When a randomized algorithm elects a leader on anonymous networks, initial information (which is called in general initial condition in this paper) of some sort is always needed. In this paper, we study common properties of initial conditions that enable a randomized algorithm to elect a leader. In the previous papers, the author introduced the notion of transformation between initial conditions using distributed algorithms. By using this notion of transformation, we investigate the property of initial conditions for the leader election. We define that an initial condition C is p(N)-complete if there exists some randomized algorithm that elects a leader with probability p(N) on any size N network satisfying C. We show that we can divide p(N)-completeness into four types as follows. 1. p(N)=1: For any 1-complete initial conditions, there exists a deterministic distributed algorithm that can compute the size of the network for any initial information satisfying the initial condition. 2. inf p(N) >0: For any p(N)-complete initial conditions with inf p(N) >0, there exists a deterministic distributed algorithm that can compute an upper-bound for the size of the network for any initial information satisfying the initial condition. 3. inf p(N) converges to 0: The set of p(N)-complete initial conditions varies depending on the decrease rate of p(N). 4. p(N) decreases exponentially: Any initial condition is regarded as p(N)-complete.

In this paper, we propose a method to reconstruct current distributions in the human brain from neuromagnetic measurements. The proposed method is based on the weighted lead-field synthetic (WLFS) filtering technique with the weighting factors calculated from the results of previous source space scanning. In this method, in addition to the depth normalization technique, weighting factors of the WLFS are determined by the cost values previously calculated based on the multiple signal classification (MUSIC) scan. We performed computer simulations of this method under noisy measurement conditions and compared the results to those obtained with the conventional WLFS method. The results of the simulations indicate that the proposed method is effective for the reconstruction of the current distributions in the human brain using magnetoencephalographic (MEG) measurements, even if the signal-to-noise ratio of the measured data is relatively low. We applied the proposed method to the magnetoencephalographic data obtained during a mental image processing task that included object recognition and mental rotation operations. The results suggest that the proposed method can extract the neural activity in the extrastriate visual region and the parietal region. These results are in agreement with the results of previous positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) studies.

Generalized Pulse Spectrum Technique (GPST) is a method to solve the inverse problems of wave-propagation and diffusion-dominated phenomena, and therefore has been popularly applied in image reconstruction of time-resolved diffuse optical tomography. With a standard GPST for simultaneous reconstruction of absorption and scattering coefficients, the products of the gradients of the Green's function and the photon-density flux, based on the photon-diffusion equation, are required to calculate the diffusion-related Jacobian matrix. The adversities are of two-folds: time-consuming and singular in the field near the source. The latter causes a severe insensitivity of the algorithm to the scattering changes deep inside tissue. To cope with the above difficulties, we propose in this paper a modified GPST algorithm that only involves the Green's function and the photon-density flux themselves in the scattering-related matrix. Our simulated and experimental reconstructions show that the modified algorithm can significantly improve the quality of scattering image and accelerate the reconstruction process, without an evident degradation in absorption image.

In this paper, a new image synthesis model based on a set of wavelet bases is proposed. In the proposed model, images are approximated by the sum of synthesis functions that are translated to image edge positions. By applying the proposed model to sketch-based image coding, no iterative image recovery procedure is required for image decoding. In the design of the synthesis functions, we define the synthesis functions as a linear combination of wavelet bases. The coefficients for wavelet bases are obtained from an iterative procedure. The vector quantization is applied to the vectors of the coefficients to limit the number of the synthesis functions. We apply the proposed synthesis model to the sketch-based image coding. Image coding experiments by eight synthesis functions and a comparison with the orthogonal transform methods are also given.

In recent years, several inverse solutions of magnetoencephalography (MEG) have been proposed. Among them, the multiple signal classification (MUSIC) method utilizes spatio-temporal information obtained from magnetic fields. The conventional MUSIC method is, however, sensitive to Gaussian noise and a sufficiently large signal-to-noise ratio (SNR) is required to estimate the number of sources and to specify the precise locations of electrical neural activities. In this paper, a new algorithm for solving the inverse problem using the fourth order MUSIC (FO-MUSIC) method is proposed. We apply it to the MEG source estimation problem. Numerical simulations demonstrate that the proposed FO-MUSIC algorithm is more robust against Gaussian noise than the conventional MUSIC algorithm.

