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| 2. |
- Fronthaler, Hartwig, et al.
(författare)
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Pyramid-based Image Enhancement of Fingerprints
- 2007
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Ingår i: 2007 IEEE Workshop on Automatic Identification Advanced Technologies proceedings : 7-8 June 2007, Alghero, Italy. - Piscataway, NJ. : IEEE Press. - 1424413001 ; , s. 45-50
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Konferensbidrag (refereegranskat)abstract
- Reliable feature extraction is crucial for accurate biometric recognition. Unfortunately feature extraction is hampered by noisy input data, especially so in case of fingerprints. We propose a method to enhance the quality of a given fingerprint with the purpose to improve the recognition performance. A Laplacian like image-scale pyramid is used for this purpose to decompose the original fingerprint into 3 smaller images corresponding to different frequency bands. In a further step, contextual filtering is performed using these pyramid levels and 1D Gaussians, where the corresponding filtering directions are derived from the frequency-adapted structure tensor. All image processing is done in the spatial domain, avoiding block artifacts while conserving the biometric signal well. We report on comparative results and present quantitative improvements, by applying the standardized NIST FIS2 fingerprint matcher to the FVC2004 fingerprint database along with our as well as two other enhancements. The study confirms that the suggested enhancement robustifies feature detection, e.g. minutiae, which in turn improves the recognition (20% relative improvement in equal error rate on DB3 of FVC2004).
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| 3. |
- Faraj, Maycel, 1979-, et al.
(författare)
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Synergy of lip motion and acoustic features in biometric speech and speaker recognition
- 2007
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Ingår i: IEEE Transactions on Computers. - New York : IEEE Press. - 0018-9340 .- 1557-9956. ; 56:9, s. 1169-1175
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the scheme and evaluation of a robust audio-visual digit-and-speaker-recognition system using lip motion and speech biometrics. Moreover, a liveness verification barrier based on a person's lip movement is added to the system to guard against advanced spoofing attempts such as replayed videos. The acoustic and visual features are integrated at the feature level and evaluated first by a support vector machine for digit and speaker identification and, then, by a Gaussian mixture model for speaker verification. Based on ap300 different personal identities, this paper represents, to our knowledge, the first extensive study investigating the added value of lip motion features for speaker and speech-recognition applications. Digit recognition and person-identification and verification experiments are conducted on the publicly available XM2VTS database showing favorable results (speaker verification is 98 percent, speaker identification is 100 percent, and digit identification is 83 percent to 100 percent).
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| 4. |
- Hoang, Hoai, 1976-
(författare)
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Enhancing the Performance of Distributed Real-time Systems
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Advanced embedded systems can consist of many sensors, actuators and processors that are deployed on one or several boards, while having a demand of interacting with each other and sharing resources. Communication between different components usually has strict timing constraints. There is thus a strong need to provide solutions for time critical communication. This thesis focuses on both the support of real-time services over standard switched Ethernet networks and the improvement of systems' real-time characteristics, such as reducing delay and jitter in processors and on communication links.Switched Ethernet has been chosen in this work because of its major advantages in industry; it supports higher bit-rates than most other current LAN (Local Area Network) technologies, including field buses, still at a low cost. We propose using a star network topology with a single Ethernet switch. Each node is connected to a separate port of the switch via a full-duplex link, thereby eliminating collisions. A solid real-time communication protocol for switched Ethernet networks is proposed in the thesis, including a real-time layer between the Ethernet layer and the TCP/IP suite. The network has the capability of supporting both real-time and non real-time traffic and assuring adaptation to the surrounding protocol standards.Most embedded systems work in a dynamic environment, where the precise behavior of the network traffic can usually not be predicted. To support real-time services, we have chosen the Earliest Deadline scheduling algorithm (EDF) because of its optimality, high efficiency and suitability for being used in adaptive schemes. To be able to increase the amount of guaranteed real-time traffic, the notion of Asymmetric Deadline Partitioning Scheme (ADPS) is introduced. ADPS allows distribution of the end-to-end deadline of a message, sent from any source node in the network to any destination node via the switch, into two sub-deadlines, one for each hop according to the load of the physical link that it must traverse.For the EDF scheduling algorithm, the feasibility test is one of the most important techniques that provides us with information about whether or not the real-time traffic can be guaranteed by the network. With the same computational complexity as the feasibility test, a method has been developed to compute the minimum EDF-feasible deadline for a real-time task. The importance of this method in real-time applications lies in that it can be effectively used to reduce the response times of specific control activities or limit their input-output jitter. To allow more flexibility in the control of delay and jitter in real-time systems, a general approach for reducing task deadlines according to the requirements of individual tasks has been developed. The method allows the user to specify a deadline reduction factor for each task in order to better exploit the available slack according to the tasks' actual requirements.
