A Hierarchical Cubic Network (HCN) is a hierarchical hypercube network proposed by Ghose. The HCN is topologically superior to many other similar networks, in particular, the hypercube. It has a considerably lower diameter than a comparable hypercube and is realized using almost half the number of links per node as a comparable hypercube. In this paper, we propose the shortest routing algorithm in HCN(n, n) and show that the diameter of HCN(n, n) with 22n nodes is n(n1)/31 which is about 2/3 of that of a comparable hypercube. We also propose the optimal routing algorithm in HCN(m, n) where mn and obtain that its diameter is n(m1)/31. Typical parallel algorithms run in HCN(m, n) with the same time complexity as a hypercube and the hypercube topology can be emulated with O(1) time complexity in it.

In this paper, we propose a method, called Kernel Hidden Unit Analysis, to reduce the network size. The kernel hidden unit analysis in composed of two principal components: T-component and S-component. The T-component transforms original networks into the networks which can easily be simplified. The S-component is used to select kernel units in the networks and construct kernel networks with kernel units. For the T-component, an entropy function is used, which is defined with respect to the state of the hidden units. In a process of entropy minimization, multiple strongly inhibitory connections are to be generated, which tend to turn off as many units as possible. Thus, some major hidden units can easily be extracted. Concerning the S-component, we use the relevance and the variance of input-hidden connections and detect the kernel hidden units for constructing the kernel network. Applying the kernel hidden unit analysis to the symmetry problem and autoencoders, we perfectly succeeded in obtaining kernel networks with small entropy, that is, small number of hidden units.

Efficiency of network resource can be improved by statistical multiplexing in ATM networks. If cell traffic characteristics of each connection could be obtained beforehand, we could admit maximum connections while satisfying the QoS (Quality of Service) objective. Since such traffic characteristics as an average rate and a mean burst length are difficult to anticipate, only peak rate will be used for CAC (connection admission control). The peak rate assignment strategy will, however, lead to inefficient network utilization for bursty traffic. This paper proposes an adaptive admission control using real-time traffic measurements to overcome the above problem. This scheme is based on two-state cell stream model composed of overload and underload states. The two-state model simplifies the measuring algorithm, which is suited for online processing. Performance of this scheme is investigated through simulation study for multiplexing of on-off sources with a wide spectrum of traffic characteristics. Since the proposed control scheme exploits measurements of cell streams, it achieves nearly optimum bandwidth efficiency.

A number of flexible control mechanisms used in buffer management, congestion control and bandwidth allocation have been proposed to improve the performance of ATM networks by introducing parameters, such as threshold, push-out probability and incremental bandwidth size of a virtual path, which are adjustable by network providers. However, it is difficult to adaptively adjust these parameters, since the traffic in ATM networks is further complicated by accommodating various kinds of services. To overcome the problem, we propose in this paper a control scheme based on the genetic algorithms and the neural estimator. The neural estimator forecasts the future QOS values for each candidate parameter set, and the genetic algorithms select the best one to control the real network. An example of buffer management in an ATM switch is examined in this paper. Simulation results show the effectiveness of the proposed control scheme in adaptively adjusting the parameter set even when the traffic environment and the QOS requirements are dynamically changing.

The recent progress of B-ISDN signaling systems has enabled networks to handle calls which require a wide variety of ATM connection sets. This paper is concerned with the circuit group which handles calls requesting asymmetric forward and backward multi-connections, and has the capability of both bandwidth negotiation and bandwidth reservation as a traffic control for enhancing call blocking performance. A model of the circuit group is first established focusing on the call level characteristics of the group, and then a method based on the reduced load approximation and an approximate analysis of a multirate group is proposed for calculating approximate blocking probabilities. The accuracy of the approximation method is evaluated numerically by comparing with an exact method and simulation. Further the impact of bandwidth negotiation and reservation on call blockings is examined based on numerical examples.

This paper describes reverse modulation carrier recovery with a tank-limiter for Offset QPSK (OQPSK) burst signals. Acquisition performance is discussed taking into account hardware implementation errors in the carrier recovery circuit. The results indicate hardware implementation errors cause a significant recovered carrier phase error during BTR (Bit Timing Recovery) of OQPSK burst signals. A phase error reduction technique by modifying the BTR code for OQPSK burst signals is proposed to improve the acquisition performance. Computer simulation and hardware experiments confirmed its improvement. The performance of a prototype OQPSK burst demodulator using the proposed carrier recovery scheme is also presented.

