In fully connected Multilayer perceptron (MLP), all the hidden units are activated by samples from the whole input space. For complex problems, due to interference and cross coupling of hidden units' activations, the network needs many hidden units to represent the problem and the error surface becomes highly non-linear. Searching for the minimum is then complex and computationally expensive, and simple gradient descent algorithms usually fail. We propose a network, where the input space is partitioned into local sub-regions. Subsequently, a number of smaller networks are simultaneously trained by overlapping subsets of the input samples. Remarkable improvement of training efficiency as well as generalization performance of this combined network are observed through various simulations.

For mobile communication systems with code division multiple access (CDMA), a new modulation scheme, π/2-shift BPSK, is proposed. The performance has been evaluated in terms of relative out-of-band power, bit-error rate (BER), and spectral efficiency. As the result, it is shown that the proposed scheme has an advantage over conventional BPSK, conventional QPSK, and π/4-shift QPSK under nonlinear amplification.

The construction of fault-tolerant processor arrays with interconnections of cube-connected cycles (CCCs) by using an advanced spare-connection scheme for k-out-of-n redundancies called "generalized additional bypass linking" is described. The connection scheme uses bypass links with wired OR connections to spare processing elements (PEs) without external switches, and can reconfigure complete arrays by tolerating faulty portions in these PEs and links. The spare connections are designed as a node-coloring problem of a CCC graph with a minimum distance of 3: the chromatic numbers corresponding to the number of spare PE connections were evaluated theoretically. The proposed scheme can be used for constructing various k-out-of-n configurations capable of quick broadcasting by using spare circuits, and is superior to conventional schemes in terms of extra PE connections and reconfiguration control. In particular, it allows construction of optimal r-fault-tolerant configurations that provide r spare PEs and r extra connections per PE for CCCs with 4x PEs (x: integer) in each cycle.

The authors previously proposed a reconfigurable architecture called the "XL-scheme" in order to cope with processor element (PE) faults as well as link faults. However, they described an algorithm for compensating only for link faults. They determined the potential ability to tolerate faults of the XL-scheme for simultaneous faults of links and PEs, and left a reconstruction algorithm for simultaneous PE and link faults to be studied in the future. This paper briefly explains the XL-scheme and gives a reconstruction algorithm for simultaneous PE and link faults. The algorithm first replaces faulty PEs with healthy ones and then replaces faulty links with healthy ones. We then compute the reliabilities of the mesh-arrays with simultaneous PE and link faults by simulation. We compare the reliability of the XL-scheme with that of the one-and-half track switch model. It is seen that the former is much larger than the latter. Furthermore, we show the result for processing time.

Methods of automatically adjusting delay time and feedback gain in controlling chaos by delayed feedback control are proposed. These methods are based on a gradient-descent procedure minimizing the squared error between the current state and the delayed state. The method of adjusting delay time and that of adjusting feedback gain are applied to controlling chaos in numerical calculations of Rossler Equation and Duffing equation, respectively. Both methods are confirmed to be successful.

JUMP-1 is currently under development by seven Japanese universities to establish techniques for building an efficient distributed shared memory on a massively parallel processor. It provides a coherent cache with reduced hierarchical bit-map directory scheme to achieve cost effective and high performance management. Messages for coherent cache are transferred through a fat tree on the RDT (Recursive Diagonal Torus) interconnection network. RDT router supports versatile functions including multicast and acknowledge combining for the reduced hierarchical bit-map directory scheme. By using 0.5µm BiCMOS SOG technology, it can transfer all packets synchronized with a unique CPU clock (50MHz). Long coaxial cables (4m at maximum) are directly driven with the ECL interface of this chip. Using the dual port RAM, packet buffers allow to push and pull a flit of the packet simultaneously.

A novel approach to the cache coherent Multistage Interconnection Network (MIN) called the MINC (MIN with Cache control mechanism) is proposed. In the MINC, the directory is located only on the shared memory using the Reduced Hierarchical Bit-map Directory schemes (RHBDs). In the RHBD, the bit-map directory is reduced and carried in the packet header for quick multicasting without accessing the directory in each hierarchy. In order to reduce unnecessary packets caused by compacting the bit map in the RHBD, a small cache called the pruning cache is introduced in the switching element. The simulation reveals the pruning cache works most effectively when it is provided in every switching element of the first stage, and it reduces the congestion more than 50% with only 4 entries. The MINC cache control chip with 16 inputs/outputs is implemented on the LPGA (Laser Programmable Gate Array), and works with a 66 MHz clock.

In this letter, the absolute exponential stability result of neural networks with asymmetric connection matrices is obtained, which generalizes the existing one about absolute stability of neural networks, by a new proof approach. It is demonstrated that the network time constant is inversely proportional to the global exponential convergence rate of the network trajectories to the unique equilibrium. A numerical simulation example is also given to illustrate the obtained analysis results.

