A simple method of compensating the DC drift of LiNbO3 Mach-Zehnder intensity modulators for very high speed optical transmission systems is proposed. This method adds low frequency perturbation to the modulator driving signal, and controls the bias voltage using the detected envelope of the modulator output signal. The control circuit is successfully demonstrated to work with less than a 0. 1-dB power penalty.

A group-oriented cipher communication method is developed and implemented on a WWW-based (World Wide Web) network system. In this method, a group key common to all entities of the group is generated based on the group name or the identities of entities belonging to the group. The group key, in turn, is used for encrypting the data being shared among the group via the WWW server. The data theft at the WWW cache sites on the intermediate communication line is prevented, establishing a unified feature of the good WWW cache performance and security. A prototype of our method proved the feasibility and the efficiency.

This paper proposes a secure electronic sealed-bid auction protocol (SEAP) that provides an auction service on the Internet by combining three providers: an auction service provider, a key service provider, and a time service provider. The SEAP uses public key cryptography and the concept of a time-key certificate. The most important property of this protocol is that time-dependent security requirements can be strictly satisfied. The SEAP satisfies the following nine security requirements: (a) no one can deny having made a bid; (b) the protocol should be secure against malicious acts; (c) no bidder can act for another bidder; (d) no one can know who else is bidding until the time comes for the bids to be opened; (e) no one can discover the contents of any of the bids until the time comes for the bids to be opened; (f) the successful bid must have been submitted before the bidding deadline; (g) all bidders can verify that the auction policy has been correctly implemented; (h) the successful bidder can be identified without being required to make himself or herself known; and (i) the bidding contents cannot be altered. The protocol consists of three subprotocols: the Registration Subprotocol, the Bidding Subprotocol, and the Auction Subprotocol. The protocol parameters and algorithm are described in detail.

In this paper a public key certification scheme, which protects privacy of user of the public key certificate, is proposed. In the proposed scheme a certification authority issues anonymous public key certificates, with which a certificate user having his/her own secret key can make use of public key cryptography and a certificate verifier can confirm the authenticity of the cryptographic communication of the certificate user. The anonymity of their users is preserved against the verifier. In general, user's activities should not be linked each other from the viewpoint of privacy protection. The use of the same certificate results in the linkage of the cryptographic communications. So, ideally, a certificate should be used only once, and such a certificate is called a one-time certificate. In the proposed scheme one-time certificates are realized with low cost of communication and computation for the certificate user. Multiple certificates can be issued without interaction between CA and the user. The additional computation of the user to obtain a new anonymous public key certificate is one modular exponentiation. In addition, only one secret key is required for multiple certificates. Therefore, the proposed scheme is useful for applications which require anonymity, unlinkability, and efficiency.

The Non-stop Service-Enhanceable Software (NOSES) platform was developed as part of our overall plan to establish a communications software platform that can be customized for use by various communications systems, such as STM, ATM and IN. The developed NOSES techniques are call-recovery restart, system file update, and on-line partial file modification, so called "Plug-in"; they were achieved by using dynamic program modification. A system-file update inevitably affects calls in service, despite efforts to save in-service calls by copying the call data from the old file to the new one. We therefore developed a different approach: Plug-in modification. This paper evaluates the applicability of the plug-in mechanism of the NOSES platform. Plug-in is a dynamic partial-file modification technique that does not affect calls in service in a communication switching system. In order to apply plug-in program modification widely, the static and dynamic properties of the modified software must be considered. Therefore, an applicability judgement matrix is introduced. The evaluated applicability of plug-in based on case studies and field data was about 60% for service feature additions and modifications. Thus, plug-in is effective for file maintenance of switching systems from the viewpoint of quick provisioning of new service features and bug fixes.

This paper proposes a new method for estimating route outage probability in non-regenerative repeater digital microwave radio systems. In this method, the route outage probability is estimated by various means, including path correlation of fading occurrence and C/N degradation corresponding to the number of non-regenerative repeater stations with and without demodulator devices. In the conventional method, the path correlation is treated as 0 and the C/N degradation is taken as a constant value on each path. To confirm the proposed method's effectiveness, a field test is carried out in which 16QAM signals pass through two non-regenerative repeater stations. The results obtained are in good agreement with the estimated outage probability.

