Computational Science and Its Applications — ICCSA 2003

Mobile networks face an exponential traffic increase and growing importance to users. It is therefore increasingly important that mobile networks support various applications without disruption. This paper proposes a new recovery algorithm in the WDM based Universal Mobile Telecommunications System (UMTS) networks that guarantee dynamic utilization of backup paths, considering traffic characteristics such as priority and Shared Risk Link Group (SRLG). This paper also has developed an analytical model and performed performance analysis for the proposed algorithms in terms of two performance factors: restoration time and blocking probability.

Channels make use of queuing method for reducing blocking rate of calls in mobile networks. In this paper we propose the queuing model of channel allocation for multiple priority calls which Image/ Voice/Data calls can wait in the queue in the Multimedia Mobile Networks (MMN). The proposed scheme is provided with an analytic model, wherein a three- dimensions Markov process. In numerical results, we can see that the proposed scheme reduces the blocking rate of channel allocation by changing performance parameters such as threshold value, traffic density and mixing ratio of priority traffics.

For detecting the intrusion effectively, many researches have developed data mining framework for constructing intrusion detection modules. Traditional anomaly detection techniques focus on detecting anomalies in new data after training on normal data. To detect anomalous behavior, precise normal pattern is necessary. For this, the understanding of the characteristics of data on network is inevitable. In this paper we propose to use clustering and association rules as the basis for guiding anomaly detection in mobile environment. We present dynamic transaction for generating more effectively detection patterns. For applying entropy to filter noisy data, we present a technique for detecting anomalies without training on normal data.

Recently the number of Internet users has very sharply increased, and the number of intrusions has also increased very much. Consequently, security products are being developed and adapted to prevent systems and networks from being hacked and intruded. Even if security products are adapted, however, hackers can still attack a system and get a special authorization because the security products cannot prevent a system and network from every instance of hacking and intrusion. Therefore, the researchers have focused on an active hacking prevention method, and they have tried to develop a traceback system that can find the real location of an attacker. At present, however, because of the Internet’s diversity real-time traceback is very difficult. To overcome this problem, a traceback system is proposed in this paper that have a possibility to be adapted to the current Internet environment. The system is a Network-based Real-Time Connection Traceback System (NRCTS) that uses the packet marking technique.

This paper propose a system to edit copyrighted documents for the administration of copyrightable documents and has established the application of a possible copyright model to the mobile broadcasting system. The copyright model can be defined each participating user in the distribution of the broadcasting contents, and can be analyzed the provisions of a claim from the contents broadcasting contents, and can be established the content to the buyer himself and each person’s role within the process. In a copyright model for information copyright in circulation broadcasting, we define other contents of the system circulation with the copyrights to be protected while broadcasting. The proposed model analyzes the required facts necessary for the distribution of information copyrights in broadcasting and provides single surroundings which are able to define copyrights model for mobile broadcasting.

In International Mobile Telecommunication-2000 (IMT-2000) networks, the location management method to which has been used has a structural drawback: as the number of users increase, Home Location Register (HLR) should be used in the third generation Mobile Networks (MNs). In this paper we propose a new mobile management where the trace of mobile terminals is left in the Visitor Location Registers (VLRs), so that a call can be connected by querying only to the VLRs rather than to the HLR when the terminal-terminated- call occurs. The proposed method distributes messages to VLRs and effectively reduces mobility management cost. In the number results, the proposed scheme shows the improvement.

This paper proposes a method for effectively analyzing a lot of design information written from various design viewpoints on theWeb. It provides a way of extracting the inherent role of the design contents, as well as easily accessing and understanding the other related ones on the Web. For this method, it defines a series of methods to correctly capture relationships between the contents and the other related ones, and to translate them into a Web object equipped with hypertext links corresponding the relationships and to navigate all the related contents with the links.

The objective is to determine confidence limits for the outputs of a mathematical model of a physical system that consists of many interacting computer codes. Each code has many modules that receive inputs, write outputs, and depend on parameters. Several of the outputs of the system of codes can be compared to sensor measurements. The outputs of the system are uncertain because the inputs and parameters of the system are uncertain. The method uses sensitivities to propagate uncertainties from inputs to outputs through the complex chain of modules. Furthermore, the method consistently combines sensor measurements with model outputs to simultaneously obtain best estimates for model parameters and reduce uncertainties in model outputs. The method was applied to a test case where ADIFOR2 was used to calculate sensitivities for the radiation transport code MODTRAN.

Computer simulations are an essential part in computational science and engineering disciplines and they provide a valuable tool toward designing new and accurate models describing underlying physical phenomena observed in actual experiments. The adjustment of model parameters, also known as parameter identification, requires the use of numerical optimization algorithms if it is to provide credible and useful results. We report on the use of a modular framework, named EFCOSS (Environment For Combining Optimization and Simulation Software), to solve a particular parameter identification problem arising from the modeling of falling films. The underlying computer model is formulated using the multi-purpose computational fluid dynamics package FLUENT. The derivatives required in the parameter identification are obtained by applying the automatic differentiation tool ADIFOR to FLUENT. By using EFCOSS we point out, in a systematic way, areas of validity and needed improvements of a proposed model of a wavy falling film.

We propose a methodology for adjoint-based optimum design that combines hand-coding with Automatic Differentiation in the reverse mode, therefore managing to keep the memory cost acceptable. This methodology also involves improvements to the reverse mode differentiation, based on dataflow information on the original program. We validate the method on a real-size 3D optimum design problem: reducing the sonic boom under a supersonic aircraft.

We present a prototype of a Carbon Cycle Data Assimilation System (CCDAS), which is composed of a terrestrial biosphere model (BETHY) coupled to an atmospheric transport model (TM2), corresponding derivative codes and a derivative-based optimisation routine. In calibration mode, we use first and second derivatives to estimate model parameters and their uncertainties from atmospheric observations and their uncertainties. In prognostic mode, we use first derivatives to map model parameters and their uncertainties onto prognostic quantities and their uncertainties. For the initial version of BETHY the corresponding derivative codes have been generated automatically by FastOpt’s automatic differentiation (AD) tool Transformation of Algorithms in Fortran (TAF). From this point on, BETHY has been developed further within CCDAS, allowing immediate update of the derivative code by TAF. This yields, at each development step, both sensitivity information and systematic comparison with observational data meaning that CCDAS is supporting model development. The data assimilation activities, in turn, benefit from using the current model version. We describe generation and performance of the various derivative codes in CCDAS, i.e. reverse scalar (adjoint), forward over reverse (Hessian) as well as forward and reverse Jacobian plus detection of the Jacobian’s sparsity.

We consider the solution of a (generalized) eigenvalue problem arising in physical oceanography that involves the evaluation of both the tangent-linear and adjoint versions of the underlying numerical model. Two different approaches are discussed. First, tangent-linear and adjoint models are generated by the software tool TAF and used separately. Second, the two models are combined into a single derivative model based on optimally preaccumulated local gradients of all scalar assignments. The coupled tangent-linear / adjoint model promises to be a good solution for small or medium sized problems. However, the simplicity of the example code at hand prevents us from observing considerable run time differences between the two approaches.

We present a hierarchical scheme to extend the applicability of automatic differentiation (AD) by vertex elimination from the basic block level to code with branches and subroutine calls. We introduce the EliAD tool that implements our scheme. Results from computational fluid dynamics (CFD) flux linearisations show runtime speedup by a typical factor of two over both finite-differencing and traditional forward and reverse modes of AD.

