This paper describes packaging techniques based on a novel passive alignment technique as key techniques for module assembly. A laser diode (LD) is passively positioned by detecting a pair of alignment marks located on the LD and Si substrate. A single-mode fiber is self aligned on a Si V groove. A simple receptacle structure for the module output port is also newly designed. This structure is more suitable for the automatic assembly line as well as the module mounting process on circuit board. In this paper, an advanced module applications such as a hybrid integrated wave guide module and a surface mountable (SMT) LD module is introduced.

The link properties of double-layered constellation composed of inclined orbits for an advanced global satellite communications network connected by optical inter-satellite links (ISLs) have been evaluated. The constellation consists of lower layer satellites for mobile and personal satellite communications, and upper layer satellites for large-capacity fixed satellite communications and feeder links. Optical inter-satellite links, which can perform high-capacity communications with small terminals, are used for all inter-satellite data transmission. Although a satellite constellation using polar orbits in both layers offers the merit of simplicity in network configurations, it has disadvantages caused by the satellite consentration above high latitudes. The inclined orbit constellation offers the potential for reducing the required number of satellites improving ling properties, and enhancing the coverage in middle and low latitudes, by selecting the optimum orbital inclinations. The link properties between the satellites and terminals on the ground, optical ISL properties, and required number of satellites were evaluated for constellations using inclined orbits, and compared with those of a polar orbit constellation. Three kinds of inclined orbit constellations achieving continuous double coverage, which is a minimum requirement for future advanced satellite communications applying satellite diversity, were assumed for each layer.

We analyze additive effects of nonlinear dynamics for conbinatorial optimization. We apply chaotic time series as noise sequence to neural networks for 10-city and 20-city traveling salesman problems and compare the performance with stochastic processes, such as Gaussian random numbers, uniform random numbers, 1/fα noise and surrogate data sets which preserve several statistics of the original chaotic data. In result, it is shown that not only chaotic noise but also surrogates with similar autocorrelation as chaotic noise exhibit high solving abilities. It is also suggested that since temporal structure of chaotic noise characterized by autocorrelation affects abilities for combinatorial optimization problems, effects of chaotic sequence as additive noise for escaping from undesirable local minima in case of solving combinatorial optimization problems can be replaced by stochastic noise with similar autocorrelation.

In this paper we discuss the limiting behavior of the search direction of the steepest descent method in minimizing the Rayleigh quotient. This minimization problem is equivalent to finding the smallest eigenvalue of a matrix. It is shown that the search direction asymptotically alternates between two directions represented by linear combinations of two eigenvectors of the matrix. This is similar to the phenomenon in minimizing the quadratic form. We also show that these eigenvectors correspond to the largest and second-smallest eigenvalues, unlike in the case of the quadratic form.

For finite Volterra series systems, this paper investigates the stability of the exact model matching (EMM) control we have already presented. First, in order to analyze the stability of the EMM system, we present modified small gain theorems depending on the magnitude of the external input (s) in the cases of one input and two inputs. Next, with the help of the theorem for feedback systems with two inputs, we clarify the condition under which the control system is stable for the reference input magnitude within a certain range, and is also robust for small disturbances. The modified small gain theorems are effective for the stability analysis of the nonlinear feedback control systems which do not have affine finite gain.

Roundoff error due to iterative computation with finite wordlength degrades the quality of decoded images in fractal image coding that employs a deterministic iterated function system. This paper presents a state-space approach to roundoff error analysis of fractal image coding for grey-scale images. The output noise variance matrix and the noise matrix are derived for the measures of error and the output noise variance is newly defined as the pixel mean of diagonal elements of the output noise matrix. A quantitative comparison of experimental roundoff error with analytical result is made for the output noise variance. The result shows that our analysis method is valid for the fractal image coding. Our analysis method is useful to design a real-time and low-cost decoding hardware with finite wordlength for fractal image coding.

The present paper examines a two-dimensional (2-D) joint-process lattice estimator and its implementation for image restoration. The gradient adaptive lattice (GAL) algorithm is used to update the filter coefficients. The proposed adaptive lattice estimator can represent a wider class of 2-D FIR systems than the conventional 2-D lattice models. Furthermore, its structure possesses orthogonality between the backward prediction errors. These results in superior convergence and tracking properties versus the transversal and other 2-D adaptive lattice estimators. The validity of the proposed model for image restoration is evaluated through computer simulations. In the examples, the implementation of the proposed lattice estimator as 2-D adaptive noise cancellator (ANC) and 2-D adaptive line enhancer (ALE) is considered.

