This letter describes a new computational method to obtain the bifurcation parameter value of a limit cycle in nonlinear autonomous systems. The method can calculate a parameter value at which local bifurcations; tangent, period-doubling and Neimark-Sacker bifurcations are occurred by using properties of the characteristic equation for a fixed point of the Poincare mapping. Conventionally a period of the limit cycle is not used explicitly since the Poincare mapping needs only whether the orbit reaches a cross-section or not. In our method, the period is treated as an independent variable for Newton's method, so an accurate location of the fixed point, its period and the bifurcation parameter value can be calculated simultaneously. Although the number of variables increases, the Jacobian matrix becomes simple and the recurrence procedure converges rapidly compared with conventional methods.

The dipole-dipole interaction among excitons is shown to give rise to an intrinsic nonlinearity, which yields a localized mode in a forbidden band, providing a coherent state for quantum computation. Employing this mode, a quantum XOR (exclusive OR) gate is proposed. A block structure of quantum dot arrays is also proposed, to implement quantum circuits comprising the quantum XOR gates for computation.

A modified frequency domain method for analyzing nonlinear waveform distortion in a magnetic recording process is presented. The measurement technique combines a 5th harmonic measurement technique, which uses a specific 30-bit pattern including dibits, and a precompensation technique for the dibits. The 5th harmonic voltage ratio given by the former technique includes the amount of NLTS (Nonlinear transition shift) and PE (Partial erasure) in dibits. The latter precompensation technique is employed to evaluate the PE as the minimum in the 5th harmonic voltage ratio. The true NLTS can be estimated from the amount of distortion and the evaluated PE. The high accuracy of the technique was confirmed by an examination using a pulse pattern generator with varied phase and amplitude. Finally, the effects of medium properties such as coercivity and squareness on the nonlinear distortions have been investigated by applying the technique to particulate flexible media. The NLTS increased with squareness from 3.5% to 7% while PE was less than 6% for any squareness at a recording density of 76 kFRPI. When coercivity became large, NLTS and PE decreased. The direction of NLTS for Ba-ferrite media agreed with that for a perpendicular Co-Cr thin-film medium.

Time decay of magnetic properties in perpendicular magnetic recording media was studied. It was suggested that magnetization in media with a low energy ratio, KV/kT, of 50 is thermally stable in the absence of a demagnetizing field while coercivity exhibits a large time dependence. Magnetization in perpendicular recording media exhibited an appreciable time decay even for films with a large energy ratio of 300. The decay is attributed to the small perpendicular squareness due to a large perpendicular demagnetizing field acting in the media. The recording density dependence of the time decay in the output was explained in terms of the change in the demagnetizing field with the density. It is concluded that the use of media with large squareness as well as large energy ratio effectively reduces time decay in the output.

In this paper, we propose a new switching network architecture with output queueing, The proposed switch, FBSF (FAB Banyan Switching Fabrics) can deliver up to 2r packets simultaneously destined for the same outlet in a single time slot. The switch fabrics consist of Batcher sorter, a radix-r double shuffle network r-packet distributors, two FAB networks, and output buffer modules. The performance of the switch fabric is evaluated by measures of throughput, average queue length, average waiting time, and packet loss rate. Numerical and simulation results indicate that the switch exhibits very good delay-throughput performance over a wide range of input traffic.

This paper first proposes a new approach to designing high-quality, low-diameter, small mean-internode-distance (MID), k-subcubic-connected cyclic networks. The approach is a modification of the k-cubic-connected cyclic (k-ccc) network in which there are N=k2k-1 instead of N=k2k nodes in the k-ccc network. The special features of this network are: (1) It fills the gap between the number of nodes in k-ccc and (k+1)-ccc networks, but retains a constant number of link (3) per node in the network, (2) it allows higher quality, smaller diameters and mean internode distances hypercube networks with the same numbers of nodes. A second novel approach consists of a k+-sccc network with the same number of nodes as the k-ccc but with smaller diameters and mean internode distances. A generalized k-ccc network formed by nodes N=k2m is introduced for n-cube and k-ccc (modified or normal) networks that allows minimum network quality to be obtained where m may or may not equal to k. A routing algorithm for 4-sccc is also presented.

For the solutions of linear systems of equations with unsymmetric coefficient matrices, we propose an improved version of the quasi-minimal residual (IQMR) method by using the Lanczos process as a major component combining elements of numerical stability and parallel algorithm design. For Lanczos process, stability is obtained by a coupled two-term procedure that generates Lanczos vectors scaled to unit length. The algorithm is derived such that all inner products and matrixvector multiplications of a single iteration step are independent and communication time required for inner product can be overlapped efficiently with computation time. Therefore, the cost of global communication on parallel distributed memory computers can be significantly reduced. The resulting IQMR algorithm maintains the favorable properties of the Lanczos process while not increasing computational costs. The efficiency of this method is demonstrated by numerical experimental results carried out on a massively parallel distributed memory computer, the Parsytec GC/PowerPlus.

