Dense WDM techniques that exploit the enormous bandwidth of dispersion-shifted fibers (DSFs) while avoiding the impairments due to nonlinear effects are described. First, the nature of four-wave mixing (FWM), the dominant impairment factor in WDM transmission systems, is investigated using DSF installed in the field and laboratory experiments. This provides useful information for the practical design of WDM networks based on DSF. Second, practical techniques to reduce FWM impairment, unequal channel allocation and off-lambda-zero channel allocation (equal channel allocation in the novel 1580 nm band) along with gain-shifted erbium-doped fiber amplifiers for the 1570 to 1600 nm band, is described. Comparisons between off-lambda-zero and unequal channel allocation are provided in terms of the maximum transmission distance for various numbers of channels. Two schemes to immunize WDM systems against group velocity dispersion, span-by-span dispersion compensation and optical duobinary format, are presented. The combination of unequal channel allocation with off-lambda-zero channel allocation as well as the combination of two bands: the conventional 1550 nm band and the novel 1580 nm band are proven to be very useful in expanding the usable bandwidth of DSFs.

The results of experiments on the effect of the height and diameter of the cup on cup microstrip antennas are presented. The results show that the optimum height of the cup for the narrowest beamwidth and the highest gain is about 1/3 λ, and that the beamwidth decreases and the gain increases as the diameter of the cup increases.

To improve speech coding quality, in particular, the long-term dependency prediction characteristics, we propose a new nonlinear predictor, i. e. , a fully connected recurrent neural network (FCRNN) where the hidden units have feedbacks not only from themselves but also from the output unit. The comparison of the capabilities of the FCRNN with conventional predictors shows that the former has less prediction error than the latter. We apply this FCRNN instead of the previously proposed recurrent neural networks in the code-excited predictive speech coding system (i. e. , CELP) and shows that our system (FCRNN) requires less bit rate/frame and improves the performance for speech coding.

This paper discusses a design technique for multidimensional (M-D) multirate filters which cause no checkerboard distortion. In the first part of this paper, a necessary and sufficient condition for M-D multirate filters to be checkerboard-distortion-free is derived in the frequency domain. Then, in the second part, this result is applied to a scanning line conversion system for television signals. To confirm the effectiveness of the derived condition, band-limiting filters with and without considering the condition are designed, and the results by these filters are compared. A reducibility of the number of delay elements in such a system is also considered to derive efficient implementation.

In this paper, a two-dimensional (2-D) binary-valued (BV) lapped transform (LT) is proposed. The proposed LT has basis images which take only BV elements and satisfies the axial-symmetric (AS) property. In one dimension, there is no 2-point LT with the symmetric basis vectors, and the property is achieved only with the non-overlapping basis which the Hadamard transform (HT) has. Hence, in two dimension, there is no 22-point separable ASLT, and only 2-D HT can be the 22-point separable AS orthogonal transform. By taking non-separable BV basis images, this paper shows that a 22-point ASLT can be obtained. Since the proposed LT is similar to HT, it is referred to as the lapped Hadamard transform (LHT). LHT of larger size is shown to be provided with a tree structure. In addition, LHT is shown to be efficiently implemented by a lattice structure.

The checkerboard effect is caused by the periodic time-variant property of multirate filters which consist of up-samplers and digital filters. Although the conditions for some one-dimensional (1D) multirate systems to avoid the checkerboard effect have been shown, the conditions for Multidimensional (MD) multirate systems have not been considered. In this paper, some theorems about the conditions for MD multirate filters without checkerboard effect are derived. In addition, we also consider MD multirate filter banks without checkerboard effect. Simulation examples show that the checkerboard effect can be avoided by using the proposed conditions.

The authors have proposed a design method for two-dimensional (2-D) separable-denominator (SD) periodically time-variant digital filters (PTV DFs) and confirmed their superiority over 2-D time-invariant DFs. In that result, the periodicity matrix representing the periodicity of the varying filter coefficients is, however, restricted to two cases. This paper extends that idea so that the input-output relation of 2-D SD PTV DFs with an arbitrary periodicity matrix can be determined. This enables us to design wide range of 2-D PTV DFs.

