Active replication is a common approach to building highly available and reliable distributed software applications. The redundant nested invocation (RNI) problem arises when servers in a replicated group issues nested invocations to other server groups in response to a client invocation. Automatic suppression of RNI is always a desirable solution, yet it is usually a difficult design issue. If the system has multithreading support, the difficulties of implementation increase dramatically. Intuitively, to design a deterministic thread execution control mechanism is a possible approach. Unfortunately, some modern operating systems implement thread on kernel level for execution fairness. For the kernel thread case, modification on thread control implies modifying the operating system kernel. This approach loses system portability which is one of the important requirements of CORBA or middleware. In this work, we propose a mechanism to perform the auto-suppression of redundant nested invocation in an active replication fault-tolerant (FT) CORBA system. Besides the mechanism design, we discuss the design correctness semantic and the correctness proof of our design.

Many parallel applications involve different independent tasks with their own data. Using the MPMD model, programmers can have a modular view and simplified structure of the parallel programs. Although MPI supports both SPMD and MPMD models for programming, MPI libraries do not provide an efficient way for task communication for the MPMD model. We have developed a programming environment, called ClusterGOP, for building and developing parallel applications. Based on the graph-oriented programming (GOP) model, ClusterGOP provides higher-level abstractions for message-passing parallel programming with the support of software tools for developing and running parallel applications. In this paper, we describe how ClusterGOP supports programming of MPMD parallel applications on top of MPI. We discuss the issues of implementing the MPMD model in ClusterGOP using MPI and evaluate the performance by using example applications.

We describe a next generation service creation environment (SCE), which is designed to support efficient service application development for IP networks. Considering the IP-network environment we extract the features required for the next generation SCE and propose an architecture for the next generation SCE based on design concepts to provide these features. In our approach, we do not create large components, such as service features, or construct chains of them. Instead, we define application-programming interface (API) control flows through which we utilize existing APIs, such as open APIs. Since service providers, such as ASPs and third parties, must have some knowledge of the APIs, this capability will enable the development of services that correspond to various service provisioning patterns as well as to differentiation of services from those offered by other providers, without the addition of service components. The feasibility and productivity of the next generation SCE are evaluated by developing sample services, including a general Voice over IP (VoIP) service using a Parlay API and a presence service using a presence and availability management (PAM) API. Evaluation shows that the environment not only assists in the development of service applications but also raises the productivity of the next generation SCE itself, thus confirming its effectiveness the rapid, economical development of high-quality IP network services.

In this paper, a new method for displaying a surface deformation is proposed to provide sufficient realism in virtual environment. The approach selected in this paper is based on the fuzzy model and it is sufficient that only one additional rule be added to the fuzzy model to display a surface deformation. Furthermore, designers can easily determine which parameters should be used and how much they should be changed in order to alter shapes as required. The proposed method, thus, is a simple, but effective technique that can also be applied to real time operation and makes it possible to act on several surface points simultaneously. The results of the computer simulation are also given to demonstrate the validity of the proposed algorithm.

This paper considers a wireless LAN system operated in a multiple-cell environment with universal frequency reuse. A key technical goal is to increase cell-capacity within a cell. A very high-rate wireless LAN system, maximum data rates of over 100 Mbit/s, is proposed that offers an expanded signal-bandwidth compared to that specified in IEEE802.11a. The system employs OFDM and MC/CDMA signals in packet mode. It falls back from OFDM signals with low subcarrier modulation orders to MC/CDMA signals. A link level performance comparison shows that OFDM has superior performance to MC/CDMA at over 32 Mbit/s. Under 16 Mbit/s, however, MC/CDMA can establish wireless link connections unlike OFDM. Thus the fallback technique, which is triggered by the CIR environment, should select OFDM if the data rate exceeds 32 Mbit/s. It should fallback to MC/CDMA if the rate is less than 16 Mbit/s. We also evaluate the proposed scheme in a multiple-cell environment with universal frequency reuse, where the severe co-channel (other-cell) interference is present. We derive a cell capacity criterion for wireless LAN systems, and show that the proposed scheme offers a 2.2 times larger available transmission distance than the OFDM-only scheme. In addition, it is found that the proposed scheme offers a 1.3 times improvement in cell capacity compared to the MC/CDMA-only scheme, even if all other-cell interference is considered.

Learning behaviors of hierarchically structured stochastic automata operating in a general nonstationary multiteacher environment are considered. It is shown that convergence with probability 1 to the optimal path is ensured by a new learning algorithm which is an extended form of the relative reward strength algorithm. Several computer simulation results confirm the effectiveness of the proposed algorithm.