Many network protocols for routing messages have been proposed for mobile computing environments. In this paper, we consider the query processing strategy which operates over these network protocols. To begin with, we introduce five fundamental location update methods based on ideas extracted from the representative network protocols. They are the single broadcast notification (SBN), the double broadcast notification (WBN), the single default notification (SDN), the double default notification (WDN), and the no notification (NN). As a network protocol, each method is strong in performance in some system enrivonment, but weak in others. In practical situations, where various kinds of applications are used for various purposes, however, it is required to use a single method. We therefore propose an adaptive query processing strategy where these five location update methods can be dynamically selected. Moreover, we analyze the performance of this adaptive query processing strategy via the Markov chain. We also use the statistical approach to estimate the traffic of individual hosts. Finally, we show the efficiency of our proposed strategy over a wide area of system environments.

This paper compares three cell transfer quality control schemes, namely HPS, DAS and ORS, which integrate a preventive congestion control and a reactive congestion control in ATM switch. Simulation results showed that ORS achieves the largest network utilization, and HPS provides enough large throughput compared with DAS only when many VBR connections are multiplexed.

Given the tremendous growth in the cellular phone system and the Personal Hadny-phone System (PHS), it is to be expected that demands for mobile computing using those wireless infrastructures, that is mobile computer access, will dramatically increase. This paper describes high-quality and high-speed data transmission technology for PHS mobile computing and current PHS data transmission standardization activities. Furthermore, wireless agent communication and a service example are presented together with the concept of background communication for the coming wireless multimedia services.

In this paper, a new trial for the signal processing is proposed along the same line as a previous study on the extended regression analysis based on the Bayes' theorem. This method enables us to estimate a response probability property of complicated systems in an actual case when observation values of the output response are roughly observed due to the quantization mechanism of measuring equipment. More concretely, the main purpose of this research is to find the statistics of the joint probability density function before a level quantization operation which reflects every proper correlation informations between the system input and the output fluctuations. Then, the output probability distribution for another kind of input is predicted by using the estimated regression relationship. Finally, the effectiveness of the proposed method is experimentally confirmed by applying it to the actually observed input-output data of the acoustic system.

A multicast (point-to-multipoint) protocol of a satellite broadcast channel by a source and many destinations is presented and its performance characteristics are analyzed. We propose a new time-domain multicast scheme for packet satellite channels, retransmission via collisions protocol (called RVCP). RVCP is classified to the automatic repeat request (ARQ) of the multi-selective-repeat scheme and does not require individual channels for each receiving station to request for broadcast packets that have been received incorrectly. Our analytical models show that RVCP performs considerably better than the other protocols, particularly in the situation that packet error rate is less than 10-4 or there are a large number of destinations. It is an excellent characteristic of RVCP that the equipment of the source station need not increase in proportion to the number of destinations, too. And since RVCP is a relatively simple protocol, it is easy to be implemented.

A new compression algorithm for fingerprint images is introduced. A modified wavelet packet scheme which uses a fixed decomposition structure, matched to the statistics of fingerprint images, is used. Based on statistical studies of the subbands, different compression techniques are chosen for different subbands. The decision is based on the effect of each subband on reconstructed image, taking into account the characteristics of the Human Visual System (HVS). A noise shaping bit allocation procedure which considers the HVS, is then used to assign the bit rate among subbands. Using Lattice Vector Quantization (LVQ), a new technique for determining the largest radius of the Lattice and its scaling factor is presented. The design is based on obtaining the smallest possible Expected Total Distortion (ETD) measure, using the given bit budget. At low bit rates, for the coefficients with high-frequency content, we propose the Positive-Negative Mean (PNM) algorithm to improve the resolution of the reconstructed image. Furthermore, for the coefficients with low-frequency content, a lossless predictive compression scheme is developed. The proposed algorithm results in a high compression ratio and a high reconstructed image quality with a low computational load compared to other available algorithms.

Mixed Quasi Newton simulation algorithm that is capable of calculating analog circuits containing mixed level of element models is presented. Conventional circuit simulators usually apply Newton method to solve nonlinear system equations resulted from circuit equations. At each Newton iteration step, it is necessary to reevaluate the Jacobian stamp of circuit elements. However, obtaining the Jacobian stamp of elements described by complex behavior models is a computationally expensive process. To reduce the number of Jacobian evaluations, we combine Newton method and Quasi-Newton method as a new updating scheme. The simulation results show that our algorithm can reduce the number of Jacobian evaluations and improve the simulation time, particularly when simulating circuits containing many behavior model elements.