This paper presents an experimental result of polarimetric detection of objects buried in a sandy ground by a synthetic aperture FM-CW radar. Emphasis is placed on the reduction of surface clutter by the polarimetric radar, which takes account of full polarimetric scattering characteristics. First, the principle of full polarimetric imaging methodology is outlined based on the characteristic polarization states for a specific target together with a polarimetric enhancement factor which discriminates desired and undesired target echo. Then, the polarimetric filtering technique which minimizes a surface reflection is applied to detect a thin metallic plate embedded in a sandy ground, demonstrating the potential capability of reducing surface clutter which leads to an improvement of underground radar performance, and validating the usefulness of FM-CW radar polarimetry.

The state of the art of low-voltage (LV) analog circuit design techniques is reviewed, and fundamental design techniques are identified and classified as follows: 1) current-mode, 2) series-to-parallel, 3) signal range sharing, 4) dynamic bias, 5) linear bias, and 6) LV regulator. A relatively wide variety of low frequency application circuits have been developed, but future development is expected for wide-bandwidth application circuits such as a voltage-controlled-oscillator (VCO), a balanced multiplier, etc. The circuit techniques such as current-mode, signal range sharing, and dynamic bias will probably be most important for advanced future circuit designs.

This paper deals with an efficient radix-2 divider design theory that uses carry-propagation-free adders based on redundant binary{1, 0, 1} representation. In order to compute the division fast, we look ahead to the next step quotient-digit selection embedded in the current partial remainder calculation. The solution is a function of the four most significant digits of the current partial remainder, when scaling the divisor in the range [1, 9/8). In gate depth, this result is better than the higher radix-4 case without the look-ahead quotient-digit selection and the design is simple.

First, the necessity of examining the numerical calculation of the Bessel function Jν(x) of complex order ν is explained. Second, the possibility of the numerical calculation of Jν(x) of arbitrary complex order ν by the use of the recurrence formula is ascertained. The rounding error of Jν(x) calculated by this method is investigated next by means of theory and numerical experiments when the upper limit of recurrence is sufficiently large. As a result, it was known that there is the possibility that the rounding error grows considerably when ν is complex. Counterplans against the growth of the rounding error will be described.

A problem of obtaining an optimal file transfer on a file transmission net N is to consider how to distribute, with a minimum total cost, copies of a file with some information from a vertex of N to all vertices of N by the respective vertices' copy demand numbers (i.i., needed numbers of copies). The maximum number of copies of file which can be made at a vertex is called the copying number of the vertex. In this paper, we consider as N an arborescence-net with constraints on copying numbers, and give a necessary and sufficient condition for a file transfer to be optimal on N, and furthermore propose an O(n2) algorithm for obtaining an optimal file transfer on N, where n is the number of vertices of N.

Switched-capacitor chaotic neurons fabricated in a full-custom integrated circuit are used to investigate the behavior of 2- and 3-neuron chaotic neural networks. Various sets of parameters are used to visualize the dynamical responses of the networks. Hysteresis of the network is also demonstrated. Lyapunov exponents are approximated from the measured data to characterize the state of each neuron. The effect of the finite length of data and the rounding effect of data acquisition system to the computation of Lyapunov exponents are briefly discussed.

In the actual sound environmental systems, it seems to be essentially difficult to exactly evaluate a whole probability distribution form of its response fluctuation, owing to various types of natural, social and human factors. We have reported a unified probability density expression in the standard expansion form of Hermite type orthonormal series taking a well-known Gaussian probability density function (abbr. p.d.f.) as the basis for generally evaluating non-Gaussian, non-linear correlation and/or non-stationary properties of the fluctuation phenomenon. However, in the real sound environment, there still remain many actual problems on the necessity of improving the above standard type probability expression for practical use. First, a central point in this paper is focused on how to find a new probabilistic theory of practically evaluating the variety and complexity of the actual random fluctuations, especially through newly introducing an equvivalence transformation toward the standard type probability expression mentioned above in the expansion form of Hermite type orthonormal series. Then, the effectiveness of the proposed theory has been confirmed experimentally too by applying it to the actual problems on the response probability evaluation of various sound insulation systems in an acoustic room.

