Several gateway-based congestion control mechanisms have been proposed to support an end-to-end congestion control mechanism of TCP (Transmission Control Protocol). One of promising gateway-based congestion control mechanisms is a RED (Random Early Detection) gateway. Although effectiveness of the RED gateway is fully dependent on a choice of control parameters, it has not been fully investigated how to configure its control parameters. In this paper, we analyze the steady state behavior of the RED gateway by explicitly modeling the congestion control mechanism of TCP. We first derive the equilibrium values of the TCP window size and the buffer occupancy of the RED gateway. Also derived are the stability condition and the transient performance index of the network using a control theoretic approach. Numerical examples as well as simulation results are presented to clearly show relations between control parameters and the steady state behavior.

Besides single byte errors which are caused by single chip failures, semiconductor memories used in some applications, such as satellite memory systems, are highly vulnerable to random double bit errors. It is therefore necessary to design Double bit Error Correcting--Single b-bit byte Error Correcting (DEC-SbEC) codes which correct both random double bit errors and single b-bit byte errors. This correspondence proposes a class of generic DEC-SbEC codes that are applicable to computer memory systems using recent high density DRAM chips with wide I/O data, such as, 8, 16 or 32 bits per chip. The proposed DEC-S8EC codes are suitable for memory systems using DRAM chips with 8-bit I/O data, and require 24 check bits for practical information lengths such as 64 and 128 bits.

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.

Progress on a single wavelength channel OTDM terabit/s transmission is described. In particular, we focus on 1.28 Tbit/s OTDM transmission over 70 km which we realized recently. A pre-chirping technique using a high speed phase modulator is emphasized to simultaneously compensate for third- and fourth-order dispersion. The input pulse width was 380 fs, and the pulse broadening after a 70 km transmission was as small as 20 fs. All 128 channels time-division-demultiplexed to 10 Gbit/s had a bit error rate of less than 110-9, in which we employed a lot of new technique for pulse generation, dispersion compensation and demultiplexing. These techniques help pave the path for OTDM technology of the 21 century.

We propose a call admission control (CAC) scheme for the reverse link of direct sequence-code division multiple access (DS-CDMA) systems with multi-class traffic, in which the admissibility of the set of requested channels is decided by checking the outage probability of the total composite power at a cell-site receiver. The reverse link capacities under various traffic conditions are evaluated. From numerical results, we see that the proposed scheme can utilize a given radio resource more effectively as compared with the existing scheme using constraints on the individual power levels.

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.

In this paper, we propose a channel assignment scheme for integrated voice and data traffic in reservation multiple access protocol. In the proposed scheme, a voice packet never contends with a data packet and takes over the slot which is previously assigned to a data packet. Thus, a larger number of voice terminals can be accommodated without degradation of quality and throughput even in the situation that data were integrated. We evaluate the voice packet dropping probability, throughput and packet delay through computer simulation. The results show that the proposed scheme has better performance than the conventional PRMA and DQRUMA systems.

Teletraffic characteristics of a mobile packet communication network, which supports mobile Internet, were quantitatively evaluated by using a terminal migration model in which the cell dwell time possesses self-similarity. I used a migration model in which the migration speed of the terminal is determined by the density of the dwell terminals in a cell (determined from measured vehicular mobility characteristics). The transmission rates per terminal in a cell were estimated as teletraffic on the mobile packet communication networks using this migration model. I found that when there is self-similarity in the terminal cell dwell time, communicating terminals may be concentrated in the cell and restricted for an indefinite period of time to using only a narrow bandwidth.

The purpose of our study is to estimate the imaging of ischemic myocardial muscles in rats. The magnetocardiograms (MCG) of rats were measured by a 12-channel high resolution gradiometer, which consisted of 5 mm diameter pick-up coils with a 7.5 mm distance between each coil. MCGs of seven male rats were measured in a magnetically shielded room pre and post coronary artery occlusion. The source imaging was estimated by minimum norm estimation (MNE). Changes of the current source imaging pre- and post coronary artery occlusion were clarified. As a result, in the ST segment, the current distribution significantly increased at the ischemic area. In the T wave, the direction of the current distribution clearly shifted to the left thorax. We proved that the increased area of the current distribution in the ST segment was related to the ischemic area of the ventricular muscles.

