Ice depolarization characteristics are discussed using cross-polarization discrimination (XPD) observations of the CS-2 beacon signal (19.45GHz, right-hand circular polarization, elevation angle of 49.5) in the stratus type rainfall events, which show a clear bright band in the simultaneous X-band radar observations. Both amplitude and phase of the mean ice depolarizations are deduced in each rainfall event by subtracting theoretical rain depolarizations from the observed values. In spite of the difference in rainfall rates on the ground, the inferred depolarizations indicate much the same amplitude and phase as those directly obtained in pure ice depolarization events without appreciable rain depolarizations. The origin of the ice depolarizations in the stratus type events, as well as in the pure ice events, seems to be ice crystals near the cloud top which are not very much concerned with the ground rainfall rates. Compared with the radar measurements above the bright band, the ice depolarizations are approximately proportional to the vertical length of the ice region at least up to 3km above the bright band. This result yields the equivalent "specific depolarization" per unit path length: |Ci|610-3km-1 (44dB in XPD) for the mean ice depolarizations in each event. Using this coefficient, the ice effects (XPD), which refer to the deviations of the observed depolarizations from the theoretical rain depolarization, are well described as a function of the height ratio of the ice region to the rain region in the stratus type events. Finally, the ice effects (XPD) are calculated against vertical lengths of the ice region in the case of specific rain heights of 2-4 km. These calculations are performed for various rainfall rates of 2-15mm/h in view of ground-based rain observations.

Impact ionization () in two n+-n--n+ device structures is investigated. Data obtained from self-consistent Monte-Carlo (SCMC) simulations of the devices is used to show that the average energy () of only those high energy electrons contributing to is an appropriate variable for the modeling of . A transport model allowing one to calculate is derived from the Boltzmann transport equation (BTE) and calibrated by the SCMC simulation results. The values of and the coefficient, αii, predicted by the proposed model are in good agreement with the Monte-Carlo data.

A power converter with a new piezoelectric transformer is presented. The piezoelectric transformer, made of lead titanate solid solution ceramic, is operated with a thickness extensional vibration mode. This transformer can operate at high frequency, over several megahertz, with about 90% high efficiency. The resonant frequency for the transformer is 2 MHz. The power converter with the transformer applies the theory for a class-E switching converter using an electromagnetic transformer. Maximum output power was obtained when the switching frequency was slightly higher than the resonant frequency. 4.4 W output power was successfully obtained with 52% efficiency at 2.1 MHz switching frequency.

Via electromigration (EM) performance of aluminum based metallization (AL) systems has been investigated for vias chains of 1500-4000 vias of 1.0 micron diameter. The results show that via EM lifetime can not be enhanced by a simple increase of M2 step coverage in AL/AL vias because the EM induced voids are formed at AL/AL via interface where electrons flow from Ml to M2 even in the case of very poor M2 step coverage. The voids are induced by the boundary layer in AL/AL vias, where a temperature gradient causes discontinuity of aluminum atoms flux. The failure location is not moved though via EM lifetime can be improved by controlling stress in passivation, sputter etch removal thickness and grain size of the first metal. Next, the effect of the boundary layer are eliminated by depositing titanium under the second aluminum or depositing WSi on the first aluminum. In the both cases, via EM lifetime are improved and the failure locations are changed. Especially WSi layer suppresses the voids formation rather than titanium. Models for the failure mechanism in each metallization system are further discussed.

In this paper, we study the knowledge tightness of zero-knowledge proofs. To this end, we present a new measure for the knowledge tightness of zero-knowledge proofs and show that if a language L has a bounded round zero-knowledge proof with knowledge tightness t(|x|) 2 - |x|-c for some c 0, then L BPP and that any language L AM has a bounded round zero-knowledge proof with knowledge tightness t(|x|) 2-2-O(|x|) under the assumption that collision intractable hash functions exist. This implies that in the case of a bounded round zero-knowledge proof for a language L BPP, the optimal knowledge tightness is "2" unless AM = BPP. In addition, we show that any language L IP has an unbounded round zero-knowledge proof with knowledge tightness t(|x|) 1.5 under the assumption that nonuniformly secure probabilistic encryptions exist.

Finding DC solutions of nonlinear networks is one of the most difficult tasks in circuit simulation, and many circuit designers experience difficulties in finding DC solutions using Newton's method. Piecewise-linear analysis has been studied to overcome this difficulty. However, efficient piecewiselinear algorithms have not been proposed for nonlinear resistive networks containing the Gummel-Poon models or the Shichman-Hodges models. In this paper, a new piecewise-linear algorithm is presented for solving nonlinear resistive networks containing these sophisticated transistor models. The basic idea of the algorithm is to exploit the special structure of the nonlinear network equations, namely, the pairwise-separability. The proposed algorithm is globally convergent and much more efficient than the conventional simplical-type piecewise-linear algorithms.