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| 5. |
- Liu, Ruisheng, et al.
(författare)
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Large magnetoresistance in Co/Ni/Co ferromagnetic single electron transistors
- 2007
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Ingår i: Applied Physics Letters. - New York : American Institute of Physics. - 0003-6951 .- 1077-3118. ; 90:12, s. 123111-
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Tidskriftsartikel (refereegranskat)abstract
- The authors report on magnetotransport investigations of nanoscaled ferromagnetic Co/Ni/Co single electron transistors. As a result of reduced size, the devices exhibit single electron transistor characteristics at 4.2 K. Magnetotransport measurements carried out at 1.8 K reveal tunneling magnetoresistance (TMR) traces with negative coercive fields, which the authors interpret in terms of a switching mechanism driven by the shape anisotropy of the central wirelike Ni island. A large TMR of about 18% is observed within a finite source-drain bias regime. The TMR decreases rapidly with increasing bias, which the authors tentatively attribute to excitation of magnons in the central island.
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| 6. |
- Liu, Ruisheng, et al.
(författare)
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Nanoscaled ferromagnetic single electron transistors
- 2007
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Ingår i: [Host publication title missing]. - Piscataway, N.J. : IEEE Press. ; 1-3, s. 420-423, s. 420-421
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We report on a summary of fabricating and characterizing nanoscaled ferromagnetic single-electron transistors (F-SETs). One type of device is assembled with an atomic force microscope. A single 30 nm Au disc, forming the central island of the transistor, is manipulated with Angstrom precision into the gap between plasma oxidized Ni source and drain electrodes which are designed with different geometries to facilitate magnetic moment reversal at different magnetic fields. The tunnel resistances can be tuned in real-time during the device fabrication by re-positioning the An disc. A second type of device with Co electrodes and a central Au island is fabricated using a high-precision alignment procedure invoked during e-beam writing. Both devices exhibit single-electron transistor characteristics at 4.2K. From magnetotransport measurements carried out at 1.7K, we found that it is more efficient to realize spin injection and detection in Co/Au/Co devices fabricated with the second technique. A maximum TMR of about 4% was observed in these devices.
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| 7. |
- Åhlander, Anders
(författare)
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Efficient parallell architectures for future radar signal processing
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The processing demands on future embedded radar signal processors may stretch to several trillions of floating-point operations per second (TFLOPS). This is an increase of two to three orders of magnitude realtive to the requirements of today. Still, the tight size and power constraints are unchanged. To meet this, new, highly parallel computer systems are needed. The systems should efficiently deliver very high performance as well as being general enough. Another challenge for future signal processors is the requirement for having huge working memories that are accessed in complicated patterns.This thesis analyses the challenges of two classes of radar signal processing applications, namely Space-Time Adaptive Processing (STAP), which represents performance-intensive applications, and Synthetic Aperture Radar (SAR) processing, which represents memory-intensive applications. In addition to the actual performance and memory aspects of the applications, the desire for low-effort application development and maintenance is taken into consideration.A multiple SIMD architecture is proposed for the STAP calculations. This architecture gives a combination of the high computational density in the SIMD processing modules with the overall flexibility provided on the system level. An embedded signal processing system based on the architecture is shown to be capable of TFLOPS class performance using standard CMOS VLSI technology available in the year 2001. The system is, for the given application domain, considered to have the same generality as commercial off-the-shelf (COTS) hardware, but has several years of time lead over COTS with regard to the computational performance.The studied SAR processing is characterized by operating on huge data sets and having varying, non-linear data access paths. For this, algorithm solutions and execution schemes in inerplay with a system parallelization approach are proposed. It is shown that it is possible to obtain efficient memory accesses, despite the omplicated memory access patterns. It is also shown that the computational burden from complex interpolation kernels can be reduced through extensive calculation reuse.Efficient engineering of complex applications in this context is discussed. The use of semi-transparent, platform-based development is demonstrated for STAP and SAR, and advocated for obtaining high engineering defficiency and long system sustainability, as well as high performance efficiency.The overall conclusion drawn from this work is that a solid knowledge of the application domain and its future requirements, in combination with an understanding of its interaction with computational architectures, potentially enables several years of lead time in the realization of new, advanced signal prodcessing products. The important requirements on programmability and sustainability must also be taken into account in order to achieve a viable signal processing solution.
