Semi-Orthogonally Associative Memory neural network model (SAM) uses the orthogonal vectors in Un = {-1, 1}n as its characteristic patterns. It is necessary to select the optimum characteristic parameter n so as to increase the efficiency of this model used. This paper investigates the dynamic behavior and error correcting capability of SAM by statistical neurodynamics, and demonstrates that there exists a convergence criterion in tis recalling processes. And then, making use of these results, its optimum characteristic parameter is deduced. It is proved that, in the statistical sense, its recalling outputs converge to the desired pattern when the initial similar probability is larger than the convergence criterion and not true otherwise. For a SAM with N neurons, when its characteristic parameter is optimum, its memory capacity is N/2 ln ln N, the information storage capacity per connection weight is larger than 9/23 (bits/weight) and the radius of attractive basin of non-spurious stable state is about 0.25N. Computer simulations are done on this model and the simulation results are consistent with the results of theoretical analyses.

An optoelectronic beam forming network (BFN) is presented for a single beam, 3-element phased array antenna that utilizes electrically controllable birefringence mode nematic liquid-crystal cells (ECB mode NLC cells) for phase shifting and amplitude control. In the circuit, a microwave signal is carried by a pair of orthogonal linearly polarized lightwaves (signal and reference lightwaves) using the optical heterodyning technique. Birefringence of liquid-crystals is utilized to selectively control the phase of the signal and reference lightwaves. Because an interferometer is formed on a single signal path, the complexity of the optical circuit is much reduced, compared to the BFNs based on arrays of Mach-Zender interferometers. A prototype circuit is built using laser sources of 1.3 µm, and its performance experimentally examined. With small deviations among the three cells, phase shifts of up to 240 degrees are achived for MW signals from 0.9 GHz to 20 GHz with good stability; attenuation of more than 18dB is achieved. An optoelectronic technique for parallel control of amplitude and phase of MW signals was developed.

We present a recursive algorithm for constructing linear discrete-time systems which interpolate the desired 1st-and 2nd-order information. The recursive algorithm constructs a new system and connects it to the previous system in the cascade form every time new information is added. These procedures yield a practical realization of all the interpolants.

In this paper, we propose a new method of dialogue data collection which can be used to evaluate modules of a spoken dialogue system. To evaluate the module, it is necessary to use suitable data. Human-human dialogue data have not been appropriate to module evaluation, because spontaneous data usually include too much specific phenomena such as fillers, restarts, pauses, and hesitations. Human-machine dialogue data have not been appropriate to module evaluation, because the dialogue was unnatural and the available vocabularies were limited. Here, we propose 'Hybrid method' for the collection of spoken dialogue data. The merit is that, the collected data can be used as test data for the evaluation of a spoken dialogue system without any modification. In our method a human takes the role of some modules of the system and the system, also, works as the other part of the system together. For example, humans works as the speech recognition module and the dialogue management and a machine does the other part, response generation module. The collected data are good for the evaluation of the speech recognition and the dialogue management modules. The reasons are as follows. (1) Lexicon: The lexicon was composed of limited words and dependent on the task. (2) Grammar: The intention expressed by the subjects were concise and clear. (3) Topics: There were few utterances outside the task domain. The collected data can be used test data for the evaluation of a spoken dialogue system without any modification.

Parallel processing is a well-known approach to enhance the performance of communication subsystems. The several forms of parallelism embedded in communication protocols have been applied to the OSI protocol stack. However, the OSI protocol stack involves sequential processing due to the layered architecture. Thus, all the layers have been prevented from performing immediate processing as soon as the data arrives. To solve the problem, we apply a Multiple Instruction Single Data (MISD) parallel scheme to OSI processing for the network layer through the presentation layer. In the MISD scheme, different processors can be allocated to different layers and concurrently run the code for each layer. In contrast, the conventional approach adopts for a pipeline scheme that all the layers can be assigned to different pipeline stages and will be performed in a time interval and their dependence. The implementations have been performed to compare the pipeline scheme with the MISD scheme on the Parsytec Super Cluster consisting of 64 Transputers. The measures show that the MISD scheme has performance improvement as high as about 84% in comparison with the pipeline one.

This paper describes the performance of a predistorter implementation to a superluminescent diode (SLD) in fiber-optic wireless systems under the optical reflection. SLD intensity noise and 3rd-order intermodulation distortion (IM3) are experimentally compared with those of DFB-and FP-LD. It is observed that the IM3 of SLD has ideal 3rd characteristics and output noise remains unchanged against the number of optical connectors. It is also found that the predistorter reduces IM3 by 8 dB. Receiver sensitivity of the system is discussed from the view point of overall design. the BER performance of an SLD with predistorter using a π/4-QPSK signal as a subcarrier is also described theoretically and experimentally.