This paper presents a zero-knowledge interactive protocol that demonstrates two factors a and b of a composite number n (=ab) are really known by the prover, without revealing the factors themselves. Here the factors a and b need not be primes. The security of the protocol is based on the difficulty of computing discrete logarithms modulo a large prime.

This paper proposes a new combined fast algorithm for transversal adaptive filters. The fast transversal filter (FTF) algorithm and the normalized LMS (NLMS) are combined in the following way. In the initialization period, the FTF is used to obtain fast convergence. After converging, the algorithm is switched to the NLMS algorithm because the FTF cannot be used for a long time due to its numerical instability. Nonstationary environment, that is, time varying unknown system for instance, is classified into three categories: slow time varying, fast time varying and sudden time varying systems. The NLMS algorithm is applied to the first situation. In the latter two cases, however, the NLMS algorithm cannot provide a good performance. So, the FTF algorithm is selected. Switching between the two algorithms is automatically controlled by using the difference of the MSE sequence. If the difference exceeds a threshold, then the FTF is selected. Other wise, the NLMS is selected. Compared with the RLS algorithm, the proposed combined algorithm needs less computation, while maintaining the same performance. Furthermore, compared with the FTF algorithm, it provides numerically stable operation.

Checkpointing is one of the most powerful tools to operate a computer system with high reliability. We should execute the optimal checkpointing in some sense. This note shows the optimal checkpoint sequence minimizing the expected loss, Numerical examples are shown for illustration.

This paper is concerned with the problem of (exactly) representing given functions by fuzzy reasoning. We consider function representation by the fuzzy reasoning method using linguistic truth values, which is a generalization of fuzzy reasoning due to Zadeh. Some conditions for functions to be representable are given, by which it is shown that very large class of functions can be representable by this method. Some examples illustrating how to find "if-then rules" for fuzzy reasoning are shown. Further, in the appendix an example is given to show that the generalization is significant for the problem of function representation.

We extend the concept "optical instanton" to arbitrary dielectric media. For these general cases the exact analytical approach is no longer available. We derive an approximate analytical solution that would be valid in the vicinity of the light cone. A comparison is made between the analytical and the numerical solutions.

Observations of rain depolarization characteristics were conducted using the CS-2 and CS-3 beacon signals (19.45GHz, circular polarization, elevation angle=49.5) during seven years of 1986-1992 at Neyagawa, Osaka. The mean cross-polar phase relative to the co-polar phase of each rainfall event is distributed in a comparatively wide range from -100 to -150. This large variation is suggested to be caused by the difference of raindrop size distribution (DSD) in addition to that of rain intensity. The effects of DSD are examined by rain attenuation statistics for specific months, together with direct measurements of raindrop diameters on the ground for several rainfall events. Compared with representative DSD models, the effects of the Joss-drizzle type with relatively small raindrops primarily appear in "Baiu (Tsuyu)" period, while the effects of the Marshall-Palmer type which represents a standard type are enhanced in "Shurin (Akisame)" period. On the other hand, the effects of the Joss-thunderstorm type with comparatively large raindrops do not indicate a very clear seasonal variation. Possible improvements of XPD performed by differential phase shifters are generally found to be lower than 10dB for the rain depolarization due to the effect of residual differential attenuation after the cancellation of differential phase shift. Such XPD improvements are, however, very sensitive to the type of DSD, and it is suggested that the improvements are at least greater than 6dB for the Joss-drizzle type, whereas they are less than 6dB for the Marshall-Palmer and Joss-thunderstorm types. The effects of the XPD improvements are thus related to rainfall types, i.e., the type of DSD, and the improvements are considerably dependent upon the seasons in which each rainfall type frequently appears.

The regulatory mechanism of protein synthesis on a messenger RNA was analyzed from view point of the optimal control and discussed about availability for artificial production of peptide and protein. The transient movements of a ribozome through a messenger RNA with its production of peptide was based on the theory proposed by Gordon (1968). The optimal state of total process was defined as the state at which the time dependent change of each process of peptide synthesis has been minimized during a given time interval. This biological problem was converted into mathematical one by setting state variables and utilizing the optimal control theory with the help of Hamiltonian function. The first process of transition of a ribozome on a messenger RNA showed the largest change and with progress of state, the magnitude of change of each process decreased and became a simpler pattern. The effect of weighting coefficient relating with individual process was not confined only to its proper process but extended to all other processes. Each process was affected from all other processes. These were manifestations of effective and rational control strategies particularly for regulation of the sequential reaction in peptide synthesis. Such results were originated in the operation of the optimal control. By simulating physiological experimental data, it is possible to predict at what process and at what degree, the synthesis is regulated in order to achieve the optimal synthesis state. By analyzing the optimal synthesis process in combination with physiological experimental data, it would be possible to create artificial peptide and protein.