In this paper, we consider a two-layer hierarchy, i.e. micro and umbrella layer, cellular system, and propose a new hand-off mechanism to minimize call blocking probability of high-speed hand-off calls with reasonable performance of new and low-speed hand-off calls. We used double control for highspeed hand-off calls in micro and umbrella layer. By formulating Markov chains and using queueing analysis, we have derived call blocking probabilities for ours and those of other hand-off schemes. We have shown that our proposed policy can indeed improve blocking probabilities of high-speed hand-off calls, which leads to improved system performance. Our policy can serve as a guideline to design hand-off policies within wireless systems or inter-working policies between systems.

We have developed a novel algorithm to adjust link-bandwidths of a given multicast tree, which sends a message with size r from a source to a multiple destinations taking into consideration pipelined routing architecture for the mobile environment. The algorithm that we have developed tries to minimize the end-to-end delay time and resources such as bandwidths of a multicast tree, and performs admirably well in any given multicast tree. Our evaluation shows that the proposed algorithm dramatically reduces the end-to-end delay time and resources reserved to satisfy the time-constraints.

Recently MIP becomes more important for the macro mobility support in the emergence of the global system such as IMT-2000. However this protocol suffers from many weaknesses on the location management. MIPv4 regional registration is presented for the local registration of MNs. MIPv6 can benefit from the reduced mobility signaling with external networks by employing a local MAP, that is called HMIPv6. The total signaling cost of HMIPv6 is rapidly increased by the number of CNs of an MN when the MN moves around between MAPs. In this paper, we propose a new location management scheme in MIPv6 that reduces the total signaling cost in the location update based on HMIPv6. Here the MN does not send the BU to CNs and HA when it moves around between MAPs. Instead it informs the current location by transferring the modified BU to the previous MAP. According to the results of the performance analysis, we determine the upper bound for the number of forwarding links allowed among adjacent MAPs without the BU information.

Since the location update process requires heavy signaling traffics, reducing the location update cost has been a critical research issue. This paper proposes to employ hierarchical structure in PCS networks to reduce the location update cost. The paper also develops analytical models to evaluate the performance of the proposed approach. The evaluation shows that the proposed approach reduces the location update costs by reducing the update rate of the home location register. The reduction of the location update cost becomes larger when the degree of hierarchy is larger, the size of location area is smaller, and the average residual time of mobile users is smaller.

The majority of research on MIPv6 only considers the mobility of nodes. However, using MIPv6 for mobile network will introduce a problem such as dog-leg routing. A mobile network is composed with one or more visited mobile networks as well as mobile nodes in fixed network environment. In order to communicate from foreign network with mobile nodes, packets are usually transmitted via the home link of the mobile node. This introduces a dog-leg routing. Especially, the increasing number of visited mobile network may cause a transmission delay for the packet. Dog-leg routing may cause a transmission latency, this subsequently causes the difficulty for a real time service and the delay in binding update. Our research tries to solve the dog-leg routing by only expanding AR (access router), MR (mobile router), HA (home agent) of MR without any changes in MN, HA of MN and CN. The second part of my research outlines the performance which reduces binding update latency and the number of binding update message through regional registration.

With the popularity of mobile devices, Internet service providers are interested in supporting mobile applications. Mobile IP standards have been developed without considering multicast services. This paper explores the issues of multicasting for mobile hosts and problems of previous approaches, and proposes dual-transmission architecture for mobile multicasting (DTAMM), which provides reliable and optimal multicast communication in mobile environments. Proposed architecture is based on the standard protocols and, with some functional extensions to network components, solves most of the problems currently identified. We also developed a simple cost-analytic model to evaluate its performance.

We propose mechanisms for providing security services for source specific multicast(SSM) in networks including mobile hosts. First we categorize security requirements in SSM applications. Then we present some protocols for building multicast trees, distributing security keys, and sending messages securely in two categories of security requirements: authenticated SSM without rekeying and authenticated SSM with rekeying.

The use of cryptographic system to provide the privacy of transmitted message over network is increasing gradually. A key agreement protocol is the most important part to establish a secure cryptographic system and the effort to standardize the key agreement protocols is in rapid progress. In this paper, we study properties and operation of standard key agreement protocols and analyze the security of their protocols under several active attacker models such as active impersonation, key-compromised impersonation, (full/half ) forward secrecy, known-key passive attack, known-key impersonation attack and so on. Then, we suggest the standard for selecting key agreement protocols for each application, and find the most suitable key agreement protocol for each application.

In this paper, we propose a password authentication key exchange protocol for WLANs (Wireless LANs). We call the proposed protocol as the improved EAP-SPEKE (Extensible Authentication Protocol-Simple Password Encrypted Key Exchange). The improved EAP- SPEKE protocol supports mutual authentication and key derivation. The proposed protocol does not require any modification to the IEEE 802.1X and EAP. Before the protocol begins, the server and client compute one modulo exponentiation. Once the protocol begins, the server and client need to compute another exponentiation for mutual authentication. On the contrary, the EAP-SRP needs to compute two modulo exponentiation during the protocol. The client and server authenticate each other with three message exchanges. Therefore, the number of exchanged message decreases by one compared with the EAP-SRP. Besides, the improved EAP-SPEKE protocol works on the the ECC (Elliptic Curve Cryptosystems) base as well as the DH (Diffie-Hellman) base.

This paper deals with an IP based mobility with AAA. In particular the problem of secure and efficient mobility service is investigated for Internet service providers and mobile wireless users. For this aim, in this paper, we propose a novel AAA service mechanism using a ticket that can support authentication and authorization for the mobile node and reduce delay and risk in authenticating a mobile node in Mobile IPv6. The extended AAA infrastructure, AAA Broker model, is also proposed for reducing delay in binding updates. The simulation results show that the use of tickets for a mobile node in AAA model reduces the latency and increases the security efficiency and the AAA Broker model minimizes the latency by reducing the exchange messages.

Mobile IP gets its firm position as a layer-3 mobility protocol for the 3rd generation and beyond the 3rd generation communication system. Nevertheless, due to the security defects caused by adapting MIP for real service, several systems such as AAA infrastructure have been introduced. On the other hand, PKI infrastructure is considered to be a core standard infrastructure to handle the authentication and secure channel for the present and future network. In this paper, we suggest a secure registration scheme with authentication using PKI infrastructure. Suggested scheme produces less static key management overhead compared with legacy scheme and supports the previously deployed standard authentication infrastructure. Especially, it has a feature that supports mobile communication system. Secure re-distribution of dynamic session key using asymmetric key and the optimized authentication roundtrip time for handoffs shows such a feature.

Mobile IP Low Latency Handoffs allow greater support for real-time services on a Mobile IPv4 network by minimising the period of time when a mobile node is unable to send or receive IP packets due to the delay in the Mobile IP Registration process. However, on Mobile IP network with AAA servers that are capable of performing Authentication, Authorization, and Accounting(AAA) services, every Regional Registration has to be traversed to the home network to achieve new session keys, that are distributed by home AAA server, for a new Mobile IP session. This communication delay is the time taken to re-authenticate the mobile node and to traverse between foreign and home network even if the mobile node has been previously authorized to old foreign agent. In order to reduce these extra time overheads, we present a method that performs Low Latency Hando. without requiring further involvement by home AAA server. The method re-uses the previously assigned session keys. To provide the confidentiality of session keys in the phase of key exchange between old FA and new FA, it uses a key sharing method with a trusted third party. The proposed method allows the mobile node to perform Low Latency Hando. with fast as well as secure operation.

The paper presents a Coarse-Grained Multicomputer algorithm that solves the problem of finding the longest repeated suffix ending at each point in a word. This algorithm can be implemented in the CGM with P processors in $$ O\left( {\frac{{N^2 }} {P}} \right) $$ in time and O(P) communication steps. It is the first CGM algorithm for this problem. We present also experimental results showing that the CGM algorithm is very efficient.

