A data-parallel processing approach is promising for real-time volume rendering because of the massive parallelism in volume rendering. In data-parallel volume rendering, local results processing elements(PEs) generate from allocated subvolumes are integrated to form a final image. Generally, the integration causes an overhead unavoidable in data-parallel volume rendering due to communications among PEs. This paper proposes a data-parallel shear-warp volume rendering algorithm combined with an adaptive volume subdivision method to reduce the communication overhead and improve processing efficiency. We implement the parallel algorithm on a message-passing multiprocessor system for performance evaluation. The experimental results show that the adaptive volume subdivision method can reduce the overhead and achieve higher efficiency compared with a conventional slab subdivision method.

A procedure for radar target discrimination is presented in this paper. The scheme includes an enhancement of late-time noisy scattering data based on a proposed signal processing algorithm and a decision procedure using previously known resonance annihilation filters. The signal processing stage is specifically adapted to scattering signals and makes use of the results of the singularity expansion method. It is based on a signal reconstruction using the SVD of a data matrix with a suitable choice of the number of singular vectors employed. To justify the inclusion of this stage, this procedure is shown to maintain the signal characteristics necessary to identify the scattered response. Simulation results clearly reveal a significant improvement due to the inclusion of the proposed stage. This improvement becomes especially important when the noise level is high or the targets to be discriminated (five regular polygonal loops) have a similar geometry.

The complexity of designing communication protocols has lead researchers to develop various techniques for designing and verifying protocols. One of the most important techniques is a compositional technique. Using a compositional technique, a large and complex protocol is designed and verified by composing small and simple protocols which are easy to handle, design and verify. Unlike the other compositional approaches, we propose compositional techniques for simultaneously composing service specifications and protocol specifications based on Formal Description Techniques (FDTs) called LOTOS. The proposed techniques consider alternative, sequential, interrupt and parallel composition of service specifications and protocol specifications. The composite service specification and the composite protocol specification preserve the original behaviour and the correctness properties of individual service specifications and protocol specifications. We use the weak bisimulation equivalence (), to represent the correctness properties between the service specification and the protocol specification. When a protocol specification is weak bisimulation equivalent to a service specification, the protocol satisfies all the logical properties of a communication protocol as well as provides the services that are specified in the service specification.

In this paper, we present simulation algorithms among enhanced mesh models. The enhanced mesh models here include reconfigurable mesh and mesh with multiple broadcasting. A reconfigurable mesh (RM) is a processor array that consists of processors arranged to a 2-dimensional grid with a reconfigurable bus system. The bus system can be used to dynamically obtain various interconnection patterns among the processors during the execution of programs. A horizontal-vertical RM (HV-RM) is obtained from the general RM model, by restricting the network topology it can take to the ones in which each bus segment must be along row or column. A mesh with multiple broadcasting (MWMB) is an enhanced mesh, which has additional broadcasting buses endowed to every row and column. We present two algorithms:1) an algorithm that simulates a HV-RM of size nn time-optimally in θ(n) time on a MWMB of size nn, and 2) an algorithm that simulates a RM of size nn in θ(log2 n) time on a HV-RM of size nn. Both algorithms use a constant number of storage in each processor. Furthermore, we show that a RM of size nn can be simulated in θ((n/m)2 log n log m) time on a HV-RM of size mm, in θ ((n/m)2 m log n log m) time on a MWMB of size mm (m < n). These simulations use θ((n/m)2) storage in each processor, which is optimal.

In this paper, we study a new hybrid speech coder which employs a modified version of the harmonic sinusoidal analysis to encode the periodic contents of speech waveform and to split the speech spectrum into two frequency regions of harmonic and random components. A reliable fundamental frequency is estimated for the harmonic region using both speech and its linear predictive (LP) residual spectrum. The peak envelope of speech spectrum is encoded in terms of the coefficients of an all-pole spectrum. A harmonic tracking algorithm appropriately interpolates the sinusoidal parameters to achieve a smooth transition between the parameter update points and to reconstruct an essential level of periodicity in the synthetic voiced speech. The random part of spectrum and unvoiced speech are coded using the conventional CELP algorithm. The individual components are then combined at the decoder to obtain the synthetic speech. The proposed hybrid coder which combines the powerful features of the sinusoidal and CELP coding algorithms yeilds a high quality synthetic speech at 4.05 kbps.

We address, in this paper, the main features of hybrid modes propagating in a rectangular waveguide partially filled with pseudochiral Ω-slabs. For the particular case of a uniaxial Ω-slab, we show that LSE and LSM hybrid modes can propagate in this inhomogeneously filled rectangular waveguide. The influence of the Ω-parameter, which characterizes the magnetoelectric tensors of the bianisotropic slab, on LSM modes is analyzed--namely an increase in the bandwidth for monomodal operation is reported. In addition, a field displacement effect and a variable phase shift proportional to the change of the Ω-parameter are attained. Finally, it is shown that the propagation characteristics are independent of the direction of propagation and so, unlike the case of magnetically biased ferrite loading, reciprocal devices can be achieved.

