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Physical Sciences and Mathematics Commons™

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2004

Singapore Management University

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Articles 1 - 30 of 104

Full-Text Articles in Physical Sciences and Mathematics

High Performance P300 Speller For Brain-Computer Interface, Cuntai Guan, Manoj Thulasidas, Jiankang Wu Dec 2004

High Performance P300 Speller For Brain-Computer Interface, Cuntai Guan, Manoj Thulasidas, Jiankang Wu

Research Collection School Of Computing and Information Systems

P300 speller is a communication tool with which one can input texts or commands to a computer by thought. The amplitude of the P300 evoked potential is inversely proportional to the probability of infrequent or task-related stimulus. In existing P300 spellers, rows and columns of a matrix are intensified successively and randomly, resulting in a stimulus frequency of 1/N (N is the number of rows or columns of the matrix). We propose a new paradigm to display each single character randomly and individually (therefore reducing the stimulus frequency to 1/(N*N)). On-line experiments showed that this new speller significantly improved the …

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Method For Identifying Individuals, Manoj Thulasidas Dec 2004

Method For Identifying Individuals, Manoj Thulasidas

Research Collection School Of Computing and Information Systems

A method and system for identifying a subject comprises obtaining a digitised recording of an electrocardiogram measurement of the subject to be identified, the digitised recording being a cyclic waveform having a peak amplitude. The digitised recording is normalised to reduce variations due to physiological effects, and the normalised recording is processed to determine a feature vector in the frequency domain. The distance between the determined feature vector and a predetermined feature vector is measured to identify the subject.

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On Security Notions For Steganalysis, Kisik Chang, Robert H. Deng, Feng Bao, Sangjin Lee, Hyungjun Kim, Jongin Lim Dec 2004

On Security Notions For Steganalysis, Kisik Chang, Robert H. Deng, Feng Bao, Sangjin Lee, Hyungjun Kim, Jongin Lim

Research Collection School Of Computing and Information Systems

There have been some achievements in steganalysis recently. Many people have been making strides in steganalysis. They have approached steganalysis from different angles; from information theory to complexity theory. Anderson gave a possibility that there is a provable secure steganographic system, but there had not been complexity theoretical approaches for years. In 2002, Katzenbeisser and Petitcolas defined the conditional security of steganography and gave a possibility for a practical, provable secure steganography for the first time, and Hopper et al. introduced a provable secure steganographic algorithm in the sense of complexity theory. Chang et al. also tried to define the …

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Automatic Model Structuring From Text Using Biomedical Ontology, Joshi R., Li X., Ramachandaran S., Tze-Yun Leong Dec 2004

Automatic Model Structuring From Text Using Biomedical Ontology, Joshi R., Li X., Ramachandaran S., Tze-Yun Leong

Research Collection School Of Computing and Information Systems

Bayesian Networks and Influence Diagrams are effective methods for structuring clinical problems. Constructing a relevant structure without the numerical probabilities in itself is a challenging task. In addition, due to the rapid rate of innovations and new findings in the biomedical domain, constructing a relevant graphical model becomes even more challenging. Building a model structure from text with minimum intervention from domain experts and minimum training examples has always been a challenge for the researchers. In the biomedical domain, numerous advances have been made which may make this dream a possibility now. We are currently trying to build a general …

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Design Lessons On Access Features In Paper, Yin-Leng Theng, Dion Hoe-Lian Goh, Ming Yin, Eng-Kai Suen, Ee Peng Lim Dec 2004

Design Lessons On Access Features In Paper, Yin-Leng Theng, Dion Hoe-Lian Goh, Ming Yin, Eng-Kai Suen, Ee Peng Lim

Research Collection School Of Computing and Information Systems

Using Nielsen's Heuristic Evaluation, this paper reports a user study with six usability-trained subjects to evaluate PAPER's access features in assisting users to retrieve information efficiently, part of an on-going design partnership with stakeholders and designers/developers. PAPER (Personalised Adaptive Pathways for Exam Resources) is an improved version evolving from an earlier implementation of GeogDL built upon G-Portal, a geospatial digital library infrastructure. After two initial evaluations with student and teacher design partners, PAPER has evolved into a system containing a new bundle of personalized, interactive services with four modules: mock exam; personal coach (practice and review); trend analysis and performance …