In this paper we present a parallel wavefront algorithm for computing an alignment between two strings A and C, with |A| = m and |C| = n. On a distributed memory parallel computer of p processors each with O((m + n)/p) memory, the proposed algorithm requires O(p) communication rounds and O(mn/p) local computing time. The novelty of this algorithm is based on a compromise between the workload of each processor and the number of communication rounds required, expressed by a parameter called α. The proposed algorithm is expressed in terms of this parameter that can be tuned to obtain the best overall parallel time in a given implementation. We show very promising experimental results obtained on a 64-node Beowulf machine. A characteristic of the wavefront communication requirement is that each processor communicates with few other processors. This makes it very suitable as a potential application for grid computing.

This paper presents experimental results of a parallel implementation of a soft-computing algorithm for model discovery in multivariate time series, possibly with missing values. It uses a hybrid neural network with two different types of neurons trained with a nontraditional procedure. Models describing the multivariate time dependencies are encoded as binary strings representing neural networks, and evolved using genetic algorithms. The present paper studies its properties from an experimental point of view (using homogeneous and heterogeneous clusters) focussing on: i) the influence of missing values, ii) the factors controlling the parallel computation, and iii) the effectiveness of the time series prediction results. Results confirm that i) the algorithm possesses high tolerance to missing data, ii) Athon-based homogeneous clusters have higher throughput than Xeon-based homogeneous clusters, iii) an increase of the number of slaves reduces the processing time until communication overhead dominates (as expected), and iv) running the algorithm in parallel does not affect the RMS error (as expected). Even though much of this behavior could be qualitatively expected, appropriate tradeoffs between error and time were actually discovered, thereby enabling more effective, systematic, future uses of the system.

We present an extension to SSCRAP, our C++ environment for the development of coarse grained algorithms, that allows for easy execution of programs in an external memory setting. Our environment is well suited for regular as well as irregular problems and scales from low end PCs to high end clusters and mainframe technology. It allows running algorithms designed on a high level of abstraction in one of the known coarse grained parallel models without modification in an external memory setting. The first tests presented here in this paper show a very efficient behavior in the context of out-of-core computation (mapping memory to disk files), and even some (marginal) speed up when used to reduced cache misses for in-core computation.

An important characteristic of distributed grids is that they allow geographically separated multicomputers to be tied together in a transparent virtual environment to solve large-scale computational problems. However, many of these applications require effective runtime load balancing for the resulting solutions to be viable. This paper compares the performance of our MinEX latency-tolerant partitioner with METIS using simulated heterogeneous grid configurations. A solver for the classical N-body problem is implemented to provide a framework for the comparisons. Experimental results show that MinEX provides superior quality partitions and is competitive to METIS in execution speed.

The finite difference discretization of the Poisson equation in three dimensions results in a large, sparse, and highly structured system of linear equations. This prototype problem is used to analyze the performance of the parallel linear solver on coarse-grained clusters of workstations. The conjugate gradient method with a matrix-free implementation of the matrix-vector product with the system matrix is shown to be optimal with respect to memory usage and runtime performance. Parallel performance studies con.rm that speedup can be obtained. When only an ethernet interconnect is available, best performance is limited to up to 4 processors, since the conjugate gradient method involves several communications per iteration. Using a high performance Myrinet interconnect, excellent speedup is possible for at least up to 32 processors. These results justify the use of this linear solver as the computational kernel for the time-stepping in a system of reaction-diffusion equations.

This paper presents a parallel version of CLUSTALW, called pCLUSTAL. In contrast to the commercial SGI parallel Clustal, which requires an expensive shared memory SGI multiprocessor, pCLUSTAL can be run on a range of distributed and shared memory parallel machines, from high-end parallel multiprocessors (e.g. Sunfire 6800, IBM SP2, etc.) to PC clusters, to simple networks of workstations. We have implemented pCLUSTAL using C and the MPI communication library, and tested it on a PC cluster. Our experimental evaluation shows that our pCLUSTAL code achieves similar or better speedup on a distributed memory PC clusters than the commercial SGI parallel Clustal on a shared memory SGI multiprocessor.

Generally, existing watermarking techniques are fragile in geometric distortion and have difficulty in detecting artificial manipulation of digital data. In this paper, we propose a robust watermarking technique in geometric distortion of digital images. The proposed watermarking technique embeds the watermark by modifying phase information in the complex wavelet domain about an original image. A watermark is extracted with a hierarchical from a watermarked image, and a correlation is compared. The watermarking technique us-ing the Complex Wavelet Transform is compared with the watermarking technique which uses the existing wavelet transformation was used for performance evaluation, and proposed techniques showing a robust on a geometric distortion

We propose a Secure Zone Cooperation to protect unknown types of attack and to improve efficiency of security systems. The Secure Zone Cooperation, a framework that establishes mutual collaboration and cooperation between trusted zones, can protect systems and networks from potential attacks. This framework can predict and respond to attacks by exchanging security information and cooperating with each zone. A Secure Monitor plays a major role in detecting security events in the Secure Zone Cooperation, so its ability is a key factor that represents the safety of the Secure Zone. In this paper, we introduce the design of the Secure Monitor.

A variety of DoS attacks are incapacitating the Net infrastructures. IKEs can be easily targeted by these attacks because they force to process heavy computations, and an IKE is the beginning handshake procedure for secure communications. This paper analyzes existing DoS resistant protocols that have several inappropriateness to apply an IKE and points out DoS vulnerability of three IKE candidates. It proposes a new DoS defensive IKE against CPU and memory exhaustion DoS attacks. Moreover, the proposed IKE enhances a capacity of the responder that may be a heavily loaded web-server or a mobile device.

The randomization of scalar multiplication in ECC is one of the fundamental concepts in defense methods against side channel attacks. This paper proposes a countermeasure against simple and differential power analyses attacks through randomizing the transformed m-ary method based on a random m-ary recoding algorithm. Therefore, the power consumption is independent of the secret key. We show that the proposed algorithm has fewer computational cost than the previous countermeasures against power attacks in ECC. Accordingly, since the variable window width arrays and random computational tracks can resist against the SPA and DPA, the proposed countermeasure can provide a higher security for smartcards.

The Digital watermarking algorithm is embedding watermark into digital content without degradation of original image. The watermark should be robust against attacks to the copyrighted content. Also, extracted watermark can be able to identify the image ownership without ambiguity. In real-time watermarking system, watermark extract algorithm must be distinguishing the imitations from the originals on the instant. In this paper, the proposed watermarking algorithm shows unambiguity and security using pseudo-random linear congruention generators and binary code to decimal with student ID number. The experimental results show that the proposed algorithm successfully survives several kinds of image processing operations including JPEG lossy compression.

According to rapid growth of Internet infrastructure and information technology, anyone can get knowledge legally or illegally. Internet users can be classified as normal and abnormal user. Especially, abnormal users with hostility are getting more intelligent, so they can drain away the valuable information and use or destroy it illegally. The damage from abnormal user is also increasing, but research to detect abnormal users and to protect information is at still initial stage. The most security systems focus on how to detect and respond such an intrusion as quickly as possible of which they already have knowledge. In case of unknown intrusion, it is much harder to detect and respond it. In this paper, we implement a virtual emulation service that leads an intruder into HoneyPot, which monitors all behaviors in step by step. Building the new knowledge on the access paths and skills of intruder allows us to make a policy to protect a system from new attacks. Furthermore, we present an Active HoneyPot System, which combined with firewall and management server. In this system, firewall redirects an abnormal user to HoneyPot to learn advanced intruding skills and to respond more actively.

