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Search Results: 1 - 10 of 2864 matches for " Raymond Veldhuis "
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A Practical Subspace Approach To Landmarking
Gert Beumer,Raymond Veldhuis
Journal of Multimedia , 2010, DOI: 10.4304/jmm.5.3.276-289
Abstract: A probabilistic, maximum aposteriori approach to finding landmarks in a face image is proposed, which provides a theoretical framework for template based landmarkers. One such landmarker, based on a likelihood ratio detector, is discussed in detail. Special attention is paid to training and implementation issues, in order to minimize storage and processing requirements. In particular a fast approximate singular value decomposition method is proposed to speed up the training process and implementation of the landmarker in the Fourier domain is presented that will speed up the search process. A subspace method for outlier correction and an iterative implementation of the landmarker are both shown to improve its accuracy. The impact of carefully tuning the many parameters of the method is illustrated. The method is extensively tested and compared with alternatives.
Binary Biometric Representation through Pairwise Adaptive Phase Quantization
Chen Chun,Veldhuis Raymond
EURASIP Journal on Information Security , 2011,
Abstract: Extracting binary strings from real-valued biometric templates is a fundamental step in template compression and protection systems, such as fuzzy commitment, fuzzy extractor, secure sketch, and helper data systems. Quantization and coding is the straightforward way to extract binary representations from arbitrary real-valued biometric modalities. In this paper, we propose a pairwise adaptive phase quantization (APQ) method, together with a long-short (LS) pairing strategy, which aims to maximize the overall detection rate. Experimental results on the FVC2000 fingerprint and the FRGC face database show reasonably good verification performances.
Binary Biometric Representation through Pairwise Adaptive Phase Quantization
Chun Chen,Raymond Veldhuis
EURASIP Journal on Information Security , 2011, DOI: 10.1155/2011/543106
Predicting Face Recognition Performance Using Image Quality
Abhishek Dutta,Raymond Veldhuis,Luuk Spreeuwers
Computer Science , 2015,
Abstract: This paper proposes a data driven model to predict the performance of a face recognition system based on image quality features. We model the relationship between image quality features (e.g. pose, illumination, etc.) and recognition performance measures using a probability density function. To address the issue of limited nature of practical training data inherent in most data driven models, we have developed a Bayesian approach to model the distribution of recognition performance measures in small regions of the quality space. Since the model is based solely on image quality features, it can predict performance even before the actual recognition has taken place. We evaluate the performance predictive capabilities of the proposed model for six face recognition systems (two commercial and four open source) operating on three independent data sets: MultiPIE, FRGC and CAS-PEAL. Our results show that the proposed model can accurately predict performance using an accurate and unbiased Image Quality Assessor (IQA). Furthermore, our experiments highlight the impact of the unaccounted quality space -- the image quality features not considered by IQA -- in contributing to performance prediction errors.
Can Facial Uniqueness be Inferred from Impostor Scores?
Abhishek Dutta,Raymond Veldhuis,Luuk Spreeuwers
Computer Science , 2013,
Abstract: In Biometrics, facial uniqueness is commonly inferred from impostor similarity scores. In this paper, we show that such uniqueness measures are highly unstable in the presence of image quality variations like pose, noise and blur. We also experimentally demonstrate the instability of a recently introduced impostor-based uniqueness measure of [Klare and Jain 2013] when subject to poor quality facial images.
Performance Evaluation of Fusing Protected Fingerprint Minutiae Templates on the Decision Level
Bian Yang,Christoph Busch,Koen de Groot,Haiyun Xu,Raymond N. J. Veldhuis
Sensors , 2012, DOI: 10.3390/s120505246
Abstract: In a biometric authentication system using protected templates, a pseudonymous identifier is the part of a protected template that can be directly compared. Each compared pair of pseudonymous identifiers results in a decision testing whether both identifiers are derived from the same biometric characteristic. Compared to an unprotected system, most existing biometric template protection methods cause to a certain extent degradation in biometric performance. Fusion is therefore a promising way to enhance the biometric performance in template-protected biometric systems. Compared to feature level fusion and score level fusion, decision level fusion has not only the least fusion complexity, but also the maximum interoperability across different biometric features, template protection and recognition algorithms, templates formats, and comparison score rules. However, performance improvement via decision level fusion is not obvious. It is influenced by both the dependency and the performance gap among the conducted tests for fusion. We investigate in this paper several fusion scenarios (multi-sample, multi-instance, multi-sensor, multi-algorithm, and their combinations) on the binary decision level, and evaluate their biometric performance and fusion efficiency on a multi-sensor fingerprint database with 71,994 samples.
Review: Not for Profit
Ruud Veldhuis
Journal of Social Science Education , 2011,
Abstract: In this book Nussbaum makes a strong case for the importance of the liberal arts in education. If the economic pressure of globalization is not kept under control, the end result might be an erosion of our democracies. The book is more a manifesto (178 pages) and not an empirical study. Quantitative data have been omitted.
The Mass Spectrum in a Model with Calculable Dynamical Supersymmetry Breaking
Tonnis A. ter Veldhuis
Physics , 1995, DOI: 10.1016/0370-2693(95)01454-3
Abstract: Models with dynamical supersymmetry breaking are interesting because they may provide a solution to both the gauge hierarchy and the fine-tuning problems. However, because of strongly interacting dynamics, it is in general impossible to analyze them quantitatively. One of the few models with calculable dynamical supersymmetry breaking is a model with SU(5) gauge symmetry and two $10$'s and two $\bar 5$'s as the matter content. We determine the ground state of this model, find the vacuum energy, reveal the symmetry breaking pattern and calculate the mass spectrum. The supertrace mass relation is exploited to verify the consistency of the calculated mass spectrum, and an accidental degeneracy is explained.
Unexpected symmetries in classical moduli spaces
Tonnis A. ter Veldhuis
Physics , 1998, DOI: 10.1103/PhysRevD.60.015001
Abstract: We analyze the structure of the moduli space of a supersymmetric SU(5) chiral gauge theory with two matter fields in the 10 representation, and two fields in the \bar{5} representation. Inspection of the exact Kahler potential of the classical moduli space shows that the symmetry group of the moduli space is larger than the global symmetry group of the underlying gauge theory. As a consequence, the gauge theory has classical inequivalent vacua which yield identical low energy theories.
The Low Energy Behavior of some Models with Dynamical Supersymmetry Breaking
Tonnis A. ter Veldhuis
Physics , 1998, DOI: 10.1103/PhysRevD.58.015010
Abstract: We study supersymmetric SU(5) chiral gauge theories with 2 fields in the 10 representation, $2+N_F$ fields in the $\bar{5}$ representation and $N_F$ fields in the 5 representation, for $N_F=0,1,2$. With a suitable superpotential, supersymmetry is shown to be broken dynamically for each of these values of $N_F$. We analyze the calculable limit for the model with $N_F=0$ in detail, and determine the low energy effective sigma model in this case. For $N_F=1$ we find the quantum moduli space, and for $N_F=2$ we construct the s--confining potential.
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