NAND-structured trench capacitor cell technologies for 256 Mb DRAM and beyond have been developed. The NAND-structured cell has four memory cells connected in series. The cell size can be reduced to 56% of the conventional cell. A substrate plate trench capacitor cell was adapted to this layout. The NAND-structured trench capacitor cell can achieve sufficient storage capacitance within the restricted capacitor area. A sufficient capacitance of 40 fF was achieved when the size and depth of trench were 0.5 µm and 5.0 µm, respectively. The most important point for realizing the NAND-structured trench capacitor cell is how to reduce the leakage current from the storage node. There are two main sources; one is the leakage current to the neighboring cells, the other is the leakage current to Pwell. These leakage currents have been investigated. An experimental 256 Mb DRAM with the NAND-structured cell was fabricated using the 0.4 µm design rule. The chip size is 464 mm2, which is 68% of a conventional DRAM of the same design rule. This is the result of the reduction of the memory cell area by the NAND-structured cell and the introduction of the open-bit-line arrangement.

Any minimum test set (MLTS) for locally exhaustive testing of multiple output combinational circuits (CUTs) has at least 2w test patterns, where w is the maximum number of inputs on which any output depends. In the previous researches, it is clarified that every CUT with up to four outputs has an MLTS with 2w elements. On the other hand, it can be easily shown that every CUT with more than five outputs does not have such an MLTS. It has not been however known whether every CUT with five outputs has such an MLTS or not. In this paper, it is clarified that every CUT with five outputs has such an MLTS. First, some terminologies are introduced as preliminaries. Second, features of 5(w1) dependence matrices of CUTs with five outputs and (w1) inputs are discussed. Third, an equivalence relation between dependence matrices of two CUTs is introduced. The relation means that if it holds and one of the CUTs has an MLTS with 2w elements, then the other CUT also has such an MLTS. Based on the features described above, a theorem is established that there exists a 5w dependence matrix which is equivalent to each of the above 5(w1) matrices. Finally, it is proved by the use of the theorem that every CUT with five outputs has an MLTS with 2 w elements.

A method to design one-dimensional cellular arrays to be used as TPG circuits of BIST is described. The interconnections between cells are not limited to adjacent ones but allowed to some neighbors. Completely regular structures that have full-transition coverages for every k-dimensional subspace of state variables are first shown. Then, almost regular arrays which can operate on maximum cycles are derived based on fast parallel implementations of LFSRs.

The firing squad synchronization problem is considered for defective cellular automata. A lower bound of time tf for the problem is derived. The state complexity to solve the problem is investigated and it is shown that the state set has to be arbitrary large to obtain solutions of time complexity (n). For memory-augmented defective cellular automata a tf-time solution is given.

The dynamics of an artificial neural network derived from a biological system, and its two applications to engineering problems are examined. The model has a multi-layer structure simulating the primary and secondary components in the olfactory system. The basic element in each layer is an oscillator which simulates the interactions between excitatory and inhibitory local neuron populations. Chaotic dynamics emerges from interactions within and between the layers, which are connected to each other by feedforward and feedback lines with distributed delays. A set of electroencephalogram (EEG) obtained from mammalian olfactory system yields aperiodic oscillation with 1/f characteristics in its FFT power spectrum. The EEG also reveals abrupt state transitions between a basal and an activated state. The activated state with each inhalation consists of a burst of oscillation at a common time-varying instantaneous frequency that is spatially amplitude-modulated (AM). The spatial pattern of the activated state seems to represent the class of the input ot the system, which simulates the input from sensory receptors. The KIII model of the olfactory system yields sustained aperiodic oscillation with "1/f" spectrum by adjustment of its parameters. Input in the form of a spatially distributed step funciton induces a state transition to an activated state. This property gives the model its utility in pattern classification. Four different methods (SD, RMS, PCA and FFT) were applied to extract AM patterns of the common output wave forms of the model. The pattern classification capability of the model was evaluated, and synchronization of the output wave form was shown to be crucial in PCA and FFT methods. This synchronization has also been suggested to have an important role in biological systems related to the information extraction by spatiotemporal integration of the output of a transmitting area of cortex by a receiving area.