This paper is concened with the design and implementation of a 2-channel, 2-dimensional filter bank using rectangular (analog/digital) and quincunx (digital/digital) sampling. The associated analog low-pass filters are separable where as the digital low-pass filters are non-separable for a minimum sampling density requirement. The digital low-pass filters are Butterworth type filters, N = 9, realized as LWDFs. They, when itterated, approximate a valid scaling function (raised-consine scaling function). The obtained system can be used to compute a discrete wavelet transform.

In this paper, new wavelet bases are presented. We address problems associated with the proposed matched filter in multirate systems, using an optimum receiver that maximises the SNR at the sampling instant. To satisfy the Nyquist (ISI-free transmission) and matched filter (maximum SNR at the sampling instant) criteria, the overall system filtering strategy requires to split the narrowest filter equally between transmitter and receiver. In data transmission systems a raised-cosine filter is therefore often used to bandlimit signals from which wavelet bases are derived. Sampling in multiresolution subspaces is also discussed.

For designing the underwater transmission system using directly projected audible sound by underwater loudspeaker to prevent a diving accident and/or to give a working instrucion, it is important to estimate the transmission loss for a wall not onl for pure tones but also for wideband signal such as voice and noise. In this paper, two practical methods of evaluating the underwater insulation effect for a single wall are discussed. One is a reconfirmation that the mass law which is frequently used in air still explains the transmission loss in water. Because parameters such as surface density and sound velocity in the mass law are widely changeable depending on the depth in water, much complexity is involved in preparing a theoretical curve for every parameter. So to avoid such complexity, a unified parameter Φ(=ωm cos θ/2ρc) is introduced to describe the mass law. This newly presented curve as a function of Φ is in good agreement with all rearranged experimental data for every kind of plates. The other is a proposition of new evaluating method of insulation effect of a wall for a wideband signal, using an idea of (100-α) percentage point of the noise level probability destribution, Lα. Firstly proposed method is confirmed experimentally and secondly proposed method is confirmed by a simulation experiment.

So far, neuronal dendrites have been characterized as electrically passive cables. However, recent physiological findings have revealed complex dynamics due to active conductances distributed over dendrites. In particular, the voltage-gated calcium and calcium-activated conductances are essential for producing diverse neuronal dynamics and synaptic plasticity. In this paper, we investigate the functional significance of the dendritic calcium-activated dynamics by computer simulations. First, the dendritic calcium-activated responses are modeled in a discrete compartmental form based on the physiological findings. Second, the basic stimulus-response characteristics of the single compartment dendrite model are investigated. The model is shown to reproduce the neuronal responses qualitatively. Third, the spatio-temporal dynamics of the dendrite shafts are modeled by longitudinally connecting 10 single compartments with coupling constants which are responsible for the dendrite thickness. The thick dendrite models, corresponding to proximal dendrites, respond in a spatially cooperative manner to a localized constant or periodic current stimulation. In contrast, the highly activated compartments are forced to be localized in the neighborhood of the stimulation-site in the fine dendrite models corresponding to distal dendrites. These results suggest that dendritic activities are spatially cooperated in a site-dependent manner.

In direction of arrival estimation, the locations of point sources are usually assumed to be fixed during the observation of data, which is reasonable in many cases. If the locations of the point sources are perturbed due to some reasons in a statistical way during the observed period and the signal sources are not far away from receiver array, however, direction of arrival estimation methods based on the fixed point source assumption may provide with incorrect results. In this paper, we propose a perturved-location source model. Under the model, an estimation method based on eigen-decomposition is investigated. In addition, the asymptotic distributions of the estimation errors of the parameters are obtained to show the statistical properties of the parameters are obtained to show the statistical properties of the estimation method.

Lower bounds on the size of shares |Vi| which are more tight than |Vi>| |S| is the size of the secret, are known only for some graphical access structures. This paper shows lower bounds on |Vi| greater than |S| for some non-graphical access structures Γ. We first prove that if {P1, Pi} Γ-for any Pi P^ = {P2, , Pn} and Γ ^= 2P^ Γ is the access structure of a (k, n-1) -threshold scheme on P^, thenmaxilog|Vi>| n+k-3/n-1 log|S|for Pi {P1, P2, , Pn}. Next, we show that maxilog |Vi| 1.5log |S| holds for a wider class of access structures.

