Adaptive Agent Oriented Software Architecture (AAOSA) is a new approach to software design based on an agent-oriented architecture. In this approach, agents are considered adaptively communicating concurrent modules that are divided into a "white box" module responsible for communications and learning and a "black box" which is responsible for the independent specialized processes. An AAOSA system is actually parsing input in the interpretation phase. We will show that AAOSA can be applied to the parallel, and distributed parsing of context sensitive languages.

While the secure concurrency controllers (SCCs) in multilevel secure database systems (MLS/DBMSs) synchronize transactions cleared at different security levels, they must consider the problem of covert channel. We propose a new SCC, named Verified Order-based secure concurrency controller (VO) that founds on multiversion database. VO maintains elaborated information about ordering relationships among transactions in a way of actively investigating and renewing the ordering relationships whenever it receives operations. With the elaborated information, it becomes capable of aborting transactions selectively whose non-interfered executions definitely violate one-copy serializability and providing more recent data versions to read requests than the other multiversion-based SCCs. Therefore, it comes to reduce the abort ratio and provide data versions of improved trustworthiness to transactions. By virtue of the elaborated information, moreover, VO is able to distinguish worthful versions and worthful transactions from worthless ones, so that it is capable lightening the burdens of maintaining multiple versions and accumulated transaction ordering relationships. For the aborts that are inevitable for preserving one-copy serializability, VO achieves security by deriving the conflicts to occur between transactions that have been cleared at the same security level.

This paper presents a new design for testing SRAM-based field programmable gate arrays (FPGAs). The original FPGA's SRAM memory is modified so that the FPGA may have the facility to loop the testing configuration data inside the chip. The full testing of the FPGA is achieved by loading typically only one carefully chosen testing configuration data instead of the whole configurations data. The other required configurations data are obtained by shifting the first one inside the chip. As a result, the test becomes faster. This method does not need a large off-chip memory for the test. The evaluation results prove that this method is very effective when the complexity of the configurable blocks (CLBs) or the chip size increases.

In this paper, we propose the high-level service architecture supporting multimedia multicast. The proposed architecture specifies network-oriented and lightweight communication management, which includes group management, multiparty call control and multicast connection/multiple connections control. Many of the existing approaches handling multimedia multicast applications are dependent on specific transport technologies, such as the Internet and ATM, and lack effective communication management. On the other hand, our approach defines flexible and extensible communication management that can be applied to a variety of multimedia multicast applications, independently of transport technologies. Our architecture supports the separation of control from a terminal, which enables remote control and control mobility, so that a user can use a multicast service in a more various way. The architecture is overlaid above legacy transport networks so that the existing network protocols are used for connection control. This minimizes the modification to a legacy transport network and enhances the practicality of the architecture. In addition, terminal manager and virtual device concepts are introduced that hide the details of physical devices from an application designer. The architecture consists of several service components that effectively interact with each other on a distributed platform. To verify and evaluate our architecture, we have prototyped the high-level service architecture on a CORBA platform and analyzed the architecture using a simulation.

This paper proposes a model checking method for microcomputer programs. To deal with the state explosion problem, we adopt a compositional verification approach. Based on the proposed method, a microcomputer program for a real-life air-conditioner is verified. The program is large enough to cause state explosion. Among fourteen typical properties of the program, five properties are successfully verified by our method.

Printed transmission lines have been extensively examined so far, but results obtained there are all concerned with the waveguiding conductors with no loss and zero thickness, except very few results. We have recently studied the transmission characteristics of printed transmission lines in detail, when the waveguiding conductors have finite conductivity and thickness, and we have found an unexpected effect that we call a "mode extinction effect. " This effect results in significant changes in the dispersion behavior of the printed-transmission-line fundamental mode. For a critical thickness, it may turn out that such transmission line can not use in open structural configuration, but must always be used by putting into a packaging box. In this paper, we discuss thoroughly this important effect and related results from the standpoints of both the dispersion behavior and the vector field plots. We also show the measured results of the attenuation constant.

In this letter, we describe a four thin-film-transistor (TFT) pixel circuit based on hydrogenated amorphous silicon (a-Si:H) technology for the active-matrix organic light-emitting diode (AMOLED) display applications. The circuit uses current-writing mechanism and can automatically adjust the threshold-voltage shifts of both the organic light-emitting diodes (OLEDs) and the TFTs induced by the circuit aging or process variations. Experimental results indicate virtually no variation of the output driving current after long-term bias-temperature-stress (BTS).

The present paper modifies the algorithm to estimate harmful event frequencies and examines the definition of modes of operation in IEC 61508. As far as the continuous mode concerns, the calculated results coincide with those obtained based on the standard. However, for the intermediate region of medium demand frequencies and/or medium demand durations, the standard gives much higher harmful event frequencies than the real values. In order to avoid this difficulty, a new definition of modes of operation and a shortcut method for allocation of SILs are presented.

