Autonomous distributed manufacturing systems (ADMS) consist of multiple intelligent components with each component acting according to its own judgments. The ADMS objective is to realize more agile and adaptive manufacturing systems. This paper presents the introduction of context-dependent agents (CDAs) in ADMS that switch strategies depending on system conditions to achieve better performance than can be realized by agents that use the same strategies under all system conditions. For the real-time job scheduling problem, the paper presents a basic CDA architecture and the results of an extensive empirical evaluation of its performance relative to other rule-based schemes based on several common indices for real-time dispatch.

A siphon-trap of a Petri net N is defined as a place set S with S = S, where S = { u| N has an edge from u to a vertex of S} and S = { v| N has an edge from a vertex of S to v}. A minimal siphon-trap is a siphon-trap such that any proper subset is not a siphon-trap. The following polynomial-time algorithms are proposed: (1) FDST for finding, if any, a minimal siphon-trap or even a maximal class of mutually disjoint minimal siphon-traps of a given Petri net; (2) FDSTi that repeats FDST i times in order to extract more minimal siphon-traps than FDST. (3) STFM_T (STFM_Ti, respectively) which is a combination of the Fourier-Motzkin method and FDST (FDSTi) and which has high possibility of finding, if any, at least one minimal-support nonnegative integer invariant.

This paper presents efficient file management of a hard disk drive embedded digital satellite receiver. The digital broadcasting technology enables multimedia access via broadcasting systems. The amount of digital data to be processed is increased remarkably as compared to the previous analog broadcasting environments. The efficient digital data storage and management technology are discussed in this paper to cope with these changes. The DSR uses a new file system that is designed by considering disk cluster sizes and limited memories in the system, which is more appropriate than that of general Personal Computers. The proposed system enables us to watch broadcasting and to manage multimedia data efficiently.

Recently, information display equipment such as a navigation system has often come to be installed in a vehicle, and a variety of useful information has been offered to the driver by voice and images while driving. The necessity of improving safety when the driver receives such information has come to be stressed. As one of the means of solving this problem, we can develop a system that presents the driving and road conditions information such as a lane changing car to the driver by using a warning sound. The purpose of our study is to clarify the effectiveness of an auditory display that uses spatial sounds on such a system. An experiment for measuring the driver's reaction time and eye movements to LED lighting during actual driving has been carried out to investigate whether the spatial sound can quicken the driver's operation and decrease human error. We evaluated the effectiveness by two measures, average reaction time and the number of largely delayed reactions. We considered that the average reaction time corresponds to the quickness of the driver's operation, and the number of largely delayed reactions corresponds to the probability of human error. As a result of the experiment, the use of directional sound clearly showed better performance than the use of monaural sound and no sound in the number of largely delayed reactions. Moreover, we analyzed the factors involved in delay of the reaction by the results of eye movement measurements. Consequently, it has been found that directional sound can decrease the number of the largely delayed reactions, which lead to an accident during actual driving.

In transmitter diversity, the received signal is the superposition of signals transmitted from transmitter antennas. Thus, the separation of channel characteristics corresponding to each transmitter antennas from these signals is very important. The conventional channel estimation scheme tends to show higher computational complexity for larger channel delay profile. To reduce this computational complexity, significant-tap-catching method has been proposed. However, there is still a burden of complexity for data transmission mode. Reference [14] has shown how to reduce the complexity for data transmission mode in system with constant modulus modulation. However, this method can't reduce the complexity required for multi-level signals such as QAM. In this paper, we propose an efficient channel estimation scheme for OFDM systems with transmitter diversity using space-time trellis coding. The computational complexity of the proposed scheme is independent of channel delay profile. Also, compared with the conventional scheme, the complexity of the proposed scheme is not related to modulation methods including multi-level signals such as QAM. The performance of the proposed scheme is evaluated by computer simulation in various multipath fading environments.

Using the great one-time password concept, the widely utilized one-way authentication scheme S/Key provides well protection against replay attacks. In this paper, S/key is enhanced to secure transactions in a critical environment. The proposed scheme is free from any of server spoofing attacks, preplay attacks, and off-line dictionary attacks. A session key here is also established to provide confidentiality. Moreover, simplicity and efficiency are taken into consideration from the user's point of view. A smart card is applied to simplify the user login process and only the hash function is used to keep its efficiency. Therefore, the scheme proposed hereinafter is able to build a safer shield for sensitive transactions like on-line banking or on-line trading in bonds and securities.