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Supporting Field Study With Personalized Project Spaces In A Geographical Digital Library, Ee Peng Lim, Aixin Sun, Zehua Liu, John Hedberg, Chew-Hung Chang, Tiong-Sa Teh, Dion Hoe-Lian Goh, Yin-Leng Theng Dec 2004

Supporting Field Study With Personalized Project Spaces In A Geographical Digital Library, Ee Peng Lim, Aixin Sun, Zehua Liu, John Hedberg, Chew-Hung Chang, Tiong-Sa Teh, Dion Hoe-Lian Goh, Yin-Leng Theng

Research Collection School Of Computing and Information Systems

Digital libraries have been rather successful in supporting learning activities by providing learners with access to information and knowledge. However, this level of support is passive to learners and interactive and collaborative learning cannot be easily achieved. In this paper, we study how digital libraries could be extended to serve a more active role in collaborative learning activities. We focus on developing new services to support a common type of learning activity, field study, in a geospatial context. We propose the concept of personal project space that allows individuals to work in their personalized environment with a mix of private …

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Vertical Sensitivity For The Information Security Health Rating Of Enterprises, Arcot Desai Narasimhalu, Nagarajan Dayasindhu, Raghavan Subramanian Dec 2004

Vertical Sensitivity For The Information Security Health Rating Of Enterprises, Arcot Desai Narasimhalu, Nagarajan Dayasindhu, Raghavan Subramanian

Research Collection School Of Computing and Information Systems

INFOSeMM Maturity model was developed jointly by SMU and Infosys. It is recognized that different industry verticals will have different levels of recommended maturity levels. This paper articulates the need for developing the industry vertical benchmarks.

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Accommodating Instance Heterogeneities In Database Integration, Ee Peng Lim, Roger Hsiang-Li Chiang Nov 2004

Accommodating Instance Heterogeneities In Database Integration, Ee Peng Lim, Roger Hsiang-Li Chiang

Research Collection School Of Computing and Information Systems

A complete data integration solution can be viewed as an iterative process that consists of three phases, namely analysis, derivation and evolution. The entire process is similar to a software development process with the target application being the derivation rules for the integrated databases. In many cases, data integration requires several iterations of refining the local-to-global database mapping rules before a stable set of rules can be obtained. In particular, the mapping rules, as well as the data model and query model for the integrated databases have to cope with poor data quality in local databases, ongoing local database updates …

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A Periodic-Review Inventory Model With Application To The Continuous-Review Obsolescence Problem, Yuyue Song, Hoong Chuin Lau Nov 2004

A Periodic-Review Inventory Model With Application To The Continuous-Review Obsolescence Problem, Yuyue Song, Hoong Chuin Lau

Research Collection School Of Computing and Information Systems

In this paper we consider a stochastic-demand periodic-review inventory model with sudden obsolescence. We characterize the structure of the optimal policy and propose a dynamic programming algorithm for computing its parameters. We then utilize this algorithm to approximate the solution to the continuous-review sudden obsolescence problem with general obsolescence distribution. We prove convergence of our approximation scheme, and demonstrate it numerically against known closed-form solutions of special cases.

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Multivariate Stochastic Volatility Models: Bayesian Estimation And Model Comparison, Jun Yu, Renate Meyer Nov 2004

Multivariate Stochastic Volatility Models: Bayesian Estimation And Model Comparison, Jun Yu, Renate Meyer

Research Collection School Of Economics

In this paper we show that fully likelihood-based estimation and comparison of multivariate stochastic volatility (SV) models can be easily performed via a freely available Bayesian software called WinBUGS. Moreover, we introduce to the literature several new specifications which are natural extensions to certain existing models, one of which allows for time varying correlation coefficients. Ideas are illustrated by fitting, to a bivariate time series data of weekly exchange rates, nine multivariate SV models, including the specifications with Granger causality in volatility, time varying correlations, heavy-tailed error distributions, additive factor structure, and multiplicative factor structure. Empirical results suggest that the …