This paper studies mutually coupled integrate-and-fire type chaotic oscillators. The coupling is realized by impulsive switchings and the system exhibits various synchronous and asynchronous phenomena. We give a basic classification of the chaos synchronization phenomena and their breakdown patterns. The stability of the synchronous states can be confirmed using the piecewise exact solutions, and the basic mechanism of the phenomena can be elucidated by a simple geometric consideration. The typical phenomena are confirmed in the laboratory.

Abnormal IDDQ (Quiescent VDD supply current) indicates the existence of physical damage in a circuit. Using this phenomenon, a CAD-based fault diagnosis technology has been developed to analyze the manufacturing yield of logic LSI. This method to detect the fatal defect fragments in several abnormalities identified with wafer inspection apparatus includes a way to separate various leakage faults, and to define the diagnosis area encircling the abnormal portions. The proposed technique progressively narrows the faulty area by using logic simulation to extract the logic states of the diagnosis area, and by locating test vectors related to abnormal IDDQ. The fundamental diagnosis way employs the comparative operation of each circuit element to determine whether the same logic state with abnormal IDDQ exists in normal logic state or not.

We determine the optimum time TOPT to order a spare part for a system before the part in operation has failed. TOPT is a function of the part's failure-time distribution, the lead (delivery) time of the part, its inventory cost, and the cost of downtime while waiting delivery. The probabilities of the system's up and down states are obtained from a non-regenerative stochastic Petri net. TOPT is found by minimizing E[cost], the expected cost of inventory and downtime. Three cases are compared: 1) Exponential order and lead times, 2) Deterministic order time and exponential lead time, and 3) Deterministic order and lead times. In Case 1, it is shown analytically that, depending on the ratio of inventory to downtime costs, the optimum policy is one of three: order a spare part immediately at t = 0, wait until the part in operation fails, or order before failure at TOPT > 0. Numerical examples illustrate the three cases.

In this paper, we construct a software availability model considering the number of restoration actions. We correlate the failure and restoration characteristics of the software system with the cumulative number of corrected faults. Furthermore, we consider an imperfect debugging environment where the detected faults are not always corrected and removed from the system. The time-dependent behavior of the system alternating between up and down states is described by a Markov process. From this model, we can derive quantitative measures for software availability assessment considering the number of restoration actions. Finally, we show numerical examples of software availability analysis.

A novel protocol scheme is proposed here to compile a program or run a software package. It is a modification where a file can be detected by checking the consistency of the original file with its accompanying digital signature. When an executable program is created it may get infected with some viruses before the signature is attached to it. The infection cannot be detected by signature verification and the origin of the infection cannot be specified either. We propose a signature scheme that let one can sign right in atomic step after the creation of an executable program. Our security-related and cryptographic protocol is used to establish secure communication over insecure open networks and distributed systems. When a server compiles a source program, the compiler automatically creates both the executable program and its signature. Thus no virus can infect the executable programs without being detected. In our proposed signature scheme, the server signature is created a set of proxy secret integers, which is calculated from a compiler maker's secret key. Each server compiler is possessed by its corresponding client user and it is used only when a server secret value is fed into it. The infections of files can be detected by the ordinary server digital signatures. The proposed signature scheme together with the digital signature against infection in the preprocessing step enables us to specify the origin of the infection. Besides that, we also provide the message recovery capability to recover the original file to save the infected files. The most natural extension of this novel protocol scheme is a server-based signature that integrated together with application packages will allow client and the server to commit themselves to one another.

With conventional dynamic routing algorithms, many query messages are required in a distributed environment for efficient multicast routing of any traffic volume. We have developed a dynamic routing algorithm that uses a predetermined path search in which an appropriate multicast path is dynamically constructed by searching only a few nodes. This algorithm can construct an efficient multicast tree for any traffic volume. Simulation has shown that the proposed algorithm is advantageous compared with conventional dynamic routing algorithms when nodes are added to or removed from the multicast group during steady-state simulation.

This paper describes a transaction model for open environments based on mobile agents. Mobile agent-based transactions combine mobility and the execution of control flows with transactional semantics. The model presented represents an approach for providing reliability and correctness of the execution of distributed activities, which fulfills important requirements of applications in Open Environments. The presented transaction model is based on a protocol for providing fault tolerance when executing mobile agent-based activities. This protocol is outlined in this paper. With this protocol, if an agent executing an activity at an agency (logical "place" in a distributed agent environment) becomes unreachable for a long time, the execution of the activity can be recovered and continue at another agency. The fault tolerance approach supports "multi-agent activities," i. e. , activities where some of its parts are spawned to execute and migrate asynchronously in relation to other parts. The described transaction model, called the basic (agent-based) transaction model, is an open nested transaction model. By being based on the presented fault tolerance mechanism, subtransactions can be executed asynchronously in relation to their parent transactions and agent-based transactions can explore alternatives in the event of agent unavailability. The model fulfills requirements for supporting the autonomy of organizations in a distributed agent environment.