A blue-light-emitting Eu2+ doped CaMgSi2O6 phosphor with a long lifetime for a plasma display panel (PDP) was developed. The CaMgSi2O6:Eu2+(CMS:Eu2+) phosphors synthesized using SiO2-rich source materials show no luminance degradation during the baking process for binder burn-off, and the photoluminescence peak intensity of the Eu2+ emission band is higher than that of conventional blue phosphor BaMgAl10O17:Eu2+ (BAM) after the baking process. The test PDP using synthesized CMS:Eu2+ phosphor shows a comparable emission peak intensity to that of BAM, while the luminance of the CMS:Eu2+ panel is approximately 55% that of the BAM panel due to the narrower spectral bandwidth and shorter peak wavelength. The CMS:Eu2+ panel shows less luminance degradation than BAM under the aging test, and the CMS:Eu2+ panel retains 85% of its luminance after 300 hours driving. It is found that CMS:Eu2+ appears to be a promising blue phosphor material for PDP.

The transient phenomenon of electromagnetic waves caused by a time dependent resistive screen in a waveguide is treated by using Wiener-Hopf technique. A boundary-value problem is formulated to describe the phenomenon, in which the resistivity of screen varies from infinite to zero in dependence on time. Application of the Fourier transformation with respect to time derives a Wiener-Hopf equation, which is solved by a commonly known decomposition procedure. The transient field is derived from the solution of the equation in terms of the Fourier inverse transform. By using the incomplete Lipschitz-Hankel integral for the computation of the field, numerical examples are given and the transient phenomenon is discussed.

A fast capture algorithm of the initial attitude is proposed for the spacecraft using reaction wheels. This algorithm is composed of two steps. The first step deals with absorption of the initial angular momentum of the spacecraft into the reaction wheels and the second step a rest-to-reset large angle maneuver for sun tracking. A criterion of the initial attitude capture and a controller for the fast large angle maneuver method are presented under considering constraints of the reaction wheels. Simulation results show that the proposed algorithm has several advantages of the initial attitude capture and fast large angle maneuver. This algorithm can be applied to the near minimum time rotation control of the spacecraft.

It has been established that the criteria for space-time convolutional code (STCC) are based on the maximization of the minimum rank and the minimum determinant of distance matrix over quasistatic flat Rayleigh fading channel. This letter presents a new criterion, i.e., modified trace criterion which maximizes both the minimum trace and the average trace of distance matrix for a new STCC. A new STCC is systematically searched so as to maximize the minimum trace and the average trace, and shown to be superior to other known codes in quasistatic flat Rayleigh fading channel.

In mobile computing environments, a problem may exist between loss recovery mechanisms employed by the TCP (transmission control protocol) and RLP (radio link protocol). It is because that local retransmissions performed by the RLP could interfere with the TCP end-to-end error recovery when there are long and correlated packet losses due to bursty channel errors. That is, a spurious timeout would occur at the transport layer. In this paper, a new method is proposed to effectively suppress the occurrence of TCP spurious timeouts. In this new method a small number of ACKs (acknowledgements) is buffered at the base station prior to the emergence of every bad state period in the wireless channel, and these ACKs are henceforth released by the base station one at a time to reset the TCP sender's retransmission timer. Comprehensive comparisons between the proposed method and a baseline method are conducted through simulations to show that the improvement in throughput performance can be as large as 22%.

Emerging real-time and multimedia applications in IP over ATM networks are becoming an indispensable part of the networking world. Considering the different and essential natures of IP and ATM, it seems that they complement each other. Although several approaches have been proposed for IP and ATM integration, so far a key problem (i.e., Quality of Service support) in foreseeable future networking applications remains unsolved. This paper describes a new extension to Classical IP and ARP over ATM (CLIP) protocol, Real-time and Multimedia services using CLIP (RMCLIP), providing ATM service classes to the IP end users. It defines that different service classes are mapped to the associated IP addresses. It enables different IP end user applications (e.g., real-time video, voice and data) to obtain their own dedicated VCs.