A mobile IPv6 services exposes its vulnerability when a mobile node is roaming across the subnets which belongs to the different domains. The AAA infrastructure is strongly recommended when the ISPs need to authenticate the mobile user come from the different domains. In addition to the basic requirements for AAA service, the authentication latency and AAA message overhead should be minimized for contiguity of the service. This paper considers the roaming service with AAA infrastructure in Mobile IPv6 and proposes the key distribution method to authenticate the mobile node with secure manner by reducing and optimizing the messages exchanged between AAA entities. The effectiveness of the proposed scheme is confirmed using the cost analysis. The result shows at least 50% of performance enhancement.

Organizations have evolved to the stage where critical data management and protection are intimately linked to revenues. Error margins become smaller as information importance becomes greater. Security compromises cause considerable credibility loss and frustration. In this paper, we address both proactively and retrospectively security related problems for Unix-based systems. We have designed and built a software infrastructure, which handles security issues by autonomous intelligent agents automatically and dynamically with none or minimal service interruptions. Our software has been implemented and used for more than a year as part of the production environment of a mobile phone operator and Internet provider. The evaluation results over this period have shown that autonomous intelligent agents handling security can reduce dramatically downtime caused by security related incidents.

A GUI (graphical user interface) has been a dominant platform for HCI (human computer interaction). A GUI-based interaction has made computers simpler and easier to use. The GUI-based interaction, however, does not easily support the range of interaction necessary to meet users’ needs that are natural, intuitive, and adaptive. In this paper, the modified BMA (block matching algorithm) is proposed to track a hand in a sequence of an image and to recognize it in each video frame in order to replace a mouse with a pointing device for a virtual reality. The HCI system with 30 frames per second is realized in this paper. The modified BMA is proposed to estimate a position of the hand and segmentation with an orientation of motion and a color distribution of the hand region for real-time processing. The experimental result shows that the modified BMA with the YCbCr (luminance Y, component blue, component red) color coordinate guarantees the real-time processing and the recognition rate. The hand tracking by the modified BMA can be applied to a virtual reality or a game or an HCI system for the disable.

This paper deals with face retrieval using the 1st- and 2nd-order PCA mixture model. The well-known eigenface method uses one set of holistic facial features obtained by PCA. However, the single set of eigenfaces is not enough to represent the complicated face images with large variations of poses and/or illuminations. To overcome this weakness, we propose the (1st-order) PCA mixture method that uses several eigenface sets obtained from the EM learning in PCA mixture model. Furthermore, we propose the 2nd-order PCA mixture method that combines the 2nd-order eigenface method and the PCA mixture model. In the 2nd-order eigenface method, each image is represented by a couple of feature vectors obtained by projecting the face image onto a selected approximate eigenface set and then by projecting the residual face image onto a selected residual eigenface set. Face retrieval is performed by finding the identity that provides the shortest distance in the feature space between the input image and the template image. Simulation results show that face retrieval using the 2nd-order PCA mixture method is best for face images with illumination variations and face retrieval using the 1st-order PCA mixture model is best for the face images with pose variations in terms of ANMRR (Average of the Normalized Modified Retrieval Rank) and CRR (Correct Retrieval Rate).

The recent study has been progressed the research about more semantic image indexing and retrieval. In our paper, we represent the improved concept-based image retrieval by using domain ontology. We analyze the many studies that applied the theory of ontology to concept-based image retrieval. Then, we try to solve the problems when we apply the huge ontologies in image retrieval system. There are two big problems. First, the huge ontologies that have many concepts, is out of date and changed the meaning. Secondly, the many new concepts, especially in particular domain, cannot express in existing ontologies. Therefore, in this paper we try to design and implement the domain ontology about the car based on the WordNet, which is one kinds of ontologies. The experimental result shows that the semantic distances between words are quite close when we test domain ontology than the existing WordNet.

Recently, motion capture has become one of the most promising technologies in animation. Realistic motion data can be captured by recording the movement of a real actor with an optical or magnetic motion capture system. A motion library that is an archive of reusable motion clips is also commercially available. This paper deals with motion editing by a geometric mean filter. Since the captured motion has some noises that cause a jerky motion, it needs a smoothing process to make it natural. A geometric mean filter is proposed to produce natural motions without jerky motions. Experimental results show that the geometric mean filter can effectively remove noises that cause a jerky motion and it can guarantee the most natural motions among various spatial filters. This method could be applied to the various fields such as real time animation, virtual reality applications, 3D applications, and etc.

In this paper, for broadband Internet users, high quality VOD (Video on Demand) service architecture including network and platform is presented. As the existing IP-network cannot provide a guaranteed bandwidth, a local server based network architecture is suggested and implemented. Local nodes are established to consider network traffic related to the number of users and geographical locality. Users are routed to the local node that can provide a guaranteed bandwidth. Also VoD service platform is designed to control traffic load balancing, which can distribute traffic load to local servers. The designed load balancing scheme is works well in actual environment. On the service architecture, commercial VoD(Video-on-Demand) service is now open to KT broadband Internet users (http://homemedia.megapass.net).

This paper describes a geometric query model for dynamic exploring multidimensional data. An application of the model for solving the problem of materials selection in product design is discussed. Data from database are interpreted geometrically as multidimensional points. A query window is a query solid of any shape specified by its location. The queries are formulated with geometric objects and operations over them. The geometric objects and operations are described with implicit functions. The process of query specification is visualized. The user poses the queries through graphics interface accessing dynamically multidimensional points, geometric primitives and applying geometric operations over them.

In this paper, we propose and analyze a wireless MAC protocol named APRMA, which is capable of supporting the ABR type data service and maximizing channel utilization. In original PRMA protocol, data terminals cannot reserve slot. So several types of schemes for supporting data traffiic, but most of them are too complicate to implement. So we propose an efficient and simple MAC protocol for wireless communication. In this study, the terminal which wants to request for ABR type service, acquires a minimum bandwidth from system for the first time. If the system have extra available bandwidth, ABR terminals would acquire additional bandwidth slot by slot. As a result, APRMA protocol can support the data service with loss sensitivity and maintain their channel utilization highly. Also high priority services like voice can be satisfied with their QoS by APRMA.

In this paper, we combine adaptive modulation and coding (AMC) with multiple input multiple output (MIMO) VBLAST multiplexing to improve the throughput performance of AMC in next generation mobile communication systems. In addition, we propose a system that adopts selection transmit diversity (STD) in the combined AMC-MIMO VBLAST system. The received signal-to-noise ratio (SNR) is improved by adopting STD techniques and an improved SNR increases a probability of selecting modulation and coding scheme (MCS) level that supports higher data rate. From the simulation results, the investigated MIMO-STD VBLAST system provides a throughput gain of 1Mbps compared with simply combined AMC-MIMO VBLAST system when the required SNR is 15dB. Also, the higher throughput is achieved by AMC-TD schemes and AMC-STTD scheme provides about 250kbps increase in throughput. And AMC-STD with 2 transmit antennas achieves about 420 kbps throughput improvement over the conventional AMC at 9dB SNR.

In this paper, we have evaluated the BER performance of an asynchronous DS/CDMA BPSK system using a conventional receiver under impulsive noise environments, and have proposed a selective hard limiting (SHL) receiver in order to compensate for the performance degraded by the impulsive noise. As a result, we show that, under impulsive noise environment, the performance of the proposed receiver is much better than that of the conventional CDMA receiver or the hard limiting CDMA receiver. Hence, we can conclude that the SHL receiver proposed in this paper is an effective CDMA receiver in sense of capability to overcome the impulsive noise environments.