The modeling of an application domain and its specific knowledge description language are important for developing knowledge-based systems. A rapid-prototyping approach is suitable for such developments since in this approach the modeling and language development are processed simultaneously. However, programming languages and their supporting environments which are usually used for prototyping are not necessarily adequate for developing practical applications. We have been developing an integrated development environment for knowledge-based systems, which supports all the development phases from the early prototyping phase to final commercial development phase. The environment called INSIDE is based on a Prolog abstract machine, and provides all of the functions required for the development of practical applications in addition to the standard Prolog features. This enables the development of both prototypes and practical applications in the same environment. Moreover, their efficient development and maintenance can be achieved. In addition, the effectiveness of INSIDE is described by examples of its practical application.

To overcome inefficiencies on tree-based and mesh-based scheme, overlay multicast scheme for MANET has been recently proposed to provide higher packet delivery ratio than the former as well as more efficient resource usage than the latter. However, previous all overlay multicast schemes are not designed with any considerations for dense/sparse environments resulted from unlimited movement of mobile nodes. For this reason, all packets should be transmitted in the form of unicast packet so they cannot fully make use of node's broadcast capability even though some group members are densely distributed within single-hop on the same shared media. Due to above reason, this causes extra forwarding overhead, low resource utilization as well as high packet collision. In this paper, we propose a novel hybrid overlay multicast scheme, EAOM (Environment-Aware Overlay Multicast), which uses neighboring group members' information to deliver packet with low cost. In EAOM, a group member has two modes depending on the number of neighboring group members. Under dense environment, host group model in wired network is applied. While in sparse environment, packets are delivered to each receiver along overlay DDT (Data Delivery Tree) as same as previous overlay multicast schemes. Hence, EAOM can not only remove mentioned obstacles in dense environment, but also cope with network mobility very well in sparse environment. Using simulation results, we demonstrate that EAOM has good packet delivery ratio, low control overhead as well as short end-to-end delay.

During the period from dusk to dark, when it is difficult for drivers to see other vehicles, or when visibility is poor due to rain, snow, etc., the contrast between nearby vehicles and the background is lower. Under such conditions, conventional surveillance systems have difficulty detecting the outline of nearby vehicles and may thus fail to recognize them. To solve this problem, we have developed a rear and side surveillance system for vehicles that uses image processing. The system uses two stereo cameras to monitor the areas to the rear and sides of a vehicle, i.e., a driver's blind spots, and to detect the positions and relative speeds of other vehicles. The proposed system can estimate the shape of a vehicle from a partial outline of it, thus identifying the vehicle by filling in the missing parts of the vehicle outline. Testing of the system under various environmental conditions showed that the rate of errors (false and missed detection) in detecting approaching vehicles was reduced to less than 10%, even under conditions that are problematic for conventional processing.

At the initial stage of developing parallel machines, a software monitor, which manages communication between host computers, program loading and debugging, is necessary. However, it is often a cumbersome job to develop such a monitoring system especially when the target takes a parallel architecture. To solve this problem, we developed an integrated monitor system called "Pot". "Pot" consists of a system runs on the host computer and simple code on a target machine. In order to reduce the development costs, the program on a target machine is as simple as possible while "Pot" on the host computer itself provides various functions for system development.

Recent years have witnessed a growing interest in employing animated agents for tasks that are typically performed by humans. They serve as communicative partners in a variety of applications, such as tutoring systems, sales, or entertainment. This paper first discusses design principles for animated agents to enhance their effectiveness as tutors, sales persons, or actors, among other roles. It is argued that agents should support their perception as social actors by displaying human-like social cues such as affect and gestures. An architecture for emotion-based agents will be described and a simplified version of the model will be illustrated by two interaction scenarios that feature cartoon-style characters and can be run in a web browser. The second focus of this paper is an empirical evaluation of the effect of an affective agent on users' emotional state which is derived from physiological signals of the user. Our findings suggest that an agent with affective behavior may significantly decrease user frustration.

Reliable multicast is an interesting application of distributing data to lots of clients at the same time. In heterogeneous environment, it is necessary to adjust the transmitting rate corresponding to the bandwidth of receivers. Placed at a network bottleneck point, an active server can buffer the multicast packets and control the transmitting rate to the downstream multicast receivers independently so as to absorb bandwidth differences. If wireless and wired receivers coexist, the best position for the active server is at the edge of the wired and wireless links because the bandwidth of wireless receivers are lower than that of wired receivers. However, it is not enough that an active server only controls the transmitting rate in such environment because wireless receivers tend to lose packet by the wireless transmission error. This paper proposes a scheme in which the active server independently controls a reliable multicast scheme that is robust against packet loss due to wireless transmission error. Simulation results show that rate-based reliable multicast congestion control is more appropriate than window-based control for wireless links. We also show that FEC applied only to the wireless link improves the throughput of wireless multicast receivers. Finally, we show that combining rate-based reliable multicast congestion control scheme with FEC only for the wireless link makes reliable multicast more practical and friendly with TCP even if packets are lost due to transmission errors.