We study the correspondence between problem descriptions and requirements specification documents derived from them. Based on the results of this investigation, a model that integrates the problem space and the requirements specification space is developed. This integration is based on a semantic network representation. We also propose a model of the requirements elicitation process that is consistent with our empirical studies of traceability in requirements documents. In this process, analysts derived requirements specifications from incomplete and ambiguous problem descriptions given by customers, identify missing information, completed it, and then decide the system boundaries that define which part of the problem descriptions to implement as the target system. The model can be used to complete problem descriptions given by customers and determine the system boundaries.

A 10-kW (53V/200A), forced-air-cooled DC-DC converter has been developed for fuel cell systems. This converter uses new high-voltage bipolar-mode static induction transistors (BSIT), a new driving method, a zero-voltage-switched pulse-width-modulation technique, and a new litz wire with low AC resistance. It weighs only 16.5kg, has a volume of 26,000cm3, operates at 40kHz, and has a power conversion efficiency of about 95%. The power loss of this converter is 20% less than that of conventional natural-air-cooled DC-DC converters, and the power density is 3 times as high.

Device models for a laser diode, photodetector, MESFET, HEMT, bipolar transistor, diode, and resistor are proposed and are implemented in a commercial mixed-signal simulator along with models for an optical fiber, an external optical modulator, and a pulse pattern generator. The validity of the models is confirmed by comparing simulated and experimental results. The performance of a mixed photonic/electronic circuit, which is determined by a large-signal waveform and the device noises, is estimated by the present analysis method.

This paper reports an overload control method for the Intelligent Network (IN). The IN, which is being investigated as a future communication network, facilitates both rapid introduction of new services and easy modification of existing services. In the IN, the call processing functions and data needed to achieve IN services are distributed over several nodes. Therefore, traffic demand for the various services may cause varying patterns of node overloads. It is therefore important to develop effective overload control methods and to evaluate their characteristics. We propose an overload control method and evaluate its characteristics in comparison with other methods under various overload traffic patterns with a network simulator that models all nodes and their relationships in the IN. In particular, we focus on three aspects of overload control: how can high throughput be maintained, how can an overloaded node be stabilized, and how can fair access be guaranteed.

This paper describes an O(log3n) time O(n/log n) processors parallel algorithm for determining the congruence (exact matching) of two point sets in three-dimensions on a CREW PRAM, where n is the maximum size of the input point sets. Although optimal O(n log n) time sequential algorithms were developed for this problem, no efficient parallel algorithm was known previously. In the algorithm, the original problem is reduced to the two-dimensional congruence problem by computing a three-dimensional point set cps(S) for each input point set S, where cps(S) satisfies the following conditions: 0|cps(S)|12; cps(T(S))T(cps(S)) for all isometric transformations T. The two-dimensional problem can be solved efficiently in parallel using a parallel version of a previously-known sequential algorithm. cps(S) is computed recursively in the following way: the size of a point set is reduced by a constant factor in each recursive step. To reduce the size of a point set, a convex hull is constructed and then it is regarded as a planar graph, so that combinatorial properties of a planar graph are used effectively. A sequential version of the algorithm works in O(n log n) time, so that this paper gives another optimal sequential algorithm. The presented algorithm can be applied for graphs such that each vertex corresponds to a point and each edge corresponds to a line segment connecting its endpoints. Moreover, the algorithm can be modified for computing the canonical form of a point set or a graph.

A new gloss-extracting method is proposed in this study. A spatial filter with variable resolution is used for the extraction of glossiness. Various spheres and cylinders with curvature radii from 4 to mm are used as the specimens. In all samples, a strong correlation, with a correlation coefficient of more than 0.98, has been observed between psychological glossiness Gph perceived by the human eye and glossiness Gfm extracted by this method. This method is useful for plane specimens as well as spherical and cylindrical ones.

In this study, we investigate the synchronization phenomena of coupled Wien bridge oscillators. The oscillator is characterized by a voltage controlled resistor with saturation. We use linear resistance to couple the oscillators. Two different kinds of coupling techniques, called current and voltage connections are proposed and they show completely opposite mode of synchronized oscillations. The dynamics of the two circuits are also derived to study the amplitude and phase dynamics of the synchronized state. The current connection has a simple resistive effect but stable phase mode is opposite to that of the voltage connection. The voltage connection has the coupling effect which is a combination of resistive and reactive couplings. Coupled three oscillators with current and voltage connection are also studied and stable tri-phase and in-phase synchronizations are observed, respectively. Averaging method is used to investigate the stability of synchronized mode of oscillations. Experimental results are also stated which agree well with the theory.