This paper presents a reshufflable and laziness tolerant mental card game protocol. First, our protocol can reshuffle any subset of cards. For example, some opened cards and some face down cards can be shuffled together. Next, we consider two types of honest players, currently active and currently nonactive. A player is currently nonactive if he dropped out the game or he declared "pass" and has not declared "rejoin" yet. In the proposed protocol, if more than half of the players are currently active, they can play the game. In this case, the privacy of the currently nonactive players are kept secret.

We review a fundamental weak point of the OSS digital signature scheme against cryptanalysis by Pollard et al., and propose a new scheme of digital signature which overcomes this defect. More specifically, instead of the ring of the rational integer, we use the ring of integral quaternions, which is a non-commutative Euclidean ring. Known attacks to OSS signature do not work our scheme due to the non-commutativity. On the other hand, this scheme causes little increase in the burden of generation and verification of digital signature for the legitimate users, with respect to the original OSS scheme.

In estimating the vulnerability of a block cipher to differential cryptanalysis and linear cryptanalysis, we must consider the fact that the differential probability and the linear probability vary with the key. In the case of cryptosystems where the round key is XORed to the input data of each round, the difference in both types of probability with different keys is regarded as negligible. However, this is not the case with RC5. This paper makes a primary analysis of the key-dependency of linear probability of RC5. Throughout this paper we study "precise" linear probability. We find some linear approximations that have higher deviation (bias) for some keys than the "best linear approximation" claimed by Kaliski and Yin in CRYPTO'95. Using one linear approximation, we find 10 weak keys of RC5-4/2/2 with linear probability 2-1, 2 weak keys of RC5-4/5/16 with linear probability 2-2, and a weak key of RC5-16/5/16 with linear probability 2-15.4, while Kaliski-Yin's "best biases" are 2-3, 2-9, and 2-17, respectively.

Nyberg and Knudsen proved that the maximum average of differential probability (ADPmax) and the maximum average of linear probability (ALPmax) of Feistel cipher with over 4 rounds can be evaluated as ADPmax 2DCP2max and ALPmax 2LCP2max using the maximum of defferential characteristic probability (DCPmax) and the maximum of linear characteristic probability (LCPmax) per round. This paper shows ADPmax DCP2max and ALPmax LCP2max if the F function is a bijection and the Feistel cipher has more than 3 rounds. The results prove that Feistel ciphers are stronger against differential and linear cryptanalyses than previously thought. Combining this result with that of Luby and Rackoff, the implication is that the 3-round Feistel cipher could be used as a building block cipher for the construction of provable secure block cipher algorithm.

The DQDB MAC Protocol standardized by the IEEE 802.6 Committee is a single segment bandwidth reservation scheme that only reserves bandwidth for one segment in the distributed queue. Recently, multi-segment bandwidth reservation schemes that reserve bandwidth for not only one segment in the distributed queue but also a part of or all segments in the local node queue have been proposed. In this paper, we propose a new multi-segment bandwidth reservation protocol that can quickly react to changes in a node's traffic and can quickly allocate the bandwidth fairly and waste-free. We also evaluate the mean message transmission delay and throughput convergence performance by simulation. As a result, it is shown that the mean message transmission delay can be decreased and the throughput can be quickly converged to fair bandwidth allocation.

We describe the design, fabrication, and characteristics of FDM/WDM coupler deposited by TEOS-O3 based APCVD method on silicon substrates. Due to drastically reduced birefringence by APCVD process, completely polarization independent narrow band (100 GHz) Mach-Zehnder type FDM coupler was obtained. We also fabricated 1.3/1.55 µm directional coupler type WDM coupler with very low insertion loss.

The response time of adders is mainly determined by the carry propagation delay. This letter deals with a scheme which combines the address addition and decoding together. Although addition is involved in the process, we show that it can be computed without carry propagation. Memory latency is one of the most performance limiting factors. The authors present a new decoder logic named fused add-decoder (FADEC), which performs address addition and decoding in a single process. FADEC can reduce memory latency by eliminating separate address addition cycle.