A new Neural Network Equalizer (NNE), employing multilayer feedforward neural network, is proposed as a compensation method for nonlinear and multipath distortion that arises from FTTA (Fiber To The Air) system. If a signal in a channel is affected by nonlinear distortion, the conventional Decision Feedback Equalizer (DFE) finds difficulty in perfect compensation of it. To compensate for nonlinear distortion as well as multipath distortion, an equalizer, employing neural network, is investigated. A new neural network equalizer, yielding a cubic function as unit output function, is proposed in order to compensate the nonlinear distortion effectively. We also propose an initial weights of neural network for preventing from local minimum. Computer simulation results show that the compensation performance of the new NNE is superior to the conventional DFE and the conventional NNE.

This paper describes the performance of a video communication system over mobile radio channels. Mobile channel quality changes rapidly due to various factors. When compressed video data is transmitted through these channels, it is indispensable to employ an error control scheme because reconstructed video quality is seriously degraded by channel error. To control this error, an automatic repeat request (ARQ) scheme is often employed, however, this incurs a cost. The benefit of a non-degraded reconstructed video sequence is offset by the transmission delay due to ARQ retransmission. We apply to a video communication system a selective-repeat ARQ which is combined with the coding control scheme to reduce the transmission delay. We evaluate the quality of the reconstructed video sequence and transmission delay using computer simulations and make clear its applicability over Rayleigh and Nakagami-Rican fading channels and intersymbol interference.

This paper proposes a differentially-coded-quadrature-phase-shift-keying (DQPSK) coherent demodulator using a new simultaneous carrier and bit-timing recovery scheme (SCBR). The new DQPSK SCBR (DSCBR) scheme works with a frequently used preamble, whose baseband signal alternates between two diagonal decision points, for example, a repeated bit-series of "1001." With the DSCBR scheme, the proposed demodulator achieves a significantly agile carrier and bit-timing recovery using an open-loop approach with a one-part preamble. To illustrate this, a preamble of 8 symbols is applicable with the Eb/No degradation from the theory over AWGN of 0.2 dB. It is also shown that the proposed demodulator achieves an improvement in the required Eb/No of more than 2 dB over differential detection over Ricean fading communication channels. The channels are modeled for wireless broadband communication systems with directional antennas or line of sight (LOS) paths. This paper concludes that the proposed demodulator is a strong candidate for receivers in wireles broadband communication systems.

In this paper, the evaluation of a hybrid acquisition performance has been considered for the pilot signal in direct sequence code division multiple access (DS/CDMA) forward link. The hybrid acquisition is introduced by the combination of two schemes, parallel and serial acquisitions. The mean acquisition time of the hybrid acquisition scheme is derived to consider both case 1 (the correct code-phase offsets ae included in one subset) and case 2 (the correct code-phase offsets exist at the boundary of two subsets), which are caused by the distribution of the correct code-phase offsets between two subsets. Detection, false alarm, and miss probabilities are derived for the cases of multiple correct code-phase offsets and multipath Rayleigh fading channel. Results are provided for the acquisition performance with respect to system design parameters such as postdetection integration length in the search and verification modes, subset size, and number of I/Q noncoherent correlators. Also, comparision between hybrid acquisition and parallel acquisition under the same hardware complexity is provided in terms of the minimum mean acquisition time.

When moving images are displayed on color PDPs, motional artifacts such as disturbances of gray scales and colors are often observed. Reduction of the disturbances is essential in achieving PDPs with acceptable picture quality for TV use. The moving picture quality has been improved by using a modified-binary-coded light-emission-period scheme and a 3dimensional (2D in space and 1D in time) scattering technique. In the 10-sub-field modified-binary-code scheme for 256 gray level expression, sub-field B (of period equivalent to 64) and C (128) of conventional 8-sub-field binary-coded scheme are added and then re-distributed into four sub-fields D (48). The modifiedbinary-coded scheme therefore has the light-emitting-period ratio 1:2:4:8:16:32:48:48:48:48. The maximum period, 128 of the conventional, is reduced to 48. By using the modified-binary-coded scheme, the motional artifacts are reduced significantly, but still perceptible because they appear in forms of continuous lines. In order to make the disturbance less conspicuous, a 3D scattering technique is introduced. The technique has been made possible because of the redundancies of the modified-binary-coded scheme: namely, (1) the position of sub-field-block A (63) can be placed at one of the five positions among four sub-fields D (48), (2) there are various choices when newly assigning one of the four sub-fields D, (3) one can arbitrarily choose whether or not to assign a new sub-field D between the gray levels 48-63, 96-111, 144-160, and 192-207. By randomly selecting one of these emission patterns, the disturbances change their forms from continuous lines to scattered dots. The randomization can be performed at each horizontal line of the display, at each vertical line, at each pixel, of at each TV field. An appreciable improvement of moving picture quality has been realized without influencing the still image.

An extension is made for a set of systems that have a quadratic Lyapunov function in common for the purpose of analysis and design. The nominal set of system matrices comprises stable symmetric matricies, which admit a hyperspherical Lyapunov function. Based on stability robustness results, sets of matrices are constructed so that they share the same Lyapunov function with the nominal ones.