We compared--for the same propagation conditions and parameters--the performances of distributed dynamic channel assignment (DDCA) strategies and the performance of fixed channel assignment (FCA). This comparison quantitatively showed the effects of DDCA strategies in increasing spectrum efficiency. It also showed that using DDCA with transmitter power control (TPC) increases the system capacity to 3 4 times what it is with FCA and to 1.4 1.8 times what it is when using DDCA without TPC. We also evaluated the blocking rate and the interference probability for the inside of a cell and found that these are generally much higher close to the cell border than they are near the base station.

We investigate the multipacket message transmissions and variable length message transmissions in slotted ALOHA systems with capture effect. First, we propose an approach that the transmission power level is controlled probabilistically depending on message length for multipacket messages. We consider the multipacket messages model with capture. We derive explicit equations of the effective channel utilization of the model. It is demonstrated that if we increase the numbar of power levels, we can get more effective channel utilization of the system. Secondly, we propose how to assign the slot size and show that the effective utilization of the channel is improved for variable length messages using the approach proposed for multipacket messages. Channel design issue about length of the slot depending on the number of power levels used for transmission is discussed. Thirdly, we propose the multiple messages per slot model with capture. The analytical results show that the multiple messages per slot model can achieve the highest channel utilization among the models discussed in this paper.

Packet Reservation Multiple Access (PRMA) is emerging as a possible multiple access scheme for the forth-coming Personal Communication systems, due to its inherent flexibility and to its capability to exploit silence periods to perform a statistical multiplexing of traffic sources, often characterised by a high burstiness. On the other hand, the current trend in reducing cell sizes and the more complex traffic scenarios pose major planning problems, which are best coped with by adaptive allocation schemes. The identification of adaptive schemes suitable to operate on a shorter time scale, which is typical of packetised information, disclose a number of problems which are addressed in this paper. A viable solution is provided by a well-known self-adaptive assignment method (Channel Segregation), originally developed for FDMA systems, provided it is conveniently adapted for PRMA operation. Simulations show good performance, provided that values of some system variables are correctly chosen. These results encourage further studies in order to refine adaptive methods suitable for cellular, packet switched personal communications systems.

The applicability of Dynamic Channel Assignment methods to a Reuse Partitioning system in cellular radio systems is investigated in this paper. The investigations indicate that such a system has a tendency to increase the difference between blocking probability for the partitioning two coverage areas in comparison with the conventional Reuse Partitioning system employing Fixed Channel Assignment method. Two schemes using new Channel Rearrangement algorithms are also proposed in order to alleviate the difference as a disadvantage which gives unequal service to the system. The simulation results show that the proposed schemes are able to reduce the difference significantly while increasing the carried traffic by 10% as compared with the conventional system.

This paper describes the imaging method for a human forearm in the microwave transmission CT at 3GHz. To improve the spatial resolution, the correction method of the diffraction effects is adopted and the high directivity antennas are used. A cross-sectional image of the human forearm is obtained in vivo.

In this paper, we propose a learning fuzzy network (LFN) which can be used to implement most of fuzzy logic functions and is much available for hardware implementations. A learning algorithm largely borrowed from back propagation algorithm is introduced and used to train the LFN systems for several typical fuzzy logic problems. We also demonstrate the availability of the LFN hardware implementations by realizing them with CMOS current-mode circuits and the capability of the LFN systems by testing them on a benchmark problem in intelligent control-the inverted pendulum system. Simulations show that a learning fuzzy network can be realized with the proposed LFN system, learning algorithm, and hardware implementations.

