This paper investigates some fundamental properties of alternating one-way (or two-way) pushdown automata (pda's) with sublogarithmic space. We first show that strongly (weakly) sublogarithmic space-bounded two-way alternating pda's are more powerful than one-way alternating pda's with the same space-bound. Then, we show that weakly sublogarithmic space-bounded two-way (one-way) alternating pda's are more powerful than two-way (one-way) nondeterministic pda's and alternating pda's with only universal states using the same space, and we also show that weakly sublogarithmic space-bounded one-way nondeterministic Turing machines are incomparable with one-way alternating Turing machines with only universal states using the same space. Furthermore, we investigate several fundamental closure properties, and show that the class of languages accepted by weakly sublogarithmic space-bounded one-way alternating pda's and the class of languages accepted by sublogarithmic space-bounded two-way deterministic pda's (nondeterministic pda's, alternating pda's with only universal states) are not closed under concatenation, Kleene closure, and length preserving homomorphism. Finally, we briefly investigate a relationship between 'strongly' and 'weakly'.

An ordered binary decision diagram (OBDD) is a directed acyclic graph for representing a Boolean function. OBDDs are widely used in various areas which require Boolean function manipulation, since they can represent efficiently many practical Boolean functions and have other desirable properties. However, there is very little theoretical research on the complexity of constructing an OBDD. In this paper, we prove that the optimal variable ordering problem of a shared BDD is NP-complete, and briefly discuss the approximation hardness of this problem and related OBDD problems.

Recently, a number of concurrency control algorithms have been proposed for multidatabase system (MDBS) concurrency control methods (CCMs) and the most challenging issue of them has been a concern about how to ensure global serializability (GSR). In this paper, we examine two concurrency control algorithms of MDBS through simulation approach: optimistic ticket method (OTM) and global ticket method (GTM). In historical note, OTM is known to be the first practical solution, since this approach ensures GSR by way of automatically resolving indirect conflicts among global transactions without making any restrictions on local CCMs. However, OTM is expected to yield poor performance since it enforces all global transactions to take a local ticket which causes direct conflicts between them. In GTM, the global transaction manager in an MDBS assigns a global ticket to global transactions rather than accessing a local ticket as in OTM. Our experimental results showed that GTM outperforms OTM in cases that short timeout values are given. However, in case that the timeout value relatively becomes long, our results demonstrated that OTM outperforms GTM.

We propose a new algorithm for minimizing the number of vertices of an approximate curve by keeping the error within a given bound (min-# problem) with the parallel-strip error criterion. The best existing algorithm which solves this problem has O (n2 log n) time complexity. Our algorithm which uses the Cone Intersection Method does not have an improved time complexity, but does have a high efficiency. In particular, for practical data such as those which represent the boundaries or the skeletons of an object, the new algorithm can solve the min-# problem in nearly O(n2) time.

Among three factors mainly affecting the cache access time, i. e., hit access time, miss rate and miss penalty, previous approaches were focused on reducing the hit access time and miss rate. In this paper, we propose a scheme called MPC (Miss-Predicting Cache) which achives additional reduction of the average instruction cache access time through reducing the miss penalty. The MPC scheme which predicts cache miss and starts cache miss operations in advance, therefore, is supplementary to previous cache schemes targeted for reducing the miss rate and/or hit access time. Performance of the MPC scheme was evaluated using dinero, a trace-driven cache simulator, with the estimation of silicon area using 0.8 µm CMOS standard cell library.

A two-waveguide tapered velocity coupler is presented for a variable divider of optical beams. The coupler consists of one tapered slab waveguide in dimension and the other slab waveguide with a constant film thickness. It is assumed that the device is fabricated on a LiNbO3 substrate, with a push/pull external electric field parallel with the optic axis applied only in the film regions of the coupler. Various numerical simulations through the finite difference beam propagation analysis show that a wide range of dividing ratios from - 15 dB to 15 dB or more can be achieved with considerably small values of driving-voltage electrode-length product and that the dividing characteristics are stable over a wide range of frequencies.

This paper shows that a network supplying variable bit rate services can be prevented from becoming congested if each terminal limits the capacity of its connection in terms of its rate of increase. Variable bit rate sources are adequately assessed with two new concepts: the bit rate increase per unit time (acceleration-rate=αbit/sec2) or the bit rate increase ratio (acceleration-ratio=exp (β) ). The dimension of the acceleration-ratio coefficient βis seconds-1. The upper limits α and β are regulated to guarantee the network's QoS. The proposed concepts allow the network state to be accurately estimated and avoid congestion. The proposed method can be applied to ATM networks, Frame Relay networks, Fast Reservation Protocol systems and so on.

Lightning surge protection semiconductor devices have been developed for subscriber telecommunication equipment that utilize transient thermal and low energy dissipation designs to improve surge-handling capability. A fabricated eight-cell device based on transient thermal design and a four-cell device with a thin substrate based on low energy dissipation design have a 1.83 and 1.80 times higher surge-handling capability, respectively, than a conventional device for lightning surge current waveforms of (1.5/30) µs.

A directed graph G = (V,E) is called the n-rotator graph if V = {a1a2an|a1a2an is a permutation of 1,2,,n} and E = {(a1a2an,b1b2bn)| for some 2 i n, b1b2bn = a2aia1ai+1an}. We show that for any pair of distinct nodes in the n-rotator graph, we can construct n - 1 disjoint paths, each length < 2n, connecting the two nodes. We propose a nonadaptive fault-tolerant file transmission algorithm which uses these disjoint paths. Then the probabilistic analysis of its reliability is given.