In testing the possible biological effects of electromagnetic exposure from cellular telephones in small animals such as mice, it is essential to realize a highly localized head exposure as close as possible to that due to cellular telephones in humans. In this study, a 1.5GHz exposure setup was developed which has a highly localized specific absorption rate (SAR) of 2W/kg in the mouse brain and a low whole-body averaged SAR of 0.27W/kg. The low whole-body averaged SAR was realized by using a flexible magnetic sheet attachment on the mouse holder. Its validity has been carefully examined by both numerical simulation with an anatomically based mouse model and experimental simulation with a solid mouse phantom. Good agreement was obtained between the numerical and experimental results, which confirmed the effectiveness of the magnetic sheet attachment to the mouse holder.

In recent years, information devices with network communication ability have become very popular, and many people actually own such kind of devices. Those information devices, however, do not share users' data in spite of their communication ability. This paper proposes "OCEAN: Object Communication Environment for Arbitrary Network" architecture, which provides liaison of objects stored in each device according to their profiles and situations. It eliminates redundant user operation on information devices, and enables novel communication scheme among users by sharing common objects in those devices. Furthermore, it maximizes the effective use of each device's limitation according to each environment. Finally, in this paper, we discuss our prototype of OCEAN.

A heterogeneous parallel computing environment consisting of different types of workstations and communication links plays an important role in parallel computing. In many applications on the system, collective communication operations are commonly used as communication primitives. Thus, design of the efficient collective communication operations is the key to achieve high-performance parallel computing. But the heterogeneity of the system complicates the design. In this paper, we consider design of an efficient gather operation, one of the most important collective operations. We show that an optimal gather schedule is found in O(n2k-1) time for the heterogeneous parallel computing environment with n processors of k distinct types, and that a nearly-optimal schedule is found in O(n) time if k=2.

In this paper, we discuss crosstalk equalization technique for high-speed digital transmission systems. This equalization technique makes use of the cyclostationarity of the crosstalk interferer. We first analyze the eigenstructure of the equalizer in the presence of cyclostationary crosstalk interference. It is shown that the eigenvalues of the equalizer depend upon the folded signal and interferer power spectra, and the cross power spectrum between the signal and the interferer. The expressions of the minimum mean square error (MMSE) and the excess MSE are then obtained by using the equalizer's eigenstructure. Analysis and simulation results indicate that such peculiar equalizer's eigenstructure in the presence of cyclostationary interference results in significantly different initial convergence and steady-state behaviors as compared with the stationary noise case. We also show that the performance of the equalizer varies depending on the relative clock phase of the symbol clocks used by the signal and the crosstalk interferer.

This paper presents a model called PECM (process environment coordination model) to coordinate heterogeneous PSEEs. A PSEE coordinated by PECM is associated with a standard-interfaced PECM coordinator, which provides primitive coordination functions. PECM uses shared product status to coordinate PSEEs. It is expected to offer several features. First, multiple PSEEs can be used in the same project. Second, PECM manages products and product relationships across PSEEs. Third, PECM coordinator is standard- interfaced, which is easy to use.

In this paper, we analyze the convergence and steady-state behavior of the least mean-square (LMS) adaptive filtering algorithm for a finite-length phase-splitting hybrid-type decision feedback equalizer (H-DFE). With some approximations, we derive an iterative expression for the excess mean-square error (MSE) of the H-DFE, which is composed of three statistically dependent excess MSEs; that is, the excess MSEs of the feedforward filter (FFF), intersymbol interference predictive feedback filter (ISI-FBF), and noise predictive feedback filter (NP-FBF) taps. Computer simulation and analytical results show that the average eigenvalue of the input signal for the NP-FBF taps of the H-DFE is time-varying, whereas those for the FFF and ISI-FBF taps are fixed. Nevertheless, the H-DFE can be implemented with fixed step sizes that ensure the convergence of the LMS algorithm without performance degradation from the standpoint of convergence speed, as well as steady-state performance for digital subscriber line (xDSL) applications.

In this study, a new signal model suitable for indoor environments with large angle spread is proposed to improve the performance of indoor wireless communication systems. And antenna array techniques adopted for this model are discussed. It is based on the far-field signal assumption. The optimal beamforming weight vector is obtained by applying the antenna algorithm based on the maximum signal to interference noise ratio criterion to the model. The proposed model is verified using a mathematical analysis and computer simulations.

Double Cross Cylinder (DCC) is an object created by intersecting the cylinder of Y-axis and the cylinder of the Z-axis. DCC mapping is a new method for effectively mapping the environment. This method eliminates the singularity effect caused in the environment maps and shows an almost even amount of area for the environment occupied by a single texel. The surrounding environment can also be stored more effectively through more accurate sampling. Improvement is also achieved in the rendering time of the DCC mapping method and octahedral mapping method based on DCC mapping. Therefore, the DCC mapping method is suitable to be applied on environment navigation systems due to its effective storage of the environment and faster sampling time.