In this paper we discuss how one can delegate his power to authenticate or sign documents to others who, again, can delegate the power to someone else. A practical cryptographic solution would be to issue a certificate that consists of one's signature. The final verifier checks verifies the chain of these certificates. This paper provides an efficient and provably secure scheme that is suitable for such a delegation chain. We prove the security of our scheme against an adaptive chosen message attack in the random oracle model. Though our primary application would be agent systems where some agents work on behalf of a user, some other applications and variants will be discussed as well. One of the variants enjoys a threshold feature whereby one can delegate his power to a group so that they have less chance to abuse their power. Another application is an identity-based signature scheme that provides faster verification capability and less communication complexity compared to those provided by existing certificate-based public key infrastructure.

In Chirp-Pulse Microwave Computed Tomography (CP-MCT) the images are affected by the blur which is inherent to the measurement principle and is described by a space-variant Point Spread Function (PSF). In this paper we investigate the PSF of CP-MCT including the space dependence both experimentally and computationally. The experimental evaluation is performed by measuring the projections of a target consisting of a thin low-loss dielectric rod surrounded by a saline solution and placed at various positions in the measuring region. On the other hand, the theoretical evaluation is obtained by computing the projections of the same target via a numerical solution of Maxwell's equations. Since CP-MCT uses a chirp signal, the numerical evaluation is carried out by the use of a FD-TD method. The projections of the rod could be obtained by computing the field during the sweep time of the chirp signal for each position of the receiving antenna. Since this procedure is extremely time consuming, we compute the impulse response function of the system by exciting the transmitting antenna with a wide-band Gaussian pulse. Then the signal transmitted in CP-MCT is obtained by computing the convolution product in time domain of the input chirp pulse with the impulse response function of the system. We find a good agreement between measured and computed PSF. The rationality of the computed PSF is verified by three distinct ways and the usefulness of this function is shown by a remarkable effect in the restoration of CP-MCT images. Knowledge on the space-variant PSF will be utilized for more accurate image deblurring in CP-MCT.

Space-variant approaches subject to local image characteristics are useful in practical image restoration because many natural images are nonstationary. Motivated by the success of denoising approaches in the wavelet domain, we propose a region-adaptive restoration approach which adopts a wavelet denoising technique in flat regions after an under-regularized constrained least squares restoration. Experimental results verify that this approach not only improves image quality in mean square error but also contributes to ringing reduction.

Confocal laser scanning microscope (CLSM) is capable of delivering a high axial resolution, and with this instrument even thin layers of cells can be imaged in good quality. Therefore, intracellular uptake and distribution properties of photosensitizer zinc coproporphyrin III tetrasodium salt (Zn CP-III) in human lung small cell carcinoma (Ms-1) were examined by using CLSM. In particular, the uptake of Zn CP-III in cytoplasm, plasma membrane, and nucleus was individually evaluated for the first time from fluorescence images obtained by CLSM. The results show that the Zn CP-III content in three cellular areas correlates with extracellular Zn CP-III concentration and time of incubation with Zn CP-III. Furthermore, it was found that the cytoplasmic fluorescence was approximately two times higher than that in the nucleus under all uptake conditions. In addition, cellular accumulation of Zn CP-III was compared with photodynamic cytotoxicity. The photocytotoxicity was to a great extent dependent on the uptake of the photosensitizer. The damaged site of Ms-1 cells induced by photodynamic therapy was plasma membrane. However, the content of Zn CP-III accumulated in cytoplasm was the highest among the three areas, implying that, besides the direct damage on plasma membrane, an oxidative damage to cellular component arose from the cytoplasmic Zn CP-III may also play an important role in photocytotoxicity. The quantitative information obtained in this study will be useful for further investigation of the photocytotoxicity as well as the uptake mechanism of photosensitizer.