Recently, neural networks (NNs) have been extensively applied to many signal processing problem due to their robust abilities to form complex decision regions. In particular, neural networks add flexibility to the design of equalizers for digital communication systems. Recurrent neural network (RNN) is a kind of neural network with one or more feedback loops, whereas self-organizing map (SOM) is characterized by the formation of a topographic map of the input patterns in which the spatial locations (i.e., coordinates) of the neurons in the lattice are indicative of intrinsic statistical features contained in the input patterns. In this paper, we propose a novel receiver structure by combining adaptive RNN equalizer with a SOM detector under serious ISI and nonlinear distortion in QAM system. According to the theoretical analysis and computer simulation results, the performance of the proposed scheme is shown to be quite effective in channel equalization under nonlinear distortion.

Mobile terminals with Internet services such as i-mode are in wide use, and communication bandwidths are growing even further under 3G technology. However, displays of mobile terminals will remain small in view of their portable size and power consumption. In this paper, we propose a "ubiquitous display" that can be used in combination with mobile terminals. The user operates the mobile terminal and the ubiquitous display shows any content that requires a large screen space.

Space-time turbo codes have both advantages of space-time codes and turbo codes, and the space-time turbo code proposed by Su and Geraniotis is known to achieve full coding rate and full antenna diversity. This paper presents some improvements of their space-time turbo code in a two-antenna configuration. We first propose a new condition for full antenna diversity which imposes less constraints on the interleaver. Next, by applying a method used to improve turbo trellis-coded modulation to the space-time turbo code, we propose a new decoding algorithm which utilizes more precise estimates on extrinsic information. Simulation results show that the proposed condition assures full antenna diversity and the new decoding algorithm provides a better performance than that of Su and Geraniotis'.

This paper develops a framework to support trace theoretic verification of timed circuits and systems. A theoretical foundation for classifying timed traces as either successes or failures is developed. The concept of the semimirror is introduced to allow conformance checking thus supporting hierarchical verification of timed circuits and systems. Finally, we relate our framework to those previously proposed for timing verification.

The pre-Rake system is known as a technique in TDD DS/CDMA system to reduce the mobile complexity and achieve the same BER performance like Rake receiver. The pre-Rake system itself is not optimum, since the channel impulse responses of uplink and downlink are slightly different in TDD system, so the signal- to-noise ratio (SNR) can be maximized with a matched filter based Rake receiver, which has not been considered in the conventional pre-Rake system. Furthermore pre-Rake system is sensitive to the Doppler frequency. Even though the pre-Rake system has the ability to suppress other user interference, it is not efficient to maximize the received signal in high Doppler frequency. However, Rake combiner is utilized for the detection method in our proposed system. So the maximized signal can keep the orthogonality better than the pre-Rake system and our proposed system can compensate the Doppler frequency effect. From these reasons, our system achieves better BER performance than that of the pre-Rake system with increasing the number of users in high Doppler frequency.

In this paper, we have analyzed transmission time for WAP (Wireless Application Protocol) over Bluetooth using a multi-slot segmentation scheme. In order for SAR to improve the transfer capability, the transmission of messages have been simulated using a fragmentation scheme that begins with the total package and incremental fragmentation for each layer using the WTP (Wireless Transaction Protocol) to define the resultant packet size and the level of fragmentation for each proceeding layer. The data is divided into individual packets at the baseband level. This scheme decreases transmission time of L2CAP (Logical Link Control And Adaptation Protocol) baseband packets by sending packets that span multiple slots. From the results, we were able to obtain packet transmission time and optimal WTP packet size for WAP over Bluetooth in a Rician fading channel.

The mobile system has been taking an important role as the infrastructure of the advanced information society. First, as the telecommunication infrastructure, it enabled us to communicate with anybody, anytime, and anywhere. Next, as the multimedia infrastructure, it enabled us to send, receive, and retrieve data. Now, as the IT infrastructure, it enables us to purchase commodities, transact business, and enjoy entertainment on-line. The mobile system has morphed into the third generation in almost two decades. Several mobile services have been introduced in each generation to feature the above infrastructures. This paper describes the authors' views on how mobile services have contributed to the advance of the information society in the past three generations. It also discusses what role the future mobile system should take in realizing the wealthier information society.

Today, many audiovisual delivery systems, including video streaming and video conferencing, are being developed for use over a range of networking technologies, the differing characteristics of which pose problems for service level interoperability. Multimedia transcoding is one means to provide interoperability between different types of audiovisual terminals and between terminals that connect to different networks. In this paper, we will present a multimedia transcoder system, which provides interoperability between video conferencing terminals on IP networks and mobile terminals on mobile networks.