This paper suggests a new type of 180-degree 3 dB hybrid, which consists of a cylindrical cavity and four E-plane rectangular waveguides radially coupled with it, and shows that good hybrid properties are realized by modifying the positions of the four input/output waveguides and the radius of the cylindrical cavity that are determined by the field distribution of the TE111 resonant mode. Moreover, a method of broadening the bandwidth with additional impedance steps is described. The present hybrid is marked by simple structure, and hence is useful for applications at millimeter wave frequencies and to high-power microwave systems. Experimental verification is additionally shown.

This study is aimed to explore a fast convergence method of blind equalization using higher order statistics (cumulants). The efforts are focused on deriving new theoretical solutions for blind equalizers rather than investigating practical algorithms. Under the common assumptions for this framework, it is found that the condition for blind equalization is directly associated with an eigenproblem, i. e. the lag coefficients of the equalizer can be obtained from the eigenvectors of a higher order statistics matrix. A method of blind phase recovery is also proposed for QAM systems. Computer simulations show that very fast convergence can be achieved based on the approach.

In this paper, we investigate the bit error rate (BER) performance of Direct Sequence-Code Division Multiple Access (DS-CDMA) systems under impulsive radio noise environments, and propose a novel DS-CDMA receiver which is designed to be robust against impulsive noise. At first, employing the Middleton's Class-A impulsive noise model as a typical model of impulsive radio noise, we discuss the statistical characteristics of impulsive radio noise and demonstrate that the quadrature components of impulsive noise are statistically dependent. Next, based on the computer simulation, we evaluate the BER performance of a conventional DS-CDMA system under a Class-A impulsive noise environment, and illustrate that the performance of the conventional DS-CDMA system is drastically degraded by the effects of the impulsive noise. To deal with this problem, motivated by the statistical dependence between the quadrature components of impulsive radio noise, we propose a new DS-CDMA receiver which can eliminate the effects of the channel impulsive noise. The numerical result shows that the performance of the DS-CDMA system under the impulsive noise environment is significantly improved by using this proposed receiver. Finally, to confirm the effectiveness of this proposed receiver against actual impulsive radio noise, we evaluate the BER performance of the DS-CDMA system employing the proposed receiver under a microwave oven (MWO) noise environment and discuss the robustness of the proposed receiver against MWO noise.

A complex modular process flow was developed for PRISM technology to permit increased system integration. In order to combine the required functions--submicron CMOS Logic, Nonvolatile Memories, Precision Linear, and Power Drivers--on a monolithic silicon chip, a highly structured, systematic approach to process synthesis was developed. TCAD tools were used extensively for process design and verification. The 60 V LDMOS power transistor and the Flash memory cell built in the technology will be described to illustrate the process synthesis methodology.

In this paper, we consider the working VP and backup VP routing problems jointly and employ the integer programming based approach to maximize the system resource utilization and the network survivability. The VP planning problem is formulated as a nonlinear combinatorial optimization problem. The objective function minimizes the resource usage while maximizing the network survivability. By proper transformation of the objective function and applying cutting plane method, the original formulation is transformed into an integer linear programing formulation which is suitable for applying Lagrangian relaxation techniques. After Lagrangian relaxation, the problem is further decomposed into several tractable subproblems. Unlike others' work, the candidate path set does not need to be prepared in advance and the best paths are generated while solving subproblems in our approach. Heuristic algorithms based on the solving procedure of the Lagrangian relaxation are developed. Closely examining the gap between the heuristic upper bounds and the Lagrangian lower bounds reveals that the proposed algorithm can efficiently provide a nearly optimal solution for the survivable VP layout design in ATM networks.

Although there are many multimedia presentation systems on the market, they have some shortcomings and most of them only can work on one single computer, and few of them can work on Web. Thus, in the thesis we develop a network multimedia presentation system to let users easily design the multimedia presentation without restriction on technology or presentation time and place. Our system includes 3 main components: User Interface that includes temporal specification editor, spatial specification editor and multimedia object interface, Presentation Interface and Knowledge Base. There is a dynamic homepage generator in our system and we propose a displaying algorithm based on the Allen's theory, that there exist 13 temporal relationships between two intervals, for synchronizing the media objects.

We fabricated and evaluated a second-order ΣΔ ADC with a polarity alternating feedback (PAF) comparator based on 0.4 µm InGaP/InGaAs enhancement and depletion mode high electron mobility transistors (E/D HEMT) technology. We propose a PAF technique for enhancing the sampling frequency and have applied the technique in the design of ADC circuit. The ADC has a signal-to-noise ratio (SNR) of 43 dB when operating at a differential clock frequency of 4.9 GHz, and has a power dissipation of 400 mW.