Wavelength tunable laser diodes are critical components in a wide variety of WDM and packet switching architectures. And also wavelength-tuned short pulses generated from the semiconductor laser diodes are of great importance for the developments of ultrahigh speed and WDM optical communication systems. Over the past several years, both continuously and discontinuously tunable lasers incorporating periodically sampled and chirped grating have been studied theoretically and experimentally. These laser diodes show the wide tuning range of above 60 nm, stable lasing condition, and large side-mode suppression ratio. Directly modulated semiconductor laser diodes, even those with a single mode, exhibit a dynamic frequency chirp during the on/off modulation. The dynamic linewidth broadening caused by such a large frequency chirp can result in a significant penalty in the performance of high-speed long-haul optical communication systems. The CW laser diodes integrated with an external EA modulator are an breakthrough to realize the high-speed optical systems with low chirp. And also the short pulse generation using the external modulator has been realized experimentally, whose principle of the pulse generation is the optical gating of the electroabsorption modulator. In this paper, widely tunable laser diodes incorporating periodically sampled and chirped gratings and an external modulator are analyzed using an improved time-domain dynamic model. First, it is demonstrated that the improved model is very powerful in simulating the complex laser diodes with active and passive sections. And, the dynamic properties of the sampled grating DBR and chirped grating DBR laser diodes are investigated. Second, the modulation characteristics of the laser diode integrated with the external electroabsorption modulator are studied. It is shown that the external modulation are superior to the direct modulation in the aspect of the lower frequency chirp. And the pulse generation by the optical gating of the external modulator is observed theoretically.

The microwave attenuation, which is the key factor for realizing very large bandwidths Ti:LiNbO3 optical modulators is fully studied and the causes and reduction techniques are discussed in detail. Practical realization of wide-band optical modulators with low microwave attenuation and low driving voltage is also discussed.

An experiment is reported comparing six pen input strategies for selecting a small target using five diffenent sized targets (1, 3, 5, 7 and 9 dot diameter circles respectively, 0. 36 mm per dot). The results showed that the best strategy, in terms of error rate, selection time and subjective preferences, was the "land-on2" strategy where the target is selected when the pen-tip touches the target for the first time after landing on the screen surface. Moreover, "the smallest maximum size" was determined to be 5 dots (1. 8 mm). This was the largest size among the targets which had a significant main effect on error rate in the six strategies. These results are important for both researchers and designers of pen-based systems.

Video-on-Demand (VOD)servers are becoming feasible. These servers are a building component in a heterogeneous multimedia environment but have voluminous data to store and manage. If only disk-based secondary storage systems are used to store and manage this huge amount of data the system cost would be extensively high. A tape-based tertiary storage system seems to be a reasonable solution to lowering the cost of storage and management of this continuous data. However, the usage of a tertiary storage system to store large continuous data introduces several issues. These are mainly the replacement policy on disks, the decomposition and the placement of continuous data chunks on tapes, and the scheduling of multiple requests for materializing objects from tapes to disks. In this paper we address these issues and we propose solutions based on some heuristics we experimented in a simulator.

This paper describes a classification method for rotated and scaled textured images using invariant parameters based on spectral-moments. Although it is well known that rotation invariants can be derived from moments of grey-level images, the use is limited to binary images because of its computational unstableness. In order to overcome this drawback, we use power spectrum instead of the grey levels to compute moments and adjust the integral region of moment evaluation to the change of scale. Rotation and scale invariants are obtained as the ratios of the different rotation invariants on the basis of a spectral-moment property with respect to scale. The effectiveness of the approach is illustrated through experiments on natural textures from the Brodatz album. In addition, the stability of the invariants with respect to the change of scale is discussed theoretically and confirmed experimentally.