Breakthroughs in crystal growth and conductivity control of nitride semiconductors during last two decades have led to such developments as high-brightness blue and green light-emitting diodes and long-lived violet laser diodes and so on. All of these nitride-based devices are robust and the most environmentally-friendly ones available. They enable us to save tremendous amount of energy and will be key devices in advanced information technology. Further progress in the area of crystal growth and device engineering will open up new frontier devices based on nitride semiconductors. In this paper, the evolution of nitride-based light-emitting devices is reviewed and the key issues, which must be addressed for nitrides to be fully developed, are discussed.

We present an efficient heuristic algorithm to reduce glitch power dissipation in CMOS digital circuits. In this paper, gate sizing is classified into three types and the buffer insertion is classified into two types. The proposed algorithm combines three types of gate sizing and two types of buffer insertion into a single optimization process to maximize the glitch reduction. The efficiency of our algorithm has been verified on LGSynth91 benchmark circuits with a 0.5 µm standard cell library. Experimental results show an average of 69.98% glitch reduction and 28.69% power reduction that are much better than those of gate sizing and buffer insertion performed independently.

A novel scheduling method for asynchronous multirate/multi-task processing by programmable digital signal processors (DSPs) has been developed. This mixed scheduling method combines static and dynamic scheduling, and avoids runtime overheads due to interrupts in context switching to realizes asynchronous multirate systems. The processing delay introduced when using static scheduling with static buffering is avoided by introducing deadline scheduling in the static schedule design. In the developed software design system, a block-diagram description language is extended to describe asynchronous multi-task processing. The scheduling method enables asynchronous multirate processing, such as arbitrary-sampling-ratio rate conversion, asynchronous interface, and multimedia applications, to be efficiently realized by programmable DSPs.

This paper studies security of Feistel ciphers with SPN round function against differential cryptanalysis, linear cryptanalysis, and truncated differential cryptanalysis from the "designer's standpoint." In estimating the security, we use the upper bounds of differential characteristic probability, linear characteristic probability and truncated differential probability, respectively. They are useful to design practically secure ciphers against these cryptanalyses. Firstly, we consider the minimum numbers of differential and linear active s-boxes. They provide the upper bounds of differential and linear characteristic probability, which show the security of ciphers constructed by s-boxes against differential and linear cryptanalysis. We clarify the (lower bounds of) minimum numbers of differential and linear active s-boxes in some consecutive rounds of the Feistel ciphers by using differential and linear branch numbers, Pd, Pl, respectively. Secondly, we discuss the following items on truncated differential probability from the designer's standpoint, and show how the following items affect the upper bound of truncated differential probability; (a) truncated differential probability of effective active-s-box, (b) XOR cancellation probability, and (c) effect of auxiliary functions. Finally, we revise Matsui's algorithm using the above discussion in order to evaluate the upper bound of truncated differential probability, since we consider the upper bound of truncated differential probability as well as that of differential and linear probability.

The use of the homomorphic filter technique is described in order to enhance the contrast in the mammographic images, which is adopted to the dyadic wavelet transform. The proposed method has employed the nonlinear enhancement in homomorphic filtering as well as denoising method in the wavelet domains. Experimental results show that the homomorphic filtering method improves the contrast in breast tumor images such that the contrast improvement index is increased by two fold compared to the conventional wavelet-based enhancement technique.

Low-crosstalk 1.3-µm Fabry-Perot laser diode (FP-LD) and photodiode (PD) arrays are developed. The arrays are fabricated on semi-insulating substrates and their anodes and cathodes are separated channel by channel to suppress inter-channel electrical crosstalk at high frequency. Crosstalk of less than -30 dB is achieved between neighboring LDs at 3.125 GHz. This is low enough for BER characteristics observed under asynchronous operation of a 4-channel LD array to be no worse than those under single-channel operation. Excellent uniformity of both LD and PD characteristics, high-temperature operation of the LD array, and low-voltage operation of the PD array are also attained. These arrays are suitable for low-cost high-bit-rate parallel optical communications.