Critical properties of real-time embedded systems must be verified before these systems are deployed as failing to meet these properties may cause considerable property damages and/or human casualties. Although Statechart is one of the most popular languages for modeling behavior of real-time systems, proof systems and analysis tools for Statechart so far are in research and do not fully support the semantics of the original Statechart, or have limited capabilities for proving real-time properties. This paper introduces a toolset ASADAL/PROVER for verifying temporal properties of Statechart extended with justice and compassion properties. ASADAL/PROVER is composed of two subsystems, RTTL-Prover and Model-Checker. The RTTL-Prover converts Statechart specifications into real-time temporal logic (RTTL) formulas of Ostroff, and then checks if the formulas satisfy a temporal property (also in RTTL) using theorem proving techniques. The Model-Checker supports verification of a predefined set of real-time properties using a model checking technique. The RTTL-Prover can support verification of any real-time properties as long as they can be specified in RTTL and, therefore, messages generated by the tool are general and may not be of much help in debugging Statechart specifications. The Model-Checker, however, can provide detailed information for debugging. ASADAL/PROVER has been applied successfully to some experimental systems. One of on-going researches in this project is to apply the symbolic model-checking technique by[3]to support Statecharts with a much larger global-state space. We are also extending the types of temporal properties supported by the Model-Checker.

A new low voltage high-speed CMOS composite transistor is presented. It lowers supply voltage down to |Vt|+2 Vds,sat and considerably extends input voltage operating range and achieves high speed operation. As an application example, it is used in the design of a high-speed four quadrant analog multiplier. Simulations results using MOSIS 2µm N-well process with a 3 V supply are given.

Support of collaborative work and management of spatio-temporal data has become one of the most interesting and important database applications, which is due to the tremendous progress of database and its surrounding technologies in the last decade. In this paper, we investigate the new generation database technologies that are needed to support such advanced applications. Because of the recent progress of virtual reality technology, virtual work spaces are now available. We examine a typical CSCW (Computer Supported Cooperative Work) fsystem to identify database problems that arise from it. We introduce typical approaches to database improvement based on the high-level view and the virtual reality technique. Also, in this paper, the following are introduced and discussed: the design and implementation of three- and four-dimensional spatio-temporal database systems, VRML (Virtual Reality Modeling Language) database systems, fast access methods to spatio-temporal data, and the interval-based approach to temporal multimedia databases.

Object-Oriented database systems (OODBMS) are well known for modeling complex and dynamic application domains. Typically OODBMS have to handle large and complex structured objects whose values and structures can change frequently. Consequently there is a high demand for systems which support temporal and versioning features in both objects (or database population) and schema. This paper presents a mechanism for accessing the temporal versioned objects stored in the database which supports schema versioning. The results shown here can be considered as a value-added extension of our model called TVOO described in detail in [1] and [2]. In contrast to conventional database models, in TVOO objects and classes are not physically discarded from the database after they are modified or deleted. They are time dependent and the history of the changes which occur on them are kept as Version hierarchies. Therefore our model enriches the database environment with temporal and versioning features. Also, an access mechanism which makes it possible to access any object under any schema version is defined in such a way that not only objects created under old versions of schema classes can be accessed from new versions, but also objects created by new schema class versions can be accessed from old versions of the respective class.

We present a receiver structure with joint blind equalization, carrier recovery, and timing recovery. The blind equalizer employs a decomposition transversal filtering technique which can reduce the complexity of convolution to about a half. We analyze the performance surface of the equalizer cost function and show that the global minima correspond to perfect equalization. We also derive proper initial tap settings of the equalizer for convergence to the global minima. We describe the timing recovery and the carrier recovery methods employed. And we describe a startup sequence to bring the receiver into full operation. The adaptation algorithms for equalization, carrier recovery, and timing recovery are relatively independent, resulting in good operational stability of the overall receiver. Some simulation results for cable-modem type of transmission are presented.

This paper describes a way of implementing a conceptual model for temporal data on a commercial object database system. The implemented version is provided as a class library. The library enables applications to handle temporal data. Any application can employ the library because it does not depend on specific applications. Furthermore, we propose an enhanced version of Time Index. The index efficiently processes event queries in particular. These queries search time intervals in which given events are all valid. We also investigate the effectiveness of the enhanced Time Index.

This paper presents a new efficient method for finding an "optimal" bi-decomposition form of a logic function. A bi-decomposition form of a logic function is the form: f(X) = α(g1(X1), g2(X2)). We call a bi-decomposition form optimal when the total number of variables in X1 and X2 is the smallest among all bi-decomposition forms of f. This meaning of optimal is adequate especially for the synthesis of LUT (Look-Up Table) networks where the number of function inputs is important for the implementation. In our method, we consider only two bi-decomposition forms; (g1 g2) and (g1 g2). We can easily find all the other types of bi-decomposition forms from the above two decomposition forms. Our method efficiently finds one of the existing optimal bi-decomposition forms based on a branch-and-bound algorithm. Moreover, our method can also decompose incompletely specified functions. Experimental results show that we can construct better networks by using optimal bi-decompositions than by using conventional decompositions.