Throughput response characteristics depending on the network bandwidth allocation is needed to be modeled to devise adaptive control mechanism to support QoS of the local network. In this study, we propose a dynamic system model that reveals the response characteristics of network. The adaptive traffic feedback control is applied to this model. And we simulate this system for optimization of adaptive control mechanism. Finally, we implement optimized adaptive control mechanism to the real network. Therefore we observe a good performance with adaptive control mechanism to support QoS of network.

The interworking for voice service between next generation mobile network and traditional network can be deployed better flexible and expansible network conditions with providing efficiency and economy of network at the same time. So it is essential to develop the interworking strategies together with a evolved network and traditional network.This paper describes a design and verification of internetworking protocol for CC of next generation mobile network and SIP of IP network for applying interworking technology to next generation mobile network, which can harmoniously expropraise voice service from traditional network.

To provide fluent on-demand services on Internet, the VOD servers have to possess a powerful processing ability and the network needs a vast bandwidth. The more clients request service, the more these resources are required. This paper presents a web-caching technique for providing fluent VOD services on Internet. This technique adopts some caches in the Head-End-Network that consists of a Switching-Agent (SA), some Head-End-Nodes and many clients. This technique distributively stores video streams in the order of request on some HENs which request an identical video item. Thus, storing streams on each HEN are different. When the client requests service for cached video items, connecting HEN receives streams from HENs which stored them and transmits them to client. These procedures are performed under the control of SA. Therefore this technique distributes the load of HENs, leads to equiloaded HEN and protects data duplication among HENs.

Limitation of bandwidth, restriction of resources and frequent disconnection are main characteristics of ubiquitous computing environments. To reduce these kinds of problems, a new form of data delivery was proposed in which the server broadcasts data to mobile hosts that listen to the broadcast channel. In this paper, we propose a hybrid concurrency control scheme based on broadcast invalidation report. The scheme achieves high transaction throughput, because it uses of re-ordering and locking. By simulation experiments, we show that our scheme consistently demonstrates excellent performance with low space overhead in all parameter settings.

In main-memory resident index structures, secondary cache misses have a considerable effect on the performance of index structures. Recently, several main-memory resident index structures that consider cache have been proposed to reduce the impact of secondary cache misses. However, they still suffer from full secondary cache misses whenever visiting each level of index trees. In this paper, we propose a new index structure that minimizes the total amount of cache miss latency. The proposed index structure prefetches the grandchildren of a current node. The basic structure of the proposed index structure is from CSB+-Tree that uses the concept of the node group to increase fan-out. However the insert algorithm of the proposed index structure reduces the cost of a split significantly. Also, we show the superiority of our algorithm through performance evaluation.

This study is to develop a web-based navigation tool to share various design objects generated in the whole development cycle of the software development environment based on UML, the previous stage of source code, to a version management system centering around an already existing source code between distributed development teams on the web. Furthermore, we provide a facet retrieval system based on which makes use of a object-oriented thesaurus, which supports an integrated environment through which all the project team members can share a lot of source codes and execution files as well as object files produced from the web-based collaborative development environment. Finally, we have designed and implemented a retrieval system for reusable software component that facilitates software developers to manage in their web-based search for the relationship of design information.

Even though most commercial database management systems use pessimistic concurrency control in transaction processing systems, these approaches may restrict system throughput levels inconsistent with the available processing capacity. This paper suggests an efficient hybrid concurrency control scheme that uses a deadlock-free approach and ensures that transactions are re-started at most once. By the simulation-based analysis, we show that the proposed protocol outperforms than static hybrid protocol across all range of system and workload settings.

Data replication is to improve availability and performance in distributed systems and database systems. But it is difficult to keep strict consistency in data update. Existing protocols guarantee strict consistency, but the problem is that they need much cost and time delay. In this paper, hybrid update protocol permitting eager update for original copy and lazy update for other copies in propagation will be introduced. Hybrid update protocol also permits group update in ownership. This protocol manages replica version controls for group update consistency. By combining eager and lazy update with group ownership, it is to improve consistency and performance. Simulation shows it improves transaction throughput and turnaround depending on the application and situation.

Previous studies have shown that visualization is an effective solution in finding relevant information from a huge collection of information. This paper presents experimental results of an information visualization system, which presents retrieved articles through visual abstraction. In order to address the difficulties in interpreting the color codes, the Query Fingerprinting system has been reinforced with embedded search term markings on the color codes. For a non-biased evaluation of the developed algorithms, a series of experiments has been executed on TREC-5 text collection with their corresponding queries and relevance judgments. The results show that the participants who utilized the developed method in judging the relevancy of articles showed better performance while maintaining the accuracy than the users who utilized a system based on the traditional approach. The participants also have shown a high degree of satisfaction with the search term markings in understanding the distributional patterns of queries. The experiment acknowledges the feasibility of the Query Fingerprinting with embedded search term markers as a search-supporting tool, which assists users’ decision-making processes and lessens the search activities.

With Java technology, the Internet and private networks become our computing environment. For example, users can securely access their personal information and applications when they’re far away from the office by using any computer that’s connected to the Internet. When the browser finds the class file included in Web page, it loads it over the network, if necessary, onto the computer the browser is running on. Thus, it is desirable that the class file is as little size as possible, to rapidly transmit various class files. We propose an optimization algorithm applied to Java class file.

Smart Card technology has been a promising one, because it can handle, protect and manage data within a small sized chip. Java card is the major platform for Smart card, because of its platform independence and secure mechanism. But as a limit of hardware, many functions of Java Virtual Machine are not supported. One of these functions is verifying, because verifier is complicated with large size. In this paper, we propose a very small verifier to put on-card verifier into smart card feasibly.

In this paper, we present a new efficient parallel programming environment on Grid, called DOVE-G(Distributed Object-oriented Virtual Computing Environment on Grid) based on distributed object model. DOVE-G integrates application on Grid environment by encapsulating grid services into DOVE-G object, and hence provides a unified view of distributed object model for application and Grid environments as if they are merged into one single programming environment. The design goal of DOVE-G is to provide users with an easy-to-use transparent parallel programming environment on Grid by supporting efficient parallelisms encapsulated and distributed over DOVE-G objects, while allowing to use various Grid services.

The c-commerce demands extensive interactions among multiple-stakeholders with different core competences and roles, aiming at a community goal in dynamically and opportunistically changing environments. Ultimately, this c-commerce requirement can be achieved by a computerized system that can support collaborative mechanisms among the stakeholders. From this motivation, this paper proposes a role-driven component-oriented methodology for developing c-commerce systems. The methodology consists of four phases: collaboration analysis, component analysis, component design, and implementation. The methodology is likely to help improve the system development capability and quality.

We use the naïve Bayes model to forecast software effort. A causal model is developed from the literature, and a procedure to learn Bayesian prior and conditional probabilities is provided. Using a data set of 40 real-life software projects we test our model. Our results indicate that the probabilistic forecasting models allow managers to estimate joint probability distribution over different software effort estimates. A software project manager may use the joint probability distribution to develop a cumulative probability distribution, which in turn may help the manager estimate the uncertainty that the project effort may be greater than the estimated effort.

The knowledge acquisition is considered a critical stage in the process of knowledge based systems development. In this paper, we present the knowledge acquisition approach used in the Nutri-Fuzzy-ORIXÁS. This project aim to study, acquire and manage knowledge and development systems in the nutrients bioavailability area. The process of knowledge acquisition used was proposed in ORIXÁS, a software environment development for knowledge based systems and we introduce an ontology knowledge representation. The ontology has been developed in the Nutri-Fuzzy-ORIXÁS to organize the knowledge and to guide the development of several systems specially the knowledge based system.