An analytic traffic model is presented to estimate the soft handoff rate in DS-CDMA cellular systems. The model is based on the fact that a mobile in soft handoff call is connected to two cell sites when it is in an overlapped region. The handoff rate is estimated by the mobility of mobiles, which is a function of the size and shape of cell area, and the call density and speed of mobiles in the area. Simulation results show good agreement with the analytical model.

This paper presents a clock routing technique called Balanced-Mesh Method (BMM) which incorporates the advantages of two famous conventional-clock-routing techniques. One is the balanced-tree method (BTM) where the clock net is routed as a tree so that the delay times of clock signal are balanced, and the other is the fixed-mesh method (FMM) where the clock net is routed as a fixed mesh driven by a large buffer. In BMM, the clock net is routed as a set of relatively small meshes of interconnects driven by relatively small buffers. Each mesh covers an area called a Mesh-Routing Region (MR) in which its delay and skew can be suppressed within a certain range. These small meshes are connected by a balanced tree with the chip clock source as its root. To implement BMM, we developed an MR-partitioning program that partitions the circuit into MR's according to a set of pre-determined constraints on the number of flip-flops and the area in each MR, and a clock-global-routing program that provides each mesh routing and the tree routing connecting meshes. We applied BMM to the design of an MPEG2-encoder LSI and achieved a skew of 210ps. In addition, the experimental results show BMM yields the lowest power dissipation compared to conventional methods.

A new cost function based on multi-band decomposition of the estimation error and application of a different step-size for each band is used in connection with the least-mean-square criterion to improve the fidelity of estimates as compared to those obtained with conventional least-mean-square adaptive algorithms. The basic new idea is to trade off time and frequency resolutions of the adaptive algorithm along the frequency domain by using different step-sizes in the analysis of distinct frequencies in accordance with the frequency-localized statistical behavior of the imput signal. The mathematical background for a stochatic approach to the multi-band decomposition-based scheme is presented and algorithms with fixed and variable step-sizes are derived. Computer experiments compare the performance of multiband and conventional least-mean-square methods when applied to system identification.

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.

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.

Recently, the number of users utilizing mobile communication services has increased greatly in many information and communication fields. In the future, the number of mobile communication system users will increase even faster, until the rate of diffusion ultimately reaches that of telephones. The day that each person has his own portable mobile terminal is not so far off. Moreover, the systems will not only be used as telephones but also as mobile computing for multimedia information. Digitalization technologies of mobile communication systems needed to realize such mobile computing will be introduced in this paper.

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.

Efforts have been cumulated to measure tooth mobility, in order to accurately characterize the mechanical features of periodontal tissues. This paper provides a totally new technique for accomplishing the task of measuring tooth displacement in 6 degrees of freedom, using a range finder. Its intraoral equipment comprises two elements, a moving polyhedron and a referential device, both of which are secured to a subject tooth and several other teeth splinted together. The polyhedron has 6 planar surfaces, each oriented in a distinctly different direction, with each plane facing an opposing range finder mounted on the referential part. If the sensor geometry is provided, the position and orientation of the movable part, vis-a-vis the reference, can be determined theoretically from the distances between all the range finders and their opposing surfaces. This computation was mathematically formulated as a non-linear optimization problem, the numerical solution of which can be obtained iteratively. Its error-propagation formula was also provided as a linear approximation.

Electroluminescent (EL) devices with mixed single layer that consist of fluorescent dyes, distylylbiphenyl derivative (DPVBi) and triphenylamine derivative (TPD), are studied. Blue light emission was observed from the device with DPVBi and TPD. White emission over 2,500 cd/m2 was observed from the devices with mixed single layer of DPVBi, TPD and dicyanomethylene derivative (DCM).

Within the framework of a previously proposed vision system, a new part-segmentation algorithm, that breaks an object defined by its contour into its constituent parts, is presented. The contour is assumed to be obtained using an edge detector. This decomposition is achieved in two stages. The first stage is a preprocessing step which consists of extracting the convex dominant points (CDPs) of the contour. For this aim, we present a new technique which relaxes the compromise that exists in most classical methods for the selection of the width of the Gaussian filter. In the subsequent stage, the extracted CDPs are used to break the object into convex parts. This is performed as follows: among all the points of the contour only the CDPs are moved along their normals nutil they touch another moving CDP or a point on the contour. The results show that this part-segmentation algorithm is invariant to transformations such as rotation, scaling and shift in position of the object, which is very important for object recognition. The algorithm has been tested on many object contours, with and without noise and the advantages of the algorithm are listed in this paper. Our results are visually similar to a human intuitive decomposition of objects into their parts.

Introducing a mathematical model of noise in stereo images, we propose a new criterion for intelligent statistical inference about the scene we are viewing by using the geometric information criterion (geometric AIC). Using synthetic and real-image experiments, we demonstrate that a robot can test whether or not the object is located very far away or the object is a planar surface without using any knowledge about the noise magnitude or any empirically adjustable thresholds.

This paper describes a method to distinguish phase noise and amplitude noise from total oscillator noise in circuit simulation, and derives general relationships between periodic time-varying transfer functions for oscillators and phase and amplitude noises.