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| 8. |
- Ericson, Stefan, et al.
(författare)
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Algorithms for Visual Odometry in Outdoor Field Environment
- 2007
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Ingår i: Proceedings of the 13th IASTED International Conference on Robotics and Applications. - Anaheim, Calif. : ACTA Press. - 9780889866850 - 9780889866867 ; , s. 287-292
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Konferensbidrag (refereegranskat)abstract
- In this paper different algorithms for visual odometry are evaluated for navigating an agricultural weeding robot in outdoor field environment. Today there is an encoder wheel that keeps track of the weeding tools position relative the camera, but the system suffers from wheel slippage and errors caused by the uneven terrain. To overcome these difficulties the aim is to replace the encoders with visual odometry using the plant recognition camera. Four different optical flow algorithms are tested on four different surfaces, indoor carpet, outdoor asphalt, grass and soil. The tests are performed on an experimental platform. The result shows that the errors consist mainly of dropouts caused by overriding maximum speed, and of calibration error due to uneven ground. The number of dropouts can be reduced by limiting the maximum speed and detection of missing frames. The calibration problem can be solved using stereo cameras. This gives a height measurement and the calibration will be given by camera mounting. The algorithm using normalized cross-correlation shows the best result concerning number of dropouts, accuracy and calculation time.
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| 9. |
- Wärnestål, Pontus, 1975-
(författare)
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Dialogue Behavior Management in Conversational Recommender Systems
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis examines recommendation dialogue, in the context of dialogue strategy design for conversational recommender systems. The purpose of a recommender system is to produce personalized recommendations of potentially useful items from a large space of possible options. In a conversational recommender system, this task is approached by utilizing natural language recommendation dialogue for detecting user preferences, as well as for providing recommendations. The fundamental idea of a conversational recommender system is that it relies on dialogue sessions to detect, continuously update, and utilize the user's preferences in order to predict potential interest in domain items modeled in a system. Designing the dialogue strategy management is thus one of the most important tasks for such systems.Based on empirical studies as well as design and implementation of conversational recommender systems, a behavior-based dialogue model called bcorn is presented. bcorn is based on three constructs, which are presented in the thesis. It utilizes a user preference modeling framework (preflets) that supports and utilizes natural language dialogue, and allows for descriptive, comparative, and superlative preference statements, in various situations. Another component of bcorn is its message-passing formalism, pcql, which is a notation used when describing preferential and factual statements and requests. bcorn is designed to be a generic recommendation dialogue strategy with conventional, information-providing, and recommendation capabilities, that each describes a natural chunk of a recommender agent's dialogue strategy, modeled in dialogue behavior diagrams that are run in parallel to give rise to coherent, flexible, and effective dialogue in conversational recommender systems.Three empirical studies have been carried out in order to explore the problem space of recommendation dialogue, and to verify the solutions put forward in this work. Study I is a corpus study in the domain of movie recommendations. The result of the study is a characterization of recommendation dialogue, and forms a base for a first prototype implementation of a human-computer recommendation dialogue control strategy. Study II is an end-user evaluation of the acorn system that implements the dialogue control strategy and results in a verification of the effectiveness and usability of the dialogue strategy. There are also implications that influence the refinement of the model that are used in the bcorn dialogue strategy model. Study III is an overhearer evaluation of a functional conversational recommender system called CoreSong, which implements the bcorn model. The result of the study is indicative of the soundness of the behavior-based approach to conversational recommender system design, as well as the informativeness, naturalness, and coherence of the individual bcorn dialogue behaviors.
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| 10. |
- Wärnestål, Pontus, 1975-, et al.
(författare)
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Emergent Conversational Recommendations : A Dialogue Behavior Approach
- 2007
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Ingår i: Proceedings of the 8th SIGdial Workshop on Discourse and Dialogue. - East Stroudsburg, USA : Association for Computational Linguistics. - 9789074029322 - 9074029329 ; , s. 63-66
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Konferensbidrag (refereegranskat)abstract
- This paper presents and evaluates a behavior-based approach to dialogue management, where a system's complete dialogue strategy is viewed as the result of running several dialogue behaviors in parallel leading to an emergent coherent and flexible dialogue behavior. The conducted overhearer evaluation of the behavior-based conversational recommender system CORESONG indicates that the approach can give rise to informative and coherent dialogue; and that a complete dialogue strategy can be modeled as an emergent phenomenon in terms of lower-level autonomous behaviors for the studied class of recommendation dialogue interaction. © 2007 Association for Computational Linguistics.
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