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Job Scheduling With Unfixed Availability Constraints, Hoong Chuin Lau, C. Zhang Nov 2004

Job Scheduling With Unfixed Availability Constraints, Hoong Chuin Lau, C. Zhang

Research Collection School Of Computing and Information Systems

Standard scheduling theory assumes that all machines are continuously available throughout the planning horizon. In many manufacturing and service management situations however, machines need to be maintained periodically to prevent malfunctions. During the maintenance period, a machine is not available for processing jobs. Hence, a more realistic scheduling model should take into account machine maintenance activities. In this paper, we study the problem of job scheduling with unfixed availability constraints on a single machine. We first propose a preliminary classification for the scheduling problem with unfixed availability constraints based on maintenance constraints, job characteristics and objective function. We divide our …

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Finding Constrained Frequent Episodes Using Minimal Occurrences, Xi Ma, Hwee Hwa Pang, Kian-Lee Tan Nov 2004

Finding Constrained Frequent Episodes Using Minimal Occurrences, Xi Ma, Hwee Hwa Pang, Kian-Lee Tan

Research Collection School Of Computing and Information Systems

Recurrent combinations of events within an event sequence, known as episodes, often reveal useful information. Most of the proposed episode mining algorithms adopt an apriori-like approach that generates candidates and then calculates their support levels. Obviously, such an approach is computationally expensive. Moreover, those algorithms are capable of handling only a limited range of constraints. In this paper, we introduce two mining algorithms - episode prefix tree (EPT) and position pairs set (PPS) - based on a prefix-growth approach to overcome the above limitations. Both algorithms push constraints systematically into the mining process. Performance study shows that the proposed algorithms …

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Anonymous Secure Routing In Mobile Ad-Hoc Networks, Bo Zhu, Zhiguo Wan, Mohan S. Kankanhalli, Feng Bao, Robert H. Deng Nov 2004

Anonymous Secure Routing In Mobile Ad-Hoc Networks, Bo Zhu, Zhiguo Wan, Mohan S. Kankanhalli, Feng Bao, Robert H. Deng

Research Collection School Of Computing and Information Systems

Although there are a large number of papers on secure routing in mobile ad-hoc networks, only a few consider the anonymity issue. In this paper, we define more strict requirements on the anonymity and security properties of the routing protocol, and notice that previous research works only provide Weak Location Privacy and Route Anonymity, and are vulnerable to specific attacks. Therefore, we propose the Anonymous Secure Routing (ASR) protocol that can provide additional properties on anonymity, i.e. Identity Anonymity and Strong Location Privacy, and at the same time ensure the security of discovered routes against various passive and active attacks. …

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Logistics Network Design With Differentiated Delivery Lead Time: A Chemical Industry Case Study, Michelle Lee Fong Cheong, Rohit Bhatnagar, Stephen C. Graves Nov 2004

Logistics Network Design With Differentiated Delivery Lead Time: A Chemical Industry Case Study, Michelle Lee Fong Cheong, Rohit Bhatnagar, Stephen C. Graves

Research Collection School Of Computing and Information Systems

Most logistics network design models assume exogenous customer demand that is independent of the service time or level. This paper examines the benefits of segmenting demand according to lead-time sensitivity of customers. To capture lead-time sensitivity in the network design model, we use a facility grouping method to ensure that the different demand classes are satisfied on time. In addition, we perform a series of computational experiments to develop a set of managerial insights for the network design decision making process.

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The D-Tree: An Index Structure For Planar Point Queries Location-Based Wireless Services, Jianliang Xu, Baihua Zheng, Wang-Chien Lee, Dik Lun Lee Nov 2004

The D-Tree: An Index Structure For Planar Point Queries Location-Based Wireless Services, Jianliang Xu, Baihua Zheng, Wang-Chien Lee, Dik Lun Lee

Research Collection School Of Computing and Information Systems

Location-based services (LBSs), considered as a killer application in the wireless data market, provide information based on locations specified in the queries. In this paper, we examine the indexing issue for querying location-dependent data in wireless LBSs; in particular, we focus on an important class of queries, planar point queries. To address the issues of responsiveness, energy consumption, and bandwidth contention in wireless communications, an index has to minimize the search time and maintain a small storage overhead. It is shown that the traditional point-location algorithms and spatial index structures fail to achieve either objective or both. This paper proposes …