This paper describes an improved complementary beamforming microphone array based on the new noise adaptation algorithm. Complementary beamforming is based on two types of beamformers designed to obtain complementary directivity patterns with respect to each other. In this system, during a pause in the target speech, two directivity patterns of the beamformers are adapted to the noise directions of arrival so that the expectation values of each noise power spectrum are minimized in the array output. Using this technique, we can realize the directional nulls for each noise even when the number of sound sources exceeds that of microphones. To evaluate the effectiveness, speech enhancement experiments and speech recognition experiments are performed based on computer simulations with a two-element array and three sound sources under various noise conditions. In comparison with the conventional adaptive beamformer and the conventional spectral subtraction method cascaded with the adaptive beamformer, it is shown that (1) the proposed array improves the signal-to-noise ratio (SNR) of degraded speech by more than 6 dB when the interfering noise is two speakers with the input SNR of below 0 dB, (2) the proposed array improves the SNR by about 2 dB when the interfering noise is bubble noise, and (3) an improvement in the recognition rate of more than 18% is obtained when the interfering noise is two speakers or two overlapped signals of some speakers under the condition that the input SNR is 10 dB.

We first reported the simultaneous-propagation effect that the leaky dominant mode can be present on conductor-backed coplanar strips at the same time as the conventional bound dominant mode. We have investigated here numerically and experimentally this effect in detail. Consequently, we have found that it occurs under a certain condition of structural parameters, and also have verified that it affects circuit performance significantly.

The need for responsive, flexible agents is pervasive in many application domains due to their complex, dynamic, and uncertain nature. Dynamic Adaptive Autonomy allows Sensible Agents to reorganize themselves during system operation to solve different problems in the face of these complex and dynamic environments. This paper presents both functional and implementation architectures for Sensible Agent systems. The functional architecture supports concepts from the distributed computing community by separating internal agent functionality into a discrete set of modules whose interactions are formally specified using the Interface Definition Language (IDL) from the Common Object Request Broker Architecture (CORBA). These four modules are: (1) Perspective Modeler--which contains the agent's explicit model of its local, subjective view of the world, (2) Autonomy Reasoner--determines the appropriate decision-making framework for each of the agent's goals, (3) Action Planner--interprets domain-specific goals, plans to achieve these goals and executes the generated plans, and (4) Conflict Resolution Advisor--identifies, classifies, and recommends possible solution strategies for resolving conflicts between this agent and other agents. The implementation architecture has been realized in a testbed that promotes (1) language and platform independence, (2) parallel development, (3) rapid integration of evolving representations and algorithms implementing agent functionality, (4) repeatable experimentation and testing, (5) environment and agent visualization, and (6) inter-domain application portability. The testbed uses the Inter-Language Unification (ILU) ORB from Xerox to provide the CORBA layer of inter-module and inter-agent communication. A three-dimensional visualization of the domain is provided with a CORBA-connected Virtual Reality Modeling Language (VRML) model while low-level data collection is accomplished using a CORBA-connected Java application. The combination of a distributed functional architecture with a distributed implementation architecture provides a high level of flexibility, visualization ability and experimental fidelity for evaluating the performance of Sensible Agents in complex, dynamic and uncertain environments.

Packet concentrators are used in many high-speed computer communication systems such as fast packet switches. In these systems, the time available for concentration is very short. It is therefore desirable to realize the packet concentrators as hardware chips for fast concentration. The knockout concentrator was proposed for hardware realization. In this paper, we improve this concentrator to reduce the probability of packet loss, and the improved concentrator is called wraparound knockout concentrator. This concentrator has several wraparound paths within it, and it does not require any additional pin per chip. After contention among the packets in a slot, each winner goes to a distinct output, some losers circulate along the wraparound paths for contention in the subsequent slot, and the remaining losers are discarded. In this manner, some losers are not discarded immediately and they still have the chance to go to the outputs in the subsequent slot, thereby reducing the probability of packet loss. We analyze the number of logic gates required and the probability of packet loss. The numerical results show that if the proposed concentrator has a few wraparound paths, the probability of packet loss can already be reduced by orders of magnitude.

A narrow-band digital land mobile system has been developed that operates in the frequency bands of 150 and 400 MHz, which are commonly used by transportation-related companies, local government, and public-sector organizations--and are therefore very congested. The number of users that can be accommodated in these bands is almost doubled by reducing the channel separation to 6.25 kHz, about half that of a conventional FM system. A carrier bit rate of 9.6 kbps is achieved by using π/4 shift QPSK modulation with a roll-off factor of 0.2. Laboratory and field testing showed that: (1) Without propagation delay spread, a BER of 10-2 was obtained without using space diversity. (2) With a propagation delay spread of 10 µs, a BER of 610-3 was obtained without space diversity. These measurements confirmed the technical feasibility of this narrow-band system. Its widespread implementation will help mitigate the congestion in private radio systems.