Fast packet switches for variable-size packets have become an everyday necessity with the rapid growth in the volume of Internet traffic. Such switches can be designed in two different ways, either by segmenting packets into smaller fixed-size cells and designing packet switches for such cells, or by designing generic packet switches for variable-size packets, where packet segmentation and reassembly can be omitted. The second option is investigated in this paper. The synchronous operation mode with time-limited bulk service is selected. The switching fabric is assumed to be internally non-blocking and provided with input queues. A previous maximum switch throughput analysis has been done under the assumption that the length of the time slot is fixed set to its minimum allowed value (Tmin). In this work, a so-called time-slot stretch factor (SF) is introduced. The actual time-slot length is determined by multiplying Tmin with the SF, where SF. Next, a so-called Internet traffic-source model is proposed based on findings from real IP traffic measurements. The performance implications of the proposed time-slot length modification are analyzed by discrete-event computer simulation. The maximum switch throughput is increased by increasing the SF value, e.g. for uniform packet size distribution and SF=10, the maximum switch throughput is increased from 75% to 97%. The influence of the traffic-source characteristics on the maximum switch throughput is decreased when SF value is increased. In order to prevent any possible throughput degradations, it is advisable to use integer SF values. Packet delay analysis has revealed that by increasing the SF value, the mean packet delay is also increased. Nevertheless, it is shown that the number of switch input and output ports is the most important factor to be considered when packet delay is at stake. Service class differentiation inside investigated packet switch is possible and is not affected by the increasing SF value. Such a packet switch is suitable for implementation in wide area networks, due to high transmission speeds and the small number of switch ports.

In this paper, we propose a novel electronic bearer check system (EBC). This system allows the consumer to pay any amount of money below an upper-boundary on the Internet within an expiration period. During each transaction, the consumer does not need to contact the bank's server. Furthermore, this electronic bearer check can be transferred to any third party. The off-line characteristic of our system is very convenient for the consumer. Moreover, the double spending and double depositing problem will not occur in this system. More importantly, the framework of this system provides anonymity to protect customer privacy.

We fabricated ultrafast nonlinear optical films of squarylium J-aggregates and studied their properties including the absorption spectrum, the refractive index, the third-order nonlinear optical coefficients, the extent of absorption saturation, and the recovery of absorption saturation. The transmittance of the film was increased by 30% due to absorption saturation at a pump energy of several hundreds fJ/µm2/pulse. The half decay time constant of absorption saturation was found to be approximately 100 fs for off-resonant excitation. Two-dimensional demultiplexing was demonstrated using the squarylium film as a switching material. From a train of 8 optical pulses with 100 fs duration and 1 ps interval corresponding to a bit rate of 1 Tbps, 24 spatially resolved spots were obained.

The differentiated services (Diffserv) architecture is a potential solution for providing quality of service (QoS) on the Internet. Most existing studies focus on providing service differentiation among few service classes. In this paper, we propose an approach which can achieve per-flow weighted fair rate allocation in a differentiated services network. Following the design philosophy of the Diffserv model, in the proposed approach core routers do not need to keep per-flow information. An edge router adjusts the transmission rate of a flow based on the feedback carried on control packets, which are inserted by the ingress edge router and returned by the egress edge router. Core routers periodically estimate the fair share rate of each virtual flow and mark the results in control packets. We use both simulations and analysis to evaluate the performance of the proposed approach. The analytical results show that our approach allows a system to converge to weighted fair rate allocations in limited time. Through the simulation results, we can further validate the analytical results, and demonstrate that better throughput can be achieved.