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On Semantic Caching And Query Scheduling For Mobile Nearest-Neighbor Search, Baihua Zheng, Wang-Chien Lee, Dik Lun Lee Nov 2004

On Semantic Caching And Query Scheduling For Mobile Nearest-Neighbor Search, Baihua Zheng, Wang-Chien Lee, Dik Lun Lee

Research Collection School Of Computing and Information Systems

Location-based services have received increasing attention in recent years. In this paper, we address the performance issues of mobile nearest-neighbor search, in which the mobile user issues a query to retrieve stationary service objects nearest to him/her. An index based on Voronoi Diagram is used in the server to support such a search, while a semantic cache is proposed to enhance the access efficiency of the service. Cache replacement policies tailored for the proposed semantic cache are examined. Moreover, several query scheduling policies are proposed to address the inter-cell roaming issues in multi-cell environments. Simulations are conducted to evaluate the …

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Corrective Maintenance Optimization In An Air Force, Hoong Chuin Lau, K. Y. Neo, W. C. Wan Nov 2004

Corrective Maintenance Optimization In An Air Force, Hoong Chuin Lau, K. Y. Neo, W. C. Wan

Research Collection School Of Computing and Information Systems

Successful military mission planning and execution depend critically on equipment serviceability and resupply. Due to the stochastic nature of demands, the forecast of optimal spares and resources needed to guarantee the level of serviceability is a complex problem, especially in a multi-echelon setting. In this paper, we propose a decision-support concept and software tool known as Corrective Maintenance Optimizer (CMO) that helps to optimize system availability, through proper allocation of spare parts, both strategically and operationally.

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Spatial Queries In Wireless Broadcast Systems, Baihua Zheng, Wang-Chien Lee, Dik Lun Lee Nov 2004

Spatial Queries In Wireless Broadcast Systems, Baihua Zheng, Wang-Chien Lee, Dik Lun Lee

Research Collection School Of Computing and Information Systems

Owing to the advent of wireless networking and personal digital devices, information systems in the era of mobile computing are expected to be able to handle a tremendous amount of traffic and service requests from the users. Wireless data broadcast, thanks to its high scalability, is particularly suitable for meeting such a challenge. Indexing techniques have been developed for wireless data broadcast systems in order to conserve the scarce power resources in mobile clients. However, most of the previous studies do not take into account the impact of location information of users. In this paper, we address the issues of …

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Two-Echelon Repairable Item Inventory System With Limited Repair Capacity Under Nonstationary Demands, Hoong Chuin Lau, Huawei Song Nov 2004

Two-Echelon Repairable Item Inventory System With Limited Repair Capacity Under Nonstationary Demands, Hoong Chuin Lau, Huawei Song

Research Collection School Of Computing and Information Systems

We study a repairable item inventory system under limited repair capacity and nonstationary Poisson demands, motivated by corrective maintenance of military equipment. Our goal is to minimize the cost of both spare and repair resource allocation. We propose an efficient analytical model that combines optimization modeling and queuing theory.

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Indexing And Matching Of Polyphonic Songs For Query-By-Singing System, Tat-Wan Leung, Chong-Wah Ngo Oct 2004

Indexing And Matching Of Polyphonic Songs For Query-By-Singing System, Tat-Wan Leung, Chong-Wah Ngo

Research Collection School Of Computing and Information Systems

This paper investigates the issues in polyphonic popular song retrieval. The problems that we consider include singing voice extraction, melodic curve representation, and database indexing. Initially, polyphonic songs are decomposed into singing voices and instruments sounds in both time and frequency domains based on SVM and ICA. The extracted singing voices are represented as two melodic curves that model the statistical mean and neighborhood similarity of notes. To speed up the matching between songs and query, we further adopt proportional transportation distance to index the songs as vantage point trees. Encouraging results have been obtained through experiments.