In previous papers the building of hierarchical networks made up of components using fuzzy rules was presented. It was demonstrated that this approach could be used to construct networks to solve classification problems, and that in many cases these networks were computationally less expensive and performed at least as well as existing approaches based on feedforward neural networks. It has also been demonstrated how this approach could be extended to real-valued problems, such as function approximation and time series prediction. This paper investigates the problem of choosing the best network for real-valued approximation problems. Firstly, the nature of the network parameters, how they are interrelated, and how they affect the performance of the system are clarified. Then we address the problem of choosing the best values of these parameters. We present two model selection tools in this regard, the first using a simple statistical model of the network, and the second using structural information about the network components. The resulting network selection methods are demonstrated and their performance tested on several benchmark and applied problems. The conclusions look at future research issues for further improving the performance of the clustering network.

This paper discusses the problem of reducing the number of keys required to authenticate a source state (plaintext), as well as introducing a new way of constructing authentication codes. The construction uses association schemes, which are well-defined schemes in combinatorial design theory. The association scheme on the message (ciphertext) space is established by defining two relations between any two messages: The 1st relation is when the two messages do not share a common key, and the 2nd relation is when they do. Using association schemes of the triangular and group divisible types, we are able to reduce the number of keys.

A performance estimation method has been developed that combines conventional performance evaluation with Bayesian regression analysis. The conventional method is used to estimate performance a priori; this a priori estimate is then updated through Bayesian regression analysis using monitored performance. This method compensates for modeling errors in the conventional technique without recreating complex performance models; it does not require additional traffic measurement or system behavior models. Numerical examples and applications of traffic management in ATM PVC networks have demonstrated its effectiveness.

To realize better bit error rate performance in fast fading environments, this paper proposes the open loop reverse modulation carrier recovery scheme which employs a new open loop carrier extractor and regenerator instead of using a feed back loop. The proposed scheme realizes stable regenerated carrier signals to achieve low bit error rate not only under additive white Gaussian noise environments but also under fast fading environments. Computer simulations clarify that the proposed scheme always achieves better bit error rates than conventional differential detection or coherent detection with feed back loops under the various fading environments examined.

This paper proposes a new block coded quadrature amplitude modulation (BC-QAM) scheme, which is designed by an optimization technique based on simulated annealing. Simulated annealing is an effective nonlinear optimization technique and can be applied to both the discrete and the continuous optimization problems. In this paper, the simulated annealing technique is used to design the optimum BC-QAM signal, which minimizes the upper bound on the bit error rate (BER) in a Rayleigh fading channel. The computer simulation shows that the proposed BC-QAM can improve the BER performance. This paper also proposes a simplified design method to reduce the number of variables to be optimized. The proposed simplified method optimizes the in-phase and quadrature components of the BC-QAM signal separately. The computer simulation also shows that the BC-QAM designed by the simplified method gives little degradation on the BER performance, although the simplified method can significantly reduce the number of optimization variables.

In this communication we propose to solve the problem of reconstruction from limited data using a statistical regularization method based on a Bayesian information criterion. The minimization of the Bayesian information criterion, which is used here as an objective index to measure the goodness of an estimate, gives the optimum value of the smoothing parameter. By doing so, we could reduce the inversion problem to a simple minimization of a one-variable nonlinear function. The application of such a technique overcomes the nonuniqueness of the solution of the ill-posed problem and all shortcomings of many iterative methods. In the light of simulation and application to real data, we propose a slight modification to the Bayesian information criterion to reconstruct the wave energy distribution at the ionospheric base from the observation of radio wave electromagnetic field on the ground. The achieved results in both the inversion problem and the wave direction finding are very promising and may support other works so far suggested the use of Bayesian methods in the inversion of ill-posed problems to benefit from the valuable information brought by the a priori knowledge.

This paper discusses a software verification support environment Vega which is based on a model-theoretic methodology that enables verification support for the temporal properties of protocol specifications described in the formal description technique LOTOS. In the methodology of Vega, a protocol specification is defined through the LOTOS process reflecting its practical system structure. The temporal properties to be verified are given as the requirement which the protocol needs to satisfy from the viewpoint of events and are formulated by using the branching time temporal logic defined in this paper. Verification is done by determining whether or not the given temporal properties are satisfied by the model, which corresponds to the transition system derived from the LOTOS specification of the protocol. Vega is provided with an effective interface function, as well as the function of simple model checking based on the above methodology, to give some degree of flexibility for the expression of temporal properties to be verified. Specifically, it allows the user to define useful expressions by combining builtin temporal logic formulas and enter them in Vega for use at any time. With the provision of these functions, Vega is expected to serve as a very powerful and flexible verification support tool.

