We present a volume rendering algorithm which renders images at approximately two to seven times the speed of a conventional ray caster with almost no visible loss of image quality. This algorithm traverses the volume data in object order and renders the image by performing ray casting for the pixels within the footprint of the voxel (i.e., rectangular prism) being processed. The proposed algorithm supports the rendering of both single and multiple isosurfaces with arbitrary opacity values. While the projection approach to volume rendering is not new, we present an algorithm specifically designed for the perspective projection, evaluate its rendering speed for both single and multiple isosurfaces with arbitrary opacity values, and examine how efficiently it uses cache memory.

To improve the efficiency for the threshold schemes, the major problem is that the secret shadows cannot be reused after renewing or recovering the shared secret. However, if the secret shadows cannot be reused, the established threshold scheme is limited to be used only once. It is inefficient to reconstruct the whole secret sharing system. Therefore, we introduce an efficient dynamic threshold scheme. In the new scheme, the shadowholders can reuse the secret shadows no matter that the shared secret is renewed or recovered. In addition, the new scheme provides a way by which the dealer can renew the shared secret or reconstruct the secret sharing system, efficiently. Therefore, this scheme is good for maintaining the important secrets.

A method based on clustering is presented for restoring and segmenting gray scale images. An optimum clustering obtained by a gradient method gives an image with gray scale values which vary smoothly in each segmented region. The method is also applied to restoration from sparsely sampled data.

A algorithm for designing a pattern classifier, which uses MDL criterion and a binary data structure, is proposed. The algorithm gives a partitioning of the range of the multi-dimensional attribute and gives an estimated probability model for this partitioning. The volume of bins in this partitioning is upper bounded by ο((log N/N)K/(K+2)) almost surely, where N is the length of training sequence and K is the dimension of the attribute. The convergence rates of the code length and the divergence of the estimated model are asymptotically upper bounded by ο((log N/N)2/(K+2)). The classification error is asymptotically upper bounded by ο((log N/N)1/(K+2)). Simulation results for 1-dimensional and 2-dimensional attribute cases show that the algorithm is practically efficient.

The problem of TM-wave scattering and radiation from a finite number of thick slits in a parallel plate waveguide is solved. The Fourier transform and the mode matching are used to obtain simultaneous equations for the field inside the slits. The simultaneous equations are solved to obtain a series solution which is amenable to numerical computation. The numerical computations are performed to illustrate the behaviors of scattering, transmission, and reflection in terms of incident angle, slit size and operating frequency. The presented solution is computationally very efficient and useful for slotted-waveguide leaky-wave antenna applications.

This paper discusses how to derive message sequence charts (MSCs) from a set of state transition descriptions. Recently, MSC notation has received much attention in the communications software field because it graphically shows system global behavior, So MSC handling techniques are being widely studied. These studies have recommended the design a system by a set of formal MSCs in the early stages of development and then to convert them into state transition descriptions. However, it is difficult to apply those results to existing communications software products. This is because these systems are designed based on state transition descriptions and there are no formal MSCs for them. In this paper, we propose a method of deriving MSCs based on optimized reachability analysis. This method generates MCSs that avoid state explosion. A case study using Q.931 protocol shows the feasibility of this method.

Multimedia Database Systems as the tool to extract and generate additional values from multimedia 'Contents' are discussed in this paper with putting emphasis on the mediator functions between users and contents. Firstly, we discuss about 'what to do' from the view point of four promising contents sources: 'on the network,' 'in the digital broadcasting' 'in the library' and 'in the real world.' From this view pont, four types of multimedia database systems are defined. 'What to do' for each database system is also discussed. Two concrete multimedia database systems with unique mediator functions, stream-type multimedia database platform GOLS and the intelligent access and authoring system using multiple media synchronization are proposed with experimental evaluation results and concrete multimedia database applications.

The E-polarized plane wave diffraction by a perfectly conducting strip located at the plane interface between two different media is analyzed by the Wiener-Hopf technique. Applying the boundary conditions to the integral representations for the unknown scattered field, the problem is formulated in terms of the modified Wiener-Hopf equation(MWHE), which is reduced to a pair of simultaneous integral equations via the factorization and decomposition procedure. The integral equations are solved asymptotically for large strip width via the method of successive approximations leading to the first, second and third order solutions, which are valid at high frequencies. The scattered far field expression is derived by taking the inverse Fourier transform and applying the saddle point method. It is shown that the high-frequency scattered far field comprises the geometrical optics field, the singly, doubly and triply diffracted fields and the lateral waves. Numerical examples of the radar cross section(RCS) and the lateral waves are presented, and the far field scattering characteristics discussed in detail.