Image restoration using estimated parameters of image model and noise statistics is presented. The image is modeled as the output of a 2-D noncausal autoregressive (NCAR) model. The parameter estimation process is done by using the autocorrelation function and a biased term to a conventional least-squares (LS) method for the noncausal modeling. It is shown that the proposed method gives better results than the other parameter estimation methods which ignore the presence of the noise in the observation data. An appropriate image model selection process is also presented. A genetic algorithm (GA) for solving a multiobjective function with single constraint is discussed.

In this paper, we extend the Gnaedig's results on termination of order-sorted rewriting. Gnaedig required a condition for order-sorted signatures, called minimality, for the termination proof. We get rid of this restriction by introducing a transformation from a TRS with an arbitrary order-sorted signature to another TRS with a minimal signature, and proving that this transformation preserves termination.

An efficient active noise control algorithm based on the lattice-transversal joint (LTJ) filter structure is presented, and applied to the active control of broadband noise in a 3-dimensional enclosure. The presented algorithm implements the filtered-x LMS within the LTJ structure obtained by cascading the lattice and transversal structures. Simulation results show that the LTJ-based noise control algorithm has fast convergence speed that is comparable to the lattice-based algorithm while its computational complexity is less demanding.

An optimum filter for extracting a time-varying harmonic signal from the noise-corrupted measurement is proposed. It is derived as a solution of the least mean square estimation with consideration of the pitch estimation error even without any assumption on the filter model. We obtain a comb-like impulse response which consists of homologous and dilated distribution of weights just located periodically with a pitch interval. This remarkable structure is well suited to the proportionally expanding error of pitch repetition times. Examples of the filter design are presented, and the performance of noise suppression is examined by comparison with conventional comb filters.

Secret sharing schemes are good for protecting the important secrets. They are, however, inefficient if the secret shadow held by the shadowholder cannot be reused after recovering the shared secret. Traditionally, the (t, n) secret sharing scheme can be used only once, where t is the threshold value and n is the number of participants. To improve the efficiency, we propose an efficient dynamic secret sharing scheme. In the new scheme, each shadowholder holds a secret key and the corresponding public key. The secret shadow is constructed from the secret key in our scheme, while in previously proposed secret sharing schemes the secret key is the shadow. In addition, the shadow is not constructed by the shadowholder unless it is necessary, and no secure delivery channel is needed. Morever, this paper will further discuss how to change the shared secret, the threshold policy and cheater detection. Therefore, this scheme provides an efficient way to maintain important secrets.

In this paper, we present a hierarchical technique for simultaneous pin assignment and global routing during floorplanning based on the minimum cost maximum integer flow algorithm with several heuristic cost functions. Furthermore, our algorithm handles feedthrough pins and equi-potential pins taking into account global routes. Our algorithm allows various user specified constraints such as pre-specified pin positions, wiring paths, wiring widths and critical nets. Experimental results including Xerox floorplanning benchmark have shown the effectiveness of the heuristics.

We introduce an image contour clustering method based on a multiscale image representation and its application to image compression. Multiscale gradient planes are obtained from the mean squared sum of 2D wavelet transform of an image. The decay on the multiscale gradient planes across scales depends on the Lipshitz exponent. Since the Lipshitz exponent indicates the spatial differentiability of an image, the multiscale gradient planes represent smoothness or sharpness around edges on image contours. We apply vector quatization to the multiscale gradient planes at contours, and cluster the contours in terms of represntative vectors in VQ. Since the multiscale gradient planes indicate the Lipshitz exponents, the image contours are clustered according to its gradients and Lipshitz exponents. Moreover, we present an image recovery algorithm to the multiscale gradient planes, and we achieve the skech-based image compression by the vector quantization on the multiscale gradient planes.

This paper develops a prediction model for evaluating the influence of propagation attenuation due to aircraft's flying across the earth-satellite link. This prediction model is based on the Aperture-field method of Huygens-Fresnel wave theory. Considering arriving and taking off course around airport, attenuation impairment is calculated for different types of aircrafts and flight directions. In order to verify this model's accuracy, numerical results are compared with measurement values. The calculations agree well with the measurements. Ground antenna directivity and anticipated impairment to digital broadcasting system such as Perfect TV are also discussed.