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Design And Analysis Of A Cooperative Medium Access Scheme For Wireless Mesh Networks, Arup Acharya, Archan Misra, Sorav Bansal Oct 2004

Design And Analysis Of A Cooperative Medium Access Scheme For Wireless Mesh Networks, Arup Acharya, Archan Misra, Sorav Bansal

Research Collection School Of Computing and Information Systems

This paper presents the detailed design and performance analysis of MACA-P, a RTS/CTS based MAC protocol, that enables simultaneous transmissions in wireless mesh networks. The IEEE 802.11 DCF MAC prohibits any parallel transmission in the neighborhood of either a sender or a receiver (of an ongoing transmission). MACA-P is a set of enhancements to the 802.11 MAC that allows parallel transmissions in situations when two neighboring nodes are either both receivers or transmitters, but a receiver and a transmitter are not neighbors. The performance of MACA-P in terms of system throughput is obtained through a simulation of the protocol using …

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Structuring Home Video By Snippet Detection And Pattern Parsing, Zailiang Pan, Chong-Wah Ngo Oct 2004

Structuring Home Video By Snippet Detection And Pattern Parsing, Zailiang Pan, Chong-Wah Ngo

Research Collection School Of Computing and Information Systems

Hand-held camcorders have been popularly used in capturing and documenting daily lives. Nonetheless, searching for personal memories in home videos is still a laborious task. This paper describes novel approaches in detecting snippets and patterns in home videos for content indexing. To deal with the fact that most shots are long and with handshake artifacts, a motion analysis algorithm based on Kalman filter and finite state machine is proposed to decompose videos into tables of snippets. Each snippet is represented by a set of moving and static patterns. The moving patterns are automatically detected and tracked, while the static patterns …

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Clip-Based Similarity Measure For Hierarchical Video Retrieval, Yuxin Peng, Chong-Wah Ngo Oct 2004

Clip-Based Similarity Measure For Hierarchical Video Retrieval, Yuxin Peng, Chong-Wah Ngo

Research Collection School Of Computing and Information Systems

This paper proposes a new approach and algorithm for the similarity measure of video clips. The similarity is mainly based on two bipartite graph matching algorithms: maximum matching (MM) and optimal matching (OM). MM is able to rapidly filter irrelevant video clips, while OM is capable of ranking the similarity of clips according to the visual and granularity factors. Based on MM and OM, a hierarchical video retrieval framework is constructed for the approximate matching of video clips. To allow the matching between a query and a long video, an online clip segmentation algorithm is also proposed to rapidly locate …

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Deformable Object Model Matching By Topological And Geometric Similarity, Kwok-Leung Tan, Rynson W. H. Lau, Chong-Wah Ngo Oct 2004

Deformable Object Model Matching By Topological And Geometric Similarity, Kwok-Leung Tan, Rynson W. H. Lau, Chong-Wah Ngo

Research Collection School Of Computing and Information Systems

In this paper, we present a novel method for efficient 3D model comparison. The method is designed to match highly deformed models through capturing two types of information. First, we propose a feature point extraction algorithm, which is based on “Level Set Diagram”, to reliably capture the topological points of a general 3D model. These topological points represent the skeletal structure of the model. Second, we also capture both spatial and curvature information, which describes the global surface of a 3D model. This is different from traditional topological 3D matching methods that use only low-dimension local features. Our method can …

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Chaos-Induced Escape Over A Potential Barrier, L. Y. Chew, Hian Ann, Christopher Ting, C. H. Lai Oct 2004

Chaos-Induced Escape Over A Potential Barrier, L. Y. Chew, Hian Ann, Christopher Ting, C. H. Lai

Research Collection Lee Kong Chian School Of Business

We investigate the statistical parity of a class of chaos-generated noises on the escape of strongly damped particles out of a potential well. We show that statistical asymmetry in the chaotic fluctuations can lead to a skewed Maxwell–Boltzmann distribution in the well. Depending on the direction of skew, the Kramers escape rate is enhanced or suppressed accordingly. Based on the Perron–Frobenious equation, we determine an analytical expression for the escape rate’s prefactor that accounts for this effect. Furthermore, our perturbative analysis proves that in the zeroth-order limit, the rate of particle escape converges to the Kramers rate.