Continuous nonlinearity" is stressed as a fundamental principle in pattern recognition including handprinted Kanji character recognition. Continuity" in template matching and spatial nonlinearity" in structural analysis should be unified toward deriving a higher level of recognition algorithm. At the same time, continuous nonlinearity in the temporal axis is important, as is the case of simultaneous processing of segmentation and recognition for touching characters. The above viewpoint is discussed in the following examples: nonlinear normalization, directional pattern matching, locally maximized similarity, relaxation matching, dynamic programming matching, segmentation of character string using dynamic programming, and exhaustive matching for character extraction on complex background.

In recognition of handprinted characters, it is important to dissolve distortions of character caused by writer's habits. In order to dissolve distortions and to obtain better features, many image conversion methods have been proposed. But there are distortions that cannot be dissolved by these methods. One example is the case of parallel strokes which are spread out in fan shape. In this paper, in order to dissolve distortions, we propose a new image conversion method, Transformation based on Partial Inclination Detection (TPID)", which is employed just before normalization, and is intended to dissolve several kinds of distortions in images of each character. TPID constructs transformation functions from inclination angles which are detected in some subspaces of the character's image, and converts images using the transformation functions. TPID is especially suitable for correcting the inclinations of horizontal and vertical strokes of a character. This has a powerful impact on the quality of the characteristic features. In recognition experiments using ETL9B, the largest database of handprinted characters in Japan, we have obtained a recognition rate of 99.08%, which is the best to our knowledge.

This paper describes COCE (COordinative Character Extractor), a method for extracting printed Japanese characters and their character strings from all sorts of document images. COCE is based on a multi-agent system where each agent tries to find a character string and extracts the characters in it. For the adaptability, the agents are allowed to look after arbitrary parts of documents and extract the characters using only the knowledge independent of the layouts. Moreover, the agents check and correct their results sometimes with the help of the other agents. From experimental results, we have verified the effectiveness of our approach.

Through comparing the results of two successive IPTP Character Recognition Competitions which focused on 3-digit handprinted postal codes, we herein analyze the methodologies of the submitted algorithms along with the substituted or rejected patterns of these algorithms. Regarding their methodologies, lesser diversity was apparent specifically concerning the contour-chain code based on local stroke directions and statistical discriminant functions for feature extraction and discrimination. Analysis of the patterns demonstrated that the misrecognized patterns being most often improved were categorized as a decrease in peculiarly shaped handwritten characters or heavy-handed and disconnected strokes. However, most of the remaining misrecognitions were still classed as peculiarly shaped handwriting as commonly shared between the best three algorithms. From these analyses, we could delineate a direction to be taken for developing more effective methodologies and clarify the remaining problems to be overcome by the subsequent intensive research. Furthermore, we evaluate in this article our multi-expert recognition system for achieving higher recognition performances by means of combining complementary recognition algorithms. We performed a subsequent investigation of the Candidate Appearance Likelihood Method using novel experimental conditions and a new examination of the application of the neural network as the combining method for accumulating the broader candidate appearances. The results obtained confirm that combining through the neural network constitutes one of the most effective ways of making the multi-expert recognition system a reality.

There are some results indicating that a quantum computer seems to be more powerful than ordinary computers. In fact, P.W. Shor showed that a quantum computer can find discrete logarithms and factor integers in polynomial time with bounded error probability. No polynomial time algorithms to find them using ordinary computers are known. In this paper, we show that the cycles in some kinds of periodic functions, e.g., functions proposed as pseudo-random generators, can be found in polynomial time with bounded error probability on a quantum Turing machine. In general, it is known that ordinary computers take exponential time to find the cycles in periodic functions.

For similarity methods to work well, the image must be blurred before being input. However, the relationship between the blurring operation and the similarity is not fully understood. To solve the problem of this relationship, in this paper, the effect of blurring is investigated by expressing figure f(x) in the form of the sum of higher derivatives of f (x,σ), and then a simple similarity between figures was mathematically formulated in terms of the relation between visual patterns. By modifying this formulation, we propose pluralized simple similarity to increase the allowance in different view of multiple similarity. The similarity maintains higher allowance without any discernible loss of distinguishing power. We verify the effectiveness of the pluralized simple similarity throughout some experiments.