In this paper we consider the determination of direction of arrival of VLF/ELF radio waves and their energy distribution at the ionospheric base by means of the inversion of electromagnetic data observed on the ground. The observed data are too limited, leading us to deal with a severely ill-posed problem similar to those encountered in digital image enhancement and computerized tomography. To handle this situation, the a priori information if available, is supposed to bring as much weight as the observed data do. We used a regularization based on Bayesian information criterion to reconstruct the wave distribution function at the ionosphere, that is, to determine the wave arrival direction. Using computer-generated data, two main results were obtained: first, the electromagnetic field data observed on the ground are sufficient to give a good approximation to the exit region of VLF/ELF radio waves and to reconstruct the wave energy distribution nicely at the ionospheric base. Secondly, the Bayesian information criterion is shown efficient and very promising to handle the situations where the data number is too small compared to the number of unknowns which is the case of most reconstruction problems.

A new clustering method was proposed to increase the effect of duration modeling on the HMM-based phoneme recognition. A precise observation on the temporal correspondences between a phoneme HMM with output probabilities by single Gaussian modeling and its training data indicated that there were two extreme cases, one with several types of correspondences in a phoneme class completely different from each other, and the other with only one type of correspondence. Although duration modeling was commonly used to incorporate the temporal information in the HMMs, a good modeling could not be obtained for the former case. Further observation for phoneme HMMs with output probabilities by Gaussian mixture modeling also showed that some HMMs still had multiple temporal correspondences, though the number of such phonemes was reduced as compared to the case of single Gaussian modeling. An appropriate duration modeling cannot be obtained for these phoneme HMMs by the conventional methods, where the duration distribution for each HMM state is represented by a distribution function. In order to cope with the problem, a new method was proposed which was based on the clustering of phoneme classes with plural types of temporal correspondences into sub-classes. The clustering was conducted so as to reduce the variations of the temporal correspondences in sub-classes. After the clustering, an HMM was constructed for each sub-class. Using the proposed method, speaker dependent recognition experiments were performed for phonemes segmented from isolated words. A few-percent increase was realized in the recognition rate, which was not obtained by another method based on the duration modeling with a Gaussian mixture.

This paper presents a newly developed analytical method which evaluates the virtual path bandwidth control effects for a general topology ATM (Asynchronous Transfer Mode) transport network. The virtual path concept can enhance the controllability of path bandwidth. Required link capacity to attain a specified call blocking probability can be reduced by applying virtual path bandwidth control. This paper proposes an analytical method to evaluate the call blocking probability of a general topology ATM network, which includes many virtual paths, that is using virtual path bandwidth control. A method for the designing link capacities of the network is also proposed. These methods make it possible to design an optimum transport network with path bandwidth control. Finally, a newly developed approximation technique is used to develop some analytical results on the effects of dynamic path bandwidth control are provided to demonstrate its effectiveness.

A partially ferrites and dielectric loaded water filled waveguide applicator is presented which can be used for microwave heating of tissues. The applicator can change its heating pattern by changing the external DC magnetic field applied to the ferrites. The electromagnetic (EM) field distribution inside the applicator is obtained theoretically and the simulated EM field inside the applicator is checked experimentally using 430MHz. Furthermore, on the basis of the EM field distribution inside the applicator, simulations of SAR distribution inside lossy homogeneous human tissue as muscle are performed using finite difference time domain (FD-TD) method. Simulated data of Specific Absorption Rate (SAR) distribution is compared with the experimental ones. Simulations of temperature distribution are also performed using heat transfer equation. Simulated data of temperature elevation distribution is compared with the experimental ones. The simulated results agree well with the experimental ones and it is confirmed that the heating pattern can be changed by external DC magnetic field applied to the applicator. The results obtained here show that the partially ferrites and dielectric loaded water filled waveguide applicator which operates at 430 MHz can change its heating pattern without changing its setup and can heat local target on the human body for hyperthermia treatment.