A theoretical and experimental study of a thin card-sized antenna is presented. The method of moment with a wire-grid model is used to analyze this antenna. In order to validate numerical efficiency, measurements using Wheeler method are preformed on this antenna and its wire-grid models. The experimental and theoretical results are in good agreement if the wire conductivity is well chosen. And the noise reduction of measured Wheeler efficiency using least mean square method is also examined.

A full-wave analysis for the scattering problem of infinite periodic arrays on dielectric substrates excited by a circularly-polarized incident wave is presented. The impedance boundary condition is solved by using the moment method in the spectral domain. Numerical results are given and scattering properties are discussed.

In this article, we consider a hysteresis oscillator which includes periodic thresholds. This oscillator relates to a model of human's sleep-wake cycles. Deriving a one dimensional return map rigorously, we can clarify existence regions of various periodic attractors in some parameter subspace. Also, we clarify co-existence regions of periodic attractors and existence regions of quasi-periodic attractors. Some of theoretical results are confirmed by laboratory measurements.

We propose a recognition method for HMM using a simultaneous generative histogram. Proposed method uses the correlation between two features, which is expressed by a simultaneous generative histogram. Then output probabilities of integrated HMM are conditioned by the codeword of another feature. The proposed method is applied to isolated digit word recognition to confirm its validity.

This paper presents an equation capable of briefly evaluating the length of white noise sequence to be sent as a training signal. The equation is formulated by utilizing the formula describing the convergence property, which has been derived from the IIR filter expression of the NLMS algorithm. The result revealed that the length is directly proportional to I/[K(2-K)] where K is a step gain and I is the number of the adaptive filter taps.

Fuzzy control is suitable for automotive control, because fuzzy control achieves controllability as good as control by humankind. However, since automotive control requires milli-second response and learning control, and the fuzzy system in automobiles requires fewer components (built-in type), a custom fuzzy inference LSI is needed for automotive control. We then indicated requirements of a fuzzy inference LSI suitable for automotive control and fabricated a fuzzy inference LSI using 1.5 µm CMOS process technique. This fabricated fuzzy LSI is designed to utilize in various automotive control experiments such as engine control, cruise control, brake control and steering control. The number of input variables is six, the number of output variables is two, the maximum number of production rules is 256, and the inference time is 63 microseconds (under the condition of six inputs, two outputs and 256 rules). The features of the fuzzy LSI are high speed inference, a built-in type, learning control ability and a memory structure separating into a rule memory and a membership function memory. A fuzzy control system is implemented only by the addition of two devices: the fuzzy LSI and an EPROM. The fuzzy LSI was applied to a rough road durability test aiming at the automatic driving equivalent to the human driver operation. In the test, fuzzy control and linear control were compared in terms of the compensation steering degrees. Linear steering control had a high rate of compensation steering of less than thirty degrees. On the other hand, the accumulated steering compensation of less than twenty degrees in the fuzzy control was about one third that in the linear control. The fuzzy steering control had the same steering compensations as that of human steering. The fuzzy LSI fabricated for various experiments is too large (10.7 mm10.9 mm) to adopt as automotive parts. Therefore, we studied a smaller-sized fuzzy LSI by limiting functions, by changing the parallel processing into sequential processing and by thinning out the memory data of input membership functions. The number of input variables is four, the number of output variables is two, the maximum number of production rules is 160 and the expected inference time is 140 micro-seconds (in the worst case). The obtained chip is small enough (4.8 mm4.8 mm) for automotive applications. Since the chip contains all the memories that are needed to execute fuzzy inference, the chip can be built in a microprocessor as a fuzzy inference co-processor without any other circuits.

This paper gives a model to explain one phenomenon found in the process of creative concept formation, i.e. the phenomenon that people often get trapped in some state where the mental world remains nebulous and sometimes suddenly make a jump to a new concept. This phenomenon has been qualitatively explained mainly by the philosophers but there have not been models for explaining it quantitatively. Such model is necessary in a new research field to study the systems for aiding human creative activities. So far, the work on creation aid has not had theoretical background and the systems have been built based only on trial and error. The model given in this paper explains some aspects of the phenomena found in creative activities and give some suggestions for the future systems for aiding creative concept formation.