Based on the test method proposed by Sub-Committee G of the International Special Committee on Radio Interference, most telephone receivers in Japan have insufficient immunity to acoustic noise caused by radio-frequency fields. This is because the modulation depth of the RF signal used is too high to accurately simulate the audio-frequency components of TV video signals. Reducing the modulation depth from 80% to 5% produces a more realistic simulation.

The synergistic effects obtained by adopting both space diversity reception and adaptive equalization play a very important role in circuit outage reduction. This paper quantitatively analyzes these synergistic effects when dispersive and flat fading occur simultaneously. Analytical results show that the synergistic effects are of the same magnitude as the adaptive equalizer improvement factor when only dispersive fading causes outage. The synergistic effects gradually disappear when noise is the predominant cause of outage.

We present a new method for the self-tuning control (STC) of nonminimum phase continuous-time systems based on the pole-zero placement. The long division method is used to decompose a polynomial into a stable and unstable polynomials. It is also shown that the effect of unstable zeros on the magnitude of the desired output can be cancelled. Finally, the results of computer simulation are presented to illustrate the effectiveness of the proposed method.

In anonymous survey, statistical information by attributes of respondents -such as his gender, age or adress-plays an important role in the interpretation of data. However, giving away all his attributes may cause privacy problem. That is, gathering many attributes may help identifying specifically who responded to the anonymous survey. In this paper, we propose a protocol executed among several `entities in charge' in order to compute statistical information for surveys. The advantage of adopting this protocol is that it does not release extra information of attributes on calculating statistical results. We can show that this protocol is a secure computation in the sense of Micali-Rogaway if played by semi-honest entities. We furthurly give a protocol with zero-knowledge proofs to ensure that the entities are indeed semi-honest.

Surface discharge is widely used for industrial ozonizers and toxic gas treatments, and is noise source. In this paper, an experimental investigation from the point of view of electromagnetic compatibility (EMC) has been conducted to evaluate the noise characteristics of surface discharge combustion flue gas cleaning systems. Mechanisms of propagation, coupling and formation are proposed based on the experimental observations.

This paper presents a combinatiorial characterization of broadcast authentication in which a transmitter broadcasts v messages e1(s), , ev(s) to authenticate a source state s to all n receivers so that any k receivers cannot cheat any other receivers, where ei is a key. Suppose that each receiver has l keys. First, we prove that k < l if v < n. Then we show an upper bound of n such that n v(v - 1)/l(l - 1) for k = l - 1 and n /+ for k < l - 1. Further, a scheme for k = 1 - 1 which meets the upper bound is presented by using a BIBD and a scheme for k < l - 1 such than n = / is presented by using a Steiner system. Some other efficient schemes are also presented.

A clique of a graph G(V,E) is a subset of V such that every pair of vertices is connected by an edge in E. Finding a maximum clique of an arbitrary graph is a well-known NP-complete problem. Recently, several polynomial time energy-descent optimization algorithms have been proposed for approximating the maximum clique problem, where they seek a solution by minimizing the energy function representing the constraints and the goal function. In this paper, we propose the binary neural network as an efficient synchronous energy-descent optimization algorithm. Through two types of random graphs, we compare the performance of four promising energy-descent optimization algorithms. The simulation results show that RaCLIQUE, the modified Boltzmann machine algorithm, is the best asynchronous algorithm for random graphs, while the binary neural network is the best one for k random cliques graphs.

This paper concerns multiple-valued logical function realized by asynchronous circuit that may have feed-back loops and its completeness problems. The first aim is to give mathematical definition of an asynchronous circuit over multiple-valued logical functions and of the realization of multiple-valued logical function by means of an asynchronous circuit. For asynchronous element, the definition of circuit construction and initialization are very sensitive. A slight modification may have a considerable influence on the completeness. We consider three types of completeness (LF-, GS-, NS-completeness) for a set of multiple-valued logical functions. The LF-completeness means completeness of logical functions realized loop-free cirucit. The GS-completeness means completeness under general initialization assumption. The NS-completeness measn completeness under initialization by input assumption. The second aim is to give a completeness criterion for each type of completeness. This aim is realized for LF-completeness in general case and GS-completeness in ternary case. A completeness criteria for GS-completeness and NS-completeness are given under strong conditions.

We define two restricted classes of Boolean circuits by assuming the following conditions on underlying graphs of circuits, and prove, for each class, nonlinear lower bounds on size of circuits computing cyclic shifts: for any two paths from the same input to the same output node, the sequences of depths of nodes along these paths are the same. A circuit is partitioned into subcircuits such that each subcircuit has at most o(log n) output gates and the multivalued circuit obtained from the partition is directed tree. These two conditions are driven from different points of view, and lower bounds are established for each one of them.

A program slice is a set of program statements that directly or indirectly contribute to the values assumed by a set of variables at some program execution point. A few slicing algorithms have proposed to far but none of them are considered from the viewpoint of program modification. In this paper, we define a variable dependence graph (VDG) and show a new slicing algorithm on VDG. We also compare the time complexity of the algorithm with that of other existing algorithms and discuss the suitableness of our algorithm for program modification. As the result of this, we argue our algorithm is suitable for embedding debugging systems.

The local moment functions for discrete Wigner trispectrum are examined in ambiguity and in time-frequency domain. A concept of multiple and multidimensional circular convolution in frequency domain is introduced into the discrete Wigner higher order time-frequency signal representation of any order. It is shown that this concept based on the 1st order spectra of the signal offers an insight into the properties of inconsistent local moment functions and their representation both in ambiguity and time-frequency domain. It allows to prove that midfrequency crossterms of a multicomponent signal can not be removed by any generalized 4th order ambiguity function which employ kernel function in the ambiguity domain. It is shown, that the concept of multiple convolution in frequency domain can lead to the crossterm-reduced discete time-frequency representations of any order