In general, high frequency noises included in a normal speech stream are difficult to remove from the speech stream. Because an unvoiced phoneme seems like a high frequency noise, it may be removed during denoising. A low frequency noise (hum noise), on the other hand, may come from a circuitry imbalance, a wrongly designed ground point in PCB, or imbalance among the parts mounted on a board. This experiment results show that the merging algorithm is very robust against external effects. The merging algorithm is proposed to extract valid speech-sounds in terms of position and frequency range. It needs some numerical methods for an adaptive DWT implementation and performs unvoiced/voiced classification and denoising. Since the merging algorithm can decide the processing parameters relating to voices only and is independent of system noises, it is useful for extracting valid speechsounds. The merging algorithm has an adaptive feature for arbitrary system noises and an excellent denoising SNR (signal-to-noise ratio). Its extraction shows that the denoising of compounded noise and the improved extraction and the merging algorithm can not be disturbed by an unexpected system interference.

The total processing time may vary according to the order of visit when a mobile agent is sequentially migrated to another node. An effective migration algorithm is one in which the processing time is kept to its minimum from the initial state to the destination state by ordering the process. The total time spend for the process can be minimized by adopting an effective migration algorithm. This paper proposes AMIS as the method used for the migration of the mobile agent. AMIS minimizes the total migration time of the mobile agent, and provides a firm and safe order for the migration of the mobile agent.

One serious issue for building an autonomous agent is that an agent does not understand the environment in which it is situated. To understand the world, the agent’s perception should be obtained directly from its own sensors instead of being provided indirectly by a human. Cohen suggests a physical schema as a conceptual primitive which enables an agent to percept a pattern directly. Cohen demonstrates that physical schema can be learned through the agent’s own sensorimotor activities. We propose negation as a conceptual primitive which enables an agent to recognize a schema itself. We also propose that emotive schema is necessary for building an autonomous agent as shown in the area of planning.

A speaker model in speaker recognition system is to be trained from a large data set gathered in multiple sessions. Large data set requires large amount of memory and computation, and moreover it’s practically hard to make users utter the data in several sessions. Recently the incremental adaptation methods are proposed to cover the problems. However, the data set gathered from multiple sessions is vulnerable to the outliers from the irregular ut-terance variations and the presence of noise, which result in inaccurate speaker model. In this paper, we propose an incremental robust adaptation method to minimize the influence of outliers on Gaussian Mixture Model based speaker model. The robust adaptation is obtained from an incremental version of Mestimation. Speaker model is initially trained from small amount of data and it is adapted recursively with the data available in each session. Experimental results from the data set gathered over seven months show that the proposed method is robust against outliers.

In this paper, an efficient speaker identification based on robust vector quantization principal component analysis (VQ-PCA) is proposed to solve the problems from outliers and high dimensionality of training feature vectors in speaker identification. Firstly, the proposed method partitions the data space into several disjoint regions by roust VQ based on M-estimation. Secondly, the robust PCA is obtained from the covariance matrix in each region. Finally, our method obtains the Gaussian Mixture model (GMM) for speaker from the transformed feature vectors with reduced dimension by the robust PCA in each region. Compared to the conventional GMM with diagonal covariance matrix, under the same performance, the proposed method gives faster results with less storage and, moreover, shows robust performance to outliers.

In this paper, we present an intra-speaker warping factor estimation based on pitch alteration utterance. The feature space distributions of untransformed speech from the pitch alteration utterance of intra-speaker would vary due to the acoustic differences of speech produced by glottis and vocal tract. Therefore, it may be possible to determine the amplitude warping factor by calculating the inverse ratio of input to reference pitch. As the recognition results, the error rate is reduced from 0.4% to 2.3% for digit and word decoding.

This paper describes a part of an extended use case approach for real time object-oriented software development. Its foundation is an object-oriented software design approach which partitions design schema into layered design component architecture of functional components called “design component unit”. A use case action matrix contains a collection of related scenarios each describing a specific variant of an executable sequence of use case action units, which reflects the behavioral properties of the real time system design. Proposed scenario based testing and test plan metric measure and produce an ordering of this scenario set to enhance productivity, and promote and capitalize on test case reusability of existing scenarios. To illustrate the proposed approach uses an example of real time UPS (uninterruptible power system).

In this paper, an efficient non-scan design-for-testability (DFT) method for finite state machine(FSM) is proposed. The proposed method always guarantees short test pattern generation time and complete fault efficiency. It has a lower area overhead than full-scan and other non-scan DFT methods and enables to apply test patterns at-speed. The efficiency of the proposed method is demonstrated using well-known MCNC’91 FSM benchmark circuits.

Routing protocols are being developed in a way such that they can search paths based on application needs or paths that can increase network utilization. This thesis proposes a Distributed Multiplepath Searching algorithm based on the network fault detection. This algorithm efficiently searches the loop-free multiple paths heading from one node towards all nodes within a network. Also, this algorithm is designed to search the optimal path selectively by expansion. We show our algorithm’s experimental result by simulation in a test network.

In this paper, we present an Object-Oriented Air Defense Simulation System, called ADSim, for simulating modern day combat dynamics of air defense simulation involving multiple targets and multiple platforms. ADSim has been developed on the basis of a new approach to object-oriented modeling which integrates Conceptual Model of Mission Space(CMMS) and Unified Software Development Process(USDP). We shall show that CMMS based description of simulation domain can be systematically translated to build an object-oriented simulation, and CMMS common representation templates can be effectively used to design and implement scenario based military specification. Moreover, the separation of the relatively static simulation architecture from the evolvable problem domain modeling for specific application scenario provides users with modularity and extensibility by encapsulating the sequencing information derived from the domain modeling as a part of the simulation architecture. ADSim system architecture consists of a pre-processor for battle scenario definition and simulation data set up, a main processor for triggering battle field events and advancing simulation time, and a post processor to record simulation history. ADSim is developed in the evolutionary software life cycle approach, and implemented in C++.

Multicast is an internetwork service that provides efficient delivery of packets from a single source to multiple recipients. When there are large number of members in the group, security and scalability problems arise and an attempt to solve this, gives rise to additional computational complexities at the server. A model is said to be highly efficient if only it has less computational complexity at the server for all membership events and highly secure only when it requires large number of computations to successfully break the multicast model. In this paper, the computational complexities are determined and analyzed for different multicast models. Theoretical evaluation and experimental results prove that for all the membership events, the recently proposed multicast model named LeaSel has computational complexity of O(N_SG) when compared to other models which has computational complexity of O(N), where N ≫ N_SG. It is also shown that to successfully break LeaSel, the computational complexity is O(SaN) when compared to other models whose computational complexity is O(Sn).

The model-based approach to diagnosis is one of the important approach to the system diagnosis, and the main problem for the approach is that how to generate the diagnoses. In this paper, an algorithm for computing all minimal conflicts using structured description system is introduced, then the diagnoses can be generated from all the minimal conflicts. Furthermore, an algorithm for computing diagnoses straightforwardly from the structured description is presented. The correctness of the algorithm is proved, and the time complexity of the algorithm is also analyzed. At last, the algorithms are compared with related works. The algorithms will terminate in polynomial time for some special system.

Breast cancer is one of the leading causes of death from cancer among women. Both its earlier detection and better treatment have been shown to significantly save lives and reduce high costs. Thus, breast imaging systems must recognize and locate very small lesions. This work is concerned with the finite element time domain (FETD) simulation of ultrasound wave propagation for a recent ultrasound clinical amplitude reconstruction imaging (CARI) technique for the breast tumor detection. The CARI method is especially attractive for detecting cancer surrounded by fatty tissues because they both appear dark in a conventional ultrasound image and makes it hard to recognize the size of the tumor. The mathematical modeling framework is presented. Numerical simulations are performed for a 2D and 3D breast model to assess the sensitivity of the CARI method. 3D simulations confirm the quantitative results obtained for the 2D breast model. Moreover, the study shows the effectiveness of the FETD to simulate the CARI modality.