We applied control theory to nerve-muscle in order to model and systematize the muscle system. The association between nerve stimulation frequencies and electromyogram (EMG) amplitude was studied in rat nerve-muscle under normal and hypokalemic conditions. From these results, we modeled the nerve-muscle and simulated frequency response from the nerve-muscle system which can be expressed as a closed loop transfer function.

There were researches that measured effort required to understand and adapt components based on the complexity of the component, which is some general criterion related to the intrinsic quality of the component to be adapted and understood. They, however, don't consider significance of the measurement attributes and user must decide reusability of similar components for himself. Therefore, in this paper, we propose a new method that can measure the DOR (Degree Of Reusability) of the components by considering the significance of the measurement attributes. We calculates the relative significance of them by using rough set and integrate the significance with the measurement value by using Sugeno's fuzzy integral. Lastly, we apply our method to the source code components and show through statistical technique that it can be used as the ordinal and ratio scale.

Human tissues conduct electricity about as well as semiconductors. However, there are large differences between tissues which have recently been shown to be determined mainly by the structure of the tissue. For example, the impedance spectrum of a layered tissue such as skin is very different to that of the underlying tissues. The way in which the cells are arranged and also the size of the nucleus are both important. Some of the recent developments in measurement and modelling techniques are described and the relationship between tissue structures and impedance spectra is outlined. The illustrations and examples look at the effect of premalignant changes on localised impedance spectra measured from cervical tissues. Electrical Impedance Tomographic measurements on lung tissue are used to show the maturational changes of lung structure in neonates. The conclusion contains some speculation as to what further research outcomes might occur over the next few years.

This paper presents a method to analyze volumetrically evolutions of pulmonary nodules for discrimination between malignant and benign nodules. Our method consists of four steps; (1) The 3-D rigid registration of the two successive 3-D thoracic CT images, (2) the 3-D affine registration of the two successive region-of-interest (ROI) images, (3) non-rigid registration between local volumetric ROIs, and (4) analysis of the local displacement field between successive temporal images. In the preliminary study, the method was applied to the successive 3-D thoracic images of two pulmonary nodules including a metastasis malignant nodule and a inflammatory benign nodule to quantify evolutions of the pulmonary nodules and their surrounding structures. The time intervals between successive 3-D thoracic images for the benign and malignant cases were 150 and 30 days, respectively. From the display of the displacement fields and the contrasted image by the vector field operator based on the Jacobian, it was observed that the benign case reduced in the volume and the surrounding structure was involved into the nodule. It was also observed that the malignant case expanded in the volume. These experimental results indicate that our method is a promising tool to quantify how the lesions evolve their volume and surrounding structures.

This paper reports on clich and related mechanisms appearing in a process of human design of software. During studies on human design knowledge, the authors found frequent instance of same pattern of detailing, named clich. In our study, clich is an intermediate level of design knowledge, during a hierarchical detailing step, residing in between simple reuse and creation by micro design rules, which have already been reported. These three kinds of design knowledge are of various types and have different complexities. Discussions on them, focusing on clich type, with procedures of formation of a simple clich skeleton and generation of a clich are given. The studies show a working model of Zipf's principle, and are some trials to reveal a more detail of human designs.

We propose new lossless medical image compression method based on hierarchical sorting technique. Hierarchical sorting is a technique to achieve high compression ratio by detecting the regions where image pattern varies abruptly and sorting pixel order by its value to increase predictability. In this method, we can control sorting accuracy along with size and complexity. As the result, we can reduce the sizes of the permutation-tables and reuse the tables to other image regions. Comparison using experimental implementation of this method shows better performance for medical image set measured by X-ray CT and MRI instruments where similar sub-block patterns appear frequently. This technique applies quad-tree division method to divide an image to blocks in order to support progressive decoding and fast preview of large images.

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.