Computer viruses, hackers, intrusions and ther computer crimes have recently become a serious security problem in information systems. Digital signatures are useful to defend against these threats, especially against computer viruses. This is because a modification of a file can be detected by checking the consistency of the originai file with its accompanying digital signature. But an executable program might have been infected with the viruses before the signature was created. In this case, the infection cannot be detected by signature verification and the origin of the infection cannot be specified either. In this paper, we propose a signature scheme in which one can sign right after the creation of an executable program. That is, when a user compiles a source program, the compiler automatically creates both the executable program and its signature. Thus viruses cannot infect the executable programs without detection. Moreover, we can specify the creator of contaminated executable programs. In our signature scheme, a signature is created from a set of secret integers stored in a compiler, which is calculated from a compiler-maker's secret key. Each compiler is possessed by only one user and it is used only when a secret value is fed into it. In this way a signature of an executable program and the compiler-owner are linked to each other. Despite these measures, an executable program could run abnormally because of an infection in prepro-cessing step, e.g. an infection of library files or included files. An infection of these files is detected by ordinary digital signatures. The proposed signature scheme together with digital signature against infection in the preprocessing step enables us to specify the origin of the infection. The name of the signature creator is not necessary for detecting an infection. So, an owner's public value is not searched in our scheme, and only a public value of a compiler-maker is required for signature verification. Furthermore, no one can use a compiler owned by another to create a proper signature.

GDL is the language whose membership problerm is polynomial-time Turing equivalent to the discrete logarithm problem for a general finite group G. This paper gives a characterization of GDL from the viewpoint of computational complexity theory. It is shown that GDL NP co-AM, assuming that G is in NP co-NP, and that the group law operation of G can be executed in polynomial time of the element size. Furthermore, as a natural probabilistic extension, the complexity of GDL is investigated under the assumption that the group law operation is executed in an expected polynomial time of the element size. In this case, it is shown that GDL MA co-AM if G MA co-MA. As a consequence, we show that GDL is not NP-complete unless the polynomial time hierarchy collapses to the second level.

In this paper we describa a system for Off-line Recognition of Arabic characters and Numerals. This is based on expressing the machine printed Arabic alpha-numerical text in terms of strokes obtained by MCR (Minimum Covering Run) expression. The strokes are rendered meaningful by a labeling process. They are used to detect the baseline and to provide necessary features for recognition. The features selected proved to be effective to the extent that with simple right to left analysis we could achieve interesting results. The recognition is achieved by matching to reference prototypes designed for the 28 Arabic characters and 10 numerals. The recognition rate is 97%.

This paper proposes a new approach to deal with the various quality of the reference impressions by measuring the seal to register as 3D (three-dimensional) image, that is, range image. By registering a seal as 3D image, it becomes possible to construct various 2D impressions from it according to the affixing conditions of the reference impression such as the affixing slant, the affixing pressure, the state of the ink on the seal surface and so on. Then, the accurate and easy identification of the seals will be possible by comparing the constructed impression with the reference impression. The performance is verified by experiment, and the result shows that plural 2D impressions according to the affixing conditions can be constructed from only one 3D image of the registered seal.

A new approach is presented for recovering the 3-D shape from shading image. Photometric Stereo Method (PSM) is generally based on the direct illumination. PSM in this paper is modified with the indirect diffuse illumination method (IDIM), and then applied to hybrid reflectance model which consists of two components; the Lambertian reflectance and the specular reflectance. Under the hybrid reflectance model and the indirect diffuse illumination circumstances, the 3-D shape of objects can be recovered from the surface normal vector extracted from the surface roughness, the surface reflectance ratio, and the intensity value of a pixel. This method is rapid because of using the reference table, simplifies the restriction condition about the reflectance function in prior studies without any loss in performance, and can be applied to various types of surfaces by defining general reflectance function.

In this paper we propose a new method for removing the characteristic of the piezoelectric transducer from the received signal in the pulse-echo method so that the time resolution in the determination of transit time of ultrasound in a thin layer is increased. The total characteristic of the pulse-echo system is described by cascade of distributed-constant systems for the ultrasonic transducer, matching layer, and acoustic medium. The input impedance is estimated by the inverse matrix of the cascade system and the voltage signal at the electrical port. From the inverse Fourier transform of input impedance, the transit time in a thin layer object is accurately determined with high time resolution. The principle of the method is confirmed by simulation experiments.

CAMs (Content Addressable Memories) are functional memories which have functions such as word-parallel equivalence search, bilateral 1-bit data shifting between consecutive words, and word-parallel writing. Since CAMs can be integrated because of their regular structure, massively parallel CAM functions can be executed. Taking advantage of CAMs, Ishiura and Yajima have proposed a parallel fault simulation algorithm using a CAM. This algorithm, however, requires a large amount of CAM storage to simulate large-scale circuits. In this paper, we propose a new massively parallel fault simulation algorithm requiring less CAM storage, and compare it with Ishiura and Yajima's algorithm. Experimental results of the algorithm on CHARGE --the CAM-based hardware engine developed in our laboratory--are also reported.