performance of the differential CMA is clarified via computer simulation. Next, the differential CMA is incorporated into the eigen-beamspace system in which the eigenvectors of the correlation matrix of array inputs are used in the BFN (Beam Forming Network). This BFN creates the optimum orthogonal multibeams for radio environments and works helpfully as a preprocessor of the differential CMA. The computer simulation results have demonstrated that the differential CMA with the eigen-beamspace system has much better convergence characteristics than the conventional CMA with the element space system. Furthermore, a modified algorithm is introduced which gives the stable array output voltages after convergence, and it is confirmed that the algorithm can carry out more successful adaptation even if the radio environments are changed abruptly.

The MUSIC algorithm has proven to be an effective means of estimating parameters of multiple incoherent signals. Furthermore, the forward-backward (FB) spatial smoothing technique has been considered the best preprocessing method to decorrelate coherent signals. In this paper, we propose a novel preprocessing technique based upon ideas associated with the FB and adaptive spatial smoothing techniques and report on its superiority in numerical simulations.

This paper describes the architecture and storage structure of a new interactive multimedia information system called VideoReality. VideoReality is based on a visual conducting model, which describes the information retrieval process that occurs when people observe visible objects in the real world. VideoReality provides a spatial and temporal spread of a virtual video space from a set of stored video streams. The video space has a three-layered structure similar to that of the ANSI/X3/SPARC three-schema architecture. Users can move their eyes and watch objects freely in the video space, just as if they were viewing the real world. This paper also presents a prototype application system called Electronic Aquarium'

Flora is a functional-style language for object and relational algebra. It has been designed for efficient support of advanced database languages combining rules and objects using compilation and optimization. Flora is a strongly typed language based on an OO data model and incorporating support for collection-oriented computational capabilities. In this paper, we describe the design and architecture of the Flora optimizer which is rule-based, yet doing cost-based optimization. The optimizer uniformly captures logical, semantic and implementation knowledge regarding the execution system and the applications by means of assertions. This framework eases extensibility and enables efficient query rewriting.

As the Hypertext Transfer Protocol (HTTP) becomes more popular for network communication, network loads in areas with less developed network infrastructures will be an increasing problem. This paper presents a system which extends a WWW-server with a gateway to an RDBMS and a mail program, allowing for interactive query formulation together with return of potentially large query results by e-mail. These results can then be downloaded by the user when network loads are low.

When signal subspace techniques, such as MuSIC, are used to locate a number of incident signals, an exhaustive search of the array manifold has to be carried out. This search involves the evaluation of a single cost function at a number of points which form a grid, resulting in quantization-error effects. In this paper a new algorithm is put forward to overcome the quantization problem. The algorithm uses a number of cost functions, and stages, equal to the number of incident signals. At each stage a new cost function is evaluated in a small number of "special" directions, known as characteristic points. For an N-element array the characteristic points, which can be pre-calculated from the array manifold curvatures, partition the array manifold into N-1 regions. By using a simple gradient algorithm, only a small area of one of these regions is searched at each stage, demonstrating the potential benefits of the proposed approach.

The evolution of heterogeneous and autonomous databases research has been slow compared to other areas of research. Part of the problem resides in the fact that bridging data semantics has been a difficult problem. Sharing data among disparate databases has mostly been achieved through some form of manual schema integration. The complexity of making autonomous heterogeneous databases smoothly interoperate is dependent on addressing two major issues. The first issue to address is what adequate levels of autonomy databases are guaranteed to keep. The second issue to address is what overhead cost is required to bridge database heterogeneity. The complexity of these two issues are closely dependent on how scalable multidatabase systems are. In this paper we introduce the FINDIT architecture which uses information meta-types to provide a basis for such an organization and, consequently, provides a platform for inter-operability. A distinction is made between the information and inter-node relationship spaces to achieve scalability. Tassili language primitives are used for the incremental building of dynamic inter-node relationships based upon usage considerations.