This letter gives a study of additionY=X+K mod 2w which is used in some cryptosystems as RC5. Our results enables us to express the differential and linear probability of addition as a function of addendK. To detect a good differential characteristics or linear approximation of a cryptosystem in which extended key is used as addend, we need to consider how the characteristics or approximations behave depending upon the value of the addend, which are clarified by our results.

This paper presents two types of two-dimensional (2-D) adaptive beamforming algorithm which have high rate of convergence. One is a linearly constrained minimum variance (LCMV) beamforming algorithm which minimizes the average output power of a beamformer, and the other is a generalized sidelobe canceler (GSC) algorithm which generalizes the notion of a linear constraint by using the multiple linear constraints. In both algorithms, we apply a 2-D lattice filter to an adaptive filtering since the 2-D lattice filter provides excellent properties compared to a transversal filter. In order to evaluate the validity of the algorithm, we perform computer simulations. The experimental results show that the algorithm can reject interference signals while maintaining the direction of desired signal, and can improve convergent performance.

We propose a new method for verifying synchronous circuits using the Boyer-Moore Theorem Prover (BMTP) based on an efficient use of induction. The method contains two techniques. The one is the representation method of signals. Each signal is represented not as a waveform, but as a time parameterized function. The other is the mechanical transformation of the circuit description. A simple description of the logical connection of the components of a circuit is transformed into such a form that is not only acceptable as a definition of BMTP but also adequate for applying induction. We formalize the method and show that it realizes an efficient proof.

This paper proposes practical escrow cash schemes with particular emphasis on countermeasures against social crimes such as money laundering and extortion. The proposed cash schemes restrict "unconditional" privacy in order to prevent these social crimes while preserving off-line-ness, divisibility and transferability, properties listed in [25] as criteria for ideal cash schemes.

Various techniques of single-electron circuit simulation are presented. The subjects include visualization of state probabilities, accurate yet reasonably fast steady-state analysis and SPICE-based high-speed simulation for circuits composed of Single-Electron Transistors (SETs). The visualized state probabilities allow one to grasp the dynamics of a single-electron circuit intuitively. The new algorithm for steady-state analysis uses the master equation and Monte Carlo method in combination. We suppose this is the best way to perform steady-state analysis. The SPICE-based simulator significantly outperforms the conventional reference simulator in speed. It is, to the best of our knowledge, the only simulator that can simulate SET circuits for real applications. It also facilitates the study of the integration of SETs and MOSFETs.

The basic operation characteristics of an asymmetric turnstile which transfers each electron one by one in one direction is described. A novel single electron counter circuit consisting of the asymmetric turnstiles, a load capacitor and an inverter which counts the number of high inputs is proposed. Monte Carlo circuit simulations reveal that the gate clock time of the counter circuit should be long enough to achieve allowable minimum error rate. The counter circuit implementing asymmetric single electron turnstiles is demonstrated to be applicable to a noise reduction system, a Winner-Take-All circuit and an artificial neuron circuit.

Detection of facial emotions are mainly addressed by computer vision researchers based on facial display. Also detection of vocal expressions of emotions is found in research work done by acoustic researchers. Most of these research paradigms are devoted purely to visual or purely to auditory human emotion detection. However we found that it is very interesting to consider both of these auditory and visual informations together, for processing, since we hope this kind of multimodal information processing will become a datum of information processing in future multimedia era. By several intensive subjective evaluation studies we found that human beings recognize Anger, happiness, Surprise and Dislike by their visual appearance, compared to voice only detection. When the audio track of each emotion clip is dubbed with a different type of auditory emotional expression, still Anger, Happiness and Surprise were video dominant. However Dislike emotion gave mixed responses to different speakers. In both studies we found that Sadness and Fear emotions were audio dominant. As a conclusion to the paper we propose a method of facial emotion detection by using a hybrid approach, which uses multimodal informations for facial emotion recognition.

Parallelism on heterogeneous machines brings cost effectiveness, but also raises a new set of complex and challenging problems. This paper addresses the problem of estimating the minimum time taken to execute a program on a fine-grained parallel machine composed of different types of processors. In an earlier publication, we took the first step in this direction by presenting a graph-construction method which partitions a given program into several homogeneous parts and incorporates timing constraints due to heterogeneous parallelism into each part. In this paper, to make the method easier to be applied in a scheduling framework and to demonstrate its practical utility, we present an efficient implementation method and compare the results of its use to the optimal schedule lengths obtained by enumerating all possible solutions. Experimental results for several different machine models indicate that this method can be effectively used to estimate a program's minimum execution time.