A new adaptive AR spectral estimation method is proposed. While conventional least-squares methods use a single windowing function to analyze the linear prediction error, the proposed method uses a different window for each frequency band of the linear prediction error to define a cost function to be meinemized. With this approach, since time and frequency resolutions can be traded off throughout the frequency spectrum, an improvement on the precision of the estimates is achieved. In this paper, a wavelet-like time-frequency resolution grid is used so that low-frequency components of the linear prediction error are analyzed through long windows and high-frequency components are analyzed through short ones. To solve the optimization problem for the new cost function, special properties of the correlation matrix are used to derive an RLS algorithm on the order of M2, where M is the number of parameters of the AR model. Computer simulations comparing the performance of conventional RLS and the proposed methods are shown. In particular, it can be observed that the wavelet-based spectral estimation method gives fine frequency resolution at low frequencies and sharp time resolution at high frequencies, while with conventional methods it is possible to obtain only one of these characteristics.

When circuits which include inductive loads are turned off by contact, showering noise generates across contact gap. Showering noise waveforms seem not to be stable in the case that wire-spring relay contact is used to turn on/off inductive load. It seems that various factors are concerned in the irregularity of showering noise waveforms. This paper clarifies the relation between showering noise waveform and the cathodic contact surface variation with the number of contact operation, and moving velocity of contact.

A new superresolution technique is proposed for high-resolution estimation of the scattering analysis. For complicated multipath propagation environment, it is not enough to estimate only the delay-times of the signals. Some other information should be required to identify the signal path. The proposed method can estimate the frequency characteristic of each signal in addition to its delay-time. One method called modified (Root) MUSIC algorithm is known as a technique that can treat both of the parameters (frequency characteristic and delay-time). However, the method is based on some approximations in the signal decorrelation, that sometimes make problems. Therefore, further modification should be needed to apply the method to the complicated scattering analysis. In this paper, we propose to apply a time-domain null filtering scheme to reduce some of the dominant signal components. It can be shown by a simple experiment that the new technique can enhance estimation accuracy of the frequency characteristic in the Root-MUSIC algorithm.

An ordered binary decision diagram (OBDD) is a directed acyclic graph for representing a Boolean function. OBDDs are widely used in various areas which require Boolean function manipulation, since they can represent efficiently many practical Boolean functions and have other desirable properties. However, there is very little theoretical research on the complexity of constructing an OBDD. In this paper, we prove that the optimal variable ordering problem of a shared BDD is NP-complete, and briefly discuss the approximation hardness of this problem and related OBDD problems.

A novel method of multichannel surface EMG processing has been developed to compensate for the distortion in bipolar surface EMG signals due to the movement of innervation zones. The distortion of bipolar surface EMG signals was mathematically described as a filtering function. A compensating technique for such distorted bipolar surface EMG signals was developed for the brachial biceps during dynamic contractions in which the muscle length and tension change. The technique is based on multichannel surface EMG measurement, a method for estimating the movement of an innervation zone, and the inverse filtering technique. As a result, the distorted EMG signals were compensated and transformed into nearly identical waveforms, independent of the movement of the innervation zone.

Protective layers in AC plasma display panels (PDP) are usually formed by vacuum vapor deposition or sputtering. It is important to study the protective MgO layer by means of screen-printing for fabricating a large size PDP and reducing its cost. With the objectives of enlarging the panel size and reducing cost, we studied the fabrication of the protective MgO layer by means of screen-printing. In this study, we succeeded in lowering the drive voltage by using a MgO powder prepared by vapor phase oxidation instead of conventional decomposition of the magnesium salt. Further, by adding a MgO liquid binder, we attained a good luminous efficiency twice as high as that attained with a sputtered protective layer and lowered the drive voltage. When this protective layer was combined with He-Xe gas enclosure, the half-life of luminance was 5,000 hours. With Ne-Xe gas, the luminance deteriorated no more than 40% after 5,000 hours. A screen-printed protective MgO layer containing no MgO liquid binder showed a short half-life of 800 hours even with the use of Ne-Xe gas. In this case, the discharge voltage changed greatly and some cells did not discharge. It is concluded that the combination of an ultrafine MgO powder prepared by vapor phase oxidation and a MgO liquid binder can clear the way for making AC PDPs with a long lifetime, high efficiency, and low voltage a practical reality.