This paper presents a new Adaptive Convergence Factor (ACF) algorithm without the damping parameter adjustment acoording to the input signal and/or the composition of the filter system. The damping parameter in the ACF algorithms has great influence on the convergence characteristics. In order to examine the relation between the damping parameter and the convergence characteristics, the normalization which is realized by the related signal terms divided by each maximum value is introduced into the ACF algorithm. The normalized algorithm is applied to the modeling of unknown time-variable systems which makes it possible to examine the relation between the parameters and the misadjustment in the adaptive algorithms. Considering the experimental and theoretical results, the optimum value of the damping parameter can be defined as the minimum value where the total misadjustment becomes minimum. To keep the damping parameter optimum in any conditions, the new ACF algorithm is proposed by improving the invariability of the damping parameter in the normalized algorithm. The algorithm is investigated by the computer simulations in the modeling of unknown time-variable systems and the system indentification. The results of simulations show that the proposed algorithm needs no adjustment of the optimum damping parameter and brings the stable convergence characteristics even if the filter system is changed.

Password checking schemes are human identification methods commonly adopted in many information systems. One of their disadvantages is that an attacker who correctly observed an input password can impersonate the corresponding user freely. To overcome it there have been proposed interactive human identification schemes. Namely, a human prover who has a secret key is asked a question by a machine verifier, who then checks if an answer from the prover matches the question with respect to the key. This letter examines such a scheme that requires relatively less efforts to human provers. By computer experiments this letter evaluates its resistance against a type of attack; after observing several pairs of questions and correct answers how successfully can an attacker answer the next question?

When communication network planning-design is performed, especially in a short-term case, it is important to utilize existing facilities in the construction of the new network. In this paper, link capacity assignment problem (CA problem) for packet-switched networks is investigated with the consideration of the existing network. To deal with this, per-unit cost of existing link capacity is thought to be less than that of newly installed capacity and a link cost function is modeled by a non-linear, non-differentiable one which is composed of two portions of capacity cost. After formulating the CA problem, two optimum algorithms derived from Lagrange multiplier method are presented and a modified algorithm is used for solving the CA problem in order to reduce the computation time. Some numerical results show that according to the values of link traffic flows, there will be links whose capacities must be set equally to the existing values. Moreover, when link cost difference is introduced in the CA problem, the number of links that the capacities of which have to be changed from existing values is less than that of linear cost function case, i.e., the case without consideration of the cost difference in link capacity.

Recent technical advances in WDM (Wavelength Division Multiplexing) technologies suggest that their practical application is imminent. By adopting WDM technologies in the transport network, a bandwidth abundant B-ISDN could be realized cost-effectively. This requires the introduction of WDM technologies, especially into the path layer. This paper explores optical path cross-connect (OPXC) nodes that offer very high levels of expandability because existing traffic demands, which are rather limited, must be efficiently supported while permitting easy step-wise expansion in capacity. This paper highlights modularity with regard to incoming/outgoing links. The OPXC architecture that offers the highest modularity is elaborated, and its transmission characteristics, optical loss and switching power consumption are evaluated. This paper also examines OPXC architecture considering the interface needed to connect electrical path cross-connects. The proposed OPXC architectures provide flexibility and minimum investment to encourage the early introduction of B-ISDN and also supports incremental network growth to match traffic demand. The design of OPXC parameters in terms of transmission performance is shown to ensure the applicability of the proposed OPXC architecture to long-haul optical fiber transmission networks. This is made possible with the low optical component losses offered by the OPXC. The proposed OPXC architectures will, therefore, be applied not only to regional networks, but also to global area networks. Thus they will play a key role in realizing the optical path infrastructure for the future bandwidth abundant B-ISDN.

A noise cancelling sonar-ranging system based on the adaptive filtering technique, which can automatically adapt itself to the changes in environmental noise-field and improve the passive sonar-ranging/goniometric precision, was introduced by this paper. In the meantime, the software and hardware design principle of the system using high speed VLSI (Very Large Scale Integrated) DSP (Digital Signal Processing) chips, and the practical test results were also presented. In comparison with the traditional ranging system, the system not only enhanced obviously the ranging precision but also possessed some more characteristics such as simple structure, rapid operation, large data-storage volume, easy programming, high reliability and so on.