In order to make the hyperling generation mechanism not only dynamic but also systematic, we will mainly describe the use of the querying and abstraction facilities in hypertext database systems. Our work focuses on a dynamic, abstract and systematic link generation mechanism. The prototype system named TextLink/Gem is implemented by taking an object-oriented approach, and the notions of anchor objects, query-pair links, polymorphic links and inheritable links, on which the system is based, and their implementations are described in detail.

Single-reference and multi-reference noise canceller (SRNC and MRNC) performances are investigated based on correlation between signal and noise. Exact relations between these noise canceller performances and signal-noise correlation have not been well discussed yet. In this paper, the above relations are investigated based on theoretical, analysis and computer simulation. The normalized LMS (NLMS) algorithm is employed. Uncorrelate, partially correlated, and correlated signal and noise combinations are taken into account. Computer simulation is carried out, using real speech, white noise, real noise sound, sine wave signals, and their combinations. In the SRNC problem, spectral analysis is applied to derive the canceller output power spectrum. From the simulation results, it is proven that the SRNC performance is inversely proportional to the signal-noise correlation as expected by the theoretical analysis. From the simulation results, the MRNC performance is more sensitive to the signal-noise correlation than that of SRNC. When the signal-noise correlation is high, by using a larger number of adaptive filter taps, the noise is reduced more, and, the signal distortion is increased. This means the signal components included in the noise are canceled exactly.

Tremendous progress has been made in magnetic data storage by applying theoretical considerations to technologies accumulated empirically through a great deal of research and development. In Japan, the recording demagnetization phenomenon was eagerly analyzed by many researchers because it was a serious problem in analogue signal recording such as video tape recording using a relatively thick magnetic recording medium. Consequently, perpendicular magnetic recording was proposed as a method for extremely high-bit-density recording. This paper describes the theoretical background which has resulted in the idea of perpendicular magnetic recording. Furthermore, the possibility of magnetic recording is discussed on the basis of the results obtained theoretically by magnetic recording simulators. Magnetic storage has the potential for extremely high-bit-density recording exceeding 1 Tb/cm2. We propose the idea of 'spinic data storage' in which binary digital data could be stored into each ferromagnetic single-domain columnar particle when the perpendicular magnetizing method is used.

A 2-switch node network is one of the most fundamental structure among communication nets such as telephone networks and local area networks etc. In this letter, we prove that a problem of designing a 2-switch node network satisfying capacity conditions of switch nodes and their link, which we call 2-switch node network problem, is NP-complete.

This paper discusses a coding-based selection approach to a communication aid for the severely motor disabled. Several approaches including row-column scanning are briefly described, then we propose a new selection scheme based on the theory of adaptive coding. They are compared each other with respect to average switch activations in generating some text samples.

A soft magnetic force microscope (MFM) tip was used to evaluate the magnetic recording characteristics of compositionally separated Co-Cr perpendicular media. Small magnetic bits were recorded on thick (350 nm). and thin (100 nm) films, focusing on the fineness of compositionally separated microstructures. MFM images showed bit marks 230 and 150 nm in diameter, measured at full-width at half maximum (FWHM) for the thick and thin films, respectively. These results verify that the recordable bit size can be decreased by using a thinner film with a finer compositionally separated microstructure. Simulation was used to clarify the relationship between the actual sizes of the recorded bits and the sizes of their MFM images. The recorded bit size was found to closely correspond to the FWHM of the MFM bit images.

The performance of decision-feedback equalization combined with maximum-likelihood detection (DFE/ML) using the fixed-delay-tree-search/decision feedback (FDTS/DF) algorithm was estimated analytically in terms of the length of the feedback-filter and the depth of the ML-detector. Performance degradation due to error propagation in the feedback-loop and in the ML-detector was taken into account by using a Markov process analysis. It was quantitatively shown that signal-to-noise-ratio (SNR) performance in high-density magnetic recording channels can be improved by combining an ML-detector with a feedback-filter and that the error propagation in the DFE channel can be reduced by using an ML-detector. Finally, it was found that near-optimum performance with regard to channel SNR and error propagation can be achieved, over the channel density range from 2 to 3, by increasing the sum of the feedback-filter length and the ML-detector depth to six bits.