A set of finite elements (FEs) is formulated to analyze wave propagation through inhomogeneous material when subjected to mechanical, thermal loading or piezo-electric actuation. Elastic, thermal and electrical properties of the materials are allowed to vary in length and thickness direction. The elements can act both as sensors and actuators. These elements are used to model wave propagation in functionally graded materials (FGM) and the effect of inhomogeneity in the wave is demonstrated. Further, a surface acoustic wave (SAW) device is modeled and wave propagation due to piezo-electric actuation from interdigital transducers (IDTs) is studied.

The equal width wave (EW) equation is a model partial differential equation for the simulation of one-dimensional wave propagation in nonlinear media with dispersion processes. The EW-Burgers equation models the propagation of nonlinear and dispersive waves with certain dissipative effects. In this work, we derive exact solitary wave solutions for the general form of the EW equation and the generalized EW-Burgers equation with nonlinear terms of any order. We also derive analytical expressions of three invariants of motion for solitary wave solutions of the generalized EW equation.

A method for solving exactly the Helmholtz equation in parabolic rotational coordinates is presented using separability of the eigenfunctions and the Frobenius power series expansion technique. Two examples of interest in wave physics are considered and analyzed quasianalytically: (I) the wavefunctions of an electron in a quantum dot confined by two paraboloids (forming a lens-shaped structure) and the associated energy spectrum, and (II) the acoustic eigenmodes and eigenfrequencies of the pressure field bounded by rigid walls as defined by two paraboloids. The quantum dot (acoustic enclosure) problem is a Dirichlet (Neumann) boundary condition problem. In both cases, eigenfunctions and eigenmodes are calculated and the shape-dependence of the first eigenvalue for the groundstate in the quantum dot case (and the fundamental mode in the acoustic enclosure case) is examined.

A geometrically non-linear Spectral Finite Flement Model (SFEM) including hysteresis, internal friction and viscous dissipation in the material is developed and is used to study non-linear dissipative wave propagation in elementary rod under high amplitude pulse loading. The solution to non-linear dispersive dissipative equation constitutes one of the most difficult problems in contemporary mathematical physics. Although intensive research towards analytical developments are on, a general purpose cumputational discretization technique for complex applications, such as finite element, but with all the features of travelling wave (TW) solutions is not available. The present effort is aimed towards development of such computational framework. Fast Fourier Transform (FFT) is used for transformation between temporal and frequency domain. SFEM for the associated linear system is used as initial state for vector iteration. General purpose procedure involving matrix computation and frequency domain convolution operators are used and implemented in a finite element code. Convergnence of the spectral residual force vector ensures the solution accuracy. Important conclusions are drawn from the numerical simulations. Future course of developments are highlighted.

Finite Element calculations were performed on finite nanowire superlattice (NWSL) structures with a cylindrical cross section so as to determine electronic eigenstates and energy eigenvalues. In recent years, such structures have been grown as they are good candidates for use in active regions of future optoelectronic devices. In particular, we analyzed the qualitative differences in terms of wavefunctions and energy eigenvalues between structures containing the same number of barriers and wells (asymmetrical) and structures where the number of barrier layers is one above the number of well layers (symmetrical). Dirichlet boundary conditions were imposed on the surface of the nanowire structures corresponding to the case where the nanostructure environment is vacuum. We compared our results with those available for the Kronig-Penney model describing infinite NWSLs. Asymmetrical NWSL structures show qualitative and quantitative differences as compared to both symmetrical NWSL structures and infinite periodic NWSL structures.

The Euler’s equations describing the dynamics of capillary-gravity water waves in two-dimensions are considered in the limits of small-amplitude and long-wavelength under appropriate boundary conditions. Using a double-series perturbation analysis, a general Boussinesq type of equation is derived involving the small-amplitude and longwavelength parameters. A recently introduced sixth-order Boussinesq equation by Daripa and Hua [Appl. Math. Comput. 101 (1999), 159–207] is recovered from this equation in the 1/3 Bond number limit (from below) when the above parameters bear a certain relationship as they approach zero.

A Green function technique is employed to investigate the propagation of elastic waves in a semi-infinite damped media. The calculations are based on the linear response function approach, which is very convenient to deal with this kind of problem. Both the displacement and the gradient displacement Green functions are determined. All deformations in the media are supposed to be negligible, so the motions considered here are purely elastic waves. A damping term γ is included in a phenomenological way into the wave vector expression. By using the fluctuation-dissipation theorem, the power spectrum of the elastic waves is also derived, and has interesting properties.

Numerical simulations of a spherical shock refraction have been successfully conducted by a front tracking method. We demonstrate the efficiency of the front tracking algorithm by comparing the L₁-error of spherical simulations by tracked and untracked methods. We find that the tracked algorithm is about 64 (256) times faster than the corresponding method without tracking the interface for a 2d (3d) simulation.

In this paper we describe a new conservative difference scheme and apply it to the description of the dynamics of a shape memory alloy rod. The scheme preserves the conservation of the total energy on the grid. A major emphasis is given to the description of hysteresis effects in almost-elastic, pseudoelastic and quasiplastic regimes. Stress-strain dependencies are analysed and computational experiments are presented for main thermomechanical characteristics of the material, including displacement and temperature fields.

A problem of eliminating the unwanted time-harmonic noise on a predetermined region of interest is solved by active means, i.e., by introducing the additional sources of sound, called controls, that generate the appropriate annihilating signal (anti-sound). The general solution for controls has been obtained previously for both the continuous and discrete formulation of the problem. Next, the control sources are optimized using different criteria. Minimization of the overall absolute acoustic source strength is equivalent to minimization of multi-variable complex functions in the sense of L₁ with conical constraints. The global L₁ optimum appears to be a special layer of monopoles on the perimeter of the protected region. The use of quadratic cost functions, e.g., the L₂ norm of the controls, leads to a versatile numerical procedure. It allows one to analyze sophisticated geometries in the case of a constrained minimization. Finally, minimization of power consumed by an active control system always involves interaction between the sources of sound and the surrounding acoustic field, which was not the case for either L₁ or L₂. One can, in fact, build a control system that would require no power input for operation and may even produce a net power gain while providing the exact noise cancellation. This, of course, comes at the expense of having the original sources of noise produce even more energy.

A three-dimensional reaction-diffusion model for premixed flames with radiative heat losses is studied numerically. In accordance with previous analytical predictions and two-dimensional numerical simulations, it is shown that cellular flames occurring in low Lewis number premixtures can propagate at heat-loss rates greater than the maximum that extinguishes the planar flame. At sufficiently high heat losses, the flame interface breaks up into separate self-drifting flame balls while a significant portion of the fuel remains unconsumed. A further increase in heat losses leads to a total suppression of the flame.

A modal spectral element method is developed for solving the three-dimensional Helmholtz’s equation, which is the equation governing time-harmonic acoustic waves. Computational cost for solving three-dimensional Helmholtz’s equation increases significantly as the wave number increases, due to the required resolution per wavelength. Furthermore, for a standard Galerkin finite element discretization, more nodes are needed per wavelength at high wave numbers than at low wave numbers. Therefore a more efficient numerical method based on higher-order hierarchical bases is sought. The comparison between h-extension and p-extension shows that the spectral element method leads to fewer grid points per wavelength, for the same accuracy. It also offers the same advantage as the finite element method to address complex geometry and general material property as tetrahedral elements are used. A simple example is addressed and compared with the exact solutions to confirm the accuracy of the method.