We have focused on the RIO queueing mechanism in statistical bandwidth allocation service, which uses AF-PHB. We have studied the parameterization of RIO to achieve both high throughput and low delay. We were able to parameterize RIO for that purpose in terms of both minth and maxp used in dropping OUT packets. Furthermore, we have also examined the parameterization regarding EWMA (Exponential Weighted Moving Average), i.e., weight factor wqout, and have shown that dropping OUT packets should depend upon the queue length without much delay unlike in RED. From our simulation results, we could see that our parameterization provided high throughput performance and also limited the queue length in a narrow range more effectively.

A tunable external-cavity InGaAs/AlGaAs quantum-well laser using a grating coupler monolithically integrated in a selectively disordered waveguide is demonstrated. The laser consists of an amplifier with a narrow channel for lateral single-mode guiding and a tapered section, a grating coupler for output beam collimation and wavelength dispersion, and an external half mirror. Selective quantum-well disordering technique using SiO2 caps of different thicknesses and rapid thermal annealing was employed to reduce the passive waveguide loss in the grating coupler region. Loss reduction from 40 cm-1 to 3 cm-1 was accomplished. Resultant increase of the grating coupler efficiency and expansion of the effective aperture length led to significant improvement of the laser performances. The maximum output power of 105 mW and wide tuning range of 21.1 nm centered at 997 nm were obtained. The well collimated output beam of full diffraction angles at half maximum of 0.16 0.18 was obtained.

LSR (Label Switching Router)s in MPLS (Multiprotocol Label Switching) networks map arriving IP flows into some labels on Layer 2 switching fabric and establish LSP (Label Switching Path)s. By using LSPs, LSRs not only transmit IP datagrams fast by cut-through mechanism, but also solve traffic engineering issue to optimize the delay of some IP datagram flows. So far, we have analyzed the performance of LSR focusing only on the maximum number of LSPs which can be set on Layer 2. In this paper, we will also consider the bandwidth allocated to each LSP and analyze the IP datagram transmission delay and the cut-through rate of LSR. We suppose the label mapping method as the data-driven scheme in the analytical model, so that the physical bandwidth of LSR is shared by both the default LSP for hop-by-hop transmission and the cut-through LSPs. Thus, we will investigate the impact of the bandwidth allocation among these LSPs on the performance.

Guarantees of quality-of-service (QoS) in the real-time transmission of video on the Internet is a challenging task for the success of many video applications. The Internet Engineering Task Force (IETF) has proposed the Guaranteed Service (GS) in the Integrated Service model with firm delay and bandwidth guarantees. For the GS, it is necessary to provide traffic sources with the capability of calculating the traffic characteristics to be declared to the network on the basis of a limited set of parameters statistically characterizing the traffic and the required level of QoS. In this paper, we develop an algorithm for the evaluation of the traffic parameters which characterize the video stream when a QoS requirement is given. To this end an analytical traffic model for the VBR MPEG video is introduced. Simulation results show that the proposed method can evaluate the traffic parameters precisely and efficiently.

The provisioning of QoS in the Internet is gaining an increasing attention, thus the importance of methods capable of estimating the bandwidth requirement of traffic flows is constantly growing. This information can be used for a wide range of purposes. Admission control, QoS routing and load sharing all need the same basic information in order to be able to make decisions. This paper describes a number of methods that can be used to arrive at precise estimates of the bandwidth requirement focusing on those that are based on the theory of large deviations. A methodology is presented that allows the reformulation of earlier solutions based on the estimation of some form of an overflow probability so that their output becomes a bandwidth-type quantity, the format preferred by Internet control applications. The methodology provides two tracks for the conversion: an indirect method that encapsulates the overflow probability-type approach as an embedded calculation and a direct method that immediately results in the estimate of the bandwidth requirement. The paper introduces a novel method for the direct computation of the bandwidth requirement of Internet traffic flows using the many sources asymptotic regime of the large deviation theory. The direct bandwidth estimator method reduces the computational complexity of the calculations, since it results directly in the bandwidth requirement, allowing the omission of the frequent and costly computation of the buffer overflow probability. The savings arising from the reduction in computational complexity are demonstrated in a numerical example.