We present a new scheduling policy named Value-based Processor Allocation (VPA-k) for scheduling value-based transactions in a multiprocessor real-time database system. The value of a transaction represents the profit the transaction contributes to the system if it is completed before its deadline. Using VPA-k policy, the transactions with higher values are given higher priorities to execute first, while at most k percentage of the total processors are allocated to the urgent transactions dynamically. Through simulation experiments, VPA-k policy is shown to outperform other scheduling policies substantially in both maximizing the totally obtained values and minimizing the number of missed transactions.

This paper presents a new self-organization classification algorithm for remote-sensing images. Kohonen and other scholars have proposed self-organization algorithms. Kohonen's model easily converges to the local minimum by tuning the elaborate parameters. In addition to others, S. C. Amatur and Y. Takefuji have also proposed self-organization algorithm model. In their algorithm, the maximum neuron model (winner-take-all neuron model) is used where the parameter-tuning is not needed. The algorithm is able to shorten the computation time without a burden on the parameter-tuning. However, their model has a tendency to converge to the local minimum easily. To remove these obstacles produced by the two algorithms, we have proposed a new self-organization algorithm where these two algorithms are fused such that the advantages of the two algorithms are combined. The number of required neurons is the number of pixels multiplied by the number of clusters. The algorithm is composed of two stages: in the first stage we use the maximum self-organization algorithm until the state of the system converges to the local-minimum, then, the Kohonen self-organization algorithm is used in the last stage in order to improve the solution quality by escaping from the local minimum of the first stage. We have simulated a LANDSAT-TM image data with 500 pixel 100 pixel image and 8-bit gray scaled. The results justifies all our claims to the proposed algorithm.

This paper proposes a time-interval data model in which all temporal representation and operations can be expressed with time intervals. The model expresses not only real time intervals, in which an event exists, but also null time intervals, in which an event is suspended. We model the history of a real-world event as a composite time interval, which is defined in this paper. Operations on the composite time intervals are also defined, and it is shown how these operations can be used to express temporal constraints with time intervals.

Though causal order of message delivery simplifies the design and development of distributed applications, the overhead of enforcing it is not negligible. We claim that a causal order algorithm which does not send any redundant information is efficient in the sense of communication overhead. We characterize and classify the redundant information into four categories: information regarding just delivered, already delivered, just replaced, and already replaced messages. We propose an efficient causal multicast algorithm which prevents propagation of these redundant information. Our algorithm sends less amount of control information needed to ensure causal order than other existing algorithms and can also be applied to systems whose communication channels are not FIFO. Since our algorithm's communication overhead increases relatively slowly as the number of processes increases, it shows good scalability feature. The potential of our algorithm is shown by simulation study.

A deterministic pushdown automaton (dpda) having just one stack symbol is called a deterministic restricted one-counter automaton (droca). A deterministic one-counter automaton (doca) is a dpda having only one stack symbol, with the exception of a bottom-of-stack marker. The class of languages accepted by droca's which accept by final state is a proper subclass of the class of languages accepted by doca's. Valiant has proved the decidability of the equivalence problem for doca's and the undecidability of the inclusion problem for doca's. Thus the decidability of the equivalence problem for droca's is obvious. In this paper, we evaluate the upper bound of the length of the shortest input string (shortest witness) that disproves the inclusion for a pair of real-time droca's which accept by accept mode, and present a direct branching algorithm for checking the inclusion for a pair of languages accepted by these droca's. Then we show that the worst-case time complexity of our algorithm is polynomial in the size of these droca's.

An econominal implementation of a chaos circuit onto the hardware is an important subject. In this letter, a two-dimensional digital chaos circuit realizing a Henon map is designed. Concerning the attractor and the bifurcation diagram of the proposed circuit, numerical simulations are performed to confirm the validity of the circuit algorithm. Furthermore, the proposed digital chaos circuit is designed by Verilog-HDL (Hardware Description Language). The proposed digital chaos circuit can be implemented into the form of the FPGA (Field Programmable Gate Array).