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Dynamic Access Control For Multi-Privileged Group Communications, Di Ma, Robert H. Deng, Yongdong Wu, Tieyan Li Oct 2004

Dynamic Access Control For Multi-Privileged Group Communications, Di Ma, Robert H. Deng, Yongdong Wu, Tieyan Li

Research Collection School Of Computing and Information Systems

Recently, there is an increase in the number of group communication applications which support multiple service groups of different access privileges. Traditional access control schemes for group applications assume that all the group members have the same access privilege and mostly focus on how to reduce rekeying messages upon user joining and leaving. Relatively little research effort has been spent to address security issues for group communications supporting multiple access privileges. In this paper, we propose a dynamic access control scheme for group communications which support multiple service groups with different access privileges. Our scheme allows dynamic formation of service …

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Trust Establishment In Large Scale Grid Settings, Bo Zhu, Tieyan Li, Huafei Zhu, Mohan S . Kankanhalli, Feng Bao, Robert H. Deng Oct 2004

Trust Establishment In Large Scale Grid Settings, Bo Zhu, Tieyan Li, Huafei Zhu, Mohan S . Kankanhalli, Feng Bao, Robert H. Deng

Research Collection School Of Computing and Information Systems

Trust establishment is hard in grid architecture by the ad hoc nature. To set up trust in large scale of network is more difficult. In this paper, we propose an automatic key management (AKM) model and corresponding key construction schemes. The hierarchical structure is formed automatically and scale seamlessly in arbitrary network sized. Regions are configured differently according to various levels of risks faced. The novel model provides an integrated solution for self-organized trust establishment, upon which rich appliances are securely supported. It is automatic, flexible, and scalable. Furthermore, simulation results show that computation costs due to the variations are …

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Airconn: A Framework For Tiered Services In Public Wireless Lan Hot Spots, A. Acharya, C. Bisdikian, Archan Misra, Y. Ko Oct 2004

Airconn: A Framework For Tiered Services In Public Wireless Lan Hot Spots, A. Acharya, C. Bisdikian, Archan Misra, Y. Ko

Research Collection School Of Computing and Information Systems

Access to the data services via wireless LANs at private and public hot spot sites is becoming commonplace. The goal of the airConn project is to define an architecture and a prototype implementation that enable the provision of premium and non-premium service tiers for both transient and nontransient users of wireless hot spots. airConn provides for dynamic renegotiation of service tiers and facilitates various billing modes. Thus, it enables service providers to increase their revenue opportunities via multiple flexibility manageable service offerings.

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Informal Animation Sketching: Requirements And Design, Richard C. Davis, James A. Landay Oct 2004

Informal Animation Sketching: Requirements And Design, Richard C. Davis, James A. Landay

Research Collection School Of Computing and Information Systems

We present an interface design for creating informal animations from sketches. Current tools for creating animation are extremely complex. This makes it difficult for designers to prototype animations and nearly impossible for novices to create them at all. Simple animation systems exist but severely restrict the types of motion that can be represented. To guide our design of an animation sketching interface, we conducted field studies into the needs of professional and novice animators. These studies show the wide variety of motions that users desire in informal animations and indicate how to prioritize these types of otion. The interface described …

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Comments On "A Practical (T, N) Threshold Proxy Signature Scheme Based On The Rsa Cryptosystem", Guilin Wang, Feng Bao, Jianying Zhou, Robert H. Deng Oct 2004

Comments On "A Practical (T, N) Threshold Proxy Signature Scheme Based On The Rsa Cryptosystem", Guilin Wang, Feng Bao, Jianying Zhou, Robert H. Deng

Research Collection School Of Computing and Information Systems

In a (t, n) threshold proxy signature scheme based on RSA, any t or more proxy signers can cooperatively generate a proxy signature while t-1 or fewer of them can't do it. The threshold proxy signature scheme uses the RSA cryptosystem to generate the private and the public key of the signers. In this article, we discuss the implementation and comparison of some threshold proxy signature schemes that are based on the RSA cryptosystem. Comparison is done on the basis of time complexity, space complexity and communication overhead. We compare the performance of four schemes: Hwang et al., Wen et …

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