The propagation of acoustic waves originating from stretching of intense self-similar vortices in the non-uniform mean flow is studied by numerical modeling using high-order compact approximationNear-wall stretching of initial vortex by the stagnation flow leads to sound radiation from the generated pressure quadrupole. To mimic unsteady stagnation flows and impingement jets, the stagnation flow has been switched off at some time moment. Subsonic stagnation flow and flow around a cylinder are taken as prototypes of real-world flows with strong gradients of mean pressure and velocity. Compressibility of the background mean flow and the vortex are taken into account and its effect on amplification of acoustic pressure is discussed. Generation of sound by stretching of vorticity dipole leads to formation of a three-spot wave with maximum acoustic pressure at the centerline. Since aeroacoustic applications require good physical approximations for the viscous nature of tip vortices, several semi-empirical profiles of vortex velocity were considered. The intensity and directivity of acoustic wave patterns appear to be quite different for Taylor and Vatistas vortices.

In this work, we report on the impact of flow pulsatility on the laminar mixing surface/interface formed between two converging microchannel flows. The motivation behind the study is to assess the potential for pulsatility as a possible MEMS-mixing strategy. A 3-D computational model of the converging flow at a 90/dg junction is developed using the Fluent6 CFD software and the volume-of-fluid algorithm is used to track time-dependent behavior of the interface downstream of the junction. Results thus far have shown that for certain parametric regimes a complex, evolving interfacial distortion can form which propagates and persists downstream of the junction. Time-series for the total interfacial area and the interfacial motion have been extracted from numerical data and spectral analyses have been performed; some interesting nonlinear behavior has been observed. Of particular importance, the results also show that the complexity of the interfacial structure is only significant at higher frequencies (order of kHz) which is appropriate for MEMS-based pumping devices.

This paper discusses 2D solutions of the Helmholtz equation by finite elements. It begins with a short survey of the absorbing and transparent boundary conditions associated with the DtN technique. The solution of the discretized system by means of a standard Galerkin or Galerkin Least-Squares (GLS) scheme is obtained by a preconditioned Krylov subspace technique, speci.cally a preconditioned GMRES iteration. The stabilization paremeter associated to GLS is computed using a new formula. Two types of preconditioners, ILUT and ILU0, are tested to enhance convergence.

Stringent requirements for component performance plus economic and environmental challenges for supersonic aircraft leave little room for inefficiencies in airframe design [1], making it necessary to have accurate and reliable prediction tools for boundary-layer transition to turbulence. To help develop and calibrate such tools, direct numerical simulations (DNS) of various stages during transition over both model and realistic flow configurations are necessary. This paper describes the application of a DNS solver based on high-order compact differences to supersonic swept-wing configurations. Specifically, spatial simulations of crossflow instability in swept-wing boundary layers have been performed and validated against predictions based on the simpler but nearly equally accurate parabolized stability equations. The excitation of crossflow modes due to localized surface disturbances is also investigated. To help increase the efficiency of crossflow simulations for infinite-span swept wings, a simple modification to the DNS procedure is shown to significantly reduce the total grid requirement.

The aim of this study is to find optimal conditions for the formation of carbon nanotubes in a laser furnace. This paper will describe our mathematical model and numerical algorithm, and discuss some of the fluid physics underlying this crucial technology. An axisymmetric unsteady computational gas dynamic model of plume expansion into ambiance has been developed. In the present work the vapor gas phase is modeled using the Relaxing TVD scheme in generalized coordinates. A numerical model of pulsed ablated gas is proposed based on the mass, momentum, and energy conservation laws. The proposed model implements a multi-species formulation for concentration of chemical components combined with the compressible Euler equations. To advance the solution in time, this set of equations is integrated numerically by second-order Runge-Kutta scheme.

Monte Carlo simulations are performed to study the in-plane transport of spin-polarized electrons in III-V semiconductor quantum wells. The density matrix description of the spin polarization is incorporated in the simulation algorithm. The spin-orbit interaction terms generate coherent evolution of the electron spin polarization and also cause dephasing. The spatial motion of the electrons is treated semiclassically. Three different scattering mechanisms—optical phonons, acoustic phonons and ionized impurities—are considered. The electric field is calculated self-consistently from the charge distribution. The Monte Carlo scheme is described, and simulation results are reported for temperatures in the range 77-300 K.

This research is to develop education systems that are designed to build students’ attitude and habit of environmental preservation through acquiring knowledge and functions of natural environment. These systems support diverse learning activities such as writing, drawing, listening natural sounds and music, and problem solving. These systems are technically designed on the Web to promote students’ creativity and autonomy, and also are theoretically based on constructivism to encourage the will of environmental preservation. Moreover, these Web-base systems include diverse functions such as material resources, environmental quiz pool and environmental work gallery, which motivate students. learning activities. These Web-based systems are expected to be used as effective tools to achieve the goals of environmental education such as acquiring environmental knowledge and functions, building attitude of environmental preservation, and participating in the environmental preservation activities.

The web-based instruction has been rapidly increasing in the educational environment with the development of information and communication technology, and this has brought a need for evaluating the web-based instruction. This paper evaluates the web-based instruction by investigating the levels of students satisfaction and comparing them with the lecture-based instruction to find the differences between the two instructions and the problems of the web-based instruction. The results reveal that the web-based instruction has the advantage of multimedia effects but needs to be more improved in terms of interactions. Also, the factor analysis shows that the web-based instruction is composed of two dimensions of presenting instructional materials and operating a course while the lecture-based instruction is composed of only one component. These findings suggest that the web-based instruction should be designed and implemented in consideration of the features of the web system.

With recent technical advances in Internet technologies, virtual schools become an important alternative for the traditional school. The virtual schools can overcome time and space limit in the traditional class. But, existing technologies still have some technical limitations for virtual implementation. Especially, existing transaction models are not suitable for supporting virtual schools. In this paper, we first identify transaction requirements for virtual school environments and present a new transaction model based on those requirements.

As more web-based applications are widely used, various kinds of web applications are developed. Among them, web-based learning becomes popular in many schools. As a result, virtual educations such as WBI learning, CAI, and distance learning are o.ered actively in many schools. With the advantages of web-based learning, in order to achieve feasible and efficient effects on education, a new web-based instruction model that considers the abilities, the interests, and the aptitudes of students individually is required.In this paper, a new web-based instruction model, called a Hybrid model, is proposed. In addition, we design and implement the proposed model. And then, in order to analyze the educational effects of our model and the learning fulfillment of our model, two models are applied to a computer accounting class of a commercial high school. Students attend the webbased class in a computer center for 100 minutes autonomously and then, a questionnaire is made.

With the widespread of computers and the Internet, our society has been rapidly oriented toward the use of information. This has profoundly influenced the ways in which education is carried out. In an information-oriented society, the ability of understanding information and utilizing information is important to students of special education programs as well as normal students. This research proposes an information literacy cultivation system for emotionally disturbed students. It first identifies the elements of information literacy for these students. Based on the identified elements, the system was designed and implemented to provide the diverse educational opportunities for emotionally disturbed students. The characteristics of the proposed information literacy cultivation system are as follows. First, the system adaptively introduces learning contents according to the levels of students. learning abilities. Second, the system is composed of rich teaching-learning media that can motivate students to actively participate in the learning process. Third, the system promotes the continuous interactions among teachers, students, and their parents. Finally, the system supports the individualized learning activities according to students. learning phases as well as the levels of their learning abilities.